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Biomedical subjects

J C Shih

Publications and source records attributed to J C Shih.

At least 73 records · Page 4Linked to original sources
PubMed1998

Application of the surface rendering technique of three-dimensional ultrasound in prenatal diagnosis and counselling of Klippel-Trenaunay-Weber syndrome.

Klippel Trenaunay-Weber syndrome is a complex developmental disorder characterized by a triad of cutaneous haemangioma, varicosities of the body, and unilateral limb hypertrophy. We describe the prenatal diagnosis of Klippel-Trenaunay-Weber syndrome at 15 weeks' gestation using the surface rendering technique of three-dimensional ultrasound. The vivid three-dimensional images of the affected fetus are invaluable in prenatal diagnosis and parental counselling.

Adult↗
PubMed1998

Determination of regions important for monoamine oxidase (MAO) A and B substrate and inhibitor selectivities.

MAO-A and -B are defined by their substrate and inhibitor preferences. To determine which regions of the isoenzymes confer these preferences, we have constructed six chimeric MAO enzymes by reciprocally exchanging corresponding N-terminal, C-terminal, and internal segments of MAO-A and -B then determined the catalytic properties of these chimeric enzymes. N-terminal chimerics A45B and B36A were made by exchanging amino acid segments 1-45 and 1-36 of MAO-A and -B respectively. C-terminal chimerics A402B and B393A were made by exchanging amino acid segments 403-527 and 394-520 of MAO-A and -B respectively, and internal chimerics AB161-375A and BA152-366B were made by exchanging amino acid segments 161-375 and 152-366 of MAO-A and -B respectively. The enzymatic properties observed for the chimerics suggest that the exchanged internal regions but not the N- or C-terminal regions confer substrate and inhibitor preferences.

Amino Acid Sequence↗
PubMed1998

Tissue-specific effects of estrogen on monoamine oxidase A and B in the rat.

Estrogen replacement therapy is widely used in postmenopausal women. The current study examines the effect of varying concentrations of estrogen on the levels of activity of monoamine oxidase A and -B in brain and in other tissues. Adult female rats were ovariectomized and randomized to receive a subcutaneous, slow-release preparation of either placebo or one of three doses of 17-beta-estradiol (0.05, 0.5, or 5.0 mg/pellet, estimated serum levels of 20-25 pg/ml, 100-600 pg/ml, and 1-2 ng/ml, respectively). Animals were sacrificed at 3 weeks and MAO-A and -B activity was assessed in homogenates of heart, liver, lung, uterus, kidney, adrenal and small intestine using 5-hydroxytryptamine and phenylethylamine as substrates. Cortex, amygdala and hypothalamus were microdissected from frozen sections of the brain and were also assayed for MAO-A and -B activity. High dose estrogen (5 mg/pellet) significantly decreased MAO-B activity and resulted in lesser or insignificant changes in MAO-A activity, respectively in liver (-30%, +1%), kidney (-22%, -11%), and uterus (-57%, -35%) (p < 0.05). No significant changes in enzyme activity were observed in heart, adrenal, lung and small intestine. In brain, estrogen (5 mg/pellet) decreased MAO-A activity in the hypothalamus (-28%) and amygdala (-21%), with no significant change seen in MAO-B. Our results suggest that estrogen exerts a tissue-specific, differential regulation of MAO-A and -B activity.

Animals↗
PubMed1998

Is there a "non-MAO" macromolecular target for L-deprenyl?: Studies on MAOB mutant mice.

Several irreversible inhibitors of monoamine oxidase B, can promote survival of damaged neurons in several animal models of cerebral injury. Today it is evident that this effect is not a consequence of monoamine inhibition. Instead it has been proposed that L-deprenyl may act via an unrelated non-monoamine oxidase type- of binding site. In the present study we have investigated if brain tissue from MAOB knockout mice contain such "non-MAO" binding sites for radiolabelled deprenyl. Interestingly, no binding of L-deprenyl was observed indicating that the mother compound does not act directly via a macromolecular target. This is enticing since several alternative mechanisms of action have been proposed in the literature.

Animals↗
PubMed1998

Antenatal depiction of the fetal ear with three-dimensional ultrasonography.

