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Biomedical subjects

T Cooper

Publications and source records attributed to T Cooper.

At least 37 records · Page 2Linked to original sources
PubMed1997

Clinical improvement with fluoxetine therapy and noradrenergic function in patients with panic disorder.

BACKGROUND: Central noradrenergic (NA) dysregulation has provided a major theoretical framework for understanding the pathogenesis of panic disorder (PD). Using clonidine, an alpha 2-adrenergic receptor agonist, as a probe of NA function, we investigated the hypothesis that the antipanic efficacy of the selective serotonin reuptake inhibitors may be associated with normalization of a putatively dysregulated NA system. METHODS: We report further analyses on data from 17 subjects with PD and 16 healthy volunteers who underwent measurement of the plasma NA metabolite 3-methoxy-4-hydroxyphenylglycol (MHPG) immediately before and after oral clonidine administration. Thirteen patients with PD were rechallenged after 12 weeks during open fluoxetine hydrochloride treatment using the same clonidine paradigm; 13 healthy volunteers were rechallenged at 12 weeks, not having received treatment between challenges. RESULTS: Patients with PD, compared with healthy volunteers, have markedly elevated plasma MHPG volatility during the first clonidine challenge. Volatility describes the magnitude of within-subject plasma MHPG oscillatory activity as assessed by the root of the mean square successive difference. A greater degree of clinical global improvement was predicted by a greater magnitude of basal MHPG reduction with fluoxetine treatment. Antipanic response to fluoxetine was accompanied by a significant decrease of MHPG volatility to volunteer levels. Volunteer MHPG volatility remained unchanged from the first to second clonidine challenge. CONCLUSIONS: Further evidence is provided for the hypothesis of NA dysregulation in PD as reflected by elevations of within-subjects plasma MHPG volatility during clonidine challenge. Effective selective serotonin reuptake inhibitor-antipanic treatment in this clinical sample was paralleled by normalization of dysregulated NA function.

Adult↗
PubMed1997

The molecular biology of the sperm surface. Post-testicular membrane remodelling.

The membrane of testicular spermatozoa undergoes extensive changes in the epididymis, including rearrangement, modification and loss of pre-existing components, addition of new glycoproteins from epididymal secretions, and exchange of lipid constituents. As a result, the membrane of cauda epididymidal spermatozoa has a different composition and different properties, which collectively contribute to male fertility. Special significance has been attributed to sperm surface structures that only appear post-testicularly in the epididymis, the so-called "maturation antigens". Therefore, human post-testicular proteins have been cloned by substractive screening of epididymal cDNA libraries, employing testis as the primary negative control. To date, there is scanty information on their function and mechanism of deposition on the sperm surface. However, the major maturation antigen CD52 seems to bind firmly to the sperm membrane via its GPI anchor. Its synthesis is carefully regulated by the cells of the epididymal epithelium, with temperature and androgens acting synergistically on CD52 mRNA levels.

Animals↗
PubMed1997

Effects of clozapine on plasma catecholamines and relation to treatment response in schizophrenia: a within-subject comparison with haloperidol.

We conducted a within-subject comparison of the effects of clozapine and haloperidol on plasma levels of neurotransmitters and metabolites, and related changes in specific plasma neurochemicals with clozapine response. The subjects were 14 inpatients with schizophrenia or schzoaffective disorder, who were refractory to haloperidol and at least one other typical antipsychotic medication. Subjects underwent, in the following order: a 6-week "fixed, flexible dose" haloperidol trial, followed by a 2-4 week medication-free phase, and a 6-week clozapine trial. Plasma levels of norepinephrine (NE), homovanillic acid (HVA), and 3-methoxy-4-hydroxyphenylglycol (MHPG), and objective clinical ratings of total, positive, negative, and depressive symptoms were obtained at the end of each phase. As expected, we found a substantial increase of plasma NE with clozapine but not with haloperidol. However, the increase in NE was not associated with improvement in total or positive symptomatology. There was some evidence for an association between improvement in negative symptoms and increased HVA on clozapine, as well as diminished HVA during the medication-free phase. The implications of these data for understanding the mechanisms of action of clozapine are discussed.

Aged↗
PubMed1997

Effects of pivalic acid and sodium pivalate on L-carnitine concentrations in the cauda epididymidis and on male fertility in the hamster.

