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Biomedical subjects

D E Walters

Publications and source records attributed to D E Walters.

At least 91 records · Page 5Linked to original sources
PubMed1981

The growth of human preimplantation embryos in vitro.

The parameters of the growth of human embryos in vitro between fertilization and the blastocyst are described. The data on the cleavage of embryos were subjected to statistical analysis. All the pronucleate eggs examined had two pronuclei. There was no evidence of any oocyte with three or more pronuclei, except in one examined 3 days after insemination, which may have been degenerating. Most eggs which were unfertilized remained in metaphase of the second meiotic division, with an extruded polar body. Spermatozoa were found embedded deeply in the zona pellucida of unfertilized and pronucleate eggs. A total of 417 embryos cleaved in vitro. Many were in the two-cell stage by 28 hours, four-cell stage at 43 hours, and eight-cell stage at 54 hours. Cleavage patterns were regular in the great majority. Compaction began at the 16 cell stage; the blastocyst began to form between 4 and 5 days after fertilization. Forty-two embryos were examined sufficiently often to make a statistical analysis of their growth in vitro. The mean doubling time of the cells was 15.82 hours approximately. Estimates of the mean midstage times for each stage of division were calculated. The results are discussed in relation to the cure of infertility by replanting human embryos, to the possibility of chromosomal and other disorders arising in the embryos, and to potential scientific studies on early human development.

Blastocyst↗
PubMed1981

Structure and dynamic behavior of the oligosaccharide side chain of bovine pancreatic ribonuclease B. Application of carbon 13 nuclear magnetic resonance spectroscopy.

Natural abundance 13C NMR (at 67.9 MHz) is used to study the primary structure and dynamic behavior of the carbohydrate side chain [(Man)6(GlcNAc)2-Asn] of ribonuclease B and of the shorter carbohydrate side chain [Man(GlcNAc)2-Asn] of a modified ribonuclease B (ribonuclease Bm). A comparison of the 13C NMR spectra of ribonuclease B and of the model compounds Man alpha 1 leads to 6(Man alpha 1 leads to 3)Man alpha 1 leads to 6 (Man alpha 1 leads to 3)Man beta 1 leads to 4GlcNAc beta 1 leads to 4GlcNAc beta 1 leads to Asn (Compound A) and Man alpha 1 leads to 6(Man alpha 1 leads to 3)Man alpha 1 leads to 6(Man alpha 1 leads to 2Man alpha 1 leads to 3)Man beta 1 leads to 4GlcNAc beta 1 leads to 4GlcNAc beta 1 leads to Asn (Compound B) indicates that the (Man)5(GlcNAc)2 configuration of Compound A is present as a core structure in ribonuclease B and that only up to about 30% of our sample of ribonuclease B has the (Man)6(GlcNAc)2 structure of Compound B. Spin-lattice relaxation times, nuclear Overhauser enhancements, and linewidths of the carbohydrate carbon resonances of ribonuclease Bm indicate that the mannose residue and the N-acetylglucosamine linked to mannose are undergoing fast internal rotation (at least as fast as the rate of overall molecular tumbling). The terminal mannose residues of ribonuclease B also exhibit fast internal rotation. A comparison of the chemical shifts of the nonprotonated aromatic carbons of ribonuclease B and ribonuclease A strongly suggests that the carbohydrate side chain of ribonuclease B has a negligible effect (overall or localized) on the conformation of bovine pancreatic ribonuclease.

Animals↗
PubMed1981

Changes in the food intake and body weight of protein-malnourished rats infected with Nippostrongylus brasiliensis (Nematoda).

The daily food intake and related changes in body weight were measured in young rats which were fed on synthetic diets containing 1% (3 experiments), 2% (4 experiments) and 20% (1 experiment) casein respectively. Some rats were infected with Nippostrongylus brasiliensis and allowed to feed ad libitum, some remained uninfected and were allowed to feed ad libitum, while others, which were matched by initial weight with rats from the infected group, remained uninfected and were given only the same amount of food as that consumed during the previous 24 h by their infected partners. No significant differences were detected between the rats before the start of the infection. Thereafter, the food intake of the infected undernourished rats was usually found to be significantly lower and the loss of body weight significantly greater than those of the uninfected rats. In infection periods of relatively long duration, the pair-fed uninfected rats did not lose as much weight as their infected partners even though their food intake (1% and 2% casein) was the same. Although the food intake, and consequently the weight, of infected rats fed on the diet containing 20% casein were significantly less than in their uninfected partners, no significant differences were observed between the weights of the infected and pair-fed rats fed on this diet.

