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Biomedical subjects

D A Phillips

Publications and source records attributed to D A Phillips.

At least 37 records · Page 2Linked to original sources
PubMed1998

An isoflavonoid-inducible efflux pump in Agrobacterium tumefaciens is involved in competitive colonization of roots.

Agrobacterium tumefaciens 1D1609, which was originally isolated from alfalfa (Medicago sativa L.), contains genes that increase competitive root colonization on that plant by reducing the accumulation of alfalfa isoflavonoids in the bacterial cells. Mutant strain I-1 was isolated by its isoflavonoid-inducible neomycin resistance following mutagenesis with the transposable promoter probe Tn5-B30. Nucleotide sequence analysis showed the transposon had inserted in the first open reading frame, ifeA, of a three-gene locus (ifeA, ifeB, and ifeR), which shows high homology to bacterial efflux pump operons. Assays on alfalfa showed that mutant strain I-1 colonized roots normally in single-strain tests but was impaired significantly (P < or = 0.01) in competition against wild-type strain 1D1609. Site-directed mutagenesis experiments, which produced strains I-4 (ifeA::gusA) and I-6 (ifeA::omega-Tc), confirmed the importance of ifeA for competitive root colonization. Exposure to the isoflavonoid coumestrol increased beta-glucuronidase activity in strain I-4 21-fold during the period when coumestrol accumulation in wild-type cells declined. In the same test, coumestrol accumulation in mutant strain I-6 did not decline. Expression of the ifeA-gusA reporter was also induced by the alfalfa root isoflavonoids formononetin and medicarpin but not by two triterpenoids present in alfalfa. These results show that an efflux pump can confer measurable ecological benefits on A. tumefaciens in an environment where the inducing molecules are known to be present.

Agrobacterium tumefaciens↗
PubMed1997

Occult choroidal neovascularization in age-related macular degeneration. A natural history study.

OBJECTIVE: To explore morphological and vision changes in untreated eyes with subfoveal choroidal neovascularization (CNV) that have poorly demarcated boundaries. DESIGN: Analysis of photographs of untreated patients with poorly demarcated occult CNV participating in a prospective clinical trial evaluating laser treatment compared with observation. SETTING: Two tertiary retinal referral centers. PATIENTS: Symptomatic individuals with poorly demarcated subfoveal occult CNV associated with age-related macular degeneration. MAIN OUTCOME MEASURES: Change in size of lesion, development of classic CNV, change in vision, and development of subretinal fibrosis. RESULTS: During follow-up (9-12 months), 32% of the occult choroidal neovascular lesions more than doubled their original size. Classic CNV developed in 52% of eyes that started without it. The median loss in visual acuity was 2.5 lines. Eyes with classic CNV or subretinal blood or both at baseline developed subretinal fibrosis more frequently and lost more visual acuity, but not to a statistically significant degree. CONCLUSIONS: The morphological changes of eyes with subfoveal occult CNV in which the boundaries are poorly demarcated in variable; the presence of subretinal blood or a component of classic CNV may influence the prognosis for further loss of vision.

Aged↗
PubMed1997

Ross River virus in mosquitoes (Diptera:Culicidae) during the 1994 epidemic around Brisbane, Australia.

During the summer 1994 outbreak of epidemic polyarthritis in suburban Brisbane, 29,931 adult female mosquitoes were collected by octenol-CO2 light traps and tested for virus by species in pools of approximately 20 using an in situ enzyme-linked immunoassay. Overall, 63 isolations of Ross River (RR) virus were made from 7 different mosquito species, including 23 from freshwater-breeding Culex annulirostris Skuse, 13 from peridomestic Aedes notoscriptus (Skuse), 4 from Aedes procax (Skuse), 12 from the brackish water-breeding Aedes funereus (Theobald), 9 from saltmarsh Aedes vigilax (Skuse), and 1 each from Culex sitiens Wiedemann and Aedes alternans (Westwood). The RR virus minimum infection rate in mosquitoes ranged from 1.6 to 2.5/1,000 from March to June 1994. This study implicates freshwater and brackish water mosquitoes as important suburban vectors of RR virus and indicates the need for refocusing mosquito control priorities.

Aedes↗
PubMed1997

A biotin-regulated locus, bioS, in a possible survival operon of Rhizobium meliloti.

