Structural organization of procerebrums of terrestrial molluscs: Characteristics of neuronal pattern, plasticity, and age peculiarities

In terrestrial snails and slugs, the presence of five types of neurons has been shown: typical granular, horizontal, stellate, apical, and basal cells. A peculiarity of procerebrum neurons is a loop-like segment of the basal process. Granular cells have been established to spread both as cell columns and as single cells. The number of the columns and the number of cells in each column depend on the age and individual peculiarities of the animal. In the course of ontogenesis, there also occur changes of the number of processes-outgrowths of granular cell bodies as well as of the character of thickenings and the type of endings on their main processes. Basal neurons and single granular cells of the columns form several independent tracts running from the procerebrum cell body areas to metacerebrums. The single granular cells, horizontal cells, and a part of basal neurons are considered as associative elements providing formation in procerebrums of the single system that is a basis for the synchronized activity of the whole neuronal complex. A similarity of organization of procerebrums and of associative-integrative centers of higher animals is discussed.     

Seed transmission of turnip yellow mosaic virus in winter turnip and winter oilseed rapes

This is the first record of seed transmission of turnip yellow mosaic virus (TYMV) in oilseed and turnip rapes. The seed transmission of TYMV in a naturally infected winter turnip rape (Brassica napus var. silvestris) cultivar Perko PVH was investigated. By ELISA 1.6%, 3.2% and 8.3% seed transmission of the virus was found in seed of plants from three localities. The proportion of infected seeds produced by artificially infected plants of winter oilseed rape (Brassica napus ssp. oleifera) and winter turnip rape cultivars was determined. The virus transmission rate, expressed as the proportion of virus-infected plants which germinated from the seed was for the oilseed rape cvs Jet Neuf 0.1%, Solida 0.4%, Silesia 0.8%, Darmor 1.2%, SL-507 0.2%, SL-509 0.0% and for the winter turnip rape cv. Perko 1.5%. ELISA cannot be used in direct tests on bulk seed lots to estimate proportion of infected seed, but must be used on germinated seedlings.     

The proteins encoded by the rbs operon of Escherichia coli: II. Use of chimeric protein constructs to isolate and characterize RbsC.

Chimeric genes encoding full-length copies of rbsA and rbsC connected by segments coding for short bridge peptides were constructed and expressed in Escherichia coli. Surprisingly, the chimeric genes complemented the strain in which rbsA and rbsC were deleted. The chimeric proteins were overproduced, and the products were purified by affinity chromatography. In order to obtain highly purified protein, a poly-His leader peptide was incorporated so that Ni-chelate affinity chromatography could be employed. The leader peptide and the bridge peptide were designed with factor Xa-cleavable sites to permit recovery of the individual RbsA and RbsC protein. A rbsC gene encoding a poly-His leader was also constructed and expressed. Both the chimeric RbsA-C species and the poly-HisRbsC were produced at levels that permitted isolation of the equivalent of milligram quantities of RbsC per liter of culture. This is a substantial increase in amounts from any previous RbsC production vectors. All proteins from the rbs operon have now been overproduced and substantially purified.     

The X-ray structure of human serum ceruloplasmin at 3.1 Å: nature of the copper centres

The X-ray structure of human serum ceruloplasmin has been solved at a resolution of 3.1?Å. The structure reveals that the molecule is comprised of six plastocyanin-type domains arranged in a triangular array. There are six copper atoms; three form a trinuclear cluster sited at the interface of domains 1 and 6, and there are three mononuclear sites in domains 2, 4 and 6. Each of the mononuclear coppers is coordinated to a cysteine and two histidine residues, and those in domains 4 and 6 also coordinate to a methionine residue; in domain 2, the methionine is replaced by a leucine residue which may form van der Waals type contacts with the copper. The trinuclear centre and the mononuclear copper in domain 6 form a cluster essentially the same as that found in ascorbate oxidase, strongly suggesting an oxidase role for ceruloplasmin in the plasma.     

Crystal structure of the superantigen staphylococcal enterotoxin type A.

Staphylococcal enterotoxins are prototype superantigens characterized by their ability to bind to major histocompatibility complex (MHC) class II molecules and subsequently activate a large fraction of T-lymphocytes. The crystal structure of staphylococcal enterotoxin type A (SEA), a 27 kDa monomeric protein, was determined to 1.9 A resolution with an R-factor of 19.9% by multiple isomorphous replacement. SEA is a two domain protein composed of a beta-barrel and a beta-grasp motif demonstrating the same general structure as staphylococcal enterotoxins SEB and TSST-1. Unique for SEA, however, is a Zn2+ coordination site involved in MHC class II binding. Four amino acids including Ser1, His187, His225 and Asp227 were found to be involved in direct coordination of the metal ion. SEA is the first Zn2+ binding enterotoxin that has been structurally determined.     

