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B Rinkevich

Publications and source records attributed to B Rinkevich.

50 records · Page 3Linked to original sources
PubMed1992

Evidence for a programmed life span in a colonial protochordate.

The variety of theories that have attempted to define the mechanisms of aging and life span can be broadly divided into two alternative but nonexclusive viewpoints. The first stipulates that random changes of cellular and molecular structures lead to death following progressive "wear and tear." The second argues that life span is, at least in part, genetically programmed, and therefore aging may also result from time-dependent intrinsic processes. Here we demonstrate that ramets (clonal replicates) experimentally separated from colonies of the acidian protochordate Botryllus schlosseri died months after their separation, almost simultaneously with their parent colony and sibling ramets. In addition, in experimentally joined chimeras between ramets of senescent and nonsenescent colonies, elements from different parent colonies displayed parent-colony-specific timing of mortality. Thus, the senescent phenotype was simultaneously expressed both in chimeras and in unfused ramets of the parent colony that was undergoing senescence, whereas control ramets from the other partner survived. These findings provide experimental evidence for a heritable basis underlying mortality in protochordates, unlinked to reproductive effort and other life history traits of this species.

Aging↗
PubMed1992

A novel galactose- and arabinose-specific lectin from the sponge Pellina semitubulosa: isolation, characterization and immunobiological properties.

A new lectin from the sponge Pellina semitubulosa is derived which was extracted and purified to homogeneity. The purified lectin is probably a hexamer of polypeptide chains (each M(r) 34,000) which are covalently linked via disulfide linkages; the isoelectric point is 6.1. The lectin displays the following specificities: D-galactose (50% inhibition of hemagglutination at 0.2 mM) = L-arabinose (0.2 mM) greater than D-fucose (1.5 mM) greater than D-glucose (3.0 mM). It precipitates human erythrocytes (A1, A2, A1B, B, and O) with a titer between 2(8) and 2(11) and erythrocytes from sheep and rabbits with a titer between 2(5) and 2(10). The Pellina lectin displays a strong mitogenic effect on spleen lymphocytes from mice. Immunochemical analyses revealed that both murine T- and B-lymphocytes display a capping of the lectin receptors on their cell surfaces after lectin treatment. Murine macrophages were found to endocytose the lectin. Pellina lectin at concentrations between 0.3 and 10.0 micrograms/ml potently enhances interleukin 1 (IL-1) release from mouse peritoneal macrophages and interleukin 2 (IL-2) production in mixed murine lymphocyte cultures.

Amino Acids↗
PubMed1992

Immunological and biological identification of tumour necrosis-like factor in sponges: endotoxin that mediates necrosis formation in xenografts.

Xenografts of the sponge Geodia cydonium in its closely related species G. rovinjensis resulted in a rapid rejection of the graft within a period of 5 days. We identified an immunoreactive tumour necrosis factor (TNF)-like activity in the xenograft (Mr of 30,000) two days after grafting. In-vivo injection of 5 micrograms human recombinant TNF-alpha induced cytotoxicity in sponge cells in the same pattern and time course as during natural xenograft rejection. Anti-TNF-alpha polyclonals were found to react with xenograft extracts, by Western blot analysis, as from day 2 after grafting. Using ELISA we detected the TNF-like activity from day 2 after grafting with peak levels at days 4 and 5, where the amount was 0.72 ng/micrograms tissue DNA. By day 1, gp27 (inhibitory aggregation factor) is already formed in the xenograft. In-vitro experiments on isolated G. cydonium cells showed that addition of purified gp27 induced the production of the TNF-like activity (up to 13.5 ng/ml). Evidence is presented that gp27 is a product of the gp180 lectin receptor. We conclude that gp27 induces TNF-like factor production, resulting in destruction and dissolution of the xenograft after 5 days.

Animals↗
PubMed1992

Invertebrate immunity: another viewpoint.

