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Biomedical subjects

C A Wilson

Publications and source records attributed to C A Wilson.

At least 145 records · Page 8Linked to original sources
PubMed1991

Involvement of catecholaminergic systems in the zona incerta in the steroidal control of gonadotrophin release and female sexual behaviour.

Previous reports have shown that dopamine (DA) in the zona incerta (ZI) has a stimulatory effect on gonadotrophin release. We have now investigated the possibility that steroids exert their feedback effects on the release of luteinizing hormone (LH) via catecholamine systems in the ZI. Since the same steroid regimes also stimulate female sexual behaviour, the possibility that the ZI is also involved in the control of sexual activity was investigated. Lesions in the ZI increased proceptive and receptive behaviour in oestrogen-primed ovariectomised rats that exhibited a low level of lordosis in a pre-lesion test and had no effect in receptive animals. Turnover rates (TR) of DA, noradrenaline (NA) and adrenaline were measured in the ZI, preoptic area (POA), arcuate nucleus (ARC), median eminence (ME) and ventromedial nucleus in ovariectomised rats treated 54 h before with either oil, oestradiol benzoate (OB) at 5, 10 or 50 micrograms/rat, or 5 micrograms/rat OB followed by 0.5 mg/rat progesterone (P) 48 h later. The TR as measured from the decline in concentration after alpha-methyltyrosine and changes in DOPAC concentration were correlated with the effect of the steroids on plasma LH and lordotic activity. Confirming previous reports, NA turnover in the POA and ME was increased, and DA turnover in the ME was decreased by steroids when they enhanced LH release. DA turnover in the ARC and ME was reduced when lordosis behaviour increased. Treatment with OB plus P stimulated LH release and sexual receptivity and at the same time significantly increased DA and NA turnover in the ZI. There was no correlation between these parameters after OB alone. This report shows that the DA system in the ZI may mediate the stimulatory effect of P on LH release in OB-primed rats but is not involved in the feedback effects of oestradiol alone. NA activity in the ZI is increased after OB plus P and may therefore also be concerned with stimulating LH release. The ZI is involved in the control of sexual behaviour, as electrolytic lesions in this area enhance receptivity and proceptivity, but the catecholamine systems in the ZI do not appear to mediate this control.

Animals↗
PubMed1991

Interaction of estradiol, alpha-melanocyte-stimulating hormone, and dopamine in the regulation of sexual receptivity in the female rat.

Ovariectomized and adrenalectomized rats kept in a reversed lighting system received either 5 micrograms (once) or 1 microgram estradiol benzoate (EB) daily for 2, 3, or 4 days. These treatments induced sexual receptivity in a proportion of the rats, and alpha-melanocyte-stimulating hormone (alpha-MSH; 20 micrograms/rat s.c.) enhanced this proportion. In rats made receptive by 5 micrograms EB alone, the dopamine (DA) activity in preoptic area and arcuate nucleus was significantly reduced, but the alpha-MSH concentrations were not affected 54-56 h after EB treatment. Addition of alpha-MSH significantly increased the DA activity in ventromedial nucleus (VMN) and zona incerta, but this action is unlikely to account for its stimulation of sexual receptivity, since this effect was not blocked by 0.1 mg/kg haloperidol. Treatment with 100 mg/kg Dopa, which induces a presynaptic DA action, stimulated the receptivity in the EB-primed rats and selectively increased the concentration of alpha-MSH in the VMN, while 50 mg/kg Dopa plus 50 mg/kg benserazide, which induces a postsynaptic DA activity, inhibited the receptivity and reduced the alpha-MSH levels in the VMN. It is suggested that estradiol stimulates the female sexual receptivity by reducing the activity of a dopaminergic system in arcuate nucleus and preoptic area. alpha-MSH does not appear to affect this action, although it enhances the effect of steroids on the sexual behaviour, probably at the level of the VMN. The secretion of alpha-MSH may be under a dopaminergic inhibitory control, and the peptide may autoregulate its own secretion via this dopaminergic system which is sited in zona incerta and VMN.

