Co-crystallization of sucrose at high concentration in the presence of glucose and fructose

Co-crystallization of sucrose from a highly concentrated sucrose syrup (less than or equal to 7% moisture, w/w) at 131 degreesC with 0, 5, 10, 15, and 20% of fructose, glucose, or a mixture of fructose and glucose was investigated. The crystallization of sucrose was delayed in presence of these lower molecular weight sugars. The DSC melting endotherm of cocrystallized samples exhibited a decrease in crystalline sucrose in the sample as a function of increased level of glucose and fructose. The mechanical strength of co-crystallized granules was found to be related to the moisture content and the amount of glucose or fructose content in the sample. The samples containing 10, 15, and 20% glucose in co-crystallized product demonstrated crystallization of glucose in its monohydrate form during 1 mo of storage.

Dietary chromium tripicolinate supplementation reduces glucose concentrations and improves glucose tolerance in normal-weight cats

The effect of dietary chromium supplementation on glucose and insulin metabolism in healthy, non-obese cats was evaluated. Thirty-two cats were randomly divided into four groups and fed experimental diets consisting of a standard diet with 0 ppb (control), 150 ppb, 300 ppb, or 600 ppb added chromium as chromium tripicolinate. Intravenous glucose tolerance, insulin tolerance and insulin sensitivity tests with minimal model analysis were performed before and after 6 weeks of feeding the test diets. During the glucose tolerance test, glucose concentrations, area under the glucose concentration-time curve, and glucose half-life (300 ppb only), were significantly lower after the trial in cats supplemented with 300 ppb and 600 ppb chromium, compared with values before the trial. Fasting glucose concentrations measured on a different day in the biochemistry profile were also significantly lower after supplementation with 600 ppb chromium. There were no significant differences in insulin concentrations or indices in either the glucose or insulin tolerance tests following chromium supplementation, nor were there any differences between groups before or after the dietary trial. Importantly, this study has shown a small but significant, dose-dependent improvement in glucose tolerance in healthy, non-obese cats supplemented with dietary chromium. Further long-term studies are warranted to determine if the addition of chromium to feline diets is advantageous. Cats most likely to benefit are those with glucose intolerance and insulin resistance from lack of exercise, obesity and old age. Healthy cats at risk of glucose intolerance and diabetes from underlying low insulin sensitivity or genetic factors may also benefit from long-term chromium supplementation. (C) 2002 ESFM and AAFP.

Placental growth hormone is not suppressed by oral glucose loading in normal human pregnancy

Placental growth hormone (PGH) progressively replaces pituitary growth hormone in the maternal circulation from mid-gestation onwards in human pregnancy. Our previous investigations have shown that placental growth hormone concentrations correlate well with foetal growth. Despite the apparent correlation between PGH and birthweight, the physiology of its secretion during pregnancy has not been well defined. We investigated the response of maternal serum PCH to oral glucose loading in pregnant women (n = 24) who demonstrated normal glucose tolerance at a mean gestation of 29 weeks. Mean (SEM) fasting PGH concentrations were high (36.9 [6.4] ng/ml). No suppression of PGH was noted at one, two or three hours after a 75 g oral glucose load. Similarly, no changes were noted in growth hormone binding protein or in calculated free PGH over the course of the glucose tolerance test. As expected, insulin concentrations rose sixfold and insulin like growth factor binding protein 1 concentrations fell by 20% with glucose loading. Cot-relation analysis showed maternal weight, BMI, fasting serum glucose serum insulin to be significantly correlated with the babies' birthweight. Our results support the proposition that PGH concentrations in maternal serum are not Suppressed by oral glucose loading in non-diabetic mothers.

Audit of maternal and fetal outcomes in women treated for glucose intolerance during pregnancy

Objective To determine whether one should aim for glycaemia that is statistically 'normal' or for levels of glycaemia low enough to prevent macrosomia (if such a threshold exists) when glucose intolerance is detected during pregnancy Design An audit of pregnancy outcomes in women with impaired glucose tolerance in pregnancy as compared to a local age-matched reference group with normal glucose tolerance. Results Our study suggests that for most patients, more intensive therapy would not have been justified. Maternal smoking appeared to convey some 'advantages' in terms of neonatal outcomes, with reduction in large-for-gestational-age (LGA) infants and jaundice in babies of impaired glucose tolerance (IGT) mothers. Conclusions These observations demonstrate the importance of considering risk factors other than GTT results in analysing pregnancy outcomes, while emphasising that 'normalisation' of fetal size should not be our only therapeutic endpoint. Our detailed outcome review allows us to reassure patients with GDM that with current treatment protocols, they should have every expectation of a positive pregnancy outcome.

