Theobromine intoxication in a red fox and a European badger in Sweden

A red fox (Vulpes vulpes) and a European badger (Meles meles) were found dead on a golf-course in October 1997 near Stockholm (Sweden). At necropsy, both animals were obese and the main finding was acute circulatory collapse. Theobromine intoxication was suspected as chocolate waste was available at a nearby farm and no other cause of death could be detected. Gastric contents and samples of liver from both animals were analyzed by reversed-phase high pressure liquid chromatography for the presence of methylxanthines. Theobromine and caffeine were detected in gastric contents and theobromine was identified in the liver samples from both animals. This appears to be the first report of theobromine intoxication in the red fox and the European badger.     

Widespread occurrence in Australian marsupials of neutralizing antibodies to a herpesvirus from a parma wallaby.

Serum neutralizing antibodies to a parma wallaby herpesvirus (PWHV) have been detected in a wide range of marsupials from different locations across Australia, including several islands. A study of 242 animals (mostly macropods) sampled in the wild showed that 23% had antibodies; a significantly higher frequency (41%) of 116 animals in captivity had antibodies, which were generally at higher levels than those of animals in the wild. Antibodies to PWHV were also detected among parma wallabies from a colony on Kawau Island, New Zealand. The highest antibody levels were found in a group of captive tammar wallabies during recurrent outbreaks of clinical infection. It is suggested that PWHV has evolved along with a marsupial host, and that the high antibody levels among captive animals reflects ease of virus transmission due to crowding, or to conditions of stress leading to expression of latent virus.     

Interstitial myocardial fibrosis in a captive chimpanzee (Pan troglodytes) population

The clinical and necropsy records of 36 (25 male and 11 female) chimpanzees age 10 to 40 y old that died over a 6-y period (2001 to 2006) were reviewed. All animals had annual physical exams that included electrocardiograms and serial blood pressures. Nine of the 36 animals had a complete cardiac evaluation by a board certified veterinary cardiologist, and 7 of the 36 animals (19%) were diagnosed with some form of cardiomyopathy. Systemic hypertension was noted in 3 cases. Cardiac arrhythmias (ventricular ectopy) were seen in 15 (12 male and 3 female) of the 36 animals (42%). Sudden cardiac death (SCD) occurred in 13 (11 male and 2 female) chimps (36%) and was the leading cause of death (n = 13), followed by renal failure (n = 9) and septicemia (n = 3). Histologic examination of the hearts revealed interstitial myocardial fibrosis (IMF) in 29 chimpanzees (81%), and all of the animals that died suddenly due to cardiac causes had IMF to varying degrees. More data will be needed to identify the possible causes of IMF in captive chimpanzees, and IMF may be associated with arrhythmias and SCD in these animals.     

Effects of evaporative cooling on the regulation of body water and milk production in crossbred Holstein cattle in a tropical environment

The aim of this study was to determine how evaporative cooling modifies body function with respect to water metabolism and other variables relevant to milk synthesis in crossbred cattle. The study was conducted on two groups of 0.875HF:0.125RS crossbred Holstein cattle (87.5%) housed in an open-sided barn with a tiled roof (non-cooled animals) and in a close-sided barn under an evaporative cooling system (cooled animals). The maximum ambient temperature and relative humidity for the non-cooled group were 33 degrees C and 61%, with the corresponding values for the evaporatively cooled barn being 28 degrees C and 84%, respectively. The temperature humidity index (THI) of under non-cooled conditions was higher (P < 0.05) than that in the cooled barn. Rectal temperatures and respiration rates of non-cooled animals were higher (P < 0.05) than those of cooled animals. Daily dry matter intake (DMI) of cooled animals was higher while water intakes were lower (P < 0.05) than those of non-cooled animals. The mean absolute values of plasma volume, blood volume, and extracellular fluid (ECF) of cooled animals were significantly higher (P < 0.05) than those of non-cooled animals throughout all stages of lactation. Milk yields of cooled animals were higher by 42%, 36% and 79% on average than those of non-cooled animals during early-, mid- and late-lactation, respectively. The decline in milk yields as lactation advances was markedly apparent in late-lactating non-cooled animals, while no significant changes in milk composition at different stages of lactation were observed in either group. Mean arterial plasma concentrations, arteriovenous concentration differences (A-V differences) and the extraction ratio across the mammary gland for acetate, glucose and triglyceride of cooled animals were not significantly different compared with values for non-cooled animals. No differences were seen in plasma hormonal levels for triiodotyronine (T(3)) and insulin-like growth factor-1 (IGF-1), but plasma cortisol and thyroxine (T(4)) levels tended to be lower in non-cooled animals. This study suggests that low cooling temperature accompanied by high humidity influences a galactopoietic effect, in part through increases in ECF, blood volume and plasma volume in association with an increase in DMI, which partitions the distribution of nutrients to the mammary gland for milk synthesis. Cooled animals were unable to maintain high milk yield as lactation advances even though a high level of body fluids was maintained during long-term cooled exposure. The decline in milk yield, coinciding with a decrease in net energy for lactation as lactation advances, could be attributed to a local change within the mammary gland.     

