Constitutive activation of c-kit in FMA3 murine mastocytoma cells caused by deletion of seven amino acids at the juxtamembrane domain

A peculiar point mutation results in constitutive activation of c-kit receptor tyrosine kinase (KIT) in three different tumor mast cell lines; ie, the HMC-1, P-815, and RBL-2H3. Because constitutive activation of KIT was also observed in the FMA3 mouse mastocytoma cell line, we investigated the molecular mechanism. Sequencing of the whole coding region of the c-kit showed that the point mutation found in HMC-1, P-815, and RBL-2H3 cells was absent in FMA3 cells and that the c-kit cDNA of FMA3 cells carried an in-frame deletion of 21 base pairs (bp) encoding Thr-Gln-Leu-Pro-Tyr-Asp-His at codons 573 to 579 at the juxtamembrane domain. The FMA3-type c-kit cDNA with 21 bp deletion was introduced into the IC-2 cell line, which was derived from murine cultured mast cells. IC-2 cells were dependent on interleukin (IL)-3 and did not express KIT on the surface. In IC-2 cells introduced with the FMA3-type c-kit cDNA, KIT was constitutively phosphorylated on tyrosines and activated. Moreover, the FMA3-type KIT was dimerized without the stimulation by stem cell factor (SCF), a ligand for KIT. The spontaneously dimerized FMA3-type KIT without SCF binding was not internalized even after the activation. IC-2 cells expressing the FMA3-type KIT grew in suspension culture without IL-3 and SCF and became leukemic in nude athymic mice. The deletion of seven amino acids at the juxtamembrane domain appeared to be a new activating mutation of KIT that might be involved in neoplastic growth of mast cells.

Transforming and differentiation-inducing potential of constitutively activated c-kit mutant genes in the IC-2 murine interleukin-3-dependent mast cell line

Two mutations of c-kit receptor tyrosine kinase (KIT), valine-559 to glycine (G559) and aspartic acid-814 to valine (V814), resulted in its constitutive activation. To examine the transforming and differentiation-inducing potential of the mutant KIT, we used the murine interleukin-3-dependent IC-2 mast cell line as a transfectant. The IC-2 cells contained few basophilic granules and did not express KIT on the surface. The KITG559 or KITV814 gene was introduced into IC-2 cells using a retroviral vector. KITG559 and KITV814 expressed in IC-2 cells were constitutively phosphorylated on tyrosine and demonstrated kinase activity in the absence of stem cell factor, which is a ligand for KIT. IC-2 cells expressing either KITG559 or KITV814 (IC-2G559 or IC-2V814 cells) showed factor-independent growth in suspension culture and produced tumors in nude athymic mice. In addition, IC-2G559 and IC-2V814 cells showed a more mature phenotype compared with the phenotype of the original IC-2 cells, especially after transplantation into nude mice. The number of basophilic granules and the content of histamine increased remarkably. KITG559 and KITV814 also influenced the transcriptional phenotype of mouse mast cell proteases (MMCP) in IC-2 cells. The expression of MMCP-2, MMCP-4, and MMCP-6 was much greater in IC-2G559 and IC-2V814 cells than in the original IC-2 cells. The results indicated that constitutively activated KIT had not only oncogenic activity but also differentiation-inducing activity in mast cells.

