Studies of an Inhibitor of the Thrombin-Fibrinogen Reaction Localized in Rat Liver Microsomes. Interference with the Polymerization Step

A heat-stable, macromolecular inhibitor of the thrombin-fibrinogen reaction localized in rat liver microsomes has been shown to interfere with the polymerization step in the fibrinogen-fibrin conversion. The inhibitor had no effect on thrombin activity as measured with the synthetic, chromogenic substrate Bz-Phe-Val-Arg-pNA. The amount of fibrin formed and the release of fibrinopeptide A were not affected by the inhibitor. Recording of turbidity at 350 nm and 600 nm indicated an inhibition of the lateral aggregation of the end-to-end fibrin polymers. The inhibitor was localized in both the luminal and membrane fractions of the microsomes. The inhibitor activity was not affected by warfarin treatment of the rats.

Low Protein A20 in Minor Salivary Glands is Associated with Lymphoma in Primary Sjögren's Syndrome

Patients with primary Sjögren's syndrome (pSS) have an increased risk of developing lymphomas, particularly the subtype mucosa-associated lymphoid tissue (MALT) lymphoma. Chronic antigen stimulation and increased activation of nuclear factor-κB (NF-κB) are important factors for the pathogenesis of MALT lymphomas. Protein A20 is an inhibitor of NF-κB. A recent study of pSS-associated MALT lymphomas identified potential functional abnormalities in the TNFAIP3 gene, which encodes protein A20. The present study aimed to assess protein A20 by immunohistochemistry (IHC) in minor salivary glands (MSGs) and lymphoma tissue sections of patients with pSS and investigate a potential association with lymphoma development. Protein A20 staining in lymphocytes was scored in four categories (0 = negative, 1 = weak, 2 = moderate and 3 = strong). For statistical purposes, these scores were simplified into negative (scores 0-1) and positive (scores 2-3). We investigated associations between protein A20-staining, focus scores, germinal centre (GC)-like structures and monoclonal B-cell infiltration in MSGs. MSG protein A20 staining was weaker in pSS patients with lymphomas than in those without lymphomas (P = 0.01). Weak protein A20 staining was also highly associated with a lack of GC formation (P < 0.01). Finally, weaker A20 staining was observed in the majority of pSS-associated MALT lymphoma tissues. In conclusion, we found absent or weak protein A20 immunoreactivity in MSGs of patients with pSS with lymphomas. This finding indicates that protein A20 downregulation in lymphocytes might be a mechanism underlying lymphoma genesis in patients with pSS.

Strategies for clinical implementation of TNM-Immunoscore in resected nonsmall-cell lung cancer

Immunoscore is a prognostic tool defined to quantify in situ immune cell infiltrates and appears highly promising as a supplement to the tumor-node-metastasis (TNM) classification of various tumors. In colorectal cancer, an international task force has initiated prospective multicenter studies aiming to implement TNM-Immunoscore (TNM-I) in a routine clinical setting. In breast cancer, recommendations for the evaluation of tumor-infiltrating lymphocytes (TILs) have been proposed by an international working group. Regardless of promising results, there are potential obstacles related to implementing TNM-I into the clinic. Diverse methods may be needed for different malignancies and even within each cancer entity. Nevertheless, a uniform approach across malignancies would be advantageous. In nonsmall-cell lung cancer (NSCLC), there are several previous reports indicating an apparent prognostic importance of TILs, but studies on TILs in a TNM-I setting are sparse and no general recommendations are made. However, recently published data is promising, evoking a realistic hope of a clinical useful NSCLC TNM-I. This review will focus on the TNM-I potential in NSCLC and propose strategies for clinical implementation of a TNM-I in resected NSCLC.

Saponin permeabilization of rough microsomes from rat liver reveals a novel prothrombin pool

Saponin permeabilization of rough microsomes in the presence of high salt revealed a novel pool of prothrombin associated by ionic interactions to the microsomal membrane. The lumenal content was obtained by treating rough microsomes with 0.32% saponin in a low salt (0.05 M KCl) buffer. By a subsequent treatment with 0.32% saponin in a slightly alkaline high salt buffer a fraction of peripherally associated membrane prothrombin was released from rough microsomes. Finally, the membrane-bound fraction was solubilized with 2.5% Triton X-100. The lumenal content fraction, the peripherally membrane-associated and the membrane-bound fraction from normal rats contained 55%, 29% and 16% of the total rough microsomal prothrombin, respectively. The corresponding fractions from warfarin-treated rats contained 86%, 5% and 9% of the total prothrombin. Following (14)C-gamma-carboxylation of intact microsomes for 30 min, the novel membrane-associated and the membrane-bound pool contained 42% and 33%, respectively, of labeled prothrombin. A similar distribution was found with warfarin-treated rats.

