The endocrine pancreas of alloxan-diabetic rats: microangiopathy as revealed by electron microscopy

We studied the microvasculature of the pancreatic islet with an electron microscope using 15 alloxan-diabetic and 16 control rats. These animals were morphologically examined at 2 weeks, 1, 2, and 4 months after alloxan injection (diabetic rats) or at comparable times (control rats). Control rats were non-diabetic, either sequentially treated with glucose and alloxan (injected controls) or not subjected to any medication (non-treated controls). Body weights, plasma glucose levels, and erythrocyte glycosylated hemoglobin (HbA1c) concentrations were also measured at intervals. All the diabetic rats exhibited retarded growth, hyperglycemia, and increases in HbA1c concentrations. The primary changes in diabetic islet capillaries can be grouped into four categories: (1) narrowing and closing of capillaries and occurrence of possible acellular capillaries, (2) formation of perivascular edema, (3) bulging and projection of endothelial cytoplasm, and (4) perivascular proliferation of collagen-like fibrils together with thickening of the basement membrane. These changes tended to worsen with diabetic duration. They are regarded as pathognomonic for diabetic microangiopathy. It is presumed that the present microvascular lesions of the islet play an important role in the pathogenesis and advancement of the diabetic state.

[Effect of thyroid hormone on the beta-receptor of cardiac myocytes isolated from rat ventricle]

INTRODUCTION Most of the symptoms in hyperthyroidism, such as an augmented metabolism, tachyarrhythmias and increased myocardial contractility, resemble those of increased sympathetic beta-adrenergic receptor are a major concern, but the exact mechanisms of the effects remain to be clarified. In the present study, the direct effects of triiodothyronine(T3) on the spontaneous beating and beta-receptor in relation to protein synthesis of the cultured ventricular myocytes were investigated. METHODS The cardiac myocytes were prepared from neonatal rat ventricle by enzymatic digestion and incubated at 37 degrees C in the atmosphere of 5% CO2 in air. The culture medium used was DME containing 5% fetal bovine serum and was renewed daily. The spontaneous beating frequencies of the myocytes were measured by the use of optical-video system. The cultured myocytes showed spontaneous beating dependent on Ca2+ concentration about 48 hours after the isolation. Although the beating was irregular and unstable at the beginning, it became regular and steady on the 3rd culture day. The experiments measuring spontaneous beating frequency were performed using the cells of this stage. In these experiments, the effects of T3 on the spontaneous beating frequency were studied after a 15-20 minute incubation with various concentrations of T3 (1 x 10(-10)-1 x 10(-7)M). The spontaneous beating was enhanced by isoproterenol and suppressed by Ca antagonists. The cardiac beta-receptors were identified using the hydrophilic radioligand 3H-CGP-12177 which labels specifically cell surface bound beta-receptors. The effects of T3 on protein synthesis in cultured myocytes were studied by measuring 3H-leucine uptake. RESULTS I. The effects of T3 on the spontaneous beating The effects of T3 on the spontaneous beating were investigated in two different ways. Firstly, the direct effect of T3 was studied by incubating the cells in the medium containing variable concentration of T3. T3 increased the beating frequency dose-dependently, and the maximal accelerating action was observed at the concentration of 10(-8)M. T3 at this concentration increased the spontaneous beating frequency from 131 +/- 25 min to 157 +/- 35 min after the treatment. Higher concentration of T3 induced arrhythmias and seemed to be toxic. Therefore, in the following experiments the concentration of 10(-8)M was used. The cardiac myocytes were incubated in either T3 containing or T3 free medium for 10 days. The incubation medium was renewed every day, and the change in the beating frequency was monitored continuously.(ABSTRACT TRUNCATED AT 400 WORDS)

[Three cases of Torsades de pointes]

