Localization of some steroidogenic enzymes in the ovary of the rabbit

The distribution of delta 5-3 beta-HSD, peroxidase and cytochrome oxidase in immature, sexually mature and pregnant rabbit ovary has been studied histochemically. Corpora lutea are found only in pregnant rabbits. delta 5-3 beta-HSD is present in the theca interna of mature follicles, corpora lutea and interstitial gland cells but is absent in the granulosa cells of both developing and mature follicles. The granulosa cells of mature and developing follicles, hypertrophied theca interna and the luteal cells all show intense cytochrome oxidase activity. Peroxidase is present in the corpora lutea only. It is suggested that delta 5-3 beta-HSD in the theca interna and interstitial gland cells is the enzyme responsible for steroid synthesis in the ovaries of immature as well as sexually mature rabbits, while peroxidase and delta 5-3 beta-HSD present in the corpora lutea together regulate luteal steroidogenesis during pregnancy. The intense cytochrome oxidase activity together with peroxidase and delta 5-3 beta-HSD confirms the observations that this tissue is a site of intense oxidative activity.     

Mycobacterium tuberculosis ClpX Interacts with FtsZ and Interferes with FtsZ Assembly

FtsZ assembly at the midcell division site in the form of a Z-ring is crucial for initiation of the cell division process in eubacteria. It is largely unknown how this process is regulated in the human pathogen Mycobacterium tuberculosis. Here we show that the expression of clpX was upregulated upon macrophage infection and exposure to cephalexin antibiotic, the conditions where FtsZ-ring assembly is delayed. Independently, we show using pull-down, solid-phase binding, bacterial two-hybrid and mycobacterial protein fragment complementation assays, that M. tuberculosis FtsZ interacts with ClpX, the substrate recognition domain of the ClpXP protease. Incubation of FtsZ with ClpX increased the critical concentration of GTP-dependent polymerization of FtsZ. Immunoblotting revealed that the intracellular ratio of ClpX to FtsZ in wild type M. tuberculosis is approximately 1∶2. Overproduction of ClpX increased cell length and modulated the localization of FtsZ at midcell sites; however, intracellular FtsZ levels were unaffected. A ClpX-CFP fusion protein localized to the cell poles and midcell sites and colocalized with the FtsZ-YFP protein. ClpX also interacted with FtsZ mutant proteins defective for binding to and hydrolyzing GTP and possibly for interactions with other proteins. Taken together, our results suggest that M. tuberculosis ClpX interacts stoichiometrically with FtsZ protomers, independent of its nucleotide-bound state and negatively regulates FtsZ activities, hence cell division.     

Changes in the levels of superoxide anion radical and superoxide dismutase during the estrous cycle of Rattus norvegicus and induction of superoxide dismutase in rat ovary by lutropin

Superoxide dismutase, which has been shown to be present in a number of tissues, exhibits cyclic changes during the reproductive cycle of rats. An inverse correlation is seen between the levels of superoxide dismutase and superoxide radical. In immature, pseudopregnant rats, primed with human Chorionic Gonadotropin, lutropin seemed to induce ovarian superoxide dismutase, which could be blocked significantly by the introduction of anti-LH serum. These results point out the specific induction of superoxide dismutase by lutropin. It is reasonable to postulate that during luteal functioning, luteinizing hormone induces superoxide dismutase which in turn seems to play a central role generating hydrogen peroxide from superoxide anion radicals. Hydrogen peroxide, thus formed, drives the peroxidase-ascorbate system, responsible for production of progesterone.     

Reversal of Abscisic Acid-Induced Stomatal Closure by trans-Cinnamic and p-Coumaric Acid

Abscisic acid (ABA)-induced increase in stomatal diffusive resistance (SDR) in excised leaves of bean (Phaseolus vulgaris L. cv Pencil Pod) and maize (Zea mays L. cv Golden Bantam) is inhibited by low concentrations of trans-cinnamic acid (TCA) (1 micromolar) and p-coumaric acid (PCA) (10 micromolar) when given together with ABA (10 micromolar) in the transpiration stream through the cut end of the petiole or leaf blade. A concentration effect is observed both in the ABA action and its reversal by phenolic acids. Leaves having attained a high diffusive resistance in ABA solution recover rapidly when transferred to water. ABA (10 micromolar) induced closure of the stomata in onion, Allium cepa L. and Vicia faba epidermal peels. This is associated with loss of K⁺ from guard cells. In the presence of TCA (10 micromolar) and PCA (10 micromolar) K⁺ is retained in the guard cells with open stomata. The dark closure of stomata is also inhibited by TCA and PCA. It is suggested that these phenolic acids may inhibit the ABA effect by competing with or acting on some ABA-specific site, probably located on the plasma membrane, regulating flux of K⁺ ions. A weak association of ABA with the plasma membrane is envisaged because of the rapid recovery obtained upon transferral of the leaves to water.     

Interaction of non-intercalative drugs with DNA: Distamycin analogues

Distamycin and netropsin are two oligopeptides which bind to DNA in a nonintercalative manner. Analogues of distamycin have been synthesized and their binding with poly d(A-T) studied using ultraviolet absorption spectroscopy. Preliminary biological activity tests on a gram positive bacteria using these analogues have also been carried out Based on the lecture given by Dr. V. Sasisekharan at the Royal Society of Chemistry (Deccan Section) Bangalore, 26 June 1984.     

Effect of phenolic compounds on abscisic acid-induced stomatal movement: Structure – activity relationship

Application of abscisic acid (ABA) brings about stomatal closure within 30 min in epidermal peels of Vicia faba . A number of phenolic compounds antagonise the effect of ABA. Derivatives of benzoic acid, cinnamic acid, coumarin and flavonoids have been studied in order to establish structure – activity relationship. Derivatives of benzoic acid reverse the ABA effects. Coumarin, esculetin and three hydro derivatives of cinnamic acid fail to show the anti-ABA activity. Thus, the presence of parahydroxyl group and double bond in the side chain is necessary for anti-ABA activity.     

Over-expression of superoxide dismutase and lack of surface-thiols in spermatozoa: inherent defects in oligospermia.

The infertility associated with oligospermia had been suspected to be a direct consequence of the impairment in fertilizing ability of the spermatozoa rather than the presence of low sperm number per se. This study defines some of these impairments, which include an over expression of superoxide dismutase, poor superoxide anion radical generation capacity and a lack of sperm-surface thiols in oligospermia. The abnormal biochemical make-up of spermatozoa could explain their low fertilizing ability in case of oligospermia.     

Superoxide anion radical induces lipid phase transitions that mimic temperature-induced phase-transition phenomenon of membrane lipids

A biological membrane is shown to undergo lipid-phase transition leading to increased membrane fluidity when exposed to extraneously generated superoxide anion radical. This phase-transition is several folds higher in magnitude when compared to the temperature-induced fluidity change at the transition temperatures. This finding could have significant importance since an altered membrane configuration may involve aspects of biochemistry, biophysics or physiology.