Activation of RAC-protein kinase by heat shock and hyperosmolarity stress through a pathway independent of phosphatidylinositol 3-kinase

RAC protein kinase (RAC-PK), a serine/threonine protein kinase containing a pleckstrin homology (PH) domain, was activated by cellular stress such as heat shock and hyperosmolarity. Wortmannin, which is known as a potent inhibitor of phosphatidylinositol 3-kinase and normally inhibits growth factor-induced activation of RAC-PK, did not suppress heat-shock induced activation of RAC-PK, indicating that this stress-induced activation of the kinase is not mediated by phosphatidylinositol 3-kinase. The PH domain was indispensable for stress-induced activation of RAC PK. In heat-treated cells, PKC delta, a member of the protein kinase C family, was found to associate with the PH domain of RAC-PK. This PKC subspecies was phosphorylated in vitro by RAC-PK. The results suggest that RAC-PK may play a role in the cellular response to stress through its PH domain.

Hydrochlorothiazide exacerbates nitric oxide-blockade nephrosclerosis with glomerular hypertension in spontaneously hypertensive rats

OBJECTIVE

To determine whether a diuretic can also reverse the clinical, systemic, renal and glomerular haemodynamic and pathological changes caused by nephrosclerosis.

METHODS

Three groups of 20-week-old spontaneously hypertensive rats (SHR) were investigated: control male SHR; a similar group, administered 50 mg/l NG-nitro-L-arginine methyl ester (L-NAME) for 3 weeks; and SHR treated similarly with L-NAME but also with 80 mg/kg per day hydrochlorothiazide (HCTZ) by gavage for 3 weeks.

RESULTS

The mean arterial pressure, cardiac output, effective renal plasma flow and glomerular filtration rate decreased as urinary volume increased in the SHR treated with HCTZ and L-NAME. A micropuncture study demonstrated increased glomerular capillary pressure (PG, 56 +/- 1 versus 68 +/- 3 mmHg) associated with increased efferent (2.1 +/- 0.2 versus 2.9 +/- 0.3 u) but no change in afferent arteriolar resistances compared with the SHR group treated with L-NAME only. In addition, HCTZ administration increased the juxtamedullary glomerular injury score (47 +/- 13 versus 114 +/- 29) associated with elevated urinary protein excretion (35 +/- 1 versus 53 +/- 13 mg/100 g body weight per 24 h) The afferent arteriolar injury score was not changed. The PG elevation was related not only to severe glomerulosclerosis but also to increased fibronectin and alpha-smooth muscle actin deposition.

CONCLUSION

HCTZ administration exacerbated the changes in renal and micropuncture dynamics, proteinuria and histopathological nephrosclerosis produced by L-NAME in SHR.

Factor validity and reliability for the Aberrant Behavior Checklist-Community in a Japanese population with mental retardation

To assess the factor validity and reliability for the Japanese version of the Aberrant Behavior Checklist-Community (ABC-Community), 322 subjects with moderate to profound mental retardation (188 males and 134 females, mean age 29.79 +/- 12.45) were rated by the staff at the residential facilities in Wakayama Prefecture, Japan. Rating data were analyzed by factor analysis using the principal factoring method with iteration, followed by oblique rotation. The internal consistency was estimated by Cronbach's alpha. Of these subjects, 43 were rated twice with an interval of 4 weeks to confirm the test-retest reliability and 33 were rated by pairs of raters for interrater reliability. Forty-eight of 58 items loaded most heavily on the same factors as in the original factor solution. Coefficient alpha raged from .85 to .95 across five subscales. The test-retest reliability was high with Spearman's rank correlation coefficient ranging from .84 to .90. Although the correlation coefficients for interrater reliability tests were somewhat lower (.58 to .78), they were all statistically significant (p < .001). The Japanese version of ABC Community was comparative to the original and was useful for assessing behavior problems in Japanese persons with mental retardation.

