Stac, a novel neuron-specific protein with cysteine-rich and SH3 domains

In RLGS-M (restriction landmark genomic scanning using methylation-sensitive endonuclease) displays of mouse brains, spot #91 is one of tissue-specific gel spots whose intensity changes developmentally. We have now cloned the corresponding cDNA from this spot and analyzed its structure and expression. The deduced amino acid sequence revealed that the #91 cDNA encodes a novel protein of 403 amino acids which consists of a cysteine-rich domain and a SH3 domain. We designated this gene as Stac. Northern blotting and in situ hybridization analyses demonstrated that 2.7 kb of Stac mRNA is expressed predominantly in brain and neurons, especially in hippocampus, cerebellum and inferior olive. Further, the gene product of 47 kDa was found by western blotting analysis in the soluble fractions of brain as well as Stac-expression vector-transfected NIH3T3 cells. Although the function of Stac is unknown so far, it is likely involved in a neuron-specific signal transduction.

Lysophosphatidylcholine induces Ca2+-independent cellular injury attenuated by d-propranolol in rat cardiomyocytes

In isolated rat cardiomyocytes, exogenous lysophosphatidylcholine (LPC) (15 microM) increased the intracellular Ca2+ concentration (Ca2+]i) from 72 +/- 5 to 3042 +/- 431 nM accompanied by cell injury as indicated by the hypercontracture of the cells and the increase in creatine phosphokinase (CPK) release. In order to understand whether the cell injury induced by LPC was a consequence of the elevation of [Ca2+]i, the effect of LPC was examined in the Ca2+-free solution containing EGTA. Under the Ca2+ -free conditions, LPC did not increase [Ca2+]i, whereas it still inflicted injury on the cells in terms of cell-shape change and CPK release to the same degree as that under the Ca2+-present condition. Addition of ryanodine (10 microM) failed to prevent the changes in cell-shape and CPK release induced by LPC under both Ca2+-free and Ca2+-present conditions. Preincubation of the myocytes with d-propranolol (50 microM) inhibited the LPC-induced changes in cell-shape and CPK release under both Ca2+ -free and Ca2+ -present conditions (p < 0.05). Our study provides clear evidence that the cellular injury induced by LPC could be independent of the increase in [Ca2+]i, and the Ca2+-independent cellular injury induced by LPC could be attenuated by d-propranolol, although the mechanism remains unknown.

Threonine 1342 in human topoisomerase IIalpha is phosphorylated throughout the cell cycle

To investigate the relationship between the modulation of topoisomerase II activity and its phosphorylation state during the cell cycle, a monoclonal antibody against C-terminal peptide (residues 1335-1350) of topoisomerase IIalpha containing a consensus sequence of casein kinase II, TDDE and its phosphorylated threonine were prepared. In an enzyme-linked immunosorbent assay, the antibody, named PT1342, recognized the immunogenic phosphopeptide but not the non-phosphorylated form of the peptide. The PT1342 antibody reacted only with a 170-kDa protein from HeLa cells and recognized anti-topoisomerase IIalpha immunoprecipitants. Furthermore, the antibody did not react with the human topoisomerase IIalpha mutated at codon 1342 from threonine to alanine, showing that PT1342 was directed against the phosphorylated threonine 1342. To examine the level of phosphorylation of threonine 1342 of topoisomerase IIalpha through the cell cycle, HeLa cells were stained simultaneously for phosphorylated topoisomerase IIalpha and DNA and analyzed by flow cytometry. Cells in the G2-M phase contained about double the PT1341-reacted topoisomerase IIalpha than did cells in G1 or S phases. The antibody stained the nuclei in interphase and mitotic chromosomes and its periphery, as seen with anti-topoisomerase IIalpha antibody. Thus, threonine 1342 in topoisomerase IIalpha is phosphorylated throughout the cell cycle.

