Far-field somatosensory evoked potentials in response to selective stimulation of small diameter myelinated fibers in the cat

Summary Five far-field components were identified preceding the cortical wave in response to the stimulation of the A fibers of the sural nerve. When A activity was also included in the afferent volley, a second cortical wave and additional far-field potentials were recorded. Upon blocking the A fiber activity and thus isolating the peripheral input to A fibers alone, the initial cortical wave and the far-field potentials preceding it disappeared completely, leaving the A evoked potentials intact.     

Adaptation and habituation of the vestibulo-ocular reflex in intact and inferior olive-lesioned rats

Summary The gain of the vestibulo-ocular reflex (VOR) of intact pigmented rats was adaptively modified by training protocols that created a visual-vestibular conflict. For training, head restrained animals were oscillated on a turntable in front of an optokinetic pattern projected onto a cylindrical wall. The optokinetic pattern either moved the same amplitude with the animal (in-phase: 0.05 Hz ± 20°/s) or opposite in direction (out-of-phase: turntable and pattern 0.05 Hz ± 10°/s each). VOR responses were tested in darkness before and after each 8 min training period for a duration of 40 min. During out-of-phase training the gain of compensatory eye movements measured in light was close to 2 from the beginning on and the VOR tested in darkness increased in gain progressively from 0.48 (±0.12) to 0.9 (±0.3; P < 0.05) in 5 out of 7 rats. Two rats did not adapt their VOR gain. Phase values decreased slightly by about 10°. During in-phase stimulation compensatory eye movements were almost completely suppressed (gain close to 0) from the beginning on and the VOR tested in darkness decreased gradually in gain from 0.62 (±0.17) to 0.13 (±0.1; P<0.001) in all 6 trained rats. Phase values decreased in parallel from 151° to 119° (P< 0.01). The effectiveness of the in-phase training paradigm in the absence of compensatory eye movements indicates that retinal image slip is the relevant signal for adaptation. In seven rats with histologically verified almost complete inferior olive (IO) lesions (chemically induced at least 45 days prior to training), out-of-phase and in-phase stimulation evoked compensatory eye movements with gains comparable to those in intact rats. VOR parameters measured in darkness were altered with respect to those of control rats. Gain differed extremely between individuals and phase lag re acceleration was in all IO-lesioned rats larger than in intact rats. The time constant of the VOR in response to table velocity steps was significantly longer (17 s ±4) than in intact rats (11 s ± 3). Training did not alter the gain of the VOR in 5 out of 7 IO-lesioned rats. One rat increased its gain during out-of-phase training in the first, but not during a second training session (and not during in-phase training) and another rat decreased its gain during in-phase training (but not during out-of-phase training). These changes in VOR gain might have occurred by chance rather than by learning. The absence of adaptation in IO-lesioned rats can be explained either by the absence of climbing fiber mediated slip signals in the cerebellar cortex or by lesion-induced secondary changes which result in a long-term reduction of the inhibitory efficacy of Purkinje-cells. In the absence of arousing stimuli VOR responses of intact rats exhibit a strong decrement during table oscillations in darkness. Between trials, with the rat at rest, response magnitude recovered spontaneously. Six out of 8 IO-lesioned rats expressed a very similar modification of their VOR gain. These results indicate that the neural mechanisms responsible for adaptive gain decrease during in-phase training and those responsible for a gain decrease during short-term habituation are different.     

Structural Model of the Muscle Spindle

A model of the muscle spindle was developed based on its anatomical structure. The model contains three intrafusal fibers (bag1, bag2, and chain), two efferents (dynamic efferent to the bag1 fiber and static efferent to bag2 and chain fibers), and two afferents [primary (Ia) and secondary (II)]. As in the real muscle spindle, the spindle model, under the modulation of efferents, responds to the extrafusal muscle fiber length. Both outputs (Ia and II afferents) of the model were compared extensively with published data, under both sinusoidal stretch (with different stretch amplitudes and frequencies) and ramp and hold stretch (with different stretch amplitudes and velocities) in three different fusimotor activation conditions (dynamic stimulation, static stimulation, and without stimulation). Model Ia afferent responses fit the published data well with active gamma input, but less well in the passive state. Model II afferent responses also fit the published data, although less quantitative data were available for comparison. The model correctly predicted the fractional power dependence of the primary and secondary ending responses on stretch velocity. The current model provides a powerful tool for simulation studies of neuromusculoskeletal systems, and demonstrates the feasibility of using a structural approach to model complex neurophysiological systems. © 2002 Biomedical Engineering Society. PAC02: 8719Ff, 8719La, 8719St     

