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Biomedical subjects

T Chang

Publications and source records attributed to T Chang.

At least 181 records · Page 10Linked to original sources
PubMed1988

Direct puncture of the cavernous sinus for obliteration of a recurrent carotid-cavernous fistula.

The authors report direct transcutaneous puncture of the cavernous sinus through an intact orbit for embolization of a recurrent carotid-cavernous fistula (CCF) after 10 prior operations. The fistula was obliterated completely with this technique. No significant complication was noted except temporary ptosis for about 2 months. When other approaches are difficult or impossible, this technique can be an alternate way to treat a recurrent CCF after a trapping procedure.

Adult↗
PubMed1988

Continuous electromyography for monitoring depth of anesthesia.

Utilizing a randomized, controlled study design, the clinical utility of monitoring spontaneous electromyography during methohexital anesthesia was evaluated for short outpatient gynecologic procedures. In the experimental group (n = 20), the anesthesiologist used conventional monitors as well as the Datex ABM device for determining the maintenance anesthetic requirement. The control group (n = 20) was monitored in an identical fashion, but the video monitor screen was turned off during the operation. The methohexital maintenance requirement was nonsignificantly decreased (5.0 +/- 1.2 vs 5.6 +/- 1.8 mg/min) in the experimental group. Adequacy of anesthesia (as determined by cardiorespiratory stability and the absence of purposeful movement during the maintenance period) did not differ between the two study groups. Although the awakening time for the experimental group (2.9 +/- 1.9 minutes) was decreased to a statistically significant degree compared to the control group (4.5 +/- 3.0 minutes), the difference was of no clinical significance. Thus, continuous electromyographic and EEG monitoring with the Datex ABM device did not significantly improve administration of methohexital during brief outpatient procedures.

Adjuvants, Anesthesia↗
PubMed1988

Hepatic cytochrome P-450j induction in the spontaneously diabetic BB rat.

Hepatic microsomal cytochrome P-450j has been studied using the male spontaneously diabetic BB rat as a model for insulin-dependent diabetes. This approach avoids any direct hepatotoxic effects from chemical diabetogenic agents. Both diabetic rats maintained on insulin and nondiabetic littermates were used as controls. Levels of cytochrome P-450j were increased approximately 3-fold in the diabetics 4 days after the cessation of insulin therapy. In addition, cytochrome P-450j-catalyzed enzymatic activities, aniline hydroxylation, and N-nitrosodimethylamine N-demethylation were increased by the diabetic state at this same time period. Cytochrome P-450f remained at control levels in all groups of animals. In order to test the hypothesis that ketone bodies are involved in the increase in cytochrome P-450j in the diabetic state, plasma beta-hydroxybutyrate levels were monitored. Hepatic aniline hydroxylation, N-nitrosodimethylamine N-demethylation, and cytochrome P-450j levels in individual animals were found to correlate with plasma beta-hydroxybutyrate levels (r = 0.59-0.71 p less than 0.001). In contrast, no significant correlation between levels of cytochrome P-450j and plasma glucose, insulin, or cholesterol was observed in individual animals (r = 0.07-0.23, p greater than 0.4). We conclude that cytochrome P-450j is induced in the livers of spontaneously diabetic rats, and that this induction may be associated directly or indirectly with elevated plasma ketone levels.

3-Hydroxybutyric Acid↗
PubMed1988

Evaluation of serum phenytoin monitoring in an acute care setting.

Serum phenytoin monitoring is frequently used in the management of epileptic patients because phenytoin has a narrow therapeutic index and exhibits nonlinear pharmacokinetics. This study prospectively evaluated serum phenytoin monitoring in an acute care teaching hospital. Two sets of criteria were established a priori to define (a) appropriate selection of patients with regard to serum phenytoin monitoring, and (b) inappropriate serum phenytoin determinations (SPDs). Eighty patients receiving phenytoin were studied, of whom 58 (72.5%) were appropriately selected. These included 35 patients (43.8%) for whom monitoring was indicated and was performed, and 23 patients (28.7%) for whom monitoring was not indicated and was not performed. There were 39 patients with no indications for serum phenytoin monitoring; however, 16 (41%) of them were monitored. A total of 113 SPDs were performed, of which 83 (73.5%) were deemed to be inappropriate. Seventy percent of SPDs resulted in phenytoin concentrations outside the usual therapeutic range (10-20 micrograms/ml). Overall, physicians appropriately selected patients with regard to serum phenytoin monitoring; however, when inappropriate selection did occur, it tended to involve monitoring of patients who did not require it. The majority of SPDs performed were deemed to be inappropriate, since they were done too soon after admission or a change in therapy to reliably indicate steady-state serum concentrations.

Acute Disease↗
PubMed1987

Toxicity domain in presynaptically toxic phospholipase A2 of snake venom.

