A parallel path model forNecturus proximal tubule

Summary A parallel path model based on the principles of nonequilibrium thermodynamics was developed for theNecturus proximal tubule. The cellular path was represented as a luminal membrane followed by an irreversible active NaCl transport system in the peritubular barrier. The shunt pathway was described as three coarse barriers in series: tight junction, lateral intercellular spaces, and basement membrane with connective tissue. Volume and solute flows were predicted by the model equations as a function of applied electric current. Variations of the model parameters revealed the quantitative importance of the shunt path properties and the relative insensitivity of epithelial transport to changes in most cell parameters. Circulation of electric current and solute within the epithelium were shown to significantly influence the bahavior of the tubule in the presence of an electric field. Values for all transport parameters of the shunt path and epithelium were calculated and compared with available experimental evidence. Volume flow and electric currents predicted by the model compared favorably with experimental observations.     

Trabecular architecture and joint loading of the proximal humerus in extant hominoids,Ateles, and Australopithecus africanus

Objectives

Several studies have investigated potential functional signals in the trabecular structure of the primate proximal humerus but with varied success. Here, we apply for the first time a “whole‐epiphyses” approach to analysing trabecular bone in the humeral head with the aim of providing a more holistic interpretation of trabecular variation in relation to habitual locomotor or manipulative behaviors in several extant primates and Australopithecus africanus.

Materials and methods

We use a “whole‐epiphysis” methodology in comparison to the traditional volume of interest (VOI) approach to investigate variation in trabecular structure and joint loading in the proximal humerus of extant hominoids, Ateles and A. africanus (StW 328).

Results

There are important differences in the quantification of trabecular parameters using a “whole‐epiphysis” versus a VOI‐based approach. Variation in trabecular structure across knuckle‐walking African apes, suspensory taxa, and modern humans was generally consistent with predictions of load magnitude and inferred joint posture during habitual behaviors. Higher relative trabecular bone volume and more isotropic trabeculae in StW 328 suggest A. africanus may have still used its forelimbs for arboreal locomotion.

Discussion

A whole‐epiphysis approach to analysing trabecular structure of the proximal humerus can help distinguish functional signals of joint loading across extant primates and can provide novel insight into habitual behaviors of fossil hominins.

     

Drug-eluting stents in the treatment of proximal vertebral artery stenosis

The objective of the study was to evaluate the efficacy of endovascular revascularization treatment using drug-eluting stents in patients with atherosclerotic proximal vertebral artery (VA) stenosis. Thirty-two patients (61 ± 10 years old) were implanted with 35 sirolimus and tacrolimus eluting stents (3 patients had them from two sides). 27 patients (84%) had vertebrobasilar symptoms at enrollment. All patients were pretreated with dual antiplatelet therapy. The intervention was technically successful in 89% cases. No stroke, myocardial infarction, or death occurred in perioperative period. On duplex scanning the stents remained completely functional. In the late postoperative period 29 (91%) patients, with 32 implanted stents were followed- up. The mean follow-up was 9.5 months. No stroke occurred in patients during this period. Recurrence of vertebrobasilar insufficiency symptoms was noted in 3 patients. VA renarrowing was detected in 16 (50%) arteries in 15 patients, and 12 (80%) of them were asymptomatic. Restenosis ≥50% (n = 13) and reocclusion (n = 3) were more frequent in those with implantation of tacrolimus eluting stents compared to those with sirolimus eluting stents: 10 (71%) of 14 observations to 6 (33%) of 18 cases (p = 0.1794), respectively. Stent fracture was observed in 2 cases (6%), followed by restenosis. Restenosis rate prevailed in men (p = 0.0173). Thus, stenting of VA extracranial portion is reasonably safe procedure with a good clinical effect. The use of drug-eluting stents looks promising but does not solve the problem of high restenosis rate in the late postoperative period.     

