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Biomedical subjects

K Gordon

Publications and source records attributed to K Gordon.

At least 91 records · Page 5Linked to original sources
PubMed1995

The role of endothelin-1 in regulating human granulosa cell proliferation and steroidogenesis in vitro.

The effects of endothelin-1 (ET-1) on luteinized human granulosa cells (L-HGCs) have not been examined. It is well known that there are differences of actions of several autocrine/paracrine regulators between L-HGCs and GCs of other species, and therefore the present study was designed to examine the effects of ET-1 1) on intracellular Ca2+ concentrations ([Ca2+]i) using the Ca(2+)-responsive fluorescent indicator Fura-2, 2) on cell proliferation by the nonradioactive method using bromodeoxyuridine, and 3) on basal and gonadotropin-stimulated steroidogenesis, and to examine the expression of ET receptor messenger RNA (mRNA) using freshly isolated and cultured L-HGCs obtained from patients undergoing in vitro fertilization. ET-1 increased [Ca2+]i in L-HGCs in a dose-dependent manner between 1 and 1000 nmol/L. High concentrations (100-1000 nmol/L) of ET-1 produced a more rapid and transient increase in [Ca2+]i than that observed with low concentrations (1-10 nmol/L) of ET-1. The increase in [Ca2+]i elicited by ET-3 (1000 nmol/L) and IRL-1620 (1000 nmol/L), a selective ETB receptor agonist, was 16% and 3% (vs. ET-1, 100%), respectively. BQ-123 (1000 nmol/L), an ETA receptor antagonist, inhibited the increase in [Ca2+]i elicited by ET-1 (by 50% at 1000 nmol/L ET-1 and by > 90% at < 500 nmol/L ET-1). mRNAs for the two known receptor subtypes (ETA and ETB) were also present in L-HGCs; however, the expression of ETA receptor mRNA was much greater than that of ETB receptors. ET-1 stimulated cell proliferation in L-HGCs in a dose-dependent manner (1000 nmol/L, 210.5 +/- 13.1%; 100 nmol/L, 198 +/- 11%; 10 nmol/L, 146 +/- 18%; and 1 nmol/L, 103 +/- 9%; vs. control, 100%). These stimulatory effects were completely blocked by BQ-123 (1000 nmol/L). ET-3 and IRL-1620 had no effects on cell proliferation in L-HGCs. Significant stimulatory effects on cell proliferation by the calcium ionophore, ionomycin (10-1000 nmol/L), were observed. ET-1, ET-3, and IRL-1620 attenuated basal progesterone secretion in L-HGCs. These results suggest that ETA receptor predominantly exist in L-HGCs and that ET-1 may stimulate cell proliferation of L-HGCs by increasing [Ca2+]i via ETA receptors.

Calcium↗
PubMed1995

Antiovulatory actions of RU 486: the pituitary is not the primary site of action in vivo.

Continuous administration of RU 486 impairs follicular development and inhibits ovulation in women. Yet, the mechanism of ovulation inhibition remains unknown. To characterize the mechanism(s) of ovulation inhibition, we studied six regularly menstruating cynomolgus monkeys for three consecutive (control-rest-treatment) cycles. Monkeys received 1 mg/kg.day RU 486 in between cycle days 2-22. Basal and GnRH-stimulated (1 and 50 micrograms GnRH, iv, 2 h apart) secretion of LH and FSH was assessed using serial blood samples (every 15 min for 12 h) collected on cycle day 10. Serum levels of estradiol (E2), progesterone (P4), RU 486, cortisol, LH, FSH, and PRL were analyzed by RIAs, the bioactivity of LH was assessed using a mouse Leydig cell assay. The mean cycle length was prolonged by RU 486 treatment from 31.8 to 69.8 days (P = 0.008). During RU 486 treatment, patterns of E2 secretion varied considerably; the mean +/- SD E2 level was 204 +/- 139 pmol/L. LH peaks and P4 profiles compatible with luteal function were seen only before resumption of menstruation. However, one monkey had an increase in P4 after the GnRH challenge-induced LH secretion. Basal levels of LH varied between suppressed and apparently normal values, whereas basal FSH seemed little affected by RU 486 treatment. In two monkeys with E2 secretion indicative of normal follicular development, minor peaks of LH, but no rises in serum P4, were seen. The ratio of bioactive/immunoactive LH was reduced in these monkeys during RU 486 treatment compared to that during the washout period of the treatment cycle. Surprisingly, the pituitary responsiveness to acute GnRH challenge was not affected by RU 486 administration. The individual levels of RU 486 were similar during the treatment period (mean, 40 nmol/L). A resumption of ovulatory cycles occurred when RU 486 concentrations were below 2.5 nmol/L. We conclude that in cynomolgus monkeys, inhibition of ovulation by RU 486 occurs mainly at the level of the hypothalamus, with possible additional effects on the granulosa cell function and alterations of LH bioactivity.

