Nutrients and pH regulate algicide accumulation in cultures of the cyanobacterium Oscillatoria laetevirens

• The change in algicide synthesis in response to nutrients and pH in axenic cultures of the planktonic cyanobacterium, Oscillatoria laetevirens is reported. • Analytical and bioassay techniques were used to determine the effects of nitrogen (N), sulpher (S), phosphorus (P), magnesium (Mg²⁺ ), calcium (Ca²⁺ ) and hydrogen (H⁺ ) on Oscillatoria laetevirens growth, secondary metabolite accumulation and minimum inhibitory concentration in culture filtrates. • Growth and secondary metabolite production were affected by nutrient addition. High algicide production, which was not dependent on optimal growth, correlated with deficiences of magnesium and phosphate, and high pH. Algicidal activity in the culture medium was not detected following organic nitrogen addition while optimal growth was sustained; however, ammonia reduced biomass yield but did not affect algicide formation. The differential algicide concentration inside the cells and in the culture medium indicated secretion by an efflux mechanism rather than leakage from aging cells. • Algicide production by Oscillatoria laetevirens was negatively regulated by both phosphate and magnesium, and by pH. The interactive influence of nutrients and allelopathy is discussed in species succession and dominance in the maintenance of freshwater blooms.

Influence of a counteradvertising media campaign on initiation of smoking: the Florida "truth" campaign

OBJECTIVES

The purpose of this study was to assess the short-term effects of television advertisements from the Florida "truth" campaign on rates of smoking initiation.

METHODS

A follow-up survey of young people aged 12 to 17 years (n = 1820) interviewed during the first 6 months of the advertising campaign was conducted. Logistic regression analyses were used to estimate the independent effects of the campaign on smoking initiation while other factors were controlled for.

RESULTS

Youths scoring at intermediate and high levels on a media effect index were less likely to initiate smoking than youths who could not confirm awareness of television advertisements. Adjusted odds ratios between the media index and measures of initiation were similar within categories of age, sex, susceptibility, and whether a parent smoked.

CONCLUSIONS

Exposure to the "truth" media campaign lowered the risk of youth smoking initiation. However, the analysis did not demonstrate that all such media programs will be effective.

Structural perturbation of proteins in low denaturant concentrations

The presence of very low concentrations of the widely used chemical denaturants, guanidinium chloride and urea, induce changes in the tertiary structure of proteins. We have presented results on such changes in four structurally unrelated proteins to show that such structural perturbations are common irrespective of their origin. Data representative of such structural changes are shown for the monomeric globular proteins such as horseradish peroxidase (HRP) from a plant, human serum albumin (HSA) and prothrombin from ovine blood serum, and for the membrane-associated, worm-like elongated protein, spectrin, from ovine erythrocytes. Structural alterations in these proteins were reflected in quenching studies of tryptophan fluorescence using the widely used quencher acrylamide. Stern-Volmer quenching constants measured in presence of the denaturants, even at concentrations below 100 mM, were higher than those measured in absence of the denaturants. Both steady-state and time-resolved fluorescence emission properties of tryptophan and of the extrinsic probe PRODAN were used for monitoring conformational changes in the proteins in presence of different low concentrations of the denaturants. These results are consistent with earlier studies from our laboratory indicating structural perturbations in proteins at the tertiary level, keeping their native-like secondary structure and their biological activity more or less intact.

Requirement of the Lec35 gene for all known classes of monosaccharide-P-dolichol-dependent glycosyltransferase reactions in mammals