Endoscopic trigonoplasty in pediatric patients with primary vesicoureteral reflux: preliminary report

PURPOSE

We investigated the preliminary surgical results of endoscopic trigonoplasty in pediatric patients with primary vesicoureteral reflux.

MATERIALS AND METHODS

We performed endoscopic trigonoplasty in 6 pediatric patients (11 refluxing ureters). Reflux was grade II in 4 reno-ureteral units, grade III in 5, grade IV in 1 and grade V in 1 (international classification). Surgery was done using laparoscopic and endoscopic instruments.

RESULTS

Vesicoureteral reflux disappeared 3 to 12 months postoperatively. Analgesics were administered postoperatively to 4 patients for 24 hours and to 2 for 48 hours. No bladder irritability or postoperative upper urinary tract dilatation was observed in the early postoperative period.

CONCLUSIONS

Minimally invasive endoscopic trigonoplasty can be an effective surgical procedure for pediatric patients with vesicoureteral reflux.

[The effect of herbal medicines on the immunodeficient animals by injecting cancer chemotherapeutic agent-special reference to age related recovery of the function]

The acquired immunodeficiency of the host plays an essential role in the occurrence of infections even with low pathogenic bacteria. The increase of cases with MRSA and/or pseudomonas infection is one of the serious problems in hospital management in Japan for the elderly as well as pediatric patients. In the present study, mitomycin C (MMC)-treated hosts were prepared in young, adult and old mice to test the immunopotentiating action of the promising Chinese herbal medicine, Tohki-Rikuoh-Toh (TRT), Hotyu-Ekki-Toh (HET) and Juzen-Taiho-Toh (JTT). The effect of these herbal medicines on organ structure and its function in the MMC-treated hosts is clarified and discussed for medical use. 4-5, 8-10 and over 50 week old male C57BL/6 (Clea Japan Inc.) were injected with MMC at a dosage of 3 to 5 mg/kg to inhibit the bone marrow, thus creating a mouse model with reduced immunopotential. A powder extract of TRT, HET and JTT was administrated orally at a dosage of 500 mg/kg/day for seven consecutive days. The white cell number and the subset analysis were carried out by the FACS method. The bactericidal effect of the host was monitored by NBT reduction test. Peritoneal macrophages were prepared by the adherence technique. The macrophage phagocytic activity was examined by an ACAS system. After the administration of TRT, HET and JTT, the body weights recovered as much as 90%, especially in young animals which had been reduced to 75% of their normal values. After MMC-treatment, with the herbal medicines, HET was good for young mice while JTT was effective for the old ones. As for the effect on B cells, the plaque-forming cells (PFC) of spleen cells were compared among the groups. As a result, PFC in the HET group was 184% and the other two were 80 approximately 95% as compared to 76% in the MMC-treated ones. The number of white blood cells in the MMC-treated mice returned to 80% of their normal value. In addition, the phagocytic activity of macrophages increased to 50% although that of the non-treated group was only 20%. The phagocytic activity also recovered in the JTT and TRT of 131% to 95%, respectively compared to 11% in the MMC-treated control. When TRT, HET and JTT were administered orally to mouse models whose immunopotential had been inhibited, the herbal medicines activated both quantitatively and qualitatively, showing themselves to be effective interstitial medicines. In addition, the data from the animal models showed no side effects, confirming the complete efficacy of the drug. Moreover, there was no direct anti-bactericidal effect from these medicines, suggesting that the immunomodulating action of this medicine is host-mediated. It is interesting that quantitative and qualitative recovery were seen when HET was administered to MMC-treated young hosts while JTT was good for the old. With this investigation, the effective components are still unknown for different generations, and we need to clarify this aspect for better understanding of the efficacy of herbal medicines.

