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PubMed1996

Linear and nonlinear contributions to step responses in cat retinal ganglion cells.

We measured excitatory and inhibitory step responses of cat retinal ganglion cells to square wave contrast reversal of stationary sinusoidal gratings. In most Y-cells the initial increase in firing rate (early peak) of the excitatory responses was followed by a distinct second increase in firing rate (late peak). Analysis of the spatial frequency and spatial phase dependence of the two peaks indicated that the early peak appears to be produced by the spatially linear center mechanism, while the late peak appears to be produced by the rectifying subunits described by Hochstein and Shapley (1976) Journal of Physiology, London, 262, 237-264, 265-284. These results indicate that the presence of two peaks in ganglion cell step responses is the result of two excitatory inputs with different time courses, and that inhibitory inputs are not required to explain the appearance of these responses.

Action Potentials↗
PubMed1991

Lectin localization in human nerve by biochemically defined lectin-binding glycoproteins, neoglycoprotein and lectin-specific antibody.

Molecular recognition can be mediated by protein (lectin)-carbohydrate interaction, explaining the interest in this topic. Plant lectins and, more recently, chemically glycosylated neoglycoproteins principally allow to map the occurrence of components of this putative recognition system. Labelled endogenous lectins and the lectin-binding ligands can add to the panel of glycohistochemical tools. They may be helpful to derive physiologically valid conclusions in this field for mammalian tissues. Consequently, experiments were prompted to employ the abundant beta-galactoside-specific lectin of human nerves in affinity chromatography and in histochemistry to purify and to localize its specific glycoprotein ligands. In comparison to the beta-galactoside-specific plant lectins from Ricinus communis and Erythrina cristagalli, notable similarities were especially detectable in the respective profiles of the mammalian and the Erythrina lectin. They appear to account for rather indistinguishable staining patterns in fixed tissue sections. Inhibitory controls within affinity chromatography, within solid-phase assays for each fraction of lectin-binding glycoproteins and within histochemistry as well as the demonstration of crossreactivity of the three fractions of lectin-binding glycoproteins with the biotinylated Erythrina lectin in blotting ascertained the specificity of the lectin-glycoprotein interaction. In addition to monitoring the accessible cellular ligand part by the endogenous lectin as probe, the comparison of immunohistochemical and glycohistochemical detection of the lectin in serial sections proved these methods for receptor analysis to be rather equally effective. The observation that the biotinylated lectin-binding glycoproteins are also appropriate ligands in glycohistochemical analysis warrants emphasis.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1988

Electroencephalographic monitoring for ischemia during carotid endarterectomy: visual versus computer analysis.

In a retrospective study, we compared the use of computer-generated spectral electroencephalographic descriptors with a neurologist's interpretation of raw EEG data. Data were collected from patients undergoing carotid endarterectomy and anesthetized with isoflurane in nitrous oxide and oxygen. The EEG was recorded on magnetic tape during the period immediately before and after occlusion. These tapes were then analyzed off-line using a computer to generate averaged changes in 18 spectral descriptors. A strip-chart of raw EEG before and after the carotid occlusion was interpreted by a neurologist, who assigned changes in the EEG following occlusion to one of four visual inspection groups, depending on the severity of change. A descriptive examination of the distribution of changes in spectral descriptors revealed that no single descriptor adequately reflected the neurologist's interpretation of the raw EEG. Using data from 20 patients, the percent change from preocclusion to postocclusion values for total power, spectral edge frequency, spectral variance, and log spectral variance was examined. Only for the visual inspection group judged by the electroencephalographer to have the most severe ischemic change was there a significant difference in total power and log spectral variance. Although computer-processed EEG devices are of value as trending devices for detecting visual patterns associated with inadequate cerebral perfusion, single descriptors in this study did not consistently reflect a neurologist's diagnosis of ischemia. Single descriptors of spectral EEG analysis may not be sufficient to use as alarm variables in the recognition of cerebral ischemia.

Brain Ischemia↗
PubMed1986

Patterns of memory failure after scopolamine treatment: implications for cholinergic hypotheses of dementia.

