Sex determination in the genus Oreochromis

Summary Sex ratios from 62 single-pair matings of normal broodstock O. aureus were highly heterogeneous with an overall deficit of males (41.4%). Peaks in the sex ratio frequency distribution occurred at 11, 35 and 13 (malefemale). Hybridisation of O. aureus with O. mossambicus, O. spilums and O. niloticus produced highly variable sex ratios, suggesting a complexity of hybrid sex determination. Few valid inferences could be made regarding intraspecific sex determination from these hybrid data. Sex ratios from progeny testing of sex-reversed males (13) and most sex-reversed females (10) provide evidence for female heterogamety in O. aureus. Several aberrant ratios observed suggest Mendelian inheritance of an autosomal recessive gene (F,f), epistatic to the major sex-determining gene (W,Z). Sex ratios of triploids and gynogens support the hypothesis of recombination between the centromere and the major sex-determining locus. Progeny testing of a female mitogyne demonstrated the viability of a novel WW superfemale, which gave only female offspring. Not all data could be explained by a two-factor model of sex determination. Further exceptional sex ratios may be accounted for by rare autosomal or environmental sex-modifying factors. It is concluded that O. aureus has a multifactorial mechanism of sex determination with the underlying primary mechanism of female heterogamety.     

An estimate of the amount of genetic variation in the common mussel Mytilus edulis

Allozyme variation in a population of the common mussel Mytilus edulis in Mumbles, South Wales, has been studied by starch gel electrophoresis. On the basis of data obtained for 34 loci, we estimate the proportion of loci polymorphic to be 30%. Using only the 29 loci for which individual genotypes can be accurately typed, the average heterozygosity is estimated to be 9.5 +/- 3.6%. The calculated expected average heterozygosity based on Hardy-Weinberg expectations is identical with the observed value. Allele frequency data at six polymorphic loci are given for several other British populations. There is no significant geographic heterogeneity. The results are discussed in relation to genetic adaptive strategies and are shown to be inconsistent with the predictions of the neutral hypothesis.     

Growth of a Molecular Base for Feeding: The Mind Body Dualism

It is often difficult to identify the ‘who, when, and where’ of advances in medicine and surgery because it's a rare advance indeed (such as the use of digitalis by William Withering) that can be clearly related to the astuteness of one person at one time and place.     

A Hidden Markov Model approach to variation among sites in rate of evolution

The method of Hidden Markov Models is used to allow for unequal and unknown evolutionary rates at different sites in molecular sequences. Rates of evolution at different sites are assumed to be drawn from a set of possible rates, with a finite number of possibilities. The overall likelihood of phylogeny is calculated as a sum of terms, each term being the probability of the data given a particular assignment of rates to sites, times the prior probability of that particular combination of rates. The probabilities of different rate combinations are specified by a stationary Markov chain that assigns rate categories to sites. While there will be a very large number of possible ways of assigning rates to sites, a simple recursive algorithm allows the contributions to the likelihood from all possible combinations of rates to be summed, in a time proportional to the number of different rates at a single site. Thus with three rates, the effort involved is no greater than three times that for a single rate. This "Hidden Markov Model" method allows for rates to differ between sites and for correlations between the rates of neighboring sites. By summing over all possibilities it does not require us to know the rates at individual sites. However, it does not allow for correlation of rates at nonadjacent sites, nor does it allow for a continuous distribution of rates over sites. It is shown how to use the Newton-Raphson method to estimate branch lengths of a phylogeny and to infer from a phylogeny what assignment of rates to sites has the largest posterior probability. An example is given using beta-hemoglobin DNA sequences in eight mammal species; the regions of high and low evolutionary rates are inferred and also the average length of patches of similar rates.      

Cytopathogenesis of Sendai Virus in Well-Differentiated Primary Pediatric Bronchial Epithelial Cells

