Fluctuations during growth of the plasma membrane H(+)-ATPase activity of Saccharomyces cerevisiae and Schizosaccharomyces pombe

The plasma membrane H⁺-ATPase activity was determined under various growth conditions using the yeastsSaccharomyces cerevisiae andSchizosaccharomyces pombe. Under early batch-growth conditions in a rich medium, the budding yeastS. cerevisiae ATPase specific activity increased 2-to 3-fold during exponential growth. During late exponential growth, a peak of ATPase activity, followed by a sudden decrease, was observed and termed “growth-arrest control”. The growth arrest phenomenon ofS. cerevisiae could not be related to the acidification of the culture medium or to glucose exhaustion in the medium or to variation of glucose activation of the H⁺-ATPase. Addition of ammonium to a proline minimum medium also stimulated transiently the ATPase activity ofS. cerevisiae. Specific activity of the fission yeastS. pombe ATPase did not show a similar profile and steadily increased to reach a plateau in stationary growth. Under synchronous mitotic growth conditions, the ATPase activity ofS. cerevisiae increased during the cell division cycle according to the “peak” type cycle, while that ofS. pombe was of the “step” type.     

Synchronized changes to relative neuron populations in postnatal human neocortical development

Mammalian prenatal neocortical development is dominated by the synchronized formation of the laminae and migration of neurons. Postnatal development likewise contains “sensitive periods” during which functions such as ocular dominance emerge. Here we introduce a novel neuroinformatics approach to identify and study these periods of active development. Although many aspects of the approach can be used in other studies, some specific techniques were chosen because of a legacy dataset of human histological data (Conel in The postnatal development of the human cerebral cortex, vol 1–8. Harvard University Press, Cambridge, 1939–1967). Our method calculates normalized change vectors from the raw histological data, and then employs k-means cluster analysis of the change vectors to explore the population dynamics of neurons from 37 neocortical areas across eight postnatal developmental stages from birth to 72 months in 54 subjects. We show that the cortical “address” (Brodmann area/sub-area and layer) provides the necessary resolution to segregate neuron population changes into seven correlated “k-clusters” in k-means cluster analysis. The members in each k-cluster share a single change interval where the relative share of the cortex by the members undergoes its maximum change. The maximum change occurs in a different change interval for each k-cluster. Each k-cluster has at least one totally connected maximal “clique” which appears to correspond to cortical function.     

The pattern of sensory discharge can determine the motor response in young Xenopus tadpoles

Young Xenopus tadpoles were used to test whether the pattern of discharge in specific sensory neurons can determine the motor response of a whole animal. Young Xenopus tadpoles show two main rhythmic behaviours: swimming and struggling. Touch-sensitive skin sensory neurons in the spinal cord of immobilised tadpoles were penetrated singly or in pairs using microelectrodes to allow precise control of their firing patterns. A single impulse in one Rohon-Beard neuron (= light touch) could sometimes trigger “fictive” swimming. Two to six impulses at 30–50 Hz (= a light stroke) reliably triggered fictive swimming. Neither stimulus evoked fictive struggling. Twenty-five or more impulses at 30–50 Hz (= pressure) could evoke a pattern of rhythmic bursts, distinct from swimming and suitable to drive slower, stronger movements. This pattern showed some or all the characteristics of “fictive” struggling. These results demonstrate clearly that sensory neurons can determine the pattern of motor output simply by their pattern of discharge. This provides a simple form of behavioural selection according to stimulus. Accepted: 28 November 1996     

Beyond the binary case in random nets

Experiments on random binary, ternary, etc. (P=2, 3,…, 10) switching nets are reported. Behavioral cycle lengths are examined as functions of output variety,P, input connectance,K, and net size,N. Overall, output variety appears an influential, well-behaved net property. Strong, but well-behaved interactions appear among net variables. In high connectance nets, median cycle length grows approx. asP ^N/2. Other factors constant, one-connected nets show the shortest cycles, and connectance effects appear to converge asymptotically aroundN. Data for cycle length as a function of net size suggest a concavity not compatible with the Kauffman “square root law” (Kauffman, 1969). Evidence of a positive relationship between cycle length and run-in length is found in two-input nets; weaker evidence is obtained that in higher connectance nets this relationship becomes negative in sign. The “modular complexity” ofP>2 nets is examined briefly.     

