EGF-dependent translocation of green fluorescent protein-tagged PLC-gamma1 to the plasma membrane and endosomes

Growth factor-dependent translocation of phospholipase C-gamma1 (PLC-gamma1) was investigated using a green fluorescent protein-tagged PLC-gamma1 (PLC-gamma1-GFP) expressed in human epidermoid carcinoma A-431 cells. In the absence of growth factors, PLC-gamma1-GFP was present throughout the cytoplasm of A-431 cells. Treatment of the cells with epidermal growth factor (EGF) produced a very rapid redistribution of PLC-gamma1-GFP to the plasma membrane in a nonuniform manner. This translocation to the plasma membrane was insensitive to an inhibitor of phosphatidylinositol 3-kinase and was independent of cell adhesion. However, the translocation was disrupted by an agent which depolymerizes the actin cytoskeleton. At later times following the addition of EGF, PLC-gamma1-GFP appeared associated with intracellular vesicles. Stimulation of A-431 cells by Texas red-conjugated EGF for more than 10 min resulted in punctate intracellular PLC-gamma1-GFP distribution that colocalized with Texas red-conjugated EGF. This suggests that PLC-gamma1 is translocated to endosomes after EGF treatment, probably by associating with the internalized and autophosphorylated EGF receptor. Fractionation studies demonstrated that the EGF-induced plasma membrane-localized PLC-gamma1 is concentrated in caveolae microdomains. Disruption of caveolae with methyl-beta-cyclodextrin resulted in the ablation of EGF-induced, but not bradykinin-induced, mobilization of intracellular Ca(2+). This treatment, however, only partially decreased PLC-gamma1 membrane translocation.

Spontaneous biliary perforation presenting as gastric outlet obstruction

Spontaneous biliary perforation (SBP) is a rare, surgically correctable cause of jaundice in neonates. The presenting feature is usually biliary ascites, and in rare cases, biliary peritonitis. This article reports a case of SBP, which presented with features of gastric outlet obstruction, leading to an erroneous preoperative diagnosis. Most probably this is the first report of such an unusual presentation of SBP. The child underwent exploratory laparotomy and a bilio-enteric bypass with drainage of the right subhepatic space, which led to a prompt resolution of the symptoms.

Prevention of adrenocortical hyperactivity by dietary casein in rats exposed to forced swimming stress

Adrenal weight, adrenal hydroxysteroid dehydrogenase activity and serum corticosterone level were significantly higher in rats fed with 5% casein diet after 7 days of swimming stress (45 min/day) as compared to their controls. All the parameters were similar to their control levels in rats receiving 20% casein diet and exposed to swimming stress. The results suggest that casein can play an important role in preventing adrenocortical hyperactivity in swimming stressed rats.

Role of disulfides and sulfhydryl groups in agonist and antagonist binding in serotonin1A receptors from bovine hippocampus

I. The serotonin1A (5-HT1A) receptors are members of a superfamily of seven-transmembrane-domain receptors that couple to G-proteins. They appear to be involved in various behavioral and cognitive functions. Mutagenesis and modeling studies point out that the ligand-binding sites in serotonin receptors are located in the transmembrane domain. However, these binding sites are not very well characterized. Since disulfide bonds and sulfhydryl groups have been shown to play vital roles in the assembly, organization, and function of various G-protein-coupled receptors, we report here the effect of disulfide and sulfhydryl group modifications on the agonist and antagonist binding activity of 5-HT1A receptors from bovine hippocampus. 2. DTT or NEM treatment caused a concentration-dependent reduction in specific binding of the agonist and antagonist in 5-HT1A receptors from bovine hippocampal native and solubilized membranes. This is supported by a concomitant reduction in binding affinity. 3. Pretreatment of the receptor with unlabeled ligands prior to chemical modifications indicate that the majority of disulfides or sulfhydryl groups that undergo modification giving rise to inhibition in binding activity could be at the vicinity of the ligand-binding sites. 4. In addition, ligand-binding studies in presence of GTP-gamma-S, a nonhydrolyzable analogue of GTP, indicate that sulfhydryl groups (and disulfide bonds to a lesser extent) are vital for efficient coupling between the 5-HT1A receptor and the G-protein. 5. Our results point out that disulfide bonds and sulfhydryl groups could play an important role in ligand binding in 5-HT1A receptors.