Bergmann's rule: a biophysiological rule examined in birds

The most studied ecogeographic rule is Bergmann's rule, but aspects of the original paper are often presented incorrectly even though Bergmann (1847) is explicitly cited. The goal of this paper is to 1) summarize the contents of Bergmann's paper, supported by direct translations, and 2) to discuss the main issues surrounding Bergmann's rule based on Bergmann's intentions and early definitions of the rule. Although Bergmann himself never formulated an explicit rule, based on Bergmann's (1847) intentions and early definitions of Bergmann's rule, Bergmann's rule is: “Within species and amongst closely related species of homeothermic animals a larger size is often achieved in colder climates than in warmer ones, which is linked to the temperature budget of these animals.” Bergmann (1847) assumed that the surface area of an animal is a measure for heat dissipation and an animal's volume a measure of its heat production. As body size increases, an animal's surface area increases less than its volume; however, modifications in morphology and behaviour will also influence the temperature budget. Bergmann hypothesized that when everything but size is equal, the smaller animals should live in warmer areas. This was supported by empirical data on > 300 bird species belonging to 86 genera. Recommendations for use of the term Bergmann's rule include 1) inclusion of a thermoregulatory mechanism, 2) application only to homoeothermic animals, 3) but to any taxonomic group, 4) tests of the rule should test the assumption that larger animals have to produce less heat to increase body temperatures, and 5) future authors should either go back to the original publication (Bergmann 1847) when referring to it or simply not cite it at all. Synthesis Based on Bergmann's (1847) intentions and early definitions, Bergmann's rule is: “Within species and amongst closely related species of homeothermic animals a larger size is often achieved in colder climates than in warmer ones, which is linked to the temperature budget of these animals.” Recommendations for use of the term Bergmann's rule include 1) inclusion of a thermoregulatory mechanism, 2) application only to homoeothermic animals, 3) and to any taxonomic group, 4) tests of the rule should examine whether larger animals have to produce less heat to increase body temperatures, and 5) authors should go back to the original publication (Bergmann 1847) when referring to it.     

Mitochondrial dysfunction as a mediator of hippocampal apoptosis in a model of hepatic encephalopathy

In this study, we describe the presence of apoptosis, associated with a mitochondrial dysfunction in the hippocampus of animals in an experimental model defined as minimal hepatic encephalopathy (MHE). This experimental model was studied after 10 days of induced portal vein calibrated stricture, leading to portal hypertension and to a moderate hyperammonemia, without the presence of other evident central nervous system changes. The molecular mechanisms here proposed indicate the presence of apoptotic intrinsic pathways that point to hippocampal mitochondria as an important mediator of apoptosis in this experimental model. In this model of MHE, the presence of DNA fragmentation is documented by 2.3-times increased number of TUNEL-positive cells. These findings together with a higher ratio of the Bcl-2 family members Bax/Bcl-xL in the outer mitochondrial membrane of the MHE animals together with 11% of cytochrome c release indicate the presence of apoptosis in this experimental model. A detailed analysis of the hippocampal mitochondrial physiology was performed after mitochondrial isolation. The determination of the respiratory rate in the presence of malate plus glutamate and ADP showed a 45% decrease in respiratory control in MHE animals as compared with the sham group. A marked decrease of cytochrome oxidase (complex IV of the electron transport chain) was also observed, showing 46% less activity in hippocampal mitochondria from MHE animals. In addition, mitochondria from these animals showed less ability to maintain membrane potential (ΔΨ _m) which was 13% lower than the sham group. Light scattering experiments showed that mitochondria from MHE animals were more sensitive to swell in the presence of increased calcium concentrations as compared with the sham group. In addition, in vitro studies performed in mitochondria from sham animals showed that mitochondrial permeability transition (MPT) could be a mitochondrial mediator of the apoptotic signaling in the presence of NH₄ ⁺ and calcium.     

