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M F Barbe

Publications and source records attributed to M F Barbe.

13 recordsLinked to original sources
PubMed1997

Patterning and specification of the cerebral cortex.

Regionalization of the cerebral cortex occurs during development by the formation of anatomically and functionally discrete areas of the brain. Descriptive evidence based on expression of molecules and structural features suggests that an early parcelation of the cerebral wall may occur during fetal development. Experimental strategies using tissue transplants and cell culture models have explored the nature of the timing of areal specification. New signaling systems displaying the sensitivity of precursor cells to environmental cues that define the fate of neurons destined for specific areas of the cortex have been discovered. Studies in the field now suggest mechanisms of regulating cell phenotype in the cortex that are common to all parts of the neuraxis.

Animals↗
PubMed1995

The limbic system-associated membrane protein is an Ig superfamily member that mediates selective neuronal growth and axon targeting.

The formation of brain circuits requires molecular recognition between functionally related neurons. We report the cloning of a molecule that participates in these interactions. The limbic system-associated membrane protein (LAMP) is an immunoglobulin (Ig) superfamily member with 3 Ig domains and a glycosyl-phosphatidylinositol anchor. In the developing forebrain, lamp is expressed mostly by neurons comprising limbic-associated cortical and subcortical regions that function in cognition, emotion, memory, and learning. The unique distribution of LAMP reflects its functional specificity. LAMP-transfected cells selectively facilitate neurite outgrowth of primary limbic neurons. Most striking, administration of anti-LAMP in vivo results in abnormal growth of the mossy fiber projection from developing granule neurons in the dentate gyrus of the hippocampal formation, suggesting that LAMP is essential for proper targeting of this pathway. Rather than being a general guidance cue, LAMP likely serves as a recognition molecule for the formation of limbic connections.

Amino Acid Sequence↗
PubMed1995

Age-dependent specification of the corticocortical connections of cerebral grafts.

To investigate further the factors involved in the development of cerebral cortical circuitry, we examined the organization of corticocortical connections of heterotopic grafts of fetal cortex placed into neonatal rat cortices. Presumptive perirhinal or sensorimotor areas of the cerebral wall were removed as slabs from embryonic day 12 (E12), E13, or E14 rats and transplanted heterotopically into either rostral perirhinal or sensorimotor cortical areas of neonatal rats. Two weeks later, the afferent cortical connections of the grafts were labeled by placing DilC18(-3) (Dil) into each transplant site. Both the E12 and E13 heterotopic transplants of presumptive perirhinal cortex contain mostly precursor cells. When these grafts are placed into sensorimotor cortex, callosal connections are formed primarily with the contralateral sensorimotor (Sml) area, the normal projection of Sml cortex. In contrast, the E14 heterotopic transplants of the perirhinal cortical wall, containing many more postmitotic neurons, developed contralateral connections with both sensorimotor and rostral perirhinal cortices. Thus, when precursor cells are transplanted heterotopically, by using E12/E13 donor tissue, the grafts receive projections that are similar to those of the host cortical area. When older cortical neurons, together with precursors, are transplanted into a heterotopic cortical area, by using E14 donor tissue, their cortical connections exhibit both host and original donor phenotypes. The data are consistent with our previous analysis of thalamocortical connections of grafts (Barbe and Levitt, 1992b) and suggest the existence of a cell-cell recognition system for thalamocortical and corticocortical circuit formation, whose mechanisms of action may be linked to the timing of neurogenesis.

Animals↗
PubMed1994

Induction of heat shock (stress) protein 70 and its mRNA in the normal and light-damaged rat retina after whole body hyperthermia.

In situ hybridization and immunocytochemistry were used to investigate the distribution of the 70 kDa heat shock or stress protein (hsp70) and its mRNA in specific layers of the retina of adult rats at 0, 4, 18, and 48 or 50 hr after a brief whole body hyperthermic treatment. Induction of hsp70 mRNA was noted in the photoreceptor layer of the retina within 4 hr after hyperthermia. Pronounced accumulation of inducible hsp70 immunoreactivity was observed in cytoplasmic extensions of the photoreceptor cells, especially the inner segment zone which attained peak levels at the 18 hr time point. Selective destruction of photoreceptors by light damage prior to hyperthermia inhibited the post-hyperthermic rise in newly synthesized retinal hsp70. Our results suggest that the photoreceptor cell layer is the primary site of synthesis of hsp70 in the rat retina and that the greatest increase in hsp70 immunoreactivity following such a hyperthermic stress occurs in that layer. This stress response of the photoreceptors is discussed in relation to their location and function in the retina.

Animals↗
PubMed1993

Progressive acquisition of cortical phenotypes as a mechanism for specifying the developing cerebral cortex.

The formation of the cerebral cortex requires the assembly of a complex array of neurons that exhibit specific patterns of laminar distribution, connectivity, and macromolecular expression. The problem of how various areas become specified relies to a large extent on the ability to assay certain characteristics of a particular cortical area during development. Certain phenotypic features appear to be acquired early in histogenesis, whereas others have a relatively late onset of expression. This pattern of progressive acquisition of traits suggests that each feature may be regulated by a different set of genomic-environmental interactions. This would lead to an early framing of cortical regions through the commitment of cells to area-specific phenotypes, but allow modifications of later developing traits through changes in certain environmental features.

