Body Wt Day Research Articles

Arsenic speciation in Australian-grown and imported rice on sale in Australia: implications for human health risk.

Rice is an important route of arsenic (As) exposure to humans, especially populations with rice-based diets. Human health risk of As varies greatly with rice variety and country of origin. The purpose of the present study was to determine total and speciated As in Australian-grown and imported rice on sale in Australia to assess their health risk to consumers. The total As (tAs) concentrations in Australian-grown organic brown, medium grain brown, and organic white rice were 438±23, 287±03, and 283±18 μg kg(-1) dry weight (d wt), respectively. In Bangladeshi, Indian, Pakistani, and Thai rice imported and on sale in Australia, tAs concentrations were 56±05, 92±10, 82±06 and 172±24 μg kg(-1), respectively. Asian rice contained mainly inorganic As (iAs; 86-99%), whereas 18-26% of the tAs in Australian-grown rice was dimethylarsinic acid (DMA). Relatively higher concentrations of tAs in Australian-grown rice than that in imported rice of Asian origin suggest that Australian-grown rice may be a health risk for the consumers. It was estimated that Australian-grown organic brown rice can contribute up to 98% of the FAO/WHO recommended maximum tolerable daily intake limit of iAs (2.1 μg kg(-1) body wt day(-1)) for Asian immigrants. However, other Australian consumers including European immigrants are unlikely to be at risk to As from rice diets due to their lower rice consumption rates than that of Asian immigrants. The risk assessment showed that imported rice on sale in Australia was likely to pose a lower health risk to consumers than Australian-grown rice.

Effect of olive pomace extracts on hyperlipidaemia

In this study, we have examined the hypolipidemic effect of olive pomace extracts. Identification and quantitation of maslinic acid and oleanolic acid as the potentially effective components of the pomace extracts were carried out by high performance liquid chromatography methods. Hyperlipidaemia was induced in male Sprague Dawley rats by feeding them with a high cholesterol diet for 30 days. The olive pomace extracts were supplemented (200 mg kg−1 body wt day−1) for 15 days. The levels of serum total cholesterol, triglyceride, high density lipoprotein-cholesterol, low density lipoprotein-cholesterol, aspartate aminotransferase and alanine aminotransferase increased in rats with hyperlipidaemia. Treatment with the olive pomace extracts significantly modulated the abnormalities induced by hyperlipidaemia. Lipid accumulation was decreased in histological findings. This study provides the possibility of utilising the olive pomaces for the prevention and treatment of hyperlipidaemia.

Role of melatonin in modulation of oxidative stress induced by delta- aminolevulinic acid in adult male albino rats.

Backgrounds: Delta-aminolevulinic acid (ALA) is a heme precursor that accumulates in acute intermittent porphyria (AIP) due to enzymatic deficiencies in the heme biosynthetic pathway, its accumulation has been associated with several symptoms because it works as an endogenous source of reactive oxygen species, which can exert oxidative damage to cell structures. The present work was designed to examine the ability of melatonin, a well known antioxidant and a free radical scavenger secreted from the pineal gland, to revert ALA-promoted damage in brain, liver and kidney of rats. Results: The present data demonstrated that chronically ALA-treated rats (40 mg / kg body wt day after day for 14 days) exhibited very highly significant increases in malondialdehyde (MDA) and protein carbonyl (PC) whereas the level of glutathione (GSH) was significantly diminished in the tissue homogenates of all tested organs (brain, kidney & liver). Among antioxidant enzymes, superoxide dismutase (SOD), catalase (CAT), glutathione reductase (GSH-Rd), glutathione-S-transferase (GST) activities were significantly diminished by ALA treatment. Intraperitoneal injection of melatonin (10 mg / kg body weight, every day for 14 consecutive days) significantly ameliorated all the tested parameters. Melatonin moderately increased SOD, CAT, GSH-Rd and GST activities, thereby counteracting the oxidative stress induced by ALA. Nevertheless, exogenous ALA caused a strong net rise in MDA and PC and a significant decrease in GSH when given together with ALA, melatonin antagonized these effects and largely protected the integrity of tissue structures. From the present data, the protection of melatonin against ALA oxidative stress is obviously, so it is well recommended to use melatonin in patients suffering from symptoms related to ALA accumulation.

Role of melatonin in modulation of oxidative stress induced by delta- aminolevulinic acid in adult male albino rats.