Torsades de Pointes is an atypical ventricular tachycardia, a characteristic sinusoidal twisting of QRS complex around the base line, first described by Dessertenne et al in 1966. Since their original description, many literatures including both reviews and case reports have been issued. However, the exact causes, mechanism and its true relation to usual ventricular tachycardia and fibrillation remain to be elucidated. In the present report, three cases of Torsades de Pointes (TDP) were described. All these patients revealed a prolonged QT and QTc interval as has been recognized at the occasion of TDP attacks together with low serum potassium concentration. In addition, one had hypertrophic cardiomyopathy (case 1), cholelithiasis (case 2) and uterus cancer (case 3), respectively. Regarding to the treatment, direct current counter shock was applied to terminate the TDP in all 3 cases, the correction of low serum potassium concentration was also done in each case. Lidocaine was ineffective in case 3 to terminate the TDP, while verapamil was effective in case 3 to convert TDP to normal sinus rhythm. In case 2, no antiarrhythmic drugs were applied, however, cardiac massage and normalization of serum potassium concentration succeeded to recover normal sinus rhythm. The diversity of the causes and treatments of TDP in these three cases was discussed in relation to the genesis of TDP.

The effect of prednisolone on cyclosporin-induced damage of pancreatic B cells in Wistar rats

The combined effects of cyclosporin (CYA) and prednisolone (PSL) on the function and morphology of pancreatic B cells of Wistar rats were investigated. Four 13-day treatment groups were compared; these were the O group (olive oil alone, p.o.), the P group (PSL 3 mg/kg/day, i.m.), the C group (CYA 20 mg/kg/day, p.o.), and the PC group (PSL 3 mg/kg/day, i.m. plus CYA 20 mg/kg/day, p.o.). Glucose tolerance was equally impaired in the C and PC groups. The pancreatic insulin content in the C group was 49.7% of that of the O group, whereas that in the PC group was 81.1%. Morphometric analysis using modified aldehyde-fuchsin staining revealed that 'percent beta-granule area' in the islet was 17.5%, 15.0%, 6.5%, and 7.8% in the O, P, C, and PC groups, respectively. Ultrastructurally, pancreatic B cells in the PC group showed CYA damage; however, a significant number of B cells exhibited hypertrophy of the rough endoplasmic reticulum and the Golgi apparatus, suggesting concomitant B cell hyperactivity in this group. These findings suggest that PSL does not aggravate the toxic effects of CYA on pancreatic B cells during short-term treatment; rather, it might be protective.

Serum-free culture of insulin-secreting clonal cells from a hamster insulinoma

We experimented with a wide range of serum-free media to find the best one for culturing insulinoma cells from the Syrian golden hamster, cell line In-R1-I10. Optimum cell growth came with a mixture of equal proportions of Dulbecco's modified Eagle's medium and Ham's F-12, supplemented with 10(-6) M insulin, 10 micrograms/ml transferrin, and 10(-9) M triiodothyronine (what we labeled DF-ITT medium). In addition to testing different varieties of basal media, we also experimented with different concentrations of known stimulants of cell proliferation, including transferrin, ferrous sulfate, insulin, epidermal growth factor, triiodothyronine, hydrocortisone, monoethanolamine, prolactin, proteose peptone, and selenium. Cells cultured in DF-ITT medium grew as well as those in serum-containing medium for 94 consecutive generations. Their insulin secreting capacity was maintained. The substitution of epidermal growth factor (10 ng/ml) for the insulin did not reduce either the growth rate or the insulin secreting capacity of the culture cells.

Protective role of potentially lethal damage repair in the neoplastic transformation of Balb/c 3T3 cells treated with N-methyl-N'-nitro-N-nitrosoguanidine

To determine the role of repair of potentially lethal damage (PLD) in the initiation process of neoplastic transformation, Balb/c 3T3 cells treated with N-methyl-N'-nitro-N-nitrosoguanidine (MNNG) were temporarily exposed to conditioned medium obtained from density-inhibited Chinese hamster cell cultures, as a post-treatment for the induction of PLD repair. With or without this exposure, cell survival and transformation frequencies were simultaneously determined by colony-formation and focus-formation assays, respectively. Temporary exposure to conditioned medium resulted in a 20-30% increase in cell survival compared with no exposure. Post-treatment with conditioned medium resulted in a 60-65% reduction in transformation frequencies. At the molecular level, the repair of MNNG-induced single-strand breaks of DNA occurred much more rapidly in conditioned medium. These data suggest that PLD repair reduces the in vitro neoplastic transformation through excision repair operative during the cessation of DNA replication. Thus, PLD repair appears to be preventive against neoplastic fixation in initiation of neoplastic development.

