Exploring spatial distributions of larval yellow perch Perca flavescens, bluegill Lepomis macrochirus and their prey in relation to wind.

The objectives of the present study were to determine if spatial differences existed between zooplankton, larval yellow perch Perca flavescens and bluegill Lepomis macrochirus (<13 mm total length, L(T)) in Pelican Lake (332 ha), NE, U.S.A. It was hypothesized that wind could act as a transport mechanism for larval fishes in this shallow lake, because strong winds are common at this geographic location. Potential spatial differences were explored, relating to zooplankton densities, size structure and densities of larval P. flavescens and L. macrochirus. Density differences (east v. west side of the lake) were detected for small- (two occasions), medium- (two occasions) and large-sized (one occasion) L. macrochirus larvae. No density differences were detected for small P. flavescens larvae; however, densities of medium- and large-sized P. flavescens were each higher on the west side of the lake on two occasions. There was no evidence that larval P. flavescens and L. macrochirus distributions were related to wind because they were not associated with large wind events. Likewise, large wind event days did not result in any detectable spatial differences of larval P. flavescens and L. macrochirus densities. There appeared to be no spatial mismatch between larval densities and associated prey in the years examined. Thus, wind was not apparently an influential mechanism for zooplankton and larval P. flavescens and L. macrochirus transport within Pelican Lake, and spatial differences in density may instead be related to vegetation and habitat complexities or spawning locations within this shallow lake.

The dorsal column pathway facilitates visceromotor responses to colorectal distention after colon inflammation in rats.

Recent clinical studies have demonstrated that a midline lesion of the dorsal columns (DC, limited midline myelotomy) reduces pain of visceral origin in patients with pelvic cancer. Animal experiments showed that a DC lesion leads to decreased activation of thalamic neurons by visceral stimuli, lowers the impact of noxious colon stimulation in behavioral tests and suggested that the effect is mediated mainly by postsynaptic DC neurons. In the present experiments we examined the effect of bilateral DC or ventrolateral (VL) spinal cord lesions on visceromotor reflex EMG activity evoked by graded colorectal distention (30, 60, 80 mmHg) under control conditions and after colon inflammation with mustard oil. The colon inflammation increased significantly the visceromotor responses so that the response to a 30 mmHg distention was larger than that produced by 80 mmHg before inflammation. The DC lesion did not affect the visceromotor reflex response under control conditions but reduced the increased responses after colon inflammation back to control levels and prevented the potentiation of the reflex responses by colon inflammation when performed before the inflammation. Our results suggest that the role of the DC pathway in transmission of visceral pain is augmented under inflammatory conditions when symptoms of visceral allodynia and hyperalgesia may be present. The VL lesions eliminated the visceromotor reflex, presumably by interrupting a facilitatory pathway that involves the brain stem.

Transient inhibition of responses to thermal stimuli of spinal sensory tract neurons in monkeys during sensitization by intradermal capsaicin.

A secondary zone of cutaneous hyperalgesia in humans is characterized by increased pain to mechanical stimuli. In contrast, the perception of heat stimuli delivered to a secondary zone of hyperalgesia in humans often shows a paradoxical decrease in magnitude. A number of studies have shown that the responses of spinal cord neurons to cutaneous mechanical stimuli after peripheral injury model well the mechanical hyperalgesia. However, the responses of dorsal horn neurons to thermal stimuli after peripheral injury have not been as carefully studied. The present study examined the effects of intradermal capsaicin on the responses of spinal sensory projection neurons to cutaneous mechanical and thermal stimuli. Our observations indicate that the responses of identified sensory projection neurons to heat are transiently reduced at the same time that responses of these cells to mechanical stimuli are increased. These results confirm a role for sensory projection cells in signaling the sensory discriminative aspects of pain in humans and underscore the emerging complexity of dorsal horn circuitry and sensory processing.

Using a monoclonal antibody to identify patients with type I and type II von Willebrand's disease.

Three monoclonal antibodies produced against vWF:Ag by conventional hybridoma technique did not inhibit factor VIII coagulant activity (F. VIII:C) but did inhibit VIII ristocetin cofactor activity. The antibodies were used in an indirect competitive ELISA for quantifying von Willebrand's antigen (vWF:Ag) and compared with values obtained by the Laurell technique using commercial antibody by means of a ratio: ELISA/Laurell. For one monoclonal BD2-CC9, vWF:Ag values obtained in the two assays were in good agreement for normal and hemophilia A plasmas (normal, n = 19, ratio = 1.13 +/- .17, hemophilia A, n = 10, ratio = 0.91 +/- .15). However, type II vWD patients had a disproportionately low value of vWF:Ag with the ELISA. Use of the ratio normalized the difference among individual plasma values and allowed a significant separation of type II vWD plasma (n = 9, ratio = 0.46 +/- .19) from normal plasma (p = .0001) and type I vWD plasma (n = 8, ratio = 1.52 +/- .34) from type II vWD plasma (p = .0003) using BD2-CC9. Although the sample size was small, the greater degree of discrimination among the vWD plasmas tested with BD2-CC9 (compared with the other two antibodies [CA3-AE4, CC6-BG10]) suggests that this antibody may recognize conformational epitopes that reflect the degree of multimeric polymerization of the vWF molecule rather than simply recognize a decreased number of antigenic sites in a basic subunit. BD2-CC9 may be valuable in investigating the various types of vWD and/or the process of polymerization of this complex protein.

Inhibition of isoproterenol positive atrial chronotropic effect by methylmethacrylate polymer and monomer.

Atria from rats exposed in vivo to methylmethacrylate polymer or monomer were superfused and chronotropic responses to isoproterenol determined. Control and polymer-exposed atria superfused with oxygen-saturated buffer yielded dose-response curves which were essentially identical with regard to maximal increase and potency of isoproterenol. Control atria superfused with buffer containing 70% of possible oxygen saturation showed a 10-fold decrease in isoproterenol potency and a maximal effect approximately 75-80% that of fully oxygenated atria. Atria exposed to methylmethacrylate polymer and superfused with 70% oxygen saturated buffer showed a 100-fold decrease in isoproterenol potency and a maximal effect approximately 25% that of fully oxygenated control atria. Exposure of rats to methylmethacrylate monomer in vivo resulted in complete abolition of the chronotropic response to isoproterenol in atria superfused with 70% oxygen saturated media.

Inhibition of the positive atrial chronotropic effect of isoproterenol by exposure to an acrylate floor finish.

Application of a commercial acrylate sealer/finish to the floor of our animal quarters resulted in almost complete elimination of the positive chronotropic response of the hypoxic rat atria to isoproterenol. Forty-eight hours exposure to this sealer/finish decreased sensitivity to isoproterenol by approximately 1000-fold and decreased maximal response by 70%. The elimination of the response to isoproterenol was associated with the resin portion of the sealer/finish and was reversible on removal of the rats from exposure to the product.