Alcohol use among people who inject drugs living with HIV in Kenya is associated with needle sharing, more new sex partners, and lower engagement in HIV care.

We assessed the prevalence and correlates of alcohol use among 870 people who inject drugs living with HIV in Kenya, with attention toward (1) sexual and injecting risk behaviors for HIV transmission and (2) HIV care engagement. We defined heavy alcohol use as > 14 drinks/week for men and > 7 drinks/week for women, moderate alcohol use as any lesser but non-zero amount, and any alcohol use as either moderate or heavy use. Approximately 39% of participants reported any alcohol use and 15% heavy use. In multivariate analysis, any alcohol use compared to no use was associated with needle sharing, > 3 new sex partners in the past 3 months, being unaware of HIV status, never enrolling in HIV care, and not being on ART (all p < 0.05). Heavy alcohol use as compared to no use was associated with needle sharing (aOR = 2.72; 95% CI 1.43, 5.13), injection equipment sharing (aOR = 1.80; 95% CI 1.00, 3.16), > 3 new sex partners in the past 3 months (aOR = 1.99; 95% CI 1.12, 3.49), and being unaware of HIV status (aOR = 2.77; 95% CI 1.46, 5.19). There was no association between any measure of alcohol use and unsuppressed viral load. Alcohol use among people who inject drugs living with HIV may carry elevated risk of HIV transmission mediated by sexual and injecting practices and is associated with lower engagement in multiple stages of the HIV care cascade.

Candida albicans expresses an unusual cytoplasmic manganese-containing superoxide dismutase (SOD3 gene product) upon the entry and during the stationary phase.

We report here that in addition to a cytoplasmic copper-zinc-containing superoxide dismutase (SOD) and a mitochondrial manganese-containing SOD, Candida albicans expresses a third SOD gene (SOD3). The deduced amino acid sequence contains all of the motifs found in previously characterized manganese-containing SODs, except the presence of a mitochondrial transit peptide. Recombinant Sod3p expressed and purified from Escherichia coli is a homotetramer with a subunit mass of 25.4 kDa. Mass absorption spectrometry detected the presence of both iron and manganese in purified Sod3p but, as determined by metal replacement experiments, the enzyme displays activity only when bound to manganese. Overexpression of SOD3 was shown to rescue the hypersensitivity to redox cycling agents of a Saccharomyces cerevisiae mutant lacking the cytoplasmic copper-zinc-containing SOD. Northern blot analyses showed that the transcription of SOD3 is induced neither by the transition from the yeast to the mycelial form of C. albicans nor by drug-induced oxidative stress. In continuous cultures, the expression of SOD3 was strongly stimulated upon the entry and during the stationary phase, concomitantly with the repression of SOD1. We conclude that Sod3p is an atypical cytosolic manganese-containing superoxide dismutase that is involved in the protection of C. albicans against reactive oxygen species during the stationary phase.

Lack of CD40-dependent B-cell proliferation in B lymphocytes isolated from patients with persistent polyclonal B-cell lymphocytosis.

Persistent B-cell lymphocytosis (PPBL) is a haematological disorder diagnosed primarily in adult female smokers that is characterized by a polyclonal increase in peripheral blood B lymphocytes and a moderate elevation of serum IgM. B lymphocyte-associated cellular abnormalities, such as the occurrence of multi-lobed nuclei, increased bcl2/Ig gene rearrangements and the identification of an extra long-arm chromosome (i3)(q10) in the B-cell population, indicate that PPBL could be part of a multi-step process leading to the emergence of a malignant B lymphoproliferation. However, the resulting impact on cellular functional properties remains to be elucidated. Our goal was to address that aspect via the study of B-cell activity following stimulation through CD40, a key molecule of the tumour necrosis factor receptor superfamily involved in B lymphocyte development. In contrast to normal B cells, PPBL B lymphocytes were unable to respond to the proliferative signal delivered in vitro by CD40, indicating a defect in the CD40 activation pathway. Polymerase chain reaction amplification and sequencing of the receptor as well as FACScan analysis of patient B lymphocytes dismissed the possibility of a defect in either CD40 structure or expression. Moreover, Western blot analysis of tyrosine phosphorylation, an early event in the CD40-signalling cascade, was similar in patients and controls, leading to the conclusion that the defect affecting B lymphocytes in PPBL patients is probably located downstream of that signalling cascade.

