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PubMed2002

The influence of a chemical boundary layer on the fixity, spacing and lifetime of mantle plumes.

Seismological observations provide evidence that the lowermost mantle contains superposed thermal and compositional boundary layers that are laterally heterogeneous. Whereas the thermal boundary layer forms as a consequence of the heat flux from the Earth's outer core, the origin of an (intrinsically dense) chemical boundary layer remains uncertain. Observed zones of 'ultra-low' seismic velocity suggest that this dense layer may contain metals or partial melt, and thus it is reasonable to expect the dense layer to have a relatively low viscosity. Also, it is thought that instabilities in the thermal boundary layer could lead to the intermittent formation and rise of mantle plumes. Flow into ascending plumes can deform the dense layer, leading, in turn, to its gradual entrainment. Here we use analogue experiments to show that the presence of a dense layer at the bottom of the mantle induces lateral variations in temperature and viscosity that, in turn, determine the location and dynamics of mantle plumes. A dense layer causes mantle plumes to become spatially fixed, and the entrainment of low-viscosity fluid enables plumes to persist within the Earth for hundreds of millions of years.

Journal Article↗
PubMed2005

Polychlorobiphenyls and polycyclic aromatic hydrocarbons in the sea-surface micro-layer and the water column at Gerlache Inlet, Antarctica.

The enrichment of PCBs (polychlorobiphenyls) and PAHs (polycyclic aromatic hydrocarbons) in the sea-surface micro-layer and depth profile of these pollutants in the water column were investigated at Gerlache Inlet, Terra Nova Bay, Antarctica. Depth profile samplings were repeated three times during the Antarctic summer (from November to February). PCBs and PAHs showed a concentration range in the water column of 30-120 pg l(-1) and 150-400 pg l(-1), respectively, and these values were very much dependent on the suspended matter content. A nearly two-fold decrease in the pollutant concentration was also observed in the depth profile obtained in February, i.e. late summer, which might be correlated both with the high content of suspended matter and the reduction of the pollutant input. Moreover, isomer ratios of PAHs, such as LMW/HMW and PHE/ANT, highlight that the main PAH source might be petrogenic in nature, whereas the pyrolytic source seems to be less important. Sea surface micro-layer (SML) and sub-surface sea water (SSW) samples were simultaneously collected in the same site by a remote controlled rotating drum-based sampling system, a prototype named MUMS (Multi-User Micro-layer Sampler). Sea surface micro-layer samples showed a total content of PCBs and PAHs in the range 400-450 pg l(-1) and 2000-3000 pg l(-1), respectively, whereas the mean content of the sub-surface sea water samples was 48 pg l(-1) and 325 pg l(-1), respectively. The mean enrichment factors of PCBs and PAHs in sea-surface micro-layer were about 10 and 7, respectively. The surface excess concentrations of PCBs and PAHs were about 35 000 and 200 000, respectively. A fairly good correlation was observed between the concentration of pollutants and water solubility. Based on the assumption that POPs are confined in a very thin top layer of the SML about 0.01-0.001 microm thick, namely the sea-surface nano-layer, and also on an estimated thickness of the sampled sea-surface layer of about 100 microm, an enrichment factor of 10(5)-10(6) for the sea-surface nano-layer was calculated. Such a very high concentration increase was related to the two-fold increase of PAH concentration observed in the underlying 20 cm of the water column in late summer.

Antarctic Regions↗
PubMed1997

Cell-surface display of a Pseudomonas aeruginosa strain K pilin peptide within the paracrystalline S-layer of Caulobacter crescentus.

