Biomedical subjects

H Dick

Publications and source records attributed to H Dick.

At least 19 recordsLinked to original sources

PubMed2006

Suspected transmission of methicillin-resistant Staphylococcus aureus between domestic pets and humans in veterinary clinics and in the household.

OBJECTIVE: To describe MRSA infection and colonization in household pets, and transmission of MRSA between animals and humans. METHODS: MRSA infection and colonization in household pets and human contacts were evaluated during investigations initiated after identification of MRSA infection or colonization of a household pet in order to determine if there had been transmission between animals and humans. All MRSA isolates were screened for Panton-Valentine leukocidin (PVL) genes by use of polymerase chain reaction, and isolate relatedness was determined by use of pulsed-field gel electrophoresis (PFGE). RESULTS: Investigations of six situations where MRSA was identified in one or more animals in a household or veterinary facility were performed. MRSA was isolated from 8 animals (5 dogs and 3 cats) with clinical infections, 1 cat that was in contact with 2 infected cats and 14/88 (16%) of household contacts or veterinary personnel. Both animal-to-human and human-to-animal transmission were suspected. An indistinguishable MRSA isolate was recovered from at least one human that was in contact with each animal case. All isolates were classified as Canadian epidemic MRSA-2, the predominant community-associated MRSA clone in humans in Canada. No isolates possessed genes encoding for the PVL. CONCLUSIONS: Transmission of MRSA between humans and animals, in both directions, was suspected. MRSA appears to be an emerging veterinary and zoonotic pathogen.

Animals↗

PubMed2002

Pathological evaluation, clinical chemistry and plasma cholecystokinin in neonatal and young miniature swine fed soy trypsin inhibitor from 1 to 39 weeks of age.

The potential toxicity of dietary soy trypsin inhibitor (TI) was evaluated in neonatal miniature swine. From 1 to 6 weeks of age, two groups of male piglets were artificially reared in an Autosow and automatically fed either TI or control liquid diet. From 6 to 39 weeks of age, these two groups were fed either TI or control chow diet. A third group, sow control (SC), suckled from birth to 6 weeks of age, were also weaned to control chow from 6 to 39 weeks of age. Clinical chemistry and plasma cholecystokinin (CCK) determined at 6, 18, 30 and 39 weeks of age, and serum amylase activity with gross and histopathological analyses of major organs at 6 and 39 weeks of age are reported. TI had no effect on plasma CCK, serum amylase activity, or numerous clinical chemistry values. TI-fed piglets had a larger relative liver weight at 6 weeks of age. Relative pancreas weight decreased with age but was not affected by TI. Gross and histopathological analyses of major organs, except the spleen, were within normal limits. Increased incidence of extramedullary hematopoiesis was noted in the spleen of the TI group at 6 but not at 39 weeks of age. There was no consistent pattern in immunohistochemical foci for secretin, gastrin releasing polypeptide or CCK, and no change in DNA, RNA, mitotic index or nuclear density of pancreatic cells. At 6 weeks of age, TI increased pancreatic protein and amylase activity but not trypsin or chymotrypsin activity. None of the effects suggested that this dose of TI was toxic to either the neonatal or sexually mature miniature male swine.

Administration, Oral↗

PubMed1997

Kinematics of goal-directed arm movements in neglect: control of hand in space.

The present study investigated unrestrained, three-dimensional arm movements during goal-directed pointing in five patients with clinically manifest neglect to targets positioned either in the center or the left and right hemispace. Five patients with unilateral right hemispheric lesions without neglect and six healthy subjects served as controls. All subjects were able to point to these targets. Terminal accuracy of pointing did not differ between the three groups along the horizontal, vertical and anterior-posterior axis. Subjects' hand trajectories did not reveal direction-specific deviations from a straightline hand path. Our data show that deviations in the trajectories toward the ipsilesional side are not characteristic for patients with spatial neglect. We argue that exploratory and goal-directed motor behavior might not share the same egocentric, body-centered reference frame. A spatial reference frame for exploratory behavior is disturbed in patients with neglect resulting in a failure to explore the contralesional part of space by eye or limb movements. Its failure does not induce a spatial bias in hand trajectory formation during goal-directed arm movements in peripersonal space. Such deviations of reaching or pointing rather seem to be characteristic for patients with optic ataxia.

