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Biomedical subjects

R Tawashi

Publications and source records attributed to R Tawashi.

At least 37 records · Page 2Linked to original sources
PubMed1982

Tack behavior of coating solutions I.

The tackiness of various tablet coating solutions was determined using a parallel plate technique with a tensile testing machine in conjunction with an oscilloscope where the separation force was displayed as a function of time. Measurements were made at various rates of separation on liquid films of constant thickness. Results showed that the force required to split a liquid film increases with an increase in rate of separation, and that tackiness increases with an increase in viscosity. The relation between tack and viscosity was not linear, and a modified Stefan equation was proposed.

Chemistry, Pharmaceutical↗
PubMed1982

Growth and characterization of calcium oxalate dihydrate crystals (weddellite).

Conditions are given for the growth of calcium oxalate dihydrate crystals (weddellite) in aqueous solution. The crystals obtained were characterized by scanning electron microscopic, spectroscopic, and thermal methods. The dissolution kinetics and electrophoretic mobility were determined; the thermodynamically unstable calcium oxalate dihydrate had a higher dissolution rate and a lower zeta potential than the monohydrate and underwent a phase transformation into the more stable calcium oxalate monohydrate. The results obtained on the chemical stability and the surface charge of calcium oxalate dihydrate offered additional information for assessing the current theories on the formation of calcium oxalate renal stones.

Calcium Oxalate↗
PubMed1982

Crystallisation of calcium oxalate dihydrate in normal urine in presence of sodium copper chlorophyllin.

A method is described for the growth of calcium oxalate dihydrate in normal urine. Soluble chlorophyllin, at a concentration of 20 microgram/ml inhibited the crystallisation and the growth kinetics of the dihydrate crystals. The inhibitory capacity of chlorophyllin was compared with previous results. Data obtained suggest that the food and drug colourant chlorophyllin might be useful in the treatment of calcium oxalate stone disease.

Calcium Oxalate↗
PubMed1982

Study of the microstructure of renal stones: uric acid and calcium oxalate.

This paper represents the results of experimental study on the microstructure of uric acid and calcium oxalate crystallites in renal stones. The size distribution parameters and morphological characteristics of the microcrystals forming the stone were determined using SEM and image analysing system. Information on the fabric of the renal stones examined indicates that the mean volume diameter is 15.5 microns for uric acid and 32 microns for calcium oxalate stones. The polydispersity index gamma, the shape factor phi, and the distribution of particle shape show close similarity. Quantitative studies on stone microstructure could furnish valuable information on stone genesis.

Calcium Oxalate↗
PubMed1980

Size distribution characteristics of mineral phase in renal stones.

The size distribution of the mineral phases in three renal stones (whewellite, struvite, and whitlockite) was determined using a particle-counting technique after removal of the organic matrix. The multisized crystallites of the investigated stones revealed close similarity in size distribution characteristics. Whewellite size parameters were in good agreement with the parameters of calcium oxalate monohydrate crystals formed in the kidneys of rats injected with L-4-hydroxyproline. However, these parameters differed significantly from the values calculated from the size distribution of calcium oxalate crystals voided in the urine of recurrent stone formers. The data obtained suggest that critical size distribution characteristics may be instrumental in causing the mineral phase to agglomerate and adopt a close packing in renal stones.

Animals↗
PubMed1980

Effect of the organic matrix on the dissolution of uric acid stones.

Surface dissolution from a rotating disk of anhydrous uric acid crystals and a uric acid stone was determined at different pH levels and agitation intensities. The resistance of the organic matrix to the dissolution of uric acid from the stone was quantitatively measured. The significant effect of fluid motion on the matrix resistance is demonstrated.

Chemical Phenomena↗
PubMed1980

Effect of sodium copper chlorophyllin on the formation of calcium oxalate crystals in rat kidney.

We induced the deposition of calcium oxalate crystals in rat kidney by intraperitoneal administration of 4-hydroxy-L-proline or sodium oxalate and studied the amounts and size distribution characteristics of the deposited crystals. Intravenous administration of sodium copper chlorophyllin inhibited the deposition and growth of calcium oxalate crystals induced by 4-hydroxy-L-proline or sodium oxalate. This finding may be of importance in calcium oxalate urolithiasis.

