Extracellular matrix of lymphoid tissues in the chick

We describe the immunohistochemical distribution of components of the extracellular matrix of the chick lymphoid system. In the thymus, basement membranes of epithelial cells bordering the lobules were intensely stained by laminin antibodies; fibronectin antibodies labeled the capsule and the septal matrix, and similar reactivity was seen with tropoelastin and gp 115 antibodies. No positivity was detected with any of the antibodies within the cortical parenchymal cells. Laminin was not detected in the medullary parenchyma, whereas fibronectin was present as coarse fibers. Tropoelastin and gp 115 appeared as a finer and more diffuse meshwork. In the bursa, laminin antibodies outlined the epithelial cells separating the cortex from the medulla. Fibronectin, tropoelastin, and gp 115 antibody stained the interfollicular septa and the cortical matrix, although to a different extent. Laminin was also detected in association with the interfollicular epithelium (IFE) basement membrane, whereas no staining was found underneath the follicle-associated epithelium (FAE). FAE cells not only lack a proper basement membrane but are also not separated from medullary lymphocytes by any of the other extracellular matrix components were investigated. Consequently, medullary lymphocytes are not sequestered, and can come easily into contact with antigens present in the intestinal lumen. All four antibodies stained the spleen capsule and spleen blood vessels, tropoelastin and gp 115 antibodies giving the strongest reactivity. A fine trabecular staining pattern was detected with gp 115 antibodies in the white pulp.     

Increased Resistance Against Oxidative Stress Is Observed During A Short Period of Renal Reperfusion After A Temporal Ischaemia

Reperfusion of rat kidney submitted to temporal ischaemia induces a decrease in glutathione content. Lipid peroxidation is not detected in kidney homogenates but microsomes obtained after periods of reperfusion longer than 60 minutes show increased malondialdehyde values correlated with high oxygen consumption and superoxide free radical generation. Microsomes obtained from kidneys submitted to 15 or 60 minutes of reperfusion are resistant to NADPH-induced lipid peroxidation but after 120 minutes of reperfusion an increased lipid peroxidative response is observed. Although the mechanism of the protection found in microsomes against the induction of oxidative stress in the first 60 minutes of reperfusion is unknown, it is postulated that this subcellular fraction plays an important role in the oxidative stress observed after longer periods of reperfusion.     

Certain withanolides from Iochroma gesnerioides antagonize ecdysteroid action in a Drosophila melanogaster cell line

Sixteen withanolides isolated from Iochroma gesnerioides (Kunth) Miers (Solanaceae) have been assessed for their activities as ecdysteroid agonists and antagonists. None of the compounds showed any agonistic activity, but several showed significant antagonistic activity. With a 20-hydroxyecdysone concentration of 5 × 10^–8 M, the ED₅₀ values for 2,3-dihydro-3-methoxywithaferin A, 2,3-dihydro-3-methoxywithacnistine, 2,3-dihydro-3-methoxyiochromolide and 2,3-dihydro-3-hydroxywithacnistine are 3.5 × 10^-5 M, 1 × 10^–5 M, 5 × 10^–6 M and 2.5 × 10^–6 M, respectively.     

Cell death,gliosis, and synaptic remodeling in the hippocampus of epileptic rats

Seizures set in motion complex molecular and morphological changes in vulnerable structures, such as the hippocampal complex. A number of these changes are responsible for neuronal death of CA3 and hilar cells, which involves necrotic and apoptotic mechanisms. In surviving dentate granule cells seizures induce an increased expression of tubulin subunits and microtubule-associated proteins, suggesting that an overproduction of tubulin polymers would lead to a remodeling of mossy fibers (the axons of granule cells). In fact, these fibers sprout in the dentate gyrus to innervate granule cell dendrites, creating recurrent excitatory circuits. In contrast, terminal mossy fibers do not sprout in the CA3 field. Navigation of mossy fiber's growth cones may be facilitated by astrocytes, which would exert differential effects by producing and excreting cell adhesion and substrate molecules. In the light of the results discussed here, we suggest that in adult brain activated-resident astrocytes (nonproliferating, tenascin-negative, neuronal cell-adhesion molecule-positive astrocytes) could contribute to the process of axonal outgrowth and synaptogenesis in the dentate gyrus, while proliferating astrocytes, tenascin-positive, could impede any axonal rearrangement in CA3. © 1995 John Wiley & Sons, Inc.     

Neutralization sensitivity of human immunodeficiency virus type 1 is determined in part by the cell in which the virus is propagated.

