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Biomedical subjects

B K Rao

Publications and source records attributed to B K Rao.

At least 19 recordsLinked to original sources
PubMed2002

Giant magnetic moments of nitrogen-doped Mn clusters and their relevance to ferromagnetism in Mn-doped GaN.

Calculations based on density-functional theory show that the stability and magnetic properties of small Mn clusters can be fundamentally altered by the presence of nitrogen. Not only are their binding energies substantially enhanced, but also the coupling between the magnetic moments at Mn sites remains ferromagnetic irrespective of their size or shape. In addition, these nitrogen-doped Mn clusters carry giant magnetic moments ranging from 4mu(B) in MnN to 22mu(B) in Mn5N. It is suggested that the giant magnetic moments of MnxN clusters may play a key role in the ferromagnetism of Mn-doped GaN which exhibit a wide range (10-940 K) of Curie temperatures.

Journal Article↗
PubMed2002

Magic numbers in metallo-inorganic clusters: chromium encapsulated in silicon cages.

A systematic theoretical study of the equilibrium geometries and total energies of Cr encapsulated in Si clusters reveals that Cr@Si(12) is more stable than its neighbors. The origin of this enhanced stability is consistent with the 18-electron sum rule commonly used in the synthesis of stable chemical complexes, and may provide a criterion for a systematic search of magic numbers in metalloinorganic clusters. The 6 mu(B) magnetic moment of the caged Cr atom, the largest among the 3d transition metal atoms, is completely quenched. This effect of caging on the properties of transition metal atoms may lead to the synthesis of novel cluster based materials.

Journal Article↗
PubMed2001

Pyoderma vegetans.

BACKGROUND: Pyoderma vegetans is a rare condition that is clinically characterized by large verrucous plaques with elevated borders and multiple pustules. The etiology of this disorder remains unknown. OBJECTIVES: We describe a 24-year-old woman with rapidly evolving pyoderma vegetans. Our patient had the unique additional findings of a highly elevated serum IgE level and a history of hidradenitis suppurativa. CONCLUSIONS: Pyoderma vegetans is diagnosed on clinical and histological criteria. Differentiation must be made from disorders such as pyoderma gangrenosum, Sweet's syndrome, and deep fungal infections. We illustrate a case of pyoderma vegetans and review the literature on this rare disorder. Clinical and histological criteria for diagnosis are presented, as well as differentiation from some mimicking disorders.

Adult↗
PubMed2001

Electronic structure and properties of transition metal-benzene complexes.

A comprehensive theoretical study of the geometries, energetics, and electronic structure of neutral and charged 3d transition metal atoms (M) interacting with benzene molecules (Bz) is carried out using density functional theory and generalized gradient approximation for the exchange-correlation potential. The variation of the metal-benzene distances, dissociation energies, ionization potentials, electron affinities, and spin multiplicities across the 3d series in MBz complexes differs qualitatively from those in M(Bz)(2). For example, the stability of Cr(Bz)(2) is enhanced over that of CrBz by almost a factor of 30. On the other hand, the magnetic moment of Cr(Bz)(2) is completely quenched although CrBz has the highest magnetic moment, namely 6 mu(B), in the 3d metal-benzene series. In multidecker complexes involving V(2)(Bz)(3) and Fe(2)(Bz)(3), the metal atoms are found to couple antiferromagnetically. In addition, their dissociation energies and ionization potentials are reduced from those in corresponding M(Bz)(2) complexes. All of these results agree well with available experimental data and demonstrate the important role the organic support can play on the properties of metal atoms/clusters.

Journal Article↗
PubMed2001

AlH(3) and Al(2)H(6): magic clusters with unmagical properties.

Enhanced stability, low electron affinity, and high ionization potential are the hallmarks of a "magic" cluster. With an electron affinity of 0.28 eV, ionization potential of 11.43 eV, and a large binding energy, AlH(3) satisfies these criteria. However, unlike other magic clusters that interact only weakly with each other, two AlH(3) clusters bind to each other with an energy of 1.54 eV. The resulting Al(2)H(6), while also a magic cluster in its own right, possesses the most unusual property that the difference between its adiabatic and vertical detachment energy is about 2 eV--the largest of any known cluster. These results, based on density functional theory, are verified experimentally through photodetachment spectroscopy.

Journal Article↗
PubMed2001

Lipid peroxidation and antioxidant enzyme status in Type 2 diabetics with coronary heart disease.

