Biomedical subjects

T M Lau

Publications and source records attributed to T M Lau.

16 recordsLinked to original sources

PubMed1999

Lack of correlation between vascular endothelial growth factor production and endothelial cell proliferation in the human endometrium.

The role of vascular endothelial growth factor (VEGF) in endometrial angiogenesis was examined by measuring its production in human endometrial tissues from different stages of the menstrual cycle and relating these data to endothelial cell proliferation in the same tissues. Conditioned medium was collected from explant, and separated glandular epithelial and stromal cells cultured from 24 normal human endometrial biopsies and VEGF measured by enzyme-linked immunosorbent assay (ELISA). Immunohistochemistry was also used to assess VEGF and the percentage of proliferating microvessels in the samples. Wide variation in results between individual endometrial samples at each stage of the menstrual cycle was observed for all parameters measured. There was no significant difference in VEGF secretion by explant, glandular epithelial or stromal cell cultures across the menstrual cycle, or in the percentage of proliferating vessels. VEGF immunostaining in the stroma was elevated during the early proliferative stage (P = 0.03). Epithelial cells secreted more VEGF than stromal cells (1.76 +/- 0.46 versus 0.46 +/- 0.06 ng per 10(5) cells; P = 0.002). There was no correlation between VEGF secreted by cultured explants, epithelial or stromal cells, VEGF immunostaining and the proportion of proliferating microvessels. These results show that the majority of endometrial VEGF is produced by glands, but neither total glandular nor stromal VEGF is correlated with endometrial endothelial cell proliferation. There is still no clear understanding on the regulation of human endometrial angiogenesis.

Adult↗

PubMed1999

The effects of levonorgestrel implants on vascular endothelial growth factor expression in the endometrium.

Vascular endothelial growth factor (VEGF) expression and the microvascular density of the endometrium were studied in Norplant users and normal controls, using immunohistochemistry on formalin-fixed paraffin-embedded endometrial sections. The VEGF staining index was quantified using computerized image analysis. The VEGF staining index between stages of the menstrual cycle and between normal and Norplant endometria were compared. Norplant VEGF staining index was analysed for correlation with microvascular density, duration of Norplant use, the number of bleeding/spotting days in the reference period up to 90 days prior to biopsy, and the length of time since the last bleeding/spotting episode. The results showed that immunoreactive VEGF was detected predominantly in endometrial glands but weakly expressed in the stroma throughout the menstrual cycle, and also in Norplant users. Large variation in the VEGF staining index between individuals was observed and no significant difference in the VEGF staining index was detected between stages of the menstrual cycle for the glands and stroma. The glandular and stromal VEGF staining indices were significantly higher in Norplant than in normal endometrium (P<1x10(-4)). No correlation was found between the Norplant VEGF staining index and endometrial microvascular density, duration of Norplant use, the number of bleeding/spotting days in the reference period, and the length of time since the last bleeding/spotting episode. The VEGF staining index was higher in glands than stroma for both normal and Norplant endometrium. The results suggest a differential control of endometrial glandular versus stromal VEGF expression, and possible positive effects of levonorgestrel on VEGF expression.

Adult↗

PubMed1996

Oestrogen treatment for increased bleeding in Norplant users: preliminary results.

