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Biomedical subjects

R Dunn

Publications and source records attributed to R Dunn.

At least 127 records · Page 7Linked to original sources
PubMed1985

Alterations of capillary flow during sepsis.

Normal red cells are flexible and can thus negotiate small capillaries with ease. Impaired red cell deformability (RCD) has been found in patients with uremia, peripheral vascular disease, and diabetes. This study was performed in order to determine if impaired RCD is present during sepsis. The RCD of citrated whole blood (WB) and citrated buffy coat-poor whole blood (BCP) from ten septic patients was compared to ten age-, sex-, and race-matched control patients. The samples were passed through polycarbonate 5 micron pore filters at -10 cm H2O pressure according to the technique of Reid. A red cell deformability index was calculated for each patient by multiplying the volume of blood flowing through the apparatus in a 1-minute period by the hematocrit. The results show very highly significant decreases of flow in both the WB and BCP blood in the septic group. Alterations in flow in the WB can be explained on the basis of changes in the buffy coat fraction and/or the red cell deformability. A decrease in flow in the BCP blood can be explained in terms of a diminished deformability of the red cells themselves. This increased rigidity of the red cells could, in part, explain the AV shunting and decreased microcirculatory flow seen in the septic state.

Capillaries↗
PubMed1984

THRM forum: My boss.

Explore the source record for details and available documents.

Health Facility Administrators↗
PubMed1983

Late prognostic value of scintigraphic parameters of acute myocardial infarction size in complicated myocardial infarction without heart failure.

Perfusion scintigraphy with thallium-201, infarct scintigraphy with technetium-99m pyrophosphate (TcPYP), and equilibrium blood pool scintigraphy were performed during the initial hospitalization for acute myocardial infarction (MI) in 25 patients without evidence of heart failure who presented with advanced electrocardiographic rhythm and conduction disturbances requiring treatment. Scintigraphic findings during short-term hospitalization were related to the late clinical follow-up performed an average of 14 months later, where patients were grouped as asymptomatic, 8 patients; symptomatic, 9 patients; and deceased, 8 patients. Quantitation of perfusion abnormalities, TcPYP image abnormalities, and left ventricular ejection fraction (EF) revealed that the deceased group had significantly larger TcPYP abnormalities (36 +/- 20 cm2), absolute perfusion abnormalities (32 +/- 16 cm2), and perfusion abnormalities expressed as a percentage of the projected left ventricular area (42 +/- 8%) than the asymptomatic group (13 +/- 8 cm2, 14 +/- 6 cm2, and 20 +/- 9%; p less than 0.05, p greater than 0.05, and p less than 0.01, respectively). The percent perfusion abnormality was significantly larger in the deceased group (42 +/- 8%, p less than 0.01) than in either the symptomatic group (35 +/- 13%, p less than 0.01) or the asymptomatic group (20 +/- 9%), and this parameter in the symptomatic group also differed from that in the asymptomatic group (p less than 0.01). The study indicates that patients with rhythm and conduction disturbances and without congestive heart failure during acute MI may follow an uncomplicated or a complicated late clinical course. Early scintigraphic measurements of MI and perfusion correlate well with this outcome; however, EF could not differentiate among prognostic subgroups.

Adult↗
PubMed1983

Althesin in the management of head injuries: a preliminary report.

The aggressive treatment of major craniocerebral trauma has received recent attention. Barbiturate administration has been beneficial in some cases of sustained, uncontrolled intracranial hypertension. One major disadvantage of pentobarbital narcosis is the long half-life of the drug (15 to 48 hours). We have used Althesin, an intravenous steroid anesthetic (alfaxalone and alfadolone acetate; Glaxo Laboratories Ltd., Greenford, Middlesex, England), in eight seriously head-injured patients. Althesin combines the theoretical advantages of pentobarbital in the management of head trauma with almost immediate reversibility (serum half-life, 1.6 minutes). Raised intracranial pressure and clinical outcome seem to be influenced favorably and the side effects are negligible when the drug is administered by continuous intravenous infusion over several days. Further study of this compound in the management of head trauma seems warranted.

Adolescent↗
PubMed1982

The phase image: its relationship to patterns of contraction and conduction.

To determine the relationship of phase changes and abnormalities of ventricular contraction and conduction, we performed phase image analysis of blood pool scintigrams in 29 patients. Eleven patients had no evidence of blood pool contraction or ECG conduction abnormalities, four had contraction abnormalities, seven had abnormal conduction and seven had abnormalities of both variables. The phase delay generally related to the degree of contraction abnormality. The mean phase delay in hypokinetic segments differed from that in normokinetic segments in the same patient (p less than 0.025), the phase delay of akinetic and dyskinetic segments differed from that in normokinetic segments (p less than 0.001) and the phase delay in dyskinetic segments differed from that in akinetic segments (p less than 0.005), but there was a significant overlap in the phase delay in normal and hypokinetic segments. Also, in patients with conduction abnormalities, the minimal associated regional phase delay presented a phase dispersion and a pattern of contraction consistent with the pattern of conduction and different from normal. A single study performed both at rest and with stress demonstrated the effect of heart rate on phase assessment and confirmed the independent effects of contraction and conduction on phase delay. Acquisition and analytic methods should add significantly to the resolution of the phase method.