Animals↗
PubMed1995

Participation of glomerular endothelial cells in the capillary repair of glomerulonephritis.

In many glomerular diseases severe injury to the mesangium may occur, leading to matrix dissolution and damage to the glomerular capillaries. Although the destruction of glomerular architecture may lead to permanent injury, in some cases spontaneous recovery occurs. The mechanisms that mediate this recovery are unknown. In this study we provide evidence for glomerular capillary repair (angiogenesis) in the adult injured glomerulus. Injection of anti-Thy 1 antibody into rats results in severe mesangiolysis with capillary ballooning, microaneurysm formation, and loss of endothelial cells in addition to mesangial cells. Although mesangial proliferation is a major response to injury, proliferation of endothelial cells also can be documented from days 2 to 14 in association with repair of the capillaries. The endothelial cell proliferation peaks on days 2 and 7, when it is seven- to ninefold greater than normal. Many of the endothelial cells display morphological features of angiogenesis. The initial wave of endothelial cell proliferation can be reduced by 40% with neutralizing anti-basic fibroblast growth factor antibodies (P < 0.001). The later glomerular endothelial cell proliferation is associated with upregulated expression of vascular permeability factor/endothelial cell growth factor (VPF/VEGF) and an increase of flk, a VPF/VEGF receptor. Although PDGF is expressed in this model, anti-PDGF antibody treatment did not affect the endothelial cell proliferative response. In summary, glomerular endothelial cells have an active role in the glomerular response to injury. Glomeruli are capable of healing microaneurysms, and the mechanism involves basic fibroblast growth factor- and VPF/VEGF-mediated endothelial proliferative responses.

Animals↗
PubMed1994

Hypothalamo-pituitary effects of RU486: inhibition of progesterone-induced hyperprolactinaemia.

Monkeys given oestrogen priming at physiological levels for at least 1 week become hyperprolactinaemic upon the addition of physiological progesterone administration. Here, using RU486, we test whether that this oestrogen/progestin-induced hyperprolactinaemia results from classical progesterone actions at the hypothalamo-pituitary level. Blood samples were collected daily from study day 1-67. Each monkey (n = 2) received daily injections of 25 micrograms/kg oestradiol benzoate, i.m., on study days 5-60. Progesterone-filled silastic capsules (3 cm) were inserted on study day 14 and removed on day 53. On study days 39-45, each monkey received RU486 (25 mg/day, p.o.). Serum samples were stored at -20 degrees C until assayed for prolactin, oestradiol, progesterone and RU486 by radioimmunoassay. Hyperprolactinaemia was induced in all three monkeys upon insertion of progesterone capsules. Prolactin concentrations fell sharply during RU486 treatment to nadirs some 10-fold less than prior to RU486 treatment. The time series was modelled by the Box-Jenkins autoregressive-integrated moving average (ARIMA) method with progesterone producing a gradual increase in prolactin concentrations and RU486 producing a sudden decrease. Statistically significant effects of progesterone and RU486 were found. Thus, the addition of progesterone to an oestrogenized milieu significantly increased prolactin concentrations, and RU486 fully reversed this effect. This evidence indicates that the progesterone-induced hyperprolactinemia in an oestrogenized milieu results from classical progesterone effects.

