Molecular analysis of cystinosis: probable Irish origin of the most common French Canadian mutation.

Infantile nephropathic cystinosis, an autosomal recessive disease characterized by a lysosomal accumulation of cystine, presents as failure to thrive, rickets and proximal renal tubular acidosis. The cystinosis gene, CTNS, which maps to chromosome 17p13, encodes a predicted 55 kDa protein with characteristics of a lysosomal membrane protein. We have conducted extensive linkage analysis in a French Canadian cystinosis cohort identifying a founding haplotype present in approximately half (21/40) of the chromosomes studied. Subsequent mutational analysis, in addition to identifying two novel mutations, has unexpectedly revealed a mutation which has been previously found in Irish (but not French) cystinotic families on these 21 French Canadian chromosomes. Haplotype analysis of two Irish families with this mutation supports the hypothesis that Celtic chromosomes represent an extensive portion of cystinosis chromosomes in French Canada. Our analysis underlines the genetic heterogeneity of the French Canadian population, reflecting a frequently unrecognized contribution from non-Gallic sources including the Irish.

The influence of K(+)-induced membrane depolarization on insulin secretion in islets of lean and obese (ob/ob) mice.

The present study was undertaken to determine whether factors that affect K+ permeability produce differences in insulin secretion in the islets of obese versus lean mice. At basal glucose (3 mM), the obese islets secreted more insulin for a given increment in depolarizing K+ concentration and responded to a wider range of K+ concentrations (5-45 mM) than the lean islets (5-25 mM). In contrast, the membrane potential changes induced by increments in pK+ were not significantly different in the two types of islets. The islets of lean and obese mice treated with pertussis toxin showed a qualitatively similar response to glucose and to epinephrine, but only the control and pertussis toxin treated obese islets responded to K+ depolarization when deprived of calcium. Abnormal responses to quinine and apamin were identified in the islets of obese mice. These findings show that the abnormal insulin secretory response of the obese islet is due, at least in part, to a defect independent of glucose metabolism. This is best explained by an altered sensitivity of voltage-dependent events, most likely the result of differential effects of an intracellular element acting on ATP-sensitive and Ca2(+)-activated K+ channels, both of which are implicated in membrane repolarization.

Infant feeding practices and socio-demographic factors in Ottawa-Carleton.

Parents of 320 infants 6-18 months of age were interviewed to determine infant feeding practices and socio-demographic factors contributing to parental choices. 76% of women breastfed initially. Social class was directly related to the incidence of breastfeeding. 50% of the women who started breastfeeding continued to do so at 6 months, a figure which is higher than that previously reported in Canada. Although social class was a major determinant in parents' choice of infant feeding, cultural factors were also very important. A higher proportion of mothers who spoke languages other than English or French in the home (including mainly Polish, Italian, Spanish, and East Indian) breastfed their infants than did mothers who spoke French, even though more of them were in the lowest socio-economic group. The reason for the relatively low incidence of breastfeeding by Francophone mothers is unclear.

Abnormal regulation of cAMP accumulation in pancreatic islets of obese mice.

The present study was undertaken 1) to determine whether a defect in the regulation of adenosine 3',5'-cyclic monophosphate (cAMP) accumulation was present in the beta-cell of the ob/ob mouse, 2) to determine how such a defect, if present, would alter the regulation of insulin secretion in these islets, and 3) to find out if epinephrine had similar effects on insulin secretion and cAMP production in islets of lean and obese mice. In the obese mouse, inhibitory modulators neither inhibited cAMP accumulation in intact islets nor adenylate cyclase activity in islet homogenates. These anomalies in the modulation of cAMP accumulation were not correlated with a failure to inhibit insulin secretion. It is concluded that, first, a defect in cAMP modulation is present in the islets of Langerhans of the obese mouse; second, epinephrine produces its effects on insulin secretion and cAMP accumulation via distinct mediators; and third, an anomaly in the adenylate cyclase system is unlikely to be the cause of the exaggerated insulin secretion in the islet of the ob/ob mouse. It is more likely that the exaggerated insulin secretion is due to a faulty cation gating mechanism that, in turn, may contribute to the impaired ability of the islet to accumulate cAMP.

