[A case of traumatic diaphragmatic hernia accompanied with rupture of pericardium]

We experienced a case of left traumatic diaphragamatic hernia accompanied with rupture of pericardium after blunt trauma by traffic accident. A 55-year-old man who had suffered blunt chest and upper abdominal trauma because of smash of two cars when he had been turning to right in the corner was admitted to our hospital. On arrival at the hospital, the patient complained severe dyspnea that reduced by lying on his right. Another position couldn't be taken because of deterioration of dyspnea. Chest X-ray showed disappeared left diaphragmatic line and abnormal transparent mass that suggest alimentary canal in the left intrapleural space. Cardiac ultrasonography showed abnormal tubular mass close to the left side of mediastinum that deviated to right. The patient was diagnosed as traumatic diaphragmatic hernia and emergency operation was performed. Left diaphragma was lacerated sagitally toward its top for about 12 cm in length. Left pleuropericardium was seen to be lacerated longitudinally for about 8 cm in length in front of the phrenic nerve intraoperatively. Both lacerations were closed by direct suture. The patient discharged on the 37th postoperative day without phrenic nerve palsy. At making diagnosis of patient with chest and abdominal trauma, injure of diaphragma and/or pericardium also must be considered. If it is possible, operation must be performed without hesitation in order to get good prognosis.

Proteolytic activity of IGFBP-3 in various clinical conditions during childhood studied by means of western immunoblotting

Insulin-like growth factors (IGFs) have 6 types of binding proteins (IGFBPs), and IGFBP-3 is the major IGFBP in human sera. A proteolytic enzyme for IGFBP-3 has recently been reported to be present in human and animal pregnant sera. Although the physiological significance of a pregnancy-associated IGFBP-3 protease remains to be established, the proteolysis could result in lowering the affinity for IGFs, thereby enhancing their delivery to target tissues by increasing free IGFs in the circulation. The methods for detection of IGFBP-3 protease which have been widely used so far are a method reported by Lamson et al. which used affinity crosslinking or western ligand blotting. These methods need radioactive materials (iodinated IGFs and IGFBP-3) and it takes at least a few days to get the results. We have now developed a simple assay for the proteolysis of IGFBP-3. The method is western immunoblotting without radioactive materials. The results can be obtained in a day. With this method, we proved the absence of significant proteolytic activity in sera from rapidly growing children (early stage of puberty or precocious puberty), and sera from a severe type of growth hormone deficiency. Significant proteolytic activity, as in pregnant women, was detected in 6 out of 11 patients with acute disorders such as measles, Kawasaki disease, bacterial meningitis and mycoplasma pneumonia, some of whom were probably in a catabolic condition. These data suggests that the proteolysis of IGFBP-3 might also be important in modulating IGF action in some acute diseases during childhood. The increased bioavailability of IGFs by IGFBP-3 proteolysis may play a role in overcoming catabolic conditions.

G beta gamma directly binds to the carboxyl terminus of the G protein-gated muscarinic K+ channel, GIRK1

beta gamma Subunits of heterotrimeric GTP-binding proteins (G beta gamma) activate the inwardly rectifying muscarinic K+ channel, GIRK1. The significant role for the carboxyl (C) terminus of GIRK1 in this interaction has been suggested. However, it is still unknown whether G beta gamma directly interacts with GIRK1. To elucidate the molecular basis of G beta gamma-activation of GIRK1, we examined the binding properties of G beta gamma to the C terminus of GIRK1 cloned from mouse brain cDNA library (MB-GIRK1). The C terminus of MB-GIRK1 fused with glutathione S-transferase directly bound to purified G beta gamma. Incubation of the C terminus with Gi pretreated with GTP gamma S, but not with GDP, resulted in the binding of Gi beta gamma to the protein. Purified G alpha-GDP, but not G alpha-GTP gamma S, inhibited the binding of G beta gamma to the fusion protein. These results indicate that G beta gamma dissociated from G alpha may directly bind to the C terminus of GIRK1.

