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Biomedical subjects

P Chan

Publications and source records attributed to P Chan.

At least 253 records · Page 14Linked to original sources
PubMed1976

3H-deoxythymidine incorporation in graft-versus-host disease in the Norway rat. I. Liquid scintillation studies.

Graft-versus-host-disease was produced in newborn Brown Norway (BN) rats with an intravenous (iv) injection of adult allogeneic Lewis (L) lymph node cells (experimental) and the response was compared to littermates injected with adult syngeneic BN cells (control). By 4 days the reaction in the spleen of experimental animals was such that the spleen index was 1.70 and 2.58 on day 7, and continued to increase until death. A one hour iv pulse of tritiated deoxythymidine (3HdT) administered to experimental and control animals revealed a whole organ peak incorporation of 3HdT on day 6 in experimental spleens. A second larger peak occurred on day 10 in the experimental spleen as compared to a single peak at days 6 or 7, respectively, in the experimental mesenteric and combined superficial lymph nodes. However, analysis of the incorporation of 3HdT with respect to organ weight revealed a peak incorporation in animals receiving L cells on day 4--6 with a second smaller peak on day 10 in the experimental spleen and again a single peak on day 5 or 6 in the lymph nodes. Total 3HdT incorporation within both experimental lymph node compartments became less than controls by day 15 even though experimental nodes had a larger mass. 3HdT incorporation per milligram tissue weight decreased in all tissue compartments of experimental animals by day 13--14. The contribution of donor and host cell proliferation to the various peaks observed is discussed.

Animals↗
PubMed1976

3H-deoxythymidine incorporation in graft-versus-host disease in the Norway rat. II. Autoradiographic studies.

A sequential analysis was made of various areas within the lymph nodes and spleen of newborn Brown Norway (BN) rats suffering from graft-versus-host disease (GVHD) subsequent to an allogeneic injection of adult Lewis (L) lymph node cells (experimental). One micron thick autoradiographs were compared between such experimental and control littermates having received the same number of syngeneic adult BN cells. Both experimental and control animals received tritiated deoxythymidine (3HdT) one hour before killing. The autoradiographs revealed a 2.25 and 2.50 times higher thymidine labeling index of lymphocytes in the deep cortex of mesenteric lymph nodes and white pulp of the spleen, respectively, for experimental animals. The experimental effect occurred within one day. The majority of the labeled cells in experimental animals were large lymphoblasts with prominent nucleoli. The labeling index within these areas remained significantly higher than control values until day 8 in the spleen and through day 14 within the lymph nodes. However, differences in labeled cells present in high powered microscopic fields reached a peak on day 3 within compartments in experimental animals but fell significantly below control values by day 9 owing to a pronounced disappearance of both small and large lymphocytes from these areas, and a decreased intensity of individual cell labeling as the reaction progressed. In contradistinction the concentration of labeled cells present in high powered microscopic fields of lymph nodes' medulla became 3.13 times controls by day 4. Most of these labeled cells contained a more basophilic cytoplasm than those found in the deep cortex and some were distinctly plasma cell precursors. In contrast to the deep cortex their concentration remained approximately three times control values until death. The data indicates that the major proliferative events within the spleen and lymph nodes in neonatal rat GVHD are initially restricted to donor cell localization areas of these tissue compartments. Subsequently the GVHD-related events may be attributed to other areas and possibly cell types. Thus any proliferation contributing to splenomegaly in the latter stages of GVHD appears to occur in the red pulp and that contributing to lymph node enlargement a medullary response.

Animals↗
PubMed1975

Small bowel extracts in the inhibition of tumour growth.

Results presented in this paper confirm earlier experiments which showed that microsomal extract of small bowel, preincubated with tumour cells, resulted in complete inhibition of tumour growth. However, experiments in vitro have shown that this effect is due to direct cytotoxicity of the extract and that (a) it is not specific for the small bowel; (b) it is not specific for tumour cells; and (c) the activity is predominantly in the mitochondrial fraction.

Animals↗
PubMed1971

Increased prothrombin time and metabolic changes with high serum aluminum levels following long-term exposure to Bayer-process alumina.