A novel biotin-inducible DNA locus, bioS, was found in Rhizobium meliloti 1021 by mutation with a transposable promoter probe. The promoterless nptII reporter responded to 40 nM biotin with a sixfold increase in NPTII protein. Stationary-phase mutant cells accumulated 50% more 14C-biotin than corresponding wild-type cells. The prototrophic mutant competed equally with the wild type in biotin-free medium but poorly when 40 nM biotin was present. The 588-bp bioS is located among three genes showing homology to survival operons of other bacteria, and it may be part of a system that R. meliloti uses to respond to plant biotin signals.

Biotin↗
PubMed1997

Occurrence of flavonoids and nucleosides in agricultural soils.

AN ECOLOGICALLY RELEVANT SOIL EXTRACTION PROCEDURE SEPARATED TWO TYPES OF MOLECULES IMPORTANT FOR BACTERIA: flavonoids and small hydrophilic organic compounds. Two flavonoids, identified previously as inducers of nodulation genes in Rhizobium meliloti, were detected in rhizosphere soil from alfalfa (Medicago sativa L.). In addition, biologically significant quantities (micromoles per kilogram) of ribonucleosides and deoxyribonucleosides were found in all soils tested. Long-term wheat (Triticum aestivum L.) plots that had received manure contained elevated amounts of nucleosides, and in a separate experiment, the presence of legumes in a wheat-cropping sequence increased soil nucleosides. Intact bacterial cells accounted for less than 1% of the free nucleosides detected. These results suggest new testable hypotheses for molecular ecologists and differ from those obtained with older, harsher techniques.

Journal Article↗
PubMed1996

An outbreak of Japanese encephalitis in the Torres Strait, Australia, 1995.

OBJECTIVES: To determine the distribution of virus infection during an outbreak of Japanese encephalitis (JE) in the Torres Strait, and to describe the environmental factors facilitating the outbreak. DESIGN: Human and porcine serological surveys for JE virus activity throughout the Torres Strait, and mosquito and household surveys on the island of Badu. SETTING: The island of Badu (where the clinical cases occurred) and the other islands of the Torres Strait, Australia, during April-May 1995. RESULTS: The serological surveys identified recent JE virus infection among residents or domestic pigs on at least nine outer Torres Strait islands. A JE virus, confirmed by nucleotide sequencing, was isolated from two asymptomatic Badu residents. Virus isolations and mosquito surveys implicated Culex annulirostris as the major vector involved in the outbreak. There was prolific Cx. annulirostris breeding in a variety of water bodies close to and within the Badu community. Over half (53%) of the households kept pigs in pens, and many (63%) of the pigpens were situated near standing water; in 56% of these "wet" pigpens Cx. annulirostris was breeding. CONCLUSIONS: There was evidence of widespread JE virus activity throughout the outer islands of the Torres Strait. We suggest that migratory birds and/or wind-blown mosquitoes could have imported the virus into the Torres Strait from a focus of viral activity, possibly in Papua New Guinea, thereby initiating the outbreak. A combination of environmental factors, with large numbers of domestic pigs in close proximity to human dwellings and mosquito breeding sites, undoubtedly facilitated the outbreak on Badu.

Adult↗
PubMed1996

Biotin and other water-soluble vitamins are key growth factors for alfalfa root colonization by Rhizobium meliloti 1021.

Rhizosphere growth limitations imposed on Rhizobium meliloti by availability of biotin, thiamine, and riboflavin were overcome by adding nanomolar amounts of these vitamins. Studies done with R. meliloti 1021 showed that both synthesis and uptake of biotin promote colonization of alfalfa roots. Two lines of evidence indicated that plant-derived biotin normally promotes root colonization: (i) adding avidin significantly (P < or = 0.01) reduced rhizosphere growth of R meliloti 1021, and (ii) growth of Tn5-induced biotin auxotrophs still increased 10-fold in the rhizosphere. Synthesis, however, is the more important source of biotin for R. meliloti 1021 because in root colonization tests biotin auxotrophs competed very poorly with the parent strain. Mutations conferring biotin auxotrophy were closely linked on a single restriction fragment, and one was complemented with the Escherichia coli bio operon. Initial nucleotide sequencing and DNA-DNA hybridization tests showed the biotin synthesis genes in R. meliloti are quite different from those in E. coli.