A clinical study was conducted to assess the effects of oestrogen in controlling increased endometrial bleeding problems in the first year of Norplant use. Three treatment groups were studied: (i) 50 micrograms ethinyl oestradiol (EE); (ii) a combined pill containing 30 micrograms EE and 150 micrograms levonorgestrel (LNG); and (iii) placebo. Based on menstrual diary records, women with prolonged, frequent or irregular bleeding, as defined by World Health Organization criteria, were randomly allocated to one treatment for 21 days. A first endometrial biopsy was taken before commencing treatment and a second biopsy at either day 14 or 21 of treatment. Following treatment, all subjects kept a menstrual diary card for 90 days. In this preliminary study, 48 subjects had completed the full 90 day post-treatment record. Within 21 days of EE treatment, the number of bleeding/spotting days was reduced significantly (P < 0.02). In the 90 days following treatment, the administration of EE and EE + LNG significantly decreased the number of bleeding/spotting days (P < 0.05). There was no reduction in the number of bleeding/spotting episodes in the EE and EE + LNG groups, but the length of each bleeding/spotting episode was significantly shorter (P < 0.05). Histopathological findings of endometrium on day 0 revealed consistent progestogenic effects, and there was no apparent change in response by day 14 or 21 of EE or EE + LNG treatment. The results of this study confirm the clinical effectiveness of EE and EE + LNG for the treatment of irregular, frequent and prolonged bleeding in Norplant users.

Adult↗

PubMed1996

Progesterone receptor in Norplant endometrium.

Endometrial progesterone receptor plays an important role in determining the biological activity of progestogens in fertility regulation. Studies during the normal menstrual cycle have shown that the concentrations of endometrial progesterone receptor and its mRNA vary in glandular epithelia but remain steady in stromal cells. There is general agreement between progesterone receptor mRNA and protein levels during the normal menstrual cycle. Norplant endometrium had an increase in immunoreactive progesterone receptor concentration but a reduction in progesterone receptor mRNA levels compared with controls. An immunohistochemical study, using the expression of the lysosomal protease cathepsin D as a marker for the functional status of progesterone receptors, failed to confirm the functionality of the receptors in Norplant endometrium. Together, these results suggest that (i) there is a differential sensitivity of glandular and stromal progesterone receptors to steroid regulation during the normal menstrual cycle; (ii) there appears to be a dissociation between the concentrations of progesterone receptor and its mRNA in Norplant endometrium; and (iii) there was significantly more progesterone receptor mRNA and lower plasma oestrogen concentrations in Norplant subjects with amenorrhoea than with endometrial bleeding. The clinical significance of the differences in progesterone receptor mRNA levels and plasma oestrogen concentrations between the amenorrhoea group and the bleeding group requires further investigation.

Contraceptive Agents, Female↗

PubMed1996

Immunohistochemical detection of cathepsin D in endometrium from long-term subdermal levonorgestrel users and during the normal menstrual cycle.

A previous report has shown that progesterone up-regulates cathepsin D expression in human endometrial cell culture. In women using the levonorgestrel-releasing Implant Norplant, the plasma levonorgestrel and immunoreactive endometrial progesterone receptor concentrations are elevated. However, the functional status of these receptors is not known. This study used endometrial cathepsin D expression both as an indirect marker for the functional status of endometrial progesterone receptors, and to identify the cell types that express cathepsin D. The results show that cathepsin D is primarily found in glandular epithelia and luminal epithelia in control and Norplant endometria. There is no significant difference in cathepsin D expression between the control and Norplant endometria, between the various stages of the menstrual cycle, or between Norplant users with varying degrees of breakthrough bleeding. Cathepsin D is also detected in cells scattered in the stroma in both control and Norplant endometria. The majority of these cells are macrophages. These data indicate that there is no evidence for progesterone regulation of cathepsin D in the human endometrium. Cathepsin D thus cannot be used as a marker for the functional status of progesterone receptors found in the Norplant-exposed endometrium.

Cathepsin D↗

PubMed1996

Immunohistochemical study of endometrial microvascular basement membrane components in women using Norplant.

