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Biomedical subjects

P Hopkins

Publications and source records attributed to P Hopkins.

At least 19 recordsLinked to original sources
PubMed2004

Rating method for evaluating distribution-system odors compared with a control.

A new sensory method was developed and tested at a full-scale water treatment plant. The method evaluates changes in aesthetic water quality during transit in the distribution system. A paired comparison format is used to determine if the odor of a distribution-system sample is different from that of a control sample. The control sample represents the "ideal" water, such as treated water leaving the plant. The method can rapidly determine whether or not a problem exists in the distribution system, and, if one does exist, it allows for characterization of the problem. Over a three-month period a 4-member odor panel evaluated 118 distribution samples by this new procedure. Among the 118 samples tested, 39 samples yielded a consensus among the analysts as to the odor characteristics of the sample; 35 were rated "not different from the control" (about 90%), and only 4 were rated "different from control" (about 10%). The 79 samples for which no consensus was generated had only slight rating differences between analysts and for odor intensity. No taste-and-odor problems were reported by consumers during the time period for this study and the method indicated that no major odor problems existed in the distribution system.

Community Participation↗
PubMed2001

Diagnostic value of follow-up transbronchial lung biopsy after lung rejection.

Although transbronchial lung biopsy (TBBx) is widely acknowledged as the "gold standard" for diagnosis of acute rejection, controversy exists regarding the need to perform follow-up procedures. Over a 5-yr period, we performed 1,142 TBBx of which 173 were follow-up TBBx in 99 patients with pulmonary allograft rejection greater than or equal to International Society for Heart and Lung Transplantation (ISHLT) grade A(2) on initial TBBx. Rejection on the previous 173 TBBx was associated with lymphocytic bronchiolitis/bronchitis (LBB) > or = ISHLT grade B(2) in 82 patients and with cytomegalovirus (CMV) pneumonitis in 16 patients. Persistent rejection (> or = A(2)) was observed in 45 of 173 (26%) follow-up TBBx. Persistent B grade rejection (> or = B(2)) was present in 28 patients whereas new B grade rejection developed in 11 patients with > or = A(2) grade rejection. Rejection > or = B(2) was significantly (p < 0.05) associated with rejection > or = A(2). Fifteen follow-up TBBx showed new B grade rejection without signs of > or = A(2) rejection. A new diagnosis of CMV pneumonitis was made in 33 of 173 (19%). CMV pneumonitis occurred in 35 follow-up TBBx, four associated with > or = A(2) rejection and eight with > or = B(2) rejection. The overall incidence of bronchiolitis obliterans syndrome (BOS) in both groups was similar. Patients with persistent rejection on follow-up TBBx developed BOS at a median of 1.3 yr and median of 2.0 yr (p = not significant [NS]) posttransplantation. The practice of follow-up TBBx after rejection within 2 yr posttransplant is clinically useful as it provides valuable diagnostic information.

Adolescent↗
PubMed2001

Linkage of left ventricular contractility to chromosome 11 in humans: The HyperGEN Study.

Impaired left ventricular (LV) contractility is a major cause of cardiovascular death, especially congestive heart failure. The identification of susceptibility genes that contribute to impaired LV contractility may uncover mechanisms underlying LV contractile impairment and the development of congestive heart failure. The Hypertension Genetic Epidemiology Network (HyperGEN) collected echocardiographic measurements of myocardial contractility in a large biethnic sample of hypertensive siblings (390 blacks and 398 whites in 179 and 165 sibships, respectively). All participants expressed hypertension before age 60 years, and the mean age of siblings was 52 years in blacks and 61 years in whites. We adjusted myocardial contractility for gender, age, and age(2), and we calculated standardized residuals separately for men and women in both ethnic groups. We conducted multipoint variance components linkage analysis using GENEHUNTER2 and 387 anonymous markers (CHCL8 marker set). We found evidence for significant linkage to a microsatellite marker, D11S1993 (lod, 3.93 in blacks), approximately 54 cM from the tip of the short arm of chromosome 11, that accounted for 72% of the phenotypic variation in LV contractility. A chromosome 22 locus showed suggestive evidence for linkage (lod, 2.83 in whites and 1.15 in blacks). The chromosome 11 peak coincides with the region containing myosin-binding protein C. Mutations in this gene are linked to familial hypertrophic cardiomyopathy. Our results show strong evidence for linkage of a region of chromosome 11 with LV contractility in blacks and suggest that an important gene for impaired LV contractility is harbored in this region.

