Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts:   Target Concepts:
Query: UNIPROT:P01275 (glucagon)
 26,492 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

In the present study we report methods for the isolation and culture of colonic peptide YY (PYY) cells and have tested the effects of sodium oleate and other chemotransmitters on PYY release. Enzyme-dispersed canine colonic mucosa cells were separated by a Beckman elutriation rotor, and the enriched PYY fraction was cultured on type I collagen in full growth medium. After 42-48 h of culture PYY cells had selectively adhered to the collagen. Forty to 45% of the adherent cells contained PYY (5.5 +/- 0.5 pmol/24-mm well), and 10-15% of the cells contained glucagon-like immunoactivity (GL29-LI; 0.95 pmol/24-mm well). The effect of various secretagogues on PYY release from these cultures was monitored. Sodium oleate stimulated PYY release in a time-dependent fashion over a dose range from 10 microM to 10 mM. However, sodium oleate at a dose of 100 mM produced disproportionately large PYY release. During a 2-h incubation 5.1% of the total cell content of PYY was released in response to 0.1 mM sodium oleate compared with basal release of 1.1%. At doses less than 10 mM sodium oleate did not release GL29-LI, whereas concentrations of 10 and 100 mM resulted in marked GL29-LI release. These findings suggest that lower concentrations of sodium oleate selectively release PYY, whereas higher concentrations nonselectively induce peptide release probably by effects on membrane stability. We also found that bombesin, epinephrine, and forskolin, but not carbachol, produced time- and dose-dependent release of PYY from these cultures.
 ...
PMID:Primary culture of PYY cells from canine colon. 337 82

The aim of the present study was to further evaluate the significance of circulating platelet aggregates induced by somatostatin in insulin-dependent diabetic subjects. Eight insulin-dependent diabetics and eight normals were infused with somatostatin at increasing doses (250, 500, and 750 microgram/h), each dose for 30 min. In diabetics, somatostatin induced the appearance in blood of platelet aggregates in a dose-dependent fashion, the highest level being observed with the highest dose (750 microgram/h), p less than 0.005). In normals, circulating platelet aggregates were detected only with the infusion of the highest rate of somatostatin (p less than 0.025). This effect of somatostatin was reversible, since it tended to disappear 30 min after the infusion was stopped. In six additional insulin-dependent diabetics, a previous infusion of phentolamine (0.5 mg/min) completely prevented the appearance of platelet aggregates by somatostatin. No significant variation of the aggregation response to both ADP and collagen and the platelet count was seen in both experiments. Somatostatin, as expected, reduced the basal concentration of plasma glucose, glucagon, and C-peptide in both diabetics and normals. On the basis of these results, we suggest that somatostatin has some proaggregating capacity in vivo, probably by interacting with adrenergic mechanisms.
 ...
PMID:Further studies on the significance of circulating platelet aggregates induced by somatostatin in man. 611 Jan 60

The present study was undertaken to reevaluate the influence of somatostatin on platelet function in insulin-dependent diabetics and in normal subjects. In in vivo studies, nine insulin-requiring diabetics were infused with cyclic somatostatin (250 microgram/hour) for 120 minutes or with saline, in randomized order. This dose of somatostatin, sufficient to depress the basal concentrations of plasma glucose, glucagon and C-peptide, resulted in no significant change of platelet aggregation response to either ADP or collagen. By contrast, a progressive and significant reduction of platelet aggregation response to ADP was found during saline infusion. A similar pattern of response was seen in normal subjects. In all diabetics, but not in normals, somatostatin induced the appearance of circulating platelet aggregates. In in vitro studies, somatostatin augmented the aggregation response to epinephrine in both normals and diabetics. In conclusion, somatostatin counteracts the decrease of platelet aggregation response to ADP seen in saline studies, induces the appearance of platelet aggregates in diabetics and potentiates the aggregation response to epinephrine (in vitro) in both normals and diabetics. These actions of somatostatin suggest some aggregating capacity of the peptide in man.
 ...
PMID:Circulating platelet aggregates induced by somatostatin in insulin-dependent diabetic subjects. 611 May 70

