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At least 883 records · Page 49Linked to original sources
PubMed2005

Soft lithographic patterning of supported lipid bilayers onto a surface and inside microfluidic channels.

We present simple soft lithographic methods for patterning supported lipid bilayer (SLB) membranes onto a surface and inside microfluidic channels. Micropatterns of polyethylene glycol (PEG)-based polymers were fabricated on glass substrates by microcontact printing or capillary moulding. The patterned PEG surfaces have shown 97 +/- 0.5% reduction in lipid adsorption onto two dimensional surfaces and 95 +/- 1.2% reduction inside microfluidic channels in comparison to glass control. Atomic force microscopy measurements indicated that the deposition of lipid vesicles led to the formation of SLB membranes by vesicle fusion due to hydrophilic interactions with the exposed substrate. Furthermore, the functionality of the patterned SLBs was tested by measuring the binding interactions between biotin (ligand)-labeled lipid bilayer and streptavidin (receptor). SLB arrays were fabricated with spatial resolution down to approximately 500 nm on flat substrate and approximately 1 microm inside microfluidic channels, respectively.

Dimethylpolysiloxanes↗
PubMed1981

The problem of periodic patterns in embryos.

A segmented body-plan has developed at least twice during metazoan evolution: in the lineage including annelids and arthropods, where the segment is the unit of body structure, and in the ancestors of vertebrates, where a primary segmentation of the middle, mesodermal cell layer of the embryo imposes a spatially periodic character upon derivatives of other layers. The mechanism controlling the development of these periodic patterns has the property that the number of the serially homologous structures formed within each species is largely independent of the linear dimension, or scale, at which pattern formation occurs in individual cases. In this they contrast with other patterns of dispersed, homologous structures occurring in animal epidermis and dermis. The performance of various classes of model for the control of number in vertebrates somite formation are compared, in the light of experimentally and naturally observable properties of this aspect of pattern.

Animals↗
PubMed2000

Expression of mRNA encoding IGF-I, IGF-II and type 1 IGF receptor in bovine ovarian follicles.

IGFs regulate gonadotrophin-stimulated proliferation and differentiation of granulosa and theca cells in vitro. However, the detailed pattern of mRNA expression of IGFs in bovine follicles remains controversial. The objectives of this study were therefore to describe the temporal and spatial pattern of expression of mRNA encoding IGF-I, IGF-II and the type 1 IGF receptor in bovine follicles in vivo. The expression of mRNA encoding IGF-II was detected in theca tissue from around the time of antrum formation up to and during the development of dominance. No IGF-II mRNA expression was detected in granulosa cells. In the majority of follicles we were unable to detect mRNA encoding IGF-I in either granulosa or theca tissue from follicles at any stage of development. Occasionally low amounts of mRNA encoding IGF-I were detected in the theca externa and connective tissue surrounding some follicles. Type 1 IGF receptor mRNA was detected in both granulosa and theca cells of preantral and antral follicles. Expression was greater in granulosa tissue compared with theca tissue. We also measured IGF-I and -II mRNA in total RNA isolated from cultured granulosa and theca cells using reverse transcriptase PCR. In contrast to the in vivo results, IGF-II mRNA was detected in both granulosa and theca tissue. IGF-I mRNA was detected in theca tissue and in very low amounts in granulosa cells. Using a specific IGF-I RIA we were unable to detect IGF-I immunoreactivity in granulosa conditioned cell culture media. Using immunohistochemistry we detected IGF-I immunoreactivity in some blood vessels within the ovarian stroma. We conclude from these results that IGF-II is the principal intrafollicular IGF ligand regulating the growth of bovine antral follicles. In preantral follicles the expression of mRNA encoding type 1 IGF receptor but absence of endogenous IGF-I or -II mRNA expression, highlights a probable endocrine mechanism for the IGF regulation of preantral follicle growth.

Animals↗
PubMed1998

Role of the ZWILLE gene in the regulation of central shoot meristem cell fate during Arabidopsis embryogenesis.

Postembryonic development in higher plants is marked by repetitive organ formation via a self-perpetuating stem cell system, the shoot meristem. Organs are initiated at the shoot meristem periphery, while a central zone harbors the stem cells. Here we show by genetic and molecular analyses that the ZWILLE (ZLL) gene is specifically required to establish the central-peripheral organization of the embryo apex and that this step is critical for shoot meristem self-perpetuation. zll mutants correctly initiate expression of the shoot meristem-specific gene SHOOT MERISTEMLESS in early embryos, but fail to regulate its spatial expression pattern at later embryo stages and initiate differentiated structures in place of stem cells. We isolated the ZLL gene by map-based cloning. It encodes a novel protein, and related sequences are highly conserved in multicellular plants and animals but are absent from bacteria and yeast. We propose that ZLL relays positional information required to maintain stem cells of the developing shoot meristem in an undifferentiated state during the transition from embryonic development to repetitive postembryonic organ formation.