In vivo implantation of human osteosarcoma cells in nude mice induces bones with human-derived osteoblasts and mouse-derived osteocytes

Two human osteosarcoma cell lines, Hu09 and OST, were suspended in Matrigel (Becton Dickinson Labware, Bedford, Massachusetts) and implanted subcutaneously in the backs of nude mice. To study phenotypic changes of tumor cells and host cells, expression of mRNA for osteopontin (OPN), osteocalcin (OC), and osteonectin (ON) was analyzed by in situ hybridization. Bone tissue was formed in the tumors derived from Hu09 cells. OPN mRNA was transcribed predominantly in osteocyte-like cells within the bone, whereas OC mRNA was transcribed in osteoblast-like cells that surrounded the bone. ON mRNA was detected in both types of cells. The similarity of the expression pattern of OPN, OC, and ON during osteogenesis of Hu09 cells to that of normal skeletal development suggests that the bone formed in Hu09-implanted mice is the same as normal bone tissue. By DNA-DNA in situ hybridization using a human-specific Alu probe and a mouse-specific m-L1 probe, osteoblast-like cells in Hu09 tumorous bone were, however, of human origin, whereas osteocyte-like cells were of mouse origin. In the tumors derived from OST cells, no osteogenesis was observed during the experimental period, and the expression of OPN, OC, and ON was not detected in tumor cells. An endochondral bone formation was not evident when these cells were simply implanted into muscle tissue. An endochondral bone was, however, reactively induced in the host mUscle tissue either when 1 alpha-hydroxyvitamin D3 and all-transretinoic acid were administered to OST-implanted mice or when Hu09 cells were pretreated with dexamethasone before implantation. Hu09 implantation seems to be a useful tool not only for the study of the differentiation of osteosarcoma cells but also for the investigation of the mechanism of bone formation. This system, using Hu09 and OST, may provide us with a new tool for the isolation of the unidentified factors that induce or inhibit osteogenesis in vivo.

Chemoprevention of 4-nitroquinoline 1-oxide-induced rat oral carcinogenesis by the dietary flavonoids chalcone, 2-hydroxychalcone, and quercetin

The modifying effects of dietary exposure of three flavonoids, chalcone, 2-hydroxychalcone, and quercetin, during the initiation and postinitiation phases of oral tumorigenesis initiated with 4-nitroquinoline-1-oxide (4-NQO) were investigated in male F344 rats. At 6 weeks of age, animals were divided into experimental and control groups. At 7 weeks of age, all animals except those treated with test chemicals alone and the untreated control group were given 4-NQO [20 parts/million (ppm)] in the drinking water for 8 weeks to induce oral neoplasms. For chemopreventive study by feeding of test compounds during the initiation phase, groups of animals were given diets containing 500 ppm chalcone, 500 ppm 2-hydroxychalcone, or 500 ppm quercetin for 10 weeks, starting 1 week before 4-NQO exposure. Seven days after stopping 4-NQO exposure, these groups were switched to the basal diet and kept on this diet until the end of the experiment. For chemopreventive study by treatment with test chemicals during the postinitiation phase, starting 1 week after the cessation of 4-NQO administration, the groups given 4-NQO and the basal diet were switched to the diets mixed with test chemicals and maintained on these diets for 22 weeks. The other groups consisted of rats fed diets containing 500 ppm test chemicals alone or of untreated rats. Thirty-two weeks after the start of the study, the incidence of tongue neoplasms and preneoplastic lesions, polyamine levels in the tongue epithelium, and cell proliferation activity estimated by bromodeoxyuridine labeling index were compared among the different dietary groups. Feeding of all test chemicals during either initiation or postinitiation phases caused a significant reduction in the frequency of tongue carcinoma (68-88% reduction; P < 0.05). Dietary administration of these test chemicals also significantly decreased the bromodeoxyuridine labeling index of the tongue squamous epithelium (P < 0.05). In addition, polyamine levels in the oral mucosa were lowered in rats treated with 4-NQO and test chemicals when compared to those given 4-NQO alone. These results indicate that the flavonoids chalcone, 2-hydroxychalcone, and quercetin present in our daily foods have an inhibitory effect on oral carcinogenesis initiated with 4-NQO, and such a modifying effect may be related partly to the suppression of cell proliferation.

Relationship between vitellogenin and its related egg yolk proteins in Sakhalin taimen (Hucho perryi)

Vitellogenin (Vg) and its three egg yolk protein products, lipovitellin (Lv), phosvitin (Pv) and beta'-component, were isolated from mature female Sakhalin taimen (Hucho perryi). Vg had an apparent molecular weight of 540 kDa and appeared as a major 240 kDa band in SDS-PAGE, which resolved into two major bands (165 and 125 kDa) after reduction. The estimated molecular weights of purified Lv, Pv, and beta'-component were 330, 23, and 30 kDa, respectively. Lv appeared as a main band of 150 kDa in SDS-PAGE which resolved into two smaller bands (92 and 29 kDa) after reduction. beta'-component appeared as a 34 kDa band before and as a 17kDa band after reduction. Except for Pv, the purified proteins all reacted with an antiserum to Vg. In SDS-PAGE, Pv appeared as a 23 kDa band and a second < 6.5 kDa diffuse band. An antiserum to Pv dephosphorylated by alkaline phosphatase (Ap) was prepared. In Western blots, the antiserum reacted with dephosphorylated Pv and Vg, but not with Lv and beta'-component. This is the first immunological proof that three egg yolk proteins (Lv, Pv, and beta'-component) are derived from Vg in fish.

