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Biomedical subjects

L A van der Walt

Publications and source records attributed to L A van der Walt.

At least 19 recordsLinked to original sources
PubMed1993

Dose-dependent effects of exogenous gonadotrophins on the endometrium of the rat.

We compared the serum levels of oestrogen and progesterone and the endometrial morphology of normal pregnant rats at 5,5 days' gestation with those of pregnant rats given either low (10 IU) or high (20 IU) doses of two gonadotrophins: follicle-stimulating hormone (FSH) and human chorionic gonadotrophin (HCG). Evidence of ovarian hyperstimulation was observed in the high- but not the low-dose group; both treatment regimens caused significant changes in the endometrial surface, epithelial height, the microvillous border, the glycocalyx, the subepithelial stromal cells and the mitotic activity of the surface epithelial and stromal connective tissue cells. The effects of the high-dose treatment were more severe than those of the low-dose treatment. The serum oestradiol and progesterone levels of the treated groups were not significantly different from those of the control group. The changes in the endometrium after both treatment regimens may interfere with normal trophoblastic-endometrial interactions and could influence the maintenance of pregnancy. This investigation demonstrated that even low doses of gonadotrophins, which do not cause obvious ovarian stimulation, affect uterine morphology. The findings have important implications for in vitro fertilisation and embryo transfer programmes.

Animals↗
PubMed1991

Characterization of human progesterone receptor by high performance hydrophobic interaction chromatography.

High performance hydrophobic interaction chromatography has been used to separate progestin receptors (PRs) from human uterus and from the T47D human breast cancer cell line. Reproducible separations of high resolution were achieved using a TSK Phenyl-5PW column and a reverse salt gradient of 400 mM to 0 mM sodium sulfate in phosphate buffer, pH 7.4. Peaks of radioactivity exhibiting hydrophobic behaviour were isolated, as well as a smaller proportion of specific bound receptors located in the void volume fraction. No differences in retention times were observed between uterine and breast cell line samples. When the technique was used in conjunction with rapid vertical tube sucrose density gradient centrifugation, the 8S sedimenting PR from fresh, low-salt cytosol always eluted with a retention time of 24 min. The natural 4S receptor chromatographed as a single peak at 29 min while the 4S receptor species from high-salt cytosol appeared as two distinct peaks of radioactivity with retention times of 29 and 33 min. While specific binding was shown to occur in the void volume of the column, the origin of these receptors were indeterminate. These results would suggest that under these conditions the 8S receptor occurs as a single hydrophobic class of protein, whereas the data provides evidence that transformed 4S receptor may be proportioned into two unequal entities as a function of exposure to salt.

Breast Neoplasms↗
PubMed1990

Endocrine profile associated with estrogen and progesterone receptors in leiomyoma and normal myometrium.

In leiomyoma and normal myometrium estrogen receptors act independently at low or high levels of the normal serum steroid range in the menstrual cycle. It might be an inherent characteristic of leiomyomas, which results in their progressive growth in the absence of any abnormal stimulation. In the secretory phase of the menstrual cycle, serum progesterone suppresses estrogen receptor concentrations in leiomyoma. In the present study serum follicle-stimulating hormone (FSH) and luteinizing hormone (LH) showed direct as well as inverse correlations with estrogen and progesterone receptors in different phases of the menstrual cycle.

Estradiol↗
PubMed1989

Plasma lactoferrin content in pregnancy.

Plasma lactoferrin concentration, leucocyte count, serum prolactin concentration and storage iron status were studied in 313 women at various stages of pregnancy. The mean serum iron value, percentage saturation of transferrin and geometric mean serum ferritin concentrations decreased as pregnancy progressed. In contrast, the total iron-binding capacity showed a highly significant increase with advancing gestation. Plasma lactoferrin concentration showed a mild progressive increase during pregnancy (peaking 29-32 weeks). The increase in lactoferrin concentration was, however, disproportionately small when compared with the concomitant pregnancy-related elevation in leucocyte count. The ratio of plasma lactoferrin concentration to leucocyte count therefore appeared to be abnormally low during pregnancy suggesting an acquired defect of lactoferrin release by leucocytes of pregnant women. It is unlikely that prolactin was the factor responsible for the reduced leucocyte release of lactoferrin. The lactoferrin:leucocyte ratio was already significantly reduced early in pregnancy at a time when prolactin concentration was relatively low. Furthermore, the correlation between prolactin concentration and both lactoferrin concentration and lactoferrin:leucocyte ratio was positive. Pregnancy appears to be associated with an acquired abnormality of leucocyte degranulation, the cause of which is not clear at present.

Adult↗
PubMed1989

Multidimensional chromatographic separation of estrogen receptors.

