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Biomedical subjects

A Kiss

Publications and source records attributed to A Kiss.

At least 397 records · Page 22Linked to original sources
PubMed1978

Cloning of an E. coli ribosomal RNA gene and its promoter region from lambdarifd18.

The DNA of the specialized transducing phage lambdarifd18, which carries a bacterial rRNA transcription unit, was digested with restriction enzymes EcoRI and/or BamHI. Attempts were made to clone fragments containing the presumed rRNA promoter region or the entire rRNA gene in RSF2124 or pBR313 plasmid vectors with the following results: (1) We failed to clone an EcoRI fragment with the rRNA promoter region in plasmid RSF2124. (2) A smaller EcoRI-BamHI fragment with the rRNA promoter was also unclonable by itself, but one recombinant was found containing this fragment together with another large (7 Mdaltons) fragment, derived from phage lambda. The presence of this large fragment proved to be essential. The identity of these DNA fragments in the recombinant clone was confirmed by redigestion with several restriction enzymes, hybridization with rRNA, and in vitro transcription experiments, which showed preferential rRNA transcription. (3) A BamHI fragment encompassing the entire rRNA gene was easily cloned. Such stable clones carried a doubled number of rRNA genes. In vitro transcription using the recombinant plasmid resulted in 70% rRNA transcription. These recombinant clones allow the easy purification of the relevant DNA fragments for further investigation including sequencing.

Chromosome Mapping↗
PubMed1978

Ependyma and supraependymal structures in some areas of the fourth ventricle in the rat.

The ependyma was investigated in five areas of the rat ventricle system by means of both light and electron microscopy. The columnar, cuboidal and flattened types of the ependymal cells were mainly seen. All of them were seen in the fourth ventricle, while in the aqueductus cerebri and in the central canal the flattened type of the cell was lacking. An unusual variation as to the form of the ependymal cells was found on the roof of the fourth ventricle. Three groups of intraventricular structures were found in all investigated parts of the ventricle system: supraependymal globular structures containing irregularly arranged cristae, supraependymal protrusions appearing as homogeneous contents, and nerve profiles including nerve endings and nerve axons. The morphological characteristics of the ependyma and intraventricular profiles in the fourth ventricle allow to suppose a certain role of these structures in the exchange of various materials between the CSF, ependyma and neuropile.

Animals↗
PubMed1977

A new sequence-specific endonuclease (Bsp) from Bacillus sphaericus.

A new restriction endonuclease has been isolated from Bacillus sphaericus R. The purification procedure includes Bio-Gel filtration, (NH4)2SO4 fractionation and phosphocellulose chromatography. After the phosphocellulose step the enzyme preparation is free of non-specific nucleases. Bsp cleaves double-stranded DNA with the same specificity as Bacillus subtilis (Bsu) and Haemophilus aegyptius (HaeIII) restriction endonucleases, as concluded from digests and double-digests of phiX174 replicative form DNA with Bsu and Bsp. The 5'-terminal nucleotide of the cleavage products was shown to be C. Bacillus sphaericus R produces Bsp in extremely large quantities and the enzyme can be easily purified in high yield.

Bacillus↗
PubMed1977

Histological observations on the ependyma of the ventriculus mesencephali in the guinea pig.

The ventriculus mesencephali is localized in front of the cerebellum and forms a recessus of the dorsal wall of the aquaeductus mesencephali. The ependyma was found one-layered; in some places clusters of cubic or cylindrical ependymal cells occur. Some cells show basal processes. Supra-ependymally there are homogeneous globules and intraventricular nerve fibres. The occurrence of different types of ependymal cells indicates a morphological variability of ependyma even within this small part of the ventricle system of the brain.

Animals↗
PubMed1977

Conditions of transformation by DNA of Neurospora crassa.