OBJECTIVE: To evaluate the feasibility of examining the fetal ear with three-dimensional ultrasound. METHODS: In 125 pregnancies between 19 and 38 weeks of gestation, fetal ears were evaluated by three-dimensional ultrasound. The volume images with surface rendering were analyzed to depict the morphology, lying axis, orientation, and cranial location of the fetal ears. RESULTS: Three-dimensional images of one or both ears were successfully reconstructed in 105 fetuses. Among them, 18 fetuses had anomalous ears. The anomalous ears, including microtia, low-set ear with slope axis, abnormal ear orientation, and edematous ear, were confirmed after delivery. Three-dimensional ultrasound consistently displayed fetal ear abnormalities with greater accuracy and clarity. CONCLUSION: Because anomalous ears may be a part of complex fetal malformations, it is important to recognize ear abnormalities. Due to the complexity of the fetal ear, three-dimensional ultrasound offers more important information than two-dimensional ultrasound, which simply gives auricular geometry. We suggest that three-dimensional ultrasound can be used better to examine the fetal ear and may prove to be useful for prenatal diagnosis and genetic counseling.

Ear, External↗
PubMed1998

Abnormal stress response and increased fighting behavior in mice lacking the bcr gene product.

The in vivo function of proteins which regulate activity of the GTPase Rac is largely unknown. Here we establish that mice lacking bcr, a known GTPase activating protein for Rac, exhibit a defect in the regulation of both hormonal and behavioral stress responses. Bcr null mutants demonstrate prolonged elevation of plasma glucocorticoids and increased fighting in males in response to physiological and social stress, respectively. Combined biochemical and behavioral data indicate that bcr is involved in mediating the cellular effects of glucocorticoids, specifically down-regulation of the stress-activated hippocampal hypothalamic-pituitary-adrenal axis.

Aggression↗
PubMed1998

Two-dimensional and three-dimensional power Doppler sonographic classification of vascular patterns in cervical lymphadenopathies.

Vascular patterns may reflect some pathologic behaviors of tumors and lymph nodes. Power Doppler ultrasonography, with improved sensitivity and better noise contrast, were used to depict vasculature in 289 cases of cervical lymphadenopathy. Four patterns of vasculature, in addition to avascular nodes, were classified. Benign lymphadenopathies represented 89% and 83% of avascular and hilar type nodes, respectively. However, malignant lymphadenopathies dominated in nodes that were of spotted (72%), peripheral (60%), and mixed type (80%). Correlation between nodal sizes and chronologic changes of vascular patterns in malignant lymphadenopathies implied a reasonable classification. Three-dimensional power angiography, with the advantage of less plane-sampling bias, was further used to validate our classification.

Angiography↗
PubMed1997

Selective enhancement of emotional, but not motor, learning in monoamine oxidase A-deficient mice.

Mice deficient in monoamine oxidase A (MAOA), an enzyme that metabolizes monoamines such as norepinephrine and serotonin, have elevated norepinephrine and serotonin levels in the frontal cortex, hippocampus, and cerebellum, compared with normal wild-type mice. Since monoamines in these areas are critically involved in a variety of behaviors, we examined learning and memory (using emotional and motor tasks) in MAOA mutant mice. The MAOA-deficient mice exhibited significantly enhanced classical fear conditioning (freezing to both tone and contextual stimuli) and step-down inhibitory avoidance learning. In contrast, eyeblink conditioning was normal in these mutant mice. The female MAOA-deficient mice also displayed normal species-typical maternal behaviors (nesting, nursing, and pup retrieval). These results suggest that chronic elevations of monoamines, due to a deletion of the gene encoding MAOA, lead to selective alterations in emotional behavior.

Animals↗
PubMed1997

Serotonin2A receptor gene polymorphism in mood disorders.

Genes that regulate the serotonin (5-HT) system including 5-HT receptors may be involved in mood disorders. We studied 5-HT2A receptor exons and the adjacent intron regions in 102 patients with mood disorders (71 depressive disorders and 31 bipolar disorders). In 34 mood disorder cases, the gene encoding the 5-HT1A receptor had been sequenced, but no disease-specific polymorphism was found. The substitution of C for T at position 102 in exon 1, which had been reported by Warren et al., was confirmed. The corresponding amino acid, serine, did not change. The allele frequency of C [corrected] at position 102 was significantly higher in patients with depressive disorders than in those with bipolar disorders and healthy control subjects. Furthermore, the mean age of onset in the patients heterozyous for the T and C alleles was lower than that in those homozygous for the C allele. No other polymorphism in the gene was found.

Adolescent↗
PubMed1997

Localization of monoamine oxidase A and B mRNA in the rat brain by in situ hybridization.

