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Biomedical subjects

V de Vos

Publications and source records attributed to V de Vos.

At least 37 records · Page 2Linked to original sources
PubMed1988

Parotid salivary gland of the African elephant (Loxodonta africana): structure and composition of saliva.

Specimens from parotid salivary glands of full-grown elephant (Loxodonta africana) a (n=6) and saliva aspirated from their main excretory ducts were examined macroscopically and microscopically and analyzed biochemically. The composition of the saliva was compared to that of the blood. The parotids (n=12; mean = 7.4 kg) are homocrine and of a seromucous nature. Myoepithelial cells are well-developed along intercalated ducts and their processes extend to proximal portions of allied acini. The saliva is hypotonic and contains relatively low concentrations of sodium and glucose and high concentrations of potassium, urea, calcium and phosphorus. Absence of detectable levels of alpha-amylase negates a digestive role and the voluminous secrete evidently aids swallowing by moisturising and lubricating the large mass of ingested leaves, grass and bark.

Animals↗
PubMed1987

Nematode parasites from Burchell's zebras in South Africa.

Twenty-five Burchell's zebras (Equus burchelli antiquorum) which were culled at monthly intervals in the Kruger National Park were examined for helminths. Twenty-nine species of nematodes belonging to the families Atractidae, Habronematidae, Onchocercidae, Oxyuridae, Strongylidae, Strongyloididae and Trichostrongylidae were recovered. The cyathostomes (small strongyles) most abundant were Cyathostomum tetracanthum, Cylicostephanus calicatus, Cylindropharynx sp. (? C. intermedia Theiler, 1923) and Cylicocyclus auriculatus. Cyathostomum alveatum, Cyathostomum montgomeryi, Cylicostephanus calicatus and Cylindropharynx sp. (? C. intermedia Theiler, 1923) were the most prevalent cyathostomes (small strongyles) while Craterostomum acuticaudatum was the most prevalent of the large strongyles. Of all the species recovered those most abundant were Crossocephalus viviparus and Probstmayria vivipara with intensities of 100 to 3,857,772 and 18,400 to 104,120,467, respectively. Four new species, two Triodontophorus spp. (Strongylidae) and two Habronema spp. (Habronematidae) were identified. Furthermore, this study furnishes a first report of Triodontophorus minor in zebras. The fourth stage cyathostomes as well as the adults of 11 of the 14 species were present in significantly greater intensities in autumn and winter.

Animals↗
PubMed1987

Parasites of domestic and wild animals in South Africa. XXII. Ixodid ticks on domestic dogs and on wild carnivores.

Ixodid ticks were collected from 4 dogs on smallholdings near Grahamstown, eastern Cape Province, on 1 or more occasions each week for periods ranging from 9-36 months. Fourteen tick species were recovered and the seasonal abundance of adult Haemaphysalis leachi and adult Rhipicephalus simus was determined. Complete collections of ticks were made from 50 caracals (Felis caracal) in the Cradock, Graaff-Reinet and Southwell regions in the eastern Cape Province. The animals from Cradock and Graaff-Reinet harboured 13 ixodid tick species. The caracals from Southwell were infested with 11 tick species and the seasonal abundance of Ixodes pilosus on these animals was determined. A small-spotted genet (Genetta genetta), 1 bat-eared fox (Otocyon megalotis), 1 aardwolf (Proteles cristatus) and 6 black-backed jackal (Canis mesomelas) from various localities in the eastern Cape Province were examined for ticks and 9 species were collected. Complete tick collections were made from a side-striped jackal (Canis adustus), 2 wild dogs (Lycaon pictus), a spotted hyaena (Crocuta crocuta), a several (Felis serval), 2 African civets (Civettictis civetta), 2 leopards (Panthera pardus) and a lion (Panthera leo) in the Kruger National Park in the north-eastern Transvaal. Twelve ixodid tick specis were recovered from these animals.

Animals↗
PubMed1987

Seasonal abundance of carrion-frequenting blow-flies (Diptera: Calliphoridae) in the Kruger National Park.

