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G Rindi

Publications and source records attributed to G Rindi.

At least 109 records · Page 6Linked to original sources
PubMed1990

Development of neuroendocrine tumors in the gastrointestinal tract of transgenic mice. Heterogeneity of hormone expression.

Expression of hormones in endocrine tumors and derived cell lines of transgenic mice carrying insulin-promoted oncogenes has been investigated by histochemical, immunohistochemical, ultrastructural, and radioimmunologic means. Tumors of the pancreas, small intestine, mesentery, and liver were examined. Insulin-immunoreactive cells were prevalent in pancreatic tumors, with a significant subpopulation of pancreatic polypeptide-immunoreactive elements. Conventional ultrastructural and immunogold analysis identified insulin-storing beta granules in pancreatic tumor cells. In contrast, the largest immunoreactive subpopulation of intestinal tumors expressed secretin (53% of total cells), followed by proglucagon-related peptides (15%), glucose-dependent insulinotropic polypeptide (7%), gastrin (7%), pancreatic polypeptide (2%), neurotensin (2%), and somatostatin (1%). No detectable immunoreactivity for either insulin or serotonin was observed. Electron microscopy and immunogold labeling showed that intestinal tumor cells contained secretin-storing S-type granules. Lymph node and liver tumors contained secretin-immunoreactive cells with ultrastructural features similar to those of intestinal tumors. In addition, high levels of circulating insulinlike and secretinlike immunoreactants were detectable. Analogous hormone profiles were identified in tumor cell lines and culture media. Large T-antigen immunoreactivity was detected in all the nuclei of neoplastic cells, as well as in insulin-immunoreactive elements of non-neoplastic islets and pancreatic ducts and in some secretin-immunoreactive cells of small intestinal mucosa. These data indicate that neuroendocrine tumors arise both in beta cell and S-cell subpopulations of transgenic mice.

Animals↗
PubMed1990

Different distribution of thiaminpyrophosphatase activity in neuronal and glial cell enriched fractions from human and rat brain: an isoelectric focusing investigation.

Enriched fractions of neuronal and glial cells from rat and human (autoptical specimens of frontal cortex) brains were assayed for thiaminpyrophosphatase (TPPase) activity by isoelectric focusing (IEF). Glial and neuronal fractions yielded about 0.16 and 0.03 g/g of wet tissue respectively. Purity was estimated to be 85-90%. The isolated fractions were homogenized in the presence of 1% Triton X-100, and IEF was carried out on thin layer polyacrylamide gel in a pH range of 3.5-9.5, using Ampholine PAG plates. TPPase activity of the protein bands was assayed by laser-densitometry, after incubation with thiaminpyrophosphate in an appropriate buffer and PbS staining. IEF analysis showed that TPPase activity was present almost exclusively in the neuronal fraction (at levels 16-fold higher than those found in the glial fraction). After IEF, TPPase activity was present in 10 distinct protein bands with different isoelectric points. These preliminary data suggest that TPPase may be involved in the neuronal activity of rat and human brain.

Aged↗
PubMed1989

Enterochromaffin-like cell populations in human fundic mucosa: quantitative studies of their variations with age, sex, and plasma gastrin levels.

The human gastric fundal mucosa contains a variety of endocrine cells, the most numerous of which are the so-called enterochromaffin-like (ECL) cells. We have studied the variations with age and sex of the ECL cell populations, utilizing an assessment based on multiple endoscopic biopsies from four groups of subjects. Plasma gastrin levels were also determined in these subjects. In males, endocrine cell densities declined with age but the ECL cell numbers in females opposed this trend. ECL cell counts showed no appreciable differences between young and old females. In older females, there was a high rate of gastritis and increased levels of circulating gastrin. Concentrations in older females (29.6 +/- 8.7 pmol/l) were higher than in both younger (less than 45 years) males (5.3 +/- 1.1 pmol/l) and older (greater than 55 years) males (6.3 +/- 0.6 pmol/l) (P less than 0.05). The plasma gastrin level was also higher in older females than in young females (13.1 +/- 4.5 pmol/l), although this difference failed to reach statistical significance. In conclusion, clinically silent gastritis, raised gastrin levels, and maintenance or rise of ECL cells numbers, in opposition to a general decrease in endocrine cells with age, appear to be features of women of more than 55 years of age. The variations in ECL cell populations reported here should be taken into account when evaluating possible pathological alterations of the stomach.

