Elevated basal corticosterone levels increase disappearance risk of light but not heavy individuals in a long-term monitored rodent population

According to the cort-fitness hypothesis, glucocorticoid levels correlate negatively with fitness. However, field studies found mixed support for this hypothesis, potentially because the association between glucocorticoids and fitness might depend on prevailing environmental conditions. Based on the long-term monitoring of a natural rodent population, we tested whether individuals with elevated corticosterone levels were more likely to disappear, accounting for individual condition and among-year variation in food availability, population density and predation pressure. We used basal corticosterone levels measured at the onset of the pre-breeding season in 331 African striped mice from six generations. While basal corticosterone levels were highly repeatable within individuals, between-individual variation was large. Survival analysis revealed that disappearance risk over the pre-breeding season increased with elevated basal corticosterone levels for light but not for heavy individuals. High levels of corticosterone may be more deleterious to smaller individuals (i.e. through allostatic overload), eventually increasing their mortality risk, and disappearance would represent actual death. An alternative non-exclusive explanation could be that high levels of corticosterone selectively trigger dispersal in light individuals, and disappearance would rather reflect their departure from the population. Although environmental conditions varied considerably among generations, none of the interactions between corticosterone and environmental variables were significant. Disappearance probability was positively correlated with both predation pressure and with food availability, a factor favoring dispersal. In sum, elevated basal corticosterone levels increased disappearance in light striped mice, either directly via reduced survival prospects and/or indirectly via dispersal.

Different regulation of cortisol and corticosterone in the subterranean rodent Ctenomys talarum: Responses to dexamethasone, angiotensin II, potassium, and diet

When harmful environmental stimuli occur, glucocorticoids (GCs), cortisol and corticosterone are currently used to evaluate stress status in vertebrates, since their secretions are primarily associated to an increased activity of the hypothalamic-pituitaryadrenal (HPA) axis. To advance in our comprehension about GCs regulation, we evaluated the subterranean rodent Ctenomys talarum to assess cortisol and corticosterone response to (1) the negative feedback of the HPA axis using the dexamethasone (DEX) suppression test, (2) angiotensin II (Ang II), (3) potassium (K⁺) intake, and (4) different diets (vegetables, grasses, acute fasting). Concomitantly, several indicators of individual condition (body mass, neutrophil to lymphocyte ratio, blood glucose, triglycerides and hematocrit) were measured for diet treatments. Results confirm the effect of DEX on cortisol and corticosterone in recently captured animals in the field but not on corticosterone in captive animals. Data suggest that Ang II is capable of stimulating corticosterone, but not cortisol, secretion. Neither cortisol nor corticosterone were responsive to K⁺ intake. Cortisol levels increased in animals fed with grasses in comparison to those fed with vegetables while corticosterone levels were unaffected by diet type. Moreover, only cortisol responded to fasting. Overall, these results confirm that cortisol and corticosterone are not interchangeable hormones in C. talarum.

Rodent Abundance and Hantavirus Infection in Protected Area, East-Central Argentina

We captured 3 hantavirus rodent hosts in Otamendi Natural Reserve, Argentina, during 2007-2012. Hantavirus antibodies were found only in Akodon azarae grass mice, mainly in males and old animals. Higher abundance of this species was associated with warm and rainy weather and high water levels, which peaked after a strong El Niño event.

[Parental Care and Testosterone Secretion in Forest Rodent Males: Sensitization and Androgenic Stimulation of Parental Behavior]

The reaction of males of three forest rodent species (Myodes clethrionomys, M. rutilus, Apodemus uralensis) to young animals in comparison with their dimensional characteristics and androgenization level was studied. Demonstration of parental care was detected in males of two vole species (M. clethrionomys and M. rutilus) in case of regular contacts with them (sensitization effect). It was demonstrated that the testosterone concentration in the blood serum, as well as the testosterone content in the testicles of the M. clethrionomys males (demonstrating the parental care), was higher than in the sample of males inclined to infanticide. An increased testosterone content in the testicles and blood serum was also found in the M. rutilus males that had contact with young animas. Neither demonstration of parental care nor significant differences in the testosterone concentration in the testicles and blood serum were detected in the A. uralensis males.

Haematology and Serum Biochemistry Parameters and Variations in the Eurasian Beaver (Castor fiber)

Haematology parameters (N = 24) and serum biochemistry parameters (N = 35) were determined for wild Eurasian beavers (Castor fiber), between 6 months - 12 years old. Of the population tested in this study, N = 18 Eurasian beavers were from Norway and N = 17 originating from Bavaria but now living extensively in a reserve in England. All blood samples were collected from beavers via the ventral tail vein. All beavers were chemically restrained using inhalant isoflurane in 100% oxygen prior to blood sampling. Results were determined for haematological and serum biochemical parameters for the species and were compared between the two different populations with differences in means estimated and significant differences being noted. Standard blood parameters for the Eurasian beaver were determined and their ranges characterised using percentiles. Whilst the majority of blood parameters between the two populations showed no significant variation, haemoglobin, packed cell volume, mean cell haemoglobin and white blood cell counts showed significantly greater values (p<0.01) in the Bavarian origin population than the Norwegian; neutrophil counts, alpha 2 globulins, cholesterol, sodium: potassium ratios and phosphorus levels showed significantly (p<0.05) greater values in Bavarian versus Norwegian; and potassium, bile acids, gamma globulins, urea, creatinine and total calcium values levels showed significantly (p<0.05) greater values in Norwegian versus Bavarian relict populations. No significant differences were noted between male and female beavers or between sexually immature (<3 years old) and sexually mature (≥3 years old) beavers in the animals sampled. With Eurasian beaver reintroduction encouraged by legislation throughout Europe, knowledge of baseline blood values for the species and any variations therein is essential when assessing their health and welfare and the success or failure of any reintroduction program. This is the first study to produce base-line blood values and their variations for the Eurasian beaver.

Phlebotomine fauna, natural infection rate and feeding habits of Lutzomyia cruzi in Jaciara, state of Mato Grosso, Brazil

Visceral leishmaniasis (VL) in Brazil is transmitted by the phlebotomine Lutzomyia longipalpis and in some midwestern regions by Lutzomyia cruzi. Studies of the phlebotomine fauna, feeding habits and natural infection rate by Leishmania contribute to increased understanding of the epidemiological chain of leishmaniases and their vectorial capacity. Collections were performed in Jaciara, state of Mato Grosso from 2010-2013, during which time 2,011 phlebotomines (23 species) were captured (68.70% Lu. cruzi and 20.52% Lutzomyia whitmani). Lu. cruzi females were identified by observing the shapes of the cibarium (a portion of the mouthpart) and spermatheca, from which samples were obtained for polymerase chain reaction to determine the rates of natural infection. Engorged phlebotomines were assessed to identify the blood-meal host by ELISA. A moderate correlation was discovered between the number of Lu. cruzi and the temperature and the minimum rate of infection was 6.10%. Twenty-two females were reactive to the antisera of bird (28%), dog (3.30%) and skunk (1.60%). We conclude that Lu. cruzi and Lu. whitmani have adapted to the urban environment in this region and that Lu. cruzi is the most likely vector of VL in Jaciara. Moreover, maintenance of Leishmania in the environment is likely aided by the presence of birds and domestic and synanthropic animals.