Localization of Bax and Bcl-2 proteins, regulators of programmed cell death, in the human central nervous system

Bax and Bcl-2 proteins are identified as regulating molecules for programmed cell death. In the central nervous system, programmed cell death or apoptosis is considered to be an important phenomenon that is related to neuron vulnerability to a variety of toxic effects, including ischaemic insult. In this study, localization of Bax and Bcl-2 proteins was investigated in the human central nervous system using autopsy cases without any neurological disorder. Results were compared with findings in the rat. Most neurons in human cerebral cortex, basal ganglia and brain stem were positive for both Bax and Bcl-2 proteins, whereas Purkinje cells in cerebellum and neurons in hippocampal CA1, CA2 and CA3 regions were positive for Bax but negative or weakly positive for Bcl-2. Glial cells examined in all sections were negative for both proteins. Choroid plexus, ependymal cells and arachnoid villi showed positive reactivity for both proteins. A possible relationship between the localization of Bax or Bcl-2 proteins and the cell vulnerability in central nervous system is discussed.

Dilazep and its derivative, K-7259, attenuate mechanical derangement induced by palmitoyl-L-carnitine in the isolated, perfused rat heart

The effect of dilazep, a potentiator of the adenosine-mediated effects, on the palmitoyl-L-carnitine (PALCAR)-induced mechanical derangement was studied in the isolated rat heart and compared with that of K-7259, a dilazep derivative having less potentiating action on the adenosine-mediated effects. The heart was perfused aerobically by the Langendorff's technique at a constant flow and driven electrically. PALCAR (5 microM) decreased the left ventricular developed pressure and increased the left ventricular end diastolic pressure in the heart (i.e., mechanical dysfunction). These mechanical alterations induced by PALCAR were attenuated by dilazep (1 microM) and K-7259 (1 microM). In contrast, adenosine (10 or 100 microM) did not attenuate the PALCAR-induced mechanical derangement. On the other hand, neither dilazep nor K-7259 modified the mechanical function of the normal (PALCAR-untreated) heart. These results suggest that dilazep and K-7259 attenuate the PALCAR-induced mechanical derangement and that the protective action of both drugs is not due to potentiation of adenosine-mediated effects.

Human T-cell lymphotropic virus type-I associated myelopathy complicated by optic neuritis

A 48-year-old Japanese woman from Kyushu was admitted to the Nippon Medical School First Hospital with complaints of numbness in both legs, gait disturbance, and urinary problems. On examination, her lower extremities were spastic with increased reflexes and positive Babinski sign. Sensation was absent below the T4 spinal level. The cerebrospinal fluid contained HTLV-I antibodies and she was diagnosed with HTLV-I associated myelopathy. Her symptoms were resolved with prednisolone, but six months later a visual disturbance of the left eye edema developed. Orbital CT scans showed that left optic nerve was edematous. T2 enhanced MRI revealed a high intensity lesion of the left optic nerve. ERG was normal and no VEP was detected in response to flashing stimulation to the left eye. The HTLV-I antigen titer of CBF was very high. Her optic neuritis improved following oral administration of prednisolone and retrobulbar injections of dexamethasone. This is the first case report of HTLV-I associated myelopathy complicated by optic neuritis.

