Emergency aortic valve replacement for critical aortic stenosis

Objective: To demonstrate that emergency aortic valve replacement can be successfully performed in patients with critical aortic stenosis and reduced left ventricular function even in cardiogenic shock with associated severe multiple organ failure. Design: Retrospective, consecutive case series. Setting: Multidisciplinary intensive care unit of a tertiary care university hospital. Patients: Five patients admitted to the intensive care unit with critical aortic stenosis (aortic valve area 0.56 ± 0.13 cm²) and greatly reduced left ventricular ejection fraction (20 ± 3 %) in prolonged cardiogenic shock and associated multiple organ failure (Multiple organ failure score 6.8 ± 0.5; Acute Physiology, Age, and Chronic Health Evaluation III score 91 ± 27). Intervention: Emergency aortic valve replacement. Results: All patients survived with full recovery of organ function. At follow-up (18 ± 10 months) all patients were in New York Heart Association functional class I or II with improvement of left ventricular ejection fraction to 48 ± 25 %. Conclusions: This excellent outcome suggests that emergency aortic valve replacement should be strongly considered in patients with critical aortic stenosis even in cardiogenic shock and multiple organ failure.     

Experimental photoablation of meniscus cartilage by excimer laser energy

Summary Excimer lasers have been demonstrated to provide a very precise and circumscribed ablation of synthetic polymers and biological tissues. We investigated in vitro the use of ultrashort pulsed ultraviolet excimer-laser energy for controlled removal of meniscus cartilage under the aspects of arthroscopic meniscectomy. A krypton-fluorine gas mixture was used to achieve laser emission of 248-nm wavelength. A total of 22 human menisci obtained either by operation or necropsy were irradiated over a range of energy fluence (2.15–3.07 J/cm²/pulse), repetition rates (5–20 Hz), and exposure time (15–60 s). Ablation rates of 4.00–5.76 m per pulse were obtained. Light-microscopic examinations demonstrated tissue ablation without any evidence of pathological changes associated with continuous-wave laser irradiation. Effects of laser energy were clearly limited to the target of the laser beam, and tissue removal proceeded without production of heat or smoke. Due to the lack of pathological alterations observed, excimer-laser irradiation of meniscus cartilage may prove to be advantageous for precisely cutting and removing menisci without injury to the surrounding normal tissue. Clinical application of excimer-laser irradiation includes the development of suitable fiberoptics and laser coupling, as well as modification of fiber tips.Funds were received from theFonds zur Förderung der wissenschaftlichen Forschung (Ministry of Science and Research, Austria)     

Thymic stromal cell specialization and the T-cell receptor repertoire

Ten years ago, we proposed a model for thymus function in which thymic epithelial cells are primarily responsible for imprinting major histocompatibility complex (MHC)-restricted specificity, and bone marrow-derived macrophages or dendritic cells are responsible for the induction of self-tolerance. Since then, transgenic and knockout models have allowed for a dissection of thymic stromal components in vivo, leading to a new understanding of their specialized functions. We have determined that with regard to class II-restricted CD4 T-cell development, two distinct subsets of thymic epithelium help shape the repertoire: Cortical epithelium appears solely responsible for positive selection, whereas a fucose-bearing subset of medullary epithelium is specialized for negative selection. This absolute separation of positive and negative selection into two distinct spatial and temporal compartments leads to a much simpler view of the process of repertoire selection. Finally, a novel view of the function of the thymic medulla is discussed.     

川芎嗪诱导大鼠骨髓间质干细胞分化为神经元样细胞的研究

目的用川芎嗪(ligustrazin hydrochloride)在体外定向诱导SD青年鼠骨髓间质干细胞(mesenchymal stem cells，rMSCs)分化为神经元样细胞。方法用低糖DMEM冲洗骨髓腔，收集骨髓细胞悬液，接种在塑料培养瓶中。经体外扩增、纯化，选用第5代后的骨髓间质干细胞进行诱导分化。用10μg／LbFcF预诱导24h，更换成含川芎嗪的无血清培养基DMEM诱导间质干细胞分化为神经元样细胞。用免疫组织化学SABC法鉴定神经丝蛋白(NF—M)、神经元特异性烯醇化酶(NSE)、巢蛋白(nestin)、微管联合蛋白-2(MAP-2)、生长相关蛋白-43(GAP-43)、胶质纤维酸性蛋白(GFAP)的表达。结果第5代间质干细胞形态达到均一，呈梭形。用川芎嗪诱导15min到3h，间质干细胞胞体逐渐增大，并伸出细长突起形似神经元样细胞。免疫组织化学显示NF-M、NSE、nestin、MAP-2和GAP-43表达阳性，而GFAP阴性。对照组上述染色均为阴性。结论川芎嗪可诱导骨髓间质干细胞分化为神经元样细胞。     

