The autoimmune regulator (AIRE) is a DNA-binding protein

The autoimmune regulator (AIRE) protein is a putative transcription regulator with two plant homeodomain-type zinc fingers, a putative DNA-binding domain (SAND), and four nuclear receptor binding LXXLL motifs. We have shown here that in vitro, recombinant AIRE can form homodimers and homotetramers that were also detected in thymic protein extracts. Recombinant AIRE also oligomerizes spontaneously upon phosphorylation by cAMP dependent protein kinase A or protein kinase C. Similarly, thymic AIRE protein is phosphorylated at the tyrosine and serine/threonine residues. AIRE dimers and tetramers, but not the monomers, can bind to G-doublets with the ATTGGTTA motif and the TTATTA-box. Competition assays revealed that sequences with one TTATTA motif and two tandem repeats of ATTGGTTA had the highest binding affinity. These findings demonstrate that AIRE is an important DNA binding molecule involved in immune regulation.

Sperm disposal system in spermatic granuloma: a link with superoxide radicals

Spermatic granulomas are believed to maintain "physiological harmony" in the male reproductive tract by maintaining a balance of hydrostatic pressure post-vasectomy. The mechanism for the disposal of deposited spermatozoa in the granuloma core is not clear. A fourfold rise in the production of superoxide along with ascorbyl and dienyl radicals and a 50% drop in the production of nitric oxide (NO) radicals by granuloma tissue hints that a reaction between NO and superoxide radicals could lead to the formation of peroxynitrite species which may contribute to the disposal of spermatozoa in the granuloma core. A higher protease activity and low hypoxanthine content in the granuloma indicates that a free radical driven sperm disposal system is active in granulomas.

Regional variations in thiol distribution pattern and superoxide dismutase activity of the male reproductive tract of the rat modulate the transport of spermatozoa through the epididymis and vas deferens

BACKGROUND

Contractile activity of the muscular coat of the epididymis wall is considered the major driving force for the propulsion of sperm through the male reproductive tract.

METHODS

Region-specific changes in the status of membrane thiols and the free radical scavening potential of the male reproductive tract of the rat were observed.

RESULTS

The present study shows that the local biochemical milieu has some influence on the transport of spermatozoa through the male reproductive tract. The vas deferens showed a higher level of superoxide dismutase activity and a low profile of thiol exposure.

CONCLUSION

We conclude that the strong scavenging potential and the lesser thiol exposure of the vas create an apparently inert vas lumen which facilitates the transit of spermatozoa through the vas.

Increased appearance of inducible nitric oxide synthase in the uterus and embryo at implantation

The aim of this study was to investigate the presence of iNOS in the murine uterus and embryo at implantation. Western blot analysis showed the presence of a 130-kDa band with strong reactivity to anti-iNOS antibody in the pre- and peri-implantation stage uteri. This band was faint in the postimplantation uteri. Immunocytochemical studies showed a heavy localization of iNOS specifically on the apical cells of the uterine endometrium in the pre- and peri-implantation stages. But the postimplantation uteri showed resorbed endometrium showing weaker expression of iNOS. The iNOS was induced by estrogen and the induction was intensified when progesterone was given along with estrogen. This truly mimics the in vivo situation since implantation in mice occurs when an estrogen surge occurs on a background of progesterone. The embryos too express iNOS at the peri-implantation stage. We suggest that iNOS expressed at peri-implantation would lead to enhanced NO production, which could act as a vasodilator and an angiogenic mediator. These effects could promote the attachment of the blastocyst to the uterus.

Altered molecular dynamics and antioxidant status in the spermatozoa in testosterone-induced oligospermia in mouse

Though supraphysiological doses testosterone (T) and its derivatives are known to suppress spermatogenesis in mammals by interfering with the hypothalamus-pituitary axis leading to oligozoospermia, no study has been performed to evaluate the integrity of the sperm cells produced by such individuals. In T-induced oligozoospermia in the mouse, the spermatozoa showed suppressed zona-binding ability though the motility and viability remained unchanged. In order to assess whether this decreased zona-binding ability is due to perturbations in the mechanical properties of the sperm membranes, we attempted to examine the molecular dynamics employing a lipophilic spin label (16-doxyl stearate) and a protein-binding label (Mal-Net) in two sets of independent experiments. The results showed that the rotational freedom of lipophilic molecules reduced significantly within the first week of T-treatment. During weeks 1 through 4, the protein rotation was found to be retarded significantly. We observed a sharp increase in the ascorbyl radical associated with the cauda epididymal spermatozoa and epididymal fluid of testosterone-treated mice. Moreover, the glutathione (GSH) content in the spermatozoa and the epididymal fluid increased significantly after testosterone-treatment. Further, there was a elevation in the superoxide dismutase (SOD) activity and suppression in the superoxide anion radical generated by the cauda epididymal spermatozoa of testosterone-treated animals. A change in the mechanical properties of a bilayer could modify both the mechanical properties and the function of incorporated proteins. In many instances, a liquid-crystalline bilayer is necessary for protein function. It is likely that the change in the physical properties of sperm membranes might cause the inhibition of enzymes associated with spermatozoa after T-treatment. The alterations in the sperm membrane structure and the antioxidant potentials of both the spermatozoa and the cauda epididymal fluid could also account for the decrease in the zona-binding index of the spermatozoa in T-treated animals. Thus, this study demonstrates for the first time that supraphysiological doses of testosterone could modify the mechano-dynamic properties of sperm membranes and could perturb the redox status of both spermatozoa and the epididymal fluid.

