Root development in simple and complex tropical successional ecosystems

Fine and coarse root mass and fine root surface area were studied during 5 yr following the felling and burning of a tropical forest near Turrialba, Costa Rica. Five experimental ecosystems were established: 1) natural successional vegetation, 2) successional vegetation enriched by seed applications, 3) imitation of succession (built by substituting investigator-selected species for natural colonizers), 4) monocultures (two maize crops followed by cassava andCordia alliodora), and 5) a bare plot. Fine roots grew rapidly in all treatments during the first 15 wk, at which time there were 75 gm⁻² in the monoculture and 140 gm⁻² in the enriched and natural successions. Subsequent growth was slower, and fine-root mass decreased during the first dry season. After 5 yr coarse root mass to a depth of 85 cm was about 800, 1370, and 1530 gm⁻² in the succession, enriched succession and imitation of succession, respectively. At the final harvest, the 3.5 yr-oldC. alliodora plantation had 1000 g m⁻² of coarse-root biomass. Roots <1 mm in diameter were concentrated in the upper 5 cm of soil and accounted for most fine-root surface area. Total fine-root surface area was greatest in the enriched successional vegetation and usually lowest in the monoculture.     

Activation of metabotropic glutamate receptors in conjunction with postsynaptic depolarization triggers a long-term depression of the N-methyl-D-aspartate receptor-mediated synaptic potential in the rat hippocampus

The mechanism responsible for long-term depression (LTD) of pharmacologically isolated N-methyl-D-aspartate (NMDA) receptor-mediated excitatory postsynaptic potential (EPSP_NMDA) was studied. Intracellular recordings were made from CA1 cells of rat hippocampal slices in the presence of 6-cyano-7-nitroquinoxaline-2,3-dione (10 µM) and picrotoxin (50 µM), which block non-NMDA and GABA_A receptors, respectively. Intracellular injections of depolarizing pulses (500 ms, 0.3–0.7 nA) at 1 Hz for 5 min in the absence of synaptic stimulation caused a persistent increase in the amplitude of EPSP_NMDA. However, coupling postsynaptic depolarization with synaptic activity induced LTD. The EPSP_NMDA LTD could be blocked byL-2-amino-3-phosphonopropionic acid (50 µM) or (RS)--methyl-4-carboxyphenylglycine (200 µM), specific antagonists for metabotropic glutamate receptors (mGluR). Furthermore, application oftrans-1-aminocyclopentane-1,3-dicarboxylic acid (t-ACPD, 50 µM), a specific mGluR agonist, in conjunction with postsynaptic depolarizing elicited LTD. In contrast, the mGluR agonists quisqualate or t-ACPD when given alone produced a sustained enhancement of EPSP_NMDA. Finally, coupled depolarization did not evoke LTD in slices pretreated with the protein kinase C (PKC) inhibitor calphostin c (60 nM). The present results demonstrate that activation of mGluR is necessary for the induction of LTD of EPSP_NMDA and suggest that NMDA receptors are subject to bidirectional regulation by mGluR. Furthermore, the induction of LTD is likely to involve the stimulation of PKC.     

Foraging on buds and bark of mulberry trees by Japanese monkeys and their range utilization

The Japanese monkey (Macaca fuscata) winter range utilization and the effects of foraging on mulberry trees (Morus bombycis) were studied in the Shimokita Peninsula during four winter seasons. The monkeys ate mainly winter dormancy buds when they visited the mulberry tree clumps for the first time within the winter, but they ate mainly bark when they visited for the second or third times. In the areas utilized by the monkeys over the recent three years, the mulberry trees compensated for the decrease in their number of shoots by producing longer shoots with more buds against the monkey foraging. In the areas used every year for more than four years, however, the mulberry trees were unable to compensate for the foraging pressure. Thus, although the monkeys had apparently operated prudent herbivory within three years, they did not do so on a longer time-scale. They shifted their utilization ranges after having over-exploited the mulberry trees.     

