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At least 19 recordsLinked to original sources
PubMed1976

Polyploid amphibians: three more diploid-tetraploid cryptic species of frogs.

The nominal African species Pyxicephalus delalandii and Dicroglossus occipitalis have diploid and tetraploid populations. There are also cryptic tetraploid and diploid species similar to Bufo kerinyagae. These represent the first bisexual polyploid "species" so far encountered in the major frog families Ranidae and Bufonidae. The contention that polyploidy is a widespread and important evolutionary phenomenon in anuran amphibians is supported.

Africa↗
PubMed1976

Oildroplets in the eyes of adult anuran amphibians: a comparative survey.

Oildroplets in the eyes of terrestrial vertebrates are spherical cellular organelles that stain for lipids, have no discernible internal structure, and often contain carotenoids and possibly other chemicals. A survey of 97 species of anuran amphibians (frogs and toads) revealed that all species of 16 families surveyed possessed yellow oildroplets of varying size in the cells of the pigment epithelium, except for three species that appear to have secondarily lost them during evolution. Furthermore, 25 species of six families also possess colorless oildroplets at the distal end of the inner segments of single cones and principal cones of the double-cone system; two species of the Ranidae appear to have secondarily lost such retinal oildroplets. Every species possesses epithelial or retinal oildroplets or both. Lastly, small oildroplet-like inclusions were discovered in the red blood cells of two species. All of Walls' ('42) summary generalizations about anuran oildroplets are incorrect: oildroplets are not restricted to the Ranidae, are not yellow when found in the cones, and do not correlate with photoactic behavior in 87 species. Evidence is reviewed suggesting that the primary function of anuran oildroplets is chemical storage, perhaps related to the visual pigment cycle. Oildroplets in the cones may additionally act as filters of ultraviolet radiation.

Amphibians↗
PubMed1976

Muscle relaxant properties of chloramphenicol.

Experiments with the guinea pig ileum, guinea pig trachea, rat fundal strip, rat colon, rat vas deferens, and toad heart indicated that chloramphenicol inhibited smooth muscles, decreasing both the height and frequency of spontaneous contraction. Chloramphenicol-induced relaxation was not mediated through adrenergic, cholinergic, or histaminergic mechanisms. The degree of muscle relaxation was related to the concentration of chloramphenicol, and the relaxant effect could be reversed by removing chloramphenicol from site of action by washing. Its action appears to be direct on the muscle, possibly by interfering with the energy-generating mechanism.

Animals↗
PubMed1978

Shape: its development and regulation capacity during embryogenesis.

Although several theoretical approaches consider general methods for dealing with shape, recent observations and experimental data show that embryos exhibit marked changes in the properties of the biological material involved in shape development and shape regulation capacity. In vivo experiments have shown that the amphibian embryo gradually develops from a situation in which it is not able to maintain its shape to one in which it can not only maintain its shape but also possesses a maximal tolerance towards deformation together with a maximal shape regulation capacity. So far two especially clear conclusions have emerged: (i) the form of the embryo appears to be determined by cell activities intrinsic to each stage, and (ii) the morphogenetic programme can be executed normally within wide limits notwithstanding dramatic deformations of the embryo during quite a long period. Thus the hypothesis may be advanced that shape and morphogenesis to some extent become independent phenomena during embryonic development.

Animals↗
PubMed1977

A new cell type in the taste buds of anurans. A scanning and transmission electron microscopic study.

A hitherto undescribed cell type within the fungiform papillae of the tongue of the toad, Bufo bufo (L.) and the taste-disks of the soft palate of Bombina variegata L. was identified by means of scanning and transmission electron microscopy. This cell type is characterized by an apical protrusion carrying numerous microvilli. Bundles of filaments are present in the cytoplasm of the protrusion. Vesicles with electron lucent content and microtubules are present thoughout the cytoplasm of the cell.

Animals↗
PubMed1975

DNA replication in the amphibia.

Autoradiographic techniques were used to measure rate of replication and length of the replication unit in cultured cells of Scaphiopus couchi, Bufo cognatus, Rana clamitans, and Triturus viridescens, having nuclear DNA amounts in the ratio 1:4:7:39 respectively. The autoradiographic experiments were designed to show whether the larger amounts of nuclear DNA are correlated with more rapid rates of synthesis and/or with longer replication units. -- The DNA replication rate was 2.5 mu/minute (corrected for two growing points) with 10 minutes 3H-thymidine label at 22 degrees C, but decreased with longer labelling durations. The length of the replication unit (estimated by the distance from the center of one autoradiograph to the center of the next in sequence) was most commonly in the 10-25 mu range with a 30 minute label, in all four species. The average center-to-center distance was 8 mu at 10 minutes and increased with label duration, to over 45 mu with 24 hours label. Replication was predominantly but not exclusively bidirectional. Neither rate of replication nor length of the replication unit was proportional to the amount of DNA in these species.

Amphibians↗
PubMed1979

Computer analysis of Feulgen hydrolysis kinetics.

A least squares fit of Feulgen hydrolysis time curves to the Bateman function is performed using an especially adapted parameter transformation together with a standard conjugate gradients iteration procedure. The method has been applied to a large number of measured data, and the use and limits of the computer evaluation are discussed.

Animals↗
PubMed1978

Enterobacteria of emerging pathogenic significance from clinical cases in man and animals and detection of toads and wall lizards as their reservoirs.

