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Biomedical subjects

D A Phillips

Publications and source records attributed to D A Phillips.

At least 55 records · Page 3Linked to original sources
PubMed1992

Traumatic aortic tear: screening with chest CT.

Dynamic chest computed tomography (CT) was performed in 326 patients who had undergone abdominal CT for blunt trauma to evaluate the role of chest CT in screening for thoracic aortic injury. Evidence of mediastinal bleeding constituted an abnormal CT examination. The results were correlated with those from aortography in 131 patients. The chest radiographs were abnormal in 127 patients (39%). Of those 127 patients, chest CT scans were abnormal in 39 patients; an aortic tear was present in eight of those patients (21%). The remaining 88 patients had normal CT scans and no aortic injury. Of the 199 patients with normal radiographs, 15 had abnormal CT scans and 184 had normal CT scans and no aortic injury. There were no false-negative CT scans; 79% of patients with normal CT scans had false-positive chest radiographs. With CT there was a significant improvement over plain radiography in specificity, accuracy, and predictive value of positive results. If chest CT were used as an adjunct to chest radiography in the screening for traumatic aortic tear, the need for aortography would decrease by 56%. Chest CT can safely help discriminate candidates for aortography, is cost-effective, and, in hemodynamically stable patients, should be incorporated in the screening for traumatic aortic tear.

Aorta, Thoracic↗
PubMed1992

Beyond beliefs: parent and child behaviors and children's perceived academic competence.

Examined the relations of parent and child behaviors with children's perceptions of their academic competence. 74 high-achieving third-grade children, with varying levels of perceived academic competence, were observed working with mothers and fathers both on solvable tasks (Period 1) and during a period that included some unsolvable tasks (Period 2). Results indicated that children's perceived academic competence was positively related to father warmth, both at Period 1 and at Period 2. Children's perceived academic competence was also positively related to their own behavior when working with fathers at Period 2. Specifically, children with higher perceived academic competence showed more emotional restraint and were more self-reliant when working on tasks at Period 2 than were children with lower perceived academic competence. The results indicate that there are systematic, observable correlates of children's self-reports of their perceived academic competence.

Achievement↗
PubMed1991

Gastric tonometry and venous oximetry in cardiac surgery patients.

OBJECTIVE: To determine the relationship between gastric intramucosal pH and several other indices of splanchnic perfusion in patients undergoing cardiopulmonary bypass. DESIGN: Prospective, single-arm study. SETTING: University Hospital. METHODS: Elective cardiac surgery patients (n = 8), free of hepatic disease, were studied. Before anesthetic induction, a triple-lumen, heparin-bonded fiberoptic catheter was inserted into the hepatic vein under fluoroscopic guidance. An identical catheter was inserted into the pulmonary artery. After endotracheal intubation, a nasogastric tube modified to permit measurement of gastric intramucosal pH was inserted into the stomach. Systemic oxygen delivery (DO2), and arterial, mixed venous, hepatic venous, and femoral venous blood gases and lactate concentrations were recorded at the following times: immediately before induction of anesthesia (time 1); during atrial cannulation (time 2); after 30 mins of hypothermic cardiopulmonary bypass (time 3); 15 mins after termination of cardiopulmonary bypass (time 4); and 1 hr after arrival in the ICU (time 5). Hepatic venous hemoglobin saturation (SO2) and mixed venous hemoglobin saturation (SvO2) were monitored continuously from times 1 to 5. Gastric intramucosal pH was recorded at times 2, 3, 4, and 5. The hepatic catheter was removed as soon as the last samples were collected in the ICU. RESULTS: The square of the weighted mean correlation coefficients (rw)2 for gastric intramucosal pH vs. hepatic venous lactate concentrations, gastric intramucosal pH vs. hepatic venous PO2, and gastric intramucosal pH vs. hepatic venous pH were (rw)2 = .50, (rw)2 = .58, and (rw)2 = .32, respectively. Systemic DO2, hepatic venous lactate concentrations, hepatic venous PO2, and hepatic venous pH were significant determinants in the multiple regression model for gastric intramucosal pH (r2 = .89). There were significant differences between SvO2 and hepatic venous SO2 at times 4 and 5. CONCLUSION: Gastric intramucosal pH may provide a minimally invasive way to monitor the adequacy of splanchnic DO2 in patients undergoing cardiopulmonary bypass. Additional data are necessary to determine whether low gastric intramucosal pH is truly a marker of supply-dependent oxygen uptake across the hepatosplanchnic vascular bed under these conditions.