3,4-Dihydroxyphenylacetic Acid↗
PubMed1991

Treatment of experimental preretinal neovascularization using photodynamic thrombosis.

Retinal or preretinal neovascularization (NV) is the result of many ischemic conditions of the retina and is an important factor leading to severe visual loss in diabetic retinopathy. Panretinal photocoagulation does not always control its growth or bleeding sequelae. A potential new treatment modality, photodynamic therapy (PDT), was evaluated for limiting the progression of experimental NV in the rabbit eye. The NV was produced by injecting cultured dermal fibroblasts into the preretinal vitreous space after combined enzymatic and mechanical vitreolysis. This method results in traction retinal detachment with a rapid and consistent growth of NV. After administration of the photosensitizing dye rose bengal (20 mg/kg intravenously), PDT was done using a slit-lamp light source focused through a fundus contact lens (45 J/cm2). The NV was treated on two separate occasions during the active phase of growth (on days 13 and 21 after fibroblast injection). Control animals were exposed to light before injection of rose bengal. Eight randomly assigned animals in each group were followed between treatments and for 28 days after the second treatment. The appearance of NV was documented by frequent photography and fluorescein angiography. The PDT resulted in thrombosis of NV for at least 3 days. Reperfusion, however, was consistently noted at 7 days. Thrombosis was associated with a delay in the growth and maturation of NV fronds, which resumed after reperfusion. Twenty-eight days after the second treatment, NV in both experimental and control eyes had undergone atrophy. At that time (the conclusion of follow-up), however, the size of treated NV fronds (estimated from computerized image analysis of fluorescein angiograms) was significantly less than that of controls.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1991

Blood-retinal barrier breakdown investigated by real-time magnetic resonance imaging after gadolinium-diethylenetriaminepentaacetic acid injection.

Recent magnetic resonance imaging (MRI) studies show that gadolinium-diethylenetriaminepentaacetic acid (Gd-DTPA) entry into the vitreous space can be used as a qualitative marker of blood-retinal barrier (BRB) disruption. To determine if a more quantitative measurement of BRB breakdown could be obtained, the utility of acquiring real-time, T1-weighted proton images was studied after Gd-DTPA injection. Two days before the MRI experiment, panretinal photocoagulation was done. The mean signal intensity over selected regions-of-interest (ROI) in the vitreous and anterior chamber was followed before and after (0, 10, 20, 30, 45, and 60 min) Gd-DTPA injection (1.0 mmol/kg, intravenously). At every laser power setting used in this study (0, 200, 400, 600, and 800 mW), the change in the mean signal intensity could be approximated by a simple exponential equation. However, the time constants determined for these curves were too imprecise to be useful as correlates between laser power and BRB breakdown. The slope of the line fit to the data in the first 20 min postinjection (ie, an initial-rate analysis) was a more precise correlate between BRB breakdown and laser power. This slope represented the rate of change in mean signal intensity in the ROI as a result of the entry of Gd-DTPA, and it was called the "leakiness" parameter. The leakiness parameter reflected changes in the permeability surface area product of the BRB if the blood flow and the Gd-DTPA arterial concentration immediately after injection were approximately the same between animals.

Animals↗
PubMed1991

Photodynamic retinal vascular thrombosis. Rate and duration of vascular occlusion.