Effects of noxious cooling of the skin on pain perception in man

By means of somatosensory evoked brain potentials following painful CO2 laser stimulation (pain SEPs) and a pain visual analogue scale (VAS), we investigated changes in pain perception caused by noxious cooling of the skin in normal subjects. Pain SEPs were recorded from scalp electrodes following laser stimulation applied to the leg under various conditions as follows: (1) control (without any interference); (2) 46 degrees C foot (dipping the foot ipsilateral to the stimulated leg in hot water at 46 degrees C); (3) 0 degrees C foot (dipping the foot ipsilateral to the stimulated leg in ice water at 0 degrees C); and (4) 0 degrees C hand (dipping the hand contralateral to the stimulated leg in ice water at 0 degrees C). Marked decreases in amplitude of pain SEPs and VAS were observed under all conditions as compared with the control (P < 0.001); the degree of pain relief was significantly correlated with changes in pain SEPs. These changes were greatest in the '0 degrees C hand' condition, followed in decreasing order by '0 degrees C foot' and '46 degrees C foot', and there was a significant difference between '0 degrees C hand' and the '46 degrees C foot' condition. We considered that the decrease in pain is due to the diffuse noxious inhibitory control (DNIC). The reason why the degree of pain relief in '0 degrees C foot' condition was less than that in '0 degrees C hand' condition is unclear, but some particular spatial summation of two kinds of nociceptive impulses mediated by the same pathway might take place.

Intracerebral interactions caused by bilateral median nerve stimulation in man: a magnetoencephalographic study

Somatosensory evoked magnetic fields (SEFs) following stimulation of the median nerves bilaterally ('bilateral' waveform) were examined in normal subjects to determine the interference effects of activation of sensory areas in bilateral hemispheres. SEFs following right median nerve stimulation and those following left median nerve stimulation were summated ('summated' waveform). A 'difference' waveform was induced by subtraction of the 'bilateral' waveform from 'summated' waveform. Short-latency deflections showed no consistent differences between the 'summated' and 'bilateral' waveforms, but the middle-latency deflection. N60m-P60m, in the 'bilateral' waveform was significantly (P < 0.01) smaller than that in the 'summated' waveform. The long-latency deflection, the N90m-P90m, in the 'bilateral' waveform was markedly (P < 0.001) reduced in amplitude as compared with the 'summated' waveform. The differences were clearly identified in the 'difference' waveform, in which the main deflections, U90m-D90m, were found in all subjects. Equivalent current dipoles (ECDs) of the short- and middle-latency deflections were located in the primary sensory cortex (SI) contralateral to the stimulated nerve, but ECDs of the N90m-P90m and U90m-D90m were located in bilateral second sensory cortices (SII) which are considered to receive ascending signals from bilateral sides of the body.

[Treatment outcome of 288 cases of renal cell carcinoma]

The clinical outcome was analyzed on 288 patients with renal cell carcinoma who were admitted to the Niigata Cancer Center Hospital during the 33 years from 1961 to 1993; 254 patients had had nephrectomy and 244 of them had undergone curable operations. The survival rate was calculated by the Kaplan-Meier method. The 3-, 5- and 10-year survival rates by all causes of death in all 288 patients were 64.8, 55.9 and 36.4%, respectively. According to the stage based on the general rules for clinical and pathological studies on renal cell carcinoma (The 2nd Edition), the 5-year survival rate was 89.5, 78.7, 51.1 and 13.7% for stages I (n = 31), II (n = 128), III (n = 38) and IV (n = 83), respectively. The 5-year survival rate for the patients (n = 88) from 1961 to 1985 was 40.9%, while the rate for the patients (n = 200) from 1986 to 1993 was 64.3%. This improvement of survival rate for the patients after 1986 was brought by the increase of the stage I or II cases and by the improvement of the survival in the stage III cases after 1986. The 5-year disease-specific survival rate for the patients over 50 years old was 55.5%, while the rate for the patients under 50 years old was 83.6%. Female, low pT, low grade and small tumor size were proven to be favourable prognostic factors in renal cell carcinoma.

Chronic forced swim stress of rats increases frontal cortical 5-HT2 receptors and the wet-dog shakes they mediate, but not frontal cortical beta-adrenoceptors

We studied the effects of chronic forced swim stress on 5-HT2 receptors and beta-adrenoceptors in the rat frontal cortex. The number of 5-HT2 receptors was increased immediately after the last chronic stress, but not after an acute stress. In vivo, the number of wet-dog shakes induced by a 5-HT2 receptor agonist, (+/-)-1-(2,5-dimethoxy-4-iodophenyl)-2-aminopropane (DOI), was increased 24 h after the last chronic stress. However, the concentrations of 5-HT and 5-hydroxyindole acetic acid (5-HIAA), measured by high pressure liquid chromatography (HPLC), were not altered by this stress. Binding sites for [3H]CGP-12177, i.e., beta-adrenoceptor sites, were unchanged after both the acute and the chronic stress. These results suggest that, in the rat, the chronic forced swim stress increases the number of frontal cortical 5-HT2 receptors and the number of wet-dog shakes mediated by these receptors, while the number of frontal cortical beta-adrenoceptors is not increased by this treatment.

