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Biomedical subjects

D A Phillips

Publications and source records attributed to D A Phillips.

At least 91 records · Page 5Linked to original sources
PubMed1983

Effect of the host legume on acetylene reduction and hydrogen evolution by Rhizobium nitrogenase.

The relative efficiency (RE) of N(2) fixation (RE = 1 - [H(2) evolved in air]/[acetylene reduced]) was investigated in a Rhizobium strain lacking uptake hydrogenase activity (Hup(-)). Variation in RE of such strains presumably reflects changes in the electron allocation coefficient of nitrogenase. By artificially extending the normal dark period of 24-day-old Pisum sativum L. cv ;Alaska' inoculated with the Hup(-)R. leguminosarum strain 3740, reproducible changes in RE were obtained. The RE showed no change during a normal 8-hour night, but a significant increase in RE was measured after 20 hours in the dark. Upon returning to the normal 550 microEinsteins per square meter per second light treatment, RE declined to previous levels within 2 hours. If, after the 20-hour dark treatment, plants were returned to 90 or 190 microEinsteins per square meter per second or maintained in the dark, RE did not decline significantly. The RE varied inversely with changes in soluble sugar content of root nodules. A similar pattern of changes in RE during an extended dark period and subsequent light treatment was measured in 28-day-old Alaska peas and in the Hup(-)R. trifolii strain 162X99 in symbiosis with Trifolium subterraneum L. cv ;Woogenellup.' These results suggest that Rhizobium cells may produce short-term alterations in the electron allocation coefficient of nitrogenase in response to physiological changes. The observed changes in the bacterial RE favored N(2) reduction over proton reduction when soluble sugars provided by the host plant declined.

Journal Article↗
PubMed1983

Host Plant Cultivar Effects on Hydrogen Evolution by Rhizobium leguminosarum.

The effect of host plant cultivar on H(2) evolution by root nodules was examined in symbioses between Pisum sativum L. and selected strains of Rhizobium leguminosarum. Hydrogen evolution from root nodules containing Rhizobium represents the sum of H(2) produced by the nitrogenase enzyme complex and H(2) oxidized by any uptake hydrogenase present in those bacterial cells. Relative efficiency (RE) calculated as RE = 1 - (H(2) evolved in air/C(2) H(2) reduced) did not vary significantly among ;Feltham First,' ;Alaska,' and ;JI1205' peas inoculated with R. leguminosarum strain 300, which lacks uptake hydrogenase activity (Hup(-)). That observation suggests that the three host cultivars had no effect on H(2) production by nitrogenase. However, RE of strain 128C53 was significantly (P </= 0.05) greater in symbiosis with cultivar JI1205 than in root nodules of Feltham First. At a similar rate of C(2)H(2) reduction on a whole-plant basis, nearly 24 times more H(2) was evolved from the Feltham First/128C53 symbiosis than from the JI1205/128C53 association. Root nodules from the Alaska/128C53 symbiosis had an intermediate RE over the entire study period, which extended from 21 to 36 days after planting. Direct assays of uptake hydrogenase by two methods showed significant (P </= 0.05) host cultivar effects on H(2) uptake capacity of both strain 128C53 and the genetically related strain 3960. The (3)H(2) incorporation assay showed that strains 128C53 and 3960 in symbiosis with Feltham First had about 10% of the uptake hydrogenase activity measured in root nodules of Alaska or JI1205. These data are the first demonstration of significant host plant effects on rhizobial uptake hydrogenase in a single plant species.

Journal Article↗
PubMed1983

Allergy to laboratory animals: a retrospective and a prospective study.

