Genetic variability for regional brain gangliosides in five strains of young mice

The quantitative and qualitative distributions of gangliosides were determined in the cerebrum, cerebellum, and brain stem of five inbred strains (C57BL/6J, DBA/2J, LG/J, C3H/HeJ, BALB/cJ) of mice at 21 days of age. Genetic differences were found among the strains for wet weight, absolute amount of gangliosides per region, and concentration of ganglioside (expressed on both a wet and a dry weight basis) in all three regions of the brain. The water content of the various brain regions showed the least amount of genetic variability. Coefficients of genetic determination were used to estimate the magnitude of genetic influence on these traits in each brain region. Significant differences were also found among the five strains for the distribution of certain gangliosides. The DBA strain, which is susceptible to audiogenic seizure at this age, had the highest level of the myelin-enriched ganglioside G_M1 in all brain regions. Most of the genetic variation that influences the content and distribution of gangliosides among neurologically normal mice can be considered polygenic. Several possible sources of this genetic variation that may contribute to the differences observed among the strains are discussed.This work was supported by USPHS Grant NS 11853 and by a grant from the Swebilius Fund. T. N. S. is the recipient of a USPHS postdoctoral fellowship (1F32NS0443).     

Leishmania tropica: pathogenicity and in vitro macrophage function in strains of inbred mice.

Of seven strains of inbred mice and one hybrid that were infected intracutaneously with 5, 10, or 20 × 10⁶ active promastigotes of Leishmania tropica major, two strains (CBA/Ca and C₃H/He) recovered from the infection and their lesions healed within 3 to 5 months. The other strains, with the possible exception of C57B1/6 animals, remained infected, carrying large cutaneous ulcers throughout their lives. These included DBA/2, A/Jax, Balb/c, athymic nude mice of Balb/c origin (nu/nu) and the heterozygote Balb/c (nu⁺). The responses of C57B1/6 animals were of intermediate type with a tendency toward nonhealing at higher doses of the parasite. The cutaneous infection of athymic nude mice invariably gave rise to fulminating visceral infections and death. This condition was never observed in the other strains tested. Concanavalin A (Con A)-stimulated syngeneic or allogeneic lymphocytes of intact mice activated peritoneal macrophages of both healer and nonhealer mice, resulting in complete destruction of phagocytosed L. enriettii within 24 to 48 hr. The destruction of ingested L. tropica was confined to macrophages of healer mice and required 72 to 96 hr to reach completion. However, removal of Con A-stimulated lymphocytes from macrophage cultures and regular pulsing of the cells with a lymphokine-rich supernatant produced a state of sustained activation, resulting in destruction of L. tropica inside macrophages of both healer and nonhealer mice. The ability of Con A-stimulated lymphocytes of nonhealer animals to induce effective levels of activation in healer macrophages on one hand, and eventual destruction of L. tropica in macrophages of nonhealer mice under condition of sustained activation on the other, had indicated that so far as the in vitro situation is concerned, there is no inherent defect in lymphocytes or macrophages of nonhealer animals, although the threshold of activation necessary for killing of the parasite seems to be higher for cells of nonhealer origin.     

Strain distribution and linkage relationship of a mouse embryonic hemoglobin variant

Search for structural variants of three globin chains (x, y, z), synthesized only during mouse embryonic hematopoiesis, was carried out by electrophoretic analysis of blood from 12-day embryos, all with C57BL/6 mothers, and fathers from 115 inbred stocks selected for their diverse genetic origins. Structure of the -chains of adult hemoglobins differed among the tested strains, with 57 carrying the Hbb ^sallele, 56 the Hbb ^dallele, and two the Hbb ^pallele. The search revealed no x- or z-chain variants but confirmed and extended knowledge of a previously described y-chain variant. Blood of all embryos sired by males from the 57 Hbb ^sstrains contained only y¹-chains, while blood of all embryos sired by Hbb ^dor Hbb ^pmales contained y2-chains as well as the y¹-chains inherited from their C57 BL/6 mother. The locus controlling structure of the y-chain of mouse embryonic hemoglobins is thus extremely closely linked to the locus controlling structure of adult hemoglobin -chain, with maximum possible recombination frequency less than 0.019.This work was supported in part by Grants CA-01074 from the National Cancer Institute, USPHS, and GM 18684 from the National Institute of General Medical Sciences, in part by Grant ACS-VC58 from The American Cancer Society, in part by grants to the Jackson Laboratory from the Bushrod H. Campbell and Adah F. Hall Charity Fund and the Robert Sterling Clark Foundation, and in part by the Jackson Laboratory Endowment Fund. The Jackson Laboratory is fully accredited by the American Association for Accreditation of Laboratory Animal Care.     

