Diamantina lombardii – an odd Brazilian member of the Podostemaceae

This paper complements the diagnosis of the recently described genus Diamantina and its only species Diamantina lombardii Novelo, Philbrick and Irgang from Minas Gerais (Brazil). Four new features not known from other Podostemaceae–Podostemoideae are documented by microtome sections and SEM graphs: (i) The digitate foliage leaves lack vascular tissue completely. (ii) Leafy shoots produce one or two flowers in terminal and subterminal position. The spathella subtending the subterminal flower is scale-like and positionally homologous to a digitate bract (leaf), whereas the spathella covering the terminal flower bud is tubular (as usual for Podostemoideae). (iii) The usually rudimentary androecium consists of two stamens which form a complete whorl together with three inconspicuous tepals around the gynophore. (iv) The bilocular ovary has an apical cleft. Each carpel tip (hollow inside) is topped by a prominent horn-like stigma. Additional peculiar features of D. lombardii (already mentioned in Philbrick et al., 2004. Syst. Bot. 29, 109–117) are shown: presence of a prominent gynophore (mainly known from African Podostemoideae), and digitate leaves (as found in Cladopus from Eastern Asia to NE Australia).     

Morphology of haemoglobin-containing human erythrocyte ‘ghosts’

Resealed erythrocyte ‘ghosts’ have been proposed as in vivo carriers for enzymes in the therapy of inherited metabolic diseases. A long life-span of this carrier is required when the erythrocyte ‘ghost’ is intended to be the site of substrate degradation in the circulation. Erythrocyte ‘ghosts’ have been prepared that show cell content and membrane transport characteristics that are closely similar to those of normal erythrocytes. Since the morphology of these ‘ghosts’ could probably also affect the in vivo life-span, haemoglobin-containing human erythrocyte ‘ghosts’ have been studied using scanning electron-microscopy.Preparation of the erythrocyte ‘ghosts’ involved a method of hypo-osmotic dialysis and consecutive iso-osmotic dialysis. Samples for scanning electron microscopy were prepared by fixation in glutaraldehyde, with post-fixation in osmium tetroxide. Dehydration was obtained by increasing concentrations of ethanol and critical-point-drying. Control experiments with normal erythrocytes showed no major artefacts by the methods used. Erythrocyte ‘ghosts’ showed polymorphic shapes. Two thirds were stomatocytes, but echinocytes and cells with deep invaginations or inter-twisted infoldings were also observed. Distribution of the different cell types could be affected by the preparation techniques used. Washing of the erythrocyte ‘ghosts’ at very low centrifugation speeds resulted in 60% of the cells appearing as biconcave discoids and one third as stomatocytes.The results demonstrate that the preparation disturbed the balance of the biconcave shape of resealed erythrocyte ‘ghosts’. Minor alterations of the methods allowed the preparation of erythrocyte ‘ghosts’, the majority of which showed morphology closely similar to that of normal erythrocytes. Attention must be given to all preparation factors to avoid irreversible damage and therefore prior to use of these cells in patients or when methods are altered, the morphology of these cellular carriers must be closely controlled.     

Organ identity of the thalloid plant body of Griffithella hookeriana and Polypleurum stylosum – Podostemoideae (Podostemaceae)

The morphological nature of the thalloid plant body of podostemads has remained controversial for long. The present investigation was carried out on two members of the Podostemoideae i.e. Griffithella hookeriana and Polypleurum stylosum to understand their organ identity. The origin of the plant body was traced from the embryo by germinating the seeds under aseptic conditions. Mature embryo of both species does not show an identifiable shoot apical meristem (SAM) and root apical meristem (RAM). Upon germination, the radicular pole does not form a primary root but differentiates adhesive hairs. At the cotyledonary junction, SAM is initiated that differentiates 6–9 leaves apically (primary axis) and a primordium laterally. This primordium subsequently emerges from the hypocotyl and develops into a thalloid plant. The latter has been interpreted as a flattened stem because it not only shows tunica-corpus like organization at the tip but also originates endogenously from the same SAM that forms the `primary axis'.     

