Co-variation of ionic conductances supports phase maintenance in stomatogastric neurons

Neuronal networks produce reliable functional output throughout the lifespan of an animal despite ceaseless molecular turnover and a constantly changing environment. Central pattern generators, such as those of the crustacean stomatogastric ganglion (STG), are able to robustly maintain their functionality over a wide range of burst periods. Previous experimental work involving extracellular recordings of the pyloric pattern of the STG has demonstrated that as the burst period varies, the inter-neuronal delays are altered proportionally, resulting in burst phases that are roughly invariant. The question whether spike delays within bursts are also proportional to pyloric period has not been explored in detail. The mechanism by which the pyloric neurons accomplish phase maintenance is currently not obvious. Previous studies suggest that the co-regulation of certain ion channel properties may play a role in governing neuronal activity. Here, we observed in long-term recordings of the pyloric rhythm that spike delays can vary proportionally with burst period, so that spike phase is maintained. We then used a conductance-based model neuron to determine whether co-varying ionic membrane conductances results in neural output that emulates the experimentally observed phenomenon of spike phase maintenance. Next, we utilized a model neuron database to determine whether conductance correlations exist in model neuron populations with highly maintained spike phases. We found that co-varying certain conductances, including the sodium and transient calcium conductance pair, causes the model neuron to maintain a specific spike phase pattern. Results indicate a possible relationship between conductance co-regulation and phase maintenance in STG neurons.     

Role of vagus nerve in postprandial antropyloric coordination in conscious dogs

It is generally believed that gastric emptying of solids is regulated by a coordinated motor pattern between the antrum and pylorus. We studied the role of the vagus nerve in mediating postprandial coordination between the antrum and pylorus. Force transducers were implanted on the serosal surface of the body, antrum, pylorus, and duodenum in seven dogs. Dogs were given either a solid or a liquid meal, and gastroduodenal motility was recorded over 10 h. Gastric emptying was evaluated with radiopaque markers mixed with a solid meal. Dogs were treated with hexamethonium, N(G)-nitro-l-arginine methyl ester (l-NAME), or transient vagal nerve blockade by cooling. A postprandial motility pattern showed three distinct phases: early, intermediate, and late. In the late phase, profound pyloric relaxations predominantly synchronized with giant antral contractions that were defined as postprandial antropyloric coordination. A gastric emptying study revealed that the time at which gastric contents entered into the duodenum occurred concomitantly with antropyloric coordination. Treatment by vagal blockade or hexamethonium significantly reduced postprandial antral contractions and pyloric relaxations of the late phase. l-NAME changed pyloric motor patterns from relaxation dominant to contraction dominant. Solid gastric emptying was significantly attenuated by treatment with hexamethonium, l-NAME, and vagal blockade. Postprandial antropyloric coordination was not seen after feeding a liquid meal. It is concluded that postprandial antropyloric coordination plays an important role to regulate gastric emptying of a solid food. Postprandial antropyloric coordination is regulated by the vagus nerve and nitrergic neurons in conscious dogs.     

Phase Maintenance in the Pyloric Pattern of the Lobster (Panulirus interruptus) Stomatogastric Ganglion

The extent to which individual neural networks can producephase-constant motor patterns as cycle frequency is altered has notbeen studied extensively. I investigated this issue in thewell-defined, rhythmic pyloric neural network. When pyloric cyclefrequency is altered three- to fivefold, pyloric inter-neuronaldelays shift by hundreds to thousands of msec, and all pyloricpattern elements show strong phase maintenance. The experimentalparadigm used is unlikely to activate exogenous inputs to thenetwork, and these delay changes are thus likely to arise fromphase-compensatory mechanisms intrinsic to the network. Pyloricinter-neuronal delays depend on the time constants of the networkssynapses and of the membrane properties of its neurons. The observeddelay shifts thus suggest that, in response to changes in overallcycle frequency, these constants vary so as to maintain patternphasing.     

