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At least 973 records · Page 54Linked to original sources
PubMed1997

The role of H. pylori infection in the pathophysiology of duodenal ulcer disease.

The discovery of H. pylori infection and the recognition of its effects on gastric physiology has significantly advanced our understanding of the pathophysiology of ulcer disease, In DU patients H. pylori gastritis is mainly confined to the antral mucosa. It stimulates increased release of gastrin by the antral mucosa and this is accompanied by high acid output by the oxyntic mucosa. This high acid response to gastrin stimulation by the oxyntic mucosa in DU patients is due to the combination of a high parietal cell mass and the fact that the function of these parietal cells is not impaired by any body gastritis. The increased acid secretion results in an increased duodenal acid load with the development of gastric metaplasia within the duodenal bulb and then actual ulceration. The reason why only some subjects develop this antral predominant pattern of H. pylori gastritis and associated acid hypersecretion is unclear but may be explained by a premorbid high acid output protecting the oxyntic mucosa form H. pylori gastritis.

Duodenal Ulcer↗
PubMed1999

Abnormal calcification on plain radiographs of the abdomen.

The purpose of this pictorial review is to facilitate recognition and understanding of calcifications seen on conventional radiographs of the abdomen. Calcifications can be categorized by organ system and location in the abdomen. Both common and rare calcifications in the urinary tract, liver, gallbladder, spleen, pancreas, adrenal glands, digestive tract, genital tract, peritoneal cavity, and retroperitoneum are illustrated. Abnormal calcifications in the urinary tract are subcategorized by kidneys, ureters, bladder, and urethra. The density, shape, size, margins, pattern, position, and mobility of calcifications are emphasized for differential diagnoses.

Adrenal Glands↗
PubMed1994

The craniofacial dysostosis syndromes. Current reconstructive strategies.

The author's preferred approach to the management of the craniofacial dysostosis syndromes is to stage the reconstruction to coincide with the facial growth patterns, visceral (brain and eye) function, and psychosocial development. Recognition for the need for a staged reconstruction approach serves to clarify the objectives of each phase of treatment for the surgeon, the craniofacial team, and the family unit. By continuing to define the rationale for the timing and extent of surgical intervention, then objectively evaluating both functional and morphologic outcomes, surgeons will further improve the long-term function and facial aesthetics for patients born with these complex syndromes.

Brain↗
PubMed1991

Speech recognition by an artificial neural network using findings on the afferent auditory system.

An artificial neural network which uses anatomical and physiological findings on the afferent pathway from the ear to the cortex is presented and the roles of the constituent functions in recognition of continuous speech are examined. The network deals with successive spectra of speech sounds by a cascade of several neural layers: lateral excitation layer (LEL), lateral inhibition layer (LIL), and a pile of feature detection layers (FDL's). These layers are shown to be effective for recognizing spoken words. Namely, first, LEL reduces the distortion of sound spectrum caused by the pitch of speech sounds. Next, LIL emphasizes the major energy peaks of sound spectrum, the formants. Last, FDL's detect syllables and words in successive formants, where two functions, time-delay and strong adaptation, play important roles: time-delay makes it possible to retain the pattern of formant changes for a period to detect spoken words successively; strong adaptation contributes to removing the time-warp of formant changes. Digital computer simulations show that the network detect isolated syllables, isolated words, and connected words in continuous speech, while reproducing the fundamental responses found in the auditory system such as ON, OFF, ON-OFF, and SUSTAINED patterns.

Acoustic Stimulation↗
PubMed2002

Social regulation of gonadotropin-releasing hormone.

Behavioral interactions among social animals can regulate both reproductive behavior and fertility. A prime example of socially regulated reproduction occurs in the cichlid fish Haplochromis burtoni, in which interactions between males dynamically regulate gonadal function throughout life. This plasticity is mediated by the brain, where neurons that contain the key reproductive regulatory peptide gonadotropin-releasing hormone (GnRH) change size reversibly depending on male social status. To understand how behavior controls the brain, we manipulated the social system of these fish, quantified their behavior and then assessed neural and physiological changes in the reproductive and stress axes. GnRH gene expression was assessed using molecular probes specific for the three GnRH forms in the brain of H. burtoni. We found that perception of social opportunity to increase status by a male leads to heightened aggressiveness, to increased expression of only one of the three GnRH forms and to increases in size of GnRH-containing neurons and of the gonads. The biological changes characteristic of social ascent happen faster than changes following social descent. Interestingly, behavioral changes show the reverse pattern: aggressive behaviors emerge more slowly in ascending animals than they disappear in descending animals. Although the gonads and GnRH neurons undergo similar changes in female H. burtoni, regulation occurs via endogenous rather than exogenous social signals. Our data show that recognition of social signals by males alters stress levels, which may contribute to the alteration in GnRH gene expression in particular neurons essential for the animal to perform in its new social status.