To test the idea that scopolamine provides a suitable pharmacological model of the memory defects associated with cortical or subcortical dementias, we assessed memory on a battery of tasks in healthy young normal subjects who received 0.5 mg scopolamine, 0.1-0.2 mg glycopyrrolate or physiological saline, once each on three separate occasions, and compared the pattern of memory failure induced by scopolamine to that observed on the same tasks in patients with Alzheimer's disease (AD) or Huntington's disease (HD). In agreement with previous reports, scopolamine impaired acquisition and delayed recall of a 14-word list and disrupted retention on the Brown-Peterson distractor task, whereas the peripherally active anticholinergic glycopyrrolate was without effect. However, under scopolamine the pattern of errors made on these memory tasks was quite different from that seen in patients with AD. Scopolamine did not increase the number of false positive errors on delayed recognition of the word list and also failed to increase the number of prior-item intrusions on the Brown-Peterson task. Also, scopolamine did not impair learning of a symbol-digit paired-associate task, and did not reduce the number of words retrieved or increase the number of words repeated on a standardized verbal fluency test. When the effects of scopolamine on memory were compared to the pattern of impairments observed in demented patients with HD, several differences were found. Although scopolamine clearly produces deficits on some measures of anterograde memory, the present findings question whether anticholinergic drugs adequately mimic the full range of memory impairments observed in cortical or subcortical dementias.

Adult↗
PubMed1998

CD161 (NKR-P1A) costimulation of CD1d-dependent activation of human T cells expressing invariant V alpha 24 J alpha Q T cell receptor alpha chains.

A population of human T cells expressing an invariant V alpha 24 J alpha Q T cell antigen receptor (TCR) alpha chain and high levels of CD161 (NKR-P1A) appears to play an immunoregulatory role through production of both T helper (Th) type 1 and Th2 cytokines. Unlike other CD161(+) T cells, the major histocompatibility complex-like nonpolymorphic CD1d molecule is the target for the TCR expressed by these T cells (V alpha 24(invt) T cells) and by the homologous murine NK1 (NKR-P1C)+ T cell population. In this report, CD161 was shown to act as a specific costimulatory molecule for TCR-mediated proliferation and cytokine secretion by V alpha 24(invt) T cells. However, in contrast to results in the mouse, ligation of CD161 in the absence of TCR stimulation did not result in V alpha 24(invt) T cell activation, and costimulation through CD161 did not cause polarization of the cytokine secretion pattern. CD161 monoclonal antibodies specifically inhibited V alpha 24(invt) T cell proliferation and cytokine secretion in response to CD1d+ target cells, demonstrating a physiological accessory molecule function for CD161. However, CD1d-restricted target cell lysis by activated V alpha 24(invt) T cells, which involved a granule-mediated exocytotic mechanism, was CD161-independent. In further contrast to the mouse, the signaling pathway involved in V alpha 24(invt) T cell costimulation through CD161 did not appear to involve stable association with tyrosine kinase p56(Lck). These results demonstrate a role for CD161 as a novel costimulatory molecule for TCR-mediated recognition of CD1d by human V alpha 24(invt) T cells.

Animals↗
PubMed1993

Menstrual cycle effects on a VDT-based simulation task: cognitive indices and subjective ratings.

It is unclear whether the menstrual cycle affects the basics of performance, mainly task performance and cognitive functions. We examined menstrual cycle effects on VDT-based task performance, cognitive indices based on the signal-detection theory, and subjective ratings in questionnaires. We experimented in three phases: premenstrual, menstrual and postmenstrual phases. Previous studies reported premenstrual tension syndrome (PMST) in the premenstrual phase. Women used physiological and psychological strategies to cope during the menstrual phase. However, task performance, cognitive indices and subjective ratings showed no menstrual cycle effects. Thus, we can conclude that the information processing for the VDT-based task was not affected by menstrual cycle.

Adult↗
PubMed1988

Effect of microenvironment and cell-line type on carbohydrate-binding proteins of macrophage-like cells.

