Cost–benefit analysis of funding smoking cessation before surgery

Background

Smoking at the time of surgery is associated with postoperative complications. Quitting smoking before surgery is linked to fewer complications during the hospital stay. This work analysed whether a smoking cessation intervention before surgery is economically worthwhile when funded by the National Health System (NHS) in Spain.

Methods

The economic analysis considered costs and benefits of the intervention to the NHS for the year 2016. The population who would benefit comprised adult smokers who were ready to quit and for whom surgery requiring admission to hospital was planned. The intervention, a combination of medical counselling and use of a smoking cessation drug which should occur 12 weeks before surgery, considered one attempt only to quit smoking. Benefits were costs avoided by averting postoperative complications if cessation was successful. The analysis compared the net economic outcome (benefit minus cost of intervention) and the return on investment, for intervention funded by the NHS versus the current situation without funding.

Results

Smoking cessation increased by 21·7 per cent with funding; the rate was 32·5 per cent when funded versus 10·7 per cent without funding, producing 9611 extra quitters. The cost per averted smoker was €1753 with a benefit of €503, achieving a net economic benefit of €4·8 million per year. Given the annual cost of the intervention (€17·4 million, of which €5·6 million (32·5 per cent) represents drugs), the return on investment was 28·7 per cent annually, equivalent to €1·29 per €1 of investment.

Conclusion

From the perspective of the Spanish NHS, the benefit of funding smoking cessation before surgery, in terms of healthcare cost savings, appears to greatly outweigh the costs.

Tolerance of Chromosomal Instability in Cancer: Mechanisms and Therapeutic Opportunities

Chromosomal instability (CIN) is the result of ongoing changes in the number (aneuploidy) and structure of chromosomes. CIN is induced by chromosome missegregation in mitosis and leads to karyotypic diversity within the cancer cell population, thereby adding to intratumor heterogeneity. Regardless of the overall pro-oncogenic function of CIN, its onset is typically detrimental for cell fitness and thus tumors must develop CIN-tolerance mechanisms in order to propagate. There is overwhelming genetic and functional evidence linking mutations in the tumor suppressor TP53 with CIN-tolerance. However, the pathways leading to p53 activation following chromosome missegregation remain controversial. Recently, additional mechanisms have been identified in CIN-surveillance, resulting in a more complex network of pathways acting independently or in cooperation with p53. Tolerance might also be achieved by modifying aspects of the cancer cell physiology in order to attenuate CIN or by adaptation to the consequences of aneuploid karyotypes. In this review, we summarize the current knowledge about p53-dependent and -independent mechanisms of CIN-tolerance in cancer, the adaptations observed in CIN cells buffering CIN levels, its consequences for cellular homeostasis, and the potential of exploiting these adaptations in order to design new cancer therapies.

APC/C Dysfunction Limits Excessive Cancer Chromosomal Instability

Intercellular heterogeneity, exacerbated by chromosomal instability (CIN), fosters tumor heterogeneity and drug resistance. However, extreme CIN correlates with improved cancer outcome, suggesting that karyotypic diversity required to adapt to selection pressures might be balanced in tumors against the risk of excessive instability. Here, we used a functional genomics screen, genome editing, and pharmacologic approaches to identify CIN-survival factors in diploid cells. We find partial anaphase-promoting complex/cyclosome (APC/C) dysfunction lengthens mitosis, suppresses pharmacologically induced chromosome segregation errors, and reduces naturally occurring lagging chromosomes in cancer cell lines or following tetraploidization. APC/C impairment caused adaptation to MPS1 inhibitors, revealing a likely resistance mechanism to therapies targeting the spindle assembly checkpoint. Finally, CRISPR-mediated introduction of cancer somatic mutations in the APC/C subunit cancer driver gene CDC27 reduces chromosome segregation errors, whereas reversal of an APC/C subunit nonsense mutation increases CIN. Subtle variations in mitotic duration, determined by APC/C activity, influence the extent of CIN, allowing cancer cells to dynamically optimize fitness during tumor evolution.

SIGNIFICANCE

We report a mechanism whereby cancers balance the evolutionary advantages associated with CIN against the fitness costs caused by excessive genome instability, providing insight into the consequence of CDC27 APC/C subunit driver mutations in cancer. Lengthening of mitosis through APC/C modulation may be a common mechanism of resistance to cancer therapeutics that increase chromosome segregation errors. Cancer Discov; 7(2); 218-33. ©2017 AACR.See related commentary by Burkard and Weaver, p. 134This article is highlighted in the In This Issue feature, p. 115.