NADPH dependent superoxide generation in the ovary and uterus of mice during estrous cycle and early pregnancy

NADPH dependent O2- production in the ovary and uterus of cycling and pregnant mice was estimated employing a novel technique of time-lapse electron spin resonance enhancement of a superoxide-trapping spin trap. The NADPH dependent O2- generation in the mouse ovary increased during the early pre-ovulatory phase in cycling females and during extended luteal phase in pregnant animals. A peak of uterine NADPH dependent O2- production at proestrous in the cycling animals at pre-implantation phase in pregnant animals suggested a contribution of this enzyme towards generating high levels of superoxide anion radical during the respective stages. Both ovarian and uterine NADPH dependent O2- production appeared to be LH-inducible.

Regional heterogeneity in intracellular distribution of superoxide and hydrogen peroxide within the sperm and its relation to sperm development

This study was performed to understand the regional distribution of superoxide anion radicals and hydrogen peroxide within the spermatozoa of mice during both normal and altered situations of epididymal maturation. The intracellular O2*- levels were probed employing dichlorodihydrofluorescein diacetate (DDF) as a reporter. The testicular spermatozoa from normal animals showed strong regional heterogeneity in the DDF fluorescence patterns over the various domains. Vasectomy resulted in strong inhibition in the O2* levels of spermatozoa at all stages of maturation. Interestingly, the fluorescein diacetate staining pattern was strong in the head of spermatozoa from the testis, caput, corpus, and cauda region. Further. there was a progressive reduction in the fluorescence in the head region in the spermatozoa toward the cauda region. The midpiece and tail showed moderate fluorescence, which also diminished as the spermatozoa matured. The spermatozoa from the vas deferens exhibited a weak fluorescence over the head domain, with the other domain staining extremely weak. Here again, vasectomy introduced considerable loss in the fluorescence intensity. The implications of programmed production of reactive oxygen species in specific domains of the spermatozoa during various stages of development are discussed.

Role of ions and ion channels in capacitation and acrosome reaction of spermatozoa

Capacitation and acrosome reaction are important prerequisites of the fertilization process. Capacitation is a highly complex phenomenon occurring in the female genital tract, rendering the spermatozoa capable of binding and fusion with the oocyte. During capacitation various biochemical and biophysical changes occur in the spermatozoa and the spermatozoal membranes. Ions and ion channels also play important roles in governing the process of capacitation by changing the fluxes of different ions which in turn controls various characteristics of capacitated spermatozoa. Along with the mobilization of ions the generation of free radicals and efflux of cholesterol also plays an important role in the capacitation state of the spermatozoa. The generation of free radical and efflux of cholesterol change the mechanodynamic properties of the membrane by oxidation of the polyunsaturated lipids and by generating the cholesterol free patches. The process of capacitation renders the spermatozoa responsive to the inducers of the acrosome reaction. The glycoprotein zona pellucida 3 (ZP3) of the egg coat zona pellucida is the potent physiological stimulator of the acrosome reaction; progesterone, a major component of the follicular fluid, is also an inducer of the acrosome reaction. The inducers of the acrosome reaction cause the activation of the various ion-channels leading to high influxes of calcium, sodium and bicarbonate. The efflux of cholesterol during the process of capacitation alters the permeability of the membrane to the ions and generate areas which are prone to fusion and vesiculation process during the acrosome reaction. This review focuses mainly on effects of the ion and ion-channels, free radicals, and membrane fluidity changes during the process of capacitation and acrosome reaction.