Twenty four volunteers who had been allergic to laboratory animals for some years were examined by means of a questionnaire paying particular attention to symptoms associated with rats and by serological and skin tests with extracts of rat urine (retrospective study). Nasal and eye symptoms were reported by 21 and 16 individuals respectively: 13 had asthma. Positive skin tests and high levels of specific IgE antibody to rat urine extract were found in 17 of the more severely affected individuals and this group included 12 of those with asthma. Latent periods of work with animals before symptoms appeared varied from 0.5 to 12 years. Also 148 individuals were studied during their first year of work with animals (prospective study). Symptoms developing during the year were reported by 15%, asthma by 2%. IgE antibody levels to rat urine were raised in 40% of affected and 6% of the unaffected individuals but there was no significant correlation between symptoms and either antibody levels or positive skin tests. Allergic symptoms developing during the first year of postemployment were, on the whole, much milder than those seen in the retrospective study. A tentative conclusion is that most individuals who become allergic to laboratory animals develop the condition in a mild form during their first year of employment but it appears probable that atopic individuals, although having an equal chance of developing allergy as compared with non-atopic individuals, may eventually progress to a more severe form of the disease.

Allergens↗
PubMed1982

Water Stress Effects on Nitrogen Assimilation and Growth of Trifolium subterraneum L. Using Dinitrogen or Ammonium Nitrate.

The relative effects of water stress on growth parameters of subterranean clover (Trifolium subterraneum L. cv. Woogenellup) dependent on either N(2) or 8 millimolar NH(4)NO(3) for N were examined. Whole-plant carbon exchange rate (CER), acetylene reduction (AR), dry matter production, and Kjeldahl N accumulation were measured on uniform, intact swards of clover that were maintained under adequately watered conditions or were subjected to three cycles of water stress (leaf water potential </=-30 bar) over an 18-day period. In the absence or presence of water stress, growth rate, net N accumulation rate, and total N concentration of plants dependent on N(2) were 25 to 26, 45 to 50, and 20 to 21% less, respectively, than plants supplied with 8 millimolar NH(4)NO(3). The water stress treatment produced less than a 50% decrease in CER regardless of plant N source, a 90% inhibition of AR in plants dependent on N(2), and a 41% decline in dry matter production on both N sources. Water stress decreased reduced N accumulation 55% in N(2)-dependent plants and 50% in NH(4)NO(3)-dependent plants. Changes in growth and N accumulation caused a 10 to 11% decrease in total plant N concentration of water-stressed plants compared to adequately irrigated controls, but water stress decreased the N concentration of tissue synthesized during the 18-day treatment period in N(2)-grown plants more than in plants supplied 8 millimolar NH(4)NO(3). Thus, the relative effect of water stress on growth under the two N regimes was similar, but N accumulation by N(2)-dependent clover was inhibited to a slightly greater extent (P </= 0.001) than in NH(4)NO(3)-dependent plants.

Journal Article↗
PubMed1982

Effect of changes in shoot carbon-exchange rate on soybean root nodule activity.

The effect of short- and long-term changes in shoot carbon-exchange rate (CER) on soybean (Glycine max [L.] Merr.) root nodule activity was assessed to determine whether increases in photosynthate production produce a direct enhancement of symbiotic N(2) fixation. Shoot CER, root + nodule respiration, and apparent N(2) fixation (acetylene reduction) were measured on intact soybean plants grown at 700 microeinsteins per meter per second, with constant root temperature and a 14/10-hour light/dark cycle. There was no diurnal variation of root + nodule respiration or apparent N(2) fixation in plants assayed weekly from 14 to 43 days after planting. However, if plants remained in darkness following their normal dark period, a significant decline in apparent N(2) fixation was measured within 4 hours, and decreasing CO(2) concentration from 320 to 90 microliters CO(2) per liter produced diurnal changes in root nodule activity. Increasing shoot CER by 87, 84, and 76% in 2-, 3-, and 4-week-old plants, respectively, by raising the CO(2) concentration around the shoot from 320 to 1,000 microliters CO(2) per liter, had no effect on root + nodule respiration or acetylene-reduction rates during the first 10 hours of the increased CER treatment. When the CO(2)-enrichment treatment was extended in 3-week-old plants, the only measured parameter that differed significantly after 3 days was shoot CER. After 5 days of continuous CO(2) enrichment, root + nodule respiration and acetylene reduction increased, but such changes reflected an increase in root nodule mass rather than greater specific root nodule activity. The results show that on a 24-hour basis the process of symbiotic N(2) fixation in soybean plants grown under controlled environmental conditions functioned at maximum capacity and was not limited by shoot CER. Whether N(2)-fixation capacity was limited by photosynthate movement to root nodules or by saturation of metabolic processes in root nodules is not known.