BCL9L Dysfunction Impairs Caspase-2 Expression Permitting Aneuploidy Tolerance in Colorectal Cancer

Chromosomal instability (CIN) contributes to cancer evolution, intratumor heterogeneity, and drug resistance. CIN is driven by chromosome segregation errors and a tolerance phenotype that permits the propagation of aneuploid genomes. Through genomic analysis of colorectal cancers and cell lines, we find frequent loss of heterozygosity and mutations in BCL9L in aneuploid tumors. BCL9L deficiency promoted tolerance of chromosome missegregation events, propagation of aneuploidy, and genetic heterogeneity in xenograft models likely through modulation of Wnt signaling. We find that BCL9L dysfunction contributes to aneuploidy tolerance in both TP53-WT and mutant cells by reducing basal caspase-2 levels and preventing cleavage of MDM2 and BID. Efforts to exploit aneuploidy tolerance mechanisms and the BCL9L/caspase-2/BID axis may limit cancer diversity and evolution.

Generation of a disease-specific iPS cell line derived from a patient with Charcot-Marie-Tooth type 2K lacking functional GDAP1 gene

Human CMT2-FiPS4F1 cell line was generated from fibroblasts of a patient with Charcot-Marie-Tooth disease harbouring the following mutations in the GDAP1 gene in heterozygosis: p.Q163X/p.T288NfsX3. This patient did not present mutations in the PM22, MPZ or GJB genes. Human reprogramming factors OCT3/4, KLF4, SOX2 and C-MYC were delivered using a non-integrative methodology that involves the use of Sendai virus.

Dysfunctional mitochondrial fission impairs cell reprogramming

We have recently shown that mitochondrial fission is induced early in reprogramming in a Drp1-dependent manner; however, the identity of the factors controlling Drp1 recruitment to mitochondria was unexplored. To investigate this, we used a panel of RNAi targeting factors involved in the regulation of mitochondrial dynamics and we observed that MiD51, Gdap1 and, to a lesser extent, Mff were found to play key roles in this process. Cells derived from Gdap1-null mice were used to further explore the role of this factor in cell reprogramming. Microarray data revealed a prominent down-regulation of cell cycle pathways in Gdap1-null cells early in reprogramming and cell cycle profiling uncovered a G2/M growth arrest in Gdap1-null cells undergoing reprogramming. High-Content analysis showed that this growth arrest was DNA damage-independent. We propose that lack of efficient mitochondrial fission impairs cell reprogramming by interfering with cell cycle progression in a DNA damage-independent manner.

Early ERK1/2 activation promotes DRP1-dependent mitochondrial fission necessary for cell reprogramming

During the process of reprogramming to induced pluripotent stem (iPS) cells, somatic cells switch from oxidative to glycolytic metabolism, a transition associated with profound mitochondrial reorganization. Neither the importance of mitochondrial remodelling for cell reprogramming, nor the molecular mechanisms controlling this process are well understood. Here, we show that an early wave of mitochondrial fragmentation occurs upon expression of reprogramming factors. Reprogramming-induced mitochondrial fission is associated with a minor decrease in mitochondrial mass but not with mitophagy. The pro-fission factor Drp1 is phosphorylated early in reprogramming, and its knockdown and inhibition impairs both mitochondrial fragmentation and generation of iPS cell colonies. Drp1 phosphorylation depends on Erk activation in early reprogramming, which occurs, at least in part, due to downregulation of the MAP kinase phosphatase Dusp6. Taken together, our data indicate that mitochondrial fission controlled by an Erk-Drp1 axis constitutes an early and necessary step in the reprogramming process to pluripotency.

Neurons of the dentate molecular layer in the rabbit hippocampus

The molecular layer of the dentate gyrus appears as the main entrance gate for information into the hippocampus, i.e., where the perforant path axons from the entorhinal cortex synapse onto the spines and dendrites of granule cells. A few dispersed neuronal somata appear intermingled in between and probably control the flow of information in this area. In rabbits, the number of neurons in the molecular layer increases in the first week of postnatal life and then stabilizes to appear permanent and heterogeneous over the individuals' life span, including old animals. By means of Golgi impregnations, NADPH histochemistry, immunocytochemical stainings and intracellular labelings (lucifer yellow and biocytin injections), eight neuronal morphological types have been detected in the molecular layer of developing adult and old rabbits. Six of them appear as interneurons displaying smooth dendrites and GABA immunoreactivity: those here called as globoid, vertical, small horizontal, large horizontal, inverted pyramidal and polymorphic. Additionally there are two GABA negative types: the sarmentous and ectopic granular neurons. The distribution of the somata and dendritic trees of these neurons shows preferences for a definite sublayer of the molecular layer: small horizontal, sarmentous and inverted pyramidal neurons are preferably found in the outer third of the molecular layer; vertical, globoid and polymorph neurons locate the intermediate third, while large horizontal and ectopic granular neurons occupy the inner third or the juxtagranular molecular layer. Our results reveal substantial differences in the morphology and electrophysiological behaviour between each neuronal archetype in the dentate molecular layer, allowing us to propose a new classification for this neural population.

