Regressive Events Research Articles

Dendrites of rod bipolar cells sprout in normal aging retina

The aging nervous system is known to manifest a variety of degenerative and regressive events. Here we report the unexpected growth of dendrites in the retinas of normal old mice. The dendrites of many rod bipolar cells in aging mice were observed to extend well beyond their normal strata within the outer plexiform layer to innervate the outer nuclear layer where they appeared to form contacts with the spherules of rod photoreceptors. Such dendritic sprouting increased with age and was evident at all retinal eccentricities. These results provide evidence of retinal plasticity associated with normal aging.

Axon pruning: an essential step underlying the developmental plasticity of neuronal connections

Regressive events play a key role in modifying neural connectivity in early development. An important regressive event is the pruning of neuronal processes. Pruning is a strategy often used to selectively remove exuberant neuronal branches and connections in the immature nervous system to ensure the proper formation of functional circuitry. In the following review, we discuss our present understanding of the cellular and molecular mechanisms that regulate the pruning of axons during neuronal development as well as in neurological diseases. The evidence suggests that there are several similarities between the mechanisms that are involved in developmental axon pruning and axon elimination in disease. In summary, these findings provide researchers with a unique perspective on how developmental plasticity is achieved and how to develop strategies to treat complex neurological diseases.

Late Holocene stratigraphic evolution of a back-barrier tidal basin in the East Frisian Wadden Sea, southern North Sea: transgressive deposition and its preservation potential

The late Holocene stratigraphic evolution of a back-barrier tidal basin in the East Frisian Wadden Sea, southern North Sea, was investigated on the basis of a conceptual model relating the rate of sea-level rise to the rate of sediment supply. For this purpose, more than 20 vibra-cores and box-cores were evaluated, complemented by 14C ages of in situ peats and historical charts. In spite of interspersed short regressive events, the late Holocene stratigraphy generally reveals upward-coarsening grain-size trends indicative of transgressive deposition in the course of sea-level rise rather than erosion and redeposition by migrating channels. A particular feature is the general absence of down-core bioturbation traces, which stands out in sharp contrast to the intensely burrowed modern surface layer. Thus, in the Wadden Sea, high sediment turnover in the course of rapid transgression evidently obliterates most bioturbation traces and other tidal signals such as minor regressive deposits, thereby emphasising the importance of preservation potential.

Diversity patterns of Carboniferous and Permian rugose corals in South China

AbstractThe diversity and changing patterns of rugose corals in the Carboniferous and Permian of South China are analysed by statistical analyses of 45 families, 284 genera, and 1979 species from 14 consecutive time intervals. The ancestors of Carboniferous rugose corals originated early and underwent preliminary radiation in the late Famennian, but were eliminated by the Hangenberg global regressive event, which marks the Devonian—Carboniferous boundary. Radiation of typical Carboniferous rugose corals began in the late Tournaisian, when they were represented by an abundance of columellate taxa such asKueichouphyllumand a significant diversification ofKeyserlingophyllum. A decrease in the diversity of rugose genera occurred in the Serpukhovian, followed by a change in the composition of the rugose coral assemblages at the Mid‐Carboniferous Serpukhovian—Bashkirian boundary, where large dissepimented taxa with complex axial structures disappeared. In the Bashkirian the Serpukhovian taxa were replaced by compound rugosan taxa of the Geyerophyllidae, Kepingophyllidae and Waagenophyllidae. This compositional change was associated with a global regressive event, recognized in South China by the absence of upper Serpukhovian strata in many places and by several erosional surfaces in carbonate sequences in the Lower Yangtze region. This regressive event was probably caused by an episode of glaciation in Gondwana. Subsequent transgression occurred in South China during the early Bashkirian, where a wide, uniform shallow‐water platform developed in South China, on which were deposited tidal‐flat dolostone and pure limestone containing compound rugose corals. Another change in the rugose coral assemblages, at the Sakmarian‐Artinskian boundary, resulted in the absence from the Artinskian of representatives of typical Pennsylvanian and Early Permian families such as the Bothrophyllidae, Lithostrotionidae, Cyathopsidae, and Petalaxidae. Families uniquely typical of the Permian, characterized by Waagenophyllidae and Kepingophyllidae, dominate post‐Sakmarian strata. This faunal change may be related to a major, worldwide regression, recognized at the end of the Sakmarian. Extinction of rugose corals at the end of the Permian occurred in two phases in South China. The first phase occurred at the end of the Capitanian and eliminated 47% of the families and 45% of the genera. Extrusion of the Omeishan Basalt, which is widely distributed in the western part of South China, and/or a global regression at the end of the Guadalupian could be the principal causes of this first phase of mass extinction. The second phase, which occurred at the end of the Changhsingian and is the largest extinction event in Earth's history, eliminated all remaining rugose corals. Copyright © 2006 John Wiley & Sons, Ltd.

