Substrate recognition by the ClpA chaperone component of ClpAP protease

ClpA, a member of the Clp/Hsp100 ATPase family, is a molecular chaperone and regulatory component of ClpAP protease. We explored the mechanism of protein recognition by ClpA using a high affinity substrate, RepA, which is activated for DNA binding by ClpA and degraded by ClpAP. By characterizing RepA derivatives with N- or C-terminal deletions, we found that the N-terminal portion of RepA is required for recognition. More precisely, RepA derivatives lacking the N-terminal 5 or 10 amino acids are degraded by ClpAP at a rate similar to full-length RepA, whereas RepA derivatives lacking 15 or 20 amino acids are degraded much more slowly. Thus, ClpA recognizes an N-terminal signal in RepA beginning in the vicinity of amino acids 10-15. Moreover, peptides corresponding to RepA amino acids 4-13 and 1-15 inhibit interactions between ClpA and RepA. We constructed fusions of RepA and green fluorescent protein, a protein not recognized by ClpA, and found that the N-terminal 15 amino acids of RepA are sufficient to target the fusion protein for degradation by ClpAP. However, fusion proteins containing 46 or 70 N-terminal amino acids of RepA are degraded more efficiently in vitro and are noticeably stabilized in vivo in clpADelta and clpPDelta strains compared with wild type.

Formation of fibrillar multimers of oat beta-glucosidase isoenzymes is mediated by the As-Glu1 monomer

Oat beta-glucosidase (EC 3.2.1.21) exists in two isomeric forms of homomultimer (type I) and heteromultimer (type II), which are comprised of two 60 kDa monomers of As-Glu1 and As-Glu2. The cDNA of As-Glu2 was cloned in this study, whereas As-Glu1 was previously cloned as As-P60. The As-Glu2 cDNA encodes a plastid-directing transit peptide of 57 amino acid residues and a mature protein of 521 amino acid residues. The amino acid sequence of As-Glu2 is highly homologous to that of As-Glu1, except for their C-terminal portions. When the two cDNAs of the mature proteins were expressed as T7.Tag-fused proteins in Escherichia coli, they produced soluble and enzymatically active T7.Tag-As-Glu1 and T7.Tag-As-Glu2 proteins. The T7.Tag-As-Glu1 was assembled into a donut-shaped hexamer ring which was in turn stacked in integer numbers to form long fibrillar homomultimers of different lengths with a molecular mass of up to several million daltons. On the other hand, the T7.Tag-As-Glu2 primarily formed a dimer rather than a multimer. When both cDNAs of As-Glu1 and As-Glu2 were co-expressed as T7.Tag-fused mature proteins, they were also assembled into a hexamer ring comprised of the two monomers in a 1:1 stoichiometry. The heteromeric hexamer was stacked in smaller numbers to form the heteromultimer of T7. Tag-As-Glu1 and -As-Glu2. The results indicate that the As-Glu1 monomer plays a crucial role in the formation of both the As-Glu1 homomultimer and the As-Glu1 and As-Glu2 heteromultimer. We describe here a unique structure for the oat beta-glucosidase fibrillar multimer that is formed by stacking the hexamer rings composed of As-Glu1 and/or As-Glu2.

A new caffeoyl quinic acid from aster scaber and its inhibitory activity against human immunodeficiency virus-1 (HIV-1) integrase

The phytochemical study of the aerial parts of Aster scaber Thunb. (Asteraceae) yielded a new caffeoyl quinic acid, (-) 3,5-dicaffeoyl-muco-quinic acid (2) and three known compounds, (-) 3,5-dicaffeoyl quinic acid (1), (-) 4,5-dicaffeoyl quinic acid (3), (-) 5-caffeoyl quinic acid (4). The structures were established by high resolution spectroscopic methods. The antiviral effects against HIV-1 integrase of the compounds was evaluated. (-) 3,5-Dicaffeoyl-muco-quinic acid (2) exhibited potent antiviral activity with an IC50 value of 7.0 +/- 1.3 microg/ml.

