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Biomedical subjects

D E Roberts

Publications and source records attributed to D E Roberts.

At least 73 records · Page 4Linked to original sources
PubMed1985

Fluid replacement during hypothermia.

Hypothermia produces acidosis, depressed cardiac function, hypovolemia and hypotension. This study was designed to examine the cardiovascular dynamics involved with restoration of the hypovolemia before rewarming. Mixed breed splenectomized adult dogs (n = 16) were anesthetized with pentobarbital and cooled to a right atrial temperature of 25 degrees C at a rate of 3 degrees C X h-1. The animals were maintained at 25 degrees C for 6 h and rewarmed at 3 degrees C X h-1. Group 1 was given no fluid, Group 2 was given saline (20% of plasma volume infused in 10 min). 2 h after reaching 25 degrees C and Group 3 received saline just prior to rewarming. The hematocrit was elevated in all groups (p less than 0.05) upon cooling, but did not differ between groups even after saline was given. Cardiac output (Co) at 25 degrees C was 35% of precooled values. Group 2 increased their Q by 15% with fluid and this Q was maintained at higher levels than Groups 1 or 3 for the next 4 h. Plasma volume, heart rate, and cardiac contractility returned to control levels upon rewarming, but Q remained low (less than 10%). The level of Q at the start of rewarming did not affect the final level of Q.

Acid-Base Equilibrium↗
PubMed1985

Induced vasodilation as a home treatment for Raynaud's disease.

Ten patients with Raynaud's disease treated themselves at home using induced vasodilation 3 times/day, every other day, for 18 treatment days. The patients, dressed in indoor clothing, immersed both hands in warm tap water (43-45 degrees C) for 8-10 min while exposed to naturally occurring ambient cold. Results of pre- and posttreatment cold exposures showed a significant mean increase in digital temperature of 3.4 degrees C (p less than .001). Conditioning therapy appears to be an effective, feasible alternative to drug or surgical therapy.

Adult↗
PubMed1984

New Tn10 derivatives for transposon mutagenesis and for construction of lacZ operon fusions by transposition.

We describe below several new variants of the tetracycline-resistance transposon Tn10 which are more useful than the wild-type transposon for many types of genetic and physical analysis of bacteria. These derivatives have one or more of the following new properties: (i) new drug resistance markers; (ii) high transposition frequencies; (iii) removal of the transposase gene to a position outside of the transposing segment; (iv) internal deletions which eliminate the ability of Tn10 to make adjacent deletion/inversions; or (v) addition of a trp-lac operon fusion segment just inside one terminus such that insertion can automatically generate a transcriptional fusion to the interrupted operon. Phage and plasmid vehicles carrying these new elements are described.

DNA Transposable Elements↗
PubMed1983

A simple oral antimicrobial regimen effective in severe chronic bronchial suppuration associated with culturable Haemophilus influenzae.

Three grams of amoxycillin administered twice daily for seven days, as an oral powder (Amoxil 3G sachets, Bencard) dispersed in water, to 17 patients with bronchiectasis resulted in striking clinical, spirometric and bacteriological improvement in 11 of 12 patients who were producing purulent sputum from which Haemophilus influenzae was cultured by a selective bacteriological technique (Roberts & Cole, 1980). In the five patients from whose sputum this organism could not be cultured, and in one from whom it could, there was no improvement. Untoward effects were limited to nausea in one patient and acceptability of the regimen by the remaining patients was unanimous. There was no evidence of accumulation of the drug in serum or sputum. The rapidity of effect and oral form of the treatment suggest that it may provide a simple out-patient regimen for chronic bronchial sepsis and severe purulent exacerbations of chronic bronchitis from which H. influenzae can be cultured.

Adult↗
PubMed1982

Effect of tissue anisotropy on extracellular potential fields in canine myocardium in situ.

The extracellular epicardial potential fields produced by simple depolarization waves in the in situ canine left ventricular myocardium were analyzed. A mathematical model that included tissue anisotrophy was developed to explain the observed fields. Values of intracellular (i), extracellular (o), longitudinal (l), and transverse (t) resistivity which gave the best fit between the model and experimental data were (in ohm-cm, mean +/- SD): rol = 852 +/- 232, rot = 1247 +/- 210, ril = 291 +/- 38, rit = 1677 +/- 331. The potential fields around simple stimulated waves on the epicardium can best be explained if the extracellular wavefront voltage is (mean +/- SD) 74 +/- 7 mV for a wave propagating parallel to the local muscle fibers, and 43 +/- 6 mV for a wave propagating perpendicular to these fibers. We conclude that the anisotrophy of the electrical conductivity of cardiac muscle has important effects on he propagation of waves of depolarization and on the potential fields produced by depolarization in the intact heart.

Action Potentials↗
PubMed1982

Induced vasodilation as treatment for Raynaud's disease.

