Is c-Jun involved in nerve cell death following status epilepticus and hypoxic-ischaemic brain injury?

Clusterin accumulates in dying neurons following status epilepticus

Clusterin is a protein that has been implicated in cell death and remodelling in a number of different tissues. To further investigate the role of clusterin in nerve cell death its expression was measured in the rat brain at various times after status epilepticus (SE) induced by 1 h of hippocampal stimulation, by using in situ hybridization, immunocytochemistry, and immunoblotting. SE lead to a dramatic time-dependent increase in clusterin mRNA in non-nerve cells resembling astrocytes in the hippocampus beginning after 24 h. There was also an earlier induction of clusterin mRNA in dentate granule cells, that survive SE. Only a low mRNA signal was observed over the CA1 pyramidal cells, which die after SE. In contrast to these mRNA results, massive clusterin-like immunoreactivity was observed in CA1 pyramidal cells and dentate hilar neurons (and both of these neuronal populations die after SE), but not in dentate granule cells. We speculate that astrocytes produce clusterin after SE and that the clusterin is then secreted and taken up by hippocampal neurons destined to die. Thus, the role of clusterin in nerve cell death/ regeneration warrants further investigation.

ASTRO Research Fellowship: apoptosis as a predictor of tumor response to radiation in stage IB cervical carcinoma. American Society for Therapeutic Radiology and Oncology

PURPOSE

Levels of apoptosis predict for tumor responsiveness to radiation in various animal systems. To investigate the potential role of apoptosis as a predictor of response in human tumors, a retrospective review was undertaken of patients with adenocarcinoma of the cervix whose primary lesion at presentation measured at least 4 cm and who underwent definitive radiation therapy. A previous report had indicated that roughly half this group of patients should have a long-term relapse free survival.

METHODS AND MATERIALS

Pretreatment biopsy specimens of 44 patients with Stage IB adenocarcinoma of the cervix, whose primary lesion at presentation measured at least 4 cm in greatest dimension, were scored for apoptosis by two independent investigators without knowledge of the treatment outcome, and the results were averaged. Actuarial methods were used to assess overall survival, disease-free survival, determinate survival, and local control as a function of the baseline level of apoptosis. Patients ranged in age from 21 to 87 years and were treated with definitive radiotherapy between 1964 and 1989. Follow-up for the surviving patients ranged from 1 to 278 months, with a mean of 101 months.

RESULTS

Patients whose tumors had a baseline level of apoptosis above the median value (2%) had a better overall survival than those with lower levels of apoptosis (p = 0.056). A similar trend for disease-free survival (p = 0.32) and determinate survival (p = 0.27) did not reach statistical significance, perhaps because of the small number of patients. Because only 6 of the 44 patients (13%) had a local tumor failure, it was not possible to establish a correlation between the pretreatment level of apoptosis and the local tumor control by radiation.

CONCLUSION

The baseline level of apoptosis predicted for survival in patients with Stage IB cervical adenocarcinoma. Further investigation of the measurement of apoptosis as a potential predictive assay is warranted in other human tumor systems.

Neurochemical and morphological changes associated with human epilepsy

To date a multitude of studies into the morphology and neurochemistry of human epilepsy have been undertaken with variable, and often inconsistent, results. This review summarises these studies on a range of neurotransmitters, neuromodulators, neuropeptides and their receptors. In addition to this, novel changes in cell viability and sprouting have been identified and are discussed. Whether the alterations observed are a result of the seizures or are a contributory factor is unclear. However, it may be that following an initial insult (such as febrile convulsions, status epilepticus or head injury) secondary processes occur both of an anticonvulsant nature in an attempt to compensate for seizure activity, and in a kindling type of fashion, resulting in an increased susceptibility to seizures, leading to future seizures. Many of the alterations documented in this study probably represent one or both of these processes. Clearly no single chemical abnormality or morphological alteration is going to explain the clinically diverse disorder of epilepsy. However, by drawing together the neurochemistry and morphology of epilepsy, we may begin to understand the mechanisms involved in seizure disorders.

