Blood pressure reduction in “borderline” hypertensives following physical training

One hundred and sixty-five middle-aged, apparently normal men were submitted to a six-month conditioning program. On the basis of a casual blood pressure measurement during the pre-training evaluation, 37 individuals (23%) were classified as “borderline” hypertensive. The remaining subjects (n = 128) were normotensive. At the conclusion of the program both groups exhibited significant reductions in systolic and diastolic blood pressures at rest and after submaximal work. Moreover, the reductions of the resting systolic and diastolic and of the exercise (300 kg.m./min.) systolic blood pressures were significantly greater for the hypertensives.     

Dependence of red blood cell dynamics in microvessel bifurcations on the endothelial surface layer’s resistance to flow and compression

Red blood cells (RBCs) make up 40–45% of blood and play an important role in oxygen transport. That transport depends on the RBC distribution throughout the body, which is highly heterogeneous. That distribution, in turn, depends on how RBCs are distributed or partitioned at diverging vessel bifurcations where blood flows from one vessel into two. Several studies have used mathematical modeling to consider RBC partitioning at such bifurcations in order to produce useful insights. These studies, however, assume that the vessel wall is a flat impenetrable homogeneous surface. While this is a good first approximation, especially for larger vessels, the vessel wall is typically coated by a flexible, porous endothelial glycocalyx or endothelial surface layer (ESL) that is on the order of 0.5–1 µm thick. To better understand the possible effects of this layer on RBC partitioning, a diverging capillary bifurcation is analyzed using a flexible, two-dimensional model. In addition, the model is also used to investigate RBC deformation and RBC penetration of the ESL region when ESL properties are varied. The RBC is represented using interconnected viscoelastic elements. Stokes flow equations (viscous flow) model the surrounding fluid. The flow in the ESL is modeled using the Brinkman approximation for porous media with a corresponding hydraulic resistivity. The ESL’s resistance to compression is modeled using an osmotic pressure difference. One cell passes through the bifurcation at a time, so there are no cell–cell interactions. A range of physiologically relevant hydraulic resistivities and osmotic pressure differences are explored. Decreasing hydraulic resistivity and/or decreasing osmotic pressure differences (ESL resistance to compression) produced four behaviors: (1) RBC partitioning nonuniformity increased slightly; (2) RBC deformation decreased; (3) RBC velocity decreased relative to blood flow velocity; and (4) RBCs penetrated more deeply into the ESL. Decreasing the ESL’s resistance to flow and/or compression to pathological levels could lead to more frequent cell adhesion and clotting as well as impaired vascular regulation due to weaker ATP and nitric oxide release. Potential mechanisms that can contribute to these behaviors are also discussed.

     

Changes of red cell phospholipids in β-thalassemia minor

Lipid and phospholipid concentrations were determined in the red cells of β-thalassemia minor patients. A reduced concentration of total lipids and total phospholipids in red cells was found. Phosphatidylcholine and sphingomyelin were increased while phosphatidylethanolamine, phosphatidylserine, and phosphatidylinositol concentrations were decreased. These changes are similar to, though less pronounced, than those seen in β-thalassemia major. The relation of these lipids changes, free hemoglobin chains which damage the red cell membrane, and the increased rate of hemolysis is unclear.     

Fabrication and biocompatibility of a porous bioglass ceramic in a Na2OCaOSiO2P2O5 system

A porous bioglass ceramic was prepared from a finely pulverized bioglass powder mixed with particles of two sizes (5 and 500 μm) of 30% by weight with the foaming agent polyethylene glycol 4000 (HO (C₂H₄O) nH). The batch composition of the bioglass was Na₂O 12%, CaO 28%, SiO₂ 50% and P₂O₅ 10% by weight. The specimens, formed by pressing, were sintered in a high temperature furnace. In this study we are concerned with the preparation and microstructure of the material and its performance in biological tests. The microstructure and crystalline phases of the material were investigated by differential thermal analysis, X-ray diffraction analysis, transmission electron microscopy and scanning electron microscopy. In a biomedical examination, it was shown that the porous material was compatible with animal tissues. The microstructure of the implant indicated that newly grown bone interlocked well with the glass ceramic and that macropores and micropores were distributed uniformly in the material, which provided channels for bone ingrowth and improved the microscopic bioresorption.     