A novel ATP-dependent inward rectifier potassium channel expressed predominantly in glial cells

We have isolated a novel inward rectifier K+ channel predominantly expressed in glial cells of the central nervous system. Its amino acid sequence exhibited 53% identity with ROMK1 and approximately 40% identity with other inward rectifier K+ channels. Xenopus oocytes injected with cRNA derived from this clone expressed a K+ current, which showed classical inward rectifier K+ channel characteristics. Intracellular Mg.ATP was required to sustain channel activity in excised membrane patches, which is consistent with a Walker type-A ATP-binding domain on this clone. We designate this new clone as KAB-2 (the second type of inward rectifying K+ channel with an ATP-binding domain). In situ hybridization showed KAB-2 mRNA to be expressed predominantly in glial cells of the cerebellum and forebrain. This is the first description of the cloning of a glial cell inward rectifier potassium channel, which may be responsible for K+ buffering action of glial cells in the brain.

[Significance of silent ischemia in dipyridamole perfusion scintigraphy: evaluation in patients with angina]

The significance of silent myocardial ischemia detected by dipyridamole perfusion scintigraphy was evaluated in 80 patients with stable angina and reversible defects (RD) but no infarction. The patients were divided into two groups: 26 patients with silent RD (62 +/- 7 years) and 54 patients with painful RD (65 +/- 7 years). Coronary risk factors, extent of coronary lesions, localization and degree of RD, and prognosis were compared. There was no significant difference in the incidence of coronary risk factors between these two groups, except for hyperlipidemia which was less frequently observed in patients with silent RD than in those with painful RD (8% vs 41%, p < 0.01). Coronary angiography revealed a higher prevalence of insignificant lesions or single vessel disease in patients with silent RD than in those with painful RD (73% vs 39%, p < 0.05). Dipyridamole perfusion scintigraphy revealed a lower degree of RD in patients with silent RD than in those with painful RD (4.4 +/- 3.3 vs 9.0 +/- 4.1 segments, p < 0.05), though there was no significant difference in the localization of RD between these two groups. Treadmill stress testing revealed a lower incidence of chest pain in patients with silent RD than in those with painful RD (26% vs 65%, p < 0.05), despite the mean exercise-duration being significantly longer in the former than in the latter (5.5 +/- 1.7 vs 3.9 +/- 1.7 min, p < 0.05). There was no significant correlation between the late peak serum ML-1 level and LV volume, and the size and motion of infarcted areas in group B.(ABSTRACT TRUNCATED AT 250 WORDS)

Acute, subacute and chronic oral toxicity studies of the new serotonin (5-HT)3-receptor antagonist ramosetron in beagle dogs

The oral toxicity of ramosetron ((R)-5-[(1-methyl-3-indolyl) carbonyl]-4,5,6,7-tetrahydro-1H-benzimidazole hydrochloride, CAS 132907-72-3, YM060), a new compound having serotonin (5-HT)3 receptor antagonist activity was investigated in beagle dogs. To evaluate the acute toxicity, two groups of beagle dogs, each comprised of one male and one female, were given YM060 bulk powder in gelatin capsules at dose of 0, 3 mg/kg or 0, 30 and 60 mg/kg in ascending order in at least 7-day intervals. After the final dose, animals were observed for 2 weeks. No deaths were observed at any dose. At 60 mg/kg, the male exhibited frequent vomiting, salivation and prone position 1-3 h after administration, when the plasma concentration of the unchanged drug reached Cmax or was close to Cmax. The female exhibited no changes except vomiting. No effects on either the male or the female were detected in body weight, food consumption, electrocardiography, hematology, plasma biochemistry or urinalysis. To evaluate the subacute toxicity of YM060, three male and 3 female beagle dogs per group received doses of 0, 1, 3, 10 and 20 mg/kg/d for 13 weeks. YM060 was triturated 10-fold using lactose and filled in gelatin capsules before use. The plasma concentration of unchanged drug increased almost dose-dependently, peaked about 2 h post-dosing and subsequently decreased with time. The plasma concentration-time profile after the final dose at week 13 was not different from that after the initial dose. No treatment-related changes were observed up to 3 mg/kg/d.(ABSTRACT TRUNCATED AT 250 WORDS)

Clinical usefulness of thyroid-stimulating antibody measurement using Chinese hamster ovary cells expressing human thyrotropin receptors

