Search PubMed⌕ Search

Biomedical subjects

C H Chang

Publications and source records attributed to C H Chang.

At least 415 records · Page 23Linked to original sources
PubMed1992

Tubal embryo transfer for the treatment of infertility.

The outcome of treatment for male factor infertility with either gamete intrafallopian transfer (GIFT) or in vitro fertilization and embryo transfer (IVF/ET) has been unsatisfactory. A better approach may be tubal embryo transfer (TET). In our medical center, from November 1989 to December 1990, 80 couples (male factor, n = 35, non-male factor, n = 45) entered our program for TET. Superovulation was conducted with either human menopausal gonadotropins (hMG) or gonadotropin-releasing hormone agonist (GnRH-a, buserelin)/hMG. Ovum retrieval (OR) was possible in 73 patients and successful fertilization after insemination occurred in 64 of them. TET was performed only when there was at least one grade III-V embryo. The mean number of embryos transferred was 3.92 +/- 0.13 (range 1-5). There were 35 pregnancies out of 55 TET (64% per TET, 48% per OR). In the group with male factor infertility, OR occurred in 32, and 24 achieved fertilization. Ten pregnancies were achieved after 19 TET (53% per TET, 31% per OR). In comparison, the group with non-male factor infertility had a higher pregnancy rate (69% per TET and 61% per OR). There have been 15 live births, 14 ongoing pregnancies (eight sets of twins and 21 singletons), five abortions and one ectopic pregnancy. Our results indicate that: 1) TET is a valuable treatment for non-tubal factor infertility; and 2) in the group with male factor infertility, it has the advantages of demonstrating fertilization in vitro and preventing unrewarding laparoscopies.

Embryo Transfer↗
PubMed1992

Antithrombin III activity in normal and toxemic pregnancies.

From August 1989 to October 1990, 83 pregnant Chinese women were the subjects for measuring the levels of plasma functional antithrombin III (AT III) activity. The correlations of AT III activity with perinatal outcome and the changes in maternal hepatorenal function were analyzed. The population was divided into four groups: Group I (n = 30), normal pregnancies; Group II (n = 23), mild pre-eclampsia; Group III (n = 26), severe pre-eclampsia; and Group IV (n = 4), eclampsia. The results demonstrated that: 1) AT III activity decreased with the severity of toxemia (p < 0.001), 2) AT III activity correlated with the degree of perinatal outcome and maternal morbidity, and 3) reduction of AT III activity correlated with impairment of maternal hepatorenal function. In conclusion, plasma AT III activity is a valuable parameter in the evaluation of toxemia.

Adult↗
PubMed1992

A knowledge-based computer-aided design and manufacturing system for total hip replacement.

A knowledge-based computer-aided design and manufacturing system (CAD-CAM) has been developed for total hip replacement. Knowledge-based refers to the fact that the design process is a computer program that has been provided with preprogrammed design rules. Compared with conventional CAD-CAM systems, the knowledge-based system is automated, requires less designer intervention, and increases the accuracy of the design process. The capabilities of the system make it ideal for the design of standard and custom total hip replacement. A full-fill, press-fit custom total hip replacement has been designed using the knowledge-based system. The early clinical results of a series of 37 replacements in 31 patients is described in this paper.

Adult↗
PubMed1992

[Valve replacement for aortic stenosis].

We retrospectively reviewed 122 consecutive patients with aortic stenosis from January 1977 to December 1990. There were 68 male and 54 female patients. Their age ranged from 5 to 73 years old (47 +/- 16, mean +/- SD). Sixty eight patients also had associated mitral valve lesion, 13 patients had tricuspid valve lesion, and 3 patients had coronary artery disease. Aortic valve replacement was performed on all patients. Mechanical valves were implanted in 86 cases and tissue valves in 36 cases. Associated procedures were performed in 54 cases: mitral valve replacement in 34 cases, mitral valve repair in 18 cases and coronary artery bypass grafting in 2 cases. A bicuspid aortic valve was found in 20 cases (16.4%). Hospital mortality was 4.9% (6 cases). Follow-up was completed in 95% of the surviving cases (110 cases). The survival rate was 82 +/- 3% at 13 years and redo-free rate was 73 +/- 8% at 13 years. Seven cases required redo operation, due to tissue valve degeneration in 5 and thrombosis of the mechanical valve in 2. All 7 patients survived. Late death occurred in 6 cases: 3 from malignancy, 2 from stroke and 1 from ventricular arrhythmia. We concluded that valve replacement for aortic stenosis is a safe and satisfactory procedure with good long-term results.