Effect of estradiol and selected antiestrogens on pro- and antioxidant pathways in mammalian uterus

In this study, we examined the effect of 17 beta-estradiol and selected antiestrogens on uterine NADPH-oxidase activity, superoxide dismutase (SOD) activity, hydride (H.-), dienyl radical and O2 -radical generation, and membrane fluidity. NADPH oxidase activity was positively modulated in estradiol-treated animals and negatively regulated in animals that received injections of AF-45, RU-39411, tamoxifen, or ICI-182780. The SOD activity was markedly reduced in estradiol-treated animals when compared with the control animals. A positive modulation of SOD activity was observed upon treatment with AF45, RU39411, tamoxifen, and ICI 182780, though the potency varied among the individual test compounds. We observed detectable H(.-)-radical generation as evidenced from MNP H.- adduct formation in the uterine cell preparations from untreated control animals. Estradiol produced a tremendous augmentation in the superoxide radical profiles in uterine cell preparations compared to the control levels. All the other compounds that were tested significantly lowered the superoxide levels in the test set-up. AF-45, RU-39411, tamoxifen, and ICI-182780 induced varying orders of suppression of H(.-)-radical generation in the test subjects. There was a significant enhancement in membrane fluidity, hydride radical levels, and dienyl radical generation in the estradiol-treated group. All the antiestrogens did not exhibit a similar action on these parameters. RU-39411 exhibited antiestrogen-like activity in modulating hydride levels and membrane fluidity, whereas it stimulated dienyl radical generation. Thus our tests showed that the selected antiestrogens failed to show estrogen-like activity in these assays. It appears that estradiol exerts feedback control over pro- and antioxidant pathways and that markers of oxidative status could be used as a measure to evaluate the antiestrogenic activity of estradiol agonists/antagonists.

Active oxygen species in blue light mediated signal transduction in coleoptile tips

Coleoptile tip is a blue-light sensitive tissue possessing a "blue light receptor" which, upon activation, elicits a signal cascade resulting in phototropic curvature of the coleoptile. In this context, the nature of the photoreceptors and the exact mechanism through which the photoreceptors transduces the signal across the membrane are not clear. In this study, we attempted to examine whether the blue light receptor perturbs redox status of the coleoptile tip and sensitizes molecular oxygen as part of the signal reactions. Coleoptile tips of Sorghum bicolor and wheat (Triticum vulgare) grown in the dark showed pronounced ascorbate free radical signal, which diminished upon illumination with weak blue light for one minute. Concomitantly, the generation of superoxide radical by the coleoptile tip was augmented upon illumination with blue light. Various thiol blockers tested in this study caused powerful inhibition of blue light induced superoxide anion radical generation. Treatment with these thiol blockers, with the exception of NEM, resulted in marked increase in the levels of ascorbic acid free radical in the blue light irradiated coleoptiles. The blue light stimulated O*-2-generation by the coleoptile tip homogenate is also inhibited by the inhibitors of blue light responses viz phenylacetic acid, potassium iodide, and sodium azide. Based on our observations, we postulate that the activated blue light receptor present in the coleoptile tip sensitizes molecular oxygen to superoxide anion radical in the tip initializing the blue light signal cascade reactions.

Influence of a melatonin implant on the free radical load in avian thyroid and its relation with thyroid hormonogenesis

The primary aim of this study was to evaluate the effect of melatonin on the oxiradical load in avian thyroid. The superoxide free radicals have been spin trapped by EPR spectroscopy in the thyroid gland of Indian rock pigeon Columbia livia following melatonin implantation for two weeks. Melatonin implantation resulted in augmentation in the levels of superoxide radical in the thyroid gland of pigeons with a concomitant decrease in the levels of the total superoxide dismutase activity. This was also associated with increased lipid peroxidation. Melatonin implantation caused a significant increase in plasma levels of glucose. Plasma levels of thyroxine (T4) and triiodothyronine (T3) were lower in the melatonin-treated pigeons. However, the T3/T4 ratio was higher following melatonin implantation. Since iodination of tyrosine is an H2O2-dependent phenomenon, the inhibition in the activity of SOD could lead to impaired thyroid hormone synthesis.

Bicarbonate-dependent lipid ordering and protein aggregation are part of the nongenomic action of progesterone on capacitated spermatozoa

The nongenomic action of progesterone (P) on capacitated sperm in mediating acrosomal exocytosis operates through transmembrane signal transduction involving increased intracellular calcium ions and modulation of protein kinases and phospholipid metabolism through a second messenger pathway. Conflicting views exist regarding the nature of the nongenomic receptor of P. It is thought to be a cell-surface receptor having the properties of a calcium channel, chloride channel, bicarbonate/chloride exchanger, and gamma aminobutyric acid type A (GABA(A)). In this study, we tried to understand the role of bicarbonate and/or P in inducing membrane perturbations in capacitated and acrosome-reacting spermatozoa. We also attempted to characterize the membrane responses in P-stimulated and bicuculline-poisoned sperm. The presence of a high level of bicarbonate in the medium favored high rotational mobility of lipids and proteins in capacitated sperm. However, the capacitated sperm exhibited low lipid ordering and unaltered protein ordering in response to the high bicarbonate concentration. P and bicuculline appeared to bind to the same or similar binding sites, probably a GABA(A) receptor, eliciting similar motional perturbations in sperm membranes. It appears that both P and bicuculline can induce receptor aggregation and lipid ordering in sperm membranes, which alter the capability of sperm to bind zona pellucida, and that the P action on sperm takes effect through a bicarbonate-dependent signal transduction mechanism.