Aged↗
PubMed1991

Flavonoids Released Naturally from Alfalfa Seeds Enhance Growth Rate of Rhizobium meliloti.

Alfalfa (Medicago sativa L.) releases different flavonoids from seeds and roots. Imbibing seeds discharge 3',4',5,7-substituted flavonoids; roots exude 5-deoxy molecules. Many, but not all, of these flavonoids induce nodulation (nod) genes in Rhizobium meliloti. The dominant flavonoid released from alfalfa seeds is identified here as quercetin-3-O-galactoside, a molecule that does not induce nod genes. Low concentrations (1-10 micromolar) of this compound, as well as luteolin-7-O-glucoside, another major flavonoid released from germinating seeds, and the aglycones, quercetin and luteolin, increase growth rate of R. meliloti in a defined minimal medium. Tests show that the 5,7-dihydroxyl substitution pattern on those molecules was primarily responsible for the growth effect, thus explaining how 5-deoxy flavonoids in root exudates fail to enhance growth of R. meliloti. Luteolin increases growth by a mechanism separate from its capacity to induce rhizobial nod genes, because it still enhanced growth rate of R. meliloti lacking functional copies of the three known nodD genes. Quercetin and luteolin also increased growth rate of Pseudomonas putida. They had no effect on growth rate of Bacillus subtilis or Agrobacterium tumefaciens, but they slowed growth of two fungal pathogens of alfalfa. These results suggest that alfalfa can create ecochemical zones for controlling soil microbes by releasing structurally different flavonoids from seeds and roots.

Journal Article↗
PubMed1991

Release and Modification of nod-Gene-Inducing Flavonoids from Alfalfa Seeds.

Traces of luteolin, an important rhizobial nod gene inducer in Rhizobium meliloti, are released by alfalfa (Medicago sativa L.) seeds, but most luteolin in the seed exudate is conjugated as luteolin-7-O-glucoside (L7G). Processes affecting the production of luteolin from L7G in seed exudate are poorly understood. Results from this study establish that (a) seed coats are the primary source of flavonoids, including L7G, in seed exudate; (b) these flavonoids exist in seeds before imbibition; and (c) both the host plant and the symbiotic R. meliloti probably can hydrolyze L7G to luteolin. Glycolytic cleavage of L7G is promoted by glucosidase activity released from sterile seeds during the first 4 hours of imbibition. Thus, L7G from imbibing alfalfa seeds may serve as a source of the nod-gene-inducing luteolin and thereby facilitate root nodulation by R. meliloti.

Journal Article↗
PubMed1991

Anthocyanidins and Flavonols, Major nod Gene Inducers from Seeds of a Black-Seeded Common Bean (Phaseolus vulgaris L.).

Eleven compounds released from germinating seeds of a black-seeded bean (Phaseolus vulgaris L., cv PI165426CS) induce transcription of nod genes in Rhizobium leguminosarum biovar phaseoli. Aglycones from 10 of those compounds were identified by spectroscopic methods (ultraviolet/visible, proton nuclear magnetic resonance, and mass spectroscopy), and their biological activities were demonstrated by induction of beta-galactosidase activity in R. leguminosarum strains containing nodA-lacZ or nodC-lacZ fusions controlled by R. leguminosarum biovar phaseoli nodD genes. By making comparisons with authentic standards, the chemical structures for aglycones from the 10 molecules were confirmed as being anthocyanidins (delphinidin, petunidin, and malvidin) and flavonols (myricetin, quercetin, and kaempferol). All anthocyanidins and flavonols had 3-O-glycosylation and free hydroxyl groups at the 4', 5, and 7 positions. Hydrolysis experiments showed that the mean concentration required for half-maximum nod gene induction (I(50)) by the 10 glycosides was about half that of the corresponding aglycones. The mean I(50) value for the three anthocyanidins (360 nanomolar) was less (P </= 0.05) than that of the three flavonol aglycones (980 nanomolar). Each seed released approximately 2500 nanomoles of anthocyanidin and 450 nanomoles of flavonol nod gene inducers in conjugated forms during the first 6 hours of imbibition. Based on amounts and activities of the compounds released, anthocyanins contributed approximately 10-fold more total nod-inducing activity than flavonol glycosides. These anthocyanidins from bean seeds represent the first nod-inducing compounds identified from that group of flavonoids.

