Chemotherapy of systemic mycoses (second of two parts).
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Galanin (GAL) is widely distributed in the peripheral and the central nervous systems. In the brain, the highest GAL concentrations are observed within the hypothalamus and, particularly, in nerve terminals of the median eminence. This location, as well as GAL actions on prolactin, growth hormone, luteinizing hormone (LH), and LH-releasing hormone (LHRH) secretion, suggest the possibility that GAL may act as a putative hypothalamic-hypophysiotropic hormone. To establish this, GAL and LHRH levels were measured in hypophyseal portal plasma samples using specific radioimmunoassays. Rat galanin (rGAL) concentrations in portal blood were approximately 7-fold higher than those observed in peripheral plasma in male and female (estrus, diestrus) rats, indicating an active secretory process of rGAL into the portal vasculature. Frequent (10 min) sampling revealed that rGAL and LHRH were secreted into the portal circulation in a pulsatile manner with a pulse frequency of one pulse per hour. Interestingly, both hormone series depicted a high degree of coincident episodes. In fact, the probability of random coincidence, calculated by the algorithm HYPERGEO, was less than 0.01. Moreover, the retrograde tracer Fluoro-Gold, when given systemically, was taken up by GAL neurons in the hypothalamus, including a subset of neurons expressing rGAL and LHRH, strengthening the notion of the existence of a GAL neuronal system connected to the hypophyseal portal circulation. These observations reinforce the concept that GAL regulates pituitary hormone secretion. To analyze this in further detail, the effects of rGAL on LH secretion were evaluated under basal and stimulated conditions. rGAL induced a small but dose-dependent increase in LH secretion from cultured, dispersed pituitary cells. Interestingly, rGAL enhanced the ability of LHRH to stimulate LH release. The tight link between GAL and LHRH neuronal systems is strengthened by the observation that during the estrous cycle of the rat, rGAL and LHRH contents in the median eminence show an identical profile (r = 1.00). These data indicate that GAL should be considered as a hypothalamic-hypophysiotropic hormone and as an important neuromodulator of LHRH secretion and action. The colocalization and cosecretion of GAL and LHRH and the cooperative action at the level of the anterior pituitary afford important evidence for the functional significance of coexistence of neurotransmitters in neurons of the central nervous system.
The superior colliculus is a layered structure in the mammalian midbrain serving multimodal sensorimotor integration. Its intermediate layers are characterized by a compartmental architecture. These compartments are apparent through the clustering of terminals of major collicular afferents, which in many instances match the heterogeneous distribution of tissue components such as acetylcholinesterase, choline acetyltransferase, substance P, and parvalbumin. The present study was undertaken to determine whether efferent cells observe this compartmental architecture. It was found that subpopulations of both descending and ascending collicular efferents originate from perikarya situated in characteristic positions relative to the collicular compartments defined by elevated acetylcholinesterase activity and that their dendrites appear to be specifically coordinated with the heterogeneous environment. With the specific interlocking of afferent and efferent neurons through spatially distinguished neural networks, the compartmental architecture apparently constitutes an essential element for the determination of information flow in the superior colliculus.
A method for simultaneous iontophoretic injections of the anterograde tracer Phaseolus vulgaris leukoagglutinin and the retrograde tracer fluorogold was used to characterize in the rat a hypothalamothalamocortical pathway ending in a region thought to regulate attentional mechanisms by way of eye and head movements. The relevant medial hypothalamic nuclei receive pheromonal information from the amygdala and project to specific parts of the thalamic nucleus reuniens and anteromedial nucleus, which then project to a specific lateral part of the retrosplenial area (or medial visual cortex). This cortical area receives a convergent input from the lateral posterior thalamic nucleus and projects to the superior colliculus. Bidirectional connections with the hippocampal formation suggest that activity in this circuit is modified by previous experience. Striking parallels with basal ganglia circuitry are noted.
