Overexpression of glucose transporter 2 in GT1-7 cells inhibits AMP-activated protein kinase and agouti-related peptide expression

Glucose transporter 2 (GLUT2) has been proposed as a glucose sensor in pancreatic beta cells. GLUT2 has been found widely expressed in the brain and GLUT2 in the hypothalamus and hindbrain has been suggested to be involved in the central glucose sensing and regulation of glucose homeostasis and food intake. In this study, we overexpressed GLUT2 in GT1-7 neuroblastoma cells and investigated the effect of GLUT2 overexpression on cellular energy status in these cells. Compared with control cells, GLUT2 overexpression resulted in significantly increased cellular ATP levels at 5 and 25 mM glucose concentrations, more inhibition of agouti-related peptide (AgRP) mRNA and AMP-activated protein kinase (AMPK) phosphorylation by glucose, and attenuated stimulation of AgRP mRNA and AMPK by 2-deoxy-d-glucose (2DG), implicating that brain GLUT2 may be important in the regulation of food intake.

Effects of resistant starch, a non-digestible fermentable fiber, on reducing body fat

OBJECTIVE

To assess the effects of energy dilution with non-fermentable and fermentable fibers on abdominal fat and gut peptide YY (PYY) and glucagon-like peptide (GLP)-1 expressions, three rat studies were conducted to: determine the effects of energy dilution with a non-fermentable fiber, compare similar fiber levels of fermentable and non-fermentable fibers, and compare similar metabolizable energy dilutions with fermentable and non-fermentable fibers.

RESEARCH METHODS AND PROCEDURES

In Study 1, rats were fed one of three diets with different metabolizable energy densities. In Study 2, rats were fed diets with similar fiber levels using high amylose-resistant cornstarch (RS) or methylcellulose. In Study 3, rats were fed diets with a similar dilution of metabolizable energy using cellulose or RS. Measurements included food intake, body weight, abdominal fat, plasma PYY and GLP-1, gastrointestinal tract weights, and gene transcription of PYY and proglucagon.

RESULTS

Energy dilution resulted in decreased abdominal fat in all studies. In Study 2, rats fed fermentable RS had increased cecal weights and plasma PYY and GLP-1, and increased gene transcription of PYY and proglucagon. In Study 3, RS-fed rats had increased short-chain fatty acids in cecal contents, plasma PYY (GLP-1 not measured), and gene transcription for PYY and proglucagon.

DISCUSSION

Inclusion of RS in the diet may affect energy balance through its effect as a fiber or a stimulator of PYY and GLP-1 expression. Increasing gut hormone signaling with a bioactive functional food such as RS may be an effective natural approach to the treatment of obesity.

Peptide YY and proglucagon mRNA expression patterns and regulation in the gut

OBJECTIVE

Peptide YY (PYY) and glucagon-like peptide-1 are important in the control of energy homeostasis and are both secreted from the gut in response to ingested nutrients. However, more studies are needed on nutrient regulation of their gene expression patterns in specific areas of the gut. This study detailed PYY and proglucagon (the gene that encodes glucagon-like peptide-1) gene expression patterns and regulation in the gut. We further examined the regulation of PYY and proglucagon mRNA by a diet containing fermentation-resistant starch (in vivo) and butyrate (in vitro).

RESEARCH METHODS AND PROCEDURES

Quantitative real time reverse transcriptase-polymerase chain reaction was used to measure PYY and proglucagon gene expression in epithelial cells collected from the duodenum, jejunum, cecum, and colon in normal Sprague-Dawley rats and in rats fed a resistant starch diet for 4 weeks. The same measurements were also performed in primary epithelial cells collected from the cecum and colon of normal rats after the cells were incubated with butyrate for 3 hours.

RESULTS

The gene expression patterns for PYY and proglucagon are similar to their peptide distribution patterns in the gut. Also, PYY and proglucagon mRNA expression were up-regulated in the cecum and colon in resistant-starch-fed rats. Butyrate increased PYY and proglucagon gene expression in a dose-dependent manner in vitro.