[Ecoepidemiology of rickettsial infection in rodents, ectoparasites and humans in northeastern Antioquia, Colombia]

INTRODUCTION

Rickettsia spp. are tick, flea or lice-borne pathogenic bacterium, usually carried by rodents. In the last decade three outbreaks of rickettsial disease including fatalities, occurred in the provinces of Antioquia and Córdoba in northwestern Colombia.

OBJECTIVE

The purpose of this study was to perform an ecological and epidemiological description of the Rickettsia spp infection in the recently affected region of Colombia.

MATERIALS AND METHODS

Samples were obtained from 354 rodents and their parasites captured in the municipalities of Apartadó, Turbo and Necoclí. Likewise, 220 human sera were also collected, for detection of infection by Rickettsia spp.

RESULTS

Indirect immunofluorescence assay (IFA) revealed that 130 (43%) of the rodents and 53 (24%) of the humans produced antibodies to Rickettsia spp. Additionally, rickettsial DNA was amplified by PCR from 23 (6.8%) rodent liver samples using primers directed to the genus specific gltA gene. While gltA sequences from rodent samples exhibited a 98.7% similitude with R . prowazekii, a sequence amplified from larvae of Amblyomma sp exhibited identities of >99% similarity with R. tamurae .

CONCLUSION

These results demonstrate the presence of rickettsia in rodents, ectoparasites and humans throughout the municipalities studied.

Applications of serum protein electrophoresis in exotic pet medicine

Serum Protein Electrophoresis (SPE) is a useful diagnostic and prognostic tool in human and companion animals medicine: several experiences show that it can be useful in exotic practice as well. The fundamentals of SPE interpretation as well as some normal and pathological patterns for the species most commonly seen in practice are provided.

Evidence for novel hepaciviruses in rodents

Hepatitis C virus (HCV) is among the most relevant causes of liver cirrhosis and hepatocellular carcinoma. Research is complicated by a lack of accessible small animal models. The systematic investigation of viruses of small mammals could guide efforts to establish such models, while providing insight into viral evolutionary biology. We have assembled the so-far largest collection of small-mammal samples from around the world, qualified to be screened for bloodborne viruses, including sera and organs from 4,770 rodents (41 species); and sera from 2,939 bats (51 species). Three highly divergent rodent hepacivirus clades were detected in 27 (1.8%) of 1,465 European bank voles (Myodes glareolus) and 10 (1.9%) of 518 South African four-striped mice (Rhabdomys pumilio). Bats showed anti-HCV immunoblot reactivities but no virus detection, although the genetic relatedness suggested by the serologic results should have enabled RNA detection using the broadly reactive PCR assays developed for this study. 210 horses and 858 cats and dogs were tested, yielding further horse-associated hepaciviruses but none in dogs or cats. The rodent viruses were equidistant to HCV, exceeding by far the diversity of HCV and the canine/equine hepaciviruses taken together. Five full genomes were sequenced, representing all viral lineages. Salient genome features and distance criteria supported classification of all viruses as hepaciviruses. Quantitative RT-PCR, RNA in-situ hybridisation, and histopathology suggested hepatic tropism with liver inflammation resembling hepatitis C. Recombinant serology for two distinct hepacivirus lineages in 97 bank voles identified seroprevalence rates of 8.3 and 12.4%, respectively. Antibodies in bank vole sera neither cross-reacted with HCV, nor the heterologous bank vole hepacivirus. Co-occurrence of RNA and antibodies was found in 3 of 57 PCR-positive bank vole sera (5.3%). Our data enable new hypotheses regarding HCV evolution and encourage efforts to develop rodent surrogate models for HCV.

Sociality, glucocorticoids and direct fitness in the communally rearing rodent, Octodon degus

While ecological causes of sociality (or group living) have been identified, proximate mechanisms remain less clear. Recently, close connections between sociality, glucocorticoid hormones (cort) and fitness have been hypothesized. In particular, cort levels would reflect a balance between fitness benefits and costs of group living, and therefore baseline cort levels would vary with sociality in a way opposite to the covariation between sociality and fitness. However, since reproductive effort may become a major determinant of stress responses (i.e., the cort-adaptation hypothesis), cort levels might also be expected to vary with sociality in a way similar to the covariation between sociality and fitness. We tested these expectations during three years in a natural population of the communally rearing degu, Octodon degus. During each year we quantified group membership, measured fecal cortisol metabolites (a proxy of baseline cort levels under natural conditions), and estimated direct fitness. We recorded that direct fitness decreases with group size in these animals. Secondly, neither group size nor the number of females (two proxies of sociality) influenced mean (or coefficient of variation, CV) baseline cortisol levels of adult females. In contrast, cortisol increased with per capita number of offspring produced and offspring surviving to breeding age during two out of three years examined. Together, our results imply that variation in glucocorticoid hormones is more linked to reproductive challenge than to the costs of group living. Most generally, our study provided independent support to the cort-adaptation hypothesis, according to which reproductive effort is a major determinant, yet temporally variable, influence on cort-fitness covariation.

Efficacy of Ixodes ricinus as a vector of zoonotic babesiosis in Sinai Peninsula, Egypt

Ticks and blood samples were collected every month from March 2009 through April 2010 from different sites in Sinai to detect babesial parasites using PCR assay based on nuclear small subunit rRNA gene. Ticks were found to contain babesial DNA. Sequence determination and analysis of amplified portions of nss-rDNA revealed their identity with B. bovis and a high degree of homology with B. bigemina and B. divergens. The results represent the first genetic evidence of different species of Babesia and identified the role of Ixodes ricinus as a vector of zoonotic B. microti infection. Rodent isolate (HK) and American isolate (GI) were studied in transmission experiments. The present study used in vitro culture of zoonotic Babesia sp. EU1 from blood samples of rodent in Sinai. This study provides an evidence of transovarian and transstadial transmissions of the parasite within I. ricinus, which emphasizes that this tick could be a vector and reservoir of EU1

A novel blood-cell-two-compartment model for transferring a whole blood time activity curve to plasma in rodents

The term input function usually refers to the tracer plasma time activity curve (pTAC), which is necessary for quantitative positron emission tomography (PET) studies. The purpose of this study was to acquire the pTAC by independent component analysis (ICA) estimation from the whole blood time activity curve (wTAC) using a novel method, namely the FDG blood-cell-two-compartment model (BCM). This approach was compared to a number of published models, including linear haematocrit (HCT) correction, non-linear HCT correction and two-exponential correction. The results of this study show that the normalized root mean square error (NRMSE) and the error of the area under curve (EAUC) for the BCM estimate of the pTAC were the smallest. Compartmental and graphic analyses were used to estimate the metabolic rate of the FDG (MR(FDG)). The percentage error for the MR(FDG) (PE(MRFDG)) was estimated from the BCM corrected pTAC and this was also the smallest. It is concluded that the BCM is a better choice when transferring wTAC into pTAC for quantification.