Reverse NaCa exchange requires internal Ca and/or ATP in squid axons

Classical NaCa exchange models are based on a symmetric carrier system where Na and Ca competing from the same site, can produce net movement of the other against its electrochemical gradient. We have explored this symmetric assumption by studying the Ca_o and Na_o-dependent Na efflux in dialyzed squid axons in which proper control of both external and internal medium was achieved. The results show: (1) In axons dialyzed without Ca_i and ATP, Ca_o-dependent Na efflux cannot be detected even in the absence of Na_o. Under these conditions, the level of Na efflux (1 pmol · cm⁻² · s⁻¹) is close to that predicted by an electrical ‘leak’. (2) In axons dialyzed with Ca_i (100 μM) and without ATP, Na efflux measured in 440 mM Na_o, is about 4–5 pmol · cm⁻² · s⁻¹ and rather insensitive to Ca_o between 0 and 10 mM. However, in the absence of Na_o, a Ca_o-dependent Na efflux is observed similar in magnitude to that found in the presence of external Na. (3) In the presence of both Ca_i and ATP, Na efflux into artificial sea-water (440 mM Na, 10 mM Ca) is 18 pmol · cm⁻² · s⁻¹. In the absence of Na_o the efflux of Na is 7.5 pmol · cm⁻² · s⁻¹. In the absence of both Na_o and Ca_o the efflux is close to ‘leak’. With full Na_o but no Ca_o, the Na efflux average 12.6 pmol · cm⁻² · s⁻¹. These results indicate a marked asymmetry in the modus operandi of the NaCa exchange system with respect to Ca_i and ATP. These two substrates are required from the cis side to promote Ca_o-dependent Na efflux (reversal NaCa exchange).     

Hibernation in reptiles—II. Changes in blood cell glucose,haemoglobin, red blood cell count,protein and non-protein nitrogen

• 1.1. The level of blood glucose, red blood cell count, haemoglobin, serum protein and non-protein nitrogen were studied during summer and winter periods.
• 2.2. During hibernation, the first four blood constituents were respectively decreased by 62·35 per cent, 34·18 per cent, 35·33 per cent and 7·19 per cent as there is no food supply during the inactive hibernation season.
• 3.3. Non-protein nitrogen was increased by 115·27 per cent during hibernation. This is due to the accumulation of nitrogenous excretory end metabolites as excretion of the animal is impaired during this period.

     

Does decreasing extracellular Na inhibit in vitro renin secretion by affecting NaCa exchange?

It has been shown previously that in vitro renin secretion is inhibited by partial replacement of extracellular NaCl with either mannitol or choline chloride; the inhibitory effect is attributed to an increase in intracellular Ca, resulting from a decreased rate of Ca efflux via Na-Ca exchange. In the present experiments, we confirmed that partially replacing NaCl with choline chloride inhibited renin secretion from rat renal cortical slices, but we found that atropine completely blocked the effect, suggesting cholinergic mediation. Partially replacing NaCl with mannitol also inhibited renin secretion, but the effect could not be attributed specifically to a reduction in extracellular Na. Moreover, the stimulatory effect of Ca chelation on renin secretion was antagonized by either mannitol- or choline chloride -containing incubation media. These results do not support the hypothesis that lowering extracellular Na inhibits renin secretion by a mechanism involving decreased Ca efflux via Na-Ca exchange.     

Catecholamine-induced transport systems in trout erythrocyte. Na+/H+ countertransport or NaCl cotransport?

