The tip-sample water bridge and light emission from scanning tunnelling microscopy

The light emission spectrum from a scanning tunnelling microscope (LESTM) is investigated as a function of relative humidity and shown to provide a novel and sensitive means for probing the growth and properties of a water meniscus on the nanometre scale. An empirical model of the light emission process is formulated and applied successfully to replicate the decay in light intensity and spectral changes observed with increasing relative humidity. The modelling indicates a progressive water filling of the tip-sample junction with increasing humidity or, more pertinently, of the volume of the localized surface plasmons responsible for light emission; it also accounts for the effect of asymmetry in structuring of the water molecules with respect to the polarity of the applied bias. This is juxtaposed with the case of a non-polar liquid in the tip-sample nanocavity where no polarity dependence of the light emission is observed. In contrast to the discrete detection of the presence/absence of a water bridge in other scanning probe experiments through measurement of the feedback parameter for instrument control, LESTM offers a means of continuously monitoring the development of the water bridge with sub-nanometre sensitivity. The results are relevant to applications such as dip-pen nanolithography and electrochemical scanning probe microscopy.

Amniotic fluid embolism

The disastrous entry of amniotic fluid into the maternal circulation leads to dramatic sequelae of clinical events, characteristically referred to as Amniotic fluid embolism (AFE). The underlying mechanism for AFE is still poorly understood. Unfortunately, this situation has very grave maternal and fetal consequences. AFE can occur during labor, caesarean section, dilatation and evacuation or in the immediate postpartum period. The pathophysiology is believed to be immune mediated which affects the respiratory, cardiovascular, neurological and hematological systems. Undetected and untreated it culminates into fulminant pulmonary edema, intractable convulsions, disseminated intravascular coagulation (DIC), malignant arrhythmias and cardiac arrest. Definite diagnosis can be confirmed by identification of lanugo, fetal hair and fetal squamous cells (squames) in blood aspirated from the right ventricle. Usually the diagnosis is made clinically and by exclusion of other causes. The cornerstone of management is a multidisciplinary approach with supportive treatment of failing organs systems. Despite improved modalities for diagnosing AFE, and better intensive care support facilities, the mortality is still high.

Prenatal cocaine exposure enhances responsivity of locus coeruleus norepinephrine neurons: role of autoreceptors

Children exposed to cocaine during gestation have a higher incidence of neurobehavioral deficits. The neurochemical bases of these deficits have not been determined, but the pharmacology of cocaine and the nature of the abnormalities suggest that disruptions in catecholaminergic systems may be involved. In the current study, we used a rat model of prenatal cocaine exposure to examine the impact that this exposure has on the locus coeruleus (LC) noradrenergic system in offspring. Pregnant rats received twice-daily i.v. injections of cocaine (3 mg/kg) or saline between gestational days 10 and 20, and progeny were tested as juveniles. Exposure to a mild stressor elevated an index of norepinephrine turnover in the prefrontal cortex and also increased Fos expression in tyrosine hydroxylase-positive LC neurons in rats exposed to prenatal cocaine but not in rats exposed to prenatal saline. No change in the number of tyrosine hydroxylase-positive neurons in the LC was observed between the two prenatal treatment groups. Specific binding of [125I]-para-iodoclonidine, a radioligand with specificity for high affinity alpha2A-adrenergic receptors, was decreased in the LC of rats exposed to prenatal cocaine compared with prenatal saline controls. As alpha2-adrenergic receptors on LC norepinephrine neurons function as autoreceptors, their down-regulation by prenatal cocaine exposure provides a plausible mechanism for the observed heightened reactivity of norepinephrine neurons in these animals. These data indicate that prenatal cocaine exposure results in lasting changes to the regulation and responsivity of rat LC norepinephrine neurons. A similar dysregulation of LC norepinephrine neurons may occur in children exposed to cocaine during gestation, and this may explain, at least partly, the increased incidence of cognitive deficits that have been observed in these subjects.

