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Biomedical subjects

A Dasgupta

Publications and source records attributed to A Dasgupta.

At least 199 records · Page 11Linked to original sources
PubMed1992

Rare variant of acute promyelocytic leukaemia.

Acute promyelocytic leukaemia (APL) is a peculiar sub-type of acute myeloblastic leukaemia characterised by presence of atypical promyelocytes in bone marrow and peripheral blood and common occurrence of haemorrhagic episodes associated with disseminated intravascular coagulation. Two morphological forms of APL are recognised--typical hypergranular and microgranular or M3 variant. This microgranular form of APL is rare but has got some peculiar features and often can be diagnosed by peripheral blood smear examination alone without bone marrow examination. Three cases of microgranular form of APL observed during a period of 6 months are reported here.

Adult↗
PubMed1991

Poliovirus proteinase 3C converts an active form of transcription factor IIIC to an inactive form: a mechanism for inhibition of host cell polymerase III transcription by poliovirus.

In HeLa cells, RNA polymerase III (pol III)-mediated transcription is severely inhibited by poliovirus infection. This is due primarily to a reduction in the transcriptional activity of TFIIIC, a transcription factor which binds in a sequence specific manner to the internal promoter of pol III genes. Using gel retardation assays, we have shown previously that inhibition of pol III transcription by poliovirus is correlated with disappearance of a transcriptionally active form of TFIIIC (complex I) concomitant with the appearance of a faster mobility, transcriptionally inactive form of TFIIIC (complex III). We show here that a poliovirus with a point mutation in the proteinase 3C (3Cpro) region failed to produce complex III and is limited in its ability to inhibit pol III transcription compared with the wild-type virus. Incubation of purified 3Cpro, expressed in Escherichia coli, with transcriptionally active TFIIIC (complex I) in vitro resulted in generation of the transcriptionally inactive complex III form of TFIIIC. In an in vitro transcription assay, treatment of the complex I form of TFIIIC with 3Cpro almost completely inhibited pol III transcription. Finally expression of the 3Cpro gene in transfected HeLa cells resulted in significant inhibition of pol III-mediated transcription. The results presented here suggest that proteolysis of the transcriptionally active form of TFIIIC by poliovirus 3Cpro is a mechanism by which poliovirus inhibits host cell RNA pol III transcription.

3C Viral Proteases↗
PubMed1991

Dialyzability and binding of digoxin-like immunoreactive factors (DLIF) with serum macromolecules in uremic patients on hemodialysis.

Digoxin-Like Immunoreactive Factors (DLIF) which cross-react with antidigoxin antibodies are present in elevated concentrations in patients on hemodialysis, uremia, hypertensives, liver failure, pre-eclampsia and premature birth. DLIF may have a potential role as a natriuretic hormone with a speculated low molecular weight (less than 1000). We studied the dialyzability and bindings of DLIF with serum components in hemodialysis patients. We analyzed DLIF concentrations in sera and protein free ultrafiltrates of 31 patients and 22 normal volunteers using a fluorescence polarization assay for digoxin. The DLIF concentrations were expressed as nmol/L Digoxin Equivalent. The gel filtration analysis was done using three different Bio-Gel columns with molecular weight cut-offs of 10,000, 20,000 and 40,000. Molecules with lower molecular weight than cut-off were absorbed in the column. Only 3 out of 22 normal volunteers (13.6%) showed measurable DLIF. However 23 out of 31 patients (74.2%) showed measurable DLIF. The concentrations of DLIF were significantly higher in patients with renal failure on hemodialysis (P less than 0.05) by both chi-squared and Fisher's exact test. We observed no statistically significant difference in the concentrations of DLIF in pre and post-dialysis sera, indicating that DLIF were not filtered during hemodialysis. We observed no DLIF activity in the protein free ultrafiltrates of any DLIF positive sera (patients and normal volunteers), indicating that unlike digoxin (where we observed 70-80% of total digoxin concentrations in ultrafiltrates), DLIF were strongly bound to serum components. With Bio-Gel filtration experiments (five different serum pools), we recovered all DLIF activities in the fraction equivalent to the void volume of the column with Bio-Gel P6 and P10 columns, indicating that DLIF were almost completely bound to serum components with molecular weight greater than 20,000. On the other hand, we recovered no DLIF activities in the void volume when the same serum pools were passed through the Bio-Gel P30 column, indicating that DLIF were strongly bound to serum macromolecules with molecular weight less than 40,000. In sharp contrast, when serum containing digoxin was subjected to the same series of experiments, we recovered only 20-30% of digoxin concentrations in void volume with all three columns as expected since digoxin is only 25% bound to albumin (MW 67,000).