Composite grafts in the treatment of osteosarcoma of the proximal humerus

Treatment of osteosarcoma (OSA) of the proximal humerus poses many difficulties and challenges to the treating team. Between 1993 and 2000, we treated 11 patients (three women, eight men; age range, 17–74 years) suffering from OSA of the proximal humerus by composite: massive allografts and long humeral prosthesis. At presentation, 10 patients were at stage 2-B and one at stage 3-B of OSA. One patient presented with a pathologic fracture. All patients except patient No. 6, received preoperative chemotherapy followed by limb salvage surgery and postoperative chemotherapy.Surgical margins were graded as wide in all patients. Postoperative complications included non-union at the allograft/host junction (which united after auto grafting) and superficial wound infections that resolved after antibiotic therapy. All surgical procedures were performed by a team headed by an orthopedic oncologist and shoulder surgeon. At latest follow-up (December 2001) all patients, with the exception of one (who was at stage 3-B at presentation) were alive, and had good function of the upper limb. It is our opinion that the team approach comprising an orthopedic oncologist and shoulder surgeon greatly contributed to the good surgical outcome, and hence the good survival and functional results of the patients. Bone allograft offers a modular malleable durable solution to the resected bone segment.     

Multimeric self-assembly equilibria involving the histone-like protein H-NS. A thermodynamic study

The thermodynamic parameters affecting protein-protein multimeric self-assembly equilibria of the histone-like protein H-NS were quantified by "large zone" gel-permeation chromatography. The abundance of the different association states (monomer, dimer, and tetramer) were found to be strictly dependent on the monomeric concentration and affected by physical (temperature) and chemical (cations) parameters. On the basis of the results obtained in this study and the available structural information concerning this protein, a mechanism is proposed to explain the association behavior also in relation to the functional properties of the protein.     

The hominoid proximal radius: re-interpreting locomotor behaviors in early hominins

Studies of fossil hominins are traditionally taxonomically narrow and often exclude comparisons with hylobatids. Hence, results of functional analyses of postcrania, interpreted as indicating that early hominins are "African-ape-like" in their postcranial skeletons and positional behaviors, may reflect an artifact of inadequate taxonomic and morphological breadth of the comparative sample. To address this problem and better understand early hominin positional behaviors, this study included hylobatids in a comparative analysis, focusing on the hominoid elbow joint. Specifically, morphometric variables of the proximal radius were derived from measurements from a sample of all genera of extant hominoids and casts of extinct hominin species. Univariate and multivariate analyses were performed on these data. Results show that early hominins are morphologically diverse and are not, as a group, similar to any one extant group. Instead, the fossils resemble Pan, Gorilla, and Hylobates, and are not like modern Homo sapiens or Pongo. This suggests that the morphology of Hylobates may reflect a morphotype for all later hominoids, thus complicating the functional interpretations of fossil hominins. The implications of these results are that the proximal radius is not a sensitive indicator of locomotor behavior among hominoids since the morphology in hylobatids and Gorilla and Pan is similar despite widely varying positional repertoires. Furthermore, inferences of function from form in extinct hominins can be drastically affected by the comparative outgroup selection. A re-evaluation of the functional morphology of the proximal radius in early hominins is addressed.     

Trabecular architecture in the forelimb epiphyses of extant xenarthrans (Mammalia)

Background

Bone structure has a crucial role in the functional adaptations that allow vertebrates to conduct their diverse lifestyles. Much has been documented regarding the diaphyseal structure of long bones of tetrapods. However, the architecture of trabecular bone, which is for instance found within the epiphyses of long bones, and which has been shown experimentally to be extremely plastic, has received little attention in the context of lifestyle adaptations (virtually only in primates). We therefore investigated the forelimb epiphyses of extant xenarthrans, the placental mammals including the sloths, anteaters, and armadillos. They are characterised by several lifestyles and degrees of fossoriality involving distinct uses of their forelimb. We used micro computed tomography data to acquire 3D trabecular parameters at regions of interest (ROIs) for all extant genera of xenarthrans (with replicates). Traditional, spherical, and phylogenetically informed statistics (including the consideration of size effects) were used to characterise the functional signal of these parameters.

Results

Several trabecular parameters yielded functional distinctions. The main direction of the trabeculae distinguished lifestyle categories for one ROI (the radial trochlea). Among the other trabecular parameters, it is the degree of anisotropy (i.e., a preferential alignment of the trabeculae) that yielded the clearest functional signal. For all ROIs, the armadillos, which represent the fully terrestrial and fossorial category, were found as characterised by a greater degree of anisotropy (i.e., more aligned trabeculae). Furthermore, the trabeculae of the humeral head of the most fossorial armadillos were also found to be more anisotropic than in the less fossorial species.