Human thyrotropin (TSH) receptors were expressed in Chinese hamster ovary (CHO) cells using eukaryotic expression plasmid pCXN2, which contains beta-actin promoter. We measured cAMP stimulation in CHO cells expressing human TSH receptors (CHO-hTSH-R cells) by immunoglobulin G (IgG) of patients with Graves' disease and Hashimoto's thyroiditis, and compared the results with a conventional thyroid-stimulating antibody (TS-Ab) assay using porcine thyroid cells and a TSH-binding inhibiting immunoglobulin (TBII) assay. Nineteen untreated patients with Graves' disease, including a case who developed hyperthyroidism after interferon -alpha therapy for chronic hepatitis C, and 13 treated patients with Graves' disease, 10 patients with Hashimoto's thyroiditis and 8 control subjects were studied. In 19 untreated patients with Graves' disease, 17 patients showed positive CHO-hTSH-R cell stimulation, 11 patients showed positive porcine thyroid cell stimulation and 15 patients showed positive TBII. All the untreated patients showed positive results in at least one assay. Although significantly positive correlations were observed among CHO-hTSH-R cell stimulation, porcine thyroid cell stimulation and TBII activities, the IgG of several patients showed significant discrepancy in the assay results. In a patient with interferon-induced hyperthyroidism only CHO-hTSH-R cell stimulation was positive, while porcine thyroid cell stimulation and TBII were negative. After the treatment with propylthiouracil for 6 months, CHO-hTSH-R cell stimulation became negative. The IgG of patients with Hashimoto's thyroiditis did not show significant stimulation of CHO-hTSH-R cells. These results suggest that the CHO-hTSH-R cell stimulation assay is clinically useful for the diagnosis and follow-up of patients with Graves' disease.

Relation of early menarche to high bone mineral density

The study of background factors in individuals with high bone mineral density (BMD) may provide useful information in the prevention of osteoporosis. We investigated the relationship of reproductive factors to BMD. In 519 female volunteers (327 postmenopausal and 192 premenopausal women) ranging in age from 21 to 74 (mean 52.3 +/- 11.8) years, spinal BMD values were obtained using both quantitative computed tomography and dual x-ray absorptiometry. The z score was calculated from the mean BMD in each 5-year age group, and high BMD and low BMD was defined as BMD with z score > + 1.5 and < -1.5, respectively. Normal BMD was defined as BMD within the range - 1.0 < z score < +1.0. Long reproductive period, early menarche, and late menopause were associated with high BMD. Among these, the reproductive period showed the strongest association with BMD. In postmenopausal women, early menopause had a significant relationship with low BMD, and early menarche also had some relation to high BMD. In premenopausal women, there was a significant relationship between early menarche and high BMD. The age at menarche may have a strong association with peak bone mass, as suggested by the positive correlation of early menarche with high BMD observed in this study. It is considered important to prevent risk factors that disturb the beginning of menstruation in adolescent girls.

Immediate hypersensitive reactions to buckwheat ingestion and cross allergenicity between buckwheat and rice antigens in subjects with high levels of IgE antibodies to buckwheat

BACKGROUND

Immediate hypersensitive reactions induced by buckwheat ingestion are considered to be IgE-mediated. Some subjects, however, develop no immediate adverse reactions after buckwheat ingestion despite high levels of buckwheat-specific antigens IgE. The mechanism is unknown.

OBJECTIVE

To investigate the mechanisms.

METHODS

RAST for buckwheat and rice and RAST inhibition between these antigens were performed using sera from 23 buckwheat-sensitive subjects and 30 buckwheat-tolerant subjects who had IgE antibodies for both buckwheat and rice.

RESULTS

RAST values for buckwheat and rice were significantly correlated with each other (P < .01) in the buckwheat-tolerant group, but not in the buckwheat-sensitive group. This suggests the IgE antibodies from the subjects without any overt symptoms after buckwheat ingestion recognize the cross-reactive epitope between buckwheat and rice, whereas the IgE antibodies from those with immediate reactions to buckwheat ingestion do not. RAST inhibition assays were performed to evaluate this. RAST inhibition of heterogeneous combination of inhibitor and disc antigen such as rice and buckwheat was significantly smaller than that of homologous combination of rice and rice or buckwheat and buckwheat in the group with immediate symptoms after buckwheat ingestion. There was no significant difference in RAST inhibition between homologous and heterogeneous combinations in the group without the symptoms.