Utilisation pattern of blood in a teaching hospital of Kolkata

An annual utilisation of blood transfusion services at several depts. of R.G. Kar Medical College and Hospital, Kolkata were assessed among a sample of 3122 patients selected by Systematic Random Sampling Technique from the register made available in the blood bank there. Record analysis revealed that overall 79.4% of supplied blood units were actually transfused, wastage of 21.6%. Wastage was maximum in the Department of Gynae & Obstetrics (33.11%) and Surgery (32.87%). Only single unit of blood was requisitioned and transfused for 5.44% & 30.90% of the patients respectively. Most common indications of blood transfusion were for surgical cases (37.92%), followed by anaemia (34.80%) and haemorrhage (26.92%). The use of blood and blood products merit attention, appraisal and instructional guiding accordingly.

Bioremediation of DDT in soil by genetically improved strains of soil fungus Fusarium solani

Bioremediation of DDT in soil by genetically improved recombinants of the soil fungus Fusarium solani was studied. The parent strains were isolated from soil enriched with DDD or DDE (immediate anaerobic and aerobic degradation products of DDT), as further degradation of these products are slow processes compared to the parent compound. These naturally occurring strains isolated from soil, however, are poor degraders of DDT and differed in their capability to degrade its metabolites such as DDD, DDE, DDOH and DBP and other organochlorine pesticides viz. kelthane and lindane. Synergistic effect was shown by some of these strains, when grown together in the medium containing DDD and kelthane under mixed culture condition. No synergism in DDE degradation was observed with the strains isolated from enriched soil. DDD-induced proteins extracted from individual culture filtrate (exo-enzyme) when subjected to SDS-Polyacrylamide Gel Electrophoresis (SDS-PAGE) showed complementary polypeptide bands in these strains i.e., each strain produced distinct DDD degrading polypeptide bands and the recombinant or hybrid strains produced all of the bands of the two parents and degraded DDD better than the parental strains. Recombinant hybrid strains with improved dehalogenase activity were raised by parasexual hybridisation of two such complementary isolates viz. isolate 1(P-1) and 4(P-2) showing highest complementation and are compatible for hyphal fusion inducing heterokaryosis. These strains are genetically characterised as Kel+Ben(R)DBP-Lin- and Kel-Ben(r)DBP+Lin+ respectively. Recombinants with mixed genotype, i.e., Kel+Ben(R)DBP+Lin+ showing superior degradation quality for DDT were selected for bioremediation study. Recombination was confirmed by polypeptide band analysis of DDD induced exo-proteins from culture filtrate using SDS-Polyacrylamide Gel Electrophoresis (PAGE) and RAPD (Random Amplified Polymorphic DNA) of genomic DNA using PCR (Polymerase Chain Reaction) technique. SDS-PAGE showed combination of DDD induced polypeptide bands characteristic of both the parents in the recombinants or the hybrids. PCR study showed the parent specific bands in the recombinant strains confirming gene transformation.

Glimpses of the advancement of medical science as depicted in the Mahäbhärata

The Mahabharata of Vedavyasa is an encyclopaedic work, which has got some importance from the standpoint of Indian medical science also. According to it Ayurveda was a compulsory subject which was taught to everybody. Perhaps, Mahabharata is the first epic which presents the term Ayurveda. The fundamentals of Ayurveda are discussed in it very well. Circulations of blood described here reminds us the same of sushruta samhita. Three types of poisons and a number of metals and jewels have also been given in Mahabharata.