The Social Behaviour of Wild and Domestic Rattus norvegicus in Dyadic Encounters

The social behavour of trapped wild rats, laboratory-bred descendants of wild rats, and agouti laboratory rats, all Rattus norvegicus , was compared in encounters between pairs of adult males. Pairs of rats of the same type shared a large cage divided by a partition, which was removed at the beginning of each 20 minute observation period. Ten defined categories of behaviour were recorded. The Wild rats Attacked and Threatened and Ran Away more often than the other groups, while the Agoutis were generally more active, especially in investigatory behaviour, and maintained their initial levels of activity in the second encounter. The third group was intermediate in most respects. These findings are related to differences in genotype and environment.     

Mapping G-bands on human prophase chromosomes.

OHNUKI's method for demonstrating coils in human metaphase chromosomes also reveals a fine G-band pattern on prophase chromosomes of sufficient clarity to justify an attempt at mapping. Maps are provided for each chromosome to show the maximum number of prophase bands observed, and an intermediate stage in chromosome contraction, tracing the pathways of apparent band fusion as the cell progresses to metaphase, is presented. The prophase bands on many chromosomes tend to occur in distinct groups, the members of which ultimately merge to give the dark G-bands of metaphase chromosomes. Every G-band of the standard metaphase chromosomes. Every G-band of the standard metaphase pattern is compounded from two or more prophase bands. In at least contracted prophase chromosomes examined, some bands are seen which have no obvious metaphase counterpart. There are marked similarities between banded prophases and the chromoomere pattern seen at meiotic prophase. However, since chromosome contraction is a dynamic process, agreement between maps will be expected only for corresponding degrees of chromosome contraction.     

Motor patterns in the stomatogastric ganglion of the lobster Panulirus argus.

1. Acitivity patterns arising from the thirty cells of the stomatogastric ganglion of Panulirus argus are described for both a semi-intact preparation and an isolated one. 2. The thirty or so cells can be divided so far into two functional groupings: the gastric mill group, with at least ten motor elements, and the pyloric group with at least fourteen. There is some, but not extensive, interaction between groups. 3. The main gastric mill activity is arranged in two sets of elements, each of which is composed of reciprocating elements innervating antagonistic muscles. Thus alternation in activity between the single LC and the two LG neurones results in alternate closing and opening of the lateral teeth; alternation between the four GM and single CP units results in alternate protraction and retraction of the medial tooth. 4. The two sets are phased to each other in such a way that they cause gastric mill teeth to operate effectively to masticate food. 5. The main pyloric activity is arranged in a three-part cycle with each of three sets of units active in sequence. Activity in two PD and one AB unit is followed by bursts in IC and LP units followed in turn by activity in up to seven PY units. Activity in a single VD neurone is locked to this cycle in a more complex pattern.     

Predictors of long-term weight loss in adults with modest initial weight loss, by sex and race

Effective weight management interventions could reduce race-sex disparities in cardiovascular disease (CVD), yet little is known about factors associated with successful weight loss maintenance in race-sex subgroups. In the Weight Loss Maintenance trial (WLM), overweight/obese (BMI 25-45 kg/m(2)) adults who lost ≥4 kg in a 6-month behavioral weight loss intervention (phase I) were randomized into one of three 30-month maintenance interventions (phase II). To investigate predictors in subgroups, randomized groups were combined for this analysis. Of 1,685 phase I participants, 1,032 (61%) entered phase II, including 12% black men (BM), 26% black women (BW), 25% white men (WM), and 37% white women (WW). Weight change over the 36-month study ranged from -2.3% (95% confidence interval = -3.1 to -1.5%) in BW to -4.5% (95% confidence interval = -5.7 to -4.0%) in WM, the result of differential weight loss during phase I. Within race, men lost significantly more weight than women, but within sex group, weight loss did not differ significantly between races. Although participants regained weight during phase II, regain did not differ by race-sex group, and mean weight at the end of the study was significantly lower than phase I entry weight for each subgroup. In regression models, phase I weight loss predicted overall 36-month weight loss in all race-sex groups. Healthy dietary pattern at entry, improvement in dietary pattern, or both were predictive in three of four race-sex groups. Few other variables other than initial weight loss and dietary pattern were predictive. Future research should identify additional modifiable influences on long-term maintenance after a modest weight loss.     