Modulation of α-Amino-3-Hydroxy-5-Methylisoxazole-4-Propionic Acid (AMPA) Binding Sites by Nitric Oxide

Abstract: Nitric oxide release is reported to be involved in physiological processes associated with altered sensitivity of the α-amino-3-hydroxy-5-methylisoxazole-4-propionic acid (AMPA) class of glutamate receptor. A series of compounds liberating nitric oxide were therefore tested for their ability to modulate in vitro the characteristics of [³H]AMPA binding to sections of rat brain. Pretreatment of forebrain or cerebellar sections with sodium nitroprusside (1 m M ), S -nitroso- N -acetylpenicillamine (SNAP, 200 µ M ), glyceryl trinitrate (1 µ M ), or isosorbide dinitrate (0.5 m M ) all increased the binding of 3 n M [³H]AMPA by 15–30%. These actions were reproduced by 8-bromo-cyclic GMP (200 µ M ) in the cerebellum but not in the forebrain. In a similar manner, the effect of SNAP was attenuated by an inhibitor of cyclic GMP-dependent protein kinase in the cerebellum but not in the forebrain. The elevated [³H]AMPA binding observed after pretreatment with SNAP was caused by an increase in binding affinity, but the capacity of the sites was unchanged. Autoradiographic analysis showed that forebrain binding was enhanced in the cerebral cortex and hippocampus but not in the striatum. Nitric oxide therefore appears to be able to increase the affinity of AMPA binding sites via two distinct mechanisms in different brain areas. This action may contribute to synaptic plasticity associated with nitric oxide release.     

Parental nonemployment in childhood and children’s health later in life

While the effects of joblessness on the health of the non-employed are well-documented, its long-term spillover consequences on the health of their relatives, especially children, remain poorly understood. This research explores the long-term associations of parental nonemployment spells experienced during early, mid and late childhood on children’s mental and physical health. The analysis exploits data drawn from the British Household Panel Survey (BHPS) and the UK Household Longitudinal Study (UKHLS), linking detailed parental socioeconomic information with their children between the years 1993 and 2013. This paper employs a Correlated Random Effects (CRE) probit model that allows accounting for unobserved heterogeneity as well as a non-linear Generalized Estimating Equations (GEE) random effects estimator accounting in addition for the dependency structure of the data. Results indicate that experiencing parental nonemployment during early and late childhood has a negative association on the children’s likelihood of suffering from long-standing illnesses later in life, while experiencing parental nonemployment during middle childhood negatively affects the young adult’s mental health. Moreover, experiencing parental nonemployment during late childhood increases the probability of both reporting poor or fair self-assessed health and the likelihood of consuming prescribed medicines in early adulthood. However, there seems to be a considerable effect heterogeneity by family socioeconomic status, parents’ gender, and frequencies of parental nonemployment spells. Current adulthood circumstances, such as level of educational attainment, job situation and household demographics, are used to explore the potential mechanisms affecting results. These findings may help policymakers shape appropriate responses to mitigate the psychological and physical burden derived from parental nonemployment, especially among already disadvantaged households.     

Optimization of isolation and storage of sperm cells from pollen of perennial ryegrass (Lolium perenne L.)

Summary A procedure for isolating sperm cells of perennial ryegrass (Lolium perenne L.) was developed. The sperm cells were released from the pollen grains by osmotic shock, with the right combination of pH and osmolality being important for optimal release. Various combinations of vitamins E, C and fetal calf serum were tested with the aim of improving yield and long-term viability, and their possible mode of action as important components for improvement of these two parameters is discussed. Under optimized conditions, a yield of 12% was established, and the storage time after which 50% of the sperm cells were still viable was improved to 60 h. Cytological observations demonstrated that sperm cells of perennial ryegrass are true protoplasts, which may allow future fusion experiments to be carried out.     

Long-term and transgenerational effects of cryopreservation on rabbit embryos

The short-term effects of cryopreservation and embryo transfer are well documented (reduced embryo viability, changes in pattern expression), but little is known about their long-term effects. We examined the possibility that embryo vitrification and transfer in rabbit could have an impact on the long-term reproductive physiology of the offspring and whether these phenotypes could be transferred to the progeny. Vitrified rabbit embryos were warmed and transferred to recipient females (F0). The offspring of the F0 generation were the F1 generation (cryopreserved animals). Females from F1 generation offspring were bred to F1 males to generate an F2 generation. In addition, two counterpart groups of noncryopreserved animals were bred and housed simultaneously to F1 and F2 generations (CF1 and CF2, respectively). The reproductive traits studied in all studied groups were litter size (LS), number born alive at birth (BA), and postnatal survival at Day 28 (number of weaned/number born alive expressed as percentage). The reproductive traits were analyzed using Bayesian methodology. Features of the estimated marginal posterior distributions of the differences between F1 and their counterparts (F1 − CF1) and between F2 and their counterparts (F2 − CF2) in reproductive characters found that vitrification and transfer procedures cause a consistent increase in LS and BA between F1 and CF1 females (more than 1.4 kits in LS and more than 1.3 BA) and also between F2 and CF2 females (0.96 kits in LS and 0.94 BA). We concluded that embryo cryopreservation and transfer procedures have long-term effects on derived female reproduction (F1 females) and transgenerational effects on female F1 offspring (F2 females).     

