Hematology and serum chemistry of harp (Phoca groenlandica) and hooded seals (Cystophora cristata) during the breeding season, in the Gulf of St. Lawrence, Canada

Standard hematologic and serum chemistry parameters were determined from 28 harp seals (Phoca groenlandica) and 20 hooded seals (Cystophora cristata) sampled from 6 March 2001 to 13 March 2001 during the breeding season. Whole blood was collected immediately postmortem from harp seal mother-pup pairs and from six hooded seal pups, and from live-captured adult hooded seals and three hooded seal pups; blood was analyzed within 24 hr at a local human hospital. A certified veterinary laboratory validated subsamples of whole blood and analyzed all serum chemistry parameters. Significant interlaboratory differences in mean values of packed cell volume (PCV) and mean cell volume (MCV) were found. Significant differences were found between samples from the five seal groups (adult male hooded seals, lactating female hooded seals, unweaned hooded seal pups; lactating female harp seals, and unweaned harp seal pups) for hematology and most serum chemistry parameters. In general, age-class influenced mean values of PCV, hemoglobin (HB), red blood cell (RBC) counts, MCV, mean cell hemoglobin (MCH), mean cell hemoglobin concentration (MCHC), and nucleated red blood cell (NRBC) counts per 100 leucocytes, but most age-related variations were species specific. Harp seal pups had significantly lower mean values of HB, PCV, MCH, and MCHC than did other seal groups, and significantly lower mean RBC counts than did hooded seal pups. Mean NRBC counts per 100 leukocytes were more than three times higher in harp seal pups than in hooded seal pups, but this difference was not statistically significant. Mean MCV were significantly lower in harp and hooded seal pups compared to those of adult harp and hooded seals. Differences in hemograms between pup species were likely because of the precocious development of hooded seal pups, which are weaned within 4 days, compared to 12 days for harp seal pups. Among adult seal groups, male hooded seals had significantly higher mean values of PCV and HB than did female harp and hooded seals, and significantly higher mean RBC counts than did adult female hooded seals. Among adult females, mean values of MCH and MCHC were statistically higher in hooded seals than in harp seals. Adult female harp and hooded seals did not differ significantly in other RBC parameters and mean leukocyte counts. Mean values of glucose, blood urea nitrogen, total bilirubin, alanine aminotransferase (ALT), alkaline phosphatase (ALP), total protein, and albumin showed species-specific variations between adults and pups. Except for ALP, few significant differences in mean enzyme activities of aspartate aminotransferase (AST), ALT, creatine kinase and gamma-glutamyltransferase were found between seal groups. Mean concentrations of electrolytes (calcium, phosphorus, sodium, potassium, chloride, magnesium, and total carbon dioxide) varied with age class, but variations in potassium and magnesium were species specific. Harp seal pups had significantly higher mean phosphorus and potassium levels compared to other seal groups.     

Tartrate-resistant acid phosphatase (TRAP) activity in serum: potential use in assessing bone resorption in patients with multiple myeloma

We measured serum tartrate-resistant acid phosphatase (TRAP) activity in 120 healthy subjects and 35 patients with multiple myeloma as well as urinary hydroxyproline excretion in the myeloma patients. Young subjects (0-18 years) showed higher TRAP levels (ANOVA p less than 0.01) compared with the other age classes due to the more active bone remodelling processes associated with growth. Myeloma patients with bone lytic lesions (MM+) showed higher serum TRAP values than controls (p less than 0.01). Hydroxyproline excretion was higher in MM+ patients but the difference between patients with and without bone lesions was not statistically significant. Our data suggest that serum TRAP activity may be a suitable, simple biochemical test to assess bone turnover in patients with multiple myeloma but that its clinical usefulness as a marker of bone resorption needs further evaluation.     

Strain-gauge plethysmographic measurement of the systemic bioavailability of oral nitroglycerin in liver cirrhosis

7 cirrhotic (M = 3, F = 4, mean age 55, range 35-74) and 7 healthy subjects (M = 6, F = 1, mean age 24, range 23-40) were studied. 2.5mg% nitroglycerin were administered per os. This drug is quite completely metabolized in its first pass through the liver (first pass effect). Peripheric vascular effect of nitroglycerin was evaluated by venous occlusion strain-gauge plethysmography, ECG-coupled (Rest Flow measurement RF, in ml/min/100 ml). No statistically significant differences were found between pre-drug RF in the two groups and between pre and post-drug measurements in healthy subjects. Post-drug RF decreased in cirrhotic subjects when compared either to pre-drug values or to post-drug values in normal subjects (statistically significant after the third minute, p ranging less than 0.05 and less than 0.001). The different peripheric vascular effect found in the two groups was considered as a consequence of the increased drug bioavailability in cirrhotics, caused by portosystemic shunts.     

