instruction:
In this task, you are given an abstract of article. Your task is to generate title for this article. Preferred titles are under thirty words.
question:
The twin-arginine translocation (Tat) protein export system is present in the cytoplasmic membranes of most bacteria and archaea and has the highly unusual property of transporting fully folded proteins. The system must therefore provide a transmembrane pathway that is large enough to allow the passage of structured macromolecular substrates of different sizes but that maintains the impermeability of the membrane to ions. In the Gram-negative bacterium Escherichia coli, this complex task can be achieved by using only three small membrane proteins: TatA, TatB and TatC. In this Review, we summarize recent advances in our understanding of how this remarkable machine operates.
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The twin-arginine translocation (Tat) protein export pathway

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Patients with inflammatory bowel disease have an increased prevalence of osteoporosis, and suffer high rates of spinal bone loss. Hormone replacement therapy (HRT) is effective in the treatment and prevention of osteoporosis but has not been studied in patients with inflammatory bowel disease. A two year prospective study of HRT in inflammatory bowel disease was performed in 47 postmenopausal women aged 44 to 67 years with ulcerative colitis (25) or Crohn's disease (22). Patients had radial and spinal bone density measured annually by single photon absorptiometry and quantitative computed tomography respectively. The mean (95% confidence intervals) annual change in radial bone density was +1.42%/yr (+0.58 to +2.26; P < 0.005) and for spinal bone +2.60%/yr (+1.06 to +4.15; p < 0.005). There was no significant correlation between rates of change of bone density at the two sites, or between the rates of change and the initial bone density either in the radius or spine. Twelve patients were given prednisolone during the study, and their rates of change for spinal bone density were lower, but values were not statistically significantly different from those who did not receive corticosteroids. Changes in bone density for patients with ulcerative colitis and Crohn's disease were not significantly different. The change in bone density did not correlate with the patients' age or number of years after the menopause. It is concluded that HRT is effective in prevention of bone loss in postmenopausal women with inflammatory bowel disease.
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Hormone replacement therapy prevents bone loss in patients with inflammatory bowel disease.

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The recognition that myocyte mitosis occurs in the fetal, neonatal, adult, and hypertrophied heart and that a pool of primitive, undifferentiated cells is present in the myocardium has put forward a different view of the biology of the heart. The new paradigm suggests that myocyte formation is preserved during postnatal life, in adulthood or senescence, pointing to a remarkable growth reserve of the heart throughout the course of life of the organism. This article reviews a large body of novel information, which has been obtained in the last 2 decades, in favor of the notion that the mammalian heart has the inherent ability to continuously replace its parenchymal cells and that this unexpected characteristic has important implications in understanding myocardial homeostasis, cardiac aging, and tissue repair. The paradigm that the heart is a postmitotic organ incapable of regenerating parenchymal cells was established in the 1970s, and this dogma has profoundly conditioned basic and clinical research in cardiology for the last 3 decades. On the basis of this paradigm, cardiomyocytes undergo cellular hypertrophy1,2 but cannot be replaced either by entry into the cell cycle of a subpopulation of nonterminally differentiated myocytes or by activation of a pool of primitive cells that become committed to the myocyte lineage. The only response of cardiomyocytes to stress is hypertrophy and/or death. Therefore, a tremendous effort was made to identify the molecular mechanisms of myocyte hypertrophy and their genetic control. A sophisticated knowledge of various signaling pathways has been achieved, and our understanding of the biology of hypertrophic myocyte growth has advanced markedly.3 An array of new technologies has been introduced that has led to a scientific revolution in terms of questions, approaches, and interpretation of experimental results. Despite this enormous progress in our understanding of basic mechanisms of hypertrophy, however, very little
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Life and death of cardiac stem cells: a paradigm shift in cardiac biology.