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Results for “Deep generative model”

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PubMed1998

Spatial and temporal expression of c-Fos protein in the spinal cord of anesthetized rat induced by subcutaneous bee venom injection.

In order to study central neuronal components involved in subcutaneous (s.c.) bee venom-induced persistent pain (a new tonic pain model), we use Fos immunostaining technique to study the spatial and temporal patterns of neuronal activity in the spinal cord of anesthetized rats. Following intraplantar bee venom injection, Fos-like immunoreactive (ir) neurons were only seen from L1 to S3 rostrocaudally with distinct distribution at L4-5 segments. At segments of L1-2 and S1-3, Fos-ir labelings were diffusely and symmetrically distributed on both sides of the gray matter; however, at L4-5 segments, Fos-ir neurons were densely localized in medial portion of laminae I-II, less densely in laminae V-VI and a few in laminae VII and X ipsilateral to the injection side. No Fos labeling was seen in ventral horn of the spinal cord at L4-5 segments. Fos protein began to express only within lamina I at 0.5 h, but increased over the whole dorsal horn at 1 h and reached peak labeling at 2 h after bee venom. Expression of c-Fos in laminae I-II decreased at 4 h, and completely disappeared at 24 h, however, labeling in laminae V-VI disappeared much slowly and existed even at 96 h after bee venom. Within laminae III-IV, Fos-ir neurons could not be seen at 0.5 h, but began to be seen at 1 h and appeared to exist even at 24 h after bee venom. Systemic morphine suppressed c-Fos expression dose-dependently in both superficial and deep layers of dorsal horn and the latter region was much more sensitive to morphine than the former one. The present results demonstrated that prolonged neuronal activities in superficial and deep layers of dorsal horn were essential to mediation of bee venom induced tonic pain and may have different roles in generation and/or modulation of spontaneous pain and hyperalgesia and allodynia.

Analgesics, Opioid↗

PubMed1999

The effect of deep pore mutations on the action of phenylalkylamines on the Kv1.3 potassium channel.

We investigated the action of the phenylalkylamines verapamil and N-methyl-verapamil on the Kv1.3 potassium channel using the whole-cell configuration of the patch-clamp technique. Our goal was to identify their binding as a prerequisite for using the phenylalkylamines as small, well-defined molecular probes, not only to expand the structural findings made with peptide toxins or by crystallization, but also to use them as lead compounds for the generation of more potent and therefore more specific K+ channel modulators. Competition experiments with charybdotoxin, known to interact with external residues of Kv1.3, showed no interaction with verapamil. The internal application of quarternary N-methyl-verapamil in combination with verapamil suggested competition for the same internal binding site. Verapamil affinity was decreased 6 fold by a mutation (M395V) in a region of the internal pore which forms part of the internal tetraethylammonium (TEA+) binding site, although mutations at neighbouring residues (T396 and T397) were without effect. Modification of C-type inactivation by mutations in the internal pore suggest that this region participates in the inactivation process. The action of phenylalkylamines and local anaesthetics on L-type Ca2+ channels and Na channels, respectively, and verapamil on Kv1.3 indicate very similar blocking mechanisms. This might allow the use of these compounds as molecular probes to map the internal vestibule of all three channel types.

Amino Acid Sequence↗

PubMed2002

Efficacy of laser debridement with autologous split-thickness skin grafting in promoting improved healing of deep cutaneous sulfur mustard burns.

The consequences of receiving a cutaneous sulfur mustard (SM) burn are prolonged wound healing and secondary infection. This study was undertaken to find a treatment that promotes quick healing with few complications and minimal disfigurement. Multiple deep SM burns (4 cm diameter) were generated on the ventrum of weanling pigs and treated at 48 h. Four treatments were compared: (1) full-thickness CO(2) laser debridement followed by skin grafting; (2) full-thickness sharp surgical tangential excision followed by skin grafting, the "Gold Standard" used in deep thermal burns management; (3) partial-thickness laser ablation with no grafting; and (4) partial-thickness sharp excision with no grafting. A computer controlled, raster scanned, high-powered continuous wave (cw) CO(2) laser was utilized. Ulceration, wound geometry, and wound contraction were evaluated during a 36-day healing period. Histopathological evaluations were conducted at the end of the healing period. Engraftment rates were similar between both methods of debridement. Laser debridement followed by skin grafting was as efficacious in improving the wound healing of deep SM burns as the "Gold Standard." Full-thickness laser debridement of these small total body surface area (TBSA) burns was time efficient and provided adequate beds for split-thickness skin grafting. Laser debridement offered additional benefits that included hemostatic control during surgery and minimal debridement of normal perilesional skin. Mid-dermal debridement by sharp excision or laser ablation without grafting produced less desirable results but was better than no treatment.

