Search PubMed⌕ Search

Biomedical subjects

S Ward

Publications and source records attributed to S Ward.

At least 145 records · Page 8Linked to original sources
PubMed1998

The influence of mini-BAL cultures on patient outcomes: implications for the antibiotic management of ventilator-associated pneumonia.

STUDY OBJECTIVE: To determine the influence of mini-BAL culture results on subsequent changes in antibiotic therapy and patient outcomes. DESIGN: Prospective, single-center, cohort study. SETTING: Medical ICU of Barnes-Jewish Hospital, St. Louis, a university-affiliated teaching hospital. PATIENTS: One hundred thirty mechanically ventilated patients undergoing mini-BAL for suspected ventilator-associated pneumonia (VAP). INTERVENTIONS: Mini-BAL, prospective patient surveillance, and data collection. MEASUREMENTS AND RESULTS: Sixty (46.2%) patients had mini-BAL cultures that yielded at least one pathogen potentially accounting for the clinically suspected episode of VAP (64 bacterial, 3 viral, 2 fungal). Among the 60 patients with microbiologically positive mini-BAL cultures, 44 (73.3%) were classified as receiving inadequate antibiotic therapy (ie, identification of a microorganism resistant to the prescribed antibiotic regimen). Prior antibiotic administration or its absence remained unchanged in 51 (39.2%) patients based on the mini-BAL culture results, while in another 51 (39.2%) patients, antibiotic therapy was either begun (n=7) or the existing antibiotic regimen was changed (n=44), and in the remaining 28 (21.6%) patients, antibiotic therapy was discontinued altogether. The hospital mortality rates of these three groups were statistically different: 33.3%, 60.8%, and 14.3%, respectively (p<0.001). The most common pattern of antibiotic resistance resulting in an antibiotic change following mini-BAL was the identification of a Gram-negative bacteria resistant to a prescribed third-generation cephalosporin in 23 of 44 (52.3%) patients. Twenty-one of these 23 patients (91.3%) received prior therapy with a cephalosporin class antibiotic during the same hospitalization. Having an immunocompromised state (adjusted odds ratio [OR]=2.45; 95% confidence interval, 1.56 to 3.85; p=0.047) and the presence of a pathogen in the mini-BAL culture resistant to the empirically prescribed antibiotic regimen (adjusted OR=3.28; 95% confidence interval, 2.12 to 5.06; p=0.006) were identified as risk factors independently associated with hospital mortality by logistic regression analysis. CONCLUSIONS: These data suggest that antibiotic selection prior to obtaining the results of lower airway cultures is an important determinant of outcome for patients with suspected VAP. A delay in initiating adequate antibiotic therapy was associated with a greater mortality. Therefore, the initial selection of antibiotics for the empiric treatment of VAP should be broad enough to cover all likely pathogens, including antibiotic-resistant bacteria. This appears to be especially important in patients having received prior antibiotics.

Adult↗
PubMed1997

Identification of the tuberous sclerosis gene TSC1 on chromosome 9q34.

Tuberous sclerosis complex (TSC) is an autosomal dominant disorder characterized by the widespread development of distinctive tumors termed hamartomas. TSC-determining loci have been mapped to chromosomes 9q34 (TSC1) and 16p13 (TSC2). The TSC1 gene was identified from a 900-kilobase region containing at least 30 genes. The 8.6-kilobase TSC1 transcript is widely expressed and encodes a protein of 130 kilodaltons (hamartin) that has homology to a putative yeast protein of unknown function. Thirty-two distinct mutations were identified in TSC1, 30 of which were truncating, and a single mutation (2105delAAAG) was seen in six apparently unrelated patients. In one of these six, a somatic mutation in the wild-type allele was found in a TSC-associated renal carcinoma, which suggests that hamartin acts as a tumor suppressor.

Amino Acid Sequence↗
PubMed1997

Increased competitiveness of nematode sperm bearing the male X chromosome.