S and G2 phase roles for Cdk2 revealed by inducible expression of a dominant-negative mutant in human cells

Cyclin-dependent kinase 2 (Cdk2) is essential for initiation of DNA synthesis in higher eukaryotes. Biochemical studies in Xenopus egg extracts and microinjection studies in human cells have suggested an additional function for Cdk2 in activation of Cdk1 and entry into mitosis. To further examine the role of Cdk2 in human cells, we generated stable clones with inducible expression of wild-type and dominant-negative forms of the enzyme (Cdk2-wt and Cdk2-dn, respectively). Both exogenous proteins associated efficiently with endogenous cyclins. Cdk2-wt had no apparent effect on the cell division cycle, whereas Cdk2-dn inhibited progression through several distinct stages. Cdk2-dn induction could arrest cells at the G1/S transition, as previously observed in transient expression studies. However, under normal culture conditions, Cdk2-dn induction primarily arrested cells with S and G2/M DNA contents. Several observations suggested that the latter cells were in G2 phase, prior to the onset of mitosis: these cells contained uncondensed chromosomes, low levels of cyclin B-associated kinase activity, and high levels of tyrosine-phosphorylated Cdk1. Furthermore, Cdk2-dn did not delay progression through mitosis upon release of cells from a nocodazole block. Although the G2 arrest imposed by Cdk2-dn was similar to that imposed by the DNA damage checkpoint, the former was distinguished by its resistance to caffeine. These findings provide evidence for essential functions of Cdk2 during S and G2 phases of the mammalian cell cycle.

Regulation of gene expression and cell growth in vivo by tetracycline using the hollow fiber assay

The hollow fiber assay presents a potentially unique tool to study the effects of regulated gene expression in cell lines that do not form tumors in vivo. The hollow fibers allow small molecules to pass freely through while keeping the cells within the fibers and segregated from host cells. OSp16.1 cells, derived from the U24 clone of the U2-OS osteogenic sarcoma tumor line, express the p16INK4a tumor suppressor under the regulation of tetracycline (tet) (Mitra J et al. Mol Cell Bio 19:3916, 1999). The in vitro induction of p16 in the OSp16.1 cell line is regulated by tet. The hollow fiber assay was used to determine whether the regulation of the p16 gene could be achieved in vivo, since these cells did not grow in the xenograft model. There were no differences in the in vivo growth pattern of U24 cells loaded into the hollow fibers with and without tet: 807% and 839% net growth, respectively. OSp16.1 cells in fibers in mice receiving 3.33 mg/kg/day tet had a 644% net growth after 21 days. There was a 194% net growth without tet. Immunoblotting of extracts prepared from the hollow fibers confirmed that p16 was induced in the absence of tet. These data demonstrate this assay is a useful tool for studying the effects of regulated gene expression in vivo.

The geographical data of the Kāśyapa Samhitā

One of the parameters in ascertaining the date of the Kashyapa Samhita is the data of geography referred to there in. Geography abounds various spheres like country, province, city, river, mountain and sea. The whole geographical material is mentioned in the chapter "Bhojana Kalpa" of the Kalpasthana, 22nd and 25th chapters of the Khilasthana.

Induction of p21(WAF1/CIP1) and inhibition of Cdk2 mediated by the tumor suppressor p16(INK4a)

The tumor suppressor p16(INK4a) inhibits cyclin-dependent kinases 4 and 6. This activates the retinoblastoma protein (pRB) and, through incompletely understood events, arrests the cell division cycle. To permit biochemical analysis of the arrest, we generated U2-OS osteogenic sarcoma cell clones in which p16 transcription could be induced. In these clones, binding of p16 to cdk4 and cdk6 abrogated binding of cyclin D1, p27(KIP1), and p21(WAF1/CIP1). Concomitantly, the total cellular level of p21 increased severalfold via a posttranscriptional mechanism. Most cyclin E-cdk2 complexes associated with p21 and became inactive, expression of cyclin A was curtailed, and DNA synthesis was strongly inhibited. Induction of p21 alone, in a sibling clone, to the level observed during p16 induction substantially reproduced these effects. Overexpression of either cyclin E or A prevented p16 from mediating arrest. We then extended these studies to HCT 116 colorectal carcinoma cells and a p21-null clone derived by homologous recombination. In the parental cells, p16 expression also augmented total cellular and cdk2-bound p21. Moreover, p16 strongly inhibited DNA synthesis in the parental cells but not in the p21-null derivative. These findings indicate that p21-mediated inhibition of cdk2 contributes to the cell cycle arrest imposed by p16 and is a potential point of cooperation between the p16/pRB and p14(ARF)/p53 tumor suppressor pathways.