On the regulation of the expressed L-type calcium channel by cAMP-dependent phosphorylation

The Ca²⁺ channel subunits _1C-a and _1C-b were stably expressed in Chinese hamster ovary (CHO) and human embryonic kidney (HEK) 293 cells. The peak Ba²⁺ current (I _Ba) of these cells was not affected significantly by internal dialysis with 0.1 mM cAMP-dependent protein kinase inhibitor peptide (mPKI), 25 M cAMP-dependent protein kinase catalytic subunit (PKA), or a combination of 25 M PKA and 1 M okadaic acid. The activity of the _1C-b channel subunit expressed stably in HEK 293 cells was depressed by 1 M H 89 and was not increased by superfusion with 5 M forskolin plus 20 M isobutylmethylxanthine (IBMX). The _1C-a·₂·₂/ complex was transiently expressed in HEK 293 cells; it was inhibited by internal dialysis of the cells with 1 M H 89, but was not affected by internal dialysis with mPKI, PKA or microcystin. Internal dialysis of cells expressing the _1C-a·₂·₂/ channel with 10 M PKA did not induce facilitation after a 150-ms prepulse to +50 mV. The Ca²⁺ current (I _Ca) of cardiac myocytes increased threefold during internal dialysis with 5 M PKA or 25 M microcystin and during external superfusion with 0.1 M isoproterenol or 5 M forskolin plus 50 M IBMX. These results indicate that the L-type Ca²⁺ channel expressed is not modulated by cAMP-dependent phosphorylation to the same extent as in native cardiac myocytes.     

γδ T Lymphocytosis Associated with Common Variable Immunodeficiency1

We present the case of a 28-year-old Caucasian female with common variable immunodeficiency (CVID) since age 5 who had a long history of hospitalizations for unexplained fevers and pulmonary infiltrates. The patient developed mild lymphocytosis 7 months prior to our evaluation. Flow cytometry of peripheral blood revealed an expansion of T lymphocytes, mild CD4 T lymphocytopenia, and a reduced CD4/CD8 ratio (0.2). Two subpopulations of T lymphocytes were found (CD3⁺/CD4^–/CD8⁺, 47%; CD3⁺/CD4^–/CD8^–, 53%), the vast majority of which expressed V-1. An infectious cause for the patient's T lymphocytosis could not be found. The sputum was chronically colonized with Staphylococcus aureus, and the organism produced TSST-1 in vitro. A bronchoalveolar lavage (BAL) revealed marked lymphocytosis, but T lymphocytes were not overrepresented in the BAL. Lymphocyte functional studies revealed poor proliferative responses to mitogens and staphylococcal superantigens and diminished cytokine production. V-1 T lymphocytes from the patient's blood were not expanded in vitro in response to staphylococcal superantigens. TCR gene rearrangement studies confirmed the presence of J and J1 clonal rearrangements accounting for only a small subpopulation of the T lymphocytes. These studies were repeated 5 months later and were unchanged. A bone marrow biopsy was negative for leukemia. Hence, the cause of the patient's T lymphocytosis could not be determined despite evaluation for underlying malignancy, occult infection, or superantigen-driven stimulation. The patient ultimately died of progressive respiratory insufficiency. The state of current knowledge regarding T lymphocytosis, decreased production of T lymphocytes, and a low CD4/CD8 ratio in association with CVID is discussed.     

Activity in myelinated cutaneous nerve fibers in response to cooling in cats

By means of the colliding impulses method and methods improving the signal to noise ratio in antidromic action potentials recorded from a cutaneous nerve, afferent impulses in its fibers were analyzed in response to cooling in cats. Fibers of group A₁ and A₂ were shown to conduct impulses during cooling of the skin receptors. A small group of fibers with conduction velocities of 13.0–7.5 m/sec showed inhibition of activity in response to cooling. A group of mixed fibers mainly responded by inhibition of activity, and only a new fibers of this group responded by excitation to cooling of the skin receptors.Department of Bionics and Biocybernetics, Institute of Applied Mathematics and Cybernetics, N. I. Lobachevskii Gor'kii University. (Presented by Academician of the Academy of Medical Sciences of the USSR, V. N. Chernigovskii.) Translated from Byulleten' Éksperimental'noi Biologii i Meditsiny, Vol. 86, No. 10, pp. 400–403, October, 1978.     