Male offspring, which cannot reproduce independently, represent a cost of sexual reproduction. This cost is eliminated by the production of hermaphroditic offspring in the self-fertilizing nematode Caenorhabditis briggsae. However, these hermaphrodites can outcross by mating with males. Half the sperm received from males contain no sex chromosome and therefore give rise to male progeny. Mating with males should thus impose the cost of making male offspring. We found that male sperm took immediate precedence over hermaphrodite sperm, resulting in maximized outcrossing, but the appearance of male progeny was delayed after mating. This delay is caused by the male X-bearing sperm outcompeting their nullo-X counterparts. The competitive advantage of X-bearing sperm over nullo-X sperm is limited to sperm from males; it did not occur in a mutant hermaphrodite that produces both types of sperm. The chromosomal effect on sperm competitiveness in C. briggsae, which has not been observed in other species, suggests that the X chromosome has evolved a form of meiotic drive, selfishly increasing the competitiveness of sperm that bear it over those that do not. Thus, the multiple levels of sperm competitiveness found in C. briggsae maximize outcrossing after mating while delaying the cost of making male offspring.

Animals↗
PubMed1997

Mutations in the TSC2 gene: analysis of the complete coding sequence using the protein truncation test (PTT).

Mutations in the TSC2 gene on chromosome 16p13.3 are responsible for approximately 50% of familial tuberous sclerosis (TSC). The gene has 41 small exons spanning 45 kb of genomic DNA and encoding a 5.5 kb mRNA. Large germline deletions of TSC2 occur in <5% of cases, and a number of small intragenic mutations have been described. We analysed mRNA from 18 unrelated cases of TSC for TSC2 mutations using the protein truncation test (PTT). Three cases were predicted to be TSC2 mutations on the basis of linkage analysis or because a hamartoma from the patient showed loss of heterozygosity for 16p13.3 markers. Three overlapping PCR products, covering the complete coding sequence of mRNA, were generated from lymphoblastoid cell lines, translated into 35S-methionine labelled protein, and analysed by SDS-PAGE. PCR products showing PTT shifts were directly sequenced, and mutations confirmed by restriction enzyme digestion where possible. Six PTT shifts were identified. Five of these were caused by mutations predicted to produce a truncated protein: (i) a sporadic case showed a 32 bp deletion in exon 11, and a mutant mRNA without exon 11 was produced; the normal exon 10 was also spliced out; (ii) a sporadic case had a 1 bp deletion in exon 12 (1634delT); (iii) a TSC2-linked mother and daughter pair had a G-->T transversion in exon 23 (G2715T) introducing a cryptic splice site causing a 29 bp truncation of mRNA from exon 23; (iv) a sporadic case showed a 2 bp deletion in exon 36; (v) a sporadic case showed a 1 bp insertion disrupting the donor splice site of exon 37 (5007+2insA), resulting in the use of an upstream exonic cryptic splice site to cause a 29 bp truncation of mRNA from exon 37. In one case, the PTT shift was explained by in-frame splicing out of exon 10, in the presence of a normal exon 10 genomic sequence. Alternative splicing of exon 10 of the TSC2 gene may be a normal variant. Three 3rd base substitution polymorphisms were also detected during direct sequencing of PCR products. Confirmed mutations were identified in 28% of the families studied and on the assumption that half of the sporadic cases should have TSC2 mutations, a crude estimate of the detection rate would be 60%. This compares favourably with other screening methods used for TSC2, notably SSCP, and since PTT involves much less work it may be the method of choice.

Alternative Splicing↗
PubMed1997

Vitamin A deficiency and mutations of RXRalpha, RXRbeta and RARalpha lead to early differentiation of embryonic ventricular cardiomyocytes.

