Sustained expression of interleukin-1beta in mouse hippocampus impairs spatial memory.

Glial activation and neuroinflammation occur in neurodegenerative disease and brain injury, however their presence in normal brain aging suggests that chronic neuroinflammation may be a factor in age-related dementia. Few studies have investigated the impact of sustained elevation of hippocampal interleukin-1beta, a pro-inflammatory cytokine upregulated during aging and Alzheimer's disease, on cognition in mice. We utilized the IL-1beta(XAT) transgenic mouse to initiate bilateral hippocampal overexpression of interleukin-1beta to determine the influence of sustained neuroinflammation independent of disease pathology. Fourteen days following transgene induction, adult male and female IL-1beta(XAT) mice were tested on non-spatial and spatial versions of the Morris water maze. For the spatial component, one retention trial was conducted 48 h after completion of a 3 day acquisition protocol (eight trials per day). Induction of IL-1beta did not impact non-spatial learning, but was associated with delayed acquisition and decreased retention of the spatial task. These behavioral impairments were accompanied by robust reactive gliosis and elevated mRNA expression of inflammatory genes in the hippocampus. Our results suggest that prolonged neuroinflammation response per se may impact mnemonic processes and support the future application of IL-1beta(XAT) transgenic mice to investigate chronic neuroinflammation in age- and pathology-related cognitive dysfunction.

Removal of oesophageal foreign bodies in dogs: use of the fluoroscopic method and outcome.

The case records of dogs with a diagnosis of oesophageal foreign body were reviewed and the owners of affected dogs contacted by telephone to ascertain whether there had been any long-term adverse sequelae. Case records of admissions between August 1993 and August 1998 were used. There were 65 admissions for this problem during the period. In 61 instances, forceps manipulation orally under fluoroscopic guidance was attempted to remove the foreign body. This was successful in 51 instances. Animals were followed up for a median of 24 months (minimum of four months). Three animals died or were euthanased in hospital. Two further animals died within two weeks of discharge. In the cases for which follow-up was available, 42 were reported to be normal, one animal had a recurrence, one had a voice change and two had occasional coughing. Fluoroscopic-guided forceps retrieval appears to be an effective method of treatment and long-term complications are uncommon.

Age-dependency of 45calcium accumulation following lateral fluid percussion: acute and delayed patterns.

This study was designed to determine the regional and temporal profile of 45calcium (45Ca2+) accumulation following mild lateral fluid percussion (LFP) injury and how this profile differs when traumatic brain injury occurs early in life. Thirty-six postnatal day (P) 17, thirty-four P28, and 17 adult rats were subjected to a mild (approximately 2.75 atm) LFP or sham injury and processed for 45Ca2+ autoradiography immediately, 6 h, and 1, 2, 4, 7, and 14 days after injury. Optical densities were measured bilaterally within 16 regions of interest. 45Ca2+ accumulation was evident diffusely within the ipsilateral cerebral cortex immediately after injury (18-64% increase) in all ages, returning to sham levels by 2-4 days in P17s, 1 day in P28s, and 4 days in adults. While P17s showed no further 45Ca2+ accumulation, P28 and adult rats showed an additional delayed, focal accumulation in the ipsilateral thalamus beginning 2-4 days postinjury (12-49% increase) and progressing out to 14 days (26-64% increase). Histological analysis of cresyl violet-stained, fresh frozen tissue indicated little evidence of neuronal loss acutely (in all ages), but considerable delayed cell death in the ipsilateral thalamus of the P28 and adult animals. These data suggest that two temporal patterns of 45Ca2+ accumulation exist following LFP: acute, diffuse calcium flux associated with the injury-induced ionic cascade and blood brain barrier breakdown and delayed, focal calcium accumulation associated with secondary cell death. The age-dependency of posttraumatic 45Ca2+ accumulation may be attributed to differential biomechanical consequences of the LFP injury and/or the presence or lack of secondary cell death.

Quantitative assessment of longitudinal metabolic changes in vivo after traumatic brain injury in the adult rat using FDG-microPET.

