Donald E. Yorde

Basal lamina components are concentrated in premuscle masses and at early acetylcholine receptor clusters in chick embryo hindlimb muscles

As an initial step in characterizing the function of basal lamina components during muscle cell differentiation and innervation in vivo, we have determined immunohistochemically the pattern of expression of three components--laminin, proteins related to agrin (an acetylcholine receptor (AChR)-aggregating protein), and a heparan sulfate proteoglycan--during the development of chick embryo hindlimb muscles. Monoclonal antibodies against agrin were used to purify the protein from the Torpedo ray and to characterize agrin-like proteins from embryonic and adult chicken. In early hindlimb buds (stage 19), antibodies against laminin and agrin stained the ectodermal basement membrane and bound to limb mesenchyme with a generalized, punctate distribution. However, as dorsal and ventral premuscle masses condensed (stage 22-23), mesenchymal immunoreactivity for laminin and agrin-like proteins, but not the proteoglycan, became concentrated in these myogenic regions. Significantly, the preferential accumulation of these molecules in myogenic regions of the limb preceded by 1-2 days the appearance of muscle-specific proteins, myoblast fusion, and muscle innervation. All three basal lamina components were preferentially associated with all AChR clusters from the time we first observed them on newly formed myotubes at stage 26. Localization of these antigens in three-dimensional collagen gel cultures of limb mesenchyme, explanted prior to innervation of the limb, paralleled the staining patterns seen during limb development in the embryo. These results indicate that basal lamina molecules intrinsic to limb mesenchyme are early markers for myogenic and synaptic differentiation, and suggest that these components play important roles during the initial phases of myogenesis and synaptogenesis.

Relationship between distention and absorption in rat intestine: I. Effect of luminal volume on the morphology of the absorbing surface

Previous studies in vivo have suggested that distention of the intestinal lumen may enhance intestinal absorption by augmenting absorptive surface area. The precise anatomic mechanism for this increase in surface area, however, has not been explored in detail. We developed methods for rapidly freezing and fixing intestinal segments in situ in the nondistended or distended state. Distention led to a reduction in villus height (309.2 +/- 9.9 to 230.7 +/- 11.8 micron) and a marked increase in the width of intervillus space in both the transverse (50.4 +/- 4.8 to 298.0 +/- 24.8 micron) and longitudinal (15.2 +/- 3.4 to 76.0 +/- 10.6 micron) dimensions. There was, however, no absolute change in total mucosal surface area. The changes in morphology occurred instantaneously, were entirely reversible, and were demonstrated at pressures that occur spontaneously in the mammalian intestine. These studies demonstrate that luminal distention results in marked alterations in intestinal histology that promote increased access of luminal contents to intervillus transport sites in the intestine in vivo. The resulting alterations could lead to an increase in functional rather than absolute absorptive surface area.

Examination of a competitive enzyme-linked immunoassay (CELIA) technique and a laser nephelometric immunoassay technique for the measurement of apolipoprotein B

A competitive enzyme-linked immunoassay (CELIA) technique for quantitative measurement of apolipoprotein B (Apo B) was developed. The method is a non-isotopic immunoassay that utilizes a soluble enzyme/antibody complex as a universal labeling reagent. The method was characterized according to precision, sensitivity, recovery and parallelism. The CELIA Apo B method was compared to a commercially available laser nephelometric immunoassay. We found that the nephelometric results were highly correlated with triglyceride levels and the nephelometric assay was susceptible to interference from lipemia or turbidity. The range of values obtained on 56 apparently healthy, fasting young adults was 0.35-1.25 g/l by the CELIA method and 0.40-1.00 g/l by the nephelometric immunoassay. The nephelometric method was more precise (coefficient of variation 5%) than the CELIA technique (CV 10%); however, the CELIA method seems to be less sensitive to interferences.

APOLIPOPROTEIN B (APO B) IN VEIN GRAFT ATHEROSCLEROSIS An Immunoperoxidase Study

An immunoperoxidase procedure was used to localize the apolipoprotein B in the atherosclerotic lesions of vein grafts removed 5 years after an aortocoronary bypass operation and preserved by embedding in paraffin. Apolipoprotein B was mainly found at the cell-rich interface of the lesion proper and the underlying fibrous tissue. The findings of this study indicate that the immunoperoxidase procedure can be used to investigate the localization of immunoactive components in paraffin-embedded tissue sections.