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Biomedical subjects

S Levin

Publications and source records attributed to S Levin.

At least 91 records · Page 5Linked to original sources
PubMed1995

Near-infrared measurement of cerebral oxygenation. Correlation with electroencephalographic ischemia during ventricular fibrillation.

BACKGROUND: The application of phase-modulated near-infrared techniques for measurement of the oxygen saturation of cerebral tissue requires both validation by conventional measures of cerebral oxygenation and determination of normal and abnormal values. This study was undertaken to validate phase-modulated near-infrared measurements of cerebral oxygen saturation by comparing them with electroencephalographic evidence of cerebral ischemia during implantation of cardioverting defibrillators. This comparison also yields an estimate of the ischemic threshold as measured with near-infrared techniques. METHODS: Electroencephalograms and near-infrared measurements were performed during 85 episodes of ventricular fibrillation in ten patients. Light at 754, 785, and 816 nm was modulated at 200 MHz, transmitted through the skull, and the path lengths of the reflected light were determined by measuring the phase shifts. The electroencephalogram was inspected for changes during the hypotension associated with the arrhythmia and the oxygen saturation was calculated from the near-infrared path lengths. Changes in oxygen saturation were then compared with electroencephalographic evidence of cerebral ischemia. RESULTS: The mean saturation before fibrillation was 56.5% +/- 1.2 (SEM). In 40 (47%) of the events, electroencephalographic evidence of ischemia was observed. Such changes were related to the minimum saturation observed during ventricular fibrillation (44% +/- 2.5 vs. 56% +/- 1.9 in the absence of electroencephalographic changes; P < 0.001). The ischemic threshold was estimated to be 47% saturation. The sensitivity of this technique was estimated to be 0.6, the specificity 0.84, and the predictive accuracy 0.73. CONCLUSIONS: Near-infrared measurements reflect changes in cerebral oxygenation as indicated by electroencephalographic evidence of cerebral ischemia.

Aged↗
PubMed1995

Estimation of body fat and lean tissue distribution by dual energy X-ray absorptiometry and abdominal body fat evaluation by computed tomography in Cushing's disease.

Body composition determined by dual energy x-ray absorptiometry and the abdominal visceral fat component determined by computed tomographic scanning were examined in women with Cushing's disease and compared with those in obese women with the same anthropometric parameters and those in nonobese women. Patients with Cushing's had no increase in total body fat or the trunk region (android) component, but had a higher intraabdominal fat area compared to the obese subjects. The total lean tissue mass was slightly reduced in Cushing's compared to that in the obese subjects due to a significant decrease in the muscle of the legs and arms; the reduced amounts of fat and lean tissue masses in the arms were the most significant findings in hypercortisolism. The body mineral and bone calcium contents were slightly reduced in Cushing's compared to those in the obese controls. Thus, although obese subjects had more fat and lean tissue and mineral masses than their normal weight counterparts, the Cushing's patients, with the same total fat mass and its components (except in the arms) as obese individuals, present total lean tissue and fractions, including body mineral and bone calcium contents, similar to those in nonobese subjects due to the depletion of the protein depots, as seen in hypercortisolism.

Absorptiometry, Photon↗
PubMed1994

Direct correlation between cell membrane fluctuations, cell filterability and the metastatic potential of lymphoid cell lines.

Cell membrane fluctuations, which reflect local bending deformability of the cell surface, are composed of submicron aperiodic reversible displacements of the cell membrane in the frequency range of 0.5-20Hz. Measurements of time-dependent light scattering from small areas (0.25 micron 2) of the cell surface reveal a higher level of cell membrane fluctuations in high metastatic BW5147 T-lymphoma derived cell lines than in their corresponding non-metastatic cell lines. Filterability measurements, carried out by recording the passage time of equal volumes of cell suspensions and media through 8 microns and 10 microns pores of a polycarbonate filter, demonstrate a higher filterability (lower rigidity index) for the high metastatic cell lines than their matched non-metastatic ones. Hence, the present study demonstrates a positive correlation between the metastatic potential of BW5147 lymphoma derived cell lines, their relative level of cell membrane fluctuations and their in-vitro cell filterability.

Animals↗
PubMed1994

Structural features affecting chiral discrimination of terpene derivatives on a carbamated amylose stationary phase.

