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Biomedical subjects

J K Chan

Publications and source records attributed to J K Chan.

At least 361 records · Page 20Linked to original sources
PubMed1980

LSH hamster model of syphilitic infection.

The inbred LSH/Se LAK strain of hamster can be infected with Treponema pallidum Bosnia A, the causative agent of endemic syphilis. When infected, this strain consistently produced extensive chronic skin lesions that persisted for 6 to 9 months, even in the presence of peak antitreponemal antibody titers. The lymph nodes increased in weight and contained measurable numbers of treponemes. This infection also gave the hamster cross-immunity to T. pallidum Nichols and Treponema pertenue, the causative agents of venereal syphilis and frambesia, respectively. LSH hamsters are thus an excellent model to study the immune response mechanisms to syphilitic infection.

Animals↗
PubMed1979

Endemic syphilis: passive transfer of resistance with serum and cells in hamsters.

Serum or spleen cells from hamsters immune to infection with Treponema pallidum strain Bosnia A conferred partial protection against syphilitic infection by the same strain on recipient hamsters. Cutaneous lesions did not develop, and in the lymph nodes the average weight and number of treponemes detected were significantly lower than in normal and control hamsters. Treatment of the immune spleen cells with antithymocyte serum and complement abolished their ability to transfer resistance. This is the first direct evidence that thymus-derived cells are involved in resistance to syphilitic infection.

Animals↗
PubMed1979

Effects of Fildes enrichment on antibiotic susceptibility testing of Haemophilus influenzae in the Autobac.

The results of this investigation showed that the Autobac could be used to determine the susceptibility of Haemophilus influenzae to ampicillin, chloramphenicol, and tetracycline when eugonic broth was supplemented with 1.5% Fildes enrichment. An excellent correlation was obtained between the susceptibilities as determined by the agar dilution minimal inhibitory concentration method and the Autobac. For ampicillin all H. influenzae isolates with minimal inhibitory concentrations of </=1 mug/ml had light scattering indexes of >/=0.60. Those isolates with minimal inhibitory concentrations of >/=4 mug/ml had light scattering indexes of </=0.49. For chloramphenicol and tetracycline all isolates had minimal inhibitory concentrations of </=1 mug/ml and light scattering indexes of >/=0.71.

Ampicillin↗
PubMed1979

Inability of immune cells treated with anti-thymocyte serum to confer on hamsters resistance to cutaneous infection with Treponema pertenue.

The mechanism by which hamsters acquire resistance to yaws or frambesia is poorly understood. This investigation has shown that immune lymphoid cells (spleen and lymph node) could confer on hamsters resistance to infection with Treponema pertenue. Treatment of these immune cells with a specific antithymocyte serum (ATS) inhibited the transfer of resistance. Twenty-one days after infection, recipients of immune cells treated with ATS had cutaneous lesions, in contrast to recipients of immune cells treated with normal rabbit serum. Treatment of immune cells with ATS, however, did not completely abolish resistance to treponemal infection. The weight and number of treponemes in the lymph nodes of recipients were significantly lower than those infused with normal cells treated with ATS or normal rabbit serum. The specificity of the ATS was demonstrated by its failure to inhibit functional antibody-producing cells and its high cytotoxic activity for thymocytes. These results present direct evidence that ATS-sensitive cells are involved in resistance to frambesial infection.

Animals↗
PubMed1979

Ability of enriched immune T cells to confer resistance in hamsters to infection with Treponema pertenue.

This investigation presents the first direct evidence that T cells are involved in resistance to challenge with Treponema pertenue. Enriched T cells from immune hamsters were obtained by sequential filtration through glass and nylon-wool columns. This procedure removed the majority of functional antibody-producing and immunoglobulin-bearing cells. The fractionated cell suspensions were less responsive to stimulation by phytohemagglutinin, lipopolysaccharide, and dextran sulfate, but they were enriched with antithymocyte-sensitive cells and were more responsive to stimulation with concanavalin A. Hamsters receiving fractionated or unfractionated immune cells had no cutaneous lesions 21 days after infection and had significantly lower lymph node weights and fewer treponemes per node than hamsters that received fractionated or unfractionated normal cells. Resistance was transferred with immune cell suspension enriched in T cells despite an absence of anamnestic antibody response to specific treponemal antigens.