Changing trends in clinical manifestations of laryngeal tuberculosis

OBJECTIVES/HYPOTHESIS

Despite the dramatic decrease in the incidence of laryngeal tuberculosis, the disease has gained new interest as a result of claims that it has changed its clinical patterns. The aim of this study is to evaluate the changing trends in clinical manifestations of laryngeal tuberculosis.

STUDY DESIGN

Retrospective clinical analysis.

METHODS

Clinical analysis of 22 patients with pathologically confirmed laryngeal tuberculosis was carried out retrospectively.

RESULTS

Patients' ages ranged from 22 to 75 years. The male-to-female ratio was 2.14 to 1. The most frequent chief complaint was hoarseness. The true vocal cord and the false vocal cord were commonly involved, and 11 patients showed single lesions. Among 22 patients, only 7 had active pulmonary tuberculosis, and 9 were proven to have normal lung status. The patients with active pulmonary tuberculosis showed more ulcerative and multiple lesions. The patients with normal lung status showed nonspecific, polypoid, and single lesions. All patients responded satisfactorily to antituberculous medication.

CONCLUSIONS

The clinical manifestations of laryngeal tuberculosis have changed and seem to be different from those of classic reports. It can even occur without pulmonary tuberculosis, and the characteristics of lesions seem to be more nonspecific. It might be important to consider tuberculosis in the differential diagnosis of nonspecific laryngeal disease.

Effects of physostigmine on the pharmacokinetics of intravenous parathion in rats

It was reported that the area under the plasma concentration-time curve from time zero to time infinity (AUC) of parathion was significantly smaller, and the time-averaged total body clearance (Cl) of parathion was significantly faster after intravenous administration of parathion to rats pretreated with dexamethasone than those in control rats. This was supported by significantly faster intrinsic clearance of parathion to form paraoxon in hepatic microsomal fraction of rats pretreated with dexamethasone. The above data suggested that parathion was metabolized to paraoxon by dexamethasone-inducible hepatic cytochrome P450 (CYP) 3A in rats. The purpose of this study is to explain the protective effects of physostigmine against paraoxon toxicity by suppressing CYP3A, and hence, decreasing formation of a toxic metabolite, paraoxon. The pharmacokinetic changes of parathion and paraoxon were investigated after intravenous administration of parathion, 3 mg/kg, to control Sprague-Dawley rats, and the rats pretreated with physostigmine (100 microg/kg, intraperitoneal injection 30 min before parathion administration). After a 1-min intravenous infusion of parathion to rats pretreated with physostigmine, the AUC of parathion (60.4 compared with 73.7 microg min/mL) was significantly greater, Cl of parathion (49.7 compared with 40.7 mL/min/kg) was significantly slower, and amount of paraoxon recovered from liver, mesentery and large intestine at 5 min was smaller than those in control rats. Based on in vitro rat hepatic microsomal studies, physostigmine inhibited significantly the erythromycin N-demethylase activity (1.03 compared with 0.924 nmol/mg protein/min), mainly mediated by hepatic cytochrome P450 3A in rats. The above data suggested that the formation of paraoxon was inhibited in rats pretreated with physostigmine by inhibiting CYP3A.

Abdominal tuberculous lymphadenopathy: MR imaging findings

BACKGROUND

The purpose of this study was to evaluate the utility of magnetic resonance imaging (MRI) as a diagnostic tool in abdominal tuberculous lymphadenopathy.

METHODS

MRI studies of 11 patients with histologically proven abdominal tuberculous lymphadenopathy were reviewed with regard to anatomic distribution, size, shape, degree, and pattern of enhancement and relation of the lesions to adjacent structures.

