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Advances in participatory occupational health aimed at good practices in small enterprises and the informal sector.

Participatory programmes for occupational risk reduction are gaining importance particularly in small workplaces in both industrially developing and developed countries. To discuss the types of effective support, participatory steps commonly seen in our "work improvement-Asia" network are reviewed. The review covered training programmes for small enterprises, farmers, home workers and trade union members. Participatory steps commonly focusing on low-cost good practices locally achieved have led to concrete improvements in multiple technical areas including materials handling, workstation ergonomics, physical environment and work organization. These steps take advantage of positive features of small workplaces in two distinct ways. First, local key persons are ready to accept local good practices conveyed through personal, informal approaches. Second, workers and farmers are capable of understanding technical problems affecting routine work and taking flexible actions leading to solving them. This process is facilitated by the use of locally adjusted training tools such as local good examples, action checklists and group work methods. It is suggested that participatory occupational health programmes can work in small workplaces when they utilize low-cost good practices in a flexible manner. Networking of these positive experiences is essential.

Accident Prevention↗

A computational model for the neurobiological substrates of visual attention.

Two interesting and complex tasks are performed by the brain in the process of perception: the integration of characteristics leading to an easier recognition of a pattern as a whole (binding), and the extraction of properties that need to be detailed and analyzed (attention). Attention seems to have a reciprocal relation with binding, inasmuch as the latter promotes the composition of features and their dependencies, while the former selects a single characteristic independently of the remainder. Classically, binding is viewed as a process whereby sets of properties are gathered in representative entities, which are themselves linked to form higher level structures, in a sequence that culminates in the total integration of the pattern features in a localized construct. The convergent axonal projections from one cortical area to another would be the neurobiological mechanism through which binding is achieved. Attention comprises the selective excitation of neuronal networks or pathways that stand for specific pattern properties. The thalamus and its reticular nucleus would then be the anatomical substrate of the attentional focus. In this paper we propose a computational model aiming at bringing together the main (and apparently diverging) ideas about binding and attention. Based on experimental data, a neuronal network representing cortical pyramidal cells is assembled, and its structure and function are related to the binding and attention phenomena. Actually, the convergent projections that enlarge the visual receptive field are associated to binding, while a specific change in the pyramidal cell behavior is responsible for attention. Computer simulations are shown which reproduce the electrophysiology of pyramidal cells and mimic some interesting experimental results in visual attention. We conclude by conjecturing that attention is a driven interruption in the regular process of binding.

Algorithms↗

Estramustine induces disorganization of microtubules, perinuclear retraction of vimentin and endoplasmatic reticulum, and inhibits cell migration.

The effects of the mitotic inhibitor estramustine on the cytoskeleton of DU 145 and AG 1518 cells were studied. Estramustine caused a partial disassembly of microtubules and withdrawal of microtubules from the cell periphery, disorganized microtubules and delayed regrowth of disassembled microtubules. It also induced a spheroid cellular morphology and affected cellular adhesion and survival. Sometimes microtubules seemed to be organized from several microtubule-organizing centers. The cytoskeleton-dependent cell migration was inhibited in the presence of estramustine and the microtubule-interacting vimentin and endoplasmatic reticulum retracted to the perinuclear area. Our results show that not only a complete disassembly of microtubules, but also disturbances of the microtubule network can have dramatic effects on microtubule-dependent processes and localization of cellular organelles. These effects could be of importance in the treatment of prostatic carcinoma with estramustine.

Cell Adhesion↗

Commentary: saccadic eye movements: overview of neural circuitry.

Recent neuroanatomical, neurophysiological, clinical, and brain imaging studies have generated a wealth of data describing the neural control of saccadic eye movements and visual fixation. These studies have identified many of the cortical and subcortical structures involved in controlling the behavior. Critical nodes in the network include regions of the parietal and frontal cortices, basal ganglia, thalamus, superior colliculus, cerebellum, and brainstem reticular formation. Specific functions are likely not localized to only one brain area, but rather, they may be distributed across multiple areas. This commentary is used to review briefly the neural circuitry controlling saccadic eye movements and visual fixation.