Temperature-induced conformational changes in prosomatostatin-II: implications for processing

Somatostatin (SRIF) is a 14-residue peptide hormone synthesized in the hypothalamus and pancreatic islets. SRIF-14 and an N-terminally extended form, SRIF-28, are generated by the proteolytic processing of an approx. 102-residue precursor prosomatostatin (proSRIF) at a single set of paired basic residues (Arg-Lys) and at a monobasic (Arg) site respectively. Previous work in our laboratory demonstrated that the propeptide of SRIF mediates intracellular sorting; we suggested that this information resides in the prohormone structure. To identify putative sorting domains we have investigated structural features of recombinant anglerfish proSRIF-II purified from Escherichia coli. Two species of proSRIF-II were obtained: a monomeric form and a disulphide-linked dimer. CD analyses revealed that monomeric proSRIF-II lacks appreciable periodic secondary structure; however, on slow heating (2 degrees C/min) and cooling, it assumed a predominantly alpha-helical conformation. When subjected to a second heating-and-cooling cycle, the alpha-helical conformation was maintained. In contrast, the dimeric form of proSRIF-II was predominantly alpha-helical and its helicity did not increase in response to heating and recooling. Our results suggest that proSRIF-II might exist in several different folding intermediate states.

An assessment of missed opportunities for immunization in children and pregnant women attending different health facilities of a state hospital

The present study carried out in Calcutta National Medical College, Calcutta, has revealed problem of missed opportunities of immunisation in children and pregnant women and factors contributing to the problem. The percentage of missed opportunity in children and pregnant woman are 30% and 7% respectively. The major cause in case of children were that all the vaccines are not administered in all the days of week (71.05%) and in pregnant woman were wrong ideas about contraindication (42.86%) and indifferent attitude of the health worker (42.86%). All the missed opportunities were attributed to the health care providers.

Epidemiology of group-A streptococcal infection amongst children of different ethnic groups in Darjeeling

The carrier rate of Group A Streptococcus (GAS) was studied amongst 932 children from 1+ upto 12 years of age in three major racial groups in the foothills of the Darjeeling district of West Bengal. It was altogether 13 per cent and was found to be evenly distributed in the three ethnic groups as Gurkhas: 11 per cent, Rajbanshis: 15 per cent and Cosmopolitans: 13 per cent, but the incidence of Rheumatic fever and/or Rheumatic heart diseases were unnoticed among the Gurkha children who also had significant low ASO titres.

Regulation of the acquisition of meiotic competence in the mouse: changes in the subcellular localization of cdc2, cyclin B1, cdc25C and wee1, and in the concentration of these proteins and their transcripts

During their development, mammalian oocytes acquire the ability to resume meiosis. We demonstrate that the concentration of p34cdc2 increases during the acquisition of meiotic competence, as determined by immunoblotting, whereas the concentration of cyclin B1 decreases. Laser-scanning confocal microscopy corroborated these changes and furthermore indicate that an increase occurs in the nuclear concentration of each protein. Results of immunoblotting experiments demonstrate that associated with the acquisition of meiotic competence is an increase in the concentration of cdc25C, an activator of p34cdc2/cyclin B kinase, and a decrease in wee1, an inhibitor of cdc2/cyclin B kinase. These changes were again corroborated by laser-scanning confocal microscopy, which also indicates that an increase in the nuclear concentration of wee1 occurs. The concentration of the transcripts encoding these proteins, however, is essentially similar in meiotically incompetent and competent oocytes. Thus, these changes in protein concentration that occur during oocyte development likely reflect changes in the translational efficiency of their mRNAs. Consistent with this is that the relative rate of synthesis of p34cdc2 in meiotically competent oocytes is approximately 3 times greater than that in meiotically incompetent oocytes, whereas the stability of newly synthesized p34cdc2 is essentially the same in each cell type.