Effects of an oral health program on the occurrence of oral candidosis in a long-term care facility.

OBJECTIVES: The aim was to evaluate the effectiveness of a preventive oral health program on the prevalence of oral candidosis in 237 frail or dependent residents in a long-term care facility. Half of the residents were included in an experimental group which benefited from a preventive oral hygiene program including instruction of the carers and implementation of a recall program for professional oral hygiene care. METHODS: Intraoral examinations and yeast cultures from the oral mucosa and the fitting denture surface were carried out at baseline and 18 months later. The outgrowth of yeast was estimated on Oricult-N dip slides using the scale: no growth; 1-20 colonies; 21-100 colonies; >100 colonies. RESULTS: At baseline (n = 237) and at 18 months (n = 159) the experimental and the control groups were similar with regard to the residents' distribution by age, sex, dental and prosthetic status and prevalence of denture stomatitis. The 78 residents lost had the same baseline characteristics as the survivors, except for being older. In the experimental group the severity of the inflammation of the palate decreased (P = 0.005) as well as the prevalence of glossitis (P = 0.005). At baseline high yeast scores from the mucosa (>20) were observed in about 50% of the residents in the experimental as well as the control group. At 18 months this figure was 23.4% for the experimental and 48.7% for the control group (P = 0.001). There was also a reduction of the number of residents with positive cultures and the denture yeast scores at 18 months in the experimental group (P = 0.05). CONCLUSIONS: This study has shown that the preventive program was effective in reducing the colonization of the oral mucosa and dentures by Candida and thereby improving the health of the oral mucosa.

Expression cloning of the Candida albicans CSA1 gene encoding a mycelial surface antigen by sorting of Saccharomyces cerevisiae transformants with monoclonal antibody-coated magnetic beads.

The mycelial surface antigen recognized by monoclonal antibody (mAb) 4E1 has previously been shown to be present predominantly in the terminal third of the hyphal structures in Candida albicans. We report here the expression cloning of the corresponding gene (CSA1 ) by mAb 4E1-coated magnetic beads sorting of Saccharomyces cerevisiae transformants expressing a C. albicans genomic library. The strategy is both highly selective and highly sensitive and provides an additional genetic tool for the cloning and characterization of C. albicans genes encoding surface proteins. CSA1 is an intronless gene encoding a 1203-residue protein composed of repetitive motifs and domains. Northern analysis indicates that CSA1 is preferentially expressed during the mycelial growth phase, although a low level of CSA1 mRNA can be detected in the yeast form. As evidenced by indirect immunofluorescence microscopy with mAb 4E1, Csa1p is not randomly distributed over the surface of yeast cells, but localizes predominantly in the growing buds. This suggests that the distribution of Csa1p may be restricted to sites of cell surface elongation. Both heterozygous and homozygous C. albicans csa1Delta mutants are viable. Upon induction of mycelial growth, the number and size of hyphal structures derived from the mutants are similar to those observed in the parental wild-type strain. The physiological role of Csa1p has yet to be determined. However, the presence in Csa1p of repeated cysteine-rich hydrophobic domains with significant sequence similarity to motifs found in surface proteins (Ag2 and Pth11) from two distantly related fungal pathogens (Coccidioides immitis and Magnaporthe grisea respectively) suggests a common function in host interaction.

Proteolytic activation of the interleukin-1beta precursor by Candida albicans.

