Troponin C regulates the rate constant for the dissociation of force-generating myosin cross-bridges in cardiac muscle

It is well known that cardiac troponin C (cTnC) regulates the association of force-generating myosin cross-bridges. We report here evidence for an additional role for cTnC. This hypothesis states that Car²⁺ binds more strongly to cTnC when force-generating myosin cross-bridges are attached to actin and that removal of this bound Ca²⁺ accelerates the dissociation of force-generating myosin cross-bridges. Intact Fura-2-loaded rat papillary muscles and skinned (permeabilized) ventricular preparations were used. The preparations were mounted in the Guth Muscle Research System which is capable of measuring simultaneously fluorescence and force in response to length perturbations. All mechanical perturbations of muscle length (isotonic shortening, quick stretches and releases, and length vibrations) which cause dissociation of force-generating myosin cross-bridges during a twitch resulted in Ca²⁺ being released from troponin as judged from changes in the Ca²⁺ transients (Fura-2 (340/380) fluorescence ratio). Thus dissociation of force-generating myosin cross-bridges cause Ca²⁺ to be released from cTnC. Conversely, it would be expected that removal of strongly bound Ca²⁺ from cTnC would result in an increase in the rate of dissociation of force-generating myosin cross-bridges. To test this hypothesis actomyosin ATPase (NADH fluorescence change) and isometric force were measured in skinned cardiac preparations. The ratio of the ATPase/Force is proportional to the rate constant (g_app) for the dissociation of force-generating myosin cross-bridges. The data showed that decreasing the amount of Ca²⁺ bound to cTnC in skinned cardiac fibers caused an increase in the ratio of ATPase/Force, the rate of dissociation (g_app) of force-generating myosin cross-bridges.     

Translocation chromosome 7 of A431 cells contains amplification and rearrangement of EGF receptor gene responsible for production of variant mRNA

The epidermal growth factor (EGF) receptor, along with several oncogene protein products, possesses tyrosine-specific protein kinase activity. Furthermore, the EGF receptor has structural similarity to the putitive v-erb-B transforming protein. Because of these closely shared characteristics, it is important to elucidate the possible involvement of the EGF receptor in malignant transformation. The epidermal carcinoma cell line A431 exhibits an abnormally high number of EGF receptors, which is associated with the presence of translocation chromosome M4. Recently, A431 cells have been shown to contain amplified sequences for the EGF receptor gene(s) and also to produce a variant mRNA which diverges from the normal EGF receptor mRNA at the 3 end. Here we report, using the human EGF receptor cDNA probe pE7, that the chromosome M4 has a six-to sevenfold amplification of the EGF receptor gene. Furthermore, the presence of M4 in somatic cell hybrids correlates with the production of the variant 2.9-kb mRNA. This aberrant mRNA is apparently generated by an intrachromosomal rearrangement which was detected using as a probe a fragment of the pE15cDNA encoding the variant mRNA.     

Fludarabine-based conditioning secures engraftment of second hematopoietic stem cell allografts (HSCT) in the treatment of initial graft failure.

Graft failure is associated with a high mortality rate. To date, regimens invoked for second transplants have resulted in inconsistent engraftment with high transplant-related mortality (TRM). We here report 16 consecutive patients, aged 4-59 years, who received second HSCT (HSCT-2) at a median of 45 days following primary or secondary failure of an initial unmodified (N = 3) or T cell-depleted (TCD) (N = 13) HSCT (HSCT-1). HSCT-1 was administered after myeloablative total body irradiation (TBI)- or alkylator-based conditioning for acute leukemias (N = 7), MDS (N = 6), CML (N = 2), and Fanconi anemia (N = 1). All patients experienced 1 or more infectious complications between HSCT-1 and HSCT-2, and 10 patients had active infections at the time of HSCT-2. Cytoreduction regimens used for HSCT-2 included fludarabine (Flu) in combination with cyclophosphamide (CTX) (N = 9), or thiotepa (Thio) (N = 5). In addition, 1 patient received Flu alone and 1 patient Thio combined with CTX. Antithymocyte globulin (ATG) (N = 11) or Alemtuzumab (N = 3) was added pretransplant to prevent rejection. For HSCT-2, donors included HLA-matched (N = 3) or mismatched (N = 8) related, or matched (N = 2) or mismatched (N = 3) unrelated donors. The primary graft donor was used in 6 of 16 cases. The grafts administered were unmodified peripheral blood stem cell transplantation (PBSCT) (N = 5) or bone marrow transplantation (BMT) (N = 3), TCD PBSCT (N = 8). All patients achieved engraftment at a median of 12 days and evaluable patients achieved complete donor chimerism. Six patients are alive with a median follow-up of 49 months, including 4/9 conditioned with Flu/CTX. In this series, outcome was statistically superior for younger patients (相似文献   

The effects of nandrolone, testosterone and their decanoate esters on murine lupus

Treatment of NZB/NZW F1 (B/W) female and castrated male mice with testosterone or 19-nortestosterone (nandrolone), either by implantation in silastic tubing or by subcutaneous injections of their decanoate esters, reduced in a dose-dependent manner symptoms associated with murine lupus (proteinuria, IgG antibodies to DNA) and prolonged survival. These phenomena were observed under both prophylactic (start at 3-4 weeks) and therapeutic treatments (start 27-29 weeks). Nandrolone and its decanoate ester were at least as potent as testosterone and testosterone decanoate. As the unwanted androgenic properties of nandrolone and its ester are significantly less pronounced than those of testosterone and its ester, also in these NZB/NZW mice, the beneficial effect on murine lupus does not seem to be associated with these properties.     

