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31.
The possibility of a hypothalamo-pituitary involvement in the intracranial self-stimulation phenomenon was investigated. Threshold and optimal stimulation currents were identified by means of the method of limits, in rats with bipolar electrodes implanted in the lateral hypothalamus. Total or sham hypophysectomies were performed after the establishment of these current values, and found to have no effect on reinforcing brain stimulation. It was concluded that a hypothalamo-pituitary mechanism does not subserve reinforcing brain stimulation. 相似文献
32.
Philippe Normand Pascal Simonet Luc Giasson Patrick Ravel-Chapius J. -André Fortin Maurice Lalonde 《Current genetics》1987,11(4):335-338
Summary A plasmid-like molecule was detected in a strain of the ascomycete Ceratocystis fimbriata Ell. & Halst., a pathogenic fungus of Populus spp. The DNA replicon, designated pFQ501, was found to have a linear structure with a length of 6.0 kb (3.9 × 106 daltons) and a density of 1.685 g/cc. This molecule was found to be associated with the mitochondria and was isolated from the gel; its restriction map was deduced from single and double digestions. 相似文献
33.
The effects of the behavioural context on the properties of slow and fast phases of the horizontal optokinetic nystagmus (OKN) and on the electromyographic neck response (EMG) were investigated in head-fixed pigeons. Responses in two situations were compared: (i) animals were hung in a harness ('resting' condition); (ii) animals in harness were subjected to a frontal airflow that provoked a flight posture ('flying' condition). During optokinetic stimuli the neck muscles responded in synchrony and in synergy with the eye nystagmus in both the 'resting' and the 'flying' conditions. In the 'resting' condition the neck activity was essentially correlated to the slow phase velocity of the eyes (eye SPV) whereas in the 'flying' condition, the neck response was also correlated to the eye position. The neck response was independent of the retinal slip velocity during the OKN. The velocity of the slow and fast phases of the OKN was not modified by flight. However, the 'flying' condition provoked an increase of the neck response by augmenting both its velocity gain (neck EMG/eye SPV) and its position gain (neck EMG/eye position). These results show that although an optokinetic stimulation results in synchronised eye and head motor commands in head-fixed pigeons, only the head motor command is modified by the behavioural context ('flying' vs. 'resting'). This strategy could help pigeons in reorienting their gaze during the flight. 相似文献
34.
Tieno Germann Maurice K. Gately David S. Schoenhaut Michael Lohoff Frank Mattner Susanne Fischer Shen-Chu Jin Edgar Schmitt Erwin Rüde 《European journal of immunology》1993,23(8):1762-1770
At least two subsets of CD4+ T helper cell lymphocytes termed Th1 and T h, 2 exist in the mouse and probably in humans. They are characterized by the secretion of different lymphokines and by their functional behavior. Dysregulated expansion of one or the other subset may be one reason for the development of certain diseases. Thus, it is of importance to define the signals involved in the differentiation and activation of the two Th cell subsets. It is known and has been confirmed in this report that the cytokine interleukin (IL)-1 acts onTh2 cells but not on Th1 cells. We now report that a previously identified cytokine which was provisionally termed T cell stimulating factor is identical with IL-12 and exhibits a reciprocal behaviour to IL-1. IL-12 has several effects on Th1 cells. It can induce the proliferation of certain Th1 cells in combination with IL-2. Synthesis of interferon (IFN)-γ by Th1 cells can be triggered by IL-2 plus IL-12. In contrast to the IFN-γ production observed after T cell receptor (TcR) CD3 stimulation of Th1 cells with lectin Concanavalin A the IFN-γ production induced by IL-12+IL-2 is insensitive to the immunosuppressive drug cyclosporin A. Furthermore, IL-12 enhances the TcR/CD3-induced synthesis of IFN-γ of several Th1 clones. Finally, IL-12 (+ IL-2) induces homotypic cell aggregation of Th1 clones. This type of cell aggregation depends on the participation of LFA-1 and ICAM-1 molecules. In all activation systems with Th1 cells no effect of IL-1 was demonstrable. In contrast, only IL-1 but not IL-12 served as a co-stimulatory signal for several Th2 cell lines activated via the TcR/CD3 complex. 相似文献
35.
In order to characterize the localization of the sigma(1) receptor in the adult rat central nervous system, a polyclonal antibody was raised against a 20 amino acid peptide, corresponding to the fragment 143-162 of the cloned sigma(1) receptor protein. Throughout the rostrocaudal regions of the central nervous system extending from the olfactory bulb to the spinal cord, intense to moderate immunostaining was found to be associated with: (i) ependymocytes bordering the entire ventricular system, and (ii) neuron-like structures located within the parenchyma. Double fluorescence studies confirmed that, throughout the parenchyma, sigma(1) receptor-immunostaining was essentially associated with neuronal structures immunostained for the neuronal marker betaIII-tubulin. In all rats examined, high levels of immunostaining were always associated with neurons located within specific regions including the granular layer of the olfactory bulb, various hypothalamic nuclei, the septum, the central gray, motor nuclei of the hindbrain and the dorsal horn of the spinal cord. In contrast, only faint immunostaining was associated with neurons located in the caudate-putamen and the cerebellum. Electron microscope studies indicated that sigma(1) receptor immunostaining was mostly associated with neuronal perikarya and dendrites, where it was localized to the limiting plasma membrane, the membrane of mitochondria and of some cisternae of the endoplasmic reticulum. At the level of synaptic contacts, intense immunostaining was associated with postsynaptic structures including the postsynaptic thickening and some polymorphous vesicles, whereas the presynaptic axons were devoid of immunostaining.These data indicate that the sigma(1) receptor antibody prepared here, represents a promising tool for further investigating the role of sigma(1) receptors. 相似文献
36.
