Observation of Seven Astrophysical Tau Neutrino Candidates with IceCube

We report on a measurement of astrophysical tau neutrinos with 9.7 yr of IceCube data. Using convolutional neural networks trained on images derived from simulated events, seven candidate ν_{τ} events were found with visible energies ranging from roughly 20 TeV to 1 PeV and a median expected parent ν_{τ} energy of about 200 TeV. Considering backgrounds from astrophysical and atmospheric neutrinos, and muons from π^{±}/K^{±} decays in atmospheric air showers, we obtain a total estimated background of about 0.5 events, dominated by non-ν_{τ} astrophysical neutrinos. Thus, we rule out the absence of astrophysical ν_{τ} at the 5σ level. The measured astrophysical ν_{τ} flux is consistent with expectations based on previously published IceCube astrophysical neutrino flux measurements and neutrino oscillations.

Electrocardiography of Atrioventricular Block

Delayed atrioventricular (AV) conduction most commonly occurs in the AV node, resulting from AH prolongation on an intracardiac electrocardiogram and PR prolongation on a surface electrocardiogram. AV conduction may be blocked in a 2:1 manner, with a normal PR interval and wide QRS suggesting infranodal disease, whereas a prolonged PR interval and narrow QRS are more suggestive of AV nodal disease. Block within the His is suspected when there is 2:1 AV block with normal PR and QRS intervals. Complete heart block occurs when the atrial rhythm is totally independent of a junctional or lower escape rhythm.

Observation of high-energy neutrinos from the Galactic plane

The origin of high-energy cosmic rays, atomic nuclei that continuously impact Earth's atmosphere, is unknown. Because of deflection by interstellar magnetic fields, cosmic rays produced within the Milky Way arrive at Earth from random directions. However, cosmic rays interact with matter near their sources and during propagation, which produces high-energy neutrinos. We searched for neutrino emission using machine learning techniques applied to 10 years of data from the IceCube Neutrino Observatory. By comparing diffuse emission models to a background-only hypothesis, we identified neutrino emission from the Galactic plane at the 4.5σ level of significance. The signal is consistent with diffuse emission of neutrinos from the Milky Way but could also arise from a population of unresolved point sources.

Design and Preclinical Evaluation of Nicotine-Stearic Acid Conjugate-Loaded Solid Lipid Nanoparticles for Transdermal Delivery: A Technical Note

This study aimed to develop and evaluate nicotine--stearic acid conjugate-loaded solid lipid nanoparticles (NSA-SLNs) for transdermal delivery in nicotine replacement therapy (NRT). Nicotine conjugation to stearic acid prior to SLN formulation greatly increased drug loading. SLNs loaded with a nicotine-stearic acid conjugate were characterized for size, polydispersity index (PDI), zeta potential (ZP), entrapment efficiency, and morphology. Pilot in vivo testing was carried out in New Zealand Albino rabbits. The size, PDI, and ZP of nicotine-stearic acid conjugate-loaded SLNs were 113.5 ± 0.91 nm, 0.211 ± 0.01, and -48.1 ± 5.75 mV, respectively. The entrapment efficiency of nicotine-stearic acid conjugate in SLNs was 46.45 ± 1.53%. TEM images revealed that optimized nicotine-stearic acid conjugate-loaded SLNs were uniform and roughly spherical in shape. Nicotine-stearic acid conjugate-loaded SLNs showed enhanced and sustained drug levels for up to 96 h in rabbits when compared with the control nicotine formulation in 2% HPMC gel. To conclude, the reported NSA-SLNs could be further explored as an alternative for treating smoking cessation.

Ripple mapping in ventricular tachycardia substrate mapping and ablation of nonischemic ventricular tachycardia

INTRODUCTION

Substrate-based ablation for ventricular tachycardia (VT) using Ripple map (RM) is an effective treatment strategy for patients with ischemic cardiomyopathy but has yet to be evaluated in patients with nonischemic cardiomyopathy (NICMO). The aim of this study is to determine the feasibility and effectiveness of an RM-based ablation for NICMO patients.

METHODS AND RESULTS

This was a single-center, retrospective study including all NICMO patients undergoing VT ablation at St Vincent Hospital between January 1, 2018 and January 12, 2019. Retrospective RM analysis was performed on those that had a substrate-based ablation to identify the location and number of Ripple channels as well as their proximity to ablation lesions. Thirty-three patients met the inclusion criteria and had a median age of 65 (58, 73.5) with 15.2% of the population being female, and were followed for a median duration of 451 (217.5, 586.5) days. Of these patients, 23 (69.7%) had a substrate-based ablation with a median procedural duration of 196.4 (186.8, 339) min, 1946 (517, 2750) points collected per map, and 277 (141, 554) points were within the scar. Two (8.6%) procedural complications occurred, and 7 (30.4%) patients had VT recurrence during follow-up. RM analysis revealed an average of two Ripple channels and the patients without VT recurrence had ablation performed closer to the Ripple channels: 0 (0, 4.7) versus 14.3 (0, 23.5) cm; p = .02.

CONCLUSION

An RM-based substrate ablation can be performed in NICMO patients and ablation within Ripple channels is a predictor of VT freedom.

Search for Unstable Sterile Neutrinos with the IceCube Neutrino Observatory

We present a search for an unstable sterile neutrino by looking for a resonant signal in eight years of atmospheric ν_{μ} data collected from 2011 to 2019 at the IceCube Neutrino Observatory. Both the (stable) three-neutrino and the 3+1 sterile neutrino models are disfavored relative to the unstable sterile neutrino model, though with p values of 2.8% and 0.81%, respectively, we do not observe evidence for 3+1 neutrinos with neutrino decay. The best-fit parameters for the sterile neutrino with decay model from this study are Δm_{41}^{2}=6.7_{-2.5}^{+3.9}  eV^{2}, sin^{2}2θ_{24}=0.33_{-0.17}^{+0.20}, and g^{2}=2.5π±1.5π, where g is the decay-mediating coupling. The preferred regions of the 3+1+decay model from short-baseline oscillation searches are excluded at 90% C.L.

