Biomedical subjects

I Levin

Publications and source records attributed to I Levin.

At least 19 recordsLinked to original sources

PubMed2005

DNA markers for identifying biotypes B and Q of Bemisia tabaci (Hemiptera: Aleyrodidae) and studying population dynamics.

The two most widespread biotypes of Bemisia tabaci (Gennadius) in southern Europe and the Middle East are referred to as the B and Q-type, which are morphologically indistinguishable. In this study various DNA markers have been developed, applied and compared for studying genetic diversity and distribution of the two biotypes. For developing sequence characterized amplified regions (SCAR) and cleaved amplified polymorphic sequences (CAPS) techniques, single random amplified polymorphic DNA (RAPD) fragments of B and Q biotypes, respectively, were used. The CAPS were investigated on the basis of nuclear sodium channel and the mitochondrial cytochrome oxidase I genes (mtCOI) sequences. In general, complete agreement was found between the different markers used. Analysis of field samples collected in Israel for several years, using these markers, indicated that the percentage of the Q biotype tends to increase in field populations as time progresses. This may be attributed to the resistance of the Q biotype to neonicotinoids and pyriproxyfen and the susceptibility of the B biotype to these insecticides.

Animals↗

PubMed2005

Expression of albumin in nonhepatic tissues and its synthesis by the bovine mammary gland.

Albumin is a well-characterized product of the liver. In the present study, objectives were to determine if the albumin gene is also expressed in various nonhepatic tissues in the bovine; whether mammary gland epithelial cells synthesize albumin; and how its synthesis is affected by bovine mastitis. Albumin expression was monitored using reverse transcription-polymerase chain reaction. Tissues examined were: liver, mammary gland, tongue, intestine, lymph gland, testicle, ovary, and uterus. All tissues except the ovary expressed the albumin gene, albeit less so than the liver. The highest level of expression (other than liver) was found in the lymph nodes but expression was also found in the mammary gland. Incubation of mammary gland explants with the labeled amino acid L-[(35)S] methionine resulted in formation of labeled immunoprecipitable albumin, newly synthesized in the explant. Immunoprecipitable albumin in the medium verified that newly synthesized albumin was also secreted into the medium. This shows that the gland itself is a source of milk albumin. Albumin mRNA expression was approximately 4 times higher in mammary gland tissue from 6 mastitic cows compared with expression in mammary tissue from 6 healthy glands. Further, secretion of albumin was increased 3.5-fold from explants of mastitic mammary glands compared with secretion from explants of healthy mammary glands. Addition of lipopolysaccharide increased the synthesis and secretion of albumin in mammary gland cells in a dose-dependent manner. Exposure to lipopolysaccharide accelerated albumin synthesis in a time-dependent manner up to 48 h. These results lead us to suggest that the secretion of albumin by the mammary gland is part of the innate nonspecific defense system.

Albumins↗

PubMed2004

Increased erythrocyte aggregation in ovarian hyperstimulation syndrome: a possible contributing factor in the pathophysiology of this disease.

BACKGROUND: Many theories regarding the pathophysiology leading to ovarian hyperstimulation syndrome (OHSS) have been proposed and tested. Increased erythrocyte aggregation is associated with capillary slow flow and tissue hypoxaemia. We performed this study in order to assess the degree of erythrocyte aggregation in the peripheral blood of individuals with OHSS and undergoing controlled ovarian stimulation (COH). METHODS: Twenty women with severe OHSS, 20 women undergoing COH under IVF protocol, and 20 healthy matched controls were recruited for this prospective study. Blood samples were drawn for determination of erythrocyte aggregation as well as haematological indices. The percentage of slide covered by the cells ('erythrocyte percentage': EP) was determined using a simple slide test and image analysis. Lower EP values correspond to higher degrees of aggregation. RESULTS: The respective measures of EP were 59.2 +/- 3.0, 42.0 +/- 3.0 and 35.0 +/- 2.4% micro m for the controls, women with COH and OHSS (P < 0.01 between controls and the two stimulation groups). CONCLUSIONS: The degree of erythrocyte aggregation is enhanced in the peripheral venous blood of patients with both COH and OHSS. This finding, known to cause capillary leak, may contribute to the pathophysiology of the OHSS.