The pattern of sugar inhibition of rosette formation, a model for intercellular interaction between cultured cells and glutaraldehyde-fixed, trypsinated rabbit erythrocytes, served to infer the presence of carbohydrate-binding proteins. This profile from cell extracts for the two murine macrophage-like cell lines, P388D1 and J774A.1, was comparatively analyzed by affinity chromatography on supports with immobilized carbohydrates (lactose, L-fucose, N-acetyl-D-glucosamine, N-acetyl-D-galactosamine, and maltose) or with the immobilized mannose-rich yeast glycoprotein mannan or fetuin-derived glycopeptides containing sialic acid residues. After elution with specific sugar in the absence of Ca2+ ions, the proteins were separated by sodium dodecyl sulfate - polyacrylamide slab gel electrophoresis. The composition of carbohydrate-binding proteins of the two lines clearly exhibited quantitative and qualitative differences. Moreover, the pattern of P388D1 cells was also demonstrated to change significantly in response to alterations in the conditions of the physiological environment. These alterations were imposed by in vitro growth, by subsequent in vivo growth in nude mice, and by re-adaptation of cells to culture after in vivo passage. Collectively, our observations and other physiological and biochemical reports on macrophage lectins indicate that the presence of sugar receptors with different specificities may be an indicator of macrophage differentiation, being reversibly modulated to a considerable extent by external factors, e.g., microenvironment. Extensive but selective alterations in this respect could play an important role in the control of recognition and effector mechanisms within diverse functions of macrophage subpopulations.

Animals↗
PubMed1999

Fighting infection: the role of lipopolysaccharide binding proteins CD14 and LBP.

An invading pathogen must be held in check by the innate immune system until a specific immune response is mounted. Nonclonal pattern recognition receptors like CD14 or lipopolysaccharide (LPS) binding protein (LBP) recognize ubiquitous pathogen-associated molecular patterns, e.g. LPS. LBP mediates the binding of minute amounts of LPS to membrane-bound CD14 (mCD14) triggering a proinflammatory response of macrophages, which is crucial for keeping an infection under control. Moreover, in vitro mCD14 and LBP are involved in recognition and phagocytosis of heat-killed bacteria. Living Salmonella typhimurium or Escherichia coli depend on the presence of LBP to induce the generation of reactive oxygen species in human or murine macrophages. Using LBP-deficient mice it could be demonstrated that LBP is essential to control low dose (100 CFU S. typhimurium) infection. Therefore, LPS binding proteins play a pivotal role in physiology as well as pathophysiology of Gram-negative infection.

Acute-Phase Proteins↗
PubMed1985

Regeneration of axons and synaptic connections by touch sensory neurons in the leech central nervous system.

In studies of axonal regeneration, it has been difficult to determine (a) whether growth along the normal pathway is important for restoration of connections with previous targets and (b) whether the new synapses resemble the old in strength and location. To address these problems at the level of individual nerve cells, we have studied touch (T) sensory neurons in the leech after their axons have been severed and we have confirmed that their axons regenerate electrical connections with some of their usual synaptic targets in the central nervous system. Injections of horseradish peroxidase and Lucifer Yellow dye into separate T cells in unoperated animals showed that T cell axons typically run close to one another within single ganglia or from ganglion to ganglion. Knowledge of one T cell's arborizations thus revealed the groundplan of others in the same ganglia and the sites of apparent contact with its synaptic targets. For regenerating axons, those sprouts that encountered the normal pathway (as marked by homologous axons) grew preferentially along it. Despite the striking coincidence of old and new pathways, regenerated branching patterns within the ganglionic neuropils were usually incomplete and sometimes had atypical branches. Synaptic connections with normal targets (other T cells as well as S and C cells) were abnormally weak physiologically. The numbers of apparent contacts seen with the light microscope were also lower than normal. In addition, the strength of the synaptic potentials, normalized to the number of contacts (calculated as microvolts per contact), was generally smaller in the regenerated connections than in the controls, and smallest at earliest times, during the first 6 weeks following injury. It thus appears to be characteristic of T cell regeneration that axon regrowth is aided by the recognition of specific pathways and that successful regeneration, as assayed anatomically and physiologically, occurs frequently but usually incompletely.

Animals↗
PubMed2007

Respiratory transformation of nitrous oxide (N2O) to dinitrogen by Bacteria and Archaea.

