Charcoal hemoperfusion in the treatment of phenytoin overdose

In the case of phenytoin, a drug that is generally highly protein bound, there is a lack of consensus on the use of charcoal hemoperfusion in cases of overdose. We performed charcoal hemoperfusion on a phenytoin-overdosed patient to assess the effectiveness of this treatment. The plasma concentrations of total and free phenytoin fell rapidly, from 40.0 microg/mL and 3.6 microg/mL to 16.2 microg/mL and 1.5 microg/mL, respectively, after 3 hours of hemoperfusion. The total phenytoin elimination half-life was 3.9 hours. The fraction of protein-bound phenytoin was constant (90.8% +/- 0.5%) before, during, and after the procedure. The relations between the in vitro protein binding and adsorption of phenytoin to activated charcoal were also examined. Interestingly, bound phenytoin was found to dissociate from plasma proteins in the presence of activated charcoal and subsequently became adsorbed to the activated charcoal. Considering that phenytoin is bound to albumin with a large number of binding sites (n = 6) and a small binding constant (K = 6 x 10(3/)mol/L), the extent of adsorption to activated charcoal may depend on the magnitude of the binding constant of the drug to plasma proteins. The current results suggest that charcoal hemoperfusion is effective for the removal of drugs that bind to plasma proteins with a low binding constant.

Increase of vasopressin mRNA in the hypothalamus of inbred polydipsic mice

The genetically inbred polydipsic mice, STR/N strain, are characterized by extreme polydipsia and polyuria without arginine vasopressin (AVP) deficiency. The expression of AVP gene in the hypothalamus of polydipsic and non-polydipsic mice was examined by Northern blot analysis and in situ hybridization histochemistry. Northern blot analysis revealed that the total amount of AVP mRNA in the hypothalamus of the STR/N mice was approximately three-fold of that in the control, ICR mice. In situ hybridization histochemistry showed that the signals of AVP mRNA in the paraventricular (PVN) and supraoptic nuclei (SON) of the STR/N were stronger than those in the ICR. Although AVP gene transcripts were detected in the anteroventral parts of the PVN (avPVN) in the STR/N, there was a few AVP transcripts in the same area (avPVN) in the ICR. There were no differences in plasma osmolality and hematocrit between STR/N and ICR mice. These results suggest that upregulation of AVP mRNA in the hypothalamus of STR/N may be involved in the central mechanism responsible for the polydipsia in genetically polydipsic mice.

Temporal modulation of cytokine expression following focal cerebral ischemia in mice

There is increasing evidence that the inflammatory response plays an important role in CNS ischemia. The murine model of focal ischemia, however, remains incompletely characterized. In this study we examined expression of several cytokines and the vascular adhesion molecule E-selectin, in order to characterize the molecular events following stroke in the C57BL/6J mouse. Using a multi-probe RNAse protection assay (RPA), mRNA for 19 cytokines was analyzed following permanent and transient occlusion of the middle cerebral artery in mice. In addition, samples from the same mice were analyzed by reverse transcriptase-polymerase chain reaction (RT-PCR) to evaluate E-selectin mRNA expression levels. Several cytokine mRNAs showed a similar expression pattern in both permanent and transient CNS ischemia while others showed a temporal expression pattern that was dependent on the type of stroke. For both models, mRNA levels of TNFalpha rose early (4 h) followed by IL-6 (10-18 h) and a comparatively late increase (96 h) in TGFbeta1. IL-1alpha, IL-1beta and IL-1ra levels showed a model dependent shift in temporal expression. Reperfusion appeared to delay the induction of these cytokines. Temporal changes in cytokine mRNA expression in the mouse CNS occur following ischemic damage. Our findings demonstrate the utility and power of multi-probe RPA for evaluation of changes in cytokine mRNA levels. Moreover, this study is, to our knowledge the first to show temporal changes in cytokine mRNA in mouse cerebral ischemia, forming a basis for further exploration of the roles of these cytokines in modulating ischemic neuronal damage in this model.