The paracrystalline surface (S)-layer of Caulobacter crescentus is composed of a single secreted protein (RsaA) that interlocks in a hexagonal pattern to completely envelop the bacterium. Using a genetic approach, we inserted a 12 amino acid peptide from Pseudomonas aeruginosa strain K pilin at numerous semirandom positions in RsaA. We then used an immunological screen to identify those sites that presented the inserted pilin peptide on the C. crescentus cell surface as a part of the S-layer. Eleven such sites (widely separated in the primary sequence) were identified, demonstrating for the first time that S-layers can be readily exploited as carrier proteins to display 'epitope-size' heterologous peptides on bacterial cell surfaces. Whereas intact RsaA molecules carrying a pilin peptide could always be found on the surface of C. crescentus regardless of the particular insertion site, introduction of the pilin peptide at 9 of the 11 sites resulted in some proteolytic cleavage of RsaA. Two types of proteolytic phenomena were observed. The first was characterized by a single cleavage within the pilin peptide insert with both fragments of the S-layer protein remaining anchored to the outer membrane. The other proteolytic phenomenon was characterized by cleavage of the S-layer protein at a point distant from the site of the pilin peptide insertion. This cleavage always occurred at the same location in RsaA regardless of the particular insertion site, yielding a surface-anchored 26 kDa proteolytic fragment bearing the RsaA N-terminus; the C-terminal cleavage product carrying the pilin peptide was released into the growth medium. When the results of this work were combined with the results of a previous study, the RsaA primary sequence could be divided into three regions with respect to the location of a peptide insertion and its effect on S-layer biogenesis: (i) insertions in the extreme N-terminus of RsaA either produce no apparent effect on S-layer biogenesis or disrupt surface-anchoring of the protein; (ii) insertions in the extreme C-terminus either produce no apparent effect on S-layer biogenesis or disrupt protein secretion; and (iii) insertions more centrally located in the protein either have no apparent effect on S-layer biogenesis or result in proteolytic cleavage of RsaA. These data are discussed in relation to our previous assignment of the RsaA N- and C-terminus as regions that are important for surface anchoring and secretion respectively.

Bacterial Outer Membrane Proteins↗
PubMed1998

Comparison of the electrophysiology and morphology of layers III and II neurons of the rat medial entorhinal cortex in vitro.

The basic membrane characteristics of neurons in layers II and III of the medial entorhinal cortex (MEA) were recorded using the intracellular current clamp technique in in vitro slices of the rat brain. Two types of cells were distinguished according to the presence of a time-dependent inward rectification (SAG current) with hyperpolarizing current pulses. The cells in which this inward rectification was not observed (No-SAG cells) had a larger input resistance, a more negative resting membrane potential and a more depolarized firing threshold. They more often displayed a strongly adapting firing pattern, and their action potentials had a slower decay rate and lacked a depolarizing afterpotential, compared with the SAG cells. SAG cells typically had a prominent rebound depolarization at the end of a hyperpolarizing current and membrane potential oscillations (7 Hz) upon subthreshold depolarizations. Cs+ blocked the time-dependent inward rectification. The rebound depolarization persisted, even in the presence of tetrodotoxin. Biocytin labelling showed that layer III consisted mainly of pyramidal-shaped cells. Most layer III cells were of the No-SAG type. All cells in layer II, stellate and pyramidal cells, were classified as SAG cells. We conclude that the cells in MEA layers II and III display different electroresponsiveness, but that this appears to be more related to the layer where they are located than to a specific morphology. As layer III consisted mainly of cells of the No-SAG type, we suggest that layer III cells are less excitable than the SAG type layer II cells.

Animals↗
PubMed1999

Carbachol-induced changes in excitability and [Ca2+]i signalling in projection cells of medial entorhinal cortex layers II and III.

The entorhinal cortex (EC) is a major gateway for sensory information into the hippocampus and receives a cholinergic input from the forebrain. Therefore, we studied muscarinic effects on excitability and intracellular Ca2+ signalling in layer II stellate and layer III pyramidal projection neurons of the EC. In both classes of neurons, local pressure-pulse application of carbachol (1 mM) caused small, atropine-sensitive membrane depolarizations that were not accompanied by any detectable changes in [Ca2+]i. At a higher concentration (10 mM), carbachol induced a larger membrane depolarization associated with synaptic oscillations and epileptiform activity in both classes of neurons. In contrast to the intrinsic theta rhythm in stellate cells with one dominant peak frequency at approximately 7 Hz, the synaptically mediated oscillation induced by carbachol showed three characteristic peaks in the theta and gamma frequency range at approximately 11, 23 and 40 Hz. Although carbachol-induced epileptiform activity was associated with increases in intracellular free Ca2+ in both layer II and III cells, the observed [Ca2+]i accumulation was significantly larger in layer III than in layer II cells. Responses to intracellular current injections showed differences in Ca2+ accumulation in layer II and III cells at the same membrane potentials, suggesting a dominant expression of low- and high-voltage-activated Ca2+ channels in these layer II and III cells, respectively. In conclusion, we present evidence for significant differences in the [Ca2+]i regulation between layer II stellate and layer III pyramidal cells of the medial EC.

