REDUCED GENETIC DIVERSITY AND INCREASED POPULATION DIFFERENTIATION IN PERIPHERAL AND OVERHARVESTED POPULATIONS OF GIGARTINA SKOTTSBERGII (RHODOPHYTA,GIGARTINALES) IN SOUTHERN CHILE1

This study assesses two hypotheses on the genetic diversity of populations of Gigartina skottsbergii Setchell et Gardner (Rhodophyta, Gigartinales) at the border of the species distribution: 1) peripheral populations display a reduced genetic diversity compared with central populations, and 2) genetic differentiation is higher among peripheral than among central populations. Two peripheral and four central populations were sampled along the Chilean coast and 113 haploid individuals were analyzed using 17 random amplification of polymorphic DNA loci. The genetic diversity was estimated by allele diversity (H_e), allele richness (Â), and the mean pair‐wise differences among multilocus genotypes. All three estimates consistently and significantly indicated a lower genetic diversity within the peripheral than within the central populations. Genetic differentiation between the two peripheral populations was stronger (F_ST=0.35) than between central populations at similar spatial scales (F_ST ranging from 0 to 0.25). In addition, it appeared from the distribution of pair‐wise differences that peripheral populations are in demographic expansion after a recent bottleneck. The results are discussed in the specific context of potential overharvesting of these wild populations.     

Phototropism in hypocotyls of radish. VI. No exchange of endogenous indole-3-acetic acid between peripheral and central cell layers during first and second positive phototropic curvatures

Using a physicochemical method, the distribution of endogenous indole-3-acetic acid (IAA) was measured in the peripheral and central cell layers, as well as in the illuminated and shaded sides of phototropically stimulated radish hypocotyls (Raphanus sativus var. hortensis f. gigantissimus Makino). The IAA was evenly distributed over the illuminated and shaded sides in the first and second positive phototropic curvatures induced by a pulse or a continuous unilateral illumination with blue light. Also, no net exchange of the IAA between the peripheral and central cell layers was observed during these curvatures. These results suggest that phototropism of radish hypocotyls cannot be described by the Cholodny-Went theory.     

Non-random distribution of the pericentromeric heterochromatin in meiotic prophase nuclei of mammalian spermatocytes

The central or peripheral distribution of condensed chromatin (CC) was studied in pachytene spermatocyte nuclei in Mus domesticus, 2n=40; Pudu puda, 2n=70; Ctenomys opimus, 2n=26 and Octodon degus, 2n=58. Species were chosen according to the morphological characteristics of their chromosomal complements and in particular, the terminal or medial chromosomal localisation of the pericentromeric constitutive heterochromatin. Counts were made by defining the areas corresponding to peripheral and central location in each nuclear section from a series. The null hypothesis (i.e. random distribution of CC) was rejected. In the nuclear sections of Mus domesticus and Pudu puda, 69% and 74% of CC, respectively, was found in the peripheral nuclear space, while in those of Octodon degus and Ctenomys opimus, 69% and 65% of CC, respectively, was found in the central nuclear space. We estimate that if the CC measured in spermatocyte nuclei corresponds mainly to pericentromeric constitutive heterochromatin, the distribution found is consistent with that expected in accordance with the nuclear architecture model for meiocytes (Fernández-Donoso, 1982; Fernández-Donoso & Berrios, 1985). This model proposes a peripheral nuclear localisation for pericentromeric heterochromatin of telocentric bivalents and a relatively central nuclear localisation for pericentromeric heterochromatin of metacentric bivalents. We also discuss some of the biological consequences that could arise from the conservation of such distributions. This revised version was published online in July 2006 with corrections to the Cover Date.     

Biologic Response to Peripheral and Central Administration of Recombinant Human Leptin in Dogs