Pyrolysis-gas chromatography of the fungus Metarhizium anisopliae: An aid to strain identification

Six strains of the entomopathogenic fungus Matarhizium anisopliae var. anisopliae from North and South America and one strain of M. anisopliae var. major from Samoa were compared by pyrolysis-gas chromatography of conidia. Two strains established to be very similar by other methods proved 98% similar by pyrolysis-gas chromatography. Similarities of the other strains ranged from 62 to 88%. The method is proposed as a simple technique for routine identification of M. anisopliae strains.     

利用地域野生资源创制地方适栽的优质香菇新品种

香菇是我国深受欢迎的食药用菌,产量居食用菌产业之首。为拓宽栽培香菇菌株的遗传背景,解决现有主栽香菇菌株种性退化的问题,本研究以香菇‘808’菌株与3个香菇野生资源、3个栽培菌株（辽抚4号、BY1和荷香）开展单-双杂交育种,开发适合当地栽培环境的主栽品种。研究结果显示：在270对单-双杂交组合中,通过锁状联合观察和与亲本的拮抗试验,鉴定出89个杂交子,进一步通过栽培试验筛选出10个性状相对优良的候选菌株;最终通过农艺性状对比试验,筛选出ZJXG 5和ZJXG 8两个优良杂交菌株,这两个菌株均以当地长白山野生资源S1和本地主栽菌株BY1为双核杂交亲本选育而来,表现出超亲显著、菇形圆整、颜色呈浅褐色的特性,前4潮生物学效率在86%-88%之间。本研究结果揭示,在香菇杂交育种中,当亲本菌株来源地域与杂交后代菌株筛选地域相近时,单双杂交亲和率、杂交菌株的出菇率和丰产性指标较高,这提示我们,利用当地野生香菇资源更有利于创制适合当地自然环境的地方品种。     

A full body musculoskeletal model based on flexible multibody simulation approach utilised in bone strain analysis during human locomotion

Load-induced strains applied to bone can stimulate its development and adaptation. In order to quantify the incident strains within the skeleton, in vivo implementation of strain gauges on the surfaces of bone is typically used. However, in vivo strain measurements require invasive methodology that is challenging and limited to certain regions of superficial bones only such as the anterior surface of the tibia. Based on our previous study [Al Nazer et al. (2008) J Biomech. 41:1036–1043], an alternative numerical approach to analyse in vivo strains based on the flexible multibody simulation approach was proposed. The purpose of this study was to extend the idea of using the flexible multibody approach in the analysis of bone strains during physical activity through integrating the magnetic resonance imaging (MRI) technique within the framework. In order to investigate the reliability and validity of the proposed approach, a three-dimensional full body musculoskeletal model with a flexible tibia was used as a demonstration example. The model was used in a forward dynamics simulation in order to predict the tibial strains during walking on a level exercise. The flexible tibial model was developed using the actual geometry of human tibia, which was obtained from three-dimensional reconstruction of MRI. Motion capture data obtained from walking at constant velocity were used to drive the model during the inverse dynamics simulation in order to teach the muscles to reproduce the motion in the forward dynamics simulation. Based on the agreement between the literature-based in vivo strain measurements and the simulated strain results, it can be concluded that the flexible multibody approach enables reasonable predictions of bone strain in response to dynamic loading. The information obtained from the present approach can be useful in clinical applications including devising exercises to prevent bone fragility or to accelerate fracture healing.     

A closer look at prion strains

Prions are infectious proteins that are responsible for transmissible spongiform encephalopathies (TSEs) and consist primarily of scrapie prion protein (PrP^Sc), a pathogenic isoform of the host-encoded cellular prion protein (PrP^C). The absence of nucleic acids as essential components of the infectious prions is the most striking feature associated to these diseases. Additionally, different prion strains have been isolated from animal diseases despite the lack of DNA or RNA molecules. Mounting evidence suggests that prion-strain-specific features segregate with different PrP^Sc conformational and aggregation states.

Strains are of practical relevance in prion diseases as they can drastically differ in many aspects, such as incubation period, PrP^Sc biochemical profile (e.g., electrophoretic mobility and glycoform ratio) and distribution of brain lesions. Importantly, such different features are maintained after inoculation of a prion strain into genetically identical hosts and are relatively stable across serial passages.

This review focuses on the characterization of prion strains and on the wide range of important implications that the study of prion strains involves.