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Biomedical subjects

N Lin

Publications and source records attributed to N Lin.

At least 55 records · Page 3Linked to original sources
PubMed1992

DnaK-mediated alterations in human growth hormone protein inclusion bodies.

Protein overproduction in microbes frequently results in protein misfolding and aggregation though the molecular basis for this process is unclear. The HSP70 chaperonin, DnaK, was identified as an important factor controlling heterologous protein aggregation in Escherichia coli. Co-overproduction of DnaK significantly reduced human growth hormone (HGH) protein inclusion body formation and the extent of HGH aggregation.

Bacterial Proteins↗
PubMed1992

Protein kinase C subspecies in rabbit corneal epithelium: increased activity of alpha subspecies during wound healing.

Protein kinase C (PKC) has been implicated in cell proliferation and differentiation. Multiple forms of PKC have been isolated, principally from the brain where PKC is most abundant. In rabbit corneal epithelium, two distinct major peaks of PKC activity were resolved by hydroxyapatite column chromatography. Peak 2, with 65% of the total PKC activity, corresponds to alpha-PKC, based on its mobility in the column and Western blot analysis using specific monoclonal antibodies. Peak 1 did not react with either polyclonal or monoclonal antibodies to PKC alpha-, beta-, and gamma-isoforms suggesting the presence of isoforms specific to the corneal epithelium, or of another member of the PKC family. To investigate possible changes in the amounts of the various PKC subspecies during wound healing, the enzyme activities of the isolated subspecies were assayed 2, 5, and 7 days after corneal de-epithelialization. Two days after wounding, by which time the migratory limbal epithelium had covered the denuded area, total PKC activity was unchanged but alpha-PKC activity had increased to 77% of the total activity, compared with 65% in non-wounded epithelium. An increased proportion of alpha-PKC activity was also observed 5 and 7 days after wounding, during which time proliferation of epithelium continued. We hypothesize that alpha-PKC plays a role in long-term responses after injury such as gene expression and corneal epithelial proliferation. Moreover, these studies indicate that the cornea provides a good model of in vivo wound healing for PKC studies.

Animals↗
PubMed1991

Antisense oligonucleotides from the stage-specific myeloid zinc finger gene MZF-1 inhibit granulopoiesis in vitro.

Zinc finger proteins are transcriptional regulators of other genes, often controlling developmental cascades of gene expression. A recently cloned zinc finger gene, MZF-1, was found to be preferentially expressed in myeloid cells. Using complementary radiolabeled MZF-1 RNA hybridized to human bone marrow smears in situ, it was discovered that the expression of MZF-1 is essentially limited to the myelocyte and metamyelocyte stages of granulopoiesis. Antisense but not sense oligonucleotides from MZF-1 significantly inhibited granulocyte colony-stimulating factor-driven granulocyte colony formation in vitro.

Adult↗
PubMed1991

Erythropoietin receptor characteristics on primary human erythroid cells.

Erythropoietin (EP) exerts its effects on erythropoiesis by binding to a cell surface receptor. We examined EP receptor expression during normal human erythroid differentiation and maturation from the burst-forming unit-erythroid (BFU-E) to the reticulocyte level. In contrast to previous studies, we assessed EP receptor number and affinity in erythroid precursors immunologically purified from fresh bone marrow aspirates or fetal liver samples and in reticulocytes purified from peripheral blood. EP receptors were quantitated by equilibrium binding experiments with 125I EP. We found that purified primary erythroblasts from both adult and fetal sources exhibited a single high-affinity (kd 100 pmol/L) binding site for EP under our experimental conditions, and 135 or 250 receptors per cell, respectively. Reticulocytes were devoid of EP receptors. We compared these data to in vitro-derived BFU-E progeny at both early and late stages of maturation. Cultured BFU-E progeny also displayed a single class of receptors of slightly lower affinity (210 to 220 pmol/L). Preparations enriched in colony-forming units-erythroid (CFU-E) and proerythroblasts (day 9 BFU-E progeny) displayed approximately 1,100 receptors per cell, whereas populations containing mature erythroblasts (day 14 BFU-E progeny) exhibited approximately 300 receptors per cell. Furthermore, information from binding experiments was complemented by autoradiography in both enriched BFU-E preparations, cultured BFU-E progeny (days 9 and 14), and marrow mononuclear cells. These studies are consistent with a peak in EP receptor expression at the CFU-E/proerythroblast stage and a decrease with further maturation to undetectable levels at the reticulocyte stage. These data examining EP receptor characteristics on freshly isolated erythroid precursor cells complement previous data on EP receptor biology using culture-derived erythroblasts.