In this study, administration of pivalic acid or its sodium salt was found to decrease the L-carnitine concentration in the epididymal lumen of the hamster; it also tested whether this decrease affected sperm cell motility, chromatin structure, or fertilizing capacity. Provision of pivalic acid or its sodium salt (20 mM or 40 mM) in the drinking water of mature male golden hamsters for 30 days reduced (by 72%, 75%, and 83% in three experiments) the L-carnitine concentration of the cauda epididymidis but did not inhibit sperm chromatin condensation, as assessed by flow cytometry. The treatments did not alter the location of motile sperm in the epididymidis nor did they appreciably affect the motility of sperm obtained from the distal cauda epididymidis. The numbers and percentage of ova that reached the 2-cell stage 36-40 h after uterine insemination with spermatozoa from control and treated hamsters served as a measure of sperm fertility. Treatment with pivalic acid or sodium pivalate did not render male hamsters infertile although it appeared to reduce the fertilizing ability of their spermatozoa. These results suggest that the high concentration of L-carnitine present in the lumen of the cauda epididymidis is not required for maturation of sperm chromatin or development of sperm motility.

Animals↗
PubMed1997

Variability in PAH-DNA adduct measurements in peripheral mononuclear cells: implications for quantitative cancer risk assessment.

Biomarkers such as DNA adducts have significant potential to improve quantitative risk assessment by characterizing individual differences in metabolism of genotoxins and DNA repair and accounting for some of the factors that could affect interindividual variation in cancer risk. Inherent uncertainty in laboratory measurements and within-person variability of DNA adduct levels over time are putatively unrelated to cancer risk and should be subtracted from observed variation to better estimate interindividual variability of response to carcinogen exposure. A total of 41 volunteers, both smokers and nonsmokers, were asked to provide a peripheral blood sample every 3 weeks for several months in order to specifically assess intraindividual variability of polycyclic aromatic hydrocarbon (PAH)-DNA adduct levels. The intraindividual variance in PAH-DNA adduct levels, together with measurement uncertainty (laboratory variability and unaccounted for differences in exposure), constituted roughly 30% of the overall variance. An estimated 70% of the total variance was contributed by interindividual variability and is probably representative of the true biologic variability of response to carcinogenic exposure in lymphocytes. The estimated interindividual variability in DNA damage after subtracting intraindividual variability and measurement uncertainty was 24-fold. Inter-individual variance was higher (52-fold) in persons who constitutively lack the Glutathione S-Transferase M1 (GSTM1) gene which is important in the detoxification pathway of PAH. Risk assessment models that do not consider the variability of susceptibility to DNA damage following carcinogen exposure may underestimate risks to the general population, especially for those people who are most vulnerable.

Adult↗
PubMed1997

Serotonergic modulation of dopamine measured with [11C]raclopride and PET in normal human subjects.

OBJECTIVE: This study was undertaken to measure serotonergic modulation of dopamine in vivo by using positron emission tomography (PET), a radiotracer for the striatal dopamine D2 receptor ([11C]raclopride), and a pharmacologic challenge of the serotonin system (d,l-fenfluramine). METHOD: Two PET studies using [11C]raclopride were performed in 11 normal male subjects before administration of the serotonin-releasing agent and reuptake inhibitor fenfluramine (60 mg p.o.) and 3 hours afterward. A graphical analysis method was used with the [11C]raclopride data to derive the distribution volume of D2 receptors. Plasma levels of fenfluramine, norfenfluramine, homovanillic acid (HVA), cortisol, and prolactin were determined. RESULTS: Levels of fenfluramine and prolactin were elevated 2 hours after fenfluramine administration and remained significantly elevated during the second scan, while levels of HVA and cortisol were not altered significantly during the time of scanning. A significant decrease in the specific binding (striatum) and the nonspecific binding subtracted from the specific binding (striatum minus cerebellum) of [11C]raclopride was observed. The rate of metabolism of [11C]raclopride and the nonspecific binding (cerebellum) were not significantly altered by the fenfluramine intervention. CONCLUSIONS: The observed decrease in [11C]raclopride binding is consistent with an increase in dopamine concentrations and with the ability of serotonin to stimulate dopamine activity. The ability to measure serotonergic modulation of dopamine in vivo may have implications for the study of etiologic and therapeutic mechanisms in schizophrenia, major depressive disorder, obsessive-compulsive disorder, and substance abuse.

Aged↗
PubMed1997

Blunted serotonin response to fenfluramine challenge in premenstrual dysphoric disorder.

