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Biomedical subjects

S Weinstein

Publications and source records attributed to S Weinstein.

At least 91 records · Page 5Linked to original sources
PubMed1986

Mechanism of oligonucleotide loop formation in solution.

We have studied the tridecadeoxynucleotide CGCGAATTACGCG (I), which contains an additional A at position 9 compared to the dodecanucleotide of which the crystal structure has been determined. Sequence I exhibits no distinct melting curve and also has a concentration-dependent pattern of peaks on reverse-phase chromatography. This behavior is explained by a slow equilibration between loop and duplex forms in solution. We have characterized this equilibrium by proton NMR spectroscopy and shown that it is fully reversible by monitoring the two thymine methyl resonances, each of which occurs in two environments. Lower temperature and higher concentration favor the duplex; the midpoint of the transition is such that the loop predominates at room temperature. We have measured the van't Hoff enthalpy of formation of the duplex and the activation energy by temperature-jump and saturation-transfer experiments. The results are compared with those for the 17-mer sequence CGCGCGAATTACGCGCG (II), which contains two additional base pairs in the stem of the loop. The thermodynamic parameters and the effect of increasing salt concentration on the rate of conversion of the loop and duplex forms lead us to presume that the mechanism of interconversion involves complete strand separation and re-formation rather than cruciform formation and branch migration.

Base Sequence↗
PubMed1986

Emotional and health impact of home monitoring on mothers: a controlled prospective study.

The psychologic and health effects of home monitoring were evaluated in mothers, whose infants (epidemiologically not at high risk for sudden infant death syndrome) were placed on electronic surveillance because of results obtained from a laboratory sleep study conducted at 4 weeks of age. Mothers of these infants were studied prospectively at several periods following the infants' births: 6 weeks, 12 weeks, and 1 year. The initial sample consisted of 56 mothers. Evaluation procedures included the Neonatal Perception Inventories, Anxiety Inventory (State and Trait), Depression Inventory, Brief Symptom Inventory, and a Recent Life Changes Questionnaire. The results obtained from these women were compared with those of women who had delivered at about the same time but whose infants were not placed on a home monitoring program. A total of 57 women started in the control group. Very few statistically significant group differences were observed between the two subject groups: 2 weeks after initiating the home monitoring program, monitor mothers (when compared to nonmonitor mothers) perceived their infant's behavior differently (although not more bothersome) and had an increased degree of situational anxiety (although not to an abnormal degree). There were no statistically significant differences between the two groups 12 weeks or 1 year after giving birth. These results suggest that a home monitoring program, which includes an aggressive and readily available support system, does not impose a marked health hazard to mothers.

Analysis of Variance↗
PubMed1985

Conformation of the gramicidin A channel in phospholipid vesicles: a fluorine-19 nuclear magnetic resonance study.

The membrane conformation of the peptide ionophore gramicidin A is shown by 19F NMR to be described by the N-terminal to N-terminal beta LD helical dimer model proposed by Urry [Urry, D.W. (1971) Proc. Natl. Acad. Sci. U.S.A. 68, 672-676]. Fully active analogues of gramicidin with 19F labels at both the N- and C-termini are prepared synthetically. Labeled peptides are incorporated into small unilamellar vesicles of dimyristoylphosphatidylcholine. Measurements of the accessibility of the labels to either aqueous or lipophilic paramagnetic probes show that the N-terminus of gramicidin is located in the membrane interior and the C-terminus is at the membrane surface. Of the specific models proposed for the structure of gramicidin, these data are consistent only with that of Urry. The C-terminal 19F NMR peak in vesicles actually consists of three overlapping peaks. Experiments with the aqueous shift reagent Tm3+ show that C-terminal 19F nuclei in the inner and in the outer leaflets of vesicles resonate at different frequencies. The outer leaflet peak in turn consists of two overlapping peaks, possibly due to a local rearrangement of the C-terminal label.

Amino Acids↗
PubMed1985

Effect of exercise training and diet modification on serum lipids and lipoproteins in coronary artery disease patients treated with thiazides.

The effects of chronic exercise training and diet modification on serum lipids and lipoproteins were measured in 17 hypertensive males and 41 normotensive males with documented coronary artery disease (CAD). Exercise consisted of aerobic activities which were performed at approximately 75-85% of the symptom-limited maximum heart rate for 30-40 minutes, three times weekly for 3 months. Each participant's diet was also controlled, the recommended daily intake of fat and cholesterol was no more than 40 g/day and 200 mg/day, respectively. Significant increases in estimated VO2max and total cholesterol/high density lipoprotein (HDL) and a significant decrease in serum triglycerides were documented after training. Significant differences in serum cholesterol and triglycerides between the nondiuretic and diuretic patients were also noted. No significant changes were found in low density lipoprotein (LDL), HDL, or body weight. Vigorous aerobic training and diet modification can favorably modify the deleterious effects of diuretic medications on serum triglycerides and total cholesterol/HDL in patients with documented CAD.

