Neuropeptide Y (NPY)-like immunoreactivity in guinea pig uterus is reduced during pregnancy in parallel with noradrenergic nerves

Neuropeptide Y (NPY) is a recently discovered neuropeptide with vasoconstrictor effects when given in vivo. It occurs in many sympathetic neurons, where it appears to coexist with noradrenaline (NA). It is wellknown that profound changes in the levels of uterine NA occur in many species during pregnancy. Therefore we have investigated the distribution of catecholamine neurons and NPY by immunohistochemistry in the pregnant and nonpregnant guinea pig uterus. In the virgin uterus NPY-like immunoreactivity was present in nerve fibres and terminals in the smooth muscle layers of the uterine horns and around blood vessels. The distribution of NPY fibres was very similar to that of noradrenergic nerves visualized with antibodies against the catecholamine synthesizing enzyme tyrosine hydroxylase (TH). In the pregnant uterus, NPY- and TH-like immunoreactivity disappeared almost completely. In the cervix, a slight decrease of immunoreactivity was observed, whereas in the ovaries no changes were noted between the pregnant and nonpregnant condition. The results indicate that NPY and catecholamines coexists in the adrenergic neurons of the guinea pig uterus, cervix and ovary and that they vary together in the myometrium during pregnancy. We suggest that NPY may be of functional importance for the pregnant uterus.     

Neuropeptide Y (NPY)-like immunoreactivity in guinea pig uterus is reduced during pregnancy in parallel with noradrenergic nerves

Summary Neuropeptide Y (NPY) is a recently discovered neuropeptide with vasoconstrictor effects when given in vivo. It occurs in many sympathetic neurons, where it appears to coexist with noradrenaline (NA). It is wellknown that profound changes in the levels of uterine NA occur in many species during pregnancy. Therefore we have investigated the distribution of catecholamine neurons and NPY by immunohistochemistry in the pregnant and nonpregnant guinea pig uterus. In the virgin uterus NPY-like immunoreactivity was present in nerve fibres and terminals in the smooth muscle layers of the uterine horns and around blood vessels. The distribution of NPY fibres was very similar to that of noradrenergic nerves visualized with antibodies against the catecholamine synthesizing enzyme tyrosine hydroxylase (TH). In the pregnant uterus, NPY- and TH-like immunoreactivity disappeared almost completely. In the cervix, a slight decrease of immunoreactivity was observed, whereas in the ovaries no changes were noted between the pregnant and nonpregnant condition. The results indicate that NPY and catecholamines coexists in the adrenergic neurons of the guinea pig uterus, cervix and ovary and that they vary together in the myometrium during pregnancy. We suggest that NPY may be of functional importance for the pregnant uterus.     

Expression of glycerokinase in brown adipose tissue is stimulated by the sympathetic nervous system

The effect of cold exposure (4 degrees C) or prolonged norepinephrine infusion on the activity and mRNA levels of glycerokinase (GyK) was investigated in rat interscapular brown adipose tissue (BAT). Cold exposure for 12 and 24 h induced increases of 30% and 100%, respectively, in the activity of BAT GyK, which was paralleled by twofold and fourfold increase in enzyme mRNA levels. BAT hemidenervation resulted in reductions of 50% and 30% in GyK activity and in mRNA levels, respectively, in denervated pads from rats kept at 25 degrees C, and suppressed in these pads the cold-induced increases in both GyK activity and mRNA levels. The increase in GyK activity induced by cold exposure was not affected by phenoxybenzamine, but was markedly inhibited by previous administration of propranolol or actinomycin D. BAT GyK activity did not change significantly after 6 h of continuous subcutaneous infusion of norepinephrine (20 microg/h), but increased twofold and fourfold after 12 and 24 h, with no further increase after 72 h of infusion. Norepinephrine infusion also activated mRNA production, but the effect was comparatively smaller than that on enzyme activity. beta-Adrenergic agonists also stimulated GyK activity with the following relative magnitude of response: CL316243 (beta(3)) > isoproterenol (non-selective) > dobutamine (beta(1)). In vitro rates of incorporation of glycerol into glyceride-glycerol were increased in BAT from rats exposed to cold. The data suggest that in conditions of a sustained increase in BAT sympathetic flow there is a stimulation of GyK gene expression at the pretranslational level, with increased enzyme activity, mediated by beta-adrenoreceptors, mainly beta(3).     

