Circadian system controlling release of sperm in the insect testes.

Release of mature sperm from the testis into seminal ducts of the gypsy moth exhibits a circadian rhythm. The rhythm of sperm release was shown to persist in vitro, in isolated complexes of testis and seminal ducts cultured in light-dark cycles or in constant darkness. The phase of the rhythm was also reset in vitro by exposure to shifted light-dark cycles. Therefore, the testis-seminal ducts complex from the gypsy moth is photosensitive and contains a circadian pacemaker, which controls the rhythm of sperm movement. This finding extends the range of structures in multicellular organisms that are known to contain circadian oscillators and provides a new model system in which circadian mechanisms may be studied.

Identification of a neuropeptide hormone that regulates sex pheromone production in female moths.

A pheromone biosynthesis activating neuropeptide (PBAN) hormone that controls sex pheromone production in female moths was identified from the brain-subesophageal ganglion complexes of the adult corn earworm, Heliothis zea. PBAN has 33 amino acid residues and a molecular weight of 3900. Its amino acid sequence has no significant homology with any of the fully characterized peptide hormones. The synthetic peptide, at a dose of between 2 and 4 picomoles, induced production of a normal quantity of sex pheromone in ligated H. zea females. The peptide also induced pheromone production in six other species of moths, thus indicating that this or similar peptides may be responsible for the regulation of pheromone production in moths.

Transplantation and functional integration of an identified respiratory interneuron in Lymnaea stagnalis.

The possibility that damaged neural circuitries can be repaired through grafting has raised questions regarding the cellular mechanisms required for functional integration of transplanted neurons. Invertebrate models offer the potential to examine such mechanisms at the resolution of single identified neurons within well-characterized neural networks. Here it is reported that a specific deficit in the respiratory behavior of a pulmonate mollusc, caused by the ablation of a solitary interneuron, can be restored by grafting an identical donor interneuron. The transplanted interneuron not only survives and extends neurites within the host nervous system, but under specific conditions forms synapses with appropriate target neurons and is physiologically integrated into the host's circuitry, thereby restoring normal behavior.

Pesticide use in agriculture.

During the last three decades, the use of modern organic synthetic pesticides has increased about 40-fold. Total U.S. production, for domestic and expert use, in 1976 was about 1.4 million pounds. Crops receiving the most intensive application of various pesticides were cotton for insecticides, corn for herbicides, and fruits and vegetables for fungicides. Examination of use trends of pesticides indicates that the volume in pounds of herbicides used on crops is increasing, whereas the quantities of insecticides and fungicides remain stable. New chemical classes of compounds such as the synthetic pyrethroid insecticides are being introduced, but are not yet significant in terms of their share of the market. The increased usage of pesticides, together with knowledge of some of their adverse effects, has alerted the public to the need for regulation. To assist in the regulatory decision-making process, emphasis is being placed on benefit-cost analyses. Additional and improved biological inputs and methodologies are needed to provide accurate analyses.

Release of neurite outgrowth promoting factors by Helisoma central ganglia depends on neural activity.

Identified buccal neurons B5 and B19 from the mollusc, Helisoma trivolvis, were plated into cell culture in order to assay for neurite outgrowth promoting factors released from central ring ganglia. The release and attachment of neurite promoting factors to the substratum of poly-lysine coated dishes could be inhibited by blocking spontaneous bioelectric activity in central ring ganglia used to condition the medium and dishes. Bioelectric activity within neurons in central ring ganglia was assayed by intracellular recording and found to be inhibited by exposure to the sodium channel blocker, tetrodotoxin (TTX; 2 x 10(-5) M), or CoCl2 (10 mM). Neither of these agents appeared to be toxic over a three day period since activity within neurons in central ring ganglia was restored following superfusion with saline. To examine the effect of blocking neural activity on the ability of central ring ganglia to release neurite outgrowth promoting factors, we compared the percentage of neurons that extended processes under 5 different conditions: (1) dishes containing conditioned medium and substrate attached growth factors (Super SAM); (2) dishes with substrate attached growth factors only and defined medium (SAM); (3) dishes containing substrate attached growth factors prepared in the presence of TTX; or (4) CoCl2; and (5) dishes containing unconditioned defined medium. The percentage of neurons extending processes under the 5 conditions were: (1) 71% (n = 32); (2) 51% (n = 33); (3) 14% (n = 37); (4) 15% (n = 47); (5) 0% (n = 40), respectively.(ABSTRACT TRUNCATED AT 250 WORDS)

Identification and localization of a [Met5]-enkephalin-like peptide in the mollusc, Lymnaea stagnalis.

The goal of this study was to determine whether [Met5]-enkephalin, or an analog, is present in identified neurons in the central nervous system (CNS) of the freshwater snail, Lymnaea stagnalis. High performance liquid chromatography and radioimmunoassay of CNS tissue homogenates revealed both [Met5]-enkephalin and oxidized [Met5]-enkephalin. NO [Leu5]-enkephalin, [Met5]-enkephalin-Arg6-Phe7 or [Met5]-enkephalin-Arg6-Gly7-Leu8 were detected. Quantification of [Met5]-enkephalin, by radioimmunoassay, revealed that the Lymnaea CNS contains approximately 2.2 fmol/CNS (undigested tissue) and 4.5 fmol/CNS (tissue enzymatically digested with trypsin and carboxypeptidase B). The increased amount of [Met5]-enkephalin following tissue digestion indicates the presence of as yet unidentified extended forms of [Met5]-enkephalin in Lymnaea. Using indirect immunocytochemistry, a [Met5]-enkephalin-like peptide was localized to individual cells and cell clusters within the CNS, as well as to fibers in the atrium of the heart. A neuronal map depicting [Met5]-enkephalin-like immunoreactive cells was produced. Among the immunoreactive neurons were four identified, well-characterized, giant cells: VD1, RPD2, LB1 and RB1. Identifiable [Met5]-enkephalin-like immunoreactive neurons were characterized electrophysiologically and morphologically. Additionally, neurons VD1 and RPD2 were confirmed to be immunoreactive to Lymnaea alpha-peptide. The lack of both cross reactivity and sequence homology between alpha-peptide and [Met5]-enkephalin suggests that a [Met5]-enkephalin-like peptide and alpha-peptide are co-localized within these neurons.