Oligoclonality of rat intestinal intraepithelial T lymphocytes: overlapping TCR beta-chain repertoires in the CD4 single-positive and CD4/CD8 double-positive subsets

Previous studies in humans and mice have shown that gut intraepithelial lymphocytes (IELs) express oligoclonal TCR beta-chain repertoires. These studies have either employed unseparated IEL preparations or focused on the CD8+ subsets. Here, we have analyzed the TCR beta-chain repertoire of small intestinal IELs in PVG rats, in sorted CD4+ as well as CD8+ subpopulations, and important differences were noted. CD8alphaalpha and CD8alphabeta single-positive (SP) IELs used most Vbeta genes, but relative Vbeta usage as determined by quantitative PCR analysis differed markedly between the two subsets and among individual rats. By contrast, CD4+ IELs showed consistent skewing toward Vbeta17 and Vbeta19; these two genes accounted collectively for more than half the Vbeta repertoire in the CD4/CD8 double-positive (DP) subset and were likewise predominant in CD4 SP IELs. Complementarity-determining region 3 length displays and TCR sequencing demonstrated oligoclonal expansions in both the CD4+ and CD8+ IEL subpopulations. These studies also revealed that the CD4 SP and CD4/CD8 DP IEL subsets expressed overlapping beta-chain repertoires. In conclusion, our results show that rat TCR-alphabeta+ IELs of both the CD8+ and CD4+ subpopulations are oligoclonal. The limited Vbeta usage and overlapping TCR repertoire expressed by CD4 SP and CD4/CD8 DP cells suggest that these two IEL populations recognize restricted intestinal ligands and are developmentally and functionally related.

Sequential development of intraepithelial gamma delta and alpha beta T lymphocytes expressing CD8 alpha beta in neonatal rat intestine: requirement for the thymus

Previous studies in congenitally athymic nude rats have suggested that the thymus is important for the development of intestinal T cells. Here we have examined the effect of the nude mutation on intraepithelial lymphocyte (IEL) development from the perinatal period. By immunohistochemistry it was shown that CD3(-)CD8 alpha alpha + putative IEL precursors colonized the epithelium of both normal and athymic neonatal rats. Mature T cells, however, did not develop in athymic neonates. In normal rats, gamma delta T cells were present at birth and alpha beta T cells appeared within 8 days of postnatal life. At this age, the composition and relative number of intraepithelial T cells were similar to that in normal adult rats, with the exception that most neonatal T-cell receptor-gamma delta + and -alpha beta + IEL expressed CD8 beta. By contrast, extrathymic T-cell maturation in the gut of congenitally athymic rats occurred slowly, as CD3+ IEL did not appear until 4-6 months of age. These intraepithelial T cells displayed variable phenotypes and appeared to be induced by environmental antigens as they were not found in isolator-kept old nudes. In conclusion, the present results indicate that the major colonization of the gut epithelium with gamma delta and alpha beta T cells expressing CD8 alpha beta takes place perinatally and requires the presence of the thymus. The developmental relationship between these neonatal T cells and more immature CD3- CD8 alpha alpha +/- IEL remains elusive.

Regional phenotypic specialization of intraepithelial lymphocytes in the rat intestine does not depend on microbial colonization

Recent studies in mice and humans have provided evidence for regional specialization of gut intraepithelial lymphocytes (IEL). Here the authors report striking regional variability in the composition of IEL in rat small and large intestine. Two-colour immunofluorescence in situ analysis showed that the distribution of the CD3+ and CD3- IEL subpopulations varied, the proportion of T cells (CD3+) being higher in the ileum than in the jejunum and smallest in the colon. These differences were explained by variable numbers of the T-cell receptor (TCR)alpha/beta + (both CD8+ and CD4+) but not the TCR gamma/delta + subset. Moreover, the various IEL subpopulations showed distinct intraepithelial distribution patterns with CD4+ and CD8 alpha beta + T cells situated near the lamina propria, while CD3- IEL were located preferentially towards the adluminal part of the epithelium. Regional phenotypic variation did not depend on intestinal colonization because analogous results were obtained in germ-free rats. Conventionalization nevertheless caused a marked relative increase of small intestinal TCR alpha/beta + but not TCR gamma/delta + IEL. This increase was more sustained in the jejunum than ileum and eventually reduced the phenotypic IEL differences between the two sites. By contrast, microbial colonization of the colon induced only a transient increase of intraepithelial TCR alpha/beta + cells with no permanent phenotypic alterations. Both CD3+ and CD3- IEL contained subpopulations that expressed NKR-P1 independent of intestinal colonization. These results demonstrate phenotypic specialization of IEL at different levels of the gut and suggest that the indigenous flora is not essential to this end.

