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Biomedical subjects

J Cohen

Publications and source records attributed to J Cohen.

At least 829 records · Page 46Linked to original sources
PubMed1993

Sex distribution in arrested precompacted human embryos.

Evidence of sexual dimorphism before fetal gonadal differentiation in mammals has been accumulating, suggesting that male embryos develop faster than female ones. The current investigation was performed to evaluate whether the development rate of precompacted human embryos is controlled by sex chromosomes. Sex was determined by polymerase chain reaction and fluorescence in situ hybridisation in 172 arrested embryos derived from in vitro fertilisation. The sex ratio (1.02:0.98) did not differ significantly from 1:1. Although more males appeared to have greater fragmentation, the difference between the sex ratios of highly fragmented and normal embryos (1.08:0.92) was not significant. Arrested female embryos had a tendency to exhibit more than five nuclei and less than 10% fragmentation, but the trend was not statistically significant. The current results suggest that the first developmental block in human embryos occurs prior to and shortly after genomic activation and is not determined by the presence of the Y chromosome.

Blastomeres↗
PubMed1993

Fixed time versus fixed distance protocols for the blood lactate profile in athletes.

Laboratory studies of blood lactate accumulation often use a fixed time protocol to define the onset (4 mM) of blood lactate accumulation (OBLA) or other indices of blood lactate concentration. For practical reasons, field studies with athletes often use a fixed distance protocol to accomplish the same goal. Whether these variations of protocol are comparable has not been established. We studied 10 subjects in the laboratory during fixed time (4 minute) and fixed distance (2 km) exercise protocols on a racing bicycle attached to a wind load simulator. The fixed distance studies required 3-6 minutes to complete. We also studied the subjects during fixed distance (2 km) rides in the field. In the laboratory there were no systematic differences in the velocity (34.3 4.6 vs 34.2 +/- 4.6 km.hr-1), VO2 (2.78 +/- 0.60 vs 2.84 +/- 0.62 liters.min-1), or heart rate (159 +/- 16 vs 155 +/- 14 beats.min-1) at OBLA in the fixed time vs fixed distance protocols. The correlation coefficients for velocity (r = 0.97), VO2 (r = 0.97) and heart rate (r = 0.94) further indicate the similarity of results. In the field study there was a significant difference in velocity (29.9 +/- 4.8 vs 34.2 +/- 4.6 km.hr-1) but not heart rate (155 +/- 18 vs 155 +/- 15 beats.min-1) at OBLA versus the fixed distance laboratory study. The correlations for velocity (r = 0.47) and heart rate (r = 0.93) support these data. The results suggest that the practical modification of the lactate profile technique of using fixed distance versus fixed time exercise stages does not systematically influence the outcome, at least for exercise stage durations approximating 4 minutes.

Female↗
PubMed1993

An intervention that delays institutionalization of Alzheimer's disease patients: treatment of spouse-caregivers.

Spouse-caregivers of Alzheimer's disease patients were randomly assigned to either a treatment group (individual and family counseling, support group participation, and ad hoc consultation) or a control group (only routine support). In the first year after intake, the treatment group had less than half as many nursing home placements as the control group. This suggests that a comprehensive counseling program can reduce the socioeconomic impact of Alzheimer's disease. Nursing home placement also was affected by the patient's need for assistance with activities of daily living, patient income, and the age of the patients and caregivers.

Aged↗
PubMed1993

Microsurgical correction of partially degenerate mouse embryos promotes hatching and restores their viability.