Ultrastructure of a complex epithelial system: the pharyngeal lining of the larval lamprey Petromyzon marinus.

Electron microscopy shows that the pharyngeal lining of the larval lamprey Petromyzon marinus is a structurally complex epithelial system that can be separated into eight epithelial types: gill lamellar, gill interlamellar, goblet cell, protective, terminal (taste) bud, preciliated, ciliated in tracts, and ciliated in grooves. Furthermore, these epithelial types encompass at least sixteen different cell types based on ultrastructure and, in some cases, correlative histochemistry (PAS, Alcian blue). Common to nearly all the epithelial types are basal cells and intermediate cells. These two cell types are seen as undifferentiated. Among mature cells, structural specialization as proceeded in three directions: 1) elaboration of mitochondria, probably related to molecular transport (ion-uptake cells, chloride cells); 2) ciliogenesis (preciliated and ciliated cell types); and 3) production of mucous secretory granules (mucous-platelet cells, goblet cells, superficial protective cells, columnar mucous cells, "cobblestone" cells, and marginal and dark cells in the terminal buds). Many of the functions of the cell types relate to the process of suspension feeding in this animal.

Clinical and radiographic signs in primary and metastatic esophageal neoplasms of the dog.

Esophageal neoplasms were diagnosed in 8 of 49,229 dogs seen over the last 11 years at the Veterinary Medical Teaching Hospital of the University of California at Davis. The neoplasms were primary in 2 dogs and metastatic to the esophagus in 6 dogs, with thyroid carcinoma being the most common site of the primary tumor. The most common clinical signs were regurgitation, dysphagia, weight loss, development of neck masses, and respiratory difficulties. It was concluded that the clinical signs often can be misleading. The interpretation of survey radiographs, barium contrast studies, or fluoroscopic studies often provide the initial data base. The final diagnosis requires histologic examination. Retention of air in the esophagus (with or without esophageal displacement) and motor dysfunction (with or without gross morphologic changes) are the most important criteria for radiographic diagnosis.

In vitro evidence for multiple neuritogenic factors in the central nervous system of pulmonate molluscs.

Previous work has shown that neurons of the fresh water pond snails, Lymnaea and Helisoma, require soluble factors produced by neural tissues for neurite outgrowth to occur in vitro. In the present study, we show that mammalian nerve growth factor (NGF) stimulates neurite outgrowth of specific Lymnaea neurons. In contrast to motoneurons and interneurons, which show a robust dose response to NGF, no response was observed in neurosecretory cells. In an attempt to localize neuritogenic activity to specific ganglia or organs, we show that the dorsal bodies, endocrine structures of the cerebral ganglia, promote neurite outgrowth of specific neurons. In general, however, the spectrum of neurons that respond to dorsal body cell conditioned medium differs from that which respond to NGF. We conclude that Lymnaea neurons respond both to NGF and also to a separate factor derived from the dorsal body cells.

In vitro connections between Lymnaea and Helisoma identified interneurons and their follower cells.

The mechanisms that underly the specificity of synaptic connections are poorly understood. In this study we used two homologous interneurons, the giant dopamine cell (GDC), in two species of pond snails, Lymnaea and Helisoma. We examined the ability of the Lymnaea GDC to form specific synapses with known follower or non-follower cells in vitro. Similar tests were performed for the Helisoma GDC. Both of these interneurons form appropriate connections not only with homologous follower neurons, but also with follower neurons from the alternative species. These results suggest that common mechanisms of cell recognition and synapse formation exist in the nervous systems of these two different families of molluscs.

Regeneration of an interneuronal network in Helisoma: re-establishment of synaptic contacts.

We have identified a network of three interneurons located in the central ring ganglia of Helisoma. Two of these interneurons, designated Left Pedal Dorsal 1 (LPeD1) and Right Pedal Dorsal 1 (RPeD1), are the largest neurons of the pedal ganglia and appear to contain dopamine and serotonin, respectively. A third interneuron, identified as Visceral Dorsal 4 (VD4), is a small FMRFamide immunoreactive cell located on the dorsal surface of the visceral ganglion. Monosynaptic chemical connections exist between all these interneurons. For instance, a reciprocal inhibitory connection exists between LPeD1 and RPeD1, whereas VD4 has inhibitory effects on both LPeD1 and RPeD1. Furthermore, LPeD1, but not RPeD1, has an excitatory connection with VD4. We demonstrate that following axotomy these interneurons not only regenerate their axons but re-establish their appropriate synaptic connections.

Neuronal mapping studies on the central nervous system of the pulmonate snail Helisoma trivolvis.

The need for a generalized system for mapping neurons in the central ring ganglia of the freshwater pulmonate snail, Helisoma trivolvis, has recently become apparent. In the present study we have used retrograde staining of nerves to identify neurons projecting to the periphery. This map was combined with histochemical information to produce a map of neuronal clusters and landmark cells. Our mapping strategy was formulated to make direct comparison with maps already established for closely related species, i.e., Lymnaea stagnalis.