A rapid and highly sensitive chromogenic microplate assay for quantification of rat and human prothrombin

A rapid and highly sensitive chromogenic microplate assay for quantification of rat and human prothrombin in subcellular fractions and large series of plasma samples has been developed. The assay is based on the conversion of prothrombin to thrombin, using Echis carinatus venom as an activator, and the subsequent cleavage of a chromogenic thrombin specific substrate, D-cyclohexylglycyl-L-alanyl-L-arginine-p-nitroanilide dihydroacetate. para-Nitroaniline being released by the cleavage is then measured at 410 nm with a microplate reader. The method is suitable for analyses of a large number of samples in a short time, measuring prothrombin in the nanogram range (0.3-2.4 ng/40 microliters of sample).

Mucosal immunity--a major adaptive defence mechanism

The epithelial glycoprotein called secretory component (SC) is quantitatively the most important receptor of the immune system because it is responsible for external transport of locally produced polymeric IgA (pIgA) to generate remarkably large amounts of secretory IgA. Antibodies of this type constitute the major mediators of specific humoral immunity. Transmembrane SC belongs to the Ig supergene family and functions as a common pIg receptor, also translocating pentameric IgM externally to form secretory IgM. The B cells responsible for mucosal pIg production are initially stimulated in organized mucosa-associated lymphoepithelial structures, particularly the Peyer's patches in the distal small intestine; from these inductive site they migrate as memory cells to exocrine tissues all over the body. Mucous membranes are thus furnished with secretory antibodies in an integrated way, ensuring a variety of specificities at every secretory effector site. There is currently great interest in exploiting this integrated or "common" mucosal immune system for oral vaccination against pathogenic infectious agents and also to induce tolerance in T cell-mediated autoimmune diseases. However, much remains to be learned about mechanisms for antigen uptake and processing necessary to elicit stimulatory or suppressive mucosal immune responses. Moreover, evidence is emerging for the existence of considerable regionalization with regard to functional links between inductive sites and effecter sites of mucosal immunity.

Microbial colonization influences composition and T-cell receptor V beta repertoire of intraepithelial lymphocytes in rat intestine

Studies in mice have shown that the composition of intestinal intraepithelial lymphocytes (IEL) may be markedly altered by gut microbial colonization. Such modulation was studied in a rat model by the use of germ-free and conventionalized animals from which IEL from the small intestine were isolated and analysed by flow cytometry. Conventionalization caused expansion as well as phenotypic alterations of T-cell receptor (TCR) alpha/beta + IEL in that the proportions of CD4+ and CD8 alpha beta + TCR alpha/beta + cells were increased, while the double negative (CD4- CD8-) fraction was reduced. microbial colonization also influenced the TCR V beta repertoire of CD8+ IEL in that the proportions of V beta 8.2+ and V beta 10+ cells were increased, whereas V beta 8.5+ and V beta 16+ cells were relatively decreased. Moreover, conventionalization influenced the levels of TCR cell surface expression in the same V beta subsets. Three-colour flow-cytometric analysis demonstrated that skewing of the V beta repertoire was most pronounced in the CD8 alpha alpha + subset, although the numerical increase of IEL mainly included the CD8 alpha beta + subset. In contrast to IEL, the TCR V beta repertoire in mesenteric lymph nodes was unchanged after intestinal colonization. These results confirm that TCR alpha/beta + IEL subpopulations respond dynamically to the microbial gut flora and suggest that their V beta repertoire can be shaped by luminal microbial antigens.