Chronic inflammation rather than invasion is characteristic of some forms of superficial candidiasis such as denture stomatitis. We hypothesized that Candida albicans may play a critical role in the pathogenesis of inflammatory lesions observed in chronic candidiasis by activating the proinflammatory cytokine interleukin-1beta (IL-1beta) from epithelial stores of the precursor. The aim of this study was therefore to demonstrate the proteolytic cleavage and activation of the inactive precursor of IL-1beta (pro-IL-1beta) by C. albicans. After incubation of either blastospores or hyphae with the inactive precursor, proteolytic cleavage was monitored by sodium dodecyl sulfate-polyacrylamide gel electrophoresis Western immunoblotting analysis, and the biological activity of the cleavage products was tested in a bioassay. We report here that late-stationary-growth-phase blastospores as well as hyphae of C. albicans, but not exponentially growing cells, can efficiently cleave pro-IL-1beta to yield fragments of molecular masses compatible with mature biologically active IL-1beta (17 to 19 kDa). Assays conducted in the presence of selected proteinase inhibitors suggest that the cleavage of pro-IL-1beta involves the participation of one or more aspartyl proteinases. Cleavage products showed a dose-dependent IL-1beta-like activity in a thymocyte proliferation bioassay, which was inhibited by anti-IL-1beta neutralizing antibodies. The present data thus suggest a role for C. albicans proteinases in the activation and maintenance of the inflammatory response at epithelial surfaces.

Activation of the interleukin-1beta precursor by Treponema denticola: a potential role in chronic inflammatory periodontal diseases.

There are several indications suggesting that interleukin-1beta (IL-1beta) may play an important role in inflammatory periodontal diseases. We hypothesized that periodontal sites would represent a unique combination of both cellular sources of IL-1beta precursor (pro-IL-1beta) and microbial proteases and proposed that Treponema denticola, a suspected periodontal pathogen, would play a critical role in the inflammatory nature of adult chronic periodontitis by activating pro-IL-1beta. The aim of this study was thus to demonstrate the proteolytic cleavage and activation of the inactive precursor pro-IL-1beta by T. denticola. After incubation of bacterial cells with recombinant pro-IL-1beta, proteolytic cleavage was monitored by Western immunoblotting, and the biological activity of the digestion products was tested in a bioassay. We report here that T. denticola can cleave pro-IL-1beta to yield two fragments with molecular masses of 18 and 19 kDa. Cleavage products showed a dose-dependent biological activity in the thymocyte proliferation bioassay, and this activity was inhibited by anti-IL-1beta neutralizing antibodies. These results suggest that T. denticola may have a proinflammatory role in periodontal diseases.

Oral carriage of Candida albicans in murine AIDS.

Oral candidiasis is a common fungal infection in patients infected with the human immunodeficiency virus (HIV). Although rare at the time of primary HIV infection, it is frequently found throughout the asymptomatic phase and is predictive of progressive immunodeficiency. However, the precise immune defect which results in outgrowth of commensal Candida albicans in HIV infection has not been identified. Mice infected with the Du5H(G6T2) mixture of mouse leukemia viruses develop a syndrome, designated murine AIDS (MAIDS), that has many of the immune abnormalities found in HIV infection. Retrovirus-infected C57BL/6 mice were examined for their ability to resist the development of oral candidiasis from the carrier state established after a self-limiting acute infection and to clear a subsequent secondary inoculum of oral C. albicans. Most of the mice orally colonized with C. albicans and then inoculated with the retrovirus mixture maintained a low-level oral carriage of C. albicans, while 30% of coinfected mice developed recurring 2- to 3-week episodes of acute Candida proliferation, separated by transient recoveries to the carrier state. The frequencies of CD4+ and CD8+ lymphocytes were, respectively, unchanged and significantly decreased (P < 0.05) in both cervical lymph nodes and spleens of coinfected mice compared to the corresponding frequencies in C. albicans-carrying, virus-free, age-matched control animals. Secretion of gamma interferon by concanavalin A (ConA)-stimulated spleen cells from Candida-carrying, retrovirus-infected mice was significantly decreased (P < 0.05) compared to that of C. albicans-carrying, retrovirus-free mice, in accordance with known abnormalities associated with MAIDS. However, production of this cytokine by ConA-stimulated or unstimulated cervical lymph node cells from coinfected mice was enhanced compared to that of virus-free animals colonized with C. albicans. Acquired resistance to reinfection with C. albicans was maintained in retrovirus-infected mice and was associated with a mucosal recruitment of CD8+ cells not observed in control mice. These results suggest that alterations in mucosal immunity which occur in MAIDS differ substantially from defects observed at other sites and that surrogate epithelial defense mechanisms may function locally to limit Candida proliferation.

Evidence for degradation of gastrointestinal mucin by Candida albicans secretory aspartyl proteinase.

