Naoto Kawakita

Inhibitory Effect of Dopamine on Gastric Motility in Rats

BACKGROUND There is disagreement with regard to the involvement of dopamine (DA) receptors in gastric motility. The mechanisms of the inhibitory effect of DA on rat gastric motility was investigated in association with acetylcholine (Ach) release in the present study. METHODS In vivo vagotomized, splanchnicectomized rats and control rats were used, and gastric movement was determined as the gastric motility index after DA administration. In vitro study of Ach release from the circular muscle strips of the gastric corpus was investigated after administration of domperidone, SCH23390, phentolamine, or propranolol. RESULTS In the in vivo study DA inhibited gastric motility in a dose-dependent manner. Vagotomy and splanchnicectomy had no effect on the inhibitory effect of DA. In vitro study DA inhibited [3H]-Ach release in a dose-dependent manner. The inhibitory effect of DA was antagonized by domperidone but not by phentolamine, propranolol, or SCH23390. CONCLUSIONS Inhibition of gastric motility by dopamine is independent of extrinsic innervation and seems to be mediated by DA2 receptors in the gastric wall.

Ultrastructural localization of protein kinase C β-subspecies in the axon terminal of rat neuromuscular junction

Ultrastructural localization of protein kinase C (PKC) beta-subspecies in neuromuscular junctions of the rat lumbrical muscle was investigated by the immunoperoxidase and immunofluorescence methods. By light microscopy, PKC beta-like immunoreactivity (PKC beta-LIR) was found in the axon terminal expansions as well as in the preterminal axons. By confocal laser scanning microscopy, the staining for PKC beta-like immunoreactivity was more intense in the presynaptic regions just in contact with the acetylcholine receptor stained by FITC-alpha-bungarotoxin. By electron microscopy, PKC beta-like immunoreactivity was distributed non-uniformly in the terminal expansions. In the terminal expansions, PKC beta-like immunoreactivity was accumulated in the presynaptic regions in contact with the post-synaptic folds. This accumulation was approximately 0.1-0.2 microns in diameter, which comprised a part of the presynaptic plasma membrane and a group of synaptic vesicles adjacent to it. Weak immunoreactivity was also found diffusely in the axoplasmic matrix. The discrete presynaptic accumulation of PKC beta-subspecies may represent the strategical localization specialized for the effective regulation of neurotransmitter release.

The effect of dopamine on rat gastric motility.

SummaryThe inhibitory mechanism of dopamine (DA) on rat gastric motility was investigated in association with DA receptors. Gastric movement was assessed according to the method of Jacoby et al and was expressed with the system of Ludwick et al. (1968). DA inhibited gastric movement in both the corpus and antrum in a dose-dependent manner. Domperidone, a specific antagonist of DA2 receptor, suppressed DA-induced inhibition of gastric movement in a dose-dependent manner. SCH23390, a specific antagonist of DA1 receptor did not affect DA-induced inhibition of gastric movement. LY171555, a specific agonist of DA2 receptor, inhibited gastric movement in both the corpus and antrum in a dose-dependent manner. SKF38393, a specific agonist of DA1 receptor, did not affect gastric movement. These results indicate that DA plays an important role in the inhibitory regulation of gastric motility, through DA2 receptor but not DA1 receptor.

Protein kinase C ?-, ?- and y-subspecies in basal granulated cells of rat duodenal mucosa