RESULTS

The most common site of involvement was the periportal area (n = 6), followed by the peripancreatic (n = 5), mesenteric (n = 1), and paraaortic (n = 1) areas. Eight patients were readily diagnosed as having tuberculous lymphadenopathy on abdominal computed tomography. Three patients had a heterogeneously enhancing masslike lesion adjacent to the pancreas and were initially diagnosed as having cystic tumor of the pancreas. On MRI, 11 lesions showed T1 iso- or hypointensity and central T2 hyperintensity. Two lesions showed T1 iso- or hypointensity and central T2 hypointensity. The lesions with different T2 signal intensities showed different patterns of enhancement on contrast-enhanced dynamic studies. The relations between the enlarged lymph nodes and adjacent bile ducts or vascular structures were well depicted on MRI.

CONCLUSION

MRI was useful in differentiating enlarged lymph nodes abutting the pancreas initially diagnosed as cystic neoplasms on abdominal computed tomography.

Mapping of a new target region of allelic loss at 21q22 in primary gastric cancers

To determine the minimal region of deletion on 21q22 in gastric cancer, we performed a high-density loss of heterozygosity (LOH) study with eight polymorphic microsatellite markers. Among the 43 tumors examined, 20 (50%) of 40 informative carcinomas showed LOH at one or more loci. The peak LOH frequency was identified at D21S1820 (34.2%) in 21q22.3. This data suggests that this locus might harbor a new tumor suppressor gene in an area <0.332 Mb in physical map distance defined by D21S1820 and D21S49. Thus, we speculate that trefoil factor family 1 (TFF1), located in this narrow region, might be the most probable candidate gene involved in gastric cancer carcinogenesis.

The protection of the retina from ischemic injury by the free radical scavenger EGb 761 and zinc in the cat retina

We investigated the effects of a free radical scavenger (EGb 761) and zinc in experimentally induced ischemic injury in the cat retina. Total retinal ischemia for 90 min was produced in the left eyes of 40 cats by raising intraocular pressure. In group 1, 10 cats were used as control. The free radical scavenger (EGb 761, 100 mg/kg) in group 2 (10 cats) and zinc chloride (250 microg/kg) in group 3 (10 cats) were administered intravenously at the end of ischemia. In group 4, both EGb 761 (100 mg/kg) and zinc chloride (250 microg/kg) were injected into 10 cats. ERG and a histologic study were performed 1 h, 1 day, 3 days, 1 week and 2 weeks after ischemia. The amplitude of the ERG b-wave was 62.73+/-0.32, 84.31+/-6.10, 83.65+/-12.23 and 102.4+/-14.27%, and the summed amplitude of oscillatory potentials was 66.16+/-16.42, 99.44+/-14.92, 95.45+/-6.42 and 99.62+/-12.32% in each group 2 weeks after ischemia. There was no significant effect in animals that received zinc alone (group 3) by the end of 1 week but some additive effect in combining EGb 761 and zinc chloride (group 4) 1 h after ischemia. These findings suggest that the free radical scavenger EGb 761 may efficiently protect the retina from ischemic injury and zinc may have an additive effect when combined with a radical scavenger.

Urinary soluble HLA class I antigen in patients with minimal change disease: a predictor of steroid response

