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Biomedical subjects

T M Chang

Publications and source records attributed to T M Chang.

391 records · Page 22Linked to original sources
PubMedDate not supplied

Liver, spleen and tumor volume measured by personal computer.

BACKGROUND/AIMS: Computed tomography (CT) scans are common examinations for patients with chronic liver diseases. To quantitate the organ or tumor volume from the scans and to accomplish the task in an efficient way with the most economic equipment, we developed a system based on a personal computer. METHODOLOGY: We used color-markers and transparency to sketch the edges of liver, hepatoma, and spleen. Each organ or tumor of interest is marked out by fine-point markers on pieces of transparency. The sketch was scanned into a digitized image format on a personal computer (Pentium 133). The calculation involves edge detection, three-dimensional reconstruction, and voxel counting. By using summation-of-the-area and trapezoid approximation technique, the voxels of each structure are counted. In this study, we illustrate the potential application in the management of a hepatic cancer patient. RESULTS: After digitalization, the data size of CT images is about 1 to 1.5 megabytes. It takes less than 5 min to complete volume calculation. CONCLUSIONS: By this method, tumor load before and after chemotherapy can be estimated easily and accurately. This would be helpful in clinical practice.

Carcinoma, Hepatocellular↗
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Acute colonic intramural hematoma due to blunt abdominal trauma.

Trauma to the colon is uncommon and accounts for only 3-5% of all blunt abdominal injuries. Among them, intramural hematoma of the colon is a rare complication and the acute form is rarer than the chronic form. We report a 37-year-old man who presented with abdominal pain followed by intestinal obstruction due to a blunt trauma. The initial diagnosis was done by sonography and proved by computed tomography (CT). Abdominal sonography also detected an increment in the size of the hematoma with progressive abdominal cramping pain that prompted urgent laparotomy. Ileocolic segmental resection with end-to-end ileocolostomy was performed and the patient recovered uneventfully. Based on our experience with a patient suffering from an intramural colonic hematoma following blunt abdominal trauma (BAT) and based on a review of the literature, we discuss the different clinical manifestations, difficulties of diagnosis, and different treatment modalities of this disease entity. We conclude that acute colonic hematoma can be diagnosed by sonography and/or CT in contrast to the early reported cases, in the pre-CT era, when they could only be diagnosed at laparotomy. Endoscopy may also be helpful for diagnosis in some cases. Although expectant therapy may be successful in some cases, the majority of the cases may need operation.

Abdominal Injuries↗
PubMedDate not supplied

Rationale for the use of the acac microcapsule artificial kidney for the treatment of patients with chronic renal failure.

The A C A C microcapsule artificial kidney is prepared to have 300 gr. of albumin-coated cellulose nitrate microincapsulated activated charcoal with a total area surface of 2,5 m2. The membrane thickness is 0,05 micron, at least 100 times thinner than the standard hemodialysis membrane. By Albumin microencapsulation it is possible to prevent charcoal embolism, hemolysis, platelet and fibrin consumtion. The resistance to blood flow is smaller than in the kill artificial kidney. We have carried out a clinical trial in uremic patients, in 3 of them up to 8 months; their general feeling of well-being after two hours of AC A C microcapsule hemoperfusion is better than after 6 hours hemodialysis, in case of water and electrolyte retention one run of 6 hours hemodialysis a week was required, Reticolocyte, platelet count and hemoglobulin level improved appreciably. Clearance of middle molecules is much higher than in standard hemodialysis and preliminary reports show a lower middle molecules peak after hemoperfusion. It would appear that the present microcapsule artificial kidney, if supplemented with further development for the removal of water and electrolyte, may eventually become a compact inexpensive, simple way of treating uremic patients.

Blood Cell Count↗
PubMedDate not supplied

Hybrid artificial cells: microencapsulation of living cells.