Capillaries↗

PubMed2004

Nasojejunal feeding in hyperemesis gravidarum--a preliminary study.

Hyperemesis gravidarum is a severe form of nausea and vomiting during the first trimester of pregnancy. Our objective was to assess the feasibility of nasojejunal feeding in our patients. Eleven pregnant women aged 23-46 years with hyperemesis gravidarum, persisting in spite of an in-hospital treatment of 2-15 days by intravenous fluids and antiemetic drugs and accompanied by weight loss, consented to have a nasojejunal feeding tube inserted endoscopically. Mean in-hospital weight loss prior to tube insertion was 2.2+/-1.1 kg (range 0.9-5.1 kg). A clear reduction in the extent of vomiting was already apparent within the first 48 h after tube insertion, but vomiting ceased completely after a mean of 5+/-4 days (range 1-13 days). Weight gain was recorded in six patients who stayed on tube feeding for more than 4 days. Patients were encouraged to start drinking and eating along tube feeding after 3-4 days. Ceasing vomiting and a concomitant sufficient oral intake of at least 1000 kcal/day resulted in the decision to remove the tube after 4-21 days. In three cases, however, the tube was expelled by recurrent vomiting after 1-4 days, or was blocked as in one case. The tube was not reintroduced and patients did not resume vomiting. There were no complications associated with this feeding approach in this population. Only one patient was readmitted. None of the rest resumed vomiting after tube withdrawal.The above suggests that nasojejunal enteral feeding can be an effective option in hyperemesis gravidarum persisting despite intravenous fluids and antiemetic drugs.

Adult↗

PubMed2004

[Preservation of alveolar bone of un-restorable traumatized maxillary incisors for future].

UNLABELLED: Anterior maxillary implantation is a challenging treatment for both the surgeon and prosthodontist due to high esthetic demands in this area. However, it is the most traumatized and most exposed region to habits. Prompt and appropriate management can significantly improve prognosis of many dentoalveolar injuries, especially in young patients. Unfortunately, many traumatized teeth are overtreated or left untreated, which lead to a much more complicated treatment at the time of permanent restoration at adulthood. The facial cortical plate over the roots of the maxillary teeth is thin and porous. Periapical infections, as well as prolonged and stubborn surgical treatments (repeated root end surgeries) can cause resorption of the labial plate, migrate to a more palatal position, and may later require an augmentation procedure prior to implant placement. The treatment-options of traumatized, anterior maxillary, un-restorable fractured root and ankylosed infraocluded teeth, in relation to preservation of the adjacent alveolar bone for future use of dental implantation will be discussed. The recommended treatment of crown-root fracture of permanent incisor includes removal of the coronal fragment and supragingival restoration of the fractured root. In severe cases in which the fracture line positions deeply under the gingival margin, this treatment may be supplemented by gingivectomy and/or osteotomy, as well as surgical or orthodontic extrusion of the root. In young patients, use of these treatment options as temporary treatment to preserve the facial cortical plate is important. Preservation of alveolar dimension will enable implantation after the completion of growth and development. Dento-alveolar ankylosis accompanied by replacement resorption is a serious complication following severe injury to the periodontal membrane. This complication develops mainly following avulsion and intrusion but also following lateral luxation and root fracture. Replacement resorption develops after severe damage to the periodontal ligament cells that cover the root surface. As a result of this damage, the periodontal ligament is replaced by bone tissue, causing ankylosis between bone and tooth. Following ankylosis, resorption of cementum and root dentin occurs. These processes eventually result in replacement of the entire root by bone. In young children it could arrest the growth of the alveolar process and create an infra-occluded tooth, resulting in a severe bony defect that is difficult to correct. In addition, loss of the maxillary incisor leads to serious esthetic and restorative problems, particularly when the trauma occurs at a young age. Therefore, ankylosed teeth should be treated as soon as diagnosed. Alternative treatments include intentional extraction and immediate replantation of the ankylosed tooth to its socket after embedding the tooth and the socket in Emdogain. This treatment is indicated only when the ankylosis or the replacement resorption is diagnosed at an early stage or has affected only a small area of the root. When the resorption is diagnosed at a later stage, auto transplantation of first lower pre-molar to the anterior region or decoronation of the ankylosed tooth may be considered. Decoronation is a simple and safe surgical procedure for preservation of alveolar bone prior to implant placement. It should be considered as a treatment option for teeth affected by replacement resorption. The alternative treatment of surgical extraction of an ankylosed tooth often leads to considerable bone loss and reduced bone volume in the oro-facial dimension. This may later necessitate an augmentation procedure. CONCLUSION: Scrupulous diagnosis of teeth and the alveolar bone after a traumatic injury is necessary. Treatment is multidisciplinary, requiring endodontic, surgical, orthodontic, operative and prosthetic compliance. An individual treatment plan for each patient is necessary. General rule do not apply. Periodic check-up is essential.