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PURPOSE: To count retrogradely labeled retinal ganglion cells by Fluoro-Gold. METHODS: Retinal ganglion cells were retrogradely labeled using bilateral injections of Fluoro-Gold into the superior colliculus. One week after injections, retinas were dissociated and immunolabeled using specific antibody against Fluoro-Gold. The Fluoro-Gold labeled cells were then counted using flow cytometry. RESULTS: Flow cytometry revealed that approximately 7% of the dissociated retinal cells were ganglion cells retrogradely labeled by Fluoro-Gold (Fig. 1B). Based on the total count of retinal cells per eye, the total number of retinal ganglion cells was estimated at approximately 131,250 +/- 2,542 per rat eye. The coefficient of variation of counts was calculated as 1.98%. CONCLUSIONS: The use of flow cytometry facilitates simple, reproducible and rapid quantification of virtually all of the retinal ganglion cells labeled by Fluoro-Gold in a single rat eye.
PURPOSE: The aim of this study was to determine whether the phosphatidylinositol 3-kinase (PI3K)/Akt signaling pathway can function as a neuroprotective pathway following induced retinal injury. METHODS: The activation of Akt was assessed by immunoblot analysis, and the role of PI3K/Akt pathway was evaluated by TUNEL staining and counting the number of retrogradely-labeled retinal ganglion cells (RGCs) in the whole retina at 168 h after injury with or without PI3K specific inhibitor, LY294002. RESULTS: Akt was induced within one hr and reached a maximum 6 hrs after optic nerve clamping. The activation was observed in the RGC layer including RGCs, the inner plexiform layer, inner nuclear layer, and in the photoreceptor outer segments. The number of surviving RGCs was decreased significantly 168 hrs after injury. LY294002 partially inhibited the activation of Akt, and significantly decreased the number of surviving RGCs as compared with that of injury alone. CONCLUSIONS: These results indicate that the PI3K/Akt signaling pathway is activated intrinsically and has a neuroprotective effect on injured RGCs.
The vanilloid receptor VR1 and the vanilloid receptor-like protein VRL-1 are associated with polymodal nociceptors, and may be important for pain processing in normal and injured teeth. Using immunohistochemistry, we have studied the distribution of these receptors in rat pulpal or gingival trigeminal ganglion neurons that were identified through retrograde labeling with fluoro-gold. Twenty-one percent to 34% of tooth pulp-innervating neurons were VRl-positive, while 32%-51% were VRL-1-immunoreactive. However, double-labeling experiments revealed that VR1 and VRL-1 rarely co-existed in the same cells, but rather seemed to be confined to separate subpopulations. Among the gingival neurons, about 25% were VR1-positive and about 41% were VRL-1-immunoreactive. A lesion of the inferior alveolar nerve, which supplies mandibular teeth and gingiva, resulted in a marked down-regulation of VR1 in the affected trigeminal ganglion cells. A down-regulation of VRL-l was also indicated. The results suggest that both VR1 and VRL-1 could have significant roles in pulpal and gingival nociceptive transduction.
In situ hybridization for trkA mRNA in trigeminal ganglion neurons retrogradely labeled with FluoroGold from the mandibular incisor demonstrated limited expression of the high-affinity nerve growth factor (NGF) receptor in this presumptive nociceptor population. Immunocytochemistry using polyclonal anti-trkA antibodies confirmed this result and extended it to show low levels of trkA protein expression in afferents labeled from the cornea. Less than 10% of the cells innervating the incisor, and approximately 15% of those innervating the cornea, were trkA-positive in adult and neonatal mice. This proportion is considerably lower than that observed in Dorsal Root Ganglion nociceptors, in which approximately 80% in neonates and approximately 40% in adults express trkA (Molliver and Snider, J. Comp Neurol 381: 428-438, 1997). Presumptive trigeminal nociceptors were further identified on the basis of expression of Calcitonin gene related peptide. In the entire ganglion, approximately 43% of the trkA-positive cells were CGRP-positive, and approximately 44% of the CGRP-positive cells were trkA-positive. Most trkA-positive cells that were CGRP-negative were medium-to-large diameter, while most of those that were CGRP-positive but trkA-negative were small diameter. Only approximately 5% of trkA-positive cells labeled from the incisor, and approximately 10% from the cornea, were CGRP-positive. Approximately 15% of the corneal or pulpal afferent neurons expressed ret-immunoreactivity. These results suggest that trigeminal nociceptors differ from spinal nociceptors in several significant ways. Differences in neurotrophic requirements may be related to differences in target tissues, in embryonic origin of some trigeminal ganglion cells, or in the timing of down-regulation of trkA expression in trigeminal ganglion cells.