Adult↗
PubMed1985

In vivo effects of snake venoms on passive and facilitated glucose transport across blood-ocular and blood-CSF barriers of the rat.

The transport of (3H)-3-0-methyl-D-glucose (mD-glu) and (14C)-L-glucose (L-glu) across blood-ocular and blood-CNS barriers was studied in rats with previously introduced (i.v.) lethal doses of lyophilized venom from one of three venomous snakes; mojave rattlesnake, Crotalus scutulatus; cottonmouth mocassin, Agkistrodon piscivorus; yellow cobra, Naja nivea. Transport rate constants calculated for mD-glu are taken as an indication of carrier-mediated transport, whereas L-glu constants are considered a measure of passive barrier permeability. C. scutulatus venom increased L-glu transport (+121%) across the blood-vitreous barrier. A passive increase in blood-vitreous permeability was also observed with mD-glu. This venom also increased passive L-glu entry rate into CSF (+160%). A. piscivorus venom also increased passive L-glucose entry into vitreous. However, whereas rattlesnake venom had little effect on blood-aqueous transport, cottonmouth venom may have also decreased carrier transport across this barrier. In addition, mD-glu transport from blood into CSF is decreased, suggesting a loss of carrier function across this barrier. N. nivea venom decreased the transport of both L-glu and mD-glu across the blood-aqueous, blood-vitreous and blood-CSF barriers, suggesting a possible decrease in cerebral blood flow as causative. There is also a possible increase in passive transport across the vitreous barriers, which may be in part countered by the decreased blood flow. Transport from aqueous into lens and cornea remained unchanged by the three venoms tested. It is suggested that components of rattlesnake and cottonmouth venoms alter transport barrier properties, with the blood-vitreous barrier being most susceptible to damage, whereas cobra venom likely decreases the supply of blood-borne substances to brain and ocular fluids and tissues by decreasing cerebral blood supply.

3-O-Methylglucose↗
PubMed1985

Ataxia telangiectasia with hepatocellular carcinoma in a 15-year-old girl and studies of her kindred.

We studied a case of familial ataxia-telangiectasia in a 15-year-old girl who had a clinical history of cerebellar ataxia and recurrent pulmonary infections. She was found at autopsy to have a hepatocellular carcinoma, which has been described twice previously in the literature as occurring with this disorder. Family studies on the majority of her seven siblings (the product of one father and two mothers who were identical twins) showed one brother to have classic features of cerebellar ataxia, IgA deficiency, markedly elevated alpha-fetoprotein levels, and characteristic chromosomal abnormalities. This boy also died later of hepatocellular carcinoma in 1984. An affected sister had previously died of a respiratory tract infection.

Adolescent↗
PubMed1984

Photochemically induced nuclear polarization study of the accessibility of tyrosines in insulin.

The accessible tyrosines of bovine insulin were studied by the photochemically induced dynamic nuclear polarization (photo-CIDNP) method. Tyrosine 1H nuclear polarization is observed in acidic, neutral, and basic solutions at all concentrations studied, in the absence of added salts as well as in the presence of 0.05-0.1 M chloride or phosphate. At pH 2.1 in the presence of chloride, at concentrations of 640 microM and above, most of the nuclear polarization at delta 6.82 originates from one group of tyrosines. On the basis of the crystallographic model, these are assumed to be the A14 tyrosines. We explored the possibility of a genuine concentration dependence of the photo-CIDNP intensity of insulin due to aggregation. In order to discern between such effects and trivial kinetic effects traceable to the optical irradiation method, the effects of concentration changes on polarization were examined in three apparently nonassociating trypsin inhibitor proteins. In insulin, the intensity of Tyr-A 14 polarization changes slowly at concentrations above 1 mM, suggesting that these residues are similarly accessible in all association states. At insulin concentrations below 320 microM, additional tyrosine emission signals were observed. These signals are probably due to B16 and B26 tyrosines of monomers. Polarization transfer effects from Tyr-A14 are evident in the tetramer and hexamer. Enhanced absorption effects in the two histidines (B5 and B10) of the insulin monomer were observed at pH 10 in the presence of 0.1 M phosphate.

Animals↗
PubMed1984

Morphologic analysis of upper lip area following maxillary osteotomy via the tunneling approach.

Preservation of favorable upper lip morphology is a critical factor in assessing the success of maxillary osteotomy surgery. Unesthetic postsurgical lips often appear thin and tight, with the vermilion border shortened and rolled inward. Clinical observation of patients who had undergone total maxillary alveolar process osteotomies by means of vertical buccal incisions and a tunneling approach suggests that presurgical lip morphology is minimally changed. This study investigates the presence and degree of change in upper lip morphology following this technique. Pre- and postoperative cephalometric radiographs of ten patients were compared by superimposition of acetate tracings on cranial base landmarks. Cross-sectional lip area was calculated by compensating polar planimetry presurgically and at four intervals following intervention: 1 to 3 days, 1 to 3.5 months, 6 to 9 months, and more than 10 months. Analysis showed the cross-sectional upper lip area, compared to the presurgical baseline, to be as follows: Immediately following surgery, the area increased by a mean of 27.8% (range, 15.0% to 36.9%; SE = 4.72). At 1 to 3.5 months postsurgery, the increase was reduced to 3.3% (range, 0 to 7.7%; SE = 0.82). At 6 to 9 months, lip area remained minimally increased, at + 0.78% (range, -5.0% to 7.6%; SE = 1.68). At 10 months or longer, the mean increase from preoperative values was 0.61% (range, -6% to 6.4%; SE = 1.38). The results of this study indicate that the upper lip cross-sectional area returns to its presurgical value at 6 months following surgery and remains constant at subsequent measurements. The performance of maxillary surgery with this flap design appears to preserve presurgical lip morphology.