Advances in in-vitro bioequivalence testing methods for complex ophthalmic generic products

The United States Food and Drug Administration (USFDA) demands that the generic industry prove topical ocular products' pharmaceutical and bioequivalence (BE). In contrast to generic oral drugs, topical ocular product BE testing has proved difficult. New generic versions are compared to an authorized drug product known as a Reference Listed Drug (RLD) to demonstrate their bioequivalence. If the excellent in-vitro results may support the presumption of equivalence in-vivo performance and the only clinically significant difference between the generic and RLD is in its physicochemical qualities and drug release rate, then in-vivo BE studies may be waived. Proving BE through dissolution tests is a golden standard for most conventional dosage forms. However, due to the limited number of biorelevant in-vitro drug release testing (IVRT) approaches capable of differentiating their performance based on product quality and physicochemical properties, the development of generic ophthalmic products has been slow and time-consuming. Often, BE of topical ophthalmic formulations cannot be proved using a single in-vitro test; therefore, an elaborated discussion on various IVRT methods performed to demonstrate bioequivalence of complex generis like ophthalmic emulsions, suspensions, ointments, and gels is necessary. This manuscript aims to review the status of biowaiver criteria for complex ophthalmic products concerning the product-specific FDA guidance to the generic industry.

Strong Constraints on Neutrino Nonstandard Interactions from TeV-Scale ν_{μ} Disappearance at IceCube

We report a search for nonstandard neutrino interactions (NSI) using eight years of TeV-scale atmospheric muon neutrino data from the IceCube Neutrino Observatory. By reconstructing incident energies and zenith angles for atmospheric neutrino events, this analysis presents unified confidence intervals for the NSI parameter ε_{μτ}. The best-fit value is consistent with no NSI at a p value of 25.2%. With a 90% confidence interval of -0.0041≤ε_{μτ}≤0.0031 along the real axis and similar strength in the complex plane, this result is the strongest constraint on any NSI parameter from any oscillation channel to date.

Search for Relativistic Magnetic Monopoles with Eight Years of IceCube Data

We present an all-sky 90% confidence level upper limit on the cosmic flux of relativistic magnetic monopoles using 2886 days of IceCube data. The analysis was optimized for monopole speeds between 0.750c and 0.995c, without any explicit restriction on the monopole mass. We constrain the flux of relativistic cosmic magnetic monopoles to a level below 2.0×10^{-19}  cm^{-2} s^{-1} sr^{-1} over the majority of the targeted speed range. This result constitutes the most strict upper limit to date for magnetic monopoles with β≳0.8 and up to β∼0.995 and fills the gap between existing limits on the cosmic flux of nonrelativistic and ultrarelativistic magnetic monopoles.

Rate Control Versus Rhythm Control in Patients with Left Ventricular Assist Devices and Atrial Fibrillation

Background

Atrial fibrillation (AF) is a common comorbidity in patients with left ventricular assist devices (LVAD) with no defined guideline treatment strategy of rate versus rhythm control. The purpose of this study is to determine the effects of rate versus rhythm control for AF on the outcomes of patients with LVAD at our institution.

Methods

Consecutive patients who underwent LVAD implantation at St Vincent Hospital from January 1, 2015 to December 31, 2017 were retrospectively evaluated. Patients with AF were identified and divided into rate control or rhythm control groups. The primary outcome evaluated was a composite of death, heart failure admission, gastrointestinal bleed, ventricular tachycardia, cerebrovascular accident, hemolysis, and pump thrombosis. Secondary outcomes included the individual variables from the primary outcome.

Results

Out of 201 patients that underwent LVAD implantation, 81 had AF after implantation and were included with a median follow-up period of 384 days. The rate control group (n = 31; 38%) and the rhythm control group (n = 51; 62%) had no difference in composite outcomes (61% vs 59%, p = 0.83). When taken individually there was no difference in outcomes between the two groups. Thirteen patients underwent electrical cardioversion and successful conversion to normal sinus rhythm occurred in 71% of cases with a 60% recurrence rate.

Conclusions

There was no difference in primary outcome between rate and rhythm control groups. These data suggest that maintenance of sinus rhythm may not be necessary in all patients with LVAD.

Electrocardiography of Atrioventricular Block

Delayed atrioventricular (AV) conduction most commonly occurs in the AV node, resulting from AH prolongation on an intracardiac electrocardiogram and PR prolongation on a surface electrocardiogram. AV conduction may be blocked in a 2:1 manner, with a normal PR interval and wide QRS suggesting infranodal disease, whereas a prolonged PR interval and narrow QRS are more suggestive of AV nodal disease. Block within the His is suspected when there is 2:1 AV block with normal PR and QRS intervals. Complete heart block occurs when the atrial rhythm is totally independent of a junctional or lower escape rhythm.

eV-Scale Sterile Neutrino Search Using Eight Years of Atmospheric Muon Neutrino Data from the IceCube Neutrino Observatory

The results of a 3+1 sterile neutrino search using eight years of data from the IceCube Neutrino Observatory are presented. A total of 305 735 muon neutrino events are analyzed in reconstructed energy-zenith space to test for signatures of a matter-enhanced oscillation that would occur given a sterile neutrino state with a mass-squared differences between 0.01 and 100  eV^{2}. The best-fit point is found to be at sin^{2}(2θ_{24})=0.10 and Δm_{41}^{2}=4.5  eV^{2}, which is consistent with the no sterile neutrino hypothesis with a p value of 8.0%.

Evaluation of Formulation Parameters on Permeation of Ibuprofen from Topical Formulations Using Strat-M® Membrane

Topical drug delivery is an attractive alternative to conventional methods because of advantages such as non-invasive delivery, by-pass of first pass metabolism, and improved patient compliance. However, several factors such as skin, physicochemical properties of the drug, and vehicle characteristics influence the permeation. Within a formulation, critical factors such as concentration of drug, physical state of drug in the formulation, and organoleptic properties affect the flux across the skin. The aim of the study was to develop and investigate topical semisolid preparations (creams and gels) with ibuprofen as the model drug and investigate the effect of various formulation parameters on the in-vitro performance across the Strat-M® membrane using flow-through cells. In addition, the physical stability of the developed formulations was investigated by studying viscosity, pH, and appearance. All the formulations developed in the study had appealing appearance with smooth texture and no signs of separation. Viscosity and pH of the formulations were acceptable. Cumulative amount of drug permeated at the end of 24 h was highest for clear gel (3% w/w ibuprofen; F6: 739.6 ± 36.1 µg/cm2) followed by cream with high concentration of ibuprofen in suspended form (5% w/w; F3: 320.8 ± 17.53 µg/cm2), emulgel (3% w/w ibuprofen; F5: 178.5 ± 34.5 µg/cm2), and cream with solubilized ibuprofen (3% w/w; F2A: 163.2 ± 9.36 µg/cm2). Results from this study showed that permeation of ibuprofen was significantly influenced by formulation parameters such as concentration of ibuprofen (3% vs. 5% w/w), physical state of ibuprofen (solubilized vs. suspended), formulation type (cream vs. gel), mucoadhesive agents, and viscosity (high vs. low). Thus, findings from this study indicate that pharmaceutical formulation scientists should explore these critical factors during the early development of any new topical drug product in order to meet pre-determined quality target product profile.

