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T J Hara

Publications and source records attributed to T J Hara.

17 recordsLinked to original sources
PubMed1992

Ciliated and microvillar receptor cells degenerate and then differentiate in the olfactory epithelium of rainbow trout following olfactory nerve section.

We used scanning (SEM) and transmission (TEM) electron microscopy to examine ultrastructural changes in the olfactory epithelium (OE) of rainbow trout following unilateral olfactory nerve section. Both ciliated receptor cells (CRC) and microvillar receptor cells (MRC) degenerated and subsequently differentiated from unidentified precursor cells. The following changes took place in fish that were held at 10 degrees C at the stated period following olfactory nerve section: on day 7, MRC and CRC contained intracellular vacuoles; on day 12, the olfactory knobs appeared disrupted; by day 26, olfactory receptor cells were absent from the OE; on day 42, there were receptor cell bodies and a few CRC with short cilia at the apical surface; and on day 55, a small number of both CRC and MRC had differentiated. By day 76, both CRC and MRC repopulated the OE. Degenerative changes in the cytoplasm of the sustentacular cells (SC) and ciliated nonsensory cells (CNC) were observed in the first 26 days following olfactory nerve section, but these cells remained intact throughout the experiment. The degeneration and subsequent differentiation of CRC and MRC supports and extends previous observations that both cell types are olfactory receptor neurons with axons that extend along the olfactory nerve to the olfactory bulb.

Animals↗
PubMed1991

Sex pheromones selectively stimulate the medial olfactory tracts of male goldfish.

The olfactory tracts of teleost fish are comprised of medial and lateral sub-tracts which previous studies suggest convey responses to pheromones and food odors respectively. This study tested this possibility by recording electrical responses from the medial and lateral tracts of male goldfish exposed to sex pheromones and food odors. Only the medial olfactory tract responded to pheromones and both tracts responded to an L-amino acid and crude food odor. These findings verify earlier studies of peripheral olfactory sensitivity to pheromones and confirm that pheromonal information is carried within the medial tracts. They also suggest that the neural processes responsible for food recognition are more complex than previously supposed.

Animals↗
PubMed1991

Effects of cortisol on aspects of 3,5,3'-triiodo-L-thyronine metabolism in rainbow trout (Oncorhynchus mykiss).

Aspects of 3,5,3'-triiodo-L-thyronine (T3) metabolism were studied in fed rainbow trout (Oncorhynchus mykiss) held at 11.5-14 degrees and intraperitoneally implanted with hydrogenated corn oil (controls) or oil containing cortisol. Cortisol implants caused dose-related plasma cortisol elevations within the physiological range for 2-3 weeks, loss in body weight, and depression in plasma T3 and free T3 index with no consistent change in plasma thyroxine (T4) or free T4 index. Plasma T3 clearance rate and plasma T3 appearance rate were both increased by cortisol, with no change in hepatic microsomal T4 5'-monodeiodinase activity (Km or Vmax), but with a significant decrease in muscle T3 concentration. It is concluded that chronic physiologic cortisol treatment enhances plasma T3 clearance without change in hepatic T4 to T3 conversion, resulting in a decline in T3 concentration in both plasma and tissue (muscle) compartments.

Animals↗
PubMed1991

The olfactory system, not the terminal nerve, functions as the primary chemosensory pathway mediating responses to sex pheromones in male goldfish.

Studies of the neural mechanisms underlying responsiveness to sex pheromones in male goldfish suggest that, contrary to a currently popular hypothesis, the olfactory system (cranial nerve 1), and not the terminal nerve (cranial nerve 0), mediates chemosensory responses to pheromones. When the olfactory epithelium of male goldfish was exposed to two identified sex pheromones, 17 alpha, 20 beta-dihydroxy-4-pregnen-3-one and a mixture of prostaglandin F2 alpha and its metabolite 15-keto-prostaglandin F2 alpha, the spontaneous activity of olfactory neurons located in the medical portion of the olfactory bulb changed, while activity of terminal nerve cell bodies did not. A variety of other synthetic and natural odors also failed to alter the activity of terminal nerve cell bodies as did visual, magnetic, thermal, and auditory cues. Terminal nerve activity was, however, inhibited by tactile stimulation, suggesting that this system may have a modulatory role associated with the physical interactions that characterize goldfish spawning behavior.