It has previously been shown (Baroin, A., F. Garcia-Romeu, T. Lamarre, and R. Motais. 1984a, b. Journal of Physiology. 350:137, 356:21; Mahé, Y., F. Garcia-Romeu, and R. Motais. 1985. European Journal of Pharmacology. 116:199) that the addition of catecholamines to an isotonic suspension of nucleated red blood cells of the rainbow trout first stimulates a cAMP-dependent, amiloride-sensitive Na+/H+ exchange. This stimulation seems to be transient. It is followed by a more permanent activation of a coupled entry of Na+ and Cl-, which is inhibited by amiloride but also by inhibitors of band 3 protein (DIDS, furosemide, niflumic acid). The coupled entry of Na+ and Cl- could therefore result from the parallel and simultaneous exchange of Na+out for H+in (via the cAMP-dependent Na+/H+ antiporter) and Cl- out for HCO3- in (via the anion exchange system located in band 3 protein). However, in view of the following arguments, it had been proposed that NaCl uptake does not proceed by the double-exchanger system but via an NaCl cotransport: (a) Na+ entry requires Cl- as anion (in NO3- medium, the Na uptake is strongly inhibited, whereas NO3- is an extremely effective substitute for Cl- in the anion exchange system); (b) Na uptake is not significantly affected by the presence of HCO3- in the suspension medium despite the fact that in red cells, Cl-/HCO3- exchange occurs more readily than the exchanges of Cl- for basic equivalents in a theoretically CO2-free medium (the so-called Cl-/OH- exchanges). The purpose of the present paper was a reassessment of the two models by using monensin, an ionophore allowing Na+/H+ exchange. From this study, it appears that NaCl entry results from the simultaneous functioning of the Na+/H+ antiporter and the anion exchange system. The apparent Cl dependence is explained by the fact that, in these erythrocytes, NO3- clearly inhibits the turnover rate of the Na+/H+ antiporter. As Na+/H+ exchange is the driving component in the salt uptake process, this inhibition explains the Cl requirement for Na entry. The lack of stimulation of cell swelling by bicarbonate is explained by the fact that the rate of anion exchange in a CO2-free medium (Cl-/OH- exchange) is roughly equivalent to that of Na+/H+ exchange and thus in practice is not limiting to the net influx of NaCl through the two exchangers.(ABSTRACT TRUNCATED AT 400 WORDS)     

ANNEXIN 8 negatively regulates RPW8.1‐mediated cell death and disease resistance in Arabidopsis

Study on the regulation of broad‐spectrum resistance is an active area in plant biology. RESISTANCE TO POWDERY MILDEW 8.1 (RPW8.1) is one of a few broad‐spectrum resistance genes triggering the hypersensitive response (HR) to restrict multiple pathogenic infections. To address the question how RPW8.1 signaling is regulated, we performed a genetic screen and tried to identify mutations enhancing RPW8.1‐mediated HR. Here, we provided evidence to connect an annexin protein with RPW8.1‐mediated resistance in Arabidopsis against powdery mildew. We isolated and characterized Arabidopsis b7‐6 mutant. A point mutation in b7‐6 at the At5g12380 locus resulted in an amino acid substitution in ANNEXIN 8 (AtANN8). Loss‐of‐function or RNA‐silencing of AtANN8 led to enhanced expression of RPW8.1, RPW8.1‐dependent necrotic lesions in leaves, and defense against powdery mildew. Conversely, over‐expression of AtANN8 compromised RPW8.1‐mediated disease resistance and cell death. Interestingly, the mutation in AtANN8 enhanced RPW8.1‐triggered H₂O₂. In addition, mutation in AtANN8 led to hypersensitivity to salt stress. Together, our data indicate that AtANN8 is involved in multiple stress signaling pathways and negatively regulates RPW8.1‐mediated resistance against powdery mildew and cell death, thus linking ANNEXIN's function with plant immunity.     

