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Biomedical subjects

Y Xie

Publications and source records attributed to Y Xie.

At least 433 records · Page 24Linked to original sources
PubMed1989

Rice alcohol dehydrogenase genes: anaerobic induction, organ specific expression and characterization of cDNA clones.

Anaerobiosis rapidly induces alcohol dehydrogenase (ADH), an enzyme of the fermentation pathway, in different parts of rice seedlings. After initiation of anaerobiosis, the activity of the enzyme increases linearly for 3 days or more. The ADH activity is anaerobically inducible even in mature rice leaves in contrast to maize which shows no induction in mature leaves. Rice ADH activity can also be induced by an auxin analog, 2,4-dichlorophenoxyacetic acid, under aerobic conditions. The experimental results show that anaerobiosis increases the ADH mRNA level, indicating that the ADH enzyme is regulated at the transcriptional level. Starch gel electrophoresis of a protein extract from rice shows 3 distinct forms of ADH. The amounts of the 3 forms vary with the organ, suggesting that the expression of ADH genes is organ-specific. Sequencing data show that the two different cloned cDNA copies of ADH mRNAs are derived from two different genes.

2,4-Dichlorophenoxyacetic Acid↗
PubMed1989

Effect of barbiturate treatment on post-ischemic protein biosynthesis in gerbil brain.

The effect of barbiturate treatment on post-ischemic cerebral protein biosynthesis was studied in gerbils subjected to 5 min transient occlusion of carotid arteries followed by 2 h or 48 h recirculation. Ischemia induced a remarkable decline of amino acid incorporation into brain proteins in most forebrain structures. The initial inhibition recovered to near normal after 2 days recirculation in all regions except the vulnerable CA1 sector. Barbiturate treatment, which previously has been shown to prevent delayed neuronal death in CA1 sector, did not ameliorate the initial inhibition of protein synthesis but it significantly improved subsequent recovery, especially in the vulnerable CA1 sector of hippocampus. These observations indicate that delayed neuronal death in CA1 sector of hippocampus results from selective failure of post-ischemic recovery and not from selective ischemic injury of the protein synthesizing machinery. This explains that delayed neuronal death can be prevented by therapeutic interventions which are initiated during the post-ischemic recirculation phase.

Animals↗
PubMed1989

Ischemic threshold of brain protein synthesis after unilateral carotid artery occlusion in gerbils.

The threshold of the relation between regional cerebral blood flow and regional cerebral protein synthesis was investigated in gerbils submitted to a 1-hour occlusion of the left common carotid artery. Blood flow was measured with [131I]iodoantipyrine and protein synthesis with [14C]leucine using double-tracer autoradiography and trichloroacetic acid wash-incubation for removal of nonincorporated tracer radioactivity. Specific activity of blood and brain leucine and [14C]leucine incorporation into brain proteins was also measured by conventional high-performance liquid chromatography to validate the autoradiographic approach. In control gerbils, gray matter blood flow ranged between 180 and 220 ml/100 g/min and fractional amino acid incorporation was approximately 80%. Unilateral carotid artery occlusion resulted in graded ischemia with blood flow between 10 and 100 ml/100 g/min. Regional cerebral protein synthesis gradually declined at blood flows of less than 100 ml/100 g/min and approached 0 at a blood flow of 40 ml/100 g/min. This threshold for complete suppression of protein synthesis is much higher than that for maintenance of tissue energy state and suggests that the size of an infarct after focal ischemia is determined by the suppression of protein synthesis rather than by the breakdown of energy metabolism.

Amino Acids↗
PubMed1989

An alternative purging method: controlling the composition-dependent interaction in an analysis of rates.

The purging method controlling for the composition-group interaction developed by Clogg and his associates has proven useful in demographic research. This article proposes an alternative method, partial CD purging, that controls the interaction between composition and the dependent variable. The purged rates from this new method are invariant to changes in the marginal distribution of composition, but those from the earlier purging method are not. Mathematical relationships between the proposed method and other techniques are also explored.

Confounding Factors, Epidemiologic↗
PubMed1988

Presence of the atrial natriuretic factor (ANF) in human ascitic fluid.

Presence of atrial natriuretic factor (ANF)-like material was demonstrated by radioimmunoassay in ascitic fluid of 14 patients with cirrhosis of the liver. Immunoreactive ANF concentrations (M +/- SEM) were 2.4 +/- 0.5 fmol/ml in ascites, significantly lower (p less than 0.001) than the corresponding plasma concentrations of 15.5 +/- 2.6 fmol/ml. High performance gel permeation chromatography and reverse phase high performance chromatography of the ascitic ANF immunoreactivity showed correspondence to the alpha human ANF (99-126). ANF levels in ascites were significantly (p less than 0.01) correlated to levels in plasma (r = 0.66).