Androgen receptor YAC transgenic mice carrying CAG 45 alleles show trinucleotide repeat instability

X-linked spinal and bulbar muscular atrophy (SBMA) is caused by a CAG repeat expansion in the first exon of the androgen receptor (AR) gene. Disease-associated alleles (37-66 CAGs) change in length when transmitted from parents to offspring, with a significantly greater tendency to shift size when inherited paternally. As transgenic mice carrying human AR cDNAs with 45 and 66 CAG repeats do not display repeat instability, we attempted to model trinucleotide repeat instability by generating transgenic mice with yeast artificial chromosomes (YACs) carrying AR CAG repeat expansions in their genomic context. Studies of independent lines of AR YAC transgenic mice with CAG 45 alleles reveal intergenerational instability at an overall rate of approximately 10%. We also find that the 45 CAG repeat tracts are significantly more unstable with maternal transmission and as the transmitting mother ages. Of all the CAG/CTG repeat transgenic mice produced to date the AR YAC CAG 45 mice are unstable with the smallest trinucleotide repeat mutations, suggesting that the length threshold for repeat instability in the mouse may be lowered by including the appropriate flanking human DNA sequences. By sequence-tagged site content analysis and long range mapping we determined that one unstable transgenic line has integrated an approximately 70 kb segment of the AR locus due to fragmentation of the AR YAC. Identification of the cis - acting elements that permit CAG tract instability and the trans -acting factors that modulate repeat instability in the AR YAC CAG 45 mice may provide insights into the molecular basis of trinucleotide repeat instability in humans.      

An increased frequency of autoantibody-inducing CD4+ T cells in pre-diseased lupus-prone mice

Pathogenic autoantibody production in murine models of lupus is dependent on autoreactive CD4+ helper T cells. However, the mechanisms which permit the selection and maintenance of this autoantibody-inducing CD4+ T-cell repertoire are currently unknown. We hypothesized that the peripheral CD4+ T-cell repertoire of lupus-prone mice was enriched with autoantibody-inducing specificities. To test this, we utilized the splenic focus assay to determine if pre-diseased lupus-prone (NZB x NZW)F(1) mice have an elevated frequency of autoreactive CD4+ T lymphocytes capable of supporting autoantibody production. The splenic focus limiting dilution assay permits anti-nuclear antibodies to be generated from contact-dependent T-B interactions in vitro. We show that young, pre-diseased lupus-prone mice have an elevated frequency of autoantibody-inducing CD4+ T cells. Interestingly, these autoantibody-inducing CD4+ T-cell responses are also present in the thymus. Therefore, an elevated frequency of autoantibody-inducing CD4+ T cells predisposes lupus-prone mice to the development of autoantibodies.     

Cellular localization of complement C3 and C4 transcripts in intestinal specimens from patients with Crohn's disease

It has been suggested that the increase in C3 and C4 levels in jejunal perfusates of patients with Crohn's disease (CD) results from local intestinal synthesis of complement. The present study evaluated the expression of these complement genes in inflamed tissues from patients with CD. Surgically resected specimens from patients with CD and control tissue obtained from subjects with adenocarcinoma of the colon were evaluated for C3 and C4 gene expression by the use of 35S-labelled anti-sense RNA probes. All tissue samples, diseased and normal tissue, expressed C4 mRNA throughout in the intestinal epithelium. C3 mRNA was not detected in epithelial cells in histologically normal tissue, but in diseased specimens there was a focal distribution of C3 mRNA in epithelial cells of the crypts, but not in villous epithelium. Focal C3 gene expression correlated with crypt abscess formation and the presence of polymorphonuclear leucocytes in the lumen of the crypts. In addition, C3 mRNA was also found in macrophages of the submucosa. These macrophages were CD68+, fusiform with faint cytoplasm and morphologically different from the large rounded lamina propria macrophages, which do not express C3 mRNA. Multinucleated giant cells did not express either C3 or C4 genes. In addition to its presence in intestinal epithelium, C4 mRNA was also expressed in mast cells, which however did not express C3 mRNA. These observations identify cells in the intestinal wall expressing complement genes and support the hypothesis that there is local regulated production of complement in the intestine of patients with CD, and subsequent complement activation may contribute to the inflammatory process.     

