Immunohistochemical localization of type IV collagen fibronectin and laminin in the juxtaglomerular apparatus of the rat kidney

The juxtaglomerular apparatus (JGA) is a complex structure containing several components: the vessels, the extraglomerular mesangium and the distal tubule. These structures include cellular elements and an extracellular matrix (ECM). Collagenous (type IV collagen) and noncollagenous components of the basement membranes were studied. The localization of type IV collagen and of two extracellular glycoproteins (laminin and fibronectin) was investigated using immunofluorescent and immunoperoxidase labelled antibodies. Type IV collagen and laminin have the same localization on the JGA basement membranes. On the other hand, fibronectin is limited to the entrance of the glomerular stalk. On electron microscopy, type IV collagen is found in the basement membrane while fibronectin is restricted to certain areas of the extracellular matrix. These findings confirm data concerning the distribution of these three components in basement membranes and allow a better understanding of the histoarchitecture of the juxtaglomerular apparatus.     

Determination of protein mobility in mitochondrial membranes of living cells

Molecular mobility in membranes of intracellular organelles is poorly understood, due to the lack of experimental tools applicable for a great diversity of shapes and sizes such organelles can acquire. Determinations of diffusion within the plasma membrane or cytosol are based mostly on the assumption of an infinite flat space, not valid for curved membranes of smaller organelles. Here we extend the application of FRAP to mitochondria of living cells by application of numerical analysis to data collected from a small region inside a single organelle. The spatiotemporal pattern of light pulses generated by the laser scanning microscope during the measurement is reconstructed in silico and consequently the values of diffusion parameters best suited to the particular organelle are found. The mobility of the outer membrane proteins hFis and Tom7, as well as oxidative phosphorylation complexes COX and F₁F₀ ATPase located in the inner membrane is analyzed in detail. Several alternative models of diffusivity applied to these proteins provide insight into the mechanisms determining the rate of motion in each of the membranes. Tom7 and hFis move along the mitochondrial axis in the outer membrane with similar diffusion coefficients (D = 0.7 μm²/s and 0.6 μm²/s respectively) and equal immobile fraction (7%). The notably slower motion of the inner membrane proteins is best represented by a dual-component model with approximately equal partitioning of the fractions (F₁F₀ ATPase: 0.4 μm²/s and 0.0005 μm²/s; COX: 0.3 μm²/s and 0.007 μm²/s). The mobility patterns specific for the membranes of this organelle are unambiguously distinguishable from those of the plasma membrane or artificial lipid environments: The parameters of mitochondrial proteins indicate a distinct set of factors responsible for their diffusion characteristics.     

Interleukin-2-dependent regulation of Na/K pump in human lymphocytes

The present study provides the first evidence that the abundance of catalytic alpha1-subunit of Na,K-ATPase increases in the course of T cell blast transformation. Immunodepressant cyclosporin A at anti-proliferative doses diminished the induction of alpha1 protein in activated lymphocytes. Furthermore, in competent T cells, IL-2 increases both the transport activity of Na/K pump and the content of Na,K-ATPase alpha1 protein in a time-dependent manner. A correlation was found between the long-term elevation in ouabain-sensitive Rb influxes and the increase in alpha1 protein content in late activated T cells. These results suggest that (1) the increased expression of Na,K-ATPase proteins underlie the cell cycle-dependent upregulation of ion pump during T cell transformation, and (2) IL-2 is involved in the regulated expression of Na,K-ATPase in human lymphocytes.     

An unusual new species of the genus Brachypalpus Macquart (Diptera: Syrphidae) from Eastern Asia

Brachypalpus (Brachypalpus) longifacies sp. nov. is described and illustrated from Eastern Asia (Russian Far East and Japan). It differs from other species of the nominative subgenus by several unusual characters, i.e. face in profile weakly convex dorsally and concave ventrally, antennae very elongated, and abdomen with reddish transversal maculae on 2nd tergum (male) or 2nd and 3rd terga (female). A key is given for known species of the subgenus Brachypalpus.LSID: urn:lsid:zoobank.org:pub:634CB6E2-B2C1-40EC-8811-BF3DD4BDE69A     

Efficient GA3-assisted plant regeneration from cell suspensions of three grape genotypes via somatic embryogenesis