[Studies on serum ketone bodies in patients with hyperthyroidism]

In order to investigate effects of thyroid hormone on ketone bodies metabolism, fasting levels of serum ketone bodies, serum free fatty acids (FFA), serum insulin (IRI), plasma glucagon (IRG) and plasma glucose were examined in 29 untreated patients with hyperthyroidism and 20 healthy subjects. In 21 patients the levels of serum ketone bodies were re-examined when euthyroidism was achieved after treatment. In all of healthy subjects and 17 patients changes in the levels of serum ketone bodies after oral glucose load were examined. The results were as follows: 1). Fasting levels of serum FFA and total ketone bodies (TK), acetoacetate (AcAc), 3-hydroxy-beta-butylate (3OHBA), ratio of 3OHBA to AcAc in the patients were significantly higher than those in healthy subjects. The levels of IRI, IRG or ratio of IRG to IRI in the patients were not different from those in healthy subjects. In the patients, the fasting level of TK was significantly correlated with the level of FFA. 2). After oral glucose load the levels of TK and FFA in the patients decreased gradually. 3). The fasting levels of TK and FFA in the patients decreased when euthyroidism was achieved after treatment. It was suggested that the fasting levels of serum ketone bodies in patients with hyperthyroidism elevated probably due to activated lipolysis.

Ultrastructural and functional studies of pancreatic B cells in Wistar rats treated with immunotherapeutic doses of cyclosporin

Cyclosporin (CYA) was administered to Wistar rats at immunotherapeutic doses (20 mg/kg) and the functional and morphological effects on pancreatic B cells were observed. Serum CYA levels were kept in the range that is often encountered in clinical immunotherapy in humans. The treated rats had slightly elevated plasma glucose levels; on treatment days 6 and 13, their serum immunoreactive insulin and pancreatic insulin contents were low. Plasma immunoreactive glucagon levels were slightly elevated during treatment. Glucose tolerance was impaired on day 13. These functional abnormalities disappeared 2 weeks after drug withdrawal. B cells showed ultrastructural evidence of CYA toxicity, including cytoplasmic degranulation, nuclear inclusions, and cisternal dilatation of both the rough endoplasmic reticulum and the Golgi apparatus. These changes were observed on the third day of treatment and became more pronounced on the 6th and 13th days of treatment. By the second week after drug withdrawal, most of the B cells presented a normal ultrastructure. We confirmed that a dose of CYA similar to that used in clinical immunotherapy in humans produces ultrastructural disturbances in the pancreatic B cells of Wistar rats after relatively short-term administration.

Aggregate size and viscoelastic property of a highly concentrated suspension

Flow of Latex suspension with high concentration between plate glasses was observed through an optical microscope. Size of aggregates of Latex particles was estimated by measuring area of a region without particles behind an obstacle in the flow region (this technique had been developed by one of the authors). At the same time, viscosity and elasticity of the suspension were measured by a cone-plate viscometer, and relations between the aggregate size and these properties were obtained. A simple model based on the Stokes law of resistance and the Maxwell model for viscoelastic materials is proposed to explain these relations. The theoretical results agree with the present experiment.

