Biomedical subjects

C H Yang

Publications and source records attributed to C H Yang.

At least 127 records · Page 7Linked to original sources

PubMed1997

mirror encodes a novel PBX-class homeoprotein that functions in the definition of the dorsal-ventral border in the Drosophila eye.

The Drosophila eye is composed of dorsal and ventral mirror-image fields of opposite chiral forms of ommatidia. The boundary between these fields is known as the equator. We describe a novel gene, mirror (mrr), which is expressed in the dorsal half of the eye and plays a key role in forming the equator. Ectopic equators can be generated by juxtaposing mrr expressing and nonexpressing cells, and the path of the normal equator can be altered by changing the domain of mrr expression. These observations suggest that mrr is a key component in defining the dorsal-ventral boundary of tissue polarity in the eye. In addition, loss of mrr function leads to embryonic lethality and segmental defects, and its expression pattern suggests that it may also act to define segmental borders. Mirror is a member of the class of homeoproteins defined by the human proto-oncogene PBX1. mrr is similar to the Iroquois genes ara and caup and is located adjacent to them in this recently described homeotic cluster.

Amino Acid Sequence↗

PubMed1997

Carbachol induces inward current in rat neostriatal neurons through a G-protein-coupled mechanism.

Our recent study demonstrated that carbachol can act at M1-like muscarinic receptors to reduce the membrane K+ conductance and excite the neostriatal neurons. In the present study, we further studied the molecular mechanism by which carbachol induced inward currents in neostriatal neurons. In acutely isolated neostriatal neurons held at-60 mV, pressure application of carbachol (30 microM) induced a transient inward current underlying whole-cell voltage-clamp mode. In cells loaded with the stable GDP analogue guanosine 5'-0-(2-thiodiphosphate) (GDP-beta-S, 1 mM), the carbachol-induced inward current was significantly diminished. However, the carbachol response was not affected by intracellular dialysis of the neostriatal neurons with either protein kinase C (PKC) inhibitors, PKCI 19-36 (5 microM) or NPC-15437 (20 microM), or a potent cAMP-dependent protein kinase (PKA) inhibitor, Rp-cAMPS (25 microM). These results show that a G-protein-coupled mechanism mediates carbachol-induced inward current in the neostriatal neurons and that neither PKC- nor PKA-dependent intracellular transduction pathways are involved in the carbachol response.

Animals↗

PubMed1997

Behavioural disturbances in psychiatric inpatients with dementia of the Alzheimer's type in Taiwan.

This report studied behavioural disturbances in psychiatric inpatients with dementia of the Alzheimer's type (DAT) in Taiwan. The sample consisted of 75 inpatients with DAT who were consecutively admitted to the geropsychiatric ward. Their behavioural disturbances were obtained from semistructured interviews with families and ward observation. There were eight main behavioural disturbances: getting lost, repetitive phenomena, sleep disturbance, aggression, wandering, hyperphagia, hoarding behaviour, and inappropriate sexual behaviour. Number of behavioural disturbances, wandering, hyperphagia and sleep disturbance were significantly associated with the severity of cognitive impairment.

Aged↗

PubMed1997

Community-acquired Acinetobacter pneumonia: a case report.

A 35-year-old male with glucose-6-phosphate dehydrogenase (G6PD) deficiency was admitted because of right chest (pleuritic) pain, fever, cough with scarce production of blood-tinged sputum, and generalized yellowish discolouration of skin for 2 days. Radiographic examination revealed right lower lobe necrotizing pneumonia. Hypotension, dyspnoea and severe haemolysis was noted the next day. Echo-guided lung aspiration and sputum cultures both grew Acinetobacter baumannii. Antibiotic therapy was started immediately, but fever persisted and abscess formation was noted 1 week later. After aggressive supportive and antibiotic therapy, he made a slow but complete recovery from the pneumonia, and was then discharged in a stable condition. Acinetobacter baumannii is a well-known causative agent of nosocomial infections, particularly in intensive units. Community-acquired pneumonia, however, is quite rare, and usually has a fulminant course and high case fatality rate.

Acinetobacter↗

PubMed1997

Intraocular lens position and anterior chamber angle changes after cataract extraction in eyes with primary angle-closure glaucoma.

