Personality and reminiscence — An experimental study of the “reactive inhibition” and the “conditioned inhibition” theories

Twenty-eight extraverted Ss and 23 introverted Ss were administered the pursuit-rotor twice for 5 min., with a rest of 10 min. intervening. Reminiscence scores were found to be significantly higher for the extraverted group. Plotting of the performance data showed that the observed differences were due to post-rest superiority in performance of the extraverts, as predicted by the “conditioned inhibition” hypothesis, and not to pre-rest inferiority of the extraverts, as predicted by the “reactive inhibition” hypothesis. The results were interpreted in terms of the writer's three-factor theory of reminiscence.     

On the structure and function of “chlorosomes” of green bacteria

An assertion is substantiated that what is widely termed the chlorosomes of green bacteria are not bioparticles, but simply microscopic bacteriochlorophyll c crystals. Apparently, formation of a ??chlorosome?? represents the first, largely unsuccessful, evolutionary attempt to create a regulatory mechanism that would respond to variations in the intensity of solar light reaching the earth surface. Without bacteriochlorophyll cooperation with proteins, this was a dead end.     

CD109-mediated degradation of TGF-β receptors and inhibition of TGF-β responses involve regulation of SMAD7 and Smurf2 localization and function

Transforming growth factor-β (TGF-β) is a multifunctional cytokine that regulates a wide variety of cellular processes including proliferation, differentiation, and extracellular matrix deposition. Dysregulation of TGF-β signaling is associated with several diseases such as cancer and tissue fibrosis. TGF-β signals through two transmembrane proteins known as the type I (TGFBR1) and type II (TGFBR2) receptors. The levels of these receptors at the cell surface are tightly regulated by several mechanisms, including degradation following recruitment of the E3 ubiquitin ligase SMAD ubiquitination regulatory factor (Smurf) 2 by SMAD7. In addition, TGF-β co-receptors can modulate TGF-β signaling receptor activity in a cell-specific manner. We have previously identified a novel TGF-β co-receptor, CD109, a glycosyl phosphatidylinositol (GPI)-anchored protein that negatively regulates TGF-β signaling. Despite CD109's potential relevance as a regulator of TGF-β action in vivo, the mechanisms by which CD109 regulates TGF-β signaling are still incompletely understood. Previously, we have shown that CD109 downregulates TGF-β signaling by promoting TGF-β receptor localization into the lipid raft/caveolae compartment and by enhancing TGF-β receptor degradation. Here, we demonstrate that CD109 enhances SMAD7/Smurf2-mediated degradation of TGFBR1 in a ligand-dependent manner. Moreover, we show that CD109 regulates the localization and the association of SMAD7/Smurf2 with TGFBR1. Finally, we demonstrate that CD109's inhibitory effect on TGF-β signaling and responses require SMAD7 expression and Smurf2 ubiquitin ligase activity. Taken together, these results suggest that CD109 is an important regulator of SMAD7/Smurf2-mediated degradation of TGFBR1.     

Growth and mortality of individual plants as a function of “available area”

Summary We looked at the relationship between available area, as defined by Thiessen polygons around individual plants, and plant size and mortality in even-aged green-house populations of Lapsana communis L. Polygon area was a good predictor of plant weight in these populations. After nine weeks growth, just prior to the onset of self-thinning, the dry weight of plants was directly proportional to the square root of polygon area. After the onset of selfthinning, plant weight appeared to be directly related to polygon area to the 3/2 power. Plants in small polygons were much more likely to die than those in larger areas. Thinning changed the frequency distribution of polygon sizes from highly skewed and unequal to normal and more equal, while inequality in surviving plant sizes did not appear to be affected by thinning.     