Characterization of secretory responses of a glucagon-producing In-R1-G9 cell line

The In-R1-G9 cell line is one of the clones derived from the In-111-R1 hamster insulinoma cell line and produces glucagon. The secretory responses of In-R1-G9 cells were further examined to characterize the nature of the cells. Vincristine had no effect on glucagon secretion and colchicine enhanced glucagon secretion slightly after a short incubation. Two calmodulin inhibitors, trifluoperazine and chlorpromazine, did not affect glucagon secretion. Monensin at 10(-8) M suppressed glucagon secretion by 50%. Secretion of glucagon was calcium-dependent. The addition of A23187 to the incubation medium resulted in a 180% increase over control for 1 h and calcium deprivation from the medium suppressed glucagon secretion markedly. Theophylline, a phosphodiesterase inhibitor, caused a 230% increase in glucagon secretion. An experiment using cycloheximide suggested that newly synthesized glucagon appears in the medium at 30 min. This cell line should be useful for various experiments in many fields of research.

A case of arrhythmogenic right ventricular dysplasia with prominent late potential

A case of arrhythmogenic right ventricular dysplasia with frequent episodes of ventricular tachycardia (VT) in a 57-year-old man is reported. His electrocardiogram showed a normal axis and inverted T waves in V1-V3 during sinus rhythm and a left bundle branch block pattern during VT. The VT could be terminated by either intravenous administration of lidocaine or procainamide or by cardioversion. Echocardiogram and right ventriculography showed reduced wall motion of the apex and infundibulum of the dilated right ventricle. No evidence of ischemic heart disease was found by left ventriculography, coronary arteriography and RI scintigraphy. A prominent late potential following the QRS complex was recorded by averaging and magnifying the surface electrocardiogram. The combination of oral mexiletine and disopyramide partially suppressed the VT attacks and relieved the subjective symptoms, however the late potential remained almost unchanged.

The complete cancellation of abnormal Q waves due to an old anteroseptal infarction following subsequent acute posterior myocardial infarction

A rare case of multiple infarction is described. An abnormal Q wave due to an old anteroseptal infarction was completely masked by a new contralateral posterior myocardial infarction. Coronary angiogram revealed multiple stenoses of segments 1 (100%), 7 (99%), 12 (90%) and 13 (99%). Left ventriculography also showed akinesis of segments 2, 3 4 and 6, and reduced wall motion in segments 1, 5 and 7. These findings, together with electrocardiographic changes from before the present attack reinforce the above interpretation.

Encephalomyocarditis (EMC) virus-induced diabetes mellitus prevented by Corynebacterium parvum in mice

Corynebacterium parvum prevented the development of encephalomyocarditis virus-induced diabetes in mice, when it was given 3-14 days before the virus infection. This treatment inhibited virus replication in the pancreas of the infected mice at an early stage of the infection.

Microencapsulation of pancreatic islets. A technique and its application to culture and transplantation

Hamster pancreatic islets were encapsulated by a biocompatible membrane composed of the molecular sequence of alginate-polylysine-alginate. The encapsulated islets released insulin into the culture medium in response to secretagogues in short-term incubation. In long-term culture, the encapsulated islets maintained their insulin-releasing capacity for 28 days at a level similar to that of the unencapsulated islets. No overgrowth of fibroblastic cells was observed inside the capsule even after 70 days of culture. Further, the encapsulated hamster islets were xenotransplanted to streptozotocin-induced diabetic rats intraperitoneally. Some of the encapsulated islets, which were recovered from a recipient 27 days after transplantation, were found to be viable, although prolonged normalization of fasting plasma glucose levels of the recipients could not been achieved. On the contrary, the unencapsulated islets were replaced by massive connective tissue elements and insulin-positive B cells were hardly detected within the grafts 22 days after transplantation. The results of this study seem to confirm the potential of the application of the encapsulating technique to primary culture of parenchymal cells and to transplantation of pancreatic islets.

