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Biomedical subjects

Y Levin

Publications and source records attributed to Y Levin.

At least 19 recordsLinked to original sources
PubMed2001

Counterion correlations and attraction between like-charged macromolecules.

A simple model is presented for the appearance of attraction between two like-charged polyions inside a polyelectrolyte solution. The polyions are modeled as rigid cylinders in a continuum dielectric solvent. The strong electrostatic interaction between the polyions and the counterions results in counterion condensation. If the two polyions are sufficiently close to each other their layers of condensed counterions can become correlated resulting in attraction between the macromolecules. To explore the counterion induced attraction we calculate the correlation functions for the condensed counterions. It is found that the correlations are of very short range. For the parameters specific to the double stranded DNA, the correlations and the attraction appear only when the surface-to-surface separation is less than 7 A.

Biophysics↗
PubMed2001

Criticality in confined ionic fluids.

A theory of a confined two-dimensional electrolyte is presented. The positive and negative ions, interacting by a 1/r potential, are constrained to move on an interface separating two solvents with dielectric constants epsilon(1) and epsilon(2). It is shown that the Debye-Hückel type of theory predicts that this two-dimensional Coulomb fluid should undergo a phase separation into a coexisting liquid (high-density) and gas (low-density) phases. We argue, however, that the formation of polymerlike chains of alternating positive and negative ions can prevent this phase transition from taking place.

Journal Article↗
PubMed2001

Two-stage evaluation and intervention program for control of methicillin-resistant Staphylococcus aureus in the hospital setting.

The aim of this study was to develop a 2-stage evaluation and intervention program for control of methicillin-resistant Staphylococcus aureus (MRSA) in the hospital setting. The first stage included evaluation of MRSA prevalence throughout the entire hospital; the presence of MRSA was determined in patients or medical staff who had a high risk of carrying it (i.e. as a result of contact with surgical wounds). In the second stage, "contact isolation" (which included the use of gloves, hand washing before and after treatment of a patient and isolation of patients' personal belongings) was carried out in every patient from whom MRSA was isolated in 4 intervention departments-Surgery, Orthopaedics, General ICU and Neonatal ICU-while the same policy of attempting to isolate MRSA was maintained. Both stages lasted 7 months. A comparison between MRSA prevalence in the evaluation and intervention stages disclosed a decrease in MRSA isolates from 91 to 56 in the entire hospital (p = 0.2) and from 45 to 24 in the intervention departments (p = 0.05), respectively; while the number of patients with MRSA decreased from 87 to 55 in the entire hospital (p = 0.2) and from 45 to 18 in the intervention departments (p = 0.007). The number of patients treated with vancomycin decreased from 48 before intervention to 23 after "contact isolation" was started in the entire hospital (p = 0.02) and from 31 to 5 in the intervention departments (p = 0.001). These results provide additional evidence in favor of establishing a program to control MRSA spread.

Anti-Bacterial Agents↗
PubMed2001

[The effect of gastro-esophageal reflux therapy on respiratory diseases in children].

UNLABELLED: In order to examine the effect of reflux therapy on Hyper Reactive Airway Disease (HRAD) and apnea severity, 107 children, 78 with HRAD and 29 with apnea, underwent pH monitoring in the Pediatric Surgery Unit of Wolfson Hospital and the Dana Children's Hospital during the years 1995-1998. Pathological reflux was defined by means of the Boix-Ochoa and RI (Reflux Index) scores. In patients with positive reflux, anti-reflux treatment was initiated. Prior to and following pH monitoring, the respiratory status of all patients (both with and without reflux) was evaluated by a pediatric pulmonologist employing commonly used scores to determine severity. RESULTS: Subject age ranged between one day and 15 years (mean: 15.44 +/- 29 months, median: 6.37 months). In HRAD, following anti-reflex treatment the reflux positive group showed a significant score improvement, from an average of 2.9 +/- 1.1 units to 1.54 +/- 1.2 units (p < 0.0001); a decrease in the number of patients treated with oral corticosteroids (p < 0.01); a close to significant decrease (p = 0.069) in the average dose of inhaled corticosteroids; and a decrease in the number of patients using bronchodilators (p = 0.042). The reflux-negative group, not treated for reflux, displayed no significant improvement, with only a decrease in the severity scores from 2.44 +/- 1.0 to 1.78 +/- 1.2 units (p = 0.14), and no change on any of the other parameters. In apnea, all patients improved, from an average score of 2.34 +/- 0.77 to 0.03 +/- 0.19 units (p < 0.0001), with no significant difference between the reflux positive and the reflux negative groups. In view of these findings, it is postulated that anti-reflux therapy may have an additive effect on HRAD severity, beyond that of spontaneous respiratory improvement. We therefore find it appropriate for every severe HRAD patient (frequent exacerbations or high corticosteroid dose) to undergo pH monitoring in order to treat those with proven reflux. In respect to apnea, we cannot attribute any significance to the existence of reflux or to anti-reflux treatment.

Adolescent↗
PubMed2000

Rare Jatropha multifida intoxication in two children.