Journal Article↗
PubMed1991

Rhizobium nod Gene Inducers Exuded Naturally from Roots of Common Bean (Phaseolus vulgaris L.).

Four compounds exuded from young roots of a black-seeded bean (Phaseolus vulgaris L., cv PI165426CS) induce transcription of nod genes in Rhizobium leguminosarum biovar phaseoli. The three most active nod gene inducers were identified by spectroscopic methods (ultraviolet/visible absorbance, proton nuclear magnetic resonance, and mass spectrometry) as being eriodictyol (5,7,3',4' -tetrahydroxyflavanone), naringenin (5,7,4' -trihydroxyflavanone), and a 7-O-glycoside of genistein (5,7,4' -trihydroxyisoflavone). Comparisons with authentic standards verified the chemical structures of the aglycones and their capacity to induce beta-galactosidase activity in R. leguminosarum strains containing nodA-lacZ or nodC-lacZ fusions controlled by R. leguminosarum biovar phaseoli nodD genes. Roots of 9-day-old seedlings released 42, 281, and 337 nanomoles per plant per day of genistein, eriodictyol, and naringenin, respectively. Genistein and naringenin induced higher maximum beta-galactosidase activities and required lower concentrations for half-maximum induction than eriodictyol. Comparing the nod gene-inducing activity of seed rinses with root exudate from PI165426CS bean showed that root flavonoids were released at about 6% the rate of those from seeds on a molar basis, but on average the individual compounds from roots were approximately three times more active than nod gene inducers from seeds.

Journal Article↗
PubMed1991

Flavonoids released naturally from alfalfa promote development of symbiotic glomus spores in vitro.

Because flavonoids from legumes induce transcription of nodulation genes in symbiotic rhizobial bacteria, it is reasonable to test whether these compounds alter the development of vesicular-arbuscular mycorrhizal (VAM) fungi that infect those plants. Quercetin-3-O-galactoside, the dominant flavonoid released naturally from alfalfa (Medicago sativa L.) seeds, promoted spore germination of Glomus etunicatum and Glomus macrocarpum in vitro. Quercetin produced the maximum increases in spore germination, hyphal elongation, and hyphal branching in G. etunicatum at 1 to 2.5 muM concentrations. Two flavonoids exuded from alfalfa roots, 4',7-dihydroxyflavone and 4',7-dihydroxyflavanone, also enhanced spore germination of this fungal species. Formononetin, an isoflavone that is released from stressed alfalfa roots, inhibited germination of both Glomus species. These in vitro results suggest that plant flavonoids may facilitate or regulate the development of VAM symbioses and offer new hope for developing pure, plant-free cultures of VAM fungi.

Journal Article↗
PubMed1990

Clinical and subclinical Barmah Forest virus infection in Queensland.

Barmah Forest virus is a mosquito-borne agent (alphavirus) reported to cause both clinical and subclinical infections in New South Wales. This report describes 29 cases of clinical Barmah Forest virus infection diagnosed between July 1988 and March 1989 (21 from Queensland, six from New South Wales and two from Victoria) and provides evidence of extensive subclinical infection with this virus (0.23% of the population per annum) throughout Queensland. It also includes a description of the first isolation of Barmah Forest virus from a patient. Data obtained in the course of the study suggest that Barmah Forest virus infections may not be diagnosed correctly in many instances because of the similarity of the symptoms of this disease to those of epidemic polyarthritis and the small number of laboratories providing the necessary serological services.

