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Biomedical subjects

M Lai

Publications and source records attributed to M Lai.

At least 109 records · Page 6Linked to original sources
PubMed1996

[The application of Ultrasound Biomicroscope in anterior segment contusion].

PURPOSE: To study the clinical value of Ultrasound Biomicroscope in anterior segment contusion. METHODS: Seven eyes with anterior segment contusion were examined by regular ophthalmic examination, ophthalmic B-scan, and Ultrasound Biomicroscope. RESULTS: Ultrasound Biomicroscope can show angle recession, cyclodialysis, iridodialysis, zonular breaking, lens dislocation and vitreous protrusion to posterior chamber. In most cases cyclodialysis and shallow detachment of choroid can not be diagnosed because shallow anterior chamber and hypton. CONCLUSION: The result suggests that Ultrasound Biomicroscope has high clinical value in diagnosis of anterior segment contusion, especially in cornea edema, hyphemia, hypton, Ultrasound Biomicroscope can refer precise diagnosis of anterior segment contusion.

Adult↗
PubMed1995

Dopamine hypersensitivity in migraine: role in apomorphine syncope.

There is some evidence supporting a potential role of hypersensitivity of the dopaminergic system in the pathogenesis of migraine. In this case report, we describe a syncopal episode in a patient with migraine without aura after the administration of a very low dose of apomorphine, a classical agonist of dopaminergic receptors. The absence of cardiovascular risk factors in this patient suggests that the clinical event might have been caused by hypersensitivity of the dopaminergic system.

Adult↗
PubMed1994

Structural and molecular changes in intestinal smooth muscle induced by Trichinella spiralis infection.

Infection with Trichinella spiralis in the rat causes altered intestinal motility and jejunal smooth muscle contractility by day 6 postinoculation. The purpose of this study was to determine structural and molecular changes in the smooth muscle that could account for the functional changes that have been reported. By day 6 postinoculation, there was an increase in thickness of both muscle layers of the jejunum. This increase in mass was accompanied by an increase in total protein content of the seromuscular tissues. When specific proteins were analyzed, increases in actin and myosin heavy chain contents were found. On the other hand, there was no increase in collagen content. Alterations in gene expression at the pretranslational level were determined by monitoring total RNA and the proportion of mRNA that codes for alpha-smooth muscle actin. There was an increase in both parameters in longitudinal muscle from the jejunum of infected animals. The increase appeared to be site selective because there were no increases in either parameter in longitudinal muscle of the distal intestine. These results indicate that pretranslational upregulation of gene expression for actin isoforms occurs in smooth muscle of the proximal but not distal intestine during the early enteric phase of infection with T. spiralis. Thus the altered smooth muscle contractility that has been reported in experimental trichinosis may be related in part to an increased expression of smooth muscle protein.

Actins↗
PubMed1994

Antibodies to islet 37k antigen, but not to glutamate decarboxylase, discriminate rapid progression to IDDM in endocrine autoimmunity.

Apart from islet cell antibodies (ICAs), antibodies to glutamate decarboxylase (GAD), insulin autoantibodies (IAAs), and a novel islet antigen (37k antigen) are potential markers for insulin-dependent diabetes mellitus (IDDM). GAD is also an antigen in stiff-man syndrome (SMS), and both SMS and IDDM are associated with ICAs and autoimmunity to other endocrine organs. We investigated possible links between antibody responses to islet antigens with autoimmunity to other endocrine organs and determined which specific antibodies can identify individuals who progress to IDDM. Antibodies to GAD were detected in > or = 90% of both diabetic and nondiabetic patients with ICAs and other endocrine autoimmunity, in 59% of ICA-positive IDDM patients without endocrine autoimmunity, in all patients with SMS, but in only 1-3% of healthy (nondiabetic) and autoimmune disease control subjects. GAD antibody levels were increased in ICA-positive IDDM patients with polyendocrine autoimmunity compared with those without. In contrast, antibodies to 37k antigen were only detected in patients who developed acute-onset IDDM. IAAs were also associated with IDDM. Thus, certain factors enhance antibody responses to GAD in polyendocrine autoimmunity, but this does not necessarily lead to development of IDDM or SMS. Antibodies to 37k antigen are strongly associated with acute-onset IDDM and are useful serological markers for disease.

