Polyol pathway in aorta: regulation by hormones.

Aldose reductase is present in human and rabbit aortas and provides a mechanism whereby hyper-glycemia can alter the metabolism of the arterial wall. Aortic sorbitol concentration is regulated by ambient glucose concentration and is increased by epinephrine, isoproterenol, dibutyryl-3',5'-adenosine monophosphate, ouabain, and angiotensin II.

Effects of elevated glucose concentrations on the metabolism of the aortic wall.

The effects of elevated glucose concentrations on the metabolism of the aortic wall were examined in a preparation of tubular segments of rabbit descending thoracic aorta comprised of intima and media only. Increased medium glucose concentrations (20-50 mm) resulted in increased aortic sorbitol and fructose concentrations and an increased rate of fructose release into the medium. This increased flux through the polyol pathway can be explained as a consequence both of an increased free intracellular glucose concentration and of the kinetic characteristics of the alditol: NADP oxidoreductase and the l-iditol: NAD oxidoreductase isolated and partially purified from rabbit thoracic aorta. Incubation with elevated glucose concentrations for 2 or more hr was also associated with a significant increase in the water content of the tissue without a significant increase in the inulin space. The oxygen uptake of the tissues incubated with elevated glucose concentrations was significantly reduced; this appears to result from a limitation imposed by oxygen diffusion at physiological oxygen tensions. A compensatory increase in glycolysis and an increase in the aortic lactate/pyruvate concentration ratio were also observed. The oxygen uptake and lactate production of tissue incubated with 50 mm glucose could be preserved at rates observed in tissue incubated with a physiological glucose concentration by the addition of 40 mm mannitol to the medium. Aortic intima and media from alloxan-diabetic rabbits also exhibit an increased water content and a decreased rate of oxygen uptake. These observations suggest that elevated ambient glucose concentrations result in significant alterations in the metabolism of aortic intima and media.

Morphology and metabolism of an aortic intima-media preparation in which an intact endothelium is preserved.

An in vitro preparation of rabbit aortic "intima-media" previously shown to exhibit stable rates of respiration and glucose metabolism and the high rate of aerobic glycolysis considered characteristic of the metabolism of this tissue was subjected to electron microscopic examination. In samples examined immediately after the aortae were dissected free of adipose tissue and adventitia, under conditions similar to those now in common use, marked and widespread alterations in endothelial cell structure were present, including loss of cell integrity. The vascular smooth muscle cells retained a normal electron microscopic (EM) appearance. During subsequent incubation with 5 mM glucose in Krebs-Ringer bicarbonate (KRB), pH 7.4, under the conditions usually employed in studies of this preparation, large zones of the luminal surface were rapidly denuded of endothelium, and the remaining endothelial cells exhibited a wide range of ultrastructural alterations. The smooth muscle cells, however, continued to maintain a normal EM appearance. A method was developed to prepare segments of rabbit aortic intima-media which retained an intact layer of endothelium resembling that observed in tissue fixed in situ. During a 1-h incubation with 5 mM glucose in KRB, pH 7.4, gas phase 5% CO2/95% O2, containing 6% bovine serum albumin, the intact aortic intima-media preparation retains an essentially unmodified EM appearance and exhibits linear rates of respiration. Under these conditions the intact aortic intima-media preparation exhibits significantly higher rates of O2 uptake and glucose uptake than those observed in our previous preparation or in other reported aortic intima-media preparations. The intact aortic intima-media does not exhibit the high rate of aerobic glycolysis during in vitro incubation that has been considered characteristic of the metabolism of rabbit, rat, and swine aortic intima-media. In addition, the magnitude of the Pasteur effect was far greater than that observed in other aortic intima-media preparations. The data suggest that component cells of the aortic intima-media may derive a major fraction of their energy requirements from respiration; they raise further questions concerning the significance of the high rate of aerobic glycolysis observed when aortic intima-media preparations are incubated in vitro, and they suggest that documentation of the EM appearance of the endothelium in such preparations is desirable.

The effects of anoxia on the morphology and composite metabolism of the intact aortic intima-media preparation.

