PubMed Health⌕ Search

Biomedical subjects

C C Zhang

Publications and source records attributed to C C Zhang.

At least 37 records · Page 2Linked to original sources
PubMed1994

[Memory-enhancing effects of argipressin and its relationship with periaqueductal gray].

Wistar rats were trained to perform shuttle-box active avoidance response. In experiment A, 43 rats were implanted cannulae in bilateral periaqueductal gray (PAG) and argipressin (Arg) was injected. Arg 0.15 or 0.3 ng but not 0.05 ng retarded the extinction of avoidance response. In experiment B, 37 rats were set up bilateral electrolytic lesions of PAG or sham lesioned. Arg (6 micrograms.kg-1, ip) was injected after training. PAG lesions blocked the influence of ip Arg on memory enhancement. The results indicated that Arg may act directly on CNS to modulated memory and PAG may play an important role in this process. This observation provided further support to the previous suggestion that certain limbic midbrain structures were involved in memory-enhancement by Arg.

Animals↗
PubMed1993

A gene encoding a protein related to eukaryotic protein kinases from the filamentous heterocystous cyanobacterium Anabaena PCC 7120.

Protein kinases play essential roles in the development of eukaryotic cells. These enzymes display various degrees of sequence similarity in their catalytic domains. This conservation has allowed the identification of protein kinases in a variety of organisms, including the Gram-negative bacterium Myxococcus xanthus. In this study, sequences related to those encoding eukaryotic protein kinases were amplified by PCR from DNA of Anabaena PCC 7120, a filamentous cyanobacterium that differentiates cells specifically for nitrogen fixation, called heterocysts, under conditions of combined nitrogen limitation. Results from Southern hybridization and sequencing of PCR products suggest the presence of a family of similar protein kinases in this strain. One of the corresponding genes (pknA) was isolated from a gene library. The N-terminal region of its amino acid sequence shows significant similarity to the catalytic domains of eukaryotic-type protein kinases. Expression of this gene was found to be developmentally regulated. Inactivation of pknA led to colonies that appeared light green and rough in the absence of combined nitrogen. Mutant filaments produce fewer heterocysts than wild-type ones. These results suggest that pknA is required for both normal cellular growth and differentiation of Anabaena PCC 7120.

Amino Acid Sequence↗
PubMed1993

[Design of the scorpion-like dynamic nitinol osteo-connector and its use in the treatment of fractures and the nonunion of the upper extremity tubular bones].

Preparation of the scorpion-like dynamic nitinol osteo-connector (NT-SDOC) and its clinical application in 57 cases were reported. The apparatus was designed with two longitudinal pressure hooks and two to eight semicircular fixation hooks, which could exert an axial continuing stress of 24-56kg on the fracture ends until bone union. Of the 57 cases 31 were fracture and 26 were nonunion, as no plaster cast was applied postoperatively, all patients could exercise their injured arms early. Follow-up was 4 to 32 months with an average of 13.7 months. The osteo-plate substitution was shown at the fracture site at an average of 2.2 months in 31 cases, and at the nonunion site with an average of 3.64 months in 26 cases. No postoperative infection, nonunion and other complications were observed NT-S DOC was removed in 46 cases at about 6 months postoperatively. No refracture occurred at the osteo-plate substitution site.

Adult↗
PubMed1992

Segmental determination in Drosophila conferred by hunchback (hb), a repressor of the homeotic gene Ultrabithorax (Ubx).

The activity of homeotic genes in Drosophila cells determines segment-specific morphogenesis. Here, we provide evidence that the product of hunchback (hb), a segmentation gene, acts as a direct repressor or "silencer" of the homeotic gene Ultrabithorax (Ubx) and thus prevents ectopic activity of this gene: we show, by stable integration of reporter gene constructs, that hb protein binding sites are capable of repressing at a distance the activity of an embryonic Ubx enhancer outside the Ubx expression domain. This silencing activity is observed at advanced embryonic stages, at a time when the hb gene product is no longer detectable or required, and is dependent on the function of Polycomb (Pc). We propose a working hypothesis as to how hb protein in a "hit-and-run" fashion may effect stable and heritable silencing of the Ubx gene throughout advanced stages of development, thus mediating repression of this homeotic gene outside its realm of function.

Animals↗
PubMed1992

[Effects of intrahippocampal injection of 6-OHDA on acquisition and retention of avoidance response in rats].

The role of hippocampal noradrenergic and dopaminergic transmission in the acquisition and retention of active conditioned avoidance behavior was investigated in rats by injection of 6-hydroxydopamine (6-OHDA) into dorsal hippocampus. The main results are as follows: (1) After injection of 6-OHDA the contents of dopamine, particularly norepinephrine (P < 0.01) in the hippocampus was decreased significantly. (2) The acquisition of conditioned avoidance behavior was markedly impaired. (3) The facilitating effect of AVP on retention of active conditioned avoidance behavior could be eliminated by prior injection of 6-OHDA bilaterally into hippocampus.