The role of conserved CXXXRXG motif in the expression and function of the human norepinephrine transporter

Highly conserved motifs in the monoamine transporters, e.g. the human norepinephrine transporter (hNET) GXXXRXG motif which was the focus of the present study, are likely to be important structural features in determining function. This motif was investigated by mutating the glycines to glutamate (causing loss of function) and alanine, and the arginine to glycine. The effects of hG117A, hR121G and hG123A mutations on function were examined in COS-7 cells and compared to hNET. Substrate K-m values were decreased for hG117A and hG123A, and their K values for inhibition of [3 H]nisoxetine binding were decreased 3-4-fold and 4-6-fold, respectively. Transporter turnover was reduced to 65% of hNET for hG117A and hR121G and to 28% for hG123A, suggesting that substrate translocation is impaired. K values of nisoxetine and desipramine for inhibition of [H-3]norepinephrine uptake were increased by 5-fold for hG117A, with no change for cocaine. The K-i value of cocaine was increased by 3-fold for hG123A, with no change for nisoxetine and desipramine. However, there were no effects of the mutations on the K-d of [H-3]nisoxetine binding or K-i values of desipramine or cocaine for inhibition of [H-3]nisoxetine binding. Hence, glycine residues of the GXXXRXG motif are important determinants of NET expression and function, while the arginine residue does not have a major role. This study also showed that antidepressants and psychostimulants have different NET binding sites and provided the first evidence that different sites on the NET are involved in the binding of inhibitors and their competitive inhibition of substrate uptake. (C) 2002 Elsevier Science B.V. All rights reserved.

Temporal and spatial expression of fibroblast growth factor receptor 4 isoforms in murine tissues

Fibroblast growth factor receptors (FGFRs) undergo highly regulated spatial and temporal changes of expression during development. This study describes the use of quantitative reverse transcriptase-polymerase chain reaction and immunochemistry to assess the changes in expression of FGFR4 as compared to its FGFR4-17a and -17b isoforms in mouse tissues, from early embryogenesis through to adulthood. Compared to FGFR4, the expression of the isoforms is more restricted at all developmental stages tested. The reverse transcriptase-polymerase chain reaction demonstrated that FGFR4 is expressed in more tissue types than either of its isoforms: it was found predominantly in lung, liver, brain, skeletal muscle and kidney, whereas the FGFR4-17a form was detected in lung and skeletal muscle, and the FGFR4-17b form only in lung, liver, skeletal muscle and kidney. Immunohistochemistry confirmed strong FGFR4-17b expression in the postnatal lung. When combined, the results suggest that FGFR4 variants play important roles particularly in lung and skeletal muscle development.

Distribution of two splice variants of the glutamate transporter GLT1 in the retinas of humans, monkeys, rabbits, rats, cats, and chickens

Antibodies have been generated against two carboxyl-terminal splice variants of the glutamate transporter GLT1, namely, the originally described version of GLT1 and GLT1-B, and labelling has been examined in multiple species, including chickens and humans. Although strong specific labelling was observed in each species, divergent patterns of expression were noted. Moreover, each antibody was sensitive to the phosphorylation state of the appropriate protein, because chemical removal of phosphates using alkaline phosphatase revealed a broader range of labelled elements in most cases. In general, GLT1-B was present in cone photoreceptors and in rod and cone bipolar cells in the retinas of rabbits, rats, and cats. In the cone-dominated retinas of chickens and in marmosets, GLT1-B was associated only with cone photoreceptors, whereas, in macaque and human retinas, GLT1-B was associated with bipolar cells and terminals of photoreceptors. In some species, such as cats, GLT-B was also present in horizontal cells. By contrast, GLT1 distribution varied. GLT1 was associated with amacrine cells in chickens, rats, cats, and rabbits and with bipolar cells in marmosets and macaques. In the rat retina, rod photoreceptor terminals also contained GLT1, but this was evident only in enzymatically dephosphorylated tissues. We conclude that the two variants of GLT1 are present in all species examined but are differentially distributed in a species-specific manner. Moreover, each cell type generally expresses only one splice variant of GLT1. J. Comp. Neurol. 445:1-12, 2002. (C) 2002 Wiley-Liss, Inc.

