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PubMed2005

Analysis of the human brain in primary progressive multiple sclerosis with mapping of the spatial distributions using 1H MR spectroscopy and diffusion tensor imaging.

Primary progressive multiple sclerosis (ppMS; n=4) patients and controls (n=4) were examined by 1H magnetic resonance spectroscopy (MRS) and diffusion tensor imaging (DTI) in order to map choline (Cho), creatine and N-acetylaspartate (NAA), the fractional anisotropy (FA) and the apparent diffusion constant (ADC). After chemical shift imaging (point-resolved spectroscopy, repetition time/echo time 1,500 ms/135 ms) of a supraventricular volume of interest of 8x8x2 cm3 (64 voxels) MRS peak areas were matched to the results of DTI for the corresponding volume elements. Mean FA and NAA values were reduced in the ppMS patients (P<0.01, both) and the ADC increased (P<0.02). The spatial distribution of NAA showed strong correlation to ADC in both ppMS patients and controls (r =-0.74 and r= -0.70; P<0.00001, both), and weaker correlations to FA (r=0.49 and r=0.41; P<0.00001, all). FA and ADC also correlated significantly with Cho in patients and controls (P<0.00001, all). The relationship of Cho and NAA to the ADC and the FA and thus to the content of neuronal structures suggests that these metabolite signals essentially originate from axons (NAA) and the myelin sheath (Cho). This is of interest in view of previous reports in which Cho increases were associated with demyelination and the subsequent breakdown of neurons.

Adult↗
PubMed1999

Stochastic model of central synapses: slow diffusion of transmitter interacting with spatially distributed receptors and transporters.

A detailed mathematical analysis of the diffusion process of neurotransmitter inside the synaptic cleft is presented and the spatio-temporal concentration profile is calculated. Using information about the experimentally observed time course of glutamate in the cleft the effective diffusion coefficient Dnet is estimated as Dnet approximately 20-50 nm(2) microseconds(-1), implying a strong reduction compared with free diffusion in aqueous solution. The tortuosity of the cleft and interactions with transporter molecules are assumed to affect the transmitter motion. We estimate the transporter density to be 5170 to 8900 micrometer(-2) in the synaptic cleft and its vicinity, using the experimentally observed time constant of glutamate. Furthermore a theoretical model of synaptic transmission is presented, taking the spatial distribution of post-synaptic (AMPA-) receptors into account. The transmitter diffusion and receptor dynamics are modeled by Monte Carlo simulations preserving the typically observed noisy character of post-synaptic responses. Distributions of amplitudes, rise and decay times are calculated and shown to agree well with experiments. Average open probabilities are computed from a novel kinetic model and are shown to agree with averages over many Monte Carlo runs. Our results suggest that post-synaptic currents are only weakly potentiated by clustering of post-synaptic receptors, but increase linearly with the total number of receptors. Distributions of amplitudes and rise times are used to discriminate between different morphologies, e.g. simple and perforated synapses. A skew in the miniature amplitude distribution can be caused by multiple release of pre-synaptic vesicles at perforated synapses.

Animals↗
PubMed1988

Diurnal growth of tall fescue leaf blades : I. Spatial distribution of growth, deposition of water, and assimilate import in the elongation zone.