Neuron Activity in the Prefrontal Cortex of the Brain in Rats with Different Typological Characteristics in Conditions of Emotional Stimulation

Male Wistar rats were separated according to the emotional resonance method (groups of animals avoiding (altruists) and not avoiding (egotists) the pain cries of partner rats) and neuron activity in the prefrontal areas of the cortex was studied in the right and left hemispheres. Assessments were made of changes in the frequency of nerve cell spike activity (in relation to the baseline activity of neurons in sated animals) in rats subjected to one day of food deprivation and after electrical stimulation of emotionally positive (lateral hypothalamus) and negative (tegmentum of the midbrain) brain structures and after exposure to the pain cries of partner rats. The results of these experiments revealed a series of differences in the cell activities of the two groups of rats. In conditions of hunger, the discharge frequency in the altruists was higher than that in egotists. Cortical neuron responses to positive stimulation were greater than those to negative stimulation in rats of both groups. Intracerebral stimulation produced significantly greater increases in discharge frequency in neurons of both prefrontal areas of the cortex in altruists than in egotists. In both groups of rats, neurons in the right hemisphere responded to emotionally negative stimulation with significantly greater activation than cells in the left hemisphere, while activity in the left hemisphere was greater in conditions of emotionally positive stimulation. Altruists showed significantly greater neuron responses during exposure to pain cries from victim rats in both the right and left hemispheres. The responses of egotists to victim cries were not significantly different from baseline activity levels.     

Activation of atrial muscarinic K+ channels by low concentrations ofβγ subunits of rat brain G protein

Effects of G protein subunits from rat brain on cardiac K⁺ channel was examined in single atrial cells of guinea-pig, using patch clamp techniques. We found that 10 pM concentration of rat brain subunits preparation could activate the atrial muscarine receptor-gated K⁺ channel (I_K.ACh). Neither the detergent, CHAPS, used to suspend nor the boiled preparation activated I_K.ACh. Furthermore, preincubation of subunits preparation in Mg²⁺-free solution, which easily inactivated -GTP-S, did not affect -activation of I_K.ACh. We concluded, therefore, that subunits themselves can activate I_K.ACh.Supported by the grants from the Ministry of Education, Culture and Science of Japan and from the Calcium Signal Workshop on Cardiovascular Systems     

Chloride channel regulation in the skeletal muscle of normal and myotonic goats

External intercostal muscle biopsies from normal and congenitally myotonic goats were studied in vitro at 30° C using a two-microelectrode square-pulse cable analysis assisted by computer. The resting chloride conductance (G _cl) was estimated from the difference between the mean membrane conductance in chloride-containing and chloride-free bathing media. The protein kinase C (PKC) activator, 4--phorbol-12,13-dibutyrate, (0.1–2.0 M) blocks a maximum of 76% of G _cl in normal goat fibers and induces myotonic hyperexcitability similar to that of congenitally myotonic goat fibers. The G _cl block was partially antagonized by pretreatment with the PKC inhibitor, staurosporine (10 M). The inactive 4-phorbol-12, 13,didecanoate had no effect at 50 M, whereas the active 4- isomer blocked 41% G _cl at 1 M. The nearly absent G _cl of congenitally myotonic goat fibers was not restored by treatment with high concentrations of the PKC inhibitors staurosporine, 1-(5-isoquinolinesulfonyl)-2-methylpiperazine (H7), or tetrahydropapaveralone (THP). Also, forskolin and cholera toxin, which may increase cyclic adenosine monophosphate (cAMP) levels, or the R(+) clofibric acid enantiomers and taurine, which increase G _cl in normal fibers, were also unable to restore G _cl in myotonic goat fibers. The data suggest that PKC may be a chloride channel regulator in normal goat skeletal muscle fibers, however the molecular defect of congenitally myotonic fibers does not appear to be due to excessive activity of PKC.     

