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Biomedical subjects

C W Chang

Publications and source records attributed to C W Chang.

At least 91 records · Page 5Linked to original sources
PubMed1990

14-Fluorobacteriorhodopsin and other fluorinated and 14-substituted analogues. An extra, unusually red-shifted pigment formed during dark adaptation.

Five vinyl-substituted fluororetinal analogues (8-F, 10-F, 12-F, 14-F, and 13,14-F2) were found to give bacteriorhodopsin analogues with properties similar to those of the parent system. Of these, only 14-fluororetinal was found to give an extra red-shifted BR analogue (lambda max less than or equal to 680 nm) in equilibrium with the normal 587-nm pigment. The 680-nm pigment was enriched upon irradiation. It rearranged to the 587-nm pigment at room temperature (delta E [symbol: see text] = 20.8 kcal/mol). Chromophore extraction experiments revealed the all-trans geometry for the 680-nm pigment. 14-Chlororetinal gave a similarly red-shifted pigment while 14-methylretinal did not. A scheme for dark adaptation of the 14-halogenated bacteriorhodopsins has been proposed in which the new red-shifted pigment was assigned the all-trans, 15-syn geometry.

Bacteriorhodopsins↗
PubMed1990

Spinal nerve stimulation in the diagnosis of lumbosacral radiculopathy.

Direct spinal nerve stimulation was compared with needle electromyography (EMG) in 40 patients who were suspected of having an L5 or S1 radiculopathy. For spinal nerve stimulation, we adapted a monopolar needle electrode inserted deep into the paraspinal muscle. The minimal latency, amplitude, and negative phase area of compound muscle action potential from myotomal muscles were recorded with computer assistance. Abnormality was considered to be significant when the value fell outside of 2 SD of control mean values. Among 17 patients with clinical evidence of radiculopathy, needle EMG was abnormal in 10 patients (58.8%), whereas in the nerve stimulation test the abnormalities were shown in 16 patients (94.1%); in amplitude difference and the abnormal area, differences were shown in 12 patients (70.6%). Among 23 patients with only subjective symptoms of radiculopathy, needle EMG was abnormal in nine patients (39.1%), whereas the abnormal amplitude differences were shown in 18 patients (78.3%) and 15 patients (65.2%) with abnormal area difference by spinal nerve stimulation, respectively. Direct spinal nerve stimulation is recognized as an objective and sensitive test in the diagnosis of lumbosacral radiculopathy.

Action Potentials↗
PubMed1990

Sensory nerve conduction study in forearm segment of superficial radial nerve: standardization of technique.

Sensory nerve conduction velocity (SNCV) over the forearm segment of the superficial radial nerve was studied by an antidromic method in 76 nerves of 50 normal volunteers ranging in age from 16 to 70 years. The mean SNCVs were 53.3 +/- 3.6 m/sec (1 SD) and the mean amplitudes of sensory nerve action potentials were 15.2 +/- 9.8 microV (1 SD). This method of obtaining SNCV over the forearm segment of the superficial radial nerve is easily performed and the findings are consistent.

Action Potentials↗
PubMed1990

Posterior antebrachial cutaneous neuropathy. Case report.

Posterior antebrachial cutaneous (PABC) neuropathy is rare. Two original cases are reported here. In case 1, the neuropathy is probably due to a traction injury in a reduction operation for humeral fracture. In case 2, it is injured associately with an operation in taking a myocutaneous flap. On examination, both cases showed a decreased sensation to pin-prick over the PABC nerve territories and a positive Tinel's sign near the injured sites. Sensory nerve conduction study of the PABC nerves revealed a low amplitude of the compound nerve action potential (CNAP) and a slow sensory nerve conduction velocity (SNCV) in case 1, and absent CNAP in case 2. Our study showed the sensory nerve conduction test is useful in confirming PABC neuropathy.

Adult↗
PubMed1989

Posterior antebrachial cutaneous neuropathy: case report.

We are reporting the first case of posterior antebrachial cutaneous (PABC) neuropathy which was confirmed by the sensory nerve conduction test. PABC neuropathy and radial nerve palsy developed after an intramuscular injection in this case. Sensory nerve conduction study of the PABC nerve showed slow nerve conduction velocity but normal amplitude of compound nerve action potential (CNAP). Follow-up testing revealed an increase in the CNAP amplitude and normalization of nerve conduction velocity in the PABC nerve. Our study demonstrates that PABC neuropathy can be confirmed by the sensory nerve conduction test.

Adult↗
PubMed1987

Regional myocardial perfusion of cardioplegic solutions.

We compared the regional myocardial perfusion of blood cardioplegic solution (BCP) and crystalloid cardioplegic solution (CCP) in 14 mongrel dogs. Cardiopulmonary bypass was established at 28 degrees C, and a hydraulic occluder was placed around the proximal left anterior descending (LAD) coronary artery. In group 1 (N = 7) collateral coronary arteries were ligated; in group 2 (N = 7) collateral coronary arteries were left in situ. After the aorta was clamped, BCP and CCP were alternately perfused at 200 ml/min. The occluder was inflated to produce moderate, severe, and critical LAD stenosis, and regional perfusion was measured by xenon-133 washout with the Silicon Avalanche Radiation Detector. BCP infusion produced a consistently higher aortic pressure, but CCP flow was better than BCP flow under all conditions, particularly without coronary collaterals (p less than .05). Regional myocardial perfusion of CCP is superior to BCP.

Animals↗
PubMed1987

Pharmacokinetics of metronidazole in patients with alcoholic liver disease.