Relationships between Trophic State, Paleosalinity and Climatic Changes during the First Holocene Marine Transgression in Rocha Lagoon, Southern Uruguay

Paleolimnological data are presented on trophic development, climatic change and sea level variations in Rocha Lagoon, a 72 km2 coastal lagoon in southern Uruguay. Using a sediment core that extended from 7000 to about 3700 yr BP, analyses of organic matter, carbonate, diatoms and chrysophyte cysts were used to track the early Holocene paleolimnological conditions of Rocha Lagoon. Opal phytoliths were also counted and identified, both temperature and humidity indices were calculated, and Opal Phytolith Association Zones (OPAZ) were identified by performing Principal Coordinates Analysis (PCO). Diatom Association Zones (DAZ) corresponding to marine/brackish and brackish/freshwater episodes were closely related to changes in trophic state. Those DAZ representing marine/brackish stages exhibited a lower trophic state than those DAZ dominated by brackish and freshwater diatoms. This highlights that during the first Holocene marine transgression, Rocha Lagoon did not continuously exhibit marine/brackish conditions as reported in previous papers. Instead, three brackish/freshwater episodes related to sea level variation and changes in humidity were identified. The first episode, by ~6000 yr BP, was related to sea level change as no significant changes in either temperature or humidity indices were observed. The second episode, between 5000 and 4400 yr BP, was related to both a sea level decrease and an increase in humidity, as a transition from humid to very humid climate was inferred. Concomitant decreases in salinity and increases in trophic state were also observed. The third episode, after ~4000 yr BP, was related to the end of the first Holocene regressive phase when sea level was slightly below present levels. Further decreases in salinity and increases in trophic state were detected. The paleoclimatic trends inferred in this study were in close agreement with other regional studies on climatic change, as cool temperatures were inferred. However, major changes in humidity were also detected. A humid to very humid climate was inferred for ~7000–4500 yr BP, but the occurrence of a semiarid/arid climate was inferred for ~4500–3700 yr BP. Our data suggest that during transgressive and regressive events there might be higher frequency and lower amplitude sea level oscillations that might lead to changes in salinity and trophic state of coastal aquatic systems. Such oscillations could only be tracked by high resolution analyses of sedimentary records and could be best interpreted with complementary data on paleoclimate. In addition, microfossils such as diatoms and opal phytoliths were shown to be very sensitive to such paleoenvironmental changes.

Retinoid-Related Orphan Receptor α Controls the Early Steps of Purkinje Cell Dendritic Differentiation

Dendritic differentiation involves both regressive and growth events. The mechanisms controlling the regressive events are poorly understood. This study is aimed at determining the role of the nuclear receptor retinoid-related orphan receptor alpha (RORalpha) in Purkinje cell (PC) dendritic differentiation in organotypic cultures. As observed in vivo, in these cultures, fusiform PCs with embryonic bipolar shape undergo regression before the outgrowth of the ultimate dendritic tree. We show that lentiviral-mediated hRORalpha1 overexpression in fusiform PCs leads to a cell-autonomous accelerated progression of dendritic differentiation. In addition, RORalpha is necessary for the PC regressive events: whereas staggerer RORalpha-deficient PCs remain in the embryonic fusiform stage, replacement of hRORalpha1 restores normal dendritogenesis. These results demonstrate that RORalpha expression in fusiform PCs is crucial for the dendritic regression and progression of the following step of extension of dendritic processes. However, it does not seem to participate to the last stage of dendritic growth. This study identifies RORalpha as a nuclear receptor crucial for the control of dendritic remodeling during development.

