Biomedical subjects

Z D Chen

Publications and source records attributed to Z D Chen.

30 records · Page 2Linked to original sources

PubMed1991

[Effects of stimulation of locus coeruleus on cardiac contractility and renal nerve activity].

Experiments were performed on 64 cats anesthetized with chloralose-urethane, paralyzed and artificially ventilated. Electrical stimulation of locus coeruleus (LC) elicited increases in BP, HR, LVSP, dP/dt max and RNA. Buffer nerve section had no effect on the increase of these parameters, but could prolong the time of rise of BP and recovery phases. Injection of L-glutamate into LC, on the other hand, could decrease BP, HR, LVSP and dP/dt max. Intra-LC injection of kainic acid could also decrease BP. When the LC neurons showed degeneration or depolarization block after kainic acid injection, electrical stimulation of the LC could still elicit marked pressor response. The results suggest that the pressor response induced by electrical stimulation of LC might be mediated by the fibers passing through LC, while activation of LC neurons themselves would result in the depressor response.

Animals↗

PubMed1990

Cloning of a cDNA encoding adenylosuccinate lyase by functional complementation in Escherichia coli.

Adenylosuccinate lyase was cloned by functional complementation of an Escherichia coli purB mutant using an avian liver cDNA expression library. The derived amino acid sequence is homologous to the bacterial purB-encoded adenylosuccinate lyase which catalyzes the same two steps in purine biosynthesis as the enzyme from animals. Avian adenylosuccinate lyase also shows regions of extensive sequence similarity to the urea cycle enzyme, argininosuccinate lyase. This homology suggests a similar mechanism for catalysis. Homology of adenylosuccinate and argininosuccinate lyases is intriguing because chickens do not utilize the urea cycle in nitrogen excretion. This is the first report of the cloning of a eukaryotic cDNA encoding adenylosuccinate lyase, and it affords a route to isolate the corresponding human gene which has been suggested to be defective in autistic children.

Adenylosuccinate Lyase↗

PubMed1990

Cloning of a chicken liver cDNA encoding 5-aminoimidazole ribonucleotide carboxylase and 5-aminoimidazole-4-N-succinocarboxamide ribonucleotide synthetase by functional complementation of Escherichia coli pur mutants.

We have used functional complementation of Escherichia coli pur mutants to clone avian cDNA encoding 5-aminoimidazole ribonucleotide (AIR) carboxylase-5-aminoimidazole-4-N-succinocarboxamide ribonucleotide (SAICAR) synthetase, the bifunctional enzyme catalyzing steps 6 and 7 in the pathway for de novo purine nucleotide synthesis. Mutational analyses have been used to establish the structure-function relationship: NH2-SAICAR synthetase-AIR carboxylase-COOH. The amino acid sequence of the SAICAR synthetase domain is homologous to that of bacterial purC-encoded enzymes, and the sequence of the following AIR carboxylase domain is homologous to that of bacterial purE-encoded enzymes. In E. coli, AIR carboxylase is the product of genes purEK with the purK subunit postulated to have a role in CO2 binding. The avian enzyme lacks sequences corresponding to purK yet functions in E. coli. Functional complementation of E. coli pur mutants can be used to clone additional avian cDNAs for de novo purine nucleotide synthesis.

Amino Acid Sequence↗

PubMed1989

Adrenal autotransplantation with attached blood vessels for treatment of Cushing's disease.

A case of Cushing's disease was treated successfully by staged total adrenalectomy, left adrenal autotransplantation with the attached blood vessels and pituitary irradiation. In the first stage the left adrenal gland was removed with its attached blood vessels intact, and adrenal autotransplantation then was performed. An end-to-end anastomosis was made between the adrenal central vein and the right inferior epigastric artery. The anastomosis between the right saphenous vein and the adrenal middle artery was accomplished by intussuscepting the artery into the vein followed by suturing. The second stage operation was total right adrenalectomy. Steroid replacement therapy was stopped 7 days postoperatively and all laboratory studies were normal. Two months after total right adrenalectomy the patient had a sensation of facial fullness. Plasma cortisol and 24-hour urinary 17-hydroxycorticosteroid levels were elevated. Part of the graft was excised with the patient under local anesthesia. The symptoms disappeared and the laboratory studies returned to normal. Pituitary irradiation was administered as supplementary treatment of Cushing's disease. This method for the treatment of Cushing's disease has proved feasible. The inguinal region is the optimal site for adrenal autotransplantation.

Adrenal Glands↗

PubMed1989

[Interrupted aortic arch--report of two cases].

UNLABELLED: Interrupted aortic arch is a rare congenital heart malformation frequently associated with other extra or intracardiac congenital defects. These anomalies are divided into three types, depending on the site of aortic interruption. The diagnosis may be suspected clinically in patients with diminished femoral pulses and when the partial pressure and saturation of oxygen in the blood from arteries proximal to the interruption are higher than those from arteries distal to the interruption. The characters of heart murmurs are not of help in the diagnosis, which can be confirmed only by an ascending aortogram. SURGICAL TREATMENT: A two-stage approach has been routinely used in newborns. This consists of initial repair of the aortic interruption with left subclavian arteries (type A) or with a prosthetic tube (type B, C) and concomitant closure of the proximal end of the ductus by ligation or suturing, to be followed by closure of the intracardiac defect at a later date. Correction of the interrupted aortic arch and intracardiac malformation in elder children can be done at one sitting.

Adolescent↗

PubMed1989

[Inhibition of renal sympathetic efferent activities induced by stimulation of the paraventricular nucleus of the hypothalamus(PVH) in rabbits].

Experiments were performed on rabbits anesthetized with chloralose-urethane mixture, paralyzed with gallamine triethiodide, and ventilated artificially. Bilateral vagi, aortic and carotid sinus nerves were severed. Renal sympathetic efferent discharge (RSED) and its histogram were recorded, while the blood pressure (BP) of the femoral artery was monitored. When PVH was strongly stimulated, a transient increase of RSED was observed, which was followed by an inhibition of RSED. The inhibition of RSED was divided into two phases: the initial inhibitory phase without change in BP and the late inhibitory phase with an increase of BP. It was found that both the duration of total inhibition and the late, but not initial, inhibitory phase were positively correlated with the alterations of BP. When PVH was weakly stimulated, no change in BP was observed, but the inhibition of RSED still appeared. The inhibition duration was shortened remarkably following cutting of baroreceptor nerves. In some experiments, the RSED inhibition was not accompanied by a definite excitatory response. The present results indicate that 1) an inhibitory mechanism of PVH-renal sympathetic efferent system is present in the central nervous system; 2) the initial inhibitory phase of RSED originates from central mechanisms, while the late inhibitory phase is associated with the baroreceptor reflex and a direct action of the central nervous system; 3) the inhibition of RSED seems not to be a post-excitation depression, but an active inhibition exerted by the PVH on the spinal sympathetic preganglionic neurons.

Animals↗

PubMed1988