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Biomedical subjects

M Marcus

Publications and source records attributed to M Marcus.

At least 199 records · Page 11Linked to original sources
PubMed1969

Genetic analysis of the glutamate permease in Escherichia coli K-12.

The glutamate permeation system in Escherichia coli K-12 consists of three genes: gltC, gltS, and gltR. The genes gltC and gltS are very closely linked, and are located between the pyrE and tna loci, in the following order: tna, gltC, gltS, pyrE; gltR is located near the metA gene. The three glt genes constitute a regulatory system in which gltR is the regulator gene responsible for the formation of repressor, gltS is the structural gene of the glutamate permease, and gltC is most probably the operator locus. The synthesis of glutamate permease is partially repressed in wild-type K-12 strains, resulting in the inability of these strains to utilize glutamate as the sole source of carbon. Derepression due to mutation at the gltC locus enables growth on glutamate as a carbon source both at 30 C and at 42 C. Temperature-sensitive gltR mutants capable of utilizing glutamate for growth at 42 C but not at 30 C were found to be derepressed for glutamate permease when grown at 42 C and partially repressed (wild-type phenotype) upon growth at 30 C. These mutants produce an altered thermolabile repressor which can be inactivated by mild heat treatment (10 min at 44 C) in the absence of growth.

Carbon Isotopes↗
PubMed1967

Genetic analysis of glutamate transport and glutamate decarboxylase in Escherichia coli.

The location of the Escherichia coli K-12 genes determining or regulating glutamate transport, and the location of the gene determining glutamate decarboxylase synthesis, were established by conjugation. The ability to grow on glutamate as the sole source of carbon and energy was used to select for glutamate transport recombinants. Two genes determining the ability to grow on glutamate as the sole source of carbon and energy were mapped. One (gltC) is located near mtl (mannitol), and the other (gltH) appears to be located between the gal (galactose) and trp (tryptophan) loci. The glutamate decarboxylase gene (gad) is strongly linked to gltC. The gltC(+) recombinants grow on glutamate much faster and accumulate this amino acid to a greater extent than do the gltH(+) recombinants. The gltH(+) gene functioned only in one female strain (P678), whereas the gltC gene functioned in all the female strains tested (P678, C600, W1).

Biological Transport↗
PubMedDate not supplied

Postpartum depression and postpartum adaptation: overlapping constructs?

In order to examine the course of normal postpartum adjustment compared to the symptomatology of postpartum depression, 25 postpartum women who met Research Diagnostic Criteria for either major or minor depression were compared to 24 non-depressed postpartum women. The Schedule for Affective Disorders and Schizophrenia (SADS) and the Beck Depression Inventory (BDI) were administered to all subjects. Results suggest that sleep disturbances and loss of sexual interest are common concomitants of normal postpartum adjustment. A discriminant function analysis indicated that the cognitive-affective symptoms of loss of energy, guilt, difficulties in concentration, and loss of interest in usual activities discriminated between depressed and non-depressed women most efficiently. Finally, there was a lack of concordance between the BDI and the SADS interviews, which suggests that the BDI may not be an appropriate instrument for diagnosing depression in a postpartum sample.

Adaptation, Psychological↗
PubMedDate not supplied

Assessment of reproductive disorders and birth defects in communities near hazardous chemical sites. II. Female reproductive disorders.

Members of the workgroup on female reproductive disorders discussed methods to evaluate five principal functions: menstrual dysfunction, infertility, pregnancy loss, lactation disorders, and pregnancy complications. To test each function, a nested strategy was considered, based on progressive levels of effort available to conduct field investigations. This strategy was analogous to the three-tier classification of biomarkers used by other workshops. The lowest level of effort, corresponding to Tier 1, consists only of questionnaires, diaries, and reviews of maternal and infant medical records. The medium level of effort (Tier 2) collects data from questionnaires and diaries, and some biologic specimens. Suggested laboratory analyses included measurement of progesterone in saliva and several glycoprotein hormones in urine that evaluate menstrual dysfunction, infertility, and pregnancy loss. The highest level of effort (Tier 3) involves prospective collection of diary information and simultaneous collection of biological specimens.