Autoradiography↗
PubMed1991

Platelet-activating factor (PAF) accumulation correlates with injury in the cornea.

This study reports the accumulation of platelet-activating factor (PAF) in corneas injured with either 0.1 N NaOH or 1 N NaOH. The degree of injury in corneas exposed to alkali for 5, 10, 20, or 60 sec was assessed by light microscopy and scanning electron microscopy. PAF accumulation in vivo increased with time (up to 24 hr) after injury and also according to the severity of the alkali injury. PAF was isolated by high-performance liquid chromatography (HPLC) and assayed by platelet aggregation of the HPLC fraction containing PAF. The specificity of the aggregating bioactivity was ascertained from inhibition of platelet aggregation by selective PAF antagonists. BN 50726, a new synthetic PAF antagonist, applied in vivo topically or subconjunctivally, was effective in inhibiting PAF formation. Because PAF is accumulated in vivo as soon as 30 min after corneal injury, this lipid mediator seems to be synthesized by corneal cells and not be recruited inflammatory cells, since they arrive later. Moreover, if the injury causes stromal edema and endothelial damage, the amount of PAF accumulated is even greater. Results from isolated corneas stimulated in vitro with calcium ionophore A23187 suggest that PAF synthesis is the result of stimulation of phospholipase A2 to form lyso-PAF and subsequent activation of an acetyltransferase.

Animals↗
PubMed1991

Prolonged effect of a new platelet-activating factor antagonist on ocular vascular permeability in an endotoxin model of uveitis.

Platelet-activating factor (PAF) is a membrane-derived lipid mediator involved in inflammatory responses. In the present study, the effect of a new, synthetic PAF antagonist, BN 50726, on ocular-blood barrier breakdown was investigated in a model of anterior uveitis produced by injection of 5 microL 0.1% endotoxin into the midstroma of rabbit corneas. Severe keratitis and anterior uveitis were induced in 3-4 days. BN 50726 was applied once subconjunctivally and then topically four times daily for 5 days in a blind-designed experiment. Vascular permeability was measured each day with an automated fluorophotometer after injection of fluorescein-conjugated dextran. BN 50726 significantly decreased ocular vascular permeability up to the fifth day of treatment. In another series of animals, slit-lamp observation showed significant reduction in iris erythema and epithelial damage with BN 50726 treatment. These results show that the PAF antagonist reduces early and late responses in uveitis. The possibility that PAF interacts with other inflammatory mediators to affect breakdown of the blood-aqueous barrier is discussed.

Animals↗
PubMed1991

The life stress paradigm and psychological distress.

The paper focuses on two forces (stressors and resources) in the life stress process as they affect psychological distress. Utilizing three waves of panel data from a representative community sample in upstate New York, six causal models of the life stress process are tested with indicators of two types of stressors (social and physiological) and two types of resources (social and psychological). Both deterring and coping models are tested. Analysis shows that: (1) stressors and resources in the social environment have a direct impact on depressive symptoms, (2) social resources mediate the effects of social stressors on psychological distress, and (3) psychological resources indirectly affect distress by enhancing social resources. The critical role played by the social environment in the life stress process involving psychological distress is substantiated. The implications of these and other findings are discussed.

Adaptation, Psychological↗
PubMed1991

[Pathologic study on megakaryocytes in chronic myeloproliferative disorders].

