A reliable test to detect impending pump failure during long-term support on the Novacor N100 Left Ventricular Assist System

The Durastudy is a new surveillance protocol to detect impending pump failure in Novacor N100 Left Ventricular Assist Systems implanted for the long term. Our patient, a 54-year-old man with a history of dilated cardiomyopathy and contraindications for heart transplantation, received a Novacor pump in May 1995 and did not experience sustainable ventricular recovery during the subsequent 3 years. After more than 3 years of support, symptoms of pump wear were detected in this patient, through application of the Durastudy protocol. This enabled us to electively exchange the pump at 3.8 years. Our patient remained in New York Heart Association functional class I until he died in July 1999 of causes unrelated to the pump, after some 1,514 days of support. This, we believe, still constitutes a world record.

The effect of acarbose on insulin sensitivity and proinsulin in overweight subjects with impaired glucose tolerance

Insulin sensitivity is impaired in overweight subjects with IGT and is accompanied by hyperinsulinemia, a condition, that might promote early B-cell exhaustion. Twelve subjects were recruited for a double-blind trial using either 100 mg of acarbose or placebo for three months. Insulin sensitivity was measured by hyperglycemic clamp and with the minimal model. Baseline characteristics such as body weight, BMI, blood glucose, HB-A1c and serum lipids did not change throughout the study period. The steady state glucose infusion rate (SSGIR) improved significantly following acarbose. The insulin sensitivity as measured by clamp (MI) or minimal model, (SI), however, increased only descriptively (p = 0.08). The fasting proinsulin was raised in all subjects during pretreatment. Following acarbose, the proinsulin dropped from 20.3 +/- 12.9 to 13.6 +/- 7.1 ng/ml, but remained unchanged in the placebo group. Due to the high variability of values and the low number of subjects in this study, differences were only descriptive and did not reach significance (p = 0.08). The proinsulin/insulin ratio, however, significantly decreased after 3 months of acarbose treatment. Acarbose might therefore be considered recommendable for the protection of the B-cell function and for delaying the transition of IGT to overt NIDDM.

Recovery from end-stage ischemic cardiomyopathy during long-term LVAD support

A patient with ischemic cardiomyopathy and extremely reduced left ventricular function (left ventricular ejection fraction=0.10) presented to our institution for cardiac transplantation. Because of his worsening condition he was placed on the Novacor left ventricular assist device. During 3 months of support his left ventricular function recovered and he successfully underwent percutaneous transluminal coronary angioplasty and minimally invasive direct coronary artery bypass grafting procedures; subsequently he could be weaned from the left ventricular assist device and discharged. The patient is no longer considered for cardiac transplantation.

Intensive therapy in adult insulin-dependent diabetes mellitus is associated with improved insulin sensitivity and reserve: a randomized, controlled, prospective study over 5 years in newly diagnosed patients

Optimal blood glucose levels and normal insulin sensitivity are aims in the treatment of insulin-dependent diabetes mellitus (IDDM). Insulin sensitivity and insulin reserve are closely interrelated. It is essential to know more about both of these parameters at clinical diagnosis, because their preservation may delay the occurrence of diabetes-related complications. B-cell function is likely to be retained for a longer period in patients with adult onset of the disease compared with children. In this study, intensive insulin treatment was initiated in newly diagnosed adult patients to determine if it preserved endogenous insulin secretion longer than conventional therapy. Forty-nine patients with newly diagnosed diabetes were carefully categorized as having IDDM according to clinical and serological criteria. They were randomized to an intensive (I group) or conventional (C group) insulin therapy and evaluated for 5 years. Every 6 months, a check-up included glucagon-stimulated C-peptide (GSCP), hyperglycemic glucose clamp with arginine bolus, euglycemic-hyperinsulinemic clamp, and screening for microalbuminuria, retinopathy, and neuropathy. At the end of the study, hemoglobin A1c (HbA1c) was 6.3% +/- 1.9% in the I patients and 8.1% +/- 2.1% in the C patients (P < .001). Blood glucose concentrations less than 3.5 mmol/L were more frequent in the I group than in the C group (P < .05). Insulin sensitivity (M/I) and GSCP were higher in intensively treated patients after 5 years (M/I, I group 40 +/- 10 nmol x kg(-1) x min(-1) x pmol/L1 v C group 21 +/- 11, P < .005; GSCP, I group 0.6 +/- 0.2 nmol/L v C group 0.19 +/- 0.11, P < .005). The prevalence of peripheral neuropathy was significantly lower in the I group at the end of the study. In conclusion, intensive therapy is more effective in the preservation of insulin action and reserve. In our patients, no case of severe hypoglycemia was observed, indicating that intensive therapy was safe in these patients.