A highly sensitive chromogenic microplate assay for quantification of rat and human plasminogen

A simple and highly sensitive chromogenic microplate assay for quantification of rat and human plasminogen in plasma samples and subcellular fractions has been developed. The assay is based on a conversion of plasminogen to plasmin, using urokinase as an activator, and a subsequent cleavage of a chromogenic plasmin substrate D-alanyl-L-cyclohexylalanyl-L-lysine-p-nitroanilide-dihydroacet ate. p-Nitroaniline being released by the cleavage is then measured at 410 nm with a microplate reader. The assay includes an acidification step to make plasminogen more readily activated to plasmin. The method is suitable for analyses of a large number of samples, measuring plasminogen in the nanogram range (0.5-50 ng/50 microliters of sample).

The time courses of intracellular transport of some secretory proteins of rat liver are not affected by an induced acute phase response

To study the effects of changed synthesis on intracellular transport of secretory proteins, an acute phase response was induced in rats. The synthesis and secretion of haptoglobin, complement C3, transferrin and albumin were then investigated by pulse labeling with [3H]leucine. Maximal increase in the syntheses of the positive acute phase proteins was observed after 24 h, amounting to an increase of nine, three and twofold for haptoglobin, C3 and transferrin, respectively. The synthesis of albumin decreased to a minimum after 48 h, reaching approximately one fourth of normal synthesis. The time courses for transit through rough endoplasmic reticulum and for secretion were determined after 36 h, and were found to be roughly unchanged for all four proteins despite the different changes in synthesis. The fraction of haptoglobin associated with the microsomal membrane was reduced during the acute phase response, but there was no significant change in membrane association as a function of time after labeling with [3H]leucine. It is concluded that the altered protein synthesis during an acute phase response in vivo has little effect on the time course of secretion of the proteins studied. Furthermore, the basal mechanisms for intracellular transport appear relatively unchanged during this condition.

IgG subclass distribution in serum and rectal mucosa of monozygotic twins with or without inflammatory bowel disease

Serum samples from 26 monozygotic twin pairs concordant or discordant with regard to inflammatory bowel disease, and rectal biopsies from 42 twins of the same subject group, were examined for IgG subclasses. They were all compared with normal controls. Almost all affected twins were in clinical remission. Paired immunofluorescence staining of the rectal mucosa showed that those with ulcerative colitis had a significantly higher (p < 0.01) proportion of IgG1 producing mucosal immunocytes than normal controls (78.1% v 55.9%). Conversely, the IgG2 cell fraction was significantly reduced (15.9% v 34.6%). Healthy twins from ulcerative colitis pairs tended to show a raised proportion of IgG1 cells and the IgG2 cell fraction was significantly reduced (p < 0.05). In discordant ulcerative colitis twin pairs, no difference appeared in the cellular IgG subclass pattern between healthy and affected twins. Furthermore, the proportion of IgG1 in these healthy and diseased twins showed good correlation (T = 0.867). The results in rectal mucosa of twins with Crohn's disease were widely scattered and affected twins did not differ significantly from normal controls. Healthy twins, however, showed a marginally raised IgG1 cell proportion, but no correlation was seen between the IgG subclass fractions in discordant Crohn's disease twin pairs. The serum concentrations of IgG1 and IgG2 did not differ from normal controls in twins of either category. These results suggested that in ulcerative colitis, the aberrant mucosal production of IgG1 and IgG2 does not depend on active disease, but is apparently at least partially explained by a genetic impact. Conversely, the mucosal IgG subclass pattern in Crohn's disease appears to be determined mainly by exogenous variables.

A novel enzyme immunoassay for quantitation of rat prothrombin in microsomal subfractions

An enzyme linked immunoassay (ELISA) for quantitation of rat prothrombin, based on a biotin-streptavidin alkaline phosphatase system is described. The assay utilizes rabbit antiserum raised against purified rat prothrombin. The assay was twenty fold more sensitive than a rat prothrombin assay based on amidolytic activity following activation by Echis carinatus venom. Results obtained with the two assays show good correlation. The ELISA is a valuable tool for quantitation of minute amounts of prothrombin in subcellular fractions and large series of plasma samples.

