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K Raman

Publications and source records attributed to K Raman.

At least 19 recordsLinked to original sources
PubMed2002

Fast nuclear spin relaxation in hyperpolarized solid 129Xe.

We report extensive new measurements of the longitudinal relaxation time T1 of 129Xe nuclear spins in solid xenon. For temperatures T<120 K and magnetic fields B>0.05 T, we found T1 on the order of hours, in good agreement with previous measurements and with the predicted phonon-scattering limit for the spin-rotation interaction. For T>120 K, our new data show that T1 can be much shorter than the phonon scattering limit. For B = 0.06 T, a field often used to accumulate hyperpolarized xenon, T1 is approximately 6 s near the Xe melting point T(m) = 161.4 K. From T = 50 K to T(m), the new data are in excellent agreement with the theoretical prediction that the relaxation is due to (i) modulation of the spin-rotation interaction by phonons, and (ii) modulation of the dipole-dipole interaction by vacancy diffusion.

Journal Article↗
PubMed1993

Substituted thiosemicarbazides and corresponding cyclized 1,3,4-oxadiazoles and their anti-inflammatory activity.

Several 1-(4-biphenoxyacetyl)-4-substituted arylthiosemicarbazides and their corresponding cyclized 2-(4-biphenoxymethyl)-5-arylamino-1,3,4- oxadiazoles were synthesized and characterized by elemental analyses and IR, mass, and nuclear magnetic resonance spectra. All compounds were evaluated for anti-inflammatory activity by determining their ability to provide protection against carrageenin-induced edema in rat paw. The anti-inflammatory activity possessed by substituted thiosemicarbazides [100 mg/kg, intraperitoneal(ip)] ranged from 22 to 68%, whereas substituted 1,3,4-oxadiazoles (100 mg/kg, ip) provided protection of 10-76%. Hydrocortisone (10 mg/kg, ip) and oxyphenbutazone (40 mg/kg, ip), used as standard reference drugs, decreased edema in rat paw by 44.6 and 52.9%, respectively. All compounds (1 mM) possessed antiproteolytic activity that was reflected by their ability to cause in vitro inhibition of trypsin-induced hydrolysis of bovine serum albumin. This inhibition ranged between 43 and 72% for substituted thiosemicarbazides and 30 and 83% for substituted 1,3,4-oxadiazoles.

Animals↗
PubMed1989

Anti-inflammatory activity of substituted 1,3,4-oxadiazoles.

Various 2-(4-biphenoxymethyl)-5-arylamino-1,3,4-oxadiazoles were synthesized by cyclization of the corresponding 1-(4-biphenoxyacetyl)-4-substituted thiosemicarbazides. These compounds were characterized by their elemental analyses and infrared, mass, and nuclear magnetic resonance spectral data. All substituted thiosemicarbazides (100 mg/kg, ip) and cyclized substituted oxadiazoles (100 mg/kg, ip) possessed anti-inflammatory activity, as reflected by their ability to provide protection against carrageenin-induced edema in the rat paw which ranged from 28 to 68% and 36 to 76%, respectively. Cyclization of the substituted thiosemicarbazides, in general, resulted in an increase in the anti-inflammatory activity of their corresponding substituted oxadiazoles, with the exception of those containing 2,4-dimethyl and 3,4-dimethyl substituents in their molecular structure. Hydrocortisone (10 mg/kg, ip) and oxyphenbutazone (40 mg/kg, ip) were used as the standard reference drugs and these provided 45 and 53% protection, respectively. All compounds (1 mM) possessed antiproteolytic activity and the in vitro inhibition of trypsin-induced hydrolysis of bovine serum albumin ranged from 13 to 75% for substituted thiosemicarbazides and 39 to 70% for substituted oxadiazoles. There was no relationship between the anti-inflammatory activity of substituted thiosemicarbazides and substituted oxadiazoles and their antiproteolytic effectiveness. The low toxicity of these compounds was reflected by their high approximate LD50 values, ranging from 500 to 1000 mg/kg.

Animals↗
PubMed1988

Impermeant potential-sensitive oxonol dyes: II. The dependence of the absorption signal on the length of alkyl substituents attached to the dye.