Ascites↗
PubMed1988

Effect of autologous clot embolism on regional protein biosynthesis of monkey brain.

Focal cerebral ischemia was produced in monkeys by injection of autologous clots into the left internal carotid artery. Regional protein synthesis was studied 2 hours after embolism by autoradiographic and biochemical evaluation of [3H]phenylalanine incorporation into brain proteins, and the results were correlated with electrophysiologic (electroencephalogram, evoked potentials) and light microscopic observations. Ischemic territories were clearly identified on autoradiograms as sharply demarcated areas with reduced radioactivity. The localization of regions with reduced protein biosynthesis correlated with the early postembolic suppression of evoked potentials but not with the (improved) functional state and the morphologic alterations at the end of the experiment. Suppression of amino acid incorporation, in consequence, is a long-lasting event that allows documentation of the initial embolic impact for at least 2 hours irrespective of the subsequent recovery process.

Animals↗
PubMed1988

[Pathophysiologic and clinical relevance of atrial natriuretic factor in patients with cirrhosis of the liver].

Defects of the ANF system in cirrhosis have not been demonstrated in terms of absolute deficiency of plasma levels or by evidence of major abnormalities of processing in patients with cirrhosis. In the present study, the responsiveness of the ANF system to acute volume stimulation by water immersion and the diuretic and natriuretic effects of ANF infusion were examined. Stimulation of ANF release by 1-h immersion was significantly blunted in ten cirrhotic patients with ascites (increase of plasma ANF by 46 +/- 18%), whereas 11 cirrhotics without ascites showed a 104 +/- 16% increase, similar to the 117 +/- 29% stimulation in 25 healthy controls. Immersion increased urinary volume by 3.6 +/- 0.6/2.0 +/- 0.8/0.7 +/- 0.4 ml/min and urinary sodium excretion by 146 +/- 38/75 +/- 43/43 +/- 19 mumol/min in controls/cirrhotics without/cirrhotics with ascites. Infusion of ANF for 30 min prompted an increase in diuresis and natriuresis in seven cirrhotic patients, which was less marked in patients with ascites, as compared to patients without ascites. Thus, the stimulus response coupling for ANF may be impaired in patients with cirrhosis and ascites.

Ascites↗
PubMed1986

Resistance to hypoglycemia of cerebellar transplants in the rat forebrain.

Prolonged insulin-induced hypoglycemia causes widespread loss of neurons and permanent brain damage with irreversible coma. Although the deprivation of carbohydrate stores affects all brain regions, the breakdown of energy metabolism and cessation of protein synthesis occur predominantly in the cerebral cortex, caudoputamen and hippocampus. The cerebellum, brain stem and hypothalamus are largely resistant. Following transplantation of the cerebellar anlage of rat fetuses (day 15 of gestation) into the caudoputamen of adult rats, the grafts were allowed to differentiate for a period of 8 weeks. The host animals were then subjected to 30 min of severe hypoglycemia with isoelectric EEG ('coma'). In contrast to the surrounding vulnerable brain structures, protein synthesis was fully preserved within the cerebellar transplant. Grafting of fetal forebrain cortex to the same location did not result in escape from hypoglycemic cell injury. This indicates that resistance to hypoglycemia is part of the programmed differentiation of the cerebellum and develops irrespective of its location and functional integration within the nervous system.

Animals↗
PubMed1986

Persistent inhibition of protein synthesis precedes delayed neuronal death in postischemic gerbil hippocampus.

Regional cerebral protein synthesis was investigated in the Mongolian gerbil during recovery from forebrain ischemia produced by bilateral common carotid artery occlusion for 5 min. At various recirculation periods up to 72 h animals received a single dose of L-(3,5-3H)tyrosine and were killed 30 min later. Brains were processed for autoradiography using the stripping film technique. During the initial 30 min of recirculation autoradiographs revealed an almost complete inhibition of protein synthesis in all forebrain structures with the exception of the medio-dorsal thalamic nuclei. Between 30 min and 12 h of recirculation amino acid incorporation was completely restored in neurons of the cerebral cortex, basal ganglia, hippocampal CA3 and CA4 zones and the dentate gyrus. In CA1, early (90-min postischemia) and progressive recovery of a few irregularly dispersed neurons was observed, but the vast majority of pyramidal cells never regained their normal biosynthetic activity. Between 3 and 6 h of recirculation CA1 neurons showed faint labeling, followed by a secondary deterioration resulting in complete lack of incorporation within 12 h after restoration of blood flow. Autoradiographs at all subsequent time points exhibited persistent inhibition of protein synthesis in CA1 until neuronal necrosis occurred 2-3 days later. Thus, in contrast to ischemia-resistant cell populations with rapid progressive and complete restoration of protein synthesis, hippocampal neurons undergoing delayed necrosis are characterized by an early incomplete recovery immediately followed by a secondary persistent inhibition.