Temporalspatial patterns of expression of metallothionein-I and -III and other stress related genes in rat brain after kainic acid-induced seizures

Kainic acid-induced seizures in the rat brain cause severe brain damage that is thought to result, in part, from oxidative stress. In this study, we examine the consequences of systemic administration of kainic acid on expression of several genes that encode proteins thought to play roles in protection from oxidative stress, including metallothionein-I, and -III. Kainic acid causes an increase in metallothionein-I and heme oxygenase-I mRNAs, as well as an increase in c-fos, heat shock protein-70, and interleukin-1 beta mRNAs. The induction of these mRNAs is seizure dependent, and is greater in brain areas with extensive damage (e.g. piriform cortex) than in areas with minimal damage (e.g. frontal cortex and cerebellum). In contrast, little or no change in mRNA for metallothionein-III, manganese superoxide dismutase, copper-zinc superoxide dismutase, glutathione-s-transferase ya subunit or glutathione peroxidase occur. The prolonged and robust concordant induction of the metallothionein-I and heme oxygenase-I genes may reflect the oxidative stress produced by kainic acid-induced seizures. In addition, the induction of interleukin-1 beta gene expression suggests an inflammatory response in brain regions damaged by kainic acid-induced seizures. Delineating the regulation of genes associated with oxidative and inflammatory responses can contribute to a fuller understanding of seizures and associated brain damage.

The role of inducible transcription factors in apoptotic nerve cell death

Recent studies have shown that certain types of nerve cell death in the brain occur by an apoptotic mechanism. Researchers have demonstrated that moderate hypoxic-ischemic (HI) episodes and status epilepticus (SE) can cause DNA fragmentation as well as other morphological features of apoptosis in neurons destined to die, whereas more severe HI episodes lead to neuronal necrosis and infarction. Although somewhat controversial, some studies have demonstrated that protein synthesis inhibition prevents HI-and SE-induced nerve cell death in the brain, suggesting that apoptotic nerve cell death in the adult brain is de novo protein synthesis-dependent (i.e., programmed). The identity of the proteins involved in HI-and SE-induced apoptosis in the adult brain is unclear, although based upon studies in cell culture, a number of potential cell death and anti-apoptosis genes have been identified. In addition, a number of studies have demonstrated that inducible transcription factors (ITFs) are expressed for prolonged periods in neurons undergoing apoptotic death following HI and SE. These results suggest that prolonged expression of ITFs (in particular c-jun) may form part of the biological cascade that induces apoptosis in adult neurons. These various studies are critically discussed and in particular the role of inducible transcription factors in neuronal apoptosis is evaluated.

Combinatorial expression of immediate early genes in single neurons

To address the question how relatively small numbers of immediate early gene (IEG) could specifically couple a wide range of stimulus-response cascades, we examined the possibility that IEG could be expressed heterogeneously in individual neurons. Analysis of multiple IEG in single neurons revealed that many individual DRG neurons express several IEGs. The combinatorial expression of IEGs by individual DRG displays substantial heterogeneity. Analysis of mRNA species encoding AP-1 composition in single cells also revealed coordinated change of mRNAs coding for AP-1 factors after membrane depolarization. Our results indicate that differential expression of IEG in individual cells, and the possible interaction among them may represent a mechanism by which the specificity in stimulation-response coupling may be achieved by IEGs.