PURPOSE: To prospectively study the anterior chamber angle in eyes with chronic primary angle-closure glaucoma (PACG) having posterior chamber intraocular lens (IOL) implantation and evaluate IOL position and intraocular pressure (IOP). SETTING: National Taiwan University Hospital, Taipei, Taiwan. METHODS: Using Scheimpflug image processing, the anterior chamber angles were studied in 20 consecutive eyes with chronic PACG and 10 control eyes before and after posterior chamber IOL implantation. Anterior chamber depth, chamber angle width, IOL position, and IOP change were evaluated. RESULTS: Mean anterior chamber depth in the PACG group was 2.04 +/- 0.29 mm preoperatively and 3.44 +/- 0.16 mm postoperatively. The anterior chamber angle widened significantly in relation to the superior, inferior, temporal, and nasal quadrants after surgery. The degree of IOL tilting and decentration was the same in both the PACG and control groups. All eyes in the PACG group maintained an IOP under 21 mm Hg during the 6 month follow-up. Eighty-four percent maintained or decreased their antiglaucoma medication; 16% required increased medication. CONCLUSION: Cataract extraction with posterior chamber IOL implantation in eyes with PACG controlled IOP well in most cases.

Aged↗

PubMed1997

Effect of exercise and exogenous glucocorticoid on serum level of intact parathyroid hormone.

Most previous studies suggest that physical exercise, or physiological response to exercise such as cortisol and adrenaline secretion regulate parathyroid hormone (PTH) secretion in humans. To investigate the effects and possible interaction of exercise and excessive glucocorticoid on PTH secretion, we examined the serum of levels of intact-PTH, cortisol, adrenocorticotrophic hormone (ACTH), calcium, magnesium and phosphorus before and during one-hour of bicycle-ergometric exercise at 60% of maximal oxygen uptake. These exercise tests were performed on eight Chinese male volunteers aged between 20 and 25 years, once with and once without pretreatment with 0.5 mg of dexamethasone taken orally 9.5 hours in advance. The results showed that dexamethasone pretreatment significantly lowered basal levels of cortisol and ACTH, but intact PTH did not change. After 60 minutes of bicycling, intact PTH level increases by 50% of baseline both with and without dexamethasone pretreatment. Serum levels of calcium, corrected for changes in serum albumin concentration, phosphorus and magnesium also increased in both cases. This study demonstrated an increase of intact-PTH with exercise which was not associated with hypocalcemia or hypomagnesemia, and was not altered in the presence of mild exogenous glucocorticoid excess and suppressed endogenous cortisol secretion.

Adrenocorticotropic Hormone↗

PubMed1997

Inhibition of RPE cell-mediated matrix adhesion and collagen gel contraction by crovidisin, a collagen-binding snake venom protein.

PURPOSE: Cell-mediated collagen gel contraction plays an important role in the pathogenesis of proliferative vitreoretinopathy (PVR). Anti-adhesion therapy has been suggested as a promising strategy in the treatment of PVR. Crovidisin, a snake venom protein isolated from Crotalus viridis, has been shown to bind selectively to collagen and to inhibit collagen-induced platelet aggregation. In the present study, the effectiveness of crovidisin in inhibiting the attachment of retinal pigment epithelial (RPE) cells to collagen, and RPE cell-mediated collagen gel contraction, was evaluated. METHODS: Fluorescein isothiocyanate (FITC)-conjugated crovidisin was prepared and used to evaluate its binding affinity for collagen type I, fibronectin, vitronectin, and laminin. The inhibitory effect of crovidisin on RPE cell-mediated extracellular matrix attachment and collagen gel contraction was evaluated by cell adhesion and type I collagen gel contraction assays. The cytotoxic effect of crovidisin was examined with a cell proliferation assay, using the Alamar blue method. Flavoridin, an Arg-Gly-Asp-containing peptide from viper venom, was used for comparison. RESULTS: FITC-conjugated crovidisin bound selectively to collagen type I with high affinity. It did not bind to other matrix proteins, including fibronectin, vitronectin and laminin, nor to RPE cells. Crovidisin inhibited RPE cell attachment to type I collagen in a dose-dependent manner. This inhibitory effect was enhanced by the presence of flavoridin. Crovidisin also dose-dependently inhibited RPE cell-mediated type I collagen gel contraction. Crovidisin was non-toxic to RPE cells. CONCLUSIONS: Crovidisin, a snake venom-derived collagen-binding protein, possessing an inhibitory activity on RPE cell-collagen interaction and RPE cell-mediated collagen gel contraction, may be a useful tool for studying cell-collagen interaction, and a potential anti-adhesion therapeutic agent for ocular disorders in which cell-collagen interaction in involved, such as PVR.

Animals↗

PubMed1997

Evidence for the essential histidine residues in geranylgeranyl transferase type I from bovine testis.