The chiral discrimination of enantiomeric derivatives of alpha-pinene was studied using amylose tris(3,5-dimethylphenylcarbamate) as a chromatographic stationary phase. The effect of structural features of these enantiomeric pairs on their chromatographic resolution was systematically studied to understand further the correlation between these features and chiral discrimination by the carbamated amylose. Structural analysis by molecular mechanics indicated that the conformation of the alpha-pinene skeleton was preserved with substitution in all its derivatives. However, in spite of the rigidity of the molecular backbone of these molecules, their resolution capabilities were different. Apparently, the site of the hydrogen-bonding substituents affected chiral discrimination by the stationary phase rather than conformational changes. Separation was achieved in spite of the fact that none of the members in the series had an aromatic moiety, and therefore pi-pi interactions with the stationary phase were insignificant. Hence it was concluded that the most important interaction of the terpene derivatives with the carbamated amylose was hydrogen bonding.

Amylose↗
PubMed1994

Effect of surfactants on the diffusion coefficients of proteins, measured by analytical SPLITT fractionation (ASF) in the diffusion mode.

This work reports further studies of protein transport parameters in the new technique called analytical SPLITT fractionation. The SPLITT fractionation channel mimics a dialysis-like separation utilizing differential transport across an ultra-thin lamina flowing through a channel. The flowing stream is split into two sub-streams at the channel outlet, between which the protein is distributed. The cell is capable of rapidly measuring diffusion coefficients of proteins, based on their differential transport across the channel thickness, which affects the distribution between the two outlet sub-streams. The sub-stream next to the sample introduction port is more enriched than the sub-stream at the counter port when the diffusion coefficients is small. The smaller the diffusion coefficient, the higher the degree of retrieval of the protein at the sample side outlet. The entire process is realized within a short time, and a quantitative treatment of the signals of the two sub-streams yields a retrieval factor which is used for the determination of the diffusion coefficient. The conditions under which the selectivity of the diffusion SPLITT cell is optimal were examined. Analytical SPLITT fractionation has proven successful, using a number of proteins under various conditions. Results showed that the technique can detect subtle changes in proteins diffusion coefficients, and confirm that addition of small concentrations of surfactants does not change their transport parameters significantly.

Chromatography, High Pressure Liquid↗
PubMed1994

Characterization of submicron MCT o/w emulsions using sedimentation field-flow fractionation (FFF) with power field programming.

Sedimentation field-flow fractionation (SdFFF) operated with power-based field programming, was shown to be effective in the characterization of submicron investigational pharmaceutical emulsions. Field programming, in which the decrease of field strength with time gradually decreases the retention of sample components, extends the capabilities of sedimentation field flow fractionation in handling polydisperse and multicomponent samples. The emulsions were made of medium chain triglycerides (MCT) oil in water emulsified by phospholipids. They were analysed by different rates of field decay and different flow rates. Identical size distribution profiles were obtained under all circumstances, using the appropriate stop-flow times. Fractions were collected from the SdFFF eluting bands, and diameters were analysed by photon correlation spectroscopy, showing good agreement with values given by the FFF instrument at high flow rates and low rates of field decay. Accurate and highly reproducible size distribution profiles were obtained under various conditions. The detector response was shown to consist mostly of light scattering and was linear with concentration.

Chemical Fractionation↗
PubMed1994

Benign familial nocturnal alternating hemiplegia of childhood.

In infancy, two brothers developed recurrent attacks of alternating or bilateral hemiplegia arising exclusively out of sleep. The episodes were terminated by even brief sleep. Neither child had hypotonia, dystonic attacks, paroxysmal eye movement abnormalities, or other features characteristic of the now-classic form of alternating hemiplegia of childhood (AHC). The development of the brothers has so far remained normal. Both parents have a history of migraine. In the older boy, magnetic resonance spectroscopy (MRS) of muscle showed increased inorganic phosphate similar to what is found in children with AHC. In the younger brother and parents, MRS of muscle was normal. Other investigations were unrevealing. Flunarizine greatly reduced the duration of attacks. This genetically determined disorder represents a specific entity that is probably migraine-related and is easily misdiagnosed as AHC. Because of its benign course, particularly as far as mental development is concerned, it must be distinguished from classic AHC, which has a terrible prognosis.

Adult↗
PubMed1994

Inherited glutathione-S-transferase deficiency is a risk factor for pulmonary asbestosis.

