Ikuo Imamura

Alanyl-glutamine-enriched total parenteral nutrition restores intestinal adaptation after either proximal or distal massive resection in rats

This study was designed to determine whether alanyl glutamine-containing total parental nutrition (TPN) can restore the impaired adaptive process of the remaining intestine, observed with administration of conventional TPN, after massive small-bowel resection. Seventy-four male Sprague-Dawley rats weighing 250 g were randomly divided into seven groups. Group I rats (n = 10) were killed after overnight fasting. Group II animals (n = 32) underwent massive small bowel resection (85%) with preservation of the first 15 cm of jejunum. Group III animals (n = 32) were also submitted to massive small-bowel resection with preservation of 15 cm of terminal ileum. Three different TPN solutions were prepared. Solution A was a conventional formulation that did not contain glutamine. Solution B contained 1.88 times the amino acid concentration of solution A. Solution C was prepared by adding alanyl glutamine (2 g/100 mL) to solution A. Solutions B and C were isonitrogenous and isocaloric. Each solution was infused to groups II and III, which were subdivided into groups IIA (n = 10), IIB (n = 11), IIC (n = 11), IIIA (n = 10), IIIB (n = 11), and IIIC (n = 11). After 1 week of TPN (270 kcal/kg per day), the experimental animals were killed and the intestine was taken for examination. Final body weight did not differ significantly among the groups, and there was no difference in nitrogen balance among the animals that received solution B or C.(ABSTRACT TRUNCATED AT 250 WORDS)

The Dipeptide Alanyl-Glutamine Prevents Intestinal Mucosal Atrophy in Parenterally Fed Rats

This study was performed to determine whether the addition of alanyl-glutamine (Ala-Gln) can prevent intestinal mucosal atrophy induced by standard solution of total parenteral nutrition (S-TPN). Forty-one male Sprague-Dawley rats weighing 250 g were randomly divided into four groups: group I was killed after overnight fasting; group II received S-TPN. The other groups received S-TPN supplemented with amino acids other than glutamine (group III) or supplemented with Ala-Gln 2 g/100 mL (group IV); both solutions were isocaloric and isonitrogenous. After 1 week of TPN the rats were killed, and the duodenum, proximal jejunum, mid-small bowel, and distal ileum were obtained for morphologic and functional analysis. Weight gain did not differ significantly among these four groups, and there was no difference in nitrogen balance between groups III and IV. Serum glutamine in group IV (102.8 +/- 13.3 mumol/dL) was significantly increased (p less than .05) compared with groups I, II, and III (66.2 +/- 3.9, 55.7 +/- 7.8, and 61.3 +/- 10.8 mumol/dL, respectively). Mucosal wet weight, protein, RNA, sucrase, and maltase of group IV were significantly increased (p less than .05) compared with groups II and III. Villus height was significantly increased (p less than .05) in the jejunum of group IV rats compared with groups II and III, but not in any other segments of the intestine. No significant changes were observed in crypt depth among all groups. Diamine oxidase in groups II, III, and IV was significantly decreased (p less than .05) compared with group I in all segments except for the ileum.(ABSTRACT TRUNCATED AT 250 WORDS)

Effects of Capsaicin Desensitization on Nasal Allergy-like Symptoms and Histamine Release in the Nose Induced by Toluene Diisocyanate in Guinea Pigs

Intranasal application of toluene diisocyanate (TDI) induced nasal allergy-like symptoms of sneezing and watery rhinorrhea and decreased the histamine content of the nasal mucosa in guinea pigs. However, in the animals pretreated with capsaicin (capsaicin desensitization) before sensitization with TDI, nasal allergy-like symptoms were not induced. Capsaicin desensitization also inhibited histamine release in the nasal mucosa induced by TDI. These findings suggest that antidromic impulses of capsaicin-sensitive sensory nerves stimulated by TDI cause histamine release from mast cells in the nasal mucosa, resulting in nasal discharge and sneezing in guinea pigs. Thus neurogenic inflammation via an axon reflex in the nose may contribute to the pathogenesis of vasomotor rhinitis.

Histamine content, synthesis and degradation in nasal mucosa and lung of guinea‐pigs treated with toluene diisocyanate (TDI)

We have reported the presence of a histamine synthesizing enzyme, histidine decarboxylase (HDC), and histamine degrading enzymes, histamine N‐methyltransferase (HMT) and histaminase (diamine oxidase, DAO) in human nasal mucosa and the histamine content of the mucosa. In this study, we demonstrate the influences of the toluene diisocyanate (TDI) treatment on the histamine content and these enzyme activities in guinea‐pigs as an animal model of respiratory hypersensitivity. Application of TDI to the nasal vestibuli induced intense nasal allergy‐like and mild asthma‐like responses in TDI‐sensitized guinea pigs. Increases in the histamine content and HDC and HMT activities were observed in the nasal mueosa and lung of TDI‐sensitized guinea pigs. No apparent changes in the histaminase activities were observed in either the nasal mucosa or the lung. These data suggest that the turnover rate of histamine is increased in the nasal mucosa and the lung of guinea pigs with respiratory hypersensitivity.

