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Biomedical subjects

S Clark

Publications and source records attributed to S Clark.

At least 37 records · Page 2Linked to original sources
PubMed2000

Relation between phase of menstrual cycle and emergency department visits for acute asthma.

Hormonal fluctuations during the menstrual cycle are hypothesized to influence the course of asthma among women. A recent study found that almost 50% of emergency department (ED) visits occur during the perimenstrual phase. Our prospective cohort study in 64 EDs examined the relation between phase of menstrual cycle and visits for acute asthma. A total of 288 women with acute asthma were evaluated with a standardized patient interview and medical record review after excluding subjects who were pregnant, on hormonal therapy, postmenopausal, status post hysterectomy, had incomplete reproductive data, or whose ED visit fell more than 28 d after their last menstrual period. Only 13% reported reproductive factors as a personal asthma trigger. For all subjects, ED asthma visits were classified by menstrual phase: 33% were preovulatory (Days 5 to 11), 26% were periovulatory (Days 12 to 18), 20% were postovulatory (Days 19 to 25), and 21% were perimenstrual (Days 26 to 4), p = 0.008. There was no significant association between phase of menstrual cycle and asthma severity. Our data indicate that ED visits for acute asthma among women are more frequent during the preovulatory phase in contrast to other studies reporting more visits in the perimenstrual phase.

Acute Disease↗
PubMed2000

A pilot study examining changes in dust lead loading on walls and ceilings after lead hazard control interventions.

The U.S. Department of Housing and Urban Development (HUD) guidelines on lead hazard control instruct contractors to clean floors, windows, walls, ceilings, and other horizontal surfaces to remove lead-contaminated dust and debris after lead interventions are conducted. This dust removal activity adds costs to each project. The need to clean floors and windows is well documented in the HUD guidelines. However, there is substantially less documentation to support the recommendation to clean walls and ceilings. We examined whether it is necessary to clean walls and ceilings after lead hazard control (LHC) interventions by comparing dust lead loadings measured on these surfaces before an LHC intervention to dust lead loadings after the intervention. Twenty-two dwelling units undergoing substantial LHC measures consistent with the HUD guidelines were enrolled in the study. There was a significant increase in dust lead loading on walls and ceilings between the pre- and postintervention. The change in wall dust lead loading was substantial and created potentially harmful lead exposures. Although statistically significant, the change in ceiling dust lead loading was minimal and the postintervention dust lead loadings were far below the existing federal floor dust lead clearance standard. These results strongly support the recommendations in the HUD guidelines to clean walls after LHC interventions and do not provide sufficient justification to alter the current recommendation to clean ceilings after lead work.

Child↗
PubMed2000

Albinism: its implications for refractive development.

PURPOSE: Albinism involves the mutation of one or more of the genes associated with melanin synthesis and has many ramifications for vision. This study focuses on the refractive implications of albinism in the context of emmetropization. METHODS: Refractive, biometric, and visual acuity data were collected for a group of 25 albino individuals that included the following: 18 oculocutaneous (13 tyrosine positive, 5 tyrosine negative); 7 ocular (2 autosomal recessive, 5 sex-linked recessive). Their age range was 3 to 51 years. All exhibited horizontal pendular nystagmus. RESULTS: There were no statistically significant differences relating to albino subtype for any of the measured parameters. All the subjects had reduced visual acuity (mean: 0.90, logMAR) and overall, there was a bias toward hyperopia in their refractive errors (mean: + 1.07 D). However the refractive errors of the group covered a broad range (SD: 4.67 D) and included both high myopia and high hyperopia. An axial origin to the refractive errors is implied by the high correlation between refractive errors and axial lengths. Refractive astigmatism averaged 2.37 D and was consistently with-the-rule and highly correlated with corneal astigmatism, which was also with-the-rule. Meridional analysis of the refractive data indicated that the vertical meridian for hyperopic subjects was consistently nearer emmetropia compared to their horizontal meridian. Myopic subjects showed the opposite trend. CONCLUSIONS: The overall refractive profile of the subjects is consistent with emmetropization being impaired in albinism. However, the refractive errors of hyperopic subjects also can be explained in terms of "meridional emmetropization." The contrasting refractive profiles of myopic subjects may reflect operational constraints of the emmetropization process.

Adolescent↗
PubMed2000

Son preference and sex composition of children: evidence from India.

