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Biomedical subjects

T S Chang

Publications and source records attributed to T S Chang.

At least 109 records · Page 6Linked to original sources
PubMed1983

An analysis of tibial component design in total knee arthroplasty.

An axisymmetric finite element model of the proximal tibia and cemented tibial component subject to nonaxisymmetric loading is presented. Model variations included polyethylene components and steel reinforced polyethylene components both with and without a central fixation post. Central fixation posts of 35 and 70 mm were modeled. A vertically oriented load applied unilaterally to the tibial component was found to generally cause the largest magnitude peak stresses within the various components of the structure. The addition of steel reinforcement to tibial components without central fixation post is predicted to significantly reduce stress levels within the polymethylmethacrylate and underlying cancellous bone. Although to a lesser extent, the addition of a relatively short central fixation post to the steel reinforced tibial component further reduced these stress levels. The longer steel central fixation post can appreciably reduce proximal cement and bone stress levels. The tibial component condylar width is predicted to have little effect on polymethylmethacrylate and cancellous bone stresses, with the exception that proximal tibial cancellous bone compressive stresses are reduced with wide steel reinforced components.

Biomechanical Phenomena↗
PubMed1983

A critical method of evaluating tests for male infertility.

Considerable uncertainty surrounds the selection of test values that separate infertile from fertile men in the evaluation of male infertility. We herein describe an objective method of determining these values, referred to as threshold values, for different infertility tests. Using test results from fertile men threshold values were chosen such that 96 per cent of the semen samples from the fertile men were scored as fertile. These threshold values then were used to evaluate 100 semen samples from 74 men presenting for evaluation of infertility. Using this method we constructed infertility profiles on each of the 100 semen samples presented for infertility evaluation and found that the zona pellucida-free hamster egg penetration test (a measure of a spermatozoon's ability to undergo capacitation and penetrate an egg) identified 66 per cent of these samples as infertile, while multiple exposure photomicrography (a quantitative measure of sperm motility) identified 54 per cent of these samples as infertile. This compares with results from routine semen analyses using the same method, which identified none of the samples as infertile by sperm motility grade, 1 per cent by semen pH, 4 per cent by the percentage of motile sperm, 7 per cent by the total count of motile sperm, 10 per cent by the total sperm count, 11 per cent by the semen leukocyte concentration, 12 per cent by the concentration of motile sperm, 13 per cent by ejaculate volume, 16 per cent by sperm concentration and 27 per cent by sperm morphology. This method of analyzing infertility test results provides insight into the potential causes of male infertility and offers a critical approach towards understanding the complex problem of male fertility dysfunction.

Female↗
PubMed1983

Immunochemical studies to purify rabbit and chicken immunoglobulin G antibody by protein A-Sepharose chromatography.

The immunoglobulin (Ig) G binding properties of protein A made affinity chromatography with protein A an acceptable method for isolation of IgG in mammals. Rabbit IgG was isolated by fractionation of serum on a column containing protein A coupled to Sepharose. The IgG molecules of subclasses 1, 2, and 4 and their fragments containing the Fc region had this affinity, but not IgG-3. The second peak, after washing with 1M acetic acid eluate (pH 7.0) as shown in the Ouchterlony agar immunodiffusion test, was the IgG fraction. Similar studies on normal and hyperimmune chicken sera indicated that chicken IgG does not bind to protein A molecules. Further studies indicated that chicken plasminogen did not bind covalently to protein A molecules and subsequently did not interfere in the affinity of protein A to bind to IgG molecules. The inhibition of binding of chicken IgG to protein A molecule is still unknown.

Animals↗
PubMed1982

The free forearm flap--a report of 25 cases.

In 25 cases using microvascular techniques, free forearm flaps were used for reconstruction of various tissue defects. 15 flaps were used for repair of hand injuries, 5 for facial defects, 1 for lower extremity deformity and 4 for total rhinoplasty. All flaps survived. The arterial blood supply of the forearm flap comes from the cutaneous branches of the radial artery while its venous drainage is via cephalic vein and the radial comitantes veins. The forearm flap has a thin layer of subcutaneous fatty tissue, can provide quite large area of soft tissue and the vascular pedicle is long with moderately large calibre vessels. The donor area, however, has to be skin grafted, leaving an unsightly scar over the forearm which is one of the shortcomings of this flap. Secondly it means sacrificing a major arterial supply to the hand on the donor side.

Adult↗
PubMed1980

Reconstruction of esophageal defects with microsurgically revascularized jejunal segments: a report of 13 cases.

Experimental free transfer of a jejunal segment to a recipient bed in the neck was successfully performed in 5 mongrel dogs. This was followed by clinical application of 2 different microvascular procedures in 13 patients for repair of esophageal defects. In 7 of these patients a free jejunal transfer was used; in 6 of these patients a pedicled jejunal graft with revascularization of its distal end by microvascular anastomosis was used. The esophageal defects were located in the cervical portion in 7 cases, the cervicothoracic portion in 5 cases, and the thoracic portion in 1 case. Ten (77%) of the 13 procedures were successful.

Adolescent↗
PubMed1980

Involvement of an acrosinlike proteinase in the sulfhydryl-induced degradation of rabbit sperm nuclear protamine.

