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Biomedical subjects

B Chang

Publications and source records attributed to B Chang.

At least 163 records · Page 9Linked to original sources

[Analysis of the linear migration of the radionuclide along meridians in perfused extremities of monkey].

On the basis of researches in human body, further experiment in monkeys was conducted and the result has demonstrated that: 1. There was a close and complicated relation between the migration of 99mTc injected into acupoints and the blood circulation. 2. The location of the migration was mainly in the subcutaneous lay. 3. There were no direct relationship between the migration and periphery nerve system.

Animals↗

Accuracy of the Denver-II in developmental screening.

One of the oldest and best known developmental screening tests was recently restandardized and revised as the Denver-II. Because it was published without evidence of its accuracy, the present study was undertaken with 104 children between 3 and 72 months of age attending one of five day-care centers. To determine the presence of developmental problems, children were administered individual measures of intelligence, speech-language, achievement, and adaptive behavior. A second psychological examiner, blind to the outcome of the diagnostic battery, administered the Denver-II. Developmental problems including language impairments, learning disabilities, mild mental retardation, and/or functional developmental delay were found in 17% of the children. The Denver-II identified correctly 83% and thus had high rates of sensitivity. However, more than half the children with normal development also received abnormal, questionable, or untestable Denver-II scores. Thus the test had limited specificity (43%) and a high overreferral rate. The alternative scoring method, categorizing questionable/untestable scores as normal, caused sensitivity to drop to 56% although specificity rose to 80%. Since neither scoring method produced acceptable levels of accuracy, an effort was made to locate the sources of accuracy and inaccuracy within the test. Only items in the language domain were modestly helpful in discriminating children with and without difficulties. The findings suggest that the authors of the Denver-II need to engage in further development of the instrument including revising scoring criteria and item placement in relation to children's ages. In the interim, test users should employ screening tests which are more accurate such as the Minnesota Inventories or the Battelle Developmental Inventory Screening Test.

Child, Preschool↗

Analysis of diuretic doping agents by HPLC screening and GC-MSD confirmation.

The simultaneous analysis of 14 diuretics in human urine (belonging to five different pharmacological groups) by reversed-phase high-performance liquid chromatography (HPLC) with a diode-array detector was developed by using a gradient elution with acetonitrile and phosphate buffer containing propylamine hydrochloride on a Bondclone-ODS (10 microns) column. The method was applied to the screening test of several diuretics abused by athletes. The confirmation analysis was performed by gas chromatography-mass spectrometry with ion-selective detection (GC-MSD). The characteristic mass fragment ions obtained by electron-impact (EI) ionization (70 eV) provided sufficient identification of these diuretic agents. During the 1990 weight-lifting contest of Asia in Kao-Hsiung, Republic of China, one urine sample was found positive for the diuretic hydrochlorothiazide.

Chromatography, High Pressure Liquid↗

Sodium nitroprusside degenerates cultured rat striatal neurons.

Incubation of a primary culture of rat striatal neurons with sodium nitroprusside (SNP), a known source of nitric oxide (NO), showed a concentration-dependent increase in cyclic GMP levels with an EC50 value of 13.7 microM. Twenty-four hours following incubation with 10 microM SNP, striatal neurons underwent degeneration as assessed immunohistochemically and biochemically. In contrast, potassium ferricyanate at concentrations up to 1 mM had no effect on striatal neuron viability. These results indicate that SNP has neurotoxic actions in-vitro, an effect that may involve NO as a second messenger.

Animals↗

Formation of endothelium-derived relaxing factor in porcine kidney epithelial LLC-PK1 cells: an intra- and intercellular messenger for activation of soluble guanylate cyclase.

Oxytocin, bradykinin, melittin and A23187 increased cyclic GMP levels through activation of soluble guanylate cyclase in cultured porcine kidney epithelial cells, LLC-PK1. NG-monomethyl-L-arginine, an inhibitor of endothelium-derived relaxing factor/nitric oxide formation, decreased both basal and stimulated levels of cyclic GMP in a concentration-dependent manner. L-Arginine, but not D-arginine, augmented basal as well as stimulated levels of cyclic GMP and prevented the inhibition induced by NG-monomethyl-L-arginine. Similar effects of L-arginine were also observed with L-argininamide, L-arginine ethyl ester, L-arginine methyl ester and the dipeptide L-arginyl-L-aspartic acid. NG-monomethyl-L-arginine did not affect cyclic GMP accumulation induced by sodium nitroprusside, an activator of soluble guanylate cyclase, and atrial natriuretic factor, an activator of particulate guanylate cyclase. Stimulatory effects of oxytocin, glyceryl trinitrate, sodium nitroprusside, bradykinin, melittin and A23187 on cyclic GMP accumulation were enhanced with superoxide dismutase and diminished with oxyhemoglobin. However, atrial natriuretic factor-induced cyclic GMP accumulation was not affected. Furthermore, endothelium derived relaxing factor-like activity was detected in the conditioned medium from LLC-PK1 cells stimulated with oxytocin. Based on these data, we conclude that endothelium-derived relaxing factor is produced in this cell type and participates in the regulatory mechanism of cyclic GMP formation as an intra- and intercellular messenger for activation of soluble guanylate cyclase.