Adult↗
PubMed1989

Transgenic mouse models and peptide producing endocrine tumours: morpho-functional aspects.

Three transgenic mouse models which proved to develop endocrine tumours are reviewed and discussed. The neoplasms were induced through the production of the transforming oncoprotein simian virus 40 (SV40) large T-antigen. The SV40/metallothionein-growth hormone (MGH), the insulin/SV40 (INS/SV40) and the vasopressin/SV40 (AVP/SV40) transgenic mice models all developed endocrine tumours of pancreas mainly composed of insulin-producing B cells, with a minor PP cell component. In the pancreata of INS/SV40 and AVP/SV40 transgenic mice, non-tumour lesions (hyperplasia and dysplasia) were also described. AVP/SV40 transgenic mice presented tumour genesis in anterior pituitary too. The usefulness of transgenic mouse models in reproducing human pathology is outlined with special reference to genetically dependent tumours.

Animals↗
PubMed1989

Studies on thiamine metabolism in thiamine-responsive megaloblastic anaemia.

We have investigated thiamine metabolism and transport in the erythrocytes of two patients from unrelated families with thiamine responsive megaloblastic anaemia associated with diabetes mellitus and sensorineural deafness. Both patients had low concentrations of thiamine compounds in plasma and red blood cells. When erythrocytes were incubated with thiazole-[2-14C]-thiamine or [35S]-thiamine in vitro, the concentration of label within the cells was markedly reduced compared with controls. In addition, thiamine pyrophosphokinase activity was deficient in haemolysates prepared from the patients. Some relatives of the patients showed abnormal parameters of thiamine status and transport. In both patients treatment with a lipophilic compound corrected the haematological abnormalities and diabetes and in one patient has so far prevented the progression of deafness. We propose that the disorder is caused by an inherited defect of thiamine transport, possibly related to deficient pyrophosphokinase activity, leading to intracellular depletion of active thiamine metabolite derivatives.

Anemia, Macrocytic↗
PubMed1989

The distribution of GAWK-like immunoreactivity in neuroendocrine cells of the human gut, pancreas, adrenal and pituitary glands and its co-localisation with chromogranin B.

GAWK is a recently discovered peptide isolated from extracts of human pituitary gland and subsequently shown to be identical to sequence 420-493 of human chromogranin B. The distribution of this peptide was studied in human gut, pancreas, adrenal and pituitary glands using antisera to two portions of the 74 amino acid peptide (sequences 1-17 and 20-38). In addition, the co-existence of GAWK immunoreactivity with other peptides and chromogranin B was investigated using comparative immunocytochemistry. In the gut, GAWK was localised mainly to serotonin-containing cells of the mucosal epithelium, where electron microscopy showed it to be stored in typical electron-dense (250 nm diameter) granules, and to a moderate population of nerve fibres in the gut wall. Considerable quantities of GAWK-like immunoreactivity were measured in the gut, up to 36.3 +/- 18 pmol GAWK 1-17/g wet weight of tissue (mean +/- SEM) and 12.4 +/- 2.9 pmol GAWK 20-38/g. Chromatography of gut extracts revealed several GAWK-like immunoreactive peaks. GAWK-like immunoreactivity was also detected in endocrine cells of pancreas, pituitary gland and adrenal medulla, where the highest concentrations of GAWK-like immunoreactivity were measured (GAWK 1-17 2071.8 +/- 873.2 and GAWK 20-38 1292.7 +/- 542.7 pmol/g). Endocrine cells containing GAWK-like immunoreactivity were found also to be immunoreactive for chromogranin B. Our results define a discrete distribution of GAWK immunoreactivity in human endocrine cells and nerves and provide morphological support for the postulated precursor-product relationship between chromogranin B and GAWK. Details of the functions of this peptide are awaited.

Adrenal Glands↗
PubMed1989

Effect of chronic ethanol administration on thiamine transport in microvillous vesicles of rat small intestine.