Geranylgeranyl transferase was purified 30,000-fold by sequential use of 30-50% ammonium sulfate fractionation, Q-Sepharose anion exchange chromatography, Phenyl Superose hydrophobic interaction chromatography, Sephacryl S-300 gel filtration chromatography, and peptide (YREKKFFCAIL) affinity chromatography. Geranylgeranyl transferase, when incubated with diethyl pyrocarbonate (DEPC), a histidine-specific reagent, shows time-dependent inactivation, and the activity is restored by the addition of neutral hydroxylamine. The inactivation follows pseudo-first order kinetics with a second order rate constant of 0.319 M-1min-1. The overall results thus provide evidence that a histidine residue in the active site is involved in the catalytic mechanism of the geranylgeranyl transferase reaction.

Alkyl and Aryl Transferases↗

PubMed1997

Anterior chamber angles shallowing and intraocular pressure after topical pilocarpine.

Pilocarpine has been well recognized as the drug of choice for acute angle-closure glaucoma. The purpose of this study is to clarify quantitatively the change of anterior chamber angle and depth with the passage of time after pilocarpine drop administration. Chamber angles of the four quadrants and chamber depths were measured in 18 normal subjects by Scheimpflug Video Image prior to and 30, 60, and 180 minutes after administration of one drop of 4% pilocarpine in one eye, while the opposite eye served as control. The anterior chamber angle and depth showed a significant shallowing at 30, 60 and 180 minutes after 4% pilocarpine administration with a maximal effect of -3.61 degrees and -0.15 mm at 30 minutes, respectively, while the reduction of intraocular pressure reached its maximal effect at 180 minutes. These facts should be well understood in the treatment of angle-closure glaucoma.

Adult↗

PubMed1997

A transgenic mutant of Lactuca sativa (lettuce) with a T-DNA tightly linked to loss of downy mildew resistance.

One hundred and ninety-two independent primary transformants of lettuce cv. Diana were obtained by co-cultivation with Agrobacterium tumefaciens carrying constructs containing maize Ac transposase and Ds. R2 families were screened for mutations at four genes (Dm) for resistance to downy mildew. One family, designated dm3t524, had lost resistance to an isolate of Bremia lactucae expressing the avirulence gene Avr3. Loss of resistance segregated as a single recessive allele of Dm3. The mutation was not due to a large deletion as all molecular markers flanking Dm3 were present. Loss of Dm3 activity co-segregated with a T-DNA from which Ds had excised. Genomic DNA flanking the right border of this T-DNA was isolated by inverse polymerase chain reaction. This genomic sequence was present in four to five copies in wild-type cv. Diana. One copy was missing in all eight deletion mutants of Dm3 and altered in dm3t524, indicating tight physical linkage to Dm3. Three open reading frames (ORFs) occurred in a 6.6-kb region flanking the insertion site; however, expression of these ORFs was not detected. No similarities were detected between these ORFs and resistance genes cloned from other species. Transgenic complementation with 11-to 27-kb genomic fragments of Diana spanning the insertion site failed to restore Dm3 function to two ethyl methanesulfonate (EMS)-induced mutants of Dm3 or to cv. Cobham Green, which naturally lacks Dm3 activity. Therefore, either the T-DNA inserted extremely close to, but not within, Dm3 and the mutation may have been caused by secondary movement of Ds, or Dm3 activity is encoded by a gene extending beyond the fragments used for complementation.

DNA, Bacterial↗

PubMed1997

Epidural dexamethasone reduces the incidence of backache after lumbar epidural anesthesia.

We performed a prospective, randomized, double-blind study to compare the effect of epidural dexamethasone on the incidence of postepidural backache after nonobstetric surgery. One thousand unpremedicated ASA physical status I or II patients scheduled for hemorrhoidectomy were randomly assigned to two groups: Group I patients received 25 mL 2% lidocaine with epinephrine 1:200,000 and 1 mL dexamethasone (5 mg) epidurally. Patients were interviewed at 24,48, and 72 h postoperatively using a standard visual analog scale (VAS) for evaluation of postepidural backache. A patient was considered to have postepidural backache when the postoperative VAS score was higher than the preoperative score. The incidence of postepidural backache in Group I patients for the 3 days were 22.8%, 17.4%, and 9.2%, all of which were significantly more frequent than observed in Group II patients (7.4%,5.6%, and 2.8%, P < 0.01). The severity and duration of postepidural backache were also significantly decreased in Group II patients. In our study, there was a significant association between postepidural backache and multiple attempts at epidural needle insertion. In summary, epidural dexamethasone reduced the incidence and severity of postepidural backache.