Investigation of a possible correlation between rates of secretion and microsomal membrane association of plasma proteins synthesized by rat liver

The rates of secretion of complement C3, haptoglobin and plasminogen have been determined after pulse labelling with [3H]leucine, and compared to the secretion of prothrombin, albumin and transferrin investigated previously (Kvalvaag, A.H., Tollersrud, O.K. and Helgeland, L. (1988) Biochim. Biophys. Acta 937, 319-327). To study membrane association, rough microsomes were treated with increasing concentrations of saponin, sodium deoxycholate or Triton X-100. All six proteins were quantitated in the soluble and membrane fraction by enzyme immunoassays. At concentrations of saponin from 0.08% to 0.32%, each secretory protein showed a characteristic distribution, almost identical to that obtained with 0.05% sodium deoxycholate or 0.08% Triton X-100. Albumin and transferrin with half-times for secretion (t1/2) 30 and 75 min, respectively, are both almost exclusively found in the luminal fraction (greater than 95%). Prothrombin and plasminogen, which both show an intermediate t1/2 (approx. 55 min), are partially associated with the membranes, as only about 60% was released. Haptoglobin and complement C3 also show some association with the membranes (80-85% released). C3 is secreted at the same rate as prothrombin and plasminogen (t1/2 = 55 min), whereas haptoglobin is secreted more rapidly (t1/2 = 40 min). Accordingly, no correlation between kinetics of secretion and membrane association was demonstrated.

A simple and rapid method for purification of rat haptoglobin for production of antiserum

Plasma from rats with acute inflammatory response was fractionated on Blue Sepharose CL 6B, to separate haptoglobin from albumin and lipoproteins. Affinity chromatography on Blue Sepharose proved to be a convenient method for crude fractionation of plasma. Pure haptoglobin was obtained by the subsequent affinity chromatography on a rabbit-haemoglobin Sepharose column. Minor amounts of rabbit haemoglobin co-eluted from the haemoglobin Sepharose column but did not influence the monospecificity of the antiserum raised in rabbits. By use of the antiserum in single radial immunodiffusion, the concentration of haptoglobin in plasma from normal rats was measured to be 0.5 g/l.

Isotype distribution of mucosal IgG-producing cells in patients with various IgG subclass deficiencies

The subclass distribution of IgG-producing immunocytes was examined by immunohistochemistry in nasal and rectal mucosa of infection-prone patients with untreated IgG subclass deficiencies. Biopsy specimens from the two sites were obtained in 18 clinically and serologically well-characterized adult subjects; only a nasal or rectal sample was available from nine similar patients. Chronic lung disease was common in the patient groups with selective serum IgG1 deficiency and combined IgG1 and IgG3 deficiency, whereas the other categories of patients had mainly upper airway and other mild infections. Serum IgG2 or IgG3 deficiency was usually expressed also at the cellular level in rectal mucosa, and the proportion of rectal IgG1 cells was significantly correlated with the IgG1 level (r = 0.90, P less than 0.001). Likewise, there tended to be a decreased expression of the actual subclass at the cellular level in nasal mucosa of patients with serum IgG1 or IgG2 deficiency. Conversely, the median nasal proportion of IgG3 cells was remarkably unaffected by a deficiency of this subclass in serum and rectal mucosa. Interestingly, these patients rather tended to have raised IgG3 and reduced IgG2 cell proportions in their nasal mucosa, although this apparent local IgG3 compensation was nevertheless strongly correlated with the serum IgG3 level (r = 0.87, P less than 0.002). These disparities may reflect different antigenic and mitogenic exposure of the two tissue sites; for example, a persistent protein bombardment of the nasal mucosa that could conceivably override locally a B cell maturation defect. The possible clinical consequences of such variable mucosal expression of IgG subclass deficiencies remain to be studied.

Biosynthesis and clearance of prothrombin in warfarin-treated rats

The steady-state concentration of abnormal plasma prothrombin in warfarin-treated rats (10 mg/kg) was found to be approx. 6% of the plasma prothrombin level in normal rats. The clearance of abnormal plasma prothrombin in warfarin-treated rats was studied using either cycloheximide, to inhibit the synthesis, or vitamin K, to block the appearance of abnormal prothrombin in plasma. The clearance of abnormal plasma prothrombin corresponded to a half-life of approx. 6 h, which is similar to the half-life of normal plasma prothrombin. The de novo synthesis of prothrombin in warfarin-treated and normal rats was compared by measuring the incorporation of [3H]leucine into plasma prothrombin 90 min after an intravenous injection of the isotope. In warfarin-treated rats, accumulated prothrombin precursor was carboxylated and transported into circulation by injecting vitamin K 30 min after isotope administration. On comparing the incorporation of [3H]leucine into plasma prothrombin in warfarin-treated and normal rats, no significant difference in the de novo synthesis was detected. Our results suggest that the secretion of prothrombin in warfarin-treated rats is decreased to 6% of the normal rate. As the de novo synthesis is not affected by warfarin treatment, more than 90% of the newly synthesized prothrombin appears to be degraded intracellularly.