A staining procedure for micronucleus test using new methylene blue and acridine orange: specimens that are supravitally stained with possible long-term storage

The micronucleus test has been widely used as an in vivo cytogenetic test. It employs two different kinds of supravital staining methods which use either new methylene blue (N) and Giemsa (G) or acridine orange (AO). We have developed a new staining procedure for the preparation of specimens supravitally stained with possible long-term storage, using both N and AO. This N/AO-staining method involves three steps; (1) combination of the target tissue or target cells with an equivalent volume of 0.5% solution of new methylene blue (N-staining step), (2) immediate smear of the mixture, followed by treatment with methanol for 10 min for fixation and removal of N and drying (referred to as fixed-decolorized specimens), and (3) staining with 0.007% solution of AO for 3 min, followed by washing with Sörensen's buffer (pH 6.8) and covering of specimens before observation (AO-staining step). To examine whether the N/AO-staining method is useful for the micronucleus test, comparisons were made between N-, N/AO-, and AO-stained specimens prepared supravitally from peripheral blood of rats with and without treatment of cyclophosphamide. The results indicate that N/AO-stained specimens can be supravitally observed after long-term storage with the same coloration and comparable frequencies of micronucleated reticulocytes with a positive response as AO-stained specimens, if the staining process is temporarily stopped before AO-staining (as fixed-decolorized specimens), or if the AO-staining step is repeated. The results also showed that separated reticulocyte types are supravitally stained in a similar fashion to N-stained specimens but not to AO-stained specimens, indicative of the preservation of the supravital feature of N-staining. Taken together these results suggest that the N/AO-staining procedure could offer an additional useful staining tool for the micronucleus test.     

Stand development and regeneration during a 33-year period in a seral Picea glehnii forest, northern Japan

Stand development and regeneration were studied during a 33-year period (1965-1998) in a 1-ha plot in a seral Picea glehnii forest in northern Japan. P. glehnii was mono-dominant in the upper canopy layer, but its understory trees were rarely found in 1965. Other species were scarcely observed in 1965. Many recruited saplings of Abies sachalinensis which had grown to > 5 cm diameter at breast height (DBH) by 1998 had become dominant in the understory layer. Mortality of P. glehnii canopy trees was low. Therefore, the stand basal area increased during the census period due to the growth of surviving canopy trees. Stand development brought about intense competition among trees by increasing local crowding for each tree, and promoted dominance of larger trees and suppression of smaller trees. Although growth rates of understory trees of the two conifers decreased with the increase in local crowding, the growth rate of A. sachalinensis was consistently higher than that of P. glehnii at all extents of local crowding. The recruitment rate (growing to 5 cm DBH) of the two conifers was less affected by local crowding. However, the number of recruits of P. glehnii was only about a quarter of that of A. sachalinensis during the census period because the regeneration of P. glehnii was largely restricted to fallen logs and within 1 m of the base of any live tree > 20 cm DBH. Therefore, our long-term study suggests that A. sachalinensis will dominate over P. glehnii in the seral forest because of higher recruitment and growth rates of the former than the latter in the understory.An erratum to this article can be found at     

Long-term potentiation and olfactory memory formation in the carp (<Emphasis Type="Italic">Cyprinus carpio</Emphasis> L.) olfactory bulb

Long-term potentiation of synaptic transmission is considered to be an elementary process underlying the cellular mechanism of memory formation. In the present study we aimed to examine whether or not the dendrodendritic mitral-to-granule cell synapses in the carp olfactory bulb show plastic changes after their repeated activation. It was found that: (1) the dendrodendritic mitral-to-granule cell synapses showed three types of plasticity after tetanic electrical stimulation applied to the olfactory tract—long-term potentiation (potentiation lasting >1 h), short-term potentiation (potentiation lasting <1 h) and post-tetanic potentiation (potentiation lasting <10 min); (2) Long-term potentiation was generally induced when both the dendrodendritic mitral-to-granule cell synapses and centrifugal fiber-to-granule cell synapses were repeatedly and simultaneously activated; (3) long-term enhancement (>1 h) of the odor-evoked bulbar response accompanied the electrically-induced LTP, and; (4) repeated olfactory stimulation enhanced dendrodendritic mitral-to-granule cell transmission. Based on these results, it was proposed that long-term potentiation (as well as olfactory memory) occurs at the dendrodendritic mitral-to-granule cell synapses after strong and long-lasting depolarization of granule cells, which follows repeated and simultaneous synaptic activation of both the peripheral and deep dendrites (or somata).