Common Molecular Components Research Articles

Low-voltage scanning electron microscopy study of lampbrush chromosomes and nuclear bodies in avian and amphibian oocytes.

Nucleus is a highly compartmentalized part of the cell where the key processes of genome functionality are realized through the formation of non-membranous nuclear domains. Physically nuclear domains appear as liquid droplets with different viscosity stably maintained throughout the interphase or during the long diplotene stage of meiosis. Since nuclear body surface represents boundary between two liquid phases, the ultrastructural surface topography of nuclear domains is of an outstanding interest. The aim of this study was to examine ultrathin surface topography of the amphibian and avian oocyte nuclear structures such as lampbrush chromosomes, nucleoli, histone-locus bodies, Cajal body-like bodies, and the interchromatin granule clusters via low-voltage scanning electron microscopy. Our results demonstrate that nuclear bodies with similar molecular composition may differ dramatically in the surface topography and vice versa, nuclear bodies that do not share common molecular components may possess similar topographical characteristics. We also have analyzed surface distribution of particular nuclear antigens (double stranded DNA, coilin and splicing snRNA) using indirect immunogold labeling with subsequent secondary electron detection of gold nanoparticles. We suggest that ultrastructural surface morphology reflects functional status of a nuclear body.

Forcing cells into shape: the mechanics of actomyosin contractility.

Actomyosin-mediated contractility is a highly conserved mechanism for generating mechanical stress in animal cells and underlies muscle contraction, cell migration, cell division and tissue morphogenesis. Whereas actomyosin-mediated contractility in striated muscle is well understood, the regulation of such contractility in non-muscle and smooth muscle cells is less certain. Our increased understanding of the mechanics of actomyosin arrays that lack sarcomeric organization has revealed novel modes of regulation and force transmission. This work also provides an example of how diverse mechanical behaviours at cellular scales can arise from common molecular components, underscoring the need for experiments and theories to bridge the molecular to cellular length scales.

Association between etiopathogenesis of morbidly adherent placenta and adenomyosis

The association between etio-pathogenesis of morbidly adherent placenta (MAP) or placenta cretas and adenomyosis has never been described in medical literature. Contrary to the believe that MAP is due to direct invasion of trophoblastic tissues into the adjacent normal myometrium due to prior uterine surgeries, this article describes how pre-existence of adenomyosis acts as a precursor for the development of placenta cretas. It elucidates how prior uterine traumas such as surgeries, repeated childbirths and endometritis cause endometrial tissues to invade the myometrium as a result of disruption of decidua basalis. The invaded endometrial tissues cause hyper-plasia and hypertrophy of surrounding myometrium to form the clinical entity called adenomyosis. The over-expression of bcl-2 oncogene in the endometrium causes inhibition of apoptosis of endometrial cells removing the barrier of trophoblastic tissues to invade the myometrium to form MAP. This hypothesis is based on the similarity of their clinical perspectives, similar pathological description of the two disease entities and their common molecular components. Both diseases increase with age; more in women older than 35 years and also in those with history of previous endometrial traumas such as surgeries, childbirth and endometritis. Both diseases also share common pathological factors and molecular components due to absence of deciduas basalis and over-expression of bcl-2 oncoprotein gene, inhibition of cell apoptosis and failure to find genetic abnormalities such as mutations of K-ras, P53 or LOH. An ongoing study looking at uterine specimens from cesarean hysterectomies and pelvic MRI evaluation of patients with retained placentas to prove that pre-existing adenomyosis may be a precursor to the development of morbidly adherent placenta is near to conclusion.

Laminin‐332–β1 integrin interactions negatively regulate invadopodia

Adhesion of epithelial cells to basement membranes (BM) occurs through two major structures: actin-associated focal contacts and keratin-associated hemidesmosomes, both of which form on laminin-332 (Ln-332). In epithelial-derived cancer cells, additional actin-linked structures with putative adhesive properties, invadopodia, are frequently present and mediate BM degradation. A recent study proposed that BM invasion requires a proper combination of focal contacts and invadopodia for invading cells to gain traction through degraded BM, and suggested that these structures may compete for common molecular components such as Src kinase. In this study, we tested the role of the Ln-332 in regulating invadopodia in 804G rat bladder carcinoma cells, a cell line that secretes Ln-332 and forms all three types of adhesions. Expression of shRNA to Ln-332 gamma2 chain (gamma2-kd) led to increased numbers of invadopodia and enhanced extracellular matrix degradation. Replating gamma2-kd cells on Ln-332 or collagen-I fully recovered cell spreading and inhibition of invadopodia. Inhibition of alpha3 or beta1, but not alpha6 or beta4, phenocopied the effect of gamma2-kd, suggesting that alpha3beta1-mediated focal contacts, rather than alpha6beta4-mediated hemidesmosome pathways, intersect with invadopodia regulation. gamma2-kd cells exhibited alterations in focal contact-type structures and in activation of focal adhesion kinase (FAK) and Src kinase. Inhibition of FAK also increased invadopodia number, which was reversible with Src inhibition. These data are consistent with a model whereby actin-based adhesions can limit the availability of active Src that is capable of invadopodia initiation and identifies Ln-332-beta1 interactions as a potent upstream regulator that limits cell invasion.