Microwave technique in histopathology and its comparison with the conventional technique

125 formalin fixed human tissues from different organs and 50 fresh animal tissues were taken. Each tissue piece was divided into two. Fresh animal tissues were fixed and processed in a domestic microwave oven and formalin fixed tissue were only processed in microwave oven. Simultaneous conventional processing was also carried out. Among the fresh tissues, 34 pieces were fixed in 10% formalin and 16 were stabilized in normal saline, with microwave irradiation. For histoprocessing graded ethanol (70% and absolute) for 150 tissues and graded isopropanol (70% and absolute) for 25 tissues were used for dehydration in microwave technique. Chloroform for 95 tissues, xylene for 15 tissues and isopropanol for 65 tissues were used as clearing agent in microwave technique. Liquid paraffin was impregnating agent in all 175 cases. The oven was operated at 50% power for 10 cases and 40% power for 165 cases. Recording of temperature could not be done. Regarding fixation with formalin 80% cases gave satisfactory result, while with normal saline, only 30% cases were satisfactory. Regarding dehydration with ethanol 80% were satisfactory and with isopropanol 60% were satisfactory. Regarding clearing--both chloroform and isopropyl alcohol gave satisfactory results in 80% cases but with, xylene tissues were fragmented and brittle.

Effect of alcohols on G-protein coupling of serotonin(1A) receptors from bovine hippocampus

The serotonin(1A) (5-hydroxytryptamine [5-HT](1A)) receptors are members of a superfamily of seven transmembrane domain receptors that couple to G-proteins. Serotonergic signalling has been shown to play an important role in alcohol intake, preference and dependence. G-protein coupling of the 5-HT(1A) receptor serves as an important determinant for serotonergic signalling. We have studied the effect of alcohols on G-protein coupling of bovine hippocampal 5-HT(1A) receptors in native membranes. This was done by monitoring the modulation of ligand (agonist and antagonist) binding in presence of alcohols by guanosine-5'-O-(3-thiotriphosphate) (GTP-gamma-S), a non-hydrolyzable analogue of GTP. Our results show that alcohols inhibit the specific binding of the agonist 8-hydroxy-2-(di-N-propylamino)tetralin (except in case of ethanol) and the antagonist 4-(2'-methoxy)-phenyl-1-[2'-(N-2"-pyridinyl)-p-fluorobenzamido]eth yl- piperazine to 5-HT(1A) receptors in a concentration-dependent manner. Further, we show here that the action of alcohols on the bovine hippocampal 5-HT(1A) receptors could be modulated by guanine nucleotides and that the mode of action of ethanol on the 5-HT(1A) receptor may be quite different than that of other alcohols. The effect of GTP-gamma-S on the agonist and the antagonist binding is found to be markedly different. Our results could be significant in the overall context of the role of G-protein coupling in serotonergic neurotransmission and its role in alcohol tolerance and dependence.

Emperor Akbar as a healer and his eminent physicians

Akbar, however, was himself considered to be a healer to be healer by his miraculous powers. The court physician was one of the top-most officers of the court. Hakim Humam was such a physician who was one of the nine jewels (nauratnas) of Akbar. In 1581, Akbar curtailed the powers of Sadr (or Sadr-i-Jahan, the chief Justice and Administrator of the Empire) and he divided the empire in six zones with a Sadr in charge of each. Out of these six Sadrs, five were his physicians who were Hakim Abul Fath, Shaikh Fayzi, Hakim Humam, Hakim Ali, Hakim Ain-ul-Mulk. Tobacco was introduced either in 1604 or in 1605. Hakim Abul Fath opposed its circulation but Akbar permitted it. It was Abul Fath who found out a remedy for counteracting the pernicious effects of tobacco on health. His opinion was that if the smoke of tobacco passed through water the harmful effects would be minimised. So hukka was invented by him.

