Site-specific recombinational circularization of bacteriophage P1 DNA.
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Bacteriophage lambda↗
Biomedical subjects
G Cohen
Publications and source records attributed to G Cohen.
Electron microscopy study of early lytic replication forms of bacteriophage P1 DNA.
P1 replication intermediates were isolated from the intracellular DNA of lytically infected cells and analyzed by electron microscopy. At early times in infection replication intermediates were mainly of two types, circular theta- and sigma-shaped molecules plus a small proportion of linear bubble-shaped molecules. At later times in infection sigma molecules were the predominant replicating form. In contrast, sigma molecules were rarely found in recombination deficient, recA, infected cells. These observations show that early P1 DNA synthesis occurs, in part, by a circular mode of replication and imply that transition to a later, probably rolling circle, phase of replication is controlled by the bacterial general recombination system.
Coliphages↗
Requirement of E. coli DNA synthesis functions for the lytic replication of bacteriophage P1.
P1 lytic growth was examined in a number of different temperature sensitive mutants of E. coli that affect chromosomal replication. Growth was analyzed by measurements of phage burst sizes and specific DNA synthesis. Efficient P1 growth required each of the bacterial elongation functions dnaE (polC), dnaZ (sub units of E. coli polymerase III holoenzyme), and dnaG (primase) but was not dependent on the elongation function dnaB (mobile promoter). Of two initiation functions tested the dnaA function was found to be dispensable for normal growth whereas the dnaC function was essential. Temperature shift experiments with different dnaC mutants showed that the initiation component of the dnaC function was needed continuously throughout at least the first half of the lytic cycle, while the dnaC elongation activity was probably required during the entire cycle for normal phage yields. In two respects the dependence of P1 lytic growth on E. coli DNA synthesis functions was significantly different from that reported for P1 plasmid replication (Scott and Vapnek, 1980). Thus, lytic replication was far more dependent on a functional polC gene product than was plasmid replication and did not require the bacterial dnaB product.
Coliphages↗
Age differences in performance on two information-processing tasks: strategy selection and processing efficiency.
Matched groups of old and young adults were compared in two information-processing tasks. In the rotated figures task the participant had to decide whether a figure displayed upright or inverted, faced forwards or backwards, held a ball in its right or left hand. In the sentence verification task the individual had to decide whether an affirmative or negative sentence was true or false as a description of a pattern. From the pattern of reaction times and from the respondents' verbal reports it was possible to identify the strategies used by individuals on each task. The numbers of participants selecting each of the different strategies were similar for old and young groups, but age differences were greater with some strategies than with others. The age difference was minimized when older adults adopted strategies that reduced the amount of processing. The older adults, however, were more disadvantaged when employing strategies that imposed greater processing demands or a heavy memory load.
Adult↗
Word recognition: age differences in contextual facilitation effects.
A series of experiments compared contextual facilitation of word recognition in old (63-80) and young (19-34) subjects. Visual word recognition was examined in a lexical decision task. Sentence contexts or no context preceded words or non-words. Both groups responded faster when context was supplied. For high predictability words, there was no age difference in the magnitude of the contextual facilitation effect. For low predictability words and non-words, the old showed greater contextual facilitation than the young. Auditory word recognition was tested with target words spoken with or without sentence context in a background of white noise. Old subjects, again, showed superior contextual facilitation. It was concluded that old people compensate for deterioration in stimulus quality by more effective use of contextual information.
Adult↗
Detailed analysis of the portion of the herpes simplex virus type 1 genome encoding glycoprotein C.
We previously showed that the right third of HindIII fragment L (0.59 to 0.65) of herpes simplex virus type 1 (HSV-1) encodes a family of mRNAs some members of which appear to be related by splicing. In the experiments described in this communication, we determined the nucleotide sequence of the DNA encoding this mRNA family and precisely located the mRNAs associated with this DNA sequence. The major mRNA species is unspliced and encoded by a 2.520-nucleotide region. Just upstream of the 5' end are TATA and CAT box sequences characteristic of HSV-1 promoters. The 3' end maps near a region containing a nominal polyadenylation signal. Three minor species (2,400, 2,200, and 1,900 bases, respectively) appear to share a very short leader sequence with the 5' end of the major mRNA and are then encoded by uninterrupted DNA sequences beginning about 100, 400, and 625 bases downstream of the 5' end of the major unspliced mRNA. These positions map at or very near positions which agree reasonably well with consensus splice acceptor sequences. The fourth mRNA is encoded by a contiguous 730-nucleotide sequence at the 3' end of the major unspliced mRNA and has its 5' end just downstream of recognizable TATA and CAT box sequences. We suggest that this mRNA is controlled by its own promoter. The nucleotide sequence data, in combination with the mRNA localization, demonstrate four potential polypeptides encoded by the region. The largest is 1,569 bases long and defines a 523-amino acid protein with sequence features characteristic of a glycoprotein. This was confirmed to be HSV-1 glycoprotein C by immune precipitation of the in vitro translation product of the major unspliced mRNA, performed with a polyspecific antibody to HSV-1 envelope glycoproteins (anti-env-1 serum), and by comparison of tryptic peptides of this translation product with those of authentic HSV-1 glycoprotein C. Polypeptides encoded by some of the minor species also were tentatively identified.
