The association between selective dry cow therapy, milking routine and dry cow management practices with somatic cell count in early lactation cows from 21 commercial grazing dairy herds.

This observational study aimed to explore the association of farmer-driven selective dry cow therapy (DCT), milking routine and dry cow management practices with somatic cell count (SCC) in early lactation cows from 21 commercial dairy herds. Milking routine practices evaluated referred to cow preparation for milking, in-lactation mastitis management and recording. Dry cow management practices related to dry cow environment and cleaning, dry-off procedure, milk cessation strategy and calving environment. Data from 2,016 multiparous cows in 21 commercial spring-calving grazing dairy herds were available for the study. Herd owners self-reported DCT (the assignment and administration of DCT was at the discretion of the herd owners with no involvement from the research team), management practices during milking and the dry period. Cow-level last test-day SCC records in 2020 [range = 105 to 285 d in milk (DIM)] and first test-day records in 2021 (range = 5 to 60 DIM) were obtained from milk recording databases. Quarter-level milk sampling was carried out on all cows in late lactation of 2020 (range = 240 to 261 DIM) for bacterial culturing. Bacteriological results were used to define cows with intramammary infection (IMI) when ≥ 1 quarter sample resulted in bacterial growth and there were no contaminated samples from that cow. Mixed model analyses were used to evaluate the association of selective DCT, milking routine and dry cow management practices with cows' first test-day log 10 SCC (logSCC) in 2021. At dry-off in 2020, 47.6% of the cows were administered an internal teat sealant alone (ITS) while 52.4% were administered an antibiotic plus an internal teat sealant (AB+ITS). The mean herd-level percentage of cows with IMI was 19.7% (range = 9.8% to 39.5%); Staphylococcus aureus accounted for the majority of cow-level IMI (89.9%, 357/397). Between herds, the proportion of cows administered ITS ranged from 17.7% (14/79; in a herd with an IMI prevalence of 10.1%) to 86.8% (66/76; in a herd with an IMI prevalence of 27.6%). In total, 11.8% (105/889) and 29.8% (292/980) of cows that were administered ITS or AB+ITS had an IMI in late lactation 2020, respectively. The mean untransformed SCC at the last test-day in 2020 of cows administered ITS and AB+ITS was 55,000 and 197,200 cells/mL, respectively. The statistical analysis showed a significant interaction between selective DCT and milk yield at last test-day in 2020; cows with a milk yield of 15 kg and administered ITS had a 0.1 higher (untransformed SCC of 19,000 cells/mL higher) first test-day logSCC compared with cows administered AB+ITS. Additionally, greater parity, IMI in late lactation, higher log SCC at the last test-day in 2020 and longer dry periods were associated with higher logSCC at the first test-day in 2021. The current study identified cow- and herd-level management practices that could aid dairy farmers in improving the outcome of selective DCT and decrease early lactation SCC.

Evaluation of test-day milk somatic cell count to predict intramammary infection in late lactation grazing dairy cows.

Use of selective dry cow antimicrobial therapy requires to precisely differentiate cows with an intramammary infection (IMI) from uninfected cows close to drying-off to enable treatment allocation. Milk somatic cell count (SCC) is an indicator of an inflammatory response in the mammary gland and is usually associated with IMI. However, SCC can also be influenced by cow-level variables such as milk yield, lactation number and stage of lactation. In recent years, predictive algorithms have been developed to differentiate cows with IMI from cows without IMI based on SCC data. The objective of this observational study was to explore the association between SCC and subclinical IMI, taking cognizance of cow-level predictors on Irish seasonal spring calving, pasture-based systems. Additionally, the optimal test-day SCC cut-point (maximized sensitivity and specificity) for IMI diagnosis was determined. A total of 2,074 cows, across 21 spring calving dairy herds with an average monthly milk weighted bulk tank SCC of ≤200,000 cells/mL were enrolled in the study. Quarter-level milk sampling was carried out on all cows in late lactation (interquartile range = 240-261 d in milk) for bacteriological culturing. Bacteriological results were used to define cows with IMI, when ≥1 quarter sample resulted in bacterial growth. Cow-level test-day SCC records were provided by the herd owners. The ability of the average, maximum and last test-day SCC to predict infection were compared using receiver operator curves. Predictive logistic regression models tested included parity (primiparous or multiparous), yield at last test-day and a standardized count of high SCC test-days. In total, 18.7% of cows were classified as having an IMI, with first parity cows having a higher proportion of IMI (29.3%) compared with multiparous cows (16.1%). Staphylococcus aureus accounted for the majority of these infections. The last test-day SCC was the best predictor of infection with the highest area under the curve. The inclusions of parity, yield at last test-day, and a standardized count of high SCC test-days as predictors did not significantly improve the ability of last test-day SCC to predict IMI. The cut-point for last test-day SCC which maximized sensitivity and specificity was 64,975 cells/mL. This study indicates that in Irish seasonal pasture-based dairy herds, with low bulk tank SCC control programs, the last test-day SCC (interquartile range days in milk = 221-240) is the best predictor of IMI in late lactation.