Knock-out of the mouse RXRalpha gene was previously shown to result in a hypoplastic heart ventricular wall, histologically detectable in 12.5 dpc fetuses. We show here that a precocious differentiation can be detected as early as 8.5 dpc in ventricular cardiomyocytes of RXRalpha(-/-) mutants. This precocious differentiation, which is characterized by the presence of striated myofibrils, sarcoplasmic reticulum and intercalated disks, is found after 9.5 dpc in about 50% of RXRalpha(-/-) subepicardial myocytes. In contrast, wild-type subepicardial myocytes remain morphologically undifferentiated up to at least 16.5 dpc. A similar precocious differentiation was observed in 9.5 dpc subepicardial myocytes of several RXRbeta(-/-) and RARalpha(-/-) mutants, as well as in vitamin A-deficient embryos. The proportion of differentiated subepicardial myocytes almost reached 100% in RXRalpha/RXRbeta double null mutants, indicating a partial functional redundancy between RXRalpha and RXRbeta. This differentiation defect was always paralleled by a decrease in the mitotic index. In addition, subepicardial myocytes of RXRalpha(-/-), RXRalpha(-/-)/RXRbeta(-/-) or vitamin A deficient, but not of RXRbeta(-/-) and RARalpha(-/-) embryos, were often flattened and more loosely connected to one another than those of WT embryos. Thus, retinoids are required at early stages of cardiac development to prevent differentiation, support cell proliferation and control the shape of ventricular myocytes, and both RXRs and RARs participate in the mediation of these functions.

Animals↗
PubMed1997

A nematode gene required for sperm vesicle fusion.

During maturation of spermatids to motile spermatozoa in Caenorhabditis elegans, large vesicles called membranous organelles (MOs) fuse with the spermatid plasma membrane. Mutations in the gene fer-1 cause abnormal spermatozoa in which the MOs do not fuse, although they abut the plasma membrane normally. Here we describe the fer-1 gene, which we found to be approximately 8.6 kb in length and to encode a 6.2 kb transcript whose expression is limited to the primary spermatocytes, the cells in which the MOs form. fer-1 is predicted to encode a 235 kDa protein which is highly charged except for a putative transmembrane domain near the C terminus. We identified the mutations associated with five fer-1 alleles, all of which are missense mutations causing single amino acid changes. FER-1 is not similar to any characterized proteins in sequence databases, nor does it contain known functional motifs other than the predicted transmembrane domain. The C-terminal transmembrane domain makes FER-1 resemble some viral fusion proteins, suggesting it may play a direct role in MO-plasma membrane fusion. FER-1 does show significant sequence similarity to several predicted human proteins of unknown function. Two of the identified fer-1 mutations are located in regions of similarity between FER-1 and two of these predicted proteins. This strengthens the biological significance of these similarities and suggests these regions of similarity represent functionally important domains of FER-1 and the human proteins.

Amino Acid Sequence↗
PubMed1997

Infection with Plasmodium berghei alters benzodiazepine receptor in rat brain.

The purpose of this study was to assess the effect of malaria infection on benzodiazepine binding in rat brain. Young male Wistar rats were infected with the rodent parasite Plasmodium berghei, while age-matched control rats (n = 5) received normal saline intraperitoneally. Parasitemia was determined in blood of infected animals. Animals were killed after two weeks, and synaptosomal brain membrane homogenate was prepared from cerebral cortex. Membrane homogenate was incubated in duplicate with 3H-flunitrazepam (0.2-10 nM in buffer, pH 7.4) and binding parameters determined. The number of receptors (Bmax) was decreased marginally but significantly (P = 0.047) in malaria-infected (MI) rats (MI rats: 1.12 +/- 0.1 pmol.mg-1 protein; control rats: 1.42 +/- 0.08 pmol.mg-1 protein) while binding affinity (Kd) was not altered (MI rats: 1.18 +/- 0.3 nM; control rats: 1.02 +/- 0.15 nM). These results suggest that malaria may be associated with decreased benzodiazepine activity.

Animals↗
PubMed1996

Effects of aging on neuroendocrine activation in subjects and patients in the presence and absence of heart failure with left ventricular systolic dysfunction.