Effect of phorbol esters on glucagon secretion from a glucagon-secreting clonal cell line. Synergistic effects of A23187 and theophylline

The cell line In-R1-G9 is one of the clones from the hamster insulinoma cell line, In-111-R1, and it produces glucagon. Phorbol esters markedly enhanced glucagon secretion and the stimulatory effect was found to be correlated to their biological activity as tumor promoters. At a concentration of 200 nM, 12-O-tetradecanoylphorbol 13-acetate (TPA) stimulated glucagon secretion 13-fold more than the control in 10 min. The effect of TPA was not influenced by actinomycin D, cycloheximide, colchicine or vincristine. Depletion of calcium from the incubation medium inhibited TPA-induced glucagon secretion by approximately 50% and dibucaine also suppressed glucagon secretion to 67.4%. An addition of A23187 to TPA induced 150% enhancement over the TPA-stimulated glucagon level, and the maximum secretory response was observed when the cells were stimulated with the simultaneous addition of TPA, A23187 and theophylline.

Isolation of glucagon-secreting cell lines by cloning insulinoma cells

Six glucagon-secreting cell lines designated as In-R1-G1, -G3, -G7, -G9, -G10, and -G11 were isolated from insulinoma cells (In-111-R1) by single cell cloning. A small amount of insulin was also detectable in the incubation medium when hormone secretion was stimulated by the addition of arginine or theophylline. These cell lines grew as monolayers and the population doubling times varied from 16.8 to 28.8 h. Karyologically these clones were aneuploid and the modes of chromosome numbers were 61 to 70. Electron microscopic examination of one of these clones showed that these cells contained moderately developed Golgi apparatus and a few secretory granules, which more or less resembled alpha-cell granules. By gel filtration study of the incubation medium, glucagon and glucagonlike material were eluted. The molecular weight of the latter was approximately 9000, which suggested the concomitant secretion of proglucagon into the medium. The levels of secreted glucagon in basal state were 0.3 to 3.0 ng/10(6) cells/2 h. Glucagon secretion was markedly enhanced in the presence of amino acids. Glucagon secretion increased slightly in the presence of high concentration of glucose in Hanks' balanced salt solution; however it was not affected by the varying concentrations of glucose when the cells were incubated in complete media with amino acids. Glucagon secretion was also stimulated by the addition of theophylline. These clonal cell lines seem to provide a useful tool for investigating the mechanism of glucagon secretion.

Combined effects of glucose and oxygen concentrations upon the ultrastructure of cultured islet cells and insulin accumulation in culture media

Rat pancreatic islets cultured for 6 days at 100 or 500 mg/dl glucose and 20 or 7% O2 were examined electron-microscopically, and insulin accumulation in the culture media was assayed immunologically. In the islets cultured at 500 mg/dl glucose and 20% O2, B cells exhibited hypertrophy of granular endoplasmic reticulum and Golgi apparatus, an abundance of free ribosomes, degranulation and the margination of secretory granules. In islets cultured at 500 mg/dl glucose and 7% O2, B cells exhibited dilatation of endoplasmic reticulum cisternae and dominance of Golgi vesicles in addition to the above-mentioned changes. These changes, together with the correlated data on insulin accumulation, are discussed with special reference to the effects of glucose and oxygen upon the synthesis and release of insulin in B cells.

The relationship between molecular and cellular repair from potentially lethal damage induced by N-methyl-N'-nitro-N-nitrosoguanidine in Chinese hamster V79 cells

The relationship between molecular and cellular repair from potentially lethal damage (PLD) induced by N-methyl-N'-nitro-N-nitrosoguanidine (MNNG) was investigated in exponentially growing V79 Chinese hamster cells. We compared the repair processes by an alkaline sucrose sedimentation analysis and a colony formation assay. MNNG-treated cells were exposed to the conditioned medium (CM) from density-inhibited plateau-phase V79 cell cultures, as a post-treatment for the induction of PLD repair. When MNNG-treated cells were postincubated in CM, cell survival continuously increased for 18 h, and during this period, DNA replication was substantially suppressed. CM did not inhibit the rejoining of the single-strand breaks of parental DNA. Rather, parental DNA fragments sedimented more rapidly when postincubated in CM than in fresh medium. These data indicate that cellular recovery from MNNG-induced PLD increases in proportion to the resealing of MNNG-induced single-strand breaks of DNA during the suppression of DNA replication, suggesting that excision repair is involved in the PLD repair process.