Hepatocytes isolated as a relatively pure population from normal adult rats were maintained in primary monolayer culture for 4 to 7 days on plastic dishes. Factors affecting activity of gamma-glutamyltranspeptidase (GGT) in culture were investigated to establish a basis for in vitro studies on carcinogen-induced changes in GGT. Freshly plated cultures contained few GGT-positive cells (0.4%) and very low total GGT activity, but with all media tested, activity increased progressively with time in culture, the extent of increase depending on medium composition. For hepatocytes in modified Waymouth medium alone (control cultures), there was a slow rise in activity after a 1- to 2-day lag period. This increase was enhanced up to 10-fold in the presence of 3 microM dexamethasone for cells on plastic but only 2- to 3-fold for cells on collagen gels. The time- and dose-dependent action of dexamethasone was prevented by cycloheximide, partly blocked by actinomycin D, and reversed after several hr by removing the steroid, when GGT activity decreased with a maximum half-life of 60 to 80 hr. These observations suggest that dexamethasone caused reversible enzyme induction dependent on continuing RNA and protein synthesis. Cell maintenance with fetal calf serum or with N6,O2'-dibutyryl adenosine 3':5'-monophosphate or glucagon markedly reduced the extent of induction by dexamethasone and slightly lowered activity in control cultures. Maintenance at lower pH within the range of 7.2 to 7.8 or at higher glucose concentrations within the range of 2.8 to 28 mM also resulted in markedly lower GGT activities in control or dexamethasone-induced cultures. Glucose repression was independent on insulin concentration. The reversible induction and repression of GGT may reflect broad changes in hepatocyte gene expression rather than specific controls of GGT function. Since GGT in cultured hepatocytes is subject to regulation by a variety of noncarcinogens, caution is required in its use as a preneoplastic marker. Nevertheless, the identification of culture media which preserve low activity may allow studies on carcinogen-induced changes in GGT as a probe of the early events in vitro hepatocarcinogenesis.
 ...
PMID:Regulation of gamma-glutamyltranspeptidase in rat hepatocyte monolayer cultures. 612 Jul 59

Serum-free, hormonally defined media have been developed for optimal growth of a rat hepatoma cell line. The cells' hormonal requirements for growth are dramatically altered both qualitatively and quantitatively by whether they were plated onto tissue culture plastic or collagenous substrata. On collagenous substrata, the cells required insulin, glucagon, growth hormone, prolactin, and linoleic acid (bound to BSA), and zinc, copper, and selenium. For growth on tissue culture plastic, the cells required the above factors at higher concentrations plus several additional factors: transferrin, hydrocortisone, and triiodothyronine. To ascertain the relative influence of hormones versus substratum on the growth and differentiation of rat hepatoma cells, various parameters of growth and of liver-specific and housekeeping functions were compared in cells grown in serum-free, hormonally supplemented, or serum-supplemented medium and on either tissue culture plastic or type I collagen gels. The substratum was found to be the primary determinant of attachment and survival of the cells. Even in serum-free media, the cells showed attachment and survival efficiencies of 40-50% at low seeding densities and even higher efficiencies at high seeding densities when the cells were plated onto collagenous substrata. However, optimal attachment and survival efficiencies of the cells on collagenous substrata still required either serum or hormonal supplements. On tissue culture plastic, there was no survival of the cells at any seeding density without either serum or hormonal supplements added to the medium. A defined medium designed for cells plated on tissue culture plastic, containing increased levels of hormones plus additional factors over those in the defined medium designed for cells on collagenous substrata, was found to permit attachment and survival of the cells plated into serum-free medium and onto tissue culture plastic. Growth of the cells was influenced by both substrata and hormones. When plated onto collagen gel substrata as compared with tissue culture plastic, the cells required fewer hormones and growth factors in the serum-free, hormone-supplemented media to achieve optimal growth rates. Growth rates of the cells at low and high seeding densities were equivalent in the hormonally and serum-supplemented media as long as comparisons were made on the same substratum and the hormonally supplemented medium used was the one designed for that substratum. For a given medium, either serum or hormonally supplemented, the saturation densities were highest for tissue culture plastic as compared with collagen gels.(ABSTRACT TRUNCATED AT 400 WORDS)
 ...
PMID:Regulation of growth and differentiation of a rat hepatoma cell line by the synergistic interactions of hormones and collagenous substrata. 613 87

The adenylate cyclase system and the number and affinities of receptors for insulin and glucagon were studied in rats treated with CCl4 and in rats that received colchicine in addition to CCl4. Liver glycogen, cAMP and total collagen content were also measured in those animals. Rats received only mineral oil or only colchicine were used as controls. In this latter group, all parameters measured were normal. Differences in liver collagen content between groups treated with CCl4 and CCl4 + colchicine were not statistically significant. Basal adenylate cyclase activity was 2-fold increased in the CCl4 group. In the animals receiving CCl4 and colchicine, adenylate cyclase activity was normal. Adenylate cyclase activity stimulated by fluoride or by glucagon was also increased in the CCl4 group. However, this increase was due to to the enhanced basal activity. The number of receptors and the affinities of the receptors of glucagon and insulin were normal in all groups. cAMP levels were found increased in the CCl4 treated animals and this was accompanied by a 90% reduction in liver glycogen. In the group treated with CCl4 + colchicine, cAMP was normal and liver glycogen was only reduced 25%. These results suggest that part of the clinical and biochemical improvements observed in the colchicine treated animals were due in part to a reversal of the alterations of the adenylate cyclase system induced by CCl4.
 ...
PMID:Colchicine improves the alterations in the liver adenylate cyclase system of cirrhotic rats. 617 Jan 33

