Biomedical subjects

K Yang

Publications and source records attributed to K Yang.

At least 19 recordsLinked to original sources

PubMed1992

Functional implication of disulfide bond, Cys250 -Cys283, in bovine chymosin.

The reduction, carboxymethylation and mercuration of disulfide bond, Cys250-Cys283, located on the surface of bovine chymosin molecule resulted in the loss of about 25% of enzyme activity, suggesting that Cys250-Cys283 is not intimately involved in catalytic mechanism. Cys250 and Cys283 were substituted with Asp. and Ser. by site- directed mutagenesis of the structural gene coding for bovine prochymosin B. All three mutants (C250D/C283S, C250D, C283S) failed to be activated to chymosin in acid, indicating that Cys250-Cys283 might have some contribution to the correct refolding of the unfolded prochymosin.

Animals↗

PubMed1992

Precancerous lesions of the human esophagus: multiparametric study of esophageal biopsies from a high-risk population in Linxian, China.

Histopathology, morphometry, tritiated thymidine incorporation and immunohistochemistry were studied in 221 esophageal biopsies from subjects with cytologica hyperplasia in Linxian, China. A spectrum of 7 morphologic entities were found: (1) normal/near normal (NN); (2) basal cell hyperplasia 0 (BHO); (3) simple hyperplasia (SH); (4) mixed basal and spinous cell hyperplasia (MBS); (5) basal cell hyperplasia 1 (BH1); (6) dysplasia (D); and (7) non-proliferative lesion (NP). Forty percent of the biopsies had combinations of histologic types. The thickness of the epithelium was increased in SH, MBS, and BH1, but not in BHO and NP. Elongation of papillae was frequently seen in SH, MBS, BH1, and D. Papillary bleeding was very prevalent in the esophageal specimens studied. A variety of cellular changes were found in peripapillary areas especially when bleeding occurred. [3H]-thymidine labeling index was dramatically increased in the entire epithelium in dysplasia, and also increased in cell layer 3 of MBS, BH1 and D. Blood group antigen LeY and lectin WGA showed consistent positivity in cellular membranes of the squamous cells, and these changes occurred before gross morphologic alterations. These findings provide a hypothesis for the sequence of pathogenetic events leading to esophageal carcinoma, and define each step with corresponding biomarkers for cancer prevention studies.

Biopsy↗

PubMed1992

Microtubule-associated protein 2 levels decrease in hippocampus following traumatic brain injury.

We examined microtubule-associated protein 2 (MAP2) levels in hippocampal and cortical tissue 3 h following moderate traumatic brain injury (TBI) in the rat. MAP2 levels were assayed by quantitative immunoreactivity in tissue fractions obtained from naive, sham-injured, or fluid percussion-injured animals. Tissues were homogenized in the presence of protease inhibitors (0.3 mM phenylmethylsulfonyl fluoride, PMSF), a specific calpain inhibitors (0.1 mM leupeptin), and chelators (2 mM ethylene glycol-bis-tetraacetic acid, EGTA; 1 mM ethylenedinitrilo-tetraacetic acid, EDTA) to eliminate in vitro MAP2 proteolysis during tissue processing. Compared to naive rats, sham injury had no effect on soluble MAP2 levels in either cortex (105.0 +/- 4.4% of naive value) or hippocampus (106.6 +/- 5.2% of naive value). However, TBI caused a significant (p < 0.005) decrease in hippocampal MAP2 levels (55.7 +/- 5.9% of sham-injured controls). The effect appeared to be regionally selective, since the MAP2 decrease did not occur in cortex (89.1 +/- 1.4%). The degree of MAP2 decrease in hippocampus was similar in both membrane (57.8%) and cytosolic (55.7%) fractions, ruling out the possibility of partitioning artifacts. The data suggest that sublethal alterations of neuronal structure and function caused by MAP2 degradation may play an important role in the development of TBI-induced functional deficits. Since MAP2 is exclusively associated with the cytoskeleton in somal and dendritic compartments of neurons, the pathophysiology of sublethal magnitudes of TBI may also involve dendritic and somal dysfunction.

