Effects of rutin-fed caterpillars on an invertebrate predator depend on temperature

Summary A factorial experiment examined the effects of varying concentrations of the allelochemical rutin in caterpillars and the length of time the caterpillars had fed on the behavioral interactions of predatory stinkbugs (Podisus maculiventris) and their prey (Manduca sexta). Diet had no significant effect on defensive behavior of the caterpillars. The length of time that the caterpillars had fed (1 vs. 24 h) only influenced the frequency of caterpillars knocking the attacking stinkbugs away, with caterpillars knocking the stinkbugs away more often after 24 h of feeding. A second experiment tested the effects of diet (prey fed various concentrations of rutin), temperature (18° C and 28° C) and gender on consumption and growth parameters of fifth instar stinkbugs. At the cooler temperature, the bugs ate more, gained more weight but took twice as long to complete the stadium and consequently had reduced relative consumption and relative growth rates. Diet had no significant effect on biomass gained or stadium duration, but rutin-fed caterpillars did depress the stinkbugs' relative consumption rates. The effect of food quality on relative growth rate (RGR) was temperature dependent; rutin had no significant effect at the cooler temperature, but a high dose of rutin reduced RGR at the warmer temperature. Rutin had a greater negative impact on the females than the males. The effect of rutin on these predators was different than the effect on their prey (this study compared to Stamp (1990, 1992)): the negative effects of rutin seem to impact on the stinkbug's growth rather than on molting.     

The role of ovarian sympathetic innervation in the control of estrous responsiveness in the rat

This study examined the contribution of the superior ovarian nerve (SON) to estrous responsiveness and ovarian function in cycling rats. Section of the SON was carried out at 1100 on proestrus, and lordotic responsiveness was measured at 1500, 1700, and 2100 on that day and at 0900, 1200, and 1500 on the day of estrus. SON section decreased lordosis intensity significantly at 1500 and 1700 on proestrus and at 0900 on estrus. Pacing of sexual contacts with males was decreased at 2100 in nerve-sectioned (Nervx) animals when compared with sham-operated controls (SHAM). Serum progesterone (P) concentrations were significantly lower in Nervx animals than in Sham animals 30 min after surgery, but were not different between groups at 4.5 hr. Serum estradiol (E2) concentrations did not differ between groups at either time. In addition, Nervx and Sham groups did not differ on measures of pregnancy/pseudopregnancy initiation or on measures of ovarian function 10 days after surgery. These data suggest that the integrity of the SON is necessary for the display of full estrous responsiveness in cycling rats, and suggest that the acute decreases in serum P occurring as a consequence of SON section may be responsible for the deficits seen in Nervx animals.     

Trimethyloxonium modification of single batrachotoxin-activated sodium channels in planar bilayers. Changes in unit conductance and in block by saxitoxin and calcium

Single batrachotoxin-activated sodium channels from rat brain were modified by trimethyloxonium (TMO) after incorporation in planar lipid bilayers. TMO modification eliminated saxitoxin (STX) sensitivity, reduced the single channel conductance by 37%, and reduced calcium block of inward sodium currents. These effects always occurred concomitantly, in an all-or-none fashion. Calcium and STX protected sodium channels from TMO modification with potencies similar to their affinities for block. Calcium inhibited STX binding to rat brain membrane vesicles and relieved toxin block of channels in bilayers, apparently by competing with STX for the toxin binding site. These results suggest that toxins, permeant cations, and blocking cations can interact with a common site on the sodium channel near the extracellular surface. It is likely that permeant cations transiently bind to this superficial site, as the first of several steps in passing inward through the channel.     

Effect of 5 alpha-dihydrotestosterone on sexual receptivity and neural progestin receptors in ovariectomized rats given pulsed estradiol

Experiments were carried out to examine the mechanism whereby 5 alpha-dihydrotestosterone (DHT) antagonizes the stimulatory effects of estrogen plus progesterone (P) on sexual receptivity (lordosis) in the ovariectomized rat. Estradiol (E2; 1 microgram s.c. in 10% ethanol) was administered in a discontinuous (pulsed) treatment regimen thought to mimic phase requirements of estrogen action; two injections of E2 were given either 6 or 12 h apart (first injection, Hour 0). Progesterone (0.5 mg in oil) was injected at Hour 20, and behavioral testing occurred at Hour 24. Dihydrotestosterone (2.5 mg s.c. in 10% ethanol/propylene glycol) inhibited lordosis when it was given before (-12 or -3 h), between (+3, or -3 and +3 h), or after (+8 h) the two E2 injections, but was not effective when given at +20 h. Significant inhibition of E2 + P-induced lordosis was achieved by 2.5 but not 1.0 or 0.2 mg DHT at -3 h, while uterine weights in the same animals were reduced significantly by 2.5 and 1.0 mg DHT. Serum E2 and DHT concentrations peaked rapidly after injection, declining to near baseline by 3 and 12 h, respectively. Induction of cytosolic progestin receptors (cPR) in the preoptic area and medial basal hypothalamus by estrogen was not prevented by DHT when animals were given the two pulsed E2 injections or daily injections of estradiol benzoate, although P was able to override the inhibitory behavioral effects of DHT in the latter but not the former group.(ABSTRACT TRUNCATED AT 250 WORDS)     