Aggression↗
PubMed1980

Central peripheral temperature gradient. Its value and limitations in the management of critically iii surgical patients.

Monitoring the central peripheral temperature gradient in critically ill surgical patients is a simple, sensitive, noninvasive and inexpensive method that can accurately reflect the state of peripheral circulation. It serves as an early warning sign, and its return to normal is a good measure of the efficacy o f therapy. Recognition of the cause of an abnormal gradient is essential to successful management since it can result from pain as well as hypovolemia. Warm-up patterns vary, and every patient should be treated individually. Forcing vasodilatation is usually unnecessary and amy be dangerous in hypothermic patients and in patients with hypovolemia if blood volume is not corrected simultaneously. Peripheral vascular disease, central hypothermia and the use of vasoactive drugs limit the usefulness of this method.

Adolescent↗
PubMed1999

Neuroethology has pregnant agendas.

Two of the many agendas of neuroethology are illustrated with examples. The first issue is what cells or assemblies of cells and what patterns of activity are sufficient to accomplish recognition of ethologically important stimulus configurations and initiation of behavioral action. The theme is the opportunities available in relatively neglected approaches to these objectives. As an example, the approach is developed of gentle microstimulation of loci in the brain where cells have been found to be responsive to complex, natural stimuli, under conditions conducive to the performance of tell-tale behavior. Other approaches include: (a) microinjection of modulatory substances into regions with such complex recognition cells, and (b) recording in efficient and informative ways, by using multiple electrode arrays, registering wideband activity, in behaving animals. The second issue is what brain and behavior differences has evolution produced between major taxa at distinct grades of complexity. Emphasized are our relative ignorance of basic aspects of connectivity, physiology and cognitive capacities in the major grades and the probability of surprises from new studies that employ comparison.

Animals↗
PubMed1990

Cell recognition and pattern formation in the developing nervous system.

The topographic map of cell position in the avian retina is conserved and inverted when retinal ganglion neurons synapse with neurons in the optic tectum. Developmental mechanisms based on molecular gradients that specify positional information and pattern formation have been postulated in the establishment of these topographic maps of cells in retina and optic tectum. Two cell surface proteins in retina, TOP(DV) and TOP(AP), are distributed in dorsoventral and anteroposterior topographic gradients, respectively. Corresponding gradients of TOP molecules present in the tectum are inverted with respect to the retinal gradients. These orthogonal gradients of TOP(DV) and TOP(AP) molecules provide a possible Cartesian coordinate system for designation of cell position at all points in the retinotectal map.

Animals↗
PubMed1999

Electrocochleographic documentation of temporal findings of speech perception in normal and hearing-impaired individuals.

Compound action potentials (CAPs) evoked by the short Japanese syllables /a/ and /ka/ were recorded by extratympanic electrocochleography in 17 subjects with normal hearing (17 ears) and 34 patients with sensorineural hearing losses (35 ears) to investigate the temporal aspects of speech coding for perception. In normal ears, three characteristics were found common to the temporal patterns of all CAPs: (1) a prominent CAP at the beginning of both stimuli; (2) periodic CAPs with the same interval as the pitch period through the vowel part of both stimuli; (3) absence of a prominent CAP at the onset of voice. These characteristics may help to produce consonant recognition. Among the subjects with sensorineural hearing loss, some ears showed the following two characteristics different from those with normal hearing: (1) a significantly lower CAP at the onset of both stimuli than in those with normal hearing; (2) decay of CAPs during the voiced part. These findings may result in abnormal loudness perception in sensorineural hearing loss as produced by loudness recruitment and pathological adaptation. Such different temporal patterns of CAPs may have an adverse influence on the speech discrimination of patients with sensorineural hearing impairments.

Acoustic Stimulation↗
PubMed2000

Functional mosaic organization of mouse olfactory receptor neurons.

In contrast to rapid progress in the molecular biology of olfaction, there are few physiological data to characterize the odor response properties of different populations of olfactory receptor neurons (ORNs) and their spatial distributions across the epithelium, which is essential for understanding the coding mechanisms underlying odor discrimination and recognition. We have tested the hypothesis that the ORNs are arranged in a functional mosaic, using an intact epithelial preparation from the mouse, in which odor responses of many ORNs in situ can be monitored simultaneously with calcium imaging techniques. ORNs responding to a given odor were widely distributed across epithelium and intermingled with ORNs responding to other odors. Tight clusters of ORNs responding to the same odor were observed. For a given odor, more ORNs were recruited when the concentration was increased. ORNs were able to distinguish between pairs of enantiomers by showing distinct but somewhat overlapping patterns. The results provide evidence regarding the response spectra of ORNs in situ, supporting the combinatorial coding of odor quality and intensity by different ORN subsets.

