Is a certain amount of cysteine prerequisite to produce brain damage in neonatal rats?

In this study, various manipulations were used to determine if certain amounts of cysteine are essential to damage the neonatal rat brain. The information gathered from this study indicated that concentration of free cysteine may be 0.6 mol/g of wet brain weight or more to cause the toxicity to produce the brain damage, and the results were discussed in the light that free cysteine might itself be the cause of brain damage.     

How Does Joint Remodeling Work?: New Insights in the Molecular Regulation of the Architecture of Joints

Remodeling of joints is a key feature of inflammatory and degenerative joint disease. Bone erosion, cartilage degeneration and growth of bony spurs termed osteophytes are key features of structural joint pathology in the course of arthritis, which lead to impairment of joint function. Understanding their molecular mechanisms is essential to tailor targeted therapeutic approaches to protect joint architecture from inflammatory and mechanical stress. This addendum summarizes the new insights in the molecular regulation of bone formation in the joint and its relation to bone resorption. It describes how inflammatory cytokines impair bone formation and block the repair response of joints towards inflammatory stimuli. It particularly points out the key role of Dickkopf-1 protein, a regulator of the Wingless signaling and inhibitor of bone formation. This new link between inflammation and bone formation is also crucial for explaining the generation of osteophytes, bony spurs along joints, which are characterized by new bone and cartilage formation. This mechanism is largely dependent on an activation of wingless protein signaling and can lead to complete joint fusion. This addendum summarized the current concepts of joint remodeling in the limelight of these new findings.Key words: joint remodeling, arthritis, bone formation, bone erosion, osteoblasts, osteoclasts, Dickkopf, wingless proteinsJoints face profound remodeling in the course of arthritis. In humans, pathologic joint remodeling manifests as (i) destruction of joints due to bone erosion (rheumatoid arthritis), (ii) fusion of joints due to formation of bony spurs such as osteophytes, spondylophytes and syndesmophytes (ankylosing spondylitis) or (iii) a mixture of both changes (psoriatic arthritis). The molecular mechanisms determining these different forms of joint remodeling are not fully clarified, Insights in these mechanisms however are a clue to a deeper understanding of the architectural changes of human joints.Similar to systemic bone turnover, which most is most prominent in the trabecular bone compartment of the spine and long bones, joints are hot spots of bone remodeling during inflammatory disease. Cytokines expressed by inflammatory cells in the synovial membrane regulate local bone homeostasis and enable to remodel joints during disease—a process which can either lead to crippling and functional loss or to fusion and stabilization of the affected joint. Rheumatoid arthritis is characterized by bone erosions, which are the result of an enhanced bone resorption. In rheumatoid arthritis osteoclasts, the primary bone resorbing cells, accumulate and degrade the periarticular bone as well as the mineralized cartilage.¹ Molecularly increased osteoclast formation is based on the expression of macrophage colony-stimulating factor (MCSF) and receptor-antagonist of NFκB ligand (RANKL) in the synovial tissue, which both drive the differentiation of osteoclasts from monocytic precursors.^2–4 Osteoclasts are specialized cells to resorb bone and their local accumulation in the joint leads to a catabolic state, which by far outweighs bone formation resulting in a negative net effect of bone remodeling. Inflammatory cytokines, such as TNF, IL-1, IL-6 and IL-17 induce osteoclast formation by enhancing the expression of RANKL and promoting differentiation of osteoclast precursor cells to mature osteoclasts.^5–8 Abundance of proinflammatory cytokines in the synovial membrane of patients with RA, their induction of molecules involved in osteoclast formation and the influx of monocytes/macrophages serving as osteoclast precursor cells represent ideal prerequisites for osteoclast formation in joints.⁹The fact that appropriate repair strategies are virtually absent in patients with RA and that bone is hardly rebuilt when bone erosions have emerged, suggests activation of molecular signals, which blunt bone formation. Bone formation itself is regulated by growth factors and hormones, which stimulate differentiation and activity of osteoblasts. Typical regulators of bone formation constitute parathyroid hormone, prostaglandins, bone morphogenic proteins (BMPs) and wingless proteins (Wnt). Particularly the role of Wnt proteins in bone formation have achieved growing interest during the past few years, leading to identification of the LRP5/6 receptor as a key molecule for anabolic skeletal responses. Wnt proteins bind to the LRP5/6 receptor and lead to activation of a signal pathway involving GSK3 and β-catenin, which drive differentiation of mesenchymal cells into osteoblastogenesis.¹⁰ Regulators of Wnt- induced bone formation are Dickkopf (DKK) proteins, which competitively bind to LRP5/6 and prevent signaling activation by additionally engaging a negative coreceptor termed Kremen-1.^11,12 DKK proteins thus regulate bone homeostasis by interference with Wnt signaling.¹³We recently showed that inflammatory cytokines such as TNF induce DKK-1, a member of the DKK- family, which inhibits Wnt signaling. DKK-1 is highly expressed in inflammatory lesions of experimental arthritis and human rheumatoid arthritis.¹⁴ Moreover, increased levels can be detected in the serum of patients with RA, which depend on TNF. This is supported by the normalization of elevated DKK-1 levels in RA patients upon initiation of systemic TNF- blockade. Inhibition of DKK-1 in mice completely abolishes bone erosions in different models of experimental arthritis and leads to increased bone growth, which manifests as osteophyte formation in the joint.DKK-1 links the inflammation with bone formation as RANKL links inflammation with bone resorption. The fact that TNF and presumably also other inflammatory mediators induce both proteins explains the profound negative effect of inflammation on bone. Inflammation uncouples the balance between bone resorption and formation, enhancing the former by inducing RANKL and by repressing the latter by DKK-1. Also appears to be a tight cross talk between the Wnt- and RANKL-pathways.¹⁵ Inhibition of DKK-1 in arthritic mice lead to protection from bone erosions and osteoclasts did not appropriately form. This effect is based on the induction of osteoprotegerin (OPG) a natural decoy receptor for RANKL, which blocks RANKL and thus osteoclast formation. OPG is induced by Wnt proteins and shifts the balance from bone resorption to bone formation.In contrast to rheumatoid arthritis joints in ankylosing spondylitis and also in degenerative joint disease (osteoarthritis) show an attempt towards joint fusion rather than joint destruction. These bony spurs are the result of endochondral bone formation starting from the periosteum close to the joints, where osteoblasts differentiate build up bone matrix. We could demonstrate that Wnt proteins are crucially involved in this process since inhibition of DKK-1 lead to emergence of osteophytes and even complete fusion of joints. Taken together these data suggest that the balance of the Wnt/DKK system determines the remodeling of joints by governing bone destruction as well as osteophyte formation in joints (Fig. 1).Open in a separate windowFigure 1Patterns of joint remodeling.     