All vertebrates and invertebrates manifest self/non-self recognition. Any attempt to answer the question of adaptive significance of recognition must take into account the universality of receptor-mediated responses. These may take two forms: (1) rearranging, clonally distributed antigen-specific receptors that distinguish in the broadest sense between self and non-self, and non-self A from non-self B, latecomers on the evolutionary scene; (2) pattern recognition receptors, the earliest to evolve and still around, necessitating the requirement for induced second signals in T- and B-cell activation. Either strategy need not force upon invertebrates the organization, structure and adaptive functions of vertebrate immune systems. Thus, we can freely delve into the unique aspects of the primitive immune mechanisms of invertebrates. In contrast, using the opposite strategy which is still problematic, i.e. linking invertebrate and vertebrate defence, seems to give us an approach to universality that might eventually reveal homologous kinship.

Animals↗
PubMed1991

Interpopulational allogeneic reactions in the colonial protochordate Botryllus schlosseri.

Botryllus schlosseri is a cosmopolitan encrusting colonial tunicate which undergoes a natural transplantation reaction. When the growing edges of two colonies come into direct contact by interaction between their extracorporeal blood vessel termini, the ampullae, they either reject each other or fuse. This phenomenon is controlled by a single gene locus (Fu/HC) with multiple codominantly expressed alleles. Rejecting colonies share no alleles. Here we analyze allogeneic responses of Monterey (Mon), California, versus Woods Hole (WH), Massachusetts, colonies. Of 42 Mon x WH pairs tested, allogeneic rejection reactions occurred in all. Necrotic lesions (points of rejection, PORs) were produced and developed only by Woods Hole ampullae, either within the Woods Hole tunic, in the borderline between the paired colonies, or within the Monterey tunic. Four types of PORs were characterized. All types involved reactions of blood cells and vessels, including infiltration, hemorrhage formation, retraction and ampullae amputation. These findings were observed in single WH x Mon pairs, in multiple subclones of WH x Mon from two parental colonies (seven independent colony pairs were assayed), and on multiple repeats of interactions from pairs that had already undergone a rejection reaction. In all cases, the range of reaction types, the location of PORs, and the timing of the responses could be found in primary as well as repeat reactions.

Animals↗
PubMed1990

Failure to find alloimmune memory in the resorption phenomenon of Botryllus cytomictical chimera.

It has been previously shown that mixed-cell chimeras may be established between different colonies of the compound tunicate Botryllus schlosseri given that they share one allele in common on the fusibility locus. However, one of the partners in each chimera is often resorbed. Here we tested for the existence of a memory component to this response, as measured by the accelerated interval to resorption of a second set of semiallogeneic colonies. Eight genetically unrelated colonies gave rise to eighteen chimeras. After a complete resorption of the "inferior" partners in these chimeras, secondary and tertiary sets of chimeras were established with some of them by fusion of the "superior" with naive subclones of the "inferior" partners. It is shown here that (a) when multiple chimeras are prepared using the same pair of colonies, subclones of only one of the partners are resorbed; (b) high variation in the time for resorption is recorded when several chimeras are prepared from any specific pair of colonies, and (c) the time for resorption is not related to the number of vessels connecting between the partners in the chimera, nor to their relative body sizes. Allospecific memory is not documented here and reasons for its absence are discussed.

Animals↗
PubMed1990

Botryllus schlosseri (Tunicata) whole colony irradiation: do senescent zooid resorption and immunological resorption involve similar recognition events?