Adolescent↗
PubMed1992

[Migration of Kirschner wire from the right sternoclavicular joint into the main pulmonary artery. A case report].

The use of Kirschner wires (K-wires) for bone and joint fixation carries the risk of migration of the wire from the fixation site over time. However, review of the literatures disclosed rather few reports on this issue. We describe such a case in order to emphasize the potential complication and serious hazard that migration of such metallic devices can result in, especially when the fixation site is close to the thoracic cavity.

Adult↗
PubMed1991

Direct radiolabeling of monoclonal antibodies with generator-produced rhenium-188 for radioimmunotherapy: labeling and animal biodistribution studies.

The use of 188Re from an alumina-based 188W/188Re generator has been investigated for antibody radiolabeling. It was found that, with simple labeling techniques, 188Re can be used immediately after elution. The direct radiolabeling of intact antibodies with 188Re is described. Lyophilized antibody preparations have been reconstituted with 188Re taken directly from the generator at specific activities of up to 15 mCi of 188Re per mg of antibody. Radiolabeling yields of 90 to 98% have been obtained, with the incorporation rate being dependent upon time and the relative concentrations of the reagents. It was determined that the conjugates were immunoreactive and stable when challenged by serum in vitro, with 188Re-immunoglobulin G showing adequate resistance to reoxidation with no transfer of 188Re to serum protein. 188Re-antibody conjugates were shown to clear from the blood faster than the corresponding 131I-labeled antibody, giving rise to good tumor/nontumor ratios at 24 to 72 h postinjection, while serum samples taken from the animals have shown that the circulating 188Re remained bound to immunoglobulin G. The combination of the technologies of the 188W/188Re generator, the direct labeling methodology, and the use of single-vial lyophilized antibody makes the use of 188Re-radiolabeled monoclonal antibodies a simple and convenient method of cancer radioimmunotherapy with a beta-emitting radionuclide.

Animals↗
PubMed1991

Calcium reveals different mechanisms of guanylate cyclase activation by atrial natriuretic factor and ATP in rat lung membranes.

CaCl2 inhibited ATP-stimulated guanylate cyclase activity, but had little effect on basal and atrial natriuretic factor-stimulated guanylate cyclase activity in rat lung membranes. LaCl3 had similar effects as CaCl2 on basal and stimulated guanylate cyclase activity. LiCl and other monovalent salts inhibited ATP-stimulated guanylate cyclase activity more than basal enzyme activity. However, atrial natriuretic factor somehow stabilized the enzyme against the inhibitory effect of LiCl. These results suggest that ATP and atrial natriuretic factor activate the enzyme through different mechanisms. Since the effect of calcium on guanylate cyclase activity is different from that of monovalent salts and can be mimicked by lanthanum, it may be mediated by a specific calcium binding site or binding protein.

Adenosine Triphosphate↗
PubMed1991

Structure of the membrane-bound protein photosynthetic reaction center from Rhodobacter sphaeroides.

The structure of the photosynthetic reaction center (RC) from Rhodobacter sphaeroides was determined at 3.1-A resolution by the molecular replacement method, using the Rhodopseudomonas viridis RC as the search structure. Atomic coordinates were refined with the difference Fourier method and restrained least-squares refinement techniques to a current R factor of 22%. The tertiary structure of the RC complex is stabilized by hydrophobic interactions between the L and M chains, by interactions of the pigments with each other and with the L and M chains, by residues from the L and M chains that coordinate to the Fe2+, by salt bridges that are formed between the L and M chains and the H chain, and possibly by electrostatic forces between the ends of helices. The conserved residues at the N-termini of the L and M chains were identified as recognition sites for the H chain.