What is the role of PIWI family proteins in adult pluripotent stem cells? Insights from asexually reproducing animals,planarians

Planarians have a remarkable regenerative ability owing to their adult pluripotent stem cells (aPSCs), which are called “neoblasts.” Planarians maintain a considerable number of neoblasts throughout their adulthood to supply differentiated cells for the maintenance of tissue homeostasis and asexual reproduction (fission followed by regeneration). Thus, planarians serve as a good model to study the regulatory mechanisms of in vivo aPSCs. In asexually reproducing invertebrates, such as sponge, Hydra, and planaria, piwi family genes are the markers most commonly expressed in aPSCs. While piwi family genes are known as guardians against transposable elements in the germline cells of animals that only sexually propagate, their functions in the aPSC system have remained elusive. In this review, we introduce recent knowledge on the PIWI family proteins in the aPSC system in planarians and other organisms and discuss how PIWI family proteins contribute to the regulation of the aPSC system.     

cGMP: a second messenger for acetylcholine in the brain?

Already 30 years ago, it became apparent that there exists a relationship between acetylcholine and cGMP in the brain. Acetylcholine plays a role in a great number of processes in the brain, however, the role of cGMP in these processes is not known. A review of the data shows that, although the connection between NO-mediated cGMP synthesis and acetylcholine is firmly established, the complexities of the heterosynaptic pathways and the oligosynaptic structures involved preclude a clear definition of the role of cGMP in the functioning of acetylcholine presently.     

What are the characteristics of cycling cells in the adult central nervous system?

