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Biomedical subjects

S Greenfield

Publications and source records attributed to S Greenfield.

At least 181 records · Page 10Linked to original sources
PubMed1972

Nonfunctional tricarboxylic acid cycle and the mechanism of glutamate biosynthesis in Acetobacter suboxydans.

Acetobacter suboxydans does not contain an active tricarboxylic acid cycle, yet two pathways have been suggested for glutamate synthesis from acetate catalyzed by cell extracts: a partial tricarboxylic acid cycle following an initial condensation of oxalacetate and acetyl coenzyme A. and the citramalate-mesaconate pathway following an initial condensation of pyruvate and acetyl coenzyme A. To determine which pathway functions in growing cells, acetate-1-(14)C was added to a culture growing in minimal medium. After growth had ceased, cells were recovered and fractionated. Radioactive glutamate was isolated from the cellular protein fraction, and the position of the radioactive label was determined. Decarboxylation of the C5 carbon removed 100% of the radioactivity found in the purified glutamate fraction. These experiments establish that growing cells synthesize glutamate via a partial tricarboxylic acid cycle. Aspartate isolated from these hydrolysates was not radioactive, thus providing further evidence for the lack of a complete tricarboxylic acid cycle. When cell extracts were analyzed, activity of all tricarboxylic acid cycle enzymes, except succinate dehydrogenase, was demonstrated.

Acetates↗
PubMed1969

Isocitrate dehydrogenase and glutamate synthesis in Acetobacter suboxydans.

Acetobacter suboxydans is an obligate aerobe for which an operative tricarboxylic acid cycle has not been demonstrated. Glutamate synthesis has been reported to occur by mechanisms other than those utilizing isocitrate dehydrogenase, a tricarboxylic acid cycle enzyme not previously detected in this organism. We have recovered alpha-ketoglutarate and glutamate from a system containing citrate, nicotinamide adenine dinucleotide (NAD), a divalent cation, pyridoxal phosphate, an amino donor, and dialyzed, cell-free extract. Aconitase activity was readily detected in these extracts, but isocitrate dehydrogenase activity, measured by NAD reduction, was masked by a cyanide-resistant, particulate, reduced NAD oxidase. Isocitrate dehydrogenase activity could be demonstrated after centrifuging the extracts at 150,000 x g for 3 hr and treating the supernatant fluid with 2-heptyl-4-hydroxyquinoline N-oxide. It is concluded that A. suboxydans can utilize the conventional tricarboxylic acid cycle enzymes to convert citrate to alpha-ketoglutarate which can then undergo a transamination to glutamate.

Acetobacter↗
PubMedDate not supplied

Patients' participation in medical care: effects on blood sugar control and quality of life in diabetes.

To maximize disease control, patients must participate effectively in their medical care. The authors developed an intervention designed to increase the involvement of patients in medical decision making. In a 20-minute session just before the regular visit to a physician, a clinic assistant reviewed the medical record of each experimental patient with him/her, guided by a diabetes algorithm. Using systematic prompts, the assistant encouraged patients to use the information gained to negotiate medical decisions with the doctor. A randomized trial was conducted in two university hospital clinics to compare this intervention with standard educational materials in sessions of equal length. The mean pre-intervention glycosylated hemoglobin (HbA1) values were 10.6 +/- 2.1% for 33 experimental patients and 10.3 +/- 2.0% for 26 controls. After the intervention the mean levels were 9.1 +/- 1.9% in the experimental group (p less than 0.01) and 10.6 +/- 2.22% for controls. Analysis of audiotapes of the visits to the physician showed the experimental patients were twice as effective as controls in eliciting information from the physician. Experimental patients reported significantly fewer function limitations. The authors conclude that the intervention is feasible and that it changes patient behavior, improves blood sugar control, and decreases functional limitations.

Clinical Trials as Topic↗
PubMedDate not supplied

In pursuit of the abnormal serum alkaline phosphatase: a clinical dilemma.

The serum alkaline phosphatase (ALP) is often included among the tests used for case-finding among ambulatory patients. To determine the positive predictive value of the ALP, test results for all adults screened by a health maintenance organization between March and December 1969 were obtained by computer. The authors reviewed the charts of all 661 patients with abnormal tests whose primary source of medical care was at this facility. Complete two-year follow-up data were available for 91% of these patients. There were 56 patients (9%) with a diagnosis that could have explained an abnormal ALP. Of those cases in which ALP would have been clinically useful all but one could have been diagnosed by a simple, noninvasive workup, and in that one case, no management change would have occurred. The authors conclude that in the absence of a small number of specific indications, extensive testing need not be performed to evaluate an isolated abnormal ALP obtained from a screening examination.

Alcoholism↗
PubMedDate not supplied

Comorbidity assessment in hemodialysis and peritoneal dialysis using the index of coexistent disease.

The purpose of this paper is to describe the ICED, summarize outcomes of prior studies in which it was used, and describe the adaptations that have lead to the present instrument. We will then demonstrate its use in quantifying the burden of comorbid conditions in a sample of hemodialysis and peritoneal dialysis patients from our center, and show the relationship between ICED levels and outcomes in peritoneal dialysis patients.

Comorbidity↗
PubMedDate not supplied

Use of exposure databases for status and trends analysis.

Exposure databases are useful for monitoring status and trends in environmental health. However, other supporting data are usually needed to infer human exposure or internal dose. Program planning and evaluation, environmental health surveillance, epidemiologic research, and contributions to international efforts are four major purposes for monitoring environmental exposure status and trends. Although databases play an important role in monitoring human exposure, certain methodological problems need to be overcome. The work group developed six criteria for meeting information needs for human exposure assessment. Areas that need attention are (1) specification of location, (2) specification of facility and chemical identifiers, (3) documentation of special populations at risk, (4) provision of early warning of new problems, (5) monitoring changes over time, and (6) enhancement of documentation. We tested these criteria by examining six available databases that might be used for monitoring exposure to contaminants in drinking water. Available data fell short of information needs. We drew four conclusions and offered several recommendations for each. First, available data systems lack adequate measures of human exposure. Second, data for monitoring exposures for many important population subgroups and environmental settings are inadequate. Third, an "early warning" system that monitors human exposures is needed. Fourth, designers of data-collection systems should consider the needs of users who monitor status and trends of human exposure.

Data Collection↗
PubMedDate not supplied

Methodologic issues in the conduct and interpretation of pediatric effectiveness research.

Effectiveness research represents a number of methodologic challenges not shared with randomized, controlled clinical trials. This practice-based research attempts to translate clinical practices to a wide variety of different practice settings and situations and to diverse patient subgroups. However, because study designs most often used in the conduct of effectiveness research limit the ability to establish firm causal links between medical care and outcomes, it is important to address key methodologic features to generate sound, useable findings. Such features include selection of appropriate outcome measures (with a priori hypotheses linking care to the outcomes chosen), specification of appropriate primary sampling unit, specification of unit of analysis, establishment of appropriate comparison groups, and case-mix adjustment. Conduct of this type of research in pediatrics presents a number of unique methodologic concerns that either do not apply in adult medicine or are particularly acute in pediatrics. To alert policy makers and funders to the unique aspects of pediatric health services research and to provide guidance for the conduct and interpretation of pediatric effectiveness studies, we have organized and described the methodologic issues associated with the specific type of pediatric care under study (eg, specific disease-prevention, "bundled" care for chronic disease, care for problems with social etiologies, etc). We conclude with a summary of the methodologic steps that are critical to the conduct of sound effectiveness research in pediatrics.

Child↗