The role of endotoxin in the pathogenesis of experimental multiple system organ failure: a preliminary report

In this study, an animal model of multiple system organ failure (MSOF) in rabbits, engendered by feeding E. coli prior to severe hemorrhagic shock, was used for the purpose of investigating 1) the relationship between lipopolysaccharide (LPS) and MSOF, and 2) the effectiveness of Re-LPS antiserum in preventing MSOF. The results showed that endotoxemia occurred very early, and its degree correlated well with that of organ dysfunction. Re-LPS antiserum administration abated the toxic effects and lowered the incidence of MSOF. These results suggest that sequential analysis of circulating LPS levels may be useful for the early diagnosis of MSOF, and that gut-derived endotoxin might play an important role in the pathogenesis of experimental MSOF.

Molecular cloning of the transmembrane component of the 13762 mammary adenocarcinoma sialomucin complex. A new member of the epidermal growth factor superfamily

Ascites sublines of the 13762 rat mammary adenocarcinoma have a cell surface sialomucin complex composed of the sialomucin ascites sialoglycoprotein-1 (ASGP-1) and the membrane-associated glycoprotein ASGP-2. The sialomucin complex is synthesized as a high M(r) precursor, pre-sialomucin complex (pSMC-1). To characterize the structure of the membrane-associated component of this complex, a lambda gt11 cDNA expression library was constructed using mRNA from 13762 rat mammary adenocarcinoma cells and screened with polyclonal antibody against ASGP-2. The strongest antibody-binding clone, designated lambda ASGP2.9-1, had a 1.3-kilobase (kb) insert, and hybridized to a 9-kb transcript in 13762 cell mRNA. The large size of this transcript was expected, since the estimated molecular mass of pSMC-1 is greater than 250 kDa. To obtain the full sequence of ASGP-2, a longer cDNA (5.4 kb), designated pASGP1/2.1, was subsequently cloned by screening a plasmid library with an oligonucleotide complementary to the 5' end of the phage insert. The amino acid sequence derived from nucleotide sequence of pASGP1/2.1 showed a 12-amino acid identity with amino acid sequence obtained from the NH2 terminus of ASGP-2, indicating the entire ASGP-2 coding region was included in the cDNA. Furthermore, an 18-amino acid identity with the NH2 terminus of a 6-kDa CNBr fragment of ASGP-2 was also observed in the cDNA sequence. The polypeptide contains several distinct domains, including a hydrophobic transmembrane domain, a short (20 residue) COOH-terminal cytoplasmic tail, and a large extracellular domain with 24 potential N-glycosylation sites. These properties correspond to features of ASGP-2 and pSMC-1 predicted by previous biochemical studies. Most interestingly, the extracellular domain contains two cysteine-rich sequences, each of which has a segment with strong similarities to proteins with epidermal growth factor activity. Since our recent studies show that ASGP-2 can modulate epidermal growth factor receptor phosphorylation activity, these results provide structural evidence to support the role of the heterodimeric sialomucin complex as a bifunctional modulator of cellular interactions and cell proliferation.

Multiple organ injuries after abdominal high energy wounding in animals and the protective effect of antioxidants

Multiple organ injuries caused by high energy abdominal wounds were studied in 8 pigs and 24 dogs, and at the same time the protective effect of antioxidants in 14 dogs with multiple organ injuries was also studied. The experimental results showed that: 1) more than two organs (six organs at most) were wounded in each of the animals studied; 2) the injuries were characterized by hemorrhaging, tissue rupture and hematoma, and the main pathologic changes were local edema and necrosis; 3) the marked increase of lipid peroxide (LPO) levels in the vital organs indicated that multiple organ injuries could also involve the molecular level; 4) the injuries were due to the direct effect of pressure waves and ischemic reperfusion and not to shock or infection; and 5) antioxidants (vitamin E and Salvia miltiorrhiza Bge.) exhibited significant protective effects against multiple organ injuries through a free radical mechanism.

