Nitric Oxide in the Control of the in vitro Proliferation and Differentiation of Human Hematopoietic Stem and Progenitor Cells

Hematopoietic stem and progenitor cell (HSPC) transplantation is the best-studied cellular therapy and successful in vitro control of HSPCs has wide clinical implications. Nitric oxide (NO) is a central signaling molecule in vivo and has been implicated in HSPC mobilization to the blood stream in mice. The influence of NO on HSPC behavior in vitro is, however, largely obscure due to the variety of employed cell types, NO administration systems, and used concentration ranges in the literature. Additionally, most studies are based on murine cells, which do not necessarily mimic human HSPC behavior. Thus, the aim of the present study was the systematic, concentration-dependent evaluation of NO-mediated effects on human HSPC behavior in vitro. By culture in the presence of the long-term NO donor diethylenetriamine/nitric oxide adduct (DETA/NO) in a nontoxic concentration window, a biphasic role of NO in the regulation of HSPC behavior was identified: Low DETA/NO concentrations activated classical NO signaling, identified via increased intracellular cyclic guanosine monophosphate (cGMP) levels and proteinkinases G (PKG)-dependent vasodilator-stimulated phosphoprotein (VASP) phosphorylation and mediated a pro-proliferative response of HSPCs. In contrast, elevated NO concentrations slowed cell proliferation and induced HSPC differentiation. At high concentrations, s-nitrosylation levels were elevated, and myeloid differentiation was increased at the expense of lymphoid progenitors. Together, these findings hint at a central role of NO in regulating human HSPC behavior and stress the importance and the potential of the use of adequate NO concentrations for in vitro cultures of HSPCs, with possible implications for clinical application of in vitro expanded or differentiated HSPCs for cellular therapies.

Iron Nanoparticle Composite Hydrogels for Studying Effects of Iron Ion Release on Red Blood Cell In Vitro Production

Growing numbers of complex surgical interventions increase the need for blood transfusions, which cannot be fulfilled by the number of donors. Therefore, the interest in producing erythrocytes from their precursors-the hematopoietic stem and progenitor cells (HSPCs)-in laboratories is rising. To enable this, in vitro systems are needed, which allow analysis of the effects of essential factors such as iron on erythroid development. For this purpose, iron ion-releasing systems based on poly(ethylene glycol) (PEG)-iron nanocomposites are developed to assess if gradual iron release improves iron bioavailability during in vitro erythroid differentiation. The nanocomposites are synthesized using surfactant-free pulsed laser ablation of iron directly in the PEG solution. The iron concentrations released from the material are sufficient to influence in vitro erythropoiesis. In this way, the production of erythroid cells cultured on flat PEG-iron nanocomposite hydrogel pads can be enhanced. In contrast, erythroid differentiation is not enhanced in the biomimetic macroporous 3D composite scaffolds, possibly because of local iron overload within the pores of the system. In conclusion, the developed iron nanoparticle-PEG composite hydrogel allows constant iron ion release and thus paves the way (i) to understand the role of iron during erythropoiesis and (ii) toward the development of biomaterials with a controlled iron release for directing erythropoiesis in culture.

Magnetic Macroporous Hydrogels as a Novel Approach for Perfused Stem Cell Culture in 3D Scaffolds via Contactless Motion Control

There is an urgent need for 3D cell culture systems that avoid the oversimplifications and artifacts of conventional culture in 2D. However, 3D culture within the cavities of porous biomaterials or large 3D structures harboring high cell numbers is limited by the needs to nurture cells and to remove growth-limiting metabolites. To overcome the diffusion-limited transport of such soluble factors in 3D culture, mixing can be improved by pumping, stirring or shaking, but this in turn can lead to other problems. Using pumps typically requires custom-made accessories that are not compatible with conventional cell culture disposables, thus interfering with cell production processes. Stirring or shaking allows little control over movement of scaffolds in media. To overcome these limitations, magnetic, macroporous hydrogels that can be moved or positioned within media in conventional cell culture tubes in a contactless manner are presented. The cytocompatibility of the developed biomaterial and the applied magnetic fields are verified for human hematopoietic stem and progenitor cells (HSPCs). The potential of this technique for perfusing 3D cultures is demonstrated in a proof-of-principle study that shows that controlled contactless movement of cell-laden magnetic hydrogels in culture media can mimic the natural influence of differently perfused environments on HSPCs.