With the advent and emerging importance of neurobiology and its relation to behavior, scientists desire the capability to apply noninvasive, quantitative imaging of neuronal activity to small rodents. To this end, the authors' laboratory has developed microPET, a high-resolution positron emission tomography (PET) scanner that is capable of performing in vivo molecular imaging at a resolution sufficient to resolve major structures in the rat brain. The authors report in this article that, in conjunction with 2-[18F]fluoro-2-deoxyglucose (FDG), microPET provides accurate rates of cerebral glucose metabolism (59.7 to 108.5 micromol/100 g x min) in conscious adult rats as validated by within-subject autoradiographic measurements (59.5 to 136.2 micromol/100 g x min; r = 0.88; F[1,46] = 168.0; P < 0.001). By conducting repeated quantitative scanning, the authors demonstrate the sensitivity and accuracy of FDG-microPET to detect within-subject metabolic changes induced by traumatic brain injury. In addition, the authors report that longitudinal recovery from traumatic brain injury-induced metabolic depression, as measured by quantitative FDG-microPET, is significantly correlated (r = 0.65; P < 0.05) to recovery of behavioral dysfunction, as assessed by the Morris Water Maze performance of the same rats, after injury. This is the first study to demonstrate that FDG-microPET is quantitative, reproducible, and sensitive to metabolic changes, introducing a new approach to the longitudinal study of small animal models in neuroscience research.

Dynamic changes in cerebral glucose metabolism in conscious infant monkeys during the first year of life as measured by positron emission tomography.

Recently, advances in spatial resolution have provided the opportunity to utilize positron emission tomography (PET) to examine local cerebral metabolic rates for glucose (lCMR(glc)) in large animals noninvasively, thereby allowing repeated lCMR(glc) measurements in the same animal. Previous studies have attempted to describe the ontogeny of cerebral glucose metabolism in anesthetized nonhuman primates using [18F]fluorodeoxyglucose (FDG) and PET. However, the use of sedation during the tracer uptake period may influence lCMR(glc). This study was conducted to describe lCMR(glc) in conscious infant vervet monkeys (Cercopithecus aethiops sabaeus) during the first year of life utilizing FDG-PET. Cross-sectional studies (n=23) displayed lowest and highest lCMR(glc) in all structures at the 2-3 and 8-9 month age groups, respectively. The metabolic pattern suggested an increase in lCMR(glc) values between 2 and 8 months of age with decreased metabolism observed at 10-12 months of age in all regions. Peak lCMR(glc) values at 8 months were an average of 84+/-24% higher than values seen at the youngest age examined quantitatively (2-3 months). The regions of greatest and smallest increases in lCMR(glc) at 8 months were the cerebellar hemispheres (90%) and the thalamus (39%), respectively. Longitudinal analysis in 4 animals supported this developmental pattern, demonstrating the ability to detect changes in cerebral glucose metabolism within animals and the potential for FDG-PET in nonhuman primate models of brain maturation. By determining the normative profile of lCMR(glc) during development in monkeys, future application of FDG-PET will provide the opportunity to longitudinally assess the effects of environmental or pharmacological intervention on the immature brain.

A comparison of flexible and constrained haptens in eliciting antibody catalysts for paraoxon hydrolysis.

A new amine-oxide hapten was employed as an antigen, producing seven monoclonal antibodies (mAbs) from a panel of 20 that catalyzed paraoxon hydrolysis. The current hapten design differs from that previously described in that the molecule is inherently more flexible than its constrained predecessor. One of the seven antibody catalysts, mAb 1H9, showed the highest activity and was selected for detailed study. At pH = 8.77, the catalytic hydrolysis of paraoxon by mAb 1H9 followed Michaelis Menten kinetics affording a k(cat) = 3.73 x 10(-4) min(-1) and a Km = 1.12 mM with a rate acceleration k(cat)/k(uncat) = 56. The hapten was found to be a competitive inhibitor of antibody-catalyzed paraoxon hydrolysis with a Ki = 0.54 mM. A comparison of both the number and proficiency of antibody catalysts obtained when utilizing a flexible versus constrained hapten indicates that, for paraoxon hydrolysis, constrained haptens elicit superior catalysts, suggesting that further development should begin with the use of constrained haptens in producing more proficient antibody catalysts for paraoxon hydrolysis.

Application of positron emission tomography to determine cerebral glucose utilization in conscious infant monkeys.