Animals↗
PubMed1980

Growth retardation of weddellite (calcium oxalate dihydrate) by sodium copper chlorophyllin.

We studied the growth of calcium oxalate dihydrate crystals (weddellite) in simulated urine and its transformation into the more stable monohydrate (whewellite). Sodium copper chlorophyllin in a concentration of 100 microgram per ml inhibited the growth of calcium oxalate dihydrate crystals in simulated urine. The size distribution parameters of the dihydrate crystals in the presence and absence of chlorophyllin suggest that soluble chlorophyllin could be of clinical significance in calcium oxalate urolithiasis.

Calcium Oxalate↗
PubMed1978

Methylene blue as an inhibitor of stone formation.

Kinetics of growth and dissolution of calcium oxalate monohydrate were examined in the presence of small concentrations of methylene blue. The data presented show moderate retardation in growth and dissolution rates. It was also found that methylene blue decreased the decalcification rate of calcium oxalate renal calculi. The implications of these findings in the treatment of urolithiasis are discussed.

Calcium↗
PubMed1978

Growth retardation of calcium oxalate by sodium copper chlorophyllin.

Earlier reports from our laboratories described the inhibitory effect of Mg++ and pyrophosphate on the dissolution and growth of calcium oxalate. In this report, growth of Ca oxalate in presence of very low concentration of chlorophyllin was followed by the Coulter counter and a multichannel analyser. The effect of chlorophyllin concentration on crystal formation was studied at different levels of supersaturation. A concentration of 0.1 microgram/ml produced a remarkable retardation of the induction period and the growth rate. The findings obtained in this study are discussed in the light of the crystal poisoning theory. Comparison was made between chlorophyllin and other growth inhibitors.

Calcium↗
PubMed1977

Calcite growth under controlled diffusion.

The growth of calcite was studied in a gelatin-gel medium under variable environmental conditions by 2 different methods. The results suggest that the organic matrix, the temperature, the diffusion fluctuation depending on ionic concentrations, and the presence of additives exert a fine control on the evolution of single crystals, polycrystalline aggregates, and highly structured concretions of calcite.

Calcification, Physiologic↗
PubMed1977

Scanning electron microscopic study of calcium oxalate concretions grown in gel system and calcium oxalate stones.

Calcium oxalate concretions grown in gelatin gel medium, and calcium oxalate renal stones were studied by polarized light and scanning electron microscopy. In both cases, the results obtained confirm that the surface crystals have random axial orientation and that the gross configuration seems to be determined by the fibrous organic matrix. In vitro concretions grown in the gelatin gel medium are more resistant to EDTA demineralization and to ultrasonic irradiation than calcium oxalate stones.

Calcium↗
PubMed1976

Retardation of dissolution and growth of calcium oxalate monohydrate.

The kinetics of dissolution and growth of calcium oxalate monohydrate were examined in the presence of small concentrations of pyrophosphate, chlorophyll, and other agents. Data presented show that the retardation in mass transport in both processes is controlled by the nature of the additive, its concentration, and the way the additives are combined in the dissolution medium. Dissolution was studied using a particle counter method, and growth was conducted in a gel system under the slow diffusion of the reacting ions. Results obtained show that chlorophyll is more active than other inhibitors studied and suggest a higher surface adsorption intensity on the primary sources of the crystal surface.

Chlorophyll↗
PubMed1975

Growth of calcium oxalate in gel systems.

Methods are described for growing calcium oxalate in silica and gelatin gels under different conditions. The results obtained indicate that, in silica gel, calcium oxalate grows into single individual crystals, twins, and rosettes. Bipyramidal calcium oxalate dihydrate crystals similar to those present in the urine of stone formers were prepared in the silica gel system. The gelatin gel offered a suitably structured substrate on which calcium oxalate monohydrate crystals grow into aggregates. The orientation pattern of calcium oxalate crystals suggests that the growth process is controlled by the stereospecificity of the gelatin medium supporting growth.

Calcium↗