Synthesis of a Cu-infiltrated Zr-doped SBA-15 catalyst for CO2 hydrogenation into methanol and dimethyl ether.

A catalytically active nanoassembly comprising Cu-nanoparticles grown on integrated and active supports (large pore Zr-doped mesoporous SBA-15 silica) has been synthesized and used to promote CO2 hydrogenation. The doped mesoporous material was synthesized using a sol-gel method, in which the pore size was tuned between 11 and 15 nm while maintaining a specific surface area of about 700 m2 g-1. The subsequent Cu nanoparticle growth was achieved by an infiltration process involving attachment of different functional groups on the external and internal surfaces of the mesoporous structure such that 7-10 nm sized Cu nanoparticles grew preferentially inside the pores. Chemisorption showed improved absorption of both CO2 and H2 for the assembly compared to pure SBA-15 and 15% of the total CO2 was converted to methanol and dimethyl ether at 250 °C and 33 bar.

Proinsulin/C-peptide ratio, glucagon and remission in new-onset Type 1 diabetes mellitus in young adults.

AIMS: After initiation of treatment in Type 1 diabetes, a period with lower insulin requirement often follows, reflecting increased insulin sensitivity and improved insulin secretion. We explored if efficiency of proinsulin processing is associated with the remission phenomenon. METHODS: Seventy-eight patients with new-onset Type 1 diabetes were followed prospectively for 3 years. Daily insulin dosage, HbA(1c) , plasma glucose, proinsulin, C-peptide, glucagon concentrations and islet antibodies were determined at diagnosis and after 3, 6, 9, 12, 18, 24, 30 and 36 months. We studied remission, defined as an insulin dose ≤ 0.3 U kg(-1) 24 h(-1) and HbA(1c) within the normal range, in relation to the above-mentioned variables. RESULTS: A rise and subsequent decline in plasma proinsulin and C-peptide concentrations was observed. Forty-five per cent of the patients experienced remission at one or more times, characterized by higher proinsulin and C-peptide levels, and lower proinsulin/C-peptide ratios, indicating more efficient proinsulin processing, compared with those not in remission. Non-remission also tended to be associated with higher glucagon values. Patients entering remission were more often men, had higher BMI at diagnosis, but did not differ at baseline with respect to islet antibody titres compared with patients with no remission. CONCLUSIONS: Remissions after diagnosis of Type 1 diabetes were associated with lower proinsulin/C-peptide ratios, suggesting more efficient proinsulin processing, and tended to have lower glucagon release than non-remissions. This indicates that, in remission, the residual islets maintain a secretion of insulin and glucagon of benefit for control of hepatic glucose production.

Role of cage material, working style and hearing sensitivity in perception of animal care noise.

During daily care, laboratory animals are exposed to a variety of sounds which may have effects on welfare and also cause physiological and behavioural changes. So far, almost no attention has been paid to individual sounds or the sound level caused by animal care or the sound level inside the animal cage. In this study, sounds from selected rat care procedures were recorded: pulling cage out of the rack, placing it onto a table and replacing the cage back into the rack; with measurements made inside the rat cage and in the adjacent cage. Diet was poured into the food hopper and sounds were recorded inside the cage and also the adjacent cage. The work was repeated in a calm and also in a hurried style, using stainless steel and polycarbonate cages. Finally, the sounds produced by running tap water were recorded. Differences between rat and human hearing were compared using novel species-specific sound level weightings: R-weighting for rats dB(R) and H-weighting for human dB(H). Hurried work with steel caused sound exposure levels exceeding 90 dB(R) when the cages were placed into the rack and about 80 dB(R) when pulling them out of the rack or placing onto a table. With polycarbonate, the levels were 10-15 dB(R) lower. Unhurried calm working produced lower sound exposure levels than hurried working in many procedures. When the procedures were repeated with measurements in the adjacent cage, the sound exposure levels were lower, but the results were similar. Pouring food pellets into a hopper above the rat's head caused 15 dB(R) higher sound exposure levels than pouring food to an adjacent cage. In general, humans hear these sounds about 10-15 dB louder than rats. In conclusion, cage material, working style and hearing sensitivity all have an impact on the sound exposure level in the rodent cage. With correct working methods, high sound levels can be efficiently avoided in most cases.

