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Biomedical subjects

M H Chen

Publications and source records attributed to M H Chen.

At least 163 records · Page 9Linked to original sources
PubMed1991

Effects of ginseng stem-leaves saponins on one-way avoidance behavior in rats.

Using a multiple-trial, training-to-criterion procedure, the effects of repeated administrations of ginseng stem-leaves saponins (GSLS) on learning and memory of one-way avoidance in rats were studied in shuttle-box. In acquisition, GSLS 10, 30, and 60 mg.kg-1 ip shortened the latency of avoidance in a bell-shaped manner from 1.0 +/- 0.2 s in saline rats to 0.8 +/- 0.5, 0.5 +/- 0.1, 0.8 +/- 0.2 s (d 3 learning) and from 0.9 +/- 0.2 s to 0.8 +/- 0.2, 0.7 +/- 0.1, and 0.8 +/- 0.2 s (10 x 24 h memory), and the best dose was 30 mg.kg-1. GSLS 30 mg.kg-1 ip shortened the latency of avoidance prolonged by scopolamine 0.8 mg.kg-1 sc from 5.2 +/- 1.3 s to 3.9 +/- 0.8 s (d 1 learning acquisition) and from 2.2 +/- 0.6 s to 0.8 +/- 0.3 s (3 x 24 h memory acquisition). In retention, GSLS 30 mg.kg-1 ip shortened the latency prolonged by cycloheximide 2.5 and 5 mg.kg-1 ip from 3.4 +/- 1.0 s to 1.4 +/- 0.5 s (4 h memory) and from 1.6 +/- 0.3 s to 0.9 +/- 0.2 s (24 h memory), and increased the avoidance number decreased by cycloheximide 5 mg.kg-1 from 38.1 +/- 8.8% to 72.4 +/- 10.8% (4 h memory). The results indicate that GSLS facilitated the acquisition of learning and memory in rats, and improved the scopolamine amnesia and cycloheximide amnesia.

Amnesia↗
PubMed1990

Ischaemic brain damage associated with tissue hypermetabolism in acute subdural haematoma: reduction by a glutamate antagonist.

Ischaemia results in elevated extracellular glutamate concentrations, and drugs which act at the N-methyl-D-aspartate sub-type of glutamate receptor have been shown to decrease ischaemic brain damage. Because almost all patients who die after severe head injury demonstrate ischaemic brain damage, and acute subdural haematoma (ASDH) is one of the commonest complications of severe head injury, we have studied this condition in a rat model. Using double-label autoradiography, we have measured the effects of ASDH on cerebral glucose utilization and cerebral blood flow (RCBF). Following ASDH, increased glucose utilisation was observed in some cortical and hippocampal structures, without concomitant increases in blood flow. Directly below the ASDH, blood flow and glucose utilization were profoundly reduced. Pre-treatment with D-CPP-ene, a competitive NMDA antagonist, resulted in amelioration of hypermetabolism induced by the ASDH. The results suggest that NMDA antagonists may prevent ischaemic brain damage after ASDH by reducing hypermetabolism, induced by glutamatergic mechanisms.

Acute Disease↗
PubMed1990

Focal cerebral ischemia in the cat: pretreatment with a competitive NMDA receptor antagonist, D-CPP-ene.

The effects of the competitive N-methyl-D-aspartate (NMDA) receptor antagonist D-(E)-4-(3-phosphonoprop-2-enyl)piperazine-2-carboxylic acid (D-CPP-ene; SDZ EAA 494) upon ischemic brain damage have been examined in anesthetized cats. Focal cerebral ischemia was produced by permanent occlusion of the middle cerebral artery (MCA) and the animals were killed 6 h later. The amount of early ischemic brain damage was assessed in coronal sections at 16 predetermined stereotaxic planes. Pretreatment with D-CPP-ene (15 mg/kg i.v. followed by continuous infusion at 0.17 mg/kg/min until death), 15 min prior to MCA occlusion, significantly reduced the volume of ischemic brain damage (from 20.6 +/- 9.9% of the cerebral hemisphere in vehicle-treated cats to 7.2 +/- 4.4% in drug-treated cats; p less than 0.01). The competitive NMDA receptor antagonist D-CPP-ene is as effective as noncompetitive NMDA antagonists in reducing the amount of ischemic brain damage in this model of focal cerebral ischemia in a gyrencephalic species.

