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Biomedical subjects

J L Edwards

Publications and source records attributed to J L Edwards.

81 records · Page 5Linked to original sources
PubMed1967

Spectrophotometric Measurements of Phytochrome in vivo and Their Correlation with Photomorphogenic Responses of Phaseolus.

Direct in vivo measurements of phytochrome have been made in Phaseolus vulgaris by 2-filter difference spectrophotometry (Ratiospect). All measurements were made at 730 versus 800 nm and it is assumed that the Delta (DeltaOD) is directly proportional to the PFR concentration of phytochrome present. Dose response curves were determined for both physiological and spectrophotometric responses for red induction and far-red photoinactivation. For induction, saturation occurs at 100 mj/cm(2) and for inactivation at 30 mj/cm(2). The rate of hook opening and the physiological response measured 20 hours after induction are both shown to be directly proportional to the initial amount of PFR present spectrophotometrically. The sensitivity of the tissue correlates well with the absolute amount of phytochrome present, the inner portion of the hook having the maximum concentration of 0.042 Delta (DeltaOD)/g fresh weight. If the total reversible phytochrome concentration is reduced by exposure to red light and allowing PFR to decay out of the system the remaining sensitivity of the tissue is shown to be directly correlated with the amount of PR remaining in the tissue. PFR disappears rapidly in the dark at 25 degrees , and is not detectable after 6 hours. There is no indication that PFR reverts in the system to PR. At 4 degrees , PFR does not disappear measurably up to 1 hour and is nearly totally reversible to PR.

Journal Article↗
PubMed1965

Thermal inactivation characteristics of Bacillus subtilis spores at ultrahigh temperatures.

The thermal inactivation characteristics of Bacillus subtilis A spores suspended in skim milk with the use of large-scale ultrahigh temperature (UHT) processing equipment were investigated in terms of survival as measured with two plating media. Data on survival immediately after UHT treatments were recorded in temperature-survivor curves, time-survivor curves, and decimal reduction time (DRT) curves. The temperature-survivor curves emphasized that inactivation is accelerated more by increases in the treatment temperature than by increases in the exposure time. Time-survivor curves and DRT curves were not linear. Generally, exceedingly concave time-survivor curves were observed with the standard plating medium; however, only slightly concave curves were observed when CaCl(2) and sodium dipicolinate were added to the medium. For a given UHT sample, larger D values were obtained by use of the medium with the added CaCl(2) and sodium dipicolinate. The DRT curves of all data were concave and appeared to have two discrete slopes (z(D) values). The z(D) values observed in the upper UHT range (above 260 F; 127 C) were twice those observed at lower test temperatures.

Bacillus subtilis↗
PubMed1965

Heat injury of Bacillus subtilis spores at ultrahigh temperatures.

The following three criteria indicated that Bacillus subtilis A spores were injured, but not completely inactivated, by ultrahigh temperature treatment. (i) Significant reductions in survivors were observed when spores were enumerated with a standard medium but not when the medium contained added CaCl(2) and sodium dipicolinate. (ii) After a damaging heat treatment, more survivors were enumerated with the standard medium after incubation at 32 C than at 45 C, which was opposite to the result with untreated or slightly heated spores. (iii) Apparent numbers of survivors increased during the initial period of 3 C storage when enumerated with the standard medium at 45 C. No injury was evident when survivors were enumerated at either incubation temperature with the medium containing added CaCl(2) and sodium dipicolinate. Heat activation of the spores did not significantly influence the appearance of heat injury. The data suggested that the heat injury occurred in a germination system which was required in the absence of CaCl(2) and sodium dipicolinate.

Bacillus subtilis↗
PubMedDate not supplied

Prospective randomized comparison of esophageal variceal sclerotherapy agents: sodium tetradecyl sulfate versus sodium morrhuate.

We designed a prospective randomized study to evaluate differences in efficacy and complication rate between the two most commonly used sclerosing agents, sodium tetradecyl sulfate (STD) and sodium morrhuate (MOR). Of 41 patients with acute index variceal bleeding initially evaluated, 21 were randomized to receive 0.75% STD and 20 to receive 1.6% MOR diluted with 50% dextrose. Overall mortality for the STD group was 38% and that for the MOR group was 25% (NS). Control of acute bleeding was achieved in 86% of the STD patients and 90% of the MOR patients (NS). Overall, obliteration was achieved in only 33% of the STD group and 25% of the MOR group; but in those patients who remained in the study over 3 months, obliteration was achieved in 87 and 83%, respectively (NS). There was a trend toward higher rebleeding in the STD group compared with the MOR group (81% vs. 51%) (p = 0.078), but there was no significant difference between the STD and MOR patients with regard to transfusion requirements (8.4 units/patient vs. 8.7 units/patient), ulceration (53% vs. 40%), or stricture formation (9.5% vs. 0.0%). The results of this study suggest that STD and MOR are clinically equivalent sclerosing solutions, and that bias favoring use of one agent over the other may be unfounded.

Esophageal and Gastric Varices↗
PubMedDate not supplied

Quantitation of fluoride ion released sarin in red blood cell samples by gas chromatography-chemical ionization mass spectrometry using isotope dilution and large-volume injection.

A new method for measuring fluoride ion released isopropyl methylphosphonofluoridate (sarin, GB) in the red blood cell fraction was developed that utilizes an autoinjector, a large-volume injector port (LVI), positive ion ammonia chemical ionization detection in the SIM mode, and a deuterated stable isotope internal standard. This method was applied to red blood cell (RBC) and plasma ethyl acetate extracts from spiked human and animal whole blood samples and from whole blood of minipigs, guinea pigs, and rats exposed by whole-body sarin inhalation. Evidence of nerve agent exposure was detected in plasma and red blood cells at low levels of exposure. The linear method range of quantitation was 10-1000 pg on-column with a detection limit of approximately 2-pg on-column. In the course of method development, several conditions were optimized for the LVI, including type of injector insert, injection volume, initial temperature, pressure, and flow rate. RBC fractions had advantages over the plasma with respect to assessing nerve agent exposure using the fluoride ion method especially in samples with low serum butyrylcholinesterase activity.

Animals↗