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Biomedical subjects

M Chen

Publications and source records attributed to M Chen.

At least 775 records · Page 43Linked to original sources
PubMed1991

An antibody to beta amyloid and the amyloid precursor protein inhibits cell-substratum adhesion in many mammalian cell types.

An epitope-specific antibody directed against the first 16 amino acids of the beta amyloid protein (anti-BP16) immunoprecipitated the secreted form of the amyloid precursor protein (APP) from the conditioned medium of PC12 cells. This antibody caused neurite retraction in differentiated PC12 cells and inhibited cell-substratum adhesion in many neuronal and non-neuronal cell types. The inhibitory effect of anti-BP16 was abolished by preabsorption of the antibody with BP16 peptide. Antibodies directed against other domains of APP did not inhibit cell adhesion. The secreted form of APP may be important for cell adhesion in many different mammalian cell types.

Adrenal Gland Neoplasms↗
PubMed1991

Cleavage of a smooth muscle myosin heavy chain near its C terminus by alpha-chymotrypsin. Effect on the properties of myosin.

Limited proteolysis of gizzard myosin by alpha-chymotrypsin converted the heavy chain doublet pattern, seen by gel electrophoresis, to a single band. Light chain degradation was not observed and only minor cleavage occurred at other heavy chain sites. Using a polyclonal antibody raised against a unique sequence from the slower-migrating heavy chain (SM1) it was shown that this conversion was due to the loss of a peptide approximately 4000 daltons from the C terminus of SM1. The peptide was isolated and sequenced, and the cleavage site was identified between phenylalanine 1943 and alanine 1944. Addition of antibody before protease protected SM1 from cleavage. The following changes were observed (a) the Mg2(+)-dependence of actin-activated ATPase of digested phosphorylated myosin was altered and activity was relatively high at low Mg2+ levels, i.e. similar to phosphorylated heavy meromyosin; (b) the KCl dependence of Mg2(+)-ATPase of the digested myosin, particularly the phosphorylated form, showed an altered pattern consistent with the stabilization of the 6 S conformation; (c) the tendency for aggregation was increased by proteolysis of phosphorylated myosin. These results show that the C-terminal region of a gizzard myosin heavy chain can modify some of the properties of myosin. It is suggested that the observed modifications reflect an enhanced tendency of the digested myosin to aggregate.

Actin Cytoskeleton↗
PubMed1991

[Ultrasonography as a supplemental technique for the diagnosis of adhesion and invasion of abdominal tumors].

Diagnostic capability of ultrasonography (US) concerning with adhesion and/or invasion of the tumors to the surrounding tissues in the abdominal region including pelvis was evaluated in 54 patients with comparison to that of CT. All the lesions reached the surface of the organ and whether the adhesion or invasion of the lesion to the surrounding organ or tissue was a problem. All the patients underwent US and CT. US was performed not only in the usual real-time manner, but with "supplemental" techniques: respiration, drinking water, rectal infusion and bimanual examination. Accuracy of US reached 72% with one or some of those four US supplemental techniques, while accuracy of CT which yields only stable image was 30% (p less than 0.005 by chi 2 test). US with suitable supplemental techniques should be applied to those cases with suspected adhesion or invasion of the tumor in the abdomen, and when CT is not reliable to judge this problem.

Abdominal Neoplasms↗
PubMed1991

Evaluation of a competitive NMDA antagonist (D-CPPene) in feline focal cerebral ischemia.

The effects of a competitive, N-methyl-D-aspartate (NMDA) receptor antagonist, D(-)E-4-(3-phosphonoprop-2-enyl)-piperazine-2-carboxylic acid (D-CPPene), on the volume of ischemic brain damage was assessed by quantitative histological study in 35 chloralose-anesthetized cats. Focal cerebral ischemia was produced by permanent occlusion of one middle cerebral artery and the animals were killed by transcardiac perfusion fixation 6 hours later. Pretreatment with D-CPPene (1.5, 4.5, or 15 mg/kg, administered intravenously 15 minutes prior to occlusion, with subsequent drug infusions to maintain a plateau in the plasma drug concentrations) effected dose-dependent reductions in the volume of ischemic brain damage. At the highest dose studied (15 mg/kg, plus an infusion of 170 micrograms/kg/min), D-CPPene reduced the volume of ischemic damage in the cerebral cortex by more than 75% compared to vehicle-treated control animals. The plasma concentration of D-CPPene, which is associated with a half maximal reduction in the volume of ischemic damage, was estimated to be 24 micrograms/ml during the initial 120 minutes after the middle cerebral artery occlusion. Treatment with D-CPPene (15 mg/kg, plus an infusion of 170 micrograms/kg/min) initiated 1 hour after occlusion reduced the volume of ischemic brain damage in the cerebral cortex by 30%, but this response did not achieve statistical significance. Precise definition of dose dependency for the anti-ischemic effects of NMDA antagonists and the therapeutic time window are influenced greatly by brain pharmacokinetics of the agents.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1991