Clinical hematology of rodent species

Pet rodents, such as rats, guinea pigs, and chinchillas, differ from more traditional companion animal species in many aspects of their hematologic parameters. Animals within this order have much diversity in size, anatomy, methods of restraint, and blood collection technique. Appropriate sample collection is often the most challenging aspect of the diagnostic protocol, and inappropriate restraint may cause a stress response that interferes with blood test results. For many of these patients, sedation is required and can also affect results as well. In most cases, however, obtaining a standard database is necessary and very possible when providing medical care for this popular group of pets.

Rickettsial infection in capybaras (Hydrochoerus hydrochaeris) from São Paulo, Brazil: serological evidence for infection by Rickettsia bellii and Rickettsia parkeri

INTRODUCTION

In Brazil, capybaras (Hydrochoerus hydrochaeris) are important hosts for Amblyomma ticks, which in turn can transmit rickettsiae to humans and animals. Therefore, capybaras are potential sentinels for rickettsial infection.

OBJECTIVE

The present study evaluated rickettsial infection in capybaras in different areas of the state of São Paulo, where rickettsiosis has never been reported. Materials and methods. Blood sera from 73 capybaras from six localities in São Paulo were tested by indirect immunofluorescence assay using Rickettsia rickettsii, Rickettsia parkeri, and Rickettsia bellii antigens. Capybara spleens were tested by PCR, targeting a fragment of the rickettsial gltA gene. Ticks were collected from each capybara sample and taxonomically identified to species.

RESULTS

A total of 94 positively reacting capybara samples, 19 (26.0%), 25 (34.2%), and 50 (68.5%) capybara sera reacted to R. rickettsii, R. parkeri, and R. bellii, respectively. Twenty-five capybara sera showed titers to R. bellii at least four-fold higher than to any of the other two antigens. These sera were considered homologous to R. bellii. Using the same criteria, 3 capybara sera were considered homologous to R. parkeri. No sera were be considered homologous to R. rickettsii. No rickettsial DNA was detected in capybara spleen samples. Ticks collected on capybaras were Amblyomma dubitatum and Amblyomma cajennense.

CONCLUSIONS

The first evidence is reported of R. bellii natural infection in vertebrate hosts, and the first evidence of R. parkeri infection in capybaras. While R. parkeri is known to infect and cause disease in humans, no similar evidence for human infection has been indicated by R. bellii.

Haematology, blood chemistry and urine parameters of free-ranging plains viscachas (Lagostomus maximus) in Argentina determined by use of a portable blood analyser (i-STAT) and conventional laboratory methods

Haematology, blood chemistry and urine values were determined for 44 adult free-ranging plains viscachas (Lagostomus maximus; Rodentia, Chinchillidae) in their pampas habitat in central Argentina. The study animals were captured in the wild and anaesthetized with a ketamine-xylazine combination for physical examination and sampling. Blood was obtained by venipuncture of the saphenous vein. Results for many of the blood parameters fall within the reference ranges for pet chinchillas. Differentiation of white blood cells revealed a predominantly neutrophil count for plains viscachas, while chinchillas have predominantly lymphocytes. Mean values for blood urea nitrogen, creatinine, aspartate aminotransferase and sodium were higher than the upper limit of the reference range for pet chinchillas. The results of seven analytes (haematocrit, haemoglobin, glucose, blood urea nitrogen, sodium, potassium, chloride) were compared by using both a portable blood analyser (i-STAT) in the field and conventional laboratory methods. In general, correlation and agreement between the two methods were low for most parameters.

Monkeypox zoonotic associations: insights from laboratory evaluation of animals associated with the multi-state US outbreak

At the onset of the 2003 US monkeypox outbreak, virologic data were unavailable regarding which animal species were involved with virus importation and/or subsequent transmission to humans and whether there was a risk for establishment of zoonotic monkeypox in North America. Similarly, it was unclear which specimens would be best for virus testing. Monkeypox DNA was detected in at least 33 animals, and virus was cultured from 22. Virus-positive animals included three African species associated with the importation event (giant pouched rats, Cricetomys spp.; rope squirrels, Funisciuris sp.; and dormice, Graphiuris sp.). Virologic evidence from North American prairie dogs (Cynomys sp.) was concordant with their suspected roles as vectors for human monkeypox. Multiple tissues were found suitable for DNA detection and/or virus isolation. These data extend the potential host range for monkeypox virus infection and supports concern regarding the potential for establishment in novel reservoir species and ecosystems.

Increased levels of IgE and autoreactive, polyreactive IgG in wild rodents: implications for the hygiene hypothesis

To probe the potential role of Th1 versus Th2 reactivity underlying the hygiene hypothesis, intrinsic levels of Th1-associated and Th2-associated antibodies in the serum of wild rodents were compared with that in various strains of laboratory rodents. Studies using rat lung antigens as a target indicated that wild rats have substantially greater levels of autoreactive, polyreactive immunoglobulin G (IgG), but not autoreactive, polyreactive IgM than do laboratory rats, both on a quantitative and qualitative basis. Increased levels of serum IgG and IgE were observed in both wild rats and wild mice relative to their laboratory-raised counterparts, with the effect being most pronounced for IgE levels. Further, wild rats had greater intrinsic levels of both Th1- and Th2-associated IgG subclasses than did lab rats. The habitat (wild versus laboratory raised) had a more substantial impact on immunoglobulin concentration than did age, strain or gender in the animals studied. The presence in wild rodents of increased intrinsic, presumably protective, non-pathogenic responses similar to both autoimmune (autoreactive IgG, Th1-associated) and allergic (IgE, Th2-associated) reactions as well as increased levels of Th1-associated and Th2-associated IgG subclasses points toward a generally increased stimulation of the immune system in these animals rather than a shift in the nature of the immunoreactivity. It is concluded that, at least to the extent that feedback inhibition is a controlling element of immunoreactivity, an overly hygienic environment may affect the threshold of both types of immune responses more so than the balance between the different responses.