Therapeutic effect of CHF5074, a new γ-secretase modulator,in a mouse model of scrapie

In transmissible spongiform encephalopathies (TSEs) and Alzheimer disease (AD) both misfolding and aggregation of specific proteins represent key features. Recently, it was observed that PrP^c is a mediator of a synaptic dysfunction induced by Aβ oligomers. We tested a novel γ-secretase modulator (CHF5074) in a murine model of prion disease. Groups of female mice were intracerebrally or intraperitoneally infected with the mouse-adapted Rocky Mountain Laboratory prions. Two weeks prior infection, the animals were provided with a CHF5074-medicated diet (375 ppm) or a standard diet (vehicle) until they showed neurological signs and eventually died. In intracerebrally infected mice, oral administration of CHF5074 did not prolong survival of the animals. In intraperitoneally-infected mice, CHF5074-treated animals showed a median survival time of 21 d longer than vehicle-treated mice (p &lt; 0.001). In these animals, immunohistochemistry analyses showed that deposition of PrP^Sc in the cerebellum, hippocampus and parietal cortex in CHF5074-treated mice was significantly lower than in vehicle-treated animals. Immunostaining of glial fibrillary acidic protein (GFAP) in parietal cortex revealed a significantly higher reactive gliosis in CHF5074-treated mice compared with the control group of infected animals. Although the mechanism underlying the beneficial effects of CHF5074 in this murine model of human prion disease is unclear, it could be hypothesized that the drug counteracts PrP^Sc toxicity through astrocyte-mediated neuroprotection. CHF5074 shows a pharmacological potential in murine models of both AD and TSEs thus suggesting a link between these degenerative pathologies.     

The role of serotonin-modulated anticonsolidation protein in memory formation in rats in a shuttle box

Two series of experiments were carried out in Wistar male rats. In the first series, rats were trained to acquire conditioning in a shuttle box to 50% and 80% learning criteria. In the animals of the experimental group that achieved 50% learning criterion, a significant decrease in the levels of serotonin-modulated anticonsolidation protein (SMAP) (solid phase, indirect ELISA-test) was observed in the temporal cortex as compared to the animals of the active control group. In the animals of the experimental group that achieved 80% learning criterion, such a decrease was found in the occipital and temporal cortex. In the second series of the experiments, animals of the experimental group were injected with SMAP in saline at a concentration of 1.5 mg/ml in a volume of 10 microl through the cannula implanted into the left lateral ventricle of the brain. Control animals were administered with heating-inactivated SMAP in the same amount. The substances were injected to the animals under light ether anesthesia daily 40 min prior to learning sessions. Learning sessions were carried out in the shuttle box for several days to 50% learning criterion. The experimental rats achieved learning criterion within 7-8 days, whereas intact and control animals reached the same criterion within 4 days. Furthermore, the experimental group of animals differed in increased levels of fear, anxiety and aggression which did not decline throughout the whole learning period. The conclusion was made that SMAP participated in negative regulation of the memory trace formation.     

Improved immune functions with administration of a low-fat diet in a burn animal model

The purpose of this study was to characterize the impact of a low-fat (LF; 1% fat) diet, a high-fat (HF; 25% fat) diet, and a standard (SD; 5% fat) diet on immune and oxidative parameters in a 20% body surface area burn animal model fed ad libitum for 10 days postinjury. Although the mechanisms are poorly understood, the amount of dietary lipid in nutritional support has been shown to have immunomodulatory effects after burn injury. Burned mice fed the LF diet showed a normal response in activated splenocyte proliferation compared to burned animals that received the SD or HF diet. Animals fed the SD and HF diets presented increased production of nitric oxide and prostaglandin E2 response after burn injury, which is associated with inhibited splenocyte proliferation. The total thiol concentration in spleen cells from burned animals kept on the HF diet was significantly higher than that in unburned animals, while no increase in these oxidative parameters was observed in LF-fed burned animals. Moreover, the LF diet significantly reduced hepatic lipid peroxidation, as measured by malonaldehyde concentration, compared to the other two diets. These results suggest that the administration of a LF diet in mice after a burn injury prevents inhibition of in vitro splenocyte proliferation and reduces the intensity of oxidative stress.     

