Lipid peroxidative stress and antioxidative enzymes in brains of milk-supplemented rats

Skim milk cultured with lactic acid bacteria has been previously reported to reduce lipid peroxidation in rat livers. In this study, the effects of skim milk and cultured milk supplementation on peroxidative stress in brains of weanling rats were investigated. We observed a reduction of brain thiobarbituric acid reacting substances (TBARS) concentration in milk-supplemented animals as compared with controls. In brains of control rats, the superoxide dismutase (SOD) enzyme levels were significantly higher than those from the milk-supplemented animals. In addition, SOD activity in control animal brains had a positive correlation with the TBARS concentration. There was no significant differences in the brain glutathione-S-transferase (GST) levels of all the three groups of animals. The results suggest that milk supplementation may be beneficial in reducing peroxidative stress in the developing rat brain.

Induction of neuronal and inducible nitric oxide synthase in the motoneurons of spinal cord following transient abdominal aorta occlusion in rats

BACKGROUND

Motoneurons in the spinal cord are especially vulnerable to ischemic injury and selectively destroyed after transient ischemia. Nitric oxide (NO) has been implicated in both neurodegneration and neuroprotection to ischemic insult. To evaluate the role of NO in pathophysiology to spinal cord ischemia, the expression of neuronal and inducible nitric oxide synthase (n-NOS and i-NOS) and nicotinamide adenine dinucleotide phosphate diaphorase (NADPH-d) in the motoneurons of the lumbosacral spinal cord was examined in a rat model with transient abdominal aorta (TAA) occlusion.

MATERIALS AND METHODS

Male Sprague-Dawley rats were divided into sham-operated (n = 12) and TAA occlusion (n = 24) groups. TAA occlusion was induced by placement of a microvascular clamp around the abdominal aorta for 20 min. Three sham-operated and six TAA occlusion animals were sacrificed at each time interval at 4, 24, and 48 h and 7 days after operation. Tissue sections obtained from the lumbosacral spinal cord were processed for n-NOS, i-NOS, NADPH-d, and hematoxylin-eosin (HE) staining. Histological changes of motoneurons in ventral horn were assessed by HE staining.

RESULTS

In sham-operated control animals, n-NOS-, i-NOS-, and NADPH-d-positive neurons were barely detectable in the ventral horn of the spinal cord. At 4 h after TTA occlusion, n-NOS and NADPH-d expression became evident in the motoneurons and was markedly enhanced at 24 and 48 h. i-NOS expression was also induced in the ventral horn motoneurons of the lumbosacral spinal cord at the same time points. Enzymatic expression in the motoneurons was diminished 7 days after operation. Hyperchromatic neurons indicative of cell death were observed in HE-stained specimens 7 days following TAA occlusion.

CONCLUSIONS

The rapid induction of n-NOS, i-NOS, and NADPH-d in the motoneurons of ventral horn suggests that NO may be involved in the selective and delayed neuronal death in the spinal cord to the ischemic insult.

Emperipolesis of lymphoid cells in vagal efferent neurons following an intraneural injection of ricin into the vagus nerve in rats

Injection of a minute amount of the toxic lectin, Ricinus communis agglutinin-60 (RCA-60) into the vagus nerve resulted in a selective destruction of the vagal efferent neurons in the ipsilateral dorsal motor nucleus (DMN). This has elicited a massive influx of mononuclear leucocytes, notably macrophages and T-lymphocytes, as detected with ED-1 and OX-19 antibodies, respectively. A small number of B-lymphocytes as identified by OX-33 antibody, were also observed in the neuropil of DMN. The influx of mononuclear leucocytes into the neuropil of DMN was by way of diapedesis, peaking in frequency at 4-6 days after the RCA administration. The infiltrated lymphocytes were closely associated with or penetrated the soma of the vagal neurons, some bearing intact axo-somatic synaptic contacts. The entrapped lymphocytes in neurons underwent degeneration and subsequently disintegrated. Macrophages and plasma cells in the neuropil did not appear to penetrate the neuronal soma. It is concluded that emperipolesis of lymphocytes, presumably cytotoxic T-cells, in RCA-poisoned neurons may represent a form of effector-target cell contact leading to cytotoxicity. In doing so, however, the invading lymphocytes were destroyed by the contents of RCA picked up by the neurons. The absence of macrophages and plasma cells in the RCA-poisoned neurons suggests the cellular specificity of emperipolesis.

Effects of melatonin on macrophages/microglia in postnatal rat brain

The present study examined the response of macrophages/microglia to multiple injections of melatonin in the pineal gland and different regions of the brain. The macrophages/microglia showed a significant increase in cell numbers and upregulation of complement type 3 receptors (CR3), major histocompatibility complex class I (MHC I) and class II (MHC II) antigens, and antigens of monocyte/macrophage lineage, as detected by the antibodies OX-42, OX-18, OX-6, and ED1, respectively. The upregulation of the above antigens was observed in 1-d-old rats given daily injections of melatonin and killed at 7-11 d of age; no noticeable change was observed at earlier time intervals. The macrophages/microglia expressing the above antigens appeared round and showed a vacuolated cytoplasm compared with ramified cells in the control rats. Upregulation of CD4 antigens as detected with the antibody W3/25 was also observed in macrophages/microglia in the corpus callosum and epiplexus cells in the lateral ventricles, but not in the pineal gland and the cerebral cortex in the same age group. In rats killed between 2 and 5 d, and at 14 d of age after melatonin treatment, the immunoreactivities of macrophages/microglia with the above mentioned antibodies were comparable to cells in the control rats. Immunoreactive cells were not detected in any of the age groups in melatonin-treated or control rats with the antibodies W3/13 and OX-33, which are markers for T and B lymphocytes. It is concluded that CR3 receptors, MHC antigens, and CD4 antigens on macrophages/microglia are upregulated following melatonin administration. On the other hand, once the melatonin treatment is discontinued the expression of the various antigens/receptors returns to normal levels, suggesting that increased immune potentiality and its maintenance in these cells require the continuous action of the drug.

Induction of NADPH diaphorase/nitric oxide synthase in the spinal cord motor neurons of rats following a single and multiple non-penetrative blasts

The present study has demonstrated the induction of nicotinamide adenine dinucleotide phosphate-diaphorase (NADPH-d) reactivity and nitric oxide synthase-like immunoreactivity (NOS-LI) in the ventral horn motoneurons of the spinal cord in rats subjected to a single or multiple underground, or a single surface blast. Both enzyme activities were first detected in some motoneurons in laminae VIII and IX of Rexed, 3 hours after the blast. Some NADPH-d and NOS-LI positive neurons were also distributed in laminae VI and VII. The number and intensity of the labelled cells appeared to increase progressively, peaking at 2-3 days after the blast but were drastically reduced thereafter, so that at 7 days after the blast only a few positive neurons were observed. In rats killed at 2 weeks and in longer surviving intervals, i.e. up to 1 month, NADPH-d/NOS reactivity in the ventral horn motor neurons had diminished. The functional significance of the transient expression of neuronal NADPH-d/NOS after the blasts remains uncertain, although from a speculative point of view, the induction of these enzymes probably would reflect an increased production of nitric oxide (NO). In view of the lack of atrophic changes in most, if not all, of motor neurons, it is suggested that the increased levels of NO production after the blast injury may be involved in a neuroprotective function.

Microglial reaction in some CNS nuclei following nerves transection in BALB/c and interferon-gamma gene knockout mice

The present study was aimed to ascertain if the endogenous IFN-gamma is necessary for induction of microglial reaction associated with the CNS neurons after neurectomy of the vagus and hypoglossal nerves in IFN-gamma gene knockout mice and BALB/c mice serving as controls. Vigorous microglial reaction as detected by Mac-1 antibody was elicited in the brainstem nuclei in both strains of mice. Increased Mac-1 immunoreactivity in microglia was detected as early as 1 day post-operation in the ipsilateral dorsal nucleus of vagus, nucleus ambiguus and the hypoglossal nucleus; a similar feature was observed in the nucleus tractus solitarius bilaterally. Mac-1 immunoreactivity in reactive microglia appeared to increase with survival intervals and was comparable throughout in both strains of mice. It is therefore concluded that endogenous IFN-gamma is not responsible for upregulation of complement type 3 receptor immunomolecules in reactive microglia following nerves sectioning.