Reinitialization of evolutionary clocks during sublethal environmental stress in some invertebrates

This paper describes the influence of high environmental stress on evolutionary trends in some selected Mesozoic ammonite lineages and some protists. During extinction periods, many ammonoids are affected by drastic simplifications of their shell geometry, ornamentation and suture line. We observe that relatively tightly coiled ammonites can give rise to highly evolute forms or uncoiled heteromorphs with simple ornamentation and almost ceratitic suture line—a phenomenon called “proteromorphosis”. Such simplifications often correspond to a reappearance of ancestral geometries (primitive ornamentation, evolute coiling or uncoiling) which suggest that the evolutionary clock of these organisms can be reinitialized by extreme, sublethal, environmental stress such as giant volcanism (including its consequences on diverse pollutions and on climatic changes) and major regressive events.

The Santonian-Campanian phosphatic chalks of England and France

Phosphatic chalks were deposited during the mid-Santonian to early Campanian between 85 Ma and 83 Ma in NE France and southern England. The beds contain abundant brown granular phosphate, largely consisting of phosphate-filled and coated foraminiferal tests, phosphatized macrofossil fragments, faecal pellets, phosphatized intraclasts and vertebrate remains. Phosphate contents typically range from 5–20% P 2 O 5 . Beds 1–20 m thick occur within elongate 1 km long, 250 m wide and 30 m deep erosional basins (‘cuvettes’), cut into the underlying Coniacian-Santonian white chalks. Several superimposed cuvettes with consistent orientations may occur. Cuvettes are floored by phosphatized, bored and encrusted hardgrounds, and contain unique faunal assemblages that include ahermatypic colonial corals, and encrusting oyster and worm patches. Belemnites, fish and reptile remains are common. Extensive reworking by currents and biota occurred during the deposition of the phosphate. Gravity flow led to the dislocation and redeposition of basal hardground blocks and the formation of synsedimentary slump folds. Phosphatic chalks accumulated in water depths of between 70 m and a few hundred metres in oxic, current-swept areas of an open epicontinental sea of normal salinity. High surface productivity, moderate organic-carbon fluxes, reduced sedimentation rates and high rates of sediment mixing led to the precipitation of phosphate within hardground surfaces and carbonate grains. Bacterial decomposition of organic matter raised phosphate contents in pore waters and promoted the geochemical conditions necessary for phosphate precipitation. Phosphate precipitates, now transformed to carbonate fluorapatite, include um-sized ovoid bodies and massive coatings interpreted to be of microbial origin. Phosphatization was a rapid process occurring under mixed aerobic/anaerobic redox conditions in the upper decimetre of the sediment column, close to the sediment-water interface. Phosphatization took place predominantly within the confines of the cuvettes, where phosphate grains became concentrated by current winnowing and transport. Phosphatic chalk sedimentation occurred on the NE and northern margins of the Anglo-Paris Basin following regressive events that enabled bottom currents to erode the cuvettes and maintain productivity and the other sedimentary conditions necessary for phosphate accumulation.

MIDDLE ORDOVICIAN (CHAZYAN) SEA-LEVEL CHANGES AND THE EVOLUTION OF THE ORDOVICIAN CONODONT GENUS CAHABAGNATHUS BERGSTRÖM, 1983

Two lineages exist for Cahabagnathus. Lineage 1 is C. friendsvillensis–C. chazyensis–C. sweeti–C. carnesi. Three new species are proposed in lineage 2, which consists of C. baueri n. sp.–C. directus–C. cooperi n. sp. and C. craigi n. sp. The distribution pattern of Cahabagnathus was strongly influenced by Chazyan sea-level changes. The wide distributions of C. friendsvillensis and C. sweeti correspond to two large transgressions and the more narrow distribution of C. chazyensis and C. carnesi correspond to regression events. A similar relationship exists between sea-level change and the distribution of species in lineage 2. Evolution of the cahabagnathids was apparently influenced by the rise of sea level, which widely distributed taxa, and the fall of sea level, which isolated taxa. We propose that it was from peripheral isolates of widely distributed taxa that endemic Cahabagnathus taxa (C. baueri, C. cooperi, C. craigi, C. chazyensis, and C. carnesi) evolved.