Lipid peroxides are thought to be formed by free radicals and may play an important role in the development of atheromatous vascular diseases. The relationship between serum lipids, lipoproteins, lipid peroxides [thiobarbituric acid reactive substances (TBARS)] and erythrocyte antioxidant enzymes [catalase (CAT), glutathione peroxidase (GPx) and superoxide dismutase (SOD)] was investigated in non-insulin-dependent diabetic patients with and without coronary heart disease (CHD), and a comparison was made for all the above parameters with non-diabetic patients with CHD. Lipid peroxide concentrations were significantly increased in both groups of diabetic patients and also in non-diabetic patients with CHD, compared to those in control subjects. Diabetic patients with CHD had higher levels of TBARS compared to those diabetics without CHD. Hyperlipidaemia and abnormal lipoprotein levels were observed in all three groups of patients. Increased total cholesterol and LDL-cholesterol were observed in diabetics with CHD compared to those without CHD. Among the erythrocyte antioxidant enzymes, CAT activity was increased, GPx activity was decreased and no change was observed in SOD activity in both groups of diabetic patients and non-diabetic patients with CHD compared to those in controls. A clear correlation was observed between the CAT activity and lipid peroxide concentrations in all the diabetic patients. These observations suggest that there are similar abnormalities in lipid metabolism and erythrocyte antioxidant enzymes in diabetic patients and non-diabetic patients with CHD.

Catalase↗
PubMed2001

Antihyperglycemic activity of Momordica cymbalaria in alloxan diabetic rats.

Aqueous, ethanolic and hexane fractions of Momordica cymbalaria fruits were prepared and given individually at different doses to different batches of rats (both normal and alloxan diabetic rats) after an overnight fast. The blood glucose levels were measured at 0, 1, 3, 5 and 7 h after the treatment. The aqueous extract of Momordica cymbalaria at a dosage of 0.5 g/kg b.w. is showing maximal blood glucose lowering effect in diabetic rats. The same dosage did not produce any hypoglycemic activity in normal rats. The antihyperglycemic activity of Momordica cymbalaria fruit was compared with the treatment of Glibenclamide, an oral hypoglycemic agent.

Animals↗
PubMed2001

Typical dermoscopic patterns of benign melanocytic nevi.

Dermoscopy often is an effective diagnostic tool for differentiating benign and malignant pigmented skin lesions. The observed dermoscopic structures and patterns of lesions provide valuable sources of information that are not accessible by routine clinical examination. Recognition and interpretation of these dermoscopic structures and patterns require training and experience. Mentioned here are some fundamental guidelines for differentiating malignant and benign lesions. Some of the classic patterns associated with a list of benign melanocytic nevi also have been illustrated. Additional research is needed to identify other patterns of these benign lesions. More importantly, analysis of the prevalence of various patterns associated with the various benign lesions will be helpful to clinicians having the responsibility of making in vivo diagnoses of benign compared with malignant melanocytic neoplasms.

Dermatology↗
PubMed2001

Hypoglycemic and antihyperglycemic activity of Syzygium alternifolium (Wt.) Walp. seed extracts in normal and diabetic rats.

Aqueous, ethanolic and hexane fractions of Syzygium alternifolium seeds were prepared and given different doses of these extracts individually to different batches of rats (both normal and alloxan diabetic rats) after an overnight fast. The blood glucose levels were measured at 0, 1, 3, 5 and 7 hours after the treatment. The aqueous extract of Syzygium alternifolium at a dosage of 0.75 g/kg b.w. is showing maximum blood glucose lowering effect in both normal and alloxan diabetic rats. The ethanol and hexane fractions are also showing hypoglycemic and antihyperglycemic activity, but the effect is significantly less than that of aqueous extract. The antihyperglycemic activity of Syzygium alternifolium seed was compared with the treatment of Glibenclamide.

Alloxan↗
PubMed2000

Inhibitory copper binding site on the spinach cytochrome b6f complex: implications for Qo site catalysis.

The isolated cytochrome (cyt) b(6)f complex from spinach is inhibited by Cu(2+) with a K(D) of about 1 microM at pH 7.6 in the presence of 1.6 microM decyl-plastoquinol (C(10)-PQH(2)) as a substrate. Inhibition was competitive with respect to C(10)-PQH(2) but noncompetitive with respect to horse heart cyt c or plastocyanin (PC). Inhibition was also pH-sensitive, with an apparent pK at about 7, above which inhibition was stronger, suggesting that binding occurred at or near a protonatable amino acid residue. Equilibrium binding titrations revealed ca. 1.4 tight Cu(2+) binding sites with a K(D) of about 0.5 microM and multiple (>8) weak (K(D) > 50 microM) binding sites per complex. Pulsed electron paramagnetic resonance (EPR) techniques were used to identify probable binding sites for inhibitory Cu(2+). A distinct enhancement of the relaxation time constant for the EPR signal from bound Cu(2+) was observed when the cyt f was paramagnetic. The magnitude and temperature-dependence of this relaxation enhancement were consistent with a dipole interaction between Cu(2+) and the cyt f (Fe(3+)) heme at a distance of between 30 and 54 A, depending upon the relative orientations of Cu(2+) and cyt f heme g-tensors. Two-pulse electron spin-echo envelope modulation (ESEEM) and 4-pulse 2-dimensional hyperfine sublevel correlation (2D HYSCORE) measurements of Cu(2+) bound to isolated cyt b(6)f complex indicated the presence of a weakly coupled nitrogen nucleus. The nuclear quadrupole interaction (NQI) and the hyperfine interaction (HFI) parameters identified one Cu(2+) ligand as an imidazole nitrogen of a His residue, and electron-nuclear double resonance (ENDOR) confirmed the presence of a directly coordinated nitrogen. A model of the 3-dimensional structure of the cytochrome b(6)f complex was constructed on the basis of sequences and structural similarities with the mitochondrial cyt bc(1) complex, for which X-ray structures have been solved. This model indicated three possible His residues as ligands to inhibitory Cu(2+). Two of these are located on the "Rieske" iron-sulfur protein protein (ISP) while the third is found on the cyt f protein. None of these potential ligands appear to interact directly with the quinol oxidase (Q(o)) binding pocket. A model is thus proposed wherein Cu(2+) interferes with the interaction of the ISP protein with the Q(o) site, preventing the binding and subsequent oxidation of plastoquinonol. Implications for the involvement of ISP "domain movement" in Q(o) site catalysis are discussed.