Base Sequence↗
High-resolution characterization of herpes simplex virus type 1 transcripts encoding alkaline exonuclease and a 50,000-dalton protein tentatively identified as a capsid protein.
Four partially overlapping mRNAs (1.9, 2.3, 3.9, and 4.5 kilobases [kb]) were located between 0.16 and 0.19 map units on the herpes simplex virus type 1 genome. Their direction of transcription was found to be from right to left. The 2.3-kb mRNA was found to be early (beta), whereas the others were late (beta gamma). Partial sequence analysis of the DNA encoding these genes indicated that the promoter for the 2.3-kb mRNA shares structural features with other early (beta) promoters. In vitro translation of hybrid-selected mRNA indicated that among the proteins these mRNAs encode are an 82,000-dalton (d) polypeptide reactive with a monoclonal antibody against herpes simplex virus type 2 alkaline exonuclease and a 50,000-d polypeptide weakly reactive with a polyclonal antibody made against the capsid protein VP19C. Further experiments suggested that the 2.3-kb mRNA encodes the 82,000-d polypeptide, whereas one (or both) of the larger mRNAs encodes the 50,000-d protein. A novel finding was that the 1.9-kb mRNA appears to share part of the translational reading frame for alkaline exonuclease, but any polypeptide it encodes does not react with the monoclonal antibody to this enzyme.
Base Sequence↗
Translating research into education: programs and practice.
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Aged↗
Explant cultures of dog substantia nigra and striatum: a model for the study of nigro-striatal dopamine neurons.
The development of organotypic co-cultures of substantia nigra and striatum from newborn dog brain was studied. Histofluorescence demonstrated the presence of catecholamine containing neurons in the substantia nigra. These neurons extended fluorescing processes that entered the striatum. High performance liquid chromatography identified the catecholamine as dopamine (DA). The DA was metabolized to homovanillic acid, which was accumulated in the feeding medium. The synthesis of DA was inhibited by the tyrosine hydroxylase inhibitor alpha-methyl tyrosine. The striatal tissue contained DA receptors, which increased during the development of the cultures. Electron microscopy demonstrated the presence of DA containing axons in the striatum; some of the axons established synaptic contacts with small dendritic branches. Several types of neurons could be identified in the striatum by electron microscopy. The presence of GABA in some striatal neurons was indicated by their ability to accumulate exogenous 3H-GABA. These observations suggest that the organotypic nigro-striatal cultures develop several of the characteristics of the same structures in the brain and therefore could be used as a model for the study of the DA containing neurons of the substantia nigra.
Animals↗
The pathobiology of Parkinson's disease: biochemical aspects of dopamine neuron senescence.
The intracellular generation of reactive forms of reduced oxygen, namely, hydrogen peroxide, superoxide and hydroxyl radical, can damage dopamine neurons. Oxy-radicals, and hydrogen peroxide generated by monoamine oxidase, can contribute to increased rates of senescence of dopamine neurons in Parkinson's disease. The evidence that oxy-radicals and monoamine oxidase are potentially cytotoxic is reviewed, and a pathobiology of dopamine neuron senescence in Parkinson's disease is proposed.
Animals↗
[Interruptions of the inferior vena cava].
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Humans↗
[Ureterovesical reimplantation. A technic derived from Lich and Gregoir's procedure].
Fifty-five uretero-neocystostomies were carried out using a technique derived from the Lich-Gregoir technique. Tightness is ensured anastomosis and burying over the vesical dome, with minimal vesical opening; the anti-reflux system is effective. Urinary complication of this ureter transplantation method are now rare, in our series, only two complications due to necrosis of the ureteral segment were observed. This technique could be used in all obliterations of the ureter, whether accidental or by necessity, located near the bladder.
Humans↗
Ethane exhalation as an index of in vivo lipid peroxidation: concentrating ethane from a breath collection chamber.
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Adsorption↗
Interleukin 1 activity in the synovial fluid of patients with rheumatoid arthritis.
