Peripheral urocortin delays gastric emptying: role of CRF receptor 2

Urocortin, a new mammalian member of the corticotropin-releasing factor (CRF) family has been proposed to be the endogenous ligand for CRF receptor 2 (CRF-R2). We studied the influence of intravenous urocortin on gastric emptying and the role of CRF-R2 in peptide action and postoperative gastric ileus in conscious rats. The intravenous doses of rat CRF and rat urocortin producing 50% inhibition of gastric emptying were 2.5 and 1.1 microgram/kg, respectively. At these intravenous doses, CRF and urocortin have their actions fully reversed by the CRF-R1/CRF-R2 antagonist astressin at antagonist/agonist ratios of 5:1 and 67:1, respectively. Astressin (12 microgram/kg iv) completely prevented abdominal surgery-induced 54% inhibition of gastric emptying 3 h after surgery while having no effect on basal gastric emptying. The selective nonpeptide CRF-R1 antagonists antalarmin (20 mg/kg ip) and NBI-27914 (400 microgram/kg iv) did not influence intravenous CRF-, urocortin- or surgery-induced gastric stasis. These results as well as earlier ones showing that alpha-helical CRF9-41 (a CRF-R2 more selective antagonist) partly prevented postoperative ileus indicate that peripheral CRF-R2 may be primarily involved in intravenous urocortin-, CRF-, and abdominal surgery-induced gastric stasis.

Effects of ranitidine on gastric vesicles containing H+,K(+)-adenosine triphosphatase in rats

BACKGROUND

To ascertain the mechanism for rebound acid hypersecretion after treatment with an H2-receptor blocker, we investigated the effects of ranitidine on gastric H+,K(+)-adenosine triphosphatase (ATPase) in rats.

METHODS

Male Wistar rats received ranitidine (1-50 mg/kg body weight intraperitoneally twice a day for 5 days). The rats were starved for 15 h after the last treatment and then killed, and gastric vesicles containing H+,K(+)-ATPase were prepared.

RESULTS

Treatment with ranitidine dose-dependently increased protein content in the gastric vesicular fraction purified from the gastric mucosa without changing total protein content. Ranitidine also increased the content of a 94,000-dalton protein, the catalytic subunit of H+,K(+)-ATPase. On the other hand, ranitidine did not affect the specific activity of the enzyme (mumol/min/mg of the gastric vesicular protein). Since gastric vesicles in the fasting state mainly consist of the tubulovesicular membrane, these results suggest that ranidine administration increases total tubulovesicular H+,K(+)-ATPase content (mumol/min/rat) by increasing the number of tubulovesicles per parietal cell. The ranitidine-induced increase in total tubulovesicular H+,K(+)-ATPase activity was still evident 1 week after treatment and returned to control level 1 month later.

CONCLUSIONS

All these findings suggest that the increased content and total activity of tubulovesicular H+,K(+)-ATPase after ranitidine treatment may contribute to the mechanism for acid rebound after H2-blocker therapy.

Peripheral corticotropin-releasing factor (CRF) induces stimulation of gastric contractions in freely moving conscious rats: role of CRF receptor types 1 and 2

BACKGROUND

Peripheral corticotrophin-releasing factor (CRF) plays an important role in stress-induced alterations of gastrointestinal motility. CRF injected peripherally inhibits gastric emptying, but its effect on gastric contractions has not been clarified in freely moving conscious rats.

METHODS

Intraluminal gastric pressure waves were measured in freely moving conscious non-fasted rats using the perfused manometric method. We assessed the area under the manometric trace as the motor index (MI), and compared this result with those obtained 1 h before and after drug administration.

KEY RESULTS

Subcutaneous injection (sc) of CRF (15 μg kg(-1)) increased the MI significantly. Pretreatment with intravenous astressin (100 μg kg(-1)), a non-selective CRF antagonist, blocked the sc CRF (15 μg kg(-1))-induced response, but astressin(2)-B (200 μg kg(-1), sc), a selective CRF receptor type 2 (CRF(2)) antagonist, enhanced the CRF-induced increase in MI significantly. Meanwhile urocortin 2 (15 μg kg(-1), sc), a selective CRF(2) agonist, did not alter the basal MI, but it inhibited the sc CRF (15 μg kg(-1))-induced stimulation of gastric contractions. The intraperitoneal injection of cortagine (30 μg kg(-1)), a selective CRF receptor type 1 (CRF(1)) agonist, mimicked the response induced by sc CRF.