The Lec35 gene product (Lec35p) is required for utilization of the mannose donor mannose-P-dolichol (MPD) in synthesis of both lipid-linked oligosaccharides (LLOs) and glycosylphosphatidylinositols, which are important for functions such as protein folding and membrane anchoring, respectively. The hamster Lec35 gene is shown to encode the previously identified cDNA SL15, which corrects the Lec35 mutant phenotype and predicts a novel endoplasmic reticulum membrane protein. The mutant hamster alleles Lec35.1 and Lec35.2 are characterized, and the human Lec35 gene (mannose-P-dolichol utilization defect 1) was mapped to 17p12-13. To determine whether Lec35p was required only for MPD-dependent mannosylation of LLO and glycosylphosphatidylinositol intermediates, two additional lipid-mediated reactions were investigated: MPD-dependent C-mannosylation of tryptophanyl residues, and glucose-P-dolichol (GPD)-dependent glucosylation of LLO. Both were found to require Lec35p. In addition, the SL15-encoded protein was selective for MPD compared with GPD, suggesting that an additional GPD-selective Lec35 gene product remains to be identified. The predicted amino acid sequence of Lec35p does not suggest an obvious function or mechanism. By testing the water-soluble MPD analog mannose-beta-1-P-citronellol in an in vitro system in which the MPD utilization defect was preserved by permeabilization with streptolysin-O, it was determined that Lec35p is not directly required for the enzymatic transfer of mannose from the donor to the acceptor substrate. These results show that Lec35p has an essential role for all known classes of monosaccharide-P-dolichol-dependent reactions in mammals. The in vitro data suggest that Lec35p controls an aspect of MPD orientation in the endoplasmic reticulum membrane that is crucial for its activity as a donor substrate.

Preparation and in vitro dissolution of isoniazid from ethylcellulose microcapsules

Microcapsules of isoniazid were prepared by phase separation coacervation process induced by non-solvent addition and using ethylcellulose (EC) as coating polymer. When polyisobutylene (PIB)--a protective colloid was present at sufficient concentration, film coated drug particles were formed. At 0-6% PIB concentration, the microcapsules were aggregated. Increase of colloid concentration produced microcapsules of less aggregation and higher drug content because coating became progressively thinner. PIB concentration also controlled the particle size and the release rate of drug from microcapsules. Wall thickness and EC loss were calculated from drug content. Microcapsules coated with EC were prepared with 7-9% PIB. Scanning Electron Microscopy was used to study the nature of aggregation and coating behaviour. The in vitro dissolution study confirmed the first order release pattern and also the Higuchi Matrix model.

Computer supported studies on design and evaluation of solid dispersions of carbamazepine

The main advantages of solid dispersions (the drug could be maintained in a bioavailable form, dosage reduction and cleaner manufacturing conditions) provide scope for the continued interest in field. Additionally, their use in providing a sustained or controlled release of drugs has only been tentatively examined. In the present study, Carbamazepine has been used to develop a dosage form which will provide a booster amount followed by sustained release of the drug for effective control of epileptic seizures while keeping the serum level of the drug at minimum. Enteric polymers CAP and CAT have been used to retard the release till the formulation reaches the intestine. Either individually or combined fractions of the formulations may be used in the therapy of epilepsy.

Current understanding of pathogenesis of coronary artery disease and its future implications

Coronary artery disease (CAD) is the most important cause of morbidity and mortality in a population. Percutaneous coronary intervention and coronary artery by-pass grafting have greatly changed the treatment of CAD, still many questions remain unanswered. Atherosclerosis is a normal consequence of ageing but some patients may experience it at an earlier age. As regarding pathogenesis of atherosclerosis, it is described often as a focal process which is diffuse in nature primarily involving the vessel intima. Salient features of 'lesion prone areas' in atherosclerosis include increased endothelial permeability to an intimal accumulation of plasma proteins, including albumin, fibronogen and LDL. The clinical expression of atherosclerotic disease activities is determined by pathologic events leading to coronary thrombosis. A vulnerable plaque has the characteristics of: Extracellular lipid pool occupies a large proportion of overall plaque volume, the fibrous cap which separates the lipid core from luminal blood is thinner within, and high macrophage density. Typically these plaques cause < 50% cross-sectional stenosis of the artery. The contribution of CAD is clearly of both genetic and environmental in origin. An increase in shedding of cell adhesion molecules may be a characteristic of atherosclerotic lesion. There is also suggestion that plasminogen activation inhibitor type I (PAI-1) has an important role in atherogenesis. Angiogenic growth factors and their endothelial receptors function as major regulators of blood vessel formation. Thereapeutic angiogenesis can be achieved by exogenously adding VEGF and/or other angiogenic growth factors.

Electronic structure of Sr2FeMoO6

We have analyzed the unusual electronic structure of Sr2FeMoO6 combining ab initio and model Hamiltonian approaches. Our results indicate that there are strong enhancements of the intra-atomic exchange strength at the Mo site as well as the antiferromagnetic coupling strength between Fe and Mo sites. We discuss the possibility of a negative effective Coulomb correlation strength ( U(eff)) at the Mo site due to these renormalized interaction strengths.

