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Biomedical subjects

C Y Ko

Publications and source records attributed to C Y Ko.

33 records · Page 2Linked to original sources
PubMed1996

Safe ischemia time in free-flap surgery: a clinical study of contact-surface cooling.

Although the effectiveness of cooling in extending tolerable ischemia time is well-established experimentally, most free-flap surgeons are still concerned about this problem and try to limit the ischemic period to less than 1 hr. Clinically, contact-surface cooling has been used empirically to prolong the limits of ischemia time; however, its applications are unproven. It also remains unknown whether contact-surface cooling has detrimental effects on flap tissue, such as vessel spasm leading to thrombosis. The purpose of this study was to determine, in a clinical setting, if skin, muscle, and bone free flaps of considerable size could tolerate prolonged cold ischemia without adverse effects. Flap size, cold ischemia time, and surgical outcomes were studied in 189 consecutive free flaps. Microvascular thrombosis occurred in 5/378 (1.3 percent) of anastomoses. The overall flap complication/flap loss rate was 7/189 (3.7 percent). Mean ischemia time for all flaps was 2 hr and 6 min (range: 30 min to 5 hr, with one case at 6 hr and 8 min). The mean ischemia time for cases with flap complications was 2 hr 20 min, while ischemia time for cases with thrombosis averaged 2 hr 13 min. The one flap loss had an ischemia time of 1 hr 35 min. No statistically significant correlations existed between duration of ischemia time or duration of contact-surface cooling and the incidence of thrombosis, flap complication, or flap failure. Among the conclusions were that, within a 4-hr period of cold ischemia, the application of the surface-cooling technique is not detrimental to free flap surgery; thus, concern for ischemia, and especially the "no reflow" phenomenon, generally should not interfere with efficient and orderly free-flap surgery.

Humans↗
PubMed1996

Salvage of a below-the-knee amputation with a fillet of foot free flap: a 15-year follow-up.

In the setting of traumatic injury, obtaining suitable coverage to salvage a below-the-knee amputation has been performed by using a variety of tissue flaps, including the fillet of foot free flap. This flap is a free tissue transfer that utilizes the soft tissues of the foot for stump coverage. In this report, we present a 15-year follow-up of a patient with a fillet of foot free flap to demonstrate its applicability and long-term efficacy. We also discuss technical aspects for performing this procedure. In this follow-up, we have found the flap to be extremely durable, even when placed in the weight-bearing position of the stump, and also lacking many of the usual complications associated with the weight-bearing portion (e.g., blisters, ulcerations). We conclude that the fillet of foot free flap is an excellent salvage flap for providing long-term length, coverage, and durability in an amputated, weight-bearing extremity.

Accidents, Traffic↗
PubMed1996

Capsular synovial metaplasia as a common response to both textured and smooth implants.

Recent reports suggested that the presence of synovial metaplasia in the capsular tissues of breast implants is greater with textured-shelled implants compared with smooth. Textured implants, however, have become popular only in the last few years. Therefore, the studies do not address the possibility that synovial metaplasia may be a dynamic process related to time (e.g., implant age) rather than implant shell surface. In the current study, 159 implant capsules (85 patients) removed between February of 1992 and July of 1993 at UCLA Medical Center were evaluated histologically and correlated with clinical data, including the age of implants. Synovial metaplasia was identified in 40 percent (64 of 159) of the capsule specimens. A logistic regression analysis that removed the effect of implant age demonstrated no correlation of implant shell type (textured versus smooth) with the presence of synovial metaplasia. Gel bleed, implant location, pericapsular fluid, implant rupture, and capsular contracture also did not have any significant association with synovial metaplasia in the current study. The incidence of synovial metaplasia appears to decrease with age (77 percent at < 5 years; 22 percent at > 15 years). Our findings suggest that synovial metaplasia is not rare and in fact may be a fairly common transitional histologic finding. It may be part of the common progression that occurs at the implant-capsule interface. The clinical significance remains unknown.

Adult↗
PubMed1996

Microbial evaluation: 139 implants removed from symptomatic patients.

