Intracellular ion activities and Cl-transport mechanisms in bullfrog corneal epithelium

Cell membrane potentials, cell membrane resistances, and intracellular ionic activities were measured in bullfrog corneal epithelium. Equivalent circuit analysis was performed by adding adenosine to the apical surface and assuming that only the apical membrane is initially affected. From single-ion substitutions in the apical bathing solution, the apical membrane was found to have a high Cl- permeability, a low K+ permeability, and an unmeasurably small Na+ permeability. Under control conditions intracellular Cl- activity (aCli) was 22 +/- 2 (SE) mM, intracellular Na+ activity (aNai) was 14 +/- 3 mM, and intracellular K+ activity (aKi) was 106 +/- 5 mM. The electrical potential differences across apical and basolateral membranes were about 50 and 67 mV, respectively, both cell negative. aCli and aKi are higher, whereas aNai is much lower than predicted for equilibrium distribution. Inasmuch as Cl- is transported from the basolateral (stromal) to the apical (tear) side, basolateral entry of this anion is uphill and apical exit is downhill. Basolateral entry is Na+ dependent, as evidenced by a fall of aCli to near-equilibrium values after basolateral Na+ removal. The electrochemical gradient for Cl- efflux across the apical membrane is large enough to account for Cl- transport by electrodiffusion only. Na+ removal from the basolateral solution causes a reversible decrease of apical membrane Cl- permeability. The results support the hypothesis that net transepithelial Cl- transport results from coupled NaCl entry (or an equivalent process) at the basolateral membrane and electrodiffusional Cl- exit at the apical membrane.     

Nitric oxide synthase neurons in the rodent spinal cord: distribution, relation to Substance P fibers, and effects of dorsal rhizotomy

The indirect immunofluorescent method was employed to investigate the distribution of neuronal nitric oxide synthase-like immunoreactivity(nNOS-LI) in the spinal cord of the golden hamster and to compare it to data obtained from rats. Immunoreactive neurons were found throughout the cervico-sacral extent in the dorsal horn (mainly in laminae I-III) and in the preganglionic autonomic regions, i.e., the sympathetic intermediolateral nucleus (IML), lateral funicle (LF), intercalated region (IC), the area surrounding the central canal (CA), and the sacral preganglionic parasympathetic cell group. While the distribution of immunoreactive cells was generally similar in both species, some differences were observed. For example in the hamster LF, a higher percentage of stained neurons was seen than in the IML, while the situation was rather inverse in the rat. In order to study the coincidence of nNOS-LI in the population of preganglionic sympathetic neurons (PSN) that innervate the superior cervical ganglion (SCG), these were identified by retrograde axonal transport of fluoro-gold (FG) following unilateral injection into the SCG. PSN were localized ipsilateral to the injection site mainly in the IML and LF of spinal segments C7-Th4. The portion of double-labeled neurons of the IML were lower in hamster (17% in C7, 34% in C8) of FG-labeled cells) than in rat (47% in C8, 77% in Th2), while in the LF of segments C8-Th2 in both species the majority of FG-neurons contained nNOS. While only very few double-labeled neurons were detected in the IC in hamster and rat, a striking difference was observed in the CA, where no double-labeled neurons were found in hamster, but up to 50% in rat. Double immunofluorescence detection of nNOS and substance P (SP) showed that in both the autonomic regions and the dorsal horn, SP-LI fibers and puncta were present in close spatial relationship to nNOS-LI cell bodies. These results were basically identical in the hamster and rat. Unilateral transection of the dorsal roots of segments C6-Th2 in rats resulted in a clear reduction of SP-LI structures in the dorsal horn 5 days after rhizotomy, but not in the autonomic regions. Compared to the unlesioned side, the numbers of nNOS-LI neurons in the superficial laminae of the dorsal horn were reduced to 32-46% in the lesioned segments, and to 53% and 87%, respectively, in the two segments cranial to the rhizotomized segments but remained unchanged caudally to the lesion. Numbers of nNOS-LI cell bodies in the autonomic regions were not altered following dorsal root transection. The present study provides data on the widespread distribution of nNOS in the spinal cord of golden hamster and describes the partial coincidence of the enzyme in PSN. The effects of dorsal rhizotomy on nNOS-LI neurons in the dorsal horn reveal that primary-afferent fibers provide a stimulatory influence on neurons of the dorsal horn to generate the gaseous neuroactive substance, nitric oxide.     