Electrophoretic karyotypes of <Emphasis Type="Italic">C. neoformans</Emphasis> serotype A recovered from Thai Patients with AIDS

Thirty-seven clinical isolates of C. neoformans were recovered from AIDS patients and all were serotype A according to standard typing tests. They were further analyzed using RAPD, PCR fingerprinting, and PFGE along with 2 additional reference isolates ATCC 34871 (serotype A) and RV 45981 (serotype D). Using 2 different RAPD primers, all of the clinical isolates and the reference serotype A (ATCC 34871) gave similar RAPD patterns while serotype D (RV 45981) gave distinctive pattern. Corresponding result was also obtained upon PCR by using a primer for microsatellite (GACA)₄. However, using a primer specific to minisatellite M13 + 1, all PCR fingerprinting gave similar gel patterns (M1) for 35/37 of the clinical isolates and the reference serotype A while two clinical isolates generated different patterns called M2 and M3. The reference serotype D gave distinctive pattern called M4. PFGE gave 17 different karyotypes that could be categorized into 4 groups named EKA (1–6), EKB (1–5), EKC (1– 5) and EKD (1). The reference serotype A fell into group EKA as EKA6 while the reference serotype D fell into group EKC as EKC5. Among the clinical isolates, EKA group (20/37 isolates) and type EKA1 (16/20) dominated with only one isolate each for types EKA2 to EKA5. The next most prevalent was group EKB (12/37 isolates) which dominately fell in type EKB1 (8/12) and only one isolate each for types EKB2 to EKB5. Group EKC (4/37 isolates) and group EKD (1/37) had only one isolate for each type (EKC1 to EKC 4 and EKD1). The 2 predominant karyotypes (EKA1, 16/37 and EKB1, 8/37) may represent two originally common clones of C. neoformans expose among the patients. The high discriminatory power of PFGE infers the benefit of subtyping which lead to better understanding on the epidemiology and pathogenic potential of C. neoformans subtypes. Moreover, PCR fingerprinting and RAPD infer the feasibility of detail analysis between serotypes A and D for unencapsulated C. neoformans.     

Life-history variation in a hybrid species complex ofDaphnia

Summary Life-history variation was examined among members of theDaphnia longispina group, which consists ofD. galeata, D. hyalina, D. cucullata, and hybrids. Factorial experiments were conducted at two temperatures (14° and 20° C) and two food concentrations (0.2 and 1.0 mg Cl⁻¹). Differences in life-history features (size at maturity, age at first reproduction, size of first clutch, offspring size in first clutch) under the different environmental conditions were assessed among eightDaphnia clones, which represented members of this species complex. Significant differences between parentals and hybrids for most life-history features were observed under various treatments; generally, hybrid clones showed intermediate life-history traits when compared with parentals. When comparisons were made among clones within a given species (i.e.D. galeata, D. galeata xcucullata, D. cucullata), clonal differences were also noted for certain life-history traits. The data are discussed with reference to the formation and maintenance of hybrid species complexes in nature. This paper is dedicated to the memory of Hans Georg Wolf, who died suddenly in May 1990 at the age of 39 years.     

