Rolipram, a phosphodiesterase-4-selective inhibitor, promotes the survival of cultured rat dopaminergic neurons

We evaluated the effects of rolipram, a selective inhibitor of phosphodiesterase (PDE) 4, on the survival of dopaminergic neurons in 13-day culture. Rolipram did not affect the survival of dopaminergic neurons in the absence of forskolin, but significantly enhanced the survival of dopaminergic neurons in the presence of 10(-5) M forskolin in a concentration-dependent manner (10(-8) - 10(-5) M). Rolipram also enhanced the neurotrophic effect of forskolin on total neurons including dopaminergic and non-dopaminergic neurons at a high concentration (10(-5) M), but did not affect the survival of cells containing glutamate or gamma-aminobutylic acid. A non-selective PDE inhibitor, 1-isobutyl-3-methylxanthine, caused a marked increase of dopaminergic neurons, whereas selective inhibitors of PDE2 and PDE3 showed far weaker effects. A PDE1 inhibitor, on the other hand, caused non-specific cell death in the presence or absence of forskolin. These findings suggest that rolipram has a potential to enhance the survival of dopaminergic neurons selectively by way of PDE4 inhibition.

Thymolipoma associated with myasthenia gravis

In a 29-year-old woman with myasthenia gravis and no visible mediastinal mass, the resected thymus was found to contain a small thymolipoma. Relief of the neuromuscular symptoms followed thymectomy. A very small thymolipoma may be associated with myasthenia gravis even if the content of though thymic tissue is low.

Cervical cord ependymoma with numerous microrosettes

"Microrosette ependymoma," which is ependymoma with numerous microrosettes throughout the tumor, has rarely been reported. We describe an autopsy case of cervical cord ependymoma with two unusual features: the presence of numerous microrosettes and the formation of trabecular architecture. The tumor originated in the C2 segment of a man aged 23 years and gradually expanded over the following 15 years and 10 months until the entire cervical cord was involved. Beside the low grade of malignancy, the tumor cells exhibited a strong tendency to form microrosettes and trabecular architecture, which formed many perivascular pseudorosettes. The microrosettes mostly consisted of only two or a few more cells, in the absence of large rosettes. Thus the constituent cells were those forming perivascular pseudorosettes. Electron microscopy and immunohistochemistry characterized the ependymal properties of the microrosettes, whose lumina frequently contained fibril bundles similar to those of the Reissner's fiber fibrils, in addition to cilia and microvilli. The pathogenesis of the occurrence of numerous microrosettes is unknown; however, a defect in the mechanism of regulation of rosette formation and enlargement is the most likely explanation.

Elastin expression is up-regulated by retinoic acid but not by retinol in chick embryonic skin fibroblasts

Effects of retinoid derivatives (retinol and retinoic acid) on elastin expression and cell proliferation in chick embryonic skin fibroblasts were studied. Retinoic acid inhibited cell proliferation one half of control at the concentration 10(-5) M. Retinoic acid exhibited stimulatory effect on elastin synthesis with a maximum stimulation of 2.0-fold at the concentration of 10(-6) M for 24 h treatment. Elastin level detected by Western blot analysis in the pooled conditioned medium was compatible with the increase of elastin synthesis by retinoic acid treatment. Comparable increase in elastin mRNA level was observed by retinoic acid treatment. Retinol showed no significant effects on either cell proliferation or elastin expression. The results indicate that retinoic acid was potentially active and retinol was inactive for modulation of cell proliferation and elastin expression.

Complementary DNA cloning and chromosomal mapping of a novel phosphatidylinositol kinase gene

A cDNA for a putative new member for phosphatidylinositol kinase family was cloned from an adult human whole brain cDNA library. The predicted translation product was composed of 961 amino acid residues and contained a sequence feature characteristic for lipid/protein kinases. The messenger RNA was ubiquitously expressed in various tissues, while relatively higher expression was observed in heart, skeletal muscle and testis. The chromosomal location of the gene was determined by fluorescence in situ hybridization and PCR-based analyses with both a human/rodent monochromosomal hybrid cell panel and a radiation hybrid mapping panel.

