Immunocytochemical and electron-microscopic study of the elasmobranch nucleus sacci vasculosi

Summary The elasmobranch nucleus sacci vasculosi was studied by means of electron microscopy (in the dogfish) and immunocytochemistry (in the dogfish and the skate) by using antibodies against tyrosine hydroxylase, alpha-melanocyte-stimulating hormone, somatostatin, serotonin, and substance P. Ultrastructural study of the dogfish nucleus sacci vasculosi shows the presence of medium-sized cells that possess numerous mitochondria but that have no dense-core vesicles in the cytoplasm or in cell processes. Fibres of the conspicuous tractus sacci vasculosi have a beaded appearance and form conventional synapses with dendrites and cell perikarya of the nucleus sacci vasculosi. The perikarya of this hypothalamic nucleus were not immunoreactive to any of the antibodies tested, and fibres immunopositive to tyrosine hydroxylase, alpha-melanocyte-stimulating hormone, somatostatin, serotonin, and substance P were scarce within this nucleus, in both the dogfish and the skate. Dorsal to the nucleus sacci vasculosi, there are numerous positive neuronal processes in addition to many small neurons that show immunoreactivity to alpha-melanocyte-stimulating hormone, somatostatin and tyrosine hydroxylase. Two types of neuron occur in this dorsal region, displaying dense-core vesicles of either 100–160 nm or 60–100 nm diameter in their cytoplasm; they were identified as peptide-containing and monoamine-containing neurons, respectively. The neuropil of this region has a significantly different ultrastructure from that of the nucleus sacci vasculosi, with many processes containing dense-core vesicles. This group of neurons, located dorsal to the nucleus sacci vasculosi and showing (a) immunoreactivity to neuropeptides or to monoamine-synthesizing enzyme, and (b) cytoplasm with dense-core vesicles, was considered not to be a part of the nucleus sacci vasculosi but rather part of the nucleus tuberculi posterioris. These results support the non-peptidergic and non-aminergic character of the nucleus sacci vasculosi.     

Nucleus praeopticus and nucleus lateralis tuberis of Salmo salar and Salmo gairdneri: Structure and relationship to the hypophysis

Summary The nucleus praeopticus (NPO) is located on both sides of the preoptic recess and is composed of a pars parvocellularis and a pars magnocellularis. Only in the rainbow trout does the pars magnocellularis consist of separately located medium-sized cells and very large cells. Cytologically, three cell types can be distinguished: 1) unipolar cells ending in the cerebrospinal fluid (CSF), 2) bipolar cells also ending in the CSF and forming an axon, and 3) multipolar cells which generally do not have a direct connection with the ventricle.Axons originate from the cell bodies forming the paired preopticohypophysial tract that runs along the border of the diencephalon and the optic tract. A considerable number of NPO fibers leading to the hypophysis makes close contact with the cell bodies of the pars lateralis of the nucleus lateralis tuberis, indicating a functional relationship. Most NPO fibers terminate in the caudal part of the neurohypophysis, around blood capillaries and at the basal lamina of the pars intermedia. Far fewer fibers appear to terminate near the boundary of the neurohypophysis and the rostral and proximal pars distalis.The nucleus lateralis tuberis (NLT) is located in the caudal hypothalamus, beginning at the rostral end of the horizontal commissure and extending caudally beyond the hypophysial stalk. It consists of the partes rostralis, medialis, lateralis and ventrolateralis. In both species the p. rostralis contains small subependymal neurons and some larger ones. Only in the p. medialis of the Atlantic salmon are large cells present. In both species the most prominent part is the p. lateralis, which consists solely of large cells. Cells situated between the p. medialis and the p. lateralis are grouped in the p. ventrolateralis. It was impossible to trace the axons originating in the NLT, since the cyto- and axoplasm could not be stained specifically.The structure of the NPO and NLT in the two salmonid species is compared with that of other teleosts.     

Ultrastructure of the “smooth endoplasmic reticulum cell” in the nucleus recessus lateralis of Salmo gairdneri Richardson

Summary The fine structure of one of the cellular components of the nucleus recessus lateralis of trout is described. These cells have an enormously developed smooth endoplasmic reticulum which makes their identification easy. The relationship of this cell type with the ventricular cavity, neighbouring cells and the presence of synaptic contacts with these cells are also described.     