Amino Acid Sequence↗
PubMed2003

Comparative analysis of fatty acid amide hydrolase and cb(1) cannabinoid receptor expression in the mouse brain: evidence of a widespread role for fatty acid amide hydrolase in regulation of endocannabinoid signaling.

Fatty acid amide hydrolase (FAAH) catalyses hydrolysis of the endocannabinoid arachidonoylethanolamide ("anandamide") in vitro and regulates anandamide levels in the brain. In the cerebellar cortex, hippocampus and neocortex of the rat brain, FAAH is located in the somata and dendrites of neurons that are postsynaptic to axon fibers expressing the CB(1) cannabinoid receptor [Proc R Soc Lond B 265 (1998) 2081]. This complementary pattern of FAAH and CB(1) expression provided the basis for a hypothesis that endocannabinoids may function as retrograde signaling molecules at synapses in the brain [Proc R Soc Lond B 265 (1998) 2081; Phil Trans R Soc Lond 356 (2001) 381] and subsequent experimental studies have confirmed this [Science 296 (2002) 678]. To assess more widely the functions of FAAH in the brain and the potential impact of FAAH activity on the spatiotemporal dynamics of endocannabinoid signaling in different regions of the brain, here we have employed immunocytochemistry to compare the distribution of FAAH and CB(1) throughout the mouse brain, using FAAH(-/-) mice as negative controls to validate the specificity of FAAH-immunoreactivity observed in wild type animals. In many regions of the brain, a complementary pattern of FAAH and CB(1) expression was observed, with FAAH-immunoreactive neuronal somata and dendrites surrounded by CB(1)-immunoreactive fibers. In these regions of the brain, FAAH may regulate postsynaptic formation of anandamide, thereby influencing the spatiotemporal dynamics of retrograde endocannabinoid signaling. However, in some regions of the brain such as the globus pallidus and substantia nigra pars reticulata, CB(1) receptors are abundant but with little or no associated FAAH expression and in these brain regions the spatial impact and/or duration of endocannabinoid signaling may be less restricted than in regions enriched with FAAH. A more complex situation arises in several regions of the brain where both FAAH and CB(1) are expressed but in a non-complementary pattern, with FAAH located in neurons and/or oligodendrocytes that are proximal but not postsynaptic to CB(1)-expressing axon fibers. Here FAAH may nevertheless influence endocannabinoid signaling but more remotely. Finally, there are regions of the brain where FAAH-immunoreactive neurons and/or oligodendrocytes occur in the absence of CB(1)-immunoreactive fibers and here FAAH may be involved in regulation of signaling mediated by other endocannabinoid receptors or by receptors for other fatty acid amide signaling molecules. In conclusion, by comparing the distribution of FAAH and CB(1) in the mouse brain, we have provided a neuroanatomical framework for comparative analysis of the role of FAAH in regulation of the spatiotemporal dynamics of retrograde endocannabinoid signaling in different regions of the brain.

Amidohydrolases↗
PubMed2004

Developmental expression of otoconin-22 in the bullfrog endolymphatic sac and inner ear.

In amphibians, calcium carbonate crystals are present in the endolymphatic sac and the inner ear. The formation of these crystals is considered to be facilitated by a protein called otoconin-22. We examined the spatial and temporal expression of otoconin-22 during the development of the bullfrog (Rana catesbeiana) using RT-PCR, in situ hybridization (ISH), and immunofluorescence techniques. By RT-PCR, otoconin-22 mRNA was first detected in embryos at Shumway stage 20, and this expression pattern continues in late stages. The first otoconin-22 mRNA-positive reaction was detected in stage 22 embryos in the placode of the endolymphatic sac. Otoconin-22 protein was observed in the epithelial cells of the endolymphatic sac at stage 24. On the other hand, a whole-mount ISH technique showed the first expression of otoconin-22 mRNA in the inner ear, in addition to the endolymphatic sac, at the mid-phase of Shumway stage 25. We discuss the role of otoconin-22 in the formation of calcium carbonate crystals in the endolymphatic sac and inner ear.