Effect of diet-induced obesity and metabolic syndrome on skeletal muscles of Ossabaw miniature swine

Ossabaw swine fed excess kilocalorie diet develop metabolic syndrome (MS) characterized by obesity, hypertension, insulin resistance, and glucose intolerance with/without dyslipidemia. The purpose of this study was to test the hypothesis that MS would have a detrimental effect on skeletal muscle structure and cause changes in the expression of myosin heavy chains (MHCs). Adult male Ossabaw swine were fed for 24 wk high-fructose or high-fat/cholesterol/fructose diets to induce normolipidemic MS (MetS) or dyslipidemic MS (DMetS), respectively, and were compared with the lean swine on control diet. MetS swine showed mild MS, lacking increases in total and low density lipoprotein (LDL) cholesterol, both of which were highly upregulated in DMetS swine. There was an ∼1.2-fold increase in the cross-sectional areas of muscle fibers in MetS and DMetS groups compared with control for biceps femoris and plantaris muscles. In plantaris muscles, DMetS diet caused an ∼2-fold decrease in slow MHC mRNA and protein expression and an ∼1.2- to 1.8-fold increase in the number of intramyocellular lipid (IMCL) droplets without large changes in the size of the droplets. There was a trend to the decrease in slow MHC expression in muscles of swine on MetS diet. The number of IMCL droplets in muscle fibers of the MetS group was comparable to controls. These data correlate well with the data on total plasma cholesterol (control = 60, MetS = 70, and DMetS = 298 mg/dl) and LDL (control = 29, MetS = 30, and DMetS = 232 mg/dl). We conclude that structural changes observed in skeletal muscle of obese Ossabaw swine correlate with those previously reported for obese humans.

Effect of dietary intake on steroid feedback on release of luteinizing hormone in ovariectomized cows

This study tested the hypothesis that the decline in pulsatile release of luteinizing hormone (LH), resulting from steroid negative feedback, is greater in animals fed a low, compared with a high, plane of nutrition. Two-year-old cows were ovariectomized and six days later were fed diets to provide 1.5 x maintenance requirements (n = 6, supplemented) or 0.5 x maintenance requirements (n = 6, restricted) (Round 1). Pulsatile release of LH was measured over a 14-h period on the fifth day of feeding these diets (Day 1); at 6 h, all animals were treated with an intravaginal insert containing 1.38 g progesterone, which remained in place until the end of Day 3. Pulsatile release of LH was again measured for 14 h on Day 3; at 6 h, all animals were injected intramuscularly with oestradiol benzoate (ODB; 1 mg per 500 kg live weight). Three days later, this protocol was repeated, in a cross-over design, with cows that were previously restricted now being supplemented and those cows previously supplemented, now restricted (Round 2). Plasma concentrations of progesterone after intravaginal progesterone treatment were 1.01 ng mL(-1) higher in restricted cows compared with supplemented cows (P < 0.001) and were also higher in Round 1 than in Round 2 and on Day 1 than on Day 3 (P < 0.001). Plasma concentrations of oestradiol following injection with ODB did not differ between supplemented and restricted cows (P > 0.1). Dietary intake did not affect mean concentrations of LH, pulse frequency or amplitude during the 6-h period before steroid treatment or the change in these variables following steroid treatment; however, the slope of the decline in concentrations of LH following progesterone treatment was significantly more negative in cows fed restricted diets compared with those fed supplemented diets. In Round 2, mean concentrations of LH were higher preceding, and decreased more following, progesterone treatment compared with the decrease after ODB treatment. In conclusion, acute dietary restriction resulted in a more rapid decline in the release of LH following treatment with intravaginal progesterone, and was associated with higher concentrations of progesterone in plasma.

Effect of treatment with progesterone and oestradiol benzoate on ovarian follicular turnover in postpartum anoestrous cows and cows which have resumed oestrous cycles

Two experiments were carried out to determine the effect of a low dose of progesterone (P) with and without the addition of an injection of oestradiol benzoate (ODB) on ovarian follicle dynamics, oestradiol production and LH pulsatility in postpartum anoestrous cows, compared with cows which had resumed oestrous cycles (cycling cows). In the first experiment, anoestrous Jersey cows were treated with (AN+P, n=8) or without (AN-3, n=3) a previously used intravaginal progesterone releasing (CIDR) device for 10 days, commencing 3 or 4 days after emergence of a new dominant follicle (DF1) as determined by transrectal ultrasonography. Contemporary cycling cows (CYC+P, n=8) were similarly treated with used CIDR devices and injected with prostaglandin F(2alpha) (PGF) at the time of device insertion. Follicle turnover was monitored by daily ultrasonography and pulsatile release of LH was measured on the ninth day after device insertion. During the period of CIDR device insertion, a second dominant follicle emerged in 4/8 of the CYC+P group and 7/8 of the AN+P group (P=0.14). Maximum diameter of DF1 was greater in cows in the CYC+P compared with the AN+P group (P=0.02), but did not differ between cows in the AN+P and AN-P groups (P>0.1). Frequency of LH pulses was greater in cows in the CYC+P than AN+P group (P=0.06), and in cows in the AN+P than AN-P group (P=0.02). In the second experiment, anoestrous (n=20) and cycling (n=11) Friesian cows were treated with a new CIDR device for 6 days commencing 3 days after emergence of a new dominant follicle (DF1). Cycling cows were also injected with PGF on the day of device insertion. Half of the cows in each group were injected with 2mg ODB on the day of device insertion. Daily ultrasonography was used to monitor follicular dynamics throughout the experimental period. Follicular turnover was increased by ODB in cycling (5/5 versus 1/6; P<0.05), but not anoestrous cows (5/9 versus 4/11). Persistence of DF1 was reduced by ODB treatment in both cycling and anoestrous cows (P<0.001). Maximum diameter of DF1 was influenced by ODB treatment and reproductive status (P<0.05). In anoestrous cows in which a second dominant follicle did not emerge during the period of device insertion, the interval from emergence of DF1 to emergence of a second dominant follicle was significantly delayed by treatment with ODB (P=0.04). In conclusion, P treatment of anoestrous cows increased pulsatile release of LH, but did not induce the development of persistent follicles. Injection of ODB in association with P treatment reduced the persistence of dominant follicles in both cycling and anoestrous cows, but delayed subsequent follicular development in a proportion of anoestrous cows.