Amino Acids↗
PubMed1991

Comparison of reaction centers from Rhodobacter sphaeroides and Rhodopseudomonas viridis: overall architecture and protein-pigment interactions.

Photosynthetic reaction centers (RCs) from the photosynthetic bacteria Rhodobacter sphaeroides and Rhodopseudomonas viridis are protein complexes closely related in both structure and function. The structure of the Rps. viridis RC was used to determine the structure of the RC from Rb. sphaeroides. Small but meaningful differences between the positions of the helices and the cofactors in the two complexes were identified. The distances between helices AL and AM, between BL and BM, and between bacteriopheophytins BPL and BPM are significantly shorter in Rps. viridis than they are in Rb. sphaeroides RCs. There are a number of differences in the amino acid residues that surround the cofactors; some of these residues form hydrogen bonds with the cofactors. Differences in chemical properties and location of these residues account in some manner for the different spectral properties of the two RCs. In several instances, the hydrogen bonds, as well as the apparent distances between the histidine ligands and the Mg atoms of the bacteriochlorophylls, were found to significantly differ from the Rb. sphaeroides RC structure previously described by Yeates et al. [(1988) Proc. Natl. Acad. Sci. U.S.A. 85, 7993-7997] and Allen et al. [(1988) Proc. Natl. Acad. Sci. U.S.A. 85, 8487-8491].

Amino Acids↗
PubMed1991

Effects of 2-chloro-9-(2-deoxy-2-fluoro-beta-D-arabinofuranosyl)adenine on K562 cellular metabolism and the inhibition of human ribonucleotide reductase and DNA polymerases by its 5'-triphosphate.

2-Chloro-9-(2-deoxy-2-fluoro-beta-D-arabinofuranosyl)-adenine (Cl-F-ara-A) has activity against the P388 tumor in mice on several different schedules. Biochemical studies with a chronic myelogenous leukemia cell line (K562) grown in cell culture have been done in order to better understand its mechanism of action. Cl-F-ara-A was a potent inhibitor of K562 cell growth. Only 5 nM inhibited K562 cell growth by 50% after 72 h of continuous incubation. The 5'-triphosphate of Cl-F-ara-A was detected by strong anion exchange chromatography of the acid-soluble extract of K562 cells incubated with Cl-F-ara-A. Competition studies with natural nucleosides suggested that deoxycytidine kinase was the enzyme responsible for the metabolism to the monophosphate. Incubation of K562 cells for 4 h with 50 nM Cl-F-ara-A inhibited the incorporation of [3H]thymidine into the DNA by 50%. Incubation with 0.1, 1, or 10 microM Cl-F-ara-A for 4 h depressed dATP, dCTP, and dGTP pools but did not affect TTP pools. Similar inhibition of deoxyribonucleoside triphosphate pools was seen after incubation with 2-chloro-2'-deoxyadenosine. Both Cl-F-ara-ATP and Cl-dATP potently inhibited the reduction of ADP to dADP in crude extracts of K562 cells (concentration producing 50% inhibition, 65 nM). The effect of Cl-F-ara-ATP on human DNA polymerases alpha, beta, and gamma isolated from K562 cells grown in culture was determined and compared with those of Cl-dATP and 9-beta-D-arabinofuranosyl-2-fluoroadenine triphosphate (F-ara-ATP). Cl-F-ara-ATP was a potent inhibitor of DNA polymerase alpha. Inhibition of DNA polymerase alpha was competitive with respect to dATP (Ki of 1 microM). The three analogue triphosphates were incorporated into the DNA by DNA polymerase alpha as efficiently as dATP. The incorporation of Cl-F-ara-AMP inhibited the further elongation of the DNA chain, similarly to that seen after the incorporation of F-ara-AMP. Extension of the DNA chain after the incorporation of Cl-dAMP was not inhibited as much as it was with either Cl-F-ara-AMP or F-ara-AMP. Cl-F-ara-ATP was not a potent inhibitor of DNA polymerase beta, DNA polymerase gamma, or DNA primase.(ABSTRACT TRUNCATED AT 400 WORDS)

Adenine Nucleotides↗
PubMed1991

The amino acid sequence and properties of an edema-inducing Lys-49 phospholipase A2 homolog from the venom of Trimeresurus mucrosquamatus.