Backgrounds: Delta-aminolevulinic acid (ALA) is a heme precursor that accumulates in acute intermittent porphyria (AIP) due to enzymatic deficiencies in the heme biosynthetic pathway, its accumulation has been associated with several symptoms because it works as an endogenous source of reactive oxygen species, which can exert oxidative damage to cell structures. The present work was designed to examine the ability of melatonin, a well known antioxidant and a free radical scavenger secreted from the pineal gland, to revert ALA-promoted damage in brain, liver and kidney of rats. Results: The present data demonstrated that chronically ALA-treated rats (40 mg / kg body wt day after day for 14 days) exhibited very highly significant increases in malondialdehyde (MDA) and protein carbonyl (PC) whereas the level of glutathione (GSH) was significantly diminished in the tissue homogenates of all tested organs (brain, kidney & liver). Among antioxidant enzymes, superoxide dismutase (SOD), catalase (CAT), glutathione reductase (GSH-Rd), glutathione-S-transferase (GST) activities were significantly diminished by ALA treatment. Intraperitoneal injection of melatonin (10 mg / kg body weight, every day for 14 consecutive days) significantly ameliorated all the tested parameters. Melatonin moderately increased SOD, CAT, GSH-Rd and GST activities, thereby counteracting the oxidative stress induced by ALA. Nevertheless, exogenous ALA caused a strong net rise in MDA and PC and a significant decrease in GSH when given together with ALA, melatonin antagonized these effects and largely protected the integrity of tissue structures. From the present data, the protection of melatonin against ALA oxidative stress is obviously, so it is well recommended to use melatonin in patients suffering from symptoms related to ALA accumulation.

An absorption study of dietary administered acrylamide in swine

Acrylamide is a food toxicant suspected to be carcinogenic to humans. It is formed in the heat processing of carbohydrate-rich food. A current issue in food safety is whether acrylamide actually represents a risk for human health. At present, available information is insufficient to reach any conclusions. Inter alias, a still unclear matter is the fraction of acrylamide ingested by food that is absorbed and metabolized. This study compared the in vivo relative absorption of acrylamide formed in cooked food with that of the pure compound dissolved in drinking water using the pig (25 Italian Large White females) as the animal model. Acrylamide intakes of about 0.8 and 8 μg kg −1 pig body wt day −1 equal to one and ten times, respectively, the maximum average acrylamide daily intake for humans from the diet (expressed on a body wt basis) in industrialized countries, were chosen for the study. Adducts with the N-terminal valine of haemoglobin formed by acrylamide and its epoxide metabolite glycidamide, were used as exposure markers. Analyses were carried out by gas chromatography/mass spectrometry following in-house method validation. Both for the low and the high dose regimen, the glycidamide adduct levels in swine globins were lower of the limit of quantification of the method. As concerns acrylamide adducts, it was found that the relative absorption of acrylamide from feed and water was the same and that there is a direct proportionality between the adduct concentration and acrylamide intake.

Polybrominated diphenyl ethers and organochlorine pesticides in human breast milk from Massachusetts, USA

Concentrations of polybrominated diphenyl ethers (PBDEs), and organochlorine pesticides (OCPs; DDTs, HCHs, CHLs, and HCB) were measured in human breast milk samples collected across Massachusetts, USA, in 2004. Seventeen PBDE congeners were found in the samples, ranging in concentration from 0.06 to 1910 ng g(-1) lipid wt. BDE-47 (2,2',4,4'-tetraBDE), BDE-99 (2,2',4,4',5-pentaBDE), and BDE-100 (2,2',4,4',6-pentaBDE) were the major congeners detected in breast milk samples. Overall mean (+/-SD) concentrations of DDTs, HCHs, CHLs, and HCB were 64.5 +/- 75, 18.9 +/- 19, 32.4 +/- 36, and 2.3 +/- 2.2 ng g(-1) lipid wt, respectively. Concentrations of PBDEs were strongly correlated with concentrations of OCPs in the samples. Based on the concentrations of organohalogens and the intake rates of breast milk by infants in the United States, daily ingestion rates of contaminants were calculated. The median ingestion rates for PBDEs, HCHs, DDTs, CHLs, and HCB were 4.0, 212, 141, 44, and 5.79 ng kg(-1) body wt day(-1), respectively. The estimated daily intake of organohalogens by infants was compared with threshold reference values suggested by the United States Environmental Protection Agency (USEPA) and the Agency for Toxic Substances and Disease Registry (ATSDR), for calculation of hazard quotients (HQs). HQs for individual organohalogens and the sum of HQ for all organohalogens were calculated as HQ indices (HQI). The results suggest that one or more of the contaminants analyzed in this study exceeded the threshold reference values in at least 26% of the breast milk samples.