We have evaluated the effects of degeneration of blastomeres on the developmental fate of mouse embryos. Micromanipulation techniques were used first to destroy one or two blastomeres of a 4-cell embryo (thereby creating three-quarter and half embryos), and later to repair the anomaly by removing the degenerate material. The embryos were either cultured in protein-free or protein-supplemented medium. When cultured in protein-supplemented medium, three-quarter embryos hatched at the same rate as intact embryos (84 and 91%, respectively), but this rate was reduced (54%; 67/125) when the embryos were cultured in a protein-free environment. Destruction of two blastomeres of a 4-cell embryo and culture in protein-free medium was detrimental, as only 3.2% (4/124) hatched. By supplementing the culture medium with protein, some of these half embryos were rescued, as shown by a 34% (32/95) hatching rate. A more dramatic increase in hatching was achieved, however, after repair of the half embryos by microsurgical removal of the degenerate material. In this case, 72% (78/109) of the repaired embryos were able to hatch. These findings may have implications for human in-vitro fertilization where partial embryonic degeneration or fragmentation often leads to embryonic demise and reduced implantation. Moreover, these observations may provide important clues to mechanisms of mammalian embryonic hatching.

Animals↗
PubMed1993

Diagnosis of major chromosome aneuploidies in human preimplantation embryos.

A short fluorescence in-situ hybridization (FISH) procedure using fluorochrome and digoxigenin labelled DNA probes was developed for application in human preimplantation embryos in order to analyse the five chromosomes most involved in human aneuploidy (X, Y, 18, 13 and 21). The chromosomes were fluorescent-stained and detected simultaneously in 157 blastomeres from 30 human embryos. Successful FISH analysis was achieved in 93% of the blastomeres. Aberrations for these chromosomes were found in 70% of abnormally developing monospermic embryos. The majority of normally developing monospermic embryos obtained from older patients were also chromosomally abnormal. By analysing all or most of the cells from these embryos, true mosaicism was distinguished from technique failure. Mosaic embryos, polyploid embryos with ploidies as high as 8n, haploid embryos, embryos monosomic for 13/21 and for X, and embryos trisomic for 13/21 and 18, were common in abnormally developing embryos. In contrast, aneuploidy was the main chromosome abnormality found in normally developing monospermic embryos.

Adult↗
PubMed1993

Primer extension preamplification for detection of multiple genetic loci from single human blastomeres.

A new technology called primer extension preamplification (PEP), which has been applied to single spermatozoa, increases the amount of polymerase chain reaction (PCR) templates by amplifying DNA of the whole genome. The current investigation was aimed at applying PEP to single human blastomeres. Two blastomeres with nuclei from arrested embryos were selected for this study. Using three different PEP protocols (experiments I, II and III), DNA from single blastomeres was amplified using 15-base oligonucleotide random primers. The efficiency of the procedure was determined by further amplifications of aliquots of the PEP products with two specific sequences. Three aliquots from each PEP product were used as PCR templates for the human X chromosome (X) or the exon 10 of the cystic fibrosis gene (CF). PCR amplified products were analysed by gel electrophoresis. In experiment I, when X primers were used, positive signals were detected in all 10 embryos (100%), 90.0% (18/20) of the blastomeres, and in 80.0% (96/120) of the replicates. When CF primers were amplified, all embryos (100%, 10/10), 90.9% (18/20) of the blastomeres and 78.3% (47/60) of the replicates were positive. In experiment II, efficiency was significantly reduced when total time for the procedure was minimized from 8 h to 5 h and 45 min. Although the time was further reduced to 4 h and 40 min in experiment III, the efficiency remained the same as in experiment I when the volume of PEP was reduced from 60 microliters (experiments I and II) to 40 microliters. One out of 132 control replicates (0.8%) was contaminated.(ABSTRACT TRUNCATED AT 250 WORDS)

Blastomeres↗
PubMed1993

Opening of the mouse zona pellucida by laser without a micromanipulator.

A contact-free laser system is described for ablation of the embryonic mouse zona pellucida using a pulsed excimer 308 nm laser. Effects on further embryonic development were evaluated. Zonae of 8- to 16-cell mouse embryos were either lased (n = 189), zona-drilled with acidified Tyrode's solution (n = 183) or left zona-intact (n = 188). Blastocyst formation (99-100%) was similar in the three groups. Hatching occurred earlier in lased embryos compared to those of the control group. These blastocysts hatched through the laser ablated area. Significantly more embryos were hatching on day 4 in the conventionally drilled group when compared to the laser treated group (50% versus 24% respectively). On day 7 of development, significantly (P < 0.05) more embryos conventionally zona-drilled (37%) were intact than those which were previously laser treated (10%). Abnormal development was also noted in a small group of embryos which were lased just on the outside of the zona in comparison to 1/3 of an embryonic width away from the zona. The current results suggest that apparently precise zona laser ablation with an excimer laser at 308 nm may have potential adverse effects which may only be manifested after a prolonged period of culture past the cavitation stage. However, implantation rates of morphologically normal laser abalated embryos were not impaired when compared to control embryos.