[The mammals of Guinea as reservoirs and carriers of arboviruses]

A great body of data on the fauna and ecology of wild mammals and their participation in the circulation of arboviruses were collected when the ecology of the latter of the Republic of Guinea was studied in 1978 to 1989. A hundred and eighteen species belonging to 10 orders were identified. Over 2,000 biological specimens were virologically and serologically examined. Six arboviruses were isolated. These included Dugbe virus (from the hussar monkey Cercopithecus (Erythrocebus patas) and 5 viruses from chiropters: Rift valley fever, from Micropteropus pusillus, Miniopterus schreibersi, and Hipposideros caffer, Saboya, Fomede, and Ank 6909 from Nycteris gambiensis and Kolenter from Hipposideros sp. Fomede, Kolente, and Ank 6909 viruses turned out to be new species for science. Rodents were found to have viral antigens of Lass fever (Mastomys natalensis, Tatera valida kempi and Rattus rattus), Dugbe and Chikungunya fevers (M. natalensis) and West Nile fever (Mus sp.). A serological survey of mammals revealed that the latter had antibodies to 12 arboviruses. Thus, the mammals of Guinea participate in the circulation of 18 arboviruses, 13 of them are pathogenic for man.

[Natural foci of leptospirosis in Moscow in 1995 - 2004]

The article deals with the results of the 10-year study of the synanthropic urban foci of leptospirosis on the territory of Moscow. Information on the manifestation of the activity of the foci under study, rodents serving as the reservoir of infection in these foci, the etiological structure of the leptospires among these rodents, the state of leptospirosis morbidity among humans is presented.

Blood-Meal Analysis for the Identification of Reservoir Hosts of Tick-Borne Pathogens in Ireland

The results of analysis of blood-meal remnants in unfed nymphs, despite relatively low detection levels (49.4%, n = 322), support the conclusion from an earlier study that small rodents are relatively unimportant as reservoir hosts of B. burgdorferi s.l. in this particular area, and suggest that songbirds (Passeriformes) are the most significant hosts in this respect. Tick (Ixodes ricinus) abundance was greater in the present study, but the overall Borrelia burgdorferi s.l.-infection prevalence of nymphal ticks was the same (12.2%), and the relative proportions of the various Borrelia burgdorferi s.l. genospecies were similar. B. garinii and B. valaisiana were the most frequent, B. burgdorferi s.s the least frequent, and B. afzelii of intermediate frequency. An unusually high proportion of nymphs (39%) with multiple infections of different B. burgdorferi genospecies was detected, and Borrelia spp. related to relapsing-fever spirochetes were detected in Ireland for the first time. The results of the present study contribute to the validation of blood-meal analysis as a means of determining the host origin of certain pathogens in unfed questing ticks, and raise some questions concerning the extent of B. burgdorferi s.l. host specificity.

Kurloff Cells in Peripheral Blood and Organs of Wild Capybaras

Peripheral blood and tissue from twenty-two free-ranging, hunter-killed capybaras (Hydrochaeris hydrochaeris) collected between December 1996 and April 1997 in Casanare, Colombia (5 degrees 58'N and 71 degrees 33'W), were examined by light microscopy for Kurloff cells (KCs). Kurloff cells were observed in the blood of one pregnant adult female, and in organs from all the animals, including spleen (21 of 22 animals), liver (18 of 21), lungs (13 of 21), ovary (8 of 11), uterus (7 of 10), bone marrow (13 of 20), kidney (8 of 22), adrenal gland (6 of 20), and lymph node (4 of 14). The anatomic distribution of the KC in the wild capybaras was similar to that of the guinea pig.

Neutralization of venoms from two Southern Pacific Rattlesnakes (Crotalus helleri) with commercial antivenoms and endothermic animal sera

The Southern Pacific Rattlesnake (Crotalus helleri) is found in southwestern California (USA), southward through north Baja California (MX) into the northern part of southern Baja California (MX). In this study, the venoms from two Southern Pacific Rattlesnakes were characterized. The two venoms were different in color, concentration, and enzyme activities. Two commercial antivenoms neutralized both C. helleri venoms differently. Antivipmyn (Fab2H) and CroFab (FabO) neutralized both venoms but had different ED50. Four times more Fab2H antivenom was required to neutralize the C. helleri venom No. 011-084-009 than the venom from the snake No. 010-367-284. The hemorrhagic activity of two C. helleri venoms were neutralized differently by endothermic animal sera having a natural resistance to hemorrhagic activity of snake venoms. Opossums and Mexican ground squirrel sera did not neutralize the hemorrhagic activity of the venom No. 010-367-284. The sera of gray woodrats and hispid cotton rats neutralized all hemorrhagins in both C. helleri venoms. This is the first reported case in which opossum serum has not neutralized hemorrhagic activity of pit viper venom. Differences in the compositions of C. helleri venoms and their ability to be neutralized may help explain why snakebites are a difficult medical problem to treat and why effective polyvalent antivenoms are difficult to produce.

Blood glucose concentration in caviomorph rodents

Hystricomorph rodents are a group of species that belong to the suborder Hystricognathi. They mainly inhabit South American (caviomorph) and African (phiomorph) habitats. This group of rodents has a divergent insulin structure. For example, insulin in this group of rodents exhibits only 1-10% of biological activity in comparison to other mammals. Therefore, hystricomorph rodents may hypothetically be unable to regulate blood glucose concentration as non-hystricomorph mammals. In this work we evaluated blood glucose concentration in nine species of caviomorph rodents, with emphasis on species belonging to the families Abrocomidae, Ctenomyidae and Octodontidae. Specifically we: (1) measured glucose concentrations after a fasting period; and (2) conducted a glucose tolerance test. In the latter assay we used Octodon degus as a representative species of the genus Octodon. Results showed that blood glucose concentration values after fasting, and in the glucose tolerance test, were within the expected range for mammals. We postulate that this group of rodents has compensatory traits that may permit the maintenance of standard values of plasma glucose.

Hematologic and serum biochemistry values in two species of free-ranging porcupines (Coendou prehensilis, Coendou melanurus) in French Guiana

Individuals of two porcupine species (Coendou prehensilis and Coendou melanurus) were translocated during the flooding of a forest at a hydroelectric dam site in French Guiana. Blood samples were collected for 11 mo to determine hematologic and serum chemistry reference mean values and ranges and to look for blood parasites. Male C. prehensilis had significantly higher hemoglobin levels, packed cell volumes, and creatinine and potassium values than did females of the same species. Coendou prehensilis had significantly lower amylase levels but higher creatinine, calcium, lactate dehydrogenase, and gamma glutamyl transferase levels than C. melanurus.

Molecular adaptation to hibernation: the hemoglobin of Dryomys nitedula

The oxygen binding properties of Dryomys nitedula hemoglobin (Hb) were investigated as a function of pH both in the absence and in the presence of its physiological cofactors (i.e. chloride ions and 2,3-biphosphoglyceric acid) and at different temperatures. Moreover, the alpha- and beta-chains of the Dryomys Hb were partially sequenced. The results obtained show that the effects of Bohr protons, chloride ions, organic phosphates and temperature are significantly lower for Dryomys Hb than for human Hb. Thus, the increase in Hb oxygen affinity, resulting from the reduction of red cell organic phosphates and body temperature that occurs during hibernation, is advantageous for loading oxygen at the lung level without compromising oxygen release at the tissues, as could occur if Dryomys Hb had similar functional properties to those of other non-hibernating mammals. Furthermore, it is possible that the reduced Bohr effect may moderate the potential effects of increased CO(2) associated with prolonged apnea on the loading and unloading of oxygen. Moreover, the overall heat of oxygenation (Delta H) for Dryomys Hb is much less exothermic than that of the human Hb and it is completely independent of the 2,3-biphosphoglyceric acid concentration.