Blood Proteins↗
PubMed1991

Prediction of free phenytoin levels based on [total phenytoin]/[albumin] ratios. Potential errors with hypoalbuminemia.

Therapeutic monitoring of the pharmacologically active (free drug) fraction of protein-bound medications (e.g., phenytoin) represents a major diagnostic challenge in clinical and laboratory medicine. While free drug levels may be beneficial in many clinical situations, current methods for predicting free phenytoin concentrations are unreliable and not recommended for general use. The authors have demonstrated a linear relationship (r2 = 0.98) between serum levels of total and bound phenytoin in 56 patients with seizure disorders. No significant correlations were observed when total phenytoin and albumin levels were compared independently to measured concentrations of free phenytoin or percent free phenytoin. A good correlation (r2 = 0.89) existed between free phenytoin levels and [total phenytoin]/[albumin] ratios in patients with normal or elevated albumin levels, but significantly weaker correlations were found in patients with hypoalbuminemia. Thus, [total phenytoin]/[albumin] ratios may have clinical value in predicting free phenytoin levels in uncomplicated patients without hypoalbuminemia.

Humans↗
PubMed1991

Elevated lipoprotein(a) levels in renal transplantation and hemodialysis patients.

Hyperlipidemia poses a risk for cardiovascular disease in both hemodialysis and renal transplantation patients. Although lipid profiles differ between the 2 populations, we evaluated the possibility that both groups have similar abnormalities of lipoprotein(a) [Lp(a)]. Mean serum Lp(a) and standard error of the mean (SEM) in hemodialysis and transplant recipients was 16.6 +/- 4.7 and 18.3 +/- 3.6 mg/dl, respectively, compared with 10.7 +/- 4.1 mg/dl in healthy controls, p less than 0.05. That serum Lp(a) levels are significantly elevated in dialysis and renal transplantation patients suggests at least 1 common pathogenic mechanism for the high incidence of atherosclerosis in both groups.

Adult↗
PubMed1991

Analytical performance of EMIT cyclosporine assay evaluated.

We evaluated the EMIT Cyclosporine Assay (Syva Co., Palo Alto, CA), using the Cobas-Mira analyzer to assess the precision, accuracy, and analytical recovery from whole-blood samples supplemented with cyclosporine. We also performed comparative analysis of whole-blood samples containing cyclosporine from liver and kidney transplant patients by using EMIT, HPLC, and RIA (IncStar Cyclo-Trac, SP assay). Before assay by EMIT or RIA, cyclosporine was extracted from whole blood with methanol. For the HPLC method, whole blood containing cyclosporine was hemolyzed with 300 mL/L acetonitrile in water; cyclosporine was extracted from the hemolysate with acetonitrile. The within-run and between-run CVs for the EMIT assay of cyclospoprine were 9.9% (means = 72.6, SD = 7.2 micrograms/L; n = 20) and 13.5% (means = 75.0, SD = 10.1 micrograms/L; n = 26) for the low control; 3.5% (means = 194.7, SD = 6.8 micrograms/L; n = 20) and 8.1% (means = 189.0, SD = 15.3 micrograms/L; n = 26) for the medium control; and 7.0% (means = 332.5, SD = 23.3 micrograms/L; n = 20) and 7.1% (means = 340.0, SD = 24.2 micrograms/L; n = 24) for the high control (Bio-Rad, whole-blood controls). Analytical recovery of cyclosporine from drug-supplemented samples averaged 99% for EMIT, 104% for HPLC, and 90% for RIA over a concentration range of 50-500 micrograms/L. Analysis of 196 specimens by HPLC (x) vs EMIT (y) gave the following regression statistics: y = 1.27x + 16.44; IncStar's RIA (x') vs EMIT: y = 1.12x' - 2.50; HPLC vs RIA: x' = 1.10x + 23.87.

Chromatography, High Pressure Liquid↗
PubMed1991

Displacement of phenytoin from serum protein carriers by antibiotics: studies with ceftriaxone, nafcillin, and sulfamethoxazole.

