[Role of the brain in the regulation and in the evolution of certain metabolic functions and in temperature regulation in the rat].
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Animals↗
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Brain injury: the pathophysiology of the first hours.'Talk and Die revisited'.
In the 25 years since the 'Talk and Die' paper there have been substantial advances in the management of patients with severe closed head injury. This paper discusses developments in understanding of primary and secondary injury. Current management focuses on preventing secondary brain injury. That this has been successful is illustrated by a fall in mortality in recent decades. Evidence based guidelines have set standards of management but they do not take into account variations between individuals, between regions of the brain and variations with time from injury. Various monitoring techniques such as transcranial doppler, jugular venous oxygen saturation and ICP waveform analysis attempt to set individual therapeutic endpoints and to target therapy appropriately. Primary injury is no longer seen as a single irreversible event occurring at the time of impact, but rather as a process initiated by the impact and evolving over subsequent hours and days. Experimental studies have identified agents which reduce the evolution of brain injury and improve outcome. An experimental model of brain injury developed by the Adelaide He ad Injury Group identifies diffuse axonal injury as a target for therapeutic manipulation. Magnesium has been shown in other studies to improve outcome after diffuse brain injury. This has now been linked with upregulation of beta amyloid precursor prote in. Although this and several other experimental therapies have shown great promise, they have not so far produced benefit in large clinical studies. Avoiding secondary insults will remain the goal of management for the foreseeable future. Halting the evolution of the primary injury remains a highly sought after goal. Although elusive so far, it is likely to be the next major advance in clinical care.
Axons↗
Schizophrenia-an evolutionary enigma?
The term 'schizophrenia' refers to a group of disorders that have been described in every human culture. Two apparently well established findings have corroborated the need for an evolutionary explanation of these disorders: (1) cross-culturally stable incidence rates and (2) decreased fecundity of the affected individuals. The rationale behind this relates to the evolutionary paradox that susceptibility genes for schizophrenia are obviously preserved in the human genepool, despite fundamental reproductive disadvantages associated with the disorders. Some researchers have therefore proposed that a compensatory advantage must exist in people who are carriers of these genes or in their first-degree relatives. Such advantages were hypothesised to be outside the brain (e.g. greater resistance against toxins or infectious diseases), or within the social domain (e.g. schizotypal shamans, creativity). More specifically, T.J. Crow has suggested an evolutionary theory of schizophrenia that relates the disorders to an extreme of variation of hemispheric specialisation and the evolution of language due to a single gene mutation located on homologous regions of the sex chromosomes. None of the evolutionary scenarios does, however, fully account for the diversity of the symptomatology, nor does any one hypothesis acknowledge the objection that the mere prevalence of a disorder must not be confused with adaptation. In the present article, I therefore discuss the evolutionary hypotheses of schizophrenia, arguing that a symptom-based approach to psychotic disorders in evolutionary perspective may improve upon the existing models of schizophrenia.
Adaptation, Biological↗
Ciliary photoreceptors with a vertebrate-type opsin in an invertebrate brain.
For vision, insect and vertebrate eyes use rhabdomeric and ciliary photoreceptor cells, respectively. These cells show distinct architecture and transduce the light signal by different phototransductory cascades. In the marine rag-worm Platynereis, we find both cell types: rhabdomeric photoreceptor cells in the eyes and ciliary photoreceptor cells in the brain. The latter use a photopigment closely related to vertebrate rod and cone opsins. Comparative analysis indicates that both types of photoreceptors, with distinct opsins, coexisted in Urbilateria, the last common ancestor of insects and vertebrates, and sheds new light on vertebrate eye evolution.
Amino Acid Sequence↗
Mapping studies of two G protein-coupled receptor genes: an amino acid difference may confer a functional variation between a human and rodent receptor.
We recently isolated two orphan human G protein-coupled receptor genes designated GPR1 and GPR6. The gene GPR1 was shown to be transcribed abundantly but only in the hippocampus. Here we report the cloning of the rat GPR1 gene and report the absence of expression in hippocampus, demonstrating a functional variation for this receptor in these two species. The evolutionary history of an important sequence difference in the gene GPR1 in primate and rodent species has been examined. In contrast extensive mapping of gene GPR6 mRNA in rat brain was in keeping with the described distribution in human brain.