Effect of dietary protein intake on insulin secretion and glucose metabolism in insulin-dependent diabetes mellitus

Adult-onset insulin dependent diabetes mellitus (IDDM) is associated with significant residual insulin secretion. The process leading to the ultimate destruction of B cells may be influenced, among other factors, by the quality and amount of ingested protein. Using a standardized food questionnaire, we matched 13 individuals with normal protein (NP; 0.74 +/- 0.08 g/kg.day) and high protein (HP; 1.87 +/- 0.26 g/kg.day) intake from a sample of 117 newly diagnosed IDDM patients according to sex, age, body mass index, and energy intake. Nondiabetic control subjects were also selected. Dietary habits did not change significantly over an observation period of 1 yr. Glucagon-stimulated C peptide was significantly higher in the NP compared to the HP group (0.71 +/- 0.06 vs. 0.50 +/- 0.04 nmol/L; P < 0.002). NP food was associated with higher overall insulin sensitivity in both patients and nondiabetic subjects. Hepatic glucose output was significantly increased in individuals with HP intake [HP IDDM, 14.8 +/- 0.6 vs. NP IDDM, 12.7 +/- 0.7 (P < 0.01); HP control, 12.2 +/- 0.5 vs. NP control, 10.9 +/- 0.5 (P < 0.01 mumol/kg.min). Insulin-mediated suppression of hepatic glucose production was impaired in diabetic patients with high protein intake, but not in patients with normal protein diet. Gluconeogenesis estimated from 13C enrichment in breath and plasma was increased in individuals on a HP diet. We conclude that a NP diet is accompanied by delayed progression of the continuous loss of endogenous insulin in IDDM. This phenomenon is possibly due to decreased insulin demand on the B cells and/or reduced hepatic glucose production favoring enhanced insulin sensitivity.

A diet enriched in protein accelerates diabetes manifestation in NOD mice

Diet modifies the development of insulin-dependent diabetes mellitus in animals and in humans. We examined female non-obese-diabetic (NOD) mice, a diabetes-prone mouse strain with 70% spontaneous diabetes incidence and metabolic abnormalities in non-overtly diabetic litters. They were fed a diet containing 55% (n = 27) or 15% (n = 26) protein, respectively, after weaning. At an age of 30 weeks, non-diabetic NOD mice were submitted to an intravenous glucose tolerance test (0.5 g/kg body weight; blood samples were taken after 2, 4, 8, 10, 15, 20 and 30 min) and to perfusion of the pancreas (stimulation media were Krebs-Ringer-Hepes buffer with 5 mmol/l glucose, 30 mmol/l glucose and 5 mmol/l glucose plus 19 mmol/l arginine). Diabetic mice were removed from the experiment. Serum glucose concentration and body weight were monitored weekly. Food ingestion was checked at an age of 11 weeks. On average, the onset of diabetes was diagnosed in mice on a high-protein diet (19.7 +/- 1.3 weeks) 4 weeks earlier than in mice on a low-protein diet (23.5 +/- 1.1 weeks; P < 0.05). Non-diabetic NOD mice on a high-protein diet showed significantly better glucose tolerance (as determined by the glucose disappearance rate) and mean insulin secretion (at 30 mmol/l glucose). No difference in the serum glucose concentration between non-diabetic mice on the low-protein diet or high-protein diet could be proved. In non-diabetic mice on the high-protein diet the body weight and food ingestion exceeded those of mice on the low-protein diet (P < 0.05). High insulin secretion and glucose tolerance in non-diabetic mice may reflect the capacity of beta-cells to adapt; however, beta-cells tend to be destroyed under such circumstances. Thus, a high-protein diet promoted the onset of diabetes, but it did not increase significantly the incidence of the disease.