Journal Article↗
PubMed1982

Balloon occlusion superior mesenteric arteriography for improved venous opacification: a clinical trial.

Balloon occlusion superior mesenteric arteriography and nonocclusion superior mesenteric arteriography were compared prospectively and retrospectively for adequacy of mesenteric and portal venous visualization. Prospective, occlusion studies in 20 patients were uniformly judged of excellent visual quality, while retrospectively, only 30% of nonocclusion studies from 20 other patients were considered optimal. In 10 of the patients who had balloon occlusion superior mesenteric arteriography, the procedure was preceded by a control nonocclusion superior mesenteric arteriography study. In only two (20%) patients was the nonocclusion study rated of excellent visual quality. Each study was assessed a rating of 0-3, according to how well the mesenteric and portal venous system visualized. Prospectively, all 20 balloon occlusion superior mesenteric arteriography studies were given the highest obtainable rating (3). Retrospectively, only six (30%) 20 nonocclusion superior mesenteric arteriography studies received a rating of 3; hence, 14 (70%) of the nonocclusion studies were rated less than excellent in visual quality when looked at retrospectively. No complications occurred with balloon occlusion superior mesenteric arteriography, and the occlusion procedure consistently gave excellent visualization of the mesenteric and portal venous anatomy.

Angiography↗
PubMed1981

Nitrogen Stress and Apparent Photosynthesis in Symbiotically Grown Pisum sativum L.

Pea plants (Pisum sativum L. cv. Alaska) were inoculated individually with one of 15 Rhizobium leguminosarum strains and grown under uniform environmental conditions in the absence of combined N. Differences in effectiveness of the Rhizobium strains produced plants with differing rates of whole plant apparent N(2) fixation and total N content at the same morphological stage of development. Plants were analyzed to determine interactions between N(2) fixation, N allocation, apparent photosynthesis, and growth. Total leaf N increased linearly with total N(2) fixation (R(2) = 0.994). The proportion of total N allocated to leaves, the per cent N content of individual leaves, and the photosynthetic efficiency of individual leaves showed a curvilinear response with increasing plant N content. Differences in allocation patterns of leaf N between plants with low and high N content resulted in differences in the relationship between total N content and plant dry weight. Results from this study show that N(2) fixation interacts with leaf photosynthetic efficiency and plant growth in a manner that is dependent upon the allocation of symbiotically fixed N.

Journal Article↗
PubMed1981

Carbon and nitrogen limitations on soybean seedling development.

Carbon and nitrogen limitations on symbiotically grown soybean seedlings (Glycine max [L.] Merr.) were assessed by providing 0.0, 1.0, or 8.0 millimolar NH(4)NO(3) and 320 or 1,000 microliters CO(2)/liter for 22 days after planting. Maximum development of the Rhizobium-soybean symbiosis, as determined by acetylene reduction, was measured in the presence of 1.0 millimolar NH(4)NO(3) under both levels of CO(2). Raising NH(4)NO(3) from 0.0 to 8.0 millimolar under 320 microliters CO(2)/liter increased plant dry weight by 251% and Kjeldahl N content by 287% at 22 days after planting. Increasing NH(4)NO(3) from 1.0 to 8.0 millimolar under 320 microliters CO(2)/liter increased total dry weight and Kjeldahl N by 100 and 168%, respectively, on day 22. Raising CO(2) from 320 to 1,000 microliters CO(2)/liter during the same period had no significant effect on Kjeldahl N content of plants grown with 0.0 or 1.0 millimolar NH(4)NO(3). The maximum CO(2) treatment effects were observed in plants supplied with 8.0 millimolar NH(4)NO(3), where dry weight and Kjeldahl N content were increased 64% and 20%, respectively. An increase in shoot CO(2)-exchange rate associated with the CO(2)-enrichment treatment was reflected in a significant increase in leaf dry weight and starch content for plants grown with 1,000 microliters CO(2)/liter under all combined N treatments. These data show directly that seedling growth in symbiotically grown soybeans was limited primarily by N availability. The failure of the CO(2)-enrichment treatment to increase total plant N significantly in Rhizobium-dependent plants indicates that root nodule development and functioning in such plants was not limited by photosynthate production.

