Biomedical subjects

J Brindle

Publications and source records attributed to J Brindle.

At least 19 recordsLinked to original sources

PubMed2000

The properties of a tRNA-specific adenosine deaminase from Drosophila melanogaster support an evolutionary link between pre-mRNA editing and tRNA modification.

Pre-mRNA editing involving the conversion of adenosine to inosine is mediated by adenosine deaminases that act on RNA (ADAR1 and ADAR2). ADARs contain multiple double-stranded RNA(dsRNA)-binding domains in addition to an adenosine deaminase domain. An adenosine deaminase acting on tRNAs, scTad1p (also known as scADAT1), cloned from Saccharomyces cerevisiae has a deaminase domain related to the ADARs but lacks dsRNA-binding domains. We have identified a gene homologous to scADAT1 in the region of Drosophila melanogaster Adh chromosome II. Recombinant Drosophila ADAT1 (dADAT1) has been expressed in the yeast Pichia pastoris and purified. The enzyme has no activity on dsRNA substrates but is a tRNA deaminase with specificity for adenosine 37 of insect alanine tRNA. dADAT1 shows greater similarity to vertebrate ADARs than to yeast Tad1p, supporting the hypothesis of a common evolutionary origin for ADARs and ADATs. dAdat1 transcripts are maternally supplied in the egg. Zygotic expression is widespread initially and later concentrates in the central nervous system.

5' Untranslated Regions↗

PubMed1996

Protective effect of antioxidants on the impairment of sperm motility by activated polymorphonuclear leukocytes.

OBJECTIVE: To test the ability of antioxidants to reduce the loss of sperm motility caused by reactive oxygen species generated by polymorphonuclear leukocytes (PML). DESIGN: Standardized preparations of leukocyte-contaminated semen were created by suspending known concentrations of purified spermatozoa and PML in seminal plasma. After the stimulation of reactive oxygen species generation with phorbol ester, the spermatozoa were washed and incubated in culture medium before an analysis of their movement. The ability of antioxidants to counteract the free radical-induced loss of sperm motility observed under these circumstances was assessed. SETTING: An institutional research laboratory. PARTICIPANTS: The semen was obtained from normal volunteers. INTERVENTIONS: The following were tested: vitamins C and E, dimethylsulfoxide, catalase, hypotaurine, N-acetylcysteine, and reduced glutathione. MAIN OUTCOME MEASURES: Reactive oxygen species generation was monitored by luminol-dependent chemiluminescence. Sperm motility was assessed manually and by computer-aided semen analysis. RESULTS: Consistent impairment of sperm motility and average path velocity was observed in the presence of activated PML. This effect was reduced by the concomitant presence of glutathione, N-acetylcysteine, hypotaurine, and catalase. CONCLUSION: Antioxidants can protect against the damaging effect of leukocyte-derived reactive oxygen species on sperm movement and may be of clinical value in assisted conception procedures.

Antioxidants↗

PubMed1996

On the use of paramagnetic beads and ferrofluids to assess and eliminate the leukocytic contribution to oxygen radical generation by human sperm suspensions.

PROBLEM: To develop a methodology to determine a) the leukocytic contribution to reactive oxygen species generation by human sperm suspensions and b) the therapeutic value of removing these cellular contaminants. METHODS: Leukocytes were removed with paramagnetic beads or colloidal ferrofluids coated with anti-CD45 antibody. The sperm suspensions were monitored for oxidant generation by chemiluminescence, leukocyte contamination by immunocytochemistry, and fertilizing potential using zona-free hamster oocytes. RESULTS: Percoll -prepared human sperm suspensions exhibited a competence for PMA-induced reactive oxygen species generation which was significantly correlated with leukocyte contamination. However, the purified spermatozoa remaining after paramagnetic bead treatment, also demonstrated an intrinsic capacity for PMA-responsive reactive oxygen species generation and, freed from the oxidative stress created by the leukocytes, exhibited a significantly enhanced capacity for sperm-oocyte fusion. CONCLUSIONS: Although human spermatozoa can generate reactive oxygen species, sperm function is inhibited by the additional oxidative stress created by contaminating leukocytes. Removal of these cells with paramagnetic beads enhances fertilizing potential.