Animals↗
PubMed1981

Effects of pregnancy on the febrile responses in sheep.

Pyrogens were injected into unshorn pregnant and non-pregnant Soay and Clun Forest sheep and the effects on rectal temperature and thermoregulatory mechanisms monitored. Plasma concentrations of unconjugated oestrogens, progesterone and cortisol were measured in the sheep tested in late pregnancy. The effect of pyrogens was also examined in ovariectomized ewes treated with oestrogen and with oestrogen plus progesterone. In contrast to reports of work on shorn sheep all sheep developed a fever even when close to term but the increase in peripheral vasomotor tone normally induced by pyrogens was attenuated in the pregnant Clun Forest ewes. The hormone-treated ovariectomized animals developed normal fevers and provided little indication of a possible relation between peripheral levels of ovarian steroids and the degree of fever. The question of whether an endogenous antipyretic substance is present in pregnant sheep is discussed.

Animals↗
PubMed1981

Protein, prostaglandin and steroid synthesis in caruncular and intercaruncular endometrium of sheep before implantation.

The effect of the presence of a preimplantation embryo on protein concentration, rate of protein synthesis, beta-glucuronidase and acid phosphatase activities, steroid metabolism and prostaglandin F production in caruncular and intercaruncular tissue have been studied for sheep at Day 15 of pregnancy. The rate of protein synthesis in both tissues was greater in pregnant than in non-pregnant animals, although the difference was only significant in caruncular endometrium. The effect in caruncular tissue was mimicked in ovariectomized animals treated with oestradiol. Localized changes in the caruncular tissue were observed in respect of PGF with an increased tissue concentration, an enhanced basal release when the tissue was incubated in the presence of indomethacin, and a decreased net production. Maximum production of PGF in the 2 tissues was unaffected by the presence of an embryo but it was enhanced by oestradiol or progesterone treatment in intercaruncular tissue of ovariectomized ewes. beta-Glucuronidase and acid phosphatase activities and steroid metabolism were unaffected by pregnancy. However, in ovariectomized animals oestradiol treatment stimulated beta-glucuronidase activity in endometrium and myometrium. Progesterone treatment stimulated acid phosphatase activity in the intercaruncular endometrium. The results show that amongst several endometrial constituents investigated relatively few changes were detected by Day 15 post coitum, one day before definitive attachment. Those changes that did occur were associated with the dynamics of PGF production and the rate of protein synthesis, and were consistent with the production of a PGF binding component in caruncular endometrium which may be concerned with the protection of luteal function by redirection of uterine PGF production. Canonical variate analysis revealed that changes on Day 15 of pregnancy were mimicked most closely in caruncular tissue by treatment of ovariectomized ewes with oestradiol and progesterone, and in intercaruncular tissue by oestradiol treatment only.

Acid Phosphatase↗
PubMed1981

Selective effect of gonadotrophins on cell coupling, nuclear maturation and protein synthesis in mammalian oocytes.

Individual gonadotrophic hormones were used to examine the degree to which changes in intercellular coupling between somatic and germ cells initiate meiotic maturation, regulate protein synthesis or alter the ultrastructure of the ovine oocyte. Follicle Stimulating Hormone (FSH; 50 ng ml-1) suppressed intercellular coupling to the same extent as that observed during oocyte maturation in vivo. At low concentrations FSH did not, however, initiate resumption of meiosis. By contrast, luteinising hormone (LH; 100-500 ng ml-1) invariably initiated meiosis in oocytes cultured within the follicle but did not disrupt intercellular coupling. We conclude that nuclear maturation is not dependent upon the disruption of cell contact between the oocyte and the surrounding follicle cells. The profile of proteins synthesized by untreated oocytes differed greatly from that of oocytes matured for 18 h in follicles treated with a combination of FSH and LH. Pretreatment of follicles with either FSH or LH at low concentrations resulted in the synthesis of an intermediate and more variable pattern of proteins. No correlation was found between changes in protein synthesis and the extent of junctional communication between the cumulus cells and oocyte. Membrane vesiculation and lysosomal change in the transzonal processes are early structural changes associated with the suppression of intercellular coupling in oocytes. These changes in coupling probably result in the relocation of intracellular organelles in the final stages of oocyte maturation.

