Postal survey of physicians and laboratories: practices and perceptions of molecular oncology testing.

BACKGROUND: Molecular oncology testing (MOT) to detect genomic alterations underlying cancer holds promise for improved cancer care. Yet knowledge limitations regarding the delivery of testing services may constrain the translation of scientific advancements into effective health care. METHODS: We conducted a cross-sectional, self-administered, postal survey of active cancer physicians in Ontario, Canada (N = 611) likely to order MOT, and cancer laboratories (N = 99) likely to refer (i.e., referring laboratories) or conduct (i.e., testing laboratories) MOT in 2006, to assess respondents' perceptions of the importance and accessibility of MOT and their preparedness to provide it. RESULTS: 54% of physicians, 63% of testing laboratories and 60% of referring laboratories responded. Most perceived MOT to be important for treatment, diagnosis or prognosis now, and in 5 years (61% - 100%). Yet only 45% of physicians, 59% of testing labs and 53% of referring labs agreed that patients in their region were receiving MOT that is indicated as a standard of care. Physicians and laboratories perceived various barriers to providing MOT, including, among 70% of physicians, a lack of clear guidelines regarding clinical indications, and among laboratories, a lack of funding (73% - 100%). Testing laboratories were confident of their ability to determine whether and which MOT was indicated (77% and 82% respectively), and perceived that key elements of formal and continuing education were helpful (75% - 100%). By contrast, minorities of physicians were confident of their ability to assess whether and which MOT was indicated (46% and 34% respectively), and while majorities considered various continuing educational resources helpful (68% - 75%), only minorities considered key elements of formal education helpful in preparing for MOT (17% - 43%). CONCLUSION: Physicians and laboratory professionals were enthusiastic about the value of MOT for cancer care but most did not believe patients were gaining adequate access to clinically necessary testing. Further, our results suggest that many were ill equipped as individual stakeholders, or as a coordinated system of referral and interpretation, to provide MOT. These challenges should inspire educational, training and other interventions to ensure that developments in molecular oncology can result in optimal cancer care.

Informing parents about expanded newborn screening: influences on provider involvement.

OBJECTIVE: Expanded newborn screening (NBS) identifies some disorders for which clinical benefit is uncertain, as well as "incidental" findings (eg, carrier status), thus enhancing the need to inform parents about NBS before sample collection. METHODS: A self-complete survey was sent to a cross-sectional, stratified, random sample of 5 provider groups in Ontario (obstetricians, midwives, family physicians, pediatricians, and nurses). Univariate and multivariate analyses were used to investigate the effects of core beliefs, perceived barriers, and demographic characteristics on the reported frequency of informing parents about NBS before sample collection. RESULTS: Virtually all of the midwives and almost half of the nurses reported discussing NBS with parents, whereas less than one sixth of the physicians did so. Providers who perceived a responsibility to inform parents were 3 times more likely to report doing so than those who did not perceive this responsibility (odds ratio: 2.9 [95% confidence interval: 2.1-4.1]). Those who lacked confidence to inform parents were 70% less likely to discuss NBS with parents compared with those who did not experience this cognitive barrier (odds ratio: 0.3 [95% confidence interval: 0.2-0.4]). Controlling for these covariates, family physicians and obstetricians were more likely than pediatricians to inform parents. CONCLUSIONS: These results provide guidance for capacity building among providers who are positioned to inform parents about NBS before sample collection. Our findings call for targeted educational interventions that consider patterns of provider practice related to prenatal and NBS care, seek to redress confidence limitations, and engage key provider groups in the importance of this professional responsibility.

Secretion of water and ions by malpighian tubules of larval mosquitoes: effects of diuretic factors, second messengers, and salinity.

