Cyclic AMP transport across membrane vesicles of ultra-violet light irradiatedEscherichia coli

Transport of cyclic AMP acrossEscherichia coli membrane was studied using membrane vesicles. Uptake of cyclic AMP was measured using normally oriented vesicles, whereas uptake in everted vesicles was taken as a measure of the efflux of cyclic AMP. Ultra-violet irradiation of the cells led to an inhibition of both uptake and efflux of cyclic AMP across the membrane. The presence of cyclic AMP in the growth medium prior to ultra-violet irradiation caused an enhancement of the uptake and efflux. The uptake and efflux of cyclic AMP were less in vesicles from glucose grown cells as compared to the uptake and efflux by the vesicles prepared from glycerol grown cells. Similarly both uptake and efflux of cyclic AMP were more in vesicles prepared from cells grown on glycerol or glucose in the presence of cyclic AMP than in vesicles from cells grown in absence of cyclic AMP. It is suggested that the number of cyclic AMP carrier molecules were reduced in cells under catabolite repression by glucose as well as by ultra-violet irradiation     

Conserved autonomy of replication of the X-chromosomes in hybrids of Drosophila miranda and Drosophila persimilis

The chromosome complement of hybrid males from the cross between Drosophila miranda female and D. persimilis male provides an interesting chromosomal situation where an autosome, the 3rd chromosome of D. persimilis, coexists with a homologue that developed into a sex chromosome, the X₂ in D. miranda. Except for certain inversions and a few minor translocations, these two chromosomes (X₂ and the 3rd) still look alike as polytene elements. However, in hybrid males pairing of the two chromosomes, the X₂ and 3rd, is rare, while in female hybrids it occurs frequently. — ³H-TdR labeling shows that while the X₂ and 3rd chromosomes replicate synchronously in hybrid female, in the hybrid male the former completes its replication earlier than the 3rd chromosome, as do the two arms of the X₁ (XL and XR). The frequency and relative intensity of ³H-TdR labeling of each site of the X₂ and that of the 3rd chromosome in hybrid males closely agree with those of the corresponding sites in the X₂ of the miranda male and the 3rd chromosome of the persimilis male (or female), respectively. The results suggest that timing and rate of replication of the X₂ are determined autonomously and follow the pattern in the respective parental species.     

Toward a complete linkage map of the human X chromosome: regional assignment of 16 cloned single-copy DNA sequences employing a panel of somatic cell hybrids.

Closely linked restriction fragment length polymorphisms (RFLPs) are potentially useful as diagnostic markers of genetic defects, and, in principle, RFLPs can be employed to construct a complete linkage map of the human genome. On the X chromosome, linkage studies are particularly rewarding because in man more than 120 X-linked genes are known. Thus, it is probable that each X-specific RFLP will be of use as a genetic marker of one or several X-linked disorders. To facilitate the search for closely linked RFLPs, we have regionally assigned 16 cloned DNA sequences to various portions of the human X chromosome, employing a large panel of somatic cell hybrids. These probes have been used to correlate genetic and physical distances on Xp, and it can be extrapolated from these data that the number and distribution of available Xq sequences will also suffice to span the long arm of the X chromosome.     

A triterpene acid constituent of Salvia lanata

The petrol extract of the whole plant (aerial parts and roots) of Salvia lanata yielded a new triterpene acid, 3-epi-ursolic acid.     

Factors modifying radiation induced stimulation in plants: Pre-irradiation seed moisture content

Summary The effect of moisture content of seeds at the time of irradiation in relation to radiation-induced stimulation was investigated on rice (Oryza sativa c.v. D-6-2-2). The optimum moisture content was 8% for stimulation measured as seedling height. It is concluded that seed moisture at the time of irradiation plays an important role in the expression of stimulation and its reproducibility.     

Relationship of Cob characters with Grain Morphology in Maize (Zea mays,Poaceae)

Twenty varieties of maize (Zea mays, Poaceae) were studied through 11 attributes in three to seven randomly selected plants of each variety with a view to understanding the effect of cob characters on technologically desirable grain qualities. Canonical discriminant analysis showed thatproductivity (determined by total grain weight/cob, cob diameter and average grain weight) was the most discriminating among varieties followed by round grains fraction (represented by whole top and middle flat grains, number of rows and grain count/surface area), middle flat grains (composed of middle flat grains and grain count/surface area) and shape of the cob (determined by shape index, total grain weight/cob and cob diameter), which accounted for 35.1, 18.3, 12.2, and 9.8% of the total variance, respectively. In the light of these results, tentative norms have been suggested to evolve maize varieties of superior technological properties and yet retain high productivity. A cylindrical cob of large diameter with highest number of grains/area and smallest possible number of rows together constituted an ideal combination to achieve the objectives. Such possibilities in the light of available information are discussed.     

Effect of selective muscarinic receptor agonists and antagonists on active-avoidance learning acquisition in rats

Effect of some selective muscarinic receptor agonists and antagonists was investigated on learning acquisition in an active-avoidance paradigm in rats which records an anticipatory conditioned avoidance apart from the classical conditioned avoidance response. The muscarinic M1 agonists, arecholine, pilocarpine and McN-A-343, facilitated learning acquisition, which was attenuated by the selective M1 antagonist, pirenzepine. On the other hand, M2 receptor agonist, carbachol, and physostigmine, induced a dose-related dual response, with lower doses retarding and higher doses facilitating the learning acquisition. The former effect was attenuated by gallamine, a muscarinic M2 antagonist, while the latter response was inhibited by pirenzepine, indicating that these putative M2 receptor agonist lose their receptor specificity on dose increment. The selective M2 receptor antagonists, gallamine and AF-DX 116, facilitated learning acquisition, which was inhibited by pirenzepine and the acetylcholine synthesis inhibitor hemicholinium. The results support the cholinergic hypothesis of learning and memory and indicate that M1 receptor agonists and M2 receptor antagonists are likely to prove beneficial in memory deficits. The data also indicates that the clinical dose of some drugs, like physostigmine, needs to be carefully established for optimum therapeutic benefit.     

Effects of muscarinic receptor agonists and antagonists on response of non-extensor rats to maximal electroshock

Rats which do not respond consistently to maximal electroshock by exhibiting the classical hindlimb extensor response, are designated as 'flexors', and can serve as a useful experimental model for investigating seizure mechanisms. 20-25% Charles Foster rats exhibit the flexor status and were used in this study. The flexor rats were converted to extensors by acetylcholine (icv), physostigmine (ip) and the selective muscarinic M1 receptor agonists, arecholine (ip) and McN-A-343 (icv). This conversion of flexors to extensors was significantly attenuated by M1 receptor antagonists scopolamine (ip) and pirenzepine (icv). The M2 receptor agonist, carbachol (icv), had no effect in lower doses but induced conversion of flexor rats to the extensor status only in very high doses which may be due to loss of receptor specificity on dose increment. The M2 receptor antagonists, gallamine (icv) and AF-DX 116 (ip), also induced significant conversion of flexors to extensors, which was dependent upon the availability of neuronal acetylcholine since the effects were attenuated following pretreatment with hemicholinium, an inhibitor of acetylcholine synthesis. The results suggest that the central cholinergic system has a facilitatory pro-convulsant effect, mediated through the muscarinic M1 receptors, an action modulated by the M2 receptors.