Insect repellent, N,N-diethyl-m-toluamide, effect on ammonia metabolism.

There appear to be at least three mechanisms for systemic reactions to diethyltoluamide. As with most substances, allergy is possible. The ingestion of large doses can produce seizures and coma by a direct action on the CNS. This occurs in experimental animals in which seizures and coma followed by death can be produced rapidly if sufficiently large doses are given. Finally, with smaller systemic doses as may occur with absorption during heavy topical use, there is also the possibility of a perturbation of ammonia metabolism. Diethyltoluamide may then pose a substantial hazard to individuals with defects in ammonia metabolism.

Different insulin-secretory responses to calcium-channel blockers in islets of lean and obese (ob/ob) mice.

The purpose of these experiments was to determine whether the activity of the voltage-dependent Ca2+ channel was modulated in the same manner in islets of the ob/ob mouse as in islets of homozygous lean mice of the same strain. The effect of agents that are known to alter the concentrations and movements of intracellular Ca2+ were investigated in relation to glucose-stimulated insulin secretion and in relation to the effect of forskolin. In islets of obese mice, verapamil and nifedipine both inhibited glucose-induced insulin release, nifedipine being the more potent inhibitor. Forskolin-stimulated secretion was inhibited either not at all (verapamil) or much less (nifedipine) in islets of the ob/ob mouse compared with those of lean mice. At basal glucose concentrations, verapamil initiated insulin secretion in islets of the ob/ob mouse and acted synergistically with forskolin to evoke a secretory activity that was 3-fold greater than that evoked by 20 mM-glucose. Nifedipine also initiated secretion at basal glucose concentrations and acted synergistically with forskolin, but its effect was considerably smaller than that of verapamil. A comparison of the effect of forskolin in the presence of Ca2+-channel blockers and in the absence of Ca2+ suggests that, in the obese mouse, the operation of the voltage-dependent Ca2+ channel is impaired.

Abnormal regulation of insulin secretion in the genetically obese (ob/ob) mouse.

To determine whether the abnormal insulin-secretory activity encountered in obese mice is due to an anomaly in the production of cyclic AMP, islets of lean and obese mice were incubated with forskolin under various conditions. Our data show that, in addition to the well-known quantitative differences in insulin-secretory activity between islets of lean and obese mice, there are important qualitative differences. The islets of obese mice accumulated less cyclic AMP than did those of lean mice in response to given doses of forskolin, yet their insulin secretion was enhanced to much higher values. In the islets of obese mice, but not in those of lean mice, the stimulatory effect of forskolin on insulin secretion was evident even at non-stimulatory concentrations of glucose or in Ca2+-deprived incubation media, showing that the islet of the obese mouse is less dependent on a primary stimulus (glucose) and on the provision of normal concentrations of Ca2+ in the bathing medium than is the islet of the lean mouse.

The occult insulinoma operative localization by quick insulin radioimmunoassay.

Hypoglycemia secondary to organic hyperinsulinism in children can be caused by diffuse or localized pancreatic lesions. Differentiation between these two types of lesions is of utmost importance since the surgical approach will be different. Some tumors escape detection by all preoperative investigations including ultrasound, scintiscan, arteriography, and computerized tomography. We are reporting on a 12-year-old boy with organic hyperinsulinism in whom we were unable to localize a tumor preoperatively. Peroperative determination of insulin levels from a number of sites on the pancreas enabled us to localize an insulin-producing pancreatic adenoma. This technique can be done easily by catheterizing the splenic and portal vein through a branch of the splenic vein and by serial sampling at 2 cm intervals along the portal and splenic veins. Insulin levels at these sites were determined by quick double-antibody radioimmunoassay, which allows the determination of the insulin levels within 50 minutes after sampling. There was a perfect biochemic and anatomic correlation allowing us to perform a precise distal pancreatectomy. The technique can be used to localize pancreatic adenomas and to decide how much pancreas to remove in diffuse lesions avoiding "blind" pancreatectomies.

