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Biomedical subjects

L Lundell

Publications and source records attributed to L Lundell.

At least 181 records · Page 10Linked to original sources
PubMed1976

Diamines and polyamines in DMBA-induced breast carcinoma containing mast cells resistant to compound 48/80.

In female rats, mammary carcinoma were induced by DMBA (7,12-dimethylbenz(alpha)anthracene) administration. The activities of histidine and ornithine decarboxylases and the concentrations of histamine, putrescine and polyamines were determined in tumour extracts and urine. In the tumour tissue, formation of histamine and putrescine took place at much higher rates than in normal mammary tissue. Administration of compound 48/80 in doses that mobilized about 70% of histamine contained in the ear failed to release histamine contained in the tumour; 48/80 also failed to produce histological signs of degranulation of the tumour mast cells. It thus appears that these cells are different from mast cells in most normal tissues, a distinction that calls for further study.

Animals↗
PubMed1976

Further studies on the mode of action of isoprenaline on gastric secretion in the conscious rat.

1 The effect of isoprenaline on gastric secretion evoked by various means has been studied in conscious rats provided with Pavlov and Heidenhain pouches. 2 Interdigestive acid secretion in the Pavlov pouch was reduced by isoprenaline, whereas pepsin secretion was unaltered. 3 Central vagal stimulation effected by 2-deoxy-D-glucose injection evoked a gastric secretory response that was substantially reduced by isoprenaline. 4 2-Deoxy-D-glucose increased the mobilization of gastric mucosal histamine, an effect that was prevented by isoprenaline. 5 Isoprenaline infusion alone induced a slight increase in histamine mobilization and also a considerable elevation of immunoreactive serum gastrin concentration. 6 The secretory response to food in the Pavlov pouch was almost abolished by isoprenaline. 7 Although the acid response to histamine in the Heidenhain pouch was susceptible to isoprenaline inhibition, that to methacholine was not. 8 Pepsin secretion in the Heidenhain pouch preparation stimulated by histamine or methacholine seemed to be enhanced by isoprenaline.

Animals↗
PubMed1976

The role of cholinergic excitation in the formation of histamine within the rat gastric mucosa.

In the absence of the antrum, central vagal excitation and distension of the stomach accelerated the rate of formation of gastric mucosal histamine. The effect of vagus stimulation was abolished by truncal vagotomy or atropine whereas that of distension by atropine. After truncal vagotomy, distension was still effective in accelerating the formation of the amine. Furthermore, mucosal histamine formation in the fasting state was reduced by truncal vagotomy and atropine injection.

Animals↗
PubMed1976

Histamine metabolism of the guinea-pig gastric mucosa.

1. The mobilization of gastric mucosal histamine as reflected by changes in formation and content has been studied in guinea-pigs on feeding and after injections of pentagastrin or 2-deoxy-D-glucose. 2. Re-feeding fasting guinea-pigs as well as injections of pentagastrin or 2-deoxy-D-glucose raised the rate of mucosal histamine formation; pentagastrin induced a fourfold rise. 3. Some properties of the enzyme catalysing the formation of histamine were examined. The results indicated that this enzyme is histidine decarboxylase, L-histidine carboxy-lyase, E.C. 4.1.1. 22. 4. The enzyme imidazole-N-methyl transferase, E.C. 2.1.1.8, which carries out methylation of the imidazole ring to yield 1-methyl-4-(beta-aminoethyl)imidazole (methylhistamine), was found in high amounts in the mucosa. The enzyme did not change upon stimulation of the mucosa. 5. The metabolism of histamine within the gastric mucosa is discussed in relationship to a suggested role of the amine in exciting acid secretion.

Animals↗
PubMed1975

Displacement by metiamide of the dose-response curves to pentagastrin and methacholine in the conscious rat.

1. The effect of a specific histamine H2-receptor antagonist, metiamide, on the acid dose-response curves for pentagastrin or methacholine was studied in rats provided with Heidenhain pouches. 2. Metiamide induced a shift to the right of the dose-response curve to pentagastrin and lowered the maximal secretion. 3. In contrast, metiamide only increased the ED50 for methacholine but did not alter the calculated maximal response. 4. The effect of metiamide on pentagastrin and methacholine-induced secretion is in agreement with the previously suggested difference in the part played by mucosal histamine in the mode of action of the two stimulatory agents.

Animals↗
PubMed1975

Elicidation by a H-2-receptor antagonist of the significance of mucosal histamine mobilization in exciting acid secretion.