Journal Article↗
PubMed1981

Therapeutic embolization of the gastroduodenal artery in hepatic artery infusion chemotherapy.

Transcatheter embolization of the gastroduodenal artery with Gelfoam was performed in 12 patients undergoing percutaneous hepatic artery catheterization for infusion chemotherapy of metastatic liver disease. The purpose of the embolization was to prevent chemotherapeutic drugs from reaching the stomach and duodenum and thereby inducing gastrointestinal toxicity in patients in whom the catheter tip could not be satisfactorily positioned beyond the gastroduodenal origin. Embolization proved safe and effective in eight cases. Three other patients experienced clinical problems that may or may not have been related to embolization. The final patient had a significant complication (necrosis of the pancreatic head and gastric mucosa) that was felt to be directly related to the embolization. Transcatheter gastroduodenal occlusion may help reduce gastrointestinal toxicity of intraarterial infusion chemotherapy. However, it may on occasion be associated with significant complications, particularly in patients who are debilitated due to metastatic disease.

Adult↗
PubMed1980

Carbon exchange rates of shoots required to utilize available acetylene reduction capacity in soybean and alfalfa root nodules.

The CO(2)-exchange rate required to make full use of available N(2)-fixation capacity, measured as acetylene reduction, was determined in soybean and alfalfa. Carbohydrates of root systems were depleted during a 40-hour dark treatment; then plants were exposed to a 24-hour light period during which different CO(2)-exchange rates were maintained with various CO(2) concentrations. In three- and four-week-old soybeans and four-week-old alfalfa plants, acetylene-reduction capacity was used fully with CO(2)-exchange rates as low as 10 milligrams CO(2) per plant per hour. In six-week-old alfalfa plants, however, acetylene reduction rates increased linearly, and apparent N(2)-fixation capacity was not used fully when CO(2)-exchange rates were higher than 40 milligrams CO(2) per plant per hour. Under the conditions established, the energy cost of N(2) fixation, measured as Delta(respiration of roots + nodules)/Deltaacetylene reduction over dark-treatment values, was 0.453 milligrams CO(2) per micromole C(2)H(4) for all rates of acetylene reduction and for both ages of soybean and alfalfa plants. Thus, root-plus-nodule respiration was not promoted by higher rates of apparent photosynthesis after C(2)H(2)-reduction capacity became saturated, and all available capacity for apparent N(2) fixation had the same energy requirement.

Journal Article↗
PubMed1980

Effect of irradiance on development of apparent nitrogen fixation and photosynthesis in soybean.

Soybeans grown with 2 millimolar NO(3) (-), which optimized apparent N(2) fixation by Rhizobium symbionts, showed significantly different rates of apparent photosynthesis and C(2)H(2) reduction during seedling development at two irradiances. Those physiological processes were lower for several weeks in plants grown at 1,500 microeinsteins per meter(2) per second than in those exposed to 700 microeinsteins per meter(2) per second. The irradiance-induced retardation was evident in short-term rates of apparent photosynthesis and N(2) fixation, as well as in measures of dry matter and total N accumulation. In spite of their previously inhibited development, plants grown at 1,500 microeinsteins per meter(2) per second were indistinguishable by day 28 from those exposed to 700 microeinsteins per meter(2) per second in terms of whole-shoot CO(2)-exchange rate; by day 35 they were identical in terms of whole-plant C(2)H(2)-reduction rate. On day 38 there was no significant difference in dry weight or N content between treatments. Shifting plants between irradiance treatments on day 21 showed that the higher irradiance also had a short-term inhibitory effect on C(2)H(2) reduction. The fact that 16 millimolar NO(3) (-) prevented the continuous exposure to 1,500 microeinsteins per meter(2) per second from inhibiting apparent photosynthesis suggested that seedlings grown on 2 millimolar NO(3) (-) with Rhizobium were N-limited. Although rates of apparent photosynthesis were similar by day 28, the additional week required to produce equal rates of apparent N(2) fixation between irradiance treatments showed that physiological adaptations of shoots, as well as photosynthesis per se, can affect root nodule activity.