A zone of extracellular digestion of the mucin layer around Candida albicans blastoconidia was observed by transmission electron microscopy in the jejunum of mice inoculated intragastrically (G. T. Cole, K. R. Seshan, L. M. Pope, and R. J. Yancey, J. Med. Vet. Mycol. 26:173-185, 1988). This observation prompted the hypothesis that a putative mucinolytic enzyme(s) may contribute to the virulence of C. albicans by facilitating penetration of the mucus barrier and subsequent adherence to and invasion of epithelial cells. Mucinolytic activity was observed as zones of clearing around colonies of C. albicans LAM-1 grown on agarose containing yeast nitrogen base, glucose, and hog gastric mucin. In addition, concentrated culture filtrate obtained after growth for 24 h in yeast nitrogen base, supplemented with glucose and mucin as the sole nitrogen source, contained proteolytic activity against biotin-labelled mucin which was inhibited by pepstatin A. Sodium dodecyl sulfate-polyacrylamide gel electrophoresis of the culture filtrate revealed two components of 42 and 45 kDa, with pIs of 4.1 and 5.3, respectively. A zymogram showed that mucin was degraded only by the 42-kDa component, which was also recognized by immunoblotting with an anti-secretory aspartyl proteinase (anti-Sap) 2p monoclonal antibody. The N-terminal sequence of the first 20 amino acids matched that reported for Sap2p. These results demonstrate that Sap2p is responsible for proteolysis of mucin by C. albicans in vitro and may be involved as a virulence factor in the breakdown of mucus and penetration of the mucin barrier by C. albicans.

Dynamic expression of cell-surface antigens probed with Candida albicans-specific monoclonal antibodies.

IgG hybridomas were produced with preferentially reacted with cell-surface antigens of either yeast cells or hyphae of Candida albicans. Four mAbs were used in an immunostaining procedure to follow the expression dynamics of these antigens in media supplemented with glucose or galactose. Yeast cell growth was analysed during the lag phase, the early- and late-exponential phases and the stationary phase, and mycelium formation was analysed between 0.5 and 24 h induction at 37 degrees C. It appears that yeast cell-surface antigens 5C11 and 2E11 are expressed throughout all phases of yeast cell growth as well as on young hyphae after up to 1 h induction. Longer hyphae only faintly react with these two mAbs as they switch to hyphal cell-surface antigens 2G8 and 4E1 after 3 h induction. The reactivity to mAbs 2G8 and 4E1 was induced after a 3 h temperature shift and was confined to the terminal third of growing mycelia. Growth and hyphae induction in galactose prolonged the reactivity of young hyphae with the two anti-yeast-cell mAbs, whereas the expression of surface antigens 2G8 and 2E11 appeared delayed and desynchronized on hyphae. Whereas a similar reactivity was found with ten ATCC strains of C. albicans, four clinical isolates had a unique pattern of reactivity. Immunoblot analyses of DTT extracts of cell-surface constituents indicated that the antigens were proteinaceous in nature and showed that yeast-cell antigens 5C11 and 2E11 are detected in four bands between 68 and 104 kDa, whereas mycelial antigens 4E1 and 2G8 are detected in 117 kDa and 104 kDa bands found in mycelial but not in yeast-cell extracts. Present data support the concept of a dynamic balance in the expression of phase-specific antigens in C. albicans.

Topical application of a corticosteroid destabilizes the host-parasite relationship in an experimental model of the oral carrier state of Candida albicans.

Using an experimental model in the mouse we have shown that both local and central lines of defense, involving CD4+ T cells, participate in a dynamic interaction to maintain a long-term carrier state of Candida albicans in the oral cavity. We have tested the impact of a predisposing factor to oral candidiasis in the form of a topical application of a corticosteroid (Topsyn gel) to the oral mucosa for 75 mice twice a day for a 20-day period. Very rapidly after the treatment was initiated, i.e. on day 4, the residual population of Candida increased up to 40-fold and by day 21, the population was 400-fold that of the carrier state. The resident population of intraepithelial CD4+ T cells in the oral mucosa virtually disappeared during the treatment. A topical corticosteroid application also resulted in a massive depletion of T cells in the lymph nodes and in the transient abrogation of the DTH reaction to Candida antigens. On cessation of treatment, normal levels of both Candida and intraepithelial CD4+ T cells were also quickly restored. These results suggest that resistance to superficial invasion by Candida is linked to the presence of an oral mucosal line of defense and that topical application of corticosteroids may dramatically shift the host-parasite relationship in favor of Candida.

