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Biomedical subjects

A Lord

Publications and source records attributed to A Lord.

50 records · Page 3Linked to original sources
PubMed1980

Epidemic outbreaks of adenovirus 7 with special reference to the pathogenicity of adenovirus genome type 7b.

Adenovirus type 7 (Ad 7) is the serotype among the 36 recognized adenovirus types which most frequently has been associated with severe illness. Three different epidemic patterns of Ad 7 infection can be distinguished: 1) the first appears during the winter among infants with median age below two years, has characteristic symptoms of high fever and pneumonia and an outcome that may be fatal: 2) the second appears in the fall among children with median age seven years, has characteristic symptoms of high fever, pneumonia, abdominal symptoms and meningism and an outcome that is favorable; 3) and the third has been seen as acute respiratory disease among military recruits. In the United States, the last mentioned outbreaks require prophylaxis in the form of a live enteric-coated vaccine. DNA restriction site mapping demonstrated the occurrence of three distinct viral entities of Ad 7, which have been designated Ad 7 prototype, Ad 7a (the vaccine strain) and the Ad 7b genome type. In the present study, 36 isolates obtained from outbreaks with the first and the second epidemic patterns were analyzed by restriction endonucleases Bam HI and Sma I. All were identified as the newly recognized Ad 7b genome type. It is concluded that this genome type is responsible for a large portion of the severe infections caused by Ad 7. The epidemic nature of Ad 7 and the severe illness noted among infants indicate that vaccination of institutionalized infants could be considered during years when Ad 7 epidemics appear.

Adenoviridae Infections↗
PubMed1978

Serological studies in the elderly.

Sera from 108 elderly patients in psychiatric and general hospitals were tested for antibodies to seven viruses. Measles virus antibody levels were significantly higher in patients from the psychiatric hospital, regardless of diagnosis, than in those from other hospitals. Demented patients, regardless of their hospital, had significantly higher levels of antibody to adenovirus than control patients.

Adenoviridae Infections↗
PubMed1978

Properties of poly(ADP-ribose) synthetase from rat pancreas and poly(ADP-ribosylation) of basic nuclear proteins.

The isolated nuclei of rat pancreas contain an enzyme system that will incorporate 3H-labeled NAD into an acid-insoluble product, which is shown to be poly(ADP-ribose). The enzyme has an optimum pH of 7.8 and the optimum temperature is between 20 and 30 degrees C. Optimum Mg2+ concentration is 8 mM and dithiothreitol also stimulates the enzyme at a concentration of 8 mM. Under standard conditions, the Km value for the reaction is 0.25 mM and an inhibition by the substrate is observed at high substrate concentrations. It has also been found that only one basic nuclear protein, that is, histone H1, is modified by the synthetase. An average chain length of 5.0 is found in the nuclei and of 4.5 on histone H1. Radioautographic studies show that poly(ADP-ribose) is closely associated with chromatin.

Animals↗
PubMed1977

Ultrastructural and radioautographic investigation of the nucleolar cycle in Physarum polycephalum. Characterization of DNA-containing subunits.

The present study has been mainly focused on the nucleolar cycle in the slime mould Physarum polycephalum. The ultrastructural characteristics of the interphase nucleolus, in this species, are quite similar to those of nucleoli in other organisms: it is essentially constituted of large particulate zones surrounding denser regions which are predominantly fibrillar in texture. The latter nucleolar zones, following fixation with osmium tetroxide, are characterized by the presence of opaque granules approximately 25 nm in diameter. Contrary to the situation which generally prevails in other eukaryotes, the late prophase nucleolus fragments into numerous globular bodies which are recognizable by the presence of opaque particles. These fibrillogranular nucleolar fragments persist during mitosis and are observed to become incorporated in the newly formed nucleolus. High-resolution radioautographic observations reveal that these nucleolar remnants contain DNA. The present observations together with recent biochemical data from other authors on the characteristics and mode of duplication of nucleolar DNA in P. polycephalum have led us to the hypothesis that the nucleolus, in this organism, contains several distinct globular subunits each containing ribosomal DNA as a key component. The existence of such morphological subunits appears to account for the unusual behaviour of the nucleolus during the cell cycle.

Autoradiography↗
PubMed1977

A light- and electron-microscope study of nuclear structure throughout the cell cycle in the euglenoid Astasia longa (Jahn).