Animals↗

PubMed1966

An attempt to analyse colour reception by electrophysiology.

1. The problem of colour reception is that we do not know the action spectra of the visual pigments involved, the nature of the signals generated nor the interaction between these signals. We only know the incident light and the electric results of interaction.2. In Part 1 we show that S-potentials from red/green (R/G) units saturated with deep red light show this property: added green light pulls down the ceiling of depolarization, but more added red had no power to raise it again. Thus lights that depress the deep red ceiling equally stimulate the green pigment equally. From this the action spectrum of the green pigment can be obtained.3. If we assume that only two visual pigments are involved in the R/G unit, and that lights which do not pull down the deep red ceiling are below the threshold for green cones, then in this range only the red pigment is excited and we may obtain its action spectrum. Its maximum is at 680 nm where no visual pigment so far has been found.4. In Part 2 we consider the following mathematical problem: ;Is it possible that two pigments of given action spectra could combine their outputs in such a way that the resultant would be identical with the output of a third pigment of given action spectrum, for every intensity of every monochromatic light?' The solution shows that this is always mathematically possible, and the necessary interaction function is deduced.5. It is shown further that if the log action spectra are the ;visual parabolas' that resemble Dartnall's nomogram, then the interaction function is simply a linear transform such as Hartline & Ratliff (1957) have found with lateral inhibition in Limulus and Donner & Rushton (1959) with silent substitution in the frog.6. An interaction that matches a single pigment to perfection for all monochromatic lights will not match it for certain mixtures. By this criterion the 680 nm excitability is a pigment and not the resultant of two other pigments, i.e. pigments more excitable in other spectral regions.7. In Part 3 monochromatic lights are matched by red+green mixtures that give identical responses. From this the action spectrum of the red pigment may be obtained without involving nerve organization (except as a null detector). The result, which has one arbitrary constant, is given by the curves of Fig. 10, the continuous curve R or one of the dotted curves. Of these only curve R is acceptable.8. Knowing the action spectra for red and green cones we may consider what signals are generated and how they interact to give the records. Figure 11 suggests a model that will account for the size and sign of S-potentials as function of the quantum catch by the two pigments. It does not embrace the time or space parameters which can be very complex.

Animals↗

PubMed2006

A procedure to analyze surface profiles of the protein molecules visualized by quick-freeze deep-etch replica electron microscopy.

Quick-freeze deep-etch replica electron microscopy gives high contrast snapshots of individual protein molecules under physiological conditions in vitro or in situ. The images show delicate internal pattern, possibly reflecting the rotary-shadowed surface profile of the molecule. As a step to build the new system for the "Structural analysis of single molecules", we propose a procedure to quantitatively characterize the structural property of individual molecules; e.g. conformational type and precise view-angle of the molecules, if the crystallographic structure of the target molecule is available. This paper presents a framework to determine the observed face of the protein molecule by analyzing the surface profile of individual molecules visualized in freeze-replica specimens. A comprehensive set of rotary-shadowed views of the protein molecule was artificially generated from the available atomic coordinates using light-rendering software. Exploiting new mathematical morphology-based image filter, characteristic features were extracted from each image and stored as template. Similar features were extracted from the true replica image and the most likely projection angle and the conformation of the observed particle were determined by quantitative comparison with a set of archived images. The performance and the robustness of the procedure were examined with myosin head structure in defined configuration for actual application.

Freeze Etching↗

PubMed2005

Differential expression and regulation of the cAMP-selective phosphodiesterase type 4A splice variants in rat brain by chronic antidepressant administration.

