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Biomedical subjects

M Levy

Publications and source records attributed to M Levy.

At least 145 records · Page 8Linked to original sources
PubMed1996

Effect of age on sperm fertility potential: oocyte donation as a model.

OBJECTIVE: To determine the effect of age on sperm fecundability using oocyte donation as an in vivo model. SETTING: Oocyte donation and IVF programs at the Instituto Valenciano de Infertilidad. DESIGN: Retrospective study in which four groups of oocyte donation cycles were established according to age of the male providing the semen sample: group 1 (n = 31) < 30 years; group 2 (n = 195) 31 to 40 years; group 3 (n = 98) 41 to 50 years; group 4 (n = 21) > 51 years, the oldest being 64 years. All donated oocytes were obtained from patients < 35 years old. MAIN OUTCOME MEASUREMENTS: Male age, sperm characteristics (volume, concentration, motility, morphology), fertilization, embryo quality, pregnancy, implantation, and abortion rates among recipients. RESULTS: Similar sperm characteristics in fresh as well as after preparation for IVF were observed among males of different ages. Fertilization, embryo quality, pregnancy, and implantation were similar among the established groups. The mean age of the females included in each group significantly increased from group 1 to group 4. CONCLUSIONS: Age (up to 64 years) does not affect sperm characteristics or its ability to fertilize human eggs. Similarly, embryo development in vitro as well as implantation in recipient uteri are not affected by age of the male providing the semen sample.

Abortion, Spontaneous↗
PubMed1996

Molecular cloning of a carotenoid-associated protein from Cucumis sativus corollas: homologous genes involved in carotenoid sequestration in chromoplasts.

Chromoplasts are carotenoid-accumulating plastids found in the corollas and fruits of many higher plants. In most cases, the pigment in these plastids is accumulated with the aid of carotenoid-associated proteins located within unique structures. This paper reports the isolation and characterization of the cDNA (CHRC) from Cucumis sativus corollas which encodes the chromoplast-specific carotenoid-associated protein CHRC. The transit peptide cleavage site was determined and, using a chloroplast uptake system, it is shown that CHRC can be post-translationally targeted to these plastids where it is peripherally associated with thylakoids. Analysis of CHRC transcript level in Cucumis sativus revealed its temporal and tissue-specific regulation: the transcript was detected only in corollas, where its level increased in parallel to flower development, peaking just before anthesis. CHRC shares significant homology (59%) with the gene coding for fibrillin-a protein in Capsicum annuum red fruits whose function is essentially identical to that of CHRC. A CHRC fragment including the potential active site of the protein was used as a probe in Northern blot analyses of floral and fruit tissues from various plants containing chromoplasts of different types: CHRC homologs of similar sizes were revealed in all cases. The existence of a group of homologous genes coding for chromoplast-specific proteins which aid in the sequestration of carotenoids within specific structures is proposed.

Amino Acid Sequence↗
PubMed1996

Neuropsychiatric Syndromes in Neurodegenerative Disease: Frequency and Signficance.

Neurodegenerative diseases have neuropsychological, neuropsychiatric, and neurological effects manifested as cognitive, emotional, and physical alterations. These primary effects have secondary consequences on activities of daily living, patient and caregiver distress, and quality of life. Neuropsychiatric manifestations are products of brain dysfunction that are associated with institutionalization, vulnerability to abuse by the caregiver, and use of medications and restraints. Behavioral alterations can often be ameliorated by psychotropic drugs, and the effects of medications contribute to understanding the mechanisms of behavioral changes. Allocation of health service resources for dementia patients is partially determined by the neuropsychiatric dimension of these diseases, and the importance of the neuropsychiatric aspects of degenerative disorders has been underemphasized.

Journal Article↗
PubMed1996

Oocyte donation in women with recurrent pregnancy loss.