Animals↗
PubMedDate not supplied

Results of electroencephalographic monitoring during 367 carotid endarterectomies. Use of a dedicated minicomputer.

Three hundred sixty-seven carotid endarterectomies were monitored using routine electroencephalographic (EEG) techniques. In 9.8%, changes in the EEG followed clamping of the internal carotid artery and could roughly be grouped into 6 patterns. The most common (47%) was rapid unilateral or bilateral attenuation of background anesthetic-induced fast EEG activity. Conclusions drawn from studies of the 9 patients who had immediate postoperative neurological deficits of varying degrees are presented as they illustrate monitoring techniques that are useful for early recognition of cerebral ischemia. Thirty-five patients were monitored with both routine and computerized techniques--the latter proved more useful than the former on all counts.

Anesthesia↗
PubMed2000

E-selectin expression and function in a unique placental trophoblast population at the fetal-maternal interface: regulation by a trophoblast-restricted transcriptional mechanism conserved between humans and mice.

Trophoblast are the earliest differentiated cells to emerge during mammalian ontogeny. Proper differentiation and maturation of trophoblast contributes to the fetal-maternal vascular interface of the mature placenta and is required for all subsequent stages of embryogenesis. Although lineage commitment and early differentiation of trophoblast have been investigated experimentally, molecular markers and regulatory mechanisms operating later in trophoblast development remain uncertain. We now report that E-selectin is expressed in a unique pattern in secondary trophoblast giant cells, trophoblast lining the central artery, and a subpopulation of labyrinthine trophoblast all located at the fetal-maternal interface of the murine placenta. These cells line vascular channels but express a unique profile of gene products not displayed by vascular endothelium. Placentae lacking E-selectin show increased trophoblast glycogen cells and fewer labyrinthine neutrophils compared with normal placentae, suggesting that recognition of E-selectin on trophoblast by counter-receptors on other cells contributes to placental development. Novel, distant first exons direct E-selectin expression in both murine and human placentae, suggesting that evolutionarily conserved and lineage-restricted transcriptional mechanisms regulate expression in homologous trophoblast populations in both species. These results define, at molecular and anatomic levels, a unique population of trophoblast located at the physiologically critical fetal-maternal vascular interface in mice. We also present initial functional characterization of E-selectin in placenta. These results support the general hypothesis that endothelial-leukocyte adhesion molecules performing specialized functions in adults may also function in development of human and murine hemochorial placentae.

Animals↗
PubMed2003

Characterisation of bacterial polysaccharides: steps towards single-molecular studies.

Techniques used in studies of polysaccharides, including chemical composition, linkage pattern, and higher order structures are in constant development. They provide information necessary for understanding of the polysaccharide properties and functions. Here, recent advancements in studies of the polysaccharides at the single-molecule level are highlighted. Over the last few years, single-molecule techniques such as force spectroscopy have improved in sensitivity and can today be used to detect forces in the pN range. In addition, these techniques can be used to investigate properties of single molecules close to physiological conditions. The challenges in the interpretation of the observations are aided by control experiments using well-characterised polysaccharides and by data provided by complementary methods. This field is expected to have increasing impact on the further advancement of the molecular understanding of the role of polysaccharides in various biological processes such as recognition and cell adhesion.

Biochemistry↗
PubMed1986

Cerebrospinal fluid pulsation: benefits and pitfalls in MR imaging.

Physiologic cerebrospinal fluid (CSF) pulsation causes a harmonic modulation of proton precessional phase with two-dimensional Fourier transform (2DFT) imaging, which results in predictable regions of signal loss and the presence of phase-shift images ("ghost images"). CSF that is not pulsating exhibits a higher signal than does pulsatile CSF. This phenomenon can be diagnostically useful in disease entities associated with decreased CSF pulsation amplitude, such as arachnoid cyst, intraventricular cyst, spinal stenosis, and spinal block caused by extramedullary or epidural tumor. Unfortunately, this increased signal can also mimic disease such as epidural tumor in the spine or acoustic neuroma in the internal auditory canal. An abnormal pattern of CSF pulsation, as occurs in patients with arachnoiditis, can cause unusual areas of signal loss, which complicate image interpretation and can mimic pathologic conditions. Recognition of CSF pulsation effects will increase in importance as thin-section magnetic resonance imaging becomes more common, because thin sections enhance these effects with 2DFT.

