Mitchell Bush

The cheetah is depauperate in genetic variation

A sample of 55 South African cheetahs (Acinonyx jubatus jubatus) from two geographically isolated populations in South Africa were found to be genetically monomorphic at each of 47 allozyme (allelic isozyme) loci. Two-dimensional gel electrophoresis of 155 abundant soluble proteins from cheetah fibroblasts also revealed a low frequency of polymorphism (average heterozygosity, 0.013). Both estimates are dramatically lower than levels of variation reported in other cats and mammals in general. The extreme monomorphism may be a consequence of a demographic contraction of the cheetah (a population bottleneck) in association with a reduced rate of increase in the recent natural history of this endangered species.

Reproductive and genetic consequences of founding isolated lion populations

Species survival is critically dependent on reproductive performance, a complex physiological process under rigorous genetic control. Classical studies of inbreeding in laboratory animals and livestock have shown that increased homozygosity can adversely affect spermatogenesis, ovulation and perinatal mortality and morbidity1–3. For wild populations, the consequences of inbreeding depression have not been examined intensively, although our recent studies of the African cheetah revealed a striking degree of genetic uniformity4,5 combined with an extremely high incidence of structurally abnormal spermatozoa (>70%) in captive6 as well as free-ranging7 males. In this study, we report definitive evidence that the reproductive function of free-ranging mammals can be impaired as a result of demographic contraction followed by inbreeding. In an examination of three distinct lion populations (two from the Serengeti ecosystem in East Africa and a third descended from lions in the Gir Forest of western India), a direct correlation was observed between genetic variability and two physiological traits, incidence of abnormal sperm and circulating testosterone, a critical hormone for spermatogenesis.

Cryptosporidium in Snakes with Hypertrophic Gastritis

Fourteen captive snakes of three genera and four species had severe chronic hypertrophic gastritis. Persistent postprandial regurgitation and firm midbody swelling were the most common clinical signs. Fecal smears had many roughly spherical organisms confirmed by ultrastructural study to be oocysts of Cryptosporidium. Pathologic changes included hypertrophy of gastric mucosa and atrophy of granular cells. There were cystic changes in gastric glands and focal mucosal necrosis. Many Cryptosporidium lined microvillar surfaces. All developmental forms were identified by ultrastructure. Characteristic oocysts were found in abundance.

Ancient papillomavirus-host co-speciation in Felidae.

BackgroundEstimating evolutionary rates for slowly evolving viruses such as papillomaviruses (PVs) is not possible using fossil calibrations directly or sequences sampled over a time-scale of decades. An ability to correlate their divergence with a host species, however, can provide a means to estimate evolutionary rates for these viruses accurately. To determine whether such an approach is feasible, we sequenced complete feline PV genomes, previously available only for the domestic cat (Felis domesticus, FdPV1), from four additional, globally distributed feline species: Lynx rufus PV type 1, Puma concolor PV type 1, Panthera leo persica PV type 1, and Uncia uncia PV type 1.ResultsThe feline PVs all belong to the Lambdapapillomavirus genus, and contain an unusual second noncoding region between the early and late protein region, which is only present in members of this genus. Our maximum likelihood and Bayesian phylogenetic analyses demonstrate that the evolutionary relationships between feline PVs perfectly mirror those of their feline hosts, despite a complex and dynamic phylogeographic history. By applying host species divergence times, we provide the first precise estimates for the rate of evolution for each PV gene, with an overall evolutionary rate of 1.95 × 10-8 (95% confidence interval 1.32 × 10-8 to 2.47 × 10-8) nucleotide substitutions per site per year for the viral coding genome.ConclusionOur work provides evidence for long-term virus-host co-speciation of feline PVs, indicating that viral diversity in slowly evolving viruses can be used to investigate host species evolution. These findings, however, should not be extrapolated to other viral lineages without prior confirmation of virus-host co-divergence.

Antral follicles develop in xenografted cryopreserved african elephant (Loxodonta africana) ovarian tissue

The preservation of germ plasm from endangered species could augment captive breeding programs aimed at maintaining genetic diversity. Mammalian female germ plasm (oocytes) is extremely difficult to collect and cryopreserve; however, a promising alternative is the cryopreservation of ovarian tissue. In the present study, athymic nude (nu/nu) Balb/C mice were used to evaluate in vivo viability of cryopreserved ovarian tissue from Institute of Cancer Research genotype (ICR) mice or elephants. Female mice were ovariectomized prior to transplant of cryopreserved-thawed ovarian tissue from ICR mice (n=4) or elephants (n=6). Control mice were sham operated (n=4) or ovariectomized (n=5). Transplants were in the ovarian bursa, enabling in vivo ovulation and pregnancies from allografts. Vaginal cytology was monitored daily, and the intervals between and duration of epithelial cells present in smears were evaluated. Appearance of epithelial cells in sham-operated and allografted mice were at intervals of 4.3+/-0.6 and 3.3+/-0.5 days, lasting for 1.4+/-0.1 and 1.6+/-0.2 days, respectively. Sporadic incidence of epithelial cells in ovariectomized animals occurred at longer intervals (8.6+/-3.8 days). Females with xenografted elephant ovarian tissue demonstrated epithelial cells in vaginal smears at intervals of 4.5+/-1.0 days, for 2.5+/-0.5 days duration, which was significantly longer than the other groups (P < 0.05). Histological evaluation of tissues at the time of epithelial cells in smears demonstrated well-developed antral follicles, although oocytes were of poor morphological appearance or only cumulus-like complexes were seen. The nude mouse model is effective for assessing cryopreserved ovarian tissue xenograft function which can support the development of antral follicles.

