Soft optoelectronic sensory foams with proprioception.

In a step toward soft robot proprioception, and therefore better control, this paper presents an internally illuminated elastomer foam that has been trained to detect its own deformation through machine learning techniques. Optical fibers transmitted light into the foam and simultaneously received diffuse waves from internal reflection. The diffuse reflected light was interpreted by machine learning techniques to predict whether the foam was twisted clockwise, twisted counterclockwise, bent up, or bent down. Machine learning techniques were also used to predict the magnitude of the deformation type. On new data points, the model predicted the type of deformation with 100% accuracy and the magnitude of the deformation with a mean absolute error of 0.06°. This capability may impart soft robots with more complete proprioception, enabling them to be reliably controlled and responsive to external stimuli.

Levels of free PABP are limited by newly polyadenylated mRNA in early Spisula embryogenesis.

The poly(A) tail of eukaryotic mRNAs regulates translation and RNA stability through an association with the poly(A)-binding protein (PABP). The role of PABP in selective polyadenylation/deadenylation and translational recruitment/repression of maternal mRNAs that occurs in early development is not fully understood. Here, we report studies including UV-crosslinking and immunoblotting assays to characterise PABP in the early developmental stages of the clam Spisula solidissima. A single, 70 kDa PABP, whose sequence is highly homologous to vertebrate, yeast and plant PABPs, is detected in oocytes. The levels of clam PABP are constant in early embryogenesis, although its ability to crosslink labelled poly(A) is 'masked' shortly after fertilisation and remains so until the larval stage. Full RNA-binding potential of PABP in embryo lysates was achieved by brief denaturation with guanidinium hydrochloride followed by dilution for binding and crosslinking or by controlled treatment of lysates with Ca(2+)-dependent micrococcal nuclease. Masking of PABP, which accompanies cytoplasmic polyadenylation in maturing oocytes and in in vitro activated oocyte lysates, is very likely due to an association with mRNAs that bear new PABP target binding sites and thus prevent protein binding to the labelled A-rich probe. Functional implications of these findings as well as the potential application of this unmasking method to other RNA-binding proteins is discussed.

Keratinolytic activity of Aspergillus fumigatus fresenius.

Aspergillus fumigatus can utilize chicken feather keratin as its sole carbon and nitrogen source. Because enzymatic conversion of native keratin into readily usable products is of economic interest, this fungus was studied for its capacity to produce and secrete keratin-hydrolyzing proteinases. Substantial keratin-azure hydrolyzing activity was present in the culture fluid of keratin-containing media. Considerably lower activity was present in cultures containing glucose and nitrate as the carbon and nitrogen sources, or keratin plus glucose and nitrate. Secretion of keratin-hydrolyzing activity in A. fumigatus was induced by keratin but repressed by low-molecular-weight carbon and nitrogen sources. The amount of keratinolytic enzyme present in the culture fluid was dependent on the initial pH of the culture medium. The crude enzyme also hydrolyzed native keratin and casein in vitro. Hydrolysis was optimal at pH 9 and 45 degrees C. The crude enzyme was remarkably thermostable. At 70 degrees C, it retained about 90% of its original activity for 1.5 h. The obtained results indicated that the A. fumigatus keratinolytic enzyme may be suitable for enzymatic improvement of feather meal.

Identification of vascular sphincters at the junction between alveolar capillaries and pulmonary venules of the mouse lung.

BACKGROUND: A peculiar feature of lung circulation in the lung is the pronounced variations in blood volume observed in alveolar capillaries that occur because of the changes in the conformation of the alveolar wall that are associated with the respiratory movements. This phenomenon has led to the postulate that mechanisms of postcapillary control of blood flow are to be present in the lung vessels. In the present study we searched for microanatomical evidence of vascular sphincters in the deep lung tissue of mice, namely in alveolar capillaries and pulmonary veins. METHODS: We have used scanning electron microscopy (SEM) to examine two types of samples of normal lung tissue of CD-1 mice: 1) vascular corrosion casts made by vascular perfusion with Mercox resin, and 2) routinely made gold/platinum-coated replicas of sectioned lung tissue. RESULTS: Careful scrutiny of the vessels of the deep lung tissue led to the identification of sphincters in alveolar capillaries. These sphincters were located at the junction between capillary and pulmonary veins. They corresponded to areas of the vascular wall showing circular swellings where a radial organization was observed, since they were made up of alternating grooves and bulges. Transmission electron microscopy showed that smooth muscle cells participated in the formation of the sphincters. CONCLUSIONS: Our data reveal a new location for vascular sphincters in pulmonary vessels and, because these novel sphincters are located at the capillary-vein junction, they offer a structural setting for the existence of postcapillary control of blood flow in the pulmonary circulation of mice.