Chronic antidepressant treatment up-regulates the cAMP cascade in limbic brain regions, suggesting that activation of this pathway contributes to the therapeutic efficacy of antidepressants. A role for cAMP signaling is supported by the finding that rolipram, a selective inhibitor of cAMP-specific phosphodiesterases type 4 (PDE4), has antidepressant efficacy in behavioral models of depression and in clinical trials. To elucidate further the role of PDE4 isozymes, we characterized the expression and regulation of PDE4A splice variants (i.e. PDE4A1, PDE4A5, PDE4A8 and PDE4A10) in rat brain by chronic antidepressant treatment. Initial in situ hybridization studies (ISH) revealed high levels of PDE4A1 mRNA in medial septum, diagonal band, olfactory system, hippocampus and cerebellum. PDE4A5 mRNA expression was restricted to the olfactory nuclei, deep cortical layers, dentate and CA1 pyramidal layers. PDE4A10 mRNA was localized in the dentate gyrus and CA1 pyramidal layers. PDE4A8 mRNA was absent in rat brain. We determined the influence of chronic fluoxetine or electroconvulsive seizure (ECS) treatments on PDE4A splice variants expression in various brain regions. ISH analysis indicated that chronic fluoxetine or ECS treatments significantly increased PDE4A1, but not PDE4A5 or PDE4A10, mRNA levels in frontal and parietal cortices. ECS increased PDE4A5 levels in the anterior cingulate and frontoparietal cortices, CA1 and dentate gyrus, whereas chronic fluoxetine or ECS treatment increased PDE4A10 levels in the hippocampus. The differential up-regulation of PDE4A splice variants suggests compensatory region-specific responses to the antidepressant-induced increase in cAMP signaling and suggests that these splice variants may be relevant as targets for antidepressant intervention.

3',5'-Cyclic-AMP Phosphodiesterases↗

PubMed1999

The effects of external compression on venous blood flow and tissue deformation in the lower leg.

External pneumatic compression of the lower legs is effective as prophylaxis against deep vein thrombosis. In a typical application, inflatable cuffs are wrapped around the patient's legs and periodically inflated to prevent stasis, accelerate venous blood flow, and enhance fibrinolysis. The purpose of this study was to examine the stress distribution within the tissues, and the corresponding venous blood flow and intravascular shear stress with different external compression modalities. A two-dimensional finite element analysis (FEA) was used to determine venous collapse as a function of internal (venous) pressure and the magnitude and spatial distribution of external (surface) pressure. Using the one-dimensional equations governing flow in a collapsible tube and the relations for venous collapse from the FEA, blood flow resulting from external compression was simulated. Tests were conducted to compare circumferentially symmetric (C) and asymmetric (A) compression and to examine distributions of pressure along the limb. Results show that A compression produces greater vessel collapse and generates larger blood flow velocities and shear stresses than C compression. The differences between axially uniform and graded-sequential compression are less marked than previously found, with uniform compression providing slightly greater peak flow velocities and shear stresses. The major advantage of graded-sequential compression is found at midcalf. Strains at the lumenal border are approximately 20 percent at an external pressure of 50 mmHg (6650 Pa) with all compression modalities.

Blood Flow Velocity↗

PubMed1992

[Temperature distribution and geometry of the electrodes in RF interstitial hyperthermia using circular and interstitial electrodes].

To evaluate the feasibility of clinical application of a newly developed interstitial hyperthermia system, which consists of an 8 MHz radiofrequency generator, interstitial needle electrodes, and a superficial circular electrode, we conducted preclinical experiments using an agar phantom and VX-2 carcinoma in the rabbit. In the experiment with an agar phantom, four 4 cm needle electrodes were placed in a square array at intervals of 1.0, 1.5, and 2.0 cm. Thermography demonstrated homogeneous temperature distribution at electrode intervals of 1.0 and 1.5 cm, but hot spots around the electrodes at an interval of 2.0 cm. When electrode deviation was less than 8 degrees from the parallel plane, no temperature deviation was observed. Using two 2 cm electrodes and two 4 cm electrodes in square array, thermography demonstrated a homogeneous temperature distribution in the area surrounded by the electrodes. Even if the electrodes were located at the periphery of the agar phantom, a homogeneous temperature distribution was obtained in the area surrounded by the electrodes. Using four 4 cm electrodes at intervals of 1.5 cm in VX-2 carcinoma in the rabbit, ideal heating was obtained: 42 degrees C at the periphery of the tumor and 43 degrees C at the center. These data suggest that the newly developed interstitial hyperthermia apparatus provides homogeneous heat distribution at electrode intervals of 1.5 cm or less and can be used in a Phase I study for deep-seated or superficial tumors.