Development of the avian iris and ciliary body: mechanisms of cellular differentiation during the smooth-to-striated muscle transition

The avian iris and ciliary body undergoes a transition from smooth-to-striated muscle during embryonic development. Using antibodies specific for smooth muscle-specific alpha-actin and myosin heavy chain, we confirm that a smooth-to-striated muscle transition occurs between E8 and E17 in both iris and ciliary body of the chick. To study the mechanisms regulating the transition in muscle type, we analyzed the fate of quail clones derived from E7 iris cells. When cells were cloned alone, 45/71 colonies differentiated into smooth muscle and 10/71 became striated muscle. None of the colonies were mixed with respect to muscle phenotype, indicating a lack of pluripotent stem cells. Furthermore, clones giving rise to nonstriated muscle could not be forced to incorporate into myotubes when cocultured with chick myocytes. Clones grown in coculture with chick embryo fibroblasts or E11 iris cells had very high cloning efficiencies (>98%). Significantly more clones differentiated into striated muscle when cocultured with E11 cells (60/156) than when cocultured with fibroblasts (29/108). This was due to an increased recruitment of undifferentiated cells into striated muscle, rather than a change in the percentage of cells differentiating into smooth muscle. In vivo and in vitro, various smooth and striated muscle-specific markers including contractile proteins, acetylcholine receptor subtypes, and transcription factors were colocalized in cells. Although our data argue against a multipotent stem cell for smooth and striated muscle cells, they cannot exclude a role for transdifferentiation. Cumulatively these results suggest that both smooth muscle and migratory myoblasts contribute to the development of myotubes in the avian iris and that this process is regulated in a non-cell-autonomous fashion by locally generated signals.

Activin A and follistatin influence expression of somatostatin in the ciliary ganglion in vivo

An important developmental question concerns whether neurotransmitter phenotype is an inherent property of neurons or is influenced by target tissues. This issue can be addressed in the avian ciliary ganglion (CG) which contains two cholinergic populations, ciliary and choroid neurons, that differentially express the peptide cotransmitter, somatostatin. The present study tests the hypothesis that differences in the level of expression of activin A and its endogenous inhibitor follistatin in CG neuron target tissues are responsible for selective expression of somatostatin in choroid neurons. Intraocular injection of activin A or follistatin (300 ng injected at E10/E11) in cultured embryos resulted in a 39% increase or a 23% decrease, respectively, in somatostatin-positive neurons relative to controls. Chorioallantoic membrane application of follistatin (1 microgram daily from E7 to E13) reduced somatostatin positive neurons by 54%. Neuron number, size, and target tissue morphology were unaffected by these treatments. Together with our previous studies, these data suggest that activin A and follistatin are target-derived molecules that regulate neuropeptide phenotype in the ciliary ganglion.

Development of the avian iris and ciliary body: the role of activin and follistatin in coordination of the smooth-to-striated muscle transition

Although general principles have been established in the regulation of vetebrate organogenesis, the specific molecules responsible for such signaling are just being identified. We have studied differentiation in the avian iris and ciliary body which undergoes a transition from smooth to striated muscle. Using heterochronic cocultures, we have found that striated muscle differentiation in pretransition (E8) cells is induced by midtransition (E11) cells through a secreted and soluble activity. In addition, contact-mediated mechanisms among pretransition cells prevented precocious striated muscle differentiation. We have tested the role of activin and its antagonist follistatin, as candidate regulators of this muscle transition. Activin induced smooth muscle differentiation while repressing striated muscle development. Conversely, follistatin promoted the emergence of striated muscle, while inhibiting smooth muscle differentiation. Significantly, secreted follistatin activity was found to increase during the smooth-to-striated muscle transition. Moreover, the striated muscle inducing activity from midtransition iris and ciliary body cell conditioned medium was depleted with an activin-affinity column which binds follistatin. These results suggest that activin and follistatin coordinate differentiation in the avian iris and ciliary body.

