Smooth muscle and myofibroblast-like cells in the perimedullary stromal basket of kidneys from ringed seals (Phoca hispida)

Summary The medullary pyramid of renculi in kidneys of ringed seals (Phoca hispida) is enclosed by a basket composed of ribbons of stromal tissue continuous with the wall of the calyx. Branched smooth muscle cells with well-developed Golgi complexes and rough endoplasmic reticulum and only an incomplete external lamina are the principal cells in sites near the origin of the ribbons from the calycal wall. Deeper in the corticomedullary junctional region, smooth muscle is progressively replaced with stellate or spindle-shaped cells exhibiting structural characteristics intermediate between those of fibroblasts and smooth muscle fibers. These myofibroblast-like cells contain arrays of parallel microfilaments 6–8 nm thick with associated focal densities and subplasmalemmal dense plaques, caveolae, elongate, often deeply wrinkled nuclei, and well-developed Golgi complexes and rough endoplasmic reticulum. Material resembling external lamina is associated with parts of the surfaces of most myofibroblast-like cells and intermediate junctions are present. Fibroblasts lacking arrays of parallel microfilaments are a minority at any level in the stromal ribbons. Interstitial cells in the vicinity of the corticomedullary junction show similar myofibroblast-like characteristics. The smooth muscle and myofibroblast-like cells presumably assist expression of urine from the papilla and calyx, and possibly participate as pacemakers for the urinary tract.     

Active interfacial dynamic transport of fluid in a network of fibrous connective tissues throughout the whole body

Fluid in interstitial spaces accounts for ~20% of an adult body weight and flows diffusively for a short range. Does it circulate around the body like vascular circulations? This bold conjecture has been debated for decades. As a conventional physiological concept, interstitial space is a micron‐sized space between cells and vasculature. Fluid in interstitial spaces is thought to be entrapped within interstitial matrix. However, our serial data have further defined a second space in interstitium that is a nanosized interfacial transport zone on a solid surface. Within this fine space, fluid along a solid fibre can be transported under a driving power and identically, interstitial fluid transport can be visualized by tracking the oriented fibres. Since 2006, our data from volunteers and cadavers have revealed a long‐distance extravascular pathway for interstitial fluid flow, comprising at least four types of anatomic distributions. The framework of each extravascular pathway contains the longitudinally assembled and oriented fibres, working as a fibrorail for fluid flow. Interestingly, our data showed that the movement of fluid in a fibrous pathway is in response to a dynamic driving source and named as dynamotaxis. By analysis of previous studies and our experimental results, a hypothesis of interstitial fluid circulatory system is proposed.     

Changes in gravity inhibit lymphocyte locomotion through type I collagen

Summary Immunity relies on the circulation of lymphocytes through many different tissues including blood vessels, lymphatic channels, and lymphoid organs. The ability of lymphocytes to traverse the interstitium in both nonlymphoid and lymphoid tissues can be determined in vitro by assaying their capacity to locomote through Type I collagen. In an attempt to characterize potential causes of microgravity-induced immunosuppression, we investigated the effects of simulated microgravity on human lymphocyte function in vitro using a specialized rotating-wall vessel culture system developed at the Johnson Space Center. This very low shear culture system randomizes gravitational vectors and provides an in vitro approximation of microgravity. In the randomized gravity of the rotating-wall vessel culture system, peripheral blood lymphocytes did not locomote through Type I collagen, whereas static cultures supported normal movement. Although cells remained viable during the entire culture period, peripheral blood lymphocytes transferred to unit gravity (static culture) after 6 h in the rotating-wall vessel culture system were slow to recover and locomote into collagen matrix. After 72 h in the rotating-wall vessel culture system and an additional 72 h in static culture, peripheral blood lymphocytes did not recover their ability to locomote. Loss of locomotory activity in rotating-wall vessel cultures appears to be related to changes in the activation state of the lymphocytes and the expression of adhesion molecules. Culture in the rotating-wall vessel system blunted the ability of peripheral blood lymphocytes to respond to polyclonal activation with phytohemagglutinin. Locomotory response remained intact when peripheral blood lymphocytes were activated by anti-CD3 antibody and interleukin-2 prior to introduction into the rotating-wall vessel culture system. Thus, in addition to the systemic stress factors that may affect immunity, isolated lymphocytes respond to gravitational changes by ceasing locomotion through model interstitium. These in vitro investigations suggest that microgravity induces non-stress-related changes in cell function that may be critical to immunity. Preliminary analysis of locomotion in true microgravity revealed a substantial inhibition of cellular movement in Type I collagen. Thus, the rotating-wall vessel culture system provides a model for analyzing the microgravity-induced inhibition of lymphocyte locomotion and the investigation of the mechanisms related to lymphocyte movement.     

