Biomedical subjects

H S Liu

Publications and source records attributed to H S Liu.

At least 91 records · Page 5Linked to original sources

PubMed1990

In vitro motor activity and compliance of the caecum in streptozotocin diabetic rats.

In order to characterize the diabetic gastrointestinal disorders such as constipation, the motor activity and the compliance of the caecum of streptozotocin diabetic rats were studied in vitro. The time course of enlargement of the caecum was also examined. Significant enlargement of the caecum was noticed in diabetic rats, 10 days after streptozotocin injection (65 mg/kg). It reached two times heavier in 30 days and three times in 90 days when compared with age-matched controls. The motor activity as studied by in vitro recording of the intraluminal pressure changes associated with spontaneous activity revealed the depression both in amplitude and frequency. The compliance was noticed to be significantly increased in the diabetic caecum as compared to age-matched controls when studied by passive Krebs solution injection. Threshold intraluminal pressure for inducing the reflex motor activity of the diabetic caecum was larger than that of the normal. These factors may contribute to the retention of content inside of the diabetic caecum.

Animals↗

PubMed1990

Mechanism of estrogen-induced 17-beta-hydroxysteroid dehydrogenase in ovariectomized rat uterus.

Estradiol (E2), progesterone or medroxyprogesterone acetate can induce biosynthesis of the 17-beta-hydroxysteroid dehydrogenase (17-beta-HSD) in the mammalian uterus. For further understanding the 17-beta-HSD induction which may be mediated by the conjugation of the E2 to its receptor, premature ovariectomized rats were treated with E2, or with a synthetic steroid, diethylstilbestrol (DES), an agonist for the E2 receptor but not a substrate for 17-beta-HSD. Histological observation and uterus weight were examined as parameters to evaluate uterine response to those hormones at different durations of treatment. The 17-beta-HSD in ovariectomized rat uterus of each group was also examined by histochemical and biochemical assays. The results showed that the 17-beta-HSD activity in the uterus can be induced by E2 or DES, after daily treatment for 1, 14 and 28 days, but much higher in DES treated animals. The uterus weight demonstrated a "negative linear correlation" to the enzyme activity in all E2 treated groups, but not in DES or control rats. Accordingly, it was indicated that the 17-beta-HSD induction was regulated by conjugation of E2 or DES to its receptor. Therefore, we believe that the 17-beta-HSD gene in the rat uterus is another estrogen responsive gene.

17-Hydroxysteroid Dehydrogenases↗

PubMed1990

[Dose-response relationships of propofol in Chinese].

Propofol is a new intravenous anesthetic which possesses the rapid induction and recovery of anesthesia. It has been approved to be used in clinical anesthesia and critical care medicine since 1989. From the dose-response study of propofol, we can get the ED50 and induction dose of propofol and compare those with other anesthetics. Sixty young patients, ASA I-II, both sexes, were allocated into six groups of ten patients. All of patients did not receive premedicants. Groups I-VI were given intravenously over 25 sec 1.0 mg/kg, 1.2 mg/kg, 1.4 mg/kg, 1.6 mg/kg, 1.8 mg/kg and 2.0 mg/kg, respectively. Blood pressure and heart rate were monitored and recorded before and 1 min, 3 min, 5 min after the injection of propofol. Induction of anesthesia by propofol is considered to be successful as a patient closes his eyes and does not response to simple command. As a patient obeys the order to open his eyes, he is judged to emerge from anesthesia. Induction and recovery times were recorded in each successfully-induced patient. Data were analyzed using Litchfield and Wilcoxon, and Student's t tests. The ED50 of propofol was found to be 1.46 mg/kg (95% confidence interval: 1.35 mg/kg to 1.58 mg/kg). Induction and recovery times at 1.0 mg/kg, 1.2 mg/kg, 1.4 mg/kg, 1.6 mg/kg, 1.8 mg/kg and 2.0 mg/kg were 40 sec and 5.6 min, 38 sec and 6.0 min, 38 sec and 6.2 min, 36.8 sec and 6.7 min, 36.3 sec and 7.2 min, 35.5 sec and 7.2 min, respectively.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗

PubMed1989

D-alanine-D-alanine ligase (ADP) from Salmonella typhimurium. Overproduction, purification, crystallization and preliminary X-ray analysis.