Ref-1 expression in adult mammalian neurons and astrocytes

Ref-1 is a nuclear protein that possesses DNA repair activity and has a role in the redox activation of Fos and Jun transcription factors. Using an antibody to Ref-1 we investigated the expression and distribution of this protein in the adult rat brain. Ref-1 was located in the nucleus of neurons and glial fibrillary acidic protein-positive astrocytes throughout the brain. Levels were particularly high in granule cells of the dentate gyrus, piriform cortex neurons, and Purkinje cells of the cerebellum, and lower in CA1 pyramidal cells, striatal neurons, and the neurons of the neocortex. These results suggest that the action of inducible transcription factors such as c-Jun in mammalian neurons is likely to be regulated by constitutively expressed Ref-1, in particular in dentate granule cells. The high levels of Ref-1 in glial fibrillary acidic protein-positive astrocytes suggest that it may also modulate the action of inducible transcription factors in these cells, particularly after brain injury. The possibility also exists that Ref-1 may primarily function as a DNA repair enzyme in brain cells.

Mechanisms of delayed cell death following hypoxic-ischemic injury in the immature rat: evidence for apoptosis during selective neuronal loss

The mechanisms leading to delayed cell death following hypoxic-ischemic injury in the developing brain are unclear. We examined the possible roles of apoptosis and microglial activation in the 21-day-old rat brain following either mild (15 min) or severe (60 min) unilateral hypoxic-ischemic injury. The temporal and spatial patterns of DNA degradation were assessed using gel-electrophoresis and in-situ DNA end-labelling. Microglial activation, mitochondrial failure and cell death were examined using lectin histochemistry, 2,3,5,triphenyl-H-tetrazolium chloride (TTC) staining and acid fuchsin staining, respectively. Selective neuronal death produced by the 15 min injury was associated with the development of apoptotic morphology, DNA laddering and acidophilia from 3 days post-hypoxia. The 60 min injury accelerated this process with some cells showing signs of DNA degradation at 10 h post-hypoxia. However, in the cortex, which developed infarction after the 60 min injury, a different pattern of cell loss occurred. The DNA and mitochondria remained intact, and cells basophilic, until after 10 h post-hypoxia, then widespread necrosis developed by 24 hr. In contrast to regions of selective neuronal loss, DNA degradation was initially random (at 24 hr), with 180bp DNA ladders not detected until 3 days post-hypoxia. There was no morphological evidence of apoptosis. Microglial activation coincided with the onset of DNA degradation in regions of selective neuronal loss but not infarction, suggesting a possible role in selective neuronal death. The results suggest that cortical infarction, which was delayed for at least 10 h, was necrotic, and occurred independently of microglial activation and apoptosis. In contrast, selective neuronal death was apoptotic.

A potential role for apoptosis in neurodegeneration and Alzheimer's disease

Previous studies have shown that beta-amyloid (A beta) peptides are neurotoxic. Recent data suggest that neurons undergoing A beta-induced cell death exhibit characteristics that correspond to the classical features of apoptosis, suggesting that these cells may initiate a program of cell death. This chapter explores the criteria and precautions that must be applied to evaluate mechanisms of cell death in vitro and in vivo, discusses the evidence supporting an apoptotic mechanism of cell death in response to A beta in cultured neurons, and describes potential correlations for these findings in the Alzheimer's disease brain. In addition, cellular signaling pathways that may be associated with apoptosis in response to A beta are examined, and support for apoptosis as a mechanism of cell death for other neurodegeneration-inducing stimuli (e.g., oxidative injury) is described. The connection of multiple stimuli that induce neuronal cell death to an apoptotic mechanism suggests that apoptosis could play a central role in neurodegeneration in the brain.

[Pharmacologic brain protection: specific agents]

Dysfunctional sodium influx is the first step in the ischaemic cascade. It has been recently demonstrated that reducing ionic flux through voltagegated Na channels shortens the NMDA receptor activity of cultured hippocampal slices in which oxidative phosphorylation and glycolysis have been blocked. The implication of this finding is that blocking initial events in the ischaemic cascade, events which do not directly cause neuronal damage, will reduce the damage done by downstream events. It also seems intuitively reasonable to suppose that truncating initial steps of the ischaemic cascade, as distinct from blocking glutamate receptors and scavening free radicals, will reduce the probability of interfering with endogenous mechanisms of repair. Clinically useful, substantive, prophylactic, pharmacological cerebral protection will come from drugs that work upstream. And for pharmacological protection that can only be initiated subsequent to an ischaemic event, the more we learn about endogenous repair, or genetic pharmacology, the closer we will come to maximizing the benefits and minimizing the costs of downstream intervention.

