Biomedical subjects

C L Shen

Publications and source records attributed to C L Shen.

At least 37 records · Page 2Linked to original sources

PubMed1996

A strategy for designing inhibitors of beta-amyloid toxicity.

beta-Amyloid peptide is the major protein component of Alzheimer's plaques. When aggregated into amyloid fibrils, the peptide is toxic to neuronal cells. Here, an approach to the design of inhibitors of beta-amyloid toxicity is described; in this strategy, a recognition element, which interacts specifically with beta-amyloid, is combined with a disrupting element, which alters beta-amyloid aggregation pathways. The synthesis, biophysical characterization, and biological activity of such an inhibitor is reported. This prototype inhibitor is composed of residues 15-25 of beta-amyloid peptide, designed to function as the recognition element, linked to an oligolysine disrupting element. The inhibitor does not alter the apparent secondary structure of beta-amyloid nor prevent its aggregation; rather, it causes changes in aggregation kinetics and higher order structural characteristics of the aggregate. Evidence for these effects includes changes in fibril morphology and a reduction in thioflavin T fluorescence. In addition to its influence on the physical properties of beta-amyloid aggregates, the inhibitor completely blocks beta-amyloid toxicity to PC-12 cells. Together, these data suggest that this general strategy for design of beta-amyloid toxicity inhibitors is effective. Significantly, these results demonstrate that complete disruption of amyloid fibril formation is not necessary for abrogation of toxicity.

Amyloid beta-Peptides↗

PubMed1996

Dietary (n-3) and (n-6) polyunsaturates and acetylsalicylic acid alter ex vivo PGE2 biosynthesis, tissue IGF-I levels, and bone morphometry in chicks.

This study examined the effects of dietary (n-6) and (n-3) polyunsaturated fatty acids (PUFA) and acetylsalicylic acid (ASA) on bone ash content, morphometry, fatty acid composition, ex vivo PGE2 biosynthesis, tissue IGF-I concentration, and serum alkaline phosphatase (ALPase) activity in chicks. Newly hatched chicks were fed a semipurified diet containing soybean oil (S) or menhaden oil / safflower oil (M) at 90 g/kg. At 4 days of age, chicks were divided into four equal treatment groups receiving 0 mg [symbol: see text] or 500 mg [symbol: see text] of ASA/kg of diet: S[symbol: see text]ASA, M[symbol: see text]ASA, S[symbol: see text]ASA, and M[symbol: see text]ASA. Lipid and ASA treatments did not affect bone length, bone ash, or bone mineral content in chicks. Chicks fed M had increased fractional labeled trabecular surface and tissue level bone formation rates, independent of ASA treatment, compared with those given S. A significant fat x ASA interaction effect was found for trabecular bone volume, thickness, separation, and number. Chicks fed S had higher 20:4(n-6) but lower 20:5(n-3) concentrations in liver and bone compared with those given M. Ex vivo PGE2 biosynthesis was higher in liver homogenates and bone organ cultures of chicks fed S compared with the values for those given M at 17 days. ASA treatment decreased ex vivo PGE2 production in liver homogenates and bone organ cultures of chicks, independent of the dietary lipids. Chicks fed ASA had a lower concentration of IGF-I in tibiotarsal bone compared with those not given ASA at 19 days. Serum ALPase activity was higher in chicks given M compared with those fed S, but the values were reversed with ASA feeding. This study demonstrated that both dietary fat and ASA modulated bone PGE2 biosynthesis, and that (n-3) PUFA and fat x ASA interactions altered bone morphometry.

Alkaline Phosphatase↗

PubMed1996

Ultrastructure of the middle ear mucosa in patients with chronic otitus media with cholesteatoma.