Gravity responses of Purkinje cells in the nodulus

Summary In cats, either decerebrated or under chloralose anaesthesia, Purkinje cells (P-cells) of the cerebellar nodulus have been examined with the animal under static lateral tilt (roll±20°). The cell activity was extracellularly recorded and both simple and complex spike discharge patterns were studied.In 20 cells out of a population of 198, simple spike firing was found to be affected by static roll. Ten cells had an -type response, 8 a -type, while only single examples of and activations were found.Out of 67 Purkinje cells tested for complex spike activation, 5 were found to be sensitive to static roll, 4 with an or response and one with a response.The results are to be attributed to pure otolith activation and show that this input is able to modulate P-cell activity in the nodulus through both the mossy fibre and the climbing fibre systems.     

Interferon β1a Treatment Modulates TH1 Expression in γδ + T Cells from Relapsing-Remitting Multiple Sclerosis Patients

A paradigm exists that multiple sclerosis is causally related to dysregulation of T_H1 inflammatory cytokines and T_H2 antiinflammatory cytokines. The cytokine source(s) that initiate the imbalances are unknown. In this study, , CD4, and CD8 T cell receptor-positive (TCR+) cells were isolated from the blood of 26 definitive relapsing-remitting multiple sclerosis patients prior to interferon -1a (IFN1a) therapy and following 8–10 weeks of this therapy. The bioactivities of interferon (IFN), interleukin 10 (IL10), and interleukin 12 (IL12) were determined. The concentrations of IFN, IL10, and IL12 from each cell type did not change significantly with IFN1a treatment. The IL10 secreted by TCR+ cells strongly correlated with the IL12 secreted by the same TCR+ cells, supporting the paradigm. Furthermore, IFN1a therapy decreased the TCR+ cell secretion of T_H1 cytokines after 8–10 weeks of therapy.     

Antidromic vasodilation in frog: identification of the nerve fiber types involved

In anesthetized, immobilized frogs arteriolar vasodilation in the submaxillaris muscle in response to electrical stimulation of the submaxillar nerve (peripheral end) was observed directly and vasodilation in the hind leg in response to stimulation of the sciatic nerve (peripheral end) measured by plethysmography. With pulses of 0.1 ms duration at 20 Hz, the threshold for arteriolar vasodilation in the submaxillaris muscle was close to 3 T, where T was the activation threshold of the most excitable fraction of motor fibers of the submaxillar nerve. Atropine had no effect on the arteriolar vasodilation. When the sciatic nerve was stimulated with pulses of 0.1 ms duration, the threshold for vasodilation in the hind leg was 3.6±1.2 T (mean ± SEM). The thresholds for excitation of the A , A and C-afferent fibers in the sciatic nerve and the range of stimulus intensities for recruiting each of these fiber groups were evaluated by recording compound action potentials in the VIII–X dorsal roots. Excitation of A -afferent fibers was found to occur in the same intensity range as that which evoked vasodilation in the hind leg. It is concluded that, in the frog, these myelinated afferent fibers are capable of dilating the blood vessels by antidromic action in both submaxillaris muscle and hind leg. This finding is in accordance with recent reports of an antidromic vasodilator action of A -afferent fibers in rabbit and rat skin.     

Occult hepatosplenic T-γδ lymphoma

We report on a patient with a rare hepatosplenic T-cell lymphoma ( TCL) presenting clinically with B-symptoms, hepatosplenomegaly and pancytopenia. During the initial stage of the disease the sparse malignant cells could not be detected histologically. Furthermore, their identification was obscured by massive macrophage proliferation with haemophagocytosis in the spleen. Diagnosis was established by detection of a clonal T-cell receptor (TcR) rearrangement and, retrospectively, by demonstration of rare cells expressing an aberrant T-cell phenotype. The findings in this patient emphasize that minimal neoplastic T-cell infiltrates can lead to severe clinical symptoms. Initial biopsy findings may be misinterpreted as benign. TCL may elaborate lymphokines that suppress haematopoiesis, leading to pancytopenia and macrophage proliferation.     

