The "five-sites" rule and the evolution of red and green color vision in mammals

Amino acid changes S180A (S-->A at site 180), H197Y, Y277F, T285A, and A308S are known to shift the maximum wavelength of absorption (lambda max) of red and green visual pigments toward blue, essentially in an additive fashion. To test the generality of this "five-sites" rule, we have determined the partial amino acid sequences of red and green pigments from five mammalian orders (Artiodactyla, Carnivora, Lagomorpha, Perissodactyla, and Rodentia). The result suggests that cat (Felis catus), dog (Canis familiaris), and goat (Capra hircus) pigments all with AHYTA at the five critical sites have lambda max values of approximately 530 nm, whereas rat (Rattus norvegicus) pigment with AYYTS has a lambda max value of approximately 510 nm, which is accurately predicted by the five-sites rule. However, the observed lambda max values of the orthologous pigments of European rabbit (Oryctolagus cuniculus), white-tailed deer (Odocoileus virginianus), gray squirrel (Sciurus carolinensis), and guinea pig (Cavia procellus) are consistently more than 10 nm higher than the predicted values, suggesting the existence of additional molecular mechanisms for red and green color vision. The inferred amino acid sequences of ancestral organisms suggest that the extant mammalian red and green pigments appear to have evolved from a single ancestral green-red hybrid pigment by directed amino acid substitutions.      

Cytogenetic analyses of eight species in the genus <Emphasis Type="Italic">Leptodactylus</Emphasis> Fitzinger, 1843 (Amphibia,Anura, Leptodactylidae), including a new diploid number and a karyotype with multiple translocations

Background

The karyotypes of Leptodactylus species usually consist of 22 bi-armed chromosomes, but morphological variations in some chromosomes and even differences in the 2n have been reported. To better understand the mechanisms responsible for these differences, eight species were analysed using classical and molecular cytogenetic techniques, including replication banding with BrdU incorporation.

Results

Distinct chromosome numbers were found: 2n = 22 in Leptodactylus chaquensis, L. labyrinthicus, L. pentadactylus, L. petersii, L. podicipinus, and L. rhodomystax; 2n = 20 in Leptodactylus sp. (aff. podicipinus); and 2n = 24 in L. marmoratus. Among the species with 2n = 22, only three had the same basic karyotype. Leptodactylus pentadactylus presented multiple translocations, L. petersii displayed chromosome morphological discrepancy, and L. podicipinus had four pairs of telocentric chromosomes. Replication banding was crucial for characterising this variability and for explaining the reduced 2n in Leptodactylus sp. (aff. podicipinus). Leptodactylus marmoratus had few chromosomes with a similar banding patterns to the 2n = 22 karyotypes. The majority of the species presented a single NOR-bearing pair, which was confirmed using Ag-impregnation and FISH with an rDNA probe. In general, the NOR-bearing chromosomes corresponded to chromosome 8, but NORs were found on chromosome 3 or 4 in some species. Leptodactylus marmoratus had NORs on chromosome pairs 6 and 8. The data from C-banding, fluorochrome staining, and FISH using the telomeric probe helped in characterising the repetitive sequences. Even though hybridisation did occur on the chromosome ends, telomere-like repetitive sequences outside of the telomere region were identified. Metaphase I cells from L. pentadactylus confirmed its complex karyotype constitution because 12 chromosomes appeared as ring-shaped chain in addition to five bivalents.

Conclusions

Species of Leptodactylus exhibited both major and minor karyotypic differences which were identified by classical and molecular cytogenetic techniques. Replication banding, which is a unique procedure that has been used to obtain longitudinal multiple band patterns in amphibian chromosomes, allowed us to outline the general mechanisms responsible for these karyotype differences. The findings also suggested that L. marmoratus, which was formerly included in the genus Adenomera, may have undergone great chromosomal repatterning.

     

Routine prophylactic antibiotic use in the management of snakebite

Background  

Routine antibiotic prophylaxis following snakebite is not recommended but evidence suggests that it may be common practice in Zimbabwe. This study set out to determine and describe the extent of this practice at Parirenyatwa Hospital, a large teaching hospital in Zimbabwe     

Effects of Chronic Treatment With the CB1 Antagonist,Rimonabant on the Blood Pressure,and Vascular Reactivity of Obese Zucker Rats