Black People↗
PubMed2000

Genomic structure of the human p47-phox (NCF1) gene.

The cytosolic factor p47-phox, encoded by the NCF1 gene, is an essential component of the phagocyte NADPH-oxidase system. Upon activation of this multicomponent system, p47-phox translocates to the membrane and participates in the electron transfer from NADPH to molecular oxygen. A deficiency or absence of p47-phox is the most common autosomal form of chronic granulomatous disease (CGD). We have cloned and characterized the NCF1 gene from four bacteriophage clones, a P1 clone and genomic DNA from normal individuals. The gene is 15,236 base pairs long and includes 11 exons. It is 98.6% homologous in sequence to at least one pseudogene that maps to the same region of chromosome 7q11.23. Slightly more than half (50.37%) of the wild-type NCF1 gene consists of repetitive elements. In particular, the density of Alu sequences is high (1.4 Alu/kb); there are 21 Alu repeats interspersed through 10 introns. These findings are consistent with the observation that recombination events between the wild-type gene and its highly homologous pseudogenes account for the majority of potentially lethal mutations in p47-phox-deficient chronic granulomatous disease. Analysis of 1.96 kb of sequence 5' of the start of translation revealed a high homology (99.6%) between wild-type and pseudogene clones. Characterization of NCF1 establishes a foundation for detailed molecular analysis of p47-phox-deficient CGD patients as well as for the study of the regulation of the NCF1 gene and pseudogenes, both of which are present as full-length transcripts in normal individuals.

5' Untranslated Regions↗
PubMed2000

Effect of general practitioner hospitals on district general hospital bed use in the Highlands of Scotland.

OBJECTIVE: To examine hospital bed use by General Practices with and without access to General Practitioner beds. DESIGN: Information from the Contract Management System for General Medicine and Surgery, and from SMR returns for Geriatric Medicine and GP beds was used to compare hospital bed use in District General Hospitals (DGHs) and in General Practitioner beds for practices with and without access to GP beds. Age adjusted rates were calculated for overall use of each specialty. SETTING: All General Practices in the Highland Health Board area for December 1995-April 1997. RESULTS: Compared to practices with no access to GP beds, practices with access used 39.4% fewer bed days per 1000 patients for medical specialties; 18% fewer bed days for surgical specialties; 34.5% fewer bed days for geriatric medicine, and 4.9% fewer bed days for other DGH specialties. Taking into account GP bed day use, practices with access to GP beds used 6.1% more hospital bed days per 1000 patients than did practices with no access. CONCLUSION: These findings largely replicate work in England that found substantial decreases in General Medical and Geriatric Medicine bed use in Practices with access to GP beds, combined with an overall increase in occupied bed day use of 6-8% per 1000 patients. The lower use of surgical beds was unexpected, and may reflect more flexible use of GP beds in the Highlands for observation or rehabilitation, possibly related to the far greater distances involved than in the English studies.

Adolescent↗
PubMed1999

Efficacy and safety of lovastatin in adolescent males with heterozygous familial hypercholesterolemia: a randomized controlled trial.