Nonshivering thermogenesis in a marsupial (the tasmanian bettong Bettongia gaimardi) is not attributable to brown adipose tissue

The Tasmanian bettong (Bettongia gaimardi, a marsupial) is a rat-kangaroo that increases nonshivering thermogenesis (NST) in response to norepinephrine (NE). This study attempted to assess whether brown adipose tissue (BAT), a specialized thermogenic effector, is involved in NST in the bettong. Regulatory NST, indicated by resting oxygen consumption (Vo2) of the whole body, was measured under conscious conditions at 20 degrees C with various stimuli: cold (4 degrees -5 degrees C) or warm (25 degrees C) acclimation, NE injection, and the beta3-adrenoceptor agonist (BRL) 37344. In line with the functional studies in vivo, the presence of BAT was evaluated by examining the expression of the uncoupling protein 1 (UCP1) with both rat cDNA and oligonucleotide probes. Both NE and BRL 37344 significantly stimulated NST in the bettong. After cold acclimation of the animals (at 4 degrees -5 degrees C for 2 wk), the resting Vo2 was increased by 15% and the thermogenic effect of NE was enhanced; warm-acclimated animals showed a slightly depressed response. However, no expression of UCP1 was detected in bettongs either before or after cold exposure (2 wk). These data suggest that the observed NST in the marsupial bettong is not attributable to BAT.     

‘Nothing is permanent but change’† – antigenic variation in persistent bacterial pathogens

Pathogens persist in immunocompetent mammalian hosts using various strategies, including evasion of immune effectors by antigenic variation. Among highly antigenically variant bacteria, gene conversion is used to generate novel expressed variants from otherwise silent donor sequences. Recombination using oligonucleotide segments from multiple donors is a combinatorial mechanism that tremendously expands the variant repertoire, allowing thousands of variants to be generated from a relatively small donor pool. Three bacterial pathogens, each encoded by a small genome (< 1.2 Mb), illustrate this variant generating capacity and its role in persistent infection. Borrelia burgdorferi VlsE diversity is encoded and expressed on a linear plasmid required for persistence and recent experiments have demonstrated that VlsE recombination is necessary for persistence in the immunocompetent host. In contrast, both Treponema pallidum TprK and Anaplasma marginale Msp2 expression sites and donors are chromosomally encoded. Both T. pallidum and A. marginale generate antigenic variants in vivo in individual hosts and studies at the population level reveal marked strain diversity in the variant repertoire that may underlie pathogen strain structure and the capacity for re‐infection and heterologous strain superinfection. Here, we review gene conversion in bacterial antigenic variation and discuss the short‐ and long‐term selective pressures that shape the variant repertoire.     

Ice ages leave genetic diversity ‘hotspots’ in Europe but not in Eastern North America

After the last glacial cycle, temperate European trees migrated northward, experiencing genetic bottlenecks and founder effects, which left high haplotype endemism in southern populations and clines in genetic diversity northward. These patterns are thought to be ubiquitous across temperate forests, and are therefore used to anticipate the potential genetic consequences of future warming. We compared existing and new phylogeographic data sets (chloroplast DNA) from 14 woody taxa in Eastern North America (ENA) to data sets from 21 ecologically similar European species to test for common impacts of Quaternary climate swings on genetic diversity across diverse taxa and between continents. Unlike their European counterparts, ENA taxa do not share common southern centres of haplotype endemism and they generally maintain high genetic diversity even at their northern range limits. Differences between the genetic impacts of Quaternary climate cycles across continents suggest refined lessons for managing genetic diversity in today's warming world.     

‘Myrosin cells’ are not a prerequisite for aphid feeding on oilseed rape (Brassica napus) but affect host plant preferences

The enzyme myrosinase (EC 3.2.3.1.147) is present in specialised myrosin cells and forms part of the glucosinolate–myrosinase system, also known as ‘the mustard oil bomb’, which has an important role in the defence system of cruciferous plants against insect pests. Transgenic Brassica napus MINELESS have been produced by transgenic ablation of myrosin cells. This prompted us to investigate the importance of myrosin cells in plant–aphid interactions. In order to study this, we challenged transgenic MINELESS and wild‐type cultivar Westar seedlings with the aphids Brevicoryne brassicae (a specialist) and Myzus persicae (a generalist). Our study included aphid free‐choice and aphid fecundity experiments. Data from these experiments showed that B. brassicae prefers wild‐type seedlings and M. persicae prefers MINELESS. B. brassicae and M. persicae showed significant variation in establishment on plants regardless of whether they were wild type or MINELESS and also differed significantly in affecting plant parts. Myrosinase activity in MINELESS control seedlings was 83.6% lower than the wild‐type control seedlings. Infestation with either of the two aphid species induced myrosinase levels in both wild‐type and MINELESS seedlings. Infestation with M. persicae reduced the concentration of most glucosinolates while B. brassicae had the opposite effect. B. brassicae enhanced the formation of glucosinolate hydrolysis products both in wild‐type and MINELESS seedlings. However, M. persicae decreased All ITC but increased 3,4ETBut NIT in wild‐type seedlings. Taken together, the investigation shows that the presence of myrosin cells affects the preference of generalist and specialist aphid species for Brassica napus plants.     