CONCLUSIONS

There was cross-reactivity with IgE antibodies between buckwheat and rice and IgE antibodies from the buckwheat-tolerant subjects with high levels of IgE antibodies from the buckwheat might recognize the epitopes on buckwheat antigens which cross-react with rice antigens, whereas IgE antibodies from the buckwheat-sensitive subjects might bind to buckwheat-specific epitopes.

Multiple endocrine neoplasia type 1 accompanied by duodenal carcinoid tumors and hypergastrinemia: a familial case

A 38-year-old female was admitted for investigation of the cause of hypergastrinemia, hypercalcemia and an elevated plasma parathyroid hormone (PTH) level. Her siblings, elder brother and sister who had duodenal carcinoid tumor with hypergastrinemia and parathyroid adenomas, were diagnosed as multiple endocrine neoplasia (MEN) type 1. In the present patient, endoscopic examination showed a carcinoid tumor of the duodenum, but examinations by computed tomography (CT) and ultrasonography of the abdomen failed to reveal pancreatic lesions. Serum gastrin levels of this patient and her siblings improved to the normal level after resection of carcinoid tumors. The hypergastrinemia accompanying MEN type 1 in these cases might be due to carcinoid tumor of the duodenum.

Pulmonary tumor thrombotic microangiopathy

Pulmonary tumor thrombotic microangiopathy (PTTM) is characterized by widespread fibrocellular intimal proliferation of the small pulmonary arteries and arterioles in patients with metastatic carcinoma. Microscopic pulmonary tumor emboli have frequently occurred in patients with malignant tumors; however, few cases of PTTM have been reported. A rare case of a patient with gastric adenocarcinoma who presented with acute dyspnea and lethal respiratory failure is described. Histologically, diffuse fibromuscular intimal thickening causing luminal stenosis and obstruction but containing rather few cancer cells was observed in the small pulmonary arteries and arterioles. These findings were consistent with PTTM. Although PTTM is a rare phenomenon, PTTM should be considered in the differential diagnosis of acute dyspnea or pulmonary hypertension in patients with carcinoma.

Specific disruption of samAB genes in a 60-megadalton cryptic plasmid of Salmonella typhimurium

The expression of umuDC operon is required for UV and most chemical mutagenesis in Escherichia coli. The closely related species Salmonella typhimurium has two sets of umuDC-like operons, i.e., umuDCST in the chromosome and samAB in a 60-megadalton cryptic plasmid. In this study, we specifically disrupted the samAB genes to investigate their exact roles in UV mutagenesis in S. typhimurium. The specific gene disruption was carried out by the preligation method. Deletion of samAB did not lower the UV mutability of S. typhimurium TA2659 but rather increased the UV mutability about twofold. The samAB-umuDCST double deletion mutant as well as the umuDCST deletion mutant was UV nonmutable. These results suggest that the samAB genes do not considerably contribute to the UV mutability of S. typhimurium and raise the question of why such quiet umuDC-like genes are present in the cryptic plasmid of S. typhimurium.

[Mass-screenings for osteoporosis using computed X-ray densitometry (CXD): in a mobile unit]

The early diagnosis and treatment of osteoporosis is considered to be important for the prevention of fractures which often cause elderly to become bed-ridden. Computed X-ray densitometry (CXD), a method to measure bone mineral content in the metacarpus II utilizing a simple X-ray image, has been used for mass-screening of osteoporosis, because of its utility and reliability. However, due to its requiring adequate X-ray equipment, this method is often unsuitable for use in small facilities in a remote mountain areas. The use of CXD for osteoporosis screening, was attempted in a mobile unit for tuberculosis screening, by our public health center. The results showed that it is possible to use CXD in combination with a mobile unit, correcting the obtained values according to the radiographic conditions. With this set-up, CXD was used for mass-screening of osteoporosis in a total of 1150 subjects living in mountainous areas of Yoshino-gun, Nara prefecture, and CXD was found to be convenient and effective for mass-screening. The use of CXD in a mobile chest X-ray unit can be expected to be useful for mass-screening of osteoporosis especially in remote mountainous areas having inadequate X-ray equipment.