DISCUSSION

Our data provide evidence that the distal part of the gut has the ability to sense nutrients such as butyrate, resulting in the up-regulation of PYY and proglucagon gene expression.

Adenosine A2A receptors are expressed by GABAergic neurons of medulla oblongata in developing rat

During early development, adenosine contributes to the occurrence of respiratory depression and recurrent apneas. Recent physiological studies indicate that GABAergic mechanisms may be involved in this inhibitory action of adenosine, via their A(2A) receptors. In the present study, in situ hybridization with ribonucleotide probes for A(2A) receptor (A(2A)R) mRNA was combined with the immunolabeling technique for parvalbumin and transneuronal retrograde tracing method using green fluorescent protein expressing pseudorabies virus (GFP-PRV) to (1) characterize age-dependent changes in the expression of adenosine A(2A)Rs mRNA in brain stem regions where GABAergic neurons are located; (2) determine whether GABA-containing neurons express A(2A)R mRNA traits, and (3) identify whether bulbospinal GABAergic neurons projecting to phrenic nuclei contain A(2A)R mRNA. Results revealed expression of A(2A) receptors in regions of medulla oblongata containing GABAergic neurons, namely in the ventral aspect of the medulla, within the Bötzinger region and caudal to it, the gigantocellular reticular nucleus, midline neurons and the caudal ventrolateral medulla oblongata. Furthermore, a subpopulation of identified GABAergic neurons, projecting to the phrenic motor nuclei, possess A(2A)R mRNA. It is concluded that adenosine A(2A)Rs expressed by GABAergic neurons are likely to play a role in mediating adenosine-induced respiratory depression.

Current treatment options for asthma in adults

Asthma is a common disorder with an increasing prevalence in the developed world. It is a serious health problem affecting health care costs, lost productivity, and death. Unfortunately, uncontrolled asthma is common and often unrecognized by physicians; of equal concern, uncontrolled asthma is accepted by asthmatic patients as they are uneducated as to what to expect from asthma therapy. Many learn to live with the limitations of daily activity and to overuse their rescue inhalers and yet when asked by their physicians, ''How's your asthma?'' the answer is ''okay''. The pursuit of more revealing questions regarding frequency in the use of rescue medications, nocturnal symptoms, activity limitations, and compliance with controller medications may be then overlooked. To achieve the goal of normal life on as few medications as possible will start with a well-educated patient. Understanding intermittent from persistent asthma and then tailoring the best regimen for each patient is imperative. The treatment options and the advances in the understanding of the pathophysiology of asthma in the past 3 decades have been remarkable. There are increasing resources for both physicians and patients available to facilitate a better understanding of asthma management and the several treatment options. Currently established guidelines are an excellent starting point for initiating therapy for intermittent and mild, moderate, and severe persistent asthma. The short-acting beta 2 agonists are first-line therapy for intermittent asthma, exercise-induced asthma, and acute exacerbations. Long-acting Beta 2 agonists, cromolyn and nedocromil, and leukotriene modifiers may also be used for exercise. Systemic corticosteroids may be needed for acute exacerbations. The treatment of choice for persistent asthma is ICS and, depending on the severity, add-on therapy with long-acting beta 2 agonists, theophylline, and leukotriene modifiers are next. Lastly, omalizumab, anti-IgE therapy, will make an important place for its use in certain persistent moderate and severe asthma. This will be particularly true if the cost of the medication is reduced in the future. Asthma control, morbidity, and mortality will improve with a careful and comprehensive medical regimen using the current multiple treatment options.