The AAT1 locus is critical for the biosynthesis of esters contributing to ‘ripe apple’ flavour in ‘Royal Gala’ and ‘Granny Smith’ apples

The ‘fruity’ attributes of ripe apples (Malus × domestica) arise from our perception of a combination of volatile ester compounds. Phenotypic variability in ester production was investigated using a segregating population from a ‘Royal Gala’ (RG; high ester production) × ‘Granny Smith’ (GS; low ester production) cross, as well as in transgenic RG plants in which expression of the alcohol acyl transferase 1 (AAT1) gene was reduced. In the RG × GS population, 46 quantitative trait loci (QTLs) for the production of esters and alcohols were identified on 15 linkage groups (LGs). The major QTL for 35 individual compounds was positioned on LG2 and co‐located with AAT1. Multiple AAT1 gene variants were identified in RG and GS, but only two (AAT1‐RGa and AAT1‐GSa) were functional. AAT1‐RGa and AAT1‐GSa were both highly expressed in the cortex and skin of ripe fruit, but AAT1 protein was observed mainly in the skin. Transgenic RG specifically reduced in AAT1 expression showed reduced levels of most key esters in ripe fruit. Differences in the ripe fruit aroma could be perceived by sensory analysis. The transgenic lines also showed altered ratios of biosynthetic precursor alcohols and aldehydes, and expression of a number of ester biosynthetic genes increased, presumably in response to the increased substrate pool. These results indicate that the AAT1 locus is critical for the biosynthesis of esters contributing to a ‘ripe apple’ flavour.     

The origin of a ‘true’ worker caste in termites: phylogenetic evidence is not decisive

The phylogenetic study of the origin of a ‘true’ worker caste in termites by Thompson et al. [J. Evol. Biol. 13 (2000) 869] did not take into account all possibilities of character coding and character optimization on the phylogenetic tree. Actually, contrary to the authors' statements, the phylogenetic evidence presented does not permit to answer decisively most of the questions asked concerning the origin and evolution of worker castes in termites. Particular attention was paid to assumptions implied by the coding of the characters of interest, namely concerning the homology between pseudergates and a ‘true’ worker caste and the kind of the cockroach life type.     

Long term ‘marine diet’ in Eskimos is not associated with altered urinary excretion of total tetranor prostaglandin metabolites

The total urinary excretion of tetranor prostaglandin metabolites, measured as tetranorprostanedioic acid (TPD), was quantified in traditionally living Greenland Eskimos (E) and compared with that in Caucasian Danes (D). TPD excretion (μg/24h) was not significantly different between both groups, neither for males (331 ± 62.4 (E) vs. 331 ± 25.7 (D), mean ± SEM, n = 9 and 10) nor for females (190 ± 31.7 (E) vs. 264 ± 27.4 (D), n = 11 and 10, P₂ > 0.05). Since urinary prostaglandin metabolites are thought to reflect the total prostaglandin turnover in vivo, these results suggest that a long-term intake of relatively large amounts of polyunsaturated fatty acids of the (n-3) family does not alter total prostaglandin turnover in vivo. This is in contrast to stimulated prostanoid formation in vitro, and thus suggests a different regulatory role of dietary and tissue fatty acids for ‘stimulated’ and ‘basal’ prostaglandin production.     

Mechanisms of phytohaemagglutinin (PHA) stimulation of normal human lymphocytes: ‘trigger’, ‘push’ or both?

Abstract. The growth in volume of human peripheral blood lymphocytes after stimulation with various concentrations of PHA was measured with an electronic particle counter. The percentage of growing cells and averaged values describing their growth rates during the elapsed period of culture were estimated by fitting to the observed data the volume distributions derived from a mathematical model. With sub-optimal doses, the percentage of cells stimulated, and their incremental growth rate, increased with increasing dose of PHA, but the time-course of recruitment into the G₁-phase was similar with all PHA concentrations studied. The results provide strong support for the 'trigger' hypothesis that there is a distribution of stimulation thresholds within the lymphocyte population: consequently, increasing mitogen concentration will be expected to result in increased numbers of responding cells within the suboptimal concentration range.     