Characterization of a Trypanosoma cruzi poly(A)-binding protein and its genes.

We have characterized the biochemical properties of a 66-kDa poly(A)-binding protein (PABP1) in the protozoan Trypanosoma cruzi and isolated two classes of cDNAs encoding the protein. In concordance, Southern blots showed the presence of 2 gene copies. The two cDNA classes differ in the length of adenosine-rich segments in the 5' untranslated region and in point changes scattered throughout the sequence, but their 1650-bp open reading frames encode identical proteins. A single mRNA of 5.5 kb was detected, indicating that the noncoding regions are unusually long. Both the mRNA and the protein are constitutively expressed in all stages of T. cruzi life cycle. The biochemical properties and sequence comparisons show that the T. cruzi PABP1 is similar to the PABP1 of other eukaryotic organisms. These results indicate that PABP1 has been conserved throughout eukaryotic evolution.

Neoformation of blood vessels in association with rat lung fibrosis induced by bleomycin.

We have used intratracheal instillation of bleomycin in rats to study the microanatomical changes of blood vessels associated with lung fibrosis. Bleomycin is a toxic cytostatic drug employed in classical models of lung fibrosis. Wistar rats were submitted to intratracheal injection of 1.5 units of bleomycin and sacrificed 2.5 months later, a timing when marked fibrosis of the lung is observed. We casted the vascular tree of the rat lungs by perfusion with a methacrylate resin. These casts were studied by scanning electron microscopy. Lung tissue was also studied by light microscopy and thin section electron microscopy. The major vascular modifications observed in the bleomycin-treated rats were: (1) neoformation of an elaborate network of vessels located in the peribronchial domains of the lung, and (2) distortion of the architecture of alveolar capillaries. By light microscopy, it was clear that the newly formed vascular network was located in regions of fibrosis (which in the resin casts were digested away). These neoformed vessels appeared to originate from bronchial arteries. Thin section electron microscopy revealed that endothelial cells of the neoformed vessels were plump, presented large nuclei, and showed numerous pinocytotic vesicles that were also observed in subendothelial pericytes. The alveoli of the bleomycin-treated rats were heterogeneous in size and shape in contrast with the homogeneity of alveoli of control animals. The alveolar capillaries of fibrotic lungs appeared to occupy a larger volume of the alveolar wall than alveolar capillaries of control rats. Our findings indicate that lung fibrosis encompasses marked changes of the vascular system, namely, the neoformation of vessels and the rearrangement of alveolar capillaries. These structural changes suggest that fibrotic transformation of the lung is associated with the local generation of angiogenic stimuli.

Anatomy of Clara cell secretion: surface changes observed by scanning electron microscopy.

The microanatomical alterations of the surface of lung Clara cells were studied during secretion. Stimulation of Clara cells was induced in rats by chronic inflammation caused by a single intratracheal instillation of bleomycin performed 2.5 months before the animals were killed. Bleomycin treatment resulted in marked stimulation of secretion by the bronchiolar Clara cells, 31% of the Clara cells from the treated rats showing signs of active secretion whereas only 6.3% of Clara cells in control rats presented similar features. High-resolution views of lung airways were obtained by scanning electron microscopy of critical point dried tissue samples. The surface of Clara cells underwent several modifications associated with the secretory events. These alterations followed 3 major phases: (1) formation of a smooth apical dome made up of a large volume of cytoplasm; (2) progressive narrowing of this dome-like body at its base with the formation of a cap-like structure; (3) in toto release of the cytoplasmic cap-like body. In favourable views, thin pedicles linking the cap-like bodies to the remaining cytoplasm of the Clara cell were detected. In other instances, release of the cap-like body occurred without the previous formation of stalks. Secretion of intracellular granules was observed in some cells before severance of the cap-like body. It is concluded that: (1) the cap-like bodies are not artifactual features of Clara cells; (2) Clara cell secretion is both apocrine and merocrine, the former predominating; (3) chronic inflammation is associated with an increased formation and release of the secretory cap-like bodies by Clara cells.

Metacyclogenesis of Leishmania (Viannia) braziliensis in vitro: evidence that lentil lectin is a marker of complement resistance and enhanced infectivity.

