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Biomedical subjects

S Chen

Publications and source records attributed to S Chen.

At least 1,405 records · Page 78Linked to original sources
PubMed1989

Effect of immunodepletion of MHC class II-positive cells from pancreatic islets on generation of cytotoxic T-lymphocytes in mixed islet-lymphocyte coculture.

In vitro manipulation of pancreatic islets to decrease islet immunogenicity before transplantation has largely been directed at eliminating the major histocompatibility complex (MHC) class II-positive passenger leukocytes from the islets. The mixed islet-lymphocyte coculture (MILC) system was used to quantitate the efficacy of immunodepletion of MHC class II-positive cells from pancreatic islets in terms of reducing immunogenicity. With these experiments we compared the in vitro immunogenicity of MHC class II-depleted islets with untreated islets. B10.BR (H-2k) islets were treated with anti-Iak alloserum followed by complement. This treatment successfully eliminated MHC class II-positive cells from the islets, as demonstrated by indirect immunofluorescence techniques. Depleted islets generated slightly lower amounts of allospecific cytotoxic T-lymphocyte (CTL) activity when exposed to C57BL/6 (H-2b) splenocytes in the MILC than untreated control islets. Although the amount of CTL generated by the depleted islets was slightly less than that generated by untreated islets, there was significant stimulation of CTL by the MHC class II-depleted islets. Therefore, the presence or absence of MHC class II cells within the islet is unlikely to be the decisive factor contributing to islet immunogenicity.

Animals↗
PubMed1989

Generation of allospecific cytolytic T-lymphocytes stimulated by pure pancreatic beta-cells in absence of Ia+ dendritic cells.

A murine mixed islet-lymphocyte coculture system (MILC) was used to quantitate the immunogenicity of a pure population of pancreatic beta-cells to more clearly define whether stimulator major histocompatibility complex (MHC) class II-positive dendritic cells are a major component leading to islet immunogenicity. Pancreatic beta-cells express MHC class I antigen but not class II antigen. These experiments compared the in vitro immunogenicity of fluorescence-activated cell sorted (FACS-IV) pure beta-cells (MHC class I-positive cells only) relative to unpurified dispersed islet cells (MHC class I-positive cells and class II-positive cells). The results demonstrated the surprising finding that pure DBA/2J (H-2d) pancreatic beta-cells stimulated a strong cytotoxic T-lymphocyte (CTL) response when exposed to C57BL/6 (H-2b) allosplenocytes in the MILC, similar to DBA/2J nonpurified dispersed islet cells. Furthermore, the stimulation of CTL by both purified beta-cells and nonpurified dispersed islet cells was blocked by addition of MHC-specific anti-class I monoclonal antibody directed against stimulator MHC antigen. The data imply that the highly immunogenic MHC class II-positive passenger leukocytes present in the islets were not necessary for the generation of the immune response in the presence of MHC class I-positive beta-cells. Although most of the pretreatment regimens attempting to decrease islet immunogenicity have been directed at eliminating the MHC class II-positive passenger leukocytes from the islets, this work suggests that modulation of MHC class I antigen may be an important approach.

Animals↗
PubMed1989

[Free calcium in platelets and the serum in essential hypertension].

Intracellular free calcium of platelets was studied in 45 patients with essential hypertension and in 6 patient's normotensive offspring. Intracellular free calcium of platelets in hypertensive patients was significantly higher than those in normotensive subjects (223 +/- 26 vs 170 +/- 28 nmol/lL, P less than 0.001). There was a positive correlation between intracellular free calcium of platelets and blood pressure (r = 0.653 approximately 0.729, P less than 0.001). No increase of intracellular free calcium of platelets was found in patient's normotensive offspring. 33 patients also had serum free calcium measured simultaneously. There was no difference between patients and the normotensive control (1.10 +/- 0.15 vs 1.09 +/- 0.10 mmol/L, P greater than 0.05). However, a positive correlation between serum free calcium and blood pressure (r = 0.363, P less than 0.05) and a weak positive correlation between serum free calcium and intracellular free calcium of platelets (r = 0.337, r 0.05 = 0.344) were found. These results indicated that intracellular free calcium was involved in the regulation of blood pressure, it was postulated that the intracellular free calcium of smooth muscle cell in the peripheral arteriole with resistance might have the similar changes seen in platelets. The changes of intracellular free calcium of platelets might be valuable in the prevention and treatment of hypertension and its vascular complications.

Adult↗
PubMed1989

Treatment of 570 cases of oral squamous cell carcinoma.