Distal 5q deletion syndrome: phenotypic correlations

We describe the phenotypes of two male sibs with partial monosomy of chromosome 5 [46,XY,der(5)inv ins(1;5)(p32;q35.4q34)]; maternally derived from a balanced insertion of 1 and 5 [inv ins (1;5)(p.32;q35.4q34)]. One sib had microcephaly, cleft lip and palate, facial anomalies, atrial (ASD) and ventricular (VSD) septal defects, camptodactyly 4th and 5th fingers, and developmental delay. The other sib showed microcephaly, facial anomalies, ASD, hypotonia, primary optic nerve hypoplasia, and developmental delay. Only seven other patients with 5q deletions distal to 5q33 have been reported and none showed the putative breakpoints identified in our two patients. All nine showed developmental delay or malformations of the CNS and facial anomalies; six of nine had defects of cardiac septation. Our two patients and one other were shown to have only one copy of the cardiac specific hCSX gene that defines in part the etiology of their ASD and VSD. The other components of their phenotypes cannot be related at present to genes identified in the deleted segments.

Interstitial duplication of the short arm of chromosome 1 in a newborn with congenital heart disease and multiple malformations

Interstitial duplications of chromosomes 1p are rare, with only 14 cases previously reported in the literature, and those have not revealed a unique syndrome. The phenotypes include multiple congenital abnormalities and both intra- and extra-uterine growth retardation. In general, the patients do poorly and do not survive beyond the age of several months. We report a newborn male with karyotype 46, XY, inv dup(1)(qter--> p34.3::p34.3-->p32.3::34.3-->pter) with multiple congenital abnormalities including congenital heart disease and co-existing portal and pulmonary hypertension. The chromosome 1 origin of the extra material was confirmed with fluorescent in situ hybridization (FISH). Review of the GDB [Human Genome Database, 1990] reveals that the duplicated region includes the locus EDN2 that encodes endothelin-1, a potent vasoconstrictor, making genetic overdosage of this protein a likely etiology of the pulmonary hypertension. The diffuse abnormalities show effects in multiple cell lines and suggest that this region of chromosome 1p could be involved in determining cell migration and/or differentiation during organogenesis.

Molecular and cytogenetic analysis of familial Xp deletions

Five families in which an Xp deletion is segregating and two families in which an X chromosome rearrangement including a deletion of the short arm is segregating were ascertained for study. Normal fertility was seen in all families. Members from 5 of the 7 families manifested short stature (height <5th centile), while normal height was present in two families. Studies of both the FMR-1 and the androgen receptor loci using PCR based X-inactivation analysis demonstrated that in all families analyzed, there is preferential inactivation of one X chromosome. Molecular cytogenetic analysis showed that members of 3 of the 7 families share a common breakpoint in an approximate 2-3 Mb region at Xp22.12, suggesting a possible hotspot for chromatin breakage. Previous genotype-phenotype correlations and deletion mapping have indicated that a gene for stature resides within the pseudoautosomal region in Xp22.33. Our findings indicate that the loss of this region is not always associated with short stature, suggesting that other factors may be involved.

Cancer genetics for the clinician: recommendations on screening for BRCA1 and BRCA2 mutations

Mutations in the BRCA1 and BRCA2 genes confer a greatly increased risk of breast cancer, ovarian cancer, and other malignant diseases. This paper offers recommendations about who should be screened for BRCA mutations, and insights into the ramifications of BRCA testing.

Effect of ventilation and filtration on submicrometer particles in an indoor environment

The effect of filtration and ventilation on reduction of submicrometer particle concentration indoors was investigated in an office building. The air-handling system consisting of dry media filters and an air-conditioning unit, reduced particle concentration levels by 34%. The characteristics of indoor airborne particles were dominated by, and followed the pattern of, outdoor air, with vehicle combustion aerosols as the main pollutant. The ratio indoor/outdoor particle concentration varied between 14 and 26% for different sub-zones. The presence of significant source of particles indoors was not observed. A simple mathematical model predicting evolution of particles indoors is presented. The model, based on a particle number balance equation, was validated with experimental data and showed very good agreement between predicted and measured parameters.

Relation between indoor and outdoor exposure to fine particles near a busy arterial road

Various studies on indoor and outdoor particulate matter in the urban environment in the vicinity of busy arterial roads in the centre of the subtropical city of Brisbane have indicated that the revised United States Environmental Protection Agency National Ambient Air Quality Standards (US EPA NAAQS) for Particulate matter PM2.5 could be exceeded not only outdoors but also indoors. The aim of this work was to investigate outdoor exposure to submicrometer particles and their relationship with indoor exposure in a hypothetical office building located in the vicinity of a busy arterial road. The outdoor exposure values and trends were measured in terms of particle number in the submicrometer size range and were then recalculated to represent mass concentration trends. The results of this study indicate that exposure to PM0.7 particles in ambient air close to a busy road often exceeds the levels of the annual and 24-hour US EPA NAAQS PM2.5 standards. It is likely that exposure to PM2.5 is even higher, and may significantly exceed these standards.

Insemination at the second of two induced oestrous periods in anoestrous dairy cows increases conception rates to first service

AIM

To determine whether mating previously anoestrous cows on their second, rather than first, oestrus post pm-turn could increase conception rates to that service.

METHODS

Cows diagnosed as anovulatory anoestrus were allocated to two groups, starting treatment on Day -17 (OES2) or on Day -7 (OESI) where the date of the planned start of mating = Day 0. All cows were treated with intravaginal progesterone (CIDR device) for 6 days and an injection of 1 mg oestradiol benzoate 24 h after removal of the device. Cows in the OES2 group were also injected with prostaglandin F2alpha on Day 0.

RESULTS

During the first 7 days of mating, 61.8% (207/335) and 88.2% (328/372) of cows in the OES2 and OESl groups, respectively, were inseminated on detection of oestrus (p <0.001). Oestrus without ovulation occurred in 1.5% of cows in the OES2 group and 6.2% of cows in the OESl group during this period (p <0.01). Of those cows inseminated in the first week of mating, conception rates were 54.0% in the OES2 group and 45.5% in the OESl group (p = 0.05). There was no significant difference in median interval from start of mating to conception between the two groups (24 and 22 days for OES2 and OESl, respectively, p >0.05).