Two children were admitted to the Emergency Department (ED) after ingesting a large amount of fruit of a plant identified as Jatropha multifida. They were mildly obtunded, had intractable vomiting, and seemed dehydrated. Intravenous fluid replacement and urine alkalinization were initiated. After stabilization, their 5-day hospital stays were uneventful except for a subclinical rise of liver enzymes. Jatropha species contain the toxalbumin ricin, which causes severe vomiting and diarrhea, dehydration, shock, and renal and hepatic impairment. Ricin also has cardiotoxic and hemolytic effects and several deaths have been documented. Children are attracted by the shape and the color of the Jatropha fruits. Mortality can be prevented by immediate fluid and electrolyte replacement.

Child↗
PubMed1999

Brucellosis outbreak: analysis of risk factors and serologic screening.

Israel is one of the Mediterranean countries in which Brucellosis is endemic. As recently there has been a Brucellosis outbreak in a kibbutz, the aim of this study is to identify asymptomatic infected Kibbutz members, and to delineate the manner of infection in this setting. Therefore, all the asymptomatic Kibbutz members were screened by the Rose Bengal test for Brucellosis, while both patients and healthy members were asked to fill in a questionnaire in order to pinpoint the manner of infection, and signs and symptoms of the disease. In addition to the 14 patients with Brucellosis, 2 other Kibbutz members were also found to be infected by the screening tests. Analysis of the data of the questionnaires from 142 healthy and 16 patients disclosed that almost all of the infected patients (15/16) worked in the cowshed, as opposed to only 24 out of 142 (16.9%) of the healthy members. The infected tended to participate more in calf deliveries, and had contact with cow's blood and placenta, compared with the healthy subjects (P<0.001), while there were no significant differences with respect to having cuts on hands, or working in the cowshed without gloves. In addition, 15 out of 16 (93.8%) infected persons also drank unpasteurized milk, as compared with only 17 of the 142 (12%) healthy members (P<0.001), and thus were exposed to 2 major risk factors (working in the cowshed and consumption of unpasteurized milk). As the cows of the Kibbutz's cowshed were affected by Brucella melitensis (which usually affects flocks of goats and sheep rather than cows), the microbe was probably transmitted to the cowshed from neighboring flocks by wandering dogs, and then to the infected humans.

Adult↗
PubMed1994

A double-blind trial of carbamazepine in negative symptom schizophrenia.

Twenty-eight residual schizophrenics hospitalized in a chronic institution with a 9 to 30 year history of disease, with predominantly negative symptoms were given carbamazepine. Carbamazepine was administered in a double-blind trial and therapeutic effects were measured by the Scale for the Assessment of Negative Symptoms (SANS). Patients were also assessed for positive symptoms using the Brief Psychiatric Rating Scale (BPRS), for depression using the Hamilton Depression Scale, for extrapyramidal symptoms by the Simpson and Angus scale, to rule out these symptoms as sources of secondary negative symptoms. The study continued for 7 weeks with therapeutic carbamazepine levels achieved during the last 5 weeks. There was no significant positive effect of carbamazepine on negative symptoms.

Adult↗
PubMed1993

Histidine2 of the alpha-factor of Saccharomyces cerevisiae is not essential for binding to its receptor or for biological activity.

Seven His2 analogs of the Saccharomyces cerevisiae [Nle12]alpha-factor, WXWLQLKPGQP(Nle)Y, where X = beta-D-thienylalanine, beta-L-thienylalanine, 1-D-methylhistidine, 1-L-methylhistidine, 3-D-methylhistidine, 3-L-methylhistidine, and beta-3-L-pyridylalanine, were synthesized and purified to homogeneity. Assays were carried out on binding to the alpha-factor receptor and of biological activity determined by either growth arrest or morphological changes in target cells. In the L-isomer, replacement of the imidazole of histidine by thiophene or 3-pyridyl groups or derivatization of either nitrogen of the imidazole ring by methylation resulted in a 2-100-fold decrease in bioactivity. D-Isomers of the beta-thienylalanyl-, 1-methylhistidinyl-, or 3-methylhistidinyl-alpha-factors did not possess measurable bioactivity with the exception of comparatively low activity of the 3-D-methylhistidinyl and 1-D-methylhistidinyl-alpha-factors in the morphogenesis assay. In contrast, both active and inactive analogs demonstrated binding affinities 10-20-fold less than that of [Nle12]alpha-factor. These results indicate that the histidine residue of alpha-factor is not required for binding to the receptor or for biological activity and that bioactivity and binding can be dissociated through the use of pheromone analogs.

Amino Acid Sequence↗
PubMed1992

Effects of antipsychotic drugs on memory functions of schizophrenic patients.

In this research we investigated the effects of 4 antipsychotic drugs with different anticholinergic components on different memory functions of schizophrenic patients. Drugs were administered in cumulative doses and memory was tested 90 min after each drug was administered. The results show that chlorpromazine and thioridazine impaired short-term verbal memory after 6 h of sequential administration. Trifluoperazine and haloperidol improved short-term verbal memory from the third to the fifth administration. Immediate memory, long-term memory and visual short-term memory were not impaired by any drug.

Adult↗