The prognosis of couples with recurrent miscarriage is controversial despite efforts made during this century to learn about the physiopathology and treatment of this troublesome condition. Here we present our experiences of employing oocyte donation in eight couples in whom the woman was a low responder to gonadotrophin stimulation and had a previous history of recurrent abortion with negative routine infertility work-up for repeated pregnancy loss. Patients were desensitized with gonadotrophin-releasing hormone analogues and supplemented with oestradiol valerate for a minimum of 15 days until oocytes were donated from in-vitro fertilization and fertile donors. Then, progesterone was added until day 100 of pregnancy. A total of 12 oocyte donation cycles were performed in these patients. Clinical pregnancy and delivery rates per cycle were 75.0 and 66.6% respectively. The delivery rate per patient was 85.7% in this series, and the miscarriage rate per cycle was 11.1%. The results of ovum donation compared favourably with low responders without a history of recurrent abortion undergoing this treatment during the study period. These results strongly suggest that the oocyte may be the origin of infertility in women with idiopathic recurrent miscarriages. In addition, the results question the role of maternal local and systemic factors in early recurrent pregnancy loss, as well as the paternal contribution to its aetiology.

Abortion, Habitual↗
PubMed1996

Multiple segmental gradual distraction of facial skeleton: an experimental study.

The method of distraction osteogenesis was used to move several facial segments in different directions with formation of new bone. On 3 young adult sheep a Le Fort II osteotomy, combined with circumferential orbital osteotomies, was performed. The periosteum over the osteotomies was preserved. Titanium bone screws were placed as bone markers. The segments were fixed with pins and plates to a combined distraction apparatus in order to advance the segments in different directions. By a gradual distraction, the midface was advanced forward by 30 mm. The left orbit was moved laterally 20 mm and the right orbit was moved forward 20 mm. In both orbits there was a concomitant globe movement. New bone formation in the distracted area was obvious radiographically, clinically, and histologically. In conclusion, multiple segmental distraction is possible in the adult sheep face and may offer three-dimensional (3D), controlled correction of complex face deformities.

Animals↗
PubMed1996

Myasthenia gravis and hepatitis C virus infection.

Chronic hepatitis C virus (HCV) infections are often associated with extrahepatic immunological manifestations, including various autoimmune disorders. The aims of this study were to determine the prevalence of HCV markers in patients with myasthenia gravis (MG) and to determine any relationship with HCV infection. Eighty-three patients with MG. 40 men aged 20-93 years and 43 women aged 13-87 years (mean age 54 years) were studied. The MG patients were positive for antibody to acetylcholine receptor in addition, their sera was analysed for antibody to HCV (HCVAb) and HCV RNA, HCVAb was detected in two of the 83 patients (2.4%). Four patients were repeatedly HCV RNA positive. They were infected by HCV genotype 1 (one patient), HCV genotype 2a (two patients) and an undetermined HCV genotype in one patient. They received plasmapheresis or intravenous immunoglobulin treatment. Among the four patients, one was infected after the onset of MG without receiving a blood transfusion or using intravenous drugs. The other three had chronic hepatitis C which was discovered at the same time as MG and only one patient had been exposed to blood products. The prevalence of HCV markers in patients with MG (4.8%) was higher than that reported for the general French population, about 1%. This prevalence is similar to that occurring in patients exposed to plasmapheresis or intravenous immunoglobulin. In conclusion, HCV appears to play little, if any, role in causing MG. The higher prevalence of infection among MG patients may be related to transmission in the course of therapy.

Adolescent↗
PubMed1996

"On the spot' vaccination: does it work?