Effect of irradiation and/or leucocyte filtration on RBC storage lesions

Red blood cell (RBC) storage lesions have been shown to be associated with some adverse reactions; numerous studies have focused on the lesions caused by storage, and few data on the RBC storage lesions caused by prestorage treatments of leucocyte filtration and irradiation. In this study, we examined the changes related with the RBC storage lesions, including 2,3-diphosphatidylglyceric acid (2,3-DPG), pH, free hemoglobin (Hb), supernatant free K+ and Na+ concentration, mean corpuscular volume (MCV), mean corpuscular hemoglobin (MCH). Along with the increasing storage time, decreases in 2, 3-DPG levels, pH and Na+ concentration, increases in K+ and free Hb concentrations, and significant morphological changes in RBC in all groups were found. The changes in the groups of irradiation, leucocyte filtration and the combined irradiation and leucocyte filtration were more significant than those in the untreated group. Meanwhile, the MCV levels of the three treated groups were significantly lower than those in the untreated group, while the MCH variations were significantly higher. Our results suggest that irradiation and leucocyte filtration before storage may aggravate blood storage lesions.     

Hematologic and blood chemical characteristics of feral horses from three management areas

Blood was collected from 486 feral horses of mixed sex and age classes captured from three wild horse management areas in Nevada and Oregon from December 1985 to February 1986. Males were significantly outnumbered by females in the Flanigan area, but both sexes were represented in approximately equal numbers in the Wassuk and Beaty's Butte areas. Hematology and chemistry values averaged 16.4 +/- 0.11, 46.3 +/- 0.28, 9.9 +/- 0.07, 6.9 +/- 0.10, 47.1 +/- 0.24, 16.6 +/- 0.09, 35.2 +/- 0.09, 10.4 +/- 0.14 and 23.4 +/- 0.25 for hemoglobin (HGB), hematocrit (HCT), red blood cells (RBC), white blood cells (WBC), mean corpuscular volume (MCV), mean corpuscular hemoglobin (MCH), mean corpuscular hemoglobin concentration (MCHC), cortisol (F) and serum urea nitrogen (SUN), respectively. Statistically significant differences in HGB, HCT, RBC, WBC, MCV and MCH levels occurred with respect to age (P less than or equal to 0.001). Serum F levels were lower in immature animals than in either subadult or adults in all areas. Flanigan horses appeared in the poorest condition and had the lowest HGB, HCT and RBC counts while the values for Wassuk horses were significantly higher (P less than or equal to 0.001). Serum F levels were lowest in the Flanigan horses. A significantly lower (P less than or equal to 0.001) proportion of adult mares had progesterone levels consistent with pregnancy in the Flanigan horses versus those from the other two areas. These data are consistent with a subjective evaluation of the condition of the horses.     

Comparative studies on erythrocyte sialic acid levels in apparently healthy indigenous Nigerian poultry species

The erythrocyte surface sialic acid levels of 200 apparently healthy indigenous Nigerian poultry species (pigeons, guinea fowls, ducks and chickens, n = 50 for each species) presented for slaughter at a poultry abattoir in Zaria, Nigeria was determined. Other parameters determined were packed cell volume (PCV) and plasma total protein (TP) concentration. The mean erythrocyte surface sialic acid concentration of pigeons, guinea fowls, ducks and chickens were 7.88 +/- 2.51, 14.6 +/- 2.51, 17.6 +/- 2.51 and 14.2 +/- 2.51 mg mg(-1) respectively. There was a statistically significant difference between the mean erythrocyte surface sialic acid concentration of all the species of poultry sampled (P < 0.05). The high erythrocyte surface sialic acid concentration in the indigenous Nigerian poultry species could be responsible for their resistance to infectious diseases, whose aetiologic agents produce neuraminidases. The mean PCV of the pigeons, guinea fowls, ducks and chickens were 46.22 +/- 6.91, 38.24 +/- 6.91, 36.50 +/- 6.91 and 36.46 +/- 6.91% respectively. The difference between the mean PCV values of pigeons on the one hand and guinea fowls, ducks and chickens on the other was statistically significant (P < 0.05). A negative correlation (r = -0.36, P < 0.05) between mean erythrocyte surface sialic acid concentrations and PCV was observed, i.e. the birds with the highest mean PCV values had the lowest levels of erythrocyte surface sialic acid. There was no correlation between TP concentration and either erythrocyte surface sialic acid concentration or PCV values. It is suggested, based on this study, that erythrocyte sialic acid types in these species should be determined, as the results may be vital in selective breeding.     