LEBEL, CARL, AMY BOURDEAU, DAVID LAU, AND PAMELA HUNT. Biologic response to peripheral and central administration of recombinant human leptin in dogs. Obes Res. Objective: Because leptin is believed to act within the central nervous system, the objective of this study was to test that presumption by comparing the biologic responses to recombinant human leptin (rHuLeptin) when delivered either subcutaneously or intrathecally in a large animal species, the beagle dog. Methods and Procedures: Adult beagle dogs were used for all studies (n = 3 to 14). Treatment with rHuLeptin was either as daily subcutaneous or intermittent intrathecal injections. Results: Subcutaneously administered rHuLeptin was absorbed with peak concentrations appearing at 2 to 4 hours. After intrathecal administration, cerebral spinal fluid concentrations declined in a bi-phasic manner with a terminal half-life of ?6 to 8 hours. When lean beagles were given leptin subcutaneously, at 0. 05 to 5 gkglday for up to 6 months, reductions in body weight (up to 30%) and food intake (up to 75%) were observed. Body fat loss was observed in both lean and obese dogs, and confirmed by dual energy X-ray absorptiometry and histology of adipose tissue. When rHuleptin was delivered intrathecally at 4 to 1000 μg/dose for up to 3 months, the primary effects observed were reductions in body weight and food intake. In general all findings reported in the intrathecal studies were consistent with those noted in the subcutaneous studies; however, the required intrathecal dose was substantially lower than that for subcutaneous delivery. Discussion: These studies demonstrate that both subcutaneous and intrathecal treatment of rHuLeptin was associated with effects on body weight, food intake, and body fat in dogs. These results support the concept that the central nervous system is the probable primary site of action for leptin and suggest that rHuLeptin has similar physiologic activities that influence body weight, body fat, and metabolism in large animals to those reported previously in rodents.     

A Qualitative and Quantitative Study of a Sensory Epithelium in the Inner Ear of a Fish (Colisa labiosa; Anabantidae)

The macula lagenae of the anabantide fish Colisa labiosa was studied with light and transmission electron microscopy. (1) The sensory area is naturally divided in a central area (A) surrounded by a peripheral part (B). (2) Generally the central hair cells are separated by supporting cells, while the peripheral hair cells are found in groups. The cells of a group are not separated by supporting cells. (3) Tubuli-like structures, hexagonal in cross section, are found in all cells. In peripheral hair cells the longitudinally oriented tubuli-like structures are aggregated in thick bundles. (4) Variation in shape, electron density, stereocilia arrangement and size of mitochondria was found in different hair cells. (5) The central hair cells contain large accumulations of presynaptic bodies (10–44). Contrarily, the peripheral hair cells contain only a few pre-synaptic bodies (1–3). (6) The central hair cells are innervated by thick afferent (6–15 μm) and fine presumed efferent (less than 1 μm nerve fibres, while the peripheral hair cells are innervated by thin (1–6 μm) afferent nerve fibres only.     

The role of brain‐derived neurotrophic factor in learned fear processing: an awake rat fMRI study

Brain‐derived neurotrophic factor (BDNF) signaling is implicated in the etiology of many psychiatric disorders associated with altered emotional processing. Altered peripheral (plasma) BDNF levels have been proposed as a biomarker for neuropsychiatric disease risk in humans. However, the relationship between peripheral and central BDNF levels and emotional brain activation is unknown. We used heterozygous BDNF knockdown rats (BDNF^+/?) to examine the effects of genetic variation in the BDNF gene on peripheral and central BDNF levels and emotional brain activation as assessed by awake functional magnetic resonance imaging (fMRI). BDNF^+/? and control rats were trained to associate a flashing light (conditioned stimulus; CS) with foot‐shock, and brain activation in response to the CS was measured 24 h later in awake rats using fMRI. Central and peripheral BDNF levels were decreased in BDNF^+/? rats compared with control rats. Activation of fear circuitry (amygdala, periaqueductal gray, granular insular) was seen in control animals; however, activation of this circuitry was absent in BDNF^+/? animals. Behavioral experiments confirmed impaired conditioned fear responses in BDNF^+/? rats, despite intact innate fear responses. These data confirm a positive correlation [r = 0.86, 95% confidence interval (0.55, 0.96); P = 0.0004] between peripheral and central BDNF levels and indicate a functional relationship between BDNF levels and emotional brain activation as assessed by fMRI. The results demonstrate the use of rodent fMRI as a sensitive tool for measuring brain function in preclinical translational studies using genetically modified rats and support the use of peripheral BDNF as a biomarker of central affective processing.     

Physiological regeneration of the digestive parenchyma in Convoluta convoluta and Oxyposthia praedator (Turbellaria,Acoela)

Autoradiography has been applied to two acoel turbellarians, Convoluta convoluta and Oxyposthia praedator, to determine the distribution and fate of proliferative cells. In C. convoluta, mitotic figures and nuclei that labelled with [³H]thymidine could be observed in the peripheral parenchyma but not in the middle zone of the central parenchyma. The time required for regeneration of physiologically competent digestive cells was about 10–15 days. In O. praedator, mitotic figures (in metaphase and telophase) were observed in the peripheral parenchyma while none were found in the epidermis either in untreated animals or after treatment with colchicine. Mitotic figures were found only rarely in the central parenchyma and only in its marginal zone. Autoradiographs of O. praedator demonstrated [³H]thymidine incorporation into both the nuclei and the cytoplasm of peripheral parenchymal cells. In the central parenchyma, no nuclei with primary labelling were observed. The digestive parenchyma of the acoels is regarded as a unique histological system involving both specialized cells of the central parenchyma and stem cells located in the peripheral parenchyma.     