Axenic culture in modified Grace's medium was used to induce metacyclogenesis of Leishmania (Viannia) braziliensis in vitro. Morphological characteristics, lectin agglutination profiles, susceptibility to complement lysis, and infectivity in vivo were compared between metacyclic promastigotes and promastigotes in mid-log phase growth. Short, arrow-like promastigotes and round, oval promastigotes were defined as putative metacyclic forms on the basis of being highly motile and free swimming, with a small cell body and long flagellum. These forms increased during metacyclogenesis to > 80% whereas long-bodied, slender promastigotes and intermediate slender promastigotes declined progressively. Lentil lectin selectively agglutinated L. braziliensis after the induction of metacyclogenesis, whereas concanavalin A, wheat germ agglutinin and peanut agglutinin similarly agglutinated metacyclic promastigotes and mid-log phase promastigotes. Metacyclic promastigotes survived in 7.5%-20% human serum whereas mid-log phase promastigotes did not. Five hundred metacyclic promastigotes were highly infective to hamsters whereas 500 mid-log phase promastigotes rarely caused any lesion. Specific agglutination by lentil lectin should allow purification of metacyclic organisms for standardization of immunoprotection and challenge experiments.

Scanning electron microscopy of the deep lymphatic network of the murine lung as viewed in corrosion casts.

The lymphatic microvessels of the deep lung tissue were studied in corrosion casts, which were observed by scanning electron microscopy (SEM) after injection of a methacrylate resin (Mercox) through the trachea of CD-1 mice. We found that the deep lymphatics of the murine lung were composed of two interconnecting networks: a poorly developed capillary system located at the interacinar region, and a rich plexiform complex surrounding the bronchus. Lymphatic capillaries did not penetrate the alveolar area, thus leaving most of the lung parenchyma devoid of direct access to lymphatic drainage. Lung lymphatic vessels showed a small luminal surface and a low density of endothelial nuclei. Pulmonary lymphatic capillaries often formed star-like anastomoses. The structural features of pulmonary lymphatics, including their three-dimensional organization, were distinctly separate from those of the blood microvasculature of the lung.

Inflammatory response of the lung to tungsten particles: an experimental study in mice submitted to intratracheal instillation of a calcium tungstate powder.

Tungsten has been implicated as a cause of a severe form of pneumoconiosis in humans, the so-called "hard metal" lung disease. We have investigated the effect of intratracheal instillation of a powder of calcium tungstate on the pulmonary tissue of CD-1 mice. The tungsten-induced alterations were studied using 3 microanatomical methods: cytologic study of exudates obtained by bronchoalveolar lavage (BAL); histologic examination of paraffin-embedded sections of the lung; and scanning electron microscopic (SEM) examination of lung samples using x-ray microanalysis to detect tungsten in situ. The animals were sacrificed 1, 3, 7, 14 and 21 days after a single intratracheal instillation of 250 micrograms calcium tungstate particles suspended in 100 microliters of saline. We found that the metal particles induced a marked inflammatory response in the bronchoalveolar space characterized by a biphasic attraction of leukocytes with cellular peaks observed at day 1 and 14. More than 50% of the BAL macrophages showed ingested tungsten. In the lung parenchyma, the inflammatory infiltrates were predominantly located at the periphery of the bronchiolar walls. From 7 days on after the tungsten deposition, large inflammatory exudates were seen invading focal areas of the alveolar domain of the lung. SEM views revealed that the tungsten particles could be inside alveolar macrophages, in cells making up the alveolar wall, or inside periacinar lymphatics. Our data document that tungsten particles cause a marked inflammatory response in the lung tissue and that the leukocyte exudates may invade alveolar areas of the lung.(ABSTRACT TRUNCATED AT 250 WORDS)

Morphological evidence for migration of particle-laden macrophages through the interalveolar pores of Kohn in the murine lung.

We have investigated the topography of particle-laden macrophages in the pulmonary tissue of CD-1 mice after intratracheal instillation of a suspension of 250 micrograms of calcium tungstate. The mice were sacrificed 1, 3, 7 and 14 days after the particle deposition. Lung fragments were studied by scanning electron microscopy (SEM) coupled with X-ray microanalysis that allowed in situ elemental identification of tungsten in the lungs. Tungsten-positive macrophages were distinctly located in the lungs of mice sacrificed at 1-3 days when compared with samples from mice killed 7-14 days after the calcium tungstate instillation. At 1-3 days, the tungsten-carrying macrophages were accumulated near the terminal bronchioles whereas they were seen predominantly in the alveolar ducts and sacs in the 7- to 14-day groups of mice. This suggests that during pulmonary inflammation there is a redistribution of the particle-containing macrophages throughout the deep lung tissue. In high-magnification SEM views, we observed that the tungsten-positive macrophages presented numerous surface microvilli. Tungsten-laden phagocytes were detected in interalveolar fenestrae, at the so-called Kohn pores. This finding documents that the Kohn pores may be used by inflammatory cells as a pathway for the migration of phagocytes in between adjacent alveolar sacs.

