The orienting response of Lake Michigan mottled sculpin is mediated by canal neuromasts.

Lake Michigan mottled sculpin, Cottus bairdi, exhibit a naturally occurring and unconditioned orienting response that can be triggered by both live prey and chemically inert vibrating spheres, even in blinded animals. CoCl(2)-induced reductions of the orienting response demonstrate that the lateral line is required for this behavior in the absence of non-mechanosensory cues (such as vision), but shed no light on the relative contributions of superficial and canal neuromasts to this behavior. To determine the relative roles of these two subsystems, we measured the frequency with which mottled sculpin oriented towards a small vibrating sphere before and after two treatments: (i) immersion of fish in a solution of gentamicin, an aminoglycoside antibiotic that damages hair cells in canal, but not superficial, neuromasts; and (ii) scraping the skin of the fish, which damages the superficial, but not the canal, neuromasts. To ensure that both superficial and canal neuromasts were adequately stimulated, we tested at different vibration frequencies (10 and 50 Hz) near or at the best frequency for each type of neuromast. At both test frequencies, response rates before treatment were greater than 70 % and were significantly greater than 'spontaneous' response frequencies measured in the absence of sphere vibration. Response rates fell to spontaneous levels after 1 day of gentamicin treatment and did not return to pre-treatment levels for 10-15 days. In contrast, response rates stayed approximately the same after superficial neuromasts had been damaged by skin abrasion. Scanning electron microscopy confirmed hair cell damage (loss of apical cilia) in canal, but not superficial, neuromasts of gentamicin-treated animals after as little as 24 h of treatment. The sensory epithelium of canal neuromasts gradually returned to normal, following a time course similar to behavioral loss and recovery of the orienting response, whereas that of superficial neuromasts appeared normal throughout the entire period. This study shows that the orienting response of the mottled sculpin is mediated by canal neuromasts.

Distribution and innervation of taste buds in the axolotl.

Adult axolotls have approximately 1,400 taste buds in the epithelium of the pharyngeal roof and floor and the medial surfaces of the visceral bars. These receptors are most dense on the lingual surfaces of the upper and lower jaws, slightly less dense throughout lateral portions of the pharyngeal roof and floor, and more sparse within medial portions of the pharyngeal roof and floor, except for a median oval patch of receptors located rostrally between the vomerine tooth fields. Each taste bud is a pear-shaped organ, situated at the center of a raised hillock and averaging 80 and 87 microm in height and width, respectively. Each comprises 50 to 80 cells, which can be classified as basal, dark fusiform, or light fusiform, based on differences in their morphology. The distal ends of the apical processes of the fusiform cells reach the surface of each hillock, forming a single taste pore with an average diameter of 15 microm. Each apical process terminates in one of three ways: as short, evenly spaced microvilli; as long clustered microvilli; or as large, stereocilia-like microvilli. The pharyngeal epithelium and associated taste buds in axolotls are innervated solely by rami of the facial, glossopharyngeal and vagal nerves. Approximately, the rostral one half of the pharyngeal roof is innervated by the palatine rami of the facial nerve, whereas the caudal one half of the pharyngeal roof is innervated by the pharyngeal rami of the glossopharyngeal and vagal nerves. The lingual surface of the lower jaw is innervated by the pretrematic (mandibular) ramus of the facial nerve. The dorsal two-thirds of the visceral arches, and the ventral one-third of the visceral arches and the pharyngeal floor, are innervated by both the pretrematic and post-trematic rami of the glossopharyngeal and vagal nerves, respectively.

The overlapping roles of the inner ear and lateral line: the active space of dipole source detection.

