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R Cannon

Publications and source records attributed to R Cannon.

17 recordsLinked to original sources
PubMed2002

New upper limit on the total neutrino mass from the 2 degree field galaxy redshift survey.

We constrain f(nu) identical with Omega(nu)/Omega(m), the fractional contribution of neutrinos to the total mass density in the Universe, by comparing the power spectrum of fluctuations derived from the 2 Degree Field Galaxy Redshift Survey with power spectra for models with four components: baryons, cold dark matter, massive neutrinos, and a cosmological constant. Adding constraints from independent cosmological probes we find f(nu)<0.13 (at 95% confidence) for a prior of 0.1<Omega(m)<0.5, and assuming the scalar spectral index n=1. This translates to an upper limit on the total neutrino mass m(nu,tot)<1.8 eV for "concordance" values of Omega(m) and the Hubble constant.

Journal Article↗
PubMed2000

Candida albicans: adherence, signaling and virulence.

The focus of this symposium was to present new information on the morphogenesis of Candida albicans, particularly how it relates to signal transduction pathways and other genes involved in the regulation of morphogenesis. In addition, we discuss the role of adherence and colonization of the oral cavity by the organism and discuss the role of mannan as an adhesin that recognizes the human red blood cell. C. albicans utilizes at least two signal pathways to regulate its conversion from a yeast form to filamentous growth (hyphae). One of these two pathways is similar to the Saccharomyces cerevisiae pseudohyphal/mating pathway, which utilizes the regulatory protein, Cphlp. The other pathway is not totally defined but requires a second regulatory protein, referred to as Efg1p. Other signal pathways may exist, which include a two-component histidine kinase and response regulator proteins. The latter pathway(s) may include proteins such as Chk1p, Ssk1p, Shi1p and Cos1p/Nik1p. Mutations in strains, which specifically target these proteins, result in morphogenesis defects and avirulence or attenuation of strains. A growth regulatory gene has also been recently defined whose expression is associated with growth cessation and which appears to be a necessary prerequisite in conversion of the organism to a filamentous growth form. Starvation of yeast cells induces exponentially grown cells (and usually non-germinative) to germinate. This phenomenon is also observed in cells that are transiently treated with metabolic inhibitors. During each of these treatments (starvation, metabolic inhibition), expression of a growth regulatory gene (CGRI) increases. Adherence of C. albicans to host cells and tissues is complex; several proteins, which appear to have host recognition functions, have been defined. In the oral cavity, C. albicans selectively adheres to salivary proteins, which are absorbed to many oral surfaces. This mechanism enables the cells to colonize surfaces of the oral cavity. An understanding of these interactions may lead to strategies to prevent oral disease. Mannan from C. albicans may provide a host recognition function for C. albicans. Recent experiments indicate that mannan binds to human red blood cells and causes hemolysis. Binding of mannan to the band 3 protein of human red blood cells has been established. This activity may be associated with the ability of the organism to utilize hemoglobin (and iron).

Candida albicans↗
PubMed1998

Endogenous pacemaker activity of rat tumour somatotrophs.

1. Cells derived from a rat pituitary tumour (GC cell line) that continuously release growth hormone behave as endogenous pacemakers. In simultaneous patch clamp recordings and cytosolic Ca2+ concentration ([Ca2+]i) imaging, they displayed rhythmic action potentials (44.7 +/- 2.7 mV, 178 +/- 40 ms, 0.30 +/- 0.04 Hz) and concomitant [Ca2+]i transients (374 +/- 57 nM, 1.0 +/- 0.2 s, 0.27 +/- 0.03 Hz). 2. Action potentials and [Ca2+]i transients were reversibly blocked by removal of external Ca2+, addition of nifedipine (1 microM) or Ni2+ (40 microM), but were insensitive to TTX (1 microM). An L-type Ca2+ current activated at -33.6 +/- 0.4 mV (holding potential (Vh), -40 mV), peaked at -1.8 +/- 1.3 mV, was reduced by nifedipine and enhanced by S-(+)-SDZ 202 791. A T/R-type Ca2+ current activated at -41.7 +/- 2.7 mV (Vh, -80 or -60 mV), peaked at -9.2 +/- 3.0 mV, was reduced by low concentrations of Ni2+ (40 microM) or Cd2+ (10 microM) and was toxin resistant. Parallel experiments revealed the expression of the class E calcium channel alpha1-subunit mRNA. 3. The K+ channel blockers TEA (25 mM) and charybdotoxin (10-100 nM) enhanced spike amplitude and/or duration. Apamin (100 nM) also strongly reduced the after-spike hyperpolarization. The outward K+ tail current evoked by a depolarizing step that mimicked an action potential reversed at -69. 8 +/- 0.3 mV, presented two components, lasted 2-3 s and was totally blocked by Cd2+ (400 microM). 4. The slow pacemaker depolarization (3.5 +/- 0.4 s) that separated consecutive spikes corresponded to a 2- to 3-fold increase in membrane resistance, was strongly Na+ sensitive but TTX insensitive. 5. Computer simulations showed that pacemaker activity can be reproduced by a minimum of six currents: an L-type Ca2+ current underlies the rising phase of action potentials that are repolarized by a delayed rectifier and Ca2+-activated K+ currents. In between spikes, the decay of Ca2+-activated K+ currents and a persistent inward cationic current depolarize the membrane, activate the T/R-type Ca2+ current and initiate a new cycle.

