Biomedical subjects

R Radhakrishnan

Publications and source records attributed to R Radhakrishnan.

62 records · Page 4Linked to original sources

PubMed1979

A computer program for topographic analysis of biomolecular systems.

This program essentially generates a picture of a space filling molecular model. By precise simulation of the intersections between atoms, leaving out the 'hidden line', a good perspective is produced. Additional three dimensional information is provided by simulating reflection spots on the surface. This program has been used to visualise three dimensional surface features of biologically important molecules (e.g., valinomycin). With slight modification the program can be used to visualise enzyme active sites and receptor surfaces. It can also be used to create animated motion pictures of molecular dynamics.

Chemical Phenomena↗

PubMed1979

Intermolecular crosslinking of fatty acyl chains in phospholipids: use of photoactivable carbene precursors.

Phospholipids containing photolysable carbene precursors (beta-trifluoro-alpha-diazopropionoxy and m-diazirinophenoxy groups) in omega-positions of sn-2 fatty acyl chains were prepared. Photolysis of their vesicles produced crosslinked products in 40-60% yields. Crosslinking was mostly intermolecular and occurred by carbene insertion into the C-H bonds of a second fatty acyl chain. Crosslinking products were characterized by (i) their gel permeation behavior, (ii) analysis of products formed by base-catalyzed transesterification, (iii) degradation with phospholipases A2 and C, (iv) gas chromatography/mass spectrometry, and (v) use of mixtures of phospholipids carrying the carbene precursors and a phospholipid containing radioactively labeled fatty acyl groups. Nitrenes generated from the aliphatic or aromatic azido groups in phospholipids were unsatisfactory for forming crosslinks by insertion in C-H bonds.

Chemical Phenomena↗

PubMed1977

Glycerophospholipid synthesis: improved general method and new analogs containing photoactivable groups.

Current methods for phospholipid synthesis involving acylation of sn-glycero-3-phosphorylcholine, lysolecithins, and related glycerophosphate esters are not satisfactory. With N,N-dimethyl-4-aminopyridine as a catalyst and moderate amounts of fatty acid anhydrides (1.2-1.5 mol equiv per OH group), diacyl or 1,2-mixed diacylphosphatidylcholines, N-protected phosphatidylethanolamines, and phosphatide acids now can be conveniently prepared in high yields (75-90%). New phospholipids containing photoactivable groups, such as trifluorodiazopropionyl, diazirinophenoxy, 2-nitro-4-azidophenoxy, m-azidophenoxy, and alpha, beta-unsaturated keto groups, in the fatty acyl chains have been prepared. These phospholipids are of interest in studies of lipid-lipid and lipid-protein interactions in biological membranes.

Acylation↗

PubMedDate not supplied

In vivo study of angiotensin II tachyphylaxis in freely moving normo- and hypertensive rats.

In vivo tachyphylaxis to the angiotensin II-induced increase in mean arterial blood pressure was studied in conscious freely moving rats by telemetry blood pressure monitoring. The animals studied were the normotensive Sprague Dawley rats (SD), the spontaneously hypertensive rats (SHR), and two models of experimentally-induced hypertensive rats, namely, the left renal artery stenosed SD hypertensive rat (LRAS) and the deoxycorticosterone acetate/salt SD hypertensive rat (DOCA). Two consecutive dose-response curves to angiotensin II in each rat were obtained. The increase in mean arterial pressure (MAP) at each bolus dose of the first dose-response curve was found not to be significantly different from the corresponding value of the second dose-response curve in the four models of rat studied (i.e. no significant difference in the intra-rat response to AII). In addition, the slope of the dose-response curve is similar for each model of rat indicating that there was no inter-model variation to the response of AII. The results show that the response to AII in the SD and the three models of hypertensive rats was remarkably similar and that they did not develop tachyphylaxis to the pressor response of AII at concentrations ranging from circulating level of 0.0005 nmoles/kg (10(-11) M) to 10 nmoles/kg (2 x 10(-7) M). This was despite the fact that the SD had normal blood pressure and the genesis of hypertension in each model of the hypertensive rats was different.(ABSTRACT TRUNCATED AT 250 WORDS)

Angiotensin II↗

PubMedDate not supplied

Recurrent delusions of pregnancy in a male.

Delusions of pregnancy in men have been reported rather infrequently. This case report is of a male schizophrenic patient who developed a delusion of pregnancy on two successive occasions each time when his wife became pregnant. The authors view briefly various aetiological hypotheses of delusions of pregnancy and whether the couvade phenomenon had any role in the origin of this delusion.

Adult↗

PubMedDate not supplied

Nanocomposite magneto-rheological fluids with uniformly dispersed Fe nanoparticles.

A systematic study of the magnetic and rheological properties of magneto-rheological (MR) fluids containing micron-size and nano-size iron particles is presented. The MR fluids were prepared with hydraulic oil as the carrier liquid and lecithin as an effective surfactant medium that promotes uniform particle dispersion. Magnetic measurements on micron-, hybrid-(nano + micron), and nano-MR fluids clearly indicate that the partial replacement of the micro-size particles by nanoparticles results in a better suspension and robust chain formation under applied external magnetic fields. For nano-MR fluids, the measured yield stress was found to be lower than micron-MR fluids. However, better flow properties and sharper magnetic switching make nanoparticle-based MR fluids appealing for microfluidics device applications where higher yield stress is not required.

Crystallization↗

PubMedDate not supplied

Myiasis in filarial lymphoedema due to Chrysomyia bezziana.

In patients with filarial lymphoedema of the limbs, infestation by maggots is extremely rare. We saw three patients with lymphoedema who harboured Chrysomyia bezziana in leg ulcers and in one of them 128 maggots were recovered. A course of local dressing, antibiotics and anti-inflammatory drugs resulted in healing of the wounds. Ulcers in patients with lymphoedema should be carefully tended with cleaning and dressing otherwise myiasis may supervene.

Adult↗

PubMedDate not supplied

Fistulization of hepatic hydatid cyst into duodenum.

Though rupture of hepatic hydatid cyst is not uncommon, fistulization into the gut following rupture is rare. We report a case in whom a hepatic hydatid cyst ruptured into the first part of the duodenum.

Adult↗