Nuclear androdioecy and gynodioecy

We formulate two single-locus Mendelian models, one for androdioecy and the other one for gynodioecy, each with 3 parameters: t the male (female) fertility rate of males (females) to hermaphrodites, s the fraction of the progeny derived from selfing; and g the fitness of inbreeders. Each model is expressed as a transformation of a 3 dimensional zygotic algebra, which we interpret as a rational map of the projective plane. We then study the dynamics for the evolution of each reproductive system; and compare our results with similar published models. In this process, we introduce a general concept of fitness and list some of its properties, obtaining a relative measure of population growth, computable as an eigenvalue of a mixed mating transformation for a population in equilibrium. Our results concur with previous models of the evolution of androdioecy and gynodioecy regarding the threshold values above which the sexual polymophism is stable, although the previous models assume constant the fraction of ovules from hermaphrodites that are self pollinated, while we assume constant the fraction of the progeny derived from selfing. A stable androdioecy requires more stringent conditions than a stable gynodioecy if the amount of pollen used for selfing is negligible in comparison with the total amount of pollen produced by hermaphrodites. Otherwise, both models are identical. We show explicitly that the genotype fitnesses depend linearly on their frequencies. Simulations show that any population not at equilibrium always converges to the equilibrium point of higher fitness. However, at intermediate steps, the fitness function occasionally decreases.     

A novel locus for autosomal dominant nonsyndromic hearing loss (DFNA44) maps to chromosome 3q28–29

Hereditary non-syndromic sensorineural hearing loss (NSSHL) is a genetically highly heterogeneous group of disorders. Autosomal dominant forms account for up to 20% of cases. To date, 39 loci have been identified by linkage analysis of affected families that segregate NSSHL forms in the autosomal dominant mode (DFNA). Investigation of a large Spanish pedigree with autosomal dominant inheritance of bilateral and progressive NSSHL of postlingual onset excluded linkage to known DFNA loci and, in a subsequent genome-wide scan, the disorder locus was mapped to 3q28-29. A maximum two-point LOD score of 4.36 at theta=0 was obtained for marker D3S1601. Haplotype analysis placed the novel locus, DFNA44, within a 3-cM genetic interval defined by markers D3S1314 and D3S2418. Heteroduplex analysis and DNA sequencing of coding regions and exon/intron boundaries of two genes (CLDN16 and FGF12) in this interval did not reveal disease-causing mutations.     

Effects of cortisol and prolactin on Na+ and Cl- transport in cultured branchial epithelia from FW rainbow trout

The electrophysiological and ion-transporting properties of cultured gill epithelia from freshwater (FW) rainbow trout were examined in the presence of cortisol and prolactin as media supplements. Epithelia were of the double-seeded insert (DSI) type containing both pavement cells (PVCs) and mitochondria-rich cells (MRCs) and were grown in Leibovitz's L15 media on filters allowing exposure to different apical media conditions. Experiments were carried out in two series after 7-9 days symmetrical (L15 apical-L15 basolateral) culture. In both series, 100% L15 was maintained as the basolateral medium throughout and supplemented with physiologically relevant doses of either prolactin (50 ng/ml), cortisol (500 ng/ml), or cortisol + prolactin (500 + 50 ng/ml, respectively). In series 1, epithelia were exposed to progressively diluted apical media (100, 75, 50, 25, 12.5% L15, and FW) at 24-h intervals. The preparations retained integrity [high transepithelial resistance (TER); low ion efflux rates] during this prolonged dilution protocol. Cortisol, or cortisol + prolactin, resulted in a greater TER and reduced ion efflux rates during dilution, likely an effect on junctional permeability of PVCs, but did not promote active Na+ and Cl- uptake from apical FW. In series 2, epithelia were directly exposed to apical FW and ion fluxes measured over the first 6 h. Under these conditions, cortisol or cortisol + prolactin promoted active uptake of both Na+ and Cl- simultaneously from apical FW, probably attributable to actions on the MRCs. However, Na+-K+-ATPase activities were not significantly altered by any of the treatments in either series. Overall, prolactin alone did not appear to promote FW adaptation but exhibited synergism with cortisol. These results provide further support for the cultured DSI epithelium as an in vitro model for ion transport in FW fish.     