Overexpression of ciliary neurotrophic factor in vivo rescues chick ciliary ganglion neurons from cell death

Ciliary ganglion (CG) neurons undergo target-dependent cell death during embryonic development. Although ciliary neurotrophic factor (CNTF) was identified in vitro by its ability to support the survival of chick CG neurons, its function as a target-derived neurotrophic factor has been questioned by those working on mammalian-derived forms of CNTF. We have purified and cloned a chicken CNTF [chCNTF; formerly growth-promoting activity (GPA)] that is expressed in CG targets during the period of cell death and is secreted by cells transfected with chCNTF. In the present study we used a retroviral vector, RCASBP(A), to overexpress chCNTF in CG target tissues. Elevation of chCNTF biological activity three- to fourfold in the embryonic eye rescued an average of 31% of the neurons that would have normally died in vivo. In some individuals, nearly all of the neurons were rescued. ChCNTF had no effect on the number of neurons observed prior to cell death, nor were there any deleterious effects of either viral infection or overexpression of CNTF. These results show that chCNTF is able to function in vivo as a trophic factor for CG neurons, and suggest that limited availability of trophic support is one of the factors regulating CG neuron survival during development.

Opposing effects of activin A and follistatin on developing skeletal muscle cells

Activin and the activin-binding protein follistatin modulate a variety of biological processes and are abundant at sites of muscle development. Activin and follistatin were expressed in developing chick pectoral muscle in vivo and in primary cell culture. Addition of recombinant activin inhibited muscle development in a dose-dependent manner as measured by the number of nuclei in myosin heavy chain positive cells and creatine phosphokinase activity. Conversely, follistatin potentiated muscle development. The effects of activin were found to be distinct from those of the related protein transforming growth factor (TGF) beta1. Muscle development was repressed by activin at all time points investigated and did not recover with the removal of activin following a limited exposure. In contrast, while myogenic differentiation in TGFbeta1 was initially repressed, muscle marker expression recovered to control levels--even in the continued presence of TGFbeta1. Fibroblast growth factor (FGF) had little effect on inhibiton of muscle development caused by activin A. However, inhibition of development produced by TGFbeta increased with increasing concentrations of FGF. Finally, early expression of myoD and myf5 mRNA by muscle cultures in the presence of activin and follistatin was analyzed. Activin-treated cultures expressed reduced myoD and myf5 levels at 1.5 days after plating. Myf5 levels in follistatin-treated cultures were elevated, but, surprisingly, these cultures showed a reduction in myoD levels. These data suggest that endogenously expressed activin and follistatin are important modulators of muscle development.

Identification of functional receptors for ciliary neurotrophic factor on chick ciliary ganglion neurons

Ciliary neurotrophic factor and an avian homolog, growth promoting activity, are members of the cytokine/neurokine family of trophic factors and have been proposed to function as survival and developmental factors for ciliary ganglion neurons in vivo. Here we identify for the first time functional receptors for ciliary neurotrophic factor and growth promoting activity on cultured ciliary ganglion neurons. [(125)I]Rat ciliary neurotrophic factor binding studies indicate that rat ciliary neurotrophic factor and growth promoting activity bind to these receptors with a single affinity, while human ciliary neurotrophic factor recognizes both a high- and low-affinity site. Comparison of the relative potency of human ciliary neurotrophic factor and avian growth promoting activity in biological assays indicates that growth promoting activity is three to five times more active in promoting survival and in regulating acetylcholine receptors. The binding of ciliary neurotrophic factor is specific, sensitive to phosphatidylinositol-specific phospholipase C and partially inhibited by leukemia inhibitory factor, but not inhibited by other members of the human neurokine family, including interleukin-6, interleukin-22 and oncostatin M. Cross-linking of [(125)I]rat ciliary neurotrophic factor to ciliary neurons results in the specific labeling of three proteins with estimated molecular masses of 153,000, 81,000 and 72,000. Only the 81,000 molecular weight component is released from the cells after treatment with phosphatidylinositol-specific phospholipase C, suggesting a membrane attachment via a glycosylphosphatidylinositol linkage. Stimulation with ciliary neurotrophic factor or growth promoting activity, but not by other neurokines, results in the rapid tyrosine phosphorylation of a 90,000 molecular weight protein that is inhibited by pretreatment with phosphatidylinositol-specific phospholipase C. In conclusion, we report here the pharmacological and functional properties of ciliary neurotrophic factor receptors on embryonic ciliary ganglion neurons. These results provide the means for elaborating the molecular mechanisms of ciliary neurotrophic factor action and understanding its physiological role in a defined neuronal population.