Adolescent↗

PubMed1994

Effects of glucocorticoids on 5-HT1A presynaptic function in the mouse.

8-OH-DPAT, a selective 5-HT1A agonist, produced a hypothermic response in mice at a dosage of 0.5 mg/kg. Administration of corticosterone-21-acetate (0.5, 5 and 50 mg/kg, daily for 3 and 10 days) produced a dose-dependent attenuation of this hypothermic response in mice. When all controls and corticosterone treated mice were retested, 14 days after initial testing, they did not differ in the hypothermic responses induced by 8-OH-DPAT. Mice treated with aldosterone (50 mg/kg), dexamethasone (50 mg/kg) and the specific type 2 corticosteroid receptor agonist, 11b,17b-dihydroxy-21-methyl-17a-pregna-1,4,6-trien-20-yn+ ++-3-one (RU26988, 30 mg/kg) for 10 days, did not differ from vehicle treated controls in the hypothermic response to 8-OH-DPAT. Mice administered corticosterone-21-acetate (30 mg/kg, daily) for 10 days displayed a motor behavioural syndrome, which was not seen in controls, when injected with 5-hydroxytryptophan (5-HTP, 100 mg/kg) 15 min after the injection of carbidopa (25 mg/kg). This was significantly decreased by pretreatment with the 5-HT1A receptor antagonist 1-(2-methoxyphenyl)-4-(4-phthalimidobutyl)-piperazine (NAN-190 5 mg/kg, 30 min prior to administration of carbidopa). Taken together, this evidence is compatible with a specific corticosterone induced facilitation of 5-HT release due to attenuation of inhibitory 5-HT1A autoreceptor function.

5-Hydroxytryptophan↗

PubMed1994

Diurnal variation of mood and neuropsychological function in major depression with melancholia.

20 DSM-III-R melancholics with clinically evident diurnal symptoms and 20 controls were assessed with a battery of neuropsychological tests, a test of maximum voluntary hand-grip, and neuroendocrine measures of hypothalamic-pituitary-adrenal axis function morning and evening in a 24-h period, using a balanced design. The morning pattern of neuropsychological impairment in the melancholics was comprehensive, affecting attention and concentration/working memory, episodic memory, reaction time and, strikingly, the speed of simultaneous match to sample, which was performed more slowly than the version of the task delayed to 0 or 4 s. The melancholics were significantly weaker than controls, on a measure of maximal voluntary contraction. Significantly improved neuropsychological function was seen in the melancholic patients in the evening, in line with diurnal improvement in mood; there was also a large increase in strength. Slowing on the digit symbol substitution test, the simultaneous match to sample task, total errors on the match to sample and hand-grip remained impaired in the evening compared to controls; other neuropsychological measures were no longer statistically different from control values which were often worsened. Neuroendocrine measures showed significantly raised levels of cortisol and ACTH morning and evening in the melancholics. Morning cortisol in the melancholics correlated with the diurnal improvement in neuropsychological functioning. The results have implications for the timing of neuropsychological assessment in major depression. Indices of neuropsychological and motor function may be as reliable quantitative estimates of illness severity as subjective estimates of mood.

Adrenocorticotropic Hormone↗

PubMed1993

The elevation of plasma beta-endorphin levels in major depression.

Day-time plasma beta-endorphin/beta-lipotrophic hormone (beta-ENDO/beta-LPH), ACTH and cortisol have been determined in 26 patients with major depression and 25 controls. beta-ENDO/beta-LPH and cortisol were significantly elevated in patients, while ACTH was not. Cortisol levels were significantly negatively correlated with age in controls as were beta-ENDO/beta-LPH and ACTH. In patients, by contrast, cortisol levels were positively, albeit not significantly, related to age. Peptide levels were not related to age in the patient group. Instead, beta-ENDO/beta-LPH was negatively correlated with clinical ratings of symptom severity in patients and positively associated with an acute psychosocial precipitant. The findings cast further light on beta-ENDO/beta-LPH as a measure of hypothalamic-pituitary over activity in depressive illness. A negative association with symptom severity suggests that beta-ENDO/beta-LPH responses are, like those of ACTH, down-regulated in the course of depressive illness.