Histopathology of skin lesions in chronic arsenic toxicity--grading of changes and study of proliferative markers

Chronic arsenic toxicity (CAT) manifests predominantly as cutaneous lesions in the form of melanosis, keratosis and neoplastic changes. We have studied skin biopsies from 42 patients of CAT. Histological study of H/E stained sections showed--hyperkeratosis in 13, parakeratosis in 13, acanthosis in 12, papillomatosis in 24, elongation of reteridges in 21, increased basal pigmentation in 27 and dysplastic changes in 8 cases. Squamous cell carcinoma was present in 2, basisquamous in 1 and basal cell carcinoma in 1 case. Changes of skin lesions after drug DMSA and DMPS therapy compared to placebo were studied. The result was inconclusive. Proliferative activity of skin lesions in CAT were studied by AgNOR stain to assess the biological behaviour of the lesions. AgNOR score showed--normal control 1.08, benign changes (e.g. Hyperkeratosis, parakeratosis, acanthosis, papillomatosis etc.) without dysplasia--1.35, mild to moderate dysplasia--1.735, severe dysplasia--3.0 and carcinoma--3.56. Thus, AgNOR score gives some idea on the biological behaviour of CAT lesions. It is suggested that AgNOR staining should be done regularly along with H&E staining for proper assessment of the cases.

Protective effect of erythropoietin on the oxidative damage of erythrocyte membrane by hydroxyl radical

Treatment of red blood cells with the copper (II) ascorbate system causes increased lipid peroxidation, increased membrane microviscosity, and phospholipid translocation with a concurrent decrease in cytosolic catalase and glutathione peroxidase activities. All these changes are prevented if the cells are treated with erythropoietin prior to the exposure to copper (II) ascorbate. The present investigation further indicates that the oxidative damage brought about by copper (II) ascorbate is due to generation of hydroxyl radical and that erythropoietin plays a unique role in protecting the membrane from oxidative damage.

The Tughlaqs and medicine

Muhammed Tughlaq established hospitals. A versatile scholar, Muhammed used to sit by the patients and watch the symptoms of extra ordinary diseases. His successor Firoz Tughlaq established a hospital where patients used to get free medical help and also food and drinks. This hospital was open to all. Though Firoz was known for his bigotry, we find no discrimination made between muslims and non-muslims in case of patients in this hospital. Firoz invented an eye-ointment in which, skin of black snake was used. It cured many kinds of eye diseases. This fact supports the Ayurvedic theory of and prescriptions for curing blindness with the ointment prepared with the flesh of cobras. Firoz himself was a good bone-setter.

Gender differences in socioeconomic returns to family migration in Malaysia: the role of family decision making versus labor market stratification

In this article the author examines gender differences in the effect of family migration on socioeconomic attainment in Malaysia. The analysis discerns the relative importance of gender roles in household migration decisions, compared to gender stratification in the labor market. The Malaysian economy has undergone rapid industrialization and great structural changes which have opened up new economic opportunities, particularly for women. Despite the somewhat advantaged position of women compared to men in the Malaysian labor market, the author finds that men experience much greater socioeconomic gains than women from family migration. Hence indicating that family migration decisions in Malaysia, rather than optimizing family gains, compensate for the gender effect in the labor market. However, the gains of Malaysian men are more assured when they move alone. Data for the study come from the second round of the Malaysian Family Life Survey.

Antitesticular effect of copper chloride in albino rats

Copper chloride treatment adversely affects testicular activity in albino rats. To investigate its antitesticular effects mature (120 days) Wistar strain albino rats were treated intraperitoneally (i.p.) with copper chloride at doses of 1000, 2000 and 3000 micrograms/kg body weight/day for 26 days. Significant reduction of testicular and accessory sex organs (seminal vesicle, ventral prostate) weight, along with inhibition of testicular delta 5-3 beta-hydroxysteroid dehydrogenase (delta 5-3 beta-HSD) and 17 beta-hydroxysteroid dehydrogenase (17 beta-HSD) activity and reduction in plasma testosterone level, were observed at the doses of 2000 and 3000 micrograms/kg body weight/day. The degree of inhibition in all the parameters were increased with the increase of dosage. But no significant change was observed in the above parameters when the animals were treated with 1000 micrograms/kg body weight/day dose. This suggests that copper produces a suppressive influence on male reproductive activity, mainly on testicular weight and steroidogenesis and accessory sex organ weight in a dose-dependent manner.