Increased concentrations of free phenytoin in serum, attributable to the displacement of this anticonvulsant by other drugs, e.g., valproic acid and salicylic acid, have been reported. We observed in vitro and in vivo displacement of phenytoin by the antibiotics ceftriaxone, nafcillin, and sulfamethoxazole. In vitro studies demonstrated statistically significant (P less than 0.05) increases in free phenytoin after the addition of specific antibiotics to patients' sera and to phenytoin-supplemented sera from controls. Concentrations of free phenytoin in vivo, predicted by an equation we have found to be accurate for albumin concentrations greater than or equal to 32 g/L, were consistently underestimated in patients receiving concomitant therapy with the antibiotics studied. The concentrations of free phenytoin decreased towards the predicted values when the antibiotic therapy was discontinued. We conclude that ceftriaxone, nafcillin, and sulfamethoxazole can displace phenytoin from the usual protein carriers found in serum, in vitro and in vivo.

Carrier Proteins↗
PubMed1990

Elevated lipid peroxidation products and depleted transferrin levels in the plasma of kidney transplant recipients.

Lipid peroxidation products were measured in the plasma of 24 kidney transplant patients and 12 healthy volunteers (controls) by: (1) 2-thiobarbituric acid assay and (2) the intensity of fluorescence products of malonaldehyde cross-linked proteins. Plasma levels of creatinine, ceruloplasmin, transferrin, prealbumin, albumin and total protein were also measured. Elevated lipid peroxidation products and lowered transferrin levels were observed in transplant patients compared to controls. Ceruloplasmin levels were slightly but significantly elevated in recent transplant recipients (less than 6 months, n = 12, Group A) while no difference was observed between older transplant recipients (greater than 6 months, n = 12, Group B) and controls. Serum, creatinine levels were also slightly but significantly elevated in both groups of patients compared to controls. Serum prealbumin, albumin and total protein levels in both groups of transplant recipients were not different from controls or reference range values.

Blood Proteins↗
PubMed1990

Quantitative variations in A, B, Ht1 and Ht2 antigens on erythrocytes in leukemia and lymphoma.

Using an immunoradiometric assay, A, B, Ht1 and Ht2 antigens on erythrocyte membranes were quantitated in 192 leukemia and 23 lymphoma patients. A and B antigens were reduced in 37% and 50% of leukemia cases respectively. A wide range of antigenic reduction was observed for A antigen, while B antigenic reduction was generally 16-20%. Passive absorption of Ht1 antigen from plasma onto erythrocytes was greater in leukemic compared to normal subjects. Among patients with reduced A and B antigens, 27% had increased and 37% decreased Ht2 antigens. Incidence of reduction in antigens was significantly higher (p less than 0.001) in untreated compared to treated patients.

ABO Blood-Group System↗
PubMed1990

Loss of a phosphorylated form of transcription factor CREB/ATF in poliovirus-infected cells.

Host cell RNA synthesis is inhibited by poliovirus infection. We have studied the mechanism of poliovirus-induced inhibition of RNA polymerase II-mediated transcription by using the adenovirus early region 3 (E3) promoter. In vitro transcription from the E3 promoter was severely inhibited in extracts prepared from poliovirus-infected HeLa cells. Four regions in the E3 promoter have been shown to serve as binding sites for cellular transcription factors. These regions contain binding sites for transcription factors NF-1 (site IV), AP-1 (site III), CREB/ATF (site II), and the TATA factor (site I). Binding to these four regions was not significantly altered by poliovirus infection as assayed by DNase I footprinting analysis; furthermore, gel retardation assays failed to reveal dramatic differences in the total amount of CREB/ATF-, AP-1-, and NF-1-binding activity present in mock- or poliovirus-infected cell extracts. Gel retardation assays, however, did reveal significant qualitative differences in the DNA-protein complexes formed with a CREB/ATF-binding site in extracts prepared from poliovirus-infected cells as compared to mock-infected cell extracts. Radioimmunoprecipitation reactions performed with antiserum against CREB/ATF revealed a severe reduction in a phosphorylated form of the protein present in poliovirus-infected cell extracts. However, in vitro kinase reactions demonstrated that mock- and poliovirus-infected cell extracts contained similar levels of CREB/ATF. Expression from the E3 promoter was shown to be activated by CREB/ATF in vivo; this induction was dependent upon the phosphorylation of CREB/ATF. Thus, we propose that poliovirus infection inhibits transcription from the E3 promoter, at least in part, through the dephosphorylation of CREB/ATF.