Animals↗
PubMed1991

Regulation of achaete-scute gene expression and sensory organ pattern formation in the Drosophila wing.

Adult Drosophila possess a large number of sensory organs, including large and small bristles and other types of sensilla, each arising from a single mother cell at particular positions in a reproducible pattern. Genetic studies have shown that sensory organ pattern formation is partly coordinated by a number of structurally similar, potential heterodimer-forming, helix-loop-helix (HLH) regulatory proteins. Here, by localizing regulatory gene expression during the development of normal and mutant imaginal discs, we show that two positive regulators of sensory neurogenesis, the proneural achaete and scute proteins, initially trans-activate each other and are transiently expressed in identical patterns, including clusters of wing ectodermal cells and the individual sensory mother cells that arise from them. Two negative regulators, hairy and extramacrochaete, suppress sensory neurogenesis by selectively repressing achaete and scute gene expression, respectively, but in different spatial domains and at different developmental stages. Surprisingly, we also find that the level of achaete-scute activity influences the level of hairy expression, thereby providing feedback control upon achaete-scute activity and sensory organ formation. Some or all of these interactions may involve specific dimerization reactions between different combinations of HLH proteins.

Animals↗
PubMedDate not supplied

Acromial spur formation in patients with rotator cuff tears.

In this study we analyzed the acromial spurs of 15 patients with impingement syndrome undergoing open rotator cuff repair. Mineral apposition analysis and quantitative cytochemical techniques for glucose-6-phosphate dehydrogenase (G6PD) activity (pentose phosphate pathway), alkaline phosphatase (ALP) activity (osteoblast activity), and tartrate-resistant acid phosphatase (TRAP) activity (osteoclast phenotype) were used to examine the distribution and level of activity of selected marker enzymes within the acromial spur insertion into the coracoacromial ligament in order to establish whether local behavior of bone cells is consistent with the proposed secondary development of the acromial spur. Our results indicate that G6PD and ALP activity was higher in osteoblasts on the inferior surface compared with the superior surface of the acromial spur in all patients (P <.001). This area correlated to the most intense area of mineral apposition shown by dual tetracycline labeling. TRAP activity revealed a heterogeneous distribution within the samples. A greater G6PD activity per cell (mean increase of 87%) was seen at the tip compared with that in post- and pre-tip zones within the coronal plane (P <.0002). The qualitative and quantitative enzyme analyses show that the acromial insertion of the coracoacromial ligament is actively involved in bone turnover. The spatial distribution patterns of metabolically active bone-forming osteoblastic cells compared with a heterogeneous distribution of TRAP-positive osteoclasts provide evidence of bone remodeling consistent with the morphologic contours of the acromial enthesis. The sites of oxytetracycline labeling appear to correlate with the sites of high ALP and G6PD activity, which supports the concept of spur formation being a secondary phenomenon in the presence of established rotator cuff tears.

Acid Phosphatase↗
PubMed2006

Cooperation between the hippocampus and the entorhinal cortex in spatial memory: a disconnection study.

It has been recently shown that lesions of parahippocampal areas including the entorhinal cortex do not disrupt place learning in the water maze, suggesting that the hippocampo-cortical circuitry is not important for spatial memory [Burwell RD, Saddoris MP, Bucci DJ, Wiig KA. Corticohippocampal contributions to spatial and contextual learning. J Neurosci 2004;24:3826-36]. The aim of the present study was to tax more directly the cooperation between the hippocampus and entorhinal cortex in two different spatial tasks, a place navigation task and a spontaneous object exploration task, using a disconnection procedure. Damaging the entorhinal-hippocampal system induced impairments in the two tasks but only in the spatial object exploration task rats with contralateral lesions displayed a greater deficit than rats with ipsilateral lesions. The results suggest that the cooperation between the hippocampus and the entorhinal cortex is modulated by the nature of the task and the cognitive processes involved in formation of spatial memory.

Animals↗
PubMed2000

Working memory, metacognitive uncertainty, and belief bias in syllogistic reasoning.

