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Biomedical subjects

D A Scott

Publications and source records attributed to D A Scott.

At least 37 records · Page 2Linked to original sources
PubMed2002

An observational clinic-based study of diarrheal illness in deployed United States military personnel in Thailand: presentation and outcome of Campylobacter infection.

Campylobacter is a leading cause of traveler's diarrhea in Thailand. Since resistance to quinolones is high among Campylobacter isolates, empiric therapy with quinolones for traveler's diarrhea may be ineffective in this region. We conducted an observational study among 169 U.S. military personnel with acute diarrhea and compared their microbiologic findings to those of 77 asymptomatic personnel deployed to Thailand in May 1998. Of 146 pathogenic bacterial isolates, the most common were nontyphoidal Salmonella (n = 31), enterotoxigenic Escherichia coli (n = 24), and C. jejuni/coli (n = 23). Campylobacter was strongly associated with disease (odds ratio = 5.9; 95% confidence interval = 1.3-37.3), with a more severe clinical presentation, and with a reduced functional ability at presentation (P = 0.02). In vitro resistance to ciprofloxacin was observed in 96% of the Campylobacter isolates. Sub-optimal treatment response to ciprofloxacin was observed in 17% of the cases of Campylobacter infection versus 6% due to other causes. These results highlight the importance of Campylobacter as a cause of severe traveler's diarrhea in Thailand and illustrates the ongoing problem with antibiotic-resistant strains and associated treatment problems.

Adult↗
PubMed2001

TcSCA complements yeast mutants defective in Ca2+ pumps and encodes a Ca2+-ATPase that localizes to the endoplasmic reticulum of Trypanosoma cruzi.

Intracellular Ca(2+) in Trypanosoma cruzi is mainly located in an acidic compartment named the acidocalcisome, which among other pumps and exchangers possesses a plasma membrane-type Ca(2+)-ATPase. Evidence for an endoplasmic reticulum-located Ca(2+) uptake has been more elusive and based on indirect results. Here we report the cloning and sequencing of a gene encoding a sarcoplasmic-endoplasmic reticulum-type Ca(2+)-ATPase from T. cruzi. The protein (TcSCA) predicted from the nucleotide sequence of the gene has 1006 amino acids and a molecular mass of 109.7 kDa. Several sequence motifs found in sarcoplasmic-endoplasmic reticulum-type Ca(2+)-ATPases were present in TcSCA. Expression of TcSCA in yeast mutants deficient in the Golgi and vacuolar Ca(2+) pumps (pmr1 pmc1 cnb 1) restored growth on EGTA. Membranes were isolated from the pmr1 pmc1 cnb1 mutant transformed with TcSCA, and it was found that the TcSCA polypeptide formed a Ca(2+)-dependent and hydroxylamine-sensitive (32)P-labeled phosphoprotein of 110 kDa in the presence of [gamma-(32)P]ATP. Cyclopiazonic acid, but not thapsigargin, blocked this phosphoprotein formation. Transgenic parasites expressing constructs of TcSCA with green fluorescent protein exhibited co-localization of TcSCA with the endoplasmic reticulum proteins BiP and calreticulin. An endoplasmic reticulum location was also found in amastigotes and trypomastigotes using a polyclonal antibody against a COOH-terminal region of the protein. The ability of TcSCA to restore growth of mutant pmr1 pmc1 cnb 1 on medium containing Mn(2+) suggests that TcSCA may also regulate Mn(2+) homeostasis by pumping Mn(2+) into the endoplasmic reticulum of T. cruzi.

Amino Acid Sequence↗
PubMed2001

Validation of smoking status in clinical research into inflammatory periodontal disease.

BACKGROUND: Tobacco smoking is an accepted risk factor for periodontal disease. Most studies in the periodontal literature rely on reported smoking habits which can be unreliable. This review specifically addresses this problem. METHODS: Methods of assessing tobacco smoke exposure, variation in individual smoking habits, classification of former/ex-smokers, and validation of abstinence in smoking cessation studies receive attention. DISCUSSION: Additionally, clinical studies that have examined periodontal health in subjects with validated smoking status are discussed.

Bias↗
PubMed2001

Neuropsychologic testing within 18 hours after cardiac surgery.