Adrenocorticotropic Hormone↗

PubMed1992

The effects of corticosterone on 5-HT receptor function in rodents.

In the mouse, administration of corticosterone-21-acetate (30 mg/kg, s.c. daily) for 3 and 10 days produced an attenuation of the hypothermic response to the 5-HT1A receptor agonist 8-hydroxy-2-(di-n-propylamino)tetralin (8-OH-DPAT), which was not present after administration for 1 day. A similar effect was observed in the rat after administration of corticosterone-21-acetate (30 mg/kg, s.c. daily) for 10 days. Mice which had been given corticosterone for 10 days displayed the serotonin syndrome when injected with 5-hydroxytryptophan (5-HTP, 100 mg/kg, s.c.), 15 min after injection of carbidopa (25 mg/kg, i.p.). This was not seen in control animals. The serotonin syndrome was also induced in mice using 8-OH-DPAT; this increased in a dose-dependent manner and could be significantly decreased by pre-treatment with 1-(2-methoxyphenyl)-4-(4-phthalimidobutyl)-piperazine (NAN-190 5 mg/kg, i.p., 30 min prior to administration of 8-OH-DPAT), a 5-HT1A receptor antagonist. Administration of corticosterone (30 mg/kg, s.c. daily) did not significantly alter the serotonin syndrome induced in treated mice, compared with controls. Mice pre-treated for 3 or 10 days with corticosterone did not differ from controls in the number of head-twitches induced by 5-HTP and carbidopa or 5-methoxy-N,N-dimethyltryptamine, nor did they differ from controls in their response to the putative 5-HT1B agonist 5-methoxy-3 (1,2,3,6-tetrahydropyridin-4-yl)1-H indole (RU 24969, 3 mg/kg, i.p.).(ABSTRACT TRUNCATED AT 250 WORDS)

5-Hydroxytryptophan↗

PubMed1992

The effects of cortisol infusion upon hormone secretion from the anterior pituitary and subjective mood in depressive illness and in controls.

The aims of this study were to determine whether the administration of cortisol has a significant effect on mood in patients with depression and whether the effects of cortisol on changes in plasma hormone concentrations are like those of synthetic corticosteroids. Twelve patients had major depression and one each had dysthymic disorder and a depressive adjustment disorder. Five were male and nine were female. All were in-patients. Eight normal subjects, two females and six males, were used as controls. Basal beta-endorphin concentrations were 2- to 3-fold higher in depressed patients than in control subjects, but there were no significant differences between the patient and control groups in the basal (pre-infusion) plasma concentrations of ACTH, cortisol, growth hormone or prolactin. Cortisol, but not saline infusion resulted in a significant improvement in self rated mood. Surprisingly, cortisol infusion at first increased plasma beta-endorphin concentrations. At later times after cortisol infusion, plasma beta-endorphin concentrations decreased as did the plasma concentrations of ACTH and growth hormone; prolactin levels were increased. These results show (i) that cortisol infusion raises mood significantly in major depression, (ii) that plasma beta-endorphin concentration is a potential marker of major depression (iii) that rather than blunting of corticosteroid effects, responses to cortisol may even be enhanced in depressive illness. The unexpected, initial increase in beta-endorphin stimulated by cortisol, suggests that the action of cortisol is not simply one of negative feedback inhibition, but may involve mineralocorticoid, as well as glucocorticoid receptors.

Adrenocorticotropic Hormone↗

PubMed1992

Lactation, nutrition and fertility and the secretion of prolactin and gonadotrophins in Mopan Mayan women.