2-Amino-5-phosphonovalerate↗
PubMed2000

Comparison of modified one- and two-layer microsurgical vasovasostomy.

OBJECTIVE: To compare the outcome of a modified one-layer and two-layer vasovasotomy (VV) in two groups of similar men undergoing vasectomy reversal. PATIENTS AND METHODS: The charts and surgical records of all surgical procedures performed on men undergoing a modified one- or two-layer VV between June 1992 and July 1994 were retrospectively reviewed. A successful outcome (patency) was defined as sperm present at follow-up (mean follow-up 8 weeks). A modified one-layer VV was used in 17 men (group 1) and a two-layer VV in 23 (group 2). RESULTS: Sperm were present in both groups if surgery was undertaken after vasal obstruction lasting < 36 months. The modified one- and two-layer VV had equal patency (88% and 90%, respectively) when undertaken after an obstructed interval of 36-96 months; outcomes were poorer if surgery was performed after > 96 months. The mean operative duration was 96 min for a modified one-layer VV and 167 min for the two-layer VV. CONCLUSIONS: The simpler and faster modified one-layer VV provides sufficient accuracy for successful vasectomy reversal in most cases. For most patients, both procedures have equivalent patency.

Adult↗
PubMed1981

[Electron spectroscopy for chemical analysis. (ESCA). Examinations on formation and re-formation of the passive layer on vitallium (author's transl)].

The passive layer of a metal implant is responsible for its tolerance in a biological environment. A report is given on ESCA-investigations on the passive layer on Vitallium implants which consists largely of Cr-oxide and is only approx. 3-5 micrometer thick. This passive layer can easily be damaged with OP-instruments. The oxide layers rebuilt on exposure to air or on sterilization in boiling water were also investigated by ESCA. Oxide layers normally formed are very similar to the original passive layer. Accumulations of Co- and Mo-oxides are also observed, however. Some short implantation experiments show that the thin Cr-oxide layer is indeed effective as a passive layer. The analytical findings indicate that the formation or re-formation of the passive layer is due to a selective dissolution process. This accords with results obtained by the neutron activation analysis of the serum.

Chromium Alloys↗
PubMed2006

SNARE complex zero layer residues are not critical for N-ethylmaleimide-sensitive factor-mediated disassembly.

Membrane-anchored SNAREs assemble into SNARE complexes that bring membranes together to promote fusion. SNARE complexes are parallel four-helix bundles stabilized in part by hydrophobic interactions within their core. At the center of SNARE complexes is a distinctive zero layer that consists of one arginine and three glutamines. This zero layer is thought to play a special role in the biology of the SNARE complex. One proposal is that the polar residues of the zero layer enable N-ethylmaleimide-sensitive factor (NSF)-mediated SNARE complex disassembly. Here, we studied the effects of manipulating the zero layer of the well studied synaptic SNARE complex in vitro and in vivo. Using a fluorescence-based assay to follow SNARE complex disassembly in real time, we found that the maximal rate at which NSF disassembles complexes was unaffected by mutations in the zero layer, including single replacement of the syntaxin glutamine with arginine as well as multiple replacement of all four layer residues with non-polar amino acids. To determine whether syntaxin with arginine instead of glutamine in its zero layer can support SNARE function in vivo, we introduced it as a transgene into a Caenorhabditis elegans syntaxin-null strain. Mutant syntaxin rescued viability and locomotory defects similarly to wild-type syntaxin, demonstrating that SNARE complexes with two glutamines and two arginines in the zero layer can support neurotransmission. These findings show that residues of the zero layer do not play an essential role in NSF-mediated disassembly.

Aldicarb↗
PubMed2003

Relative bio-availability and utilisation of phosphatic fertilisers as sources of phosphorus in broilers and layers.

