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Conyza spp. are among the most common weeds found in perennial crops, and resistance to several herbicides has already occurred worldwide. In the present study, pot and laboratory experiments were conducted to evaluate differences in glyphosate and triclopyr susceptibility between different biotypes of Conyza spp. Plant material was obtained from seeds collected in perennial crops in Greece. Seeds of four Conyza spp. biotypes were sown in separate pots and treated with glyphosate at the rosette stage, while seeds of six different Conyza spp. biotypes were sown and treated with triclopyr. Twenty-four hours after the herbicide treatment, the aboveground part of the weeds was manually collected and plant samples were prepared to determine the analytes with LC-MS/MS. In two C. bonariensis biotypes, the glyphosate concentration was 50% to 52% lower than for other biotypes; therefore, they could be considered as potentially resistant to glyphosate because the resistant biotype had a stronger and faster metabolism than the sensitive biotype, transforming glyphosate into non-toxic metabolites. The higher glyphosate concentration was detected in C. canadensis biotypes, which proved to be potentially susceptible to glyphosate. Three C. bonariensis biotypes and one C. albida biotype were less susceptible to triclopyr because analytes were detected in 63% to 82% higher concentrations than the two C. canadensis biotypesthat were susceptible to triclopyr. These results reveal significant differences between the three species, confirm the problem of herbicide resistance, and suggest that glyphosate and triclopyr efficacy in Conyza spp. is merely due to herbicide metabolism to other compounds.

Wireless ad hoc networks are characterized by their limited capabilities and their routine deployment in unfavorable environments. This creates the strong requirement to regulate energy expenditure. We present a scheme to regulate energy cost through optimized transmission scheduling in a noisy epidemic dissemination environment. Building on the intrinsically cross-layer nature of the adaptive epidemic dissemination process, we strive to deliver an optimized mechanism, where energy cost is regulated without compromising the network infection. Improvement of data freshness and applicability in routing are also investigated. Extensive simulations are used to support our proposal. © 2018, Springer Science+Business Media, LLC, part of Springer Nature.

During the interval 2012 March 7-11 the geospace experienced a barrage of intense space weather phenomena including the second largest geomagnetic storm of solar cycle 24 so far. Significant ultra-low-frequency wave enhancements and relativistic-electron dropouts in the radiation belts, as well as strong energetic-electron injection events in the magnetosphere were observed. These phenomena were ultimately associated with two ultra-fast (>2000 km s-1) coronal mass ejections (CMEs), linked to two X-class flares launched on early 2012 March 7. Given that both powerful events originated from solar active region NOAA 11429 and their onsets were separated by less than an hour, the analysis of the two events and the determination of solar causes and geospace effects are rather challenging. Using satellite data from a flotilla of solar, heliospheric and magnetospheric missions a synergistic Sun-to-Earth study of diverse observational solar, interplanetary and magnetospheric data sets was performed. It was found that only the second CME was Earth-directed. Using a novel method, we estimated its near-Sun magnetic field at 13 Ro to be in the range [0.01, 0.16] G. Steep radial fall-offs of the near-Sun CME magnetic field are required to match the magnetic fields of the corresponding interplanetary CME (ICME) at 1 AU. Perturbed upstream solar-wind conditions, as resulting from the shock associated with the Earth-directed CME, offer a decent description of its kinematics. The magnetospheric compression caused by the arrival at 1 AU of the shock associated with the ICME was a key factor for radiation-belt dynamics. © 2016. The American Astronomical Society. All rights reserved.

Aim: To develop a new optical device (prostate optical device, POD) for assessment of prostate tissue stiffness and evaluate its sensitivity and specificity in prostate cancer detection. Patients and Methods: POD was tested in prostate phantoms and in patients with indications for prostate biopsy. Its sensitivity and specificity were compared to digital rectal examination (DRE) and transrectal ultrasonography (TRUS). Results: POD was able to identify stiffness differences on each prostate phantom. 45 patients were included in the study. Sensitivity of TRUS (40%) was significantly lower to POD (85.7%) and DRE (74.3%) (p = 0.000 and p = 0.003, respectively). There was no statistical difference between POD and DRE (p = 0.221). The combination of POD and DRE showed the highest sensitivity (88.6%), positive predictive value (81.6%), and negative predictive value (42.9%) among all diagnostic tests. Conclusions: POD identified prostatic stiffness differences with the same sensitivity of DRE performed by an experienced urologist providing an objective indication for prostate biopsy and early prostate cancer detection.

This study examines the key elements that underlie collaborative forms of governance in infrastructure project delivery. Data are obtained from interviews conducted with senior managers involved in the delivery of collaborative projects in Greece. The findings suggest that issues concerning inequality between partners, ownership of the delivery through collaborative governance and the time needed to take decisions and solve problems may hinder collaboration. The findings contribute to extant literature by showing that the challenges of adopting collaborative governance practices in Greece’s transitional economy may be related to under-developed systems that are not only unable to support the full exploitation of the practice, but also fail adequately to leverage emerging innovation. In terms of practical implications, the study contributes to an understanding of how stakeholders involved in public–private partnership projects view collaborative governance in project delivery, along with the conditions and difficulties that are present, and potential outcomes governance. © 2018 ICE Publishing. All Rights Reserved.

