John P. Riehm

Bio: John P. Riehm is an academic researcher from University of West Florida. The author has contributed to research in topics: Uca pugilator & FMRFamide. The author has an hindex of 14, co-authored 22 publications receiving 1039 citations.

The ultrastructure of nerve endings containing pigment-dispersing hormone (PDH) in crustacean sinus glands: Identification by an antiserum against a synthetic PDH

Abstract: A high-liter antiserum has been obtained from two rabbits immunized with a glutaraldehyde conjugate of synthetic pigment-dispersing hormone (PDH) from Uca pugilator and bovine thyroglobulin. The antiserum blocked melanophore-dispersing activity of the peptide in vivo. In sinus glands (SG) of Carcinus maenas, Cancer pagurus, Uca pugilator and Orconectes limosus, electron-microscopic immunocytochemistry revealed sparsely distributed axon endings containing a distinct PDH-immunoreactive type of neurosecretory granules (diameter 90–130 nm). Exocytotic figures indicating release of the content of these granules into hemolymph lacunae were occasionally observed. Preservation of fine structure and antigenicity of the PDH granules were markedly dependent on the fixation procedure used. A preliminary experiment with C. maenas showed that preterminal axon dilatations near the basal lamina seemed to accumulate PDH-granules when animals were kept in complete darkness for three days. Immunodot blotting of fractions after high pressure liquid chromatography (HPLC) of extracts from SGs of C. maenas and O. limosus revealed a strongly immunoreactive substance at a retention time very similar to those of synthetic PDHs of Uca pugilator and Pandalus borealis. It is also coincident with a zone of biological activity. Thus, the antigen demonstrated by immunocytochemistry is identical or very similar to one of the known PDHs.

Pigment-dispersing hormones.

Abstract: Crustaceans display rapidly reversible integumental color changes and eye pigment movements. The color changes result from intracellular pigment movements within epithelial chromatophores. Eye pigment movements involve the translocation of screening pigments within cells located in the ommatidia of the compound eyes. These screening pigment movements may occur exclusively in the retinular cells (photoreceptor cells) or may also be evident in certain extraretinular pigment cells in the eye.‘ Whereas pigment movements within retinular cells are elicited mainly by a direct action of light, pigment translocations within extraretinular eye pigment cells and epithelial chromatophores are under hormonal In decapod crustaceans, the pigmentary-effector hormones are present in the eyestalks (which contain an elaborate neurosecretory system, including the neurohemal organs known as sinus glands) and in extraeyestalk nervous tissues. Extracts of any of these tissues may trigger a multitude of responses, light or dark adaptation of the eye as well as dispersion or concentration (aggregation) of chromatophoral pigments, depending on the initial states of the effectors in the test system. These complex responses are attributable to the widespread distribution of mutually antagonistic neurosecretory hormones in various parts of the nervous system.'^^ Although the total number of p~gmentary-effector hormones present in any given species remains unknown, they can be clearly separated into two sets. The hormones triggering chromatophoral pigment concentration and dark-adaptational eye pigment migration belong to one set, and they are distinct from the hormones eliciting chrornatophoral pigment dispersion and light-adaptational eye pigment movements. Among hormones in the first set, the primary structure of only one hormone (red pigment concentrating hormone, RPCH) is known. This hormone, an octapeptide (

A NOVEL FMRFamide-RELATED PEPTIDE IN HELIX: pQDPFLRFamide

Abstract: A novel FMRFamide-like peptide, purified from the ganglia of Helix aspersa, has the amino acid sequence: pyroglutamyl-aspartyl-prolyl-phenylalanyl-leucyl-arginyl-phenylalanine amide (pQDPFLRFamide). Synthetic pQDPFLRFamide was prepared; it is chromatographically and biologically indistinguishable from the natural peptide, confirming the sequence. pQDPFLRFamide is about a hundred times more potent than FMRFamide on the isolated Helix heart, but slightly less potent than FMRFamide on the Busycon radula protractor muscle. Since pQDPFLRFamide occurs in Helix blood at levels sufficient to excite the isolated Helix heart, it may act as a cardioregulatory hormone.