Amino Acid Sequence↗
The diencephalon of the channel catfish, Ictalurus punctatus. I. Nuclear organization.
A detailed cytoarchitectonic description of the diencephalon in the channel catfish reveals more than 40 distinct cell groups. Of these, 4 are located in the preoptic area, 8 in the hypothalamus, 7 in the thalamus, 2 in the epithalamus, 15 in the posterior tuberculum and 7 in the synencephalon. A comparison of the diencephalon of Ictalurus punctatus to that of goldfish, which has previously been described, indicates major differences in the diencephalon between these two species. Channel catfish lack the superficial pretectum and the nucleus 'glomerulosus' of goldfish, whereas the anterior tuberal nucleus of the hypothalamus, the paracommissural nucleus of the synencephalon and the nucleus lobobulbaris of the posterior tuberculum are all better developed in channel catfish than in goldfish. The nucleus electrosensorius in the synencephalon of channel catfish is probably homologous to the nucleus of the same name in gymnotoid teleosts, but it appears to have no homologue in the diencephalon of goldfish. An analysis of interspecific variation in the diencephalon among catfishes, goldfish and several other teleosts reveals that some areas of the diencephalon are more variable across species than others. Specifically, the migrated portions of both the posterior tuberculum and the synencephalon appear to be most variable, whereas the epithalamus and the preoptic area are the most conservative. It is hypothesized that the relatively conservative areas of the brain may have a greater number of afferent connections, and probably also a greater number of distinct behavioral functions, than the more variable areas.
Animals↗
Effect upon brain weight and cholesterol content of maintaining rats of various ages at constant weight.
Rats weighing 400 g were maintained at constant weight for 500 days. Their diet consisted of 14 g/day for the first 150 days and 13 g/day thereafter. A second group of rats weighing 350 g was fed 11.5 g/day for 400 days; at the end of the experiment, these rats weighed 382 g. Under these conditions, the increase in brain weight and in quantity and concentration of cholesterol in the brain as a function of time was identical to that observed in the control rats fed ad libitum. Rats weighting 250 g fed 8.5 g/day for 200 days showed a body weight increase of 16 g. Up to the age of 115 days, the evolution of brain weight in terms of time did not differ from that observed in control rats. Rats weighting 100 g and fed 4.5 g/day showed an increase of 28 g after 300 days. The increase in brain weight and in brain cholesterol content as a function of time was less than that observed in the control rats. A curve deduced from these results has the practical interest of indicating the daily energy requirement for maintaining rats at a chosen constant weight. Expressed in terms of body surface area, the daily energy intake appears constant. It was also observed that, when conditions of minimal economy are imposed upon the adult rat, brain nutrition is not modified. But for young rats (100 g),brain development under these nutrtional conditions is affected.
Age Factors↗
Astroglial architecture of the carp (Cyprinus carpio) brain as revealed by immunohistochemical staining against glial fibrillary acidic protein (GFAP).
The present paper is the first comprehensive study on the astroglia of a teleost fish that is based on the immunohistochemical staining of GFAP (glial fibrillary acidic protein, an immunohistochemical marker of astroglia). The ray-finned fishes (Actinopterygii) and their largest group, the Teleostei, represent a separate pathway of vertebrate evolution. Their brain has a very complex macroscopic structure; several parts either have no equivalents in tetrapods or have a very different shape, e.g., the telencephalon. The results show that the teleost brain has a varied and highly specialized astroglial architecture. The primary system is made up of radial glia, which are of ependymal origin and cover the pial surface with endfeet. The tendency is, however, that the more caudal a brain area is, the less regular is the radial arrangement. A typical radial glia dominates some parts of the diencephalon (median eminence, lobus inferior and habenula) and the telencephalon. In the rest of the diencephalon and in the mesencephalon, the course of the glial fibers is modified by brain tracts. The most specialized areas of the teleost brain, the optic tectum and the cerebellum, display elaborate variations of the original radial system, which is adapted to their layered organization. In the cerebellum, an equivalent of the Bergmannglia can be found, although its fiber arrangement shows meaningful differences from that of mammals or birds. In the lower brain stem radial glia are confined to fibers separating the brain tracts and forming the midline raphe. A dense ependymoglial plexus covers the inner surface of the tectum and the bottom of the rhombencephalic ventricle, intruding into the vagal and facial lobes. The structure and the position of the rhombencephalic plexus suggest that it corresponds to a circumventricular organ that entirely occupies the bottom of the ventricle. Perivascular glia show an unusual form as they consist of long fibers running along the blood vessels. In the large brain tracts long glial fibers run parallel with the course of the neural fibers. At least in the diencephalon, these glial fibers seem to be modified radial fibers. Real astrocytes (i.e., stellate-shaped cells) can be found only in the brain stem and even there only rarely. The glial specialization in the various areas of the teleost brain seems to be more elaborate than that found either in amphibia or in reptiles.