[A new approach to the understanding of the mechanism of ischemia/reperfusion damage in the heart and the effects of anti-ischemic drugs]

The classical understanding of the mechanism of anti-anginal or anti-ischemic drugs is an increase in blood supply to the heart and/or a decrease in oxygen consumption of the heart, maintaining energy balance in the heart between supply and demand and hence maintaining the tissue levels of high-energy phosphates. This scheme is reasonable. During reperfusion following ischemia, however, there is more serious damage to the heart, although the tissue levels of high-energy phosphates increase. This is probably because toxic substances are generated in the heart during ischemia/reperfusion. We propose that both lysophosphatidylcholine and palmitoyl-L-carnitine that accumulate in the myocardium during ischemia/reperfusion are candidates for the toxic substances that accelerate ischemia/reperfusion damage to the heart. Therefore, drugs that have anti-lysophosphatidylcholine and/or anti-palmitoyl-L-carnitine effects are promising for the treatment of ischemic heart diseases. We found that K-7259, a novel derivative of dilazep having a minimal effect on the normal heart, is a drug that attenuates the deleterious effects of both lysophosphatidylcholine and palmitoyl-L-carnitine on the heart, and therefore attenuates the ischemia/reperfusion damage.

Rapid method of preparation of lysoglycosphingolipids and their confirmation by delayed extraction matrix-assisted laser desorption ionization time-of-flight mass spectrometry

We have recently developed a rapid method for the preparation of lysoglycosphingolipids on a small scale, in high yield. This procedure of microwave-mediated saponification of about 1 mg of glycosphingolipid with 0.5 ml of 0.1 M NaOH in methanol for two minutes can be easily repeated if larger amounts of lyso-compounds are needed. We have also found that the new methodology of delayed extraction matrix-assisted laser desorption ionization time-of-flight mass spectrometry in the reflector mode is extremely effective for the confirmation of different lysoglycosphingolipids together with their long chain base components. The combined method of preparation and confirmation of lysoglycosphingolipids is also important for the identification of long chain bases of various sphingolipids, because the usual analytical method of long-chain bases of sphingolipids depends on acidic methanolysis, which results in the formation of by-products such as O-methylsphingosines and threo-sphingosines.

Involvement of nitric oxide in spinally mediated capsaicin- and glutamate-induced behavioural responses in the mouse

The intrathecal (i.t.) injection of capsaicin (0.1 nmol/mouse) through a lumbar puncture elicited scratching, biting and licking responses. Pretreatment with the nitric oxide synthase inhibitor NG-nitro-L-arginine methyl ester (L-NAME) (320 nmol), by i.t. injection, resulted in a significant inhibition of the behavioural response produced by i.t. capsaicin (0.1 nmol/mouse). Similar behavioural responses were induced by i.t. injections of NMDA (0.4 nmol), kainate (0.05 nmol) or AMPA (0.05 nmol), which were all inhibited by co-administration of L-NAME (20-80 nmol). L-Arginine (600 mg/kg, i.p.) but not D-arginine (600 mg/kg, i.p.) reversed the inhibitory effect of L-NAME on capsaicin-, NMDA-, kainate- and AMPA-induced behavioural response. Scratching, biting and licking responses induced by tachykinin receptor agonists, substance P, [Sar9,Met(O2)11]substance P, neurokinin A and neurokinin B were not affected by co-administration of L-NAME (40 and 80 nmol). These results suggest that spinal nitric oxide may play a significant role in mechanisms of the behavioural response to capsaicin, probably through the release of glutamate, but not tachykinins.

The combination of different types of antitumor topoisomerase II inhibitors, ICRF-193 and VP-16, has synergistic and antagonistic effects on cell survival, depending on treatment schedule

VP-16 and ICRF-193 are different types of antitumor topoisomerase II inhibitors, being cleavable and non-cleavable complex-stabilizing types, respectively. To examine the possibility of enhancing the efficacy of combination chemotherapy, we carried out simultaneous and sequencial treatment of cells with the two drugs. When KB cells were exposed continually to low concentrations (0.05 - 0.2 microM) of the drugs, the effects were synergistic. In contrast, when the cells were treated with high concentrations of ICRF-193 and VP-16 for 1 hour, the VP-16-induced cytotoxicity was prevented by ICRF-193 and the degree of prevention was increased by the pretreatment of cells with ICRF-193, while post-treatment with ICRF-193 had little effect on the cytotoxicity of VP-16. ICRF-193 at 1 microM was found to interact with about half molecules of topisomerase IIa and II beta in cells, as judged by increased amounts of a salt-stable complex. ICRF-193 inhibited in vitro VP-16-induced cleavable complex formation, but a much higher concentration was needed to reverse the cleavage already generated by VP-16. Thus, the antagonistic or synergistic effects of ICRF-193 and VP-16 depend on the concentration of the drug, as it may be critical as to how many molecules of cellular topoisomerase II interact with the drugs.