Many regions of the adult central nervous system contain cycling cells. Such cells comprise a relatively small fraction of the total population of the CNS. Work over decades has attempted to determine the normal fates of these cells and their fates under pathological conditions. The recent interest in \"stem\" cells and \"progenitors\" in the adult CNS has sparked a much revived exploration into the nature of these cells and in the signals by which they may be induced to differentiate into mature neurons or glia. This population has not yet been fully characterized, although it has become clear that this is a heterogeneous group of cells, differing in morphology, antigen expression, migratory capacity, and potential fates.     

Is there a probenecid sensitive transport system for monoamine catabolites at the level of the brain capillary plexus?

Probenecid inhibits the transport of the small monocarboxylic acids lactate and propionate from blood to brain but does not affect the transport of 5HIAA or HVA. Neither lactate, 5HIAA, HVA, nor probenecid itself inhibits probenecid uptake into brain from blood and neither lactate nor 5HIAA itself inhibits 5HIAA uptake. These results indicate first that probenecid inhibits the lactate carrier but is itself not transported by that carrier and second that 5HIAA and probenecid are independently transported from blood to brain by a low affinity system, probably by diffusion. Preloading animals with both tryptophan and probenecid increased the apparent transport of lactate, probenecid and 5HIAA but not the transport of glucose. This indicates that the transport of 5HIAA, lactate and probenecid from brain to blood involves a common, saturable carrier. These two sets of data indicate that either the brain capillary transport system is asymmetric or that probenecid-inhibited transport of monoamine catabolites from brain occurs at sites other than the capillary transport system of the blood-brain barrier.     

Matrix metalloproteinases in the adult brain physiology: a link between c-Fos,AP-1 and remodeling of neuronal connections?

Matrix metalloproteinases (MMPs), together with their endogenous inhibitors (TIMPs) form an enzymatic system that plays an important role in a variety of physiological and pathological conditions. These proteins are also expressed in the brain, especially under pathological conditions, in which glia as well as invading inflammatory cells provide the major source of the MMP activity. Surprisingly little is known about the MMP function(s) in adult neuronal physiology. This review describes available data on this topic, which is presented in a context of knowledge about the MMP/TIMP system in other organs as well as in brain disorders. An analysis of the MMP and TIMP expression patterns in the brain, along with a consideration of their regulatory mechanisms and substrates, leads to the proposal of possible roles of the MMP system in the brain. This analysis suggests that MMPs may play an important role in the neuronal physiology, especially in neuronal plasticity, including their direct participation in the remodeling of synaptic connections-a mechanism pivotal for learning and memory.     

Presence of adrenocorticotropin and β-Endorphin immunoreactivities in the magnocellular neurosecretory system of the rat hypothalamus

Summary Antisera raised against ACTH (1–39), -endorphin and the 16K proopiocortin were used, in association with the immunoperoxidase reaction, to localize positively-staining cell bodies and nerve fibres in the hypothalamus of the rat. Antigens, cross-reactive against anti-ACTH (1–39) serum were detected in a fibre system in the rostro-dorsal hypothalamus situated between the optic chiasm and the third ventricle while immunoreactive 16K-like material was present in fibres localized in the caudal hypothalamus, dorso-lateral to the arcuate nucleus. This latter system was also associated with the appearance of ACTH (1–39) and ACTH (17–39) immunoreactivity.Cells of the arcuate nucleus stained positively for ACTH (1–39), 16K antigen and -endorphin, and on examining adjacent thin sections it was observed that cells that contained 16K antigen-like material, also gave a positive immunoreaction with ACTH (1–39) and -endorphin antisera. In the magnocellular system, cells of the supraoptic (SON) and paraventricular (PVN) nuclei also gave a positive immunoreaction with anti-ACTH (1–39), 16K antigen and -endorphin serum. As in the case of the arcuate nucleus, common cells stained for these three antigens.On the basis of the precursor theory for the synthesis of ACTH, 16K antigen and -endorphin, it was not unexpected to find these three fragments of pro-opiocortin localized together in cells of the arcuate nucleus. That ACTH (1–39), 16K antigen and -endorphin-like materials are present in the magnocellular neurosecretory system would suggest that cells of the SON and PVN are not only involved in the synthesis of neurophysin and the neurohypophysial hormones, but also of some products of the pro-opiocortin molecule. Whether the biochemical nature of the ACTH and -endorphin in cells of the SON and PVN is identical to that of anterior pituitary origin remains to be established, as does the biosynthetic relationship between neurophysin and oxytocin/ vasopressin and these fragments of pro-opiocortin.Drs. M.M. Wilkes, S.S.C. Yen, G. Pelletier, B.A. Eipper and R. Walter are thanked for supplying some of the antisera and antigens used in this study. Thanks also go to Ciba-Geigy Ltd. and Organon Inc. for supplies of ACTH (17–39) and ACTH (1–24) respectively. This work was financed by The Medical Research Council of New Zealand     