[Serotype determination of enteroviruses that cause hand-foot-mouth disease; identification of enterovirus 71 and coxsackievirus A16 from clinical specimens by using specific probe]

Coxsackievirus A16 (CA16) and enterovirus 71 (EV71) are known to be major causative agents of hand-foot-and-mouth disease prevalent in summer in Japan. Discrimination and identification of these viruses were often hampered by a nonneutralizable or nontypable virus. Therefore, a Southern blot hybridization that utilizes mixed probes specific to serotype was developed. Firstly, an approximately 650 bases spanning 5'-noncoding region to one third of VP2 including entire VP4 was amplified with a set of primers containing enterovirus common sequences and a genomic RNA as template. Secondary, the nucleotide sequences were determined using seven CA16 and eighteen EV71 strains including the standard strains, and the deduced amino acid sequences of VP4 were searched to find residues which are conserved in the same serotypes but diverged among different serotypes. Candidate positions for the mixed probes were defined at the carboxyl terminus of VP4. Thirdly, Southern blot analyses were carried out using thirty-nine enterovirus standard strains, seven CA16 isolates and sixty-six EV71 isolates previously identified by the neutralization test. The results revealed that each mixed probe exclusively bound to the homologous DNAs but not to the heterologous ones. In an attempt to determine serotypes without virus isolation, clinical specimens from hand-foot-and-mouth disease were examined. Of 78 throat swabs and 15 vesicular fluids, 71 (91.0%) and 13 (86.7%) specimens were clearly identified, indicating that the method described here offer advantages over the traditional neutralization assay: It is rapid, specific and less labor-consuming.

Inhibitory mechanism of mizoribine on the antibody production of mouse B cells stimulated with lipopolysaccharide

It has been reported that the immunosuppressant mizoribine (MZR) inhibits T cell proliferation by depleting intracellular guanine nucleotides via competitive inhibition of inosine 5'-monophosphate (IMP) dehydrogenase in the purine metabolism pathway. This study was performed to determine if the mechanism by which MZR suppresses the proliferation of mouse B cells and antibody production by these cells is dependent on the depletion of intracellular guanine nucleotides. Stimulation of purified splenic B cells of mice with lipopolysaccharide (LPS), a mitogen to B cells, increased both proliferation and antibody production. MZR suppressed both of these functions in a dose-dependent fashion. MZR also caused a decrease in the amount of intracellular guanosine 5'-triphosphate (GTP). When the cultures were grown on plates containing guanosine plus 8-aminoguanosine, the amount of intracellular GTP, which had been reduced by MZR, was restored. Furthermore, the repletion of GTP pools restored both proliferation and antibody production almost to their previous levels. These results suggest that MZR suppresses antibody production and proliferation of B cells by acting directly on B cells. Furthermore, it is suggested that the inhibitory effect of MZR on antibody production, as well as on T cell proliferation, is dependent on the decrease in intracellular guanine nucleotide pools of mouse B cells.

Japanese families with autosomal dominant pure cerebellar ataxia map to chromosome 19p13.1-p13.2 and are strongly associated with mild CAG expansions in the spinocerebellar ataxia type 6 gene in chromosome 19p13.1

Autosomal dominant cerebellar ataxia is a group of clinically and genetically heterogeneous disorders. We carried out genomewide linkage analysis in 15 families with autosomal dominant pure cerebellar ataxia (ADPCA). Evidence for linkage to chromosome 19p markers was found in nine families, and combined multipoint analysis refined the candidate region to a 13.3-cM interval in 19p13.1-p13.2. The remaining six families were excluded for this region. Analysis of CAG-repeat expansion in the alpha1A-voltage-dependent calcium channel (CACNL1A4) gene lying in 19p13.1, recently identified among 8 small American kindreds with ADPCA (spinocerebellar ataxia type 6 [SCA6]), revealed that 8 of the 15 families studied had similar, very small expansion in this gene: all affected individuals had larger alleles (range of CAG repeats 21-25), compared with alleles observed in neurologically normal Japanese (range 5-20 repeats). Inverse correlation between the CAG-repeat number and the age at onset was found in affected individuals with expansion. The number of CAG repeats in expanded chromosomes was completely stable within each family, which was consistent with the fact that anticipation was not statistically proved in the SCA6 families that we studied. We conclude that more than half of Japanese cases of ADPCA map to 19p13.1-p13.2 and are strongly associated with the mild CAG expansion in the SCA6/CACNL1A4 gene.

