Metastable states in NO2+ probed with Auger spectroscopy.

High-resolution N 1s and O 1s photoelectron spectra (PES) of NO are presented together with spectra of the subsequent Auger decay. The PES are analyzed by taking spin-orbit splitting of the (2)Π ground state into account providing detailed information on equilibrium distances, vibrational energies, and lifetime widths of the core-ionized states. In the Auger electron spectra (AES) transitions to five metastable dicationic final states are observed, with two of them previously unobserved. A Franck-Condon analysis of the vibrational progressions belonging to these transitions provides detailed information on the potential-energy curves of the dicationic final states as well as on the relative Auger rates. The present calculations of the potential-energy curves of NO(2+) agree well with the experimental results and allow an assignment of the two hitherto unresolved Auger transitions to excited states of NO(2+), C(2)Σ(+)and c(4)Π.

Substitution effects in elastic electron collisions with CH3X (X=F, Cl, Br, I) molecules.

We report absolute elastic differential, integral, and momentum transfer cross sections for electron interactions with the series of molecules CH(3)X (X=F, Cl, Br, I). The incident electron energy range is 50-200 eV, while the scattered electron angular range for the differential measurements is 15 degrees-150 degrees. In all cases the absolute scale of the differential cross sections was set using the relative flow method with helium as the reference species. Substitution effects on these cross sections, as we progress along the halomethane series CH(3)F, CH(3)Cl, CH(3)Br, and CH(3)I, are investigated as a part of this study. In addition, atomic-like behavior in these scattering systems is also considered by comparing these halomethane elastic cross sections to results from other workers for the corresponding noble gases Ne, Ar, Kr, and Xe, respectively. Finally we report results for calculations of elastic differential and integral cross sections for electrons scattering from each of the CH(3)X species, within an optical potential method and assuming a screened corrected independent atom representation. The level of agreement between these calculations and our measurements was found to be quite remarkable in each case.

Valence photoelectron spectroscopy of N2 and CO: recoil-induced rotational excitation, relative intensities, and atomic orbital composition of molecular orbitals.

Recoil-induced rotational excitation accompanying photoionization has been measured for the X, A, and B states of N(2)(+) and CO(+) over a range of photon energies from 60 to 900 eV. The mean recoil excitation increases linearly with the kinetic energy of the photoelectron, with slopes ranging from 0.73×10(-5) to 1.40×10(-5). These slopes are generally (but not completely) in accord with a simple model that treats the electrons as if they were emitted from isolated atoms. This treatment takes into account the atom from which the electron is emitted, the molecular-frame angular distribution of the electron, and the dependence of the photoelectron cross section on photon energy, on atomic identity, and on the type of atomic orbital from which the electron is ejected. These measurements thus provide a tool for investigating the atomic orbital composition of the molecular orbitals. Additional insight into this composition is obtained from the relative intensities of the various photolines in the spectrum and their variation with photon energy. Although there are some discrepancies between the predictions of the model and the observations, many of these can be understood qualitatively from a comparison of atomic and molecular wavefunctions. A quantum-mechanical treatment of recoil-induced excitation predicts an oscillatory variation with photon energy of the excitation. However, the predicted oscillations are small compared with the uncertainties in the data, and, as a result, the currently available results cannot provide confirmation of the quantum-mechanical theory.

Assessing infrared intensity using the evaporation rate of liquid hydrogen inside a cryogenic integrating sphere for laser fusion targets.

Infrared (IR) heating processes have been studied to form a deuterium layer in an inertial confinement fusion target. To understand the relationship between the IR intensity and the fuel layering time constant, we have developed a new method to assess the IR intensity during irradiation. In our method, a glass flask acting as a dummy target is filled with liquid hydrogen (LH2) and is then irradiated with 2-µm light. The IR intensity is subsequently calculated from the time constant of the LH2 evaporation rate. Although LH2 evaporation is also caused by the heat inflow from the surroundings and by the background heat, the evaporation rate due to IR heating can be accurately determined by acquiring the time constant with and without irradiation. The experimentally measured IR intensity is 0.66 mW/cm2, which agrees well with a value estimated by considering the IR photon energy balance. Our results suggest that the present method can be used to measure the IR intensity inside a cryogenic system during IR irradiation of laser fusion targets.