An ant’s eye view of culture: propagation of new traditions through triggering dormant behavioural patterns

We consider a previously unknown way of propagation of behavioural traditions in animal communities using hunting in ants as an example. We experimentally revealed that common litter dwelling ants Myrmica rubra effectively hunt jumping prey and the way the hunting behavioural pattern is distributed within ant colonies is rather sophisticated. Comparison of our results with those obtained on vertebrates enables us to suggest that “distributed social learning” plays an important role in spreading new traditions in animal communities: initial performances by a few carriers of an “at once and entirely” available behavioural pattern propagate this pattern among specimens which have only dormant “sketches” of it. Spread of these behaviours in populations is based on relatively simple forms of social learning such as social facilitation which underlies species’ predisposition to learn certain sequences of behavioural acts. To be triggered, carriers of dormant “sketches” of a relevant behavioural pattern should encounter performances of this pattern with sufficient frequency. We call this strategy triggering of dormant behavioural patterns. Integration of behaviour thus takes place not only at the individual level but at the population level as well.     

On the analysis of substrate cycles in large metabolic systems

The simultaneous operation of paired, opposing reactions (substrate cycles) or parallel reactions (dual pathways) with seeming wastage of ATP is widespread in cellular metabolism. Analysis of such “futile” pathways has hitherto been limited to loci with only two or three interconnecting fluxes. We introduce here a method that allows straightforward analysis of more complex systems. The method involves the linear superposition of “fundamental” modes, one or more of which may be energetically wasteful. Decomposition of a flux pattern into such modes allows computation of the amount of free energy “wasted” at any locus. Appropriate normalizations of energy wastage yield a number of indices useful for assessing the energetic impact of futile pathways on the cell and for comparing the degree of regulation of substrate cycles or dual pathways under different metabolic conditions. This approach is applied to steady-state flux data obtained in the protozoanTetrahymena pyriformis and in isolated rat hepatocytes under a variety of conditions.     

A mathematical model of decision-making neural circuits controlling behavioral model selection

Mathematical models of mutually interacting reverberatory neural circuits exhibit decision-making properties that can account for behavioral mode selection in terms of identifiable neural subsystems and measurable variables, without the need for invoking concepts such as “drive,” “motivation,” or “instinct”. The models can account for an animal's ability to persist in a given behavioral mode under appropriate stimulus conditions and to rapidly switch modes in response to significant stimulus changes via the properties of stable steady states, thresholds for steady-state transitions, and the lack of intrinsic oscillations.     

A theory of steady-state activity in nerve-fiber networks II: The simple circuit

It is found that for a simple circuit of neurons, if this contains an odd number of inhibitory fibers, or none at all, or if the product of the activity parameters is less than unity, then the stimulus pattern always determines uniquely the steady-state activity. For circuits not of one of these types, it is possible to classify exclusively and exhaustively all possible activity patterns into three types, here called “odd”, “even”, and “mixed”. For any pattern of odd type and any pattern of even type there always exists a stimulus pattern consistent with both, but in no other way can such an association of activity patterns be made.     

Mycobacterium leprae — The outer lipoidal surface

There is now a considerable body of evidence to suggest that the phthiocerol-containing lipids, including the phenolic glycolipids, comprise the so-called “peribacillary substance”, “spherical droplets”, “foamy structures” and “capsular materials” ofMycobacterium leprae. Thus, the phthiocerol-containing lipid capsule may be directly responsible for the intracellular survival ofMycobacterium leprae.     

Malaria: Origin of the Term “Hypnozoite”

The term “hypnozoite” is derived from the Greek words hypnos (sleep) and zoon (animal). Hypnozoites are dormant forms in the life cycles of certain parasitic protozoa that belong to the Phylum Apicomplexa (Sporozoa) and are best known for their probable association with latency and relapse in human malarial infections caused by Plasmodium ovale and P. vivax. Consequently, the hypnozoite is of great biological and medical significance. This, in turn, makes the origin of the name “hypnozoite” a subject of interest. Some “missing” history that is now placed on record (including a letter written by P. C. C. Garnham, FRS) shows that Miles B. Markus coined the term “hypnozoite”. While a PhD student at Imperial College London, he carried out research that led to the identification of an apparently dormant form of Cystoisospora (synonym: Isospora). In 1976, he speculated: “If sporozoites of Isospora can behave in this fashion, then those of related Sporozoa, like malaria parasites, may have the ability to survive in the tissues in a similar way.” He adopted the term “hypnozoite” for malaria in 1978 when he wrote in a little-known journal that this name would “… describe any dormant sporozoites or dormant, sporozoite-like stages in the life cycles of Plasmodium or other Haemosporina.” At that time, the existence of a hypnozoite form in the life cycle of Plasmodium was still a hypothetical notion. In 1980, however, Wojciech A. Krotoski published (together with several co-workers) details concerning his actual discovery of malarial hypnozoites, an event of considerable importance.     