Modulation of the clastogenic activity of gamma-irradiation in buthionine sulphoximine-mediated glutathione depleted mammalian cells

PURPOSE

Chromosome aberrations (CA) were used as an end-point to investigate the effect of buthionine sulphoximine (BSO), a potent glutathione-depleting agent, on the radiosensitivity of mammalian cells. The aim was to obtain information about the role of glutathione (GSH) in physicochemical and biochemical processes in irradiated cells.

MATERIALS AND METHODS

CA were scored from first cycle metaphases in irradiated BSO-pretreated and untreated samples. BSO exposure was for 10h in mouse bone marrow cells in vivo and 5 h for human lymphocytes in vitro. In further experiments fresh blood was irradiated on ice and immediately after irradiation GSH/GSH-ester was added.

RESULTS

In both the systems BSO-treated samples showed higher sensitivity to radiation than BSO untreated samples. The frequency of all types of CA increased except exchange aberrations. GSH/GSH-ester treatment given after irradiating the cells at 4 degrees C reduced the frequency of deletions and increased the frequency of exchange aberrations.

CONCLUSIONS

Data indicate that BSO-mediated GSH depletion increased radiation-induced chromosome aberrations, apart from exchange aberrations. This could be due to reduction in the free-radical scavenging effect of GSH, a failure in rejoining of DNA double-strand breaks, or induction of apoptosis.

The role of individual SH2 domains in mediating association of phospholipase C-gamma1 with the activated EGF receptor

The two SH2 (Src homology domain 2) domains present in phospholipase C-gamma1 (PLC-gamma1) were assayed for their capacities to recognize the five autophosphorylation sites in the epidermal growth factor receptor. Plasmon resonance and immunological techniques were employed to measure interactions between SH2 fusion proteins and phosphotyrosine-containing peptides. The N-SH2 domain recognized peptides in the order of pY1173 > pY992 > pY1068 > pY1148 >> pY1086, while the C-SH2 domain recognized peptides in the order of pY992 > pY1068 > pY1148 >> pY1086 and pY1173. The major autophosphorylation site, pY1173, was recognized only by the N-SH2 domain. Contributions of the N-SH2 and C-SH2 domains to the association of the intact PLC-gamma1 molecule with the activated epidermal growth factor (EGF) receptor were assessed in vivo. Loss of function mutants of each SH2 domain were produced in a full-length epitope-tagged PLC-gamma1. After expression of the mutants, cells were treated with EGF and association of exogenous PLC-gamma1 with EGF receptors was measured. In this context the N-SH2 is the primary contributor to PLC-gamma1 association with the EGF receptor. The combined results suggest an association mechanism involving the N-SH2 domain and the pY1173 autophosphorylation site as a primary event and the C-SH2 domain and the pY992 autophosphorylation site as a secondary event.

Differential discrimination of G-protein coupling of serotonin(1A) receptors from bovine hippocampus by an agonist and an antagonist

We have studied the effect of guanosine-5'-O-(3-thiotriphosphate) (GTP-gamma-S), a non-hydrolyzable analogue of GTP, on agonist and antagonist binding to bovine hippocampal 5-hydroxytryptamine (5-HT)(1A) receptor in native membranes. Our results show that the specific binding of the agonist is inhibited with increasing concentrations of GTP-gamma-S along with a reduction in binding affinity. In sharp contrast to this, antagonist binding to 5-HT(1A) receptor shows no significant reduction and remains invariant over a large range of GTP-gamma-S concentrations. The binding affinity of the antagonist also remains unaltered. This shows that the agonist and the antagonist differentially discriminate G-protein coupling of 5-HT(1A) receptors from bovine hippocampus.

