Electrophysiological and behavioral correlates of sleep in the desert iguana, Dipsosaurus dorsalis Hallowell

The circadian behavior of the desert iguana, Dipsosaurus dorsalis, was investigated on the basis of behavioral observation and electrophysiological recording. D. dorsalis adequately complies with accepted criteria for both behavioral sleep and paradoxical sleep. At 20 degrees C, 12% of the photophase is spent in sleep, 95% of the scotophase is spent in sleep. Paradoxical sleep occurs at all times of the year, but only at temperatures of 20 and 30 degrees C. Amounts of behavioral sleep are affected by both temperature and time of year. Total sleep increases with decreased day length and decreased temperature. Daytime sleep increases with decreased temperature.     

On the Structure-Bounded Growth Processes in Plant Populations

If growing cells in plants are considered to be composed of increments (ICs) an extended version of the law of mass action can be formulated. It evidences that growth of plants runs optimal if the reaction–entropy term (entropy times the absolute temperature) matches the contact energy of ICs. Since these energies are small, thermal molecular movements facilitate via relaxation the removal of structure disturbances. Stem diameter distributions exhibit extra fluctuations likely to be caused by permanent constraints. Since the signal–response system enables in principle perfect optimization only within finite-sized cell ensembles, plants comprising relatively large cell numbers form a network of size-limited subsystems. The maximal number of these constituents depends both on genetic and environmental factors. Accounting for logistical structure–dynamics interrelations, equations can be formulated to describe the bimodal growth curves of very different plants. The reproduction of the S-bended growth curves verifies that the relaxation modes with a broad structure-controlled distribution freeze successively until finally growth is fully blocked thus bringing about “continuous solidification”.     

Widespread occurrence of AP in amyloidotic tissues. An immunohistochemical observation

Plasma (P)-component of amyloid (AP or SAP), while not an integral part of the amyloid fibril, has been considered to be intimately associated with virtually every different type of amyloid. In the present study, we evaluated the distribution of AP in the organs frequently involved in two forms of human systemic amyloidosis (AA and AF) and in mouse AA amyloidosis, by use of immunohistochemistry with anti-AP. Although the amyloid deposits generally showed moderate reactions with anti-AP, they were not always clearly distinguished from the surrounding non-amyloid tissue elements which often stained as well. The basement membrane often showed even stronger reaction to anti-AP than the adjacent amyloid deposits, and liver sections demonstrated such a high overall reaction to anti-AP that the anti-AP reaction on the amyloid deposits was often obscurred. The present results suggest that the binding between AP and the amyloid fibril may not be monospecific, that AP by this technique occurs rather widely throughout the body, and therefore that anti-AP may not be considered as specific a marker for amyloid deposits in immunohistochemical and perhaps other studies as well.     

Faster evolution of highly conserved DNA in tropical plants

A faster rate of nuclear DNA evolution has recently been found for plants occupying warmer low latitudes relative to those in cooler high latitudes. That earlier study by our research group compared substitution rates within the variable internal transcribed spacer (ITS) region of the ribosomal gene complex amongst 45 congeneric species pairs, each member of which differed in their latitudinal distributions. To determine whether this rate differential might also occur within highly conserved DNA, we sequenced the 18S ribosomal gene in the same 45 pairs of plants. We found that the rate of evolution in 18S was 51% faster in the tropical plant species relative to their temperate sisters and that the substitution rate in 18S correlated positively with that in the more variable ITS. This result, with a gene coding for ribosomal structure, suggests that climatic influences on evolution extend to functionally important regions of the genome.     

Effect of temperature on growth of guanidine-resistant mutants of poliovirus

Guanidine-resistant (gr) mutants of poliovirus were previously categorized into four groups by electrophoretic properties and peptide maps of nonstructural virus protein 2C. Growth of mutants in the presence of guanidine depends upon temperature of incubation. The four groups of gr variants respond differently to temperature when guanidine is included in the culture medium. The data suggest clustering of gr mutations at several sites in the guanidine locus.     

Perturbation of growth and differentiation of Friend murine erythroleukemia cells by 5-bromodeoxyuridine incorporation in early S phase.

Cultured Friend murine erythroleukemia cells (Friend cells) are induced to undergo erythroid differentiation when grown in the presence of dimethylsulfoxide (DMSO) and other compounds. The effects of unifilar substitution of bromouracil (BU) for thymidine in the DNA (BU-DNA) of Friend cells were examined. Cells were grown in the presence of 5-bromodeoxy-uridine (BrdU) for one generation, then centrifuged and resuspended in medium containing DMSO without BrdU. These cells exhibited a delay in the appearance of heme-producing, benzidine-reative (B+) cells and a decreased rate of cell proliferation in comparison to the control not containing BU-DNA. A transient inhibition of entry into S phase was observed when control cells or cells containing BU-DNA were grown in the presence of DMSO) for 10 to 20 hours. This transient inhibition was increased in the BrdU culture. Thus BU-substitution in Friend cells alters other cellular functions in addition to erythroid differentiation. The rate of increase in the percent of cells committed to differentiate (those forming B+ colonies in plasma clots) was similar in the BrdU and control cultures until 40 to 50 hours. After this time, a delay in the appearance of committed cells was observed in the BrdU culture. The effect of BrdU on the appearance of B+ cells was more pronounced and occurred earlier than its effect on the rate of commitment. Therefore, the delay in the appearance of B+ cells in the BrdU culture was due primarily to perturbation of post-commitment events such as the accumulation of hemoglobin. We also examined the effect on growth and differentiation after BrdU was incorporated during different intervals of S phase in cells synchronized by centrifugal elutriation or by double thymidine block and hydroxyurea treatment. The delay in the appearance of B+ cells and inhibition of cell proliferation were only observed when BrdU was incorporated in the first half of S phase. BrdU (10 muM) had no effect on growth or differentiation when present during late S or G1 and G2. These results, using two very different methods to achieve cell synchrony, indicate that the effects of BrdU on growth and differentiation described above are due to its incorporation into DNA sequences replicating during early S.