OBJECTIVE: Indirect evidence suggests that abnormalities in serotonergic function may be involved in the pathogenesis of premenstrual dysphoric disorder. The goal of this study was to test the hypothesis of serotonergic deficiency in premenstrual dysphoric disorder by measuring the prolactin response to fenfluramine. METHOD: The authors administered the serotonin-releasing drug dl-fenfluramine in a placebo-controlled protocol to nine women with premenstrual dysphoric disorder and 11 healthy female volunteers in the luteal phase of the menstrual cycle. RESULTS: Compared to the normal subjects, the women with premenstrual dysphoric disorder had a significantly blunted prolactin response to fenfluramine. CONCLUSIONS: Premenstrual dysphoric disorder appears to be associated with serotonergic deficiency.

Adult↗
PubMed1997

Resource utilization and work or school loss reported by patients with diabetes: experience in diabetes training programs.

Diabetes exerts a major economic impact on healthcare in the United States both in terms of direct and indirect costs. Diabetes management and education programs designed to assist patients in achieving more optimal glycemic control represent a potential mechanism for reducing the morbidity and costs associated with diabetes. The relationship between HbA1c and patient hospitalizations and between HbA1c and days lost from work or school related to diabetes within the past year were evaluated. A cohort of 2359 patients with diabetes (188 type I, 2171 type II) referred to a comprehensive diabetes self-management training program was included in the analyses. Overall, 350 (14.8%) patients reported hospitalization, and 212 (9.0%) reported days lost from work or school. Patients with type I diabetes reported more hospitalizations (26.1% vs 13.9% and days lost (19.2% vs 8.1%) than type II patients. For the hospitalization outcome, the multivariate analyses indicated that younger age, the number of co-morbidities, and the duration of diabetes exerted a greater influence on the reported numbers of hospitalization than glycemic control. For the days lost outcome, the multivariate analyses indicated that there was a marginally significant association between patients with poor glycemic control and reported work or school loss related to diabetes (odds ratio = 1.5; 95% confidence interval, 1.0-2.2). These data suggest that interventions that improve glycemic control may decrease indirect costs related to diabetes.

Absenteeism↗
PubMed1997

Identification of drug-related cognitive impairment in older individuals. Challenge studies with diphenhydramine.

The authors tested the use of repeated cognitive measures to identify those older individuals who experience cognitive decline after administration of a centrally acting medication. Subjects were 30 medically stable, older volunteers, mean age 71.4. Administration was a double-blind, placebo-controlled, crossover "challenge" from baseline to placebo, 50 mg, or 75 mg of diphenhydramine. More patients exhibited significant cognitive decrements after 75 mg of diphenhydramine than after placebo on the Buschke Selective Reminding Test Total Recall and the Trails B test. Data were consistent with models based on prediction intervals. Quantitative algorithms using prediction equations can characterize the normal limits of within-subject variability and define excessive cognitive change in elderly subjects, showing promise for use in monitoring patients to identify those who experience mild cognitive toxicity from prescribed medications.

Age Factors↗
PubMed1996

Neurohormonal and behavioral response to methylphenidate in cocaine abstinence.

We investigated prolactin (PRL) and growth hormone (GH) secretion during acute and late abstinence following methylphenidate (MP) administration. Ten male patients who were undergoing acute cocaine abstinence and nine control subjects were randomly assigned into one of two possible sequences of MP and placebo, with each experimental condition occurring on two successive days. This procedure was repeated after 7 days for the patients. Baseline measures were analyzed by analysis of variance (ANOVA) with post hoc tests. Measures of MP challenge were analyzed by analysis of covariance (ANCOVA) with baseline as the covariate. Acute abstinence was compared with control values and then to late abstinence. Plasma levels of PRL, GH, and MP were measured along with a measure of clinical symptoms. Patients had higher basal PRL concentrations during acute abstinence compared with controls, and patients showed no difference when compared to themselves after 7 days (late abstinence). Provocation with MP yielded exaggerated PRL and GH responses in patients during acute abstinence compared with control values, and ANCOVA also revealed a significant increase in PRL response during late abstinence compared with acute abstinence. GH was a less sensitive indicator than PRL. Craving was exacerbated by MP during both acute and late abstinence and was possibly increased at late abstinence. This indicates that the perturbation in dopamine regulation persists and may be increased as clinical recovery occurs for most subjective symptoms. Blood pressure changes were variable and interpretation was uncertain.