Ca2+ dependent activation of rat uterine glycerylphosphorylcholine diesterase: presence of a positive modulator protein in uterine secretion

The rat uterine secretory enzyme glycerylphosphorylcholine (GPC) diesterase (EC 3.1.4.2) had been purified and characterized previously with respect to its mol. wt., size, amino acid, carbohydrate composition and estrogen inducible properties. This enzyme is observed to have exclusive specificity for GPC and exhibits characteristic hyperbolic kinetics with Ca2+ in an ethyleneglycolbis N'N'N'N' tetraacetic acid (EGTA) buffered system. Ca2+ reduces Km of the enzyme for GPC from 0.65 to 0.25 mM. The Km for GPC of the partially purified enzyme is found to be 0.35 mM without addition of calcium which indicates the presence of a positive modulator of the enzyme in this fraction. Based on this rationale, a protein activating factor for the enzyme was isolated from this fraction which has a native size of 18 KD as observed on Sephacryl S-200 chromatography and strikingly stimulates enzyme activity at around 0.55 microM.

Association of glycerylphosphorylcholine with human sperm and effect of capacitation on their metabolism

The presence and localization of glycerylphosphorylcholine (GPC) on the surface of human sperm, as well as the metabolism of its breakdown product L-glycerol 3 phosphate (G3P), were investigated. GPC was found to be associated with sperm after penetrating cervical mucus and was present after repeated washing of the sperm. GPC was partially released by treatment with 0.4 M NaCl in 0.01 M sodium phosphate buffer (pH 7.4) and localized to the head region after sperm fractionation. G3P did not increase O2 uptake of uncapacitated human sperm. However, under aerobic conditions, lactate accumulated when exogenous G3P or uterine GPC diesterase was added to sperm in suspension. The uptake of O2 by washed capacitated sperm pre-incubated with 1 unit of rat uterine GPC diesterase for 30 min was significant. This effect was inhibited by 2 microM oligomycin indicating that oxidative phosphorylation had occurred. The present study indicates that GPC may play a role in the metabolism of human sperm after capacitation.

Measuring the interactions of the determinants of health

Considering environmental sanitation and health care services as most important determinants of health, this study was undertaken to know their impacts in an urban slum area of Calcutta. The families were studied in-depth and detail in relation to their health status in the form of morbidities and utilisation of preventive and promotive services. The health service impact was mainly assessed through comparative study between these who availed the services and to these who did not. Similarly, environmental sanitation services impact on health was measured through comparing the slum group with those who lived in Pucca houses. The criteria of priority decision on determinants was attempted through analysis of cost of these services and comparing their beneficial effects on health.

Intramedullary sodium cyanide injection on respiratory and vasomotor responses in cats

To examine the effect of hypoxia confined to the ventrolateral medulla we microinjected NaCN into the cat medulla (1.0 mm below the ventral surface) unilaterally and investigated cardio-respiratory changes. We studied anesthetized artificially ventilated animals and measured the electrical activity of phrenic and cervical sympathetic nerves and blood pressure. Histotoxic hypoxia depressed phrenic amplitude and elevated sympathetic tone and blood pressure. These responses were obtained predominantly from the region 5.0-8.0 mm caudal to the foramen caecum and 3.0-5.0 mm lateral to the midline (intermediate area). A study with 14C-cyanide showed that total and covalently bound cyanide was confined within a 1 mm diffusion sphere following microinjection. Isolated areas in both rostral and caudal medulla responded to cyanide with elevated sympathetic tone in the absence of phrenic nerve depression, suggesting dissociation of respiratory and vasomotor responses to hypoxia. Thus, the respiratory depression and vasomotor excitation produced by central hypoxia can be reproduced by hypoxia limited to discrete regions of the ventrolateral medulla.