Paired samples of an intact rabbit aortic intima-media preparation were incubated for short periods under aerobic or anoxic conditions in Krebsbicarbonate buffer containing 6% albumin and 5 mM glucose. During aerobic incubation for as long as 1 h the preparation retained an electron microscopic (EM) appearance similar to that of tissue fixed in situ, and scanning EM confirmed the presence of an uninterrupted endothelial surface. After 2.5 min of anoxia there was widespread endothelial swelling, but the alterations in the EM appearance of these cells were not striking and did not progress during a subsequent 30 min aerobic incubation in fresh medium. After 10 min of anoxia there were marked and widespread alterations in endothelial cell structure, including loss of cell integrity, and numerous discrete interruptions in the endothelium were consistently observed on both transmission and scanning EM. After a subsequent 30 min aerobic incubation in fresh buffer, a major fraction of the luminal surface was denuded of endothelium. The aortic vascular smooth muscle cells did not exhibit evidence of irreversible anoxic injury after 2.5 or 10 min of anoxia or after subsequent aerobic incubation for 30 min. Exposure to anoxia for 10 min induced persistent alterations in the composite metabolism of the preparation during subsequent aerobic incubation in fresh medium; O(2) uptake was reduced, and the fraction of the glucose uptake that was accounted for by lactate production increased approximately 100%. The observations suggest that aortic endothelial cells are dependent upon respiration for the preservation of normal ultrastructure and cell integrity, and probably derive the major fraction of their energy requirements from reactions linked to respiration. Under the conditions employed in these experiments, short periods of anoxia did not induce EM evidence of irreversible anoxic injury in aortic vascular smooth muscle cells; this negative result is not incompatible with other data suggesting that these cells normally derive the major fraction of their energy requirements from respiration. Aortic intima-media does not exhibit a high rate of aerobic glycolysis under aerobic conditions which preserve a normal EM appearance of the preparation, but this pattern of metabolism can be induced by prior anoxic exposure.

Metabolic alterations in the human erythrocyte produced by increases in glucose concentration. The role of the polyol pathway.

Human erythrocytes incubated in medium containing 50 mM glucose have increased intracellular sorbitol and fructose concentrations as compared with samples incubated with 5 mM glucose. Increased medium glucose concentration did not significantly alter total glucose consumption or lactate production. However, the intracellular lactate:pyruvate ratio rose, the concentrations of fructose diphosphate, and triose phosphates increased, and the 2,3-diphosphoglycerate concentration fell. [(14)C]O(2) production from glucose-1-(14)C also increased with increased medium glucose concentration. These changes are believed to reflect changes in the redox states of the diphosphopyridine nucleotide/reduced form of diphosphopyridine nucleotide (NAD/NADH) and nicotinamide-adenine dinucleotide phosphate/reduced form of nicotinamide-adenine dinucleotide phosphate (NADP/NADPH) couples resulting from increased activity of the polyol pathway. Addition of pyruvate to the incubation media prevented these changes. These studies illustrate that an increase in the red cell's normal substrate, glucose, can produce changes in red cell metabolism.

The novel endocannabinoid receptor GPR55 is activated by atypical cannabinoids but does not mediate their vasodilator effects.

BACKGROUND AND PURPOSE: Atypical cannabinoids are thought to cause vasodilatation through an as-yet unidentified 'CBx' receptor. Recent reports suggest GPR55 is an atypical cannabinoid receptor, making it a candidate for the vasodilator 'CBx' receptor. The purpose of the present study was to test the hypothesis that human recombinant GPR55 is activated by atypical cannabinoids and mediates vasodilator responses to these agents. EXPERIMENTAL APPROACH: Human recombinant GPR55 was expressed in HEK293T cells and specific GTPgammaS activity was monitored as an index of receptor activation. In GPR55-deficient and wild-type littermate control mice, in vivo blood pressure measurement and isolated resistance artery myography were used to determine GPR55 dependence of atypical cannabinoid-induced haemodynamic and vasodilator responses. KEY RESULTS: Atypical cannabinoids O-1602 and abnormal cannabidiol both stimulated GPR55-dependent GTPgammaS activity (EC50 approximately 2 nM), whereas the CB1 and CB2-selective agonist WIN 55,212-2 showed no effect in GPR55-expressing HEK293T cell membranes. Baseline mean arterial pressure and heart rate were not different between WT and GPR55 KO mice. The blood pressure-lowering response to abnormal cannabidiol was not different between WT and KO mice (WT 20+/-2%, KO 26+/-5% change from baseline), nor was the vasodilator response to abnormal cannabidiol in isolated mesenteric arteries (IC50 approximately 3 micro M for WT and KO). The abnormal cannabidiol vasodilator response was antagonized equivalently by O-1918 in both strains. CONCLUSIONS: These results demonstrate that while GPR55 is activated by atypical cannabinoids, it does not appear to mediate the vasodilator effects of these agents.