Although the effect of son preference on sex composition of children ever born is undetectable in national-level estimates that aggregate across all families, this article provides empirical evidence from India that son preference has two pronounced and predictable family-level effects on the sex composition of children ever born. First, data from India show that smaller families have a significantly higher proportion of sons than larger families. Second, socially and economically disadvantaged couples and couples from the northern region of India not only want but also attain a higher proportion of sons, if the effects of family size are controlled.

Decision Making↗
PubMed2000

Telephone follow-up after the emergency department visit: experience with acute asthma. On behalf of the MARC Investigators.

STUDY OBJECTIVE: This study explored how a variety of demographic and illness-related factors were associated with telephone follow-up among patients visiting the emergency department for acute asthma. METHODS: We performed a prospective cohort study as part of the Multicenter Airway Research Collaboration (MARC). The study was performed at 77 EDs in 22 US states and 4 Canadian provinces. ED patients, ages 2 to 54 years, who presented with acute asthma underwent a structured interview during their visit. Two weeks later, research personnel attempted to contact participants by telephone, using numbers obtained during the ED interview. RESULTS: A total of 1,847 adult and 1,184 pediatric patients were interviewed in the ED. Of these, 1,308 (71%) adult patients and 1,026 (87%) pediatric patients were successfully reached for 2-week telephone follow-up. Multivariate analyses revealed the factor most strongly related to contact was age, with pediatric patients being 2.5 times more likely to be reached than adults (95% confidence interval 2.0 to 3.2). Also, participants who were black, low in socioeconomic status, lacking a primary care provider, and exposed to tobacco smoke were significantly less likely to have been reached (all P <.001). CONCLUSION: In contrast to some reports in the literature, telephone contact rates were high. However, successful contact was not equally likely among all patient groups. Although the high contact rates support the feasibility of telephone follow-up of asthmatic patients visiting the ED, the results also act as a reminder of the potential biases that may arise when using telephone contact for clinical, quality assurance, and research reasons.

Adolescent↗
PubMed2000

Is medical abortion acceptable to all American women: the impact of sociodemographic characteristics on the acceptability of mifepristone-misoprostol abortion.

OBJECTIVE: To determine whether mifepristone-misoprostol medical abortion is more acceptable to some American women than to others. METHODS: Using previously reported acceptability data from a large US multicenter study (n = 2121), we conducted a more detailed analysis to test whether characteristics such as race/ethnicity, education, age, gestational age, and geographic location affect acceptability. RESULTS: In the United States, Asian women were more than twice as likely as other women to choose this method because they believed it was safer, while white women were twice as likely to select it because they considered it more natural. More educated women were likely to select this method to show support for greater choice and were more pleased about being able to avoid surgery. Particular features of the protocol also appealed to different women. White and African-American women as well as women with more education would feel significantly more comfortable taking one or both of the drugs at home than they would in the clinic. Nearly all groups of women were equally satisfied with this method and found it highly acceptable. The data showed surprisingly few differences among women's overall satisfaction level, their willingness to choose the method again, or to recommend it to others. CONCLUSION: Mifepristone-misoprostol medical abortion has widespread appeal to a broad range of women, but different women choose and prefer this method for different reasons.

Abortifacient Agents, Nonsteroidal↗
PubMed2000

What do family planning clients and university students in Nairobi, Kenya, know and think about emergency contraception?

Currently, emergency contraception is seldom used in Kenya. As part of a larger study designed to provide insight into the possible roles for the method in Kenya, we assessed the knowledge of and attitudes towards emergency contraception in two groups of potential users, and we focus on these data specifically in this paper. We interviewed clustered samples of clients at ten family planning clinics in Nairobi (n = 282) and conducted four focus group discussions with students at two universities in Kenya (n = 42). Results show that despite relatively low levels of awareness and widespread misinformation, when the method was explained, both clients and students expressed considerable interest, but also expressed some health and other concerns.

Adult↗
PubMed1999

Molecular determinants of the granulocyte-macrophage colony-stimulating factor receptor complex assembly.