Focal adhesion kinase promotes phospholipase C-gamma1 activity

The nonreceptor tyrosine kinase FAK ("focal adhesion kinase") is a key mediator of integrin signaling events controlling cellular responses to the extracellular matrix, including spreading, migration, proliferation, and survival. Integrin-ligand interactions stimulate FAK tyrosine phosphorylation and activation of FAK signaling functions. Here evidence is presented that the FAK autophosphorylation site Tyr-397 mediates a direct interaction with the C-terminal Src homology 2 domain of phospholipase C (PLC)-gamma1 and that this is required for both adhesion-dependent association of the two molecules and increased inositol phosphate production in mouse embryo fibroblasts. Overexpression of FAK and PLC-gamma1 in COS-7 cells increases PLC-gamma1 enzymatic activity and tyrosine phosphorylation, also dependent on FAK Tyr-397. However, FAK appears incapable of directly phosphorylating PLC-gamma1. These observations suggest a role for FAK in recruiting PLC-gamma1 to the plasma membrane at sites of cell-matrix adhesion and there promoting its enzymatic activity, possibly by releasing the repression caused by intramolecular interactions of the PLC-gamma1 Src homology domains and/or by positioning it for phosphorylation by associated Src-family kinases. These findings expand the known signaling functions of FAK and provide mechanistic insight into integrin-stimulation of PLC-gamma1.

A comparative study of balloon mitral valvuloplasty and closed mitral commissurotomy in patients with rheumatic mitral stenosis

Rheumatic mitral stenosis is frequently encountered in our country. It affects younger population and is a major cause of morbidity Mitral valvotomy is the definitive therapy for this disease and can be achieved by closed mitral commissurotomy (CMC), open mitral commissurotomy (OMC) or by percutaneous transluminal mitral valvuloplasty (PTMV). Compared to CMC, PTMV is less invasive but more expensive at this moment. With the reduction of cost, PTMV may become the procedure of choice for the treatment of rheumatic mitral stenosis in future.

Physiological requirement for both SH2 domains for phospholipase C-gamma1 function and interaction with platelet-derived growth factor receptors

Two approaches have been utilized to investigate the role of individual SH2 domains in growth factor activation of phospholipase C-gamma1 (PLC-gamma1). Surface plasmon resonance analysis indicates that the individual N-SH2 and C-SH2 domains are able to specifically recognize a phosphotyrosine-containing peptide corresponding to Tyr 1021 of the platelet-derived growth factor (PDGF) beta receptor. To assess SH2 function in the context of the full-length PLC-gamma1 molecule as well as within the intact cell, PLC-gamma1 SH2 domain mutants, disabled by site-directed mutagenesis of the N-SH2 and/or C-SH2 domain(s), were expressed in Plcg1(-/-) fibroblasts. Under equilibrium incubation conditions (4 degrees C, 40 min), the N-SH2 domain, but not the C-SH2 domain, was sufficient to mediate significant PLC-gamma1 association with the activated PDGF receptor and PLC-gamma1 tyrosine phosphorylation. When both SH2 domains in PLC-gamma1 were disabled, the double mutant did not associate with activated PDGF receptors and was not tyrosine phosphorylated. However, no single SH2 mutant was able to mediate growth factor activation of Ca2+ mobilization or inositol 1,4,5-trisphosphate (IP3) formation. Subsequent kinetic experiments demonstrated that each single SH2 domain mutant was significantly impaired in its capacity to mediate rapid association with activated PDGF receptors and become tyrosine phosphorylated. Hence, when assayed under physiological conditions necessary to achieve a rapid biological response (Ca2+ mobilization and IP3 formation), both SH2 domains of PLC-gamma1 are essential to growth factor responsiveness.

Effect of oxidative stress and erythropoietin on cytoskeletal protein and lipid organization in human erythrocytes

Phenylhydrazine (PHX)-mediated damage in human red blood cells has been assessed by monitoring the release of tyrosine from cell proteins as well as using sodium dodecyl sulfate polyacrylamide gel electrophoresis (SDS-PAGE). PHX-treated red blood cells exhibited concentration- and time-dependent tyrosine release. ATP has no effect on the release of tyrosine. This observation is supported by SDS-PAGE pattern of RBC membrane proteins, which shows a correlation between tyrosine release and cytoskeletal protein degradation. PHX requires the presence of erythrocyte cytosolic fraction for the degradation, possibly due to the presence of a proteolytic enzyme in the cytosol. PHX treatment renders the membrane proteins susceptible to the proteolytic attack. Treatment of PHX-exposed erythrocyte with bee venom phospholipase A2 induces the translocation of phosphatidylserine (PS) and phosphatidylethanolamine (PE) to the outer surface of the cell membrane. At the same time, phosphatidylcholine (PC) was translocated towards the inner surface, altering the membrane phospholipid asymmetry. Interestingly, increased tyrosine production followed by translocation of phospholipids across the red blood cell membrane by PHX treatment is completely inhibited by 0.2 units of erythropoietin (EP). Our findings suggest that exposure of red blood cells to an oxidant like PHX causes degradation of cytoskeletal protein by an ATP-independent proteolytic pathway and this in turn allows the transbilayer movement of phospholipids across the cell membrane. EP, by scavenging the hydroxyl radicals produced during interaction of PHX with red blood cells, protects the erythrocytes from oxidative attack.