Megakaryocytes in 42 cases of Chronic Myeloproliferative Disorders were studied pathologically, and a classification of these disorders was suggested. Abnormal megakaryocytes were classified as immature, mature, naked-nuclear, micro-, giant, multinucleated and dysplastic types based on the degree of maturity, the number of ploidy, and the presence or absence of atypia. Immunohistochemical studies indicated that antibodies against platelet glycoprotein Ib, IIb/IIIa as well as VIII R:Ag are highly specific for the detection of megakaryocytes, especially the morphologically unrecognizable ones. With regard to the identification of micromegakaryocytes, nuclear size, shape and degree of cytoplasmic maturity were emphasized. In addition to the classification, the clinic-pathological significance of abnormal megakaryocytes is discussed.

Antibodies, Monoclonal↗
PubMed1990

Dynamics of erythropoietin receptor expression on erythropoietin-responsive murine cell lines.

We examined erythropoietin receptor expression in two murine cell lines, B6SUtA and DA-1, that respond to erythropoietin in different ways. While B6SUtA cells undergo erythroid differentiation with limited proliferation after addition of erythropoietin, DA-1 cells show only a proliferative response. Equilibrium binding experiments with 125I-erythropoietin revealed that both B6SUtA and DA-1 cells express a single class of erythropoietin receptors. In the absence of erythropoietin, B6SUtA cells exhibited 145 receptors per cell with a dissociation constant (kd) of 380 pmol/L. Six days after induction with erythropoietin, the B6SUtA cells displayed 310 receptors per cell without a change in binding affinity; exposure to erythropoietin also increased cellular hemoglobin content. DA-1 cells adapted to erythropoietin-dependent growth over a period of months and exhibited a progressive increase in erythropoietin receptor expression, from 85 per cell (kd = 540) to 550 per cell (kd = 530), although the cells remained uniformly benzidine-negative. We interpret the data with B6SUtA cells to indicate that early erythroid differentiation stages are attended by an increase in erythropoietin receptor display, coordinate with the initiation of expression of erythroid-specific genes. In contrast, the results with DA-1 cells are most compatible with clonal selection as the mechanism underlying enhanced receptor expression. Thus, display of the erythropoietin receptor is dynamic and can be modulated during the course of erythropoietin-induced differentiation.

Cell Differentiation↗
PubMed1990

Continuous monitoring of intracranial pressure in Reye's syndrome--5 years experience.

Monitoring of intracranial pressure (ICP) and efforts to keep the ICP below the critical level are vital in the treatment of Reye's syndrome. Continuous monitoring of ICP was carried out in 21 cases of Reye's syndrome who were at or beyond stage III at the time of admission to the Veterans General Hospital, between January 1981 and August 1986. Seventeen had ICP ranging from 15 mmHg to 67 mmHg. Three patients died, 1 in stage V with an ICP of 67 mmHg received a craniectomy, and 2 others were in stage IV with ICP's of 66 mmHg and 25 mmHg, respectively. The fatality rate was 14% (3/21). Among 18 patients, 5 had moderate psychomotor retardation (PMR), 4 had severe PMR and 2 had mild PMR. The remaining 7 patients survived without sequelae. Blood exchange transfusion could further reduce ICP and seemed to improve neurologic outcome. Blood ammonia higher than 400 micrograms% is indicative of a bad prognosis. Hyperventilation was the most rapid and effective means of reducing moderate degrees of increased ICP. During intensive supportive care, we also found that coughing, endotracheal intubation, seizures, asynchronous respiration to an artificial respirator, suction of the airway and any painful stimulation caused further increases in ICP and worsened the situation. Care should be given to avoid these factors.

Ammonia↗
PubMed1990

[An autopsy case of quadruple carcinoma].

Discussed is a case of male cancer patient whose initial lesion was a transitional cell carcinoma of the left renal pelves. A bladder tumor (TCC) was subsequently found 6 months after a left nephro-ureterectomy. After treatment of these tumors, the patient remained well for 8 years. An inoperable lung cancer (squamous cell carcinoma) then developed 6 months prior to death. The patient died of an aneurysmal rupture of the ascending aorta. At autopsy, 2 latent carcinomas were identified, one in the prostate and the their in the thyroid gland. If the renal pelvic and the bladder tumors and the lung carcinomas were all independent, this would seem to be a case of six-fold carcinoma.

Adenocarcinoma↗
PubMed1989

Measuring depressive symptomatology in China.