The effect of lactation on menstrual cycles, ovulation and conception was studied in a group of non-contracepting Amerindian Mopan Mayan women. Anthropological observations of relevant events were made over a 21-month period. Blood samples were assayed to determine the plasma concentrations of prolactin, luteinising hormone, follicle stimulating hormone, human chorionic gonadotrophin, placental lactogen, oestrogen, progesterone and cortisol. The data show that: frequent and prolonged breast-feeding was associated with a marked increase in plasma prolactin concentrations to levels similar to those in lactating Gaing but higher than those in lactating Scottish women; ovulatory menstrual cycles and pregnancy occurred during frequent lactation; in lactating menstruating women there was an inverse correlation between fat weight and months post-partum. These data suggest that other factors as well as suckling account for the effects of lactation on fecundity.

Belize↗

PubMed1992

Atrial natriuretic peptide is involved in the ACTH response to stress and glucocorticoid negative feedback in the rat.

The role of atrial natriuretic peptide (ANP) in the ACTH response to stress and the glucocorticoid negative feedback control of ACTH release was investigated in adult male homozygous Brattleboro and adrenalectomized Wistar rats respectively, using the technique of immunoneutralization. The relatively low ACTH response to stress and the lack of arginine vasopressin make the homozygous Brattleboro rat a more rigorous and simpler preparation in which to test the hypothesis that ANP is involved in the ACTH response to stress. In both sets of experiments, blood sampling and injection of sheep anti-ANP or control serum were carried out in conscious animals through intra-atrial cannulae implanted 2 days previously under halothane anaesthesia. A 30-s exposure to ether resulted in a brisk twofold increase in the plasma ACTH concentrations in homozygous Brattleboro rats infused with anti-ANP, but not control serum. The injection of either dexamethasone, a potent glucocorticoid receptor agonist, or corticosterone resulted in a rapid and marked reduction in the plasma concentrations of ACTH in Wistar rats which had been adrenalectomized, under halothane anaesthesia, at least 21 days before experimentation. The inhibitory action of dexamethasone, but not corticosterone, was significantly reduced in animals infused with anti-ANP serum. These results show that the inhibition of ANP release into hypophysial portal blood is probably important for triggering the ACTH response to stress and that ANP may play a role in corticosteroid negative feedback control of ACTH release mediated by type II (glucocorticoid) receptors.

Adrenalectomy↗

PubMed1991

Effect of adrenalectomy and dexamethasone on neuropeptide content of dorsal root ganglia in the rat.

Neuropeptides, including substance P (SP), calcitonin gene-related peptide (CGRP) and somatostatin (SS) in dorsal root ganglia (DRG) may play a role in neurogenic inflammation and pain transmission. Adrenal corticosteroids regulate neuropeptide synthesis in some areas of the CNS and may modulate neurogenic inflammation and sensory perception. We have investigated the effects of adrenalectomy and dexamethasone (0.2 mg/kg/day) treatment on neuropeptide content of rat cervical DRG using specific and sensitive radioimmunoassays. In control animals, a differential distribution of neuropeptide was found; SP and CGRP content increased from C4 to C7 in contrast to SS content, which decreased from C4 to C7. Ten days following adrenalectomy, the mean SS content of cervical DRG decreased significantly to 79.6 +/- 4.5% of sham-operated controls. In contrast, SP and CGRP content increased significantly 10 days after adrenalectomy to 134.6 +/- 6.9% and 132.0 +/- 11.6% of sham-operated controls, respectively. The effects of adrenalectomy on CGRP and SS were reversed by administration of dexamethasone. These results suggest that glucocorticoids affect the neuropeptide content of DRG in the adult rat.

Adrenalectomy↗

PubMed1991

The effects of lithium discontinuation and the non-effect of oral inositol upon thyroid hormones and cortisol in patients with bipolar affective disorder.