Animals↗
PubMed1988

Morphological and physiological development of olfactory receptor cells in rainbow trout (Salmo gairdneri) embryos.

The morphological and functional differentiation of the olfactory receptor cells were investigated in developing rainbow trout (Salmo gairdneri) embryos by means of light and electron (transmission and scanning) microscopy and electrophysiology. Ciliated receptor cells first appeared when the olfactory placode was folded to form a groovelike structure rostrad to the eye at stage 24 (day 18; 18 days postfertilization). Ciliated receptor cells predominated until immature microvillar receptor cells developed in stage 28 (day 26) embryos. At stage 29, the day of hatching, the anterior edge of the olfactory epithelium contained only ciliated receptor cells, and the midregion contained both ciliated and microvillar receptor cells. Spontaneous neural firing activity was recorded from the olfactory mucosa as early as stage 25. The neural responses to amino acids were initially recorded from stage 26 embryos, containing sparse ciliated receptor cells with a few short cilia. The D-enantiomers of amino acids were less effective. From these results we concluded that in rainbow trout the olfactory receptor cell has two separate morphological forms, ciliated and microvillar. These are ontogenetically distinct; the ciliated receptor cells preceded the microvillar. The ciliated receptor cells respond to amino acid stimulation.

Action Potentials↗
PubMed1988

F prostaglandins function as potent olfactory stimulants that comprise the postovulatory female sex pheromone in goldfish.

This study establishes that ovulated female goldfish release F type prostaglandins (PGFs) to the water where they stimulate male spawning behavior and comprise the goldfish postovulatory pheromone. We first demonstrated that ovulated and prostaglandin-injected female goldfish release immunoreactive PGFs to the water. Next, using electro-olfactogram recording (EOG), we determined that waterborne prostaglandins function as potent olfactory stimulants for mature male goldfish. Prostaglandin F2 alpha (PGF2 alpha) and its metabolite 15-keto-prostaglandin F2 alpha (15K-PGF2 alpha) were the most potent prostaglandins; the former had a detection threshold of 10(-10) M and the latter a detection threshold of 10(-12) M. Studies of prostaglandin-injected fish indicated that PGF metabolites are an important component of the pheromone. Cross-adaptation experiments using the EOG demonstrated that goldfish have separate olfactory receptor sites for PGF2 alpha and 15K-PGF2 alpha that are independent from those that detect other olfactory stimulants. Finally, we established that male goldfish exposed to low concentrations of waterborne PGFs exhibit reproductive behaviors similar to those elicited by exposure to the odor of ovulated fish. Together with our recent discovery that a steroidal maturational hormone functions as a preovulatory "priming" pheromone for goldfish, these findings suggest that hormones and their metabolites may commonly serve as reproductive pheromones in fish.

Animals↗
PubMed1986

A protocol for estimation of cortisol plasma clearance in acid-exposed rainbow trout (Salmo gairdneri).

The cortisol metabolic clearance rate (MCR) and degradation rate (DR) were determined in acid (H2SO4)-stressed and control rainbow trout (260 g) cannulated via the dorsal aorta. Recovery from catheterization, as judged by plasma cortisol, glucose, protein, and packed cell volume (PCV), was complete by 6 days. However, serial blood sampling increased plasma cortisol. Furthermore, although no major or consistent diel change in plasma cortisol occurred in terminally sampled free-swimming control trout, fluctuations were observed in serially bled catheterized trout. These findings preclude cortisol MCR estimation by any serial sampling method. Although plasma cortisol was temporarily elevated by constant infusion (70 microliter hr-1) of saline:ethanol vehicle, a satisfactory protocol was established for determining cortisol MCR by infusion of labeled cortisol to constant plasma specific activity. The MCR for control trout in water, pH 7.7, for 7 days was 30.3 +/- 4.2 ml hr-1 100 g-1, which did not differ from that of trout in water, pH 5.0. However, the cortisol DR was greater at pH 5.0 (2.13 +/- 0.46 micrograms hr-1 100 g-1) than at pH 7.7 (0.56 +/- 0.12) due primarily to increased plasma cortisol at pH 5.0.