The colonial tunicate Botryllus schlosseri undergoes cyclic blastogenesis where feeding zooids are senescened and resorbed and a new generation of zooids takes over the colony. When non-identical colonies come into direct contact, they either reject each other or fuse. Fusion is usually followed by the resorption of one of the partners in the chimera (immunological resorption). The striking morphological similarities between the two resorption phenomena suggest that both may involve tissue destruction following self-nonself recognition events. Here we attempt to modify these two events by whole colony gamma irradiation assays. Three sets of experiments were performed: 1) different doses of whole colony irradiation for determination of irradiation effects (110 colonies, up to 8,000 rads); 2) pairs of irradiated-nonirradiated isografts of clonal replicates for the potential of reconstruction of the irradiated partners (23 pairs); 3) chimeras of irradiated-nonirradiated partners for analysis of resorption hierarchy. Mortality increased with the irradiation dose. All colonies exposed to more than 5,000 rads died within 19 days, while no colony died below 2,000 rads. The average mortality periods, in days, for doses of 6,000-8,000, 5,000, and 2,500-4,000 rads were 14.4 +/- 3.1 (n = 24), 19.8 +/- 6.0 (n = 15), and 19.6 + 5.1 (n = 22), respectively. Younger colonies (3-6 months old) may survive radiation better than older ones (more than 13 months). Many morphological alterations were recorded in irradiated colonies: ampullar contraction and/or dilation, accumulation of pigment cells within ampullae, abnormal bleeding from blood vessels, sluggish blood circulation, necrotic zones, reduction in bud number, and irregularities in zooid and system structures. With doses of 3,000-4,000 rads and above, irradiation arrested the formation of new buds and interrupted normal takeover, turning the colony into a chaotic bulk of vessels, buds, and zooid segments. Death supervened after a period of up to 1 month of poor condition, which was also characterized by loss of organization in systems. In isografts of irradiated-nonirradiated parts, the normal subclone resorbed all zooids and buds of the irradiated one within less than 1 week, even if it was up to 13 times smaller, without showing any sign of harmful effects. Thus, the irradiated subclone is not reconstituted by sharing blood circulation with a syngeneic part. Under 2,000 rads some of the irradiated zooids within this type of union started to regenerate, and at 1,000 rads no resorption was recorded, even though the number of zooids decreased in the irradiated part.(ABSTRACT TRUNCATED AT 400 WORDS)

Animals↗
PubMed1990

Allorecognition histocompatibility in a protochordate species: is the relationship to MHC somatic or structural?

Colonial tunicates are complex marine invertebrates (in fact protochordates) that undergo a variety of histocompatibility reactions in their intraspecific competition for feeding surfaces. By means of these reactions colonies fuse with kin, extend domination over a feeding surface, while isolating unrelated conspecifics. The primary determinant of fusion (with kin) or rejection (of non-kin) is a single, highly polymorphic, histocompatibility gene locus (or haplotype), called Fu/HC. Following fusion with nonidentical kin sharing 1 or more Fu/HC allele(s), the fused pair expands both chimeric partners via an asexual budding process, further extending domination over a feeding surface. However, at some later time point an intense set of histoincompatibility reactions occurs between fused kin, resulting in the destruction of all individuals of one of the genotypes, ending the chimeric state. In this review we describe what is known of the genetics and several biological properties encoded by the Fu/HC, and the several independent gene loci that control the colony resorption phenomena that return the colony to the province of a single genotypic individual.

Animals↗
PubMed1986

Does germanium interact with radular morphogenesis and biomineralization in the limpet Lottia gigantea?

Specimens of Lottia gigantea were incubated in germanium enriched seawater [( Ge]/[Si] = 0.2-783) for 1-8 days. The siliceous radulae were examined histologically. No visible changes, degenerations or deformations were found in all 62 experimental radulae, although germanium is known to be a competitive inhibitor of silicon. In high concentrations, germanium was toxic to the limpets and killed them. Germanium was incorporated into the radular teeth in a distribution similar to silicon. Two suggestions are discussed for the apparent noninhibitory result.

Animals↗
PubMedDate not supplied

Allogeneic resorption in colonial protochordates: consequences of nonself recognition.

Colonial tunicates (protochordates of the subfamily Botryllinae) have the property of forming natural chimeras in the wild or in the laboratory with other members of the same species if both individuals share at least one allele at a single highly polymorphic locus, termed the fusibility/histocompatibility (Fu/HC) locus. Laboratory studies revealed that after the establishment of a common blood circulatory system between a fusible pair one of the colonies in the chimera is usually resorbed, a phenomenon that occurs after an interval of 1 week or extends to up to 8 months. In the present article, we review this allogeneic resorption in Botryllus schlosseri, a cosmopolitan protochordate. The studies on allogeneic resorption in B. schlosseri revealed 13 typical characteristics. However, several processes interrupt successful resorption, such as the retreat growth phenomenon, chimeric death, and others. It was also found that allogeneic resorption is not only genetically controlled but is also controlled by a polymorphic hierarchial phenomenon, including the Fu/HC locus and additional unrelated loci. One basic rule for this genetic system is that colonies heterozygotic on the resorption elements will resorb more homozygotic partners. This colony resorption, expressed by a morphological elimination of one partner, is probably manifested by cellular elements circulating in the tunicate blood system. However, it was also shown that some blood-borne cells of the inferior partner, such as the stem cells, may escape resorption, a phenomenon that raises the threat of germ/somatic cell parasitism.