We treat the problem of movement prediction as a classification task. We assume the existence of a (gradually populated and/or trained) knowledge base and try to compare the movement pattern of a certain object with stored information in order to predict its future location. We introduce a novel distance metric function based on weighted spatial and velocity context used for location prediction. The proposed distance metric is compared with other distance metrics in the literature on real traffic data and reveals its superiority. © 2014, Springer Science+Business Media New York.

Axial pile load tests are considered within the design procedure of most major construction projects that include pile foundations, aiming to determine both the ultimate bearing capacity and the pile stiffness at working load level. Commonly used pile spacings of 3–4 pile diameters between the test pile and the reaction piles cause significant interaction with drastic effect on to the load-settlement relationship. The objective of this paper is to evaluate the influence of this interaction on both bearing capacity and stiffness of single piles and pile groups. For this purpose, a back analysis of a pile load test was initially performed which facilitated the determination of the single pile response and the verification of the soil properties. Subsequently, a numerical analysis was carried out to establish load-displacement relationships for several different layouts of pile groups. Based on these non-linear analyses the effect of the interaction was quantified for both the pile load test and pile group layouts examined.

Ad hoc networks are characterized by limited resources (e.g. energy, bandwidth). Efficient information dissemination while avoiding excessive energy cost can be achieved through the suitable design of a network. To this end we propose an information dissemination scheme which couples epidemic dissemination with adaptive modulation and coding (AMC). The proposed scheme tunes the message forwarding probability and the coding and modulation mode in order to achieve a balance between maximum coverage over the network and minimum energy expenditure. We achieve this based on the evaluation of suitably defined indicators related to the lower network layers and exploiting information on the current status of the wireless medium. Building on established previous AMC-related work, our simulation results indicate that our scheme brings significant improvement over non-adaptive approaches, comparable with other adaptive epidemic dissemination schemes. Our findings are quite promising for adaptive epidemic-based information dissemination schemes with a strong cross-layer component. © 2013 Springer Science+Business Media New York.

Summary We estimated the rates per base per generation of specific types of mutations, using our direct estimate of the overall mutation rate for hemophilia B and information on the mutations present in the United Kingdom's population as well as those reported year by year in the hemophilia B world database. These rates are as follows: transitions at CpG sites 9.7×10 −8 , other transitions 7.3×10 −9 , transversions at CpG sites 5.4×10 −9 , other transversions 6.9×10 −9 , and small deletions/insertions causing frameshifts 3.2×10 −10 . By taking into account the ratio of male to female mutation rates, the above figures were converted into rates appropriate for autosomal DNA—namely, 1.3×10 −7 , 9.9×10 −9 , 7.3×10 −9 , 9.4×10 −9 , 6.5×10 −10 , where the latter is the rate for all small deletion/insertion events. Mutation rates were also independently estimated from the sequence divergence observed in randomly chosen sequences from the human and chimpanzee X and Y chromosomes. These estimates were highly compatible with those obtained from hemophilia B and showed higher mutation rates in the male, but they showed no evidence for a significant excess of transitions at CpG sites in the spectrum of Y-sequence divergence relative to that of X-chromosome divergence. Our data suggest an overall mutation rate of 2.14×10 −8 per base per generation, or 128 mutations per human zygote. Since the effective target for hemophilia B mutations is only 1.05% of the factor IX gene, the rate of detrimental mutations, per human zygote, suggested by the hemophilia data is ∼1.3.

Mobile context-aware applications are capable of predicting the context of the user in order to operate proactively and provide advanced services. We propose an efficient spatial context classifier and a short-term predictor for the future location of a mobile user in cellular networks. We introduce different variants of the considered location predictor dealing with location (cell) identifiers and directions. Symbolic location classification is treated as a supervised learning problem. We evaluate the prediction efficiency and accuracy of the proposed predictors through synthetic and real-world traces and compare our solution with existing algorithms for location prediction. Our findings are very promising for the location prediction problem and the adoption of proactive context-aware applications and services. © Springer Science+Business Media, LLC 2011.

Context-awareness is viewed as one of the most important aspects in the emerging pervasive computing paradigm. Mobile context-aware applications are required to sense and react to changing environment conditions. Such applications, usually, need to recognize, classify and predict context in order to act efficiently, beforehand, for the benefit of the user. In this paper, we propose a novel adaptive mobility prediction algorithm, which deals with location context representation and trajectory prediction of moving users. Machine Learning (ML) is used for trajectory classification. Our algorithm adopts spatial and temporal on-line clustering, and relies on Adaptive Resonance Theory (ART) for trajectory prediction. The proposed algorithm applies a Hausdorff-like distance over the extracted trajectories handling location prediction. Since our approach is time-sensitive, the Hausdorff distance is considered more advantageous than a simple Euclidean norm. Two learning methods (non-reinforcement and reinforcement learning) are presented and evaluated. Finally, we compare our algorithm with Offline kMeans and Online kMeans algorithms. Our findings are very promising for the use of the proposed algorithm in mobile context aware applications. © Springer Science+Business Media, LLC 2011.