OBJECTIVE: To undertake neuropsychologic testing within 18 hours of cardiac surgery after fast-track anesthesia. DESIGN: Prospective study. SETTING: University hospital, single center. PARTICIPANTS: Fifty patients undergoing first-time elective coronary artery surgery. INTERVENTIONS: A neuropsychologic test battery was administered preoperatively and 18 hours and 5 days after surgery. MAIN RESULTS: Seven patients were withdrawn, and 9 patients did not attempt the postoperative tests (on both occasions) because of medical complications. Thirty patients completed > or =4 tests at both postoperative occasions. Of these, 9 patients (30%) showed a deficit in > or =2 tests at 18 hours postoperatively, and 3 (10%) showed a deficit at 5 days postoperatively. CONCLUSION: In the absence of medical complications and despite the difficulties, early postoperative neuropsychologic testing is possible after fast-track anesthesia. Such testing has the potential to more clearly define the course of cognitive decline after cardiac surgery.

Aged↗
PubMed2001

Blood loss in elective coronary artery surgery: a comparison of centrifugal versus roller pump heads during cardiopulmonary bypass.

OBJECTIVES: To compare the effects of centrifugal pumps versus roller pumps for cardiopulmonary bypass (CPB) in routine cardiac surgery on hematologic parameters in the context of modern practice. DESIGN: Prospective, randomized, partially blinded. SETTING: University teaching hospital. PARTICIPANTS: Elective coronary artery surgery patients (n = 113) INTERVENTION: Patients were randomized to be perfused with either a roller head (group R, n = 56) or a centrifugal head (group C, n = 57) pump. Patients received epsilon-aminocaproic acid before and during CPB. Core body temperatures were allowed to drift down to approximately 32 degrees C. MEASUREMENTS AND MAIN RESULTS: Postoperative chest tube blood loss, blood product requirements, hemoglobin, and platelet counts were assessed. There were no significant differences in preoperative or intraoperative parameters, including CPB time, complexity of procedure, and minimum core temperature. There were the expected reductions in hemoglobin and platelet levels post-CPB in both groups to a similar extent. Chest tubes remained in situ for similar durations, and the final volume of drainage was not significantly different (group C, 1300 +/- 92 mL; group R 1117 +/- 83 mL; p = 0.14). Allogeneic blood was given to 23% of patients in group C and 18% in group R (p = 0.63). Aspirin was associated with an increase in early chest tube drainage. CONCLUSIONS: In this surgical and perfusion environment, the authors were unable to show an advantage, from the hematologic point of view, in the routine use of a centrifugal pump head in elective coronary artery surgical patients. The use of antifibrinolytic agents and mild hypothermia may have effects on hemostasis that overshadow the influence of pump head design in this type of surgery.

Aged↗
PubMed2001

Dose-years as an improved index of cumulative tobacco smoke exposure.

In assessing the link between tobacco smoking and disease, it is important to determine longterm, cumulative exposure to tobacco smoke as accurately as possible. Conventional methods of assessing exposure to tobacco smoke each have intrinsic limitations. Self-reporting of tobacco use, and the conversion of this data to pack-years, can be prone to error due to individuals wishing to conceal smoking habits, inaccurate reporting of daily cigarette consumptions or years of smoking, and failure to take into account the variation that exists in inter-individual smoking experiences. Measurement of cotinine, a major metabolite of nicotine in humans, is a reliable method of monitoring recent doses of tobacco smoke exposure. Cotinine concentrations, however, may remain stable in smokers over the longer term. Therefore, dose-years, and more specifically cotinine-years, may represent an improved index of cumulative tobacco smoke exposure.

Biomarkers↗
PubMed2001

Elevated systemic concentrations of soluble ICAM-1 (sICAM) are not reflected in the gingival crevicular fluid of smokers with periodontitis.