Connecting photosynthesis and cellular respiration: Preservice teachers' conceptions

AbstractThe biological processes of photosynthesis and plant cellular respiration include multiple biochemical steps, occur simultaneously within plant cells, and share common molecular components. Yet, learners often compartmentalize functions and specialization of cell organelles relevant to these two processes, without considering the interconnections as well as the significance of the plant as an independent biological system functioning as a nested component within local and global ecosystems. Understanding connections among biological systems at macro and micro levels is important to biological literacy. This study examined preservice elementary teachers' conceptions of photosynthesis and plant cellular respiration, with attention to interconnections and systems. Participants were limited in their understanding of the processes impacting multiple ecological levels, and they held inadequate representations of interconnections between the processes. Participants' views were laden with sociological and egocentric components. They often compared plant functions with analogous human functions. Most participants viewed plants as dependent on humans while having societal use. Justifications for views included nominal knowledge of the processes; experiential authoritarian reasoning; and anthropomorphism. We discuss instructional implications in light of the findings. © 2009 Wiley Periodicals, Inc. J Res Sci Teach 46: 791–812, 2009

Metastasis-Inducing S100A4 Protein: Implication in Non-Malignant Human Pathologies

The role of S100A4 in tumor progression and metastasis is well documented in numerous research articles and summarized in several reviews. Currently S100A4 is categorized as an essential metastasis-promoting factor whose production and secretion from "activated" stromal cells (fibroblasts, immunocytes and vascular cells) is initiated and stimulated by signals derived in tumor cells (cytokines, growth factors and others). However recent data gained from experimental and clinical studies significantly extend our knowledge on S100A4. Implications of S100A4 in various non-malignant pathological conditions have been demonstrated by number of research groups. In the mini-review we attempted to highlight the role of S100A4 in other than cancer important human pathologies, such as autoimmune inflammation (RA) and disorders in cardio-vascular, nervous and pulmonary systems. We suggest that diverse human diseases might have common molecular components and pathway(s). Possibly, inflammatory machinery and S100A4 as its intrinsic constituent could contribute to the pathogenesis of various disorders. Therefore, we presume that facts on S100A4 performance could be attractive for broad range of researchers and clinicians.

DjCBC‐1, a conserved DEAD box RNA helicase of the RCK/p54/Me31B family, is a component of RNA‐protein complexes in planarian stem cells and neurons

The stem cells of planarians, known as neoblasts, can give rise to all cell types in planarians. Neoblasts can be identified by electron microscopy as cells with electron-dense chromatoid bodies, which are large RNP (ribonucleoprotein) complexes, in their cytoplasm. However, the components and function of chromatoid bodies are still relatively unknown. Here we identified a DEAD box RNA helicase gene of the RCK/p54/Me31B family from a planarian EST database and showed the localization of its product in chromatoid bodies by immunoelectron microscopy. We named this gene Djcbc-1 (Dugesia japonica chromatoid body component 1). Djcbc-1 was also strongly expressed in the brain and in the germline stem cells of sexualized planarians. We observed chromatoid body-like electron-dense bodies in brain neurons, where DjCBC-1 was also expressed. These observations suggest that common molecular components of RNP complexes may be involved in the regulation of somatic and germline stem cells, and neurons in planarians.

Laboratory Simulation of 11-15 μm Spectra Associated with Polycyclic Aromatic Hydrocarbon Molecules

We have obtained 11-15 μm spectra of thin films of hydrogenated amorphous carbon assembled from carbon nanoparticles. Well-defined, narrow features similar to the interstellar emission bands attributed to polycyclic aromatic hydrocarbons (PAHs) are observed at 11.3, 12, 12.8, 13.5, and 14.2 μm. These features are reproduced in many samples prepared under a variety of conditions, indicating that they involve common molecular components. We suggest that these are based on compact ring structures such as coronene, C 24H12, but that these molecules have peripheral substitutions involving additional aromatic rings. They may also be substituted with sp- or sp2-bonded carbon chains. All bands exhibit slight energy shifts in different samples in response to changes in preparation conditions. These shifts replicate variations in wavelength and profile of the 11-15 μm bands seen in different type of emission source. None of the nanoparticle samples exhibit all of the 11.3, 12, 12.8, 13.5, and 14.2 μm features. This implies that the interstellar bands are produced by a limited variety of PAH structures, rather than by a single dominant species.