Adult↗
PubMed1996

Metabolism of (-)-deprenyl and PF-(-)-deprenyl in brain after central and peripheral administration.

We examined the cerebral metabolism of L-deprenyl and its fluoro-derivative pF-deprenyl, assaying the parent compounds, their metabolites desmethyl deprenyl, L-amphetamine, and L-methamphetamine, and the fluoro analogs of these metabolites. We compared the levels of the metabolites after subcutaneous injection with those after intracerebral administration (via microdialysis) of the parent compounds. The assay of the parent compounds and their metabolites was by GC-MS measurement of the components of brain microdialysate samples. After their subcutaneous administration, deprenyl and F-deprenyl rapidly entered the brain and then their concentration decreased, with an approximate half-life of 4.5 h. After the intracerebral administration the diffusion from the site of administration was minor. A small fraction (a few percent) of the intracerebrally administered deprenyl was metabolized in situ in the brain possibly by a nonenzymatic process. Metabolism of pF-deprenyl was somewhat more rapid. The higher cerebral levels of metabolites after the subcutaneous administration indicate their exogenous origin-metabolism of parent compounds in the periphery and penetration of the brain by the metabolites.

Amphetamine↗
PubMed1996

Scrotal elephantiasis associated with hidradenitis suppurativa.

Hidradenitis suppurativa is a chronic relapsing infection of the apocrine sweat glands. Its association with penoscrotal lymphedema is not well recognized. A case of massive scrotal elephantiasis associated with chronic hidradenitis of the perineum and scrotum is described. A wide resection of the scrotal mass and perineum was performed, with reconstruction of the perineum and penis carried out using local skin flaps and split-thickness skin grafts. This one-stage treatment yielded an excellent cosmetic and functional outcome.

Elephantiasis↗
PubMed1996

Evaluation of a single injection method, using iohexol, for estimating glomerular filtration rate in cats and dogs.

OBJECTIVE: To evaluate the utility of a method for estimating glomerular filtration rate (GFR) after single IV administration of iohexol. DESIGN: The plasma clearance of iodine (PCI), taken as the quotient of the administered dose of iodine (300 to 600 mg of l/kg of body weight) divided by the area under the plasma iodine concentration versus time curve determined by 4 methods (PCI1-PCI4). The results for PCI were compared with simultaneously obtained values for the urinary clearance of exogenously administered creatinine (CCr), a widely accepted method for the measurement of GFR in cats and dogs. ANIMALS: Cats and dogs that were renal intact (n = 5 cats; n = 1 dog) or had renal mass reduced by partial nephrectomy (n = 5 cats; n = 7 dogs). RESULTS: Values for PCI were closely related (R2 values ranged from 0.947 to 0.992; P < 0.0001 in all cases) to CCr. Despite this close correlation between CCr and PCI, the 95% confidence interval for the difference between PCI3 and CCr included values that exceeded 1.4 ml/min/kg, which represents 50% of the mean value for CCr in renal-intact cats. CONCLUSIONS: Determination of PCI provided a reliable estimate of GFR in cats and dogs of this study. However, differences between 1 of the methods (PCI3) and CCr are clinically important, emphasizing the need to use more than simple linear regression analysis and correlation coefficients when attempting to validate new measurement techniques. CLINICAL RELEVANCE: The determination of PCI provided a reliable estimate of GFR in cats and dogs of this study.

Animals↗
PubMed1995

Tyramine conjugation deficit in migraine, tension-type headache, and depression.

This study was designed to investigate tyramine sulfate conjugation in patients with migraine or tension-type headache, as defined by the newly introduced International Headache Society (IHS) criteria and to examine whether this relationship is mediated by major depression. A total of 62 subjects completed the study: 38 with migraine (22 with aura and 16 without aura), 12 with tension-type headache, and 12 controls. Patients with migraine had significantly lower urinary tyramine sulfate excretion following oral tyramine challenge than normal control. Tension-type headache was also associated with low tyramine conjugation, but only when comorbid with depression. Although mean tyramine sulfate output was lower among subjects with major depression within each of the subtypes of headache, no significant main effect emerged for depression or major subtype thereof. The lower tyramine sulfate excretion values among patients with both migraine and depression compared to those of migraine alone or depression alone in our data and those of others suggests that comorbid migraine with depression may represent a more severe form of migraine than migraine alone. The findings underscore the importance of comorbidity in clinical and epidemiological studies of migraine.

Adult↗