Fibronectin-degrading proteases from the membranes of transformed cells

The local degradation of fibronectin substrata by Rous sarcoma virus-transformed chick embryonic fibroblasts requires cell-contact-related metalloendoprotease and serine-protease activities. Using fibronectin-containing SDS gels, two large proteases with apparent molecular weights of 120K and 150K were found only in the membrane fraction of transformed cells and were absent in normal cells. Both 120K and 150K proteases were active at neutral pH, but showed preferential inhibitor sensitivities of serine and metal proteases, respectively. The 150K protease appeared to account for most of the proteolytic activity since metalloendoprotease inhibitors completely blocked proteolytic activity of the 150K in fibronectin gels, more than 80% of the fibronectin-degrading activity of solubilized membranes, and largely suppressed the appearance of fibronectin degradation spots in cultures of transformed cells.     

Phosphodiester bond cleavage outside mitochondria is required for the completion of protein import into the mitochondrial matrix

The present studies show that hydrolysis of a phosphodiester bond, most likely ATP, is a distinct, second step required to complete import of the F1-ATPase beta-subunit into the mitochondria. This step follows a membrane potential-dependent first step. We show, using an inhibitor of adenine nucleotide transport and the analogue beta,gamma-AMP-PCP, that the activity required for this phosphodiester hydrolysis-dependent completion of protein import resides outside the mitochondrial inner membrane. This activity is proposed to act on the precursor at the site of translocation either to render it competent or to catalyze its vectorial movement directly through the import apparatus. This activity shares properties ascribed to proteins of the heat-shock family, which are proposed to participate in the ATP-dependent refolding of partially denatured proteins and nascent peptides.     

Effect of hydrophobicity of utilization of peptides by ruminal bacteria in vitro

When mixed ruminal bacteria were incubated with a pancreatic casein hydrolysate and free amino acids of a similar composition, rates of ammonia production were much greater for peptides than for amino acids. The pancreatic digest of casein was then fractionated with 90% isopropyl alcohol. Hydrophobic peptides which dissolved in alcohol contained an abundance of phenolic and aliphatic amino acids, while the hydrophilic peptides which were precipitated by alcohol contained a large proportion of the highly charged amino acids. The Km values of the mixed ruminal bacteria for each fraction were similar (0.88 versus 0.98 g/liter), but the Vmax of the hydrophilic peptides was more than twice that of the hydrophobic peptides (18 versus 39 mg of NH3 per g of bacterial protein per h). Pure cultures of ruminal bacteria had a similar preference for hydrophilic peptides and likewise utilized peptides at a faster rate than free amino acids. Since peptide degradation rates differed greatly, hydrophobicity is likely to influence the composition of amino acids passing unfermented to the lower gut of ruminant animals.     

Big Moose Basin: simulation of response to acidic deposition

The ILWAS model has been enhanced for application to multiple-lake hydrologic basins. This version of the model has been applied to the Big Moose basin, which includes Big Moose Lake and its tributary streams, lakes, and watersheds. The basin, as defined, includes an area of 96 km², with over 20 lakes and ponds, and 70 km of streams. Hydrologic and chemical calibrations have been made using data from seven sampling stations. When total atmospheric sulfur loading to the basin is halved, the model predicts, after four years of simulation, a decreasing sulfate concentration and to a lesser extent a rising alkalinity at Big Moose Lake outlet. At the end of four years, the results show an increase in pH of 0.1 to 0.5 pH units depending upon season.     

犬脑内动脉构筑的显微X线解剖学研究

犬脑11只,经生理盐水冲洗脑血管后,注入20％钡胶液,切成0.2～1.0厘米的厚片,用显微X线法研究犬脑内各级动脉的构筑,其结果:1.皮质动脉的管径平均为25.9±0.005微米,平均长度为888.0±0.241微米。其形态与发出部位有关,分别呈栅状和瓶刷状。2.髓质动脉的管径平均为49.9±0.007微米。呈直线或孤形向心走行。3.皮质下动脉的管径平均为38.7±0.009微米。呈新月形或蟹钳状分布。4.豆纹动脉和内囊动脉的平均管径为70.0±0.021微米。呈锐角、反血流方向发自母干,再呈“S”形上升。5.丘脑动脉的平均管径为63.7±0.019微米,主要从下方进丘脑,呈树枝状分支。     

Protein translocation into Escherichia coli membrane vesicles is inhibited by functional synthetic signal peptides

A synthetic peptide corresponding to the signal sequence of wild type Escherichia coli lambda-receptor protein (LamB) inhibits in vitro translocation of precursors of both alkaline phosphatase and outer membrane protein A into E. coli membrane vesicles (half-maximal inhibition at 1-2 microM). By contrast, the inhibitory effect was nearly absent in a synthetic peptide corresponding to the signal sequence from a mutant strain that harbors a deletion mutation in the LamB signal region and displays an export-defective phenotype for this protein in vivo. Two peptides derived from pseudorevertant strains that arose from the deletion mutant and exported LamB in vivo were found to inhibit in vitro translocation with effectiveness that correlated with their in vivo export ability. Controls indicated that these synthetic signal peptides did not disrupt the E. coli membrane vesicles. These results can be interpreted to indicate that the presequences of exported proteins interact specifically with a receptor either in the E. coli inner membrane or in the cytoplasmic fraction. However, biophysical data for the family of signal peptides studied here reveal that they will spontaneously insert into a lipid membrane at concentrations comparable to those that cause inhibition. Hence, an indirect effect mediated by the lipid bilayer of the membrane must be considered.     