CONCLUSION

Mating previously anoestrous cows on their second, rather than first oestrus post partum increased conception rates to that service. However, median intervals from start of mating to conception were not altered.

Combined assessment of myocardial perfusion and left ventricular function with exercise technetium-99m sestamibi gated single-photon emission computed tomography can differentiate between ischemic and nonischemic dilated cardiomyopathy

The purpose of this study was to determine whether exercise technetium-99m sestamibi gated single-photon emission computed tomography (SPECT) accurately distinguishes between patients with ischemic cardiomyopathy and patients with nonischemic left ventricular systolic dysfunction. Noninvasive tests have previously failed to accurately separate patients with ischemic cardiomyopathy from those with nonischemic cardiomyopathy. Technetium-99m gated SPECT imaging offers advantages that have the potential to overcome the limitations of previous studies. Thirty-seven adults with a left ventricular ejection fraction < or = 35%, including 24 patients with nonischemic cardiomyopathy and 13 patients with ischemic cardiomyopathy, were prospectively evaluated using symptom-limited metabolic exercise treadmill testing with technetium-99m sestamibi gated SPECT imaging. Interpretation of myocardial perfusion and regional wall motion was performed, using a 17-segment model. Summed stress, rest, and reversibility perfusion defect scores were determined, and the variance of segmental wall motion scores was computed. Summed stress, rest, and reversibility perfusion defect scores were significantly lower in nonischemic cardiomyopathy patients, compared with those with ischemic cardiomyopathy (summed stress defect score: 6.9 +/- 3.8 vs 32.9 +/- 7.7, respectively, p <0.001). Variability in segmental wall motion was also significantly lower in patients with nonischemic cardiomyopathy compared with those with ischemic cardiomyopathy (variance: 0.3 +/- 0.3 vs 1.2 +/- 0.8, respectively, p <0.001). Thus, assessment of myocardial perfusion and regional ventricular function with exercise technetium-99m sestamibi gated SPECT imaging can reliably distinguish between patients with ischemic cardiomyopathy and patients with nonischemic dilated cardiomyopathy.

An experience with "research by committee"

The Nursing Research Committee of a community hospital describes the difficulties and unexpected pitfalls encountered during an attempt to conduct "research by committee." The steps of the process, from initial development of a research question through research design and implementation and termination of the project, are related. A retrospective analysis of the difficulties encountered serves as a basis for recommendations to others who might consider research by committee. Although a valid means for conducting research, the experiences of this committee indicate how forces, in their control and beyond their control, might influence completion of a project.

Predictors of referral to cardiac rehabilitation and cardiac exercise self-efficacy

Cardiac rehabilitation (CR) has known benefits after myocardial infarction (MI) or coronary artery bypass surgery (CABG). Yet, only a small percentage of patients are referred for outpatient CR after hospital discharge. This study investigates patient characteristics related to referral to CR and cardiac exercise self-efficacy, a salient predictor of health behavior change and maintenance. Two hundred nineteen patients enrolled in the study. Of the 185 patients who were CR candidates, 74 were referred to CR. Logistic regression analysis was used to identify variables related to CR referral. Results indicate that patient characteristics of having had fewer MIs or CABGs, having attended CR in the past, and being less physically active during leisure time are related to an increased likelihood of being referred to CR. Multiple regression analysis indicates that leisure physical activity is a predictor of cardiac exercise self-efficacy. Implications for nurses who recruit patients for CR are discussed.

A new approach to assessment and documentation of conscious sedation during endoscopic examinations

Assessment and documentation of patient responses to treatment and/or invasive procedures are important facets of nursing care. The purpose of this article is to describe a tool for assessing and quantifying a patient's response to sedation and tolerance of a specific diagnostic and/or therapeutic procedure. Use of the conscious sedation scale will allow the nurse to objectively measure the patient's outcome. This tool will also facilitate better patient care and documentation and substantiate nursing intervention.

Effects of hypertonicity on water intake in the elderly: an age-related failure

Dehydration is a common clinical syndrome associated with many illnesses and treatments in the elderly. Prior studies have shown diminished sensation of thirst during water deprivation. It is currently unclear whether age-related decreases in thirst perception impair the defense against a hyperosmolar challenge. To examine the impact of water ingestion during hyperosmolality, young and old subjects were allowed free access to water during and after an intravenous infusion of 5% hypertonic saline. Cumulative water intake and serum osmolality were compared between seven healthy young (20-28 yrs) and seven healthy old (72-89 yrs) volunteers during and following a two hour hypertonic saline infusion at a rate of 0.06 mlxkg(-1) min(-1). Serum osmolality and water intake were markedly different between the two groups. In the old group, serum osmolality increased by 17 mosmol/kg above baseline despite free access to water. In contrast, serum osmolality increased to only 7 mosmol/kg above baseline in the young group and did not rise further. By ingesting water, the young were able to defend against an additional increase in serum osmolality. The young drank approximately twice that of the old during the infusion period. Healthy older individuals drink less than young despite a significantly increased serum osmolality. This hypodipsia in old individuals increases their susceptibility to hypertonicity.

Urinary cyclic GMP, endothelin, and prostaglandin E2 in normal pregnancy and preeclampsia

Cyclic GMP, endothelin and prostaglandin E2 (PGE2) all have systemic vasoactive properties (with cyclic GMP acting as a second messenger of nitric oxide). Intrarenally they act as natriuretics and urinary levels reflect intrarenal production. Cyclic GMP and PGE2 also act as important inhibitors of platelet activation and thrombosis. The purpose of this study was to determine if urinary levels of cyclic GMP, endothelin, and PGE2 differ in preeclamptic as compared to normal pregnancies. Parameters were compared in 13 normotensive, nonpreeclamptic pregnancies, and 32 preeclamptic pregnancies. Preeclamptic women had significantly lower levels of urinary cyclic GMP (0.67 +/- 0.12 vs. 2.1 +/- 0.5 nmol/g creatinine), endothelin (0.88 +/- 0.09 vs. 3.75 +/- 1.4 ng/g creatinine), and PGE2 (26 +/- 4 vs. 9 ng/g creatinine) as compared to normals (p < 0.05). Intrarenal production of cyclic GMP, endothelin, and PGE2 are all disturbed in preeclampsia and may have implications in the sodium retention, hypertension, and intrarenal thrombosis and vasospasm of preeclamptic pregnancy.