[Endoventricular patch-plasty for reconstruction of ventricular geometry and pump function in myocardial aneurysm]

This report deals with the first experience with endoventricular patch plasty in patients suffering from left ventricular aneurysm. The early postoperative results in 18 patients operated upon during January and May 1995 are encouraging. All patients survived the procedure. In contrast to patients operated on according to a linear resection technique the postoperative outcome and the early results are much better with this technique. We recommend the endoventricular patch plasty on a beating heart.

Clinical spectrum of the MELAS mutation in a large pedigree

INTRODUCTION

MELAS is most often due to an mentally transmitted A-G transition mutation of mitochondrial DNA (mtDNA) at position 3243. In this study we report on the clinical spectrum associated with the mutation in the largest family reported so far.

PATIENTS AND METHODS

In a family with three MELAS cases we identified 47 persons at risk for the mutation; sufficient data was available on 29. Mitochondrial disease was diagnosed in two of 9 deceased numbers (posthumous molecular analysis in one); 27 surviving family members underwent examination and 25 a molecular analysis of mt DNA from lymphoblasts. Then had a muscle biopsy and two were later autopsied.

RESULTS

All 26 cases investigated by molecular analysis showed the mutation at position 3243. The 18 symptomatic patients without stroke-like episodes had sensorineural hearing loss in 15 cases, diabetes in 6, nephropathy in 7, mild myopathy in 4, cardiomyopathy in 2, cerebellar disease in 4 and mental retardation in 2 cases. Eight carriers were asymptomatic. Autopsy showed > 80% mutant mt DNA in all tissues except blood (20%) examined in a MELAS patients, but < 20 mutant mt DNA in all tissues except lever (40%) and kidney (70%) in a patient with hepatopathy, renal failure and diabetes. Histologic and biochemical studies of muscle biopsy were often non-informative.

CONCLUSIONS

The mutation of mt DNA at position 3243 causes a multisystem disorder with a variable phenotype due to heteroplasmy. Most carriers are oligosymptomatic with hearing loss and a variety of neurological and internal medical symptoms. Diabetes, cardiomyopathy and renal disease, which is newly reported here for this mutation, are frequent. The blood test is a reliable screening tool in affected families, but is of prognostic value only combined with examination of other tissues.

Natural course of insulin sensitivity and insulin reserve in early insulin-dependent diabetes mellitus

Preservation of endogenous insulin in insulin-dependent diabetes mellitus (IDDM) may prevent the occurrence of diabetes-related complications. Therefore, it is important to known about insulin reserve and insulin sensitivity at clinical manifestation. Twenty-four patients (aged 23 +/- 6 years) were evaluated for 2 years starting at the day of clinical manifestation. Insulin secretion was stimulated by glucagon, arginine, and glucose on separate days. Insulin sensitivity was evaluated by hyperinsulinemic-euglycemic clamp. Two control groups were established, one consisting of age-, weight-, and sex-matched healthy individuals, the other of patients with diabetes of long duration (6 to 13 years). Sensitivity improved from 30% of normal at baseline to 84% after only 2 weeks in the newly manifested patients. Subsequently, insulin released by nonglucose stimuli increased by 75%. Glucose-induced first-phase insulin secretion did not recover. After 2 years, sensitivity was 20% less than normal and glucagon-stimulated C-peptide (GSCP) was 0.64 +/- 0.20 nmol/L (0.41 +/- 0.19 at baseline, P < .002). Insulin sensitivities in euglycemic and hyperglycemic conditions were closely correlated. In conclusion, improvement of insulin sensitivity precedes and is possibly a prerequisite for the recovery of residual insulin in early IDDM.