Characterization of renal interstitial fibroblast-specific protein 1/S100A4-positive cells in healthy and inflamed rodent kidneys

Fibrosis is considered as a central factor in the loss of renal function in chronic kidney diseases. The origin of fibroblasts and myofibroblasts that accumulate in the interstitium of the diseased kidney is still a matter of debate. It has been shown that accumulation of myofibroblasts in inflamed and fibrotic kidneys is associated with upregulation of fibroblast-specific protein 1 (FSP1, S100A4), not only in the renal interstitium but also in the injured renal epithelia. The tubular expression of FSP1 has been taken as evidence of myofibroblast formation by epithelial–mesenchymal transition (EMT). The identity of FSP1/S100A4 cells has not been defined in detail. We originally intended to use FSP1/S100A4 as a marker of putative EMT in a model of distal tubular injury. However, since the immunoreactivity of FSP1 did not seem to fit with the distribution and shape of fibroblasts or myofibroblasts, we undertook the characterization of FSP1/S100A4-expressing cells in the interstitium of rodent kidneys. We performed immunolabeling for FSP1/S100A4 on thin cryostat sections of perfusion-fixed rat and mouse kidneys with peritubular inflammation, induced by thiazides and glomerulonephritis, respectively, in combination with ecto-5-nucleotidase (5NT), recognizing local cortical peritubular fibroblasts, with CD45, MHC class II, CD3, CD4 and Thy 1, recognizing mononuclear cells, with alpha smooth muscle actin (SMA), as marker for myofibroblasts, and vimentin for intracellular intermediate filaments in cells of mesenchymal origin. In the healthy interstitium of rodents the rare FSP1/S100A4+ cells consistently co-expressed CD45 or lymphocyte surface molecules. Around the injured distal tubules of rats treated for 3–4 days with thiazides, FSP1+/S100A4+, 5NT+, SMA+, CD45+ and MHC class II+ cells accumulated. FSP1+/S100A4+ cells consistently co-expressed CD45. In the inflamed regions, SMA was co-expressed by 5NT+ cells. In glomerulonephritic mice, FSP1+/S100A4+ cells co-expressed Thy 1, CD4 or CD3. Thus, in the inflamed interstitium around distal tubules of rats and of glomerulonephritic mice, the majority of FSP1+ cells express markers of mononuclear cells. Consequently, the usefulness of FSP1/S100A4 as a tool for detection of (myo)fibroblasts in inflamed kidneys and of EMT in vivo is put into question. In the given rat model the consistent co-expression of SMA and 5NT suggests that myofibroblasts originate from resident peritubular fibroblasts.Ivan Hegyi and Michel Le Hir contributed equally to the study     

Energy metabolism response to calcium activation in isolated rat hearts during development and regression of T3-induced hypertrophy

The present paper shows that cultured bovine endothelial cells can be labeled with³H-carnitine by incubation. This process is slow and is uphill, requiring Na⁺/K⁺ATPase activity. After 3 days incubation isotopic equilibrium is reached, when the cells contain about 0.5 mM (total) carnitine at a medium concentration of about 3 M. The plasmamembrane barrier is rather resistant to acidosis and oxygen free radicals (OFR). The rate of carnitine release increases, significantly only at pH below 5.8 At pH 6.0 the release of stored carnitine can be initiated by the addition of D- or L-lactate. OFR, generated by the addition of xanthine and xanthine oxidase, did not affect carnitine release. Both mild acidosis and OFR left plasmamembranes of endothelial cells intact as judged by the absence of lactate dehydrogenase loss from the cells. Therefore, the known increase of capillary permeability during ischemia and reperfusion may not be due to plasmalemmal disruption of individual endothelial cells, but to increase of inter-endothelial spaces.     

The tubulogenic effect of aldosterone is attributed to intact binding and intracellular response of the mineralocorticoid receptor

Little is known about the extra- and intracellular stimuli inducing renal stem/progenitor cells to develop into three-dimensionally structured tubules. To study this specific development in a controlled environment, we used an advanced culture technique. Embryonic tissue derived from neonatal rabbit kidney was placed in a perfusion culture container at the interface of an artificial interstitium made of a polyester fleece. Culture was carried out in chemically defined Iscove’s Modified Dulbecco’s Medium (IMDM) for 13 days. Development of tubules was histochemically detected on cryosections labeled with Soybean Agglutinin (SBA). The experiments showed that aldosterone exerts a specific tubulogenic effect. Application of aldosterone (1 × 10⁻⁷ M) raised numerous SBA-labeled tubules, while in the absence of the steroid hormone the development of tubules was lacking. Specificity of hormone action was analyzed by the use of aldosterone antagonists. Administration of spironolactone (1 × 10⁻⁴ M) and canrenoate (1 × 10⁻⁵ M) completely inhibited the development of tubules. Finally, disrupting the intracellular molecular complex of the mineralocorticoid receptor (MR) and heat shock proteins by geldanamycin (2 μg/ml) prevented the development of tubules. Our results suggest that the tubulogenic effect induced by aldosterone is attributed to both hormone binding and an undisturbed intracellular response of the MR.     