A total of 416 samples comprising faecal samples from diarrhoeic cases of man, calves, sheep and goats, and urine samples from patients with urinary tract infections, were examined for the presence of enterobacteria of emerging pathogenic significance. Citrobacter freundii from 20, C. intermedius biotype-a from four, Serratia marcescens (serotype 05:H13, bactericin type 16) from one and Erwinia herbicola from two human stool samples were isolated. Only two urine samples yielded C. freundii. Citrobacter freundii was isolated from 10 and C. intermedius biotype-a from two calves. From sheep and goats, two isolates of C. freundii and three of C. intermedius biotype-a were obtained. None of these samples yielded Edwarsiella tarda or Yersinia enterocolitica. The examination of 99 toads and 145 wall lizards revealed that toads were reservoirs for C. freundii, C. intermedius biotype-a and Salmonella brijbhumi, whereas wall lizards were reservoirs for C. freundii, C. intermedius biotype-a, E. herbicola, Enterobacter cloacae and Salmonella spp. These bacteria were present in the range of 2.0 x 10(6) to 6.0 x 10(11) organisms per gram of intestinal contents. In addition, toads were carriers for Edwardsiella tarda (new serotypes 04167:H1 and 05159: non-motile). None of the toads and wall lizards proved positive for C. intermedius biotype-b (C. koseri), S. marcescens and Y. entercolitica. C. freundii, C. intermedius biotype-a, E. herbicola and S. marcescens were resistant to penicillin and erythromycin whereas E. tarda isolates were also resistant to gentamycin, neomycin, colistin and sulfamethaxazole.

Animal Diseases↗
PubMed1978

Changes in ionic conductances and in sensitivity to amiloride during the natural moulting cycle of toad skin (Bufo viridis, L.).

The resistance of the apical membranes of toad skin (Bufo viridis) was measured during its natural moulting cycle using a fast flow technique. The skin behaved in all periods of the moulting cycle as a nearly perfect sodium electrode. In the presence of amiloride (10(-4)M), the total resistance of the same skin was identical with solutions which contained either sodium or potassium. The resistance of the skin with potassium was sensitive to amiloride in the period just after moulting. The resistance of skins which were made shunted by treating them with urea on the outside area was insensitive to amiloride in solutions containing potassium; a small effect was still observed with sodium. It is suggested that the transient sensitivity to amiloride, with potassium, is the result of differentiation of the sodium specific sites at the apical membranes of the skin.

Amiloride↗
PubMed1977

Mode of action of amiloride in toad urinary bladder. An electrophysiological study of the drug action on sodium permeability of the mucosal border.

The effect of amiloride on the sensitivity to Na of the mucosal border of toad urinary bladder was investigated by recording Na concentration-dependent transepithelial potential difference (Vt) and the intracellular potential. When mucosal Na concentration was normal, amiloride added to the mucosal solution at 10(-4) M markedly reduced the mucosal membrane potential (Vm) and altered the potential profile from a two-step type to a well type. Similar changes were observed when Na was totally eliminated from the mucosal medium. The serosal membrane potential was insensitive to amiloride and elimination of mucosal Na. In the absence of amiloride, the Vt could be described by the Goldman-Hodgkin-Katz equation in the range of mucosal Na concentration from 0 to 16 mM, and amiloride extended this concentration range. By using the Goldman-Hodgkin-Katz equation. Na permeability was calculated from the data of Vt's obtained in the allowed ranges of Na concentration and compared before and after the addition of amiloride. The results show that Na permeability decreases to 1/600 of control when the maximum dose of amiloride (10(-4) M) is applied. The relationship between Na permeability and amiloride concentration is well explained on the basis of assumptions that amiloride binds to the Na site of the mucosal border in one-to-one fashion and in a competitive manner with Na and that Na permeability reduces in proportion to increase in number of the sites bound with amiloride.

Amiloride↗
PubMed1976

Influence of gonadal hormones on the developing amphibian brain: changes in ribonucleic acid, protein and activity levels of acetylcholinesterase on in vivo administration of progesterone.

The levels of RNA and protein and activity levels of acetylcholinesterase decreased in the brain of developing tadpoles of 13-15-day-old Bufo melanostictus on in vivo administration of progesterone (200 mug/0.1 ml refined peanut oil). These changes suggest decelaration in the activity of the protein-synthetic machinery in progesterone administered animals.

Acetylcholinesterase↗
PubMed1978

Comparison of toad bladder aldosterone-induced proteins and proteins synthesized in vitro using aldosterone-induced messenger RNA as template.

Using double-labeled isotope techniques, it can be shown that aldosterone induces the synthesis of several proteins in the mitochondria-rich (MR) cells of the toad's urinary bladder. Induced proteins have been identified both in the plasma membrane (mol wt = 170,000, 85,000 and 12,000) and the cytosol (mol wt = 36,000, 12,000 and 6,000) fractions of these mucosal cells. We have also shown that aldosterone (Aldo) induces the synthesis of a class of RNA having the properties of messenger RNA (mRNA). mRNA isolated from Aldo-treated mucosal cells was used as template in a cell-free protein-synthesis system prepared from rabbit reticulocytes. Preparations charged with mRNA from Aldo-treated cells synthesized two proteins that were not labeled when mRNA from control tissues was used as template. The electrophoretic mobility of one of these proteins was similar to an Aldo-induced membrane protein (mol wt = 70,000) found in the intact tissue.

Aldosterone↗