Role of neuronal energy status in the regulation of adenosine 5'-monophosphate-activated protein kinase, orexigenic neuropeptides expression, and feeding behavior

Nutrient sensing in the hypothalamus is tightly related to food intake regulation. However, the mechanisms by which the nutrient-sensing cells of the brain translate this signal of energy need into feeding behavior via regulation of neuropeptide expression are not known. To address this issue, we investigated two neuronal cell lines expressing agouti-related protein (AgRP), ex vivo hypothalamic tissues, and in vivo whole animals. Maintaining cells in a low cellular ATP concentration generated by low glucose, 2-deoxyglucose (2-DG), ATP synthesis inhibitor, and 5-aminoimidazole-4-carboxamide 1-beta-d-ribofuranoside increased phosphorylation of AMP-activated protein kinase (AMPK) and increased AgRP expression, whereas maintaining cells in high ATP status by high glucose and pyruvate supplementation in 2-DG-treated cells decreased phosphorylation of AMPK and decreased AgRP expression. Overexpression of a dominant-inhibitory mutant of AMPK significantly decreased low-glucose- or 2-DG-induced AgRP expression. Furthermore, ex vivo hypothalamus culture in high glucose concentrations decreased both expression and phosphorylation of AMPK and expression of both AgRP and neuropeptide Y, whereas pyruvate supplementation suppressed a 2-DG-induced AgRP expression. Finally, our in vivo studies clearly show that central administration of pyruvate dramatically delayed 2-DG-induced food intake. These data indicate that modulation of ATP levels in neuronal cells triggers a cascade of events via AMPK that modulate feeding behavior to restore energy status of cells.

Bronchodilators and corticosteroids in the treatment of asthma

Despite advancements in treatment, the incidence of asthma, asthma-related deaths and hospitalizations for asthma have increased significantly during the past decade. Although asthma mortality may now be decreasing, reasons for the worsening of morbidity and mortality in asthma remain unclear. These unexpected changes in asthma severity have sparked renewed interest in research into the pathogenesis and treatment of the condition. Beta(2)-Adrenergic agonists are the most commonly used class of drugs for the treatment of asthma. Recent concerns about safety issues for beta-agonists caused reevaluation of prescribing practices, and using them on an as-needed basis is now more frequently accepted and recommended. In acute asthma, a beta(2)-adrenergic agonist is still the medication of choice. Long-acting salmeterol and formoterol, administered only twice daily, can decrease symptoms of asthma during day and nighttime. On the other hand, the role of tolerance to their bronchodilator and bronchoprotective effects is still to be determined in the treatment of asthma. Theophylline, whose use has been limited by the potential for serious toxicity, may regain an important position in asthma treatment with the development of the knowledge about its antiinflammatory actions. Dosing theophylline on a time- related basis also improves the risk/benefit ratio and makes it a useful drug for nocturnal asthma. Ipratropium bromide, an anticholinergic drug, still awaits a defined role in the treatment of asthma. Studies on its use for acute asthma have not achieved consensus and, for nocturnal asthma, the short duration of effect limits the benefits. Corticosteroids, including inhaled steroids, have measurable effects on symptoms, lung function, bronchial responsiveness and inflammation associated with asthma. Side effects of chronic use limit systemic, but not inhaled administration. Newer preparations, like budesonide, flunisolide and fluticasone, decrease the incidence of possible side effects related to inhaled steroids by having better ratio of topical to systemic potency. Daily doses up to 1600 micro g of beclomethasone (or equivalent) are considered safe and higher doses should be reserved for patients with moderate to severe asthma. Although future trials are necessary to clarify many issues related to dosing of inhaled steroids, chronotherapy studies have shown that single administration between 3 and 5:30 p.m. may be as effective as 4 times a day dosing.