Human synovial mast cell involvement in rheumatoid arthritis and osteoarthritis. Relationship to disease type, clinical activity, and antirheumatic therapy.

Mast cells were isolated by enzymatic digestion of synovium obtained from 48 patients with rheumatoid arthritis (RA) and 42 patients with osteoarthritis (OA). A significantly lower percentage of stainable synovial mast cells was obtained by tissue digestion from patients with clinically active RA compared with those with less active disease. The 54 patients treated with nonsteroidal antiinflammatory drugs had a significantly lower percentage of stainable synovial mast cells in cell suspension than did the other 36 patients. When anti-IgE antibody was used as a secretagogue in vitro, significantly greater histamine release was observed from synovial mast cells of RA patients compared with OA patients. Greater histamine release in response to anti-IgE was observed in the RA patients with more clinically active disease and those who were treated with prednisone, compared with RA patients without these features. Synovial mast cells of RA patients treated with a disease-modifying antirheumatic drug had a significantly lower mean histamine content than did cells from patients not receiving such treatment. Our data suggest that there are differences between synovial mast cells from tissues of patients with RA and OA and suggest that synovial mast cells may be activated in clinically active RA. In addition, the data indicate an effect of systemic antirheumatic therapy on mast cells isolated from synovium of patients with arthritis.

Adult↗
PubMed1991

Lack of immunity to hepatitis B virus among the expatriates residing in southern Taiwan.

Taiwan is an endemic area for hepatitis B virus (HBV) infection. There are more than 3-million carriers on this island. Chronic HBV infections may result in liver cirrhosis and hepatocellular carcinoma, which are common in Taiwan. However little information is available concerning the immunity and the susceptibility to HBV among the expatriate-population (non-permanent residents from foreign countries) in Taiwan. Thus controversies exist on the indications for HBV vaccination among the foreign visitors and expatriates. This study evaluated the serological status of those who attended the Kaohsiung Adventist Clinic between May 1986 and August 1989. Hepatitis B surface antigen (HBsAg) and antibody (anti-HBs) were determined by ELISA. A total of 152 expatriates (85M, 67F, aged 5 to 64 years, duration of residence in Taiwan: 2 weeks to 11 years) without previous HBV vaccination, were tested. HBsAg and anti-HBs were not detected in 125 (82%). Anti-HBs was found in 22 (15%). There was no correlation between the duration of residence and anti-HBs positivity. However, there was an increased prevalence of anti-HBs with increasing age after 30. For those expatriates who were anti-HBs positive, 64% had a history of sexual contact with a partner from an endemic area of HBV. HBsAg was detected in 5 (3%). Three were symptomatic with abnormal liver function tests. Four had a history of sexual exposure. Their children were not antigenemic. It is concluded that most (greater than 82%) of the expatriates residing in southern Taiwan have no immunity to HBV and sexual contact is a major route (70%) of transmission.(ABSTRACT TRUNCATED AT 250 WORDS)

Adolescent↗
PubMed1991

Skeletal muscle atrophy in old rats: differential changes in the three fiber types.

