Immunfluorescence study of neuropeptides in identified neurons of the rat auditory superior olivary complex

 The present study was conducted to investigate the distribution and immunohistochemical characteristics of ascending and descending projection neurons of the rat superior olivary complex (SOC), a group of interrelated brainstem nuclei. Ascending neurons were identified by injection of cholera toxin B subunit (CTB) into the central nucleus of the inferior colliculus (IC), descending neurons were labeled by application of Fluoro-Gold (FG) into the scala tympani of the cochlea, ipsilaterally to the IC injection. In accordance with the literature, we observed neurons innervating the IC located in the lateral superior olivary nucleus (LSO) and dorsal periolivary groups (DPO) on both sides, in the superior paraolivary nucleus (SPO) predominantly ipsilateral, as well as in the ipsilateral medial superior olivary nucleus (MSO) and the medial nucleus of the trapezoid body (MNTB). Cochlear projection neurons were found predominantly in the ipsilateral LSO as well as in the bilateral SPO, DPO, MSO and MNTB. In addition, a considerable population of neurons in the ipsilateral LSO and SPO were identified as being both ascending and descending. To further characterize these double-projecting neurons, brainstem sections were incubated in antisera directed against different neuroactive substances. The majority of ascending/descending cells in the LSO contained calcitonin gene-related peptide, but not substance P (SP), met-enkephalin (ENK) or tyrosine hydroxylase (TH). Some of these neurons apparently were contacted by ENK- or SP-immunoreactive fibers and terminals. In addition, we found TH-immunoreactive neurons in the lateral MNTB region. These neurons, which were labeled upon tracer injection into the cochlea (but not upon IC injection), probably belong to the C1 catecholaminergic cell group and may represent a division of the uncrossed olivocochlear bundle. The present results reveal the existence of a previously unknown subpopulation of SOC neurons that project to both the cochlea and the inferior colliculus. Their CGRP immunoreactivity and their uncrossed projection pattern provide evidence that they may belong to the cholinergic, putatively excitatory cell group. Received: 4 January 1999 / Accepted: 17 February 1999     

Increased lymphocytic aminopeptidase N/CD13 promoter activity after cell‐cell contact

Aminopeptidase N (APN)/CD13 is a transmembrane ectoenzyme expressed on a wide variety of cells. With respect to haematopoietic cells, APN/CD13 has been considered specific for the myeloid lineage, because granulocytes and monocytes/macrophages, but not lymphocytes of peripheral blood, show a surface expression of CD13 antigen. However, we could recently show that cell‐cell contact of lymphocytes with endothelial cells, monocytes, and fibroblast‐like synoviocytes (SFCs) results in an increase of steady‐state APN/CD13 mRNA and a rapid expression of cell‐surface protein on the lymphocytes. In this study using the Dual‐Luciferase reporter assay, we demonstrate that interaction of the T‐cell line Jurkat with SFCs results in a higher activity of the APN/CD13 myeloid promoter in T cells. An enhancer located between the myeloid and epithelial APN/CD13 promoter increases the response of the promoter to the cell‐cell contact‐induced expression of APN/CD13 in lymphocytes. Adhesion of lymphocytes to extracellular matrix did not result in increased promoter activity. The lymphocytic promoter response induced by direct cell‐cell contact with SFCs is not affected by mutations of a proximal promoter element (nucleotides −48 to −35), which has a possible functional role in the basal APN/CD13 gene expression in lymphocytes. Upregulated peptidase‐promoter activity via cell‐cell contact shown in this study for the first time is discussed as a general mechanism in peptidase induction. J. Cell. Biochem. 80:115–123, 2000. © 2000 Wiley‐Liss, Inc.     