In primary minimal change disease (MCD) and focal segmental glomerulosclerosis (FSGS), increased lymphocyte reactivity to renal antigens has been defined. Soluble HLA class I antigen (sHLA-I) is actively secreted by T and B lymphocytes when they are stimulated by mitogens, antigens and lymphokines. To determine if serum and urine sHLA-I levels could predict steroid response in patients with MCD and differentiate those from FSGS, we have investigated 45 healthy controls, biopsy-proven 17 patients with MCD (edema and 24-hour urine protein > 3.5 g/day), 8 patients with FSGS (24-hour urine protein > 1 g/day) and 10 patients with membranous nephropathy (MGN) (24-hour urine protein > 1 g/day). Before and after prednisone therapy (1 mg/kg/day or 2 mg/kg/EOD for 8 weeks), the levels of serum and urinary sHLA-I were measured by ELISA (sHLA-STAT; Sangstat Co., Calif., USA). After 8 weeks of treatment, 10 patients with MCD were responders (MCD-CR) while the other 7 patients with MCD were nonresponders (MCD-NR). Three of 7 patients with MCD-NR were re-biopsied and finally diagnosed as FSGS. They were included in the data of patients with FSGS. In healthy controls, serum sHLA-I was detected (415 +/- 256 ng/ml), but urinary sHLA-I was not. At entry, there were no differences in age, sex, serum Cr and 24-hour urine protein among the patients with MCD-CR, MCD-NR and FSGS, but serum albumin was significantly elevated in patients with FSGS and MGN (p < 0.05). Serum sHLA-I levels were notably elevated in MCD-CR (1,040 +/- 1,066 ng/ ml), in MCD-NR (668 +/- 315 ng/ml) and in FSGS (713 +/- 790 ng/ml), but not in patients with MGN (444 +/- 86 ng/ml) when compared with controls (p < 0.05). On the other hand, urinary sHLA-I levels in MCD-NR (541 +/- 239 ng/mg Cr) and in FSGS (457 +/- 239 ng/mg Cr) were significantly higher than those in MGN (125 +/- 28 ng/mg Cr) and in MCD-CR(100 +/- 42 ng/mg Cr, p < 0.05) and these substantial differences were maintained for 8 weeks. In all patients, serum and urinary sHLA-I levels were not reduced during 8 weeks of steroid therapy. We conclude that elevated serum and urinary sHLA-I levels reflect increased cellular immune response and disease activity in patients with MCD and FSGS. In patients with MCD, urinary sHLA-I may be an easily measurable indicator of predicting steroid response, while MCD-NR with high urinary sHLA-I levels might be re-evaluated for the possibility of FSGS.

Brassinolide and [26, 28-2H6]brassinolide are differently demethylated by loss of C-26 and C-28, respectively, in Marchantia polymorpha

Metabolism of brassinolide in Marchantia polymorpha was investigated by use of in vivo suspension cultured cells. GC-MS analysis of metabolites derived from non-labelled brassinolide and [26, 28-2H6] brassinolide revealed that brassinolide was converted to 26-norbrassinolide while [26, 28-2H6]brassinolide to [26-2H3]28-norbrassinolide. It seems that Marchantia cells recognized [26, 28-2H6]brassinolide as a xenobiotic rather than brassinolide and deteriums attached to C-28 significantly affect demethylation reaction due to isotopic effect. Thus, demethylation of brassinolide in planta seems to proceed by loss of C-26 rather than C-28. The present finding is the first evidence for demethylation metabolism of brassinosteroids. The biological activity of 26-norbrassinolide was 10-fold reduced as shown by the rice lamina inclination test. However, because of its high biological activity, it remains difficult to conclude whether or not C-26 demethylation serves as an important deactivation process of brassinolide.

Intestinal protein loss in patients with haemorrhagic fever with renal syndrome

BACKGROUND

In haemorrhagic fever with renal syndrome (HFRS) vascular dysfunction has been observed in various organs, but the involvement of the intestine has not yet been reported. This study was performed to evaluate the association of intestinal protein loss in this disease with other clinical parameters reflecting vascular permeability or disease severity.

METHODS

Twenty patients with HFRS were included in this study. Intestinal protein loss was measured by (99m)Tc-human serum albumin ((99m)Tc-HSA) scintigraphy in the acute stage, and quantitative analysis of protein loss was measured by the faecal clearance of alpha 1-antitrypsin (C(AT)) in the acute and the recovery stages. C(AT) was then compared with clinical parameters reflecting disease activity and vascular permeability.

RESULTS

(99m)Tc-HSA scintigraphy was positive in 13 (65%) patients, and C(AT) in the acute stage was significantly increased as compared with C(AT) in the recovery stage (40.5+/-24.1 vs 9.2+/-4.2 ml/day, P<0.001). C(AT) was associated with serum albumin levels, frequency of hypotensive episodes, severity of acute renal failure, and degree of thrombocytopenia.

