Inability to work following COVID-19 vaccination-a relevant aspect for future booster vaccinations

OBJECTIVES

COVID-19 vaccination is a key prevention strategy to reduce the spread and severity of SARS-CoV-2 infections. However, vaccine-related inability to work among healthcare workers (HCWs) could overstrain healthcare systems.

STUDY DESIGN

The study presented was conducted as part of the prospective CoVacSer cohort study.

METHODS

This study examined sick leave and intake of pro re nata medication after the first, second, and third COVID-19 vaccination in HCWs. Data were collected by using an electronic questionnaire.

RESULTS

Among 1704 HCWs enrolled, 595 (34.9%) HCWs were on sick leave following at least one COVID-19 vaccination, leading to a total number of 1550 sick days. Both the absolute sick days and the rate of HCWs on sick leave significantly increased with each subsequent vaccination. Comparing BNT162b2mRNA and mRNA-1273, the difference in sick leave was not significant after the second dose, but mRNA-1273 induced a significantly longer and more frequent sick leave after the third.

CONCLUSION

In the light of further COVID-19 infection waves and booster vaccinations, there is a risk of additional staff shortages due to postvaccination inability to work, which could negatively impact the already strained healthcare system and jeopardise patient care. These findings will aid further vaccination campaigns to minimise the impact of staff absences on the healthcare system.

Does COVID-19 Infection Increase the Risk of Diabetes? Current Evidence

PURPOSE OF REVIEW

Multiple studies report an increased incidence of diabetes following SARS-CoV-2 infection. Given the potential increased global burden of diabetes, understanding the effect of SARS-CoV-2 in the epidemiology of diabetes is important. Our aim was to review the evidence pertaining to the risk of incident diabetes after COVID-19 infection.

RECENT FINDINGS

Incident diabetes risk increased by approximately 60% compared to patients without SARS-CoV-2 infection. Risk also increased compared to non-COVID-19 respiratory infections, suggesting SARS-CoV-2-mediated mechanisms rather than general morbidity after respiratory illness. Evidence is mixed regarding the association between SARS-CoV-2 infection and T1D. SARS-CoV-2 infection is associated with an elevated risk of T2D, but it is unclear whether the incident diabetes is persistent over time or differs in severity over time. SARS-CoV-2 infection is associated with an increased risk of incident diabetes. Future studies should evaluate vaccination, viral variant, and patient- and treatment-related factors that influence risk.

Effect of SARS-CoV-2 Infection and Infection Severity on Longer-Term Glycemic Control and Weight in People With Type 2 Diabetes

OBJECTIVE

To evaluate the association of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection and severity of infection with longer-term glycemic control and weight in people with type 2 diabetes (T2D) in the U.S.

RESEARCH DESIGN AND METHODS

We conducted a retrospective cohort study using longitudinal electronic health record data of patients with SARS-CoV-2 infection from the National COVID Cohort Collaborative (N3C). Patients were ≥18 years old with an ICD-10 diagnosis of T2D and at least one HbA1c and weight measurement prior to and after an index date of their first coronavirus disease 2019 (COVID-19) diagnosis or negative SARS-CoV-2 test. We used propensity scores to identify a matched cohort balanced on demographic characteristics, comorbidities, and medications used to treat diabetes. The primary outcome was the postindex average HbA1c and postindex average weight over a 1 year time period beginning 90 days after the index date among patients who did and did not have SARS-CoV-2 infection. Secondary outcomes were postindex average HbA1c and weight in patients who required hospitalization or mechanical ventilation.

RESULTS

There was no significant difference in the postindex average HbA1c or weight in patients who had SARS-CoV-2 infection compared with control subjects. Mechanical ventilation was associated with a decrease in average HbA1c after COVID-19.

CONCLUSIONS

In a multicenter cohort of patients in the U.S. with preexisting T2D, there was no significant change in longer-term average HbA1c or weight among patients who had COVID-19. Mechanical ventilation was associated with a decrease in HbA1c after COVID-19.