1. Different concentrations of non-phytate phosphorus (NPP, 2.5, 3.0, 3.5, 4.0 and 4.5 g/kg diet) were given to broilers (8 to 42 d of age) to establish regressions between dietary NPP concentration and body weight gain and tibia ash content. Second and third experiments were conducted to study the feasibility of utilisation of different phosphatic fertilisers [ammonium phosphate (AP), ammonium polyphosphate (APP), single super phosphate (SSP), NPK (17:17:17, NPK) and NP (28:28:0, NPK)] in commercial broilers (8 to 42 d) and White Leghorn layers (252 to 364 d). 2. Phosphatic fertilisers were incorporated both in broiler (10 g calcium and 4.5 g NPP/kg) and layer (35 g calcium and 3.5 g NPP/kg) diets by replacing dicalcium phosphate (DCP) in toto. 3. The logarithmic curves obtained for predicting the body weight gain and tibia ash content at different levels of NPP used in experiment 1 were Y = 156.27 + 2,468.8 logX (r2= 0.958) and Y = 530.82 + 144.26 log X (r2 = 0.916), respectively. 4. Body weight gain and food intake in broilers given APP- or NP-supplemented diets were comparable to these in the DCP-fed group. Feeding of NPK, AP or SSP resulted in significant depression in weight gain and food intake and high excreta moisture content. Food/gain, Ca and P contents in tibia ash and serum were not influenced by the use of phosphatic fertilisers as P sources in broiler diets. 5. Tibia ash content in broilers fed on diets containing fertilisers was either similar to or significantly higher than that in the DCP-fed group. Broilers on AP or SSP retained more P and had higher tibia ash content than those on DCP. AP, SSP or NPK caused degenerative and necrotic changes in liver, kidney and intestine of broilers. 6. Relative bio-availability of P from APP or NP was better for body weight gain than AP, SSP or NPK, while the reverse was true for bone calcification. 7. APP and NP gave hen-d egg production similar to that of DCP-fed layers. Food intake was significantly reduced in layers fed on diets containing fertilisers. However, food/egg mass, egg weight and serum Ca and inorganic P contents were not influenced by inclusion of fertilisers in layer diets. 8. Except for AP, inclusion of fertilisers in layer diets reduced shell weight and shell thickness compared with the DCP-fed group. However, no apparent eggshell defects were found which could be attributable to diet. 9. Results of these experiments suggest that APP and NP can be used as the sole source of P both in broiler and layer diets, replacing DCP in toto. However, when utilising these P sources in layers, due attention should be given to shell quality. Fertilisers containing high F (AP and SSP) or K (NPK) reduced performance in broilers and layers and caused microscopic changes in liver, kidney and intestine in broilers.

Animal Feed↗
PubMed2006

Estimation on the self recovery behavior of low-conductivity layer in landfill final cover by laboratory conductivity tests.

This study examined the application of a Self Recovering Sustainable Layer (SRSL) as a landfill final cover. Low-conductivity layers in landfill covers are known to have problems associated with cracking as a result of the differential settlement or climatic changes. A SRSL is defined as a layer with chemical properties that reduces the increased hydraulic conductivity resulting from cracking by forming low-conductivity precipitates of chemicals contained in the layer. In this study, the formation of precipitates was confirmed using a batch test, spectroscopic analysis and mineralogical speciation tests. The possibility of secondary contamination due to the chemicals used for recovery was evaluated using a leaching test. A laboratory conductivity test was performed on a single layer composed of each chemical as well as on a 2-layer system. The recovery performance of the SRSL was estimated by developing artificial cracks in the specimens and observing the change in hydraulic conductivity as a function of time. In the laboratory conductivity test, the hydraulic conductivity of a 2-layer system as well as those of the individual layers that comprise the 2-layer system was estimated. In addition sodium ash was found to enhance the reduction in conductivity. A significant increase in conductivity was observed after the cracks developed but this was reduced with time, which indicated that the SRSL has a proper recovering performance. In conclusion, a SRSL can be used as a landfill final cover that could maintain low-conductivity even after the serious damages due to settlement.

Calcium Compounds↗
PubMed2002

Musculoskeletal disorders among floor layers: is prevention possible?