Mucosa of the middle ear was obtained from the promontory wall in each of 20 patients during cholesteatoma surgery. Specimens were processed for both scanning and transmission electron microscopy. Non-ciliated mucosal cells were commonly found, with most being secretory cells with secretory droplets and microvilli. The patterns of distribution of microvilli on the surface of these cells were variable. The interciliary spaces were stagnated with secretion. Bacilli were present in five cases. Falloff of mucosal cells was common and intercellular spaces were widened. Compound cilia were observed sporadically. Polymorphic nuclear inflammatory cells, macrophages and fibroblasts appeared in the submucosal area. These findings indicate that although remaining adjacent mucosa after removal of cholesteatoma looks free of disease under the operating microscope, it is actually in a diseased condition with impaired mucociliary function. The cells and bacteria seen microscopically may account for postoperative inflammation, thus warranting continued postoperative antimicrobial medication.

Bacterial Infections↗

PubMed1996

6-Hydroxydopamine induces thymocyte apoptosis in mice.

6-Hydroxydopamine (6-OHDA) induces degeneration of noradrenergic nerves and has been shown to alter the immune responses. In this study, intraperitoneal administration of 6-OHDA induces mouse thymus atrophy. The lowest levels of thymus weight and cell number were reached at days 3 and 5 in mice receiving 6-OHDA treatment; they gradually recovered thereafter. On flow cytometry analysis, the most substantial reductions were recorded for CD4+CD8+ thymocytes, although the numbers of other subpopulations, i.e. CD4+CD8-, CD4-CD8+ and CD4-CD8- cells were also reduced. DNA fragmentation, a characteristic of apoptosis, was detected in the thymocytes following 6-OHDA injection. Pretreatment with desipramine greatly blocked the reduction in thymus size and thymocyte number, the changes in thymocyte subpopulations, the percentage of subdiploid (apoptotic) cells and the appearance of DNA fragmented bands. Furthermore, 6-OHDA-induced thymocyte apoptosis could also be detected in vitro, and was blocked by desipramine treatment. These results indicate that 6-OHDA induces mouse thymocytes to undergo apoptosis both in vivo and in vitro, and this effect is inhibited by catecholamine uptake blocker.

Animals↗

PubMed1995

Solvent effects on self-assembly of beta-amyloid peptide.

beta-amyloid peptide (A beta) is the primary protein component of senile plaques in Alzheimer's disease patients. Synthetic A beta spontaneously assembles into amyloid fibrils and is neurotoxic to cortical cultures. Neurotoxicity has been associated with the degree of peptide aggregation, yet the mechanism of assembly of A beta into amyloid fibrils is poorly understood. In this work, A beta was dissolved in several different solvents commonly used in neurotoxicity assays. In pure dimethylsulfoxide (DMSO), A beta had no detectable beta-sheet content; in 0.1% trifluoroacetate, the peptide contained one-third beta-sheet; and in 35% acetonitrile/0.1% trifluoroacetate, A beta was two-thirds beta-sheet, equivalent to the fibrillar peptide in physiological buffer. Stock solutions of peptide were diluted into phosphate-buffered saline, and fibril growth was followed by static and dynamic light scattering. The growth rate was substantially faster when the peptide was predissolved in 35% acetonitrile/0.1% trifluoroacetate than in 0.1% trifluoroacetate, 10% DMSO, or 100% DMSO. Differences in growth rate were attributed to changes in the secondary structure of the peptide in the stock solvent. These results suggest that formation of an intermediate with a high beta-sheet content is a controlling step in A beta self-assembly.

Alzheimer Disease↗

PubMed1995

Mannitol increases cerebral arteriovenous oxygen difference in patients undergoing craniotomy.