Distribution of two splice variants of the glutamate transporter GLT-1 in rat brain and pituitary

We have performed immunocytochemistry on rat brains using a highly specific antiserum directed against the originally described form of the glutamate transporter GLT-1 (referred to hereafter as GLT-1alpha), and another against a C-terminal splice variant of this protein, GLT-1B. Both forms of GLT-1 were abundant in rat brain, especially in regions such as the hippocampus and cerebral cortex, and macroscopic examination of sections suggested that both forms were generally regionally coexistent. However, disparities were evident; GLT-1alpha was present in the intermediate lobe of the pituitary gland, whereas GLT-1B was absent. Similar marked disparities were also noted in the external capsule, where GLT1A labeling was abundant but GLT-1B was only occasionally encountered. Conversely, GLT-1B was more extensively distributed, relative to GLT-1alpha, in areas such as the deep cerebellar nuclei. In most regions, such as the olfactory bulbs, both splice variants were present but differences were evident in their distribution. In cerebral cortex, patches were evident where GLT-1B was absent, whereas no such patches were evident for GLT-1alpha. At high resolution, other discrepancies were evident; double-labeling of areas such as hippocampus indicated that the. two splice variants may either be differentially expressed by closely apposed glial elements or that the two splice variants may be differentially targeted to distinct membrane domains of individual glial cells. (C) 2002 Wiley-Liss, Inc.

Distribution of two splice variants of the glutamate transporter GLT-1 in the developing rat retina

The distributions of a carboxyl terminal splice variant of the glutamate transporter GLT-1, referred to as GLT-1B, and the carboxyl terminus of the originally described variant of GLT-1, referred to hereafter as GLT-1alpha, were examined using specific antisera. GLT-1B was present in the retina at very early developmental stages. Labelling was demonstrable at embryonic day 14, and strong labelling was evident by embryonic day 18. Such labelling was initially restricted to populations of cone photoreceptors, the processes of which extended through the entire thickness of the retina and appeared to make contact with the retinal ganglion cells. During postnatal development the GLT-1B-positive photoreceptor processes retracted to form the outer plexiform layer, and around postnatal day 7, GLT-1B-immunoreactive bipolar cells appeared. The pattern of labelling of bipolar cell processes within the inner plexiform layer changed during postnatal development. Two strata of strongly immunoreactive terminals were initially evident in the inner plexiform layer, but by adulthood these two bands were no longer evident and labelling was restricted to the somata and processes (but not synaptic terminals) of the bipolar cells, as well as the somata, processes, and terminals of cone photoreceptors. By contrast, GLT-1alpha appeared late in postnatal development and was restricted mainly to a population of amacrine cells, although transient labelling was also associated with punctate elements in the outer plexiform layer, which may represent photoreceptor terminals, (C) 2002 Wiley-Liss, Inc.

Quantitation of human brain GABAA receptor isoforms by competitive RT-PCR

We have developed a competitive RT-PCR assay, adapted from Lewohl et al. [Brain Res. Brain Res. Protoc. 1 (1997) 347]. for the quantitation of GABA, receptor beta isoforms in human brain using an internal standard that shares high sequence homology to the targets. The internal standard is identical to the beta(1) sequence except for a 61 bp deletion and the incorporation of a Hind III restriction enzyme site. Unlike traditional competitive RT-PCR, which requires a range of internal standard concentrations to be titrated against a constant amount of unknown, this method relies on a standard curve for quantitation of each sample and thus permits increased sample throughput. This method is suitable for the quantitation of beta(1), beta(2) and beta(3) isoforms of the GABA(A) receptor in human alcoholic and control brain. (C) 2003 Elsevier Science B.V. All rights reserved.

