Response of mouse plantaris muscle to functional overload: comparison with rat and cat

Functional overload (FO) of a muscle by removing its synergists results in a compensatory hypertrophy of the muscle. However, the extent of the response appears to be dependent, at least in part, on the activity and/or loading levels of the muscle following surgery. Thus, differences in the inherent physical activity levels across species may be an important factor to consider. In the present study, the effects of 8 weeks of FO on the isometric mechanical properties of the plantaris of mice (highly active) were determined and the findings compared with the results from previous studies performed on the plantaris of rats (highly active) and cats (less active). FO resulted in approximately a doubling of the mass, the physiological cross-sectional area and the maximum tetanic tension per unit cross-sectional area, was similar in the plantaris of control and FO mice. Isometric twitch speed properties were unaffected, but the tension enhancement in response to an increase in the rate of stimulation showed the pattern of a "faster" muscle following FO. The fatigue resistance of the plantaris in FO mice was significantly higher than in control mice. Although the degree of hypertrophy that occurred in the mouse plantaris was similar to that observed after FO in rats and in cats that are exercised intermittently at high intensities, there were differences in the mechanical properties that may be related to the adaptability of species and/or the behavioral responses to the overload.     

Distribution of myosin heavy chain isoforms in non-weight-bearing rat soleus muscle fibers

The effects of 14 days of spaceflight (SF) or hindlimb suspension (HS) (Cosmos 2044) on myosin heavy chain (MHC) isoform content of the rat soleus muscle and single muscle fibers were determined. On the basis of electrophoretic analyses, there was a de novo synthesis of type IIx MHC but no change in either type I or IIa MHC isoform proportions after either SF or HS compared with controls. The percentage of fibers containing only type I MHC decreased by 26 and 23%, and the percentage of fibers with multiple MHCs increased from 6% in controls to 32% in HS and 34% in SF rats. Type IIx MHC was always found in combination with another MHC or combination of MHCs; i.e., no fibers contained type IIx MHC exclusively. These data suggest that the expression of the normal complement of MHC isoforms in the adult rat soleus muscle is dependent, in part, on normal weight bearing and that the absence of weight bearing induces a shift toward type IIx MHC protein expression in the preexisting type I and IIa fibers of the soleus.     

Measurements of isoprene-derived organosulfates in ambient aerosols by aerosol time-of-flight mass spectrometry - part 1: single particle atmospheric observations in Atlanta

Organosulfate species have recently been identified as a potentially significant class of secondary organic aerosol (SOA) species, yet little is known about their behavior in the atmosphere. In this work, organosulfates were observed in individual ambient aerosols using single particle mass spectrometry in Atlanta, GA during the 2002 Aerosol Nucleation and Characterization Experiment (ANARChE) and the 2008 August Mini-Intensive Gas and Aerosol Study (AMIGAS). Organosulfates derived from biogenically produced isoprene were detected as deprotonated molecular ions in negative-ion spectra measured by aerosol time-of-flight mass spectrometry; comparison to high-resolution mass spectrometry data obtained from filter samples corroborated the peak assignments. The size-resolved chemical composition measurements revealed that organosulfate species were mostly detected in submicrometer aerosols and across a range of aerosols from different sources, consistent with secondary reaction products. Detection of organosulfates in a large fraction of negative-ion ambient spectra - ca. 90-95% during ANARChE and ~65% of submicrometer particles in AMIGAS - highlights the ubiquity of organosulfate species in the ambient aerosols of biogenically influenced urban environments.     

Plastic surgery: the rainbow profession

Trehalose is a disaccharide that can stabilise cell membranes under various stressful conditions. We have studied the effect of trehalose on the ischaemic tolerance of fat skeletal muscle flaps. A rat gracilis model was used to evaluate the prolongation of ischaemic preservation of the modified solution in which trehalose was substituted for glucose in Euro-Collins solution. Four groups of animals were studied. In two groups, flaps were preserved in Euro-Collins solution or trehalose Euro-Collins solution for various ischaemic intervals (6, 12, 24, 48, 72, and 96 hours). In two additional groups, after storage for various periods in the two solutions, muscle flaps were replanted into the original animals with microvascular anastomoses, and were investigated by light and electron microscopy on the seventh postoperative day. Trehalose Euro-Collins solution significantly prolonged ischaemic tolerance compared with Euro-Collins solution alone at 24 and 48 hours.     

Influence of two weeks of non-weight bearing on rat soleus motoneurons and muscle fibers

OBJECTIVES: To analyse the ethical implications of informing patients about their do-not-resuscitate status (DNR). DESIGN: Questionnaire. SETTING: Nationwide, 6 months after the publication of guidelines on DNR in 1994. SUBJECTS: A 10% random sample of the members of the Swedish Cardiac Society. 104 physicians and 196 nurses. MAIN OUTCOME MEASURES: To what extent are patients, physicians and nurses involved in decisions about DNR, and how should the ethical conflict involved in informing patients about their DNR status be described and analysed? RESULTS: Of 73% responding, 84% of the physicians and 8% of the nurses had made a DNR decision. The decision was regarded as ethically right and well timed and it was discussed with 33% of the competent patients. Half of the respondents believed that DNR orders should be discussed with the competent patient. but still only one third of the patients are involved. The ethical conflict is analysed using the principles of autonomy and nonmaleficence as value premises. CONCLUSIONS: Many physicians are still reluctant to find out what the patient wants. Being ignorant they risk harming the patient. It is recommended that information about DNR status should be given incrementally and that the attitudes of the old and chronically ill in-hospital patients are studied. Do they want to be informed, and if so, how and when do they want it to be done?     

Side-effects of high pressure irrigation

This study was undertaken to identify side-effects of high pressure irrigation. Standardized surgical wounds made in Yorkshire pigs were subjected to high pressure syringe and pulsatile irrigation. As a result of these treatments, fluids were disseminated into the adjacent tissue of the wound, predominantly in a lateral direction. Bacteria did not accompany this disseminated fluid and apparently were filtered out by the surface tissues. This treatment results in a tissue injury which impairs its defenses, making the wound more susceptible to infection. However, the remarkable cleansing capacity of high pressure irrigation appears to outweigh this side-effect, since heavily contaminated wounds subjected to this treatment heal per primum without infection.