Tall fescue leaf blades elongate at near constant rates during most of the light and dark periods of the diurnal cycle, with the dark rate being higher by 60 to 65%. Our objective was to determine relationships among diurnal rates of leaf elongation, deposition of water and deposition of dry matter (DM) into the elongation zone. Two separate experiments were conducted, both with a 15-hour photoperiod and constant 21 degrees C at the growth zone. Increased rates of leaf elongation in darkness were due to proportionally increased rates of elongation of 4-millimeter segments of the elongation zone. Length of the total elongation zone was 30 millimeters in both light and darkness. The spatial distribution of water contents in the elongation zone varied little during the diurnal cycle. Thus, dark stimulation of leaf elongation rate (+65%) and of water deposition (+77%) into elongation zones were similar. Water content per unit leaf length increased by 50% between the basal and distal limits of the elongation zone, indicating that tissue also grew in the lateral and vertical dimensions. Longitudinal growth of tissue, however, allowed 5 to 7 times more water deposition into the elongation zone than growth in cross-sectional area. This relationship was similar in light and darkness. In both light and darkness net rates of DM deposition (microgram per millimeter leaf length per hour) increased from the zone of cell division towards the region of most active elongation, 10 to 15 millimeters from the ligule, then decreased towards the distal end of the elongation zone. Net DM deposition rates (microgram per hour) integrated over the 30-millimeter elongation zone were similar during light and darkness. Thus, DM in the elongation zone was diluted during darkness as a result of increased water deposition. Net DM deposition rates at and above the distal end of the elongation zone were clearly positive during the light, but were close to zero or negative in darkness. Thus, DM deposition into the elongation zone and the adjacent recently expanded tissue was differentially affected in the diurnal cycle, DM deposition occurred in both tissues in light, but was restricted to the elongation zone in darkness.

Journal Article↗
PubMed2004

Nonperturbing measurements of spatially distributed underwater acoustic fields using a scanning laser Doppler vibrometer.

Localized changes in the density of water induced by the presence of an acoustic field cause perturbations in the localized refractive index. This relationship has given rise to a number of nonperturbing optical metrology techniques for recording measurement parameters from underwater acoustic fields. A method that has been recently developed involves the use of a Laser Doppler Vibrometer (LDV) targeted at a fixed, nonvibrating, plate through an underwater acoustic field. Measurements of the rate of change of optical pathlength along a line section enable the identification of the temporal and frequency characteristics of the acoustic wave front. This approach has been extended through the use of a scanning LDV, which facilitates the measurement of a range of spatially distributed parameters. A mathematical model is presented that relates the distribution of pressure amplitude and phase in a planar wave front with the rate of change of optical pathlength measured by the LDV along a specifically orientated laser line section. Measurements of a 1 MHz acoustic tone burst generated by a focused transducer are described and the results presented. Graphical depictions of the acoustic power and phase distribution recorded by the LDV are shown, together with images representing time history during the acoustic wave propagation.

Journal Article↗
PubMed2002

Spatial distribution of total, ammonia-oxidizing, and denitrifying bacteria in biological wastewater treatment reactors for bioregenerative life support.

Bioregenerative life support systems may be necessary for long-term space missions due to the high cost of lifting supplies and equipment into orbit. In this study, we investigated two biological wastewater treatment reactors designed to recover potable water for a spacefaring crew being tested at Johnson Space Center. The experiment (Lunar-Mars Life Support Test Project-Phase III) consisted of four crew members confined in a test chamber for 91 days. In order to recycle all water during the experiment, an immobilized cell bioreactor (ICB) was employed for organic carbon removal and a trickling filter bioreactor (TFB) was utilized for ammonia removal, followed by physical-chemical treatment. In this study, the spatial distribution of various microorganisms within each bioreactor was analyzed by using biofilm samples taken from four locations in the ICB and three locations in the TFB. Three target genes were used for characterization of bacteria: the 16S rRNA gene for the total bacterial community, the ammonia monooxygenase (amoA) gene for ammonia-oxidizing bacteria, and the nitrous oxide reductase (nosZ) gene for denitrifying bacteria. A combination of terminal restriction fragment length polymorphism (T-RFLP), sequence, and phylogenetic analyses indicated that the microbial community composition in the ICB and the TFB consisted mainly of Proteobacteria, low-G+C gram-positive bacteria, and a Cytophaga-Flexibacter-Bacteroides group. Fifty-seven novel 16S rRNA genes, 8 novel amoA genes, and 12 new nosZ genes were identified in this study. Temporal shifts in the species composition of total bacteria in both the ICB and the TFB and ammonia-oxidizing and denitrifying bacteria in the TFB were also detected when the biofilms were compared with the inocula after 91 days. This result suggests that specific microbial populations were either brought in by the crew or enriched in the reactors during the course of operation.