Structural artifacts and advantages of cytocentrifugation of cells as viewed by scanning electron microscopy.

Cytocentrifugation of cell suspensions onto glass slides is a widely used procedure in contemporary cytology. We employed here scanning electron microscopy (SEM) to investigate putative morphological changes induced in cells submitted to cytocentrifugation. The fine structure of murine pleural exudate cells (macrophages mainly) processed by spinning was compared with that of similar cells treated without centrifugation (poly-L-lysine attachment of the cells to glass slides at 1 g). Cells of cytocentrifuged preparations showed a significant increase in diameter and smoothening of the cell surface as compared with the morphology of non-centrifuged cells. Cytocentrifugation also induced the formation of thin elongations coming out of the cellular outlines. The centrifugation-induced flattening of the pleural macrophages improved the detection of large intracellular inclusions (containing tungsten particles): these bodies were readily identified by secondary-electron imaging mode of SEM in cytospinned cells whereas their detection in non-centrifuged spherical cells required the use of the backscattered-electron imaging mode of SEM. We conclude that the cytocentrifugation methodology, on one hand, requires caution on the interpretation of the microanatomy of the cells and, on the other hand, the procedure may be an adequate method to improve the identification of large intracellular inclusions by routine (secondary-electron imaging mode) SEM.

Blood vasculature of the lymph node in the dog: anatomical evidence for participation of extrahilar arterial vessels in the blood supply of the cortex.

The organization of the arterial vessels of dog lymph nodes (LN) was studied using methods of visualization of the vasculature by systemic injection of different tracers (colloidal carbon, Micropaque resin and methylmethacrylate) followed by observation of the samples by light microscopy (after clearing of the thick sections of LN) or scanning electron microscopy (corrosion casts). LN from all of the three groups of nodes studied (tracheobronchial, paratracheal and popliteal) showed an extensive network of arterial vessels encircling the capsule of the organ. We found that branches of these capsular arteries penetrated deeply into the cortical domain of LN. The capsule-originating vessels appeared to have a significant participation in the blood supply of the LN parenchyma at the cortical domains of the organs. Our findings are in contrast with current views on the angiology of the LN that consider that virtually all of the arterial capillaries of the LN parenchyma come from hilar arteries. We propose, therefore, that important segments of the LN cortex receive their blood supply from capsular arteries rather than from hilar vessels.

Blood vessel architecture in lymph nodes of the dog viewed by scanning electron microscopy.

Scanning electron microscopy was used to investigate the submicroscopic organization of the blood vessels of dog lymph nodes (LN). The LN vessels were casted by systemic perfusion of the animals vasculature with two resins of distinct viscosity. This resulted in the retrieval of two types of LN vascular replicas that depicted either the arterial blood system alone (methacrylate casting) or both the arterial and venous blood systems (Mercox casting). We found that the dog LN showed a significantly higher density of arterial vessels in the cortex than in the medulla. In the cortical domain, a subcapsular layer stood out because of its rich content in arterial capillaries. The use of the high-resolution resin (mercox) resulted in excellent structural detail of the luminal surface of the LN vessels that allowed a clear distinction between arterioles and venules based on the geometrical pattern of the imprints left in the replicas by the nuclei of endothelial cells. At the cortex-medulla frontier, most arterioles showed narrowings of their lumen that suggested the existence of sphincters at this level. Our findings document that the microanatomical arrangement of blood vessels in the LN of the dog is different from that of LN from other mammals studied so far, in particular from rodents where vascular-poor microdomains have been reported in the LN cortex. The arteriolar sphincters that we detected at the innermost zone of the cortex may represent the structural counterpart of the physiological modulation of the blood supply of the cortex exerted by arterial branches coming from the hilus.

Time course and distribution of tungsten-laden macrophages in the hilar lymph nodes of the dog lung after experimental instillation of calcium tungstate into the left apical bronchus.