Locally different role of atrial natriuretic peptide (ANP) in the pericardial fluid

Pericardial fluid (PF) contains several vasoactive agents in higher concentrations than venous plasma (VP). However, with human atrial natriuretic peptide (ANP) controversial data have been reported in earlier studies performed on a limited number of patients (less than 20). The present study was designed to characterize the ANP levels in human PF and cardiac tissues, and to ascertain whether myocardial ischemic state is a major factor in determining ANP production of the human heart. In a total of 316 consecutive patients undergoing open heart surgery ANP levels in VP, PF, atrial and ventricular tissues were measured by radioimmunoassay and analyzed by high-performance liquid chromatography (HPLC). The data are presented as median and 25th-75th percentiles. Our results showed ANP concentration [ANP] of PF significantly exceeded that of VP and [ANP] in the atrial tissue was significantly higher than in the ventricular tissue (p < 0.001). In patients without myocardial ischemia (valvular heart disease) [ANP] in the PF was 258.3 (189.9-342.5) pg/ml, in the VP 28.4 (11.7-57.6) pg/ml and 151.7 (78.4-447.6) ng/mg in the atrial, 0.4 (0.2-1.6) ng/mg in the ventricular tissue. The corresponding values for patients with coronary artery disease were 208.1 (153.8-318.9) pg/ml in the PF, 19.8 (9.4-27.9) pg/ml in the VP, 129.6 (66.5-455.0) ng/mg in the atrial and 1.0 (0.1-1.8) ng/mg in the ventricular tissue. The ventricular tissue levels correlated to the atrial tissue levels (r = 0.317; p < 0.05). Great difference (p < 0.001) was found in the atrial tissue levels between females [414.6 (119.7-734.4) ng/mg] and males [105.4 (65.3-204.2) ng/mg]. In HPLC analysis the majority of the pericardial fluid and tissue ir-ANP coeluted with human ANP [99-126]. In conclusion, [ANP] in PF of cardiosurgical patients is higher by an order of magnitude than in VP. Intrapericardial ANP may reflect the peptide concentration in the myocardial interstitium and may represent a paracrine regulatory mechanism, which seems independent of ANP-induced putative antiischemic influences.     

Mass kinetics of apolipoprotein A-I in interstitial fluid after administration of intravenous apolipoprotein A-I/lecithin discs in humans

Apolipoprotein kinetics are customarily determined by modeling time curves of specific radioactivity or isotopic enrichment in plasma after intravenous infusion of radiolabeled lipoproteins or stable isotope-enriched amino acids. However, this provides no information on the fractional rate of transfer of the apolipoprotein from plasma to interstitial fluid (k(p-if)) or its mean residence time in interstitial fluid (MRT(if)). To determine these parameters for a pharmacologic dose of exogenous apolipoprotein A-I (apoA-I) given intravenously as apoA-I/lecithin discs, we measured apoA-I in plasma and prenodal leg lymph in five healthy men before, during, and after a 4 h infusion at 10 mg/kg/h. ApoA-I concentrations in plasma and lymph were modeled by linear compartmental models (SAAM II version 1.1), using lymph albumin to adjust for the effects of variations in lymph flow rate. k(p-if) averaged 0.75%/h (range, 0.33-1.32), and MRT(if) averaged 29.1 h (14.1-40.0). Neither parameter was correlated with the distribution volume (57-105 ml/kg) or the fractional elimination rate (1.44-2.91%/h) of apoA-I, determined by modeling plasma apoA-I concentration alone. Although used here to study the mass kinetics of apoA-I, if combined with infusion of a tracer, analysis of lymph could also expand the modeling of endogenous apolipoprotein kinetics.     

Developmental changes in testicular interstitium in the Najdi Ram Lambs

This experiment was designed to study the relationship between growth rate and sexual development in Najdi ram lambs. Forty-five Najdi ram lambs were used in nine age groups (1–9th month age), keeping 5 lambs in each group. Results show that mean testis size and scrotal circumference increased at a constant rate, reaching a maximum value of 392.00 ± 2.00 g and 25.00 ± 0.32 cm respectively, at the age of 9 months. A similar trend of growth was observed for the mean body weight, reaching a maximum value of 40.2 ± 0.20 kg at the age of 9 months. There was a positive correlation between the increasing rates of body weight and size of the testis. There were significant differences (P < 0.05) in testis size, scrotal circumference and body weight of lambs between all ages (1–9 months). The histological section of testis showed that a small number of mature sperms appeared in the eighth month of age and their numbers increased in the ninth month. In conclusion, the current findings indicated that puberty in Najdi rams occurs between the 8th and 9th months of age.     

心脏交感神经和心肌间质重塑的共同通路——蛋白激酶C途径

心脏交感神经和心肌间质对维持正常心功能有重要作用。心血管患病时,两者均发生不同程度的重塑,并互相影响,这些变化对疾病进展发挥重要影响。研究证据显示,两者间的相互作用可能通过蛋白激酶C介导,对交感神经功能异常和心肌纤维化都发挥重要作用。