First-instar aphids produced late by the fundatrix ofCeratovacuna nekoashi (Homoptera) defend their closed gall outside

The fundatrix ofCeratovacuna nekoashi attacks an axillary bud ofStyrax japonica to form a “cat's-paw” gall with a number of completely closed subgalls. Larvae produced early by the fundatrix enter subgalls, but late-produced ones cannot because the subgalls close too early. The average number of these “outsiders” produced per gall was 3.81±2.37 (n=26). In spite of their small numbers, outsiders attacked caterpillars placed on the gall. Thus outsiders function to defend their gall against external attacks such as those from lepidopterous predators.     

Baboon sexual swellings and male response: A possible operational mammalian supernormal stimulus and response interaction

Experimental work using coagulated masturbatory seminal emissions from nine adult male chacma baboons (Papio ursinus)as a dependent variable revealed that males show a greater sexual arousal response to female conspecifics exhibiting exaggerated perineal swellings. The menstrual cycles of the “superswollen” females did not differ in length or patterning from the controls. Since additional experimental work, including behavioral observations on females with normal and supersized swellings, failed to reveal differences in female proceptivity, the male’s increased arousal response appears dependent upon the perineal size per se.The males’ responses suggest that the supersized swellings may be an example of an operational visual supernormal stimulus and response interaction.     

A revision of<Emphasis Type="Italic">Poposaurus gracilis</Emphasis> (Archosauria: Suchia) based on two new specimens from the Late Triassic of the southwestern U.S.A.

Two associated partial skeletons, one from the McCarty ranch (MOTTU site 0690) near Kalgary, Texas, Tecovas Formation, and the other from the Petrified Forest Member of the Chinle Formation, outside the Petrified Forest, Arizona, represent the most complete specimens ofPoposaurus gracilis found to date, and increase our understanding of the osteology of this rare pseudosuchian archosaur. The cervical centrum of TTUP-10419 possesses an accessory dorsal parapophyseal rib facet, as in “Lythrosuchus”. The ilia of these new fossils are the first ofPoposaurus to preserve the complete preacetabular blade, which is long and “blade-like” rather than “paddle-shaped” as previously thought. These specimens also confirm that isolated elements previously referred toPoposaurus (fused sacral vertebrae, the pubes and the ischia), but not present in the holotype indeed belong to that taxon. The morphology of the cervical centrum and the preacetabular blade of the ilium are identical to the much larger type of“Lythrosuchus” langstoni, suggesting that “Lythrosuchus” is a junior synonym ofPoposaurus. However, we retain the speciesPoposaurus langstoni nov. comb. on the basis of larger size, absence of a distinct ridge on the lateral surface of the ilium, and the lack of a pit on the proximal end of the ischium. A phylogenetic analysis suggests a monophyletic Poposauroidea and a paraphyletic “Rauisuchia”.     

Age changes of the carpal bones in macaques: Application of the fourier analysis on the radiographs

A method based on the Fourier analysis is proposed, which describes and analyzes the contour morphology of carpal bones by separating morphology into factors of shape and size. Here, “size” refers to the average diameter of the contour. The “shape” is expressed byshape factors which are derived from the Fourier series and the “shape” of a monkey is expressed by ashape index which is calculated fromshape factors. The age change in the morphology of the lunate and capitate ofMacaca fuscata fuscata was analyzed by this method. The development of “shape” approximately completes by 3 years of age, whereas increase in “size” begins its spurt at that age as do body weight and anterior trunk length. By applying this method to other macaque species, it was found thatM. mulatta, M. f. yakui andM. cyclopis exhibit similar patterns of growth and development of carpal bones to those ofM. f. fuscata. Patterns found inM. fascicularis differ in that its bones develop faster than in the other macaques with respect to the “shape,” but remain small with respect to the “size.”     

Seasonal structural and functional changes in the photosynthetic apparatus of evergreen conifers

We conducted a detail study of the photosynthetic apparatus in assimilating organs of three introduced evergreen conifer species: Taxus cuspidate S. et Z. ex E. (Far-Eastern yew), Thuja occidentalis L. (arbovitae “green”), and Th. occidentalis f. “Reingold” (arbovitae “yellow”) at various times in their life cycle. We studied the potential photosynthesis rate; composition and ratios of pigments, including primary carotenoids; the violaxanthin cycle (VC) activity, the synthesis of a secondary carotenoid, rhodoxanthin; and chloroplast ultrastructure. In winter and spring, β-carotene and lutein (primary carotenoids) contents were relatively constant in yew and arbovitae “yellow”. In December, the VC in yew was balanced and in arbovitae “yellow” unbalanced. In arbovitae “yellow”, the zeaxanthin pool was heterogeneous, and only part of it took part in the VC. It can be assumed that the other part of the pool can be oxidized to form a secondary carotenoid, rhodoxanthin. This secondary carotenoid was also accumulated in arbovitae “green”; its synthesis took place during the season, when the photosynthesis rate of plants was the lowest, and a significant chloroplast reorganization occurred (the number of thylakoids in grana decreased and plastoglobules appeared). We suppose that rhodoxanthin forms a filter for the light under the conditions of high insolation in winter. Thus, the evergreen conifer plants studied, which are adapted to growing at high latitudes where temperature is low and insolation is high in winter and spring, have a system for protecting the photosynthetic apparatus against photodestruction. In the basis of this system, the primary and secondary carotenoids lie, whose content changes during the year.     