Pain-related somatosensory evoked magnetic fields

Somatosensory evoked magnetic fields (SEFs) following painful electrical stimulation of the finger were investigated in 5 normal subjects. Equivalent current dipoles (ECDs) of deflections shorter than 100 msec in latency were located in the primary sensory cortex (SI) in the hemisphere contralateral to the stimulated finger following either non-painful or painful stimulation. Two main deflections, N100m-P100m and N250m-P250m, were independently identified following painful stimulation, although they were not found in SEFs following non-painful weak stimulation. ECDs of the N100m-P100m were considered to be located in the bilateral second sensory cortices (SII). ECDs of the N250m-P250m were identified in the bilateral cingulate cortices and SII, but the intersubject difference was large. Therefore, we considered that contralateral SI and bilateral SII were initially activated by painful noxious stimulation, and then multiple areas including bilateral SII and cingulate cortices were activated. In EEG recordings (evoked potentials), no potential corresponding to N100m-P100m was found, probably because it was difficult to record activation in SII by EEG recordings. The P250 potential which corresponded to the N250m-P250m was clearly identified, probably because activation of multiple areas generated large long-duration EEG potentials which were maximal around the vertex, unlike MEG recordings.

Expression of vascular endothelial growth factor and its receptor mRNA in angiosarcoma

BACKGROUND

Vascular endothelial growth factor (VEGF), a specific mitogen for endothelial cells in vitro, can be angiogenic factor in vivo. VEGF is known to be produced by several tumor cells and plays an important role for neovascularization in tumor tissue. Recently, tyrosine kinase encoded by the flt gene was identified as a receptor for VEGF. Angiosarcoma (AS) is a rare malignant tumor that arises from endothelium. At present, little is known about a mechanism of proliferation of the AS.

EXPERIMENTAL DESIGN

In an immunohistochemical study of 99 cases of AS, 11 cases showing a positive reaction for anti-VEGF Ab were selected for the present study. In these cases, expression of VEGF and its receptor (flt) mRNA was examined by in situ hybridization: sense and antisense probes for VEGF and flt mRNA were used.

RESULTS

In situ hybridization study with antisense probes revealed that the VEGF mRNA was expressed in AS cells and mononuclear cells in all but one case. Intensity of VEGF staining by immunohistochemistry correlated well with VEGF mRNA expression. The flt mRNA was expressed in AS cells in all 10 cases that were positive for VEGF mRNA. Sense probe for VEGF and flt mRNA gave no positive reactions.

CONCLUSIONS

These findings suggest a presence of paracrine or autocrine mechanism of proliferation in AS through VEGF and its receptor flt.

Pyruvate kinase deficiency of mice associated with nonspherocytic hemolytic anemia and cure of the anemia by marrow transplantation without host irradiation