Adolescent↗
PubMed1994

Comparison of different monoclonal antibodies for the immunohistochemical assessment of cell proliferation in routine colorectal biopsy specimens.

In a series of paraffin-embedded colorectal biopsy specimens the monoclonal antibodies 19F4 and PC10 against the proliferating cell nuclear antigen (PCNA) and the antibody mib1, which recognizes the Ki67 antigen in formalin-fixed material, were compared with the Ki67 method on equivalent frozen sections to assess the applicability of these 'proliferation markers'. A high correspondence was found between the localization of the mib1 and the Ki67 immunoreaction product, associated with a highly significant quantitative correlation of the two indices (r = 0.70, p < 0.001). In contrast, after formalin fixation the two PCNA antibodies additionally stained cells outside the proliferative compartment so that a reliable assessment of cell proliferation was only possible after controlled paraformaldehyde or methacarn fixation. In the routine material mib1 was superior to PC10 because of its ability to distinguish the differences in cell proliferation among normal colorectal mucosa (29.1 +/- 6.8% positive cells), adenomas (43.3 +/- 10.6%), and carcinomas (52.9 +/- 8.7%), which PC10 did not possess (normal, 41.4 +/- 5.6%; adenomas, 37.5 +/- 8.7%; carcinomas, 51.5 +/- 8.2%).

Adult↗
PubMed1994

Low-dose cyclophosphamide in combination with cisplatin or epirubicin plus rhG-CSF allows adequate collection of PBSC for autotransplantation during adjuvant therapy for high-risk cancer.

Six patients with advanced ovarian carcinoma (OvCa), and six patients with stage II or III resectable breast cancer (BrCa) were treated with low-dose CY (LD-CY, 1500 mg/m2) and cisplatin (CDDP) 100 mg/m2 (OvCa) or epirubicin (EPR) 120 mg/m2 (BrCa) plus recombinant human G-CSF (rhG-CSF). Twelve days after chemotherapy, all patients underwent PBSC collection on an outpatient basis. Following the completion of the induction programme, all patients underwent high-dose chemotherapy (HDC) with carboplatin 1200 mg/m2, etoposide 900 mg/m2 and melphalan 100 mg/m2 with the reinfusion of PBSC. LD-CY plus rhG-CSF in combination with CDDP or EPR mobilised a very large number of PBSC. After a median of 13 days from chemotherapy, the concentration of PBSC in the peripheral blood was 40-fold higher than the same patient's baseline value. Each collection yielded a median of 10.8 x 10(4)/kg colony-forming unit granulocyte-macrophage. Severe myelosuppression occurred in all patients following HDC, but the infusion of PBSC produced a rapid and sustained haemopoietic recovery. After a median of 11 days from reinfusion, haemopoietic engraftment was complete and 80% of the patients had platelets > 100 x 10(9)/l and PMN > 1 x 10(9)/l within 14 days after reinfusion. We can conclude that the present therapeutic approach is an excellent option for mobilisation, collection and transplantation of PBSC during intensive dose adjuvant polychemotherapy of high-risk cancer.

Adult↗
PubMed1994

Novel subtype of peroxisomal acyl-CoA oxidase deficiency and bifunctional enzyme deficiency with detectable enzyme protein: identification by means of complementation analysis.