Serum aluminum levels twice to three times those in controls were found in 30 of 36 workers in a factory in an atmosphere of alumina dust. Inorganic phosphate and total alkaline phosphatase levels were within normal range, with no clinical evidence of phosphate depletion syndrome. Serum intestinal alkaline phosphatase, acid phosphatase and adenosine triphosphate levels were significantly reduced in the group with high levels of aluminum. The finding that the mean prothrombin time was significantly prolonged is of particular interest with respect to beneficial antithrombogenic effect.

Adenosine Triphosphate↗
PubMedDate not supplied

The management of carcinoma of the nasal vestibule.

Forty-two patients with squamous cell carcinoma of the nasal vestibule were reviewed. The patients were treated at either the Southern California Permanente Medical Group or the UCLA Medical Center. Thirty-eight patients (90%) had early lesions and 4 (10%) had late disease (involving the nodes or bone). The following conclusions were formed from this study: (1) Patients without bone destruction or lymph node metastases will do well with either irradiation or surgery. Those with bone destruction or lymph node metastases will do poorly in spite of radical treatment. (2) Early lesions can often be cured with either partial rhinectomy or irradiation. (3) A surgical recurrence following partial rhinectomy can be salvaged with irradiation. (4) A radiation recurrence of an early lesion can be salvaged with surgery. (5) The routine use of total rhinectomy for early carcinoma or radiation failure is unwarranted. (6) Other primary cancers are not uncommon when followup is extended to the 5- to 10-year interval.

Adult↗
PubMedDate not supplied

Subchronic toxicity of a medium-chain chlorinated paraffin in the rat.

Groups of ten male and female weanling Sprague-Dawley rats were fed diet containing 0, 5, 50, 500 or 5000 ppm of a medium-chain chlorinated paraffin (C14-17, 52% chlorination) for a period of 13 weeks. Increased relative liver weight was observed at 500 and 5000 ppm in females and at 5000 ppm in males. Relative kidney weight was increased at 5000 ppm in both sexes. Serum cholesterol was increased in the females in a dose-related manner starting at 50 ppm. At 5000 ppm, animals of both sexes had elevated hepatic UDP-glucuronosyltransferase activity while only females showed increased aminopyrine N-demethylase activity. Increased urinary N-acetylglucosaminidase activity occurred at 5000 ppm in females. Increased urinary ascorbic acid excretion monitored at week 12 and a decreased hepatic vitamin A level were detected in females receiving the 500 ppm diet and male and female rats at 5000 ppm. Mild, adaptive histopathological changes were detected in the liver of rats of both sexes at 500 and 5000 ppm, and in the thyroid of males and females starting at 500 and 50 ppm respectively. Minimal changes were observed in the kidney proximal tubules of male rats fed the 5000 ppm diet and in the inner medulla tubules of female rats fed the 500 and 5000 ppm diets. These data indicate that the medium-chain chlorinated paraffin produces biochemical and histological changes at dietary levels of greater than or = 50 ppm in females and greater than or = 500 ppm in males.

Animals↗
PubMedDate not supplied

Training for minimally invasive surgery. Need for surgical skills.

Controversy exists regarding the training of surgeons for the performance of minimally invasive surgical procedures. The use of live animals is essential, especially in teaching dissection techniques. Seventeen percent of animals experienced excessive operative hemorrhage, which contributed to premature mortality during training exercises, demonstrating the need for live animals in this component of the training. A number of abdominal procedures can be performed with minimally invasive techniques without suturing by utilizing a rapidly expanding array of devices. However, other procedures cannot be successfully accomplished without suturing skills. Laparoscopic suturing skills are particularly demanding; thus specific training and practice prior to hands-on exercises in animal models is recommended. Emphasis on acquisition of advanced laparoscopic surgical skills is a necessity.

Animals↗
PubMedDate not supplied

Diagnostic imaging of Salmonella-related mycotic aneurysm of aorta by CT.