Thyroid and adrenal function was assessed in euthymic bipolar patients, stable on prophylactic lithium for at least 1 year, before and after lithium discontinuation in a randomised double-blind placebo-controlled trial. All hormonal measurements were within the reference range, but a significant increase (P less than 0.001) in plasma thyroxine (T4) levels and a decrease (P less than 0.01) in TSH levels were observed 1 month after lithium withdrawal; cortisol concentrations showed a non-significant decrease in the same period. No relationship could be demonstrated between the magnitude of the change in hormone levels and the probability of relapse of manic symptoms. In the second part of this study, inositol was added for 11 days to the diets of bipolar patients being treated with prophylactic lithium and normal controls. No modification was shown in T4 and TSH in either group before or after inositol administration. Inositol did not alleviate other side-effects such as tremor and thirst in the patient group. This result suggests that short-term dietary inositol is not equivalent to lithium withdrawal and is of no value in reducing hormonal and other adverse effects of lithium prophylaxis.

Adult↗

PubMed1991

Psychological, hormonal and biochemical changes following carbohydrate bingeing: a placebo controlled study in bulimia nervosa and matched controls.

The responses of thirteen patients with bulimia nervosa and sixteen controls matched for age and weight are described following the ingestion of a carbohydrate and a calorie-free placebo mixture in simulated binges. Psychological, hormonal and biochemical parameters were measured before and at 15 minute intervals for two hours after the simulated binge. At baseline, the bulimics were clearly more symptomatic than the controls. The control population showed a specific satiating effect of carbohydrate upon hunger ratings. Bulimic patients responded differently showing a blunting of the normal sensation of hunger and an enhanced rating for nausea. Prolactin, growth hormone (GH) and cortisol failed to show a carbohydrate-mediated stimulation in either population. The bulimic patients showed a different pattern of GH release, but this was independent of the challenge condition. Large neutral amino acid (LNAA) levels fell following carbohydrate ingestion, but produced an increase of up to 20% in the tryptophan: LNAA ratio in both bulimic patients and the control group. Thus, while this increase in tryptophan availability failed to provoke hormone release, the time course of the carbohydrate specific effect on the sensations of hunger and nausea is compatible with a mechanism based on increased tryptophan availability. The confusion of satiety with nausea may provide a useful focus for the future treatment of patients with bulimia nervosa.

Adult↗

PubMed1991

Atrial natriuretic peptide is a physiological inhibitor of ACTH release: evidence from immunoneutralization in vivo.

The brain is thought to exert a predominantly stimulatory action on ACTH secretion mediated mainly by corticotrophin-releasing factor-41 (CRF-41) and arginine vasopressin (AVP). Several data, however, also point to the existence of an ACTH-inhibiting factor. Atrial natriuretic peptide (ANP), at concentrations found in hypophysial portal blood, inhibits ACTH release in vitro. The aim of the present studies was to use ANP immunoneutralization to determine whether ANP does in fact inhibit ACTH release in vivo. Intracerebroventricular infusion (1 microliters/min for 30 min) of sheep anti-ANP serum into male rats anaesthetized with sodium pentobarbitone had no significant effect on jugular venous plasma concentrations of ACTH or LH but did decrease significantly the plasma concentrations of prolactin. Intravenous infusion of 0.8 ml sheep anti-ANP serum but not control (non-immune) sheep serum, through an indwelling intra-atrial cannula in conscious male rats resulted in a marked and significant increase in plasma ACTH and corticosterone concentrations. The ACTH and corticosterone response to a 30-s ether stress was not significantly potentiated in the same conscious rats infused with anti-ANP serum. Intra-atrial infusion of anti-ANP did not significantly affect plasma prolactin, LH, glucose or sodium concentrations or plasma osmolality. These results show for the first time that ANP is a potent inhibitor of ACTH secretion in the conscious male rat and that, therefore, ANP is a hypothalamic neurohormone which is likely to play an important inhibitory role in the neural control of ACTH release.

Adrenocorticotropic Hormone↗

PubMed1989

Bright white light does not improve narcoleptic symptoms.