Shape engineering boosts antibacterial activity of chitosan coated mesoporous silica nanoparticle doped with silver: a mechanistic investigation.

In this study, mesoporous silica nanoparticles (MSPs) of different size and shape were developed, and their surface coatings were utilized to study their differential effects in enhancing antibacterial activity. In brief, MSPs with three different aspect ratios (1, 2 and 4) were prepared, doped with silver ions and finally coated with the polymer chitosan. Both Gram-positive and Gram-negative bacteria were treated with the MSPs. Results indicate that silver ion doped and chitosan coated MSPs with the aspect ratio of 4 (Cht/MSP4:Ag+) have the highest antimicrobial activity among the prepared series. Further studies revealed that Cht/MSP4:Ag+ was most effective against Escherichia coli (E.coli) and least effective against Vibrio cholerae (V. cholerae). To investigate the detailed inhibition mechanism of the MSPs, the interaction of the nanoparticles with E.coli membranes and its intracellular DNA was assessed using various spectroscopic and imaging-based techniques. Furthermore, to increase the efficiency of the MSPs, a combinatorial antibacterial strategy was also explored, where nanoparticles, in combination with kanamycin (antibiotic), were used against Vibrio Cholerae (V. cholerae). Toxicity screening of these on MSPs was conducted on Caco-2 cells, and the results show that the dose used for antibacterial screening is below the limit of the toxicity threshold. Our findings show that both shape and surface engineering contribute positively towards killing bacteria, and the newly developed silver ion-doped and chitosan-coated MSPs have good potential as antimicrobial nanomaterials.

GAD autoantibodies in IDDM, stiff-man syndrome, and autoimmune polyendocrine syndrome type I recognize different epitopes.

Glutamic acid decarboxylase (GAD) is a major islet cell autoantigen in insulin-dependent diabetes mellitus (IDDM), and autoantibodies are found in high frequencies in patients with recent-onset IDDM, stiff-man syndrome (SMS), and autoimmune polyendocrine syndrome type I (APS I). Antigens in autoimmune disorders are often enzymes, and autoantibody binding frequently inhibit their activity. In this study, we examined the reactivity of anti-GAD-containing sera from 7 patients with IDDM, 4 patients with SMS, and 5 patients with APS I. All sera immunoprecipitated GAD from [35S]methionine-labeled rat islet lysates and the sera from patients with SMS and APS I, but none of the IDDM patients' sera, identified the GAD protein in Western blots. Two of four SMS patients' sera and 5 of 5 APS I patients' sera, in contrast to 0 of 7 IDDM patients' sera, inhibited the enzymatic activity of GAD. When the various sera were tested with the GAD65 and GAD67 isoforms, produced separately by transient expression in COS cells, the enzymatic activity of GAD65 was inhibited by sera from patients with SMS and APS I, whereas no effect on the GAD67 activity was observed. Taken together, the results demonstrate that the GAD autoantibodies in these three disorders display marked differences in epitope recognition and indicate that, during the development of the diseases, the autoantigen is being presented to the immune system through separate pathogenetic mechanisms.

High-glucose stimulation of 64,000-Mr islet cell autoantigen expression.

This study examined the effect of various extracellular glucose concentrations on the expression of a previously described 64,000-Mr islet cell autoantigen associated with insulin-dependent diabetes mellitus. The protein was precipitated from patient serums incubated with Triton X-100 lysates of [35S]methionine-labeled rat pancreatic islets that had been cultured in 5, 11, or 28 mM glucose for 6 h or 3 days. In both types of experiment, 28 mM glucose was the most efficient stimulator of 64,000-Mr autoantigen production. In contrast, the class I antigens of the major histocompatibility complex, precipitated by a rabbit polyclonal antiserum, were not influenced by differences in glucose concentrations. Our data indicate that expression of islet cell antigens may be increased during the course of hyperglycemia and suggest that the functional activity of islet cells influences their antigenicity.

Diazoxide treatment at onset preserves residual insulin secretion in adults with autoimmune diabetes.