Frequent occurrence of hepatocytic apoptosis in acute rejection of the grafted rat liver

The present study was conducted to examine the histopathological changes of rat liver grafts in the early post-transplantation period. A total of 44 orthotopic liver transplantations were performed using cuff techniques without anastomosis of the hepatic artery. They were divided into four groups: (i) group 1 (syngeneic, Lewis-->Lewis; n = 10); (ii) group 2 (allogeneic, ACI-->Lewis; n = 20); (iii) group 3 (allogeneic with immunosuppression, ACI-->Lewis; n = 12); and (iv) long-surviving grafts (PVG-->Lewis; n = 2). The histological findings were classified into four categories: (i) mild dilatation of Disse's spaces due to ischemia; (ii) bile duct proliferation; (iii) acute rejection; and (iv) zonal necrosis. Bile duct proliferation occurred on day 6 in all three groups and in one of the two long-surviving grafts (120 days). Acute rejection occurred on day 3 and progressed in groups 2 and 3. Zonal necrosis developed in group 2 after day 6, while acute rejection subsided after day 4 in group 3 receiving 15-deoxyspergualin. A few single cell deaths or acidophilic bodies were variably noted. Most of these cells showed signals by in situ nick end-labeling in their nuclei, implying the cells were undergoing apoptosis. The number of apoptotic hepatocytes increased as the progress and decreased with the regression of acute rejection in group 3. Thus, the extent of hepatocytic apoptosis may reflect the magnitude of acute rejection. More frequent distribution of apoptotic hepatocytes in periportal areas suggests that apoptosis may be induced by a variety of pathological stimuli, including the direct cytotoxic effects of lymphocytes, various cytokines and local circulatory disturbances.

Role of protein tyrosine phosphorylation in rat corneal neovascularization

BACKGROUND

Recent studies have suggested that tyrosine kinase pathways that are activated by angiogenic growth factors may play a role in corneal neovascularization.

METHODS

Corneal neovascularization was induced in rat corneas by chemical cauterization. At 6, 24, 48, 96, and 168 h after chemical cauterization the rat corneas without the corneal epithelium were prepared for gel electrophoresis. Total protein profiles of the corneal samples were examined by staining gels with Coomassie brilliant blue. Tyrosine-phosphorylated proteins, three angiogenic growth factors (basic fibroblast growth factor, vascular endothelial growth factor, and platelet-derived growth factor-B chain), and three intracellular signal proteins in the tyrosine kinase pathways (phospholipase C gamma, SHC, and mitogen-activated protein kinase) in the corneal samples were examined by western blot analysis. A topical treatment of genistein eye drop (5 mg/ml) was used for inhibition of corneal neovascularization after chemical cauterization in rats.

RESULTS

In total protein profiles, three bands in the corneal samples were increased after cauterization. Overall tyrosine-phosphorylated proteins and all three angiogenic growth factors increased with progression of corneal neovascularization. The tyrosine-phosphorylated forms of three intracellular signal proteins were also increased after cauterization. Treatment with topical genistein was effective in inhibiting corneal neovascularization in rats.

CONCLUSION

Protein tyrosine phosphorylation was involved in inflammation-induced corneal neovascularization. Tyrosine kinase inhibitors may have utility as inhibitors of corneal neovascularization.