The DNA uptake and transformation of inositol-requiring recipient Neurospora strains were investigated. Exponentially growing cultures can accumulate 5-10 fold quantities of donor DNA than older ones. The rate of DNA uptake depends on the physiological state of the recipient cell, and on the molecular weight of donor DNA. The exocellular DNase activity of the recipient culture may influence the DNA uptake and the transformation process. "Young" inositol-requiring Neurospora crassa cultures can be transformed by wild type DNA reproducibly, but with low efficiency.

Chromosome Mapping↗
PubMed1977

Investigations on myo-inositol-1-phosphate synthase from the wild type and the inositol-dependent mutant of Neurospora crassa.

The inositol-dependent mutant of Neurospora crassa lacks inositol-1-phosphate synthetase activity. This defect can be revorted by the addition of high-molecular DNA isolated from the wild type. To elucidate the biochemical background of inositol dependence, inositol-1-phosphate synthetase was studied. A method has been developed fro the isolation of the enzyme from the wild type strain in 10 mg scale by salt fractionation, gel filtration and ion-exchange chromatography. The specific activity of the purified enzyme is 4750 U/mg protein and its purity has increased about 100-fold. Polyacrylamide gel electrophoresis indicated that, in addition to the main enzymatically active band, several accompanying proteins occur in very small amount. The molecular weight of the enzyme is 225,000 daltons. Probably it consists of four subunits, two with a molecular weight of 64,000 daltons and another two of 50,000 daltons. An enzymatically inactive protein has been isolated from the mutant with the same procedure as that of the enzyme; it migrated at gel electrophoreis similarly to the enzyme. It may be supposed that the isolated protein is the defective enzyme molecule.

Carbohydrate Epimerases↗
PubMed1977

The ependyma of the ventriculus mesencephali in the rat.

The ventriculus mesencephali in the rat proceeds in the colliculi posterior region from the mesencephalic aqueduct in the dorsal direction. The ependymal lining is formed by flat, cuboid and cylindrical cells. The cylindrical cells, which occur in all parts of the ventriculus mesencephali, are the most numerous. The cuboid cells are localized mainly in the anterior part, the flat ones in the posterior part of the ventriculus mesencephali. Some cuboid and cylindrical cells have short basal processes. Among the ependymal cells, there are cells with long basal processes. The ependyma is at sites interrupted by flocks of ependymal cells. On the cell surface, there area cilia, microvilli and protoplasmic extrusions. The cell nuclei are spherical to oval. Supraependymally, there are homogeneous globules and intraventricular fibres. The histological variability of ependymal cells may point to the active participation of these cells in functional processes, even within such a small part of the ventricle system as the ventriculus mesencephali.

Animals↗
PubMed1976

Specific patterns of neuron arrangement and of synaptic articulation in the medial geniculate body.

Golgi and electron microscopic analysis of the known cellular layers in concentric shells of the ventro-lateral portion of the medial geniculate body revealed a flat grid of high density neuropil filling the space between the geniculocortical relay cells, forming essentially a single cell layer in each lamina. The "skeleton" of this neuropil grid is made up by the interdigitating dendritic tufts of the geniculocortical relay cells, joined together by a rich system of desmosomoid adhesion plaques. The "holes" of the "skeleton" are filled in by the multilobed dendritic appendages of Golgi type II interneurons and the grape-like terminals of the inferior collicular specific afferents. Additional axon terminals of other sources--terminals of descending corticogenicular fibers, axons of the Golgi type II interneurons and terminals of the initial collaterals of the geniculocortical relay cells--contribute only to a very insignificant fraction of neuropil volume. The Golgi type II interneurons are oriented in perpendicular direction to the cell layers so that they may bridge with their dendrites several successive layers. Although the general expression "synaptic glomeruli" used in other relay nuclei for this type of specific synaptic arrangement is hardly applicable to this grid-like neuropil, the essential synaptic articulation pattern of all thalamic relay nuclei is well maintained. The specific inferior collicular afferents are presynaptic to both relay cell dendrites and to the multilobed dendritic appendages of Golgi type II cells, which in turn are presynaptic to the same dendritic regions of the relay cells receiving the bulk of the specific afferents.