[Combined acute ascending aneurysm and chronic descending thoracic aneurysms]

A 66-year-old woman with a known chronic descending thoracic dissecting aneurysm was admitted following a chest X-ray which revealed a widening in the mediastinum and an increased cardiothoracic ratio. Echocardiography and chest CT showed a combined ascending thoracic dissecting aneurysm with a tripple lumen, pericardial effision, moderate aortic regurgitation, and the chronic descending thoracic dissection with incompletely thrombosed aneurysm. The chest CT also showed a normal aortic arch. The diagnosis was then made as combined acute ascending aortic dissection (DeBakey II) and chronic descending aortic dissection (DeBakey III). A 2-stage operation was planned, involving first a graft replacement of the ascending aorta, and then one month later a graft replacement of the descending aorta.

Expression of proteolipid protein gene is directly associated with secretion of a factor influencing oligodendrocyte development

Oligodendroglial cell death in the myelin proteolipid protein (PLP) mutants can be partially rescued by the environment factor(s) supplied by the wild-type cells in vivo and in vitro. It is possible that the presence of PLP or DM-20 results in secretion of a factor or factors in the CNS influencing oligodendrocyte development. We previously showed that DM-20 mRNA is produced in G26 mouse oligodendroglioma, B104 rat neuroblastoma, and B16 mouse melanoma but not in NIH3T3 mouse fibroblast cell lines. Culture supernatants from these cell lines were added to primary glial cell cultures from embryonic day 17 mouse brain. After 4 days, the number of oligodendrocytes present in cultures with supernatants from DM-20-producing cells (G26, B104, and B16) was significantly higher than that of control cultures but not with the NIH3T3 supernatant. To investigate more directly whether the PLP gene expression is involved in this process, NIH3T3 cells (nonneural cells) were forced to produce PLP or DM-20. By addition of the supernatants from the PLP/DM-20 transformants, the number of oligodendrocytes in the mixed glial cell cultures increased. This clearly demonstrates that the expression of the PLP gene is sufficient for and directly associated with secretion of a factor, which influences the oligodendrocyte development.

The calmodulin-binding domain in the mouse type 1 inositol 1,4,5-trisphosphate receptor

We determined the amino acid sequence responsible for the calmodulin (CaM)-binding ability of mouse type 1 Ins(1,4,5)P3 receptor (IP3R1). We expressed various parts of IP3R1 from deleted cDNA and examined their CaM-binding ability. It was shown that the sequence stretching from Lys-1564 to Arg-1585 is necessary for the binding. The full-length IP3R1 with replacement of Trp-1576 by Ala lost its CaM-binding ability. Antibody against residues 1564-1585 of IP3R1 inhibited cerebellar IP3R1 from binding CaM. The fluorescence spectrum of the peptide that corresponds to residues 1564-1585 shifted when Ca(2+)-CaM was added. From the change in the fluorescence spectrum, we estimated the dissociation constant (KD) between the peptide and CaM to be 0.7 microM. The submicromolar value of KD suggests an actual interaction between CaM and IP3R1 within cells. The CaM-binding ability of other types of IP3Rs was also examined. A part of the type 2IP3R, including the region showing sequence identity with the CaM-binding domain of IP3R1, also bound CaM, while the expressed full-length type 3 IP3R did not.

Abnormal gene product identified in hereditary dentatorubral-pallidoluysian atrophy (DRPLA) brain

Dentatorubral-pallidoluysian atrophy (DRPLA) is associated with the expansion of an unstable CAG repeat. Using antibodies against a synthetic peptide corresponding to the sequence of the DRPLA gene product C terminus, we have identified the DRPLA gene product in normal human brains as a approximately 190 kD protein. We also find a larger approximately 205 kD protein specifically in DRPLA brains. Immunohistochemically, the DRPLA gene product is observed mainly in the neuronal cytoplasm. Our results demonstrate the existence of the expanded CAG repeat gene product and support the possibility that the expanded CAG-encoded polyglutamine stretch may participate in the pathological process of the similar trinucleotide repeat diseases.