Aspects of hadrosaurian cranial anatomy

Supraorbital bones in Saurolophus angustirostris are described, and their presence in all hadrosaurs is suggested. Frontal-nasal and premaxillar-nasal fontanellae are distinguished in hadrosaurs; their presence is explained as connected with growth and considered to he responsible for the variability of crest structures. New data indicating the presence of a cartilaginous diverticulum nasi within the circumnarial depression in Saurobphus ongustirostris are presented. A physiological (respiratory and/or thermoregulatory) function of the nasal diverticulum is proposed.     

Sensory cells in the head skin of pond snails

Summary Several types of receptor endings were identified with scanning electron microscopy and silver-impregnation techniques in the skin of the tentacles, lips, dorsal surface of the head and mouth region of the pond snails Lymnaea stagnalis and Vivipara viviparus. Sensory endings at the tips of dendrites of primary receptor neurones, scattered below the epithelium, differ in structure, i.e., the endings exposed to the surface of the skin possess different proportions of cilia and microvilli, which vary in number, length, and packing. Type-I endings have microvilli and a few (1–5) cilia, 5–12 m in length. Type-2 endings have abundant (20–40), interwoven long (9–12 m) cilia and random microvilli. Type-3 endings show typical packing of 10–25 cilia in the form of bundles or brushes. They may be composed either of long (9–18 m) or short (2–7 m) cilia, or of both long and short ones. Microvilli here are absent. Type-4 endings have only microvilli. Two other types of skin receptors do not extend their sensory endings to the surface and can be indentified only in silver-stained preparations. Type-5 endings are branching dendrites of skin receptors cells that terminate among epithelial cells. In type-6, the sensory endings also terminate among epithelial cells but their cell bodies are located outside of the skin. In both species all skin regions examined possess the receptors of all six types differing only in their relative proportion. Possible functional roles of different receptors are discussed.     

On the synthesis of viral ribonucleic acids and ribonucleoproteins in the submitochondrial system completely free of interfering cytoplasmic contaminations

Summary The synthesis of virus-specific macromolecules was studied in the reconstituted system containing inner membrane-matrix fraction from rat liver mitochondria and infectious RNA of Venezuelian equine encephalomyelitis (VEE) virus. In a series of preliminary experiments it was shown that isolated submitochondrial fraction was completely free of interfering cytoplasmic contaminations and particularly, of cytoplasmic 80S ribosomes. VEE RNA when added to submitochondrial system caused significant stimulation of RNA and protein synthesis. These processes were resistant to actinomycin D which inhibited profoundly the synthesis of proper mitochondrial macromolecules. The stimulating effect of VEE RNA in experiments with submitochondrial system was about three times higher than that with intact mitochondria. The stimulation of¹⁴C-amino acid incorporation increased as a function of incubation time; a certain lag-period being observed. The newly formed virus-specific RNA's and ribonucleoproteins were identified with the aid of sedimentation analysis. In particular, radioactive RNA's with sedimentation coefficients 40S and 26-18S were isolated from the incubated system. These RNA's are similar respectively to VEE genome RNA and doublestranded VEE replicative RNA. In double labelling experiments with³H-uridine and¹⁴Camino acids it was shown that VEE RNA induced synthesis of ribonucleoproteins containing newly formed RNA and protein. These RNP possessed sedimentation coefficients 60-80S, 140S and 300S in sucrose gradient and buoyant densities 1.32 and 1.50 g/cm³ in cesium chloride gradients. These properties of ribonucleoproteins synthesized de novo in submitochondrial system are close to those of RNP intermediates of VEE virus reproduction in the infected cells. We concluded that viral RNA could program virus-specific synthesis in the submitochondrial system under conditions that eliminated the contribution of cytoplasmic ribosomes.     

Effect of aeration on lysine biosynthesis in nutrient media with different concentrations of components]

The lysine synthesis by the culture M. glutamicus T-3 on nutrient media with varying molasses concentrations was studied during cultivation under different aeration conditions. With an increase in the nutrient concentration the relationship between the lysine yield and aeration rate became very manifest. An elevation of aeration (Kv) from 1.2 to 6.3 g O2 1/hr increased the yield of lysine in the 15, 20 and 28% molasses medium by 3, 6 and 11 times, respectively. A decline in aeration decreased the biomass yield and increased the content of lactic acid and alanine in the culture liquid (to 19 and 4 g/l, respectively). The rate of respiration of the culture in the filtrate of the culture liquid measured in the Warburg apparatus depended on the cell age and molasses concentration in the nutrient medium and not on the aeration rate.     

Comparative analysis of the nervous system structure of polymorphic zooids in marine bryozoans

The nervous system structure was compared for the first time in avicularia and vibracula in seven species of the cheilostome bryozoans from six families by immunohistochemical methods and confocal scanning microscopy. Regardless of significant differences in heterozooid shape, size, and position in a colony, their muscular and nervous systems have a common structure, which suggests their parallel evolution.