CONCLUSIONS & INFERENCES

Peripheral CRF stimulates gastric contractions through CRF(1). CRF(2) activation inhibits the response induced by CRF, suggesting that CRF(2) may have a modulatory action to CRF(1) signaling in gastric motor activity.

Effect of immobilization stress on in vitro and in vivo thermogenesis of brown adipose tissue

Repetitive intermittent stress such as immobilization has been shown to induce an improved cold tolerance through an enhanced capacity of nonshivering thermogenesis (NST), causing positive cross adaptation between nonthermal stress and cold. In the present study, effect of 3-h-daily immobilization stress for 4-5 weeks was investigated on in vitro and in vivo thermogenesis of interscapular brown adipose tissue (BAT). In vitro thermogenesis was measured in the minced tissue blocks incubated in Krebs-Ringer phosphate buffer with glucose and albumin at 37 degrees C, using a Clark-type oxygen electrode. The stressed rats showed less body weight gain during the experiment. The BAT weight, its protein and DNA contents were significantly greater in the stressed rats. Basal, noradrenaline- and glucagon-stimulated oxygen consumptions were significantly greater in the stressed rats. In vivo thermogenesis was assessed by the changes of temperatures in colon (Tcol), BAT (TBAT), and tail skin (Tsk) induced by noradrenaline or glucagon infusion in the anesthetized rats. Noradrenaline and glucagon increased the TBAT and the extent of increase was greater in the stressed rats. These results indicate that cross adaptation between nonthermal stress and cold may be mediated through an enhanced thermogenic activity of BAT.

Frozen-section services by telepathology: experience of 100 cases in the San-in District, Japan

The early experience is reported here of the use of intra-operative frozen-section service by telepathology using the integrated Service Digital Network (ISDN), a commercially available system that is being connected between the Department of Pathology of Tottori University and Matsue City Hospital, a distance of 30 km. The transfer rate is currently 64 kbit/s. The frozen-section service was conducted for a total of 117 tissue specimens (organs) from 100 patients between August 1993 and May 1995. The average time taken for examination of each specimen of frozen section was 13 min, ranging between 2 and 42 min. The average number of transmitted images was 6.2. Six cases necessitated more than 11 transmitted images to make a diagnosis, while 13 cases could be diagnosed from two images only. Correct and permissible diagnoses were obtained in 109 (93.2%) out of 117 specimens when comparing the telepathology diagnosis with that of direct microscopy. Improper or misdiagnosis was made for eight cases (specimens), which were misinterpreted as papillary carcinoma in Basedow's disease, adenoma and hyperplasia in two pheochromocytomas, solid-tubular carcinoma in phyllodes tumor, mastopathy in invasive carcinoma, metastatic carcinoma in astrocytoma, follicular lymphoma in reactive hyperplasia, and lymphadenitis in follicular lymphoma. In retrospect, diagnosis of these cases should have been deferred. From the results, it was concluded that the intraoperative frozen-section service by telepathology may be a worthwhile substitute for hospitals with limited accessibility to local pathology service, in spite of pitfalls in some cases. Well prepared, high-quality frozen section, sufficient verbal communication with surgeons, and a rather conservative attitude on the part of a well-trained pathologist seem to be the essential ingredients for reaching an accurate decision when using telepathology.

Malignant intestinal schwannoma: a case report and a review of the literature in Japan

We report the rare case of malignant intestinal schwannoma, not accompanied with von Recklinghausen's disease. The main tumor was located in the ileum with multiple small tumors observed on the peritoneum. Histologically the tumor was composed of spindle cells exhibiting a nuclear palisading formation and abnormal mitotic figures were observed. The tumor was immunohistochemically positive for S-100 protein, glial fibrillary acidic protein, vimentin and neuron-specific enolase, but negative for desmin. Electron microscopically the tumor cell exhibited morphological findings characteristic of schwann cell differentiation. On the basis of these results, the tumor was diagnosed as malignant schwannoma occurring in the ileum.

