PubMed Health⌕ Search

Biomedical subjects

D S Hill

Publications and source records attributed to D S Hill.

At least 19 recordsLinked to original sources
PubMed1998

Functions encoded by pyrrolnitrin biosynthetic genes from Pseudomonas fluorescens.

Pyrrolnitrin is a secondary metabolite derived from tryptophan and has strong antifungal activity. Recently we described four genes, prnABCD, from Pseudomonas fluorescens that encode the biosynthesis of pyrrolnitrin. In the work presented here, we describe the function of each prn gene product. The four genes encode proteins identical in size and serology to proteins present in wild-type Pseudomonas fluorescens, but absent from a mutant from which the entire prn gene region had been deleted. The prnA gene product catalyzes the chlorination of L-tryptophan to form 7-chloro-L-tryptophan. The prnB gene product catalyzes a ring rearrangement and decarboxylation to convert 7-chloro-L-tryptophan to monodechloroaminopyrrolnitrin. The prnC gene product chlorinates monodechloroaminopyrrolnitrin at the 3 position to form aminopyrrolnitrin. The prnD gene product catalyzes the oxidation of the amino group of aminopyrrolnitrin to a nitro group to form pyrrolnitrin. The organization of the prn genes in the operon is identical to the order of the reactions in the biosynthetic pathway.

Blotting, Western↗
PubMed1997

Stability of Legionella urinary antigens over time.

Twenty-two urine samples positive for Legionella pneumophila serogroup 1 antigen by EQUATE radioimmunoassay (RIA) (Binax, Portland, ME, USA) were stored at various temperatures and the RIA repeated at 1, 7, 30, 90, and 120 days to evaluate stability of the urinary antigens. The mean ratios of patient/negative control remained stable. Although there was a 10% decrease in the mean ratios after 1 month, changes were not significant. However, individual samples with ratios close to 3 may fall to < 3.

Antigens, Bacterial↗
PubMed1997

Mothers' and fathers' singing to infants.

Mothers and fathers sang a song of their choice, once to their infant and once as if to their infant (simulated). The pitch of songs was higher and the tempo slower for infant-directed than for simulated versions. Listeners varying in child-care experience, musical background, and cultural origin reliably identified which of the two versions was infant-directed (Experiment 1). Identification accuracy was enhanced by musical training, knowledge of the singers' language and culture, and by greater pitch and tempo differences between versions. Other adult listeners who rated the singer's emotional engagement assigned significantly higher ratings to infant-directed than to simulated versions (Experiment 2). Differences in pitch and tempo between both versions predicted emotional engagement ratings. Finally, rating differences between infant-directed and simulated versions were highly correlated with identification accuracy.

Adolescent↗
PubMed1997

Four genes from Pseudomonas fluorescens that encode the biosynthesis of pyrrolnitrin.

Pyrrolnitrin is a secondary metabolite of Pseudomonas and Burkholderia sp. strains with strong antifungal activity. Production of pyrrolnitrin has been correlated with the ability of some bacteria to control plant diseases caused by fungal pathogens, including the damping-off pathogen Rhizoctonia solani. Pseudomonas fluorescens BL915 has been reported to produce pyrrolnitrin and to be an effective biocontrol agent for this pathogen. We have isolated a 32-kb genomic DNA fragment from this strain that contains genes involved in the biosynthesis of pyrrolnitrin. Marker-exchange mutagenesis of this DNA with Tn5 revealed the presence of a 6.2-kb region that contains genes required for the synthesis of pyrrolnitrin. The nucleotide sequence of the 6.2-kb region was determined and found to contain a cluster of four genes that are required for the production of pyrrolnitrin. Deletion mutations in any of the four genes resulted in a pyrrolnitrin-nonproducing phenotype. The putative coding sequences of the four individual genes were cloned by PCR and fused to the tac promoter from Escherichia coli. In each case, the appropriate tac promoter-pyrrolnitrin gene fusion was shown to complement the pyrrolnitrin-negative phenotype of the corresponding deletion mutant. Transfer of the four gene cluster to E. coli resulted in the production of pyrrolnitrin by this organism, thereby demonstrating that the four genes are sufficient for the production of this metabolite and represent all of the genes required to encode the pathway for pyrrolnitrin biosynthesis.