Rate of activation and deactivation of K∶Cl cotransport by changes in cell volume in hemoglobin SS,CC and AA red cells

Red blood cells (RBC) of subjects homozygous for hemoglobin A (AA), C (CC) and S (SS) exhibit different cell volumes which might be related to differences in cell volume regulation. We have investigated how rapidly K:Cl cotransport is activated and deactivated to regulate the cell volume in these cells. We measured the time course of net K⁺ efflux after step changes in cell volume and determined two delay times: one for activation by cell swelling and a second for deactivation by cell shrinkage. Cell swelling induced by 220 mOsm media activated K⁺ efflux to high values (10–20 mmol/ liter cell x hr) in CC and SS; normal AA had a threefold lower activity. The delay time for activation was very short in blood with a high percentage of reticulocytes (retics): (SS, 10% retics, 1.7±0.3 min delay, n=8; AA, 10% retics, 4±1.5 min, n=3; CC, 11.6% retics, 4±0.3, n=3) and long in cells with a smaller percentage of reticulocytes: (AA, 1.5% retics, 10±1.4 min, n=8; CC whole blood 6% retics, 10±2.0 min, n=10, P<0.02 vs. SS). The delay times for deactivation by cell shrinking were very short in SS (3.6±0.4 min, n=8, P<0.02) and AA cells with high retics (2.7±1 min, n=3) and normal retics (2.8±1 min, n=3), but 8–15-fold longer in CC cells (29±2.8 min, n=9).Density fractionation of CC cells (n=3) resulted in coenrichment of the top fraction in reticulocytes and in swelling-activated cotransport (fourfold) with short delay time for activation (4±0.3 min) and long delay for deactivation (14±4 min). The delay time for activation, but not for deactivation, increased markedly with increasing cell density. These findings indicate that all CC cells do not promptly shut off cotransport with cell shrinkage and high rates of cellular K⁺ loss persist after return to isotonic conditions.In summary, (i) K:Cl cotransport is not only very active in young cells but it is also very rapidly activated and deactivated in young AA and SS cells by changes in cell volume. (ii) Delay times for cotransport activation markedly increased with RBC age and in mature cells with low cotransport rates, long delay times for activation were observed. (iii) The long delay time for deactivation exhibited even by young CC cells induces a persistent loss of K⁺ after cell shrinkage which may contribute in vivo to the uniformly low cell volume, low K⁺ and water content of CC cells.This research was supported by National Institutes of Health grants Shannon Award HL-35664, HL-42120, Sickle Cell Center grant HL-38655, and a Grant-in-Aid of the New York Branch of the American Heart Association. The technical help of Sandra M. Suzuka, M.S. is gratefully acknowledged.     

Influence of hyperosmotic shrinkage and β-adrenergic stimulation on red blood cell volume regulation and oxygen binding properties in rainbow trout and carp

Whole blood from rainbow trout and carp was subjected to hyperosmotic shock and subsequent beta-adrenergic stimulation (isoprenaline) at different oxygen tension ( PO(2)) and carbon dioxide tension ( PCO(2)) levels with the aim to evaluate changes in red blood cell (RBC) volume, pH and ion concentrations and their ultimate effect on blood O(2) transport characteristics. Hyperosmolality (addition of NaCl) induced RBC shrinkage, which was followed by a regulatory volume increase (RVI) that was larger at low than at high PO(2)and more complete in carp than in trout. Carp RBC showed practically full volume recovery within 140 min at low PO(2)and partial recovery at high PO(2), whereas RVI was partial under all PO(2)and PCO(2)conditions in trout. The RVI increased intracellular [Na(+)], water content, and, in carp, also pH (pHi), suggesting activation of Na(+)/H(+) exchange. In trout RBCs, activation of RVI was rapid but succeeded by deactivation. In carp RBCs, activation of Na(+) influx was slower but it continued, allowing full volume recovery. Shrinkage of the RBCs was associated with only minor decreases in blood oxygen saturation and oxygen affinity in both species. Thus, the oxygen affinity decrease expected on the basis of the increased concentration of intracellular haemoglobin and organic phosphates was small, and it appeared to some extent countered during RVI by an oxygen affinity increase via increased pHi. Addition of isoprenaline increased RBC volume and pHi and increased Hb oxygen saturation. The beta-adrenergic response was stronger at low compared to high PO(2) and at high compared to low PCO(2). The PO(2) dependency was largest in carp, whereas the PCO(2) (pH) dependency was more expressed in trout. The adrenergic response of trout RBCs was similar under isoosmotic and hyperosmotic conditions. In carp RBCs, the response was absent at high PO(2) under isoosmotic conditions, but interestingly it could be induced under hyperosmotic conditions. The data suggest that the RBC shrinkage occurring in fish moving from freshwater to seawater has minimal impact on blood O(2) binding properties.     