Animals↗
PubMed1985

The characteristics of the electro-olfactogram (EOG): its loss and recovery following olfactory nerve section in rainbow trout (Salmo gairdneri).

Electro-olfactograms (EOGs) were recorded from both sensory and non-sensory epithelia on the olfactory lamellae and from other areas within the rosette of rainbow trout (Salmo gairdneri). The trout EOG induced by amino acids was a monophasic negative voltage composed of a phasic component which declined to a steady level (tonic component) that was maintained throughout stimulus duration. The time period (2 min) for complete recovery of the EOG was obtained by applying two identical stimuli (10(-5) mol/liter L-serine for 5 s) successively at increasing intervals. EOG response to amino acids increased nearly exponentially with concentration and no saturation was reached. Gradual deterioration of olfactory receptor cells occurred within 14 days after olfactory nerve section (axotomy) as indicated by phospholipid staining. Regeneration of the receptor cells started at 56 days postaxotomy, reached approximately normal density and the elongate form of mature neurons at 84 days. In axotomized fish the magnitude of EOG response decreased relative to the controls at 7 days with minimal sensitivity between 14 and 28 days postaxotomy. EOGs were not evoked by L-serine nor L-leucine in most fish 17-22 days postaxotomy. Restoration of the EOG response coincided with morphological repopulation of receptor neurons after 84 days. EOG recovery was only 50% of the control values at 230 days. The EOG responses evoked by HCl in sensory and non-sensory epithelia were indistinguishable from each other, indicating that receptor neurons are not likely to be their primary origin.

Amino Acids↗
PubMed1975

Olfaction in fish.

1. Recent progress in the studies on olfaction in fish, with particular emphasis on electrophysiological and behavioral responses to biological odors and related chemicals, is reviewed. 2. One of the most characteristic features in fish olfaction is that it takes place entirely in the aquatic environment. The carrier of stimulant molecules is not air but water; therefore, chemicals that are detected olfactorily by fish need not be volatile, but must be soluble in water. 3. The olfactory organs of fishes are diversely developed. At one extreme they are well developed (macrosmatic) such as in sharks and eels, and at the other they are poorly developed (microsmatic) such as in pike and stickleback. 4. The nasal cavity is lined with the olfactory epithelium, which is raised from the floor of the organ into a series of lamellae to make a rosette. The arrangement, shape and degree of development of the lamallae in the rosette vary considerably from species to species. 5. It is doubtful whether simple relation exists between the surface area of the olfactory epithelium and sensitivity to odors, since the sensory epithelium is not distributed uniformly over the surface of the olfactory lamellae. 6. The olfactory epithelium of fish, like other vertebrates, consists of three cell types: receptor cells, supporting cells and basal cells. 7. The receptor cell, which is a bipolar primary sensory cell, sends a slender cylindrical dendrite toward the surface of the epithelium and is directly connected with the olfactory bulb by its axon. The dendrite terminates in a minute swelling (olfactory knob) which bears a variable number of cilia. 8. The information from the receptor cell is conveyed into the olfactory bulb, the first relay station, where signals are processed and integrated. The dominant feature of the bulb is the synaptic contact between the primary and secondary olfactory neurones in the form of glomerulus. 9. All the available evidence points to a great acuity of the olfactory sense in many fish species both in the capability and discriminating odorous chemicals. However, much discrepancies exist among data obtained by behavioral and electrophysiological techniques mainly because of the lack of systematic investigations. 10. Electrophysiological studies of olfaction have been hampered by the extremely small size of the olfactory neurones. 11. A slow negative monophasic potential is induced in the olfactory epithelium when stimulated with odorous chemicals (electro-olfactogram, EOG).(ABSTRACT TRUNCATED AT 400 WORDS)

Animals↗