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Biomedical subjects

L Yang

Publications and source records attributed to L Yang.

At least 793 records · Page 44Linked to original sources
PubMed1990

Pharmacokinetics and autoradiography of [3H] or [14C]stepholidine.

After iv [3H]stepholidine (SPD) 12 MBq/kg, the concentration-time curve in rats was found to be a two-compartment open model. The distribution phase T1/2 alpha = 3.6 min, the elimination phase T1/2 beta = 168 min. The absorbed radioactivities of [3H] SPD in 15-30 min were 80-87%. The amounts of [3H]SPD bound to plasma protein, liver and kidney homogenates were estimated to be 37, 31, and 30%, respectively. During 3 d after ip [3H]SPD 50 MBq/kg, 56% of the radioactivity was excreted in urine and 5% in feces, thus, it suggested that [3H]SPD was mainly excreted by kidneys. After iv a single dose of [14C]SPD in mice, the whole-body autoradiography showed that [14C]SPD was rapidly distributed among various tissues. High radioactivities were found in kidneys, liver, brain, salivary glands, Harder's glands, heart blood and muscle at 2 min and intensively localized in kidneys and stomach mucosa at 30 min. The radioactivities in these tissues disappeared 4 and 8 h later, while that in intestine could not be detected 24 h later.

Animals↗
PubMed1990

[The effect of intrapartum and neonatal asphyxia on the cognitive and behavioral development of children].

The present study includes 4 groups of subjects: 30 children with a history of intrapartum asphyxia, 30 children with a history of mild neonatal asphyxia, 15 children with a history of severe but transitory neonatal asphyxia, and 30 children who had normal deliveries. Psychological and neuropsychological assessments were done at 6 years of age. There are no significant difference among 4 groups in IQ, social maturity age, most neuropsychological functions and incidence of attention deficit disorder with hyperactivity. 4 test scores in Halstead-Reitan Battery infer to visual-motor functioning showed backwardness in asphyxiated groups. Behavior problems are more frequently seen in the asphyxiated groups than in the control group.

Asphyxia Neonatorum↗
PubMed1990

[Relation of the changes in hemorheologic indices and the site and size of cerebral infarction].

According to the CT findings, 83 cases of cerebral infarction were divided into two groups. One group consisted of cases with occlusion of the cerebral arterial main trunks and the other of those with occlusion of the penetrating arteries. The HCT and the whole blood viscosity were higher in the former group, whereas the rate of platelet aggregation was higher in the latter group. These results suggested that the physiopathology involved in the formation of the large cerebral infarction in the cerebral cortex and subcortex was different from that of the small infarction in the deep cerebral structures. Besides, it was found that the blood viscosity has positive relationship with the size of the cerebral infarction in the former group. It was presumed that the HCT and the blood viscosity should be reduced immediately for treating the larger cerebral infarction, but to lower the rate of platelet aggregation for treating the small infarction in the deep cerebral structures would be of benefit.

Adult↗
PubMed1989

Quinacrine decreases the slow inward current and force in guinea pig ventricular tissue.

In guinea pig isolated ventricular myocytes, quinacrine (40 microM) decreases the action potential amplitude and duration, and markedly decreases the slow inward current (Isi). A lower quinacrine concentration (20 microM) has similar but smaller effects. In guinea pig papillary muscles, quinacrine decreases contractile force reversibly. Thus, in myocardial fibers the decrease in Isi by quinacrine appears to predominate over the inhibition of Na-Ca exchange found in membrane vesicles.

Action Potentials↗
PubMed1989

Identification of a developmentally regulated gene for a 140-kDa secretory protein in salivary glands of Chironomus tentans larvae.

Secretory proteins are synthesized in salivary glands of the insect, Chironomus tentans, and assemble in vivo into silk-like threads which aquatic larvae use to construct tubes for filter feeding and pupation. Thus far, all known secretory protein genes contain repetitious protein-coding sequences and are located in cytological structures known as Balbiani rings, giant puffs found on polytene secretory cell chromosomes. In this paper we describe the identification of another secretory protein gene which is comprised of repeated sequences; however, this gene is not located in a Balbiani ring. Two partial cDNA clones from a 3.6-kilobase pair poly(A)+ RNA were sequenced and found to contain two open reading frames for protein synthesis. Antibodies were raised against synthetic oligopeptides whose sequences were derived from these two open reading frames. An immunoaffinity-purified antibody for one of these peptides bound specifically to a 140-kDa secretory protein (sp140). The cDNA sequences contain tandem repeats of 42 base pairs which encode a repeat of 14 amino acids with a composition and oligopeptide sequence similar to other secretory proteins. The C. tentans genome contains about 70 copies of this 42-base pair repeat organized as a contiguous block of 3 kilobase pairs or less. The sp140 gene was mapped by in situ hybridization to polytene chromosome band I-17-B. Developmental studies of protein accumulation, steady-state levels of mRNA, and relative transcription rate suggested that the sp140 gene is developmentally regulated so that maximal expression is achieved during the prepupal stages of the fourth larval instar. Based upon these results we proposed that sp140 gene belongs to a prepupal class of secretory protein genes. While the sp140 gene shares structural and expression characteristics with other secretory protein genes, its unique chromosomal location shows that this multigene family is not restricted to Balbiani rings.

