Mitogen-induced B-cell differentiation in Xenopus laevis

Abstract. Four genes are known to affect pigmentation in the Mexican axolotl. The purpose of this article is to review previous information pertinent to these genes and to reevaluate such information in light of new evidence that demonstrates (in a preliminary way) how pigments, and subsequently phenotypes, are affected by the various pigment genes. Each of the mutant phenotypes – m (melanoid), ax (axanthic), a (albino), and d (white) - is compared to the wild type (D). All of these genes are recessives, all of them affect phenotypic changes during development, and three of the four ( m, a , and d ) also affect specific biochemical (i.e., pigment) changes during development. In the axolotl, color patterns can be directly correlated to the presence(or absence) of a variety of pigments that are normally found in discrete pigment cells. Qualitative and quantitative analyses of the bright-colored pigments (pteridines and flavins in this case) present in axolotl skin demonstrate that these pigments vary significantly among the various phenotypes under consideration. These analyses raise some interesting questions with regard to how each of the pigment genes is believed to act, and numerous possibilities for continued experimentation are suggested.     

Multiple redundant circadian oscillators within the isolated avian pineal gland

Summary The avian pineal gland contains a circadian pacemaker that oscillates in vitro. Using a flow-through culture system it is possible to measure melatonin production from very small subsections of an individual gland. We have used this technique to attempt to localize the oscillators in the pineal. Progressive tissue reduction did not affect the rhythmicity of cultured pineals. Multiple pieces (up to eight) from a single pineal all were capable of circadian oscillation — establishing directly that a pineal gland contains at least eight oscillators. All pineal pieces were responsive to light, and single light pulses shifted the phase of the melatonin rhythm. Because pieces equivalent to less than one per cent of the whole gland were rhythmic and because the capacity for oscillation was distributed throughout the gland, an individual pineal appears to be composed of a population of circadian oscillators.     

Analysis of intestinal cell proliferation after guanethidine-induced sympathectomy

Summary Guanethidine-induced sympathectomy in the rat during the neonatal period (injection of 20 g/g body weight every 48 h from day of birth until day 14) produces an absolute reduction in the number of sympathetic ganglion cells, but no significant alteration of body weight. Superior cervical ganglia show 79.8 % fewer cell bodies at 15 days and 92.3 % at 45 days; coeliac ganglia exhibit an 81.0 % reduction at 15 days and 89.6 % at 45 days in guanethidine-treated rats as compared to normal controls. The sympathetic ganglion cells that remain after treatment have an abnormal morphological appearance with distended mitochondria and depletion of endoplasmic reticulum. Sympathectomy produces a prolongation of the generation cycle time (Tc) as measured by the colchicine-induced mitotic arrest technique, and a decrease in labelling, mitotic, and migration indices. In addition, sympathectomy suppresses the amplitude of the circadian rhythm in mitotic activity. The general suppression of this activity in the intestinal epithelium is more pronounced in the jejunum and ileum than in the duodenum. Variation in the effectiveness of sympathectomy on the inhibition of intestinal cell proliferation may be related to segmental differences in cell proliferation, to segmental differences in innervation, and/or to segmental variation in the effectiveness of guanethidine.Supported by N.I.H. grant DE04557 to R.M.K. and N.I.H. grant 5-SO1-RR5373 to the University of Kansas Medical Center. The authors wish to acknowledge Charles A. Brownley, CIBA-Geigy, Summit New Jersey, U.S.A. for the gift of guanethidine-sulfate     

Gas-chromatographic resolution of the enantiomers of 3-(3,4-dihydroxyphenyl)alanine and its α-methyl analog

Methylation of (R,S)-DOPA with diazomethane gave the trimethyl derivative in which the phenolic hydroxy groups and the carboxy group were methylated. N-Methylated side products were also formed. N-Acylation of the racemic trimethyl derivative with (S)-α-methoxy-α-trifluoromethylphenylacetyl chloride gave two diastereomeric amides which were resolved by gas chromatography, the diastereomer derived from (S)-(−)-DOPA cluting first. The procedure was also applied to α-methyl-DOPA.     

Evidence for the influence of seagrasses on the benthic nitrogen cycle in a coastal plain estuary near Beaufort,North Carolina (USA)

A study was undertaken to evaluate the interrelationship between the presence of seagrasses, Zostera marina and Halodule wrightii, and the physical and chemical properties of sediments in a coastal plain estuary near Beaufort, North Carolina. In sediments underlying a cover of seagrass, silt-clay, organic matter, exchangeable ammonium, ammonium dissolved in pore waters and total nitrogen were larger than in unvegetated profiles. The magnitude of the physical and chemical properties of sediments varied according to the location of the station in relation to the vegetation, as well as the continuity in the distribution of the seagrass. The largest pools of nitrogen, the finest sediment texture, and the greatest organic matter content were in sediments associated with the mid bed regions of seagrass meadows, intermediate at the edges of the bed and small isolated patches of grass, and least in unvegetated substrate.General conclusions from this study are: 1) once established, seagrasses appear capable of modifying the sediment texture as well as the organic matter and nitrogen content; 2) nitrogen accumulates beneath the vegetation suggesting that vegetated sediments are sinks; however, functional recycling mechanisms seem to be operating as suggested by the larger magnitude of remineralized nitrogen in the vegetated profiles; and 3) the establishment of seagrasses in this geographical region are not necessarily restricted by the sediment properties measured in this study. These data and conclusions are discussed in regard to an application of contemporary theories of ecosystem development to seagrass systems.Contribution Number 82-22-B     

On Leeuwenhoek's magnifications

The thesis of this communication is that the secret method of Leeuwenhoek was the augmentation of the magnification of his single glass lens by the refraction at the quasi-hemispherical surface of a column of liquid containing the microorganisms. The linear increase in magnification thus secured could be as much as three-fold, depending on the degree of curvature of the liquid surface, the diameter of the column of liquid, and the index of refraction of the medium. This increase is more than adequate to account for the magnifications necessary for observation of details beyond the resolution of his best glass lenses. The hypothesis also accounts for the second part of the secret method, the high density of microorganisms in a single field of view, by successive reconstitutions of the curved surface of the medium.     

Circadian complexes: Circadian rhythms under common gene control

Summary Circadian rhythms for food and water consumption were measured in five inbred strains of mice under a photoperiod of 16 h light and 8 h dark (16:8 LD), and under constant light (LL).Significant strain differences were observed which indicate that a common gene difference, or set of differences inMus musculus influences both the phase angle () associating the rhythms with the light-dark cycle, and the periods (_LL) of circadian rhythms for food and water consumption. The biological clock mechanism influenced by this genetic variance is common to both food and water circadian rhythms, and differs among the five inbred strains. A positive genetic correlation was observed between the phase angle () and the period (_LL) of each rhythm. This observation can be understood in terms of a functional relationship between phase and period proposed by Pittendrigh and Daan (1976b) for the entrainment of a circadian oscillator by a light-dark cycle in nocturnal rodents.These results suggest that circadian rhythms for food and water consumption in mice are regulated by a common physiological mechanism, and would respond to natural selection as a single circadian complex under common gene control.