Immunohistochemical and in situ hybridization analysis of galectin-3, a β-galactoside binding lectin, in the urinary system of adult mice

Galectin is an animal lectin that has high affinity to β-galactoside of glycoconjugates. In the present study, cellular expression of galectin subtypes in the urinary system of adult mice was examined by in situ hybridization and immunohistochemistry. The major subtype expressed in the murine urinary system was galectin-3, which was expressed continuously from the kidney to the distal end of the urethra. The renal cortex expressed galectin-3 more intensely than the medulla. Renal galectin-3 immunoreactivity was strongest in the cortical collecting ducts, where principal cells were the sole cellular source. All cell layers of the transitional epithelium from the renal pelvis to the urethra strongly expressed galectin-3 at the mRNA and protein levels. An electron microscopic study demonstrated diffuse cytoplasmic localization of galectin-3 in principal cells of the collecting ducts and in the bladder epithelial cells. Urethral galectin-3 expression at the pars spongiosa decreased in intensity near the external urethral orifice, where the predominant subtype of galectin was substituted by galectin-7. The muscular layer of the ureter and urinary bladder contained significant signals for galectin-1. Taken together, the observations indicate that the adult urinary system shows intense and selective expression of galectin-3 in epithelia of the uretic bud- and cloaca-derivatives.     

Neuronal migration in the adult brain: are we there yet?

The generation and targeting of appropriate numbers and types of neurons to where they are needed in the brain is essential for the establishment, maintenance and modification of neural circuitry. This review aims to summarize the patterns, mechanisms and functional significance of neuronal migration in the postnatal brain, with an emphasis on the migratory events that persist in the mature brain.     

Distinct subcellular localization of β-tubulin epitopes in the adult mouse brain

 A panel of monoclonal antibodies specific of α-tubulin (TU-01, TU-09) and β-tubulin (TU-06, TU-13) subunits was used to study the location of N-terminal structural domains of tubulin in adult mouse brain. The specificity of antibodies was confirmed b immunoblotting experiments. Immunohistochemical staining of vibratome sections from cerebral cortex, cerebellum, hippocampus, and corpus callosum showed that antibodies TU-01, TU-09, and TU13 reacted with neuronal and glial cells and their processes, whereas the TU-06 antibody stained only the perikarya. Dendrites and axons were either unstained or their staining was very weak. As the TU-06 epitope is located on the N-terminal structural domain of β-tubulin, the observed staining pattern cannot be interpreted as evidence of a distinct subcellular localization of β-tubulin isotypes or known post-translational modifications. The limited distribution of the epitope could, rather, reflect differences between the conformations of tubulin molecules in microtubules of somata and neurites or, alternatively, a specific masking of the corresponding region on the N-terminal domain of β-tubulin by interacting protein(s) in dendrites and axons. Accepted: 11 November 1996     

Synthesis of life in the lab? Defining a protoliving system

The synthesis of a living system in the lab has been judged by a number of critics as partly attained by the proteinoid microsphere because of its primitive properties of metabolism, growth, and reproduction. These same critics, however, judge the organism as not alive, or as being 50 to 75 percent alive (Baltscheffsky and Jurka, 1984), owing to the absence of a nucleic acid genetic coding mechanism. The experiments in retracing evolution suggest, however, that the self-sequencing of amino acids was the evolutionary precursor of modern nucleic acid templating; the genetic memory is the molecule. The proteinoid microsphere is not a modern living system, but does represent at least a protoliving system (Fox and Dose, 1972). Berra (1990, p. 75) has commented on other difficulties in defining a protoliving system. In Berra's opinion, metabolism, reproduction, responsiveness to stimuli, and cellularity constitute or describe aliveness. These properties characterize proteinoid microspheres. A number of experiments demonstrate that amino acids in aminoacyl adenylates yield specific products, whereas nucleotides are without effect. For this and related reasons, especially the demonstrated self-sequencing of amino acids when they are warmed, resultant bio-functional properties of self-assembled microstructures, and demonstrated self-sequencing of amino acids in modern systems, the results appear to bridge from the chemical era to the biological period. All the above emerges from a departure in style of research (Young, 1984; Pauling and Zuckerkandl, 1972). The latter authors said, "It appears likely that biogenesis is the passage from a 'non-living system' existing in a large number of states to a 'living' system also existing in a large number of states."(ABSTRACT TRUNCATED AT 250 WORDS)     