The mechanisms responsible for progestogen-induced breakthrough bleeding remain unexplained. The aim of the present study was to examine the expression of three basement membrane components, collagen IV (CIV), laminin and heparan sulphate proteoglycan (HSPG), by immunohistochemistry in sections of endometrium from women receiving the subdermal levonorgestrel implant (Norplant) and normally cycling women. Control biopsies were obtained from 20 normal subjects from Melbourne, Australia, and pre- and post-Norplant-insertion biopsies were obtained from 11 women from Sydney, Australia, with between 3 and 6 months Norplant exposure. It was postulated that in Norplant users a decrease in the amount of basement membrane material present around endometrial vessels may be responsible for increased capillary fragility. The results, however, showed that for all three components, Norplant biopsies exhibited vascular basement membrane immunostaining at least as intense as that found in the mid-late secretory phase of the normal cycle. During the normal cycle, HSPG was only detected in approximately 40% of vessels with CIV and laminin immunoreactivity, and menstrual biopsies demonstrated reduced staining for all three components. Several biopsies exhibited a degree of regional variability in staining intensity, and Norplant biopsies exhibited areas of discrete, decidual-like stromal immunostaining for CIV and laminin. Although no differences were found in microvascular basement membranes in Norplant users that might explain capillary fragility, it is possible that other techniques could yield information on changes in the integrity of basement membrane components that might influence basement membrane strength.

Adolescent↗

PubMed1996

Expression of progesterone receptor mRNA in the endometrium during the normal menstrual cycle and in Norplant users.

The expression of endometrial progesterone receptor mRNA during the human menstrual cycle and in Norplant users was studied using digoxigenin-labelled ribonucleic probes for in-situ hybridization on 6 microns paraffin embedded endometrial sections. The staining intensity was scored blind semi-quantitatively. Blood ovarian steroid concentrations were measured in Norplant users. All data were analysed by analysis of variance. Glandular progesterone receptor mRNA concentrations were low during the menstrual-to-early proliferative stage but increased during the early-to-mid to late-proliferative stage then declined non-significantly over the secretory stage. No such variation was observed in stromal cells. Progesterone receptor mRNA concentrations were lower in Norplant than controls during early-to-mid to late-proliferative stages (in glandular epithelium and stroma) and during secretory stage (in stroma only). Norplant subjects with amenorrhoea had higher concentrations of stromal progesterone receptor mRNA but lower plasma oestrogen concentrations than subjects with breakthrough bleeding. The pattern of variation in progesterone receptor mRNA concentrations during the normal menstrual cycle resembles the published pattern for the receptor protein. The results demonstrate: (i) a differential sensitivity of glandular and stromal progesterone receptors to steroid regulation; (ii) in contrast to previous findings of an increase in immunoreactive progesterone receptor protein in Norplant endometrium, progesterone receptor mRNA concentrations in these tissues were reduced; and (iii) there was significantly more progesterone receptor mRNA in subjects with amenorrhoea than in those with breakthrough bleeding.

Contraceptive Agents, Female↗

PubMed1996

Microvascular density in conditions of endometrial atrophy.

Irregular menstrual bleeding in users of hormonal contraception represents the single major reason for discontinuation of these contraceptive methods. The mechanisms which underlie these bleeding disturbances are poorly understood, but appear to be associated with changes in the endometrial microvasculature following abnormal patterns of sex steroid exposure. Endometrial microvascular density is known to be increased in users of the low-dose levonorgestrel contraceptive implant, Norplant. This study explores microvascular density in other conditions of spontaneous (post-menopausal) and induced (danazol and goserelin) endometrial atrophy. Endometrial biopsies were fixed, paraffin-embedded and sections were immunostained using anti-CD34 antibody to identify vascular endothelial cells. The mean microvascular density (+/-SEM) for control samples was 186 +/- 8 vessels/mm2. There were no statistically significant changes in vascular density observed across the menstrual cycle. Mean microvascular density in spontaneous and induced endometrial atrophy did not differ significantly from that observed in the control population. The mean microvascular density was 230 +/- 17 vessels/mm2 in 31 postmenopausal women, 269 +/- 67 vessels/mm2 in 25 subjects treated with danazol was and 191 +/- 45 vessels/mm2 in nine subjects treated with goserelin. These findings suggest that the mechanisms controlling microvascular density in conditions of endometrial atrophy may vary according to the nature of the atrophic stimulus.

