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Biomedical subjects

B K Nayak

Publications and source records attributed to B K Nayak.

At least 19 recordsLinked to original sources
PubMed2006

Nuclear translocation and DNA-binding activity of NFKB (NF-kappaB) after exposure of human monocytes to pulsed ultra-wideband electromagnetic fields (1 kV/cm) fails to transactivate kappaB-dependent gene expression.

The objective of this study was to investigate whether exposure of human monocytes to a pulsed ultra-wideband electromagnetic field (EMF) of 1 kV/cm average peak power triggers a signaling pathway responsible for the transcriptional regulation of NFKB (NF-kappaB)-dependent gene expression. Human Mono Mac 6 (MM6) cells were exposed intermittently to EMF pulses for a total of 90 min. The pulse width was 0.79+/-0.01 ns and the pulse repetition rate was 250 pps. The temperature of the medium was maintained at 37 degrees C in both sham- and EMF-exposed flasks. Total NFKB DNA-binding activity was measured in the nuclear extracts by the electrophoretic mobility shift assay. Cells exposed to the EMFs and incubated for 24 h postexposure showed a 3.5+/-0.2-fold increase in the NFKB DNA-binding activity. Since activation of NFKB was observed, the possibility of kappaB-dependent gene expression in response to exposure to the EMFs was investigated using NFKB signal-specific gene arrays. The results revealed no difference in the NFKB-dependent gene expression profiles at 8 or 24 h postexposure, indicating that activated NFKB does not lead to the differential expression of kappaB-dependent target genes. To determine whether the absence of the kappaB-dependent gene expression was due to compromised transcriptional regulation of NFKB, the functional activity of NFKB was examined in cells transiently transfected with Mercury Pathway constructs containing 4x NFKB binding sites associated either with the luciferase reporter system or a control vector. Pulsed EMF exposure did not induce NFKB-driven luciferase activity in these cells, indicating that the activation of NFKB at 24 h after the 1 kV/cm EMF exposure is functionally inactive. From these results, it is clear that the EMF-induced NFKB activation is only a transient response, with minimal or no downstream effect.

Active Transport, Cell Nucleus↗
PubMed2003

A composite chiral pair of rotational bands in the odd-A nucleus 135Nd.

High-spin states in 135Nd were populated with the 110Pd(30Si,5n)135Nd reaction at a 30Si bombarding energy of 133 MeV. Two DeltaI=1 bands with close excitation energies and the same parity were observed. These bands are directly linked by DeltaI=1 and DeltaI=2 transitions. The chiral nature of these two bands is confirmed by comparison with three-dimensional tilted axis cranking calculations. This is the first observation of a three-quasiparticle chiral structure and establishes the primarily geometric nature of this phenomenon.

Journal Article↗
PubMed2002

Revalidation of the isobaric multiplet mass equation.

We have determined the energy of the J(pi) = 1/2(+), T = 3/2 resonance in 32S(p,p) to be E(p) = 3374.7+/-0.8 keV. This disagrees with the previously accepted value of E(p) = 3370+/-1 keV by Abbondanno et al. [Nuovo Cimento 70A, 391 (1970)] and solves a problem raised by recent observations of unexpected deviations from the isobaric multiplet mass equation. This resonance is also important in calibrating the beta-delayed proton spectra from 33Ar and 32Ar, and our findings may modify previous conclusions.

Journal Article↗
PubMed1999

Differential binding of NF1 transcription factor to P53 gene promoter and its depletion in human breast tumours.

Different transcription factors activate and repress the p53 gene expression. Recently, a tissue specific binding of NF1/YY1 to p53 promoter has been reported and further, it has been demonstrated that NF1/YY1 activates p53 promoter activity. The deregulated expression of p53 appears to be a central feature of malignant transformation and the basis of this deregulation is not well defined. Hence, an attempt has been made to know the binding of NF1/YY1 to p53 promoter taking breast tumour as a model system. Results have indicated a differential binding of NF1 to p53 promoter and a depletion or low level of NF1 in majority of breast tumour samples. Further, a correlation between NF1 and p53 has indicated the presence of p53 RNA even without NF1. Hence it is assumed that p53 expression is not NF1-dependent in breast tumours. However, the results clearly demonstrate a deregulation of NF1 transcription factor in breast tumours.

Breast Neoplasms↗
PubMed1999

Rearrangement in the coding and 5' region of p53 gene in human oral tumors.

