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Biomedical subjects

Y Cheng

Publications and source records attributed to Y Cheng.

At least 271 records · Page 15Linked to original sources
PubMed1994

[A plasmid-mediated SHV type extended-spectrum beta-lactamase in Beijing isolate of Enterobacter gergoviae].

By conjugation experiment, an extended-spectrum beta-lactamase (ESb1a) encoded on a transferable plasmid of approximately 60 Kilobases was found in a clinical strain of Enterobacter gergoviae isolated from Peking Union Medical College Hospital. Its E. coli transconjugant was resistant to all beta-lactams tested except cefoxitin and imipenem. Clavulanic acid, a classical beta-lactamase inhibitor, inhibited its activity. Hybridization with an intragenic probe for SHV-1 revealed that this ESb1a may be related to, or derived from SHV enzyme.

Ceftazidime↗
PubMed1993

Enterostatin--its ability to inhibit insulin secretion and to decrease high-fat food intake.

Enterostatin is a peptide which has been found to decrease food intake with a specificity for the fat contained in the food. In this work we have investigated the effect of enterostatin (Val-Pro-Asp-Pro-Arg) and its proteolytic fragments, des-arg-enterostatin (Val-Pro-Asp-Pro) and the tripeptide Asp-Pro-Arg, on insulin secretion. It was found that enterostatin and desarg-enterostatin inhibited insulin secretion from isolated rat islets by 55.3% (P < 0.05) and 53.6% (P < 0.05) at 1.6 x 10(-4) M concentration, while the tripeptide Asp-Pro-Arg at 1.6 x 10(-4) M concentration had no significant effect and increased insulin secretion by 33.0%. Enterostatin at 200 ng after intraventricular administration was found to inhibit the intake of a high-fat diet by 45.0%, while des-arg-enterostatin (200 ng) had no effect, in agreement with previous findings. The tripeptide Asp-Pro-Arg (200 ng) had no effect on the intake of a high-fat diet compared to saline injection. The ability of enterostatin to inhibit high-fat food intake and decrease insulin secretion may be important for the prevention of obesity and type II diabetes, conditions linked through hyperinsulinemia.

Amino Acid Sequence↗
PubMed1992

The biochemical mechanisms of the excitotoxicity of kainic acid. Free radical formation.

Kainic acid (KA) is a known potent neuroexcitotoxin, although the biochemical mechanism producing its underlying neurotoxic effect is not quite clear. Histopathological examination of gerbil brains 24 h after systemic injection of KA revealed severe neuronal lesions in different regions of the brain, especially the cerebellar and hippocampal areas. We have detected free radical formation in the brain 1 h after KA administration by using an in vivo spin trapping technique. We have also observed increased lipid peroxidation in the brain after KA-treatment by analyzing thiobarbituric acid reactive substances and conjugated diene formation. Diminished brain specific (Na+, K+)-ATPase activity was also found 2 h after KA injection and persisted to 24 h. It is possible that the free radical reaction is a primary cause of neuronal degeneration after KA administration.

Animals↗
PubMed1992

Maternal marijuana smoking alters respiratory timing in the fetal lamb.

The effect of single and repeated maternal marijuana smoke exposure on fetal breathing movements (FBMs) was investigated in 13 fetal lambs in the third trimester. These animals were surgically instrumented for long-term intrauterine recording of diaphragmatic electromyogram (EMG). Maternal inhalation of marijuana smoke [1.84% tetrahydrocannabinol (THC)] increased FBMs and resulted in a more continuous and regular breathing pattern. There was a significant increase in the number of breaths/h (p < 0.01) and the incidence of FBMs (p < 0.001) in the second hour. Breathing activity returned to presmoke level by the third hour. Duration of the longest breathing epoch was significantly increased from 16.8 +/- 3.3 min to 31.9 +/- 5.2 min (p < 0.005). Instantaneous breathing rate was much more stable in the second hour after marijuana exposure (p < 0.01). Inhalation of placebo smoke did not result in any significant change in either overall breathing activity or continuity and stability of the breathing rate. The effects of marijuana smoke on fetal breathing were not observed after repeated smoke exposure. These results suggest that tolerance develops rapidly to the respiratory stimulating effect of marijuana smoke in the fetus.

Animals↗
PubMed1992

Effect of emeriamine on exocrine and endocrine pancreatic function in normal and diabetic rats.