Hemostatic profile of bovine ovarian follicular fluid

The hemostatic profile of bovine ovarian follicular fluid was evaluated and the levels of procoagulant, fibrinolytic, and inhibitory activity compared with plasma. The results of the prothrombin time assay and the presence of fibrinogen along with factor VII and factor X activity indicate that bovine follicular fluid possesses components of the "extrinsic" or "tissue factor" coagulation system. The absence of factor VIII:C activity, along with the extremely low levels of factors IX and XI, indicates that there is not a functional "intrinsic" coagulation pathway. The fluid derived from large follicles exhibited increased levels of factors VII and X activity and a shorter prothrombin time compared with fluid obtained from the less mature small follicles. Similar alterations in the levels of the inhibitory proteins antithrombin III and alpha 2-macroglobulin were observed. Overall the amount of antithrombin III was similar to that in plasma, the levels of fibrinogen and factor X were approximately 2-fold lower, and the levels of factor VII and factor X were approximately 10-fold lower than in plasma. The fibrinolytic activity in follicular fluid was greater than the procoagulant or inhibitory activity. Plasminogen activator activity was 5-fold higher, while both plasminogen and antiplasmin values were similar to plasma levels.

Churg-Strauss syndrome associated with third nerve palsy and mononeuritis multiplex of the legs

We present the rare case of a 62-year-old woman with Churg-Strauss syndrome associated with a left third nerve palsy and a mononeuritis multiplex. Cranial nerve palsies are unusual in patients with Churg-Strauss syndrome, and the most frequent cranial nerve lesion observed is an ischemic optic neuritis. Third nerve involvement secondary to vasculitis-induced ischemia is extremely rare in this disorder.

Aggregated form of dextransucrases from Leuconostoc mesenteroides NRRL B-512F and its constitutive mutant

Purified dextransucrases [EC 2.4.1.5], DSW-D and DSW-G, from Leuconostoc mesenteroides B-512F were obtained from affinity chromatography with DEAE-Sephadex A-50 by elution with clinical dextran and guanidine-HCl, respectively. DSM-G was purified from the B-512F mutant strain SH 3002, which produces dextransucrase constitutively. Although the sugar contents of the purified enzymes were different, their molecular masses by SDS-PAGE were all 170 kDa. DSW-D and DSW-G were highly aggregated and the all the activities were eluted at the void volume (V0) on Sepharose 6B, while the DSM-G was eluted at 1.2 x V0 volume. On rechromatography, DSM-G was separated into three peaks corresponding to the aggregated form, monomeric form, and partially digested form, respectively. The aggregation of Leuconostoc dextransucrase was looser than that of streptococcal glucosyltransferases, but the structures of these enzymes had high homology with each other.

Stimulatory effect of butoctamide hydrogen succinate on REM sleep in normal humans

1. The efficacy of butoctamide hydrogen succinate (BAHS) was compared with that of nitrazepam on the basis of the polysomnograms and the subjective assessments. 2. Twelve healthy male students were divided into three groups consisting of 4 subjects each with were administered BAHS 600 mg, nitrazepam 5 mg, and BAHS 600 mg + nitrazepam 5 mg, respectively. 3. Polygraphic recordings were made for 8 consecutive nights for each subject, and the polysomnograms were evaluated by computerized automatic analysis using the interval histogram method. 4. An inert placebo was administered on the first 3 nights and on the seventh and eighth nights, and the test article regimen was administered on the fourth, fifth and sixth nights. 5. The test articles and the placebo were administered orally at 22:30 hr, and the recording of polysomnograms was started at 23:00 hr and ended at 8:00 hr the next morning. 6. The subjects were requested to fill out the subjective assessment of sleep before falling asleep and after arising the next morning. 7. BAHS increased REM sleep and decreased stage 2 sleep significantly; however, it failed to affect stage 1, 3 or 4 sleep. 8. Nitrazepam increased significantly the total sleep time and stage 2 sleep but decreased significantly the stage 3 sleep and decreased slightly the stages 1, 4 and REM sleep. 9. The combined treatment with BAHS and nitrazepam did not alter the sleep parameters except for increasing the total sleep time. 10. No obvious changes were observed in the subjective assessments after administration of the drugs. 11. These findings suggest that BAHS results in a unique sleep pattern different from benzodiazepines, and that BAHS may be suitable for treating insomnia in elderly patients and those with drug abuse, manic-depressive illness or schizophrenia.

