PubMed Health⌕ Search

Biomedical subjects

P Han

Publications and source records attributed to P Han.

At least 19 recordsLinked to original sources
PubMed1992

Evidence for heat-stable liver cytosol substance(s) capable of causing oxidative activation of fructose 1,6-bisphosphatase.

The endogenous fructose 1,6-bisphosphatase (FBPase) in chicken liver extract undergoes a drastic increase in activity if the pH of the extract is in the alkaline range. Greater and more consistent activation occurs when purified FBPase, placed inside dialysis sack, is incubated in liver extract. Maximal activation (over 16-fold) is accompanied by the disappearance of 4 highly reactive sulfhydryl groups (SH) per molecule of enzyme. The activating effect of the extract remains essentially unchanged after heating to 100 degrees C. Activation can be reversed by dithiothreitol. These data show the existence in liver cytosol of heat-stable substance(s) capable of activating FBPase presumably by forming disulfide bonds with the enzyme's highly reactive SH groups.

Animals↗
PubMed1992

Serum ferritin measurement and the degree of agreement using four techniques.

Four commercial assay kits to measure serum ferritin were compared to establish the degree of agreement and interchangeability between the different techniques based on the intraclass correlation coefficient (ri). Radioimmunoassay, microparticle enzyme immunoassay, enzyme-linked immunosorbent assay, and chemiluminescent immunoassay systems were used. The Pearson product-moment correlation factor (r) between any two methods was at least 0.98, and the intercept of the regression equations ranged from -0.613 to 3.797, indicating that the methods were comparable. Furthermore, the intraclass correlation coefficient (ri) was at least 0.98, suggesting that the methods were interchangeable.

Analysis of Variance↗
PubMed1992

Mechanism of action of the papillomavirus E2 repressor: repression in the absence of DNA binding.

Repression of papillomavirus E2-dependent gene expression was studied by using transient transfections into mouse embryo fibroblast cells. Cotransfection of a gene corresponding to the naturally occurring repressor E2-TR along with the full-length E2 gene resulted in up to 98% repression of E2-dependent reporter gene expression. A series of E2 DNA-binding domain mutants were transferred into the E2-TR form and characterized for their ability to repress E2-dependent transactivation. All mutants which were defective for DNA binding but were dimerization competent repressed E2 transactivation as well or nearly as well as the wild-type repressor. E2 mutants which lacked dimerization activity repressed transactivation poorly or not at all. These results indicate that the E2 repressor can inhibit transcription, in the absence of DNA binding, by forming heterodimers with full-length E2.

Amino Acid Sequence↗
PubMed1992

Tissue expansion as an alternative to skin grafting for closure of skin deficits.

Recent advances in the technical aspects of tissue expanders for closure of skin deficits have led to an overall reduction in the high rate of complications typically associated with their usage. The authors provide a review of the recent refinements in the technique of the tissue expansion process. A discussion of current and future applications using this technique in the treatment of various lower extremity pathologies, including clubfoot, is presented. A case report on the use of a subcutaneous tissue expander for the treatment of a failed skin graft of the medial ankle is included.

Adult↗
PubMed1992

Thrombospondin and other possible related matrix proteins in malignant and benign breast disease. An immunohistochemical study.

Thrombospondin (TSP), which plays an important hemostatic role, is a 450-kd cytoadhesive protein present in the alpha granules of platelets. In vitro experiments using cultured malignant cells suggest that it may help to mediate malignant cell attachment to extracellular matrix and may be important in cancer invasiveness. The authors studied a group of malignant and benign breast tissues for the expression of TSP and provide evidence that TSP may have a role in tumor invasiveness. Using immunohistochemical techniques, the authors found in 48 fresh specimens of breast carcinoma that TSP stained strongly in the desmoplastic stroma or at the basement membrane associated with the malignant ductal epithelium. Tumor cells abutting these tissues revealed cytoplasmic staining for TSP. Stronger TSP staining was seen in the poorly differentiated tumors. These findings were compared with those of normal and benign breast tissue, which showed no TSP staining apart from reactivity in the large distended cysts of fibrocystic disease and faint staining in the stroma of fibroadenomas. Staining for integrin was positive in lymphocytes of both malignant and benign breast disease and equivocally also in the stromal cells of the breast cancer tissue. Immunoreactivity to TSP in tissues was also compared with that of fibronectin, laminin, and collagen type I, III, and IV. The overall findings suggest that thrombospondin may have a role in the tumor biology of invasiveness.