Animals↗
PubMed1992

[Arterioembolization with shape memory angioembolus. Experimental study and clinical application].

The results of experimental study and clinical application of arterio-embolization induced by the conical spiral or rugby spiral type of shape memory angioembolus(Nitinol-Conical Rugby Embolus, NT-CRE) were reported. The NT-CRE has a spring coil as its base line and is formed like a conical spiral or rugby spiral which has a two-way memory effect. Through a period of 1-48 weeks observation on 74 angiographic and histological specimens of 39 target arteries from 20 experimental dogs showed that the NT-CRE has good histocompatibility and is effective for embolization in large-bored arteries. Clinical application on target arteries of 7 patients showed successful occlusion of blood flow in 5-18 minutes in arteries with internal diameters of 3.33-5.83 mm. The NT-CRE being of the two-way memory effect and its configuration of relatively close state render its catheterization and release into target vessel simple, save, rapid and effective. In the researches we have not found any complication of hemorrhage from ruptured blood vessels and misembolization from regurgitation.

Adult↗
PubMed1992

[Effect of hippocampal injection of oxytocin on shuttle-box avoidance behavior of rats].

Bilateral dorsal hippocampal injection of oxytocin (Oxy, 50 pg, on each side) in rats impaired the acquisition of conditioned avoidance behavior and accelerated the extinction of conditioned avoidance behavior in shuttle-box. The data suggested that the effect of Oxy on shuttle-box conditioned avoidance behavior of rats was at least partly accomplished via the hippocampus; Oxy affected short-term memory as well as long-term memory.

Animals↗
PubMed1991

Target sequences for hunchback in a control region conferring Ultrabithorax expression boundaries.

Boundaries of Ultrabithorax expression are mediated by long-range repression acting through the PBX or ABX control region. We show here that either of these control regions confers an early band of beta-galactosidase expression which is restricted along the anteroposterior axis of the blastoderm embryo. This band is succeeded by a stripe pattern with very similar anteroposterior limits. Dissection of the PBX control region demonstrates that the two patterns are conferred by distinct cis-regulatory sequences contained within separate PBX subfragments. We find several binding sites for hunchback protein within both PBX subfragments. Zygotic hunchback function is required to prevent ectopic PBX expression. Moreover, the PBX pattern is completely suppressed in embryos containing uniformly distributed maternal hunchback protein. Our results strongly suggest that hunchback protein directly binds to the PBX control region and acts as a repressor to specify the boundary positions of the PBX pattern.

Animals↗
PubMed1991

[Effects of cholinergic agonists and antagonists on unit discharge of dorsal hippocampal CA1 area in rat].

The effects of icv cholinergic agonists (acetylcholine 6 micrograms, physostigmine 10 micrograms, and nicotine 20 micrograms) and cholinergic antagonists (scopolamine 40 micrograms and hexamethonium 250 micrograms) on 174 cells unit discharges of the dorsal hippocampal CA1 area in 42 rats were studied. The frequencies of the unit discharges were increased in 41 cells over 84 cells by icv M or N receptor cholinergic agonists, but reduced in 22 cells over 42 by M or N receptor cholinergic antagonists. After the electrolytic lesion of the septal region, the effects of acetylcholine and nicotine on unit discharges disappeared. The results indicated that the cholinergic agents changed the electric activity of cholinergic sensitive neurons via the septum-hippocampal cholinergic pathway.

Acetylcholine↗
PubMed1990

Effects of alfentanil on isolated cardiac tissues of the rabbit.

Alfentanil causes cardiac stimulation or depression in intact animals and in clinical practice; there is no information concerning its direct effects on the heart. Therefore, we studied the effects of alfentanil on isolated cardiac tissues from young adult rabbits. The right atrium with sinoatrial node (SA node) was beating spontaneously, and the left atrium and papillary muscle were stimulated. Isometric contraction was monitored. Alfentanil, in concentrations of 0.05-0.5 mM, decreased by 6%-55% the frequency of contractions of the right atrial-SA node in a dose-related manner. In left atria and right atrial-SA node, but not in papillary muscle, alfentanil in concentrations greater than or equal to 0.01 mM increased the peak developed force and its maximum rate of increase. The time-to-peak developed force was prolonged in papillary muscle but not in right atrial-SA node and left atria. The maximum rate of fall of peak developed force was increased in left atria and decreased in papillary muscle by the administration of alfentanil. The time-to-50% relaxation of peak developed force was not consistently affected by alfentanil in all three muscle preparations. The same concentrations of alfentanil (greater than or equal to 0.01 mM) increased resting force in papillary muscle but not in left atria or right atrial-SA node. It is concluded that alfentanil has direct positive inotropic and negative chronotropic effects on the heart and that it causes contracture of ventricular myocardium.

Alfentanil↗
PubMed1989

Intracellular mechanisms of halothane's effect on isolated aortic strips of the rabbit.