This paper presents results of treatment in 570 cases with oral cancers. The overall 5-year survival rate was 64.5% and 92.8%, 84.9%, 50.2% and 16.4%, respectively for Stages I, II, III and IV. Five kinds of therapy have been used and discussed. The mortality rate of operation was 0.35%. The 5-year survival rate of 127 and 443 cases with and without cervical node metastases was 28.3% and 74.7% respectively. The 5-year survival rates of 81, 30 and 16 cases with involvement of 1, 2 and more than 3 nodes were 33.6%, 27.9% and 6.3% respectively. The 5-year survival rates were 35.5%, 14.4% and 0% when upper, middle and lower cervical nodes were respectively involved. Forty-six cases recurred and were operated on again, their 5-year survival rate was 23%.

Adult↗
PubMed1989

A fast atom bombardment-mass spectrometric method to quantitate lysophosphatidylserine in rat brain.

A method to quantitate lysophosphatidylserine by fast atom bombardment-mass spectrometry using 1-hexa-decanoyl-sn-glycero-3-phospho-L-serine as internal standard is described. The standard curve is linear with a correlation coefficient r2 = 0.999 from 10 to 1000 ng. This curve has been used to quantitate LPS in rat brain using phosphorus assay as a test control. We found 475 +/- 70 ng of LPS in 1 mg of tissue (n = 3). This method presents advantages due to its sensitivity and its capability to give molecular information of the unmodified compound.

Animals↗
PubMed1988

The monocyte differentiation antigen, CD14, is anchored to the cell membrane by a phosphatidylinositol linkage.

CD14 is a myeloid differentiation Ag expressed primarily on peripheral blood monocytes and macrophages. Although its function is unknown, the CD14 gene maps to a region encoding several myeloid growth factors and receptors. Analysis of the CD14 protein sequence deduced from the cDNA shows that although the CD14 protein contains a characteristic leader peptide, it lacks a characteristic transmembrane region, suggesting that CD14 may be anchored to the membrane via glycosylphosphatidylinositol (PI). Treatment of monocytes as well as a CD14-expressing neuroglioma cell line with PI-phospholipase C removed CD14 from the cell surface. Furthermore, monocytes from a patient with paroxysmal nocturnal hemoglobinuria, a disease characterized by lack of expression of other PI-linked proteins, failed to express CD14. Interestingly, the CD14-expressing neuroglioma cell line, which had been transfected with a single CD14 cDNA, released a soluble form of CD14 into the supernatant. Soluble forms of CD14 have previously been observed in serum of normal individuals and in culture supernatants of CD14+ cells. Biosynthetic experiments reveal that this soluble form of CD14 (48 kDa), which is smaller than the form released from the membrane by PI-phospholipase C (53 kDa), does not contain ethanolamine, the first constitutent of the PI-anchoring system. These studies demonstrate that CD14 is a member of the family of PI-anchored proteins and suggest that soluble forms of CD14 represent molecules that completely lack the PI-anchoring system.

Amino Acid Sequence↗
PubMed1988

Developmental factors related to abnormal cerebellar foliation induced by methylazoxymethanol acetate (MAM).

Quantitation of mid-sagittal sections of the molecular layer, and both the external and internal granular layers between control and methylazoxymethanol acetate (MAM)-treated rats, at various stages of cerebellar development revealed a much smaller area of these layers in sagittal profile, however, the fiber core was not significantly affected by the drug. The expansion of the pial surface length was parallel to the length of the Purkinje cell layer, although comparison of a fissure index revealed hypofissuration in the experimental group. In histological examination, there was perforation, patching, and agenesis of the external granular layer. Mushroom expansion of the external granular layer occurred at patches producing a gyrating folial pattern rather than parallel ones. The number of lobules and their basic pattern remained normal. We conclude that the deficits in the external granular layer interrupted the growth force that produces the normal rostrocaudal organization of parallel coronal foliation and this resulted in shallow periodic fissuration along the sagittal extent. Fissurations forming lobules arose largely independent of the external granular layer by directed expansion of the central fiber core while normal parallel foliation is an elaboration of the lobular surface controlled by growth forces defined by both distribution of the external granular layer and the underlying fiber core with associated Purkinje cells.

Aging↗
PubMed1988

A dye release assay for determination of lysostaphin activity.

We describe a method for determination of lysostaphin activity using Remazol Brilliant Blue R (RBB)-dyed staphylococcal cells or RBB-dyed staphylococcal peptidoglycan as substrate. The dyed substrates are easy to prepare and are stable for at least 6 months. Soluble hydrolytic products released by lysostaphin are measured spectrophotometrically at 595 nm after the insoluble substrate is removed by filtration or centrifugation. The dye release assay is more sensitive and more accurate than the previously described turbidimetric assay.