Spore Morphology of Pteridophytes from China Ⅵ .Pteridaceae

The spore morphology of 30 species 4 variety of 2 genera of Pteridaceae from China was investigated under scanning electron microscope (SEM) . Among them, 29 species 4 variety belong to the genus Pteris . The spores of Pteris are trilete , radiosymmetrical , subtriangular in polar view and hemispherical or subhemispherical in equatorial view . The polar axes are 26 - 54μm long , and equatorial axes are 34 - 97μm long . The perispore is thin and the surface ornamentation is formed by the exospore . The types of ornamentation are tuberculiform-rugulate , verruciform-rugulate or lophate , the spore of most species with the equatoial flange, some species with proximal ridge and distal ridge . The spore morphology of Pteris is stable, and the difference between species is distinct , but the features of spore and sporophyte are not related. The spore of Histiopteris is monolete and bilaterally symmetrical, elliptical in polar view and kidney-shaped in equatorial view . The polar axes are 22 - 23μm long , and equatorial axes are 29 - 36 μm long . The perispore is thin and the surface ornamentation is formed by the exospore . The surface is rugulate . The spore morphology of Histiopteris and Pteris is very differential , put genus Histiopteris in family Pteridaceae is not suitable, according to the feature of spore morphology .     

The Yin–Yang of Dendrite Morphology: Unity of Actin and Microtubules

Actin and microtubules (MT) are targets of numerous molecular pathways that control neurite outgrowth. To generate a neuronal protrusion, coordinated structural changes of the actin and MT cytoskeletons must occur. Neurite formation occurs when actin filaments (F-actin) are destabilized, filopodia are extended, and MTs invade filopodia. This process results in either axon or dendrite formation. Axonal branching involves interplay between F-actin and MTs, with F-actin and MTs influencing polymerization, stabilization, and maintenance of each other. Our knowledge of the mechanisms regulating development of the axon, however, far eclipses our understanding of dendritic development and branching. The two classes of neurites, while fundamentally similar in their ability to elongate and branch, dramatically differ in growth rate, orientation of polarized MT bundles, and mechanisms that initiate branching. In this review, we focus on how F-actin, MTs, and proteins that link the two cytoskeletons coordinate to specifically initiate dendritic events. Penelope C. Georges and Norell M. Hadzimichalis contributed equally.     

Morphology and coexistence of congeneric ectoparasite species: reinforcement of reproductive isolation?

Assuming that differences or similarities in morphology among congeneric parasite species living in the same habitat are not a random pattern, several hypotheses explaining morphological differences were tested: (i) reproductive isolation, (ii) niche restriction resulting from competition, and (iii) niche specialization. Congeneric monogenean (platyhelminth) ectoparasites parasitizing the gills of one host species were used as an ecological model. Morphometric distances of the attachment organ and morphometric distances of the copulatory organ between species pairs were calculated, Levin's niche size and Renkonen niche overlap indices were applied. Our results support the prediction that the function of niche segregation is to achieve reproductive isolation of related species in order to prevent hybridization (reinforcement of reproductive barriers). Parasite species living in the same niche differ greatly in the size of copulatory organ. Moreover, species coexistence is facilitated by an increase in morphometric distances of copulatory organ and niche centre distances. Our results also show that species living in overlapping niches have similar attachment organs, which supports the prediction that morphologically similar species have the same ecological requirements within one host and suggests small effects of interspecific competition for the evolution of morphological diversity of attachment organs. Specialist adaptations also seem to facilitate species coexistence and affect the niche distribution within host species. Parasite species that can colonize more than one host species, i.e. generalists, occupy more distant niches within host species than strictly host-specific parasites. © 2002 The Linnean Society of London, Biological Journal of the Linnean Society , 2002, 76, 125–135.     

