Cytochemical changes in hepatocytes of rats with endotoxemia or sepsis: localization of fibronectin, calcium, and enzymes

Bacterial lipopolysaccharide (LPS) is known to be implicated in the pathogenesis of endotoxemia and septic shock. The liver is the first vital organ to exhibit pathological alterations in shock. The present studies include immunoelectron microscopic localization of tissue fibronectin and cytochemical localization of calcium and enzymes in hepatocytes of animals with LPS-induced endotoxemia or cecal ligation-induced septic shock. The results showed increased staining of fibronectin in the basal (perisinusoidal) surfaces and in the cisternae of rough endoplasmic reticulum and the Golgi complex of hepatocytes in rats with endotoxemia or septic shock. Intracellular calcium content was significantly increased in the LPS-treated or septic rats. Calcium pyroantimonate precipitate was deposited predominantly on the outer surfaces of the RER of hepatocytes. In addition, diminution or depletion of glycogen, reduction of catalase-containing peroxisomes, increase of G-6-Pase activity, and depletion of cytochrome c oxidase in many mitochondria were also observed in hepatocytes of experimental animals. The overall results suggest that LPS stimulates: (a) hepatic synthesis and secretion of fibronectin; (b) uptake of calcium by hepatocytes; and (c) G-6-Pase activity. LPS treatment also leads to reduced numbers of peroxisomes and depletion of cytochrome c oxidase.     

Complex of N-phosphonacetyl-L-aspartate with aspartate carbamoyltransferase. X-ray refinement, analysis of conformational changes and catalytic and allosteric mechanisms

The allosteric enzyme aspartate carbamoyltransferase of Escherichia coli consists of six regulatory chains (R) and six catalytic chains (C) in D3 symmetry. The less active T conformation, complexed to the allosteric inhibitor CTP has been refined to 2.6 A (R-factor of 0.155). We now report refinement of the more active R conformation, complexed to the bisubstrate analog N-phosphonacetyl-L-aspartate (PALA) to 2.4 A (R-factor of 0.165, root-mean-square deviations from ideal bond distances and angles of 0.013 A and 2.2 degrees, respectively). The antiparallel beta-sheet in the revised segment 8-65 of the regulatory chain of the T conformation is confirmed in the R conformation, as is also the interchange of alanine 1 with the side-chain of asparagine 2 in the catalytic chain. The crystallographic asymmetric unit containing one-third of the molecule (C2R2) includes 925 sites for water molecules, and seven side-chains in alternative conformations. The gross conformational changes of the T to R transition are confirmed, including the elongation of the molecule along its threefold axis by 12 A, the relative reorientation of the catalytic trimers C3 by 10 degrees, and the rotation of the regulatory dimers R2 about the molecular twofold axis by 15 degrees. No changes occur in secondary structure. Essentially rigid-body transformations account for the movement of the four domains of each catalytic-regulatory unit; these include the allosteric effector domain, the equatorial (aspartate) domain, and the combination of the polar (carbamyl phosphate) and zinc domain, which moves as a rigid unit. However, interfaces change, for example the interface between the zinc domain of the R chain and the equatorial domain of the C chain, is nearly absent in the T state, but becomes extensive in the R state of the enzyme; also one catalytic-regulatory interface (C1-R4) of the T state disappears in the more active R state of the enzyme. Segments 50-55, 77-86 and 231-246 of the catalytic chain and segments 51-55, 67-72 and 150-153 of the regulatory chain show conformational changes that go beyond the rigid-body movement of their corresponding domains. The localized conformational changes in the catalytic chain all derive from the interactions of the enzyme with the inhibitor PALA; these changes may be important for the catalytic mechanism. The conformation changes in segments 67-72 and 150-153 of the regulatory chain may be important for the allosteric control of substrate binding. On the basis of the conformational differences of the T and R states of the enzyme, we present a plausible scheme for catalysis that assumes the ordered binding of substrates and the ordered release o     

Collagen autoimmunity and arthritis

Collagen-induced arthritis in animals is an example of polyarthritis that sufficiently resembles human rheumatoid arthritis to be used as a model. It is caused by immunizing susceptible animals with type II collagen isolated from articular cartilage. Susceptibility is genetically determined and linked to the major histocompatibility locus. It is important because some human arthritis is also associated with major histocompatibility genes and may be caused or aggravated by the presence of autoimmunity to normal cartilage components. Collagen-induced arthritis is also important because it is an example of immunologically mediated joint destruction, which may share some of the mechanisms present in human disease. Although it is caused by autoimmunity to collagen, susceptibility and responsiveness to type II collagen are not completely correlated, and there are examples of animals with high levels of collagen immunity who do not develop arthritis. The initial lesion appears to be the deposition of an antibody on the surface of articular cartilage, which precedes development of overt arthritis by several days. Disease can be readily transferred with specific antibody. Arthritogenic antibodies appear to have restricted epitope specificity, which may partially explain the disparities between responsiveness to immunization with collagen and susceptibility to arthritis, but precise delineation of the epitopes involved has not yet been accomplished. Complement activation also appears to be intimately involved since the disease correlates with the presence of high levels of complement-binding IgG isotypes, and passive transfer is possible only into complement-sufficient recipients. Inflammation progresses rapidly so that cartilage destruction and marginal erosion develop over a period of a few days. Collagen-induced arthritis offers a unique opportunity to study autoimmune-mediated arthritis in which the inducing antigen is well characterized and readily available. Analysis of the disease has permitted the proposal of a schema for its pathogenesis.     