The effects of emeriamine, a new anti-diabetic drug, on exocrine and endocrine pancreatic function in normal and diabetic rats have been studied both in vivo and in vitro. It was found that emeriamine dose-dependently normalized the symptoms of hyperingestion and hyperposia in streptozotocin (STZ)-induced diabetic rats, with fasting glucose levels significantly decreased and insulin levels not changed. In STZ-induced diabetic rats, there was a significant increase in pancreatic lipase and trypsin contents and a sharp decrease in amylase content. These changes in lipase and trypsin, but not in amylase were normalized by administration of emeriamine. In the normal rat, emeriamine had no effect on either serum glucose or insulin levels, but significantly decreased the pancreatic amylase, lipase as well as trypsin contents by 68%, 58% and 51%, respectively. In vitro, emeriamine (10(-8) - 10(-4) mol l-1) had no effect on enzyme release from pancreatic acini either under basal or carbachol-stimulated conditions. Emeriamine inhibited glucose-induced insulin release from isolated pancreatic islets. In conclusion, emeriamine has an inhibitory effect on synthesis of pancreatic enzymes and on glucose-stimulated insulin release.

Amylases↗
PubMed1992

Developmental changes in continuity and stability of breathing in the fetal lamb.

Developmental changes in the continuity and stability of fetal breathing patterns were studied in 27 fetal lambs with chronically implanted electromyographic electrodes in the diaphragm throughout the third trimester (102-140 days). The results showed that there was a progressive decrease in the incidence of fetal breathing movements throughout the third trimester (P less than 0.001). This reduction in incidence of fetal breathing movements was due, in part, to a 20% decrease in the total number of breathing bursts at approximately 125 days (P = 0.05). The breathing patterns in both immature (less than 120 days) and mature fetal lambs were fragmented by a large number of pauses (interburst interval 6-10 s) and apneas (interburst interval greater than 10 s). Increase in gestational age was associated with a decrease in the number of pauses and apneas but longer apnea durations. The breathing pattern in fetuses less than 120 days old was more continuous than that in those greater than 120 days old, as demonstrated by significantly longer epoch durations (P = 0.013). There was no significant change in the continuity of the breathing pattern after 120 days. However, there was a significant increase in the stability of the instantaneous breathing rates throughout the third trimester. This was indicated by a significant increase in the percent of breathing bursts that occurred in stable clusters (P = 0.046), the number of bursts per cluster (P = 0.013), and cluster duration (P = 0.018). Thus an increase in stability appears to be the major developmental change in breathing control in late gestation.

Animals↗
PubMed1992

Fractal properties in fetal breathing dynamics.

The dynamic pattern of fetal breathing was studied in 17 fetal lambs with chronically implanted electromyographic electrodes in the diaphragm. The instantaneous breathing rate time series appeared similar on different time scales, with clusters of faster breathing rates interspersed with periods of relative quiescience, suggesting self-similarity. Distribution histograms of the interbreath intervals (IBIs) showed log-normal distribution for IBIs less than 1 s and inverse power-law distribution for IBIs greater than 1 s. The ratio of log-normal distribution to power-law distribution varied from approximately 2 at 102 days to approximately 30 by 130 days of gestation. Fast Fourier transform of the breathing rate time series revealed 1/f beta power spectra for all animals, with beta increasing linearly from 0.43 to 0.88 between 102 and 139 days. Studies in the newborn lamb showed further maturation in both the distribution characteristics of the IBIs, as well as in the 1/f power spectra, with beta approaching 1.0 at 2 days after birth. The inverse power-law relationship in the distribution of the IBIs, together with the 1/f beta power spectra, indicate scale invariance and suggest that fractal mechanisms are involved in the regulation of fetal breathing.

Animals↗
PubMed1992

[Effect of ketanserin on arterial baroreflex-blood pressure control in conscious hypertensive rats].

The effect of ketanserin on arterial baroreflex-blood pressure control (ABR-BP) were studied in conscious freely-moving spontaneously hypertensive rats (SHR) and renovascular hypertensive rats (RVHR). The ABR-BP was measured by using a new method comparing with the pressor responses (in area) to angiotensin II before and after blocking the baroreflex efferent pathway by guanethidine and methyl atropine. It was found that ketanserin enhanced markedly the ABR-BP in both groups of hypertensive rats (SHR: 51% to 74%; RVHR: 59% to 77%). This suggests that the enhancement of ABR-BP may be involved in the anti-hypertensive effects of ketanserin.