The structure of nuclei of Astasia longa in synchronized cultures was examined at the light- and electron-microscope levels. Three types of nuclei, differing mainly in chromatin conformation, were observed during interphase and were tentatively classed in the G1, S and G2-periods. The fibrillar nucleolar regions exhibited a most complex organization and appeared to consist of convoluted, coarse filaments or nucleolonemata approximately 0.15 micrometer in diameter. Chromosome condensation was evidenced first by the longer, thicker profiles of chromatin observed in late prophase. Furthermore, the nucleolus, that persists throughout mitosis, began to elongate at late prophase. Furthermore, the nucleolus, that persists thorughout mitosis, began to elongate at this stage, simultaneously with the appearance of short, unoriented profiles of intranuclear microtubules. Chromosome condensation was complete by mid-metaphase and the nucleolus was elongated into a cylindrical shape with irregular extremities. Microtubule profiles were longer than in prophase; they were now oriented parallel to the nucleolus and frequently lay closely appressed to its sides. In anaphase, the chromosomes segregated into 2 groups, one towards each extremity of the dumb-bell-shaped nucleolus. The telophase chromosomes assumed a random orientation with respect to the still intact nucleolus. Throughout the division stages the persiting nucleolus maintained its ultrastructural organization and consisted partly of conspicuous nucleolonemal profiles which tended to be oriented along the major axis of this organelle. Nucleolar separation into 2 fragments occurred late in telophase and was followed by a reformation of daughter nuclei and initiation of cell fission during cytokinesis.

Animals↗
PubMed1976

An ultrastructural and radioautographic study of the chromocentric interphase nucleus in plant meristematic cells (Raphanus sativus).

In Raphanus sativus, the mitotic chromosomes are quite short and, on reaching the cell poles, soon undergo extensive unravelling. By late telophase and early interphase, only a few chromosome segments, believed to correspond to the centromeric regions, are still visible in the form of chromocentres closely associated with the nuclear envelope. Although interphase nuclei show little internal structural differentiation, high-resolution radioautography has permitted us to establish which of them have reached the early, mid and late S periods. In early S nuclei, only the nucleolus and the euchromatin which pervades the nuclear cavity become labelled. By the mid S-period, the diffuse chromatin and nucleolus incorporate less thymidine and DNA synthesis is initiated within the peripheral chromocentres. Subsequently, the radioautographic grains become restricted to the chromocentres. The finding that certain late S nuclei exhibit loosely organized chromocentres strongly suggests that these heterochromatic chromosome segments undergo important conformational modifications during DNA replication. Finally, the presence of radioautographic grains over the lacunar regions of the nucleolus in early and mid S nuclei demonstrates that intranucleolar DNA replicates during the earlier portion of the S-period.

Autoradiography↗
PubMed1975

Recovery of adenovirus type 7 from human brain cell cultures.

A strain of adenovirus type 7 was recovered from cultured brain cells, taken at necropsy from a patient aged 71 years with chronic schizophrenia. This recovery may indicate the reactivation of a latent infection with one of the few adenoviruses that has regularly-if rarely-been associated with clinical encephalitis.

Adenoviridae↗
PubMed1969

The organization of the nucleolus in meristematic plant cells. A cytochemical study.

The architecture of the nucleolus in Allium porum and Triticum vulgare meristematic cells has been investigated by means of digestions with various enzymes. After staining with azure B at pH4, plant nucleoli exhibit lighter regions which, under electron microscopy, correspond to the fibrillar zones characterizing these organelles. Evidence is presented indicating that these latter zones contain coarse convoluted filaments quite similar to the loops first demonstrated by La Cour (24) and which are assumed to originate from the nucleolar-organizing chromosomes. These coarse, 0.2micro wide filaments are remarkably resistant to the action of deoxyribonuclease, ribonuclease, pepsin, trypsin, or of various combinations of these enzymes and, moreover, they show insignificant incorporation of labeled thymidine even after long exposure to this DNA precursor. The clearing action of pepsin on different regions of the nucleolus lends support to the hypothesis that an amorphous material or matrix pervades the mass of this organelle. This effect is particularly striking within the particulate nucleolar zones themselves. Both ribonuclease and trypsin disorganize the RNP (ribonucleoprotein) nucleolar particles. The effect of the latter enzyme on the RNP particles is taken to indicate that they contain proteins particularly susceptible to trypsin which are essential for maintenance of their morphological integrity. Trypsin also interferes with azure B-staining of the nucleolar mass as a whole and, according to radioautographic data, extracts RNA throughout this organelle. Accordingly, the hypothesis is considered that RNA is complexed with proteins not only within the particulate nucleolar portions, as is already well known, but also in the fibrillar zones.

Autoradiography↗