Immune regulation of the L5178Y murine tumor-dormant state. II. Interferon-gamma requires tumor necrosis factor to restrain tumor cell growth in peritoneal cell cultures from tumor-dormant mice

L5178Y lymphoma cells are restrained from progressive growth in peritoneal cell ("in vitro tumor-regressor" PC) cultures prepared from many DBA/2 mice which harbor the tumor cells in the peritoneal cavity in a tumor-dormant state. Treatment of these PC cultures with 'antibodies to murine interferon-gamma (MuIFN-gamma) and murine tumor necrosis factor (MuTNF) but not with antibody to interleukin 2 (IL-2) receptors eliminated the restraint on tumor cell growth and permitted their progressive proliferation. L5178Y cells were found to be resistant to the direct toxic effects of large concentrations (3,000 U/ml) of MuIFN-gamma and of MuTNF, either alone or in combination. Treatment of PC cultures from tumor-dormant mice, in which tumor cells grew progressively ("in vitro tumor-progressor"), but not PC cultures from normal mice, with exogenous MuIFN-gamma resulted in a marked inhibition of tumor cell growth. The MuIFN-gamma-induced cytotoxic activity was cell-mediated since no soluble tumor-cytotoxic factors could be detected in the cultures. MuIFN-gamma induced cytotoxic activity in plastic-adherent peritoneal cell (AD-PC) cultures, but induced no cytotoxic activity in nonadherent-PC cultures unless small numbers (2%) of AD-PC were present, and inclusion of antibody to MuTNF in these mixed PC cultures blocked the development of cytotoxic activity. Antibody to MuTNF also blocked the development of cytotoxic activity in cultures of MuIFN-gamma-treated whole PC and AD-PC from tumor-dormant mice. These results indicate that MuIFN-gamma and MuTNF are both important in restraining tumor cell growth in PC cultures from tumor-dormant mice, and that MuIFN-gamma requires the presence of MuTNF to induce cytotoxic activity in these cultures.     

The androgen-dependent mouse seminal vesicle secretory protein IV: characterization and complementary deoxyribonucleic acid cloning

Seminal vesicle secretory protein IV of a mouse has been isolated, and the cDNA coding for its mRNA has been cloned and sequenced. The 556-nucleotides encode 16 amino acid signal peptides and 92 residues of mature protein. Considerable homology between mouse and rat SVS IV cDNA was found. In the leader peptide and 3'-noncoding region there is 92% and 85% homology, respectively. The other regional homologies are 86% for the first 12, 68.5% for the last 35, and 40% for the middle 44 amino acids. The expression of mouse SVS IV mRNA is under the control of androgen. Administration of testosterone to castrated mice resulted in induction of the mRNA level to 50% of the mature male in 96 h of hormone treatment. Secretion of the protein after testosterone injection follows a similar pattern.     

Antimutagenic effect of garlic (Allium sativum L.) on 4NQO-induced mutagenesis in Escherichia coli WP2

Aqueous extract prepared from garlic bulbs markedly suppressed the mutagenesis in both E. coli WP2 trp- and E. coli WP2 trp- uvrA- induced by 4-nitroquinoline 1-oxide (4NQO), but not that induced by UV. Cellular toxicity, inhibition of the expression of the Trp+ phenotype and delay of the first cell division after 4NQO treatment were not observed in the presence of the extract. Since the extract showed identical antimutagenic effects against 4NQO in both test strains but no effect on the mutagenesis of UV, it seems that the extract might act by inactivating the electrophilic group(s) of 4NQO or inhibiting its metabolic activation.     

Thermotolerance of isolated mitochondria associated with heat shock proteins

Mitochondria isolated from 2-day-old etiolated soybean (Glycine max) seedlings which had been subjected to various heat shock treatments, i.e. (A) 28°C (2 h), (B) 38°C (2 h), (C) 38°C (2 h)-42.5°C (0.5 h), and (D) 38°C (2 h)-42.5°C (0.5 h)-28°C (4 h), were monitored for O₂ uptake using an oxygen electrode. Mitochondria isolated after all four heat shock treatments were active in O₂ consumption at 28°C in response to succinate and ADP (derived P/O ratios were 1.6, 1.7, 1.3, and 1.3, respectively.) The mitochondria from all four treatments were also active in O₂ uptake at 42.5°C. However, only mitochondria isolated after treatment (C) were tightly coupling at 42.5°C (derived ADP/O ratio was about 1.4). Combined with our earlier findings on the subcellular localization of heat shock proteins, our present data demonstrate that association of heat shock proteins with mitochondria by treatment (C) enables them to phosphorylate at 42.5°C (i.e. they become thermotolerant). Isolated mitochondria from treatment (C) and treatment (A) were compared by electron microscopy. They appeared to be very similar and no significant ultrastructural differences were noted.