Animals↗

PubMed1992

Cloning of an ovine 11 beta-hydroxysteroid dehydrogenase complementary deoxyribonucleic acid: tissue and temporal distribution of its messenger ribonucleic acid during fetal and neonatal development.

Glucocorticoids promote the development of many organ systems vital for extrauterine survival, and fetal cortisol provides the trigger for birth in sheep. The activity of glucocorticoids may be influenced at a cellular level by 11 beta-hydroxysteroid dehydrogenase (11 beta-HSD), which is responsible for the interconversion of cortisol and cortisone. To examine 11 beta-HSD gene expression during fetal development, two overlapping clones which yield a 1.4 kilobase (kb) complementary DNA encoding sheep 11 beta-HSD from a liver library were isolated by using a rat 11 beta-HSD cDNA as the probe. This cDNA contains a 879 base pair open reading frame for a protein of 292 amino acids that has more than 70% sequence identity to rat and human 11 beta-HSDs. To define the tissue distribution of 11 beta-HSD messenger RNA in sheep, selected tissues were collected from one fetus at day 130 and term (approximately 145 days), and from a nonpregnant ewe. Cellular RNA was extracted and subjected to Northern blot analysis, and a single 1.8 kb transcript was detected in the fetal and adult liver, lung, hypothalamus, anterior pituitary, and placenta. This was undetectable in adrenals and kidneys, but a smaller (1.5 kb) transcript was present in fetal and adult kidney RNA. The relative abundance of 11 beta-HSD mRNA was greatest in fetal and adult livers, and it was much higher in adult liver, lung, and kidney than in the corresponding fetal tissues. To examine whether 11 beta-HSD gene expression is developmentally regulated in the fetal sheep, liver, lung, and kidney tissues were taken from fetuses at day 60-70, day 100-110, day 125-130, at term, and from newborn lambs (24-48 h old). In the lung and kidney, the relative abundance of 11 beta-HSD mRNA did not change from day 60 to term but increased in the lungs of newborn lambs. In contrast, 11 beta-HSD mRNA levels in the liver increased between day 125 and term and rose further in the newborn. Collectively, these results demonstrate that 11 beta-HSD gene expression in sheep is regulated in a tissue-specific and developmentally programmed manner.

11-beta-Hydroxysteroid Dehydrogenases↗

PubMed1992

Characterization of an ovine glucocorticoid receptor cDNA and developmental changes in its mRNA levels in the fetal sheep hypothalamus, pituitary gland and adrenal.

Fetal sheep tissues possess glucocorticoid receptors (GR), and these change in number during the last two-thirds of gestation. There is, however, no information about developmental changes in tissue GR mRNA levels which might account for alterations in fetal GR content. We have therefore cloned and sequenced a 942 bp GR cDNA from a sheep liver cDNA library, and used it to study the relative abundance of GR mRNA in fetal and neonatal sheep tissues. Analysis of the cDNA revealed a partial sequence of the ovine GR which displayed over 80% identity with residues 143-453 in human GR and 163-472 in rat GR. Furthermore, the first zinc finger motif in these receptors was perfectly conserved among species. The relative abundance of GR mRNA was studied in hypothalami, anterior pituitary glands and adrenals in fetuses at days 60-70, 100-110, 125-130 and at term (approximately 145 days), and in newborn lambs. Total RNA extracts (20 micrograms) were analysed by Northern blot analysis. A single 5.6 kb transcript was detected in all three fetal tissues, and its relative abundance did not change significantly throughout gestation. However, in newborn lambs, levels of GR mRNA increased significantly in the hypothalamus and pituitary gland but decreased to undetectable levels in the adrenal. These tissue-specific changes in the relative abundance of GR mRNA did not correlate with alterations in GR content in fetal tissues, which suggests that the latter may reflect alterations in GR mRNA translation, subsequent modifications and/or GR turnover. In addition, the pattern of developmental changes in GR mRNA content of the adrenal differs from that of the hypothalamus and pituitary gland in neonatal lambs, and indicates that tissue-specific factors may influence GR gene expression in neonatal sheep.

Adrenal Glands↗

PubMed1992

Regulation of gene expression in the ovine fetus.