Intergroup Phylogenies in Drosophila as Determined by Comparisons of Salivary Banding Patterns

A salivary gland chromosome phylogeny is presented which summarizes the evolutionary relationships of twenty-two species belonging to the sub-genus Drosophila, and members of the twelve species groups: D. melanica, D. repleta, D. carbonaria, D. polychaeta, D. annulimana, D. robusta, D. carsoni, D. virilis, D. funebris and the "picture-wing," D. mimica and D. crassifemur groups (of Hawaii).-Photographic salivary chromosome maps were prepared for all twenty-two species studied. While the chromosomes of different species belonging to the same group can usually be homologized almost completely, so that construction of intragroup phylogenies is easy, chromosomes of members of different groups are so modified structurally that in most cases only short sections can be fully homologized, and these in only one or two chromosome elements.-Broadly homologous chromosome elements were compared for three species at a time, and on the basis of overlapping homologous sections, or overlapping inversions included within homologous sections, the trio of chromosomes, and the species to which they belonged can often be arranged in a two-step phylogenetic series. Detection of many such ordered trios permits construction of a single phylogenetic scheme encompassing all species.-D. nigromelanica, of the D. melanica group is found to be chromosomally intermediate between the rest of its group and the species belonging to other groups, suggesting that it is the most nearly ancestral member of its group. When trios of species including D. nigromelanica and members of two other species groups are compared, it is found that in twelve of fourteen such comparisons the chromosomes of D. nigromelanica are structurally intermediate between those of the members of the other two species groups, indicating the central position of D. nigromelanica in the phylogeny as a whole.-Available cytological evidence indicates that among the nine continental groups studied, it is the D. robusta group which is chromosomally closest to the Hawaiian "picture-wing" groups. Among the members of the Hawaiian groups it is D. primaeva and D. attigua which are found to be closest to the continental species. This finding tends to confirm the earlier conclusion of Carson and Stalker, based on different evidence, that the above two species were in an ancestral position in the Hawaiian phylogeny.-The relationship of the D. robusta and D. melanica groups demonstrated in this paper, the phylogenies within each of these two groups earlier worked out by Narayanan and by Stalker, and the present geographical distributions of the species within them, require that at least three Asiatic-New World migrations must have occurred during the evolution of the two groups.     

Group fission in Nilgiri langurs (Presbytis johnii)

During a field study on habituated groups of wild Nilgiri langurs (Presbytis johnii),four cases of group fission were observed which differed markedly from group changes reported in other species of the same genus. All fissions occurred in groups with more than one mature male and roughly coincided with the onset of loud call vocalization by the second mature male group member. As a result of the fission the founder group factions acquired the structure of a onemale group. The filial factions consisted of both mature males and females and occupied, at least temporarily, a part of, or an area adjacent to, the founder group. During fission, the amount of aggressive interactions between the two mature males increased. However, the majority of agonistic interactions involved ritualized threat and intimidation behavior without physical aggression. In at least three cases the two mature males involved in the fission had not joined recently but had lived in these groups for three years or more. Although the presence of all male bands and single males in the two study populations indicate that male replacement by invasive takeovers may occur, it is suggested that in Nilgiri langurs, noninvasive fissions are probably another common mechanism for the foundation and maintenance of bisexual one-male groups.     

Taxonomy of the Clostridia: ribosomal ribonucleic acid homologies among the species.

rRNA homologies have been determined on reference strains representing 56 species of Clostridium. Competition experiments using tritium-labelled 23S rRNA were employed. The majority of the species had DNA with 27 to 28% guanine plus cytosine (%GC). These fell into rRNA homology groups I and II, which were well defined, and a third group which consisted of species which did not belong in groups I and II. Species whose DNA was 41 to 45% GC comprised a fourth group. Thirty species were placed into rRNA homology group I on the basis of having 50% or greater homology with Clostridium butyricum, C. perfringens, C. carnis, C. sporogenes, C. novyi or C. pasteurianum. Ten subgroups were delineated in homology group I. Species in each subgroup either had high homology with a particular reference species or a similar pattern of homologies to all of the reference organisms. The eleven species in rRNA homology group II had 69% or greater homology to C. lituseburense. Species in groups I and II had intergroup homologies of 20 to 40%. The six species in group II had very low homologies with groups I and II. Negligible homology also resulted when five of the species were tested against the sixth, C. ramosum. The five species having DNA with 41 to 45% GC were C. innocuum, C. sphenoides, C. indolis, C. barkeri and C. orotic um. Little rRNA homology was apparent between C. innocuum and the other high % GC species or with several Bacillus species having similar %GC DNA. Correlations between homology results and phenotypic characteristics are discussed.     

