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Biomedical subjects

K D Roberts

Publications and source records attributed to K D Roberts.

At least 73 records · Page 4Linked to original sources
PubMed1983

Sex steroid concentrations in plasma from the canine deferential vein.

Sex steroid concentrations in plasma collected from the canine deferential vein were measured, after separation, by radioimmunoassay. The concentrations found were compared with those in the peripheral plasma. The mean concentrations of androstenedione, testosterone, 5 alpha-dihydrotestosterone, 5 alpha-androstane-3 alpha, 17 beta-diol, 5 alpha-androstane-3 beta, 17 beta-diol and oestradiol-17 beta were 13.2, 14.7, 8.9, 4.6, 8.0 and 7.5 fold higher respectively in plasma from the deferential vein than in peripheral plasma. A close anatomical relationship was found between the vasa deferentia, the deferential vein and the peripheral plasma as well as between the deferential vein and the prostate gland. These findings emphasize and extend earlier conclusions that high levels of sex steroids present in the deferential vein could have a local influence on the growth of the prostate.

Androstane-3,17-diol↗
PubMed1983

Fertilizing capacity and sperm antibodies in vasovasostomized men.

In order to explain the discrepancy between the patency rate (80%) and the pregnancy rate (46%) in a series of vasovasostomies, attention was focused on a group of patients who became normospermic. The mean age at vasectomy, the duration of vasobstruction, and the parameters of semen analysis were not different for those couples who achieved a pregnancy (n = 8), compared with those couples without pregnancy (n = 7). In the group with pregnancy, six of the eight patients had low titers of serum agglutinins (absent to 1:32), and the fertilizing capacity of their spermatozoa was normal. None had immobilizing antibodies. In the group without pregnancy, six of the seven patients had elevated serum agglutinins (greater than 1:256), and four had agglutinating antibodies in their seminal plasma as well as serum immobilizing antibodies. The spermatozoa of seven patients failed to fertilize zona-free hamster ova. It is concluded that a loss of fertilizing ability of the spermatozoa due to sperm antibodies is an important cause of infertility in vasovasostomized men.

Adult↗
PubMed1982

Nucleolar specific acidic phosphoprotein C23 is highly methylated.

Protein C23 (Mr = 110,000; pI, 5.5) is the major phosphoprotein in the nucleolus of Novikoff hepatoma cells and comprises 9.5% of the total nucleolar protein. In addition to being highly phosphorylated (1.2 mol % of phosphoserine), it is also highly methylated. Protein C23 contains 1.3 mol % of NG,NG-dimethylarginine and a trace of NG-monomethylarginine.

Amino Acids↗
PubMed1982

Sites of in vivo extraction and interconversion of estrone and estradiol in the dog.

The interconversion and extraction of estrone and estradiol-17beta across and within different tissues or areas have been studied in the dog by the constant infusion technique. The results were calculated estradiol obtained from afferent and efferent blood and tissues at equilibrium. From these results it is concluded that: (1) there is no significant difference between metabolic clearance rates of estrone and estradiol, (2) blood transfer constants indicates a higher conversion of estradiol to estrone than of estrone to estradiol, (3) the transtissue interconversion favors the formation of estrone while the intratissue interconversion favors the formation of estradiol, (4) no interconversion of the two estrogens is observed in adipose tissue, (5) the extraction of estradiol entering a tissue was lower than the extraction of estradiol formed in these tissues, (6) calculation of the tissue metabolic clearance rates show that 63% of the total metabolism of estrone and estradiol, respectively, occurs in the splanchnic bed, and (7) the contribution of each tissues to the total interconversion of estrone and estradiol show that more than 90% of this interconversion occurs extrahepatically.

Adipose Tissue↗
PubMed1982

Androgen levels in the lipid of the canine vas deferens and peripheral plasma.

