The outlook for cosmic company.

The last 100 million years or so has seen a continued increase in encephalization for several terrestrial species. Intelligence has survival value. Developments in astrobiology suggest that what was once considered enormously improbable, namely life, is now suspected of being ubiquitous. It may be that the evolution of intelligence is unlikely, but in a finite, breathtakingly large universe (10(22) stars) small probability likely does not matter. Even if nature is indifferent to producing intelligence, SETI might still succeed. Biological intelligence may be rare, but it has the potential for creating engineered synthetic intelligence, capable of rapid and directed self-evolution. The galaxy could be rife with such long-lived, communicating devices, even if intelligent protoplasm is both rare and fleeting. SETI is looking for narrow-band, microwave signals that are not produced naturally. Ultimately, SETI is more exploration than experimentation.

Reproductive, metabolic, and endocrine responses to feed restriction and GnRH treatment in primiparous, lactating sows.

The current experiment was carried out to determine whether exogenous GnRH treatment in primiparous, lactating sows undergoing feed restriction would improve reproductive performance after weaning. Sows were allocated to one of three treatments: AA sows (n = 8) were fed to appetite throughout a 28-d lactation, AR (n = 12) and AR + GnRH (n = 12) sows were fed as AA sows from farrowing to d 21 of lactation, and feed intake was reduced to 50% of the ad libitum intakes from d 22 to 28. The AR + GnRH sows received 800 ng of GnRH i.v. every 6 h from d 22 to 28 of lactation, and AA and AR sows received saline. Sow weight, backfat, and litter weight were recorded weekly. Within 2 d after farrowing, litter size was standardized to 8 to 10. At d 17 of lactation, an indwelling jugular catheter was surgically implanted in each sow. Blood samples were taken for characterization of plasma LH, FSH, insulin, IGF-I, and leptin by RIA at d 21 and before and after weaning on d 28 of lactation. After weaning, all sows were given ad libitum access to feed, checked for onset of standing estrus twice daily with mature vasectomized boars, and inseminated 12 and 24 h after onset of standing estrus with pooled semen from the same fertile boars (3 x 10(9) sperm/AI). After breeding, feed allowance was reduced to NRC (1988) requirements for gestation. At d 28 +/- 3 of gestation, sows were killed and ovulation rate and embryo survival were determined. Restricted sows lost more weight during lactation than AA sows (P < .02). During the period of feed restriction, plasma IGF-I and postprandial insulin and leptin in AR and AR + GnRH sows, and LH pulse frequency in AR sows, were lower than those in AA sows (P < .04). Associations (P < .004) between plasma insulin and leptin and between leptin and mean LH concentrations were established. The LH pulse frequency in AR + GnRH sows did not differ from that in AA sows before weaning. After weaning, maximum, mean, and minimum LH concentrations in the AA and AR sows, and FSH concentrations in AR sows, increased (P < .05) in response to weaning. Paradoxically, GnRH treatment in lactation seemed to suppress the expected LH and FSH responses to weaning. Ovulation rate and embryo survival were not different among the three groups. In conclusion, although exogenous GnRH therapy restored LH secretion in feed-restricted sows, it did not improve overall reproductive performance.

A symbiogenetic theory for the origins of cnidocysts in Cnidaria.

Did cnidarian cnidocysts originate from cnidocyst-bearing protoctistans living as symbiotic partners with an epithelial placula? If an increase in the fitness of symbiotic partners was "locked in" by an evolutionary stable strategy, co-evolution and compartmentalization could have led phyletically separate, eukaryotic symbionts to fuse and undergo nuclear merger. Traits originating in the symbiotic partners would have been brought to the "synthetic" organism and reworked through evolution into the development of an integrated organism. Support for the theory of symbiogenetic origins of Cnidaria rests on traces of symbiosis detected in the relationship of cnidarian epithelium to interstitial cells (I-cells), the precursors of cnidocyst-producing cnidoblasts: (1) epithelium and I-cell are autonomous and differ in morphology, cellular dynamics, the relationship of differentiation to proliferation and the variety of cell types formed; (2) hydras and planulas can be "cured" of I-cells and their derivatives, thereby creating "epithelial" animals which lack responsiveness but retain vegetative properties. (3) The reintroduction of I-cells into "epithelial" animals which lack responsiveness but retain vegetative properties. (3) The reintroduction of I-cells into "epithelial" animals restores missing differentiated cell and organismic characteristics. Symbiogenesis as a source of metazoan species has consequences for concepts of development, from the origins of cell lines to the evolution of differentiation.

Total and free thyroid hormones in plasma of tropical marine teleost fish.