Adult↗
PubMed1991

Lack of agreement of chromogenic and clotting assays for factor X and protein C in warfarinised plasma.

Coagulation serine proteases can be measured with either a chromogenic substrate assay or a clotting assay using deficient plasmas. It is a concern whether both assays give similar quantitative results, in particular in plasma obtained from patients on long term warfarin therapy. If these two assay methods were interchangeable, then the chromogenic substrate assay has the advantages of precision as well as laboratory automation. We used the intraclass correlation coefficient (rI) to assess the agreement between the two methods in measuring factor X and protein C levels in warfarinised plasma. The results indicate that the extent and pattern of agreement of the two methods for the measurement of the two variables in warfarinised plasma are poor, despite high Pearson product moment coefficients of correlation.

Blood Chemical Analysis↗
PubMed1991

Transactivation of heterologous promoters by HIV-1 tat.

To determine whether HIV-1 tat can transactivate a heterologous promoter lacking HIV sequences other than the TAR element, TAR was placed downstream of the chicken beta-actin promoter. Tat increased expression directed by the actin-TAR promoter to a degree equal to tat induction of the HIV-1 LTR. Optimal transactivation was observed when TAR was positioned downstream of the actin promoter such that the expected cap site of transcripts from this promoter would be the same as in transcripts directed by the HIV-1 LTR. Tat was able to transactivate, though to a lesser extent, a promoter consisting solely of a TATA element fused to TAR. Thus, tat induction does not require HIV-1 LTR promoter sequences other than TAR. Tat, when fused to the DNA binding domain of BPV-1 E2, was able to transactivate a truncated SV40 promoter containing upstream E2 binding sites, indicating that tat may be capable of transactivation when directed by a DNA binding protein to an upstream site in a heterologous promoter lacking all HIV sequences. Substitution of Ala for Lys at position 41 of tat in the tat-E2 fusion, a mutation which dramatically decreases tat transactivation of the HIV-1 LTR, eliminated this transactivation.

3T3 Cells↗
PubMed1991

Discriminant analysis of iron deficiency anaemia and heterozygous thalassaemia traits: a 3-dimensional selection of red cell indices.

The two main causes of microcytic and hypochromic anaemia are iron deficiency and thalassaemia traits. Discriminant analysis based on a simple combination of classical red cell indices have been used to differentiate between iron deficiency anaemia and thalassaemia with varying degree of accuracy. Two new indices are now available from modern cell counters: red cell distribution width (RDW) and haemoglobin concentration distribution (HDW). Our discriminant analysis suggests that RBC, MCHC and RDW contribute significantly to the differentiation between iron deficiency anaemia and thalassaemia in both healthy donors and hospital-patient groups. In the discriminating process, previous workers have overlooked the heterogeneity of anaemia between anaemic groups as well as biological differences in MCV and MCH among the alpha and beta thalassaemia subjects. This study took into account of these biases and proved, for the first time, that differentiation between iron deficiency and thalassaemia by discriminant analysis was clinically reliable and not significantly biased by the severity of anaemia. The diagnostic accuracy of discriminant analysis was confirmed retrospectively by the reallocation algorithm using the jack-knife principle and prospectively by testing the discriminant functions on independent new samples. Selection of the red cell indices contributing to the discrimination of microcytic hypochromic anaemia was based on biological and statistical considerations. The clear separation of red cell index data of iron deficiency anaemia and thalassaemia traits was shown 3-dimensionally by surface plots.

Anemia, Hypochromic↗
PubMed1991

Erythropoietin levels and inhibition of erythropoiesis in end-stage renal failure.