1. The consequence of H-2-receptor blockade for the secretory responses of the gastric mucosa to hormonal or cholinergic stimulation was studied in conscious rats with Heindenhain pouches or Pavlov pouches with the antrum retained or resected. 2. Metiamide almost completely abolished acid secretion induced by pentagastrin without altering significantly the amount of histamine excreted in the urine. Histamine mobilization on pentagastrin infusion determined in vitro, seemed to be larger during H-2-receptor blockade than with pentagastrin alone. 3. CCK-PZ mobilized mucosal histamine to a considerable extent; the secretory response to this hormone was completely abolished by H-2-receptor blockade. 4. Acid secretion in response to 2-deoxy-D-glucose was inhibited by H-2-receptor blockade in the presence or absence of the antrum; however the inhibition was less complete than with hormone-induced secretion. 5. The acid secretory response to 100 mg/kg of 2-deoxy-D-glucose appeared to be less susceptible to H-2-receptor blockade than that of 50-mg/kg of 2-deoxy-D-glucose. 6. Feeding induced a secretory response in the Pavlov pouch which initially was more effectively inhibited by H-2-receptor blockade than the response to 2-deoxy-D-glucose. In the absence of antral gastrin secretion by either stimulus was equally inhibited. 7. Methacholine-induced acid secretion was inhibited by infusion of the H-2-receptor antagonist, an inhibition that was absent when pentagastrin was concomitantly infused. 8. Although acid secretion induced by cholinergic stimuli was readily inhibited by the H-2-receptor antagonist, slight or nor inhibition was noted on pepsin secretion. 9. The role of histamine as a physiological stimulus for the parietal cell is discussed in view of the fact that the secretory effect of natural stimuli, known or demonstrated to mobilize mucosal histamine, is restrained by H-2-receptor blockade.

Animals↗
PubMed1975

Alterations in secretory patterns following antrectomy in rats with Pavlov pouches.

1. In conscious rats provided with Pavlov pouches, with the antrum retained or resected,the gastric secretory response to various stimuli has been studied. Each acid secretory response was related to that obtained with maximal doses of methacholine and histamine in combination, presumed to reflect the maximal secretory capacity of the mucosa. 2. Three weeks after the operation, the maximal acid secretory capacity was 60 percent lower in the antrectomized than in the intact Pavlov pouch rats; the difference was still larger at 6 weeks and 3-5 months, owing to a gradual increase in the rats with the antrum retained. 3. Antrectomy reduced interdigestive secretion of acid to the same degree as the concomitant reduction in maximal secretory capacity. 4. Acid secretion in response to a maximal infusion of pentagastrin was reduced by about 50 percent at 3 and about 65 percent at 6 weeks after antrectomy. No significant difference was, however, noted between the antrectomized and intact rats when the responses were related to the maximal secretory capacity. The dose response curve to pentagastrin revealed a redcued responsiveness to submaximal doses of this agent following antrectomy. 5. The maximal acid secretory response to histamine was reduced after antrectomy, although the sensitivity to submaximal infusions of histamine appeared to be increased. 6. The mean secretroy output to 2-deoxy-D-glucose was reduced by about 65 percent and that to food by about 85 percent following antrectomy. 7. After antrectomy a background infusion of pentagastrin enhanced the secretory responses to 2-deoxy-D-glucose and to food but did not restore the responses to the levels in the intact rats. The feeding responses as related to the maximal secretory capacity were, however, similar in the two groups on infusing pentagastrin in the antrectomized rats. 8. Interdigestive secretion of pepsin was reduced by about 60 percent after antrectomy, while the peak response to 2-deoxy-Dglucose was about twice the interdigestive level in both groups. Pepsin secretion in response to food showed an increased secretion above the interdigestive level of longer duration in the antrectomized than in the intact Pavlov pouch rats. 9. The irreversibily reduced responsiveness of the gastric mucosa after antrectomy is discussed in relation to known morphological and biochemical changes.

Animals↗
PubMed1974

Implication of gastric mucosal histamine in inhibition by isoprenaline of pentagastrin-induced gastric secretion.

1 The effect of isoprenaline on pentagastrin-induced gastric secretion was studied in conscious rats with Heidenhain pouches. The influence of isoprenaline on pentagastrin-induced release and formation of gastric mucosal histamine was also examined.2 Isoprenaline strongly inhibited pentagastrin-induced acid secretion, an inhibition which could not be overcome by increasing the dose of pentagastrin.3 Propranolol blocked the inhibitory effect of isoprenaline on pentagastrin-induced acid secretion.4 Isoprenaline enhanced pepsin secretion induced by pentagastrin, an effect which was blocked by propranolol.5 Isoprenaline reduced the increase in formation and release of gastric mucosal histamine following pentagastrin infusion, an inhibitory influence which was almost completely blocked by propranolol.6 The inhibition by isoprenaline of pentagastrin-induced acid secretion is tentatively related to alterations in gastric mucosal histamine occurring simultaneously.

Adrenergic beta-Antagonists↗
PubMed1974

Histamine metabolism of the gastric mucosa following antrectomy.