The Epstein-Barr virus (EBV) alters the B cell glycolipid which is recognized by the human monoclonal antibody to i-blood group antigen

To analyze the differentiation-related glycolipids, we have recently developed human monoclonal anti-i antibodies (mAbs) using a combination of EBV-transformation and bovine i-active glycolipid (NeuAc alpha 2-->3Gal beta 1-->4GlcNAc beta 1-->3Gal beta 1-->4GlcNAc beta 1-->3Gal beta 1-->4Glc beta 1-->1Cer)-containing liposome immune lysis assay (LILA). Using complement cytolysis with these mAbs, we found the occurrence of a surface antigen (Ag) in the EBV-negative but not in the EBV-positive cell lines. The fresh EBV infection reveals that the suppressed expression of the antigen was a result of the EBV infection. The Ag recognized with these mAbs appeared to have a very low density on the B cell lines. Unexpectedly, thin layer chromatogram (TLC)-immunostaining using the mAbs revealed that the major immunoreactive substance in the EBV-negative B cell lines was an extremely minor glycolipid that was distinct from the i-active glycolipid however, this was not the case in the EBV-positive B cell lines.

Prostacyclin-stimulating factor, novel protein, and diabetic angiopathy

We recently purified and cloned a new protein that stimulates the synthesis of prostacyclin (PGI2) by the vascular endothelial cells (ECs). We have termed this protein "PGI2-stimulating factor" (PSF). The present study evaluated the expression of PSF mRNA in tissues of Wistar rats, including the kidneys of rats with streptozotocin-induced diabetes, and in cultured cells. Furthermore, we evaluated the presence of PSF in human sera and the immunohistochemical localization of PSF in tissues of patients obtained at autopsy. The latter included a coronary atherosclerotic lesion of a patient who died of acute myocardial infarction. PSF was observed by Northern blot analysis to be expressed in all rat tissues examined (brain, lung, liver, kidney, skeletal muscle, and fat tissue) and was expressed in cultured vascular ECs, smooth muscle cells (SMCs), and fibroblast cells (FCs). A decreased expression of PSF was observed in the kidneys of diabetic rats versus those of normal rats. The presence of PSF in human serum was confirmed by Western blot analysis. In humans, PSF was mainly localized in vascular ECs and SMCs of arterial media and in SMCs of bronchi. Reduced staining for PSF was found in an atherosclerotic versus a normal coronary artery of humans. PSF may be involved in the production of PGI2 in the vessel wall and may participate in the maintenance of vascular homeostasis. PSF abnormalities may be involved in the development of such vascular lesions as atherosclerosis and diabetic angiopathy.

[Hautmann's ileal neobladder: experience of 37 cases]

Between April 1993 and August 1995, a Hautmann's ileal neobladder was created in 37 men after total cystectomy for bladder cancer. Ureteroileostomy was performed using a submucosal tunnel instead of the Le-Duc Camey procedure. There was no operative mortality and only a few early complications. The mean postoperative follow-up time was 16 months, with a range of 3 to 31 months. Hydronephrosis occurred in 3 patients, being caused by stenosis at the uretero-ileo anastomosis in 2 and by proximal stenosis in 1. Neobladder-ureteral reflux did not occur in any of the patients. Postoperative ileus developed in 3 patients, and one required laparotomy. Stenosis of the urethro-ileal anastomosis developed in 3 patients, who were successfully treated by transurethral incision. Thirty five patients achieved daytime continence, while 2 patients had slight incontinence. Twenty nine patients achieved nighttime continence, and most of the patients awoke 1-4 times to prevent overflow incontinence. The mean maximum flow rate, average flow rate and post-voiding residual urine volume were respectively 15.3 ml/sec, 5.5 ml/sec and 81 ml at 6 months postoperatively, and 14.9 ml/sec, 5.4 ml/sec and 76 ml at 12 months. Four patients with more than 100 ml of residual urine required sterile intermittent catheterization 2-4 times a day. Urethral recurrence was detected in 2 patients. One was treated with transurethral resection and cisplatinum-based systemic chemotherapy, and the other required urethrectomy and urinary diversion using a new continent efferent limb.