Fundamental cryobiology of selected African mammalian spermatozoa and its role in biodiversity preservation through the development of genome resource banking

Fundamental cryobiological characteristics of spermatozoa from threatened or endangered species must be determined for successful cryopreservation techniques to be established. In this study, spermatozoa from four diverse species, impala (Aepyceros melampus), wart hog (Phacochoerus aethiopicus), elephant (Loxodonta africana), and lion (Panthera leo), were collected by electroejaculation or epididymal aspiration. Spermatozoal plasma membrane permeability to water (hydraulic conductivity, Lp) and the osmotically inactive fraction of the sperm cell (Vb) were determined from each species. Changes in cell volume were measured over time using an electronic particle counter. A Kedem-Katchalsky membrane transport model was used to theoretically characterize the data to determine Lp and Vb for each species. In addition to determining plasma membrane characteristics, spermatozoa were also studied to determine their sensitivity to low temperatures and to permeating cryoprotectant solutes. Cells maintained at room temperature (20-22 degrees C) were slowly or rapidly exposed to cold temperatures (1-4 degrees C), and percent motility was estimated to determine the sensitivity of the cells to cooling. Spermatozoa were also in media containing 1 M glycerol, dimethyl sulfoxide or ethylene glycol, and percent motility was measured at 15, 30 and 60 min intervals to determine the sensitivity of the cells to the cryoprotectant agent over time. Results indicate that sperm motility is significantly effected by decreased temperatures and the presence of cryoprotectant agents.

The pathology of nephrotoxicity of gentamicin in snakes. A model for reptilian gout.

Two gopher snakes (Pitophis melanoleucus catenifer) each were given 5 mg/kg body weight of gentamicin every 72 hours (group 1); two snakes each were given 5 mg/kg/day (group 2). Doses for both groups were given over a 2-week period. After the second week, the dose for one snake in each group was increased to 50 mg/kg/day for 2 more weeks and then discontinued. Weekly renal biopsies taken from snakes in group 1 showed no abnormalities by light microscopy during and at the completion of the experiment. Snakes in group 2 had cloudy swelling of the proximal tubules at 2 and 4 weeks after the gentamicin was administered. Snakes given the high dose of gentamicin had hydropic degeneration of the proximal tubules 2 weeks after the dose was raised to 50 mg/kg/day. This progressed to tubular necrosis 1 week after the gentamicin was discontinued. These snakes (high dose) also developed visceral gout, apparently as the result of the extensive tubular necrosis. Tophi were in the pericardium, serosal membranes and parenchyma of the kidneys, liver, spleen and lungs.

HAEMATOLOGIC PARAMETERS ON VARIOUS SPECIES OF STRIGIFORMES AND FALCONIFORMES

Normal mean values for packed cell volume, total erythrocyte count, total leukocyte count, total protein and mean corpuscular volume were obtained from 37 species of Strigiformes and Falconiformes representing 207 individuals.

Primary Mycobacterium avium Complex Infections Correlate with Lowered Cellular Immune Reactivity in Matschie's Tree Kangaroos (Dendrolagus matschiei)

The National Zoological Park has maintained a breeding colony of Matschies tree kangaroos (Dendrolagus matschiei) since 1975 with a documented history and continued prevalence of Mycobacterium avium complex (MAC) infections. No evidence of immunosuppressive retrovirus infections or loss of heterozygosity that may have led to an immune dysfunction in these animals was found. Isolates of MAC organisms from affected tree kangaroos and from their environment had no common restriction fragment DNA types. Cellular immune reactivity in apparently healthy tree kangaroos was 3- to 6-fold lower than in humans and other marsupial and eutherian mammals, as determined by lymphocyte proliferative assays. Thus, while MAC infections are typically opportunistic in humans and other mammals, tree kangaroos commonly develop primary progressive disease with MAC from random sources. Comparative information derived from this study should benefit both the endangered tree kangaroo and humans with immunosuppressive disorders that lead to mycobacterial infections.

Reference cardiopulmonary physiologic parameters for standing, unrestrained white rhinoceroses (Ceratotherium simum).

Abstract Chemical restraint is an important tool for the management and medical care of both captive and free-ranging rhinoceroses. Current anesthetic protocols for the white rhinoceros (Ceratotherium simum) are reported to cause varying degrees of hypertension, tachycardia, muscular stiffness and fasciculation, acidosis, and, most importantly, respiratory depression with resulting hypoventilation, hypoxia, and hypercapnea. To assist in the assessment and development of new and improved anesthetic techniques for the white rhinoceros, the following cardiopulmonary reference parameters for standing, unrestrained white rhinoceroses were generated (mean ± standard error [minimum − maximum]): heart rate = 39 ± 0.8 beats/min (32–42), respiratory rate = 19 ± 0.6 breaths/min (16–23), corrected indirect systolic blood pressure = 160 ± 2.9 mm Hg (146–183), corrected indirect diastolic blood pressure = 104 ± 2.3 mm Hg (88–117), corrected indirect mean blood pressure = 124 ± 2.2 mm Hg (108–135), end tidal CO2 = 45.1 ± 0.7 mm Hg (41.7–48.0), rectal temperature = 36.8 ± 0.1°C (36.6–37.2), arterial blood pH = 7.391 ± 0.007 (7.346– 7.431), arterial partial pressure of oxygen = 98.2 ± 1.4 mm Hg (90.2–108.6), arterial partial pressure of CO2 = 49.0 ± 0.9 mm Hg (44.4–53.7), base excess = 3.5 ± 0.4 mmol/L (1.9–5.9), bicarbonate = 29.3 ± 0.4 mmol/L (27.3–32.2), and arterial hemoglobin oxygen saturation (SaO2) = 97.2 ± 0.1% (96.6–98.0).