Increase in [3H]PN 200-110 binding to cardiac muscle membrane in streptozocin-induced diabetic rats.

Voltage-sensitive Ca2+ channels in cardiac left ventricular muscle membranes isolated from nondiabetic control and diabetic rats were measured with [3H]PN 200-110, a dihydropyridine derivative, as a ligand. The binding site (Bmax) of [3H]PN 200-110 in cardiac membranes isolated from streptozocin-induced diabetic (STZ-D) rats (128 +/- 10 fmol/mg protein) significantly (P less than 0.01) increased by 64% compared with that of control rats (78 +/- 4 fmol/mg protein) 10 wk after STZ administration without a significant change in Kd. However, the significant increase in Bmax of [3H]PN 200-110 binding in diabetic rats depended on the duration of diabetes such that the increase was not found until 6 wk after STZ injection. An 8-wk intensive insulin treatment, which was initiated 2 wk after STZ injection, normalized the increase in [3H]PN 200-110 binding in STZ-D rats to control levels (85 +/- 4 fmol/mg protein). Furthermore, [3H]PN 200-110 binding to control cardiac membranes was dose-dependently inhibited in the presence of verapamil, a phenylalkylamine Ca2+ antagonist, but that was not the case in cardiac membranes isolated from STZ-D rats. These results indicate that voltage-sensitive Ca2+ channels in cardiac muscle isolated from STZ-D rats are quantitatively and qualitatively altered, because the course of diabetes and the increase in the channels can be prevented by treatment with insulin.

Glycation, oxidative stress, and scavenger activity: glucose metabolism and radical scavenger dysfunction in endothelial cells.

It has been reported that oxidative stress is increased in vivo in the diabetic state. Increased oxidative stress is caused not only by accelerated production of oxygen-free radicals but also by decreased scavenging of those molecules. Endothelial cells are extremely sensitive to oxidative stress, resulting in impairments of various endothelial cell function. In this report, we studied the association of intracellular glucose metabolism and oxygen radical scavenging function via the glutathione redox (GR) cycle in cells exposed to high-glucose conditions using cultured human umbilical vein endothelial cells. Glutathione-dependent H2O2 degradation in cells exposed to 33 mmol/l glucose (HG) for 5-7 days was reduced by 48% vs. 5.5 mmol/l glucose (NG). This impairment under the oxidative stress was D-glucose-specific and concentration-dependent and was also associated with a 42% decrease in intracellular NADPH content. Exposure of cells to 200 micromol/l H2O2 stimulated the GR cycle and the pentose phosphate pathway (PPP) at the same time. In the HG condition, activation of PPP was reduced by 50%, which was consistent with a decrease in NADPH content. Inhibition of glycolysis by H2O2 was less marked in HG cells versus NG cells. Activation of polyol pathway in HG cells is not responsible for the decrease in intracellular NADPH content. These results indicate that activation of the PPP and NADPH supply to the GR cycle is impaired in HG cells exposed to H2O2, which may result in increased oxidative stress to endothelial cells.

Pyruvate improves deleterious effects of high glucose on activation of pentose phosphate pathway and glutathione redox cycle in endothelial cells.

In our previous study (Diabetes 44:520-526, 1995), endothelial cells cultured in high glucose condition showed impairment of an oxidant-induced activation of the pentose phosphate pathway (PPP) and a reduced supply of NADPH to the glutathione redox cycle. To gain insight into the mechanisms of this impairment, the protective effect of pyruvate was studied in human umbilical vein endothelial cells cultured in either 5.5 mmol/l glucose (normal glucose [NG] condition) or 33 mmol/l glucose (high glucose [HG] condition). Through pretreatment of cells with 0.2 mmol/l pyruvate for 5-7 days in the HG condition, glucose oxidation through the PPP and total cellular NADPH content in the presence of 0.2 mmol/l H2O2 were increased by 54 (P < 0.05) and 34%, respectively, and glutathione-dependent degradation of H2O2 in HG cells was enhanced by 41% (P < 0.01), when compared with those cells to which pyruvate was not added. The addition of pyruvate significantly reduced the fructose 1,6-bisphosphate (FDP) content and free cytoplasmic NADH/NAD ratio, estimated by increased pyruvate/lactate ratio in NG and HG cells exposed to H2O2. Furthermore, the addition of pyruvate also showed a 46% reduction (P < 0.01) of endothelial cell damage induced by H2O2 in HG cells. These results indicate that abnormalities in PPP activation and glutathione redox cycle activity induced by H2O2 in HG cells are compensated, and that the accentuated reductive stress is improved by an addition of pyruvate. These pyruvate effects are associated with protection against an oxidant-induced endothelial cell injury in the high glucose condition.