BACKGROUND: Monitoring the jugular venous oxygen saturation (SjVO2) and cerebral arteriovenous oxygen difference (AVDO2) is valuable in detecting cerebral ischemia. In the present study, we investigated the effect of mannitol on SjVO2 and AVDO2 in patients undergoing craniotomy. METHODS: We studied 25 ASA class II-III patients undergoing craniotomy. Anesthesia was induced with thiopental, fentanyl and vecuronium. Immediately after induction, a 16-gauge central venous catheter was placed in the internal jugular vein, ipsilateral to the lesion side with cephalic insertion and anchorage in the jugular bulb. Anesthesia was maintained with continuous infusion of fentanyl (10 micrograms/kg/h), 0.5-1% isoflurane in 60% oxygen (oxygen/air) and supplemental dose of vecuronium for muscle relaxation as needed. Samples of arterial and jugular venous blood were obtained for the measurements of SjVO2 and AVDO2 in the following time intervals: (1) normocapnia (PaCO2 38-40 mmHg); (2) hypocapnia (PaCO2 28-30 mmHg); and (3) 30 min after mannitol (0.5 g/kg) infusion. RESULTS: Hyperventilation resulted in a significant decrease in SjVO2 (96% patients) and increase in AVDO2 (88% patients). Hypocapnia followed by mannitol administration led to a further decrease and increase of SjVO2 and AVDO2 in 72% and 68% patients, respectively. CONCLUSIONS: Mannitol may produce a further reduction in SjVO2 accompanied by an increase in AVDO2, suggesting a reduction of cerebral blood flow (CBF) during hyperventilation. Therefore, it should be given cautiously in neurosurgical patients under hyperventilation.

Adult↗

PubMed1995

Immunohistochemical analysis of neurotransmitters of the subfornical organ.

The localizations of peptides and putative neurotransmitters in the subfornical organ of the rabbit, rat and guinea pig were analyzed by using immunohistochemical methods. The variations that occurred in the three species were investigated. Immunoreactivities including serotonin (5-HT), neurotensin (NT), vasopressin (VP), luteinizing hormone releasing hormone (LHRH) and FMRFamide (Phe-Met-Arg-Phe-NH2) were examined in the subfornical organ. Nerve fibers that displayed 5-HT-positive immunoreactivity were observed in all species examined. Some immunoreactive perikarya were detected in guinea pigs and rabbits. Neurotensin-positive immunoreactivity was weak in the subfornical organ. LHRH immunoreactivity was detected in the rabbit only. Conspicuous vasopressin-positive immunoreactive cell bodies and fibers were detected in the subfornical organ of the rat, rabbit and guinea pig. Mild FMRFamide-positive immunoreactive fibers were observed in the rabbit and rat and no reaction was shown in the guinea pig by the PAP immunolabeling technique. Each neurotransmitter had a specific pattern of distribution in the SFO, though there were some overlapping reactive areas. Dramatic differences were demonstrated for fiber density among species.

Amino Acid Sequence↗

PubMed1994

Effect of acid predissolution on fibril size and fibril flexibility of synthetic beta-amyloid peptide.

beta-amyloid peptide (A beta) is the major protein component of senile plaques and cerebrovascular amyloid deposits in Alzheimer's patients. Several researchers have demonstrated that A beta is neurotoxic in in vitro and in vivo systems. Peptide aggregation state and/or conformation might play a significant role in determining the toxicity of the peptide. The size and flexibility of fibrils formed from the synthetic peptide beta (1-39), corresponding to the first 39 residues of A beta, were determined. Samples were prepared either directly from lyophilized peptide or diluted from a 10 mg/ml stock solution in 0.1% trifluoroacetic acid (TFA). All samples had a final peptide concentration of 0.5 mg/ml, a final pH of 7.4, and a final NaCl concentration of 0.14 M. The molecular weight and linear density of the fibrils increased with increasing pre-incubation time in TFA, based on static light scattering measurements. Analysis of the angular dependence of the intensity of scattered light indicated that the fibrils were semi-flexible chains and that the fibril flexibility decreased with increasing pre-incubation time in TFA. There was a concomitant change in phase behavior from precipitation to gelation with the decrease in fibril flexibility.

Alzheimer Disease↗

PubMed1994

Protective effects of arginine-vasopressin on aspirin-induced gastric mucosal damage in anaesthetized dogs.