Raised serum levels of soluble intercellular adhesion molecule-1 (sICAM-1) in smokers could have immunomodulatory effects in periodontitis. The aim of this study was to compare serum and gingival crevicular fluid (GCF) concentrations of sICAM-1 in smokers and non-smokers with periodontal disease. sICAM-1 in serum and GCF collected from age- and gender-matched smokers (n = 14) and non-smokers (n = 14) with periodontitis were measured by ELISA. Mean serum sICAM-1 concentrations were significantly elevated in smokers (331 ng mL(-1)), compared with non-smokers (238 ng mL(-1), p = 0.008). However, the concentration of sICAM-1 in the GCF was significantly lower in the smokers (83 ng mL(-1)), compared with non-smokers (212 ng mL(-1), p = 0.013). The difference between concentrations of sICAM-1 in GCF and serum was significant only in smokers (p < 0.001). Since GCF is a serum-derived tissue exudate, these results suggest that, in smokers, circulating sICAM-1 molecules are affected either in their passage from the periodontal microvasculature or within the periodontal tissues.

Adult↗
PubMed2001

Eliciting public preferences for healthcare: a systematic review of techniques.

BACKGROUND: Limited resources coupled with unlimited demand for healthcare mean that decisions have to be made regarding the allocation of scarce resources across competing interventions. Policy documents have advocated the importance of public views as one such criterion. In principle, the elicitation of public values represents a big step forward. However, for the exercise to be worthwhile, useful information must be obtained that is scientifically defensible, whilst decision-makers must be able and willing to use it. AIMS AND OBJECTIVES: The aim was to identify techniques that could be reasonably used to elicit public views on the provision of healthcare. Hence, the objectives were: (1) to identify research methods with the potential to take account of public views on the delivery of healthcare; (2) to identify criteria for assessing these methods; (3) to assess the methods identified according to the predefined criteria; (4) to assess the importance of public views vis-à-vis other criteria for setting priorities, as judged by a sample of decision-makers; (5) to make recommendations regarding the use of methods and future research. METHODS: A systematic literature review was carried out to identify methods for eliciting public views. Criteria currently used to evaluate such methods were identified. The methods identified were then evaluated according to predefined criteria. A questionnaire-based survey assessed the relative importance of public views vis-à-vis five other criteria for setting priorities: potential health gain; evidence of clinical effectiveness; budgetary impact; equity of access and health status inequalities; and quality of service. Two techniques were used: choice-based conjoint analysis and allocation of points technique. The questionnaire was sent to 143 participants. A subsample was followed up with a telephone interview. RESULTS: The methods identified were classified as quantitative or qualitative. RESULTS - QUANTITATIVE TECHNIQUES: Quantitative techniques, classified as ranking, rating or choice-based approaches, were evaluated according to eight criteria: validity; reproducibility; internal consistency; acceptability to respondents; cost (financial and administrative); theoretical basis; whether the technique offered a constrained choice; and whether the technique provided a strength of preference measure. Regarding ranking exercises, simple ranking exercises have proved popular, but their results are of limited use. The qualitative discriminant process has not been used to date in healthcare, but may be useful. Conjoint analysis ranking exercises did well against the above criteria. A number of rating scales were identified. The visual analogue scale has proved popular within the quality-adjusted life-year paradigm, but lacks constrained choice and may not measure strength of preference. However, conjoint analysis rating scales performed well. Methods identified for eliciting attitudes include Likert scales, the semantic differential technique, and the Guttman scale. These methods provide useful information, but do not consider strength of preference or the importance of different components within a total score. Satisfaction surveys have been frequently used to elicit public opinion. Researchers should ensure that they construct sensitive techniques, despite their limited use, or else use generic techniques where validity has already been established. Service quality (SERVQUAL) appears to be a potentially useful technique and its application should be researched. Three choice-based techniques with a limited application in healthcare are measure of value, the analytical hierarchical process and the allocation of points technique, while those more widely used, and which did well against the predefined criteria, include standard gamble, time trade-off, discrete choice conjoint analysis and willingness to pay. Little methodological work is currently available on the person trade-off. RESULTS - QUALITATIVE TECHNIQUES: Qualitative techniques were classified as either individual or group-based approaches. Individual approaches included one-to-one interviews, dyadic interviews, case study analyses, the Delphi technique and complaints procedures. Group-based methods included focus groups, concept mapping, citizens' juries, consensus panels, public meetings and nominal group techniques. Six assessment criteria were identified: validity; reliability; generalisability; objectivity; acceptability to respondents; and cost. Whilst all the methods have distinct strengths and weaknesses, there is a lot of ambiguity in the literature. Whether to use individual or group methods depends on the specific topic being discussed and the people being asked, but for both it is crucial that the interviewer/moderator remains as objective as possible. The most popular and widely used such methods were one-to-one interviews and focus groups. (ABSTRACT TRUNCATED)

Data Collection↗
PubMed2001

A rapid and systematic review of the clinical effectiveness and cost-effectiveness of paclitaxel, docetaxel, gemcitabine and vinorelbine in non-small-cell lung cancer.