Animals↗
PubMed1994

What types of epilepsy are preceded by febrile seizures? A population-based study of children.

In a population of 850,000, the authors studied afebrile seizures that follow febrile seizures. Review of all paediatric EEGs identified 504 children with epilepsy beginning between 1977 and 1985. Follow-up averaged 85 months. 14.9 per cent had preceding febrile seizures: 13 per cent complex partial, 13 per cent partial/secondary generalized and 22 per cent generalized tonic-clonic. The rate of preceding febrile seizures did not vary with the cause of epilepsy. Prolonged febrile seizures were not associated with any particular afebrile seizure type. Of 17 with preceding prolonged febrile seizures, seven developed intractable epilepsy: 17.9 per cent of the total intractable cases. Only two developed idiopathic intractable complex partial seizures after prolonged febrile seizures. The authors conclude that febrile seizures most often precede generalized tonic-clonic afebrile seizures. Prolonged febrile seizures rarely precede idiopathic intractable complex partial seizures. The febrile seizure tendency may be a fundamental marker of an individual's seizure threshold.

Adolescent↗
PubMed1994

Postpartum anovulation in non-nursing monkeys: hypothalamic-pituitary-ovarian refractoriness is not induced by the milieu of early pregnancy.

To evaluate the role of the early pregnancy milieu in inducing postpartum refractoriness of the hypothalamic-pituitary-ovarian axis, pregnancies in rhesus monkeys were terminated on either day 35 of gestation or near term at 162 days. Non-nursing mothers with gestations interrupted near term resumed ovulation at a mean of 56 +/- 12 (mean +/- SE) days postpartum, in contrast to the 17 +/- 2 days required for the females having had abortions at day 35. These results demonstrate that the early pregnancy milieu is not determinant of the hypothalamic-pituitary-ovarian refractoriness observed in non-nursing mothers delivering at term.

Abortion, Induced↗
PubMed1994

Existence of P2-purinoceptors on human and porcine granulosa cells.

This study examines the possible roles of extracellular purine nucleotides in regulating ovarian granulosa cell function. Using luteinized human (L-hGC) and porcine granulosa cells (PGC), we examined the effects of purine nucleotides on intracellular free Ca2+ concentrations ([Ca2+]i), and whether they have any effect on steroidogenesis and cell proliferation. L-hGC and PGC were responsive to ATP and ADP at concentrations ranging from 0.1-100 mumol/L in a dose-dependent manner. There was a difference between L-hGC and PGC in the rank orders of agonist potencies for stimulating [Ca2+]i; for L-hGC, UTP > ATP > ATP gamma s > ADP > AMPPNP >> AMP and adenosine; for PGC, 2-methylthio ADP (2-meS ADP) > ADP > ATP = ATP gamma s = UTP > AMPPNP >> AMP and adenosine. No apparent additivity between the responses elicited by UTP and the purine nucleotides (ATP and ADP) was shown in L-hGC. On the other hand, an apparent additive effect between the responses to ADP and UTP was shown on PGC. Furthermore, ATP was a competitive antagonist of the action of ADP on [Ca2+]i levels in PGC. ATP, ADP, and AMP as well as adenosine stimulated basal progesterone and estradiol secretion from L-hGC, however, UTP had no effect on steroidogenesis in L-hGC. On the other hand, purine nucleotides and UTP as well as adenosine inhibited progesterone and estradiol secretion on PGC. However, 2-meS ADP, the most potent agonist for P2T-purinoceptors, did not affect steroidogenesis in PGC. Purine nucleotides had no influence on cell proliferation of L-hGC and PGC. These results indicate the existence of P2U-purinoceptors on L-hGC and P2U- plus P2T-purinoceptors on PGC, and that the inhibitory effect of purine nucleotides on steroidogenesis in PGC is most likely due to A1-adenosine receptors and also P2U-purinoceptors.