Circadian rhythm in airway responsiveness and airway tone in patients with mild asthma.

To determine the characteristics and reproducibility of circadian rhythms of airway responsiveness to histamine and methacholine and their relationship to airway tone in patients with mild asthma, we studied nine subjects with complaints of nighttime awakening due to dyspnea and/or cough at least once a week. Their mean age was 31.4 yr (range 17-65) and their mean daytime FEV1 was 99 +/- 14 (SD) % predicted. Forced expiratory volume in 1 s (FEV1) and the provocative concentrations of histamine and methacholine necessary to decrease FEV1 by 20% (PC20FEV1) were determined every 4 h for 13 consecutive measurements. Three subjects were measured with histamine, three with methacholine, and three with both histamine and methacholine. Data were evaluated on an individual basis. PC20FEV1 to histamine and methacholine showed significant and reproducible circadian variations in all cases (P less than 0.01 each) with a mean amplitude of 1.00 +/- 0.17 (SD) doubling concentrations for histamine and 1.35 +/- 0.29 doubling concentrations for methacholine. The amplitude of PC20FEV1 was significantly larger (P less than 0.05) and the time of maximum responsiveness was significantly earlier (P less than 0.05) with methacholine compared with histamine. FEV1 showed significant (P less than 0.05) circadian variations in three of nine subjects, and peak expiratory flow rate showed variations in two subjects. Correlation between the variations of FEV1 and PC20FEV1 was significant (P less than 0.05) in 5 of 12 cases.(ABSTRACT TRUNCATED AT 250 WORDS)     

Different patterns of central and peripheral beta EP, beta LPH and ACTH throughout life

The aim of the present study was to evaluate the relationship between central and peripheral concentrations of proopiocortin-related peptides in different periods of life. One hundred and eighty-nine plasma samples from normal subjects (18-87 years) obtained in basal conditions, and 20 cerebrospinal fluid (CSF) samples obtained by lumbar puncture from healthy volunteers (18-75 years) were studied. beta Lipotropin (beta LPH), beta endorphin (beta EP) and ACTH were measured by specific RIA after silicic acid plasma extraction and gel chromatography (beta LPH and beta EP). No sex differences were found in the patterns of the three peptides either in the plasma or in CSF. In the plasma samples, both beta LPH and beta EP concentrations showed a pattern throughout life which was expressed by a paraboloid function with the lowest values found in young and old subjects and with peaks at 51.3 and 48.2 years, respectively. On the contrary, ACTH values failed to be represented by a significant linear or curvilinear regression and presented only a slight decrease in subjects over 75 years of age. CSF levels of beta LPH were significantly lower in 45-76 year old subjects (18.8 +/- 12.6 fmol/ml, M +/- SD) than in 18-44 year old subjects (34.5 +/- 15.8; p less than 0.05), as were those of beta EP (elderly: 41.2 +/- 19.7; young: 94.2 +/- 36.7; p less than 0.05), which showed a significantly linear inverse correlation with age (r = 0.6062, p less than 0.01). These CSF samples did not show any ACTH variations connected with age.(ABSTRACT TRUNCATED AT 250 WORDS)     

Magnesium,zinc, and manganese in atherosclerosis of the aorta

Atomic absorption spectrometry was used in a quantitative study of zinc, magnesium, and manganese on 71 postmortal human aortas. Samples were obtained from accident victims 35-65 years of age. Fibrous plaques had higher levels of all three elements when compared to normal aortic tissue. The difference was significant for zinc (p less than 0.001) and magnesium (p less than 0.01). The high elemental levels may be both a cause and effect of atherosclerosis or the result of another unknown parameter.     