Recent innovations in asthma therapy

Guidelines for the diagnosis and management of asthma have been published since 1990 and already new versions are being published. The recommendations for the treatment of asthma were organized around four components of effective asthma management: i) use of objective measures of lung function to assess the severity of asthma and to monitor the course of therapy, ii) environmental control measures to avoid or eliminate factors that precipitate asthma symptoms or exacerbations, iii) comprehensive pharmacologic therapy for long-term management designed to reverse and prevent the airway inflammation characteristic of asthma as well as pharmacologic therapy to manage asthma exacerbations, and iv) patient education that fosters a partnership among the patient, family and clinicians. Newly released medications include anti-leukotriene (LTs) agents which function either by blocking the interaction of LTs with receptors (receptor antagonists) or by inhibiting leukotriene synthesis (synthesis inhibitors). Representatives of the antagonists discussed here are zafirlukast, pranlukast and montelukast. Zafirlukast (20 mg twice daily) improves pulmonary function indices and days without symptoms and decreases the asthma exacerbation frequency. Pranlukast, the first leukotriene receptor antagonist to be marketed, improves lung function and symptoms when 450 mg twice daily is used. A study with montelukast demonstrated similar positive results irrespective of the use of concomitant inhaled corticosteroid. This indicates that leukotriene receptor antagonists may have additive effects to steroid therapy. They may also be a potential alternative to inhaled steroids, although more studies need to be performed before defining the role of receptor antagonists in the treatment of asthma. Zileuton, a leukotriene synthesis inhibitor, has been shown to improve lung function, reduce symptoms and reduce use of beta-agonists and asthma exacerbations. These positive effects are dose-dependent and liver function abnormalities seem to be a relevant issue during zileuton use in some patients. Other compounds that inhibit LTs synthesis are in development and, like zileuton, need more tests. Phosphodiesterases (PDE), enzymes that break down cAMP and cGMP, have been a target for new compounds developed to treat asthma. Inhibition of PDE enzymes increases intracellular cAMP or cGMP which then produces bronchodilation. Recent studies have also shown antiinflammatory effects by suppressing some PDE isoenzymes, including PDE III and PDE IV. These effects were detected by studies in vitro and in animal models. Clinical trials are necessary to determine which PDE inhibitors can be useful for the treatment of asthma.

Evidence for hypothalamic KATP+ channels in the modulation of glucose homeostasis

Several lines of evidence support the hypothesis that ATP-sensitive K+ channels (K+(ATP)) participate in the brain's regulation of peripheral glucose homeostasis. In testing this hypothesis we conducted a series of in vivo experiments using albino rats and bilateral intrahypothalamic injections of K+(ATP) channel blockers, glibenclamide and repaglinide. The results show that 0.2 and 2.0 nM injections of glibenclamide lowered blood glucose in a dose-dependent manner. During mild insulin-induced hypoglycemia, hypothalamic glibenclamide delayed recovery to normoglycemia. The impaired recovery was associated with a reduction in plasma norepinephrine (P<0.001), though circulating epinephrine and glucagon were not reduced. In a separate experiment, 2-deoxy-D-glucose (200 mg/kg) was intraperitoneally administered to produce neuroglucopenia. Hypothalamic injections of either glibenclamide or repaglinide significantly blunted compensatory hyperglycemic responses (P<0.01). In a feeding study, 2.0, but not 0.2 nM of hypothalamic glibenclamide, reduced chow intake over a 2-h period (P<0.01). The results support the hypothesis that hypothalamic K+(ATP) channels participate in central glucose-sensing and glucose regulation.

Changes in adenosine transport associated with melaminophenyl arsenical (Mel CY) resistance in Trypanosoma evansi: down-regulation and affinity changes of the P2 transporter

Studies of the kinetics of adenosine transport were carried out on the P1 and P2 transporters of drug-sensitive Trypanosoma evansi and its cloned derivative, resistant to the melaminophenyl arsenical Mel CY. Characterization of adenosine uptake was made by estimation of the maximum concentration taken up at time infinity (Amax). Amax on the P2 transporter of sensitive T. evansi was greater than Amax on the P1 transporter. Amax of the P2 transporter was significantly decreased in drug-resistant trypanosomes. The effect of adenosine concentration and inhibitors, on the rate of adenosine uptake, was described by Michaelis-Menten equations. In sensitive T. evansi, the maximum velocity of adenosine uptake (Vmax) of the P2 transporter was 2-fold greater than Vmax of the P1 transporter. The Vmax of the P2 transporter in resistant parasites was reduced 9-fold. The binding constants Km and Ki on the P2 transporter of resistant T. evansi, showed that resistance was associated with an increased affinity for adenosine, and a decreased affinity for adenine and Berenil. We suggest that resistance to melaminophenyl arsenicals in T. evansi, occurs via 2 mechanisms: (1) a reduction in the number of expressed P2 transporter molecules resulting in decreased uptake of melaminophenyl arsenicals; (2) a change in the binding properties of the P2 transporter.