Regulation of lens aldose reductase activity by nitric oxide

To examine the regulation of aldose reductase (AR) activity by nitric oxide (NO) in human lens epithelial cells (HLEC), cultured rat lens, and normal and diabetic rat lens, we have incubated HLEC or cultured rat lenses with 1 m m of the NO donors S-nitroso- N-acetylpenicillamine (SNAP) or S-nitrosoglutathione (GSNO), and the AR activity and sorbitol content were measured. Non-diabetic and diabetic (treated with streptozotocin 65 mg kg −1 body wt, i.p.) rats were injected with the nitric oxide synthase (NOS) inhibitor, l-NAME (50 mg kg −1 body wt day −1, ×10 days i.p.) or NOS substrate, l-arginine (200 mg kg −1 body wt day −1, ×10 days i.p.). In a separate group of rats, a nitroglycerin (NG)-patch that releases 200 ng min −1 NO was applied to the dorsal neck region. After 10 days of treatment, the lenses were removed and their AR activity and sorbitol content were measured. Incubation of HLEC with SNAP or GSNO reduced AR activity. A similar reduction in AR activity and sorbitol accumulation was observed when diabetic and non-diabetic rat lenses were cultured in the presence of SNAP and GSNO. Total protein-SSG in diabetic lens was lower compared to normal lens. Treatment of diabetic and non-diabetic rats with l-NAME enhanced AR activity and sorbitol accumulation, whereas NG patch and l-arginine significantly decreased AR activity and sorbitol accumulation in diabetic lenses compared to non-diabetic. Increased S-glutathiolation of AR was observed in the presence of SNAP. These results suggest that decreased glutathiolation of cellular proteins in diabetic rat lens compared to non-diabetic lens is related to decreased NO availability in diabetic rats which would decrease GSNO. Restoring the NO levels in diabetic animals increases glutathiolation of cellular proteins, inhibits AR activity and prevents sorbitol accumulation. Exogenous delivery of NO may represent a potentially useful strategy for preventing or delaying diabetic cataractogenesis and the development of other diabetic complications.

Combined efficacy of tamoxifen and coenzyme Q10 on the status of lipid peroxidation and antioxidants in DMBA induced breast cancer

An increasing amount of experimental and epidemiological evidence implicates the involvement of oxygen derived radicals in the pathogenesis of cancer development. It is well known that chemical carcinogenesis is multistage process. Free radicals arefound to be involved in both initiation and promotion of multistage carcinogenesis. Tamoxifen (TAM) is a potent antioxidant and a non-steroidal antiestrogen drug most used in the chemotherapy and chemoprevention of breast cancer. Besides its anticarcinogenic potential, it also produces some adverse toxic side effects, while taken for a long time. In order to minimise the side effects and to improve the antioxidant efficacy of tamoxifen, coenzyme Q10 (CoQ10) was added. Hence the present study was designed to investigate the combined efficacy of TAM along with CoQ10 in 7, 12 dimethyl benz(a)anthracene (DMBA) induced peroxidative damage in rat mammary carcinoma. The experimental setup comprised of one control and five experimental groups and it was carried out in adult female Sprague-Dawley rats. Mammary carcinoma was induced by oral administration of DMBA (25 mg kg(-1) body wt) and the treatment was started by the oral administration of TAM (10 mg kg(-1) body wt day(-1)) and CoQ10 (40 mg kg(-1) body wt day(-1)) dissolved in olive oil and continued for 28 days. Rats induced with DMBA showed a decline in the thiol capacity of the cell accompanied by high malondialdehyde content levels along with lowered activities of antioxidant status (superoxide dismutase, catalase, glutathione peroxidase and reduced glutathione). In contrast, glutathione metabolising enzymes (glutathione reductase, glucose-6-phosphate dehydrogenase and glutathione-S-transferase) were increased significantly in chemically induced carcinoma bearing rats. Administration of TAM along with CoQ10 restored the activities to a significant level thereby preventing cancer cell proliferation. This study highlights the increased antioxidant enzyme activities in relation to the susceptibility of cells to carcinogenic agents and the response of tumour cells to the chemotherapeutic agents.

Protective effect of lipoic acid on adriamycin induced lipid peroxidation in rat kidney.