Zinc supplementation attenuates insulin secretory activity in pancreatic islets of the ob/ob mouse.

The purpose of this study was to establish whether a relationship may exist between the hyperinsulinemia, the exaggerated insulin secretion, and the resistance to insulin characteristic of the obese-hyperglycemic syndrome and the zinc status of the ob/ob mouse. To this end, mice were given control and zinc-supplemented diets, and the effects of zinc supplementation on insulin secretion in vivo and in vitro as well as on glucose tolerance were studied. These data were compared with those obtained with oxytetracycline treatment, which is known to ameliorate the insulin sensitivity and glucose tolerance of these animals. The levels of zinc were measured in several tissues of lean and obese mice and the results show that zinc supplementation attenuated the exaggerated insulin secretion in vivo and in vitro without improving the tolerance to glucose. Zinc levels were significantly higher in the tissues of the obese than of the lean mice, with the exception of bone and pancreas. The results suggest a maldistribution of zinc in the tissues of the obese mouse.

Serum enzymes in the BB rat before and after onset of the overt diabetic syndrome.

As part of a six-month prospective study of the effects of neonatal thymectomy in the spontaneously diabetic BB Wistar rat, activities of the following enzymes were determined: alkaline phosphatase (AP), lactate dehydrogenase (LDH), creatine phosphokinase (CPK), glutamic-oxaloacetic transaminase (GOT), glutamic-pyruvic transaminase (GPT) and UDP-galactosyltransferase (UDPG). In prediabetics, AP and LDH levels were higher than in sham-operated, non-diabetic controls; however, this increase was seen in nearly all diabetes-prone BB rats, diminishing the usefulness of these changes in discerning potential diabetics from asymptomatic, diabetes-prone rats. After onset of the syndrome, there was a striking elevation of AP values in all diabetics with no similar alteration in asymptomatic, diabetes-prone rats suggesting this was a diabetes-related phenomenon. By contrast, UDPG was the only enzyme to decrease immediately following the onset of the syndrome. Both UDPG and AP levels correlated with blood glucose, the former negatively and the latter positively, suggesting a close relationship with changes occurring after onset of the syndrome. The remaining enzymes increased only in a portion of diabetics alone (GOT, GPT) or in a portion of both diabetics and asymptomatic, diabetes-prone BB rats (LDH, CPK).

Control mechanisms in brown adipose tissue plasma membrane.

It is generally agreed that the site of heat production during nonshivering thermogenesis is the brown adipose tissue (BAT) and that the triggering event for heat production is the interaction of noradrenaline (NA) with its receptor on the plasma membrane. Following this initial event, several changes occur which result in increased rates of cAMP synthesis, redistribution of ions across the membrane, enhanced rates of lipolysis, and increased mitochondrial oxidation of substrates. BAT is also a target for the anabolic effect of insulin. Available evidence shows that insulin receptors are present on the BAT plasma membrane and that insulin can oppose the metabolic effects of catecholamine on BAT. We have studied more particularly the response of BAT adenylate cyclase to catecholamines in an animal model (the ob/ob mouse) which has a defective thermogenic response. The capacity of adenylate cyclase to be stimulated by catecholamines was significantly less in the tissue of obese mice than in lean controls. To produce a response equal to the half-maximal response in the lean mouse, a 10-fold increase in the NA concentration was required in the BAT of the obese mouse. These results are in harmony with those of others showing that the lipolytic response to catecholamines is abnormal in the BAT of the obese mouse. The adenylate cyclase activity can be altered by changes in the lipid composition of the diet and by manipulation of hormone levels. It is likely that the alteration in adenylate cyclase responsiveness is one of the contributing factors in the impaired thermogenesis and obesity in this animal.