Animals↗
PubMed1992

Central opioid modulation of breathing dynamics in the fetal lamb: effects of [D-Pen2,D-Pen5]-enkephalin and partial antagonism by naltrindole.

The effects of opiates on fetal breathing movements (FBM) have been shown to be complicated, with stimulation at low doses and suppression at higher doses. Recent studies have shown that morphine-induced stimulation of FBM can be blocked by naloxonazine (NALZ), suggesting action at the mu 1 opioid receptor. To examine the role of delta receptors in modulating FBM, the effects of [D-Pen2,D-Pen5]-enkephalin (DPDPE) on breathing dynamics were studied in fetal lambs with chronically implanted diaphragmatic electromyographic electrodes. DPDPE given i.c.v. (4.6-465 nmol/hr) caused significant time and dose-related increases in the number of breaths/hr and the incidence of fetal breathing movements, without significant changes in blood pH, PCO2 or PO2. Higher doses resulted in an attenuation of the responses, with a significant decrease in breaths/hr at 465 nmol/hr. DPDPE also induced a much more continuous and regular breathing pattern. All DPDPE effects were completely abolished by pretreatment with i.v. naloxone, but were unaffected by naloxonazine pretreatment. Naltrindole did not alter the effects of DPDPE on breath number or incidence of FBM, but blocked the effects on continuity and regularity of the breathing pattern. These results demonstrate that DPDPE stimulates breathing activity as well as alters breathing dynamics in the fetal lamb. The differential sensitivity of these two actions to naltrindole suggest that they may be mediated by different delta receptor subtypes, and that the mu 1 receptor is not involved.

Analgesics↗
PubMed1992

Effects of ketanserin on blood pressure variability in conscious spontaneously hypertensive rats.

Computerized analysis of blood pressure (BP) was used to study for the effects of ketanserin (Ket) on BP and blood pressure variability (BPV). Rats were instrumented chronically and BP was sampled every 4 ms by a computer from 2:00 to 14:00. Then a single dose of Ket (3 mg.kg-1) was given iv. BP and heart period (HP) were recorded for the next 30 min. The results showed that Ket lowered systolic BP (26.7 kPa to 21.1 kPa), diastolic BP (20.5 kPa to 15.8 kPa), and systolic BPV (1.3 kPa to 0.94 kPa). Otherwise, a positive relationship was found between antihypertensive effects of Ket and BPV. These findings may be of importance in antihypertensive treatment.

Animals↗
PubMed1992

Pharmacokinetics and relative bioavailability of ofloxacin tablets in 12 healthy volunteers.

Single oral dose of tablet A (Daiichi Pharmaceutical Co Ltd, Japan) and B (Jining Pharmaceutical Factory, Shandong, China) of 300 mg ofloxacin (Ofl) were given to 12 Chinese healthy male volunteers in an open, randomized crossover study. Drug concentrations in serum and urine were assayed by HPLC and partial least squares spectrophotometric method, respectively. The serum concentration-time course after medication conformed to a 2-compartment open model with a first order absorption. Pharmacokinetic parameters after tablet B did not differ significantly from the corresponding values after tablet A. The bioavailability of tablet B was comparable to that of tablet A.

Adult↗
PubMed1991

Suppression of cyclobutane and mean value of 6-4 dipyrimidines formation in triple-stranded H-DNA.

We have determined the effect of H-DNA formation on the distributions of two ultraviolet (UV) light induced photoproducts--cyclobutane dipyrimidines and mean value of 6-4 dipyrimidines. A region of DNA containing the sequence (dT-dC)18.(dA-dG)18 was treated under conditions that specifically yield the triple-stranded H-y3 or H-y5 DNA structure and then irradiated with UV. The positions of cyclobutane dipyrimidines and mean value of 6-4 dipyrimidines were determined by T4 endonuclease V cleavage and by hot piperidine cleavage, respectively. Formation of H-DNA structures greatly decreased the photoproduct yield in the (dT-dC)18.(dA-dG)18 region but not elsewhere in the DNA. Suppression of photoproduct formation is greater in half of the repeat, reflecting whether the DNA is in the H-y3 or H-y5 conformation. Within the repeat, the suppression was less in the middle and toward the ends. Models for the suppression of photoproduct formation in H-DNA and the possible utility of our findings are discussed.

Base Composition↗