Biomedical subjects

Z K Chen

Publications and source records attributed to Z K Chen.

33 records · Page 2Linked to original sources

PubMed1997

[Tissue concentration and secretion of renin in human placental villi during early pregnancy].

In this study, tissue concentrations of renin and angiotensins in human placental villi during early pregnancy and contents of renin and angiotensin I (A I) secreted by cultured chorion were measured by radioimmunal assay (RIA). The results are as follows. During early pregnancy, the human chorion contains renin and A II. The activity of renin is much higher at 6th week of gestation, but as gestation proceeds, it decreases gradually, while A II shows somewhat increased change. The activity of renin secreted by cultured chorion can also be measured. A I in human placental villi can not be detected by RIA in chorion leaves or their culturing fluid. These results indicate that renin-angiotensin system may exist independently in human placental villi during early pregnancy.

Angiotensin I↗

PubMed1996

Amplification of natural regulatory immune mechanisms for transplantation tolerance.

There is a need to derive donor-specific tolerance in clinical organ transplantation, where potential benefits remain overshadowed by chronic rejection and side effects of continual immunosuppressive therapy. It is known that the mature immune system in mice can be reprogrammed to accept a foreign graft as if it were "self." Here we show that, once generated, this state of operational tolerance becomes self-sustaining, imposing itself on new cohorts of lymphocytes as they arise. These new cohorts retain specificity for the tolerizing antigen and can be selectively amplified to tolerate new antigens that have linked expression with the original tolerogen. Regulation is critically dependent upon the continuous presence of tolerizing antigen and is mediated by the CD4+ lymphocyte population. We propose that such natural mechanisms of immune regulation may eventually be exploited for transplantation tolerance, even in fully immune-competent recipients.

Animals↗

PubMed1995

[Effects of stimulating rabbit's cerebral cortex on respiratory frequency and amplitude].

The effects on respiration upon stimulation of different areas of cerebral cortex were studied in 38 urethance anesthetized rabbits after both vagotomy and section of the maxillary division of trigeminal nerves. The results showed that: (1) Light continuous stimulations of the limb motor area (L) enforced inspiration by increasing respiratory frequency (RF) and tidal volume (TV). Stimulation of the facial motor area (F) increased RF notably, but depth of expiration and inspiration were notably decreased. Upon stimulation of the masticatory motor area (M), expiration or inspiration was accentuated, RF and TV were obviously increased. Upon stimulation of the posterior orbital area RF and TV were decreased markably. No obvious effects on respiration were observed on stimulation of the other areas of the cortex. (2) With shortened total period of stimulation, a stimulating L, F or M area would cause a longer period of apnoea after expiration and resumption of inspiration insured an increased TV.

Animals↗

PubMed1992

[Antidotal effects of 2,3-dimercaptopropane-1-sulfonate sodium (DMPS) and combined with diazepam on acute poisoning caused by sodium ammonium dimethyl-2-propano-1,3-dithiosulfate monohydrate (SCD)].

In mice, DMPS (250 mg/kg, i.v.) combined with diazepam (1.25 mg/kg, i.p.) could increase LD50 of p. o. SCD 5.3 times. DMPS (62.5 mg/kg, i.v.) antagonized completely the respiratory depression and neuromuscular blockade caused by SCD(7.5 mg/kg, i.v.) in rabbits. SCD (15 mg/kg, i.v.) caused tremor, tonic convulsion and the abnormal paroxysmal discharges in EEG in rabbits. DMPS (0.5 mg/kg, i.c.v) could not eliminate the abnormal paroxysmal discharges in EEG of rabbits. DMPS (62.5 mg/kg, i.v.) combined with diazepam (5 mg/kg, i.v.) completely and rapidly antagonize these toxic symptoms and the abnormal changes in EEG.

Animals↗

PubMed1990

[Neuromuscular blocking and respiratory depressing actions of sodium ammonium dimethyl-2-(propano-1,3-dithiosulfate) monohydrate].

The neuromuscular blocking and respiratory depressing actions of the new insecticide sodium ammonium dimethyl-2-(propano-1,3-dithiosulfate) monohydrate (SCD) were investigated. In peroneal-tibialis anterior nerve-muscle preparations of urethane anesthetized rabbit, SCD 6.5 mg/kg iv completely depressed the indirectly elicited twitch tension but not the directly elicited one. This compound also caused initial potentiation of the indirectly elicited twitch tension. In the partially paralyzed preparations, potentiation of contractions occurred following a brief period of indirectly tetanic stimulation. Nereistoxin but not SCD blocked the indirectly elicited twitch tension of isolated rat diaphragm. The neuromuscular blockade induced by SCD and nereistoxin was antagonized by neostigmine and 4-aminopyridine. SCD and nereistoxin had little or no effect on arterial blood pressure and phrenic nerve discharge of rabbits. The results indicated that SCD-poisoned rabbits died of respiratory paralysis following the neuromuscular blockade.

Animals↗

PubMed1990

[Antidotal effects of sulfhydryl compounds on acute poisonings by sodium ammonium dimethyl-2-(propane-1,3-dithiosulfate) monohydrate, nereistoxin and cartap].

Sodium dimercaptopropanesulphonate (DMPS) and sodium dimercaptosuccinate (DMS) were discovered to be effective antidotes for acute poisoning of insecticides SCD [sodium ammonium dimethyl-2-(propane-1,3-dithiosulfate) monohydrate], nereistoxin (4-N,N-dimethylamino-1,2-dithiolane) and cartap (dihydronereistoxin dicarbamate). In mice, DMPS (250 mg/kg) or DMS (1000 mg/kg) ip 20 min before SCD increased LD50 of ig SCD from 97 to 374 or 251 mg/kg, respectively. The prophylactic effect of DMPS was better than that of DMS. Administration of DMPS prior to cartap increased LD50 of ig cartap from 130 to 375 mg/kg. The therapeutic effect of DMPS was also demonstrated in SCD-poisoned conscious rabbits. DMPS 62.5 mg/kg or DMS 500 mg/kg iv completely antagonized the neuromuscular blockade and respiratory depression caused by SCD, nereistoxin and cartap in anesthetized rabbits. The antagonism of SCD-induced neuromuscular blockade by cysteine (400 mg/kg, iv) was less effective and of shorter duration than that by DMPS and DMS. Dimercaprol 50 mg/kg im showed little effect on SCD-induced paralysis. The antagonistic actions of sulfhydryl compounds on neuromuscular blockade induced by these insecticides probably belong to chemical antagonism.

Animals↗

PubMed1986