Conclusions

Most parameters were marked by an important intraspecific variability and by a size effect, which could, at least partly, be masking the functional signal. But for some parameters, the degree of anisotropy in particular, a clear functional distinction was recovered. Along with data on primates, our findings suggest that a trabecular architecture characterised by a greater degree of anisotropy is to be expected in species in which the relevant epiphyses withstand a restricted range of load directions. Trabecular architecture therefore is a promising research avenue for the reconstruction of lifestyles in extinct or cryptic species.

     

Urate transport across the apical membrane of renal proximal tubules

Since the molecular cloning of the renal apical urate/anion exchanger URAT1 (SLC22A12), several membrane proteins relevant to urate transport have been identified. In addition, the identification of PDZ (PSD-95, DglA, and ZO-1) domain protein PDZK1 as a binding partner of URAT1, and the emerging role of PDZ scaffold for renal apical transporters have led to a new concept of renal urate transport: urate-transporting multimolecular complex, or "urate transportsome," that may form an ultimate functional unit at the apical membrane of renal proximal tubules. Elucidation of urate transportsome will lead to the new drug development for hyperuricemia.     

A symmetrical approach to the analysis of cardiocyte electrical and contractile activity]

Based on the systemic symmetrical approach, experimentally determined parameters of action potential and contractile response of frog myocardial strip were analyzed prior to and after the administration of several physiologically active drugs (caffeine, neoepinephrine, nembutal, ouabain) into the perfusate. It was shown that the satisfactory functional state of preparation was characterized by an interrelation between parameters in the form of a harmonic proportion with relatively constant coefficient. When the functional state of subject is affected by a physiologically active substance, the interrelation between the parameters is considerably changed. Based on the analysis of the data of literature, it was found that the interrelation between temporary parameters of action potential in various structures from human heart has the form of a harmonic proportion with a constant coefficient close to the invariant of "Gold Wurf" proportion. The similarity is underlined of principles of cardiac function temporary arrangement at levels of cell, organ and organism.     

Catecholamines and angiotensinogen gene expression in kidney proximal tubular cells

To investigate the molecular mechanism(s) of action of catecholamines on the expression of the angiotensinogen (ANG) gene in kidney proximal tubular cells, we used opossum kidney (OK) cells with a fusion gene containing the 5-flanking regulatory sequence of the rat ANG gene fused with a human growth hormone (hGH) gene as a reporter, pOGH (rANG N-1498/+18), permanently integrated into their genomes. The level of expression of the ANG-GH fusion gene was quantified by the amount of immunoreactive-hGH (IR-hGH) secreted into the medium. The addition of norepinephrine (NE), isoproterenol (a ₁/₂-adrenergic receptor (AR) agonist) and iodoclonidine (an ₂-AR agonist) stimulated the expression of the ANG-GH fusion gene in a dose-dependent manner, whereas the addition of epinephrine and phenylephrine (₁-AR agonist) had no effect. The stimulatory effect of NE was blocked by the presence of propranolol (-AR blocker), atenolol (₁-AR blocker), yohimbine (₂-AR blocker), Rp-cAMP (an inhibitor of cAMP-dependent protein kinase AI & AII) and staurosporine (an inhibitor of protein kinase C), but was not blocked by ICI 118, 551 (₂-AR blocker) and prazosin (₁-AR blocker). The addition of a combination of isoproterenol and iodoclonidine or a combination of 8-Bromo-cAMP (8-Br-cAMP) and phorbol 12-myristate (PMA) synergistically stimulated the expression of the ANG-GH fusion gene as compared to the addition of isoproterenol, iodoclonidine, 8-Br-cAMP or PMA alone. Furthermore, the addition of NE, 8-Br-cAMP or PMA stimulated the expression of pOGH (rANG N-806/-779/-53/+18), a fusion gene containing the putative cAMP responsive element (CRE, ANG N-806/-779) upstream of the ANG promoter (ANG N-53/+18) in OK cells, but had no effect on the expression of fusion genes containing the mutant of the CRE. Gel mobility shift assays revealed that the ANG-CRE binds with the DNA-binding domain (bZIP 254-327) of the cAMP-responsive binding protein (CREB). The binding of the labeled ANG-CRE to CREB (bZIP254-327) was displaced by unlabeled ANG-CRE and the CRE of the somatostatin gene but not by the mutants of the ANG-CRE. Finally, NE stimulated the phosphorylation of CREB in OK cells. These studies demonstrate that the molecular mechanism(s) of NE action on the expression of the ANG gene in OK cells may be mediated via both the PKA and PKC signalling pathways and via the phosphorylation of CREB. The phosphorylated CREB then interacts with the CRE in the 5-flanking region of the ANG gene and subsequently stimulates the gene expression.     

