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Biomedical subjects

Z Shen

Publications and source records attributed to Z Shen.

At least 325 records · Page 18Linked to original sources
PubMed1993

Diagnostic value of left ventricular dyssynergy patterns in ischemic and non-ischemic cardiomyopathy.

BACKGROUND: The distinction between ischemic and non-ischemic cardiomyopathy has important clinical implications. The objective of the present study was to investigate whether left ventricular dyssynergy patterns, detected by quantitative analysis of ultrasound images, differed in these two pathological processes. METHODS: Fifty-six consecutive patients with congestive heart failure (New York Heart Association functional class II-IV) secondary to depressed left ventricular systolic function (ejection fraction < or = 35% during diagnostic cardiac catheterization) were studied. Twenty patients were eliminated from further analysis because they met one or more exclusion criteria. The remaining 36 were divided into two groups based on the presence (ischemic cardiomyopathy) or absence (non-ischemic cardiomyopathy) of a > or = 50% narrowing of the luminal diameter in one or more coronary arteries. In all patients, a standard two-dimensional echocardiographic study was obtained. Apical four- and two-chamber views with optimal endocardial and epicardial resolution were selected for analysis, and the left ventricular contour was divided into six segments of interest. Optimal endocardial and epicardial resolution were defined according to an original internal quality score system. For each of the six segments of interest, regional ejection fraction and regional segmental thickening were estimated. Data analysis was then performed on the average values of regional ejection fraction and regional segmental thickening obtained across the entire left ventricular contour. In each patient, regional ejection fraction range and regional segmental thickening range were calculated by subtracting the minimum from the maximum value of regional ejection fraction and regional segmental thickening obtained across a left ventricular contour. RESULTS: Regional ejection fraction and regional segmental thickening did not differ significantly between the two groups. However, regional ejection fraction range and regional segmental thickening range were significantly greater in patients with ischemic cardiomyopathy than in patients with non-ischemic cardiomyopathy [28.32 +/- 11.17 versus 14.74 +/- 7.73% (P < 0.001) and 47.80 +/- 16.00 versus 24.64 +/- 9.39% (P < 0.001), respectively]. Overlap of findings was observed in 20% of the values for regional ejection fraction range but in only 14% of those for regional segmental thickening range. CONCLUSIONS: Patients with ischemic cardiomyopathy demonstrate a non-uniform dyssynergy that can be differentiated from a more uniform hypokinesis observed in those with non-ischemic cardiomyopathy. Computerized ultrasonic image analysis can distinguish characteristic dyssynergic patterns in patients with cardiomyopathy. Measurements of segmental wall thickening provide a more accurate assessment of regional function.

Adult↗
PubMed1993

Purification and characterization of fatty acyl-acyl carrier protein synthetase from Vibrio harveyi.

A Vibrio harveyi enzyme which catalyzes the ATP-dependent ligation of fatty acids to acyl carrier protein (ACP) has been purified 6,000-fold to apparent homogeneity by anion-exchange, gel filtration, and ACP-Sepharose affinity chromatography. Purified acyl-ACP synthetase migrated as a single 62-kDa band on sodium dodecyl sulfate-polyacrylamide gel electrophoresis and as an 80-kDa protein by gel filtration under reducing conditions. Activity of the purified enzyme was lost within hours in the absence of glycerol and low concentrations of Triton X-100. Acyl-ACP synthetase exhibited Kms for myristic acid, ACP, and ATP of 7 microM, 18 microM, and 0.3 mM, respectively. The enzyme was specific for adenine-containing nucleotides, and AMP was the product of the reaction. No covalent acyl-enzyme intermediate was observed. Enzyme activity was stimulated up to 50% by iodoacetamide but inhibited > 80% by N-ethylmaleimide: inhibition by the latter was prevented by ATP and ACP but not myristic acid. Dithiothreitol and sulfhydryl-directed reagents also influenced enzyme size, activity, and elution pattern on anion-exchange resins. The function of acyl-ACP synthetase has not been established, but it may be related to the capacity of V. harveyi to elongate exogenous fatty acids by an ACP-dependent mechanism.