Anaemia of chronic renal failure is multifactorial. Twenty-one patients with end-stage renal disease (ESRD) and 21 normal subjects were studied to determine the significance of serum erythropoietin levels and erythropoiesis inhibition in the aetiology of renal anaemia. Serum erythropoietin levels and erythropoiesis inhibition were measured by determining the incorporation of labelled-thymidine into the DNA of rabbit bone marrow cells. The mean haemoglobin concentration was 9.0 +/- 0.5 g/dl (mean +/- SEM) in ESRD and 14.4 +/- 0.4 g/dl in normal controls. Serum erythropoietin levels (99.9 +/- 17.9 mU/ml in ESRD vs 74.9 +/- 9.7 mU/ml in normal controls) and inhibition of erythropoiesis (252 +/- 28.9 in ESRD vs 186.2 +/- 19.4 in normal controls) were not significantly different in both groups. However, erythropoiesis inhibition had a significant correlation with the degree of anaemia (p less than 0.01). The results suggest that erythropoiesis inhibition play a significant role in the pathogenesis of renal anaemia.

Adult↗
PubMed1991

Lymphocyte changes in secondary dengue fever: use of the Technicon H*1 to monitor progress of infection.

Secondary dengue fever as dengue hemorrhagic fever or dengue shock syndrome is a potentially fatal complication of an infection that presents with few clinical signs that help in the diagnosis. Previous workers have reported the value of buffy coat determinations of atypical lymphocytes as an aid to the diagnosis. We report here the use of an automated white blood cell differential counter, the Technicon H*1 in the monitoring of the atypical lymphocyte count as a measure of the progress of the infection in a retrospective study of serial full blood counts in 45 serologically confirmed patients. Technicon H*1 'basophil' and large unstained cell counts and manual atypical lymphocyte counts rose in tandem with the drop in platelets and decreased when the platelets recovered. In a sub-study, the atypical lymphocytes were immunophenotyped and found to be predominantly derived from T lymphocytes. We conclude that the Technicon H*1 is a useful monitor of the activity of the infection in dengue hemorrhagic fever.

Basophils↗
PubMed1991

Immunophenotypic characterisation of monocytoid differentiation markers in acute non-lymphoblastic leukaemias.

The FAB classification of acute non-lymphoblastic leukaemias has been shown to have some clinical use in the prognostication of patient survival. ANLL with monocytoid features (M4, M5) fare worse than those which are predominantly myeloblastic (M1, M2). Classification is, however, sometimes difficult if non-specific esterase activity is not strongly expressed. Monoclonal antibody characterisation of myeloid differentiation antigens may be of some use as a supplementary aid. We immunophenotyped the blast cells from 26 cases for HLA-Dr, CD14 (Mo2, My4), CD13 (My17) and CD33 (My9) expression using the APAAP method. A combination of CD14 and CD33 used together was useful in differentiating myeloblastic from monocytoid acute non-lymphoblastic leukaemias. We conclude that the use of surface markers is a useful adjunct to the diagnostic means presently available.

Antibodies, Monoclonal↗
PubMed1990

Platelet-associated immunoproteins (PAIg): specificity of measurement.

Platelet-associated Ig (PAIg) is raised in patients with idiopathic thrombocytopenic purpura. However, it is also raised in conditions not traditionally considered to be immune mediated. The latter finding suggests that raised PAIg may be an epiphenomenon of thrombocytopenia. The assays currently available do not distinguish between PAIg present due to a specific Fab binding or present due to non-specific binding of Ig via Fc or complement receptors. In this paper we show that by prior incubation with normal rabbit serum, an assay for PAIg can be made specific for Fab binding.

Blood Platelets↗
PubMed1990

Cytogenetic analysis in myeloid malignancies.