Animals↗
PubMed1990

Ischemic brain damage in a model of acute subdural hematoma.

Ischemic brain damage is the most important neuropathological finding in humans who die after acute subdural hematoma; however, its causes are poorly understood. We have produced acute subdural hematoma in the rat by injecting 400 microliters of autologous blood (approximately 20% of intracranial volume) into the subdural space. Extensive areas of ischemic damage, involving 14 to 16% of the volume of the hemisphere, developed in this model at 4 and 24 hours after the lesion. The hematomas were associated with a brief peak in intracranial pressure (51 mm Hg), which remained at three times normal levels (14 mm Hg) for 3 hours. In this model, therefore, ischemic damage appears to be due to the local effects of blood overlying the cortex at 4 hours after the ictus, rather than to globally raised intracranial pressure. The implications for the pathophysiology of acute subdural hematomas in humans are discussed.

Animals↗
PubMed1990

Study on growth kinetics of unstable recombinant Saccharomyces cerevisiae.

A mathematical model is suggested to describe effects of intracellular inhibition on growth of the recombinant yeast cells. The inhibition of the growth of the Leu+ phenotype cells depends upon the increase of plasmid concentration, the copy numbers and the accumulated amount of hepatitis B surface antigen protein, the expressed gene product. Simulating the growth of plasmid-free cells gives possible age-time distribution corresponding to their formation. According to the growth trajectories of these two different phenotype cells, a relation between Leu- phenotype cell growth and recombinant plasmid loss frequency is obtained. Consequently the instability of recombinant plasmid appearing in fermentation by genetically engineered S. cerevisiae is affected mainly due to (1) regular partitioning of Leu- phenotype combined with asymmetric plasmid segregation, and (2) different growth rates of plasmid-containing and plasmid-free cells in complex medium.

Cell Division↗
PubMed1990

Focal ischemic damage is reduced by CPP-ene studies in two animal models.

We have studied a new high-affinity competitive N-methyl-D-aspartate antagonist, D-CPP-ene (SDZ-EAA 494), in two models of focal cerebral ischemia. In the cat middle cerebral artery occlusion model (6 hours' survival), pretreatment with D-CPP-ene reduced infarct size by 64% (15 mg/kg dose) and 60% (4.5 mg/kg dose). There was no reduction in infarct size at a dose of 1.5 mg/kg. Treatment 1 hour after the occlusion reduced infarct size slightly, but not significantly. In a new model of subdural hematoma in the rat, the zone of cortical ischemic damage beneath the blood clot was reduced by 54% with D-CPP-ene pretreatment. Neuroprotective efficacy in a gyrencephalic species comparable to that of noncompetitive antagonists thus can be achieved with this agent. These experiments also indicate that competitive N-methyl-D-aspartate antagonists may be clinically useful after traumatic intracranial hematomas.

Animals↗
PubMed1989

Promoting effect of croton oil on the induction of cervical and vaginal cancers with herpes simplex virus types 1 and 2 in mice.

Hybrid Swiss virgin mice (Kuan-min strain) were challenged intravaginally with uv-inactivated herpes simplex virus type 1 (HSV-1) or type 2 (HSV-2) twice a week for 16 times and subsequently with croton oil or control medium twice a week for 27 times. After a period of 180 days the exposure to HSV-2 plus control medium induced premalignant and malignant lesions of the cervix and vagina in 50.0% of the mice. The exposure to HSV-2 plus croton oil induced similar lesions in 78.2% of the mice. The exposure to HSV-1 combined with either control medium or croton oil induced lesions in 37.2 and 58.3% of the mice, respectively. No malignant lesions were found in the control mice. These results reveal that (1) HSV-1 and HSV-2 have a similar oncogenic potential, and (2) croton oil can promote the induction of cervical and vaginal cancers with HSV-1 and HSV-2. Additionally, these results suggest that the virus-induced carcinogenesis of cervix and vagina might be similar to the classical two-stage carcinogenesis model. This animal model seems to be more suitable for studying the prevention and treatment of cervical and vaginal cancers because the period of this experiment is significantly shorter than that of experiments reported by other investigators and the frequency of the malignant lesion is significantly higher than or similar to that of the same lesion reported in other experiments.