BACKGROUND: The incidence of lung cancer is declining following a drop in smoking rates, but it is still the leading cause of death from cancer in England and Wales, with about 30,000 deaths a year. Survival rates for lung cancer are poor everywhere, but they appear to be better in the rest of the European Community and the USA than in the UK. Only about 5 per cent of people with lung cancer survive for 5 years, and nearly all of these are cured by surgery after fortuitously early diagnosis. At present, only a small proportion of patients (probably about 5 per cent) with non-small-cell lung cancer are being given chemotherapy. Some centres treat a greater proportion. OBJECTIVES: This review examines the clinical effectiveness and cost-effectiveness of four of the newer drugs - vinorelbine, gemcitabine, paclitaxel and docetaxel - used for treating the most common type of lung cancer (non-small-cell lung cancer). The first three drugs are used for first-line treatment, but at present docetaxel is used only after first-line chemotherapy has failed. METHODS: This report was based on a systematic literature review and economic modelling, supplemented by cost data. RESULTS - NUMBER AND QUALITY OF STUDIES: A reasonable number of randomised trials were found - three for docetaxel, six for gemcitabine, five for paclitaxel and 13 for vinorelbine. The quality of the trials was variable but good overall. There was a wide range of comparators. Some trials compared chemotherapy with best supportive care (BSC), which involves care that aims to control symptoms, with palliative radiotherapy if needed, but not to prolong life. Others compared the newer drugs against previous drugs or combinations. RESULTS - SUMMARY OF BENEFITS: The gains in duration of survival with the new drugs are modest - a few months - but worthwhile in a condition for which the untreated survival is only about 5 months. There are also gains in quality of life compared with BSC, because on balance the side-effects of some forms of chemotherapy have less effect on quality of life than the effects of uncontrolled spread of cancer. RESULTS - COSTS: The total cost to the NHS of using these new drugs in England and Wales might be about GBP 10 million per annum, but is subject to a number of factors. There would be non-financial constraints on any increase in chemotherapy for the next few years, such as staffing; the number of patients choosing to have the newer forms of chemotherapy is not yet known; and the costs of the drugs may fall, for example, as generic forms appear. RESULTS - COST PER LIFE-YEAR GAINED: The available data did not provide an entirely satisfactory basis for cost-effectiveness calculations. The main problem was the lack of direct comparisons of the new drugs. In order to strengthen the analysis, three different modelling approaches were used: pairwise comparisons using trial data; cost-minimisation analysis, as if all the new regimens were of equal efficacy; and cost-effectiveness analysis pooling the results of several trials with different comparators, giving indirect comparisons of the new drugs by using BSC as the common comparator. A number of different scenarios were explored through extensive sensitivity analysis in each model. Outcomes were expressed in incremental cost per life-year saved or incremental cost, versus BSC. There was insufficient evidence from which to derive cost per quality-adjusted life-year. In first-line treatment, vinorelbine, gemcitabine, and the lower-dose paclitaxel plus cisplatin combinations generally performed well against BSC under a range of different scenarios and especially when given as a maximum of 3 cycles. Incremental cost per life-year gained (LYG) versus BSC varied depending on scenario, but baseline figures based on trial data and protocols were: single-agent vinorelbine, pound 2194 per LYG; vinorelbine plus cisplatin, pound 5206; single-agent gemcitabine, pound 5690; gemcitabine plus cisplatin, pound 10,041; and paclitaxel plus cisplatin, pound 8537. In second-line chemotherapy, docetaxel gave a cost per LYG of pound 17,546, again well within the range usually accepted as cost-effective. However, in routine care, the impact of therapy would be regularly reviewed, and continuation would depend on response, side-effects, patient choice and clinical judgement. Chemotherapy would be stopped in non-responders, making chemotherapy more cost-effective. A 'real-life' scenario in which 60 per cent of patients receive only 1 or 2 cycles of chemotherapy gives much lower costs per LYG, with single-agent gemcitabine, single-agent vinorelbine, and paclitaxel plus platinum appearing to be cost-saving compared with BSC; the incremental cost of gemcitabine plus cisplatin would be pound 2478 per LYG, and of vinorelbine plus cisplatin, pound 2808. At the very least, gains in duration of survival were achieved without diminution of quality of life (at best, they improved quality) and with relatively low incremental cost. Comparisons among the individual drugs should be viewed with caution because they have had to be based on indirect comparisons. RESULTS - LIMITATIONS OF THE ANALYSIS: Each of the three models had limitations. The cost-effectiveness estimates from the pairwise comparisons were based on single studies. The cost-minimisation analysis assumed that the regimens have equal efficacy in practice. The cost-effectiveness analysis had to be based on pooling data from individual trials. The costs of BSC, inpatient stay and outpatient visits were from Scottish data. Median rather than mean data on duration of survival have been used in the analysis, because most of the trials reported only median data. Median survival and number of drug cycles were calculated by averaging across a number of studies, rather than being reliant on one particular study. The costs of the less expensive antiemetics cited in the trials were omitted. The use of more modern and costly antiemetics would have a modest detrimental effect on cost-effectiveness. In the absence of published data, an estimate was made of the cost of side-effects of chemotherapy, in particular hospital admissions, and applied to all the new regimens. In practice, admissions related to side-effects and their respective costs are likely to vary by regimen. CONCLUSIONS: The new drugs for non-small-cell lung cancer extend life by only a few months compared with BSC, but appear to do so without net loss in quality of life and at a cost per LYG that is much lower than for many other NHS activities. Depending on assumptions used, these new drugs range from being cost-effective, as conventionally accepted, to being cost-saving. CONCLUSIONS - IMPLICATIONS OF THE NEWER DRUGS: One of the present constraints on chemotherapy is availability of inpatient beds. The advent of newer and gentler forms of chemotherapy given on an outpatient basis would not only overcome this, but it would allow more patients to be treated. This might apply particularly to older patients. The treatment of more patients would increase workload for oncologists, cancer nurses and pharmacists. The Government has already announced increased expenditure on staff for cancer care. The previously pessimistic attitudes to chemotherapy in non-small-cell lung cancer are changing in the wake of the newer agents, and this shift is likely to increase referral. CONCLUSIONS - NEED FOR FURTHER RESEARCH: Recent advances in chemotherapy are welcome, but their effects remain small for patients with non-small-cell lung cancer. Much more research is needed into better drugs, better combinations, new ways of assessing the likelihood of response and especially direct comparisons between the new regimens. This research would be aided by having a greater proportion of patients involved in trials, but there will be infrastructure implications of increased participation.