Social structure modulates the evolutionary consequences of social plasticity: A social network perspective on interacting phenotypes

Organisms express phenotypic plasticity during social interactions. Interacting phenotype theory has explored the consequences of social plasticity for evolution, but it is unclear how this theory applies to complex social structures. We adapt interacting phenotype models to general social structures to explore how the number of social connections between individuals and preference for phenotypically similar social partners affect phenotypic variation and evolution. We derive an analytical model that ignores phenotypic feedback and use simulations to test the predictions of this model. We find that adapting previous models to more general social structures does not alter their general conclusions but generates insights into the effect of social plasticity and social structure on the maintenance of phenotypic variation and evolution. Contribution of indirect genetic effects to phenotypic variance is highest when interactions occur at intermediate densities and decrease at higher densities, when individuals approach interacting with all group members, homogenizing the social environment across individuals. However, evolutionary response to selection tends to increase at greater network densities as the effects of an individual's genes are amplified through increasing effects on other group members. Preferential associations among similar individuals (homophily) increase both phenotypic variance within groups and evolutionary response to selection. Our results represent a first step in relating social network structure to the expression of social plasticity and evolutionary responses to selection.     

Group fission in free-ranging rhesus monkeys of Tughlaqabad,Northern India

A population of rhesus monkeys (Macaca mulatta)at Tughlaqabad on the southeastern outskirts of New Delhi has grown rapidly in the past 4 years, and the largest group (Group A) has given rise to three smaller groups. Fissioning, or new group formation, was not consistently associated with any particular season of the year or stage of the reproductive cycle, but it did occur in each case when the parent group reached approximately 120 monkeys. The fissioning process was not preceded or accompanied by unusual aggressive behavior. It occurred quietly and appeared to be a loss of cohesion within the large group by which a subgroup achieved behavioral and spatial independence. Some aggressive interactions did occur following each fission when the new group approached or attempted to reenter the parent group. Each newly formed group was subordinate to the parent group and all other groups in the population.     

活跃性和社会性对中华倒刺鲃集群行为的影响

为考察群体中不同的个性组成对鱼类集群行为的影响及其内在机制,选取中华倒刺鲃(Spinibarbus sinensis)幼鱼为实验对象,依次测定其活跃性和社会性,随后分别根据活跃性和社会性的高低分为高、低和混合活跃性(或社会性)鱼群,考察鱼群中不同个性组成对集群时的整体运动特征以及每尾鱼的个体运动特征的影响。研究发现：(1)中华倒刺鲃的个性特征稳定且个体间变异较大;(2)高活跃性鱼群的运动时间比和速度同步性均大于低活跃性鱼群,而混合鱼群位于二者之间且与两个同质性鱼群均无显著差异;高社会性鱼群速度同步性显著小于低社会性和混合社会性鱼群,而后两者之间没有显著差异。(3)活跃性特征与集群运动时每尾鱼的运动特征(速度及其同步性等)相关,社会性特征不仅与上述运动特征关联,还与凝聚力大小(距鱼群质心距离)相关。研究表明：(1)鱼群的活跃性和社会性组成均对集群行为产生重要影响,但其内在机制截然不同。主要表现为：就活跃性而言,群体的运动状态是由群体中所有成员共同决定(平均决定机制);就社会性而言,少数低社会性成员对鱼群的运动水平表现有着主导作用(少数决定机制);(2)实验鱼的活跃性在集群行为中得到了较大...     