Impaired activation of glucose oxidation and NADPH supply in human endothelial cells exposed to H2O2 in high-glucose medium.

The effects of glucose concentration on D-glucose oxidation and reduced nicotinamide adenine dinucleotide phosphate (NADPH) supply were studied during exposure of cultured human umbilical vein endothelial cells to hydrogen peroxide (H2O2). The activation of glucose oxidation via the pentose phosphate pathway (PPP), induced by exposure of cells to 200 mumol/l H2O2 for 1 h, was reduced by 50% (P < 0.01) in cells cultured for 5-7 days in 33 mmol/l D-glucose (HG) versus those cultured in 5.5 mmol/l D-glucose without (NG) or with (HR) 27.5 mmol/l D-raffinose. The intracellular NADPH content in HG cells, but not in NG or HR cells, was decreased by 42% (P < 0.01) by exposing cells to 200 mumol/l H2O2. The decrease in NADPH was dependent on D-glucose concentration in the medium and was prevented in glutathione (GSH)-depleted cells. The latter observation suggests that the decrease in NADPH is associated with activation of the GSH redox cycle. In the presence of 200 mumol/l H2O2, lactate release into the medium, NADH/NAD ratio, and phosphofructokinase activity in HG cells were 56, 53, and 68% greater, respectively, than in the NG group, which indicates that inhibition of glycolysis by H2O2 is less marked in the HG group compared with NG group. These results indicate that activation of the PPP was impaired in endothelial cells cultured under conditions of high-glucose and oxidative stress, resulting in a decreased supply of NADPH to various NADPH-dependent pathways, including the GSH redox cycle.

Usefulness of revised fasting plasma glucose criterion and characteristics of the insulin response to an oral glucose load in newly diagnosed Japanese diabetic subjects.

OBJECTIVE: To examine the usefulness of the revised criterion for fasting plasma glucose (FPG) in the diagnosis of diabetes recommended by the American Diabetic Association (ADA) (126 mg/dl, 7 mmol/l), and to characterize insulin response during the 75-g oral glucose tolerance test (OGTT) in newly diagnosed Japanese diabetic subjects. RESEARCH DESIGN AND METHODS: A series of 2,121 Japanese subjects underwent a 75-g OGTT (0-3 h) and were divided into three groups (normal glucose tolerance [NGT], impaired glucose tolerance [IGT], and diabetes mellitus [DM] according to the current World Health Organization criteria. After the cutoff values of FPG that distinguish NGT and IGT from diabetes were analyzed, the usefulness of the ADA criterion for FPG was examined by comparing diagnostic parameters (sensitivity, specificity, and accuracy) with those for the cutoff value of 140 mg/dl. To assess insulin response, both the insulinogenic index (IsIx), a marker of early secretion, and the area under the insulin response curve (AUCins), a marker of total secretion, were compared between the DM, NGT, and IGT groups. RESULTS: First, the FPG cutoff value distinguishing NGT from diabetes was 109 mg/dl. An FPG of 126 mg/dl showed a higher sensitivity (0.52 vs. 0.31), the same specificity (1.00), and a higher accuracy (0.82 vs. 0.74) than an FPG of 140 mg/dl, and it had a higher specificity (1.00 vs. 0.86) with a slightly lower accuracy (0.82 vs. 0.85) than an FPG of 109 mg/dl. Second, the FPG cutoff value differentiating IGT from diabetes was 113 mg/dl. An FPG of 126 mg/dl showed a higher sensitivity (0.52 vs. 0.31) and accuracy (0.80 vs. 0.74) and a similar specificity (0.97 vs. 1.00) compared with an FPG of 140 mg/dl, and it had a higher specificity (0.97 vs. 0.82) with the same accuracy (0.80) as an FPG of 113 mg/dl. Third, the DM group showed the lowest IsIx among the three groups at all FPG values. The AUCIns in the DM group increased along with FPG, reached the maximum level at an FPG of 110 mg/dl, and declined thereafter. AUCIns was higher in the DM group than in the NGT group at FPG values > or = 100 mg/dl. CONCLUSIONS: The revised ADA criterion for FPG of 126 mg/dl may improve diagnostic sensitivity without loss of specificity in Japanese diabetic subjects when compared with an FPG criterion of 140 mg/dl. Although early insulin secretion was impaired, total insulin secretion did not seem to be reduced in newly diagnosed Japanese diabetic subjects.