Animals↗
PubMed1994

Tubulointerstitial disease in glomerulonephritis. Potential role of osteopontin (uropontin).

Interstitial inflammation and tubular injury accompany most types of glomerulonephritis and are likely to mediate progressive renal injury. We hypothesized that the interstitial monocyte/macrophage accumulation in nephritis involves osteopontin, a cell attachment glycoprotein that avidly binds macrophages in vitro and induces a macrophage-rich infiltrate on subcutaneous injection in mice (Singh et al, J Exp Med, 1990, 171: 1931). In this study, we demonstrate that osteopontin messenger RNA and protein levels are up-regulated in a proportion of proximal and distal tubules in three experimental models of glomerulonephritis. In all three models, the expression of osteopontin initially precedes histological evidence of tubular injury, but is correlated with subsequent sites of monocyte/macrophage accumulation and tubular damage. Osteopontin expression also correlates with the severity of the tubulointerstitial injury, being greatest in amino-nucleoside nephrosis. These data suggest that 1) osteopontin is up-regulated in tubules in glomerular disease; 2) osteopontin may be important for macrophage accumulation at specific sites in diseased tissue; and 3) osteopontin may therefore have a role in the pathogenesis of the tubulointerstitial injury that accompanies glomerulonephritis.

Animals↗
PubMed1994

Probability, risk, and care of pediatric patients with epilepsy

Physicians must apprise their patients of the risks associated with epilepsy and its management. Probability is integral to this communication. The way in which parents perceive and understand this information comprises the area of risk perception. Prospective outcomes are evaluated by families to make the decisions that ultimately effect the management of their child's epilepsy. What is said, heard and decided may vary considerably.

Journal Article↗
PubMed1993

18q-mosaicism associated with Rett syndrome phenotype.

Rett syndrome consists of a characteristic progressive encephalopathy in females. The cause of this syndrome is unknown. We present a patient with 18q-mosaicism who, along with the characteristics of this autosomal deletion, also fulfills the clinical criteria for Rett syndrome. This may demonstrate heterogeneity within this as yet clinically defined syndrome. A thorough chromosomal analysis should be performed in suspected cases of Rett syndrome.

Adult↗
PubMed1993

Which child will have a febrile seizure?

OBJECTIVE: To identify risk factors predictive of a first febrile seizure. DESIGN: Case-control study. SETTING: Regional referral pediatric hospital emergency department. PATIENTS: Seventy-five patients aged 6 months to 4 years presenting with a first febrile seizure were age-matched to two febrile and two afebrile noninfectious controls who had never had a seizure. METHODS: Telephone interview of parents. MAIN OUTCOME MEASURES: Risk factors assessed included family history of febrile or afebrile seizures, neurodevelopmental abnormality, and child-care arrangement. Analysis was done by matched case-control and logistic regression. RESULTS: Factors associated with a significant increase in risk of a first febrile seizure were febrile seizures in first-degree relative (odds ratio [OR], 4.5) or second-degree relative (OR, 3.5); neonatal discharge at 28 days or later (OR, 5.6); parental report of "slow" development (OR, 4.9); and day-care attendance (OR, 3.1). For children with two risk factors (an estimated 3% of the population), the risk of developing febrile seizures is approximately 28% (assuming a population incidence of febrile seizures of 4%).

Case-Control Studies↗
PubMed1993

Inhibition of T cell activation and adhesion functions by soluble CD2 protein.