Journal Article↗
PubMed1979

Effect of Bentazon, a Hill Reaction Inhibitor, on Symbiotic Nitrogen-fixing Capability and Apparent Photosynthesis.

Symbiotic associations of bean plants (Phaseolus vulgaris L. cv. Blue Lake) and Rhizobium phaseoli strain 127K17 were treated with the Hill reaction inhibitor bentazon (3-isopropyl-1 H-2,1,3-benzothiadiazin-4-(3H)-one-2,2-dioxide). Plants receiving foliar and root treatments of 1.8 kilograms per hectare bentazon were assayed at 6 hour intervals for N(2)-fixing capacity by measuring C(2)H(2)-dependent C(2)H(4) production and H(2) evolution and for CO(2) exchange rates. In foliar treated plants greatest measured inhibition of CO(2) exchange rates and N(2)-fixing capacity occurred 6 and 12 hours after treatment, respectively. In root-treated plants maximum inhibition of both processes was delayed by 6 hours, and was less severe than in foliar treated plants. Nitrogen-fixing capacity and CO(2) exchange rate recovered to control levels in all plants. Application of higher rates of bentazon resulted in greater inhibition of CO(2) exchange rate and N(2)-fixing capacity. Inhibition of the two processes was positively correlated (r = 0.985). The results indicate that inhibition of N(2)-fixing capacity was not caused by bentazon directly, but indirectly through limiting the availability of photosynthate to support root nodule activity.

Journal Article↗
PubMed1979

Variation in nitrogenase and hydrogenase activity of alaska pea root nodules.

Hydrogenase activity of root nodules in the symbiotic association between Pisum sativum L. and Rhizobium leguminosarum was determined by incubating unexcised nodules with tritiated H(2) and measuring tissue HTO. Hydrogenase activity saturated at 0.50 millimolar H(2) and was not inhibited by the presence of 0.10 atmosphere C(2)H(2), which prevented H(2) evolution from nitrogenase. Total H(2) production from nitogenase was estimated as net H(2) evolution in air plus H(2) exchange in 0.10 atmosphere C(2)H(2). Although such an estimate of nitrogenase function may not be quantitatively exact, due to uncertain relationships between H(2) exchange and H(2) uptake activity of hydrogenase, differences observed in H(2) exchange under various conditions represent an indication of changes in hydrogenase activity. Hydrogenase activity was lower in associations grown under higher photosynthetic photon flux densities and decreased relative to total H(2) production by nitrogenase. Total H(2) production and hydrogenase activity were maximum 28 days after planting. Thereafter, hydrogenase activity and H(2) production declined, but the potential proportion of nitrogenase-produced H(2) recovered by the uptake hydrogenase system increased. Of five R. leguminosarum strains tested two possessed hydrogenase activity. Strains which had the potential to reassimilate H(2) had significantly higher rates of N(2) reduction than those which did not exhibit hydrogenase activity.

Journal Article↗
PubMed1978

Impedance plethysmography: its limitations as a substitute for phlebography.

Impedance plethysmography (IPG) was used to study 132 legs: 100 in normal volunteers not subjected to radiocontrast phlebography, seven in patients whose limbs were phlebographically normal, and 25 proven by phlebography to have deep venous thrombosis (DVT). There were no false positive IPG results when a maximum venous outflow of 0.2% was the discriminant. However, in the 25 legs with thrombosis in calf, popliteal, femoral, and iliac veins, clots were not detected by IPG in 44--51% of legs, depending upon the discriminant. These results, which are in agreement with data reported elsewhere, indicate that it is reasonable to use the IPG method as the sole diagnostic maneuver when the test result is clearly abnormal, but that if the result is not abnormal, a radiocontrast phlebogram is necessary.

Adult↗
PubMed1978

Interdependence of Nitrogen Nutrition and Photosynthesis in Pisum sativum L: I. Effect of Combined Nitrogen on Symbiotic Nitrogen Fixation and Photosynthesis.