Monthly population fluctuations of carrion-frequenting blow-flies over a 24-month period were monitored using 2 carrion-baited traps in the southern Kruger National Park (KNP) and 3 in the northern KNP. All species displayed a clear seasonality. Chrysomyia marginalis and Chrysomyia albiceps were by far the most abundant. C. marginalis attained maximum abundance between November and March, with relatively low numbers present between May and September. C. albiceps maintained high population numbers between January and March in the northern KNP, with minimum numbers between May and August. In the southern KNP, C. albiceps became abundant from November to February, with low population levels between April and September. Although present only in relative low numbers, populations of Lucilia cuprina showed a clear increase in winter. Chrysomyia chloropyga, Chrysomyia putoria and Chrysomyia bezziana were trapped in significant numbers in the southern KNP, the latter 2 species reaching relative abundance in the warmer months, whereas C. chloropyga increased in cooler months from June to September. Graphic illustrations of monthly abundance are provided for all species.

Animals↗
PubMed1986

Influence of cryoprotective diluent on post-thaw viability and acrosomal integrity of spermatozoa of the African elephant (Loxodonta africana).

Electroejaculates from free-ranging, African elephants were frozen to test various seminal diluents, freezing methods and thawing media on post-thaw sperm viability and structural integrity. In Study I, each ejaculate was tested with each of 7 cryoprotective diluents. After cooling to 5 degrees C and equilibration on ice (4 degrees C) for 120 min, each aliquant was pellet frozen on solid CO2, stored in liquid nitrogen and thawed (37 degrees C) in saline or tissue culture solution. Amongst all diluents, post-thaw sperm motility, motility duration in vitro (37 degrees C) and acrosomal integrity were greatest (P less than 0.05) when diluent BF5F was used. Thawing medium had no effect on results. In Study II, the optimal diluent from Study I (BF5F) was compared with the diluent SGI. Results were not affected by a 90- or a 150-min cooling-equilibration interval in an electronic cooler (5 degrees C); however, post-thaw sperm motility rating and duration of motility in vitro were greater (P less than 0.01) with the pellet than the straw container freezing method. When the pelleting method was used, diluents BF5F and SGI provided comparable cryoprotection. Duration of post-thaw motility was enhanced 2-fold and up to 12 h by maintaining thawed semen at 21 rather than 37 degrees C (P less than 0.05). All diluents provided some protection on acrosomal integrity, but the overall proportion of intact acrosomes after thawing was markedly less in Study II, apparently as a result of the slower initial cooling rate (approximately 1.5 degrees C/min) compared to that of Study I (approximately 6.5 degrees C/min). This study demonstrates the feasibility of cryopreserving semen from free-ranging African elephants and indicates that spermatozoa must effectively survive freezing when the BF5F or SGI diluent is used in conjunction with the pelleting method.

Acrosome↗
PubMed1986

Parasites of domestic and wild animals in South Africa. XX. Arthropod parasites of the Cape mountain zebra (Equus zebra zebra).

The arthropod parasite burdens of 14 Cape mountain zebra (Equus zebra zebra), shot for survey purposes in the Mountain Zebra National Park in the eastern Cape Province, were determined. Three species of Gasterophilus larvae and 9 ixodid tick species were recovered. Larvae of Gasterophilus pecorum were the most numerous of the fly larvae recovered and Margaropus winthemi was the most abundant tick. Two horses examined in the park were infested with 3 species of Gasterophilus larvae and 7 species of ixodid ticks.

Animals↗
PubMed1985

Blood chemical parameters in shot Cape Mountain Zebra Equus zebra zebra.

Serum levels of cortisol, sodium, potassium, chloride, urea, creatinine, total protein, albumin, phosphorus, aspartate transaminase, creatine kinase, lactate dehydrogenase, iron, total magnesium, total calcium, alkaline phosphatase, alanine transaminase and gamma-glutamyltranspeptidase were determined in 11 short Cape Mountain Zebra Equus zebra zebra.

Animals↗
PubMed1984

Electroejaculation, semen characteristics and serum testosterone concentrations of free-ranging african elephants (Loxodonta africana).