Involvement of two basic residues (Lys-17 and Arg-39) of mouse lung carbonyl reductase in NADP(H)-binding and fatty acid activation: site-directed mutagenesis and kinetic analyses

Mouse lung carbonyl reductase, a member of the short-chain dehydrogenase/reductase (SDR) family, shows a strong coenzyme preference for NADP(H) over NAD(H), and is uniquely activated by fatty acids. Previous chemical modification and X-ray crystallography studies show that interactions responsible for the coenzyme specificity include salt linkages between the 2'-phosphate of NADPH and side-chains of Lys-17 and Arg-39 of the enzyme. Although Arg-39 is highly conserved in NADP(H)-dependent enzymes of the SDR family, Lys-17 is substituted with Arg in about half of the NADP(H)-dependent enzymes. The present study shows that mutations of Lys-17 to His (K17H) or Ser (K17S) and of Arg-39 to Ala (R39A) bring about decreases (from 5 to 90-fold) of the affinities for NADP(H), but minor changes in the affinity for NAD+. The binding energy arising from the mutations on the binding of the 2'-phosphate of NADP+ was decreased by 38-66% from the value of 4.8 kcal/mol calculated for the wild-type enzyme. In contrast, the mutation of Lys-17 to Arg (K17R) had little effect on the kinetic or thermodynamic properties. The activation by fatty acids was completely attenuated by the mutations of K17H and K17S, but not by K17R or R39A. These results indicate that the 2'-phosphate group of NADP(H) is recognized by both Lys-17 and Arg-39, of which Lys-17 is a component of the binding site for the activator, probably interacting with the negatively charged carboxylate group of fatty acids, and also suggest that the existence of a positively charged residue (either Lys or Arg) at position 17 is required for both NADP(H) specificity of the SDR family enzymes and fatty acid activation of the pulmonary carbonyl reductase.

A microwave-mediated saponification of galactosylceramide and galactosylceramide I3-sulfate and identification of their lyso-compounds by delayed extraction matrix-assisted laser desorption ionization time-of-flight mass spectrometry

Small amounts of galactosylceramide (cerebroside) and galactosylceramide I3-sulfate (sulfatide) obtained from porcine spinal cord and equine kidney were deacylated by a rapid method of microwave-mediated saponification to prepare their lyso-compounds. Mass spectra of their protonated or deprotonated molecular ion peaks were detected by recently developed new technology of a delayed extraction matrix-assisted laser desorption ionization time-of-flight mass spectrometer with reflector detector in positive or negative ion mode. Long chain bases of lysocerebroside and lysosulfatide were different between porcine spinal cord and equine kidney, but similar to each other in the same organ, suggesting their common synthetic pathway. It is noted that the new rapid method can be similarly applied to the deacylation of both cerebroside and sulfatide in contrast to our classical method which was able to be applied to cerebroside, but not to sulfatide.

Molecular cloning of a gene encoding acid alpha-glucosidase from Tetrahymena pyriformis

Lysosomal acid alpha-glucosidase is essential for the degradation of glycogen to glucose in lysosomes. The ciliated protozoan Tetrahymena pyriformis secretes acid alpha-glucosidase into its culture medium. We have earlier reported the purification and characterization of acid alpha-glucosidase from T. pyriformis. The exact molecular mechanism of secretion of this enzyme has not yet been clarified. In the present study we have isolated a full length cDNA clone encoding acid alpha-glucosidase from T. pyriformis. The isolated clone (3019 bp) contained an open reading frame encoding 923 amino acids, and has an estimated molecular mass of 104 kDa. Northern blot analysis revealed that the isolated cDNA hybridized to a 2.8-kb mRNA transcript. N-terminal amino acids after the first methionine fulfilled the requirement of a signal peptide. The deduced amino acid sequence contains the amino acid sequences determined of several peptides derived from the purified enzyme, and was found to have 34% identity and 45% similarity with that of human lysosomal enzyme, with 75% identity in the 16 amino acids at the proposed active site.