CONTEXT: Heterozygous familial hypercholesterolemia (HeFH) is a common disorder associated with early coronary artery disease, especially in men. The age at which drug therapy should be started is still controversial, as is the use of 3-hydroxy-3-methylglutaryl coenzyme A reductase inhibitors (statins). OBJECTIVE: To assess the lipid-lowering efficacy, biochemical safety, and effect on growth and sexual development of lovastatin in adolescent boys with HeFH. DESIGN: One-year, double-blind, placebo-controlled, balanced, 2-period, 2-arm randomized trial. In the first period (24 weeks), lovastatin was increased at 8 and 16 weeks and the dosage remained stable during the second period (24 weeks). The study was conducted between 1990 and 1994. SETTING: Fourteen pediatric outpatient clinics in the United States and Finland. PATIENTS: Boys aged 10 to 17 years with HeFH. Of 132 randomized subjects (67 intervention, 65 placebo), 122 (63 intervention, 59 placebo) and 110 (61 intervention, 49 placebo) completed the first and second periods, respectively. INTERVENTION: Lovastatin, starting at 10 mg/d, with a forced titration at 8 and 16 weeks to 20 and 40 mg/d, respectively, or placebo. MAIN OUTCOME MEASURES: The primary efficacy outcome measure was low-density lipoprotein cholesterol (LDL-C). Primary safety measures were growth and sexual development. RESULTS: Compared with placebo, LDL-C levels of patients receiving lovastatin decreased significantly (P<.001) by 17%, 24%, and 27% receiving dosages of 10, 20, and 40 mg/d, respectively, and remained 25 % lower than baseline at 48 weeks. Growth and sexual maturation assessed by Tanner staging and testicular volume were not significantly different between the lovastatin and placebo groups at 24 weeks (P = .85) and 48 weeks (P = .33); neither were serum hormone levels or biochemical parameters of nutrition. However, the study was underpowered to detect significant differences in safety parameters. Serum vitamin E levels were reduced with lovastatin treatment consistent with reductions in LDL-C, the major carrier of vitamin E in the circulation. CONCLUSIONS: This study in adolescent boys with HeFH confirmed the LDL-C-reducing effectiveness of lovastatin. Comprehensive clinical and biochemical data on growth, hormonal, and nutritional status indicated no significant differences between lovastatin and placebo over 48 weeks, although further study is required.

Adolescent↗
PubMed1998

Proton stoichiometry of the overexpressed uracil symport of the yeast Saccharomyces cerevisiae.

Information about the molecular biology of the uracil carrier of Saccharomyces cerevisiae is now available but its properties as a symport are unexplored. We have now studied its proton stoichiometry at pH 6.5, 4.8 and 4.2, in a yeast strain overexpressing the symport and unable to metabolize uracil. After the depletion of cellular ATP, uracil uptake followed an approximately exponential time course to reach a plateau. Proton uptake was then indistinguishable from the basal rate shown in controls without added uracil. It was concluded that more than 87% of the uracil flux through the system was coupled to symported protons. Because the basal rate was a significant fraction of the total rate of proton uptake at pH 4.2 or 4.8, the ratio of the proton and uracil flows could not be defined uniquely during the initial near-linear phase of uptake. However, the average rate of proton uptake during increasing time intervals up to 120 s was shown to be a linear function of the corresponding average rate of uracil uptake. This relationship, defining approx. 90% of the eventual uracil uptake, was used to deduce the mean proton stoichiometry as approx. 3 at pH 4.2, falling to near 2 at pH 6.5. The rate of uracil uptake increased 4-fold when the negative proton gradient (Delta mu(H)) acting across the plasma membrane increased from 60 to 200 mV. The rate fell markedly after depolarization by KCl. The maximum uracil gradient (Delta mu(S)) was less affected by depolarization. The ratio Delta mu(S)/Delta mu(H) fell from approx. 2 to near 1 as Delta mu(H) increased in the above range. In contrast with the starved yeast, uracil accumulation during energy metabolism followed a pump-leak model.

Biological Transport↗
PubMed1998

Effect of vitamin B6 supplementation in McArdle's disease: a strategic case study.

A patient-blind study into the effect of a 10-week cessation of long-term vitamin B6 supplementation on B6 status and performance in McArdle's disease is reported. Muscle performance was assessed both subjectively and objectively by an ischaemic fatiguing protocol of the adductor pollicis muscle. Nine weeks after withdrawal of supplementation, vitamin B6 status had changed from adequacy to inadequacy and the force loss during the ischaemic fatiguing protocol had increased at all frequencies studied. The patient reported decreased exercise tolerance after 7 weeks and by the tenth week was experiencing an increase in muscle cramps. Vitamin B6 status and muscle performance may be linked in McArdle's disease and there is potential for enhancement of performance by B6 supplementation.

Dietary Supplements↗
PubMed1996

Cytosine accumulation as a measure of the proton electrochemical gradient acting on the overexpressed cytosine permease of Saccharomyces cerevisiae.