Animals↗
PubMed1980

Tautomeric states of the histidine residues of bovine pancreatic ribonuclease A. Application of carbon 13 nuclear magnetic resonance spectroscopy.

Natural abundance 13C NMR (at 67.9 MHz) is used to study the nonprotonated aromatic carbons of bovine pancreatic ribonuclase A. The C gamma resonances of the 4 histidines are identified and assigned to specific residues. The effect of pH on the chemical shifts of these resonances yields information about the tautomeric state of the imidazole form of each histidine residue. Only His-119 exists predominantly or entirely in the "common" N epsilon 2-H (N tau-H) tautomeric state. His-12 and HIS-48 exist mainly or entirely in the N delta 1-H (N tau-H) tautomeric state. His-105 exhibits about 50 to 90% of the N delta 1-H tautomer. These results, when taken together with known crystallographic coordinates for ribonuclease A, strongly suggest that H delta 1 of His-105 is hydrogen bonded to the COOH-terminal carboxylate group, that H delta 1 of His-48 is hydrogen bonded to the carboxylate group of Asp-14 or (less likely) to the hydroxyl oxygen of Thr-17, and that H delta 1 of His-12 is probably hydrogen bonded to the hydroxyl oxygen of Thr-45.

Animals↗
PubMed1980

Caecal growth in the domestic fowl following surgical manipulation.

1. Some effects of removing increasing proportions of the left caecum on the remaining caecal tissue and on the right caecum were studied in young chicks during a period of 35 d. The chicks were 22 d old when the operations were carried out. 2. No differences were detected between the gains in weight of the control and experimental groups of birds. 3. A marked negative linear relationship was observed between the dry weight of the amount of caecal tissue removed when the birds were 22 d old and weight of the left caecum at the end of the experiment. 4. The average growth rate of the left caecum (g dry tissue/week) was found to be dependent on the estimated weight of caecal tissue remaining after surgery. 5. No evidence was obtained to indicate that the growth of the right caecum responded to the removal of the left caecal tissue. 6. The morphology and histology of the operated caeca were found to be similar to the equivalent regions of the unoperated caeca. Surgical interference was not followed by any major changes in mucosal architecture. 7. In birds which had experienced unilateral caecectomy, the discharge of caecal faeces usually stopped for about 2 d. When caecal defaecation was resumed, the pattern of defaecation appeared to be the same as that observed in sham-operated birds with both caeca intact.

Animals↗
PubMed1979

A study of the growth of the alimentary tract of the young cockerel.

1. The growth of the alimentary tract of male domestic fowl has been described from measurements of the dry weight of the whole and component parts of the tract from hatching to 10 weeks of age. 2. Quadratic regression equations were derived to express the growth of the birds and the growth of their alimentary tracts. 3. From hatching to 2 weeks there were marked alterations in the proportions which the different parts represented of the size of the whole tract.

Aging↗
PubMed1979

Influence of dose, repeated treatment and batch of hormone on ovarian response in heifers treated with PMSG.

The effect of two dose levels (1000 and 2000 i.u.) of three different commercially available batches of PMSG on the ovarian response (ovulations and follicles greater than 10 mn) of 42 heifers was examined in a randomized incomplete block experiment. Each animal was subjected to two consecutive but different treatments. A significant effect of dose was observed and there were fewer ovulations, but no reduction in the number of follicles, after the second PMSG treatment. There was no evidence that the ovarian response was affected by the PMSG batch used.

Animals↗
PubMed1979

Interaction of ovarian tissues in the control of follicular steroidogenesis in culture.