An iron dioxygenase from Alcaligenes faecalis catalyzing the oxidation of pyruvic oxime to nitrite

An enzyme which participated in the oxidation of hydroxylamine to nitrite from was partially purified Alcaligenes faecalis, and some of its properties were studied. The enzyme oxidized aerobically pyruvic oxime to nitrite in the presence of hydroxylamine or ascorbate. As molecular oxygen equimolar to nitrite formed was consumed in the enzymatic oxidation of pyruvic oxime to nitrite, the enzyme was thought to be a dioxygenase. It was an iron protein, and a reducing reagent was required to keep the iron in the ferrous state for the action of the enzyme.

Effects of asymmetric dynamic and isometric liftings on strength/force and rating of perceived exertion

A laboratory study was undertaken to determine the postural and physical characteristics and subjective stress during dynamic lifting of a usual load (10 kg) compared with during isometric lifting. The authors also aimed to clarify the effects of asymmetric lifting on these parameters. The subjects were thirteen male college students. They were asked to lift a box weighing 10 kg. They performed sixteen different lifting tasks from the floor to a height of 71 cm, involving a combination of three independent factors: two lifting modes (isometric lifting and dynamic lifting), four lifting angles in relation to the sagittal plane (sagittal plane, right 45 degree, right 90 degree and left 90 degree planes) and two lifting postures (squat and stoop). For each lifting task, strengths or forces and ground reaction forces were measured. At the end of each task, the authors asked the subjects to rate their perceived exertion (RPE) during lifting at ten sites of the body. Angle factor had a significant effect on isometric strengths and dynamic peak forces. Isometric strengths during the maximum 3 s were highest in lifting in the right 45 degree plane, followed by that in the sagittal plane, while those in the right 90 degree and left 90 degree planes were the lowest. However, peak forces in dynamic lifting were the highest in the lifting in the sagittal plane, followed by that in the right 45 degree plane, while those in the right 90 degree and left 90 degree planes were the lowest. Postural factor had a significant effect on height at peak force, which is higher in squat lifting than in stoop lifting. RPEs for the left arm, the backs and the right whole body in isometric lifting were significantly higher than in dynamic lifting of 10 kg. There were remarkably high RPEs for the ipsilateral thigh to the box in right 90 degree and left 90 degree planes during both isometric and dynamic liftings. Locations of the resultant force consisting of three component forces on the force plate were closer to the foot on the same side as the box in asymmetric lifting. Thus, some similarities and differences were found between isometric lifting and dynamic liftings regarding the indexes of strength used in this experiment. The authors consider that the subjects used the foot nearer to the box as a fulcrum during asymmetric lifting. Dynamic measurement using the 10 kg weight is less stressful than the conventional isometric measurement. It was possible to obtain the height data at peak force and time-based changes in the force and the box location during lifting only through dynamic lifting measurement. The results provide new knowledge about the biomechanical features of dynamic lifting tasks.

[Emergency surgical salvage for a type A early thrombosed aortic dissection complicated cardiac tamponade in a 80-year-old-patient]

A 80-year-old woman underwent emergency operation for a type A early thrombosed aortic dissection associated with cardiac tamponade. Her preoperative chest CT (not enhanced) showed high density area in the false lumen that indicated early thrombosis and the projection of true lumen at antero-left-lateral portion of ascending aorta that means "ulcer-like projection" called on aortogram. After the relief of the cardiac tamponade by pericardiocenthesis, we emergently performed the graft replacement of the ascending aorta under the extracorporeal circulation combined with selective cerebral perfusion. Her postoperative course was uneventful and satisfactory.