Cytotoxin genes of Helicobacter pylori in chronic gastritis, gastroduodenal ulcer and gastric cancer: an age and gender matched case-control study

Helicobacter pylori (H. pylori) infection is involved in many gastrointestinal diseases, such as chronic gastritis (CAG), peptic ulcer and gastric cancer (GCA). Both host factors and H. pylori strain differences may contribute to differences in the diseases. Thus, we conducted an age and gender matched case-control study of 35 patients each with CAG, gastric ulcer (GUL), duodenal ulcer (DUL) and gastric cancer (GCA) to examine the role of strain differences of the H. pylori cytotoxin genes cagA and vacA in these diseases. We employed polymerase chain reaction to examine the gastric juice for H. pylori DNA. The test was positive for 26 (74.3%) CAG, 29 (82.9%) GUL, 28 (80.0%) DUL and 27 (77.1%) GCA patients, showing no statistically significant difference among the diseases (P = 0.84). cagA and vacA genes (picked up by using a vacA1 + vacA2 primer pair which detected non-variable regions of the vacA gene) were detected by PCR in the H. pylori DNA-positive cases as follows: CAG, 92.3% and 76.9%; GUL, 100% and 86.2%; DUL, 89.3% and 89.3%; GCA, 92.6% and 85.2%, respectively. No statistically significant differences were found in the frequencies of these cytotoxin genes in H. pylori-positive cases among the various gastric diseases (P = 0.39 for cagA and P = 0.64 for vacA).

Genistein, a protein tyrosine kinase inhibitor, ameliorates retinal degeneration after ischemia-reperfusion injury in rat

PURPOSE

The authors sought to determine the effect of genistein, a naturally occurring protein tyrosine kinase inhibitor, in a model of ischemia-reperfusion injury in the rat retina.

METHODS

Ischemia-reperfusion injury was induced by temporary optic nerve ligation. A dose of 0.034 mg, 0.34 mg, and 3.4 mg of genistein or dimethyl sulfoxide (DMSO) alone was injected intraperitoneally 1 hour before the ligation of the optic nerve and just after the start of reperfusion. After 48 hours of reperfusion, the effect of genistein on overall protein tyrosine phosphorylation in the retina was studied using Western blot analysis. After 168 hours, the effect of increasing doses of genistein on retinal degeneration was examined by quantitative morphometric analysis of histologic sections of the retina.

RESULTS

The authors found that tyrosine phosphorylation was increased after 48 hours of reperfusion in the ischemia-reperfusion-injured eyes treated with DMSO alone. A severe inner retinal degeneration was observed in the animals treated with DMSO alone after 168 hours of reperfusion. The treatment with 3.4 mg genistein inhibited the increase in tyrosine phosphorylation and protected the eyes significantly from the induced ischemic retinal degeneration by morphometric analysis of the mean thickness of the inner limiting membrane to the outer limiting membrane, the inner plexiform layer, and the inner nuclear layer (P < 0.02). Treatments with lower amounts of genistein (0.034 mg and 0.34 mg) did not show a significant protection of retinal degeneration after the injury.

CONCLUSIONS

Systemic administration of high dose of genistein, a dietary-derived isoflavone, can ameliorate an ischemia-reperfusion-induced retinal degeneration. Genistein may be useful to prevent neuronal degeneration in the inner retina as a result of ischemic injury.

[Role of endothelin-B receptors in the pulmonary circulation]

Endothelin-1 (ET-1) is a potent vasoactive peptide and is thought to play an important role in the regulation of vascular tone. ET-1 can both constrict blood vessels, via endothelin-A (ET-A) receptors in vascular smooth muscle cells, and dilate then via endothelin-B (ET-B) receptors in endothelial cells in the systemic circulation. To determine the role of ET-B receptors in the pulmonary circulation, we examined the hemodynamic effects of a selective ET-B receptor agonist (IRL 1620) in rats. In rat lungs perfused with a salt solution, IRL 1620 caused pulmonary vasoconstriction in a dose-dependent manner. In lungs perfused with a hypoxic half-blood solution (10% O2), doses of IRL 1620 less than 10 nM caused pulmonary vasodilation, but higher doses caused pulmonary vasoconstriction. IRL 1620 caused transient vasodilation of the systemic circulation at every dose used (0.1, 1, and 5 nmol/kg) in anesthetized rats. In contrast, the effects of IRL 1620 on the pulmonary circulation varied with the dose. Small doses (0.1 or 1 nmol/kg) caused pulmonary vasodilation, but a higher dose (5 nmol/kg) caused pulmonary vasoconstriction. These results show tachyphylaxis in the pulmonary vasodilator response to IRL 1620, but not in the systemic vasodilator response. The present data show the dual action (vasoconstriction and vasodilation) of ET-B receptors.