Context-awareness is viewed as one of the most important aspects in the emerging pervasive computing paradigm. Mobile context-aware applications are required to sense and react to changing environment conditions. Such applications, usually, need to recognize, classify and predict context in order to act efficiently, beforehand, for the benefit of the user. In this paper, we propose a mobility prediction model, which deals with context representation and location prediction of moving users. Machine Learning (ML) techniques are used for trajectory classification. Spatial and temporal on-line clustering is adopted. We rely on Adaptive Resonance Theory (ART) for location prediction. Location prediction is treated as a context classification problem. We introduce a novel classifier that applies a Hausdorff-like distance over the extracted trajectories handling location prediction. Since our approach is time-sensitive, the Hausdorff distance is considered more advantageous than a simple Euclidean norm. A learning method is presented and evaluated. We compare ART with Offline kMeans and Online kMeans algorithms. Our findings are very promising for the use of the proposed model in mobile context aware applications. © Institute for Computer Sciences, Social-Informatics and Telecommunications Engineering 2010.

The Pervasive Computing paradigm has raised issues such as conceptual semantic descriptions and ambient management of information resources. The probabilistic theory on the other hand provides uncertain knowledge representation schemes that are semantically inefficient. However, security models related to attacks exploit both semantic and probabilistic modeling. Issues such as attack prediction and classification of attacker’s intentions are of high importance in IDS environments. In this paper we propose a novel Breadth and Depth Bayesian classifier and an inference probabilistic algorithm. The inference algorithm is applied over well defined conceptual information integrated in a hybrid IDS by means of ontologies.

About 5.5% of all UK hemophilia B patients have the base substitution IVS 5+13 A-->G as the only change in their factor (F)IX gene (F9). This generates a novel donor splice site which fits the consensus better than the normal intron 5 donor splice. Use of the novel splice site should result in a missense mutation followed by the abnormal addition of four amino acids to the patients' FIX. In order to explain the prevalence of this mutation, its genealogical history is examined. Analysis of restriction fragment length polymorphism in the 21 reference UK individuals (from different families) with the above mutation showed identical haplotypes in 19 while two differed from the rest and from each other. In order to investigate the history of the mutation and to verify that it had occurred independently more than once, the sequence variation in 1.5-kb segments scattered over a 13-Mb region including F9 was examined in 18 patients and 15 controls. This variation was then analyzed with a recently developed Bayesian approach that reconstructs the genealogy of the gene investigated while providing evidence of independent mutations that contribute disconnected branches to the genealogical tree. The method also provides minimum estimates of the age of the mutation inherited by the members of coherent trees. This revealed that 17 or 18 mutant genes descend from a founder who probably lived 450 years ago, while one patient carries an independent mutation. The independent recurrence of the IVS5+13 A-->G mutation strongly supports the conclusion that it is the cause of these patients' mild hemophilia.

We present a case of an extradural thoracic spinal angiolipoma in a 27-vear-old woman. The epidural tumor was evaluated with computerized tomographic scans and magnetic resonance imaging scans. The tumor was removed, and the clinical symptoms improved remarkably. © 1995 Lippincott-Raven Publishers, Philadelphia.

Three commercially available dental silane primers, two single-phase prehydrolyzed and one two-component system were investigated for their composition, extent of hydrolysis, surface interactions, bond strength and interfacial topography when used on three representative porcelain alloys (Au-Pd, high-Pd, Ni-Cr). Five tests, 1H FT-NMR, FTIR, GPC, ESCA and EPMA, were used to determine the composition and the surface interaction profiles. Shear tests were performed to assess the bond strength values. According to the results, all the primers contain gamma-methacryloxypropyltrimethoxysilane (gamma-MPTS) at concentrations of 1.15-18.86 g/100 mL, two in ethanol and one in isopropanol. Traces of acetic acid were found in the prehydrolyzed primers. All the primers demonstrated partial hydrolysis of the methoxy groups. Prehydrolyzed primers exhibited a higher rate of hydrolysis and better orientation of hydrolyzed methoxy groups towards the Ni-Cr alloy surface. Due to the extent of surface oxidation, the Ni-Cr alloy provided more bonding sites for silanols than the other two types of alloys. The Ni-Cr alloy demonstrated the highest shear bond strength values on smooth surfaces regardless of the type of primer used. The results of the present study suggest that active prepolymerized primers may provide significant advantages over two-component systems in the repair of Ni-Cr porcelain fractures involving removal of the metal oxide layer.

International audience; Because proton secretion and K+ reabsorption in the late distal tubule of amphibians are active, we evaluated whether these processes could be mediated by an H(+)-K(+)-ATPase similar to the gastric H(+)-K+ pump and to the K(+)-ATPase previously described in the terminal segments of the mammalian nephron. K(+)-stimulated ATPase activity was detected in microdissected segments of frog and Necturus nephron: its activity was high in the late distal and collecting tubules, whereas it was undetectable in the proximal convoluted tubule and early distal tubule. In frog collecting tubule, K(+)-ATPase had a high affinity for K+ (Km approximately 0.30 mM), was inhibited by vanadate, omeprazole, and the imidazopyridine Sch 28080, and was insensitive to ouabain. Furthermore, in vivo administration of Sch 28080 to anesthetized Necturus induced a significant rise of the steadystate intratubular pH in the late distal tubule, demonstrating that this drug inhibited tubular fluid acidification. It is suggested that K(+)-ATPase present in the terminal segments of amphibian nephron is similar to the gastric H(+)-K+ pump and is involved in urinary acidification.