The role of the hypothalamic paraventricular nuclei for the regulation of pineal melatonin synthesis: new aspects derived from the vasopressin-deficient Brattleboro rat

There is evidence for an involvement of the hypothalamic paraventricular nuclei (PVN) in the regulation of pineal melatonin synthesis in rats. Since electrical stimulation of the PVN or the systemic administration of arginine-vasopressin (AVP) result in a depression of the nocturnal melatonin surge, this neuropeptide appears to be pivotal for the transduction of PVN-efferent, pinealopetal signals. We therefore used an AVP-deficient animal model, the Brattleboro rat, to further investigate the mechanisms responsible for pineal regulation. Anesthetized adult male animals received 2 min of bilateral electrical stimulation of the PVN either during the day or at night. Thirty min later, pineal glands were removed and pineal N-acetyltransferase (NAT) activities and melatonin contents were determined. Stimulation resulted neither during the day nor at night in any significant alterations of pineal NAT activity or melatonin content when compared to control or sham-stimulated animals. These data further support the proposed modulatory role of AVP for the regulation of melatonin synthesis in the Epiphysis cerebri of genetically intact rats.     

Electrophysiological investigations on the central innervation of the rat and guinea-pig pineal gland

Summary The possible influence of central nervous structures on the electrical activity of single pineal cells was investigated in rat and guinea-pig.In the rat electrical stimulation of the hippocampal formation elicited both single cell responses with different latencies and mostly long-term excitations in single pineal cells, while stimulation of the habenular nuclei caused clear orthodromical responses with different latencies, alterations in the rate of spontaneous electrical activity and evoked discharges of silent units.In the guinea-pig electrical stimulation of the paraventricular nucleus influenced predominantly cells in the deeper layers of the posterior part of the pineal gland. Electrical stimulation of both the superior and inferior colliculi elicited field potentials with a constant latency, indicating a functional relationship between the corpora quadrigemina and the pineal organ.Intrapineal stimulation and recording in the guinea-pig indicate functional connections between anterior and posterior parts of the pineal organ and that information can be conducted in both directions of the pineal axis.The data from the rat pineal gland are part of a thesis presented by St. Reuss in partial fulfillment for the degree of Dr. rer. nat. Preliminary data have been presented at the NATO Symposion The pineal gland and its endocrine role, Sicily 1982 (cf. Semm, 1983) and at the 6th European Neuroscience Congress, Malaga 1982 (cf. Reuss andSemm, 1982). — Financial support of the Stiftung Volkswagenwerk is gratefully acknowledged.     

Nitric oxide synthase in trigeminal ganglion cells projecting to the cochlea of rat and guinea pig

Nitric oxide (NO) influences electrophysiological and morphological parameters of the mammalian cochlea. Recently, the isoform of the NO-producing enzyme neuronal NO synthase (nNOS) has been demonstrated in spiral ganglion cells and olivocochlear neurons. The cochlea is also innervated by fibers stemming from the trigeminal ganglion (TG) and superior cervical ganglion (SCG). Whether these ganglion cells contain nNOS is not known yet. We therefore identified TG and SCG cells upon injection of Fluoro-Gold (FG) into the cochlea and retrograde neuronal transport of FG in rat and guinea pig. These ganglion cells were investigated for neuronal NOS immunohistochemically. Perikarya labeled by FG were found in the ipsilateral TG and SCG. In both species investigated, a considerable number of FG-labeled TG cells were also nNOS-immunoreactive whereas SCG cells were not. These data, demonstrating the existence of nNOS-containing TG cells that project to the cochlea, provide evidence that these neurons are further sources of nitric oxide in the cochlea.     