Different postreplicative, transcriptional, and translational mechanisms responsible for p53 gene inactivation are slowly unfolding. Rearrangement of the p53 gene is a very rare event in human solid tumors and has been reported only in osteosarcomas. From our laboratory we have recently reported rearrangement only in the coding region of the p53 gene in breast tumors. In this report we have undertaken a systemic investigation of p53 in oral tumors. Results have shown rearrangement in the coding region of p53 in 20% of cases and in the 5' region of p53 gene in approximately 8% of cases. No allelic loss and amplification of p53 gene was observed in these tumor samples. In our earlier studies on breast tumors, we found no abnormality in the 5' region of p53. However, in the present study we report for the first time rearrangement in the 5' region of p53 in oral tumors. Correlation of p53 gene rearrangement with p53 expression of RNA and protein indicates that rearrangement in the 5' region of p53 might not have a role in p53 expression. However, rearrangement in the coding region of p53 might play a critical role in controlling p53 gene activity in the process of tumorigenesis.

5' Untranslated Regions↗
PubMed1998

Rearrangement of the p53 gene in human breast tumours.

Rearrangement of the p53 gene is frequent in virus transformed cell lines and in chronic myelogenous leukemia. It is a rare event in solid tumours and has been reported only in osteosarcomas. In this study we have examined rearrangement of the p53 gene in human breast tumours. We found rearrangement in 35% of the patients (7 of 20 tumours examined). Normal tissue from these patients had an unrearranged gene, indicating that the genetic abnormality in the tumour is acquired during the natural process of tumorigenesis. No intronic rearrangement or allelic loss of the p53 gene was found in the breast tumour samples studied. Further, rearrangement of the p53 gene has been correlated with the p53 transcriptional status. Only two patients with rearranged p53 showed a high level of p53 RNA as well as protein expression. Thus, for the first time we report the rearrangement of the p53 gene in breast tumours, which may play a role in the process of tumorigenesis.

Blotting, Southern↗
PubMed1997

Differential binding of nuclear proteins to the TP53 gene promoter in male breast tumour.

It is well established that TP53 regulates the expression of many genes, but the regulation of expression of TP53 itself is poorly understood. Recently, it has been shown that there is a tissue-specific binding of nuclear proteins in the TP53 gene promoter. The aim of this study was to determine the nuclear proteins that bind to the TP53 promoter elements (between -104 and -458) in male breast cancer. The results of our study, using the electrophoretic mobility shift assay (EMSA) and Southwestern analysis, have showed: (1) nuclear proteins or factors other than p53 bind to the TP53 promoter; (2) the levels of at least four nuclear proteins vary between normal and tumour breast tissue; and (3) two newly discovered nuclear proteins bind to the TP53 promoter in tumour tissue but are absent in normal tissue. This differential binding of nuclear proteins to the TP53 gene promoter might play a critical role in TP53 transcription and cancer progression in male breast tumours.

Breast Neoplasms, Male↗
PubMed1996

p53 gene mutation in relation to p53 protein accumulation in male and female breast cancer.

The aim of this investigation was to study the prevalence of p53 gene mutations in male and female breast cancers and to find out the relationship between this event and p53 protein expression. Genomic p53 was amplified by polymerase chain reaction (PCR). Exons 5-8 were screened for mutations using single stranded conformation polymorphism (SSCP) analysis. P53 protein expression was detected by immunohistochemistry (IHC) with the monoclonal antibody DO-1. In female breast cancer, p53 gene mutation was detected in 33% cases in either exon 5 or 6. However, in male, mutation was detected only in exon 6 in 90% cases. On the other hand, p53 protein expression was observed in all of these cases. Moreover, p53 protein immunostaining was observed in some of those cancer tissues, where no mutation was detected in exons 5-8. P53 dysfunction, as indicated by mutation or increased protein expression, common in both male and female breast cancer, but rate of occurrence or site of mutation differ from each other. Our results in male breast tumors indicate a positive correlation between p53 mutation and p53 protein overexpression, whereas the results in female breast tumors indicate an overexpression of p53 protein even without p53 gene mutation. Therefore, it may be presumed that p53 protein accumulation can result primarily from mutation. In addition, stabilization of p53 through binding to other proteins is another possible reason of p53 overexpression.

Breast Neoplasms↗
PubMed1989

Trace element profiles in oesophageal neoplasms determined by proton-induced X-ray emission.