Animals↗
Primary structure of glucagon from an elasmobranchian fish. Torpedo marmorata.
Glucagon has been isolated from the pancreas of Torpedo marmorata, an elasmobranchian cartilaginous fish, and purified to homogeneity using only reverse-phase high-performance liquid chromatography. Amino acid sequence analysis indicates that the molecule differs from mammalian glucagon at position 3 (glutamic acid for glutamine), position 16 (asparagine for serine), and position 20 (lysine for glutamine). Extracts of T. marmorata intestine and brain were associated with glucagon-like immunoreactivity determined by radioimmunoassay using antisera directed against the C-terminal and N-terminal to central regions of porcine glucagon. Although elasmobranchian and teleostean fish are believed to have diverged from the main line of vertebrate evolution at about the same time, the structure of two glucagons from the teleost, Lophius americanus (anglerfish) differ from mammalian glucagon by seven and nine residues. This study supports the assertion that the structure of glucagon has been highly conserved during evolution and suggests that the considerable morphological development of the pancreas is teleosts was associated with an accelerated rate of molecular evolution.
Amino Acid Sequence↗
Multimodality monitoring in severe head injury.
PURPOSE OF REVIEW: This review describes recent advances in multimodal neuromonitoring of patients following severe head injury during the period from 2001 to 2002. RECENT FINDINGS: Monitoring intracranial pressure is considered a standard part of therapy despite a lack of randomized studies comparing patients with and without intracranial pressure monitoring. Jugular oximetry and brain tissue oxygen pressure monitoring are being used more frequently as part of a treatment protocol. Intracerebral microdialysis, despite the widespread use as a research tool, still cannot be considered a standard in clinical monitoring. These new monitoring devices may provide useful insight into the evolution of brain injury. SUMMARY: Technology is rapidly changing the nature of neuromonitoring. New devices are becoming available which make the monitoring truly multimodal. Studies are needed to determine how to best incorporate these new parameters into effective management protocols.
Journal Article↗
Progressive grey matter atrophy in clinically early relapsing-remitting multiple sclerosis.
Brain atrophy appears to occur in patients with multiple sclerosis (MS) in excess of that associated with normal ageing, and may be observed early in the clinical course of the disease. The dynamics and tissue specificity of this process remain unclear This preliminary study explored the evolution of brain grey matter (GM) and white matter (WM) volume loss (as fractions of total intracranial volumes) in 13 subjects with relapsing-remitting MS (mean disease duration 1.9 years at first scan), compared with nine normal control (NC) subjects. Subjects were scanned every six months for 18 months. In MS compared with NC subjects, significant differences in WM fractional volumes were observed at baseline (mean - 5.8%, P = 0.008) but no apparent progressive WM tissue loss was detected. In contrast, while no significant differences in GM fractional volumes were observed at baseline, there was significantly greater time-related volume loss in MS compared with NC subjects over the follow-up period (circa - 0.0086 per year in MS subjects, - 0.0021 per year in the NC subjects, difference P = 0.010). These results suggest that while both GM and WM atrophy are seen early in the clinical course of MS, they may not occur concurrently and may evolve at different rates.
Adult↗
The serial transformation hypothesis of vertebrate origins: comment on "The new head hypothesis revisited".