Sialic acid concentration of brain gangliosides: variation among eight mammalian species

Sialic acid is a vital component of brain gangliosides which play an essential role in the transmission and storage of information in the brain. The concentration of bound sialic acid in gangliosides and free sialic acid in the brain cortex of eight different mammals [human, chimpanzee (Pan troglodytes), rat (Rattus norvegicus), mouse (Mus musculus), rabbit (Oryctolagus cuniculus), sheep (Ovis aries), cow (Bos indicus) and pig (Sus scrofa)] were compared. Total sialic acid concentration (890+/-103 microg/g wet weight tissue, mean+/-SE, n = 6) was 2-4 times higher in the human brain compared with the other species studied (0.001 < p < 0.05). There was no significant difference between human males and females. The rank order of adult brain sialic acid after humans (in microg/g) was rat (493+/-23, n = 12), mouse (445+/-29, n = 16), rabbit (380+/-18, n = 6), sheep (323+/-43, n = 6), cow (304+/-14, n = 6) and pig (252+/-14, n = 6). Apart from the cow vs the sheep, the differences between species were statistically significant (p < 0.05). In the mouse, cow and sheep, total sialic acid concentration increased during maturation by 18-32% (p < 0.05). In a 2-year-old chimpanzee, the sialic acid concentration in the left lobe of the brain cortex was 25% higher than that of right lobe at 6 weeks of age (p < 0.05). Free sialic acid was higher in the human brain cortex (41+/-3 microg/g) than that of the rat and mouse (32+/-3 and 25+/-5 microg/g respectively) and absent from other species. Variation in brain sialic acid concentration among different animals has implications for the evolution of the brain and may affect learning ability in animals.     

Do colonic bacteria contribute to cholesterol gall-stone formation? Effects of lactulose on bile.

Ten healthy middle-aged women volunteered for a study to test the effect of lactulose--a synthetic, non-absorbable disaccharide--on the colonic metabolism of bile acids and on bile lipid composition. Lactulose (60 g daily in eight cases, 39 g daily in two) was taken as a proprietary syrup for six weeks, and bile was collected by duodenal intubation before and immediately after six weeks. All subjects showed a fall in the percentage of the 7-alpha-dehydroxylated bile acid deoxycholic acid (mean 28.4 +/- SEM 3.7 to 15.6 +/- 2.4; p less than 0.002) and a rise in the percentage of the primary bile acid chenodeoxycholic acid (mean 33.2 +/- 42.9 +/- 2.9; p less than 0.001). The percentage of cholic acid rose in eight subjects but mean values did not differ significantly. Bile was initially super-saturated with cholesterol in most subjects and became less saturated with cholesterol in all but one (mean saturation index 1.40 +/- 0.11 to 1.19 +/- 0.07; p less these 0.005). These data support the theory colonic bacteria contribute to cholesterol gall-stone formation.     

Babesia caballi and Babesia equi: implications of host sialic acids in erythrocyte infection

The present study investigated the involvement of host sialic acids in the erythrocyte infection by two equine Babesia parasites, Babesia equi and Babesia caballi. We observed that the in vitro growth of both parasites is influenced by the removal of sialic acids from the surface of equine erythrocytes (RBC). When the parasites were cultured with neuraminidase (Nm, EC 3.2.1.18)-treated RBC, in which alpha2-3-linked sialic acid residues were removed from four membrane proteins of the RBC, B. caballi showed a significant inhibition of the erythrocyte invasion, while the intracellular development of B. equi seemed to be significantly affected. The possible involvement of host sialic acid in the erythrocyte invasion by B. caballi was also supported by a significant reduction in the parasite growth accompanied by an increased number of extracellular merozoites after the addition of exogenous 3'-sialyllactose (Neu5Acalpha(2-3)Galbeta(1-4)Glc) into the culture. These results suggest that the alpha2-3-linked sialic acid residues on host RBC play important roles in the erythrocyte infections by B. caballi and B. equi.     

Erythrocyte membrane bound and plasma sialic acid during aging

Sialic acid, a nine-carbon sugar, is an acetylated derivative of neuraminic acid predominantly found in vertebrates, a few higher invertebrates, and certain types of bacteria. Red blood cells (RBCs) have a net negative surface charge and this bulk charge is due to ionized sialic acid. Decreased surface charge and sialic acid content have been reported in older erythrocytes, and it is postulated that the decreased electro-negativity may be related to cell senescence. In the present study we report the RBC and plasma sialic acid content during aging in rats. Our results show a significant decrease in RBC sialic acid content and increase in plasma sialic acid as a function of rat aging. The decreased sialic acid in erythrocyte membrane with increasing rat age presents a good biomarker of the aging process. The elevated plasma sialic acid may be a manifestation of several factors including increased expression of acute phase proteins and increased damage to various organs.     