Antineoplastic Agents↗
PubMed2001

Pre-exposure anti-Campylobacter jejuni immunoglobulin a levels associated with reduced risk of Campylobacter diarrhea in adults traveling to Thailand.

Diarrhea history questionnaires were administered to 369 U.S. military volunteers before and after deployment to Thailand. Additionally, blood samples obtained from a subset of 221 volunteers 1-3 weeks previously and 3-4 weeks after their deployment were tested by enzyme-linked immunosorbent assay for immunoglobulin A to Campylobacter jejuni. Stool samples from personnel (including volunteers) contracting diarrhea in Thailand were cultured for enteric pathogens. Overall, 35.2% (130 of 369) of questionnaire respondents reported one or more diarrhea episodes during their trip. Volunteers with pretravel anti-C. jejuni reciprocal titers < or = 450 were 1.6 times as likely to have had diarrhea during their stay in Thailand compared with those with pretravel titers > 450 (39.7% versus 25.3%; P = 0.05). The symptomatic seroconversion, or attributable Campylobacter diarrhea attack rate, for the 1-month exercise was 12.7% (28 of 221). The symptomatic seroconversion rate in nonimmune (titer < or = 450) volunteers was 17.1%, whereas that in immune volunteers was only 4.0% (P = 0.002). Campylobacter jejuni or C. coli were recovered from 32.9% (56 of 170) of stool samples cultured and were the most commonly identified enteropathogens. Campylobacter diarrhea was associated with elevated temperatures, fecal red cells, and fecal white blood cells. The results of this study show that Campylobacter continues to represent a significant health threat to Western travelers to Thailand, but many of these travelers have preexisting Campylobacter immunity that protects them from clinically significant Campylobacter enteritis.