Morphology and Physiology of the Intracellular Development of Bacillus subtilis Bacteriophage φ25

The morphology of the intracellular development of bacteriophage phi25 in Bacillus subtilis 168M has been correlated with nucleic acid synthesis in infected cells. Host deoxyribonucleic acid (DNA) synthesis was shut off by a phage-induced enzyme within 5 min after infection, and another phage-mediated function extensively degraded host DNA at the time of cell lysis. Synthesis of phage DNA in infected cells began within 5 min and continued until late in the rise period. After phage DNA synthesis and coinciding with lysis, much of the unpackaged, newly synthesized phage DNA was degraded. Studies of thin sections of phi25 infected cells suggested that unfilled capsids may be precursors to filled capsids in the packaging process. To assess dependence of capsid formation on phage DNA replication, cells were either treated with mitomycin C and infected with normal phage or infected with ultraviolet-irradiated (99% killed) phi25. Only empty capsids were found in these cells, indicating that capsid production may be independent of the presence of newly synthesized viral DNA.     

Morphology of the “spindle-shaped body” in the developing tail of human spermatids

Summary At the beginning of the late cap phase of the normal differentiation of human spermatids, a unique structure, the spindle shaped body, occupies part of the future middlepiece. This spindle-shaped body was followed throughout its development, and its functional relationship to the formation of the fibrous sheath is discussed. The spindle-shaped body disappears when the fibrous sheath is completed and the annulus moves down, giving rise to the middle-piece.Supported by Grants from the Deutsche Forschungsgemeinschaft.     

The embryo sac ofPodostemum subulatus (Podostemaceae) — a reinvestigation

The female gametophyte ontogeny inPodostemum subulatus is of the Apinagia type and not the Podostemum type as reported earlier. The independent existence of the Podostemum type in the family is questioned.     

Influence of Environmental Conditions on Hyphal Morphology in Pellets of Aspergillus niger: Role of β-N-Acetyl-D-Glucosaminidase

The influence of modifications of the environmental conditions of growth on β-N-acetyl-D-glucosaminidase (EC 3.2.1.30) activity and on hyphal morphological patterns in pellets of Aspergillus niger was studied. It was found that changes in the degree of branching and, to a lesser extent, in the number of bulbous cells were directly related to the activity of the enzyme. Nevertheless, since β-N-acetyl-D-glucosaminidase is not the only enzyme involved in the lytic potential of the fungus, these findings do not exclude the possibility that other enzymes may be involved. Received: 30 December 1998 / Accepted: 9 March 1999     

Cranial Morphology of the Brachystelechid ‘Microsaur’ Quasicaecilia texana Carroll Provides New Insights into the Diversity and Evolution of Braincase Morphology in Recumbirostran ‘Microsaurs’

Recumbirostran ‘microsaurs,’ a group of early tetrapods from the Late Carboniferous and Early Permian, are the earliest known example of adaptation to head-first burrowing in the tetrapod fossil record. However, understanding of the diversity of fossorial adaptation within the Recumbirostra has been hindered by poor anatomical knowledge of the more divergent forms within the group. Here we report the results of μCT study of Quasicaecilia texana, a poorly-known recumbirostran with a unique, broad, shovel-like snout. The organization of the skull roof and braincase of Quasicaecilia is found to be more in line with that of other recumbirostrans than previously described, despite differences in overall shape. The braincase is found to be broadly comparable to Carrolla craddocki, with a large presphenoid that encompasses much of the interorbital septum and the columella ethmoidalis, and a single compound ossification encompassing the sphenoid, otic, and occipital regions. The recumbirostran braincase conserves general structure and topology of braincase regions and cranial nerve foramina, but it is highly variable in the number of ossifications and their extent, likely associated with the reliance on braincase ossifications to resist compression during sediment compaction and mechanical manipulation by epaxial and hypaxial musculature. Expansion of the deep ventral neck musculature in Quasicaecilia, autapomorphic among recumbirostrans, may reflect unique biomechanical function, and underscores the importance of future attention to the role of the cervical musculature in contextualizing the origin and evolution of fossoriality in recumbirostrans.     