A regimented electroejaculation protocol (120 electrical stimulations; 10-30 V) was used to collect semen and characterize ejaculate quality from 9 adult, free-ranging African elephants under anaesthesia. Eight of the 9 ejaculates contained high concentrations of progressively motile spermatozoa. The overall mean ejaculate volume, sperm concentration/ml ejaculate, sperm motility, sperm status and ejaculate pH were 93.3 ml, 2408.6 X 10(6) spermatozoa/ml, 70%, 3.9 and 7.4, respectively. A high percentage (mean 77.5%) of spermatozoa within each ejaculate was morphologically normal. Of the aberrant spermatozoa, 72% had a cytoplasmic droplet defect. When sperm viability was tested in vitro at 37 degrees C, sperm motility rating declined by at least half of the initial assessment within 3.5 h of semen collection. Generally, spermatozoa maintained motility in vitro for less than 6 h. Serum testosterone ranged from 1.4 to 8.2 ng/ml in 4 males evaluated in the morning (07:30-08:00 h). In 4 of the 5 bulls assessed in the afternoon (15:00-18:00 h), testosterone levels were less than 0.9 ng/ml. The remaining bull, evaluated at 16:00 h, had exceptionally high testosterone concentrations (peak 25.6 ng/ml) and a preputial discharge potentially indicative of 'musth'. The present study demonstrates that high quality semen can be collected consistently from the African elephant and that striking differences exist in serum testosterone amongst free-ranging males which may be due, in part, to a diurnal rhythm.

Animals↗
PubMed1984

Nodular abomasitis in impala (Aepyceros melampus) caused by the nematode Longistrongylus sabie.

The periodic occurrence of nodular abomasitis associated with the trichostrongylid nematode Longistrongylus sabie was observed in impala lambs of the Kruger National Park, Republic of South Africa. The condition was seen predominantly in animals less than 1 yr of age. Peak incidences occurred in the spring and fall, when more than 50% of the lambs studied had from several to numerous nodules in their abomasal mucosae. The nodular lesions in the lambs were macroscopically larger than, but microscopically similar to, those observed in domestic ruminants with ostertagiosis; however, L. sabie worm burdens were much lower than those in clinical cases of ostertagiosis, and no evidence of diarrhea could be found in any of the lambs studied. The physical condition of lambs with moderate to severe nodular abomasitis did not differ noticeably from that of lambs with mild involvement or those without lesions. Nodular abomasitis caused by this parasite was of minimal significance to impala herds in the Park under the circumstances prevailing at the time of the study.

Abomasum↗
PubMed1984

Blood composition in culled elephants and buffaloes.

Blood composition of succinyldicholine culled elephants and buffaloes was compared with that of undisturbed animals shot in the brain. The results show statistically significant differences in a number of variables including plasma ACTH and cortisol concentrations. The observed changes are attributed to stress induced by a combination of herding and darting with succinyldicholine and asphyxia. Extrapolation from blood oxygen tensions suggests that this stress may be perceived for an undetermined period which is probably longer in elephants than buffaloes.

Acid-Base Equilibrium↗
PubMed1983

Concentration and composition of plasma proteins in wild mammals.

Total protein concentrations from a variety of wild mammalian species were measured by the Lowry and Biuret techniques and compared with results obtained or derived by refractometry. Values obtained with the Lowry method were the highest and certain derived refractometry results, the lowest. It is suggested that the Biuret method provides the most acceptable values but that care should be exercised in using the correct standard. The percentage composition of plasma from 22 species of wild mammals is also presented and the observations discussed with relation to methodology and A/G ratio.

Animal Population Groups↗
PubMed1978

Some infectious diseases of wild vervet monkeys (Cercopithecus aethiops pygerythrus) in South Africa.

Our surveys indicate that nearly all batches of vervet monkeys arriving at the National Institute for Virology from various areas of South Africa, are infected with foamy viruses and there is evidence that intra-urterine infection also occurs. Monkeys from certain areas of South Africa are apparently infected with the protozoal parasite Entopolypoides macaci in a sub-clinical state which becomes active when the monkeys are splenectomised. Serological studies indicate that infections with schistosomes, tick-bite fever (Rickettsia conori), chlamydsiae and occasionally by leptospirae, occur in monkeys in the Kruger National Park. Complement fixation tests for antibodies to R. mooseri and R. prowazeki were also sometimes positive; a finding of doubtful importance. There was a high percentage with positive antibody tests to chikungunya virus in a certain age group suggesting that there had been an outbreak of this disease in the Kruger Park in the late summer and autumn of 1976. This coincided with a human outbreak. Large numbers of vervet and baboon sera were tested for antibodies against SA 12 virus, a polyoma virus. A high percentage of baboons but only a small number of monkeys was found to be positive and it is concluded that SA 12 is probably a baboon virus which is occasionally transmitted to monkeys by contact. It is pointed out that these studies only indicate diseases from which monkeys recover and they do not indicate prevalence of severe disease causing grave illness or death.

Animal Population Groups↗