Characterization of the interaction between RhoA and the amino-terminal region of PKN

The yeast two-hybrid system and in vitro binding assay were carried out to characterize the interaction between PKN and a small GTP-binding protein, RhoA. It was revealed that the region corresponding to the amino acid residues 33-111 in the amino-terminal region of PKN was sufficient to confer the ability to associate with RhoA. Each synthetic peptide fragment corresponding to the amino acid residues 74-93 and 94-113 of PKN inhibited the interaction between PKN and RhoA in the in vitro binding assay, suggesting that this region is important in the association with RhoA. The endogenous and the GAP-stimulated GTPase activity of RhoA was inhibited by the interaction with PKN, suggesting the presence of a regulatory mechanism that sustains the GTP-bound active form of RhoA.

Amyloid associated muscle pseudohypertrophy: amelioration of motor dysfunction with plasmapheresis and dimethylsulphoxide

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Escherichia coli gpt gene sensitizes rat glioma cells to killing by 6-thioxanthine or 6-thioguanine

Genes that encode enzymes that convert inactive "prodrugs" into anticancer metabolites may be therapeutically useful against brain tumors. Unlike other genes tested to date in brain tumor models, the Escherichia coli gpt gene is unique in that it not only sensitizes cells to the prodrug 6-thioxanthine (6TX) but also encodes resistance to a different regimen (mycophenolic acid, xanthine, and hypoxanthine), thus providing a means to select for gpt-positive cells. In the present study, rat C6 glioma cells were infected with a retrovirus vector that transduces this gene. A clonal line (C6GPT-7) was derived that exhibited significant 6TX susceptibility in vitro with an ID50 of 2.5 mumol/L, whereas 50% growth inhibition of parental C6 cells was not achieved at concentrations tested (up to 50 mumol/L). This line also exhibited significant sensitivity to 6-thioguanine (6TG), with an ID50 of 0.05 mumol/L, whereas 50% growth inhibition of parental C6 cells was achieved at 0.5 mumol/L. In a "bystander" assay, C6GPT-7 tumor cells efficiently transferred 6TX sensitivity to C6 cells at ratios as low as 1:9 (C6GPT-7:C6). This in vitro bystander effect was abrogated when C6GPT-7 and C6 cells were separated by a microporous membrane, suggesting that it was not mediated by highly diffusible metabolites. In vivo both 6TX and 6TG significantly inhibited the growth of subcutaneously transplanted C6GPT-7 cells but not that of C6 cells in athymic mice. In an intracerebral model, both 6TX and 6TG exhibited significant antiproliferative effects against tumors formed by C6GPT-7 cells. These findings provide a basis for exploring further gene therapy strategies based on in vivo transfer of the E coli gpt gene to provide chemosensitivity against 6TX and 6TG.

PKN associates and phosphorylates the head-rod domain of neurofilament protein

PKN is a fatty acid-activated serine/threonine kinase that has a catalytic domain highly homologous to that of protein kinase C in the carboxyl terminus and a unique regulatory region in the amino terminus. Recently, we reported that the small GTP-binding protein Rho binds to the amino-terminal region of PKN and activates PKN in a GTP-dependent manner, and we suggested that PKN is located on the downstream of Rho in the signal transduction pathway (Amano, M., Mukai, H., Ono, Y., Chihara, K., Matsui, T., Hamajima, Y., Okawa, K., Iwamatsu, A., and Kaibuchi, K. (1996) Science 271, 648-650; Watanabe, G., Saito, Y., Madaule, P., Ishizaki, T., Fujisawa, K., Morii, N., Mukai, H., Ono, Y. Kakizuka, A., and Narumiya, S. (1996) Science 271, 645-648). To identify other components of the PKN pathway such as substrates and regulatory proteins of PKN, the yeast two-hybrid strategy was employed. By this screening, a clone encoding the neurofilament L protein, a subunit of neuron-specific intermediate filament, was isolated. The amino-terminal regulatory region of PKN was shown to associate with the head-rod domains of other subunits of neurofilament (neurofilament proteins M and H) as well as neurofilament L protein in yeast cells. The direct binding between PKN and each subunit of neurofilament was confirmed by using the in vitro translated amino-terminal region of PKN and glutathione S-transferase fusion protein containing the head-rod domain of each subunit of neurofilament. PKN purified from rat testis phosphorylated each subunit of the native neurofilament purified from bovine spinal cord and the bacterially synthesized head-rod domain of each subunit of neurofilament. Polymerization of neurofilament L protein in vitro was inhibited by phosphorylation of neurofilament L protein by PKN. The identification and characterization of the novel interaction with PKN may contribute toward the elucidation of mechanisms regulating the function of neurofilament.