The Evolution of Hemoglobin A1c Targets for Youth With Type 1 Diabetes: Rationale and Supporting Evidence

The American Diabetes Association 2020 Standards of Medical Care in Diabetes (Standards of Care) recommends a hemoglobin A1c (A1C) of <7% (53 mmol/mol) for many children with type 1 diabetes (T1D), with an emphasis on target personalization. A higher A1C target of <7.5% may be more suitable for youth who cannot articulate symptoms of hypoglycemia or have hypoglycemia unawareness and for those who do not have access to analog insulins or advanced diabetes technologies or who cannot monitor blood glucose regularly. Even less stringent A1C targets (e.g., <8%) may be warranted for children with a history of severe hypoglycemia, severe morbidities, or short life expectancy. During the "honeymoon" period and in situations where lower mean glycemia is achievable without excessive hypoglycemia or reduced quality of life, an A1C <6.5% may be safe and effective. Here, we provide a historical perspective of A1C targets in pediatrics and highlight evidence demonstrating detrimental effects of hyperglycemia in children and adolescents, including increased likelihood of brain structure and neurocognitive abnormalities, microvascular and macrovascular complications, long-term effects, and increased mortality. We also review data supporting a decrease over time in overall severe hypoglycemia risk for youth with T1D, partly associated with the use of newer insulins and devices, and weakened association between lower A1C and severe hypoglycemia risk. We present common barriers to achieving glycemic targets in pediatric diabetes and discuss some strategies to address them. We aim to raise awareness within the community on Standards of Care updates that impact this crucial goal in pediatric diabetes management.

Blunted muscle mitochondrial responses to exercise training in older adults with HIV

BACKGROUND

Muscle mitochondrial dysfunction associated with HIV and antiretroviral therapy (ART) may improve with exercise.

METHODS

Muscle specimens obtained before and after 24 weeks of exercise in older PWH (n=18; ART >2 years) and uninfected controls (n=21) were analyzed for citrate synthase (CS) activity and complexes (C) I-V, manganese superoxide dismutase (MnSOD), peroxisome proliferator-activated receptor-γ coactivator-1 (PGC1α), and voltage-dependent anion channel 1 (VDAC1) content.

RESULTS

Only controls had increased CS, MnSOD, PGC1 and CIV (P≤0.01; P< 0.01 vs PWH) after training.

CONCLUSIONS

The blunted mitochondrial adaptations to training in PWH suggests the need for different types of exercise-induced stimulation.

Impact of Regulatory Guidance on Evaluating Cardiovascular Risk of New Glucose-Lowering Therapies to Treat Type 2 Diabetes Mellitus: Lessons Learned and Future Directions

Responding to concerns about the potential for increased risk of adverse cardiovascular outcomes, specifically myocardial infarction, associated with certain glucose-lowering therapies, the US Food and Drug Administration and the Committee for Medicinal Products for Human Use of the European Medicines Agency issued guidance to the pharmaceutical industry in 2008. Glucose-lowering therapies were granted regulatory approval primarily from smaller studies that have demonstrated reductions in glycated hemoglobin concentration. Such studies were overall underpowered and of insufficient duration to show any effect on cardiovascular outcomes. The 2008 guidance aimed to ensure the cardiovascular safety of new glucose-lowering therapies to treat patients with type 2 diabetes mellitus. This resulted in a plethora of new cardiovascular outcome trials, most designed primarily as placebo-controlled noninferiority trials, but with many also powered for superiority. Several of these outcome trials demonstrated cardiovascular benefits of the newer agents, resulting in the first-ever cardiovascular protection indications for glucose-lowering therapies. Determining whether the guidance continues to have value in its current form is critically important as we move forward after the first decade of implementation. In February 2018, a think tank comprising representatives from academia, industry, and regulatory agencies convened to consider the guidance in light of the findings of the completed cardiovascular outcome trials. The group made several recommendations for future regulatory guidance and for cardiovascular outcome trials of glucose-lowering therapies. These recommendations include requiring only the 1.3 noninferiority margin for regulatory approval, conducting trials for longer durations, considering studying glucose-lowering therapies as first-line management of type 2 diabetes mellitus, considering heart failure or kidney outcomes within the primary outcome, considering head-to-head active comparator trials, increasing the diversity of patients enrolled, evaluating strategies to streamline registries and the study of unselected populations, and identifying ways to improve translation of trial results to general practice.