Possible adverse effects of microbial organisms have been implicated in symptomatic silicone implant patients. In the literature, numerous authors have investigated the possible role of infection with respect to implant problems. To date, various bacterial species have been reported, including Staphylococcus aureus, Staphylococcus epidermidis, peptostreptococci, and Clostridium perfringens. Infections in polyurethane-coated prostheses also have been shown to prolong morbidity. Antibiotic use has been relatively empirical in this regard. The purpose of this study was, first, to determine the frequency, type, and clinical relevance of microbial colonization on implant surfaces removed from symptomatic patients and, second, to determine possible effects of microbial colonization on implant integrity (gel bleed, rupture). A total of 139 implants from 72 symptomatic patients were entered into the prospective clinical study between February of 1993 and July of 1994 at the UCLA Medical Center. The implant shell types included smooth (79 percent), polyurethane (8 percent), textured (7 percent), and smooth and Dacron (6 percent). The implant locations were subglandular (71 percent), submuscular (28 percent), and subcutaneous (1 percent). Of the 139 implants removed, 69 percent were intact and 31 percent were ruptured. Forty-seven percent of 139 implants were culture-positive. Propionibacterium acnes was isolated most frequently (57.5 percent), followed by Staphylococcus epidermidis (41 percent), and then Escherichia coli (1.5 percent). No fungal infections were identified. Culture positivity was not significantly associated with systemic symptoms. Sixty-seven percent of the positive culture implants were intact; 33 percent were ruptured. The frequency (47 percent) and types (P. acnes and S. epidermidis) of microbial colonization are determined in symptomatic silicone implant patients.

Adult↗
PubMed1996

Abdominal tuberculosis: the surgical perspective.

The increasing incidence of pulmonary tuberculosis (TB) has led many to predict a corresponding increase in abdominal TB. This study reports the incidence, presentation, and outcome of abdominal TB to elucidate factors that might assist the surgeon to treat this potentially curable disease. A retrospective review of patients diagnosed with tuberculosis between 1993 and 1995 was performed at two hospitals. Diagnosis of abdominal TB was based on acid fast bacilli on tissue stains and/or culture. Seven patients were diagnosed with abdominal TB. Two patients were HIV positive; six were recent immigrants. Abdominal pain, fever, and significant weight loss were the most common symptoms. All preoperative radiologic tests failed to demonstrate findings suggestive of TB. All patients were brought to operation. Indications included perforated viscus (2), acute abdomen (1), small bowel obstruction (1), colocutaneous fistula (1), pelvic neoplasm (1), and biliary colic (1). Abdominal TB was either diagnosed or suspected intraoperatively in six patients. Postoperative anti-TB chemotherapy was promptly instituted. Although abdominal TB can be cured medically if treated early enough, the nonspecific presentation delays diagnosis in the majority of cases. Diagnosis of abdominal TB can be made or at least highly suspected intraoperatively such that anti-TB medications can be initiated promptly. Appropriate surgical therapy and prompt initiation of anti-tuberculosis medications can successfully treat abdominal TB.

Adolescent↗
PubMed1995

Is surface cooling effective for tissue preservation in free-flap surgery?

Effective tissue cooling can extend the period of safe ischemia. To determine whether the technique of surface cooling could produce an effectively low core temperature (4 degrees to 10 degrees C) in the flap core in a reasonable amount of time, bovine muscle/subcutaneous fat flaps, weighing 400, 800, and 2000 g, were brought to 37 degrees C and then surface cooled. Temperatures were then recorded every 5 min. All flaps were able to attain 4 degrees C in the core; the average times for the 400, 800, and 2000 g flaps to reach 4 degrees C were 136, 153, and 194 min, respectively. Although a clear inverse relationship existed between flap weight and effectiveness of core cooling, even relatively large flaps (2000 g) could still achieve sufficiently low core temperatures from surface cooling well within tolerable warm ischemia time. Concern for ischemia time generally should not interfere with efficient, orderly, free-flap surgery.

Animals↗
PubMed1995

Clinical significance of intracapsular fluid in patients' breast implants.

