Metabolic response to beet fibre test meals

Test meals with 10.9 g dietary fibre from sugar beet and corresponding control meals were given to eight healthy subjects, aged 67 ± 9 years. The postprandial glucose, triglyceride, hormone and glycerol responses were monitored during 3 hours. After the beet fibre meal the insulin and C-peptide areas were reduced by 28 ( P < 0.01) and 22% ( P > 0.025), respectively, and the somatostatin levels increased by approximately 30% ( P > 0.05). Further, the maximum relative postprandial reduction of plasma glycerol levels was less evident after the fibre-rich meal than after the control meal (36 ± 4% v. 46 ± 4%, P < 0.05). There was no apparent difference in the overall glycaemic response between the meals. The triglyceride levels were similar after both test meals.
Suspension of beet fibre bread given to rats by oro-gastric intubation induced lower blood glucose response than a control bread at 15 and 30 min ( P < 0.001), respectively, but a similar insulin response.
The results suggest an effect of beet fibre on the rate of carbohydrate absorption, expressed as a lower insulin response in the healthy volunteers and a reduced glucose response in the rat.
The mechanism behind this effect in healthy subjects could possibly be mediated by an increased somatostatin response.     

Mid-infrared spectroscopy on skin using a silver halide fibre probe in vivo

Background/aim: Mid-infrared spectroscopy is a versatile method for in vivo investigation of skin after topical treatment with skin care products.
Methods: FTIR-spectrometer (Bruker Optics) with a flexible silver halide fibre probe (Infrared Fiber Sensors).
Results: Absorbance spectra from 700 to 3000 cm⁻¹ have been recorded to gain information about proteins (amide-I and amide-II vibrations at 1650 and 1550 cm⁻¹), esters (1740 cm⁻¹), carboxylic acid (1710 cm⁻¹), polyalcohols (1050 cm⁻¹) and hydrocarbons (CH _n vibrations at 2800–3000 cm⁻¹).
Conclusions: Using the particular light guide, we were able to measure for the first time the effects of lip care products on lips directly. Furthermore, water binding and glycerol content of the skin could be determined simultaneously, as well as the replenishment of lipids by lipid-enriched bath oil.     

Physiological Effects of Mental Stress and Orthostasis in Young Insulin-Dependent Diabetic Patients

ABSTRACT. The effects of procedures which stimulate sympathetic activity, viz. mental stress induced by a colour-word conflict test (CWT) for 20 min, and orthostasis (ORT) for 8 min were studied in 8 young (16-20 yr) insulin-dependent diabetes mellitus (IDDM) patients and 9 age and sex-matched healthy controls. The IDDM patients showed no signs of neuropathy or retinopathy and their mean HbA_1c value was 8.4 ±0.6% (normal value < 5.0 %). Blood pressure and heart rate increased significantly during CWT and ORT in both groups. The changes in systolic blood pressure and heart rate were comparable in both groups during CWT; the IDDM group showed a higher ( p < 0.05) heart rate after 8 min of orthostasis, however. CWT and ORT elicited equivalent increases in noradrenaline in venous plasma in both groups ( p < 0.05), but the IDDM patients had 50% lower values ( p < 0.01) at rest, during CWT and at rest after CWT than controls. CWT and ORT evoked equivalent plasma adrenaline increases in both groups. The lipolysis marker, plasma glycerol, was about 40 % lower ( p < 0.05) in the IDDM group before and after CWT. Yet, mental stress evoked equivalent increases in glycerol levels ( p < 0.01) in both groups. These findings indicate that sympathetic activity in the young diabetic patients without signs of neuropathy may be blunted.     

模拟医学生物化学实验血清标本的探讨

用蛋白胨、三油酸甘油酯、鼠肝、葡萄糖等材料模拟血清标本,通过测定该血清中蛋白、血脂、谷丙转氨酶、血糖以及部分物理参数,探讨了模拟血清从外观和实验项目上满足实验教学的可行性。结果表明,模拟血清实用、简便易得,既能解决医学生物化学实验教学标本来源困难问题,又能防止实验室污染和节省大量实验经费。     

