The Question of a Vomer in Brachiopterygian Fish

Abstract The term vomer was coined over four centuries ago to denote one of the 23 bones normally comprising an adult human skull. As time went on more and more craniates were designated vomerate. To date, however, the issue as to whether brachiopterygian fish are or are not vomerate has remained unresolved. Those who consider these fish to be vomerate have suggested at least three different palatal bones as the homologue of the human vomer. Examination of embryological material of Polypterus senegalus shows that this brachiopterygian actually develops a vomer which eventually becomes united indistinguishably with the anterior part of the parasphenoid. The vomer is suggested to have arisen through the fusion of dental plates belonging to a supplementary set of buccopharyngeal denticulate bones. The other subethmoidal bones of the brachiopterygian palate seem likely to be derivatives of the tooth plates which originally were applied to the first two pairs of infrapharyngeals. When these endoskeletal elements were put to use for encapsulation of the organs of smell early in craniate phylogeny, some of the tooth plates that covered their inner surfaces fused to provide anterior palatal bones. Identified at one time or another as vomers, these bones are here termed glochinals and dacnils.     

Further characterization of cytochrome P450 involved in phytoalexin synthesis in soybean: cytochrome P450 cinnamate 4-hydroxylase and 3,9-dihydroxypterocarpan 6a-hydroxylase.

Two cytochrome P450 enzymes, cinnamate 4-hydroxylase (C4H) and 3,9-dihydroxypterocarpan 6a-hydroxylase (D6aH), were isolated from elicitor-challenged soybean (Glycine max) cell cultures (G. Kochs and H. Grisebach, 1989, Arch. Biochem. Biophys. 273, 543-553). An earlier purification protocol was improved by the use of new chromatographic media, leading to a higher yield of enzymatic activity. After separation of C4H from D6aH on hydroxyapatite, the C4H was identified using anti-C4H antibody from Jerusalem artichoke (Helianthus tuberosus) (B. Gabriac et al., 1991, Arch. Biochem. Biophys. 288, 302-309). The two proteins show molecular weights of about 58,000 for C4H and about 55,000 for D6aH on sodium dodecyl sulfate-polyacrylamide gel electrophoresis. Both enzyme activities are dependent on NADPH:cytochrome P450 reductase and cross-react with their respective antibodies. Both cytochrome P450 subspecies show substrate binding and CO-difference spectra typical for cytochrome P450 and were found to be glycoproteins by their cross-reaction with biotinylated lectins in Western blot. The N-terminal sequence of C4H from soybean shows high similarity to the N-terminus of C4H from Jerusalem artichoke.     

Plant regeneration from protoplasts of the monocotyledonous Haworthia magnifica v. Poelln.

Calli were initiated from flower buds, gynoecia and inflorescence segments of Haworthia magnifica v. Poelln. and subcultured on solid medium. Two liquid culture steps were necessary to prepare the calli for the isolation of protoplasts capable of sustained cell divisions. Plants were regenerated from protoplast-derived calli. The influence of both the osmolality of the culture media and exudates on the viability of protoplasts and protoplast-derived cell colonies is briefly discussed.     

N-Terminal Sequence of Pig Brain Choline Acetyltransferase Purified by a Rapid Procedure

A procedure is reported that allows the purification and amino terminal sequencing of pig brain choline acetyltransferase. The enzyme (present in extremely low amounts in this tissue) is eluted together with its antibody from an affinity column by a mild pH shift and the resulting enzyme-antibody complex separated by gel electrophoresis. The band corresponding to the enzyme is electroeluted from the gel using volatile solutions allowing the direct determination of the amino acid composition and partial sequence. The first 11 residues are: Pro-Ile-Leu-Glu-Lys-Thr-Pro-Pro-Lys-Met-Ala.     