Amino Acid Sequence↗
PubMed1995

Four new derivatives of the broad-host-range cloning vector pBBR1MCS, carrying different antibiotic-resistance cassettes.

Four new antibiotic-resistant derivatives of the broad-host-range (bhr) cloning vector pBBR1MCS have been constructed. These new plasmids have several advantages over many of the currently available bhr vectors in that: (i) they are relatively small (< 5.3 kb), (ii) they possess an extended multiple cloning site (MCS), (iii) they allow direct selection of recombinant plasmid molecules in Escherichia coli via disruption of the LacZ alpha peptide, (iv) they are mobilizable when the RK2 transfer functions are provided in trans and (v) they are compatible with IncP, IncQ and IncW group plasmids, as well as with ColE1- and P15a-based replicons.

Bacteria↗
PubMed1994

Exponential smoothing method for forecasting drug expenditures.

A model for forecasting a hospital pharmacy drug budget is described, and its results in 10 hospital pharmacy departments are evaluated. A model for forecasting inpatient drug expenditures was developed based on the method of exponential smoothing. Exponential smoothing predicts a value based on the forecast for the prior period, with adjustment for the error of that forecast. Recent data are weighted more heavily than older data; as data become older, weights decline exponentially. The model incorporates changes in workload in addition to drug expenditure data. The variable used for workload can vary from one hospital to another, depending on the statistics that are available. The model was designed to be more accurate than current methods, easy and quick to use, and usable with a minimal knowledge of statistics and forecasting theory. The model was tested on fiscal 1988-1992 drug budget data from 10 British Columbia hospital pharmacy departments. Four departments had insufficient data; of the remaining six, the forecasting model performed better than the hospitals' current methods in four departments. The mean absolute deviation between budgeted (by current methods) and actual drug expenditures was 8.70% (range, 6.19-15.16%). The forecasting model yielded a mean absolute deviation of 5.93% (range, 3.13-7.66%). Better forecasts resulted when pharmacy medication-order volume was used as a workload variable, as compared with hospital inpatient days. An exponential smoothing model improved the accuracy of drug-budget forecasts in four of six pharmacy departments.

British Columbia↗
PubMed1994

Possible antiestrogenic properties of chloro-s-triazines in rat uterus.

Several published reports have indicated that certain chloro-s-triazine herbicides may alter endocrine function in rats, possibly by androgen receptor binding. In direct tests of estrogenic bioactivity, oral doses of up to 300 mg/kg/d of atrazine, simazine, or the common metabolite diaminochlorotriazine (DACT) did not significantly increase uterine weight of ovariectomized Sprague-Dawley female rats. The highest dose, which was approximately 10% of the LD50 for these compounds, did cause body weight loss. When administered concomitantly with sc injections of estradiol (2 micrograms/kg), 300 mg/kg of orally administered chlorotriazines significantly reduced uterine weight in comparison to animals given estrogen alone. Neither atrazine, simazine, nor DACT, at oral doses up to 300 mg/kg/d, stimulated incorporation of [3H]thymidine into uterine DNA of immature Sprague-Dawley female rats. However, oral treatment at doses of 50 mg/kg and higher significantly reduced thymidine incorporation into uterine DNA extracted from immature rats given a single injection of 0.15 microgram estradiol. Oral doses of 300 mg/kg of atrazine, simazine, or DACT significantly reduced expression of progesterone receptor binding in cytosol fractions prepared from uteri of ovariectomized rats injected sc with 1 microgram estradiol; 50 mg/kg triazine was not effective in this case. Uterine progesterone receptor levels were not stimulated in rats given oral doses up to 300 mg/kg of these triazines without estradiol injections. These results suggest that atrazine, simazine, and DACT possess no intrinsic estrogenic activity but that they are capable of weak inhibition of estrogen-stimulated responses in the rat uterus. This inhibition may play a role in the previously observed disruptive actions of chlorotriazines on reproductive endocrine function of female rats.

Administration, Oral↗
PubMed1994

Chloro-s-triazine antagonism of estrogen action: limited interaction with estrogen receptor binding.