Dye-sensitized photochemical thrombosis is a new method of producing vascular occlusion in the eye for experimental purposes. The rate and duration of photodynamic occlusions of branch retinal vessels was measured in pigmented and albino rat eyes after intravenous injection of the photosensitizing dye, rose bengal. Selected vessels were exposed to focused, white light until vascular occlusion was observed biomicroscopically. A slit lamp was used for a light source in this procedure, allowing adjustment of spot size, shape, and orientation. Arterioles occluded more rapidly than venules, and the time required to produce vascular occlusion decreased when animals breathed pure oxygen administered by face mask. Rose bengal doses of 40 and 80 mg/kg were effective, 20 mg/kg was partially effective, and 1 and 10 mg/kg were ineffective in producing branch arteriole occlusion at a light intensity of 73.5 mW/cm2. The total light energy required to produce occlusion increased from an average of 0.06 J using 80 mg/kg to 0.50 J using 20 mg/kg of rose bengal. Lower light intensities produced vessel occlusion less rapidly (46 mW/cm2) or not at all (17.5 mW/cm2). The rate of retinal arteriolar occlusion was not affected by ocular pigmentation. The duration of branch vessel occlusion depended on length of vessel treated and did not exceed 3 days in arterioles and 4 days in venules. Histologic sections showed discrete areas of retinal and choroidal vascular thrombosis confined to the area of direct light exposure. Choroidal vascular thrombosis and outer retinal damage predominated in eyes treated at low light intensity. Thrombosis usually extended into the deep choroidal vessels in albino but not pigmented eyes.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1991

Oxygen kinetics in the vitreous substitute perfluorotributylamine: a 19F NMR study in vivo.

Perfluorocarbon (PFC) vitreous substitutes yielded promising results in the surgical management of retinal detachments. This success is due primarily to their physical properties. However, oxygen kinetics in PFC in vivo have not been investigated. The oxygen flux in the vitreous substitute perfluorotributylamine (FTBA) was assessed in the rabbit eye by monitoring the partial oxygen pressure (PO2) in real-time using Fluorine-19 nuclear magnetic resonance spectroscopy (19F NMR) The spin-lattice relaxation rate (T1)-1 of the CF3 resonance of FTBA is a rapid and sensitive index of PO2. T1-derived PO2 from the FTBA-filled rabbit eye was followed at regular time intervals under different oxygenation protocols. In the first series of experiments, FTBA in the vitreous space was oxygenated by ventilating the rabbit with a mixture of 95% O2 and 5% CO2. The oxygen uptake profile could be approximated by a simple exponential function with a time constant of 159 +/- 110 min (mean +/- SD, n = 3). A more reproducible correlate was obtained by performing an initial rate analysis on the first hour of ventilation with high oxygen levels. This analysis showed that the rate of increase in FTBA PO2 was 2.34 +/- 0.67 mm Hg/min (mean +/- SD, r2 = 0.99, n = 7). After the animal was removed from the 95% O2/5% CO2 gas and was ventilated with room air, the oxygen clearance profile could be approximated in all cases by a single exponential with a time constant of 59.8 +/- 9.6 min (mean +/- SD, n = 4).(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1990

Efficacy of ivermectin against benzimidazole-resistant nematodes of sheep.

Two trials involving a total of 36 Dorset horn lambs were conducted to assess the anthelmintic efficacy of ivermectin against experimental infections of benzimidazole-resistant strains of Haemonchus contortus and Ostertagia circumcincta. Two resistant strains of each of the two species were used and in each trial the lambs were allocated to three groups. One group was given 200 micrograms ivermectin/kg bodyweight orally, the second group was given 5 mg oxfendazole/kg bodyweight orally and the third group remained untreated as controls. Fourteen days after treatment the lambs were necropsied. Ivermectin was found to be more than 99 per cent to 100 per cent effective against all four benzimidazole-resistant strains, whereas oxfendazole was 78.6 per cent and 83.8 per cent effective against the H contortus strains, and 25.6 per cent and 39.8 per cent effective against the O circumcincta strains.

Animals↗
PubMed1990

IL-1 beta modulation of spontaneous autoimmune diabetes and thyroiditis in the BB rat.