Minimizing impairment in laborers with finger losses distal to the proximal interphalangeal joint by second toe transfer

Traditionally, toe-to-hand transfers have been reserved for thumb amputations or for use after severe mutilating injuries. The authors report their experience with the use of second toe-for-finger amputations with preserved or reconstructible proximal interphalangeal joints in manual workers. The aim of the procedure was to reduce impairment and to upgrade the hand from a functional and cosmetic standpoint. Fifteen second-toe wrap-around or variations were carried out on 11 adults (18 to 41 years old). Four patients with two or more finger amputations received two sequential second toes; four patients with two finger amputations received one toe; and each of three patients with single-digit amputation received a single toe. All but one amputation were performed less than 3 weeks after the accident. All toes survived. Range of motion at the native proximal interphalangeal joint was more than 90 percent in all patients but one; however, it was minimal at the transplanted joints. Patient satisfaction was high from a cosmetic and functional standpoint. Ten of 11 laborers resumed their previous activity. On the basis of this experience, a classification with aesthetic and functional implications is proposed to help in the decision-making process when dealing with multidigital injuries. It is concluded that second-toe transfer is an excellent choice for finger amputation distal to the proximal interphalangeal joint in laborers. Its prime indication is for amputations of two fingers where at least one toe should be transferred, as required, to achieve an "acceptable hand" (three-fingered hand). Early transfer allows salvage of critical structures from the damaged finger, such as joints, tendons, and bone, that otherwise would be lost. Early transplantation is highly recommended.     

Plausibility and parameter sensitivity of micro-finite element-based joint load prediction at the proximal femur

A micro-finite element-based method to estimate the bone loading history based on bone architecture was recently presented in the literature. However, a thorough investigation of the parameter sensitivity and plausibility of this method to predict joint loads is still missing. The goals of this study were (1) to analyse the parameter sensitivity of the joint load predictions at one proximal femur and (2) to assess the plausibility of the results by comparing load predictions of ten proximal femora to in vivo hip joint forces measured with instrumented prostheses (available from www.orthoload.com). Joint loads were predicted by optimally scaling the magnitude of four unit loads (inclined \(-20^{\circ }\) to \(100^{\circ }\) with respect to the vertical axis) applied to micro-finite element models created from high-resolution computed tomography scans (\(30.3~\upmu \)m voxel size). Parameter sensitivity analysis was performed by varying a total of nine parameters and showed that predictions of the peak load directions (range 10\(^{\circ }\)–\(30^{\circ }\)) are more robust than the predicted peak load magnitudes (range 2344.8–4689.5 N). Comparing the results of all ten femora with the in vivo loading data of ten subjects showed that peak loads are plausible both in terms of the load direction (in vivo: \(18.2\pm 2.0^{\circ }\), predicted: \(20.0^{\circ }\)) and magnitude (in vivo: \(2707.6\pm 443.3~\hbox {N}\), predicted: \(3372.2\pm 597.9~\hbox {N}\)). Overall, this study suggests that micro-finite element-based joint load predictions are both plausible and robust in terms of the predicted peak load direction, but predicted load magnitudes should be interpreted with caution.     

