Possible radical scavenging properties of cicletanine and renal protection in Dahl salt sensitive rats

Much interest in cicletanine, a novel antihypertensive drug, has grown because it uniquely stimulates prostacyclin (PGI2) production and may, thereby, provide further cardiovascular protection. We postulated that cicletanine may be an antioxidant, and assessed its ability to protect the kidney in Dahl salt-sensitive (Dahl S) rats on a high salt diet. Cicletanine eradicated in vitro a stable radical, DPPH, and decreased the lipid peroxidation both in rat brain homogenate and in a xanthine-xanthine oxidase (X-XOD) superoxide generating system. Furthermore, cicletanine attenuated the inhibition of PGI2 synthase activity by 15HPETE. However, cicletanine did not exhibit superoxide dismutase-like activity in X-XOD system, suggesting that it behaves primarily as a hydroxy radical scavenger. A 6 week cicletanine treatment reduced blood pressure in Dahl S rats fed a high salt diet, and ameliorated functional and morphological injury to the kidney. This attenuation of glomerular sclerosis correlated with the attenuation of lipid peroxidation in the kidney homogenate. These data indicate that cicletanine is an antioxidant that protects the kidney from salt-induced hypertension in Dahl salt-sensitive strain rats.

A transcription initiation site for the hepatitis B virus X gene is directed by the promoter-binding protein

Recent studies have demonstrated the transacting function of the X gene product of hepatitis B virus. However, little information is available on the regulation of X gene expression. In this report, we first investigate a cellular factor regulating X gene transcription by DNA transfection, using the human hepatoma cell line HuH-7, which is permissive for HBV replication as well as X mRNA transcription. A sequence-specific cellular factor was found to bind to the promoter region upstream of the first ATG (nucleotide [nt] 1248) of the X open reading frame. DNase I footprinting analysis showed the binding sequence of this factor to be situated between nt 1097 and 1119, where an 8-bp palindrome structure resides. S1 nuclease analysis of X gene transcripts demonstrated the binding site to be adjacent to two major start sites (nt 1117 and 1125) of X mRNA. Second, we demonstrate that introduction of a mutation into the binding site gives rise to a loss of the binding with a concomitant shift of the transcription start site of X mRNA beyond the 8-bp palindrome structure, causing it to become more heterogeneous. Thus, the promoter-binding protein appears to be involved in directing the transcription initiation site of the X gene toward the downstream region of the X promoter when X protein is produced from X mRNA.

Cloning of a Ca(2+)-ATPase gene of Plasmodium falciparum and comparison with vertebrate Ca(2+)-ATPases

A Ca(2+)-ATPase gene was cloned from the genomic libraries of Plasmodium falciparum. From the deduced amino acid sequence of the gene, a 139 kDa protein with a total of 1228 amino acids was predicted. Sequence of a partial cDNA clone of the gene identified two introns near the 3′-end at the regions identical to the regions assumed for the Ca(2+)-ATPase gene of P. yoelii, a rodent malaria species. As compared with a variety of Ca(2+)-ATPases, the P. falciparum Ca(2+)-ATPase had the highest amino acid sequence homology (78%) to the P. yoelii Ca(2+)-ATPase, moderate homology (45-50%) to vertebrate sarcoplasmic/endoplasmic reticulum Ca(2+)-ATPases (SERCAs), and lowest homology (20%) to a plasma membrane Ca(2+)-ATPase. The P. falciparum protein conserved sequences and residues that are important for the function and/or structure of the organellar type Ca(2+)-ATPase, such as high affinity Ca(2+)-binding sites, fluorescein isothiocyanate (FITC)-binding regions, and the phosphorylation site, but the protein did not contain calmodulin-binding regions that occur in the plasma membrane type Ca(2+)-ATPase. Thus we concluded the cloned gene was the organellar type Ca(2+)-ATPase of P. falciparum. In a region between the phosphorylation site and FITC-binding region, the P. falciparum protein was about 200 residues longer than the rabbit SERCA and lacked a sequence that binds to phospholamban, a protein that regulates the activity of the rabbit SERCA.(ABSTRACT TRUNCATED AT 250 WORDS)

Hybrid dysgenesis in natural populations of Drosophila melanogaster in Japan. III. The P-M system in and around Japan

The P-M system of hybrid dysgenesis in Drosophila melanogaster was investigated on the basis of gonadal dysgenesis, using 1,590 strains from 28 natural populations in Japan, and 20 populations from Southeast Asia, the Pacific area and Africa. Strong P strains were found sporadically in several populations in Japan. Few strong M strains were observed. Q strains were present at a high frequency in most populations. Thus, most populations in these areas were regarded as Q populations. The distribution of the P element and the evolution of P, Q and M populations are also discussed.