Increased expression of transferrin receptors and iron in amoeboid microglial cells in postnatal rats following an exposure to hypoxia

This study was aimed to ascertain the effects of hypoxia on regulation of iron in the brain of newborn rats. At 3 h and 1 day after hypoxic exposure transferrin receptor expression as detected immunohistochemically with the antibody OX-26, and the iron content as shown by Perls' staining of amoeboid microglial cells was markedly increased. The induced changes, however, were not evident at 10 min and in longer surviving rats killed at 3 and 7 days. It is suggested that the upregulation of transferrin receptor expression coupled with iron uptake by amoeboid microglial cells in the periventricular regions is a protective mechanism to facilitate the sequestration of excess iron that may have been released either from the iron-rich oligodendrocytes, or accumulated due to a disruption of its normal transportation following the hypoxic insult. This would help protect the brain from harmful effects of iron.

Effects of dexamethasone on antigen expressions and proliferation of amoeboid microglial cells in fetal rat brain

The present study examined the effect of maternal administration of dexamethasone (DEX) on amoeboid microglial cells (AMC) in fetal rats extending from 16 to 20 days postconception (E16 to E20). After an intraperitoneal injection of DEX into pregnant rats at E10, the external morphology and distribution of immunolabelled AMC as detected with OX-42 and ED1 monoclonal antibodies remained unaltered when compared with those of the controls. The major effect of dexamethasone was on microglial cell population. Thus, with OX-42 and ED1, the numbers of immunolabelled AMC in the intermediate zone lateral to the striatum (IZS) of DEX-treated fetuses which remained relatively unchanged at E16 were significantly reduced at E18. However, OX-42 labelled cells showed an unexpected increase in number at E20 following DEX treatment. Microglial response to DEX was also analyzed in sections stained with the isolectin, GSA I-B4, which specifically binds alpha-D-galactosyl glycoproteins on microglia. The number of GSA I-B4 labelled AMC was significantly increased at E16, declined at E18 and remained constant thereafter in DEX-treated rats when compared with that of the controls. A major finding after DEX treatment was the wider occurrence of AMC double labelled with anti-BrdU antibody and GSA I-B4 or OX-42 at E16 compared with those in the controls suggesting that the initial increase of GSA I-B4 labelled AMC may be attributed to their proliferation. The drastic reduction of OX-42 and ED1 positive microglial cells notably at E18 may be due to the downregulation of surface antigens as a result of possible suppressive action of dexamethasone. On the basis of present findings, it is concluded that the antigenic expressions of fetal AMC may be modulated by DEX administrated maternally. Such however appeared to be extremely selective as reflected by the varied expression for certain immune molecules at different stages of brain development. This information would be useful in potential use of glucocorticoids in prenatal therapy of brain pathology via maternal circulation.

Localization of nicotinamide adenine dinucleotide phosphate-diaphorase reactivity and nitric oxide synthase immunoreactivity in the lumbosacral dorsal root ganglia in guinea pigs

This study examined the distribution of reduced nicotinamide adenine dinucleotide phosphate diaphorase (NADPH-d) reactivity and nitric oxide synthase (NOS) immunoreactivity in the lumbosacral dorsal root ganglia (DRG) in male guinea pigs. A differential distribution of NADPH-d reactivity and NOS immunoreactivity was detected in neurons of DRG at different segmental levels. There were numerically more intensely stained NADPH-d and NOS reactive cells in the rostral (L1-L3) DRG compared with those at the caudal (L6-S4) levels. In the corresponding DRG, NADPH-d reactivity was not paralleled by NOS immunoreactivity. This was evidenced by the wide distribution of afferent neurons in the lumbosacral DRG stained for NADPH-d, yet only a small number of them exhibited NOS immunoreactivity. Double labelling study has shown that some of the NADPH-d positive neurons were NOS negative. Ultrastructurally, NADPH-d reaction product was associated with the membranes of various subcellular organelles, including the rough endoplasmic reticulum (rER), Golgi saccules, mitochondria and some segments of the nuclear envelop, whereas NOS immune-precipitate was patchily distributed throughout the cytoplasm. Present results suggest that nitric oxide (NO) may function as a neurotransmitter in the afferent pathways at lumbosacral segments. On the other hand, in view of their marked disparity in numbers and the lack of total one-to-one correspondence, it seems likely that the NOS positive neurons represent only a subpopulation of the NADPH-d positive cells in the lumbosacral DRG.

Degenerative changes of afferent neurons in the lumbosacral dorsal root ganglia following complete urethral obstruction in guinea pigs

OBJECTIVE

The ultrastructural changes in the bladder afferent neurons were examined in the guinea pig following acute complete urethral obstruction.

MATERIAL AND METHODS

Complete urethral ligation was carried out in nine guinea pigs under anaesthesia and the animals were sacrificed at 12, 24 and 48 h postoperatively. Three sham-operated animals were sacrificed at 48 h postoperatively as controls. The dorsal root ganglia (DRG) at L6, S1 and S2 spinal segments of the animals in each group were removed and processed for electron microscopic study.

RESULTS

In the control groups, all the DRG neurons at L6-S2 segments appeared normal. At 12 h after urethral ligation, a few neurons in the DRG at various segments showed signs of structural changes, notably the mitochondria. Mitochondrial swelling was more pronounced at 24 h, and by 48 h most of them became vacuolated and lysed. It was estimated by semiquantitative study that 18.6% and 22% of DRG neuronal profiles at 24 and 48 h, respectively, displayed severe mitochondrial swelling and vacuolation.

CONCLUSIONS

The observed degenerative changes in DRG neurons following complete urethral obstruction may be a cellular reaction in response to the axonal injury elicited by bladder overdistension. This may account for alterations in visceral sensation in patients with acute urinary retention.

Propentofylline attenuates microglial reaction in the rat spinal cord induced by middle cerebral artery occlusion

This study examines the effect of Propentofylline (PPF) on reactive microglia in the lumbar spinal cord in rats following focal cerebral ischaemia produced by permanent occlusion of the middle cerebral artery (MCA). Our results showed that daily treatment of PPF beginning at 24 h after MCA occlusion for 2 or 4 consecutive days markedly suppressed the microglial response as detected immunohistochemically with OX-42. The most dramatic effect was the prevention of transformation of ramified microglia into amoeboidic form as well as formation of perineuronal microglia in close association with the soma of motoneurons. This has greatly amplified the potentiality of PPF used as a neuroprotective drug against microglia-related neuron damage induced by cerebral ischaemia.

Studies of lectin receptors of rat microglia in culture: receptor distribution and internalization

The present study examined the lectin labeling of diverse morphological forms of microglia in culture. Similar to amoeboid microglial cells in vivo, polymorphic microglia showed lectin labeling at their plasma membranes, as well as in a few cytoplasmic vesicles and vacuoles. This labeling pattern was observed in cultured microglia incubated with isolectin at 4 degrees C for 30 min. Five minutes after the temperature was raised to 37 degrees C, the surface lectin receptors appeared to be internalized, as shown by the occurrence of many subsurface lectin-labeled vesicles, vacuoles and tubule-like structures. With longer incubation (up to 1-2 h at 37 degrees C), many lysosomes and a few trans-Golgi saccules and associated lysosome-like structures became labeled. Concomitant with these changes was a reduction of lectin labeling at the plasma, with labeling having vanished in most of the cells after 1-2 h of incubation. By 24 h, only a few cells retained surface lectin labeling. It appears, therefore, that irrespective of morphology, lectin labeling (including its intracellular pathway) of microglia in culture parallels that of amoeboid microglia in vivo. This would offer a useful model for the study of lectin turnover in microglia and help to explain the roles of such receptors in microglial differentiation and function.

Nitric oxide synthase--its distribution and alteration in the intramural ganglia of the urinary bladder in normal and urethra-obstructed guinea pigs

Nitric oxide (NO) has been proposed to function as an inhibitory neurotransmitter in the lower urinary tract. This study investigates the distribution of NO-containing neurons and its changes following urethral obstruction in the guinea-pig. By using nicotinamide adenine dinucleotide phosphate diaphorase (NADPH-d) histochemistry and NO synthase (NOS) immunohistochemistry, the highest frequency of NO-containing neurons was observed in the bladder base. Double labelling studies showed that 70.9% of NADPH-d reactive neurons co-expressed NOS immunoreactivity. Acetylcholinesterase reactivity was present in the majority of the intramural neurons with 54% of them expressed NOS immunoreactivity. NADPH-d reactivity was colocalized with vasoactive intestinal polypeptide, calcitonin gene-related peptide and substance P immunoreactivities in both neurons and fibres. Colocalization study also revealed that NADPH-d reactive neurons formed a distinct cell population from tyrosine hydroxylase positive neurons. At 12 hours after urethral obstruction, NADPH-d reactivity in the intramural ganglion cells was noticeably enhanced and this was sustained till 24 hours whence some intensely stained neurons appeared to undergo degenerative changes. Neuronal degeneration was more drastic at 48 hours so that the number of NADPH-d positive neurons was significantly reduced. The present study suggests that NO is an important neurotransmitter in the urinary bladder and that it may be involved in the relaxation activity in the bladder base during micturition. It is speculated that the increased NADPH-d reactivity in intramural ganglion cells elicited by urethral obstruction may be responsible for the cell death. It is suggested that the resulting cell loss or bladder denervation may account for the urinary dysfunction such as frequency and urgency of micturition in patients with urethral obstruction.