Enhancement of erythroid progenitor cell growth in medium conditioned by a human cancer cell line, KONT

Erythroid-potentiating activity (EPA) was detected in culture medium conditioned by a human cancer cell line (KONT) that produces colony-stimulating activity (CSA), using erythroid colony formation in vitro. EPA in the medium conditioned by the KONT cells (KONT-CM) was markedly heat stable. After treating KONT-CM at 80 degrees C for 30 min, 30% EPA remained, while CSA was completely inactivated. Both EPA and CSA appeared in approximately the same fractions of the gel filtration, indicating a molecular weight of approximately 30,000 daltons. EPA bound partially to Concanavalin-A Sepharose, whereas CSA almost did not bind. Our results indicate that EPA can be separated from CSA based on heat stability and binding to Concanavalin-A Sepharose.

The role of thymic immunity and insulitis in the development of streptozocin-induced diabetes in mice

This article is concerned with the role of thymic immunity in the development of diabetes experimentally induced by multiple injections of subdiabetogenic doses of streptozocin (STZ). Euthymic +/+, +/nu, and athymic nu/nu mice of CD-1 and BALB/cAJcl origin were studied. Daily intraperitoneal (i.p.) injections of 30 mg/kg body wt of STZ for 5 consecutive days in CD-1 +/+ and +/nu mice resulted in hyperglycemia and mononuclear cell infiltrations of islets (insulitis). The CD-1 nu/nu mice developed neither insulitis nor hyperglycemia after the same treatment. In the nu/nu mice, when thymic immunity was restored by thymus grafting, both insulitis and hyperglycemia developed, thus demonstrating that thymic immunity was a prerequisite for the development of insulitis and hyperglycemia. There was a positive correlation among the degrees of thymic immunity, insulitis, and hyperglycemia in CD-1 +/nu, nu/nu with thymus grafts, and nu/nu mice, indicating that thymic immunity may amplify the diabetogenic effect of STZ by eliciting insulitis. In contrast, in BALB/cAJcl mice, a nonsusceptible strain to insulitis, no significant differences in plasma glucose levels were observed between the +/nu and nu/nu or between the nu/nu and thymus-grafted nu/nu mice. Furthermore, no significant difference was found in plasma testosterone levels between the +/nu and nu/nu mice of both CD-1 and BALB/cAJcl origin. In conclusion, our data indicate that thymic immunity enhances the diabetogenic effect of STZ by eliciting insulitis in susceptible mice.

Establishment of glucagon-producing cells by cell hybridization

Glucagon-producing cell lines were established by fusing pancreatic islet cells of adult hamster and 6-thioguanine-resistant hamster insulinoma cells. Under phase-contrast microscopy, the morphology of cultured hybrid cells was intermediate between those of the parental cells. The hybrid cells contained A-like granules, though few in number, and were stained with anti-glucagon antibody. The mode of chromosome number decreased to 78 or 79 by 3 mo after hybridization in comparison with the expected chromosome number of the heterokaryon of 104, and showed a minute decrease in 4 of 6 cell lines after 6 mo. The population doubling time ranged from 24 to 38 h, while that of parental insulinoma cells was 22.8 h. There was no correlation between the expression of cellular function and the stability of chromosome number or the length of population doubling time. The capacity of glucagon secretion was between that of the parental cells. The glucagon secreted into the medium, as assayed by the glucagon-specific antibody, was 0.6-2.5 ng/10(6) cells for 2 h, which was about 40% of total glucagon-like immunoreactivity secreted. Secretion of glucagon was not affected by high concentration of glucose, was markedly increased by theophylline, and was suppressed by exogenous insulin. All of the hybrid cells produced tumors on transplantation 6 mo after hybridization. The tumor-bearing hamsters exhibited high levels of plasma glucagon and blood glucose as well as a high level of serum insulin.