Plasma levels of L-thyroxine (T4) and 3,5,3'-triiodo-L-thyronine (T3) and the percentage of plasma T4 and T3 present in the free (dialyzable) form (%FT4 and %FT3) were measured in 16 species (11 families) of tropical marine teleosts from an inshore Barbados reef. Mean plasma T4 varied from 0.2 ng/ml to 42 ng/ml; mean plasma T3 varied from < 0.2 ng/ml to 50 ng/ml. The highest T4 and T3 levels were recorded in parrot-fish and the lowest levels in filefish. The %oFT4 and %FT3 varied from 0.05-3.41%. Estimated levels of plasma free T4 and free T3 levels ranged from 0.4-466 pg/ml. The extremely wide inter- and intra-species ranges in levels of free T4 and T3 do not support a previous suggestion, based on temperate freshwater salmonid species, that free T4 and T3 levels in fish may fall within a relatively range narrow comparable to that of homeothermic vertebrates.

Effects of catecholamines on plasma thyroid hormone levels in arctic charr, Salvelinus alpinus.

Plasma levels of L-thyroxine (T4) and 3,5,3'-triiodo-L-thyronine (T3) were measured in arctic charr at 2, 6, or 24 hr after single intraperitoneal injection of epinephrine (E) or norepinephrine (NE). At a dose of approximately 1 microgram/g body wt (sufficient to cause a submaximal dermal melanophore pallor response) plasma T4 was usually elevated at 2 hr, consistently depressed at 6 hr, and unaffected at 24 hr. There was no effect of E on plasma [125I]T4 kinetics or [125I]T4 5'-monodeiodination to [125I]T3. Plasma T3 showed no consistent response to E or NE at any sampling time. At an E dose of 4 ng/g body wt (probably sufficient to cause a physiological elevation in plasma E level), neither plasma T4 nor T3 levels were altered at 6 hr. Acute depression in plasma T4 by the high doses of E and NE may reflect a local neurotransmitter role of catecholamines in inhibiting thyroidal T4 release through action at thyroidal, hypophysial, or hypothalamic levels.

Influences of temperature and pH on free T4 and free T3 in charr and trout plasma.

The influences of temperature and pH on the percentages of T4 (L-thyroxine) or T3 (3,5,3'-triiodo-L-thyronine) in the free form (%FT4 or %FT3) were determined by equilibrium dialysis on Arctic charr and rainbow trout plasma. %FT4 and %FT3 of plasma from trout or charr acclimated at 12-13 degrees increased with dialysis temperature (5-19 degrees). When charr plasma was dialyzed at fish acclimation temperature (5, 13, 20 degrees), %FT4 and %FT3 also increased with temperature. However, when plasma from charr acclimated at 5, 13, or 20 degrees was dialyzed at 13 degrees, %FT4 and %FT3 showed no dependence on previous thermal acclimation. %FT4 of charr plasma increased with dialysis pH (7.0-7.8); %FT3 was less responsive to pH but was lower at pH 7.0-7.4 than at pH 7.6-8.0. It is concluded that acute in vitro physiologic changes in either temperature or pH alter the proportions of plasma T4 and T3 in the free form; comparable in vivo effects could explain aspects of environmentally modified T4 and T3 metabolism.

Free T4 and T3 in relation to total hormone, free hormone indices, and protein in plasma of rainbow trout and arctic charr.

The percentages of total L-thyroxine (TT4) and total 3,5-3'-triiodo-L-thyronine (TT3) in the free form (%FT4 and %FT3) were measured in plasma from trout or charr by equilibrium dialysis at 12 degrees and by an index employing miniature G-25 Sephadex columns at room temperature. Dialysis estimates of both %FT4 and %FT3 were highly correlated with their respective column indices (rT4 = 0.84; rT3 = 0.92) validating the latter as a rapid and convenient method for monitoring alterations in plasma T4 or T3 binding. Binding depended on both pH and buffer composition. In charr, %FT4 (usual range 0.15-0.28%) exceeded %FT3 (usual range 0.09-0.17%); similar values were obtained for trout. The %FT4 values were much higher and the %FT3 values somewhat lower than those reported for mammals and birds. However, when TT4 and TT3 were taken into account, mean estimated concentrations of charr free T4 (FT4) and free T3 (FT3) were respectively 5.0 and 3.2 fmol/ml. These values are comparable to those in birds and mammals and suggest that FT4 and FT3 correspond more closely between various vertebrates than either TT4 and TT3 or %FT4 and %FT3. Plasma protein levels were correlated inversely with %FT4 (r = -0.54) and with %FT3 (r = -0.81) and correlated directly with TT4 (r = 0.45) and TT3 (r = 0.64). Despite these trends, FT4 and FT3 were highly correlated with their respective total hormone levels (r T4 = 0.95; rT3 = 0.94). Thus, for this charr population at least, TT4 and TT3 are representative of peripheral thyroidal status, as judged by the theoretically more physiologically relevant FT4 and FT3 levels.