Altered gene expression in neurons during programmed cell death: identification of c-jun as necessary for neuronal apoptosis

We have examined the hypothesis that neuronal programmed cell death requires a genetic program; we used a model wherein rat sympathetic neurons maintained in vitro are deprived of NGF and subsequently undergo apoptosis. To evaluate gene expression potentially necessary for this process, we used a PCR-based technique and in situ hybridization; patterns of general gene repression and selective gene induction were identified in NGF-deprived neurons. A temporal cascade of induced genes included "immediate early genes," which were remarkable in that their induction occurred hours after the initial stimulus of NGF removal and the synthesis of some required ongoing protein synthesis. The cascade also included the cell cycle gene c-myb and the genes encoding the extracellular matrix proteases transin and collagenase. Concurrent in situ hybridization and nuclear staining revealed that while c-jun was induced in most neurons, c-fos induction was restricted to neurons undergoing chromatin condensation, a hallmark of apoptosis. To evaluate the functional role of the proteins encoded by these genes, neutralizing antibodies were injected into neurons. Antibodies specific for either c-Jun or the Fos family (c-Fos, Fos B, Fra-1, and Fra-2) protected NGF-deprived neurons from apoptosis, whereas antibodies specific for Jun B, Jun D, or three nonimmune antibody preparations had no protective effect. Because these induced genes encode proteins ranging from a transcription factor necessary for death to proteases likely involved in tissue remodeling concurrent with death, these data may outline a genetic program responsible for neuronal programmed cell death.

The effects of reduced perfusion and reperfusion on c-fos and HSP-72 protein immunohistochemistry in gestational day 21 rat brains

Metabolic stressors such as hyperthermia, seizures and ischemic hypoxia result in the induction of c-fos and heat-shock proteins (HSP) in affected brain cells of the adult rodent, especially within the hippocampal region, which normally has high metabolic demands. Here we ligated the uterine vessels of gestational day (GD) 21 rat pups to produce ischemic hypoxia. We confirmed that HSP-72 protein, as previously reported, was activated in the perinatal rat pup, especially in the hippocampal CA3 region. However, the capability of hippocampal cells to produce c-fos protein following drug-induced seizures has been reported to develop only after postnatal day 13. Here, ischemic hypoxia caused CA1 hippocampal cells to produce immunohistochemically detectable c-fos protein in GD-21 rats. These results seem to contradict the previous reports of no c-fos induction in rats this young by demonstrating a functional c-fos translational mechanism by GD-21. However, seizure vs ischemic hypoxia-induced c-fos expression may involve several different pre-translational pathways. A delayed development of a receptor, second messenger, or genomic element for regulating c-fos transcription remain as possible explanations for the late maturity of responsivity to seizures.

Two models for determining the mechanisms of damage and repair after hypoxic-ischaemic injury in the developing rat brain

Hypoxic-ischaemic (HI) brain injury can lead to selective neuronal loss or pannecrosis. Different mechanisms of damage and recovery may be associated with either pattern of cell loss. Two preparations were developed to investigate the role of growth factors and other mechanisms associated with either of these patterns of damage in the developing brain. Twenty-one-day-old Wistar rats underwent permanent unilateral right carotid artery ligation. Following surgery, ligated rats were warmed for 2 h at 34 degrees C with 85 +/- 5% relative humidity and then exposed to either 15 or 60 min of 8% O2. The rats were killed and brains perfusion fixed 5 days post-hypoxia for histological analysis. Rats exposed to 15 min of hypoxia-ischaemia suffered no mortality and 90% developed selective neuronal loss in the frontoparietal cortex and hippocampal CA1 region of the ipsilateral hemisphere. Rats exposed to 60 min of hypoxia consistently developed cortical pannecrosis and cellular loss in the striatum, thalamus, hippocampus and dentate gyrus of the ipsilateral hemisphere. The advantage of these models were ease of preparation, consistent neuronal loss scores and low mortality. The ability to induce either selective neuronal loss or pannecrosis provides an opportunity to investigate the mechanisms of damage or recovery associated with each pattern of cell loss.