Evidence for a glycerol pathway through aquaporin 1 (CHIP28) channels

Permeabilities to glycerol and small non-electrolytes of three Aquaporin 1 CHIP (AQP1) water channels were measured in AQP1 cRNA-injected Xenopus laevis oocytes and in human AQP1 channels reconstituted in proteoliposomes. By an osmotic swelling assay, significant increases of ethylene glycol, glycerol and 1,3-propanediol apparent permeability coefficients (P_solutes) were found in oocytes expressing human, rat and frog AQP1. p-Chloromercuribenzene sulphonate (PCMBS) and CuSO₄ inhibited, by 95% and 58% respectively, apparent glycerol permeability (P _gly) in oocytes expressing human AQP1. pCMBS inhibition was reversed by -mercaptoethanol and CuSO₄ inhibition was partly reversed by the Cu²⁺-binding peptide Gly-Gly-His. Tritiated glycerol uptakes confirmed the augmented P _gly value of AQP1 cRNA-injected oocytes. In contrast, no increases of urea, meso-erythritol, D- or L-threitol, xylitol and mannitol uptakes were detected. Stopped-flow light scattering experiments performed with human AQP1 proteoliposomes also revealed a much greater increase of P _gly than did those with protein-free liposomes; the initial rate of proteoliposomes also swelling was inhibited by 96.2% with HgCl₂ and by 72.5% with CuSO₄. In AQP1 cRNA-injected oocytes and in proteoliposomes, the value of the glycerol reflection coefficient was 0.74–0.80, indicating that water and glycerol share the same pathway. All these results provide strong evidence that water and certain small solutes permeate the AQP1 channels expressed at the surface of X. laevis oocytes or reconstituted in proteoliposomes. The urea exclusion suggests that the selectivity of the AQP1 channels not only depends on the size of the solutes but probably also on their flexibility and their ability to form H-bonds.     

Interactions of γ-immunoglobulins with lipid mono- or bilayers and liposomes. Existence of two conformations of γ-immunoglobulins of different hydrophobicities

Interactions between rabbit-γ-immunoglobulins and model membranes (lipid monalayers, planar lipid bilayers, liposomes) have been investigated. No significant interaction was observed with immunoglobulins. However, immunoglobulins dialysed first vs aqueous buffer having pH 2 or 3 and then dialysed against pH 7 buffer presumably adopt a new conformation which allows their bindings to model membranes. This binding is hydrophobic and the immunoglobulin region interacting with the lipid acyl chains is probably located in the heavy chain, as suggested by labelling in this region by a photosensitive probe previously incorporated into the lipid hydrophobic core. Cleavage at the hinge region by papain or pepsin, or heating above 38°C, induces the loss of the hydrophobic conformation responsible for hydrophobic bindings. The binding capacity of immunoglobulins heated above 38°C is restored after momentary dialysis at pH 2. The possible existence of two Ig isomers is discussed in relation to the mechanism of γ-immunoglobulin passage through the endoplasmic membrane and fixation into the plasma membrane.     

AMPK as a metabolic switch in rat muscle,liver and adipose tissue after exercise

An increasing body of evidence has revealed that activation of adenosine monophosphate (AMP)‐activated protein kinase (AMPK)‐activated protein kinase increases fatty acid oxidation by lowering the concentration of malonyl coenzyme A (CoA), an inhibitor of carnitine palmitoyl transferase 1. Studies carried out primarily in skeletal muscle suggest that AMPK modulates the concentration of malonyl CoA by concurrently phosphorylating and inhibiting acetyl CoA carboxylase (ACC), the rate limiting enzyme in malonyl CoA synthesis, and phosphorylating and activating malonyl CoA decarboxylase (MCD), an enzyme involved in its degradation. We have recently observed that AMPK and MCD activities are increased and ACC activity diminished in skeletal muscle, liver and, surprisingly, in adipose tissue 30 min following exercise (treadmill run) in normal rats. In liver and adipose tissue these changes were associated with a decrease in the activity of glycerol‐3‐phosphate acyltransferase (GPAT), which catalyses the first committed reaction in glycerolipid synthesis and, which like ACC, is phosphorylated and inhibited by AMPK. Similar changes in ACC, MCD and GPAT were observed following the administration of 5‐aminoimidazole 4‐carboxamide‐riboside (AICAR), further indicating that the exercise‐induced alterations in these enzymes were AMPK‐mediated. Conclusions: (1) AMPK plays a major role in regulating lipid metabolism in multiple tissues following exercise. (2) The net effect of its activation is to increase fatty acid oxidation and diminish glycerolipid synthesis. (3) The relevance of these findings to the regulation of muscle glycogen repletion in the post‐exercise state and to the demonstrated ability of AMPK activation to decrease adiposity and increase insulin sensitivity in rodents remains to be determined.     

Rapid molecular cytogenetic analysis of X-chromosomal microdeletions: Fluorescence in situ hybridization (FISH) for complex glycerol kinase deficiency

Diagnosis of X-chromosomal microdeletions has relied upon the traditional methods of Southern blotting and DNA amplification, with carrier identification requiring timeconsuming and unreliable dosage calculations. In this report, we describe rapid molecular cytogenetic identification of deleted DNA in affected males with the Xp21 contiguous gene syndrome (complex glycerol kinase deficiency, CGKD) and female carriers for this disorder. CGKD deletions involve the genes for glycerol kinase, Duchenne muscular dystrophy, and/or adrenal hypoplasia congenita. We report an improved method for diagnosis of deletions in individuals with CGKD and for identification of female carriers within their families, using fluorescence in situ hybridization (FISH) with a cosmid marker (cosmid 35) within the glycerol kinase gene. When used in combination with an Xq control probe, affected males demonstrate a single signal from the control probe, while female carriers demonstrate a normal chromosome with two signals, as well as a deleted chromosome with a single signal from the control probe. FISH analysis for CGKD provides the advantages of speed and accuracy for evaluation of submicroscopic X-chromosomal deletions, particularly in identification of female carriers. In addition to improving carrier evaluation, FISH will make prenatal diagnosis of CGKD more readily available. © 1995 Wiley-Liss, Inc.     