Base Sequence↗
PubMed1996

Recombinant Rhizobium meliloti strains with extra biotin synthesis capability.

The growth of Rhizobium meliloti 1021 in an experimental alfalfa (Medicago sativa L.) rhizosphere was stimulated by adding nanomolar amounts of biotin. To overcome this biotin limitation, R. meliloti strains were constructed by conjugating the Escherichia coli biotin synthesis operon into biotin auxotroph R. meliloti 1021-B3. Transconjugant strains Rm1021-WS10 and Rm1021-WS11 grew faster in vitro and achieved a higher cell density than did R. meliloti 1021 and overproduced biotin on a defined medium. The increase in cell yield was associated with as much as a 99% loss in viability for Rm1021-WS11, but data suggested that a separate stabilizing factor in the E. coli DNA reduced cell death in Rm1021-WS10. In rhizosphere tests, the recombinant strains showed delayed growth and competed poorly against Rm1021.

Base Sequence↗
PubMed1995

Plant isoflavonoids, pathogens and symbionts.

It has recently been discovered that when symbiotic Rhizobium and Bradyrhizobium cells are outside the plant they are also exposed to the isoflavonoid phytoalexins that are normally associated with pathogenic infections. How the symbionts elicit and respond to isoflavonoids may help to define the mechanisms that are used by other beneficial soil microorganisms to colonize plant roots.

Isoflavones↗
PubMed1995

Midfacial degloving for the management of nasal, sinus, and skull-base neoplasms.

The midfacial degloving approach to the midfacial orbital and anterior skull base structures is very versatile. It provides excellent access to a wide range of resections, such as medial maxillectomy, radical maxillectomy with and without orbital exenteration, anterior skull base cranifacial resection, and partial rhinectomy. This technique is useful for removal of benign and malignant lesions. The postoperative complications are rare. Because of absence of external skin incisions the cosmetic results are excellent.

Adult↗
PubMed1994

Child care for children in poverty: opportunity or inequity?

Data from a nationally representative survey of child care centers and a 5-site, observational study of centers were used to examine the quality of care provided to children from low-income families. Comparisons were made to a national sample of centers; among Head Start, public school-sponsored, and other community-based subsidized centers; and among centers that served families from differing socioeconomic groups. The quality of care in centers that served predominantly low-income children was adequate, but highly variable, with structural indices exhibiting higher quality than observations of global quality and of staff-child interactions. When compared to Head Start and public school-sponsored centers, the community-based centers had smaller groups and fewer children per teacher for preschoolers, but also had less well educated and compensated staff. Centers that predominantly served children from upper-income families provided the highest quality of care across multiple indices, and those that predominantly served children from middle-income families almost uniformly provided the poorest quality of care. The centers that served children from low-income families did not differ significantly in quality from the upper-income centers on most indices. However, the teachers in these programs were observed to be less sensitive and more harsh than teachers in the centers that served more advantaged families. The implications of the findings for research and policy are discussed.

Child Day Care Centers↗
PubMed1993

Isolation of Rhizobium meliloti nod Gene Inducers from Alfalfa Rhizosphere Soil.

Methanolic extracts of alfalfa rhizosphere soil induce more nod gene transcription in Rhizobium meliloti than extracts of nonrhizosphere soil. Six peaks of nod-inducing activity were separated by high-performance liquid chromatography from rhizosphere soil extract, and one compound was identified by H nuclear magnetic resonance, mass spectrometry, and UV-visible spectra as a formononetin-7-O-glycoside that activates both NodD1 and NodD2 proteins. The unanticipated presence of a glycoside in rhizosphere soil suggests either that large amounts of the glycoside were exuded by roots or that some glycosides are unexpectedly stable in soil.

Journal Article↗
PubMed1993

Combined effects of urokinase and heparin on PTT values during thrombolytic therapy.