The ontogeny of the vascular cambium inGinkgo biloba roots

Observation was made on early ontogeny of vascular cambium in the developing root ofGinkgo biloba L. After completion of root elongation, the vascular meristem gradually acquires cambial characteristics. Strips of the periclinal division of cells in transverse section are observed on the inner side of phloem when the primary xylem and phloem in the stele have been established. The strips are united into a continuous layer between phloem and xylem. In tangenital section, the procambium shows a homogeneous structure, which is initially composed of short cells with transverse end walls and subsequently, of long cells with tapering ends. Then, the procambium is organized into two systems of cells; axial strands of short cells with transverse end walls resulting from the sporadic transverse divisions of long cells, and long cells with tapering ends. Still later, the short cells are divided frequently in a trasverse plane exhibiting one or a few cells in width and several decades of cells in height, while the long cells are elongated. The frequency of transverse divisions of the short cells decreases in subsequent stages. Eventually, the short cells in axial strands are vertically separated from one another by the elongation of neighboring long cells and by the decrease in the frequency of transverse divisions of short cells themselves. Cambial initials occur in two forms; ray initials a few cells in height and one cell in width derived from the short cells, and fusiform initials with tapering ends derived from the long cells.     

Adenosine: a novel ulcer modulator in stomachs.

Adenosine has been demonstrated for its actions on gastric secretion and stress-induced gastric ulceration in animals. We examined the pharmacological actions of adenosine on ethanol-evoked gastric lesions and gastric mucosal blood flow (GMBF) in rats, because both of them are closely related. Adenosine pretreatment, in dose of 7.5 mg/kg increased GMBF and protected against ethanol-evoked gastric lesion formation. However, this antiulcer action was followed by an aggravation of gastric lesions and reduction in GMBF. We further investigated whether these actions could act through the adenosine A1 or A2 receptors, therefore L-phenylisopropyladenosine (L-PIA) or N-ethylcarboxamidoadenosine (NECA), the adenosine A1 or A2 receptor agonists, respectively, were used. The drugs given in doses of 10 or 50 micrograms/kg for L-PIA and 1 or 5 micrograms/kg for NECA, dose-dependently inhibited GMBF and potentiated ethanol-induced gastric damage. When the two drugs were given together to animals, they did not further aggravate the severity of ulceration and reduction of GMBF. These findings indicate that the antiulcer action of adenosine is not mediated via the adenosine A1 and A2 receptors but if acts through different adenosine receptor subtypes. It was because the lesion worsening effects of adenosine at the second stage of the biphasic responses were similar to the actions of L-PIA and NECA, the ulcer potentiating effect is probably acting through adenosine A1 and A2 receptors in anaesthetised rats.     

Metacercarial infections of Paragonimus westermani in freshwater crabs sold in markets in Seoul

Status of metacercarial infections of Paragonimus westermani was observed in freshwater crabs, which were purchased at 3 markets in its peak season of 1990. All of 85 crabs were Eriocheir japonicus. No other species of Eriocheir were found. When crushed muscle and viscera was examined individually, the infection rate was 11.8%; and mean number of metacercariae was 2.1 per infected crab. Unless adequately cooked, freshwater crabs are still potential sources of human paragonimiasis.     

A case of anisakiasis causing intestinal obstruction

A 31-year old salesman living in Seoul developed suddenly abdominal pain due to intestinal obstruction. Exploratory laparotomy exhibited segmental jejunal cellulitis caused by penetrating Anisakis larva. The patient had eaten raw fish. The typical history of intestinal anisakiasis was presented with a short review of Korean patients of anisakiasis.     

Component proteins in crude extract of adult Paragonimus westermani purified by immunoaffinity chromatography using monoclonal antibodies.

The nature of 2 component proteins in crude saline extract of adult Paragonimus westermani was investigated. By immunoaffinity chromatography using monoclonal antibodies (MAb) as ligands, the proteins were purified from the crude extract. Band 1 protein in disc-polyacrylamide gel electrophoresis (PAGE) was purified by PFCK-136 MAb. The protein, known to have molecular mass of 440 kDa, was composed of 23, 46 and 92 kDa subunits when observed by reducing SDS-PAGE and SDS-PAGE/immunoblot. This protein was originated from eggs of the worm as revealed by immunohistochemical staining with PFCK-136 Mab. Another affinity purified protein utilizing PFCK-44 MAb was the band 4 protein of 17 kDa in disc-PAGE. This was a monomer protein in reducing SDS-PAGE and SDS-PAGE/immunoblot. The protein was produced at intestinal epithelium of the worm.     

Determination of the vector species of tsutsugamushi disease in Korea

In order to determine the vector species of tsutsugamushi disease in Korea, chiggers were individually dissected, and internal contents were tested for Rickettsia tsutsugamushi organisms by means of indirect FA test, and each exoskeleton was mounted on slide for identification. Among 4,142 chiggers collected from 48 Apodemus agrarius at nine different localities during the period of July-November, 1989, 990 chiggers of 10 species of Trombiculidae were dissected and tested. Rickettsiae were confirmed in two Leptotrombidium pallidum larvae out of 447 tested, giving 0.4% of the infection rate. The chiggers of the other species tested were found negative.