Cleavage and gastrulation in the shrimp Sicyonia ingentis: invagination is accompanied by oriented cell division.

Embryos of the penaeoidean shrimp Sicyonia ingentis were examined at intervals during cleavage and gastrulation using antibodies to beta-tubulin and DNA and laser scanning confocal microscopy. Cleavage occurred in a regular pattern within four domains corresponding to the 4-cell-stage blastomeres and resulted in two interlocking bands of cells, each with similar spindle orientations, around a central blastocoel. Right-left asymmetry was evident at the 32-cell-stage, and mirror-image embryos occurred in a 50:50 ratio. Gastrulation was initiated by invagination into the blastocoel at the 62-cell-stage of two mesendoderm cells, which arrested at the 32-cell-stage. Further invagination and expansion of the archenteron during gastrulation was accompanied by rapid and oriented cell division. The archenteron was composed of presumptive naupliar mesoderm and the blastopore was located at the site of the future anus of the nauplius larva. In order to trace cell lineages and determine axial relationships, single 2- and 4-cell-stage blastomeres were microinjected with rhodamine-dextran. The results showed that the mesendoderm cells which initiated gastrulation were derived from the vegetal 2-cell-stage blastomere, which could be distinguished by its slightly larger size and the location of the polar bodies. The mesendoderm cells descended from a single vegetal blastomere of the 4-cell-stage. This investigation provides the first evidence for oriented cell division during gastrulation in a simple invertebrate system. Oriented cell division has previously been discounted as a potential morphogenetic force, and may be a common mechanism of invagination in embryos that begin gastrulation with a relatively small number of cells.     

Adhesion-mediating molecules of human monocytes

Adhesion of monocytes to each other and to T cells and substrates is increased by phorbol esters. In the presence of these compounds monocyte aggregation was almost completely inhibited (greater than 90%) by monoclonal antibody 60.3. This antibody recognizes GP90 (CD18), a leukocyte surface glycoprotein which is separately and noncovalently associated to either GP160 (CD11a), GP155 (CD11b), or GP130 (CD11c). Anti-LFA-1 antibody (CD11a) was only partially inhibitory (35%) while antibodies 60.1 (CD11b) and anti-Leu-M5 (CD11c) had a minimal inhibitory effect (10%). Antibody LB-2 recognizing a single glycoprotein distinct from the GP90-GP160 complex and expressed on activated B and T cells, monocytes, and vascular endothelial cells was partially inhibitory (22%). Monoclonal antibodies anti-C3bR (CD35), T29/33 (CD45, leukocyte common antigen 200). TA-1 (CD11a), OKM1 (CD11b), F10-44-2 (brain-leukocyte antigen), OKM5 (monocyte-endothelial cell antigen) and to class I or class II molecules exerted no inhibition on the monocyte aggregation. Fab fragments of antibody 60.3 efficiently inhibited not only monocyte aggregation in the absence or presence of phorbol esters but also adhesion of these cells to autologous or allogeneic T lymphocytes and, to a lesser extent, to plastic surfaces. It is thus concluded that GP90, either alone or associated to the larger glycoproteins, and LB-2 antigen mediate monocyte adhesion.     

Cryptic chemotactic activity of fibronectin for human monocytes resides in the 120-kDa fibroblastic cell-binding fragment

Monocytes and lymphocytes form a second wave of infiltrating blood leukocytes in areas of tissue injury. The mechanisms for monocyte accumulation at these sites are not completely understood. Recently, however, fragments from extracellular matrix proteins including collagen, elastin, and fibronectin have been shown to induce monocyte chemotaxis. In this report we demonstrate that chemotactic activity for human monocytes is expressed when a 120-kDa fragment containing the RGDS cell-binding peptide is released from intact fibronectin or from larger fibronectin fragments. Monocytes, either from mononuclear cell Ficoll-Hypaque preparations (10-20% monocytes, 89-90% lymphocytes) or from elutriation preparations (95% monocytes, 5% lymphocytes), but not lymphocytes, migrated toward 120-kDa fragment preparations (10(-7) M) in blind-end chambers when the cells were separated from the chemoattractant by a 5-micron pore polycarbonate filter either alone or overlying a 0.45-micron pore nitrocellulose filter. Neutrophils migrated toward zymosan-activated serum but not toward 10(-5)-10(-8) M concentrations of the 120-kDa fragment. Intact fibronectin had no chemotactic activity for human monocytes. Fibronectin was isolated from citrated human plasma by sequential gelatin-Sepharose affinity and DEAE ion-exchange chromatography in the presence of buffers containing 1 mM phenylmethylsulfonyl fluoride to prevent fragmentation. Controlled enzymatic digestion with thermolysin cleaved fibronectin into 30 kDa fibrin, 45 kDa collagen, and 150/160-kDa cell and heparin domains. Upon prolonged digestion, purified 150/160-kDa fragments were cleaved into 120-kDa cell and 30/40-kDa heparin-binding fragments. Even though the intact fibronectin molecule, the 150/160-kDa fragments, and the 120-kDa fragment, have cell binding activity for Chinese hamster ovary fibroblasts, only the 120-kDa fragment expressed chemotactic activity for human monocytes. Thus, the 120-kDa fibroblastic cell-binding fragment contains a cryptic site for monocyte chemotaxis which is expressed upon enzymatic cleavage of fibronectin.     