Dynamic changes in the composition of the AP-1 transcription factor DNA-binding activity in rat brain following kainate-induced seizures and cell death

Kainate, a potent excitatory and neurotoxic agent, has also proved useful in studies on other glutamate-driven phenomena, such as neuronal plasticity. Long-term effects of kainate are apparently dependent on its influence on the expression of various genes, including those encoding the AP-1 transcription factor, consisting of proteins belonging to the Fos and Jun families. In our studies we analysed c-fos, fos B, c-jun, jun B and jun D mRNA levels as well as a functional feature of AP-1, its DNA-binding activity, in the rat brain following systemic injection of kainate. Two phases of elevated AP-1 DNA-binding activity were observed in the hippocampus and entorhinal cortex, and were correlated with period of seizures (2 and 6 h after kainate injection) and neuron damage (48-72 h). At 72 h after kainate treatment DNA fragmentation, believed to be diagnostic of apoptotic processes typical of programmed cell death phenomena, was noted. Two and six hours after the treatment, AP-1 consisted predominantly of Fos B, c-Fos, Fra-2 and Jun B, while at 72 h Jun D constituted the major AP-1 component in place of Jun B, and no c-Fos was detected. Only a slight AP-1 increase was seen 24 h after kainate treatment. In the sensory cortex, only the late phase of AP-1 elevation was detected. Contrary to AP-1, no effect of kainate on levels of two other transcription factors, CREB/ATF (cAMP-responsive element binding proteins) and OCT (octamer element DNA-binding activity) was seen.(ABSTRACT TRUNCATED AT 250 WORDS)

The transcription factor CREB is not phosphorylated at serine 133 in axotomized neurons: implications for the expression of AP-1 proteins

The present study has investigated whether nerve fiber transection alters the phosphorylation of serine at position 133 (Ser133) of the transcription factor CREB (phosphoCREB). Activation of CREB by phosphorylation has a major function in the control of gene transcription. PhosphoCREB was visualized by antisera that specifically react with an epitope comprising the phosphorylated Ser133 of CREB as well as of CREM and ATF1 proteins. In untreated rats, nuclear immunoreactivity (IR) of phosphoCREB was consistently visible, e.g. in the cortex, thalamic and hypothalamic compartments and central termination areas of primary somatosensory afferents. Transection of peripheral (sciatic nerve), cranial (hypoglossal and facial nerve) and central (medial forebrain bundle and mammillo-thalamic tract) nerve fibers did not increase phosphoCREB-IR in the axotomized neurons between 5 min and 30 days post-axotomy. In contrast, phosphoCREB-IR appeared after 24 h in glial cells adjacent to the axotomized motoneurons and persisted up to 4 weeks. This increase in glial phosphoCREB-IR was paralleled by enhanced expression of the CREB protein itself. Between 20 min and 24 h following sciatic nerve transection, the number of phosphoCREB labeled nuclei also increased in neurons of the ipsilateral superficial dorsal horn of lumbar L3-L5 spinal cord segments. These data suggest that phosphorylation of Ser133 in CREB/CREM/ATF1 proteins is not involved in the transcriptional control of early-response genes such as c-jun in axotomized neurons following nerve transection. This is in contrast to the reported phosphorylation of CREB and its trans-acting effects on immediate-early genes such as c-fos after transynaptic neuronal excitation.