Benzoquinones↗
PubMed2000

Wrinkling due to mid-dermal elastolysis: two cases and literature review.

BACKGROUND: Mid-dermal elastolysis is an acquired disorder of elastic tissue clinically characterized by diffuse fine wrinkling, most often of the trunk and arms. Histologically, a clear band of elastolysis is present in the mid-dermis. OBJECTIVE: Although examples of diffuse elastolysis are well known, only a small number of patients with mid-dermal elastolysis have been reported to date. We present two patients with clinical and histological evidence of mid-dermal elastolysis, review the literature, and summarize the salient features of some common disorders of elastic tissue. METHODS: The first patient presented with fine wrinkles and papules over the upper arms, upper chest, and axillae, and demonstrated increased laxity of the eyelids. The second patient had striking wrinkles extending in a band-like pattern on her arms, upper chest, back, and abdomen. Neither one of our patients had a previous history of skin inflammation, urticaria, or any other underlying diseases related to their skin changes. Skin biopsies were taken from lesional and perilesional skin of both patients, and were stained with hematoxylin and eosin, and with elastic tissue stain. In addition, a tissue sample from Patient 1 was fixed for electron-microscopy. RESULTS: Hematoxylin and eosin stains did not demonstrate specific changes or diagnostic patterns. However, elastic tissue stains revealed a band-like loss of elastic tissue in the mid-dermis. Elastic tissue in the remaining superficial and deep dermis stained normally. Electron-microscopy was consistent with these findings and revealed significant loss of elastic tissue limited to the mid-dermis. CONCLUSION: We have presented two cases of mid-dermal elastolysis and reviewed the literature. To date, the pathophysiology of mid-dermal elastolysis had not been elucidated and no definitive therapy exists.

Adult↗
PubMed1999

Antidiabetic and hypolipidemic effects of Momordica cymbalaria Hook. fruit powder in alloxan-diabetic rats.

This study was undertaken to investigate the effect of Momordica cymbalaria fruit powder on blood glucose and other biochemical parameters in alloxan-induced diabetic rats. The treatment was given for 15 days. After the treatment, a significant reduction was observed in fasting blood glucose levels in the treated diabetic rats, but no hypoglycaemic activity in the treated normal rats. M. cymbalaria treatment showed considerable lowering of serum cholesterol and triglycerides in the treated diabetic group. There was a significant improvement in hepatic glycogen level in treated diabetic rats close to normal level after the treatment with M. cymbalaria. These results suggest that the M. cymbalaria fruit powder possesses antidiabetic and hypolipidemic effects in alloxan-induced diabetic rats.

Alloxan↗
PubMed1998

Risk of melanoma in medium-sized congenital melanocytic nevi: a follow-up study.

BACKGROUND: The risk of the occurrence of malignant melanoma (MM) in medium-sized (1.5 to 19.9 cm in diameter) congenital melanocytic nevi (CMN) is the subject of controversy. Universally accepted recommendations regarding the management of such lesions have not been made. OBJECTIVE: Our purpose was to assess the risk of MM arising in medium-sized CMN. METHODS: The study included 230 medium-sized CMN in 227 patients, first seen in a private dermatology practice from 1955 to 1996, who were followed up for MM arising within their CMNs. Criteria for entry into the study included (1) a clinically diagnosed medium-sized CMN, (2) minimum follow-up period of 1 year, and (3) a photograph of the lesion in the patient's medical record. RESULTS: No MM occurred in a medium-sized CMN during an average follow-up of 6.7 years (median, 5.8 years) to an average age of 25.5 years (median, 19.1 years). CONCLUSION: The results of this short-term follow-up study do not support the view that there is a clinically significantly increased risk for MM arising in banal-appearing medium-sized CMN or that prophylactic excision of all such lesions is mandatory. Lifelong medical observation seems a reasonable alternative for many medium-sized CMN.

Adolescent↗