Groundwater discharge to a Gobi desert lake during Mid and Late Holocene dry periods

High levels of Lake Eastern Juyanze and a wetter climate in the Gobi desert (NW China) were recorded between 5100 and 4100 cal. year BP from ostracod distribution, shell geochemistry, sedimentology and palynological data. After about 4100 cal. year BP lake levels decreased and groundwater discharge became dominant source of water during short-term regressive events at about 4000, 3800 and 3500 cal. year BP as suggested by a significant difference in modern river water and groundwater chemistry and the geochemical signal of fossil ostracod shells. The overall trend towards lower lake levels culminated in repeated episodes of desiccation of Lake Eastern Juyanze between 3200 and 2900 cal. year BP. Individual regressive events as well as the rapid environmental fluctuations of Lake Eastern Juyanze at about 3000 cal. year BP were likely caused by Mid to Late Holocene temperature fluctuations, recorded by the Dunde ice core [Yao, T., Thompson, L.G., 1992. Trends and features of climatic changes in the past 5000 years recorded by the Dunde ice core. Annals of Glaciology 16, 21–24] and shifts of the southeastern Asian monsoon.

Cellular mechanisms of dendrite pruning inDrosophila: insights from in vivo time-lapse of remodeling dendritic arborizing sensory neurons

Regressive events that refine exuberant or inaccurate connections are critical in neuronal development. We used multi-photon, time-lapse imaging to examine how dendrites of Drosophila dendritic arborizing (da) sensory neurons are eliminated during early metamorphosis, and how intrinsic and extrinsic cellular mechanisms control this deconstruction. Removal of the larval dendritic arbor involves two mechanisms: local degeneration and branch retraction. In local degeneration, major branch severing events entail focal disruption of the microtubule cytoskeleton, followed by thinning of the disrupted region, severing and fragmentation. Retraction was observed at distal tips of branches and in proximal stumps after severing events. The pruning program of da neuron dendrites is steroid induced; cell-autonomous dominant-negative inhibition of steroid action blocks local degeneration, although retraction events still occur. Our data suggest that steroid-induced changes in the epidermis may contribute to dendritic retraction. Finally, we find that phagocytic blood cells not only engulf neuronal debris but also attack and sever intact branches that show signs of destabilization.

Expression of complement protein C5a in a murine mammary cancer model: tumor regression by interference with the cell cycle

The C5a anaphylatoxin protein plays a central role in inflammation associated with complement activation. This protein is commonly regarded as one of the most potent inducers of the inflammatory response and a C5a peptide agonist was used as a molecular adjuvant. However, the full length C5a protein has not been tested as a potential tumor therapy. In this report, we describe the creation of a mini-gene construct that directs C5a expression to any cell of interest. Functional expression could be demonstrated in the murine mammary sarcoma, EMT6. When C5a expressing cells were injected into syngeneic mice, most C5a-expressing clones had significantly reduced tumor growth. Further characterization of a clone expressing low levels of C5a demonstrated that one-third of mice injected with this line had complete tumor regression. The mice whose tumors regressed were immune to subsequent challenge with unmodified EMT6 cells, suggesting that a component of the innate immune response can be used to augment adaptive immunity. Cellular analyses demonstrated that a significant difference in actual tumor cell number could be detected as early as day 10. A block in cell cycle progression was evident at all time points and high levels of apoptosis were observed early in the regression event. These data demonstrate that the complement protein C5a can play a significant protective role in tumor immunity.