Clinical reports on the incidence and clinical significance of intracapsular fluid are lacking in the literature. It remains unknown whether the presence of intracapsular fluid has any relation to implant infection or colonization. The purpose of this study was to determine the frequency and type of intracapsular fluid, specifically, whether intracapsular fluid causes implant infection, implant rupture, or bacterial colonization. A total of 139 implants from 72 symptomatic patients were entered into the prospective clinical study. Our study demonstrated the presence of intracapsular fluid in 21 of 139 (15%) implants. Positive microbial cultures were identified in 39% of the implants in the positive intracapsular fluid group, compared to 43% in the negative fluid group. There was no statistically significant difference between these groups. Also, no adverse clinical relationship was demonstrated between local symptoms and presence of intracapsular fluid. There was, however, a positive trend toward the presence of fluid when implant shell types were nonsmooth (polyurethane and textured silicone implants). Further studies are indicated to elucidate the fluid production mechanism and possible secretory activity of prosthetic capsules interfacing the textured breast implant surface.

Adult↗
PubMed1995

Estrogen receptors in gallbladder cancer: detection by an improved immunohistochemical assay.

Although gallbladder carcinoma is the most common malignancy of the extrahepatic biliary tract, patients with this disease have a very poor prognosis. Previous investigations have documented the presence of estrogen receptors (ER) in gallbladder cancers for possible therapeutic benefit; however, the methods used for detection were largely imprecise, which led to a wide range of results. In light of these unclear results obtained with inferior techniques, we have attempted to determine more accurately the prevalence of ER positivity in gallbladder cancer using an improved, more specific immunohistochemical assay (IHA) for estrogen receptors. The IHA, which used a pronase pretreatment and the H222 monoclonal antibody, was performed on archival tumor specimens of 25 patients. There were no strongly or moderately positive specimens. Three specimens stained weakly positive, and 22 specimens (88%) were negative. The three specimens that were weakly positive showed neither statistical significance nor any identifiable trends with respect to patient sex, tumor stage, or histologic type. We conclude that, contrary to previous reports, weak estrogen receptor staining occurs in a very small percentage of gallbladder carcinomas. Furthermore, although the minimum concentration of ER required for potential therapeutic benefit is unclear, the addition of hormonal therapy in patients with gallbladder cancer is not likely to alter the outcome of this malignancy.

Aged↗
PubMed1982

Purification and characterization of a collagenous protein secreted by a murine teratocarcinoma-derived cell line.

A collagenous protein could be precipitated by (NH4)2SO4 from the culture medium of a murine teratocarcinoma-derived cell line (Ko, C.Y., Johnson, L.D. and Priest, R.E. (1979) Biochim. Biophys. Acta 581, 252-259). Further purification of this protein was achieved by combining DEAE-cellulose chromatography with either CM-cellulose or molecular sieve chromatography. The collagenous polypeptides had subunit molecular weights of 160 000, if determined by molecular sieve chromatography, or 190 000, if determined by sodium dodecyl sulfate-polyacrylamide gel electrophoresis, and they are not linked by disulphide bridges. Amino acid composition of this collagen is similar to that of a murine type IV collagen isolated from EHS sarcoma (Timpl et al. (1978) Eur. J. Biochem. 84, 43-52). The most prominent peptides resulting from cleavage of the protein by CNBr had estimated molecular weights of 25 000, 23 000, 11 700 and 9400. Pepsin treatment of this collagen under non-denaturing conditions produced three major fragments having molecular weights of 70 000, 45 000 and 43 000. We conclude that the collagen secreted by the murine teratocarcinoma-derived cell culture is a type IV basement membrane collagen. Therefore, this culture system should provide a continuous source of type IV collagen, which may be used to study the interaction of this collagen with other basement membrane components.

Amino Acids↗
PubMed1980

High-performance liquid chromatographic assay of codeine in acetaminophen with codeine dosage forms.

An accurate, rapid, and specific high-performance liquid chromatographic (HPLC) assay was developed for codeine in acetaminophen with codeine combination products. The internal standard (chlorpheniramine maleate), codeine, acetaminophen, and several other test compounds or impurities were well separated. A complete analysis took < 10 min. The relative standard deviations of the retention time, precision, and accuracy were 0.5, 0.4, and 0.5%, respectively. An excellent linear correlation was obtained between the HPLC and GLC methods.

