Reduction In Immunostaining Research Articles

Evolution of cortical responsiveness subsequent to multiple forelimb nerve transections: an electrophysiological study in adult cat somatosensory cortex.

Multiunit recordings along mediolateral rows in the primary somatosensory cortex of the animals described by C. Avendaño, D. Umbriaco, R.W. Dykes, and L. Descarries (1995, J. Comp. Neurol. 354:321-332) provided information about the functional status of the regions in and near the deafferented cortex. Responses changed along this axis from normally organized receptive fields in the hindlimb representation through a transition zone of unusually small receptive fields into the clearly deafferented forelimb representation, where receptive fields were uncommon and often had unusual characteristics. The most abrupt change along this axis was the appearance of a repetitive, bursting discharge pattern in the multiunit activity near the border of the deprived cortex. The appearance of this pattern was used as a reference to describe differences between normal and deprived cortices. The nature of these differences evolved with time. Much of the deprived cortex lacked identifiable receptive fields for months after the nerve transections and, 1 year later, still only about half of the recording sites within the deprived region displayed organized receptive fields. Some sites within the deprived region lacking definable receptive fields could be excited at long latencies by somatic stimuli anywhere on the body. With time, regions of normal cortex near the border with the deprived zone became more involved in these processes. Spontaneous activity and thresholds also changed with time in both normal and deprived cortices.(ABSTRACT TRUNCATED AT 250 WORDS)

Expression of histone H1° in transcriptionally activated supraoptic neurons

This study has analysed by immunocytochemistry the expression pattern of histone H1 zero after the osmotically induced activation of transcription in supraoptic nucleus neurons of the rat. In control rats, histone H1 zero was constitutively expressed in neuronal and glial cell nuclei of supraoptic nucleus. After chronic neuronal stimulation by intermittent salt-loading, the majority of neuronal cell nuclei exhibited a marked reduction of immunostaining, which was confirmed by densitometric analysis of immunoreactivity. This effect was reversible, since optical density values returned to control levels when the stimulation of supraoptic neurons was suppressed by rehydration. Ultrastructural immunocytochemistry of histone H1 zero showed that immunogold particles specifically decorated chromatin fibers, with the highest accumulation of particles being on the condensed inactive chromatin. These results indicate that transcriptional activation in supraoptic neurons is accompanied by a depletion of the chromatin-associated histone H1 zero, and also suggest that this transcription-dependent expression of histone H1 zero may be involved in regulating chromatin condensation and gene expression in mature neurons that constitutively express this protein.

Effects of Acute Xylene Exposure on the Enkephalinergic Neuromodulatory System in Rats.

Xylene is a neurotoxic organic solvent widely used in industry. However, the neurochemical mechanism of its action on the central nervous system is to date relatively unknown. In this work, the effect of subacute xylene exposure on met-enkephalin like immunostaining in different brain regions is described. Acute treatment with xylene generates a reduction in immunostaining for met-enkephalin in the globus pallidus, the olfactory tubercule and the hypothalamic medial preoptic area, without changes in the parietal cortex, caudatus-putamen and the central amygdaloid nuclei. It is suggested that enkephalins could play a role in xylene neurotoxic mechanism in the brain.

Effect of electric field pulses on the viability and on the membrane‐bound immunoglobulins of LPS‐activated murine B‐lymphocytes: Correlation with the cell cycle

The effects of microsecond electropulses (1-5 kV/cm) on the viability of murine B lymphocytes and on their binding of antibodies by surface immunoglobulin (Ig) were studied in relation to the cell cycle. Before electropulsing, cultures given 48 h mitogenic stimulation showed at least two cell subpopulations, which were distinguishable by their levels of surface-Ig expression as assessed with FITC-labelled antibodies against mouse Ig. The immunofluorescence intensity of cells in S and G2/M phases was higher than that of G0/G1 cells. After exposure of the mitogen-stimulated lymphocytes to three exponentially decaying (time constant tau = 5-40 microseconds) electric field pulses, dye exclusion assay showed that pulsing at 1 or 2 kV/cm (at 4 degrees C or 20 degrees C) did not cause permeabilization. Field strengths of 3, 4, or 5 kV/cm resulted in 20%, 45%, or 70% of dye-permeable cells, respectively, if the pulsed cells were transferred to phosphate-buffered saline on ice for 30 min. Incubation in full medium at 37 degrees C for 30 min ("resealing") significantly decreased the percentage of permeabilized cells. Electropulsed G0/G1 cells were not only more resistant to direct electric exposure (tolerated higher field strengths) than S + G2/M cells but also responded better to resealing. The surface Ig of lymphocytes pulsed at higher fields and low temperature (4 or 5 kV/cm, tau = 5 microseconds, three pulses, 4 degrees C) was less easily immunostained than in controls or in cells pulsed at 2 kV/cm or less. At 5 kV/cm those cells that were not permeabilized showed a greater reduction in immunostaining, especially if resealed.