A review of the literature on elastomeric impression materials, is presented in this paper. The article mentions the composition and the most important properties of the elastomeric impression materials used in dental practice. The clinical significance of these materials, physical and mechanical properties are also emphasized. In addition some new elastomeric impression materials with improved properties and a new (experimental) light-cured impression material, are mentioned. Another part of this article is the biocompatibility of these materials. In the end the great significance of handling is outlined.

Ordering temperatures and magnetizations versus applied fields have been measured for the hexagonal phases RAu3.6. The compound PrAu3.6 can be regarded as a Van Vleck paramagnet with appreciable exchange. The Sm, Tb and Dy compounds show antiferromagnetic behaviour. HoAu3.6 may have an ordering point below 5 K. GdAu3.6 has two ordering points. The Curie paramagnetic temperatures of all RAu3.6 compounds are negative with values between −12.5 K (Tb) and −0.7 K (Nd). The observed effective moments are almost the same as the rare earth trivalent ion moments.

Glaphenine, a nonsteroid analgesic compound, administered by gastric gavage in rats (800 mg/kg), induced nonoliguric reversible acute renal failure (ARF). Intratubular deposits were found in medullary collecting ducts. Intratubular hydrostatic pressure (Pt) increased from 11.7 +/- 0.7 to 30.0 +/- 0.9 mmHg. Renal failure was almost completely prevented by concomitant high water and solute diuresis, achieved by furosemide infusion in Wistar rats and by high salt intake in Brattleboro rats with diabetes insipidus. In the latter protected animals, Pt was only slightly elevated (17.0 +/- 0.5 mmHg). Urinary excretion of prostaglandin E2 (PGE2) dropped dramatically after glaphenine administration in Wistar rats; the fall was slight in Brattleboro rats in which PGE2 excretion was normally low. We conclude that tubular obstruction plays a prominent role in glaphenine-induced ARF in the rat. High water and solute diuresis prevented tubular obstruction. Reduced renal PGE2 synthesis is probably not involved in the pathophysiology of this ARF model, inasmuch as Brattleboro rats on a high salt intake were protected despite low basal urinary excretion of PGE2.

The effects of d -glucose addition to a glucose-free luminal perfusate were investigated in the proximal tubule of Necturus kidney, by electrophysiological techniques. The main findings are: (1) In the presence of sodium, d -glucose produces 10.5 mV ± 1.1 (S.E.) depolarization. (2) Phlorizin reduces the magnitude of this response to 2.1 ± 0.1 mV . (3) The glucose-evoked depolarization, ΔV G , does not alter the intracellular K+ activity nor is it affected by peritubular addition of ouabain. (4) Isosmotic reduction of Na+ concentration in luminal perfusate from 95 to 2 mmol/l (choline or Li+ substituting for Na+) does not change the magnitude of ΔV G ; complete removal of sodium from the lumen lowers the value of ΔV G ( 3.2 ± 0.2 mV ) but the response is not abolished. This observation suggests that the d -glucose carrier of renal tubules in Necturus is poorly specific with regard to the cotransported cation species.

The transepithelial potential difference (VTE) and transepithelial resistance (RTE) were determined along the length of the distal tubule of the amphibian Triturus alpestris. The site of impalements was determined at the end of each experiment by latex injection and microdissection. Two segments, differing by their distribution at the surface of the kidney, by their respective diameters and by their electrical properties could be identified: the early distal tubule (EDT) and the late distal tubule (LDT). VTE was invariably positive in the EDT; it increased from approximately + 5 mV to approximately + 22 mV within the first 30% of this segment and remained roughly constant distally to this site. RTE was estimated at 57 omega X cm2 in the EDT. The LDT exhibited essentially negative VTE figures with the exception of its very initial portion; the peak negativity at the end of the LDT was -35 mV. RTE was assessed from 8 measurements performed in the first 30% of the LDT; the tentative transepithelial resistance was 530 omega X cm2. Provisional evidence suggests that the transepithelial resistance of the terminal portion of the LDT may be substantially larger than the resistance measured in other parts of this segment.