The effects of changes in the salinity of the rearing medium on Malpighian tubule fluid secretion and ion transport were examined in larvae of the freshwater mosquito Aedes aegypti and the saltwater species Ochlerotatus taeniorhynchus. For unstimulated tubules of both species, the K(+) concentration of secreted fluid was significantly lower when larvae were reared in 30% or 100% seawater (O. taeniorhynchus only), relative to tubules from freshwater-reared larvae. The Na(+) concentration of secreted fluid from unstimulated tubules of O. taeniorhynchus reared in 30% or 100% seawater was higher relative to tubules from freshwater-reared larvae. The results suggest that changes in salinity of the larval rearing medium lead to sustained changes in ion transport mechanisms in unstimulated tubules. Furthermore, alterations of K(+) transport may be utilized to either conserve Na(+) under freshwater (Na(+)-deprived) conditions or eliminate more Na(+) in saline (Na(+)-rich) conditions. The secretagogues cyclic AMP [cAMP], cyclic GMP [cGMP], leucokinin-VIII, and thapsigargin stimulated fluid secretion by tubules of both species. Cyclic AMP increased K(+) concentration and decreased Na(+) concentration in the fluid secreted by tubules isolated from O. taeniorhynchus larvae reared in 100% seawater. Interactions between rearing salinity and cGMP actions were similar to those for cAMP. Leucokinin-VIII and thapsigargin had no effect on secreted fluid Na(+) or K(+) concentrations. Results indicate that changes in rearing medium salinity affect the nature and extent of stimulation of fluid and ion secretion by secretagogues.

Na+ competes with K+ in bumetanide-sensitive transport by Malpighian tubules of Rhodnius prolixus.

We examined the effects of bathing saline Na+/K+ ratio, bumetanide and hydrochlorothiazide on fluid and ion transport by serotonin-stimulated Malpighian tubules of Rhodnius prolixus. Previous pharmacological and electrophysiological studies indicate that a bumetanide-sensitive Na+/K+/2Cl- cotransporter is the primary route for basolateral ion entry into the cell during fluid secretion. The goal of this study was to resolve the apparent conflict between relatively high secretion rates by tubules bathed in K+-free saline and the evidence that Na+/K+/2Cl- cotransporters described in other systems have an absolute requirement for all three ions for translocation. Our measurements of fluid secretion rate, ion fluxes and electrophysiological responses to serotonin show that fluid secretion in K+-free saline is bumetanide sensitive and hydrochlorothiazide insensitive. Dose-response curves of secretion rate versus bumetanide concentration were identical for tubules bathed in K+-free and control saline with IC50 values of 2.6 x 10(-6) mmol l(-1) and 2.9 x 10(-6) mmol l(-1), respectively. Double-reciprocal plots of K+ flux versus bathing saline K+ concentration showed that increasing Na+ concentration in the bathing fluid increased Kt but had no effect on Jmax, consistent with competitive inhibition of K+ transport by Na+. We propose that the competition between Na+ and K+ for transport by the bumetanide-sensitive transporter is part of an autonomous mechanism by which Malpighian tubules regulate haemolymph K+ concentration.

Inhibition of the SAPK/JNK pathway blocks the stimulatory effects of glutamine on fluid secretion by the Malpighian tubules of Rhodnius prolixus.

Physiological levels of amino acids such as glutamine, glutamate, aspartate and proline increase the rates of fluid secretion and ion transport by serotonin-stimulated Malpighian tubules (MTs) of Rhodnius prolixus. Here, we examine the proposal that the effects of glutamine are mediated through activation of specific kinases to produce the observed increases in fluid secretion. The glutamine-dependent increase in MT fluid secretion rate was blocked by two chemically unrelated inhibitors of the stress activated protein kinase (SAPK) pathway, SP600125 and dicumarol. Inhibitors of phosphatidyl inositol-3 kinase, p38 mitogen activated protein kinase (MAPK), extracellular-signal regulated kinases and MAPK kinase did not block glutamine's effects on fluid secretion rate when applied at commonly used concentrations. Inhibitors of protein kinase A or C reduced fluid secretion rates of serotonin-stimulated MTs, but did not block the response to glutamine. The glutamine-dependent increase in fluid secretion was also insensitive to cytoskeletal disrupting agents and protein synthesis inhibitors. Results of this study are the first to suggest a role for the SAPK pathway in the control of fluid secretion rates by insect MTs.