Transsynaptic changes of neurons and associated microglial reaction in the spinal cord of rats following middle cerebral artery occlusion

This study investigated transsynaptic neuronal damage and microglial reaction in the spinal cord contralateral to focal cerebral ischaemia in rats induced by permanent occlusion of the right middle cerebral artery (MCA). Three and five days after MCA occlusion, some neurons in the dorsal horn of lumbar spinal cord underwent degeneration and they appeared to be engulfed by reactive microglia; on the other hand, the ventral horn neurons remained ultrastructurally intact. It is suggested that the neuronal degeneration in the dorsal horn was attributed to deafferentation of the local neurons following ischaemic lesion of the corticospinal neurons which are the main source of afferent inputs.

Properties of activated microglia and pharmacologic interference by propentofylline

Ameboid microglia are activated macrophages in the developing brain. With age, these cells undergo gradual transformation into the adult form, known as ramified or resting microglia. In response to neuronal insults, microglia change their morphology and immunophenotype and proliferate to become full-blown brain macrophages. Microglia release a battery of neurotoxic substances. Responses to neuronal damage occur at various intervals after the insult, suggesting that microglia may be an attractive target for pharmacologic intervention. The cerebrospinal fluid (CSF) of Alzheimer disease (AD) patients contains antibodies that recognize activated microglia in the developing rat and in the ischemic gerbil brain. These results suggest that AD shares common mechanisms related to the activation of microglia with both these experimental models. In vitro, the xanthine derivative propentofylline (PPF) depresses the production of reactive oxygen intermediates produced by macrophages. To appreciate in vivo interactions of PPF, two models were employed: developing rats and adult gerbils exposed to ischemia. Newborn rats were administered PPF (10 mg/kg) for 7 days. Gerbils were exposed to 5 min of transient forebrain ischemia and received PPF (10 mg/kg) 24 h later until the day before sacrifice. Animals were sacrificed at 7 or 14 days after reperfusion. Brains were processed for immunocytochemistry. Reactive microglia were visualized with monoclonal antibodies OX18 and OX42 or AD-CSF microglia antibodies. In the case of ischemia, an antibody against the amyloid precursor protein (APP) (residues 676-695) was included. Newborn rats receiving PPF for 7 days displayed a dramatic reduction in the number of activated microglia compared with untreated littermates. Ischemic control in gerbils showed complete nerve death, accumulations of APP, and enhanced microglial reactivity. In gerbils receiving PPF, APP accumulation was absent or very slight, and activated microglia were downregulated. The ability of PPF to interfere with activated microglia suggests that this agent may be useful for slowing progressive nerve cell death associated with AD, which is considered to be largely influenced by pathologic glial reactions.

Neuronal degeneration and microglial reaction in the fetal and postnatal rat brain after transient maternal hypoxia

This study examined the neuropathological changes in different areas of the brain of fetal and postnatal rats after transient maternal hypoxia. At different time intervals following hypoxia, reactive microglia as determined immunohistochemically with the antibody OX-42 that recognizes complement type three (CR3) receptors, responded vigorously to the hypoxic stress. Microglial activation was particularly evident in the cingulate cortex and the corpus callosum between 3 h and 14 days after hypoxia. Massive cell degeneration as determined ultrastructurally and significant neuronal loss as evaluated by cell counts were observed in the cingulate cortex at 1 and 3 days after hypoxic insults; thereafter, however, the neuronal density was restored to normal levels. Present results suggest that the cingulate cortex is most vulnerable to the hypoxic injury probably due to a redistribution of cerebral blood flow and/or metabolic changes. Besides being involved in the phagocytosis of cellular debris, it is suggested that the reactive microglial cells may have both neurotoxic and neurotrophic functions.

Effects of interleukin-3 injection on supraventricular amoeboid microglial cells in neonatal BALB/c and athymic mice

The present study investigated the effects of interleukin-3 (IL-3) on supraventricular amoeboid microglial cells (SAMC) of neonatal BALB/c and athymic mice. After four consecutive daily intraperitoneal injections of IL-3 at the age of 1 day postnatum and perfusion at the age of 5 days, BALB/c and athymic mice showed a 20% and 37% increase, respectively, in the number of Mac-1 positive SAMC. In mice receiving seven successive injections of IL-3 and perfused at the age of 8 days postnatum, Mac-1 labelled SAMC were increased by 14% and 19%, respectively. The increased number of SAMC could be the result of cytokine stimulation of their progenitor cells, viz., the stem cells of bone marrow or monocytes, or the result of direct stimulation of the SAMC themselves.

Colocalization of nitric oxide synthase and some neurotransmitters in the intramural ganglia of the guinea pig urinary bladder

The distribution of nitrergic neurons was investigated by using nicotinamide adenine dinucleotide phosphate-diaphorase (NADPH-d) histochemistry and nitric oxide synthase (NOS) immunohistochemistry in wholemount preparations of the urinary bladder in guinea pigs. Both NADPH-d+ and NOS+ neurons were located predominantly in the bladder base. Double staining showed that 70.9% of the NADPH-d+ neurons coexpressed NOS. Acetylcholinesterase histochemistry revealed that a majority of the intramural neurons were reactive, and about half of them (51.4%) were double labelled for NOS. Tyrosine hydroxylase-positive neurons were also distributed mainly in the bladder base but in a neuronal population that was separate from the preponderant NADPH-d+ neurons. Vasoactive intestinal polypeptide immunoreactivity was also detected in the some of intramural ganglion cells, in which 21.3% of them coexpressed NADPH-d. Calcitonin gene-related peptide and substance P immunoreactivities were confined to nerve fibers, often in close association with NADPH-d+ cells or extended along the blood vessels. These results have demonstrated the colocalization of NADPH-d and NOS in the majority of intramural ganglion cells. Many of the nitrergic neurons are apparently cholinergic, indicating that they are parasympathetic postganglionic neurons, and this underscores NO as the major neuromodulator in the parasympathetic nerves in the bladder walls. The localization of vasoactive intestinal polypeptide in nitrergic neurons suggests that the peptide may complement NO for regulation of micturition reflex. The close relationship of NADPH-d-reactive intramural neurons with calcitonin gene-related peptide and substance P fibers, most probably derived from dorsal root ganglion cells, suggests that NO released from the local neurons may exert its influence on the sensory neural pathways in the urinary bladder.

Expression of Fos in the spinal motoneurons labelled by horseradish peroxidase following middle cerebral artery occlusion in rat

The study was aimed at the investigation of the rat corticospinal system both functionally and anatomically using as a functional marker the immediate early gene c-fos, combined with retrograde tracing with horseradish peroxidase (HRP). This was achieved by mapping c-fos induction immunocytochemically in the spinal cord as a result of occlusion of the middle cerebral artery (MCA). Following left-sided MCA occlusion, Fos-like immunoreactivity (Fos-LI) was localized in both the dorsal and ventral horn neurons at the lumbar segment of the spinal cord. Labelling was often bilateral but was generally more substantial ipsilaterally. In the ventral horn, some of the Fos-positive neurons were confirmed to be somatic motoneurons innervating the tibialis anterior muscle of the lower extremity contralateral to MCA occlusion, as shown by their retrograde labelling with horseradish peroxidase injected into the muscle. Fos-LI was absent in the ventral horn of the spinal cord at cervical, thoracic, and sacral segments in both experimental and sham-operated rats. These findings suggest that the expression of c-fos may be used as a sensitive transneuronal marker for the study of neuronal activity in the spinal cord elicited by brain damage, viz. focal cerebral ischaemia, and when coupled with injection of HRP as a retrograde tracer, the method may prove to be useful for the study of transneuronal effect of the damage of the corticospinal motor system. While the expression of c-fos in the spinal motoneurons was most probably attributable to transneuronal effect following MCA occlusion, the possibility of that c-fos can be induced by altered hindlimb activity after the cerebral ischaemic insult cannot be excluded.

