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Biomedical subjects

A Michael

Publications and source records attributed to A Michael.

At least 37 records · Page 2Linked to original sources
PubMed2000

Altered salivary dehydroepiandrosterone levels in major depression in adults.

BACKGROUND: The authors sought to examine whether levels of dehydroepiandrosterone are abnormal in depression. METHODS: Three groups of subjects aged 20-64 were studied: 44 major depressives, 35 subjects with partially or completely remitted depression, matched as far as possible for age and drug treatment, and 41 normal control subjects. Dehydroepiandrosterone and cortisol in saliva were determined from specimens taken at 8:00 AM and 8:00 PM on 4 days. RESULTS: The mean age of the three groups did not differ. Dehydroepiandrosterone was lowered at 8:00 AM and 8:00 PM compared with control subjects. Values for the remitted group were intermediate. Dehydroepiandrosterone levels at 8:00 AM correlated negatively with severity of depression and were not related to drug treatment or smoking, but decreased with age (as expected). Cortisol was elevated in depression in the evening. The molar cortisol/dehydroepiandrosterone ratio also differentiated those with depression from the control group. CONCLUSIONS: Lowered dehydroepiandrosterone levels are an additional state abnormality in adult depression. Adrenal steroid changes are thus not limited to cortisol. Because dehydroepiandrosterone may antagonize some effects of cortisol and may have mood improving properties, these findings may have significant implications for the pathophysiology of depression.

Adult↗
PubMed2000

Glycogen synthase kinase-3beta is a negative regulator of cardiomyocyte hypertrophy.

Hypertrophy is a basic cellular response to a variety of stressors and growth factors, and has been best characterized in myocytes. Pathologic hypertrophy of cardiac myocytes leads to heart failure, a major cause of death and disability in the developed world. Several cytosolic signaling pathways have been identified that transduce prohypertrophic signals, but to date, little work has focused on signaling pathways that might negatively regulate hypertrophy. Herein, we report that glycogen synthase kinase-3beta (GSK-3beta), a protein kinase previously implicated in processes as diverse as development and tumorigenesis, is inactivated by hypertrophic stimuli via a phosphoinositide 3-kinase-dependent protein kinase that phosphorylates GSK-3beta on ser 9. Using adenovirus-mediated gene transfer of GSK-3beta containing a ser 9 to alanine mutation, which prevents inactivation by hypertrophic stimuli, we demonstrate that inactivation of GSK-3beta is required for cardiomyocytes to undergo hypertrophy. Furthermore, our data suggest that GSK-3beta regulates the hypertrophic response, at least in part, by modulating the nuclear/cytoplasmic partitioning of a member of the nuclear factor of activated T cells family of transcription factors. The identification of GSK-3beta as a transducer of antihypertrophic signals suggests that novel therapeutic strategies to treat hypertrophic diseases of the heart could be designed that target components of the GSK-3 pathway.

Animals↗
PubMed2000

Cognitive impairment in remission in bipolar affective disorder.

BACKGROUND: Although the traditional view of bipolar affective disorder is that the majority of patients have full remission between episodes, recent evidence suggests that residual cognitive deficits are present. The aim of this study was to determine whether memory and executive deficits were present in a well-defined clinically remitted group of patients. METHODS: This was a case-control study of bipolar patients in remission (N = 18). Subjects had to fulfil stringent clinical criteria for inclusion into the study and had to have been in remission for at least 4 months. Subjects also had no history of substance dependence. The cognitive battery examined memory and executive function. RESULTS: Patients in excellent clinical remission and who reported good social adaptation showed imipairment on tests of visuospatial recognition memory. Accuracy on four tests of executive function was not impaired in patients in remission compared with controls, although response latency on these executive tests was still impaired. CONCLUSIONS: As our group and others have shown, patients with mania and unipolar depression show generalized impairment on tests of memory and executive function. In comparison, this study has demonstrated that patients in remission show a relatively specific impairment in memory with recovery of accuracy measures on executive function task. The increased response latency on the executive tasks suggests a possible small residual impairment. These findings suggest that in netIroanatomical terms, more posterior cortical function (temporal lobe) has not improved but there is at least some recovery of frontal lobe function in remission.

Adult↗
PubMed1999

A rare coding variant within the wolframin gene in bipolar and unipolar affective disorder cases.

