Wall Morphology (wall + morphology)

Distribution by Scientific Domains

Selected Abstracts


Pieter Vanormelingen
Desmodesmus species taxonomy is one of the most long-standing issues in green microalgal systematics due to problems associated with phenotypic plasticity. Whereas more recent species descriptions and identifications are mainly based on cell wall structures and the use of cultures, comparisons with molecular phylogenies are largely lacking. In this study, the phylogenetic relationships between 22 clones identified as Desmodesmus costato-granulatus (Skuja) E. H. Hegew. were assessed using ITS2 rDNA sequence data in combination with cell wall morphology. The unrooted ITS2 phylogeny showed that the clones cluster into five groups, which also differ in their cell wall structures. Therefore, the taxon is split into five species: D. costato-granulatus, D. elegans, D. fennicus, D. regularis, and D. ultrasquamatus. Compared with other Desmodesmus species, intraspecific sequence variation is extensive and may contain additional (pseudo)cryptic diversity. Compensatory base changes were near-absent within the species and varied from one to 11 between species. Relationships among the species were unresolved. Despite this, they clustered together with the two other Desmodesmus species having a combination of small and large warts in a well-supported lineage. Remarkably, ITS2 sequence variation in this lineage is as high as between all other included Desmodesmus species, even though the morphology of its members is rather uniform. [source]

Functional analysis of the Alternaria brassicicola non-ribosomal peptide synthetase gene AbNPS2 reveals a role in conidial cell wall construction

SUMMARY Alternaria brassicicola is a necrotrophic pathogen causing black spot disease on virtually all cultivated Brassica crops worldwide. In many plant pathosystems fungal secondary metabolites derived from non-ribosomal peptide synthetases (NPSs) are phytotoxic virulence factors or are antibiotics thought to be important for niche competition with other micro-organisms. However, many of the functions of NPS genes and their products are largely unknown. In this study, we investigated the function of one of the A. brassicicola NPS genes, AbNPS2. The predicted amino acid sequence of AbNPS2 showed high sequence similarity with A. brassicae, AbrePsy1, Cochliobolus heterostrophus, NPS4 and a Stagonospora nodorum NPS. The AbNPS2 open reading frame was predicted to be 22 kb in length and encodes a large protein (7195 amino acids) showing typical NPS modular organization. Gene expression analysis of AbNPS2 in wild-type fungus indicated that it is expressed almost exclusively in conidia and conidiophores, broadly in the reproductive developmental phase. AbNPS2 gene disruption mutants showed abnormal spore cell wall morphology and a decreased hydrophobicity phenotype. Conidia of abnps2 mutants displayed an aberrantly inflated cell wall and an increase in lipid bodies compared with wild-type. Further phenotypic analyses of abnps2 mutants showed decreased spore germination rates both in vitro and in vivo, and a marked reduction in sporulation in vivo compared with wild-type fungus. Moreover, virulence tests on Brassicas with abnps2 mutants revealed a significant reduction in lesion size compared with wild-type but only when aged spores were used in experiments. Collectively, these results indicate that AbNPS2 plays an important role in development and virulence. [source]

Descriptions of Protospathidium serpens (Kahl, 1930) and P. fraterculum n. sp. (Ciliophora, Haptoria), Two Species Based on Different Resting Cyst Morphology

Abstract. Protospathidium serpens (Kahl, 1930) is frequent in semiterrestrial and terrestrial habitats worldwide. Conventionally, all populations are considered as conspecific because they have very similar overall morphologies and morphometrics. We studied in detail not only the morphology of the vegetative cells but also the resting cysts using live observation, protargol impregnation, and scanning electron microscopy. These revealed a cryptic diversity and biogeographic pattern in details of the dorsal brush and cyst wall morphology. The cyst wall is spiny in the Austrian specimens, while smooth in the South African and Antarctic populations. Accordingly, P. serpens consists of at least two species: P. serpens (with spiny cyst wall) and P. fraterculum n. sp. (with smooth cyst wall); the latter is probably composed of two distinct taxa differing by the absence (South African)/presence (Antarctic) of a monokinetidal bristle tail in brush row 3, the number of dikinetids comprising brush row 1 (seven versus three), and the total number of brush dikinetids (29 versus 17). Protospathidium serpens is neotypified with the new population from Austria. The significance of resting cyst morphology is discussed with respect to alpha-taxonomy and overall ciliate diversity. [source]

The Effect of Ovariectomy on Rat Vaginal Tissue Contractility and Histomorphology

F. Fatih Ínol MD
ABSTRACT Introduction., Ovarian hormones have an important role in age-related genital arousal disorders; however, our knowledge regarding possible vaginal wall morphology and contractility changes in low-hormonal states is limited. Aims., To investigate morphological and functional alterations in the vaginal tissue in a rat ovariectomy model and to show the differences between proximal and distal vagina. Methods., Six weeks following ovariectomy, vaginal tissues were examined under light and electron microscopy. Circularly cut distal and proximal tissues were studied in the organ bath under isometric tension and compared with age-matched controls. Contractile responses to electrical field stimulation (EFS), phenylephrine, carbachol, and the effects of alpha-1 and alpha-2 blockade on EFS-induced contractility were investigated. Relaxation responses to EFS and vardenafil were investigated in precontracted strips. Main Outcome Measures., Differences between control and ovariectomy groups in terms of vaginal tissue contractility and histomorphological properties. Results., Distal vagina showed different epithelial characteristics and a better-developed muscularis compared with proximal vagina. Ovariectomy caused thinning of the epithelium, severe degeneration in epithelial architecture, and smooth muscle atrophy. Contraction and relaxation responses of distal strips were significantly lower in ovariectomized rats. Contractile responses to neuropharmacological stimulation were insignificant in proximal strips of both groups. EFS-induced contractions in distal strips diminished significantly after alpha-1 and alpha-2 adrenergic blockade. EFS caused frequency-dependent relaxation responses in precontracted distal strips, which were significantly decreased after nitric oxide synthase inhibition. Conclusions., Ovariectomy causes significant alteration in rat vaginal tissue morphology and contractility. Contraction and relaxation responses of distal vagina are significantly greater compared with morphologically distinct proximal vagina. Alpha-1 and alpha-2 receptors are the main mediators of contraction in distal rat vaginal tissue whereas nitric oxide pathway may have at least a partial role in relaxation. Main mediators of the rat vaginal tissue relaxation and the effect of ovariectomy on this regulation are yet to be defined. Ínol FF, Ercan F, and Tarcan T. The effect of ovariectomy on rat vaginal tissue contractility and histomorphology. J Sex Med 2006;3:233,241. [source]

Growth hormone deficiency and vascular risk

Roland W. McCallum
Summary The importance of growth hormone deficiency (GHD) in adult life has become more apparent over the last decade. As well as a distinct clinical syndrome there is a significant excess risk of cardiovascular disease. Although it is difficult to ascertain what part is played by the original pituitary disorder and the concomitant replacement hormonal therapies, there is clear evidence that GHD is associated with known cardiovascular risk factors such as body shape, lipid profile, insulin resistance, blood pressure, vessel wall morphology and haemostatic factors. Novel means of assessing vascular risk such as pulse wave velocity and flow-mediated dilatation can also estimate the risk without invasive procedures. The role of possible mediators of endothelial function such as nitric oxide and free radicals is being investigated further. Replacement of GH in GH-deficient patients leads to many effects on the above indices, some but not all of which are associated with reduced vascular risk. Long-term follow-up studies of morbidity and mortality are required for an accurate assessment of the beneficial effects of therapy. [source]