CONCLUSIONS

Our data suggest that the increased vascular permeability of HFRS is associated with the increased intestinal loss of plasma proteins, which might represent one of the parameters of disease severity in HFRS.

Antitumor activity of Bifidobacterium spp. isolated from a healthy Korean

The antitumor activity of Bifidobacterium breve K-110, and K-111, and B. infantis K-525 was investigated. These Bifidobacterial cells and their cell wall preparations (WPG) significantly increased the survival rate of mice who had been intraperitoneally implanted with sarcoma 180 cells. Solid tumor growth was inhibited even when the sarcoma 180 cells were implanted into the groins of the mice. However, the Bifidobacterial cells did not show in vitro cytotoxicity against tumor cell lines. Cell kinetic studies revealed that these WPGs induced neutrophils, which were followed by macrophages, at the site of peritoneal injection. The WPGs directly activated these cells to inhibit the growth of tumor cells in in vitro assays. Our results suggest that Bifidobacterial WPGs induce and activate nonspecific phagocytes in situ to reject growing tumor cells in the mouse peritoneal cavity.

The effects of Pva/chitosan/fibroin (PCF)-blended spongy sheets on wound healing in rats

The effects of poly vinyl alcohol (PVA)/Chitosan/Fibroin (PCF)-blended sponge on wound healing in rats were investigated. We excised the skin of a rat, including the dermis, approximately 2 x 2 cm in size. The wound was covered with PCF-blended spongy sheets. The spongy sheets absorbed the exudate, and gained flexibility and softness. Histopathological inspection of the wound 12 d later showed an increase of vascular ingrowth and the absence of inflammatory cells. Regeneration of the skin around the wound was faster than that of the control. We also tested wound healing effects of PVA, Chitosan and Fibroin, alone or in various combinations. Wound healing was accelerated in the order of PCF-blended sponge>Chitosan/Fibroin (CF)-blended sponge>Fibroin (F) sponge > PVA/Chitosan-blended sponge (PC) > Chitosan (C) sponge.

Successful treatment of protein-losing enteropathy due to AA amyloidosis with somatostatin analogue and high dose steroid in ankylosing spondylitis

Secondary amyloidosis is an occasional complication of ankylosing spondylitis (AS) and in most cases renal amyloidosis presents with proteinuria, nephrotic syndrome and decreased renal function. We describe a 32-year-old male patient with AS manifested by frequent diarrhea, intermittent abdominal pain and low serum albumin levels. He has suffered from severe inflammatory back pain for 14 years with multiple peripheral joint involvement. Protein-losing enteropathy due to gastrointestinal amyloidosis was diagnosed with 99mTc-human albumin scintigraphy, fecal alpha-1 antitrypsin clearance and colonoscopic biopsy with Congo red staining. Somatostatin analogue octreotide and prednisolone were introduced with successful result.

Parenting practices and adolescent depressive symptoms in Chinese American families

This study examined parenting practices and adolescent depressive symptoms among Chinese Americans. First, confirmatory factor analyses revealed that self-reported parenting practices by mothers and fathers and adolescent perception of parenting practices loaded adequately on three subscales: Inductive Reasoning, Monitoring, and Harsh Discipline. Second, parents' depressive symptoms were related to disrupted parenting practices, which, in turn, were significantly related to the negative evaluation of these behaviors by the adolescents. Adolescents' perceptions of such parenting practices were significantly associated with their depressive symptoms. Third, the relationships were robust even after parental income, education, and generation status were statistically controlled. Overall, the relationships between parenting practices and adolescent depressive symptoms among Chinese Americans seemed to echo those found among European Americans.