This study was undertaken to reevaluate the effects of ageing on skeletal muscle mass and on mitochondrial and glycolytic enzyme levels in the different types of skeletal muscle in rats. It was found that some muscles atrophy with ageing, while others do not, in male rats. Atrophy appears to occur in weight-bearing muscles, and is most marked in those with a high proportion of type IIb fibers. The muscles that did not atrophy are non-weight-bearing, and include the epitrochlearis (predominantly type IIb fibers) and the adductor longus (predominantly type I fibers). The average cross-sectional area of muscle fibers in the plantaris muscles of 28-30-month-old rats was approximately 30% smaller than that of 9-10-month-old animals, providing evidence that the approximately 30% lower weight of the plantaris in the old group was entirely due to fiber atrophy. The proportion of type IIa fibers was decreased and the proportion of type I fibers was increased in the plantaris of the old rats. The respiratory capacity of the soleus muscle (predominantly type I fibers), and the glycolytic capacity of the superficial, white (type IIb) and deep, red (predominantly type IIa) portions of the vastus lateralis, were reduced in the old rats. Our results provide evidence that ageing has differential effects on the three types of skeletal muscle fiber, and on weight-bearing and non-weight-bearing muscles, in the rat.

Aging↗
PubMed1991

Cortical cells' physiology following visual split brain in developing cats.

We have studied physiologically whether visual cortex cells in areas 17 and 18 of split-brain cats preserve their performance despite the blockage of both binocularity and of interhemispheric communication. The absolute majority of the cells in cats underwent split-brain surgery as kittens and adults and were driven by the ipsilateral eye, resulting in the absence of interhemispheric interaction. Similar results were found in cats and kittens that underwent only chiasm split surgery, although some recovery of callosal transfer was found in the latter. A remarkable loss of binocularity was found when only callosal transection was performed, both in adult cats and in kittens, although some ipsilateral eye dominance was observed in the latter. As to the deprived cats, while in the inexperienced hemisphere (ipsilateral to the deprived eye), the majority of the cells was visually unresponsive, in the contralateral (experienced) hemisphere, the majority was responsive. A considerable reduction in responsiveness was found in the callosally transected cats and kittens. Generally, a degradation of function was found in the various properties as a result of chiasmal and/or callosal transection. The main effect is the increased number of cells with diffuse and incomplete receptive fields. There was also a reduction in the proportion of orientation-selective cells, mainly in the split-brain cats. It was concluded that, despite the high amount of hemispheric independency in the normal brain, the integrity and simultaneous action of the two hemispheres are needed for the normal functioning of visual cortex cells.

Aging↗
PubMed1991

Calcium in bacteria: a solution to which problem?

Calcium and calcium-binding proteins including those resembling calmodulin are implicated in numerous diverse processes in bacteria. These processes include chemotaxis, sporulation, virulence, the transport of sugars and proteins, phosphorylation, heat shock, the initiation of DNA replication, septation, nucleoid structure, nuclease activity and recombination, the stability of the envelope, and phospholipid synthesis and configuration. That such varied processes should have a common factor, calcium, suggests major underlying principles of calcium metabolism which have yet to be discovered.

Bacteria↗
PubMed1991

Morphea profunda.

Explore the source record for details and available documents.

Adolescent↗
PubMed1991

Myoblast transfer therapy for Duchenne muscular dystrophy.

A randomly selected extensor digitorum brevis (EDB) muscle in each of three Duchenne muscular dystrophy (DMD) boys aged 9 to 10 was injected with approximately 8 x 10(6) myoblasts. The contralateral EDBs were sham-injected with carrier solution. Donor myoblasts were derived from cell culture of muscle biopsies from the normal ward or normal brothers of the recipients. Cyclosporine (CsA) treatment began two days before myoblast injection and continued for three months. Three days prior to myoblast injection and three months after, the isometric twitch and maximum voluntary contraction of the left and the right EDBs were measured. Myoblast-injected EDBs showed increases in tensions whereas sham-injected EDBs showed reductions. Both immunocytochemical staining and immunoblot revealed dystrophin in the myoblast-injected EDBs. Dystrophic characteristics such as fiber splitting, central nucleation, phagocytic necrosis, variation in fiber shape and size, and infiltration of fat and connective tissues were less frequently observed in these muscles. Sham-injected EDBs exhibited significant structural and functional degeneration and no dystrophin. Throughout the study, there was no sign of erythema, swelling or tenderness at the injection sites. Serial laboratory evaluation including electrolytes, creatinine, and urea did not reveal any significant changes before or after myoblast transfer. We conclude that myoblast transfer therapy is a safe and efficacious procedure to improve the biochemistry, structure, and function of degenerative EDB muscles in DMD.

