Biomedical subjects

S D Chang

Publications and source records attributed to S D Chang.

70 records · Page 4Linked to original sources

PubMed1996

Keratitis in methamphetamine abusers.

We report four cases of severe corneal ulceration in methamphetamine abusers. Methamphetamine abuse has been increasing in California and may exceed cocaine abuse in some regions. Methamphetamine's extensive physiologic effects, inconsistent street purity, and multiple routes of administration offer many possibilities for injury to the cornea. Potential causes of methamphetamine-related keratitis can be divided into four categories resulting from (a) direct pharmacologic and physical effects of methamphetamine; (b) the toxic effects of diluting or "cutting" agents such as lidocaine and quinine; (c) effects related to the route of drug administration (intravenous, inhalation, smoking); and (d) manufacture-related effects of exposure to unintentional caustic contaminants in the final product. The increasing prevalence of methamphetamine abuse and the severity of the associated ulcers should alert ophthalmologists to the problem of methamphetamine-related keratitis.

Adult↗

PubMed1996

Factors influencing graft clarity.

Successful penetrating keratoplasty depends on both host- and donor-related factors. We compared the results of keratoplasty in a group with a wide range of donor ages to gauge the effect of donor age on graft success. We conducted a retrospective review of donor data, recipient age, preoperative diagnosis, and postoperative complications with respect to graft clarity at 24 months after surgery in 99 consecutive patients in an effort to determine the role of donor age in graft clarity. The only factors that we isolated that appeared to influence graft clarity at 24 months postoperatively were a preoperative diagnosis classified as inflammatory/traumatic and the occurrence of postoperative complications. There was no association between graft clarity and recipient age, donor age, death-to-preservation time, or preservation-to-surgery time.

Age Factors↗

PubMed1995

Expectant management in severe preeclampsia: does magnesium sulfate prevent the development of eclampsia?

Although magnesium sulfate has been traditional or standard treatment for severe preeclampsia and eclampsia to prevent convulsions, its efficiency has always been in doubt and its induced side-effects also make it controversial for use. In this study, 64 patients, diagnosed with severe preeclampsia, were randomized into group I (34 patients) managed with MgSO4, and group II (30 patients) managed without MgSO4. There were no occurrences of eclampsia in either group. Although there was no statistical significance in the final delivery method, group I had a higher rate in cesarean section, in which most were significantly due to fetal distress (p < 0.05). Furthermore, group I had significantly more babies with poor apgar score than group II (p = 0.019). During the treatment period for those with a gestational age of less than 34 weeks, there were two patients with abruptio placentae in group I and the treatment periods were noted to be longer in group II than in group I. From the results of monitoring serum magnesium level in group I, when therapeutic level was achieved, magnesium sulfate induced great discomfort which might have led to the deterioration of the patients' condition. According to this study, magnesium sulfate's minimal efficiency, and its adverse side-effects, also make magnesium sulfate a poor choice in the management of preeclampsia. Therefore, because of our poor understanding of the etiology of preeclampsia, suitable management should be undertaken without magnesium sulfate. Improvement of the patient's pathophysiological condition or termination of pregnancy as early as possible, is recommended.

Adult↗

PubMed1995

Laparoscopic surgical procedures for early ovarian cancer.

Early stage la ovarian cancer diagnosed at the time of laparoscopic procedure was managed by laparoscopy accordingly. The procedures included oophorectomy, contralateral ovarian biopsy, total omentectomy, paraaortic lymphadenectomy and appendectomy. The patient tolerated the procedures smoothly and resumed work in two days.

Adult↗

PubMed1993

Stimulant effect of human gamma globulin on smooth muscle preparations.

The effects of human gamma globulin on the contractile activity of spontaneously active rat mesenteric portal vein and guinea-pig taenia caeci and quiescent rat aorta and guinea-pig trachea muscles were studied in vitro. Human gamma globulin significantly increased the contractile activity of the spontaneously active muscles with respect to both amplitude and frequency of contraction whereas it had no significant effect on the contractile activity of quiescent muscle preparations. These findings suggest that immunoglobulins directly modulate smooth muscle including vasculature by modifying the membrane electrical activity associated with the generation of spontaneous activity.

Animals↗

PubMed1992

Mechanism of the vasodilator action of calcitonin gene-related peptide in conscious rats.

