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C M Li

Publications and source records attributed to C M Li.

86 records · Page 5Linked to original sources
PubMed1986

Urea-induced transformation of native estrogen receptor and evidence for separate DNA-and ATP-binding sites.

We have investigated the involvement of hydrophobic receptor domains during transformation of the native estrogen receptor to a form(s) with high affinity for immobilized DNA and ATP. In the presence of 6 M urea the intact estrogen-receptor complex was completely (greater than 90%, n = 12) transformed into a DNA-binding configuration but only partially (35-45%, n = 8) transformed into an ATP-binding state. Similar experiments performed with unliganded receptor preparations further distinguished the receptor's DNA and ATP binding properties. While the urea-induced increase in receptor affinity for DNA-agarose was estrogen-dependent, the urea-induced increase in affinity for ATP-agarose was steroid-independent. This is the first direct evidence that hydrophobic receptor domains may be involved in the steroid-dependent exposure of the DNA binding site. This event is partially reversible and suggests that electrostatic interactions alone may not be sufficient to accurately describe receptor recognition of specific DNA acceptor sites.

Adenosine Triphosphate↗
PubMed1986

Experimental study of intracranial hypertension.

The present investigation was made in rabbits and cats with perfusing mock cerebrospinal fluid into fourth ventriculus to produce experimental diffusion intracranial hypertension. Under normoxia and acute hypoxia conditions, the changes in cerebral blood flow, spontaneous electrocortical activity, direct cortical response, electrocardiogram, blood pressure and cerebral perfusion pressure were measured as intracranial hypertension caused by step elevation and abrupt elevation; at the same time, the relationship mentioned above was also investigated. The experimental results are very important to clinic treatment and to the patients suffering from anoxia with intracranial hypertension.

Animals↗
PubMed1980

Secretion of the rat cauda epididymidis.

A method has been developed to study the mechanism of epididymal secretion in the anesthetized rat in vivo. Secretion of the cauda epididymidis was affected by altering the intraluminal calcium ion concentration. Removal of calcium caused a rise and high calcium (10 X normal) caused a fall in the rate of secretion. Exocytosis did not seem to be operative in the epididymidis. The perfusate collected from the cauda epididymidis stimulated the forward motility of the washed caudal epididymal spermatozoa. This effect was concentration-dependent. At low concentration the perfusate stimulated the forward motility and at high concentration it caused a fall. A similar relationship between concentration and effect was noted for the epididymal plasma. When the diluted perfusate was used as the stimulant, there was a time lag of 15 min before any stimulation of forward motility was observed. However, the effect of the diluted epididymal plasma was immediate. The effect of the perfusate but not the plasma was inhibited by pretreatment of the sperm with cyclohexamide (10(-4) M). This difference in the action of the two fluids was discussed in relation to the proteins present in the fluids as revealed by SDS polyacrylamide gel electrophoresis.

Animals↗
PubMedDate not supplied

A new implantable burst generator for skeletal muscle powered aortic counterpulsation.

Skeletal muscle (SM) can be used for long-term circulatory assist. To generate contractions of appropriate duration and strength, SM requires bursts of electrical pulse trains. Presently, the implantable pulse train stimulator for SM assist is unable, at different heart rates, to adjust pulse burst duration or delay time, adversely affecting timing of counterpulsation. A prototype implantable microprocessor based stimulator (Medtronic Prometheus) has been developed to address this issue. The purpose of this study was to test this generator in an acute dog model. A dual chambered counterpulsation device was connected to the aorta in six dogs, using the latissimus dorsi to power the pump. The generator was connected by sensing/stimulating leads to the heart/left thoracodorsal nerve, programmed to give bursts of 2 V, 30 Hz, and pulse widths of 180 microsecs. Burst delay and duration was set as a fixed percent of the R-R interval of the EKG. The baseline aortic pressures ranged from 75/33 to 118/87 mmHg. During counterpulsation, diastolic pressure increased from 17 to 50 mmHg (30-111% increase). With changing heart rates, the pulse generator spontaneously readjusted its burst delay and duration, maintaining optimal diastolic counterpulsation without systolic interference. We conclude that this new pulse generator can stimulate SM for counterpulsation at varying heart rates, and is suitable for implantation in chronic studies.

Animals↗