Relationships between Holocene sea-level variations, trophic development, and climatic change in Negra Lagoon, Southern Uruguay

Paleolimnological data are presented on trophic development, climatic change and sea level variations in Negra Lagoon, a 142 km2 coastal lagoon in southern Uruguay. Using a sediment core that extended to the early Holocene, analyses of organic matter, carbonate, diatoms and opal phytoliths allowed us to track changes in trophic state and paleosalinity levels, which were closely related to Holocene sea level variation, temperature and humidity. Diatom Association Zones (DAZ) corresponding to transgressive events were dominated by marine/brackish taxa and relatively low organic matter values, while those DAZ corresponding to regressive events showed increases in brackish/freshwater diatoms and organic matter. Opal Phytoliths Association Zones (OPAZ) also were identified, temperature and humidity indices were calculated, and climatic trends were inferred. During the middle Holocene (i.e., ~5000–4000 yr BP), cool–dry climatic conditions were established. After ~4000 yr BP, a transition from cool to warm–humid conditions was observed, but fully warm humid conditions established only after ~1700 yr BP. Such climatic amelioration led to increases in trophic state.

The Devonian–Lower Carboniferous succession in Northwest Peninsular Malaysia

A new stratigraphic nomenclature is proposed for the approximately 600 m thick, mainly clastic transitional sequence between the underlying Mempelam Limestone and overlying Kubang Pasu/Singa Formation in northwest Peninsular Malaysia. This sequence represents shallow marine deposits of the continental margin of the Sibumasu Terrane during the Middle Palaeozoic (Devonian–Carboniferous). It is separated into several formations. The Timah Tasoh Formation is an approximately 76 m sequence consisting of 40 m of laminated tentaculitid shales at the base, containing Monograptus yukonensis Jackson and Lenz and Nowakia (Turkestanella) acuaria Alberti, giving an Early Devonian (Pragian–Emsian) age, and about 36 m of rhythmically interbedded, light coloured argillo-arenites. The Chepor Formation is about 90 m thick and consists mainly of thick red mudstone interbedded with sandstone beds, of Middle to Late Devonian age. A new limestone unit is recognized and named the Sanai Limestone, which contains conodonts of Famennian age. The Binjal Formation consists of red and white mudstone interbedded with sandstone beds showing Bouma sequences. The Telaga Jatoh Formation is 9 m thick and consists mainly of radiolarian chert. The Wang Kelian Formation is composed of thick red mudstone beds interbedded with silty sandstone, and contain fossils indicative of an Early Carboniferous (Visean) age. The succession was deposited on the outer shelf, with depositional environments vertically fluctuating from prodelta to basinal marine. The Devonian–Carboniferous boundary is exposed at Hutan Aji and Kampung Guar Jentik, and indicates a major regressive event during the latest Devonian.

Long-lived glaciation in the Late Ordovician? Isotopic and sequence-stratigraphic evidence from western Laurentia

The timing and causes of the transition to an icehouse climate in the Late Ordovician are controversial. Results of an integrated δ13C and sequence stratigraphic analysis in Nevada show that in the Late Ordovician Chatfieldian Stage (mid-Caradoc) a positive δ13C excursion in the upper part of the Copenhagen Formation was closely followed by a regressive event evidenced within the prominent Eureka Quartzite. The Chatfieldian δ13C excursion is known globally and interpreted to record enhanced organic carbon burial, which lowered atmospheric p CO2 to levels near the threshold for ice buildup in the Ordovician greenhouse climate. The subsequent regressive event in central Nevada, previously interpreted as part of a regional tectonic adjustment, is here attributed in part to sea-level drawdown from the initiation of continental glaciation on Gondwana. This drop in sea level—which may have contributed to further cooling through a reduction in poleward heat transport and a lowering of p CO2 by suppressing shelf-carbonate production—signals the transition to a Late Ordovician icehouse climate ∼10 m.y. before the widespread Hirnantian glacial maximum at the end of the Ordovician.