1. The aim of this study was to investigate whether the hypotensive effect of rat alpha-calcitonin gene-related peptide (alpha CGRP) in conscious rats is mediated by endothelium-derived nitric oxide (NO) or the opening of adenosine 5'-triphosphate (ATP)-sensitive potassium (KATP) channels. 2. Dose-mean arterial pressure (MAP)-response curves of alpha CGRP were examined in the presence of vehicle, phenylephrine, KATP channel antagonist glibenclamide or NO synthase inhibitors, NG-nitro-L-arginine methyl ester (L-NAME) and NG-nitro-D-arginine methyl ester (D-NAME). Dose-MAP-response curves for sodium nitroprusside were also constructed in the presence and absence of L-NAME and D-NAME. 3. alpha CGRP and nitroprusside produced dose-dependent reductions in MAP which were potentiated by phenylephrine. Both L-NAME and D-NAME attenuated the depressor response to alpha CGRP but not nitroprusside. 4. Dose-MAP-response curves for pinacidil, a KATP-channel activator, were also examined in the presence of glibenclamide or vehicle. Glibenclamide attenuated pinacidil- but not alpha CGRP-induced reductions in MAP. 5. It is concluded that the hypotensive effects of alpha CGRP are partially mediated via endothelium-derived NO but not via the opening of KATP channels.

Adenosine Triphosphate↗

PubMed1991

Laparoscopic management of tubal pregnancy.

Early detection of an unruptured tubal pregnancy has been made possible by the recent use of vaginal sonograms, thus more conservative management can be undertaken. From February 1989 to June 1989, we attempted to treat tubal pregnancies by surgical laparoscopy at the Keelung Chang Gung Memorial Hospital. Fourteen consecutive cases of tubal pregnancy were treated by surgical laparoscopy with a success rate of 70% (10 out of 14). Six of the 10 successfully treated cases were managed conservatively. Use of the laparoscope may be considered as a major trend towards conservative tubal pregnancy treatment, such as salpingotomy for women with an unruptured ectopic pregnancy who want to conserve fertility. These 10 cases of tubal pregnancy benefited enormously from the surgical laparoscopic technique which led to a shorter hospital stay, early ambulation and resume point of normal activities within days. No complications related to surgical laparoscopy were noted in this series. Our conclusion is that surgical laparoscopy should be considered an alternative to laparotomy for the treatment of tubal pregnancy.

Evaluation Studies as Topic↗

PubMed1990

Simple management of poor cervical progression during labor by continuous epidural analgesia.

A series of 112 primiparous parturients in labor with poor cervical progression were managed according to the double-lined labor nomogram. These patients all had labor progression beyond the alert line which were defined as poor cervical progression. Continuous low concentrated marcaine (0.125%) epidural analgesia were then offered to these indicated patients. These 112 poor labors were compared with 143 poor cervical progression labors without epidural analgesia in terms of mode of delivery and maternal morbidities. The results showed a decrease in cesarean section rate in cases with epidural analgesia (20.5% vs 34.3%, p less than 0.05) but no increase use of instrumentation was noted, also, maternal morbidities were much less in epidural cases compared to poor labors without epidural analgesia (6 in 112 vs 19 in 143, p less than 0.05). Continuous epidural analgesia performed on labors with poor progression improved the labor outcome and decrease maternal morbidities satisfactorily.

Analgesia, Epidural↗

PubMed1989

Appendicitis during pregnancy.

Twenty-four pregnant women with acute appendicitis received exploratory laparotomy during an 8-year period. Abdominal pain accompanied with nausea and vomiting were the most common symptoms. Abdominal tenderness and rebounding pain were the most reliable physical signs. Leukocytosis with WBC count greater than 15,000/cu mm and granulocytes greater than 87% and prolonged symptomatic duration were indications that appendiceal perforation might have occurred. A McBurney's incision and spinal anesthesia were preferred for appendectomy during pregnancy. In cases of uncomplicated appendicitis, tocolytic agents and antibiotics were not routinely used. Premature labor occurred in 21% of patients during postoperative period.

Adult↗

PubMed1989

In vitro fertilization, gamete intrafallopian transfer and combined IVF-GIFT results: three-year experience at Chang Gung Memorial Hospital.