Internal teat sealants alone or in combination with antibiotics at dry-off - the effect on udder health in dairy cows in five commercial herds.

In the dairy industry, the dry period has been identified as an area for potential reduction in antibiotic use, as part of a one health approach to preserve antibiotic medicines for human health. The objective of this study was to assess the impact of dry cow treatment on somatic cell count (SCC), intramammary infection (IMI) and milk yield on five commercial Irish dairy herds. A total of 842 cows across five spring calving dairy herds with a monthly bulk tank SCC of < 200 000 cells/mL were recruited for this study. At dry-off, cows which had not exceeded 200 000 cells/mL in the previous lactation were assigned one of two dry-off treatments: internal teat seal (ITS) alone (Lo_TS) or antibiotic plus ITS (Lo_AB + TS). Cows which exceeded 200 000 cells/mL in the previous lactation were treated with antibiotic plus ITS and included in the analysis as a separate group (Hi_AB + TS). Test-day SCC and lactation milk yield records were provided by the herd owners. Quarter milk samples were collected at dry-off, after calving and at mid-lactation for bacteriological culture and quarter SCC analysis. Cow level SCC was available for 789 cows and was log-transformed for the purpose of analysis. Overall, the log SCC of the cows in the Lo_TS group was significantly higher than the cows in Lo_AB + TS group and not statistically different to the cows in the Hi_AB + TS group in the subsequent lactation. However, the response to treatment differed according to the herd studied; the log SCC of the cows in the Lo_TS group in Herds 3, 4 and 5 was not statistically different to the cows in Lo_AB + TS group, whereas in the other two herds, the log SCC was significantly higher in the Lo_TS when compared to the Lo_AB + TS group. There was a significant interaction between dry-off group and herds on SCC and odds of infection in the subsequent lactation. The results of this study suggest that the herd prevalence of IMI may be useful in decision-making regarding the treatment of cows with ITS alone at dry-off to mitigate its impact on udder health.

Abnormalities detected at pre-purchase examination of National Hunt racehorses presented at sale.

BACKGROUND: Few studies are available concerning prevalences of abnormalities in the Thoroughbred horse population. OBJECTIVES: Determine the prevalence of commonly observed abnormalities in a National Hunt Thoroughbred population using results of pre-purchase examinations conducted at Thoroughbred sales venues. STUDY DESIGN: Retrospective cross-sectional study. METHODS: Veterinary pre-purchase examination certificates for 13,603 3- and 4-year-old Thoroughbred National Hunt horses from Tattersalls Ireland, Goffs Ireland and Doncaster Bloodstock Sales Ltd. (DBS) Sales were analysed. All conditions noted by the veterinarians were recorded to determine the prevalence of abnormalities. RESULTS: Abnormalities were recorded in 73.6% of horses; 12.0% had abnormalities likely to prejudice their use for racing. Metacarpal/metatarsal exostoses and tarsal-plantar desmitis affected 17.1 and 19.4% of the sample respectively, while 9.9% were found to make abnormal respiratory noises and 5.3% had recurrent laryngeal neuropathy. Age, year of birth and sex significantly affected the prevalence of many abnormalities (P<0.001). The proportions of horses sold differed significantly between horses with and without some abnormalities, with unaffected horses significantly more likely to be sold (e.g., prejudicial findings present vs. non-prejudicial/none, 38.1% vs. 77.6% respectively, P<0.001). A range of abnormalities significantly negatively affected the price at sale (P<0.001). Significantly higher proportions of horses in the lower price categories had multiple abnormalities (P<0.001). MAIN LIMITATIONS: The study consisted only of horses entered into store horse sales and presented for sale. Horses kept for racing or breeding purposes or horses withdrawn prior to the panel veterinary pre-purchase examination were not included. The upper respiratory tract was only examined endoscopically in horses found to have an abnormal respiratory noise. CONCLUSIONS: A large proportion of 3- and 4-year-old Thoroughbred National Hunt horses intended for sale are affected by abnormalities. The prevalence of many abnormalities increases with age and certain abnormalities are viewed negatively by purchasers, affecting sale of the horse and achieved sale price.

Effect of using internal teat sealant with or without antibiotic therapy at dry-off on subsequent somatic cell count and milk production.