We have measured the potential-dependent light absorption changes of 43 impermeant oxonol dyes with an oxidized cholesterol bilayer lipid membrane system. The size of the signal is strongly dependent on the chain length of alkyl groups attached to the chromophore. Dye molecules with intermediate chain lengths give the largest signals. To better understand the dependence of the absorbance signal on alkyl chain length, a simple equilibrium thermodynamic analysis has been derived. The analysis uses the free energy of dye binding to the membrane and the "on-off" model (E.B. George et al., J. Membrane Biol., 103:245-253, 1988a) for the potential-sensing mechanism. In this model, a population of dye molecules in nonpolar membrane binding sites is in a potential-dependent equilibrium with a second population of dye that resides in an unstirred layer adjacent to the membrane. Dye in the unstirred layer is in a separate equilibrium with dye in the bulk bathing solution. The equilibrium binding theory predicts a "sigmoidally shaped" increase in signal with increasing alkyl chain length, even for very nonpolar dyes. We suggest that aggregation of the more hydrophobic dyes in the membrane bathing solution may be responsible for their low signals, which are not predicted by the theory.

Adsorption↗
PubMed1983

Venous thrombosis after elective hip replacement--the influence of preventive intermittent calf compression and of surgical technique.

The effect of preventive intermittent calf compression on the incidence, distribution and extent of venous thrombosis after elective hip replacement was examined by randomized trial in 90 patients who were screened for postoperative thrombosis with 125I-fibrinogen leg scanning and impedance plethysmography, followed by routine venography on the seventh postoperative day. Venography showed that leg compression reduced the incidence of calf vein thrombosis from 45 per cent (21/47) in untreated patients to 16 per cent (7/43) (P less than 0.005), but not that of proximal (i.e. popliteal or femoral) vein thrombosis, which occurred in 23 per cent of treated and 26 per cent of untreated patients. However, proximal vein thrombosis appeared to be less extensive in treated patients. Proximal vein thrombosis was found in 40 per cent of patients who had hip replacement by a modified Charnley technique (17/43 patients), and 9 per cent of patients in whom a posterior surgical approach was used (4/43 patients) (P less than 0.005), strongly suggesting that surgical technique may influence the proximal vein thrombosis rate after elective hip replacement.

Aged↗
PubMed1979

Anticonvulsant, analgesic and monoamine oxidase inhibitory properties of newer 4-hydroxy-4-phenylpiperidinocarbamides.

Fourteen 1-[N-acetyl(4-hydroxy-4-phenyl-piperidino)]-3-aryl carbamides were synthesized, characterized and evaluated for their anticonvulsant, analgesic and monoamine oxidase inhibitory properties. All carbamides (100 mg/kg, i.p.) provided 20--60% protection against pentylenetetrazol-induced seizures in mice. The analgesic activity possessed by these carbamides, with the exception of two compounds, was reflected by their ability to provide 17--67% protection against tail pinch response in mice. All carbamides (1 mM) inhibited (5--90%) in vitro activity of rat brain monoamine oxidase. The low toxicity of these carbamides was reflected by their higher approximate LD50 values which ranged from 500 - greater than 1000 mg/kg.

Analgesics↗
PubMed1978

Anti-inflammatory and antiproteolytic properties of 2-[acyl-N-(substituted benzylidene)hydrazino]5-phenyltetrazoles.

Ten 2-[acyl-N-(substituted benzylidene)hydrazino]5-phenyltetrazoles were synthesized, characterized and evaluated for anti-inflammatory and antiproteolytic activity. The protection afforded by these tetrazoles at a dose of 100 mg/kg i.p., against carrageenin-induced edema in rats, ranged from 11 to 46%. Oxyphenbutazone (40 mg/kg i.p.), and hydrocortisone (10 mg/kg i.p.), used as reference drugs, exhibited protection of 54 and 47%, respectively. The antiproteolytic activity of these tetrazoles, as reflected by their ability to inhibit trypsin-induced hydrolysis of bovine serum albumin, ranged from 17 to 57%. The antiproteolytic activity was found to be unrelated to the anti-inflammatory activity possessed by these tetrazoles.

Animals↗
PubMed1978

Antihemolytic, antiproteolytic and anticonvulsant properties of 10-substituted hydrazonoacetyl phenothiazines.