Ammonia↗
PubMedDate not supplied

Spatial distribution of keratan sulfate in the rabbit cornea following photorefractive keratectomy.

PURPOSE: To examine the keratan sulfate content of the stroma and to assess its correlation with the healing process (epithelialization and keratocyte density) after photorefractive keratectomy (PRK). METHODS: Using an Aesculap Meditec MEL 70(G-scan) excimer laser, -6.0 diopters (6.0-mm diameter, 82 microm photoablation depth), PRK was carried out on the right eye of 32 New Zealand pigmented rabbits. After enucleation (at days 1, 4, 7, 14, and 28 and months 2, 3, and 7; sub-groups of 4 animals), fluorescent immunohistochemistry was performed on sections from the central comea using monoclonal mouse anti-keratan-sulfate antibody, immunohistochemistry with proliferative cell nuclear antigen antibody, and hematoxylin-eosin histology. The left, untreated eyes served as controls. Cellular morphology and spatial distribution of keratan sulfate were recorded, stromal thickness measured, and keratocyte density calculated. RESULTS: Keratan sulfate was found on the surface of migrating epithelial cells in the early stage (from days 1 to 7). In the stroma, three phases were noted. (Phase 1) Day 1 to 14, intense granular fluorescence appeared in the anterior stroma with hypocellularity. (Phase 2) Month 1 to 2, newly synthesized lamellar keratan sulfate restored the repopulating anterior stroma. Endothelial cells became keratan sulfate positive, while in the posterior stroma, lamellar-form keratan sulfate increased from week 1 and peaked at month 1 (100% increase). (Phase 3) Month 2 to 7, remodeling and deposition of keratan sulfate was noted, which was produced in phase 2. CONCLUSIONS: Keratan sulfate was found in the epithelium, stroma, and endothelium. By controlling the interlamellar spacing, keratan sulfate plays a role in postoperative edema, remodeling of the corneal stroma, and simultaneous regulation of inflammation after PRK.

Animals↗
PubMed1990

The magnitude, time course and spatial distribution of current induced in salamander rods by cyclic guanine nucleotides.

1. Cyclic GMP was introduced into isolated salamander rods through a tight-seal electrode attached to the inner segment while the outer segment was held in a suction electrode; nucleotide-induced membrane current was recorded by both electrodes. After 3-15s of nucleotide exposure the cells were stimulated with intense, brief flashes, which suppressed 90-95% of the induced membrane current. 2. The magnitude of the induced light-sensitive current depended little on the pipette cyclic GMP concentration in the range 10-20 nM: the mean whole-cell current magnitude was 1256 +/- 160 pA (mean +/- 2 S.E.M., n = 41). 3. Experiments and analyses addressed hypotheses about the nature of the magnitude limitation on the induced current. It was shown that the spatial distribution of nucleotide, the residual series resistance of the whole-cell electrode, and the diminution of the ion gradients driving the induced current did not limit the current magnitude by more than 20%. 4. In contrast, the hypothesis that outer segment internal longitudinal resistance severely limits the magnitude of the cyclic GMP-induced current was supported by experiments in which various lengths of the outer segment were drawn into the suction electrode. These showed that the ratio of nucleotide-induced light-sensitive current collected by the suction electrode to that collected by a whole-cell electrode decreased steeply as a function of outer segment length excluded from the suction electrode, having an apparent space constant of 5-7 microns. 5. A cable model of the rod was developed and used to analyse the magnitude of the nucleotide-induced currents. The data are consistent with an outer segment longitudinal resistance of 1-4 M omega microns-1, and a maximum (space-clamped) light-sensitive current density of 313 pA microns-1, equivalent to a total induced current of 7200 pA (23 microns outer segment). 6. A diffusion model was developed and combined with the non-linear cable model to provide an account for the time course of the induced membrane currents. The results are consistent with an effective longitudinal diffusion coefficient of cyclic GMP in the outer segment of 3-10 microns2 s-1, and Hill coefficient of 2-3 for the cyclic GMP gating of the light-sensitive conductance. 7. 8-Bromo-cyclic GMP also caused the light-sensitive membrane current to increase to about the same magnitude as did cyclic GMP.(ABSTRACT TRUNCATED AT 400 WORDS)

Action Potentials↗
PubMed1995

Spatially distributed responses induced by contrast reversal in cat visual cortex.

