The interference of medical radionuclides with occupational in vivo gamma spectrometry.

Radiation workers undergo routine monitoring for the evaluation of external and internal radiation exposures. The monitoring of internal exposures involves gamma spectrometry of the whole body (whole body counting) and measurements of excreta samples. Medical procedures involving internal administration of radioactive radionuclides are widely and commonly used. Medical radionuclides are typically short-lived, but high activities are generally administered, whereas occupational radionuclides are mostly long-lived and, if present, are found generally in relatively smaller quantities. The aim of the present work was to study the interference of some common medical radionuclides (201Tl, 9mTc, 57Co, and 131I) with the detection of internal occupational exposures to natural uranium and to 137Cs. Workers having undergone a medical procedure with one of the radionuclides mentioned above were asked to give frequent urine samples and to undergo whole body and thyroid counting with phoswich detectors operated at the Nuclear Research Center Negev. Urine and whole body counting monitoring were continued as long as radioactivity was detectable by gamma spectrometry. The results indicate that the activity of medical radionuclides may interfere with interpretation of occupational intakes for months after administration.

Validity of chromium-51 labelling of human erythrocytes as an assay for their survival after photodynamic therapy in vitro for blood sterilization.

Labelling of human erythrocytes with 51CrO42- is used as an assay for survival of red blood cells (RBC) in the circulation. To ascertain whether the assay is valid for RBC treated with sulfonated aluminium phthalocyanine and red light, a procedure designed for viral deactivation in RBC concentrates, we followed release of 51Cr and haemolysis after photosensitization. The results shows that 51Cr release does not occur until about 3 h prior to haemolysis. The absence of 51Cr loss from cells not committed to lysis indicates that the label technique is valid for determination of survival photosensitized RBC in the circulation.

A convenient synthesis of N-succinimidyl-3-iodo-[125I]benzoate, a reagent for protein iodination.

A convenient procedure has been developed for the synthesis of N-succinimidyl-3-iodo-[125I]benzoate. The procedure involved the synthesis of chloromercuribenzoic acid, its esterification with N-hydroxysuccinimide (NHS) and exchanging the mercury moiety with radioactive iodine in the presence of an oxidant. The obtained product was attached to human serum albumin and its stability was compared with Chloramine-T (Ch-T) radioiodinated protein. The results indicated that the reagent-radiolabeled protein was stable for longer periods and the deiodination rate was significantly lower.

The role of glycolysis and univalent ions in phthalocyanine-sensitized photohaemolysis of human erythrocytes.

Phthalocyanines sensitize human erythrocytes to red light in vitro and in vivo. The mechanism of photosensitization of haemolysis of red blood cells was studied using haemoglobin release in vitro as an endpoint. We have previously shown that the cation present in the incubation medium determines the rate of photohaemolysis, with the rate increasing in the order Li+, Na+, K+, Cs+, Rb+. With halogen anions, the rate increases in the order F-, Cl-, Br-. With F- in isotonic solution the rate was about two orders of magnitude slower than with Cl-, so that haemolysis was practically prevented. Fluoride slowed haemolysis at very low concentrations (less than 1 mM) with an apparent K1 of 0.1 mM in isotonic NaCl. Most of the effect disappeared when F- was added after light exposure, with a half-time of 1 min. The effect of F- was specific to phthalocyanine. Neither Photofrin-induced photohaemolysis nor gramicidin-induced haemolysis were inhibited by fluoride. Addition of 10 mM deoxyglucose prior to photosensitization enhanced haemolysis and reduced cellular ATP levels by about 50% compared to controls containing glucose. Haemolysis was preceded by a reduction in ATP levels in the presence of both glucose and deoxyglucose. No significant decrease in ATP levels was found following light exposure in the presence of 0.75 mM F-. It is concluded that glycolysis and ATP are important in preventing photohaemolysis. The protective effect of F- may be related to its inhibition of a fast early reaction which triggers the events leading to photohaemolysis induced by phthalcyanine.

Neonatal low-dose gamma irradiation-induced impaired fertility in mature rats.

The reproductive capacity of mature rats at the age of 8 days was studied following neonatal exposure to 0.06 Gy dose of gamma-radiation. Decreased litter size and reduced body weight of the pups on weaning day, but not at parturition, were observed in female rats. The reduced litter size was not associated with impaired ovulation, impaired uterine implantation or mortality in utero, but resulted from increased death rate or at near parturition. Of the neonatally irradiated males 29% were found to be sterile and had degenerated or necrotic testes. The testicular damage and the reduced growth rate of the offspring of the irradiated females demonstrate the extreme sensitivity of the immature reproductive system to ionizing radiation, even at very low doses.

The reproductive system of male rats exposed to very low doses of ionizing radiation, 1: Hormonal profile of animals exposed after sexual maturity.

Adult male rats were treated with a single, whole body exposure to a dose of 0.001, 0.01 or 0.1 Gy (1 Gy = 100 rad). The animals were sacrificed 1, 7, 30, 100 or 180 days following exposure. Serum testosterone, serum and hypophyseal LH, FSH and prolactin as well as hypothalamic LHRH were measured. In the 0.1 Gy irradiated rats, serum LH and FSH were 100% higher and serum prolactin was 30% lower as compared to controls, 30 days after irradiation. The concentrations of these hormones remained significantly different from control values even after 180 days after exposure. On the other hand, the hypophyseal content of LH, FSH and prolactin decreased in the 0.1 Gy treated rats, 100 days after irradiation. In the group of the 0.01 Gy irradiated rats, serum FSH increased by 70% and hypophyseal FSH decreased. No changes were observed in serum testosterone and hypothalamic LHRH in any of the irradiated groups and no changes were observed in the group exposed to 0.001 Gy. It may be concluded that a long term damage to the reproductive system of the male rat was induced by a single, whole body exposure to 0.1 Gy of gamma radiation.

Multiple labelling of immunoglobulin G, albumin and testosterone with a fluorescent terbium chelate for fluorescence immunoassays.

Human immunoglobulin G, human serum albumin and testosterone were labelled with the 4-aminosalicylic acid derivative of diethylenetriaminepentaacetic acid complexed with terbium ions. An exceptionally large amount of label, of the order of a few hundred moles of complex per mole of analyte, could be conjugated to the compounds tested by the use of poly-L-lysine. Self-quenching appears to be minimal, even with this high local concentration of fluorophores. The tracers were stable at 4 degrees C, and gave competitive calibration graphs at physiological concentrations.