Molecular and morphological changes in placenta and embryo development associated with the inhibition of polyamine synthesis during midpregnancy in mice

Polyamines play an essential role in murine development, as demonstrated by both gene ablation in ornithine decarboxylase (ODC)-deficient embryos and pharmacological treatments of pregnant mice. However, the molecular and cellular mechanisms by which ODC inhibition affects embryonic development during critical periods of pregnancy are mostly unknown. Our present results demonstrate that the contragestational effect of alpha-difluoromethylornithine (DFMO), a suicide inhibitor of ODC, when given at d 7-9 of pregnancy, is associated with embryo growth arrest and marked alterations in the development of yolk sac and placenta. Blood island formation as well as the transcript levels of embryonary globins alpha-like x chain and beta-like y-chain was markedly decreased in the yolk sac. At the placental level, abnormal chorioallantoic attachment, absence of the spongiotrophoblast layer and a deficient development of the labyrinthine zone were evident. Real-time RT-PCR analysis showed that transcript levels of the steroidogenic genes steroidogenic acute regulatory protein, 3beta-hydroxysteroid dehydrogenase VI, and 17alpha-hydroxylase were markedly decreased by DFMO treatment in the developing placenta at d 9 and 10 of pregnancy. Plasma values of progesterone and androstenedione were also decreased by DFMO treatment. Transcriptomic analysis also detected changes in the expression of several genes involved in placentation and the differentiation of trophoblastic lineages. In conclusion, our results indicate that ODC inhibition at d 8 of pregnancy is related to alterations in yolk sac formation and trophoblast differentiation, affecting processes such as vasculogenesis and steroidogenesis.

Opposite sexual dimorphism of 3,4-dihydroxyphenylalanine decarboxylase in the kidney and small intestine of mice

3,4-Dihydroxyphenylalanine decarboxylase (DDC; also known as l-amino acid decarboxylase) is involved in the synthesis of dopamine, norepinephrine, and serotonin, and also acts as an androgen receptor co-regulator protein. In contrast to other amino acid decarboxylases that are modulated by sex hormones, little is known about the influence of these hormones on DDC regulation. In the present work, we studied the influence of gender in the expression of DDC in different mouse tissues. Among the different organs studied, including brain, liver, kidney, intestine, heart, adrenal gland, and skeletal muscle, only kidney and small intestine showed a sex-dependent dimorphism in DDC expression. In the kidney, levels of DDC activity, DDC mRNA, and protein were remarkably higher in females than in males. On the contrary, in the small intestine, male mice displayed higher levels of DDC activity than females but they did not correlate precisely with mRNA levels. This dimorphism was dependent on androgens, since male castration and treatment of female mice with testosterone propionate, oppositely affected DDC levels in kidney and small intestine. However, estrogen ablation or treatment with estradiol did not significantly affect DDC activity in these tissues. Immunocytochemical analysis revealed that DDC was mainly located in the proximal straight tubular cells of the kidney and in the cytoplasm of enterocytes. These data and the fact that renal DDC inversely correlated with renal sodium reabsorption suggest that renal and intestinal gender dimorphism in DDC could be related to sex-related differences in sodium balance observed between males and females.

Sexual dimorphism of ornithine decarboxylase in the mouse adrenal: influence of polyamine deprivation on catecholamine and corticoid levels

Adrenal sexual dimorphism is thought to be important in explaining sex-related differences regarding prevalent diseases and the responses to stress and drugs. We report here that in CD1 mice there is marked sexual dimorphism affecting not only gland size and corticoid hormone secretion but also adrenal ornithine decarboxylase (ODC), polyamine, and catecholamine levels in which testosterone appears to be a major determinant. Our results show that adrenal weight, ODC activity, and corticosterone and aldosterone secretion were higher in female than in male mice and that orchidectomy brought these male parameters closer to the values found in females. mRNA levels of steroidogenic proteins SF-1, Dax-1, steroid 21-hydroxylase, and aldosterone synthase appeared to be slightly higher in female than in male adrenals. Immunocytochemical analysis of adrenal ODC revealed that immunoreactivity was higher in females than in males and was located mainly in the cortical cells, and especially in zona glomerulosa, whereas no sex differences in ODC mRNA levels were observed. These results suggest that sex-associated differences in the expression of ODC in the mouse adrenal gland appear to be related mainly to posttranscriptional mechanisms. Combination treatment of mice with alpha-difluoromethylornithine (a suicide inhibitor of ODC) and a polyamine-deficient diet produced a marked decrease in adrenal polyamine and catecholamine levels and a significant reduction in plasma corticosterone and aldosterone concentrations that were not associated with a decrease in the mRNA levels of steroidogenic proteins. All of these data suggest a relevant role for testosterone, ODC, and polyamines in the mouse adrenal function.