N2O is a potent greenhouse gas and stratospheric reactant that has been steadily on the rise since the beginning of industrialization. It is an obligatory inorganic metabolite of denitrifying bacteria, and some production of N2O is also found in nitrifying and methanotrophic bacteria. We focus this review on the respiratory aspect of N2O transformation catalysed by the multicopper enzyme nitrous oxide reductase (N2OR) that provides the bacterial cell with an electron sink for anaerobic growth. Two types of Cu centres discovered in N2OR were both novel structures among the Cu proteins: the mixed-valent dinuclear Cu(A) species at the electron entry site of the enzyme, and the tetranuclear Cu(Z) centre as the first catalytically active Cu-sulfur complex known. Several accessory proteins function as Cu chaperone and ABC transporter systems for the biogenesis of the catalytic centre. We describe here the paradigm of Z-type N2OR, whose characteristics have been studied in most detail in the genera Pseudomonas and Paracoccus. Sequenced bacterial genomes now provide an invaluable additional source of information. New strains harbouring nos genes and capability of N2O utilization are being uncovered. This reveals previously unknown relationships and allows pattern recognition and predictions. The core nos genes, nosZDFYL, share a common phylogeny. Most principal taxonomic lineages follow the same biochemical and genetic pattern and share the Z-type enzyme. A modified N2OR is found in Wolinella succinogenes, and circumstantial evidence also indicates for certain Archaea another type of N2OR. The current picture supports the view of evolution of N2O respiration prior to the separation of the domains Bacteria and Archaea. Lateral nos gene transfer from an epsilon-proteobacterium as donor is suggested for Magnetospirillum magnetotacticum and Dechloromonas aromatica. In a few cases, nos gene clusters are plasmid borne. Inorganic N2O metabolism is associated with a diversity of physiological traits and biochemically challenging metabolic modes or habitats, including halorespiration, diazotrophy, symbiosis, pathogenicity, psychrophily, thermophily, extreme halophily and the marine habitat down to the greatest depth. Components for N2O respiration cover topologically the periplasm and the inner and outer membranes. The Sec and Tat translocons share the task of exporting Nos components to their functional sites. Electron donation to N2OR follows pathways with modifications depending on the host organism. A short chronology of the field is also presented.

Amino Acid Sequence↗
PubMed2007

A carbohydrate-based mechanism of species recognition in sea urchin fertilization.

In the present review, we describe a systematic study of the sulfated polysaccharides from marine invertebrates, which led to the discovery of a carbohydrate-based mechanism of sperm-egg recognition during sea urchin fertilization. We have described unique polymers present in these organisms, especially sulfated fucose-rich compounds found in the egg jelly coat of sea urchins. The polysaccharides have simple, linear structures consisting of repeating units of oligosaccharides. They differ among the various species of sea urchins in specific patterns of sulfation and/or position of the glycosidic linkage within their repeating units. These polysaccharides show species specificity in inducing the acrosome reaction in sea urchin sperm, providing a clear-cut example of a signal transduction event regulated by sulfated polysaccharides. This distinct carbohydrate-mediated mechanism of sperm-egg recognition coexists with the bindin-protein system. Possibly, the genes involved in the biosynthesis of these sulfated fucans did not evolve in concordance with evolutionary distance but underwent a dramatic change near the tip of the Strongylocentrotid tree. Overall, we established a direct causal link between the molecular structure of a sulfated polysaccharide and a cellular physiological event - the induction of the sperm acrosome reaction in sea urchins. Small structural changes modulate an entire system of sperm-egg recognition and species-specific fertilization in sea urchins. We demonstrated that sulfated polysaccharides - in addition to their known function in cell proliferation, development, coagulation, and viral infection - mediate fertilization, and respond to evolutionary mechanisms that lead to species diversity.

Acrosome Reaction↗
PubMed1998

Thermal tolerance reduces hyperthermia-induced disruption of working memory: a role for endogenous opiates?

