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Biomedical subjects

R Guerrero

Publications and source records attributed to R Guerrero.

At least 145 records · Page 8Linked to original sources
PubMed1978

Further taxonomic characterization of the genus Bdellovibrio.

Cultures of Bdellovibrio isolated from different geographic locations have been studied in terms of deoxyribonucleic acid analysis (% G + C, genome size, and DNA hybridization), cytochrome spectrum, and host range. Isolates of the genus exhibit a broad range of % G + C ranging from 37 to 51% and the genome sizes extend from 1300 x 10(6) to 1700 x 10(6) daltons. DNA hybridization continues to reveal a high level of genetic heterogeneity. Bdellovibrio 3294 exhibits 32% relative reassociation to Bdellovibrio W, 37% to Bdellovibrio stolpii Uki2, and an undetectible level to Bdellovibrio starrii A3.12 Bdellovibrio W is 23% related to B. starri A3.12 and 28.5% to B. stolpii Uki2. For the first time differential absorption techniques have revealed peaks of cytochrome b. The analysis of the cytochrome spectrum seems to be limited as a taxonomic tool since most of the recent isolates studied share a common cytochrome spectrum. Host-range studies have been found to be dependent on the experimental conditions, and with the exception of one isolate (B. starrii A3.12) the taxonomic significance of such techniques must be taken with caution.

Bdellovibrio↗
PubMed1976

Studies on the pattern of circulating steroids in the normal menstrual cycle. I. Simultaneous assays of progesterone, pregnenolone, dehydroepiandrosterone, testosterone, dihydrotestosterone, androstenedione, oestradiol and oestrone.

In an attempt to analyze the multiple changes and interactions in circulating steroid levels in the peri-ovulatory and peri-menstrual periods, the plasma levels of immunoreactive luteinizing hormone (LH), progesterone and unconjugated pregnenolone, dehydroepiandrosterone, testosterone, oestradiol and oestrone were assayed daily during a complete cycle in 17 normally menstruating women. In 14 of the 17 subjects studied androstenedione and unconjugated dihydrotestosterone were also estimated. The day of the LH-peak and the first day of menstruation, respectively, were used to synchronize the peri-ovulatory and peri-menstrual plasma levels of the various steroids. With the exception of dehydroepiandrosterone and dihydrotestosterone, the plasma levels of all steroids exhibited significant, but different changes during the cycle. Testosterone levels showed a slight but significant increase around the LH-peak, whereas the levels of pregnenolone and androstenedione were higher in the post-ovulatory than in the pre-ovulation periods. The levels of oestradiol and oestrone, as well as the ratios of oestradiol to oestrone gradually increased from the low values observed in the early proliferative phase to pre-ovulatory peak values. The relationship between peaks of oestradiol and oestrone and that of LH exhibited great individual variation. The same was true for the individual oestradiol to oestrone ratios. The combination of several steroidal signals did not improve the predictive value of the analyses. However, an increase of individual progesterone values by at least 0.35 ng/ml from the day preceding the LH-peak to the day of the LH-peak was observed in 13 of the 17 subjects. It is suggested that for the early detection of the LH surge and prediction of the subsequent ovulation daily assays of plasma progesterone are of more value than the assay of the other steroids investigated.

Adult↗
PubMed1975

Spontaneous abortion and aging of human ova and spermatozoa.

To test the hypothesis that aging of human gametes within the genital tract increases the chance of abortion, we measured the probabilities of abortion after insemination on a given day of the menstrual cycle in relation to the day of the shift in the basal body temperature in 965 patients. Cases came from family-planning and sterility clinics where basal body temperature and coital records are kept routinely. The probability of abortion diminished significantly (P less than 0.001) as the shift in temperature was approached and the increased to its highest point (24 per cent) three days later. Animal experiments have shown that aging of both spermatozoa and ova before fertilization is accompanied by higher probabilities of abortion. Present evidence indicates that this higher prevalence is also true for human beings.

Abortion, Spontaneous↗
PubMed1975

Prostaglandins and post-abortion luteolysis in early pregnancy.