Amino acids modulate ion transport and fluid secretion by insect Malpighian tubules.

Insect haemolymph typically contains very high levels of free amino acids. This study shows that amino acids can modulate the secretion of ions and water by isolated Malpighian tubules of Rhodnius prolixus and Drosophila melanogaster. Secretion rates of Rhodnius tubules in amino-acid-free saline increase after addition of serotonin to a peak value, then slowly decline to a plateau. Addition of glutamine, glutamate or aspartate to such tubules increases secretion rates dramatically relative to the controls in amino-acid-free saline, and these increases are sustained for 1-2 h. Seven other amino acids have more modest stimulatory effects, whereas lysine and arginine are inhibitory. Secreted fluid pH and Na(+) concentration increase and K(+) concentration decreases in response to glutamine. Pre-incubation of unstimulated tubules in saline solutions containing amino acids followed by stimulation with serotonin in amino-acid-free saline shows that the effects of amino acids far outlast the duration of exposure to them. Amino acids do not appear to be important as metabolites in Rhodnius tubules, nor do they act to draw significant amounts of water into the lumen by osmosis. Significant stimulation of fluid secretion can be achieved by physiological levels of particular amino acids, whereas those amino acids that inhibit fluid secretion only do so at concentrations much above those at which they occur naturally in the haemolymph. Secretion rates of unstimulated or stimulated Drosophila tubules are increased by pre-incubation in saline solutions containing glutamine or methionine or by continuous exposure to glutamine, methionine or tyrosine. Cysteine dramatically inhibited fluid secretion by Drosophila tubules, but only at concentrations well above the physiological range. We suggest that the amino acids probably function as compatible intracellular osmolytes that are necessary for sustained secretion at high rates by the Malpighian tubules.

Intracellular ion activities in Malpighian tubule cells of Rhodnius prolixus: evaluation of Na+-K+-2Cl- cotransport across the basolateral membrane.

Intracellular ion activities (a(ion)) and basolateral membrane potential (Vbl) were measured in Malpighian tubule cells of Rhodnius prolixus using double-barrelled ion-selective microelectrodes. In saline containing 103 mmol l(-1) Na+, 6 mmol l(-1) K+ and 93 mmol l(-1) Cl-, intracellular ion activities in unstimulated upper Malpighian tubules were 21, 86 and 32 mmol l(-1), respectively. In serotonin-stimulated tubules, aCl was unchanged, whereas aNa increased to 33 mmol l(-1) and aK declined to 71 mmol l(-1). Vbl was -59 mV and -63 mV for unstimulated and stimulated tubules, respectively. Calculated electrochemical potentials (deltamuF) favour passive movement of Na+ into the cell and passive movement of Cl- out of the cell in both unstimulated and serotonin-stimulated tubules. Passive movement of K+ out of the cell is favoured in unstimulated tubules. In stimulated tubules, deltamuF for K+ is close to 0 mV. The thermodynamic feasibilities of Na+-K+-2Cl-, Na+-Cl- and K+-Cl- cotransporters were evaluated by calculating the net electrochemical potential (deltamu(net)/F) for each transporter. Our results show that a Na+-K+-2Cl- or a Na+-Cl- cotransporter but not a K+-Cl- cotransporter would permit the movement of ions into the cell in stimulated tubules. The effects of Ba2+ and ouabain on Vbl and rates of fluid and ion secretion show that net entry of K+ through ion channels or the Na+/K+-ATPase can be ruled out in stimulated tubules. Maintenance of intracellular Cl- activity was dependent upon the presence of both Na+ and K+ in the bathing saline. Bumetanide reduced the fluxes of both Na+ and K+. Taken together, the results support the involvement of a basolateral Na+-K+-2Cl- cotransporter in serotonin-stimulated fluid secretion by Rhodnius prolixus Malpighian tubules.