Bacterial resistance to arsenic protects against protist killing

Protists kill their bacterial prey using toxic metals such as copper. Here we hypothesize that the metalloid arsenic has a similar role. To test this hypothesis, we examined intracellular survival of Escherichia coli (E. coli) in the amoeba Dictyostelium discoideum (D. discoideum). Deletion of the E. coli ars operon led to significantly lower intracellular survival compared to wild type E. coli. This suggests that protists use arsenic to poison bacterial cells in the phagosome, similar to their use of copper. In response to copper and arsenic poisoning by protists, there is selection for acquisition of arsenic and copper resistance genes in the bacterial prey to avoid killing. In agreement with this hypothesis, both copper and arsenic resistance determinants are widespread in many bacterial taxa and environments, and they are often found together on plasmids. A role for heavy metals and arsenic in the ancient predator–prey relationship between protists and bacteria could explain the widespread presence of metal resistance determinants in pristine environments.     

Dietary Spectrum of Two Sympatric Canid Species in Ladakh,India

We have conducted a study between May and August 2013 to understand the dietary spectrum of two canid species: Tibetan wolf (Canis lupus chanco) and Red fox (Vulpes vulpes) in one of the most inhospitable landscape of the world. Ladakh is characterized by harsh environmental conditions and low primary productivity and therefore animal populations, particularly of large and medium sized herbivores are also low and sparsely distributed. This in turn poses a challenge to the survival of predators. We have attempted to investigate the ways by which the two sympatric canid species are optimizing feeding for their survival in an environment where there is scarcity of wild prey base. Scats of the two species were collected from Chiktan and Rangdum valleys and undigested food remnants were identified. The dietary spectrum of Tibetan wolf was composed of six prey species (2 wild and 4 livestock species). The share of livestock species in the diet was maximum (RO: 62.0%). The Red fox being an opportunistic feeder consumed 19 forgeable items, including small and medium sized mammals, birds, reptiles, insects, plant material, eggs, stones and debris. The livestock species contributed maximum to the diet of Red fox (RO: 22.9%). The dietary niche breadths of both species were more or less similar (0.53 and 0.58) and indicating a generalist feeding behavior. Both the species are surviving in the same environment with a dietary overlap of 0.60. The given information is expected to aid further studies in Indian Trans-Himalaya.     

A simple method for estimating recombination percentages and linkage intensities from F2 data: examples from Triticum monococcum and other self-fertilizing diploid plant species

Summary We offer an alternative approach to the extensively used maximum likelihood and product methods for calculating recombination values and linkage intensities from F₂ data. This new method which we designate as the square root approach is simpler than the ones in current use in that it obviates the need for formulae and tables. It can be applied to autosomal F₂ data from F₁'s heterozygous in both the coupling and repulsion phases. It has greater applicability than the product method in that it can be used in all cases involving 2-, 3-, 4-, 6- and 9-class segregations regardless whether gene interaction occurs or not, provided the double recessive and other specific phenotypes are each determined by one particular genotype. The proposed method is based on the same well established genetic facts as the other two approaches. Percent recombinant gametes and therefore percent recombination are calculated by deriving the square root of the proportion of the F₂ population that expresses the double recessive or equivalent phenotype. The recombination values obtained by our method are compared with those derived by product method for 17 crosses in 7 different species and were found to be insignificantly different from the latter. The advantages and disadvantages of the square root method compared with the two most used ones are discussed.     

Evidence for the presence of immunoreactive histidyl-proline diketopiperazine [Cyclo (His-Pro)] in the adult human brain

The current study was undertaken to evaluate the presence of cyclo (His-Pro) in adult human brain tissues obtained at autopsy. We found evidence for immunoreactive cyclo (His-Pro), which diluted in parallel to the radioimmunoassay standard curve and which had mobility on HPLC that was similar to synthetic cyclo (His-Pro), in several regions of the adult human brain. Whereas the levels of cyclo (His-Pro) in the pituitary stalk-median eminence were high (2.2 ng/mg protein), the concentrations in the whole hypothalamus were much lower (0.105 ng/mg protein). Among the extrahypothalamic brain regions examined, the levels of cyclo (His-Pro) were highest in the cerebellar hemisphere (0.168 ng/mg protein) and olfactory bulbs (0.180 ng/mg protein) and were lowest in the hippocampus (0.080 ng/mg protein) and occipital cortex (0.079 ng/mg protein). Thus, immunoreactive cyclo (His-Pro) has widespread distribution in the adult human brain and the potential exists for this cyclic diepeptide to play a role in human brain function.     

Secretion patterns of growth hormone in growing captive mithuns (Bos frontalis)

A study was conducted in May 2003 to characterize plasma growth hormone (GH) pattern in growing mithuns (Bos frontalis), a rare semi-wild ruminant. Six mithun calves averaging 235 day of age and 124 kg were maintained in semi-intensive system and group-fed once daily. Animals gained at a mean rate of 0.54 kg/day, with individuals ranging from 0.34 to 0.66 kg/day. Blood samples collected at 15-minute intervals starting from 0600h for nine-hour period were assayed for plasma GH. Growth hormone patterns consisted of frequent pulses of varying amplitude. Growth hormone pulses occurred at an average frequency of 0.69/h, the rate did not differ markedly among mithuns nor hour of day. The magnitude of GH secretory pulses varied significantly among mithuns. Growth hormone peaks averaged 95.0 and 45.2 ng/ml in mithuns having the highest and lowest GH peaks, respectively. Peak and mean GH levels were associated positively (r=0.98, P<0.001) and both were associated negatively (r=-0.97 and -0.98, respectively; P<0.01) with rates of gain. Results from the study show that 1) GH peaks occur at frequent intervals throughout the sampling period and 2) alteration in GH levels and patterns are elicited more by pulse amplitude than frequency modulation.     

New orally active spiro 1,2,4-trioxanes with high antimalarial potency

A new series of functionalized 1,2,4-trioxanes 10-21 have been prepared and assessed for antimalarial activity in mice. Several of these trioxanes show significant activity. Trioxane 16, the most active compound of the series, has shown activity by oral route which is comparable with that of the clinically used drug, beta-arteether.     

Secretion patterns of luteinizing hormone in growing mithuns (Bos frontalis)

To characterize the luteinizing hormone (LH) secretion patterns in growing mithun (Bos frontalis), a semi-wild ruminant, six female mithuns (1 year old; BW: 145.5 kg) were maintained in a semi-intensive system. Plasma progesterone (P(4)) level was measured in twice-a-week samples collected for six weeks to assess ovarian status. This was followed by a frequent sampling period. Blood samples collected at 15 min intervals for 9 h were assayed for plasma LH. Luteinizing hormone patterns consisted of pulses of varying amplitudes. Luteinizing hormone pulses occurred at an average rate of 0.54/h ( approximately 5 pulses/9 h). The rate did not differ among mithuns. The mean plasma LH levels was correlated with body weight (r=0.82; p<0.05) and pulse amplitude (r=0.87; p<0.01). Neither the LH amplitude nor the frequency was affected by time (p>0.05). The mean plasma P(4) concentration was 0.37 ng/ml. In conclusion, we demonstrated a pulsatile nature of LH secretion in growing mithuns. In addition, the mean plasma LH level and LH amplitude were positively correlated with body weight. It appears that in contrast to cattle, five LH pulses per nine hours recorded in mithuns were not an indication of approaching puberty.