The interaction between developing antral follicles and other ovarian tissues in sheep was examined in vitro. Small follicles (2.0--2.9 mm in diameter) were co-cultured with a single ovarian component for 48 h, then separated and cultured singly for a further 72 h during which time changes in follicular steroidogenesis and structure were measured. Control follicles, cultured together for 48 h before separation, had a mean total daily steroid output during the 72 h test period of 180.4 +/- 12.6 (S.E.M.) pmol mg tissue-1 24 h-1; oestrogen (61.7 +/- 8.2 pmol mg-1 24 h-1) and testosterone (84.4 +/- 9.2 pmol mg-1 24 h-1) accounted for 81% of the steroid secreted by control follicles. The presence of stromal tissue during co-culture depressed (P less than 0.01) the subsequent output of total steroid by 22%, oestrogen by 81% and testosterone by 38%; progesterone output was, however, over twice that of the controls. There was no distinctive structural differences between follicles in the control and stromal groups. Luteal tissue enhanced (P less than 0.01) the output of total steroid by 51%, testosterone by 55% and progesterone by 242%; oestrogen output was similar to that in the controls. Follicles co-cultured with luteal tissue were characterized by extensive hypertrophy of the theca interna. Developing follicles co-cultured with large non-atretic follicles had a similar total steroid output, a slightly higher oestrogen output and more thecal hypertrophy than the controls. Follicles co-cultured with large atretic follicles differed from controls only with respect to their greater capacity to synthesize progesterone.

Animals↗
PubMed1979

Comparison of the direct antiglobulin rosetting reaction (DARR) and direct immunofluorescence (DIF) for demonstration of sIg-bearing lymphocytes in pigs, sheep and cattle.

Tests with untreated and trypsin-treated red cells (rbc) from a variety of species showed that anti-Ig-coupled pig RBC are good indicator cells for the study of ruminant blood sIg + lymphocytes by the DARR test; coupled donkey and rabbit RBC are suitable for investigating pig lymphocytes. The different species showed the following percentages of sIg + lymphocytes (M +/- SE) by direct immunofluorescence (DIF) and the direct antiglobulin rosetting reaction (DARR) respectively:pigs 9.2 +/- 0.7% and 16.3 +/- 1.2%; sheep 20.2 +/- 1.2% and 33.1 +/- 1.6%; Cattle 13.5 +/- 1.4% and 28.9 +/- 3.5%. The mean ratio of sIg + lymphocytes shown by the two tests (DARR/DIF) for each species was 1.80 +/- 0.08 for pigs, 1.73 +/- 0.7 for sheep and 2.15 +/- 0.18 for cattle. Preincubation of pig and sheep lymphocytes at 37 degrees for 1 h did not alter the proportion of sIg + lymphocytes detected by either test. Thus the DARR test reveals a further population of sIg + lymphocytes in addition to that detected by immunofluorescence, whose number is proportional to the B population as measured by DIF and whose sIg is intimately associated with the membrane.

Animals↗
PubMed1978

Pituitary responsiveness to LH-RH and TRH and the effects of progesterone or progesterone and oestradiol treatment in anoestrous sheep.

Pituitary responsiveness to 200 microgram synthetic LH-RH and to 10 microgram TRH was determined in anoestrous sheep before and after treatment for 3 weeks with progesterone (100 mg/day), or oestradiol (250 microgram/day) plus progesterone (100 mg/day). There was a marked decrease in pituitary responsiveness to LH-RH after progesterone (P is less than 0.01), or oestradiol plus progesterone (P is less than 0.01) treatments, and an increase in response to TRH after oestradiol plus progesterone (P is less than 0.01) treatment. The results demonstrate selective and simultaneous feedback effects of oestradiol and progesterone on pituitary responsiveness to two hypothalamic releasing hormones.

Anestrus↗
PubMed1978

Steroidogenesis in preovulatory follicles of patients given human menopausal and chorionic gonadotrophins as judged by the radioimmunoassay of steroids in follicular fluid.