Expression of genes encoding pro-opiomelanocortin (POMC), glucocorticoid receptors and 11 beta-hydroxysteroid dehydrogenase (11 beta-HSD) was studied in sheep fetuses during development. POMC mRNA was present in the anterior pituitary by day 60 of gestation (term approximately 145 days), and its relative amount did not change significantly until after days 125-130. The amount of POMC mRNA in the pituitary increased significantly at days 138-143, remained high at term and increased further in newborn lambs. In contrast, POMC mRNA could not be detected in the hypothalamus and adrenal glands of fetuses at all ages studied. These results suggest that the prepartum rise in plasma adrenocorticotrophin (ACTH) concentrations in sheep fetuses is due to increased expression of POMC gene in the pituitary. The number of glucocorticoid receptors, but not the amount of glucocorticoid receptor mRNA changed significantly with gestational age in the hypothalamus, anterior pituitary and adrenal glands of the fetus. Changes in glucocorticoid receptor content of fetal tissues may reflect alterations in translation of glucocorticoid receptor mRNA, subsequent modifications, or glucocorticoid receptor turnover or a combination of these factors. However, in newborn lambs, amounts of glucocorticoid receptor mRNA increased significantly in the hypothalamus and pituitary but decreased to undetectable amounts in the adrenal glands, indicating that tissue-specific factors may influence expression of glucocorticoid receptor gene in neonatal sheep. The interconversion of cortisol and cortisone requires 11 beta-HSD. Since cortisone is biologically inactive, 11 beta-HSD may regulate the activity of intracellular cortisol. We cloned and sequenced a cDNA encoding sheep 11 beta-HSD. By northern blot analysis, this cDNA detected a single 1.8 kb transcript in the fetal and adult sheep liver, lung, hypothalamus, anterior pituitary and placenta. This could not be detected in the adrenal glands and kidneys, but a smaller (1.5 kb) transcript was present in the fetal and adult kidneys. During fetal development, the relative amount of 11 beta-HSD mRNA did not change significantly in the kidney and lung, but increased in lungs from newborn lambs. In contrast, amounts of hepatic 11 beta-HSD mRNA not only increased significantly in the fetus at term but also displayed a further increase in the newborn. These results clearly indicate that expression of ovine 11 beta-HSD gene in the fetus and newborn is regulated in a tissue-specific and developmentally programmed manner.

11-beta-Hydroxysteroid Dehydrogenases↗

PubMed1992

[A study on the effect of stimulating auricular points on the biliary tract].

We have developed an animal model to study the effect of stimulating auricular points on the function of hepato-biliary system. The preliminary result shows that 14 of 18 rabbits acquired a marked increase (P less than 0.05) in the amount of heptic bile secretion 3 min and 7 min after point No. 3 stimulated with 58V.

Acupuncture Points↗

PubMed1991

Effect of central RAS on one-kidney Grollman hypertension in rats and its mechanism.

The effect of central renin-angiotensin system (RAS) on one-kidney Grollman hypertension during the maintaining phase and its mechanism were investigated in rats. The arterial blood pressure (ABP) and the content of angiotensin II (A II) and norepinephrine (NE) in brain regions was measured respectively. 4 weeks after operation the ABP was elevated significantly, and it sustained at high level 8 weeks post-operatively. However, ABP in the control group underwent no significant changes at the same period. The A II and the NE content in the brain regions of the operated group were significantly higher than in those of the age-matched control group. During the maintaining phase of hypertension captopril (150 micrograms/10 microliters) was injected into the lateral cerebroventricle at 0.5 h, 1.0 h and 1.5 h respectively, and ABP and content of A II and NE were determined at the corresponding time. The results showed that the above three parameters decreased consistently at 0.5 h and 1.0 h, and increased gradually at 1.5 h, suggesting that the central RAS might play an important role in the maintaining phase of one-kidney Grollman hypertension in rats.

Angiotensin II↗

PubMed1991

Lectin soybean agglutinin: measurements in colonic epithelial cells of human subjects following supplemental dietary calcium.