Study of the protective effects of hyperimmune immunoglobulins G and M against endotoxin in mice and rats 总被引:1,自引:0,他引:1
We prepared solutions of human IgM and IgG to various lipopolysaccharide (LPS) species. These were then tested, along with
solutions of non-LPS specific human IgG or IgM, for their ability to confer passive immunity against experimental endotoxemia
in two animal models. The immunoglobulins were first tested for an effect on the lethality induced by seven different LPSs
in actinomycin-D sensitized mice, or by three different bacteria in normal mice. When the immunoglobulins were administered
1 h before challenge, a small protective effect was observed. This protection was dependent upon both the anti-LPS agent,
the chemical composition of the LPS, or the strain of Gram-negative bacteria used for injection. The anti-LPS IgM and IgG
preparations reduced the mortality induced by Escherichia coli but not by Serratia marcescens or Klebsiella pneumoniae, indicating protection by strain-specific antibodies. When the antibodies were preincubated with LPS or bacteria for 30 min
before administration, almost complete protection was seen. The influence of these immunoglobulin preparations or of human
albumin (as a control) on the hypotensive and vascular-permeabilizing effects of LPS in rats was then studied. A dose-dependent
inhibitory effect was observed with IgG preparations and albumin. At 200 mg/kg, anti-LPS IgG reduced the effects of LPS, while
at 400 mg/kg, both anti-LPS and normal IgG preparations showed protection, as did human albumin used at the same dose. The
IgM-enriched preparation worsened the initial hypotensive phase after LPS, whereas the anti-LPS IgM significantly reduced
the second phase of the hypotension, but only at the largest dose of 400 mg/kg. In this second model using the rat, a clear
difference between the activity of IgG and IgM was thus observed. We conclude that pretreatment with human immunoglobulins
from large plasma pools modestly, but significantly, attenuated the effects of murine and rat Gram-negative sepsis, but that
protection was incomplete. Our results suggest that single regimen intervention strategies may not be sufficient to influence
the course of the disease.
Received: 12 December 1998 相似文献
37.
The distribution and metabolism of ACTH and the dynamics of the adrenal cortical response to this tropic hormone were characterized
in the rat, through mathematical models involving data derived from experiments, where plasma corticosterone concentrations
were measured following both single injections and infusions of ACTH. The models, which incorporate a previously established
model of the dynamics of plasma corticosterone, were statistically validated. The simulated dynamics of the different processes
linking ACTH secretion by the adenohypophysis to corticosterone secretion by the adrenal cortex include: (1) a variable MCR
for plasma ACTH, modeled as the sum of a constant and a saturable degradation process; (2) the ability of the adrenal gland
to secrete at a maximal rate aven after the plasma ACTH concentration has become negligible, modeled as the accumulation of
an intermediary productZ directly controlled by the plasma ACTH concentration; (3) a saturable secretion with a small time constant and which, for
single injections, always starts in the same fashion, modeled as a “synthesis process” whose input is a saturable function
ofZ; (4) an immediate fall of the plasma corticosterone concentration at the end of the ACTH infusions, modeled as a “release
process” also controlled byZ.
Supported by grants from the Medical Research Council of Canada (MT-1205, MT-1555, and MA-4970), and from INSERM, France (CRL-76-5-020-4). 相似文献
38.
39.
Peak Identification in Visual Evoked Potentials 总被引:2,自引:0,他引:2
Robert A. Hall Maurice Rappaport H. Kenneth Hopkins Ralph B. Griffin 《Psychophysiology》1973,10(1):52-60
Waveform patterns evoked by 4 intensities of flash in normal subjects were studied in relation to intersubject variability. Time-frequency distribution curves of all peaks occurring between 11 and 280 msec after flash onset and meeting minimal criteria were obtained from 46 males. These distributions closely corresponded to similar data reported by others for single intensity stimulation. An algorithm was developed which identified in 67 to 100% of instances a single “peak event’ within the time ranges of each of 6 peak distributions. Many peak events appeared and disappeared within the 4 intensity sets of individuals. Latencies were obtained for these peak events. Application of the algorithm to a replicate sample of 29 Ss, which included 8 females, indicated generalizability. Test-retest data on 15 Ss showed its reliability. The data suggest that methodology significantly contributes to the variability of peak identification among subjects. This may be reduced by employing multiple intensities of stimulation. 相似文献
40.