Animals↗
PubMed1992

Attraction of specific thalamic input by cerebral grafts depends on the molecular identity of the implant.

The cerebral cortex of mammals differentiates into functionally distinct areas that exhibit unique cytoarchitecture, connectivity, and molecular characteristics. Molecular specification of cells fated for limbic cortical areas, based on the expression of the limbic system-associated membrane protein (LAMP), occurs during an early period of brain development. The correlation between this early molecular commitment and formation of specific thalamocortical connections was tested by using a transplantation paradigm. We manipulated the phenotype of donor limbic and sensorimotor neurons by placing them in different cortical areas of host animals. Labeling of transplanted tissue with the lipophilic dye 1,1'-dioctadecyl-3,3,3'3'-tetramethylindocarbocyanine was used to assay host thalamic neurons projecting to the donor tissue. We found that limbic thalamic axons successfully projected into cortical transplants (i) when LAMP was expressed by early committed limbic cortical neurons, irrespective of their host location, and (ii) when LAMP was expressed by uncommitted sensorimotor progenitor cells whose fate was altered by their new host locale. Thus, the response of cortical neurons to both intrinsic and environmental cues that influence their molecular phenotype has an important anatomical correlate, the development of specific patterns of thalamocortical connectivity.

Animals↗
PubMed1991

The early commitment of fetal neurons to the limbic cortex.

The limbic-system-associated membrane protein (LAMP) is expressed early in cerebral cortical development by migrating and postmigratory neurons in limbic regions such as the prefrontal and perirhinal cortices (Horton and Levitt, 1988), but not by nonlimbic neurons such as in the primary sensory and motor cortices. In the present study, we used LAMP expression to evaluate the timing and potential cell-lineage and environmental determinants of the commitment of cerebral cortical neurons to limbic and nonlimbic phenotypes. The cerebral wall, containing either presumptive perirhinal or sensorimotor cortex, was removed prior to [embryonic day (E) 12, 14] or just after (E17) the onset of LAMP expression, labeled with fast blue, and placed into cavities in either perirhinal or sensorimotor regions of postnatal day (P) 1 hosts. Host animals were allowed to survive until at least P10, and surviving transplanted cells were counted and evaluated for LAMP expression. Sensorimotor cortical neurons transplanted at E14 or E17, in either homotopic or heterotopic locations, did not express LAMP. In contrast, a high percentage of perirhinal cortical neurons transplanted at either E14 or E17, whether situated in sensorimotor or perirhinal regions of the host, expressed the limbic marker protein. Surprisingly, neurons from E12 donors exhibited patterns of LAMP expression that reflected their new location in the host rather than their embryonic origin. The data suggest that there is an early pliant period in which precursor and early differentiating cells remain uncommitted to a particular cortical regional phenotype. After this period, one aspect of the molecular phenotype (determined by LAMP expression) of neurons destined for sensorimotor and allo- and mesocortical regions has become immutable by environmental factors in the host.

Animals↗
PubMed1990

Induction of stress (heat shock) protein 70 and its mRNA in rat corneal epithelium by hyperthermia.

Because stress proteins are believed to play an important role in cellular repair and survival mechanisms, we investigated accumulation of the 70-kilodalton stress protein (SP70) and its mRNA in the rat corneal epithelium after hyperthermia. In the corneal epithelium of control rats, in situ hydridization with a radioactive probe for SP70 mRNA followed by autoradiography revealed very few silver grains. Eighteen hours after the rats were subjected to hyperthermia, the density of silver grains was greatly increased and this elevated level of corneal epithelium SP70 expression continued through 50 hours after heat treatment. Immunostaining for SP70 in the corneal epithelium was consistent with the in situ hybridization, being weak and mainly confined to the basal cells in control rats and increasing by 18 hours in the heat-treated rats. At 50 hours post-heat treatment, the immunostaining was denser than control in all corneal epithelial cells, especially in the apical portions of the basal and wing cells. These results suggest that SP70 may be an important factor in the response of the corneal epithelium to adverse environmental changes.

Animals↗
PubMed1989

A membrane glycoprotein associated with the limbic system mediates the formation of the septo-hippocampal pathway in vitro.

The ability of a neuronal surface glycoprotein to mediate the formation of neuronal connections was tested in an explant culture system. A monoclonal antibody against the limbic system-associated membrane protein (LAMP) was used in co-cultures containing cholinergic neurons of the septum and their hippocampal target neurons. Antibody treatment had no effect on general axon outgrowth, but significantly diminished the ability of septal cholinergic axons to invade and collateralize in the hippocampus. The results suggest that factors regulating general axon outgrowth may be distinct from those regulating the patterns of outgrowth that define the formation of neural circuits.

Animals↗
PubMed1988

Hyperthermia protects against light damage in the rat retina.

An increase in the synthesis of heat shock proteins that is induced in cells in vitro by hyperthermia or other types of metabolic stress correlates with enhanced cell survival upon further stress. To determine if a similar increase in stress tolerance could be elicited in vivo, rats were made hyperthermic, and then their retinas were tested for sensitivity to light damage. This treatment resulted in a marked decrease in photoreceptor degeneration after exposure to bright light as compared to normothermic animals. Concomitant with such protection was an increase in retinal synthesis of three heat shock proteins. Thus, a physiological rise in body temperature enhances the stress tolerance of nerve tissue, perhaps by increasing heat shock protein production.

Animals↗