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Biomedical subjects

L Clark

Publications and source records attributed to L Clark.

At least 127 records · Page 7Linked to original sources
PubMed1989

Enhancer binding protein (EBP1) makes base and backbone contacts over one complete turn of the DNA double helix.

The simian virus 40 (SV40) enhancer consists of multiple DNA sequence motifs that represent the binding sites for a large number of trans-acting factors. We have purified one such factor, EBP1, which binds to a region encompassing the "core" of the SV40 enhancer, and appears to be involved in transcriptional activation. The interaction of EBP1 with its recognition site has been analysed by nuclease protection and by a variety of chemical probes. Enhancer sequences protected from cleavage with DNase I in the presence of EBP1 extend from position 232 to 250 on one strand and from 233 to 251 on the other strand. Methylation protection and alkylation interference studies have identified purine bases and backbone phosphate groups that participate in the formation of a specific EBP1-DNA complex. Within a ten base-pair region, every purine base interferes with binding when methylated and six phosphate groups on each strand interfere with binding when the attached oxygen groups are ethylated. "Footprinting" with hydroxyl radicals, generated by the 1,10-orthophenanthroline-copper ion, revealed sugar residues in the binding site that were protected from cleavage in the presence of EBP1. Computer graphics analyses of the contact point data indicate that EBP1 makes base and backbone contacts with the DNA over one complete turn of the DNA double helix, and suggest a model in which EBP1 makes sequence-specific contacts in the major groove, although binding may be influenced by interactions in the minor groove. Comparison of the EBP1 contact points with that of other known DNA-binding proteins indicates that EBP1 employs a unique mechanism to recognize a specific DNA sequence.

Base Sequence↗
PubMed1989

Sequence requirement for specific interaction of an enhancer binding protein (EBP1) with DNA.

Short DNA sequence motifs have been identified in viral and cellular enhancers which represent the binding sites for a variety of trans- acting factors. One such HeLa cell factor, EBP1, has been purified and shown to bind to sequences in the SV40 enhancer. The PRDII element in the human beta-interferon gene regulatory element (IRE) shows strong sequence similarity to the EBP1 binding site in the SV40 enhancer. We demonstrate here that EBP1 binds to its sites in the SV40 enhancer and IRE in a similar manner, making base specific contacts over one complete turn of the DNA double helix. Mutational analysis of the EBP1 sites in the IRE and SV40 enhancer has identified the DNA sequence requirements necessary for specific EBP1/DNA complex formation. In addition, 34 DNA sequences related to the EBP1 binding site were analysed for their ability to bind EBP1. Sequences constituting high affinity binding sites possess the sequence 5'-GG(N)6CC-3'. Single base pair changes in the region between the conserved Gs and Cs can generally be tolerated although it is clear that these intervening bases contribute to binding affinity. Mutations in the recognition site which could lead to gross structural changes in the DNA abolish EBP1 binding.

Animals↗
PubMed1989

A randomized trial of laparoscopy and transvaginal ultrasound-directed oocyte pickup for in vitro fertilization.

Ninety-four (94) couples undergoing IVF for the usual spectrum of clinical reasons and who were suitable for either laparoscopic or vaginal ovum pickup (OPU) were randomly assigned at the commencement of 166 treatment cycles to one of two OPU procedures. Both patient and clinician were informed of the allocation. If either wished to change this, then that cycle was eliminated from the trial. After a period of 15 months, 103 cycles were appropriate for analysis, of which 64 had been subject to ultrasound and 39 to laparoscopic OPU. Patients in the two groups did not differ significantly in terms of age or diagnosis, and the treatment cycles did not differ significantly in terms of stimulation used, commencing or maximum estradiol (E2) concentrations, E2 per follicle aspirated, or characteristics of the semen used for IVF. The rate of oocyte recovery (number of oocytes obtained per follicle aspirated), the average number of embryos available for transfer, and the pregnancy rate per oocyte recovery procedure did not differ significantly in the two groups. Ovum recovery for IVF using vaginal aspirations and ultrasound guidance is as efficacious as that which uses laparoscopy.

Female↗
PubMed1989

Evaluation of a worksite wellness program: impact on exercise, weight, smoking, and stress.

This study evaluated the effects of a wellness program at the workplace in relation to its impact on exercise, weight, smoking, and stress of the employee participants. A quasi-experimental design was selected in which data were collected at three specific intervals: before and immediately after program completion, and three months after program completion. The sample consisted of experimental and control groups. Persons (n = 59) who did participate in the wellness program made up the experimental group, and those (n = 49) who did not participate in the wellness program served as controls. Descriptive statistics were used to summarize the data. No significant differences were noted between participants and nonparticipants in the areas of exercise, weight, smoking, and stress between the initial evaluation and after completing the wellness program. The areas of stress reduction and increased exercise were emphasized more in the participants than the nonparticipants, however.

Adult↗
PubMed1989

Perceived home care needs of cancer patients and their caregivers.