Cell Separation↗

PubMed1995

Analysis of sperm movement in relation to the oxidative stress created by leukocytes in washed sperm preparations and seminal plasma.

The addition of luminol to unprocessed semen samples resulted in the generation of chemiluminescent signals, the intensity of which was highly correlated with the level of leukocyte contamination. Despite the spontaneous oxidant-generating capacity of seminal leukocytes, no correlations were observed between leukocyte contamination and the fertility status of the subjects or any aspect of the semen profile, including the motility of the spermatozoa or their performance in a hyaluronate penetration assay. Luminol-dependent chemiluminescence and leukocyte contamination were also correlated in washed sperm suspensions prepared either by repeated centrifugation or on discontinuous Percoll gradients. However, in such sperm suspensions, the spontaneous generation of oxidants by contaminating leukocytes (> 2 x 10(4) leukocytes/ml) was invariably associated with a decreased capacity for movement. Moreover, causative associations between leukocyte contamination, reactive oxygen species generation, lipid peroxidation and impaired sperm motility were revealed by experiments involving the selective addition or removal of activated leukocytes. From these observations we can conclude that low concentrations of leukocytes are a common feature of the human ejaculate and can impair sperm function, particularly in the absence of seminal plasma. These findings have implications for our understanding of the importance of leukocytospermia in defining the fertility of human spermatozoa in vivo and in vitro.

Antibodies, Monoclonal↗

PubMed1994

Recombinant human zona pellucida protein ZP3 produced by chinese hamster ovary cells induces the human sperm acrosome reaction and promotes sperm-egg fusion.

Studies on the role of specific molecules in the human fertilization process and additional assessments of potential applications for these proteins are hampered by the limited amount of available biological material. However, this drawback might be circumvented by the recent cloning of several gamete-specific genes, which opens possibilities for the production of recombinant proteins. By use of cDNA and genomic DNA fragments of the human ZP3 gene, which encodes a major constituent of the zona pellucida surrounding the oocyte, a 2.7-kb minigene was constructed containing the natural third and fourth introns of the gene and a truncated intron between exons 2 and 3. This ZP3 DNA was transfected to Chinese hamster ovary cells, and a single-cell clone producing the recombinant ZP3 protein (recZP3) was generated. Western blot analysis of culture medium from these cells showed that recZP3 has a molecular mass +/- 5 kDa smaller than that of natural ZP3. Under reducing conditions, it migrates at an apparent molecular mass of 55-60 kDa. RecZP3 induced the sperm acrosome reaction and promoted fusion of human spermatozoa with zona-free hamster oocytes, indicating that the recombinant protein is biologically active. RecZP3 provides an attractive tool for studying the initial stage of the human fertilization process. Furthermore, it might have clinical applications in the development of diagnostic tests for male infertility and serve as target antigen in the design of contraceptive vaccines.

Acrosome↗

PubMed1992

Combined chemotherapy and radiotherapy compared with radiotherapy alone in patients with cancer of the esophagus.

BACKGROUND: The efficacy of conventional treatment with surgery and radiation for cancer of the esophagus is limited. The median survival is less than 10 months, and less than 10 percent of patients survive for 5 years. Recent studies have suggested that combined chemotherapy and radiation therapy may result in improved survival. METHODS: This phase III prospective, randomized, and stratified trial was undertaken to evaluate the efficacy of four courses of combined fluorouracil (1000 mg per square meter of body-surface area daily for four days) and cisplatin (75 mg per square meter on the first day) plus 5000 cGy of radiation therapy, as compared with 6400 cGy of radiation therapy alone, in patients with squamous-cell carcinoma or adenocarcinoma of the thoracic esophagus. The trial was stopped after the accumulated results in 121 patients demonstrated a significant advantage for survival in the patients who received chemotherapy and radiation therapy. RESULTS: The median survival was 8.9 months in the radiation-treated patients, as compared with 12.5 months in the patients treated with chemotherapy and radiation therapy. In the former group, the survival rates at 12 and 24 months were 33 percent and 10 percent, respectively, whereas they were 50 percent and 38 percent in the patients receiving combined therapy (P less than 0.001). Seven patients in the radiotherapy group and 25 in the combined-therapy group were alive at the time of the analysis. The patients who received combined treatment had fewer local (P less than 0.02) and fewer distant (P less than 0.01) recurrences. Severe and life-threatening side effects occurred in 44 percent and 20 percent, respectively, of the patients who received combined therapy, as compared with 25 percent and 3 percent of those treated with radiation alone. CONCLUSIONS: Concurrent therapy with cisplatin and fluorouracil and radiation is superior to radiation therapy alone in patients with localized carcinoma of the esophagus, as measured by control of local tumors, distant metastases, and survival, but at the cost of increased side effects.

