Effects of skeletal muscle sarcomere length on in vivo capillary distensibility

The structural integrity of the capillary wall is such that capillary luminal distensibility is largely determined by support provided by the tissue in which it is located. Given that O2 flux density is greatest across the skeletal muscle capillary endothelium, any changes in capillary diameter (dc) would be expected to affect O2 diffusing capacity as well as hemodynamic resistance. We used intravital microscopy techniques to study the maximally vasodilated rat (n = 5) spinotrapezius muscle microcirculation in vivo within the physiological sarcomere length range, at high and low mean arterial pressures (MAP) systematically altered by blood withdrawal and infusion. We tested the hypothesis that in vivo capillary diameter alterations in response to changes of MAP would be reduced at extended sarcomere lengths. At 2.4-microm sarcomere length, mean dc (dc) within the spinotrapezius increased from 5.6 +/- 0.1 to 5.9 +/- 0.1 microm (P < 0.01) as MAP increased from 33 to 94 mm Hg. However, there was absolutely no change (i.e., 5.2 +/- 0.1 vs 5.2 +/- 0.1 microm) in dc in response to changes in MAP at 3.2-microm sarcomere length. Furthermore, at sarcomere lengths <2.8 microm there was a significant increase (P < 0.01) in dc (n = 40) as MAP increased, whereas dc (n = 49) remained unchanged with alterations of MAP when sarcomere length was >/=2.8 microm (P > 0.05). These data suggest that pressure-induced alterations in capillary luminal diameter and thus "in vivo capillary distensibility" are dependent upon the presiding sarcomere length. Furthermore, we conclude that the MAP-induced increases in capillary luminal diameter at the shorter sarcomere lengths are modest ( approximately 5%) and unlikely to affect O2 diffusing capacity and vascular resistance appreciably.     

The Kheda malaria project: the case for environmental control

The Kheda project experience has shown that bio-environmentalcontrol of malaria is feasible, cost effective and ecologicallysound. It clearly brings out the need to consider health issuesat the planning stage of all developments. Bio-environmentalcontrol of malaria is suggested as the first line of attackfor the control of mosquitoes, malaria and other mosquito-bornediseases. Insecticides may be reserved for short-term use. Thiswill enable judicious and selective use of insecticides in solelyepidemic situations. The growing problem of resistance to insecticidesin mosquitoes as well as environmental pollution, can then besolved on a long term basis.     

Colorectal neoplasms: accuracy of US in demonstrating the depth of invasion

Six normal and 16 neoplastic colorectal specimens were examined with 8.5-MHz ultrasound (US). An articulated system facilitated precise spatial correlation between US and histologic sections. Images were blindly interpreted and then compared with histologic results. All six normal specimen showed five distinct echo layers and were distinguished from neoplastic specimens by all the observers. The central echogenic layer, corresponding to the submucosa, is useful in determining the depth of origin of a neoplasm and the presence of submucosal invasion. US had an accuracy of 92.5% in demonstrating invasion of the submucosa and 77% for invasion of the muscularis externa. For mucosal neoplasms with invasion through the muscularis externa and extension into the subserosal tissues, nearly 90% of US interpretations were correct. High-frequency US may be useful in determining the depth of invasion of mucosal tumors with respect to the submucosa and in differentiating mucosal from extramural masses.     

Acute renal rejection versus acute tubular necrosis in a canine model: MR evaluation

Findings of magnetic resonance (MR) imaging in acute renal rejection and acute tubular necrosis (ATN) were studied in dogs. On T1-weighted images, corticomedullary differentiation was absent in kidneys undergoing acute rejection. The loss of corticomedullary differentiation in these kidneys was secondary to a decrease in the relative signal intensity of the cortex, indicating prolongation of the T1 relaxation time of the cortex. In contrast, corticomedullary differentiation was preserved on T1-weighted images of autotransplanted kidneys and kidneys with ATN. MR imaging findings correlated with changes in water content in these three groups of kidneys. Kidneys undergoing acute rejection showed a marked increase in water content compared with kidneys in the other two groups. No change in fat content was found in any group.     

Is ownership more important than the scientific credibility of audit protocols? A survey of medical audit advisory groups

BACKGROUND: It is commonly accepted that ownership is an important factor in determining the acceptability and use of protocols or guidelines. OBJECTIVES: We aimed to determine whether Medical Audit Advisory Groups (MAAGs) are prepared to accept and use audit protocols developed systematically by an external agency. METHOD: A postal questionnaire was sent to all 105 MAAG chairmen in England and Wales to seek their views on the external development of protocols, the inclusion of evidence-based prioritized criteria, the general design of the protocols issued by the Lilly Audit Centre and the numbers of practices reported by MAAGs as making use of at least one of the first four protocols issued. RESULTS: Ninety-five MAAGs (90%) responded. Of these, 86% were in favour of the external development of protocols, and 98% and 94%, respectively, found evidence-based and prioritized criteria valuable; 98% felt the overall design and content of the Audit Centre protocols were excellent or good. A total of 1018 practices was known to have made use of one of these protocols, 261 taking part in multi-practice audits organized by their MAAGs. CONCLUSION: Ownership is not necessarily more important than scientific credibility and/or perceived utility. Externally developed audit protocols containing evidence-based, prioritized review criteria are acceptable to MAAGs, which are prepared to recommend their use in practice. Accordingly, such systematically developed protocols offer a promising and practical method for improving clinical effectiveness. Further research is needed, however, to determine the comparative impact on standards of care of protocols and other methods such as clinical guidelines.