Field potentials were recorded from cat striate cortex, either between an epidural screw electrode and a cannula-electrode inserted deep in the gray matter (transcortical recording) or with a pair of metal microelectrodes. Electrodes were placed bilaterally near the cortical projection of the area centralis. The horizontal separation of the recording tips was approximately 2 mm and approximately 300 microns, respectively. The area of the visual field providing input to the recording site (receptive field) was determined by measuring the field potentials generated by contrast reversal of high-contrast, achromatic bar gratings. Five-degree-diameter grating patches were presented individually over a large area of the visual field. The gratings were contrast-reversed at 4, 6 or 10 Hz, while also being swept in spatial frequency between 0.56 and 5.24 c/deg. The receptive fields were approximately 20 deg across or more, substantially larger than expected on the basis of cortical retinotopy. Responses were also elicited by stimulation of the hemi-field contralateral to that contributing to the classical receptive field, implicating the presence of a callosal projection. The large, spatially distributed receptive fields consisted of patches of high and low sensitivity. Continuous cortical infusion of either 100 microM tetrodotoxin or 10 mM muscimol at the recording site totally suppressed the transcortically recorded field potentials, proving that the local field potentials were generated postsynaptically. The present findings suggest that a cluster of cortical cells near the projection site of the area centralis receives input from remote cortical regions to an extent that is comparable with that of anatomically demonstrated long-range lateral connections.

Animals↗
PubMed2000

Differential spatial distribution and temporal regulation of tissue inhibitor of metalloproteinase mRNA expression during rat central nervous system development.

The elucidation of the cellular and molecular mechanisms governing the maturation of the central nervous system (CNS) is rapidly emerging. Cell-cell and cell-matrix interactions play critical roles in all phases of developmental tissue remodeling. Throughout development, an intricate balance between extracellular matrix synthesis and degradation is preserved by the opposing actions of matrix metalloproteinases (MMPs) and their specific inhibitors, the tissue inhibitors of metalloproteinases (TIMPs). Although recent evidence suggests that TIMPs exert diverse cell biological functions distinct from their MMP-inhibitory activities, few studies have investigated MMP or TIMP expression during CNS development. The present report analyzes the mRNA expression of the four known TIMPs throughout the course of embryonic and postnatal rat CNS development. The results clearly demonstrate the unique spatial distribution and temporal regulation of TIMP expression and suggest a distinct role for each TIMP during CNS development.

Animals↗
PubMed1994

Spatial distribution of carotid intimal-medial thickness as measured by B-mode ultrasonography.

BACKGROUND AND PURPOSE: Measurements of intimal-medial thickness (IMT) of the carotid artery by B-mode ultrasonography are widely used as markers of atherosclerosis. This report describes empirical features of these measurements to characterize their distribution within arterial wall segments, to explore their potential as study outcome measures, and to examine their links with traditional risk factors for cardiovascular disease. METHODS: Sequential transverse measurements of IMT in the carotid arteries were made in 899 participants from the Asymptomatic Carotid Artery Progression Study (ACAPS) at baseline. Data from 17 intrasegment sites in each of 12 arterial wall segments were used to describe patterns of thickness and visualization and to characterize cross-sectional area, severity, and roughness/irregularity by the intrasegment averages, maxima, and SDs of IMT, respectively. RESULTS: Serial correlations of IMT measurements indicated localized and diffuse features of disease. The spatial distribution of IMT had two dominant features: overall mass and mass relative to roughness. The validity of these features was demonstrated by their correlation to known risk factors for carotid atherosclerosis: body mass index, age, high-density lipoprotein cholesterol, systolic blood pressure, smoking, and sex. CONCLUSIONS: Both the mean and maxima of intrasegment measurements appear to be good candidates for use in clinical studies. B-mode ultrasonography has validity for the description of IMT roughness and shape. Both of these features are linked to cardiovascular risk factors, which supports the multifaceted nature of atherosclerosis.