Glucose-induced alterations of the metabolism of an isolated capillary preparation.

A preparation of blood capillaries was isolated from the rete mirabile of the eel swin bladder. The capillaries, incubated for two hours at 37 degrees C. in Krebs-Ringer bicarbonate buffer with 5 mM glucose, contained 29.3 +/- 4.6 nmoles of sorbitol per gram and released in the medium 725 +/- 60 nmoles of fructose per gram. When glucose in the medium was raised from 5 to 30 mM, capillary sorbitol and medium fructose rose by approximately 100 per cent. There were no accompanying changes in capillary water content as determined by the ratio of wet weight to dry weight and by the difference between water-3H space and inulin-14C space. Respiration of capillary tissue was lower at 30 mM glucose than at 5 mM glucose. The addition of 30 mM mannitol to a medium containing 30 mM glucose did not restore the oxygen uptake by capillary tissue to values obtained with a medium containing 5 mM glucose alone. It is concluded that the polyol pathway is operative in vertebrate blood capillaries. At high medium glucose concentration, the activity of the pathway is enhanced, respiration is depressed, and water content is unchanged

Prevalence and significance of retinopathy in subjects with type 1 diabetes of less than 5 years' duration screened for the diabetes control and complications trial.

OBJECTIVE: The Diabetes Control and Complications Trial (DCCT) demonstrated the powerlul impact of glycemic control on the progression of diabetic retinopathy. A large number of individuals (2,771) underwent stereoscopic color photography and fluorescein angiography as part of screening for participation in the DCCT. A subgroup of those individuals screened participated in the DCCT and underwent evaluation of their retinal vasculature semiannually for 4-9 years. These data were evaluated to determine how the 2000 American Diabetes Association position statement would apply to the DCCT experience. Specifically, the position statement indicates that the first dilated eye examination should be performed after 3-5 years' duration of diabetes because vision-threatening retinopathy virtually never develops in patients with type 1 diabetes during that interval RESEARCH DESIGN AND METHODS: We examined the experience of the DCCT in evaluating retinal photographs in 1,613 patients with type 1 diabetes of <5 years' duration and follow-up photographs every 6 months for 4-9 years in 855 members of that group. RESULTS: Of 1,613 subjects with type 1 diabetes of <5 years' duration screened for the DCCT, 716 (44.4%) had stereo-color photographic evidence of diabetic retinopathy, and 6 had preproliferative or worse pathology. Fluorescein angiography revealed retinopathy in 158 of 713 subjects with no evidence of retinopathy on color photographs. Thus, 874 (54.2%) of the original 1,613 subjects had retinopathy at baseline. DCCT follow-up identified 341 additional individuals in whom retinopathy was developing before 5 years; 1,083 of 1,613 (67.1%) individuals screened for the DCCT had retinopathy before 5 years' duration of diabetes. Those with retinopathy before 5 years had more rapid three-step progression of vascular pathology than those with no retinopathy. CONCLUSIONS: Dilated eye examinations and retinal photography should be included in the routine management of type 1 diabetes during the first 5 years to identify the individuals at greatest risk for vision-threatening problems.

Rapid glucose-dependent increases in phosphatidic acid and phosphoinositides in rat pancreatic islets.

Glucose effects on islet phospholipids were examined during direct incubation or after 3 days of 32P prelabeling in primary culture. In both cases, glucose increased the 32P content of phosphatidic acid (PA), phosphatidylinositol (PI), and polyphosphoinositides (PPI). Glucose-induced increases in PA, PI, and PPI in the culture-prelabeling experiments were evident within 1 min, dose related, and reflective of increases in phospholipid mass, which was confirmed in direct incubations by measurement of PI phosphorus. Thus, in addition to increasing PI-PPI hydrolysis, glucose increases de novo phospholipid synthesis in pancreatic islets. The latter may result from enhanced glycolysis and substrate availability for PA-PI-PPI synthesis, since glyceraldehyde and pyruvic acid also increased PI levels. Our findings raise the possibility that increases in PA, PI, and PPI synthesis could serve as a mechanism to enhance the generation of intracellular mediators, which are purported to regulate insulin secretion.

Diabetic cardiomyopathy and carnitine deficiency.