Trace element concentrations were determined in surgically resected, cancerous human oesophageal tissue by proton-induced X-ray emission (PIXE) analysis. Each sample was divided into six zones, E3 and E4 formed the central tumour region, E1 and E2 were proximal to the oesophagus and E5 and E6 distal to the oesophagus. Malignancy was confirmed histopathologically in all cases. Samples were dissolved in NaOH solution and pipetted onto a thin mylar film for analysis by a proton beam from a Van de Graaff accelerator. Titanium, Fe, Cu, Zn, As, Rb, Br and Pb were detected in varying concentrations. Of these, Ti, Fe, Cu, Zn and As showed specific behaviour in the six zones.

Carcinoma↗
PubMed1987

A comparison of cycloplegic and manifest refractions on the NR-1000F (an objective Auto Refractometer).

The manifest (dry) and cycloplegic refractions of 50 eyes of 25 patients aged 8 to 28 years were studied on the Nikon Auto Refractometer NR-1000F (AR) and compared with the results of clinical refraction (CR) under homatropine and the final clinical acceptance on postmydriatic testing. Only patients in the younger age groups with low to moderate refractive errors were included in this study; high myopes and hypermetropes and patients with aphakia and mixed astigmatism were excluded. The degree of agreement for spherical equivalents, sphere components, and cylinder components was analysed separately for both cycloplegic and manifest refractions on the AR and CR. The results showed that the fixation target in the NR-1000F induces significant instrument myopia during manifest refraction in the younger patients with lower refractive errors. We recommend that caution should be exercised in interpreting manifest refractions on the AR, especially in younger patients. A cycloplegic automatic refraction would be acceptably accurate.

Adolescent↗
PubMed1987

A method for fundus evaluation in children with oral fluorescein.

A procedure is described for the ophthalmoscopic examination of the fundus in children after 1% or 2% oral fluorescein ingestion without sedation or anaesthesia. No major complications or any allergic reactions were observed. In the ophthalmoscopically normal fundi of the five healthy children studied the fluorescence of the nerve head and retinal blood vessels could be visualised at 15 minutes, increasing at 30 minutes, and declining by 60 minutes. The possible problems of the technique are discussed.

Administration, Oral↗
PubMed1987

Role of oral fluorescein in the diagnosis of early papilloedema in children.

Nine eyes of suspected papilloedema, 21 with incipient papilloedema, and 16 with pseudopapilloedema in 23 children aged 1 month to 10 years were examined after oral fluorescein. In pseudopapilloedema the retinal vascular fluorescence and slight disc head fluorescence with sharp margins at 30 minutes markedly declined by 60 minutes. These features were similar to our earlier findings with oral fluorescein in the normal fundi of children. Of the 30 eyes with suspected or incipient papilloedema late disc and peripapillary 'staining', polar or diffuse was observed in 12, the 60 minutes fluorescence being more than at 30 minutes in nine and of equal in intensity in three. In these 12 'positive' eyes, and four more of the 18 'negative' eyes, the retinal vascular fluorescence at 60 minutes was significantly more than at 30 minutes. The problems of interpretation after oral fluorescein in the early diagnosis of papilloedema in children and the possible fallacies are discussed.

Administration, Oral↗
PubMed1987

An evaluation of the NR-1000F Auto Refractometer in high refractive errors.

The manifest refractions of 37 high myopic and 16 high hypermetropic eyes in a total of 28 patients, aged 5 to 42 years, were determined on the Nikon NR-1000F Auto Refractometer. The data obtained were compared with the final clinical prescriptions for these eyes and analysed for degree of agreement for the spherical equivalents, sphere components, and cylinder powers and axes. The Auto Refractometer recordings for all the different refractive components were observed to skew towards more minus in the high myopic eyes but more plus in the high hypermetropes. The possible significance of these skewing patterns is discussed with reference to our earlier studies.

Adolescent↗
PubMed1986

Critical evaluation of the NR-1000F Auto Refractometer.

The manifest (dry) refractions of 165 eyes of 86 patients, aged 6 to 75 years, were studied on the Nikon Auto Refractometer NR-1000F. The results obtained were compared with the clinical refractive data, and they were analysed for degree of agreement of various refractive components in different types and grades of refractive errors in the separate age groups. On the NR-1000F the spherical and cylindrical components and spherical equivalents skewed towards more minus (or less plus), especially so in emmetropes, low hypermetropes, and low myopes. This error declined with increasing age over 40 years and was also significantly lower in aphakia and mixed astigmatism. Determination of cylinder axis was found to be reliable on the NR-1000F. In spite of the obvious utility of the device its inbuilt automatic fogging system does not seem adequately to neutralise the patient's accommodative efforts, as the fixation target probably induces instrument myopia.

Adolescent↗