Adriamycin, which is widely used in the treatment of various neoplastic conditions, exerts toxic effects in many organs. The present study was designed to investigate the effect of lipoic acid upon adriamycin induced peroxidative damages in rat kidney. The increase in peroxidated lipids on adriamycin administration was accompanied by alterations in the antioxidant defense systems. The extent of nephrotoxicity induced by adriamycin was evident from the decreased activities of the enzymes gamma-glutamyl transferase and beta-glucuronidase in the rat renal tissues. The study was carried out with adult male albino rats of Wistar strain, which comprised of one control and three experimental groups. Group I rats served as controls. Group II rats received adriamycin (1 mg kg(-1) body wt day(-1)) intravenously through the tail vein. Group III rats were given lipoic acid (35 mg kg(-1) body wt day(-1)) intraperitoneally. Group IV rats were given lipoic acid 24 h before the administration of adriamycin. Rats subjected to adriamycin administration showed a decline in the thiol capacity of the cell accompanied by high malondialdehyde levels along with lowered activities of catalase, superoxide dismutase, glutathione peroxidase and glutathione metabolizing enzymes (glutathione reductase, glucose-6-phosphate dehydrogenase, glutathione-S-transferase). Lipoic acid pretreatment also restored the activities of gamma-glutamyl transferase and beta-glucuronidase nearly to control levels thereby suggesting nephroprotection. The study has highlighted the beneficial effects of lipoic acid pretreatment in reversing the damages caused by adriamycin and thereby bringing about an improvement in the oxidative stress parameters.

The influence of lipoic acid on adriamycin induced nephrotoxicity in rats.

Adriamycin, which is widely used in the treatment of various neoplastic conditions, exerts toxic effects in several organs. Adriamycin nephrotoxicity has been recently documented in a variety of animal species. The present study was designed to investigate the effect of lipoic acid on the nephrotoxic potential of adriamycin. The study was carried out with adult male albino rats of Wistar strain. Test animals were divided into four groups of six rats each as follows: Group I (control) received only normal saline throughout the course of the experiment. Group II (ADR) received intravenous injections of adriamycin through the tail vein (1 mg kg(-1) body wt day(-1)) once a week for a period of 12 weeks. Group III (LA) received lipoic acid (35 mg kg(-1) body wt day(-1)) intraperitoneally once a week for a period of 12 weeks. Group IV (ADR + LA) received a single injection of lipoic acid intraperitoneally 24 h prior to the administration of adriamycin through the tail vein once a week for a period of 12 weeks. Intravenous injections of adriamycin resulted in decreased activities of the glycolytic enzymes; hexokinase, phosphoglucoisomerase, aldolase and lactate dehydrogenase in the rat renal tissue. The gluconeogenic enzymes, glucose-6-phosphatase and fructose-1,6-diphosphatase, showed a decline in their activities on adriamycin administration. The transmembrane enzymes namely the Na+,K+-ATPase, Ca2+-ATPase, Mg2+-ATPase and the brush-border enzyme alkaline phosphatase also showed a decrease in their activities. This decrease in the activities of ATPases and alkaline phosphatase suggests basolateral and brush-border membrane damage. Decreased activities of the TCA cycle enzymes isocitrate dehydrogenase, succinate dehydrogenase and malate dehydrogenase, suggest a loss in mitochondrial function and integrity. Nephrotoxicity was evident from the increased excretions of N-acetyl-beta-D-glucosaminidase and gamma-glutamyl transferase in the urine of adriamycin administered rats. These biochemical disturbances were effectively counteracted on pre-treatment with lipoic acid, which brought about an increase in the activities of glycolytic enzymes, ATPases and the TCA cycle enzymes. On the other hand, the gluconeogenic enzymes showed a further decrease in their activities on lipoic acid pretreatment. LA pretreatment also restored the activities of the urinary enzymes to normal. These observations shed light on the nephroprotective action of lipoic acid rendered against experimental aminoglycoside toxicity.

Alterations in isoforms of glutathione S-transferase in liver and kidney of cadmium exposed rhesus monkeys: purification and kinetic characterization.