Pulmonary diseases attributable to asbestos exposure constitute a significant public health burden, yet few studies have investigated potential genetic determinants of susceptibility to asbestos-related diseases. The glutathione-S-transferases are a family of conjugating enzymes that both catalyze the detoxification of a variety of potentially cytotoxic electrophilic agents and act in the generation of sulfadipeptide leukotriene inflammatory mediators. The gene encoding glutathione-S-transferase class mu (GSTM-1) is polymorphic; approximately 50% of Caucasian individuals have a homozygous deletion of this gene and do not produce functional enzyme. Glutathione-S-transferase mu (GST-mu) deficiency has been previously reported to be associated with smoking-induced lung cancer. We conducted a cross-sectional study to examine the prevalence of the homozygous deletion for the GSTM-1 gene in members of the carpentry trade occupationally exposed to asbestos. Members of the United Brotherhood of Carpenters and Joiners of America attending their 1991 National Union conference were invited to participate. Each participant was offered a chest X-ray and was asked to complete a comprehensive questionnaire and have their blood drawn. All radiographs were assessed for the presence of pneumoconiosis in a blinded fashion by a National Institute for Occupational Safety and Health-certified International Labor Office "B" reader. Individual GSTM-1 status was determined using polymerase chain reaction methods. Six hundred fifty-eight workers were studied. Of these, 80 (12.2%) had X-ray abnormalities associated with asbestos exposure. Individuals genetically deficient in GST-mu were significantly more likely to have radiographic evidence of nonmalignant asbestos-related disease than those who were not deficient (chi 2 = 5.0; P < 0.03).(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1993

Resolution of chiral cannabinoids on amylose tris(3,5-dimethylphenylcarbamate) chiral stationary phase: effects of structural features and mobile phase additives.

The separation of six pairs of chiral cannabinoids was achieved using a dimethylphenylcarbamate derivative of amylose, immobilized on silica gel (ChiralPak AD, Daicel), using 2-propanol and ethanol as the modifiers of n-hexane in the mobile phase. Good separation was achieved for most of the solutes in both solvent systems under various conditions. The chromatographic parameters of various cannabinoids in the two solvent systems were determined. The pairs differ from each other in small structural features such as the degree of saturation, position of a double bond and closure of a pyran ring. Therefore, a comparative study could give some clues regarding the mechanism of discrimination between the enantiomeric pairs on the chiral stationary phase. Preliminary measurements of limit of determination showed that it was possible to assess 99.9% enantiomeric purity of the cannabinoids, owing to the high efficiency of the separation. Enantiomers of two monoterpenes, used as intermediates or as starting materials in the chiral synthesis of cannabinoids, were also separated, hence the described procedure is capable of assessing whether the chiral centres in the molecules were sustained throughout the synthetic procedures.

Amylose↗
PubMed1993

Too soon to panic.

Health Care: The small-business lobby says Clinton's mandatory plan will kill off jobs. But Mom and Pop may end up breathing easier.

Commerce↗
PubMed1993

Rapid diffusion coefficient measurements using analytical SPLITT fractionation: application to proteins.

This work reports a new technique for the rapid measurement of diffusion coefficients using a special flow cell called a SPLITT cell. Such SPLITT cells, designed for continuous SPLITT fractionation, utilize differential transport across a thin (approximately 100 microns) ribbonlike lamina flowing through the cell. The liquid stream in the cell is split into two substreams at the outlet. The relative concentration in the two outlet substreams of a dilute component introduced into one of two inlet substreams is mathematically related to the appropriate transport coefficient, in this case the diffusion coefficient D. Thus D can be calculated from measured values of relative outlet concentrations. This approach has been tested using a number of dilute protein solutions. The results at different stream-splitting ratios are reasonably self-consistent and agree with most literature values for D within 5%. This approach provides a simple, rapid, and predictable means for determining the diffusion coefficients of proteins and other substances.

Animals↗
PubMed1993

Factors related to integrating persons with chronic mental illness into a peer social milieu.

Client characteristics and their perceptions of the milieu in a psychosocial rehabilitation program were used to predict the clients' level of involvement in the peer-based social network. 81 clients in a psychosocial rehabilitation program participated in the study. The results indicated that client perceptions of higher support and clarity in the staff-client milieu, and being female, were strongly related to higher peer social involvement. Milieu factors were generally more important than client characteristics in predicting client social functioning. The implications of these findings for psychosocial intervention and for research on the social functioning of this population are discussed.