Characterization of a pigment-dispersing hormone in eyestalks of the fiddler crab Uca pugilator.

Abstract: A pigment-dispersing hormone (PDH) from eyestalks of the fiddler crab Uca pugilator has been purified by gel filtration, ion-exchange chromatography, partition chromatography, and reversed-phase liquid chromatography. Based on automated gas-phase sequencing and subsequent identification of carboxyl-terminal amide, we have assigned the primary structure of this peptide as Asn-Ser-Glu-Leu-Ile-Asn-Ser-Ile-Leu-Gly-Leu-Pro-Lys-Val-Met-Asn-Asp-Ala-NH 2. We have confirmed the sequence by synthesizing this peptide and demonstrating that the synthetic PDH and the native PDH display identical chromatographic behavior and biological activity. This hormone is a member of a family of invertebrate neuropeptides that includes a light-adapting/pigment-dispersing octadecapeptide hormone from the prawn Pandalus borealis. In assays for melanophore pigment dispersion in destalked fiddler crabs, Uca PDH was 21-fold more potent than Pandalus PDH. These two hormones share a hexapeptide core sequence (residues 5-10: -Ile-Asn-Ser-Ile-Leu-Gly-) as well as the amino- and carboxyl-terminal residues but differ at positions 3, 4, 11, 13, 16, and 17. These results point to speciesrelated or group-specific structural differences among crustacean PDHs.

Crustacean neuropeptides: structures, functions and comparative aspects.

Abstract: In this article, an attempt is made to review the presently known, completely identified crustacean neuropeptides with regard to structure, function and distribution. Probably the most important progress has been made in the elucidation of a novel family of large peptides from the X-organ-sinus gland system which includes crustacean hyperglycemic hormone (CHH), putative molt-inhibiting hormone (MIH) and vitellogenesis (=gonad)-inhibiting hormone (VIH). These peptides have so far only been found in crustaceans. Renewed interest in the neurohemal pericardial organs has led to the identification of a number of cardioactive/myotropic neuropeptides, some of them. unique to crustaceans. Important contributions have been made by immunocytochemical mapping of peptidergic neurons in the nervous system, which has provided evidence for a multiple role of several neuropeptides as neurohormones on the one hand and as local transmitters or modulators on the other. This has been corroborated by physiological studies. The long-known chromatophore-regulating hormones, red pigment concentrating hormone (RPCH) and pigment-dispending hormone (PDH), have been placed in a broader perspective by the demonstration of an additional role as local neuromodulators. The scope of crustacean neuropeptide research has thus been broadened considerably during the last years.

Facets of Vision

Abstract: 1 Compound Eyes and the World of Vision Research.- 2 Autrum's Impact on Compound Eye Research in Insects.- 3 Optics and Evolution of the Compound Eye.- 4 Photoreceptor Optics, Theory and Practice.- 5 Variations in the Structure and Design of Compound Eyes.- 6 Visual Pigments of Compound Eyes - Structure, Photochemistry, and Regeneration.- 7 Distribution of Insect Visual Chromophores: Functional and Phylogenetic Aspects.- 8 Pigments in Compound Eyes.- 9 Phototransduction in Limulus Ventral Photoreceptors: Roles of Calcium and Inositol Trisphosphate.- 10 The Retina-Lamina Pathway in Insects, Particularly Diptera, Viewed from an Evolutionary Perspective.- 11 Coding Efficiency and Design in Visual Processing.- 12 Neurotransmitters in Compound Eyes.- 13 Circadian Rhythms in the Invertebrate Retina.- 14 Color Vision in Honey Bees: Phenomena and Physiological Mechanisms.- 15 Polarization Sensitivity in Compound Eyes.- 16 Beneath the Compound Eye: Neuroanatomical Analysis and Physiological Correlates in the Study of Insect Vision.- 17 Directionally Selective Motion Detection by Insect Neurons.- 18 Neural Mechanisms of Visual Course Control in Insects.- 19 Size and Distance Perception in Compound Eyes.