The neurobiology of splitbrain crayfish

Background: They crayfish brain is segmented into two symmetrical hemiganglia. Normally both hemiganglia are in direct communication through a series of well-defined neural bridges that cross de midline to form reciprocal cross connections.Methods: An original study was carried out in the Department of Physiology of the Faculty of Medicine, UNAM during the period from August 2019 to August 2020. 13 Crayfish Procambarus clarkii weighing between 1g to 30g were used. Each eyestalk of the animals was tied to a displacement transducer coupled with a polygraph so that optomotor or electrical activity was bilaterally recorded. The separation of the right from the left hemiganglia from the cerebral or supraesophageal ganglion was performed with a sagittal section, splitbrain (SB).Results: The normal photo motor reflex in crayfish eye is measured as a gradual decrease in the ERG amplitude. During tactile stimulation, the visual activation of both eyestalks in normal crayfish leads to a highly regular bilateral activity. The regular activity can only be altered by disturbing the mechanoreceptors located in the shell surrounding the eyestalks.Conclusions: The procedure presented in this article provides unique characteristics for the study of the nervous system such as a detailed response of the bilateral optomotor reflex.

The Drosophila l(2)35Ba/nocA gene encodes a putative Zn finger protein involved in the development of the embryonic brain and the adult ocellar structures.

The Drosophila l(2)35Ba/nocA gene is involved in the development of the adult ocelli and the embryonic head. Mutations in this gene lead to at least two distinct phenotypes. Several larva lethal l(2)35Ba alleles cause both hypertrophy and mislocation of the embryonic supraesophageal ganglion (brain) to the dorsal surface of the embryo. A second class of mutant alleles (nocA) is homozygous viable, but the surviving adults either lack or have greatly reduced ocelli and associated bristles. The l(2)35Ba/nocA gene encodes an approximately 3.0-kb transcript doublet; all l(2)35Ba alleles which have been physically mapped delete or disrupt the transcribed region, whereas all of the viable nocA alleles are caused by gross chromosomal aberrations with breakpoints near the 3'-flanking region of the gene. Several nocA breakpoint alleles downregulate the level of l(2)35Ba/nocA transcripts in adults, and their defective ocellar phenotype also fails to be complemented by the lethal alleles, implying that l(2)35Ba and nocA are different phenotypic manifestations of mutations in the same gene. In the l(2)35Ba mutant embryos, cells from the procephalic lobe which normally migrate over and overlie the supraesophageal ganglion during head involution can become incorporated into the supraesophageal ganglion; many of these misplaced cells, which normally form the frontal sac, also adopt a neuronal fate. Sequence analysis of two full-length l(2)35Ba/nocA cDNAs with distinct polyadenylation sites shows that they encode the same deduced protein of 537 amino acids with a serine- and threonine-rich N-terminal region, two putative zinc finger motifs near the carboxyl terminus, and several alanine-rich domains. Consistent with the observed embryonic phenotype, l(2)35Ba/nocA shows a complex embryonic expression pattern which includes the procephalic lobe.

The Drosophila l(2)35Ba/nocA gene encodes a putative Zn finger protein involved in the development of the embryonic brain and the adult ocellar structures

The Drosophila l(2)35Ba/nocA gene is involved in the development of the adult ocelli and the embryonic head. Mutations in this gene lead to at least two distinct phenotypes. Several larva lethal l(2)35Ba alleles cause both hypertrophy and mislocation of the embryonic supraesophageal ganglion (brain) to the dorsal surface of the embryo. A second class of mutant alleles (nocA) is homozygous viable, but the surviving adults either lack or have greatly reduced ocelli and associated bristles. The l(2)35Ba/nocA gene encodes an approximately 3.0-kb transcript doublet; all l(2)35Ba alleles which have been physically mapped delete or disrupt the transcribed region, whereas all of the viable nocA alleles are caused by gross chromosomal aberrations with breakpoints near the 3'-flanking region of the gene. Several nocA breakpoint alleles downregulate the level of l(2)35Ba/nocA transcripts in adults, and their defective ocellar phenotype also fails to be complemented by the lethal alleles, implying that l(2)35Ba and nocA are different phenotypic manifestations of mutations in the same gene. In the l(2)35Ba mutant embryos, cells from the procephalic lobe which normally migrate over and overlie the supraesophageal ganglion during head involution can become incorporated into the supraesophageal ganglion; many of these misplaced cells, which normally form the frontal sac, also adopt a neuronal fate. Sequence analysis of two full-length l(2)35Ba/nocA cDNAs with distinct polyadenylation sites shows that they encode the same deduced protein of 537 amino acids with a serine- and threonine-rich N-terminal region, two putative zinc finger motifs near the carboxyl terminus, and several alanine-rich domains. Consistent with the observed embryonic phenotype, l(2)35Ba/nocA shows a complex embryonic expression pattern which includes the procephalic lobe.