Toxic effects of hexane derivatives on cultured rat Schwann cells

The cytotoxic effects of the following five hexane-related compounds were examined on Schwann cell DNA synthesis: 2,5-hexanedione (2,5-HD), 2-hexanol (2-OH), 2-hexanone (MnBK), 2,5-dimethylfuran (DF) and gamma-valerolactone (VL). Schwann cells were isolated from the sciatic nerves of neonatal Sprague-Dawley rats and cultured. [(3)H]-thymidine incorporation into Schwann cell nuclei was measured by scintillation spectrometry and autoradiography when hexane derivatives were added to the culture medium. All of the hexane-related compounds suppressed [(3)H]-thymidine incorporation in a concentration-dependent manner. DF was the most cytotoxic for the inhibition of Schwann cell DNA synthesis among the compounds. The finding suggests that DF-mediated cytotoxicity should be taken into account as a possible additional mechanism of hexane intoxication, especially in the impairment of mitotic cells.

[A longitudinal study of hearing level aggravation due to aging]

It has been reported that hearing aggravation due to aging is predominantly in the high frequency range and that there are rapid and slow phase of aggravation in hearing level. In the present study, the pattern of aggravation of hearing level due to aging was investigated in 387 adults of over 35 years of age who had visited the Kitasato Health Science Center for a regular health check-up annually for more than 5 years, and were diagnosed as having neither external of middle ear diseases nor hearing impairment of obvious origin at their first visit. The subjects were divided into 8 groups according to their ages in increments of 5 years. Their audiograms were obtained annually, and the results were used to obtain the distribution of the hearing level at each test frequency. All of the subjects were examined for individual changes in audiograms and those who showed 20 dB or more aggravation of hearing in a 1-year period without subsequent improvement were defined as having a rapid phase of aggravation. There were clustering points in hearing distribution at around 30 dB and 60 dB at the test frequency of 8 kHz in those subjects showing a rapid phase of aggravation. Similar clustering points were also noted in those subjects who showed gradual aggravation of 20 dB or more in a 5-year period and who had 20 dB or more aggravation in one year but showed later improvement. As for the test frequencies lower than 4 kHz, there appeared to be a clustering point at around 30 dB. The incidence of the rapid phase of aggravation was then determined in each group, in order to investigate the relationship between aging and the appearance of the rapid phase of aggravation. The rapid phase was already noted in the youngest age group (range, 35-39 years), while the incidence gradually increased up to the 50-54-year group and stayed at a constant level in the 55-69-year groups. The incidence markedly decreased thereafter. The results suggest that hearing aggravation due to aging does not occur at any particular age. Rather, the hearing aggravation appeared to be closely related to the hearing level, and to manifest itself when the hearing level approaches 30 dB or 60 dB.

Noninvasive evaluation of malignancy of brain tumors with proton MR spectroscopy

PURPOSE

To test clinical proton MR spectroscopy as a noninvasive method for predicting tumor malignancy.

METHODS

Water-suppressed single-voxel point resolved spectroscopy in the frontal white matter of 17 healthy volunteers and 25 patients with brain tumors yielded spectra with peaks of N-acetyl aspartate (NAA), choline-containing compounds (Cho), creatine/phosphocreatine (Cre), and lactate. These peak intensities were semiquantitated as a ratio to that of the external reference. The validity of the semiquantitation was first evaluated through phantom and volunteer experiments.