Developmental instability of vascular plants in contrasting microclimates at ‘Evolution Canyon’

Rocellaria dubia bores into subtidal rocks of karsted limestone in the Adriatic Sea and elsewhere. It also bores into the shells of various bivalve species. The mechanism of boring has hitherto been debated, but examination of occupied shells suggest that this is achieved by mechanical (the shell) abrasion and chemical etching using secretions produced from glands in the anterior mantle. Fast‐growing bivalves such as Ostrea edulis and Pinna nobilis carry heavy R. dubia burdens, and encapsulate the borer in secreted calluses. Slow‐growing bivalves such as the burrowing Venus verrucosa and Glycymeris violacescens carry low R. dubia burdens, are less able to encapsulate the borers, and probably incur enhanced mortalities as a result. Individuals of R. dubia removed from their limestone boreholes re‐secreted adventitious tubes around their siphons, probably from glands in the posterior mantle. The lifestyle of R. dubia is now better understood, and its ability to bore bivalve shells in particular suggests how the more advanced tropical gastrochaenids Cucurbitula and Eufistulana have evolved from initial (as juveniles) bivalve shell borers into occupants of adventitious crypts and tubes, respectively. It is further argued that the Gastrochaenidae show convergent similarities with the similar crypt‐ and tube‐building representatives of the Clavagelloidea. © 2011 The Linnean Society of London, Biological Journal of the Linnean Society, 2011, 104 , 786–804.     

Assessment of species limits in African ‘brown buntings’ (Emberiza,Passeriformes) based on mitochondrial and nuclear sequence data

We estimated a phylogeny for 10 taxa currently placed in four polytypic species that collectively encompass the African ‘brown buntings’: Cape Bunting Emberiza capensis, Cinnamon‐breasted Bunting Emberiza tahapisi, Lark‐like Bunting Emberiza impetuani and House Bunting Emberiza striolata. We made use of the mitochondrial cytochrome b gene and the nuclear introns 6–7 of ornithine decarboxylase (ODC), and intron 2 of myoglobin. There was substantial cytochrome b sequence divergence between taxa currently treated as conspecific: sahari vs. striolata (2.6–3.1% (uncorrected‐p); 3.0–3.6% (HKY + I)), and goslingi vs. tahapisi (4.4–4.7% (uncorrected‐p); 5.4–5.9% (HKY + I)). The degree of divergence of the nuclear loci among taxa was limited, and these loci lacked reciprocal monophyly, most likely as a consequence of incomplete lineage sorting. A single representative of the taxon septemstriata, generally treated as a member of the dark‐throated tahapisi group, here appears to be genetically consistent with the grey‐throated goslingi, and may be of hybrid origin. All other taxa allocated to E. striolata and E. tahapisi make up four reciprocally monophyletic groups consistent with sahari, striolata, tahapisi and goslingi, respectively. The extent of genetic evidence suggests that these taxa have been evolving as separate evolutionary lineages for a long time. This is further manifested in several morphological and vocal characteristics described previously, and we propose that these divergent taxa be treated as separate species: Cinnamon‐breasted Bunting Emberiza tahapisi, Gosling's Bunting Emberiza goslingi, Striolated Bunting Emberiza striolata and House Bunting Emberiza sahari. We do not propose any taxonomic changes regarding Emberiza impetuani or Emberiza capensis.     

Oncogenic transformation of 3T3 cells is associated with conversion from an ‘adult’ to an ‘embryonic’ esterase isoenzyme pattern

Soluble esterases from virus-transformed sublines of 3T3 Swiss mouse fibroblasts exhibit an isoenzyme pattern in polyacrylamide gel electrophoresis similar to the pattern exhibited by primary mouse embryo cells but distinct from that exhibited by 3T3 cells. The soluble esterase isoenzyme pattern exhibited by 3T3 cells is similar to that exhibited by primary and secondary fibroblastoid cells derived from adult Swiss mouse kidney, suggesting that, despite its embryonic origin, 3T3 is an ‘adult’ cell line selected and maintained in that state by the requirement that it exhibits a low saturation density and a characteristic morphology in culture. The pattern of soluble esterase isoenzymes is similar in growing and non-growing 3T3 cells, although the specific activity is higher in preparations from non-growing cells. Sparse 3T3 cells contain at least three detergent-soluble esterase isoenzymes present at much lower levels in denser cultures.The esterase and amidase enzyme activities measured in solution with the fluorogenic substrates fluorescein diacetate and rhodamine diacetate, respectively, are substantially higher in three subcellular fractions from virus-transformed 3T3 mouse fibroblasts than in the corresponding fractions from 3T3 mouse fibroblasts or from primary mouse embryo cells. The largest increases in activity associated with viral transformation were observed in membrane-associated esterases.