Animals↗

PubMed2003

Recovery from gastric mucus depletion in the intact guinea pig mucosa.

BACKGROUND: In developed countries one-third of the population is infected with the gastric pathogen Helicobacter pylori. In the early stages of H. pylori-induced gastritis, typical symptoms include gastric erosions and mucus depletions. Artificial mucus depletion was generated, demonstrating both consequent irritation and recovery processes in the mucosa. METHODS: The mucus depletion was examined by removing a small cylinder of mucus from the surface of the explanted guinea pig corpus mucosa, leaving the epithelial surface intact. pH microelectrodes were inserted into the mucosa in vitro, measuring the epicellular mucus pH, the pH(i) of the underlying epithelial cells and the pH inside the gastric glands during mucus regeneration. Using infrared microscopy, the same process of mucus layer renewal was followed in anaesthetized animals. RESULTS: The depletion exposed the tissue surface to low luminal pH levels. At a luminal pH of 2.5, a decrease was observed in the crypt outlet pH and surface cell pH(i), while deeper cells were less affected. However, a subsequent neutralization in the deep gland lumen was found. During the repair process, a quarter of the mucus layer was regenerated within the first 5 min. This newly secreted mucus formed a structure similar to that before depletion. Within 45 min, pH(i) and tissue-near pH values had fully recovered. CONCLUSION: Following mucus depletion, there is a decrease in surface cell pH(i) and crypt outlet pH values. The repair process is then characterized by extensive mucus secretion and local cessation of acid secretion.

Animals↗

PubMed2003

Statistical analysis of the protein environment of N-glycosylation sites: implications for occupancy, structure, and folding.

We recently reported statistical analysis of structural data on glycosidic linkages. Here we extend this analysis to the glycan-protein linkage, and the peptide primary, secondary, and tertiary structures around N-glycosylation sites. We surveyed 506 glycoproteins in the Protein Data Bank crystallographic database, giving 2592 glycosylation sequons (1683 occupied) and generated a database of 626 nonredundant sequons with 386 occupied. Deviations in the expected amino acid composition were seen around occupied asparagines, particularly an increased occurrence of aromatic residues before the asparagine and threonine at position +2. Glycosylation alters the asparagine side chain torsion angle distribution and reduces its flexibility. There is an elevated probability of finding glycosylation sites in which secondary structure changes. An 11-class taxonomy was developed to describe protein surface geometry around glycosylation sites. Thirty-three percent of the occupied sites are on exposed convex surfaces, 10% in deep recesses and 20% on the edge of grooves with the glycan filling the cleft. A surprisingly large number of glycosylated asparagine residues have a low accessibility. The incidence of aromatic amino acids brought into close contact with the glycan by the folding process is higher than their normal levels on the surface or in the protein core. These data have significant implications for control of sequon occupancy and evolutionary selection of glycosylation sites and are discussed in relation to mechanisms of protein fold stabilization and regional quality control of protein folding. Hydrophobic protein-glycan interactions and the low accessibility of glycosylation sites in folded proteins are common features and may be critical in mediating these functions.

Amino Acids↗

PubMed2005

Optical clearing for improved contrast in second harmonic generation imaging of skeletal muscle.

Using second harmonic generation (SHG) imaging microscopy, we have examined the effect of optical clearing with glycerol to achieve greater penetration into specimens of skeletal muscle tissue. We find that treatment with 50% glycerol results in a 2.5-fold increase in achievable SHG imaging depth. Signal processing analyses using fast Fourier transform and continuous wavelet transforms show quantitatively that the periodicity of the sarcomere structure is unaltered by the clearing process and that image quality deep in the tissue is improved with clearing. Comparison of the SHG angular polarization dependence also shows no change in the supramolecular organization of acto-myosin complexes. By contrast, identical treatment of mouse tendon (collagen based) resulted in a strong decrease in SHG response. We suggest that the primary mechanism of optical clearing in muscle with glycerol treatment results from the reduction of cytoplasmic protein concentration and concomitant decrease in the secondary inner filter effect on the SHG signal. The lack of glycerol concentration dependence on the imaging depth indicates that refractive index matching plays only a minor role in the optical clearing of muscle. SHG and optical clearing may provide an ideal mechanism to study physiology in highly scattering skeletal or cardiac muscle tissue with significantly improved depth of penetration and achievable imaging depth.