Animals↗

Effects of retinoic acid on the in vivo growth of human neuroblastoma cells.

We have investigated the effects of retinoic acid (RA) on the development and growth in nude mice of tumors derived from the human neuroblastoma cell line LA-N-5. When cells were treated with 4 x 10(-6) M RA in vitro there was a marked reduction in the number of mice developing tumors when compared to solvent-treated controls. In vivo treatment with RA reduced tumor formation when the retinoid was given for 5 days before tumor injection and continued for 14 days thereafter. In established tumors, RA inhibited progressive tumor growth. There was no demonstrable effect of RA in vivo on the morphologic phenotype of the tumor cells when these regimens were used. We conclude that oral retinoid administration may prove useful in inhibiting or arresting the growth of neuroblastoma, particularly when there is a small initial tumor burden.

Animals↗

Characterization of ATP-stimulated guanylate cyclase activation in rat lung membranes.

Many of the effects of ANP are mediated through the elevation of cellular cGMP levels by the activation of particulate guanylate cyclase. While the stimulation of this enzyme is receptor-mediated, the molecular mechanism of activation remains unknown. In this study we present evidence that ATP as well as its analogues adenosine-5'-O-(3-thiotriphosphate) (ATP gamma S) and adenylylimidophosphate (AMPPNP) activates guanylate cyclase from rat lung membranes and markedly potentiates the effect of ANP on the enzyme. The order of potency is ATP gamma S greater than ATP greater than AMPPNP. The enzyme activation by adenine nucleotide and ANP together is much more than the sum of the individual activations, suggesting that ATP may be the physiological component essential for the ANP-stimulated guanylate cyclase activation. The ATP gamma S-stimulated guanylate cyclase activity diminishes in the presence of various kinds of detergents, suggesting either that the conformation of an ATP binding site in guanylate cyclase is altered by detergents or that protein-protein interaction may be involved in the activation of guanylate cyclase by ATP. Guanylate cyclase from rat lung membranes is poorly activated by ANP and/or ATP gamma S after removing the cytosolic and weakly membrane-associated proteins or factors by centrifugation. Pre-incubation of the membranes with ATP gamma S retains enzyme activation after membrane washing. These results suggest either that ATP gamma S stabilizes the conformation of nucleotide binding site in guanylate cyclase from denaturation by membrane washing, or that the stimulatory effect of ATP on guanylate cyclase activity may be mediated by accessory proteins or non-protein cofactors which are lost during membrane washing, but remain bound to membranes by ATP gamma S pretreatment.

Adenosine Triphosphate↗

N omega-nitro-L-arginine: a potent inhibitor of endothelium-derived relaxing factor formation.

Endothelium-derived relaxing factor (EDRF) released from cultured endothelial cells was assayed by examining changes in cyclic GMP levels of rat lung fibroblasts. N omega-nitro-L-arginine and NG-monomethyl-L-arginine inhibited basal and A23187-, ATP- and melittin-induced EDRF release, and the inhibition was prevented with L-arginine. The IC50 values of N omega-nitro-L-arginine and NG-monomethyl-L-arginine for EDRF release evoked with 1 microM A23187 were 230 nM and 16 microM, respectively. N omega-nitro-L-arginine and NG-monomethyl-L-arginine did not affect cyclic GMP accumulation in the fibroblasts with atrial natriuretic factor or sodium nitroprusside. Thus, N omega-nitro-L-arginine is 70 times more potent than NG-monomethyl-L-arginine as a specific inhibitor of EDRF formation/release.

Adenosine Triphosphate↗

Effects of 13-cis retinoic acid therapy on human antibody responses to defined protein antigens.

We have evaluated the in vivo effects of 13-cis retinoic acid (13-cis RA) on human antibody responses to immunization with tetanus toxoid (TT) and keyhole limpet hemocyanin (KLH). Subjects with severe cystic acne were immunized with suboptimal doses (10 micrograms) of KLH 7 d and 3 months after starting retinoid therapy (13-cis RA, 1 mg/kg/day for 4 mo). A standard booster immunization with TT was given along with the initial KLH sensitization. A control group of acne patients received identical immunization regimens, but no 13-cis RA. Plasma retinoid levels were evaluated by reverse-phase HPLC and confirmed that blood-level concentrations of 13-cis RA and metabolites in these acne patients reached values previously demonstrated to be immunomodulatory in vitro. The retinoid had no effect on responses to TT as reflected by the characteristics of increased anti-TT IgG levels or the isotype distribution of the antibody. In contrast, the anti-KLH response was significantly enhanced in the 13-cis-RA-treated group. Whereas anti-KLH antibody was detected in only 4 of 13 control subjects after the secondary immunization, 10 of 13 retinoid-treated subjects had measurable levels of anti-KLH IgG (p less than 0.05). Among the responders, no differences were noted in the isotype distribution of anti-KLH antibody. These results showing enhanced anti-KLH responses induced by 13-cis RA therapy represent the first demonstration in humans that in vivo administration of a retinoid can modulate antigen-specific immune responses.