Habitual fission-fusion and social organization of the Hakone troop T of Japanese macaques in Kanagawa prefecture,Japan

To analyze the socioecological factors of habitual fission-fusion of troop members, which is an underreported phenomenon in Japanese macaques, the seasonal pattern of fission-fusion within the Hakone troop T in Kanagawa Prefecture, Japan, was examined. Although almost all the study troop members were included in a large-sized group in winter, a portion of its members of ten formed small subgroups from spring to autumn. The frequencies and age-sex composition of these subgroups changed seasonally. All troop members participated, more or less, in subgroup formation. Subgroups tended to be composed of animals of the same age-sex class. Troop members did not fission along matrilineal lines. Although the study troop members repeatedly joined with and parted from subgroups, the characteristic social structure of Japanese macaque troops was maintained. Habitual fission-fusion among troop members may be one of a number of foraging strategies that facilitate efficient food gathering when the population density exceeds and /or reaches the carrying capacity of the area. The seasonal variation of pattern and composition type of each subgroup could be attributed to alternation of attractive food plant species, as well as age, rank, and sexual activity of both sexes.     

Definitions of state variables and state space for brain-computer interface

Neocortical state variables are defined and evaluated at three levels: microscopic using multiple spike activity (MSA), mesoscopic using local field potentials (LFP) and electrocorticograms (ECoG), and macroscopic using electroencephalograms (EEG) and brain imaging. Transactions between levels occur in all areas of cortex, upwardly by integration (abstraction, generalization) and downwardly by differentiation (speciation). The levels are joined by circular causality: microscopic activity upwardly creates mesoscopic order parameters, which downwardly constrain the microscopic activity that creates them. Integration dominates in sensory cortices. Microscopic activity evoked by receptor input in sensation induces emergence of mesoscopic activity in perception, followed by integration of perceptual activity into macroscopic activity in concept formation. The reverse process dominates in motor cortices, where the macroscopic activity embodying the concepts supports predictions of future states as goals. These macroscopic states are conceived to order mesoscopic activity in patterns that constitute plans for actions to achieve the goals. These planning patterns are conceived to provide frames in which the microscopic activity evolves in trajectories that adapted to the immediate environmental conditions detected by new stimuli. This circular sequence forms the action-perception cycle. Its upward limb is understood through correlation of sensory cortical activity with behavior. Now brain-machine interfaces (BMI) offer a means to understand the downward sequence through correlation of behavior with motor cortical activity, beginning with macroscopic goal states and concluding with recording of microscopic MSA trajectories that operate neuroprostheses. Part 1 develops a hypothesis that describes qualitatively the neurodynamics that supports the action-perception cycle and derivative reflex arc. Part 2 describes episodic, “cinematographic” spatial pattern formation and predicts some properties of the macroscopic and mesoscopic frames by which the embedded trajectories of the microscopic activity of cortical sensorimotor neurons might be organized and controlled. URL: http://sulcus.berkeley.edu     

Molecular analysis of a cruciferin storage protein gene family of Brassica napus

We have isolated a five-member gene subfamily which encodes cruciferin, a legumin-like 12S storage protein of Brassica napus L., and have analyzed the structure and expression of the family members in developing embryos. Sequence analysis has shown that the coding regions of all five genes are highly similar, with the two most divergent members of the family retaining 89% sequence identity. The analysis of this cruciferin gene family's expression indicates that the developmental pattern of expression of each gene is similar, and the steady-state mRNA levels of each gene are approximately equivalent to each other at all developmental stages.     

Compatibility groups in Ascobolus immersus — an indication of speciation

Summary The mating pattern between 38 strains collected at various places in Europe and Southern India was determined. There are at least three compatibility groups: A (23 strains) and B (9 strains) comprising the European isolates, and C (6 strains), the Indian isolates. Within each compatibility group sexual reproduction is, as expected, controlled by a bipolar mechanism of homogenic incompatibility. No fertile offspring are obtained in any intergroup crossing showing that there is genetic separation by heterogenic incompatibility. However, the European group B seems to be closer related to the Indian (C) group in that sterile fruit bodies are produced between + and – mating types. An indication for a further subdivision is the occurrence of a barrage-like phenomenon between representatives of all three groups. The data thus indicate how the start of speciation may be occurring in Ascobolus immersus by means of both spatial and genetic isolation.