Phytoalexin synthesis in soybean cells: elicitor induction of reductase involved in biosynthesis of 6'-deoxychalcone

Chromatofocusing on Mono P proved to be an efficient purification procedure for the NADPH-dependent reductase from soybean (Glycine max L.) cell cultures which acts together with chalcone synthase in the biosynthesis of 2',4',4-trihydroxychalcone (6'-deoxychalcone). By isoelectric focusing the pI of reductase was determined to be 6.3. Addition of pure soybean reductase to cell-free extracts from stimulated cell cultures of parsley and bean (Phaseolus vulgaris) and from young flowers of Dahlia variabilis caused in each case synthesis of 6'-deoxychalcone. When 4-coumaroyl-CoA was replaced by caffeoyl-CoA in the reductase assay, formation of 2',4',3,4-tetrahydrochalcone (butein) was observed. A polyclonal antireductase antiserum was raised in rabbits and proved to be specific in Ouchterlony diffusion experiments, Western blots and immunotitration. The reductase antiserum showed no cross-reactivity with soybean chalcone synthase (CHS). A biotin/[125I]streptavidin system provided a quantitative Western blot for the reductase. Changes in the activities, amounts of protein, and mRNA activities of reductase and CHS were determined after challenge of soybean cell cultures by elicitor (from Phytophthora megasperma f.sp. glycinea or yeast). For both enzymes a pronounced and parallel increase in activity and amounts of protein was observed after elicitor addition with a maximum at about 16 h after challenge. Parallel increases in mRNA activities occurred earlier. The results indicate a parallel induction of de novo synthesis of reductase and CHS which coact in synthesis of 6'-deoxychalcone.     

SEM observations on seeds ofStriga spp. andBuchnera americana (Scrophulariaceae)

Seeds of the root parasitesStriga (several spp.) andBuchnera americana were examined by means of SEM. The surface patterns of the seeds in both genera resemble each other closely, especially those ofS. angustifolia andB. americana. SomeStriga spp. can be clearly distinguished by their surface characteristics, while this is quite difficult in others. The taxonomic value of the seed surface features ofStriga andBuchnera is discussed.     

Adhesion of canine and human uropathogenicEscherichia coli andProteus mirabilis strains to canine and human epithelial cells

Escherichia coli strains causing urinary tract infections in dogs produce fimbriae composed of fimbrial subunits closely related to the F12 and F13 fimbriae of human uropathogenic strains [4]. The adhesins carried by the fimbriae of human and canine isolates differ, however, as concluded from a different hemagglutination pattern and from the fact that the dog strains do not agglutinate latex beads coated with P-fimbriae receptor. This possible difference in adhesive specificity was confirmed by experiments in which the adhesion of human and dog isolates to dog kidney epithelial cells (MDCK cells) and human bladder epithelial cells (T24 cells) was compared. Dog uropathogenic strains, in contrast to human uropathogenicE. coli strains, adhere to MDCK cells but hardly to T24 cells. Adhesion to MDCK cells correlates with the presence of F12 or F13 fimbriae on the dog strains. These results suggest that homologous fimbrial subunits can carry different adhesin molecules and that these adhesin molecules can be responsible for species-specific adherence. On the contrary, adhesion of a number of dog uropathogenicProteus mirabilis strains to MDCK and T24 cells was not species specific; it depended on the mere presence of fimbriae.     

Filtration rate capacities in 6 species of European freshwater bivalves

Summary Filtration rate capacities in undisturbed freshwater bivalves were determined by means of two different methods (indirect clearance and suction methods) in Anodonta anatina (L.), Unio tumidus Philipsson, Unio pictorum (L.), Unio crassus Philipsson, Dreissena polymorpha (Pallas) and Sphaerium corneum (L.). In A. anatina, D. polymorpha, and S. corneum the filtration rate (FR, 1 h^-1) at 19–20°C as a function of dry tissue weight (DW, g) or ash-free dry weight (AFDW, g) could be expressed by the equations: 1.10 DW^0.78, 6.82 DW^0.88, and 2.14 AFDW^0.92, respectively. In U. tumidus, U. pictorum, and U. crassus filtration rates were comparable with those of A. anatina. In D. polymorpha the b value of the corresponding regression of gill area on dry weight was 0.87. The rates of water transport in freshwater bivalves are 2–8 times lower than in marine bivalves of comparable size. A corresponding difference in the filtration rate per gill area unit is found. The measured filtration rates in undisturbed bivalves are substantially higher (at least 4 times) than previously reported. This indicates that the impact of bivalve water processing on freshwater ecosystems is greater than hitherto suggested.