The ultrastructure of campaniform sensilla on the eye of the cricket,Gryllus campestris

Summary The structure of the campaniform sensilla of the cricket eye was investigated by light and electron microscopy. Each sensillum is innervated by a single bipolar neuron. Its axon extends through the retina into a side-branch of the nervus tegumentarius. The dendrite extends through a cuticular channel to the surface of the cornea. The distal part of the dendrite, the sensory process, contains a tubular body and is attached to a cuticular cap which is obliquely inserted into the exocuticle between the corneal lenslets. Some particular structural features as well as the function of the campaniform sensillum of the cricket eye are discussed.Supported by the Deutsche Forschungsgemeinschaft, grant Ho 463/10The authors are indebted to Prof. H. Altner, University of Regensburg, and Mrs. Evelyn Thury, Contron GmbH, München for use of the scanning electron microscope facilities     

Role of unstirred layer in intestinal absorption of phenylalanine in vivo

The appearance rate of l- and d-phenylalanine in the venous blood of rat jejunal loops in vivo is increased up to 60% if the intraluminal solution is mixed more efficiently by the simultaneous perfusion of air. The effect decreases as the luminal concentration is increased to 100 mmol/1. Thus, the apparent Michaelis constants are by 50% lower in the case of the reduced unstirred layer (26 to 17 for l- and 9 to 6 mmol/1 for d-phenylalanine).The enhancement of the absorption and the reduction of the Michaelis constants can be attributed to the reduction of the effective unstirred layer thickness by about 400–500 μm.     

Induction of avian serum apolipoprotein II and vitellogenin by tamoxifen

Apo II and vitellogenin were detected in sera of nonestrogenized roosters by radioimmunoassay. Tamoxifen (30mg/kg) raised basal serum apo II more than 50 fold and vitellogenin more than 15 fold. Serum accumulation of apo II was biphasic in response to increasing doses of tamoxifen. This biphasic response was reflected in the relative rates of hepatic apo II synthesis. The tamoxifen metabolites, hydroxytamoxifen and desmethyltamoxifen, and the triphenylethylene antiestrogen, CI 628, also increased serum apo II. These studies show that the expression of vitellogenin and apo II genes occurs at a basal rate prior to exogenous estrogen treatment. These experiments also demonstrate that the triphenylethylene antiestrogens have agonist activity in the chicken when very sensitive techniques are used to measure estrogen-regulated proteins.     

A tale of two controversies: defining both the role of peroxidases in nitrotyrosine formation in vivo using eosinophil peroxidase and myeloperoxidase-deficient mice, and the nature of peroxidase-generated reactive nitrogen species

Nitrotyrosine is widely used as a marker of post-translational modification by the nitric oxide ((.)NO, nitrogen monoxide)-derived oxidant peroxynitrite (ONOO(-)). However, since the discovery that myeloperoxidase (MPO) and eosinophil peroxidase (EPO) can generate nitrotyrosine via oxidation of nitrite (NO(2)(-)), several questions have arisen. First, the relative contribution of peroxidases to nitrotyrosine formation in vivo is unknown. Further, although evidence suggests that the one-electron oxidation product, nitrogen dioxide ((*)NO(2)), is the primary species formed, neither a direct demonstration that peroxidases form this gas nor studies designed to test for the possible concomitant formation of the two-electron oxidation product, ONOO(-), have been reported. Using multiple distinct models of acute inflammation with EPO- and MPO-knockout mice, we now demonstrate that leukocyte peroxidases participate in nitrotyrosine formation in vivo. In some models, MPO and EPO played a dominant role, accounting for the majority of nitrotyrosine formed. However, in other leukocyte-rich acute inflammatory models, no contribution for either MPO or EPO to nitrotyrosine formation could be demonstrated. Head-space gas analysis of helium-swept reaction mixtures provides direct evidence that leukocyte peroxidases catalytically generate (*)NO(2) formation using H(2)O(2) and NO(2)(-) as substrates. However, formation of an additional oxidant was suggested since both enzymes promote NO(2)(-)-dependent hydroxylation of targets under acidic conditions, a chemical reactivity shared with ONOO(-) but not (*)NO(2). Collectively, our results demonstrate that: 1) MPO and EPO contribute to tyrosine nitration in vivo; 2) the major reactive nitrogen species formed by leukocyte peroxidase-catalyzed oxidation of NO(2)(-) is the one-electron oxidation product, (*)NO(2); 3) as a minor reaction, peroxidases may also catalyze the two-electron oxidation of NO(2)(-), producing a ONOO(-)-like product. We speculate that the latter reaction generates a labile Fe-ONOO complex, which may be released following protonation under acidic conditions such as might exist at sites of inflammation.     