Studies of syllogistic reasoning have shown that the size of the belief bias effect varies with manipulations of logical validity and problem form. This paper presents a mental models-based account, which explains these findings in terms of variations in the working-memory demands of different problem types. We propose that belief bias may reflect the use of a heuristic that is applied when a threshold of uncertainty in one's processing--attributable to working-memory overload--is exceeded during reasoning. Three experiments are reported, which tested predictions deriving from this account. In Experiment 1, conclusions of neutral believability were presented for evaluation, and a predicted dissociation was observed in confidence ratings for responses to valid and invalid arguments, with participants being more confident in the former. In Experiment 2, an attempt to manipulate working-memory loads indirectly by varying syllogistic figure failed to produce predicted effects upon the size of the belief bias effect. It is argued that the employment of a conclusion evaluation methodology minimized the effect of the figural manipulation in this experiment. In Experiment 3, participants' articulatory and spatial recall capacities were calibrated as a direct test of working-memory involvement in belief bias. Predicted differences in the pattern of belief bias observed between high and low spatial recall groups supported the view that limited working memory plays a key role in belief bias.

Concept Formation↗
PubMed1993

The Drosophila rhomboid gene mediates the localized formation of wing veins and interacts genetically with components of the EGF-R signaling pathway.

The rhomboid (rho) gene, which encodes a transmembrane protein, is a member of a small group of genes (ventrolateral genes) required for the differentiation of ventral epidermis in the Drosophila embryo. The ventrolateral genes include spitz, which encodes an EGF-like ligand, and Star. The receptor for spitz may be the gene encoding the Drosophila epidermal growth factor-receptor (Egf-r) because the phenotype resulting from partial loss of function of Egf-r is similar to that of ventrolateral group mutants. Among ventrolateral genes encoding cell-surface or secreted proteins, rho is the only member expressed in a localized pattern corresponding to cells requiring the activity of the ventrolateral pathway. In this paper we provide evidence that spatial localization of rho plays an analogous role in establishing vein pattern in the adult wing. rho is expressed in early wing disc cells likely to be wing vein primordia and later is sharply restricted to developing veins. Flies homozygous for the viable rho(ve) allele have missing veins and rho fails to be expressed in rho(ve) mutant wing discs. Ectopic expression of rho during wing development leads to the formation of extra veins. Gene dosage studies among ventrolateral genes suggest that the rho product (Rho) may facilitate Spi-EGF-R signaling, resulting in activation of RAS. We discuss models for how localized expression of Rho may amplify signaling mediated by ubiquitously distributed ligand and receptor components.

Animals↗
PubMed2005

Neurite outgrowth on well-characterized surfaces: preparation and characterization of chemically and spatially controlled fibronectin and RGD substrates with good bioactivity.

Study of axonal growth and ligand-receptor interactions requires specificity and careful characterization of the biomaterial substrates to which the neurons bind. It would be impossible to predict the effects of important variables such as composition, surface density, spatial distribution, and conformation of the ligands on axonal growth of a neuron without highly specific surface characterization. Here, we compare two methods of surface modification (hereafter referred to as "Heterobifunctional Crosslinker" and "Pluronics" methods) used for immobilization of fibronectin (FN) and FN-derived, RGD-containing peptides to the substrates. We also characterized their performance in neurite outgrowth experiments. Various surface analytical techniques such as contact angle measurement, XPS, and time-of-flight secondary ion mass spectrometry (TOF-SIMS) were used for the analysis of the substrates at each step of the two different chemistries involved. FN-patterned surfaces were created by micro-contact printing methods and confirmed by imaging TOF-SIMS, and AFM techniques. After immobilization of FN and/or FN-derived RGD-containing peptide, including the formation of micron-scale patterns of FN, the modified surfaces were plated with neurons from postnatal rat dorsal root ganglia (DRG) and incubated in serum-free medium. Both the peptide- and/or protein-modified substrates supported significantly greater neurite outgrowth than controls, and outgrowth on both substrate chemistries was inhibited by the addition of soluble RGD peptide. Patterned FN surfaces were successful in spatially controlling the neuron attachment and outgrowth.

Adsorption↗
PubMed2001

UV-induced replication arrest in the xeroderma pigmentosum variant leads to DNA double-strand breaks, gamma -H2AX formation, and Mre11 relocalization.

UV-induced replication arrest in the xeroderma pigmentosum variant (XPV) but not in normal cells leads to an accumulation of the Mre11/Rad50/Nbs1 complex and phosphorylated histone H2AX (gamma-H2AX) in large nuclear foci at sites of stalled replication forks. These complexes have been shown to signal the presence of DNA damage, in particular, double-strand breaks (DSBs). This finding suggests that UV damage leads to the formation of DSBs during the course of replication arrest. After UV irradiation, XPV cells showed a fluence-dependent increase in the yield of gamma-H2AX foci that paralleled the production of Mre11 foci. The percentage of foci-positive cells increased rapidly (10-15%) up to fluences of 10 J.(-2) before saturating at higher fluences. Frequencies of gamma-H2AX and Mre11 foci both reached maxima at 4 h after UV irradiation. This pattern contrasts sharply to the situation observed after x-irradiation, where peak levels of gamma-H2AX foci were found to precede the formation of Mre11 foci by several hours. The nuclear distributions of gamma-H2AX and Mre11 were found to colocalize spatially after UV- but not x-irradiation. UV-irradiated XPV cells showed a one-to-one correspondence between Mre11 and gamma-H2AX foci-positive cells. These results show that XPV cells develop DNA DSBs during the course of UV-induced replication arrest. These UV-induced foci occur in cells that are unable to carry out efficient bypass replication of UV damage and may contribute to further genetic variation.