Mutant mice with splenomegaly and nonspherocytic hemolytic anemia were found in an inbred colony of the CBA/N (hereafter CBA) strain maintained in the Japan SLC Haruno farm (Shuchi-gun, Shizuoka, Japan). The activity of pyruvate kinase (PK) in red blood cells (RBCs) of the anemic mutants decreased to 16.2% of normal (+/+) CBA mice. Because the mutant CBA mice showed a remarkable reticulocytosis (41.6%) and because the PK activity of reticulocytes is much higher than that of mature RBCs, the PK activity in mature RBCs of the mutant CBA mice was calculated to be 2.8% that of mature RBCs of CBA-(+/+) mice. Because RBC type PK is encoded by the Pk-1 locus of the mouse (chromosome 3), we designated the mutant locus as Pk-1slc. The anemia and PK deficiency of CBA-Pk-1slc/Pk-1slc mice were cured by bone marrow transplantation (BMT) from CBA-(+/+) mice. Prior irradiation was not necessary for the curative BMT. On the other hand, the BMT from CBA-Pk-1slc/Pk-1slc mice to nonirradiated CBA-(+/+) mice did not result in the decrease of RBCs and the reduction of PK activity. The present results indicate that CBA-Pk-1slc/Pk-1slc mice are a potentially useful animal model for studying pathophysiology of PK deficiency and for developing new therapeutic methods to correct PK deficiency.

Clinicopathological study of clear-cell tumors of the thyroid: an evaluation of 22 cases

Twenty-two cases of partial or wholly composed clear-cell thyroid tumors were reviewed to differentiate between a primary nodule and metastatic clear-cell renal carcinoma in the thyroid. Pathological reevaluation of HE-stained specimens, immunohistochemical observation using anti-thyroglobulin (TG) antibody, and periodic acid-Schiff (PAS) staining were performed. The pathological characteristics in metastases from the kidney have a greater tendency to demonstrate a strikingly clear cytoplasm with small nuclei, rich vascularization, and a trabecular arrangement of tumor cells than do primary thyroid cases. The immunohistochemical TG staining in conjunction with PAS staining for the recognition of follicular colloid could provide much more reliable information of primary cases compared to that using TG staining alone. Clinically, in primary cases, the female:male ratio is substantially higher while the mean age is lower than in metastatic cases reflecting differentiated thyroid carcinoma. In conclusion, immunohistochemical staining for TG with PAS staining for the recognition of follicular colloid proved to be the most sensitive method for identifying primary clear cell thyroid tumors. In addition, a careful assessment of past and/or present kidney disorders to rule out metastatic renal cell carcinoma is advisable. Age, gender, and physiological findings are also informative when differentiating between them.

Neuroprotective effects of NBQX on hypoxia-induced neuronal damage in rat hippocampus

Models of cerebral ischaemia were used for analysis of mechanism of neuronal cell death and/or damage. Ischaemia is caused dominantly by severe hypoxia and hypoglycaemia: in the present study, we examined the influence of severe in vivo hypoxia (5% O2/95% N2 for 30 min at 22 degrees C). After hypoxia, neuronal damage was observed in the CA3 and dentate gyrus (DG) after 3 and 21 days of survival, but not in the CA1.2,3-Dihydroxy-6-nitro-7-sulphamoyl-benzo(F)quinoxaline (NBQX), an antagonist for AMPA/kainate receptors, showed neuroprotective effects in the CA3 and DG. These results suggest that hypoxia may induce neuronal damage in the CA3 and DG through activation of AMPA/kainate receptors.

[The evaluation of surgical management for metastatic lesions of renal cell carcinoma]

The clinical experience with 29 renal cell carcinoma patients who underwent resection of their metastatic lesions was reviewed. Fourteen patients had no metastatic lesions when nephrectomy was performed initially (initial M0 group) and 15 patients already had detected metastases at diagnosis of their renal tumors (initial M1 group). The final point of follow-up was May 31, 1994. Eighteen patients (M0 9, M1 9) were curatively resected and 11 (M0 5, M1 6) underwent non-curative resection. In the curatively resected group, 7 patients (3 lung, 2 adrenal gland, 1 brain, 1 bone metastasis) were alive with no recurrence followed from 50 to 174 months. Eight died from tumor recurrences, 1 was alive with tumor recurrence and 2 died from other diseases. The 3-year and 5-year survival rates in the curatively resected group (16 patients, excluding 2 who died from other diseases) were 87.5% and 61.9%, respectively, according to the Kaplan-Meier method. On the other hand, the 3-year and 5-year survival rate in the non-curatively resected group were 36.4% and 27.3%, respectively. Between the curatively resected group and non-curatively resected group, a significant difference was shown concerning the survival rate (3 year: P = 0.0018, 5 year: P = 0.003, generalized Wilcoxon method). We concluded that curative resection was the most important prognostic factor in the treatment of metastatic lesions.