NMDA-induced acetylcholine release in mouse striatum: role of NO synthase isoforms

Striatal cholinergic interneurons are stimulated by glutamatergic inputs from thalamus and cortex via NMDA receptors. The present microdialysis study was designed to characterize the role of nitric oxide (NO) in this process and to identify the NO synthase (NOS) isoform responsible for this effect. For this purpose, we studied the effects of NMDA and 3-morpholino sydnonimine (SIN-1) perfusions on the release of acetylcholine (ACh) in mouse striatum. In wild-type C57/Bl6 mice, perfusion of NMDA (100 micro m) induced a two-fold stimulation of ACh release. This effect was attenuated in mice lacking endothelial NOS but was completely absent in mice lacking neuronal NOS. Local perfusion of SIN-1 (300 micro m), an NO donor, increased ACh release by more than two-fold in all three mouse lines. We conclude that NO synthesized by neuronal NOS provides a nitrergic link in the glutamatergic stimulation of striatal cholinergic interneurons.     

A single amino acid change in rabies virus glycoprotein increases virus spread and enhances virus pathogenicity

Several rabies virus (RV) vaccine strains containing an aspartic acid (Asp) or glutamic acid (Glu) instead of an arginine (Arg) at position 333 of the RV glycoprotein (G) are apathogenic for immunocompetent mice even after intracranial inoculation. However, we previously showed that the nonpathogenic phenotype of the highly attenuated RV strain SPBNGA, which contains a Glu at position 333 of G, is unstable when this virus is passaged in newborn mice. While the Glu(333) remained unchanged after five mouse passages, an Asn(194)-->Lys(194) mutation occurred in RV G. This mutation was associated with increased pathogenicity for adult mice. Using site-directed mutagenesis to exchange Asn(194) with Lys(194) in the G protein of SPBNGA, resulting in SPBNGA-K, we show here that this mutation is solely responsible for the increase in pathogenicity and that the Asn(194)-->Lys(194) mutation does not arise when Asn(194) is exchanged with Ser(194) (SPBNGA-S). Our data presented indicate that the increased pathogenicity of SPBNGA-K is due to increased viral spread in vivo and in vitro, faster internalization of the pathogenic virus into cells, and a shift in the pH threshold for membrane fusion. These results are consistent with the notion that the RV G protein is a major contributor to RV pathogenesis and that the more pathogenic RVs escape the host responses by a faster spread than that of less pathogenic RVs.     

Expression of mutated cationic trypsinogen reduces cellular viability in AR4-2J cells

Mutations in the human cationic trypsinogen are associated with hereditary pancreatitis. The cDNA coding for human cationic trypsinogen was subcloned into the expression vector pcDNA3. The mutations R122H, N29I, A16V, D22G, and K23R were introduced by site directed mutagenesis. We constructed an expression vector coding for active trypsin by subcloning the cDNA of trypsin lacking the coding region for the trypsin activating peptide behind an appropriate signal peptide. Expression of protein was verified by Western blot and measurement of enzymatic activity. AR4-2J cells were transiently transfected with the different expression vectors and cell viability and intracellular caspase-3 activity were quantified. In contrast to wild-type trypsinogen, expression of active trypsin and mutated trypsinogens reduced cell viability of AR4-2J cells. Expression of trypsin and R122H trypsinogen induced caspase-3 activity. Acinar cells might react to intracellular trypsin activity by triggering apoptosis.