[Chronic expanding hematoma following pneumonectomy managed with a thoracic balloon: a case report]

A 64-year-old male was treated for a chronic expanding hematoma three years after pneumonectomy for left lung cancer (p T2N2M0, Stage IIIA). Two years prior to admission a left pleural effusion shadow was detected on a follow-up chest X ray, and since then there had been a progressive mediastinum shift to the right. The suspected diagnosis on referral was recurrent lung cancer or giant intrathoracic hematoma. Chest CT scans and thoracentesis led to a diagnosis of a chronic expanding hematoma developing after pneumonectomy. Surgery was performed because of the severity of symptoms and the progressive nature of the tumor. Histopathological examination confirmed the diagnosis of chronic expanding hematoma. During the operation, it was difficult to achieve hemostasis, but bleeding was effectively managed with a thoracic balloon.

[A case of post-poliomyelitis muscular atrophy with cranial nerve signs and widespread muscular atrophy of the extremities]

Here we report a case of a 56-year-old male with post-poliomyelitis muscular atrophy (PPMA), who presented with cranial nerve signs and widespread atrophy of the extremities. He had suffered from poliomyelitis at the age of 2 years. After recovery from the acute stage, the paralysis remained in his left arm. He noticed muscle weakness of the right upper and lower extremities at the age of 45 years and the muscle atrophy progressed to his arms, hip and thigh at the age of 55 years. Neurological examination revealed muscle atrophy of the neck and disturbance of left V, VIII, IX, X and bilateral XI cranial nerves. We diagnosed this case as PPMA from his history and electromyographic and muscle biopsy findings which suggested chronic denervation. Among the 21 PPMA cases in the past in which the acute poliomyelitis had resulted in paralysis of the only one limb, ours was the only case that had muscle atrophy of all the limbs. Cranial nerve involvement is known to occur in acute poliomyelitis; therefore, there is a possibility that the involvement of the cranial nerves in our case might be a delayed progressive symptoms.

[A case of frontal gait apraxia caused by hypoxic encephalopathy]

We reported a rare case who had hypoxic-encephalopathy causing frontal apraxia of gait. The patient, a 34-year-old female, was admitted in July, 1994, complaining of difficulty in walking after anoxic brain damage caused by ventricular arrhythmia. She had difficulty in raising her feet, which appeared to be rooted to the floor. There was no evidence of motor paralysis, spasticity, rigidity or sensory loss, but she did show frontal lobe signs such as foot grasp reflex and Gegenhalten. Cranial MRI showed slight atrophy of the frontal lobe. On T2 weighted image, high-intensity areas were detected at the posterior internal capsule and corona radiata. Single photon emission CT (123I-IMP) demonstrated a low perfusion area which included the inferomedical part of the frontal lobe. After 8 months of hospitalization, her postural instability and unsteady gait slowly improved without treatment as frontal signs such as foot grasp reflex disappeared. We speculate that her apraxia of gait may result from grasp reflex and Gegenhalten.

Detection of MAGE-4 protein in sera of lung cancer patients

We investigated the level of MAGE-4 protein in sera of patients with primary lung cancer to understand better the biological roles of the MAGE proteins. MAGE-4 protein was detected as a non-degraded form in both the supernatant of a MAGE-4+ tumor cell line and in a patient's serum. Serum level of the MAGE-4 protein in lung cancer patients (n=100, mean=1.17 ng/ml) was significantly higher than that in either patients with benign pulmonary diseases (n=80, 0.33 ng/ml) or healthy donors (n=68, 0.32 ng/ml). It was higher than the cutoff level (1.15 ng/ml) in 34 of 100 cancer patients, but not in anyone in the other groups.