A review is presented summarizing the IVF-ET, GIFT and combined IVF-ET-GIFT experienced at Chang Gung Memorial Hospital. Since the building of an aseptic dust free laboratory next to the operation room, the clinical pregnancy rate has been 12.2% per embryo transfer in IVF-ET, 16.7% in the GIFT program and 30.0% in the combined IVF-GIFT program. The overall clinical pregnancy rate was 14.9%. The overall pregnancy rate appeared to be independent of the causes of infertility, be it tubal factor, endometriosis or unexplained infertility. It was lower in couples with male factor or combined factors. The different regimens for follicular stimulation were hMG-hCG, clomiphene-hMG-hCG and FSH-hMG-hCG. No one regimen showed a better pregnancy rate than the others. The methods of oocyte retrieval were laparascopy, laparotomy, transbladder ultrasound-guided, and transvaginal ultrasound-guided retrieval. There were 4.53 oocytes retrieved pertreatment cycle. The transvaginal ultrasoundguided oocyte retrieval has greatly simplified the procedures in the IVF-ET program. The patient selection was important not only for the indications but also for the methods of IVF-ET, GIET and combined IVF-GIFT.

Evaluation Studies as Topic↗

PubMed1987

Comparison of different dietary amino acids as inducers of intestinal amino acid transport.

Intestinal amino acid (AA) transporters are known to be induced by raised levels of dietary protein or free AA mixtures, but little is known about whether certain AAs are more potent inducers than others. Hence we compared, in mouse jejunum, the inductive effects of seven different AAs (given to mice as dietary supplements) on the brush-border uptake of five solutes predominantly taken up via different transporters. The AAs tested as dietary supplements included one imino acid, two acidic AAs, two basic AAs, and two neutral AAs. The solutes whose uptakes we studied were D-glucose plus preferential substrates for the acidic AA, basic AA, neutral AA, and imino acid transporter. Mouse growth rates were consistently higher for dietary supplementation with nonessential than essential AAs, but there were no ration-related differences in intestinal morphometric parameters and almost none in active D-glucose uptake. AA transport is regulated independently of D-glucose transport. The four AA transporters are regulated semi-independently on each other: e.g., aspartate is a good inducer for only two of the four transporters, arginine for one or two, lysine for just one. Different AAs differ in their potencies at inducing the same AA transporter. In a few cases good substrates make good inducers (e.g., aspartate of the acidic AA transporter, valine of the neutral AA transporter). But often this is not true: the acidic AA aspartate is the best inducer of the basic AA transporter; the basic AA arginine but not lysine is a good inducer of the acidic AA transporter; and the imino acid proline is not a good inducer of the imino acid transporter. The adaptive significance of these discrepancies between inducers and transported substrates is unclear. Thus the differing dietary values of different AAs may be related to their differing values as inducers of AA transport, in addition to their well-known differing biosynthetic values as essential or nonessential nutrients.

Amino Acids↗

PubMed1985

Is intestinal transport of sugars and amino acids subject to critical-period programming?

Physiological responses include three sorts: reversible within an individual's lifetime, fixed irreversibly at some critical period in life, and genetic. Examples of the first and third but not the second sort have been demonstrated for intestinal nutrient transport. Hence, we searched for critical-period programming of sugar and amino acid transport by mouse small intestine. Mice were maintained on either of two rations from gestation through birth, lactation, and weaning until adulthood: a high-carbohydrate, maintenance-protein ration and a carbohydrate-free, high-protein ration. The two groups of mice were then compared in adulthood while both groups were on the former or the latter ration. Early diet has irreversible effects on gut and body size; because of higher growth rates until weaning mice receiving high-carbohydrate diets achieved and maintained higher weights, longer guts, and heavier proximal guts than the mice receiving carbohydrate free diets. This difference increased with litter size and may have arisen from limitations on nursing mothers' ability to convert dietary protein into milk carbohydrate or fat. Early diet appears to exert some general effects on adult intestinal transport as a result of these differences in body and gut size but does not appear to exert specific irreversible effects on transport of D-glucose, L-proline, L-leucine, L-lysine, or L-aspartate or on passive glucose permeability. Active and passive glucose transport increases reversibly on a high-carbohydrate diet, whereas amino acid transport increases reversibly on a high-protein diet.

Amino Acids↗

PubMed1978

Constancy of the shift-up point in two temperature-sensitive mammalian cell lines that arrest in G1.