Although the activity of glucose-6-phosphatase in rat liver is altered markedly following the administration of a variety of hormones in vivo, it is not certain whether the hormones act directly on the hepatocyte. To study this problem hepatocytes were isolated by a collagenase-perfusion technique and cultured on collagen gel/nylon mesh membranes. The activity of glucose 6-phosphatase in cells cultured with fetal calf serum and with Dulbecco's modified Eagle's medium or Leibovitz L-15 medium decreased to less than 10-30% of the activity in freshly isolated cells by 96 h. However, when L-15 plus newborn or fetal calf serum was supplemented with glucagon (10(-6)M), epinephrine (10(-6)M), triiodothyronine (10(-6)M), and dexamethasone (10(-5)M) (L-15-GETD), the activity of glucose-6-phosphatase was maintained so that, after 144 h, the activity was at least 80% of that detected in freshly isolated cells. In cells cultured in L-15 plus serum for 72 or 96 h and then in L-15-GETD, glucose-6-phosphatase increased 30-50% over that in control cultures after 24 h. Insulin, which decreases glucose-6-phosphatase activity when administered to intact animals, also decreased the glucose-6-phosphatase activity in cultured hepatocytes to 20-50% of that in controls.
 ...
PMID:Effects of hormones on the activity of glucose-6-phosphatase in primary cultures of rat hepatocytes. 631 98

The effect of 1 mg of intravenous glucagon on platelet aggregation has been investigated in 12 normal subjects pre-treated with salicylate. All subjects demonstrated the expected inhibition of collagen-induced secondary aggregation but retained the normal adenosine diphosphate (ADP)-induced primary aggregation phase 18 h after the salicylate therapy (600-1,200 mg). Subsequent administration of glucagon caused a significant increase in the ADP-induced primary aggregation phase in the 12 subjects. This data indicates that glucagon increases the reactivity of platelets to ADP and may help to explain the common clinical association of raised plasma glucagon, increased platelet aggregation and vascular disease.
 ...
PMID:Increased platelet aggregation induced by glucagon administration. 677 77

A human colon carcinoma cell line, HC84S, was established in serum-supplemented medium from a colon tumor line T84 transplanted in nude mice. These cells also grew in a serum-free, synthetic medium supplement with insulin, glucagon, epidermal growth factor, transferrin, hydrocortisone, triiodothyronine, selenium, and ascorbic acid. HC84S cells grew 3 times faster in this medium than in serum-containing medium and formed gland-like structures closely resembling the original tumor morphologically. In serum-containing medium, the cells grew as a monolayer and did not form such structures. Primary cultures from transplantable human colon tumor lines maintained in nude mice and a primary tumor from a patient were established directly in this hormone-supplemented medium in collagen-treated plastic dishes without fibroblast overgrowth. The hormone-supplemented medium may be generally useful for the establishment of human colon carcinoma cell lines.
 ...
PMID:Hormonal control of human colon carcinoma cell growth in serum-free medium. 693 31

The procarcinogen, 2-acetylaminofluorene, the direct-acting carcinogen, methyl methanesulfonate, and two other hepatocarcinogens, thioacetamide and urethan, were tested for their ability to elicit unscheduled DNA synthesis in adult rat hepatocytes maintained in primary culture on collagen gel-nylon mesh. The carcinogens, dissolved in dimethyl sulfoxide were added to 6-hr or to 28-hr cultures along with [methyl-3H]thymidine (1 muCi/ml medium) in the presence of 10 mM hydroxyurea. Twelve hr later, the hepatocytes were harvested from the cultures with collagenase, and their DNA was purified on CsCl isopyknic gradients. Unscheduled DNA synthesis was measured as the increase in [methyl-3H]thymidine radioactivity incorporated per microgram DNA of the carcinogen-treated cultures as compared with that of control cultures. Both 2-acetylaminofluorene and methyl methanesulfonate demonstrated a concentration-dependent stimulation of unscheduled DNA synthesis in the 6-hr hepatocyte cultures. However, the response of the 28-hr cultures to these two carcinogens was absent unless the hepatocytes were preincubated for 22 hr in culture medium supplemented with 10(-5) M dexamethasone and 10(-6) M glucagon or in a more complete hormone-supplemented medium. Thioacetamide and urethan, on the other hand, failed to elicit a concentration-dependent unscheduled DNA synthesis under these conditions. The results obtained with this culture system are similar to those of other short-term tests for chemical carcinogenicity and support the potential use of the collagen gel-nylon mesh-hepatocyte primary culture as an in vitro screen for chemical carcinogens. Furthermore, this study suggests the importance of specific hormones in maintaining the capability for repair of DNA damage produced by carcinogenic and mutagenic chemicals in cultured hepatocytes.
 ...
PMID:Use of primary cultures of adult rat hepatocytes on collagen gel-nylon mesh to evaluate carcinogen-induced unscheduled DNA synthesis. 700 Mar 42


<< Previous 1 2 3 4 5 6 7 8 9 10 Next >>