Localization and environment of tryptophans in soluble and membrane-bound states of a pore-forming toxin from Staphylococcus aureus

The location and environment of tryptophans in the soluble and membrane-bound forms of Staphylococcus aureus alpha-toxin were monitored using intrinsic tryptophan fluorescence. Fluorescence quenching of the toxin monomer in solution indicated varying degrees of tryptophan burial within the protein interior. N-Bromosuccinimide readily abolished 80% of the fluorescence in solution. The residual fluorescence of the modified toxin showed a blue-shifted emission maximum, a longer fluorescence lifetime as compared to the unmodified and membrane-bound alpha-toxin, and a 5- to 6-nm red edge excitation shift, all indicating a restricted tryptophan environment and deeply buried tryptophans. In the membrane-bound form, the fluorescence of alpha-toxin was quenched by iodide, indicating a conformational change leading to exposure of some tryptophans. A shorter average lifetime of tryptophans in the membrane-bound alpha-toxin as compared to the native toxin supported the conclusions based on iodide quenching of the membrane-bound toxin. Fluorescence quenching of membrane-bound alpha-toxin using brominated and spin-labeled fatty acids showed no quenching of fluorescence using brominated lipids. However, significant quenching was observed using 5- and 12-doxyl stearic acids. An average depth calculation using the parallax method indicated that the doxyl-quenchable tryptophans are located at an average depth of 10 A from the center of the bilayer close to the membrane interface. This was found to be in striking agreement with the recently described structure of the membrane-bound form of alpha-toxin.

The influence of deletion mutations on phospholipase C-gamma 1 activity

Phospholipase C-gamma1, a substrate for many growth factor receptor and nonreceptor tyrosine kinases, produces second messenger molecules that are elements of signal transduction pathways related to cell proliferation. The influence of deletion mutations, which do not intrude on the domains required for catalytic function, on the basal activity of this enzyme is reported. Removal of the first 74 amino-terminal residues increases phospholipase C activity, while deletion of the carboxy-terminal 81 residues decreases enzyme activity. Deletion of the SH2-SH2-SH3 central region, which separates the two domains (X, Y) responsible for catalytic function, also increases enzymatic activity. Interestingly, addition of a recombinant SH2-SH2-SH3 fragment of phospholipase C-gamma1 to the holoenzyme inhibits its phospholipase activity at pH 7.0, but not at pH 5.0. However, addition of individual SH2 or SH3 domains does not influence activity of the holoenzyme. All three deletion mutants, in contrast to the holoenzyme, are relatively resistant to V8 proteolysis and activation induced by the epidermal growth factor receptor tyrosine kinase, which require, respectively, specific proteolysis and phosphorylation sites within the SH region. This suggests a conformational change is induced in the SH region by deletion at either the amino- or carboxy-terminus.

Modulation of agonist and antagonist interactions in serotonin 1A receptors by alcohols

The serotonin type IA (5-HT1A) receptors are members of a superfamily of seven transmembrane domain receptors that couple to GTP binding regulatory proteins (G-proteins). Serotonergic signalling has been shown to play an important role in alcohol tolerance and dependence. We have studied the effects of alcohols on ligand (agonist and antagonist) binding to bovine hippocampal 5-HT1A receptor in native as well as solubilized membranes. Our results show that alcohols inhibit the specific binding of the agonist OH-DPAT and the antagonist p-MPPF to 5-HT1A receptors in a concentration-dependent manner.