In "The New Head Hypothesis Revisited," R.G. Northcutt (2005. J Exp Zool (Mol Dev Evol) 304B:274-297) evaluates the original postulates of this hypothesis (Northcutt and Gans, 1983. Quart Rev Biol 58:1-28). One of these postulates is that the brain-particularly the forebrain-evolved at essentially the same time as many neural crest and neurogenic placode derivatives-including sensory ganglia, dermal skeleton and sensory capsules of the head, and branchial arches. Northcutt's subsequent paper in 1996 concluded with the idea that transitional forms might not have occurred at the origin of vertebrates. Butler proposed a "Serial Transformation" hypothesis in 2000, which disputed the latter idea in that paired eyes and an enlarged brain (but lacking telencephalon) were envisioned to have been gained before elaboration of most neural crest and neurogenic placodal derivatives. In 2003, J. Mallatt and J.-Y. Chen analyzed fossils of the Cambrian animal Haikouella, which strongly support its affinity to craniates and aspects of several hypotheses, including Butler's transformational model, because although branchial bars are present, most other neural crest and placodal derivatives are absent, while paired eyes and an enlarged brain (but probably without telencephalon) are present. A more complete picture of vertebrate origins can be realized when the various hypotheses are constructively reconciled.
Anatomy, Comparative↗
Regional brain morphometry and lissencephaly in the Sirenia.
Neuroanatomical structure was examined in the brains of West Indian manatees (Trichechus manatus) using computer-based morphometric methods. Although manatees have a small relative brain size, volume estimates of the major brain regions indicate that the telencephalon comprises 71% of total brain volume and is 90% cerebral cortex. These values are comparable to those seen among a diversity of taxa having large relative brain size, including many primates. Manatee brains also exhibit well-defined cortical lamination. The measured gyration index (an index of cortical folding) was 1.06, representing a highly lissencephalic condition. These findings demonstrate that small relative brain size and lissencephaly do not constrain the elaboration of internal brain structures. The marked lissencephalic condition is unusual for brains of this absolute size range, and may be related to the thickness of the cortical gray matter and underlying white matter.
Animals↗
[Associative neurons as correlators].
The paper continues the series of studies devoted to the hypothesis that the brain functioning occurs with the participation of correlation methods. The processing of signals by these methods is sufficiently versatile to provide the solution of diversified problems, which has been shown in studies of the mechanisms of animal echo location (a correlation model of echo location) and recognition of objects at any modality of sensor signals. It was shown that the mode of processing performed by neurons correlometers corresponds to the character of signals coming from the habitat of animals. Problems related to both the peculiarities of a reference signal formed by synaptic inputs of an associative neuron and the process of calculating the correlation function by this neuron were resolved. Two mathematically equivalent ways of physical execution of calculating the correlation function, by a correlometer and a passive correlated filter, were compared. The advantages of the brain that performs the correlation processing of signals by using the aggregates of neurons functioning as systems of correlometers rather than passive filters are analyzed.
Algorithms↗
Aging, dementia, and brain atrophy: a longitudinal computed tomographic study.
Studies involving linear measurements of ventricular size and a volumetric measurement of the cerebrospinal fluid (CSF) space were performed on elderly subjects with mild dementia of the Alzheimer type and on age-matched controls. Forty-five subjects were studied twice at a 1 year interval; linear ventricular measurements showed not only a greater degree but a more rapid evolution of brain atrophy in individuals with mild dementia as compared with controls. An additional 12 normal subjects were studied twice over a 1 year period with volumetric estimates of the CSF space, which demonstrated development of significant brain atrophy within 1 year, while linear measurements on the same scans showed no significant change. The volumetric method is regarded as a more sensitive indicator of brain volume and is potentially useful in further studies in dementia.
Aged↗
Inactivation of a novel neuropeptide Y/peptide YY receptor gene in primate species.