Identification of a haemomycoplasma species in anemic reindeer (Rangifer tarandus)

During an 18-mo period (May 2002-November 2003), 10 animals in a herd of 19 reindeer (Rangifer tarandus) at the National Animal Disease Center (NADC) experienced episodes of anemia. Affected animals had histories of weight loss, unthriftiness, occasionally edema of dependent parts and moderate anemia characterized by microcytosis or macrocytosis, hypochromasia, schistocytosis, keratocytosis, acanthocytosis, and dacryocytosis. Numerous basophilic punctate to ring-shaped bodies, measuring less than 1.0 microm, were found on the surface of red blood cells and were often observed encircling the outer margins of the cells. Based on cytologic findings, DNA preparations from selected affected animals in the NADC herd and one animal from a private herd experiencing similar episodes of anemia were assayed by polymerase chain reaction (PCR) for the presence of hemotropic bacteria using primers targeting the 16S rRNA genes of Mycoplasma (Eperythrozoon) suis, Mycoplasma (Haemobartonella) haemofelis, Anaplasma marginale, Anaplasma spp., and Ehrlichia spp. Amplification products were detected from four of the affected animals using primers specific for the 16S rRNA gene of M. haemofelis and Mycoplasma haemocanis. Product from one of the animals was sequenced and internal primers were designed from the resulting sequence to perform a nested PCR assay. Samples from 10 reindeer were positive using the nested PCR reaction and products from seven animals were sequenced; BLAST searches and phylogenetic analysis were performed on the resulting sequences. Sequence data from six animals revealed homology to an organism most closely related to Mycoplasma ovis, Mycoplasma wenyonii, and Mycoplasma haemolamae; sequence from a single animal was most closely related to M. haemofelis and M. haemocanis. This represents the first identification of a haemomycoplasma species in reindeer. Although several animals were also infected with abomasal nematodes, the presence of this newly described haemomycoplasma may have contributed to the anemic syndrome.     

Use of field data in pig genomic selection schemes: a simulation study

The aim of this study was to test how genetic gain for a trait not measured on the nucleus animals could be obtained within a genomic selection pig breeding scheme. Stochastic simulation of a pig breeding program including a breeding nucleus, a multiplier to produce and disseminate semen and a production tier where phenotypes were recorded was performed to test (1) the effect of obtaining phenotypic records from offspring of nucleus animals, (2) the effect of genotyping production animals with records for the purpose of including them in a genomic selection reference population or (3) to combine the two approaches. None of the tested strategies affected genetic gain if the trait under investigation had a low economic value of only 10% of the total breeding goal. When the relative economic weight was increased to 30%, a combination of the methods was most effective. Obtaining records from offspring of already genotyped nucleus animals had more impact on genetic gain than to genotype more distant relatives with phenotypes to update the reference population. When records cannot be obtained from offspring of nucleus animals, genotyping of production animals could be considered for traits with high economic importance.     

Antioxidant and antiplatelet effects of rosuvastatin in a hamster model of prediabetes

The objectives of this study were to determine the relationships among Type II diabetes (T2DM)-dependent elevations in platelet-derived reactive oxygen species (ROS), platelet-surface protein disulfide isomerase (psPDI) NO-releasing activity, and platelet aggregation and to evaluate the efficacy of rosuvastatin in normalizing these parameters in primary cells derived from a hamster model of prediabetic insulin resistance induced by fructose feeding. Platelets from rosuvastatin-treated non-fructose-fed (NFF) and fructose-fed (FF) hamsters were analyzed for aggregability and psPDI-denitrosation activity. Platelets from NFF animals treated with xanthine/xanthine oxidase (X/XO) were assessed for the same parameters and primary aortic endothelial cells (AEC) cultivated with a range of [rosuvastatin] +/- mevalonate were analyzed for ROS production. Platelets from FF hamsters displayed statistically significant enhanced ROS production, diminished psPDI-mediated NO-releasing activity, and hyperaggregability. Suggestively, platelets from NFF animals treated with X/XO displayed characteristics similar to platelets from FF animals. Rosuvastatin elicited a normalizing effect on all parameters measured in platelets from FF animals. Further, ROS production in primary AEC from FF animals could be blunted to that of NFF animals by concentrations of rosuvastatin in the range of those achieved in the bloodstream. Diminished psPDI-dependent NO-releasing activity and increased initial aggregation rates of FF platelets may result from elevated vascular ROS production under conditions of insulin resistance. Normalization of ROS production and platelet aggregation by rosuvastatin indicates its potential use as a vasculoprotective agent.     

