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Biomedical subjects

S Han

Publications and source records attributed to S Han.

At least 289 records · Page 16Linked to original sources
PubMed1990

[The clinical use of sodium hyaluronate eyedrops as a substitute for tears].

The present paper reports on the curative effect of the 0.1% Sodium hyaluronate (Na-HA) eyedrops jointly manufactured by Guangzhou Red Cross Hospital and Guangzhou Institute of Medical & Pharmaceutical Industry. 70 cases were studied. There were kerato-conjunctivitis sicca, lagophthalmos corneal fluorescein diffuse punctate epithelial lesion caused by contact lens, and keratitis punctata superficialis. The results showed effective treatment which occupied 95.7%. In the discussion, the authors point out that Na-HA has the same stagnatisity and elasticity as biotears because of its adhesion to the corneal epithelium. Moreover, it has the water-retaining microsponge action similar to that of mucopolysaccharide. Hence, Na-HA has protective effects on corneal epithelium. Finally, the authors conclude that Na-HA eyedrop is so far the most ideal substitute for tears and superior to other artificial tears.

Adult↗
PubMed1987

Calcium homeostasis after parathyroidectomy in normal and shocked states.

The natural history of parathyroidectomy was studied for 75 weeks in two dogs. After parathyroidectomy, the dogs required intravenous and intramuscular calcium supplementation for 1 week. Despite calcium supplementation, in 2 weeks the ionized calcium (Ca++) level fell from 4.67 mg/dl to 2.39 mg/dl. The Ca++ level rose to 4.25 mg/dl by 7 weeks after which the intramuscular calcium supplement was gradually weaned so that no calcium was given after 20 weeks. The Ca++ level stabilized at 3.15 to 3.25 mg/dl after 20 weeks. Postoperative parathormone (PTH) levels remained low. The response to hemorrhagic shock in these two calcium-independent dogs was compared with that seen in two calcium-dependent dogs 4 weeks after parathyroidectomy and to that seen in two euparathyroid dogs. Shock caused a sharp decrease in Ca++ in all animals that had parathyroid ectomy. Prostaglandin E2 (PGE2) was elevated preoperatively in these dogs and fell markedly during shock. Ca++ remained normal and PGE2 increased slightly after shock in the euparathyroid dogs. Cardiac output rose with resuscitation in the euparathyroid dogs but remained constant in the calcium-dependent dogs and increased slightly in the calcium independent parathyroidectomized animals. PTH levels were low in the parathyroidectomy groups and did not react to shock. PTH increased markedly after resuscitation in the euparathyroid dogs, suggesting its role as an acute-phase hormone. All levels returned to baseline levels within 3 days after shock. Adaptation to hypocalcemia occurs in parathyroidectomized dogs and involves PGE2 as well as other factors. Hemorrhagic shock exceeds this compensatory response which in euparathyroid dogs involves active PTH release in response to hypocalcemia.

Animals↗
PubMed1985

Neurospora crassa and S1 nuclease cleavage in hsp 83 gene chromatin.

We have examined the distribution of Neurospora crassa and S1 nuclease cleavage products in the chromatin of the hsp 83 heat shock gene from the Drosophila melanogaster cytogenetic locus 63 BC. Both of these nucleases generate double strand breaks in chromatin at specific sites close to the 5' end of the hsp 83 gene. With N. crassa nuclease we observe one major 5' fragment which is derived from nuclease cleavage in a DNA segment mapping approximately 120 base-pairs from the beginning of the transcription unit. With S1 nuclease we observe one major fragment which overlaps the transcription start site. In addition to the major hypersensitive sites at the beginning of the gene, the hsp 83 transcription unit is also sensitive to attack by these nucleases both before and after heat shock; however, the yield of cleavage products from within the gene is considerably greater after heat induction.

Animals↗
PubMed1985

Identification and quantitation of O-phosphoserine in human plasma fibronectin.

O-Phosphoserine was positively identified as the phosphorylated moiety in human plasma fibronectin by 31P-NMR of intact peptides. These data correlated completely with chemical analyses which demonstrated the presence of O-phosphoserine at a concentration of 2 residues/molecule. Neither O-phosphothreonine nor O-phosphotyrosine was detected in partial acid and partial alkaline hydrolysates, respectively.

Fibronectins↗
PubMed1985

Chromatin structure of the 87A7 heat-shock locus during heat induction and recovery from heat shock.