Antisense oligonucleotide inhibits the expression of procollagen type III gene in mouse fibroblasts

The effects of transfection of phosphorothioate antisense oligonucleotides (ASOs) into BALB/c 3T3 mouse fibroblasts on procollagen type III production were examined. Immunohistochemistry and Western blots showed that the expression of procollagen type III decreased. Semi-quantitative reverse transcription polymerase chain reaction revealed that the expression of procollagen type III mRNA was inhibited. ASOs were effective for inhibiting procollagen type III production at the gene level, although the effect was transient.

Primary structure of murine red blood cell-type pyruvate kinase (PK) and molecular characterization of PK deficiency identified in the CBA strain

To clarify the molecular abnormality of pyruvate kinase (PK) deficiency identified in the mutant mice of CBA-Pk-1slc/Pk-1slc, we cloned murine red blood cell-type PK (R-PK) cDNA of those animals. The cDNA sequence spans 1827 bp, including an open reading frame that can encode 574 amino acids. Homology in the coding sequences between murine and human R-PK was 86.1% at nucleotide and 91.5% at amino acid levels. A homozygous missense mutation at nucleotide 1013 GGT-->GAT was identified in the cDNA sequence of the mutant, causing a single amino acid substitution at no. 338Gly-->Asp of the murine R-PK. Six amino acid residues, 335Val-336Ala-337Arg-338Gly-339Asp-340L eu, were encoded in exon 8 of both human and rat L (liver-type)/R-PK genes and were evolutionarily conserved in PK from bacteria through humans. 337Arg was reported to be important for substrate binding, suggesting that the amino acid change would impair substrate affinity of the PK subunit. A homozygous missense mutation at the catalytic domain has been identified in a human PK variant, PK Hong Kong (941ATT-->ACT, 314 Ile-->Thr). Although both 1013A and 941C gave rise to an amino acid change adjacent to the active site and may interfere with substrate binding to the subunit, the degree of anemia was much more severe in the human case. The erythroid-progenitor cell number increased in the spleen of Pk-1slc/Pk-1slc mice to a level approximately 66 times higher than that in normal CBA mice, suggesting that compensatory extramedullary erythropoiesis in the spleen of the mutant mice, but not in the human variant, might account for the observed difference in the phenotype.

[Clinical and pathological studies of renal cell carcinoma with vein involvement]

To clarify the meaning of vein involvement, the clinical and pathological findings of the patients with renal cell carcinoma were examined. Out of 288 patients treated for renal cell carcinoma-from 1961 to 1993 at Niigata Cancer Center Hospital, 238 patients were examined for vein involvement. Tumor stages were evaluated according to the general rules for clinical and pathological studies on renal cell carcinoma (2nd edition). In 154 patients, the stage was pV0, in 41 pV1a, in 23 pV1b and in 20 pV2. The 5-year survival rate was 72.2% in pV0, 60.1% in pV1a, 51.9% in pV1b and 30.0% in pV2. Histological findings as grade, tumor size, regional lymph node metastasis and distant metastasis were proportional to vein involvement. The difference in the survival rate and histological findings of primary tumor between pV1a and pV1b group was small but the difference between pV0 and pV1a was significant. Therefore, the histological and clinical studies of the cases with pV1a must be done carefully. The 5-year survival rate of the patients with pV2 and without distant metastasis was 50.0%. However, the prognosis of the patients with pV2 and with distant metastasis was poor. Therefore aggressive treatment was not recommended for these patients.