Evidence that both Ca(2+)-specific sites of skeletal muscle TnC are required for full activity

To investigate the role of the Ca2(+)-specific (I and II) sites of fast skeletal muscle troponin C (TnC) in the regulation of contraction, we have produced two TnC mutants which have lost the ability to bind Ca2+ at either site I (VG1) or at site II (VG2). Both mutants were able to partially restore force to TnC-depleted skinned muscle fibers (approximately 25% for VG1 and approximately 50% for VG2). In contrast, bovine cardiac TnC (BCTnC), which like VG1 binds Ca2+ only at site II, could fully reactivate the contraction of TnC-depleted fibers. Higher concentrations of both mutants were required to restore force to the TnC-depleted fibers than with wild type TnC (WTnC) or BCTnC. VG1 and VG2 substituted fibers could not bind additional WTnC, indicating that all of the TnC-binding sites were saturated with the mutant TnC's. The Ca2+ concentration required for force activation was much higher for VG1 and VG2 substituted fibers than for WTnC or BCTnC substituted fibers. Also, the steepness of force activation was much less in VG1 and VG2 versus WTnC and BCTnC substituted fibers. These results suggest cooperative interactions between sites I and II in WTnC. In contrast, BCTnC has essentially the same apparent Ca2+ affinity and steepness of force activation as does WTnC. Thus, cardiac TnC must have structural differences from WTnC which compensate for the lack of site I, while in WTnC, both Ca2(+)-specific sites are probably crucial for full functional activity.

[Survey of Bacillus thuringiensis and Bacillus sphaericus from soils of four provinces of China and their principal biological properties]

A number of isolates of Bacillus thuringiensis and Bacillus sphaericus were obtained from soils of Southwestern Area and Shaanxi Province of China. Among isolates of B. thuringiensis were under 13 sorts of serotype in total of 23 sorts of B. thuringiensis and about 20% of auto-agglutinate strains. Rules of ecologic distribution of two sorts of bacteria were analysed. Toxicities on six species of insects, morphology and crystal proteins of B. thuringiensis, as well as toxicities, morphology and crystal proteins of B. sphaericus, were investigated. 22 strains of more efficient of B. thuringiensis and 2 strains of more efficient of B. sphaericus were obtained. It was shown that B. thuringiensis is actually soil microorganism, and resource of B. thuringiensis is much fruitful in Southwestern Area of China.

Expression, purification and characterization of a 41 kDa insulin receptor tyrosine kinase domain

An active 41 kDa cytoplasmic domain of the insulin receptor tyrosine kinase (CIRK-41) encompassing amino acid residues 946 and 1303 of the native protein with an additional three amino acids (HAI) at the N-terminus has been overexpressed using the baculovirus pAC 373 expression system. The recombinant protein termed CIRK-41 has been purified to homogeneity. CIRK-41 was capable of autophosphorylation and up to 1.9 moles of phosphate were incorporated per mole of enzyme when it was incubated in the presence of 10 mM manganese chloride and 0.5 mM ATP. Autophosphorylation resulted in stimulation of CIRK-41 activity towards its exogenous substrate, indicating that CIRK-41 may be used as a model molecule to study the role of phosphorylation and dephosphorylation in the control of the insulin receptor tyrosine kinase activity.

Isolation and partial characterization of ascites sialoglycoprotein-2 of the cell surface sialomucin complex of 13762 rat mammary adenocarcinoma cells

Sialomucins are the dominant components of the cell surfaces of some carcinoma ascites cells and have been postulated to inhibit recognition of tumours by the immune system. The sialomucin ASGP-1 (ascites sialoglycoprotein-1) of the 13762 rat mammary adenocarcinoma is associated with the cell surface as a complex with a concanavalin-A-binding glycoprotein called ASGP-2. This sialomucin complex has been purified from ascites cell microvilli by extraction with Triton X-100 and CsCl density-gradient centrifugation. ASGP-1 (which has been purified previously) and ASGP-2 were dissociated in 6 M-guanidine hydrochloride and separated by gel filtration. The molecular mass of the undenatured detergent complex of ASGP-2, estimated by gel filtration and velocity sedimentation in Triton X-100, was 148 kDa. Since the apparent molecular mass by SDS/polyacrylamide-gel electrophoresis was about 120 kDa, ASGP-2 must be a monomer as extracted from the membrane. Studies of its chemical composition indicate that it contains about 45% carbohydrate by weight, including both mannose and galactosamine. Alkaline borohydride treatment of ASGP-2 converted approx. half of the N-acetylgalactosamine to N-acetylgalactosaminitol, demonstrating the presence of O-linked oligosaccharides. Analyses of mannose-labelled Pronase glycopeptides from ASGP-2 by lectin-affinity chromatography on concanavalin A and leucocyte-agglutinating phytohaemagglutinin suggested that 40% of the label was present in high-mannose/hybrid oligosaccharides, 20% in triantennary oligosaccharides substituted on the C-2 and C-4 mannose positions and 40% in tri- or tetra-antennary oligosaccharides substituted on C-2 and C-6. The presence of polylactosamine sequences on these oligosaccharides was suggested by lectin blots and by precipitation from detergent extracts with tomato lectin. From chemical analyses and lectin-affinity studies, we estimate that ASGP-2 contains four high-mannose and 13 complex N-glycosylated oligosaccharides, plus small amounts of polylactosamine and O-linked oligosaccharides. The presence of four different classes of oligosaccharides on this glycoprotein suggests that it will be an interesting model system for biosynthetic comparisons of the different glycosylation pathways.