In 1965, the use of artificial cells for the microencapsulation of living cells was demonstrated. At that time, this technique was also proposed for use in immunoisolation of endocrine cells, islets, and hepatocytes as hybrid artificial organs. Progress in the biotechnology of cell culture in the last 10 years has allowed this approach to be extensively investigated by an increasing number of centers. The author's recent studies concentrated on microencapsulation of hepatocytes as a model system. Such cells were implanted to increase the survival of galactosamine induced fulminant hepatic failure rats, or to decrease the high bilirubin levels in Gunn rats and xenografts of microencapsulated rat hepatocytes into mice provided immunoisolation. Furthermore, hepatocyte secreted hepatic stimulating factors (mw 110,000 D) accumulating in the microcapsules helps to increase the viability of the hepatocytes. In addition to these studies, a novel, two step cell encapsulation method was developed to improve immunoisolation and biocompatibility. Microencapsulation of microorganisms was also carried out using a model microorganism to convert serum cholesterol to carbon dioxide.

Animals↗
PubMedDate not supplied

The potential of a microencapsulated urease-zeolite oral sorbent for the removal of urea in uremia.

Although successful in reducing urea levels, the use of oral microcapsules containing a urease-silica adduct and a zirconium phosphate ion exchanger result in a number of problems, including a negative calcium balance. In this study, it is demonstrated that the use of microcapsules containing a urease-zeolite preparation may be a potential route to urea removal. The use of zeolite ion exchangers, and zeolite W in particular, can alleviate the problems encountered with zirconium phosphate. Unlike zirconium phosphate, zeolite W is nonselective toward calcium ions and is stable at the high pH found in the intestinal tract. Zeolite W, when present in the sodium form, has a high ammonium capacity of 3.6 mEq NH4+/g zeolite under simulated intestinal conditions; its reactivity to ammonium is also higher. The application of enzyme envelopes to zeolite particles is a novel immobilization procedure that does not involve the use of colloidal silica and can reduce the amount of ingested material by as much as 25%. The current in vitro study shows that cellulose acetate butyrate microcapsules, containing a urease-zeolite preparation, remove up to 80% of urea in less than 1 hour. These microcapsules can be dried and retain activity when sealed in a jar at 4 degrees C.

Aluminum Silicates↗
PubMedDate not supplied

Physical properties of starch meals in vivo and in vitro and their influence on gastric emptying and oral glucose tolerance test.

In study A, consisting of four groups of six subjects each, we measured the differences in pH, viscosity, and osmolality of in vivo and in vitro samples of steamed rice, congee, and 16.6 and 5% glucose solutions in 300-ml volumes. The physical properties of starch meals in vivo are different from in vitro samples, which may account for discrepancies among previous studies of glucose tolerance and gastric emptying. In study B, test meals of 300 ml of steamed rice, congee, 16.6% glucose, 5% glucose or a combined congee-metoclopramide meal (in which 10 mg metoclopramide i.v. was given 15 min before the congee was eaten) were given to seven subjects. Blood samples were taken, and the serum glucose and insulin responses were determined. The meals were labeled with 99mTc pentetic acid microcapsules, and the gastric emptying rates were calculated. Metoclopramide increased the gastric emptying of congee to that approaching steamed rice. The incremental glucose response to steamed rice was greater than that to congee, but the incremental insulin response was greatest with congee plus metoclopramide. The physical form of the food influences the blood glucose and insulin response and the rate of gastric emptying. The gastric emptying rate may be the major mechanism for the increased insulin response.

Adult↗
PubMedDate not supplied

Brain edema and the blood brain barrier in galactosamine-induced fulminant hepatic failure rats. An animal model for evaluation of liver support systems.

Rats with galactosamine-induced fulminant hepatic failure (FHF) have been a popular animal model for the evaluation of liver support systems. Because development of brain edema is a major and frequent complication during FHF, it was studied for this report. The degree of hepatocyte necrosis closely paralleled the severity of coma. Abnormalities in the orientation of hepatocellular organelles were evident as early as grade I hepatic coma, 24 hr after galactosamine-induced liver damage. Galactosamine caused a characteristic pattern of hepatocyte necrosis such that the endoplasmic reticulum completely surrounded the nucleus to cause karyolysis and subsequent cell death. Quantitative measurements of brain water content revealed evidence of brain edema with increasing severity of coma. Brain edema resulted in a greater than 4% swelling of the brain during this period. Light microscopy showed increasing cerebral and cerebellar edema during progressive stages of FHF. Electron microscopy studies revealed evidence of progressive cerebral edema, particularly in the perivascular region of cerebral capillaries. Marked swelling of perivascular astrocytes was evident as early as 24 hr after galactosamine-induced FHF when the animals were in Grade I hepatic coma. Abnormal swelling and distortion of astroglia, including its subcellular organelles, and the presence of cytoplasmic vacuoles, was clearly evident during the deeper stages of hepatic coma (Grades II-IV). Trypan blue dye infusion studies revealed evidence of extensive blood-brain barrier (BBB) breakdown beginning in Grade III coma.