Three phospholipase A2 enzymes or homologs were purified from the venom of Trimeresurus mucrosquamatus (Taiwan habu). The most abundant one was found to be a phospholipase homolog without enzyme activity, and its complete amino acid sequence was determined using oligopeptide fragments derived from digestion by endopeptidases Glu-C, Asp-N, Lys-C and alpha-chymotrypsin, and by means of gas-phase sequencing. The sequence revealed that the protein belonged to the Lys-49 family of snake venom phospholipase A2. This protein's function was characterized as edema-inducing. The Lys-49 protein has the potential to bind membrane phospholipid and Ca2+ (Kd = 1.6 x 10(-4) M) as shown by ultraviolet difference spectra; however, the catalytic site appeared to be inactive and the edematous response was independent of the protein's hydrolytic activity. Mast cells and platelets were shown to be subject to activation by the Lys-49 protein.

Amino Acid Sequence↗
PubMed1991

Focal scleroderma and severe cardiomyopathy. Patient report and brief review.

A 21-month-old infant presented with simultaneous localized scleroderma and severe cardiomyopathy with heart failure. Cardiac abnormalities and serological changes (positive rheumatoid factor assay, elevated IgM and IgG levels, and elevated erythrocyte sedimentation rate) reverted to normal with prednisone therapy, and there was substantial, though incomplete, resolution of her skin changes during the same period. To our knowledge, this is the first patient with definite, clinically significant cardiac involvement associated with focal scleroderma. The possibility of internal organ involvement, including cardiac involvement, must be considered with focal scleroderma as well as with progressive systemic sclerosis.

Cardiomyopathy, Dilated↗
PubMed1991

Septal ventricular pacing in the immature canine heart: a new perspective.

Cardiac pacing initiated from epicardial or transvenous apical right ventricular electrodes causes asynchronous ventricular contraction. This alters myocardial stress vectors and results in adverse cellular and subcellular changes in the experimental animal. Clinically, such changes may contribute to the adverse hemodynamics reported with long-term ventricular pacing. To determine the feasibility of direct stimulation of the ventricular specialized conduction systems and therefore the potential for maintenance of normalized depolarization patterns, 13 beagle puppies were studied. Baseline ventricular activation and contraction patterns were obtained using intracardiac electrograms and multigated nuclear acquisition (MUGA) imaging. Septal electrode insertion from the aortoatrial groove was accomplished by use of two-dimensional echocardiography and continuous electrocardiographic (ECG) monitoring of the surface ECG during pacemaker implantation in five puppies. Standard right ventricular epicardial electrodes were implanted in five additional animals, with three remaining as age-matched non-paced controls. After 4 months of observation, repeat MUGA imaging and intracardiac electrograms demonstrated nearly normal biventricular activation and contraction patterns among the septal-paced group. Histopathologic examination illustrated normal cellular morphology in the septal-paced animals. This study demonstrates that pacing electrode insertion into the proximal interventricular septum is feasible and results in utilization of the normal ventricular conduction pathway. Such an approach to initiation of ventricular stimulation may attenuate the adverse effects of long-term ventricular pacing.

Animals↗
PubMed1991

Intrapericardial pheochromocytoma.