Cerebral glucose metabolism has been used as a marker of cerebral maturation and neuroplasticity. In studies addressing these issues in young non-human primates, investigators have used positron emission tomography (PET) and [18F]2-fluoro-2-deoxy-D-glucose (FDG) to calculate local cerebral metabolic rates of glucose (1CMRG1c). Unfortunately, these values were influenced by anesthesia. In order to avoid this confounding factor, we have established a method that permits reliable measurements in young conscious vervet monkeys using FDG-PET. Immature animals remained in a conscious, resting state during the initial 42 min of FDG uptake as they were allowed to cling to their anesthetized mothers. After FDG uptake, animals were anesthetized and placed in the PET scanner with data acquisition beginning at 60 min post-FDG injection. FDG image sets consisted of 30 planes separated by 1.69 mm, parameters sufficient to image the entire monkey brain. Our method of region-of-interest (ROI) analysis was assessed within and between raters and demonstrated high reliability (P < 0.001). To illustrate that our method was sensitive to developmental changes in cerebral glucose metabolism, quantitative studies of young conscious monkeys revealed that infant monkeys 6-8 months of age exhibited significantly higher 1CMRG1c values (P < 0.05) in all regions examined, except sensorimotor cortex and thalamus, compared to monkeys younger than 4 months of age. This method provided high resolution images and 1CMRG1c values that were reliable within age group. These results support the application of FDG-PET to investigate questions related to cerebral glucose metabolism in young conscious non-human primates.

Effects of insulin-like growth factor-1 on luteinizing hormone secretion in sheep.

Circulating insulin-like growth factor-1 (IGF-1) may be involved in nutritional modulation of reproductive status. Acute effects of IGF-1 on luteinizing hormone (LH) secretion were studied in two experiments, each using eight castrate male sheep surgically prepared with an elevated carotid artery, four with (E+) and four without (E-) subcutaneous oestradiol implants. Blood samples were taken every 12 min for 8 h at weekly intervals, with IGF-1 given at 4 h. In Experiment 1, sheep were fed to maintain live weight (maintenance) and IGF-1 doses tested were 25, 50, 100 and 150 micrograms kg-1 given via the carotid (i.c.). Plasma LH concentrations were 6.2 +/- 0.35 (E-) and 4.2 +/- 0.49 (E+) ng ml-1 pre-IGF-1, were increased after 25 micrograms kg-1 IGF-1 (E-, 15%; E+, 11%) but were either unaltered (E-) or decreased (E+, -16%) after 150 micrograms kg-1; thus, mean LH response was negatively related to IGF-1 dose (E-, b = -0.007, P < 0.01; E+, b = -0.011, P < 0.05). LH pulse frequencies (p.f.) were 4.6 +/- 0.42 (E-) and 3.9 +/- 0.35 (E+) pulses per 4 h pre-IGF-1, were unaltered after 25 micrograms kg-1 IGF-1, but were decreased after 150 micrograms kg-1 (E-, -33%; E+, -51%); thus, p.f. was also negatively related to IGF-1 dose (E-, b = -0.016, P < 0.01; E+, b = -0.019, P > 0.05). LH pulse amplitude and baseline were not significantly altered by IGF-1. Plasma glucose concentrations decreased after 100 and 150 micrograms kg-1 IGF-1 from 3.40 to 2.50 and 2.34 mmol l-1, respectively (SED 0.314, P < 0.001), but were not significantly altered after lower doses. Thus, hypoglycaemia caused LH inhibition after higher doses of IGF-1, which counteracted (E-) or overcame (E+) the stimulatory effects on LH seen after lower doses. In Experiment 2, sheep were fed 50% maintenance; saline vehicle i.c., then IGF-1 doses 25 and 50 micrograms kg-1 given i.c. or i.v. were tested. In E- and E+ sheep, respectively, mean LH pre-IGF-1 was 8.7 +/- 0.97 and 1.9 +/- 0.16 ng ml-1, p.f. was 3.8 +/- 0.44 and 0.8 +/- 0.44 pulses per 4 h, and amplitude was 3.6 +/- 0.49 and 0.4 +/- 0.08 ng ml-1. Saline vehicle had no effect on LH. IGF-1 at both doses and by both administration routes in E- sheep increased mean LH (22-29%, P < 0.001), and in E+ sheep increased mean LH (12-36%, P < 0.001), p.f. (94-219%, P < 0.001) and amplitude (125-803%, P < 0.01). Thus, low doses of peripherally-administered IGF-1 stimulated LH output in sheep, consistent with its putative physiological role as a nutritional modulator of reproduction.