Effects of prostaglandins and indomethacin on gastric emptying in the rat

Prostaglandins have been shown to stimulate contraction of gastrointestinal smooth muscle in vitro, and their synthesis has been reported in different gastrointestinal diseases. The aim of this study was to determine the different effects of PGs and indomethacin on gastric emptying in the rat in vivo, and to investigate their possible role as modulators of osmolarity induced changes in gastric emptying. Rats were fed via gastric tube with suspensions of various osmolarity containing different prostaglandins or indomethacin. Gastric emptying, measured by the quantity of food remaining in the stomach, was studied by a noninvasive technique using orally administered nonabsorbable marker 141Cerium. PGE2 given orally and its synthetic analogue 16-16-dimethyl PGE2 given subcutaneously caused significant delay of gastric emptying, while PGF2 alpha increased gastric emptying regardless of the administration route. Tube-feeding with high osmolarity suspension significantly reduced emptying rate of 141Cerium compared to feeding with low osmolarity suspension. Gastric emptying rate of the tracer was significantly higher in rats fed with low osmolarity test meal, in comparison to those fed with high osmolarity test meal. This effect was completely antagonized by indomethacin. Due to the known inhibitory effect of indomethacin on cyclooxygenase, the effects observed in the present study are also presumably mediated by the action of prostaglandins.

Impaired agglutination of IgM resulting from non-enzymatic glycation in diabetes mellitus

Non-enzymatic glycation of circulating immunoglobulin G, A and M, measured by boronic acid affinity chromatography was found to be significantly increased in diabetes mellitus. The mean value of glycated IgM was already high in the control group: 49.58% (+/- 10.3% SD) and increased up to a mean value of 61.00% (+/- 8.5%) in the diabetic group. Similarly IgG and IgA glycation was significantly higher in the diabetic group than in controls: IgG 21.6% (+/- 3.4%) vs. 14.1% (+/- 2.9%; P less than 0.01); IgA 14.7% (+/- 4.9%) vs. 7.7% (+/- 1.3%; P less than 0.01). To investigate how glycation would alter IgM function, serum proportions from diabetic patients with blood group O were separated into glycated and non-glycated fractions by affinity chromatography and, adjusted to the same concentrations, tested against group A1 erythrocytes. Agglutination, which is mainly an IgM-mediated reaction, was significantly lower in the glycated than in the non-glycated fraction of IgM. The correlation between glycation of IgM and the reduction of agglutination titres in the glycated fraction was significant (r = 0.88, P less than 0.001). We conclude that impaired IgM function may be caused by non-enzymatic glycation in diabetes mellitus with possible consequences for host resistance in the early phase of infection.

Bioactivity and pharmacokinetics of human proinsulin in comparison to human insulin after intravenous and subcutaneous injection

The hypoglycemic actions of human insulin (1 IU/kg b.w.) and biosynthetic human proinsulin in about equimolar amounts were studied after intravenous and subcutaneous injection in rabbits. Blood samples were taken up to four hours after injection for the determination of blood glucose and immunoreactive levels of both insulin and human C-peptide. For the determination of human C-peptide, serum taken after proinsulin injection was divided into two fractions. One was examined directly by the human C-peptide radioimmunoassay and the other after incubation with a protein-A-sepharose coupled insulin antibody to find "free human C-peptide". Proinsulin in amounts equimolar to 1 IU insulin/kg b.w., exerted a 34% stronger hypoglycemic action after subcutaneous injection than after intravenous administration (area under curve estimation). Proinsulin-induced hypoglycemia did not last longer after intravenous administration than that induced by intravenous insulin. Although subcutaneous proinsulin did not show the same maximum decrease of blood glucose compared to subcutaneous insulin, its action was significantly prolonged (up to 180 min). Specific measurement of free human C-peptide showed no evidence of conversion of proinsulin to insulin and C-peptide.

[Blood glucose and insulin levels in healthy persons and diabetics after intake of coarse wholemeal preparations, especially fresh grain muesli]

In a study of seven type II diabetics the effects of the usual diabetic diet were compared with those of a cereal of whole-meal (both having the same energy content and nutrients proportions). The cereal gave a more even blood-glucose curve at a significantly lower level (maximal rise after the first breakfast with the cereal was 20 mg/100 ml, after the usual diabetic breakfast 75 mg/100 ml). In addition, in 12 metabolically healthy persons comparison was made of post-prandial blood-glucose and insulin levels after intake of raw and of heated wheat and corn whole-meal preparations. The raw wheat variant produced much flatter blood-glucose and insulin curves than the heated test meals (maximal rise of blood-glucose 6 vs 27-38 mg/100 ml; blood insulin 8 vs 35-50 microU/ml), while the raw corn (oat) variant achieved only a small flattening of the curve compared with that after the heat-treated preparation. Measurement of H2 exhalation provided no evidence for differential malabsorption between raw and heated test meals. Fresh-corn muesli with unheated wheat whole-meal is suitable in the diet of type II diabetics to counteract high postprandial levels of blood-glucose and thus improve the diabetic metabolic state.