Why is the number of days required for induction of adult diapause in the linden bug Pyrrhocoris apterus fewer in the larval than in the adult stage?

Adult females of Pyrrhocoris apterus, programmed for diapause by short-day (SD) photoperiod and those programmed for reproduction by long-day (LD) retain photoperiodic information in continuous darkness (DD) until death. However, if the interruption of SD by DD is made in the course of diapause programming in adults, then the incidence of diapause depends on the number of SD cycles received before DD, with no evidence that the photoperiodic clock is free-running at DD to complete diapause induction. These results indicate that the photoperiodic clock is stopped after transfer to DD and the information accumulated before transfer to DD is maintained. Diapause programming in the adult stage requires 9–10 SD cycles to induce diapause in 80% of individuals. However, if the diapause programming starts after ecdysis of LD-larvae to the last instar, only 3 SD cycles before transfer to DD are required for diapause in 80% of individuals. Surprisingly, if the newly ecdysed last instar LD-larvae, sensitive to photoperiod, are transferred to DD (thus they did not experience any SD), diapause occurs in 40% of the individuals. Thus, diapause ‘information’ is present in LD-larvae and is responsible for a lower number of SD required for diapause induction in the larval than in the adult stage.     

A role for the interferon system in the pathogenesis of multiple sclerosis?

MS may be caused by an as yet unidentified virus whose life-long persistence in the body may deregulate the immune system so as to make it react against central nervous system tissue. Interferon are endogenous, hormone-like proteins with antiviral and immunomodulatory properties. This paper analyses current knowledge on the production and action of these proteins in the perspective of their possible involvement in the pathogenesis of MS. It also reviews observations made sofar on interferon production and action in MS patients.     

Outsourcing in the brain: Do neurons depend on cholesterol delivery by astrocytes?

Brain function depends on the cooperation between highly specialized cells. Neurons generate electrical signals and glial cells provide structural and metabolic support. Here, I propose a new kind of job-sharing between neurons and astrocytes. Recent studies on primary cultures of highly purified neurons from the rodent central nervous system (CNS) suggest that, during development, neurons reduce or even abandon cholesterol synthesis to save energy and import cholesterol from astrocytes via lipoproteins. The cholesterol shuttle may be restricted to compartments distant from the soma including synapses and may be regulated by electrical activity. Testing these hypotheses will help to improve our still insufficient understanding of brain cholesterol metabolism and its role in neurodegeneration.     

What to expect from MRI in the investigation of the central nervous system?

Functional magnetic resonance imaging (fMRI) has appeared as a new tool that is very powerful for cognitive neuroscience, offering the potential to look at the dynamics of cerebral processes underlying cognition, non-invasively and on an individual basis. Work remains to be done to optimize the technique and to better understand its basic mechanisms, but one may expect to build in a foreseeable future a functional list of the main brain cortical networks implicated in sensory-motor or cognitive processes. Still, the real understanding of brain function requires direct access to the functional unit consisting of the neuron, so that one may look at the transient temporal relationships that exist between largely distributed groups of hundreds or thousands of neurons. Furthermore, communication pathways between networks, which are carried by brain white matter, must be identified to establish connectivity maps at the individual scale, taking into account individual variability resulting from genetic factors and cerebral plasticity. In this respect, MRI of molecular diffusion is very sensitive to water molecular motion and, thus, to tissue dynamic microstructure, such as cell size and geometry. Preliminary data suggest that diffusion MRI visualizes dynamic tissue changes associated with large neuronal activation and space orientation of large bundles of myelinated axons in the white matter.