Adult↗

PubMed2003

Clinical and economic benefit of HPV-load testing in follow-up and management of women postcone biopsy for CIN2-3.

This study aimed to evaluate the clinical and economic implications of integrating human papilloma virus (HPV) load testing into the follow-up and management protocol of women postconisation for high-grade cervical intraepithelial neoplasia (CIN2-3). We evaluated 130 suitable women: 63 were screened biannually by Pap smears ('conventional approach') and 67 also had HPV-load testing ('HPV approach'). More stringent criteria for undergoing colposcopy or reconisation were observed by the former group compared to the latter. Both approaches were analysed for cost effectiveness. There were 33 out of 67 (49.2%) colposcopic referrals and 24 out of 67 (35.8%) reconisation/hysterectomies with the 'conventional approach' compared to 9 out of 63 (14.2%) and 7 out of 63 (11.1%) with the 'HPV approach'. Cervical intraepithelial neoplasia 2-3 residual disease was detected in 7 out of 67 (10.5%) and 7 out of 63 (11.1%) women. The 'conventional approach' had more negative colposcopic biopsies and more negative reconisation/hysterectomy histologies than the 'HPV approach'. The respective cost per detection of one case of residual disease was US$3573 and US$3485. The 'HPV approach' required fewer colposcopic and reconisation procedures to detect one case of residual CIN2-3. Its higher positive predictive value than that of cytology provided a significant decrease in false positive rates and a reduction of US$88 per detected case.

Adolescent↗

PubMed2003

Multi-functional T-DNA/Ds tomato lines designed for gene cloning and molecular and physical dissection of the tomato genome.

In order to make the tomato genome more accessible for molecular analysis and gene cloning, we have produced 405 individual tomato (Lycopersicon esculentum) lines containing a characterized copy of pJasm13, a multifunctional T-DNA/modified Ds transposon element construct. Both the T-DNA and the Ds element in pJasm13 harbor a set of selectable marker genes to monitor excision and reintegration of Ds and additionally, target sequences for rare cutting restriction enzymes (I-PpoI, SfiI, NotI) and for site-specific recombinases (Cre, FLP, R). Blast analysis of flanking genomic sequences of 174 T-DNA inserts revealed homology to transcribed genes in 69 (40%), of which about half are known or putatively identified as genes and ESTs. The map position of 140 individual inserts was determined on the molecular genetic map of tomato. These inserts are distributed over the 12 chromosomes of tomato, allowing targeted and non-targeted transposon tagging, marking of closely linked genes of interest and induction of chromosomal rearrangements including translocations or creation of saturation-deletions or inversions within defined regions linked to the T-DNA insertion site. The different features of pJasm13 were successfully tested in tomato and Arabidopsis thaliana, thus providing a new tool for molecular/genetic dissection studies, including molecular and physical mapping, mutation analysis and cloning strategies in tomato and potentially, in other plants as well.