Analyses of estrogen and progesterone receptors in biopsies of breast carcinoma play a vital role in the selection of patients likely to respond to hormone manipulation. Sucrose density gradient centrifugation has been the reference method in the determination of estrogen receptors in human breast carcinoma cytosols. To reduce assay time and circumvent prolonged manipulation of labile receptor preparations, high performance liquid chromatography techniques in the size-exclusion and ion-exchange modes were compared as potential alternate methods for the rapid separation of receptor isoforms. Multidimensional analyses were performed by reapplying estrogen receptor isoforms obtained from high performance size-exclusion and ion-exchange chromatography to sucrose density gradients and vice versa. This confirmed that the estrogen-binding components identified by high performance liquid chromatography appear to correspond to estrogen receptor species from sucrose density gradients.

Breast Neoplasms↗
PubMed1988

Oestrogen receptor assay by ER-D5 immunocytochemistry fails to correlate with ligand-binding assay in breast cancer.

Results obtained with a conventional reference ligand-binding assay were compared with those from an immunocytochemical method employing ER-D5 antigen, a supposedly oestrogen-receptor-related protein. In a group of 144 histologically proven breast carcinomas, no direct correlation could be established. Only 52% of cases would have corresponded in diagnosis. The incidence of false-negatives by ER-D5 immunocytochemistry is of the order of 70% while 32% of patients were false-positive by this method. Since both methods are employed to predict therapeutic responses to hormonal manipulation, the discrepancy between the methods is alarming. While the prognostic and predictive index of conventional oestrogen-receptor assays is well documented, correlation of these assays with ER-D5 immunocytochemistry has not been demonstrated. On the basis of these results, and pending further investigation, the replacement of conventional oestrogen-receptor methods by immunocytochemistry using this antibody is not recommended.

Antibodies, Monoclonal↗
PubMed1988

High-resolution separation of molybdate-stabilized progestin receptors using high-performance liquid chromatography.

Molecular heterogeneity of the human uterine progestin receptor was investigated employing sucrose density gradient centrifugation and high-performance liquid chromatography (HPLC) in size-exclusion (HPSEC), ion-exchange (HPIEC) and chromatofocusing (HPCF) modes. Synthetic progestomimetic ligands, [3H]R5020 and [3H]ORG-2058, were used to identify these receptors. Rapid centrifugation with a vertical tube rotor showed both 8-9 S and 4-5 S receptor species in the presence of 10 mM sodium molybdate with a 90-96% recovery. [3H]R5020 displayed greater nonspecific binding than [3H]ORG-2058. When separated receptor preparations were labeled, each with a different ligand, mixed and separated on optimized gradients, at least two receptor isoforms were identified in the components sedimenting at 8-9 S. HPSEC confirmed the presence of receptor isoforms displaying different molecular size and shape dependent upon the progestin ligand used. When the surface charge properties were examined by HPIEC using AX-1000, two distinct species were observed irrespective of the radioactive ligand. The first peak appeared in the void volume similar to the position of free steroid, indicating the possibility of ligand stripping by the column. The second peak bound steroid specifically and eluted with 100 mM phosphate. If either 8-S or 4-S progestin receptors were first separated by gradient centrifugation then by HPIEC, both receptor isoforms eluted with 60 mM phosphate. Re-chromatography of these on HPIEC also gave the isoform eluting at 60 mM phosphate. HPCF of ligand-bound receptors on AX-500 columns also identified one isoform eluting at pH 5.6-6.1. Using a combination of HPLC techniques and sucrose gradient centrifugation, heterogeneity of the progestin receptor has been demonstrated.

Centrifugation, Density Gradient↗
PubMed1988

Enhanced phosphorylation of progesterone receptor by protein kinase C in human breast cancer cells.

Affinity-isolated progesterone receptor (PR) from human breast cancer cells incubated with [32P]orthophosphate was shown to exist as a phosphoprotein. Exposure of the cells to 10 nM phorbol-12-myristate-13-acetate (PMA) for 10 min increased by 30-40% the amount of label incorporated into the 116-kDa receptor protein. A two-fold increase in the total number of steroid binding sites was also observed in cells receiving PMA treatment. This apparent unmasking of PR binding sites by phosphorylation probably involved conformational changes to existing receptor complexes and affected the eventual state of receptor dissociation or transformation. An increase primarily in the 8 S sedimenting molecular species was observed but PMA treatment also led to the appearance of a smaller, 2-3 S form of receptor (10% of total) that was not present in control samples. When cytosols were partially transformed in vitro by ATP and salt, all molecular species of receptor (8, 4, and 2-3 S) from the PMA-treated samples consistently migrated faster in sucrose gradients. The larger amount of 2-3 S receptor in PMA-treated samples disappeared when ATP, but not salt, was the transforming agent. These results suggest a major role for phosphorylating reactions in the receptor-mediated action of steroids by regulating hormone-binding and influencing receptor transformation. Tumor promoters such as the phorbol esters may act by artificially increasing the level of processing of steroid receptor.