Expression of a chicken ciliary neurotrophic factor in targets of ciliary ganglion neurons during and after the cell-death phase

Ciliary ganglion (CG) neurons, like other neuronal populations, become dependent on their targets for survival during development. We have previously purified and cloned a secreted ciliary neurotrophic factor that was called growth-promoting activity (GPA). We report here the expression and purification of a highly active form of recombinant GPA, the preparation of GPA-specific polyclonal and monoclonal antibodies, and the use of these antibodies to investigate the cellular location and timing of GPA expression in tissues innervated by CG neurons. Virtually all of the trophic activity in extracts of embryonic eyes could be depleted by GPA-specific antibodies. GPA-like immunoreactivity was found in both targets of the CG: the arterial vasculature of the choroid layer and the ciliary body of the eye. In the choroid layer, GPA was localized to smooth muscle cells surrounding the choroid arteries. Staining in the choroid layer was first detectable at embryonic day (E) 10, or about 2 days after cell death has begun in the ganglion, then increased in intensity through E19. Quantification of trophic activity from whole eye extracts at various ages showed a small increase in activity observed between E9 and E12 and at least a 10-fold increase between E12 and E18. The presence of GPA protein in target cells of CG neurons during the specific developmental period when these neurons undergo cell death is consistent with its proposed function as a target-derived ciliary neurotrophic factor.

Does ciliary neurotrophic factor serve a different function in the rat versus the chicken?

Ciliary neurotrophic factor (CNTF) was first identified as a trophic activity that was able to support the survival of chick ciliary ganglion (CG) neurons in vitro. CNTF from rabbit and rat were subsequently purified from sciatic nerve and their cDNA sequences cloned. Another trophic molecule for CG neurons was identified as a growth promoting activity (GPA). GPA was purified from chicken sciatic nerve and cloned from embryonic chicken eye. The rat and rabbit CNTFs have a considerable amount of structural homology and are not secreted in significant quantities, whereas GPA is less similar in that it is only 49% homologous with rabbit and rat CNTF and is secreted by cells. This review discusses other similarities and differences in biological activities, molecular structure, receptor signaling and cellular distribution between CNTF and GPA and suggests that these molecules may have different functions in rodents and birds.

Autonomic and sensory neuron cultures

This chapter has provided a rather detailed protocol for the dissection, dissociation, and culture of autonomic and sensory neurons from the chicken embryo. These protocols are by no means absolute. Many other laboratories that routinely culture these neurons may use techniques that differ significantly from the ones detailed in this chapter. All of the protocols described in this chapter can also be applied to quail embryos, which develop more rapidly but are of comparable size to chicken embryos until about E9. The list of suppliers for the various reagents described in these protocols is also limited. Many other vendors of cell culture products are probably equally reliable.

Image forming optics with a common aperture for fast switching between TEM magnified image and selected area diffraction

Image-forming optics that can switch between a magnified image and its diffraction pattern without any movement of aperture is proposed. Both the images are alternately taken and are simultaneously shown in a monitor. This type of optics is applied to the design of an ultrahigh-voltage electron microscope (H-3000) and is tested at 100 kV TEM.

Activin A and follistatin expression in developing targets of ciliary ganglion neurons suggests a role in regulating neurotransmitter phenotype

The avian ciliary ganglion contains choroid neurons that innervate choroid vasculature and express somatostatin as well as ciliary neurons that innervate iris/ciliary body but do not express somatostatin. We have previously shown in culture that activin A induces somatostatin immunoreactivity in both neuron populations. We now show in vivo that both targets contain activin A; however, choroid expressed higher levels of activin A mRNA. In contrast, follistatin, an activin A inhibitor, was higher in iris/ciliary body. Iris cell-conditioned medium also contained an activity that inhibited activin A and could be depleted with anti-follistatin antibodies. These results suggest that development of somatostatin is limited to choroid neurons by differential expression of activin A and follistatin in ciliary ganglion targets.