The effect of long-term ethanol administration on the membrane mechanism of thiamine entry in rat enterocytes was investigated by using microvillous vesicles of small intestine. Experiments were carried out in three groups of Wistar albino rats of both sexes (290-400 g of initial body wt). Group I did not receive any treatment, group II received 4.7 g of ethanol/kg body wt (as a 50% hydroalcoholic solution) daily by gastric gavage for 35 days and group III (pair-fed controls) received a daily solution of saccharose (isoenergetic with the dose of ethanol administered to group II) by gastric gavage for 35 days. Ethanol or saccharose were administered in the morning and a standard diet was given throughout the treatment period. All animals were killed by decapitation 24 hr after the last administration, when the blood level of ethanol was virtually zero. Microvillous small intestinal vesicles were incubated with 3H-thiamine (3H-T) at 25 degrees C and the amount of 3H-T taken up was measured by a rapid filtration method. Compared with data obtained in groups I and III, chronic ethanol administration was found to induce a statistically significant decrease in 3H-T vesicular uptake at 4 sec (determined at 3H-T concentrations ranging from 0.12 to 7.5 microM) and a decrease in the apparent Jmax (maximal transport rate) value of the saturable component, without affecting the apparent Km (half-saturation concentration) value. These results indicate that in rats chronic ethanol administration may impair the intestinal absorption of thiamine by reducing thiamine entry into the enterocyte.

Alcoholism↗
PubMed1989

A recombinant hepatitis B core antigen polypeptide with the protamine-like domain deleted self-assembles into capsid particles but fails to bind nucleic acids.

We have cloned in Escherichia coli both the complete core gene of hepatitis B virus and a truncated version of it, leading to the synthesis of high levels of a core-antigen-equivalent polypeptide (r-p22) and of an e-antigen-equivalent polypeptide (r-p16), respectively. We then compared the structural and antigenic properties of the two polypeptides, as well as their ability to bind viral nucleic acids. r-p16 was found to self-assemble into capsid-like particles that appeared similar, when observed under the electron microscope, to those formed by r-p22. In r-p16 particles, disulfide bonds linked the truncated polypeptides in dimers, assembled in the particle by noncovalent interactions. In r-p22 capsids, further disulfide bonds, conceivably involving the carboxy-terminal cysteines of r-p22 polypeptides, joined the dimers together, converting the structure into a covalently closed lattice. The protamine-like domain was at least partly exposed on the surface of r-p22 particles, since it was accessible to selective proteolysis. Finally, r-p22, but not r-p16, was shown to bind native and denatured DNA as well as RNA. Taken together, these results suggest that the protamine-like domain in core polypeptides is a nucleic acid-binding domain and is dispensable for the correct folding and assembly of amino-terminal and central regions.

Capsid↗
PubMed1989

Qualitative studies of gastric endocrine cells in patients treated long-term with omeprazole.

A total of 543 endoscopic biopsies (a mean of three tissue samples each) were taken from the gastric oxyntic mucosa of 122 patients suffering from reflux oesophagitis or peptic ulcer resistant to H2-receptor antagonist therapy. All were treated with omeprazole, 40 mg/day, until healing and then assigned to 20 mg/day for a mean of 13 months. Proliferative changes of endocrine cells were evaluated according to an internationally agreed classification and the paraffin sections were stained with haematoxylin-eosin and Sevier-Munger silver. Only hyperplastic (no dysplastic or neoplastic) lesions of endocrine cells were observed in 11-19% of patients examined, the incidence and severity of these lesions being unaffected by treatment. A relationship between linear and/or micronodular hyperplasia and chronic gastritis was observed.

Biopsy↗
PubMed1988

A morphological analysis endocrine tumour genesis in pancreas and anterior pituitary of AVP/SV40 transgenic mice.