Modulatory effects of the GABAergic basal ganglia neurons on the PPN and the muscle tone inhibitory system in cats

Pedunculopontine tegmental nucleus (PPN) contributes to the control muscle tone by modulating the activities of pontomedullary reticulospinal systems during wakefulness and rapid eye movement (REM) sleep. The PPN receives GABAergic projection from the substantia nigra pars reticulata (SNr), an output nucleus of the basal ganglia. Here we examined how GABAergic SNr-PPN projection controls the activity of the pontomedullary reticulospinal tract that constitutes muscle tone inhibitory system. Intracellular recording was made from 121 motoneurons in the lumbosacral segments in decerebrate cats (n=14). Short train pulses of stimuli (3 pulses with 5 ms intervals, 10-40 mA) applied to the PPN, where cholinergic neurons were densely distributed, evoked eye movements toward to the contralateral direction and bilaterally suppressed extensor muscle activities. The identical PPN stimulation induced IPSPs, which had a peak latency of 40-50 ms with a duration of 40-50 ms, in extensor and flexor motoneurons. The late-latency IPSPs were mediated by chloride ions. Microinjection of atropine sulfate (20 mM, 0.25 ml) into the pontine reticular formation (PRF) reduced the amplitude of the IPSPs. Although conditioning stimuli applied to the SNr (40-60 mA and 100 Hz) alone did not induce any postsynaptic effects on motoneurons, it reduced the amplitude of the PPN-induced IPSPs. Subsequent injection of bicuculline (5 mM, 0.25 ml) into the PPN blocked the SNr effects. Microinjections of NMDA (5 mM, 0.25 ml) and muscimol (5 mM, 0.25 ml) into the SNr reduced and increased the amplitude of the PPN-induced IPSPs, respectively. These results suggest that GABAergic basal ganglia output controls postural muscle tone by modulating the activity of cholinergic PPN neurons which activate the muscle tone inhibitory system. The SNr-PPN projection may contribute to not only control of muscle tone during movements in wakefulness but also modulation of muscular atonia of REM sleep. Dysfunction of the SNr-PPN projection may therefore be involved in sleep disturbances in basal ganglia disorders.

Water avoidance stress induces visceral hyposensitivity through peripheral corticotropin releasing factor receptor type 2 and central dopamine D2 receptor in rats

BACKGROUND

Water avoidance stress (WAS) is reported to induce functional changes in visceral sensory function in rodents, but the results which have been demonstrated so far are not consistent, i.e., hypersensitivity or hyposensitivity. We determined the effect of WAS on visceral sensation and evaluated the mechanisms of the action.

METHODS

Visceral sensation was assessed by abdominal muscle contractions induced by colonic balloon distention, i.e., visceromotor response (VMR), measured electrophysiologically in conscious rats. The electromyogram electrodes were acutely implanted under anesthesia on the day of the experiment. The threshold of VMR was measured before and after WAS for 1 h. To explore the mechanisms of WAS-induced response, drugs were administered 10 min prior to the initiation of WAS.

KEY RESULTS

WAS significantly increased the threshold of VMR, and this effect was no longer detected at 24 h after. Intraperitoneal injection of astressin2 -B (200 μg/kg), a corticotropin releasing factor (CRF) receptor type 2 antagonist abolished the response by WAS. Subcutaneous (sc) injection of sulpiride (200 mg/kg), a dopamine D2 receptor antagonist blocked the response, while sc domperidone (10 mg/kg), a peripheral dopamine D2 receptor antagonist did not alter it. Naloxone (1 mg/kg, sc), an opioid antagonist did not modify it either.

CONCLUSIONS & INFERENCES

WAS induced visceral hyposensitivity through peripheral CRF receptor type 2 and central dopamine D2 receptor, but not through opioid pathways. As altered pain inhibitory system was reported to be observed in the patients with irritable bowel syndrome, CRF and dopamine signaling might contribute to the pathophysiology.

[Distribution of lithium and its effects on electrolyte and norepinephrine metabolism in discrete areas of the rat brain]

Lithium carbonate (Li2CO3) or lithium chloride (LiCl) was administered to rats, and distribution in discrete areas of the brain as well as the effects on electrolytes in the urine, blood and whole brain were investigated. Further, the effects of Li with or without methamphetamine on electrolytes and norepinephrine (NE) metabolism in discrete areas of rat brain were examined. After a single administration of Li2CO3 (2.7 mEq/kg p.o.), the Li concentration in all regions of the brain except the hypothalamus reached the maximum level at 12 hr and decreased gradually. A relatively high concentration was observed in the hypothalamus, a short time after the administration. After repeated administration of Li2Co3 (2.7 mEq/kg/day for 5 or days p.o.), the Li concentration did not increase in any region of the brain in comparison with after a single administration and there were no marked changes in the balance of electrolytes in the plasma and brain despite significant changes in the urinary electrolytes and urine volume. Acute administration of LiCl (2.4 mEq/kg and 1.2 mEq/kgx2 for 2 hr i.p.) did not affect the levels of NE and its metabolites in any region of the brain. Subacute administration of LiCl (2.5mEq/kg X 2/day for 4.5 days i.p.) concomitant with methamphetamine increased the deaminated metabolites of NE in the hypothalamus and hippocampus, whereas no influence was observed on the concentrations of sodium and potassium in any region of the brain. From these results, it is suggested that the hypothalamus is one area where Li exerts its action.