Functional domains of c-Myc involved in the commitment and differentiation of murine erythroleukemia cells

In the early event of the induction of mouse erythroleukemia (MEL) cell differentiation, c-myc mRNA levels show a drastic change. The elevated expression of a transfected c-myc gene inhibits the commitment and differentiation of MEL cell transformants. In the present work, we have introduced human c-myc mutants into MEL cells under the inducible promoter to define the functional domains of c-Myc involved in erythroid differentiation. The c-Myc domains necessary for commitment and differentiation are not co-localized; almost entire regions are required for inhibition of commitment, whereas domains II and IV that are essential for co-transforming activity with ras are required for inhibition of differentiation. Interestingly, mutants that delete domains for c-Myc dimerization motifs enhanced differentiation. These results suggest that c-Myc may regulate commitment and differentiation by interacting with proteins through different domains.

[Mechanism of hepatocarcinogenesis by hepatitis B virus]

The X gene product of hepatitis B virus (HBV) has a trans-activation function. The AP-1, AP-2, kappa B-like, and C/EBP-like sequences, and the 26-bp element in HBV enhancer were identified as X-responsive elements. Although the X protein possesses a transcriptional activation domain, it doesn't bind to the X-responsive elements. However, CREB/ATF-2 becomes able to bind to a CRE-related sequence in the 26-bp element once it complexes with X protein. In addition, X protein was shown to have amino acid sequences homologous to the essential domain of Kunitz-type serine protease inhibitors and directly interacted with the protease, tryptase TL2. Results suggest that X protein modulates the tryptase TL2 activity, which may be involved in the proteolytic cleavage of cellular transcription factors.

[Prognostic significance of auditory brainstem responses in full-term newborn infants with intracranial hemorrhages]

Auditory brainstem response (ABR) was recorded in 41 full-term newborn infants with intracranial hemorrhages (ICH; 10 infants with and 31 infants without neurological sequela) and the data were compared with those obtained in normal full-term newborn infants as controls. The wave-I peak latency was significantly prolonged in the non-sequela group than in the control group and in the sequela group than in the non-sequela group. The wave-III and wave-V peak latencies were significantly prolonged in the ICH group (sequela and non-sequela groups) than in the control group but did not significantly differ between the sequela and non-sequela group. The wave I-V interpeak latency did not significantly differ among the three groups. Among 10 infants in the sequela group, 9 had a V/I amplitude ratio (the amplitude of wave-I divided by the amplitude of wave- V) of less than 1.0. This suggests that the V/I amplitude ratio is of prognostic value in ICH infants.

Measurement of local directional pressures in the brain with mass

In order to understand the effects and the direction of pressure transmitted from a mass lesion through various brain structures, miniature strain gauges were inserted in different brain locations in eight anesthetized monkeys. Mass lesions were created by inflating a balloon in either of two locations--subcortical in four animals (Group I) and deep (lateral to the caudate nucleus) in the other four animals (Group II). Anterior-posterior directed pressures were thus measured from a gauge placed in the parietal lobe, and lateromedially directed pressures (LM-dPs) were measured from gauges in the temporal lobe and midbrain. Intracranial pressure, systemic mean arterial pressure, and cerebral blood flow were also monitored. After balloon inflation was begun, temporal changes in pressure were recorded from gauges as percentage increase or decrease from baseline measurements. In both groups, balloon inflation caused a gradual increase in the parietal lobe anterior-posterior directed pressure with a concomitant increase in intracranial pressure and a decrease in cerebral blood flow. The temporal lobe gauge in Group I recorded an initial negative followed by a positive LM-dP with further balloon inflation. In Group II, this gauge recorded a positive LM-dP throughout. The midbrain gauges in both groups recorded an initial positive followed by a negative LM-dP. This reversal in the direction of pressure in the midbrain occurred just before the supratentorial pressure reached a peak and was noted to be concurrent with a sudden rise in mean arterial pressure and a decline in cerebral blood flow.(ABSTRACT TRUNCATED AT 250 WORDS)