We describe four infants with a novel subtype of an isolated deficiency of one of the peroxisomal beta-oxidation enzymes with detectable enzyme protein. The patients showed characteristic clinical and biochemical abnormalities, including hypotonia, psychomotor retardation, hepatomegaly, typical facial appearance, accumulation of very-long-chain fatty acids, and decreased lignoceric acid oxidation. However, beta-oxidation enzyme proteins were detected by immunoblot analyses, and large peroxisomes were identified by immunofluorescence staining. In order to identify the underlying defect in these patients, complementation analysis was introduced using fibroblasts from these patients and patients with an established deficiency of either acyl-CoA oxidase or bifunctional enzyme, as identified by immunoblotting. In the complementing combinations, fused cells showed increased lignoceric acid oxidation, resistance against 1-pyrene dodecanoic acid/UV selection, and normalization of the size and the distribution of peroxisomes. The results indicate that two patients with a more severe clinical course were suffering from bifunctional enzyme deficiency and that the other two infants, who were siblings and had a less severe clinical presentation, were the first patients with acyl-CoA oxidase deficiency with detectable enzyme protein.

3-Hydroxyacyl CoA Dehydrogenases↗
PubMed1993

Depletion of mesolimbic dopamine during behavioral despair: partial reversal by chronic imipramine.

Exposure of rate to the behavioral despair test (an animal model of depression) for 40 min resulted in a long-lasting depletion of mesolimbic dopamine output to about 40% of baseline values. The decrease in extracellular dopamine was partially prevented by chronic pretreatment with imipramine (20 mg/kg per day i.p. for 21 days). The results suggest that a fall in mesolimbic dopamine output may be associated with depressive states and indicate that changes in the functional status of the dopamine system contribute to the mechanism of action of imipramine.

3,4-Dihydroxyphenylacetic Acid↗
PubMed1993

Corticotropin-releasing hormone stimulates adenylyl cyclase activity in the retinas of different animal species.

In the present study we investigated the presence of corticotropin-releasing hormone (CRH)-stimulated adenylyl cyclase activity in the retinas of different animal species. CRH significantly stimulated adenylyl cyclase activity in homogenates of calf, pig, rabbit and guinea pig retinas. The stimulatory effects were concentration-dependent with half-maximal responses occurring at 20-30 nM CRH. The enzyme activities increased by 37-80% at the maximal concentration of CRH (1 microM). On the other hand, adenylyl cyclase activities of chicken and pigeon retinas were poorly stimulated by CRH. In calf, pig and rabbit retinas, the CRH effect was completely antagonized by the CRH receptor antagonist alpha-helical CRH 9-41 and required the presence of GTP. The stimulatory response elicited by CRH was also found to be not additive with that produced by either vasoactive intestinal peptide or dopamine. These results provide evidence for the presence in retinas of different animal species of functional CRH receptors, an important criterion for the classification of CRH as a retinal neurotransmitter.

Adenylyl Cyclases↗
PubMed1993

An investigation into the role of reactive oxygen species in the mechanism of 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine toxicity using neuronal cell lines.

The study of oxygen radical generation and effects during 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP) metabolism was undertaken in an in vitro test system. Three neurochemically discrete neuronal cell lines, B50 (cholinergic) and B65 rat cell lines and SKNSH human neuroblastoma (both catecholaminergic), were exposed to MPTP (0-200 microM). Parallel experiments were performed using reagent H2O2, an intermediate which may be generated during MPTP metabolism, to determine whether MPTP and H2O2 had any selectivity of toxicity and whether the mechanisms of cell death were similar. MPTP toxicity was shown to be reduced by monoamine oxidase B inhibitors, pargyline (P < 0.01) and selegiline (P < 0.05), indicating that toxicity was due to metabolism of MPTP rather than the parent compound. Cytotoxicity was also decreased in the presence of antioxidants, most notably in the presence of superoxide dismutase and catalase together (P < 0.01), suggesting that reactive oxygen species (ROS) play a role in MPTP-induced cell death. Attempts to determine the intracellular target for oxidative attack did not identify significant levels of lipid peroxidation products, but did demonstrate nucleoid expansion, possibly the result of double stranded DNA breaks induced by ROS.