The magnitude of the proton gradient (delta mu H+) driving solute accumulation in Saccharomyces cerevisiae has long been in doubt, principally because of the lack of an agreed method for assaying its electrical component, the membrane potential (delta psi). In the present work, the size of the cytosine gradient (delta mu cyt) that the yeast generated was used as a measure of the driving gradient (delta mu H+). The selected yeast lacked cytosine deaminase and overexpressed cytosine permease, a 1 H+/cytosine system. delta mu cyt, assayed in washed cell suspensions fermenting glucose and containing 0.5 or 50 mM KCl, was about 260 mV at pH 4 or 5, falling to about 194 mV at pH 7. As a first estimate, -delta mu H+ was thus at least as large at the respective pH value. A 20 mM solution of the lipophilic cation tetraphenylphosphonium lowered delta mu cyt to a value roughly equal to the magnitude of the pH gradient (delta pH). A mathematical model was used to correct the first estimates of delta mu H+ for the effect of cytosine leakage outside the symport. In such a system, delta mu cyt cannot exceed the equivalent ratio Vmax/KmL, where Vmax and Km are kinetic parameters of the symport and L is the rate coefficient for leakage. The feasibility of assaying delta mu H+ depends on it not being much larger than that ratio. The model was tested successfully against observations made with yeast preparations depleted of ATP. After correction, -delta mu H+ during fermentation was estimated to be up to 25 mV larger than delta mu cyt and at least 70 mV larger than previous estimates in the literature involving lipophilic cations. From a knowledge of delta pH, delta psi was in turn deduced and compared with the maximum methylamine gradient (delta mu M) the yeast formed. The results supported the claim in the literature that, at acid pH, delta mu M is a measure of delta psi.

Biological Transport↗
PubMed1996

Relapsing polychondritis and aseptic meningitis.

Aseptic meningitis is a rare complication of relapsing polychondritis. We describe a 60-year-old man who developed a prolonged episode of aseptic meningitis for which no cause could be determined and, that resolved spontaneously. He then developed classic relapsing polychondritis 14 months later. He subsequently had another episode of prolonged meningitis complicated by hydrocephalus. No infectious cause for the meningitis could be determined after extensive investigation including meningeal biopsy. The patient responded to corticosteroids and antituberculous therapy.

Biopsy↗
PubMed1995

McArdle's disease: molecular genetics and metabolic consequences of the phenotype.

McArdle's disease is defined as a lack of functional muscle glycogen phosphorylase. Analysis of the myophosphorylase gene has demonstrated substantial heterogeneity in the mutations that cause the disease, but in almost all individuals, the molecular phenotype is the absence of the protein in skeletal muscle. Muscle glycogen phosphorylase is a major repository of vitamin B6 in the body, accounting for at least 80% of the total body pool. In McArdle's patients, this pool is therefore missing, introducing the possibility that vitamin B6 metabolism might be altered in these individuals. Preliminary data have shown that McArdle's patients show signs of a subclinical vitamin B6 deficiency, and that oral vitamin B6 supplementation can improve vitamin B6 status and enhance fatigue resistance in muscle.

Base Sequence↗
PubMed1994

Proton and charge circulation through substrate symports in Saccharomyces cerevisiae: non-classical behaviour of the cytosine symport.

A yeast strain lacking cytosine deaminase activity and over-expressing the cytosine proton symport has been used to study three aspects of symport function. (1) The proton flow during cytosine uptake after depletion of cellular ATP implies that the distribution of cytosine eventually approaches equilibrium with the proton gradient, one proton being absorbed with each molecule of cytosine. After correction for the presence of a minor leak pathway for cytosine, the cytosine distribution during energy metabolism was used to assay the magnitude of delta microH. Values of about 280 mV at pH 5 were obtained in this way. (2) Certain other substrates of the cytosine symport (hypoxanthine and especially fluorocytosine) cause the uptake of more than one equivalent of protons, but nevertheless accumulate to the same extent as cytosine. This phenomenon appears to be distinct from that of proton slip and is termed pseudochannelling. (3) The recycling of symported protons through the proton pump is an ill-defined process in plants and fungi. It usually occurs only after a distinct time lag during which the change in bulk intracellular pH may be relatively small. We have found conditions where there is no apparent time lag before protons entering yeast with glycine or histidine are recycled. This behaviour is discussed in relation to the possible voltage characteristics of the proton pump, its putative regulation by delta microH and the metabolic consequences of ATP hydrolysis being accelerated.

Adenosine Triphosphate↗