Drinking water biofilms on copper and stainless steel exhibit specific molecular responses towards different disinfection regimes at waterworks

Biofilms growing on copper and stainless steel substrata in natural drinking water were investigated. A modular pilot-scale distribution facility was installed at four waterworks using different raw waters and disinfection regimes. Three-month-old biofilms were analysed using molecular biology and microscopy methods. High total cell numbers, low counts of actively respiring cells and low numbers of cultivable bacteria indicated the high abundance of viable but not cultivable bacteria in the biofilms. The expression of the recA SOS responsive gene was detected and underlined the presence of transcriptionally active bacteria within the biofilms. This effect was most evident after UV disinfection, UV oxidation and UV disinfection with increased turbidity at waterworks compared to chemically treated and non-disinfected systems. Furthermore, live/dead staining techniques and environmental scanning electron microscopy imaging revealed the presence of living and intact bacteria in biofilms on copper substrata. Cluster analyses of DGGE profiles demonstrated differences in the composition of biofilms on copper and steel materials.

Cytosolic heat-stress proteins Hsp17.7 class I and Hsp17.3 class II of tomato act as molecular chaperones in vivo

Small heat-stress proteins (sHsps) are the most abundant stress-induced proteins with up to 20 different members in higher plants. In the cytoplasm, two different classes can be distinguished. Two cDNA clones from tomato Lycopersicon peruvianum (L.) Mill., each coding for one of the cytoplasmic sHsp subfamilies, were analyzed with respect to their transcript and protein expression, genome organization and chaperone activity. Neither type was present under control conditions but both appeared upon heat stress and in mature fruits. Expression of the class II transcript was found to be induced at slightly lower temperatures than the class I transcript. Protein analysis using class-specific antibodies revealed an identical expression pattern of both corresponding proteins. Transient expression in an Arabidopsis thaliana (L.) Heynh. cell culture showed that, despite the difference in their amino acid sequence, both classes are functionally active as chaperones in vivo, as shown by their ability to prevent thermal inactivation of firefly luciferase in a cellular environment.

Cellular motility in vitro as revealed by scanning acoustic microscopy depends on cell-cell contacts

A new method is described for observing and quantifying an aspect of contact inhibition of cell movement that is sometimes called "contact paralysis". Based on the scanning acoustic microscope (SAM), the method can detect changes in the mechanical properties of cells, as well as changes in their motility and may therefore be more sensitive to some dynamic changes than methods based on optical microscopy. With this method intracellular motility of normal and transformed cells of epithelial and fibroblastic origin was investigated. By subtraction of SAM images patterns of motility, domains were detected that changed in a characteristic way among various cell lines. Wave-like and nucleating domains could be distinguished; they were also used for the quantification of motility. Like migration intracellular motility is influenced by cell-cell contacts. In zones where a cell touches its neighbours motility domains change or disappear depending on the cell type. In immortalized epithelial cells (XTH-2 cells) large quiescent zones developed in the region where contact with neighbouring cells was established, whereas in fibroblastic (3T3) cells motility was reduced less and did not change in domain pattern. Epithelial and fibroblastic cells were less motile when in contact with other cells or in confluent cultures than when solitary, i.e. their motility was contact inhibited. Transformed (SV40 3T3) cells, however, did not reduce their motility when in contact to or enclosed by other cells. The molecular basis for motility domains remains to be investigated.

Development of branchiomeric and lateral line nerves in the axolotl

The differentiation of neural crest and ectodermal placodes was examined in the axolotl in order to clarify the contribution of these tissues to the formation of the sensory ganglia of the branchiomeric and lateral line cranial nerves in salamanders. The most rostral branchiomeric nerves, the profundal and trigeminal nerves, appear to arise solely from an ectodermal placode and from neural crest, respectively. The sensory ganglia of the more caudal branchiomeric nerves--the facial, glossopharyngeal, and vagal nerves--are formed by a medial component that differentiates from the dorsomedial surface of migrating bands of neural crest associated with each of the developing branchial arches and with one or more lateral components that arise from epibranchial placodes located immediately dorsal and caudal to each pharyngeal pouch. Neuroblasts destined to form these sensory ganglia begin to differentiate from the epibranchial placodes as early as stage 26, whereas neural crest-derived neuroblasts can be recognized by stage 30. Centrally directed neurites of both groups of neuroblasts enter the medulla by stage 34, and their peripherally directed neurites form recognizable rami by stage 35. Five cranial lateral line nerves, in addition to the octaval nerve, can be recognized in axolotls. Each of these nerves arises from a separate dorsolateral placode that initially gives rise to the neuroblasts of a sensory ganglion whose peripheral neurites innervate sensory receptors subsequently formed from each placode. The time course of the differentiation of these nerves and receptors is comparable to that of the branchiomeric nerves. The possible roles of rhombomeres and their associated regulatory genes and pharyngeal pouches in the induction and specification of neural crest and ectodermal placodes are explored.