Acyl Carrier Protein↗
PubMed1993

Evaluation of 90:10 poly(D,L-lactide-co-glycolide) microspheres containing norethisterone: drug release and biodegradation.

Poly(D,L-lactide-co-glycolide) (PLG, 90:10) microspheres containing 20% norethisterone (NET) were prepared by solvent evaporation method. Microspheres in the size ranges of 65 to 100 microns were sterilized by irradiation and used for further study. In vitro release showed fairly constant release of NET from the above microspheres over more than 90 days. However, in vivo drug release determined by residual NET analysis after i.m. injection in rats indicated a faster release rate. About 95% of NET was released in a period of 45 days. At the dose of 80 mg of microspheres, vaginal estrus cycles were inhibited for 45 days compared to 27 days for the same dose of NET crystals in rats. Biodegradation of the microspheres was tested by direct measurement of molecular weight losses and SEM observation of morphological changes of the microspheres, which showed continuous erosion in the internal matrix of microspheres with the decrease of molecular weight of PLG until total collapse of microspheres, and biodegradation was faster in rats than in human serum at 37 degrees C in vitro. Total degradation of 90:10 PLG microspheres was less than 7 months in rats and more than 9 months in vitro.

Animals↗
PubMed1993

Cycle sequencing using degenerate primers containing inosines.

A modified protocol for cycle sequencing DNA amplified by polymerase chain reaction (PCR) is described. The method involves two sequential linear PCR amplifications using a small amount of double-stranded DNA as a template and a stringent annealing temperature: 1) alpha-35S-dATP labeling of specific primers initially in degenerate primer mixture and 2) dideoxy-ribonucleotide termination of the extended and alpha-35S-dATP-labeled specific primers. The method does not require end labeling and is useful in sequencing PCR-amplified DNA sequences from highly degenerate primers when the sequences of the regions flanking those to be primed are unknown.

Animals↗
PubMed1993

Experiments in cardiac xenotransplantation. Response to intrathymic xenogeneic cells and intravenous cobra venom factor.

Permanent tolerance to an experimental cardiac allograft can be achieved by pretransplantation intrathymic inoculation of donor-specific lymphoid cells. We studied the effects of intrathymic inoculation of xenogeneic cells and intravenous cobra venom factor in a rodent model of cardiac xenotransplantation. Lewis rats underwent intraabdominal heterotopic heart transplantation with Syrian hamster donors. In untreated animals, mean graft survival time was 3 days. Five rats had 1 ml of antilymphocyte serum administered intraperitoneally. One day later, 2.5 x 10(7) hamster spleen cells were inoculated into the thymus under direct vision. Twenty-one days after antilymphocyte serum was given, heterotopic heart transplantation with a hamster donor was carried out. In all cases, rejection was accelerated and occurred between 20 minutes and 1 day after transplantation. Mean graft survival time was 5.2 hours (p < 0.0001 versus control). Six animals treated with antilymphocyte serum and intrathymic xenogeneic cells had 0.5 ml of cobra venom factor, a complement antagonist, administered intravenously 3 hours before transplantation and every other day thereafter. Mean graft survival was 3 days, which was not different from the response of naive animals. Animals treated with antilymphocyte serum only had no prolongation of graft survival (mean survival time 3 days, p = not significant). Animals treated with cobra venom factor alone (n = 5) before transplantation and on alternate days subsequently had mild graft prolongation with a mean survival time of 4 days (p = 0.0133). In contrast to experimental allograft models, intrathymic inoculation of xenogeneic cells produces hyperacute rejection in these naturally concordant species. The administration of cobra venom factor abrogates the hyperacute response, but the combination of cobra venom factor and intrathymic inoculation does not produce long-term graft survival.