Histamine content, synthesis and degradation in human nasal mucosa

Histamine content and enzyme activities of histamine metabolism, histidine decarboxy‐lase (HDC), histamine N‐methyltransferase (HMT) and histaminase (diamine oxidase, DAO) in human nasal mucosa were determined with a highly sensitive and specific fluorescent method which was combined with high performance liquid chromatography. Histamine content and HDC activity were determined in 10 specimens of nasal polyp, nine specimens of maxillary sinus and five specimens of inferior turbinate. HMT and histaminase activities were determined in 15 specimens of nasal polyp, nine specimens of maxillary sinus and five specimens of inferior turbinate obtained during surgical therapy. Histamine and activities of HDC, HMT and histaminase were detected in all specimens except the case of histaminase activity in one specimen of nasal polyp. The mean values of histamine content and activities of HDC, HMT and histaminase of human nasal mucosa were 137.3 nmol/g wet weight, 26.3 fmol/min/mg protein, 26.4 pmol/min/mg protein and 0.5 pmol/min/mg protein, respectively. Histamine content in the mucosal tissue of the maxillary sinuses was significantly higher than that of nasal polyps or inferior turbinates. There were no significant differences in HDC activities among three kinds of nasal mucosa. Activities of HMT and histaminase, including their kinetic constants (Km and Vmax values for histamine) indicated that HMT has a greater potential than histaminase for histamine degradation in the human nasal mucosa. The presence of these enzymes suggests that these activities constitute an important modulating factor in histamine mediated allergic and inflammatory reactions in human nasal mucosa.

Effect of cholecystokinin receptor antagonists, MK-329 and L-365,260, on cholecystokinin-induced acid secretion and histidine decarboxylase activity in the rat

To elucidate the regulatory mechanism of acid secretion by cholecystokinin (CCK) in vivo, we compared the effects of CCK and gastrin on acid secretion and histidine decarboxylase (HDC) activity. We also examined the effects of MK-329, a specific antagonist for pancreatic-type CCK receptor, and L-365,260, a specific antagonist for gastrin-type CCK receptor, on the action of CCK. Graded doses of CCK or gastrin were intravenously infused into conscious rats with gastric fistula. Gastrin-17 I infusion up to 10 nmol/kg/h resulted in dose-related increases in acid secretion. CCK-8 infusion also caused an increase in acid secretion. However, it reached a peak with 0.3 nmol/kg/h CCK-8 and attenuated with higher concentrations of CCK-8. This attenuating effect of a higher dose of CCK was reversed by MK-329, but not by L-365,260. Both CCK and gastrin were potent in increasing fundic HDC activity, and the effect of CCK on HDC activity was significantly inhibited by L-365,260, but not by MK-329. Taken together, the present study suggests that CCK and gastrin stimulate histamine formation via a gastrin-type CCK receptor, and the attenuating action of CCK with higher concentrations on acid secretion in vivo is mediated by a pancreatic-type CCK receptor.

Molecular cloning of guinea-pig aromatic-L-amino acid decarboxylase cDNA.

Guinea-pig aromatic-L-amino acid decarboxylase (DOPA decarboxylase, DDC), but not rat DDC, reacts with the antibody against rat histidine decarboxylase (HDC). For determination of the molecular reaction for this cross-reactivity, a cDNA clone of guinea-pig DDC was isolated. Guinea-pig DDC consists of 480 amino acids and its molecular weight is 54,148. The sequence identify of guinea-pig DDC with rat DDC is 86%. Guinea-pig DDC has a region showing 100% sequence identity with rat HDC, but only 67% sequence identity with rat DDC, suggesting that this region is related with the cross-reactivity of guinea-pig DDC and anti-rat HDC antibody.

Marked increase in gastric histidine decarboxylase activity in patients with hypergastrinemia

Histidine decarboxylase (HDC) activity and histamine content were measured in endoscopic gastric biopsy specimens of 19 control subjects with normogastrinemia and 6 patients with hypergastrinemia. In controls, the HDC activity was 3 fold higher in fundic mucosa (120 +/- 13 fmol/min/mg protein, mean +/- S.E.) than in antral mucosa (39 +/- 5 fmol/min/mg protein). In patients with hypergastrinemia, an extremely high HDC activity (713 +/- 181 fmol/min/mg protein) was observed in fundic mucosa, although the HDC activity in antral mucosa was not significantly different from that of controls. The histamine content in fundic mucosa was also significantly higher in patients with hypergastrinemia than in controls but no significant difference was seen in histamine content in antral mucosa between the two groups. These results are compatible with the hypothesis that in man, as well as in rat, histamine synthesis in fundic mucosa is enhanced by gastrin.

High-performance liquid chromatographic determination of histamine N-methyltransferase activity

A method for the determination of histamine N-methyltransferase (HMT) activity by high-performance liquid chromatography based on post-column derivatization with omicron-phthalaldehyde is described. The determination involves the separation of the substrate, histamine, from its product. N tau-methylhistamine, using a weak cation exchanger, followed by on-line derivatization of these imidazoleamines with omicron-phthalaldehyde and their detection and quantitation with a fluorimetric detector. This assay method is suitable for the measurement of HMT activity during enzyme purification.

Determination of histidine decarboxylase mRNA in various rat tissues by the polymerase chain reaction

Histidine decarboxylase (HDC) mRNA in various rat tissues were quantitated by using a reverse transcription-polymerase chain reaction (RT-PCR) in which a mouse mRNA was used as an internal standard. The stomach HDC mRNA level was the highest followed by the brain, skin, jejunum, spleen and liver. There was no measurable HDC mRNA in the kidney. The stomach HDC activity was also the highest followed by the brain, skin, spleen, jejunum, liver and kidney. A significant correlation (r = 0.940,p < 0.0001) was observed between the HDC mRNA levels and HDC activities in these tissues. We have also examined the HDC mRNA levels in fasting rats and found that HDC mRNA levels in the stomach were reduced after the 48-hr-fasting with the decrease in HDC activities. These observations indicate that there may exist a gene regulation, at least at the basal level, for the HDC activities in the rats.