A genetic system involving superoxide causes F1 necrosis in wheat (T. aestivum L.)

A genetic system in wheat is described in which F1 produced by crossing a drought tolerant cultivar C306 and high yielding cultivar WL711 exhibits leaf necrosis leading to the death of the plant. The mechanism underlying hybrid necrosis is not yet known. The hybrid exhibited a higher level of superoxide anion compared to the healthy leaves of parents at similar developmental stages. This increase in superoxide generation preceded necrotic lesion formation and displayed a gradient from the leaf tip to base. The leaf tip where necrotic lesions make their first appearance exhibited a higher level of superoxide compared to the base. Superoxide anion thus appears to play a vital role in necrosis of leaves in F1 hybrid. This genetic system can be a model system for understanding cell death in higher plants.

Acrosome reaction inducers impose alterations in repulsive strain and hydration barrier in human sperm membranes

Spin labeling studies of the lipophilic domains of human spermatozoa during capacitation and during acrosome reaction (AR) under the influence of selected AR-inducers were performed. Significantly enhanced rotational function of molecules was obvious during capacitation, with no significant changes in membrane packaging or the lateral diffusion of molecules. The AR inducers appeared to restrict the rotational freedom of molecules, dramatically enhancing the lateral diffusion and ordering coefficients. A significant decrease in superoxide anion generation was observed in the acrosome reacted groups when compared to the non-acrosome reacted groups. A high level of superoxide anion radical (O2.-) level maintained in capacitated spermatozoa would add to the Van der Waal's repulsive forces at the polar head of phospholipids, holding the membrane in strain where the molecular enjoy little freedom for lateral motion. A sudden drop in the levels of O2.- in spermatozoa upon addition of AR inducers could abruptly release the local hydrophobic repulsive strain within the membrane. This loss of hydration barrier explains the observed enhancement in lateral diffusion profiles of lipids and the packaging of molecules. It is reasonable to assume that these phenomena could be amplified further by interplay of Ca2+ by modifying the local charge aggregation. Thus, we would conclude that AR inducers release the oxyradical load in capacitated spermatozoa, which would modify the repulsive strain and hydration barrier forces in the lipophilic domains permitting vesiculation of the membranes. It appears that various acrosome reaction inducers act as effectors of grossly similar physical alterations in sperm membranes and that the resulting signal cascades proceed through intercalating biochemical sequences.

Superoxide anion radical generation as a temperature stress response in the gills of freshwater catfish Heteropneustes fossilis: role in mucus exudation under elevated temperature

Temperature induced superoxide anion radical (O2-) generation in vivo has been demonstrated in the gills of Heteropneustes fossilis by electron spin resonance (ESR) spin trapping. Temperature exposures from 25 degrees C to 37 degrees C for various times (1-4 hr) caused generation of O2- in the gill. The acid mucopolysaccharide test was conducted in gill sections during elevated temperatures. The results showed an increased activity of mucopolysaccharide in gills which indicate an increased mucus secretion in gills during elevated temperatures. The detectable stable levels of O2- in the gill at 32 and 37 degrees C temperature exposures point towards a probable role for this radical in the exudation of mucus under elevated temperature.

Regulation of superoxide anion radical-superoxide dismutase system in the avian thyroid by TSH with reference to thyroid hormonogenesis

This study shows that superoxide dismutase is present in the thyroid gland of pigeons as a constitutive enzyme serving as an antioxidant against oxygen toxicity. Exogenous administration of thyrotropin induced thyroidal superoxide dismutase with a simultaneous burst in superoxide anion radical levels during the initial phase of hormone treatment. The superoxide radical generated was completely scavenged by SOD during the late phase of TSH-treatment, presumably as an adaptive measure to check the oxygen burst. TSH failed to augment serum T3 levels, although the thyroxine level in the serum was elevated. The peak level of SOD activity profile in the thyroid gland correlated very well with the peak level of thyroxine concentrations in the serum of pigeon. It is reasonable to postulate that the thyroidal SOD in homeotherms serves a dual role, firstly as a strategic antioxidant enzyme to protect the thyroid gland against the degenerative influence of toxic oxyradicals and secondly to provide H2O2 for thyroid hormone biosynthesis. Our results confirm the previous observations that TSH is mainly thyrotropic in birds and that it has no influence on the peripheral activation of thyroxine to triiodothyronine by stimulating the extra thyroidal 5'-deiodinase activity.