Identification of an apical Cl-/HCO-3 exchanger in rat kidney proximal tubule

SLC26A6 (or putative anion transporter 1, PAT1) is located on the apical membrane of mouse kidney proximal tubule and mediates exchange in in vitro expression systems. We hypothesized that PAT1 along with a exchange is present in apical membranes of rat kidney proximal tubules. Northern hybridizations indicated the exclusive expression of SLC26A6 (PAT1 or CFEX) in rat kidney cortex, and immunocytochemical staining localized SLC26A6 on the apical membrane of proximal tubules, with complete prevention of the labeling with the preadsorbed serum. To examine the functional presence of apical exchanger, proximal tubules were isolated, microperfused, loaded with the pH-sensitive dye BCPCF-AM, and examined by digital ratiometric imaging. The pH of the perfusate and bath was kept at 7.4. Buffering capacity was measured, and transport rates were calculated as equivalent base flux. The results showed that in the presence of basolateral DIDS (to inhibit cotransporter 1) and apical EIPA (to inhibit Na⁺/H⁺ exchanger 3), the magnitude of cell acidification in response to addition of luminal Cl^– was 5.0-fold higher in the presence than in the absence of . The Cl^–-dependent base transport was inhibited by 61% in the presence of 0.5 mM luminal DIDS. The presence of physiological concentrations of oxalate in the lumen (200 µM) did not affect the exchange activity. These results are consistent with the presence of SLC26A6 (PAT1) and exchanger activity in the apical membrane of rat kidney proximal tubule. We propose that SLC26A6 is likely responsible for the apical (and Cl^–/OH^–) exchanger activities in kidney proximal tubule. putative anion transporter 1; chloride/formate exchanger; SLC26A6     

The proximal region of the beta-tubulin C-terminal tail is sufficient for axoneme assembly

We have used Drosophila testis-specific beta2-tubulin to determine sequence requirements for different microtubules. The beta2-tubulin C-terminal tail has unique sperm-specific functions [Dev Biol 158:267-286 (2003)] and is also important for forming stable heterodimers with alpha-tubulin, a general function common to all microtubules [Mol Biol Cell 12(7):2185-2194 (2001)]. beta-tubulins utilized in motile 9 + 2 axonemes contain a C-terminal sequence "axoneme motif" [Science 275 (1997) 70-73]. C-terminal truncated beta2-tubulin cannot form the sperm tail axoneme. Here we show that a partially truncated beta2-tubulin (beta2Delta7) containing only the proximal portion of the C-terminal tail, including the axoneme motif, can support production of functional motile sperm. We conclude that these proximal eight amino acids specify the binding site for protein(s) essential to support assembly of the motile axoneme. Males that express beta2Delta7, although they are fertile, produce fewer sperm than wild type males. Beta2Delta7 causes a slightly increased error rate in spermatogenesis attributable to loss of stabilizing properties intrinsic to the full-length C-terminal tail. Therefore, beta2Delta7 males would be at a selective disadvantage and it is likely that the full-length C-terminus would be essential in the wild and in evolution.     

A Model of Relationships between Different Systems of Characters and the Adaptation Potential of the Body in Early Adulthood

Relationships of the adaptation potential with sets of somatic, functional, and dermatoglyphic parameters; personality traits; and polymorphisms of certain genes (FTO, DAT1, and VDR) were studied using data from anthropological examination and psychological testing of 655 healthy students aged 17–25 years from various higher education schools. The study employed two methods that allow premorbid diagnosis of the functional (physical) condition and adaptation and are recommended for large-scale preventive examinations in adults. The methods address the functional status according to Pirogova et al. and the adaptation potential according to Bayevsky et al. An original model of relationships between different sets of traits (somatic, functional, dermatoglyphic, and personality traits) and the adaptive potential in early adulthood was proposed on the basis of significant canonical correlations and Pearson’s contingency coefficients with due regards to the effects that the gene polymorphisms exert on the formation of trait sets.     

