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Biomedical subjects

S Levin

Publications and source records attributed to S Levin.

At least 73 records · Page 4Linked to original sources
PubMed1996

Modified thioglycolate medium: a simple and reliable means for detection of Trichomonas vaginalis.

Despite the declining rate of sexually transmitted diseases in developed countries, trichomoniasis is still one of the most common venereal infections. While diagnosis of this condition is commonly based on the microscopic wet-mount method, culture remains the most accurate single procedure for detecting the presence of Trichomonas vaginalis in clinical samples. In the present study, the efficacy of a modified formula of the commonly available thioglycolate medium was compared with that of the standard Diamond's medium for detection of T. vaginalis in samples from 176 women with vaginal symptoms. Thioglycolate medium supplemented with yeast extract, horse serum, and antimicrobial agents was as reliable as Diamond's medium for detection of T. vaginalis in vaginal fluid samples. Modified thioglycolate medium may be used as a readily available, low-cost substitute for the standard medium for culturing T. vaginalis.

Animals↗
PubMed1996

Treatment of Rasmussen's syndrome with ganciclovir.

Since cytomegalovirus (CMV) has been implicated in the pathogenesis of Rasmussen's syndrome, we treated four patients with ganciclovir, a potent anti-CMV drug. A 7-year-old girl with seizures escalating to 60/day over 3 months despite triple antiepileptic drug therapy became seizure-free 5 days after initiation of treatment with no recurrence at 1.5 years follow-up. Focal neurologic signs, cognitive function, and the EEG returned to normal. Two patients treated 34 and 72 months after disease onset in association with epilepsy surgery had a reduction in seizures and one had no response. CMV genome was detected in the brains of two of the three patients in whom it was assessed. The response to antiviral therapy supports a viral etiology for chronic encephalitis of Rasmussen. If the disease is suspected, treatment with ganciclovir should be considered as early as possible.

Adult↗
PubMed1996

Evaluations of retinopathy in the VA Cooperative Study on Glycemic Control and Complications in Type II Diabetes (VA CSDM). A feasibility study.

OBJECTIVE: The main goal of the study of 153 male veterans was to determine whether a statistically and clinically significant difference in HbA1c could be achieved between a standard therapy and an intensively treated group of patients with type II diabetes. A second major goal was to assess the feasibility of collecting reliable high-quality endpoint data, including microvascular and macrovascular events. Retinopathy was defined as a key microvascular endpoint. RESEARCH DESIGN AND METHODS: This was a randomized prospective trial of 153 men between the ages of 40 and 69 years, with type II diabetes for 15 years or less. Of the patients, 78 were assigned to the standard therapy arm and 75 to the intensive therapy arm. The goal of standard therapy was good general medical care and well-being and avoiding excessive hyperglycemia, glycosuria, ketonuria, or hypoglycemia. This was generally accomplished with one shot of insulin per day. The goal of intensive therapy was to obtain an HbA1c within two standard deviations of the mean of nondiabetic subjects (4.0-6.1%). This was obtained by a four-step management technique, with patients moving to the next step only if operational goals were not met. The steps were as follows: step 1: evening intermediate or long-acting insulin only; step 2: evening insulin with daytime glipizide; step 3: insulin, twice a day, no glipizide; and step 4: more than two injections of insulin, no glipizide. Retinopathy was assessed at baseline, 12, and 24 months by seven-field stereo fundus photography done at each of the five participating VA medical centers and read at the Central Reading Center at the Department of Ophthalmology, University of Wisconsin Medical School, Madison. Visual acuity was determined by ophthalmologists at each of the participating hospitals. RESULTS: After the 6th month of the 24-month study, an average HbA1c of approximately 7.1% in the intensively treated group was sustained for the full study and was significantly lower than that seen in the standard group (9.2%, P < 0.001). Compliance in obtaining fundus photographs was excellent. Near normalization of glycemia did not cause transient worsening of retinal morphology nor did it prevent the onset or delay the progression of retinopathy. There was no effect on visual acuity. CONCLUSIONS: 1) A glycemic control intervention study in people with type II diabetes is feasible and safe; 2) intensive control did not cause transient deterioration of retinopathy; and 3) although no improvement was seen in retinopathy, the follow-up was 24 months, an interval shorter than the 3 years or more of intensive therapy before improvement is seen in type 1 diabetic studies. This does not rule out the possibility that longer periods of intensive therapy would have improved retinopathy. A full-scale intervention trial in type II diabetes is needed to resolve this issue.