Animals↗
PubMed1992

A novel neuropeptide, pituitary adenylate cyclase-activating polypeptide (PACAP), in human intestine: evidence for reduced content in Hirschsprung's disease.

A novel neuropeptide, pituitary adenylate cyclase-activating polypeptide (PACAP), exhibits sequence homology with vasoactive intestinal polypeptide (VIP) and occurs in the mammalian brain, lung and gut. The distribution of PACAP in ganglionic and aganglionic portions of the large intestine of patients with Hirschsprung's disease was examined by immunohistochemistry and radioimmunoassay. PACAP-immunoreactive nerve fibers were distributed in all layers of the ganglionic and aganglionic segments of the intestine, although they were less numerous in the latter, and PACAP-immunoreactive nerve cell bodies were seen in the ganglionic portion of the intestine. The concentration of immunoreactive PACAP was lower in the aganglionic than in the ganglionic segment of the intestinal wall. PACAP and VIP were found to coexist in both ganglionic and aganglionic segments of the intestine. Apparently, PACAP participates in the regulation of gut motility. The scarcer PACAP innervation of the aganglionic segment may contribute to the defect in intestinal relaxation seen in patients with Hirschsprung's disease.

Ganglia↗
PubMed1992

Preparation of fatty-acylated derivatives of acyl carrier protein using Vibrio harveyi acyl-ACP synthetase.

A simple two-step purification of Vibrio harveyi fatty acyl-acyl carrier protein (acyl-ACP) synthetase, which is useful for the quantitative preparation and analysis of fatty-acylated derivatives of ACP, is described. Acyl-ACP synthetase can be partially purified from extracts of this bioluminescent bacterium by Cibacron blue chromatography and Sephacryl S-300 gel filtration and is stable for months at -20 degrees C in the presence of glycerol. Incubation of ACP from Escherichia coli with ATP and radiolabeled fatty acids (6 to 16 carbons in length) in the presence of the enzyme resulted in quantitative conversion to biologically active acylated derivatives. The enzyme reaction can be monitored by a filter disk assay to quantitate levels of ACP or by sodium dodecyl sulfate-polyacrylamide gel electrophoresis and fluorography to detect ACP in cell extracts. With its broad fatty acid chain length specificity and optimal activity in mild nondenaturing buffers, the soluble V. harveyi acyl-ACP synthetase provides an attractive alternative to current chemical and enzymatic methods of acyl-ACP preparation and analysis.

Acyl Carrier Protein↗
PubMed1992

Regulation of transcription of the cell division gene ftsA during sporulation of Bacillus subtilis.

Three distinct 5' ends of ftsA mRNA were identified by S1 mapping and by primer extension analysis. These are thought to represent three transcription start sites. The transcripts from the downstream and upstream sites were detected throughout growth. The transcript from the middle site was not detected during exponential growth but was detected within 30 min of the start of sporulation, when it was the predominant transcript. Insertion of a cat cassette in the middle promoter, ftsAp2 (p2), did not affect vegetative growth but prevented postexponential symmetrical division and spore formation. Transcription from p2 was dependent on RNA polymerase containing sigma H, and promoter p2 resembled the consensus sigma H promoter. Transcription from p2 did not require expression of the spo0A, spo0B, spo0E, spo0F, or spo0K loci. Northern (RNA) blot analysis indicated that ftsA is cotranscribed with the adjacent ftsZ gene. Multiple promoters provide a mechanism by which essential vegetative genes can be subjected to sporulation control independent of control during vegetative growth. In the case of ftsA,Z, the promoters provide a mechanism to permit septum formation in conditions of nutrient depletion that might be expected to shut down the vegetative division machinery.

Amino Acid Sequence↗
PubMed1992

The cadC gene product of alkaliphilic Bacillus firmus OF4 partially restores Na+ resistance to an Escherichia coli strain lacking an Na+/H+ antiporter (NhaA).