Induction of the cytochrome P450 gene CYP26 during mucous cell differentiation of normal human tracheobronchial epithelial cells

In this study, the expression of CYP26 is examined in relation to retinoid-induced mucosecretory differentiation in human tracheobronchial epithelial (HTBE) cells and compared with that in human lung carcinoma cell lines. In HTBE cells, retinoic acid (RA) inhibits squamous differentiation and induces mucous cell differentiation as indicated by the suppression of transglutaminase I and increased expression of the mucin gene MUC2. The latter is accompanied by increased expression of CYP26 mRNA. RA is required but not sufficient to induce RARbeta, CYP26, and MUC2 mRNA because induction is only observed in confluent but not in logarithmic cultures, suggesting that additional factors are critical in their regulation. CYP26 mRNA can be induced by the RAR-selective retinoid 4-(5,6,7,8-tetrahydro-5,5,8,8-tetramethyl-2-anthracenyl)-benzoic acid (TTAB) but not by the RXR-selective retinoid SR11217 or the anti-activator-protein 1-selective retinoid SR11302. RARalpha-, beta-, and gamma-selective retinoids are able to induce CYP26; this induction is inhibited by the RARalpha-selective antagonist Ro41-5253. TTAB is able to induce CYP26 mRNA expression in only a few of the lung carcinoma cell lines tested. The lack of CYP26 induction in many carcinoma cell lines may relate to previously reported defects in the retinoid-signaling pathway. The induction of CYP26 correlated with increased metabolism of RA into 18-hydroxy-, 4-oxo-, and 4-hydroxy-RA. The latter metabolite was shown to be able to induce MUC2 and MUC5AC expression in HTBE cells. Our results demonstrate that in normal HTBE cells, CYP26 expression is closely associated with mucous cell differentiation and that many lung carcinoma cells exhibit increased RA metabolism and a defective regulation of CYP26.

Riboflavin-sensitized photochemical changes in beta-lactoglobulin in an aqueous buffer solution as affected by ascorbic acid

The effects of ascorbic acid on the riboflavin-sensitized photochemical changes in beta-lactoglobulin in an aqueous buffer solution as determined by high performance gel permeation liquid chromatography (HPGPLC), insoluble protein content, and individual amino acid content during fluorescent light illumination were studied. The riboflavin-sensitized photochemical degradation of beta-lactoglobulin was effectively inhibited by ascorbic acid, and its inhibitory effectiveness was concentration dependent. The 0.1% ascorbic acid treatment showed 74.4% inhibition of beta-lactoglobulin degradation as determined by a HPGPLC during 6 h light illumination. Insolubility of beta-lactoglobulin in a buffer solution during light illumination was also effectively decreased by ascorbic acid treatment. The riboflavin-sensitized photochemical reduction of cysteine, histidine, lysine, methionine, and tryptophan in beta-lactoglobulin was high during 6 h fluorescent light illumination. The 0.1% ascorbic acid treatment exhibited 20.8% inhibition of total amino acid degradation in beta-lactoglobulin during 6 h light illumination, showing strong inhibitory activity against the degradation of arginine, aspartic acid, cystein, glycine, histidine, phenylalanine, proline, serine, and tryptophan.

Patients with recognized psychiatric disorders in trauma surgery: incidence, inpatient length of stay, and cost

BACKGROUND

Although psychiatric disturbances are highly prevalent among traumatically injured inpatients, few investigations have assessed the impact of these disorders on surgical length of stay (LOS) and cost.

METHODS

The authors identified all trauma-registry recorded psychiatric diagnoses among patients admitted to University of California Davis Medical Center between January 1993 and December 1996. Linear and logistic regressions were used to assess the unique effects of psychiatric diagnoses on inpatient LOS and cost.

RESULTS

A total of 29% of patients had one or more registry-recorded psychiatric diagnosis. Patients with alcohol abuse diagnoses demonstrated 10% to 12% decreases in LOS and cost (p < 0.01), whereas patients with stress disorders, delirium, and psychoses demonstrated 46% to 103% increases in LOS and cost (p < 0.01).

CONCLUSION

Patients with recognized psychiatric disorders uniquely impact inpatient trauma surgery LOS and cost. Additional investigations of the processes and outcomes of care could lead to cost-effective performance improvement efforts that target the amelioration of comorbid psychiatric disorders among physically injured trauma survivors.