Mechanisms of corticofugal control of the activity of “vagal” viscerosensory neurons in theNucleus tractus solitarii

In experiemnts on cats under chloralose-nembutal anesthesia, we studied viscerosensory neurons in thenucl. tractus solitarii identified by their responses to stimulation of then. vagus. The responses of these cells to stimulation of the secondary sensorimotor cortex (zoneS2) and dorsal regions of field 25 of the limbic cortex (DLC) were recorded. A substantial part of the “vagal” viscerosensory units demonstrated convergent properties and responded toS2 and DLC stimulations by phasic responses. The short latencies of these responses were indicative of oligosynaptic and, in some cases, even monosynaptic transmission of corticofugal influences on a considerable part of such neurons. Using paired stimulation allowed us to demonstrate that the effects of stimulation of the visceral afferent fiber undergo long-lasting suppression exerted by descending corticofugal volleys. The mechanisms of cortical control of the activity of bulbar viscerosensory neurons are discussed.     

Nuclear development in locust fat body: the influence of juvenile hormone on inclusion bodies and the nuclear matrix

The hormonal induction of vitellogenesis in insects and in oviparous vertebrates are prime models of gene regulation in eukaryotes. In vertebrates the process is under estrogenic control and normally confined to females, although males can be artificially induced. In locust in contrast, juvenile hormone (JH) is central to fat body development in both males and females, yet the response is strongly sex limited not only for vitellogenin production but also in terms of total protein, DNA and RNA synthesis and nuclear ploidy levels. To differentiate further possible sex and/or JH related developmental aspects in locusts, large-scale nuclear events were examined during normal adult maturation and in animals treated with antiallatropins and JH analogs. Fat body nuclei undergo extensive restructuring during normal development in both sexes. This included progressive nuclear enlargement, accompanied by extensive proliferation of nuclear matrix components and elaboration of complex inclusion bodies (NB). The isolated protein matrix was unusually complex relative to similar structures from vertebrates and the NB were firmly anchored to it. Although matrix proteins were qualitatively similar to those from other sources, as assessed by SDS polyacrylamide gel electrophoresis, several major matrix polypeptides, including lamins A and B, and components greater than 150 kD, fluctuated quantitatively during development and in concert with nuclear enlargement. The number and morphology of the NB were unrelated to sex, but increased in direct proportion to absolute nuclear volumes. All changes were more pronounced in females, where higher ploidy levels, larger nuclei and correspondingly more internal matrix elements occurred. Suppression of JH production by precocene prevented all foregoing nuclear changes, but re-exposure to methoprene rapidly induced normal development. The results are compared to analogous nuclear changes in steroid responsive vertebrate tissues.     

Effects of ozone on cell organelles of alfalfa (Medicago sativa L.) seedlings

Seedlings of alfalfa (Medicago sativa L.) were exposed to different concentrations of atmospheric ozone (20–30 (control), 40–60, 65–80, and 85–120 ppb) in four distinct areas in the Riyadh region, so as to decide how ozone affected some of the seedling cellular organelles. Results acquired utilizing transmission electron microscopy demonstrated certifiable impacts to exist on the cell organelles in the tissues of both the leaf mesophyll and stem cortex; contrasted with control plants, the chloroplasts seemed enlarged, irregular, different sizes, decomposed, and possibly dissolved, while the plastoglobules seemed deformed, more widely spaced, and enlarged, also the vacuoles contained no clear non-living components. Moreover, some parts of the cytoplasmic membranes were ruptured, with only a few vesicles created at all concentrations, particularly in plants exposed to concentrations of 65–80 and 85–120 ppb, while no effects were noted in these organelles in control plants or plants exposed to 40–60 ppb. High concentrations (85–120 ppb) led to enlarged, irregularly shaped nuclei and chromatin intensification; however, no clear effects of ozone were noted on the shapes of chloroplast starch grains or the mitochondria in leaf mesophyll and cortex cells in the stem. The high ozone concentrations can cause negative effects on the growth of alfalfa seedlings, leading to imbalances in their vital functions and acceleration of aging, thus potentially decreasing the total plant yield. The discoveries hence propose that alfalfa plants should not be planted near polluted areas, and that they can be utilized as bioindicators of air pollution by ozone.     