SAT-175 (-)-Epicatechin Modulates Cellular Signaling and Mitochondrial Redox in Endothelium

Diabetes mellitus affects 451 million people worldwide, and people with diabetes are 3-5 times more likely to develop cardiovascular disease. In vascular tissue, mitochondrial function is important for vasodilation and arterial stiffness, both of which are abnormal in diabetes. Diabetes-mediated generation of excess reactive oxygen species (ROS) may be contributing to this problem. We have identified (-)-epicatechin (EPICAT), a plant compound and known vasodilator, as a potential therapy. We hypothesized that mitochondrial ROS accumulation in cells treated with high glucose (HG) or antimycin A (AA, a compound targeting complex III) could be diminished by EPICAT. We further hypothesized that reduction of ROS would correlate with improved mitochondrial dynamics and cellular signaling. To test this hypothesis, we employed human umbilical vein endothelial cells (HUVEC) treated with HG, AA, and/or 0.1 or 1.0 µM of EPICAT, and measured mitochondrial and cellular superoxide, mitochondrial dynamics, and cellular signaling upstream of mitochondrial function. AA significantly increased mitochondrial width (p=0.012) and decreased mitochondrial length (p=0.0001), but we observed no impact of EPICAT. We measured superoxide production by electron paramagnetic resonance spectroscopy using two spin probes specific to mitochondrial (Mito-TEMPO-H) and total cell (CMH) superoxide. No impact of HG treatment was detected in the total cell superoxide; however, an increase in mitochondrial superoxide was measured in cells treated with HG as compared to control (0.42 µM superoxide vs. 0.31 µM superoxide, respectively). We found that both concentrations of EPICAT significantly attenuated mitochondrial superoxide production when treated with HG (HG alone=0.44 µM superoxide, HG + 0.1 µM EPICAT=0.34 µM superoxide, HG + 1.0 µM EPICAT= 0.34 µM superoxide, p=0.02 EPICAT effect), but not with AA treatment. We found that in combination with HG, 0.1 µM EPICAT significantly increased eNOS expression (p<0.05). At 1.0 µM, EPICAT also increased peNOS expression (p<0.05) and attenuated a decrease in pAMPK (p<0.05) in response to HG. EPICAT at both concentrations significantly increased mitochondrial complex II expression (p<0.05 for both). In summary, HG-induced mitochondrial ROS is responsive to EPICAT, whereas AA-induced ROS is not, suggesting that EPICAT is useful in mitigating moderate ROS concentrations and may be modulating mitochondrial activity upstream of complex III. Our data further illustrate that EPICAT may be a tool to modulate both cellular and mitochondrial glucose toxicity through the regulation of AMPK and eNOS, upstream of mitochondrial activity, as well as bolstering endogenous antioxidant defenses.

Efficacy and safety of once-weekly glucagon-like peptide 1 receptor agonist albiglutide (HARMONY 1 trial): 52-week primary endpoint results from a randomized, double-blind, placebo-controlled trial in patients with type 2 diabetes mellitus not controlled on pioglitazone, with or without metformin

AIMS

To show that albiglutide, a glucagon-like peptide-1 receptor agonist, is an effective and generally safe treatment to improve glycaemic control in patients with type 2 diabetes mellitus whose hyperglycaemia is inadequately controlled with pioglitazone (with or without metformin).

METHODS

In this 3-year, randomized, double-blind, placebo-controlled study, 310 adult patients on a regimen of pioglitazone (with or without metformin) were randomly assigned to receive additional treatment with albiglutide [30 mg subcutaneous (s.c.) once weekly, n = 155] or matching placebo (n = 155). The primary efficacy endpoint was change from baseline to week 52 (intention-to-treat) in glycated haemoglobin (HbA1c).

RESULTS

The model-adjusted change from baseline in HbA1c at week 52 was significantly better with albiglutide than with placebo (-0.8%, 95% confidence interval -1.0, -0.6; p < 0.0001). Change from baseline fasting plasma glucose was -1.3 mmol/l in the albiglutide group and +0.4 mmol/l in the placebo group (p < 0.0001); a significantly higher percentage of patients reached the HbA1c goals with albiglutide (p < 0.0001), and the rate of hyperglycaemia rescue up to week 52 for albiglutide was 24.4 versus 47.7% for placebo (p < 0.0001). Albiglutide plus pioglitazone had no impact on weight, and severe hypoglycaemia was observed rarely (n = 2). With few exceptions, the results of safety assessments were similar between the groups, and most adverse events (AEs) were mild or moderate. The 52-week incidence rates for gastrointestinal AEs for albiglutide and placebo were: 31.3 and 29.8%, respectively (diarrhoea: 11.3 and 8.6%; nausea: 10.7 and 11.3%; vomiting: 4.0 and 4.0%).

CONCLUSIONS

Albiglutide 30 mg administered once weekly as an add-on to pioglitazone (with or without metformin) provided effective and durable glucose lowering and was generally well tolerated.

