The Circulatory System of Amphioxus (Branchiostoma lanceolatum (Pallas))

The morphology of the circulatory system of Amphioxus ( Branchiostoma lanceolatum (Pallas)) has been investigated using a new intravascular injection technique. A survey of the vessels of Amphioxus using this technique is given. The dorsal arteries and their ramifications are described in detail. The new injection technique brought to light myoseptal plexi, supplied from the dorsal arteries, between every two myomeres. Also the ventral parietal arteries have a much more complicated course than hitherto accepted. They are connected with an atrial plexus which is a continuous net of small vessels in the whole length of the dorso-lateral wall of the atrial cavity. It is postulated that this plexus has a supplementary function in respiration. Plexi of minute vessels in the gonads and a real blood circulation with afferent and efferent gonadal vessels have been demonstrated. Two vessels connecting the liver plexus with the cardinal vein (or the atrial plexi) have been noticed, the v. communicans accessoria anterior mentioned in 1900 by Burchardt, and a so-called oblique vessel never described before. The vessels of the caudal region are analyzed completely and also here a real blood circulation appears possible.     

The ultrastructure of the blood vessels of Branchiostoma lanceolatum (Pallas) (Cephalochordata)

Summary The ultrastructure of the blood vessels in the caudal region of Branchiostoma is described in specimens injected with indian ink. None of the vessels have endothelial cells delimiting the luminal surface. The vessels are delimited either by dense connective tissue or by the characteristic basement lamella underneath the basal lamina of the myocoelic epithelium. It is proposed that the main blood flow in the caudal region follows different pathways depending on the activity of the animal. During swimming the muscle activity of the caudal muscles may have the effect that more blood flows from the aorta to the myoseptal plexi and is drained to the caudal vessel. In the resting animal it is possible that the blood flow through the myosepta is insignificant, and that the caudal blood flow is more or less restricted to the direct connections between the aorta and the caudal vessel: the dorsoventral anastomosis and the segmental connecting vessels.Supported by a grant from the Danish Natural Science Research Council     

The ultrastructure of the blood vessels of Branchiostoma lanceolatum (Pallas) (Cephalochordata)

Summary The ultrastructure of the blood vessels of Branchiostoma has been studied using selected characteristic vessels as examples. It is shown that the vessels are a part of the original blastocoelic cavity and are delimited either by the basal laminae of adjacent epithelia or by connective tissue developed in the blastocoelic space. A brief account of the kinds of connective tissue is given. The observed contractility of some vessels depends on two types of contractile filaments situated in the basal part of the surrounding coelomic epithelia. Amoebocytelike cells are present in the blood. They may sometimes lie in contact with the wall of the vessels or with each other, but never form a typical endothelium with junctional complexes and a basal lamina of its own. Actually, there is no endothelium in any part of the vascular system. It is suggested that the term endothelium should be reserved for a closed cellular lining (with junctions) on the luminal side of the vessel wall, standing on a basal lamina of its own and forming a barrier for the exchange between blood and surrounding tissue. It is concluded that the principal structure of the vascular system of Branchiostoma is different from that of vertebrates, but the same as that of other coelomate invertebrates. The blood vessels in these animals are typically delimited directly by a basal lamina secreted by epithelia (epidermal, coelomic or intestinal) lying peripheral to this lamina, and a true endothelium is not present (with a few questionable exceptions).Abbreviations ac atrial cavity - ace atrial epithelium - ao aorta - ap atrial plexus - ax axon bundle - bc blood cell - bl basal lamina - bl ₁ basal lamina of intestinal epithelium - bl ₂ basal lamina of visceral coelomic epithelium - bl ₃ basal lamina of parietal coelomic epithelium - bl ₄ basal lamina of atrial epithelium - bll basement lamella - cf contractile filaments - co coelomic cavity - coe coelomic epithelium - coe _p parietal coelomic epithelium - coe _v visceral coelomic epithelium - ct dense connective tissue - dv longitudinal dorsal vessel - ep epidermis - epe epipharyngeal groove epithelium - epg epipharyngeal groove - fb fibroblast (?) - fi collagen fiber - fl fibril layer - go gonad - hd hemidesmosome - ie intestinal epithelium - in intestine proper - ip intestinal plexus - iv afferent intestinal vessel - ld liver diverticulum - lu vascular lumen - me myocoelic epithelium - ml muscle lamella - mp myoseptal plexus - ms myoseptum - my myomer - myc myocoelic cavity - nc notochord - ns notochordal sheath - ph pharynx - suc subchordal coelom - sv subintestinal vessel - svv segmental ventral vessel - vv longitudinal ventral vessel Supported by a grant from the Danish Natural Science Research Council     

Isolation and characterization of BanLec-I, a mannoside-binding lectin from Musa paradisiac (banana).