Animals↗

Prediction of N-terminal protein sorting signals.

Recently, neural networks have been applied to a widening range of problems in molecular biology. An area particularly suited to neural-network methods is the identification of protein sorting signals and the prediction of their cleavage sites, as these functional units are encoded by local, linear sequences of amino acids rather than global 3D structures.

Chloroplasts↗

Hemianopic anosognosia.

In a prospective study of 32 consecutive patients with homonymous visual field defects due to ischemic infarcts we found hemianopic anosognosia (HAN), defined as the unawareness of visual loss in the homonymous hemifield (or hemiquadrant), in 20 patients (62%). HAN, although occurring predominantly in right-side lesions in 16 of 26 patients (62%) was also present in four of six patients (or 67%) with left-side lesions. This group of patients has been presented in a prior report on positive spontaneous visual phenomena. HAN was associated with somatic anosognosia in nine patients and hemineglect in 17 patients. Dissociation between somatic and hemianopic anosognosia, as well as between hemineglect and HAN, was present in several patients, indicating that these phenomena may be independent of each other. Eight patients had pure homonymous hemianopia; that is, hemianopia without cognitive, motor, or somatosensory deficits. Four of these patients (Group A) had awareness of the visual deficit, whereas three patients (Group B) had HAN. Patients in these two groups had similar anatomic lesions. Patients with phosphenes, photopsias, or visual hallucinations were usually aware of their visual field loss. We suggest that HAN is most often related to failure of discovery of the deficits, occasionally to severe visual hemineglect, sometimes to generalized cognitive impairment, or to a combination of these factors. We further conclude (1) there is no specific cortical area for conscious visual perception; (2) visual awareness is processed by a distributed network including multiple visual cortices, parietal and frontal lobes, the pulvinar, and lateral geniculate bodies (lesions localized at various nodes or centers in the network may produce similar phenomena); and (3) both hemispheres are involved in visual processing and conscious awareness.

Aged↗

Cortical localization of reading in normal children: an fMRI language study.

BACKGROUND: fMRI provides a noninvasive means of identifying the location and organization of neural networks that underlie cognitive functions. OBJECTIVE: To identify, using fMRI, brain regions involved in processing written text in children. METHODS: The authors studied nine normal right-handed native English-speaking children, aged 10.2 years (range 7.9 to 13.3 years), with two paradigms: reading Aesop's Fables and "Read Response Naming" (reading a description of an object that was then silently named). Data were acquired using blood oxygen level-dependent fMRI. Group data were analyzed with statistical parametric mapping; individual data sets were analyzed with a region-of-interest approach from individual study t maps. The number of activated pixels was determined in brain regions and an asymmetry index (AI = [L - R]/[L + R]) calculated for each region. RESULTS: The authors found strong activation in the left middle temporal gyrus and left midfrontal gyrus and variable activation in left inferior frontal gyrus for both reading tasks in the group analysis (z > 5.5 to 9.1). All subjects had strong left-sided lateralization for both tasks in middle/superior temporal gyrus, inferior frontal gyrus, and middle frontal gyrus (AI = 0.76 to 1.0 for t = 4). Reading Fables activated twice as many pixels in temporal cortex as the Read Response Naming task; activation in dorsolateral prefrontal cortex was similar for both tasks. Small homologous right middle temporal region activation was seen with reading a fable. CONCLUSIONS: The neural networks that process reading appear to be lateralized and localized by middle to late childhood. Reading text paradigms may prove useful for identifying frontal and temporal language-processing areas and for determining language dominance in children experiencing epilepsy or undergoing tumor surgery.

Brain Mapping↗

[Experimental studies on the diffusion of excitation on the right ventricular surface in the dog, during normal and stimulated beats].