In an accompanying article (see pp. 183-196), it was reported that administration of very high doses of the chlorotriazine herbicides atrazine, simazine, and diaminochlorotriazine (DACT), a common metabolite, expressed antiestrogenic activity in uteri of female Sprague-Dawley rats without expressing intrinsic estrogenic activity. In the present article, studies of chlorotriazine interaction with rat uterine estrogen receptors (ER) are reported. Under equilibrium conditions, none of the triazine compounds showed an ability to compete against binding of radiolabeled estradiol to ER. A weak competition was evident only if cytosols were preincubated with triazines at 25 degrees C prior to introduction of tracer. Competition was very weak, with kl estimates of 10-100 microM. A limited Scatchard analysis suggested a competitive type of inhibition. Sucrose gradient analysis of cytosol incubations showed that triazine interaction with the 4S isoform of ER may be greater than with the 8S form. When administered to ovariectomized rats for 2 d at 300 mg/kg/d, atrazine, simazine, or DACT all reduced uterine ER binding capacity by approximately 30%. Results from the receptor binding studies indicated that triazine competition against ER binding occurred to a much lesser degree than inhibition of estrogen-mediated responses reported in accompanying articles. This suggests that the complete responses to triazines may include inhibition of events other than or in addition to ER binding of estrogen.

Animals↗
PubMed1993

Delta retinoic acid receptor isoform delta 1 is distinguished by its exceptional N-terminal sequence and abundance in the limb regeneration blastema.

In amphibian limb regeneration memory for position in the proximal-distal axis can be respecified by retinoic acid. The favoured candidates to mediate this effect are the retinoic acid receptors (RARs) and of the RARs identified in the regeneration blastema, the delta receptor is the most abundant. The presence in blastemal mesenchyme of at least two delta receptor isoforms, delta 1 and delta 2, alternatively spliced at the A-B junction, was demonstrated in expression studies and by PCR cloning. The delta 1 receptor is abundant in regenerative structures such as the limb and tail, whereas the delta 2 and alpha receptors show a more uniform pattern of expression across adult newt tissues. Full-length cloning of the delta 1 receptor established the presence of an unusually long open reading frame and N-terminal sequence that appears unique among vertebrate retinoic acid receptors. Transient transfection of expression constructs into COS cells followed by Western blotting confirmed the existence of at least three potential initiation sites for delta 1 translation. The possibility that delta 1 RAR expression may specify positional memory directly was tested in RNase protection experiments. delta 1 receptor message is increased on amputation, but does not exhibit a pronounced differential distribution along the proximal-distal axis in normal and regenerating limbs, nor does it show a persistent alteration in expression levels following a dose of retinoic acid sufficient to respecify position. The possibility that the morphogenetic effects of RA may be mediated through receptor interactions is raised by the finding that single mesenchymal blastemal cells in culture can express multiple RAR subtypes (delta 1 and alpha) and isoforms (delta 1 and delta 2).

Amino Acid Sequence↗
PubMed1993

Isoform-specific immunological detection of newt retinoic acid receptor delta 1 in normal and regenerating limbs.

Retinoic acid (RA) exerts a variety of effects on the regenerating urodele limb including positional respecification of the blastema. The major RA receptor expressed in the newt limb and blastema is the delta 1 isoform and, in order to detect delta 1 in this context, we have made five affinity-purified antibodies against fusion proteins and peptides from non-overlapping regions of the molecule. These antibodies have been evaluated by reaction with transfected COS-7 cells, newt limb cells in culture and newt limb tissue sections. The most informative antibodies were RP6, directed against N-terminal region A sequence, and RP8, directed against C-terminal sequence. In western blots of blastemal extracts, delta 1 protein was detected as two major bands of immunoreactivity at positions consistent with the employment of two candidate methionine initiators identified by cDNA sequencing. Staining of adult limb sections with RP6 and RP8 showed reactivity in half of the nuclei in epidermal and mesenchymal tissues, a heterogeneity that was observed with adjacent nuclei in muscle fibres. In the regenerating limb, nuclei in the blastemal mesenchyme and wound epidermis were strongly reactive, although no axial variation in expression was detected.

Animals↗
PubMed1989

Physical and biological characterization of linear DNA plasmids of the yeast Pichia inositovora.