Neutralizing antibody responses to human immunodeficiency virus type 1 (HIV-1) vary widely and have not been reproducibly associated with prognosis or disease progression. We have found that both low-passage clinical isolates and laboratory-adapted strains of HIV-1 have different sensitivities to neutralization by the same antiserum, depending on the host cell in which the viral stock is prepared. One such isolate (VL069) grown in H9 cells was neutralized by 20 human sera at a geometric mean titer of 1:2,047; this same isolate prepared in peripheral blood mononuclear cell (PBMC) culture was neutralized at a mean titer of < 1:10 by the same sera. Adsorption and mixing experiments indicated that neither antibody to H9 cell components nor blocking by excess viral antigen was responsible for the differences observed. This host cell effect is rapidly reversible upon passage of the virus from PBMCs to H9 cells and back into PBMCs. In contrast, the neutralization characteristics remained remarkably stable over extended culture in PBMCs. Two laboratory strains and five clinical isolates were evaluated in expanded studies of this phenomenon. While the neutralization characteristics of most of the strains studied were affected by the host cell in which the strain was propagated, two of the strains (one clinical isolate and one laboratory strain) appeared antigenically unaffected by their cell of origin. Host cell effect was also evident in neutralization by monoclonal antibodies directed against the CD4-binding region and the V2, V3, and gp41 regions. Possible mechanisms for this host cell effect include (i) mutation during passaging; (ii) selection in different host cells of different subpopulations of the (uncloned) viral stock; and (iii) cell-specific posttranslational modifications. To explore these possibilities, the V3 through V5 region of gp120 was sequenced in preparations made by passing VL069 into H9 cells and into PBMCs; HIVMN grown in CEM-SS cells and in PBMCs was also sequenced. In both cases, a few amino acid changes outside the V3 region were found. Studies are currently under way to assess the significance of these changes.     

Primary renal hemangiosarcoma in a moustached tamarin

A wild-caught adult female Saguinus mystax died after 54 months in captivity. At necropsy, a small reddish zone in the renal cortex of one kidney was shown histologically to be a hemangiosarcoma.     

Study of β-1,3-glucanase activity during autolysis of Aspergillus nidulans by FPLC ion-exchange chromatography

The behaviour of β-1,3-glucanase activity during Aspergillus nidulans autolysis was studied in a basal medium and in the same medium supplemented with 0.5 g l^-1 of microcrystalline cellulose, laminarin, pectin, seedling of Lycopersicum esculentum extract, chitin and xylan respectively. In any case β-1,3-glucanase activity was detected in the culture fluid before the onset of the autolysis, but afterwards a progressive increase of β-1,3-glucanase activity took place with incubation time. In the media supplemented with pectin and seedling of Lycopersicum esculentum extract higher activity in the first days of autolysis was found. The activity at the end of the studied process by sample was 2.5, 2.1, 2.5, 1.9, 2.2, 2.3 and 2.3 U, and the specific activity 83, 53, 85, 55, 64, 90 and 53 mU mg^-1 of protein for each medium respectively. The β-1,3-glucanase activity in Aspergillus nidulans seems to be related to autolysis and not to the presence of different substances in the culture medium. The behaviour of β-1,3-glucanase activity during the degradative process was followed by FPLC ion-exchange chromatography. Three proteins (I, II, III) with β-1,3-glucanase activity were separated and quantified. These proteins have similar behaviour in all the media. Proteins I and II increase progressively with incubation time but protein III is only present at the first and last days of autolysis.     

In vitro characterization of estrogen induced syrian hamster renal tumors: Comparison with an immortalized cell line derived from diethylstilbestrol-treated adult hamster kidney

Summary Primary diethylstilbestrol-induced kidney tumors from Syrian hamsters were grown in vitro and maintained in culture for 6 mo. Combined immunohistochemical studies using antibodies to intermediate filaments and ultrastructural studies of tumor cells in culture exhibited characteristics similar to tumor cells in vivo. Furthermore, the cells manifested transformed properties in culture; they grew both as multilayered colonies attached to the tissue culture substrate and as floating multicellular colonies (spheroids). When cultured cells were injected into diethylstilbestrol-treated recipient hamsters, tumors developed at the injection sites. In contrast, renal tubules or whole kidney cortex from control hamsters cultured in the same medium underwent only short-term growth, with senescence developing after approximately 1 mo. However, cell cultures of kidney cortex from animals treated in vivo for 5 mo. with diethylstilbestrol formed a cell line. This diethylstilbestrol-induced cell line has been maintained in culture for 1.5 yr and has the following characteristics: a) it is anchorage-dependent, b) it is negative in in vivo tumorigenicity tests, and c) cultured cells are histochemically and ultrastructurally similar to cultured tumor cells. This culture system should prove to be of use in studying hormonal carcinogenesis in vitro. This study was supported by the Medical Research Service, Department of Veterans Affairs, Washington, DC, and by grant CA-22008 from the National Cancer Institute, NIH, DHHS, Bethesda, MD.