The objective of this study was to assess the effect of treating cows with teat sealant only compared with antibiotic plus teat sealant at drying off on weekly somatic cell count, potential intramammary infection, and milk production across the entire subsequent lactation. In 3 research herds in the south of Ireland, cows with SCC that did not exceed 200,000 cells/mL in the previous lactation (LowSCC) were randomly assigned to 1 of 2 treatments at drying off: internal teat sealant alone (ITS) or antibiotic plus teat sealant (AB+ITS). Cows with SCC that exceeded 200,000 cells/mL in the previous lactation were treated with AB+ITS and included in the analyses as a separate group (HighSCC). Weekly individual animal composite SCC records were available for 654 cow lactations and were transformed to somatic cell scores (SCS) for the purpose of analysis. Data were divided into 3 data sets to represent records obtained (1) up to 35 DIM, (2) up to 120 DIM, and (3) across the lactation. Foremilk secretions were taken from all quarters at drying off, at calving, 2 wk after calving, and in mid-lactation and were cultured to detect the presence of bacteria. The LowSCC cows treated with ITS alone had higher daily milk yield (0.67 kg/d) across lactation compared with LowSCC cows treated with AB+ITS. The LowSCC cows treated with ITS alone had higher SCS in early, up to mid, and across lactation compared with LowSCC cows treated with AB+ITS. We detected no difference in weekly SCS of LowSCC cows treated with ITS alone and SCS of HighSCC cows. The least squares means back-transformed SCC across lactation of the LowSCC cows treated with ITS alone, LowSCC cows treated with AB+ITS, and HighSCC cows were 41,523, 34,001, and 38,939 cells/mL respectively. The odds of LowSCC cows treated with ITS alone having bacteria present in their foremilk across lactation was 2.7 (95% confidence interval: 1.91 to 3.85) and 1.6 (1.22 to 2.03) times the odds of LowSCC cows treated with AB+ITS and of HighSCC cows treated with AB+ITS, respectively. In this study, Staphylococcus aureus was the most prevalent pathogen isolated from the population. Recategorizing the threshold for LowSCC cows as ≤150,000 cells/mL or ≤100,000 cells/mL in the previous lactation had no effect on the results. The results indicate that herds with good mastitis control programs may use ITS alone at dry-off in cows with SCC <200,000 cells/mL across lactation with only a small effect on herd SCC.

Prevalence of exposure to bovine viral diarrhoea virus (BVDV) and bovine herpesvirus-1 (BoHV-1) in Irish dairy herds.

Bovine viral diarrhoea virus (BVDV) and bovine herpesvirus 1 (BoHV-1) are contagious bovine viral agents. The objectives of this study were to use quarterly bulk milk and 'spot' testing of unvaccinated youngstock to establish the national prevalence of exposure to BVDV and/or BoHV-1 in Irish dairy herds. Seasonality of bulk milk ELISA results was also examined. From a geographically representative population of 305 dairy herds, 88% and 80% of herds yielded mean annual positive bulk milk readings for BVDV and BoHV-1, respectively. Of these, 61% were vaccinated against BVDV and 12% against BoHV-1. A total of 2171 serum samples from weanlings having a mean age of 291 days yielded 543 (25%) seropositive for BVDV, and 117 (5.4%) seropositive for BoHV-1. A significant seasonal trend in bulk milk antibody ELISA readings and herd status was recorded for BVDV, with more herds categorised as positive in the latter half of the year.

The molecular epidemiology of equine influenza in Ireland from 2007-2010 and its international significance.

REASONS FOR PERFORMING THE STUDY: Antigenic and genetic drift of equine influenza (EI) virus is monitored annually by the Expert Surveillance Panel (ESP), which make recommendations on the need to update vaccines. Surveillance programmes are essential for this process to operate effectively and to decrease the risk of disease spread through the international movement of subclinically infected vaccinated horses. Not only is surveillance necessary to inform vaccine companies which strains are in circulation, but it serves as an early warning system for horse owners, trainers and veterinary clinicians, facilitating the implementation of appropriate prophylactic and control measures. OBJECTIVE: To summarise the genetic analysis of EI viruses detected in Ireland from June 2007 to January 2010. METHODS: The HA1 gene of 18 viruses was sequenced and phylogenetic analysis undertaken. RESULTS: All viruses belonged to the Florida sublineage of the American lineage. Clade 2 viruses predominated up to 2009. The viruses identified on 4 premises in 2007 displayed 100% nucleotide identity to A/eq/Richmond/1/07, the current clade 2 prototype. The first clade 1 virus was identified in November 2009 and, thereafter, clade 1 viruses were responsible for all the outbreaks identified. The Irish clade 1 viruses differ from the clade 1 virus responsible for the EI outbreaks in Japan and Australia in 2007. No virus of the Eurasian lineage was isolated during this surveillance period. CONCLUSIONS: In 2010 the ESP recommended that the vaccines should not include a H7N7 virus or a H3N8 virus of the Eurasian lineage but that they should contain both a clade 1 and clade 2 virus of the Florida sublineage. The surveillance data presented here support these recommendations and indicate that they are epidemiologically relevant. POTENTIAL RELEVANCE: These data also serve as a scientific basis for investigating the source of epizootics and outbreaks both nationally and internationally.