Expression of vascular permeability factor (VPF/VEGF) messenger RNA by plasma cells: possible involvement in the development of edema in chronic inflammation

Edema occurs in some types of chronic inflammation such as nasal polyps, uterine cervical polyps and gastric hyperplastic polyps. However, the factors or cellular components involved in the development of edema in chronic inflammation remain to be clarified. Recently, the gene encoding vascular permeability factor (VPF) or vascular endothelial growth factor (VEGF) and the genes encoding its receptors (kinase insert domain-containing receptor (KDR) and fms-like tyrosine kinase-1 [fit-1]) have been cloned. VPF/VEGF induces vascular hyperpermeability and vascular endothelial proliferation through KDR or fit-1 receptors. As there is a possibility that VPF/VEGF may play a role in the development of edema in chronic inflammation, we examined the messenger (m) RNA expression of VPF/VEGF and its receptors in nasal polyp tissues, which is an example of chronic inflammation with remarkable edema. Using northern blotting, all nasal polyp tissues examined expressed mRNA of VPF/VEGF and KDR. In situ hybridization revealed that VPF/VEGF mRNA-expressing cells were scattered in the edematous stroma of nasal polyps. In the adjacent sections, these cells showed the morphological features of plasma cells and expressed mRNA of immunoglobulin light chains. Human B cell leukemia and plasmacytoma cell lines expressed VPF/VEGF mRNA but human mast-cell leukemia and T cell leukemia cell lines did not. The alternatively spliced pattern of VPF/VEGF transcripts observed in nasal polyp tissues was consistent with that in plasmacytoma cell lines. Taken together, the VPF/VEGF mRNA-expressing cells in nasal polyps appeared to be plasma cells, suggesting that plasma cells may play an important role in the development of edema in chronic inflammation through the production of VPF/VEGF.

High incidence of ultraviolet-B-or chemical-carcinogen-induced skin tumours in mice lacking the xeroderma pigmentosum group A gene

Xeroderma pigmentosum (XP) is an autosomal recessive disorder characterized by a high frequency of skin cancer on sun-exposed areas, and neurological complications. XP has a defect in the early step(s) of nucleotide-excision repair (NER) and consists of eight different genetic complementation groups (groups A-G and a variant). We established XPA (group-A XP) gene-deficient mice by gene targeting of mouse embryonic stem (ES) cells. The XPA-deficient mice showed neither obvious physical abnormalities nor pathological alterations, but were defective in NER and highly susceptible to ultraviolet-B- or 9,10-dimethyl-1,2-benz[a]anthracene-induced skin carcinogenesis. These findings provide in vivo evidence that the XPA protein protects mice from carcinogenesis initiated by ultraviolet or chemical carcinogen. The XPA-deficient mice may provide a good in vivo model to study the high incidence of skin carcinogenesis in group A XP patients.

Expression of bone-related protein messenger RNA in human meningiomas: possible involvement of osteopontin in development of psammoma bodies

Meningiomas often contain concentric calcified foci, referred to as psammoma bodies. Since calcium phosphate deposits in both psammoma bodies and bone tissues, we examined whether messenger (m) RNA of bone-related extracellular matrix proteins and bone morphogenetic proteins (BMP) were expressed in human meningioma tissues. Northern blotting demonstrated the expression of osteopontin (OPN), matrix Gla protein (MGP), osteonectin (ON) and BMP-4 mRNA but not bone sialoprotein, osteocalcin and BMP-2 mRNA. In situ hybridization revealed that most OPN mRNA-expressing cells were located around the psammoma bodies in meningothelial whorls. Moreover, combination of in situ hybridization and immunohistochemistry on serial sections showed that the OPN mRNA-expressing cells were CD68-positive, suggesting they were macrophages. Immunohistochemistry with anti-OPN antibody and von Kossa staining on the adjacent section showed that the deposition site of OPN protein was consistent with that of calcium phosphate. Neither MGP nor ON mRNA expression appeared to correlate with the calcification. The present result suggests that OPN produced by CD68-positive macrophages may play a significant role for development of psammoma bodies in meningiomas.