The protective effects of graded doses of arginine-vasopressin (AVP) on acidified acetylsalicylic acid (ASA) solution-induced changes in gastric prostaglandin E2 (PGE2) secretion, mucus production, acid back-diffusion and mucosal damage were studied in the bilateral truncal vagotomized stomach of anaesthetized dogs. After 1-4 h intragastric irrigation of the stomach with AVP (1-100 ng kg-1) plus 20 mM acidified ASA solution, a significant (P < 0.05) inhibition in gastric mucosal lesions and acid back-diffusion produced by acidified ASA solution was observed. The reduction in the gastric PGE2 secretion and in mucus production provoked by the same dose of acidified ASA solution was also diminished. Furthermore, a correlation (r = 0.883; P < 0.01) between AVP-induced inhibition in ASA-provoked reduction in gastric PGE2 secretion and in mucus production was found. During the experiment, the heart rate, the peripheral arterial blood pressure and the gastric arterial blood pressure were not altered by AVP (1-100 ng kg-1). Thus, intragastric AVP protects gastric mucosa against ASA-induced damage without producing cardiovascular side effects. The inhibitory effects of AVP (100 ng kg-1) on acidified ASA-induced reduction in PGE2 and mucus secretion, as well as on ASA-induced enhancement in acid back-diffusion and erosion production were dose-dependently reversed by a specific V1 antagonist, 1-(beta-mercapto-beta,beta-cyclopenta-methylene-propionic acid), 2-(o-methyl)tyrosine-Arg8-vasopressin.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗

PubMed1994

Presence of neuropeptides in human nasal polyps.

The pathophysiological effects of non-cholinergic, non-adrenergic neuropeptides are well known in the nasal mucosa, but unclear in the polyps. Since the pathophysiological roles of neuropeptides depend on their presence in the target tissue, specimens of nasal polyps were removed from 20 patients and examined for the presence of vasoactive intestinal peptide (VIP), neuropeptide Y (NPY), dopamine-beta-hydroxylase (DBH), substance P (SP) and calcitonin gene-related peptide (CGRP). To visualize these neuropeptide fibers, immunohistochemical staining by the peroxidase-anti-peroxidase method and color reaction by Nickel enhancement of diaminobenzidine (DAB) were used. Fine varicose neuropeptides immunostained fibers were predominantly distributed in the pedicle of the polyps. No neuropeptides were found in the mucosal epithelium and subepithelium. NPY fibers were predominantly seen around the thick wall vessels, whereas the VIP fibers were mainly to be found in close proximity to the submucosal glands and fairly close to the vessels. SP or CGRP fibers were not found in the polyps. VIP and NPY in the pedicle of the polyps may be present in connection with mucosal inflammation, tissue edema and cystic degeneration of the glands in the early stage of polyp formation. Thus these neuropeptides may contribute to the development and growth of nasal polyps.

Calcitonin Gene-Related Peptide↗

PubMed1994

Rubrospinal tract in the Formosan monkey: HRP and autoradiographic studies.

Neurons projecting from the red nucleus to the spinal cord in the Formosan monkey were identified with retrograde horseradish peroxidase and tritiated proline and fucose antegrade autoradiographic tracing methods. A topographic organization of projections from the red nucleus to the spinal cord was demonstrated. Medial and dorsal portions of the rostral red nucleus projected to the rostral half of the spinal cord. Neurons in the ventrolateral part of the red nucleus emitted fibers which terminated in the caudal half of the spinal cord. The spinal projections from the red nucleus are bilateral, but contralateral projection is dominant. These results indicated a well developed rubrospinal tract existence in the Formosan monkey.

Animals↗

PubMed1994

Localization of fmrfamide-like immunoreactivity in the peripheral organs and its cross reaction with neuropeptide Y in the rat.