Management and environmental factors involved in equine influenza outbreaks in Ireland 2007-2010.

REASONS FOR PERFORMING STUDY: Outbreaks of equine influenza (EI) in endemic populations continue to cause economic loss despite widespread vaccination. HYPOTHESIS: To identify the key management and environmental factors that determine the risk of horses contracting EI in an endemic country and to identify control strategies. METHODS: Real time-polymerase chain reaction (RT-PCR), virus isolation and haemagglutination inhibition were carried out on nasopharyngeal swabs and clotted blood samples collected from horses and ponies showing signs of respiratory disease. On premises where a diagnosis of EI was confirmed, the attending veterinary surgeon was asked to participate in an epidemiological investigation. RESULTS: Between June 2007 and January 2010, EI outbreaks were diagnosed on 28 premises located in 13 of the 32 counties of Ireland. Veterinary advice was sought on average more than 5 days after the first clinical signs were observed. The majority of diagnoses were made by RT-PCR. Data from 404 horses on 16 premises were used in the epidemiological analysis. In 15 premises, EI was identified following movement of horses. Housing type, teaser stallions or fomites/personnel contributed to virus spread. Vaccination status, number of years vaccination, time since last vaccination and age influenced disease expression. Isolation and vaccination were effective control measures on the premises where they were implemented. CONCLUSIONS: Preventative measures include: isolation, clinical monitoring, serological testing and vaccination of new arrivals, booster vaccination of horses at 6 monthly intervals, maintenance of effective boundaries between equine premises and avoidance of stabling in single air spaces. Control measures include: prompt isolation of suspected cases, rapid diagnosis by RT-PCR, booster vaccination of cohorts and implementation of biosecurity measures to avoid transmission by fomites and personnel. POTENTIAL RELEVANCE: Implementation of these preventative and control measures should reduce the economic losses associated with outbreaks of EI.

Real-time RT-PCR for the detection and quantitative analysis of equine rhinitis viruses.

REASONS FOR PERFORMING STUDY: Equine rhinitis viruses (ERV) cause respiratory disease and loss of performance in horses. It has been suggested that the economic significance of these viruses may have been underestimated due to insensitive methods of detection. OBJECTIVES: To develop a sensitive, rapid, real-time RT-PCR (rRT-PCR) assay suitable for the routine diagnosis and epidemiological surveillance of the A and B variants of ERV. METHODS: TaqMan primer probe sets for ERAV and ERBV were designed from conserved regions of the 5' UTR of the ERV genome. Over 400 samples from both clinically affected and asymptomatic horses were employed for validation of the assays. ERAV samples positive by rRT-PCR were verified by virus isolation and ERBV positive samples were verified by rRT-PCR using a different set of primers. RESULTS: The detection limit of the rRT-PCR for both viruses was 10-100 genome copies. Of 250 archival nasal swabs submitted for diagnostic testing over a 7 year period, 29 were ERAV positive and 3 were ERBV positive with an average incidence rate per year of 10 and 1.5%, respectively. There was evidence of co-circulation of ERAV and ERBV with equine influenza virus (EIV). Of 100 post race urine samples tested, 29 were ERAV positive by rRT-PCR. Partial sequencing of 2 ERBV positive samples demonstrated that one was 100% identical to ERBV1 from a 270 bp sequence and the other was more closely related to ERBV2 than ERBV1 (95% compared to 90% nucleotide identity in 178 bp). CONCLUSIONS: The rRT-PCR assays described here are specific and more sensitive than virus isolation. They have good reproducibility and are suitable for the routine diagnosis of ERAV and ERBV. POTENTIAL RELEVANCE: These assays should be useful for investigating the temporal association between clinical signs and rhinitis virus shedding.

Influenza A viruses with truncated NS1 as modified live virus vaccines: pilot studies of safety and efficacy in horses.