Immediate intraplumular distribution of macromolecular syntheses following floral induction in Pharbitis nil

Uridine and thymidine incorporation into the peripheral vs.central zone of the Japanese Morning Glory apex, as well asinto the apical leaves, was measured a few hours before andbeyond the end point of the inducing long night. The enhancedincorporation was greatest in the peripheral zone and in theapical leaves suggesting that immediate pre-prefloral effectsare mainly expressed "vegetatively". (Received December 11, 1974; )     

Effects of soil heterogeneity and clonal integration on Alternanthera philoxeroides populations with a radial ramet aggregation

Some clonal plants can spread their ramet populations radially, and soil heterogeneity and clonal integration may greatly affect the establishment of these types of populations. We constructed Alternanthera philoxeroides populations with a radial ramet aggregation, allowing old ramets of clonal fragments to concentrate in central pots and younger ramets to root in peripheral pots. The peripheral pots were supplemented either with three different levels (high, medium and low) of soil nutrients to simulate a heterogeneous soil environment, or only one medium level of soil nutrients to simulate a homogeneous environment. Stolon connections between the central older ramets and the peripheral younger ramets were left intact or severed to test the effect of clonal integration. The maintenance of stolon connection could induce the division of labor between different‐aged ramets, by increasing the root investment in central ramets and the above‐ground growth in peripheral ramets. The maintenance of stolon connection could improve the growth of the central and peripheral ramets, clonal fragments and even the whole population. However, the positive consequence in peripheral ramets and whole fragments was only detected in the high‐nutrient patch of heterogeneous treatment. In sum, in the population with the radial ramet aggregation, clonal integration can play a key role in the rapid recruitment of young ramets of A. philoxeroides fragments, as well as the expansion of the whole population. The magnitude of clonal integration also became more obvious in the peripheral young ramets and whole fragments that experienced high‐nutrient patches.     

Delayed onset of single dose tolerance to morphine analgesia

Rats received either 20 mg/Kg of morphine sulfate I.P. or 5 μgm of morphine sulfate microinjected into the periaqueductal gray area of the brain. The analgesic effect of the morphine was determined by comparing pre- and postinjection tailflick latencies. To test for tolerance following a single injection, the procedure was repeated 6, 12 or 24 hours after the first injection and tests. Tolerance was not observed 6 hours after the original injection, tolerance was observed at 12 hours and increased tolerance was present at 24 hours. Single dose tolerance to morphine appears to develop slowly over a period of several hours and during much of this time, the amount of opiate present in the brain was insufficient to produce analgesia. Similarity between central and peripheral administration suggests a central mechanism of single dose tolerance.     

Localization of carbonic anhydrase in the salivary glands of the cockroach,Periplaneta americana

Carbonic anhydrase (CA) activity was localized in the salivery glands of the cockroach, Periplaneta americana, by (1) Hansson's histochemical technique, and (2) the use of the fluorescent sulphonamide, 5-dimethyl-amino-naphthalene-1-sulphonamide (DNSA). Both techniques reveal the same distribution pattern of CA in the four morphologically different cell types of the glands: peripheral cells, central cells, inner acinar duct cells, and distal duct cells. Positive reactions with Hansson's cobalt/phosphate technique were found in the apical regions of the peripheral cells and the distal duct cells, and were inhibited by 10^–5 M acetazolamide in control experiments. No staining could be detected in the central cells and the inner acinar duct cells. The fluorescent CA inhibitor DNSA (10^–4 M) specifically stained the peripheral cells and the distal duct cells in methanolfixed cryostat sections, whereas the central cells and the inner acinar duct cells remained unstained. The role of CA in the peripheral cells is not clear. CA activity in the distal duct cells may provide the protons needed to run the vacuolar-type H⁺-ATPase on the apical infoldings of the cells. This ATPase may be involved in modification of the primary saliva.     