Animals↗
PubMed1989

Transfer function analysis of autonomic regulation. II. Respiratory sinus arrhythmia.

An efficient new technique was developed to investigate heart rate control at all physiologically relevant frequencies by using respiratory activity as a frequency probe of the autonomic nervous response. The transfer function from respiratory activity to heart rate was determined during 6-min periods in which the respiratory rate was voluntarily controlled in a predetermined but erratic fashion. Changes in posture were used to manipulate autonomic balance. Respiratory sinus arrhythmia was determined to be a frequency-dependent phenomenon with the magnitude and phase characteristics of a low-pass filter. In agreement with previous work, at typical respiratory frequencies (greater than 0.15 Hz) increases in heart rate occurred simultaneously with the onset of inspiratory activity; however, at frequencies less than 0.15 Hz the phase relationship was quite different, such that increases in heart rate preceded inspiration. Between 0.15 and 0.45 Hz, the transfer magnitude was consistently lower while the subjects were in the upright posture than when in the supine posture, but below 0.15 Hz, it was equal in both postures. A model for respiratory modulation of heart rate, based on the atrial rate response characteristics determined in the companion paper [Am. J. Physiol. 256 (Heart Circ. Physiol. 25): H142-H152, 1989], suggests that the magnitude and phase characteristics of the subjects in the supine and upright postures differ because of relatively increased sympathetic outflow in the upright posture. A precise and efficient characterization of respiratory sinus arrhythmia can yield considerable insight into the autonomic regulation of the heart.

Adult↗
PubMed1989

Effects of culture medium composition and temperature on hepatitis B surface antigen expression by recombinant yeast in fermentation processes.

Hepatitis B surface antigen (HBsAg, an exogenous protein) was produced by fermenting recombinant Saccharomyces cerevisiae containing the HBsAg gene. The relative HBsAg concentrations increased from 3.89 to 8.12 when glucose content was reduced and the culture medium was supplemented with glycerol and sucrose; specific activity also increased by a factor of 2.69. The temperature variation sequence for fermentation processes was established from experimental results. The amount of HBsAg gene expressed reached 13.51 in relative concentration terms. The stability of the recombinant plasmid containing the HBsAg gene was studied by the varying fermentation temperatures in a fed-batch process. There was a conversion activity distribution for the yeast containing the exogenous DNA, which affected HBsAg production by the genetically engineered yeast in fermentation processes.

Cloning, Molecular↗
PubMed1989

Effect of pH value and dissolved oxygen concentration on expression of hepatitis B surface antigen by genetically engineered yeast in fermentation processes.

Both cell growth and expression of hepatitis B surface antigen (HBsAg) interact with each other in fermentation to produce exogenous protein HBsAg by genetically engineered yeast, S. cerevisiae, which contains the HBsAg gene. Since both processes required proper pH values in order to improve the overall yield, a suitable pH value sequence was determined. It is important that dissolved oxygen concentration in fermentation should be controlled to maintain the stability of recombinant plasmids and to obtain the high HBsAg expression. When the concentration of dissolved oxygen was controlled at 70% saturation, the stability of recombinant plasmid was maintained at 73%, and the relative concentration of HBsAg expression was found to be 98.6.

Fermentation↗
PubMed1989

Viral etiology of cervical carcinoma. Human papilloma virus and herpes simplex virus type 2.

