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At least 415 records · Page 23Linked to original sources
PubMed2006

Cryopreservation of spermatozoa from wild-born Namibian cheetahs (Acinonyx jubatus) and influence of glycerol on cryosurvival.

Sperm cryopreservation is a valuable tool for the genetic management of ex situ populations. This study was conducted to assess: (1) semen characteristics of wild-born cheetahs; and (2) the impact of three types of glycerol influence (duration of exposure, temperature, and method of addition) on sperm cryosensitivity. To evaluate the impact of duration of glycerol exposure, spermatozoa were incubated in Test Yolk Buffer (TYB) with 4% glycerol at ambient temperature (approximately 22 degrees C) for 15 vs. 60 min before cryopreservation. To evaluate the influence of temperature and method of glycerol addition, spermatozoa were resuspended at ambient temperature either in TYB with 0% glycerol followed by addition of 8% glycerol (1:1 v/v; at ambient temperature vs. 5 degrees C) or directly in TYB with 4% glycerol. All samples were cryopreserved in straws over liquid nitrogen vapor and evaluated for sperm motility and acrosomal integrity after thawing. Semen samples (n = 23; n = 13 males) contained a high proportion (78%) of pleiomorphic spermatozoa. Ejaculates also contained a high proportion of acrosome-intact (86%) and motile spermatozoa (78%). Immediately after thawing, a significant proportion of spermatozoa retained intact acrosomes (range, 48-67%) and motility (range, 40-49%). After thawing, incubation in glycerol for 60 min at ambient temperature before freezing decreased (p < 0.05) sperm motility and acrosomal integrity at one time-point each (pre-centrifugation and post-centrifugation, respectively). However, method or temperature of glycerol addition had no (p > 0.05) impact on sperm cryosurvival. In summary, (1) wild-born cheetahs produce high proportions of pleiomorphic spermatozoa but with a high proportion of intact acrosomes; and (2) resuspension in 4% glycerol, followed by exposure for up to 60 min at ambient temperature, had minimal effect on sperm motility and acrosomal integrity after cryopreservation. Results indicate the feasibility of cryopreserving cheetah spermatozoa under field conditions, providing a user-friendly method to capture and store gametes to enhance genetic management.

Acinonyx↗
PubMed1996

Strongylus asini (Nematoda, Strongyloidea): genetic relationships with other Strongylus species determined by ribosomal DNA.

Genomic DNA was isolated from adult Strongylus asini collected from zebra. The second ribosomal transcribed spacer (ITS-2) was amplified and sequenced using polymerase chain reaction (PCR) based techniques. The DNA sequence was compared with previously published data for 3 related Strongylus species. A PCR-linked restriction fragment length polymorphism method allowed the 4 species to be differentiated unequivocally. The ITS-2 sequence of S. asini was found to be more similar to those of S. edentatus (87.1%) and S. equinus (95.3%) than to that of S vulgaris (73.9%). This result confirms that S. Asini and S vulgaris represent separate species and supports the retention of the 4 species within 1 genus.

Animals↗
PubMed1998

Quantification of insulin in dried blood spots.

A method has been developed in which the concentrations of insulin in dried blood spots on filter paper can be estimated. The technique involves elution of blood from the paper, evaporation, and rehydration in assay buffer. The resuspended samples are then assayed by radioimmunoassay. The ratio of control plasma to control dried blood spot insulin values is used as a conversion factor for unknown samples on paper to express the dried blood spot insulin concentration in plasma equivalents. Intra-assay variability was 14%, and interassay variability was 25%, but the elution conversion factor had a variability of about 40% among individuals. This technique has substantial advantages for field studies, but elevated values should be confirmed by a venous plasma sample measurement in a conventional radioimmunoassay.

Blood Proteins↗
PubMed1998

Comparison and characterization of the venoms of three Parabuthus scorpion species occurring in southern Africa.

Parabuthus transvaalicus, P. granulatus, and P. villosus are three medically important scorpion species occurring in southern Africa which can cause severe envenoming among people. In contrast to many other genera, no data is available on the venom composition of scorpions belonging to the genus Parabuthus. Here we have investigated the components which may contribute to the venomous potential. The constancy of venom composition within each of the three species and between the three species was investigated by means of gel filtration chromatography. The venoms of the three species each were characterized by a constant and typical elution pattern, resulting in a 'gel filtration fingerprint' which allows distinction between each species. It appears that certain components in the venoms are common to either all three species, or to two of the three species. This points to a clear interspecies relationship within the genus. We also describe the isolation and characterization of some of the polypeptide toxins present in the venoms of P. villosus, P. transvaalicus and P. granulatus by means of reversed phase chromatography and screening of the toxic components on voltage-activated potassium and sodium channels. Our results confirm that toxins which inhibit potassium channels and alter sodium channel gating are present in the venoms studied.