Influence of ovarian ornithine decarboxylase in folliculogenesis and luteinization

LH plays a relevant role in folliculogenesis, ovulation, and luteinization. Although ornithine decarboxylase (ODC), a key enzyme in polyamine biosynthesis, is a target of LH in the ovary, the functional significance of ODC induction has remained elusive. Our study reveals that the blockade of the induction of ovarian ODC by means of the specific inhibitor alpha-difluoromethylornithine (DFMO) affects folliculogenesis and luteinization. In immature female mice, DFMO was found to inhibit ovarian growth, the formation of Graafian follicles, and the secretion of progesterone and estradiol. In adult cycling females, the administration of DFMO on the evening/night of proestrus markedly decreased plasma progesterone levels at diestrus, which was associated to the decrease in the expression of steroidogenic factor 1, cytochrome cholesterol side chain cleavage enzyme, and steroidogenic acute regulatory protein in the ovary and to a reduced vascularization of the corpora lutea. These effects were not reverted by the administration of gonadotropins or prolactin. ODC immunoreactivity was also stimulated by LH in theca and granulosa cells of antral follicles but not in preantral follicles. Overall, these experiments demonstrate that elevated ODC values found in the ovary of immature and adult mice play a relevant function in ovarian physiology and that ODC/polyamines must be considered as important mediators of some of the effects of LH on follicular development and luteinization.

Retrograde transport of sodium selenite and intracellular injection of micro-ruby: a combined method to describe the morphology of zinc-rich neurones

Zinc is found in synaptic vesicles in a large number of glutamatergic systems. Its involvement in neurotransmission and neurological disorders has been suggested. There are methods for tracing these circuits, but they do not fill the dendritic tree. In this study, extracellular selenite injections in vivo were combined with intracellular injection of fluorochromes in fixed tissue to reveal the morphology of these zinc-rich neurones. Intraperitoneal and intracerebral injections of sodium selenite alone or intracerebral injections of selenite combined with bisbenzimide were made in the visual cortex of the rat in order to locate the somata of zinc-rich neurones. After 24 h of retrograde transport, animals were killed and fluorescent markers were injected intracellularly into fixed slices to show neuronal morphology: (a) Lucifer Yellow (LY) followed by biocytin, (b) LY coupled to biocytin or (c) micro-ruby (MR) (dextranamines bound to rhodamine and biotin). Double-labelled somata (selenite+fluorochrome) were plotted. Details of the dendritic morphology were then revealed by incubation in avidin-biotin complex and development in 3,3'-diaminobenzidine and H(2)O(2). Camera lucida drawings showed that zinc-rich neurones in layers II-III involved in cortico-cortical visual projections were typical pyramidal neurones. This technique is noteworthy for its analysis of the morphology (and connections) of zinc-rich neurones.

Cytochemical techniques for zinc and heavy metals localization in nerve cells

Zinc is one of the most abundant oligoelements in the living cell. It appears tightly bound to metallothioneins, loosely bound to some metalloproteins and nucleic acids, or even as free ion. Small amounts of zinc ions (in the nanomolar range) regulate a plentitude of enzymatic proteins, receptors, and transcription factors; thus, cells need accurate homeostasis of zinc ions. Some neurons have developed mechanisms to accumulate zinc in specific membrane compartments ("vesicular zinc") which can be revealed using histochemical techniques. This article is a short report on the different direct-indirect experimental approaches for zinc and heavy metal detection in neurons. Substances giving a bright color or emitting fluorescence when in contact with divalent metal ions are currently used to detect them inside cells; their use leads to the so called "direct" methods. The fixation and precipitation of metal ions as insoluble salt precipitates, their maintenance along the histological process, and their demonstration after autometallographic development are essential steps for other methods, the so-called "indirect methods" (Timm and Danscher Neo-Timm methods).

[Synaptic zinc in the central nervous system]

Apart from iron, zinc is the most abundant oligoelement in the nervous tissue. Although the majority of zinc constitutes a stable fraction that is tightly bound to molecules and molecular complexes (structural or metabolic zinc), a small proportion (10 15% of cerebral zinc) remains as an ion and it is stored inside membranous compartments (ionic vesicular zinc). In neurons, most of this ionic zinc can be found inside synaptic vesicles and it is released outside the neuron during synaptic transmission: this is the synaptic zinc. In the surroundings of the synapse, zinc acts over a variety of neuronal receptors and ionic channels, playing a modulatory role that is not yet fully understood. The prolonged presence of zinc in the vicinity of the synapse allows its translocation to postsynaptic neurons, which lack the defensive mechanisms (membrane transporters that store zinc into vesicles). In this case, zinc acts as a neurotoxic and it can induce neuronal cell death. Neurons and glial cells have very efficient, although not well known, cleaning mechanisms that eliminate synaptic zinc from the extracellular space; it probably is simultaneous with glutamate clearance. It is feasible that dysfunction of these zinc cleaning systems could induce compensatory mechanisms (precipitation induced by amyloid precursor protein) which in turn could potentiate ethiologic factors of Alzheimer s disease.