The purpose of this study was to describe possibilities for the prevention of work-related musculoskeletal disorders among floor layers and to analyze the factors that promote or constrain innovation in prevention. A questionnaire study included 102 floor layers and 180 apprentice floor layers. Questionnaires were used to register musculoskeletal complaints, psychosocial factors, and proposals for prevention. Interviews were carried out of key persons from the trade, selected from the floor layers, employers, and their trade association, with the purpose of getting more knowledge about the barriers to innovation. The results indicate that musculoskeletal disorders are still a great problem in skilled floor layers, and also in apprentices. Primary prevention of work-related knee disorders and accompanying stress requires a reduction in work tasks performed in kneeling positions. Tools that can be used in standing positions for floor laying work tasks are considered useful for prevention of musculoskeletal disorders. Throughout their training, young apprentice floor layers slowly become socialized into the group, and absorb the same identity, attitude to problem-solving, and use of tools and working methods as the adult floor layers. Deep-rooted habits are very resistant to change. The intensity of the work, time pressures, frequent changes of work locations, and the trade's pattern of working in small firms are also factors that make it difficult to introduce good practice innovations in the floor laying trade. Work-related strain can be decreased in the trade by combining changes in tools, materials, and working methods. It is necessary to include educational training of apprentices and skilled floor layers, and also foremen and employers. Breaking down the barriers to change demands education and instruction by people who know the trade well, who can communicate effectively with the floor layers, and who are accepted by the trade.

Adolescent↗
PubMed2000

Ultrastructural analysis of the eggshell: contribution of the individual calcified layers and the cuticle to hatchability and egg viability in broiler breeders.

1. Scanning electron microscopy was used to assess the relationship between the layers of the eggshell and egg viability. The relative thickness (absolute and %) of the mammillary, palisade, vertical crystal and cuticle layers relative to the total eggshell were measured over a 30-week laying period in 2 broiler breeder lines having different hatchability rates. 2. A significant difference in hatchability of 5.5% between the breeder lines was observed. However, there was no significant difference in either egg viability or fertility between lines. 3. The relative thickness of the individual calcified layers and the cuticle did not differ between lines. Therefore, variations in the thickness of the individual eggshell layers are unlikely to explain the 5.5% difference in hatchability rate between lines. 4. The thickness of the calcified region did not alter as the broiler hen aged. However, the percent contribution of each calcified layer significantly differed over the egg production period. 5. The cuticle was significantly thinner at the beginning and at the end of the laying period compared to 38 weeks of age. 6. No significant correlation was observed between egg viability and the relative thicknesses of the mamillary, palisade or cuticle layers. In contrast, there was a positive relationship between egg viability and the thickness of the vertical crystal layer. 7. The percent contribution of the mammillary and palisade layers was similar in the thinnest and thickest eggshells, suggesting conservation of the proportions of these layers independent of eggshell thickness.

Animals↗
PubMed2000

Influence of tableting forces and lubricant concentration on the adhesion strength in complex layer tablets.

The strength of adhesion in complex two-layer tablets is assessed using statistical methods with respect to the applied tableting forces for the first layer and for applying the second layer on the first, as well as regarding the fraction of the lubricant. These results, obtained on a single-punch tablet press, are compared with the results for three-layer tablets produced on a rotary press at production scale. The strongest negative influence on adhesion strength was exerted by the amount of lubricant in the central layer. As expected, compression forces for central-layer tableting also had a negative effect, whereas the compression forces for complex layer tableting exerted a positive effect on layer adhesion. The validity of the derived model equation was proved by experiments: It was shown that the adhesion strength in complex layer tablets produced in production scale can be predicted from laboratory-scale experiments. This makes optimization of the formulation and parameter settings at an early stage of development possible.

Adhesiveness↗
PubMed1987

Sequential expression and differential function of multiple adhesion molecules during the formation of cerebellar cortical layers.

We have correlated the times of appearance of the neural cell adhesion molecule (N-CAM), the neuron-glia cell adhesion molecule (Ng-CAM), and the extracellular matrix protein, cytotactin, during the development of the chicken cerebellar cortex, and have shown that these molecules make different functional contributions to granule cell migration. Immunofluorescent staining showed distinct spatiotemporal expression sequences for each adhesion molecule. N-CAM was present at all times in all layers. However, the large cytoplasmic domain polypeptide of N-CAM was always absent from the external granular layer and was enriched in the molecular layer as development proceeded. Ng-CAM began to be expressed in the premigratory granule cells just before migration and later disappeared from cell bodies but remained on parallel fibers. Cytotactin, which is synthesized by glia and not by neurons, appeared first in a speckled pattern within the external granular layer and later appeared in a continuous pattern along the Bergmann glia; it was also enriched in the molecular layer. After we established their order of appearance, we tested the separate functions of these adhesion molecules in granule cell migration by adding specific antibodies against each molecule to cerebellar explant cultures that had been labeled with tritiated thymidine and then measuring the differential distribution of labeled cells in the forming layers. Anti-N-CAM showed marginal effects. In contrast, anti-Ng-CAM arrested most cells in the external granular layer, while anti-cytotactin arrested most cells in the molecular layer. Time course analyses combined with sequential addition of different antibodies in different orders showed that anti-Ng-CAM had a major effect in the early period (first 36 h in culture) and a lesser effect in the second part of the culture period, while anti-cytotactin had essentially no effect at the earlier time but had major effects at a later period (18-72 h in culture). The two major stages of cerebellar granule cell migration thus appear to be differentially affected by distinct adhesion molecules of different cellular origins, binding mechanisms, and overall distributions. The results indicated that local cell surface modulation of adhesion molecules of different specificities at defined stages and sites is essential to the formation of cerebellar cortical layers.