Sendai virus (SeV) is a murine respiratory virus of considerable interest as a gene therapy or vaccine vector, as it is considered nonpathogenic in humans. However, little is known about its interaction with the human respiratory tract. To address this, we developed a model of respiratory virus infection based on well-differentiated primary pediatric bronchial epithelial cells (WD-PBECs). These physiologically authentic cultures are comprised of polarized pseudostratified multilayered epithelium containing ciliated, goblet, and basal cells and intact tight junctions. To facilitate our studies, we rescued a replication-competent recombinant SeV expressing enhanced green fluorescent protein (rSeV/eGFP). rSeV/eGFP infected WD-PBECs efficiently and progressively and was restricted to ciliated and nonciliated cells, not goblet cells, on the apical surface. Considerable cytopathology was evident in the rSeV/eGFP-infected cultures postinfection. This manifested itself by ciliostasis, cell sloughing, apoptosis, and extensive degeneration of WD-PBEC cultures. Syncytia were also evident, along with significant basolateral secretion of proinflammatory chemokines, including IP-10, RANTES, tumor necrosis factor (TNF)-related apoptosis-inducing ligand (TRAIL), interleukin 6 (IL-6), and IL-8. Such deleterious responses are difficult to reconcile with a lack of pathogenesis in humans and suggest that caution may be required in exploiting replication-competent SeV as a vaccine vector. Alternatively, such robust responses might constitute appropriate normal host responses to viral infection and be a prerequisite for the induction of efficient immune responses.Sendai virus (SeV) is a nonsegmented negative-strand RNA virus of the Paramyxoviridae family. Recombinant SeV (rSeV) has been extensively studied as a vector for vaccines, cancer immunotherapy, and gene therapy (14, 22, 34, 41, 43). SeV is virulent in rodents, but despite extensive antigenic and genetic similarity to human parainfluenza virus type 1 (hPIV1), it is not known to cause disease in humans (33). Interest in rSeV as a vector is exemplified by the fact that (i) its genome can easily be manipulated to stably express heterologous genes (9), (ii) it does not undergo homologous recombination, (iii) cell transduction is independent of the cell cycle, (iv) there is no DNA phase during replication and hence no possibility of cell transformation, and (v) its cell or tissue tropisms and replication competency may be modulated by reverse genetics and appropriate rescue systems (5, 8).Much of the research on rSeV as a vector involves monolayer cells and animal models and employs both replication-competent and transmission-incompetent viruses. In view of its respiratory tract tropism, particular attention was paid to its use as a gene therapy vector for lung diseases such as cystic fibrosis (CF) (2, 13, 14, 43). Indeed, early studies demonstrated its capacity to efficiently overcome a series of extra- and intracellular barriers in the respiratory tract, such as the glycocalyx, mucus layer, mucociliary clearance, and cell membranes (13, 14, 43). However, in vivo studies demonstrated that rSeV-mediated gene transduction was transient (lasting ∼7 days) and that repeated administration was inefficient (16). The reasons for this transient transduction remain unclear.In contrast, the capacity to efficiently and transiently transduce host cells is of considerable interest from a vaccine vector viewpoint. Indeed, promising rSeV-vectored vaccine candidates have been described for other respiratory viruses, such as respiratory syncytial virus (RSV), hPIV1, hPIV2, hPIV3, and systemic viruses, such as HIV-1 (22, 40, 44). Despite its considerable promise as a viral vector, little is known about how rSeV interacts with human airway epithelial cells (HAE).To address this, we established an ex vivo/in vitro model of respiratory virus infection based on well-differentiated primary pediatric bronchial epithelial cells (WD-PBECs) in air-liquid interface (ALI) cultures. The pediatric origin of the primary bronchial cells allowed us to investigate SeV-host interactions in a pediatric context. The need for CF gene therapy or respiratory virus vaccines for infants or children emphasizes the relevance of this ex vivo/in vitro pediatric model. Using rSeV expressing enhanced GFP (rSeV/eGFP), we comprehensively investigated the consequences of SeV infection in these cultures, including the types of cells infected, virus growth kinetics, cytopathic effects (CPE), and inflammatory responses. Our data provided novel insights into the interaction of SeV with pediatric airway epithelium and the limitations and/or advantages of its use as a vector.     

Nasal Epithelial Cells Can Act as a Physiological Surrogate for Paediatric Asthma Studies

Introduction

Differentiated paediatric epithelial cells can be used to study the role of epithelial cells in asthma. Nasal epithelial cells are easier to obtain and may act as a surrogate for bronchial epithelium in asthma studies. We assessed the suitability of nasal epithelium from asthmatic children to be a surrogate for bronchial epithelium using air-liquid interface cultures.

Methods

Paired nasal and bronchial epithelial cells from asthmatic children (n = 9) were differentiated for 28 days under unstimulated and IL-13-stimulated conditions. Morphological and physiological markers were analysed using immunocytochemistry, transepithelial-electrical-resistance, Quantitative Real-time-PCR, ELISA and multiplex cytokine/chemokine analysis.

Results

Physiologically, nasal epithelial cells from asthmatic children exhibit similar cytokine responses to stimulation with IL-13 compared with paired bronchial epithelial cells. Morphologically however, nasal epithelial cells differed significantly from bronchial epithelial cells from asthmatic patients under unstimulated and IL-13-stimulated conditions. Nasal epithelial cells exhibited lower proliferation/differentiation rates and lower percentages of goblet and ciliated cells when unstimulated, while exhibiting a diminished and varied response to IL-13.