About 42 complete amino-acid sequences of phospholipases A2 (phosphatidylcholine 2-acylhydrolase, EC 3.1.1.4) are known, including those of 13 presynaptically toxic enzymes, but the structural features responsible for the neurotoxicity and distinguishing the toxins from the non-neurotoxic enzymes are far from being clear. In this study, we examined the charged-residue distributions and hydrophobic characteristics based on the sequence data and the predicted tertiary structure and proposed a possible toxicity domain. We found that the presynaptically toxic enzymes have three or four more basic amino-acid residues than the non-neurotoxic enzymes at positions 59, 60, 65, 70-73 and 97 or 98. These residues appear to cluster near the surface region at the N-terminal side. The cationic nature of this basic cluster in the toxin is enhanced by the alpha-amino group of the N-terminus and the dipole moment of helices 96-110 and 1-10. Moreover, these toxic-site residues are usually associated with hydrophobic regions at 1-7, 64-81 and 97-109.

Amino Acid Sequence↗
PubMed1987

Cloning and sequencing of a carp beta s-crystallin cDNA.

The mRNAs were extracted from common carp (Cyprinus carpio) lenses, purified, reverse transcribed, dC tailed and cloned into Escherichia coli with pBR322 as vector. The cloning efficiency was around 1 X 10(7) colonies per micrograms of mRNA. A clone (pC20) was found by hybrid-arrested to contain the cDNA related to carp crystallins. However, comparison of the derived amino-acid sequence with bovine gamma-II and beta s-crystallins indicates that this carp crystallin sequence resembles closely the bovine beta s-crystallin and should be better classified as such except that this fish sequence does not contain the N-terminal 'arm' of four amino-acid residues present in bovine beta s-crystallin.

Amino Acid Sequence↗
PubMed1987

Preclinical and clinical pharmacokinetics of pirmenol.

Metabolic disposition and pharmacokinetics of pirmenol were studied in laboratory animals and in patients with premature ventricular beats. After intravenous administration, pirmenol pharmacokinetics were adequately characterized by a 2-compartment body model with elimination half-lives of 3 to 4 hours in animals and 6 to 9 hours in patients. Oral absorption of pirmenol was complete and devoid of significant first-pass metabolism. Systemic oral bioavailability averaged 87% in humans. Pirmenol was 83% to 90% bound to human plasma proteins. Animal studies showed that pirmenol was widely distributed in tissues resulting in higher drug concentrations in tissue than in plasma. Pirmenol was partly eliminated as unchanged drug and partly metabolized. Tracer studies in animals showed that approximately 40% to 50% of the administered radioactive dose was excreted in the urine and the remainder in the feces. The latter route was due to excretion of radioactivity in the bile. Evidence of enterohepatic recycling was established in bile duct-cannulated monkeys. Approximately 23% to 31% of the administered pirmenol dose was recovered unchanged in human urine.

Administration, Oral↗
PubMed1987

Microsurgical vasoepididymostomy to corpus epididymidis in treatment of inflammatory obstructive azoospermia.

A unilateral microsurgical vasoepididymostomy utilizing 35 mm of epididymis was performed in a patient with postinflammatory epididymal obstruction. Success was verified with multiple semen analyses, the hamster egg penetration test, and a pregnancy. These results demonstrate that surgical bypass of inflammatory tubal obstruction in the distal epididymis can result in the return of normal epididymal function and fertility.

Adult↗
PubMed1987

Electron density profile of two-dimensionally crystalline membranous cytochrome c oxidase at low resolution.

Unilamellar vesicles of membranous cytochrome c oxidase have been isolated whose distribution of protein in the membrane plane was predominantly crystalline. The vesicles were collapsed via controlled partial dehydration, resulting, at first, in the formation of unoriented, mostly unstacked, membrane pairs. Further controlled partial dehydration resulted in the formation of oriented multilayers of stacks of membrane pairs, retaining the in-plane crystallinity. The above were monitored by electron microscopy and x-ray diffraction. Analysis of the x-ray diffraction from unoriented, unstacked membrane pairs by two independent methods provided the membrane electron density profile to 30 A resolution.

Animals↗
PubMed1987

Physicochemical characterization of lens crystallins from the carp and biochemical comparison with other vertebrate and invertebrate crystallins.