Animals↗
PubMedDate not supplied

Conversion of ammonia or urea into L-leucine, L-valine, and L-isoleucine using artificial cells containing an immobilized multienzyme system and dextran-NAD+. Glucose dehydrogenase for co-factor recycling.

Artificial cells containing glucose dehydrogenase (EC 1.1.1.47), leucine dehydrogenase (EC 1.4.1.9), urease (EC 3.5.1.5), and dextran-NAD+ were prepared. Ammonia or urea could be converted into L-leucine, L-valine, and L-isoleucine with artificial cells. Low-specific-activity glucose dehydrogenase could effectively regenerate dextran-NADH, which was recycled at a rate of 0.4 to 0.5 cycle per minute under reaction conditions. The effects of ammonium salts and urea on the conversion rate for the leucine dehydrogenase multienzyme system were also studied. The relative activities in ammonium salts solutions were 40 to 70% of those in urea solutions.

Amino Acid Oxidoreductases↗
PubMedDate not supplied

Coated charcoal haemoperfusion.

We have made use of the principle of artificial cells to microencapsulate charcoal by coating an ultrathin membrane directly on to the surface of individual activated charcoal granules. This way the enclosing membrane prevents any free powder from going into the circulation. At the same time, blood platelets are prevented from being removed by the activated charcoal. Since 1970, we have been carrying out clinical trials in patients for acute drug poisoning, chronic renal failure, liver failure and other conditions. Our earlier results have stimulated a number of other polymer coated charcoal systems to be studied and produced in a number of other centres. At present there are at least ten coated charcoal haemoperfusion devices being used. They vary somewhat in membrane thickness, membrane permeability, blood compatibility and efficiency. It is therefore important not to make generalizations based on the results obtained for the less effective and less blood compatible systems. Collodion (cellulose nitrate) membrane coated charcoal is sufficiently blood compatible for use in uraemia and acute intoxication. In conditions with very sensitive platelets (e.g., hepatic failure) we showed earlier that by adsorbing albumin on to collodion, a highly blood compatible system can be obtained. This approach has been extended in three ways: instead of albumin, protein A can be incorporated into the collodion coating, resulting in an immunosorbent system for clinical trial in cancer therapy; albumin can be used to coat synthetic immunoadsorbent for blood group antibody to allow clinical application; albumin can also be used to coat resins to make them blood compatible.(ABSTRACT TRUNCATED AT 250 WORDS)

Aluminum↗
PubMedDate not supplied

In vitro and clinical studies of the removal of cortisol, thyroxine, insulin, and thyroid-stimulating hormone by coated charcoal haemoperfusion.

This study was carried out to assess the removal of free and protein-bound hormones by ACAC (albumin-collodion coated activated charcoal) and uncoated activated charcoal. Adsorptions of cortisol, thyroxine, insulin and thyroid-stimulating hormone from aqueous solution or plasma were studied in vitro. The effects of ACAC haemoperfusion on the systemic levels of these hormones were also studied in patients. Studies in vitro show that both types of charcoal efficiently remove hormones from protein-free solution. Removal of hormones from plasma depends on the proportions of free and protein-bound hormones in the plasma. Clinical results show only a low clearance for hormones which are strongly protein bound. The results suggested that the removal of hormones by activated charcoal is largely dependent on (1) the affinity of charcoal for the particular hormone, (2) molecular size of the hormone and (3) the degree of protein binding of the hormone. The results also show that ultrathin membrane coating does not alter the adsorption of the activated charcoal compared with uncoated charcoal.

Adsorption↗