Animals↗
PubMed1999

In vivo determination of the optical properties of muscle with time-resolved reflectance using a layered model.

We have investigated the possibility of determining the optical coefficients of muscle in the extremities with in vivo time-resolved reflectance measurements using a layered model. A solution of the diffusion equation for two layers was fitted to three-layered Monte Carlo calculations simulating the skin, the subcutaneous fat and the muscle. Relative time-resolved reflectance data at two distances were used to derive the optical coefficients of the layers. We found for skin and subcutaneous fat layer thicknesses (l2) of up to 10 mm that the estimated absorption coefficients of the second layer of the diffusion model have differences of less than 20% compared with those of the muscle layer of the Monte Carlo simulations if the thickness of the first layer of the diffusion model is also fitted. If l2 is known, the differences are less than 5%, whereas the use of a semi-infinite model delivers differences of up to 55%. Even if l2 is only approximately known the absorption coefficient of the muscle can be determined accurately. Experimentally, the time-resolved reflectance was measured on the forearms of volunteers at two distances from the incident beam by means of a streak camera. The thicknesses of the tissues involved were determined by ultrasound. The optical coefficients were derived from these measurements by applying the two-layered diffusion model, and results in accordance with the theoretical studies were observed.

Adipose Tissue↗
PubMed2004

Characterization of dual layer phoswich detector performance for small animal PET using Monte Carlo simulation.

A positron emission tomograph dedicated to small animal imaging should have high spatial resolution and sensitivity, and dual layer scintillators have been developed for this purpose. In this study, simulations were performed to optimize the order and the length of each crystal of a dual layer phoswich detector, and to evaluate the possibility of measuring signals from each layer of the phoswich detector. A simulation tool GATE was used to estimate the sensitivity and resolution of a small PET scanner. The proposed scanner is based on dual layer phoswich detector modules arranged in a ring of 10 cm diameter. Each module is composed of 8 x 8 arrays of phoswich detectors consisting of LSO and LuYAP with a 2 mm x 2 mm sensitive area coupled to a Hamamatsu R7600-00-M64 PSPMT. The length of the front layer of the phoswich detector varied from 0 to 10 mm at 1 mm intervals, and the total length (LSO + LuYAP) was fixed at 20 mm. The order of the crystal layers of the phoswich detector was also changed. Radial resolutions were kept below 3.4 mm and 3.7 mm over 8 cm FOV, and sensitivities were 7.4% and 8.0% for LSO 5 mm-LuYAP 15 mm, and LuYAP 6 mm-LSO 14 mm phoswich detectors, respectively. Whereas, high and uniform resolutions were achieved by using the LSO front layer, higher sensitivities were obtained by changing the crystal order. The feasibilities for applying crystal identification methods to phoswich detectors consisting of LSO and LuYAP were investigated using simulation and experimentally derived measurements of the light outputs from each layer of the phoswich detector. In this study, the optimal order and lengths of the dual layer phoswich detector were derived in order to achieve high sensitivity and high and uniform radial resolution.

Animals↗
PubMedDate not supplied

The occipitoparietal pathway of the macaque monkey: comparison of pyramidal cell morphology in layer III of functionally related cortical visual areas.