REASONS FOR PERFORMING STUDY: Three previously described NS1 mutant equine influenza viruses encoding carboxy-terminally truncated NS1 proteins are impaired in their ability to inhibit type I IFN production in vitro and are replication attenuated, and thus are candidates for use as a modified live influenza virus vaccine in the horse. HYPOTHESIS: One or more of these mutant viruses is safe when administered to horses, and recipient horses when challenged with wild-type influenza have reduced physiological and virological correlates of disease. METHODS: Vaccination and challenge studies were done in horses, with measurement of pyrexia, clinical signs, virus shedding and systemic proinflammatory cytokines. RESULTS: Aerosol or intranasal inoculation of horses with the viruses produced no adverse effects. Seronegative horses inoculated with the NS1-73 and NS1-126 viruses, but not the NS1-99 virus, shed detectable virus and generated significant levels of antibodies. Following challenge with wild-type influenza, horses vaccinated with NS1-126 virus did not develop fever (>38.5 degrees C), had significantly fewer clinical signs of illness and significantly reduced quantities of virus excreted for a shorter duration post challenge compared to unvaccinated controls. Mean levels of proinflammatory cytokines IL-1beta and IL-6 were significantly higher in control animals, and were positively correlated with peak viral shedding and pyrexia on Day +2 post challenge. CONCLUSION AND CLINICAL RELEVANCE: These data suggest that the recombinant NS1 viruses are safe and effective as modified live virus vaccines against equine influenza. This type of reverse genetics-based vaccine can be easily updated by exchanging viral surface antigens to combat the problem of antigenic drift in influenza viruses.

Occlusal angles of cheek teeth in normal horses and horses with dental disease.

The angle between the occlusal surface of the tooth and the horizontal plane of 687 cheek teeth from the skulls of 22 horses without gross dental disorders and 11 horses with dental disorders were measured by using stiff malleable wire as an imprint. Each measurement was repeated five times and the mean angle was recorded. In the normal skulls, the mean occlusal angles of the mandibular cheek teeth ranged from 19.2 degrees at the Triadan 06 position to 30 degrees at the 11 position, and these angles were significantly greater than the occlusal angles of the opposing maxillary cheek teeth (range 12.5 degrees to 18 degrees) at all the positions except the 06. The rostral mandibular cheek teeth had significantly lower occlusal angles than the caudal mandibular cheek teeth, but the converse was true for the maxillary teeth. In the skulls with dental disorders the occlusal angles of the mandibular cheek teeth ranged from 15.6 degrees to 28.5 degrees , and of the maxillary cheek teeth from 9.2 degrees to 16.4 degrees. They were not significantly different from the angles of the teeth from the normal skulls, except at the 06 position, where they were smaller.

Effects of milking frequency on phagocytosis and oxidative burst activity of phagocytes from primiparous and multiparous dairy cows during early lactation.

The objective of this study was to investigate the effect of milking frequency on the phagocytosis and respiratory burst activity of polymorphonuclear neutrophils (PMN) and monocytes of primiparous and multiparous cows under 2 nutritional management regimens during early lactation. At calving, 12 primiparous and 12 multiparous cows were randomly assigned to 1 of 4 treatments, in which animals were milked once (OAD) or twice a day at a high or low nutritional level. Blood samples were taken 1 to 7 d before calving (prepartum) and 1 to 7, 14 to 21, and 42 to 49 d postpartum. Phagocytic and oxidative burst activity of PMN and monocytes were determined in whole blood and analyzed separately by flow cytometry. Once-a-day milking reduced significantly the percentage of phagocytic PMN and tended to decrease the number of bacteria ingested by these cells. The percentage of oxidative burst positive cells and overall respiratory burst activity of monocytes also tended to be reduced by OAD milking. The reduction of oxidative burst activity of monocytes was more pronounced 1 to 7 d postpartum compared with the prepartum sample and other postpartum samples. Oxidative burst activity of PMN and monocytes of multiparous cows was impaired compared with primiparous cows. The percentage of oxidative burst positive monocytes from multiparous cows was reduced prepartum and also 1 to 7 d postpartum. Once-a-day milking reduced the mean respiratory burst activity of PMN from primiparous cows to levels similar to that of multiparous cows. Therefore, an OAD milking regimen reduces phagocytic activity of PMN and monocytes and would be detrimental for the immune system in high-yielding dairy cows during early lactation.

Age-related changes in pro-inflammatory cytokines, acute phase proteins and cortisol concentrations in neonatal piglets.