Anthraquinones↗
PubMed1988

The effect of oral betaine on vertebral body bone density in pyridoxine-non-responsive homocystinuria.

Five pyridoxine-non-responsive homocystinuric patients aged 5 to 32 years were treated with oral betaine, 3 g b.i.d, in a double-blind, placebo-controlled, two-year crossover study of its effect on bone mineralization. Betaine therapy significantly reduced mean plasma homocystine (36 +/- 9 (SEM) mumol L-1 to 9 +/- 4 mumol L-1), with variable increases in plasma methionine and no adverse effects. Bone density, measured by computerized tomographic scanning of vertebral bodies, was below normal in all patients at the start of the study, and was not significantly altered by betaine therapy administered according to this protocol.

Adolescent↗
PubMed1988

In vitro generated allospecific cytolytic T lymphocytes injure pancreatic islets.

The role of cytotoxic T lymphocytes in the rejection of pancreatic islet allografts remains poorly defined. The present study was designed to assess the ability of in vitro generated cytolytic T lymphocytes to produce allospecific functional and structural damage of mouse pancreatic islets. A mixed lymphocyte-islet coculture model (MLIC) has been developed, in which islets from DBA/2J mice (H-2d) stimulate the generation of allospecific cytolytic T lymphocytes (C57B1/6, H-2b), as measured by lysis of allospecific chromium-labeled tumor targets. Responder C57B1/6 splenocytes sensitized to DBA/2J islets were harvested from the MLIC on Day 5 and cocultured with either freshly isolated DBA/2J or B10.BR (H-2K) islets. Islet injury was determined by assessment of beta cell function after 8 hr (as measured by insulin release in response to a glucose challenge) and islet destruction after 24 hr of coculture with the sensitized splenocytes. Whereas coculture of third party B10.BR islets with MLIC-sensitized C57B1/6 anti-DBA splenocytes had no effect on insulin release or structure, incubation of allospecific DBA/2J islets with these splenocytes resulted in inhibition of insulin release after 8 hr and disintegration of the islets by 24 hr. The depletion of MLIC-sensitized C57B1/6 anti-DBA splenocytes with anti-Lyt2 monoclonal antibody, but not anti-L3T4 monoclonal antibody, prevented the allospecific destruction of fresh islets by the splenocytes in culture. This study suggests that allospecific, cytotoxic T lymphocytes may play an important role in the effector mechanism of pancreatic islet allograft destruction.

Animals↗
PubMed1988

Perinatal methylazoxymethanol acetate uncouples coincidence of orientation of cerebellar folia and parallel fibers.

Perinatal administration of methylazoxymethanol acetate in the rat, as a one time injection on gestational day 21, postnatal days 0, 1 or 2, altered the parallel orientation of cerebellar folia. The effect persisted into adulthood. In animals injected on one of the postnatal days 3, 4 or 5, the folial pattern was not altered. Even when the injection was repeated for three days on postnatal days 3, 4 and 5, changes in the cerebellar surface were not found. However, in animals receiving a low protein diet during the last five days of gestation, the three injection regimen produced a distortion of the folial pattern. The surface of cerebella of animals injected on gestational day 21 through postnatal day 2 was covered with small blebs resembling the surface of a cauliflower head. In sagittal sections, islands of cortical laminae appeared to be isolated from the arbor vitae. However, serial reconstruction of the granular layer from sections revealed that these pieces were continuous with the arbor vitae. Surprisingly, cerebella having malaligned folia also had varying degrees of Purkinje cell somas distributed throughout the granule cell layer rather than in a single layer. This occurred even when the granule cell layer approached normal thickness. Analysis of cerebellar weight from the group injected on the day of birth revealed three levels of weight reduction: severe (greater than 40%), moderate (20-40%) and mild (less than 20%). The granule cell deficit was directly related to the weight reduction of the cerebella. In the severely-affected cerebella, areas of the cortex were virtually devoid of granule cells. The moderately-affected cerebella had a continuous granular layer which was thick and thin. In the mild type, the layer was relatively normal in thickness but, nevertheless, the cerebellar surface was highly distorted. In all animals treated with methylazoxymethanol acetate on days G21 through P5, parallel fibers were disoriented. This occurred even though the folia appeared normal in the G20, P3, P4, P5 and P3-5 injected groups. Bundles of parallel fibers crisscrossed in the plane of the cerebellar surface in all areas where a molecular layer was found.(ABSTRACT TRUNCATED AT 400 WORDS)

Animals↗