The granulocyte-macrophage colony-stimulating factor (GM-CSF) receptor (GMR) is composed of two chains that belong to the superfamily of cytokine receptors typified by the growth hormone receptor. A common structural element found in cytokine receptors is a module of two fibronectin-like domains, each characterized by seven beta-strands denoted A-G and A'-G', respectively. The alpha-chain (GMRalpha) confers low affinity GM-CSF binding (K(d) = 1-5 nM), whereas the beta-chain (beta(c)) does not bind GM-CSF by itself but confers high affinity binding when associated with alpha (K(d) = 40-100 pM). In the present study, we define the molecular determinants required for ligand recognition and for stabilization of the complex through a convergence of several approaches, including the construction of chimeric receptors, the molecular dynamics of our three-dimensional model of the GM.GMR complex, and site-directed mutagenesis. The functional importance of individual residues was then investigated through ligand binding studies at equilibrium and through determination of the kinetic constants of the GM.GMR complex. Critical to this tripartite complex is the establishment of four noncovalent bonds, three that determine the nature of the ligand recognition process involving residues Arg(280) and Tyr(226) of the alpha-chain and residue Tyr(365) of the beta-chain, since mutations of either one of these residues resulted in a significant decrease in the association rate. Finally, residue Tyr(365) of beta(c) serves a dual function in that it cooperates with another residue of beta(c), Tyr(421) to stabilize the complex since mutation of Tyr(365) and Tyr(421) result in a drastic increase in the dissociation rate (Koff). Interestingly, these four residues are located at the B'-C' and F'-G' loops of GMRalpha and of beta(c), thus establishing a functional symmetry within an apparently asymmetrical heterodimeric structure.

3T3 Cells↗
PubMed1999

Safety and immunogenicity of a new Neisseria meningitidis serogroup C-tetanus toxoid conjugate vaccine in healthy adults.

UNLABELLED: We evaluated the safety and immunogenicity of a single dose of a new serogroup C O-deacetylated meningococcal polysaccharide-tetanus toxoid conjugate vaccine in 30 healthy adult volunteers. The vaccine was well tolerated with no serious adverse events and minimal local reactions and systemic symptoms. All subjects developed a fourfold or greater increase in serum bactericidal antibody (SBA) to serogroup C meningococcus. SBA geometric mean titre increased from 11 to 3649 (p<0.001). Serogroup C-specific IgG levels increased postvaccination from 0.65 to 17.02 microg/ml (p<0.001). Bactericidal titres pre- and postimmunisation showed significant correlation with serogroup C-specific IgG (r(2)=0.693). Antibody levels fell by 6 months postvaccination, however, meningococcal C IgG avidity increased indicating the successful induction of a T-cell-dependent antibody response. CONCLUSION: meningococcal C-tetanus toxoid conjugate vaccine is immunogenic and well tolerated in healthy adults.

Adult↗
PubMed1999

Helicobacter pylori infection and early onset myocardial infarction: case-control and sibling pairs study.

OBJECTIVES: To examine the association between coronary heart disease and chronic Helicobacter pylori infection. DESIGN: Case-control study of myocardial infarction at young ages and study of sibling pairs with one member affected and the other not. SETTING: United Kingdom. PARTICIPANTS: 1122 survivors of suspected acute myocardial infarction at ages 30-49 (mean age 44 years) and 1122 age and sex matched controls with no history of coronary heart disease; 510 age and sex matched pairs of siblings (mean age 59 years) in which one sibling had survived myocardial infarction and one had no history of coronary heart disease. MAIN OUTCOME MEASURES: Serological evidence of chronic infection with H pylori. RESULTS: 472 (42%) of the 1122 cases with early onset myocardial infarction were seropositive for H pylori antibodies compared with 272 (24%) of the 1122 age and sex matched controls, giving an odds ratio of 2.28 (99% confidence interval 1.80 to 2.90). This odds ratio fell to 1.87 (1.42 to 2.47; P<0.0001) after smoking and indicators of socioeconomic status were adjusted for and to 1.75 (1.29 to 2.36) after additional adjustment for blood lipid concentrations and obesity. Only 158 of the 510 pairs of siblings were discordant for H pylori status; among these, 91 cases and 67 controls were seropositive (odds ratio 1.33 (0.86 to 2.05)). No strong correlations were observed between H pylori seropositivity and measurements of other risk factors for coronary heart disease (plasma lipids, fibrinogen, C reactive protein, albumin, etc). CONCLUSION: In the context of results from other relevant studies, these two studies suggest a moderate association between coronary heart disease and H pylori seropositivity that cannot be fully accounted for by other risk factors. But even if this association is causal and largely reversible by eradication of chronic infection, very large randomised trials would be needed to show this.

Adult↗
PubMed1999

Nutrient-induced insulin resistance.

