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Biomedical subjects

D Mark

Publications and source records attributed to D Mark.

At least 37 records · Page 2Linked to original sources
PubMed1995

Anemia is prevalent in an urban, African-American adolescent population.

OBJECTIVE: To determine the prevalence of anemia in urban indigent African-American adolescents. DESIGN: Cross-sectional sample of hemoglobin values. SETTING: School-based clinic and health fair in an inner-city, predominantly African-American public high school. SUBJECTS: Ninety-nine adolescents presenting for preparticipation athletic physical examinations between August and December 1990 and 76 adolescents participating in screening activities at a high school health fair on March 12, 1991. METHODS: Finger-stick and venipuncture hemoglobin samples were obtained from presumably healthy adolescents. The percentage of anemic students was determined by means of a hemoglobin cutoff of less than 120 g/L, and with the exclusion of samples from pregnant students or those positive for sickle cell trait or disease. MAIN OUTCOME MEASURES: Hemoglobin values in 169 students. RESULTS: The mean +/- SD hemoglobin level for girls was 115 +/- 15 g/L; 50% of the girls had hemoglobin levels less than 120 g/L. The mean hemoglobin level for boys was 129 +/- 13 g/L; 16.5% of boys had hemoglobin levels less than 120 g/L. CONCLUSION: Anemia may be a common condition in inner-city African-American adolescents.

Adolescent↗
PubMed1995

Flexible sigmoidoscopy plus air-contrast barium enema versus colonoscopy for evaluation of symptomatic patients without evidence of bleeding.

One hundred forty-nine patients aged 40 years or more with symptoms suggestive of colonic disease but without evidence of gastrointestinal bleeding (absence of hematochezia, normal serum levels of hemoglobin, and at least one test negative for fecal occult blood) were randomized to undergo either initial colonoscopy or initial flexible sigmoidoscopy plus air-contrast barium enema. Patients with incomplete initial colonoscopy and certain patients with polyps seen on flexible sigmoidoscopy plus barium enema underwent the alternative procedure (barium enema or colonoscopy). The main results were as follows: First, the overall prevalence of cancer in the study was very low (0.67%). Second, initial flexible sigmoidoscopy plus barium enema detected more patients with diverticulosis than did initial colonoscopy (46% versus 31%; p = .01). Initial colonoscopy detected more persons with adenomas (p = .06) than did initial flexible sigmoidoscopy plus barium enema. Patients undergoing initial flexible sigmoidoscopy plus barium enema require the alternative procedure (24%) than were patients undergoing initial colonoscopy (6%; p = .002). Third, sensitivity analyses suggested that for most areas in the United States, initial colonoscopy would be more cost-effective for the outcomes of detection of adenomas and detection of large adenomas, although very few patients in the study had large adenomas. We conclude that the prevalence of colorectal cancer in persons with colonic symptoms but no evidence of bleeding is low and is comparable with the prevalence in an asymptomatic population. Cost-effective selection of imaging strategies in this population can be based on demographic factors such as age and sex, which are better predictors of the presence of adenomas than are symptoms.

Adenoma↗
PubMed1995

Survey of growth hormone treatment practices by 251 pediatric endocrinologists.

We wished to determine current GH treatment practices of pediatric endocrinologists and to see whether those practices related to physician characteristics. We analyzed questionnaires completed by 251 of 413 (61%) pediatric endocrinologists attending a national meeting focused on growth research. In general, laboratory testing is little used in deciding to begin or to end GH therapy. Auxological criteria account for 6 of 8 decision items always used by more than 50% of physicians for starting GH treatment and for 5 of 6 items always used for stopping therapy. Although 80% of respondents use 2 GH stimulation tests, only 32% believe such tests predict the response to therapy, 40% do not know which type of assay their lab uses, and 82% use GH in short, poorly growing children regardless of stimulation tests results. Ten percent treat short, normally growing children who pass GH stimulation tests. The median number of syndromes treated off-label was 6. There were no striking differences between faculty and private practitioners in the use of laboratory screening tests, in the use of auxological or laboratory criteria, in perceptions of risk of therapy, or in the number of syndromes treated, nor were there significant differences based on practice volume. Respondents support growth screening in schools and guidelines for the uniform use of GH treatment. Despite the ambiguities and controversies in current GH therapy, pediatric endocrinologists share many diagnostic and therapeutic philosophies.

Data Collection↗
PubMed1995

Are PRO discharge screens associated with postdischarge adverse outcomes?