The purpose of this study was to identify perceived home care needs of outpatients receiving treatment for cancer and their caregivers. The purposive subsample consisted of 16 subjects, 8 patients receiving treatment as outpatients and their 8 caregivers. Two interview guides, one for the patients and the other for their caregivers, were based on the Neuman Systems Model to assess patient and caregiver stressors The data were analyzed in relation to intrapersonal stressors (within the individual), interpersonal stressors (between the individual and others), and extrapersonal stressors (between the individual and the environment) Several stressors within each category were identified by both the patients and caregivers. Intrapersonal stressors included treatment uncertainty and role change, the interpersonal stressor of lack of social support, and the extrapersonal stressors of lack of transportation and limited finances. In addition, patients identified specific intrapersonal stressors in relation to their situation. These included assistance in coping with physical restrictions resulting in subsequent anger and depression. On the other hand, intrapersonal stressors identified by the caregivers included support in coping with the added responsibilities in relation to patient care, the fear of being alone, guilt, and the interpersonal stressor of limited knowledge regarding the patient situation. The stressors identified by both the patients and caregivers can serve as a beginning means to explore the needs encountered by this population group.

Aged↗
PubMed1988

The temporal relationship in arterial and venous prostacyclin and thromboxane activity during 24 hours of intraaortic balloon counterpulsation in dogs.

We studied the effects of intraaortic balloon counterpulsation (IABCP) on prostacyclin (PGI2) and thromboxane (TXB2) levels in dogs during 24 hours of 1:1 IABCP or a sham procedure in which the balloon was positioned but left deflated. The arterial PGI2 levels in the IABCP group increased from control values of 95 +/- 20 pg/ml to 268 +/- 95 pg/ml at 1 hour, 429 +/- 95 pg/ml at 4 hours, and 1,884 +/- 532 pg/ml at 24 hours. The arterial PGI2 levels were consistently higher in the IABCP group. Although the TXB2 measurements revealed no significant differences between groups, the IABCP group consistently had a higher level than the sham group. The platelet count in the control group decreased to 45% of baseline levels versus 55% for the IABCP group. We conclude that prolonged IABCP results in either net production of PGI2 or decreased degradation. The correlation between TXB2 and platelet counts is unclear and remains to be defined.

Animals↗
PubMed1988

Identification and purification of EBP1: a HeLa cell protein that binds to a region overlapping the 'core' of the SV40 enhancer.

The SV40 enhancer consists of multiple DNA sequence motifs that are recognized by a variety of trans-acting factors. Using DNase I protection and a gel electrophoresis DNA-binding assay, we identified a HeLa cell protein (EBP1) that binds to the 'core' region of the SV40 enhancer. A short double-stranded synthetic oligonucleotide containing the binding site for EBP1 was used to assay for EBP1 activity and to purify a 57,000-m.w. polypeptide by recognition site affinity chromatography. Bromodeoxyuracil cross-linking identified a 60,000-m.w. species as the polypeptide responsible for the DNA-binding activity. Analysis of the DNA sequences required for EBP1 binding indicated that EBP1 could be distinguished from a number of recently characterized proteins (EBP20, AP-2, and AP-3) by its binding to a variety of mutant templates. Correlation of the in vivo transcriptional activity of wild-type and mutated enhancers with EBP1 binding indicates that this protein may be important for SV40 enhancer activity because mutations that abolish EBP1 binding also have a severe deleterious effect on transcription.

Base Sequence↗
PubMed1988

Antispermatozoal antibodies in three men with infertility due to congenital aplasia of the vasa deferentia.

Men presenting with azoospermia due to aplasia of the vas deferens have commonly been considered to be infertile without hope of treatment. With improved methods of artificial insemination however, and more particularly with the advent of in vitro fertilization, it has been suggested that unusable spermatozoa may be able to be drawn from the epididymes of such men so that fertilization is achieved. The clinical situation of such men is analogous to that of long term vasectomised patients, 60% of whom are known to produce antibodies to spermatozoa which would interfere with the fertilization process. It was therefore decided to attempt to draw fluid from the epididymes of three such patients and at the same time conduct immunological studies on their sera, seminal fluid and, where available, epididymal fluid. Unfortunately, the spermatozoa obtained from all three men lacked sufficient progressive motility for use in in vitro fertilization. In addition, all men had antispermatozoal antibodies in their sera. Two of them also had antispermatozoal antibodies in their epididymal fluid and on their sperm, one at the same titer as in his serum. Since it is known that antibodies coating sperm reduce the changes of fertilization it is suggested that their presence should be assessed in all such men being considered for treatment. In addition, these studies demonstrate that antispermatozoal antibodies can enter the male tract at the level of the epididymis or higher and there were strong suggestions of local antibody production at this level in the tract.

Adult↗
PubMed1988

Hypomethylation of host cell DNA synthesized after infection or transformation of cells by herpes simplex virus.

Infection of rat embryo cells with herpes simplex virus type 2 caused undermethylation of host cell DNA synthesized during infection. DNA made prior to infection was not demethylated, but some of its degradation products, including methyl dCMP, were incorporated into viral DNA. The use of mutant virus showed that some viral DNA synthesis appears to be required for the inhibition of methylation. Inhibition of methylation cannot be explained by an absence of DNA methyltransferase as the activity of this enzyme did not change during the early period of infection. Inhibition of host cell DNA methylation may be an important step in the transformation of cells by herpesviruses, and various transformed cell lines tested showed reduced levels of DNA methylation.

Animals↗