Long term effects of in vivo treatment with human rIL-1 beta on diabetogenesis and thyroid disease were determined in the Biobreeding rat. Administration of high dose (10 micrograms/kg) IL-1 beta accelerated the onset of insulin-dependent diabetes mellitus compared to saline-injected controls. High dose treatment resulted in goiter development, pronounced LT, reduced serum T4 levels, and overall growth reduction. In contrast, low dose IL-1 beta (0.5 microgram/kg) administration significantly reduced the frequency of insulin-dependent diabetes mellitus (48%) compared to placebo (86%) and high dose IL-1 beta (93%) treatment groups. Rats protected by low dose IL-1 beta had unaffected growth rates and minimal to no pancreatic and thyroid pathology. Our results demonstrate that exogenous administration of IL-1 beta modulates Biobreeding rat idiopathic autoimmune diabetes and thyroid disease in a dose-dependent manner.

Animals↗
PubMed1990

Neonatal serotonin reduction alters the adult feminine sexual behaviour of golden hamsters.

HPLC analysis of hamster hypothalamic 5HT indicated higher levels in females than in males on day 12 after birth. Levels of 5HT and 5HIAA could be reduced in both sexes by pCPA administration. Male and female hamster pups were treated on days 1-7 or 7-14 after birth with either pCPA, 5HTP or buffer, and tested for feminine and masculine sexual behaviour in adulthood. 5HTP had no effect on behaviour in either sex. pCPA had no effect on masculine sexual behaviour nor did it affect feminine sexual behaviour when given between days 1-7. When administered on days 7-14, pCPA significantly decreased the time that females spent displaying feminine sexual behaviour, while significantly increasing it in males. We, therefore, suggest that serotonin may be modulating a neural substrate already differentiated by androgens.

Aging↗
PubMed1990

Hormonal manipulation and neonatal imprinting of carbonic anhydrase isozymes in rat liver.

Thyroidectomy has a feminizing effect on the carbonic anhydrase isozymes II and III in male rat liver. These isozymes are known to be sexually differentiated but no treatment so far administered has produced total feminization and this is also true for thyroidectomy. Neonatal castration, however, does produce this result, suggesting the possibility of androgen imprinting for these isozymes during the neonatal period.

Age Factors↗
PubMed1990

Role of gamma-aminobutyric acid in the zona incerta in the control of luteinizing hormone release and ovulation.

gamma-Aminobutyric acid (GABA) neurones are present in the zona incerta (ZI) where other systems have been shown to influence gonadotrophin release. This report investigates the effect of GABA agents in the ZI on ovulation and luteinizing hormone (LH) release. In intact females under Saffan anaesthesia, bilateral stereotactic injections into the ZI of two GABA transaminase inhibitors [amino(oxy)acetic acid and gamma-acetylene GABA] on the morning of pro-estrus or two GABA agonists on the afternoon of pro-estrus inhibited ovulation. The selective GABA B agonist baclofen was effective at 0.05 nM; muscimol, a mixed GABA A and B agonist, was 50-fold less potent, while the selective GABA A agonist isoguvacine had no effect at 500 nM. Administration of baclofen at 0.05 and 5 nM into the ZI significantly reduced plasma LH concentration in untreated ovariectomized rats and also prevented the rise in LH normally induced in ovariectomised rats primed with 5 micrograms oestradiol benzoate (OB) plus 0.5 mg progesterone. In ovariectomised rats primed with 5 micrograms OB alone, administration of the selective GABA A antagonist bicuculline (200 and 260 pg/side) had no effect on plasma LH, while the GABA B antagonist phaclofen (10 pg/side) stimulated a rise in plasma LH, 40 and 60 min after injection. These results indicate that GABA activity in the ZI exerts an inhibitory effect on LH release and ovulation and this is preferentially exerted via GABA B receptors.

4-Aminobutyrate Transaminase↗
PubMed1990

Gonadotrophin glycosylation and function.