Adult↗
PubMed1995

Spatial distribution of L-selectin (CD62L) on human lymphocytes and transfected murine L1-2 cells.

We have examined the topographical distribution of L-selectin on surface membrane domains of human lymphocytes and murine L1-2 cells transfected to express human L-selectin. L-selectin was immunolocalized using murine monoclonal DREG 200 Fab antibody and a 12 nm colloidal gold-conjugated secondary antibody. Cell surface morphology and surface distribution of gold-labelled L-selectin were visualized using backscatter electron images obtained by high-resolution, field emission scanning electron microscopy. The topographical morphologies of lymphocytes of both types were complex. The surface of human lymphocytes was composed of both microvilli and ruffles; that of the murine cells was composed of long microvilli and few, if any, ruffles. L-selectin on human lymphocytes was observed primarily as focal clusters on the apical surfaces of ruffles and microvilli. Similarly, on the transfected murine cells, L-selectin was detected predominantly on the apical surface of microvilli. We conclude that L-selectin has a common spatial distribution and clustered organization on all leukocytes examined to-date, and that these features of receptor expression likely facilitate rolling of circulating leukocytes on the endothelial surface.

Animals↗
PubMed2003

Estimating and analyzing the spatial distribution of soil organic carbon in China.

Research on the terrestrial carbon cycle is an important component in the study of global change. Soil organic carbon, as the main part of the terrestrial carbon reservoir, plays an important role in the Earth's carbon cycle. To accurately estimate soil organic carbon storage, its composition and dynamic change must be determined. This presents a challenge to research on the soil carbon cycle, especially in China where the nationwide soil organic carbon reservoir largely remains unknown. This paper reports a research project that attempts to estimate the nationwide soil organic carbon reservoir. Data from 2473 soil profiles from the second national soil survey were collected and GIS technology was employed to quantify the national soil carbon reservoir. The analytical results show that the total amount of soil organic carbon is about 92.4 Pg (Pg = 10(15) g) and that the average carbon density is about 10.53 kg C m(-2). The spatial distribution of soil organic carbon was also analyzed and mapped. This study presents basic data and an analysis method for carbon-cycle studies and also provides scientific support for policy-making efforts to control CO2 emissions in China.

Carbon↗
PubMed1980

Spatial distribution of somatosensory responses evoked by tapping the tongue and finger in man.

Early components of the somatosensory potential (SEP) evoked by tactile stimulation of the tongue were recorded from the scalp in 7 normal subjects and compared with those resulting from taps on the middle finger. (1) Unipolar but not bipolar recording of SEP to tapping the tongue failed to differentiate the early components from large EEG deflections of myogenic origin. No such contamination was seen in either unipolar or bipolar recording of SEP following taps on the finger. (2) The early components evoked by tapping the tongue consisted of 4 main deflections; the first negative wave (N1) peaking at about 13 msec after the stimulus was followed by the first positive (P1), second negative (N2) and second positive (P2) wave peaking at about 23, 32 and 44 msec, respectively. Each wave had a shorter latency by several msec than the corresponding wave elicited by taps on the finger. (3) To demonstrate the spatial distribution of a SEP wave over the scalp, a method of amplitude transformation of bipolar records was developed. Topography of the transformed amplitudes of P1 wave, thus obtained while tapping the tongue differed from that obtained while tapping the finger; the former indicated bilateral distribution of the P1 with the maximal amplitude at contralateral (T3 or T5) and ipsilateral (T4 or T6) temporal loci, whereas, in the latter, the distribution was most prominent over the contralateral posterior quadrant with the maximum at parietal locus (C3). P1 wave in SEP thus appeared to represent excitation of the primary cortical neurons responding to tactile stimulation of the different body areas.