Animals↗
PubMed1993

Unsuitability of multinucleated human blastomeres for preimplantation genetic diagnosis.

Multinucleated blastomeres (MNBs) were detected in 30.4% of 230 cleaved but subsequently arrested human embryos, and in 66.7% of 21 cleaved embryos rejected after preimplantation genetic diagnosis. A total of 71 MNBs from both groups of embryos was analysed by fluorescence in-situ hybridization (FISH) using simultaneous X and Y chromosome detection. The sex chromosome analyses of these MNBs suggests the existence of at least three mechanisms of MNB generation. In 95% of the embryos in which mononucleated and multinucleated blastomeres were analysed, the sex of the MNBs corresponded with the sex of the entire embryo. However, the number of sex chromosomes per MNB and their distribution in each nucleus varied greatly, indicating their unsuitability for aneuploidy diagnosis at the preimplantation stage.

Blastomeres↗
PubMed1993

Co-culture with granulosa cells does not increase the fertilization rate in couples with previous fertilization failures.

Ten couples included in our in-vitro fertilization programme, selected because of one of more previous total fertilization failures or a low fertilization rate (< 20%), were entered in an experimental protocol of egg insemination on autologous granulosa cells. Half the oocytes from each patient were randomly assigned to either a control or a co-culture group. We observed no difference in the fertilization rate between the control (16.2%) and co-culture groups (12.1%). Only two couples benefited from this technique since fertilization was obtained only in co-culture. The poor efficiency of this protocol led us to propose the use of sperm micro-injection if all classical attempts to improve fertilization were unsuccessful.

Cells, Cultured↗
PubMed1993

Observations on the role of tumor necrosis factor-alpha in a murine model of shock due to Streptococcus pyogenes.

OBJECTIVE: To examine the effect of a monoclonal antibody to tumor necrosis factor-alpha (TNF-alpha) in a murine model of shock due to Streptococcus pyogenes. DESIGN: Prospective, multiexperimental, randomized, controlled trial. SETTING: University hospital research laboratory. INTERVENTIONS: An LD90 murine model of Gram-positive shock using S. pyogenes, associated with the presence of significant concentrations of TNF-alpha in the circulation. Prophylactic administration of antibody with concomitant saline controls. A 500-micrograms TN3-19.12 (hamster monoclonal antibody to recombinant murine TNF), or saline, by intravenous injection was administered. MEASUREMENTS AND MAIN RESULTS: Administration of 0.3 mL of 6 x 10(8) colony-forming units/mL of S. pyogenes H250 to mice resulted in 90% to 100% mortality rates in 72 hrs. Serum TNF-alpha concentrations peaked at 2 hrs after bacterial challenge and were 67.7 +/- 18.6 ng/mL. Treatment with anti-TNF-alpha monoclonal antibody abolished the serum TNF-alpha concentrations but did not affect the mortality rate. Serum endotoxin concentrations were < 50 pg/mL before challenge and at 0.5, 1, 2, 5, and 24 hrs after challenge. CONCLUSIONS: Pretreatment with an anti-TNF monoclonal antibody was not protective in this model of S. pyogenes sepsis, despite the presence of significant amounts of TNF in the circulation. These data suggest that TNF-alpha may not play such a crucial role in the pathogenesis of shock due to S. pyogenes.

Animals↗
PubMed1993

Use of inpatient services by a national population: do benefits make a difference?