Action Potentials↗
PubMed1997

Biliary obstruction in infants with cystic fibrosis requiring Kasai portoenterostomy.

Cystic fibrosis is associated with an inspissated bile syndrome producing cholestasis secondary to plugging of macroscopically normal bile ducts. In extreme neonatal forms, with early profound intrahepatic cholestasis, the process can be associated with a marked decrease in ductal diameter, varying from hypoplasia to atresia. From 1990 to 1995 three infants were identified with cystic fibrosis, persistent jaundice, and complete absence of biliary excretion despite expectant and conservative treatment including choleretics and surgical biliary irrigation. Abdominal ultrasounds showed contracted gallbladders and no evidence of dilated ducts. Liver biopsy results in two infants showed portal fibrosis, paucity of bile ducts, and minimal inflammation. The third infant had moderate inflammation, bile duct replication, and plugging. Two infants had undergone intestinal resection followed by hyperalimenation for complications of meconium ileus in the newborn period. Surgical exploration was undertaken at 7 to 12 weeks of age. Gross findings were typical of biliary atresia with microgallbladders and nonpatency of the cystic duct. Cholangiograms failed to document ductal patency in two patients who were then treated with a Kasai portoenterostomy. The third infant had patent hypoplastic ducts and underwent only biliary irrigation. Although bile flow was transiently achieved, jaundice recurred, and at reexploration at 16 weeks of age a Kasai poroenterostomy was performed. Histological review of the biliary specimens showed microscopically patent ducts in two patients and proximal patency and distal atresia in the third. All the ducts had mural fibrosis with cystic changes. Bile drainage was achieved in each instance, although in one patient with hypoplastic ducts scant output of highly concentrated bile proved insufficient to arrest progressive liver failure. The subsequent two patients responded with resolution of hyperbilirubinemia and normalization of liver function. They remain free of biliary complications at 30 and 40 months postoperatively. This manifestation of cystic fibrosis in infants is suggested by prolonged jaundice unresponsive to choleretics, nondilated bile ducts and gallbladder on ultrasound, absent biliary excretion on nuclear scan, and characteristic liver biopsy. Exploration is warranted, and discovery of atrophic bile ducts may be best managed with reconstruction.

Biliary Atresia↗
PubMed1997

Comparison of analytical performance and biological variability of three bone resorption assays.

We have compared the analytical performance and biological variability of three commercially available bone resorption assays: Pyrilinks-D, Osteomark, and CrossLaps, for the measurement of urinary free deoxypyridinoline (Dpd), cross-linked N-telopeptides of type I collagen (NTx), and linear C-telopeptides of type I collagen (CTx), respectively. The intraassay and interassay CVs for precision of the Dpd and NTx assays were < 10% for analyte concentrations greater than the second calibrator (i.e., 3 nmol/L Dpd or 30 nmol bone collagen equivalents/L NTx). The CTx assay demonstrated poor precision for analyte concentration lower than the third calibrator (i.e., 200 micrograms/L). The NTx assay exhibited nonlinear recovery for sample dilutions prepared in buffer; however, this nonlinear recovery could be corrected for sample dilutions made in urine at a low analyte concentration. Supplement recoveries of each of the three assays were within 100% +/- 10% on average. All three analytes showed stability through five freeze-thaw cycles. The mean day-to-day variations were 16% for Dpd, and 23% for both NTx and CTx. Similar diurnal rhythm was observed for all three assays on average, with the peak in the early morning and the nadir in the afternoon. Mean amplitude of the diurnal variation was 37% for Dpd and NTx, and 57% for CTx. Variations within the reference intervals for a healthy premenopausal population were 28% for Dpd, 57% for NTx, and 56% for CTx. Pyrilinks-D has demonstrated analytical precision and accuracy equal or superior to Osteomark and CrossLaps in all areas. Dpd exhibits the least biological variability day-to-day, within individuals across the diurnal cycle, and within a healthy premenopausal population.

Adult↗
PubMed1992

Heterogeneous in vivo MR images of soft tissue tumors: guide to gross specimen sampling.

Twelve soft tissue tumors preoperatively studied with magnetic resonance (MR) imaging contained areas of inhomogeneous intralesional signal intensity. The pathologist's selection of biopsy sites from gross specimens was based on specific MR images selected by a radiologist and depended on close cooperation between the radiologist and pathologist. The histopathology so sampled, further depended on the lesion's size, careful gross specimen orientation, discrete sampling, and a specially developed Grid Analysis technique. Our initial experience indicates that (1) histology may vary within different and often neighboring sites of a single soft tissue lesion; (2) that such variability is common in soft tissue tumors; (3) that histological variability within different sites of a single lesion influences signal heterogeneity; and (4) that although differing MR signal intensities per se are not tissue specific, MR may enhance the histopathological accuracy of pathologists who can be directed to particular gross specimen sites by magnetic resonance images. To our knowledge such a specific, detailed effort has not been made.