Origin, nature, and some functional considerations of intraventricular macrophages, with special reference to the epiplexus cells

Intraventricular macrophages encompass the supraependymal, free-floating, and epiplexus (Kolmer) cells; the supraependymal cells lie in close apposition to the ventricular ependyma, the epiplexus cells are closely associated with the choroid plexus epithelium, and the free-floating cells are at a variable distance from the epithelial surface. Although the three cell types are regarded as one cellular entity, the epiplexus cells preponderate. On scanning electron microscopy, the epiplexus cells display diverse morphological forms, ranging from round to bipolar to stellate, and bear a variable number of cytoplasmic processes. Transmission electron microscopy shows the presence of large numbers of lysosomes. The phagocytic nature of epiplexus cells is shown by their intense staining for nonspecific esterase and active uptake of tracers, e.g., horseradish peroxidase and rhodamine isothiocynate, administered intravenously or intraperitoneally. The mode of entry of these tracers in the cerebral ventricles is by way of transepithelial transport. In rats, the population of intraventricular macrophages increases steadily after birth until 17 days of age; thereafter, their cell population remains relatively unchanged. The early upsurge is attributed to proliferation of residential cells and/or influx of circulating monocytes/stromal macrophages through the process of "emperipolesis." The immunophenotypic features of intraventricular macrophages are consistent with other mononuclear phagocytes being immunoreactive for OX-42, OX-18, OX-6, and OX-1 and ED1 for the detection of CR3 receptors, MHC class I and II antigens, leucocyte common antigen, and macrophage antigen, respectively. The expression of these antigens is noticeably enhanced following the injection of lipopolysaccharide (LPS) into postnatal rats. Remarkably, the intraventricular macrophages are induced to express MHC class II (Ia) antigen after LPS or interferon-gamma injections. Furthermore, the expression of transferrin receptors as detected with OX-26 is also upregulated after these treatments. Epiplexus cells are also elicited to display a de novo expression of nitric oxide synthase-like immunoreactivity following intracerebral injection of LPS. They also respond vigorously to a single nonpenetrative blast. Results of our series of studies suggest that, besides their primary function as scavenger cells, the intraventricular macrophages partake in possible immunological responses and iron regulation in the ventricular system or the brain as a whole.

Remodeling of membrane-bound glycoproteins containing alpha-D-galactose in the cerebral endothelial cells of rats during blood-brain barrier maturation and alteration

In the course of the development of cerebral endothelia, the lectin labelling of alpha-D-galactosyl residues on the luminal front of the endothelial cells was gradually increased but that on the abluminal surface was concomitantly attenuated. In the latter, the isolectin (GSA I-B4) decoration was totally diminished with the maturation of the brain. Associated with this change, the end feet of astrocytes resting on the endothelia became lectin positive. Numerous cytoplasmic vacuoles, Golgi apparatus, vesicles and tubule-like structures were strongly labelled in the cerebral endothelia in the early stages of development but only sparse vacuoles and vesicles remained lectin-stained in the mature cerebral endothelia. Labelled pericytes closely associated with the wall of blood vessels, displayed a lectin binding pattern similar to that of the developing cerebral endothelia. Following the blood-brain barrier damage induced by a cold lesion, the altered cerebral endothelia that were surrounded by densely-stained macrophages/microglia or pericytes remained unstained with the isolectin. Present results suggest that during blood-brain barrier maturation, the brain endothelia develop a functional polarity whereby their membrane glycoprotein is down regulated. The membrane glycoprotein, however, underwent remodeling when the blood-brain barrier was disrupted.

Induction of Fos-like immunoreactivity in the hypothalamic, medullary and thoracic spinal cord neurons following middle cerebral artery occlusion in rats

This study is a sequel of our previous work which demonstrated the expression of Fos-like immunoreactivity (Fos-LI) in the spinal cord motoneurons of rat following permanent occlusion of the middle cerebral artery (MCA). We report here Fos-LI in the hypothalamic, medullary and thoracic spinal cord neurons some of them are believed to be involved in cardiovascular regulation after the cerebral ischaemic insult. At 1 and 2 h, especially in the latter after right sided MCA occlusion, Fos-LI confined to the cell nucleus, was detected bilaterally in cells of the supraoptic nucleus (SON) and the paraventricular nucleus (PVN) of the hypothalamus, the nucleus of the solitary tract (NTS), the area postrema and ventrolateral medulla (VLM). A few Fos-like immunoreactive neurons were observed in the nucleus raphe pallidus and obscurus, and in the intermediolateral nucleus of the thoracic spinal cord. In the corresponding areas in sham-operated animals, Fos-like immunoreactive neurons were sparsely distributed or absent. Colocalization study showed that a variable number of the Fos-like immunoreactive neurons in NTS and VLM coexpressed tyrosine-hydroxylase (TH) immunoreactivity. Such double labelled neurons appeared to be more common in the latter. It is suggested that the induction of Fos-LI in neurons of the hypothalamus, medulla and thoracic spinal cord was linked to cardiovascular regulation following the middle cerebral artery occlusion.

Neuronal connections between the auricular skin and the sympathetic pre- and postganglionic neurons of the dog as studied by using pseudorabies virus

Pseudorabies virus (PrV) as a neuronal tracer was microinjected into the concave surface of the puppy's left pinna to establish the morphological basis of somato-visceral linkage. The virus infected neurons were detected by FITC conjugated with polyclonal swine anti-PrV serum. Labelled neurons were localized in: (1) the trigeminal, geniculate and superior vagal ganglia; (2) the subnucleus caudalis of the spinal trigeminal nucleus; (3) the intermediolateral column (IML) of the thoracolumbar segments and (4) the sympathetic chain ganglia. Present results suggest that when injected into the peripheral nerves, PrV was retrogradely transported to the nerve cell bodies located in the respective sensory ganglia. From the first order sensory neurons, the virus would self-replicate and was transported trans-synaptically via the brainstem nuclei and IML to reach the neurons in the sympathetic ganglia.

Induction of microglial and astrocytic response in the adult rat lumbar spinal cord following middle cerebral artery occlusion

The response of microglia and astrocytes, as detected immunohistochemically by the monoclonal antibody OX-42 and anti-glial fibrillary acidic protein (GFAP) respectively, was studied in the rat lumbar spinal cord following focal cerebral ischaemia produced by permanent occlusion of the middle cerebral artery (MCA) above the rhinal fissure. At 1 and 2 days after right-sided MCA occlusion, OX-42 immunoreactivity of microglia in both the contralateral dorsal and ventral horns of the lumbar spinal cord was moderately increased compared with cells of the ipsilateral side. The microglial reaction was progressive, with some cells transformed into amoeboid form considered to be macrophages at day 3. By 5 days, many of the reactive microglia, notably in the ventral horn, appeared to encircle the soma of motoneurons. At 7 days, the microglial reaction had subsided while astrocytes in the same area were hypertrophied to replace the perineuronal microglia. The microglial response in both the cerebral cortex and lumbar spinal cord was effectively reduced by the N-methyl-D-aspartate (NMDA) receptor antagonist, MK-801. Present results suggest that following MCA occlusion, the vigorous response of microglia, and subsequently astrocytes, in the spinal cord in extra-focal areas far removed from the primary site of ischaemia may be mediated by glutamate released from the ischaemic corticospinal neurons through NMDA receptors on the postsynaptic spinal cord neurons.

Expression of NADPH-diaphorase and nitric oxide synthase in lumbosacral motoneurons after knee joint immobilisation in the guinea pig

The expression of nicotinamide adenine dinucleotide phosphate-diaphorase (NADPH-d) and nitric oxide synthase (NOS) in spinal ventral horn neurons was studied in the guinea pig after right knee joint immobilisation (RKJI). At 1 wk after RKJI, neurons in the ipsilateral ventral horn from L4 to S1 segments showed a moderate reactivity for NADPH-d staining. At 2 wk, NADPH-d labelled neurons were also observed in the contralateral ventral horn. Ipsilateral NOS immunoreactive cells were not detectable until wk 2. The intensity of NADPH-d and NOS labelled neurons in the bilateral ventral horns was sustained, peaking at the 4th wk after RKJI. In guinea pigs subjected to 4 wk of RKJI and subsequently released from the immobilisation for 2 and 4 wk, NADPH-d and NOS reactivity in ventral horn neurons diminished. The expression of NADPH-d positive neurons differed from that of NOS labelled neurons in terms of time interval, cell number and staining intensity, the latter being later, fewer and weaker. It is suggested that the induction and upregulation of NADPH-d and NOS are attributable to reduced activity of muscles acting on the knee joint after RKJI; the changes are reversible. It is speculated that increased levels of NO production are involved in protective mechanisms against possible neuronal degeneration as a consequence of target dysfunction.