Lox10, a member of the NK-2 homeobox gene class, is expressed in a segmental pattern in the endoderm and in the cephalic nervous system of the leech Helobdella

A novel leech homeobox gene, Lox10, is shown to encode a homeodomain sequence characteristic of a phyletically widespread NK-2 homeobox gene class. Lox10 expression was examined in leech embryos of various ages by in situ hybridization. In the unsegmented cephalic region, Lox10 RNA is expressed in a subset of the cells descended from the a' and b' micromeres, including a small cluster of cells, believed to be postmitotic neurons, within the supraesophageal ganglion of the central nervous system. Hybridization signal was not detected in either the mesoderm or ectoderm of the trunk segments, and the apparent restriction of Lox10 ectodermal expression to the nonsegmented cephalic domain resembles the restricted forebrain expression pattern of its mammalian homologues. Lox10 is also expressed within the endodermal tissues of the leech midgut, which arises by cellularization from a polynucleate syncytium. Endodermal expression is organized into a pattern of transverse stripes and spots which are aligned with the intersegmental septa, and which prefigure the pattern of gut wall constrictions observed at later stages of development. Lox10 is the first molecular marker of segmentally periodic endoderm differentiation reported for any animal species.

Immunocytochemical identification of peptidergic neurons in compartment 4 of the supraesophageal ganglion of the leech Theromyzon tessulatum (O.F.M.)

The use of polyclonal antibodies directed against mammalian peptide hormones and of monoclonal antibodies raised against molecules of supraesophageal ganglion neurons of the leech Theromyzon tessulatum has led to the identification of more than half of the 30 neurons present in compartment 4 of the supraesophageal ganglion. Six cellular types were characterized at stage 3B of the life cycle: (1) a group of four or five large angiotensin II and γ-melanocyte stimulating hormone (γ-MSH) immunopositive cells also immunoreactive with monoclonal antibodies Tt-7 and Tt-159 (cells of class I), (2) a group of five small growth hormone releasing factor (GRF) positive cells, (3) three motilin-positive cells, (4) one met-enkephalin-positive cell, (5) one oxytocin-positive cell that also immunoreacts with monoclonal antibody Tt-1, and (6) one vasopressin-positive cell immunoreactive with monoclonal antibody Tt-9. This study shows the heterogeneity of the neurons constituting compartment 4 and demonstrates that most of them have secretions of a peptidergic nature. The co-localization of epitopes recognized by anti-γ-MSH and anti-angiotensin II is demonstrated in cells of class I. The number of immunoreactive cells found in compartment 4 is not always constant and can vary for the following reasons: (i) changes in the physiological status of the leech, as is the case with anti-GRF and anti-motilin, (ii) individual variations for some cellular types (cells of class I), (iii) variability in the situation of the connective-tissue septum separating compartments 4 and 5.

Immunocytochemical evidence for the presence of histamine and GABA in photoreceptors of the barnacle (Balanus nubilus)

Biochemical evidence indicates that GABA and histamine may both be synthesized by barnacle photoreceptors (Koike & Tsuda, 1980; Timpe & Stuart, 1984; Callaway & Stuart, 1989b). We used antisera against GABA- and histamine-protein conjugates to determine whether the photoreceptors contain either or both of these antigens. Both antisera labeled all of the photoreceptors in each of the three ocelli. Histamine-like immunoreactivity was found throughout each photoreceptor cell but was most intense at their presynaptic terminals. Histamine-like immunoreactivity was blocked by preincubation of the antibody either with histamine or with a histamine-protein conjugate. GABA-like immunoreactivity was found in all parts of the photoreceptors including the cell body, axon, rhabdomeric dendrites, and presynaptic terminals. GABA-protein conjugates blocked the GABA-like labeling of the photoreceptors, while protein conjugates with histamine, L-glutamate, L-glutamine, β-alanine, and taurine did not. Histamine-like immunoreactivity in the supraesophageal ganglion was confined to the photoreceptor terminals and a second, loose plexus of endings in the main neuropil. GABA-like immunoreactivity, in contrast, was found in approximately twenty-five pairs of neurons of this ganglion. In the cirral nerves, which are expected to contain inhibitory motoneurons, unidentified axons also labeled with the GABA antiserum.

Mise en évidence et évolution, au cours du cycle biologique, de neurones producteurs d'une substance apparentée à la motiline porcine dans le ganglion supraoesophagien de la sangsue Theromyzon tessulatum

The life cycle of Theromyzon tessulatum has been divided into stages defined on the basis of feeding pattern and reproductive activity. The use of an antiserum raised against porcine motilin demonstrated the presence of immunoreactive cells and fibers in the supraesophageal ganglion throughout the life of the leech. Immunopositive fibers are present in the neurohemal area of the dorsal commissure. The highest number of immunopositive neurons is found during stages 3B, 3C, and 3D, which precede egg-laying. The control of oogenesis by a substance related to porcine motilin is postulated.