Cystic echinococcosis in a wild population of the brush-tailed rock-wallaby (Petrogale penicillata), a threatened macropodid

Infection of small macropodids with the larval stage of Echinococcus granulosus can cause fatalities as well as significant pulmonary impairment and other adverse sequelae. The brush-tailed rock-wallaby (Petrogale penicillata) is a small macropodid listed as vulnerable on the IUCN's Red List of Threatened Species. This study used radiographic techniques to determine the prevalence and severity of pulmonary hydatid infection and growth rates of hydatid cysts in a wild population of this macropodid. The overall prevalence was 15.3% (9/59 animals) with 20.0% (8/40 animals) of adults infected. During the study period, the death of at least 1 infected animal was directly attributed to pulmonary hydatidosis. Rapid cyst growth occurred in some animals (up to 43% increase in cyst volume in 3 months). Cyst volume reduced lung capacity by up to 17%. Secondary pulmonary changes were uncommon but, in 1 animal, resulted in reduction in lung capacity by approximately 50%. Infection was associated with a higher blood urea concentration, but no significant differences in other blood variables were detected. These results indicate that hydatid infection may be a significant risk to threatened populations of small macropodids and should be addressed in conservation management plans for these animals.     

Mental time travel in animals: a challenging question

Humans have the ability to mentally recreate past events (using episodic memory) and imagine future events (by planning). The best evidence for such mental time travel is personal and thus subjective. For this reason, it is particularly difficult to study such behavior in animals. There is some indirect evidence, however, that animals have both episodic memory and the ability to plan for the future. When unexpectedly asked to do so, animals can report about their recent past experiences (episodic memory) and they also appear to be able to use the anticipation of a future event as the basis for a present action (planning). Thus, the ability to imagine past and future events may not be uniquely human.     

Genetic differences based on a beef terminal index are reflected in future phenotypic performance differences in commercial beef cattle

The increased demand for animal-derived protein and energy for human consumption will have to be achieved through a combination of improved animal genetic merit and better management strategies. The objective of the present study was to quantify whether differences in genetic merit among animals materialised into phenotypic differences in commercial herds. Carcass phenotypes on 156 864 animals from 7301 finishing herds were used, which included carcass weight (kg), carcass conformation score (scale 1 to 15), carcass fat score (scale 1 to 15) at slaughter as well as carcass price. The price per kilogram and the total carcass value that the producer received for the animal at slaughter was also used. A terminal index, calculated in the national genetic evaluations, was obtained for each animal. The index was based on pedigree index for calving performance, feed intake and carcass traits from the national genetic evaluations. Animals were categorised into four terminal index groups on the basis of genetic merit estimates that were derived before the expression of the phenotypic information by the validation animals. The association between terminal index and phenotypic performance at slaughter was undertaken using mixed models; whether the association differed by gender (i.e. young bulls, steers and heifers) or by early life experiences (animals born in a dairy herd or beef herd) was also investigated. The regression coefficient of phenotypic carcass weight, carcass conformation and carcass fat on their respective estimated breeding values (EBVs) was 0.92 kg, 1.08 units and 0.79 units, respectively, which is close to the expectation of one. Relative to animals in the lowest genetic merit group, animals in the highest genetic merit group had, on average, a 38.7 kg heavier carcass, with 2.21 units greater carcass conformation, and 0.82 units less fat. The superior genetic merit animals were, on average, slaughtered 6 days younger than their inferior genetic merit contemporaries. The superior carcass characteristics of the genetically elite animals materialised in carcasses worth €187 more than those of the lowest genetic merit animals. Although the phenotypic difference in carcass traits of animals divergent in terminal index differed statistically by animal gender and early life experience, the detected interactions were generally biologically small. This study clearly indicates that selection on an appropriate terminal index will produce higher performing animals and this was consistent across all production systems investigated.     