Vasectomy-induced superoxide dismutase inactivation in the male reproductive tract of rat: a prerequisite for spermatic granuloma formation

Post vasectomy spermatic granuloma formation is considered as a favourable development for vasectomized subjects as it maintains physiological hydrostatic pressure within the male reproductive tract. But, the 'state of the art' of the formation of granuloma after vasectomy is not well defined. The present study reveals a link between the postvasectomy free radical status of the male tract and spermatic granuloma formation after vasectomy. A surge in the rate of ascorbyl radical production, directly correlated with oxyradical stress and an abrupt fall in superoxide dismutase activity in the granuloma, indicates 'switching on' of a free radical-dependent machinery for the formation of granuloma after vasectomy.

Superoxide anion radical mediated dissection of rat sperm: an in vitro study

Sperm is highly sensitive to superoxide radical surge in the granuloma interior. To investigate possibility of a superoxide radical bomb, the role of an oxyradical on the spermatozoon was studied in vitro using potassium superoxide, a potent superoxide radical producer. Results confirm that the superoxide radical has a unique site-specific scissoring power.

Free radical mediated sperm-load management in the vagina of rats

The postcoitus phagocytic engulfment of spermatozoa following disintegration of a sperm cell has not been well understood until now. By monitoring the free radical status of the vagina in accordance with the various stages of the estrous cycle and the sperm-cutting power of vaginal flushing, a positive correlation has been detected that favors the superoxide theory of the sperm-cutting technique in vivo. This finding is also consistent with the previous experience of free radical bombing of spermatozoa in spermatic granuloma.

Activity profile of placental superoxide-superoxide dismutase system in pregnant mice and its possible relation with placental steroidogenesis

Placenta in mouse generate increasing quantities of superoxide dismutase from day 13 of pregnancy until parturition. This is associated with a concomitant reduction in the activity of superoxide radical. This findings points to the steroidogenic control of the later half of pregnancy by the placental axis. Parturition is associated with an abrupt spurt in superoxide radical. This is a novel finding and could be a consequence of the estrogen surge at labour. It is suggested that this abrupt increase in superoxide radical level at parturition may remould the placental membrane fluid at the point of its attachment with uterine membranes so as to facilitate the separation of placenta from uterus.

A programmed oxyradical burst causes hatching of mouse blastocysts

The emergence of the mammalian blastocysts from their thick glycoprotein investment known as the zona pellucida is an important, but poorly understood, event in embryogenesis. In this paper, we demonstrate that peri-hatching blastocysts generate a considerably high quantum of an active oxyradical species for an extremely short period of time when compared to the pre-hatching (unhatched) and post-hatching (hatched) blastocysts. Hatching could be induced in pre-hatching blastocysts by exposing them to superoxide artificially generated to match the observed peri-implantation stage specific levels of superoxide, without impairing their viability. These observations suggest the operation of a superoxide-dependent hatching initiation in developing mammalian embryos.

Neutralization of pregnancy-preventing activity of cabergoline, a dopamine agonist with progesterone

Cabergoline (Cab), a dopamine agonist, inhibits the production and/or release of prolactin and reduces progesterone biosynthesis. Cab at doses of 20 microg/kg/d and higher administered on Days 1, 2 and 3 of pregnancy prevented implantation of fertilized ova in all treated female rats. The pregnancy-preventing activity of Cab is attributed to a deficiency of progesterone since estradiol levels remain unchanged. To validate the hypothesis that progesterone deficiency is the cause of the infertility, exogenous progesterone was administered to Cab-treated pregnant female rats and their fertility assessed. Progesterone at a dose of 5 mg/kg/d sc was administered on Days 1 to 7 of pregnancy to female rats treated with Cab (20 and 60 microg/kg/d) on Days 1, 2 and 3 of pregnancy. All progesterone-treated animals became pregnant, and all mated female rats treated with Cab (60 microg/kg/d) and progesterone (5 mg/kg/d) on Days 1 to 7 inclusive became pregnant. In conclusion, progesterone can neutralize the pregnancy preventing activity of Cab. Pregnant female rats treated with Cab can be used to assay for progestagenic activity of compounds.