Mitochondrial aldehyde dehydrogenase in diabetes associated with mitochondrial tRNA(Leu(UUR)) mutation at position 3243.

OBJECTIVE: To ascertain why alcohol is prone to manifest unpleasant effects in diabetes associated with mitochondrial tRNA(Leu(UUR) mutation at position 3243 (DM-Mt3243), we investigated the genotype of aldehyde dehydrogenase (ALDH) 2 and alcohol dehydrogenase 2 (ADH2) in DM-Mt3243. RESEARCH DESIGN AND METHODS: Nineteen unrelated patients with DM-Mt3243 were included in the study (12 men and 7 women). They were recruited from approximately 700 diabetic patients at three different institutes, without prior information of alcohol habit. ALDH2, ADH2, and 3243 mutation were genotyped by polymerase chain reaction (PCR)-restriction fragment length polymorphism (RFLP) methods. There were 461 unrelated Japanese individuals and 170 non-3243 mutant NIDDM patients enrolled as control subjects. RESULTS: In the DM-Mt3243 group, 15 (79%) patients had inactive ALDH2 and 18 (95%) had atypical ADH2. The frequency of the inactive ALDH2 genotype was higher than that in the normal control subjects (P < 0.002) and that in the NIDDM control subjects (P < 0.003). However, the frequencies of ADH2 genotype in the DM-Mt3243 group, the normal control subjects, and the NIDDM control subjects were not different. CONCLUSIONS: Inactive ALDH2 genotype was frequently observed in DM-Mt3243. It suggests that DM-Mt3243 is associated with ALDH2 inactivity. We speculate the trait of acetaldehyde accumulation on ALDH2 inactivity may favor mitochondrial DNA abnormalities, thereby worsening ATP production and impairing insulin secretion. In addition, the interaction of ALDH1 and ALDH2 may alter the retinoid metabolism in the pancreas, thereby influencing insulin secretion and precipitating diabetes. Thus, this association of ALDH2 genotype with DM-Mt3243 provides insight into the etiology of diabetes in the mitochondrial diseases.

Diabetes associated with a novel 3264 mitochondrial tRNA(Leu)(UUR) mutation.

OBJECTIVE: To present a novel mitochondrial DNA mutation in a diabetic family RESEARCH DESIGN AND METHODS: The proband was a 64-year-old man. In the family, diabetes was maternally inherited. He had diabetes, cerebellar ataxia, cervical lipoma, hearing loss, olfactory dysfunction, ophthalmoplegia, and facial nerve bilateral palsy. On examination, early insulin secretion was blunted, and the M value on glucose clamp test was low. In muscle, ragged red fibers were not found. T-to-C mutation at position 3264 was detected in the proband (0.5% mutant DNAs in leukocyte and 30% in muscle), but was not detected in 201 normal individuals. RESULTS: Heteroplasmy of mutation, maternal inheritance of diabetes, and symptoms related to mitochondrial dysfunction suggest the pathogenecity of this 3264 mutation. As for diabetes etiology, both impaired insulin secretion and decreased insulin sensitivity seem to be important. In phenotypic characteristics, the combination of cerebellar ataxia and lipoma is a symptom sometimes found in myoclonic epilepsy and ragged red fibers (MERRFs). Ophthamoplegia is a symptom of chronic progressive external ophthalmoplegia (CPEO). These suggest that our proband had phenotypic overlap with MERRF and CPEO. Conversely, facial nerve bilateral palsy is a rare finding. The pictures that focused on his cranial nerves were thus unique, suggesting the heterogeneity of mitochondrial DNA (mtDNA)-related diabetes. CONCLUSIONS: A novel 3264 mitochondrial DNA mutation in diabetes gives new insight to the etiology of mitochondrial diabetes. Its pathogenecity supports the belief that the tRNA(Leu)(UUR) gene is an etiological hot spot of mitochondrial diseases.