A lectin (BanLec-I) from banana (Musa paradisiac) with a binding specificity for oligomannosidic glycans of size classes higher than (Man)6GlcNAc was isolated and purified by affinity chromatography on a Sephadex G-75 column. It did not agglutinate untreated human or sheep erythrocytes, but it did agglutinate rabbit erythrocytes. BanLec-I stimulated T-cell proliferation. On size-exclusion chromatography, BanLec-I has a molecular mass of approx. 27 kDa, and on SDS/PAGE the molecular mass is approx. 13 kDa. The isoelectric point is 7.2-7.5. BanLec-I was found to be very effective as a probe in detecting glycoproteins, e.g. on nitrocellulose blots.     

Isolation and partial characterization of a lectin from a false brome grass (Brachypodium sylvaticum).

Purified rat renal brush-border membrane vesicles possess a heat-labile enzyme activity which hydrolyses NAD+. A reciprocal relationship exists between the disappearance of NAD+ and the appearance of adenosine; 2 mol of Pi are liberated from each mol of NAD+ incubated with brush-border membrane vesicles. Freezing and thawing brush-border membrane vesicles does not enhance the initial rate of NAD+ hydrolysis. Preincubation of brush-border membrane vesicles with NAD+ results in inhibition of Na+-dependent Pi-transport activity, whereas Na+-dependent glucose transport is not affected. EDTA, which prevents the release of Pi from NAD+ and which itself has no direct effect on brush-border membrane Pi transport, reverses the NAD+ inhibition of Na+-dependent Pi transport. These results suggest that it is the Pi liberated from NAD+ and not NAD+ itself that inhibits Na+-dependent Pi transport.     

Ultrastructural Study of the Filum Terminate and Caudal Ampulla of the Spinal Cord of Amphioxus (Branchiostoma lanceolatum Pallas)

The filum terminale and caudal ampulla of amphioxus were studied by electron microscopy. The filum terminale consists of ependymal cells whose cilia are directed caudally. Remarkably, nerve fibres course through the filum terminale and caudal ampulla and end on the basal lamina forming neuro-connective structures. Moreover, these nerve boutons are divisible into several classes according to their vesicle content. Boutons containing large dense-cored vesicles are very similar in appearance to the neurosecretory terminals found in the caudal spinal cord of some vertebrates. These observations on nerve fibres suggest that a primitive neurosecretory system similar to the fish urophysis is present in the amphioxus.     

Glycoconjugate profiles of the lancelet (Branchiostoma lanceolatum) ovary: a lectin histochemical study by laser confocal microscopy

The presence and the distribution of carbohydrate moieties in ripe lancelet (Branchiostoma lanceolatum) oocytes (mean diameter 130 microm) was studied by lectin histochemistry in combination with enzyme and chemical treatments. Binding sites for eight lectins with specificities towards different glycan moieties were studied on sections of the whole body of mature female lancelets. Only three of the lectins tested reacted positively. Concanavalin-A (ConA)-binding glycoconjugates were localized in the cytoplasm, namely in yolk granules, whereas Artocarpus integrifolia (AIA) and Ricinus communis (RCA) agglutinins bound strongly to extracellular coats of the oocyte identified as the jelly coat and vitelline layer. No other tissues of the lancelet body were found to be positive to any lectin tested, except gut enterocytes which reacted strongly with AIA. Reactivity to ConA was abolished by pretreatment of sections with N-glycosidase F but not by mild alkaline hydrolysis, confirming that the glycoconjugates were of the N-linked type. On the contrary, chemical removal of O-linked chains by mild alkaline hydrolysis abolished AIA and RCA reactivity but had no effect on ConA positivity.     

Analysis of the cDNA and gene encoding a cytoplasmic intermediate filament (IF) protein from the cephalochordate Branchiostoma lanceolatum; implications for the evolution of the IF protein family.

We report the molecular cloning of a full-length cDNA encoding a non-neuronal cytoplasmic intermediate filament (IF) protein of the cephalochordate Branchiostoma lanceolatum. Sequence and structural characteristics of IF-1 reveal a close relation to vertebrate IF proteins: they all lack the extended coil 1b version and the lamin tail homology found in protostomic IF proteins. This implies that divergence of type I to IV IF genes from a common ancestor either coincided with the origin of chordates or occurred at an earlier stage in the evolution of deuterostomes. The structural organization of the cephalochordate gene shows a closer relation to vertebrate type III genes than to type I or II genes. The single gene (approximately 19 kb) is composed of 7 exons and 6 introns which are all located within the sequence encoding the rod domain. The positions and phases of the introns show perfect homology to vertebrate type III genes. In line with the absence of protein sequence similarity of the tail domain, the Branchiostoma gene does not possess the introns interrupting this region in type III genes of vertebrates.     

The single calmodulin gene of the cephalochordate Branchiostoma

The cDNA and gene for calmodulin (CaM) from the cephalochordate Branchiostoma were isolated and characterized. The nucleotide sequence of the Branchiostoma CaM cDNA is about 80% identical to the CaM of Drosophila and Aplysia. However, all nucleotide substitutions are silent, therefore the amino acid sequences of all these CaMs are identical. Branchiostoma and Aplysia CaM genes have the same exon/intron organization. PCR, Northern and genomic Southern analyses showed that Branchiostoma CaM is encoded by a single copy gene, while fish are known to have at least four CaM genes. These results fit the hypothesis that major gene duplication events occurred close to the origin of vertebrates, i.e., after the divergence of the cephalochordate lineage.     

