Pieces Of Pancreas Research Articles

Cations and the secretion of insulin from rabbit pancreas in vitro.

1. Insulin secretion from pieces of rabbit pancreas incubated in vitro was studied in media of different ionic compositions.2. Insulin secretion stimulated by glucose was abolished by removal of calcium from the incubation medium and inhibited by a twofold rise in the calcium concentration to 10.2 m-equiv/l. Removal of magnesium from the medium did not affect glucose-stimulated secretion but a tenfold rise in the extracellular magnesium concentration to 24 m-equiv/l. abolished secretion.3. The replacement of calcium by an equivalent amount of barium (5.1 m-equiv/l.) stimulated insulin secretion. Barium stimulation declined with time and was inhibited by the presence of calcium, 5.1 m-equiv/l., or abolished by the presence of magnesium, 24 m-equiv/l., in the incubation medium.4. The interactions of mono- and divalent cations on insulin secretion were studied by using ouabain or potassium as tools to raise intracellular sodium concentration and barium as a calcium analogue. Ouabain and potassium were effective stimuli only in the presence of calcium, and barium only stimulated insulin secretion in the presence of sodium.5. The results of these experiments suggest that both calcium and sodium must act at the beta cell membrane or enter the cell before insulin release can occur in response to a variety of stimuli.

Cytology of beta-cells in rabbit pancreas pieces incubated in vitro; Effects of glucose and tolbutamide.

The electron microscopic appearances of rabbit pancreas β-cells takenin vivo and afterin vitro incubation have been compared and the effects of high glucose and tolbutamide stimulation of insulin releasein vitro on β-cell cytomorphology investigated. Normal structure was maintained onin vitro incubation in a proportion of β-cells; this varied in different samples from 35–100 per cent. The cause of this variation was not apparent but it was not influenced by the time of incubation, medium glucose concentration or tolbutamide. Quantitative measurements have been made of the proportion of β-cell profiles showing marginal distribution of granules, of the number of contacts between granule sac membranes and the plasma membrane, of the number of granule sacs showing perforations, of the population density of specific secretion granules, lysosomes and autophagic bodies, and estimates have been made of the extent of the Golgi apparatus in cross section. No consistent change in these parameters was observed following stimulation of insulin release with glucose or tolbutamide. There was no evidence in any of the specimens examined of continuity between the interior of a granule sac and the outside of a β-cell. Calculations based on the rate of release of insulin and the insulin content of the pancreas indicate that the chance of visualising granule extrusion by electron microscopy is small. The significance of these results in relation to the emiocytosis theory of insulin release (Lacy andHartroft) is discussed.

The role of sodium and potassium in insulin secretion from rabbit pancreas

1. Insulin secretion from pieces of rabbit pancreas incubated in vitro was studied in media of different ionic composition and in response to different substances added to the media.2. Experiments were performed which demonstrated that a sodium pump played a role in insulin secretion and that inhibition of the pump by ouabain, or by the omission of extracellular potassium, stimulated insulin secretion.3. A rise in extracellular potassium concentration stimulated insulin secretion independently of changes in the osmolarity or sodium or chloride concentration of the incubation medium.4. The role of extracellular sodium in insulin secretion was investigated. Extracellular sodium was a pre-requisite for insulin secretion stimulated by glucose, glucagon, L-leucine, tolbutamide, potassium or ouabain.5. The presence of 3.3 mM glucose in the incubation medium was not essential for the stimulation of insulin secretion by L-leucine, tolbutamide or ouabain. Glucagon did not stimulate insulin secretion in the presence of 3.3 mM glucose but did so in the presence of 16.5 mM glucose.6. The results obtained in these experiments suggested that a transmembrane sodium flux probably in the beta cell was a fundamental event in the stimulation of insulin secretion by diverse stimuli.

A possible role for the adenylcyclase system in insulin secretion.