Early alterations of apoptosis and cell proliferation in azoxymethane-initiated rat colonic epithelium

Alterations of apoptosis and cell proliferation in the colonic epithelium of rats after exposure to azoxymethane (AOM) were estimated by means of the terminal deoxynucleotidyl transferase-mediated dUTP-biotin nick end labeling (TUNEL) method, measurement of 5-bromo-2'-deoxyuridine (BrdU) incorporation, immunohistochemical staining for proliferating cell nuclear antigen (PCNA), and counting of mitotic cells. F344 male rats were given a single s.c. injection of AOM (15 mg/kg body weight) at 6 week of age, and killed 4 h, 8 h, 3 days, and 7 days after the AOM treatment. At 4 h after the treatment, many damaged cells were already observed in the colonic epithelium, and they were positive by TUNEL staining. At 8 h, the number of TUNEL-positive cells was largest. The reduction of DNA synthesis in the colonic epithelium, confirmed by BrdU incorporation, was not distinct in comparison with the mitotic inhibition. There was no remarkable change in PCNA labeling index, except that strong expression of PCNA was detected in many damaged cells. On the 3rd day, the appearance of cell death became infrequent and an increase of cell proliferation occurred. On the 7th day, the expression of TUNEL and the cell proliferation biomarkers were at almost normal levels. These findings suggest that AOM induces apoptosis, which is associated with synchronous inhibition of mitosis. The data also indicate that PCNA immunostaining does not reflect the true proliferation state in the early phase after AOM exposure, probably due to the occurrence of cell cycle arrest or DNA repair.

Suppressing effects of 6-(2,5-dichlorophenyl)-2,4-diamino-1,3,5-triazine and related synthetic compounds on azoxymethane-induced aberrant crypt foci in rat colon

The modifying effects of dietary administration of 6-(2,5-dichlorophenyl)-2,4-diamino-1,3,5-triazine and 5 related compounds on the occurrence of azoxymethane (AOM)-induced colonic aberrant crypt foci (ACF) were investigated in rats. Male F344 rats were given s.c. injections of AOM (15 mg/kg body weight) once a week for 3 weeks to induce ACF. They also received the diet containing 200 ppm test compound for 5 weeks, starting one week before the first dosing of AOM. At the termination of experiment, all of the compounds had caused a significant reduction in ACF frequency, which might be associated with suppression of the expression of proliferation biomarkers. The apoptotic index in the colonic mucosal epithelium of rats killed at 6 h after the first AOM exposure revealed no blocking activity of the compounds.

Clinoidal meningioma arising from falciforme process of optic canal: case report and review

A 56-year-old female with an initial symptom of unilateral progressive visual disturbance presented with a clinoidal meningioma arising from a falciforme process of the optic canal. Magnetic resonance images with gadolinium-diethylenetriaminepenta-acetic acid demonstrated marked enhancement of a small mass, approximately 1 cm in diameter, roofing the right optic nerve at the intracranial opening of the optic canal. The clinoidal meningioma is rarely reported and the precise originating location of the neoplasm has not been clarified. This is the first case of clinoidal meningioma, which is confirmed by the operative observation as the origin of the neoplasm is a falciforme process of the optic canal. Magnetic resonance images with enhancement are useful for the diagnosis of such a small neoplastic lesion adjacent to bone structure and total removal without a deterioration of visual function is achieved by careful microsurgical procedure.

Effects of 6-(3-dimethylaminopropionyl)forskolin hydrochloride on energy metabolism in dog hearts in situ

The effect of NKH477 (6-(3-dimethylaminopropionyl)forskolin hydrochloride, CAS 138605-00-2) [formula: see text], a newly developed forskolin derivative, on mechanical function, carbohydrate metabolism and energy metabolism was examined in the dog heart, and compared with that of dobutamine. Intravenous injection of NKH477 (10 or 30 micrograms/kg) or dobutamine (1 or 3 micrograms/kg) increased the maximum rate of rise of left ventricular pressure (LVdP/dtmax), producing a positive inotropic effect. The duration of the effect of NKH477 was longer than that of dobutamine. In addition, NKH477 (10 or 30 micrograms/kg) increased heart rate (positive chronotropic effect). Nevertheless, neither NKH477 (10 or 30 micrograms/kg) nor dobutamine (1 or 3 micrograms/kg) modified the tissue levels of adenosine triphosphate, adenosine diphosphate, adenosine monophosphate, creatine phosphate and lactate. Glycolytic flux (as expressed by the ratio of ([glucose-6-phosphate] + [fructose-6-phosphate]) / [fructose-1,6-diphosphate]) and redox state (as expressed by the ratio of [lactate] / [pyruvate]) in the myocardial cells were not influenced by NKH477 (10 or 30 micrograms/kg) or dobutamine (1 or 3 micrograms/kg). These results suggest that NKH477 produces both positive inotropic and positive chronotropic effects, while it does not interfere with the myocardial energy and carbohydrate metabolism.

