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Biomedical subjects

D Larson

Publications and source records attributed to D Larson.

At least 55 records · Page 3Linked to original sources
PubMed1980

5' flanking sequence signals are required for activity of silkworm alanine tRNA genes in homologous in vitro transcription systems.

We have used homologous in vitro transcription to examine the nucleotide sequences required for activity of cloned Bombyx mori tRNA2Ala genes. We have compared the transcriptional properties of an intact gene and a truncated derivative of the same gene lacking all but 11 nucleotides of normal 5' flanking DNA, and we find that at least two regions of DNA are required for accurate transcription of tRNA2Ala genes by homologous B. mori extracts. One of these sites is retained in the truncated gene and may be within the tRNA coding sequence. Competition experiments with intact and truncated genes indicate that this site probably acts by binding a factor necessary for specificity in polymerase III-catalyzed transcription. The second required site is removed by the Hind III cleavage used to produce shortened genes and thus must be 11 nucleotides or more upstream from the transcription initiation point. Possible roles for this site are discussed.

Alanine↗
PubMed1979

The primary transcription product of a silkworm alanine tRNA gene: identification of in vitro sites of initiation, termination and processing.

A 13.5 Kb fragment of Bombyx mori DNA containing a single tRNA2Ala gene has been cloned, and transcribed in vitro with Xenopus germinal vesicle extracts. The primary transcription product of the tRNA2Ala gene has been isolated and shown to possess an unprocessed triphosphorylated 5' terminus. Products resulting from processing of this transcript have also been isolated and characterized. Complete nucleotide sequence analysis of this cloned alanine tRNA gene and its primary transcript shows that transcription initiates three nucleotides away from the mature tRNA2Ala 5' end and terminates in a U cluster 22 nucleotides beyond the last encoded 3' nucleotide of the mature species. Sequence determination of the products of in vitro maturation shows that in contrast to the tRNA processing mechanism characteristic of procaryotes, the extra 3'-nucleotides in this silkworm tRNA precursor are removed by a single endonucleolytic cleavage.

Alanine↗
PubMed1979

Early diagnosis of delayed posttraumatic intracerebral hematomas.

Nine cases of delayed posttraumatic intracerebral hematomas (DTICH) were found retrospectively among 656 patients with closed head injuries admitted to the Hennepin County Medical Center in a 12-month period. All cases had severe head injuries sustained with the head in motion. The interval from cranial injury to diagnosis of DTICH by computerized tomography (CT) varied from 8 hours to 13 days. Eight patients were comatose on admission, three had focal seizures, and three had focal findings. The diagnosis was made on repeat CT scans obtained because of the development of focal findings in four cases, lack of improvement in four cases, and general neurological deterioration in one case. Four patients had initially negative CT scans. Four demonstrated only extracerebral hematomas on initial CT scan. One patient showed intracerebral hematoma on the initial scan followed by new hematomas on repeat study. The cases presented are discussed in light of pertinent literature.

Accidents, Traffic↗
PubMed1978

Acute multiple sclerosis with contrast-enhancing plaques.

In a case of clinically fulminant multiple sclerosis (MS), contrast-enhancing lesions were visible by computerized axial tomography (CT). The patient died less than three weeks after the study, making neuropathologic correlation possible. It appears that areas of contrast enhancement correlate in acute MS with early demyelinative lesions, and enhancement is related to breakdown of the blood-brain barrier. That such a disturbance is important in the pathogenesis of demyelination in MS has been suggested by other data as well. The characteristic CT findings of MS must therefore include enhancing lesions that reflect disease activity and that may be the only CT abnormality.

Acute Disease↗
PubMed1978

Radical or modified neck dissection: a therapeutic dilemma.

Three hundred ten evaluable patients received a classic, functional, or spinal accessory-nerve-sparing neck dissection during 1970 to 1975. The functional procedure was at least equal to the classic procedure in the patients in whom it was employed. The spinal accessory-nerve-sparing operation is offered as an alternative to the classic procedure in all patients in whom the nerve is not directly invaded by cancer. If these guidelines are followed, the patient will rarely experience the pain and shoulder dysfunction that result from the loss of the trapezius muscle, while the chances of control of cancer in the neck remain optimal.

Head and Neck Neoplasms↗
PubMed1975

The endogenous reverse transcriptase activity of Gibbon ape lymphoma virus: characterization of the DNA product.

The DNA product of the endogenous reverse transcriptase reaction of Gibbon ape lymphoma virus has been analyzed and characterized. Data show that in simultaneous detection assays in which the type and/or concentration of divalent cation is varied the best yield of rapidly-sedimenting DNA was obtained from reactions containing 1.5 mM Mn2+. This yield is ten-fold better than the yield observed at the optimal Mg2+ concentration (5.0mM). Evidence is presented to show that DNA synthesized at the optimal concentration of either of these cations consists of large pieces varying in size from 4 to 12S. This DNA hybridizes efficiently to homologous viral RNA (greater than 60 percent annealing) and protects at least two-thirds of GALV 70S [32P]RNA from ribonuclease digestion. The hybrids formed with homologous viral RNA are stable as evidenced by their thermal elution patterns from hydroxylapatite columns. In contrast, DNA synthesized in reactions in which the concentration of Mn2+ or Mg2+ was greater than optimal was predominantly 4S or smaller in size and displayed a low level of hybridization (less than 10 percent) to homologous viral RNA.

Animals↗
PubMed1975

Competition radioimmunoassay for mason-pfizer monkey virus: comparison with recent isolates.

The major core protein of Mason-Pfizer monkey virus was purified by DEAE ion exchange column chromatography and shown to be 27,000 daltons (p27). Following the characterization of monospecific antisera prepared against p27, a radioimmunoassay was developed with these reagents and competition experiments were done with come of the recent M-PMY-like isolates as well as with other oncornaviruses. Results suggest that three of the viruses tested, AO, X-381 and FTP-1, are similar to M-PMV while J-96 virus is related, but not identical, to M-PMV. It is also shown that competition RIA can be used successfully to detect the presence of viral proteins in tissue homogenates and cell extracts.

Animals↗
PubMed1975

New method for the removal of extraneous proteins from purified oncornaviruses.

Conventional methods (i.e. gradient centrifugation) for the purification of oncornaviruses are usually not effective in complete removal of nonviral proteins. Such contaminants often prove to be a nuisance in subsequent immunological or biochemical studies. Hyperimmune sera prepared from these viruses must be absorbed to assure specificity; cell-derived proteins can be shown to interfere with studies of virus structural proteins, nucleic acids, or viral enzymes. Herein is described a method for removal of most of these contaminants. Viruses are diluted in a high concentration of NaCl to achieve a final concentration of 15%, incubated for 30 min, sedimented, and resuspended in buffer. This procedure results in reductions of up to 48% of the protein without affecting particle count. Immunological, biochemical, and biological properties are not adversely affected. Of the proteins removed, fetal calf serum components and a ribonuclease (presumably cell-derived) were identified. This technique differs significantly from other high-salt methods in that the virus is not precipitated from suspension. It is believed that absorbed proteins are desorbed and left in solution (or suspension) as the virus is sedimented by centrifugation.

Cell Line↗
PubMed1970

Microfilmed ECGs.

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Automation↗