Three cryptic DNA plasmids have been identified in a strain of the yeast Pichia inositovora that are 18, 13, and 10 kbp in size. All are sensitive to digestion by DNase I, restriction endonucleases, and exonuclease III, but are resistant to the activities of RNase A and lambda exonuclease. These results indicate that each plasmid is a linear DNA molecule whose 5' ends are protected. A restriction map has been developed for each of the plasmids, demonstrating that each is unique and confirming their linear nature. The plasmids are a major constituent of DNA prepared from whole cells, but are absent from DNA preparations of purified mitochondria and nuclei, indicating that the plasmids are located in the cytoplasm. These plasmids share many of the physical characteristics described for the linear plasmids of the yeasts Kluyveromyces lactis and Saccharomycopsis crataegensis. Unlike the linear plasmids of K. lactis, however, they appear not to be capable of killer toxin production.

Autoradiography↗
PubMed1982

Effects of nicotinic acid therapy on plasma lipoproteins and very low density lipoprotein apoprotein C subspecies in hyperlipoproteinemia.

The effects of long term treatment with nicotinic acid on lipids, lipoproteins, and the plasma distribution of very low density lipoproteins (VLDL) apoprotein C (ApoC) subspecies were studied in 33 patients with types IIa (n = 9), IIb (n = 11), and IV (n = 13) hyperlipidemias. After 6 months of treatment, a significant decrease in triglyceride, total cholesterol, and low density lipoprotein (LDL) cholesterol levels occurred. High density lipoprotein (HDL) cholesterol increased significantly by 31.1%, 41.8%, and 32.0% in types IIa, IIb, and IV, respectively (P less than 0.01 for all). A significant negative correlation existed between changes in HDL cholesterol and triglycerides (r = -0.613; P less than 0.02) in all groups studied. Therapy also produced changes in VLDL, LDL, and HDL protein concentrations. VLDL protein decreased from 20.9 +/- 3.9 to 15.2 +/- 1.0 mg/dl (P less than 0.05) in type IIa. In types IIb and IV, mean VLDL protein decreased from 44.7 +/- 8.2 to 27.1 +/- 3.9 mg/dl (P less than 0.001) and from 46.3 +/- 7.1 to 30.6 +/- 4.9 mg/dl (P less than 0.001), respectively. LDL protein decreased significantly, and HDL protein increased in type IIa only. Gel isoelectric focusing of VLDL before and after nicotinic acid in types IIb and IV hyperlipidemia produced a significant increase in the VLDL ApoC-II component with simultaneous decreases in the total VLDL ApoC-III subspecies. This resulted in increases in the ApoC-II to ApoC-III area ratio from 0.50 +/- 0.1 to 1.02 +/- 0.2 (P less than 0.001) in type IIb and from 0.62 +/- 0.07 to 0.88 +/- 0.13 (P less than 0.01) in type IV, respectively. The ApoE subspecies and the ApoE-III to ApoE-II area ratio did not change significantly. Our results show that nicotinic acid produces a significant improvement in the lipoprotein profiles of these patients.

Adult↗
PubMed1981

Renal adenocarcinoma in an asymptomatic 19-year-old female.

Renal adenocarcinoma is rare before age 20. Clinically and radiographically, it presents similarly in adults and children. Prognosis is related to the clinical stage of the tumor at surgery. Treatment methods are still under investigation.

Adenocarcinoma↗
PubMed1981

High accuracy sonographic recognition of gallstones.

Recent advances in the imaging capabilities of gray scale sonography have increased the accuracy with which gallstones may be diagnosed. Since the sonographic diagnosis of gallstones is often followed by surgery without further confirmatory studies, the avoidance of false-positive diagnoses assumes major importance. In an attempt to improve diagnostic accuracy, 420 gallbladder sonograms were evaluated for gallstones. Positive diagnoses were limited to cases in which the gallbladder was well visualized and contained densities that produced acoustic shadowing or moved rapidly with changes in position. Gallstones were diagnosed in 123 cases and surgery or autopsy in 70 of these patients confirmed stones in 69. There was one false-positive, an accuracy rate for positive diagnosis of 98.6%. Five cases were called indeterminate for stones; one of these had tiny 1 mm stones at surgery. The other four cases had no surgery. Of 276 cases called negative for stones. None of the 146 cases with negative sonograms and oral cholecystography or intravenous cholangiography had stones diagnosed by these methods. Because of its ease and simplicity, sonography is attractive as the initial study in patients suspected of having gallstones. With the criteria used here, a diagnosis of gallstones in the gallbladder can be offered with great confidence.

Cholelithiasis↗