Animals↗

PubMedDate not supplied

Knee-deep and rising: America's recycling crisis.

Every year, Americans generate 180 million tons of solid waste, 70% of which goes into landfills. Since 1979, the United States has exhausted more than two-thirds of its landfills; another one-fifth will close over the next five years. Solving the problem will require a new understanding between industry and government--an understanding that combines industry competence and government authority. But the two sides are mired in an unfortunate combination of good intentions and failed systems. A classic example that epitomizes the problem is the recycling of plastics. Two stories capture the sense of chaos that pervades the recycling of plastics. The first is a comedy of errors played out in Minneapolis, Minnesota, where the city council passed a measure that would have banned all plastic packaging from the city. In this case, the government acted without the competence of industry. The second story involves McDonald's decision to abandon its polystyrene packaging and switch to plastic-coated paper. In this case, a single business's approach to recycling proved fruitless because of the lack of government authority. According to the authors, five principles provide the underpinnings to a new solid-waste management infrastructure: business and government are partners; the infrastructure is a system and must operate in balance; economics and politics must act as partners; all levels of government have roles to play; and generating less trash and recycling more depends on a workable system. Setting up the system will require an infrastructure that balances supply and demand, an advisory committee to manage the infrastructure, and a management system that uses incentives and disincentives to balance the system.

Commerce↗

PubMed2001

Physiological aspects involved in production of xylanolytic enzymes by deep-sea hyperthermophilic archaeon Pyrodictium abyssi.

Xylanases (EC 3.2.1.8) catalyze the hydrolysis of xylan, the major constituent of hemicellulose. The use of these enzymes could greatly improve the overall economics of processing lignocellulosic materials for the generation of liquid fuels and chemicals. The hyperthermophilic archaeon Pyrodictium abyssi, which was originally isolated from marine hot abyssal sites, grows optimally at 97 degrees C and is a prospective source of highly thermostable xylanase. Its endoxylanase was shown to be highly thermostable (over 100 min at 105 degrees C) and active even at 110 degrees C. The growth of the deep-sea archaeon P. abyssi was investigated using different culture techniques. Among the carbohydrates used, beech wood xylan, birch wood glucuronoxylan and the arabinoxylan from oats pelt appeared to be good inducers for endoxylanase and beta-xylosidase production. The highest production of arabinofuranosidase, however, was detected in the cell extracts after growth on xylose and pyruvate, indicating that the intermediate of the tricarboxylic acid cycle acted as a nonrepressing carbon source for the production of this enzyme. Electron microscopic studies did not show a significant difference in the cell surface (e.g., xylanosomes) when P. abyssi cells were grown on different carbohydrates. The main kinetic parameters of the organism have been determined. The cell yield was shown to be very low owing to incomplete substrate utilization, but a very high maximal specific growth rate was determined (micromax = 0.0195) at 90 degrees C and pH 6.0. We also give information on the problems that arise during the fermentation of this hyperthermophilic archaeon at elevated temperatures.

Biomass↗

PubMed1999

Epigenetic inheritance, genetic assimilation and speciation.