The purpose of this study was to review the computed tomography (CT) appearance of mycotic aneurysm of the aorta caused by Salmonella infection. Eight patients were suggested to have mycotic aneurysm of the aorta by clinical presentation of fever, abdominal or back pain, leukocytosis, and pulsatile abdominal mass in addition to positive blood or tissue culture of salmonella. All underwent plain radiography, abdominal sonography, and CT for confirmation. Five patients died during hospitalization despite medical or surgical treatment. CT features of mycotic aneurysm of aorta included (a) hazy aortic wall with rupture; (b) gas-forming inflammation around the aneurysm; (c) retroperitoneal paraaortic fluid collection and vertebral erosion; and (d) thrombus formation within a false lumen after aneurysmal rupture. Because of its availability and noninvasiveness, CT is the major diagnostic modality to use for Salmonella-related mycotic aneurysm.

Aged↗
PubMedDate not supplied

Increased risk of wasting syndrome in HIV-infected travellers: prospective multicentre study.

HIV-infected patients from moderate regions who travel in tropical countries may experience clinical disease progression due to exposure to bacteria (including mycobacteria), fungi and parasites. In the Swiss HIV Cohort Study we examined the hypothesis that travelling increases the risk of tuberculosis, wasting syndrome, cryptosporidiosis, isosporiasis, cryptococcosis, coccidiomycosis, histoplasmosis and Salmonella septicaemia. A total of 4549 participants were included (in 1988-98) of whom 596 (13.1%) travelled at least once. During 16,800 person-years of follow-up 231 patients developed at least 1 of the diseases of interest. Wasting syndrome was the only diagnosis significantly associated with travelling (hazard ratio 2.16, 95% confidence interval 1.09 to 4.30). The risk of wasting syndrome ('slim disease') should be taken into account when counselling HIV-infected patients intending to travel in tropical regions.

AIDS-Related Opportunistic Infections↗
PubMedDate not supplied

Nigrostriatal monoamine oxidase A and B in aging squirrel monkeys and C57BL/6 mice.

In this study we assessed the two forms of monoamine oxidase (MAO) in the caudate, putamen, and substantia nigra of young (4-year-old), intermediate-aged (11-year-old), and aged (20-year-old) squirrel monkeys and in the striata of young (2-month-old) and older (10-month-old) C57Bl/6 mice. MAO A and B activities were determined by measuring the rate of oxidation of the specific substrates phenethylamine and serotonin. In squirrel monkey, the vast majority of MAO activity was MAO B with activity of this isoform 10 times greater than of MAO A, while in mice the activity of the two forms was approximately equivalent. Although mice demonstrated nearly twofold selective increases in striatal MAO B between 2 and 10 months of age, neither MAO B nor A showed statistically significant changes with age in squirrel monkeys. These results document the marked differences between nonhuman primates and rodents with respect to the relative activities and the effects of age on MAO A and B, and indicate that increased MAO is not an inevitable feature of aging.

1-Methyl-4-phenyl-1,2,3,6-tetrahydropyridine↗
PubMedDate not supplied

Controlled ovarian stimulation and ultrasound guided follicular aspiration in the baboon (Papio cynocephalus anubis).

The objective of this study was to investigate whether baboon females respond to an ovarian stimulation protocol incorporating pituitary suppression with a GnRH agonist (GnRHa) and highly purified human FSH (hphFSH) with follicular development and oocyte maturation. An ovulation induction protocol was applied to 5 adult female baboons with a history of regular menstrual cycles (33-34 days). A long-acting GnRHa implant containing goserelin acetate was placed s.c. on days 22-24 of their menstrual cycle. Daily hphFSH (75 IU im) treatments were started approximately 10 days following menses. When the majority of the follicles were > or = 5 mm in diameter and the E2 levels had reached a maximum, hCG (2000 IU i.m.) was administered to induce final maturation of the oocytes and ovulation. 30 to 34 h after hCG administration, transabdominal follicular aspiration was performed using a variable frequency transvaginal transducer with ultrasound. A total of 71 oocytes were collected (average: 17). 91% of the oocytes were morphologically normal indicating that they were appropriate for in vitro insemination.

Animals↗