Adult↗

PubMed1995

Oxytocin-induced prostaglandin F2 alpha release and endometrial oxytocin receptor concentrations throughout pregnancy in ewes.

Endometrial oxytocin receptor concentrations and oxytocin-induced plasma concentrations of 13,14,dihydro-15-keto prostaglandin F2 alpha were investigated on days 14 and 17 of the oestrous cycle and on days 14, 17, 25, 65, 85 and 145 of gestation in ewes. Total 13,14,dihydro-15-keto prostaglandin F2 alpha release in response to a bolus injection of oxytocin was significantly (P < 0.05) higher at luteolysis (day 17 of the oestrous cycle) than at any other stage of the oestrous cycle or in early gestation. On days 65, 85 and 145 of gestation, total prostaglandin release was significantly (P < 0.05) increased compared with earlier in gestation. Maximum concentrations of 13,14,dihydro-15-keto prostaglandin F2 alpha in response to oxytocin followed a similar pattern. Oxytocin receptor concentrations reflected total oxytocin-induced 13,14,dihydro-15-keto prostaglandin F2 alpha release, with increased oxytocin receptor concentrations occurring on day 17 of the oestrous cycle, compared with those observed on day 14 of the oestrous cycle and on days 14, 17 and 25 of gestation. By day 65 of gestation, oxytocin receptor concentrations were again increased. However, on days 85 and 145 of gestation, oxytocin receptor concentrations had decreased to concentrations similar to those observed in early gestation. These results indicate that oxytocin-induced 13,14,dihydro-15-keto prostaglandin F2 alpha release during early gestation is minimal despite the presence of endometrial oxytocin receptors. In mid-gestation, oxytocin-stimulated 13,14,dihydro-15-keto prostaglandin F2 alpha release is increased with a concomitant increase in uterine oxytocin receptor concentrations.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗

PubMed1993

Role of progesterone in the control of endometrial oxytocin receptors at luteolysis in sheep.

Merino ewes were given a prostaglandin synthetase inhibitor, Finadyne (50 mg flunixin meglumine ml-1), on days 14-16 of the oestrous cycle (day of oestrus = day 0), Finadyne on days 14-16 plus PGF2 alpha on days 15-16, or progesterone on days 14-17 plus PGF2 alpha on days 15-16. Blood samples were taken once a day on days 10-14 and three times a day on days 15-16 for progesterone measurement. The concentrations of oxytocin receptors were measured in the endometrial (pooled caruncular and intercaruncular) tissues collected on day 17. Treatment of ewes with Finadyne resulted in the maintenance of high plasma concentrations of progesterone and a small, but nonsignificant, reduction in the concentrations of endometrial oxytocin receptors. Co-administration of PGF2 alpha reversed this effect of Finadyne. Treatment with both progesterone and PGF2 alpha increased the concentrations of progesterone in plasma and significantly reduced the concentrations of endometrial oxytocin receptors compared with those in the control ewes. These data indicate that withdrawal of progesterone from the circulation as a result of spontaneous luteolysis or by a PGF2 alpha-induced luteolysis caused an increase in the concentrations of oxytocin receptors. However, maintenance of plasma progesterone concentrations over the period of normal luteolysis only partially inhibited the concentrations of endometrial oxytocin receptors. There results suggest that the increase in the concentrations of oxytocin receptors at luteolysis in the naturally cycling ewes may be due to the loss of the inhibitory effects of progesterone on uterine oxytocin receptors.

Animals↗

PubMed1992

Hormonal control of concentrations of endometrial oxytocin receptors in the ewe.