Cloning, Molecular↗

PubMed2002

The tomato dark green mutation is a novel allele of the tomato homolog of the DEETIOLATED1 gene.

A comprehensive, multi-generation, allele test, carried out in this study, suggests that the tomato mutations dark-green (dg) and high pigment 2(j) (hp-2(j)) are allelic. The hp-2(j) mutant is caused by a mutation in the tomato homolog of the DEETIOLATED1 (DET1) gene, involved in the signal transduction cascade of light perception and morphogenesis. This suggestion is in agreement with the exaggerated photomorphogenic de-etiolation response of homozygous dg mutants grown under modulated light conditions. Sequence analysis of the DET1 gene was carried out in dg mutants representing two different lines, and revealed a single A-to-T base transversion in the second exon of the DET1 gene in comparison with the normal wild-type sequence. This transversion results in a conserved Asparagine(34)-to-Isoleucine(34) amino-acid substitution, and eliminates a recognition site for the AclI restriction endonuclease, present in the wild-type and in the other currently known tomato mutants at the DET1 locus. This polymorphism was used to develop a PCR-based DNA marker, which enables an early genotypic selection for breeding lycopene-rich tomatoes. Using this marker and sequence analysis we demonstrate that an identical base transversion also exists in dg mutants of the cultivar Manapal, in which the natural dg mutation was originally discovered. A linkage analysis, carried out in a F(2) population, shows a very strong linkage association between the DET1 locus of dg mutant plants and the photomorphogenic response of the seedlings, measured as hypocotyl length (12 < LOD Score < 13, R(2) = 51.1%). The results presented in this study strongly support the hypothesis that the tomato dg mutation is a novel allele of the tomato homolog of the DET1 gene.

Alleles↗

PubMed2001

Regional 14CO2 offsets in the troposphere: magnitude, mechanisms, and consequences.

Radiocarbon dating methods typically assume that there are no significant tropospheric (14)CO(2) gradients within the low- to mid-latitude zone of the Northern Hemisphere. Comparison of tree ring (14)C data from southern Germany and Anatolia supports this assumption in general but also documents episodes of significant short-term regional (14)CO(2) offsets. We suggest that the offset is caused by an enhanced seasonal (14)CO(2) cycle, with seasonally peaked flux of stratospheric (14)C into the troposphere during periods of low solar magnetic activity, coinciding with substantial atmospheric cooling. Short-term episodes of regional (14)CO(2) offsets are important to palaeoclimate studies and to high-resolution archaeological dating.

Archaeology↗

PubMed2001

Morphology and spelling among Hebrew-speaking children: from kindergarten to first grade.

This study had two major objectives: (1) to analyse the development of two morphological structures in Hebrew, one inflectional and the other derivational and (2) to examine the mutual contribution of morphological knowledge and learning the written code. In a longitudinal design, 40 children were tested twice, first in kindergarten (mean age: 5; 11) and again in first grade (mean age: 6;5), on two oral tasks--inflecting nouns for possession and deriving denominal adjectives--and one written task of writing a series of noun-adjective pairs. The derivational task was found to be harder than the inflectional task, both on the stem and the suffix level, attributable to its higher semantic opacity. In both oral tests, correct stem production when suffixed was related to the morphophonological level of stem change. Correlations were found between morphological and writing scores. Moreover, children who were more advanced in morphology in kindergarten progressed more in writing vowels from kindergarten to first grade, and those who were more advanced in writing in kindergarten improved more in derivational morphology with grade.

Age Factors↗

PubMed2001

Time estimation by adults who stutter.

In view of the fact that stuttering involves time pressure in communicative contexts, the aim of this investigation was to study the effect of stuttering on time estimation. Two matching groups of 47 adults each, one consisting of stutterers and the other of fluent speakers, estimated the duration of four verbal tasks-two that involved speaking and two that did not. Two methods of time estimation were used: production and reproduction. In production, participants were required to perform a task, terminating it when they felt that the specified interval had elapsed. In reproduction, participants were asked to estimate the duration of a task immediately after being stopped by the experimenter. The results reveal that the differences in time estimation between adults who stutter and fluent speakers were task dependent, with the stutterers estimating time less accurately on oral verbal tasks. The conversation task in particular highlighted the inaccuracy of their time estimation. Furthermore, severe stutterers estimated time less accurately than mild stutterers. The greatest inaccuracy was displayed by severe stutterers when estimating the time of an oral task by the production method. The results are discussed in terms of cognitive models based on attention to time, method measurement, and mental workload. Clinical implications are also suggested.

