Different seasonal rearing conditions do not affect pheromone-sensitive receptor neurons of the adult cabbage looper moth, Trichoplusia ni

Abstract. In southern parts of the United States the cabbage looper moth, Trichoplusia ni (Hübner) (Lepidoptera: Noctuidae), is multivoltine, and therefore successive generations experience different environmental conditions during development from larvae to adults.Since environmental conditions are thought to influence pheromone communication, we tested the effects of two different temperature and light regimes (selected to mimic those occurring in the spring and summer growing seasons in the south) during rearing on the response characteristics of the adult male olfactory receptor neurons responsible for detecting the major component of the female pheromone.The dose-response functions of receptor neurons from the warm- and cold-reared insects were similar in both their slopes and thresholds to stimulation with the major component of the female-emitted pheromone, (Z)-7, dodecen-1-ol acetate and (Z)-7, dodecen-1-ol, a behavioural inhibitor.In double pulse experiments, designed to emulate the temporal dispersion of pheromone in nature, neurons were stimulated with short pulses (200 ms) of (Z)-7, dodecen-1-ol acetate separated by varying intervals.Intervals as short as 30 ms reduced the response to a second pulse by over 50%.When the intervals between pulses were longer than 2 s, significant differences were not seen between the responses to the first and to the second pulse.These temporal response patterns were similar in both warm- and cold-reared animals.     

Thyroid Hormone Receptors in the Developing Rat Brain

It is widely believed that the adult mammalian brain is insensitiveto thyroid hormones unlike the neonatal brain which is criticallydependent on these hormones for the development of normal structureand function. Recent studies have demonstrated the presenceof limited capacity, high affinity, triiodothyronine (T3) bindingnuclear sites in tissues that are considered responsive to thyroidhormones. Furthermore, there is evidence from studies on peripheraltissues that these T3 binding sites act as true receptors ininitiating thyroid hormone action. This report examines whetherthe higher sensitivity of neonatal brain to thyroid hormonesand the purported decline in sensitivity in adulthood are relatedto changes in the concentration and affinity characteristicsof thyroid hormone receptors in rat cerebral nuclei. Analysisof Scatchard plots of in vitro T3 binding data indicate thatcerebral nuclei from adult rats contain T3 specific nuclearbinding sites at a concentration comparable to that presentduring the period when the brain is critically dependent onthe presence of thyroid hormones and exceed that in the liver,a tissue generally considered thyroid sensitive. Neonatal thyroidectomysignificantly increased the number of binding sites. The resultsshow that the apparent unresponsiveness of the cerebral cortexof adult rats to thyroid hormones is not due to the absenceor a low density of T3 nuclear binding sites. The significanceof these results is discussed.     

Isolation of the Flagellar Swelling and Identification of Retinal in the Phototactic Flagellate, Ochromonas danica (Chrysophyceae)

Ochromonas danica, a freshwater, planktonic chrysophyte, is capable of sensing the light conditions of its environment. This biflagellate alga has a swelling near the base of the short flagellum and a chloroplastidic stigma in close association with it. A procedure is described for the isolation of this three dimensional flagellar swelling, the presumed photoreceptor. In contrast to an earlier method developed for the isolation of the paraflagellar swelling from Euglena gracilis, the protocol reported here for Ochromonas results in higher yields that should facilitate future biochemical investigations and could open avenues of investigation for the isolation and purification of the presumptive receptor protein. To verify the hypothesis that a rhodopsin-like protein might be present in this alga, we applied a standard extraction procedure successfully used in the identification of retinal. We here report the purification and identification of all-trans retinal in Ochromonas cells by column chromatography, HPLC and GC-MS. Since retinal is the chromophore of rhodopsin-like proteins, this finding may suggest that in these unicellular algae, too, a rhodopsin-like protein could be the photoreceptor pigment.     

Pulsed pheromone stimuli affect the temporal response of antennal receptor neurones of the adult cabbage looper moth

Abstract. Male cabbage looper moths, Trichoplusia ni (Hiibner) (Lepidoptera: Noctuidae), fly upwind in response to pheromone blends produced and released by calling conspecific females. Specialized sensilla on the male antenna contain sensitive, highly specific olfactory receptor neurones which respond to constant olfactory signals, with a phasic-tonic pattern of action potential discharge. Olfactory stimuli in nature are not uniform. They are thought to consist of pulses of odours whose distribution is shaped by wind and local environmental features. We begin to evaluate this natural situation by stimulating pheromone-sensitive sensilla with short (200 ms) paired pulses of the major component of the female's pheromone blend, (Z)-7-dodecen-l-ol acetate (Z-7,12:AC). Different stimulus protocols in which the pulses were separated from each other by varying intervals were evaluated. The interval between pulses had a large effect on the phasic component of the response. Intervals between pulses as short as 30 ms reduced the response to a second pulse by > 50%. When the intervals between pulses were longer than 3 s, significant differences were not seen between the responses to the first and second pulse. Implications for male orientation in natural, female-produced, pheromone plumes are discussed.