Influence of potassium thiocyanate on thyroid function of rainbow trout, Salmo gairdneri.

Sublethal doses of potassium thiocyanate (KSCN), an iodide competitor, depressed thyroidal radioiodide uptake of fed laboratory rainbow trout at 11 degrees, but did not depress either plasma levels of T4 (L-thyroxine) and T3 (triiodo-L-thyronine) or radioiodide incorporation into plasma iodothyronines. Furthermore, plasma T4 levels of KSCN-treated trout increased to levels comparable to those of control trout in response to bovine TSH. The apparent inability of KSCN to inhibit thyroid hormone synthesis and release may be due to non-carrier-mediated iodide diffusion into the thyroid from the high iodide concentration normally found in plasma of freshwater salmonids. In conclusion, KSCN is not a practical inhibitor of thyroid hormone release in laboratory trout, and thyroid radioiodide uptake is a highly misleading index of thyroidal status.

Reverse T3 in rainbow trout, Salmo gairdneri.

Plasma levels, peripheral metabolism and extrathyroidal in vivo production of reverse T3 (rT3 = 3,3',5'-triiodo-L-thyronine) were studied in rainbow trout at 12 degrees C. Plasma rT3 levels (less than 40 pg/ml) corresponded to the detection limit of the radioimmunoassay. By in vitro analysis, a high proportion (0.95%) of rT3 added to plasma existed in the free (dialyzable) form. Injected [125I]rT3 was cleared more rapidly from plasma (minimum MCR = 7.7 ml/hr/100 g) than T3. No phenolic (outer ring) rT3 deiodination was observed. rT3 rapidly entered the liver and up to 70% of the injected [125I]rT3 was lost via the biliary route, mainly as unidentified derivatives; about 10% of the biliary-excreted 125I label was identified as rT3 or its glucuronide conjugate. Using Sephadex column chromatography combined with specific antibody separations, it was not possible to demonstrate in vivo [125I]rT3 production from [125I]T4. It is concluded that in laboratory trout, in contrast to the situation in mammals, the T4 to rT3 pathway is not prominent and that iodothyronine deiodination is restricted to T3 formation. These findings may relate to differences in extrathyroidal iodine metabolism between trout and mammals.

Factors influencing nursing in Macaca fascicularis.

Nursing by two mother-infant pairs in a caged colony of Macaca fascicularis was monitored at 1-min intervals for 8 h beginning 8:30 a.m. BST, once a week for 3 months in the summer of 1973. Nursing occupied about 210 min in 8 daylight hours for the infants at 10 weeks of age, and the time spent nursing decreased at the average rate of 9.4 min per week until the infants were about 6 months old. The time spent nursing by the infants studied here resembles closely the times spent nursing by some other macaques and by baboons. In the course of a day the amount of time spent nursing varies significantly with a diurnal peak. If nursing by one mother-infant pair is independent of nursing by the other pair, then the time the two pairs spend nursing together would be a function of the product of the frequencies of nursing by each pair. The expected times for the pairs nursing together based on the hypothesis of independent events were significantly less than the observed times the pairs nursed together. Nursing, therefore, involves a positive influence or imitation of one nursing pair by the other. Nursing sessions involving both mother-infant pairs were longer on the average than sessions involving only one pair.

Morphogenetic gradients in moltiple-graft Hydra viridis. I. The effects of colcemid and colchicine.

The morphogenesis of so-called secondary (2 degree) heads, budding regions and feet, and separations at graft borders, is studied in multiple-graft animals containing three gastric regions (3g animals) treated with Colcemid or colchicine. Control animals consist of three non-treated pieces. Animals consisting of two non-treated and one treated piece are also employed. The main effects of Colcemid are the promotion of graft healing at the distal graft border, and of 2 degree head formation on the proximal gastric region (g-1). Colchicine also promotes graft healing at the distal graft border, but in contrast to the effect of Colcemid, promotes the formation of ectopic feet (tertiary feet) and inhibits head regeneration at the distal end of the middle gastric region (g-2). Colchicine also accelerates an inversion of polarity in 2 degree budding regions on the g-2 pieces of animals with 2 degree heads on their g-1 pieces. Treatment of a distal graft piece with Colcemid promotes 2 degree head formation on the nearest proximal piece which is not treated, but the inhibition of 2 degree head formation by colchicine occurs only on colchicine treated pieces. The morphogenetic effects of the drugs are interpreted as consequences of their actions on nerve differentiation and cell division. The paper argues that homeostatic control of a hydra's cell population depends on dividing cells influencing cell loss, and that similar mechanisms are involved in the rejection of a graft and the separation of a bud.