Animals↗
PubMed1984

Hepatitis B virus carrier state in black children in Ovamboland: role of perinatal and horizontal infection.

Hepatitis B surface antigen (HBsAg) was detected in 17% of adult males and 11% of mothers in Ovamboland , South West Africa/Namibia. Hepatitis B e antigen (HBeAg) was present in 15% of HBsAg-positive mothers. Only 1% of children less than 6 months of age were HBsAg-positive, compared with 13% of children over the age of 1 year. 27% of mothers who were HBsAg-positive had HBsAg-positive children, whereas the corresponding figure for mothers who were HBsAg-negative was 6%. 63% of mothers who were positive for both HBsAg and HBeAg had HBsAg-positive children. 37% of HBsAg-positive children had HBsAg-positive mothers, compared with 8% of HBsAg-negative children. Later "horizontal" rather than neonatal maternal-infant transmission of the hepatitis B virus (HBV) seems to be the more important mode of spread of this infection in Ovambo children. The difference in the pattern of transmission of this virus between the Far East and Africa seems to centre mainly on the differences in the HBeAg status of the mothers in these two regions.

Adolescent↗
PubMed1997

The use of seismic signals by fossorial southern African mammals: a neuroethological gold mine.

Behavioral adaptations exhibited by two African fossorial mammals for the reception of vibrational signals are discussed. The Namib Desert golden mole (Eremitalpa granti namibensis) is a functionally blind, nocturnal insectivore in the family Chrysochloridae that surface forages nightly in the Namib desert. Both geophone and microphone recordings in the substrate suggest that the golden mole is able to detect termite colonies and other prey items solely using seismic cues. This animal exhibits a hypertrophied malleus, an adaptation favoring detection of low-frequency signals. In a field study of the Cape mole-rat (Georychus capensis), a subterranean rodent in the family Bathyergidae, both seismic and auditory signals were tested for their propagation characteristics. This solitary animal is entirely fossorial and apparently communicates with its conspecifics by drumming its hind legs on the burrow floor. Auditory signals attenuate rapidly in the substrate, whereas vibratory signals generated in one burrow are easily detectable in neighboring burrows. The sensitivity to substrate vibrations in two orders of burrowing mammals suggests that this sense is likely to be widespread within this taxon and may serve as a neuroethological model for understanding the evolution of vibrational communication. Neuroethological implications of these findings are discussed.

Animal Communication↗
PubMed1998

A competitive ELISA for the specific diagnosis of contagious bovine pleuropneumonia (CBPP).

A competitive ELISA, using a specific monoclonal antibody, was designed to detect antibodies to Mycoplasma mycoides subsp. mycoides SC, the agent of contagious bovine pleuropneumonia. One monoclonal antibody was found suitable for such a test, '117/5', it does not cross-react with any of the other mycoplasma species tested, furthermore, its binding is inhibited by positive sera. The cutoff, 50% of inhibition, was determined using a set of negative sera from CBPP-free areas. The sensitivity was controlled with sera from artificially infected animals as well as from sera from areas where CBPP is enzootic. In both cases, cELISA compared favorably with CFT. The precocity of detection was similar but cELISA detected more positives and the positive titers seemed to persist longer than in the case of CFT. Lysis of the antigen used to coat the ELISA plates reduced the variability of fixation and improved the repeatability of the test. A field evaluation is now in progress which will determine the true sensitivity and specificity of the test and also check if antibodies are detected after vaccination.

Animals↗
PubMed1999

Phytotoxins from the leaves of Laggera decurrens.

Upon biological screening of a series of African medicinal plants, substantial phytotoxic activity was found in the leaves of Laggera decurrens (Vahl.) Hepper & Wood (Asteraceae), using a Lemna minor bioassay. Bioassay-guided fractionation of the leaves led to the isolation of two physiologically active compounds: 3-hydroxythymoquinone and 5-acetoxy-2-hydroxythymol, causing death of Lemna minor in the 25-100 microM range. Symptoms were a rapidly developing chlorosis, followed by necrosis of fronds. The compounds also inhibited growth and germination of the grass weed Agrostis capillaris down to 250 microM. The mode of action of both compounds could not be elucidated, but they do not appear to be photosystem II inhibitors.

Asteraceae↗
PubMed2002

Auditory communication, meteorology, and the Umwelt.

Animal communication is affected by a multitude of environmental factors including meteorological conditions, ground reflection, turbulence, and vegetative attenuation. Evolutionary and behavioral adaptations by animals to these challenges include elephant use of infrasound optimized for long-distance propagation. These adaptations in turn influence the perceptual sphere, or Umwelt, of calling animals.

Animal Communication↗