Photosynthesis, primary productivity, N content, and N(2) fixation were determined as a function of applied NH(4) (+) in peas (Pisum sativum L. cv. Alaska) which were inoculated or not inoculated with Rhizobium leguminosarum. Cabon dioxide exchange rate (CER) increased 10-fold, total N content 7-fold, and total dry weight 3-fold in 26-day-old uninoculated plants as applied NH(4) (+) was increased from 0 to 16 millimolar. In inoculated plants of the same age CER and dry weight were maximal at 2 millimolar NH(4) (+), and total N content increased between 0 and 2 millimolar NH(4) (+) but did not change significantly with higher NH(4) (+) applications. Per cent N content of uninoculated plants was significantly lower than that of inoculated plants except at the highest NH(4) (+) concentration (16 millimolar). Symbiotic N(2) fixation by inoculated plants was maximal in peas grown with 2 millimolar NH(4) (+); and apparent relative efficiency of N(2) fixation, calculated from C(2)H(2) reduction and H(2) evolution, was maximal in the 2 to 4 millimolar NH(4) (+) concentration range. The capacity to fix N(2) through the Rhizobium-legume symbiosis significantly enhanced the rate and efficiency of photosynthesis and plant N content when NH(4) (+) concentration in the nutrient solution was below 8 millimolar. Above 8 millimolar NH(4) (+) concentration uninoculated plants had greater CER, N content, and dry weight.

Journal Article↗
PubMed1978

Interdependence of Nitrogen Nutrition and Photosynthesis in Pisum sativum L: II. Host Plant Response to Nitrogen Fixation by Rhizobium Strains.

Physiological responses to infection by strains of Rhizobium leguminosarum which differed in their capacity to reduce N(2) were determined in 26-day-old pea plants (Pisum sativum L. cv. Alaska) grown under uniform environmental conditions in the absence of combined N. The highest N(2) reduction rates, calculated from H(2) evolution and C(2)H(2)-dependent C(2)H(4) production measurements, were approximately 6-fold greater than the lowest. Higher N(2) fixation rates were associated with greater CO(2) exchange rates (R(2) = 0.92) and carboxylation efficiency (R(2) = 0.99). Increases in the apparent relative efficiency of N(2) fixation [1-(H(2) evolved in air/C(2)H(2) reduced)] (acteroid efficiency) were associated with increases in whole-plant N(2) fixation efficiency (N(2)/CO(2) reduction ratio) (R(2) = 0.95). Whole-plant dry weight and total N content were related by regression analysis (R(2) = 0.98); both parameters were enhanced by increased N(2) fixation in a manner analogous to previously reported increases caused by greater external applications of NH(4) (+). These data reveal that photosynthetic parameters in genetically uniform host plants grown under identical environmental conditions are affected by N(2) fixation characteristics of the rhizobial symbiont. The measured efficiencies of micro- and macrosymbiont are directly related under uniform environments.

Journal Article↗
PubMed1978

Effect of nitroprusside on regional myocardial blood flow in coronary artery disease. Results in 25 patients and comparison with nitroglycerin.

The effect of nitroprusside on regional myocardial specific blood flow (RMBF) was evaluated in 25 patients with the xenon-133 washout technique. Six patients were normal (group 1), six patients had coronary artery disease without collateral vessels (group 2), and thirteen patients had coronary artery disease with collateral vessels (group 3). In group 1, RMBF was unchanged following nitroprusside. RMBF decreased significantly in both group 2 and group 3, including seven patients in group 3 with high-grade collateral vessels. The results were compared to the effect of nitroglycerin in 31 patients previously studied using the same technique. Mean arterial pressure and pressure-rate product were comparably reduced by both drugs. In contrast to the findings with nitroprusside, after sublingual nitroglycerin RMBF decreased markedly in normals and increased in patients with coronary artery disease and high-grade collaterals. The data suggest that nitroprusside may primarily affect resistance vessels within the coronary circulation, as opposed to the effect of nitroglycerin on conductance vessels. Thus, nitroprusside could result in redistribution of blood flow away from ischemic areas and potentially increase ischemic injury in some patients with coronary artery disease.

Blood Pressure↗