Amino Acid Sequence↗
PubMed1989

Template supercoiling during ATP-dependent DNA helix tracking: studies with simian virus 40 large tumor antigen.

Incubation of topologically relaxed plasmid DNA with simian virus 40 (SV40) large tumor antigen (T antigen), ATP, and eubacterial DNA topoisomerase I resulted in the formation of highly positively supercoiled DNA. Eukaryotic DNA topoisomerase I could not substitute for eubacterial DNA topoisomerase 1 in this reaction. Furthermore, the addition of eukaryotic topoisomerase I to a preincubated reaction mixture containing both T antigen and eubacterial topoisomerase I caused rapid relaxation of the positively supercoiled DNA. These results suggest that SV40 T antigen can introduce topoisomerase-relaxable supercoils into DNA in a reaction coupled to ATP hydrolysis. We interpret the observed T antigen supercoiling reaction in terms of a recently proposed twin-supercoiled-domain model that describes the mechanics of DNA helix-tracking processes. According to this model positive and negative supercoils are generated ahead of and behind the moving SV40 T antigen, respectively. The preferential relaxation of negative supercoils by eubacterial DNA topoisomerase I explains the accumulation of positive supercoils in the DNA template. The supercoiling assay using DNA conformation-specific eubacterial DNA topoisomerase I may be of general use for the detection of ATP-dependent DNA helix-tracking proteins.

Adenosine Triphosphate↗
PubMed1988

Identification of a downstream sequence and binding protein that regulate adenovirus major late promoter transcription in vitro.

Gel electrophoresis mobility shift and DNase I footprint assays detect a cellular nuclear protein in extracts made from uninfected human cells which binds to a downstream promoter sequence (DPS) in the human adenovirus 2 major late promoter. By DNase I footprint and mutation analyses, we have determined that this new regulatory element extends from positions +146 to +165 (relative to the cap site at position +1). We show by UV cross-linking that a 40-kDa polypeptide specifically binds to this region. Mutations within the DPS which decrease protein binding by 80-90% also cause a 2.5-3-fold decrease in in vitro major late promoter transcription efficiency. Alteration of the template in the 5'-flanking region of the DPS does not affect nuclear protein binding or transcription efficiency. Interestingly, a T----G transversion at position +160 which increases protein binding also impairs promoter activity.

Adenoviruses, Human↗
PubMed1987

Prebiotic synthesis of imidazole-4-acetaldehyde and histidine.

The prebiotic synthesis of imidazole-4-acetaldehyde and imidazole-4-glycol from erythrose and formamidine has been demonstrated as well as the prebiotic synthesis of imidazole-4-ethanol and imidazole-4-glycol from erythrose, formaldehyde and ammonia. The products were identified by TLC, HPLC, and LC-MS by comparison with authentic samples. The maximum yields of imidazole-4-acetaldehyde, imidazole-4-ethanol, and imidazole-4-glycol obtained in these reactions are 1.6, 5.4, 6.8% respectively, based on the erythrose. Imidazole-4-acetaldehyde would have been converted to histidine on the primitive earth by a Strecker synthesis, and several prebiotic reactions would convert imidazole-4-glycol and imidazole-4-ethanol to imidazole-4-acetaldehyde.

Aldehydes↗
PubMed1987

Roles of DNA topoisomerases in simian virus 40 DNA replication in vitro.

We examined the roles of DNA topoisomerases in the replication of simian virus 40 (SV40) DNA in a cell-free system composed of an extract from HeLa cells supplemented with purified SV40 tumor antigen. When the activities of both topoisomerase I (EC 5.99.1.2) and topoisomerase II (EC 5.99.1.3) in the extract were blocked with specific inhibitors or antibodies, DNA synthesis was decreased by a factor of 15-20. Addition of purified HeLa DNA topoisomerase II to extracts immunologically depleted of both topoisomerases completely restored replication, and the replication products consisted largely of monomeric daughter molecules. Addition of purified HeLa DNA topoisomerase I to depleted extracts restored DNA synthesis, but the primary products were multiply intertwined, catenated daughter molecules. We conclude that DNA topoisomerases have at least two roles in the replication of SV40 DNA. Either topoisomerase I or topoisomerase II is sufficient to provide the unlinking activity necessary for fork propagation during SV40 DNA replication. However, topoisomerase II is uniquely required for the segregation of newly synthesized daughter molecules.

DNA Replication↗
PubMed1987

Research note: sleep problems of normal Chinese adolescents.

Eight hundred and forty-six Chinese adolescents were surveyed concerning sleep behaviours including insomnia, nightmares, somniloquism, somnambulism, bruxism, and enuresis. Bruxism was reported most frequently (22%) followed by somniloquism (17%) and insomnia (14.9%). Subjects were compared by sex, age, and rearing by parents or parent surrogates. Cross cultural comparisons and the possible significance of findings are discussed.

Adolescent↗