Diabetes with the 3243 mitochondrial tRNALeu(UUR) mutation. Characteristic neuroimaging findings.

OBJECTIVE: To investigate the basis of central nervous system dysfunction in diabetes associated with the 3243 mitochondrial tRNA mutation, we studied neuroimaging findings in patients with this disease. RESEARCH DESIGN AND METHODS: We screened 205 diabetic patients. Those patients who had the 3243 mutation in leukocytes or muscle were enrolled. All the subjects underwent computed tomography (CT), magnetic resonance imaging (MRI), magnetic resonance angiography (MRA), and N-isopropyl-p-[123I]iodoamphetamine ([123I]IMP) single-photon emission computed tomography (SPECT) of the brain. RESULTS: None of the nine subjects with the 3243 mutation had the typical clinical picture of mitochondrial myopathy, encephalopathy, lactic acidosis, and stroke-like episodes, and none had neurological focal signs. CT or MRI revealed diffuse brain atrophy in three patients (33%) and cerebellar atrophy in one (11%). Abnormal high intensity areas were observed on MRI in five patients (56%). The overall prevalence of brain abnormalities was 56% (5 of 9) on CT and 78% (7 of 9) on MRI scans. MRA revealed no stenotic lesions. SPECT showed reduced accumulation of [123I]IMP in the right or left parieto-occipital region in eight patients (89%). CONCLUSIONS: Reduced accumulation of [123I]IMP in the parieto-occipital cortex was found in a high proportion of our subjects on SPECT. This imaging finding might be characteristic of diabetes associated with the 3243 mitochondrial tRNA mutation and may be a sign of latent central nervous system dysfunction.

Diabetes mellitus associated with 3243 mitochondrial tRNA(Leu(UUR)) mutation: clinical features and coenzyme Q10 treatment.

Diabetes mellitus associated with mitochondrial tRNA mutation at position 3243(DM-Mt3243) is a new disease. Patients have a distinctly different picture from MELAS (mitochondrial encephalomyopathy, lactic acidosis, and stroke-like episodes). During observations at the Saiseikai Central Hospital, the following findings were noted in DM-Mt3243 patients: DM-Mt3243 patients are diagnosed earlier with diabetes, compared to NIDDM (non-insulin dependent diabetes mellitus) controls without family history. DM-Mt3243 patients often need insulin more often than NIDDM controls without family history. Post-treatment neuropathy and insulin edema are often found in DM-Mt3243, and the two phenomena possibly have a similar pathophysiology related to mitochondrial dysfunction. Ambiguous psychiatric disorders of functional psychosis are observed frequently in DM-Mt3243. Mild headache is common in DM-Mt3243 cases. Ambiguous neuromuscular abnormalities such as sleep disturbance, paresthesia of the legs, edema of the legs, and palpitation may be symptoms associated with mitochondrial dysfunction in DM-Mt3243. Coenzyme Q may be effective in the relief of these neuromuscular symptoms.

The kallikrein-kinin system, but not vascular endothelial growth factor, plays a role in the increased vascular permeability associated with ovarian hyperstimulation syndrome.

Ovarian hyperstimulation syndrome (OHSS) is a severe complication arising from controlled stimulation treatment. Vascular endothelial growth factor (VEGF) has recently emerged as an important factor which may be responsible for the hyperpermeability seen in OHSS. The purpose of the present study was to investigate and compare the mechanisms by which ascites in patients with OHSS and ovarian carcinoma induce increases in vascular permeability in an in vitro assay and an in vivo animal experiment. We found 8-fold lower VEGF levels in ascites from patients with OHSS than in those from patients with ovarian carcinoma. Although VEGF is produced by the ovaries, it is not necessarily the factor responsible for hyperpermeability. We also demonstrated that the vascular hyperpermeability produced by OHSS ascites was not abolished by specific neutralizing anti-VEGF antibodies, and that not all of the VEGF found in the ascites fluid is biologically active. Moreover, our results strongly suggest that the vascular permeability produced by OHSS ascites may depend on activation of the kallikrein-kinin system. Possible evidence for this phenomenon was obtained by demonstrating that the hyperpermeability caused by the ascites could be blocked by Trasylol (known to inhibit bradykinin synthesis) and potentiated by captopril (a kininase II inhibitor). Taken together, the results suggest that, although VEGF is found in ascites fluid from patients with OHSS, it is unlikely that the cause of OHSS involves VEGF production by the ovaries. The kallikrein-kinin system may be more important in the hyperpermeability seen in OHSS.

