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Biomedical subjects

D Langley

Publications and source records attributed to D Langley.

At least 19 recordsLinked to original sources
PubMed2002

Impact of community neonatal services: a multicentre survey.

OBJECTIVES: To explore the impact of a community neonatal service on high risk infant survivors in the first year of life. DESIGN: Retrospective multicentre survey. Postal questionnaires were sent to selected parents. SETTING: Thirty two neonatal units in England and Wales. PATIENTS INCLUSION CRITERIA: infants over 12 months of age with birth weight < or =1500 g, or who received level I intensive care for at least 48 hours. EXCLUSION CRITERIA: multiple births, infants who had died or had severe congenital abnormalities. A total of 3367 eligible infants were selected, and their parents were sent a questionnaire; 65% responded. MAIN OUTCOME MEASURES: Length of stay on the neonatal unit from birth to initial discharge. Readmission to hospital during the first year of life. RESULTS: The median length of stay in units with a community neonatal service was 35 days compared with 37 days in units without. When adjusted for infant and parent characteristics, the median length of stay was reduced by 12.6% where a community neonatal service was provided (95% confidence interval 5.3% to 19.3%). The readmission rates were 44.6% in units with a community neonatal service and 43.5% in units without. There was no significant reduction in the adjusted odds of readmission. CONCLUSIONS: The retrospective nature of this study means that these findings cannot be definitely attributed to the presence of a community neonatal service. However, the results suggest that community neonatal services may reduce the length of stay without any subsequent increase in readmission.

Community Health Services↗
PubMed2000

The Vancomycin biosynthetic pathway is induced in oxygen-limited Amycolatopsis orientalis (ATCC 19795) cultures that do not produce antibiotic.

Vancomycin biosynthetic capacity was stimulated in oxygen-limited bioreactor culture (6.4% DOT) of Amycolatopsis orientalis, coinciding with a down-regulation of the culture growth and protein synthesis rates. However no Vancomycin was detected. ATP production was similar in oxygen-limited and oxygen-sufficient cultures (400-150 µmole(ATP). g(biomass)(-1)). Our findings suggest a critical requirement for oxygen flux through the Vancomycin biosynthetic pathway, which is only met under nutrient-limited conditions in which oxygen is in excess.

Journal Article↗
PubMed1998

Specialized distributions of mitochondria and endoplasmic reticulum proteins define Ca2+ wave amplification sites in cultured astrocytes.

This study was undertaken to examine the expression and role of the endoplasmic reticulum (ER) proteins calreticulin and ryanodine receptors, and mitochondria, in cultured astrocytes. Using several lines of investigation, we have identified a key role for mitochondria in astrocyte Ca2+ signalling: (1) a significant correlation was found between sites of regenerative Ca2+ wave amplification (possessing high amplitude ER Ca2+ release) and the location of mitochondria in the cell; (2) norepinephrine (2 microM) caused a rapid-onset increase in rhod 2 fluorescence in 34% of astrocyte mitochondria, indicating that cytosolic Ca2+ responses result in mitochondrial Ca2+ elevation; and (3) pretreatment with the protonophore carbonyl cyanide p-(trifluoromethoxy)phenylhydrazone to inhibit mitochondrial activity markedly reduced the amplitude of subsequent norepinephrine-evoked cytosolic Ca2+ responses. We then investigated the roles of several ER proteins in Ca2+ signalling by immunocytochemistry. Ryanodine receptors and calreticulin were found to be expressed in heterogeneous patterns in astrocytes. The expression pattern of calreticulin corresponded closely with the distribution of mitochondria, whereas the expression of ryanodine receptors was not similar to that of either of these cellular factors. We measured Ca2+ wave kinetics in a single astrocyte, then assessed protein distribution by immunocytochemistry in the same cell. Cross-correlation between norepinephrine-evoked Ca2+ wave amplitude and calreticulin distribution indicated a close spatial relationship between this Ca2+-binding protein and sites of regenerative wave amplification. These results demonstrate that amplification sites for Ca2+ waves in astrocytes are identifiable by accumulations of calreticulin (and type 2 InsP3Rs), and by the presence of mitochondria, which may regulate the ER Ca2+ release process.

Animals↗
PubMed1998

Pyrimidine nucleotide-stimulated thromboxane A2 release from cultured glia.