Candida albicans induces the release of inflammatory mediators from human peripheral blood monocytes

Candida albicans (C. albicans) is a major nosocomial pathogen. We examined arachidonic acid (AA) and cytokine production by monocytes stimulated with C. albicans. [¹⁴C]-AA labeled monocytes released 8.9 ±2.3% of the incorporated AA following stimulation with live C. albicans (C. albicans: monocyte of 161) (P=0.0002). Prior studies indicate that soluble-mannans and-glucans antagonize mannose and-glucan receptors, respectively. Preincubation of monocytes with-mannan (100g/ml) caused 45.8 ±5.7% inhibition of [¹⁴C]-AA release, whereas-glucan (100g/ml) yielded 43.7 ±6.0% inhibition (P<0.05 for each compared to control). Additionally, monocytes stimulated with C. albicans also released interleukin-1 (IL-1), tumor necrosis factor- (TNF), interleukin-6 (IL-6) and interleukin-8 (IL-8). However, a-mannan or-glucan failed to inhibit IL-1 release. These data indicate that C. albicans induces monocytes to release AA and inflammatory cytokines. Furthermore, AA, but not cytokine liberation, is partially mediated by a-mannan and-glucan components of the fungus.     

The role ofγδ T cells in the normal and disordered immune system

Summary A small population of T cells does not express the conventional T cell receptor characterized by the and polypeptide chains (TCR) but instead, two polypeptides termed and (TCR). This alternative receptor is able to recognize antigen. It appears early in T cell ontogeny, but its role in the thymus prior to the availability of TCR remains unclear. In selected sites such as skin or gut TCR predominates in mice which might suggest a role of T cells in the first line of defense against infection, T cells secrete lymphokines and display cytotoxic activity. However, their activation requirements may differ from what is known for T cells since MHC-nonrestricted and also CD4 and CD8 negative T cells have been described. Preferential activation by mycobacterial antigens possibly indicates a special repertoire of the T cells. In various diseases slightly increased numbers of T cells were found, but these preliminary studies have not yet provided evidence for a major pathogenetic role of T cells.List of abbreviations C constant region (immunoglobulin or TCR gene segment) - CD4 cluster of differentiation 4 (mainly on helper cells) - CD8 cluster of differentiation 8 (mainly on cytotoxic cells) - D diversity region (immunoglobulin or TCR gene segment) - DNA desoxyribonucleic acid - IL2 interleukin 2 - J joining region (immunoglobulin or TCR gene segment) - kD kiloDalton - MHC major histocompatibility complex - NK natural killer (cells) - RA rheumatoid arthritis - TCR T cell receptor - V variable region (immunoglobulin or TCR gene segment)     

Action of a serum protein on muscular contraction

Summary The mechanism of action of a serum protein isolated from human serum was assessed in several experimental preparations including glycerol-treated muscle fibers, rat heart papillary muscle and isolatedin vitro perfused rat heart. The action of the serum protein was studied also on canine and human heart papillary muscles which were made to respond to electrical stimulation with ultrasonication modified epinephrine. In addition the action of the protein on adenosine 5 triphosphate generated precipitation of purified human actomyosin was investigated.The serum protein enhanced and intensified the generation of ATP induced tension in glycerol-extracted muscle fibers. It intensified the developed tension (DT) and increased the rate of development of tension (dT/dt) without influencing the time peak tension (TPT) of capillary muscles from rat, canine and human hearts in response to electrical stimulation. The serum protein increased the force of contraction of the isolatedin vitro perfused rat heart, and accelerated the adenosine 5 triphosphate generated precipitation of purified human heart actomyosin.     

Anti-CD3-induced changes in protein kinase C isozymes expression in human CD4+ and CD8+ T lymphocytes