Adolescent↗

PubMed2000

Effect of a patient's psychiatric history on physicians' estimation of probability of disease.

A questionnaire was mailed to 300 Iowa family physicians to determine the influence of a prior psychiatric history on decision making. The response rate was 77%. Respondents were less likely to believe that a patient had serious illness when presenting with a severe headache or abdominal pain if the patient had a prior history of depression ( P <.05) or prior history of somatic complaints ( P <. 05), compared with a patient with no past history. Respondents were less likely to report that they would order testing for a patient with headache or abdominal pain if the patient had a history of depression ( P <.05, P =.08, respectively) or somatic complaints ( P <.01). Differences in likelihood of ordering tests were not significant after adjusting for differences in estimated probability of disease. We conclude that physicians respond differently to patients with psychiatric illness because of their estimation of pretest probability of disease rather than bias. We conclude that past psychiatric history influences physicians' estimation of disease presence and willingness to order tests.

Adult↗

PubMed2000

A comparison of two dose regimens in pancreatic cancer.

Forty-seven patients with pancreatic cancer were treated with two different schedules of 5-fluorouracil (5FU) and leucovorin (LCV): standard and dose-intense schedules. The standard regimen was monthly and the dose intense was biweekly. Partial response was observed in one patient (4%), no change in 12 (48%) and progression of disease in another 12 patients. Clinical benefit, measured by symptomatic improvement, was observed in 19% of all the patients, in 12% of those treated with the standard regimen and in 27% of the intense group. Median survival was 8 months for all the patients. The 1-year survival rate was 32%. Toxicity was mild. There was no survival benefit for the dose intense regimen. These results indicate that clinical benefit can be obtained with 5FU and LCV regimens despite the lack of objective response and that a dose-intense schedule is of little benefit in treating pancreatic cancer.

Adult↗

PubMed2000

Targeting exposed RNA regions in crystals of the small ribosomal subunits at medium resolution.

Within the framework of ribosomal crystallography, the small subunits are being analyzed, using crystals diffracting to 3 A resolution. The medium resolution electron density map of this subunit, obtained by multiple isomorphous replacement, show recognizable morphologies, strikingly similar to the functional active conformer of the small ribosomal subunit. It contains elongated dense features, traceable as RNA chains as well as globular regions into which the structures determined for isolated ribosomal proteins, or other known structural motifs were fitted. To facilitate unbiased map interpretation, metal clusters are being covalently attached either to the surface of the subunits or to DNA oligomers complementary to exposed ribosomal RNA. Two surface cysteines and the 3' end of the 16S ribosomal RNA have been localized. Targeting several additional RNA regions shed light on their relative exposure and confirmed previous studies concerning their functional relevance.

Crystallography, X-Ray↗

PubMed2000

[The sixth vital sign: end-tidal CO2 in pediatric trauma patients during transport].

Transport of pediatric trauma victims, within as well as between medical centers, has become a frequent event and an integral activity of pediatric critical care units. Monitoring patients during transport is of utmost importance, as an unstable environment poses an increased threat to the patient's stability. The level of monitoring and care should approximate that of the critical care unit. Monitoring end-tidal CO2 (EtCO2) has become routine for many pediatric intensive care unit patients but technical problems have limited its use during transport. Our transport team uses a transportable EtCO2 monitor of the side-stream type (NPB 75), requiring very small samples; midstream sampling overcomes humidity interference. The monitor is small and lightweight, operates on a rechargeable battery and is especially designed for the demanding environment of transport. From October 1997 through January 1999, 187 pediatric patients, 62 of whom were trauma victims, were transported for a total of 45 hours, including 2 hours of in-flight transport. Age range was 3 months to 16 years. Of the 53 monitored for EtCO2, in 9 (17%) monitoring resulted in a significant, immediate change of treatment during transport. We find EtCO2 an important adjunct in monitoring pediatric trauma patients during transport. In addition to conventional monitoring of heart rate, blood pressure, respiratory rate, body temperature and blood oxygen saturation, we suggest EtCO2 as the sixth vital sign that should be monitored.