Structural and conformational features that affect the interaction of polylactosaminoglycans with immobilized wheat germ agglutinin

We examined the interaction between immobilized wheat germ agglutinin and the large, polylactosamine-containing glycans from human erythrocytes and human K-562 erythroleukemic cells. Three classes of interaction were identified. One class of glycan was merely retarded during chromatography. The other two classes were retained and could be distinguished by their ease of displacement with N-acetylglucosamine (GlcNAc); one was a moderate-affinity fraction displaced by 0.1 M GlcNAc and the other was a high-affinity fraction subsequently displaced by 1.0 M GlcNAc. A relatively small fraction of the K-562 polylactosamines were in the high-affinity class. We explored the role that fucose and sialic acid substitutions play in the strength of the lectin-glycan interaction. Although sialic acid is recognized by wheat germ agglutinin, sialylation was not required for the high-affinity interaction, and the presence of sialic acids actually prevented some glycans from binding with high affinity. In contrast, fucose is not part of the binding determinant, yet the removal of fucose resulted in decreased affinity. The possibility that some of these changes in affinity were the result of conformational changes was explored using matrices that had wheat germ agglutinin immobilized at different densities. At low wheat germ agglutinin densities, adult and fetal erythroglycans and K-562 glycophorin-like glycans were not retained by the matrix. As the density increased, the proportion of glycans that were retarded, and ultimately retained, increased. While these increases in the proportions retained occurred in parallel for the three different glycans, the apparent affinities of the glycan-lectin interactions differed. The glycophorin-like glycans were always readily displaced by 0.1 M GlcNAc, even at higher wheat germ agglutinin densities. In contrast, as the wheat germ agglutinin density increased, the proportion of erythroglycans that could be displaced by 0.1 M GlcNAc decreased; at 10 mg/ml immobilized wheat germ agglutinin, greater than 80% of the erythroglycans exhibited this tighter interaction. We suggest that this higher affinity interaction is the result of the large glycans spanning adjacent wheat germ agglutinin molecules, and is determined by the proximity of these molecules and the conformation of the glycans.     

Characterization of the cellular basis for the inhibition of cytolytic effector cells by murine placenta

Direct suppression of cytolytic effector cell function by cells of the placenta may represent one mechanism that protects the "fetal allograft" from rejection by maternal transplantation immunity. Collagenase disaggregated murine placental cells block target cell lysis by natural killer, lymphokine-activated killer, and (CTL)-type killer cells. This inhibition is reversible and noncompetitive, similar to a previously described inhibitor of CTL found in spleens of mice undergoing an acute graft vs host (GVH) response. Velocity sedimentation separation of placental cells shows that the inhibitory activity is primarily associated with cells that cosediment with nucleated fetal erythrocytes. When these erythrocytes were lysed, an increased number of non-erythrocytic cells could be separated and under this circumstance, inhibitory activity was seen in association with either small white cells or fetal erythrocytes and with large white cells. There may be several cell populations in murine placenta that can inhibit cytolytic effector cells. The possible relevance of direct placental inhibition of cytolytic effectors to protection of the "fetal allograft" is discussed.     

Influence of Meloidogyne incognita on Resistant and Susceptible Sweet Potato Cultivars

Effects of several population densities ofMeloidogyne incognita on the sweet potato cultivars Centennial (susceptible) and Jasper (moderately resistant) were studied. Field plots were infested with initial levels (Pi) of 0, 10, 100, 1,000, 5,000, and 10,000 eggs and juveniles/500 cm³ soil in 1980 and 0, 100, 1,000, 2,000, 3,000, 4,000, and 5,000 in 1981. M. incognita population development trends were similar on both cultivars; however, at high Pi, more eggs and juveniles were recovered from Centennial than from Jasper. The highest Pi did not result in the highest mid-season (Pm) counts. Pi was negatively correlated with the number of marketable roots and root weight but positively correlated with total cracked roots, percentage of cracked roots, and cracking severity. Jasper tolerated higher Pi with greater yields and better root quality than Centennial. Cracking of fleshy roots occurred with both cultivars at low Pi.     

Selectivity of the insulin-like actions of vanadate on glucose and protein metabolism in skeletal muscle.

The 1H-n.m.r. spectrum of casein micelles consists of a small number of moderately sharp (linewidth approx. 60 Hz) resonances superimposed on the envelope of very broad lines expected for particles of this size. These sharp lines resemble, in chemical shift and relative intensity, the spectrum of the isolated 'macropeptide' released from the micelles by treatment with chymosin. The sharp lines in the casein micelle spectrum are further sharpened by addition of chymosin and broadened markedly by addition of ethanol. These observations are consistent with the proposal that the 'macropeptide' (the C-terminal 64 residues of K-casein) forms flexible 'hairs' on the surface of the micelles.     

Effects of dietary cobalt on testicular structure

Adult male rats were maintained on a diet containing 265 ppm cobalt for up to 98 days. Three rats were sacrificed weekly and assayed for testicular damage by light and electron microscopy. Testicular damage was first apparent after 70 days of treatment, followed by a progressive deterioration of cell architecture and decrease in testicular volume. The degenerative changes were of a very general nature; e.g., thickening of basal lamina and basement membranes, increased packing of red blood cells in veins and arteries, formation of "giant" cells, loss of sperm tail filaments, and degeneration of sperm mitochondria. No cobalt residues could be detected by energy dispersive x-ray microanalysis. These data indicate that testicular degeneration was not a primary response to cobalt and suggest that the testes become hypoxic due both to blockage of veins and arteries by red blood cells and to changes in permeability caused by thickening of basal lamina and basement membranes.