Breeding habitats and larval indices of Aedes aegypti and Ae. albopictus in the residential areas of Calcutta City

Aedes aegypti and Ae. albopictus larvae were found breeding in almost all indoor and outdoor, temporary and/or permanent collections of water, either alone or in association with each other in residential areas of the city, the former throughout the year (June'97-May'98) and the latter during monsoons and post-monsoons only. Ae. aegypti showed preference for breeding in chowbachhas, indoors and Ae. albopictus for collections of water in flower pots and discarded containers and outdoors. The larval indices of both the species were highest during monsoons and post-monsoons.

Prognostic implications of ventricular fibrillation in acute myocardial infarction: new strategies required for further mortality reduction

OBJECTIVE

To determine the changing risk of ventricular fibrillation, the prognostic implications, and the potential long term prognostic benefit of earlier hospital admission, after acute myocardial infarction.

DESIGN

Prospective observational study.

SETTING

A district general hospital in east London.

PATIENTS

1225 consecutive patients admitted to a coronary care unit with acute myocardial infarction.

MAIN OUTCOME MEASURES

Time of onset of pain and ventricular fibrillation, and long term survival of patients admitted with acute myocardial infarction.

RESULTS

The rate of ventricular fibrillation in these hospital inpatients was high in the first hour from onset of pain (118 events/1000 persons/h; 95% confidence interval (CI) 50.7 to 231) and fell rapidly to an almost constant low level by six hours; 27.4% of patients with early ventricular fibrillation died in hospital, compared with 11.6% of those without (p < 0.0001), but mortality in patients who survived to hospital discharge was not altered by early ventricular fibrillation (five year survival: 75.0% (95% CI 60.0% to 84.8%) with ventricular fibrillation v 73.3% (95% CI 69.6% to 76.6%) without ventricular fibrillation).

CONCLUSIONS

Patients successfully resuscitated from early ventricular fibrillation have the same prognosis as those without ventricular fibrillation after acute myocardial infarction. Faster access to facilities for resuscitation must be achieved if major improvements in the persistently high case fatality of patients after acute myocardial infarction are to be made.

Expression of estrogen receptor coactivators in the rat uterus

Nuclear receptor coactivators associate in a ligand-dependent manner with estrogen receptors (ER) and other nuclear receptors, and they enhance ligand-dependent transcriptional activation. This study examined basal coactivator expression in rat uterus to investigate if expression of these genes is regulated by estradiol-17 beta or tamoxifen. Ovariectomized mature and immature rats were injected with estradiol-17 beta, tamoxifen, or vehicle (i.e., sesame oil) alone. Uteri were collected and analyzed for changes in coactivator mRNA expression using Northern blot and in situ hybridization analyses. Constitutive uterine mRNA expression of switch protein for antagonist (SPA), SRC-1, GRIP1, RAC3, RIP140, and p300 mRNAs was observed in control uteri, and treatment with ER ligands did not alter coactivator mRNA levels. The data suggest that expression of these coactivator genes is not sensitive to estradiol or tamoxifen in the rat uterus. No cell type-specific pattern of expression was apparent in uterine sections from mature and immature rats; however, silver grains were more abundant in luminal and glandular epithelial cells compared with the stroma and myometrium, indicating that coactivator mRNA levels vary among the uterine compartments. Thus, to our knowledge, we show for the first time that there is constitutive expression of several uterine nuclear receptor coactivators in a physiological setting that remains insensitive to estrogenic regulation. Furthermore, we speculate that higher constitutive levels of coactivator expression in glandular and luminal epithelial cells may be associated with increased hormonal responsiveness by these uterine compartments.

Catalase activity of oxygenase domain of rat neuronal nitric oxide synthase. Evidence for product formation from L-arginine

Nitric oxide synthases (NOSs) catalyze the formation of nitric oxide from L-arginine. We purified the heme containing, tetrahydrobiopterin-free, oxygenase domain of rat neuronal nitric oxide synthase (nNOSox) overexpressed in Escherichia coli. We found catalase activity in nNOSox. This is significant because H(2)O(2) may also be a product of nitric oxide synthases. We found H(2)O(2) assisted product formation from N-hydroxy-L-arginine and even from L-arginine both in the presence and in absence of tetrahydrobiopterin. We propose how heme moiety of the oxygenase domain alone is sufficient to carry out both steps of the NOS catalysis.

