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Biomedical subjects

K Venu

Publications and source records attributed to K Venu.

10 recordsLinked to original sources
PubMed2004

Molecular reorientations in liquid crystals pentyloxybenzylidine hexylanilene (PBHA) and butyloxybenzylidine octylanilene (BBOA).

Molecular reorientational motions in undeuterated pentyloxybenzylidine hexylanilene (PBHA or 5O.6) and butyloxybenzylidine octylanilene (BBOA or 4O.8) as studied by the quasielastic neutron scattering (QENS) technique in their different mesophases are reported. Models are built up in stages to account for the experimental elastic incoherent structure factor (EISF). It is found that there exist simultaneous reorientational motions of the chain group and the reorientational motions of the whole molecule around its molecular axis in the smectic- G, smectic- B, and smectic- C phases. In smectic- A and nematic phases, additional body axis fluctuations are found to exist in both 5O.6 and 4O.8 systems. The average amplitude of body axis fluctuations is found to be approximately 15 degrees and 25 degrees, respectively, in the smectic- A and nematic phases of 5O.6, and approximately 14 degrees and 29 degrees, respectively, in 4O.8.

Journal Article↗
PubMed1999

Orientational order and dynamics of hydration water in a single crystal of bovine pancreatic trypsin inhibitor.

The orientational order and dynamics of the water molecules in form II crystals of bovine pancreatic trypsin inhibitor (BPTI) are studied by (2)H NMR in the temperature range 6-50 degrees C. From the orientation dependence of the single crystal quadrupole splitting and linewidth, the principal components of the motionally averaged quadrupole interaction tensor and the irreducible linewidth components for the orthorhombic crystal are determined. With the aid of water orientations derived from neutron and x-ray diffraction, it is shown that the NMR data can be accounted for by a small number of highly ordered crystal waters, some of which have residence times in the microsecond range. Most of these specific hydration sites must be located at intermolecular contacts. The surface hydration layer that is also present in dilute solution is likely to be only weakly ordered and would then not contribute significantly to the splitting and linewidth from the protein crystal. To probe water dynamics on shorter time scales, the (2)H longitudinal relaxation dispersion is measured for a polycrystalline BPTI sample. The observed dispersion is dominated by rapidly exchanging deuterons in protein side chains, undergoing restricted rotational motions on a time scale of 10 ns.

Animals↗
PubMed1999

A profile of lung cancer patients in Hyderabad.

One hundred and sixty cases of bronchogenic carcinoma were retrospectively analysed. Male to female ratio was 8.4:1, common age group being 40-60 years. The most common (38%) radiological presentation was mass lesion. The predominant histological cell type was squamous cell carcinoma (67%). Most of the patients presented in an advanced stage of the disease of inoperability. The study underlines the various diagnostic madalities in diagnosing lung cancer and emphasises the need for practising doctors to keep in mind the possibilities of bronchogenic carcinoma in all cases of unresolved pneumonia and mass lesion on chest x-ray especially in high risk patients.

Adult↗
PubMed1998

Water molecules in DNA recognition I: hydration lifetimes of trp operator DNA in solution measured by NMR spectroscopy.

The present NMR study investigates the residence times of the hydration water molecules associated with uncomplexed trp operator DNA in solution by measuring intermolecular nuclear Overhauser effects (NOE) between water and DNA protons, and the nuclear magnetic relaxation dispersion (NMRD) of the water 2H and 17O resonances. Both methods indicate that the hydration water molecules exchange with bulk water on the sub-nanosecond time scale at 4 degreesC. No evidence was obtained for water molecules bound with longer residence times. In particular, the water molecules at the sites of interfacial hydration in the trp repressor/operator complex do not seem kinetically stabilized in the uncomplexed DNA. Analysis of the crystal structures of two different trp repressor/operator complexes shows very similar structural environments for the water molecules mediating specific contacts between the protein and the DNA, whereas much larger variations are observed for the location of corresponding water molecules detected in the crystal structure of an uncomplexed trp operator DNA duplex. Therefore, it appears unlikely that the hydration characteristics of the uncomplexed DNA target would be a major determinant of trp repressor/operator recognition.

Bacterial Proteins↗
PubMed1998

Model-free analysis of stretched relaxation dispersions.