Previous reports indicate that microwave-induced hyperthermia can impair learning and memory. Here, we report that preexposure to a single 20-min period of hyperthermia can produce thermal tolerance and, thereby, attenuate future physiological and behavioral reactions to heating. Because endogenous opioids have been implicated in thermoregulation and reactions to microwave exposure, we also determined how opioid receptor antagonism might modulate these effects. In an initial experiment, rats were exposed daily, over 5 successive days, to 600-MHz microwaves (at a whole-body specific absorption rate of 9.3 W/kg) or sham exposed. In animals exposed to microwaves, thermal tolerance was evidenced by declining rectal temperatures over time. Temperature reductions following microwave exposure were prominent after a single previous exposure. Therefore, in a second study, a single hyperthermic episode was used to induce thermal tolerance. On Day 1, rats were either exposed, over a 20-min period, to 600-MHz microwaves (at a whole-body specific absorption rate of 9.3 W/kg) or sham exposed. Just prior to radiation/sham-radiation treatment, rats received either saline or naltrexone (0.1 or 10 mg/kg, intraperitoneally (i.p.)). The following day (Day 2), rats were either microwave or sham exposed and tested on a task which measures the relative time subjects explore a familiar versus a novel stimulus object. Normothermic rats spend significantly more time in contact with new environmental components and less time with familiar objects. Brain (dura) and rectal temperatures were recorded on both days of the study. Microwave exposure produced a reliable hyperthermia which was significantly lower (on Day 2) in rats receiving repeated treatments (tolerant group). On the behavioral test, rats exposed only once to microwave-induced hyperthermia (nontolerant group) exhibited significantly different patterns of object discrimination than did tolerant or sham-exposed animals. Sham-exposed and tolerant animals showed a distinct preference for the new object whereas the nontolerant animals did not. Naltrexone (10 mg/kg) antagonized the hyperthermia-induced disruption of the object discrimination task (in nontolerant rats) and produced patterns of object exploration that were similar to those of sham-irradiated and thermal-tolerant rats, suggesting that endogenous opioids play a role in the organism's response to heating. Taken together, these data are consistent with the conclusions that 1) microwave-induced hyperthermia can cause a dose-dependent disruption of the normal discrimination between new and familiar objects, 2) physiological reactions to a single hyperthermic episode can produce a thermotolerance that expresses itself in both reduced levels of hyperthermia and attenuated behavioral disruptions following microwave exposure, and 3) opioid antagonism can partially reverse some of the behavioral effects of microwave-induced hyperthermia.

Acclimatization↗
PubMed2024

Specificity profiling of deubiquitylases against endogenously generated ubiquitin-protein conjugates.

Deubiquitylating enzymes (DUBs) remove ubiquitin from proteins thereby regulating their stability or activity. Our understanding of DUB-substrate specificity is limited because DUBs are typically not compared to each other against many physiological substrates. By broadly inhibiting DUBs in Xenopus egg extract, we generated hundreds of ubiquitylated proteins and compared the ability of 30 DUBs to deubiquitylate them using quantitative proteomics. We identified five high-impact DUBs (USP7, USP9X, USP36, USP15, and USP24) that each reduced ubiquitylation of over 10% of the isolated proteins. Candidate substrates of high-impact DUBs showed substantial overlap and were enriched for disordered regions, suggesting this feature may promote substrate recognition. Other DUBs showed lower impact and non-overlapping specificity, targeting distinct non-disordered proteins including complexes such as the ribosome or the proteasome. Altogether our study identifies candidate DUB substrates and defines patterns of functional redundancy and specificity, revealing substrate characteristics that may influence DUB-substrate recognition.

Substrate Specificity↗
PubMed2004

Identification of Lewis x structures of the cell adhesion molecule CEACAM1 from human granulocytes.