Electroreceptors and mechanosensory lateral line organs arise from single placodes in axolotls

The lateral line system in salamanders consists of mechanoreceptive neuromasts and pit organs, distributed in lines on the head and trunk, and electroreceptive ampullary organs located adjacent to the cephalic lines of mechanoreceptors. Although numerous studies have documented that neuromast and pit organs and the cranial nerves that innervate these receptors arise from a dorsolateral series of placodes, there is no agreement concerning the number of these placodes, the specific groups of receptors that arise from them, or the embryonic origin of ampullary organs. A developmental model was recently proposed (Northcutt et al., 1994) in which all these placodes, except for the most posterior one, elongate to form sensory ridges whose central zones initially form neuromast and pit organ primordia and whose lateral zones subsequently form ampullary primordia. To test this model, individual placodes were unilaterally extirpated, or placodes from pigmented wild-type axolotl embryos were homotopically or heterotopically transplanted into albino hosts. Extirpation resulted in the loss of all three receptor classes, and both homotopic and heterotopic transplants produced pigmented receptors of all three classes in albino hosts. The receptors in the heterotopic transplants still formed lines which occasionally retained their normal orientation despite differentiating in an ectopic environment. These experiments demonstrated that, as previously postulated, specific lines of neuromasts and pit organs do arise from each placode, and ampullary organs also arise from many of the same placodes. The distribution of receptors that develop following incomplete extirpation or heterotopic transplantation also indicates that each placode is patterned regarding receptor classes and orientation prior to sensory ridge formation.

Retinal specificity in eye fragments: investigations on the retinotectal projections of different quarter-eyes in Xenopus laevis

According to Sperry's chemoaffinity hypothesis, the projection of a small eye fragment with a reduced amount of optic fibres should be restricted to that position in the optic tectum corresponding to its own specificity. However, previous investigations on different types of quarter-eyes in Xenopus laevis have revealed that their retinal projection was always restricted to the rostral part of the tectum, no matter what the origin of the remaining retinal quadrant. To get an indication of the state of specificity in such eye fragments, we investigated by electrophysiological and histological methods several features of the retinal projections of tempo-roventral (TV), naso-ventral (NV) and ventral (V) quarter-eyes which referred to their positional identity. Irrespective of their different origins, the projections were always located in the rostral part of the tectum, the size of the innervated tectal area depending for all fragment types on the size of the quarter-eyes, i.e. number of optic fibres. However, quantitative analyses revealed that with increasing eye size the various fragments expand their projections preferentially into those tectal areas that match their original specificity: TV projection is more concentrated in the rostral tectum, NV eyes expand their projections mainly to the caudal tectum, and V eyes enlarge their projections equally into the medial and caudal tectum. In addition, fibre-tracing experiments with cobaltic lysine showed that, according to the different origins of the quarter-eyes, retinal fibres follow the appropriate branch of the optic tract selectively: fibres of NV and V eyes pass mainly through the medial tract, and most fibres of TV eyes innervate the rostral tectum directly from a central position between the two side branches. All these findings suggest that the different types of quarter-eyes retain their original positional identity. Thus, their rostrally located retinotectal projections are not in register with their retinal specificity. We conclude that in X. laevis local positional markers in the tectum, if present at all, do not influence the development of the retinotectal projection. Instead we suggest a concept of self-sorting of the optic fibres, which can account for the partial innervation of the rostral tectum in different types of quarter-eyes.

Hygrotactic orientation of frogs in the laboratory

Abstract

The ability of green frogs (Rana esculenta) to find water in the laboratory was studied in complete darkness and in daylight. Plastic boxes with small holes in their lids were used as traps. Frogs preferred a water-containing dish to a dry dish when the humidity of the air was low (47-51%) They did not use visual cues in the localization of the water-containing dish. When the humidity of the air was higher (65-68%) preference for water could not be observed. Bilateral transection of the olfactory nerves abolished hygrotactic orientation.

