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Biomedical subjects

N Bark

Publications and source records attributed to N Bark.

At least 19 recordsLinked to original sources
PubMed2001

Adjunctive high-dose glycine in the treatment of schizophrenia.

Glycine is an agonist at brain N-methyl-D-aspartate receptors and crosses the blood-brain barrier following high-dose oral administration. In a previous study, significant improvements in negative and cognitive symptoms were observed in a group of 21 schizophrenic patients receiving high-dose glycine in addition to antipsychotic treatment. This study evaluated the degree to which symptom improvements might be related to alterations in antipsychotic drug levels in an additional group of 12 subjects. Glycine treatment was associated with an 8-fold increase in serum glycine levels, similar to that observed previously. A significant 34% reduction in negative symptoms was observed during glycine treatment. Serum antipsychotic levels were not significantly altered. Significant clinical effects were observed despite the fact that the majority of subjects were receiving atypical antipsychotics (clozapine or olanzapine). As in earlier studies, improvement persisted following glycine discontinuation.

Adult↗
PubMed2000

High-dose treatment with haloperidol: the effect of dose reduction.

High doses of antipsychotic medications are sometimes prescribed in clinical practice, although the efficacy and safety of such treatment have not been established. The purpose of this study was to determine whether high-dose, long-term antipsychotic treatment prescribed on the basis of clinical judgment can be justified. Patients who were receiving high doses of haloperidol were screened, and those patients whose plasma levels were at least 15 ng/mL were randomly assigned to an experimental group (N = 11) or to a control group (N = 12). The experimental group underwent a dose reduction to achieve the target plasma level of 10 ng/mL. The reduction was gradual over a period of 12 weeks. The control group treatment was maintained at the original level. Both groups were then followed up for another 16 weeks, during which the plasma levels of haloperidol were kept constant. The study used double-blind procedures. Both groups showed an average slight symptom reduction. There was no significant difference in the severity of symptoms between the two groups at any time point. The dose reduction had no apparent adverse effects. Thus, the results of this study did not provide justification for high-dose, long-term antipsychotic treatment. However, these results must be interpreted with caution because the sample studied here was small and biased.

Adult↗
PubMed1999

The incipient stage in thrombin-induced fibrin polymerization detected by FCS at the single molecule level.

We used fluorescence correlation spectroscopy (FCS) to study the activation of fibrinogen by thrombin and the subsequent aggregation of fibrin monomers into fibrin polymers at a very low and at physiological fibrinogen concentrations. In the labeling procedure used the fibrinogen was randomly labeled and the label was bound to the fibrinopeptide A and/or to the part of fibrinogen which after activation takes part in fibrin formation. We measured a diffusion coefficient for fibrinogen of 2.48 x 10(-7) +/- 0.10 x 10(-7) cm2/s. After activation with thrombin both fibrinopeptide A and fibrin polymerization products could be demonstrated. From our findings we suggest a model for the formation of a three-dimensional network as two parallel processes, elongation and branching and that fibrin oligomers are not only intermediates in the polymerization process but also are substrates for branching.

Algorithms↗
PubMed1998

Deaths of psychiatric patients during heat waves.

Deaths of patients in state psychiatric hospitals in the New York City area during heat waves and control periods from 1950 to 1984 were compared with those in the overall New York City population during the same periods. Psychiatric patients had twice the risk of dying during a heat wave than the general population. The risk for patients was higher in the 1950s, before the introduction of antipsychotic medications, than in the 1980s, but was highest in the 1970s, when higher dosages of antipsychotic medication were commonly used. During 1980 to 1984 the risk was the same for both populations, suggesting that both psychiatric illness and antipsychotic medications increase patients' risk of dying during heat waves but that risk can be eliminated with preventive measures.

Age Factors↗
PubMed1997

Heterogeneity of serotonergic response in treatment-refractory schizophrenia patients.

Oral metachlorophenylpiperazine (m-CPP) as a direct-acting postsynaptic serotonergic agonist was used to study serotonergic dysfunction in treatment-refractory chronic schizophrenia based on the hypothesis that some patients may show central serotonergic hypersensitivity. Seventeen DSM-III-R chronic schizophrenic patients with a history of neuroleptic nonresponse underwent double-blind challenge with oral m-CPP (0.25 mg/kg body weight) and placebo after medication washout: m-CPP significantly elevated both prolactin and cortisol levels as compared to placebo. There was a significant relationship between change in cortisol level and change in psychopathology under m-CPP; a blunted cortisol response was associated with a decrease in total psychopathology, while an increase in cortisol response related to an increase in psychopathology. Similarly, decrease in severity of the activation factor and the hostility factor was associated with a smaller cortisol response in the m-CPP condition. These results point to heterogeneity in central serotonergic sensitivity within the context of different subpopulations of serotonergic receptors.

Adult↗
PubMed1997

Analysis of a functional catechol-O-methyltransferase gene polymorphism in schizophrenia: evidence for association with aggressive and antisocial behavior.