The retrograde tracer fluoro-gold was injected into the periaqueductal grey, thalamus or hypothalamus, and spinal cord sections were processed for neuronal nitric oxide synthase (nNOS) immunohistochemistry to investigate the relationships of nNOS immunoreactive, and spinomesencephalic, spinothalamic and spinohypothalamic projection neurones. In addition, in the lateral spinal nucleus the relationship between spinomesencephalic, -thalamic and -hypothalamic projection neurones, and nNOS and interferon-gamma receptor immunoreactive structures was investigated at the lumbar level. No single retrogradely labelled spinomesencephalic, -thalamic or -hypothalamic neurone showed nNOS immunoreactivity. In the lateral spinal nucleus, however, many fluoro-gold-labelled neurones were closely apposed by both nNOS and interferon-gamma receptor immunoreactive structures, especially prominent in the hypothalamic injection cases. This study gave no evidence for nNOS immunoreactivity in spinal neurones projecting to the periaqueductal grey, thalamus or hypothalamus, but suggests that in the lateral spinal nucleus such neurones are contacted by both nNOS- and interferon-gamma receptor-containing axon terminals.
We mapped the dynamic distribution of fluoro-gold (FG) within rat brain following intracerebroventricular (icv) injection into the lateral ventricle and observed its interrelation with neural nitric oxide synthase (nNOS) using FG fluorescent microphotography combined with nNOS immunohistochemistry. We also detected the amount of icv administered FG entering the peripheral circulation using a fluorescence microplate assay. The degree of periventricular penetration of FG was significantly increased over time. At 2 min after icv injection, FG primarily labeled the choroid plexus in the lateral and third ventricles, with limited penetration into the ependyma and the subependyma of the same ventricles. Some FG/nNOS-double labeled cerebrospinal fluid-contacting neurons were observed in these ventricles as well. At 15 and 30 min, FG penetrated mainly into forebrain ventricular organs and parenchymal structures. Many FG/nNOS double labeled neurons were found at each of these sites. In addition, at 30 min intense FG labeling was found in the hypophysis, while limited periventricular penetration of FG was detected in the hindbrain circumventricular areas. In the peripheral circulation, a low concentration of FG was detected 2 min after icv injection. The concentration increased slowly, peaked at 20 min, then gradually decreased until the end of the experiment at 30 min. These findings indicate that dynamic penetration of icv administrated agents into the periventricular tissues and peripheral circulation should be considered when designing icv experiments.
The neurocircuitry responsible for excessive stress-induced cardiovascular responses in genetic hypertensive rats remains elusive. Prior studies detailed a differential cardiovascular response profile to airpuff startle stimuli between Spontaneously Hypertensive (SHR) and Wistar Kyoto (WKY) rats. We recently identified strain differential Fos expression in the rostroventrolateral medulla (RVLM) and several RVLM projecting sites following airpuff startle. The current study sought to define RVLM projecting neurons that also express Fos following placement in the test chamber and administration of the airpuff startle stimulus. Unilateral iontophoretic micro-injections of fluorogold were made into the RVLM of 9-10 week old SHR and WKY rats. Two to three weeks later, animals were subjected to a series of 60 airpuff startle stimuli. Brains were double labeled for Fos and fluorogold. Single fluorogold and single Fos cells, and double labeled cells were found in the nucleus tractus solitarius (NTS), caudal ventral lateral medulla (CVLM), Kölliker fuse (KF), ventral lateral, lateral, and dorsal central gray, lateral hypothalamus (LH), and paraventricular nucleus of the hypothalamus (PVN). These data are consistent with the notion that the RVLM receives differential excitatory and/or inhibitory input from higher brain centers, perhaps contributing to differential Fos expression in the RVLM, differential autonomic responding, or both.