Identification of Clinical Isolates of Mycobacteria with Gas-Liquid Chromatography Alone

Identification of 18 mycobacterial species was performed by analysis of profiles obtained by using gas-liquid chromatography. Organisms were saponified in methanolic NaOH, and the reaction mixture was treated with BF(3) in methanol and extracted with a hexane-chloroform mixture. An identification scheme was developed from 128 stock strains and tested against a collection of 79 clinical isolates. By using gas-liquid chromatographic profiles alone, 58% of specimens were correctly identified to species level, and an additional 41% were correctly identified to a group of two or three organisms. Use in a clinical laboratory over a 2-month period proved chromatography to be as accurate as and more rapid than concurrent biochemical testing. Of 81 isolates tested, 64% were identified to species level by chromatography alone. An additional 35% were differentiated to the same groups of two or three organisms as found in our analysis of stock strains. These groups consisted of: Mycobacterium tuberculosis, M. bovis, and M. xenopi; M. avium complex, M. gastri, and M. scrofulaceum; or M. fortuitum and M. chelonei. Identification to species level from these groups could usually be done by colonial morphology alone and could always be done by the addition of one selected biochemical test. This study demonstrated the practical application of gas-liquid chromatography in the identification of mycobacteria in a clinical laboratory. In particular, all strains of M. gordonae and M. kansasii were identified to species level. M. tuberculosis was definitively identified in 85% of cases. When it could not be definitely identified, the only alternatives were M. bovis and M. xenopi, both of which are rare causes of infection.     

Amino Acid Formula Containing Synbiotics in Infants with Cow’s Milk Protein Allergy: A Systematic Review and Meta-Analysis

Cow’s milk protein allergy (CMPA) is associated with dysbiosis of the infant gut microbiome, with allergic and immune development implications. Studies show benefits of combining synbiotics with hypoallergenic formulae, although evidence has never been systematically examined. This review identified seven publications of four randomised controlled trials comparing an amino acid formula (AAF) with an AAF containing synbiotics (AAF-Syn) in infants with CMPA (mean age 8.6 months; 68% male, mean intervention 27.3 weeks, n = 410). AAF and AAF-Syn were equally effective in managing allergic symptoms and promoting normal growth. Compared to AAF, significantly fewer infants fed AAF-Syn had infections (OR 0.35 (95% CI 0.19–0.67), p = 0.001). Overall medication use, including antibacterials and antifectives, was lower among infants fed AAF-Syn. Significantly fewer infants had hospital admissions with AAF-Syn compared to AAF (8.8% vs. 20.2%, p = 0.036; 56% reduction), leading to potential cost savings per infant of £164.05–£338.77. AAF-Syn was associated with increased bifidobacteria (difference in means 31.75, 95% CI 26.04–37.45, p < 0.0001); reduced Eubacterium rectale and Clostridium coccoides (difference in means −19.06, 95% CI −23.15 to −14.97, p < 0.0001); and reduced microbial diversity (p < 0.05), similar to that described in healthy breastfed infants, and may be associated with the improved clinical outcomes described. This review provides evidence that suggests combining synbiotics with AAF produces clinical benefits with potential economic implications.     

The midsagittal area of the corpus callosum and total neocortical volume differ in three inbred strains of mice

Differences in the midsagittal area of the corpus callosum have been reported between human males and females, between handled and nonhandled rats, and both within and between various strains of mice. This measure has, in addition, been related to handedness in humans and "pawedness" in certain strains of mice. The present study investigated the between- and within-strain differences in three inbred strains of mice, two with autoimmune disorders and spontaneously occurring developmental neuropathology, in the midsagittal area of the corpus callosum, the total neocortical volume, and the asymmetry of the neocortex. These morphometric measures were obtained from coronally sectioned celloidin-embedded material from New Zealand Black (NZB/BINJ), BXSB/MpJ, and DBA/2J mouse strains. NZB mice had a total neocortical volume larger than that of either the BXSB or DBA strains, whereas the BSXB mice had a midsagittal area of the corpus callosum larger than that of either of the other two strains. In addition, there was a positive correlation between these two measures. There was no correlation between total neocortical asymmetry and midsagittal area of the corpus callosum in any of the three strains. Finally, there were no differences in any morphometric measure between animals with or without developmental neuropathology in any given strain.