Petioles from in vitro grown plants of interspecific grapevine hybrids cvs `Bianca', `Podarok Magaracha' and `Intervitis Magaracha' were cultured on solid NN medium supplemented with 2,4-D and BA at various concentrations. The callus developed was cultured in liquid NN medium supplemented with 0.5 mg l<sup>–1</sup> BA to induce formation of somatic embryos. Somatic embryos of globular and heart-stage developed in suspensions of `Podarok Magaracha' and `Intervitis Magaracha'. In contrast, `Bianca' did not undergo embryogenesis beyond globular stage. This made it necessary to perform subculture of the suspensions to HTE liquid medium supplemented with 0.2 mg l^–1 BA for the development of globular embryos into heart stage. Heart-stage embryos developed into torpedo-stage after subculturing suspensions of all three cultivars to liquid HTE medium supplemented with 0.1 mg l^–1 IAA and 30 mg l^–1 sodium hummate. Torpedo-stage embryo suspensions were subcultured in liquid HTE medium supplemented with 0.5 mg l^–1 BA, 0.5 mg l^–1 GA₃ and 0.5 mg l^–1 GA₃ + 0.2 mg l^–1 BA. After 12 days of incubation, plantlets were cultured on solid M2MS medium: without growth regulators and with 0.5 mg l^–1 BA. Plantlets that developed in liquid HTE media with 0.5 mg l^–1 GA₃ or 0.5 mg l^–1 GA₃ + 0.2 mg l^–1 BA produced 82–90% shoots on solid M2MS medium with 0.5 mg l^–1 BA after 50 days of culture.     

Self-organization effects induced by ion-conformational interaction in biomembrane channels

It is shown that phenomena of molecular self-organization can take place in biomembrane channels. A strong interaction between charged groups of channel-forming protein and ion flux passing through the channel causes bistable or steady limit cycle regimes. These regimes are possible only far from the equilibrium state when the ion flux exceeds a certain threshold value. A number of such synergetic models is reviewed. Each time, only the simplest (monostable) regime takes place near the zero value of the ion flux. Some experimental data may be explained by this approach.     

Emergence of the Mitochondrial Reticulum from Fission and Fusion Dynamics

Mitochondria form a dynamic tubular reticulum within eukaryotic cells. Currently, quantitative understanding of its morphological characteristics is largely absent, despite major progress in deciphering the molecular fission and fusion machineries shaping its structure. Here we address the principles of formation and the large-scale organization of the cell-wide network of mitochondria. On the basis of experimentally determined structural features we establish the tip-to-tip and tip-to-side fission and fusion events as dominant reactions in the motility of this organelle. Subsequently, we introduce a graph-based model of the chondriome able to encompass its inherent variability in a single framework. Using both mean-field deterministic and explicit stochastic mathematical methods we establish a relationship between the chondriome structural network characteristics and underlying kinetic rate parameters. The computational analysis indicates that mitochondrial networks exhibit a percolation threshold. Intrinsic morphological instability of the mitochondrial reticulum resulting from its vicinity to the percolation transition is proposed as a novel mechanism that can be utilized by cells for optimizing their functional competence via dynamic remodeling of the chondriome. The detailed size distribution of the network components predicted by the dynamic graph representation introduces a relationship between chondriome characteristics and cell function. It forms a basis for understanding the architecture of mitochondria as a cell-wide but inhomogeneous organelle. Analysis of the reticulum adaptive configuration offers a direct clarification for its impact on numerous physiological processes strongly dependent on mitochondrial dynamics and organization, such as efficiency of cellular metabolism, tissue differentiation and aging.     

Observations on the prenatal development of human lymphatic vessels with focus on basic structural elements of lymph flow

BACKGROUND: The prenatal development of human lymphatic systems has not attracted enough attention by lymphatic researchers in the past. Yet clearly these critical, early events determine the fate and function of the human lymphatic system. METHODS AND RESULTS: The main focus of these studies was to investigate the embryonic development of human lymphangions including lymphatic valves and muscle cells, to better understand the prenatal formation of basic structural elements of lymph flow. This review in most of its parts is a short summary of the findings. It provides important information necessary for understanding the development and functioning of the human lymphatic system. CONCLUSIONS: The structural basis of the active lymph transport system--the lymphatic muscle cells and lymphatic valves--which is absolutely necessary for all functions of lymphatic system, is already formed during the first half of the prenatal development in humans. During the second half of this development maturation of this system is already underway. The enlargement of lymphatic muscle cells together with increases in their quantity leads to formation of the multi-layered lymphatic vessel wall, able to develop contractions strong enough to propel lymph downstream of the lymphatic channels against gravity in bipedal humans. The development of the competent valves in lymphatic vessels occurs at the same time creating the ground for effective net, unidirectional lymph flow. The data summarized here represents some of the first systematic studies of the prenatal development of lymphatic muscle cells and valves in humans.