Adult↗
PubMed2000

Cloning and functional expression of a gene encoding a vacuolar-type proton-translocating pyrophosphatase from Trypanosoma cruzi.

Acidocalcisomes are acidic Ca(2+)-storage organelles found in trypanosomatids that are similar to organelles known historically as volutin granules. Acidification of these organelles is driven in part by a vacuolar H(+)-pyrophosphatase (V-H(+)-PPase), an enzyme that is also present in plant vacuoles and in some bacteria. Here, we report the cloning and sequencing of a gene encoding the acidocalcisomal V-H(+)-PPase of Trypanosoma cruzi. The protein (T. cruzi pyrophosphatase, TcPPase) predicted from the nucleotide sequence of the gene has 816 amino acids and a molecular mass of 85 kDa. Several sequence motifs found in plant V-H(+)-PPases were present in TcPPase, explaining its sensitivity to N-ethylmaleimide and N,N'-dicyclohexylcarbodi-imide. Heterologous expression of the cDNA encoding TcPPase in the yeast Saccharomyces cerevisiae produced a functional enzyme. Phylogenetic analysis of the available V-H(+)-PPase sequences indicates that TcPPase is nearer to the vascular plant cluster and the branch containing Chara, a precursor to land plants, than to any of the other pyrophosphatase sequences included in the analysis. The apparent lack of such a V-H(+)-PPase in mammalian cells may provide a target for the development of new drugs.

Amino Acid Motifs↗
PubMed2000

Characterization of isolated acidocalcisomes of Trypanosoma cruzi.

The acidocalcisome is an acidic calcium store in trypanosomatids with a vacuolar-type proton-pumping pyrophosphatase (V-H(+)-PPase) located in its membrane. In this paper, we describe a new method using iodixanol density gradients for purification of the acidocalcisome from Trypanosoma cruzi epimastigotes. Pyrophosphatase assays indicated that the isolated organelle was at least 60-fold purified compared with the large organelle (10,000 x g) fraction. Assays for other organelles generally indicated no enrichment in the acidocalcisome fraction; glycosomes were concentrated 5-fold. Vanadate-sensitive ATP-driven Ca(2+) uptake (Ca(2+)-ATPase) activity was detectable in the isolated acidocalcisome, but ionophore experiments indicated that it was not acidic. However, when pyrophosphate was added, the organelle acidified, and the rate of Ca(2+) uptake increased. Use of the indicator Oxonol VI showed that V-H(+)-PPase activity generated a membrane potential. Use of sulfate or nitrate in place of chloride in the assay buffer did not affect V-H(+)-PPase activity, but there was less activity with gluconate. Organelle acidification was countered by the chloride/proton symport cycloprogidiosin. No vacuolar H(+)-ATPase activity was detectable in isolated acidocalcisomes. However, immunoblots showed the presence of at least a membrane-bound V-H(+)-ATPase subunit, while experiments employing permeabilized epimastigotes suggested that vacuolar H(+)-ATPase and V-H(+)-PPase activities are present in the same Ca(2+)-containing compartment.

Acids↗
PubMed2000

Vacuolar proton pyrophosphatase activity and pyrophosphate (PPi) in Toxoplasma gondii as possible chemotherapeutic targets.

The addition of PP(i) promoted the acidification of a subcellular compartment in cell homogenates of Toxoplasma gondii tachyzoites, implying the presence of a proton-translocating pyrophosphatase. The proton gradient was collapsed by addition of the K(+)/H(+) antiporter nigericin, and was also inhibited by addition of the PP(i) analogue aminomethylenediphosphonate (AMDP). Both proton transport and PP(i) hydrolysis were dependent upon K(+), but Na(+) caused partial inhibition of these activities. PP(i) hydrolysis was sensitive in a dose-dependent manner to AMDP, imidodiphosphate, NaF and to the thiol reagent N-ethylmaleimide. This activity was unaffected by common inhibitors of phosphohydrolases, except that NaO(3)V (sodium orthovanadate) stimulated the activity by 87%. Immunofluorescence microscopy, using antisera raised against conserved peptide sequences of a plant vacuolar pyrophosphatase, suggested that the pyrophosphatase in T. gondii tachyzoites was located in the plasma membrane and intracellular vacuoles of the parasite. High-field (31)P-NMR spectroscopy showed that PP(i )was more abundant than ATP in tachyzoites. Bisphosphonates (PP(i) analogues), drugs that are used in the treatment of bone diseases, inhibited proton transport and PP(i) hydrolysis in tachyzoite homogenates, and also inhibited intracellular proliferation of tachyzoites in tissue culture cells.