The dendritic morphology of pyramidal cells located at the base of layer III in the primary visual area (V1), the second visual area (V2), the middle temporal area (MT), the ventral portion of the lateral intraparietal area (LIPv) and in the portion of cytoarchitectonic area 7a within the anterior bank of the superior temporal sulcus was revealed by injecting neurons with Lucifer Yellow in fixed, flattened slices of macaque monkey visual cortex. These areas correspond to different levels of the occipitoparietal cortical 'stream', which processes information related to motion and spatial relationships in the visual field. The tissue was immunocytochemically processed to obtain a light-stable diaminobenzidine reaction product, revealing the dendritic morphology in fine detail. Retrogradely labelled MT-projecting neurons in supragranular V1 (layer IIIc of Hassler's nomenclature, corresponding to Brodmann's layer IVb) were predominantly pyramidal, although many spiny multipolar (stellate) cells were also found. The average basal dendritic field area of pyramidal neurons in sublamina IIIc of V1 was significantly smaller than that in the homologous layer of V2, within the cytochrome oxidase-rich thick stripes. Furthermore, the average basal dendritic field areas of V1 and V2 pyramidal neurons were significantly smaller than those of neurons in MT, LIPv and area 7a. There was no difference in basal dendritic field area between layer III pyramidal neurons in areas MT, LIPv and 7a. While the shape of most basal dendritic fields was circularly symmetrical in the dimension tangential to the cortical layers, there were significant biases in complexity, with dendritic branches tending to cluster along particular axes. Sholl analysis revealed that the dendritic fields of neurons in areas MT, LIPv and 7a were significantly more complex (i.e. had a larger number of branches) than those of V1 or V2 neurons. Analysis of basal dendritic spine densities revealed regional variations along the dendrites, with peak densities being observed 40-130 microns from the cell body, depending on the visual area. The peak spine density of layer III pyramidal neurons in V1 was lower than that observed in V2, MT or LIPv, which were all similar. Pyramidal neurons in area 7a had the greatest peak spine density, which was on average 1.7 times that found in V1. Calculations based on the average spine density and number of dendritic branches at different distances from the cell body demonstrated a serial increase in the total number of basal dendritic spines per neuron at successive stations of the occipitoparietal pathway. Our observations, comparing dendritic fields of neurons in the homologous cortical layer at different levels of a physiologically defined 'stream', indicate changes in pyramidal cell morphology between functionally related areas. The relatively large, complex, spine-dense dendritic fields of layer III pyramidal cells in rostral areas of the occipitoparietal pathway allow these cells to sample a greater number of more diverse inputs in comparison with cells in 'lower' areas of the proposed hierarchy.

Animals↗
PubMed1995

Differential effects of a steroidal antiestrogen, EM-139, on prostaglandin and cyclic adenosine 3',5'-monophosphate production in the circular and longitudinal layers of bovine myometrium.

The regulation of prostaglandin (PG) production and cAMP generation was studied in vitro in cultured smooth muscle cells isolated specifically from the circular or longitudinal layers of the bovine myometrium. We found that prostacyclin (PGI2) was the principal PG produced by the myometrium, especially in the longitudinal layer, followed closely by PGE2 and marginally by PGF2 alpha. The PG production (fg/ml, mean +/- SD) in the circular and longitudinal layers was, respectively, PGE2 (424.4 +/- 162.0) > PGI2 (189.5 +/- 19.0) > PGF2 alpha (9.5 +/- 3.0) versus PGI2 (751 +/- 36) > PGE2 (515.7 +/- 94.0) > PGF2 alpha (16.3 +/- 3.0); production was stimulated up to 15-fold 24 h after addition of phorbol 12-myristate (PMA; 100 nM). Hormonal control of PG production was assessed by use of a steroidal antiestrogen, EM-139. PG production was inhibited in a concentration-dependent manner by EM-139 in both circular and longitudinal layers, with maximal inhibition at 1 microM. In parallel studies, chronic treatment with EM-139 resulted in significant increases in isoproterenol-induced cAMP production in both muscle layers, but more especially in the circular layer. This antiestrogenic effect was reversed by addition of 17 beta-estradiol. These results indicate that the two smooth muscle layers of the bovine myometrium have distinct patterns of PG production and that the adenylate cyclase/cAMP response of the circular layer is more sensitive to estrogen modulation. Our findings with a cell culture model of separated myometrial layers provide strategic information for a better understanding of the regulation of uterine contractility during pregnancy.

Animals↗