The administration of human menopausal gonadotrophin (HMG) followed by human chorionic gonadotrophin (HCG) stimulated the development of various numbers of follicles in patients treated for infertility. Graafian follicles from these patients were aspirated 32-33 h after the injection of HCG and the levels of steroids in the follicular fluid and matching serum samples were measured by radioimmunoassay. The follicles could not be grouped into two distinct clusters as found in patients given HCG during the menstrual cycle but a broad classification of follicles into four groups was indicated from the dendrogram. Two of the groups were similar to the ovulatory and non-ovulatory groups found previously, whereas the other two groups of follicles were more intermediate in nature. The use of a discriminant analysis showed that these two groups had clearly been stimulated by the HMG and HCG, although they were not yet fully ovulatory. Our data indicate that the number of developing follicles is considerably increased by treatment with HMG and HCG but there is asynchrony in follicular development because the pattern of steroid synthesis differs in many follicles. The effects of this asynchronous development on oocyte maturation and disorders of the luteal phase are discussed.

Androgens↗
PubMed1978

Steroidogenesis by cultured granulosa cells aspirated from human follicles using pregnenolone and androgens as precursors.

Human granulosa cells from Graafian follicles aspirated 3-4 h before the expected time of ovulation were incubated with various steroid substrates, including pregnenolone, androstenedione, testosterone and dehydroepiandrosterone (DHA). Steroid production after 3 and 10 h of incubation was determined by radioimmunoassay. Progesterone and 17alpha-hydroxyprogesterone were the major products of granulosa cells in control short-term cultures with endogenous substrates. The addition of pregnenolone increased the synthesis of progesterone and 17alpha-hydroxyprogesterone compared with the controls, although the response varied considerably between paired short-term cultures. Little or no oestradiol-17beta was produced from endogenous precursors or short-term cultures to which pregnenolone had been added; one follicle, however, produced similar amounts of oestradiol-17beta in the control cultures and after incubation with pregnenolone. When granulosa cells were cultured with various amounts of androstenedione, DHA or testosterone, large amounts of oestradiol-17beta were produced, especially in short-term cultures in which larger amounts of substrate were added. Progesterone production continued and progesterone was synthesized more rapidly or in greater amounts in some short-term test cultures than in the controls. The results indicate that human granulosa cells are one source of oestradiol-17beta during the preovulatory phase. The data support the two-cell theory for oestradiol synthesis, for granulosa cells do not appear to undertake steroid conversion via the 5-unsaturated pathway, but aromatize androgens known to be produced by thecal cells. It is also suggested that either androgens or oestradiol-17beta stimulate progesterone production by granulosa cells, at least in vitro.

Androgens↗
PubMed1977

Ferritin and ovalbumin binding blood lymphoid cells in fetal sheep.

Lymphoid cells from blood of fetal sheep between 70 and 140 days of gestational age were examined for surface immunoglobulin (sIg) and for surface binding of horse spleen ferritin FITC and ovalbumin FITC. Fetuses of all ages had cells which bound ferritin or ovalbumin, the proportion of these cells in the lymphocyte preparations from blood decreasing with increasing age of the fetus. A similar decline in the proportion of sIg cells with age was found. The simultaneous occurrence of fetal lymphoid cells binding ferritin or ovalbumin is discussed in relation to the sIg population and to the property of the sheep fetus to respond sequentially to different antigens by the production of antibody.

Animals↗
PubMed1977

The progesterone content of rabbit uterine flushings.

A detailed study has been made of the progesterone content of uterine flushings taken from rabbits of different endocrine states. A high content of progesterone was recovered from the uterine lumen of pregnant and pseudopregnant rabbits. The amount of progesterone recovered in the flushings was not simply dependent on the concentration in the plasma, because plasma progesterone concentrations rose before detection of progesterone in the flushings and remained high after uterine progesterone content had fallen. Progesterone did not appear in the uterine fluid unless uterine protein was present. This was particularly evident in rabbits treated with progesterone in which, despite abnormally high plasma concentrations, little progesterone was found in uterine fluid until the protein content increased. After treatment of rabbits with oestrogen at the time of ovulation, uterine progesterone was present in higher amounts concomitant with an elevation of protein content although the peak values of progesterone and protein were delayed by 2--3 days. Plasma progesterone concentrations of about 5 ng/ml were necessary before progesterone appeared in the uterine lumen.

Animals↗