A study was conducted on a representative sample of 1000 residents in Tianjin, China to construct a scale of depressive symptoms. From items and criteria developed in the West and statements and expressions understood by the Chinese, a set of 26 statements was formulated. After a series of psychometric (reliability and validity) analyses, it was proposed that a set of 22 items form the Chinese Depressive Symptom Scale (CDS-22) and that a subset of 16 items (CDS-16) constitute the abbreviated version. Comparisons of the levels and patterns of symptomatology in China as measured by such scales with those found in the United States show considerable similarities.

Adult↗
PubMed1989

Study in cytotoxicity of gentamycin to corneal epithelium and endothelium in tissue culture.

A study in cytotoxicity of gentamycin to tissue-cultured bovine corneal endothelial cells and rabbit corneal epithelial cells is reported. When the cultured cells reached confluence, they were exposed to tissue culture media containing gentamycin for 6 hours. We found that 0.5% gentamycin caused significant damage to corneal epithelial cells--diffuse plasmolysis, with scattered cell necrosis and 5% loss. While corneal endothelial cells were exposed to 1.6 mg/ml gentamycin, extensive cell loss (approximately 15%) was observed. The damaged cells recovered their normal morphology after 24 hours. When the concentration of gentamycin increased twice, serious damage to cells occurred. The area of cell loss reached 40%, and the recovery of cellular morphology was much slower. This study demonstrates that gentamycin potential cytotoxicity to corneal epithelium and endothelium, suggesting that gentamycin should be rationally used in the treatment of ocular diseases.

Animals↗
PubMed1989

[Tissue culture of infant corneal endothelial cells].

The authors report a new technique to culture infant corneal endothelial cells. 38 donor corneas were from sudden death infants aged from 5 days to 18 months. Corneal endothelial cells with Descemet's membrane were stripped from the stroma. After actions of trypsin, collagenase and hyaluronidase, the pure corneal endothelial cells were cultured at 35 degrees C, in 95% air and 5% CO2. The cells grew well without adding any mitogen in the tissue culture medium and attained confluency in 2-3 weeks, when they morphologically resembled natural corneal endothelium. With this technique, sufficient quantities of normal live cells become available for researches of human corneal endothelial cells.

Culture Techniques↗
PubMed1989

[Experimental study on transplantation of tissue-cultured human corneal endothelium].

The Descemet's membrane of rabbit corneas denuded of endothelium were seeded with tissue cultured human corneal endothelial cells, which were then transplanted onto rabbit corneas. Postoperative slit lamp examination and ultrasonic pachymetry were performed, and histopathology and immunofluorescein staining of the transplants were studied 4 of 7 transplants grew clear rapidly and the corneal thickness returned to normal within 2-3 weeks. The 3 others were primary donor failures. 2 of the 4 clear transplants later showed phenomenon of immune rejection. The 2 control transplants with no endothelial cell transplantation did not clear up at all. The study demonstrated that after transplantation, tissue cultured human corneal endothelial cells were able to adhere firmly onto Descemet's membrane with normal appearance and physiological function. Also, xenogenic corneal endothelial transplantation could elicit severe immune rejection.

Animals↗
PubMed1989

[Acute peritoneal dialysis in low birth weight infants].

Between September 1986 and April 1988, five low birth weight infants weighing 950 gm to 2250 gm required acute peritoneal dialysis due to acute anuric renal failure. Severe hyaline membrane disease was the most common explanation for acute renal failure. All infants had severe electrolytes imbalance and fluid retention with generalized edema, which increased ventilation requirements and severely limited fluid intake. The volume of each exchange varied between 10-20 ml/kg. Four of five infants had good ultrafiltration (3.52 +/- 2.43 ml/kg/hr, mean +/- SD). Ultrafiltration was not achieved in one due to poor peripheral perfusion. Electrolytes imbalance were corrected in all patients. Although four infants died, one case given up further care after renal failure had improved, and one died of septic shock after renal function had recovered. Only one infant survived with complete recovery of renal function. We believe that early dialysis is likely to reduce both morbidity and mortality of acute renal failure in low birth weight infants.

Acute Kidney Injury↗