Undifferentiated carcinoma in the cardioesophageal junction which produces parathyroid hormone related protein

A 68-year-old man with undifferentiated carcinoma occurring in the cardioesophageal junction accompanied by hypercalcemia is reported. The serum level of parathyroid hormone-related protein (PTHrP) was remarkably elevated. Serum calcium and PTHrP levels decreased following chemotherapy, but this amelioration was temporary. He died of hypercalcemia. On autopsy, a significant amount of immunoreactive PTHrP was detected in the tumor tissue extract, and the tumor cells were stained strongly positive for PTHrP by immunohistochemistry. This is the first case of undifferentiated carcinoma in the gastrointestinal tract which demonstrated hypercalcemia due to PTHrP produced by the malignant tumor.

Effects of chronic administration of noradrenaline and glucagon on in vitro brown adipose tissue thermogenesis

The in vitro brown adipose tissue (BAT) oxygen consumption stimulated by noradrenaline (NA) or glucagon (G) was significantly lower in chronically NA-treated rats and that of G-treated rats did not differ as compared with that of vehicle-treated control animals. In vitro thermogenic response of BAT in NA-treated rats was consistent with that induced by cold acclimation.

[Effects of lithium chloride administered in combination with methamphetamine or a reserpine- like drug on brain norepinephrine and dopamine metabolism in rats]

Lithium chloride (LiCl) was injected acutely (2.4 mEq/kg, i.p.) or subacutely (2.5 mEq/kg X 2/day for 4.5 days, i.p.) in rats treated concurrently with methamphetamine (MAPT) or a reserpine-like drug (Ro4-1284), and effects of LiCl on behavior as well as metabolism of brain norepinephrine (NE) and dopamine (DA) were investigated. Acute administration of LiCl suppressed the MAPT-induced hyper-locomotor activity but did not affect the Ro4-1284-induced behavioral depression. LiCl administered subacutely increased the MAPT-induced stereotyped behavior, and it reduced the Ro4-1284-induced initial transient excitation in spontaneous locomotor activity and tended to facilitate the recovery from behavioral depression. As for NE and DA metabolism, LiCl administered subacutely inhibited the MAPT-induced decrease of the deaminated NE metabolites and Ro4-1284-induced decrease of DA metabolism and the Ro4-1284-induced alterations in NE metabolism. From these results, it is likely that the inhibitory effect of LiCl on the MAPT and Ro-1284-induced changes in NE and DA metabolism may to some extent be involved in the therapeutic effects on manic-depressive illness.

[Pharmacokinetics and general pharmacological actions of lithium salts administered singly or repeatedly]

Absorption, distribution and excretion after oral administration of lithium carbonate (Li2CO3) and/or lithium chloride (LiCl) were studied in Wistar rats and beagle dogs. The maximum level of concentration in the blood was seen within 4 hr after administration of Li2CO3, and a greater part of the orally dosed Li2CO3 was excreted into the urine. The blood and urine Li levels after the administration of LiCl were similar to those seen with Li2CO3. In dogs, Li2CO3 was more slowly excreted into the urine than it was in rats. Li was selectively incorporated into the thyroid and pituitary a short time after administration, and was not detected in any organ 7 days after cessation of repeated dosing for 19 days. The movement of Li into the brain was slow and relatively low levels were achieved after a single administration, but high and constant levels were shown after repeated administration. Effects of Li salts on behavior of ddy mice with repeated administration were investigated. The spontaneous motor activity was suppressed with Li2CO3 more strongly than with LiCl. The high dose of Li2CO3 suppressed not only the stimulating actions of methamphetamine and cocaine, but the ptotic and hypothermic action of reserpine. From these results, it is concluded that the repeated administration of Li salts reveals higher levels of Li ion in the brain than does a single administration, and also more responsive action on the central nervous system.