The local infusion of urokinase may be complicated by hemorrhage. Except for maintaining fibrinogen levels above 100 mg/dL, no other criteria exist for titrating the dose of urokinase to avoid hemorrhagic complications. A retrospective examination of the fibrinolytic and coagulation states was performed on 11 patients receiving local high-dose urokinase (240,000 U/hr) and heparin for thrombolysis of acute occlusions to identify parameters other than fibrinogen levels that may correlate with bleeding complications. Five patients experienced bleeding complications, 3 of whom had partial thromboplastin time (PTT) values greater than 150 seconds. None of the five patients having hemorrhagic complications had fibrinogen levels below 100 mg/dL at any time. Urokinase began to enhance the effect of heparin on PTT values as a result of reducing fibrinogen levels. In 10 of 11 patients this effect caused PTT values to at least double when compared with heparin alone. This substantial rise in PTT occurred only after fibrinogen levels approached 200 mg/dL in 8 of 11 patients. Although the number of patients is small, these data suggest that when heparin is used during thrombolysis, closer PTT monitoring should be carried out as fibrinogen levels begin to decline, especially when they approach 200 mg/dL, to avoid excessive PTT elevations and subsequent bleeding.

Aged↗
PubMed1992

Isolation of Kunjin virus from a patient with a naturally acquired infection.

OBJECTIVE: To describe the first isolation of Kunjin virus from a patient with a natural infection. CLINICAL FEATURES: A 48-year-old female egg collector presented with muscle weakness, fatigue and extreme lethargy three weeks after developing rigors, headache, photophobia and nausea. Kunjin virus was isolated from an acute phase serum sample. INTERVENTION AND OUTCOME: The patient made a partial recovery after treatment for 10 days with Catovit (Boehringer Ingelheim), one tablet twice a day, and then declined further medical contact. CONCLUSION: The isolation of Kunjin virus from this patient confirms previous serological observations which suggested that this mosquito-borne virus caused febrile episodes in humans accompanied, on occasion, by polyarthralgia or mild central nervous system signs and symptoms.

Aedes↗
PubMed1992

The social policy context of child care: effects on quality.

Examined effects on the quality of children's child care environments of (a) the stringency of state child care regulations, (b) voluntary compliance with proposed federal child care standards, and (c) the legal auspice of the center. Quality of care was assessed in 227 child care centers in five metropolitan areas. Centers in states with more stringent child care regulations tended to have better staff-child ratios, staff with more child-related training, and lower staff turnover rates. Similarly, centers that more fully complied with the ratio, group size, and training provisions of a set of proposed federal child care standards had significantly lower staff turnover rates, more age-appropriate classroom activities, less harsh and more sensitive teachers, and more teachers with specialized training. For-profit centers offered children less optimal care than did nonprofit centers. These findings are placed in the context of ecological models of research and of contemporary policy debates about child care.

Child↗
PubMed1992

Trigonelline and Stachydrine Released from Alfalfa Seeds Activate NodD2 Protein in Rhizobium meliloti.

Spectroscopic data (nuclear magnetic resonance, mass spectrometry, ultraviolet-visible) in this study identify trigonelline and stachydrine as major components of alfalfa (Medicago sativa L.) seed rinse. Moreover, biological assays show that these natural products induce nodulation (nod) gene transcription in Rhizobium meliloti by activating the regulatory protein NodD2, but not the homologous NodD1 protein. These findings contrast with the fact that the only previously identified NodD2 activator, 4,4' -dihydroxy-2' -methoxychalcone (MCh), also activates NodD1 protein. Trigonelline and stachydrine induce nod genes only at much higher concentrations than MCh, but they are released from seeds in correspondingly greater amounts. The existence of these amphoteric, nonflavonoid nod gene inducers broadens our understanding of the biochemical processes and ecological mechanisms that a legume host uses to regulate its microbial symbiont.

Journal Article↗
PubMed1992

Thresholds of quality: implications for the social development of children in center-based child care.

We assessed the quality of center child care relationships with adults and peers for 414 children (ages 14 to 54 months). Classrooms were classified by ratio and group size provisions of the Federal Interagency Day Care Requirements (FIDCR) and by the Early Childhood and Infant and Toddler Environmental Rating Scales. Children cared for in classrooms meeting FIDCR ratios were more likely to be in classrooms rated as good or very good in caregiving and activities. Children in classrooms rated as good or very good in caregiving were more likely to be securely attached to teachers. Securely attached children were more competent with peers. Children cared for in classrooms meeting FIDCR group size were more likely to be in classrooms rated higher in activities. Children in classrooms rated high in activities were likely to orient to both adults and peers. Children with social orientations to adults and peers were more competent with peers.

Child Behavior↗