Breast Neoplasms↗
PubMed1988

The effect of chronic acidification of the canine duodenum on gastrin release from the antrum transplanted into the colon.

Exogenous infusion of acid into the canine duodenum inhibits acid secretion stimulated by endogenously released and exogenously administered gastrin. The importance of this mechanism in normal acid homeostasis and in the inhibition of chronic endogenous acid hypersecretion is not established. In this study the classic Dragstedt model antral colonic transplant (ACT) was used to produce endogenous hypergastrinemia and acid hypersecretion. The effects of the ACT when the duodenum was retained in continuity with the stomach (gastroduodenostomy) were compared with those obtained when the duodenum was no longer in continuity with the stomach (gastrojejunostomy). The duodenum markedly suppressed gastrin release (p = 0.003) and gastric acid secretion (p = 0.005) in each of the four dogs. The dogs remained free of ulcers for 8 months after gastroduodenostomy and ACT. However, after conversion to gastrojejunostomy, large, chronic peptic ulcers developed after a mean of 3.5 months. The inhibitory effect of the duodenum on gastric release and gastric acid secretion protected the dog against ulceration for an extended period. The duodenum may be the major site of inhibitory control of acid secretion and endogenous gastrin release in dogs.

Anastomosis, Surgical↗
PubMed1987

Oestrogen and progesterone receptor concentrations in leiomyoma and normal myometrium.

The content of cytoplasmic 17 beta oestradiol and progesterone receptors in human uterine leiomyoma and normal myometrium in the Negroid population was determined. Eighteen women of reproductive age, at various stages of the menstrual cycle, were included in the study. The serum oestrogen and progesterone concentrations were also measured. This is the first report in the literature in which oestrogen and progesterone receptors in leiomyoma are significantly higher than in normal myometrium (P = 0.0002). The steroid dependence of the growth of leiomyomas may be related to the steroid receptor level. The presence of persistently high concentrations of oestrogen and progesterone receptors in leiomyoma should be helpful in the treatment of this benign tumour.

Adult↗
PubMed1986

Assessment of progestin receptor polymorphism by various synthetic ligands using HPLC.

Tritiated R5020 and [3H]ORG-2058 were utilized to investigate apparent polymorphism of progestin receptors by vertical-tube gradient centrifugation and HPLC in size exclusion (HPSEC), ion-exchange (HPIEC) and chromatofocusing (HPCF) modes. Rapid centrifugation (3 h) following molybdate stabilization (1 h) showed mainly 8-9S receptor species with 90-96% recovery. [3H]R5020 appeared to associate with a receptor isoform sedimenting faster than that bound to [3H]ORG-2058. Excess unlabeled R5020 did not eliminate all of the [3H]R5020 binding by the 8-9S component suggesting some nonspecific association while excess unlabeled ORG-2058 suppressed this binding by either ligand. Separate labeling of cytosol with each ligand and mixing prior to gradient separation showed at least two receptor species isoforms sedimenting in the 8-9S region with mol. wt of 190,000 and 173,000 D. Sephacryl S-300 chromatography revealed two radioactive peaks with either ligand but with slight molecular weight differences. HPSEC confirmed the presence of isoforms with different molecular size and shape as a function of the radioactive ligand employed. HPIEC showed the presence of two labeled receptor species irrespective of the ligand used. The first peak appeared at the void volume of the column (10 mM), co-eluted with free ligand, indicating the possibility of ligand stripping by the column. The second peak bound both steroids specifically and eluted with 100 mM phosphate. HPCF identified a single specific receptor eluting at a pH of 5.6-6.1, but with free steroid in the void volume irrespective of the ligand used. [3H]ORG-2058 appeared to be less prone to the stripping phenomenon than was [3H]R5020. These data suggest these ligands either bind to different progestin receptor species or they modify receptor characteristics in a fashion that allows separation based upon size and shape.

Centrifugation, Density Gradient↗
PubMed1986

Circulating thyroid hormones in primates with mild or severe hepatitis following liver transplantation.