This review emphasizes the heterogeneous structure of the gonadotrophin hormones and the influence of different oligosaccharide structures on the bioactivity of these hormones. A summary has been made of the changes in biopotency of the gonadotrophins throughout the life-cycle of the human and in different endocrine states in the rat. In general it appears that the charge of the gonadotrophin conferred by the acid radicals attached to the terminal groups on the oligosaccharide structures strongly influences biopotency. Basic structures have a greater potency in in-vitro assays, but a short half-life in the circulation, while acidic isoforms are less potent, but have a longer circulatory time and are thus more active in in-vivo estimations. More basic forms are secreted over the adult reproductive years compared with the prepubertal period and old age. The glycosyl structure of the carbohydrate groups also alters in different endocrine states and is probably also important for the bioactivity and potency of the hormone. Gonadotrophin-releasing hormone (GnRH) and gonadal steroids can influence the type of isoform synthesized and released, and therefore affect the function of gonadotrophins. GnRH enhances glycosylation, sulphation and biopotency. Oestradiol potentiates the glycosylation induced by GnRH and reduces sialylation, while testosterone increases sialylation.

Adolescent↗
PubMed1990

Drug-exposed neonates.

Drug use during pregnancy can have detrimental effects--both nonspecific and highly specific--on the perinatal outcome. Nonspecific effects include fetal growth retardation, resulting in small infants and decreased head circumference. Specific effects include facial dysmorphology and organ system anomalies such as alcohol-related birth defects. Patients abusing drugs are at an increased risk for preterm labor, thereby placing an already compromised fetus at increased risk. The number of mothers and infants being infected by the human immunodeficiency virus from sharing needles, multiple sexual contacts, and mother-to-infant transmission is increasing at an alarming rate.

Abnormalities, Drug-Induced↗
PubMed1990

Fluorescein angiography using ultra-high speed film.

We used a new ultra-high speed black-and-white film, Kodak T-MAX P3200 (ASA 3200), in routine fluorescein angiography on 51 patients and one normal volunteer. The increased film speed permitted a lower flash intensity than with other available films. Photophobia was improved subjectively in 25% of patients who had undergone prior angiography at a higher flash setting. In addition, patient cooperation was improved as evidenced by a decrease in the frequency of photographic artifacts and uninterpretable photographs compared with prior angiograms done using Kodak TRI-X Pan film (ASA 400). T-MAX yielded excellent resolution, but its grain size was slightly greater than that of TRI-X Pan. The use of ultra-high speed film and reduced light intensity may benefit the patient and improve photographic quality in some individuals with photophobia.

Evaluation Studies as Topic↗
PubMed1990

Central retinal artery obstruction in herpes zoster ophthalmicus and cerebral vasculopathy.

We present a case of acute central retinal artery obstruction in association with Herpes zoster ophthalmicus and delayed cerebral vasculopathy. Retinal vascular obstruction is rare in zoster, and its occurrence during postherpetic cerebral vasculopathy has not been reported previously to our knowledge. The syndrome of delayed cerebral vasculopathy is discussed as is its possible relationship to central retinal artery obstruction.

Aged↗
PubMed1989

An in vitro study of the antibacterial and antifungal properties of an irreversible hydrocolloid impression material impregnated with disinfectant.

The difficulties associated with the disinfection of alginate (irreversible hydrocolloid) materials have resulted in the development of an irreversible hydrocolloid impression material impregnated with an antimicrobial compound, didecyldimethyl ammonium chloride. This investigation assessed the antibacterial and antifungal properties in vitro of this innovative irreversible hydrocolloid material by using the agar well technique. The microorganisms used were Pseudomonas aeruginosa, Streptococcus mutans, Streptococcus sanguis, Lactobacillus odontolyticus rodriguez, Actinomyces odontolyticus, mixed salivary organisms, and Candida albicans. The results showed an absence of activity against Pseudomonas aeruginosa. Varying degrees of antibacterial activity were exhibited against the other microorganisms. It is concluded that it is not know whether the limited antibacterial and antifungal effect demonstrated in this study is sufficient to prevent bacterial and fungal colonization of the impression surface in the mouth during clinical practice.

Actinomyces↗