镉负荷大鼠一氧化氮和肿瘤坏死因子-α释放在介导多器官机能活动障碍中的作用

选择健康SD雄性成年大鼠36只,随机分成对照组(C组)、镉负荷中剂量组(M组)、镉负荷高剂量组(H组).将分析纯CdCl2·2.5H2O用生理盐水稀释成含镉0.4 mg/ml浓度的注射溶液,高压灭菌.M组和H组大鼠每天分别按含镉0.5和1.0 mg/kg体重腹腔注射染毒,C组用同样方法注射与H组同等剂量的生理盐水,进行急性镉负荷实验,连续观察7 d.研究急性镉负荷对大鼠血液及几种组织中一氧化氮(NO)自由基、肿瘤坏死因子-α(TNF-a)变化的影响及作用.结果显示在整个实验期内,镉负荷大鼠体重与对照组比较明显下降;睾丸、心脏和肝脏组织中的镉含量极显著上升,并随镉负荷剂量和时间而增加;血浆NO水平M组虽高于对照组,但差异不显著,而H组极显著高于对照组,M和H组血浆TNF-α明显高于对照组;在整个实验期内,镉负荷大鼠睾丸、心脏和肝脏组织匀浆中NO较对照组高或明显高于对照组,睾丸和心脏组织匀浆中TNF-a也均高于或明显高于对照组,但肝脏中的TNF-a三组间没有差异.结果提示,镉负荷诱发NO、TNF-α大量释放在导致大鼠多种器官机能活动障碍发生过程中可能起重要作用.     

Ontogeny has a phylogeny: background to adjunctive behaviors in pigeons and budgerigars

Animals coping with operant conditioning tasks often show behaviors that are not recorded by keys, levers and similar response transducers. Nevertheless, these adjunctive behaviors should not be disposed of by classifying them as incidental. Often they are found to be at least partially influenced by the experimentally programmed contingencies, and under certain conditions they can in turn influence conditioned behaviors. Here we describe the occurrence and characteristics of two such behaviors, stimulus grasping in operantly key-pecking pigeons and intra-delay stereotypies in a delayed matching-to-sample task with budgerigars. It is argued that for a proper account of these behaviors it is necessary to refer to a behavioral systems approach that appeals to longer ranging ontogenetic and phylogenetic histories than is usually considered in the psychological literature. The gaping towards on-key stimuli by pigeons is attributed to the hypothesis that operantly conditioned key-pecks probably relate to a grasp-pecking response that is normally executed towards non-edible items covering food. The intra-delay behaviors shown by the budgerigars are assumed to have originated from stress-induced displacement responses that adventitiously came under the influence of differential reinforcement contingencies. Finally, we discuss what kinds of evidence are needed to put these hypothetical explanations on a more certain footing.     

Mycobacterium leprae binds to a major human peripheral nerve glycoprotein myelin P zero (P0)

We have previously shown that a major phosphorylated 25-kDa glycoprotein of the human peripheral nerve binds to Mycobacterium leprae. In the present study, we confirm that the 25-kDa glycoprotein of the human peripheral nerve is myelin P zero (P₀) by immunoprecipitation and Western blot experiments using monoclonal antibodies to myelin P₀. Immunohistochemical studies on human nerve using these antibodies to myelin P₀ exhibited a strong immunoreactivity to the myelin and Schwann cells. Myelin P₀ is a peripheral nerve specific protein; therefore it could likely be one of the key target molecules for M. leprae binding/internalization or even contact-dependent demyelination. This finding of M. leprae binding to myelin P₀ adds to the present understanding on neural predilection of M. leprae.     