Maternal blood coagulation factor XIII is associated with the development of cytotrophoblastic shell.

We analysed the early implantation tissues of normal women and of a patient with congenital factor XIII deficiency in order to study the role of maternal subunit A of factor XIII (XIIIA) in the development of extravillous cytotrophoblast. The patient had received adequate administration of factor XIIIA concentrate only up to 7 weeks of gestation (wG). Her pregnancy was maintained until the latter half of 8 wG, but was terminated by intrauterine fetal death at 9 wG. Immunohistochemical staining of cytokeratin, XIIIA and subunit S of factor XIII was performed in the early implantation tissues of normal women and of this patient. Numerous well-formed cytotrophoblastic shells and Nitabuch's layers were detected in implantation tissues at 7-8 wG in normal women, and XIIIA was present in the intercellular space in well-formed cytotrophoblastic shells, while the cytotrophoblastic shells and Nitabuch's layers in this patient's implantation tissue were poorly-formed. Furthermore, XIIIA was not detected around them. It is suggested that when the maternal plasma activity of factor XIII is low, the concentration of XIIIA at the placental bed is also low, leading to the insufficient formation of cytotrophoblastic shell and therefore an increased probability of miscarriage in patients with congenital factor XIII deficiency.

Increase in cardiac muscle fructose content in streptozotocin-induced diabetic rats.

To evaluate the activation of the sorbitol pathway in cardiac muscle in diabetic rats, we measured sorbitol, fructose, and myo-inositol content in cardiac tissue obtained from control and streptozotocin-diabetic rats, with or without an 8-week insulin treatment, using gas chromatography-mass spectrometry (GC-MS). Cardiac fructose and sorbitol content in 10-week diabetic rats increased by 60-fold and 3.9-fold of those of control rats, respectively (P less than .001). In contrast, cardiac myo-inositol content in 10-week diabetic rats decreased to 56% (P less than .025) of the control value. The abnormalities in cardiac fructose, sorbitol, and myo-inositol content were completely normalized by the 8-week insulin treatment, which was initiated 2 weeks after the induction of diabetes. There was no difference in cardiac aldose reductase activity between control and diabetic rats. However, cardiac sorbitol dehydrogenase activity in diabetic rats was 151% (P less than .005) higher than that of control rats, although hepatic sorbitol dehydrogenase activity was not different between the two groups. These results indicate that the sorbitol pathway is significantly activated in cardiac tissue obtained from streptozotocin-induced diabetic rats, which results in the marked cardiac accumulation of fructose.

Diabetes mellitus associated with the 3243 mitochondrial tRNA(Leu)(UUR) mutation: insulin secretion and sensitivity.

To investigate the pathophysiology of diabetes mellitus associated with the 3243 mitochondrial tRNA(Leu)(UUR) mutation (DM-Mt3243), insulin secretion and sensitivity were studied using the 75-g oral glucose tolerance test (oGTT), 1-mg intravenous glucagon test, and euglycemic glucose clamp test. Twelve DM-Mt3243 patients were investigated (seven men and five women). Their ages ranged from 36 to 74 years, and the onset of diabetes occurred at 44.5 +/- 9.5 years (mean +/- SD). In the glucose tolerance test, nine patients (75.0%) showed lower C-peptide reactivity (CPR) than normal at 30 minutes, suggesting blunted insulin secretion. Three patients showed an impaired glucose tolerance (IGT) pattern, although they had absolute hyperglycemia at the onset of diabetes. In the glucagon test, 10 patients (76.3%) had CPR within the normal range at 6 minutes, indicating an adequate response. In the glucose clamp test, the M value was 8.70 +/- 2.35 mg/kg/min and was within normal limits in all patients. The glucose metabolized (M value) was negatively correlated with 24-hour urinary C-peptide excretion (r = .696, P < .05). Thus, plasma CPR to glucose loading was blunted in many DM-Mt3243 patients, but CPR to glucagon was relatively well preserved. This difference in the intrinsic insulin response to the two stimuli may be characteristic of DM-Mt3243. Although M values were normal in all subjects, the correlation with 24-hour urinary C-peptide excretion suggests a relationship between insulin sensitivity and insulin secretion. These two mechanisms may cooperate to maintain homeostasis in this disease. Since three patients did not progress with aging, this mutation may not always cause gradual beta-cell destruction.

