A maternal-effect mutation disturbs extracellular matrix organization in the early Pleurodeles waltl embryo

Summary In the early development of the urodele amphibian Pleurodeles waltl, a fibronectin-containing extracellular matrix underlies the inner face of the blastocoel roof. When gastrulation occurs, the fibronectin fibrils provide a suitable substrate for mesodermal-cell migration. Delay in morphogenetic movements of gastrulation has been described in embryos from mutant females (ac/ac) of Pleurodeles waltl. Studies of abnormal mutant gastrulae with fluorescent lectins and immunostaining for fibronectin reveal that they lack a normal matrix. The fibronectin-containing extracellular material always gives rise to a granular pattern without fibronectin-fibril formation. Fibronectin and ₅₁ syntheses occur normally in maternal-effect embryos. In vitro, mesodermal cells from early mutant gastrulae adhere and migrate on fibronectin-conditioned substrata.     

The chicken IL-1 receptor: differential evolution of the cytoplasmic and extracellular domains.

The evolutionary conservation of a sequence or part of it can help to identify the essential functional and structural domains within a protein. We have cloned and characterised a cDNA coding for the type-I interleukin-1 receptor (IL-1R) of chick (ch) embryo fibroblasts. The comparison of the amino acid (aa) sequences of the avian with that of murine (m) and human (h) IL-1Rs shows a 60% homology. The intracellular domain is the most conserved region of the chIL-1R, showing 76-79% homology to the murine and human sequences, respectively. The striking conservation of the cytoplasmic region of the receptor is confirmed by its homology with the Toll receptor protein of Drosophila melanogaster. The alignment between the chicken and D. melanogaster proteins shows the presence of four aa blocks with more than 80% homology. The possible functional significance of this homology is discussed. The extracellular binding region of the receptor has a clearly recognisable immunoglobulin-like structure although the sequence divergence is higher than in the cytoplasmic domain.     

Presence and turnover of adenosine diphosphate ribose in human erythrocytes.

ADP-ribose was detected in human red blood cells (RBC) at 0.45 +/- 0.1 microM concentrations. These levels could be estimated after purification of ADP-ribose by means of three sequential HPLC fractionations of RBC extracts. Extraction was performed by sonication of RBC either in trichloroacetic acid, followed by centrifugation, or in carbonate-bicarbonate buffer, pH 10.0, followed by rapid ultrafiltration. Neither procedure of extraction caused artefactual formation of ADP-ribose. Prolonged incubation of intact RBC in isotonic buffer containing labeled orthophosphate resulted in the slow incorporation of radioactivity into ADP-ribose. Identification of the labeled ADP-ribose was confirmed upon incubation of the purified metabolite with nucleotide pyrophosphatase, yielding radioactive 5'-AMP and ribose 5-phosphate, while its exposure to a nonspecific deaminase resulted in the quantitative formation of labeled inosine diphosphate ribose.     

Sponge predation in the oyster reef community as demonstrated with Cliona celata Grant

Predation by various invertebrates on the burrowing sponge, Cliona celata Grant, was investigated both in the laboratory and field, in order to determine the importance of predation to a sponge population and the adaptive advantage of burrowing to escape predators. Thirty-one species of molluscs, crustaceans, polychaetes, and echinoderms commonly found on oyster beds in Beaufort, North Carolina were tested for their ability to prey on C. celata. Gastropods Diodora cayenensis Lamarck, Seila adamsi, H. C. Lea and Doriopsilla pharpa Marcus, isopod Cilicaea caudata (Say), decapods Alpheus heterochaelis Say, Panopeus herbsti Milne Edwards, Neopancpe sayi (Smith) Eurypanopeus depressus (Smith), Menippe mercenaria (Say) and Pilutnnus sayi Rathbun, and echinoids Arbacia punctulata (Lamarck) and Lytechinus variegatus (Lamarck) were all found to ingest sponge. Diodora, Seila, Doriopsilla, Cilicaea, Alpheus and Arbacia frequently eat sponges in nature. All sponge predators were able to obtain sponge ventilation papillae, which extend beyond the surface of the shell housing the sponge. Papillae lost to predation were regenerated within 12 days in Cliona celata; little regeneration was noted in predator-damaged Haliclona permollis (Bowerbank), a nonburrowing sponge. Only Arbacia was able to breach sponge galleries in the shell and destroy Cliona celata 2 to 3 times faster than growth could replace lost sponge tissue. The paucity of subtidal shelly bottom sponge fauna and cryptic or high intertidal habits of oyster bed sponges in Beaufort Harbor suggest at least partial control of populations of several common sponges by predators.     

Evolution of the relaxin-like peptide family

Background  

The relaxin-like peptide family belongs in the insulin superfamily and consists of 7 peptides of high structural but low sequence similarity; relaxin-1, 2 and 3, and the insulin-like (INSL) peptides, INSL3, INSL4, INSL5 and INSL6. The functions of relaxin-3, INSL4, INSL5, INSL6 remain uncharacterised. The evolution of this family has been contentious; high sequence variability is seen between closely related species, while distantly related species show high similarity; an invertebrate relaxin sequence has been reported, while a relaxin gene has not been found in the avian and ruminant lineages.     

Differential levels of "urotensin-II-like" activity determined by radio-receptor and radioimmuno-assays

Plasma and urinary levels of "urotensin(U)-II-like" substances determined in healthy human volunteers were 12.4 +/- 0.6 ng/ml and 2.2 +/- 0.3 ng/ml by RIA, an order of magnitude lower than that seen by RRA, 167.5 +/- 9.5 ng/ml and 65.2 +/- 4.3 ng/ml. HPLC demonstrated the existence of at least three prominent activity peaks in plasma and urine, the more hydrophobic of which did not co-elute with U-II, degradation products or URP. RRA and RIA recognized these peaks with contrasting efficacy. As such, published levels of "U-II-like" activity should be interpreted with caution until a better understanding is obtained regarding what species specific RIA and RRA assay reagents interact with.     

Mutational spectrum in the neurofibromatosis type 2 gene in sporadic and familial schwannomas

Using a heteroduplex approach and direct sequencing, we have completed the screening of approximately 88% of the neurofibromatosis type 2 (NF2)-coding sequence of DNA extracted from 33 schwannomas from NF2 patients and from 29 patients with sporadic schwannomas. The extensive screening has resulted in the identification of 33 unique mutations. Similarly to other human genes, we have shown that the CpG sites are more highly mutable in the NF2 gene. The frequency, distribution, and types of mutations were shown to differ between the sporadic and familial tumors. The majority of the mutations resulted in protein truncation and were consistent with more severe phenotype, however three missense mutations were identified during this study and were all associated with milder manifestations of the disease. Received: 25 September 1995 / Revised: 19 December 1995