Forty-one patients with myeloid malignancies, majority newly diagnosed and previously untreated, were systematically karyotyped between January 1988 and December 1989 using fluorodeoxyuridine (FdU) synchronisation and Giemsa banding techniques. Eighteen patients had acute myeloid leukaemia (AML), 13 had one form or other of a myeloproliferative disorder and 10 fulfilled the clinical and morphological criteria for the myelodysplastic syndrome (MDS). Ten AML patients had cytogenetic abnormalities. All 6 chronic myeloid leukaemia (CML) patients carried the Philadelphia chromosome with 2 having additional abnormal clones. Only four MDS patients showed involvement of either chromosome 5 or 7.

Adolescent↗
PubMed1990

A simple functional protein S assay using PROTAC.

Protein S is the co-factor of the enzymic action of protein C on FV and FVIII. A functional assay for protein S is not readily available for clinical use; however, we have developed a functional protein S assay based on the prolongation of Russell viper venom (RVV) plasma clotting time by protein C activated by PROTAC. Based on this assay, median functional protein S (5-95th percentile) of 46 healthy individuals was 82% (60-120%). Median functional protein S of 15 cord blood samples was 58% (35-71%). Unexpectedly, we found relatively high levels of functional protein S in a group of patients on long-term warfarin therapy whose INR ranged from 1.1 to 3.9. The median functional protein S of these patients was 71% (40-101%). We demonstrated that the protein S was not decarboxylated, as was the case with protein C, in these warfarin plasmas.

Fetal Blood↗
PubMed1990

Alpha-thalassaemia and beta-thalassaemia traits: biological difference based on red cell indices and zinc protoporphyrin.

alpha-thalassaemia and beta-thalassaemia traits are two commonly encountered haemoglobinopathies in South East Asia. Both present with hypochromia and microcytosis. The use of modern electronic or optical cell counters which measure accurately the red cell parameters has allowed for an initial quick screening for the presence of thalassaemia. Seven red cell parameters were measured by the Technicon H1 cell analyser--red cell count, Hb, MCV, MCH, red cell distribution width (RDW) and haemoglobin distribution width (HDW). Discriminant analysis of these parameters and zinc protoprophyin (ZP) indicates that in healthy individuals, alpha-thalassaemia can be differentiated from beta-thalassaemia with an accuracy of 86% when analysed as a group. In hospitalized patients the accuracy dropped to 71% due to biases of concomitant illness. The two most important parameters for indicating differences between alpha- and beta-thalassaemia are MCV and ZP. The results confirm further that though alpha- and beta-thalassaemia have the same phenotypic expression they differ in their biology.

Adolescent↗
PubMed1990

Chemotherapy of adult acute myeloid leukaemia.

Great strides have been made in the chemotherapy of adult acute myeloid leukaemia in the last two decades. This paper describes our experience in the treatment of adult acute myeloid leukaemia from 1980-88. About two thirds of patients achieve remission with a standard chemotherapy protocol. Early disease relapse and measures to prevent it are major problems. The majority of patients with adult myeloid leukaemia, presently, are not cured with chemotherapy alone.

Adolescent↗
PubMed1989

Modulation of hepatic glucose-6-phosphate dehydrogenase activity in male and female rats by estrogen.

The effect of estradiol-17 beta on the activity of glucose-6-phosphate dehydrogenase was studied in both male and female rats to further characterize the sex differences in the activity of this enzyme. Four groups of intact and castrated rats were implanted subcutaneously with graded doses (2.4, 4.8 and 7.2 micrograms/day) of pelleted estradiol in a physiologically relevant experimental system. After fourteen days the rats were sacrificed and their livers were assayed for G6PD activities. The result indicated that: (i) the enzyme activity was 3-fold higher in normal adult female than in male rats, (ii) low doses of E2 (2.4, 4.8 and 7.2 micrograms/day) increased the activity of G6PD 6-fold in castrated males and over 2-fold in female castrates as well as intact rats (iii) E2 stimulation of G6PD activity appears to be more effective in castrated males than in female rats (IV) sex difference in the activity of G6PD disappeared after treatment with E2 in castrated rats. It is concluded that the activity of G6PD in rats is markedly enhanced by low doses of E2, which appears to be largely responsible for the sex differences in the activity of this enzyme in rats.

Animals↗