This study was undertaken to determine if post-abortion luteolysis in early pregnancy could be accelerated by the administration of 15(S)15-methyl-PGF2alpha(15-me-PGF2alpha) or delayed following pretreatment with indomethacin. Thirty-nine women were divided into four groups: 7 women were given 400mug 15-me-PGF2alpha extra-amniotically one hour prior to vacuum aspiration; 14 were pretreated with oral indomethacin (50 mg X4) over 24 hours; 7 were given indomethacin (50mg X 6) over 36 hours and 11 served as controls. Plasma progesterone and estradiol were measured at fixed intervals before and after abortion. There was a rapid drop in the plasma progesterone within the first hour after abortion followed by an exponential decline over the next 23 hours. The plasma estradiol fell rapidly duriing the same period. Under the experimental conditions of this study neither 15-me-PGF2alpha nor indomethacin exerted a significant effect on the decline in luteal function. These results are interpreted as suggesting that factors other than prostaglandins have a more significant role in post-abortion luteolysis.

Abortion, Induced↗
PubMed1975

A rapid 5 hour radioimmunoassay of progesterone and oestradiol in human plasma.

A rapid 5 h radioimmunoassay method for the determination of progesterone and oestradiol in the plasma of non-pregnant women is described. Due to the high specificity of the antisera used, it is possible to perform the radioimmunoassay directly on the ether extracts of plasma, without employing chromatographic purification of the steroids. Evidence is presented indicating that the rapid assay is almost as reliable as the previously described radioimmunoassay method which involves chromatography. The within-assay and between-assay coefficients of variation in the progesterone assay were 7-74 and 14-9 and in the oestradiol assay 7-36 and 18-1 respectively. Comparisons between increasing doses of authentic hormone and endogenous hormone extracted from plasma indicated no deviation from parallelism. Progesterone and oestradiol were assayed in 300 plasma samples by the rapid method and by the method involving chromatography. The slopes obtained by a regression analysis were close to unity for both progesterone and oestradiol (1-04 and 1-06, respectively), the y-intercepts were - 0-21 and 0-16 and the correlation coefficients 0-98 and 0-88, respectively. When the data obtained by both techniques in fourteen menstrual cycles were compared, the results were practically identical. In ten repeated studies conducted by four investigators it was shown that two workers can complete the assay of both progesterone and oestradiol in twenty-five plasma samples in duplicates with 5 h. The same time required for the assay of either progesterone or oestradiol in twenty-five duplicates by one worker.

Animals↗
PubMed1975

Oestradiol receptor levels in the human fallopian tube during the menstrual cycle.

The levels of cytoplasmic high-affinity oestradiol receptor sites were determined in the isthmus, isthmus-ampulla, ampulla and fimbria of human Fallopian tubes obtained from 23 women during the proliferative and secretory phase of the menstrual cycle and after menopause. Each segment was homogenized in 0.25 M sucrose and fractionated by differential centrifugation into an 800 g X 15 min nuclear pellet and a 100,000 g X 1 h cytoplasmic supernatant and pellet. The nuclear and cytoplasmic pellets were extracted with 0.01 M Tris/HCl pH 8.0 containing 0.25 M sucrose, 1 mM EDTA and 0.1 M KCl. The receptor levels were determined in the 100,000 g X 1 h supernatant (free receptors) and in the KCl extracts (bound receptors). Values are expressed per mug DNA. The concentration of receptors (total, free and bound) was significantly greater in the ampulla than in the isthmus in both phases of the menstrual cycle (P less than 0.001). The concentration of free receptors in the isthmus, isthmus-ampulla and ampulla obtained in the proliferative phase was not significantly different from that of the secretory phase. In the fimbria a significantly higher concentration (P less than 0.01) was observed in the proliferative phase. The bound receptors were significantly higher in all regions in the proliferative phase than in the secretory phase (P less than 0.01). As a consequence the concentration of total receptors was significantly greater along the tube in the proliferative phase (P less than 0.01). The levels of oestradiol in the nuclear pellet of each segment as measured by radioimmunoassay were significantly greater in the isthmic region (P less than 0.01) than in other regions of the tube. The inverse relationship between the concentration of oestradiol receptor sites and the nuclear levels of oestradiol along the Fallopian tube is discussed.

Adult↗
PubMed1975

Type and time of insemination within the menstrual cycle and the human sex ratio at birth.

Data that strongly suggest that the timing of insemination affects the human sex ratio at birth are presented. Two studies conducted by the author, including a total of 1,318 pregnancies, in which timing of insemination was related to the shift in basal body temperature are discussed, and previous literature is reviewed. The differential effect of type of insemination-natural versus artificial-is noted. The further question why timing and type of insemination affects the human sex ratio is also explored.

Animals↗