Previous work on the spread of excitation on the dog's ventricular surface enabled us to locate up to 30 breakthrough points (BKTPs) where excitation reaches the ventricular surface. In particular the equipotential contour maps enabled us to detect 3 to 5 BKTPs on the anterior right ventricular surface, near the a-v groove when a large part of ventricular surface was still at rest. With a view to investigating the mechanism underlying the early excitation of these basal regions, we stimulated the heart at several right ventricular BKTPs and in other points located at a distance from the BKTPs. The instantaneous equipotential maps showed that after stimulation most right ventricular BKTPs remained in the same position as observed the normal beats. The early appearance of epicardial wavefronts in the basal region and generally in other areas of the right ventricle was attributed to the rapid propagation of excitation waves through the Purkinje network, probably associated to a short transmural crossing time, due to a local thinness of the ventricular wall.

Animals↗

Minimizing the impact of drug-resistant Streptococcus pneumoniae (DRSP). A strategy from the DRSP Working Group.

Emergence of drug-resistant Streptococcus pneumoniae (DRSP) presents a challenge to the medical and public health communities since the magnitude of the problem is not known, the clinical impact of DRSP infections is not well described, national vaccination rates are low, and antimicrobial drugs are often used excessively and inappropriately. To address the problem of DRSP, a working group by Centers for Disease Control and Prevention was formed in June 1994 consisting of public health practitioners, health care providers, and clinical laboratorians representing state and federal agencies and various professional organizations. Through periodic open meetings, the working group has developed a strategy for surveillance, investigation, prevention, and control of infections due to DRSP. The strategy focuses on (1) implementing an electronic laboratory-based surveillance (ELBS) system for reporting invasive DRSP infections and providing clinically relevant feedback to clinicians, (2) identifying risk factors and outcomes of DRSP infection, (3) increasing pneumococcal vaccination, and (4) promoting judicious antimicrobial drug use. Data received through ELBS will be used to make timely estimates of the community-specific prevalence of drug-resistant pneumococci. National, regional, and local trends will be made available to health care providers and clinicians to promote optimal antimicrobial drug use and increased vaccination in targeted areas. Once in operation, the ELBS network will be adaptable to other diseases, improving the comprehensiveness and timeliness of public health surveillance. The intended outcome of the strategy is to reduce complications of DRSP infection, such as long-term sequelae of infection, health care expenditures, morbidity, and mortality.

Anti-Bacterial Agents↗

Time course and mapping of cerebral perfusion during amygdala secondarily generalized seizures.

PURPOSE: Measurement of local cerebral blood flow (LCBF) is routinely used to locate the areas involved in generation and spread of seizures in epilepsy patients. Because the spatial distribution and extent of ictal CBF depends on the epileptogenic network, but also on the timing of injection of tracer, we used a rat model of amygdala-kindled seizures to follow the time-dependent changes in the distribution of LCBF changes. METHODS: Rats were implanted in the left amygdala and were fully kindled. LCBF was measured by the quantitative [(14)C]iodoantipyrine autoradiographic technique bilaterally in 35 regions. The tracer was injected at 30 s before seizure induction (early ictal), simultaneous with the application of stimulation (ictal), at 60 s after stimulation (late ictal), at the end of the electrical afterdischarge (early postictal), and at 6 min after the stimulation (late postictal). RESULTS: Rates of LCBF increased over control levels during the early ictal phase ipsilaterally in medial amygdala, frontal cortex, and ventromedian thalamus and bilaterally in the whole hippocampus, thalamic nuclei, and basal ganglia. During the ictal phase, all regions underwent hyperperfusion (81-416% increases). By 60 s after stimulation, rates of LCBF returned to control levels in most brain areas, despite ongoing seizure activity. At later times, localized foci of hypoperfusion were observed in hippocampus bilaterally, with a slight predominance in CA1 on the side of origin of the seizures. CONCLUSION: This study shows a rapid spread of activation from the stimulated amygdala bilaterally to numerous limbic, cortical, and subcortical structures. The largest hyperperfusion was recorded during the ictal period with tracer injections simultaneous with the stimulation. The unilateral site of origin of seizures led to minor asymmetrical and lateralized findings, merely at early ictal and late postictal times, whereas intermediate tracer injections induced bilateral changes. Only late postictal measurements allowed the identification of significant changes in focal structures: the hippocampus is known to play a critical role in the spread of limbic seizures.

