Golgi apparatus and golgi zone

The author of this paper has attempted to clarify some problems concerning the nomenclature of Golgi apparatus and Golgi zone. The actual aim of this paper is to summarize — while using the more safe nomenclature—the existing knowledge about the functional relations between nucleus and cytoplasm arising from the study of the juxtanuclear zone by electron microscopy. Some observations lead to the assumption that the juxtanuclear zone is the place where cell components are formed or transformed. Considering its temporary character in proliferating cells and taking into account the connections with endoplasmic reticulum and the presence of pores, the nuclear membrane remains apparently a barrier restraining the spontaneous movement of substances and of cell components respectively between cytoplasm and karyoplasm that can be seen e.g. in the grouping of cytoplasmic formations in the juxtanuclear zone. In plant cells, within the zone mentioned agglomerations of different cell formations have been found, either the Golgi apparatus or mitochondria, secretion granules, lipid inclusions, vacuoles or plastids. Such a gathering of cytoplasmic material has been observed especially in young embryonic cells or in cells with retarded or stopped metabolism. The older and/or intensively active cells would then absolve an expansion of the cytoplasmic material into the whole cell. Similar formative mechanisms, now available for study during some ontogenic phases or at definite functional states only, could be effective even in the course of phylogenesis. From this point of view some of the formations described could be regarded as a kind of atavisms.     

Alterations in marginal zone macrophages and marginal zone B cells in old mice

Marginal zones (MZs) are architecturally organized for clearance of and rapid response against blood-borne Ags entering the spleen. MZ macrophages (MZMs) and MZ B cells are particularly important in host defense against T-independent pathogens and may be crucial for the prevention of diseases, such as streptococcal pneumonia, that are devastating in older patients. Our objective was to determine whether there are changes in the cellular components of the MZ between old and young mice. Using immunocytochemistry and a blinded scoring system, we observed gross architectural changes in the MZs of old mice, including reduction in the abundance of MZMs surrounding the MZ sinus as well as disruptions in positioning of mucosal addressin cell adhesion molecule 1 (MAdCAM-1)(+) sinus lining cells and metallophilic macrophages. Loss of frequency of MZMs was corroborated by flow cytometry. A majority of old mice also showed reduced frequency of MZ B cells, which correlated with decreased abundance of MZM in individual old mice. The spleens of old mice showed less deposition of intravenously injected dextran particles within the MZ, likely because of the decreased frequency in MZMs, because SIGN-R1 expression was not reduced on MZM from old mice. The phagocytic ability of individual MZMs was examined using Staphylococcus aureus bioparticles, and no differences in phagocytosis were found between macrophages from young or old spleens. In summary, an anatomical breakdown of the MZ occurs in advanced age, and a reduction in frequency of MZM may affect the ability of the MZM compartment to clear blood-borne Ags and mount proper T-independent immune responses.     

The ciliary transitional zone and nephrocystins

Loss of cilia and ciliary protein causes various abnormalities (called ciliopathy), including situs inversus, renal cystic diseases, polydactyly and dysgenesis of the nervous system. Renal cystic diseases are the most frequently observed symptoms in ciliopathies. Cilia are microtubule-based organelles with the following regions: a ciliary tip, shaft, transitional zone and basal body/mother centriole. Joubert syndrome (JBTS), Meckel Gruber syndrome (MKS) and Nephronophthisis (NPHP) are overlapping syndromes. Recent studies show that JBST and MKS responsible gene products are localized in the transitional zone of the cilia, where they function as a diffusion barrier, and control protein sorting and ciliary membrane composition. Nephrocystins are gene products of NPHP responsible genes, and at least 11 genes have been identified. Although some nephrocystins interact with JBST and MKS proteins, proteomic analysis suggests that they do not form a single complex. Localization analysis reveals that nephrocystins can be divided into two groups. Group I nephrocystins are localized in the transitional zone, whereas group II nephrocystins are localized in the Inv compartment. Homologs of group I nephrocystins, but not group II nephrocystins, have been reported in C. reinhardtii and C. elegans. In this review, we summarize the structure of the ciliary base of C. reinhardtii, C. elegans and mammalian primary cilia, and discuss function of nephrocystins. We also propose a new classification of nephrocystins.     

Marginal zone B cells regulate antigen capture by marginal zone macrophages

The marginal zone (MZ) of the mouse spleen contains macrophages that express receptors that trap pathogens, including the scavenger receptor macrophage receptor with a collagenous structure and the C-type lectin specific intracellular adhesion molecule-grabbing nonintegrin receptor 1 (SIGN-R1). We previously reported that expression of SIGN-R1 was decreased in CD19-deficient mice. In this study, we demonstrate that SIGN-R1 is expressed on a subset of macrophage receptor with a collagenous structure (MARCO)(+) macrophages. This subset is diminished when MZ B cells are absent due to either genetic developmental defects or following transient migration of B cells out of the MZ. When B cells return to the MZ, there is a delay in recovery of SIGN-R1-expressing macrophages. During this period, capture of Ficoll, which for the macrophages requires SIGN-R1, remains defective not only by the macrophages, but also by the B cells. Thus, MZ B cells regulate expression of molecules on macrophages that are important for trapping Ag, which, in turn, is required for Ag capture by the B cells.     