Bright white light (500lx) for 4 h/day was applied to seven narcoleptic patients (age 47-65 years, mean 55 years). The effects of the light on the disturbed sleep-wake cycle in narcoleptics were investigated by the measurement of the following parameters: (1) excessive daytime sleepiness and sustained attention (multiple sleep latency test); (2) rest-activity cycles; (3) self-ratings (mood, anxiety, tiredness); (4) urinary cycles of 6-OH melatonin sulphate and cortisol; (5) sleep EEG. Treatment with bright light showed neither objective nor subjective changes in the clinical symptoms of narcolepsy. While similar "dosage" light applications can phase shift human circadian rhythms and improve depression and hypersomnia in winter depression, it is not an appropriate treatment for narcolepsy.

Aged↗

PubMed1989

The neuroendocrine responses and psychological effects of infusion of L-tryptophan in anorexia nervosa.

The secretion of prolactin and growth hormone (GH), together with subjective ratings of sedation and hunger, were determined in 13 in-patients with anorexia nervosa and 15 controls during the intravenous infusion of L-tryptophan (100 mg/kg). Prolactin responses were not different between groups but GH responses were markedly blunted in patients. In addition sedation responses in patients were attenuated compared with controls. Hunger ratings were reduced by the infusion in controls but were too variable to be interpreted in the patients. Plasma amino acid levels were also determined before and after infusion of L-tryptophan. Tryptophan levels were comparable in the two groups as were the levels of tyrosine, phenyl alanine, valine, leucine and iso-leucine. The results suggest that some aspects of 5-hydroxytryptamine function may be attenuated in anorexia nervosa. However, they undoubtedly contrast with the finding of enhanced hormonal responses in acute dieting and may be relevant to the interpretation of similar experiments in depressive illness.

Adult↗

PubMed1989

Luteinizing hormone responses to luteinizing hormone releasing hormone (LHRH) in acute mania and the effects of lithium on LHRH and thyrotrophin releasing hormone tests in volunteers.

The endocrine responses to Luteinizing Hormone Releasing Hormone (LHRH) of eight drug-free males with mania were determined. Basal levels of Luteinizing Hormone (LH) and the plasma levels following injection of LHRH were elevated in patients compared with controls; Follicle Stimulating Hormone (FSH) and testosterone were not different. Elevated levels of LH have been described previously in recovered manic patients and have been suggested to be state-independent features of mania. In order to clarify the status of this finding, the effects of lithium administration upon hormone responses to LHRH in six male volunteers were also investigated, together with the effects upon Thyrotrophin Releasing Hormone (TRH) stimulation of Thyroid Stimulating Hormone (TSH) and prolactin release. Lithium increased the basal levels of LH and levels after injection of LHRH without effect upon FSH and testosterone. Lithium also increased basal and TRH stimulated release of TSH and basal prolactin levels. Lithium was without effect upon prolactin responses to TRH. The results are discussed in relation to current information on the mechanism of lithium's action. The implications for neuroendocrine work on recovered patients taking lithium are also explored.

Adult↗

PubMed1989

Disturbed endocrine function in the psychoses. I: Disordered homeostasis or disease process?

Plasma concentrations of prolactin, growth hormone, cortisol, TSH, and the neurophysins were measured over 17 hours in 98 newly admitted psychiatric patients and 35 control subjects. Seventy patients had been free of psychotropic medication for three months. Patients with schizoaffective mania (SAM) differed significantly from control subjects by increased plasma cortisol concentrations and decreased night-time TSH concentrations. The latter were also significantly lower than in both schizophrenic and manic disorder patients. Plasma cortisol was increased to a lesser extent in other psychotic subgroups, and increases in prolactin were most marked in the affective psychoses. There was little diagnostic specificity for psychoses other than SAM. Higher cortisol and prolactin levels may be due to the stimulatory effect of serotonergic pathways, but the neural mechanisms underlying lower night-time TSH levels in SAM are not known. The findings are not consistent with the view (a) that the hormonal changes of the psychoses simply reflect a non-specific response to stress, or (b) that the biological abnormalities of the psychoses can be accounted for by a single continuum of disturbance.

Adult↗