Effects of acute complete outlet obstruction on the NADPH-diaphorase reactivity in the intramural ganglia of the guinea pig urinary bladder: light and electron microscopic studies

PURPOSE

The present study aims to examine the effect of complete outlet obstruction on the nicotinamide adenine dinucleotide phosphate-diaphorase (NADPH-d) reactivity in the intramural ganglion cells of the guinea pig urinary bladder.

MATERIALS AND METHODS

Adult male guinea pigs were divided into control (normal and sham-operated) and urethral obstructed (12, 24, and 48 hours after complete obstruction) groups. NADPH-d reactivity in the intramural neurons of the urinary bladder was examined by light and electron microscopy.

RESULTS

At 12 hours after urethral obstruction, an increase in number of intensely stained NADPH-d intramural neurons was detected. This was sustained till 24 hours whence some of the neurons appeared to undergo degenerative changes. Neuronal degeneration was more drastic at 48 hours. Results of cell counts showed a 32% reduction in number of NADPH-d positive neurons of the urinary bladder at this time point. Electron microscopy showed that all neurons undergoing degeneration displayed NADPH-d reactivity. A large accumulation of NADPH-d reaction product was observed in degenerating neurons whose mitochondria appeared swollen along with dilatation of Golgi saccules. At 48 hours, some neurons displayed total vacuolation and lysis of mitochondria.

CONCLUSION

Present results show that acute complete outlet obstruction can lead to degeneration and consequent cell death in the intramural ganglion cells of the guinea pig urinary bladder. The increased NADPH-d reactivity in such neurons suggests that nitric oxide may be involved in neuronal death in the urinary bladder following acute urinary retention.

Expression of Fos-like immunoreactivity in the brain and spinal cord of rats following middle cerebral artery occlusion

This study examined c-fos protein expression in the brain and spinal cord of rats following permanent occlusion of the middle cerebral artery (MCA) above the rhinal fissure. At 1 h after right-sided MCA occlusion, Fos-like immunoreactivity (Fos-LI) was detected in neurons not only in the ipsilateral cerebral cortex but also in the spinal cord. In the latter, Fos-LI was localized in the nucleus and perikarya of neurons in the grey matter, notably the large motor neurons in the ventral horn. Fos-LI was most intense at 2-4 h, but became undetectable after 48 h in the cerebral cortex and 72 h in the spinal cord. In sham-operated animals, Fos-LI was almost undetectable or virtually absent. It was also not detected in the core territory supplied by the MCA at any time points after arterial occlusion. When the ischaemia-induced neuronal damage in both the cerebral cortex and spinal cord was evaluated by Nissl staining, some neurons appeared atrophic. We conclude that the induction of Fos-LI in neurons of the cerebral cortex and spinal cord is linked respectively to early onset-short stimulation and persistent excitatory or disinhibition phenomenon as a result of focal ischaemic brain injury.

Induction of major histocompatibility class II antigen on microglial cells in postnatal and adult rats following intraperitoneal injections of lipopolysaccharide

Microglial cells, notably the ramified form, were induced to express major histocompatibility complex (MHC) class II antigen in postnatal and adult rats given intraperitoneal injections of lipopolysaccharide (LPS). The immunoreactive microglia which occurred in cell colonies or clusters were detected immunohistochemically with the monoclonal antibody OX-6. Some of the widely distributed MHC II positive cells were round or amoeboidic located preferentially in the perivascular area. In view of the widespread occurrence of microglial cells showing OX-6 immunoreactivity which is negligible in normal animals, it is suggested that the effect of LPS on microglia in vivo is a widespread phenomenon and is independent of age. It is suggested that the endotoxin not only triggers off the immunological potentiality of these cells but also elicits the entry of some mononuclear cells into the brain parenchyma.

Labeling of amoeboid microglial cells and intraventricular macrophages in fetal rats following a maternal injection of a fluorescent dye

Amoeboid microglial cells (AMC) in fetal brains were labeled by rhodamine B isothiocyanate (RhIc) when injected intravenously or intraperitoneally into mother rats at late state of pregnancy. The fluorescent cells were immunostained with antibodies OX-42 and OX-18 that recognize complement type 3 (CR3) receptors and major histocompatibility complex class I (MHC-I) surface antigen, respectively. RhIc-labeled AMC were first observed in the cavum septum pellucidum and subependymal cysts associated with the cerebral aqueduct as well as the fourth ventricle, and subsequently at other sites including the corpus callosum and other subcortical white matter. The fluorescence intensity increased with time after RhIc administration so that after 1 day the cells were brightly labeled. The majority of the labeled cells were round, with some elongated ones bearing two or three processes. Besides AMC, macrophages in the ventricular system were also labeled. All fluorescent cells were double labeled with OX-42 and OX-18 antibodies. Present results suggest that when introduced into the maternal circulation, RhIc could readily gain access into the fetal brain through the inefficient placental, blood-brain and blood-cerebrospinal-fluid (blood-CSF) barriers. The avid uptake of RhIc in circulation by brain macrophages indicates an active scavenging role of these cells in fetal brain. The labeling of cells by maternal route offers a rapid method for study of distribution of brain macrophages in fetuses.

Heterogeneity of antigen expression and lectin labeling on microglial cells in the olfactory bulb of adult rats

Microglia in different layers of the rat olfactory bulb expressed a variety of membrane antigens except for CD4 (OX-35). Bulb microglial cells bearing complement receptor type 3 (OX-42) were ubiquitous and their immunoreactivity varied considerably in different bulb layers. Although very few in number, labeled microglia in all layers also expressed major histocompatibility complex class I antigen (OX-18), leukocyte common antigen (OX-1) and unknown macrophage antigen (ED-2). The latter was localized in cells distributed almost exclusively in the perivascular spaces. The immunoreactivity of ED-1, an unknown cytoplasmic or lysosomal membrane antigen in macrophages, was localized in labeled microglia which were concentrated mainly in the granule cell layer and periglomerular zone of the bulb. A variable number of microglial cells were stained with OX-6 (major histocompatibility complex class II antigen) and they were located predominantly in the periglomerular zone and at the junction between the granule cell layer and the subependymal layer. Ultrastructural study using GSA I-B4 lectin labeling showed that microglia in different layers of the bulb exhibited similar labeling patterns in their subcellular structures. A remarkable feature was the occurrence of some microglia in the olfactory nerve layer, subependymal layer and granule cell layer adjacent to the subependymal layer in which the cells showed intense lectin labeling at their Golgi apparatus, a feature which was absent in microglia of other bulb layers. Present results showed the regional differences in microglial antigen expressions and lectin labeling within the olfactory bulb. It is therefore suggested that the cells subserve very different specific functions depending on their ambient microenvironments. The heterogeneity of microglial functions in the olfactory bulb may be related to the progressive regeneration and degeneration of its containing neurons.

Effects of thymosin alpha1 on the development of amoeboid microglial cells in the corpus callosum of neonatal BALB/c and athymic mice

The present study investigated the effects of intraperitoneal injections of thymosin alpha1 on the supraventricular amoeboid microglial cells (SAMC) in the newborn athymic and normal BALB/c mice. The microglial cells labelled by the lectin GSA I-B4 and the antibody Mac-1 showed a 27% reduction in number in the athymic mice receiving thymosin alpha1 injections compared with those receiving vehicle injections, and a 37% reduction in BALB/c mice receiving thymosin alpha1 injections compared with those receiving vehicle injections. Some of the SAMC in both BALB/c and athymic mice receiving thymosin alpha1 injections became ramified, while the remainder still exhibited their normal amoeboid appearance with few filopodial processes. Ultrastructurally, the lectin reaction product was confined to the plasma membrane and some cytoplasmic vacuoles of labelled SAMC. In both BALB/c and athymic mice, some labelled microglial cells became slender or elongated after thymosin alpha1 injections. Also their cytoplasm was reduced and contained fewer organelles. Radioimmunoassay of the plasma of thymosin alpha1 and vehicle-injected mice showed that there was a significant increase in the cortisol level in BALB/c (P < 0.01) and athymic (P < 0.001) mice 5 days after thymosin alpha1 injections, compared with that of the control mice. The results point to a strong correlation between the reduction of SAMC and the increased level of plasma cortisol. Supporting this is the fact that cortisol is known to suppress the production of monocytes considered to be the precursors of amoeboid microglia.