Role of c-Myc on erythroid differentiation

In the early event of the induction of mouse erythroleukemia (MEL) cell differentiation, c-myc mRNA levels show a biphasic change. The elevated expression of a transfected c-myc gene inhibits the commitment and differentiation of MEL cell transformants. In the present work, we have introduced human c-myc mutants into MEL cells under the inducible promoter to define the functional domains of c-Myc involved in erythroid differentiation. The c-Myc domains necessary for commitment and differentiation are not colocalized; almost entire regions are required for inhibition of commitment, whereas domains II and IV that are essential for co-transforming activity with ras are required for inhibition of differentiation. Interestingly, mutants that delete domains for c-Myc dimerization motifs enhanced differentiation. Thus, c-Myc interferes with MEL cell differentiation by interacting with c-Myc partners and the induced protein(s) through dimerization domains. These results suggest that c-Myc may regulate commitment and differentiation by interacting with proteins through different domains.

OPC-13340, a new dihydropyridine calcium channel blocker attenuates rapid vascular smooth muscle cell growth in spontaneously hypertensive rats

We investigated the mechanism of the antimitotic effects of calcium channel blockers in vascular smooth muscle cells (VSMC) from spontaneously hypertensive rats (SHR). VSMC from SHR exhibited rapid proliferation through a quick transition from the G0/G1 to the DNA synthetic (S) phase and from the S to the G2/mitotic (M) phase, whereas the DNA synthetic rate itself was equal to that of Wistar-Kyoto rats (WKY). OPC-13340, a new dihydropyridine calcium channel blocker, dose-dependently decreased incorporation of [3H]thymidine into the DNA fragments in randomly cycling VSMC in SHR. Cell cycle analysis showed that the rapid transition from the S to the G2/M period was restored by OPC-13340 to the control level in WKY, whereas the quick transition from G0/G1 to S was unaffected. This antimitotic effect of OPC-13340 was reflected by attenuation of enhanced cellular protein synthesis during the G2/M period. Protein synthesis in the G0/G1 period was not influenced by OPC-13340. Thus, these data indicate that the calcium channel blocker OPC-13340 mitigates the enhanced proliferation observed in randomly cycling VSMC from SHR and that this effect is primarily due to normalization of the premature mitosis during the G2/M period.

Pharmacological aspects of arthritis induced by a muramyl dipeptide analogue in rats

Fourteen consecutive daily subcutaneous injections of 4 mg/kg of the muramyl dipeptide analogue MDP-Lys(L18) into rats caused arthritis characterized by swelling of the tarsal joint, increases in lymphocytes and monocytes in the peripheral blood, and elevated serum immunoglobulin G (IgG). The present study was performed to evaluate the effects of indomethacin, phenylbutazone, dexamethasone, D-penicillamine, aurothioglucose, cyclophosphamide and cyclosporin A on this arthritis. Administration of indomethacin, phenylbutazone or dexamethasone inhibited the development of the tarsal joint swelling, suggesting that prostaglandins may be involved in the pathogenesis of the arthritis. Cyclophosphamide reduced the arthritis, together with decreases in the lymphocyte count and the serum IgG level. Cyclosporin A worsened the arthritis in a dose-dependent manner and increased the neutrophil count without raising the serum IgG level, but inhibited the induction of adjuvant arthritis in rats with Mycobacterium bacilli. MDP-Lys(L18) may therefore induce arthritis differing in mechanism from adjuvant arthritis.

Pharmacokinetics of zonisamide; saturable distribution into human and rat erythrocytes and into rat brain

The distribution of zonisamide, a new antiepileptic drug, in erythrocytes and in brain was studied to clarify the factors influencing its distribution in epileptic patients. In both humans and rats, zonisamide was concentrated significantly in erythrocytes in a saturable manner. When the effective concentration of zonisamide in serum was compared with that in blood in nine refractory epileptic patients taking zonisamide chronically, the variation in effective serum concentration was significantly larger than that in blood concentration. In rats, the distribution in the brain also showed saturability. These results suggest that differences in saturable binding to various tissues may contribute to the wide variation that occurs in the effective serum concentration of zonisamide in epileptic patients and that monitoring of the blood concentration of zonisamide may provide useful information for treatment with this drug.