Animals↗
PubMed2000

Functional differences of the PDS gene product are associated with phenotypic variation in patients with Pendred syndrome and non-syndromic hearing loss (DFNB4).

The PDS gene encodes a transmembrane protein, known as pendrin, which functions as a transporter of iodide and chloride. Mutations in this gene are responsible for Pendred syndrome and autosomal recessive non-syndromic hearing loss at the DFNB4 locus on chromosome 7q31. A screen of 20 individuals from the midwestern USA with non-syndromic hearing loss and dilated vestibular aqueducts identified three people (15%) with PDS mutations. To determine whether PDS mutations in individuals with Pendred syndrome differ functionally from PDS mutations in individuals with non-syndromic hearing loss, we compared three common Pendred syndrome allele variants (L236P, T416P and E384G), with three PDS mutations reported only in individuals with non-syndromic hearing loss (V480D, V653A and I490L/G497S). The mutations associated with Pendred syndrome have complete loss of pendrin-induced chloride and iodide transport, while alleles unique to people with DFNB4 are able to transport both iodide and chloride, albeit at a much lower level than wild-type pendrin. We hypothesize that this residual level of anion transport is sufficient to eliminate or postpone the onset of goiter in individuals with DFNB4. We propose a model for pendrin function in the thyroid in which pendrin transports iodide across the apical membrane of the thyrocyte into the colloid space.

Alleles↗
PubMed2000

Refining the DFNB7-DFNB11 deafness locus using intragenic polymorphisms in a novel gene, TMEM2.

The combined DFNB7-DFNB11 deafness locus maps to chromosome 9q13-q21 between markers D9S1806 and D9S769. We have determined the cDNA sequence and genomic structure of a novel gene, TMEM2, that maps to this interval and is expressed in the cochlea. The mouse orthologue of this gene (Tmem2) maps to the murine dn (deafness) locus on mouse chromosome 19. Screens for transmembrane helices reveal the presence of at least one putative transmembrane domain in the TMEM2 protein. To determine whether mutations in TMEM2 cause hearing loss at the DFNB7-DFNB11 locus, we screened the coding region of this gene in DFNB7-DFNB11 affected families by direct sequencing. All DNA variants that segregated with the deafness and changed the predicted amino acid sequence of TMEM2 were common polymorphisms, as demonstrated by allele-specific amplification of pooled control DNA. Northern blot analysis showed no difference in transcript size or expression level of Tmem2 in dn/dn and control mice. The intragenic polymorphisms in TMEM2 represent a novel centromeric boundary for the DFNB7-DFNB11 interval.

Amino Acid Sequence↗
PubMed2000

Dramatic decline in circulating intercellular adhesion molecule-1 concentration on quitting tobacco smoking.

The concentration of soluble ICAM-1 (sICAM-1) is significantly elevated in smokers, but it is unclear if smoking is the direct cause of elevated sICAM-1 levels, if the relationship between smoking and sICAM-1 level is dose-dependent, and if smoking cessation may lead to a decline in sICAM-1. We sought to clarify the relationship between smoking and sICAM-1 in a group of smokers who quit smoking for 1 year (n = 30) and a control group who continued to smoke (n = 30). A dose-dependent relationship between plasma sICAM-1 concentration and daily cigarette consumption (P = 0.02), plasma cotinine level (P = 0.02), and expired CO level (P = 0.007) was observed at baseline (n = 60). The mean change in sICAM-1 concentration after 52 weeks was greater for quitters than for continuing smokers (mean difference = -71.1 ng/ml, P < 0.001). The influence of smoking on sICAM-1 needs to be carefully considered in clinical trials. Soluble ICAM-1 remains bioactive and may contribute to pathogenic processes; therefore, reduction in the concentration of circulating ICAM-1 molecules may directly contribute to the health benefits associated with smoking cessation.

Adult↗