The intracellular mechanisms of halothane action were examined in vascular smooth muscle from the aorta. Medial layers of the aorta from rabbits were mounted on photodiode tension transducers, stretched to 20 mg resting tension, and "skinned" with saponin. The skinned fiber preparations were then immersed in bathing solutions to study the effects of halothane (0.5-2%) on Ca2+ activation of the contractile proteins, and Ca2+ uptake and release from the sarcoplasmic reticulum (SR) using caffeine-induced tension transients. For comparison, isolated intact aortic rings were mounted on Blinks' dual tissue bath and attached to force transducers. The preparations were contracted with either 40 mM KCl, or norepinephrine (NE) followed by acetylcholine (ACh)- or sodium nitroprusside (SNP)-induced relaxation. At steady state contraction or relaxation, the effects of halothane (1-3%) were studied. The steady state tension during halothane was expressed as a percentage of the steady state tension before administration of halothane. In the isolated intact aortic rings, halothane (1-3%) produced biphasic effects on KCl-induced tension, i.e., an initially slight increase followed by decreases, independent of endothelium. Halothane markedly increased tension in the ACh- or SNP-relaxed state. The effects were dose-dependent. In the skinned aortic strips, halothane slightly decreased maximum Ca2+-activated tension development of the contractile proteins. Halothane decreased Ca2+ accumulation in the SR and increased Ca2+ release from the SR in a dose-dependent manner. The halothane-induced increases in Ca2+ release from the SR were blocked by ryanodine, an SR Ca2+ release channel blocker. It is concluded that halothane directly causes vascular contraction or relaxation, depending on the condition, and that halothane's effects on the SR may play a role.

Acetylcholine↗
PubMed1989

Molecular and genetical analysis of the fructose-glucose transport system in the cyanobacterium Synechocystis PCC6803.

Complementation for glucose transport capacity of deficient mutants from Synechocystis PCC6803 allowed the cloning of the corresponding gene, glcP. The protein predicted from one open reading frame (ORF) in the DNA sequence was 468 residues long. It showed 46-60% amino acid sequence homology and similarity in size and predicted structure (including twelve probable membrane-spanning regions) with a group of non-phosphorylating sugar transporters from mammals, yeasts and Escherichia coli. A second ORF, 64 base pairs downstream from glcP, was detected. Its function, dispensable under auto- and heterotrophic conditions, could not be determined. Genetic analysis of mutants confirmed that the resistance to fructose, acquired simultaneously with the deficiency in glucose transport, resulted from mutations in the glcP gene, whose approximate location could be determined.

Amino Acid Sequence↗
PubMed1989

[The endogenous opiate and nonopiate analgesic system].

A lot of researches indicate that central nervous system not only exist endogenous opiate analgesic system but also possess endogenous nonopiate analgesic system. The opiate and nonopiate analgesic systems can be selectively activated by different environmental or artificial manipulations and modulated the stimulation-produced analgesia, acupuncture analgesia and stress-induced analgesia, including the foot shock-induced analgesia, tail-shock-produced analgesia, ear-shock-induced analgesia, analgesia of cold water swim, analgesia of immobilization or of restraint and analgesia of a-Deoxy-D- glucose and so on. The existence and description of these modulatory mechanisms have it's multiplicity and important clinical implications for the treatment of pain.

Acupuncture Analgesia↗
PubMed1989

[Study of Ag-NOR, SCE and micronucleus in peripheral blood lymphocyte of chromate producers].

Ag-NOR, SCE and micronucleus test of peripheral blood lymphocyte obtained from 31 chromate producers had been studied. We found that (1) in the workers who had been exposed over eight years, the frequency of Ag-NOR, Ag-AA and SCE were 6.905 +/- 1.100, 0.380 +/- 0.652 and 8.190 +/- 3.727, but in the control group, 6.512 +/- 1.595, 0.215 +/- 0.529 and 7.171 +/- 2.683, respectively. So there was considerably significant difference between the exposed and the unexposed (P less than 0.01); (2) the frequency of micronuclei was 3.71 +/- 1.419% in the exposed group; however, in the control group it was 0.333 +/- 0.479%. So there was also remarkably significant difference between them (P less than 0.001). The observations lead the authors to conclude that the genetic material of the workers who have been working over eight years may be damaged because of being exposed to chromate.

Adult↗
PubMed1989

[Treatment of patellar fracture using an internal fixator of shape-memory alloy].

An internal fixator made of memory alloy, that can autonomously exert pressure centripetally on fragments from multi-directions (5 to 9), but mainly longitudinal (23 to 28 kg), had been designed to treat lateral fracture. Its application on 33 cases of such fracture manifested that it could restore the shape of communicated patella through progressive pressure and maintain the anatomical position until bony union. On account of firm and stable fixation, the patient was able to start drilling the limb in 1 to 7 days after surgery, and regained full extension and flexion of knee joint in 6.8 weeks on average. All of the patients resumed excellent limb function without complication.

Adult↗