Epigenetic inheritance systems enable the environmentally induced phenotypes to be transmitted between generations. Jablonka and Lamb (1991, 1995) proposed that these systems have a substantial role during speciation. They argued that divergence of isolated populations may be first triggered by the accumulation of (heritable) phenotypic differences that are later followed and strengthened by genetic changes. The plausibility of this idea is examined in this paper. At first, we discuss the "exploratory" behaviour of an epigenetic inheritance system on a one peak adaptive landscape. If a quantitative trait is far from the optimum, then it is advantageous to induce heritable phenotypic variation. Conversely, if the genotypes get closer to the peak, it is more favorable to canalize the phenotypic expression of the character. This process would lead to genetic assimilation. Next we show that the divergence of heritable epigenetic marks acts to reduce or to eliminate the genetic barrier between two adaptive peaks. Therefore, an epigenetic inheritance system can increase the probability of transition from one adaptive state to another. Peak shift might be initiated by (i) slight changes in the inducing environment or by (ii) genetic drift of the genes controlling epigenetic variability. Remarkably, drift-induced transition is facilitated even if phenotypic variation is not heritable. A corollary of our thesis is that evolution can proceed through suboptimal phenotypic states, without passing through a deep adaptive valley of the genotype. We also consider the consequences of this finding on the dynamics and mode of reproductive isolation.

Animals↗

PubMed2004

Isoflurane alters the amount of dopamine transporter expressed on the plasma membrane in humans.

BACKGROUND: Isoflurane increases extracellular dopamine concentration and causes trafficking of the dopamine transporter (DAT) in transfected cells. Also, the binding potentials of highly specific positron-emitting DAT ligands are altered by isoflurane in rhesus monkeys. The purpose of this study was to determine the dose-response curve for isoflurane altering the binding potential of one of these ligands ([F-18]FECNT) in humans. METHODS: Twenty human volunteers underwent positron emission tomography using [F-18]FECNT. All subjects were scanned while awake and then again after assignment to one of four groups (n = 5 each): awake-control, propofol-control, or light or deep isoflurane anesthesia as defined by Bispectral Index monitoring. Bispectral Index values in the light anesthesia group were 40 +/- 7 (end-tidal isoflurane, 1.02 +/- 0.08) versus 27 +/- 10 (end-tidal isoflurane, 1.6 +/- 0.3) in the deep anesthesia group. The within-subject percent change in putamen binding potential between the awake and second scans was determined for each subject, averaged within groups, and compared across groups. RESULTS: The [F-18]FECNT binding potential exhibited a biphasic shape as a function of anesthetic dose. The binding potential for the second scan in the awake-control and propofol-control groups was significantly less than the initial scan; for the light anesthesia group, the binding potential was significantly increased during anesthesia, and no change was detected between the two scans in the deeper anesthesia group. CONCLUSION: Isoflurane causes a dose-dependent change in the [F-18]FECNT binding potential for DAT consistent with isoflurane causing trafficking of the DAT between the plasma membrane and the cell interior. Concentrations of isoflurane below minimum alveolar concentration causes DAT to be trafficked to the plasma membrane from the cell interior, but no net trafficking occurs at higher concentrations. The data are most easily explained if isoflurane alters the amount of functionally expressed DAT through an indirect pathway. This phenomena should be more fully explored to help make the next generation of anesthetics more mechanistically specific and to reduce undesired side effects.

Adult↗

PubMedDate not supplied

Accelerator-based epithermal neutron beam design for neutron capture therapy.

Recent interest in the production of epithermal neutrons for use in boron neutron capture therapy (BNCT) has promoted an investigation into the feasibility of generating such neutrons with a high current proton accelerator. Energetic protons (2.5 MeV) on a 7Li target produce a spectrum of neutrons with maximum energy of roughly 800 keV. A number of combinations of D2O moderator, lead reflector, 6Li thermal neutron filtration, and D2O/6Li shielding will result in a useful epithermal flux of 1.6 x 10(8) n/s at the patient position. The neutron beam is capable of delivering 3000 RBE-cGy to a tumor at a depth of 7.5 cm in a total treatment time of 60-93 min (depending on RBE values used and based on a 24-cm diameter x 19-cm length D2O moderator). Treatment of deeper tumors with therapeutic advantage would also be possible. Maximum advantage depths (RBE weighted) of 8.2-9.2 (again depending on RBE values and precise moderator configuration) are obtained in a right-circular cylindrical phantom composed of brain-equivalent material with an advantage ratio of 4.7-6.3. A tandem cascade accelerator (TCA), designed and constructed at Science Research Laboratory (SRL) in Somerville MA, can provide the required proton beam parameters for BNCT of deep-seated tumors. An optimized configuration of materials required to shift the accelerator neutron spectrum down to therapeutically useful energies has been designed using Monte Carlo simulation in the Whitaker College Biomedical Imaging and Computation Laboratory at MIT. Actual construction of the moderator/reflector assembly is currently underway.