Retromer and sorting nexins in development

Trafficking and signaling processes involve common molecular components. The machinery that controls intracellular trafficking is vital in ensuring that signaling mechanisms take place correctly. An illustrative example of this relationship is the sustained signaling of endocytosed membrane receptors, such as receptor Tyr kinases and G-protein coupled receptors, after ligand-induced activation. An intriguing role in controlling the fate of these and other receptors at the endosome has been attributed to members of the sorting nexin protein family. The best characterized sorting nexins are subunits of a multimeric complex, termed retromer. It was first found in yeast that retromer mediates endosome-to-Golgi retrieval of receptors after they have delivered soluble hydrolase precursors into the vacuole, the organelle equivalent to the mammalian lysosome. Work in cultured mammalian cells later demonstrated that retromer performs an analogous function in higher eukaryotes. Data from genetically modified mice, and from a simpler organism such as the nematode Caenorhabtidis elegans, has revealed that retromer performs an essential role during embryogenesis. This review will discuss implications of recent work on this subject.

The Assembly of Calcium Release Units in Cardiac Muscle

Calcium release units (CRUs) are constituted of specialized junctional domains of the sarcoplasmic reticulum (jSR) that bear calcium release channels, also called ryanodine receptors (RyRs). In cardiac muscle, CRUs come in three subtypes that differ in geometry, but have common molecular components. Peripheral couplings are formed by a junction of the jSR with the plasmalemma; dyads occur where the jSR is associated with transverse (T)-tubules; corbular SR is a jSR domain that is located within the cells and bears RyRs but does not associate with either plasmalemma or T-tubules. Using transmission electron microscopy, this study followed the formation of CRUs and their accrual of four components: the L-type channel dihydropyridine receptors (DHPRs) of plasmalemma/T-tubules; the RyRs of jSR; triadin (Tr) and junctin (JnC), two homologous components of the jSR membrane; and calsequestrin (CSQ), the internal calcium binding proteins. During differentiation, peripheral couplings are formed first and the others follow. RyRs and DHPRs are targeted to subdomains of the CRUs that face each other and are acquired in a concerted manner. Overexpressions of either junction (JnC or Tr) and of CSQ, singly or in conjunction, shed light on the specific role of JnC in the structural development, organization, and maintenance of jSR cisternae and on the independent synthetic pathways and targeting of JnC and CSQ. In addition, the structural cues provided by the overexpression models allow us to define sequential steps in the synthetic pathway for JnC and CSQ and their targeting to the CRUs of differentiating myocardium.

Segmentation: mono- or polyphyletic?

Understanding the evolutionary origins of segmented body plans in the metazoa has been a long-standing fascination for scientists. Competing hypotheses explaining the presence of distinct segmented taxa range from the suggestion that all segmentation in the metazoa is homologous to the proposal that segmentation arose independently many times, even within an individual clade or species. A major new source of information regarding the extent of homology vs. homoplasy of segmentation in recent years has been an examination of the extent to which molecular mechanisms underlying the segmentation process are conserved, the rationale being that a shared history will be apparent by the presence of common molecular components of a developmental program that give rise to a segmented body plan. There has been substantial progress recently in understanding the molecular mechanisms underlying the segmentation process in many groups, specifically within the three overtly segmented phyla: Annelida, Arthropoda and Chordata. This review will discuss what we currently know about the segmentation process in each group and how our understanding of the development of segmented structures in distinct taxa have influenced the hypotheses explaining the presence of a segmented body plan in the metazoa.