A recent report has shown that Wolfram syndrome carriers (heterozygotes) are 26-fold more likely to require psychiatric hospitalization compared with non-carriers, and that Wolfram syndrome heterozygotes may constitute approximately 25% of individuals hospitalized with depression and suicide attempts. We analyzed a His611Arg polymorphism of the wolframin gene by the polymerase chain reaction (PCR) and HhaI restriction digestion, in 158 bipolar I and 163 unipolar major affective disorder cases, and 316 controls. Statistical analyses of allele or genotype frequencies do not support a major role for wolframin in affective disorder. HhaI restriction digestion and sequencing of PCR products from four affective disorder cases showed a heterozygous Ala559Thr change. The Ala559Thr variant was not detectable in 382 controls tested. Thus, the rare wolframin 559Thr allele deserves consideration as a risk allele for affective disorder.

Alleles↗
PubMed1999

Emotional bias and inhibitory control processes in mania and depression.

BACKGROUND: Despite markedly different clinical presentations, few studies have reported differences in neuropsychological functioning between mania and depression. The disinhibited behaviour characteristic of mania and evidence that subgenual prefrontal cortex is differentially activated in mania and depression both suggest that dissociable deficits will emerge on tasks that require inhibitory control and are subserved by ventromedial prefrontal cortex. METHODS: Manic patients and controls undertook computerized neuropsychological tests of memory and planning ability. In addition, manic and depressed patients were directly compared with controls on a novel affective shifting task that requires inhibitory control over different components of cognitive and emotional processing. RESULTS: Manic patients were impaired on tests of memory and planning. Importantly, affective shifting performance of manic patients differed from that of depressed patients. Manic patients were impaired in their ability to inhibit behavioural responses and focus attention, but depressed patients were impaired in their ability to shift the focus of attention. Depressed patients exhibited an affective bias for negative stimuli, and we believe this to be the first demonstration of an affective bias for positive stimuli in manic patients. CONCLUSIONS: Observed impairments on tests of memory and planning suggest a global pathology for mania consistent with previous profiles for this disorder and similar to established profiles for depression. The results on the affective shifting task demonstrate the presence of mood-congruent bias and dissociable components of inhibitory control in mania and depression. Against a background of memory and planning impairments in the two groups, these findings are consistent with a role for the ventromedial prefrontal cortex in mediating mood-cognition relationships.

Adult↗
PubMed1999

Identification and characterization of cDNA clones encoding hydroxycinnamoyl-CoA:tyramine N-hydroxycinnamoyltransferase from tobacco.

The sequences of three cDNA clones that include the complete coding region of hydroxycinnamoyl-CoA:tyramine N-hydroxycinnamoyltransferase (THT) from tobacco are reported. The three cDNAs were isolated by antibody screening of a cDNA expression library produced from poly(A)+RNA purified from tobacco leaves (Nicotiana tabacum cv. Bottom Special), previously infiltrated with an incompatible strain of Ralstonia solanacearum. The identity of these clones was confirmed by the detection of THT activity in extracts of transformed Escherichia coli and by matching the translated polypeptides with tryptic enzyme sequences. cDNA clones tht4 and tht11 differ only by their 5' leader and 3' UTRs and therefore encode the same protein, whereas tht10 and tht11 exhibit 95 and 99% sequence identity at the DNA and deduced amino acid levels, respectively. The three clones encode proteins of 226 amino acids with calculated molecular masses of 26 kDa. The deduced amino acid sequences show no similarity with the sequence of anthranilate hydroxycinnamoyl/benzoyltransferase from Dianthus caryophyllus, the only enzyme exhibiting hydroxycinnamoyltransferase activity to be cloned so far in plants. In contrast, comparison of the THT amino acid sequence with protein sequence databases revealed substantial homology with mammalian diamine acetyltransferases. The THT clones hybridized to a 0.95-kb mRNA from elicited tobacco cell-suspension cultures and also to a mRNA of similar size from wound-healing potato tubers. The messengers for THT were also found to be expressed at relatively high levels in tobacco root tissues. Southern hybridization of tobacco genomic DNA with THT cDNA suggests that several copies of the THT gene occur in the tobacco genome. Inhibition experiments using amino-acid-specific reagents demonstrated that both histidyl and cysteyl residues are required for THT activity. In the course of these experiments THT was also found to be inhibited by (2-hydroxyphenyl) amino sulfinyl acetic acid 1,1-dimethylethyl ester, an irreversible inhibitor of cinnamyl alcohol dehydrogenase.

Acyltransferases↗