Adult↗
PubMed1992

Spatial distribution of active genes implicated in the regulation of insulin-like growth factor stimulatory loops in human decidual and placental tissue of first-trimester pregnancy.

We have previously shown that the insulin-like growth factor-2 (IGF-2) gene is partially coexpressed with the IGF-1 and -2 receptor genes in proliferative cytotrophoblasts of the human extraembryonic tissue. Here we show that high levels of IGF-2 gene expression are not restricted to the embryonic tissue but can also be found in the decidua compacta. The IGF-2 gene is thus expressed at high levels in the mesenchymal stroma of the decidua to establish potentially short-range communication with primarily IGF-1 receptor-positive mesenchymal stroma cells. Conversely, the glandular and surface epithelia coexpress the IGF-1 receptor and IGF-1 genes, while the IGF-2 gene is not detected above background levels. The potential control mechanisms of these cell-cell signalling pathways were investigated by the analysis of the spatial distribution of active IGF binding proteins (IGFBP) genes. The IGFBP-3 gene is coexpressed with the IGF-2 gene in proliferative cytotrophoblasts of the embryonic placenta. While active IGFBP-1 and -2 genes in our hands cannot be detected in the embryonic placenta, all three IGFBP genes are expressed in complex and overlapping patterns in the decidua compacta. The results are discussed in terms of how the various IGFBP genes may operate in different cell types to restrict IGF local stimulatory pathways.

Blotting, Northern↗
PubMed2006

Spatial distribution of natural enrichments of arsenic, selenium, and uranium in a minerotrophic peatland, Gola di Lago, Canton Ticino, Switzerland.

Gola di Lago is a small (ca. 3 ha), minerotrophic peatland in Canton Ticino, southern Switzerland. Chemical analyses of peat show remarkable concentrations of As, Se, and U. Coring at regular intervals (19 sites) revealed several zones of pronounced accumulation, with As concentrations up to 350 mg kg(-1) (2000 mg kg(-1) on a mineral matter basis). Both Fe and S are also enriched at this depth, suggesting that redox-related transformations have affected all three elements. High concentrations of Se (up to 28 mg kg(-1)) and U (up to 470 mg kg(-1)) were also detected, representing on a mineral matter basis 350 and 2900 mg kg(-1), respectively. An intermittent stream entering the peatland contained up to 400 microg of As L(-1), but the permanent stream leaving the mire contains <2 microg L(-1). A three-dimensional map of the spatial distribution of As shows that the main source of As is the intermittent stream and not the basal, mineral sediment underlying the peatland. Arsenic is highly enriched not only in shallow peat layers at the interface between the stream and peatland today but also in deeper peat layers in the center of the mire, at what must have been the stream-peat interface in the past. By sequential extraction of fresh peat samples, 100% of the As could be extracted from a shallow sample but only 19% from a sample taken from the deeper layers. In both cases, most of the As was associated with the organic matter fraction (73% and 57% respectively). Although this peatland is an effective geochemical trap for As in the stream waters, the mechanisms of removal remain unclear.

Arsenic↗
PubMed2006

Investigation of spatial distribution of sound field parameters in ultrasound cleaning baths under the influence of cavitation.