Age-related changes have been described in the resting levels of cortisol and acute phase proteins in the neonatal pig. This study evaluated the plasma concentrations of the pro-inflammatory cytokines tumour necrosis factor-alpha (TNF-alpha), interleukin-1beta (IL-1beta), the acute phase proteins C-reactive protein (CRP), serum amyloid A (SAA) and haptoglobin (Hp), as well as cortisol during the first week of postnatal life in piglets. The influence of invasive managerial practices such as teeth clipping, ear notching and tail docking on possible age-related changes in the production of these inflammatory mediators was also assessed. A total of 96 piglets were selected from 24 litters at birth, and were randomly assigned to one of four sampling times over the first week of life and one of two treatments. Blood samples were taken at 1, 3, 5 or 7 days of age. Piglets were ear notched, teeth clipped and tail docked (NCD), or were left untreated (CON). Significant effects of age were found in plasma concentrations of TNF-alpha, SAA, Hp and cortisol (p < 0.001). Concentrations of TNF-alpha and Hp increased with age, and peak concentrations were found on day 5. SAA and cortisol levels were highest on day 1, decreasing gradually with age. NCD piglets tended to have higher levels of plasma Hp than CON animals (p = 0.066). However, no differences between NCD and CON piglets were found in any other parameter measured. Furthermore, age effects were not affected by these husbandry practices. These results indicate that age-related changes exist in several inflammatory mediators, and suggest that these managerial practices do not result in systemic inflammation in early postnatal life of piglets.

Modulator of heme biosynthesis induces apoptosis in leukemia cells.

OBJECTIVE: The purpose of this research is the investigation of the possible cause(s) of the dark-cell death phenomenon induced by 1,10-phenanthroline (Oph), a porphyrin biosynthesis modulator. SUMMARY BACKGROUND DATA: We have previously shown that porphyrin biosynthesis modulators, such as Oph, which is also an iron-chelating agent, enhance protoporphyrin IX (Proto) accumulation in mammalian neoplastic cells treated with delta-aminolevulinic acid (ALA). As a result of the enhanced Proto accumulation, a significant increase in photodynamic damage was observed under illumination. Also tetrapyrrole and heme-biosynthesis modulators have been shown to cause death in treated insect larvae in darkness, a phenomenon referred to as dark-cell death. Dark-cell death was also observed in Oph + ALA-treated transformed mammalian cells. METHODS: Neoplastic cells were treated with ALA, Oph, and ALA + Oph, and the following cell properties were investigated: growth arrest, membrane permeability, cell survival, nucleosomal cleavage, and cell cycle alterations. RESULTS: It was observed that Oph but not ALA induced growth arrest, in a T-cell leukemia line (MLA 144) as assessed by reduction in DNA synthesis. Exogenous Proto and isomers of Oph lacking the iron-chelating property of Oph also caused a dose-dependent inhibition of proliferation in MLA 144 cells. Although the plasma membrane of Oph-treated cells remained intact following 3 h of dark-incubation, the cells exhibited DNA internucleosomal cleavage, characteristic of cells undergoing apoptosis. Cell cycle analysis using the DNA intercalating dye propidium iodide (PI) coupled to flow cytometry, indicated that 81 +/- 5.6% of Oph-treated MLA 144 cells were apoptotic, with the majority of the cells arrested in the early S phase. On the other hand, treatment with either ALA or Proto did not alter the cell cycle. Also, using a double-labeling protocol with Hoechst 33342, and PI, and analysis by flow cytometry, Oph-treated cells were found to be 82% apoptotic after 3 h of dark-incubation. Apoptosis was reduced by 75% (p < 0.05) by the cytoplasmic protein synthesis inhibitor cycloheximide. CONCLUSIONS: These results indicate that in addition to enhancing Proto accumulation, the heme biosynthesis modulator Oph also induces growth arrest and apoptosis in transformed cells in darkness.

Developmental expression of insulin receptor substrate-2 during dimethylsulfoxide-induced differentiation of human HL-60 cells.

Insulin receptor substrate-2 (IRS-2) is phosphorylated on tyrosine by a number of cytokine receptors and is implicated in the activation of phosphatidylinositol 3'-kinase (PI3-kinase). Here, we demonstrate that induction of granulocytic differentiation of human promyeloid HL-60 cells leads to an increase in the amount of IRS-2 that is phosphorylated in response to insulin-like growth factor (IGF)-I. Although PI3-kinase is often activated following interaction with IRS-1, we could not detect IRS-1 protein, IRS-1 mRNA, or IRS-1-precipitable PI3-kinase enzymatic activity. However, PI3-kinase activity that was coimmunoprecipitated with either anti-phosphotyrosine or anti-IRS-2 following IGF-I stimulation was increased 100-fold. Heightened tyrosine phosphorylation of IRS-2 during granulocytic differentiation was not caused by an increase in expression of the tyrosine kinase IGF-I receptor, as measured by the amount of both the alpha- and beta-subunits. Instead, immunoblotting experiments with an Ab to IRS-2 revealed that induction of granulocytic differentiation caused a large increase in IRS-2, and this occurred in the absence of detectable IRS-1 protein. These IRS-2-positive cells could not differentiate into more mature myeloid cells in serum-free medium unless IGF-I was added. These data are consistent with a model of granulocytic differentiation that requires at least two signals, the first of which leads to an increase in the cytoplasmic pool of IRS-2 protein and a second molecule that acts to tyrosine phosphorylate IRS-2 and enhance granulocytic differentiation.