Boron↗

PubMed2003

Estrogen administration enhances thrombin generation in rats.

Venous thrombosis is a serious disorder that may be fatal if complicated by pulmonary embolism. Venous thrombosis is usually related to one of three factors: reduced blood flow, changes in vessel wall integrity, or changes in the blood composition. Factors leading to thrombosis are classified as either genetic or acquired. Puerperium and oral contraceptives are examples of the acquired factors. The risk of thrombosis during pregnancy is high compared to that in the overall population,. however, this increases by three to five times in puerperium. Deep vein thrombosis (DVT) complicated by pulmonary thromboembolism (PE) is considered the leading cause of maternal death in the United States and Europe [Am. J. Obstet. Gynecol. 164 (1991) 603; Obstet. Gynecol. 84 (1994) 240] and the third cause in Japan [M Ishikawa, Maternal mortality and pulmonary thromboembolism. Study on maternal mortality in Japan. Report from the Ministry of Health of Japan in Maternal and Child Health Research, 1996. p. 123-128]. Patients without history of familial thrombophilia have 14-fold higher risk of DVT during puerperium [Thromb. Haemost. 25 (1999) 610]. Little is known about the underlying mechanism of thrombotic disorders in puerperium. It is recognized that oral contraceptive estrogen enhances the risk of DVT [Am. J. Epidemiol. 133 (1991) 32]. However, there is little research regarding the relation between estrogen and blood coagulation, although it is known that plasma estrogen reaches extremely high levels near term. We assume that high-level plasma estrogen plays an important role in the blood coagulation activity that results in the occurrence of DVT. To assess this likely association, we studied the effects of high estrogen levels on coagulation in rat plasma.

Animals↗

PubMed1980

Dissociation of visual and saccade-related responses in superior colliculus neurons.

1. Single-unit activity was recorded from the superior colliculus (SC) of monkeys trained to look to visual targets presented on an oscilloscope screen. On one task, target localization required that information concerning the retinal position of the target be combined with information concerning current or future eye position. This task also permitted a dissociation between the site of retinal stimulation and the metrics of the saccade triggered by the stimulation. 2. Vigorous visual responses of superficial SC neurons may occur that do not result in the activation of underlying saccade-related cells. The activity of these neurons signals the occurrence of a visual stimulus, whether or not the stimulus is selected for foveal viewing. 3. Saccade-related (SR) discharges of most intermediate and deep-layer SC neurons precede saccades with particular vectors, regardless of the region of retinal activation initiating the saccade. The discharge of these neurons is tightly coupled to saccade onset, even if changes in eye position have occurred since target appearance. Thus, the discharge of these SR neurons must occur after retinal error and eye-position signals have been combined to compute the necessary saccade vector. For most SR neurons, direct retinal activation of overlying visual neurons had no effect on either the vigor or probability of a SR discharge. The discharge of overlying visual cells is neither necessary nor sufficient to activate most SR cells. 4. The discharge of some SR cells is dependent on prior activation of overlying visual cells. Of 53 SR cells, only 3 were completely dependent on visual stimulation, while another 8 discharged less vigorously if corresponding visual activation failed to occur. 5. About one-quarter of the SR cells showed long-lead preburst activity. This activation was characterized by a low level of firing, which began after the saccade signal and continued until a saccade-linked burst occurred. 6. Cells were isolated that were visually responsive yet discharged prior to saccades in the absence of appropriate retinal stimulation. No component of the discharge of these quasi-visual (QV) cells appeared to be motor in the usual sense. The activity of these neurons appears to reflect eye-position error (the difference between actual and desired eye position) and to hold this information in spatial register until a saccade occurs or is cancelled. 7. It is concluded that the presumed linkage, implied in earlier versions of the foveation hypothesis, between the superficial layers (receiving direct retinal inputs) and the deeper layers of the SC is not necessary for the activation of SR neurons. Results suggest that the SC must generate or receive a signal that combines retinal error and eye-position information. These findings are discussed in terms of current models of the saccadic-control system.

Animals↗