This study was designed to study the pathogenesis of cardiomyopathy in animals with longstanding (6 months) diabetes mellitus. Male Wistar rats were made diabetic by the injection of streptozotocin (35 mg/kg) intraperitoneal at 6 months of age. Myocardial contractility was evaluated at 1 year of age by an echocardiogram. Blood was collected at that time to measure blood glucose and hemoglobin A1c as an indicator of metabolic control. Serum carnitine was also measured on the same sample to evaluate the availability of this substance so essential for fatty acid metabolism in the myocardium. Myocardial anatomy was evaluated by both light and electron microscopy after the animals had diabetes for 6 months. It was found that the left ventricular volume was greater at the end of systole and diastole. There was the suggestion of left ventricular fractional shortening and calculated reduced ejection fraction indicating decreased contractility consistent with cardiomyopathy. The hearts had no evidence of coronary vascular occlusion, and the serum cholesterol was normal. Myocardial ultrastructure revealed abnormal-appearing mitochondria consistent with carnitine deficiency. Serum and myocardial carnitine levels in the animals with diabetes and reduced myocardial function were low. Carnitine levels and metabolism could be important in the pathogenesis of diabetic cardiomyopathy.

A computerized model for home glucose monitoring proficiency testing: efficacy of an innovative testing program.

PURPOSE: A newly instituted computerized system for proficiency testing of home glucose monitoring was evaluated comparing accuracy of patient determination of glucose with serum values measured in the laboratory. METHODS: Patients returning for routine blood glucose testing ordered by their care provider brought their glucose monitoring equipment to the laboratory. They performed a finger-stick glucose check in the laboratory while the laboratory phlebotomist drew blood for glucose determination; both results were computer analyzed. Patients with a 25% or less variation from the laboratory were considered proficient, while those with greater than 25% variation were defined as nonproficient. RESULTS: Over a 19-month period, 300 of the 3208 patients notified about the study completed proficiency testing at least once. Using the defined proficiency of 25% variation or less, 12% of the participants were nonproficient. Using a variation of 15% or less, 31% of patients were nonproficient. CONCLUSIONS: An annual methodology evaluation such as the one in this study should become a standard of care to identify patients for remedial classes to correct the source of error. The goal must be to meet or exceed the American Diabetes Association standard of 15% total error in home glucose monitoring.

Glucose concentration in the dialysate and lipid abnormalities in chronic hemodialysis patients.

In order to assess the effect of varying glucose concentrations on plasma lipids, we first compared the hormonal response of nine non-diabetic patients during dialysis with a high (200 mg/dl) and a low (100 mg/dl) glucose bath. Insulin and growth hormone production increased (p less than 0.05) only with the high glucose bath, and no hemodynamic differences were noted during either dialyses. We then compared lipid profiles of 18 patients for 6 months, changing the glucose dialysate concentrations in each patient after three months. We found that all patients had hypertriglyceridemia, mild hypercholesterolemia, low HDL, normal LDL, and high VLDL cholesterol. We therefore conclude that episodic hyperinsulinemia and episodic excessive growth hormone secretion do not contribute significantly to the lipid abnormalities of the dialysis patients.

Obstructive sleep apnea syndrome: diagnosis and management.

Increased awareness that changes in sleeping habits and daytime behaviour may be attributable to obstructive sleep apnea syndrome (OSAS) has led many patients to seek both information and definitive treatment. The purpose of this article is to provide information to dentists that will enable them to identify patients who may have OSAS and to assist these patients in making informed decisions regarding treatment options. In patients who have identifiable anatomic abnormalities of the maxilla and mandible resulting in a narrow pharyngeal airway, orthognathic surgery appears to be an excellent treatment option.

Cleft lip and palate: a review for dentists.

The goals of primary closure of cleft lip and palate include not only re-establishing normal insertions for all of the nasolabial muscles but also restoring the normal position of all the other soft tissues, including the mucocutaneous elements. Conventional surgical wisdom, which recommends waiting until growth is complete before undertaking surgical correction of the postoperative sequelae of primary cheiloplasty, carries with it many disadvantages. If, after primary surgery of the lip, orolabial dysfunctions remain, they will exert their nefarious influences during growth and will themselves lead to long term dentofacial imbalances. These imbalances can significantly influence facial harmony. Unless accurate, symmetric and functional reconstruction of the nasolabial muscles is achieved during the primary surgery, not only will the existing dentoskeletal imbalances be exaggerated, but other deformities will be caused during subsequent growth, among which the most important are nasal obstruction and mouth breathing, reduced translation of the maxilla, dysymmetry of the nose and inability of the patient to symmetrically project the upper lip

The management of first seizures in adults in a district general hospital.