OBJECTIVE: We evaluate whether patient outcomes may be affected by possible errors in care at discharge as assessed by Peer Review Organizations (PROs). DATA SOURCES/STUDY SETTING: The three data sources for the study were (1) the generic screen results of a 3 percent random sample of Medicare beneficiaries age 65 years or older who were admitted to California hospitals between 1 July 1987 and 30 June 1988 (n = 20,136 patients); (2) the 1987 and 1988 California Medicare Provided Analysis and Review (MEDPAR) data files; and (3) the American Hospital Association (AHA) 1988 Annual Survey of Hospitals. STUDY DESIGN: Multivariate logistic regression analysis was used to evaluate the association between the results of generic discharge administered by the PROs and two patient outcomes: mortality and readmission within 30 days. The analysis was adjusted for other patient characteristics recorded on the uniform discharge abstract. PRINCIPAL FINDINGS: Four discharge screens indicated an increased risk of an adverse outcome-absence of documentation of discharge planning, elevated temperature, abnormal pulse, and unaddressed abnormal test results at discharge. The other three discharge screens examined-abnormal blood pressure, IV fluids or drugs, and wound drainage before discharge-were unrelated to postdischarge adverse outcomes. CONCLUSIONS: Generic discharge screens based on inadequate discharge planning, abnormal pulse, increased temperature, or unaddressed abnormal tests may be important indicators of substandard care. Other discharge screens apparently do not detect errors in care associated with major consequences for patients.

Aged↗
PubMed1994

Screening for pediatric lead poisoning. Comparability of simultaneously drawn capillary and venous blood samples.

OBJECTIVE: To determine the ability of capillary blood lead levels to accurately reflect true blood lead levels in children at risk for lead poisoning. DESIGN: A correlation study in which lead levels of capillary blood specimens obtained by four different methods were compared with lead levels of simultaneously drawn venous blood specimens. SETTING: A central-city pediatric primary care clinic and door-to-door home visits in one central-city neighborhood. PATIENTS: Two hundred ninety-five children at high risk for lead poisoning aged 6 months to 6 years. MAIN OUTCOME MEASURES: Blood lead levels of simultaneously drawn capillary and venous blood specimens. RESULTS: Lead levels of all four capillary sampling methods were highly correlated (correlation coefficient > or = 0.96) with matched venous blood lead levels, with mean capillary-venous differences less than 0.05 mumol/L (1 microgram/dL). CONCLUSIONS: Capillary sampling is an acceptable alternative to venipuncture for lead-poisoning screening in young children.

Blood Specimen Collection↗
PubMed1993

Utilization of cardiopulmonary resuscitation in nursing homes in one community: rates and nursing home characteristics.

OBJECTIVE: To determine the rate of cardiopulmonary resuscitation use among all nursing homes in a large urban area, to examine CPR use over time, to discover whether CPR use varies among nursing homes, and to describe characteristics of patients undergoing CPR. DESIGN: Retrospective survey. SETTING: Nursing homes in a large urban area. PARTICIPANTS: One hundred ninety-six nursing home residents of 68 nursing homes underwent cardiopulmonary resuscitation over a 4-year period (1986-1989). Over this time there were 9,486 deaths in these homes, which comprised 10,252 beds. MEASUREMENTS: The CPR:death ratio was determined for each facility. The ratio was analyzed over time and by type of facility (eg, proprietary, non-profit, size of facility). The ratio was also examined among facilities with variable death rates. Patients undergoing CPR are described. RESULTS: The ratio of CPR:death over the 4-year period was 0.02. CPR:death ratio was higher (0.03) for the proprietary homes compared with the non-profit homes (0.01) P < 0.0001. A significant downward trend of CPR:death was noted over the study period for the non-profit homes; no such trend was noted in the proprietary homes. Size of nursing home did not influence the rate of CPR use. Homes with greater numbers of deaths per bed had a lower utilization of CPR. Patients undergoing CPR were old, frail, and had multiple medical problems. CPR attempts were frequent around the time of nursing home admission. CONCLUSION: The utilization of CPR in nursing homes is quite low. Non-profit homes utilize CPR less than proprietary homes. Nursing homes with the highest numbers of deaths per bed utilize CPR less than homes with lower numbers of deaths per bed. Nursing home residents receiving CPR are quite old, have multiple illnesses, and are impaired.

Activities of Daily Living↗
PubMed1991

The development of a test system for investigating the performances of personal aerosol samplers under actual workplace conditions.

The performances of new "total" aerosol samplers for use in workplaces are required to match the inhalability criteria as contained in the latest recommendations of the International Standards Organization (ISO) and the American Conference of Governmental Industrial Hygienists (ACGIH). In the past, practical evaluations have been carried out under idealized conditions in wind tunnels, and there is now the need to extend these to more realistic workplace conditions. This paper describes a new test system that was designed and built for this purpose. It consisted of a life-size mannequin mounted on a trolley so that it can be taken to and wheeled around in workplaces. The mannequin itself incorporated a robotic arm so that, under joystick control, it can be made to simulate a range of worker movements, orientations, and attitudes. An electronically controlled, compact breathing machine provided a range of typical breathing parameters for the mannequin. The pump also provided air movement for a number of personal samplers that were mounted on the torso of the mannequin and tested in that position. Sampler performance should be assessed by comparing directly the aerosol collected by the sampler with that inhaled by the mannequin (and collected on filters inside the head).