Exposure of animals to cadmium (Cd) (25 mg kg(-1) body wt day(-1)) for 10 weeks resulted in preferential accumulation of the metal in liver and kidney. Cd accumulation concomitantly increased zinc (Zn) concentration in both the organs. However, significant decrease in copper level was observed in liver, whereas kidney showed increase in copper (Cu) level. Cd exposure resulted in decreased total GST activity in liver (63%) and kidney (41%) as compared to control group monkeys on normal diet (group I). On isoelectric focusing (IEF) control liver GST segregated into thirteen isoenzymes, while in Cd-treated experimental animals (group II) liver GST resolved into nine isoenzymes. Similarly kidney GST from control animals separated into seven isoenzymes as compared to four isoenzymes from Cd-treated animals. Kinetic analysis showed that Cd exposure did not alter the affinity constant (Km) of GST for GSH and CDNB whereas maximal velocity (Vmax) for these substrates decreased as compared to controls in both the organs, indicating inhibition in GST synthesis by Cd. Cd resulted in a noncompetitive type of inhibition with respect to GSH in vitro. On isoelectric focussing GST of liver and kidney in group II resolved into nine and four isoenzymes as compared to thirteen and seven in group I, showing loss of four basic isoenzymes in case of liver and three isoenzymes in case of kidney. Monkey liver and kidney expressed all the three classes of GST isoenzymes i.e. alpha, mu and pi, which were serologically identical to human alpha, mu and pi GSTs.

Influence of dietary arginine and glycine content on thyroid function and growth of juvenile rainbow trout, Oncorhynchus mykiss (Walbaum)

Juvenile rainbow trout, held at 12°C on a 12 h light :12 h dark photocycle, were fed a constant ration (1 % of body wt day −1) of isonitrogenous and isoenergetic diets that varied in either arginine content (3.6-56.1 g kg−1 dry matter; experiment 1), or glycine (3.3–118 g kg−1 dry matter) and alanine (5.0-42.3 g kg−1 dry matter) content (experiment 2). In experiment 1, the lowest dietary level of arginine depressed growth, feed efficiency, plasma l-thyroxine (T4) and 3,5,3′-triiodo-l-thyronine (T3) levels and hepatic T4 5’monodeiodinase (5'D) activity responsible for T4-to-T3 conversion. Over the dietary range of 7.1–56.1 g arginine kg−1, there was no change in 5'D activity, despite an arginine stimulation of growth. The optimum level of arginine for growth was within the range of 14.1–28.1 g kg−1 of the diet or 32–63 g kg−1 of dietary protein. In experiment 2, an increase in dietary glycine level, at the expense of glutamic acid, increased 5'D activity without attendant elevation of the plasma T3 level. The latter finding suggests that glycine also induced a compensatory increase in T3 degradation rate. This may explain why the glycine-induced increase in 5'D activity was unaccompanied by any changes in growth indices. Alteration of dietary alanine content did not affect growth or thyroid function. We conclude that of the various dietary amino acids tested, only glycine led to a progressive stimulation of hepatic T4 5'D activity. However, because glycine likely enhanced T3 degradation, no increases in plasma T3 or growth indices were found. Glycine may serve as an advance signal that activates thyroid function immediately preceding or coincident with energy and nutrient (especially protein) intake. This, in turn, may improve the efficiency of nutrient absorption and/or post-absorptive anabolic events.

Growth and production of the Amazonian tambaqui in fixed cages under different feeding regimes

Experimental culture of the native Amazonian fish tambaqui, Colossoma macropomum, in fixed cages was carried out over a period of 8 months, in Lake Urubu (Rio Grande do Norte, Brazil), to assess the viability of fixed cage culture of tambaqui and to test the influence of diet on growth rates. Nine synthetic net cages (1 m3) were each stocked with 45-day-old fish (mean weight 3 g; mean total body length 51 mm) at a density of 34 fry m−3. During the first 2 months of culture, fish were fed a balanced formulated feed on an as-fed basis at the rate of 5% body weight day−1. During months 3–8 this continued for fish in treatment 1 while those in treatment 2 were fed tropical regional fruits, on a wet weight basis at the rate of 5% body wt day−1. Fish in treatment 3 were given no supplementary feed. Monthly biometric measurements were made on all fish. Fixed cage fish culture was shown to be a viable and simple technique. Survival in all treatments was 100%. With balanced supplementary feed, production was 14.4 kg m−3, compared with 4.9 kg m−3 and 2.1 kg m−3, respectively, in the treatments where fish were fed with fruits and were not given any supplementary feed.