Amygdala↗

Coordination of microtubules and the actin cytoskeleton is important in osteoclast function, but calcitonin disrupts sealing zones without affecting microtubule networks.

Bone-resorbing osteoclasts form sealing zones and ruffled borders toward the bone surface. The sealing zone consists of a ring-like alignment of F-actin dots and surrounds the ruffled border, from which protons are secreted into the bone surface. Vacuolar-type proton ATPase (V-ATPase) in osteoclasts is a ruffled border-associated enzyme responsible for the proton secretion. We studied the interaction between microtubules and the actin cytoskeleton in osteoclasts. Confocal microscopic observation revealed that osteoclasts on glass coverslips, dentine slices and Osteologictrade mark discs formed the ring-like structure of F-actin dots, and microtubules overlapped the top of the F-actin dots. Osteoclasts cultured on dentine formed resorption pits within 48 h. The treatment of osteoclasts with cytochalasin D, an F-actin-depolymerizing reagent, induced perturbation of the microtubules in osteoclasts on glass and inhibited their pit-forming activity on dentine in a dose-dependent and reversible manner. Conversely, nocodazole, a microtubule-depolymerizing reagent, disrupted sealing zones and inhibited pit-forming activity of osteoclasts in a dose-dependent and reversible manner. V-ATPase showed a tendency to be localized inside sealing zones in osteoclasts. Treatment of osteoclasts with calcitonin induced both disruption of sealing zones and dispersion of V-ATPase to the whole area of the cytoplasm within 60 min. The microtubule networks in osteoclasts remained unchanged for 60 min even in the presence of calcitonin. These results suggest that coordination of the actin cytoskeleton and microtubules is important in the function of osteoclasts, but calcitonin selectively affects the actin cytoskeleton and induces the dispersion of V-ATPase without causing significant changes in the microtubules.

Actins↗

Immunohistochemical localization of the small proteoglycans decorin and biglycan in human intervertebral discs.

Immunohistochemistry was used to study the presence and distribution of the core proteins of the small proteoglycans decorin and biglycan in the various compartments of human intervertebral discs. Both proteoglycans could be found in the outer tendon-like parts of the annulus fibrosus, indicating their potential role in collagen network formation and biomechanical stress resistance. The loss of both proteoglycans in the annulus of individuals older than 50 years reflects a normal age-related change. In the nucleus pulposus, decorin could be found in fibrillar areas of the interterritorial matrix, thereby indicating co-localization of decorin with fibrils containing type II collagen. Biglycan was present in the extracellular matrix of the nucleus pulposus of adults. The pericellular immunoreactive rims observed around nucleus pulposus cells and giant chondrones indicated local biosynthetic activity for these small proteoglycans. The staining patterns in cartilage endplates resembled those found in human hyaline articular cartilage.

Adolescent↗

Blood capillary distribution correlates with hemodynamic-based functional imaging in cerebral cortex.