Ultrasound cleaning baths fitting the full range from micromechanical components up to large machine parts, are regularly used in industry and in the lab. Despite the large number of applications, generally approved principles and objective criteria for parameter settings which allow an efficient operation are non-existent. The empirical selections of the running parameters often impede an optimization in terms of produce and reproducibility. One proposal for an objective description of the processes is the characterization of the sound field in the cleaning bath, which causes cavities, and subsequently, the cleaning process. Sound field measurements in the appropriate frequency range from 20kHz up to more then 1MHz incorporate a number of problems, such as large sensors disturbing the sound field, a lack of accuracy and the risk of being destroyed by cavitation bubbles. Measurement systems based on optical fiber tips and piezo-electrical hydrophones will be presented, which fulfil the accuracy requirements and withstand ultrasound fields with high power and cavitation. The spatial distribution of sound field parameters such as positive and negative peak pressure, amplitudes of fundamentals, harmonics and sub-harmonics as well as the energy density and spectral density in several frequency ranges are determined in experiments. Finally, the determined field parameters are related to the cavitation effects by means of photometric analysis of perforated aluminium foil. Perforations as well as intentions are analyzed and quantified from scanner images of the exposed foil samples using special image processing software. The experiments indicate clear differences in the structure of the sound fields and the spectral properties between the several types of cleaning baths, transducer arrangements and excitations.

Detergents↗
PubMed1995

Molecular characterization and spatial distribution of SAP97, a novel presynaptic protein homologous to SAP90 and the Drosophila discs-large tumor suppressor protein.

Synapses are highly specialized sites of cell-cell contact involved in signal transfer. The molecular mechanisms modulating the assembly and stability of synapses are unknown. We previously reported the identification of a 90 kDa synapse-associated protein, SAP90, that is localized at the presynaptic termini of inhibitory GABAergic synapses. SAP90 is a mosaic protein composed of three 90 amino acid residue repeats, an SH3 domain and a region homologous to guanylate kinases. SAP90 shares domain specific homology with a family of proteins involved in the assembly and possibly stability of sites of cell contact. These include the product of the lethal(1) discs-large-1 (dlgA) tumor suppressor gene and the zonula occludens proteins ZO-1, ZO-2. The further characterization of cDNA clones encoding components of synaptic junctions has lead to the identification of a 97 kDa protein, called SAP97, that exhibits a strong overall sequence similarity to SAP90. The present study was undertaken to determine the spatial distribution of SAP97, and to reveal further clues to the possible roles of these proteins in synapses. Light and immunoelectron microscopic analysis of the rat hippocampal formation revealed that SAP97 is localized in the presynaptic nerve termini of excitatory synapses. In other brain regions, SAP97 is found in and along bundles of unmyelinated axons. SAP97 is not restricted to the CNS, but is also present at the basal lateral membrane between a variety of epithelial cells. In cultured T84 cells, it is restricted to the cytoplasmic surface of the plasma membranes between adjacent cells, but not at the edges of cells lacking cell-cell contact suggesting a role for SAP97 in cell adhesion. These data suggest that members of the SAP90/SAP97 subfamily may be involved in the site specific assembly, stability or functions of membrane specialization at sites of cell-cell contact.

Adaptor Proteins, Signal Transducing↗
PubMed1995

Spatial distribution of epidermal growth-factor transcripts and effects of exogenous epidermal growth factor on the pattern of the mouse dental lamina.

The initiation of odontogenesis is characterized by the site-specific proliferation of mandibular epithelium in the formation of the dental lamina. The epidermal growth factor (EGF) gene is expressed in the developing mandible immediately before the appearance of the dental lamina. This expression is necessary for the formation of the dental lamina and subsequent development of teeth. Previous work has demonstrated that retinoids and EGF may interact in the establishment of the pattern of the dentition. In the present study explanted mandibles that were treated with exogenous EGF (40 ng/ml of medium) contained supernumerary buds of mandibular epithelium in the diastema region. These pattern changes were the same as in previous retinoid-treated explants. These results, in addition to the previously reported effects of retinoids on the expression of the EGF gene, support the hypothesis that retinoids and EGF interact in controlling, at least in part, the pattern of the dentition by affecting the pattern of the dental lamina. The spatial distribution of EGF transcripts was also characterized. The location of EGF transcripts in the mesenchyme adjacent to the mandibular epithelium suggests a paracrine mechanism in the stimulation of epithelial proliferation in the formation of the dental lamina.

Animals↗