Nutrient limitation in relation to phytoplankton carotenoid/chiorophyll a ratios in freshwater mesocosms

The 480/665 nm absorption ratio for pigment extracts was evaluatedas an indicator of nutrient limitation using freshwater planktoncommunities and a mesocosm approach. The mesocosm design wasused to create various nutrient regimes for the phytoplanktoncommunities, and nutrient limitation was detected by means ofgrowth response assays (¹⁴ fixation and pigment increase followingaddition of nutrients) and the 480/665 ratio. Results from fourperiods in 1993 and one period in 1994 showed that high 480/665ratios (indicative of nutrient limitation) were only found atchlorophyll a concentrations <20 µg I^–1, wherenutrient limitation was not detected. Periods with potentialnutrient limitation exhibited low 480/665 ratios. Consequently,the absolute values of the 480/665 ratio could not be used topredict nutrient limitation. However, when nutrients were addedto nutrient- limited phytoplankton communities in growth responseassays, the ratio decreased, indicating that the 480/665 ratiocan be used as a relative index to detect nutrient limitationin bioassays.     

Tracking Se Assimilation and Speciation through the Rice Plant – Nutrient Competition,Toxicity and Distribution

Up to 1 billion people are affected by low intakes of the essential nutrient selenium (Se) due to low concentrations in crops. Biofortification of this micronutrient in plants is an attractive way of increasing dietary Se levels. We investigated a promising method of Se biofortification of rice seedlings, as rice is the primary staple for 3 billion people, but naturally contains low Se concentrations. We studied hydroponic Se uptake for 0–2500 ppb Se, potential phyto-toxicological effects of Se and the speciation of Se along the shoots and roots as a function of added Se species, concentrations and other nutrients supplied. We found that rice germinating directly in a Se environment increased plant-Se by factor 2–16, but that nutrient supplementation is required to prevent phyto-toxicity. XANES data showed that selenite uptake mainly resulted in the accumulation of organic Se in roots, but that selenate uptake resulted in accumulation of selenate in the higher part of the shoot, which is an essential requirement for Se to be transported to the grain. The amount of organic Se in the plant was positively correlated with applied Se concentration. Our results indicate that biofortification of seedlings with selenate is a successful method to increase Se levels in rice.     

Toxoplasma antibodies among bobcats and other carnivores of norther California.

The prevalence of antibodies to Toxoplasma gondii was investigated among five species of wild carnivores in Norther Ccalifornia. The highest prevalence was among bobcats (Lynx rufus), with 15 of 21 tested being serologically positive. Other results included serological evidence of toxoplasmosis in two of seven raccoons (Procyon lotor), one of three badgers (taxidea taxus) and two of three coyotes (Canis latrans). Two gray foxes (Urocyon cinereoargenteus) were serologically negative. Oone badger with an indirect hemagglutination antibody titer of 1:8192 was found to harbor T. gondii in its brain tissues.     

Sodium block and depolarization diminish P2Z-dependent Caentry in human B lymphocytes

Despite a high Ca²⁺-permeability of the P2Z receptor in human B lymphocytes, extracellular ATP⁴has only a minor effect on global [Ca²⁺]_i. The aim of this study was to reveal the mechanisms responsible for this discrepancy. We investigated the relationship between ATP⁴⁻-application, Ca_i²-response, membrane current and membrane potential in two human B cell lines and in human tonsillar B cells. This was achieved by a combination of FACS- and voltage clamp measurements and the usage of appropriate voltage- and Ca²-sensitive fluorescent dyes. ATP⁴-induced changes in whole-cell current and [Ca²]_iwere blocked by extracellular as well as intracellular Na⁺. Under current clamp conditions, ATP⁴⁻-induced Na⁺-entry diminished the Ca²⁺entry via reduction of the driving force. A substantial increase in [Ca²⁺]_iinduced by ATP⁴⁻was only observed in Na⁺-free solutions.The pathway of signal transduction activated by ATP⁴via P2Z receptor of human B lymphocytes under physiological conditions seems not to operate by an increase in the global intracellular Ca₂-concentration, but rather by the depolarization of the cell membrane as a result of the Na⁺-influx.