1. Uridine triphosphate (UTP), uridine diphosphate (UDP), cytidine triphosphate (CTP), and deoxythymidine triphosphate (TTP) caused concentration-dependent increases in the release of thromboxane A2 (TXA2) from cultured glia prepared from the newborn rat cerebral cortex. Although each of the pyrimidine nucleotides displayed similar potencies, CTP and TTP were considerably less effective than either UTP or UDP. The purine nucleotide ATP was equally as potent as the pyrimidine nucleotides but was marginally less effective than either UTP or UDP. 2. The ability of UTP, UDP, TTP, and CTP to promote TXA2 release from cultured glia was inhibited in a concentration-dependent manner by suramin and was markedly reduced when incubations were performed either in Ca(2+)-free medium or on cultures which had been maintained in serum-free growth medium for 4 days prior to experimentation. 3. Challenges with UTP and UDP in combination were found to elicit a response which was no different from the effects of these nucleotides alone; in addition, their effects were reversed by the phospholipase A2 inhibitor ONO-RS-082. A slight reduction in UTP- and UDP-stimulated TXA2 release was observed in cultures grown in the presence of leucine methyl ester, a treatment reported to limit microglial survival. 4. These results suggest that glia are targets for extracellular pyrimidine nucleotides and that their ability to release eicosanoids from these cells may be important in the brain's response to damage.

Aminobenzoates↗
PubMed1996

Purine- and pyrimidine nucleotide-stimulated changes in intracellular calcium concentration in cultured astrocytes.

Cultured astrocytes prepared from the newborn rat cerebral cortex were challenged with a variety of purine and pyrimidine nucleotides and changes in intracellular Ca2+ concentration ([Ca2+]i) assessed. ATP, ADP, 2-methylthioadenosine triphosphate (2-MeSATP) and the pyrimidine nucleotide uridine triphosphate (UTP) produced Ca2+ transients which were characterized by an initial spike which decayed rapidly to a secondary plateau phase. Concentration response curves for these ligands gave the following rank order of potency: 2-MeSATP > ADP > ATP > UTP. Analysis of the number of cells responding to these nucleotides revealed that 2-MeSATP, ATP and ADP were effective in all cell fields examined whilst UTP generated a response in only 40%. In some experiments cells were challenged with various combinations of agonists. In those fields where ATP, 2-MeSATP and UTP were effective, the transients elicited by combined additions of these agonists were essentially the same as those produced by the agonists alone. Of the other nucleotides tested, uridine diphosphate was effective in only 24% of cell fields examined, moreover, its transient appeared to lack an initial spike phase. Guanosine triphosphate (GTP), cytidine triphosphate (CTP) and deoxythymidine triphosphate (TTP) were found to increase [Ca2+]i in 75%, 47% and 37% of cell fields respectively and the transients generated appeared to lack a secondary plateau phase. The responses to GTP, CTP and TTP also displayed rapid desensitization, a situation never encountered with ligands such as ATP.

Adenosine Diphosphate↗
PubMed1995

Effects of CGS 9343B (a putative calmodulin antagonist) on isolated skeletal muscle. Dissociation of signaling pathways for insulin-mediated activation of glycogen synthase and hexose transport.

The role of calmoudulin in control of carbohydrate metabolism in the absence and presence of insulin in isolated mouse soleus muscle was investigated. The calmodulin antagonist CGS 9343B had no effect on basal glycogen synthase activity, the contents of high energy phosphates, glucose-6-P, or glycogen synthesis. However, CGS 9343B inhibited the basal rates of 2-deoxyglucose uptake and 3-O-methylglucose transport by 30% (p < 0.05) and 40% (p < 0.001), respectively. Insulin activated glycogen synthase by almost 40% (p < 0.01) and this increase was not altered in the presence of CGS 9343B. Insulin increased the muscle content of glucose-6-P (approximately equal to 2-fold), as well as glycogen synthesis (approximately equal to 8-fold), 2-deoxyglucose uptake (approximately equal to 3-fold), and 3-O-methylglucose transport (approximately equal to 2-fold), and these increases were inhibited by CGS 9343B. In additional experiments on isolated rat epitrochlearis muscle, it was found that the hypoxia-mediated activation of 3-O-methylglucose transport was also inhibited by CGS 9343B. These data demonstrate that: 1) hexose transport, both in the absence and presence of external stimuli (insulin and hypoxia), requires functional calmodulin; and 2) insulin-mediated activation of glycogen synthase does not require functional calmodulin, nor can it be accounted for by increases in glucose transport or glucose-6-P.

3-O-Methylglucose↗
PubMed1994

Purine- and pyrimidine-stimulated phosphoinositide breakdown and intracellular calcium mobilisation in astrocytes.