The effect of two new glucosidase inhibitors on blood glucose in healthy volunteers and in type II diabetics

Two new glucosidase inhibitors (BAY m 1099 and BAY o 1248) were studied in volunteers and type II diabetics under various conditions. In 6 non-diabetic controls BAY m 1099 when given 3 X 50 mg/day caused a marked depression of the post-meal glucose rise. The effect was found to be more marked after breakfast than after lunch or after dinner. In type II diabetics BAY m 1099, when given in a dose of 2 X 25 mg/day over one week, had no significant effect on post-meal glucose or serum insulin levels. BAY o 1248, when given as a single dose of 15 mg in the morning to type II diabetics, induced a significant decrease of post-meal glucose rise (35 mg/dl after breakfast, 25 mg/dl after lunch) when compared to placebo. Although in parallel serum insulin levels were slightly lower, this change was statistically not significant. The drug reduced glycosuria by 50%. Both compounds induced side effects, such as flatulence or diarrhea when given in therapeutically effective amounts, but were tolerable in most cases. On a weight basis BAY o 1248 was found to have greater therapeutic effects than BAY m 1099. Both drugs can be recommended for use in unsatisfactorily controlled type II diabetics. Further studies should concentrate on the critical dosage which may strike a satisfactory balance between effects and side effects.

Virus infection islet cell antibodies and islet cell function in type I diabetes mellitus

The detection of islet cell antibodies has led to an increasing interest in autoimmune mechanisms in Type I diabetes mellitus. Other phenomena, such as insulitis in juvenile diabetics and in experimental animals, cellular immune reactions and concommitant antibodies against other endocrine organs, antinuclear antibodies and circulating immune complexes have supported such speculations. HLA-association and viral-infections could be predisposing and inducing factors. However, with one exception, the occurrence of ICA in a group of mumps infected children did not result in the development of diabetes mellitus over 3-4 years, nor could it be correlated with HLA-pattern. The islet cell antibodies block glucose stimulated insulin secretion in vitro without complement, while Type I diabetic sera with complement are beta cell cytotoxic irrespective of their ICA concentration. It is still not clear whether these mechanisms play any role in vivo. Therapeutic intervention before the clinical manifestation of the disease is as yet not possible due to the lack of markers indicating a subclinical autoimmune process.

Guar and its effects on metabolic control in type II diabetic subjects

The effect of guar mini-tablets (5 g t.i.d.) on carbohydrate and lipid metabolism of outpatients with overt diabetes mellitus with glycosuria (is greater than 5 g/24 h) was determined in an open-controlled, randomized, multicenter, crossover study. A 4-wk pretreatment period was followed by a 6-wk treatment period. The treatment period consisted of a 2-wk guar period (treatment period II), which was followed by the wash-out period. The other half of the patients received treatment in the reverse order. Out of 93 patient records, 79 (41 sulfonylurea [SU] and 38 insulin-treated) were suitable for statistical analysis. No relevant weight-reducing effect of guar could be found in both 2-wk treatment periods. At the end of treatment period II, the lowering of the 1-h postprandial values of blood glucose (SU 12%, insulin 10%), cholesterol (SU and insulin 25%) was significant after 2-wk of guar treatment compared with the wash-out period. No clinically relevant changes in the safety laboratory parameters were observed during guar treatment. Side effects were observed in 40 of the 93 patients included in the trial. Treatment had to be discontinued in 11% of the patients due to gastrointestinal side effects. On the basis of our results,guar treatment in combination with sulfonylurea and insulin can be recommended for the improvement of carbohydrate and lipid metabolism.