Tonic synaptic inhibition modulates neuronal output pattern and spatiotemporal synaptic integration

Irregular firing patterns are observed in most central neurons in vivo, but their origin is controversial. Here, we show that two types of inhibitory neurons in the cerebellar cortex fire spontaneously and regularly in the absence of synaptic input but generate an irregular firing pattern in the presence of tonic synaptic inhibition. Paired recordings between synaptically connected neurons revealed that single action potentials in inhibitory interneurons cause highly variable delays in action potential firing in their postsynaptic cells. Activity in single and multiple inhibitory interneurons also significantly reduces postsynaptic membrane time constant and input resistance. These findings suggest that the time window for synaptic integration is a dynamic variable modulated by the level of tonic inhibition, and that rate coding and temporal coding strategies may be used in parallel in the same cell type.

Currents evoked in Bergmann glial cells by parallel fibre stimulation in rat cerebellar slices

1. Whole-cell recordings were obtained from Bergmann glial cells in rat cerebellar slices. 2. The cells had low input resistances (70 +/- 38 M omega; n = 13) and a mean resting potential of -82 +/- 6 mV (n = 12) with a potassium-based internal solution. Electrical and dye coupling between Bergmann glia were confirmed. 3. Stimulation of parallel fibres induced a complex, mostly inward current which could be decomposed pharmacologically. 4. The ionotropic glutamate receptor antagonist, 6-cyano-7-nitroquinoxaline-2,3-dione (CNQX; 10 microM), but not DL-2-amino-5-phosphonopentanoic acid (DL-APV; 100 microM) consistently blocked an early inward current component that may reflect synaptic activation of AMPA/kainate receptors in Bergmann glia. 5. Addition of cadmium ions (100 microM) to inhibit transmitter release blocked most of the CNQX-APV-insensitive current. This component probably reflects electrogenic uptake of the synaptically released glutamate. 6. Tetrodotoxin (TTX; 1 microM) blocked the remaining inward current: a slow component, possibly produced by the potassium ion efflux during action potential propagation in parallel fibres. An initial triphasic component of the response was also TTX sensitive and reflected passage of the parallel fibre action potential volley. 7. The putative glutamate uptake current was further characterized; it was blocked by the competitive uptake blockers D-aspartate (0.5 mM) and L-trans-pyrrolidine-2,4-dicarboxylic acid (PDC; 0.5 mM), and by replacement of sodium with lithium. Monitoring the triphasic TTX-sensitive component showed that this inhibition did not result from changes of action potential excitation and propagation. 8. Intracellular nitrate ions increased the putative uptake current, consistent with the effect of this anion on glutamate transporters. 9. The putative uptake current was reduced by depolarization, consistent with the voltage dependence of glutamate uptake. 10. It is concluded that a large fraction of the current induced by parallel fibre stimulation reflects the uptake of synaptically released glutamate. The uptake current activated rapidly, with a 20-80% rise time of 2.3 +/- 0.7 ms (n = 10), and decayed with a principal time constant of 25 +/- 6 ms (n = 10).

Endothelin and atrial natriuretic peptide levels following radiocontrast exposure in humans

Radiocontrast exposure is associated with vasoconstriction of the renal vascular bed and, in certain circumstances, with acute renal failure. This may be influenced by the volume of contrast infused or underlying disease, such as diabetes or renal failure. Changes in circulating vascular regulators, such as endothelin and atrial natriuretic peptide (ANP), may play a role in the development and/or prevention of acute renal failure. Nineteen patients undergoing arteriographic procedures were divided into two groups: large-volume contrast (> or = 150 mL; n = 7) and small-volume contrast (< 150 mL; n = 12). Circulating endothelin levels increased significantly (from 12.3 +/- 1.1 pmol/L to 19.4 +/- 2.2 pmol/L; P < 0.05) following large-volume contrast exposure (group 1) but not following small-volume contrast exposure (group 2) (13.9 +/- 1.7 pmol/L to 12.2 +/- 0.09 pmol/L). ANP levels increased significantly in both groups: 43 +/- 15 pg/mL to 75 +/- 21 pg/mL in group 1 and 33 +/- 16 to 106 +/- 39 pg/mL in group 2. Data from an additional eight patients with underlying diabetes mellitus and/or renal insufficiency also were obtained and were considered separately. Endothelin levels were higher at baseline and increased significantly after contrast (25.7 +/- 5 pmol/L to 55.4 +/- 18 pmol/L) despite the relatively small average volume of contrast infused (112 +/- 15 mL). ANP levels were also highest in these patients (211 +/- 43 pg/mL precontrast and 323 +/- 65 pg/mL postcontrast). No group had a significant change in serum creatinine following contrast exposure. In conclusion, large-volume radiocontrast exposure is associated with an increase in both circulating endothelin and ANP levels. Patients with underlying diabetes or renal insufficiency may have higher baseline levels and a greater tendency to increase endothelin after contrast exposure. While an increase in endothelin may contribute to renal vasoconstriction following radiocontrast exposure, simultaneous increases in ANP may serve to offset this response and protect against changes in renal function.

Increased salt retention and hypertension from non-steroidal agents in the elderly

We studied blood pressure and natriuretic responses to acute salt loading, and the effect of non-steroidal anti-inflammatory agents on these responses, in five healthy normotensive women aged 65 to 71 years. Five women aged 25 to 31 years acted as controls. Intravenous saline loading, with and without prior ingestion of ibuprofen, was 15 ml/kg/h for 3 h. Baseline blood pressures were higher in the elderly. Saline infusion without ibuprofen raised systolic blood pressure (SBP) by about 25 mmHg in the older group only. Ibuprofen increased baseline SBP in the elderly (129 +/- 6 vs. 116 +/- 5 mmHg, p < 0.05). Saline loading after ibuprofen again raised blood pressure by about 25 mmHg in the elderly only. The elderly group showed markedly increased sodium excretion during saline loading, but this was reduced by ibuprofen. Ibuprofen had no effect on SBP or sodium excretion in controls. Ageing appears to increase susceptibility to salt retention and hypertension from non-steroidal anti-inflammatory agents.

