Ultrastructural features of the muscle fibers in congenital hypothyroidism

Summary Muscles of three patients (2 years, 2 years and 7 months, and 11 years of age) affected by congenital hypothyroidism due to dysgenesis of the thyroid gland were studied by electron microscope. The biopsies were performed on the quadriceps muscle. Several alterations were found in the ultrastructure of the muscle fibers. The contractile material underwent atrophy by two recessive processes: by reduction and by degeneration. The former, which affected mainly the white fibers, led to the progressive detachment of myofilaments from the periphery of the myofibrils while they maintainad a normal arrangement in the center. Consequently, their diameter decreased and their interfibrillar spaces enlarged. The latter enlargment, involving the red fibers, caused areas of dedifferentiation involving either the contractile apparatus or the other cell organelles. Modifications of the sarcolemma and basement membrane were seen in the fibers affected by the atrophying processes of the contractile material. Changes of the ultrastructure of the sarcoplasmic reticulum and of the T system were observed with numerous morphological abnormalities of the mitochondria. In addition, accumulation of glycogen and striking changes of the satellite cells were found. The ultrastructural findings are reviewed and discussed in relation to the literature on hypothyroid myopathy.     

Involvement of ERK, p38 and NF-kappaB signal transduction in regulation of TLR2, TLR4 and TLR9 gene expression induced by lipopolysaccharide in mouse dendritic cells

Toll-like receptors (TLR) are sentinel receptors capable of recognizing pathogen-associated molecule patterns (PAMP) such as lipopolysaccharide (LPS) and CpG-containing oligonucleotides (CpG ODN). TLR2 and TLR4 are major receptors for Gram-positive and Gram-negative bacterial cell wall components, respectively. TLR9 is necessary for CpG signalling. LPS or CpG ODN can activate immature dendritic cells (DC) and induce DC maturation characterized by production of cytokines, up-regulation of co-stimulatory molecules, and increased ability to activate T cells. However, little is known regarding the regulation of TLR gene expression in mouse DC. In this study, we investigated the regulation of TLR2, TLR4 and TLR9 gene expression by LPS in murine immature DC. TLR2, TLR4 and TLR9 mRNA were up-regulated following LPS stimulation. The up-regulation of TLR9 expression coincided with significantly increased production of tumour necrosis factor-alpha induced by LPS plus CpG ODN. While inhibition of extracellular signal-related kinase and NF-kappaB activation suppressed the up-regulation of the expression of TLR2, TLR4 and TLR9 mRNA, inhibition of p38 kinase prevented the up-regulation of TLR2 and TLR4 mRNA expression but enhanced the up-regulation of TLR9 expression. These results demonstrated that TLR2, TLR4 and TLR9 gene expression was differently regulated by LPS in mouse immature DC. Up-regulation of TLR2, TLR4 and TLR9 expression by LPS might promote the overall responses of DC to bacteria and help to explain the synergy between LPS and other bacterial products in the induction of cytokine production.     

IL-12p40-overexpressing immature dendritic cells induce T cell hyporesponsiveness in vitro but accelerate allograft rejection in vivo: role of NK cell activation and interferon-gamma production

Infusion of genetically modified dendritic cells (DC) expressing immunosuppressive molecules is a potential therapy for organ rejection. IL-12p70, a cytokine produced mainly by DC and macrophages, consists of two subunits, p40 and p35. IL-12p70 is an activator of T cells, while the IL-12p40 subunit serves as a natural antagonist for IL-12p70 action. The primary aim of this study was to evaluate the effect of IL-12p40 gene-modification on both the T-cell stimulatory activity of immature DC (imDC) and their ability to prolong cardiac allograft survival. IL-12p40 gene-modified imDC (DC-p40) exhibited a phenotype characteristic of imDC and displayed impaired T-cell allostimulatory ability in vitro. However, to our surprise, for murine vascularized heterotopic heart transplantation (HHT), administration of donor-derived DC-p40 7 days prior to transplantation did not prolong allograft survival but instead significantly exacerbated cardiac allograft rejection. Further study showed that DC-p40 augmented NK cell activity both in vitro and in vivo and enhanced interferon-gamma (IFN-gamma) production in vivo, which might be due to the increased IL-23 production by DC-p40. Our data suggested that although IL-12p40 gene-modified immature DC can induce T cell hyporesponsiveness in vitro, their ability to activate NK cells and induce IFN-gamma production counterbalances this, exacerbating cardiac allograft rejection. The unexpected effects of DC-p40 limit their value in promoting allograft survival in vivo and likely reflect the complexity of IL-12p40 biology.     

