In order to develop a comprehensive model of the motor control system the time-varying nature of joint dynamics must be addressed. However, it has not previously been possible to quantitatively observe changes in joint dynamics during a transition of state. In this work, a recently developed method for identification of linear time-varying dynamic systems from ensemble data has been used to obtain models of neuromuscular dynamics during a rapid contraction. The method, based on singular value decomposition, provides a series of nonparametric (impulse response function) models of a system's dynamics without a priori knowledge of its dynamic structure or time-variation, thus enabling study of the neuromuscular system during natural activity. / Application of this method to simulated and experimental data has shown it to be robust and accurate. Ankle dynamics have been tracked during voluntary isometric contraction of triceps surae, revealing behaviour more complex than second-order, characterized by a decrease in the joint's resistance to low frequency perturbations.

Heparan sulfate proteoglycan (HSPG) was isolated from the mouse Engelbreth-Holm-Swarm (EHS) tumor. Polyclonal antibodies against the isolated HSPG were raised by two separate techniques, both producing highly reactive antisera. The antisera were found to be reactive against epithelial basement membrane of the mouse foot pad, glomerular basement membrane of the kidney and the EHS tumor matrix using the techniques of light microscopic immunoperoxidase on frozen sections and electron microscopic immunogold labelling on ultrathin Lowicryl K4M sections. At high magnification of the EHS tumor matrix, the gold particles were found over 5 nm wide sets of parallel lines, referred to as "double tracks" (Inoue et al., 1989). When HSPG was incubated in 50 mM Tris buffer, pH 7.4, at 35$ sp circ$C for either 5 min or 1 hr, a precipitate resulted which was made up of 5-6 nm wide sets of parallel lines, similar to double track structures. Together these studies demonstrate that HSPG of the EHS tumor matrix is made up of double track structures, and that in vitro incubation of HSPG produces double track structures in as short a time as 5 min.

The basis of this study was to explore the potential of ultrasonic tissue characterization to accurately detect and reliably quantify the acoustic properties of lingual tissues. The purpose of the work was to establish the fundamental procedures and methodological standards for application of ultrasound characterization to study the human tongue, and to quantify, for the first time, the attenuation, velocity, and backscatter attributes of lingual tissues supported by histologic evidence. Three regions of the intrinsic musculature were sampled. Features of tissue composition, muscle fiber orientation, and macrostructural complexity were defined. The acoustic properties from these regions represented a muscular organ with ultrasonic parameters that differed from the published literature for striated musculature. Further, significant acoustic variations were noted within the intrinsic lingual musculature. / Backscatter coefficients predicted the presence of connective tissues, fat and muscle. This acoustic finding was confirmed through histologic image analysis. The concentrations of tissues varied across sample regions. Muscle fiber orientation, fat deposits, and differences in collagen and elastic fiber content supported the postulate that the size of backscatter is affected by the principal cell size and the structural organization of the tissue. The in vitro results are first steps toward a true representation of the acoustic properties of living lingual tissue. The roles of these tissues in muscle mechanics, applications to medical practice in the detection of disease states, and future areas for research are discussed.

Three proteins of stripped rough microsomes (SRM) from dog pancreas or rat liver, with apparent molecular weights of 35, 56 and 90 kDa (pgp35, pp56, pp90), were phosphorylated in vitro by both ($ tau$-32P) GTP and ($ tau$-32P) ATP. Another SRM protein of 15 kDa (pp15) was phosphorylated in vitro only by ($ tau$-32P) GTP. Comparison of the in vitro phosphorylation profile of SRM to those of other well defined subcellular fractions, i.e., plasma membranes, Golgi apparatus, lysosomes, endosomes, mitochondria and smooth microsomes, showed the four major GTP phosphorylated proteins were restricted to the endoplasmic reticulum (ER). Further characterization of these proteins showed them to be phosphorylated on serine residues at the cis face of SRM and to be integral membrane proteins. The 35 kDa protein was glycosylated, with 2 N-linked oligosaccharide sidechains, therefore possessing a luminal domain. Competition and inhibition studies showed that GTP and ATP phosphorylation of the proteins were distinct. Regulation of GTP specific phosphorylation was by adenosine nucleoside. Purification of the 35 and 90 kDa phosphoproteins was achieved, along with another nonphosphorylated glycoprotein of 25 kDa, as a phosphoglycoprotein complex which elutes from Sephacryl S300 chromatography at an apparent molecular weight of about 400,000. Partial Sequence Receptor (Weidmann et al, (1987) Nature 328: 830-833), suggesting that this phosphoglycoprotein complex may form part of the translocation apparatus of the rough ER. These results suggest a role for phosphorylation of ER membrane proteins in the process of translocation.

The association of endothelial and smooth muscle cells to elastic laminae in the developing mouse aortic wall was investigated by electron microscopy and immunohistochemistry. Early in development, bundles of contractile filaments traverse the long axis of the cell obliquely to anchor in membrane-associated dense plaques on either side. From these sites, microfibrils extend in the same direction to link the cell to the adjacent elastic laminae. The microfibrils become infiltrated with elastin to form elastin extensions, which together with the intracellular contractile filaments bundles, forms a "contractile-elastic unit". The ordered arrangement of contractile-elastic units revealed in the adult vessel provides a mechanism for the transmission of tension throughout the vessel wall. During development, endothelial cells are similarly connected to the subjacent elastic lamina by filamentous structures. These "endothelial cell connecting filaments" show morphological feature similar to microfibrils. Immunolocalization of fibrillin, a constituent protein of microfibrils, to the connecting filaments provides further evidence for their microfibrillar nature. These results suggest that microfibrils may play an important role in cell anchorage and the maintenance of tissue integrity. A longterm radioautographic study was performed to provide quantitative data concerning the stability of aortic elastin. Results from this study demonstrate the remarkable longevity of elastin in the aortic wall and suggest that, like elastin, cell to elastic lamina connections remain stable throughout development and exist as functional structures in the adult vessel.