A biomarker of cell differentiation was analyzed in normal and abnormal colonic epithelial cells. Soybean agglutinin (SBA) lectin which binds to specific carbohydrate residues was studied in normal human colonic epithelial cells, in epithelial cells in transitional colonic mucosa adjacent to carcinomas, and in colonic carcinomas. Findings revealed that increased SBA binding occurred maximally in normal, well-differentiated colonic epithelial cells, and least in colonic carcinomas. Further quantitation of SBA lectin binding also was carried out before and after supplemental dietary calcium. Findings revealed that in subjects whose colonic crypt biopsies had normal SBA lectin binding before calcium supplementation, SBA remained unchanged after calcium supplementation. However, in subjects whose biopsies initially had reduced SBA binding, the SBA increased after calcium and became more characteristic of that observed in normal colonic epithelium. In subjects receiving calcium for less than 3 months, the increased SBA was not statistically significant; but when subjects received calcium for durations of 3 months or longer SBA lectin binding was significantly increased, changing towards that observed in normal mucosa containing greater numbers of well-differentiated colonic epithelial cells.

Adenocarcinoma↗

PubMed1991

Characteristics and developmental changes of corticotrophin-releasing hormone-binding sites in the fetal sheep anterior pituitary gland.

The responses of the fetal sheep pituitary to corticotrophin-releasing hormone (CRH) change during gestation with maximum output of ACTH around days 120-130, and decreased ACTH output near term. However, there is no information available concerning the extent to which these responses may be modulated by alterations in the number of CRH receptors. Therefore we measured specific CRH-binding sites, and changes in binding characteristics in membrane preparations from fetal sheep anterior pituitaries collected at days 65-70, 85-88, 100-110, 125-130 and at term (approximately 145 days). Binding assays were carried out using 125I-labelled Tyr-ovine CRH (125I-Tyr-oCRH), incubated with crude membrane fractions for 90 min at 22 degrees C. Binding was time- and temperature-dependent, linear with protein concentration, saturable and specific for oCRH. Scatchard analysis of binding data for individual tissues revealed a single class of CRH-binding sites with high affinity (Kd congruent to 1 nmol/l) that did not change significantly with gestational age. However, the number of CRH-binding sites increased progressively from days 65-70 to a maximum at days 125-130, then decreased at term. These results demonstrate the presence of specific CRH-binding sites in the fetal sheep anterior pituitary. Furthermore, the change in CRH receptor number with advancing pregnancy follows a similar time-course to the changes reported previously in responsiveness of the fetal sheep anterior pituitary to exogenous CRH stimulation in vivo. These results suggest that alterations in CRH receptor number may contribute to changes in responsiveness of the fetal sheep anterior pituitary to CRH during gestation.

Adrenocorticotropic Hormone↗

PubMed1991

Pro-opiomelanocortin messenger RNA levels increase in the fetal sheep pituitary during late gestation.

Plasma levels of ACTH and cortisol in fetal sheep increase progressively during late pregnancy, providing the stimulus for birth. However, little information is available concerning either sources of pro-opiomelanocortin (POMC, the precursor to ACTH) or changes in POMC gene expression, which may be responsible for the elevated fetal plasma ACTH concentrations. We therefore studied the relative amount of POMC mRNA in fetal sheep hypothalami, anterior pituitaries and adrenals at discrete times of pregnancy between day 60 and term (approximately 145 days) and from newborn lambs. Total RNA from these tissues was analysed by Northern blot hybridization using a human POMC DNA probe, and the amount of POMC mRNA was expressed relative to the signal obtained for 18S ribosomal RNA. A single 1.2 kb transcript was detected by day 60 in the anterior pituitary, and its relative amount did not change significantly until after days 125-130. Pituitary POMC mRNA levels increased significantly at days 138-143, remained elevated at term and increased further in newborn lambs. In contrast, POMC mRNA was undetectable in hypothalami and adrenal glands of fetuses at all ages. The results suggested that the prepartum rise in plasma ACTH concentrations in fetal sheep is due to increased POMC biosynthesis in the fetal pituitary. The increase in POMC mRNA occurs at a time when fetal plasma cortisol concentrations are elevated, indicating that the negative feedback effects of circulating glucocorticoids on the fetal hypothalamic-pituitary axis may be obscured by other mechanisms that increase pituitary POMC mRNA accumulation during the last week of gestation.