Avian predation at a Southern Rockhopper Penguin colony on Staten Island,Argentina

We studied predation risk in relation to nest location and subcolony size in Southern Rockhopper Penguins (Eudyptes chrysocome chrysocome) during the chick-rearing period. Striated Caracaras (Phalcoboenus australis), the main predator, preferentially attacked from tussock grasses which are found in the periphery of all subcolonies (peripheral tussocks) and often scattered within them (central tussocks). The greatest numbers of predation and attempted predation events were observed on nests in the periphery of the subcolony next to peripheral tussocks, and on those nests next to central tussocks. Central tussocks offer Striated Caracaras an additional “edge” area from which to prey, much in the same way as do the peripheral tussocks. Predation rate per individual was not correlated with subcolony size possibly due to the presence of central tussocks which, by creating an extra edge area, change the subcolony shape. There is a suggestion (P = 0.06) of increased probability of nest success with subcolony size.     

The presence and location of small cardioactive‐like peptides in larvae of Crassostrea virginica

We examined the presence and location of small cardioactive peptide (SCP)‐like neuropeptides in both the central and peripheral nervous systems of D‐hinge, newly eyed, and pediveliger larvae of Crassostrea virginica. Results indicate that SCP‐like substances are present early in development (D‐hinge larvae), and that presence in the central and peripheral nervous systems increases as the larva develops toward metamorphic competence (pediveliger larvae). In addition, in newly eyed and pediveliger larvae, SCP‐like labeling is found in a varying number of neurons within all central ganglia, with the possible exception of the accessory ganglia. Varicose labeling of axons is also documented within the ganglia, commissures, and connectives, as well as in peripheral nerves. Peripheral tissues innervated by axons exhibiting SCP‐like immunoreactivity include the velum, foot, esophagus, mantle, and various musculatures. As indicated by the location of SCP‐like labeling in various organs and tissues, it is likely that these neuropeptides modulate muscle contraction or ciliary beating in molluscan larvae such as those of C. virginica.     

Sleeping and vigilance in Black-tailed Godwit

I studied the influence of position within the flock of the bird on the sleep-vigilance trade-off in individual Black-tailed Godwits Limosa limosa roosting at high tide. The peeking rate, the percentage of time during which its eyes were open and mean duration of peeks were highest in peripheral birds. The duration of the sleep posture, defined as the amount of time an individual sits or stands with its bill tucked beneath its scapulars, did not differ significantly between central and peripheral birds. The rate of agonistic encounters was minimal, in both peripheral and central birds. These observations suggest different benefits for both positions in the flock, mainly anti-predatory in the case of central birds and thermoregulatory in the case of peripheral birds. Electronic Publication     

Two types of plasticity in the tentacle withdrawal reflex of Helix aspersa are dissociated by tissue location and response measure

The tentacle withdrawal reflex of the terrestrial snail Helix aspersa was studied in vitro. The reflex is evoked by mechanical stimulation of the nose. Lesion experiments showed that 45% to 75% of the response amplitude is attributable to peripheral pathways alone. The central contribution increases with increasing stimulus intensity.Repeated stimulation produced pure habituation at low stimulus strengths, and habituation mixed with intrinsic sensitization (warm-up effect) at high stimulus strengths. The simultaneous occurrence of habituation and sensitization is consistent with the dual process theory of plasticity. Additional results differentiate the two processes. Habituation can occur without the CNS, whereas intrinsic sensitization requires the CNS. Also, the two processes are differentially effective in their influences on response amplitude and duration: habituation is more effective in determining response amplitude, while sensitization is more effective in determining response duration.Although the establishment of sensitization requires the CNS, 81% of the memory for intrinsic sensitization was localized to the periphery, by lesion experiments. Extrinsic sensitization, caused by stimulation of the medial lip nerve, had similar behavioural effects and a similar memory locus. Both types of sensitization appear to be caused by neuromuscular facilitation mediated by a central pathway.Abbreviations CNS central nervous system - PNS peripheral nervous system - S-R stimulus-response - TRM tentacle retractor muscle     

The effects of thyrotropin releasing hormone and histidyl-proline diketopiperazine on delta-9-tetrahydrocannabinol-induced hypothermia

The effects of central and peripheral administration of thyrotropin releasing hormone (TRH) and its postulated metabolite, histidyl-proline diketopiperazine (HPD) on △9-tetrahydrocannabinol (THC) induced hypothermia in mice were investigated. Intraperitoneal administration of THC produced hypothermia. The peak response was observed between 1 and 2 hours and the hypothermia lasted for 5 to 6 hours. Intracerebral or intraperitoneal administration of TRH prior to THC injection antagonized the hypothermic response of the latter. Similar effects were produced by histidyl-proline diketopiperazine given intracerebrally. However, HPD was completely ineffective when given intraperitoneally. The antagonism of THC-induced hypothermia by TRH may be mediated by its conversion to HPD in the central nervous system.     