Double-barreled, selective microelectrodes filled with liquid ion exchanger were used to determine proximal tubule cell pH (pHcell), luminal pH (pHlum), and peritubular capillary blood pH (pHbl.pt) in Necturus kidney in vivo. The average pHbl.pt of 16 animals was 7.64 +/- 0.3; pHcell was 7.36 +/- 0.02 (n = 50), and pHlum was 7.50 +/- 0.05 (n = 16). Because of the variability in pHbl.pt from one animal to another, we studied the blood/cell/lumen pH differences. We sequentially measured with a single microelectrode pHcell and pHlum, and then pHbl.pt in an adjacent peritubular capillary. In 25 such paired determinations, the average pHbl.pt - pHcell difference was 0.28 +/- 0.03, cell acid, and the pHbl.pt - pHlum difference was 0.14 +/- 0.02, lumen acid. The pHcell in this series was significantly more acid than the pHlum (by 0.14 +/- 0.02), but in a few instances the pH gradient across the apical cell membrane was inversed. All measurements were performed in the initial portion of the proximal tubule. We conclude that 1) proximal cell pH is acid with regard to peritubular blood pH, 2) the proximal tubule of Necturus kidney is capable of establishing a small transepithelial pH difference (lumen acid), and 3) pHcell is generally more acid then pHlum.

This study deals with the electrical responses of the peritubular membrane of the Necturus proximal tubule to 8 organic anions, in NaHCO3-free (trismaleate-buffered) and NaHCO3-containing solutions. The anions glutamate and gluconate brought about a small depolarization, but only in NaHCO3-free media. Benzene sulfonate did not alter significantly membrane p.d. The 5 other test-anions produced hyperpolarization. The magnitude of membrane depolarization elicited by high-K media was proportionally larger in the presence of the test-anions propionate, lactate, pyruvate, acetate and formate than with chloride: it is inferred that these anions increasedTK. The same 5 anions shifted in the negative direction the p.d. achieved at peak K-depolarization; according to a previous analysis (Anagnostopoulos, 1977), this observation suggests that their permeabilities (PA) are greater thanPCl, at least during the substitution. The association ofPA>PCl with an increase ofTK, upon exposure of the kidney to test-anions, is at best accounted for by a decrease ofPCl. The pattern of voltage attenuation along the epithelial cable during anionic substitutions is also consistent with an increase ofTK via a decrease ofPCl. In conclusion, the apparent sequence of relative anionic permeabilities, as obtained from the responses of the tissue to a single anion, irrespective of buffering procedures, is:Pacet,Plact,Ppyruv,Pprop,Pform>PCl≃Pgluc,Pglut. The test-anions propionate, lactate, pyruvate, acetate and formate tend to increaseTK, mainly by reducingPCl. The effect of glutamate and gluconate on physiologic ion permeabilities is too small to be specified with accuracy: it depends to some extent on the buffer used in the solutions.

K+-selective liquid ion-exchanger double-barreled microelectrodes were used to measure intracellular K+ activity (alpha Ki) of proximal tubular cells in Necturus kidney. SEveral methodological problems inherent in the construction and in vivo application of such microelectrodes were considered, in particular the identification of leaky impalements and the correct assessment of alpha Ki during reversible perfusion of peritubular capillaries from control to a test solution. Peritubular potassium concentration (CpK) could be altered by means of double-barreled micropipettes containing a physiologic and a high or low K solution. The control alpha Ki value averaged 57.9 +/- 8.5 mM (mean +/- SD, n = 38) and the basolateral membrane potential was -70.4 +/- 5.8 mV. Thus, the K+ equilibrium potential across the basolateral membrane (EK) was -81.1 +/- 3.4 mV. Increasing CpK from 3.0 to 30.0 mM raised alpha Ki by 7.0 +/- 1.5 mM, and lowering CpK to 0.3 mM decreased alpha Ki by 9.2 +/- 2.9 mM. Conclusions: 1) the steady-state K+ distribution across the basolateral membrane indicates that potassium is actively pumped into the cell. 2) The relative stability of alpha Ki in the face of large CpK variations underscores the effectiveness of cell homeostasis; passive mechanisms appear to contribute to this end.

To assess the mechanism(s) by which intraluminal chloride concentration is raised above equilibrium values, intracellular Cl− activity (α Cl ) was studied in the proximal tubule ofNecturus kidney. Paired measurements of cell membrane PD (V BL) and Cl-selective electrode PD (V BL Cl ) were performed in single tubules, during reversible shifts of peritubular or luminal fluid composition. Steadystate α Cl was estimated at 14.6±0.6 mmol/liter, a figure substantially higher than that predicted for passive distribution. To determine the site of the uphill Cl− transport into the cell, an inhibitor of anion transport (SITS) was added to the perfusion fluid. Introduction of SITS in peritubular perfusate decreased α Cl , whereas addition of the drug in luminal fluid slightly increased α Cl ; both results are consistent with basolateral membrane uphill Cl− transport from interstitium to the cell. TMA+ for Na+ substitutions in either luminal or peritubular perfusate had no effect on α Cl . Removal of bicarbonate from peritubular fluid, at constant pH (a situation increasing HCO 3 − outflux), resulted in an increase of α Cl , presumably related to enhanced Cl− cell influx: we infer that Cl− is exchanged against HCO 3 − at the basolateral membrane. The following mechanism is suggested to account for the rise in luminal Cl− concentration above equilibrium values: intracellular CO2 hydration gives rise to cell HCO 3 − concentrations above equilibrium. The passive exit of HCO 3 − at the basolateral membrane energizes an uphill entry of Cl− into the cell. The resulting increase of α Cl , above equilibrium, generates downhill Cl− diffusion from cell to lumen. As a result, luminal Cl− concentration also increases.