Expression of c-jun and neuronal nitric oxide synthase in rat spinal motoneurons following axonal injury

Expression of neuronal NOS, c-jun and c-fos in spinal motoneurons following axonal damage were investigated in the present study. Although either distal spinal root axotomy or root avulsion induced expression of c-jun, expression of c-jun was predominantly found in distal root-axotomized motoneurons. In contrast, expression of NOS was exclusively observed in avulsed motoneurons. c-fos was not expressed in spinal motoneurons following either distal root axotomy or root avulsion. The different expression patterns of c-jun and NOS in the injured neurons suggest that these molecules may involve in different cellular processes and might play different roles in response to the injury. Since distal root axotomy did not cause motoneuron death and root avulsion did, expression of c-jun is likely related to regenerative process while induction of NOS may be involved in the degenerative process.

Fas antigen mRNA induction in postischemic murine brain

Fas antigen mRNA induction in the brain was examined using a transient global cerebral ischemia model in BALB/C mice. Northern blot analysis revealed little Fas antigen mRNA expression in the brains of sham-operated mice. A marked induction of Fas mRNA expression was detected in the brains of mice 6 h after 30 min of cerebral ischemia. These results suggest a possible apoptotic mechanism for cell death, mediated by the Fas antigen, in postischemic brain.

Immediate-early gene protein expression in neurons undergoing delayed death, but not necrosis, following hypoxic-ischaemic injury to the young rat brain

A unilateral hypoxia-ischaemia (HI) 21-day-old rat preparation was used to assess the effects of HI on the expression of the immediate-early gene proteins (IEGPs) c-Fos/FRAs, Fos B, c-Jun, Jun B, Jun D, Krox 20, Krox 24, and on the mRNA for the neurotrophic factor, brain-derived neurotrophic factor (BDNF). Moderate HI (15 min hypoxia) produced delayed, selective neuronal death and was associated with a rapid induction of c-Fos, Fos B, Jun B, Jun D, and c-Jun proteins, but not Krox 20 protein or BDNF mRNA, in neurons on the side of HI and also a delayed expression of c-Jun (and to a lesser extent c-Fos/FRA's and Fos B) 24-48 h after HI in neurons that underwent delayed neuronal death. Krox 24 showed an initial induction followed by a long-lasting suppression of its expression in regions undergoing cell loss. Severe HI (60 min hypoxia) resulted in seizures and rapid neuronal loss and infarction (necrotic cell death) on the side of HI, and was associated with early induction of c-Fos, Fos B, c-Jun, Jun B, Jun D, Krox 20 and Krox 24 protein and BDNF mRNA in neurons on the non-ligated side of the brain. Fos, c-Jun, Jun B, Jun D and Krox 24, but not Krox 20, Fos B, or BDNF mRNA, were also induced in non-nerve cells on the damaged side of the brain after both moderate and severe HI, and many of these cells appeared to be dividing. Thus, moderate HI induces IEGP's in neurons and non-nerve cells in damaged regions, whereas severe HI induces IEGP's and BDNF in non-damaged regions. c-Jun (and to a lesser extent c-Fos/FRA's) showed a prolonged expression in neurons undergoing delayed, but not necrotic, cell death suggesting that they may be involved in the biochemical cascade that causes selective delayed neuronal death. BDNF was not induced by HI, and therefore, does not appear to play an endogenous neuroprotective role in the CNS.