Insertion into the mouse genome of the hybrid oncogene made up of bovine vasopressin gene derived 5' upstream sequences and the coding sequences of SV40 large T-antigen promoted tumours in anterior pituitary and endocrine pancreas of mice bearing this transgene. In order to investigate the morphology of the steps in the neoplastic process, we used light and electron microscopy to study these organs in 42 animals belonging to the 3rd, 4th and 5th generations, subdivided into 4 age groups from 20 days to 100 days of life. Antibodies to large T-antigen were used to identify sites of expression of the hybrid oncogene, thus monitoring the steps in neoplastic transformation. Large T-antigen immunoreactivity was identified in dysplastic lesions of younger animals and in both dysplastic lesions and tumours of older mice. Insulin (100% of cases) and pancreatic polypeptide (25% of cases) immunoreactivities were revealed in pancreatic lesions but no hormonal immunoreactivity was detected in the pituitary lesions. The ultrastructural study confirmed that the majority cell population of the pancreatic neoplasms was B-type and that the anterior pituitary tumours were poorly granulated. The subcellular localization of large T-antigen immunoreactivity was investigated by the immunogold method and was confined to the heterochromatin of tumour cell nuclei. These findings provide evidence for the dysplasia-neoplasia sequence in the genesis of endocrine tumours of pituitary and pancreas of transgenic mice. The vasopressin-SV40 large T-antigen transgenic mice may therefore be an useful model for the study of endocrine cell oncogenesis.

Animals↗
PubMed1988

Distribution of thiamine, thiamine phosphates, and thiamine metabolizing enzymes in neuronal and glial cell enriched fractions of rat brain.

The distribution of thiamine, thiamine phosphoesters, and the thiamine pyrophosphate synthetizing [thiamine-pyrophosphokinase (TPKase)] as well as hydrolyzing [thiamine pyrophosphatase (TPPase) and thiamine monophosphatase (TMPase)] enzymes was determined in neuronal and glial enriched fractions prepared from rat brain. Nucleoside diphosphatases [inosine diphosphatase (IDPase) and uridine diphosphatase (UDPase)] and nucleoside monophosphatases [uridine monophosphatase (UMPase) and inosine monophosphatase (IMPase)] were also determined. Thiamine and thiamine mono- and pyrophosphate were present in neuronal enriched fractions at concentrations 2.8, 3.6, and 4.6 times higher than in glial fractions. TMPase was found only in glial enriched fractions, whereas the levels of TPKase, UMPase, IMPase, IDPase, UDPase, and TPPase were 2.0-, 2.2-, 1.3-, 2.8-, 3.7-, and 20.8-fold higher in neuronal than in glial fractions.

Animals↗
PubMed1988

Blood-brain transport of thiamine monophosphate in the rat: a kinetic study in vivo.

To calculate the kinetic parameters of thiamine monophosphate transport across the rat blood-brain barrier in vivo, different doses of a [35S]thiamine monophosphate preparation with a specific activity of 14.8 mCi.mmol-1 were injected in the femoral vein and the radioactivity was measured in arterial femoral blood and in the cerebellum, cerebral cortex, pons, and medulla 20 s after the injection. This short experimental time was used to prevent thiamine monophosphate hydrolysis. Thiamine monophosphate was transported into the nervous tissue by a saturable mechanism. The maximal transport rate (Jmax) and the half-saturation concentration (Km) equaled 27-39 pmol.g-1.min-1 and 2.6-4.8 microM, respectively. When compared with that of thiamine, thiamine monophosphate transport seemed to be characterized by a lower affinity and a lower maximal influx rate. At physiological plasma concentrations, thiamine monophosphate transport rate ranged from 2.06 to 4.90 pmol.g-1.min-1, thus representing a significant component of thiamine supply to nervous tissue.

Animals↗
PubMed1988

The morphology and neuroendocrine profile of pancreatic epithelial VIPomas and extrapancreatic, VIP-producing, neurogenic tumors.

The histology, histochemistry, and ultrastructure of 43 VIP-producing tumors (34 from the pancreas, one jejunal, six retroperitoneal and two mediastinic), 37 of which were associated with the WDHA syndrome, have been investigated on paraffin sections of primary or metastatic tumor tissue. The pancreatic and jejunal tumors showed all structural and secretory patterns of epithelial endocrine tumors, including expression of cytokeratin, neuroendocrine markers like neuron-specific enolase, chromogranins and synaptophysin, peptides like VIP, PHM, GRH, PP, insulin, neurotensin, glucagon, somatostatin and enkephalin, secretory granules, small clear vesicles, peculiar osmiophilic bodies, and occasional formation of tubules or microacini with specialized luminal surfaces. All the remaining tumors were neurogenic, showing either neurons and nerve fibers together with Schwann cells (ganglioneuromas and ganglioneuroblastomas) or endocrine cells (pheochromocytomas) reacting with VIP, PHM, NPY, enkephalin, somatostatin, neuron-specific enolase, synaptophysin, and MAP2 (but not cytokeratin, PP, or GRH) antibodies. A possible origin of pancreatic VIPomas from transformed pancreatic PP cells or ductular stem cells partially committed to differentiation along the PP cell line is suggested.