Free radical-induced liquefaction of ejaculated human semen: a new dimension in semen biochemistry

Even though the aminopeptidase and amylase are the major liquefying factors in the liquefaction process of the ejaculated semen-coagulum, the exact nature of "switching on" phenomena has not been elucidated yet. Monitoring the rate of production of the asborbyl radical, an indirect method for oxyradical-stress measurement, this prima facie study reports the involvement of oxygen radical in the liquefaction process of coagulated semen.

Characterization of a uterine luminal fluid protein ULF-250 using N-terminal microsequencing and RT-PCR identifies a novel estrogen-regulated gene in the rat uterus

We had previously identified an estrogen responsive protein ULF-250, synthesized and secreted by the estrous rat uterus, which is immunologically distinct from complement C3 and alpha2-macroglobulin. The N-terminal microsequencing of ULF-250 followed by sequence homology analysis showed that this protein is a new member of a class of estrogen responsive proteins in the uterus. Polymerase chain reaction with a ULF-250 specific primer yielded partial sequence information of its message. The observed pattern of ULF-250 message in the uterus during the various stages of the reproductive cycle in the rat suggested a possible regulation of ULF-250 message by 17beta-estradiol. Upstream sequencing of ULF-250 message and its promoter domains would provide insight into the mechanism of its regulation by estradiol.

Estrogen surge: a regulatory switch for superoxide radical generation at implantation

This study is undertaken to identify the regulatory switch for the activation of superoxide radical generation pathway and repression of superoxide dismutase (SOD) at the time of implantation using estrogen as a control factor and delayed implantation as a model system. The results revealed high SOD activity and negligible oxyradical generation in progesterone-treated animals on day-5 and day-8 (delayed implantation) while an enormous rise in oxyradical generation and an abrupt fall in SOD in animals which received both estrogen and progesterone injections were observed on days 5 and 8 of pregnancy. These results strongly suggest that estrogen regulates superoxide anion radical generation by lowering the SOD activity.

Metal binding and resultant loss of phototoxicity of alpha-terthienyl: metal detoxification versus alpha-terthienyl inactivation

The members of the plant family asteraceae are noted for their cosmopolitan distribution and their versatility is attributed to be largely due to their morphological adaptations. Interestingly members of this family are endowed with rich levels of secondary plant metabolites, many of which are photochemically active (Bakker et al. 1979; Kagan et al. 1989). The secondary plant metabolite alpha-terthienyl derived from the plant family asteraceae is among the new class of light activated insecticide. The photobiocidal effects associated with alpha-terthienyl in presence of sunlight and ultraviolet light (300-400 nm), has stimulated a great deal of interest in its toxic mechanism of action against a number of organisms including phytopathogenic fungi, nematodes and mosquito larvae. Trials under tropical conditions indicate a very high level of activity as a larvicide to mosquito. There is no cross resistance to this compound in malathion resistant mosquito larvae (Arnason et al. 1989). Even though many researchers feel that the phototoxicity of secondary plant metabolites has arisen independently many times in evolution as a defense mechanism, the physiological impact of such biologically active compounds in the plant producing them also should be addressed (Arnason et al. 1987). Moreover, the accumulation of secondary plant metabolites in the roots of many asteraceae members as is the case with alpha-terthienyl in marigold (Tagetes sp.) roots, hints towards their functional divergence. In this study, we demonstrate a potent heavy metal quenching activity of alpha-terthienyl.

Involvement of superoxide radical in signal transduction regulating stomatal movements

Stomatal movements are regulated by alternate phase transition in the lipophilic domains of membrane initiated by blue light through activation of plasmalemma redox system. ABA blocks the blue light activated redox reactions leading to the accumulation of superoxide (O2.-) radical inducing melting of the membrane and increased fluidity. Phenolic compounds which reverse the ABA effects reduce O2.- radical and thereby reverse phase transition in lipophilic domains of membrane. Stomatal movements thus appear to be regulated by blue light activated redox reactions involving formation of O2.- radical and its reduction by the reducing equivalents available in the GCPs.

Appearance of homogeneous smectic multilamellar microenvironments in biomembranes undergoing superoxide-initiated lipid peroxidation: lipid-dienyl radical accumulation and fluidity management in lipid bilayers

Erythrocyte ghosts were exposed to various levels of oxyradical shock in order to identify the extent of accumulation of peroxidative intermediates. Malondialdehyde reacting end products were the same in all different models. But, the accumulation of dienyl radical species increased with higher intensity of oxyradical shock. These dienyl radicals may rearrange to create a homogeneous smectic multilamellar microenvironment which may be more fluid in terms of the molecular dynamics.

Photochemical reaction sequences of blue light activated flavins: sensory transduction through free radical messengers

Flavin photochemistry involves the production of transient flavin free radicals which in turn sensitize molecular oxygen to generate superoxide. The blue light induced photochemical chain reaction of flavins may be blocked at two different levels by photoresponse inhibitors. A protein-bound/lipid-bound flavin located on the biomembrane may take part in the blue-light mediated sensory transduction by 'releasing' a 'free radical messenger' equivalent into the cell interior.