Murine autoimmune exocrinopathy: the minor salivary gland network shows a dichotomous pattern of histopathologic involvement.

The minor salivary gland network of the MRL/l mouse was investigated in a kinetic study and compared with the major submandibular gland. We report that minor salivary glands adopt two mutually exclusive patterns of inflammatory lesions depending on the gland. The first pattern is characteristic of human Sjogren's syndrome. It developed during the second month, affected 89% of the animals over 20 weeks old, and consisted of an accumulation of mononuclear cells around the duct system. Only the anterior buccal gland (ABG) showed this pattern, which is shared by the major salivary glands. The ratio of CD4+ to CD8+ cells was the same in lesions and in healthy tissue. No neutrophils were found in these lesions. The second pattern affected all the minor salivary glands except the ABG. These lesions were never observed before the age of 20 weeks and affected 38% of MRL/l mice between the ages of 10-32 weeks. In this pattern, neutrophils were frequently found, but mainly gathered at the periphery of the gland lobules. That a systemic immunoregulatory defect may be expressed as two different patterns of histopathology in the minor salivary glands suggest that the network behaves as a dichotomous entity depending on particular microenvironmental influences.

Differential pattern of infection and immune response during experimental oral candidiasis in BALB/c and DBA/2 (H-2d) mice.

We used an experimental model of oral candidiasis in the mouse to investigate the impact of the introduction of Candida albicans into a Candida-free system. We report that 2 strains of mice with the same major histocompatibility complex haplotype (H-2d) display different kinetics of primary oral infection after topical application of the same inoculum. The mucosal reactions in both DBA/2 and BALB/c mice involve a similar recruitment of CD4+ and CD8+ T cells and of MAC-1+ cells in mucosal tissue during the infection. A carrier state is maintained following the resolution of the infection in both strains and is associated with the persistence of intraepithelial CD4+ T cells. However, there is a time-specific recruitment of gamma delta T cells that coincides with a dramatic decrease in viable Candida in the mucosal tissue; this occurs on day 3 in BALB/c mice and on day 6 in DBA/2 mice. The denouement of an oral contact with Candida is also different in the 2 mouse strains, cell-mediated immunity being triggered in DBA/2 mice but not in BALB/c mice. The different kinetics of Candida clearance in BALB/c vs DBA/2 mice may therefore signal a differential priming of T cell subsets whose modalities do not appear to be associated with the H-2 complex.

Acquired resistance and persistence of Candida albicans following oral candidiasis in the mouse: a model of the carrier state in humans.

In our experimental model of oral candidiasis in the CD1 mouse, the primary infection showed reproducible Candida overgrowth kinetics with a peak level on day 5 of the infection. After day 7, the population stabilized at about 300 colony-forming units per excised mucosal tissue. The primary infection triggered an inflammatory response that resolved in under 8 days. At this point, the histological pattern of the mucosa reached a new equilibrium between recruited and resident mononuclear cells. The primary infection also rapidly stimulated cellular immunity, as measured from day 4 by a delayed-type hypersensitivity footpad reaction. Following a second topical challenge with Candida 30 days after the primary infection, the infection was barely detectable and a typical local delayed-type hypersensitivity reaction occurred between 24-72 h. It is proposed that acquired resistance, in conjunction with low-level persistence of Candida in our model, mimics the carrier state in sensitized humans.

Suppressive effect of serum from pigs and dogs fed a diet deficient in vitamin E and selenium on lymphocyte proliferation.

