Uptake and dissimilation of glycerol by wild type and glycerol nonutilizing strains of Neurospora crassa

Summary Seven mutant strains defective for utilization of glycerol, glyceraldehyde or dihydroxyacetone were isolated. One strain was deficient for NAD-linked glycerol-3-phosphate dehydrogenase, two for glycerol kinase, and four had no detected enzymatic deficiency, although one of the latter strains was deficient in glycerol uptake. Glycerol uptake was increased by incubation in glycerol, glycerol-3-phosphate, erythritol, and propanediol, and was protein-mediated below 0.14 mM glycerol, but at higher concentrations free diffusion predominated. Glycerol uptake was decreased by cycloheximide and was more sensitive to sodium azide than to iodoacetate.     

The importance of mate retention and experience on breeding success in Cassin's auklet (Ptychoramphus aleuticus)

We studied the relative effects of mate retention and breedingexperience on reproductive success in Cassin's auklet (Ptychoramphusaleuticus) on Southeast Farallon Island, California, USA. Breedingsuccess of banded birds was monitored from 1985 to 1990 andanalyzed using linear and logistic regression. Breeding performanceimproved with experience and mate retention, but their relativeeffects differed. Hatching success improved with both femaleand male experience but declined with advanced experience inmales, perhaps due to reproductive senescence. In males, butnot in females, hatching success showed a quadratic relationshipwith length of the pair-bond when adjusted for experience, indicatinga greater benefit to males for mate retention. Fledging andbreeding success and weight at fledging also increased asymptoticallywith length of the pair-bond for both sexes. There was no correlationbetween mate switching and previous reproductive failure. Anincrease in weight at fledging with experience in females, butnot in males, suggests that females either became more efficientat foraging or invested greater effort in chick rearing withexperience than males.     

Clinical and functional characterisation of the combined respiratory chain defect in two sisters due to autosomal recessive mutations in MTFMT

Exome sequencing identified compound heterozygous mutations in the recently discovered mitochondrial methionyl-tRNA formyltransferase (MTFMT) gene in two sisters with mild Leigh syndrome and combined respiratory chain deficiency. The mutations lead to undetectable levels of the MTFMT protein. Blue native polyacrylamide gel electrophoresis showed decreased complexes I and IV, and additional products stained with complex V antibodies, however the overall steady state level of mt-tRNA^Met was normal. Our data illustrate that exome sequencing is an excellent diagnostic tool, and its value in clinical medicine is enormous, however it can only be optimally exploited if combined with detailed phenotyping and functional studies.     

猫脑干上涎核节前神经元电活动的观察

在麻醉的32只猫记录了电刺激颌下腺神经支引起的上涎核平均场电位和单位放电。逆行电刺激颌下腺神经支引起的上涎核平均场电位分布在同侧脑干背面闩部头端5.5—8mm处,与过去的组织学结果大致符合。用微电极在上涎核记录了68个对刺激颌下腺神经支有反应的单位,其中33个单位作了碰撞试验。有9个单位符合逆向反应标准,它们是真正的颌下腺节前神经元,逆行反应的潜伏期为14.4±2.5ms,其轴突传导速度为2.9±0.1m/s。其他不符合逆向反应标准的单位,对刺激颌下腺神经支仍能发生反应,估计多为中间神经元。在一部分单位观察了电刺激舌神经或味觉刺激舌引起的反应。根据这些观察对上涎核内存在复杂神经元回路的可能性作了讨论。     

Gene doctoring: a method for recombineering in laboratory and pathogenic Escherichia coli strains

Background  

Homologous recombination mediated by the λ-Red genes is a common method for making chromosomal modifications in Escherichia coli. Several protocols have been developed that differ in the mechanisms by which DNA, carrying regions homologous to the chromosome, are delivered into the cell. A common technique is to electroporate linear DNA fragments into cells. Alternatively, DNA fragments are generated in vivo by digestion of a donor plasmid with a nuclease that does not cleave the host genome. In both cases the λ-Red gene products recombine homologous regions carried on the linear DNA fragments with the chromosome. We have successfully used both techniques to generate chromosomal mutations in E. coli K-12 strains. However, we have had limited success with these λ-Red based recombination techniques in pathogenic E. coli strains, which has led us to develop an enhanced protocol for recombineering in such strains.     

The ontogeny of chemically mediated antipredator responses of fathead minnows Pimephales promelas

The antipredator responses of adult and larval fathead minnows Pimephales promelas to chemical alarm cues prepared throughout ontogeny were tested using various behavioural assays. Larval epidermis was also examined during ontogeny using standard haematoxylin and eosin staining techniques. Adults elicited an antipredator response to chemical alarm cue made from larvae as young as 8–17 days post‐hatch. Interestingly, larvae did not possess visible club cells until 28–37 days post‐hatch and did not respond to conspecific chemical alarm cue until 48–57 days post‐hatch. These results suggest that chemical alarm cue may not be contained within club cells and that the components of larval and adult chemical alarm cue may be similar throughout ontogeny.