Nuclear magnetic relaxation dispersion (NMRD) measurements can provide valuable information about the dynamics and structure of macromolecular solutions and other complex fluids. A large number of 1H NMRD studies of water in concentrated protein solutions and in semisolid biological samples have been reported. The observed dispersion usually extends over a wide frequency range and then cannot be described by a Lorentzian spectral density function. We propose here a model-free approach for analyzing such stretched dispersion profiles. Unlike the traditional empirical fitting procedures, the model-free approach is based on rigorous theory and produces parameters with well-defined physical significance. The model-free approach is validated with the aid of synthetic relaxation data, showing that it is robust and accurate, and is then applied to new water 1H NMRD data from solutions of the protein bovine pancreatic trypsin inhibitor (BPTI). By separating the static and dynamic information content of the relaxation dispersion, the model-free analysis shows that the dramatic salt effect observed in BPTI solutions is due almost entirely to a slowing down of protein rotation with little change of protein structure. An analysis of the same data in terms of the empirical dispersion function used in most 1H NMRD studies leads to a qualitatively different picture. We demonstrate that this widely used dispersion function is unphysical and that its parameters do not have the physical meaning usually ascribed to them.

Animals↗
PubMed1998

Rotational atherectomy for in-stent restenosis: acute and long-term results of the first 100 cases.

OBJECTIVES: This study evaluated the clinical safety and long-term results of rotational atherectomy (RA) followed by low-pressure balloon dilatation (percutaneous transluminal coronary angioplasty [PTCA]) for the treatment of in-stent restenosis (ISR). BACKGROUND: In-stent restenosis is associated with a high incidence of recurrence after interventional treatment. Because ISR is due to neointimal hyperplasia, rotational ablation may be a more effective treatment than PTCA. METHODS: Between November 1995 and November 1996, 100 consecutive patients with first-time ISR were treated by RA. Quantitative coronary angiography and intravascular ultrasound (IVUS) were used to analyze the acute procedural results. The incidence of repeat in-stent restenosis and target vessel revascularization (TVR) at follow-up was determined. RESULTS: Procedural success without any major in-hospital complications was achieved in 100% of cases. Slow flow was observed in 3% and creatine kinase-MB enzyme elevation >3x normal occurred in 2%. The mean burr-to-artery ratio was 0.68+/-0.18 and adjuvant balloon dilatation was performed at 4.2+/-2.1 atm. Minimum luminal diameter increased from 0.86+/-0.28 mm to 1.89< or =0.21 mm after RA and to 2.56+/-0.29 mm after adjunct PTCA. Quantitative IVUS analysis showed that 77% of the luminal gain occurred due to rotational ablation of the restenotic tissue and only 23% occurred after adjunct balloon dilation, and further stent expansion did not contribute to the luminal enlarge. ment. At a mean follow-up of 13+/-5 months, repeat in-stent restenosis occurred in 28% of patients with TVR of 26%. Univariate predictors of repeat restenosis were burr-to-artery ratio <0.6, ISR in <90 days of stenting, ostial lesion, stent for a restenotic lesion and diffuse type ISR. CONCLUSIONS: Rotational atherectomy is a safe and feasible technique for treatment of ISR and is associated with a relatively low recurrent restenosis in comparison to historical controls of balloon angioplasty.

Angioplasty, Balloon, Coronary↗
PubMed1997

Kinetics of DNA hydration.

The hydration of the d(CGCGAATTCGCG) B-DNA duplex in solution was studied by nuclear magnetic relaxation dispersion (NMRD) of the water nuclei 1H, 2H, and 17O, and by nuclear Overhauser effects (NOEs) in high-resolution two-dimensional 1H NMR spectra. By comparing results from the free duplex with those from its complex with netropsin, water molecules in the "spine of hydration" in the AATT region of the minor groove could be distinguished from hydration water elsewhere in the duplex. The 2H and 17O relaxation dispersions yield a model-independent residence time of 0.9(+/-0.1) ns at 4 degrees C for five highly ordered water molecules in the spine. When corrected for frequency offset effects, the NOE data yield the same residence time as the NMRD data, giving credence to both methods. At 27 degrees C, the residence time is estimated to 0.2 ns, a factor of 40 shorter than the tumbling time of the duplex. The NMRD data show that all water molecules associated with the duplex, except the five molecules in the spine, have residence times significantly shorter than 1 ns at 4 degrees C. There is thus no long-lived hydration structure associated with the phosphate backbone. In contrast to 2H and 17O, the 1H relaxation dispersion is dominated by labile DNA protons and therefore provides little information about DNA hydration.

Binding Sites↗
PubMedDate not supplied

Carcinoid tumour: laser therapy.

A 31-year-old female, pregnant (I trimester), presented with symptoms and signs of bronchial asthma. Chest roentgenogram and computerized tomography of the chest revealed right mid and lower zone opacity (collapse). Bronchoscopic examination revealed intrabronchial growth in the right middle and lower lobe bronchus. Biopsy and histopathological examination confirmed carcinoid tumour. These symptoms and signs disappeared after laser therapy. The lesion, however, recurred two years later.

Adult↗