Animals↗
PubMed1984

Regional impairment of protein synthesis in the rat brain during bicuculline-induced seizures.

Protein synthesis was investigated in rats subjected to 30 min of bicuculline-induced seizures using biochemical and autoradiographic techniques. Incorporation studies were performed on freely convulsive animals following systemic administration of either a tracer dose of L-[1-14C]tyrosine or a flooding dose (7.5 mmol/kg) of L-[1-14C]valine. Using a tracer dose, amino acid incorporation was only moderately reduced (forebrain) or slightly enhanced (cerebellum/brainstem and spinal cord) but the specific radioactivity of [14C]tyrosine in the acid-soluble pool was increased 3- to 5-fold in experimental animals. After a flooding dose of [14C]valine the specific activity of the precursor amino acid was similar in control and convulsed animals. Under these conditions incorporation rates in forebrain and cerebellum/brainstem were reduced to 54 and 75%, respectively. Reduction of amino acid incorporation was even more pronounced in extraneural tissues, e.g. liver (6%), intestine (14%) and kidney (15%). Inhibition of protein synthesis in forebrain and cerebellum/brainstem was paralleled by a similar extent of polyribosome disaggregation in these regions (53 adn 78% of controls). In anaesthetized, mechanically ventilated rats, 30 min of seizure activity reduced forebrain polyribosomes to a similar extent (57%). Extraneural (hepatic) protein synthesis was also affected in physiologically controlled rats, but cerebellar polysomes were completely preserved. Autoradiographic studies using 3H-labelled amino acids were carried out to identify nerve cell populations most heavily affected. In freely convulsive rats both tracer dose and pool overloading revealed a similar regional pattern with preferential inhibition of amino acid incorporation in forebrain cortex, thalamus and the pyramidal cell layer of the hippocampus. These sites were also affected in the physiologically controlled animal, but the focal distribution of hippocampal and thalamic neurones with reduced protein synthesis differed from that in freely convulsive rats.

Animals↗
PubMed1984

Regionally selective inhibition of cerebral protein synthesis in the rat during hypoglycemia and recovery.

Regional cerebral protein synthesis was investigated in anesthetized, mechanically ventilated rats during progressive insulin-induced hypoglycemia and the recovery period following glucose infusion. Polysome profiles from precomatose animals with slow wave/polyspike EEG revealed a slight reduction of polyribosomes and a concurrent increase in monoribosomes, but autoradiographs showed a pattern of L-[3-3H]tyrosine incorporation indistinguishable from that of control rats. During the initial 30 min of insulin-induced isoelectric EEG ("coma"), autoradiographs showed a selective inhibition of protein synthesis in neurons and glial cells of the hippocampus and cerebral cortex, i.e., regions with high susceptibility for the development of hypoglycemic brain damage. Basal ganglia were less affected and areas with low vulnerability (hypothalamus, brainstem, and cerebellum) exhibited a normal pattern of amino acid incorporation. Using a flooding dose of L-[1-14C]valine (7.5 mmol/kg; 15 microCi/mmol), the rate of incorporation in cerebral cortex and cerebellum was found to be reduced to 2% and 80% of control values, respectively. Inhibition of protein synthesis was paralleled by a breakdown of polyribosomes and a concomitant increase in ribosomal subunits, indicating a block in peptide chain initiation. After 90 min of isoelectric EEG all brain structures with the exception of hypothalamus and area postrema showed an almost complete lack of amino acid incorporation. Glucose infusion after a 30-min period of hypoglycemic coma led to a partial restoration of cortical and hippocampal protein synthesis. Within 70-90 min of recovery, L-[1-14C]valine incorporation into neocortical and cerebellar proteins amounted to 47% and 125% of fasted controls.(ABSTRACT TRUNCATED AT 250 WORDS)

Amino Acids↗