Activity Affects Dendritic Shape and Synapse Elimination during Steroid Controlled Dendritic Retraction inManduca sexta

Insect metamorphosis is a compelling example for dendritic and synaptic remodeling as larval and adult behaviors place distinct demands on the CNS. During the metamorphosis of the moth, Manduca sexta, many larval motoneurons are remodeled to serve a new function in the adult. During late larval life, steroid hormones trigger axonal and dendritic regression as well as larval synapse elimination. These regressive events are accompanied by stereotypical changes in motor behavior during the so-called wandering stages. Both normally occurring changes in dendritic shape and in motor output have previously been analyzed quantitatively for the individually identified motoneuron MN5. This study tested whether activity affected steroid-induced dendritic regression and synapse disassembly in MN5 by means of chronically implanted extracellular electrodes. Stimulating MN5 in vivo in intact, normally developing animals during a developmental period when it usually shows no activity significantly slowed the regression of high-order dendrites. Both physiological and anatomical analysis demonstrated that reduced dendritic regression was accompanied by a significant reduction in larval synapse disassembly. Therefore, steroid-induced alterations of dendritic shape and synaptic connectivity are modified by activity-dependent mechanisms. This interaction might be a common mechanism for rapid adjustments of rigid, inflexible, hormonal programs.

The Effects of Attributes on the Repeat Sales Pattern of Residential Property in Hong Kong

There has been copious research work on the development of house price models and the construction of house price indices. However, results in some studies revealed that the accuracy of such indices could be subject to selection bias when using only information from a sample of sold properties to estimate value movements for the entire housing stock. In particular, estimated house price appreciation is usually systematically higher among properties that change hands more frequently. It therefore suggests that the determination of important factors affecting the transaction frequency or intensity of a housing unit should be a more fundamental research question. This paper examines the possible factors that determine the popularity of residential unit by means of a repeated sales pattern. The Poisson regression model and event history analysis techniques are employed to assess the effect of attributes on transaction frequency and intensity. The event history analyses technique can take account of transaction-specific as well as time-dependent covariates, and therefore is recommended for analyzing repeated sales data in a real estate market. All transaction records during the period 1993–2000 from the Land Registry of one of the most popular residential estates in Hong Kong were used to illustrate the method. Unlike a response to favorable transaction price, good quality units do not necessarily inherently display a high transaction frequency. Rather, units of average quality are more likely to be transactionally active.

Upper Pleistocene and Holocene paleosalinity and trophic state changes in relation to sea level variation in Rocha Lagoon, southern Uruguay

Paleolimnological data are presented on trophic development in relation to sea level variation in Rocha Lagoon, a 72 km2 coastal lagoon in southern Uruguay. Using sediment cores that extended to ∼20,000 yr BP, analyses of grain size, organic matter, carbonate, total carbon, nutrients, and diatoms allowed us to infer changes in trophic state and paleosalinities, which were closely related to Holocene relative sea level variation. Higher trophic states were observed during regressive events, most probably due to increases in runoff and erosion as regressions progressed. Diatom Association Zones (DAZ) were identified in both cores. Those DAZ corresponding to transgressive events were dominated by marine/brackish taxa and relatively low organic matter and nutrient values, while those DAZ corresponding to regressive events showed increases in brackish/freshwater diatoms and both organic matter and nutrients. Although the lagoon formed after the first Holocene marine transgression, our data indicate the existence of a marine/brackish aquatic system during upper Pleistocene (i.e., before 15,000 yr BP), but by ∼20,000 yr BP, the system was still likely to be a semi-arid terrestrial system.