Uterine oxytocin receptors have been shown to play a major role in the regulation of uterine prostaglandin F2 alpha release during the oestrous cycle and early pregnancy in sheep. The concentration of endometrial oxytocin receptors increases sharply from around Day 13 of the oestrous cycle to reach a maximum between Days 15 and 16. The high concentration of endometrial oxytocin receptors at this time coincides with the release of endogenous uterine prostaglandin F2 alpha during luteal regression and the maximum uterine prostaglandin F2 alpha response to an oxytocin stimulus. The concentration of uterine oxytocin receptors appears to be regulated by both progesterone and oestradiol. Studies in ovariectomized ewes have shown that initially progesterone lowers the concentration of endometrial oxytocin receptors, but after prolonged treatment with progesterone the concentration of oxytocin receptors increases; this suggests that the uterine-PGF2 alpha response to oxytocin has become refractory to the inhibitory effects of progesterone. The concentration of endometrial oxytocin receptors is also lowered by short-term oestradiol treatment. However, oestrogen treatment of ewes after long-term treatment with progesterone does not result in an increase in the concentration of oxytocin receptors following the cessation of progesterone treatment. On the basis of these and other data it is proposed that in the normal oestrous cycle the concentration of endometrial oxytocin receptors is initially depressed by both oestradiol and progesterone but that the marked increase in the concentration of oxytocin receptors over Days 13-16 of the cycle is due primarily to the withdrawal of the inhibitory influence of progesterone alone. During early pregnancy the release of uterine prostaglandin F is suppressed.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗

PubMed1992

Differential effects of progesterone treatment on the oxytocin-induced prostaglandin F2 alpha response and the levels of endometrial oxytocin receptors in ovariectomized ewes.

The oxytocin-induced uterine prostaglandin (PG) F2 alpha response and the levels of endometrial oxytocin receptors were measured in ovariectomized ewes after they had been given steroid pretreatment (SP) with progesterone and estrogen to induce estrus (day of expected estrus = Day 0) and had subsequently been treated with progesterone over Days 1-12 and/or PGF2 alpha over Days 10-12 postestrus. The uterine PGF2 alpha response was measured after an i.v. injection of 10 IU oxytocin on Days 13 and 14, using the PGF2 alpha metabolite, 13,14-dihydro-15-keto-PGF2 alpha (PGFM), as an indicator for PGF2 alpha release. The levels of oxytocin receptors in the endometrium were measured on Day 14. During the treatment with progesterone, the peripheral progesterone concentrations were elevated and remained above 1.8 ng/ml until the morning of Day 14. The PGFM responses to oxytocin in untreated controls and SP controls were low on both Days 13 and 14 whereas the levels of endometrial oxytocin receptors in the same ewes were high. Treatment with progesterone either alone or in combination with PGF2 alpha significantly (p less than 0.04) increased the PGFM response on Day 14 and reduced the levels of endometrial oxytocin receptors; treatment with PGF2 alpha alone had no effect. It is concluded that progesterone promotes the PGFM response to oxytocin while simultaneously suppressing the levels of endometrial oxytocin receptors. PGF2 alpha treatment had no effect on either the uterine secretory response to oxytocin or the levels of oxytocin receptors in the endometrium.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗

PubMed1992

Increases in the oxytocin-induced prostaglandin F2 alpha response and reduction in the concentrations of endometrial oxytocin receptors in ewes in response to progesterone.

Ovariectomized ewes were given progesterone and oestrogen priming as steroid pretreatment and subsequently treated with progesterone, prostaglandin F2 alpha (PGF2 alpha), or both. In Expt 1, plasma concentrations of the metabolite 13,14-dihydro-15-keto-PGF2 alpha (PGFM) were measured after an i.v. injection of oxytocin. There was little PGFM response in the untreated control ewes or in the pretreated ewes. Treatment with PGF2 alpha alone had no effect (P greater than 0.05), whereas treatment with progesterone either alone or with PGF2 alpha significantly (P less than 0.05) increased the uterine PGFM response to oxytocin. In Expt 2, chronically ovariectomized ewes had high concentrations of endometrial oxytocin receptors. Treatment with PGF2 alpha alone did not alter the concentrations of the receptors. Treatment with progesterone either alone or with PGF2 alpha significantly (P less than 0.05) reduced the concentrations of the receptors. It is concluded that progesterone promotes the PGFM response to oxytocin, but simultaneously suppresses the concentrations of endometrial oxytocin receptors.