Twenty islet cell antibody (ICA)-positive patients, aged 19-38 years, with IDDM were randomized at onset to treatment with either diazoxide, a K+ channel opener that inhibits the release of insulin, or placebo for 3 months, in addition to multiple insulin injection therapy. The patients who were given diazoxide displayed higher residual insulin secretion than the placebo group after 1 year (basal C-peptide level, 0.40 +/- 0.04 vs. 0.25 +/- 0.04 [mean +/- SE] nmol/l; P < 0.021) and at an 18-month follow-up (0.37 +/- 0.06 vs. 0.20 +/- 0.01 nmol/l, P < 0.033). Metabolic control did not differ between the two groups. During the course of the study, no differences in islet cell or GAD autoantibodies were detected between the two groups. The results of this study warrant further trials to explore the potential of inducing target cell rest in order to halt the loss of insulin-producing cells during the early course of the disease.

K(ATP) channel openers protect rat islets against the toxic effect of streptozotocin.

We examined the influence of two K(ATP) channel openers, diazoxide and an analog (NNC 55-0118), on experimental beta-cell damage induced by streptozotocin (STZ; 0.5 mmol/l). Rat pancreatic islets were exposed to diazoxide or NNC 55-0118 for 30 min and were further incubated for 30 min after the addition of STZ. The islets were then washed and cultured for 24 h. Islets exposed to STZ alone showed extensive morphological damage, reduced glucose oxidation, low insulin content, and severely impaired glucose-stimulated insulin secretion and proinsulin biosynthesis. Islets treated with STZ in the presence of the channel openers (0.03-0.30 mmol/l) showed dose-dependent preservation of the morphology and improved glucose oxidation rates, insulin content, and secretion. NNC 55-0118 was capable of fully counteracting the STZ impairment, whereas diazoxide had a less protective effect. NNC 55-0118 did not counteract STZ-induced depression of islet NAD levels when examined 2 h after STZ exposure, which suggests that the mechanism of action by NNC 55-0118 is not through an inhibition of poly(ADP-ribose) polymerase. The results illustrate that K(ATP) channel openers can protect insulin-producing cells against toxic damage, an effect that may be of use in subjects with ongoing insulitis.

Induction of beta-cell rest in type 1 diabetes. Studies on the effects of octreotide and diazoxide.

OBJECTIVE: To evaluate the inhibitory effects of octreotide and diazoxide on insulin secretion in patients with type 1 diabetes and measurable levels of circulating C-peptide. RESEARCH DESIGN AND METHODS: Diazoxide was given to six patients during a 7-day period (100 mg three times daily), followed by a 3-week washout. Subsequently, octreotide (50 micrograms, three times daily) was administered subcutaneously for 7 days. Pre- and post- prandial blood glucose and serum C-peptide concentrations were measured before medication (control) and on day 7 of each medication period. Glucagon-stimulated C-peptide was determined in the morning before medication and on the day after each treatment period. RESULTS: Diazoxide inhibited glucagon-stimulated C-peptide secretion (mean increment 0.08 nmol/l vs. 0.18 nmol/l, P < 0.05), whereas octreotide had no such effect. Both reduced the pre- and postprandial serum C-peptide concentrations (P < 0.05), octreotide being the more potent in this respect. A reduction in basal and meal-related blood glucose was observed during octreotide treatment, whereas the glucose concentrations tended to be higher during treatment with diazoxide than during the 24-h control period. CONCLUSIONS: The study indicates that the two drugs reduce insulin output by different mechanisms. Diazoxide inhibits hormonal release directly on the beta-cells, whereas octreotide exerts its effect indirectly, presumably by multiple actions on insulin sensitivity and insulin-releasing hormones. The results suggest that each drug is capable of inducing beta-cell rest in type 1 diabetes.

Family characteristics and life events before the onset of autoimmune type 1 diabetes in young adults: a nationwide study.