Adrenal Glands↗

PubMed1991

[Central norepinephrine and angiotensin II contents in the brain regions of spontaneously hypertensive rats (SHR) and the interaction between them].

The norepinephrine (NE) and angiotensin II (A II) contents in the brain regions of SHR and WKY (Wistar Kyoto) rats at different ages were determined by fluorospectrophotometry and radioimmunoassay. The systolic blood pressure (SBP) of the rats was measured indirectly with a tail cuff technique in conscious state. The results were as follows: There was no significant difference in the central A II and NE contents between SHR and WKY rats at 8-week age. Since 12th week age the SBP of SHR has increased gradually, up to 16th to 20th week and then maintained steady level. Whereas there was no significant change of SBP in WKY rats in the same span of age. In the early and late states of hypertension the A II contents in the medulla oblongata, pons, hypothalamus and nucleus caudatus of SHR were markedly higher than those of the age-matched WKY rats. But the change of NE content of SHR in the early stage showed a different picture as compared with that of WKY rats, i.e., NE decreased in medulla oblongata and anterior hypothalamus but increased in pons, posterior hypothalamus and nucleus caudatus. However, in the late stage there was no such significant difference between SHR and WKY rats. Consequently, it is suggested that the central A II and NE participated in the development of hypertension of SHR, and that the maintenance of hypertension is mainly dependent upon the increased A II content. Microinjection of captopril or 6-OHDA in the lateral cerebroventricle of SHR elicited a decrease of BP and reduction of both A II and NE contents in the medulla and hypothalamus.(ABSTRACT TRUNCATED AT 250 WORDS)

Angiotensin II↗

PubMed1991

[Autologous bone marrow transplantation after purging by low molecular weight natural tumor suppressor in long-term marrow culture in vitro: report on 2 cases].

In the light of high sensitivity of fresh bone marrow blast progenitor of human myeloid leukemia (L-CFU) towards the action of low molecular tumor suppressor isolated from human fetal liver, massive bone marrow was aspirated from the patients suffering from acute myeloid leukemia at the stage of first complete remission and cocultured in a long-term bone marrow culture system for 9 days. The purged marrow cells were then re-infused into the patients after preconditioning with large doses of cytotoxin and acute ionizing irradiation. Hematopoiesis was reconstituted due to the autologous transplantation in vivo. After the autologous bone marrow transplantation without chemical treatment, two cases are still survival with the time of more than 17 and 15 months respectively.

Adult↗

PubMed1991

Expression of calf prochymosin gene in Escherichia coli.

The expression plasmid pTaAC containing Tac promoter and calf prochymosin B gene was constructed and transformed into E.coli JM105. Addition of 0.1 mM IPTG into the culture at logarithmic phase induced the production of prochymosin markedly. The expression of prochymosin gene was regulated by temperature in addition to the inducer IPTG. At 30 degrees C in the presence of IPTG prochymosin was barely detected, whereas at 42 degrees C in the absence of IPTG a relatively high level of prochymosin was found. The expressed protein was estimated to be 12-19% of total cell proteins by electrophoresis analysis or 80-100 mg/l by ELISA. The yield of active chymosin was 14-20 mg/l after denaturation, renaturation and activation.

Animals↗

PubMed1991

[Preliminary infection source of downy mildew of Corydalis yanhusuo W. T. Wang].

The downy mildew of Corydalis yanhusuo caused by Peronospora corydalis usually brings about devastating harm in Anhui Province. In the past, it was generally held that the spores in diseased remains buried in soil were the main source of preliminary infection. But, according to our test, it is the mycelia in tubers that are mainly the preliminary infections source.

Oomycetes↗

PubMed1990

AE1 cytokeratin reaction patterns in different differentiation states of squamous cell carcinoma of the esophagus.