We have examined the chromatin organization of the 87A7 heat-shock locus (which contains two hsp 70 genes transcribed in opposite orientation) as a function of the time of heat induction and during the course of recovery from heat shock. Our studies show that both induction and recovery from heat shock are accompanied by highly specific alterations in the nucleoprotein structure of this locus. Moreover, these changes parallel the transcriptional activity of the hsp 70 heat-shock genes. We have also examined the effect of inhibitors of transcription and translation. Cycloheximide, an inhibitor of translation, blocks both the attenuation of the heat-shock response (which occurs after a long-term incubation at elevated temperatures) and the re-establishment of the pre-induced chromatin organization of the locus during recovery from heat shock. Actinomycin D, an inhibitor of transcription, prevents some but not all of the alterations in chromatin structure which normally accompany heat induction.

Animals↗
PubMed1985

Novobiocin blocks the Drosophila heat shock response.

In the studies reported here we show that the antibiotic novobiocin, an in vitro inhibitor of topoisomerase II, blocks the Drosophila heat shock response. If novobiocin is added prior to induction, there is no detectable expression of the Drosophila heat shock genes. Moreover, analysis of the chromatin organization of the 87A7 heat shock locus indicates that the antibiotic prevents the structural alterations which normally accompany heat induction. When novobiocin is added after induction, transcription appears to be rapidly turned off, and the chromatin organization of the 87A7 locus is "fixed" in an "active" configuration. Novobiocin also prevents the re-establishment of the pre-induced 87A7 chromatin organization which occurs during recovery from heat shock. We have also presented data suggesting that this antibiotic blocks transcription at 25 degrees C. These findings raise the possibility that topoisomerase II may be required in eukaryotes for both gene activation and deactivation.

Autoradiography↗
PubMed1984

Transcriptionally active chromatin is sensitive to Neurospora crassa and S1 nucleases.

We have examined the distribution of Neurospora crassa and S1 nuclease cleavage products in the chromatin of the 87A7 heat shock locus of Drosophila melanogaster. Both of these nucleases generate single and double-strand breaks in chromatin at specific sites in the 87A7 locus. Before heat induction, we find that the 5' ends of the two 87A7 hsp 70 genes contain N. crassa and S1 nuclease hypersensitive sites, while there are only a few cleavage products from elsewhere in the locus. With N. crassa nuclease, we observe one major 5' fragment, and this is derived from cleavage in a DNA segment mapping about 90 to 115 base-pairs from the beginning of the transcription unit. With S1 nuclease, we find two 5' cleavage products. The first maps about 120 to 130 base-pairs from the beginning of the gene. Interestingly, this site is also sensitive to S1 nuclease in supercoiled but not linear naked DNA. The other fragment maps very close to the transcription start site (approximately 0 to -15 base-pairs). After heat induction, there is a transition in the chromatin architecture of 87A7. First, there is a marked reduction in the yield of the prominent 5' N. crassa and S1 nuclease fragments. Second, the entire hsp 70 gene, as well as the spacer DNA just downstream from the 3' end of the gene, becomes highly sensitive to both of these nucleases.

Animals↗
PubMed1984

Ribosomal RNA genes of Drosophila melanogaster have a novel chromatin structure.

We have examined the chromatin organization of the Drosophila melanogaster ribosomal RNA genes using both micrococcal nuclease and DNase I. Several findings are of interest. First, the transcribed DNA segments of the rRNA repeat unit appear to be packaged into an unstable or "multiphasic" nucleosome structure. Second, the 5' end of the transcription unit is preferentially exposed to nuclease attack. Third, the non-transcribed spacer immediately upstream from the transcription start site has a novel chromatin organization with micrococcal nuclease and DNase I cleavage sites spaced at intervals of about 240 base-pairs. This unusual fragment distribution appears to reflect the underlying sequence organization of the spacer DNA segment, which consists of a series of tandemly repeated 239 base-pair sequence blocks. We have also examined the chromatin structure of the rRNA repeat unit after extraction of nuclei with different concentrations of salt. Our results suggest that the higher order structures may be of importance in determining the novel chromatin organization of the rRNA repeat unit.

Animals↗
PubMed1984

HLA studies in acquired immune deficiency syndrome patients with Kaposi's sarcoma.

To investigate the possible contribution of genetic susceptibility to Kaposi's sarcoma associated with acquired immune deficiency syndrome (AIDS-KS), 21 patients were typed for HLA-A, B, C, and DR antigens. Significantly increased frequencies of HLA-Aw23, and HLA-Bw49 antigens were observed in the Caucasian AIDS-KS group. In this same group, the frequencies of HLA-DR5 and HLA-Bw44 antigens were increased at the P less than 0.1 level. Increased frequencies of HLA-A29 and HLA-Cw4 antigens and a decreased frequency of HLA-B8 antigen were also noted, but with P greater than 0.1, in the Caucasian AIDS-KS group.

Acquired Immunodeficiency Syndrome↗