Monoamine oxidases A and B (MAOA and MAOB) are the major catabolic isoenzymes of catecholamines and serotonin in the mammalian brain. Although the distribution of the monoamine oxidase protein has been mapped by ligand binding and immunohistochemistry, the sites of MAOA and MAOB synthesis have not been precisely determined. In this study, we used in situ hybridization to visualize MAOA and MAOB mRNA in the rat brain by using specific cDNA and oligonucleotide probes. MAOA mRNA was localized in major monoaminergic cell groups, such as the dorsal vagal complex, the C1/A1 groups, the locus ceruleus, the raphe nuclei, the substantia nigra, and the ventral tegmental area. MAOA mRNA was also found in forebrain structures, such as the cortex, the hippocampus, the thalamus, and the hypothalamus. In contrast to the distribution of MAOA mRNA, high levels of MAOB mRNA were present in only three brain regions: the area postrema, the subfornical organ, and the dorsal raphe. The in situ visualization of MAO mRNA demonstrates that MAOA mRNA synthesis is wide spread in many catecholaminergic and serotonergic cell groups, whereas MAOB mRNA synthesis is far more discrete and limited. The different expression patterns of MAOA and MAOB suggests that may also have different physiological functions.

Animals↗
PubMed1997

Increased stress response and beta-phenylethylamine in MAOB-deficient mice.

MAOA and MAOB are key iso-enzymes that degrade biogenic and dietary amines. MAOA preferentially oxidizes serotonin (5-hydroxytryptamine, or 5-HT) and norepinephrine (NE), whereas MAOB preferentially oxidizes beta-phenylethylamine (PEA). Both forms can oxidize dopamine (DA). A mutation in MAOA results in a clinical phenotype characterized by borderline mental retardation and impaired impulse control. X-chromosomal deletions which include MAOB were found in patients suffering from atypical Norrie's disease, which is characterized by blindness and impaired hearing. Reduced MAOB activity has been found in type-II alcoholism and in cigarette smokers. Because most alcoholics smoke, the effects of alcohol on MAOB activity remain to be determined. Here we show that targetted inactivation of MAOB in mice increases levels of PEA but not those of 5-HT, NE and DA, demonstrating a primary role for MAOB in the metabolism of PEA. PEA has been implicated in modulating mood and affect. Indeed, MAOB-deficient mice showed an increased reactivity to stress. In addition, mutant mice were resistant to the neurodegenerative effects of MPTP, a toxin that induces a condition reminiscent of Parkinson's disease.

Animals↗
PubMed1997

Expression of the Bacillus licheniformis PWD-1 keratinase gene in B. subtilis.

The kerA gene which encodes the enzyme keratinase was isolated from the feather-degrading bacterium Bacillus licheniformis PWD-1. The entire gene, including pre-, pro- and mature protein regions, was cloned with Pker, its own promoter, P43, the vegetative growth promoter, or the combination of P43-Pker into plasmid pUB18. Transformation of the protease-deficient strain B. subtilis DB104 with these plasmids generated transformant strains FDB-3, FDB-108 and FDB-29 respectively. All transformants expressed active keratinase in both feather and LB media, in contrast to PWD-1, in which kerA was repressed when grown in LB medium. With P43-Pker upstream of kerA, FDB-29 displayed the highest activity in feather medium. Production of keratinase in PWD-1 and transformants was further characterized when glucose or casamino acids were supplemented into the feather medium. These studies help understand the regulation of kerA expression and, in the long run, can help strain development and medium conditioning for the production of this industrially important keratinase.

Bacillus↗
PubMed1997

An extensive repeat structure down-regulates human monoamine oxidase A promoter activity independent of an initiator-like sequence.

The 5' flanking sequence of the human monoamine oxidase A (MAO A) gene consists of an extensive repeat structure. Two 90-bp repeats (I and II) were found in the core promoter (the 0.24-kb PvuII/DraII fragment), each containing two Sp1 binding sites. An additional six repeats were found, five of which (III-VII) were upstream and one (-I) downstream of the core promoter. Using transient transfection assay with a human growth hormone reporter gene, we found that the upstream repeating units III-VII (in a 0.78-kb BamHI/DraII fragment) down-regulate core promoter activity to 13 +/- 10% in a human glioma cell line (1242 MG) and 2 +/- 1% in a cervical carcinoma cell line (HeLa), respectively. The 0.24-kb core promoter activity was taken as 100%. Addition of the initiator (Inr)-like sequence to this 0.78-kb fragment (0.82-kb BamHI/-17 fragment) still showed decreased promoter activity (10 +/- 9% in 1242 MG cells and 8 +/- 1% in HeLa cells). Thus, the upstream sequence down-regulates promoter activity with or without the Inr-like sequence. When the Inr-like sequence was added to the core promoter (0.28-kb PvuII/-17 fragment), the promoter activity decreases significantly in both 1242 MG (55 +/- 6%) and HeLa (60 +/- 10%) cells. These results suggest that although the Inr-like sequence is present in the human MAO A promoter, it acts as a negative cis element instead of a transcription initiator.