Neuropeptide Y (NPY), peptide YY (PYY), and pancreatic polypeptide (PP) belong to a family of structurally related peptides which have numerous functions in both neural and endocrine signaling. By homology screening, we cloned a novel gene sharing the highest homology with the NPY Y1 receptor gene from humans, rabbits, and several other species. This novel gene of rabbit encodes a functional NPY/PYY receptor, designated Y2b, which prefers NPY13-36 rather than [Leu31,Pro34]NPY despite its higher identity with the Y1 receptor. Although, at low levels, mRNA was detected in the tissues and brain regions, including hypothalamus. Further, sequence data revealed that this gene is the orthologue of the recently cloned mouse novel NPY receptor, Y5. However, our study demonstrates that the receptor function of this gene has been inactivated in primates by a frameshift mutation occurring early in primate evolution. This novel NPY receptor represents the first neurotransmitter receptor identified that has universally lost its receptor function in primate species. Interestingly, despite its inactivation in humans, the transcripts were abundantly detected in the heart and skeletal muscle, suggesting a novel function of the human gene.
Amino Acid Sequence↗
[Changes in brain serotonin biosynthesis in rats with diabetes mellitus induced by streptozocin: effect of insulin treatment].
OBJECTIVE: To investigate if the changes in the activity of the tryptophan-5-hydroxylase and in brain serotonin synthesis provoked by diabetes mellitus persist or return to normal in the diabetic rats submitted to treatment with insulin. METHODS: Diabetes induced by the administration of streptozotocin in rats and their treatment with insulin was the paradigm used. At days 7, 14 and 21 of evolution, the brain serotonergic biosynthetic activity was evaluated. RESULTS: The diabetic rats showed a significant decrease of body weight. Also, they showed a low concentration of I-tryptophan, as well as a diminution in the activity of the key enzyme tryptophan-5-hydroxylase and its product serotonin in the cerebral cortex and brainstem. Interestingly, the activity of the enzyme was higher in the brainstem from day 14, accompanied with an elevation of the neurotransmitter. The diabetic rats submitted to treatment with insulin showed a complete physical recovery and a return to normal of plasma and brain I-tryptophan. The activity of the enzyme not only normalized but was elevated and with an increase of serotonin in the brainstem and cerebral cortex. CONCLUSION: The present findings confirm that diabetes mellitus produced a chronic anabolic deficit and a decrease in some brain regions of serotonin synthesis. Also, demonstrate that the diabetic rats under specific treatment with insulin had a complete physical recovery and a return to normal of the serotonin precursor in the blood and brain. However, the activity of the limiting enzyme TrpOH case was elevated with an increase of the neurotransmitter in all regions studied. Since the diabetic animal, insulin treated, does recover metabolically, the mechanism of activation of the serotonin biosynthetic path in the brain may not be dependent on the decreased availability of its precursor the free plasma I-tryptophan. Instead, it might be due to a change in the kinetics of tryptophan-5-hydroxylase, since its activity remains significantly increased in spite of plasma and brain normalization of its substrate. Altogether these changes in the biosynthesis of an important brain neurotransmitter may be of relevance in the pathophysiology of the psychoneurological complications in diabetic patients.
Animals↗
Distribution of vasotocin- and mesotocin-like immunoreactivities in the brain of typhlonectes compressicauda (Amphibia, gymnophiona): further assessment of primitive and derived traits of amphibian neuropeptidergic systems.
To further assess primitive and derived conditions, we have studied the vasotocinergic (AVT) and mesotocinergic (MST) systems by immmunohistochemistry in the brain of Typhlonectes compressicauda. This species belongs to a separate order of amphibians which differs in several morphological and behavioral aspects from anurans and urodeles which have been studied previously. Nevertheless, the vasotocinergic and mesotocinergic systems of T. compressicauda are largely comparable to those of other amphibians. Apart from a well-developed hypothalamo-hypophyseal system, extrahypothalamic AVT-and MST-immunoreactive groups of cells and extensive networks of fibers were found. A major difference, however, is that neuropeptidergic cells in the caudal hypothalamus and the midbrain tegmentum of T. compressicauda contain MST, whereas those in corresponding locations contain AVT in anurans and urodeles. This suggests that certain neuropeptidergic cell groups in the gymnophionan brain have switched from AVT to MST gene expression, and, thereby, offers a new view on the functional significance of these neuropeptidergic systems.
Amphibians↗