Influence of sialic acid on the binding activity of estrogen receptors

The influence of sialidase and sialyltransferase on the binding of 3H-estradiol to estrogen receptors in baboon uterus was investigated to ascertain if sialylation was involved. Specific binding capacity increased approximately 37% in the presence of sialidase, although Kd values essentially remained unchanged. 3H-Estradiol binding was correlated with free sialic acid in the presence of either sialidase or sialyltransferase. As sialidase concentrations were increased, 3H-estradiol binding and free sialic acid concentration increased linearly (r = 0.937, p less than 0.001). Incubation of 22 x 10(-5) U sialidase with its inhibitor, 2,3-dehydro-2-deoxy-N-acetylneuraminic acid, decreased binding capacity and sialic acid concentration (r = 0.929, p less than 0.001). Although a decrease in binding capacity and free sialic acid concentration was observed in the presence of increasing amounts of sialyltransferase, a positive correlation was found between these two parameters (r = 0.839, p less than 0.035). A negative trend that was statistically insignificant was observed between binding capacity and sialic acid concentration when 2 x 10(-4) U sialyltransferase was incubated with the inhibitor, acetylsalicylic acid (r = -0.571, p = 0.195). The sialic acid concentration increased, while the 3H-estradiol binding capacity decreased. Collectively, these results show that both sialidase and sialyltransferase affect the binding of estradiol to its receptor in opposite directions. We suggest that biological activities of estrogen receptors in target cells may be regulated by the extent of sialylation of the receptor molecule itself. This posttranslational alteration may represent a new type of control mechanism for estrogen action.     

Biorheological Action of Ascaris lumbricoides Larvae on Human Erythrocytes

Previous studies have shown that A. lumbricoides extracts capture sialic acid (SA) from human red blood cells (RBC). The aim of this work was to study hemorheological alterations in vitro caused by parasite larvae. The biorheological action of three larva concentrates of first and second larval stage on group O erythrocytes was analyzed by incubating the erythrocyte packed together with an equal volume of larvae (treated RBC) and PBS (control RBC). Distribution and parameters of aggregation (digital image analysis), aggregation kinetics (erythroaggregameter), and viscoelasticity (erythrodeformeter) were measured. The digital image analysis showed that all the larvae diminished the isolated cells percentage and increased the size of the formed aggregates. The aggregate formation velocity was lower in the treated than in the control. The deformability index (ID) values of treated RBC did not present variations with respect to those of the control, but a decrease in the erythrocyte elastic modulus (μ_m) and membrane surface viscosity (η_m) values was observed, indicating that the larvae not only induced a diminution in the membrane surface viscosity of RBC but also altered the dynamic viscoelasticity of the membrane. Experiments carried out in vitro support the conclusion that the contact between larvae and RBC produces hemorheological alterations.     

Arachidonic acid metabolites do not mediate toluene diisocyanate-induced airway hyperresponsiveness in guinea pigs

Arachidonic acid metabolites have previously been demonstrated to mediate the airway hyperresponsiveness observed in guinea pigs and dogs after exposure to ozone. Guinea pigs were treated with indomethacin (a cyclooxygenase inhibitor), U-60,257 (piriprost, a 5-lipoxygenase inhibitor), or BW775c (a lipoxygenase and cyclooxygenase inhibitor) and exposed to air or 3 ppm TDI. Airway responsiveness to acetylcholine aerosol was examined 2 h after exposure. In control animals, the provocative concentration of acetylcholine which caused a 200% increase in pulmonary resistance over baseline (PC200) was significantly less (p less than 0.05) after exposure to TDI (8.6 +/- 2.0 mg/ml, geometric mean + geometric SE, n = 10) than after exposure to air (23.9 + 2.5 mg/ml, n = 14). The airway responsiveness to acetylcholine in animals treated with indomethacin or piriprost and exposed to TDI was not different from that of control animals exposed to TDI. Treatment with BW755c enhanced the airway hyperresponsiveness observed in animals exposed to TDI without altering the PC200 of animals exposed to air. The PC200 of animals treated with BW755c and exposed to TDI (2.3 + 0.8 mg/ml, n = 8) was significantly lower than the PC200 of control animals exposed to TDI (p less than 0.025). These results suggest that products of arachidonic acid metabolism are not responsible for TDI-induced airway hyperresponsiveness in guinea pigs. BW755c, however, appears to potentiate the TDI-induced airway hyperresponsiveness to acetylcholine by an as yet unidentified mechanism.     

Seasonal variation in blood components of reared Baltic salmon, Salmo salar L.

