The anticonvulsant effect of citalopram on El mice,and the levels of tryptophan and tyrosine and their metabolites in the brain

Serotonin (5-HT) plays an important role in the seizures of El mice since the seizure threshold of El mice correlates with the 5-HT concentration in the central nervous system. In this study, the anticonvulsant effect of a 5-HT reuptake blocker, citalopram, was evaluated behaviorally and biochemically. El mouse convulsions were inhibited by oral administration of citalopram for 2 weeks. Citalopram increased tryptophan and tyrosine amounts, and decreased the 5-HT, 5-hydroxy-indoleacetic acid, kynurenine, and dopamine amounts in the brain. These findings show that citalopram depresses monoaminergic metabolism. Given the known convulsant effect of kynurenine, it is suggested that its decrease by citalopram may involve attenuation of El mice seizures.     

Nectar bacteria,but not yeast,weaken a plant–pollinator mutualism

Mutualistic interactions are often subject to exploitation by species that are not directly involved in the mutualism. Understanding which organisms act as such ‘third-party’ species and how they do so is a major challenge in the current study of mutualistic interactions. Here, we show that even species that appear ecologically similar can have contrasting effects as third-party species. We experimentally compared the effects of nectar-inhabiting bacteria and yeasts on the strength of a mutualism between a hummingbird-pollinated shrub, Mimulus aurantiacus, and its pollinators. We found that the common bacterium Gluconobacter sp., but not the common yeast Metschnikowia reukaufii, reduced pollination success, seed set and nectar consumption by pollinators, thereby weakening the plant–pollinator mutualism. We also found that the bacteria reduced nectar pH and total sugar concentration more greatly than the yeasts did and that the bacteria decreased glucose concentration and increased fructose concentration whereas the yeasts affected neither. These distinct changes to nectar chemistry may underlie the microbes'' contrasting effects on the mutualism. Our results suggest that it is necessary to understand the determinants of microbial species composition in nectar and their differential modification of floral rewards to explain the mutual benefits that plants and pollinators gain from each other.     

Epstein-Barr Virus Polypeptides: Identification of Early Proteins and Their Synthesis and Glycosylation

We have identified at least six early polypeptides induced by Epstein-Barr virus in cells or under conditions which are nonpermissive for Epstein-Barr virus DNA replication ranging in molecular weight from 140,000 to 26,000.     

Differences in liver homogenates from Donryu, Fischer, Sprague-Dawley and Wistar strains of rat in the drug-metabolizing enzyme assay and the salmonella/hepatic S9 activation test

Comparison studies for detecting differences between liver microsome and S9 preparations from 4 strains (Donryu, Fischer, Sprague-Dawley, Wistar) of young male rats were carried out with pretreatment of the animals by inducers such as PCBs and PB plus 5,6-BF. Each microsome fraction was assayed for the enzymic activity of metabolism of model substrates such as aniline, benzophetamine, BP, DMN and 7-ethoxycoumarin. The hepatic S9 sample was also compared, as regards its metabolizing ability to activate 9 pre-mutagens (2AA, AAF, o-AAT, BP, DAB, DMBA, DMN, m-PDA, quinoline) to directly acting mutagens in the Salmonella/hepatic S9 activation test by using TA98, TA100 and TA1537 strains with or without cytochrome P450 inhibitors (SKF-525A, metyrapone, 7,8-benzoflavone).In the enzymic assay with PCBs-induced microsomes, BP hydroxylation revealed a strain-specific difference: the microsomes from Fischer and Wistar rats were more effective for metabolizing BP than those from the other strains of rat. The effect of induction by PB plus 5,6-BF for Fischer rats showed relatively higher enzymic activity in the same induction group. Other microsomes prepared from rats with and without induction by PB plus 5,6-BF did not show a clear-cut strain dependency in the enzymic activities assayed.In the mutation experiments with hepatic S9 samples, the examination of DAB and quinoline revealed a marked strain difference when S9 samples prepared from PCBs-pretreated and PB-plus-5,6-BF-induced rats were used: the S9 sample from Fischer rats was available for activating the two pre-mutagens to directly acting mutagens. No marked difference in the metabolic activation of the remaining 7-pre-mutagens was observed on other S9 preparations.In examinations of mutagenicity activities with the use of three inhibitors, the two S9 preparations made with the two induction methods showed inhibition profiles closely similar to each other. However, there were minor differences in the profiles by these inhibitors.From these findings it was concluded that Fischer rat-liver S9 is useful for detecting mutagens in the metabolic activation test, when induction by PB plus 5,6-BF was used in the Ames Salmonella test.     

Establishment of hepatic stem-like cell lines from normal adult porcine liver in a poly-D-lysine-coated dish with nair-1 medium

The existence, origin, and bipotency of the hepatic stem cell (HeSC) have been investigated. However, the isolation and culture of HeSCs from adult liver tissue is not yet well established, and the mechanism by which HeSCs differentiate into mature cells remains unclear. On the other hand, the development of HeSC-isolating and -culturing methods and the in vitro clonal analysis of their mechanism of differentiation are required to enable clinical applications of regenerative medicine in the liver. For the purpose of providing HeSCs for these studies, we attempted to establish an HeSC line from a normal adult porcine liver using a unique culture system, a poly-D-lysine-coated culture dish with NAIR-1 medium (the PDL-NAIR-1 culture system). Moreover, we examined the differentiating capacity of HeSCs in vitro. We demonstrated that it was possible in the culture system that immature epithelial cells capable of proliferating grew selectively into aggregates and that two hepatic stem-like cell lines, PHeSC-A1 and PHeSC-A2, were established. The results from our data suggest that these hepatic stem-like cell lines were capable of self-renewing and differentiating into hepatocytes or biliary epithelial cells and show that the PDL-NAIR-1 culture system offers the immense advantage of isolating and culturing HeSCs from a normal adult liver. Furthermore, because of the ability to use a clonal analysis in vitro, these cell lines are useful for the investigation of various mechanisms in which HeSCs seem to participate and their application in the study of regenerative medicine in the liver.     

Drivers of vegetative dormancy across herbaceous perennial plant species

Vegetative dormancy, that is the temporary absence of aboveground growth for ≥ 1 year, is paradoxical, because plants cannot photosynthesise or flower during dormant periods. We test ecological and evolutionary hypotheses for its widespread persistence. We show that dormancy has evolved numerous times. Most species displaying dormancy exhibit life‐history costs of sprouting, and of dormancy. Short‐lived and mycoheterotrophic species have higher proportions of dormant plants than long‐lived species and species with other nutritional modes. Foliage loss is associated with higher future dormancy levels, suggesting that carbon limitation promotes dormancy. Maximum dormancy duration is shorter under higher precipitation and at higher latitudes, the latter suggesting an important role for competition or herbivory. Study length affects estimates of some demographic parameters. Our results identify life historical and environmental drivers of dormancy. We also highlight the evolutionary importance of the little understood costs of sprouting and growth, latitudinal stress gradients and mixed nutritional modes.     

A simple approach for the distribution of computationally intense tasks in an heterogeneous environment: distribution of the MDPP image-processing package

A method has been developed to link the display ability of ahigh-resolution graphics workstation with the computationalpower of a local mainframe or a remote supercomputer via anelectronic data network. The method allows this link to be establishedin a manner largely transparent to the user. The applicationof the method is illustrated by our successful distributionof the computationally intensive portions of an imaging program(MDPP) from a small VAX workstation to a VAX mainframe and CrayY-MP8/832 using a simple message-passing technique. This techniquecan be applied to almost any configuration of networked machines. Received on February 5, 1991; accepted on April 23, 1991