The effect of a saccharose-rich diet on carbohydrate and lipid metabolism of streptozotocin-diabetic rats and genetically determined 'diabetic' mice (gg-diab)

Streptocotocin-diabetic rats were fed with a saccharose-rich diet (68 per cent saccharose) for 37 weeks. Serum levels of insulin, triglycerides, and cholesterol were determined thereafter as well as the lesions of kidneys by histologically evaluation. For the second series of experiments, genetically determined diabetic mice (transient hyperglycemia, low k-value, but no glucosuria), were fed with the saccharose-rich diet for eight weeks. Thereafter the serum levels of insulin, triglycerides, and cholesterol were determined as well as secretion and biosynthesis of insulin of isolated pancreatic mouse islets. The metabolic parameters and the determination of the kidney lesions revealed that saccharose-feeding deteriorates the diabetic state of streptocotocin-diabetic rats: the levels of serum glucose, urine volume and urinary glucose rose rapidly in the saccharose-fed diabetic rats. These animals showed significantly higher levels of triglycerides and cholesterol after 18 and 37 weeks compared with diabetic rats fed a control diet (68 per cent starch). The kidney lesions became still more severely expressed by saccharose-rich diet. On the other hand, no major differences in the serum parameters of saccharose- or starch-fed genetically determined mice could be noticed: no manifestation of diabetes could be provoked in these latent-diabetic mice.

Biologic and immunologic in vivo and in vitro studies with biosynthetic human insulin

A preliminary study was performed to estimate the effect of biosynthetic human insulin (BHI) produced by the Eli Lilly Company in comparison with purified pork insulin (PPI) from the same manufacturer. Immunologic studies were done using an intradermal skin test with both insulins and in vitro studies binding with sera containing preformed antibodies against bovine and pork insulin. The studies were undertaken in eight healthy volunteers aged 24-31 yr. Insulin was given subcutaneously in an amount of 0.1 U/kg and 3 days later intravenously in an amount of 0.03 U/kg injected slowly over 1 min. Blood glucose, insulin, C-peptide, and growth hormone were measured at different times between 0 and 360 min. It was shown that BHI and PPI behaved similarly in lowering blood glucose, suppressing C-peptide, and increasing growth hormone via hypoglycemic action. After s.c. injection, BHI was found to reach higher serum concentrations after 60 min than PPI. Correspondingly, the blood glucose curve was significantly lower after BHI than after PPI. This difference was not observed after the i.v. application of both forms of insulin.

[Autotransplantation of Langerhans' islets in a case of total duodenopancreatectomy (author's transl)]

A 36-year-old man suffering from chronic pancreatitis involving the whole organ had total duodenopancreatectomy. The Langerhans' islets were isolated from the extirpated organ and transplanted into the liver via portal artery. Insulin substitution could be lowered from 50 I.U. to 12 I.U. by the 5th post operative day. Repeatedly, raised insulin levels could be verified in response to high blood sugar loads. C-peptide and glucagon were also found. 7 months after transplantation the islets still seem to be functioning.

[Experiments towards the viral etiology of a preleukemic syndrome: osteomyelofibrosis (author's transl)]

The present study describes the separation and purification of a reverse transcriptase and cellular DNA polymerases from the human spleen of a patient with myelofibrotic syndrome. The specific requirements with respect to bivalent cations and templateprimers for DNA polymerase-alpha, DNA polymerase-beta and DNA polymerase-gamma, as well as for the reverse transcriptase, are reported. Sedimentation velocity measurements of the purified enzymes gave values of 150 000, 40 000, 100 000 and 70 000 daltons for DNA polymerase-alpha, DNA polymerase-beta, and DNA polymerase-gamma and the reverse transcriptase respectively. The purified reverse transcriptase was specifically inhibited by antisera to the reverse transcriptases of the two primate viruses, SiSV and GaLV. Antisera raised against the myelofibrotic spleen reverse transcriptase inhibited the homologous enzyme and also the reverse transcriptase from SiSV and GaLV. DNA polymerases alpha, beta and gamma from the same spleen were not inhibited by the antisera. These results constitute the first indication of a possible retroviral etiology for myelofibrotic syndrome. Since SiSV and GaLV are exogenous to all primates the results indicate that this polymerase was acquired and the results are most simply interpreted as indicating that virus related to the SiSV-GaLV group is present in man.