Arrhythmias, Cardiac↗
PubMed1982

The late prognostic value of acute scintigraphic measurement of myocardial infarction size.

Infarct, perfusion and blood pool scintigraphy were performed in 62 patients during hospitalization for acute myocardial infarction. The largest measured infarct or perfusion image defect and left ventricular ejection fraction were related to the late prognosis determined a mean of 16 months after the event. Breakpoint values for all scintigraphic variables could separate those who were asymptomatic on follow-up from those who died. The best indicators for selection of survivors and nonsurvivors were a scintigraphic infarct size greater than or equal to 25 cm2 and a perfusion abnormality greater than or equal to 35% of the projected left ventricular area. Among patients with perfusion abnormalities above this limit, 61% died; 93% of those with small perfusion abnormalities survived. Scintigraphic measurements of relative myocardial perfusion and function best separated patients asymptomatic on follow-up from those who developed heart failure and also best identified those with an unfavorable evolution, who developed heart failure or died. Early scintigraphic parameters appeared more accurate than other clinical laboratory indicators for determining late prognosis and could be important in planning treatment after acute infarction.

Aged↗
PubMed1982

Choice and the relative immediacy of reinforcement.

The relative immediacy of reinforcement in concurrent-chain schedules was varied while the relative reduction in the overall average time to reinforcement associated with terminal-link entry was held constant. For each of four pigeons, choice did not vary with relative immediacy of reinforcement. Subsequently, choice by the same subjects was shown to be sensitive to relative reduction in average time to reinforcement.

Journal Article↗
PubMed1981

The bacteriorhodopsin gene.

The bacteriorhodopsin gene has been identified in a 5.3-kilobase restriction endonuclease fragment isolated from Halobacterium halobium DNA, using a cloned cDNA fragment as the probe. Of the 1229 nucleotides whose sequence was determined in the genomic fragment, 786 correspond to the structural gene of bacteriorhodopsin, 360 are upstream from the initiator methionine codon, and 83 are downstream from the COOH terminus. The bacteriorhodopsin gene codes for a precursor sequence of 13 amino acids at the NH2 terminus, 248 amino acids that are present in the mature protein and an additional aspartic acid at the COOH terminus. This determination of the DNA sequence for an archaebacterial gene reveals that the standard genetic code is used; however, there is a marked preference for either G or C in the third codon position. The gene does not contain any intervening sequences and no prokaryotic promoter can be identified in the region immediately upstream from the structural gene. The bacteriorhodopsin mRNA contains at the 5' terminus only three nucleotides beyond the initiating AUG codon and this terminus can form a hairpin structure. Immediately downstream from this structure there is a sequence complementary to the 3' terminus of H. halobium 16S rRNA.

Amino Acid Sequence↗
PubMed1981

Bacteriorhodopsin: partial sequence of mRNA provides amino acid sequence in the precursor region.

mRNA for bacteriorhodopsin from Halobacterium halobium has been partially purified. By using this mRNA as template in the presence of reverse transcriptase RNA-dependent DNA nucleotidyltransferase and a 5'-[32P] synthetic oligodeoxyribonucleotide corresponding to amino acids 9-12 of bacteriorhodopsin as primer, we have isolated the major 5'-[32P]cDNA product, approximately 80 nucleotides long, and determined its sequence. Based on the cDNA sequence, the 5'-proximal sequence of bacteriorhodopsin mRNA is G-C-A-U-G-U-U-G-G-A-G-U-U-A-U-U-G-C-C-A-A-C-A-G-C-A-G-U-G-G-A-G-G-G-G-G-U-A-U-C -G-C-A-G-G-C-C-C-A-G-A-U-C-A-C-C-G-G-A-C-G-U-C-C-G. This includes the expected sequence for amino acids 1-8 and shows that bacteriorhodopsin is synthesized as a precursor that is at least 13 amino acids longer (Met-Leu-Glu-Leu-Leu-Pro-Thr-Ala-Val-Glu-Gly-Val-Ser) at the NH2 terminus. Agarose/urea gel electrophoresis of the partially purified mRNA showed several bands; of these, a major one hybridized with 5'-[32P]cDNA. These results suggest that the bacteriorhodopsin mRNA in the partially purified preparation is homogeneous in size and that it constitutes a substantial portion of the RNA preparation subjected to electrophoresis.

Amino Acid Sequence↗
PubMed1981

Lymphocyte aromatic hydrocarbon responsiveness in acute leukemia of childhood.