RESULTS

The variation in measurements of the designated region in the volunteers was less than 10%. Normal ranges of NAA/reference, Cho/reference, and Cre/reference were 3.59 +/- 0.68, 1.96 +/- 0.66, and 1.53 +/- 0.64 (mean +/- SD), respectively. In 17 gliomas, the Cho/reference value in high-grade gliomas was significantly higher than in low-grade gliomas. Levels of NAA/reference were also significantly different in low-grade and high-grade malignancy. In eight meningiomas (four newly diagnosed and four recurrent), the level of Cho/reference was significantly higher in recurrent meningiomas than in normal white matter or in newly diagnosed meningiomas.

CONCLUSIONS

Higher grades of brain tumors in this study were associated with higher Cho/reference and lower NAA/reference values. These results suggest that clinical proton MR spectroscopy may help predict tumor malignancy.

The role of the unique motifs in the amino-terminal region of PKN on its enzymatic activity

The yeast two-hybrid system and in vitro binding assay were carried out to characterize the interaction between the amino-terminal and carboxyl-terminal region of PKN. It was revealed that the amino-terminal region containing the regulatory domain associated with the carboxyl-terminal catalytic region. A synthetic peptide, corresponding to the amino acid residues of PKN from 39 to 53, with substitution of isoleucine46 with serine was shown to become a potent substrate for PKN, and its wild type synthetic peptide inhibited the phosphorylation by PKN. These results suggest that the amino-terminal region of PKN contains the pseudosubstrate sequence and acts as an autoinhibitory region.

Determination of isonicotinic acid in the presence of isoniazid and acetylisoniazid. Studies on isonicotinic acid formation from isoniazid in isolated rat hepatocytes

In comparison with the hepatocytes obtained from intact rats and rats pretreated with phenobarbital or 3-methylchoranthrene, the amount of isonicotinic acid (INA) formed from isoniazid (INH) increased substantially after incubation at 37 degrees C using the pretreated hepatocytes. This suggests an oxidative pathway for INA formation from INH, apart from hydrolysis. In order to explore the exact mechanism of INA formation in the hepatocytes, an HPLC assay for INA in the presence of INH and acetylisoniazid was developed. In this assay, INA was extracted after the preparation of an ion pair with tetra-n-butylammonium hydroxide, and analysed using an ODS column and a mobile phase consisting of 0.067 M potassium dihydrogenphosphate solution-methanol (96:4, v/v). The method is simple, accurate and especially suitable for INA determination after incubation of INH in isolated rat hepatocytes.

Oxidative stress triggers tyrosine phosphorylation in B cells through a redox- and inflammatory cytokine-sensitive mechanism

Exposure to oxidants such as hydrogen peroxide (H2O2) and gamma-ray irradiation has been recently shown to trigger tyrosine phosphorylation in B cells as does cross-linking surface immunoglobulin (sIg) by antigens or anti-immunoglobulins. We studied the mechanism by which H2O2 induced tyrosine phosphorylation in B cells and compared it with the mechanism utilized by sIg. Both anti-immunoglobulin M (anti-IgM) and H2O2 induced tyrosine phosphorylation through protein tyrosine kinase (PTK) activation. However, the tyrosine phosphorylation caused by H2O2 but not that induced by anti-IgM, was modulated by agents affecting cellular thiols and glutathione contents including dithiothreitol, 2-mercaptoethanol, and buthionine sulphoximine. Moreover, the tyrosine phosphorylation caused by the oxidant but not that induced by anti-IgM was markedly augmented by two inflammatory cytokines, tumour necrosis factor-alpha and interleukin-1 alpha, although these agents by themselves did not stimulate PTK activity nor induce tyrosine phosphorylation. These findings demonstrate that oxidative stress but not surface IgM (sIgM) ligation triggers tyrosine phosphorylation through a mechanism that is sensitive to cellular thiols and these inflammatory cytokines.