BfCBR: a cannabinoid receptor ortholog in the cephalochordate Branchiostoma floridae (Amphioxus)

A gene encoding an ortholog of vertebrate CB(1)/CB(2) cannabinoid receptors was recently identified in the urochordate Ciona intestinalis (CiCBR; [Elphick, M.R., Satou, Y., Satoh, N., 2003. The invertebrate ancestry of endocannabinoid signalling: an orthologue of vertebrate cannabinoid receptors in the urochordate Ciona intestinalis. Gene 302, 95-101.]). Here a cannabinoid receptor ortholog (BfCBR) has been identified in the cephalochordate Branchiostoma floridae. BfCBR is encoded by a single exon and is 410 amino acid residue protein that shares 28% sequence identity with CiCBR and 23% sequence identity with human CB(1) and human CB(2). The discovery of BfCBR and CiCBR and the absence of cannabinoid receptor orthologs in non-chordate invertebrates indicate that CB(1)/CB(2)-like cannabinoid receptors originated in an invertebrate chordate ancestor of urochordates, cephalochordates and vertebrates. Furthermore, analysis of the relationship of BfCBR and CiCBR with vertebrate CB(1) and CB(2) receptors indicates that the gene/genome duplication that gave rise to CB(1) and CB(2) receptors occurred in the vertebrate lineage. Identification of BfCBR, in addition to CiCBR, paves the way for comparative analysis of the expression and functions of these proteins in Branchiostoma and Ciona, respectively, providing an insight into the ancestral functions of cannabinoid receptors in invertebrate chordates prior to the emergence of CB(1) and CB(2) receptors in vertebrates.     

Isolation and characterization of a lectin from peanut roots.

A glucose-specific lectin has been purified to apparent homogeneity from 7-day-old peanut (Arachis hypogaea) roots by affinity chromatography on a Sephadex G-50. The lectin has a 66 kDa native molecular mass and a 33 kDa subunit molecular mass as revealed by native and denaturing sodium dodecyl sulphate-polyacrylamide gel electrophoresis, respectively. The purified lectin, gives a single precipitin line with the antiserum produced against 7-day-old root extract and shows 5 bands in the pH range of 4.4-5.4 in the isoelectric focusing gel. The glucose-specific lectin activity in the peanut roots appears from the fourth day onwards. Lipopolysaccharides isolated from the host specific Rhizobium strain are a 68-fold more potent inhibitor of the lectin as compared to glucose.     

Isolation and characterization of a lectin from Annona muricata seeds

A lectin with a high affinity for glucose/mannose was isolated from Annona muricata seeds (Annonaceae) by gel filtration chromatography on Sephacryl S-200, ion exchange chromatography on a DEAE SP-5 PW column, and molecular exclusion on a Protein Pak Glass 300 SW column. Sodium dodecyl sulfate polyacrylamide gel electrophoresis (PAGE) yielded two protein bands of approximately 14 kDa and 22 kDa. However, only one band was seen in native PAGE. The Mr of the lectin estimated by fast-performance liquid chromatography-gel filtration on Superdex 75 was 22 kDa. The lectin was a glycoprotein with 8% carbohydrate (neutral sugar) and required divalent metal cations (Ca2+, Mg2+, and Mn2+) for full activity. Amino acid analysis revealed a large content of Glx, Gly, Phe, and Lys. The lectin agglutinated dog, chicken, horse, goose, and human erythrocytes and inhibited the growth of the fungi Fusarium oxysporum, Fusarium solani, and Colletotrichum musae.     

Isolation and characterization of a lectin from the seeds of Dioclea grandiflora (Mart.)

By a combination of solubility fractionation, affinity and molecular-sieve chromatography, a lectin preparation containing several closely related lectin components of different isoelectric point was isolated from the seeds of Dioclea grandiflora Mart. The lectins showed a carbohydrate specificty for D-mannose (D-glucose)-binding and had a requirement for the presence of Ca²⁺ and Mn²⁺. The results of preliminary characterization studies showed that the D. grandiflora lectins had similar properties to those of concanavalin A, the lectin from the seeds of Canavalia ensiformis, a plant also belonging to the tribe Diocleae. Thus the D. grandiflora lectins contained no covalently bound carbohydrate and had an amino-acid composition characterized by a low content of methionine and the virtual absence of cysteine. Above pH 4.8 they had molecular weight of about 100,000, while below pH 3.1 they were dissociated to half-molecules. Between these two pH values there was a fast association-dissociation equilibrium for the two species. In dissociating solvents, three subunits were obtained of the approximate size of 25–26,000, 13–14,000 and 8–9,000. The lectins from C. grandiflora similar to concanavalin A were more distantly related to the lectins obtained from the members of the tribe Vicieae although these were also specific for D-mannose (D-glucose)-binding.