The neuroendocrine profile and echocardiographic features of 40 patients (81 +/- 1 years, means +/- standard error) with heart failure and impaired left ventricular systolic function were compared with those of an age-matched group of healthy subjects, 20 younger patients with heart failure (aged 58 +/- 1 years) and 15 younger healthy subjects. Normal elderly subjects had a neuroendocrine profile similar to that of healthy younger subjects apart from elevated plasma norepinephrine (958 +/- 84 vs 302 +/- 118 pg/ml; p< 0.001) and atrial natriuretic peptide ( 40 +/- 6 vs 28 +/- 5 pg/ml; p<0.05). Despite a similar severity of heart failure, elderly patients had smaller ventricular dimensions (left ventricular internal dimension in diastole 51 +/- 2 vs 69 +/- 3 mm;p<0.0001 and greater impairment of ventricular compliance using Doppler indexes. Plasma norepinephrine was higher (1,191 +/- 80 vs 620 +/- 67 ppg/ml; p<0.01), and plasma atrial natriuretic peptide, plasma active renin, and angiotensin II were lower in elderly patients than in the younger patients with heart failure. As functional capacity declines with age, elderly patients may have less severe cardiac dysfunction for any given level of functional impairment, and this may account for most of the differences in neuroendocrine activity with age. Age appears to be an important determinant of plasma norepinephrine and may be a confounding factor in interpreting the prognostic significance of this hormone.

Aged↗
PubMed1996

Genetic and molecular analysis of spe-27, a gene required for spermiogenesis in Caenorhabditis elegans hermaphrodites.

Hermaphrodites with mutations in the spe-27 gene are self-sterile, laying only unfertilized eggs; mutant males are fertile. Hermaphrodites make spermatids that fail to activate to crawling spermatozoa so passing oocytes sweep them out of the spermatheca. These spermatids do activate and produce self-progeny if young mutant hermaphrodites are mated by fertile (or sterile) males. Spermatids isolated from either mutant males or hermaphrodites initiate activation in vitro when treated with proteases, but then arrest with spiky membrane projections that resemble those of a normal intermediate in pseudopod formation. These phenotypes are identical to spe-8 and spe-12 mutants. They can be explained if males and hermaphrodites have distinct pathways for spermatid activation, and these three genes are necessary only for the hermaphrodite pathway. Consistent with this model, when spe-27 mutant male spermatids without seminal fluid are artificially inseminated into hermaphrodites, they fail to activate. The spe-27 gene has been isolated, sequenced and its regulatory regions identified. The sequence predicts a 131 amino acid polypeptide that has no striking structural motifs and no resemblance to known proteins. Two of the mutations in spe-27 alter mRNA splicing; a third mutation is a temperature-sensitive missense mutation.

Amino Acid Sequence↗
PubMed1996

Stability of plasma concentrations of N and C terminal atrial natriuretic peptides at room temperature.

BACKGROUND: Plasma concentrations of atrial natriuretic peptide (ANP) are increased in patients with ventricular dysfunction and could have a diagnostic role in heart failure. ANP may be unstable after collection, however, limiting any practical diagnostic role. METHODS: Blood samples were obtained from 18 patients with various conditions. Aliquots were either processed optimally or kept as blood or plasma at room temperature for 6-72 h before processing. RESULTS: Concentrations of C-terminal ANP were lower in specimens kept as blood for 24 and 72 h (mean difference from control -43% and -76%, respectively, (P < 0.001) but N-terminal ANP (extracted) seemed to be stable under all conditions studied (-2% at 24 h and -7% at 72 h, not significant). CONCLUSIONS: N-terminal ANP (extracted) is stable and potentially has a role in the diagnosis of heart failure in routine clinical practice.

Aged↗
PubMed1996

Assessment of oxygen supplementation during air travel.