Gestational diabetes outcome in a single center study: higher BMI in children after six months

The aim of the study was to examine obstetric outcomes and metabolic disorders in patients with gestational diabetes mellitus (GDM) and their offspring compared to mothers without GDM and their offspring. We performed a retrospective single center cohort study of mothers with GDM using a questionnaire with items concerning the maternal medical history, neonatal complications, and child development. Mothers with gestational diabetes (GDM; n=130) and those with normal glucose tolerance (NGT; n=77) were recruited. GDM mothers were older (37.58 years vs. 34.32 years, p<0.0001) and had a greater body mass index (25.18 kg/m² vs. 23.37 kg/m², p<0.01). There were no significant differences regarding the mean birth weight, the frequency of Cesarean sections, and the prevalence of macrosomia (> 4 000 g). At follow-up (pediatric U5 screening visit after 6 months of birth) children of mothers with GDM had significantly higher BMI than the children of the NGT group (17.07 kg/m² vs. 16.59 kg/m², p=0.042). GDM women in need of insulin therapy during pregnancy had higher BMI than dieting GDM mothers and experienced more frequently an operative vaginal delivery (17.95% vs. 6.17%, OR 3.23, p=0.04). We found less significant differences between GDM mothers with treatment of impaired glucose tolerance and NGT mothers concerning the neonatal outcome than expected. Despite higher BMI of the GDM group's offspring at follow-up U5 visit, the children did not show any other development disorder. In conclusion treatment of GDM could minimize the frequency of obstetric and neonatal complications in this risk group.

Über Galvinole und Galvinoxyle, III. EPR-Spektroskopie an regellos orientierten Bis-Galvinoxyl-Biradikalen in der Glasmatrix / On Galvinols and Galvinoxyls, III. EPR Study of Zero Field Splitting in Randomly Oriented Galvinoxyl Biradicals

ESR powder spectra of several differently bridged bis-galvinoxyl biradicals have been recorded. The spectra can be interpreted in terms of a weak electron-electron dipolar coupling between the unpaired spins of randomly oriented triplet molecules. Using MO-theory and a point charge model for atomic orbitals a detailed structural analysis is performed on the basis of quantum mechanical calculations. Taking into account the twist angles between the various aryl rings the experimental data can be explained satisfactorily.

Über Galvinole und Galvinoxyle, II EPR-HFS- und elektronen-spektroskopische Untersuchung von Galvinoxyl-Mehrspinsystemen

The synthesis of several so far unknown mono- and oligo-galvinols and galvinoxyls is described. The ESR hyperfine splitting measurements in liquid solution indicate that the spin exchange frequency is greater than the hyperfine splitting in the galvinoxyl biradicals (J≫a). The electronic absorption spectra of the galvinols and galvinoxyls are discussed taking into account the different prototropic and redox equilibria, respectively. Using magnetic susceptibility measurements the singlet-triplet and doublet-quartet splitting is studied.

Effect of a randomised controlled vitamin D trial on insulin resistance and glucose metabolism in patients with type 2 diabetes mellitus

The aim of our study was to investigate the influence of a 6-month vitamin D supplementation in patients with noninsulin-requiring type 2 diabetes mellitus. We included 86 patients in a placebo-controlled, randomised, double-blind study. During 6 months patients received Vigantol oil once a week corresponding to a daily dose of 1904 IU or placebo oil, followed by 6 months of follow-up. At start and at 3-month intervals 25OHD, PTH, body mass index, HbA1c, insulin, C-peptide, and homeostasis model assessment-index were measured. The primary outcome was a change in fasting blood glucose and insulin levels. After 6 months of therapy, the verum group's 25OHD had increased to a median of 35 ng/ml in comparison to the placebo group (median 20 ng/ml, p<10-6). PTH tended to decrease in the verum group (25.5 pg/ml vs. 35.0 pg/ml, p=0.08). After 6 months of therapy, 31 patients (78%) achieved a 25OHD concentration of >20 ng/ml. Their HbA1c was significantly lower at baseline (p=0.008) and after therapy (p=0.009) than in patients with 25OHD below 20 ng/ml. C-Peptide, insulin, and HOMA-index did not change significantly in the verum group but fasting insulin was positively correlated with 25OHD concentrations after 6 months of therapy in both groups. There were no significant effects of vitamin D with a daily dose of 1904 IU on metabolic parameters in type 2 diabetes. However, the correlative findings of this study suggest a link of the 25OHD status and metabolic function in type 2 diabetes. Whether vitamin D therapy with higher doses can improve glucose metabolism needs to be investigated in follow-up trials.