The synovial fluids (SF) of patients with rheumatoid arthritis (RA) were investigated for their effects on thymocytes of C3H/HeJ mice. Of the 20 SF tested, 17 (85%) showed an augmentation of the phytohaemagglutinin (PHA) induced thymocyte stimulation. Out of 16 SF of patients with osteoarthrosis, such an activity was detected in only one (6.25%). Further characterisation of the amplification factor revealed that (1) the SF of RA patients augmented both the PHA and the Concanavalin A response of the thymocytes (2) in the absence of mitogens, SF-treated thymocytes showed an increased uptake of 3H-thymidine, (3) the SF did not propagate the growth of an interleukin 2 dependent ovalbumin specific T cell clone, but (4) the SF were found to be required for optimal interleukin 2 release by spleen cells stimulated with suboptimal doses of lectin. Based on these biological effects the factor in the SF of RA patients is suggested to represent an interleukin 1 (IL-1). IL-1 produced in cultures by activated macrophages has been shown to stimulate T and B cell functions and to induce the production of collagenase and prostaglandins by cultured synovial cells. Both properties of IL-1 could be relevant in the pathogenesis of RA.
Animals↗
Action of collagenase and elastase from human polymorphonuclear leukocytes on human articular cartilage.
Collagenase from human polymorphonuclear leukocytes (neutrophil collagenase) attacks collagen type II in solution at a rate intermediate to those of type I and III collagens. This enzyme alone is not able to initiate degradation of native human articular cartilage. If the cartilage is first treated with leukocyte elastase, collagenase slowly degrades collagen. Confirming earlier findings by other investigators, elastase has a dual action on cartilage: The enzyme removes proteoglycans, thus demasking collagen fibers and giving collagenase access to them, and solubilizes collagen at a sizable rate. Although neutrophil collagenase cleaves collagen type II in solution at a high rate, the native, cross-linked status of collagen in cartilage makes it a relatively poor substrate for this enzyme. On a weight by weight scale, elastase and collagenase display about the same collagenolytic potential on human articular cartilage. The elastase/collagenase system from human polymorphonuclear leukocytes could represent a cooperative proteolytic complex in the destruction of cartilage in rheumatoid arthritis.
Cartilage, Articular↗
Energy dependence of contrast-detail-dose and object-detectability-dose curves for CT scanners.
The energy dependence of contrast-detail-dose (CdD) and object-detectability-dose (OdD) curves for computed tomographic scanners is investigated. The effects of changes in beam energy on perceptibility are shown to be due to changes in signal-to-noise ratio resulting from changes in contrast and photon statistics. Energy-dependence analysis of OdD curves is shown to depend on the atomic composition of the phantom used to generate the curves, while such an analysis of CdD curves is independent of the atomic composition of the phantom. It is also shown that any OdD curve can be generated from CdD curves and that use of this fact rectifies any potential energy-dependent interpretation of CdD curves.
Dose-Response Relationship, Radiation↗
The differential effect of ischemia on the active uptake of dopamine, gamma-aminobutyric acid, and glutamate by brain synaptosomes.
Ischemic stroke was induced in the Mongolian gerbil by left common carotid ligation. No change in uptake of [3H]dopamine, [3H]gamma-aminobutyric acid ([3H]GABA), or [14C]glutamate in synaptosomes obtained from the ischemic hemisphere was observed for up to 8 h. At 16 h after ligation, marked decrements in uptake were observed in animals showing hemiparesis: Uptake values expressed as a percent of the corresponding control hemisphere were 15.2% for dopamine, 28.9% for GABA, and 47.5% for glutamate. The differential sensitivity of dopamine terminals compared with glutamate terminals was highly significant. Separate experiments performed with synaptosomes isolated from the corpus striatum showed that the greater sensitivity to damage was intrinsic to the dopamine nerve terminal and not the result of regional variations in ischemic damage in brain. No bilateral effect of ischemia on dopamine uptake was evident. In animals exhibiting milder behavioral deficits (circling), a smaller and comparable decrement in uptake of dopamine, GABA, and glutamate was evident at 16 h, whereas animals not affected behaviorally showed no decrement at 16 h. Following uptake, the subsequent fractional release of neurotransmitter stimulated by 60 mM-potassium ions was not affected at any time point studied. Therefore, the loss in uptake at 16 h probably represents overt destruction of nerve terminals. Experiments with urethane used in place of pentobarbital for anesthesia during carotid occlusion showed that "protection" by pentobarbital was not a factor in the delayed response to ischemia. These results show that damage or destruction of nerve terminals is a delayed event following ischemia and that dopamine terminals are intrinsically more sensitive than glutamate terminals.
Animals↗