Root Morphology and Zn^2＋ Uptake Kinetics of the Zn Hyperaccumulator of Sedum alfredii Hance

Root morphology and Zn^2＋ uptake kinetics of the hyperaccumulating ecotype （HE） and nonhyperaccumulating ecotype （NHE） of Sedum alfredii Hance were investigated using hydroponic methods and the radiotracer flux technique. The results indicate that root length, root surface area, and root volume of NHE decreased significantly with increasing Zn^2＋ concentration in growth media, whereas the root growth of HE was not adversely affected, and was even promoted, by 500μmol/L Zn^2＋. The concentrations of Zn^2＋ in both ecotypes of S. alfredii were positively correlated with root length, root surface area and root volumes, but no such correlation was found for root diameter. The uptake kinetics for ^65Zn^2＋ in roots of both ecotypes of S. alfredii were characterized by a rapid linear phase during the first 6 h and a slower linear phase during the subsequent period of investigation. The concentration-dependent uptake kinetics of the two ecotypes of S. alfredii could be characterized by the Michaelis-Menten equation, with the Vmax for ^65Zn^2＋ influx being threefold greater in HE compared with NHE, indicating that enhanced absorption into the root was one of the mechanisms involved in Zn hyperaccumulation. A significantly larger Vmax value suggested that there was a higher density of Zn transporters per unit membrane area in HE roots.     

Morphology and distribution of Müller cells in the retina of the toad Bufo marinus

We have previously shown that an antibody against neuron-specific enolase (NSE) selectively labels Müller cells (MCs) in the anuran retina (Wilhelm et al. 1992). In the present study the light- and electron-microscopic morphology of MCs and their distribution were described in the retina of the toad, Bufo marinus, using the above antibody. The somata of MCs were located in the proximal part of the inner nuclear layer and were interconnected with each other by their processes. The MCs were uniformly distributed across the retina with an average density of 1500 cells/mm². Processes of MCs encircled the somata of photoreceptor cells isolating them from each other by glial sheath, except for those of the double cones. Some of the photoreceptor pedicles remained free of glial sheath. Electron-microscopic observations confirmed that MC processes provide an extensive scaffolding across the neural retina. At the outer border of the ganglion cell layer these processes formed a non-continuous sheath. The MC processes traversed through the ganglion cell layer and spread beneath it between the neuronal somata and the underlying optic axons. These processes formed a continuous inner limiting membrane separating the optic fibre layer from the vitreous tissue. Neither astrocytic nor oligodendrocytic elements were found in the optic fibre layer. The significance of the uniform MC distribution and the functional implications of the observed pattern of MC scaffolding are discussed.     

Studies of the Chinese Woodsiaceae (2) — Comparative Morphology and Anatomy of Mature Sporophytes

the comparative studies of morphology and anatomy of 19 species of Chinese Woodsiaceae are reported in the present paper. It includes anatomy of root, rhizome, rachis and joint on stipe; comparative morphology of the fronds and its parts, trichomes and indusia and an observation of the spores under SEM. The information is applied to discussing phylogeny and systematics briefly. The anatomical studies do provide taxonomic studies with evidence so that they should not be abandoned. For example, the stipe joints of Woodsia have two types, the stipe joint below the attachment point of the base pair of pinnae and the stipe joint just at the attachment point of that; the abscission layer of the former does not have pinna trace in it and the basic chromosome number is 39. However, the abscission layer of the latter does and the basic chromosome number is 41. It is obvious that the anatomical cha-racters can be used for infrageneric subdivision of Woodsia.     