Animals↗

PubMed1992

Increase in concentration of uterine oxytocin receptors and decrease in response to 13,14-dihydro-15-keto prostaglandin F2 alpha in ewes after withdrawal of exogenous progesterone.

Ovariectomized ewes were treated with progesterone and oestradiol to induce oestrus (day of expected oestrus = day 0) and with progesterone on days 1 to 12. The concentrations of endometrial oxytocin receptors and the 13,14-dihydro-15-keto prostaglandin F2 alpha (PGFM) response induced by oxytocin were measured on days 12, 14, 16 and 18 after the cessation of progesterone treatment on day 12, by a receptor binding assay and direct radioimmunoassay, respectively. During the period of treatment, the concentrations of plasma progesterone were high and remained above 2 ng ml-1 until day 13 when they dropped rapidly to less than 0.5 ng ml-1 by day 14. The concentrations of oxytocin receptors in endometrium of control ewes were high (820.7 +/- 91.7 (SEM) fmol mg-1 protein). Treatment with progesterone significantly (P < 0.01) reduced the concentrations of the receptors on days 12 and 14 (144.1 +/- 65.0 and 200.4 +/- 45.4 fmol mg-1 protein, respectively). The receptor concentrations then increased to relatively high values on day 16 (1021.4 +/- 216.6 fmol mg-1 protein) and remained high until day 18 (677.7 +/- 103.4 fmol mg-1 protein).(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗

PubMed1988

Immunocytologic dissection of the urine sediment using monoclonal antibodies.

A method to identify nucleated nonsquamous cells in urine using monoclonal antibodies and immunoperoxidase stain is described. Cells from washed deposits of midstream urine samples were transferred to gelatinized slides in a cytocentrifuge, air-dried, acetone fixed, and subjected to microwave irradiation. Slide preparations were then treated with monoclonal antibodies with the use of a four-layer peroxidase-antiperoxidase technique. It was possible to identify granulocytes, monocytes, lymphocytes, and renal epithelial and urothelial cells. This method was found to be helpful in determining the profiles of cells in urine in acute tubular necrosis, drug-related acute interstitial nephritis, and crescentic glomerulonephritis.

Acute Kidney Injury↗

PubMed1984

Physiological responses of Bacillus species to concanavalin A. 2. Effect on growth, oxygen uptake, enzyme activities and intracellular cyclic guanosine 3',5'-monophosphate level of B. cereus ATCC 14579.

The effect of the mitogen concanavalin A (Con A) on growth and several physiological aspects of Bacillus cereus ATCC 14579 was investigated. Con A at concentrations ranging from 50 to 750 micrograms/ml stimulated growth (the growth rate increased from 0.52/h to 0.97/h, and final yield increased by 2.3-fold over the control) of the bacterial cells. Con A-treated cells also increased their oxygen uptake (1.6-fold increase when treated with 750 micrograms/ml of Con A). The activities of the membrane-bound dehydrogenase and phosphatase increased by 1.75-fold and 2.1-fold, respectively, when treated with 500 micrograms/ml of Con A. However, only a one-fold increase in alpha-glucosidase activity was observed when cells were treated with the same concentration of Con A. Con A at concentrations of 500 to 1,000 micrograms/ml stimulated the cellular synthesis of cyclic guanosine 3',5'-monophosphate (cGMP) by one-fold. It is proposed that binding of Con A to the cell envelope led to increased synthesis of cGMP which might serve as an intracellular messenger for expression of the mitogenic signal of Con A. Since the use of 50 mg/ml of alpha-methyl-D-mannopyranoside (alpha-MM), a Con A inhibitor, could reverse the stimulatory effect of Con A, it was obvious that the stimulatory action was initiated by the specific binding of Con A molecules to the cell envelope. Furthermore, the stimulatory effect was found to be Con A dosage dependent.

Bacillus cereus↗