Two forms of long-term depression in a polysynaptic pathway in the leech CNS: one NMDA receptor-dependent and the other cannabinoid-dependent

Although long-term depression (LTD) is a well-studied form of synaptic plasticity, it is clear that multiple cellular mechanisms are involved in its induction. In the leech, LTD is observed in a polysynaptic connection between touch mechanosensory neurons (T cells) and the S interneuron following low frequency stimulation. LTD elicited by 450 s low frequency stimulation was blocked by N-methyl-d-aspartic acid (NMDA) receptor antagonists. However, LTD elicited by 900 s low frequency stimulation was insensitive to NMDA receptor antagonists and was instead dependent on cannabinoid signaling. This LTD was blocked by both a cannabinoid receptor antagonist and by inhibition of diacylglycerol lipase, which is necessary for the synthesis of the cannabinoid transmitter 2-arachidonyl glycerol (2-AG). Bath application of 2-AG or the cannabinoid receptor agonist CP55 940 also induced LTD at this synapse. These results indicate that two forms of LTD coexist at the leech T-to-S polysynaptic pathway: one that is NMDA receptor-dependent and another that is cannabinoid-dependent and that activation of either form of LTD is dependent on the level of activity in this circuit. Electronic supplementary material  The online version of this article (doi:) contains supplementary material, which is available to authorized users.     

A New Method for Genome-wide Marker Development and Genotyping Holds Great Promise for Molecular Primatology

Over the last two decades primatologists have benefited from the use of numerous molecular markers to study various aspects of primate behavior and evolutionary history. However, most of the studies to date have been based on a single locus, usually mitochondrial DNA, or a few nuclear markers, e.g., microsatellites. Unfortunately, the use of such markers not only is unable to address successfully important questions in primate population genetics and phylogenetics (mainly because of the discordance between gene tree and species tree), but also their development is often a time-consuming and expensive task. The advent of next-generation sequencing allows researchers to generate large amounts of genomic data for nonmodel organisms. However, whole genome sequencing is still cost prohibitive for most primate species. We here introduce a second-generation sequencing technique for genotyping thousands of genome-wide markers for nonmodel organisms. Restriction site–associated DNA sequencing (RAD-seq) reduces the complexity of the genome and allows inexpensive and fast discovery of thousands of markers in many individuals. Here, we describe the principles of this technique and we demonstrate its application in five primates, Microcebus sp., Cebus sp., Theropithecus gelada, Pan troglodytes, and Homo sapiens, representing some of the major lineages within the order. Despite technical and bioinformatic challenges, RAD-seq is a promising method for multilocus phylogenetic and population genetic studies in primates, particularly in young clades in which a high number of orthologous regions are likely to be found across populations or species.     

Clinical Comparison of Two Contrast Agents for Oral Cholecystography: Radiologic Efficacy and Drug Safety of Iopanoic Acid and Iopronic Acid

Oral doses of either iopronic acid (4.5 g Oravue, Squibb) or iopanoic acid (3 g Telepaque, Winthrop) were given to 98 patients requiring cholecystography. Radiographs were taken 13 to 16 hours after treatment showed good to excellent gallbladder opacification in 44 percent of patients after the first dose of iopronic acid and in an additional 29 percent after a second dose. Similar opacification occurred in 42 percent of patients after the first dose of iopanoic acid and in 34 percent after a second dose. Drug-related abnormalities in blood and urine tests occurred about equally in both groups and one patient in each group exhibited a clinically adverse reaction (diarrhea). Thus, the performance (radiographic efficacy and drug safety) of the new contrast agent, iopronic acid, was similar to a widely used drug, iopanoic acid.     

Histological aspects of in situ hybridization

Summary This study examined the detection of cellular poly(A) sequences in mouse liver sections by in situ hybridization using a ³H-labelled poly(dT) probe. Parameters examined included possible losses of target poly(A) sequences from sectioned cells, access of probe to target sequences, section thickness, hybridization conditions, autoradioigraphic efficiency, specific activity of probes and specificity of reaction. An improved protocol was devised that resulted in good preservation of histological detail in sectioned tissue blocks, and a calculated hybridization efficiency of 50%–100%. With the use of probes of defined sequence, the protocol should allow detection of unique mRNA sequences within single cells with an estimated sensitivity of 6–12 unique mRNA molecules per sectioned cell.     

Presence of Locusta diuretic hormone in endocrine cells of the ampullae of locust Malpighian tubules

This is an investigation of an endocrine cell type in the midgut of the migratory locust Locusta migratoria. This cell type is found in the posterior region of the midgut and is especially common in the ampullae through which Malpighian tubules drain into the gut at the midgut-hindgut junction. Strong Locusta diuretic hormone-like immunoreactivity in these cells was colocalized with FMRFamide- and substance P-like immunoreactivities. At the ultrastructural level, immunoreactivity for Locusta diuretic hormone was found in spherical granules (mean diameter of 450 nm), the contents of which showed variable electron density. Fractionation of a methanolic extract of the ampullae by reversed-phase high performance liquid chromatography revealed the presence of two peaks of Locusta diuretic hormone-like immunoreactive material, both of which stimulate cyclic AMP production by isolated Malpighian tubules. The more hydrophobic material is most likely Locusta diuretic hormone, which has the same retention time when chromatographed under identical conditions. Received: 15 September 1995 / Accepted: 16 February 1996