Karyotypic analysis in species of the genus Dasyprocta (Rodentia: Dasyproctidae) found in Brazilian Amazon

A total of 30 animals of the genus Dasyprocta were cytogenetically studied. They belong to the following species: D. prymnolopha (N=20), D. leporina (N=6), D. fuliginosa (N=1) and Dasyprocta sp. (N=3) (Dasyproctidae, Hystricognathi). Cell suspensions were obtained by peripheral blood culture, besides bone marrow and spleen cells, from D. prymnolopha and D. leporina. The diploid number was 64/65 for all samples. The karyotypes showed similarity, and chromosomal polymorphism was not detected by Giemsa conventional staining and G banding. The constitutive heterochromatin distribution at the pericentromeric region of all the chromosomes was similar in all species. D. prymnolopha, D. leporina and Dasyprocta sp. presented variation in the heterochromatical block size at one of the homologues of the A18 pair. D. fuliginosa presented the heterochromatin uniformly distributed in all chromosomes. There was not variation in the NORs pattern in the species studied.

Hemoglobin affinity in Andean rodents

Blood hemoglobin oxygen affinity (P50) was measured in three Andean species and in the laboratory rat (control), all raised near sea level. Chinchilla lanigera (Molina, 1792) has an altitudinal habitat range from low Andean slopes up to 3000 m., while Chinchilla brevicaudata (Waterhouse, 1848) has an altitudinal range from 3000 to 5000 m. The laboratory type guinea pig, wild type guinea pig (Cavia porcellus), (Waterhouse, 1748), and laboratory rat (Rattus norvegicus) were also raised at sea level. The Andean species had high hemoglobin oxygen affinities (low P50) compared with the rat. Chinchilla brevicaudata had a higher affinity than Chinchilla lanigera. The wild type guinea pig had a higher affinity than the laboratory type. As has been shown in other species, this is another example of an inverse correlation between the altitude level and the P50 values. This is the first hemoglobin oxygen affinity study in Chinchilla brevicaudata.

Persistence of arboviruses and antiviral antibodies in vertebrate hosts: its occurrence and impacts

The recent isolation of West Nile virus from a bird in mid-winter in New York immediately raised, as one of a few explanations, the possibility of long-term persistence of arboviruses in vertebrate hosts. Although it was a highly popular topic for research many years ago, generally it has since been neglected and its meaning under appreciated. This comprehensive survey of literature worldwide uncovered, contrary to the general perception that it is a rather infrequent phenomenon, a large number of important observations involving all groups of arboviruses that have been accumulating over the years without drawing much attention. In this review, the data and observations were analysed in terms of the occurrence, role in natural transmission, mechanisms and genesis of persistence, source of problems in research and impact. The outcome of the analyses clearly demonstrates that asymptomatic, long-term infection in the absence of viraemia with or without the induction of neutralising antibody, the most frequent characteristics of arboviral persistence, presents a serious question about the validity of some of the past animal experiments that were conducted without the consideration of such a possibility. Likewise, significant impacts are felt on diverse fields ranging from epidemiology to diagnostic virology and from veterinary medicine to agricultural commerce. Published in 2001 by John Wiley & Sons, Ltd.

Coagulation and fibrinolysis in capybara (Hydrochaeris hydrochaeris), a close relative of the guinea-pig (Cavia porcellus)

Fibrinolytic and coagulation properties of capybara (Hydrochaeris hydrochaeris, LINNAEUS, 1766) plasma were analysed and the results compared to the guinea-pig (Cavia porcellus), a close relative. Capybara fibrinogen was isolated and fibrinolysis of its plasma was carried out in a homologous system and with bovine fibrin. Undiluted plasma did not have fibrinolytic activity on fibrin plates; euglobulins gave a dose-related response. Zymography of capybara and guinea-pig plasma gave the same patterns of activity as human or bovine plasma. Human urokinase (UK) and tissue plasminogen activator (t-PA) produced lysis in capybara fibrin plates. Streptokinase (SK) (500 IU/ml) did not activate capybara or guinea-pig plasma. In this system, human plasma was extensively activated. Coagulation tests for both species of rodent were prolonged. The capybara showed values for prothrombin time (PT) shorter than activated thromboplastin time (APTT). The guinea-pig, as already shown, had longer PT values. Factors X and VII were very low for capybara and guinea-pig when tested using reference curves and diagnostic kits for human plasma. It is suggested that the capybara could be a valuable laboratory animal considering its size and closeness to the guinea-pig, and this could allow for the provision of materials from one single animal when convenient or necessary.

Clinical pathology and sample collection in the laboratory rodent

Common laboratory rodents have always been a favorite choice as a pet. Although diagnostic clinical pathology has not been viewed as practical for the rodent patient, current advances in technology make processing of small samples possible. Cultivation of the technical skills necessary for rodent sample collection has the potential to improve the standard of rodent veterinary care. This article provides an overview of rodent sample collection techniques, hematology, clinical biochemistry, serology, and clinical pathology of other tissues and fluids for laboratory rodents. General principles of clinical pathology can be applied across species. This article emphasizes the subtleties of the different rodent species which may impact diagnostic interpretation.

Genetic diversities of hantaviruses among rodents in Hokkaido, Japan and Far East Russia

Seroepizootiologic surveys among wild rodents were carried out in Japan and Far East Russia in 1995 and 1996. Seropositive animals were only identified in Clethrionomys rufocanus (23/134) in Hokkaido, Japan. On the other hand, seropositives were identified in C. rufocanus (1/8), Apodemus agrarius (2/66), Apodemus spp. (2/26) and Microtus fortis (3/22) in Vladivostok, Far East Russia. Total RNA was isolated from lungs of seropositive animals and the S genome segments were amplified by PCR, cloned and sequenced. The S and M genomes of hantavirus, derived from Japanese C. rufocanus (Tobetsu genotype), were most closely related with Puumala viruses (76-79% nucleotide and 95% amino acid identities for S genome, 70-78% nucleotide and 87-92% amino acid identities for M genome). The recombinant nucleocapsid protein of Tobetsu genotype was antigenically quite similar with that of Sotkamo. These suggest that the virus endemic in Japanese C. rufocanus belongs to Puumala virus. Phylogenetic analysis indicates that the genotype forms a distinct lineage within Puumala viruses. Partial S segment (1-1251 nt), derived from seropositive M. fortis in Vladivostok, was sequenced and analyzed. The S genome segment, which was designated Vladivostok genotype, was most closely related with Khabarovsk virus (79% nucleotide and 90% amino acid identities) which was isolated from M. fortis.