Inhibitor of protein synthesis phase-shifts the circadian oscillator and inhibits the light induced-phase shift of the melatonin rhythm in pigeon pineal cells

Our recent study showed that dissociated pigeon pineal cells expressed a circadian oscillation of melatonin release which entrained to light-dark cycle and persisted under constant darkness in vitro, suggesting that pigeon pineal cells contain the circadian oscillator and photoreceptors. Six-hour pulses of anisomycin, an inhibitor of protein synthesis that acts at hte 80S ribosomal subunit, induced steady state and phase depended phase shifts of the circadian oscillation of melatonin release. The phase advances and delays were produced at CT 7.9 h and between CT 18.6 h and CT 4.5 h, respectively. The magnitudes of phase shifts were dose dependent and correlated with the magnitudes of inhibition of protein synthesis determined at CT 4.5 h. Furthermore, anisomycin blocked the light-induced phase advance. Two dimensional electrophoresis revealed that synthesis of two proteins with Mr of 17,600 and less than 5000 are stimulated by a 3-h light pulse at CT 18.6 h which corresponds to the light-induced phase advance region. These results suggest that 80S ribosomal protein synthesis is involved in normal or light-entrainment functions of the circadian oscillator in pigeon pineal cells.

Analysis of function and expression of the chick GPA receptor (GPAR alpha) suggests multiple roles in neuronal development

Growth promoting activity (GPA) is a chick growth factor with low homology to mammalian ciliary neurotrophic factor (CNTF) (47% sequence identity with rat CNTF) but displays similar biological effects on neuronal development. We have isolated a chick cDNA coding for GPA receptor (GPAR alpha), a GPI-anchored protein that is 70% identical to hCNTFR alpha. Functional analysis revealed that GPAR alpha mediates several biological effects of both GPA and CNTF. Soluble GPAR alpha supports GPA- and CNTF-dependent survival of human TF-1 cells. In sympathetic neurons, GPAR alpha mediates effects of both GPA and CNTF on the expression of vasoactive intestinal peptide (VIP) as shown by the inhibition of GPA- and CNTF-mediated VIP induction upon GPAR alpha antisense RNA expression. These results demonstrate that GPAR alpha is able to mediate effects of two neurokines that are only distantly related. GPAR alpha mRNA expression is largely restricted to the nervous system and was detected in all neurons that have been shown to respond to GPA or CNTF by increased survival or differentiation, i.e. ciliary, sympathetic, sensory dorsal root, motoneurons, retinal ganglion cells and amacrine cells. Interestingly, GPAR alpha mRNA was additionally found in neuronal populations and at developmental periods not known to be influenced by GPA or CNTF, suggesting novel functions for GPAR alpha and its ligands during neurogenesis and neuron differentiation.

Comparison of agar-gel precipitin responses among strains of fowl adenovirus using antigens prepared from chorioallantoic membranes and chicken kidney cell cultures

Agar-gel precipitin responses obtained for serologically different strains of fowl adenovirus (FAV) in tests using antigens prepared from FAV-infected chorioallantoic membranes (CAM antigen) and chicken kidney cell cultures (CKC antigen) were compared. Findings showed that both types of antigens exhibited less sensitivity to heterologous than to homologous antisera and that quantitative differences in sensitivity were present between serotypes. CAM antigens were more sensitive than CKC antigens to heterologous antisera. Polyvalent CAM antigens containing 2 or 3 antigens increased sensitivity in testing of field serum samples, resulting in a higher rate of detection.

Comparison of circadian oscillation of melatonin release in pineal cells of house sparrow, pigeon and Japanese quail, using cell perfusion systems

We compared the circadian oscillation of melatonin release from cultured pineal cells in Japanese quail, pigeon and house sparrow, to determine whether the pineal gland of these species retains the circadian oscillator function in vitro. After dissociated pineal cells have been cultured for 4 days under 12 h: 12 h light-dark (LD) cycle, they were perfused at a flow rate of 0.25 ml/h for 6-7 days under LD or constant darkness (DD). Melatonin release increased during the dark period and low during the light period in all pineal cell cultures. Under DD conditions, the circadian rhythm of melatonin release persisted for up to 3-4 cycles in pigeon and house sparrow pineal cells, but the amplitude of the rhythm decreased gradually. However, in Japanese quail pineal cell culture the circadian oscillation of melatonin release was weak or abolished under DD conditions. These results strengthen the argument that the avian pineal gland's role in circadian organization differs between species. The direct demonstration of species-specific differences in the mechanism of the circadian oscillation of melatonin release from pineal cells should provide a useful model for the analysis of the pineal's circadian system at the cellular level.