Immunohistochemical and tracer studies of macrophages/microglia in the pineal gland of postnatal rats

The pineal gland of rats of various ages (1-21 days old) was examined by immunohistochemistry and electron microscopy. Numerous widely distributed cells identified as macrophages/microglia were immunoreactive with the monoclonal antibodies OX-42, OX-18, OX-6, and ED1, indicating that they expressed complement type 3 (CR3) receptors, major histocompatibility complex class I and II antigens, and antigens of monocyte/macrophage lineage as detected by the antibodies, respectively. Following an intraperitoneal injection of rhodamine isothiocyanate (RhIC) in all age groups, the cells emitted a bright fluorescence. They were also labeled by horseradish peroxidase (HRP), as demonstrated in both light and electron microscopy. An HRP reaction was observed in vesicles and lysosomes at the ultrastructural level. A remarkable feature was the uptake of these tracers by pinealocytes. In light microscopy, the pinealocytes showed a punctate reaction product 3-24 hours after HRP injection. By electron microscopy, the reaction product was observed in vesicles, lysosomes, and some rod-like structures in the cytoplasm. On the basis of their immunophenotypic features, it is suggested that the macrophages/microglia in the pineal gland are active phagocytes which are also probably involved in the immunoregulatory function in the gland. The avid uptake of RhIC and HRP from the circulation by these cells suggests that serum-derived substances that may gain access to the parenchyma of the gland are being constantly monitored. The labeling of pinealocytes with HRP suggests that the functional activities of these cells are being modulated by serum-derived substances.

Macrophages/microglia as 'sensors' of injury in the pineal gland of rats following a non-penetrative blast

The pineal gland of adult rats was examined immunohistochemically and electron microscopically following exposure of the animals to a single blast equivalent to 110 kg TNT explosive. The most dramatic feature in rats killed at 7, 14 and 21 days after the blast was the upsurge of a large number of macrophages/microglia intensely immunostained with OX-42, OX-18, OX-6 and ED1 antibodies. These antibodies recognise the complement type three (CR3) receptors, major histocompatibility complex class I and class II (MHC I and MHC II) antigens and monocyte/macrophage antigens. Cell counts in OX-42 immunostained sections showed a two-fold increase at these intervals but returned to normal values at 28 days. The immunolabelled cells appeared extremely hypertrophic after the blast when compared with those in normal rats. In the latter and in rats killed at 28 days after the blast, immunoreactive cells were sparsely distributed. Ultrastructural study confirmed a wider occurrence of perivascular macrophages/microglia after the blast and the cells were laden with massive amounts of phagosomes resembling degenerating pinealocyte processes. It is concluded that the seemingly quiescent macrophages/microglia present normally in pineal gland were activated by the external blast force. The induced changes including the increase in cell numbers and endocytosis, however, were reversible in longer surviving animals.

Evidence of a direct projection from the cardiovascular-reactive dorsal medulla to the intermediolateral cell column of the spinal cord in cats as revealed by light and electron microscopy

To ascertain whether the dorsal medulla, a well-established vasopressor structure, would project directly to the sympathetic intermediolateral cell column of the spinal cord, we have carried out both anterograde and retrograde tracing studies in cats. For anterograde tracing, biotin-dextran was iontophoretically delivered into the cardiovascular-reactive dorsal medulla following its functional identification by electrical stimulation. The anterogradely transported biotin-dextran was then visualized using the avidin-biotin-horseradish peroxidase complex method. By light microscopy, dextran-labelled varicose axons were observed bilaterally in the intermediolateral nucleus extending from segments T1 to L3, but concentrated in segments T1-T5, notably at levels T2-T4. Electron microscopic examination revealed the localization of biotin-dextran reaction product in some small myelinated axons and axon terminals in the intermediolateral cell column. The majority of tracer-labelled axonal boutons contained spherical synaptic vesicles and made asymmetric synaptic contacts primarily with small dendrites. A few boutons contained polymorphic synaptic vesicles and tended to form symmetric axodendritic synapses. Spinally projecting neurons of the dorsal medulla were identified using the retrograde transport of horseradish peroxidase injected into the electrically cardiovascular-reactive intermediolateral nucleus. The labelled neurons were localized in the medullary dorsomedial reticular formation ventromedial to the nucleus of the solitary tract, approximately 0.5-5 mm rostral to the obex. The projection was bilateral, but was relatively denser in the rostral portion of the contralateral dorsal medulla. The present findings support the hypothesis that the dorsal medulla, through its direct pathway innervating the intermediolateral nucleus, may serve as a sympathetic premotor structure for regulation of arterial pressure.

In vivo expression of inducible nitric oxide synthase in supraventricular amoeboid microglial cells in neonatal BALB/c and athymic mice

The present study investigated whether the supraventricular amoeboid microglial cells (SAMC) in neonatal BALB/c and athymic nude mice were able to express inducible nitric oxide synthase (iNOS) after intraperitoneal injections of lipopolysaccharide (LPS) or interferon-gamma (IFN-gamma). The results showed that iNOS, undetectable in these cells in vehicle injected mice, could clearly be demonstrated immunohistochemically in a large number of them in LPS treated normal and mutant mice. Only a few iNOS-positive SAMC were observed in IFN-gamma injected mice. Immunoelectron microscopy confirmed the microglial nature of the labelled cells and that the immunoprecipitate of iNOS was cytosolic, being diffusely present throughout the cytoplasm of the cells. It is suggested that iNOS in the SAMC of neonatal BALB/c and athymic mice may be involved in the synthesis of nitric oxide which is necessitated more for host defence mechanism against bacterial endotoxin than against immunological stimuli.

Multiple inputs of GABA-immunoreactive neurons in the cuneate nucleus of the rat

Using anterograde transport of WGA-HRP and the experimental degeneration method for identification of corticocuneate (CCT) and primary afferent (PAT) terminals in conjunction with gamma-amino butyric acid (GABA) and glutamate immunocytochemistry, this study has demonstrated that the GABA-immunoreactive (GABA-IR) neurons in the rat cuneate nucleus were post-synaptic to PATs (some of them being glutamate-IR), GABA-IR and GABA-negative terminals. The HRP-labelled CCTs did not make any synaptic contacts with GABA-IR neurons but with some GABA-negative dendrites. PATs labelled by HRP or showing degenerating features made direct synaptic contacts with the dendrites of GABA-IR neurons. Beside the above GABA-IR boutons also showed axosomatic and axodendritic synapses with the GABA-IR neurons. In 'triple labeling' method for GABA, PAT and glutamate, it was found that the PATs which were usually glutamate-positive were presynaptic to the dendrites of GABA-IR neurons. Furthermore, some glutamate-IR terminals which were of non-PAT's origin also synapsed with the dendrites and somata of GABA-IR neurons. It is concluded from this study that the major inputs of GABA-IR neurons were from glutamate immunopositive PATs and glutamate terminals of non-PATs origin; other GABA-IR terminals either intrinsic or extrinsic also contributed to the afferent sources of GABA-IR neurons. The CCTs contributed very little, if any, to this input. It is suggested that the PATs and glutamate-IR terminals on GABA-IR neurons may be involved in lateral inhibition for increase of spatial precision. The synaptic contacts between GABA-IR boutons and dendrites or somata of GABA-IR neurons may provide a possible means for disinhibition.

Upregulation of nicotinamide adenine dinucleotide phosphate-diaphorase reactivity in the ventral horn motoneurons of lumbosacral spinal cord after urethral obstruction in the guinea pig

The role of nitric oxide (NO) in pathophysiology of urethral obstruction in male guinea pig was investigated by using nicotinamide adenine dinucleotide phosphate-diaphorase (NADPH-d) histochemistry. In normal and sham-operated control animals, NADPH-d reactivity in the ventral horn motoneurons at L5-L6 and S1-S2 segments of spinal cord was barely detectable or virtually absent. In animals receiving urethral ligation and killed at 6 h after operation, NADPH-d reactivity in the ventral horn motoneurons was comparable to that of control animals. At 12 h, NADPH-d reactivity in the same cells began evident and was markedly enhanced in animals killed at 24 and 48 h. In order to verify whether the increased NADPH-d reactivity was linked to neuronal death, some sections of the lumbosacral spinal cord from urethral obstructed animals were stained in Nissl staining. There was no sign of cell death or atrophy of the ventral horn neurons. Present results suggest the plasticity of NADPH-d in ventral horn neurons which is readily upregulated by urethral ligation. The enhanced NADPH-d reactivity would imply increased nitric oxide synthase (NOS) activity and consequently generation of higher levels of NO in ventral horn neurons. Such alteration maybe involved in distension-induced urethral relaxation in the external urethral sphincter following urethral ligation.