Measurements of the magnetic susceptibility of the R2In compounds from 4.2 to 270 K have been made. All compounds except Y2In and Sm2In exhibit Curie‐Weiss behavior at high temperatures with effective magnetic moments agreeing reasonably well with the free‐ion 3+ picture modified by RKKY exchange except for Gd2In, which gives an unusually high value for the effective moment. With the exception of Y2In all other members exhibit susceptibility maxima. Gd2In, Tb2In, and Dy2In order antiferromagnetically. Gd2In is a metamagnetic compound. For the three compounds Ho2In, Er2In, and Tm2In there is no indication of their type of ordering at low temperatures. The isotherm at 4.2 K of Nd2In shows a ferromagnetic or ferrimagnetic behavior.

Magnetic properties of nine RE 2 Au compounds have been studied in fields of up to 19 kOe in the temperature range 4.2K–300K. It has been found that all compounds are paramagnetic at room temperature except Gd 2 Au. The compounds with Pr, Nd, Ho, Er and Tm exhibit Curie-Weiss behaviour with paramagnetic moments in close agreement with those expected for the free RE 3+ ion. The moment of gold was found to be zero. The compounds with Pr, Nd, Tb, Dy, Er and Tm are antiferromagnetic at low temperatures. It appears that Ho 2 Au is ferromagnetically ordered below 4.5 K. No evidence for magnetic ordering was found for Y 2 Au. The compound with Tb exhibits metamagnetic behaviour.

R 5 Pd 2 compounds are antiferromagnetic with Neel temperatures between 7 K (Tm) and 38 K (Dy). The magnetic moment of the rare earth is that of the trivalent ion. Palladium seems to have zero moment. The Neel and paramagnetic points deviate slightly from De Gennes' law.

Eleven different secosteroids or steroids (10(-10) to 10(-8) M) were acutely and reversibly introduced in solutions delivered to the lumen of single proximal tubules of the amphibian Necturus kidney while recording basolateral cell membrane potential Vm. Seven of these molecules (1,25(OH)2D3, 25(OH)D3, 24,25(OH)2D3, 5,6-trans-25(OH)D3, 19-diol-cholesterol, estradiol and testosterone) resulted in changes of Vm (delta Vm) occurring in a few seconds, the largest delta Vm being observed with 1,25(OH)2D3, +6.5 +/- 0.75 mV (n = 19); these seven (seco)steroids, but not the four inactive sterols (vitamin D3, cholesterol, 1 alpha D3 and aldosterone) possess a hydroxyl group on at least one carbon of the C17 to C25 lateral chain of the sterol ring. The delta Vm effect was present in Na+-free or Cl-free media, but it was abolished in HCO3-free media. Depolarization of cell membrane potential by addition of glucose, 11 mM, in luminal perfusion fluid abolished the 1,25(OH)2D3-evoked delta Vm effect, suggesting dependence of the latter on the absolute value of membrane potential. Barium, a blocking agent of K+ conductances, suppressed the 1,25(OH)2D3-evoked delta Vm effect, even when the proper effects of barium of cell membrane potential were canceled by current clamp. Pretreatment with quinine, a putative blocker of Ca2+-dependent K+ channels also abolished the 1,25(OH)2D3-evoked depolarization. Such observations are consistent with the presence of Ca2+-dependent K+ channels at the apical cell membrane of the proximal tubule, these channels being inactivated by 1,25(OH)2D3 and probably by other (seco)steroids.

The electrical properties of the proximal tubule of the in vivo Necturus kidney were investigated by injecting current (as rectangular waves) into the lumen or into the epithelium of single tubules and by studying the resulting changes of transepithelial (VL) and/or cell membrane potential (VC) at various distances from the source. In some experiments paired measurements of VL and VC were performed at two abscissas x and x'. The luminal length constant of about 1,030 micrometer was shown to provide a good estimate of the transepithelial resistance, specific resistance (RTE = 420 omega.cm2) and/or per unit length (rTE = 1.3 x 10(4) omega.cm). The apparent intraepithelial length constant was subject to distortions arising from concomitant current spread in the lumen. The resistances of luminal membrane (rL), basolateral membrane (rB), and shunt pathway (rS) were estimated by two independent methods at 3.5 x 10(4), 1.2 x 10(4), and 1.7 x 10(4) omega.cm, respectively. The corresponding specific resistances were close to 1,200, 600, and 600 omega.cm2. There are two main conclusions of this study. (a) The resistances of cell membranes and shunt pathway are of the same order of magnitude. The figure of the shunt resistance is at variance with the notion that the proximal tubule of Necturus is a leaky epithelium. (b) A rigorous assessment of the conductive properties of concentric cylindrical double cables (such as renal tubules) requires that electrical interactions arising from one cable to another be taken into account. Appropriate equations were developed to deal with this problem.