Response of abducens internuclear neurons to axotomy in the adult cat

The highly specific projection of abducens internuclear neurons on the medial rectus motoneurons of the oculomotor nucleus constitutes an optimal model for investigating the effects of axotomy in the central nervous system. We have analyzed the morphological changes induced by this lesion on both the cell bodies and the transected axons of abducens internuclear neurons in the adult cat. Axotomy was performed by the transection of the medial longitudinal fascicle. Cell counts of Nissl-stained material and calretinin-immunostained abducens internuclear neurons revealed no cell death by 3 months postaxotomy. Ultrastructural examination of these cells at 6, 14, 24, and 90 days postaxotomy showed normal cytological features. However, the surface membrane of axotomized neurons appeared contacted by very few synaptic boutons compared to controls. This change was quantified by measuring the percentage of synaptic coverage of the cell bodies and the linear density of boutons. Both parameters decreased significantly after axotomy, with the lowest values at 90 days postlesion ( approximately 70% reduction). We also explored axonal regrowth and the possibility of reinnervation of a new target by means of anterograde labeling with biocytin. At all time intervals analyzed, labeled axons were observed to be interrupted at the caudal limit of the lesion; in no case did they cross the scar tissue to reach the distal part of the tract. Nonetheless, a conspicuous axonal sprouting was present at the caudal aspect of the lesion site. Structures suggestive of axonal growth were found, such as large terminal clubs, from which short filopodium-like branches frequently emerged. Similar findings were obtained after parvalbumin and calretinin immunostaining. At the electron microscopy level, biocytin-labeled boutons originating from the sprouts appeared surrounded by either extracellular space, which was extremely dilated at the lesion site, or by glial processes. The great majority of labeled boutons examined were, thus, devoid of neuronal contact, indicating absence of reinnervation of a new target. Altogether, these data indicate that abducens internuclear neurons survive axotomy in the adult cat and show some form of axonal regrowth, even in the absence of target connection.

Radial glia and cell debris removal during lesion-regeneration of the lizard medial cortex

Intraperitoneal injection of the neurotoxin 3-acetylpyridine (3AP) induces a rapid degeneration of the medial cerebral cortex (lizard fascia dentata) granular layer and of its zinc enriched axonal projection (lizard mossy fibres). After 6-8 weeks post-lesion the cell debris have been removed and the granular layer is repopulated by neurons generated in the subjacent ependyma. Both processes, neuron incorporation and debris removal, seem to be crucial for successful regeneration. Scavenging processes in the lesioned mammalian CNS are usually carried out by microglia and/or astrocytes. In the lizard cerebral cortex there are no free astrocytes and the only glial fibrillary acid (GFAP) immunoreactive cells are radial glia-ependymocytes, similar to those present during mammalian CNS development. Ependymocytes, in addition to their help in vertical migrations of just generated immature neurons, built the cortical glial scaffold, insulate the blood capillaries, form the outer glial limiting membrane, thus playing an essential role in the lizard cortical blood-brain barrier. In this study, by means of GFAP-immunocytochemistry and electron microscopy, we have shown that radial glial cells participate actively in the removal/phagocytosis of cellular debris generated in the lesion process: mainly degenerated synapses, but interestingly, also some neuronal somata. Cell debris taken up by ependymocyte lateral processes seem to be progressively transported to either distal (pial) or proximal (ventricular) poles of the cell, where they result in lipofuscin accumulations. The hypothetical subsequent exchange of debris from ependymoglia by microglia/macrophages and Kolmer cells is discussed.

Microglial cells during the lesion-regeneration of the lizard medial cortex

The lizard medial cortex (lizard fascia dentata) is capable of neural regeneration after being lesioned by the anti-metabolite 3-acetylpyridine (3AP). This study was aimed at detecting microglial behaviour during the medial cortex lesion-regeneration process using tomato lectin histochemistry to label microglia (both with light and electron microscopy) and proliferating cell nuclear antigen (PCNA) immunocytochemistry to label proliferating cells. As expected, 1-2 days post-injection lectin-labelled microglia cells could not be observed in the medial cortex plexiform layers, but later (7 days post-injection) abundant lectin-labelled microglia cells re-populated the regenerating medial cortex. Abundant PCNA-immunolabelled nuclei were detected both in the subjacent ependymal neuroepithelium (neuroblasts, maximum at 2 days post-injection) as well as in some parenchymal cells which were also lectin-labelled (microglia, maximum at 7-15 days post-injection). Re-invasive microglia were also detected in the vicinity of ventricular ependymal lining, blood vessels and meninges. The electron microscope demonstrated that these microglial cells participate in cell debris removal, especially of neural granular cell somata. Other cell types related to microglia (mast cells, peri-vascular cells and meningeal cells) were also present during the scavenging process. Significant numbers of microglial cells remained in close relationship with the ependymal proliferative areas, even in control non-lesioned animals. This is indirect evidence for the working hypothesis that microglia are not only implicated in cell debris removal, but also in the regulation of newly generated neuroblast incorporation onto the cortical areas. Whether they phagocytose immature neuroblasts or induce cell death in them or even prevent their migration onto the principal layer areas are likely possibilities that remain to be proven.