The effect of sera collected from either pigs or dogs previously fed a vitamin E (vit E)- and selenium (Se)-deficient diet on in vitro lymphocyte blastogenesis response to mitogens was studied. Porcine sera were obtained from pigs used in 2 different trials. In I trial, 4-wk-old pigs received either a basal diet deficient in vit E and Se or the basal diet supplemented with Vit E, Se or Vit E and Se. Pigs were maintained on their respective diet for 25 d. Canine sera were collected from pups maintained on a deficient diet for 8 wk. Four dogs and 4 pigs maintained on a commercial diet were used as donors of peripheral blood lymphocytes (PBL). The addition of sera from pigs or dogs maintained on a vit E- and Se-deficient diet markedly suppressed both porcine and canine PBL response to mitogens. Porcine PBL blastogenesis was also suppressed when porcine or canine sera were added 8, 24 or 48 h after the beginning of the incubation period to culture containing 1% of fetal bovine serum (FBS). However, the suppressive effect caused by porcine sera was less severe than the one due to canine sera. Addition of 1% FBS in the cultures was sufficient to eliminate the suppression caused by the presence of sera from pigs fed a vit E- and Se-deficient diet. Other attempts to restore the lymphocyte response to mitogens by the addition of indomethacin, diethylcarbamazine or eicosatetraynoic acid, inhibitors of prostaglandin and/or leukotriene synthesis, were not successful. Because of the severe suppression caused by sera from animals maintained on a vit E- and Se-deficient diet on the in vitro response of lymphocytes to mitogenic stimulations, it is very important to take precautions to avoid such deficiency. In vivo suppression of immunocompetent cells to antigenic stimulations may impair the capacity of the host to control infections.

The oral mucosa of the MRL/I mouse: a synoptic picture of systemic autoimmune disorders.

The oral manifestations of systemic autoimmunity were investigated in a kinetic study of the MRL/1 mouse. Lesions in the epithelium, connective tissue and minor salivary glands were characterized in serial sections of the soft palate and the cheeks with respect to 1) the type of inflammatory cells present, 2) the presence and type of vasculitis, 3) the presence of necrosis, 4) the occurrence of deposits. By the age of 16 wk, 100% of our animals had developed mild to severe lesions in at least one compartment of the mucosa. Between 16 and 32 wk of age, pathologic manifestations affected the epithelial and subepithelial tissues, the striated muscle tissue, the vascular system and, much less frequently, the minor salivary gland network.

Dynamics of growth hormone responsiveness to growth hormone releasing factor in aging rats: peripheral and central influences.

The in vivo and in vitro dynamics of somatotroph responsiveness to rGRF (1-29) NH2 (rat growth hormone releasing factor) were evaluated in 2-, 4-, 8-, 12-, and 20-month-old male rats. In vivo, using pentobarbital-anesthetized animals, we observed that the rGH (rat growth hormone) responsiveness to 0.4 and 1.6 micrograms/kg rGRF started to decline at the higher dose in 12-month-old rats and was completely blunted at both rGRF doses in 20-month-old animals. In vitro, using freshly dispersed perifused pituitary cells, we also documented a decrease of rGRF-induced rGH secretion in 12- and 20-month-old rats. Moreover, as the animals aged, the rGRF-induced rGH secretion was differentially affected by the inhibiting action of somatostatin (p less than 0.001), suggesting a loss of pituitary sensitivity to somatostatin in the presence of a high concentration of rGRF. The pituitary rGH content increased until rats reached 12 months of age, but was diminished in 20-month-old rats. In contrast, the pituitary somatostatin content increased twofold in 20-month-old rats as compared with younger rats. The hypothalamic somatostatin content was highest in 8-month-old rats and only slightly diminished in 20-month-old animals. Finally, plasma insulin-like growth factor I concentrations were highest in 8-month-old rats and lowest in 20-month-old animals. Altogether, these results indicate that the physiological loss of somatotroph responsiveness associated with the process of aging starts around 12 months of age.(ABSTRACT TRUNCATED AT 250 WORDS)

Cellular immune responses in pigs fed a vitamin E- and selenium-deficient diet.