Protective effects of dilazep and its novel derivative, K-7259, on mechanical and metabolic derangements induced by hydrogen peroxide in the isolated perfused rat heart

The effect of dilazep, a potentiator of the adenosine-mediated effects, on the hydrogen peroxide (H2O2)-induced mechanical and metabolic derangements was studied in the isolated rat heart, and compared with that of K-7259, a dilazep derivative having less potentiating action on the adenosine-mediated effects. The heart was perfused aerobically by Langendorff's technique at a constant flow and driven electrically. H2O2 (600 microM) decreased the left ventricular developed pressure and increased the left ventricular end diastolic pressure in the heart (i.e, mechanical dysfunction), decreased the tissue ATP level and increased the tissue AMP level (i.e., metabolic change) and increased the tissue level of malondialdehyde (i.e., lipid peroxidation). These mechanical and metabolic alterations induced by H2O2 were attenuated by dilazep (1 microM), and the effect of dilazep was not modified by 8-(p-sulfophenyl)-theophylline (20 microM), a nonselective adenosine receptor antagonist. K-7259 (1 microM) also attenuated the H2O2-induced mechanical and metabolic derangements. Nevertheless, neither dilazep nor K-7259 modified the tissue malondialdehyde level, which was increased by H2O2, and the mechanical function and energy metabolism of the normal (H2O2-untreated) heart. These results suggest that both dilazep and K-7259 attenuate mechanical and metabolic derangements induced by H2O2. The protective action of dilazep and K-7259 on the H2O2-induced derangements is not due to potentiation of adenosine-mediated effects, reduction of lipid peroxidation or preservation of energy.

Telomerase activity of normal tissues and neoplasms in rat colon carcinogenesis induced by methylazoxymethanol acetate and its difference from that of human colonic tissues

Telomerase activity in tissues may be related to tumor development, especially malignant conversion, in humans. However, there are few reports about telomeres and telomerase activity in animals. In this study, we examined telomerase activity in rat colon carcinogenesis and in normal rat liver tissue and compared it with that of human colon cancer tissues. This is the first report concerning telomerase activity in rats. F344 rats were used, and colon neoplasms were induced with methylazoxymethanol acetate. There was telomerase activity in not only the induced colon neoplasms but also the colon mucosa and livers of untreated rats, in contrast with the results from normal human somatic tissues in previous reports. Indeed, we also observed negative results in normal human mucosa, despite the positive results in colon-cancer tissues. These findings suggest that there is a difference in the telomerase activities in humans and rats. Because rat telomeres are very long (20-100 kp, average 50 kp) compared with human telomeres (5-15 kp, average 12 kp), the difference in the telomere lengths of rats and humans might be related to their enzyme activities, although this is still unclear. Furthermore, because the inhibition of telomerase has been proposed as a novel cancer therapy for humans, the rat model presented here, in which telomerase is expressed in somatic tissues, may be useful for studies of telomerase inhibition, including inhibition by chemopreventive agents.

Aldose reductase is a major reductase for isocaproaldehyde, a product of side-chain cleavage of cholesterol, in human and animal adrenal glands

Isocaproaldehyde (4-methylpentanal) is a product of the side-chain cleavage of cholesterol, the first step of steroid biosynthesis. Here, we report the characterization of enzymes responsible for the oxidoreduction of isocaproaldehyde in human, monkey, dog, and rabbit adrenal glands. NADPH-linked isocaproaldehyde reductase activity in the adrenal extracts of the four species was much higher than the NADH-linked reductase and NAD(P)(+)-linked dehydrogenase activities and was potently inhibited by aldose reductase inhibitors. The major species of isocaproaldehyde reductase purified from the four mammalian adrenal glands were biochemically identical with aldose reductase, and exhibited Km values of 1 microM. The contents of aldose reductase in adrenal glands of the four mammals were relatively high, and its localization in canine adrenal cortex was immunohistochemically demonstrated. In addition, the purified aldose reductases and recombinant human aldose reductase reduced other alkanals and alkenals at low Km values of 2-61 microM, and their catalytic efficiencies were higher than that of human aldehyde reductase. Thus, aldose reductase acts not only as a major reductase for isocaproaldehyde formed from steroidogenesis but also as a scavenger of aldehydes derived from lipid peroxidation in mammalian adrenal glands.