Animals↗
PubMed1979

Use of CB hamsters in the study of Treponema pertenue.

The CB/Ss LAK strain of inbred hamster was used as a model for studies of infection with Treponema pertenue and of acquired resistance to it. When infected, this strain developed cutaneous lesions which lasted for six to seven months, even in the presence of peak titres of antitreponemal antibody. The rate of appearance and resolution of these lesions varied with the size of the inoculum. The infected hamsters' inguinal lymph nodes increased significantly in weight and teemed with treponemes for several weeks. Animals infected for eight or 10 weeks obtained quick resolution of their lesions by treatment with penicillin and were thereafter resistant to reinfection.

Animals↗
PubMed1975

A novel diazonium-sulfhydryl reaction in the inactivation of yeast alcohol dehydrogenase by diazotized 3-aminopyridine adenine dinucleotide.

Diazotized 3-aminopyridine adenine dinucleotide has been found to modify four sulfhydryl groups per molecule of enzyme during the complete inactivation of yeast alcohol dehydrogenase. The reaction of sulfhydryl groups was indicated by titration studies with 5,5-dithiobis(2-nitrobenzoic acid) as well as isolation and quantitation of the cysteinyl derivative released by acid hydrolysis of the modified enzyme. The cysteinyl derivative was identified as S-(3-pyridyl)cysteine. Authentic S-(3-pyridyl)cystein was synthesized and structurally characterized for these studies. Diazonium-sulfhydryl reactions were demonstrated for a number of diazonium derivatives with cysteine, homocysteine, glutathione, and mercaptoethanol at 0-4 degrees and neutral pH. Second order rate constants were determined in reactions of these sulfhydryl compounds with diazotized 1-methyl-3-aminopyridinium chloride, diazotized 3-aminopyridine adenine dinucleotide, and diazotized 3-aminopyridine adenine dinucleotide phosphate.

Alcohol Oxidoreductases↗
PubMedDate not supplied

Large cell lymphoma with initial presentation in the bone marrow.

This report describes 14 cases of large cell lymphoma with initial presentation as marrow involvement in the absence of peripheral lymphadenopathy. The disease affected mainly the middle-aged and elderly, with male predominance. Most patients presented with swinging fever and peripheral blood cytopenia. Reactive hemophagocytic syndrome was a common finding, causing significant morbidity and mortality. Peripheral lymphadenopathy was absent (by case selection), but involvement of the liver, spleen and paraaortic lymph nodes could be demonstrated in some cases. However, in some patients, the involvement was apparently restricted to the bone marrow. Involvement of the bone marrow was often subtle, and could be missed on causal examination. Immunohistochemical studies on eight cases showed that four exhibited a B-cell phenotype, three a T-cell phenotype and one a non-T non-B phenotype. The prognosis was poor, with survival being measured in days to weeks in most patients.

Adolescent↗
PubMedDate not supplied

Solid tumour with initial presentation in the bone marrow--a clinicopathologic study of 25 adult cases.

This study reviews the clinicopathologic features of 25 adult patients without a known history of malignancy presenting with metastatic carcinoma in the bone marrow. The disease mainly affected middle-aged to elderly males (mean age, 61.6 years). Bone pain, generalized or confined to the back, was a common presenting complaint. Organomegaly was often absent. Laboratory abnormalities included anaemia, leukocytosis, thrombocytopenia and a leukoerythroblastic blood picture. Serum alkaline phosphatase level was raised in the majority of cases. In about one-third of the cases, malignancy was not suspected clinically, and bone marrow aspiration was carried out because of incidental finding of abnormal blood counts. The marrow aspirate findings were characterized by numerous to sparse cohesive tumour clusters with nuclear moulding. Over two-thirds of the patients had metastatic adenocarcinoma, and the lung was found to be the commonest site of primary disease. We conclude that since the marrow infiltration can be subtle, marrow smears should be carefully scrutinized for tumour cells in patients with leukoerythroblastic blood picture, in particular those with an elevated serum alkaline phosphatase level.