Previous studies demonstrated that proteolytic activity is associated with isolated rabbit sperm nuclei and is responsible for the degradation of nuclear protamine that occurs during thiol-induced in vitro decondensation of the nuclei (Zirkin and Chang, 1977; Chang and Zirkin, 1978). In this study, we present the results of experiments designed to characterize this proteolytic activity. Basic protein isolated from rabbit sperm nuclei incubated with 5 mM dithiothreitol (DTT) and 1 percent Triton X-100 for increasing periods of time exhibited progressively faster migrating bands on acid-urea polyacrylamide gels, reflection the progressive degradation of protamine. Ultimately, a specific and characteristic peptide banding pattern resulted. When sperm nuclei were treated with the esterase inhibitor nitrophenyl-p-guanidino benzoate (NPGB) to inhibit the nuclear-associated proteolytic activity and then incubated with one of several exogenous proteinases in addition to DTT and Triton X-100, characteristic peptide banding patterns were seen for each exogenous proteinase employed. For trypsin, chymotrypsin, pronase, and papain, the peptide banding patterns differed from one another and from the pattern characteristic of protamine degradation by the nuclear-associated proteinase. By contrast, when rabbit acrosin served as the exogenous proteinase, the peptide banding pattern seen was identical to the pattern characteristic of the nuclear-associated proteinase. These results demonstrate directly that the proteinase associated with rabbit sperm nuclei and involved in sperm nuclear decondensation in vitro is acrosinlike.

Acrosin↗
PubMed1980

Measurement of uric acid levels in chicken cecal contents.

Uric acid levels in the cecal contents of White Leghorn males aged 6, 10, and 24 weeks of age were constant at approximately 2 mg/100 ml. Fecal samples obtained from these birds contained, respectively, 99, 107, and 156 mg/100 ml uric acid. The addition of growth promoting level of antibiotics or other feed additive to the ration of 10-week-old White Leghorn males had no effect upon cecal uric acid levels.

Animals↗
PubMed1980

In vitro antibiotic activity on cecal anaerobes with emphasis on uric acid-utilizing bacteria.

A total of 741 individual colonies or representative colonial types were isolated on basal-hlf-uric acid (UA) agar plates containing various antibiotics and on two types of control media. All of the antibiotics utilized in this study were capable of reducing bacterial numbers and/or bacterial groups in vitro when compared to the control plates. None of the antibiotics were selective for the uric acid bacteria. The majority (96%) of the cecal isolates utilizing uric acid were gram-positive. The basal-half-uric acid agar was a nonselective growth medium and supported the growth of virtually every bacterial group reported to be present in the avian cecum. The cecal flora of the adult White Leghorn hens tested was observed to be composed of 23% G+ (gram-positive) rods, 24% G- (gram-negative) rods, 26% G+ cocci, 9% G- cocci, and 18% G+ coccal-bacilli.

Anaerobiosis↗
PubMed1979

Free transfer of the second toe combined with dorsalis pedis flap using microvascular technique for reconstruction of the thumb and other fingers.

The blood supply to the dorsum of the feet was studied in 100 cadaver feet specimens. The understanding of anatomical variation of branches of dorsalis pedis artery and its venous system are important in determining the success of the operation for free toe or dorsalis pedis flap transplantation. Three groups of fine branches of arterial system supplying the skin on the dorsum of the feet are classified; the central, the intermediate and the marginal groups. The central group is the dorminant blood supply to the dorsalis pedis skin flap. The first dorsal metatarsal artery which is a main branch of the dorsalis pedis artery remains to be dominant feeding artery to the second toe. From these cadaver specimens, three types of distribution are formulated, but with different percentages of distribution as compared with that of Gilbert's data. Seven consecutive cases of the second toe combined with dorsalis pedis flap transfer using microvascular technique for the reconstruction of thumb and other fingers are reported. The operation is designed to meet the demand of one stage reconstruction of the missing thumb or other fingers which are associated with surrounding soft tissue defects. Preparatory soft tissue repair by skin flap or tube flap is thus obviated.

Adult↗
PubMed1978

Proteolytic degradation of protamine during thiol-induced nuclear decondensation in rabbit spermatozoa.

Rabbit sperm nuclei decondensed when incubated with dithiothreitol and Triton X-100. Protamine isolated from these nuclei during the course of treatment exhibited marked and progressive degradation. Timed interval experiments revealed that the degradation of protamine significantly preceded sperm nuclear decondensation and reached its maximum extent before decondensation was completed. Studies with protease inhibitors demonstrated that proteolysis was involved in both nuclear decondensation and protamine degradation.

Animals↗
PubMed1978

Structural studies on the succinylated bovine serum albumin.

An analysis of succinylated bovine serum albumin showed that all of the 62 epsilon-amino groups of lysine residues, 13 hydroxyamino acid residues and 12 tyrosin residues were succinylated, but the succinylated tyrosines were later deacylated. Structural properties of the modified protein have been studied with circular dichroism and sedimentation velocity. At neutral pH (pH 7.60) and in a salt-free aqueous solution the modified protein is in an expanded form and its helical content is only 30% of that of unmodified protein. The increase of ionic strength restores the original conformation of the protein, whereas the increase of pH further disorganizes the structure of the protein. The results suggest that the electrostatic force alone is responsible for the compact structure of the protein molecule. The same mechanism is believed to underlie the effect of H3O+ and the effect of succinylation of the side chain groups on the conformation of bovine serum albumin.

Amino Acid Sequence↗
PubMed1978

Vaccination immunity to selected diseases in chickens fed the androgen analog mibolerone.

Chickens fed the androgen analog mibolerone during the first 7 weeks of life regress their bursa of Fabricius but can be properly immunized by vaccination against avian pathogens of major economic importance such as Newcastle disease virus, infectious laryngotracheitis virus, avian encephalomyelitis virus, infectious bronchitis virus, fowl pox virus, Marek's disease virus, and Pasteurella multocida, the pathogen causing fowl cholera. These findings on immunocompetence to infectious agents are important because we have previously shown that the administration of mibolerone prevents the development of lymphoid leukosis tumors.

Animals↗