Alleles↗
PubMedDate not supplied

Characteristics of allogeneic resorption in Botrylloides from the Mediterranean coast of Israel.

Some of the characteristics of allogeneic resorption have been revealed in studies of chimeras of two Botrylloides subpopulations (SP1 and SP3) inhabiting the Mediterranean coast of Israel. Both Botrylloides SPs exhibited the same outcomes, which differ significantly from the resorption documented in the well-studied botryllid ascidian, Botryllus schlosseri: 1. Resorption in Botrylloides chimeras was usually a very fast process starting 1 to 26 days after fusion and terminating in < 9 days thereafter. 2. Resorption occurs at any blastogenic stage. 3. Resorption is complete, including zooids, buds, blood vessels and ampullae. 4. Either one of the genotypes can be resorbed in multipair chimeras of any specific combination. 5. Resorption starts simultaneously in all zooids of the partner to be resorbed. 6. Time for resorption and directionality were not affected by the size ratios between the partners (0.3-1.8). As in B. schlosseri, other phenomena (disconnection, chimeric death and retreat growth) interrupt resorption in ca. 60% of the chimeras, under laboratory conditions. We propose that external stress conditions also have a significant role in a nonimmunological expression of resorption in Botrylloides.

Animals↗
PubMedDate not supplied

Evolution of cell adhesion systems: evidence for Arg-Gly-Asp-mediated adhesion in the protozoan Neoparamoeba aestuarina.

Developmental processes in multicellular organisms require structural elements, such as adhesion molecules, to stabilize cells at functional positions. In vertebrates, a series of extracellular matrix proteins, e.g. fibronectin and laminin, are involved in cell adhesion. These proteins contain Arg-Gly-Asp [RGD] at their binding sites. Here we show that at concentrations above 2 mM the peptide GRGDSPK, comprising the tripeptide RGD (Arg-Gly-Asp), prevents the adhesiveness of cells of the marine amoeba Neoparamoeba aestuarina. In addition, elevated levels of GRGDSPK cause cells to alter their shapes from those with digitiform subpseudopodia to rounded cells with small lobed pseudopodia. These cells detach from the substratum. These results are specific for the RGD sequence, because incubation in GRGESPK solution at the same concentrations had no effect on cell attachment or structure. From these data we suggest that the structural adhesion molecules identified in vertebrates show amino acid homologies with those found in unicellular protozoa.

Amino Acid Sequence↗
PubMedDate not supplied

Molecular cloning of a tyrosine kinase gene from the marine sponge Geodia cydonium: a new member belonging to the receptor tyrosine kinase class II family.

We have isolated and characterized a cDNA from the marine sponge Geodia cydonium coding for a new member of the tyrosine protein kinase (TK) family. The cDNA encodes a protein of M(r) = 68,710, termed GCTK, which is homologous to class II receptor tyrosine kinases (RTKs). GCTK contains conserved amino acids (aa) characteristic of all protein kinases, and the sequences DLATRN and PIRWMATE which are highly specific for TKs. Furthermore, the sequence N-L-Y-x(3)-Y-Y-R is highly homologous to the sequence D-[LIV]-Y-x(3)-Y-Y-R found only in class II RTKs. The sponge TK, when compared with mammalian class II RTKs, shows maximum 31% homology in the TK domain indicating that this the oldest member of class II RTK started to diverge from the common ancestral protein kinase approximately 650 million years ago. Using GCTK as a probe we identified three mRNA signals ranging from 2.6 to 0.6 kb. Kinase activity was localized only in the cell membranes from G. cydonium (M(r) = 65,000), and was not detected in the cytosol of this organism. Antibodies raised against a synthetic peptide, corresponding to the aa residues within the catalytic domain of the sponge TK, recognized strongly two proteins of M(r) = 65,000; these proteins, present in membrane fractions, also bound to the antiphosphotyrosine antibody. These data suggest that the TK cloned from the sponge is a membrane-associated 65 kDa protein. Moreover these results demonstrate that RTKs are present from the lowest group of multicellular eukaryotes, sponges, to mammals, and may suggest that RTKs are involved in a signal transduction pathway.

Amino Acid Sequence↗