The effects of anxiety management training on the control of juvenile diabetes mellitus.

The present study was designed to determine whether diabetic control could be improved through the direct psychological management of stress and anxiety. Five poorly controlled female adolescent diabetics ranging in age from 15 to 18 years were used as subjects. All were seen on an outpatient basis over a 6-month period. A single-subject format employing a multiple-baseline design across subjects was used. The independent variable used was a technique known as anxiety management training. Baseline, attention-control, and treatment data were collected on a number of dependent measures. Subjective estimates of anxiety and tension by each subject were gathered on a biweekly basis using the Multifactorial Scale of Anxiety. Diabetic control was assessed daily using the Diastix method and weekly using the 24-hr quantitative glucose method. Data on the five subjects suggested that improved control of stress and anxiety had a positive effect on diabetic regulation. Lower and more stable urine glucose levels using both urine testing methods were found. However, no decreases in the subjects' personal assessment of tension and anxiety were evident.

Insulin secretion in the obese (ob/ob) mouse. The effect of oxytetracycline on insulin release.

The effect of oxytetracycline (OTC) pretreatment on the response of the ob/ob mouse to insulin secretagogues in vivo and in vitro was investigated. With glucose loading in vivo, the peak glucose was twofold greater and the insulin levels threefold greater in obese than in lean mice. After OTC treatment, there was no significant difference an insulin levels between lean and obese mice although the peak glucose level was still obese mice although the peak glucose level was still 1.5 times as high. Glucagon increased plasma glucose 2.5-fold and plasma insulin 20-fold in the obese as compared with lean mice. After OTC treatment the glycemic response of the obese was indistinguishable from that of the lean control. The insulin levels, while higher than those of lean mice, were only 25% of those found in the untreated obese. Aminophylline produced an 8- and a 20-fold increase in peak glucose and insulin levels, respectively, as compared with lean mice. In the OTC-treated obese mice, the injection of aminophylline produced a slower rise in plasma glucose than in the obese controls, but the levels were not significantly different from those of the untreated obese mice at 90 min. On the other hand, the insulin levels attained a plateau at a value which was one-fifth that found in the control obese group. In vitro, isolated islets from obese mice showed an exaggerated response to the secretagogues. Pretreatment with OTC attenuated this response. The fraction of insulin released at 10 mM glucose was less than one-fourth that in the obese controls.(ABSTRACT TRUNCATED AT 250 WORDS)

Adenylate cyclase activity in brown adipose tissue of the genetically obese (ob/ob) mouse.

The activation of brown adipose tissue adenylate cyclase by catecholamines was studied in genetically obese (ob/ob) and lean mice. In obese mice, the maximum activation of the enzyme by several beta-adrenergic agonists was only two-thirds that in lean mice and, as an activator, noradrenaline was only one-eighth as potent. The adenylate cyclase was also less responsive to guanine nucleotides. In these respects, the defect in catecholamine-stimulated adenylate cyclase was similar in both white and brown adipose tissue of the obese mouse. The enzyme in brown adipose tissue differed from that in white adipose tissue in its sensitivity to other beta-adrenergic agonists and in its requirement for Mg2+. It is suggested that this abnormal catecholamine-activated adenylate cyclase in brown adipose tissue may be relate to the thermoregulatory defect of the obese mouse and hence may contribute to the obesity syndrome.

Enzyme immunoassay of gentamicin with the Abbott ABA-100 analyzer.

The enzyme immunoassay of gentamicin using "EMIT" reagents was adapted to take advantage of the small reagent volume required by the Abbott ABA-100. The method increases fourfold the maximum number of tests per kit. The correlation with the bacterial inhibition method was 98%.