The CD2 (T11) molecule belongs to a family of cell-surface glycoproteins that function as adhesion molecules in the immune system. Human CD2 is found exclusively on cells of the T lineage: peripheral T lymphocytes, NK cells, and thymocytes. CD2 binds specifically to the surface glycoprotein LFA-3. CD2/LFA-3 adhesion is the basis for the formation of rosettes between T cells and sheep erythrocytes (SRBC) which bear the sheep homologue of LFA-3. More importantly, CD2/LFA-3 adhesion functions in the immune system to augment T cell activation; it initiates conjugate formation between participating T cells and antigen-presenting cells (APC). We investigated the effects of soluble forms of CD2 (sCD2), produced in either baculovirus or CHO expression systems, on the rosetting of T cells with SRBC and on the activation of T cells by antigen plus major histocompatibility complex (MHC) molecules. Rosette formation between T cells and SRBC was completely inhibited by as little as 1 microM sCD2. Furthermore, sCD2 effectively inhibited (at micromolar concentrations) the T cell proliferative response to recall antigens including rubella, tetanus toxoid, and herpes simplex virus (HSV-1), as well as alloantigens in a mixed lymphocyte culture. These findings are consistent with the notion that the CD2/LFA-3 interaction augments antigen-specific T cell functions. The use of a CD2 "decoy" molecule rather than anti-CD2 or anti-LFA-3 antibodies to block the CD2/LFA-3 interaction rules out secondary antibody effects, via the Fc portion, as the basis for inhibition of T cell activation and directly stresses the importance of this adhesion interaction in T cell responses.

Antigens, CD↗
PubMed1993

Outcome of childhood epilepsy: a population-based study with a simple predictive scoring system for those treated with medication.

A population-based study was conducted in an attempt to predict which child's epilepsy will remit. Use of data from a regional electroencephalography laboratory allowed identification of all children in Nova Scotia with epilepsy onset from 1977 through 1985 (excluding those with absence and "minor motor" seizures). Children were followed for an average of 7 years. On the basis of clinical characteristics, a multivariate analysis was used to develop a scoring scheme to predict remission (defined as off medication at the end of the follow-up period). Survival curve methods were used to estimate the duration of medication treatment for those with remission. Of the 504 eligible patients, approximately 70% became seizure free long enough to discontinue medication. Approximately 70% of those stopping medication a first time remained seizure free. At the end of follow-up, 55% of the total cohort were in remission. At diagnosis, the best predictors of remission were age < 12 years at onset, normal intelligence, no prior neonatal seizures, and fewer than 21 seizures before treatment. If predicted to have a remission, then, on the basis of survival curve analysis, 80% were without medication 100 months after diagnosis. After 12 months of treatment, prediction was enhanced by including a score for the number of seizures between 6 and 12 months on treatment. We conclude that approximately 55% of childhood epilepsy will remit. Our scoring system predicts reasonably accurately who will have a remission and when medication is likely to be discontinued.

Child↗
PubMed1993

Biologic factors as predictors of social outcome of epilepsy in intellectually normal children: a population-based study.

We studied social outcome for all the normally intelligent children in our province with onset of epilepsy between 1977 and 1985 (excluding absence and "minor motor" seizures). After follow-up averaging 7 1/2 years, the 337 patients were 7 to 28 years of age. Outcome measures were age dependent. Of those old enough to be at risk, the percentage with each unfavorable outcome was as follows: school failure 34%, use of special educational resources 34%, mental health consultation 22%, psychotropic medication 5%, unemployment 20%, social isolation 27%, inadvertent pregnancy 12%, and criminal conviction 2%. In social isolation 27%, inadvertent pregnancy 12%, and criminal conviction 2%. In a multivariate model correcting for number of potential unfavorable outcomes (based on age at end of follow-up), many variables related to epilepsy, seizure control, and electroencephalographic findings were not associated with social outcome. Only two variables were associated with at least one unfavorable outcome--learning disorder (p < 0.001) and more than 21 seizures before treatment was begun (p < 0.03). The only variable with no unfavorable outcome was simple partial seizures (p < 0.003). Sensitivity and specificity of this model were 54% and 68%, respectively, indicating that social outcome for these children was often not related to biologic factors reflected by the medical details and clinical course of their disorder.

Adolescent↗