Base Sequence↗
PubMed1996

The metabolism of tyramine by monoamine oxidase A/B causes oxidative damage to mitochondrial DNA.

Monoamine oxidases A/B (EC 1.4.3.4, MAO), flavoenzymes located on the outer mitochondrial membrane, catalyze the oxidative deamination of biogenic amines, such as dopamine, serotonin, and norepinephrine. In this study, we examined whether the H2O2 formed during the two-electron oxidation of tyramine [4-(2-aminoethyl)phenol] (a substrate for monoamine oxidases A/B) may contribute to the intramitochondrial steady-state concentration of H2O2 ([H2O2]ss) and, thus, be involved in the oxidative impairment of mitochondrial matrix components. Supplementation of intact, coupled rat brain mitochondria with benzylamine, beta-phenylethylamine, or tyramine showed initial rates of H2O2 production ranging from 0.4- to 1.6 nmol H2O2/min/mg protein. ESR analysis of the oxidative deamination of tyramine by intact rat brain mitochondria revealed the formation of hydroxyl (HO.) and carbon-centered radical adducts--the latter probably originating by the (HO.-)-mediated oxidation of mannitol. The signals were substantially enhanced upon addition of FeSO4 and were abolished by catalase. The intramitochondrial [H2O2]ss calculated in terms of glutathione peroxidase activity during the metabolism of tyramine was 48-fold higher (7.71 +/- 0.25 x 10(-7) M) than that obtained during the oxidation of succinate via complex II in the presence of antimycin A (1.64 +/- 0.2 x 10(-8) M). Oxidative damage to the brain mtDNA was assessed by single strand breakage. The ratio of nicked DNA for the preparations treated with tyramine and those without the amine was 1.5 +/- 0.29 (n = 4), 2.12 +/- 0.28 (n = 8, P < or = 0.05), and 3.12 +/- 0.69 (n = 3, P < or = 0.05) at 15, 30, and 60 min, respectively . Preincubation of mitochondria with tranylcypromine (trans-2-phenylcyclopropylamine), an inhibitor to MAO A/B, abolished mtDNA oxidative damage. Catalase inhibited mtDNA strand breakage by approximately 60%. Incubation of intact, coupled rat brain mitochondria with chlorodinitrobenzene (CDNB) depleted mitochondrial GSH by 72%. Tyramine-dependent damage of mtDNA was decreased by 68% in CDNB-treated mitochondria (with 28% remaining GSH). The [H2O2]ss was slightly increased in CDNB-treated mitochondria: 1.38- and 1.28-fold increase during the oxidation of succinate in the presence of antimycin A and during the oxidation of tyramine, respectively. These results suggest that the H2O2 generated during the MAO-catalyzed oxidation of biogenic amines and possibly certain neurotransmitters at the outer mitochondrial membrane contributes to the intramitochondrial [H2O2]ss and may cause oxidative damage to mtDNA. This is effected by the intramitochondrial concentration of GSH and might have potential implications for aging and neurodegenerative processes.

Animals↗
PubMed1996

Agenesis of the ductus venosus in a case of monochorionic twins which mimics twin-twin transfusion syndrome.

We describe a pair of monochorionic twins with clinical manifestation of twin-twin transfusion syndrome, including discordant fetal growth, hydrops of the larger twin, and the 'stuck twin' phenomenon of the smaller twin. In the hydropic twin, we found agenesis of the ductus venosus and an abnormal umbilical vein draining directly into the inferior vena cava. There was also marked enlargement of the right atrium, representing the volume overload on it. We believe that the agenesis of the ductus venosus in the larger twin may have contributed to the 'unbalanced shunting' between the monochorionic twins. This then led to a clinical picture mimicking that seen in the authentic twin-twin transfusion syndrome.

Adult↗
PubMed1996

Concordant body stalk anomaly in monozygotic twinning--early embryo cleavage disorder.

We describe a case of concordant body stalk anomaly in monozygotic twins that manifested with umbilical cord agenesis, evisceration of abdominal contents, and multiple gastrointestinal, genitourinary, and skeletal anomalies. Body stalk anomaly in twin gestation is extremely rare and poses an embryological interest. We suggest that the hypothesis of 'incomplete twinning' might contribute to the pathogenesis of this syndrome complex.

Abdominal Muscles↗