Twelve 10-substituted hydrazonoacetyl phenothiazines were synthesized, characterized and evaluated for their antihemolytic, antiproteolytic and anticonvulsant properties. The degree of protection of the in vitro hypoosmotic hemolysis of human red blood cells by these compounds ranged from 30-65%, at a final concentration of 1 mM. All phenothiazine derivatives (1 mM) possessed antiproteolytic activity which was reflected by 25-71% protection observed with these compounds against in vitro trypsin-induced hydrolysis of bovine serum albumin. These compounds at a dose of 100 mg/kg provided 20-80% protection against pentylenetetrazol-induced convulsions in mice. All phenothiazine derivatives possessed low toxicity which was reflected by their approximate LD50 values ranging from 500- greater than 1000 mg/kg.

Animals↗
PubMed1978

Selective inhibition of xanthine oxidase by substituted pyridopyrimidines.

Six 2-methyl-3-substituted-pyrido-(2,3-d)-pyrimidine 4 (3H)-ones were synthesized and evaluated for their ability to inhibit xanthine oxidase and other purine catabolizing enzymes of rat liver. All compounds inhibited xanthine oxidase selectively when tested at a final concentration of 0.5 mM in vitro. Adenosine deaminase, guanosine deaminase and guanine deaminase were unaffected. The inhibition of xanthine oxidase was found to be competitive in nature.

Aminohydrolases↗
PubMed1978

Substituted oxothiazolyl acetic acids as antiinflammatory agents.

Eight 2-arylimino-3-[/3-(3,4-dimethoxyphenyl) ethy1]-4-oxothiazol-5-yl-acetic acids were synthesized, characterized, and evaluated for their antiinflammatory and antiproteolytic properties. The toxocity of the compounds was reflected by their approximate LD50 values.

Acetates↗
PubMed1978

Anticonvulsant activity and monoamine oxidase inhibitory and antihemolytic properties of some newer 4-phenylpiperidino carbamides.

Six 1-[N-acetyl(4-phenylpiperidino)]-3-aryl carbamides were synthesized, characterized and evaluated for their anticonvulsant, monoamine oxidase inhibitory and antihemolytic properties. These compounds (100 mg/kg, i.p.) provided 10--80% protection against pentylenetetrazol-induced seizures in mice. All carbamides (1 mM) inhibited (34--82%) in vitro activity of rat brain monoamine oxidase and provided 18--51% protection against in vitro hypoosmotic hemolysis of human red blood cells at a final concentration of 1 mM. Low toxicity of these carbamides was reflected by their high approximate LD50 values.

Animals↗
PubMed1978

Monoamine oxidase inhibitory and anticonvulsant properties of some newer thiosemicarbazones.

Eight 4-aryl-1-(2,3,4-trihydroxy acetophenone)-3-thiosemicarbazones were synthesised and evaluated for their ability to inhibit rat brain monoamine oxidase (MAO). All compounds exhibited concentration dependent inhibition of enzyme. The degree of enzyme inhibition was also evaluated on the basis of their I50 and I50/(S) values. Preincubation of these compounds with the enzyme system for varying lengths of time prior to the addition of substrate in no way altered their degree of inhibition. Kinetic study carried out with 4-(2-methoxyphenyl)-1-(2,3,4-trihydroxyacetophenone)-3-thiosemicarbazone revealed a competitive nature of inhibition. Anticonvulsant activity exhibited by these thiosemicarbazones (100mg/kg, i.p.) against pentylene-tetrazol-induced seizures ranged between 10-60%. Low toxicity possessed by these compounds was reflected by their approximate LD50 values ranging from 750 mg/kg to greater than 1000 mg/kg.

Acetophenones↗
PubMed1977

[Cardioplegia according to Bretschneider for valve replacement: clinical experiences and electronmicroscopical results (author's transl)].

We report about clinical experiences with the cardioplegia according to Bretschneider combined with deep selective hypothermia of the heart in 44 patients. Before, during and after cardioplegia we made biopsies from the left ventricle of 6 patients for electronmicroscopical examinations. Besides the mitochondrial changes already known we saw a break-down of the nexuses. We discuss the importance if these changes for the action of the cardioplegia. Both changes seemed to be reversible. The clinical results and the immediate and later postoperative follow-up demonstrate, that with the described technique a good myocardial protection can be done. This procedure allows operating with a low risk at a completely arrested and relaxed heart until 130 minutes.

Adult↗