α-Adrenoceptor stimulation,but not muscarinic stimulation,increases cyclic AMP accumulation in brain slices due to protein kinase C mediated enhancement of adenosine receptor effects

In the present study, using rat hippocampal slices, we have further examined the stimulatory effect of α₁ adrenoceptors on the accumulation of cyclic AMP, which is known to depend on calcium and adenosine. The addition of noradrenaline (NA) stimulated the accumulation of [³H]inositol phosphates in [³H]inositol-treated slices. This effect was shared by carbachol (10–100 μmol l^-1) but not by the adenosine receptor agonist 2-chloroadenosine (100 μmol l^-1). The stimulatory effect of the α-agonists (phenylephrine or NA + propranolol) on cyclic AMP was shared by a diacylglycerol derivative, sn-1-oleyl-2-acetyl glycerol (OAG), and by the tumour-promoting phorbol esters phorboldibutyrate (PDiBu) and tetradecanoyl phorbol acetate (TPA). PDiBu caused a translocation of protein kinase C from soluble to particulate fractions. The effects of PDiBu and α-adrenoceptor stimulation on cyclic AMP were not additive. Surprisingly, carbachol (1–1000 μmol l^-1) did not stimulate cyclic AMP accumulation in rat hippocampal slices either in the presence or in the absence of an adenosine receptor agonist. The results are compatible with the opinion that a-adrenoceptor stimulating drugs enhance the formation of inositol phosphates and diacylglycerol, which synergistically activate protein kinase C, which in turn augments the stimulation of cyclic AMP formation. Thus, a neurotransmitter whose principal biological effect is to stimulate inositol phosphate formation can influence cyclic AMP formation by virtue of an interaction with the actions of the ubiquitous neuromodulator adenosine. The fact that the effect of the α-receptor stimulation was not mimicked by a muscarinic agonist could indicate that other factors besides activation of inositol phospholipid hydrolys are important for this receptor–receptor interaction.     

Body weight set point studies in weanling rats with dorsomedial hypothalamic lesions (DMNL rats)

In order to further characterize a previously postulated "organismic" set point, weanling DMNL and control (CON) rats were maintained on lab chow ad lib (AL) for 55 post-operative days. Subsequently, some DMNL and CON rats were food-restricted (REST) to 80% of the food intake of their AL-fed counterparts for 24 days. At this point, representative rats from each group were killed by decapitation and the remaining animals were re-fed AL and killed 7 and 22 days thereafter. At the end of REST, both DMNL and CON showed significant weight loss, which was greater in CON than in DMNL rats. After 7 days of refeeding, DMNL rats normalized their body weights but re-fed CON still weighed less than AL-fed CON 22 days after refeeding. Food intake in formerly REST groups overshot on refeeding for 7 days, but this was significant only in DMNL rats. Notably, during this time formerly REST-DMNL ate as much as AL-fed CON. Efficiency of food utilization was normal in DMNL during AL feeding and became reduced on REST as it did in REST-CON. Notably, on refeeding formerly REST-DMNL rats overshot that of AL-fed DMNL rats by the same magnitude as previously REST-CON overshot the values of AL-fed CON. After 22 days of refeeding, this overshoot was still evident in DMNL but not in CON. At the end of the REST period, plasma insulin and glucose were similar in AL-fed DMNL and AL-fed CON. They were significantly and comparably reduced in both REST-DMNL and REST-CON compared to the AL-fed DMNL and AL-fed CON. On refeeding these changes normalized within seven days. At the end of REST, plasma free fatty acid concentrations were higher in REST-DMNL and REST-CON than in AL-fed DMNL and AL-fed CON. After seven days of refeeding they normalized only in formerly REST-CON. Plasma glycerol and total protein were normal throughout all groups, as was carcass protein. Carcass fat was equivalently reduced in both DMNL and CON at the end of REST and normalized 7 days after refeeding. AL-DMNL had the same carcass fat as AL-CON and REST-DMNL had the same carcass fat as REST-CON. In conjunction with previously reported normal anabolic hormone levels the data suggest that DMNL rats are not growth-retarded but are merely scaled down in size without compromise of their homeostatic competence. We take this as strong evidence for the existence of an "organismic" set point.