Effect of medium pH on glutathione redox cycle in cultured human umbilical vein endothelial cells.

Impairments of the glutathione redox cycle in cultured endothelial cells under acidic pH conditions were measured. Glutathione-dependent H2O2-degrading activities decreased by 20% (P < .01) at pH 6 and by 51% (P < .01) at pH 4 compared with activities at pH 7.4 1 hour after a change with fresh medium. Intracellular reduced glutathione (GSH) content increased by 85% (P < .01) following the change with pH 7.4 medium. Such increases in GSH content were impaired after exposure to acidic medium. After exposure to 500 mumol/LH2O2, intracellular GSH content decreased by 61% compared with the level obtained in the absence of H2O2 at pH 7.4 (P < .01). Compared with the level at pH 7.4, the H2O2-induced decrease in intracellular GSH content was 32% lower (P < .01) at pH 6 and did not change at all at pH 4. After exposure to 500 mumol/L H2O2, the intracellular oxidized glutathione (GSSG) content increased by 160% at pH 7.4 (P < .01), 370% at pH 6 (P < .01), and 90% at pH 4 compared with treatment without H2O2, respectively. After exposure to 500 mumol/L H2O2, the release of GSSG from cells at pH 6 decreased by 38% compared with the value found at pH 7.4 (P < .05), and the release at pH 4 completely disappeared. Both glutathione peroxidase (GPO) and glutathione reductase activities decreased as a function of a decrease in pH from 7.4 to 4.(ABSTRACT TRUNCATED AT 250 WORDS)

Effect of verapamil on cardiac protein kinase C activity in diabetic rats.

We examined the effect of verapamil treatment on cardiac protein kinase C (PKC) activity in streptozocin-induced diabetic rats. Basal cardiac PKC activity in diabetes increased in both cytosolic (by 94%, P less than 0.01) and membrane (by 41%, P less than 0.05) fractions as compared with that in controls. Subcutaneous administration of 8 mg/kg verapamil twice a day for 8 weeks induced a significant decrease in both cytosolic (by 59%, P less than 0.01) and membrane (by 50%, P less than 0.01) PKC activity in diabetes as compared with the activity in the non-treated diabetic groups. In contrast, cardiac cytosolic PKC activity in control rats was significantly (P less than 0.01) decreased by 41% as compared with that of the non-treated control group without there being any change in membrane PKC activity. Our data demonstrate that verapamil treatment may ameliorate the abnormal activation of cardiac PKC in diabetes.

Effects of verapamil on the cardiac alpha 1-adrenoceptor signalling system in diabetic rats.

We evaluated the effects of chronic verapamil treatment on the cardiac alpha 1-adrenoceptor signalling system in streptozocin-induced diabetic rats. The decrease in maximum cell surface [3H]bunazosin binding (Bmax) in isolated cardiac myocytes from the diabetic group (-46%, P < 0.01) was completely reversed by a 4-week course of verapamil, while Bmax in the verapamil-treated control group was unchanged. Similarly, the reduction in ventricular inositol 1,4,5-trisphosphate (IP3) production after stimulation with 10 microM noradrenaline (NA) seen in diabetes (-30%, P < 0.01) was completely normalized by verapamil, while the response in the verapamil-treated control group was unaffected. These results indicate that verapamil can induce complete recovery of the impaired cardiac alpha 1-adrenoceptor signalling system in the diabetic heart without affecting glucose metabolism.