The ddlA gene from Salmonella typhimurium coding for D-alanine-D-alanine ligase (ADP-forming) has been subcloned behind the tac promotor in the plasmid pKK223-3, with expression in Escherichia coli JM105. The overexpression system yields 58 mg of active enzyme from 12 g of wet cell paste after 40-fold purification to homogeneity. 5,5'-Dithiobis-(2-nitrobenzoic acid) titrations indicate that all four cysteine residues exist as free thiols. Two crystal forms of the 39,300 Mr enzyme have been produced. A tetragonal form grows at 21 degrees C from 10 to 15% (w/v) polyethylene glycol 8000 in space group P4(1)2(1)2, with two molecules in the asymmetric unit; it has cell constants a = b = 83.8 A, c = 220.0 A, and diffracts to 2.9 A. A monoclinic form grows from 30% (w/v) ammonium sulfate in space group P2(1), with two molecules in the asymmetric unit; it has cell constants a = 60.4 A, b = 102.1 A, c = 64.3 A, beta = 115.7 degrees, and diffracts to 2.2 A resolution.

Cloning, Molecular↗

PubMed1989

Denaturing gradient gel analysis of single-base substitutions at a mouse adenine phosphoribosyltransferase splice acceptor site.

Denaturing gradient gel electrophoresis (DGGE) can detect single-base changes in DNA. We used site-directed mutagenesis to produce all six possible single-base substitutions at a splice acceptor consensus AG dinucleotide within the mouse adenine phosphoribosyltransferase (aprt) gene. Studies of mouse and Chinese hamster cell aprt indicate a high level of both spontaneous and induced mutations in this region. We systematically evaluated each of the six mutations by DGGE. Five of the six mutant sequences could be distinguished from wildtype by DGGE analysis of a 560-bp fragment containing the mutation. However, one mutant could not be distinguished from wild-type, and some of the mutant constructs could not be distinguished from each other. Analysis of DNA heteroduplexes consisting of wild-type and mutant strands or two different mutant strands enabled all mutant constructs to be distinguished from wild-type and from each other. The pairwise mixtures resulted in 24 different heteroduplexes, all of which were less stable than the parental homoduplexes. End labeling of DNA prior to heteroduplex formation and subsequent DGGE analysis enabled us to determine the relative destabilization caused by different types of single-base mismatches.

Adenine Phosphoribosyltransferase↗

PubMed1989

Cytochemical observation of regulated bacterial beta-galactosidase gene expression in mammalian cells.

Bacterial beta-galactosidase, encoded by the lacZ gene, serves as a sensitive cytochemical marker in eukaryotic cells and tissues. In transient expression experiments, human and simian cells stain blue 48 hr after transfection with a plasmid containing a lacZ gene, whose expression is directed by a simian virus 40 promoter containing a synthetic lactose operator sequence. Transfection efficiency was about 0.6%. Incorporation of an operator sequence within the promoter permits regulation of beta-galactosidase gene expression by the lacI gene product, the lac repressor. When cells were cotransfected with the lacZ plasmid and a second plasmid containing the lacI gene, beta-galactosidase activity was extinguished. Its activity could be reestablished to original levels upon application of isopropyl beta-D-thiogalactoside to transfected cells. A cell line that stably carries both the lacI and lacZ genes was efficiently induced to synthesize beta-galactosidase after isopropyl beta-D-thiogalactoside administration. In transient expression experiments and in stably transfected lines, repression and induction of beta-galactosidase activity were predominantly at the transcriptional level.

Animals↗

PubMed1989

[Determination of thermograms of bacterial growth].

The fundamental growth thermograms of bacteria have been determined by using the microcalorimetric method. These perfect thermogram curves reflect the changes of bacterial growth patterns (including the lag phase of growth, log growth, stationary phase and the decline phase of growth). In our experiments, highly characteristic and reproducible growth patterns are observed under the same condition, therefore one can use these thermograms as "finger print" to discriminate bacteria. On the other hand, there thermogram curves contain ample information, which are very significant for the studies on microorganism metabolism, bio-thermokinetic and clinical fields.

Bacteria↗

PubMed1988

Acetylcholine and substance P responsiveness of intestinal smooth muscles in streptozotocin diabetic rats.

We found previously that in in vitro tube form preparations of isolated intestine of streptozotocin (STZ) diabetic rats, frequency of spontaneous intraluminal pressure waves was significantly reduced in duodenum when compared with normal controls. In order to elucidate further the diabetic intestinal disorders, we examined the frequency and amplitude of spontaneous length changes and contractile responses to acetylcholine (ACh) and substance P (sP) in isolated intestinal segments of normal and experimental diabetic rats. In comparison with normal controls, we could confirm the significantly decreased frequency of spontaneous length changes in isolated longitudinal and circular muscle preparations of diabetic duodenum (1 month after STZ injection). Furthermore, amplitude of spontaneous length changes was significantly decreased in circular muscle preparations of duodenum, jejunum, and ileum but not in colon nor in longitudinal muscle preparations. Dose-response curves revealed that both ACh and sP responses were significantly decreased in longitudinal and circular muscle preparations of diabetic duodenum, jejunum, and ileum but not in colon. Mechanisms of reduced contractility of diabetic intestinal smooth muscle in response to ACh and sP were discussed.

Acetylcholine↗

PubMed1988