Three-headed outer arm dynein from Chlamydomonas that can functionally combine with outer-arm-missing axonemes

A procedure was developed for isolating Chlamydomonas outer-arm dynein that can functionally combine with the axoneme of an outer-arm-missing mutant, oda1. Previous studies showed that the outer-arm dynein of this organism, containing three heavy chains (alpha, beta, gamma), dissociates upon extraction with a high-salt-concentration buffer solution into an 18-S particle containing the alpha and beta heavy chains and a 12-S particle containing the gamma heavy chain. It was found, however, that the three heavy chains did not dissociate if the high-salt extract was centrifuged in the presence of Mg2+; the three chains constituted a single species (23-S dynein) sedimenting at about 23 S and displayed a three-headed bouquet configuration in electron micrographs. Furthermore, the 23-S dynein had the activity to bind to the axonemes of oda1 and increase the reactivated motility of detergent-extracted cell models; its addition increased the beat frequency from 28 Hz to 53 Hz, a frequency comparable to that of wild-type axoneme. The 18-S and 12-S dyneins, on the other hand, were unable to increase the motility of oda1 axonemes even when added together. The new protocol thus enables purification of outer-arm dynein that retains its functional activity. It will provide a useful experimental system with which to study the mechanism of outer-arm function.

Identification of three essential regions of hepatitis B virus X protein for trans-activation function

The X protein of hepatitis B virus (HBV) consists of 154 amino acids and trans-activates various cellular and viral promoters and enhancers. To investigate the essential amino acid sequences of X protein for trans-activation function, various mutations were introduced into the X open reading frame and analysed for trans-activation activity by chloramphenicol acetyltransferase assay. The amino acid sequences 46-52 (especially Pro-46, His-49 and His-52), 61-69 (especially Cys-61, Gly-67 to Pro-68 and Cys-69) and 132-139 (especially Phe-132, Cys-137 and His-139) of HBV X protein were found to be essential for the trans-activation function. These three sequences are included in the conserved amino acid sequences among hepadna virus X proteins. The first one could form a domain-like structure characteristic of histidine/aspartic acid requirement. The second and the third are homologous to the Kunitz domain of Kunitz-type serine protease inhibitors. The amino acids 5-27 region was found to make no positive contribution to the trans-activation function like the last 12 amino acids in the carboxy-terminal region [Takada, S. & Koike, K. (1990). Proc. Natl. Acad. Sci. USA, 87, 5628-5632]. From these findings, the trans-activation function of X protein appears to be dependent on at least two types of domain-like structures.

c-Myc interferes with the commitment to differentiation of murine erythroleukemia cells at a reversible point

When murine erythroleukemia (MEL) cells, containing the transferred rat c-myc gene under the control of human metallothionein II gene promoter, are induced to differentiate with dimethyl sulfoxide, the level of differentiation is dependent on the c-Myc level, which is modulated by the addition of Zn ions. In this work, we examined the point of inhibition of differentiation by elevated levels of c-Myc in one (clone 38-2) of the typical transformants. Commitment assay indicated that elevated levels of c-Myc interfere with entry of the transformant into the commitment event, but when c-myc expression was reduced by removing Zn ions from the medium, the cells could reenter the commitment program. However, once the cells were committed, such cells could not return to the uncommitted state. In addition, time-dependent expression of two erythroid specific genes was inhibited by elevated levels of c-Myc in time-dependent manner. These results suggest that c-Myc modulates MEL cell differentiation at a reversible point of commitment.

[Inhibition of airway smooth muscle contraction by airway epithelium in human bronchus]

To clarify the mechanism underlying the inhibitory effect of epithelial cells on smooth muscle contraction, we studied two types of human bronchial tissue preparations: (1) "acceptor" bronchial strip without epithelium, (2) "donor" bronchial ring with or without epithelium. We measured the contractile responses of acceptor bronchial strip surrounded by donor bronchial ring to increasing concentrations of acetylcholine (ACh). Removal of the epithelium of the donor bronchial rings significantly enhanced the contractions of the acceptor bronchial strips. Thus, airway epithelium decreases the airway smooth muscle contraction to ACh in human bronchus. The mechanism of this inhibitory effect of airway epithelium was not due to a change in mechanical property of the airway, nor to a change in diffusion path for the chemical mediators. These results suggest that human airway epithelium may have an important role in modulating airway smooth muscle tone, possibly by the release of an epithelium-derived relaxing factor.