Radioimmunoassays were used for the measurement of several androgens in canine plasma and in the liquid of the vas deferens. Large variations in the plasma concentrations of androstenedione, testosterone and 5 alpha-dihydrotestosterone occurred during a period of 24 h, but there was no evidence of a circadian rhythm. The ratios of the androgen concentration in the liquid of the vas deferens compared with that in the peripheral plasma were: androstenedione, 4.6; testosterone, 1.9; 5 alpha-dihydrotestosterone, 13.6; 5 alpha-androstane-3 alpha, 17 beta-diol, 17.0; 5 alpha-diol, 22.4. These high levels of androgens in the liquid of the vas deferens could play a role in the development of prostatic hypertrophy.

Androgens↗
PubMed1982

Fluorometry of selenium in serum or urine.

This fluorometric procedure for determining selenium in human serum or urine is sensitive (requiring only 0.4 mL of sample), accurate, simple, and can be performed on several samples concurrently. Using this technique, we found a mean selenium concentration in the serum of normal Canadian men of 142.9 (SD 16.1) micrograms/L. The mean urinary excretion rate was 124.5 (SD 76.0) micrograms/day.

Adult↗
PubMed1981

The cellular origin of the zona pellucida antigen in the human and hamster.

The origin of the zona pellucida in follicles at different stages of maturation was studied in the hamster and human by indirect immunofluorescence microscopy using a specific anti-hamster zona pellucida serum. The earliest detection of the zona pellucida material occurred in the ooplasm of oocytes in primordial follicles. In primary follicles, the fluorescence was localized at the periphery of the oocyte. In secondary and in mature follicles a deposition of fluorescent material was visualized on the inner and outer regions of the zona pellucida. Follicular cells, other than the oocyte, failed to exhibit a fluorescent reaction with the antizona pellucida serum. It is concluded that the oocyte is an important source of the antigenic material of the zona pellucida of hamster and human ova.

Animals↗
PubMed1981

Steroid sulfotransferase in hamster epididymis.

Steroid sulfotransferase activity is present in the cytosol fraction of hamster epididymis. The activity of this enzyme is increased by magnesium ion. Cysteine is essential to assure optimal activity. Adenosine-3'-phosphate-5'-phosphosulfate is required as sulfate donor and an apparent Km of 62 microM was calculated. Inhibition studies suggest that this enzyme preferentially catalyzes the sulfurylation of the 3 beta-hydroxyl group of delta 5-steroids. An unusual feature of the enzyme is a pH optimum at pH 10.

Animals↗
PubMed1981

Proliferation and differentiation of canine prostatic epithelial cells in culture.

When cultured in monolayers, non-secretory epithelial cells from canine prostates actively synthesize DNA, RNA and proteins; subsequently, mitotic figures and an increase in cell number are observed. During this culture period, cell size and acid phosphatase activity remain constant. As the culture proceeds, these cells mature into secretory cells as evidenced by a gradual shift in their density in Percoll gradients to the density of secretory cells and by an increase in the cellular content of acid phosphatase. During maturation, the size of the non-secretory cells increases and their morphology changes and becomes similar to that of the secretory cells. When a homogeneous population of secretory cells is cultured, DNA synthesis is minimal and few mitotic figures may be observed while cell number and cell density remain constant. Early in the culture period, their size increases and by 2 weeks their acid phosphatase activity is 2--3-fold higher than that of the non-secretory cells. Thus, upon culture, the non-secretory epithelial cells enter and proceed through the cell cycle with evidence of DNA synthesis and mitosis. Those cells leaving the cycle undergo maturation into secretory cells which further differentiate with the concomitant appearance of acid phosphatase activity. This model will be useful to study prostatic hyperplasia and hypertrophy and the control mechanisms involved in these phenomena.

Acid Phosphatase↗
PubMed1981

Localization of cholesteryl sulfate in human spermatozoa in support of a hypothesis for the mechanism of capacitation.

