Malcolm Sparrow

Myosin composition and functional properties of smooth muscle from the uterus of pregnant and non-pregnant rats.

The myosin heavy chain stoichiometry and the force-velocity relation have been determined in the myometrium of the non-pregnant and pregnant rat. The relative proportions of the slower migrating heavy chain (MHC1) greatly exceeded that of the faster migrating heavy chain (MHC2) as shown by electrophoresis on SDS 4%-polyacrylamide gels. The ratios of MHC1/MHC2 were 2.2/1 in the non-pregnant rats, 2.6/1 in the pregnant rat, and contrasted with 0.8/1 in the rat portal vein. This stoichiometry was unchanged by extracting the myosin from the smooth muscle as native myosin in a salt extract, as dissociated myosin using sodium dodecyl sulphate (SDS) or by isolating the native myosin first by a non-dissociating (pyrophosphate) electrophoresis step and subsequently analysing the protein bands on the SDS 4%-polyacrylamide gel. Although the unequal proportions of the heavy chains suggested the possibility that the native myosin molecule may be arranged as homodimeric heavy chains, no evidence for or against the existence of native myosin isoforms could be obtained by electrophoresing native myosin extracts on pyrophosphate-polyacrylamide gels. The force-velocity relations of the intact electrically stimulated myometrium from the non-pregnant and pregnant rats gave isometric force of 45 and 135 mN/mm2 andVmax of 0.71 and 0.52 lengths/s (37°C) when measured at 95% of optimal length, whereas in chemically skinned uterine strips at 22°CVmax was 0.09 and 0.13 lengths/s, respectively. The length-force relationship was of similar shape in the non-gravid and gravid skinned tissues. The energetic tension cost (ATP-turnover/active stress) in skinned fibres was also similar. The mechanical and metabolic characteristics of the gravid and non-gravid uterus found in the present study do not suggest an obvious difference in the intrinsic properties of the myosin, although significant functional alterations in the tissue appear during pregnancy. This corresponds to the lack of a difference in the pattern of the heavy chains.

Changes in myosin heavy chain stoichiometry in pig tracheal smooth muscle during development

The stoichiometry of the myosin heavy chains (MHCs) has been measured in the tracheal smooth muscle of the pig after electrophoresis on SDS 4% polyacrylamide gel. The ratio of slower migrating MHC to the faster migrating MHC was 2.1 in neonates, 1.5 in young and 0.95 in old pigs (P<0.01) showing that MHC composition changes with development. The unequal proportion of MHCs was not compatible with a heterodimeric arrangement of the MHCs in the native molecule as proposed earlier by Rovner et al. [(1986) Am. J. Physiol. 250, C861–870] and it is suggested that native molecules may be composed of homodimer heavy chains.

A confocal microscopic study of solitary pulmonary neuroendocrine cells in human airway epithelium

BackgroundPulmonary neuroendocrine cells (PNEC) are specialized epithelial cells that are thought to play important roles in lung development and airway function. PNEC occur either singly or in clusters called neuroepithelial bodies. Our aim was to characterize the three dimensional morphology of PNEC, their distribution, and their relationship to the epithelial nerves in whole mounts of adult human bronchi using confocal microscopy.MethodsBronchi were resected from non-diseased portions of a lobe of human lung obtained from 8 thoracotomy patients (Table 1) undergoing surgery for the removal of lung tumors. Whole mounts were stained with antibodies to reveal all nerves (PGP 9.5), sensory nerves (calcitonin gene related peptide, CGRP), and PNEC (PGP 9.5, CGRP and gastrin releasing peptide, GRP). The analysis and rendition of the resulting three-dimensional data sets, including side-projections, was performed using NIH-Image software. Images were colorized and super-imposed using Adobe Photoshop.ResultsPNEC were abundant but not homogenously distributed within the epithelium, with densities ranging from 65/mm2 to denser patches of 250/mm2, depending on the individual wholemount. Rotation of 3-D images revealed a complex morphology; flask-like with the cell body near the basement membrane and a thick stem extending to the lumen. Long processes issued laterally from its base, some lumenal and others with feet-like processes. Calcitonin gene-related peptide (CGRP) was present in about 20% of PNEC, mainly in the processes. CGRP-positive nerves were sparse, with some associated with the apical part of the PNEC.ConclusionOur 3D-data demonstrates that PNEC are numerous and exhibit a heterogeneous peptide content suggesting an active and diverse PNEC population.

Epithelial disruption by proteases augments the responsiveness of porcine bronchial segments

1. The effect of disruption to the epithelium of intact porcine bronchi was examined by comparing the responsiveness to agonists applied to the adventitial and luminal surfaces. The development of smooth muscle tone was measured as an increase in pressure in an isovolumic bronchial segment of approximately 2 mm i.d. The reactivity and sensitivity to acetylcholine (ACh) introduced intraluminally was greatly attenuated when compared with adventitial addition.

STRUCTURE AND FUNCTION OF THE ADVENTITIAL AND MUCOSAL NERVE PLEXUSES OF THE BRONCHIAL TREE IN THE DEVELOPING LUNG

1. The aim of the present study was first to determine when airway smooth muscle first appears in the airways of the developing foetal lung and when its contractility is mature and, second, when the airway smooth muscle becomes innervated, both structurally and functionally.

Linear kinetic model to estimate protein synthesis rate after [14C]tyrosine infusion in dogs.

Received 22 March 1977 Revised version received 17 May 1977 1. Introduction 2. Methods Garlick et al. [1 ] have described a procedure for estimating protein synthesis rates in experimental animals. Radiolabetled amino acid is infused for a short time, usually 6 h, and serial plasma samples are taken during this period to determine the rate at which a steady state of labelling in the plasma is obtained. After the infusion the animal is sacrificed, the selected tissue excised and the specific radioactivities of the intraceUular free amino acid pool and the protein bound pool determined. Equations were derived to transform these data into estimates of k s , the rate constant for transfer of amino acid from the free intra- cellular pool to the protein bound pool and the procedure has been used in a number of subsequent publications by these workers [2-4]. For optimal reliability of k s estimates, serial tissue biopsies should also be taken during the infusion. While this is difficult with current technology it should become more feasible in the near future. In the meantime, however, the terminal sampling of the tissue compartments provides data which should be utilized to the fullest extent. The equations of Garlick et al. produce k s values which give no indication of their reliability. An alternative treatment is proposed here based on a 3 compartmental model which gives k s together with an estimate of its uncertainty. It is used with data on [14C]tyrosine incorporation in myocardial tissue of dogs.