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Biomedical subjects

K Jeyasingh

Publications and source records attributed to K Jeyasingh.

At least 19 recordsLinked to original sources
PubMed1988

Influence of airway calibre on the intrapulmonary dose and distribution of inhaled aerosol in normal and asthmatic subjects.

We investigated the relationship between airway calibre and the dose and distribution of inhaled aerosol in ten normal and six asthmatic subjects. Subjects inhaled saline aerosol containing 99mTcO4 delivered from a nebulizer connected to a dosimeter, and the lung fields were scanned with a gamma-camera. Right lung dose (RLD) was calculated as percentage of total dose. Intrapulmonary distribution was measured as penetration index (PI) (peripheral zone counts/central zone counts). Asthmatics had a significantly lower PI than normal subjects and there was a linear relationship between PI and baseline specific airway conductance (sGaw, p less than 0.001), and forced expiratory volume in one second (FEV1, p less than 0.05). After bronchodilatation with salbutamol (delta sGaw 101 +/- 31%, mean +/- SEM), PI increased from 0.73 +/- 0.11 to 1.09 +/- 0.15 (p less than 0.05); after bronchoconstriction with methacholine (delta sGaw 62.6 +/- 2.9%), PI decreased from 1.42 +/- 0.24 to 1.06 +/- 0.22 (p less than 0.05). Changes of PI were correlated with changes in sGaw and FEV1 (n = 20, p less than 0.001) but changes of RLD and changes in airway calibre were not. The distribution of inhaled aerosol, but not the dose, is largely dependent on airway calibre. The differences in PI between normal and asthmatic subjects may at best be explained by the differences in central airway calibre.

Administration, Inhalation↗
PubMed1979

Tissue distribution and tumour localization of 99m-technetium-labelled liposomes in cancer patients.

The possible use of liposomes (phospholipid vesicles) to direct cytotoxic drugs to tumours has led us to investigate the tissue localization of i.v. injected 99m-Tc-labelled liposomes in cancer patients. Twenty mg or 300 mg doses of liposomal lipid (7:2:1 molar ratio of phosphatidylcholine : cholesterol : phosphatidic acid) were used in a study of 13 patients with advanced cancer and one with polycythaemia rubra vera (PRV). In all cases except the patient with PRV the major site of uptake of the label was the liver and spleen. In the patient with PRV the liver uptake was greatly reduced and the major site of uptake was found in regions corresponding to marrow. With the exception of one patient with a primary hepatoma, there was no significant tumour uptake of the label.

Cholesterol↗
PubMed1978

Possible tumor localization of Tc-99m-labeled liposomes: effects of lipid composition, charge, and liposome size.

The possible in vivo distribution of liposomes after they have been directly labeled with Tc-99m has been studied in rats bearing the Walker 256 carcinoma. The importance of lipid composition, charge, and size of liposome were studied with respect to possible tumor-localizing properties. Tumor uptake was best with small, fluid-membrane, negatively charged liposomes, as indicated by the distribution of the Tc-99m label. The uptake was visualized on scintigrams.

Amines↗
PubMed1975

Phosphate compounds in bone scanning.

Bone scanning with radioactive isotopes has been used to study a wide variety of disorders. Recently certain phosphate compounds, labelled with technetium, have been used as bone scanning agents. The comparative merits of three technetium-labelled phosphate compounds currently available for bone scanning--pyrophosphate, tripolyphosphate and ethylhydroxydiphosphonate (EHDP) have been compared in rabbits. Each substance was injected into ten rabbits and blood was withdrawn at regular intervals. The animals were killed at four hours and the blood and tissue samples were assayed for radioactivity. The results show that EHDP has a more rapid blood clearance than the other two agents, with a resultant improvement in the bone to soft-tissue ratio. Of the three substances investigated technetium-labelled EHDP was the best and might allow the technique of scanning to be used on a wide scale for the general study of bone and its pathology.

Animals↗
PubMed1972

Criteria in radioisotope detection of venous thrombosis.

Forty-one patients out of a larger series undergoing elective surgery were examined for the presence of venous thrombosis in the legs by means of the (125)I-fibrinogen technique. The radioisotope data were analysed by three different methods. The percentage uptake was calculated and, by the generally accepted difference of 15%, 22 patients had evidence of thrombosis. The statistical index, which takes account of the errors due to radioactivity counting inherent in the percentage uptake calculation, indicated thrombosis in 36 patients. The relative uptake index, which allows for the errors due to unequal distribution of radioactivity throughout the normal limb as well as the errors due to radioactivity counting, provided evidence of thrombosis in a total of 34 patients, compared with only 22 patients when assessed by the "15%" criterion.

Diagnostic Errors↗