We have recently characterized a functional polymorphism in the catechol-O-methyltransferase (COMT) gene that is responsible for substantial variability in COMT enzymatic activity found in humans. A common low-activity variant of the enzyme contains a methionine residue at amino acid 158 of membrane-bound COMT whereas the common high activity variant has a valine at this site. Considering the role of COMT in dopamine metabolism and the involvement of dopaminergic pathways in the pathogenesis of schizophrenia and violence, we screened 37 patients with schizophrenia to determine whether or not a behavioral association with the COMT polymorphism exists. Patients were assessed for dangerousness on the basis of a history of violent and threatening behavior, crime, cocaine and alcohol abuse, and other antisocial behaviors. We found that schizophrenic patients who were homozygous for the low activity allele were judged by their psychiatrists to be at higher risk for aggressive and dangerous behavior than those who were homozygous for the high activity allele (Kruskal-Wallis statistic = 10.43; P = 0.003).

Adult↗
PubMed1997

Cognitive deficits and psychopathology in elderly schizophrenic patients.

The authors investigated the syndromal and cognitive profiles of 25 DSM-III-R older schizophrenic inpatients with continuous acute psychotic symptoms and compared them with 20 younger schizophrenic patients by means of a multidimensional assessment battery. Subjects were medically well and without neurological comorbidity and were comparable in length of current hospitalization and medication regimens. There were no significant differences between the two groups on various symptom rating scores or on neurological variables. The older group's mean scores for various cognitive measures did not reach the value for senile dementia. They also scored significantly better on a memory test and on formal cognitive functions. These findings support the notion of a stable encephalopathy, rather than a dementia-like process, underlying the course of the illness. Authors discussed limitations and implications of these findings.

Adult↗
PubMed1996

On the occurrence of thrombin-like enzymes in mosquitoes.

A thrombin-like enzyme has been identified in mosquitoes and partially purified. The enzyme preparation displays on SDS gel electrophoresis a major protein band of about 22 kDa and one minor of about 28 kDa. The enzyme preparation cleaves a synthetic substrate (S-2238) for thrombin with Km 113 mumol/L (as compared to 3 mumol/L for thrombin). The enzyme clots fibrinogen and plasma. During activation of fibrinogen, fibrinopeptide A (but scarcely fibrinopeptide B) is released. The enzyme is not inhibited by hirudin and activates (if at all) factor XIII differently from thrombin. Predominantly gamma-dimers are formed in the cross linking process. As compared to thrombin a larger extent of activation is required to induce gelation (clotting) by the mosquito enzyme. At a given clotting time the enzyme produces tighter gel structures than thrombin. In its action the enzyme resembles the snake venom enzyme, batroxobin.

Aedes↗
PubMed1995

Psychopathology of Schizophrenia: initial validation of a 5-factor model.

Schizophrenic psychopathology is heterogeneous and multidimensional. One of the more fruitful strategies to investigate more homogenous domains of psychopathology has been the positive-negative syndrome approach. However, this approach is unable to address a number of important issues. Most schizophrenics present a mixed syndrome; the criteria for what constitutes a positive and negative syndrome are variable; distinguishing primary from secondary negative symptoms can be difficult. In order to address some of these problems, we propose the introduction of a 5-syndrome model based on a reanalysis of factor-analytic procedures used on 240 schizophrenics assessed with the Positive and Negative Syndrome Scale: A negative, positive, excitement, cognitive and depression/anxiety factor. This 5-factor solution is supported by 4 independent and comparable factor analyses. Data on internal consistency of the 5 factors and on initial validation using demographic and clinical variables are presented.

Adolescent↗
PubMed1981

Prediction of steady state plasma and saliva levels of desmethylimipramine using a single dose, single time point procedure.

In normal volunteer study (20 subjects) where each ingested 75 mg desmethylimipramine (DMI), blood and saliva samples were collected at 1, 2, 3, 4, 5, 7, 12, 24, and 32 h post dose. Each subject then was given DMI 25 mg b.i.d. for 15 days. Blood and saliva samples were collected on days 3, 4, 12, 13, 14, and 15. All samples were analyzed for total DMI content. Strong correlations were found between the blood samples collected 12, 24, and 32 h post dose (r = 0.93, 0.96, 0.95) and saliva samples collected 24 and 32 h post single dose (r = 0.91, 0.84) and the subjects' respective steady states. Although the correlation between blood and saliva levels was weaker (r = 0.7) because of considerable interindividual variation in the saliva/plasma DMI ratio (16-fold variation), this ratio in individual subjects was stable. These data suggest that, as has been shown for other psychotropic drugs, single blood measures at 24 h post ingestion of 75 mg DMI can be used to predict optimal dosage in individual patients. Acceptable predictions of steady state plasma levels were obtained when this technique was applied to patient data available in the literature. It is also suggested that if the saliva/plasma ratio is established for each individual patient, their drug level monitoring may be possible using this noninvasive approach.

Desipramine↗
PubMed1980

Effect of antiparkinsonian medication on plasma levels of chlorpromazine.

Twenty-one chronic schizophrenics were stabilized with chlorpromazine therapy at their therapeutic dosage for one month. Trihexyphenidyl hydrochloride or identical placebo was then added according to a double-blind, split crossover design. The duration of each half of the crossover was 15 days. Steady state blood samples were drawn three times weekly during the experimental period and the amount of chlorpromazine was determined. The results indicated there were no differences in the levels obtained between the trihexyphenidyl and the placebo phases. A two-hour postdrug blood sample was also drawn at the end of each phase and again, there were no differences between the two conditions. The importance of these results is discussed.

Chlorpromazine↗