Adult↗
PubMed1993

The use of particulate hydroxyapatite and plaster of Paris in aesthetic and reconstructive surgery.

The authors describe their early investigative results of using a mixture of hydroxyapatite (HA) and plaster of Paris (PP) in skull and frontal sinus defects in a large series of cats. Histologically, bone was found to form and infiltrate the HA-PP implant over a period of months, with gradual resorption of the plaster in 6-8 weeks. Clinically, the HA-PP combination has been used in 24 patients over the past seven years for various skull, zygomatic, and mandibular defects.

Adult↗
PubMed1993

Psychosocial functioning and subjective experience in schizophrenia.

This study examines the relationship between psychosocial functioning and subjective experience in 193 individuals diagnosed with schizophrenia or schizoaffective disorder according to Research Diagnostic Criteria. Psychosocial functioning was measured as work functioning, social functioning, living situation, symptomatology, and intrapsychic aspects of the deficit syndrome. Subjective experience consisted of measures of self-esteem, satisfaction with life, and subjective distress. Multivariate analyses resulted in two major findings. The first finding is a model of psychosocial functioning that consists of two factors: disorder-related variables (symptomatology and intrapsychic deficits) and functional status variables (work, social, and living situation). The second major finding is a two-tiered model of the relationship between psychosocial functioning and subjective experience. The model suggests a primary and pervasive relationship between the disorder-related variables and subjective experience and a secondary and less pronounced relationship between functional status variables and subjective experience. The implications of these findings for treatment and rehabilitation and for the study of subjective experience in schizophrenia are discussed.

Activities of Daily Living↗
PubMed1993

Effects of two weeks of feed restriction on some common toxicologic parameters in Sprague-Dawley rats.

This study was intended to identify changes caused by short-term reduced feed intake in rats such as may occur with unpalatable feed or other forms of anorexia. For 2 wk, groups of rats (10/sex/group) were fed ad libitum (control group) or given 75% (mildly restricted group), 50% (moderately restricted group), or 25% (severely restricted group) of the amount of feed eaten the day before by controls. The control group and mildly restricted group grew steadily, but the terminal body weights of the mildly restricted group (both males and females) were only about 80% of controls. The moderately restricted group did not grow during the first week but grew slightly during the second week (terminal body weights about 65% of control). The severely restricted group lost weight throughout the study (terminal weight about 40% of control). Restricted groups exhibited hemoconcentration directly related to the degree of feed restriction. White blood cell counts were reduced (principally due to lymphopenia) in severely restricted rats. Platelet counts were decreased in all restricted groups. Total serum protein concentration was reduced (decreased globulins) in all female restricted groups and in the severely restricted males. The severely restricted rats had increased serum bilirubin, electrolyte derangements, and (in females only) decreased cholesterol. Thymus and liver weights (absolute and relative) were decreased in the moderately and severely restricted groups. All the feed-restricted groups had an increased incidence of superficial gastric erosions. The mildly and moderately restricted groups had slightly decreased hematopoietic tissue in sternal bone marrow, while the severely restricted group had bone marrow necrosis, thymic atrophy, and mild testicular degeneration. Findings in the severely restricted group were distinct from those in the other groups on the basis of their severity and were considered adverse. Changes in the mildly and moderately restricted groups were considered adaptive and innocuous since feed restriction of this degree has historically been associated with increased longevity and decreased disease incidence in chronic studies.

Alanine Transaminase↗
PubMed1993

Home parenteral antibiotic therapy for patients with cystic fibrosis.

Cystic fibrosis is a genetic disease that affects multiple organ systems. Pulmonary complications associated with it frequently require intense intravenous antibiotic therapy. Home care allows patients to be treated at home, reducing the disruption of family life. New drug administration devices allow the patient increased mobility and independence. With adequate family and nursing support, patients may be able to attend work or school. Reduced hospital stays are good for the patient and cost effective for the hospital. The success of home antibiotic therapy depends on careful selection of the candidate, antibiotic regimen, nursing agency, and home care company. Many patients and families, though motivated, cannot manage the additional stress and time commitment required for home intravenous antibiotic and chest physical therapy. This time commitment may be reduced somewhat by limiting the number of antibiotics and the frequency of their administration.

Anti-Bacterial Agents↗