Anticytokeratin antibody AE1 was studied immunohistochemically in 56 surgical specimens of esophageal carcinoma. Relationships between morphologic characteristics and AE1 reaction patterns were analyzed in carcinomas and adjacent epithelium. Infiltrating carcinomas had three types of AE1 patterns that paralleled degrees of differentiation. Type 1 pattern was present in well-differentiated carcinomas characterized by cytoplasmic staining of polyhedral cells. Types 2 and 3 were seen in poorly differentiated and undifferentiated carcinomas in different percentages, characterized by all cancer cells stained, with cellular membrane and cytoplasm stained or all unstained, respectively. In normal esophageal epithelium, basal cells were the major population that was AE1 positive. In hyperplasia basal cells showed two kinds of changes, either reduced/lost AE1 staining accompanied by AE1 expression in spinous cells or retained/increased AE1 reactivity. In dysplasia and carcinoma in situ, abnormal cells had reaction patterns in which they lost or increased AE1 expression. Findings indicate that different degrees of differentiation of infiltrating esophageal carcinoma cells have differing expressions of cytokeratins and that monoclonal antibody AE1 can serve as a biomarker identifying early abnormalities in esophageal epithelial cells having increased predisposition to malignancy. Molecular mechanisms of AE1 cytokeratin expression in esophageal epithelium are also discussed.

Antibodies, Monoclonal↗

PubMed1990

Changes in glucocorticoid receptor number in the hypothalamus and pituitary of the sheep fetus with gestational age and after adrenocorticotropin treatment.

The concentrations of ACTH and cortisol both rise in the plasma of fetal lambs during late pregnancy, reflecting maturation of the fetal hypothalamic-pituitary-adrenal axis and providing the stimulus for parturition. The failure of rising cortisol to suppress plasma ACTH may be due to altered sensitivity of glucocorticoid negative feedback. To examine the possibility that this effect might be mediated through changes in the number of glucocorticoid receptors (GR) in the fetal hypothalamus and pituitary, we measured changes in GR number in these tissues from fetuses at discrete times of pregnancy between day 60 and term (day 145) and from newborn lambs and adult sheep. We also determined the effect of intrafetal ACTH administration in amounts known to produce premature parturition on GR number in fetuses at days 125-130 of gestation. Binding of [1,2,4-N-3H]triamcinolone acetonide to dispersed cell preparations of fetal pituitary and hypothalamus was saturable, temperature dependent, glucocorticoid specific, and of high affinity (2-3 X 10(-9) M). The number of GR in the pituitary always exceeded that in the hypothalamus. In both tissues GR number rose between days 60-70 to highest values on days 100-110, then decreased until day 125. GR number in the pituitary rose again at term, paradoxically at a time of rising endogenous glucocorticoid levels. However, after ACTH administration, there was a significant decrease in GR number in both hypothalamus and pituitary. These results indicate that altered efficacy of glucocorticoid negative feedback in term fetuses is not due to a decrease in pituitary or hypothalamic GR number. The rise in GR number at term and the fall after intrafetal ACTH treatment raises the possibility that mechanisms exist in the fetus allowing normal autoregulation of GR to be overridden at term.

Adrenocorticotropic Hormone↗

PubMed1990

[Preliminary studies on the relationship between the blood pressure and renin-angiotensin system in brain and blood vessels in SHRSP].

This work analyzed the relationship between A I concentration in aorta tissue and systolic blood pressure (SBP) in stroke-prone spontaneously hypertensive rats (SHRSP) at different ages. The SBP of SHRSP increased progressively with the age until the age of 20 weeks, when the SBP of SHRSP no longer elevated but sustained at a relatively high and stable level. The A I concentration in aorta of SHRSP was much higher than that of Wistar Kyoto rats at all of the three different ages. Perfusion of captopril into the lateral cerebroventricle of SHRSP for four weeks evoked a considerable decrease of A I concentration in brain as well as a significant reduction of SBP accompanied by a decrement of A I concentration in aorta and concentration of norepinephrine and epinephrine in aorta tissue and plasma. The results further confirm the close relationship between the changed activity of renin-angiotensin system localized in blood vessels during hypertension and the pathogenesis of hypertension, and indicate the possible regulative control of A I generated from central nervous system over the production of A I from blood vessels by means of facilitating the activity of peripheral sympathetic nerve system.

Angiotensin II↗