Inhaled corticosteroids reduce the progression of airflow limitation in chronic obstructive pulmonary disease: a meta-analysis

BACKGROUND

Chronic obstructive pulmonary disease (COPD) is a syndrome of chronic progressive airflow limitation which occurs as a result of chronic inflammation of the airways and lung parenchyma. However, the role of inhaled corticosteroids in the treatment of COPD is controversial. We hypothesised that inhaled corticosteroids reduce the progression of airflow limitation in COPD.

METHODS

A comprehensive literature search was conducted and data were analysed using random effects methodology. The effect of inhaled steroids on annual change in forced expiratory volume in 1 second (FEV1) was determined for all trials, for trials with high dose treatment regimens, and for trials in subjects with moderate to severe airflow limitation.

RESULTS

Data from eight controlled clinical trials of > or =2 years were included (n=3715 subjects). Meta-analysis of all study data revealed that inhaled corticosteroids reduce the rate of FEV1 decline by 7.7 ml/year (95% confidence interval (CI) 1.3 to 14.2, p=0.02). Meta-analysis of studies with high dose regimens revealed a greater effect of 9.9 ml/year (95% CI 2.3 to 17.5, p=0.01) compared with the meta-analysis of all studies.

CONCLUSIONS

Inhaled corticosteroid treatment for > or =2 years slows the rate of lung function decline in COPD. The effect observed with high dose regimens is greater than that with all regimens combined. These data suggest a potential role for inhaled corticosteroids in modifying the long term natural history of COPD.

Short-term food restriction and refeeding alter expression of genes likely involved in brain glucosensing

Several genes involved in glucosensing of the endocrine pancreas have been proposed to serve a similar function in the brain. These genes include the glucose transporter-2 (Glut-2) and glucokinase (GK). In addition, the glucagon-like peptide 1 receptor, which serves as a downstream signal modulator in pancreatic glucosensing and centrally alters feeding, is also of interest. We used quantitative real-time RT-PCR to measure changes in hypothalamic and brainstem Glut-2, GK, and Glp-1R expression of these genes induced by food restriction and refeeding. Sprague-Dawley rats were 50% food restricted for 1 day; one-half of the food-restricted rats were refed with chow for 1 hr before sacrifice. In both hypothalamus and brainstem, gene expression of Glut-2, GK, and Glp-1R was significantly lower in refed rats compared with food-restricted rats. The measures of gene expression in two feeding control groups (ad libitum and voluntarily overfed animals) were intermediate between the food-restricted and refed groups, but were not significantly different from each other. The results indicate that putative glucosensing (GK, Glut-2, and Glp-1R) gene expression in the hypothalamus and brainstem is reduced in response to food intake, depending on prior nutritional status.

Hypercapnia-induced activation of brainstem GABAergic neurons during early development

During early development, GABAergic mechanisms contribute to the regulation of respiratory timing in response to CO2. In 5-7 day old piglets, a double labeling technique was used to determine whether GABA-containing neurons are activated by normoxic hypercapnia (10% CO2, 21% O2, and 69% N2). The c-Fos gene encoded protein (c-Fos) was employed to localize CO2 activated cells within the piglet medulla oblongata. Parvalbumin was used as a marker for GABAergic neurons. In animals breathing room air, only scant c-Fos-like immunoreactive neurons were observed. A marked increase in c-Fos positive cells was induced after a 60 min exposure to hypercapnia. Colocalization studies revealed that hypercapnia significantly increased c-Fos expression in GABA-containing neurons in the medulla oblongata, especially in the ventral aspect of the medulla, within the Bötzinger region, the gigantocellular reticular nucleus, and the caudal raphe nuclei. Only a few double-labeled cells were observed within the nucleus tractus solitarius. Therefore, brainstem GABAergic neurons are part of the neural networks that respond to CO2 and may contribute to respiratory frequency responses to hypercapnia during early development.