Aryl hydrocarbon hydroxylase (AHH) activity and inducibility were examined in mitogen-stimulated cultured lymphocytes from children with acute leukemia in remission, with nonleukemic malignancies, and with no family or personal history of malignant disease. Neither morphological differences nor differences in mitogen responsiveness were observed among the three sources of cells studied. Levels of constitutive and dibenzanthracene-induced AHH activity were found to be similar among the three groups by analysis of variance. However, when results were analyzed in terms of inducibility ratios, it was found that cells from leukemic children were significantly less inducible (p less than 0.005) than cells from unaffected children or children with nonleukemic malignancies. The reason for this difference became apparent when statistical criteria were employed for the pheontypic separation of individuals who were highly aromatic hydrocarbon responsive and minimally responsive. A significantly larger proportion (p less than 0.001) of leukemic children than unaffected children or children with nonleukemic malignancy were found to be minimally aromatic hydrocarbon responsive. Moreover, in patients with acute lymphoblastic leukemia relapsing while on therapy, longer durations of the first remission were correlated (r = 0.63, p less than 0.05) with the highly inducible AHH phenotype.

Acute Disease↗
PubMed1981

The lung in sickle cell disease: a clinical overview of common vascular, infectious, and other problems.

Acute pulmonary complications of sickle cell anemia are sickle cell lung disease and bacterial pneumonias. Chronic abnormalities in lung function include a restrictive ventilatory defect and perhaps increased venous admixture to the pulmonary circulation. Coexisting sarcoidosis may complicate sickle cell anemia and interact to potentiate sickling. Sickle cell lung disease, or acute "chest syndrome," occurs with greatest frequency in adults, is due primarily to pulmonary infarction, and may lead to cor pulmonale. On the other hand, bacterial pneumonia due to Streptococcus pneumoniae occurs with greater frequency in infancy and childhood. Mycoplasma and other organisms may also cause pneumonia with protracted illness and slow resolution. Bacteremia and meningitis may be further complications, particularly in children. Precise diagnosis of the acute febrile pulmonary episode is often difficult. In adults the illness is commonly self-limited. However, a vigorous diagnostic approach is warranted in all severely ill patients.

Adolescent↗
PubMed1980

Hybridization of tRNAs of Drosophila melanogaster to polytene chromosomes.

Highly purified tRNAs from Drosophila melanogaster were iodinated with 125I and hybridized to squashes of polytene chromosomes of Drosophila silivary glands followed by autoradiography to localize binding sites. Most tRNAs hybridize strongly to more than one site and weakly to one or more additional sites. The major sites for various tRNAs are the following: tRNA2Arg, 42A, 84F1,2; tRNA2Asp, 29DE; tRNA3Gly, 22BC, 35BC, 57BC, tRNA2Lys, 42A, 42E; tRNA5Lys, 84AB, 87B; tRNA2Met, 48B5-7, 72F1-2, 83F-84A; tRNA3Met, 46A1-2, 61D1-2, 70F1-2; tRNA4Ser, 12DE, 23E; tRNA7Ser, 12DE, 23E; tRNA3aVal, 64D; tRNA3bVal, 84d3-4, 92b1-9; tRNA4Val, 56D3-7, 70BC.

Animals↗
PubMed1980

Permanent gastrostomy as a solution to some nutritional problems in the elderly.

The number of elderly patients living in institutions is increasing. Many of them are unable to maintain an adequate nutritional status because of: 1) neurologic deficits that preclude normal swallowing; 2) obstruction of the upper gastrointestinal tract; or 3) a systemic disease that has produced profound anorexia. This report presents the data on 106 permanent-feeding gastrostomies, performed with low morbidity and low mortality. Use of a gastrointestinal anastomotic stapling device greatly facilitated the operation. The permanent gastrostomy offers an effective means of providing adequate nutrition for elderly patients who otherwise cannot maintain the necessary nutritional status.

Adult↗
PubMed1979

Isolation and characterization of recombinant DNA plasmids carrying Drosophila tRNA genes.

Recombinant plasmids carrying Drosophila melanogaster tRNA genes were constructed by ligation of HindIII-cleaved Drosophila DNA to HindIII cut pBR322 DNA. 90 clones were isolated that contained genes for one or more of eleven tRNAs. 43 of the plasmids were characterized by a number of methods: restriction nuclease digestion; agarose gel electrophoresis; hybridization with individual, purified, 125I-labelled Drosophila tRNA molecules and in situ hybridization to Drosophila chromosomes. The results show that several different tRNA genes have been isolated which code for single, specific isoacceptors. The DNAs from 8 plasmids each hybridize to single sites on Drosophila polytene chromosomes. In addition, the data show examples of two different plasmids hybridizing to different loci coding for the same tRNA; this means that we have isolated representatives of tRNA genes which map at widely separated points on the Drosophila genome.

Animals↗