Adult↗
PubMed1995

Simulation of fractograms of fat emulsions in power-programmed sedimentation field-flow fractionation (SdFFF).

A quasi-empirical approach to the simulation of fractograms was examined to verify that the elution behavior of emulsions in power-based field programmed sedimentation field-flow fractionation (SdFFF) is consistent and predictable. The approach was applied to Intralipid, a commercial soybean emulsion and to an investigational medium chain triglyceride emulsion. The simulations predicted the fractograms that were obtained under various conditions of field strength, field decay and velocity of the suspending fluid, using distribution parameters obtained from one preliminary measurement of size distribution profile. Predicted fractograms were compared to experimental ones, under various fractionating powers. Good agreement was observed in most cases, in which interference of the secondary relaxation effects was not effective. The agreement confirmed the applicability of the approach to emulsions and that the simulations can be used instead of actual experiments for the optimization of their characterization by power-programmed SdFFF.

Chemical Fractionation↗
PubMed1995

Antibiotic therapy in the allergic patient.

A variety of antimicrobial classes are now available. Thus, a careful history and skin testing for hypersensitivity reactions are often not done. It is often easier to give an alternative agent rather than to determine if the person does indeed have a hypersensitivity reaction to a particular drug. There remain situations (e.g., enterococcal endocarditis, neurosyphilis, syphilis in pregnant women), however, in which options for appropriate therapy are limited. In this setting, an accurate history accompanied by appropriate skin testing and desensitization is indicated.

Anti-Bacterial Agents↗
PubMed1995

Prevalence of central islands after excimer laser refractive surgery.

We conducted a study to determine the prevalence of central islands after refractive excimer laser surgery and the factors associated with their occurrence. A VISX Twenty/Twenty excimer laser was used to perform 157 photorefractive keratectomy (PRK) and 263 photorefractive astigmatic keratectomy (PARK) procedures. Corneal topography was assessed in 156 patients three months postoperatively using a topographic analysis system. Central islands were seen in 67% of patients; 26% had islands of 3.0 diopters (D) or more in height. Occurrence was associated with the laser suction nozzle being fixed during the procedure (P < .05). There was no demonstrable effect of central islands on visual acuity or refractive outcome, nor was there any relation to the amount of attempted correction or type of procedure (PARK or PRK). Central islands with a curvature difference of less than 3.0 D were seen more frequently than an absence of islands, suggesting these may be a "normal" postoperative topographic variation. The effect of nozzle position on island formation suggests that plume removal or corneal hydration may be important, as is corneal epithelial healing.

Adult↗
PubMed1995

Measurements of size distribution and density of a pharmaceutical fat emulsion, using field-programmed sedimentation field-flow fractionation (SdFFF).

PURPOSE: The main goal was to establish that sedimentation field-flow fractionation (SdFFF), operated with power based field programming, is effective in the characterization of a commercial emulsion, Medialipide. This emulsion is used clinically for total parenteral nutrition and it is consisted of a mixture of long-chain triglycerides (LCT, soybean oil) with medium-chain triglycerides (MCT) emulsified by phospholipids. METHODS: Different field programming methods were used in the analysis to establish the limits of applicability of the technique. RESULTS: Identical size distribution profiles were obtained under various conditions of the analysis. The density of the droplets was determined by collecting fractions from the SdFFF eluting bands, and analyzing them by photon correlation spectroscopy. The value of density of the oil droplets was changed in the SdFFF data, until best agreement with the PCS values was achieved. The value of density corresponding to the best agreement was considered as the oil density, and it was closed to the weighted average value between soybean and MCT oils. CONCLUSIONS: Field programming extends the capabilities of sedimentation field-flow fractionation in handling and characterizing complex and delicate samples as Medialipide.

Centrifugation↗
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↗