OBJECTIVE: To trial and evaluate a system of "on the spot' vaccination for children up to the age of 15 years in the Early Childhood Centres of the Central Sydney Area Health Service, at the Royal Alexandra Hospital for Children and in a number of general practices in the area. METHODOLOGY: A brief questionnaire was used to collect data from parents and health care professionals about the child's vaccination status and vaccines given "on the spot'. RESULTS: Over an 8 week period in August-September 1993, 5162 questionnaires were completed; 71% of children were up to date with their vaccination. If Haemophilus influenzae type b vaccine, which had been introduced only 2 months before commencement of the study, was excluded, 84% of the children were up to date. A total of 441 children were given 663 vaccinations "on the spot'. Very few children were too ill to be vaccinated (6%). However, only 30% of those who needed vaccination "on the spot' actually received it (441 of 1480), and only 41% (24 of 58) of a subset of those who were not vaccinated were known to have complied 1 month later. Children attending Early Childhood Centres were younger than children attending general practices or the hospital. CONCLUSIONS: A high proportion of children who attended for routine or acute health care had vaccinations overdue (30%). If this scheme could be continued and expanded it would have an important impact on vaccination coverage, and hence on the incidence of vaccine-preventable diseases.

Child↗
PubMed1996

Drugs in the aetiology of agranulocytosis and aplastic anaemia.

Agranulocytosis and aplastic anaemia are rare but serious conditions known to be caused by numerous drugs. Most of what is known or suspected about the aetiology is based on case reports, with only a few formal epidemiological studies that provide quantitative estimates of risk. Updated results have been obtained from a combined analysis of data from 3 case-control studies that used similar methods: the International Agranulocytosis and Aplastic Anemia Study (IAAAS), conducted in Israel and Europe; a study conducted in the northeast US; and a study conducted in Thailand. Totals of 362 cases of agranulocytosis, 454 cases of aplastic anaemia and 6458 controls were included in the analyses. The IAAAS and Thai study were population-based, providing estimates of the incidence of the 2 dyscrasias. The overall annual incidence of agranulocytosis in the ambulatory population was 3.4/10(6) in the IAAAS and 0.8/10(6) in Thailand; by contrast the incidence of aplastic anaemia was 2.0/10(6) in the IAAAS and 4.1/10(6) in Thailand. A total of 21 compounds were significantly associated with an increased risk of agranulocytosis in the IAAAS and US studies. Excess risks ranged from 0.06 to 13 cases/10(6) users/wk; the most strongly associated drugs were procainamide, anti-thyroid drugs and sulphasalazine. An association with drugs that had previously been suspected was also seen in Thailand. The overall aetiologic fractions of agranulocytosis due to drug use were 62% in the IAAAS, 72% in the US and 70% in Thailand. Eleven drugs were significantly associated with an increased risk of aplastic anaemia, with excess risks ranging from 1.4 to 60 cases/10(6) users in a 5-month period. The most strongly associated drugs were penicillamine, gold and carbamazepine. Aetiologic fractions were 27% in the IAAAS, 17% in the US and 2% in Thailand, which paralleled the prevalence of use of associated drugs in the 3 populations. The present results confirm that agranulocytosis is largely a drug-induced disease, with similar proportions accounted for in 3 disparate geographic regions. By contrast, although many of the expected associations were observed for aplastic anaemia, most of the aetiology is not explained by drugs. For all associated drugs, the excess risks are sufficiently low that blood dyscrasias should not figure prominently in the balancing of risks and benefits.

Agranulocytosis↗
PubMed1996

A model of fatigue and recovery in paraplegic's quadriceps muscle subjected to intermittent FES.

The objective of this paper was to propose a mathematical model for the fatigue and recovery phases of a paraplegic's quadriceps muscle subjected to intermittent functional electrical stimulation (FES). The model is based on in vivo, noninvasive, recording of fatigue related metabolic parameters recorded during stimulation and recovery. Records of the time variations of the muscle's phosphorus metabolites, particularly the phosphocreatine (PCr) and inorganic phosphorus (Pi), obtained from 31P magnetic resonance spectroscopy (MRS), were used to calculate the intracellular pH level in the muscle and this latter parameter was incorporated in a musculo-tendon model. The fatigue-recovery model allows the transition from the fatiguing phase to the recovery phase as soon as the stimulation terminates and vice versa. This model was incorporated into a Huxley type muscle model expressing the dynamics of the muscle. Two ordinary differential equations describing the musculo-tendon dynamics and the dynamics of the activation were solved simultaneously and records of the force trajectory during intermittent stimulations were obtained. Study cases ranging from 5 to 30 s for each of the stimulation and recovery alternating phases were stimulated. The force and the total impulse in the modeled quadriceps muscle were computed. It was found that the greatest impulse was produced in intermittent stimulation of 40-50 s duty cycle, with a 50 percent ratio between the stimulation and recovery intervals. An additional series of six runs, including two contractions, one of 3 min and one of 1 min, separated by rest periods of 3, 6, 9, 12, 15, and 30 min was performed. From the predicted force trajectories obtained, the maximal force values served for comparison with measured values made on one patient.