Lens crystallins were isolated from the homogenate of carp (Cyprinus carpio) eye lenses by gel permeation chromatography and characterized by gel electrophoresis, immunodiffusion, amino acid analysis, circular dichroism, and protein sequence analysis. Three well-defined fractions corresponding to alpha/beta-, beta-, and gamma-crystallins were obtained in relative weight percentages of 26, 22, and 52%. The native molecular masses of the purified fractions were determined to be 410, 60, and 20 kDa, respectively. The polypeptide compositions as determined by SDS gel electrophoresis revealed the substantial presence of beta-crystallin polypeptides in the alpha-crystallin fraction; this is also evident in the fractionation of amphibian crystallins but is not common in the case of higher classes of vertebrates. The circular dichroism spectra indicate a predominant beta-sheet structure in all three fractions, albeit with some contribution of alpha-helical structure in the gamma-crystallin, the amino acid composition of which bears a resemblance to that of squid crystallin. Sequence comparison of carp gamma-crystallin with frog and calf gamma-crystallins indicates a high degree of homology in their N-terminal segments despite the dissimilarity of amino acid compositions and weak immunological cross-reactivity.

Amino Acids↗
PubMed1987

Evaluation of a nomogram for estimating the rate of phenytoin accumulation.

This study evaluated a nomogram designed to identify a subgroup of the patients whose serum phenytoin concentrations are near steady state at a given time after initiation of therapy. A sample of 95 adult subjects with reported values of Vmax and Km was pooled from the literature, and computer simulations of phenytoin accumulation for 15 days after initiation of phenytoin acid at 300 mg/day were performed. Simulated serum concentrations on days 5, 10, and 15 were used to identify subjects who were predicted by the nomogram to be at greater than or equal to 83% of steady state, and these results were compared with those expected from the Michaelis-Menten model. In the simulations, 42, 62, and 66 subjects reached greater than or equal to 83% of steady state by days 5, 10, and 15, respectively. The nomogram correctly identified 13 (31.0%), 33 (53.2%), and 43 (65.2%) of these individuals, respectively. The frequency of erroneous predictions was low, even in subjects whose Km and volume of distribution were outside the limits set in the development of the nomogram. Use of a nomogram such as this would help a subgroup of patients to attain a desired serum phenytoin concentration earlier in therapy and with fewer serum phenytoin determinations than would otherwise be required. It would also prevent premature increases in phenytoin dose in patients whose serum concentration is still rising.

Adult↗
PubMed1987

Interindividual variation in the extent and rate of phenytoin accumulation.

Steady-state serum phenytoin concentration (Css) is known to increase nonlinearly with dose, but it is less well recognized that the rate of phenytoin accumulation is also dose dependent. This stimulation study estimated the extent and rate of phenytoin accumulation in a sample of 95 adult subjects, with known values of Vmax and Km, pooled from the literature. Simulations were done using a Michaelis-Menten model and phenytoin sodium doses of 200, 300, and 400 mg/day. The distributions of Css and the time required to reach 90% of steady state (T90) became increasingly positively skewed as dose was increased. The T90 and Css were positively correlated (r greater than or equal to 0.8880, p less than 0.00001) and subjects reached 90% or more of Css more slowly as the initial phenytoin dose was increased. At an initial dose of 300 mg/day of phenytoin sodium, mean Css was 11.0 +/- 9.10 micrograms/ml (median, 7.62 micrograms/ml), and mean T90 was 12.2 +/- 15.4 days (median, 5.98 days). Only 25.3% of the subjects would be expected to achieve therapeutic serum concentrations (10-20 micrograms/ml) on this dose, and 88.4% would reach 0.9 Css within 30 days. Phenytoin dosage must be individualized to achieve concentrations of 10-20 micrograms/ml. Multiple serum phenytoin determinations during the first 30 days or more are required to determine that steady state has been reached, but these need not be done more often than once a week.

Adolescent↗
PubMed1987

Spinal cord proliferative sparganosis in Taiwan: a case report.

A 43-year-old woman suffered from low back pain and bilateral footdrop. A cisternal myelogram unexpected revealed multiple filing defects in the spinal canal extending from the lower cervical region to the caudal equina. Diagnostic exploration revealed numerous cystic organisms adhering to the spinal cord and nerve roots. Histopathological examination showed these organisms to be proliferative sparganum cestode larvae. Although these cestode larval infections have been reported a dozen times in humans from various parts of the world, this is probably the first reported case of spinal cord infection.

Adult↗
PubMed1987

High-resolution real-time ultrasound in Peyronie's disease.

Sonography is not considered to be a radiation hazard; it is noninvasive and can be widely used for examining external genitalia. We examined six cases of Peyronie's disease of the penis by high-resolution real-time ultrasound. The sonographic findings include a thick echogenic plaque with echogenicity similar to or higher than the tunica albuginea; a calcified plaque in thickened tunica albuginea; and are occasionally associated with calcification in the corpora cavernosa. Sonography may clearly localize the abnormal thickened area of collagen deposition and calcification. Repeated sonography after intracavernosal papaverine injection may further confirm the correlation of the plaque and the abnormally curved erectile penis. Doppler ultrasound may be used for further evaluation of the vascular condition if impotence coexists.

Adult↗