Osmoregulation and water balance in the springhare (Pedetes capensis)

Springhares are large rodents that live in arid and semi-arid regions of Africa. We deprived springhares of water for periods of up to 7 days to determine what physiological adaptations. If any, enable them to survive in and regions without drinking. During water deprivation, springhares lost up to 30% body weight and produced a mean maximum urine concentration of 2548 mosmol kg-1 with a maximum of 3076 mosmol kg-1 in an individual animal. Haematocrit and plasma sodium and potassium concentrations were well regulated throughout water deprivation at 47.5 +/- 3.8% and 132.6 +/- 7.4 mmol l-1 and 3.5 +/- 0.7 mmol l-1, respectively, while plasma osmolality increased slightly from 293 +/- 12.5 mosmol kg-1 to 324 +/- 7.3 mosmol kg-1. Springhares thus appeared to be good osmoregulators and were able to maintain plasma volume during 7 days of water deprivation. In addition to the production of a relatively concentrated urine, water loss was limited by the lowered solute load and faecal water loss achieved by a reduction in food consumption and by the production of very dry faeces. These abilities, together with a favourable burrow microclimate and nocturnal activity pattern, enable them to survive in arid regions.

Expression of Lex antigen in Schistosoma japonicum and S.haematobium and immune responses to Lex in infected animals: lack of Lex expression in other trematodes and nematodes

Adults of the human parasitic trematode Schistosoma mansoni, which causes hepatosplenic/intestinal complications in humans, synthesize glycoconjugates containing the Lewis x (Lex) Galbeta1-->4(Fucalpha1-->3)GlcNAcbeta1-->R, but not sialyl Lewis x (sLex), antigen. We now report on our analyses of Lexand sLexexpression in S.haematobium and S.japonicum, which are two other major species of human schistosomes that cause disease, and the possible autoimmunity to these antigens in infected individuals. Antigen expression was evaluated by both ELISA and Western blot analyses of detergent extracts of parasites using monoclonal antibodies. Several high molecular weight glycoproteins in both S. haematobium and S. japonicum contain the Lexantigen, but no sialyl Lexantigen was detected. In addition, sera from humans and rodents infected with S.haematobium and S.japonicum contain antibodies reactive with Lex. These results led us to investigate whether Lexantigens are expressed in other helminths, including the parasitic trematode Fasciola hepatica , the parasitic nematode Dirofilaria immitis (dog heartworm), the ruminant nematode Haemonchus contortus , and the free-living nematode Caenorhabditis elegans . Neither Lexnor sialyl-Lexis detectable in these other helminths. Furthermore, none of the helminths, including schistosomes, express Lea, Leb, Ley, or the H-type 1 antigen. However, several glycoproteins from all helminths analyzed are bound by Lotus tetragonolobus agglutinin , which binds Fucalpha1-->3GlcNAc, and Wisteria floribunda agglutinin, which binds GalNAcbeta1-->4GlcNAc (lacdiNAc or LDN). Thus, schistosomes may be unique among helminths in expressing the Lexantigen, whereas many different helminths may express alpha1,3-fucosylated glycans and the LDN motif.

The binding potential of commercial antibody conjugates with sera of various small terrestrial mammals

Infectious diseases of wild animals are of increasing importance, both from an economic viewpoint and because several of these diseases are pathogenic to man. However, serosurveys to determine the circulation of infectious organisms in wildlife are complicated by the fact that antibodies to species-specific immunoglobulins are not available for use in serological assays such as enzyme-linked immunosorbent assays (ELISAs) or immunofluorescence assays. To determine the binding potential of four commercially available antibody conjugates with the sera of wild animals, sera from 27 species of small terrestrial mammals were allowed to react with alkaline phosphatase-labelled protein A, anti-rabbit IgG, anti-mouse IgG and anti-human IgG by by the use of an ELISA. It was found that sera from some species of the order Lagomorpha bound optimally to anti-rabbit IgG, while anti-mouse IgG could be used for most species of Rodentia. For all Carnivora, Insectivora, Macroscelidea, Hyracoidea and other Rodentia, staphylococcal protein A demonstrated optimal binding. None of the sera that was tested bound to anti-human IgG. These results demonstrate that commercial conjugates can be used in serological assays in which wild animal sera are used, and should be useful for future serosurveys to determine the circulation of infectious agents in small terrestrial mammals.

Changes in autonomic nervous system activity and consecutive hyperinsulinaemia: respective roles in the development of obesity in rodents

The autonomic nervous system plays a major role in metabolism regulation by modulating metabolic pathways directly or indirectly via control of hormone (particularly insulin) secretion in various organs and tissues. In addition, the system modulates the proliferation and differentiation of some cell types. This activity is directly controlled by certain brain areas, particularly those located in the hypothalamus. A feedback loop signals metabolic changes at the periphery to these brain areas. This review focuses on the role of the autonomic nervous system in the activity and plasticity of pancreas and adipose tissues under normal conditions or in obesity, with special attention to the importance of alterations in these functions.

Evidence on mammalian phylogeny from sequences of exon 28 of the von Willebrand factor gene

Phylogenetic relationships among 27 extant mammalian species (representing 15 placental orders) were studied using sequences of exon 28 of the gene encoding von Willebrand Factor (vWF), a glycoprotein which functions in blood clotting. Analysis of sequences coding for vWF revealed evidence for several subordinal and superordinal groupings, but the earliest branching sequence of placental mammals was left largely unresolved. Strong support was found for a monophyletic clade consisting of elephants, sea cows, hyraxes, aardvarks, and elephant shrews. This systematic placement of the elephant shrews agrees strongly with two other molecular data sets (interphotoreceptor retinoid binding protein and alpha-lens crystallins) and is consistent with analysis of fossil elephant shrews recently discovered in north Africa. Evidence from vWF sequences agrees with a number of previous molecular and morphological studies in providing strong support for the monophyly of both bats and rodents. The orders Primates, Proboscidea, Carnivora, Perissodactyla, and Artiodactyla were represented by more than one species which joined in each case to form a monophyletic order.

Influence of immune signals on the hypothalamic-pituitary axis of the rodent

The immune system and the hypothalamic-pituitary (H-P) axis are functionally connected, so that exposure to antigens elicits a coordinated response which allows the organism to successfully withstand immunologic challenges. An important feature of this bilateral communication is the appearance of proteins released into the circulation by activated immune cells. These proteins, called cytokines or interleukins, stimulate the activity of the H-P axis, thus increasing circulating ACTH and corticosteroid levels. This in turn induces metabolic changes such as increases in energy substrates, restrains the activity of specific immune cells, and alters the release of secretagogues important for both the immune system and neuroendocrine organs. After acute increases in blood-borne levels of cytokines, nerve terminals in the median eminence, particularly those containing corticotropin-releasing factor (CRF), represent an important site of action of these immune signals. Subsequently, changes take place within the brain in general and the hypothalamus in particular. They include the synthesis/release of peptides such as CRF and vasopressin, of neurotransmitters such as catecholamines and prostaglandins, and of cytokines themselves. Upon prolonged exposure to blood-borne immune signals additional mechanisms come into play, including those taking place directly at the pituitary level. These observations indicate that cytokines released into the general circulation act on multiple sites within the H-P axis, a phenomenon that relies on the recruitment of a large number of pathways. This review discusses these pathways and the mechanisms through which they allow cytokines to convey the occurrence of immune activation to the brain.