This study describes changes in the use of inpatient mental health services by children and adolescents under age 18. The data were insurance claims from the Blue Cross and Blue Shield Federal Employees Program. The study focused on a cut in inpatient benefits that occurred between 1978 and 1983. The rate of inpatient hospitalization dropped significantly, and the average number of days also decreased significantly from 45.8 to 27.0 days. This study is among the first to demonstrate that the rate and amount of inpatient care provided for children and adolescents is responsive to variations in benefit coverage.

Adolescent Psychiatry↗
PubMed1993

The effect of insurance benefit changes on use of child and adolescent outpatient mental health services.

Use of outpatient mental health services by dependent children younger than 18 years of age enrolled in the Blue Cross and Blue Shield Federal Employees Plan (FEP) is examined in 1978 and 1983 focusing on a cut in benefits and a shift from high- to low-option plan enrollment between those years. While use rates increased from 2.13% to 2.76% by 1983, the average number of visits decreased from 18.9 to 12.8. High-option plan use exceeded low-option plan use in both years--2.26% versus 0.81% in 1978 and 3.58% versus 1.93% in 1983. In addition to benefit plan, ethnicity, parent's education, type of provider, and type of treatment setting also significantly predicted amount of use. Despite the strong evidence of the effects of benefit coverage, it is likely that need exceeded use even in this insured population of children and adolescents. Implications of the findings are discussed in the context of recent dramatic changes in mental service delivery including privatization, managed care initiatives to cut costs, and growing pressures for national health insurance.

Adolescent↗
PubMed1993

An immunodominant cytotoxic T cell epitope on the VP7 rotavirus protein overlaps the H2 signal peptide.

C57BL/6 (H-2b) mice were primed with the bovine RF strain of rotavirus to study the induction of CD8+ cytotoxic T lymphocytes (CTLs). These rotavirus-specific CTLs were detected only after in vitro restimulation with the virus. Using a recombinant vaccinia virus we identified the RF VP7 protein as a major target of these CTLs. The response against this protein was obtained also after in vitro restimulation with simian SA11 and human WA strains of rotavirus. Using published Db and Kb allele-specific motifs to predict possible CTL epitopes in the RF VP7 protein, we synthesized and tested 18 predicted peptides of VP7. Only one peptide was able to sensitize target cells at a concentration below 5 x 10(-7) M. This CTL epitope was also induced by immunization with the RF VP7 expressed with a baculovirus vector, and was shown to be immunodominant by its capacity to inhibit, in an unlabelled target assay, the bulk response against cells infected with recombinant vaccinia virus expressing VP7. This CTL epitope overlaps the H2 signal peptide of the protein.

Amino Acid Sequence↗
PubMed1993

The anti-lipid A antibody HA-1A binds to rough gram-negative bacteria, fixes complement and facilitates binding to erythrocyte CR1 (CD35).

MoAbs to bacterial cell wall lipopolysaccharide are currently under evaluation for the treatment of Gram-negative sepsis. The mode of action of these reagents remains poorly understood. In this study we examined the ability of radiolabelled HA-1A (an IgM anti-lipid A MoAb) to bind in vitro to Salmonella minnesota (Re 595), Escherichia coli, and Streptococcus pyogenes. HA-1A was able to bind specifically to the 'rough' mutant Salm. minnesota, but not to a 'smooth' E. coli, or Strep. pyogenes. Binding to Salm. minnesota led to complement fixation which resulted in bacterial adherence to erythrocyte CR1, suggesting a possible mechanism whereby the antibody might enhance clearance of bacteria by facilitating delivery to the fixed mononuclear phagocytic system. We were not able to demonstrate the formation of immune complexes between free lipopolysaccharide and HA-1A in the presence of serum, nor the enhancement of complement-mediated binding of HA-1A:Salm. minnesota immune complexes to erythrocytes by antibiotic treatment. Binding of HA-1A to small bacterial fragments was, however, demonstrable after in vitro treatment with a beta-lactam antibiotic, which disrupts the bacterial cell wall, but not with gentamicin, an aminoglycoside antibiotic which blocks protein synthesis.

Anti-Bacterial Agents↗