In a 34-year-old man with hypertension and increased urinary catecholamine excretion for 12 years, an m-[131I]iodobenzylguanidine scan and chest computed tomography located an intrapericardial pheochromocytoma in the left atrium. The tumor was excised through a left thoracotomy with cardiopulmonary bypass and circulatory arrest. At 34-month follow-up, blood pressure and urine catecholamine levels were normal. In the 15 cases of intrapericardial pheochromocytoma treated by resection reported in the literature, all 11 survivors were symptom-free except 1 who had residual left atrial tumor and multiple skeletal metastatic lesions. Computed tomography directed by the m-[131I]iodobenzylguanidine scan can be used for detailed location of the tumor. Appropriate surgical approach and use of cardiopulmonary bypass are critical in the resection of these highly vascular tumors.

Adult↗
PubMed1991

Traumatic asphyxia.

During a 5-year period, we treated 14 cases of traumatic asphyxia. There were 12 male and 2 female patients ranging in age from 2 to 32 years. Most suffered crushing injuries at work or were run over by motor vehicles. Mild to severe cervicofacial cyanosis and petechiae developed in all patients. A fear response was reported by 12 of the patients. Subconjunctival hemorrhage was also found in 12 patients. Nine patients had tachypnea and 7 complained of dyspnea. Most of the patients suffered some associated injuries including 8 head injuries, 7 pulmonary contusions, and 6 cases of blunt abdominal trauma. Less-associated injuries were rib fractures, brachial and radial nerve injuries, hemothorax, and pneumothorax. The hospital stay ranged from 4 to 28 days (mean, 14 days) and follow-up from 10 to 60 months (mean, 32 months). Treatment for traumatic asphyxia included measurement of arterial blood gases, oxygen supplementation, and intubation with mechanical ventilation. The patients' recovery conditions were relative to the severity of injury and the associated injuries.

Adolescent↗
PubMed1991

Real-time US guidance during renal biopsy in children: a different approach. Technical note.

To minimize procedural failures and complications, a real-time ultrasound (US) approach was developed for percutaneous renal biopsy in the pediatric population. With use of a 3- or 5-MHz transducer, the medial border of the kidney is localized and a line, which parallels the renal axis, is drawn on the skin. The lower pole and renal hilum are identified, and lines are drawn perpendicular to the long axis. After the patient is sedated, the entry site is selected above the lower pole. The transducer is placed on the child's side in an oblique transverse plane parallel to the axis of the kidney, the needle is guided into the renal cortex, and a specimen is obtained. Sixty-five biopsies were performed in 63 children. Fifty-five specimens were obtained from native kidneys. Success was achieved in all cases with only three minor complications. This approach appears to be an easy, safe, and accurate guide for renal biopsy in the pediatric population.

Adolescent↗
PubMed1991

Long-term survival in treated anaplastic astrocytomas. A report of combined RTOG/ECOG studies.

This report evaluates the long-term survival of patients with histologically confirmed anaplastic astrocytoma on several combined RTOG (Radiation Therapy Oncology Group) studies. Included in this analysis are the following studies: RTOG/ECOG (Eastern Cooperative Oncology Group) 74-01, RTOG 76-11, and RTOG 79-18, with the various treatment arms separated into radiation therapy (RT) only (47 patients) radiation therapy and chemotherapy (Chemo) (78 patients) and radiation therapy, chemotherapy, and misonidazole (Mizo) (24 patients). Pretreatment characteristics of age, prior surgery, performance status, and neurological function classification are identified. Median survival for patients treated with RT only is 3.0 years. Median survival for patients treated with RT + Chemo is 2.3 years, and for patients treated with RT + Chemo/Miso is 1.2 years. Five-year survival rates are 35% for patients treated with RT only, 29% for patients treated with RT + Chemo, and 24% for patients treated with RT + Chemo/Miso. Age and performance status have been identified in previous studies as important prognostic variables and are confirmed in this analysis. Patients treated with misonidazole had a significantly worse prognosis after adjustment for differences in prognostic factors. Addition of chemotherapy did not improve survival except in less favorable prognostic categories. In general, more aggressive treatment regimens are associated with decreased survival compared to conventional postoperative irradiation.

Adolescent↗