Rimonabant (RM) is a cannabinoid CB1 receptor antagonist useful in the treatment of obesity associated cardiovascular risk factors. Since cannabinoids are vasoactive compounds, the aim of this study is to evaluate the effect of chronic treatment with RM on systolic blood pressure (SBP), and endothelial and vascular reactivity. Obese Zucker rats (OZRs) and their lean counterparts were orally treated during 20 weeks with either RM (10 mg/kg/day). Endothelial and vascular function was assessed in aorta and small mesenteric arteries (SMAs) by concentration response curves to acetylcholine (ACh) and phenylephrine (Phe), respectively. Participation of nitric oxide (NO) was evaluated by incubation with the NO synthase (NOS) inhibitor N^G‐nitro‐l‐arginine methyl ester (L‐NAME) and cyclooxygenase (COX)‐derived products involvement was analyzed by incubation with indomethacin (INDO). Plasma lipid profile, insulin and adiponectin were also analyzed. Sympathetic activity was evaluated by urinary excretion of noradrenaline. As expected, RM decreased body weight gain and enhanced adiponectin concentration. Insulin resistance and sympathetic activity were also decreased. The increase in SBP observed in OZRs was reduced by treatment with RM. Aortae and SMAs from OZRs exhibited lower contractile response to Phe, being this effect prevented by RM administration. Although ACh‐induced response and NO participation remained unaltered with obesity, enhanced COX‐derived constrictor products were found in OZRs. RM treatment neither altered endothelium‐dependent relaxation nor L‐NAME‐sensitive component of the response. Nevertheless, it was able to regulate COX‐derived vasoactive products participation. Those effects may contribute to explain some of the cardiovascular protective actions elicited by this drug.     

Inhibition of Sulfate Respiration by 1,8-Dihydroxyanthraquinone and Other Anthraquinone Derivatives

Derivatives of 9,10-anthracenedione, or anthraquinone, were shown to inhibit respiratory sulfate reduction by pure cultures of sulfate-reducing bacteria, as well as by crude enrichment cultures. Structure-activity studies showed that an increasing degree of substitution of the anthraquinone nucleus resulted in increasing 50% inhibition (I(inf50)) values for sulfate respiration. Addition of charged ring substituents also resulted in an increase in the I(inf50) concentration. Experiments carried out with 1,8-dihydroxyanthraquinone demonstrated inhibition of hydrogen-dependent sulfate respiration but not hydrogen-dependent sulfite or thiosulfate respiration. Addition of pyruvate resulted in stimulation of sulfate-dependent hydrogen oxidation in the presence of the anthraquinone. These observations, together with a direct demonstration of uncoupling in French press vesicle preparations, suggest that the underlying mechanism of inhibition is uncoupling of ATP synthesis from electron transfer reactions. The low I(inf50) values for inhibition (0.5 to 10 (mu)M) and the relatively low general toxicity of anthraquinones suggest that these compounds may be useful for inhibition of sulfide generation in situations which are incompatible with the use of broadly toxic biocides.     

Attitudinal reciprocity in food sharing among brown capuchin monkeys

Capuchin monkeys (Cebus apella) share food even if separated by a mesh restraint. Pairs of capuchins were moved into a test chamber in which one of them received apple pieces for 20 min, and the other received carrot pieces for the next 20 min. Previous research had shown a correlation between the rate of food transfer in both directions across female-female dyads. The present study confirmed this result. Reciprocity across dyads can be explained, however, by symmetry in affiliative and tolerant tendencies between two individuals, provided these tendencies determine food sharing. The present study was designed to exclude this symmetry-based explanation by testing each pair (N=16) of adult females on six separate occasions. There existed a significant covariation across tests of sharing in both dyadic directions, a result unexplained by relationship symmetry. Moreover, control procedures (i.e. testing of a food possessor without a partner, or testing of two individuals with the same food or two different foods at the same time) indicated that behaviour during food trials is not fully explained by mutual attraction or aversion. The monkeys take the quality of their own and the partner's food into account, and possessors limit transfers of high-quality foods. Instead of a symmetry-based reciprocity explanation, a mediating role of memory is suggested, and a mirroring of social attitude between partners. Copyright 2000 The Association for the Study of Animal Behaviour.     

Purge-and-trap gas chromatographic determination of styrene in urine and blood: Application to exposed workers

A simple purge-and-trap gas chromatographic method with flame ionization detection was developed for the determination of styrene in urine and blood. Styrene present in a 5 ml sample at room temperature was swept by helium at 40 ml/min for 11 min, trapped on a Tenax trap, desorbed by heating, cryofocused, and injected by flash heating into a DB-5 capillary GC column. The oven temperature program was from 80°C, held for 8 min, to 120°C at 5°C/min, and then held for 2 min. The detector temperature was 250°C. The calibration curves were linear in the range of 2.5–15 ppb styrene in urine and 25–150 ppb in blood. The detection limits calculated were 0.4 μg/l in urine and 0.6 μg/l in blood. The coefficients of variations within the day and day-to-day were 3 and 3.1%, respectively, for 2.5 ppb of styrene in urine, and 1 and 1.6% for 25 ppb of styrene in blood. The results obtained from samples taken from workers exposed to styrene were reported.