The ecotoxicological significance of cadmium intake and residues in terrestrial small mammals

Little is known about the ecotoxicological hazard of cadmium to wild small mammals. This paper reviewed laboratory and field studies to determine: (i) intake and residue lowest-observable-adverse-effect-levels (LOAELs) for the ecologically important parameters of reproduction and development; (ii) whether these LOAELs are exceeded by wild small mammals on contaminated habitats and what adverse effects result; and (iii) which species may be at most risk from cadmium. The intake LOAEL in laboratory rodents was 3.5–7.5 mg kg −1 body wt day −1 and the residue LOAEL, based on cellular damage in the kidney, was a renal cadmium concentration of 105 mg kg −1 dry wt. On contaminated habitats, these LOAELs are exceeded by common shrews Sorex araneus but not by wild rodents. However, there is little evidence of adverse cadmium-mediated effects in common shrews and this species may be tolerant to cadmium exposure. Large cadmium concentrations in body organs may simply reflect an ability to store cadmium in a nontoxic, metallothionein-bound state. In contrast, studies suggest that microtine voles may be sensitive to cadmium and, despite their relatively low cadmium intake and accumulated residues, may suffer adverse effects. The need to establish dose-residue-effect relationships for intakes and residues which are appropriate for wild species and also based on ecologically important parameters is discussed.

Calcium and Inorganic Phosphorus Metabolism in Naked Mole Rats Heterocephalus glaber Is Only Indirectly Affected by Cholecalciferol

Naked mole rats seem to be naturally deficient in cholecalciferol yet exhibit net calcium and inorganic phosphorus absorption efficiencies that approach a physiological maximum (i.e., exceed 94%). Oral supplementation with cholecalciferol therefore does not markedly enhance the efficiency of gastrointestinal absorption of these minerals, but rather exerts indirect effects on mineral metabolism by increasing food intake (1.7 ×) from 3.6 ± 0.4 to 6.2 ± 0.3 g/100 g body wt day -1. This, in turn, results in a concomitant increase in the daily rate of calcium absorption from 2.9 ± 0.3 to 4.4 ± 0.4 (mmol/100 g body wt day -1) and inorganic phosphorus absorption from 4.5 ± 0.4 to 7.9 ± 0.4 (mmol/100 g body wt day -1) with cholecalciferol supplementation. Excretion of calcium decreases from 2.9 ± 0.5 to 1.2 ± 0.4 μmol/100 g body wt day -1 with cholecalciferol supplementation whereas inorganic phosphorus excretion is unchanged (4.3 ± 0.9 to 4.3 ± 1.2 μmol/100 g body wt day -1), to give a positive mineral balance, without any evident pathology. Indeed serum calcium (2.3 ± 0.1 vs 2.5 ± 0.1 mmol/liter) and inorganic phosphorus (1.5 ± 0.3 vs 1.6 ± 0.2 mmol/liter) concentrations remain tightly regulated irrespective of vitamin D 3 status. Mineral balance in naked mole rats is concluded not to he directly influenced by cholecalciferol, rather it may be affected by pleiotropic actions of cholecalciferol on gut function.

Acetyl-homocysteine-thiolactone-induced increase of superoxide dismutase counteracts the effect of subdiabetogenic doses of streptozocin.

Acetyl-homocysteine-thiolactone (CYT) is an organic thio compound that exerts free radical scavenger activity and increases superoxide dismutase (SOD) activity. Administration of 32 mg CYT/kg body wt/day/30 days in rats increased SOD activity in erythrocytes by 126%, and in pancreatic islets by 202%. Treatment affected only the Cu-Zn fraction of the enzyme. Transmission electron microscope observations showed that the damage to the pancreatic beta cells induced by single or multiple subdiabetogenic doses of streptozocin (STZ) (45 mg/kg body wt) was attenuated in animals treated with CYT. This protective effect was not observed with 65 mg of STZ. The experimental results seem to support the hypothesis that pancreatic beta cells are particularly vulnerable to the effect of oxygen radicals and that the cytotoxic effect of STZ is related to free radical-induced peroxidation.

Urine production rate and water balance in the terrestrial crabs Gecarcinus lateralis and Cardisoma guanhumi.

1. The rate of urine production in the terrestrial crabs Gecarcinus lateralis (Freminville) and Cardisoma guanhumi Latreille maintained on s.w.-moist sand was measured by inulin clearance. 2. The inulin U/B ratios in both species rose to about unity after 48 h, and remained at this level. It was concluded that neither species withdrew water from the primary urine. 3. The relatively high rate of inulin clearance in G. lateralis (10-69% body wt day-1) was considerably reduced when animals were transferred to dry sand (2-15% body wt day-1). 4. The rate of water loss on dry sand was measured in G. lateralis and changes in the haemolymph and urine osmolality recorded. 5. The prevention of possible reabsorption of water from voided urine did not appear to affect significantly the rate of water loss in conditions of water deprivation. 6. The maintenance of urine production rates measured on s.w.-moist sand would double the water loss of G. lateralis in dry conditions.