Acne Vulgaris↗

Acute cerebral hemorrhage changes the nocturnal surge of plasma melatonin in humans.

The diurnal rhythm of plasma melatonin was studied in 46 Chinese patients with acute cerebral hemorrhage. The state of consciousness of each patient was assessed clinically. The individual sites of lesion were determined by computerized tomography scanning. One to five days after stroke, blood samples were collected by venipuncture at 1000 and 1400 h in the daytime and 0200 and 0400 h at night. Plasma melatonin was extracted by dichloromethane and determined by radioimmunoassay. It was found that patients with lesions in the brain stem or in the third and lateral ventricles had melatonin levels significantly different from the other subjects in that these values were lower and lacking a nocturnal rise. These results are consistent with the presumptive retina-pineal pathway proposed in humans. Dramatic blunting or obliteration of the nocturnal melatonin surge in the blood was also observed in some patients with lesions in the frontal lobe, fronto-parietal lobe, parieto-temporal lobe, and basal ganglia. These brain regions are not involved in the retina-pineal pathway described in rodents or humans. Thus, our results suggest that brain regions other than the presumptive retina-pineal neural pathway may play an important role in the generation and/or regulation of the diurnal production and/or secretion of pineal melatonin in humans. However, a global functional disturbance caused by cerebral hemorrhage cannot be ruled out in some cases. It should be noted that many of the lesions leading to a change in the nocturnal rise of plasma melatonin were unilateral lesions. The significance of this finding is presently unknown. In addition, patients without a nocturnal rise of plasma melatonin were mostly comatose. They had lesions in the basal ganglion, fronto-parietal lobe, brain stem, and lateral and third ventricles. The latter findings suggest that in the brain, certain regions responsible for the state of consciousness of the individual may also be important to the dirunal rhythm of pineal melatonin secretion.

Acute Disease↗

Stimulation and suppression of the mineralocorticoid hormones in normal subjects and adrenocortical disorders.

In summary, maneuvers that affect the RAS stimulate or suppress solely aldosterone and 18-OHB and have little, if any, effect on DOC, 18-OHDOC, B, or cortisol. The magnitude of aldosterone response seems to be of equal magnitude for all stimulatory or suppressive maneuvers as used in the present protocols. Although primarily originating in the ZG, some secretion of 18-OHB from the ZF is evident by its disproportionate responses (in relation to aldosterone) to maneuvers challenging ACTH. The prompt and marked increases the 18-OHDOC and B after ACTH make them the most sensitive "markers" of the ZF steroid activity. The application of those maneuvers and MCH measurements to adrenal disorders should help to further characterize their pathophysiology.

Adolescent↗

Use of OKT3 monoclonal antibody in the treatment of acute cardiac allograft rejection.

OKT3 is a murine monoclonal antibody that recognizes the T3 surface antigen present on mature T cells, and it has been used to successfully treat renal allograft rejection. We report our experience with OKT3 in the treatment of cardiac allograft rejection. Eight patients with endomyocardial biopsy evidence of moderate or severe rejection were given fourteen daily intravenous treatments of OKT3. Six of the eight patients had complete recovery following OKT3 therapy; one required additional steroid therapy for recurrence and one patient failed to respond. Five of the six patients with a complete response have experienced no further rejection (mean follow-up 437 days). Adverse reactions to OKT3 were common early in the treatment course, but were well tolerated. We concluded that OKT3 is a safe and effective treatment of cardiac allograft rejection and that a majority of patients experience long-term rejection-free periods.

Acute Disease↗

Calcium-sensitive uptake of amino acids by human placental slices.

The placenta supplies many nutrients to the fetus, including amino acids by active transport. Although the exact regulatory mechanism is unknown, a few studies have suggested a role for calcium in amino acid transport. Therefore, we examined the relationship between calcium and amino acid uptake by term human placental slices. Calcium depletion of slices significantly reduced uptake of alpha-aminoisobutyric (AIB), which is actively transported primarily by a sodium-dependent, carrier-mediated mechanism. Impairment of AIB uptake induced by calcium depletion was reversed by repletion with calcium but not with other divalent cations. In contrast, uptake of phenylalanine, which is transported primarily by a sodium-independent mechanism, was not affected by calcium depletion. Uptake of leucine and valine, which accumulate by both sodium-dependent and independent mechanisms, was partially affected by calcium depletion. Verapamil (10 microM), an inhibitor of transmembrane calcium flux, significantly reduced AIB uptake. Trifluoperazine, a calmodulin antagonist, also inhibited AIB uptake. Analysis of AIB uptake kinetic constants for control and calcium-depleted slices showed no change in the diffusion constant, a 37% reduction in Vmax, and a 2-fold increase in Km. The results indicate that calcium may be an important factor in the cellular regulation of active transport of amino acids.

Amino Acids, Branched-Chain↗