Distribution of glucokinase, glucose transporter GLUT2, sulfonylurea receptor-1, glucagon-like peptide-1 receptor and neuropeptide Y messenger RNAs in rat brain by quantitative real time RT-PCR

Glucokinase (GK), glucose transporter GLUT2, sulfonylurea receptor-1 (SUR1), glucagon-like peptide-1 receptor (GLP-1R) and neuropeptide Y (NPY) have been proposed to be involved in central glucose sensing or regulation of food intake. In this study, we combined tissue micropunch and real time reverse transcription polymerase chain reaction (RT-PCR), and measured GK, GLUT2, SUR1, GLP-1R and NPY mRNA expression in discrete areas in the hypothalamus and the hindbrain.

Regional fat pad growth and cellularity in obese zucker rats: modulation by caloric restriction

OBJECTIVE

To investigate, in young obese male Zucker rats, the effects of chronic food restriction and subsequent refeeding on: 1). parameters of nonadipose and adipose growth, 2). regional adipose depot cellularity [fat cell volume (FCV) and number], and 3). circulating leptin levels.

RESEARCH METHODS AND PROCEDURES

Obese (fa/fa) and lean (Fa/?) male Zucker rats were studied from age 5 to 19 weeks. After baseline food intake monitoring, 10 obese rats were subjected to 58 days of marked caloric restriction from ad libitum levels [obese-restricted (OR)], followed by a return to ad libitum feeding for 22 days. Ten lean control rats and 10 obese control rats were fed ad libitum for the entire experiment. All rats were fed using a computer-driven automated feeding system designed to mimic natural eating patterns.

RESULTS

After food restriction, OR rats weighed significantly less than did lean and obese rats and showed a significant diminution in body and adipose growth as compared with obese rats. Relative adiposity was not different between obese and OR rats and was significantly higher than that of lean rats. The limitation in growth of the adipose tissue mass in OR rats was due mostly to suppression of fat cell proliferation because the mean FCV in each of the four depots was not affected. Serum leptin levels of OR and obese rats were not different from each other but were significantly higher than those of lean rats.

DISCUSSION

Marked caloric restriction affects obese male Zucker rats in a manner different from that of nongenetic rodent models (i.e., Wistar rats). In comparison with the response to caloric deprivation of Wistar rats, these calorically restricted obese male Zucker rats appeared to defend their relative adiposity and mean FCV at the expense of fat cell number. These findings indicate that genetic and/or tissue-specific controls override the general consequences of food restriction in this genetic model of obesity.

"CADASIL coma": an underdiagnosed acute encephalopathy

The main clinical features of CADASIL (cerebral autosomal dominant arteriopathy with subcortical infarcts and leucoencephalopathy) are stroke, dementia, and migraine. A reversible acute encephalopathy was the principal presentation in six of 70 patients in a British prevalence study. The episodes lasted seven to 14 days, presenting with fever, acute confusion, coma, and fits; there was full recovery but in two cases identical episodes recurred some years later. All patients had a previous history of migraine with aura and were originally misdiagnosed as viral encephalitis. CADASIL should be considered in acute unexplained encephalopathies. MRI white matter changes, previous migraine with aura, and a family history of stroke and dementia may be useful pointers to the diagnosis.

Central insulin potentiates eating elicited by 2-deoxy-D-glucose

2-Deoxy-D-glucose (2DG) elicits glucoprivic food intake whether administered centrally or systemically. Insulin, on the other hand, elicits glucoprivic food intake when administered systemically but reduces food intake when administered centrally. The purpose of these experiments was to determine the interaction of centrally administered insulin with systemically administered 2DG on feeding. In the experimental condition, male Sprague-Dawley rats were administered 5 mU insulin into the third cerebral ventricle (i3vt) followed 2 h later by a subcutaneous injection of 250 mg/kg of 2DG. Contrary to expectations, third ventricular insulin significantly increased 2DG-induced hyperphagia. A replication using doses of insulin ranging from 1 to 10 mU revealed a dose-dependent response. Whereas the lowest dose of insulin (1 mU) did not reliably change food intake, doses of 2.5, 5, and 10 mU significantly enhanced 2DG-induced feeding. Consistent with previous reports, centrally administered insulin, when given alone, caused a significant reduction of 24-h body weight and chow intake. To assess if the insulin-induced hyperphagia was a result of leakage from the ventricles, we peripherally administered 5 mU of insulin and observed, if anything, a slight decrease of food intake. These studies suggest that in the presence of central glucoprivation, a distinct anabolic action of centrally administered insulin overrides the normally observed catabolic response and increases the hyperphagic feeding response induced by 2DG.