Synaptic vesicle transport and synaptic membrane transporter sites in excitatory amino acid nerve terminals in Alzheimer disease

The apparent L-[H-3]glutamate uptake rate (v') was measured in synaptic vesicles isolated from cerebral cortex synaptosomes prepared from autopsied Alzheimer and non-Alzheimer dementia cases, and age-matched controls. The initial synaptosome preparations exhibited similar densities of D-[H-3]aspartate membrane binding sites (B-MAX values) in the three groups. In control brain the temporal cortex D-[H-3]aspartate B-MAX was 132% of that in motor cortex, parallel with the L- [H-3]glutamate v' values (temporal = 139% of motor; NS). Unlike D- [H-3]aspartate B-MAX values, L- [H-3]glutamate v' values were markedly and selectively lower in Alzheimer brain preparations than in controls, particularly in temporal cortex. The difference could not be attributed to differential effects of autopsy interval or age at death. Non-Alzheimer dementia cases resembled controls. The selective loss of vesicular glutamate transport is consistent with a dysfunction in the recycling of transmitter glutamate.

Aging per se does not influence glucose homeostasis - In vivo and in vitro evidence

OBJECTIVE - To assess the effect of age on glucose metabolism by examining 1) glucose metabolism in young and middle-aged subjects when total or regional adiposity is taken into account and 2) in vitro glucose transport in adipose tissue explants from young and middle-aged women paired for total and abdominal adiposity. RESEARCH DESIGN AND METHODS - Study 1: body composition, subcutaneous abdominal and visceral adipose tissue areas, and fasting and oral glucose-stimulated glucose and insulin were measured in 84 young and 81 middle-aged men and in 110 young and 91 middle-aged women. Study 2: glucose uptake in subcutaneous abdominal and visceral adipose tissue explants were measured in eight young and eight middle-aged women. RESULTS - Study 1: young and middle-aged men showed similar subcutaneous abdominal tissue area, whereas fat mass and visceral adipose tissue were greater in middle-aged than in young men (P < 0.01). Fat mass and subcutaneous and visceral adipose tissue areas were greater in middle-aged as compared with young women (P < 0.01). Fasting plasma glucose and the glucose response to an oral glucose tolerance test were significantly higher in middle-aged than in young men and women (P < 0.001). Statistical control for visceral adipose tissue area eliminated the difference seen in glucose response in men and women. Study 2: glucose transport in subcutaneous and omental adipose tissue did not differ between young and middle-aged women. CONCLUSIONS - 1) Visceral obesity, more than age per se, correlates with glucose intolerance in middle-aged subjects; 2) aging does not influence in vitro adipose tissue glucose uptake.

Effects of glucose-insulin-potassium infusion on chronic ischaemic left ventricular dysfunction

Background: Glucose-insulin-potassium (GIK) infusion improves cardiac function and outcome during acute ischaemia. Objective: To determine whether GIK infusion benefits patients with chronic ischaemic left ventricular dysfunction, and if so whether this is related to the presence and nature of viable myocardium. Methods: 30 patients with chronic ischaemic left ventricular dysfunction had dobutamine echocardiography and were given a four hour infusion of GIK. Segmental responses were quantified by improvement in wall motion score index (WMSI) and peak systolic velocity using tissue Doppler. Global responses were assessed by left ventricular volume and ejection fraction, measured using a three dimensional reconstruction. Myocardial perfusion was determined in 15 patients using contrast echocardiography. Results: WMSI (mean (SD)) improved with dobutamine (from 1.8 (0.4) to 1.6 (0.4), p < 0.001) and with GIK (from 1.8 (0.4) to 1.7 (0.4) p < 0.001); there was a similar increment for both. Improvement in wall motion score with GIK was observed in 55% of the 62 segments classed as viable by dobutamine echocardiography, and in 5% of 162 classed as non-viable. There was an increment in peak systolic velocity after both doputamine echocardiography (from 2.5 (1.8) to 3.2 (2.2) cm/s, p < 0.01) and GIK (from 3.0 (1.6) to 3.5 (17) cm/s, p < 0.001). The GlK effects were not mediated by changes in pulse, mean arterial pressure, lactate, or catecholamines, nor did they correlate with myocardial perfusion. End systolic volume improved after GlK (p = 0.03), but only in 25 patients who had viable myocardium on dobutom ne echocardiography. Conclusions: In patients with viable myocardium and chronic left ventricular dysfunction, GlK improves wall motion score, myocardial velocity, and end systolic volume, independent of effects on haemodynamics or catecholamines. The response to GlK is observed in areas of normal and abnormal perfusion assessed by contrast echocardiography.