1-Methyl-4-phenyl-1,2,3,6-tetrahydropyridine↗
PubMed1993

JHM virus-specific cytotoxic T cells derived from the central nervous system.

Spleen cells cultured from Balb/c mice immunized with the JHM strain of mouse hepatitis virus (JHMV) have CD8+ cytotoxic T cells (CTL) specific for both the S and N proteins, but not the M or HE proteins. T cell lines were established from the brains of Balb/c mice infected with JHMV. The majority of the lines (20 of 22) were specific for JHMV. Analysis of the viral structural proteins which served as target structures indicate that most (15 of 20) were specific for the N protein. One line was specific for the S protein and four lines were specific for JHMV but the protein recognized could not be determined. These data suggest that early during infection there is a preferential recruitment of N protein specific CTL into the CNS of infected mice.

Animals↗
PubMed1991

Independent cellular and ontogenetic expression of mRNAs encoding three alpha polypeptides of the rat GABAA receptor.

Previous studies have shown that several distinct but related polypeptides can serve as alpha subunits of functional GABAA receptors. Furthermore, the diversity of these polypeptides at least partially accounts for the functional heterogeneity of GABAA receptors. In this paper, we report the results of in situ hybridization studies using probes derived from our recently reported cDNAs for alpha 1, alpha 2, and alpha 4 GABAA receptor polypeptides. We show that the mRNAs that encode these isoforms have distinct regional and cellular distributions and are present at widely varying levels within the rat brain. In addition, our Northern blot analyses indicate that each of these three alpha mRNAs has a distinct pattern of ontogenetic regulation. Differential regulation of alpha polypeptide isoforms may lead to changes in GABAA receptor function during ontogeny as well as to distinct cellular responses to GABA and GABA-related drugs.

Animals↗
PubMed1991

Purification of recombinant HIV-1 protease.

A method is described to purify recombinant HIV-1 protease from soluble extracts of Escherichia coli. The isolation involves QAE-Sepharose anion exchange chromatography, hexyl agarose hydrophobic interaction chromatography, MonoS cation exchange chromatography, and Superose 6 size exclusion chromatography. Approximately 100 micrograms of protease was obtained from 18 g E. coli paste. The protein was judged to be homogeneous due to the presence of a single band on a silver-stained SDS polyacrylamide gel.

Chromatography, Agarose↗
PubMed1991

Parents' perceptions of children with chronic illness: a study of immigrant Chinese families.

This article describes and discusses parents' perceptions of a children with a long-term health problems in 16 Chinese immigrant families and 15 Euro-Canadian families. These data are part of a larger study, the purpose of which was to explore the illness experience and help-seeking behavior of these families. The data show that the Euro-Canadian parents see the illness or disability as affecting only particular aspects of the child's life, while the child as a whole is seen as normal. The Chinese parents more frequently describe the illness as having global effects on many aspects of the child's present and future life. These differences in perception are discussed in relation to literature about Chinese culture and the experience of immigration. It is suggested that how a parent perceives a child's illness affects how a parent cares for the child and interacts with health care providers.

Attitude to Health↗
PubMed1990

Substitutions at the P2' site of gag p17-p24 affect cleavage efficiency by HIV-1 protease.

Heptapeptide substrates containing a single amino acid substitution at the p2' position of the gag p17-p24 junction (S-Q-N-Y-P-X-V where X = G, A, L, I, F, and W) were compared as substrates for HIV-1 protease. Binding of the Ile-, Leu-, and Ala- containing peptides was about equal although hydrolysis was 20-fold lower for the Ala and Leu peptides compared to Ile. Insertion of Gly or Phe at the p2' position resulted in significantly lower cleavage of the peptide while a Trp-containing peptide was not cleaved. These data suggest that a relatively small hydrophobic amino acid is important for hydrolysis and binding at this site. Structure-activity studies such as those described here may be useful in the design of specific inhibitors for HIV-1 protease.

Amino Acid Sequence↗