Eight cations were reversibly and isosmotically substituted for sodium (45 mM) in peritubular circulation of the proximal tubule of the doubly perfused Necturus kidney. Li, choline and tetramethylammonium produced small shifts in peritubular potential difference with no change in conductance. Tris- and tetraethylammonium depolarized the membrane by about 10 mV without affecting its conductance. Rb and Cs produced a decrease of membrane permeability to potassium. Potassium for sodium substitution depolarized the membrane (3.1 mV) and increased its conductance. It is concluded that none among the cations tested may be considered as readily less permeant than sodium across the peritubular membrane.

Double-barreled microelectrodes selective to either potassium or sodium were used to determine the transepithelial potential difference (VTE) and the intraluminal activity of potassium (alpha LuK) or sodium (alpha LuNa) in the early distal tubule (EDT) of Triturus waltlii in vivo; luminal activities were compared with the corresponding plasma ion activities, alpha PtK and alpha PtNa. The transepithelial equilibrium potentials for potassium (EK(TE] and sodium (ENa(TE] were computed from the respective transmural chemical distributions: they were used to assess the transepithelial electrochemical potential differences [(V-EK)TE and (V-ENa)TE]. By dividing the raw data into three groups of 30% total tubular length (0-30, 31-60, 61-90%), the following results were obtained. 1) VTE increases from +15 to +20 mV (lumen positive) between the first and second portion of the EDT but remains constant thereafter. 2) The alpha LuK/alpha PtK ratio decreases steadily along the EDT from 1.92 to 1.66 and then to 1.32. 3) The values of alpha LuNa/alpha PtNa in the same three subdivisions are 0.79, 0.44, and 0.45. 4) The (V-EK)TE difference is largely positive along the whole EDT: +32, +33, and +27 mV. 5) The (V-ENa)TE difference declines from +9 mV (first portion) to values statistically not different from zero in the last two thirds of the EDT.(ABSTRACT TRUNCATED AT 250 WORDS)

We applied the technique of renal cell fusion (8) to the proximal convoluted tubule ofNecturus kidney. Giant fused cells from this segment exhibit stable cell membrane potential, Vm, for several tens of minutes. These cells display a number of electrophysiological properties characteristic of both the apical and basolateral membranes of the proximal tubule. These include 1) significant K+ conductance, 2) no detectable Cl− conductance, 3) apical Na-glucose and Na-amino-acid electrogenic carriers, 4) basolateral ouabainsensitive Na−K pump activity and 5) basolateral Na/HCO3 cotransport.

1. Double-barrelled (selective vs. conventional) microelectrodes were used to assess the steady-state activities (a) of the ions Cl-, K+, Na+ and H+ in peritubular blood capillaries (abld) and in cell (acell) and lumen (alum) of the late distal tubule (l.d.t.) of Necturus. 2. a(cell)cl, a(lum)cl and a(bld)cl were 5.5 +/- 0.3, 11.8 +/- 1.0 and 70.5 +/- 0.1 mM, respectively. They were used to compute the chemical potentials for Cl- across the three diffusive barriers of the tissue. Basolateral and apical membrane potentials were -74.3 +/- 1.1 and -60.1 +/- 2.0 mV, respectively (cell negative); the lumen was thus negative with respect to blood, by 13.6 +/- 1.5 mV. The electrochemical potential difference (e.p.d.) for Cl- of 42 mV across the apical membrane opposes Cl- absorption, implying active apical Cl- uptake, since Cl- is known to be absorbed in the l.d.t. Basolateral Cl- exit is favoured by an e.p.d. of 10 mV. 3. a(cell)K, a(lum)K and a(bld)K were 65.8 +/- 0.8, 2.5 +/- 0.1 and 2.5 +/- 0.1 mm, respectively. The electrochemical distribution of K+ indicates that K+ absorption, if present, proceeds against an adverse apical e.p.d. of 18 mV. Basolateral K+ distribution is close to its electrochemical equilibrium, suggesting high K+ permeability at this membrane. 4. a(cell)Na was 9.0 +/- 0.4 mM, a(bld)Na 71.0 +/- 0.3 mM, and a(lum)Na was approximated at about 9 mM. Diffusive Na+ entry from lumen to cell is favoured by an e.p.d. close to 65 mV. Basolateral Na+ exit must be active, since it proceeds against an e.p.d. of 130 mV. 5. Cell, luminal and blood pH were 7.14 +/- 0.03, 6.52 +/- 0.08 and 7.37 +/- 0.04, respectively. The luminal electrochemical potential of H+ is higher than that of cell (by 91 mV) and blood (by 34 mV) indicating that proton secretion into the lumen must be active. 6. The e.p.d. of each ion across the epithelium opposes, by its orientation, the established direction of net transepithelial ion transport, suggesting that the shunt pathway may serve only for back-diffusion.

Single proximal convoluted tubules (PCT) of Necturus kidney were impaled with three microelectrodes in the sequence M1, M2, M3. M1 was used for injecting short DC current pulses, M2 for recording peritubular membrane potential, V, and M3 for injecting longer DC current steps and thereby shifting V to a new baseline potential, V'. We define the p.d. changes at M2 due to M1-induced pulses as delta V and delta V' (for baselines V and V', respectively). Our objective was to test whether delta V' was equal to delta V. The main finding is that when V depolarized by 10 to 80 mV delta V'/delta V remained close to 1.00. Care was taken to ensure that this apparent stability of the pulse ratio was not due to opposite changes of apical and basolateral membrane conductances (g(A) and g(B) respectively), to changes of the sum g(A)+g(B) compensated for by changes of the cell-to-cell junctional conductance, g(j), or to a distortion of the delta V'/delta V ratio as a function of interelectrode distance, masking voltage-dependent changes of cell membrane conductances. Hyperpolarization of V produced gradual electrical uncoupling between cells as V' became increasingly negative, by a mechanism yet to be determined.