Potential of albiglutide, a long-acting GLP-1 receptor agonist, in type 2 diabetes: a randomized controlled trial exploring weekly, biweekly, and monthly dosing

OBJECTIVE

To evaluate the efficacy, safety, and tolerability of incremental doses of albiglutide, a long-acting glucagon-like peptide-1 receptor agonist, administered with three dosing schedules in patients with type 2 diabetes inadequately controlled with diet and exercise or metformin monotherapy.

RESEARCH DESIGN AND METHODS

In this randomized multicenter double-blind parallel-group study, 356 type 2 diabetic subjects with similar mean baseline characteristics (age 54 years, diabetes duration 4.9 years, BMI 32.1 kg/m(2), A1C 8.0%) received subcutaneous placebo or albiglutide (weekly [4, 15, or 30 mg], biweekly [15, 30, or 50 mg], or monthly [50 or 100 mg]) or exenatide twice daily as an open-label active reference (per labeling in metformin subjects only) over 16 weeks followed by an 11-week washout period. The main outcome measure was change from baseline A1C of albiglutide groups versus placebo at week 16.

RESULTS

Dose-dependent reductions in A1C were observed within all albiglutide schedules. Mean A1C was similarly reduced from baseline by albiglutide 30 mg weekly, 50 mg biweekly (every 2 weeks), and 100 mg monthly (-0.87, -0.79, and -0.87%, respectively) versus placebo (-0.17%, P < 0.004) and exenatide (-0.54%). Weight loss (-1.1 to -1.7 kg) was observed with these three albiglutide doses with no significant between-group effects. The incidence of gastrointestinal adverse events in subjects receiving albiglutide 30 mg weekly was less than that observed for the highest biweekly and monthly doses of albiglutide or exenatide.

CONCLUSIONS

Weekly albiglutide administration significantly improved glycemic control and elicited weight loss in type 2 diabetic patients, with a favorable safety and tolerability profile.

Cyclic changes of vitamin D and PTH are primarily regulated by solar radiation: 5-year analysis of a German (50 degrees N) population

Cutaneous vitamin D precursor production depends on UV-exposure and is ineffective in most regions above latitudes of 50 degrees in winter. We hypothesized whether the cyclic course of vitamin D levels can be modelled with sunshine duration and would affect parathyroid hormone concentrations, but not calcium in a large patient population. We investigated 13330 blood samples from 6099 in- and out patients for 25(OH)D3, 1,25(OH)2D3, PTH, and total Ca in Frankfurt, Germany over 6.5 years. Vitamin D deficiency [25(OH)D3 <10 ng/ml] was found in 12.23% and vitamin D insufficiency [25(OH)D3 <20 ng/ml] in 40.62% of all the blood samples and more frequently during winter. We observed a significant difference between men and women, children and adults, migrants and local residents. Cycling of the curve was significantly related to Julian day for 25(OH)D3 and parathyroid hormone (PTH), but not for 1,25(OH)2D3 and Ca. The peak concentration of 25(OH)D3 was found at Aug 16th and correlated well with the length of day whereas PTH is inversely related with 25(OH)D (3). Seasonal cycling of 25(OH)D3-levels correlated significantly with Julian Day and inversely with PTH. This tight feed back ensures stable Ca concentrations within narrow limits. We conclude that changes in vitamin D levels are mainly regulated by solar radiation and to a lesser degree by other factors such as nutrition.

C-reactive protein decreases interleukin-10 secretion in activated human monocyte-derived macrophages via inhibition of cyclic AMP production

OBJECTIVE

C-Reactive protein (CRP), a cardiovascular risk marker, could also participate in atherosclerosis. Atherosclerotic plaques express CRP and interleukin (IL)-10, a major antiinflammatory cytokine. IL-10 deficiency results in increased lesion formation, whereas IL-10 delivery attenuates lesions. We tested the effect of CRP on lipopolysaccharide (LPS)-induced IL-10 secretion in human monocyte-derived macrophages (HMDMs).