Aberrations of cortical and subcortical integration during chronic administration of haloperidol to the dog

The character of evoked potentials (EPs) dynamics to signal light stimulus during elaboration of avoidance reaction, allows to assert that during formation of adaptive activity functional balance is established of sensory and integrative-triggering brain parts or functional balance of "motor" and "sensory" integration regimes. Each of the studied subcortical structures is characterized by simultaneous but specific functioning both in the motor and sensory regimes; such conclusion is based on different dynamics of their EPs parameters: the changes of ones correspond to EPs dynamics in the visual cortical area, of the others--in the motor area. During chronic haloperidol administration, the reorganizations of intercentral relations are observed in 10--12 days after the beginning of drug administration. They may be considered as a succession of disturbances of functional balance between "sensory" and "motor" integration regimes: at first the sensory regime domination appears in which subcortical structures are chiefly and uniformly involved (ncd, pall and n. acc.); "motor" regime is weakened; then, as a result, a distortion of the "motor" regime of integration takes place. In this case a bradykinesia is developed.     

Effects of functional group changes in the EcoRI recognition site on the cleavage reaction catalyzed by the endonuclease

Oligodeoxynucleotides have been prepared that contain changes in the functional group pattern present in the EcoRI recognition site. These changes involve "functional group deletions", "functional group reversals", and "displaced functional groups". Steady-state kinetic parameters have been used to characterize the interaction of these modified recognition sites with the EcoRI endonuclease. Changes in the functional group pattern have varying effects upon the cleavage reaction. Both the exocyclic amino groups of the two adenine residues and the methyl groups of the thymine residues appear to interact with the endonuclease quite differently. In both cases efficient catalysis was observed when these functional groups were present at the "outer" dA-dT base pair. Selectivity was decreased by over an order of magnitude largely via increases in Km when these functional groups were deleted. Similar modifications at the "inner" dA-dT base pair did not alter the kinetic parameters significantly from those observed with the native sequence. Addition of an amino group to the minor groove at the outer dA-dT base pair resulted in a modified recognition site that interacted with the enzyme, on the basis of observed competitive inhibition kinetics, but was not cleaved.     

Changes in the correlations of the different indices of the entire behavior of dogs under the influence of seduxen

During chronic use of seduxen various changes of correlation connections between different parameters of general behaviour are revealed in dogs. The character and degree of expressiveness of these changes depend on the drug dose and typological characteristics of animals. The most general and significant manifestation of favourable effect of the drug action on animals behaviour is an increase of the number of "strong" correlation connections (correlation coefficient is more than 0.7) of the parameters of various components of conditioned activity, reflecting the state of inner inhibition processes, and to the parameters of vegetative provision of conditioned reactions. The character of reconstructions of correlation connections between different conditioned, vegetative, neurotransmitter and general behaviour parameters allows to judge of the direction of pharmacological influence on separate functional systems and the behaviour as a whole.     

Comparison of outcomes of percutaneous coronary intervention on proximal versus non-proximal left anterior descending coronary artery, proximal left circumflex, and proximal right coronary artery: A cross-sectional study

Background

There have been few prospective studies examining the utility of routine exercise treadmill testing (ETT) early after percutaneous coronary intervention (PCI). The objective of this study was to examine the impact of a routine ETT strategy early after PCI on follow-up cardiac events and procedures.

Methods

We examined 136 patients who underwent routine ETT at 6 weeks post-PCI in the ADORE trial. The ETT was classified as positive, indeterminate, or negative. The Duke Treadmill Score (DTS) was calculated for all patients. Follow-up occurred at 9 months.

Results

ETT results at 6 weeks were: 32 (23.5%) positive, 24 (17.6%) indeterminate and 80 (58.8%) negative. At 9 months, the composite event rate was 21.9% in those with a positive ETT, 20.8% in those with an indeterminate ETT and 12.5% in those with a negative ETT (p = 0.25 positive vs. negative ETT). The sensitivity of early ETT for predicting clinical events was 41.2%, the specificity was 73.3%, the positive predictive value was 21.9% and the negative predictive value was 87.5%. At 9 months, the cardiac procedure rate was 18.8% in those with a positive test, 13.0% in those with an indeterminate test, and 6.3% in those with a negative test (p = 0.07 positive vs. negative ETT). In a multivariate logistic regression model, coronary stenting during PCI and a ≥ 85% MPHR achieved were found to be inversely associated with clinical events. However, the DTS did not independently predict clinical events.

Conclusion

Although the statistical power of the study was limited by the small number of clinical events (particularly MI and death), the results of this study support the ACC/AHA guidelines that exercise treadmill testing should not be used routinely after PCI.