Nucleus-associated actin in Amoeba proteus

The presence, spatial distribution and forms of intranuclear and nucleus-associated cytoplasmic actin were studied in Amoeba proteus with immunocytochemical approaches. Labeling with different anti-actin antibodies and staining with TRITC-phalloidin and fluorescent deoxyribonuclease I were used. We showed that actin is abundant within the nucleus as well as in the cytoplasm of A. proteus cells. According to DNase I experiments, the predominant form of intranuclear actin is G-actin which is associated with chromatin strands. Besides, unpolymerized actin was shown to participate in organization of a prominent actin layer adjacent to the outer surface of nuclear envelope. No significant amount of F-actin was found in the nucleus. At the same time, the amoeba nucleus is enclosed in a basket-like structure formed by circumnuclear actin filaments and bundles connected with global cytoplasmic actin cytoskeleton. A supposed architectural function of actin filaments was studied by treatment with actin-depolymerizing agent latrunculin A. It disassembled the circumnuclear actin system, but did not affect the intranuclear chromatin structure. The results obtained for amoeba cells support the modern concept that actin is involved in fundamental nuclear processes that have evolved in the cells of multicellular organisms.     

Inositides in the nucleus: presence and characterisation of the isozymes of phospholipase β family in NIH 3T3 cells

Previous reports from our laboratories and others have hinted that the nucleus is a site for an autonomous signalling system acting through the activation of the inositol lipid cycle. Among phospholipases (PLC) it has been shown previously that PLCβ₁ is specifically localised in the nucleus as well as at the plasma membrane. Using NIH 3T3 cells, it has been possible to obtain, with two purification strategies, in the presence or in the absence of Nonidet P-40, both intact nuclei still maintaining the outer membrane and nuclei completely stripped of their envelope. In these nuclei, we show that not only PLCβ₁ is present, but also PLCβ₂, PLCβ₃ and PLCβ₄. The more abounding isoform is PLCβ₁ followed by PLCβ₃, PLCβ₂ and PLCβ₄, respectively. All the isoforms are enriched in nuclear preparations free from nuclear envelope and cytoplasmatic debris, indicating that the actual localisation of the PLCβ isozymes is in the inner nuclear compartment.     

Changes in α-melanotropin in discrete brain areas of isolated aggressive mice

Adult male Swiss-Webster (NIH) mice were isolated for 6 weeks. Aggressive behavior was tested on 2 occasions, 24 hours apart. Immediately following the 2nd test period, aggressors and isolated non-aggressors (controls) were decapitated and α-MSH concentration was measured in discrete areas of the brain. Only the nucleus accumbens and preoptic lateralis of the aggressors, showed a higher level of α-MSH when compared to the controls. The significance of these changes is discussed.     

From humoral fever to neuroimmunological control of fever

Fever is a part of the acute phase response to infection or systemic inflammation. It is thus a part of a complex physiological defence strategy against micro-organisms invading the body of the host, or against non-microbial agents recognized as foreign by mobile immune cells of the body. The fever is induced by inflammatory mediators (prostaglandins, cytokines) released by immune cells activated by contacts with foreign molecules (exogenous pyrogens). These fever-inducing mediators, produced by the host cells (endogenous pyrogens), were originally thought to be distributed by means of the bloodstream (similarly to hormones) to different tissues of the body. Although the details of their transport across the blood–brain-barrier have not been clarified, it has been assumed that they activate the local production of inflammatory mediators within the brain, inducing a change in the thermoregulatory set-range and resulting in fever (humoral theory of fever). This concept has apparently changed in the past few years. Evidence has recently been presented supporting the possibility of the transport of immune signals to the brain via vegetative and peripheral nerves. In this review an attempt is made to describe the events leading to a fever response accompanying the systemic inflammation against a background of microbiological, immunological and physiological data. The experimental evidence published during the last five years has been reviewed, and a new concept of neuroimmunological control of fever is presented. This concept suggests that the host immune defence is coordinated through an integration of the neural, immune, hemopoietic and endocrine systems. The brain seems to be informed of any damage or antigenic challenge in the periphery of the body by a sensory host-monitoring system, and this information is confirmed by immune signals delivered by the humoral transport. The combination of these signals would allow the brain to recognize the nature of the challenge, and to activate an appropriate defence strategy. Fever as a part of many successful defence strategies against infections may thus be beneficial.