The possible role of human papilloma virus (HPV) and herpes simplex virus type 2 (HSV-2) in the viral etiology of cervical carcinoma was investigated a series of cervical lesions were studied for the presence of HPV and HSV-2 DNA sequences as well as HPV and HSV-2 antigens by DNA dot blot hybridization technique and high-specificity PAP staining method. The results obtained were correlated with the histologic diagnosis. HPV 16 DNA sequences detected in cervical carcinoma biopsies were 43%, whereas HSV-2 DNA sequences were only 8%. HPV antigens detected in cervical dysplasia were 31%, whereas those detected in cervical carcinoma and cervicitis were the least. HSV-2 antigens were detected in chronic cervicitis, dysplasia and cervical carcinoma. The difference in positive rate between the cervical carcinoma and cervicitis groups was statistically significant, (chi-square test, P less than 0.01). No HPV DNA and HSV-2 DNA sequences were found in the same specimen, although both HPV DNA sequences and HSV-2 antigens were found in the same sample in some cases. The results indicate that the viral etiology of cervical carcinoma may be multifactorial. Both HSV-2 and HPV may be associated with cervical carcinoma, but the mechanisms involved are different. HSV-2 and HPV may act synergistically in the development of cervical carcinoma.

Antigens, Viral, Tumor↗
PubMed1989

In vitro fertilization, gamete intrafallopian transfer and combined IVF-GIFT results: three-year experience at Chang Gung Memorial Hospital.

A review is presented summarizing the IVF-ET, GIFT and combined IVF-ET-GIFT experienced at Chang Gung Memorial Hospital. Since the building of an aseptic dust free laboratory next to the operation room, the clinical pregnancy rate has been 12.2% per embryo transfer in IVF-ET, 16.7% in the GIFT program and 30.0% in the combined IVF-GIFT program. The overall clinical pregnancy rate was 14.9%. The overall pregnancy rate appeared to be independent of the causes of infertility, be it tubal factor, endometriosis or unexplained infertility. It was lower in couples with male factor or combined factors. The different regimens for follicular stimulation were hMG-hCG, clomiphene-hMG-hCG and FSH-hMG-hCG. No one regimen showed a better pregnancy rate than the others. The methods of oocyte retrieval were laparascopy, laparotomy, transbladder ultrasound-guided, and transvaginal ultrasound-guided retrieval. There were 4.53 oocytes retrieved pertreatment cycle. The transvaginal ultrasoundguided oocyte retrieval has greatly simplified the procedures in the IVF-ET program. The patient selection was important not only for the indications but also for the methods of IVF-ET, GIET and combined IVF-GIFT.

Evaluation Studies as Topic↗
PubMed1989

Effects of ginsenosides on release of [3H]norepinephrine from rat vas deferens and portal vein.

The effects of ginsenosides (G) on the release of [3H]norepinephrine ([ 3H]NE) from the isolated rat vas deferens (RVD) and portal vein (RPV) preloaded with [3H]NE were studied, G (100 micrograms/ml) did not affect the spontaneous or high potassium (H-K+, 60 mmol/L)- and tyramine (Tyr 10 mumol/L)-evoked release of [3H]NE, but obviously blunted the phentolamine (Phe 10 mumol/L)-induced increase in [3H]NE release from RVD and enhanced the isoprenaline (Iso 0.1 mumol/L)-augmented [3H]NE release from RPV evoked by H-K+. It is still not known whether G can bind with adrenoceptors. We infer that G may act as a modulator in sensitizing both presynaptic alpha 2- and beta-receptors.

Animals↗
PubMed1987

Burn-induced alterations in feeding, energy expenditure, and brain amine neurotransmitters in rats.

A 30% body surface area, open-flame, full-thickness burn of adult rats induced a 4-day period of anorexia that was followed by hyperphagia beginning on postburn day 10. The hyperphagic burned rats also exhibited increased resting energy expenditure and no gain in body weight, suggesting hypermetabolism. Plasma levels of immunoreactive insulin and albumin were decreased in both groups of burned rats; immunoreactive pancreatic glucagon concentrations were elevated only in the anorectic burned rats. Plasma levels of epinephrine were elevated in the hyperphagic burned rats. In the brain, dopamine metabolism appeared to be increased in the corpus striatum, nucleus accumbens, and amygdala of anorectic burned rats; norepinephrine levels were elevated in the hypothalamus and nucleus accumbens of the hyperphagic-hypermetabolic rats. These data indicate that this animal model of major burn trauma exhibits anorexia, hyperphagia, catabolism, and hypermetabolism. Furthermore, elevated dopamine metabolism appears to be associated with the anorexia, while the hyperphagia-hypermetabolism may be mediated by norepinephrine.

Animals↗