Our study concerns the mechanisms that underlie functional imaging of sensory areas of cortex using hemodynamic-based methods such as optical imaging of intrinsic signals, functional magnetic resonance imaging and positron emission tomography. In temporal cortex of chinchilla, we have used optical imaging of intrinsic signals evoked by acoustic stimulation to define the functionally responsive area and then made (scanning electron microscopy) observations of the corresponding capillary networks prepared by corrosion cast methods. We report that intrinsic signals associated with auditory cortex correlate directly with discrete capillary beds. These capillary beds, within the cortical surface layers, are distributed across the cortex in a non-uniform fashion. Within cortex both the arterial supply and the capillary network contain various flow control structures. Our study suggests a causal relationship between the metabolic demands of local neuronal activity and both the density of the capillary network and the placement of the control structures. Such relationships will affect the ultimate spatial resolution obtainable by hemodynamic-based functional brain imaging studies. These relationships will also affect quantitative comparisons of activity levels in different areas of cortex.

Acoustic Stimulation↗

Metastable equilibrium with random local fluctuations: simulations of dynamic receptor pattern generation in a fluid mosaic membrane.

The generation of receptors in the animal cell's membrane was simulated by a model consisting of units in four possible states within a hexagonal area (playboard) of n units of a triangular network. The state of each unit was determined by the previous state of itself and of its six nearest neighbours, as regulated by a set of transition rules, which kept the mean relative frequency (m.r.f.) of each state constant. The transition rules were applied to the system exactly n times, regardless whether this involved selection of a unit on 0, 1, 2 or more occasions (programme "random selection with repeat"; RS-R). Comparison to previous results obtained by other ways of application of the rules has shown that the RS-R programme accounted for the highest m.r.f. of quiet (Q) units and Q clusters (sub-patterns), and also for the longest survival of Q configurations through several generations. Functioning of the model under the RS-R programme simulates an integrated system in metastable equilibrium with random local fluctuations, such as the cytoplasmic membrane is imagined to be in standardized environmental conditions. The formation-persistence-disintegration cycle of the sub-patterns is believed to simulate the dynamic generation of transitory receptor configurations in the cell membrane.

Animals↗

Distinct immuno-localization of mucin and other biliary proteins in human cholesterol gallstones.

BACKGROUND/AIMS: Cholesterol gallstones consist of cholesterol crystals and smaller amounts of pigments and calcium salts, arrayed on a mucin plus protein matrix. The localization of the various biliary proteins in the stones has not been characterized. We aimed to localize several biliary proteins in gallstones in order to determine their possible role in stone formation and growth. METHODS: The distribution of several matrix proteins and their relationships to the minerals were determined using immunostaining and EDAX microanalysis on hemisected cholesterol gallstones. RESULTS: Pigment areas were rich in calcium and contained Cu, P and S. These elements were absent in cholesterol regions. Mucin was identified in a three-dimensional network intercalated between cholesterol crystals and as septa between deposits of pigments and cholesterol; APF/CBP and ApN coated only the pigment deposits. No specific topographical localization was found for albumin or IgA. CONCLUSIONS: This suggests a role for mucin, APF/ CBP and ApN in the formation of cholesterol gallstones. We propose that cholesterol crystals bind directly to mucin, whereas calcium salts and pigments deposit on APF/CBP and ApN bind to the mucin.

Bile↗

Comparison of nerve growth factor's effects on development of septum, striatum, and nucleus basalis cholinergic neurons in vitro.