The industry manipulation attitudes of smokers and nonsmokers

A cross-sectional random sample was obtained of Florida youth between the ages of 12-17. Data were collected through a telephone survey after obtaining parent and child consent. Industry manipulation attitudes of three groups (self-identified nonsmokers who did not use cigarettes in the past 30 days, self-identified nonsmokers who used cigarettes in the past 30 days, and self-identified smokers who used cigarettes in the past 30 days) were compared. Constraints resulting from the method of data collection resulted in a conservative estimate of the strength of the association between industry manipulation attitudes and smoking behavior.

Review article: transcriptional events controlling the terminal differentiation of intestinal endocrine cells

Secretin-producing enteroendocrine cells arise from a multipotential endocrine progenitor in the crypts of the small intestine. As these cells migrate up the crypt-villus axis, they produce secretin and stop dividing as they terminally differentiate and die. Transcription of the secretin gene is controlled by a complex enhancer binding to multiple transcription factors. The basic helix-loop-helix protein, BETA2, binds to an E box sequence and associates with the p300 coactivator to activate transcription of the secretin gene. Basic helix-loop-helix proteins appear to play a pivotal role in the control of cellular differentiation. BETA2 induces cell cycle arrest and apoptosis in addition to activating secretin gene expression. Thus BETA2 may function as a master regulatory gene to coordinate terminal differentiation of secretin cells.

A stable latent reservoir for HIV-1 in resting CD4(+) T lymphocytes in infected children

HIV-1 persists in a latent state in resting CD4(+) T lymphocytes of infected adults despite prolonged highly active antiretroviral therapy (HAART). To determine whether a latent reservoir for HIV-1 exists in infected children, we performed a quantitative viral culture assay on highly purified resting CD4(+) T cells from 21 children with perinatally acquired infection. Replication-competent HIV-1 was recovered from all 18 children from whom sufficient cells were obtained. The frequency of latently infected resting CD4(+) T cells directly correlated with plasma virus levels, suggesting that in children with ongoing viral replication, most latently infected cells are in the labile preintegration state of latency. However, in each of 7 children who had suppression of viral replication to undetectable levels for 1-3 years on HAART, latent replication-competent HIV-1 persisted with little decay, owing to a stable reservoir of infected cells in the postintegration stage of latency. Drug-resistance mutations generated by previous nonsuppressive regimens persisted in this compartment despite more than 1 year of fully suppressive HAART, rendering untenable the idea of recycling drugs that were part of failed regimens. Thus the latent reservoir for HIV-1 in resting CD4(+) T cells will be a major obstacle to HIV-1 eradication in children.

Effect of retinoic acid on integrin receptors of B16F10 melanoma cells

The intriguing problem of metastasis requires the spreading of metastatic cells through the basement membrane barrier. The interaction of the basement membrane with the metastatic cell is a cell surface activity involving the function of integrin receptors. Integrins are a group of alpha,beta heterodimeric proteins responsible for transducing intracellular signals on binding to the extracellular matrix proteins present in the basement membrane. To understand the role of integrin receptors in tumor metastasis, the cell surface receptor functions were modulated by All Trans Retinoic Acid (ATRA) treatment in B16F10 tumor cells. Our experimental results clearly indicate that All Trans Retinoic Acid (ATRA) inhibit metastatic potential of highly metastatic B16F10 melanoma cells by 1) downregulating the cell surface integrin receptors against ECM proteins specially laminin and vitronectin and 2) by inhibiting the 72 kd collagenase activity.

"On new settings in some centrosymmetric space groups": Corrigendum

Certain mistakes in the author´s previous publication [1] have since been detected. It appears that some of the space groups listed therein cannot accommodate the alternative new settings of unit cell, because in these cases, when coordinates of equivalent points are obtained with reference to the new setting, they do not form an orbit of the particular space group. In other words, the two-fold rotation relating the old and the suggested new settings of the unit cell does not leave the configuration of the symmetry elements of such a space group undisturbed. A corrected list of centrosymmetric space groups which do allow new settings and in which, consequently, pairs of `polar´ descriptions of structures are possible, is presented below. This list replaces the one that appeared in [1].