Increase in tumor size following intratumoral injection of immunostimulatory CpG-containing oligonucleotides in a rat glioma model

The immunosuppressive environment of malignant gliomas is likely to suppress the anti-tumor activity of infiltrating microglial cells and lymphocytes. Macrophages and microglial cells may be activated by oligonucleotides containing unmethylated CpG-motifs, although their value in cancer immunotherapy has remained controversial. Following injection of CpG-containing oligonucleotides (ODN) into normal rat brain, we observed a local inflammatory response with CD8+ T cell infiltration, upregulation of MHC 2, and ED1 expression proving the immunogenic capacity of the CpG-ODN used. This was not observed with a control ODN mutated in the immunostimulatory sequence (m-CpG). To study their effect in a syngeneic tumor model, we implanted rat 9L gliosarcoma cells into the striatum of Fisher 344 rats. After 3 days, immunostimulatory CpG-ODN, control m-CpG-ODN, or saline was injected stereotactically into the tumors (day 3 group). In another group of animals (day 0 group), CpG-ODN were mixed with 9L cells prior to implantation without further treatment on day 3. After 3 weeks, the animals were killed and the brains and spleens were removed. Rather unexpectedly, the tumors in several of the animals treated with CpG-ODN (both day 0 and day 3 group) were larger than in saline or m-CpG-ODN treated control animals. The tumor size in CpG-ODN-treated animals was more variable than in both control groups. This was associated with inflammatory responses and necrosis which was observed in most tumors following CpG treatment. This, however, did not prevent excessive growth of solid tumor masses in the CpG-treated animals similar to the control-treated animals. Dense infiltration with microglial cells resembling ramified microglia was observed within the solid tumor masses of control- and CpG-treated animals. In necrotic areas (phagocytic), activation of microglial cells was suggested by ED1 expression and a more macrophage-like morphology. Dense lymphocytic infiltrates consisting predominantly of CD8+ T cells and fewer NK cells were detected in all tumors including the control-treated animals. Expression of perforin serving as a marker for T cell or NK cell activation was detected only on isolated cells in all treatment groups. Tumors of all treatment groups revealed CD25 expression indicating T cells presumed to maintain peripheral tolerance to self-antigens. Cytotoxic T cell assays with in vitro restimulated lymphocytes (⁵¹chromium release assay) as well as interferon-gamma production by fresh splenocytes (Elispot assay) revealed specific responses to 9L cells but not another syngeneic cell line (MADB 106 adenocarcinoma). Surprisingly, the lysis rates with lymphocytes from CpG-ODN-treated animals were lower compared to control-treated animals. The tumor size of individual animals did not correlate with the response in both immune assays. Taken together, our data support the immunostimulatory capacity of CpG-ODN in normal brain. However, intratumoral application proved ineffective in a rat glioma model. CpG-ODN treatment may not yield beneficial effects in glioma patients.     

MHC haplotype frequencies in a UK breeding colony of Mauritian cynomolgus macaques mirror those found in a distinct population from the same geographic origin

Background  Mauritian cynomolgus macaques have greatly restricted genetic diversity in the MHC region compared to other non-human primates; however, the frequency of common MHC haplotypes among captive-bred populations has not been reported.
Methods  Microsatellite PCR was used to determine MHC haplotype frequencies among captive macaques at a UK breeding facility. Allele-specific PCR and reference strand conformational analysis were used to determine the allele expression profile of a subset of animals.
Results  Haplotypes H3 (21%) and H1 (19%) were most common in the captive population of Mauritian cynomolgus macaques. Predicted alleles were detected by allele-specific PCR-SSP in 98% of animals. Allele expression profiles were similar in animals with identical haplotypes.
Conclusions  Mauritian cynomolgus macaques in the UK breeding facility have restricted MHC diversity comparable to a previously described population. Microsatellite-derived haplotypes are highly predictive of allele expression. A selective breeding program has been established to produce MHC-identical animals for biomedical research.     

Enhanced myogenic tone in cerebral arteries from a rabbit model of subarachnoid hemorrhage

Cerebral artery vasospasm is a major cause of death and disability in patients experiencing subarachnoid hemorrhage (SAH). Currently, little is known regarding the impact of SAH on small diameter (100-200 microm) cerebral arteries, which play an important role in the autoregulation of cerebral blood flow. With the use of a rabbit SAH model and in vitro video microscopy, cerebral artery diameter was measured in response to elevations in intravascular pressure. Cerebral arteries from SAH animals constricted more (approximately twofold) to pressure within the physiological range of 60-100 mmHg compared with control or sham-operated animals. Pressure-induced constriction (myogenic tone) was also enhanced in arteries from control animals organ cultured in the presence of oxyhemoglobin, an effect independent of the vascular endothelium or nitric oxide synthesis. Finally, arteries from both control and SAH animals dilated as intravascular pressure was elevated above 140 mmHg. This study provides evidence for a role of oxyhemoglobin in impaired autoregulation (i.e., enhanced myogenic tone) in small diameter cerebral arteries during SAH. Furthermore, therapeutic strategies that improve clinical outcome in SAH patients (e.g., supraphysiological intravascular pressure) are effective in dilating small diameter cerebral arteries isolated from SAH animals.     