Caspase activity and expression of cell death genes during development of human preimplantation embryos

It has been observed that apoptosis occurs in human blastocysts. In other types of cell, the characteristic morphological changes seen in apoptotic cells are executed by caspases, which are regulated by the BCL-2 family of proteins. This study investigated whether these components of the apoptotic cascade are present throughout human preimplantation development. Developing and arrested two pronucleate embryos at all stages were incubated with a fluorescently tagged caspase inhibitor that binds only to active caspases, fixed, counterstained with 4,6-diamidino-2-phenylindole (DAPI) to assess nuclear morphology and examined using confocal microscopy. Active caspases were detected only after compaction, at the morula and blastocyst stages, and were frequently associated with apoptotic nuclei. Occasional labelling was seen in arrested embryos. Expression of proapoptotic BAX and BAD and anti-apoptotic BCL-2 was examined in single embryos using RT-PCR and immunohistochemistry. BAX and BCL-2 mRNAs were expressed throughout development, whereas BAD mRNA was expressed mainly after compaction. Simultaneous expression of BAX and BCL-2 proteins within individual embryos was confirmed using immunohistochemistry. The onset of caspase activity and BAD expression after compaction correlates with the previously reported appearance of apoptotic nuclei. As in other types of cell, human embryos express common molecular components of the apoptotic cascade, although apoptosis appears to be suppressed before compaction and differentiation.

Caspase activity and expression of cell death genes during development of human preimplantation embryos.

It has been observed that apoptosis occurs in human blastocysts. In other types of cell, the characteristic morphological changes seen in apoptotic cells are executed by caspases, which are regulated by the BCL-2 family of proteins. This study investigated whether these components of the apoptotic cascade are present throughout human preimplantation development. Developing and arrested two pronucleate embryos at all stages were incubated with a fluorescently tagged caspase inhibitor that binds only to active caspases, fixed, counterstained with 4,6-diamidino-2-phenylindole (DAPI) to assess nuclear morphology and examined using confocal microscopy. Active caspases were detected only after compaction, at the morula and blastocyst stages, and were frequently associated with apoptotic nuclei. Occasional labelling was seen in arrested embryos. Expression of proapoptotic BAX and BAD and anti-apoptotic BCL-2 was examined in single embryos using RT-PCR and immunohistochemistry. BAX and BCL-2 mRNAs were expressed throughout development, whereas BAD mRNA was expressed mainly after compaction. Simultaneous expression of BAX and BCL-2 proteins within individual embryos was confirmed using immunohistochemistry. The onset of caspase activity and BAD expression after compaction correlates with the previously reported appearance of apoptotic nuclei. As in other types of cell, human embryos express common molecular components of the apoptotic cascade, although apoptosis appears to be suppressed before compaction and differentiation.

Are mechanisms of exocytosis neurotransmitter specific?

In their review, Langley and Grant (1997) investigate the question whether mechanisms of exocytosis are neurotransmitter specific. There is now much evidence that the mechanisms governing the exocytosis of the two principal storage organelles—granules (large dense core vesicles) and electron-lucent vesicles—differ. But much less is known concerning potential differences in the release mechanisms of electron-lucent vesicles that store different types of fast neurotransmitters or of granules in different types of neurons. It is an open question whether there is a unifying control mechanism for the exocytosis of, for example, a peptide-containing granule of a glutamatergic neuron, a chromaffin granule, a noradrenergic granule or a granule from a neurosecretory neuron in the pituitary. The small electron-lucent synaptic vesicles of various kind apparently share common molecular components of regulated release. They carry the calcium sensor synaptotagmin, small GTP-binding proteins of the rab3 group or the v-SNARE synaptobrevin. Nevertheless, there may be differences in the regulatory mechanisms. This concerns the type of calcium channel involved or the absence of some of the presynaptic molecules such as rab3a, synapsin I or the t-SNAREs SNAP-25 or syntaxin from distinct types of neurons or sensory cells.

COMPARATIVE STUDIES ON S-GLYCOPROTEINS PURIFIED FROM DIFFERENT S-GENOTYPES IN SELF-INCOMPATIBLE BRASSICA SPECIES II. IMMUNOLOGICAL SPECIFICITIES

Antisera were prepared by immunization of apparently purified S-glycoproteins; one from an S allele of Brassica campestris and two from S alleles of B. oleracea. Each antiserum was reactive not only with the homologous S-glycoprotein but also with the heterologous ones, i.e. with the S-glycoproteins of the other S alleles of the same locus. In double diffusion tests, a spur against the heterologous S-glycoproteins suggested heterogeneity of the glycoproteins. The heterogeneity appears to involve a component of the molecule in which the genotypic specificity of an S-glycoprotein resides, probably, for the recognition site. Some molecular components are common to all tested S-glycoproteins and in this respect are like the public antigens of the MHC locus of mammals. The common molecular components were recognized between the S-allele-specific glycoproteins within B. oleracea and also between them and those of B. campestris. No S-specific substances were detected in buffer soluble homogenates of style, ovary or anther. However, these homogenates contained substances that had structures similar to the corresponding common parts of the S-glycoproteins.