Impaired function of the hormone insulin (insulin resistance) is a major feature of type 2 diabetes, a condition that is expected to afflict over 200 million people by early next century. Intensive investigation has failed to find a genetic basis for insulin resistance in the majority of cases. In this brief review the evidence that insulin resistance may be caused by excess nutrient supply will be presented. Both excess glucose and excess fat can cause insulin resistance in muscle and fat tissue, while excess fat can cause impaired suppression of endogenous glucose production. Each nutrient may impair insulin action by several mechanisms, at least one of which may be common to both.

Diet↗
PubMed1999

Laser doppler imaging--a new technique for quantifying microcirculatory flow in patients with primary Raynaud's phenomenon and systemic sclerosis.

This was a pilot study to investigate the new technique of laser Doppler imaging (scanning laser Doppler) as a tool to quantify microvascular blood flow in the digits of patients with primary Raynaud's phenomenon (PRP) and systemic sclerosis (SSc), and to determine in the first instance whether the flux patterns obtained differ between patients with SSc, patients with PRP, and healthy control subjects. Laser Doppler images of the dorsum of the hand and fingers were acquired at 23 and 30 degrees C in 17 healthy control subjects, 7 patients with PRP, 9 patients with the diffuse cutaneous variant of SSc, and 24 patients with the limited cutaneous variant of SSc. Different flux parameters were compared between groups. Analysis of variance found significant differences between groups in two tests: maximum difference in flux between fingertips of the same hand at 23 degrees C (P = 0.001) and maximum gradient in flux along a finger ("distal-dorsal" flux difference) at 30 degrees C (P = 0. 019). Post hoc tests highlighted the differences between controls and patients with limited cutaneous SSc. This pilot study suggests that laser Doppler imaging may allow objective measurement of microvascular flow in patients with PRP and SSc. This new technique may overcome many of the problems inherent in single-channel laser Doppler equipment.

Adult↗
PubMed1999

Nutritionally complete prepared meal plan to reduce cardiovascular risk factors: a randomized clinical trial.

OBJECTIVE: To compare a nutritionally complete prepared meal plan that meets national dietary guidelines to usual-care dietary therapy for hypertension, dyslipidemia, and glycemic control. DESIGN: Randomized, controlled trial. SUBJECTS/SETTING: Outpatients with hypertension, dyslipidemia, or diabetes mellitus (n = 251) were recruited at 6 medical centers in the United States and Canada. INTERVENTION: The prepared meal plan, which was developed by university-based nutrition and cardiovascular scientists and food technologists at Campbell's Center for Nutrition & Wellness (CCNW), provided the optimal levels of macronutrients and micronutrients recommended for cardiovascular risk reduction in a variety of prepackaged meals and snacks. After a 4-week pretrial period to assess baseline state, participants were randomized to the CCNW plan or "usual-care" diet for 10 weeks. MAIN OUTCOME MEASURES: Blood pressure, carbohydrate metabolism, lipoproteins, homocysteine, weight, nutrient intake, compliance. STATISTICAL ANALYSES PERFORMED: Repeated measures analysis of variance. RESULTS: Lipoproteins, carbohydrate metabolism, blood pressure, and weight improved on both plans. Mean differences (+/- standard deviation) between baseline and follow-up for the CCNW plan and the usual-care plan, respectively, were total cholesterol, -0.41 +/- 0.64 and -0.20 +/- 0.50 mmol/L (between-group P < .01); plasma glucose, -0.7 +/- 1.7 and -0.3 +/- 1.3 mmol/L (P < .05); systolic blood pressure, -5.2 +/- 10.0 and -4.7 +/- 9.0 mm Hg (P = .67), diastolic blood pressure, -3.8 +/- 5.9 and -2.2 +/- 5.5 mm Hg (P < .05); and homocysteine, -1.3 +/- 3.8 and 0.2 +/- 3.4 mumol/L (P < .01). The CCNW plan led to greater weight loss than the usual-care diet (-5.5 +/- 3.8 kg vs -3.0 +/- 3.2 kg, P < .0001). APPLICATIONS/CONCLUSION: The nutritionally complete CCNW plan offers greater improvements in lipids, blood sugars, homocysteine, and weight loss than usual-care diet therapy. This prepackaged comprehensive nutrition program can augment both the prescription and practice of optimal dietary therapy.