In the central nervous system, nerve growth factor (NGF) affects basal forebrain cholinergic neurons during early development and in the adult mammalian brain. These neurons are located in medial septum, diagonal band of Broca, and nucleus basalis of Meynert. While the effects of NGF on the development of septal cholinergic neurons are well documented, only little is known about the influence of NGF on development of cholinergic neurons in the nucleus basalis. In addition to the basal forebrain cholinergic neurons, there are cholinergic interneurons in the corpus striatum, which form an anatomically and functionally distinct population of cholinergic neurons. These striatal interneurons have been reported to respond to NGF during early development; however, it is not known whether the effects of NGF on their development are similar to those on septal cholinergic neurons. We prepared cultures of dissociated cells from fetal rat septum, striatum, and nucleus basalis and investigated the development of cholinergic neurons localized in these three different areas in the presence or absence of NGF. We now report that, first, cholinergic neurons of striatum and nucleus basalis develop a more extensive fiber network and contain more acetylcholinesterase (AChE) per neuron than do cholinergic neurons of septum. The amount of choline acetyltransferase (ChAT) per cholinergic neuron is approximately the same in all three culture types when grown in the absence of NGF. Second, NGF treatment increases and anti-NGF treatment decreases the number of AChE-positive neurons in cultures of low plating density, suggesting that NGF is able to promote survival of cholinergic neurons of all three areas studied. Third, NGF increases the total length of fibers and the number of branching points of cholinergic neurons in septal cultures but not in cultures of striatum and nucleus basalis. Fourth, NGF treatment increases AChE activity in septal but not in nucleus basalis or striatal cultures, suggesting that AChE activity reflects the extent of the fiber network of cholinergic neurons of all areas. Fifth, NGF treatment produces severalfold elevations in ChAT activity in septal cultures and more modest increases in cultures of nucleus basalis and striatum, suggesting that NGF is able to stimulate ChAT activity also in the absence of a stimulatory effect on survival and fiber growth. Our results demonstrate that, during early development, NGF is able to affect survival and differentiation of all three populations of forebrain cholinergic neurons.(ABSTRACT TRUNCATED AT 400 WORDS)

Acetylcholinesterase↗

Characteristics and service use of seriously mentally ill persons living in rural areas.

OBJECTIVE: Data from a cross-sectional survey of 210 current or former inpatients at Mississippi State Hospital and 197 informants, usually patients' family members, were used to compare the demographic, clinical, and service use characteristics of patients living in rural areas with those of patients living in nonrural areas. METHODS: All subjects completed structured face-to-face interviews. Information on recent use of community mental health center (CMHC) services was obtained from CMHC records. Characteristics of rural patients (N = 107) and nonrural patients (N = 103) were compared using chi square and t tests. RESULTS: Rural patients were less likely to have completed high school and more likely to be living with family members. Although rural and nonrural subjects were clinically similar, rural subjects were less likely to have received certain community mental health services such as case management and day treatment and were more likely to have used physical health services and to have been involved with the criminal justice system. CONCLUSIONS: Differences between rural and nonrural patients in patterns of service use are most likely a reflection of less availability or accessibility of mental health services in rural areas, resulting in spillover into physical health and criminal justice sectors. Rural community mental health centers need to formally incorporate families, local medical providers, and law enforcement officials into their network of care.

Activities of Daily Living↗

Immunocytochemical evidence that GLUT4 resides in a specialized translocation post-endosomal VAMP2-positive compartment in rat adipose cells in the absence of insulin.

Insulin stimulates glucose transport in rat adipose cells through the translocation of GLUT4 from a poorly defined intracellular compartment to the cell surface. We employed confocal microscopy to determine the in situ localization of GLUT4 relative to vesicle, Golgi, and endosomal proteins in these physiological insulin target cells. Three-dimensional analyses of GLUT4 immunostaining in basal cells revealed an intracellular punctate, patchy distribution both in the perinuclear region and scattered throughout the cytoplasm. VAMP2 closely associates with GLUT4 in many punctate vesicle-like structures. A small fraction of GLUT4 overlaps with TGN38-mannosidase II, gamma-adaptin, and mannose-6-phosphate receptors in the perinuclear region, presumably corresponding to late endosome and trans-Golgi network structures. GLUT4 does not co-localize with transferrin receptors, clathrin, and Igp-120. After insulin treatment, GLUT4 partially redistributes to the cell surface and decreases in the perinuclear area. However, GLUT4 remains co-localized with TGN38-mannosidase II and gamma-adaptin. Therefore, the basal compartment from which GLUT4 is translocated in response to insulin comprises specialized post-endosomal VAMP2-positive vesicles, distinct from the constitutively recycling endosomes. These results are consistent with a kinetic model in which GLUT4 is sequestered through two or more intracellular pools in series.

Adipocytes↗