Phage modification of the capacity of γ-irradiated Escherichia coli to support virus growth

The capacity of Escherichia coli to support the growth of T-even phages is more radiation resistant than it is to support the growth of T-odd phages. Since the differential effect is seen using the same irradiated cell culture, this effect must somehow be due to the characteristics of the phage.Here we have investigated the phospholipid metabolism in γ-irradiated E. coli B cells infected with T4 and T7 phage with the viewpoint that phospholipid synthesis, hence maintenance of membrane integrity, may be an essential factor in determining the capacity of cells to support phage growth. Results obtained using cells preirradiated with 100 krads show that the rate and amount of de novo phospholipid synthesis, as followed by ³²P labeling, in T4-infected cells are greater than in T7-infected cells. The rate continually increases from 0–15 min after infection, whereas in the latter cells there is a shut-off of synthesis beginning at around 10 min into infection. Using similarly irradiated cells, we found the course of turnover in T4-infected cells of phospholipids, prelabeled with [¹⁴C]acetate prior to infection, to show a pattern opposite that in T7-infected cells. The T4-infected cells show indications of redirection of synthesis, whereas the T7-infected cells show continued degradation starting at 5 min after infection. We conclude that there is a correlation between the ability of the phage to redirect the phospholipid metabolism of the cells, which ability the T4 phage is known to have, and the capacity of the irradiated cells to support a complete cycle of infection.The threshold γ-ray dose within which the capacity of E. coli B for supporting a normal plaquing efficiency of T4 is 300 krads, whereas that capacity for T7 declines exponentially with dose. However, within this dose range, the burst size and RNA synthesis of T4-infected cells decreases exponentially with dose, while those cells still surviving capacity loss for T7 growth give roughly normal bursts of this phage.The capacity of E. coli B for T4rII growth is similar in radiation resistance to that for T4r⁺ growth. The rate and amount of de novo phospholipid synthesis in rII-infected cells (where the cells were also irradiated with 100 krads prior to infection) are similar to those found in T4r⁺-infected cells for the first 10 min of infection, but thereafter diminishes in rate.     

Endocrinology: The effect of growth hormone on granulosa cell function during in-vitro fertilization

The effect of growth hormone addition to human menopausal gonadotrophin(HMG), after pituitary down-regulation, on granulosa cell function,in in-vitro fertilization (IVF) was evaluated. Growth hormoneor placebo were added in a prospective, randomized and double-blindmanner to an existing IVF stimulation protocol. Forty-two normalovulatory women (38 years old) with mechanical factor infertilityand normal male factor were included in the study. Gonadotrophin-releasinghormone agonist (GnRHa) was given from day 21 of the previouscycle until human chorionic gonadotrophin (HCG) administration.Follicular stimulation with HMG was started after pituitarydown-regulation. Growth hormone 12 IU/day or placebo were administeredon alternate days, beginning day 1 until day 7 of HMG treatment.Granulosa cell function was evaluated, in all patients, by follicularfluid levels of ovarian steroids and insulin-like growth factor-I(IGF-I). In 14 patients, chosen arbitrarily granulosa luteincells were cultured in the presence and absence of additionalHCG. Follicular fluid levels of oestradiol, progesterone, testosteroneand IGF-I were similar in both growth hormone and placebo groups.Basal and post-HCG levels of oestradiol and progesterone didnot differ significantly between the two groups of granulosalutein cell cultures. We conclude that after pituitary down-regulation,in-vivo administration of growth hormone with HMG in young ovulatorywomen does not seem to affect granulosa cell function when comparedto the administration of HMG alone.