BACKGROUND: The aim of this study was to simulate an in flight environment at sea level with a fractional inspired concentration of oxygen (FiO2) of 0.15 to determine how much supplemental oxygen was needed to restore a subject's oxygen saturation (SaO2) to 90% or to the level previously attained when breathing room air (FiO2 of 0.21). METHODS: Three groups were selected with normal, obstructive, and restrictive lung function. Using a sealed body plethysmograph an environment with an FiO2 of 0.15 was created and mass spectrometry was used to monitor the FiO2. Supplemental oxygen was administered to the patient by nasal cannulae. SaO2 was continuously monitored and recorded at an FiO2 of 0.21, 0.15, and 0.15 + supplemental oxygen. RESULTS: When given 2 l/m of supplemental oxygen all patients in the 15% environment returned to a similar SaO2 value as that obtained using the 21% oxygen environment. One patient with airways obstruction needed 3 l/m of supplemental oxygen to raise his SaO2 above 90%. CONCLUSIONS: This technique, which simulates an aircraft environment, enables an accurate assessment to be made of supplemental oxygen requirements.

Aircraft↗
PubMed1996

Computerised augmentative communication devices for people with dysphasia: design and evaluation.

Recent developments in low-cost computer technology suggest that substantial improvements are possible in communication aids for dysphasic patients. This study describes a recently developed communication aid and reports a case study of one application. The software (EasySpeaker for Windows) provides an easily customized and flexible icon-based communication aid, which does not require the ability to read text, but which automatically records in detail the use being made of the device. The aid was given to a dysphasic patient in his own home for 4 weeks. Regular activity sessions were held throughout the period and data obtained from these sessions to identify learning and improvement on the device. Although improvements were found in speed and accuracy of operation, the use made of the aid for real communication by this patient was limited. Several possible reasons are identified for this and, in particular, the importance of illustrating specifically how such a system can be of benefit is emphasised.

Aphasia↗
PubMed1995

Sperm precedence in a hermaphroditic nematode (Caenorhabditis elegans) is due to competitive superiority of male sperm.

When male and hermaphrodite Caenorhabditis elegans mate, the male's sperm outcompete the hermaphrodite's own sperm and fertilize a majority of the offspring. Here, we investigate the mechanism of male sperm precedence. We rule out the possibility that male sperm are stronger and more competitive because they are activated later than hermaphrodite sperm. We also find that a previously known gender difference in sperm activation does not influence sperm competition. Male sperm, rinsed free of seminal fluid, retained the capacity to take precedence after artificial insemination. Therefore, we conclude that male sperm themselves are competitively superior to hermaphrodite sperm. This trait maximizes outcrossing after mating and may increase both genetic diversity and heterozygosity of offspring whose parents, due to self-fertilization, may be highly homozygous.

Animals↗
PubMed1995

Purification of human hepatic arginase and its manganese (II)-dependent and pH-dependent interconversion between active and inactive forms: a possible pH-sensing function of the enzyme on the ornithine cycle.

Purification of human liver arginase by chromatography on DEAE-Sepharose, CM-Sepharose, hydroxylapatite, and MonoS yielded protein of greater than 95% purity by sodium dodecyl sulfate-gel electrophoresis. Detailed kinetic studies of the interconversion of active and inactive forms of arginase showed the effects of metal ion addition and withdrawal, metal ion type, time, temperature, and pH. At pH 7 and 37 degrees C, removal of Mn2+ caused a first-order deactivation with half-life of 1 h. Reactivation was completed within 0.5 min (1 mM Mn2+) or 90 min (ca. 6 nM Mn2+). Activation by Mn2+ showed a hyperbolic response, with Kd for Mn2+ of about 36 nM. Mn2+ apparently displaced about 2 H+, resulting in sigmoid dependence upon concentration of OH-. Both the maximal velocity of catalysis and the Km toward arginine were markedly pH-dependent in the physiological range. The findings lead to a model where Mn2+ allosterically activates arginase by a sequential, and pH-sensitive, mechanism. The combined pH sensitivities of activation, Vmax, and Km are likely to give arginase a role in mediating the demonstrated pH control of the ornithine cycle and hence in the regulation of body pH.

Arginase↗