Histochemical study of epididymal secretions in the lizard,Lacerta vvipara

Summary The epididymis of lizards elaborates voluminous secretory granules made of a central core and a peripheral vacuole which in the species Lacerta vivipara contain respectively an insoluble protein (protein H) and a soluble protein (protein L). After their discharge these secretions mix with spermatozoa. In order to detect the presence of carbohydrates in these secretions, lectins isolated from Canavalia ensiformis (con A) and from eleven other plants (lentil, soja, pea, gorse and several mushrooms), conjugated to fluorescein isothiocyanate, have been utilized in light-microscopic histochemical investigations of frozen sections from Lacerta vivipara epididymis. Whereas lectins having affinity for Lfucose, lactose, D-galactose and N-acetyl-D-galactosamine bound to central cores, lectins having affinity to D-glucose, N-acetylglucosamine and chitobiose bound to the peripheral vacuole. D-mannose or D-glucose seem to be present both in central cores and in peripheral vacuoles.     

Role of central and peripheral mechanisms in control of excitability of segmental motor centers in insects

The role of central and peripheral mechanisms in control of excitability of segmental centers providing different motor acts in insects of phylogenic close orders, but differing by the level of activity of their locomotor systems has been studied in the locust Locusta migratoria and the cockroach Periplaneta americana. It was shown that the level of relative excitability of segmental centers in cockroaches seemed to be much determined by the peripheral mechanisms, but not by the central mechanisms as in locust. It is suggested that control of activity of segmental locomotor centers from the higher parts of CNS can be realized by different ways: predominantly via excitatory or inhibitory influences on activity id some particular locomotor systems depending on their role and significance in motor behavior of these animals.Translated from Zhurnal Evolyutsionnoi Biokhimii i Fiziologii, Vol. 40, No. 6, 2004, pp. 508–513.Original Russian Text Copyright © 2004 by Gorelkin, Severina.To the 100-Anniversary of A. K. VoskresenskayaThis revised version was published online in April 2005 with a corrected cover date.     

Central adaptation models of the vestibulo-ocular and optokinetic systems

A theoretical analysis of two models of the vestibulo-ocular and optokinetic systems was performed. Each model contains a filter element in the vestibular periphery to account for peripheral adaptation, and a filter element in the central vestibulooptokinetic circuit to account for central adaptation. Both models account for1 adaptation, i.e. a response decay to a constant angular acceleration input, in both peripheral vestibular afferent and vestibulo-ocular reflex (VOR) responses and2 the reversal phases of optokinetic after-nystagmus (OKAN) and the VOR and3 oscillatory behavior such as periodic alternating nystagmus. The two models differ regarding the order of their VOR transfer function. Also, they predict different OKAN patterns following a prolonged optokinetic stimulus. These models have behavioral implications and suggest future experiments.     

Interconnections between the stereovilli of the fish inner ear

Summary The maculae utriculi and sacculi of the inner ear from the European roach (Rutilus rutilus) were investigated by transmission electron microscopy. The stereovilli of peripherally and centrally located sensory cells differ in several features that suggest a developmental gradient. The stereovilli of the peripheral sensory cells, shown to be differentiating cells by other research groups, are short and less steeply graded in height than in central hair cells. All stereovilli in both kinds of hair bundles are interconnected. In the central bundles of stereovilli basal, tip, and vertical connectors are separated by unconnected regions. In contrast, filaments and sometimes other additional structures connect the stereovilli of peripheral bundles over their entire length, but vertical connectors are usually absent. Osmiophilic material occurring inside peripheral stereovilli is interpreted to be monomeric actin. Central and peripheral hair bundles also differ in their reaction to ruthenium red and cationized ferritin. Only the stereovilli of the central cells can be fused by these polycations. Ruthenium red also discriminates between supporting and sensory cells indicating differences in amount or distribution of extracellular material. Hair bundles, intermediate in properties and position between central and peripheral sensory cells, were also found, so that it became possible to propose a scheme of developmental steps leading from microvilli or microvillus-like stereovilli to the fully differentiated hair bundle.