Effects of macrocyclic lactone anthelmintics on feeding and pharyngeal pumping in Trichostrongylus colubriformis in vitro

The effects of macrocyclic lactone anthelmintics (MLs) on feeding by Trichostrongylus colubriformis nematodes in vitro were examined using inulin uptake as a measure of ingestion and electropharyngeograms as a record of the electrical events associated with pharyngeal pumping. Inulin uptake was inhibited by the 4 MLs tested (EC50s 0.045-4.57 nM), with an order of potency of eprinomectin (most potent), ivermectin, ivermectin monosaccharide, and ivermectin aglycone. The MLs caused both the frequency and amplitude of pharyngeal electrical events to decrease. In individual worms the inhibition of pump frequency preceded the inhibition of pump amplitude. The order of potency of the MLs as inhibitors of frequency was ivermectin aglycone, ivermectin, ivermectin monosaccharide and eprinomectin. The difference compared with the inulin assay results are probably due to the dynamics of drug uptake in the two systems. It was possible that the nematodes in the electrophysiology experiments were effectively orally ligated by enclosure of the worm's head in the recording pipette which contained no drug. Despite this difference in relative potencies, both the ingestion assays and the electrical events indicate that MLs are potent inhibitors of the pharynx in T. colubriformis in vitro. The sequence of effects on pharyngeal electrical activity suggests that ML action involves an initial inhibitory effect on the rate of pharyngeal contractions, followed by a decrease in the amplitude of the potentials associated with pharyngeal pumping events.

Diagnostic strategies in CADASIL

BACKGROUND

Cerebral autosomal dominant arteriopathy with subcortical infarcts and leukoencephalopathy (CADASIL) is an inherited autosomal dominant condition characterized by migraine, recurrent stroke, and dementia. It results from mutations in the notch3 gene but mutations may occur at multiple sites making molecular diagnosis time consuming. It has been suggested that the presence of granular osmiophilic material (GOM) on skin biopsy and involvement of the anterior temporal lobe and external capsule on MRI may help in diagnosis.

METHODS

The authors identified 83 potential index cases from the British population and screened exons 2 to 23 of notch3. MRI scans were scored using a modified Scheltens scale. Skin biopsy was performed in a subgroup.

RESULTS

Fifteen different point mutations were identified in 48 families, 73% of which were in exon 4, 8% in exon 3, and 6% in each of exons 5 and 6. Moderate or severe involvement of the anterior temporal pole on MRI had a sensitivity of 89% and specificity of 86% for diagnosis of CADASIL, whereas external capsule involvement had a high sensitivity of 93% but a low specificity of 45%. Skin biopsy, performed in 18 cases, had a sensitivity of 45% and specificity of 100%.

CONCLUSIONS

The spectrum of mutations in this study can be used to plan appropriate screening protocols; a suggested protocol is to screen exon 4, and proceed to exons 3, 5, and 6 where indicated. GOM on skin biopsy is diagnostic but can be negative. Anterior temporal pole involvement on MRI is a useful diagnostic marker.

Intracerebroventricular injection of fructose stimulates feeding in rats

2-deoxy-D-glucose (2DG) inhibits glycolysis and stimulates food intake. Previous work suggests that fructose may attenuate the hyperglycemic and hypothermic effects of 2DG. The current study examined the effect of intracerebroventricular fructose on 2DG-induced feeding. We found that concentrated fructose injected into the cerebroventricles enhanced food intake both in the presence and absence of 2DG. On the other hand, similar concentrations of glucose suppressed 2DG-induced food intake. These data suggest differences in metabolism of glucose and fructose and may provide insight into the metabolic steps monitored by brain glucoreceptors to control food intake.