Response of amoeboid and ramified microglial cells to lipopolysaccharide injections in postnatal rats--a lectin and ultrastructural study

The present study describes the response of amoeboid and ramified microglial cells in the corpus callosum to intraperitoneal lipopolysaccharide injections in postnatal rats as examined by lectin histochemical staining and electron microscopy. In 1 day old rats receiving endotoxin injections and sacrificed at various time intervals, the lectin labelling of amoeboid/ramified microglia was greatly enhanced. The increased labelling persisted in some ramified microglia in rats killed at 14 and 21 days of age; otherwise in normal or control animals of the corresponding stages, the same cells were very weakly stained. In rats killed at 2 days of age after intraperitoneal lipopolysaccharide injection, the number of microglia appeared to increase, but this was reduced at 7 days of age. The lectin-labelled amoeboid/ramified microglia were frequently seen adherent to the outer walls of the callosal blood vessels where infiltrated lymphocytes were also observed. Ultrastructurally, some lectin-labelled microglial cells underwent degeneration and were engulfed by other lectin-positive cells. After endotoxin injections, microglial cells, notably the amoeboid form, showed extensive ruffling at their cell membrane, massive accumulation of lysosomes and increased staining of lectin at their Golgi apparatus. A similar lectin labelling pattern was also observed in ramified microglia of lipopolysaccharide-injected rats. It is concluded that both amoeboid and ramified microglial cells in postnatal rats responded to endotoxin injections as reflected by their enhanced lectin labelling at the surface membrane, lysosomes and Golgi apparatus. It is suggested that such changes may be involved in synthesis and/or modification of galactosyl glycoconjugates probably for the increased production of membranous glycoproteins or lysosomal enzymes.

Ultrastructural changes of macroglial cells in the rat brain following an exposure to a non-penetrative blast

The present study examined the ultrastructural changes in astrocytes and oligodendrocytes in rats following an exposure to a non-penetrative blast. At 1 and 7 days after the blast, the astrocytes in the cerebral and cerebellar cortex were hypertrophied; their end-feet associated with the blood vessels were also swollen, bearing sparsely distributed organelles. The above changes were not observed in experimental rats when the survival interval was prolonged. It is concluded from this study that the blast could have disrupted the integrity of the blood-brain barrier resulting in possible abnormal entry of serum-derived substances thereby leading to astrocytic hypertrophy. The reversible nature of the changes is evidenced by the seemingly normal appearance of astrocytes in rats killed at 14, 21 and 28 days after the blast. Oligodendrocytes remained unaffected at various time intervals after the blast.

Microglial in neurodegenerative disorders: emphasis on Alzheimer's disease

Hallmark lesions of Alzheimer's disease (AD) are filled with reactive immunocompetent microglia, suggesting that immunological aberrations may participate in the pathophysiology of this disorder. If immune-mediated processes are closely linked to neuronal breakdown it would be of importance to have a reliable means to detect these processes. Cerebrospinal fluid microglial antibodies found mainly in AD patients are discussed as such potential sources. These antibodies recognize microglia in the developing rat brain, in neuronal cultures and on AD cortical biopsies. Treatment aimed at downregulating microglial is discussed and may have therapeutic significance for AD patients. Largely this review presents current opinions which support the concept that inflammation and similar immune mechanisms need to be considered as participating in AD pathogenesis.

Immunohistochemical study of amoeboid microglial cells in fetal rat brain

The present study examined the expression of different antigens in amoeboid microglial cells (AMC) in fetal rat brain extending from 12 to 20 d postconception (E12-E20) using a panel of monoclonal antibodies which recognised the major histocompatibility complex (MHC) class I (OX-18) and class II (OX-6) antigens, leucocyte common antigen (OX-1), CD4 receptor (OX-35), complement type 3 receptor (OX-42) or macrophage antigens of unknown function (ED1 and ED2). Of the above-mentioned antigens, ED1 and ED2-labelled AMC were observed in the neuroepithelia as early as embryonic day 12 (E12); other antigens were not detected at this stage. At E14, except for MHC class I antigen, all other antigens were expressed by AMC distributed predominantly in the developing white matter. At E16, AMC in the intermediate zone lateral to the striatum were endowed with all the above-mentioned antigens including MHC class I. At E18, the immunoreactivities of AMC stained with OX-6, OX-18, OX-35 and OX-42 antigens were noticeably reduced when compared with those cells at E16. At E20, amoeboid microglial cells exhibited full complement of antigen expression similar to those cells at E16; some of the labelled cells emitted a variable number of cytoplasmic processes. It is suggested that the successive and differential expression of various macrophage related antigens on AMC in fetal brain is related to the specific requirement of local environment in different stages of development.

The composition and central projections of the internal auricular nerves of the dog

The cranial components and central terminations of the sensory nerves supplying the concave surface of the puppy's pinna, namely, the rostral, middle and caudal internal auricular nerves (RIAN, MIAN and CIAN) were investigated using horseradish peroxidase retrograde and transganglionic labelling techniques. All the 3 internal auricular nerves received contributions from the vagus. The RIAN received additional fibres from the trigeminal nerve while the MIAN and CIAN contained fibres derived from the facial nerves. In the brainstem, collaterals from the descending fibres of the afferents were given off at all levels to the medially located spinal trigeminal nucleus (SpV) which extended rostocaudally from the principal nucleus of the trigeminal nerve, subnuclei oralis, interpolaris and caudalis of the SpV to C1 or C2 cervical segment. The greatest density of central projections was observed in the subnucleus caudalis and C1. In the latter, the terminal field in the dorsal horn was roughly wedge-shaped, tapering off medially from lamina I towards lamina V. A somatotopic organisation was observed in the spinal trigeminal tract (SpVtr) and spinal trigeminal nucleus (SpV) in which the projection fibres and terminal fields of the RIAN were located lateral to those of the MIAN and CIAN. Some nontrigeminal nuclei, e.g. paratrigeminal and cuneate nuclei, nucleus X and the nucleus of the solitary tract were also labelled following HRP application to the internal auricular nerves. The localisation of the central projections of the internal auricular nerves as well as the 2nd order neurons in some specific nuclei to which the afferent fibres project is consistent with the concept of a brainstem somatovisceral link.

Studies of the choroid plexus and its associated epiplexus cells in the lateral ventricles of rats following an exposure to a single non-penetrative blast

The choroid plexus in rats exhibited ultrastructural changes following a non-penetrative blast. The immunophenotypic features of epiplexus cells associated with the choroid plexus epithelium were also altered. In rats killed at 1 and 7 days after the blast, the intercellular spaces between the epithelial cells were greatly widened, coupled with the massive eruption and possible extrusion of the apical cytoplasm into the ventricular lumen. Associated with these changes was the passage of some monocytes/lymphocytes across the epithelium. The incidence of such a migratory phenomenon was more frequent in rats killed 7 days after the blast. In rats killed 14 days after the blast, the ultrastructural changes of the epithelial cells became less pronounced. At 21 and 28 days after the blast, the ultrastructure of the choroid plexus was comparable to that of normal specimens. The immunoreactivity of epiplexus cells in terms of their cell number and staining intensity with the monoclonal antibodies OX-42, OX-18, OX-6 and ED1 was noticeably augmented at 7 and 14 days after the blast; this, however subsided at 21 and 28 days. It is concluded that the choroid plexus is extremely sensitive to a blast wave as manifested by its structural alterations and the vigorous expression of CR3 receptors and MHC antigens by the epiplexus cells. It is suggested that a possible immune response might have been triggered in the cerebrospinal fluid ventricular system following the blast.

Ultrastructural localization of acetylcholinesterase and choline acetyltransferase in oligodendrocytes, glioblasts and vascular endothelial cells in the external cuneate nucleus of the gerbil

This study reports the reactivities of acetylcholinesterase (AChE) and choline acetyltransferase (ChAT) in some of the nonneuronal elements in the external cuneate nucleus (ECN) of gerbils. AChE reaction products were localized in some oligodendrocytes in their cisternae of rough endoplasmic reticulum, nuclear envelope and Golgi saccules. The basal lamina lining the capillary endothelia also displayed AChE reactivity. In ChAT immunocytochemistry, the reaction products were found to be associated with the vascular basal lamina as well as the endothelial plasma membrane facing the lumen. The most remarkable finding was the localization of ChAT immunoreactivity in some oligodendrocytes and occasional glioblasts (small glial precursor cells containing a thin rim of cytoplasm surrounding an irregular nucleus with homogeneous chromatin materials). The ChAT-positive oligodendrocytes consisted of two types, medium-dense and dark cells, either associated with blood vessels or ChAT-stained neuronal elements. It is suggested from these new findings that at least some of the oligodendrocytes and glioblasts in the ECN of gerbils may be involved in the synthesis, storage, release and degradation of acetylcholine.