Abortion, Spontaneous↗
PubMedDate not supplied

In situ nick-translation distinguishes between active and inactive X chromosomes.

Template-active regions of chromatin are structurally distinct from nontranscribing segments of the genome. Recently, it was suggested that the conformation of active genes which renders them sensitive to DNase I may be maintained even in fixed mitotic chromosomes. We have developed a technique of mitotic cell fixation and DNase I-directed nick-translation which distinguishes between active and inactive X chromosomes. We report here that Gerbillus gerbillus (rodent) female cells contain easily identified composite X chromosomes each of which includes the original X chromosome flanked by two characteristic autosomal segments. After nick-translation the active X chromosome in each cell is labelled specifically in both the autosomal and X-chromosomal regions. The inactive X chromosome is labelled only in the autosomal regions and in a small early replicating band within the late replicating 'original X' chromosome. Our technique opens the possibility of following the kinetics of X-chromosome inactivation and reactivation during embryogenesis, studying active genes in the inactive X chromosome and mapping tissue-specific gene clusters.

Animals↗
PubMedDate not supplied

Neurotoxic effects of solvent exposure on sewage treatment workers.

Nineteen Sewage Treatment Workers (STWs) exposed to industrial sewage that contained benzene, toluene, and other organic solvents at a primary sewage treatment plant in New York City (Plant A) were examined for evidence of solvent toxicity. Fourteen (74%) complained of central nervous system (CNS) symptoms consistent with solvent exposure, including lightheadedness, fatigue, increased sleep requirement, and headache. The majority of these symptoms resolved with transfer from the plant. Men working less than 1 yr at Plant A were more likely to complain of two or more CNS symptoms than men who were working there longer than 1 yr (p = .055). Objective abnormalities in neurobehavioral testing were found in all 4 men working longer than 9 yr at this plant, but in only 5 of 15 employed there for a shorter period (p = .03). These results are consistent with the known effects of solvent exposure. Occupational health personnel must be aware that STWs can be exposed to solvents and other industrial wastes.

Adult↗
PubMedDate not supplied

Polycyclic aromatic hydrocarbon (PAH) residues on skin in relation to air levels among roofers.

To assess the utility of skin wipes as an index of exposure to polycyclic aromatic hydrocarbons (PAHs), simultaneous skin wipe and breathing zone air samples were obtained for 10 roofers. Samples were obtained during removal of an old coal-tar pitch roof and application of a new asphalt roof. Skin wipes were obtained immediately before and after the workshift. Anthracene was present in air but not skin samples. In air samples, the relative concentrations of seven PAHs were fluoranthene greater than pyrene greater than benzanthracene greater than benzo[a]pyrene greater than benzo[b]fluoranthene greater than benzo[ghi]perylene greater than benzo[k]fluoranthene. A similar pattern, or rank concentration, was observed in matching skin wipe samples. The amount (ng) of PAH (either total or individual compounds) found in skin wipes taken after the workday was significantly correlated with that in air samples (micrograms/m3, time-weighted average) for 8 of the 9 cases with air and skin samples taken the same day (r = 0.99 for total PAH). Skin wipe PAH residues were not significantly correlated with air samples taken 4 d earlier. These findings suggest that skin wipes can provide a useful measure of exposure to PAH.

Air Pollutants↗
PubMedDate not supplied

Computer users' postures and associations with workstation characteristics.