A possible role for adenylcyclase in insulin secretion was investigated. Isoproterenol, a predominantly beta-adrenergic agent, when mixed with an alpha-adrenergic blocking agent (phenoxybenzamine), stimulated insulin secretion from pieces of the rat's pancreas in vitro. Theophylline, caffeine, 3'5'-cyclic AMP, glucagon, adrenocorticotropin (ACTH), and thyrotropin (TSH), all of which are thought to act through the adenylcyclase systems in the liver and adipose tissue, also stimulated insulin secretion in vitro; oxytocin and vasopressin, which do not stimulate lipolysis in adipose tissue, were inactive. In all cases, stimulation of insulin secretion could not be detected when glucose was absent or present in only low concentrations (less than 100 mg/100 ml) and was maximal at high levels of glucose (300 mg/100 ml). When pancreatic tissue was obtained from normoglycemic rats and contained no detectable glycogen in the Islets, the stimulant effects of glucose and of theophylline were reduced or abolished by mannoheptulose and 2-deoxyglucose. When tissue was derived from rats infused for 8-10 hr with glucose and contained glycogen, theophylline, even in the absence of glucose, stimulated secretion and this effect was reduced by 2-deoxyglucose but not by mannoheptulose. It is suggested that the beta-cell contains an adenylcyclase system through which phosphorylase and possibly phosphofructokinase could be activated; and that insulin secretion could depend upon and be regulated by hormones and other substances which influence the rate at which glycolysis proceeds within the beta-cell.

Effects of Adrenergic and Cholinergic Agents Upon Insulin Secretionin Vitro

Adrenergic drugs (epinephrine, norepinephrine and isoproterenol) inhibit insulin secretion from pieces of rat pancreas incubated with glucose (150 mg/100 ml). This inhibitory effect appears to be mediated through alphareceptors for it is blocked by alpha- but little affected by beta-blocking agents. Cholinergic drugs (acetyl choline and carbamyl choline) have a stimulant effect using media containing glucose in low concentrations (100 mg/100 ml), and this effect is suppressed by simultaneous addition of atropine. These observations suggest that the autonomic nervous system may play a role in the control of insulin secretion under physiological conditions. (Endocrinology80: 975, 1967)

Stimulation by octanoate of insulin release from isolated rat pancreas

Using pieces of rat pancreas incubated in Krebs-bicarbonate buffer containing 0.6 mg. glucose/ml., it has been found that addition of 3.0 mM. octanoate to the incubation medium significantly (p < .001) increased insulin release above control levels by 4.94 ± 0.89 μU. insulin/mg. of pancreatic tissue. Increasing the glucose concentration in the incubation medium to 3.0 mg./ml. without addition of octanoate produced a slightly smaller though significant (p < .05) increase in insulin release (2.96 ± 0.96 μU./mg.) above control levels. In conclusion, octanoate is capable of directly stimulating additional release of insulin by the beta-cells of the pancreas.

Fine structure of B-cell from pancreas pieces incubated in vitro.

Pieces of the tail of the rabbit pancreas were incubated in a shaking incubator with Ringer solution supplemented with glucose (0.6 mg/ml), pyruvate, fumarate and glutamate (5 mM each), in a gas phase of 95% O2: 5% CO2 at 38 °C. There were no significant changes in the fine structure of the islet cells attributable to the incubation. Combined glutaraldehyde and osmium fixation of such incubated slices gave good preservation of the secretory products of the B-cells. The mechanisms of degranulation and regranulation of the B-cells were observed to be the same as those reported for the animal in vivo. The intensity of secretion differed depending upon whether the animals were killed after being knocked unsonscious or after being injected with a lethal dose of anaesthesia. B-cell secretion was more prominent in the former case. The method is considered to be valid for further studies on the mechanism of granule release and synthesis in the pancreas of rabbit.

Adrenal Gland Obtained at Percutaneous Renal Biopsy

ABSTRACT To the Editor:— I was unaware that adrenal tissue had been obtained on any renal biopsies, and this is, indeed, a rare complication. No mention is made of this complication in the Ciba symposium on renal biopsy, which represented the experiences of more than 5,000 percutaneous renal biopsies. Slotkin and Madsen (J Urol87:13, 1962) did not mention this complication in a survey of an equal number of cases. At the Charity Hospital in New Orleans I was aware of only one case of adrenal tissue being obtained. This was on a liver biopsy, and the patient died as a result of that complication. It is not uncommon to obtain liver tissue, especially if the kidney biopsy is done on the right side, and once I obtained a piece of pancreas when I biopsied the left kidney.