Adolescent↗
PubMed1990

Nuclear incorporation of [adenine 14C]NAD is altered by compounds which affect poly(ADP-ribose) formation.

The use of a DNA alkylating agent, which induces poly(ADP-ribose) formation, has been employed to study the incorporation of [adenine 14C]NAD into pea root meristem nuclei, which is a prerequisite for poly(ADP-ribose) synthesis. The incorporation of [adenine 14C]NAD is significantly reduced when the poly(ADP-ribose)polymerase inhibitors, 7-methylxanthine and 3-methoxybenzamide are present and this incorporation is augmented when the DNA alkylating agent methyl methanesulfonate is added. Such information supports the hypothesis that poly(ADP-ribose) may be involved in the cell cycle regulation of pea root meristem nuclei.

Adenine↗
PubMed1990

Chrysoeriol and Luteolin Released from Alfalfa Seeds Induce nod Genes in Rhizobium meliloti.

Flavonoid signals from alfalfa (Medicago sativa L.) seed and root exudates induce transcription of nodulation (nod) genes in Rhizobium meliloti. The flavone luteolin previously was isolated from alfalfa seeds by other workers and identified as the first nod gene inducer for R. meliloti. Our recent study of ;Moapa 69' alfalfa root exudates found no luteolin but did identify three other nod gene inducers: 4,4'-dihydroxy-2'-methoxychalcone, 4',7-dihydroxyflavone, and 4',7-dihydroxyflavanone. The goal of the current study was to identify and quantify nod gene-inducing flavonoids that may influence Rhizobium populations around a germinating alfalfa seed. Aqueous rinses of Moapa 69 alfalfa seeds were collected and assayed for induction of a nodABC-lacZ fusion in R. meliloti. During the first 4 hours of imbibition, total nod gene-inducing activity was released from seeds at 100-fold higher rates than from roots of 72-hour-old seedlings. Five flavonoids were purified and identified by spectroscopic analyses (ultraviolet/visible absorbance, proton nuclear magnetic resonance, and mass spectroscopy) and comparison with authentic standards. Two very active nod gene-inducing flavonoids, chrysoeriol (3'-methoxyluteolin) and luteolin, were identified in seed rinses. Luteolin required a higher concentration (18 nanomolar) than chrysoeriol (5 nanomolar) for half-maximum induction of nodABC-lacZ in R. meliloti, and both were less active than 4,4'-dihydroxy-2'-methoxychalcone (2 nanomolar) from root exudates. Seeds exuded three other luteolin derivatives: luteolin-7-O-glucoside, 5-methoxyluteolin, and 3',5-dimethoxyluteolin. Their combined quantities were 24-fold greater than that of luteolin plus chrysoeriol. Most nod gene-inducing activity of these luteolin derivatives apparently is associated with degradation to luteolin and chrysoeriol. However, their presence in large quantities suggests that they may contribute significantly to nod gene-inducing activity in the soil. These results indicate the importance of germinating seeds as a source of nod gene-inducing flavonoids and emphasize the quantitative and qualitative differences in those compounds around the seed and root.

Journal Article↗
PubMed1990

Development and Partial Characterization of Nearly Isogenic Pea Lines (Pisum sativum L.) that Alter Uptake Hydrogenase Activity in Symbiotic Rhizobium.