[Effects of methamphetamine and a reserpine-like drug on norepinephrine and dopamine metabolism in the rat brain]

Simple and sensitive methods for the separation and determination of catecholamines and their metabolites by thinlayer microcrystalline cellulose chromatography have been developed and applied to the analysis of norepinephrine (NE) and dopamine (DA) metabolism in the brain of Wistar rats given 12C-NE or 14C-DA intraventricularly. 14C-DA in the whole brain declined more rapidly than did 14C-NE. The percentage of unchanged 14C-NE in total radioactivity in the brain of rats administered 14C-NI was high, while on the other hand, the percentage of unchanged 14C-DA in cases of 14C-DA was low. In the metabolism of 14C-DA, the deaminated and O-methylated deaminated metabolites showed transient and delayed temporary rises, respectively. Drugs which affect the metabolism of catecholamines were also examined. Methamphetamine reduced NE, deaminated and O-methylated deaminated metabolites, and markedly elevated normetanephrine in the brain of rats given 14C-NE. Regarding the metabolism of DA, methamphetamine increased 3-methoxytyramine and homovanillic acid and reduced deaminated metabolites, but had no effect on DA and NE. On the other hand, a reserpine-like drug (Ro4-1284) reduced NE and increased deaminated and O-methylated deaminated metabolites in the metabolism of NE, and reduced to a great extent DA and NE and increased homovanillic acid in the metabolism of DA. From these results, it is concluded that the effect of methamphetamine was more evident in NE metabolism than DA, while the effect of Ro4-1284 was more evident in DA metabolism than NE.

[Effects of lithium chloride on norepinephrine and dopamine metabolism in the rat brain]

Lithium chloride (LiCl) was injected acutely (2.4 mEq/kg and 1.2mEq/kg X 2 for 3 hr, i.p.) or subacutely (2.5 mEq/kg X 2/day for 4.5 days, i.p.) in rats, and behavioral effects, steady state levels of norepinephrine (NE), dopamine (DA) and serotonin (5HT) and the metabolism of intraventricularly administered 14C-NE and 14C-DA in the brain were investigated. Acute and subacute administratin of LiCl suppressed the spontaneous motor activity, but had no effect on the levels of NE, DA and 5HT in the brain. Acute administration of LiCl did not influence the total radioactivity and the levels of NE and its metabolites in NE metabolism, while subacute administration of LiCl increased the deaminated metabolites. In DA metabolism, the deaminated metabolites were decreased by acute administration of LiCl and the O-methylated deaminated metabolites were increased by subacute administration. From these results, it is suggested that LiCl stimulates the monoamine oxidase pathway in NE and DA metabolism and the behavioral sedative effects of LiCl are attributed to the reduced functional activity of brain NE and DA neurons.

[Effects of nonthermal stresses on brown adipose tissue thermogenesis]

Repetitive intermittent immobilization stress has been shown to induce an improved cold tolerance through an enhanced capacity of nonshivering thermogenesis (NST). In the present study, effects of immobilization (3 hrs daily for 4-5 weeks), exercise training (running with treadmill 30 min daily, 30 m/min under 8 degrees inclination for 4-5 weeks) and chronic corticosterone treatment (subcutaneous injection at a dose of 0.3 mg/100 g for 4-5 weeks) were investigated on in vitro and/or in vivo thermogenesis of rat interscapular brown adipose tissue (BAT). BAT thermogenesis in vitro was measured in the minced tissue blocks in Krebs-Ringer phosphate buffer using a Clark type oxygen electrode. DNA content per whole BAT pad was greater in the stressed rats, while it was not affected by exercise training and corticosterone. Noradrenaline-and glucagon-stimulated oxygen consumptions were significantly greater in the stressed rats, while significantly smaller in the trained rats as compared with respective controls. Corticosterone treatment failed to affect those values in terms with both per mg tissue and per whole tissue pad, except the less noradrenaline-stimulated oxygen consumption in terms with per mg tissue and DNA. In vivo thermogenesis was assessed by the changes of temperatures in colon (Tcol), BAT (TBAT) and tail skin (Tsk) induced by noradrenaline or glucagon infusion under anesthesia Noradrenaline and glucagon increased the TBAT and the extent of increase was greater in the stressed rats. These results indicated: 1. Repetitive immobilization stress induces the tissue hyperplasia and enhances thermogenic activity of BAT. 2. Exercise training suppresses BAT thermogenesis. 3. Chronic corticosterone administration does not affect BAT thermogenesis. It may be concluded that the enhancing or suppressing effect of nonthermal stress on BAT thermogenesis is due to other factor(s) than corticosterone.