Activation of protein tyrosine phosphorylation after retinal branch vein occlusion in cats

PURPOSE

The authors examine the effect of retinal branch vein occlusion (BVO), a common retinal vascular disorder, on protein tyrosine phosphorylation, production of angiogenic growth factors, and activation of signal proteins in the tyrosine kinase pathways in the retina.

METHODS

Retinal branch vein occlusion was induced in cat retina by coagulation of retinal veins with diathermy. At 2 days, 1, 3, and 6 weeks after induction of BVO, the retina was divided into three parts: a part within the distribution of the occluded vein (BVO[IN]) or a part outside the distribution of the occluded vein (BVO[OUT]). Each part of the retina was prepared for Western blot analysis of tyrosine-phosphorylated proteins, vascular endothelial growth factor (VEGF), basic fibroblast growth factor (bFGF), and four signal proteins in the tyrosine kinase pathways, which were phospholipase C gamma (PLC gamma), C-Src, SH2-containing protein (SHC), and mitogen-activated protein kinase (MAPK).

RESULTS

Overall, tyrosine-phosphorylated proteins were increased after BVO, especially in BVO(IN) at 2 days and 1 week. The VEGF and bFGF also were increased in BVO(IN) at 1 week and 2 days, respectively. The PLC gamma and MAPK were activated at these time points. The C-Src and SHC were not activated in the retina after BVO.

CONCLUSIONS

The BVO increased overall protein tyrosine phosphorylation in the cat retina in association with increase of angiogenic growth factors (VEGF and bFGF) and activation of two signal proteins (PLC gamma and MAPK) in the tyrosine kinase pathways. These results suggest that the protein tyrosine phosphorylation may in part play an important role in mitogenesis of vascular endothelial cells and other retinal responses after BVO.

HLA-A locus-restricted and tumor-specific CTLs in tumor-infiltrating lymphocytes of patients with non-small cell lung cancer

HLA class I restriction and tumor specificity of cytotoxicity in the IL-2-activated tumor-infiltrating lymphocytes from 16 patients with non-small cell lung cancer were investigated. Six HLA class I-restricted and tumor-specific CTL lines were established: (i) HLA A2-restricted and adenocarcinoma-specific CTLs in three (two A0201+ and one A0206+) patients with adenocarcinoma, (ii) HLA A3101- and A3302-restricted and adenocarcinoma-specific CTLs in an HLA A3101/3302+ patient with adenocarcinoma, and (iii) HLA A3302-restricted CTLs and (iv) HLA A2402-restricted CTLs recognizing tumors with different types of histology in an HLA A3302+ patient with adenocarcinoma and an HLA A2402+ patient with squamous cell carcinoma (SCC), respectively. The three HLA A2-restricted CTL lines recognized 4, 4, or 6 of 15 HLA A2+ adenocarcinoma cell lines that originated from lung, stomach, colon, and breast with different subtypes (HLA A0201, A0206, and A0207), respectively. Furthermore, the CTLs of an HLA A0206+ patient recognized five different fractions of peptides eluted from an HLA A0201+ adenocarcinoma cell line. These results showed evidence of the existence of HLA class I-restricted and tumor-specific CTLs recognizing peptide antigens on HLA-A alleles of adenocarcinoma or SCC in tumor sites of a substantial number of patients with non-small cell lung cancer.

Mediastinal parathyroid adenoma detected by 99mTc-methoxyisobutylisonitrile: report of a case

We report herein the case of a 30-year-old man in whom ectopic mediastinal parathyroid adenoma was detected by 99mTc-methoxyisobutylisonitrile scintigraphy (99mTc-MIBI). The patient presented with a history of recurrent renal stones and was diagnosed as having primary hyperparathyroidism due to elevated serum levels of calcium and intact parathyroid hormone (i-PTH) levels. On admission, his serum calcium value was 12.1 mg/dl and the i-PTH level was 137 pg/ml. Ultrasonography, computed tomography (CT), and 201TlCl-99mTcO4- subtraction scintigraphy (Tl-Tc) were performed but none of these imaging techniques was able to detect an enlarged parathyroid gland. Selective venous sampling revealed that the serum i-PTH level was highest at 422 pg/ml in the left brachiocephalic vein. Exploration of the neck also proved unsuccessful. Finally, we performed 99mTc-MIBI which revealed and delineated an enlarged parathyroid gland in the upper mediastinum. Tumor extirpation was subsequently performed through a left thoracotomy. Pathologically, the tumor was confirmed to be a parathyroid adenoma and the serum calcium and i-PTH levels returned to within the normal ranges postoperatively.