Electric Stimulation↗
PubMed1996

Surface localization of Helicobacter pylori urease and a heat shock protein homolog requires bacterial autolysis.

Helicobacter pylori is a gram-negative bacterium which causes chronic gastritis and is associated with peptic ulcer disease, gastric carcinoma, and gastric lymphoma. The bacterium is characterized by potent urease activity, thought to be located on the outer membrane, which is essential for survival at low pH. The purpose of the present study was to investigate mechanisms whereby urease and HspB, a GroEL homolog, become surface associated in vitro. Urease, HspB, and catalase were located almost exclusively within the cytoplasm in fresh log-phase cultures assessed by cryo- immunoelectron microscopy. In contrast, significant amounts of surface-associated antigen were observed in older or subcultured preparations concomitantly with the appearance of significant amounts of extracellular antigen, amorphous debris, and membrane fragments. By use of a variety of biochemical methods, a significant fraction of urease and HspB was associated with the outer membrane in subcultured preparations of H. pylori. Taken together, these results strongly suggest that H. pylori cells undergo spontaneous autolysis during culture and that urease and HspB become surface associated only concomitant with bacterial autolysis. By comparing enzyme sensitivity to flurofamide (a potent, poorly diffusible urease inhibitor) in whole cells with that in deliberately lysed cells, we show that both extracellular and intracellular urease molecules are active enzymatically. Autolysis of H. pylori is an important phenomenon to recognize since it likely exerts significant effects on the behavior of H. pylori. Furthermore, the surface properties of H. pylori must be unique in promoting adsorption of cytoplasmic proteins.

Antigens, Bacterial↗
PubMed1996

Young children's cardiovascular stress responses predict resting cardiovascular functioning 2 1/2 years later.

BACKGROUND: Since the pathogenesis of coronary heart disease (CHD) has its origins in childhood, researchers have increasingly evaluated CHD risk factors in youth. In this study we examined the hypothesized behavioral risk factor of cardiovascular responsivity as a predictor of very young children's resting cardiovascular functioning 2 1/2 years later. SUBJECTS AND METHODS: During an initial visit to the laboratory, 97 children (30 blacks and 67 whites, 45 boys and 52 girls) aged 6-7 years completed three laboratory stressor tests (forehead cold pressor, postural change, and treadmill exercise). A comprehensive cardiovascular assessment was conducted during the tests. Resting cardiovascular activity (baseline values) was also assessed. Follow-up resting cardiovascular parameters were measured in the laboratory 2 1/2 years later. RESULTS: Cardiovascular stress responses were predictive of cardiovascular follow-up resting levels 2 1/2 years later. Multiple regression was used to evaluate the independent predictive power of stress responses after controlling for traditional risk factors. Follow-up resting systolic blood pressure (SBP) was predicted by the SBP response to postural change and treadmill exercise. Follow-up resting diastolic blood pressure (DBP) was predicted by the DBP response during treadmill exercise, particularly for blacks. The follow-up resting heart rate was predicted by the heart rate response to the forehead cold pressor and treadmill exercise. CONCLUSION: These results show that in very young children, stress responses are predictive of resting cardiovascular functioning 2 1/2 years later. Further developmental and longitudinal investigations will determine whether such responses are predictive of later preclinical manifestations of cardiovascular disease. If so, incorporation of stress testing in a standardized risk identification protocol might aid the design and practice of cardiovascular preventive medicine.

Analysis of Variance↗