Some Rhizobium bacteria have H(2)-uptake (Hup) systems that oxidize H(2) evolved from nitrogenase in leguminous root nodules. Pea (Pisum sativum L.) cultivars ;JI1205' and ;Alaska' produce high Hup (Hup(++)) and moderate Hup (Hup(+)) phenotypes, respectively, in Rhizobium leguminosarum 128C53. The physiological significance and biochemical basis of this host plant genetic effect are unknown. The purpose of this investigation was to advance basic Hup studies by developing nearly isogenic lines of peas that alter Hup phenotypes in R. leguminosarum strains containing hup genes. Eight pairs of nearly isogenic pea lines that produce Hup(++) and Hup(+) phenotypes in R. leguminosarum 128C53 were identified in 173 F(2)-derived F(6) families produced from crosses between JI1205 and Alaska. Tests with the pea isolines and three strains of hup-containing R. leguminosarum showed that the isolines altered Hup activity significantly (P </= 0.05) in 19 of 24 symbiotic combinations. Analyses of Hup phenotypes in F(6) families, the F(1) population, and two backcrosses suggested involvement of a single genetic locus. Three of the eight pairs of isolines were identified as being suitable for physiological studies, because the two lines in each pair showed similar growth, N assimilation, and flowering traits under nonsymbiotic conditions. Tests of those lines under N(2)-dependent conditions with isogenic Hup(+) and negligible Hup (Hup(-)) mutants of R. leguminosarum 128C53 showed that, in symbioses with Hup(+) rhizobia, two out of three Hup(++) pea lines decreased N(2) fixation relative to Hup(+) peas. In one of those cases, however, the Hup(++) plant line also decreased fixation by Hup(-) rhizobia. When results were averaged across all rhizobia tested, Hup(+) pea isolines had 8.2% higher dry weight (P </= 0.05) and fixed 12.6% more N(2) (P </= 0.05) than Hup(++) isolines. Pea lines described here may help identify host plant factors that influence rhizobial Hup activity and should assist in clarifying how Hup systems influence other physiological processes.

Journal Article↗
PubMed1990

Concurrent Synthesis and Release of nod-Gene-Inducing Flavonoids from Alfalfa Roots.

Flavonoid signals from alfalfa (Medicago sativa L.) induce transcription of nodulation (nod) genes in Rhizobium meliloti. Alfalfa roots release three major nod-gene inducers: 4',7-dihydroxyflavanone, 4',7-dihydroxyflavone, and 4,4'-dihydroxy-2'-methoxychalcone. The objective of the present study was to define temporal relationships between synthesis and exudation for those flavonoids. Requirements for concurrent flavonoid biosynthesis were assessed by treating roots of intact alfalfa seedlings with [U-(14)C]-l-phenylalanine in the presence or absence of the phenylalanine ammonia-lyase inhibitor l-2-aminoxy-3-phenylpropionic acid (AOPP). In the absence of AOPP, each of the three flavonoids in exudates contained (14)C. In the presence of AOPP, (14)C labeling and release of all the exuded nod-gene inducers were reduced significantly. AOPP inhibited labeling and release of the strongest nod-gene inducer, methoxychalcone, by more than 90%. Experiments with excised cotyledons, hypocotyls, and roots incubated in solution showed that the flavonoids could be synthesized in and released from each organ. However, the ratio of the three flavonoids in exudates from intact plants was most similar to the ratio recently synthesized and released from excised roots. A portion of recently synthesized flavonoid aglycones was found conjugated, presumably as glycosides, in root extracts and may have been involved in the release process. Data from root extracts showed that formononetin, an isoflavonoid which does not induce nod genes, was present in conjugated and aglycone forms but was not released by normal intact roots. In contrast, roots stressed with CuCl(2) did release the aglycone formononetin. Thus, the release process responsible for exudation of nod-gene inducers appears to be specific rather than a general phenomenon such as a sloughing off of cells during root growth. The synthesis and specific concurrent release of flavonoid nod-gene inducers in this study is consistent with the physiological requirement for nodule formation of the 3-day-old seedlings used.

Journal Article↗
PubMed1990

Effects of alfalfa nod gene-inducing flavonoids on nodABC transcription in Rhizobium meliloti strains containing different nodD genes.

Transcription of the nodulation genes nodABC in Rhizobium meliloti requires a plant flavonoid signal and nodD, a family of bacterial regulatory genes (nodD1, nodD2, and nodD3). Results from this study show that all previously identified nod gene inducers released by alfalfa seeds and roots induced nodABC-lacZ transcription in R. meliloti containing extra copies of nodD1, but only 4,4'-dihydroxy-2'-methoxychalcone gave high levels of induction with extra copies of nodD2. While mixtures of the methoxychalcone and luteolin showed a positive synergism with extra NodD1 protein, they apparently competed for binding to the NodD2 protein.