Adult↗
PubMedDate not supplied

Reactive hemophagocytic syndrome in childhood--frequent occurrence of atypical mononuclear cells.

Reactive hemophagocytic syndrome, which is characterized by systemic proliferation of benign hemophagocytic histiocytes, usually presents as an acute febrile illness with pancytopenia and hepatosplenomegaly. The commoner diseases associated with the syndrome are infection and malignant lymphoma. In this report, eight cases of reactive hemophagocytic syndrome occurring in infants and young children are described. Unlike the disease occurring in adults, there is frequent occurrence of atypical mononuclear cells both in the peripheral blood and bone marrow. The morphological spectrum of these atypical cells is however still within that seen in infectious mononucleosis, and their reactive nature is substantiated by their spontaneous disappearance and subsequent recovery of the patients. It is important to distinguish this reactive proliferation from the neoplastic cells of 'malignant histiocytosis' or malignant lymphoma, since cytotoxic drugs are not warranted for treatment of this non-neoplastic condition.

Adolescent↗
PubMedDate not supplied

c-kit immunocytochemical staining in the cytologic diagnosis of metastatic gastrointestinal stromal tumor. A report of two cases.

BACKGROUND: Gastrointestinal stromal tumor (GIST) is a distinct group of mesenchymal neoplasms recently shown to exhibit differentiation toward interstitial cells of Cajal (ICC). C-kit (CD117), an immunocytochemical marker consistently expressed in normal ICC, is demonstrable in 81-100% of GISTs. We report two cases wherein immunocytochemical staining for c-kit aided in the diagnosis of metastatic GIST in the liver. CASES: Two patients, a 37-year-old female (case 1) and a 76-year-old male (case 2), presented with multiple nodules in the liver. They had a history of small bowel GIST resected 11 and 1 year earlier, respectively. Fine needle aspiration of the liver nodules showed loose aggregates or fascicles of spindle cells with elongated to oval nuclei, rare paranuclear vacuoles and eosinophilic cytoplasm. The spindle cells showed minimal (case 1) to moderate nuclear pleomorphism (case 2), with occasional mitotic figures seen in case 2. Immunocytochemical staining revealed strong and diffuse staining for c-kit; it was negative for actin, desmin, CD34 and S-100 protein. Thus, a diagnosis of metastatic GIST was rendered. Histologic review of the primary small bowel GISTs of both cases and the subsequently resected liver nodules in case 1 confirmed the diagnosis. CONCLUSION: Metastatic GIST may pose diagnostic problems due to its broad morphologic spectrum and variable cytologic atypia; in particular, distinction from leiomyosarcoma and other mesenchymal tumors is difficult. The diagnostic difficulty is compounded when the prior history of gastrointestinal tumor is not available or forgotten and when GIST is the initial presentation of the tumor. C-kit is a highly sensitive and reliable immunocytochemical marker that can aid in the diagnosis.

Adult↗
PubMedDate not supplied

Kikuchi's histiocytic necrotizing lymphadenitis. Diagnosis by fine needle aspiration.

Two cases of Kikuchi's histiocytic necrotizing lymphadenitis diagnosed by fine needle aspiration (FNA) of enlarged lymph nodes are reported. The FNA smears contained randomly activated lymphoid cells, necrotic debris, karyorrhectic cells and prominent histiocytes, suggesting the presence of reactive lymph nodes. The true nature of the lesions was evident from the examination of cell block sections prepared from tissue fragments in the aspirates, which preserved the architectural relationships of the different cell types. The same patterns were found in retrospectively and subsequently examined excised lymph nodes from these cases. The differential diagnosis of this entity, which may simulate a malignant lymphoma because of the presence of large numbers of activated lymphoid cells, is discussed and the value of preparing FNA cell blocks is emphasized. Though this rare benign disease may be suspected clinically in the more typical cases, such as young women with cervical lymphadenopathy, fever, neutropenia and otherwise excellent condition, the diagnosis cannot be made without a lymph node biopsy, which FNA may be able to provide in some instances.