A 5.6-kb fragment of alkaliphilic Bacillus firmus OF4 DNA was isolated by screening a library of total genomic DNA constructed in pGEM3Zf(+) for clones that reversed the Na+ sensitivity of Escherichia coli NM81, in which the gene encoding an Na+/H+ antiporter (NhaA) is deleted (E. Padan, N. Maisler, D. Taglicht, R. Karpel, and S. Schuldiner, J. Biol. Chem. 264:20297-20302, 1989). The plasmid, designated pJB22, contained two genes that apparently encode transposition functions and two genes that are apparent homologs of the cadA and cadC genes of cadmium resistance-conferring plasmid pI258 of Staphylococcus aureus. E. coli NM81 transformed with pJB22 had enhanced membrane Na+/H+ antiporter activity that was cold labile and that decreased very rapidly following isolation of everted vesicles. Subclones of pJB22 containing cadC as the only intact gene showed identical complementation patterns in vivo and in vitro. The cadC gene product of S. aureus has been proposed to act as an accessory protein for the Cd2+ efflux ATPase (CadA) (K. P. Yoon and S. Silver, J. Bacteriol. 173:7636-7642, 1991); perhaps the alkaliphile CadC also binds Na+ and enhances antiporter activity by delivering a substrate to an integral membrane antiporter. A 6.0-kb fragment overlapping the pJB22 insert was isolated to complete the sequence of the cadA homolog. A partial sequence of a region approximately 2 kb downstream of the cadA locus shares sequence similarity with plasmids from several gram-positive bacteria. These results suggest that the region of alkaliphile DNA containing the cadCA locus is present on a transposon that could reside on a heretofore-undetected endogenous plasmid.

Amino Acid Sequence↗
PubMed1992

The use of an external tibial fixator in the treatment of genu varum.

This paper reports 72 cases of genu varum treated by a U-shaped osteotomy of the tibia and an oblique osteotomy of the fibula in combination with immobilization effected by a specially designed external tibial fixator. Owing to this modified approach, the patients were able to stand up and move about much earlier than usual. Our trial yielded 80.7% excellent, 16.6% good and 2.7% fair results. The treatment course was shortened to two thirds of the time required when using previously described techniques.

Adolescent↗
PubMed1992

Automated detection and quantification of venous beading using Fourier analysis.

Venous beading associated with diabetic retinopathy is currently assessed by means of subjective comparison to standard photographs from the modified Airlie House classification scheme. We describe a computerized grading scheme for venous beading. The algorithm, based on Fourier analysis of vessel width measurements, generates a venous beading index (VBI) for digitized colour fundus photographs. Colour photographs of local vessel segments about 1200 microns in length were evaluated by experienced graders. A comparison between the VBI and subjective grading showed good agreement. The mean VBI values across the four levels of clinical grading were significantly different (p = 0.000). Multiple comparison testing indicated that the VBI was able to significantly differentiate between all four categories except the "questionable" (grade 1) category (p < 0.05). We also found that progression of venous beading can be followed with the VBI. The results indicate that further development of automated grading of venous beading is warranted.

Algorithms↗
PubMed1992

[Effects of caffeine on shuttle, operating behaviors, and brain metabolism in rats].

Effects of caffeine (30, 60, and 120 mg.kg-1, ip) on shuttling and operating behaviors in 80 rats were studied. Effects of caffeine (60, 120 mg.kg-1, ip) on contents of dinucleotides and pterins in 6 brain areas of 18 rats were investigated by HPLC with fluorescent detector. The results showed that the dose of caffeine that induced augment of shuttle behavior was lower than that induced operating behavior. Caffeine 120 mg.kg-1 inhibited both shuttling and operating behavior, decreased FAD content in caudate nucleus; caffeine 60 mg.kg-1 increased FAD in cerebellum and brain stem. Caffeine 60, 120 mg.kg-1 increased brain NADH contents, decreased pterin contents, and increased biopterin contents in some brain areas.

Animals↗