Amplification and differential expression of members of the erbB-gene family in human glioblastoma

The objective of the present study was to determine the frequency of amplifications of three different members of the erbB gene family in human glioblastoma multiforme (GBM). We investigated 47 glial tumors (37 GBM WHO grade IV, 5 anaplastic astrocytomas WHO III and 5 astrocytomas WHO II) by Southern and Western analysis, and immunocytochemistry. Gene amplification of erbB genes in human malignant gliomas was restricted to the EGF receptor (EGFR) gene, erbB-1. We found amplification of the EGFR gene in 49% (18/37) of GBM but not in the astrocytomas WHO II/III. The erbB-2 and erbB-3 genes showed no amplification in the tumor specimens investigated in this study. At the protein level we found overexpression of the EGF receptor in 86% (32/37) by Western analysis and in 92% (34/37) by immunocytochemistry. Expression of the ERBB2 protein was present in 54% (20/37) but immunoreactivity was much weaker than for EGF receptor and in most cases barely detectable by Western analysis and immunocytochemistry. The ERBB3 protein was not expressed in the glial tumors investigated in this study. Of the three erbB genes only gene amplification and overexpression of the EGF receptor seems to have an impact on tumor progression of human gliomas. Our data from immunohistochemistry indicate that ERBB2 expression in GBM is closely correlated with EGF receptor levels and is therefore not useful as an independent prognostic parameter.

Central projections and motor nuclei of the facial, glossopharyngeal, and vagus nerves in the mormyrid fish Gnathonemus petersii

Most of the information about the anatomy of the fish's cranial nerves was collected in the first two decades of this century. Experimental analysis of the VIIth, IXth, and Xth cranial nerves by modern tract tracing techniques started about 20 years ago. Several species have been investigated to date, including one species of Agnatha (Myxinoidea), two species of elasmobranchs, and species of some orders of Teleostei like Cyprinidae, Siluriformes, Perciformes, and Gadidae. The sensory and motor nuclei of the VIIth, IXth, and Xth cranial nerves of Gnathonemus petersii were studied by anterograde and retrograde axoplasmatic transport of horseradish peroxidase and cobaltous lysine complex. The sensory nuclei form a continuous column of cells in the brain stem extending caudal to the obex. The rostral one-fourth of this column is occupied by the overlapping terminals of the VIIth and IXth nerves. The vagus nerve has 5 roots. The first 4 of these innervate the gills and the fifth supplies viscera. Afferents from the gills terminate ipsilaterally rostral to the obex in topographic order and their terminal fields overlap. Viscerosensory fibers terminate ipsilaterally in the obex region and bilaterally in the commissural nucleus of Cajal. The facial motor nucleus is located rostral to the sensory nucleus. Facial motoneurons have pear-shaped and multipolar perikarya. Their axons form a rostrally directed knee before leaving the brain. The motoneurons of the IXth and Xth nerves have a common cell column. The vagal motoneurons form a periventricular, a medial, and an intermediate cell group rostral to the obex. In the obex region and also caudal to it, a lateral and a caudal group can be distinguished. Vagal motoneurons show a topographic arrangement that is similar to that of the sensory vagal projections. The majority of motoneurons have pear-shaped perikary and ventrolaterally oriented dendrites. In the caudal nucleus the dendrites extend dorsally and overlap the terminals of sensory fibers. The axons form a dorsolaterally directed arch before joining the sensory roots. Since G. petersii uses its electrosensory system primarily for detection of food, its gustatory system is less developed than in other fishes, which possess a large number of taste buds.

A new method for aligning histological serial sections for three-dimensional reconstruction

A new method for aligning histological serial sections for three-dimensional reconstruction by computer is introduced. This method is particularly suited for embedding structures in celloidine or paraplast. Prior to sectioning, at least three reference markers are affixed to the preparation in a direction perpendicular to the section plane, for easy identification on the finished sections. An algorithm translates and rotates the serial sections until all the reference markers are congruent. The main advantage of this method, however, is its capability to eliminate deformations caused by compression or stretching during sectioning by the determination of correction factors.