Adult↗

PubMed1997

Propofol anesthesia increases dopamine and serotonin activities at the somatosensory cortex in rats: a microdialysis study.

We sought to estimate the activities of dopamine and serotonin in animals receiving propofol anesthesia. The in vivo microdialysis technique was used in Sprague-Dawley rats (n = 6) to measure the major metabolites of dopamine and serotonin, i.e. 3,4-dihydroxyphenylacetic acid (DOPAC), homovanillic acid (4-hydroxy-3-methyphenylacetic acid; HVA) and 5-hydroxy indole acetic acid (5-HIAA) in the somatosensory cortex. We also measured the levels of propofol in the brain and blood by microdialysis sampling in another group of rats (n = 6). During the experiment, the rat was infused intravenously (IV) with propofol at a rate of 10 mg x kg(-1) x h(-1) for 60 min and 60 mg x kg(-1) x h(-1) for 40 min. We found that IV infusion of propofol at a rate of 60 mg x kg(-1) x h(-1) significantly increased DOPAC, HVA, and 5-HIAA. We also determined that these changes correlated well with propofol levels in the brain and blood. We concluded that anesthetic doses of propofol increased the functional activities of dopamine and serotonin in the cortex. These increases correlate well with propofol levels in the cortex and blood.

3,4-Dihydroxyphenylacetic Acid↗

PubMed1997

Delusions of theft in dementia of the Alzheimer type: a preliminary report.

Delusions of theft are commonly found in patients with dementia of the Alzheimer type (DAT). This report describes the frequency, onset, and characteristics of delusions of theft in DAT patients. The sample consisted of 54 geropsychiatric inpatients with DAT; delusions of theft were found in 30 (55.6%) patients. Two thirds of these patients had delusions of theft within 1 year after onset of illness. There were no significant differences in age, age of onset, duration of disease, years of education, or the Mini-Mental State Examination (MMSE) score between patients with and without delusions of theft. Delusions of theft frequently occur in the early stage of dementia, when the patients' cognitive impairments are relatively mild. The presence of this symptom may warrant a diagnosis of DAT.

Aged↗

PubMed1997

Integration specificities of two lambdoid phages (21 and e14) that insert at the same attB site.

It was shown previously that phage 21 and the defective element e14 integrate at the same site within the icd gene of Escherichia coli K-12 but that 21 integrase and excisionase excise e14 in vivo very infrequently compared to excision of 21. We show here that the reverse is also true: e14 excises itself much better than it excises an adjacent 21 prophage. In vitro integrase assays with various attP substrates delimit the minimal attP site as somewhere between 366 and 418 bp, where the outer limits would include the outermost repeated dodecamers suggested as arm recognition sites by S. J. Schneider (Ph.D. dissertation, Stanford University, Stanford, Calif., 1992). We speculate that the reason 21 attP is larger than lambda attP (240 bp) is because it must include a 209-bp sequence homologous to the 3' end of the icd transcript in order to allow icd expression in lysogens. Alteration of portions of 21 attP to their e14 counterparts shows that 21 requires both the arm site and core site sequences of 21 but that replacements by e14 sequences function in some positions. Consistent with Schneider's in vivo results, and like all other known integrases from lambdoid phages, 21 requires integration host factor for activity.

Bacterial Proteins↗

PubMed1997

Granulocyte-macrophage colony-stimulating factor receptor-targeted therapy of chemotherapy- and radiation-resistant human myeloid leukemias.

Contemporary therapies for acute myeloid leukemia (AML) commonly fail to cure patients because of the emergence of drug resistance. Drug resistance in AML is multifactorial but can be associated with the overexpression of transmembrane transporter molecules, including P-glycoprotein (Pgp) or the multidrug resistance-associated protein (MRP), or associated with inactivation of the p53 tumor suppressor gene, as well as overexpression of the anti-apoptotic protein bcl-2. We are investigating if novel recombinant biotherapeutics can circumvent these resistance mechanisms to effectively treat refractory AML. To target the lethal action of diphtheria toxin (DT) to high affinity granulocyte-macrophage colony-stimulating factor (GMCSF) receptors on AML blasts, we have produced a recombinant chimeric fusion toxin, DTctGMCSF. Since DTctGMCSF enters and kills its target cells by unique mechanisms (GMCSF-receptor binding and protein synthesis inhibition) and is not similar in structure to Pgp or MRP substrates, we postulated that it would be an active agent against therapy-resistant AML. DTctGMCSF was selectively cytotoxic (IC50 1-10ng/ml) to GMCSF-receptor positive AML cells expressing the Pgp- or MRP-associated multi-drug resistant phenotypes, despite high level resistance to conventional chemotherapeutic agents. DTctGMCSF also efficiently killed AML cells deficient in p53 expression, as well as radiation-resistant AML cells and mixed lineage leukemia cells expressing high levels of bcl-2. In addition, DTctGMCSF killed > 99% of primary leukemic progenitor cells from therapy-refractory AML patients under conditions that we have previously found to not adversely affect the proliferative capacity or differentiation of pluripotent normal hematopoietic progenitor cells. DTctGMCSF may prove useful in treating myeloid leukemias that are otherwise resistant to a wide range of conventional therapies.

