Effects of anisotropic interactions on the structure of animal groups

This paper proposes an agent-based model which reproduces different structures of animal groups. The shape and structure of the group is the effect of simple interaction rules among individuals: each animal deploys itself depending on the position of a limited number of close group mates. The proposed model is shown to produce clustered formations, as well as lines and V-like formations. The key factors which trigger the onset of different patterns are argued to be the relative strength of attraction and repulsion forces and, most important, the anisotropy in their application.     

The effect of cryopreservation on ciliary beat frequency of human respiratory epithelium

The effect of cryopreservation on ciliary activity of human nasal respiratory epithelium was evaluated. Samples were cryopreserved in a solution containing nutrient medium, 10% fetal calf serum, and two different concentrations (10 or 20%) of dimethyl sulfoxide and stored in liquid nitrogen at -196 degrees C for 2 weeks. Ciliary beat frequencies (CBF) of the samples before and after cryopreservation were compared. Mean CBF values did not differ significantly with both concentrations of dimethyl sulfoxide. The mean intrasample coefficient of variation of the CBF decreased significantly after cryopreservation. After thawing, CBF remained unchanged for at least 4 hr. It is concluded that normal ciliated epithelial cells can be frozen and stored in liquid nitrogen at 196 degrees C while maintaining their CBF.     

Hydrocortisone inhibits DMSO - induced differentiation of Friend erythroleukemia cells.

Hydrocortisone (10^?6 – 10^?7M) completely inhibited the production of hemoglobin by DMSO- and DMF-treated Friend erythroleukemia cells (FLC) in vitro without affecting either cell replication or general protein synthesis. Only 11, 17-dihydroxycorticosteroids were effective in inhibiting this expression of differentiation. Addition of hydrocortisone as late as 48 hours after the addition of DMSO (at a time at which cells were committed to differentiation) still resulted in significant inhibition of hemoglobin synthesis. Although the mechanism of this action is unknown, since it was not reversed by the addition of arachidonic acid nor a number of prostaglandins, it appears to be unrelated to the ability of corticosteroids to inhibit endogenous prostaglandin synthesis.     

An electron paramagnetic resonance study of free radicals in cells.

An electron paramagnetic resonance study was performed on cell lines of the following strains: HeLa, 37RC, L, FLC, NRK/RSV, 3T3/SV40. Unsynchronized and synchronized HeLa cells were studied with particular attention paid to the relation between growth and free radical concentration. Free radical levels were shown to be a function of the growth stage and different phases of the cell cycle.     

Tryptophanyl-tRNA synthetase-like immunoreactivity in the central nervous system and midgut of the migratory locust. Comparisons with gastrin-cholecystokinin-like and octopamine-like immunoreactivity

Summary A tryptophanyl-tRNA synthetase (TrpRS)-immunoreactivity is localized in various neurosecretory cells of all ganglia of the central nervous system of the Orthoptera Locusta migratoria, except in deutocerebrum, and in endocrine cells of the midgut. It has been observed that TrpRS-like material never co-localizes either with CCK-like or octopamine-like material.TrpRS immunoreactive perikarya and processes that ramify extensively throughout the neuropiles have been detected in the protocerebrum, optic lobes, tritocerebrum, suboesophageal, thoracic and abdominal ganglia. In the lateral protocerebrum, a particular TrpRS pathway different from the lateral gastrin cholecystokinin (CCK-8(s)) pathway is revealed, certain of these processes terminating in the glandular part of the corpora cardiaca. In the metathoracic ganglion, have been observed numerous immunoreactive cell bodies and processes in the neuropiles. Some of them constitute a major pathway and which are distinct from octopamine (OA) cells but in close vicinity with the latter. In the midgut immunopositive TrpRS-like cells are dispersed among the regenerative and digestive cells of the epithelium; they are different from gastrin-cholecystokinin positive cells.The various TrpRS-like immunoreactivities identified in Locusta indicate that TrpRS-like material may occur in different tissues of organisms other than Vertebrates. These results suggest also that TrpRS-like enzyme could be involved in functions other than aminoacylation, as in Vertebrates.