Phosphatidylinositol 3'-kinase, but not S6-kinase, is required for insulin-like growth factor-I and IL-4 to maintain expression of Bcl-2 and promote survival of myeloid progenitors.

Phosphatidylinositol 3'-kinase (PI 3-kinase) catalyzes the formation of 3' phosphoinositides and has been implicated in an intracellular signaling pathway that inhibits apoptosis in both neuronal and hemopoietic cells. Here, we investigated two potential downstream mediators of PI 3-kinase, the serine/threonine p70 S6-kinase (S6-kinase) and the antiapoptotic protein B cell lymphoma-2 (Bcl-2). Stimulation of factor-dependent cell progenitor (FDCP) cells with either IL-4 or insulin-like growth factor (IGF)-I induced a 10-fold increase in the activity of both PI 3-kinase and S6-kinase. Rapamycin blocked 90% of the S6-kinase activity but did not affect PI 3-kinase, whereas wortmannin and LY294002 inhibited the activity of both S6-kinase and PI 3-kinase. However, wortmannin and LY294002, but not rapamycin, blocked the ability of IL-4 and IGF-I to promote cell survival. We next established that IL-3, IL-4, and IGF-I increase expression of Bcl-2 by >3-fold. Pretreatment with inhibitors of PI 3-kinase, but not rapamycin, abrogated expression of Bcl-2 caused by IL-4 and IGF-I, but not by IL-3. None of the cytokines affected expression of the proapoptotic protein Bax, suggesting that all three cytokines were specific for Bcl-2. These data establish that inhibition of PI 3-kinase, but not S6-kinase, blocks the ability of IL-4 and IGF-I to increase expression of Bcl-2 and protect promyeloid cells from apoptosis. The requirement for PI 3-kinase to maintain Bcl-2 expression depends upon the ligand that activates the cell survival pathway.

The immune-endocrine loop during aging: role of growth hormone and insulin-like growth factor-I.

Why a primary lymphoid organ such as the thymus involutes during aging remains a fundamental question in immunology. Aging is associated with a decrease in plasma growth hormone (somatotropin) and IGF-I, and this somatopause of aging suggests a connection between the neuroendocrine and immune systems. Several investigators have demonstrated that treatment with either growth hormone or IGF-I restores architecture of the involuted thymus gland by reversing the loss of immature cortical thymocytes and preventing the decline in thymulin synthesis that occurs in old or GH-deficient animals and humans. The proliferation, differentiation and functions of other components of the immune system, including T and B cells, macrophages and neutrophils, also demonstrate age-associated decrements that can be restored by IGF-I. Knowledge of the mechanism by which cytokines and hormones influence hematopoietic cells is critical to improving the health of aged individuals. Our laboratory has recently demonstrated that IGF-I prevents apoptosis in promyeloid cells, which subsequently permits these cells to differentiate into neutrophils. We also demonstrated that IL-4 acts much like IGF-I to promote survival of promyeloid cells and to activate the enzyme phosphatidylinositol 3'-kinase (PI 3-kinase). However, the receptors for IGF-I and IL-4 are completely different, with the intracellular beta chains of the IGF receptor possessing intrinsic tyrosine kinase activity and the alpha and gammac subunit of the heterodimeric IL-4 receptor utilizing the Janus kinase family of nonreceptor protein kinases to tyrosine phosphorylate downstream targets. Both receptors share many of the components of the PI 3-kinase signal transduction pathway, converging at the level of insulin receptor substrate-1 or insulin receptor subtrate-2 (formally known as 4PS, or IL-4 Phosphorylated Substrate). Our investigations with IGF-I and IL-4 suggest that PI 3-kinase inhibits apoptosis by maintaining high levels of the anti-apoptotic protein Bcl-2. The sharing of common activation molecules, despite vastly different protein structures of their receptors, forms a molecular explanation for the possibility of cross talk between IL-4 and IGF-I in regulating many of the events associated with hematopoietic differentiation, proliferation and survival.

IL-4 and insulin-like growth factor-I inhibit the decline in Bcl-2 and promote the survival of IL-3-deprived myeloid progenitors.