We sprayed a tungsten powder (CaWO4) into the airway of a single lobe (left apical) of the dog lung in order to study: (a) the kinetics of particle translocation from the bronchoalveolar lining to hilar lymph nodes, and (b) the sorting in lung lymph nodes of inhaled microcrystals. We found that the transport of the tungsten particles to the regional lymph node takes at least 24 hours and reaches its peak at day 7. In situ detection of tungsten by elemental particle analysis of lymph node sections by scanning electron microscopy allowed precise mapping of the marker in the node; the method was complemented by light microscopy and thin-section electron microscopy of the same nodes. Virtually all of the lymph node tungsten was located inside macrophages. The first tungsten-positive macrophages seen in the regional lymph nodes (day 1 to day 3) were restricted to the subcapsular space. This was followed by massive filling of the same sinus and of the narrow interfollicular areas by the particle-laden macrophages (day 3 to day 7). The even distribution of the tungsten-bearing phagocytes found in these anatomical regions of the node indicated that the subcapsular area in the dog was a continuous domain rather than the segmented region observed in nodes of common laboratory animals such as the rat. By day 7 after tungsten instillation, a moderate number of tungsten-positive macrophages was also detected in the paracortical region of the node. Finally, the presence of tungsten-bearing macrophages was extended to the outer lymph node medulla (day 7 to day 14); here, the macrophages were located in association with cords of plasmacytes and showed interdigitations with these lymphocytes. Only minimal amounts of tungsten were detected inside lymphoid follicles in association with dendritic cells. Some of the tungsten initially deposited in the airway of the apical left lung lobe was detected in contralateral hilar lymph nodes. We conclude that: (i) particle translocation from the alveolus to regional lymph nodes is a slow process that is mediated by pulmonary macrophages, in agreement with the findings of Harmsen et al Science 230:1277, 1985); (ii) in the lymph node, particle-bearing macrophages are sorted through narrow interfollicular sinuses into the outer medulla where they interact extensively with plasma cells; (iii) the migrating macrophages cannot penetrate the follicular domains of the node; minute quantities of exogenous particles may, nevertheless, be transferred from macrophages to follicular dendritic cells; and (iv) contralateral drainage may be a feature of the lymphatic system in the lung.

Prosomes and heat shock complexes in Drosophila melanogaster cells.

Prosomes and heat shock protein (HSP) complexes isolated from the cytoplasm of Drosophila cells in culture were biochemically and immunologically characterized. The two complexes were found to separate on sucrose gradients, allowing the analysis of their protein constituents by two-dimensional polyacrylamide gel electrophoresis and by reaction with anti-HSP sera and prosome-specific monoclonal antibodies. All of the prosomal proteins were found to be clearly distinct from the HSP; none of the prosomal proteins was synthesized de novo in heat shock. However, an antiprosome (anti-p27K) monoclonal antibody (mouse anti-duck) recognizing the Drosophila p29K prosomal protein allowed immunoprecipitation from a heat-shocked postmitochondrial supernatant of the crude HSP complex, including the low- and the high-molecular-weight components, in particular the 70 x 10(3)-molecular weight HSP. The highly purified small 16S HSP complex still contained this preexistent p29K prosomal protein, which thus also seems to be a metabolically stable constituent of the HSP complex. The significance of this structural and possibly functional relationship between prosomes and HSP, involving the highly ubiquitous and evolutionarily conserved prosomal protein p27/29K, remains to be elucidated.

Human mRNA polyadenylate binding protein: evolutionary conservation of a nucleic acid binding motif.

We have isolated a full length cDNA (cDNA) coding for the human poly(A) binding protein. The cDNA derived 73 kd basic translation product has the same Mr, isoelectric point and peptidic map as the poly(A) binding protein. DNA sequence analysis reveals a 70,244 dalton protein. The N terminal part, highly homologous to the yeast poly(A) binding protein, is sufficient for poly(A) binding activity. This domain consists of a four-fold repeated unit of approximately 80 amino acids present in other nucleic acid binding proteins. In the C terminal part there is, as in the yeast protein, a sequence of approximately 150 amino acids, rich in proline, alanine and glutamine which together account for 48% of the residues. A 2,9 kb mRNA corresponding to this cDNA has been detected in several vertebrate cell types and in Drosophila melanogaster at every developmental stage including oogenesis.

Morphologic and biochemical characterization of Crithidia brasiliensis sp. n.

A trypanosomatid with a choanomastigote stage and, therefore, belonging to the genus Crithidia, was isolated in culture from the alimentary tract of the hemipteran genus Zelus. The trypanosomatid was able to grow at 37 C, a characteristic reported to date from only 2 other members of Crithidia, C hutneri and C. luciliae thermophila. Subsequently, the flagellate was cloned for biochemical studies which involved cleaving of kDNA by restriction endonucleases and analyses of the isoenzyme and histone patterns. In all the attributes revealed by the foregoing methods, the organism from Zelus differed from the latter 2 congeneric species. On these and morphologic grounds, this organism appears to belong in a new species for which the name Crithidia brasiliensis sp. n. is proposed.