Shyamali Mukherjee

Identification and characterization of a Mg+2-dependent and an independent Ca+2-ATPase in microsomal membranes of rat testis

Rat testicular microsomal membrane fraction contains both Mg+2-dependent and Mg+2-independent Ca+2-ATPase activity. The latter activity is about two times higher than the former. Calcium ion required for maximum activation of Mg+2-independent Ca+2-ATPase in 3.0 mM, whereas for the dependent one it is 2.5 mM. Both the enzymes are resistant to cold shock upto seven days. Histidine and imidazole buffers are found to be the most suitable for dependent and independent enzyme activities, respectively. The pH optima for dependent one is 7.5, whereas for the independent one it is 8.5. Temperature optima for the former is 37°C and for latter one it is 40°C. Among all the nuclestides tested, ATP is found to be the best substrate for both the enzymes. The optimum concentration of ATP for dependent and independent enzyme activities are 3.0 mM and 1.5 mM respectively. Divalent metal ions like Zn+2, Ba+2 and Mn+2 have been found to inhibit Mg+2-dependent Ca+2-ATPase activity whereas Mg+2-independent Ca+2-ATPase activity is inhibited by the divalent ions except zinc which is found to stimulate the enzyme activity. Both the enzymes are inhibited by vanadata, EDTA and EGTA. I50, for vanadate is 0.05 and 0.125 mM for dependent and independent activities, respectively. Sulfhydral groups modifying agents e.g., NEM, DTNB and chlorpromazine are found to affect the enzyme activities in different ways. Thus NEM and chlorpromazine are found to inhibit and DTNB stimulate the enzyme activities in both the cases.

The chlorpromazine inhibition of transport ATPase and acetylcholinesterase activities in the microsomal membranes of rat in vitro and in vivo

Chlorpromazine, an antipsychotic drug, is found to inhibit Na+,K+-ATPase activity in rat brain microsomal membranes in vitro in concentration and time dependent manner but some inconsistency is observed when the effect was studied with respect to different temperatures. Various ligands and/or substrate affect the inhibition by chlorpromazine in different ways. The in vivo study with this drug shows that the activities of Na+,K+-ATPase, Ca−2-ATPase and acetylcholinesterase in the microsomal membranes of different organs are inhibit with increases in concentration or lengths of time of treatment and then levels off.

Expression of Mn-Superoxide Dismutase Gene in Nontumorigenic and Tumorigenic Human Mammary Epithelial Cells

Manganese superoxide dismutase (Mn-SOD), localized at the mitochondrial matrix, has the ability to protect cells against oxidative damage. It has been reported that low levels of Mn-SOD gene expression cause the development of certain kind of tumors. On the other hand, overexpression of Mn-SOD gene may play an important role in the development of cancer. In our study, we find that Mn-SOD activity was higher in nonaggressive (MCF-7) and aggressive (BT-549 and 11-9-14) breast cancer cell lines compared to that of nontumorigenic (MCF-12A and MCF-12F) mammary epithelial cell lines. We also observed an increased expression of Mn-SOD gene in cancerous cell lines. The elevated level of SOD activity in nonaggressive and aggressive breast epithelial cell lines was associated with some changes in nucleotide sequence.

Mainstream and sidestream cigarette smoke exposure increases Ca2+-dependent phospholipid binding proteins in guinea pig alveolar type II cells.

We have earlier identified the presence of a 36 kDa Ca2+-dependent phospholipid-binding protein (PLBP) in guinea pig alveolar type II cells. PLBP has been suggested to act as a mediator in facilitating and regulating intracellular surfactant assembly and delivery to the plasma membrane of type II cells for secretion into alveolar space. It has been reported that cigarette smoke exposure (CSE) causes a decrease in the surfactant activity in bronchial washings. We have also reported earlier that mainstream (MS) and sidestream (SS) CSE causes desensitization of β-adrenoreceptors in guinea pig alveolar type II cells. Since both Ca2+ and β-adrenoreceptors are involved in surfactant secretion and PLBP is involved in surfactant delivery, it is important to know whether CSE causes any change in the PLBP level in alveolar type II cells. In the present study, we have demonstrated that MS and SS CSE causes a significant increase in the levels of PLBP in alveolar type II cells (107 and 150%, respectively) and in lung lavage (42 and 125%, respectively) in comparison to that in sham control (430 ng/mg protein in alveolar type II cells and 780 ng/mg protein in lung lavage). The mechanism by which smoke exposure causes an elevation in the levels of PLBP in alveolar type II cells and lung lavage remains to be investigated.

Protection Against Dimethylbenz[a] Anthracene-Induced Breast Cancer in Female Rats by α-Lactalbumin.

Consumption of α-lactalbumin as dietary protein offers a beneficial effect on breast cancer development. Breast cancer was developed by gavage administration of single dose of dimethylbenz(a)anthracene (DMBA) in female rats, maintained on AIN-76A diet with either 20% casein or α-lactalbumin (a component of whey protein). All tumors were detected by palpation. After approximately 130 days of DMBA administration, the animals were euthanized. There was a delay in the development of breast tumor in the α-lactalbumin group in comparison to the casein group. The number of tumors per rat was less in the α-lactalbumin group than that in the casein group at any time point up to 130 days after DMBA administration. Also the incidence of tumors and tumor volume was less in the α-lactalbumin group than those in the casein group. The casein group had a mixture of grade I, grade II and grade III tumors whereas the α-lactalbumin group had mostly grade I tumor. Furthermore, the proliferative index was significantly lower in the α-lactalbumin group than that in the casein group.

Hydrogen peroxide formation and lipid peroxidation in rat uterus— effect of hormones and vitamin E

The effect of estradiol-17β and progesterone given separately as well as in combination on the rate of hydrogen peroxide formation and lipid peroxidation in the uteri of ovariectomized rats was studied. Estradiol in 3μg dose per day per animal elicited maximum stimulatory response and progesterone (100μg), on the other hand, was without any such effect. However, progesterone given along with estradiol completely prevented the effect due to the latter. In the same way, vitamin E, a well known antioxidant was found to be extremelv effective in protecting the uterus from the highly peroxidative action of estradiol-17β.

Direct and Second Hand Cigarette Smoke Exposure and Development of Childhood Asthma

This is a comprehensive review about the role of direct and second hand cigarette smoke exposure in the development of childhood asthma. Smoking, both during pregnancy and postnatal have an adverse impact on the infant’s chances of developing respiratory illness. Second hand smoke exposure has also known to cause worsening of childhood asthma with an impact on hospital admissions. Correlation between maternal second hand smoke exposure during pregnancy and development of childhood asthma has also been investigated. It is, thus essential to address this prenatally as well as post-natal by reducing smoking as well as smoke exposure.

Alteration of lipid composition, Na+, K+-ATPase and Δ5-β-hydroxy steroid dehydrogenase activities in microsomal membranes of mature toad ovary in different seasons

Microsomal membranes isolated by sucrose density gradient centrifugation from mature toad ovary has been found to vary significantly in lipid composition and various enzyme activities in different seasons. Na+, K+—ATPase activity is the highest in breeding season (rainy season). Significantly the optimum temperature for enzyme activity is 30°C. The other enzyme Δ5-3β-hydroxysteroid dehydrogenase activity is also lower in hibernation period than other seasons. The total phospholipid, sterol and fatty acid contents differ significantly between seasons. The poly-unsaturated fatty acid, except arachidonic acid content in hibernation period is much lower than that during other seasons. The sterol content is also the lowest in this season. The present findings indicate that during hibernation period the membrane is more rigid and the metabolic activity of the animal is slow because of a lower level of various functionally important enzyme activities.