Regulation of insulin secretion studied with pieces of rabbit pancreas incubated in vitro.

Regulation of insulin secretion studied with pieces of rabbit pancreas incubated in vitro.

Amino acid and energy requirements of protein synthesis in rat pancreatic tissue in vitro

Rat pancreas pieces incubated in vitro were found to synthesize net protein as well as specific enzymes, viz. ribonuclease and protease zymogens. Protein synthesis in this system is dependent on the presence of (some) essential amino acids, especially tryptophan, in the incubation medium. Although ribonuclease very probably does not contain tryptophan the presence of this amino acid is required for its synthesis. The synthesis of total protein and the increases of specific proteins are closely linked, and can be correlated with a concomitant increase in oxygen uptake. Chopped pancreas appeared to deteriorate rapidly during incubation, and did not synthesize significant amounts of net protein or enzymes.

Amino acid and energy requirements of protein synthesis in rat pancreatic tissue in vitro

Rat pancreas pieces incubated in vitro were found to synthesize net protein as well as specific enzymes, viz. ribonuclease and protease zymogens. Protein synthesis in this system is dependent on the presence of (some) essential amino acids, especially tryptophan, in the incubation medium. Although ribonuclease very probably does not contain tryptophan the presence of this amino acid is required for its synthesis. The synthesis of total protein and the increases of specific proteins are closely linked, and can be correlated with a concomitant increase in oxygen uptake. Chopped pancreas appeared to deteriorate rapidly during incubation, and did not synthesize significant amounts of net protein or enzymes.

THE STAINING OF THIN SECTIONS OF MOUSE PANCREAS PREPARED BY THE FERNÁNDEZ-MORÁN HELIUM II FREEZE-SUBSTITUTION METHOD

Small pieces of mouse pancreas were rapidly frozen in helium II, substituted in methanol at -75 degrees C., and embedded in methacrylate by ultraviolet polymerization in the cold. The unstained cells show a structure similar to that after OsO(4) fixation, except that the RNP particles have little or no contrast and the mitochondria and Golgi zones appear as grey areas without internal structure. After staining the sections by floating them on solutions of lead acetate or osmium tetroxide, there is an increase in contrast of RNP particles, ergastoplasmic membranes, and zymogen granules. Mitochondrial and Golgi membranes, zymogen granule membranes, and a membrane along the outside of the ergastoplasmic cisterna appear in negative contrast. The structure of the ergastoplasm, the existence of RNP particles, and the production of negative contrast are discussed. A modification of Gomori's method for acid phosphatase produces a lead deposit around the periphery of the zymogen granules. Possibly this deposit does not represent the true site of the enzyme, but the results show the feasibility of histochemistry at the level of resolution of the electron microscope.

Eurytrema brumpti Railliet, Henry and Joyeux, 1912 (Trematoda: Dicrocoeliidae), from the Pancreas and Liver of African Anthropoid Apes