Animals↗
PubMed1976

Types of interneurons and their participation in the neuronal network of the medial geniculate body.

Three different types of interneurons can be separated in the Golgi picture, and many of their details can be identified under the electron microscope, in the medial geniculate body (MGB) of the cat: (1) typical short axon Golgi II. cells of the thalamic type, (2) somewhat larger Golgi type II cells with medium range axon, and (3) spidery neurogliform short axon cells. The most distinctive features of the two first types (1) and (2) are their irregular drumstick shape appendages, increasing in number as well as in length and irregularity of their stalks towards the periphery of the dendrites. These appendages form the vast majority of synaptic profiles in the aggregations of synaptic neuropil (glomeruli) of the nuclei, and they are both presynaptic and postsynaptic by the usual standards applied for the evaluation of the polarity of synapses. The characteristic beaded dendrites of the (3) neurogliform cell type can be recognised particulary easily in the electron microscopic picture. They are both presynaptic and postsynaptic in structural polarity. All identified process profiles of interneurons contain flattened (F-type) or pleomorphic synaptic vesicles. Membrane contacts, in which the interneurons appear to be presynaptic are either of the symmetric (Gray type II) or of an intermediate type. The membrane contacts of postsynaptic portions of the interneurons are usually of the asymmetric type (Gray type I) and the presynaptic profiles contain round (R-type) vesicles. The larger one have been shown already earlier to be derived from specific sensory (inferior collicular) afferents, while many of the smaller ones could be identified in the present study as being derived from cortico-geniculate descending pathways, arising from the auditory areas. Some of the synaptic contacts of the interneurons are apparently derived from other interneurons, the presynaptic profiles being often equivocal or more likely of axonal origin (all interneurons have clear axons in the Golgi picture). The occurrence of three distinct types of interneurons--probably all of inhibitory nature--the complexity in synaptic arrangement, and more particularly in the dendritic linkage of numerous synaptic sites does not favour such simple explanations as surround inhibition by forward or by backward inhibition, but suggests more sophisticated modes of impulse processing in the MGB.

Animals↗
PubMed1976

Attachment of ribosomes to endoplasmic membranes in mouse pancreas. Degranulation in vivo caused by the inducers of autophagocytosis neutral red, vinblastine, puromycin, and cadmium ions, and prevention by cycloheximide.

The present investigation was undertaken to discover whether in vivo inducers of autophagocytosis such as neutral red (0.40 mg/g body weight), cadmium chloride (0.15 mg/animal), vinblastine sulfate (7.5 mg/kg b.w.), and puromycin dihydrochloride (0.20 mg/g b.w.) are able to produce degranulation of rough surfaced endoplasmic reticulum (ER) of pancreatic acinar cells as we suggested earlier. Using a modified method of Blobel and Potter about 30% of the total ribosomes of untreated control pancreas were recovered in the free form, and 70% in the membrane-bound form. Cycloheximide (0.20 mg/g body weight) had no effect on this distribution of ribosomes, while neutral red, cadmium ions, vinblastine, and puromycin led to the presence of more free ribosomes: thus up to 70% of the total cytoplasmic ribosomes were recovered in the free form 30 to 60 min after treatments with the autophagic inducers. Pretreatments with cycloheximide prevented this shift and the distribution of ribosomes remained normal. On the basis of these and previous results we conclude that in pancreas an initial degranulation of the ER caused by these agents is a precondition of membrane transformation in autophagocytosis which is preventable by cycloheximide. Confirming the ultrastructural data of Longnecker et al. on rat pancreas, puromycin was shown to cause different forms of cellular injury including autophagocytosis. All forms of cellular injury were also prevented by pretreatment with cycloheximide in mouse pancreas.

Animals↗