[Autotransplantion of Langerhans islets after total duodeno-pancreatectomy in a patient with chronic pancreatitis (author's transl)]

Total duodenopancreatectomy was performed in a 36-year-old man because of global chronic pancreatitis. Islets cells were isolated by collagenase digestion from the resected pancreas and re-implanted into the liver via the portal vein. Until the sixth postoperative day the amount of insulin required fell from 54 IU initially to 10 IU per day. Serial insulin determination demonstrated secretion by the implanted cells.

The effect of high maltose and sucrose feeding on glucose tolerance

This study records an impaired glucose tolerance in rats fed a high sucrose or maltose containing diet as compared to an isocaloric starch rich food. At low sugar concentrations only the 50% sucrose containing diet produced a significantly elevated blood glucose following an oral glucose load, whereas 20% sucrose feeding exhibited no differences as compared to long-term starch feeding. While body weights and basal blood sugar levels were similar in all diet groups, the glucose-induced insulin release was significantly higher in rats with a glucose tolerance of a diabetic type. In these animals serum triglycerides were also markedly elevated. The present results indicate, that the metabolic response to the ingestion of carbohydrates depends on the type of carbohydrate in previous nutrition. In view of a known genetic susceptibility regarding sucrose, similar conditions are suggestive for maltose.

[Molecular biological aspects of oncogenesis caused by RNA tumor viruses (author's transl)]

This article concerns the molecular mechanisms by which RNA tumor viruses, commonly called as oncornaviruses, transfer their genetic information from the genomic RNA (70 s RNA) of the virions to the cellular DNA, leading to neoplastic transformations. The article describes biochemical and serological properties of reverse transcriptase, its role in the life cycle of RNA tumor viruses and broader implications to molecular biology. In this connection, the authors report their own findings on the role of reverse transcriptase in a preleukemic disease, myelofibrosis. This enzyme, discovered in their laboratory, is antigenically closely related to reverse transcriptase of certain primate RNA tumor viruses, and of human leukemic cells. The article also describes the role of reverse transcriptase inhibitors in viral oncogenesis. Of particular interest, is the partially thiolated polycytidylic acid (MPC) which has been developed by the authors, and is known to have a very high binding affinity to the viral reverse transcriptase. The implication of these basic data on the clinical effectivity of MPC in human leukemia, documented in a few cases, has been discussed.

Insulin secretion and biosynthesis in sucrose fed rats

Long term feeding of a sucrose rich diet to rats is accompanied by a decreased glucose assimilation rate, despite high plasma insulin levels. Hyperinsulinism is at least partially based on a relative obesity, with increased amounts of abdominal- and retroperitoneal fat tissue, but unchanged total body weight compared to starch fed controls. The secretory pattern of insulin release was studied following glucose, arginine, fructose and sulfonylurea administration in the isolated perfused pancreas of sucrose and isocaloric starch fed rats. In addition, isolated islets of Langerhans were used to demonstrate the effects of glucose on insulin secretion and the incorporation of H-3 leucine into the proinsulin and insulin fraction of islet proteins. Following 11 mM glucose, the dynamics of insulin release in the isolated perfused pancreas of sucrose fed rats is characterized by a markedly elevated, late plateau-like response, usually seen only at higher glucose concentrations. Hyperinsulinism, as compared to starch fed controls, can also be demonstrated following arginine and the sulfonylurea HB-419, whereas fructose has no effect in the presence of low glucose concentrations. During incubation of the pancreatic islets, the hyperinsulinism in sucrose-, compared to starch fed rats, is more pronounced at 11 mM glucose than at 5.5 mM glucose. The incorporation of H-3 leucine into the proinsulin-insulin fraction of islet proteins in sucrose compared to starch fed rats, however, is significantly greater with glucose 5.5 mM than at high glucose level. In sucrose fed rats, secretion and biosynthesis of insulin thus appear to be elevated but closely linked only at physiological glucose concentration.