The zymogenic units, which characterize the epithelium in the body region of the mouse stomach, are composed of pit, isthmus, neck and base. Electron microscopy and $ sp3$H-thymidine radioautography have been used to study kinetics of the component cells and obtain an estimate of their life duration. / The isthmus includes four immature cell types: granule free cells which function as stem cells directly giving rise to two other immature cell types named pre-pit and pre-neck cells, while the fourth or pre-parietal cells come from the stem cells and its two descendants. / Pre-pit cells evolve into pit cells, which migrate along the pit while producing dense mucous granules and, in 3 days, reach the surface where they are phagocytosed or extruded to the lumen. Pre-parietal cells become the acid-producing parietal cells, which migrate from the isthmus; about 20% up the pit and the remaining 80%, to the neck. Parietal cells in either pit or base eventually degenerate, die and are phagocytosed or released either to the unit lumen or even into connective tissue spaces after an overall life of 67 days. Pre-neck cells become neck cells which descend along the neck in 40 days while producing cored mucous granules. They then become muco-zymogenic cells, which further transform into the pepsin-producing zymogenic cells. These, after a 256 day mean life, degenerate or are attacked by connective tissue macrophages.

The postnatal changes in the various epithelial cell types of the different regions of the epididymis at the level of electron microscope (EM), and the expression of various secretory proteins has not been well characterized in developing rats. In this context, Epon embedded epididymides at postnatal days 21, 39, 49, and 56 were examined under the light and electron microscope. Furthermore, expression of two secretory proteins, namely sulfated glycoprotein-2 and immobilin, well characterized in adult animals, were immunolocalized using paraffin sections at various postnatal ages i.e. 7, 15, 21, 28, 39, 49, and 56. The latter was performed to examine the influence of testicular products, such as Sertoli cell derived factors (androgen binding protein), luminal and circulating androgens, degenerating germ cells, and spermatozoa appearing at different postnatal ages, on the morphological differentiation of the epithelial cells and expression of these proteins by these cells. (Abstract shortened by UMI.)

<p> The Ordovician strata of the Lower Member of the Vinini Formation comprise a sequence of greenstone, sandstone, shale, and siltstone representing the prograding and retrograding of submarine fans along the continental margin. Although graptolites are normally preserved within shale beds in the Lower Member of the Vinini Formation, the greatest abundance of well preserved graptolites is found within the sandstone turbidite beds. These graptolites are uniquely preserved in full relief as opposed to being flattened on shale. It is interpreted based on fragmentation and species composition within the sandstone that the graptolites flourished in an upwelling zone on the continental margin and that as their remains accumulated on the underlying seafloor, were swept downslope in turbidity currents. </p><p> Graptolites were collected from 10 beds within the stratigraphic section and represent 33 taxa from 17 genera. There are no new taxa. All taxa are described, illustrated, and compared to other collections.</p>

<p> The Sapeomithidae are a unique and poorly understood clade of Early Cretaceous birds from the Jehol Group of Liaoning Province, China. Four species of sapeomithids are known: <i>Sapeornis chaoyangensis, Didactylornis jii, Sapeornis angus tis</i>, and <i>Shenshiornis primita</i>. <i>Omnivoropteryx sinousaorum</i> is allied with sapeomithids, although its nomenclature remains a source of contention. The validity of these taxa is challenged via an in-depth anatomical revision and morphometric analyses involving 18 specimens of sapeomithids, including the aforementioned holotypes. The results reveal that the only anatomical difference separating each species is size, implying a growth series trend among the specimens. This provides clear evidence that these species are junior synonyms of <i>Sapeornis chaoyangensis</i>. In addition, critical anatomical descriptions previously unknown for these specimens expand our knowledge of this clade, paving the way for future anatomical and phylogenetic studies of this enigmatic avian taxon.</p>

The lysosomal protective protein/cathepsin A (PPCA) forms a multi-enzyme complex with beta-galactosidase and alpha-neuraminidase. Histological examination of the testis and epididymis of PPCA-/- mice from 2--10 months of age revealed cell- and region-specific abnormalities compared to their wild type counterparts. The testis showed a significant decrease in the diameter of seminiferous tubules, a significant increase in the size and number of interstitial space macrophages that became filled with pale lysosomes, and Leydig cells that showed an accumulation of pale lysosomes. The epithelial cells of the caput and corpus regions of the epididymis were highly vacuolated, containing numerous pale lysosomes, with some cells appearing to undergo degeneration. Halo cells of the entire epididymal epithelium were also highly engorged with pale lysosomes, and in the intertubular space large vacuolated macrophages were prominent. Taken together, the adverse effects on the testis and epididymis suggest that sperm in the lumen may be reduced in numbers and not acquire their full maturational state, accounting for reduced pregnancies noted in PPCA-/- mice.