Filtration profile in isolated zone 1 and zone 3 dog lungs at constant high alveolar pressure

We measured the rate of liquid filtration in isolated dog lung lobes inflated to a constant alveolar pressure of 25 cmH2O and with all open vessels filled with plasma. We measured lung weight gain at vascular pressures ranging from 5 to 40 cmH2O relative to pleural pressure. We confirmed that under zone 1 conditions the "arterial" and "venous" extra-alveolar segments have essentially the same filtration characteristics. Using the combined extra-alveolar vascular system, we determined when recruitment of filtration surface area occurred as we increased vascular pressure from 0 to 40 cmH2O. Based on an abrupt increase in filtration rate as vascular pressure approached the zone 1/3 boundary, we infer that a sudden recruitment of exchange surface area occurred at that point. Based on the slopes of the zone 1 and zone 3 filtration profiles, we conclude that extra-alveolar vascular segments contribute approximately 25% of total to filtration in the lung under zone 3 conditions, although the exact vessels filtering under zone 1 conditions have yet to be determined. Our analysis of the data supports the concept that there is a difference in the perimicrovascular pressure around alveolar and extra-alveolar vessels, which in part may account for the apparent high filtration fraction apportioned to extra-alveolar vessels.     

Optimal promising zone designs

Clinical trials with adaptive sample size reassessment based on an unblinded analysis of interim results are perhaps the most popular class of adaptive designs (see Elsäßer et al., 2007). Such trials are typically designed by prespecifying a zone for the interim test statistic, termed the promising zone, along with a decision rule for increasing the sample size within that zone. Mehta and Pocock (2011) provided some examples of promising zone designs and discussed several procedures for controlling their type‐1 error. They did not, however, address how to choose the promising zone or the corresponding sample size reassessment rule, and proposed instead that the operating characteristics of alternative promising zone designs could be compared by simulation. Jennison and Turnbull (2015) developed an approach based on maximizing expected utility whereby one could evaluate alternative promising zone designs relative to a gold‐standard optimal design. In this paper, we show how, by eliciting a few preferences from the trial sponsor, one can construct promising zone designs that are both intuitive and achieve the Jennison and Turnbull (2015) gold‐standard for optimality.     

The presynaptic active zone

Neurotransmitters are released by synaptic vesicle exocytosis at the active zone of a presynaptic nerve terminal. In this review, I discuss the molecular composition and function of the active zone. Active zones are composed of an evolutionarily conserved protein complex containing as core constituents RIM, Munc13, RIM-BP, α-liprin, and ELKS proteins. This complex docks and primes synaptic vesicles for exocytosis, recruits Ca(2+) channels to the site of exocytosis, and positions the active zone exactly opposite to postsynaptic specializations via transsynaptic cell-adhesion molecules. Moreover, this complex mediates short- and long-term plasticity in response to bursts of action potentials, thus critically contributing to the computational power of a synapse.     

Intertidal zone of Svalbard

The meiobenthos was sampled at 119 localities along 1,500 km of Svalbard shores in the summers 1988–1993. The principal taxa were determined from 5-cm-long sediment cores collected during low tide on soft sediment shores. The density ranged from 0 to > 10,000 ind/10 cm². Nematoda was the most common and abundant taxon. Nematoda and Turbellaria, along with Oligochaeta and Harpacticoida, were typical and the most frequent set of taxa. The occurrence of meiofaunal taxa was weakly correlated with geographical area; the local habitat characteristics were decisive. The most abundant meiobenthos, with mean abundance >900 ind/10 cm² and the biomass about 0.34 g dry wt per 1 m2, was found on the western coast of South Spitsbergen.     

Intertidal zone of svalbard

Summary In summer 1985–1991, the intertidal zone of the Svalbard archipelago was sampled in 242 localities. Thirty seven laxa of macrofauna and 22 of macrophytes were considered as littoral zone inhabitants. Four major littoral assemblages are described: Fucus-Balanus, Gammarus, Onisimus and Oligochaeta communities. More than 80% of the investigated coast is occupied by the Oligochaeta assemblage with mean biomass values less than 1 kJ/m². The richest benthos was found at Fucus-Balanus sites (8% of the coast line) with biomass values exceeding 2000 kJ/m². The southern tip of Spitsbergen is part of a major zoogeographical border in the littoral fauna distribution. Subarctic species like barnacles, periwinkles and Gammarus oceanieus predominate on the western coast whereas, on the Arctic East coast barren beaches, G. setosus predomination was found.     