Aerosols↗
PubMed1991

Scale model studies of the transport of airborne pollutants on coalfaces.

Studies have been carried out to investigate airflows in coalmine models, with special regard to the transport of airborne pollutants, and to examine how they relate to what happens at full-scale in an actual underground mine. If such models can be shown to provide data representative of actual mine ventilation engineering, then they can provide cost-effective alternatives to full-scale investigations. The work set out in the first instance to identify the properties of: (a) the bulk airflow and associated transport of airborne pollutants along a longwall coalface; and (b) the transport of material out of regions that were partially enclosed or poorly ventilated (e.g. in the cutting zone, in headings). For the former, an appropriate quantity is the dispersivity of the coalface airflow, for the latter the mean retention time. Both quantities may be rendered non-dimensional with respect to dimensions characteristic of the system and to velocities of the airflow. Their behaviour in relation to a third dimensionless quantity, the flow Reynolds' number is also important. Experiments were performed, using smoke or dust tracers, to investigate how these properties are interrelated and how they scale between small-scale and full-scale systems. They were carried out in a 1/10-scale laboratory model, in a full-scale surface model, and underground in an actual coalmine. The basis of most of the experiments was the 'tracer decay' method, in which the transport properties of the aerodynamic system under investigation were determined from observations of the changes in tracer concentration with time immediately following the removal of the tracer source. During these experiments, the feasibility of using small-scale models to investigate ventilation problems was clearly indicated and preliminary scaling relationships which may be used as an initial basis for predicting the transport and local build-up of pollutants in mines were developed. It is expected that applications of the ideas and methodology described will be relevant to other industries.

Air Movements↗
PubMed1990

Entry characteristics of practical workplace aerosol samplers in relation to the ISO recommendations.

In recent years, new sets of criteria for health-related aerosol sampling in workplaces have been proposed by, for example, the International Standards Organizations (ISO) and the American Conference of Governmental Industrial Hygienists (ACGIH). It is therefore timely to examine the performances of workplace aerosol samplers, both instruments that have been used in the past and ones which are beginning to emerge, in the light of these recommendations. This paper describes the results and conclusions from a study of dust samplers with a view to their possible applications in the mining industry. Their performances are assessed with special reference to their entry efficiencies, based on the philosophy contained in the most up-to-date ISO recommendations, in particular with regard to the concept of inhalability (or inspirability).

Aerosols↗
PubMed1990

The use of dust-collecting cassettes in dust samplers.

This short paper highlights a possible source of error in the use of personal samplers for airborne dust due to deposition of particles on the internal surfaces between the sampling orifice and the filters. Dust collecting cassettes, incorporating sampling orifice and filters, are proposed as a means of eliminating such errors. The benefits and drawbacks of using cassettes are discussed and experiments carried out to investigate their magnitude.

Dust↗
PubMed1989

Novel method for studying mRNA phenotypes in single or small numbers of cells.

Biological processes, such as growth control, are often governed by biochemical steps involving mRNA transcripts that are short-lived and have a low copy number. Furthermore, the cells involved in these processes are often available in low numbers from in vivo sources. We now report a method that is superior to in situ hybridization, RNA blot analysis, and the nuclease protection assay for the study of short-lived, low-copy-number mRNA transcripts. The method consists of a microprocedure for isolating RNA from one to a few thousand cells and two coupled enzymatic steps: reverse transcription of whole cellular RNA, followed by amplification of the cDNA by a specifically primed polymerase chain reaction to give specific cDNA fragments that can be visualized on agarose gels by ethidium bromide staining. With this method we have detected actin mRNA from a single cell, or less than 100 cRNA molecules, and have quantified differences in RNA concentrations of less than threefold. The reverse transcription reaction products can be divided for the polymerase chain reaction, and several mRNA species can be assayed simultaneously. Therefore, we call the method single-cell mRNA phenotyping. This technique is applicable to the analysis of low-copy-number growth factor transcripts in cells in culture and in vivo.

Actins↗
PubMed1989

Developmentally regulated use of alternative promoters creates a novel platelet-derived growth factor receptor transcript in mouse teratocarcinoma and embryonic stem cells.