Localization of parvalbumin, calretinin, and calbindin D-28k in identified extraocular motoneurons and internuclear neurons of the cat

Calcium-binding proteins have been shown to be excellent markers of specific neuronal populations. We aimed to characterize the expression of calcium-binding proteins in identified populations of the cat extraocular motor nuclei by means of immunohistochemistry against parvalbumin, calretinin, and calbindin D-28k. Abducens, medial rectus, and trochlear motoneurons were retrogradely labeled with horseradish peroxidase from their corresponding muscles. Oculomotor and abducens internuclear neurons were retrogradely labeled after horseradish peroxidase injection into either the abducens or the oculomotor nucleus, respectively. Parvalbumin staining produced the highest density of immunoreactive terminals in all extraocular motor nuclei and was distributed uniformly. Around 15-20% of the motoneurons were moderately stained with antibody against parvalbumin, but their axons were heavily stained, indicating an intracellular segregation of parvalbumin. Colchicine administration increased the number of parvalbumin-immunoreactive motoneurons to approximately 85%. Except for a few calbindin-immunoreactive trochlear motoneurons (1%), parvalbumin was the only marker of extraocular motoneurons. Oculomotor internuclear neurons identified from the abducens nucleus constituted a nonuniform population, because low percentages of the three types of immunostaining were observed, calbindin being the most abundant (28.5%). Other interneurons located within the boundaries of the oculomotor nucleus were mainly calbindin-immunoreactive. The medial longitudinal fascicle contained numerous parvalbumin- and calretinin-immunoreactive but few calbindin-immunoreactive axons. The majority of abducens internuclear neurons projecting to the oculomotor nucleus (80.7%) contained calretinin. Moreover, the distribution of calretinin-immunoreactive terminals in the oculomotor nucleus overlapped that of the medial rectus motoneurons and matched the anterogradely labeled terminal field of the abducens internuclear neurons. Parvalbumin immunostained 42% of the abducens internuclear neurons. Colocalization of parvalbumin and calretinin was demonstrated in adjacent semithin sections, although single-labeled neurons were also observed. Therefore, calretinin is proven to be a good marker of abducens internuclear neurons. From all of these data, it is concluded that parvalbumin, calretinin, and calbindin D-28k selectively delineate certain neuronal populations in the oculomotor system and constitute valuable tools for further analysis of oculomotor function under normal and experimental conditions.

Localization of parvalbumin, calretinin, and calbindin D-28k in identified extraocular motoneurons and internuclear neurons of the cat

Calcium-binding proteins have been shown to be excellent markers of specific neuronal populations. We aimed to characterize the expression of calcium-binding proteins in identified populations of the cat extraocular motor nuclei by means of immunohistochemistry against parvalbumin, calretinin, and calbindin D-28k. Abducens, medial rectus, and trochlear motoneurons were retrogradely labeled with horseradish peroxidase from their corresponding muscles. Oculomotor and abducens internuclear neurons were retrogradely labeled after horseradish peroxidase injection into either the abducens or the oculomotor nucleus, respectively. Parvalbumin staining produced the highest density of immunoreactive terminals in all extraocular motor nuclei and was distributed uniformly. Around 15-20% of the motoneurons were moderately stained with antibody against parvalbumin, but their axons were heavily stained, indicating an intracellular segregation of parvalbumin. Colchicine administration increased the number of parvalbumin-immunoreactive motoneurons to approximately 85%. Except for a few calbindin-immunoreactive trochlear motoneurons (1%), parvalbumin was the only marker of extraocular motoneurons. Oculomotor internuclear neurons identified from the abducens nucleus constituted a nonuniform population, because low percentages of the three types of immunostaining were observed, calbindin being the most abundant (28.5%). Other interneurons located within the boundaries of the oculomotor nucleus were mainly calbindin-immunoreactive. The medial longitudinal fascicle contained numerous parvalbumin- and calretinin-immunoreactive but few calbindin-immunoreactive axons. The majority of abducens internuclear neurons projecting to the oculomotor nucleus (80.7%) contained calretinin. Moreover, the distribution of calretinin-immunoreactive terminals in the oculomotor nucleus overlapped that of the medial rectus motoneurons and matched the anterogradely labeled terminal field of the abducens internuclear neurons. Parvalbumin immunostained 42% of the abducens internuclear neurons. Colocalization of parvalbumin and calretinin was demonstrated in adjacent semithin sections, although single-labeled neurons were also observed. Therefore, calretinin is proven to be a good marker of abducens internuclear neurons. From all of these data, it is concluded that parvalbumin, calretinin, and calbindin D-28k selectively delineate certain neuronal populations in the oculomotor system and constitute valuable tools for further analysis of oculomotor function under normal and experimental conditions.