Protein kinase C [cPKC: α, β (βI βII), γ], a Ca2+- and phospholipid-dependent enzyme, has been thought to play a critical role in the synthesis and secretion of gut hormones in gastrointestinal mucosa. However, the localization of PKC has not yet been clarified at the cellular level in the gastrointestinal epithelium. The present study was made to identify cPKC-containing cells immunohistochemically in the rat duodenal epithelium by light and electron microscopy and by confocal laser scanning microscopy. Special attention was paid to the demonstration of cPKC in basal granulated cells. By light microscopy, some duodenal epithelial cells were demonstrated to be immunopositive for PKC α-, β- and γ-subspecies. Their distribution and incidence were almost similar to those of cells stained by the silver impregnation method of Grimelius. By electron microscopy, profiles of secretory granules were found at the basal region of the PKC-immunopositive epithelial cells. When the cells were double-immunostained for gastrin, serotonin or somatostatin and for PKC α-, β- or γ-subspecies, these gut hormones and PKC subspecies were shown to colocalize as examined by confocal laser scanning microscopy. These findings show that cPKC (α, β, γ) is present in basal granulated cells such as G-, EC- and D-cells, presumably playing some important role in regulation of gut hormones, including their synthesis and/or secretion.

Protein kinase C (α, β, γ) in Pacinian corpuscle

Immunocytochemical demonstration of protein kinase C (PKC) subspecies (α, β, γ) was carried out in Pacinian corpuscles of rat hind feet using monoclonal or polyclonal antibodies against each of these subspecies. The inner core cells and lamellae and the Schwann cell cytoplasm of the nerve fiber innervating the corpuscle were strongly positive for PKC α-immunoreactivity (IR). In contrast, the axon terminal and the outer core did not display any positive α-IR. Very weak PKC β-IR was detected in the ultraterminal region of the axon terminal, while the trunk region showed no immunoreactivity. Very faint PKC β-IR was found also in the lamellar cells located at the periphery of the inner core and the endoneurial fibroblasts in the intermediate layer. PKC γ-IR was not detected in any part of the corpuscle. The strong PKC α-IR in the inner core and the presence of absence of PKC α-, β-, and γ-IR in the axon terminal are discussed from the point of view of the functional aspects of each part.Immunocytochemical demonstration of protein kinase C (PKC) subspecies (alpha, beta, gamma) was carried out in Pacinian corpuscles of rat hind feet using monoclonal or polyclonal antibodies against each of these subspecies. The inner core cells and lamellae and the Schwann cell cytoplasm of the nerve fiber innervating the corpuscle were strongly positive for PKC alpha-immunoreactivity (IR). In contrast, the axon terminal and the outer core did not display any positive alpha-IR. Very weak PKC beta-IR was detected in the ultraterminal region of the axon terminal, while the trunk region showed no immunoreactivity. Very faint PKC beta-IR was found also in the lamellar cells located at the periphery of the inner core and the endoneurial fibroblasts in the intermediate layer. PKC gamma-IR was not detected in any part of the corpuscle. The strong PKC alpha-IR in the inner core and the presence or absence of PKC alpha-, beta-, and gamma-IR in the axon terminal are discussed from the point of view of the functional aspects of each part.

Impaired response of gastric vessels to prostaglandin E2 in rats with persistent obstructive jaundice

We investigated the response of gastric vessels to prostaglandin (PG) E2 after intra-duodenal release of bile in rats with obstructive jaundice. The animals were divided into four groups according to duration of bile duct obstruction (BDO): control and 1 week (W), 2W, and 3W groups. Prolonged BDO decreased gastric mucosal blood flow (BF) significantly. The BF recovered after the release of BDO in the 1W and 2W groups, but not in the 3W group. BDO decreased PGE2 content in gastric mucosa in the 1W, 2W, and 3W groups. PGE2 decreased vascular perfusion pressure of the isolated stomach in the control and 2W groups, but not in the 3W group. The response of gastric vessels to PGE2 was poor in the 3W group compared with the control and 2W groups. Decreased PGE2 in the gastric mucosa and decreased response of gastric vessels to PGE2 may affect gastric blood flow in obstructive jaundice.