Carcinoembryonic antigen-related cell adhesion molecule 1 (CEACAM1) is expressed on epithelia, blood vessel endothelia, and leukocytes. A variety of physiological functions have been assigned to CEACAM1. It is involved in the formation of glands and blood vessels, in immune reactions, and in the regulation of tumor growth. As a homophilic and heterophilic adhesion receptor, it signals through different cellular pathways. The existence of special oligosaccharide structures such as Lewis x or sialyl-Lewis x glycans within this highly glycosylated protein has been postulated, but chemical proof is missing so far. Because such structures are known to be essential for different cell-cell recognition and adhesion processes, characterizing the CEACAM1 glycan structure is of pivotal importance in revealing the biological function of CEACAM1. We examine the terminal glycosylation pattern of CEACAM1 from human granulocytes, focusing on Lewis x epitopes. Lewis x-specific antibodies react with immunoaffinity-purified native CEACAM1. Antibody binding was completely abolished by treatment with fucosidase III, confirming a terminal alpha(1-3,4) fucose linkage to the N-acetylglucosamine of lactosamine residues, a key feature of Lewis epitopes. To verify these data, MALDI-TOF MS analysis after stepwise exoglycosidase digestion of the CEACAM1 N-glycan mixture was performed. A complex mixture of CEACAM1-bound oligosaccharides could be characterized with an unusually high amount of fucose. The sequential digestions clearly identified several different Lewis x glycan epitopes, which may modulate the cell adhesive functions of CEACAM1.

Antibodies↗
PubMed2005

Detection of an autologous ligand for mannan-binding lectin on human B lymphocytes.

Mannan-binding lectin (MBL) is a collectin and a major soluble pattern-recognition protein. MBL can distinguish self from nonself and altered self using its C-type carbohydrate recognition domain and may also interact via its collagen-like region with autologous cells. Recently, it was found that MBL could bind to adherent cells (monocytes) and dendritic cells in a specific and sugar-sensitive manner. We have now investigated the interaction of MBL with fresh human peripheral blood cells and report binding to B lymphocytes and natural killer cells. The binding to B lymphocytes was studied in detail and was compared with the binding of MBL to monocytes and dendritic cells. Binding of MBL to B cells was evident at physiological MBL and calcium concentrations but was optimal at supraphysiological MBL concentrations. It was readily inhibited by autologous serum, mannan, mannose, GlcNAc and (to a lesser extent) galactose but not by C1q. A similar, but not identical, inhibition profile was observed with dendritic cells, but monocytes were not sensitive to mannose or mannan. We conclude that MBL is capable of binding to differently glycosylated ligands on several autologous cell types via its carbohydrate-recognition domain. We speculate that this could have functional significance at extravascular sites, but perhaps only in individuals possessing MBL genotypes conferring MBL sufficiency.

Antibodies↗
PubMed2006

Training neonatal staff in recording and reporting continuous electroencephalography.

Continuous electroencephalography can contribute useful information to clinical decision-making in neonatal care. Equipment is now reliable and user-friendly enough that its use can be taught to medical and nursing staff so that a 24-hour capability is achieved. It is possible to teach neonatologists, in a 1-day course, background knowledge on EEG and amplitude-integrated EEG (aEEG), recognition of aEEG patterns that have clinical significance, recognition of seizures using aEEG and "raw" EEG, the essentials of electrode placement for aEEG, and interpretation of findings in the clinical context. This must be followed up by background reading, frequent peer-review sessions on EEG recordings, and a reliable system for storing and access, as well as willingness to consult experienced operators elsewhere.

Education, Medical, Continuing↗
PubMed2005

Interferons (IFNs) are key cytokines in both innate and adaptive antiviral immune responses--and viruses counteract IFN action.

Interferons (IFNs) are transcriptionally regulated cytokines and key players in the innate antiviral immune response. Upon recognition of a virus, or its molecular patterns, by the Toll-like receptors of dendritic cells (DCs), high levels of IFNs are expressed by these cells. This in turn stimulates DC maturation and the subsequent expression of proinflammatory cytokines and costimulatory molecules, leading to the transition to an adaptive antiviral immunity. Conversely, viruses have developed diverse strategies to counterattack host defenses in order to generate their progenies.

Animals↗
PubMed1982

Selective networks capable of representative transformations, limited generalizations, and associative memory.

Two parallel sets of selective networks composed of intercommunicating neuron-like elements have been connected to produce a new kind of automaton capable of limited recognition of two-dimensional patterns. Salient features of this automaton are (i) preestablished unchanging connectivity, (ii) preassigned connection strengths that are selectively altered according to experience, (iii) local feature detection in one network with simultaneous global feature correlation in the other, and (iv) reentrant interactions between the two networks to generate a new function, associative memory. No forced learning, explicit semantic rules, or a priori instructions are used.

Computers↗