OBJECTIVE: To elucidate whether family characteristics and stressful life events were associated with onset of autoimmune type 1 diabetes in young adults. RESEARCH DESIGN AND METHODS: This investigation was based on a nationwide study (Diabetes Incidence Study in Sweden) of newly diagnosed patients aged 15-34 years. Patients clinically classified as type 1 diabetic with antibodies to islet cells and/or to GAD65 were compared with age- and sex-matched control subjects via questionnaire. The questionnaire covered diabetes heredity, social environment, educational level, and life events experienced during the 12 months before diagnosis. RESULTS: The rate of response was 82% for the diabetic patients and 65% for the control subjects. Questionnaires from 349 diabetic patients and 979 control subjects were considered. Diabetes in relatives was more frequent in the patients (odds ratio [OR]2.6) who were born in Sweden and whose mothers were of Swedish origin. No major stress factors were detected in the diabetic patients; however, in comparison with the control subjects, the diabetic patients had experienced fewer conflicts with their parents and had less often broken contacts with friends. CONCLUSIONS: Young adults with recent-onset type 1 diabetes were more exposed to heredity for diabetes, but no major prediabetic stress factors were detected. Our study does not directly support the concept that psychosocial stressful life events are involved in the development of autoimmune type 1 diabetes in young adults.

Glucose regulation of the autoantigen GAD65 in human pancreatic islets.

Recent data suggest that the enzyme glutamic acid decarboxylase (GAD) may be a primary beta-cell antigen involved in the autoimmune response leading to insulin dependent diabetes mellitus (IDDM). Following three days culture of human islets at different glucose concentrations (5.6, 11 or 28 mM), there was a single 65 kDa/GAD band in the islet extracts, as assessed by immunoprecipitation both with serum from a newly diagnosed IDDM patient and a sheep anti-GAD serum. The synthesis of GAD was strongly stimulated at the higher glucose concentrations. Likewise, Western blot analysis indicated a glucose-induced increase of GAD in the islets. The data suggest that an enhanced function of human islet cells increases expression of GAD65. Possibly, this could exacerbate the autoimmune assault in the early stages of IDDM, and be of practical importance in attempts to ameliorate the autoimmune response towards the beta-cells in IDDM.

Regulation of GAD expression in islets of Langerhans occurs both at the mRNA and protein level.

The expression of the autoantigen glutamate decarboxylase in islets of Langerhans was investigated under different culture conditions, which affect the functional activity of the beta-cell. Using immunoprecipitations and analyses of enzyme activity, an increase in glutamate decarboxylase was detected in rat islets cultured at a glucose concentration of 11 mmol/l compared with those cultured at 5.6 mmol/l glucose. To determine whether the change was induced at the level of mRNA expression, total RNA was extracted from rat islets cultured at 5.6 or 11 mmol/l glucose, reverse transcribed and amplified by the polymerase chain reaction. Comparative quantitation in a phosphor imager revealed a significantly higher (82%, P < 0.005) content of glutamate decarboxylase mRNA in islets cultured at 11 mmol/l glucose. In parallel, human recombinant interleukin-1 beta, and diazoxide were tested for their effects on the expression of glutamate decarboxylase. Islets cultured at 11 mmol/l glucose in the presence of 40 U/ml of interleukin-1 beta, showed a 63% decrease (P < 0.005) in enzyme activity compared with those cultured at 11 mmol/l glucose alone, and similar decreases were noted on analysis of glutamate decarboxylase biosynthesis and mRNA. Islets cultured at 11 mmol/l glucose in the presence of 22.5 mg/ml diazoxide exhibited a significant reduction in enzyme activity (59%; P < 0.001) compared with those cultured at 11 mmol/l glucose only. This reduction, however, was not accompanied by a decrease in the content of glutamate decarboxylase mRNA.(ABSTRACT TRUNCATED AT 250 WORDS)

Beta-cell rest: a strategy for the prevention of autoimmune diabetes.

An autoantigen being recognized by specific receptors is the key reaction of an autoimmune disease. Whereas much efforts have been made to develop immunosuppressive regimens which reduce the amount of effector cells, and/or inhibit receptor activation, surprisingly little attention has been paid to reduce the ligand-receptor interaction by interfering with the amount of antigen being presented from the target cells. In this review, we discuss clinical observations in autoimmune endocrine disease which illustrate that target cell alterations can modify the disease activity and comment on recent clinical trials which indicate that beta-cell rest may be beneficial to the course of human autoimmune diabetes mellitus.