Hydroxystilbamidine isethionate, a dye capable of binding to both DNA and RNA, has been found to be a powerful inhibitor of cellular ribonucleases. A procedure has been developed that, with the aid of this compound, permits the preparative isolation of giant silk fibroin polyribosomes from the posterior silk gland of Bombyx mori. The polyribosomes contain approximately 45-112 ribosomal particles, as judged by electron microscopy. Treatment of giant fibroin polyribosomes with EDTA releases a particle that sediments at 125S. This mRNP particle contains biologically active silk fibroin mRNA, as judged by cell-free translation in an mRNA-dependent reticulocyte cell-free system.
By measuring the transient changes in each of the polarized components of fluorescence during the application of a pulsed electric field to a solution of macromolecules, a method has been developed for evaluating the binding characteristics of fluorescent chemotherapeutic agents to DNA. It is shown that whereas quinacrine and berberine intercalate the DNA helix, hydroxystilbamidine does not. Furthermore, measurements on both the native and the diol-epoxide forms of benzo(a)pyrene show that the former is consistent with an intercalation type of binding, whilst the latter appears to be more inclined to the major DNA axis and may possibly be associated with the external helical grooves. The significance of these findings is discussed.
This study examined whether continuous intramedullary infusion of brain-derived neurotrophic factor (BDNF), nerve growth factor (NGF), or neurotrophin-3 (NT-3) had either an early neuroprotective effect or a delayed effect on regeneration after spinal cord injury (SCI) in adult rats. BDNF, NGF, NT-3 or vehicle was infused at a rate of 625 ng/h into the SCI site at T3 through an implanted cannula attached to an osmotic pump. This infusion was maintained for 14 days after a 35-g clip compression injury. At 4 weeks after injury, the axonal tracer fluorogold (FG) was introduced into the spinal cord caudal to the lesion and the animals sacrificed 3 days later following behavioral assessment. The inclined plane score was significantly higher in BDNF-treated animals (45 +/- 3 degrees) compared to control animals (36 -/+ 1 degrees) at 1 week after injury (p < 0.05), although the scores were not significantly different at later times. BDNF-treated animals also showed more FG-labeled cells in the red nucleus and sensorimotor cortex (1,638 +/- 350 and 124 +/- 83, respectively) compared to controls (1,228 +/- 217 and 36 +/- 15, respectively) and a lower percent cavitation at the injury site (21.4 +/- 10.4%) compared to control animals (32.3 +/- 11.7%). Invasion & proliferation of Schwann cells and formation of peripheral myelin were more prominent at the injury site in the BDNF-treated animals than in the other groups. These results indicate that continuous intramedullary infusion of BDNF provides neuroprotection and enhances some regenerative activity after SCI.
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Latexin, a carboxypeptidase A inhibitor, is expressed in a subset of neurons in the infragranular layers of the lateral cortex in the rat. We here show that latexin-expressing neurons exhibit ultrastructural features common to cortical pyramidal neurons. We show in combined retrograde tracing and immunofluorescent experiments that latexin-expressing neurons contribute to specific corticocortical pathways. Thus, injections of the retrograde tracer fluorogold into either the primary somatosensory (SI) or the primary motor (MI) cortical area labeled many latexin-expressing neurons in the infragranular layers of the secondary somatosensory (SII) and visceral sensory (Vi) areas. In contrast, tracer injections involving the thalamus, striatum, or contralateral SII and Vi exclusively labeled latexin-nonexpressing neurons in both the SII and Vi. Finally, we show that the correct corticocortical projections can be formed in organotypic slice cultures in vitro from latexin-expressing neurons: when slices of developing SII were cocultured with those from the SI and the thalamus, latexin-immunoreactive neurons in the SII projected preferentially to their normal SI target. The specific connectivity formed in vivo and in vitro by this molecularly distinct neuronal population reveals its characteristic manner of cortical organization and provides a unique model system to analyze mechanisms underlying the formation of precise corticocortical pathways.