Biphasic induction of immediate early gene expression accompanies activity-dependent angiogenesis and myofiber remodeling of rabbit skeletal muscle

Sustained contractile activity of skeletal muscle promotes angiogenesis, as well as transformation of contractile protein isoforms and mitochondrial proliferation within myofibers. Since the products of immediate early genes such as c-fos, c-jun, and egr-1 function in many signaling pathways governing cellular responses to external stimuli, we sought to determine whether sustained contractile activity induces their expression in skeletal muscle. Low voltage electrical stimulation was applied to the motor nerve innervating rabbit tibialis anterior muscles for periods ranging from 45 min to 21 d. Northern and Western analysis demonstrated marked but transient inductions of c-fos, c-jun, and egr-1 mRNA and protein within the first 24 h. Longer durations of stimulation were associated with a secondary and sustained rise in the abundance of c-fos, c-jun, and p88egr-1 protein that, surprisingly, was not accompanied by detectable changes in mRNA. Immunohistochemistry demonstrated c-fos immunoreactivity within myofiber and vascular cell nuclei during both early and late phases of this response. These findings reveal a complex pattern of c-fos, c-jun, and egr-1 expression in response to nerve stimulation and suggest that these proteins could function in regulatory pathways that modify muscle phenotype.

Activation of pirenzepine-sensitive muscarinic receptors induces a specific pattern of immediate-early gene expression in rat brain neurons

Accumulating evidence suggests that immediate-early gene transcription factors such as c-Fos, form part of an intracellular signalling pathway linking the activation of neuronal receptors by neurotransmitters to changes in neuronal gene expression. Recently it has been demonstrated that the centrally active muscarinic receptor agonist pilocarpine induces both c-fos mRNA and protein in rat brain. In this report using immunocytochemical and in situ hybridization techniques we demonstrate for the first time that in addition to c-fos, pilocarpine administration increases the neuronal expression of jun-B, krox-20 and krox-24 (zif-268) but not related c-jun and jun-D genes in rat cortex and hippocampus. Pretreatment of animals with atropine or pirenzepine significantly reduced induction of c-fos, jun-B, krox-20 and krox-24 genes in both hippocampus and cortex. These results show that activation of pirenzepine-sensitive muscarinic receptors results in a specific pattern of immediate-early gene expression in rat brain neurons. We suggest that the combinatorial complexity of immediate-early gene induction may allow receptor-specific control of gene expression in vivo.

(-)-Deprenyl alters the survival of adult murine facial motoneurons after axotomy: increases in vulnerable C57BL strain but decreases in motor neuron degeneration mutants

The effect of (-)-deprenyl on the survival of axotomized adult murine facial motoneurons was investigated. Previously, (-)-deprenyl was shown to increase the number of rat facial motoneurons (FMns) surviving after axotomy at postnatal day 14, apparently by compensating for the loss of muscle-derived trophic factor. In the present study, three different strains of adult mice--A/J, C57BL/6J, and a congenic substrain of the C57BL/6J mice, the C57BL/Mnd mutants--underwent unilateral facial nerve transection. FMns were counted from serial sections taken through the entire length of the facial nuclei ipsilateral and contralateral to the facial nerve transections in animals sacrificed 21 days after axotomy. Subgroups of C57BL/6J and Mnd mutants were treated with either saline or 1.0 mg/kg (-)-deprenyl for 21 days. Another subgroup of Mnd mutants were treated with the metabolites of (-)-deprenyl, a mixture of (-)-amphetamine and (-)-methamphetamine, at a dosage equimolar to 1.0 mg/kg (-)-deprenyl. The number of surviving facial motoneurons in the A/J strain was 90% of unlesioned, control values which supports previous findings that adult FMns receive adequate trophic support and thus can survive loss of muscle-derived trophic support. In the C57BL/6J strain, the facial motoneuron survival was 35% and (-)-deprenyl increased the survival to 50.5%. Mnd mutants showed 62.4% survival; however, (-)-deprenyl decreased the number of motoneurons to 54.9% and amphetamine and methamphetamine treatment further decreased the motoneuron survival to 41.1%. These findings show that FMns in the Mnd mutants and their parental strain, C57BL/6J mice, show greater vulnerability to axotomy as compared to other adult strains of mice. The vulnerability is similar to that found in early postnatal life. (-)-Deprenyl increases the survival of the axotomized C57BL/6J FMns but its major metabolites, (-)-methamphetamine and (-)-amphetamine, further decrease FMn survival in the C57BL/Mnd mutants, possibly due to the induction of neurotoxic proteins causing programmed neuronal death. The efficacy of (-)-deprenyl in increasing the survival of damaged neurons would be expected to decrease as dosage increased above the dosage sufficient to induce maximum neuronal rescue (approximately 0.01 mg/kg) but would decrease as the dosage exceeded that necessary to produce toxic concentrations of the metabolites of (-)-deprenyl (1.0 mg/kg in this study).