Cells, Cultured↗
PubMed1991

Morphological aspects of synaptic plasticity in Aplysia. An anatomical substrate for long-term memory.

The morphological basis of long-term sensitization of the gill-and-siphon withdrawal reflex in Aplysia was explored by examining the structure of identified sensory neuron synapses in control and behaviorally modified animals. Following long-term training, sensitized animals displayed an increase in the number of sensory neuron synapses compared to control animals. The relative permanence of these structural changes and their similarity in time course to the behavioral duration of sensitization suggest a role for synapse number changes during long-term memory.

Animals↗
PubMed1991

Vital marker for muscle nuclei in myoblast transfer.

A new method is developed using Fluoro-Gold (FG) as a vital stain to label the nuclei of donor myoblasts in myoblast transfer studies. In vitro incubation with 0.01% FG for 16 h resulted in 100% nuclei labelling. Intensive fluorescence persisted following 9 days of subculture, when the human myoblasts were injected into the quadriceps of mouse recipients immunosuppressed with cyclosporine. Injected muscles showed mosaicism of host and donor nuclei 25 days after injection, indicating (i) survival and fusion among donor myoblasts, and (ii) fusion between host and donor cells. FG labelling was not observed in control muscles injected with an equal volume of FG-labelled dead myoblasts, 0.01% FG medium, or phosphate-buffered saline.

Adult↗
PubMed1991

Comparison of the therapeutic efficacy and side effects of a single dose of levo-praziquantel with mixed isomer praziquantel in 278 cases of schistosomiasis japonica.

A randomized double-blind study comparing the therapeutic efficacy of single dose of levo-praziquantel and mixed isomer praziquantel was carried out on 139 matched pairs of patients with schistosomiasis japonica. A single dose of either levo-praziquantel (20 mg/kg) or praziquantel (40 mg/kg) was given to each patient. Four and six months after treatment, the stool ova negative conversion rates were 94.85% and 96.27% for the levo-praziquantel group, and 97.06% and 94.03% for the praziquantel group, respectively; there was no statistically significant difference between the two treatments (P greater than 0.05). For lightly and moderately infected patients, a single 20 mg/kg dose of levo-praziquantel was as efficacious as 40 mg/kg of praziquantel. Moreover, levo-praziquantel produced fewer side effects than praziquantel. These results suggest that levo-praziquantel is the component of the mixed isomer preparation that is antihelminthic. Levo-praziquantel could be used therapeutically at half the current dose of the mixed isomer drug.

Adolescent↗
PubMed1991

Vaginal reconstruction using perineal-thigh flaps with subcutaneous pedicle.

A technique of vaginal reconstruction using bilateral, perineal-thigh flaps with subcutaneous pedicle is described. In this procedure, the flaps were raised bilaterally and introduced into an artificial space between the urinary bladder and rectum. The blood supply for the flaps flows from the perineal artery through anastomotic branches to the external pudendal artery. The authors used the technique on four patients, and all the flaps survived entirely. There was no complication. According to a more than two-year follow-up survey, the reconstructed vaginas are expansible and contract little. No stent is needed. There is good sensitivity in the wall of the artificial vagina because sensory nerves run through the flaps.

Adolescent↗
PubMed1991

An antihypertensive factor in the erythrocytes of essential hypertensive subjects--effects on blood pressure and calcium uptake by vascular tissue in rats.

An extract prepared from the erythrocytes of essential hypertensive subjects was found to significantly lower systolic blood pressure (SBP) in spontaneously (SHR) and renal hypertensive rats (RHR) following a single intravenous or intraperitoneal injection: The maximum SBP reduction was 42.8 mmHg in SHR and 38.3 mmHg in RHR. In contrast, this hypertensive factor (AHF) had little effect on normotensive Wistar Kyoto and Wistar rats. AHF was also found to significantly suppress Ca2+ uptake by vascular smooth muscle in the mesenteric artery and aorta of hypertensive and normotensive rats (P less than 0.05, respectively). Furthermore, AHF prepared from the erythrocytes of normotensive subjects was shown to have a similar effect.

Animals↗