DNA Damage↗
PubMed2002

Propagation of incoherent "white" light and modulation instability in noninstantaneous nonlinear media.

We develop a theory describing propagation of spatially and temporally incoherent light in noninstantaneous nonlinear media, and predict the existence of modulation instability of "white" light. We find that the modulation instability of white light is fundamentally a collective effect, where all the temporal frequencies participate in the formation of a pattern, and self-adjust their respective contributions.

Journal Article↗
PubMed1982

A forced-choice test improves clinical contrast sensitivity testing.

Decreased contrast sensitivity has been demonstrated in early glaucoma, but the deficit in not regularly observed. We designed a prototype for a forced-choice printed test and evaluated it with several other measures of contrast sensitivity. The results also bear on the pattern of loss and the variables which effect performance. Mildly glaucomatous patients show at 6 db (50%) loss of contrast sensitivity at all spatial frequencies tested compared with age matched controls. Moving gratings give the same information as stationary ones, and practice effects are negligible. Contrast sensitivity at or below 2 cycles/degree is poorly correlated with visual acuity and does not change with age in the forced-choice test. Subjective judgment made the apparent contrast threshold higher, age dependent, and more variable, particularly at higher spatial frequencies. The pattern of variability can explain some reports of insignificant effects and why low spatial frequency contrast sensitivity detects glaucoma better than visual acuity. Methods correlated so poorly, despite high reliabilities, that uncontrolled biases must be suspected in subjective measures. Our new forced-choice format was superior to all other tests on at least one formal criterion and always at least equal to them. Improvements in contrast sensitivity screening tests are thus indicated.

Adolescent↗
PubMed1995

Expression of interstitial collagenase during skeletal development of the mouse is restricted to osteoblast-like cells and hypertrophic chondrocytes.

We determined the expression pattern of the matrix metalloproteinase interstitial collagenase (MMP-1) during mouse embryo development using in situ hybridization and immunohistochemistry. Localized MMP-1 mRNA was first detected at 14.5 days postconceptus. The spatial and temporal expression was restricted to areas of endochondral and intramembranous bone formation, such as in the mandibula, maxilla, clavicle, scapula, in the vertebrae, and in the dorsal, but not the ventral part of the ribs. The highest levels of MMP-1 transcripts and MMP-1 protein were found in the metaphyses and diaphyses of the long bones. MMP-1 was expressed by hypertrophic chondrocytes and by osteoblastic cells localized along the newly formed bone trabeculae. No expression was detected in osteoclasts. Two other related members of the MMP family, stromelysin-1 (MMP-3) and stromelysin-2 (MMP-10), were not expressed during days 7.5 and 16.5 of mouse embryogenesis. The tissue-specific expression of MMP-1 and the exclusive ability of interstitial collagenase to digest native collagen of types I, II, III, and X, the major components of bone, cartilage, and tendon, strongly suggests an important and specific function of this enzyme in bone development and remodeling.

Animals↗
PubMed1995

Exclusion of the Wilms tumour gene (WT1) promoter as a site of frequent mutation in Wilms tumour.

WT1 is a tumour suppressor gene expressed in a specific temporal and spatial pattern in the developing kidney. Up to 15% of Wilms tumours have point mutations in the WT1 gene coding sequence. We have now investigated whether mutations in the WT1 promoter could be associated with loss of control WT1 expression and subsequent Wilms tumour formation. Using single-strand conformational polymorphism (SSCP) analysis we analysed 39 sporadic Wilms tumours for WT1 promoter mutations. We found six linked common sequence polymorphisms and two unlinked less frequent polymorphisms which allowed us to identify four tumours with loss of heterozygosity but none with point mutations, small deletions, insertions or rearrangements. We therefore conclude that WT1 promoter mutations are unlikely to play an important role in Wilms tumorigenesis.

Base Sequence↗