The significance of the "leaky" tight junction might be understood better if cells of the epithelial monolayer possessed mechanisms to regulate molecular flow through the junction. To test this possibility, Necturus gallbladder, a representative leaky epithelium, was studied before, during, and after mucosal exposure to plant cytokinins and two other microfilament-active drugs, cytochalasin B and phalloidin. Concomitant with morphological changes in microfilaments, cytokinins induced rapid reversible increases in transepithelial resistance and potential difference (PD) and decreases in NaCl dilution potentials, with no change in the ratio of relative cell membrane resistances. Cytochalasin B (0.2-1.2 microM) and phalloidin (0.6-12.7 microM) caused similar changes in transepithelial resistance and PD. When the intramembranous structure of tight junctions was studied by freeze fracture, peak cytokinin-induced increments in transepithelial resistance were associated with more disorder in the strand meshwork resulting in a small increase in tight junction depth, but there was no evidence of de novo strand assembly. These studies suggest that permeability of the tight junction of Necturus gallbladder is subject to rapid reversible modulation, possibly under cytoskeletal control.

The effects of peritubular salicylate for chloride substitution were studied in the isolated perfused Necturus kidney. This substitution resulted in changes of cell membrane p.d., varying from tubule to tubule; the withdrawal of the test-anion invariably produced a steep and prolonged depolarization. Exposure of the tissue to salicylate brought about, in addition, electrical uncoupling of junctional membranes, which was not related to concomitant changes of membrane p.d.

The effect of foreign anions on transepithelial potential difference and transepithelial input conductance was studied in the isolated perfused Necturus kidney. Two microelectrodes (recording and current-injecting) were inserted into the lumen of single proximal tubules and the peritubular perfusate was shifted reversibly for 30-60 sec from a physiologic Ringer's solution to a test solution in which chloride was replaced isosmotically by a foreign anion. The permeability sequence, obtained by potential measurements, was: lactate less than glutamate less than gluconate less than pyruvate less than benzene sulfonate less than or equal to acetate less than or equal to F less than propionate less than BrO3 less than formate less than ClO3 less than Cl than ClO4 less than I less than or equal to Br less than NO3 less than SCN. Transepithelial conductance decreased when the tissue was perfused with anions less permeable than chloride but the conductance sequence was different from the permeability sequence. Such discrepancies were more pronounced during perfusion with hyperpolarizing anions; ClO4 and I- (both more permeable than chloride) produced an important decrease in transepithelial conductance, followed by incomplete reversibility when the perfusion was shifted again to chloride Ringer's. The results are best explained by the presence of weak positive fixed charges, governing anion permeation, at the shunt pathway of the proximal tubule. An analysis of the data allows tentative estimates of shape and size of the sites.

Publisher Summary This chapter provides an overview on the technique of isolation and perfusion of individual nephron segments. This technique provides basic information on the net transport rates of salt and water on the transport potentials and on the electrical and hydraulic conductance of virtually all nephron segments. One of the general principles that emerges from a comparison of the individual data, is the paramount role that Na + /K + ATPase plays in all renal absorption processes. This is demonstrated by the correlation between the density of the salt fluxes and the density of the enzyme in different nephron segments. The chapter presents that progress has been made in the analysis of transport properties of the individual cell membranes of proximal tubules by measuring intracellular Na + , K + , Cl - , and H + ion concentrations. It also explains the analysis of cotransport systems for Na + and organic substances in the brush border membrane. It describes the new anion transport systems and their coupling stoichiometry.

This study was undertaken to determine the passive electrophysiological properties of the diffusive barriers of the late distal tubule (LDT) in Necturus. The transepithelial resistance (RT) determined by cable analysis was 1,130 omega.cm2, which puts the LDT in the class of "tight" epithelia. Using two different methods, we did not find significant cell-to-cell electrical coupling. The fractional apical resistance was 0.93, and it did not vary with distance from the current-injecting electrode. Relative permeabilities of K+, Na+, and Cl- during peritubular ion concentration changes were assessed by circuit analysis. The conclusions are as follows. The basolateral cell membrane is highly permeable to K+; its apparent K+ transference number is 0.78. Basolateral chloride transference was very small. Sodium removal from peritubular fluid produced depolarization, suggesting carrier-mediated electrogenic Na+ transport. The high fractional resistance of the apical cell membrane prevented assessment of apical transference numbers. However, Cl- removal from luminal fluid produced cell hyperpolarization; the underlying mechanism has not been established with certainty. The paracellular pathway does not discriminate between Na+, Cl-, and some of their substitutes; it is poorly permeable to gluconate and prefers K+ to Na+.