Ovarian and hormonal responses to a progesterone-releasing controlled internal drug releasing treatment in dietary-restricted goats

An experiment was conducted to evaluate the effects of dietary restriction on ovarian, endocrine (ovarian steroids and luteinizing hormone (LH) pulse) and metabolic (glucose, insulin and non-esterified fatty acid (NEFA)) profiles in goats treated with a progesterone-releasing controlled internal drug releasing (CIDR-G) device. Cycling goats were offered either a maintenance or a restricted (30% of requirement; n =4 per treatment) level of feeding. The dietary restriction was started on the day following ovulation. At 30-32 days after the start of food restriction, the goats received a prostaglandin F(2alpha) (2mg of dinoprost) injection followed by 10 days of CIDR-G treatment. Ovarian ultrasonographic images were monitored daily throughout the experiment and blood samples were collected daily just before the morning feeding for analysis of endocrine and metabolic profiles. Frequent blood samples (1 ml) were also collected at 10 min intervals for 8 h from -8 h to CIDR-G removal, and from 32 to 40 h after CIDR-G removal for analysis of LH pulses. Body weight was significantly (P < 0.05) decreased in the food-restricted animals. Oestrous behaviour and ovulation followed by a rise of plasma progesterone concentration were observed after the CIDR-G removal in all control animals but not in any of the food-restricted animals within 12 days after CIDR-G removal. The LH pulse frequency from 32 to 40 h after the CIDR-G removal was significantly (P < 0.05) lower in the food-restricted animals than in control animals (1.5 +/- 0.6 versus 3.8 +/- 0.5 pulses for 8 h). There was no significant difference in the glucose concentration in weekly plasma samples between control and food-restricted animals. Insulin concentrations from 2 weeks after the start of feed restriction were significantly (P < 0.05) lower in restricted animals than in control animals. The NEFA concentration in restricted animals was significantly (P < 0.05) increased after the start of feed restriction, and then decreased gradually to the basal level. The present results suggest that nutritionally induced anovulation after CIDR-G treatment is associated with a reduction in the frequency of LH pulses, and that insulin and NEFA, rather than the glucose concentration in the circulation, may be associated with the metabolic suppression of LH pulses.     

Repolarization abnormalities and afterdepolarizations in a canine model of sudden cardiac death

Ventricular tachyarrhythmias are the most common cause of sudden cardiac death (SCD); a healed myocardial infarction increases the risk of SCD. We determined the contribution of specific repolarization abnormalities to ventricular tachyarrhythmias in a postinfarction model of SCD. For our methods, we used a postinfarction canine model of SCD, where an exercise and ischemia test was used to stratify animals as either susceptible (VF(+)) or resistant (VF(-)) to sustained ventricular tachyarrhythmias. Our results show no changes in global left ventricular contractility or volumes occurred after infarction. At 8-10 wk postmyocardial infarction, myocytes were isolated from the left ventricular midmyocardial wall and studied. In the VF(+) animals, myocyte action potential (AP) prolongation occurred at 50 and 90% repolarization (P < 0.05) and was associated with increased variability of AP duration and afterdepolarizations. Multiple repolarizing K(+) currents (I(Kr), I(to)) and inward I(K1) were also reduced (P < 0.05) in myocytes from VF(+) animals compared with control, noninfarcted dogs. In contrast, only I(to) was reduced in VF(-) myocytes compared with controls (P < 0.05). While afterdepolarizations were not elicited at baseline in myocytes from VF(-) animals, afterdepolarizations were consistently elicited after the addition of an I(Kr) blocker. In conclusion, the loss of repolarization reserve via reductions in multiple repolarizing currents in the VF(+) myocytes leads to AP prolongation, repolarization instability, and afterdepolarizations in myocytes from animals susceptible to SCD. These abnormalities may provide a substrate for initiation of postmyocardial infarction ventricular tachyarrhythmias.