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Biomedical subjects

Z Deng

Publications and source records attributed to Z Deng.

At least 127 records · Page 7Linked to original sources
PubMed1993

[Overcoming restriction of Streptomyces hygroscopicus 10-22 by the modification of S. fradiae--an attempt to develop a transformation system for S. hygroscopicus 10-22].

No transformant was obtained when pIJ702 (tsr,mel+) from S. lividans TK24 was used to transform S. hygroscopicus 10-22. pIJ702 isolated from S. fradiae ATCC 10745, however, was transformed into 10-22 at a frequency of 10(3)-10(4) transformants/micrograms DNA. Among the transformant colonies, only 1/1000 of them were black in colour (mel+) while a great majority of them remained white (mel-). Plasraid pIJ702 band was only visualized on agarose gels from the black colonies but not from the white colonies. However, when pIJ702 isolated from both black and white transformants were used to transform S. lividans TK24, the mel gene was expressed normally in the recipients. The preparations was also successful in transforming S. hygroscopicus 10-22, and again gave rise to 1/1000 of black colonies only. When the 10-22 (pIJ702) black colonies were plated on non-selective medium, among the majority of black colonies grown, there were a few white colonies, which were proved to be host mutants of 10-22. These mutants were transformable by pIJ702 and homogeneous black colonies were obtained.

Mutation↗
PubMed1990

[The growth pattern of atherosclerotic rabbit aortic smooth muscle cells in culture].

Rabbit aortic smooth muscle cells (SMCs) both from normal and atherosclerotic (AS) animals were cultured for study on their growth activities and the relation to the cell cycle kinetics. The growth activities of different cell populations were compared by measuring cell doubling time, labelling index and mitosis index. For cell cycle analysis, 3H-TdR flash labelling method was employed. The results showed that SMCs derived from atherosclerotic rabbits grew more rapidly in culture than those from normal animals, the cell doubling time in the AS group was shorter than normal, 28.8 hrs versus 40.8 hrs, while the labelling and mitosis index in the AS group were higher. SMC cell cycle analysis showed that their generation time was 9.6-9.9 hrs and there was no significant difference of the distribution of cell cycle phases and their generation time between SMCs from AS and control group. The results indicate that the increased proliferative activities of atherosclerotic SMCs are not due to the change of their cell cycle kinetics, but having more cells emerging from G0/G1 phase into S phase.

Animals↗
PubMed1988

Site-specific degradation of Streptomyces lividans DNA during electrophoresis in buffers contaminated with ferrous iron.

Streptomyces lividans DNA contains a modification which makes it susceptible to double-strand cleavage during electrophoresis in buffers contaminated with ferrous iron (which may be present in some batches of EDTA). The cleavage of the DNA is site-specific and the average fragment size resulting from limit digestion of total S. lividans DNA is about 6kb. DNA from Streptomyces coelicolor A3(2) and several other Streptomyces strains, and from E. coli, is not cleaved under the same conditions. A S. lividans mutant has been isolated which lacks the DNA modification. We suspect that many reports of "poor" preparations of S. lividans plasmids may be due to the above effect.

Buffers↗
PubMed1986

Expression of a Streptomyces plasmid promoter in Escherichia coli.

A 166-bp DNA fragment from the Streptomyces multicopy plasmid pIJ101 with in vivo promoter activity both in Streptomyces lividans and in Escherichia coli was isolated. The start point of the RNA transcribed from this fragment, determined by high resolution S1 nuclease mapping, was the same in S. lividans and in E. coli. This suggests that the E. coli RNA polymerase recognizes the same sequence determinants and chooses the point of initiation of RNA synthesis in the same way as the corresponding S. lividans enzyme. The putative promoter sequence shows good homology to the E. coli promoter consensus sequence in the '-35' region but poor homology in the '-10' region.

Base Sequence↗
PubMed1986

Hemodynamic influences on sinus node recovery time: effects of autonomic blockade.

Ten patients with normal sinus node function were evaluated prospectively, to determine whether the decrease in blood pressure during rapid atrial pacing shortens the corrected sinus node recovery time. All patients had 30 seconds of atrial pacing at cycle lengths from 600 to 300 ms, with continuous arterial pressure monitoring, before and after intravenous administration of propranolol (0.2 mg/kg body weight) and atropine (0.04 mg/kg). In the control state, a decrease in corrected sinus node recovery time was recorded with faster atrial pacing rates, which was significantly related to the initial drop in systolic blood pressure at the onset of atrial pacing. Specifically, as the initial pressure drop increased from 15 mm Hg or less to 16 to 45 and 45 to 100 mm Hg, corrected sinus node recovery time decreased from 272 +/- 79 to 205 +/- 70 ms (p less than 0.04) and to 134 +/- 120 ms (p less than 0.04), respectively. In contrast, after autonomic blockade, the corrected sinus node recovery time was prolonged, in a near linear fashion, as atrial pacing rates increased. The magnitude of blood pressure drop with atrial pacing did not differ significantly from that in the control state at similar pacing rates. These findings suggest that hypotension during rapid atrial pacing activates autonomic reflexes that significantly shorten the corrected sinus node recovery time. Autonomic blockade negates this effect and the corrected sinus node recovery time prolongs with faster atrial pacing.

Adult↗
PubMed1986

Wide QRS tachycardia due to AV nodal reentry and a "bystander" bypass tract with slow conduction properties.

An unusual mechanism for recurrent, wide QRS complex supraventricular tachycardia is described in this report. A 25-year-old man with normal PR and QRS intervals during sinus rhythm was shown to have preexcitation with a left bundle branch block pattern during tachycardia and during atrial pacing. Electrophysiologic studies demonstrated slow and decremental conduction properties in an accessory "bystander" AV pathway utilized for antegrade conduction during AV nodal reciprocating tachycardia. The differential diagnosis of this tachycardia is discussed in detail.

Adult↗