Acyltransferases↗
PubMed1990

Delayed treatment with a t-PA analogue and streptokinase in a rabbit embolic stroke model.

Fibrinolytic therapy may be effective in the treatment of ischemic stroke, and clinical trials are under way. We evaluated two fibrinolytic agents, an analogue of tissue plasminogen activator (Fb-Fb-CF, the catalytic fragment of the tissue plasminogen activator molecule with a prolonged serum half-life, n = 10) and streptokinase (n = 7), in a rabbit model of embolic stroke. Both agents were given 3 hours after stroke onset, a time relevant to the clinical setting. Fb-Fb-CF was significantly better (p less than 0.04) than saline (n = 7) in restoring blood flow to previously occluded intracranial arteries, but streptokinase was ineffective. Neither fibrinolytic agent was associated with a substantial risk for intracerebral hemorrhagic side effects. Our study demonstrates that Fb-Fb-CF can safely and effectively reperfuse rabbit intracranial arteries 3 hours after occlusion, while streptokinase does not.

Animals↗
PubMed1990

Axillary artery compression and thrombosis in throwing athletes.

A 28-year-old major league baseball pitcher sustained an axillary artery thrombosis which was successfully treated with intraarterial urokinase. Subsequent angiography and duplex scanning with the arm elevated in the pitching position demonstrated inducible compression of the axillary artery by the humeral head as well as compression at the thoracic outlet. To determine the incidence of axillary and subclavian artery compression and to investigate the mechanism of injury, brachial artery blood pressures and duplex scans of the subclavian and axillary arteries were performed in both the neutral position and the throwing position in the 92 extremities of 19 major league baseball pitchers, 16 non-pitching major league players, and 11 nonathlete controls. A drop in blood pressure of greater than 20 mm Hg was noted in the position in 56% of extremities tested, with a loss of a detectable blood pressure in 13%. Compression of the axillary artery by the humeral head was documented in 83% of extremities, but in only 7.6% was a greater than 50% stenosis inducible. No statistical difference was found in the incidence of arterial compression between the three groups tested or between their dominant and nondominant extremities. Dissection of the axillary artery in two cadavers documented that abduction and external rotation of the arm causes compression of the axillary artery by the humeral head, which acts as a fulcrum. We conclude that the repetitive mechanical trauma of the throwing motion can cause intermittent compression and contusion of the axillary artery by the humeral head and predisposes the athlete who throws to thrombosis of the axillary artery.

Adult↗
PubMed1989

The effects of a new tissue plasminogen activator analogue, Fb-Fb-CF, on cerebral reperfusion in a rabbit embolic stroke model.

Early fibrinolytic therapy with full molecular tissue plasminogen activator (t-PA) has been observed to be both angiographically and clinically effective when employed in animal stroke models. Preliminary clinical trials with t-PA are in progress. It is possible to refine t-PA by developing fragments or analogues of the drug. Using recombinant DNA technology in the Escherichia coli system, a t-PA analogue consisting of the catalytic fragment of t-PA and a dimer of the B fragment of staphylococcal protein A (Fb-Fb-CF) has been produced. Because this analogue has a long serum half-life of 90 minutes, we employed Fb-Fb-CF in a rabbit cerebral embolic stroke model to assess its efficacy as a reperfusion agent. When given as a bolus to 10 animals 15 minutes after embolization, Fb-Fb-CF produced angiographic cerebral reperfusion in 48 +/- 21 minutes (+/- SD), while in 8 saline-treated controls, reperfusion was not observed at 180 minutes in any animal (p less than 0.01). In another experiment reperfusion was demonstrated at 66 +/- 32 minutes in 11 animals treated with Fb-Fb-CF 90 minutes after embolization as compared with 100 +/- 25 minutes in 12 saline-treated controls (p less than 0.01). A small macroscopic hemorrhage within an infarct was seen in 1 Fb-Fb-CF-treated animal in the 15-minute experiment and in none of the controls. In the 90-minute experiment, macroscopic hemorrhagic infarction was seen in 4 Fb-Fb-CF-treated animals and in 3 controls.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