Effects of curvature and cell–cell interaction on cell adhesion in microvessels

It has been found that both circulating blood cells and tumor cells are more easily adherent to curved microvessels than straight ones. This motivated us to investigate numerically the effect of the curvature of the curved vessel on cell adhesion. In this study, the fluid dynamics was carried out by the lattice Boltzmann method (LBM), and the cell dynamics was governed by the Newton’s law of translation and rotation. The adhesive dynamics model involved the effect of receptor-ligand bonds between circulating cells and endothelial cells (ECs). It is found that the curved vessel would increase the simultaneous bond number, and the probability of cell adhesion is increased consequently. The interaction between traveling cells would also affect the cell adhesion significantly. For two-cell case, the simultaneous bond number of the rear cell is increased significantly, and the curvature of microvessel further enhances the probability of cell adhesion.     

Initial steps of αand β-d-glucose binding to intact red cell membrane

Summary The kinetics of the initial phases of d-glucose binding to the glucose transport protein (GLUT1) of the human red cell can be followed by stopped-flow measurements of the time course of tryptophan (trp) fluorescence enhancement. A number of control experiments have shown that the trp fluorescence kinetics are the result of conformational changes in GLUT1. One shows that nontransportable l-glucose has no kinetic response, in contrast to d-glucose kinetics. Other controls show that d-glucose binding is inhibited by cytochalasin B and by extracellular d-maltose. A typical time course for a transportable sugar, such as d-glucose, consists of a zero-time displacement, too fast for us to measure, followed by three rapid reactions whose exponential time courses have rate constants of0.5–100 sec^+–1 at 20°C. It is suggested that the zero-time displacement represents the initial bimolecular ligand/GLUT1 association. Exponential 1 appears to be located at, or near, the external membrane face where it is involved in discriminating among the sugars. Exponential 3 is apparently controlled by events at the cytosolic face. Trp kinetics distinguish the K _d of the epimer, d-galactose, from the K _dfor d-glucose, with results in agreement with determinations by other methods. Trp kinetics distinguish between the binding of the - and -d-glucose anomers. The exponential 1 activation energy of the -anomer, 13.6 ± 1.4 kcal mol^+–1, is less than that of -d-glucose, 18.4 ± 0.8 kcal mol^+–1, and the two Arrhenius lines cross at 23.5°C. The temperature dependence of the kinetic response following -d-glucose binding illustrates the interplay among the exponentials and the increasing dominance of exponential 2 as the temperature increases from 22.3 to 36.6°C. The existence of these interrelations means that previously acceptable approximations in simplified reaction schemes for sugar transport will now have to be justified on a point-to-point basis.We should like to express our thanks to Michael R. Toon for his important contributions. This work was supported in part by a grant-in-aid from the American Heart Association, by the Squibb Institute for Medical Research and by The Council for Tobacco Research.     