Central Nervous System Diseases↗
PubMed1995

Computer-assisted decision support systems for patient management in an intensive care unit.

The application of the intelligent monitoring techniques of case-based reasoning and neural network analysis to physician decision making concerning patient care in an Intensive Car Unit (ICU) is described. Case-based reasoning offers a model for quickly matching--using a predetermined hierarchical structure--a single patient's parameters (text or numeric) to similar parameters contained in a clinical database. The output produces a group of patients which may be set to match exactly on certain characteristics and may also be set to match "as closely as possible" on a gradient of patient properties. Clinicians may thus use the system to find the group of the closest matching cases to their current patient. Aspects of the ICU history of the selected group may then be displayed graphically (e.g., mortality, length of stay, hours of ventilation, procedures utilized, and complications encountered). Neural network analysis is a pattern recognition technique which uses a training set of patient data (text or numeric) to seek mathematical relationships between various subsets of patient parameters. The discovered relationships from the training set are then applied to estimate the outcomes (e.g., mortality, length of stay, hours of ventilation) of new patients. The effects of these intelligent monitoring techniques are scheduled to be tested in a field trial held in a regional referral center ICU.

Algorithms↗
PubMed1986

A neural cocktail-party processor.

Sensory segmentation is an outstanding unsolved problem of theoretical, practical and technical importance. The basic idea of a solution is described in the form of a model. The response of "neurons" within the sensory field is temporally unstable. Segmentation is expressed by synchronization within segments and desynchronization between segments. Correlations are generated by an autonomous pattern formation process. Neuronal coupling is the result both of peripheral evidence (similarity of local quality) and of central evidence (common membership in a stored pattern). The model is consistent with known anatomy and physiology. However, a new physiological function, synaptic modulation, has to be postulated. The present paper restricts explicit treatment to the peripheral evidence represented by amplitude modulations globally present in all components of a sound spectrum. Generalization to arbitrary sensory qualities will be the subject of a later paper. The model is an application and illustration of the Correlation Theory of brain function.

Action Potentials↗
PubMed1989

Subjective contours, tilt aftereffects, and visual cortical organization.

The tilt aftereffect (TAE) was used to study interactions between real and subjective contours. Subjects adapted to either real or illusory lines and were then shown test stimuli containing real or illusory lines. In our first experiment, we found that there is a marked asymmetry in the interactions between real and subjective stimuli. Adaptation to real lines produces comparable TAEs with real and subjective test lines. With either type of test stimulus the maximum effect occurs with a 10-20 deg difference between the orientations of the adaptation and test stimuli. Also, there is a strong TAE when the adaptation and test stimuli contain only subjective lines. However, there is a significantly weaker TAE when the adaptation stimulus is subjective and the test stimulus is real. In a second experiment we find that interocular transfer of tilt aftereffects is greater when the test stimulus is subjective than when it is real. These results are consistent with physiological reports that a subset of orientation selective cells in visual cortex is responsive to subjective contours and that these cells are more binocular, on average, than those responsive only to real contours. Our findings also suggest that the perception of subjective contours is based on the activation of neurons with properties, such as orientation selectivity, which are characteristic of early visual cortical areas.

Adaptation, Ocular↗
PubMed1985

Altitude-related illness.

There are a number of conditions which can be grouped together as ARI. Many represent potentially fatal pathophysiological states that are rapidly reversible if identified and treated properly. Physiological alterations that result from the hypobaric hypoxia of altitude include cerebral vasodilatation, altered ventilatory patterns, pulmonary vasoconstriction, decreased cardiac output, and altered fluid and electrolyte balance. The various altitude-related illnesses represent a spectrum of conditions with overlapping presentations. The symptoms of AMS and HACE represent a continuum of disease that appears to be related to alterations in cerebrovascular autoregulation. High-altitude retinal hemorrhage may be related to similar vascular events in the retinal circulation. Although the etiology of HAPE remains unclear, it is likely that alterations of pulmonary vascular tone and flow play an important roles in its production. Knowledge regarding ARI is important in planning prophylaxis and instituting therapy. Gradual ascent and acclimatization are the mainstays of prophylaxis. Pharmacological prophylaxis is available for those who are prone to severe AMS. Prompt recognition, descent, and administration of oxygen constitute the major therapies for severe ARI. The ability to perform these three tasks can rapidly reverse a potentially fatal illness.

Acetazolamide↗