Changes in GABA and parvalbumin immunoreactivities in the cerebral cortex of lizards after narine occlusion

Olfactory deprivation produced by narine occlusion has been suggested to reduce the activity in the cerebral cortex of lizards. Here we analyzed the short-term changes in GABA and parvalbumin (PV) immunoreactivities in the cerebral cortex of lizards after narine occlusion. The number and distribution of GABA- and parvalbumin-immunoreactive (IR) cells have been studied by immunocytochemistry in the cerebral cortex of control and olfactory-deprived lizards. The distribution of GABA-IR cells as well as that of PV-IR cells was similar in control and deprived animals, and PV-IR cells were GABA-IR in all cases. However, significant changes were observed in the absolute number of GABA- and PV-IR cells. GABA-IR cells were more abundant in deprived animals than in control ones. In contrast, the number of PV-IR cells decreased significantly and PV immunoreactivity in dendrites and boutons was lower in deprived animals. These results suggest that the reduction in the number of PV-IR cells in olfactory-deprived lizards occurs without loss of GABA cells, and that PV expression is under the control of olfactory activity and remains plastic in the cerebral cortex of adult lizards.

Postnatal increase of GABA- and PV-IR cells in the cerebral cortex of the lizard Podarcis hispanica

The number and distribution of GABA- and parvalbumin (PV)-immunoreactive (IR) cells have been studied by immunocytochemistry in the cerebral cortex of newborn and adult lizards. The distribution of GABA-IR cells as well as that of PV-IR cells were similar in newborn and adult lizards, and PV-IR cells were GABA-IR in all cases. However, the absolute number of GABA- and PV-IR cells increased significantly during development. In addition, the rate of of GABA-IR cells also displaying PV immunoreactivity also increased after birth. Moreover, dendrites were rarely found to be PV-IR in newborn lizards, whereas they appeared stained in a Golgi-like manner in adult animals. These results suggest that the GABAergic neuronal population of the cerebral cortex of lizards experiments a significant increment in number and neurochemical maturation after birth.

Parvalbumin-containing neurons in the cerebral cortex of the lizard Podarcis hispanica: morphology, ultrastructure, and coexistence with GABA, somatostatin, and neuropeptide Y

The morphology, fine structure, and degree of colocalization with GABA, somatostatin, and neuropeptide Y of parvalbumin-containing cells were studied with immunocytochemistry in the cerebral cortex of the lizard Podarcis hispanica. Parvalbumin-containing cells make up a morphologically heterogeneous population of spine-free neurons, displaying the morphological features of nonprincipal cells previously described in Golgi studies. Electron microscopically, parvalbumin-immunoreactive cell bodies are similar in all cortical areas and layers. The perisomatic input is moderate in number, and boutons with either round clear vesicles or flattened vesicles were observed making asymmetric or symmetric synaptic contacts, respectively. Parvalbumin-immunoreactive dendrites are smooth and almost completely covered with synaptic boutons of different types, most of which establish asymmetric contacts. Parvalbumin-immunoreactive boutons are concentrated around cell bodies of principal cells. They are large, containing abundant mitochondria and small pleomorphic vesicles, and establishing symmetric synaptic contacts with somata, proximal dendritic shafts, and axon initial segments of principal cells. Colocalization studies revealed that all the parvalbumin-containing cells are GABA-immunoreactive, representing only a fraction of the GABA-immunopositive cell population, and that parvalbumin- and peptide- (somatostatin and neuropeptide Y) containing cells show a negligible overlap. These results demonstrate that in the cerebral cortex of the lizard Podarcis hispanica, parvalbumin-containing cells represent a subset of nonprincipal GABAergic neurons largely involved in perisomatic inhibition, which are different from the peptide-containing cells, and suggest that they may include both axosomatic and axoaxonic cells.

Role of GABA in the extraocular motor nuclei of the cat: a postembedding immunocytochemical study

The GABAergic innervation of the extraocular motor nuclei in the cat was evaluated using postembedding immunocytochemical techniques. The characterization of GABA-immunoreactive terminals in the oculomotor nucleus was carried out at the light and electron microscopic levels. GABA-immunopositive puncta suggestive of boutons were abundant in semithin sections throughout the oculomotor nucleus, and were found in close apposition to somata and dendrites. Ultrathin sections revealed an extensive and dense distribution of GABA-immunoreactive synaptic endings that established contacts with the perikarya and proximal dendrites of motoneurons and were also abundant in the surrounding neuropil. GABAergic boutons were characterized by the presence of numerous mitochondria, pleiomorphic vesicles and multiple small symmetrical synaptic contacts. The trochlear nucleus exhibited the highest density of GABAergic terminations. In contrast, scarce GABA immunostaining was associated with the motoneurons and internuclear neurons of the abducens nucleus. In order to further elucidate the role of this neurotransmitter in the oculomotor system, retrograde tracing of horseradish peroxidase was used in combination with the GABA immunostaining. First, medial rectus motoneurons were identified following horseradish peroxidase injection into the corresponding muscle. This was carried out because of the peculiar afferent organization of medial rectus motoneurons that contrasts with the remaining extraocular motoneurons, especially their lack of direct vestibular inhibition. Semithin sections of the oculomotor nucleus containing retrogradely labeled medial rectus motoneurons and immunostained for GABA revealed numerous immunoreactive puncta in close apposition to horseradish peroxidase-labeled somata and in the surrounding neuropil. At the ultrastructural level, GABAergic terminals established synaptic contacts with the somata and proximal dendrites of medial rectus motoneurons. Their features and density were similar to those found in the remaining motoneuronal subgroups of the oculomotor nucleus. Second, oculomotor internuclear neurons were identified following the injection of horseradish peroxidase into the abducens nucleus to determine whether they could give rise to GABAergic terminations in the abducens nucleus. About 20% of the oculomotor internuclear neurons were doubly labeled by retrograde horseradish peroxidase and GABA immunostaining. A high percentage (80%) of the oculomotor internuclear neurons projecting to the abducens nucleus showed immunonegative perikarya. It was concluded that the oculomotor internuclear pathway to the abducens nucleus comprises both GABAergic and non-GABAergic neurons and, at least in part, the GABA input to the abducens nucleus originates from this source. It is suggested that this pathway might carry excitatory and inhibitory influences on abducens neurons arising bilaterally.