Differential expression of the immediate early genes c-fos, c-jun, junB, and NGFI-B in the rat brain following transient forebrain ischemia

The temporospatial expression pattern of four immediate early genes (IEGs) (c-fos, c-jun, junB, NGFI-B) following 30 min of global ischemia was investigated in rat brains by in situ hybridization and immunohistochemistry (c-fos). All examined IEG mRNAs, as well as Fos-like immunoreactivity, increased transiently in vulnerable and resistant brain regions following ischemia, but the induction profiles were distinct. Ischemia caused a post-ischemic early-onset, transient c-fos induction in wide-spread regions, as well as a late-onset induction restricted to vulnerable regions. Late-onset c-fos induction was observed in the CA1 region and the ventral thalamus but not in the striatum or neocortex, where neurons degenerate at a quicker pace. After recirculation, c-jun mRNA appeared to be initially coinduced with c-fos mRNA, but c-jun mRNA levels remained elevated or increased in various regions, including all vulnerable regions, when c-fos mRNA had already declined to near basal levels. Compared to c-fos and c-jun, junB induction was less pronounced and confined largely to the dentate gyrus. NGFI-B mRNA increased moderately and only in brain regions exhibiting the most dramatic c-fos increases and with similar kinetics. The differential activation of the investigated IEGs suggests that rather complex long-term adaptive processes may be initiated at the genomic level after global ischemia. The present findings provide further evidence that the activation of IEGs forms part of the brain's metabolic response to ischemia, but no simple correlation appears to exist between the induction of the investigated IEGs and the phenomenon of selective vulnerability.

Induction of apoptosis in oxygen-deprived cultures of hybridoma cells

It is now well documented that apoptosis represents the prevalent mode of cell death in hybridoma cultures. Apoptotic or programmed cell death occurs spontaneously in late exponential phase of batch cultures. Until lately, no specific triggering factors had been identified. Recently, we observed that glutamine, cystine or glucose deprivation induced apoptosis in both hybridoma and myeloma cell lines whereas accumulation of toxic metabolites induced necrotic cell death in these cells. Other triggering factors such as oxygen deprivation might also be responsible for induction of apoptosis. In the present study, induction of cell death by exposure to anoxia was examined in batch culture of the SP2/0-derived hybridoma D5 clone. The mode of cell death was studied by morphological examination of acridine orange-ethidium bromide stained cells in a 1.5 L bioreactor culture grown under anoxic conditions for 75 hours. Under such conditions, viable cell density levelled off rapidly and remained constant for 25 hours. After 45 hours of anoxia, cell viability had decreased to 30% and the dead cell population was found to be 90% apoptotic. In terms of cellular metabolism, anoxia resulted in an increase in the utilization rates of glucose and arginine, and in a decrease in the utilization rate of glutamine. The lactate production rate and the yield of lactate on glucose increased significantly while the MAb production rate decreased. These results demonstrate that glycolysis becomes the main source of energy under anoxic conditions. Cells incubated for 10 hours or less under anoxic conditions were able to recuperate almost immediately and displayed normal growth rates when reincubated in oxic conditions whereas cells incubated for 22 hours or more displayed reduced growth rates. Nonetheless, even after 22 h or 29 h of anoxia, cells reincubated in oxic conditions showed no further progression into apoptosis. Therefore, upon removal of the triggering signal, induction of apoptosis ceased.