METHODS AND RESULTS

Incubation of HMDMs with CRP significantly decreased LPS-induced IL-10 mRNA and intracellular and secreted IL-10 protein and destabilized IL-10 mRNA. Also, CRP alone increased secretion of IL-8, IL-6, and tumor necrosis factor from HMDMs and did not inhibit LPS-induced secretion of these cytokines. Fc gamma receptor I antibodies significantly reversed CRP-mediated IL-10 inhibition. CRP significantly decreased intracellular cAMP, phospho-cAMP response element binding protein (pCREB), and adenyl cyclase activity. cAMP agonists reversed CRP-mediated IL-10 inhibition. Overexpression of wild-type and constitutively active CREB in THP-1 cells revealed attenuation of the inhibitory effect of CRP on LPS-induced IL-10 levels. CRP also inhibited hemoglobin:haptoglobin-induced IL-10 and heme oxygenase-1. Furthermore, administration of human CRP to rats significantly decreased IL-10 levels.

CONCLUSIONS

This study provides novel evidence that CRP, by decreasing IL-10 alters the antiinflammatory/proinflammatory balance, accentuating inflammation, which is pivotal in atherothrombosis.

Role for oxidative stress in the regeneration of islet beta cells?

In the nonobese diabetic (NOD) mouse model of type 1 diabetes, we have found that there are increased markers of oxidative stress in islet beta cells in prediabetic animals when compared with control strains. Treatment of these mice with a superoxide dismutase (SOD) mimetic can markedly reduce the level of nitrotyrosine found in islets. In a diabetes-resistant NOD congenic mouse, the NOD.Lc7 mouse, we found increased beta cell proliferation and decreased apoptosis in islets. There are also lower levels of nitrotyrosine in islets of NOD.Lc7 mice than in NOD mice, suggesting that NOD.Lc7 islets are less susceptible to oxidative damage. We hypothesize that there may be a link between the ability of islet cells to regenerate and their resistance to oxidative stress.

Role for Oxidative Stress in the Regeneration of Islet Beta Cells?

In the nonobese diabetic (NOD) mouse model of type 1 diabetes, we have found that there are increased markers of oxidative stress in islet beta cells in prediabetic animals when compared with control strains. Treatment of these mice with a superoxide dismutase (SOD) mimetic can markedly reduce the level of nitrotyrosine found in islets. In a diabetes-resistant NOD congenic mouse, the NOD.Lc7 mouse, we found increased beta cell proliferation and decreased apoptosis in islets. There are also lower levels of nitrotyrosine in islets of NOD.Lc7 mice than in NOD mice, suggesting that NOD.Lc7 islets are less susceptible to oxidative damage. We hypothesize that there may be a link between the ability of islet cells to regenerate and their resistance to oxidative stress.

Oxidative Stress in Type 1 Diabetes

We have been investigating the effects of preventing oxidative stress on pathogenesis and complications of type 1 diabetes in the NOD mouse model. Our studies have shown that damage caused by oxidative stress is higher in islets and vascular tissue of NOD mice than in nonautoimmune controls or a diabetes-resistant NOD mouse. In addition, phagocytic function and cytokine production by macrophages are aberrant in the NOD. We have demonstrated that treatment of prediabetic NOD mice for 2 weeks with a metalloporphyrin superoxide dismutase (SOD) mimetic results in marked reduction of oxidative stress in islets and vascular tissue and a reversal of macrophage defects.

[The coexistence of 2 different neuroendocrine tumors of the upper gastrointestinal tract and pancreas]

HISTORY AND CLINICAL FINDINGS

A 41-year-old obese patient presented with cramp-like abdominal pain, watery diarrhoea with partly digested food particles, projectile vomiting and newly diagnosed diabetes mellitus. For the preceding 6 years he had been treated for recurrent gastric and duodenal ulcers. Although the fasting gastrin level was raised and Zollinger-Ellison syndrome suspected, computed tomography (CT), magnetic resonance imaging (MRI) and coeliac angiography at another hospital had failed to discover a tumor.

INVESTIGATIONS

Biochemical tests were unremarkable except for an increased GPT concentration, slight fasting hyperglycemia and hypertriglyceridemia. The gastrin and chromogranin A levels were markedly elevated (15,590 pg/ml and 584.2 U/l, respectively). Gastroscopy revealed, in addition to multiple small duodenal ulcers, a round polypoid mass (diameter of 0.7 cm) lateral to the papilla of Vater, histologically an APUDoma. Endoscopic retrograde cholangiopancreatography (ERCP) revealed a 0.5 cm long compression of the duct of Wirsung in the region of the head of the pancreas. Liver metastases were excluded by magnetic resonance imaging and computed tomography. Endosonography showed a ca. 4 mm space-occupying lesion in the region of the body of the pancreas. Octreotide scintigraphy demarcated two foci at the level of the head of the pancreas (somatostatin-receptor positive).