The proto-oncogene product Bcl-2 regulates cell survival in both the immune and central nervous systems. We withdrew growth factors from IL-3-dependent murine myeloid progenitor cells (factor dependent cell progenitors (FDCP)) and measured a time-dependent 80% reduction in endogenous expression of Bcl-2. This decline in Bcl-2 is directly associated with a fourfold increase in the apoptotic population after 12 h and an eightfold increase after 24 h. Since IL-4 and insulin-like growth factor-I (IGF-I) regulate myeloid cell growth, we used IL-3-deprived FDCP cells to determine whether IL-4 and IGF-I maintain Bcl-2 expression and prevent apoptosis. We demonstrate that IL-4, like IGF-I and IL-3, promotes survival of FDCP cells by reducing the apoptotic population. Flow cytometric measurement of intracellular Bcl-2 established that IL-4 and IGF-I maintain 10-fold higher levels of Bcl-2 than in IL-3-deprived cells. Similarly, Western analysis of Bcl-2 in lysates of IL-3-deprived myeloid progenitors confirmed that both IL-4 and IGF-I share with IL-3 the ability to maintain intact Bcl-2 protein. However, IL-4 and IGF-I do not change expression of the apoptotic inducer, Bax, although they maintain high levels of Bcl-2 that coimmunoprecipitate with Bax. Collectively, these data demonstrate that IL-4 and IGF-I, like IL-3, inhibit apoptosis in myeloid progenitors and maintain high levels of Bcl-2/Bax heterodimers, suggesting that Bcl-2 is a critical convergence point in the signaling pathways used by IL-4 and IGF-I.

Coincidental changes in behavior and plasma cortisol in unrestrained pigs after intracerebroventricular injection of tumor necrosis factor-alpha.

The coincidental behavioral and physiological responses to inflammatory stimuli administered either peripherally or centrally were evaluated. In the first study, twenty castrated male pigs were injected ip with 0, 0.5, 5, or 50 microg/kg BW lipopolysaccharide (LPS). Body temperature was monitored telemetrically, and serial blood samples were collected via an indwelling jugular catheter for determination of plasma cortisol and tumor necrosis factor-alpha (TNF-alpha) concentrations. Sickness behaviors were measured during 10-min tests at 0, 2, 4, 8, 12, and 24 h post injection. The 5 and 50 microg/kg doses of LPS increased plasma concentrations of cortisol and TNF-alpha, while inducing anorexia, hypersomnia, and fever. In contrast, although 0.5 microg/kg LPS induced acute anorexia, hypersomnia, and fever, it did not increase plasma TNF-alpha; and the cortisol response was small and transient, suggesting the behavioral system in pigs is more responsive to LPS than the hypothalamic-pituitary-adrenal (HPA) axis. Because LPS-induced behavior and activation of the HPA axis involve proinflammatory cytokines in the brain, in a second study, unrestrained pigs with jugular catheters were injected intracerebroventricularly (I.C.V.) with recombinant porcine TNF-alpha. Vehicle or TNF-alpha (0, 5, or 50 ng/kg) was injected I.C.V., and plasma cortisol and behavior were determined as before. Pigs injected I.C.V. with 50 ng/kg TNF-alpha showed anorexia, hypersomnia, and an abrupt increase in plasma cortisol concentration. Whereas 5 ng/kg TNF-alpha I.C.V. also induced marked sickness behavior, it failed to stimulate the HPA axis, as indicated by plasma cortisol levels. That there was a distinct difference in the magnitude of behavioral and endocrine responses to LPS and TNF-alpha suggests that different systems that are responsive to inflammatory stimuli exhibit different sensitivities.

Hormones, lymphohemopoietic cytokines and the neuroimmune axis.

The classical distinction between hormones and cytokines has become increasingly obscure with the realization that homeostatic responses to infection involve coordinated changes in both the neuroendocrine and immune systems. The hypothesis that these systems communicate with one another is supported by the ever-accruing demonstrations of a shared molecular network of ligands and receptors. For instance, leukocytes express receptors for hormones and these receptors modulate diverse biological activities such as the growth, differentiation and effector functions. Leukocyte lineages also synthesize and secrete hormones, such as insulin-like growth factor-I (IGF-I), in response to both growth hormone (GH) and also to cytokines such as tumor necrosis factor-alpha (TNF-alpha). Since hormones share intracellular signaling substrates and biological activities with classical lymphohemopoietic cytokines, neuroendocrine and immune tissues share a common molecular language. The physiological significance of this shared molecular framework is that these homeostatic systems can intercommunicate. One important example of this interaction is the mechanism by which bacterial lipopolysaccharide, by eliciting a pro-inflammatory cytokine cascade from activated leukocytes, modulate pituitary GH secretion as well as other CNS-controlled behavioral and metabolic events. This article reviews the cellular and molecular basis for this communication system and proposes novel mechanisms by which neuroendocrine-immune interactions converge to modulate disease resistance, metabolism and growth.