[Biochemical-histological study of the effects of lithium on various organs of vizcacha (Lagostomus maximus maximus)]

Considering that the vizcacha (Lagostomus maximus maximus) is a very Lithium sensitive rodent, we planned a biochemical-histological study injecting IP doses of 1 mEq/kg/day LiCl during one month to adult vizcachas, and they were divided into three lots: Lot I the optical microscopy revealed evident renal, gonadal, hyphophyseal and adrenal damages; the biochemical analysis showed that Li significantly decreased the female serum LH levels while testosterone and estradiol levels were not affected. The male Li serum values resulted to be significantly higher than those of female animals. The damage was greater in male specimens. Lott II: the tissue recovery from the damage observed in Lot I was the following: total in hyphophysis, partial in testis, the same in kidney and was enhanced in adrenal and ovary. The Li renal clearance was determined in Lot III verifying no changes in both sexs. According to our results, Li (1 mEq/kg/day during one month) produce modifications in different tissues probably the gonadal damage may be consequence of a direct Li effect and not for a hyphophysis alteration, since in male vizcacha the LH serum level was not changed. In regard to the selective effect in the suprarenal glomerulus structure, this Li effect is produced via hyphophysis. In conclusion, the selective effect of Li on adrenal and gonada organs of this rodent is a contribution in order to warm about the possible reproduction of such effects in human beings.

Species variability in platelet and other cellular responsiveness to thrombin receptor-derived peptides

The aggregation of platelets from a variety of animal species in response to thrombin receptor-derived activating peptides was evaluated. A series of 14-(SFLLRNPNDKYEPF), 7-(SFLLRNP-NH2), 6-(SFLLRN-HN2) or 5-(SFLLR-NH2) residue peptides, the structures of which were based on the deduced amino acid sequence of the human thrombin receptor, promoted full aggregation of platelets in plasma from humans, African Green and Rhesus monkeys, baboons and guinea pigs at 4-50 microM depending on the peptide used. Platelets in plasma from rabbit, dog, pig, and hamster underwent a shape change but failed to aggregate in response to these peptides over 3 log units of peptide up to 800 microM, despite being fully responsive to human thrombin. However, because the receptor peptides induced shape change in the platelets from these non-aggregating species, they apparently can activate some of the intracellular signaling system(s) usually initiated by thrombin in these platelets. In contrast, platelets from rats did not undergo shape change or aggregate in response to the peptides. A 7-residue receptor-derived peptide based on the deduced amino acid sequence of the clone of the hamster thrombin receptor (SFFLRNP-N2) was nearly as efficacious as the corresponding human receptor-derived 7-residue peptide to promote aggregation of human platelets. However, the hamster peptide could not promote aggregation of hamster platelets in plasma at up to 800 microM peptide, while a shape change response was elicited. Platelets from rats, rabbits and pigs also did not aggregate in response to this peptide derived from the hamster thrombin receptor, but all species except the rat underwent a shape change.(ABSTRACT TRUNCATED AT 250 WORDS)

Spontaneous lytic activity against heterologous erythrocytes in cotton rat (Sigmodon hispidus) serum

Although innate immunity has been well studied in laboratory animal models, no such documentation exists for wild species possessing a diversity of physiological adaptations to their environment. We examined the blood sera of 188 hispid cotton rats (Sigmodon hispidus) for naturally occurring hemolytic activity against heterologous erythrocytes. Ninety-two percent of the blood sera samples from cotton rats lysed sheep erythrocytes. All sera tested against chicken erythrocytes showed hemolytic activity, while only 44% of the same sera could lyse bovine erythrocytes. No hemolytic activity was present in cotton rat sera against erythrocytes from other rodent species (Eastern woodrat, Neotoma floridana, and pine vole, Microtus pinetorum). Hemolytic activity was heat labile and appeared to be mediated through the classical complement pathway. The protective nature of this hemolytic factor is unclear but it is probably directed at a more relevant molecule. These data, along with other reports of naturally occurring target specific serum factors in the cotton rat, may reflect the importance of innate protective mechanisms to small mammal populations.

Subterranean mole-rats naturally have an impoverished calciol status, yet synthesize calciol metabolites and calbindins

Mole-rats (Family Bathyergidae) have no obvious source of calciol. They live in an environment devoid of sunlight and consume a herbivorous diet. Calciol status, metabolism and expression were examined in six species of Bathyergids. Serum levels of calcidiol in all species were < 5 micrograms/l and those of calcitriol were low (18.0 +/- 11.0 (SD) ng/l, N = 57) when compared to other rodents. Within 72 h of injecting animals with tritium-labelled calciol, most of the labelled prohormone had been metabolized to more polar metabolites. Three times more tritium-labelled calcitriol (19.3 +/- 2.9%) was present than (24R)-hydroxycalcidiol (6.2 +/- 10%). The natural absence of detectable circulating concentrations of calcidiol and the threefold greater amount of calcitriol to (24R)-hydroxycalcidiol produced indicate that calciol naturally is in short supply. Calciol-dependent calbindins were absent in the duodenum. Calbindin-D28k was present in the Purkinje cells of the cerebellum and in some collecting ducts and proximal and distal convoluted tubules of the kidney. Calbindin-D9k also was present but was localized uniquely in the juxtaglomerular cells of the five southern African species. These data confirm that Bathyergid mole-rats naturally have an impoverished calciol status. Despite the presence of calbindins in renal tissues, the functional importance of this hormone in calbindin synthesis and other normal mole-rat physiology is not known.

[Antioxidant properties of oxy- and metmyoglobin]

Lipid peroxide formation is inhibited by met- and oxymyoglobin. Oxymyoglobin as higher antioxidant activity than metmyoglobin. Oxymyoglobin has higher antioxidants activity in concentration of 800 ng/ml than metmyoglobin by 38.6%.

Diversities of transport of sodium in rodent red cells

1. Na-K pumps of rodent red cells reveal variations among species in terms of kinetic properties such as ouabain sensitivity, Na/K coupling and temperature sensitivity and variations within an individual organism related to such physiological challenges as K deficiency, calorie deficiency and seasonal changes in temperature. 2. Passive Na entry among rodents collectively occurs through the same routes as in red cells of other mammals, but red cells of hamsters, rats and thirteen-lined ground squirrels lack or are deficient in an amiloride-sensitive, shrinkage-activated Na-H exchange. 3. In guinea-pig this pathway appears to be both activated and uncoupled by cooling from 37 to 20 degrees C. 4. Red cells of rodents in general and hamsters in particular are rich in a Na-Mg exchange pathway. In hamsters, this appears to be the only amiloride-sensitive pathway in simple media. 5. In hamster cells, Na entry through the amiloride-sensitive Mg-activated pathway exhibits the same kinetics as previously shown for Na activation of Mg extrusion.