Adolescent↗

PubMed1999

Symmetry classification of the layered perovskite-derived AnBnX3n+2 structures.

The effects of combinations of octahedral tilts on the symmetries of layered A(n)B(n)X(3n+2) structures were considered. Two complementary approaches were used to deduce the symmetries. The space groups associated with different tilt systems were determined for structures with different layer thicknesses (n values) and for structures with different layer stacking arrangements. For the most symmetrical tilts about the orthorhombic axes of the A(n)B(n)X(3n+2) structure, maximal group/subgroup relations were established. Comparison of these results with experimental data available in the literature suggests that the symmetries of most observed A(n)B(n)X(3n+2) compounds are fully determined by the tilt systems adopted by rigid BX(6) octahedra. The most common tilt system observed at room temperature is a combination of an in-phase tilt about an orthorhombic axis parallel to the pseudo-fourfold axis of the octahedron with a tilt about an orthorhombic axis perpendicular to the layers.

Journal Article↗

PubMed1999

Elucidating the medium-resolution structure of ribosomal particles: an interplay between electron cryo-microscopy and X-ray crystallograhy.

BACKGROUND: Ribosomes are the universal cellular organelles that accomplish the translation of the genetic code into proteins. Electron cryo-microscopy (cryo-EM) has yielded fairly detailed three-dimensional reconstructions of ribosomes. These were used to assist in the determination of higher resolution structures by X-ray crystallography. RESULTS: Molecular replacement studies using cryo-EM reconstructions provided feasible packing schemes for crystals of ribosomes and their two subunits from Thermus thermophilus, and of the large subunits from Haloarcula marismortui. For the large subunits, these studies also confirmed the major heavy-atom sites obtained by single isomorphous replacement combined with anomalous diffraction (SIRAS) and by multiple isomorphous replacement combined with anomalous diffraction (MIRAS) at approximately 10 A. Although adequate starting phases could not be obtained for the small subunits, the crystals of which diffract to 3.0 A, cryo-EM reconstructions were indispensable for analyzing their 7.2 A multiple isomorphous replacement (MIR) map. This work indicated that the conformation of the crystallized small subunits resembles that seen within the 70S ribosomes. Subsequently, crystals of particles trapped in their functionally active state were grown. CONCLUSIONS: Single-particle cryo-EM can contribute to the progress of crystallography of non-symmetrical, large and flexible macromolecular assemblies. Besides confirming heavy-atom sites, obtained from flat or overcrowded difference Patterson maps, the cryo-EM reconstructions assisted in elucidating packing arrangements. They also provided tools for the identification of the conformation within the crystals and for the estimation of the level of inherent non-isomorphism.

Crystallography, X-Ray↗

PubMed1999

Metal compounds as tools for the construction and the interpretation of medium-resolution maps of ribosomal particles.

Procedures were developed exploiting organometallic clusters and coordination compounds in combination with heavy metal salts for derivatization of ribosomal crystals. These enabled the construction of multiple isomorphous replacement (MIR) and multiple isomorphous replacement combined with anomalous scattering medium-resolution electron density maps for the ribosomal particles that yield the crystals diffracting to the highest resolution, 3 A, of the large subunit from Haloarcula marismortui and the small subunit from Thermus thermophilus. The first steps in the interpretation of the 7. 3-A MIR map of the small subunit were made with the aid of a tetrairidium cluster that was covalently attached to exposed sulfhydryls on the particle's surface prior to crystallization. The positions of these sulfhydryls were localized in difference Fourier maps that were constructed with the MIR phases.

Animals↗