Fgf signaling controls the number of phalanges and tip formation in developing digits

Tetrapods have two pairs of limbs, each typically with five digits, each of which has a defined number of phalanges derived from an archetypal formula. Much progress has been made in understanding vertebrate limb initiation and the patterning processes that determine digit number in developing limb buds, but little is known about how phalange number is controlled. We and others previously showed that an additional phalange can be induced in a chick toe if sonic hedgehog protein is applied in between developing digit primordia. Here we show that formation of an additional phalange is associated with prolonged Fgf8 expression in the overlying apical ridge and that an Fgf Receptor inhibitor blocks its formation. The additional phalange is produced by elongation and segmentation of the penultimate phalange, suggesting that the digit tip forms when Fgf signaling ceases by a special mechanism, possibly involving Wnt signaling. Consistent with this, Fgfs inhibit tip formation whereas attenuation of Fgf signaling induces tip formation prematurely. We propose that duration of Fgf signaling from the ridge, responsible for elongation of digit primordia, coupled with a characteristic periodicity of joint formation, generates the appropriate number of phalanges in each digit. We also propose that the process that generates the digit tips is independent of that which generates more proximal phalanges. This has implications for understanding human limb congenital malformations and evolution of digit diversity.     

Diverging patterns of mitochondrial and nuclear DNA diversity in subarctic black spruce: imprint of a founder effect associated with postglacial colonization

High-latitude ecotonal populations at the species margins may exhibit altered patterns of genetic diversity, resulting from more or less recent founder events and from bottleneck effects in response to climate oscillations. Patterns of genetic diversity were investigated in nine populations of the conifer black spruce (Picea mariana [Mill.] BSP.) in northwestern Québec, Canada, using seed-dispersed mitochondrial (mt) DNA and nuclear (nc) DNA. mtDNA diversity (mitotypes) was assessed at three loci, and ncDNA diversity was estimated for nine expressed sequence tag polymorphism (ESTP) loci. Sampling included populations from the boreal forest and the southern and northern subzones of the subarctic forest-tundra, a fire-born ecotone. For ncDNA, populations from all three vegetation zones were highly diverse with little population differentiation (thetaN = 0.014); even the northernmost populations showed no loss of rare alleles. Patterns of mitotype diversity were strikingly different: within-population diversity and population differentiation were high for boreal forest populations [expected heterozygosity per locus (HE) = 0.58 and thetaM = 0.529], but all subarctic populations were fixed for a single mitotype (HE = 0). This lack of variation suggests a founder event caused by long-distance seed establishment during postglacial colonization, consistent with palaeoecological data. The estimated movement of seeds alone (effective number of migrants per generation, NmM < 2) was much restricted compared to that estimated from nuclear variants, which including pollen movement (NmN > 17). This could account for the conservation of a founder imprint in the mtDNA of subarctic black spruce. After reduction, presumably in the early Holocene, the diversity in ncDNA would have been replenished rapidly by pollen-mediated gene flow, and maintained subsequently through vegetative layering during the current cooler period covering the last 3000 years.     

Patterns of morphological integration in marine modular organisms: supra-module organization in branching octocoral colonies

Despite the relative simplicity of their modular growth, marine invertebrates such as arborescent gorgonian octocorals (Octocorallia: Cnidaria) generate complex colonial forms. Colony form in these taxa is a consequence of modular (polyp) replication, and if there is a tight integration among modular and supramodular traits (e.g. polyp aperture, inter-polyp spacing, branch thickness, internode and branch length), then changes at the module level may lead to changes in colony architecture. Alternatively, different groups of traits may evolve semi-independently (or conditionally independent). To examine the patterns of integration among morphological traits in Caribbean octocorals, we compared five morphological traits across 21 species, correcting for the effects of phylogenetic relationships among the taxa. Graphical modelling and phylogenetic independence contrasts among the five morphological characters indicate two groups of integrated traits based on whether they were polyp- or colony-level traits. Although all characters exhibited bivariate associations, multivariate analyses (partial correlation coefficients) showed the strongest integration among the colony-level characters (internode distance and branch length). It is a quantitative demonstration that branching characters within the octocorals studied are independent of characters of the polyps. Despite the universally recognized modularity of octocorals at the level of polyps, branching during colony development may represent an emergent level of integration and modularity.     

Synthesis and in vitro trypanocide activity of several polycyclic drimane-quinone derivatives

The Diels-Alder reaction between two polygodial-derived dienes and simple quinones to yield substituted naphtho- and anthraquinones, is described. The in vitro trypanocide activity for the series was determined. Two of the new compounds showed an activity ten and two times higher, respectively, than nifurtimox and benznidazole, the medicines of choice for the treatment of the acute Chagas' disease.