From Superior Adaptation and Function to Brain Dysfunction—The Neglect of Epigenetic factors

With optimal pregnancy conditions (natural, enriched diet which includes fish) African (Digo) infants are 3-4 weeks ahead of European/American infants in sensorimotor terms at birth, and during the first year. Infants of semi-aquatic sea-gypsies swim before they walk, and have superior visual acuity compared with us. With adverse pregnancy behaviour (fear of fat, a trend to dieting), neglecting the need for brain fat to secure normal brain development and function, we run a risk of dysfunction--death. Sudden Infant Death Syndrome victims have depressed birth weight, lower levels of marine fat in brainstem than controls, and >80 suffer multiple hypoxic episodes prior to death. Depressed birth weight (more than 10% below mean) is seen in learning and behaviour disorders, and a trend towards weights of less than 3kg is increasing, which supports a rise in antenatal sub optimality. Given marine fat deficiency in pregnancy and infancy, neurons starved for fuel could delay myelination and maturation in the latest developed Frontal Lobes. The phylogenetic oldest Lateral Frontal Lobe System (feed-back mechanism etc.) derived from olfactory bulb-amygdala, which crosses in Anterior Commisure is probably spared, while the Medial Frontal Lobe System derived from Hippocampus-Cingulum and crosses in Corpus Callosum (delayed response task) is most likely affected. The rise in infantile autism (intact vision and hearing) with deficit in delayed response task only, could suggest a deficit in the Medial Frontal Lobe System. The human species is unique; 70% of total energy to the foetus goes to development of the brain, which mainly consists of marine fat. It undergoes pervasive regressive events, before birth, in infancy and at puberty. Minimal retraction of neuronal arborisation is advantageous. Attributable to adverse pregnancy childrearing practice, excessive retraction is likely prenatally and in infancy. Pubertal age affects the fundamental property of nervous tissue, excitability: excessive excitatory drive is seen in early, and a deficiency in late puberty. It is postulated that with adequate marine fat, there is probably no risk of psychopathology at the extremes, whereas a deficiency could lead to paroxysmal (subcortical) dysfunction in early puberty, and breakdown of cortical circuitry and cognitive dysfunctions in late puberty. The post-pubertal psychoses, schizophrenia and manic-depressive psychosis at the extremes of the pubertal age continuum, with contrasting excitability and biological treatment, are probably the result of continuous dietary deficiency, which has inactivated the expression of genes for myelin development and oligodendrocyte-related genes in their production of myelin. The beneficial effect of marine fat in both disorders, in other CNS disorders as well as in developmental dyslexia (DD) and ADHD among others, supports our usual diet is persistently deficient. We have neglected the similarity of our great brain to other mammals, and our marine heritage. Given the amount of marine fat needed to secure normal brain development and function is not known, nor the present dietary level, it seems unduly conjectural to postulate that a dietary deficiency in marine fat is causing brain dysfunction and death. However, all observations point in the same direction: our diet focusing on protein mainly, is deficient, the deficiency is most pronounced in maternal nutrition and in infancy.

Regionally specific distribution of corticospinal synapses because of activity-dependent synapse elimination in vitro.

We have shown previously that the corticospinal tract (CST) with functional connections can be reconstructed in vitro in slice cocultures. Using that system, we stimulated the deep cortical layer and recorded field EPSPs (fEPSPs) along a 100 microm-interval lattice in the spinal gray matter. The specific, spatial synapse distribution on the dorsal side at 14 d in vitro (DIV) basically corresponded to the in vivo area in which CST axons terminate. Anterograde labeling of corticospinal axons with biocytin showed a similar terminal distribution on that side. In vitro development of synapse spatial distribution was investigated. fEPSPs were recorded all across the gray matter at 7 DIV, but amplitudes began to decrease on the ventral side at 9 DIV, dorsal-dominant distribution being nearly complete at 14 DIV. Anterograde labeling showed that the decrease in fEPSP amplitudes was associated with a decrease in the number of axon terminals on the ventral area. Decreases in the synaptic responses and terminals were blocked by applications of D-2-amino-5-phosphonovaleric acid and tetrodotoxin, whereas 6-cyano-7-nitroquinoxaline-2,3-dione had a partial effect. These findings suggest that this regressive event, which occurs during development, is activity and NMDA dependent. Retrograde labeling with two colors of beads and an electrophysiological study that investigated the axon reflex showed that at 7 DIV most corticospinal neurons project to both the ventral and dorsal spinal cord, indicating that synapse decrease on the ventral side is attributable primarily to axon branch elimination rather than to death of cortical cells that send axons solely to that side.