Seema Srivastava

Synthesis of phytochelatins and modulation of antioxidants in response to cadmium stress in Cuscuta reflexa--an angiospermic parasite.

Effect of cadmium on growth, antioxidative enzymes namely catalase, peroxidase, glutathione reductase, level of glutathione and phytochelatin synthesis was investigated in callus and seedlings of Cuscuta reflexa. A time, concentration and tissue dependent response of Cd was observed. Cd inhibited the growth of callus and seedlings by 50% at 300 and 500 micromol/L concentrations, respectively. Shorter exposure of low concentration of Cd led to augmentation of antioxidant activity, both in callus and seedlings, while longer exposure and high concentration of Cd led to a concentration dependent decrease in callus. Analysis of phytochelatin (PC) synthesis in callus and seedlings of C. reflexa revealed both quantitative and qualitative changes. Cd at low concentrations led to synthesis of predominantly PC4, while at higher concentrations, PC3 was the major form being synthesized. Amelioration of antioxidative systems of C. reflexa in response to Cd stress might be playing a protective role, alleviating the damaging effects of ROS, generated during Cd stress. Concomitantly, chelation and sequestering of toxic Cd ions in this parasite was mediated by synthesis of PC. The response to Cd stress shown by this holoparasitic plant was found to be similar to those of non-parasitic plants (hosts).

In search of new chemical entities with spermicidal and anti-HIV activities

Several compounds belonging to 2-isoxazolines (4,5a-c), isoxazoles (3,6a-c) and 1-amino-1-cycloalkyl-2-substituted phenyl ethanes (16-18,a-e) have been synthesised and found to possess spermicidal activity. Out of these a couple of compounds (5a and 6a) exhibit anti-HIV activity.

Syntheses and biological evaluation of 3-substituted amino-1-aryl-6-hydroxy-hex-2-ene-1-ones as antioxidant and hypolipidemic agents

A new series of compounds belonging to 3-substituted amino-1-aryl-6-hydroxy-hex-2-ene-1-ones (4-12a-e) have been synthesized and evaluated for antioxidant and hypolipidemic activities. Amongst all the synthesized compounds, seven compounds, namely 5b, 5d, 6e, 8a, 8b, 10b and 11a, exhibit better antioxidant activity than probucol. Two compounds, 5d and 10b, have been evaluated in detail for antioxidant and hypolipidemic activities and show comparable activity profile to that of probucol and guggulipid. From the present study it may be postulated that the mechanism of action of these compounds could be through activation of lecithin cholesterol acyltransferase (LCAT), liver lipolytic activity, increased faecal bile acid secretion and inhibition of hepatic cholesterol biosynthesis.

Phonons and heat capacity of poly(L-leucine)

Poly(l-leucine) is one of the poly(amino acids) having a bulky hydrophobic side chain. For want of full phonon dispersion curves and density-of-states on this biopolymer Roles et al. have interpreted their heat capacity data in a limited way. In the present paper, we report the Fourier transform infra-red (FTi.r.) spectra and an analysis of the normal modes and their dispersion based on the calculations for an infinite chain and Urey Bradley force field with intrachain interactions only. The results thus obtained agree well with our FTi.r. spectra and the Raman frequencies reported by Koenig et al. Several earlier assignments have been revised. A special feature of some dispersion curves is their tendency to bunch in the neighbourhood of the helix angle. This has been attributed to the presence of strong intramolecular coupling between different types of motions. Repulsion between the dispersion curves is also observed. The heat capacity obtained from the dispersion curves via density-of-states is in very good agreement with the experimental measurements beyond 220 K. It is observed that the main contribution to heat capacity comes from the modes involving the coupling of the backbone skeletal and side-chain motions.

Search for new chemical entities as menses inducing agents

In continuation of an ongoing program on developing nonsteroidal pregnancy interceptives to be used as a menses regulating agent, a new class of compounds belonging to 3-substituted amino-1-aryl-6-hydroxy-hex-2-ene-1-ones series has been investigated for pregnancy interceptive activity in the hamster and rat. The compounds were administered (subcutaneous) on days 4-8 (hamster) and 5-9 (rat) post coitum (PC). The animals were laparotomized on days 12 (hamster) and 16 (rat) PC. To derive percent efficacy, the total number of implantation was divided by the number of normal and resorbed implantations. Among the 14 compounds evaluated, three were found to intercept pregnancy by 100%. Another compound was active by 75%, whereas the rest were inactive. None of the active compounds were, however, active in rat with this schedule. Results indicate that the observed species- and schedule-specific activity owes its origins to differences in the implantation physiology and early post-implantation development between the two species. The study, nevertheless, offers an insight to the new class of compounds for this activity.

STABILITY AND TRANSITION IN A DNA TETRAPLEX: A MODEL FOR TELOMERES

The theory of cooperative transition has been applied to explain the stability and melting behavior in a DNA tetraplex, which is a model for telomeres. The transition profile and heat capacity curves are best explained in terms of two variable parameters, namely nucleation and propagation parameters. The effect of strand concentration and consequent change in enthalpy is reflected in the sharpness of transition and change in nucleation parameter. The same is true for greater stabilization in the presence of K+ ions, compared with the Na+ ion. It is ascribed to dipole and dipole-induced interactions.

Heat capacity and phonons in ω-helical poly-l-phenylalanine

Abstract Although several polypeptides are known to exist in ω-helical (fourfold) form, no work has yet been reported on phonon dispersion in these important biomacromolecules. As a consequence, study of the thermodynamical behavior also remains incomplete. Poly-l-phenylalanine is the simplest polypeptide which goes into this rare form. In the present communication we report a comprehensive study of the normal mode analysis, phonon dispersion, density of states, and heat capacity of ω-poly-l-phenyIalanine derived from the dispersion curves. One of the characteristic features of the dispersion curves is the repulsion between pairs of modes, viz. (1300 and 1289 cm-1), (1082 and 1053 cm-1), and (948 and 915 cm -1). In the low-frequency region the dispersion curves have regions of high density of states at multiples of half-helix angle. Such regions where (∂ω/∂κ) → 0 are akin to critical points known as Von Hove singularities.

Phonon dispersion and heat capacity in polyfuran

A study of the normal modes of vibration and their dispersion in polyfuran (Pfu) based on the Urey-Bradley force field is reported. It provides a detailed interpretation of IR and Raman spectra. Characteristic features of dispersion curves such as regions of high density-of-states, repulsion and character mixing of dispersive modes are discussed. Predictive values of heat capacity as a function of temperature are calculated.

Phonon Dispersion in Polypyrrole

A study of the normal modes of vibration and their dispersion in polypyrrole (PPY) based on the Urey-Bradley force field is reported. It gives a fuller interpretation of previously reported FTIR spectra. Characterstic features of dispersion curves, such as regions of high density-of-states, repulsion, and character mixing of dispersive modes, are discussed. Predictive values of heat capacity as a function of temperature are reported.

Accessory coracobrachialis: a case report with its morphological and clinical significance

MethodDuring the routine dissection of a male cadaver for teaching undergraduate medical students, a variation was seen in the morphology of coracobrachialis muscle.ResultsThe presence of an anomalous head of coracobrachialis muscle which had muscular origin from an abnormal site on coracoid process and thin tendinous insertion at the junction of brachialis and triceps muscle in common with insertion of coracobrachialis muscle to the medial surface of the middle of the shaft of the humerus.ConclusionCoracobrachialis muscle can have variant origin related to its embryogenesis with its clinical and surgical significance.