Free radical bombing of spermatozoa in spermatic granuloma: an attempt to prevent autoimmune switch-on

Even though vasectomy-associated reactions in subjects are established, the biochemical attributes of the granuloma cells enabling them to potently dispose of the accumulating spermatozoa remain unelucidated. This study demonstrates a careful "free-radical bombing" within the granuloma interior to efficiently disintegrate all the structural elements of the sperm cells, especially the proteins. A free radical triggered and instantaneous protein-disposal could be important in avoiding early post-vasectomy autoimmune triggering.

Photophysical alterations of erythrocyte membrane by 4,5',8-trimethyl psoralen: membrane response towards psoralen phototherapy

Despite the wide and versatile use of psoralen phototherapy in various dermal diseases including psoriasis and leukoderma, the proposed mechanism of action of psoralen is disputed. This study launches an original documentation of free-radical resulting in erythrocyte membrane damage studied by spin-labeling using the probes malnet and 5 doxyl stearate as protein and lipid domains, respectively. Both Type I and Type II photodynamics appear plausible and the therapeutic aspects of this innovation are being verified.

Abnormal physical architecture of the lipophilic domains of human sperm membrane in oligospermia: a logical cause for low fertility profiles

Three different domains of human sperm membrane, viz., the hydrophobic domains, the aqueous compartments and the surface proteins were probed to evaluate the molecular dynamics in these microenvironments in normal as well as oligospermic cases. Decreased rotational motion of the stearic spin-labels, designated rigid lipid matrix affording hindrance to the protein rotation in spermatozoa of oligospermic patients. The intrinsic tight anchoring of thiol containing proteins led to their increased ordering on the spermatozoa of such individuals. Fluorescence polarization studies revealed weaker hydrophobicity around these sperm proteins in oligospermia. Thus, this study identifies abnormal molecular mobility in the limiting membranes of oligospermic cells.

Transient thiol-expression and thiol disulphide cluster-receptor communications: a molecular basis for blastocyst-uterine interactions during implantation

The attachment of trophoblast to uterine epithelium during implantation is an intricate and complex instance of cell-cell communication, the molecular aspects of which remain rather undefined. In this study, we screened the surface domains of the pre-, peri- and post implantation mouse embryos with a thiol-specific probe. Transient thiol-expression in peri-implantation embryos suggested their involvement in implantation either through disulphide bridge establishment or through a communication between a thiol-disulphide cluster of the blastocyst and a corresponding receptor of the endometrium.

Exorbitantly enhanced protein gyration and erroneous membrane modification programs in spermatozoa after vasectomy: a biophysical basis for low infertility revival after vasectomy

Vasectomy induces an immediate biophysical incompetence in epididymal spermatozoa in terms of the erroneous execution of membrane configuration processes, premature membrane melting and untimely protein gyration. Disturbances in the planned expression 'foreign proteins' and the possible 'swinging off' of these molecules from the membrane crystals might tease the immune system and might deprive the spermatozoa of the essential recognizing terminals.

Methyl xanthine and altered biomembrane dynamics: demonstration of protein mobility and enzyme inhibition by caffeine in sperm model system

Treatment of spermatozoa with 10 mM caffeine increases the rotational mobility of thiol-containing proteins in a defined micellar micro-environment. This is associated with inhibition of superoxide dismutase activity and augmented superoxide anion radical generation. Increased sperm competence in presence of caffeine in human oligospermia is explained by these observations. Inhibition of cyclic phosphodiesterase by caffeine is suggested to be part of the observed lattice-rearrangement.

Programmed lipid peroxidation of biomembranes generating kinked phospholipids permitting local molecular mobility: a peroxidative theory of fluidity management

The lipid peroxidation profiles in the uterus of mature mice show cyclic alterations during the reproductive cycle. Similarly, during early pregnancy, alterations in lipid peroxidation are evident, keeping close pace with the superoxide anion radical levels and fluidity parameters reported elsewhere. This formulates a theory that a 'controlled' lipid peroxidation of biomembrane terminating at the accumulation of cyclic endoperoxides could rather enhance local molecular mobility because of the increased inter-molecular distance in these 'kinked-species'.