Phosphoinositide breakdown in cultured cortical astrocytes was assessed by measuring the accumulation of [3H]inositol phosphates (IP's) following incubations with various purines and pyrimidines. Dose-response relationships gave the following order of potency: 2-methylthioadenosine triphosphate (2-MeSATP) > uridine 5'-triphosphate (UTP) > ATP = ADP > inosine 5' triphosphate (ITP). However, 2-MeSATP and UTP were only half as effective as either ATP or ADP in stimulating [3H]IP production. Astrocytes were also challenged with combined additions of maximally effective concentrations of agonists. Responses to ADP plus UTP and 2-MeSATP plus UTP were essentially additive whilst ATP plus UTP evoked a response which was only partially additive. ATP-stimulated [3H]IP accumulation was markedly reduced in the presence of 2-MeSATP suggesting that the latter may be a partial agonist at these receptors. We also examined the ability of ATP and UTP to increase intracellular Ca2+ concentrations in these cells. Greater than 90% of all cells tested responded to ATP with a release from internal Ca2+ stores but less than half of these responded similarly when challenged with UTP. Our results indicate that astrocytes possess both P2Y-purinoceptors and a population of receptors which are also coupled to phosphoinositide metabolism and intracellular Ca2+ mobilisation but recognise ATP and the pyrimidine nucleotide UTP.

Adenine Nucleotides↗
PubMed1994

Ryanodine-induced intracellular calcium mobilisation in cultured astrocytes.

Changes in intracellular Ca2+ concentration were monitored in cultured cortical astrocytes challenged with ryanodine and ATP. Ryanodine elicited a modest, in comparison to ATP, increase in cytosolic Ca2+ concentration in approximately 60% of the cell fields examined. This effect was evident and, in fact, was augmented when incubations were performed in Ca(2+)-free bathing medium. In addition, ryanodine-evoked changes in intracellular Ca2+ concentration were dose dependent, desensitised rapidly, and could not be mimicked by caffeine. Exposure to ryanodine was without effect on eicosanoid release from these cells nor did it influence Ca2+ mobilisation and eicosanoid release in response to ATP. In contrast, caffeine attenuated part of the ATP-evoked increase in intracellular Ca2+ concentration in the majority of cells tested and abolished its effect on eicosanoid release.

Adenosine Triphosphate↗
PubMed1988

Is a vaccine against AIDS possible?

The need to control the spread of human immunodeficiency viruses (HIVs) is unquestioned. Options for interference in the replicative cycle of HIV have been reviewed by Mitsuya and Broder. It is possible to propose antiviral agents which would be active at each stage of the cycle, but early experience suggests that highly selective antiviral agents which are free from side effects will not be easy to design and indeed random screening of existing medicinals may prove as rewarding. The natural history of HIV infection would suggest that vaccination is a strategy which requires urgent and exhaustive investigation.

Acquired Immunodeficiency Syndrome↗
PubMed1986

Differential interaction of normal and preneoplastic hamster bronchi with adriamycin.

Advanced bronchogenic carcinoma in humans is notoriously resistant to the cytocidal actions of cancer chemotherapy. The experiments reported here were undertaken as a first step in examining the mechanisms of resistance of carcinogen-altered bronchus to the actions of the commonly used cancerocidal agent Adriamycin. Syrian Golden hamsters were treated with an endobronchial carcinogen in order to produce bronchial neoplasms or with no carcinogen as controls. Hamsters were then given i.v. Adriamycin, and the amounts and metabolism of bronchial Adriamycin were determined. Peak uptake values were found 5 min after Adriamycin administration, and the amounts of Adriamycin in normal and carcinogen-altered bronchi were found to be similar. Whereas no metabolism of Adriamycin was observed in normal bronchi, 40-60% of total Adriamycin fluorescence was found to be due to Adriamycinol and Adriamycin aglycones in bronchi with premalignant changes. In separate experiments, the susceptibility of normal and carcinogen-altered bronchial extracts to drug-induced lipid peroxidation was measured in vitro. A 50% decrease was found in the ability of carcinogen-altered bronchi to act as a substrate for lipid peroxidation mediated by Adriamycin and an approximately 30% decrease for lipid peroxidation induced by t-butyl-hydroperoxide. These results demonstrate two different mechanisms by which bronchogenic carcinomas might become resistant to the chemotherapeutic actions of Adriamycin. These are by the carcinogen induction of metabolism of Adriamycin to less toxic products and by resistance of the bronchi to free radical damage.

Animals↗
PubMed1985

Anti-idiotope vaccines: can they exist?