Target-derived molecules that influence the development of neurons in the avian ciliary ganglion

The developing avian ciliary ganglion has been a particularly amenable system for the identification, isolation, and characterization of putative target-derived molecules that mediate retrograde interactions. To date a number of biochemically distinct activities that regulate neuronal survival, transmitter phenotype, and chemosensitivity of ciliary ganglion neurons have been identified. Of these, only two survival-promoting molecules have been purified to homogeneity: ciliary neurotrophic factor and a related molecule, growth-promoting activity. A somatostatin-inducing activity found in cultured choroid cells is very likely to be chick activin A. Other molecules that regulate acetylcholine and acetylcholine receptor expression comigrate on a gel filtration column at a molecular weight of 50-60 kD, but they have yet to be isolated. Once molecules that mimic retrograde influences are identified, a number of criteria must be met before their physiological significance can be established. These criteria are (1) availability of the molecule from the target at the appropriate time in development; (2) ability of the neurons to respond to the molecule at the appropriate time in development; (3) demonstration that blocking the activity or availability of the molecule is able to block the target-derived developmental change expressed in the neurons. Of the molecules that are thought to retrogradely influence ciliary neuron development, only growth-promoting activity is known to meet criteria 1 and 2, and experiments are currently underway to test whether inhibition of growth-promoting activity in vivo will exacerbate normal cell death.

Circadian oscillation of 64-kDa polypeptide in the rat suprachiasmatic nucleus

In cell suspensions of suprachiasmatic nucleus harvested every 3 hr from rats kept under 12 hr: 12 hr light-dark cycle and constant darkness, we have detected a M(r) 64-kDa protein whose synthesis exhibits two distinct daily peaks in SDS-PAGE. Analysis of densitometer tracings revealed that the synthesis of other proteins was independent of the time of day or not reproducible. Maximum synthesis of the 64-kDa polypeptide occurred at around CT6 and CT21, which are almost coincident with the phase advance regions of circadian activity rhythm induced by anisomycin and light pulses [15], respectively. These results suggest that the 64-kDa protein in SDS-PAGE may be a part of the circadian clock mechanism.

Cellular distribution, subcellular localization and possible functions of basic and acidic fibroblast growth factors

The distribution in the rat nervous system of acidic and basic fibroblast growth factors (FGFs) was analysed by a combination of biochemical and anatomical methods. Acidic FGF (aFGF) was found to be present exclusively in specific neuronal populations, such as motor neurons and basal forebrain cholinergic neurons. Basic FGF (bFGF) was found in astrocytes and in neurons in hippocampal area CA2. Within labelled astrocytes and CA2-neurons, bFGF was detected in both the cytoplasm and the nucleus. The levels of intracellular bFGF were manipulated by antisense oligonucleotide treatment of cultures of developing neural crest cells. Results indicated that the amount of melanogenesis in the cultures is likely to be regulated by intracellular, possibly nuclear bFGF.

GPA and CNTF produce similar effects in sympathetic neurones but differ in receptor binding

The effects of growth promoting activity (GPA) on sympathetic neurone development were investigated in vitro and compared with the effects of ciliary neurotrophic factor (CNTF). GPA interfered with sympathetic neurone proliferation and induced the expression of vasoactive intestinal peptide (VIP) in neurones from 7-day-old (E7) chick embryos. The biological effects observed with saturating levels of GPA are indistinguishable from the effects of CNTF. The effects on VIP expression suggest that GPA may be involved in the specification of sympathetic neurone phenotypes. Whereas half maximal effects are achieved at lower concentrations of GPA than CNTF, GPA competes less efficiently than CNTF for the binding of 125I-labelled CNTF. This suggests similar, but not identical interactions of CNTF and GPA with receptors on chick sympathetic neurones.