A direct comparison of the single-channel properties of synaptic and extrasynaptic NMDA receptors

The assumption that synaptic and extrasynaptic glutamate receptors are similar underpins many studies that have sought to relate the behavior of channels in excised patches to the macroscopic properties of the EPSC. We have examined this issue for NMDA receptors in cerebellar granule cells, the small size of which allows the opening of individual synaptic NMDA channels to be resolved directly. We have used whole-cell patch-clamp recordings to determine the conductance and open time of NMDA channels activated during the EPSC and used cell-attached and outside-out recordings to examine NMDA receptors in somatic membrane. Conductance and open time of synaptic channels were indistinguishable from those of extrasynaptic channels in cell-attached patches. However, the channel conductance in outside-out patches was 20% lower than in cell-attached recordings. This change was partially reduced by dantrolene and phalloidin, suggesting that it may involve depolymerization of actin following Ca2+ release from intracellular stores. Our results demonstrate that synaptic and extrasynaptic NMDA receptors have similar microscopic properties. However, NMDA channel conductance is reduced following the formation of an outside-out patch.

Effects of oral and intravenous rehydration on ratings of perceived exertion and thirst

The purpose of this investigation was to compare the effects of oral and intravenous saline rehydration on differentiated ratings of perceived exertion (RPE) and thirst. Eight men underwent three randomly assigned rehydration treatments following a 2- to 4-h exercise-induced dehydration bout to reduce body weight by 4%. Treatments included 0.45% saline infusion (i.v.), 0.45% saline oral ingestion (ORAL), and no fluid (NF). Following rehydration and rest (2 h total), subjects walked at 50% VO2max for 90 min at 36 degrees C (EX). Central RPE during ORAL was lower (P < 0.05) than i.v. and NF throughout EX. Local RPE during NF was higher (P < 0.05) than i.v. and ORAL at minutes 20 and 40 of EX and overall RPE during NF was higher (P < 0.05) than ORAL at minutes 20 and 40 of EX. Significant correlations were found between overall RPE and mean skin temperature for i.v. (r = 0.72) and NF (r = 0.75), and between overall RPE and thirst ratings for i.v. (r = 0.70). Thirst ratings were not different among trials at postdehydration. Following rehydration, thirst was higher (P < 0.05) during NF than i.v. and ORAL and lower (P < 0.05) during ORAL than i.v. at all subsequent time points. Results suggest that oral rehydration is likely to elicit lower RPE and thirst ratings compared with intravenous rehydration.

Development of the Conscious Sedation Scale: establishing content validity and reliability

The purpose of this study was to determine content validity and reliability of the Consciousness Sedation Scale (CSS), an instrument developed as a documentation tool for patient response during invasive procedures using intravenous conscious sedation. Instrument items were developed to reflect goals of conscious sedation recommended by the Association of Operating Room Nurses. Content validity of the parameters and grades was established at Content Validity Index (CVI) .875. Cronbach's coefficient alpha of .69 indicated insufficient reliability of discriminatory items between grades. Further refinement of the tool was indicated.

Extrarenal potassium homeostasis with maximal exercise in end-stage renal disease

Serum potassium levels rise substantially during vigorous exercise as a result of the release of potassium from contracting muscle cells. Widespread use of erythropoietin has allowed for increased exercise capacity in patients with ESRD, raising the concern for severe exertional hyperkalemia. The aim of this study was to determine whether ESRD is associated with alterations in potassium and the neurohumoral mediators of extrarenal potassium disposal with maximal exercise. Eight stable hemodialysis patients (aged 37 +/- 16 yr, mean +/- SE) and eight healthy control subjects (aged 44 +/- 13 yr) exercised to exhaustion, using a graded cycle ergometer. There were no significant differences in exercise performance between groups as assessed by peak work rate, maximal oxygen consumption, and rate pressure product. Although the baseline potassium level was higher in the dialysis group (5.0 +/- 0.2 mEq/L) than in control subjects (4.5 +/- 0.1 mEq/L), both groups had a similar pattern of increase during exercise (with an increment of approximately 1 mEq/L) and a similar return to baseline after exercise. However, the dialysis patients had higher basal norepinephrine levels (820 +/- 104 versus 441 +/- 56 pg/mL, P < 0.01) and a greater response to exercise (3122 +/- 429 versus 1696 +/- 424 pg/mL, P < 0.01), higher basal insulin levels (11 +/- 1 versus 7 +/- 1 microU/mL, P < 0.05), higher insulin post-exercise levels (19 +/- 3 versus 11 +/- 1 microU/mL, P < 0.05), and higher basal aldosterone levels (621 +/- 250 versus 109 +/- 13 pg/mL, P < 0.05) with an increase response to exercise (1100 +/- 350 versus 350 +/- 17 pg/mL, P < 0.05). In summary, despite higher basal potassium, dialysis patients have normal potassium responses to maximal exercise. More vigorous insulin, catecholamine, and aldosterone levels may contribute to the maintenance of extrarenal potassium homeostasis in ESRD.

Evidence for a C-terminal turn in PBAN. An NMR and distance geometry study

The solution conformation of the pheromone biosynthesis activating neuropeptide (PBAN) of the moth Helicoverpa zea has been determined using homonuclear two-dimensional nuclear magnetic resonance techniques and distance geometry-restrained energy minimization. The insect peptide hormone showed a random distribution of conformers in aqueous solution, whereas in a less polar medium of trifluoroethanol and water, a reordering process was observed. In particular, the C-terminal region (Phe-Ser-Pro-Arg-Leu-NH2) adopts a type I' beta-turn conformation, residues 20-27 are in a helix conformation, and residues 1-19 exhibit a high degree of flexibility. Direct observation of the C-terminal beta-turn configuration of PBAN is consistent with a previous report that showed a rigid, cyclic analog of the C-terminal pentapeptide of PBAN retained pheromonotropic activity [Nachman, R.J., Kuniyoshi, H., Roberts, V.A., Holman, G.M. & Suzuki, A. (1993). Biochem. Biophys. Res. Commun. 661-666]. Furthermore, our results show no interaction between the C-terminal turn and the rest of the polypeptide chain, thus providing further evidence that the C-terminal turn is indeed the important conformation recognized by the PBAN receptor.