Stimulating effects of atenolol on vasodepressor prostaglandin generation in spontaneously hypertensive rats

1. To assess the role of the vasodepressor prostaglandin system in the antihypertensive properties of beta-adrenoceptor antagonist, we investigated the alterations of prostaglandin generation in the kidney and in the aorta when spontaneously hypertensive rats were treated with atenolol for 2 weeks. 2. The blood pressure reduction was associated with an increase in urinary sodium excretion and urinary prostaglandin E2 excretion. The sodium excretion was positively related to the prostaglandin E2 excretion. 3. Basal release of prostaglandin E2 from the sliced renal cortex was enhanced by the atenolol treatment. Prostacyclin-generating capacity in the aortic wall was also significantly increased. 4. Atenolol treatment stimulated prostaglandin synthesis in the kidney and vascular wall in a dose-dependent manner. However, atenolol per se did not directly stimulate prostaglandin synthesis in the vascular wall. 5. Inhibition of prostaglandin generation by a cyclooxygenase inhibitor, indomethacin, was associated with attenuation of the antihypertensive effects of atenolol. 6. Thus these data indicate that sub-chronic atenolol treatment stimulates vasodepressor prostaglandin generation in the kidney and in the aortic vessels, and this shares the antihypertensive effects of this drug with the mechanism of beta-adrenergic antagonism probably mediated through vasorelaxation and natriuresis.

Penetration of lysophosphatidylcholine into the dermis

The ability of Lysophosphatidylcholine (LPC) to penetrate into the dermis and its degradation were investigated in vivo using hairless rats. Phosphatidylcholine (PC) was used as a control. Radioactively labelled LPC and PC were applied on the surface of skin, and the radioactivities of the epidermis and dermis were measured at 8, 24, and 48 hours. The recoveries of radioactive materials of LPC and PC within the area of epidermis and dermis at 8 hours were 0.21% and 0.25%; at 24 hours, 0.68% and 0.31%; and at 48 hours, 0.42% and 0.92%. No radioactivity was detected in serum. The radioactive substances which had penetrated were identified as LPC, PC, diglycerides, and free fatty acids. It was also found that topical application of LPC did not change the structure of skin as seen by microscopical examination. These findings indicate that a small amount of LPC can penetrate without the damaging skin structure and is enzymatically degraded into several lipids. Since LPC has bactericidal and antiviral activity, this substance could be an useful agent for dermatological use.

Possible role of prostacyclin synthase in altered prostacyclin generation in DOCA-salt hypertensive rats

Prostacyclin (PGI2) synthase is one of the key enzymes for vasodepressor PGI2 biosynthesis in the vascular wall. In this study, we attempted to define the alterations in PGI2 synthase and its role in the PGI2 generation in the vascular wall of deoxycorticosterone acetate (DOCA)-salt rats. The PGI2-generating capacity was enhanced significantly when DOCA-salt rats established hypertension, whereas the generation of other arachidonate metabolites, eg, PGE2, PGF2 alpha, and thromboxane, was unaltered. Moreover, the increase in PGI2 generation was associated with an increase in PGI2 synthase activity in the vascular wall. Indeed, the averaged PGI2 generating capacity was closely correlated to the averaged PGI2 synthase activity in DOCA-salt hypertensive rats and three lines of control rats. Incontrast, phospholipase C and phospholipase A2, both of which liberate arachidonate for PGI2 synthesis, were rather lowered in DOCA-salt hypertensive rats. These data clearly indicate that vascular PGI2 generation is increased in the development of DOCA-salt hypertension and that PGI2 synthase is mainly responsible for this enhancement. The increased PGI2 synthase may be relevant to the blood pressure elevation and is expected to have beneficial effects on the vascular protection in hypertension.

Effects of dexamethasone on the expression of myelin basic protein, proteolipid protein, and glial fibrillary acidic protein genes in developing rat brain

Effects of dexamethasone (DEX) on the relative abundance of myelin basic protein (MBP), proteolipid protein (PLP) and glial fibrillary acidic protein (GFAP) mRNAs in the developing rat brain were examined. After DEX (1.0 mg/kg body weight) or saline was administered intraperitoneally to 3-day-old rats for 7 consecutive days, wet weight, DNA content and the relative abundance of the glia-specific mRNAs in cerebrum and cerebellum were analyzed at postnatal days (P) 10, 20 and 30. DEX decreased both wet weight and DNA content in cerebellum more profoundly than in cerebrum. The appearance of MBP, PLP and GFAP mRNAs in cerebellum preceded that in cerebrum in the control group. In cerebrum, the relative abundance of MBP and PLP mRNAs was significantly less in the DEX group than that in the control group at P20 and P30. The relative abundance of the GFAP mRNA was significantly less in the DEX group than in the control group at P10 and P20, but there was no significant difference at P30. In cerebellum, a significant decrease in the abundance of MBP, PLP and GFAP mRNAs in the DEX group was observed only at P10 but not at P20 and P30. Our findings indicate that DEX suppresses expression of genes related to glial functions, especially myelination when administered in the early postnatal period.