Transfers of N metabolites across the ovine liver in response to short-term infusions of an amino acid mixture into the mesenteric vein.

The effect of acute (4.5 h) infusions into the mesenteric vein of an amino acid (AA) mixture, which simulated the composition of rumen microbial protein, on net transfers of NH3, urea and total AA across the portal-drained viscera (PDV) and liver in the ovine has been examined. Four wether sheep were surgically prepared with vascular catheters across the PDV and liver (Lobley et al. 1995) and were offered a basal diet of 1000 g grass pellets/d (approximately 1.4 x energy maintenance). Each animal was infused at weekly intervals with one of four dilutions of the AA mixture. These dilutions provided 0.44, 0.88, 1.32 and 1.84 mmol AA-N/min infused, the lowest of which approximately doubled the net absorption of AA-N from the basal diet. Animals were treated with heparin to allow continuous collection of blood by peristaltic pump for 2 h preceding, and between 0.5-2.5 and 2.5-4.5 h after, the start of the AA infusions. Blood flow in the hepatic artery increased (100 v. 208 g/min; P = 0.002) in response to AA infusion, while hepatic portal venous flow decreased (2090 v. 1854 g/min; P = 0.006). The AA infusion also stimulated O2 uptake by the PDV (P < 0.001) and liver (P = 0.016). Absorption across the PDV and hepatic removal of NH3 were unchanged between basal and amino acid infusion conditions. Urea-N removal across the PDV was unaltered, but hepatic production increased (P < 0.001) with level of AA infusion. During infusions, net appearance of AA across the PDV was below the theoretical level. This may have been due to inhibition of AA uptake from the small intestine, and/or increased removal by the digestive tract of AA from the systemic circulation associated with greater arterial concentrations. Hepatic extraction of AA increased with level of infusion, both for total AA and those included in the infusate. Total hepatic urea-N production tended towards a maximum (estimated as 2 mumol N/g liver wet weight per min). The AA removed by the liver and not used for ureagenesis remained similar (170 mumol AA-N/min) between basal and AA infusions. This was presumed available for anabolic purposes (mainly synthesis of export proteins). The proportion of net AA-N appearance (absorption plus infused) across the PDV removed by the liver declined from 0.71 to 0.53 between basal and AA infusions. In contrast to findings from cattle (Wray-Cahen et al. 1997), increased AA infusion did not alter the net removal of glutamine across the liver. This may reflect differences between the studies in NH3: AA-N absorbed. Further differences between the cattle study and the current findings may relate to the different physiological state (pregnancy v. growth), which may alter the partition of AA between anabolic and catabolic fates.

Canine ureteral ectopia: an analysis of 175 cases and comparison of surgical treatments.

The case histories of 175 dogs with ureteral ectopia were reviewed; there were 156 females and 19 males. Golden retrievers, labrador retrievers and Skye terriers appeared to be over-represented. Their median age when examined was 10 months, and the males were significantly older than the females. Fifty-six animals were affected bilaterally, 50 were affected on the left side alone and 69 on the right side alone. One hundred and twenty-two cases had other abnormalities and 67 had more than one; they included hydro-ureter, hydronephrosis, pyelonephritis, bladder hypoplasia and congenital incompetence of the urethral sphincter mechanism. Forty-one cases were not treated, and the other 134 were treated by ureteronephrectomy, extravesicular ureteric transplantation or intravesicular ureteric transplantation. One hundred and twelve cases were available for follow-up for a median period of over two years (range one month to 15 years). The response to surgery and the incidence of complications was similar after each method of treatment. Sixty-five of the 112 cases were cured of incontinence and 26 were improved. The complication rate (14 per cent overall) was similar for each procedure although different types of complications occurred. Hydronephrosis occurred most commonly after extravesicular transplantation and dysuria occurred most commonly after intravesicular transplantation.