Genetical and ecological differentiation across a hybrid zone

ABSTRACT.

• 1 There is a narrow hybrid zone between two chromosomal races of the grasshopper Podisma pedestris (L.) in the French Alps.
• 2 There are no gross differences in habitat across the zone, and a multivariate analysis of the vegetation composition detected no significant transition either.
• 3 The hatch and development rates of Podisma in hybrid populations were lower than those found in matched habitat types outside the zone.
• 4 The simplest explanation for the persistence of the parapatric distribution of the two races is that hybrid disadvantage is maintaining a tension zone between them.

     

Climate change and the northern Russian treeline zone

The Russian treeline is a dynamic ecotone typified by steep gradients in summer temperature and regionally variable gradients in albedo and heat flux. The location of the treeline is largely controlled by summer temperatures and growing season length. Temperatures have responded strongly to twentieth-century global warming and will display a magnified response to future warming. Dendroecological studies indicate enhanced conifer recruitment during the twentieth century. However, conifers have not yet recolonized many areas where trees were present during the Medieval Warm period (ca AD 800-1,300) or the Holocene Thermal Maximum (HTM; ca 10,000-3,000 years ago). Reconstruction of tree distributions during the HTM suggests that the future position of the treeline due to global warming may approximate its former Holocene maximum position. An increased dominance of evergreen tree species in the northern Siberian forests may be an important difference between past and future conditions. Based on the slow rates of treeline expansion observed during the twentieth century, the presence of steep climatic gradients associated with the current Arctic coastline and the prevalence of organic soils, it is possible that rates of treeline expansion will be regionally variable and transient forest communities with species abundances different from today's may develop.     

Capillary zone electrophoresis of insulin and growth hormone

The separation power of capillary zone electrophoresis was examined using highly purified and well-characterized biosynthetic human insulin, growth hormone, their derivatives, and related proteins. Mixtures of proteins were chosen to illustrate practical applications of this technique. Proteins differing slightly in structure, but equivalent in net charge, were not completely separated. Degradation of insulin by dilute acid treatment was followed by capillary zone electrophoresis, native polyacrylamide gel electrophoresis, and reversed-phase liquid chromatography. Excellent correlation was observed between these techniques. Simple equipment requirements and analysis times on the order of 10 min make capillary zone electrophoresis attractive for analytical protein separations.     

Marginal zone macrophages and immune responses against viruses

The effective establishment of antiviral protection requires a coordinated interplay between the innate and adaptive immune system. Using osteopetrotic (op(-/-)) mice, this study investigated the influence of marginal zone macrophages in controlling and initiating a protective immune response against a cytopathic vs a non- or low-cytopathic virus. Despite the generation of potent adaptive immune responses, antiviral protection against cytopathic vesicular stomatitis virus critically depended on the presence of marginal zone macrophages. Infection with low doses (100 PFU) of non- or low-cytopathic lymphocytic choriomeningitis virus was rarely cleared and usually resulted in a carrier state in the majority of mice. This shows that the early innate immune system provides an important preparatory phase to the adaptive immune system and is particularly important for antiviral protection.     

Zone 2 and zone 3 pulmonary blood flow

In the West model of zonal distribution of pulmonary blood flow, increases in flow down zone 2 are attributed to an increase in driving pressure and a decrease in resistance resulting from recruitment and distension. The increase in flow down zone 3 is attributed to a decrease in resistance only. Recent studies indicate that, besides the pressure required to maintain flow through a vessel, there is an added pressure cost that must be overcome in order to initiate flow. These additional pressure costs are designated critical pressures (Pcrit). Because Pcrit exceed alveolar pressure, the distinction between zones in the West model becomes less secure, and the explanation for the increase in flow even in West zone 3 requires reexamination. We used two methods to test the hypothesis that the Pcrit is the pertinent backpressure to flow even in zone 3, when the pulmonary venous pressure (Ppv) exceeds alveolar pressure (PA) but is less than Pcrit in the isolated canine left caudal lobe. First, PA was maintained at 5 cmH2O, and pressure flow (P-Q) characteristics were obtained in zone 2 and zone 3. Next, with PA still at 5 cmH2O, we maintained a constant flow and measured the change in pulmonary arterial pressure as Ppv was varied. Both techniques indicated that the pertinent backpressure to flow was the greater of either Pcrit or Ppv and that PA was never the pertinent backpressure to flow. Also, our results indicate no significant change in the geometry of the flow channels between zone 2 and zone 3. These findings refine the zonal model of the pulmonary circulation.