The molluscan cardioexcitatory peptide (FMRFamide) is a tetrapeptide. Neuropeptide Y (NPY) is a 36 amino acid peptide. Functionally, NPY is classified as a co-transmitter in the vasculatures of many organs and shows potent vasoconstriction. Coexistence of FMRFamide with NPY has been demonstrated in the central nervous system. The localization and distribution of NPY in the peripheral organs have been demonstrated mainly by radioimmunoassay. The localization and distribution, however, have not been investigated by immunohistochemistry. Therefore we present and compare the distribution of NPY- and FMRFamide-like immunoactivities in several peripheral organs of rats. Analysis of these data will reflect whether there is a cross reaction of FMRFamide with NPY antiserum or not. We have demonstrated both NPY- and FMRFamide-like nerve fibers in the vasculatures of the kidney, liver, pancreas, spleen, submandibular gland, lung and small intestine. The distribution pattern of these immuno-reactivities of the peripheral organs showed some extent of similarity. Radioimmunoassay indicated that FMRFamide possessed the ability to react with NPY-antiserum. This study demonstrated that the presence of FMRFamide immuno-reactivity in rat peripheral organs represents cross-reactivity of NPY with the FMRFamide anti serum. Such a result can be explained if antisera against NPY and FMRFamide recognize the carboxy-terminal sequence of -Arg-X-amide in the respective peptides.

Amino Acid Sequence↗

PubMed1994

Gallstone images on plain film and endoscopic retrograde cholangiopancreatography.

Different compositions of gallstone merit different treatments if a non-surgical method is chosen for these patients. In this study, gallstones collected from 125 patients were classified into cholesterol (pure, combination, mixed N = 28), brown (N = 64) and black (N = 41) stones by the Gallstone Classification of the Japanese Study Group (1986). Plain film and endoscopic retrograde cholangiopancreatography (ERCP) were reviewed in an attempt to predict the composition of the stones. We found that shape and location were highly correlated with stone composition. Most of the sandy stones were black stones (15/19, 79%); and 48% (10/21) of the irregular stones were brown stones; 70% (14) of facet stones were brown stones, 30% cholesterol stones. Stones in the gallbladder tended to be of the cholesterol type (47%, 13/28), 64% (51/81) of the bile duct stones were brown stones and 69% (11/16) of the gallbladder and bile duct stones were brown stones. We therefore conclude that imaging studies using plain film and ERCP is a fairly accurate means of predicting the composition of gallstone.

Bile Duct Diseases↗

PubMed1994

Innervation of the ligament of the femoral head in the formosan rock monkey: a retrograde HRP tracing and ultrastructural study.

The innervation of the ligament attached to the femoral head of the Formosan rock monkey (Macaca cyclopis, Swinhoe) was investigated by means of the retrograde HRP tracing method and by electron microscopy. WGA/HRP was injected into the ligament of the left femoral head. Numerous neurons labelled with HRP were found in the ipsilateral lumbar sympathetic ganglia, from L1 to L7, with a peak in the L3 to L5 region. Labelled neurons were also found in the ipsilateral spinal dorsal root ganglia, from L1 to L7 and concentrated at L4. Ultrastructurally, the nerve fascicles to the ligament had an average diameter at 32.8 microns. They contained both myelinated and unmyelinated axons and accompanied the blood vessels. Sensory receptors were not found in the ligamentum proprium but free nerve endings were observed in the walls of the blood vessels. The present results indicate that the nerve fibres to the ligament of the femoral head may be involved in regulating blood vessel calibre in addition to having a sensory function.