The problems associated with the detection of sounds and other mechanical disturbances in the aquatic environment differ greatly from those associated with airborne sounds. The differences are primarily due to the incompressibility of water and the corresponding increase in importance of the acoustic near field. The near field, or hydrodynamic field, is characterized by steep spatial gradients in pressure, and detection of the accelerations associated with these gradients is performed by both the inner ear and the lateral line systems of fishes. Acceleration-sensitive otolithic organs are present in all fishes and provide these animals with a form of inertial audition. The detection of pressure gradients, by both the lateral line and inner ear, is the taxonomically most widespread mechanism of sound-source detection amongst vertebrates, and is thus the most likely primitive mode of detecting sound sources. Surprisingly, little is known about the capabilities of either the lateral line or the otolithic endorgan in the detection of vibratory dipole sources. Theoretical considerations for the overlapping roles of the inner ear and lateral line systems in midwater predict that the lateral line will operate over a shorter distance range than the inner ear, although with a much greater spatial resolution. Our empirical results of dipole detection by mottled sculpin, a benthic fish, do not agree with theoretical predictions based on midwater fishes, in that the distance ranges of the two systems appear to be approximately equal. This is almost certainly as a result of physical coupling between the fishes and the substrate. Thus, rather than having a greater active range, the inner ear appears to have a reduced distance range in benthic fishes, and the lateral line distance range may be concomitantly extended.

Schreiner organs: a new craniate chemosensory modality in hagfishes.

An extensive system of sensory organs resembling taste buds was previously known in the skin of hagfishes. These sensory organs, called here Schreiner organs, are found throughout the epidermis of both Eptatretus stoutii and Myxine glutinosa. They are found also at high densities in the prenasal sinus, nasopharyngeal duct, and pharynx, and at lower densities in the oral and velar chambers. Schreiner organs are multicellular aggregates composed of acetylated tubulin-immunoreactive receptor cells and nonimmunoreactive cells. A considerable range of variation was found in Schreiner organ morphology, but discrete classes of organs could not be recognized. Schreiner organs are innervated by all sensory trigeminal rami, the glossopharyngeal/vagal nerve, and cutaneous rami of spinal nerves, but not by the facial nerve. The central projections of these rami form a continuous tract in the trigeminal sensory zone and the dorsolateral funiculus of the spinal cord. Some Schreiner organs may be represented in the nucleus of the solitary tract, but this structure is certainly not the primary recipient zone of Schreiner organ afferents. In light of these systemic differences between vertebrate taste systems and the Schreiner organ system of hagfishes, it is concluded that Schreiner organs are not homologous to taste buds. This sensory modality of hagfishes has no direct homolog in vertebrates and appears to be a specialization of hagfishes, perhaps derived from the primitive somatosensory system of the earliest craniates.

The sensory biology of the living jawless fishes: a phylogenetic assessment.

Despite the ancient origins and aberrant appearance of living jawless fishes, none of their features may be assumed to be primitive without comparisons among hagfishes, lampreys, and gnathostomes, and with the nearest relatives of all craniates, the cephalochordates. In this review, the sensory capabilities of lampreys and hagfishes will be compared, and the major features of early craniate sensory evolution will be infered using cladistic methodology and an accepted phylogeny of the hagfishes, lampreys and gnathostomes. Lampreys have well developed olfactory, visual and octavolateralis systems, each of which is known to play a role in lamprey life and behavior. Hagfishes have poorly developed visual and octavolateralis systems, but elaborate olfactory and chemosensory systems. Unfortunately, the natural behavior and lifestyle of hagfishes are poorly known, limiting our understanding of hagfish sensory biology. Both groups of living jawless fishes show mixtures of primitive and secondarily derived sensory features and have few shared derived sensory features that would indicate close relations between the two groups.

Distribution of gonadotropin-releasing hormone immunoreactivity in the brain of the Pacific hagfish, Eptatretus stouti (Craniata: Myxinoidea).

The distribution of gonadotropin-releasing hormone (GnRH)-like immunoreactivity in the brain of a myxinoid, the Pacific hagfish (Eptatretus stouti), was investigated via immunohistochemistry, including the use of six different antisera. In the diencephalon, immunoreactive cell bodies were found in two systems: the infundibular hypothalamus, a neuromodulatory nucleus with diffuse projections of varicose fibers to most areas of the brain, and a primarily preoptic system of putatively hypophysiotropic neurons that projects to the neurohypophysis. Some potential neurovascular and CSF contacts were also identified. These findings are consistent with those of similar studies in other craniates and suggest that a preoptic hypophysiotropic system may be present in all craniates. We therefore tentatively accept the homology of this system in hagfish and vertebrates. The homology of the distributed hypothalamic system is more dubious. It may be homologous to a caudal GnRH system of modulatory neurons found in many vertebrates. Antiserum PBL-49 displays a differential affinity for the two systems, indicating that the two systems differ in the amount or identity of the immunoreactive substance. We suggest that the two systems have distinct functions in hagfish. The primitive function of GnRH-like molecules in craniates may have thus been both neuromodulatory and hypophysiotropic. These findings also indicate that the brain-pituitary axis of hagfish is more similar to that of vertebrates than has been previously suggested.