Ranges in the means of blood measurements from 121 Baltic salmon taken on nine occasions spread over an annual cycle were: packed cell volume or haematocrit; blood haemoglobin; red blood cell counts including immature erythrocytes; mean corpuscular haemoglobin concentration; mean cellular haemoglobin content and mean cellular volume. Seasonal changes appeared in all blood variables. Ontogenetic differences occurred in RBC and mean cellular volume when comparing 1 + parr with 2 + smolts in August one year apart, and in haemoglobin, RBC and immature RBC when comparing 1 + parr with adults once in November 1976. This points to greater influence upon haematological variation by season than by age. Significant regressions found within age groups, between pairs of mutually independent blood variables, are presented.     

Serum molybdenum concentration in healthy Japanese adults determined by inductively coupled plasma-mass spectrometry

The serum molybdenum (Mo) concentrations in 70 Japanese adults (35 males and 35 females) not receiving any medical care or treatment were determined by inductively coupled plasma-mass spectrometry. Serum Mo concentration in the subjects ranged from <0.1 to 9.11 ng/mL. More than half (55.7%) of the subjects showed values of less than 1 ng/mL and only 6 (8.6%) subjects showed more than 2 ng/mL. The mean+/-SD, geometrical mean (GM), range of GM+/-geometrical SD (GSD) and median value were 1.21+/-1.34, 0.81, 0.30 to 2.16, and 0.90 ng/mL, respectively. Among age, body mass index and several serum biochemical values, activities of aspartate aminotransferase and alanine aminotransferase showed significant associations with serum Mo; 15 subjects suspected of having liver dysfunction showed significantly higher serum Mo than others. We propose a range of 0.10-4.73 ng/mL, estimated as a range of GM+/-2GSD of serum Mo in the remaining 55 subjects without liver dysfunction, as a reference range of serum Mo in Japanese healthy adults.     

Changes of serum angiotensin-I-converting enzyme in patients with thyroid disorders

In 149 subjects (63 euthyroid, 21 hyperthyroid, 26 with autonomous nodules, subdivided into 20 euthyroid and 6 hyperthyroid, 17 hypothyroid subjects and 22 women taking estrogens) the serum angiotensin-I-converting enzyme (SACE) was spectrophotometrically measured and correlated with age, systolic and diastolic blood pressure, free thyroid hormones (FT4, FT3) and delta TSH level. In patients with diffuse hyperthyroidism and with regional autonomy, systolic blood pressure was elevated. The highest values for FT4 and FT3 were found in patients with hyperthyroidism and hyperthyroid autonomous nodules. SACE correlated with age for the euthyroid control group (p less than 0.05). In this group, SACE levels were higher in men than in women (p less than 0.02). Regarding all 149 subjects together, significant linear correlations between SACE and systolic blood pressure as well as with FT4 and FT3 concentrations could be demonstrated (p less than 0.01-0.001). Among the individual groups the mean SACE activities were significantly elevated in hyperthyroid patients (p less than 0.01). No significant differences could be observed between controls and euthyroid subjects with autonomous nodules as well as in hypothyroid cases. In comparison to euthyroid patients the mean SACE levels of hyperthyroid patients with autonomy were significantly (p less than 0.05) elevated. The SACE activities of women taking estrogens for contraception did not differ significantly from SACE in age-matched female controls.     

Fasting plasma magnesium concentrations and glucose disposal in diabetes.

Fasting plasma concentrations of magnesium were measured by neutron activation analysis in 30 non-diabetics and 87 diabetics (55 non-insulin-treated, 32 insulin treated). Plasma concentrations of magnesium were lowest in the insulin treated group (mean 0.84 (SEM 0.01) mmol/1; 2.0 (0.02) mg/100 ml), intermediate in the non-diabetics (mean 0.89 (SEM 0.01) mmol/1; 2.2 (0.02) mg/100 ml), and highest in the non-insulin-treated diabetics (mean 0.95 (SEM 0.02) mmol/1; 2.3 (0.05) mg/100 ml). In all diabetics plasma magnesium concentrations were inversely related to plasma glucose values (rs = -0.33; p less than 0.01) and in non-insulin-treated patients to plasma insulin concentrations (rs = -0.28; p less than 0.05), the former confirming previous observations. In 67 of the diabetics the KG constant for disposal rate of glucose during a standard intravenous glucose tolerance test was directly related to fasting plasma magnesium concentrations, and this relation persisted after controlling for age, sex, body mass index, type of treatment, and glucose and insulin values. This direct relation of plasma magnesium concentration with glucose disposal was unexplained by its influence on insulin secretion but was related to insulin sensitivity; hence magnesium may be an important determinant of insulin sensitivity in maturity onset diabetes.