Topography of somatosensory evoked magnetic fields following posterior tibial nerve stimulation

The topography of somatosensory evoked magnetic fields (SEFs) following stimulation of the right and left posterior tibial nerves was investigated in 5 normal subjects (10 nerves). The main deflections N37m-P45m-N60m-P75m and their counterparts P37m-N45m-P60m-N75m were identified in the hemisphere contralateral to the stimulated nerve. Their equivalent current dipoles (ECDs) were located in the foot area of the primary sensory cortex (SI), probably in area 3b. Restricted minor deflections, P40m-N40m and N50m-P50m, were considered to be generated in area 1 in SI. As the generator sources of P37m-N37m, P40m-N40m and N45m-P45m were temporarily changed and interfered with each other, the direction of ECDs appeared to be rotated with the passage of time. Small middle-latency deflections, N100m-P100m, were clearly identified in 2 subjects. ECDs of these deflections were found in the second sensory cortex (SII), in both hemispheres, although they were clearer in the hemisphere contralateral to the stimulated nerve. In conclusion, short- and middle-latency SEFs are mainly generated in area 3b in SI contralateral to the stimulated nerve, and responses generated in area 1 of SI and SII affect the SEFs to some degree, but interindividual differences are large compared with SEFs evoked by upper limb stimulation.

Brain histaminergic system in mast cell-deficient (Ws/Ws) rats: histamine content, histidine decarboxylase activity, and effects of (S) alpha-fluoromethylhistidine

The mast cell-deficient [Ws/Ws (White spotting in the skin)] rat was investigated with regard to the origin of histamine in the brain. No mast cells were detected in the pia mater and the perivascular region of the thalamus of Ws/Ws rats by Alcian Blue staining. The histamine contents and histidine decarboxylase (HDC) activities of various brain regions of Ws/Ws rats were similar to those of +/+ rats except the histamine contents of the cerebral cortex and cerebellum. As the cerebral cortex and cerebellum have meninges that are difficult to remove completely, the histamine contents of these two regions may be different between Ws/Ws and +/+ rats. We assume that the histamine content of whole brain with meninges in Ws/Ws rats is < 60% of that in +/+ rats. So we conclude that approximately half of the histamine content of rat brain is derived from mast cells. Next, the effects of (S) alpha-fluoromethylhistidine (FMH), a specific inhibitor of HDC, on the histamine contents and HDC activities of various regions of the brain were examined in Ws/Ws rats. In the whole brain of Ws/Ws rats, 51 and 37% of the histamine content of the control group remained 2 and 6 h, respectively, after FMH administration (100 mg/kg of body weight). Therefore, we suggest that there might be other histamine pools including histaminergic neurons in rat brain.

Disturbed intestinal movement, bile reflux to the stomach, and deficiency of c-kit-expressing cells in Ws/Ws mutant rats

BACKGROUND & AIMS

Interstitial cells of Cajal (ICCs) are believed to initiate the basic contractile activity of the gastrointestinal tract. Because ICCs in the intestine of mice express c-kit receptor tyrosine kinase and because rats are more commonly used than mice for pathophysiological investigations of the gastrointestinal tract, the number of the c-kit messenger RNA-expressing cells was compared with gastrointestinal movement in rats.

METHODS

The c-kit messenger RNA-expressing cells were detected by in situ hybridization. The autonomous contraction of excised segments of the ileum was recorded. The function of the pyloric sphincter was evaluated by measuring the content of bile acids in the stomach.

RESULTS

The c-kit messenger RNA-expressing cells were not detectable in the stomach of Ws/Ws mutant rats with a small deletion at the tyrosine kinase domain of c-kit, and the number of c-kit messenger RNA-expressing cells decreased to 7% that of normal control rats in the ileum of Ws/Ws rats. The contractile activity of the ileum was apparently impaired, and the content of bile acids in the stomach was significantly increased in Ws/Ws rats.

CONCLUSIONS

The abnormalities in the ileal movement and pyloric sphincter function in Ws/Ws rats were attributable to the deficiency of c-kit messenger RNA-expressing cells.