The effects of dietary restriction of vitamin E (Vit E) and selenium (Se) on lymphocyte proliferation, natural killer (NK) cell activity, antibody-dependent cell-mediated cytotoxicity (ADCC), and on burst respiratory response of stimulated granulocytes as measured by chemiluminescence (CL) were studied in pigs. Six male weanling pigs were maintained for 25 d on a torula yeast-based diet containing no measurable amount of alpha-tocopherol and less than .02 mg of Se per kilogram of feed. Six others received the same basal diet supplemented with 33 IU of DL-alpha-tocopheryl acetate and .2 mg of Se per kilogram of feed. All pigs were inoculated with Salmonella typhisuis on d 21 of the feeding period and killed on d 25. Tests to measure cellular immune functions were performed on cells isolated from blood samples taken on d 21 and 25. After 21 d of feeding, lymphocyte blastogenesis responses to phytohemagglutinin, concanavalin A, and pokeweed mitogen in pigs fed the Vit E- and Se-deficient diet were normal compared with the response in pigs fed the supplemented diet. Moreover, the cytotoxic activity of NK cells, the ADCC response, and the CL response of granulocytes were not affected. After 25 d, a marked suppression of lymphocyte response to mitogens occurred in pigs fed the Vit E- and Se-deficient diet when the cells were cultured in the presence of autologous serum. When fetal bovine serum replaced autologous serum in the cultures, no suppression was observed. No effect on NK activity and ADCC was observed, whereas the CL peak response of granulocytes tended to be higher in pigs fed the deficient diet.(ABSTRACT TRUNCATED AT 250 WORDS)

Alterations of pituitary growth hormone-releasing factor binding sites in aging rats.

This study was designed to determine whether growth hormone (GH)-releasing factor (GRF) binding sites are altered in parallel to the diminution of GH secretion that occurs in aging. Using [125I-Tyr10] hGRF (1-44)NH2 as radioligand, we performed cold saturation studies in 2, 8, 14 and 18-month-old Sprague-Dawley male rat pituitary homogenates. In young rats (2 months), analysis by Ligand revealed the presence of two distinct classes of binding sites (KDs = 0.86 +/- 0.15 and 400 +/- 210 nM; BMAXS = 269 +/- 47 fmol and 42 +/- 19 pmol/mg protein, respectively). In 8 and 14-month old rats, there was a concomitant decrease in capacity of the high affinity class of sites (P less than 0.01) and increase in capacity of the low affinity class of sites (P less than 0.05). In parallel, a transient increase in affinity of the high affinity class of sites was observed in 14-month-old rats (P less than 0.05). In old rats (18 months), the data were no longer statistically analyzed with a two site-model, indicating a severe blunting of the high affinity sites. As the GRF-induced GH secretion is still not diminished at 8 month of age in these animals, our results indicate: 1) that alterations of GRF binding sites precede the GH impairment, thus probably participate in the initiating of this phenomenon and 2) that the biological actions of GRF on GH secretion are likely mediated by the high affinity class of sites.

Cellular mechanism of caprylic acid-induced growth hormone suppression.

To determine the dynamic secretory pattern of growth hormone (GH) in the presence of free fatty acids (FFA), we studied the effect of caprylic acid on basal and rGRF(1-29)NH2 (GRF)-induced GH secretion in acutely dispersed and perifused rat pituitary cells. At a concentration of 3.0 mmol/L, caprylic acid inhibited both basal (P less than .05) and GRF-stimulated GH secretions (P less than .01), except when the maximal (near the EC100) GRF concentration of 100 pmol/L was used. Lower concentrations of caprylic acid such as 0.3 and 1.0 mmol/L significantly inhibited, in a concentration-dependent manner, GH secretion induced by a 6.25-pmol/L GRF. However, at a GRF concentration of 25 pmol/L, this inhibitory effect was abolished. The time-course of GH response to GRF was similar in both control and caprylic acid-treated cells. To elucidate the mechanism(s) of action of the caprylic acid-induced blockade of GH secretion, in 3-day cultured rat pituitary cells, the effect of caprylic acid on basal and GRF-stimulated GH and 3',5'-cyclic adenosine monophosphate (cAMP) release. We also tested its effect on the Ca2+ ionophore, A23187-induced GH release. Caprylic acid (0.3 to 3.0 mmol/L) significantly inhibited basal GH release and GRF- or A23187-induced GH secretion. Furthermore, it decreased both basal and GRF-stimulated cAMP release (P less than .05). In addition, the effect of caprylic acid on rGRF(1-29)NH2 affinity to GRF pituitary binding sites was determined using [125I-Tyr10]hGRF(1-44)NH2 as radioligand.(ABSTRACT TRUNCATED AT 250 WORDS)