Adult↗
PubMed1990

Effects of sedation on intradermal skin testing in flea-allergic dogs.

Effects of 4 commonly used sedatives on the wheal-and-flare response to histamine and flea antigen were evaluated in 8 flea-allergic Beagles. Skin testing was performed in 12 separate occasions, 3 to 4 days apart. Twelve intradermal injections were given during each skin test: 5 doubling dilutions of histamine phosphate, 6 doubling dilutions of flea antigen, and a phosphate-buffered saline solution (negative control). Of the 12 intradermal skin tests, 8 were control tests performed on nonsedated dogs. The remaining 4 tests were performed on dogs sedated with xylazine, ketamine and valium combination, acepromazine, or oxymorphone. Oxymorphone had the most profound effect on skin test results, significantly (P less than 0.05) decreasing skin responsiveness in 8 of 11 test sites (by objective evaluation) and in 5 of 11 test sites (by subjective evaluation). Xylazine sedation enhanced skin test results in 4 of 11 test sites (by objective evaluation) and in 1 of 11 test sites (by subjective evaluation). In non instance did xylazine significantly decrease skin responsiveness to histamine or flea antigen. Xylazine is the recommended sedative in dogs when sedation is necessary for intradermal skin testing.

Acepromazine↗
PubMed1989

In vitro evaluation of a bioartificial pancreas under various hemodynamic conditions.

A bioartificial pancreas in which isolated islets of Langerhans are placed between two polyacrylonitrile membranes, blood circulating successively above the upper and below the lower membranes following a U-shaped circuit, has been developed. The two parts are connected by an outer loop consisting of a thin tubing. The length of this tubing determines the magnitude of the flow rate of blood through the device. The aim of this work was to determine experimentally the optimal configuration of the system containing isolated rat islets and a Krebs buffer circulating through the device. The amount of insulin released by the bioartificial pancreas was determined during a 20-mM square-wave glucose stimulation. First, the inlet pressure was set at 100 mm Hg, and the effect of the length of the tubing was investigated with two devices perfused simultaneously. For a short tubing (flow rate, 20 ml/min), a sharp increase in insulin release in response to glucose was observed; it increased within 4 min from 217 +/- 50 to 761 +/- 237 microU/500 islets/min (p less than 0.05), the peak value being reached at 11 +/- 2 min following the beginning of the stimulation. For a long tubing (flow rate, 3 ml/min), the increase in insulin release was more sluggish. It increased from 133 +/- 53 to 222 +/- 43 microU/500 islets/min at 4 min, the peak value being reached only at 20 +/- 3 min. These data are consistent with a more efficient diffusional transfer of insulin in the case of the high circulating flow.(ABSTRACT TRUNCATED AT 250 WORDS)

Acrylic Resins↗
PubMed1989

The use of real-time orbital ultrasound in Graves' ophthalmopathy: a comparison with computed tomography.

Evaluation of the severity of orbital involvement and likelihood of the development of optic neuropathy in Graves' disease can be clinically difficult. We describe the use of real-time orbital ultrasound scanning to measure the medial rectus muscle width in 20 patients with Graves' ophthalmopathy and 21 normal individuals. The normal reference interval (to 2 SDs) was 1.75 to 4.07 mm. Significantly (p less than 0.001; Mann Whitney U-test) larger values were observed in the patients compared with controls, and there was good correlation between medial rectus width and a clinical index of disease severity in individual eyes (p less than 0.001; Spearman rank correlation coefficient). Comparison of the medial rectus measurements obtained using orbital computed tomography and ultrasound showed positive correlation at the p less than 0.001 significance level. Computed tomographic medial rectus measurements also correlated with horizontal and vertical muscle indices for that orbit. We suggest that real-time ultrasound of medial rectus width, using widely available equipment, provides an accurate, simple and non-invasive means of evaluating the orbits of patients with Graves' disease. Repeated measurements may be of value in identifying patients at high risk of visual failure, and in following prospectively the orbital response to therapy in patients with Graves' ophthalmopathy.

Adult↗
PubMedDate not supplied

Growth response to enteral feeding by children with cerebral palsy.

This study evaluated the growth of 51 children with cerebral palsy after the initiation of enteral tube feedings. The children were divided into three groups according to how soon after their central nervous system (CNS) insult they were started on enteral feedings. Group 1 consisted of 14 children who were within a year of their CNS insult; they were underweight for age, but had normal length as well as weight for length. Within 6 months of initiating enteral tube feedings, most children in this group had normalized their weights. Group 2 consisted of 27 children who were within 8 years of their CNS insult; they were stunted and were underweight for both their age and their length. Within 6 months of initiating enteral feeds, the group increased both weight and weight for length to near normal, but their gains in length reached a plateau at 90% of ideal for age. Group 3 consisted of 10 children who were more than 8 years after their CNS insult. This group was severely malnourished but had some improvement in their weight for age and for length but, length for age showed no significant change. We conclude that the earlier adequate nutritional management of children with severe cerebral palsy is initiated, the more readily the nutritional deficits will reverse.

Adolescent↗