NADPH-diaphorase activity in the nodose ganglion of normal and vagotomized guinea-pigs

The activity and distribution of reduced nico-tinamide adenine dinucleotide phosphate diaphorase (NADPH-diaphorase) in the nodose ganglion of normal and vagotomized guinea-pigs were examined by light and electron microscopy. Light microscopy confirmed a remarkable increase in the number of NADPH-diaphorase-reactive neurons in the nodose ganglion following unilateral cervical vagotomy. The increase was present at 5 days but became more prominent at 10 days and was sustained until at least 30 days after vagotomy when compared with the non-lesioned side. The NADPH-diaphorase reaction product was associated with the membrane of the rough endoplasmic reticulum, Golgi apparatus, mitochondria and nucleus of the nodose neurons. In animals killed 5 days post-operation, there was no noticeable degeneration in the nodose neurons. However, at 10 days, the mitochondria in some neurons appeared swollen and vacuolated with disrupted cristae. These changes were accentuated in some nodose neurons 20 and 30 days after vagotomy but there was no evidence of cell death. All the degenerating neurons exhibited NADPH-diaphorase activity. The increase in NADPH-diaphorase activity in the neuronal somata after vagotomy suggests that the enzyme is involved in either the retrograde degeneration or the recovery of the lesioned neurons.

Ultrastructural localization of NADPH-diaphorase activity in the submucous ganglia of the guinea-pig intestine after vagotomy

The reduced nicotinamide adenine dinucleotide phosphate diaphorase (NADPH-d) activity in the axon terminals presynaptic to the submucous neurons of guinea-pig intestine following unilateral cervical vagotomy was studied by electron microscopy. The reaction product of diaphorase was localized only in the axon terminals that contained predominantly small agranular vesicles, and it was usually deposited around the vesicles. The terminals that contained predominantly large granular or flattened vesicles did not display any signs of diaphorase reactivity. Although there were only few diaphorase-positive submucous neurons in the small intestine, a considerable number of diaphorase-positive axon terminals was observed in the submucous ganglia of the small intestine in the control animals. Ten days after vagotomy, the quantitative study showed that when compared with the control animals, the number of diaphorase-positive terminals in the submucous ganglia of duodenum, mid-small intestine and colon in the vagotomized animals was reduced (P < 0.05). When the NADPH-d-positive terminals were examined in closer detail, it was found that only a small proportion of them showed signs of degeneration as evidenced by the swelling and vacuolation of their contents of mitochondria, with disrupted cristae and clumping of synaptic vesicles. It was therefore concluded that at least some of the diaphorase-positive axon terminals in the submucous ganglia of guinea-pig intestine originated from the vagus nerve.

Microglial cerebrospinal fluid antibodies. Significance for Alzheimer disease

Hallmark lesions of Alzheimer disease (AD) are filled with reactive immunocompetent microglia, suggesting that immunological aderrations may participate in the pathophysiology of this disorder. If immune-mediated processes are closely linked to neuronal breakdown, it would be or importance to have a reliable means to detect these processes. Cerebrospinal fluid (CSF) antibodies are discussed as such potential sources. The seredipitous use of the developing rat central nervous system (CNS) unexpectedly demonstrated that some AD CSF recognize amoeboid microglial cells. Similarly, AD CSF specifically stains activated microglia and neural macrophages in experimentally induced lesions. A cell-culture technique is described that allows rapid screening of CSF antibodies. Examination of CSF from a diversified dementia population revealed that AD CSF, in contrast to other dementia CSF, displayed remarkable selectivity toward microglial cells. Cortical biopsies from patients suspected to have AD were incubated with the patient's own CSF and that of confirmed AD patients. Both CSF samples recognized microglial cells in the cortical biopsy. AD CSF microglial antibodies appear to be significant in view of the increasing association between microglia and neuro degenerative processes in AD. These findings add further support to the concept that inflammation and similar immune mechanisms may contribute to to AD pathogenesis.

Localization of nicotinamide adenine dinucleotide phosphate diaphorase (NADPH-d) activity in the gastrointestinal sphincters in the guinea pig

The distribution of nicotinamide adenine dinucleotide phosphate-diaphorase (NADPH-d), a marker for nitric oxide synthase (NOS), in the nerves of gastrointestinal sphincters in guinea pigs was investigated to throw some light on the role of nitric oxide (NO) in these sphincteric regions. The nerve fibres with NADPH-d activity were observed chiefly in the circular muscle layer of the wall of gastrointestinal sphincters. Compared with the adjacent non-sphincteric regions, the proportions of NADPH-d positive myenteric neurons in the lower esophageal sphincter (LES), pyloric sphincter (PS) and internal anal sphincter (IAS) were higher (P < 0.05). The densities of NADPH-d-positive fibres in the circular muscle of above sphincteric regions were also higher (in LES P < 0.01; in PS and IAS P < 0.05). Within the circular muscle of LES, some discrete NADPH-d-positive intrinsic nerve cell bodies, usually smaller than their outlying myenteric neurons, were also observed. The dense distribution of NADPH-d-positive fibres within the circular muscles of gastrointestinal sphincteric regions suggests that NO, as a non-adrenergic non-cholinergic (NANC) inhibitory neurotransmitter, might play an important role in the neuronal regulation of the guinea-pig gastrointestinal sphincters.

Ultrastructural localization of substance P-like immunoreactivity in the intermediolateral column of spontaneously hypertensive rats and Wistar-Kyoto rats

The distribution of substance P in the intermediolateral column of the upper thoracic spinal cord of spontaneously hypertensive (SHR) rats and Wistar-Kyoto (WKY) rats was studied by combined retrograde tracing of choleragen subunit-B horseradish peroxidase (CB-HRP) and immuno-electronmicroscopy. In the T(1)-T(3) segments of the spinal cord, SP-like immunoreactive products were localized in the cell bodies and dendrites of the sympathetic preganglionic neurons as well as in a few pre-axon terminals or axon terminals. In the neuropil of the intermediolateral column (ILN), different synaptic configurations were observed including synaptic contacts between SP-like positive dendrites and negative axon terminals, and between SP-like positive axon terminals and SP-like positive dendrites. Furthermore, a single SP-like positive dendrite was sometimes postsynaptic to several axon terminals, a feature typical of glomerular synapses. The present findings suggest that most of the SP-like immunoreactive elements in the ILN were of intraspinal origin derived mainly from the sympathetic preganglionic neurons in SHR and WKY rats. Since there was no ultrastructural difference in the distribution of SP between the neural elements in the ILN of SHR and WKY rats, the present findings also suggest that SP may not be directly involved in the hyperactivity of the sympathetic nervous system in hypertension.

An immunohistochemical study of the intraventricular macrophages in induced hydrocephalus in prenatal rats following a maternal injection of 6-aminonicotinamide

Hydrocephalus was induced experimentally in prenatal rats following an injection of 6-aminonicotinamide (6-AN) into pregnant rats. The most remarkable change of the dilated lateral ventricles was in a marked increase in the number of intraventricular macrophages, some of which were laden with ingested erythrocytes. The immunoreactivity of the intraventricular macrophages was noticeably enhanced with the monoclonal antibodies OX-42 and OX-18 which marked the complement type 3 receptors (CR3) and major histocompatibility complex (MHC) class I antigen, respectively. Many immunoreactive cells with similar external morphology were observed to penetrate the ependymal lining at the roof of the ventricles. This, coupled with the concomitant depletion of the conglomeration of amoeboid microglia in the supraventricular corpus callosum, suggests that the upsurge of immunoreactive intraventricular macrophages in hydrocephalus was partly due to the influx of amoeboid microglia probably in response to the damage of the ventricular walls and possible alteration in the contents of the cerebrospinal fluid. The significance of the upregulation of complement type 3 receptors and major histocompatibility complex class I antigens on epiplexus cells in hydrocephalic rats remains to be explored, although our results suggest that the surface antigens may be involved in increased phagocytosis and/or a possible immune response.