In order to determine whether there is a differential expression and activation of PKC isozymes between CD4+ and CD8+ T cells, peripheral blood mononuclear cells were stimulated with anti-CD3 monoclonal antibody (moAb) for various time intervals and the expression of calcium-dependent PKC isozymes (, , ) and calcium-independent PKC isozymes (, , ) was analyzed with dual color flow cytometry, using anti-PKC isozyme antibodies and anti-CD4 or anti-CD8 antibodies. The basal fluorescence intensity of all PKC isozymes was comparable between CD4+ T cells and CD8+ T cells. Following activation with anti-CD3 moAb a marked increase in the fluorescence intensity of all PKC isozymes in both CD4+ and CD8+ T cells, albeit to a different extent and with different kinetics was observed. Among all PKC isozymes studied, the least striking changes were observed in PKC isozyme and the most striking changes were observed in PKC- isozyme. Laser-based confocal microscopic studies confirmed that the increase in fluorescence intensity of PKC isozymes following anti-CD3 moAb stimulation, as measured by flow cytometry was accompanied by the translocation of PKC isozymes from cytosol to the plasma membrane. This study demonstrates a differential effect of anti-CD3 moAb on the expression of PKC isozymes between CD4+ and CD8+ T cells and suggests that flow cytometry can be used to study the translocation of PKC isozymes from cytosol to the plasma membrane.     

Time constants of facilitation and depression in Renshaw cell responses to random stimulation of motor axons

Summary In 9 adult anaesthetized cats, 22 lumbosacral Renshaw cells recorded with NaCl-filled micropipettes were activated by random stimulation of ventral roots or peripheral nerves. The stimulus patterns had mean rates of 9.5–13 or 20–23 or 45 pulses per second and were pseudo-Poisson; short intervals below ca. 5 ms (except in two cases) were excluded. The Renshaw cell responses were evaluated by two kinds of peristimulus-time histograms (PSTHs). Conventional PSTHs were calculated by averaging the Renshaw cell discharge with respect to all the stimuli in a train. These PSTHs showed an early excitatory response which was often followed by a longer-lasting slight reduction of the discharge probability. These two response components were positively correlated. Conditional PSTHs were determined by averaging the Renshaw cell discharge with respect to the second (test) stimulus in pairs of stimuli which were separated by varied intervals, . The direct effect of the first conditional response was subtracted from the excitation following the second (test) stimulus so as to isolate the effect caused by the second stimulus per se. After such a correction, the effect of the first conditioning stimulus showed pure depression, pure facilitation or mixed facilitation/depression. Analysis of such conditioning curves yielded two time constants of facilitation (ranges: ca. 4–35 ms and 93–102 ms) and two of depression (ranges: ca. 7–25 ms and 50–161 ms). It is concluded that these time constants are compatible with processes of short-term synaptic plasticity known from other synapses. Other processes such as afterhyperpolarization and mutual inhibition probably are of less importance.     

The penetration of the salivary glands ofRhodnius prolixus byTrypanosoma rangeli

Ultrastructural studies of the mechanism of penetration of the salivary gland of the reduviid bugRhodnius prolixus byTrypanosoma rangeli showed that trypanosomes from the haemocoele penetrate the outer membranes of the gland flagellum foremost, disrupting the inner layers, to pass between the muscle cells to reach the gland cell basement membrane. This latter is also penetrated flagellum foremost, the parasite invaginating the gland cell plasmalemma beneath, to create a vacuole in which the trypanosome crosses the gland cells to reach the central lumen, often only losing its containing vacuole just before leaving the cell.The structure of the outer membranes surrounding the salivary gland appeared similar to, and often actually part of, the basement membrane of the gland cells. These outer membranes were found to enclose large numbers of multinuleate giant form trypanosomes, whose significance is as yet unknown, but could perhaps represent a stage in the life cycle of the parasite where genetic interchange could take place.     

Density heterogeneities of hepatitis C virus in human sera due to the binding of β-lipoproteins and immunoglobulins

Heterogeneities in the density of hepatitis C virus RNA-carrying material (HCV-RNA-CM) found in human sera (1.03–1.20 g/cm³) are attributed to the binding of low-density lipoproteins and/or of IgG. In some sera HCV-RNA-CM seems to be nearly totally bound to -lipoproteins and cannot be precipitated by anti-IgG (); in others more than 95% of HCV-RNA-CM is bound to IgG and cannot be precipitated by anti--lipoprotein. Furthermore, there are sera from which HCV-RNA-CM can be completely be precipitated by either anti--lipoprotein or anti-IgG (), pointing to a binding of the two serum proteins to the same HCV-RNA-CM. There are other sera from which HCV-RNA-CM can be partially precipitated by the one or the other antiserum, leaving behind fractions, which are bound to -lipoprotein or to IgG. HCV-RNA-CM cannot be precipitated from some sera either by anti--lipoprotein or by anti-IgG ().