Micro Radiometric Method for Study of Acid-insoluble Materials in Monolayer Cell Cultures

A simple radiometric procedure for study of acid-insoluble products synthesized in monolayer cell cultures is described. Cell cultures were produced directly on the bottom surface of scintillation vials or on glass cover slips (8 X 30 mm). The cells were labeled and extracted; the radioactivity was determined while the cells remained affixed to the glass surface upon which they were grown. This procedure enabled rapid investigations of certain biosynthetic processes to be carried out by using many individual cell cultures. The method was applied to an investigation of (3)H-thymidine incorporation induced by vaccinia virus in a 5-bromodeoxyuridine-resistant cell line. (14)C-labeling was evaluated as an alternate procedure for cell quantitation.     

Relative apparent synapomorphy analysis (RASA). I: The statistical measurement of phylogenetic signal

We have developed a new approach to the measurement of phylogenetic signal in character state matrices called relative apparent synapomorphy analysis (RASA). RASA provides a deterministic, statistical measure of natural cladistic hierarchy (phylogenetic signal) in character state matrices. The method works by determining whether a measure of the rate of increase of cladistic similarity among pairs of taxa as a function of phenetic similarity is greater than a null equiprobable rate of increase. Our investigation of the utility and limitations of RASA using simulated and bacteriophage T7 data sets indicates that the method has numerous advantages over existing measures of signal. A first advantage is computational efficiency. A second advantage is that RASA employs known methods of statistical inference, providing measurable sensitivity and power. The performance of RASA is examined under various conditions of branching evolution as the number of characters, character states per character, and mutations per branch length are varied. RASA appears to provide an unbiased and reliable measure of phylogenetic signal, and the general approach promises to be useful in the development of new techniques that should increase the rigor and reliability of phylogenetic estimates.      

A general assay for restriction endonucleases and other DNA-modifying enzymes with plasmid substrates

A procedure for measuring the activities of enzymes that alter the covalent structure of DNA is described. The assay utilizes covalently closed circles of DNA as the substrate and yields quantitative data on the fraction of this DNA converted to both open-circle and linear forms.     

Field evaluation of a model of photothermal flowering responses in a world lentil collection

A model to predict flowering time in diverse lentil genotypes grown under widely different photothermal conditions was developed in controlled environments. The present study evaluated that model with a world germ plasm collection of 369 accessions using two field environments in Syria and two in Pakistan. Photoperiod alone accounted for 69% of the variance in 1/f, the reciprocal of time (d) from sowing to flower. In contrast, temperature alone did not account for a significant proportion of variation in flowering time due to the exposure of plants to supra-optimal temperatures in the late-sown Syrian trial. With the model mean pre-flowering values of photoperiod and temperature combined additively to account for 90.3% of the variance of 1/f over accessions. The correlation of field-derived estimates of temperature sensitivity of accessions to glass-house-derived estimates was significant at P = 0.05, but the equivalent correlation for estimates of photoperiodic sensitivity was higher at P < 0.01. Flowering in the field was better measured as time from sowing to 50% plants in flower rather than time to first bloom or its node number. Dissemination of the lentil crop following domestication in West Asia to the lower latitudes such as Ethiopia and India has depended on selection for intrinsic earliness and reduced sensitivity to photoperiod. Movement from West Asia to the higher latitudes accompanied by spring sowing has resulted in a modest reduction in photoperiod sensitivity and an increase in temperature sensitivity.     

Variation in heat-shock proteins among species of desert fishes (Poeciliidae, Poeciliopsis)

Analysis of the heat-shock proteins (hsps) of six closely related species of Poeciliopsis demonstrated the existence of biochemical diversity in the hsp100, hsp70, hsp60, and hsp30 protein families among species. Each species expressed five to seven hsp70-related isoforms. Constitutive 70-kD isoforms were identical among species, but four different patterns of heat-inducible isoforms were seen in these six species. Members of the hsp70 family of molecular chaperones are included among the most highly conserved proteins known, and the possibility of variation in hsp70 among closely related species has rarely been addressed. The hsp30 family is known to be less conserved than the hsp70 family, and, as expected, the Poeciliopsis hsp30 patterns showed more variation. Most of the hsp30 isoforms characteristic of a particular species were unique to that species. Hsp100 and hsp60 were identical in five of the species, but alternate isoforms were found in P. monacha. The small size and limited geographical distribution of the P. monacha population have probably contributed to the uniqueness of the monacha pattern. Two of the species were shown to acquire thermotolerance, the ability to withstand normally lethal temperatures when subjected to a gradual temperature increase. Rapid-heating protocols commonly used to establish critical thermal maxima of organisms do not include this inducible component of thermoresistance and therefore do not adequately assess an organism's capacity to withstand thermal stress.