Dynamic behaviour of α motoneurone sub-pools subjected to inhomogeneous Renshaw cell inhibition

The spinal α-motoneurone-Renshaw cell system was simulated by a meshed system of three principal negative feedback loops interconnected via “cross”-feedback pathways. Three types of α-motoneurone (MN): S-type, FR-type, and FF-type MNs, and their differing connections to and from Renshaw cells (RCs) were taken into account. The dynamic behaviour of RCs was taken from data provided by Cleveland and Ross (1977) and assumed to be given by a transfer function with one zero and two poles whose time constants τ_i depended on the overall amount of excitatory input to RCs. Also, the static gain of recurrent inhibition was taken to decrease with increasing excitatory input from α-MN axon collaterals (Cleveland et al., 1981) and to be depressed by spinally descending motor command signals. S-type MNs as well as F-type MNs were assumed to have high-pass characteristics though with slightly different cut-off frequencies. The closed-loop frequency responses of each sub-pool of MNs, S, FR, and FF, at three different levels of recruitment of these sub-pools, were calculated and shown to change significantly with recruitment level. These changes were essentially due to two reasons: firstly, to the general reduction of static gains within the recurrent inhibitory pathways with increasing motor output (recruitment), and secondly, to the increasing complexity of the whole network by recruitment of each new MN type. The particularly strong effect of the latter factor could easily be demonstrated by a comparison of the frequency responses of the MN types when these were, firstly, integrated into the network at their particular level of recruitment, and when they were, secondly, hypothetically assumed “isolated” from the remaining network, i.e., when subjected only to “self-inhibition”, the cross-inhibitory links to other MN types being cut. These results illustrate that the dynamic behaviour of α-MNs submitted to an inhomogeneously distributed recurrent and variable inhibition are not invariant, but depend upon the variable characteristics of a complex MN-RC network. This suggests that an important physiological function of recurrent inhibition via Renshaw cells, particularly of its inhomogeneous distribution, may be to adjust the dynamic MN sensitivity to the particular requirements prevailing at different motor output levels.     

Structure and function of γ-secretase

The γ-secretase complex is a prime target for pharmacological intervention in Alzheimer’s disease and so far drug discovery efforts have yielded a large variety of potent and rather specific inhibitors of this enzymatic activity. However, as γ-secretase is able to cleave a wide variety of physiological important substrates, the real challenge is to develop substrate-specific compounds. Therefore, obtaining structural information about γ-secretase is indispensable. As crystal structures of the complex will be difficult to achieve, applied biochemical approaches need to be integrated with structural information obtained from other intramembrane-cleaving proteases. Here we review current knowledge about the structure and function of γ-secretase and discuss the value of these findings for the mechanistic understanding of this unusual protease.     

A model of mate searching and territorial behaviour for “flier” type dragonflies

First, the mating system of a “flier” odonate species that continues patrolling without perching,Cordulia aenea amurensis Selys, is briefly reviewed. Adult males of this species search for mates for a long distance along the shore of a pond if male density is very low, but localize their patrol within a short range and defend the ranges if the density is high (Ubukata 1975, 1979). Secondly, a model of mate searching by vision and territoriality for flier dragonflies is proposed. The main assumptions of the model are: (1) a male with a fixed length of visual range (D) patrols with a constant velocity (V) on a straight line; (2) he turns in the opposite direction at 2 fixed points (distance=L); (3) female arrival probability is uniform in both spatial and temporal dimensions; (4) the females stay at the arrival point for a fixed time (C); (5) if a male discovers a female he copulates with her without fail and leaves the line. From the model the following are predicted: if , the species (type 1) has an optimal length of patrol range even if the female arrival rate is uniform; ifD is smaller than the right hand side of the inequality (type 2), the mating probability becomes higher as the patrol range increases, if there is no other male. On the basis of the above model the concept of an “unusurpable territory” is defined to exist at a given time after the start of patrol and the probability of unusurpability (P) is calculated as a function ofD, V, L, M (male density-1) andT (duration of patrol).P drops abruptly if the length of patrol range (L) exceeds that of unusurpable territory at high male densities. Therefore, there appears to be an optimal length of patrol range when there are other males, agreeing with the data fromC. a. amurensis. Finally, the model is discussed in comparison with some other models. Ecological studies ofCordulia aenea amurensis Selys, VIII.     