Conclusions

We conclude that morphologically, nasal epithelial cells would not be a suitable surrogate due to a significantly lower rate of proliferation and differentiation of goblet and ciliated cells. Physiologically, nasal epithelial cells respond similarly to exogenous stimulation with IL-13 in cytokine production and could be used as a physiological surrogate in the event that bronchial epithelial cells are not available.     

Symbiotic relationships between soil fungi and plants reduce N2O emissions from soil

N₂O is a potent greenhouse gas involved in the destruction of the protective ozone layer in the stratosphere and contributing to global warming. The ecological processes regulating its emissions from soil are still poorly understood. Here, we show that the presence of arbuscular mycorrhizal fungi (AMF), a dominant group of soil fungi, which form symbiotic associations with the majority of land plants and which influence a range of important ecosystem functions, can induce a reduction in N₂O emissions from soil. To test for a functional relationship between AMF and N₂O emissions, we manipulated the abundance of AMF in two independent greenhouse experiments using two different approaches (sterilized and re-inoculated soil and non-mycorrhizal tomato mutants) and two different soils. N₂O emissions were increased by 42 and 33% in microcosms with reduced AMF abundance compared to microcosms with a well-established AMF community, suggesting that AMF regulate N₂O emissions. This could partly be explained by increased N immobilization into microbial or plant biomass, reduced concentrations of mineral soil N as a substrate for N₂O emission and altered water relations. Moreover, the abundance of key genes responsible for N₂O production (nirK) was negatively and for N₂O consumption (nosZ) positively correlated to AMF abundance, indicating that the regulation of N₂O emissions is transmitted by AMF-induced changes in the soil microbial community. Our results suggest that the disruption of the AMF symbiosis through intensification of agricultural practices may further contribute to increased N₂O emissions.     

颈髓损伤的常规MRI表现与DTI技术临床应用

目的：比较不同时期颈髓损伤的MRI表现及DTI的应用价值。方法：收集急性颈髓压迫病例15例、慢性颈髓压迫病例23例、颈髓慢性压迫合并急性压迫病例12例。15例健康志愿者作为对照组。进行常规MRI检查,应用DTI检查测量表现扩散系数（ADC）值和各向异性分数（FA）。比较各组间ADC值和FA值,并进行统计学分析。结果：急性颈髓迫病例,常规MRI显示颈髓增粗,呈等T1长T2信号;慢性颈髓压迫病例,9例呈长T1长T2信号,14例呈等T1长T2信号;慢性颈髓压迫并急性压迫病例颈髓明显增粗,呈等、长T1明显长T2信号。与对照组比较：急性颈髓压迫组的ADC值和FA值均明显降低,两组的差异有显著性;慢性颈髓压迫组的FA值降低,ADC值增高,两组的差异有显著性;慢性脊髓压迫合并急性脊髓压迫组ADC值与对照组比较无差异,FA值低于对照组。颈髓压迫各组间ADC值及FA值比较差异显著。结论：不同时期颈髓损伤常规MRI图像缺乏特异性,根据ADC值及FA值可判断颈髓损伤的时期。     

Retrograde tracing and toe spreading after experimental autologous nerve transplantation and crush injury of the sciatic nerve: a descriptive methodological study

ABSTRACT: Evaluation of functional and structural recovery after peripheral nerve injury is crucial to determine the therapeutic effect of a nerve repair strategy. In the present study, we examined the relationship between the structural evaluation of regeneration by means of retrograde tracing and the functional evaluation analysis of toe spreading. Two standardized rat sciatic nerve injury models were used to address this relationship. As such, animals received either a 2 cm sciatic nerve defect (neurotmesis) followed by autologous nerve transplantation (ANT animals) or a crush injury with spontaneous recovery (axonotmesis; CI animals). Functional recovery of toe spreading was observed over an observation period of 84 days. In contrast to CI animals, ANT animals did not reach pre-surgical levels of toe spreading. After the observation period, the lipophilic dye DiI was applied to label sensory and motor neurons in dorsal root ganglia (DRG; sensory neurons) and spinal cord (motor neurons), respectively. No statistical difference in motor or sensory neuron counts could be detected between ANT and CI animals. In the present study we could indicate that there was no direct relationship between functional recovery (toe spreading) measured by SSI and the number of labelled (motor and sensory) neurons evaluated by retrograde tracing. The present findings demonstrate that a multimodal approach with a variety of independent evaluation tools is essential to understand and estimate the therapeutic benefit of a nerve repair strategy.