Adult↗
PubMed1984

A national task analysis of infection control practitioners, 1982. Part One: methodology and demography.

A task analysis survey was conducted in 1982 by the Certification Board of Infection Control ( CBIC ) to determine the tasks performed by ICPs and the knowledge and abilities needed to perform these tasks. Data were obtained from 473 (78.8%) respondents to a nationwide mail survey of 600 ICPs . The respondents represent a randomized, stratified sample of ICPs in various types of U.S. acute care hospitals ranging in size from fewer than 50 beds to more than 500 beds. The results of the survey were used, in part, to develop the Infection Control Certification Examination, offered for the first time on November 19, 1983. According to the survey results, the modal or typical ICP is a white woman between the ages of 31 and 50 years using the title of infection control nurse. She has been employed full time for 2 to 10 years in infection control practice in a Joint Commission on Accreditation of Hospitals (JCAH)--accredited community acute care hospital having 301 to 500 beds. She is working at the supervisory level, is on the nursing department payroll, votes as a member of the hospital's infection control committee, and received her last degree or diploma more than 15 years ago.

Adult↗
PubMed1984

A national task analysis of infection control practitioners, 1982. Part Two: Tasks, knowledge, and abilities for practice.

Respondents (N = 473) from a randomized stratified sample (N = 600) of U.S. hospital ICPs in a national survey sponsored by the Certification Board of Infection Control were asked to rate specific task, knowledge, and ability statements related to infection control for frequency and importance. The questions included 175 items, of which 99 were for specific tasks and 76 were for knowledge and abilities for practice. Areas covered included patient care practices, infectious diseases, epidemiology and statistics, microbiologic practices, sterilization and disinfection, education, employee health services, and management and communications. A "profile respondent" group (N = 317) was defined as persons most likely to be practicing the full scope of infection control practice and was used to identify key tasks, knowledge, and abilities for practice. Results showed that patient care practices (i.e., suctioning, dressing changes, and catheterization) were rarely performed. The development of infection control policies and procedures were key tasks. Knowledge of microbiology and infectious diseases in order to interpret laboratory reports and other patient data was rated as essential; however, few respondents actually performed laboratory procedures. Epidemiologic principles were frequently used for surveillance and problem investigation. Although presentation of epidemiologic data was rated as important, analytic statistics were rarely used. Assessment of educational needs and teaching were large components of ICPs' activities.

Certification↗
PubMed1984

A national task analysis of infection control practitioners, 1982. Part Three: The relationship between hospital size and tasks performed.

One aspect of the Certification Board of Infection Control's (CBIC) task analysis survey was to determine those tasks done most frequently and considered most important by ICPs. A randomized stratified sample of ICPs was taken from U.S. hospitals of various bed-size categories. There were 473 responses (78.8%) from a targeted sample of 600 ICPs. Statistical analyses were done to find if a relationship existed between hospital size and the tasks performed. The frequency of performance and importance of the majority of infection control tasks studied were found to vary in relation to hospital size. Some tasks were found to be both important and frequently performed by the majority of ICPs in all hospital bed-size categories. These included performing and reporting epidemiologic surveillance, educating personnel, developing infection control policies and procedures, and consulting with hospital personnel. Other tasks were found to be relatively less important and infrequently performed by the majority of ICPs in all hospital bed-size categories. These included performing bedside patient care procedures, recommending specific antimicrobial therapy, and using statistical methods. The greatest differences in the performance of tasks were found in the subsample of the ICPs from hospitals with less than or equal to 100 beds.

Communicable Disease Control↗
PubMed1984

Extensibility characteristics of human cheek--visco-elastic properties.

Using a hydraulic bellows system mounted on a maxillary partial denture, continuous force-displacement data were taken in an edentulous area in the maxillary bicuspid-molar region on ten adults. Both loading and unloading force-displacement curves showed three segments. Two visco-elastic properties - hysteresis and relaxation - were consistently evident. The maximum difference in force-magnitude of the hysteresis loop was 1.02 g. A pre-conditioning phenomenon of the cheek tissue, evidence by a reduction of the area of the hysteresis loop, was observed in a series of repeated runs. The significance of the study was that: (1) in some individuals, the cheek could be displaced, by expansion of the molars, up to 1 mm into a second stable position; and (2) the relaxation phenomenon suggests a limited adjustive capacity in cheek stiffness.

Adult↗