A study on the intracellular transport of prothrombin, albumin and transferrin in rat

The intracellular transport of prothrombin in rat has been studied and compared with the transport of albumin and transferrin. The proteins were immunoisolated from plasma samples after pulse labelling with [3H]leucine and the secretion kinetics were determined. The half-times for secretion (t1/2) were approx. 30, 53 and 75 min for albumin, prothrombin and transferrin, respectively, whereas the minimal transit time for prothrombin was approx. 30 min, and those for albumin and transferrin 15-20 min. After injection of vitamin K-1 into warfarin-treated rats, the accumulated prothrombin precursor was gamma-carboxylated and secreted with a t1/2 of 37 min. This indicates that the gamma-carboxylation of prothrombin in rough endoplasmic reticulum cannot account for the delay in the transport of prothrombin as compared to albumin. Comparison of the incorporation of [3H]leucine and [3H]glucosamine into plasma prothrombin and transferrin suggested that transferrin is secreted randomly from an intracellular pool, whereas prothrombin is transported in a more orderly sequence. Moreover, treatment of rough microsomes with 0.05% sodium deoxycholate indicated that prothrombin is more tightly associated with the membranes of rough endoplasmic reticulum than albumin and transferrin.

On the quantification of prothrombin from different species using Echis carinatus as activator

The generation of thrombin-like activity from rat, human, bovine and mouse prothrombin by Echis carinatus venom (ECV) treatment was compared using a partially purified system (i.e. whole ECV and isolated prothrombin). A rapid increase in coagulant activity was obtained within 0.5 to 2 min., being constant upon further incubation for 60 min. A large variation in coagulant activity of the ECV generated thrombin from the four species was found, whereas no differences were found for the amidolytic activities. The coagulant activities of the ECV generated thrombin was also low compared with the corresponding thrombin activities obtained by physiological activation. Coagulant activity of the ECV generated thrombin levelled off at increasing concentration of prothrombin in the sample as measured by the one-stage coagulation assay. By measuring amidolytic activity a linear relationship to the concentration of prothrombin was found, however. These findings indicate that ECV converts prothrombin from the four different species to a thrombin-like protein with properties distinct from alpha-thrombin. The lack of linearity in the ECV generated clot activity with increasing concentration of prothrombin could be explained by assuming a dimerization of the thrombin-like protein molecules making them less accessible to fibrinogen. The significance of these observations for the quantification of prothrombin from different species is discussed.

A human autoantibody to peroxisomes

A complement fixing, non-organ specific IgG autoantibody is described in 29 patients. The autoantibody gives a highly characteristic, granular staining of liver cells, proximal kidney tubules and stomach surface epithelium. By studies with various subcellular fractions from rat liver, employing two different techniques (quantitative complement fixation, and absorption combined with indirect immunofluorescence) the autoantibody was shown to react with a peroxisomal antigen. No convincing clinical correlations were found.

Effect of warfarin on ATP content, viability, glycosylation and protein synthesis in isolated rat hepatocytes

The effect of warfarin on ATP content, viability and incorporation of labelled glucosamine and leucine into protein was studied in suspensions of rat hepatocytes. When incubated with warfarin the synthesis of total protein and glycoprotein was equally inhibited, and the viability and ATP content of the cells were also lowered. These observations suggest that warfarin is not an inhibitor of glycosylation of proteins in isolated hepatocytes, however, the presence of warfarin leads to reduced ATP content of the cells which causes a decrease in protein synthesis and viability.

Vitamin K epoxidase activity of rough and smooth microsomes from rat liver

The distribution of vitamin K epoxidase activity in rough and smooth microsomes has been studied and compared to the prothrombin precursor and vitamin K-dependent carboxylase activity. All three activities were high in rough microsomes as compared to the low levels found in smooth microsomes. The results are in agreement with the suggestion that there might be a linkage between the vitamin K-dependent carboxylation and epoxidation reaction in vivo.