Peripheral Tγ lymphocyte population in head and neck cancer

Summary Peripheral T lymphocytes were measured in head and neck cancer patients and controls. The percentage was significantly higher in the 59 cancer patients than in the 46 normal controls (P<0.001). The 12 patients with recurrent disease had elevated percentages of T lymphocytes compared with the untreated group (n=31; P<0.05) and the treated, disease-free group (n=16; P<0.05). Moreover, the percentage of T lymphocytes was significantly higher in the 31 patients with regional lymph node metastasis than in the node-negative group (n=28; P<0.05). In a total of 37 patients with squamous cell carcinoma histologically graded I, II, and III, the absolute counts and percentages of T lymphocytes in the grade I group (n=13) showed significant decreases compared with those in the grade III group (P<0.05; n=6). Moreover, postoperative serial determinations of the percentage of T lymphocytes in the 14 treated, disease-free patients revealed a gradual decrease of T lymphocytes, whereas the five patients with recurrent disease had a tendency to increases in the percentage of T lymphocytes. Abbreviations used in this paper: SMF, sodium metrizoate-Ficoll; PBS, phosphate-buffered saline; SRBC, sheep erythrocytes; FCS, fetal calf serum; Hepes, hydroxyethylpiperazin elthene-sulfonic acid; E, erythrocyte; EAC, erythrocyte-antibody-complement; K, antibody-dependent killer; NK, natural killer     

Glucose inhibits 45Ca efflux from pancreatic β-cells also in the absence of Na+-Ca2+ countertransport

During perifusion with medium deprived of Ca²⁺, addition of glucose or omission of Na⁺ resulted in prompt and quantitatively similar inhibitions of ⁴⁵Ca efflux from β-cell rich pancreatic islets microdissected from ob / ob mice. Glucose had no additional inhibitory effect when Na⁺ was isoosmotically replaced by sucrose or choline⁺. When K⁺ was used as a substitute for Na⁺, the inhibitory effect of Na⁺ removal on ⁴⁵Ca efflux became additive to that of glucose. The observation that glucose can be equally effective in inhibiting ⁴⁵Ca efflux in the presence or absence of Na⁺ is difficult to reconcile with the postulate that the Na⁺-Ca²⁺ countertransport mechanism is a primary site of action for glucose.     

Is an intact cytoskeleton required for red cell urea and water transport?

In order to determine the membrane protein(s) responsible for urea and water transport across the human red cell membrane, we planned to reconstitute purified membrane proteins into phosphatidylcholine vesicles. In preparatory experiments, we reconstituted a mixture of all of the red cell integral membrane proteins into phosphatidylcholine vesicles, but found that p-chloromercuribenzenesulfonate (pCMBS), which normally inhibits osmotic water permeability by approximately 90%, has no effect on this preparation. The preparation was also unable to transport urea at the high rates found in red cells, though glucose transport was normal. White ghosts, washed free of hemoglobin and resealed, also did not preserve normal urea and pCMBS-inhibitable water transport. One-step ghosts, prepared in Hepes buffer in a single-step procedure, without washing, retained normal urea and pCMBS-inhibitable water transport. Perturbations of the cytoskeleton in one-step ghosts, by removal of tropomyosin, or by severing the ankyrin link which binds band 3 to spectrin, caused the loss of urea and pCMBS-inhibitable water transport. These experiments suggest that an unperturbed cytoskeleton may be required for normal urea and pCMBS-inhibitable water transport. They also show that the pCMBS inhibition of water transport is dissociable from the water transport process and suggest a linkage between the pCMBS water transport inhibition site and the urea transport protein.     

Peripheral immune system in aging and Alzheimer’s disease

Alzheimer’s disease (AD) represents an urgent public health mandate. AD is no longer considered a neural-centric disease; rather, a plethora of recent studies strongly implicate a critical role played by neuroinflammation in the pathogeneses of AD and other neurodegenerative conditions. A close functional connection between the immune system and central nervous system is increasingly recognized. In late-onset AD, aging represents the most significant risk factor. Here, from an immunological perspective, we summarize the prominent molecular and cellular changes in the periphery of aging individuals and AD patients. Moreover, we review the knowledge gained in the past several years that implicate specific arms of the peripheral immune system and other types of immune responses in modulating AD progression. Taken together, these findings collectively emphasize a dynamic role of a concert of brain-extrinsic, peripheral signals in the aging and degenerative processes in the CNS. We believe that a systematic view synthesizing the vast amounts of existing results will help guide the development of next-generation therapeutics and inform future directions of AD investigation.