Cholesteryl sulfate is a normal constituent of human spermatozoa. The in vitro uptake of tritiated cholesteryl sulfate resulted in the labeling of all spermatozoa as demonstrated by light-microscope radioautography. The binding of the sterol sulfate was localized mainly in the head and midpiece. Radioautography at the level of the electron microscope revealed that the sterol sulfate is localized on the plasma membrane, mostly in the region of the acrosome. Further proof of this localization was obtained by selective dissolution of the plasma membrane and acrosome of the spermatozoa with low concentrations of Triton X-100. This treatment resulted in the simultaneous removal of tritiated cholesteryl sulfate bound to the spermatozoa. A hypothesis is presented concerning the role of cholesteryl sulfate as a membrane stabilizer and enzyme inhibitor during the maturation of spermatozoa in the epididymis. According to this hypothesis, the cleavage of the sulfate moiety within the female reproductive tract triggers a cascade of events leading to sperm capacitation and fertilization.

Autoradiography↗
PubMed1980

Plasma estrone sulfate levels in postmenopausal women.

Estrone sulfate levels were measured in the plasma of 63 postmenopausal women. The assay method involved prior extraction of the free estrogens, enzyme hydrolysis of the estrone sulfate with sulfatase and radioimmunoassay of the estrone liberated. The plasma levels ranged from 37 to 320 pg/ml (expressed as free estrone) with a mean value of 178 +/- 79 pg/ml. As observed in premenopause, estrone sulfate is quantitatively the most important circulating estrogen in postmenopausal women.

Aged↗
PubMed1980

Characterization of canine prostatic cells from normal and hyperplastic glands.

Secretory and non-secretory epithelial cells and fibroblasts obtained from normal and hyperplastic canine prostate glands and from prostates of 6-week castrated dogs are cultured in monolayers. Prostatic fibroblasts are grown in non-selective culture medium and found at densities of 1.040-1.045 g/ml in Percoll gradients. Enriched populations of each epithelial cell type area obtained by varying the duration of the culture combined with the use of selective MEM D-Val mixture. When separated by centrifugation in Percoll density gradients, the secretory cells (high A.P.) are found at densities of 1.02-1.03 g/ml whereas the non-secretory cells (low A.P.) have densities of 1.05-1.06 g/ml. Both epithelial cell types are present in the normal and hyperplastic glands at the time of explantation. There is no correlation between the prostatic weight and the proportion of each cell type present in the tissue. On the basis of cell density in Percoll gradients and A.P. activity, those prostates with a high percentage of non-secretory epithelial cells yield better attachment and overall cultures than glands consisting mainly of secretory cells. Our results strongly suggest that non-secretory cells are precursors of the secretory type. In addition, the cells involved in the aging process of the culture are the secretory epithelial cells.

Acid Phosphatase↗
PubMed1980

Surgical treatment of congenital pulmonary stenosis due to dysplastic leaflets and small valve anulus.

Seven cases of pulmonary valve stenosis due to congenital dysplasia of the valvular apparatus have been corrected by patch-graft enlargement of the right ventricular outflow tract. The six surviving patients (85%) are now leading normal lives with good exercise tolerance. The satisfactory right ventricular performance, manifested by these subjects after the operation and in the long-term follow-up, supports the validity of the procedure in the presence of a normal right ventricle and tricuspid valve.

Adolescent↗
PubMed1979

The binding of sterol sulfates to hamster spermatozoa.

Spermatozoa obtained from the cauda epididymidis possess twice the ability to take up sterol sulfates in vitro when compared to sermatozoa obtained from the caput. This would suggest that a modification of the membrane composition of the spermatozoa occurs during passage through the epididymis. Free sterols are taken up in a similar pattern. Radioautographic studies reveal that, for sterol sulfates, this uptake occurs selectively in the regions of the head and mid-piece of the spermatozoa whereas the free sterols are distributed evenly throughout the length of the spermatozoa. The binding of sterol sulfates to spermatozoa appears to involve sites that are unsaturable. The possibility exists that sterol sulfates, previously implicated in membrane stabilization, may play a similar role in spermatozoa.

Animals↗