Isozyme and RAPD markers in relation to in vitro morphogenesis and in vivo development ofVigna radiata (L.) Wilczek

Vigna radiata (L.) Wilczek, popularly known as “mung bean,” is an important protein supplement in vegetarian diets in many countries of Asia. It has a short life cycle (55–70 days) and fits well into many cropping systems, including rice and sugarcane, under rain-fed and irrigated conditions. The present review deals with the data available on plant regeneration of this species. Both shoot-tip multiplication and somatic embryogenesis have been compared on the basis of retrospective as well as recent reports. Molecular markers, especially random amplified polymorphic DNA (RAPD), have been used to compare results obtained from in vitro and in vivo studies on various species ofVigna. Isozyme markers such as esterase and superoxide dismutase, which are expressed during in vitro regeneration and in vivo development ofVigna species, are also included in this article.     

Flowering response oflemna paucicostata in japan

Twenty-two strains ofLemna paucicostata collected from various districts in Japan are classified into 4 types having different morphological features and photoperiodic behaviors. (I) The “N-1” type, widely distributed in north and middle Japan, consists of many short-day strains with similar morphological characteristics. The strain of northern origin, however, has a shorter critical dark period than that of southern origin, and most of the strains flower in response to a single short day though some from middle Japan require 2 short days. (2) The “N-2” type, found in a limited area of northern Japan, is also a short-day type, but has very long critical dark periods and requires 3–5 short-day cycles for flowering. (3) The “S” type, distributed in southern Japan, never flowered in any photoperiod or culture conditions tested. (4) The “K” type, strain 351, collected at the experimental farm of Kyoto University, is a day-neutral type and flowers independently of photoperiod. Application of some SH inhibitors, tungstate or EDTA, or exposure to blue, far-red or low-intensity light caused daylength-independent flowering in short-day strain 6746 (California origin), but none of these treatments caused flowering in any short-day strain collected in Japan.     

Role of male scent in the mating behavior ofPieris melete Ménétriès (Lepidoptera: Pieridae)

APieris melete male emits species-specific scent from the wings, while a virgin female ofP. melete is frequently observed to take the so-called “mate-refusal posture” in response to courting males. The role of the male scent in the mating behavior ofP. melete was investigated experimentally by using scented and scentless male models. It is suggested that the male wing scent can function primarily as a sex pheromone to “seduce” the virgin females that assume the mate-refusal posture, and can therefore induce a successful copulation. This work was financially supported by the Japan Society for the Promotion of Science.     

Integrate-and-fire models of insolation-driven entrainment of broadcast spawning in corals

The circa-annual cycle of gametogenesis produces mature gametes at the spawning “season” for successful mass spawning of broadcast corals. We develop a bioenergetic integrate-and-fire model that reveals how annual insolation rhythms can entrain the gametogenetic cycles in tropical hermatypic corals to the appropriate spawning season, since photosynthate is their primary source of energy. In the presence of short-term fluctuations in the energy input, a feedback regulatory mechanism is likely required to achieve coherence of spawning times to within one lunar cycle, in order for subsequent signals such as lunar and diurnal light cycles to unambiguously determine the “correct” night of spawning. The feedback mechanism can also provide robustness against population heterogeneity that may arise due to genetic and environmental effects. We solve the integrate-and-fire bioenergetic model numerically using the Fokker–Planck equation and use analytical tools such as rotation number to study entrainment.     

Preliminary study of taxonomy ofAzotobacter andAzomonas by using rocket line immunoelectrophoresis

Rocket line immunoelectrophoresis was used to study the taxonomy ofAzotobacter andAzomonas assessed by reaction with antiserum to the AVO₂ strain ofAzotobacter. Forty-five cultures, comprising seventeen species in five genera, showed that antigen “β”, like high-titer somatic agglutination, was restricted to all 11 strains ofAzotobacter vinelandii and to one strain which has been namedAzotobacter macrocytogenes (10EM). A thermoresistant antigen (“γ”) was found to be shared by all strains and species ofAzotobacter andAzomonas investigated.