Effect of hypophysectomy on immunocytochemically demonstrated growth hormone releasing factor (GHRF) in the rat brain

The effect of removal of CH by long-term hypophysectomy (HPX) on the GHRF-immunoreactivity in the rat hypothalamus was studied using immunocytochemical methods. HPX resulted in a dramatic reduction in immunostaining in the median eminence (ME), indicating a significant reduction in storage of GHRF. Other regions of the hypothalamus, including the dorsomedial nucleus, the medial preoptic and suprachiasmatic regions, and the lateral hypothalamus showed the distribution and intensity of GHRF-immunoreactive structures as seen in intact animals; i.e., scattered fibers only. A few weakly stained cell bodies were seen in experimental and control animals. This could be due to a lack of storage, and/or this peptide may possibly not be present in its matured and fully immunoreactive form in the cell bodies.

Monoamines in the early chick embryo: demonstration of serotonin synthesis and the regional distribution of serotonin-concentrating cells during morphogenesis.

AbstractMonoamine compounds, such as serotonin (5‐HT), have been previously suggested to regulate the early development of the chick embryo. Possible roles for 5‐HT in chick morphogenesis were investigated further by examining the distribution of sites that concentrate 5‐HT as well as the ability of embryos to synthesize 5‐HT during this period. Following the in vitro incubation of chick embryos with 5‐HT, cells accumulating 5‐HT were localized by the formaldehyde‐induced fluorescence (FIF) technique; these sites of 5‐HT concentration were mapped and studied with respect to changes in their developmental patterns during morphogenesis. Locations of 5‐HT FIF included two regions of the brain within the floor plate of the mesencephalon and caudal myelencephalon, and within scleratome cells of somites advanced in differentiation. Additionally, two separate zones of 5‐HT FIF appeared in the neural tube caudal to the somites in conjunction with a small band of intense FIF in the caudal end of the notochord. Once established, the capabilities for 5‐HT concentration in the brain and somites persisted at the same locations during development, whereas these capabilities in caudal portions of the embryo were transient and appeared to move down the embryo as the embryo lengthened. These changes in the patterns of 5‐HT FIF in caudal segments of the neural tube and notochord correlated spatio‐temporally with the progression of caudal neuropore closure. Additional experiments, involving the use of anti‐5‐HT immunocytochemistry, were undertaken to examine the characteristics of 5‐HT concentration. The mechanism(s) of 5‐HT concentration at all locations appeared to have a high affinity and specificity for 5‐HT; however, in contrast to the transient mechanism situated more caudally in the embryos, the uptake mechanism at rostral locations required energy and was blocked by a 5‐HT uptake inhibitor (fluoxetine). The ability of embryos to synthesize 5‐HT was demonstrated by the generation of 5‐HT (localized by FIF and immunocytochemistry) in embryos treated with the 5‐HT precursors, 5‐hydroxytryptophan or L‐tryptophan. Confirming evidence of 5‐HT synthesis was provided by a marked reduction in immunostaining obtained with either precursor in the presence of 5‐HT synthesis inhibitors (R04–4602 or para‐chlorophenylalanine). Although the sites of synthesis remain uncertain, endogenous 5‐HT was detected (after monoamine oxidase inhibition) at all sites of 5‐HT concentration. These results provide further support for the suggestion that 5‐HT may be involved in various aspects of morphogenesis at specific sites within the chick embryo.