Maximum-likelihood models for mapping genetic markers showing segregation distortion. 2. F2 populations

In F₂ populations, gametic and zygotic selection may affect the analysis of linkage in different ways. Therefore, specific likelihood equations have to be developed for each case, including dominant and codominant markers. The asymptotic bias of the classical estimates are derived for each case, in order to compare them with the standard errors of the suggested estimates. We discuss the utility and the efficiency of a previous model developed for dominant markers. We show that dominant markers provide very poor information in the case of segregation distortion and, therefore, should be used with circumspection. On the other hand, the estimation of recombination fractions between codominant markers is less affected by selection than is that for dominant markers. We also discuss the analysis of linkage between dominant and codominant markers.     

Health in China. From Mao to market reform.

After the Liberation by Mao Ze Dong''s Communist army in 1949, China experienced massive social and economic change. The dramatic reductions in mortality and morbidity of the next two decades were brought about through improvements in socioeconomic conditions, an emphasis on prevention, and almost universal access to basic health care. The economic mismanagement of the Great Leap Forward brought about a temporary reversal in these positive trends. During the Cultural Revolution there was a sustained attack on the privileged position of the medical profession. Most city doctors were sent to work in the countryside, where they trained over a million barefoot doctors. Deng Xiao Ping''s radical economic reforms of the late 1970s replaced the socialist system with a market economy. Although average incomes have increased, the gap between rich and poor has widened.     

Maternal and child health in China.

China has made great progress in improving the health of women and children over the past two generations. The success has been attributed to improved living standards, public health measures, and good access to health services. Although overall infant and maternal mortality rates are relatively low there are large differences in patterns of mortality between urban and rural areas. The Chinese have developed a hierarchical network of maternal and child health services, with each level taking a supervisory and teaching role for the level below it. Maternal and child health in China came to international attention in 1995 with the promulgation of the maternal and child health law. In China this was seen as a means of prioritising resources and improving the quality of services, but in the West it was widely described as a law on eugenics.     

C to T and/or G to A transitions are responsible for loss of a MspI restriction site at the 5′-end of the human apolipoprotein AI gene

We detected the loss of a MspI restriction site by a C to T transition at +83 bp and a G to A transition at +84 bp of the 5-end non-coding region of the human apolipoprotein AI gene. This base change occurred at the hot spot (CCGG) for methylation, which may be important in the regulation of gene expression. The population frequency for the loss of the MspI site is 6.1%.     

Discrete differences between strains of different Rhizobium spp. for competitive nodule occupancy on beans

Rhizobium etli strain TAL182 and R. leguminosarum bv phaseoli strain 8002, both of which produce melanin pigment, were tested for their nodulation competitiveness on beans by paired inoculation with two strains which do not produce melanin: R. tropici strain CIAT899 and Rhizobium sp. strain TAL1145. An assay was developed to distinguish nodules formed by the melanin-producing and non-producing strains. Strain TAL182 had discrete competitive superiority over CIAT899 and TAL1145 for nodulation of beans. Nodulation competitiveness was not correlated with the ability to produce melanin pigment or the host range of the Rhizobium strains tested.The authors are with the Department of Plant Molecular Physiology, University of Hawaii, 3050 Maile Way, Gillmore 402, Honolulu, HI 96822, USA     

Transforming growth factor type beta 1 (TGF-beta 1) down-regulates interleukin-2 production and up-regulates interleukin-2 receptor expression in a thymoma cell line

Transforming growth factor type beta 1 (TGB-beta 1) belongs to a family of polypeptides with regulatory effects on growth and differentiation of a variety of cell types. TGB-beta 1 plays an important role in regulation of immune response by acting as a negative control signal for T cell proliferation through still unknown mechanisms. In this study we have analysed the effects of TGB-beta 1 on EL 4-6.1, a variant of the murine EL 4 thymoma, which can be induced by phorbol 12-myristate 13-acetate (PMA) and/or interleukin 1 (IL-1) to secrete interleukin 2 (IL-2) and express IL-2 receptors (IL-2R). Using this defined model system, we show that TGB-beta 1 simultaneously down-regulates IL-2 expression and up-regulates the number of both high and low affinity IL-2R. These changes correlate with changes at the mRNA level, suggesting an effect at the pre-translational level. The specificity of both TGF-beta 1 effects was demonstrated using a neutralizing antiserum to TGF-beta 1. Our data also suggest that TGF-beta 1 does not interfere with early activation signals of PMA and/or IL-1. This model might be useful for elucidating the complex role of TGF-beta 1 in the regulation of T cell responses.     

IFN-alpha induces autocrine production of IL-6 in myeloma cell lines.

IL-6 is a major tumor growth factor in human multiple myeloma. Myeloma cell lines, which have the same phenotypic characteristics and Ig gene rearrangements as the original fresh myeloma cells and whose growth is strictly dependent on exogenous IL-6 similar to fresh myeloma cells, have been reproducibly established. We show here that IFN-alpha stimulated the growth of five of six of these human myeloma cell lines by inducing an autocrine production of IL-6 in myeloma cells. Indeed, IFN-alpha induced IL-6 mRNA accumulation and IL-6 production in myeloma cells and the IFN-alpha-induced growth of these cells was inhibited by anti-IL-6 mAb. Moreover, IFN-alpha made possible the rapid emergence of autonomously growing myeloma cell sublines, which produced IL-6 as an autocrine growth factor. As IFN-alpha has a potential therapeutical interest for multiple myeloma, the present study opens up new directions for studying its effects on the myeloma clone in vivo.