EXPERIMENTAL CONTROL OF FLOWERING IN LEMNA. III. A RELATIONSHIP BETWEEN MEDIUM COMPOSITION AND THE OPPOSITE PHOTOPERIODIC RESPONSES OF L. PERPUSILLA 6746 AND L. GIBBA G3

Hillman , William S. (Yale U., New Haven, Conn.) Experimental control of flowering in Lemna. III. A relationship between medium composition and the opposite photoperiodic responses of L. perpusilla 6746 and L. gibba G3. Amer. Jour. Bot. 48(5): 413–419. Illus. 1961.—In a simple Hoagland-type medium, L. perpusilla 6746 flowers, irrespective of daylength; L. gibba G3 does not flower under any daylength, as long as the medium is changed frequently. Ethylenediaminetetraacetic acid (EDTA) prevents the flowering of L. perpusilla in long days but not in short, and brings about the flowering of L. gibba in long days but not in short. The same results are obtained with medium “aged” by the growth in it of L. gibba for several weeks (in any photoperiod) as well as with tartaric acid. The effectiveness of both EDTA and “aged” medium is greater at pH levels near 5 than at 4 or below, probably reflecting action through metal-chelation. These results are most easily interpreted as effects on photoperiodic sensitivity, and suggest a central role of metals in photoperiodism.     

Human breast epithelium in organ culture: Effect of hormones on growth and morphology

Summary Normal breast tissue from a 17-year-old girl was grown in organ culture for 3 weeks. A comparison was made between the effects on the epithelium of a defined culture medium containing various combinations of hormones and a serum-supplemented medium that has been used to successfully maintain other human tissues for 4 months routinely, and in some cases for up to 1 year. After culture for 3 weeks the explants were exposed to [³H]thymidine and autoradiographs were prepared and evaluated in order to determine labeling indexes. The only serum-free defined medium that permitted any significant survival or labeling of the cells contained insulin + hydroxycortisone + prolactin. However, serum-supplemented medium alone gave an even higher labeling index, and this was elevated more in media containing either progesterone or other combinations of hormones. Our study indicates that normal human breast (removed at the early postovulatory stage of the menstrual cycle) can be maintained in a differentiated state for 12 days in serum-supplemented media. By 2 weeks the cells had begun to migrate onto the surface of the explant. They then began to accumulate tonofilaments so that after 3 weeks in culture nearly all of the cells contained tonofilaments. The one exception was found in breast tissue cultured in the presence of human chorionic gonadotropin, where the cells maintained differentiated characteristics, despite the fact that they contained many lysosomes. This work was supported by Grant R01 CA20764 and in part by Contract N01-CP-95640 awarded by the National Cancer Institute.     

Group size and association patterns of the common eland (Tragelaphus oryx)

This paper presents data on aspects of the social organization of the eland antelope in the wild in Kenya, based on long-term observations of eland groups and of individual known animals. Group size varied from solitary animals to groups of several hundred. The largest groups always contained calves and juveniles, while small groups comprised adult animals only. Groups were largest in wet seasons in open grassland, and smallest in dry seasons in forest. Associations between individual eland were brief in duration, and group membership was in a constant state of flux. These findings are related to current knowledge of the social organization of antelope, and of the tribe Tragelaphini.     

Transduction in photoreceptors: Determination of the pigment transition or state coupled to excitation

Several recent reports have shown that light absorption by metarhodopsin does not contribute to the excitation of invertebrate photoreceptors at low intensities. Where the pigment transition scheme is known, this result may be used to exclude some or most of the transitions and states of the pigment as sources of the coupling to excitation. The methodology of this approach is described and illustrated.Based on material presented at the European Neurosciences Meeting, Florence, September 1978     

Gradual adjustment of circaseptan-circadian blood pressure and heart rate rhythms after a trans-9-meridian flight.

Circadian and circaseptan adjustment of blood pressure and heart rate after a transmeridian flight by a family of four was relatively fast, but it was not abrupt; it was not completed during the first week in the new setting. Gradual changes continued for the ensuing three weeks. The circadian and circaseptan rhythm characteristics and their adjustment in particular differed among variables in the husband: the circadian component of heart rate adjusted more rapidly than that of blood pressure. The adjustment also differed among two members of the family. A new phenomenon, namely a difference in circadian rhythm adjustment between husband and wife, is also described herein: the wife's circadian rhythm in blood pressure advanced by 9 hours within the 4-week span of recording following a 9-hour advance in living routine (after a 9-zone transmeridian flight); since both schedule and rhythm moved in the same direction (albeit not at the same rate), the behavior may be dubbed concursive. By contrast, the husband delayed to achieve the same adjustment: his behavior was anticursive. The phenomenon of a difference in direction of adjustment for different variables in the same subject has been described earlier as polarity, now qualified as intra-individual polarity, to separate it from the precedent of an intrafamilial or more broadly inter-individual polarity or partitioning, reported apparently for the first time and dubbed 'cursion'.     

The extended survival of tw5/tw5 mouse embryo cells in vitro

The tw5 haplotype is a recessive mutation which is lethal when homozygous in mouse embryos following implantation. This series of studies was undertaken to determine the effect of the tw5/tw5 genotype on embryos developing in vitro. Blastocyst embryos from +/tw5 inter se matings were compared with control blastocysts obtained from matings between T/+ and +/+ females and +/tw5 males for their abilities to continue development in vitro in two culture media. The data show that there are no significant differences between the percentages of experimental and control blastocyst embryos which attach and outgrow or which contain inner cell masses on any day of culture up to equivalent gestation day 21 in either media. These findings show that the life span of cells from tw5/tw5 embryos can be extended significantly by in vitro culture.