Idiotopes and idiotypes are determinants on antibody molecules and lymphocyte receptors which confer a degree of uniqueness to these molecules; a number of the idiotypes are associated with the paratope (antigen-combining site) of the antibody. Since idotypic determinants can be recognized as 'foreign' by the autologous immune system, both antibodies and lymphocyte receptors which are anti-idiotypic in function can be found. Hence, anti-idiotype antibodies against paratope-associated idiotypes (Idp) would themselves have paratopes of similar conformation to the epitope on the antigen with which the Idp-bearing antibody reacted. These are the 'internal image' anti-idiotype antibodies. Vaccination of animals with such anti-idiotype preparations should result in the production of Idp-bearing antibody molecules. If these Idp antibodies were protective against infection by a particular pathogen, then the anti-idiotope [anti-(Idp)] preparation would be considered a surrogate antigen. Such anti-idiotype surrogate antigens have been identified, but they were polyclonal and their composition is not, as yet, completely understood. Monoclonal 'internal image' anti-idiotype antibodies have not proved to be consistently successful surrogate antigens. This may reflect a requirement for a minimum avidity of reaction, and antibody specificities in addition to that of the 'internal image'. Further insight into the composition of the polyclonal surrogate antigen is required before elaboration on an 'anti-idiotope vaccine' can be provided.

Animals↗
PubMed1983

A simple modification of the Salmonella liquid-incubation assay. Increased sensitivity for detecting mutagens in human urine.

A simple modification of the Salmonella/microsome liquid-incubation procedure improves the sensitivity of the assay for detecting mutagens in human urine. Extracts from cigarette smokers' urine were used as a model complex mutagenic mixture for validation of the assay. The modification consists of adding increased numbers of bacterial cells (approximately 10(9] in a concentrated suspension to liver homogenate mix and urine extract, all in 0.2-ml volume. After 90 min incubation at 37 degrees C, the mixture is processed according to the standard Ames test protocol. This procedure is 20 times more sensitive than the standard plate-incorporation test and 13 times more sensitive than a previously reported liquid-incubation protocol. The number of spontaneous revertants did not increase under these conditions and, compared to the plate-incorporation test, 10-fold less liver homogenate and 5-fold less enzymatic cofactors were needed per plate. The procedure was approximately 14 times more sensitive in detecting the mutagenic activity of benzo[ a ]pyrene. We also used the modification to determine mutagenic activity in urine from a group of nonsmokers. The method may be generally useful for investigations of mutagenic activity in human urine samples.

Adult↗
PubMed1981

Detection of high levels of polyadenylate-containing RNA in bacteria by the use of a single-step RNA isolation procedure.

A new one-step procedure for the isolation of bacterial RNA, involving lysis by proteinase K in the presence of sodium dodecyl sulfate, is described. Pulse-labeled RNA isolated by this procedure for Bacillus brevis, Bacillus subtilis, and Escherichia coli B has been found to contain a substantial fraction (15-40%) of polyadenylated RNA as determined by adsorption to oligo(dT)-cellulose. This contrasts with RNA isolated by procedures involving phenol extraction, a process which appears to lead to the selective loss of polyadenylated RNA. The presence of polyadenylated RNA in E. coli was confirmed by an independent method which involved hybridization with [3H]polyuridylic acid. Using the proteinase K method for RNA isolation, it was possible to demonstrate the in vitro synthesis of polyadenylated RNA by toluene-treated cells of B. brevis, B. subtilis, and E. coli.

Bacillus↗
PubMed1981

Analysis of mutagenic activity in cigarette smokers' urine by high performance liquid chromatography.

Mutagenic activity in smokers' urine which had been concentrated by XAD-2 resin can be separated from approximately 90% of the non-mutagenic material by CH2Cl2 extraction. This extract appears to be stable for 3 months at -20 degrees C. High performance liquid chromatography analysis of the CH2Cl2 extract showed multiple mutagenic non-polar fractions which were better activated by rat liver homogenates prepared from 3-methylcholanthrene treated rats than from rats treated with phenobarbital. Mutagenic activity in smokers' urine was extractable by acid, but not by base. The mutagens in smokers' urine appear to be a complex mixture of relatively non-polar chemicals.

Animals↗
PubMed1979

Comparison of the effect of linear gramicidin analogues on bacterial sporulation, membrane permeability, and ribonucleic acid polymerase.

Various analogues of linear gramicidin were tested for their biological activity in restoring the normal spore phenotype of gramicidin-negative mutants of Bacillus brevis and for their ability to increase cation conductivity of black lipid membranes and to inhibit bacterial RNA polymerase. Whereas many biologically active gramicidin analogues had no effect on membrane permeability, all biologically active peptides were able to inhibit ribonucleic acid (RNA) polymerase. These observations make it unlikely that membranes are the site of action of gramicidin during bacterial sporulation, but they are consistent with the notion that gramicidin functions to control RNA synthesis during the transition from vegetative growth to sporulation (Sarkar & Paulus, 1972). The relationship between peptide structure and the ability to restore normal sporulation and inhibit RNA polymerase showed that the eight amino-terminal residues have little influence on the function of gramicidin, whereas the highly nonpolar repeating sequence D-leucyl-L-tryptophan is essential for biological activity and may represent the site of interaction with RNA polymerase.

Bacillus↗