Circadian rhythm of photosensitivity and the adaptation of reproductive function to the environment in two populations of Arvicanthis niloticus from Mali and Burkina Faso

Previous studies have shown that there is a circadian rhythm of photosensitivity in different rodent species of the Sahel (Burkina Faso) and that, despite the low amplitude of seasonal variations in daylength, the photoperiod may control reproductive function. The present investigation of Arvicanthis niloticus provides additional support for this hypothesis. Populations of Arvicanthis niloticus from two regions at the same latitude 1000 km apart but with different climates were studied. Oursi, Burkina Faso, has an arid climate (annual rainfall 315 mm) and Kamalé, Mali has a wetter climate (annual rainfall 1114 mm). The circadian rhythm of photosensitivity had the same features in both populations, involving inhibition of testicular activity, but the photosensitive phase began 11 h 30 min after dawn in the population from Burkina Faso and 45 min later in that from Mali. Comparison of these results with the annual variation of daylength showed that the photoperiod inhibits the reproductive activity of A. niloticus from April to December in Burkina Faso and only from mid-May to mid-August in Mali. The population of Arvicanthis niloticus living in an environment with a large and seasonally stable food supply (Mali) thus has a longer reproductive period. This corroborates results from field studies on annual variations of population density.

Social suppression of reproduction in male naked mole-rats, Heterocephalus glaber

To investigate possible anatomical and endocrine differences between breeding and non-breeding male naked mole-rats, 113 animals from 24 captive and 4 wild colonies were studied. While breeding males had larger reproductive tract masses compared to non-breeders relative to body mass (P less than 0.01), spermatogenesis was active in all of the non-breeding males examined histologically (n = 9) and spermatozoa were present in the epididymides. Compared with non-breeders, breeding males had significantly higher urinary testosterone concentrations (mean +/- s.e.m.: 23.8 +/- 2.3 vs 5.2 +/- 1.4 ng/mg Cr respectively; P less than 0.001), and plasma LH (10.7 +/- 1.7 vs 5.0 +/- 0.8 mi.u./ml respectively; P less than 0.01). Single doses of 0.1, 0.5 or 1.0 microgram GnRH produced a significant rise in plasma LH concentrations 20 min after s.c. injection in breeding and non-breeding males at all doses (P less than 0.001). However, there were differences in the magnitude of the LH response following administration of GnRH between breeding and non-breeding males, with non-breeding males showing a dose-response and having lower plasma LH concentrations 20 min after a single injection of 0.1 or 0.5 microgram (P less than 0.05), but not 1.0 microgram, GnRH. This apparent lack of pituitary sensitivity of non-breeding males to single doses of exogenous GnRH was reversed by 4 consecutive injections of 0.5 microgram GnRH at hourly intervals, suggesting that the reduced sensitivity may be the result of insufficient priming of the pituitary by endogenous GnRH. These results indicate that, despite the fact that non-breeding males were apparently producing mature gametes, clear endocrine deficiencies existed in male naked mole-rats.

The hypolipidemic activity of heterocyclic amine boranes in rodents

Heterocyclic amine boranes were observed to be potent hypolipidemic agents in rodents at 8 mg/kg per day lowering both serum cholesterol and triglyceride levels. These agents were also effective in lowering tissue lipids. Rat serum lipoprotein cholesterol levels were reduced in the low density lipoprotein (LDL) and very low density lipoprotein (VLDL) fractions and elevated in the high density lipoprotein (HDL) fraction after 14 days. The modes of action of the agents appear to accelerate excretion of lipids in the bile and the suppression of the activities of key hepatic regulatory enzymes of lipids synthesis.

Comparative aspects of sulfate transport in the erythrocytes of different mammalian species

The pH dependence of sulfate transport through the red cell membranes of ten mammalian (nucleated and non-nucleated) species was studied by measuring tracer exchange. The characteristic maximum of the sulfate transfer system, observed previously in the red cells of man and a number of other mammalian red cell species was found to be present in all species investigated. Although the volumes of the red cells of the various species differ by no more than a factor of 2 and the ratios of volume/surface even less, the rate constants at the respective maxima vary from 0.33 x 10(-2) min-1 (beef) to 15.50 x 10(-2) min-1 (eagle), i.e. about 45 fold. This suggests that either the number of anion transport molecules per cell and/or the turnover numbers of the individual transport molecules show considerable variations.

[Fluctuations in the level of progesterone in the peripheral blood of nutria during pregnancy]

The fluctuations in the concentrations of progesterone in peripheral blood of three intact coypus and three coypus after natural mating were investigated for the period of four months. Immediately after mating the concentrations of progesterone are low (1.5-2.4 ng.ml-1), the maximum values reach the peak between the 14th and 15th week of gravidity (12.50-20.72 ng.ml-1), whilst there is almost no change in the intact females. On the last days of gravidity the values of progesterone decrease rapidly and they are very low on the day of parturition (1.0-2.5 ng.ml-1). The concentration of progesterone in the blood plasma of intact females in the test period is low (0.09-3.18 ng.ml-1).

Cardiorespiratory responses of the woodchuck and porcupine to CO2 and hypoxia

The burrow-dwelling woodchuck (Marmota monax) (mean body wt. = 4.45 +/- 1 kg) was compared to a similar-sized (5.87 +/- 1.5 kg) but arboreal rodent, the porcupine (Erithrizon dorsatum), in terms of its ventilatory and heart rate responses to hypoxia and hypercapnia, and its blood characteristics. VT, f, T1 and TE were measured by whole-body plethysmography in four awake individuals of each species. The woodchuck has a longer TE/TTOT (0.76 +/- 0.03) than the porcupine (0.61 +/- 0.03). The woodchuck had a higher threshold and significantly smaller slope to its CO2 ventilatory response compared to the porcupine, but showed no difference in its hypoxic ventilatory response. The woodchuck P50 of 27.8 was hardly different from the porcupine value of 30.7, but the Bohr factor, -0.72, was greater than the porcupine's, -0.413. The woodchuck breathing air has PaCO2 = 48 (+/- 2) torr, PaO2 = 72 (+/- 6), pHa = 7.357 (+/- 0.01); the porcupine blood gases are PaCO2 = 34.6 (+/- 2.8), PaO2 = 94.9 (+/- 5), pHa = 7.419 (+/- 0.03), suggesting a difference in PaCO2/pH set points. The woodchuck exhibited no reduction in heart rate with hypoxia, nor did it have the low normoxic heart rate observed in other burrowing mammals.