Thymolipoma: clinical and pathological features--report of three cases and review of literature

We report three recently resected cases of thymolipoma. Two cases (case 2 and 3) were female and the other (case 1) was male. The age of these three were 41 years, 63 years, and 29 years, respectively. While two cases (case 1 and 2) were asymptomatic, the other (case 3) had associated myasthenia gravis. Preoperative examination in each case was performed using chest CT scan or chest MRI, or both. Only one case (case 1) was diagnosed as thymolipoma preoperatively, and this was by a chest MRI showing the mass in continuity with the thymus. The diagnosis of each lesion was confirmed histologically by their composition of lobules of mature adipose tissue with minute islands of thymic tissue consisting of epithelial cells, lymphocytes, and Hassall's bodies.

Enzymes involved in DNA synthesis in the testes are regulated by temperature in vitro

OBJECTIVE

Temperature is considered to be an important local regulating factor of testicular function. We investigated whether a high temperature would affect the activity of DNA polymerases alpha, beta, and gamma (EC2.7.7.7) and DNA topoisomerase I in the testes which are required for germ cell differentiation.

METHODS

An in vitro rat testis tissue culture system was used to evaluate the activity of DNA polymerases alpha, beta, and gamma and DNA topoisomerase I after incubation at 31 and 37 degrees C. The expression of proliferating cell nuclear antigen was evaluated immunohistochemically in the testis.

RESULTS

Incubation at 37 degrees C significantly reduced the activity of all four enzymes as compared with incubation at 31 degrees C. Reducing the temperature to 31 degrees C after prior incubation at 37 degrees C partially restored DNA polymerase alpha activity. Expression of proliferating cell nuclear antigen demonstrated a reduction in DNA synthesis in the seminiferous tubules after incubation at 37 degrees C CONCLUSION: These findings indicate that a high temperature of 37 degrees C reduces the activity of the enzymes involved in the testicular synthesis of DNA which may cause the impairment of spermatogenesis.

Development of cancer vaccine by tumor rejection antigens

Identification of the MAGE genes allowed us the molecular approach to identify genes encoding tumor rejection antigens expressed on human cancer cells. MAGE-1 proteins are normal tissue antigens compartmentalized in the particular testicular cells playing an important role in the early phase of the spermatogenesis. The MAGE-1, -2, -3, -4 and -6 genes are preferentially expressed in many different cancers at both the mRNA and protein levels. The MAGE genes, particularly MAGE-1, became positive in relatively advanced stages of cancers and recurrent cancers. Approximately one-third to half of human cancers except for myelo-monocytic leukemia expressed at least one of these MAGE genes. The MAGE gene products shall be appropriate target molecules for development of new cancer vaccine.

Serum of Isaacs' syndrome suppresses potassium channels in PC-12 cell lines

Blockage of K+ channels in nerve terminals by immunoglobulin is the speculated pathomechanism of Isaacs' syndrome. Using patch-clamp technique (whole-cell clamp), we investigated the effects on K+ current of serum taken from 2 patients with Isaacs' syndrome employing the clonal cell line PC-12. The addition of a patient's serum to the perfusion solution had little effect on the K+ current of P-12 cells. In contrast, K+ current was reduced by 25-80% when cells were cultured for 3-6 days with 2% serum as compared to control serum values. Suppression of the K+ current appears to develop gradually over the period of culture. Our results suggest that the pathomechanism of Isaacs' syndrome is caused by K+ channel suppression via a humoral factor(s) in the serum, which subsequently induces nerve hyperexcitability.