This investigation tested the hypotheses that (1) physical workstation dimensions are important determinants of operator posture, (2) specific workstation characteristics systematically affect worker posture, and (3) computer operators assume "neutral" upper limb postures while keying. Operator head, neck, and upper extremity posture and selected workstation dimensions and characteristics were measured among 379 computer users. Operator postures were measured with manual goniometers, workstation characteristics were evaluated by observation, and workstation dimensions by direct measurement. Considerably greater variability in all postures was observed than was expected from application of basic geometric principles to measured workstation dimensions. Few strong correlations were observed between worker posture and workstation physical dimensions; findings suggest that preference is given to keyboard placement with respect to the eyes (r = 0.60 for association between keyboard height and seated elbow height) compared with monitor placement with respect to the eyes (r = 0.18 for association between monitor height and seated eye height). Wrist extension was weakly correlated with keyboard height (r = -0.24) and virtually not at all with keyboard thickness (r = 0.07). Use of a wrist rest was associated with decreased wrist flexion (21.9 versus 25.1 degrees, p < 0.01). Participants who had easily adjustable chairs had essentially the same neck and upper limb postures as did those with nonadjustable chairs. Sixty-one percent of computer operators were observed in nonneutral shoulder postures and 41% in nonneutral wrist postures. Findings suggest that (1) workstation dimensions are not strong determinants of at least several neck and upper extremity postures among computer operators, (2) only some workstation characteristics affect posture, and (3) contrary to common recommendations, a large proportion of computer users do not work in so-called neutral postures.

Adult↗
PubMedDate not supplied

The hospital-sponsored ambulatory dental services program, Part II: An evaluation of dental services.

This paper examines the appropriateness and continuity of dental care rendered by the 25 hospital facilities participating in the Hospital-Sponsored Ambulatory Dental Services Program, a $10 million effort established by the Robert Wood Johnson Foundation from 1979 to 1983. Record review data on 5,200 patients in 13 of the hospitals show that a substantially greater number of patients entered as episodic users of the system in the final phase of the evaluation than in the baseline visit; fewer of these episodic patients made the transition to initial care in the final phase. A followup study on baseline patients indicates that only 28% of the sample had a visit after the year of first contact. The trend toward episodic care is reflected in a reduced amount of preventive and operative services from baseline to final assessments. Compared with a study of private practices in California, the emphasis on surgery in the hospitals is dramatic: a dental patient accessing a hospital clinic will lose approximately one tooth as compared with a half tooth in private practice. Private practices also perform more crown and fixed partial denture services and more services across-the-board than the hospital clinics. Telephone interviews show that overall patient satisfaction with the hospital dental services remained high during the study (87% to 89%). Fewer patient in the final sample, however, planned to return to the hospital for all or part of their care. These findings reveal that continuity of care is a problem for hospital dental clinics. The preponderance of episodic care raises questions as to the breadth of experience offered by these hospitals to general practice residents.

Continuity of Patient Care↗
PubMedDate not supplied

Carbon dioxide pneumoamnios causes acidosis in fetal lamb.

Recently developed techniques of video-endoscopic surgery may offer new hope for the future of fetal surgery. To allow this approach, the amniotic cavity has to be temporarily enlarged, either by carbon dioxide (CO2) insufflation or by amnioinfusion. In 6 anesthetized ewes, CO2 insufflation of the amniotic cavity produced severe fetal hypercapnia (from 57.6 +/- 1.6 to 87.0 +/- 7.0 torr) and acidosis (from 7.22 +/- 0.03 to 7.11 +/- 0.08) despite normal maternal CO2 pressure and pH. CO2 pneumoamnios does not therefore appear to be an ideal working medium. Fetal endoscopic surgery through amnioinfusion of physiologic fluid may be a safer alternative.

Acidosis↗
PubMedDate not supplied

Brucella meningitis and papilledema in a child.

PURPOSE: To report a rare case of Brucella meningitis with papilledema in a child and to discuss the findings of neurobrucellosis in children. METHODS: A 6-year-old girl was admitted with headache, fever, and vomiting for 1 week. Her family reported intake of raw unpasteurized goat's milk in the past. Meningeal signs were strongly positive. Bilateral moderate optic disc edema with flame-shaped hemorrhages was observed. RESULTS: The diagnosis of Brucella infection was established by positive blood culture for Brucella species, serum agglutination titer of antibodies to Brucella >1:160, and positive CSF culture. After treatment consisting of trimethoprim-sulfamethoxazole, rifampin, and doxycycline, the patient's condition gradually improved. One month later, the papilledema disappeared. One year after presentation, the patient remains free of symptoms. CONCLUSIONS: Brucella meningitis must be ruled out in symptomatic patients reporting ingestion of raw unpasteurized goat's milk. Papilledema is a frequent clinical feature, but irreversible visual impairment is extremely rare.

Agglutination Tests↗