Spermidine synthesis by Pseudomonas sp. strain Kim, previously reported to lack this polyamine.

Pseudomonas sp. strain Kim has previously been reported to be the only known naturally occurring organism lacking spermidine. We now show that it synthesizes this polyamine. The apparent lack of intracellular levels of spermidine results from an efficient conversion of spermidine to putrescine and hydroxyputrescine.

Inhibition of C1q functions by RHP, a protein elevated in sera from patients with rheumatoid arthritis.

We have previously shown that serum levels of C1q, unbound to C1r X C1s, are elevated in rheumatoid arthritis. We have also shown that RHP, a newly described serum protein which affects the C1q-anti C1q precipitin reaction, is also present at elevated levels in rheumatoid arthritis. We now show that RHP inhibits the hemolytic activity of C1q, disaggregates C1, and inhibits the ability of C1q bound to latex beads or to aggregated IgG to enhance the oxidative metabolism of neutrophils.

A method for serum C1q based on its hydroxyproline content.

The radial immunodiffusion assay overestimates the C1q in serum. Here we describe a convenient, accurate procedure for measuring C1q in 250 microL of dialyzed serum. This method is based on our previous findings that all C1q in serum precipitates with the euglobulin fraction and that all other serum proteins containing hydroxyproline are excluded from this fraction. Because C1q is 4.3% hydroxyproline, the concentration of C1q in serum can therefore be calculated from the hydroxyproline content of the euglobulin fraction. The procedure, all done in the same tube, consists of precipitating the euglobulin fraction, digesting it with HClO4, and converting hydroxyproline to the corresponding pyrrole, which is extracted with toluene and measured by absorbance at 560 nm.

Role of ribosome recycling in uptake of dihydrostreptomycin by sensitive and resistant Escherichia coli.

Exposure of streptomycin-resistant cells to puromycin results in uptake of dihydrostreptomycin comparable to that found with streptomycin-sensitive cells. This finding indicates that the enhanced phase of uptake, previously reported only in sensitive cells, may result from an increase in internal binding sites, presumably run-off ribosomes. The increased uptake of dihydrostreptomycin resulting from exposure to puromycin is greatest in both sensitive and resistant cells at concentrations below 100 microgram/ml. At 100 microgram/ml, exposure to puromycin in vivo results in significant, but not complete, polysome degradation and inhibition of protein synthesis. At 500 microgram/ml, where polysome degradation is complete in less than 2 min and where growth and protein synthesis are inhibited more than 90%, uptake of dihydrostreptomycin by both sensitive and resistant cells is inhibited. Puromycin has no effect on binding of dihydrostreptomycin to 70-S monosomes, as measured by equilibrium dialysis. The increased uptake of dihydrostreptomycin by resistant cells resulting from exposure to puromycin has no effect on viability. Addition of N-ethylmaleimide immediately and completely inhibits the puromycin-induced uptake of dihydrostreptomycin even when added after substantial polysome degradation has occurred.

Measurement of binding of chloramphenicol by intact cells.

The binding of chloramphenicol to intracellular components of intact cells was measured by procedures based on a silicone-wash technique. The number of stereospecifically bound molecules of chloramphenicol increased with external concentration to a saturation value equal to the number of ribosomes per cell. Chloramphenicol is therefore believed to be attached stereospecifically by a weak bond, most probably to a single site on the 50S ribosome. This bond was found to be temperature-dependent and appeared to be responsible for inhibition of protein synthesis.