Amyloid-β Protofibrils: Size,Morphology and Synaptotoxicity of an Engineered Mimic

Structural and biochemical studies of the aggregation of the amyloid-β peptide (Aβ) are important to understand the mechanisms of Alzheimer''s disease, but research is complicated by aggregate inhomogeneity and instability. We previously engineered a hairpin form of Aβ called Aβcc, which forms stable protofibrils that do not convert into amyloid fibrils. Here we provide a detailed characterization of Aβ₄₂ cc protofibrils. Like wild type Aβ they appear as smooth rod-like particles with a diameter of 3.1 (±0.2) nm and typical lengths in the range 60 to 220 nm when observed by atomic force microscopy. Non-perturbing analytical ultracentrifugation and nanoparticle tracking analyses are consistent with such rod-like protofibrils. Aβ₄₂ cc protofibrils bind the ANS dye indicating that they, like other toxic protein aggregates, expose hydrophobic surface. Assays with the OC/A11 pair of oligomer specific antibodies put Aβ₄₂ cc protofibrils into the same class of species as fibrillar oligomers of wild type Aβ. Aβ₄₂ cc protofibrils may be used to extract binding proteins in biological fluids and apolipoprotein E is readily detected as a binder in human serum. Finally, Aβ₄₂ cc protofibrils act to attenuate spontaneous synaptic activity in mouse hippocampal neurons. The experiments indicate considerable structural and chemical similarities between protofibrils formed by Aβ₄₂ cc and aggregates of wild type Aβ₄₂. We suggest that Aβ₄₂ cc protofibrils may be used in research and applications that require stable preparations of protofibrillar Aβ.     

Pollen Morphology of Parnassia L. （Parnassiaceae） and Its Systematic Implications

The pollen morphology of 28 species of Parnassia L. was investigated with light microscopy and scanning electron microscopy (SEM). The shape of pollen grains in this genus varies from subspheroidal to prolate in equatorial view and is three-lobed circular in the polar view. Pollen grains are usually radially symmetrical, isopolar, tricolporate or syntricolporate, with reticulate sculpture. The pollen characteristics among species are fairly similar to each other. Morphological information regarding the pollen grains shows that Parnassia is a natural genus. Based on exine ornamentation observed under SEM, three types of pollen grains were recognized: (i) type I, with foveolate-reticulate sculpture; (ii) type II, with a finely reticulate sculpture; and (iii) type III, with a coarsely reticulate sculpture. Most sections of this genus have one type of sculpture of pollen morphology, but Sect. Nectarotrilobos has three types of sculpture and Sect.Saxifragastrum has two types of sculpture. All three types of sculpture can be found in Southwest China,with species with the longest (Parnassia delavayi Franch.) and shortest (Parnassiafaberi Oliv.) colpi,implying that Southwest China is the center of diversification of the genus.     

Hearing in tsetse flies? Morphology and mechanics of a putative auditory organ

Tympanal hearing organs are widely used by insects to detect sound pressure. Such ears are relatively uncommon in the order Diptera, having only been reported in two families thus far. This study describes the general anatomical organization and experimentally examines the mechanical resonant properties of an unusual membranous structure situated on the ventral prothorax of the tsetse fly, Glossina morsitans (Diptera: Glossinidae). Anatomically, the prosternal membrane is backed by an air filled chamber and attaches to a pair of sensory chordotonal organs. Mechanically, the membrane shows a broad resonance around 5.3-7.2 kHz. Unlike previously reported dipteran tympana, a directional response to sound was not found in G. morsitans. Collectively, the morphology, the resonant properties and acoustic sensitivity of the tsetse prothorax are consistent with those of the tympanal hearing organs in Ormia sp. and Emblemasoma sp. (Tachinidae and Sarcophagidae). The production of sound by several species of tsetse flies has been repeatedly documented. Yet, clear behavioural evidence for acoustic behaviour is sparse and inconclusive. Together with sound production, the presence of an ear-like structure raises the enticing possibility of auditory communication in tsetse flies and renews interest in the sensory biology of these medically important insects.