Adult↗
PubMed1999

Emergency contraception in Nairobi, Kenya: knowledge, attitudes and practices among policymakers, family planning providers and clients, and university students.

To gauge knowledge, attitudes, and practices about emergency contraception in Nairobi, Kenya, we conducted a five-part study. We searched government and professional association policy documents, and clinic guidelines and service records for references to emergency contraception. We conducted in-depth interviews with five key policymakers, and with 93 family planning providers randomly selected to represent both the public and private sectors. We also surveyed 282 family planning clients attending 10 clinics, again representing both sectors. Finally, we conducted four focus groups with university students. Although one specially packaged emergency contraceptive (Postinor levonorgestrel tablets) is registered in Kenya, the method is scarcely known or used. No extant policy or service guidelines address the method specifically, although revisions to several documents were planned. Yet policymakers felt that expanding access to emergency contraception would require few overt policy changes, as much of the guidance for oral contraception is already broad enough to cover this alternative use of those same commodities. Participants in all parts of the study generally supported expanded access to emergency contraception in Kenya. They did, however, want additional, detailed information, particularly about health effects. They also differed over exactly who should have access to emergency contraception and how it should be provided.

Contraceptives, Postcoital↗
PubMed1999

How reliable is emergency department triage?

STUDY OBJECTIVE: To measure interrater and intrarater agreement for an emergency department triage system. METHODS: A 2-phase experimental study was conducted using previously described in-person scripted encounters with emergency nurses who perform patient triage and attending emergency physicians at a tertiary referral center. Standardized patient scenarios were presented twice over 6 weeks. Participants rated severity for each patient using a 5-tier triage system (nurses only) and estimated the probability of hospital admission, the most appropriate time frame to physician evaluation (5 choices, from "Immediate" to "More than 24 hours"), the need for a monitored ED bed, and the need for diagnostic services. Interrater agreement was measured by a coefficient of agreement for multiple raters and multiple categories. RESULTS: Of the 37 participants (fewer than 90% of those eligible), 19 (51%) completed both phases (12 nurses, 7 physicians). Four (33%) of the nurses assigned the same severity ratings for the 5 cases in phase 2 as they did in phase 1. Intrarater agreement among the 12 nurses rating triage severity was.757. Interrater agreement of nurses and physicians was substantial regarding need for ED monitoring, and moderate to substantial for other triage assessments. CONCLUSION: There was general agreement in interrater assessment of triage classification. Continued work is necessary to more fully delineate areas of variation.

Adult↗
PubMed1999

Anesthetic efficacy of the mylohyoid nerve block and combination inferior alveolar nerve block/mylohyoid nerve block.

OBJECTIVE: The purpose of this study was to measure the degree of anesthesia obtained with the mylohyoid nerve block and the combination mylohyoid nerve block/conventional inferior alveolar nerve (IAN) block in mandibular teeth. STUDY DESIGN: With the use of a repeated-measures design, 30 subjects randomly received each of 3 combinations of injections at 3 separate appointments. The combinations were as follows: mylohyoid nerve block (1.8 mL of 2% lidocaine with 1:100,000 epinephrine) + IAN block (3.6 mL of 2% lidocaine with 1:100,000 epinephrine); mock mylohyoid nerve block + IAN block (3.6 mL of 2% lidocaine with 1:100,000 epinephrine); mylohyoid nerve block (1.8 mL of 2% lidocaine with 1:100,000 epinephrine) + mock IAN block. The mylohyoid injections were aided by the use of a peripheral nerve stimulator. Mandibular anterior and posterior teeth were blindly tested with a pulp tester at 4-minute cycles for 60 minutes postinjection. Anesthesia was considered successful when 2 consecutive 80 readings were obtained. RESULTS: One hundred percent of the subjects had lip numbness with the mylohyoid nerve block + IAN block and mock mylohyoid nerve block + IAN block techniques. For these 2 techniques, anesthetic success rates were higher in posterior teeth (73% to 93%) than in anterior teeth (33% to 60%). There were no significant differences (P > .05) between the 2 techniques. The mylohyoid nerve block + mock IAN block technique resulted in a very low success rate (0% to 17%) and was significantly different (P < .05) from the mylohyoid nerve block + IAN block technique. CONCLUSIONS: The results of this study suggest that the mylohyoid nerve block does not by itself predictably provide pulpal anesthesia in mandibular teeth and does not significantly enhance pulpal anesthesia when administered in combination with the IAN block.

Adult↗