Density-related changes of potassium (86Rb) uptake by amphibian endothelial cells

Potassium influx has been investigated in XTH-2 cells, a line derived from tadpole heart endothelia. In this line, the density at which the cultures become confluent is clearly separated from the density at which growth arrest takes place. Density-related changes in K+ influx were monitored by determining the uptake of 86Rb into well adhering cells kept in culture medium. The main observations were 1) 86Rb uptake is highest in single cells, and on confluency it reaches a low level, which is kept constant at higher cell density regardless of whether the cultures are stationary or still in logarithmic growth phase; 2) the relative amount of 86Rb taken up via the Na+ -K+ -2Cl- cotransport pathway and via the Na+/K+ pump changes from low cell density to confluent cultures; 86Rb uptake of single cells is nearly insensitive to ouabain, a maximum of ouabain sensitivity is reached around confluency, whereas piretanide-sensitive 86Rb uptake is highest in single cells and seems to reach a minimum at the onset of confluency; 3) the variations in Na+/K+ pumping rate reflect neither differences in the amount of enzyme present nor changes in enzyme repartition between apical and basolateral plasma membranes; they seem to result from either "masking" or "unmasking" of the enzyme; 4) no alterations in K+ uptake occur that would be characteristic of the "stationary growth phase." The only changes that seem to be related to arrest of proliferation are concerned with the Na+/K+-ATPase, which achieves an extraordinary susceptibility to stimulation by monensin and exhibits an increase in PNPPase activity.

The retinotectal projection of quarter eyes in Xenopus laevis

Following extirpation of three quarters of the eye anlage of Xenopus laevis in stage 33/34, the remaining quadrants developed into small eyes of normal shape. Irrespective of the different portions of the eye anlage the quarter eyes originated from, the retinotectal projection was always confined to the rostrolateral part of the tectum, forming an orderly map, and its dimensions corresponded to the size of the contralateral eye. Therefore, it was suggested that during development both size and location of the projection are independent of the existence of tectal markers. Instead, they are determined by the number of ingrowing optic fibers and the direction of their growth from the rostral origin.

Expansion of the visual projection to the tectum of axolotls during metamorphosis

During artificially induced metamorphosis in axolotls, the indirect visual projection from the ipsilateral eye develops followed by the expansion of the contralateral direct projection to occupy most of the tectal surface. During expansion the ipsilateral input is temporarily lost indicating the functional interdependence of the two projections. Final stabilization of the projections and congruence of the ipsilateral and contralateral inputs is achieved a month after arrival on land.

Quantitative studies of the reactions to horizontal angular accelerations in axolotls. I. The head-turning reflexes of normal animals

1. Artifically metamorphosed axolotls were exposed to both brief (impulse) and long-lasting horizontal angular accelerations on a turn-table. The animals responded with a head-turning reaction. 2. The general course of the reaction to impulse acceleration was independent of stimulus intensity. The velocity of the head movement first increased to a maximum exponentially and then decreased in a negative exponential manner. Stimulus intensity had a linear relationship to the mean maximum velocity and mean total angle covered by head-turning. The average velocity-time curves at various stimulus intensities differed only by a velocity factor. 3. During long-lasting constant accelerations the velocity of the head-turning increased to a maximum velocity in a sigmoid time-course and then decreased, first to a constant velocity, and then further. Mean values of the maximum velocity were correlated linearly with the stimulus intensity. 4. It was concluded that the head-turning reflexes in axolotls do not agree with the accepted movements of the vertebrate cupula and therefore are not a simple ‘copy’ of the afferent input. It is also suggested that the reaction threshold differes from that for the labyrinthine input.

Quantitive studies of the reactions to horizontal angular accelerations in axolotls. II. head-turning reflexes in animals with a supernumerary pair of labyrinths

In axolotls (Ambystoma mexicanun) the labyrinths and the associated parts of the medulla were doubled artificially. In these so-called tandem-heads the vestibular afferent fibres from both labyrinths on one side united within the medulla to form common bundles. The head-turning reflexes following impulse acceleration and during long-lasting acceleration were measured quantitatively and compared with those for normal animals. The form and the time-course of the reactions were almost identical in both groups. Tandem-heads showed a linear relationship between stimulus intensity and reaction strength, parallel to that in normal animals but with a greater reaction for a given stimulus. Consequent to this shift in the relationship, there was a significant decrease in the reaction threshold. The removal of one horizontal semicircular canal in tandem-heads proved that both pairs of labyrinths were functionally connected with the brain. It was suggested that during ontogenesis there exists a kind of specificity in the connexion of vestibular fibres. From the parallel shift of the intensity functions it was concluded that the input from both pairs of labyrinths in tandem-heads is not simply accumulate but compared with a reference parameter, which is also double in tandem-heads.