Immunohistochemical study of dopamine in rat gastric mucosa with acute gastric ulcer

Recent studies have shown the presence of dopamine (DA) in gastric and duodenal mucosa, and changes in gastric mucosal DA content have been observed in patient with acute ulcers. Immunohistochemical demonstration of the distribution of DA in gastric mucosa under stress was studied by light and electron microscopy. In the control group, DA was present in the gastric gland proper in the gastric corpus and antrum on light microscopy, and on the surface of mucous granules in chief cells, mucous neck cells, and surface epithelium on electron microscopy. In the stress group, DA in gastric mucosa was almost undetectable on light and electron microscopy. Further, in this group serum DA concentration was significantly higher in the portal vein than in the abdominal aorta. Endogenous DA in gastric mucosal cells may affect gastric mucosa differently from exogenous DA, and stress may release endogenous intracellular DA into extracellular spaces.

An immunohistochemical study of glucagonoma conducted on the metastatic lymph nodes from a patient with recurrent metastatic glucagonoma: report of a case

In this report, we briefly present the case of a 67-year-old woman who developed recurrent glucagonoma with lymph node metastasis. An immunohistochemical study of the metastatic tumor revealed immunoreactivity of glucagon and protein kinase C (PKC)-α, -β, and -γ in the tumor cells, two types of which were seen by electron microscopy. One type had abundant secretory granules and mitochondria, while the other had few granules and mitochondria. Some granules were similar to typical A cell granules and others were atypical. An immunoelectron microscopic demonstration revealed PKC-α, -β, and -γ immunostaining in the cytoplasm of all the tumor cells, while some secretory granules had PKC immunostaining, and others had no immunostaining. Thus, it appears that metastatic glucagonoma and its associated granules are composed of two types of mature and immature cells or granules. As immunoreactivity of PKC-α and -γ was found in the tumor cells, but not in the normal A cells of the islets of Langerhans, the PKC subspecies α and γ, which are not present in normal pancreatic A cells, may exist in human glucagonoma cells.

Studies on 7 cases of acute mesenteric arterial occlusive disease.

当科にて経験した急性腸間膜動脈閉塞症7例を対象とし, 臨床的特徴, 予後に影響する因子などについて検討した.平均年齢は68.3歳, 全例に循環器系疾患などの併存を認めた.アシドーシスを5例 (71.2%), 白血球増多を4例 (57.1%) に認めた.全例に小腸広範囲切除を施行し, 4例 (57.1%) が直死した.直死例の平均年齢は75.8歳と高く, また発症より手術までの平均時間は78時間で, 生存例の16時間に比べて長い傾向を示した.白血球増多例の75.0%が直死したのに対して, 白血球正常例の直死は33.3%のみであった.直死4例のうち3例は, 術後再度の血行障害によると思われる縫合不全や消化管穿孔を契機として死亡した.本症の予後を向上させるためには, 術後の腸管壊死を避けるために種極的な腸切除が必要であるが, それ以前に血管造影などを駆使した早期診断が重要と思われた.

CLINICOPATHOLOGICAL AND IMMUNOHISTOLOGICAL STUDIES AND PROGNOSIS OF PRIMARY MALIGNANT LYMPHOMA OF THE SMALL INTESTINE

切除した小腸原発性悪性リンパ腫5例を対象に, 臨床病理学, 免疫組織学的検討を行った. 性別は4: 1, 手術時平均年齢は62.2歳, 病悩期間は平均3.3か月であった. 臨床症状は腹痛を全例に認めたが, 悪性リンパ腫に特異的な症状はなかった. 発生部位は空腸1例, 回腸4例, 肉眼型は潰瘍型3例, 動脈瘤型2例で, 腫瘍径は全例4cm以上 (平均8.0cm) と大きく, 多発症例は2例あった. 免疫組織学的検索では全例B細胞由来リンパ腫で, このうち, 2例に腫瘍細胞質内に免疫グロブリン局在を認め, 1例はIgGλ 型, 1例はIgMλ 型であった. 腫瘍径と予後の関連性は見出せなかったが, 深達度, リンパ節転移, 進行度との関連性は示唆できた.