1. Histamine metabolism of the gastric mucosa in rats subjected to antrectomy, antrectomy and substitution with pentagastrin and exclusion of the antrum has been investigated employing various in vivo and in vitro methods.2. Mucosal histamine formation after antrectomy fell to about one third, whereas after antrum exclusion histamine formation increased many-fold.3. After antrectomy, mucosal histamine content decreased, and increased after antrum exclusion.4. After total gastrectomy, (a) whole-body histamine formation was reduced to about half, as judged by determining histamine excretion, and (b) pentagastrin infusion did not increase histamine excretion, showing absence of histamine mobilization from extra-gastric sources. In rats with the stomach retained, infusion of pentagastrin induced a dose-dependent increase in histamine excretion.5. Kinetic studies in which [(14)C]histidine was injected and the resulting urinary [(14)C]histamine determined showed that on pentagastrin infusion after antrectomy newly formed histamine was initially mobilized to a larger extent than in the controls.6. Antrectomized rats were subjected to substitution treatment by three injections per day of pentagastrin. After 3 weeks of substitution, histamine excretion was considerably higher than without substitution. After 6 weeks of substitution, histamine excretion was about the same in the substituted antrectomized, non-substituted antrectomized and sham-operated groups. Neither time nor substitution could, however, normalize the excretion of histamine on pentagastrin stimulation after antrectomy.7. In non-substituted antrectomized rats, pentagastrin was less effective in elevating mucosal histamine formation than in the substituted and sham-operated groups.8. The indispensability of the rat in this kind of study is emphasized.

Animals↗
PubMed1974

Alterations in histamine metabolism of rat gastric mucosa following vagotomy.

1. In female rats subjected to truncal vagotomy with pyloroplasty, pyloroplasty alone or sham operation, the behaviour of gastric mucosal histamine was investigated combining in vivo and in vitro methods.2. Following truncal vagotomy with pyloroplasty mucosal histamine formation, determined in vitro, increased about fivefold and histamine content was significantly elevated. The heightened histamine formation was reflected in increased excretion of histamine in the urine.3. On pentagastrin infusion, mucosal histamine formation increased about twofold following vagotomy with pyloroplasty and sevenfold in the sham-operated controls. Histamine content concomitantly fell in both groups to about the same level. These alterations were paralleled by increased excretion of histamine in the urine.4. Kinetic studies in which [(14)C]histidine was injected and the resulting urinary [(14)C]histamine determined, indicated that during the first hour of pentagastrin infusion newly formed histamine was more slowly mobilized following vagotomy with pyloroplasty than in the controls.5. In rats subjected to a pyloroplasty alone, the increase in urinary histamine on pentagastrin infusion was significantly larger than in the sham-operated controls. Kinetic studies indicated that this was due to a larger mobilization of preformed histamine.6. The changes in mucosal histamine metabolism are discussed in relation to the pattern of acid secretion following the actual surgical procedures.

Animals↗
PubMed1973

Mobilization of gastric mucosal histamine and gastric secretion after H2-receptor blockade.

The effects of two H(2)-receptor antagonists (burimamide and metiamide) on the mobilization of gastric mucosal histamine, as shown by its urinary excretion and acid secretion following pentagastrin infusion, were studied in rats provided with Heidenhain pouches. Pentagastrin-induced secretion was completely inhibited without major Alterations in urinary excretion of histamine. These observations can easily be reconciled with the hypothesis that pentagastrin is not a direct stimulant of the parictal cell.

Animals↗
PubMed1973

Alterations in secretory patterns following vagotomy in rats with Pavlov or Heidenhain pouches.

1. In conscious rats provided with Pavlov or Heidenhain pouches, the acid and pepsin secretion in response to feeding and infusion of gastrin was established before and after truncal vagotomy. In Pavlov pouches the responses to 2-deoxy-D-glucose, methacholine and the combination of gastrin and methacholine were also studied.2. Interdigestive secretion of acid and pepsin after vagotomy was decreased in the Pavlov pouch and increased in the Heidenhain pouch.3. The acid response to feeding in the Pavlov pouch was substantially reduced after vagotomy, whereas the secretion of pepsin was only slightly diminished.4. In the Heidenhain pouch after vagotomy, feeding augmented the high interdigestive secretion.5. After vagotomy, the acid dose-response curve to gastrin was shifted to the right in the Pavlov pouch and to the left in the Heidenhain pouch.6. In the Pavlov pouch after vagotomy, the acid response to the highest dose of methacholine employed was significantly enhanced.7. A background infusion of methacholine reestablished in the Pavlov pouch the reduced responsiveness to gastrin following vagotomy.8. Pepsin secretion was stimulated by gastrin in the Heidenhain pouch and after vagotomy in the Pavlov pouch. The stimulatory effect of methacholine on pepsin secretion in the Pavlov pouch was increased after vagotomy.

Animals↗
PubMed1972

Inhibitory and stimulatory effects of secretin on gastric secretion in conscious rats.

1. The effect of pure secretin on gastrin-induced secretion has been studied in conscious rats with Pavlov or Heidenhain pouches.2. Rapid intravenous injection of secretin did not inhibit a plateau secretion of acid in the Heidenhain pouch, but infusion of the same amount of secretin over two hours inhibited secretion in both Heidenhain and Pavlov pouches.3. A rapid intravenous injection of secretin before the onset of gastrin infusion enhanced the acid secretory response to gastrin in both types of pouches.4. Secretin stimulated pepsin secretion.

Animals↗