TREATMENT AND COURSE

After a pylorus-preserving partial duodenopancreatectomy with lymph node dissection N1/N2, histology confirmed a gastrinoma of the duodenum and a glucagonoma of the pancreas (pT3pN1pMx). Postoperatively the patient became symptom-free and both the blood sugar level and the tumor marker were normal.

CONCLUSION

Combined ERCP, endosonography and scintigraphy are more sensitive than other radiological examinations (CT and MRI) in diagnosing and localizing neuroendocrine tumours of the gastrointestinal tract. Despite the low incidence of such tumours, the possible synchronous occurrence of several such tumour should not be ignored.

High-performance membrane chromatography of serum and plasma membrane proteins

Porous discs made of poly(glycidyl methacrylate) were used for high-performance membrane chromatography (HPMC) of proteins. In model experiments, separations of standard proteins by anion-exchange HPMC using a DEAE disc were carried out. The influences of sample distribution and disc diameter and thickness on separation performance were studied. The separation disc allowed a scaling-up from analytical (diameter 10 mm) to semi-preparative (diameter 50 mm) dimensions. In an application study, separations with anion-exchange and affinity HPMC were carried out using different complex samples such as rat serum and plasma membrane proteins. In all experiments the results on poly(glycidyl methacrylate) discs were comparable to those achieved on adequate high-performance liquid chromatographic (HPLC) columns. However, the separations on HPMC discs could be carried out faster than corresponding separations on HPLC columns. The pressure drop on the discs was low even at high flow-rates. The experiments show that the poly(glycidyl methacrylate) discs used are especially suitable for the isolation of proteins and other biopolymers which occur in a diluted state in complex mixtures.

Carrier membrane as a stationary phase for affinity chromatography and kinetic studies of membrane-bound enzymes

The use of membrane supports as stationary phase, coupled with ligands of choice, allows all kinds of chromatography [Dj. Josić, K. Zeilinger, Y. Lim, M. Raps, W. Hofmann and W. Reutter, J. Chromatogr., 484 (1989) 327] and offers a powerful alternative to both soft gel chromatography and high-performance liquid chromatography. In this work we present affinity membrane chromatography for purification of the enzyme carbonic anhydrase from haemolysates of human erythrocytes. Furthermore, the coupling of the enzymes to the membrane support allows kinetic investigations. As an example, kinetic experiments were carried out by means of carbonic anhydrase coupled to the membrane support using 4-nitrophenyl acetate and 2-chloro-4-nitrophenyl acetate as substrates.

Purification of monoclonal antibodies by hydroxylapatite HPLC and size exclusion HPLC

Monoclonal antibodies of both the IgG and the IgM type were purified by hydroxylapatite HPLC (HA-HPLC) under very mild conditions. The IgM type antibodies, which were isolated from ascites fluid and separated from other proteins also by means of size exclusion HPLC. It was shown that the most frequently observed disadvantage of HA-HPLC, that is the relative short life of the columns (P. Steffen (1989) GIT Fachz. Lab., Suppl. 3/89 (Chromatogr.), 50-90), is due to microbial contamination rather than lower mechanical stability. In order to monitor column performance, a test was developed based on the use of standard proteins under isocratic separation conditions. This allows a direct comparison between the respective performances of columns made from different materials, hydroxylapatite or fluoroapatite, from different sources and with different particle sizes. A problem which often occurs with HA-HPLC in the case of IgM antibody isolation, namely precipitation of the antibodies at low salt concentrations at the beginning of a chromatographic run, was avoided by adding sodium chloride to both separation buffers.

Crown ethers as ligands for high-performance liquid chromatography of proteins and nucleic acids

By immobilization of the crown ether 1,10-diaza-18-crown-6 to different porous and non-porous, epoxy-activated supports, a chromatographic sorbent was prepared, which, mediated by potassium ions, can be used for the separation of both nucleic acids and proteins. Model experiments have been carried out with ribonucleic and deoxyribonucleic acids. In experiments with standard proteins the influence of pH and the role of loading of the column with potassium ions were demonstrated. The column was used for separating complex protein mixtures, such as serum and plasma membrane extracts, in the presence of detergents.