Topography and microfilament core association of a cell surface glycoprotein of ascites tumor cell microvilli

Membrane-microfilament interactions are being investigated in microvilli isolated from 13762 rat mammary ascites tumor cells. These microvilli are covered by a sialomucin complex, composed of the sialomucin ascites sialoglycoprotein-1 (ASGP-1) and the associated concanavalin A (Con A)-binding glycoprotein ASGP-2. Limited proteolysis of the microvilli releases large, highly glycosylated fragments of ASGP-1 from the microvilli and increases the association of ASGP-2 with the Triton-insoluble microvillar microfilament core (Vanderpuye OA, Carraway CAC, Carraway, KL: Exp Cell Res 178:211, 1988). To analyze the topography of ASGP-2 in the membrane and its association with the microfilament core, microvilli were treated with proteinase K for timed intervals and centrifuged. The pelleted microvilli were extracted with Triton X-100 for the preparation of microfilament cores and Triton-soluble proteins or with 0.1 M carbonate, pH 11, for the preparation of microvillar membranes depleted of peripheral membrane proteins. These microvilli fractions were analyzed by dodecyl sulfate gel electrophoresis, lectin blotting with Con A and L-phytohemagglutinin, and immunoblotting with anti-ASGP-2. The earliest major proteolysis product from this procedure was a 70 kDa membrane-bound fragment. At longer times a 60 kDa released fragment, 30-40 kDa Triton-soluble fragments, and 25-30 kDa membrane- and microfilament-associated fragments were observed. Phalloidin shift analysis of microfilament-associated proteins on velocity sedimentation gradients indicated that the 25-30 kDa fragments were strongly associated with the microfilament core. From these studies we propose that ASGP-2 has a site for indirect association with the microfilament core near the membrane on a 15-20 kDa segment.

Hemodilution affects the pressor response to norepinephrine

A hindlimb preparation of 19 male rats was used to determine the responses to norepinephrine (NE) at different levels of hemodilution at a constant flow, at increased flow and maintained pressure, and after reversal of hemodilution. An initial series demonstrated that the preparation remained stable with unchanged blood pressure, plasma electrolytes, and blood gases; and had reproducible responses to NE throughout the experiment. Two levels of isovolumic hemodilution were achieved by blood/hetastarch exchanges equivalent to 1.5% and 3.0% body weight, which reduced hematocrit to 30.8 +/- 2% and 18.7 +/- 1.5%, respectively. Hemodilution reduced the perfusion pressure from 73.6 mmHg to 58.6 and 55.7 mmHg following 1.5% and 3.0% hemodilution, respectively. A dose-response relationship to NE (0.1, 0.3, 1.0 micrograms/kg) was obtained. The responses to NE were markedly reduced following both 1.5% and 3.0% hemodilution. Retransfusion of packed red blood cells increased the hematocrit from 21.1 +/- 2.2% during hemodilution to 41.2 +/- 2.1% (P less than .01). Concomitantly, perfusion pressure increased from 46.2 +/- 3.6 to 68.3 +/- 6.5 mmHg (P less than .001), close to prehemodilution levels (65.3 +/- 5.3 mmHg). Restoration of hematocrit levels restored responses to NE. In a third series, hemodilution was continued, but the blood flow was increased from 4.0 to 8.3 +/- 0.9 mL/min, and perfusion pressure returned to baseline values. This also restored the pressor responsiveness to NE to near normal.