A massive infection with what is apparently the same species was discovered in a young male Gorilla gorilla gorilla (Savage and Wyman) which died in New York. At death the animal weighed 30.8 pounds and was probably about two years old. It had been brought by airplane from Africa on February 7, 1949, and although it came from the Congo region the locality where it was taken is uncertain. The animal was ill on arrival and shortly thereafter one of us, (L. J. G.) veterinarian of the New York Zoological Society, was called for medical advice and treatment. Its temperature fluctuated between 99 and 102 degrees F.; there were recurrent intestinal disturbances, anorexia, intermittent diarrhea and constipation. At times there were periods of two to four days in which there were no bowel movements. The fingernails had transverse bands of roughened areas, suggesting previous nutritional deficiencies or febrile conditions. Neither anemia or jaundice was noted. One eyelid was injected with one-tenth cc. of 1 percent P.P.D. tuberculin; there was an immediate reaction. An edematous swelling of the lid completely closed the eye in a few minutes, but totally subsided within five hours. No tubercular lesions were observed at autopsy and the significance of the reaction is obscure. Several fecal examinations were made; hookworm eggs were present in large numbers but no trematode eggs were observed. To remove the hookworms, two treatments with tetrachlorethylene were administered but ova persisted in the stools. After the second treatment, diarrhea developed and the mucus contained large numbers of amoebae. Administration of carbarsone had no apparent effect on the amoebae; the dysentery continued and emetine hydrochloride was given. This treatment also proved ineffective; the stools became bloody and were unformed during the subsequent life of the animal. It failed to give the expected response to medication or to symptomatic and supportive measures. During a six week period it lost about four pounds and died of terminal pneumonia on April 2, 1949. Autopsy of the gorilla was begun within three hours after death. The carcass showed no gross lesions other than early stages of lobar pneumonia, but the hepatic and especially the pancreatic ducts were filled with enormous numbers of small trematodes. Examination of the rectal contents revealed a few trematode eggs, but the number was not at all commensurate with the intensity of the infection. A piece of pancreas about 10 by 10 by 15 mm. was teased to bits in a Petri dish containing Ringer's solution. The worms were fixed and counted; 1028 specimens were present. Pieces of the liver and pancreas were removed, fixed and cut in serial

EFFECTS OF ANTERIOR PITUITARY PREPARATIONS AND INSULIN ON ISLET CELLS OF THE PIGEON PANCREAS

HOUSSAY’S INVESTIGATIONS demonstrating the importance of the anterior pituitary in carbohydrate metabolism have stimulated many studies on the functions of the islets of Langerhans and on the control of their activity. During recent years workers in this laboratory have studied extensively the relation of pituitary hormones, and other hormones, to carbohydrate metabolism in pigeons. The present study of the pigeon pancreas describes the normal morphology of the three types of islet cells and the changes induced in them by a variety of experimental procedures and hormone treatments. White Carneau pigeons, aged 1.9 to 2.4 months from hatching, were used. Pieces of pancreas were preserved in Helly fixative prepared with neutral formaldehyde, sectioned at 5μi and stained in Heidenhain’s azan (1). Hypophysectomy (anterior lobe only) was performed according to the method developed in this laboratory (2). The several pituitary hormone preparations utilised have been carefully assayed and used in parallel studies.

Effect of Adrenalectomy and Hypophysectomy upon Experimental Diabetes in the Cat

We have previously reported some preliminary observations upon 5 adrenalectomized-depancreatized cats and upon 2 hypophysectomized-depancreatized cats. In the first series of adrenalectomized-depancreatized animals the operations were performed in 3 stages, but in the present group of 5 animals we have found it possible to remove the remaining adrenal and all the pancreas at one operation. These animals have survived 8, 9, 9, 16 and 28 days respectively. By this procedure we have avoided any loss of weight prior to total adrenalectomy and pancreatectomy, and since the results obtained are substantially identical with the previous ones the criticism of Ring that previous inanition was responsible for the effects observed would appear to be unfounded. In addition, depancreatized cats treated with insulin or cats in whom a pancreatic remnant is left lose considerable weight, but when insulin is withdrawn or the last piece of pancreas extirpated, they do not survive any longer than animals totally depancreatized in one stage. In the present series of experiments we have compared the urinary glucose, nitrogen and acetone bodies of 3 normal, 4 depancreatized, 4 hypophysectomized-depancreatized and 5 adrenalectomized-depancreatized cats. All these animals were fasting. In the case of the depancreatized cats the observations were made during the remainder of life and in the other animals for 5–7 days from the day of operation. The results are in Table I. It will be observed that the well known high excretion of glucose and nitrogen is much reduced in the doubly operated animals while the characteristic ketonuria is almost entirely absent. The latter does not become evident throughout life unless steps are taken to induce it. Rietti has reported comparable finding in the hypophysectomized-depancreatized dog, but so far as we know such observations have not been previously made in adrenalectomized-depancreatized animals.

THE INFLUENCE OF THE ADRENAL GLANDS ON RESISTANCE

THE INFLUENCE OF THE ADRENAL GLANDS ON RESISTANCE