A study of intracellular transport of secretory glycoproteins in rat liver

To study the transport of secretory glycoproteins in the endoplasmic reticulum of rat liver, the distribution of nascent glycoproteins in the membrane and luminal fraction of rough and smooth microsomes has been examined after a short-time incorporation of radioactive glucosamine in vivo. 50--60% of the radioactivity was associated with the membranes of rough and smooth microsomes, whereas about 10% of the serum albumin was found in the same fractions. The relative amount of radioactivity in the membranes was the same whether the luminal content of the microsomal vesicles was released by sonication, French press, Triton X-100, Brij 35 or sodium deoxycholate. The distribution of labeled glycoproteins between the membrane and luminal fraction of rough and smooth microsomes did not change during the time interval of 15--120 min after administration of the isotope. The similarity of the labeling patterns obtained after sodium dodecyl sulfate (SDS)-polyacrylamide gel electrophoresis indicated that the same set of glycoproteins were located in the lumen and the membrane of rough and smooth microsomes. A specific precipitation of nascent glycoproteins from both the membrane and luminal fractions of rough and smooth microsomes were obtained with rabbit antiserum against rat serum. The nascent glycoproteins associated with the membranes were not released by high ionic strength or treatment with mercaptoethanol. A slow exchange between [14C]glucosamine-labeled glycoproteins in the lumen and membrane fraction was, however, found.

Studies of an inhibitor of the thrombin-fibrinogen reaction localized in rat liver microsomes. Interference with the polymerization step

A heat-stable, macromolecular inhibitor of the thrombin-fibrinogen reaction localized in rat liver microsomes has been shown to interfere with the polymerization step in the fibrinogen-fibrin conversion. The inhibitor had no effect on thrombin activity as measured with the synthetic, chromogenic substrate BZ-Phe-Val-Arg-pNA. The amount of fibrin formed and the release of fibrinopeptide A were not affected by the inhibitor. Recording of turbidity at 350 nm and 600 nm indicated an inhibition of the lateral aggregation of the end-to-end fibrin polymers. The inhibitor was localized in both the luminal and membrane fractions of the microsomes. The inhibitor activity was not affected by warfarin treatment of the rats.

On the significance of the carbohydrate moieties of bovine prothrombin for clotting activity

Purified bovine prothrombin has been treated with different mixtures of glycosidases. Upon incubation of the prothrombin for 30 h with a combination of neuraminidase, alpha- and beta-galactosidase and beta-N-acetylglucosaminidase in 4 mM diisopropylfluorophosphate at pH 5.3 and 30 degrees C, about 70% of the carbohydrates were removed without affecting the coagulation activity. All the sialic acid and about half of the mannose, galactose and glucosamine residues were removed by this treatment.

On the presence of a heat-stable, macromolecular inhibitor of the thrombin-fibrinogen reaction in rat liver microsomes and its separation from prothrombin

By concentrating sonicates from rat liver microsomes containing prothrombin, the activity as measured by the one-stage prothrombin assay (Hjort, P., Rapaport, S. J. and Owren, P. A.(1965), J. Lab. Clin. Med. 46, 89-97) gradually decreased. Nearly a complete loss of prothrombin activity was found in sonicates being concentrated 10-fold. By adsorption of prothrombin on barium citrate and dissolving the precipitate in a solution of sodium citrate. NaCl and EDTA followed by gel filtration on a Sephadex G-50 column, the inhibitory effect on the bioassay of prothrombin disappeared. An inhibitor of the thrombin-fibrinogen reaction could be isolated from the supernatant after adsorption of prothrombin on barium citrate. The inhibitor was excluded from a Sephadex G-50 column equilibrated with 4 M NaCl in veronal buffer (pH 7.4) and was heat stable (70 degrees C for 10 min). No proteolytic or antitrypsin activity could be detected in the inhibitor preparation. The importance of removing the inhibitor of the microsomal sonicates prior to any bioassay of coagulation factors based on the thrombin-fibrinogen reaction is emphasized.

Biological and immunological activity of prothrombin in rough and smooth microsomes isolated from rat liver

1. The presence of biological and immunological activity of prothrombin in sonicates from rough and smooth microsomes has been investigated. 2. Biological activity of prothrombin was detected in both the rough and smooth microsomal fraction. The specific and the total activity of prothrombin in the sonicates from smooth microsomes were 3-4-fold higher than in the corresponding fraction from rough microsomes. 3. Prothrombin could be identified in both microsomal fractions by double immunodiffusion. 4. The presence of a macromolecular inhibitor of blood coagulation in the microsomes is reported.