In order to study the effects of acute immunologically mediated liver disease on circulating thyroid hormones, serum levels of thyroxine (T4, total and free) and triiodothyronine (T3) were measured in 8 baboons before and for 60 days after allogeneic liver transplantation. In 3 animals early rejection and jaundice developed; T4 levels declined as liver function deteriorated. In the 5 tolerant animals liver function was only temporarily deranged without jaundice and there was a consistent early rise in T4 (P less than 0.01) followed by a later fall. T3 concentrations were relatively normal in both groups. The T3 resin uptake test remained virtually unchanged in all animals. Serum T4 and T3 responses to exogenously administered bovine thyrotropin (TSH) were similar in the jaundiced and anicteric animals. We conclude that the early rise in T4 in the tolerant animals was caused by transient increases in thyroid binding globulin in (TBG) while the fall in thyroid hormones in these and in the jaundiced animals was related to a decline in TBG levels. Thyroid responsiveness to TSH is not disturbed by moderately deranged liver function.

Animals↗
PubMed1986

Thyroid hormone and carrier protein interrelationships in children recovering from kwashiorkor.

We have studied 15 infants with severe protein energy malnutrition (PEM) as a model of nutritional nonthyroidal illness. Changes in circulating thyroid hormones, binding proteins, and their interrelationships were assessed before and during recovery. Serum concentrations of total thyroxine and triiodothyronine and of thyroxine-binding proteins were extremely reduced, and increased progressively during 3 wk of refeeding. The T4:TBG molar ratio was initially 0.180 +/- 0.020, and increased progressively, parallel to the increases in TT4, to 0.344 +/- 0.038 after 21 days (p less than 0.025). The changes in free T4 estimates varied according to the methods used--FTI and analogue FT4 increased, dialysis FT4 fraction decreased. Serum TSH levels increased transiently during recovery. It is concluded 1) there is reduced binding of T4 and T3 to TBG in untreated PEM which takes 2-3 wk to recover; 2) there are methodological differences in evaluating free T4 levels in PEM; 3) increased TSH secretion appears to be an integral part of the recovery from PEM.

Carrier Proteins↗
PubMed1986

Estrogen and progestin receptors in human uterus: reference ranges of clinical conditions.

Estrogen receptor (ER) and progestin receptor (PR) levels and their respective dissociation constants (Kd) were determined by titration assay and Scatchard analyses in 319 human uteri. Levels of receptors were neither age nor uterine weight dependent. ER was higher in postmenopausal patients while PR levels were lower in women under 25 years of age. ER ranged from undetectable to 560 fmol/mg cytosol protein (mcp) while PR levels were generally 10-fold greater with a mean of 791 fmol/mcp. The mean of the Kd of ER was 4.0 X 10(-10) M while that for the PR was 9.2 X 10(-10) M. Receptor levels were not correlated with their respective Kd values nor with the Kd of the other receptor; therefore ligand affinities were not receptor concentration dependent. A population of patients was identified (12.5% of the total) in which the ER levels were undetectable while their corresponding PR ranged from 38 to 2,100 fmol/mcp. This suggests the existence of a type of PR which may not require ER for its expression and is independent of the phase of the cycle. Both ER and PR content were significantly elevated in the proliferative phase of the cycle. Evaluation of results as a function of histopathological features showed no relationship between the ER and PR of patients with anovulatory bleeding versus pathology. Uteri with leiomyomas contained ER and PR at levels comparable to those of histologically normal uteri. Adenomyosis patients tended to have lower ER and higher PR levels than the normal uteri. Reference ranges have been established for these receptors in uteri as a corollary to studies of these proteins in endometrial cancer.

Adult↗
PubMed1983

Prolactin, cortisol and thyroxine levels and the premature infant.

The relationship of prolactin, cortisol and thyroxine values in cord and maternal plasma to fetal age and weight and to the incidence of hyaline membrane disease (HMD) was investigated in 80 neonates of whom 40 were born at more than 37 weeks' gestation. Of the 40 born at less than 36 weeks 11 developed HMD. Serum cortisol has been shown to be a differentiating factor for HMD, but cord thyroxine and prolactin levels seem to be related more to age and weight than to the occurrence of HMD.

Fetal Blood↗
PubMed1982

Male chacma baboon (Papio ursinus) sexual arousal: mediation by visual cues from female conspecifics.

(1) The changes in masturbatory behavior for nine adult males exposed to, but not allowed to contact, naturally cycling stimulus females were quite similar to the changes in perineal swelling shown by these females. (2) Serum testosterone concentrations of seven adult males exposed to a cycling stimulus female were related to their masturbatory behavior, with high levels occurring during the females follicular phase, (3) Graded estradiol benzoate treatments of ovariectomized stimulus females revealed individual dosage levels below which there was no positive effect on the occurrence of visually stimulated male masturbation, (4) The present series of experiments documents the importance which visual cues have in the sexual interactions of this particular species.

Animals↗