This study considered the management of first seizures in adults in Stirling Royal Infirmary over a six month period. Thirty-four patients presented of whom 19 were admitted to medical wards. Alcohol was implicated in 35% of cases. Blood tests were done in many but provided little useful information. CT Scan was performed in 53% and was abnormal in 15% (five patients). EEG was requested for 21% and failed to influence management in any. Six patients (18%) were started on anticonvulsant therapy. It was recorded in only three cases that advice on driving had been given. The literature concerning single seizures is complex, especially with regards to recurrence risk and treatment benefits. We await with interest the publication of the SIGN (Scottish Intercollegiate Guidelines Network) guidelines for seizure investigation and treatment in Scotland.

rKv1.2 overexpression in the central medial thalamic area decreases caffeine-induced arousal.

The voltage-gated potassium channel Kv1.2 belongs to the shaker-related family and has recently been implicated in the control of sleep profile on the basis of clinical and experimental evidence in rodents. To further investigate whether increasing Kv1.2 activity would promote sleep occurrence in rats, we developed an adeno-associated viral vector that induces overexpression of rat Kv1.2 protein. The viral vector was first evaluated in vitro for its ability to overexpress rat Kv1.2 protein and to produce functional currents in infected U2OS cells. Next, the adeno-associated Kv1.2 vector was injected stereotaxically into the central medial thalamic area of rats and overexpression of Kv1.2 was showed by in situ hybridization, ex vivo electrophysiology and immunohistochemistry. Finally, the functional effect of Kv1.2 overexpression on sleep facilitation was investigated using telemetry system under normal conditions and following administration of the arousing agent caffeine, during the light phase. While no differences in sleep profile were observed between the control and the treated animals under normal conditions, a decrease in the pro-arousal effect of caffeine was seen only in the animals injected with the adeno-associated virus-Kv1.2 vector. Overall, our data further support a role of the Kv1.2 channel in the control of sleep profile, particularly under conditions of sleep disturbance.

Mitochondrial dysfunction triggered by loss of HtrA2 results in the activation of a brain-specific transcriptional stress response.

Cellular stress responses can be activated following functional defects in organelles such as mitochondria and the endoplasmic reticulum. Mitochondrial dysfunction caused by loss of the serine protease HtrA2 leads to a progressive movement disorder in mice and has been linked to parkinsonian neurodegeneration in humans. Here, we demonstrate that loss of HtrA2 results in transcriptional upregulation of nuclear genes characteristic of the integrated stress response, including the transcription factor CHOP, selectively in the brain. We also show that loss of HtrA2 results in the accumulation of unfolded proteins in the mitochondria, defective mitochondrial respiration and enhanced production of reactive oxygen species that contribute to the induction of CHOP expression and to neuronal cell death. CHOP expression is also significantly increased in Parkinson's disease patients' brain tissue. We therefore propose that this brain-specific transcriptional response to stress may be important in the advance of neurodegenerative diseases.

Free-grafting of mandibular condyle fractures: clinical outcomes in 10 consecutive patients.

"Free-grafting" of the superior segment, either alone or in combination with a posterior ramus osteotomy, is occasionally required when managing displaced condylar neck fractures. This allows ideal reduction and fixation, but carries the risk of proximal segment resorption, possibly requiring secondary reconstruction. The purpose of this study was to evaluate the clinical and radiographic outcomes of this technique in all patients who underwent this procedure during a seven-year period at a tertiary care centre. Ten patients who had undergone 11 free graft procedures were included in the study. Three patients required secondary costochondral reconstruction due to advanced resorption of the free-grafted condylar segment, this occurring from 3 to 9 months following the initial trauma surgery. All but one of the remaining patients exhibited varying degrees of condylar resorption/flattening radiographically, occurring within the first year only. However, no occlusal changes occurred in this group either objectively or subjectively during this year or during the subsequent follow-up period. The mean inter-incisal opening was 47mm (range 40-56). With the exception of one patient that had a non-painful reciprocal click of the treated side, no patients demonstrated either objective or subjective signs of TMJ pathology. No patients reported dietary limitations, and all reported satisfaction with treatment to date. Based on objective and subjective evaluation, free grafting of the fractured condylar segment in this patient population had a 70% success rate. All failures occurred within 9 months and required secondary costochondral reconstruction.