Gene amplification in methotrexate-resistant mouse cells. II. Rearrangement and amplification of non-dihydrofolate reductase gene sequences accompany chromosomal changes

Total amplified DNA in methotrexate-resistant mouse lymphoma EL4 cells and mouse melanoma PG19 cells has been characterized in two ways. Metaphase spreads show the presence of additional chromosome forms that are either “homogeneously staining” chromosomes or “double minute” and ring chromosomes. Gel electrophoresis of restriction enzyme-digested nuclear DNA shows the presence of amplified sequences, the pattern of which is unique in each of five cell lines. We conclude that extensive DNA rearrangement has taken place during amplification.     

The transition point for protein synthesis in late S-G2 may be delayed by genome bromosubstitution without affecting the time of entry into mitosis

Bromosubstitution for most of the S period in synchronous populations of Allium cepa L. meristematic cells resulted in a delay in the late S-G2 transition point where protein synthesis is needed for later mitotic entrance to occur. This retardation in the position of the transition point was not accompanied by the expected delay in the entrance into mitosis, suggesting that such protein synthesis is a requisite, but not a timer for prophase triggering.     

Survival and activity of Salmonella typhimurium and Escherichia coli in tropical freshwater

The survival of Salmonella typhimurium LT2 and Escherichia coli was studied in situ in a tropical rain forest watershed using membrane diffusion chambers. Numbers were determined by acridine orange staining and a Coulter counter. Population activity was determined by microautoradiography, cell respiration, frequency of dividing cells, and by nucleic acid composition. Numbers of Salm. typhimurium and E. coli decreased less than 1 log unit after 105 h as measured by direct count methods. Activity as measured by respiration, acridine orange activity, frequency of dividing cells, and microautoradiography indicated that both bacteria remained moderately active during the entire study. After 24 h, E. coli was more active than Salm. typhimurium , as measured by nucleic acid composition, and frequency of dividing cells. Both E. coli and Salm. typhimurium survived and remained active in this tropical rain forest watershed for more than 5 d, suggesting that Salm. typhimurium may be of prolonged public health significance once it is introduced into tropical surface waters. As E. coli was active and survived for a long time in this natural environment, it would seem to be unsuitable as an indicator of recent faecal contamination in tropical waters.     

Iron metabolism in iron-deficient male quail

1. Male quails submitted 20 and 120 days to a low iron diet (7 ppm) were compared to female laying quails, exposed for 30 days to the same low iron regime, in order to compare the response of the iron metabolic control under a single (erythropoiesis) or a doubled (erythropoiesis and egg formation) iron demand. 2. Iron deposit in storage organs, the classical hematology and the intestinal iron absorption were analyzed in these animals. 3. In males, after 120 days, the iron deposits were reduced 50 and 75%, but hematological values (hematocrit and hemoglobin concentration) were normal, although in laying quails, after 30 days, an anemic condition was evident in both blood parameters and iron deposits, provoking an iron deficient erythropoiesis. 4. The enhancement of the intestinal iron uptake, confirms the anemic character of these birds.     

An “orientation sphere” visualization for examining animal head movements

1. Animal behavior is elicited, in part, in response to external conditions, but understanding how animals perceive the environment and make the decisions that bring about these behavioral responses is challenging.
2. Animal heads often move during specific behaviors and, additionally, typically have sensory systems (notably vision, smell, and hearing) sampling in defined arcs (normally to the front of their heads). As such, head‐mounted electronic sensors consisting of accelerometers and magnetometers, which can be used to determine the movement and directionality of animal heads (where head “movement” is defined here as changes in heading [azimuth] and/or pitch [elevation angle]), can potentially provide information both on behaviors in general and also clarify which parts of the environment the animals might be prioritizing (“environmental framing”).
3. We propose a new approach to visualize the data of such head‐mounted tags that combines the instantaneous outputs of head heading and pitch in a single intuitive spherical plot. This sphere has magnetic heading denoted by “longitude” position and head pitch by “latitude” on this “orientation sphere” (O‐sphere).
4. We construct the O‐sphere for the head rotations of a number of vertebrates with contrasting body shape and ecology (oryx, sheep, tortoises, and turtles), illustrating various behaviors, including foraging, walking, and environmental scanning. We also propose correcting head orientations for body orientations to highlight specific heading‐independent head rotation, and propose the derivation of O‐sphere‐metrics, such as angular speed across the sphere. This should help identify the functions of various head behaviors.
5. Visualizations of the O‐sphere provide an intuitive representation of animal behavior manifest via head orientation and rotation. This has ramifications for quantifying and understanding behaviors ranging from navigation through vigilance to feeding and, when used in tandem with body movement, should provide an important link between perception of the environment and response to it in free‐ranging animals.

     

Changes in plasma thyroid hormones, luteinizing hormone (LH), estradiol, progesterone and corticosterone of laying hens during a forced molt

1. Circulating concentrations of iodothyronines, luteinizing hormone(LH), estradiol(E2), progesterone and corticosterone were measured in hens before, during, and after a forced molt induced by fasting. 2. Corticosterone increased at the onset of molt, peaked at the maximal molt and returned to pre- and post-molt levels. LH, E2 and progesterone declined during the molt, and the decline was coincident with the cessation of egg production. 3. Thyroxine(T4), triiodothyronine (T3) and reverse triiodothyronine(rT3) increased during the molt. The increases of T4 and T3 were not abolished even if the forced molt was conducted in mild weather.     

Intracellular calcium redistribution during mating in Chlamydomonas reinhardii

Gametes of the unicellular green alga Chlamydomonas reinhardii recognize and adhere to cells of the opposite mating type by flagellar contact. Adhesion between these specialized organelles signals a rapid series of mating events which result in gamete fusion. The sequence of morphological changes (flagellar tip activation, cell wall loss, and mating structure elongation), which occur as a consequence of the sexual signalling, have been characterized. The signalling mechanisms have, however, not been defined. Calcium is known to be involved during fertilization of animal species. Increased intracellular free calcium, which can be achieved either by calcium influx or by mobilization of ions from intracellular stores, has been observed during activation of both eggs and sperm. A recent report by Bloodgood & Levin that gametes of C. reinhardii preloaded with 45Ca showed a transient increase in Ca efflux following mating, suggests that intracellular Ca redistribution may also accompany mating in this algal species. We have used X-ray microanalysis to analyze the subcellular distribution of bound calcium during mating in Chlamydomonas reinhardii. X-ray maps reveal that calcium is sequestered in discrete granules within the gamete cell body prior to mating and that during activation and cell fusion, calcium is diffuse throughout the cell. This suggests the possibility that calcium serves as a second messenger in this species.     

The spread of somatosensory-evoked potentials within the nervous system

Four thalamic and cortical recordings were carried out in 5 patients. The thalamic-evoked potentials were typical and revealed a triphasic complex, but their latencies showed a relatively high standard deviation. They could be divided into two groups according to their latencies, both of which had low SD. These data suggested that there could be two types of latency of thalamic SEP, because the 4 patients' body sizes were very similar. More detailed surface, cortical and depth recordings are needed to resolve these questions.