Lesion and regeneration in the medial cerebral cortex of lizards

The cerebral cortex of Squamate reptiles (lizards and snakes) may be regarded as an archicortex or "reptilian hippocampus". In lizards, one cortical area, the medial cortex, may be considered as a true "fascia dentata" on grounds of its anatomy, connectivity and cyto- chemo-architectonics of its main zinc-rich axonal projection. Moreover, its late ontogenesis and postnatal development support this view. In normal conditions, it shows delayed postnatal neurogenesis and growth during the lizard's life span. Remnant neuroblasts in the medial cortical ependyma of adult lizards seasonally proliferate. The late-produced immature neurocytes migrate to the medial cortex cell layer where they differentiate and give off zinc-containing axons directed to the rest of cortical areas. This results in a continuous growth of the medial cortex and its zinc-rich axonal projection. Perhaps the most important characteristic of the lizard medial cortex is that it can regenerate after having been almost completely destroyed. Recent experiments in our laboratory have shown that chemical lesion of its neurons (up to 95%) results in a cascade of events; first, those related with massive neuronal death and axonal-dendritic retraction and, secondly, those related with a triggered neuroblast proliferation and subsequent neo-histogenesis, and the regeneration of an almost new medial cortex that shows itself undistinguishable from a normal undamaged one. This is the only report to our knowledge that an amniote central nervous centre may regenerate by new neuron production and neo-histogenesis. Perhaps the medial cortex of lizards may be used as a model for neuronal regeneration and/or transplant experiments in mammals or even in primates.

Neuron regeneration reverses 3-acetylpyridine-induced cell loss in the cerebral cortex of adult lizards

Systemic administration of the neurotoxin 3-acetylpyridine to adult lizards results in extensive loss of neurons in the medial cerebral cortex, other brain areas remaining largely unaffected. After the neurotoxic trauma, new cells are produced by mitotic division of cells in the ventricular wall. The new cells migrate along radial glial fibers and replace lost neurons in the medial cortex. Electron microscopic examination of cells labeled with [3H]thymidine confirms that the newly generated cells are neurons. Thus, neuron regeneration can occur in the cerebral cortex of adult lizards.

GABAergic neurons in the septum of the lizard, Podarcis hispanica

With an antibody to gamma-aminobutyric acid (GABA), GABA-immunoreactive somata and boutons were identified in the septum of a lizard brain. GABA-positive somata occur at all rostrocaudal levels and in all septal nuclei. Parallel acetylcholinesterase (AChE) staining revealed a similar distribution of AChE-positive neurons. GABAergic boutons were seen throughout the septal nuclei, and were more densely concentrated in the outer zone of the dorsolateral septum. Axons of the anterior pallial commissure contained GABA- and AChE-reactivity.

A new stabilizing agent for the tetramethyl benzidine (TMB) reaction product in the histochemical detection of horseradish peroxidase (HRP)

In this paper, an alternative procedure for the histochemical detection of HRP using amonium heptamolybdate (AHM) as a stabilizing agent and tetramethyl benzidine (TMB) as a chromogen is reported. This procedure avoids the two main problems that occur in previous methods using sodium nitroferricyanide (SNF) as the stabilizer, namely, the appearance of needle-shaped crystals at non-specific anatomical sites, and intensive tissue shrinkage. A comparative study of both, the TMB-AHM and TMB-SNF methods, was performed in the analysis of cerebral cortex afferent connections of the lizard Podarcis hispanica. This study demonstrates that the two methods are of similar sensitivity. The TMB-AHM reaction can be carried out at physiological pH (from 6 to 8), thus, avoiding tissue contraction. The reaction product is of an intense blue-green colour and, as with the TMB-SNF method, shows granulation. The appearance of non-specific precipitates is completely avoided when the incubation medium is maintained at a pH in excess of 5.