Adenoma, Islet Cell↗
PubMed1988

Transport of thiamine by brush-border membrane vesicles from rat small intestine.

1. Microvillous vesicles obtained by a Ca2+ precipitation method from the intestine of adult Wistar albino rats were incubated at 25 degrees C with [35S]- or [3H]thiamine of high specific activity. 2. The time course of thiamine uptake was not influenced by the presence of Na+ or K+ nor by the absence of alkaline cations in the incubation medium. 3. At concentrations below 1.25 microM, thiamine was taken up mainly by a saturable mechanism with apparent Km = 0.8 microM and Vmax = 0.35 pmol mg protein-1 4 s-1. At higher concentrations, a non-saturable uptake mechanism prevailed. 4. The thiamine taken up was transferred to the intravesicular space. No thiamine phosphoesters could be detected in the vesicles. 5. The vesicular transport of thiamine was inhibited competitively by several thiamine derivatives and structural analogues, including: cold thiamine; thiamine monophosphate (inhibition constant, Ki = 33 microM); pyrithiamine (Ki = 1.7 microM); 2'-ethylthiamine (Ki = 27 microM); 5-chloroethylthiamine (Ki = 70 microM): Amprolium (Ki = 55 microM); 4'-oxythiamine (Ki = 510 microM).

Animals↗
PubMed1988

Intestinal transport of thiamin and thiamin monophosphate in rat everted jejunal sacs: a comparative study using some potential inhibitors.

Rat everted jejunal sacs were incubated for 15 and 30 min at 37 degrees C in oxygenated Krebs-Henseleit buffer, pH 7.4, containing 0.2 microM [3H]-thiamin (3H-T) or [3H]-thiamin monophosphate (3H-TMP) with and without 10 mM 1-phenylalanine (PAL) or 2.5 mM levamisole (LEV). The concentrations of 3H-T and its phosphoesters in sac wall and serosal fluid were determined by a radiometric method after electrophoretic separation. In separate experiments, thiamin pyrophosphokinase (TPKase) and thiamin pyrophosphatase (TPPase) activities were determined in mucosal scrapings, with and without PAL or LEV, by using a radiometric and a colorimetric method, respectively. 3H-TMP was transported partly unchanged by an active mechanism similarly to 3H-T, but less efficiently. During transport, 3H-TMP was also enzymatically transformed to thiamin (T) and thiamin pyrophosphate, which accumulated in the tissue. In the serosal fluid, the concentration of 3H-TMP exceeded that of 3H-T. Presence of PAL or LEV with 3H-T or 3H-TMP in the incubation medium reduced the serosal transport and the tissue content of T compounds. LEV caused a dose-dependent inhibition of TPKase without affecting TPPase, whereas PAL inhibited both activities to about the same extent. These results indicate that the transport of TMP involves a number of different processes similar to those responsible for T transport. The effects of PAL and LEV underline the importance of phosphorylation-dephosphorylation coupling.

Animals↗
PubMed1988

A lead conversion method for staining thiamine pyrophosphatase and other phosphatases in rat brain after thin layer polyacrylamide gel isoelectric focusing.

Rat brain thiamine pyrophosphatase (TPPase) was separated by thin layer polyacrylamide gel isoelectric focusing (IF) and stained with a modification of the lead conversion method of Allen and Hyncik (1963). 10 bands with TPPase activity were observed in the pH range 4.6-7.1. The overall IF pattern of TPPase was similar to that of uridine diphosphatase and inosine diphosphatase but was clearly different from that of adenosine diphosphatase, p-nitrophenyl phosphatase, alpha-naphthyl phosphatase and thiamine monophosphatase. A semiquantitative assessment of TPPase isoenzymes has been performed using laser densitometry.

Animals↗