Modulation of beta-cell activity and its influence on islet cell antibody (ICA) and islet cell surface antibody (ICSA) reactivity.

Insulin-dependent diabetes mellitus (IDDM) is associated with the formation of autoantibodies against different antigens in the islets of Langerhans, so-called islet cell antibodies (ICA). The expression of a major autoantigen, the beta-cell specific enzyme glutamic acid decarboxylase (GAD), is glucose-dependent in vitro and correlated to insulin release in vitro. In this study the expression of islet autoantigens was examined in vivo and the relationship between beta-cell function and islet cell surface antibody (ICSA) reactivity was tested. Rats were fed for 10 days with glipizide or diazoxide, in order to stimulate or inhibit insulin release, respectively. Frozen sections of pancreata were incubated with ten ICA-positive IDDM sera and analyzed by indirect immunofluorescence. Two sera with a "beta-cell restricted" staining, five with an "all-islet cell" staining and three with a "mixed" pattern were employed. In all three groups, the highest end-point titres were obtained when pancreata of rats treated with glipizide were used. Intermediate titres were seen in control animals and the lowest titres were observed on pancreata from diazoxide-treated rats, regardless of the serum used. In contrast to these observations, no correlation between ICSA reactivity and islet cell activity could be demonstrated. Conflicting results concerning ICSA in previous reports and our failure to show a glucose regulation of ICSA reactivity, indicate that ICSA is a phenomenon with a low degree of specificity.(ABSTRACT TRUNCATED AT 250 WORDS)

Combinations of beta cell specific autoantibodies at diagnosis of diabetes in young adults reflects different courses of beta cell damage.

To explore the natural course of beta cell function in recent onset diabetes, a subgroup (n=157) of all incident cases (n=879) 15-34 years old, 1992-1993 in Sweden, and with positivity for at least one autoantibody of islet cell antibodies (ICA), glutamic acid decarboxylase antibodies (GADA) or tyrosine phosphatase antibodies (IA-2A) were followed prospectively for the first four years with annual analysis of C-peptide. The aim was to relate the course of beta cell function, measured as C-peptide, in early diabetes with the presence of different islet autoantibodies at diagnosis. We found that patients positive for ICA alone (n=11) had significantly higher C-peptide levels both at diagnosis and during the first three years compared with the other patients (n=146; p=0.022, p<0.001, p=0.004 and p=0.0022). Patients positive for GADA alone or in combination with other antibodies (n=125) had significantly lower C-peptide during the first three years after diagnosis compared with the other patients (n=32, p<0.001, p=0.0011 and p=0.0136). Patients with two or three autoantibodies had C-peptide levels similar to levels found in patients positive only for GADA. However, after four years, there were no significant differences between any of the groups of different autoantibody combinations. At diagnosis, 55% (86/157) of the patients had C-peptide levels above the lower normal range of 0.25 nmol/l, but the frequency of patients with beta cell function above this level decreased after two years to 41% (65/157; p=0.035) and after four years to 22% (35/157; p=0.0041). It is concluded that young adult diabetic patients positive only for ICA at diagnosis have a better preserved beta cell function with higher levels of C-peptide during the first three years compared with patients positive for GADA alone or in combinations with other autoantibodies.

Lack of relationship between thalamic oscillations and attention in rats: differential modulation by an alpha-2 antagonist.