Adult↗
PubMedDate not supplied

Columnar cell carcinoma of the thyroid. Fine needle aspiration findings in a case.

Columnar cell carcinoma is a recently described rare tumor of the thyroid. The fine needle aspiration cytologic findings of one example are reported. In the smears, the tumor fragments showed papillary and glandular patterns. The tumor cells were columnar and exhibited pseudostratification of the nuclei. The nuclei were oval to elongated and possessed stippled chromatin and inconspicuous nucleoli; occasional ones exhibited longitudinal grooving. It is important to distinguish this tumor from papillary carcinoma of thyroid because of its much more aggressive behavior, from metastatic adenocarcinoma for obvious treatment considerations, and from medullary carcinoma.

Adult↗
PubMedDate not supplied

Penicillium marneffei in bronchoalveolar lavage fluid.

Penicillium marneffei is a rare human pathogen that may infect either healthy or immunocompromised hosts. In methenamine silver-stained preparations of bronchoalveolar lavage fluid from a patient with dermatomyositis on steroid treatment, round-to-oval intracellular and extracellular microorganisms were found. The finding of occasional septate and elongated forms established the microorganism as probably P marneffei, which was confirmed on culture. Distinguishing this rare fungus from Pneumocystis carinii is important because these two diseases require different forms of treatment.

Bronchoalveolar Lavage Fluid↗
PubMedDate not supplied

Signet-ring cell melanoma mimicking adenocarcinoma. A case report.

The fine needle aspiration findings in a lymph node involved by signet-ring cell melanoma, a very rare variant of malignant melanoma, are reported. The patient had a history of superficial spreading melanoma of the right foot, treated 10 years earlier by below-the-knee amputation. He presented with a right groin mass. Fine needle aspiration of the mass yielded poorly cohesive, large cells with eccentric nuclei and abundant, eosinophilic cytoplasm; many of them exhibited a signet-ring appearance. Melanin pigments were identified in a small proportion of tumor cells, and a diagnosis of metastatic melanoma was made. The subsequent lymph node excision revealed a metastatic tumor composed of polygonal and signet-ring cells that were positive for S-100 protein and HMB-45 but not cytokeratin. Nearly all reported cases of signet-ring cell melanoma occurred as metastatic or recurrent disease. It is important not to mistake signet-ring cell melanoma for adenocarcinoma in aspiration cytology, and a constellation of clinical features and of histochemical and immunohistochemical findings enables a correct diagnosis to be reached.

Adenocarcinoma↗
PubMedDate not supplied

Liver transplantation--perspective from Hong Kong.

BACKGROUND/AIMS: We report our experience of 27 orthotopic liver transplantations in 26 patients performed at Queen Mary Hospital, Hong Kong during the period of October 1991 to October 1995. PATIENTS AND METHODS: There were 19 adults and 7 pediatric patients with a mean age of 29 years (range 8 months to 62 years). The underlying liver diseases of the 26 patients were biliary atresia (n = 6), Alagille syndrome (n = 1), primary biliary cirrhosis (n = 2) cryptogenic cirrhosis (n = 2), alcoholic cirrhosis (n = 5), Wilson's disease (n = 1), fulminant hepatic failure (n = 3), polycystic liver (n = 2), secondary biliary cirrhosis (n = 1), HBV cirrhosis (n = 2) and autoimmune hepatitis with hepatocellular carcinoma (n = 1). The pathology leading to re-transplantation in a pediatric patient was post-transplant hepatitis of unknown etiology. The liver grafts were obtained from 19 brainstem dead and 8 living donors. The pediatric patient requiring re-transplantation received a left lateral segment graft from her mother. Two adults received left lobe grafts from their family members. RESULTS: The overall graft survival is 88% and patient survival is 92%. There were only 2 deaths: one patient developed primary graft nonfunction and died from intracerebral bleeding 39 days after transplantation and the other died from graft rejection resistant to salvage by steroid pulse and OKT3. The other patients are well with functioning grafts. CONCLUSIONS: We hope that the current success rate can convince people in our locality in cadaveric organ donation so that living donors do not run the risk of dying from the operation, although the risk is estimated to be very small.

Adult↗