Two cell cycle-specific temperature sensitive (ts) mutants of mammalian cell lines, AF8 and K12, are known to arrest in G1 when shifted to the non-permissive temperature. We have determined the entry into S of both AF8 and K12 cells in five different growth conditions, namely: (1) quiescent sparse cultures stimulated to proliferative by serum; (2) quiescent dense cultures stimulated by serum; (3) quiescent sparse cultures stimulated by trypsinization and replating; (4) quiescent, dense cultures stimulated by trypsinization and replating; and (5) mitotic cells collected by mitotic detachment. In addition, for each cell line and for each different growth condition, we have determined the shift-up time, i.e., the time at which a shift-up to the nonpermissive temperature no longer prevents the entry of cells into S. In no case did K12 or AF8 enter S at the nonpermissive temperature. At the permissive temperature, the average time of entry into S varied in different growth conditions, and so did the shift-up time. However, in both cell lines, the distance of the average shift-up time from the average time of entry into S was remarkably constant, regardless of the growth conditions. i.e., 1.8 hours in K12 and 8.6 hours in AF8.

Cell Cycle↗

PubMed1978

Failure of reactivation of chick erythrocytes after fusion with temperature-sensitive mutants of mammalian cells arrested in G1.

Two temperature-sensitive (ts) mutants of mammalian cell lines (AF8 and cs4D3) that arrest in G1 at the nonpermissive temperature were fused with chick erythrocytes and the induction of DNA synthesis was studied in the resulting heterokaryons. While both AF8 and cs4D3 could induce DNA synthesis in chick nuclei at the permissive temperature, they both failed to do so when arrested in G1 at the nonpermissive temperature. When S phase AF8 cells were fused with chick erythrocytes, chick nuclei were reactivated even if the heterokaryons were incubated at the temperature nonpermissive for AF8. A third ts mutant, ts111, that is blocked in cytokinesis but continues to synthesize DNA, reactivated chick nuclei at both permissive and nonpermissive temperature. It is concluded that chick erythrocyte reactivation depends on the presence of S phase-specific factors.

Animals↗

PubMed1978

Effect of 5-bromodeoxyuridine on deoxyribonucleic acid-protein adducts induced by ultraviolet light on chromatin cells.

The formation of DNA-protein adducts induced by ultraviolet irradiation (254-nm. wavelength) has been analyzed by cesium chloride equilibrium sedimentation. The formation of ultraviolet-induced DNA-protein adducts is increased in 5-bromodeoxyuridine-substituted chromatin. Cross-linking is dependent in part upon the extent of 5-bromodeoxyuridine substitution, and is detectable either in chromatin irradiated in vitro or in chromatin from cells irradiated in vivo prior to the isolation of chromatin. As much as 80% of the DNA can be cross-linked to proteins by ultraviolet irradiation of 5-bromodeoxyuridine-substituted chromatin at a fluence of 2,928 Jm-2. In unsubstituted chromatin 11,712 Jm-2 are required to obtain to obtain the same effect. Under the same conditions of 5-bromodeoxyuridine replacement and ultraviolet irradiation only 10% of the total chromosomal proteins can be cross-linked to DNA, whether in vivo or in vitro. Approximately two-thirds of the cross-linked proteins chromatograph as nonhistone proteins, the remaining one-third as histones.

Bromodeoxyuridine↗

PubMedDate not supplied

Stereotactic radiosurgery of arteriovenous malformations: pathologic changes in resected tissue.

Both stereotactic radiosurgery and microsurgery are treatment modalities for arteriovenous malformations (AVM), and more recently, multimodality treatment using these approaches has been utilized. We surgically resected AVMs from 33 patients (ages 7-64 years old, mean age 30.4) 1-11 years after radiosurgery. AVM volumes were 0.8-117 cm3 (mean 21.6 cm3), and doses ranged from 4.6-45 GyE (mean 21.2 GyE). AVMs resected were submitted for pathologic review. Each AVM was evaluated for the following radiation changes, and the number of AVMs demonstrating these changes were noted: endothelial proliferation (27), hyaline (18) and calcium (10) in AVM vessel walls, partial (9) or complete (24) thrombosis of some AVM vessels, and necrosis of vessels (15) and adjacent brain tissue (11). A semiquantitative scale (mild, moderate, severe) incorporating the aforementioned changes present in each case classified the extent of radiation-induced change. There was a significant correlation (r = 0.624, p < 0.01) between extent of radiation change and dose of radiation received. There was no absolute radiation dose threshold below which radiation-induced changes were absent. However, all but one patient receiving greater than 20 GyE developed moderate to severe radiation vascular changes and the 3 patients treated with greater than 30 GyE all had severe radiation-induced changes. Radiation changes in AVMs following stereotactic radiosurgery appear to be dose-related. The correlation of dose to extent of radiation change may allow the determination of the optimal dose of radiation to treat AVMs.

Adolescent↗