Aldosterone responses to hyperkalemia in healthy elderly humans

Plasma aldosterone levels are reported to be lower in healthy elderly individuals compared with young individuals, a difference exaggerated by sodium depletion or upright posture. The aim of this study was to determine the aldosterone response to increases in serum potassium with advancing age. In the Clinical Research Center, six healthy young (20 to 35 yr of age) and six healthy elderly (65 to 85 yr of age) subjects underwent evaluation of their aldosterone responses to potassium infusion (0.5 mEq/kg over 45 min). Both young and elderly subjects had similar basal serum potassium levels (4.3 +/- 0.2 versus 4.4 +/- 0.1 mEq/L), similar sodium and potassium excretion amounts and similar increase in serum potassium levels during infusion (to 5.0 +/- 0.2 versus 5.1 +/- 0.1 mEq/L). However, elderly subjects had lower basal levels of plasma aldosterone and a blunted aldosterone response to potassium infusion (P < 0.05, analysis of variance). Advancing age is characterized by relative hypoaldosteronism in the basal state as well as in response to hyperkalemia. This may contribute to an increased susceptibility to hyperkalemia if other potassium regulatory systems fail.

Potassium homeostasis and hyperkalemic syndromes

Acute hyperkalemia can be a life-threatening consequence of a variety of pathologic, pharmacologic, and iatrogenic disorders. Recognition and prompt therapy often reverse the electrophysiologic complications within minutes. Therefore, physicians must have a thorough understanding of potassium homeostasis. The causes of hyperkalemia, intracellular-to-extracellular shifts of potassium, excess exogenous potassium loads, and pseudohyperkalemia are discussed.

Reduced renal response to low-dose dopamine infusion in the elderly

BACKGROUND

Increasing age is associated with a number of changes in renal function, including a diminished capacity to excrete salt and water loads and an increased susceptibility to acute renal failure. Dopamine is a renal autocoid important in diuresis and natriuresis and may also serve to protect against ischemic renal injury. The aim of this study was to assess the renal response to a low-dose dopamine infusion in healthy young vs elderly individuals.

METHODS

Five healthy young (28 +/- 2 yr) and elderly (68 +/- 3 yr) subjects underwent evaluation of renal function and blood pressure before, during, and after a 3-hour infusion of dopamine (1 microgram/kg/min) in the Clinical Research Center of Beth Israel Hospital.

RESULTS

Renal plasma flow, estimated by clearance of para-aminohippurate clearance, was significantly lower in the elderly than in the young subjects, but both groups increased estimated renal plasma flow by approximately 30% during dopamine infusion. Endogenous creatinine clearance was also significantly lower in the elderly. During dopamine infusion, creatinine clearance rose significantly only in the young. Both young and old had a similar natriuretic response to dopamine although urine flow and free water clearance were significantly lower in the old. Neither group had significant changes in blood pressure or heart rate.

CONCLUSIONS

Resistance to the actions of dopamine on creatinine clearance in the elderly may reflect an inability to respond to endogenous dopamine at times of physiologic stress with resulting susceptibility to azotemia.

Hypotensive response to atrial natriuretic peptide administration is enhanced with age

BACKGROUND

Plasma levels of atrial natriuretic peptide (ANP) increase with age. To test the hypothesis that the cardiovascular response to ANP is age dependent and to examine the role of the increased levels of ANP in the hypotensive response to orthostatic challenge, we compared the hemodynamic response of young and elderly subjects to ANP infusion and orthostatic challenge.

METHODS

Blood pressure, heart rate, forearm cutaneous resistance, plasma ANP, and plasma norepinephrine were measured in the supine position and following upright tilt before and after a 60-minute infusion of atrial natriuretic peptide (0.05 microgram/kg/min) in 7 young (27 +/- 4 years) and 5 elderly (74 +/- 4 years) normotensive, healthy subjects.

RESULTS

Prior to ANP infusion, the response to upright tilt was similar in both groups. Infusion of ANP produced similar steady state plasma levels of ANP in both groups (young: 435 +/- 49 pg/ml; elderly: 429 +/- 32 pg/ml). Supine systolic blood pressure decreased by 4 +/- 2 mmHg in the young subjects and by 18 +/- 8 mmHg in the elderly subjects after infusion (p < .08). In contrast, changes in supine heart rate, forearm cutaneous resistance, and plasma norepinephrine were similar in both groups (delta heart rate: young +5 +/- 3 beats/min, elderly +4 +/- 2 beats/min; delta forearm cutaneous resistance: young -38 +/- 9%, elderly -40 +/- 6%; delta norepinephrine: young +55 +/- 11%, elderly: +43 +/- 13%). ANP infusion abolished the vasoconstrictor response normally associated with orthostatic challenge in both groups, despite a significant release of catecholemines and an enhanced heart rate response. This resulted in significant systolic blood pressure reduction in both young (-7 +/- 2 mmHg, p < .05) and elderly subjects (-16 +/- 4 mmHg, p < .05). The drop in systolic blood pressure in response to upright tilt and ANP infusion was four times larger in the elderly subjects (change from pre-ANP level: young -8 +/- 3 mmHg, elderly -32 +/- 5 mmHg, p < .005).

Increased susceptibility to thiazide-induced hyponatremia in the elderly

Hyponatremia is a common cause of morbidity in the elderly, and thiazide diuretics are often implicated. Eleven healthy young volunteers, eight healthy old volunteers, and five elderly patients with a history of thiazide-induced hyponatremia were studied to determine susceptibility to thiazide-induced hypoosmolality in age. Each of the healthy subjects ingested a water load (20 mL/kg) after 3 days of hydrochlorothiazide (HCTZ) (100 mg/day) or placebo. Although there were no differences in minimum Uosm between young and old, the healthy old had lower hourly free water clearances (CH2O) as compared with the young and a greater decline in serum osmolality in response to water loading (P < 0.05). HCTZ impaired minimum urine osmolality and CH2O and delayed recovery of serum osmolality after the water load in both healthy young and old (P < 0.005, placebo versus HCTZ), but the impairment in the latter two parameters was greater in the healthy elderly (P < 0.05, young versus old). Vasopressin levels were not different between healthy young and old (1.9 +/- 0.3 versus 2.0 +/- 1.0 pm with placebo; 3.0 +/- 0.7 versus 4.4 +/- 1.0 with HCTZ). Five of the young subjects were restudied after the addition of ibuprofen (400 mg thrice daily) to the thiazide and placebo regimens. Creatinine clearance was not changed, but free water clearance and serum osmolality after water loading were significantly reduced to a degree similar to that seen in the elderly subjects on the thiazide regimen (P < 0.05), suggesting an important role for renal prostaglandins in the defense against hyponatremia.