Vesicular stomatitis virus mRNA and inhibition of translation of cellular mRNA--is there a P function in vesicular stomatitis virus?

Infection of animal cells by vesicular stomatitis virus (VSV) results in inhibition of translation of cellular mRNA. We showed previously that, in BHK cells infected by the Glasgow isolate of VSV Indiana, this is due to competition during the initiation step of protein synthesis of viral and cellular mRNA for a constant, limiting number of ribosomes. We show here that infection of the same cells with the San Juan isolate of VSV resulted in a more rapid shutoff of host protein synthesis and that this was paralleled by a more rapid accumulation of viral mRNA. Extending our conclusion that shutoff is due to mRNA competition, we show further that the average size of polysomes translating viral and cellular mRNA was threefold smaller in cells infected by VSV San Juan than by VSV Glasgow, which, in turn, was about one-half that of uninfected cells. In all cases, cellular and viral mRNA's which encoded the same-sized polypeptides were found on the same-sized polysomes, a result indicating that the efficiency of translation of both types of mRNA's is about the same in the infected cell. Also, there was no preferential sequestration of viral or cellular mRNA's in ribonucleoprotein particles. Additional correlations between the levels of viral mRNA's and the inhibition of protein synthesis came from studies of three other wild-type VSV strains and also from studies with Vero and L cells. In particular, the rate of shutoff of L-cell protein synthesis after infection by any VSV isolate was slower than that in BHK cells, and this was correlated with a slower rate of accumulation of viral mRNA. VSV temperature-sensitive mutants which synthesized, at the nonper-missive temperature, no VSV mRNA failed to inhibit synthesis of cellular proteins. Stanners and co-workers (C. P. Stanners, A. M. Francoeur, and T. Lam, Cell 11:273-281, 1977) claimed that VSV mutant R1 inhibited synthesis of L cell protein synthesis less rapidly than did its parent wild-type strain HR. They concluded that this effect was due to a mutation in an unspecified VSV protein, “P.” We found, in both L and BHK cells, that R1 infection resulted in a slightly slower inhibition of cellular mRNA translation than did HR infection and that this was correlated with a slightly reduced accumulation of VSV mRNA. The level of VSV mRNA, rather than any specific VSV protein, appeared to be the key factor in determining the rate of shutoff of host protein synthesis.     

“Glial inhibition” of memory in Alzheimer's disease

<正>Two recent studies on Nature Medicine and Nature Communications reported the unusual roles of astrocytes in the brain,that is,release gamma-aminobutyric acid(GABA)and impair hippocampal memory in Alzheimer’s disease(AD).AD represents one common form of neurodegenerative diseases,and is characterized by progressive dementia.The pathological feature of an AD brain includes the appearance     

The vocalizations and other behaviour of growing pigs in an “open field” test

The reactions of growing pigs to brief periods of social isolation in an unfamiliar enclosure were studied in three experiments. Attention was given to the relationships among the different types of vocalization, and to the suitability of such a test as a gross index of individual differences among pigs. The incidence of long grunts and squeals were sufficiently correlated, both with each other and with measures of activity and frequency of defecation, to suggest that these measures may all be influenced by some single aspect of differences among individual animals. Incidence of short grunts and the weight of feces correlated less consistently with the frequency of squeals and long grunts, and with the activity measure. Scores of individual animals on one test correlated substantially with scores on subsequent testing. When animals were tested in the presence of a partner all measures, particularly the vocalization scores, were reduced; however, housing the animals in pairs did not affect any of the measures. A complex relationship was found among the three types of vocalization with short grunts predominating when the overall frequency of vocalization was low, while long grunts and squeals were proportionately much more common at higher rates of calling. These results support the view that the different types of call form a continuum corresponding to the animal's overall rate of movement and vocalizing.