Spermine gates inward-rectifying muscarinic but not ATP-sensitive K+ channels in rabbit atrial myocytes. Intracellular substance-mediated mechanism of inward rectification

The effect of spermine, a low molecular mass aliphatic amine with positive charges, on the strongly inwardly rectifying muscarinic K+ (KACh) channel was examined in rabbit atrial myocytes. In inside-out patch membranes, the single channel current-voltage relationship of KACh channels activated by guanosine 5'-3-O-(thio)triphosphate became linear in the absence of intracellular Mg2+. The open probability (Po) of the channels did not show significant voltage dependence under these conditions. Spermine specifically reduced Po of outwardly flowing KACh channel currents without affecting the unitary current amplitude at depolarized potentials, but had no effect on inward KACh currents under hyperpolarization. This voltage dependence of Po of KACh channels in the presence of spermine resembled that normally observed in the whole cell or open cell-attached configurations. Spermine (300 nM to 3 microM) also restored the relaxation of KACh currents which had been lost in the inside-out configuration. The effect of spermine was concentration-dependent with IC50 of approximately 10 nM at +40 mV. The order of potency of polyamines in reducing Po at +40 mV was spermine > or = spermidine > putrescine > ornithine; arginine had no significant effect. Intracellular Mg2+ antagonized the effect of spermine. Neither the single channel conductance nor Po of the ATP-sensitive K+ channel, a weak inward rectifier, was affected by spermine. Because submillimolar concentrations of spermine and spermidine are available in the cytosol of most cells, these substances may be the unidentified intracellular gating factors for strong inward rectifiers such as KACh and IK1 channels.

Involvement of umuDCST genes in nitropyrene-induced -CG frameshift mutagenesis at the repetitive CG sequence in the hisD3052 allele of Salmonella typhimurium

Expression of the umuDC operon is required for UV and most chemical mutagenesis in Escherichia coli. The closely related species Salmonella typhimurium has two sets of umuDC-like operons, umuDCST on the chromosome and samAB on a 60-MDa cryptic plasmid. The roles of the umuDC-like operons in chemically induced frameshift mutagenesis of the hisD3052 allele of S. typhimurium were investigated. Introduction of a pBR322-derived plasmid carrying umuDCST increased the rate of reversion of hisD3052, following treatment with 1-nitropyrene (1-NP) or 1,8-dinitropyrene (1,8-DNP) tenfold and fivefold, respectively, whereas it did not substantially increase the rate of reversion induced by other frameshift mutagens, i.e. 2-nitrofluorene (2-NF) and 2-amino-3-methyldipyrido[1,2-a:3',2'-d]imidazole (Glu-P-1). Introduction of a pBR322-derived plasmid carrying samAB did not increase the incidence of reversion of hisD3052 observed with any of the mutagens examined. Deletion of umuDCST substantially lowered the reversion rate induced by 1-NP or 1,8-DNP, but it did not affect reversion induced by 2-NF, Glu-P-1 or N-hydroxyacetylaminofluorene (N-OH-AAF). Deletion of samAB had little impact on reversion incidence induced by any of the five frameshift mutagens. DNA amplification using the polymerase chain reaction technique followed by restriction enzyme analysis using BssHII, suggested that the mutations induced by the five frameshift mutagens were all CG deletions at the CGCGCGCG sequence in hisD3052. These results suggest that umuDCST, but not samAB, is involved in the -2 frameshift mutagenesis induced by 1-NP and 1,8-DNP at the repetitive CG sequence, whereas neither operon participates in induction of the same type of mutations by 2-NF, Glu-P-1 or N-OH-AAF.