Pseudosubstrate inhibition of protein kinase PKR by swine pox virus C8L gene product

The interferon-induced protein kinase PKR is activated upon binding double-stranded RNA and phosphorylates the translation initiation factor eIF2alpha on Ser-51 to inhibit protein synthesis in virally infected cells. Swinepox virus C8L and vaccinia virus K3L gene products structurally resemble the amino-terminal third of eIF2alpha. We demonstrate that the C8L protein, like the K3L protein, can reverse the toxic effects caused by high level expression of human PKR in yeast cells. In addition, expression of either the K3L or C8L gene product was found to reverse the inhibition of reporter gene translation caused by PKR expression in mammalian cells. The inhibitory function of the K3L and C8L gene products in these assays was found to be critically dependent on residues near the carboxyl-termini of the proteins including a sequence motif shared among eIF2alpha and the C8L and K3L gene products. Thus, despite significant sequence differences both the C8L and K3L proteins function as pseudosubstrate inhibitors of PKR.     

Peroxisomal proliferator activated receptor-γ deficiency in a Canadian kindred with familial partial lipodystrophy type 3 (FPLD3)

Background  

Familial partial lipodystrophy (Dunnigan) type 3 (FPLD3, Mendelian Inheritance in Man [MIM] 604367) results from heterozygous mutations in PPARG encoding peroxisomal proliferator-activated receptor-γ. Both dominant-negative and haploinsufficiency mechanisms have been suggested for this condition.     

Foxl2 disruption causes mouse ovarian failure by pervasive blockage of follicle development

FOXL2 mutations cause gonadal dysgenesis or premature ovarian failure (POF) in women, as well as eyelid/forehead dysmorphology in both sexes (the 'blepharophimosis-ptosis-epicanthus inversus syndrome', BPES). Here we report that mice lacking Foxl2 recapitulate relevant features of human BPES: males and females are small and show distinctive craniofacial morphology with upper eyelids absent. Furthermore, in mice as in humans, sterility is confined to females. Features of Foxl2 null animals point toward a new mechanism of POF, with all major somatic cell lineages failing to develop around growing oocytes from the time of primordial follicle formation. Foxl2 disruption thus provides a model for histogenesis and reproductive competence of the ovary.     

空肠弯曲菌HSP43诱导自身免疫机理──分子模拟和抗原优势

我们曾发现空肠弯曲菌４３ｋＤ热休克蛋白（ＨＳＰ４３）能诱导小鼠产生自身免疫应答，本文则进一步分析了这种诱导作用的机理。二株针对ＨＳＰ６０保守区序列的单克隆抗体ＩＩＨ９和ＭＬ－３０不但能结合人及小鼠细胞中ＨＳＰ６０家族成员，而且也能结合ＨＳＰ４３，表明ＨＳＰ４３、人及小鼠ＨＳＰ６０三者均属同一家族成员，具有序列上的高度同源性。小鼠用空肠弯曲菌免疫后出现了针对１０种菌体蛋白的抗体，其中最早被诱导的抗体是针对ＨＳＰ４３的，并且该种抗体在随后８０ｄ观察期间内保持了较高活性，表明ＨＳＰ４３是优势抗原。本文结果提示，ＨＳＰ４３较易被免疫系统识别而产生应答，通过和宿主ＨＳＰ６０高度序列同源性而可能呈现分子模拟，从而诱导自身免疫损伤。     

"Waste" follicular aspirate from fertility treatment--a potential source of human germline stem cells?

Fertility clinics worldwide routinely produce a large volume of 'waste' follicular aspirate, which is potentially an abundant source of immature ovarian follicles. Current attempts to cultivate these further in vitro to yield viable mature oocytes for fertility treatment have not yet achieved much success. Instead, recent lines of evidence have emerged that are suggestive of a potential stem cell niche within such immature ovarian follicles. The recent discovery of follicular renewal and putative germ-line stem cells within the postnatal mammalian ovary shook the foundations of reproductive biology by challenging the established dogma that mammalian females lose the capacity for germ cell renewal during fetal life, such that a fixed reserve of germ cells (oocytes) enclosed within follicles is endowed at birth. More intriguingly, another recent study in the Drosophila model provided compelling evidence that somatic progenies (nurse cells) of germ-line stem cells had the ability to revert back to the stem-cell-like state. This introduces the exciting possibility that within the mammalian ovarian follicle, similar somatic progenies of germ-line stem cells may also possess a greater intrinsic ability to revert back into functional stem cells. If this is the case, then a favored candidate would be the cumulus/granulosa of immature ovarian follicles, since such cells are true homologues of nurse cells found within the Drosophila ovary. The successful elucidation of a human germ-line stem cell niche within immature ovarian follicles is likely to have huge ramifications in stem cell biology and regenerative medicine.