Acetaminophen↗
PubMed1979

Isolation and characterization of hydroxyproline-containing proteins secreted by a murine carcinoma cell culture.

A collagenous protein was isolated from a murine carcinoma cell culture, which has been shown to synthesize basement membrane. The molecular weight of this protein was estimated to be 155 000. It eluted from carboxymethyl-cellulose in the region near the alpha 1 and beta 11 components of calf skin collagen. 63--69% of the peptide-bound prolines were hydroxylated, and the 4-/3-hydroxyproline ratios ranged from 12 : 1 to 14 : 1. About 95% of the hydroxylysines in the peptide were glycosylated, and almost all of them were in the glucosylgalactosyl dissacharide form. Judging from the posttranslational characteristics, this collagenous protein is probably of basement membrane type.

Animals↗
PubMed1977

Simple ureas derived from diisocyanates and their liquid chromatography on a 5-cm column.

Aliphatic and aromatic diisocyanates were converted to ureas by a chromophoric derivatizing reagent. The ureas were isolated in the pure form characterized by various methods including nuclear magnetic resonance and mass spectrometry. A chromatographic analytical separation of the urea test solutions was established. The method was used to demonstrate the derivatization of the isocyanates and direct determination of the produced ureas from the reaction mixture.

Chromatography, Liquid↗
PubMed1977

High-pressure liquid-chromatographic assay of nucleotide-pool concentrations during polysaccharide biosynthesis in four ascomycetes.

High-resolution liquid-chromatographic methods developed for analyzing nucleotide pools at the nanogram level in four representative species of ascomycetes (Penicillium citrinum, Aspergillus niger, Fusarium moniliforme, and Cladosporium herbarum) were used to study polysaccharide biosynthesis. Nucleotides extracted from the mycelial mat were preseparated from interfering polysaccharides, glycoproteins, and nucleic acids on a column of Biogel P-2. Resolution of 18 nucleotides from each fungal species was accomplished on AS-Pellionex-SAX, pellicular anion-exchanger by using a high-pressure liquid chromatograph. Nucleotides were identified by comparing peak retention-times, by differential u.v. absorption with two detectors in series at selected wavelengths, and by acid or enzymic hydrolysis with product identification by liquid chromatography. Pyrimidine bases exceeded purines by at least three fold, and uridine nucleotides often constituted 60-80 mole percent of the total nucleotides; extractable cytidine nucleotides were negligible. Uridine 5'-(2-acetamido-2-deoxy-alpha-D-glucopyranosyl disphosphate) is the preponderant nucleotide throughout the growth cycles of all four species, amounting to 30-60% of all nucleotides present. For all four fungal species, a burst of nucleotide formation was observed after the first 48h (15-30 mumol/g tissue), with fluctuations that eventually fell to 0.1 mumol/g on the tenth day.

Ascomycota↗
PubMedDate not supplied

Assay of residual organic solvents in topiramate drug substance by capillary gas chromatography.

The analysis of residual organic solvents (methanol, ethanol and toluene) in topiramate drug substance was investigated. Topiramate is a potent anticonvulsant drug under clinical evaluation. The drug is recrystallized from ethanol denatured by either methanol or toluene, and each residual solvent is controlled at 0.1% (w/w) level. A capillary gas chromatography (GC) method described in this manuscript utilizes a DB-WAX, 1 micron thick, 30 m x 0.53 mm i.d., column. Since topiramate is a thermally labile compound, the selection of the proper injector temperature is critical to the success of the analysis. The injector temperature was set at 120 degrees C to prevent degradation. The initial oven temperature was set at 55 degrees C for 8 min and programmed at a rate of 30 degrees C min-1 to a final temperature of 160 degrees C for 11 min. Helium was used as a carrier gas. The sample solvent selected was dimethylformamide pretreated with molecular sieves to remove trace amounts of alcohols that may interfere with the assay. The method was validated to be specific, linear, precise, sensitive, rugged and showed excellent recovery.

Anticonvulsants↗