Survival and differentiation of dopaminergic mesencephalic neurons are promoted by dopamine-mediated induction of FGF-2 in striatal astroglial cells

Survival of dopaminergic (DAergic) midbrain neurons during development and after lesioning depends, in part, on the presence of astroglia-derived growth factors, as, e.g., fibroblast growth factor (FGF)-2. Astrocytes express DA receptors in a brain-region-specific manner. We show here that DA (10(-3) to 10(-6) mol/liter) applied continuously for 12 h or as a 10-min pulse significantly upregulates FGF-2 immunoreactivity quantified by Western blot and densitometry in astrocytes cultured from two target areas of DAergic neurons, striatum and cortex, but not in mesencephalic astroglia. Semiquantitative competitive RT-PCR confirmed the increase in FGF-2 on the mRNA level. The effects were specific in that glutamate, which can also activate receptors on astroglial cells, did not influence FGF-2 synthesis. In addition to the DA-mediated increase in FGF-2 synthesis the capability of conditioned medium (CM) from DA-stimulated striatal and cortical astrocytes to promote survival and process formation of cultured rat DAergic neurons was significantly enhanced. These effects could be fully blocked by preincubation of the CM with an FGF-2-specific polyclonal antiserum. Our results suggest that DA released from DAergic axon terminals in target regions of DAergic neurons and astroglial FGF-2 production are interdependent in that DA triggers synthesis of FGF-2, which, in turn enhances survival and differentiation of DAergic neurons.     

Sex-specific mating pheromones in the nematode Panagrellus redivivus

Nematodes use an extensive chemical language based on glycosides of the dideoxysugar ascarylose for developmental regulation (dauer formation), male sex attraction, aggregation, and dispersal. However, no examples of a female- or hermaphrodite-specific sex attractant have been identified to date. In this study, we investigated the pheromone system of the gonochoristic sour paste nematode Panagrellus redivivus, which produces sex-specific attractants of the opposite sex. Activity-guided fractionation of the P. redivivus exometabolome revealed that males are strongly attracted to ascr#1 (also known as daumone), an ascaroside previously identified from Caenorhabditis elegans hermaphrodites. Female P. redivivus are repelled by high concentrations of ascr#1 but are specifically attracted to a previously unknown ascaroside that we named dhas#18, a dihydroxy derivative of the known ascr#18 and an ascaroside that features extensive functionalization of the lipid-derived side chain. Targeted profiling of the P. redivivus exometabolome revealed several additional ascarosides that did not induce strong chemotaxis. We show that P. redivivus females, but not males, produce the male-attracting ascr#1, whereas males, but not females, produce the female-attracting dhas#18. These results show that ascaroside biosynthesis in P. redivivus is highly sex-specific. Furthermore, the extensive side chain functionalization in dhas#18, which is reminiscent of polyketide-derived natural products, indicates unanticipated biosynthetic capabilities in nematodes.     

Sonography in Crohn disease--the conclusions of an experts' group

Sonography is adding a new dimension to diagnosis of Crohn's disease: the analysis of the transmural and peri-intestinal manifestations of the chronic inflammation. Distortions in the structure of intestinal wall are recognizable, the impact on transport of intestinal content can be judged, penetration of inflammation into the bowel surrounding as fistula, abscess, mesenteriitis und peritonitis is safely seen. Differential diagnosis on a strictly sonographic basis is difficult. The paper represents the results of an expert meeting held at the University of Frankfurt/M.     

Three methods for evaluation of left atrial volume.

AIM: To compare and contrast 3 different echocardiographic methods used to measure left atrial (LA) volume: biplane area length (AL), biplane modified Simpson (SIMP), and prolate ellipse (PE) methods. METHODS AND RESULTS: A review of consecutive patients who presented to our outpatient echocardiography laboratory for a resting transthoracic study between April 2006 and May 2006 was performed. Echocardiograms were reexamined and LA volume measured using the AL, SIMP, and PE methods. Of 102 consecutive patients evaluated, 97 had a measure of LA volume using all 3 methods. A significant difference in the measurement of mean +/- SD LA volume was noted among the 3 different methods: 37 +/- 16 mL/m(2) for AL, 34 +/- 14 mL/m(2) for SIMP, and 27 +/- 12 mL/m(2) for PE. The PE method yielded routinely smaller values compared with either the AL or SIMP method (P < 0.001). Differences increased with increased LA volume. The SIMP method derived consistently smaller (<5 mL/m(2)) values than those of the AL method, consistent across the full range of LA volumes. CONCLUSION: Significant differences exist among these 3 commonly used methods for measuring LA volume. Standardization of the measurement of LA volume is recommended.