The pharmacokinetics of metronidazole was evaluated in eight patients with alcoholic liver disease. Metronidazole (7.5 mg/kg) was administered to each patient intravenously. Serial blood samples were obtained after the dose. Serum metronidazole concentrations were determined by high-performance liquid chromatography. The following pharmacokinetic parameters (mean +/- standard deviations) were obtained: half-life, 18.31 +/- 6.06 h; elimination rate constant, 0.042 +/- 0.013 h-1; volume of distribution, 0.77 +/- 0.16 liters/kg; and total body clearance, 0.51 +/- 0.11 ml/min per kg. Compared with subjects with normal liver function, patients with liver disease showed a reduction in drug elimination rate and total body clearance. The half-life of metronizadole in serum and volume of distribution were increased. Large variations of these parameters were also observed among the patients. On the basis of these observations, a reduced dose of metronidazole should be given to patients with alcoholic liver disease to avoid accumulation of metronidazole and its metabolites. Monitoring of drug concentration in serum may also be necessary to optimize therapy.

Adult↗
PubMed1987

Structure-activity relationships of 6-(heterocyclyl)-methylene penam sulfones; a new class of beta-lactamase inhibitors.

6-(Heterocyclyl)methylene penam sulfones (1) are effective beta-lactamase inhibitors and potent ampicillin and cefazolin potentiators against both Gram-positive and Gram-negative beta-lactamase producing bacteria. Several of these analogs having a pi-deficient 2-heteroaryl substituent attached to the C6-methylene position showed better inhibitory activity than clavulanic acid, Ro 15-1903, 6 beta-bromopenicillanic acid, and sulbactam against a variety of beta-lactamases. The compounds were devoid of any antibacterial activity, but in combination with ampicillin or cefazolin, exhibited synergistic activity at least equal to clavulanic acid, Ro 15-1903, 6 beta-bromopenicillanic acid or sulbactam against beta-lactamase producing strains. Structure-activity relationships for a number of compounds are described. The structure-activity relationships can be rationalized by an enzyme inhibition mechanism which we have previously proposed on the basis of methanolysis of 6-(2-pyridyl)methylene penam sulfone (1a). Two synthetic routes to prepare compounds of structural type 1 via either a Wittig reaction or an aldol condensation are reported. beta-Lactamase inhibition and MIC data are presented.

Ampicillin↗
PubMed1986

Isolation and characterization of the structural gene for secreted acid phosphatase from Schizosaccharomyces pombe.

The Schizosaccharomyces pombe acid phosphatase structural gene (PHO 1) was isolated by complementation of an S. pombe acid phosphatase mutant with a wild type S. pombe DNA recombinant plasmid library. Northern analysis indicates that acid phosphatase is encoded by a 1.4-kilobase mRNA of which approximately 100 bases are 3'-poly(A). The gene contains no introns and the 3' and 5' untranslated regions are short. According to DNA and amino acid sequence data, the S. pombe acid phosphatase has a molecular weight of 50,600. An 18-amino acid sequence at the N terminus was found that is similar to previously identified signal peptides in other eukaryotic secretory proteins. This signal peptide is apparently removed during secretion, since it is absent in the mature secreted acid phosphatase. The gene can be induced 2--3-fold by starvation for phosphate. The signals required for this induction are contained on the isolated DNA clone. Although the gene can be expressed in Saccharomyces cerevisiae, secretion is abnormal.

Acid Phosphatase↗
PubMed1986

Evaluation of a potential drug interaction between sucralfate and aspirin.

Recent studies have demonstrated a cytoprotective effect of sucralfate on gastric mucosa in patients receiving aspirin. The potential drug interaction between sucralfate and aspirin was evaluated in a randomized crossover manner in 12 healthy men. Subjects were initially given a single dose of aspirin alone or in combination with sucralfate for 2 days. The drug dosing schedule was then reversed after 1 week. Sixteen blood samples were drawn after each aspirin dose for HPLC assay of aspirin and its metabolites. Pharmacokinetic parameters were calculated for aspirin, salicylic acid, and salicyluric acid. None of these parameters demonstrated any statistically significant differences between the two treatment groups. The combined use of sucralfate and aspirin is therefore not likely to result in a clinically significant pharmacokinetic drug interaction. The systemic therapeutic effect of aspirin is not expected to be altered when sucralfate is used concurrently in patients receiving chronic aspirin therapy.

Adsorption↗
PubMed1986

Hemodialysis clearance of metronidazole and its metabolites.

Metronidazole is now being used with increasing frequency for various infectious conditions in patients with renal failure. It is commonly administered to septic patients who have developed acute renal failure requiring hemodialysis. The hemodialysis clearances of metronidazole and its metabolites were evaluated in nine renal failure patients on maintenance hemodialysis. The mean +/- standard deviation clearance and the extraction ratio were 106.9 +/- 16.3 ml/min and 0.65 +/- 0.08, respectively, when regenerated cellulose dialysis membrane was used. The clearance and the extraction ratio with the use of cuprophan membrane were 72.1 +/- 17.3 ml/min and 0.44 +/- 0.12, respectively. The clearances and extraction ratios for the metabolites were similar to those of the parent drug. For both metronidazole and the hydroxy metabolite, the clearance and the extraction ratio demonstrated a statistically significant difference between the regenerated cellulose membrane and the cuprophan membrane. In summary, metronidazole and its metabolites were found to be highly dialyzable with different clearances depending on the specific type of membrane used. However, owing to the relatively wide therapeutic index of the drug, dosage supplementation may be necessary only in seriously ill patients to ensure therapeutic effect.

Acute Kidney Injury↗