Antineoplastic Agents↗

PubMed1997

A recombinant fusion toxin targeted to the granulocyte-macrophage colony-stimulating factor receptor.

Human granulocyte-macrophage colony stimulating factor (GMCSF) and its high affinity receptor function to regulate the proliferation and differentiation of myeloid lineage hematopoietic cells, and may participate in the pathogenesis of many malignant myeloid diseases. We have used genetic engineering based on the elucidated molecular structures of human granulocyte-macrophage colony-stimulating factor and diphtheria toxin (DT) to produce a recombinant fusion toxin, DTctGMCSF, that targets diphtheria toxin to high affinity GMCSF receptors expressed on the surface of blast cells from a large fraction of patients with acute myeloid leukemia (AML). DTctGMCSF was specifically immunoreactive with antidiphtheria toxin and anti-GMCSF antiseras, and exhibited the characteristic catalytic activity of diphtheria toxin, catalyzing the in vitro ADP-ribosylation of purified elongation factor 2. The cytotoxic effects of DTctGMCSF were examined using the 3-(4,5-dimethylthiazol-2-yl)-2,5-tetrazolium (MTT) bromide assay of cell viability and in vivo assays of protein synthesis inhibition. DTctGMCSF were specifically cytotoxic to human leukemia cell lines bearing high affinity receptors for human GMCSF with IC50 of 10(-9) to 10(-11) M. It was not toxic to mammalian hematopoietic cell lines lacking human GMCSF (hGMCSF) receptors. In receptor positive cells, cytotoxicity can be specifically blocked by a large excess of hGMCSF, confirming that its cytotoxicity is mediated through the hGMCSF receptor. THough DTctGMCSF inhibited granulocyte-macrophage colony formation by committed myeloid progenitor cells (CFU-GM), it did not significantly affect erythroid burst formation by committed erythroid progenitor cells (BFU-E), or mixed granulocyte-erythroid-macrophage-megakaryocyte colony formation by pluripotent multilineage progenitor cells (CFU-GEMM). DTctGMCSF holds promise for the treatment of myeloid lineage malignancies, and is a useful reagent to study hematopoiesis.

Animals↗

PubMed1997

EBV-elicited familial hemophagocytic lymphohistiocytosis.

Familial hemophagocytic lymphohistiocytosis (FHL) is a rapidly fatal illness, usually encountered in infancy, characterized by fever, hepatosplenomegaly, pancytopenia, and central nervous system involvement. Microscopic examination of tissue shows a non-malignant lymphohistiocytic infiltrate, with prominent erythrophagocytosis. FHL is an autosomal recessive hereditary disorder but may develop secondarily to other conditions such as immunosuppression, malignancies, fat overload and certain infections. We recently experienced a case of siblings developing FHL, which may be associated with EBV infection.

Child, Preschool↗

PubMed1997

Delusional jealousy in dementia.

BACKGROUND: Delusional jealousy is a major motive for violence and is sometimes found in demented patients. This study was undertaken to investigate the frequency and the characteristics of delusional jealousy in demented patients. METHOD: The sample population consisted of 133 demented patients admitted to the geropsychiatric ward. Patients with and without delusional jealousy were compared in terms of general characteristics and psychotic symptoms. RESULTS: Of the 133 demented patients, 21 (15.8%) showed delusional jealousy. Delusional jealousy was found in various types of dementia. There were no significant differences between the two groups in regard to age, age at onset, gender, educational level, and Mini-Mental State Examination score. All patients with delusional jealousy had at least one other psychotic symptom. CONCLUSION: Delusional jealousy is a common problem in dementia. The psychobiological factors of delusional jealousy and cognitive function in demented patients may differ. There may be various underlying factors for the development of delusional jealousy in dementia.

Age Factors↗