Somatic mutations of the trefoil factor family 1 gene in gastric cancer

BACKGROUND & AIMS

There is increasing evidence that trefoil factor family 1 (TFF1) is a stabilizer of the mucous gel overlying the gastrointestinal mucosa that provides a physical barrier against various noxious agents. TFF1 knockout mice developed multiple gastric adenomas and carcinomas, suggesting that TFF1 is a gastric-specific tumor-suppressor gene.

METHODS

We analyzed the somatic mutations and loss of heterozygosity (LOH) of the TFF1 gene using an intragenic polymorphic marker in 61 gastric tumors. The expression pattern of TFF1 was also examined by immunohistochemistry.

RESULTS

We detected a total of 8 somatic mutations-1 (5.5%) of 18 adenomas and 7 (16.3%) of 43 carcinomas-that were all missense mutations confined to the loop I and loop II structure of TFF1. We detected LOH in 5 (1 in adenoma and 4 in cancer) of 30 (16.7%) informative gastric tumors with an intragenic polymorphic marker -2 base pairs (bp) upstream of the coding region of the TFF1 gene. Although 2 cases were noninformative, the 7 gastric cancers with mutation seemed to show the loss of the remaining allele except in 1 case, suggesting that TFF1 is a tumor-suppressor gene. We found loss of TFF1 expression in 44.2% of the gastric carcinomas, but there is no correlation between immunoreactivity and genetic alterations of the TFF1 gene.

CONCLUSIONS

These results indicate that genetic alterations of TFF1 may lead to gastric mucosal barrier defects and contribute to the pathogenesis of gastric cancer.

LCC, a cerebroside from Lycium chinense, protects primary cultured rat hepatocytes exposed to galactosamine

Primary cultures of rat hepatocytes exposed to galactosamine (GalN) were used as a screening system to assess whether a new cerebroside, LCC, isolated from the fruits of Lycium chinense, exhibits hepatoprotective activity. Cultured rat hepatocytes injured with GalN routinely release glutamic pyruvic transaminase (GPT) and sorbitol dehydrogenase (SDH) into the culture medium. Treatment of these GalN-injured primary cultures with LCC markedly blocked the release of both GPT and SDH in a dose-dependent manner over concentrations of LCC ranging from 1 microM to 10 microM. To investigate the mechanism of action for the hepatoprotective activity of LCC, the extent of [(3)H]-uridine incorporation into RNA was measured in GalN-injured cultures of rat hepatocytes. [(3)H]-Uridine incorporation was significantly decreased in injured hepatocytes. LCC, however significantly restored the incorporation of [(3)H]-uridine into RNA in a dose-dependent manner over concentrations ranging from 1 microM to 10 microM. LCC also blocked the suppression of RNA synthesis caused by actinomycin D in a dose-dependent manner. These data suggest that LCC may have prominent hepatoprotective activity and that its therapeutic value should be investigated further.

Inhibition of progesterone-induced Xenopus oocyte maturation by Nm23

The Nm23 protein has been implicated in a wide variety of biological processes, including suppression of metastasis, phytochrome responses in plants, and regulation of differentiation. Here we examine whether Nm23 is involved in Xenopus laevis oocyte maturation. We found that Nm23 is present in oocytes, indicating that it has the potential to be a regulator of maturation. Furthermore, modest overexpression of Nm23 inhibited progesterone-induced oocyte maturation. This maturation-inhibitory activity was shared by both the acidic Nm23-H1 isoform and the basic Nm23-H2 isoform and by Nm23 mutants that lack nucleoside diphosphate kinase activity (Nm23-H1 H118F and Nm23-H2 H118F). Expression of Nm23 proteins delayed the accumulation of Mos and the activation of p42 mitogen-activated protein kinase (MAPK) in progesterone-treated oocytes but had no discernible effect on Mos-induced p42 MAPK activation. Therefore, Nm23 appears to act upstream of the Mos/mitogen-activated protein/extracellular signal-regulated kinase kinase/p42 MAPK cascade. These findings suggest a novel biological role for Nm23.