Macroeconomics in an open economy.

The customary treatment of national economies as closed and self-contained must be substantially modified to allow for those economies that typically trade goods, services, and securities with other countries in increasing volume. Open economy macroeconomics is essential to understanding the major events of the U.S. economy over the past half dozen years. Both the sharp rise in the dollar and the unprecedentedly large U.S. trade deficit are linked to the U.S. budget deficit, as is the drop in the rate of inflation.

A new immunodeficient mouse model for human myoblast transplantation.

Design of efficient transplantation strategies for myoblast-based gene therapies in humans requires animal models in which xenografts are tolerated for long periods of time. In addition, such recipients should be able to withstand pretransplantation manipulations for enhancement of graft growth. Here we report that a newly developed immunodeficient mouse carrying two known mutations (the recombinase activating gene 2, RAG2, and the common cytokine receptor gamma, gammac) is a candidate fulfilling these requirements. Skeletal muscles from RAG2(-/-)/gammac(-/-) double mutant mice recover normally after myotoxin application or cryolesion, procedures commonly used to induce regeneration and improve transplantation efficiency. Well-differentiated donor-derived muscle tissue could be detected up to 9 weeks after transplantation of human myoblasts into RAG2(-/-)/gammac(-/-) muscles. These results suggest that the RAG2(-/-)/gammac(-/-) mouse model will provide new opportunities for human muscle research.

Extended amplification in vitro and replicative senescence: key factors implicated in the success of human myoblast transplantation.

The limited success of human myoblast transplantation has been related to immune rejection, poor survival, and limited spread of injected myoblasts after transplantation. An important issue that has received little attention, but is nevertheless of fundamental importance in myoblast transplantation protocols, is the proliferative capacity of human satellite cells. Previous studies from our laboratory have demonstrated that the maximum number of divisions that a population of satellite cells can make decreases with age during the first two decades of life then stabilizes in adulthood. These observations indicate that when satellite cells are used as vectors in myoblast transplantation protocols it is important to consider donor age and the number of divisions that the cells have made prior to transplantation as limiting factors in obtaining an optimal number of donor derived muscle fibers. In this study, myoblasts derived from donors of different ages (newborn, 17 years old, and 71 years old) were isolated and amplified in culture. Their potential to participate in in vivo muscle regeneration in RAG2(-/-)/gamma(c)/C5 triple immunodeficient hosts after implantation was evaluated at 4 and 8 weeks postimplantation. Our results demonstrate that prolonged amplification in culture and the approach to replicative senescence are both important factors that may condition the success of myoblast transplantation protocols.

The effects of fellow patients on the emotional well-being and satisfaction with care of postoperative cosmetic surgery patients.

This article reports the findings of a quasi-experimental study that represents the first attempt to systematically examine the possibility that contact with fellow patients after cosmetic surgery significantly influences a patient's postoperative emotional well-being and satisfaction with care. Patients were assigned to rooms that either facilitated ample postoperative contact with other patients (n = 70) or to rooms that were physically located in a manner that afforded little inter-patient contact (n = 9). The results indicate that whereas postoperative depression levels did not differ, patients in the high-patient-contact condition experienced less postoperative anxiety and greater overall satisfaction with their quality of care than did patients in the low-patient-contact condition. Analyses of patients' reported postoperative affiliations suggest several additional benefits of inter-patient contact, such as added emotional support, reduction of uncertainty about what to expect, and the opportunity to compare progress and emotional reactions. The results are consistent with a growing literature that suggests fellow patients can and do serve a useful, adjunctive role in health care. Questions for future research are considered.

The mitotic clock in skeletal muscle regeneration, disease and cell mediated gene therapy.

The regenerative capacity of skeletal muscle will depend on the number of available satellite cells and their proliferative capacity. We have measured both parameters in ageing, and have shown that although the proliferative capacity of satellite cells is decreasing during muscle growth, it then stabilizes in the adult, whereas the number of satellite cells decreases during ageing. We have also developed a model to evaluate the regenerative capacity of human satellite cells by implantation into regenerating muscles of immunodeficient mice. Using telomere measurements, we have shown that the proliferative capacity of satellite cells is dramatically decreased in muscle dystrophies, thus hampering the possibilities of autologous cell therapy. Immortalization by telomerase was unsuccessful, and we currently investigate the factors involved in cell cycle exits in human myoblasts. We have also observed that insulin-like growth factor-1 (IGF-1), a factor known to provoke hypertrophy, does not increase the proliferative potential of satellite cells, which suggests that hypertrophy is provoked by increasing the number of satellite cells engaged in differentiation, thus possibly decreasing the compartment of reserve cells. We conclude that autologous cell therapy can be applied to specific targets when there is a source of satellite cells which is not yet exhausted. This is the case of Oculo-Pharyngeal Muscular Dystrophy (OPMD), a late onset muscular dystrophy, and we participate to a clinical trial using autologous satellite cells isolated from muscles spared by the disease.

Intraspinal injection of embryonic neurons maintains muscle phenotype in adult chronic spinal rats.

A suspension of monoaminergic embryonic neurons was transplanted into the spinal cord of paraplegic rats. Enzyme histochemical, morphometric, and biochemical analyses of the hindlimb musculature were carried out 2-5 months later to determine the consequences on muscle atrophy and muscle phenotypes which were compared in three groups of rats: intact, spinalized, and spinalized and transplanted with embryonic cells. Our results indicate that this transplantation does not prevent muscular atrophy, which appears highly dependent on the level of muscular activity, but partially maintains the slow phenotype, especially in the soleus muscle. We conclude that fiber phenotypes are not determined by the level of muscular activity alone but are also dependent on putative trophic factors synthesized by motoneurones.

In vivo satellite cell activation via Myf5 and MyoD in regenerating mouse skeletal muscle.

Regeneration of adult skeletal muscle is an asynchronous process requiring the activation, proliferation and fusion of satellite cells, to form new muscle fibres. This study was designed to determine the pattern of expression in vivo of the two myogenic regulatory factors, Myf5 and MyoD during this process. Cardiotoxin was used to induce regeneration in the gastrocnemius and soleus muscles of heterozygous Myf5-nlacZ mice, and the muscles were assayed for the presence of (beta)-galactosidase (Myf5) and MyoD. Adult satellite cells identified by M-cadherin labelling, when activated, initially express either MyoD or Myf5 or both myogenic factors. Subsequently all proliferating myoblasts express MyoD and part of the population is (beta)-galactosidase (Myf5) positive. Furthermore, we demonstrate that activated satellite cells, which express either Myf5 or MyoD, do not accumulate selectively on fast or slow muscle fibres.

Regenerative capacity of human satellite cells: the mitotic clock in cell transplantation.

In this communication, we will review the problems caused by cell-mediated gene therapy, taking skeletal muscle as a physiological model. In particular we have utilised vectors transferring telomerase under the control of retroviral promoters into human satellite cells. The set of results presented here has several implications regarding gene therapy trials. Nevertheless, more experiments will be required to fully validate this cellular model and to use telomerase to safely extend the lifespan of putative gene therapy vectors.