Activating Transcription Factors↗
PubMed1990

A transcriptionally active form of TFIIIC is modified in poliovirus-infected HeLa cells.

In HeLa cells, RNA polymerase III (pol III)-mediated transcription is severely inhibited by poliovirus infection. This inhibition is due primarily to the reduction in transcriptional activity of the pol III transcription factor TFIIIC in poliovirus-infected cells. However, the specific binding of TFIIIC to the VAI gene B-box sequence, as assayed by DNase I footprinting, is not altered by poliovirus infection. We have used gel retardation analysis to analyze TFIIIC-DNA complexes formed in nuclear extracts prepared from mock- and poliovirus-infected cells. In mock-infected cell extracts, two closely migrating TFIIIC-containing complexes, complexes I and II, were detected in the gel retardation assay. The slower migrating complex, complex I, was absent in poliovirus-infected cell extracts, and an increase occurred in the intensity of the faster-migrating complex (complex II). Also, in poliovirus-infected cell extracts, a new, rapidly migrating complex, complex III, was formed. Complex III may have been the result of limited proteolysis of complex I or II. These changes in TFIIIC-containing complexes in poliovirus-infected cell extracts correlated kinetically with the decrease in TFIIIC transcriptional activity. Complexes I, II, and III were chromatographically separated; only complex I was transcriptionally active and specifically restored pol III transcription when added to poliovirus-infected cell extracts. Acid phosphatase treatment partially converted complex I to complex II but did not affect the binding of complex II or III. Dephosphorylation and limited proteolysis of TFIIIC are discussed as possible mechanisms for the inhibition of pol III-mediated transcription by poliovirus.

Acid Phosphatase↗
PubMed1990

Abnormal fatty acid profile in chronic hemodialysis patients: possible deficiency of essential fatty acids.

Plasma fatty acid profiles from maintenance hemodialysis patients (n = 9) were compared with those from healthy volunteers (n = 9). Hemodialysis patients had significantly higher levels of oleic acid, 15.3 +/- 1.1 vs. 8.9 +/- 0.6% (p less than 0.0001), and lower levels of arachidonic acid (6.0 +/- 0.5 vs. 8.4 +/- 0.3%, p less than 0.0009). Linolenic and linoleic acids, the essential fatty acid and precursors of arachidonic acid, were also significantly lower than normal in the dialysis group. These data show that dialysis patients have fatty acid abnormalities suggesting relative depletion of essential fatty acids. These observations are important because these abnormalities may play an important role in the pathogenesis of some common clinical conditions associated with uremia, such as a constellation of skin problems, fragility of erythrocytes, lipid anomalies and hormonal aberrations.

Adult↗
PubMed1990

Monitoring free digoxin instead of total digoxin in patients with congestive heart failure and high concentrations of digoxin-like immunoreactive substances.

Digoxin-like immunoreactive substances (DLIS) are present in patients with conditions associated with volume expansion (including hypervolemic hypertension, renal failure, and liver failure) and in pre-eclampsia and premature birth. These strongly-protein-bound substances cross-react with anti-digoxin antibodies and cause falsely increased measured concentrations of digoxin in serum. Patients with congestive heart failure (CHF) often have volume expansion and are receiving digoxin therapy. They are also very sensitive to digoxin toxicity and have a very narrow therapeutic range (1.0-1.9 nmol/L). We found monitoring the concentrations of free digoxin (in protein-free ultrafiltrates) helpful in eliminating the interferences of DLIS in CHF patients. DLIS concentrations were measured by fluorescence polarization assay. Concentrations of DLIS were detectable in significantly more (58.3%) of the 12 CHF patients (group A) who were not receiving digoxin than in the 22 normal volunteers tested (13.6%) (P less than 0.05 by both chi-square and Fisher's exact test). Protein-free filtrates from patients or normal volunteers did not show any measurable DLIS activities. We also determined the concentrations of total and free digoxin in 12 patients with CHF who were receiving digoxin (group B) and compared the results with those for 22 patients receiving digoxin without the diagnosis of CHF or any known pathological conditions that could increase DLIS concentrations. The ratio of free to total digoxin in patients in group B was significantly lower (mean = 52.8%, SD 10.2%) than in those receiving digoxin (mean = 72.7%, SD 6.5%) for other reasons (independent two-tailed t-test, P less than 0.05).

Digoxin↗