Embryonal carcinoma and embryonic stem cells expressed a novel form of platelet-derived growth factor receptor mRNA which was approximately 1,100 base pairs shorter than the 5.3-kilobase (kb) transcript expressed in fibroblasts and other cell types. The 4.2-kb stem cell transcript was initiated within the genomic region immediately upstream of exon 6 of the 5.3-kb transcript and therefore lacked the first five exons, which encode much of the extracellular domain of the receptor expressed in fibroblasts. In stem cells, the short form was predominant, although both forms were present at low levels. Following differentiation in vitro, expression levels of the long form increased dramatically. These findings suggest that during early embryogenesis, a stem cell-specific promoter is used in a stage- and cell type-specific manner to express a form of the platelet-derived growth factor receptor that lacks much of the extracellular domain and may function independently of ligand.

Animals↗
PubMed1988

Developmental expression of PDGF, TGF-alpha, and TGF-beta genes in preimplantation mouse embryos.

Control of growth and differentiation during mammalian embryogenesis may be regulated by growth factors from embryonic or maternal sources. With the use of single-cell messenger RNA phenotyping, the simultaneous expression of growth factor transcripts in single or small numbers of preimplantation mouse embryos was examined. Transcripts for platelet-derived growth factor A chain (PDGF-A), transforming growth factor (TGF)-alpha, and TGF-beta 1, but not for four other growth factors, were found in whole blastocysts. TGF-alpha, TGF-beta 1, and PDGF antigens were detected in blastocysts by immunocytochemistry. Both PDGF-A and TGF-alpha were detected as maternal transcripts in the unfertilized ovulated oocyte, and again in blastocysts. TGF-beta 1 transcripts appeared only after fertilization. The expression of a subset of growth factors in mouse blastocysts suggests a role for these factors in the growth and differentiation of early mammalian embryos.

Animals↗
PubMed1988

Wound macrophages express TGF-alpha and other growth factors in vivo: analysis by mRNA phenotyping.

The presence of macrophages is required for the regeneration of many cell types during wound healing. Macrophages have been reported to express a wide range of mitogenic factors and cytokines, but none of these factors has been shown in vivo to sustain all the wound-healing processes. It has been suggested that transforming growth factor-alpha (TGF-alpha) may mediate angiogenesis, epidermal regrowth, and formation of granulation tissue in vivo. Macrophages isolated from a wound site, and not exposed to cell culture conditions, expressed messenger RNA transcripts for TGF-alpha, TGF-beta, platelet-derived growth factor A-chain, and insulin-like growth factor-1. The expression of these transcripts was determined by a novel method for RNA analysis in which low numbers of mouse macrophages were isolated from wound cylinders, their RNA was purified and reverse-transcribed, and the complementary DNA was amplified in a polymerase chain reaction primed with growth factor sequence-specific primers. This single-cell RNA phenotyping procedure is rapid and has the potential for quantification, and mRNA transcripts from a single cell or a few cells can be unambiguously demonstrated, with the simultaneous analysis of several mRNA species. Macrophages from wounds expressed TGF-alpha antigen, and wound fluids contained TGF-alpha. Elicited macrophages in culture also expressed TGF-alpha transcripts and polypeptide in a time-dependent manner after stimulation with modified low-density lipoproteins and lipopolysaccharide endotoxin, which are characteristic of the activators found in injured tissues.

Animals↗
PubMed1988

Clinicians can agree in assessing relationship patterns in psychotherapy. The Core Conflictual Relationship Theme method.

This study examines interjudge agreement on formulations of dynamic themes in psychotherapy, using a session-based method, namely, the Core Conflictual Relationship Theme. Agreement was assessed by two methods: one was based on themes that were tailor-made for each case, while the other was based on coding themes into a standard set of categories. To assess agreement on the tailor-made formulations, a paired-comparisons procedure was used. For a sample of 35 patients, the similarity ratings for matched cases were significantly higher than for purposely mismatched cases. Using the standard set of categories, agreement was also good; weighted kappa values ranged from .61 to .70. The results also demonstrate reliability for the location of the relationship episodes, which form the database for the Core Conflictual Relationship Theme. Our positive results suggest that this guided clinical method can be used reliably as a measure of relationship patterns in psychotherapy; our results provide the first moderate-sized sample demonstration of clinicians' agreement in formulating this complex concept.

Attitude of Health Personnel↗
PubMed1987

Comparison of criteria for defining inspirable aerosol and the development of appropriate samplers.

This paper summarizes a body of work that has been carried out to define quantitatively the aerosol fraction that is inspired by people in workplace situations. A critical comparison is made between the versions of inspirability proposed by the International Standards Organization (ISO) and the American Conference of Governmental Industrial Hygienists (ACGIH) respectively; this comparison suggests that, for some workplace aerosols, significant differences in sampled mass can arise depending on which definition is used as the basis for designing practical sampling instruments. Finally, a family of static and personal samplers for sampling aerosol according to the ACGIH inspirability criterion is described.

Aerosols↗