A five-choice serial reaction time (5-CSRT) task was used to assess attention in rats. In this behavioral paradigm, the rats are required to spatially discriminate a short visual stimulus that will occur randomly in one of five locations while maintaining a sufficient activity level. The ability of a rat to maintain attention on the task can be measured by counting the choice accuracy (percent correct responses), whereas the probability of premature responses indicates the level of impulsivity. According to previous results [24], rats performing poorly in the task have a lower choice accuracy and make more premature responses than normally behaving individuals, i.e., a clear, inverse correlation was observed between choice accuracy and impulsiveness of rats. Methylphenidate, a psychostimulant that has been shown to alleviate the symptoms in attention deficit-hyperactivity disorder (ADHD), improved the choice accuracy of poor performing rats in this task [24]. The present results show that the correlation between choice accuracy and impulsivity exists also when the rats are tested using a reduced stimulus intensity or curtailed stimulus duration. The results of a pharmacological experiment suggested that atipamezole (30, 300, or 1000 micrograms/kg), a potent and specific alpha-2 antagonist that is known to increase the activity of monoaminergic systems in the brain, did not affect the percent correct responses in poor performers or in controls tested either at the baseline conditions or at a curtailed stimulus duration (which impaired their choice accuracy). At the doses of 300 and 1000 micrograms/kg, however, atipamezole slightly increased the probability of premature responses in all group of rats. The results of an electrophysiological study indicated that the poor choice accuracy or impulsiveness of rats is not related to the amount of cortically recorded spike-wave discharges/high voltage spindle (HVS) activity, which reflect thalamo-cortical oscillation. Atipamezole dose-dependently reduced the incidence and duration of HVSs. The present data, therefore, indicate that (a) alpha-2 antagonist treatment is not superior to methylphenidate treatment when investigated using acute administrations of the agents in poor performers of the 5-CSRT task, and (b) thalamic oscillations are not the reason for the attention deficit of rats in this model of ADHD. The relationship between choice accuracy and impulsivity is discussed.

Visualization of in vivo olfactory uptake and transfer using fluorescein dextran.

Nasal administration of a 3 kDa fluorescein dextran (FD3) solution to rats resulted in transcellular absorption across the olfactory epithelium and transfer to the olfactory bulb within 15 min. After entering the lamina propria, FD3 was transferred in the connective tissue surrounding the olfactory nerve bundles to the olfactory bulb of the brain. More FD3 was absorbed across the olfactory epithelium than across the respiratory epithelium and to the nasal associated lymphoid tissue. Further, the amount of FD3 crossing the olfactory epithelium was region-dependent, with higher amounts absorbed in the turbinates than in the nasal septum. Plastic embedding and sectioning followed by fluorescence microscopy, enabled simultaneous visualization of FD3 in the mucosa and olfactory bulb, as well as the opportunity to store the tissue blocks for a prolonged period of time.

Starch microspheres induce pulsatile delivery of drugs and peptides across the epithelial barrier by reversible separation of the tight junctions.

Non-parenteral administration of peptide drugs is prevented by the limited permeability of the epithelia lining the mucosal tissues. As a new approach to non-parenteral delivery, degradable starch microspheres (dsm) were coated with insulin and administered to the mucosal side of monolayers of human intestinal epithelial (Caco-2) cells in vitro. The microspheres induced a pulsed delivery of insulin across the epithelium that lasted for 1-2 h. The pulsed delivery correlated with a reversible appearance of focal dilatations in the tight junctions between the epithelial cells, indicating that dsm enhance the delivery of insulin by the paracellular route. These results provide an explanation for the previously observed absorption enhancing properties of dsm.

Weight of sound qualities in inducing audiogenic seizure in rats.

Twelve experiments were carried out in order to establish the functional associations of the sound pressure level, the frequency, time variations and spectral properties of sound with the latency time of audiogenic seizure (AGS) in rats. The signal to silence time ratio, in addition to the sound pressure level and the frequency was found to be an important factor. As a retraction to the previous paper (Björk, E.A. and Tacke, U., 1985, Hearing Res. 17, 95-98), the harmonic spectra were shown not to be more effective than the tone and the noise in inducing AGS.

Sounds with harmonic spectra are more effective than pure tones in inducing audiogenic seizure in rats.

Twenty rats of an audiogenic seizure (AGS)-susceptible stock were exposed to four different sound stimuli and seizure severity and seizure-latency were registered. Two sounds with harmonic spectra, one pure tone and band noise were used. The harmonic spectra were found to be significantly (P less than 0.005) more effective than the other stimuli in inducing AGS when seizure-latency was taken as a parameter. Connections from the auditory pathway to the reticular formation seem to be of importance in the triggering of these seizures. AGS-susceptible rats may offer a useful tool for experimental hearing research.