We examined the efficacy of induced vasodilation as a treatment of idiopathic Raynaud's disease. Eight persons with Raynaud's disease and seven normal persons each received 27 simultaneous pairings of hand immersion in warm water (43 degrees C) for 10 minutes with exposure of the whole body to cold (0 degrees C). A second group of seven normal persons and nine persons with Raynaud's disease received no treatments. All subjects had cold test exposures (0 degrees C) at the start and end of the study. Subjects with Raynaud's disease who received treatments showed significant increases in digital temperatures (2.2 degrees C) during the cold test compared with the values of untreated subjects with Raynaud's disease (p less than 0.05); normal subjects who had received treatments showed no difference from those who had not. Digital temperatures of subjects with Raynaud's disease after treatment increased to levels approaching those of normal subjects, although they showed lower digital temperatures during initial exposure to cold (p less than 0.01). This therapy offers a practical alternative to traditional treatments.

Adult↗
PubMed1981

Genetic organization of transposon Tn10.

Transposon Tn10 is 9300 bp in length, with 1400 bp inverted repeats at its ends. The inverted repeats are structurally intact IS-like sequences (Ross et al., 1979). Analysis of deletion mutants and structural variants of Tn10, reported below, shows that the two IS10 segments contain all of the Tn10-encoded genetic determinants, both sites and functions, that are required for transposition. Furthermore, the two repeats (IS10-Right and IS10-Left) are not functionally equivalent: IS10-Right is fully functional and is capable by itself of promoting normal levels of Tn10 transposition; IS10-Left functions only poorly by itself, promoting transposition at a very low level when IS10-Right is inactivated. Complementation analysis shows that IS10-Right encodes at least one function, required for Tn10 transposition, which can act in trans and which works at the ends of the element. Also, all of the sites specifically required for normal Tn10 transposition have been localized to the outermost 70 bp at each end of the element; there is no evidence that specific sites internal to the element play an essential role. Finally, Tn10 modulates its own transposition in such a way that transposition-defective point mutants, unlike deletion mutants, are not complemented by functions provided in trans; and wild-type Tn10, unlike deletion mutants, is not affected by functions provided in trans from a "high hopper" Tn10 element.

Base Sequence↗
PubMed1981

Monoclonal antibody analysis of lipopolysaccharide from Neisseria gonorrhoeae and Neisseria meningitidis.

A hybridoma produced by the polyethylene glycol fusion of the NS-1 variant of the P3x63Ag8 BALB/c plasmacytoma to splenocytes harvested from a BALB/c mouse immunized with whole gonococci was found to be producing antibody to a common region on gonococcal lipopolysaccharide (LPS). Enzyme-linked immunosorbent assay inhibition systems were established by utilizing this antibody, designated 3F11, and 100% inhibition occurred with both LPS and the LPS-LPS and LPS-derived polysaccharides partially inhibited the enzyme-linked immunosorbent assay, whereas similar preparations isolated from Escherichia coli O:111, the J-5 mutant of this strain, and Salmonella minnesota Re595 failed to inhibit the assay. Studies utilizing whole gonococcal strains 4505 and the isogenic variant 4505r, which lacks both the LPS serotype and common determinants as inhibitors, demonstrated that the determinant recognized by the 3F11 antibody was present on the surface of 4505 and absent on 4505r. Inhibition studies were performed with beta-glucose, beta-galactose, D-glucosamine, D-galactosamine, heptose, 2-keto-3-deoxyoctanoate, N-acetylglucosamine, N-acetylgalactosamine, alpha-lactose, and beta-lactose. Complete inhibition of the enzyme-linked immunosorbent assay occurred with D-galactosamine, and partial inhibition was achieved with both alpha-lactose and beta-lactose. Based on these observations, the 3F11 antibody recognizes a site common to gonococcal LPS which is partially shared by meningococcal LPS. The chemical structure of the determinant appears to be a D-galactosamine-O-D-galactopyranosyl-(1-4)-D-glucopyranose. Additional specificity may be conferred by the steric relationship of the determinant on the intact LPS.

Antibodies, Bacterial↗
PubMed1980

Cold air inhalation and esophageal temperature in exercising humans.

This study was performed to examine the dynamics and localization of respiratory heat exchange in exercising humans breathing cold air. Eight normal individuals performed 10 min of exercise at 80% of their predicted Vo2max with inspired air at 22 degrees C, saturated with water vapor; or at -40 degrees C, dry. Rectal temperature (Tre) and temperature at various locations along the length of the esophagus were measured during the exercise period. Temperature in the lower third of the esophagus was in close agreement with Tre and was unaffected by the level of respiratory heat exchange. Upper esophageal temperature decreased substantially during exercise, the magnitude of the decrease being dependent upon proximity to intrathoracic airways and the level of respiratory heat exchange (RHE). We conclude that with high levels of RHE, the capacity of the nasopharynx and upper airways to completely condition inspired air is exceeded. As a consequence, heat and water exchange occur in regions of the respiratory tract not normally involved in this function.

Body Temperature↗
PubMed1979

Influence of cardiac fiber orientation on wavefront voltage, conduction velocity, and tissue resistivity in the dog.

When the canine epicardium is stimulated, the spread of epicardial excitation is 2.4 times faster parallel to the long axes of the cardiac fibers than perpendicular to them. Likewise, gross tissue resistivity is lower parallel to fibers by a factor of 3.2, and the voltage across the depolarization wave is approximately three times as great in the longitudinal direction. Equations are presented which relate these variables. Theoretical considerations confirm the experimental finding that the potentials around a wave of depolarization cannot be accounted for by the conventional hypothesis that the wavefront is a uniform double-layer current source.

Animals↗