Animals↗

PubMed1993

Light scattering analysis of fibril growth from the amino-terminal fragment beta(1-28) of beta-amyloid peptide.

beta-Amyloid protein (beta-A/4) is the major protein component of Alzheimer disease-related senile plaques and has been postulated to be a significant contributing factor in the onset and/or progression of the disease. In the senile plaque, beta-A/4 appears as bundles of amyloid fibrils. The biological activity of beta-A/4 may be related to its state of aggregation. In this work, self-assembly, fibril formation, and interfibrillary aggregation of beta(1-28), a synthetic peptide homologous with the amino-terminal fragment of beta-A/4, were investigated. The predominant form of beta(1-28) detected by size-exclusion chromatography and polyacrylamide gel electrophoresis was apparently a tetramer which does not bind Congo red. Aggregates containing cross-beta sheet structures which bind Congo red and thioflavin T were observed at concentrations of approximately 0.3 mg/ml or greater. Concentrations of 0.5-1 mg/ml were necessary for aggregation into fibrils to be detectable by classical or quasielastic light scattering. Both fibril elongation and fibril-fibril aggregation occur over the time scale investigated. The kinetics of aggregation were much faster at physiological salt concentrations than at lower ionic strength. Ionic strength also appeared to influence the morphology of the fibril aggregates. The data indicate that sample preparation method and sample history influence fibril size and number density.

Amino Acid Sequence↗

PubMed1993

Effect of irrigation fluids on the articular cartilage: a scanning electron microscope study.

Four irrigation solutions, two for general arthroscopic examination and two for electrosurgery, were evaluated for their effects on the ultrastructure of the articular cartilage surface using an animal model with a scanning electron microscope (SEM). The murine knee joints were irrigated continuously for 1 or 2 h with normal saline, Ringer's lactate, 3% sorbitol, or distilled water, respectively. The articular cartilage of the patella was evaluated in situ; that is, the cartilage was kept intact as it related to the underlying bone tissue, so that artifacts during the biopsy procedure could be prevented. Results of the study showed no significant differences among the four solutions and the unirrigated control group. We conclude that Ringer's lactate, normal saline, distilled water, and 3% sorbitol can all be safely used as irrigation solutions in arthroscopic surgery.

Animals↗

PubMed1993

Ultrastructure of the monkey thoracic duct and the cisterna chyli.

The ultrastructure of the thoracic duct and cisterna chyli was studied in the Formosan rock monkey. This duct is approximately 40% of the crown-rump length. Bicuspid valves ensure one-way drainage of the lymph and prevent reflux of lymph. Ultrastructural variations between the 2 sides of the valves and the functional significance of the different types of valve are discussed. The muscular organisation in the tunica media is similar to that of the human thoracic duct. The abdominal and thoracic parts of the duct contain smooth muscle and probably exhibit active peristalsis, while the cervical part is less muscular and functions like a vein.

Animals↗

PubMed1992

In vivo induction of apoptosis in immature thymocytes by staphylococcal enterotoxin B.

Staphylococcal enterotoxins are potent T cell mitogens. Recent studies have shown that the binding of these toxins to class II MHC molecules on accessory cells is essential for the stimulation of T cells which bear specific V beta segment of TCR. In the present study we show that i.v. administration of staphylococcal enterotoxin B (SEB) results in an enlargement of spleen and lymph nodes but causes thymus atrophy. Elimination of CD4+CD8+ cells predominantly accounted for the shrinkage of thymus, and the lowest level of this cell population was reached 4 days after SEB injection. Furthermore, this decrease in CD4+CD8+ cells was accompanied by a relative increase in the percentages of CD4+CD8-, CD4-CD8+ and CD4-CD8- cells, whereas their absolute numbers actually reduced on day 4. The thymus shrinkage involved apoptosis which was characterized by DNA fragmentation and morphologic changes. The depletion of Thy-1 high, TCR-alpha beta low and TCR-alpha beta intermediate cells also occurred with a kinetic correlated to the reduction of CD4+CD8+ cells. Our results further showed that the percentages of V beta 8+ cells reduced 12 h post SEB injection, increased after 2 days, and decreased again thereafter. SEB thus causes both apoptotic and stimulative effects in the thymus. Apparently, the tremendous loss of double-positive cells (greater than 90% in cell number on day 4) is not simply due to the reduction of V beta 8+ cells, the possible modulatory effect of other factors or hormones which may play a role in the cell death is discussed.

Animals↗