ABA-induced 'lipid melting' and its reversal by umbelliferone in the plasmalemma of guard cell protoplasts: a breakthrough in plant hormone-receptor binding and hormone action

The dynamics of stomatal opening and closure had to date been ascribed largely to the K(+)-fluxes and cell wall elasticity. Using protoplasts of guard cells of Vicia faba as model system, we document convincing first hand evidence a that lipid phase alterations could regulate ABA-induced closure of stomates and its reversal by umbelliferone. Backed up by the presence of plasmalemma-located ABA-receptor in guard cells, a novel theory could be put forth explaining guard cell opening and closure mediated by hormone induced reconfiguration via a probable lipid-protein lattice modification. The phase reversal of the plasmalemma by umbelliferone is postulated to be through modified hormone receptor complex structure, which is yet to be substantiated.

Enhanced axial symmetry at the Fe(3+)-heme center of peroxidase by ascorbate: a basis for the ascorbate-dependent peroxidase action

In the absence of its substrate hydrogen peroxide, peroxidase exhibits perturbations in its Fe(3+)-heme center, when incubated with ascorbic acid. The electron paramagnetic pattern sprang towards a higher g-value side, denoting a sharpening of the rhombic axial symmetry around the heme-center. The interpretation is that the ascorbate dependent peroxidase action starts with the formation of an Fe(3+)-ascorbate charge transfer complex intermediate.

Superoxide dismutase activity regulation by spermine: a new dimension in spermine biochemistry and sperm development

Amines are a group of highly important compounds of biological importance; they are known promoters of cell growth, can complex with nucleic acids and can stimulate DNA-primed RNA polymerase activity. Spermine, a polyamine abundantly present in the secretions of the male accessory sex organs, has received no functional attributes till date. This study had been a pioneer attempt to validate the hypothesis of a metalloenzyme activity modulation by spermine and implicit correlations have been drawn.

Superoxide dismutase activation in thyroid and suppression in adrenal. Novel pituitary regulatory routes

This study reports that administration of TSH in young female mice results in a concomitant augmentation of SOD activity in the thyroid gland. A strong thyroid-adrenal interdependence was also evident in the form of a marked loss of SOD activity in the adrenal gland in response to TSH administration. Very recently SOD/O2.- system had been identified as a potent H2O2 generator which provides substrate for the action of key enzyme in thyroxine and progesterone biosynthesis, viz. the peroxidase. Thus, these results strongly suggest that trophic hormones tonically stimulate hormone biosynthesis by modulating activation/suppression of specific enzymes, which could be the basis of the tuning sequence.

Changes in the superoxide radical and superoxide dismutase levels in the uterus of Rattus norvegicus during the estrous cycle and a possible role for superoxide radical in uterine oedema and cell proliferation at proestrus

Superoxide anion radical, a radical whose toxicity is well documented, is present in the uterus of albino rat. The cyclic changes that it undergoes during the reproductive cycle are also illustrated. An inverse correlation is seen between the levels of superoxide radical and the enzyme dismutating it, i.e., superoxide dismutase (EC 1.15.1.1), which is also reported to be present in the uterus of albino rat and is shown to exhibit cyclic changes during its oestrous cycle. The high levels of superoxide radical at pro-oestrus enable us to hypothesize that superoxide may be involved in regulating the oedema and cell proliferation of the uterus during proestrus.

Superoxide radical level and superoxide dismutase activity changes in maturing mammalian spermatozoa

Mammalian spermatozoa, which like other living cells are susceptible to oxygen toxicity, generate increasing quantities of superoxide radical as epididymal maturation proceeds. This is associated with a concomitant reduction in the activity of superoxide dismutase. A possible involvement of superoxide radicals in bringing about some of the reported oxidative changes occurring during epididymal maturation of mammalian spermatozoa is discussed. It is suggested that superoxide radical may be involved in regulating membrane changes accompanying sperm maturation.

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 dismutase as a regulatory switch in mammalian testicular steroidogenesis

The delta 4-pathway of testosterone biosynthesis in leydig cells, widely believed to proceed through pregnenolone--greater than pregnenedione--greater than progesterone route catalyzed by 5 delta-3 beta-hydroxysteroid dehydrogenase and delta 5-delta 4-isomerase respectively is shown to pass through an alternate pathway mediated by superoxide dismutase and peroxidase. A built-in regulatory switch is incorporated in this route, with the superoxide dismutase inducible upon LH-stimulation of the leydig cells.

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.

Activation of iodine into a free-radical intermediate by superoxide: a physiologically significant step in the iodination of tyrosine

A pivotal biochemical event in the thyroid physiology is identified unravelling a superoxide anion radical-mediated activation of iodine into an active I.- form, which could be the intermediate that is incorporated onto tyrosine. This active iodine species gives fairly stable spin-adducts with PBN that could be characterized using EPR spectroscopy. Thus, a long-lasting puzzle regarding the iodine intermediate formed before iodination of tyrosine seems to be solved.