Adenocarcinoma↗

PubMed1985

Pelvic lymphadenectomy combined with transperineal interstitial implantation of iridium-192 and external beam radiotherapy for locally advanced prostatic carcinoma: technical description.

Regardless of the treatment modality, control of locally advanced extracapsular prostatic cancer remains a therapeutic challenge. At the Mayo Clinic, we have recently developed a combined approach for surgically staged patients employing interstitial irradiation with 192 Iridium via a transperineal template. The Martinez Universal Perineal Interstitial Template (MUPIT-II) and moderate doses of external beam irradiation. The procedure consists of: 1) preoperative single dose external beam irradiation to decrease potential for tumor seeding or showering of malignant cells during MUPIT-II placement; 2) adequate surgical staging through a bilateral retroperitoneal lymphadenectomy; 3) transperineal interstitial implantation of the tumor and retropubic palpation of the needles to verify proper position; 4) intraoperative X rays are taken and used for documentation of needle position as well as for calculation and optimization of the implant dose distribution with the aid of a computerized system; 5) moderate doses of external beam irradiation postoperatively to the prostate with adequate margins. Our favorable preliminary results obtained in 18 patients treated with the above approach warrant the continuation of this trial. Details of this technique are presented.

Adenocarcinoma↗

PubMed1982

Seventh interim progress report of the british institute of radiology fractionation study of 3F/week versus 5F/week in radiotherapy of the laryngo-pharynx.

A fresh analysis of the data entered into the multicentre BIR fractionation trial of 3F/week versus 5F/week in radiotherapy of the laryngopharynx has been undertaken. Completed records of the 732 patients initially entered into the trial have now risen from 687 at the last report to 706. The data have been analysed in a manner similar to that adopted previously so as to measure the effects of the two regimes on both tumour and normal tissues, and some additional analyses have now also been made. There have been some modifications in the results in the various sub-groups which may be due to an inadequate number of patients having been followed up for long enough at the time of the previous analyses. More data for late radiation damage to normal tissues and new radiobiological findings have suggested possible explanations for the differences which have emerged between the two groups. The apparent differences between the sub-groups containing patients with highly localized tumours, which were reported in our previous report, are now less marked and not statistically significant.

Carcinoma, Squamous Cell↗

PubMed1978

Sixth interim progress report of the British Institute of Radiology fractionation study of 3F/week versus 5F/week in radiotherapy of the laryngo-pharynx.

The results are reported of the multicentre BIR fractionation trial of 3F/week versus 5F/week in radiotherapy of the laryngo-pharynx. 687 patient records have been analysed with respect to survival rates, recurrence-free rates and laryngectomy-free rates. For the group as a whole these analyses show no difference between the two fractionation regimes. Analysis of the sub-group which had early disease confined to the vocal cords does, however, show a better recurrence-free and laryngectomy-free rate for those patients treated with 5F/week, though the survival rate for the two groups remains similar. Acute and late normal tissue reactions are reported for up to six years after treatment. It appears that treatment with 3F/week can be given safely to patients with advanced disease. The differences between the two treatment groups who had early disease of the vocal cords are discussed, but until more data become available in the future the problems raised cannot be resolved.

Dose-Response Relationship, Radiation↗

PubMed1976