One-bag-fiber muscle spindles in tenuissimus muscles of the cat

Over 150 complete and 139 incomplete single muscle spindles were examined in serial transverse sections of cat tenuissimus muscles in search for spindles lacking one of the two types of nuclear bag intrafusal fiber. Several histochemical reactions were used to type the intrafusal muscle fibers and assess the spindle motor and sensory innervation. One complete spindle lacked a bag1 fiber, and another spindle lacked a bag2 fiber. Several incomplete spindles also lacked bag1 fibers. In addition, ten double tandem spindles contained one capsular unit each that lacked the bag1 fiber, and one triple tandem spindle had two such capsules. All one-bag-fiber spindles had primary sensory innervation, but none had secondary sensory innervation. Their motor innervation was similar to that of the usual two-bag-fiber spindles in the number and disposition of intrafusal motor endings. It is unclear whether the one-bag fiber spindles, either single or tandem-linked, are products of an aberrant spindle development or represent a true anatomical and functional subcategory of the cat muscle spindle.     

The topography of long nuclear chain intrafusal fibers in the cat muscle spindle

Muscle spindles were studied histochemically in serial transverse sections of specimens of the cat tenuissimus muscle. The nuclear chain intrafusal muscle fibers were separated into three subtypes, called long, intermediate and typical. The long chain and intermediate chain fibers tended to assume a particular position within the axial bundle of intrafusal fibers. The fibers were usually located in that layer of chain fibers that was positioned farthest away from the bag2 fiber. Furthermore, they were usually situated adjacent to the bag1 fiber throughout much of the extent of the spindle pole. Some long chain and intermediate chain fibers had several fiber nuclei abreast at the equator rather than a single row of central nuclei, as in most nuclear chain fibers. The relative position of intrafusal fibers within the cat spindle may reflect their order of formation during development, with the fibers retaining, to a variable degree, their association with the bag2 fiber which acted as template. Thus, the axial position of long chain and intermediate chain fibers suggests that they are among the first nuclear chain fibers to form. This may play a role in the known preferential innervation of these chain fibers by skeleto-fusimotor axons.     

Gradual morphological evolution in a late cretaceous deep‐sea benthic foraminiferan,Parkiella

This study presents a detailed, quantitative account of morphological evolution in the deep‐sea benthic foraminifer Parkiella through the last 10 million years of the Cretaceous (late Campanian to Maastrichtian). Cores taken at DSDP Sites 465 and 171, in the low‐latitude central Pacific, yielded a total of 437 specimens, from 53 samples. The shape of the apical outline of the foraminifer, its chamber arrangement, shell globularity, shell area and proloculus diameter were quantified. Significant, unidirectional changes in shell morphology were observed between sampling levels, indicating that the lineage was not in a state of morphological stasis. The occurrence of morphologically intermediate paleopopulations and the generally normal distribution of morphotypes at any given sampling level suggest that the observed pattern of evolution represents an anagenetic trend in a single, non‐branching lineage. These results confirm predictions of the plus ça change evolutionary model. Gradual evolution of this lineage may represent a reaction to changed oceanographic conditions that were established after the Maastrichtian deep‐water reversal.     

Innervation of regenerated spindles in muscle grafts of the rat

Features of the nerve supply and the encapsulated fibers of muscle spindles were assessed in grafted and normal extensor digitorum longus (EDL) muscles of rats by analysis of serial 10-microns frozen transverse sections stained for enzymes which delineated motor and sensory endings, oxidative capacity and muscle fiber type. The number of fibers was significantly more variable, and branched fibers were more frequently observed in regenerated spindles than in control spindles. Forty-eight percent of regenerated spindles received sensory innervation. Spindles reinnervated by afferents had a larger periaxial space than did spindles which were not reinnervated by afferents. Regenerated fibers innervated by afferents had small cross-sectional areas, equatorial regions with myofibrils restricted to the periphery of fibers, unpredictable patterns of nonuniform and nonreversible staining along the length of the fiber for 'myofibrillar' adenosine triphosphatase (mATPase) after acid and alkaline preincubation. In contrast, regenerated fibers devoid of sensory innervation resembled extrafusal fibers in that they usually exhibited myofibrils throughout the length of the fiber, no central aggregations of myonuclei, uniform staining for mATPase and a reversal of staining for mATPase after preincubation in an acid or alkaline medium. Approximately thirty percent of encapsulated fibers devoid of sensory innervation stained analogous to a type I extrafusal fiber, a pattern of staining never observed in intrafusal fibers of normal spindles. Groups of encapsulated fibers all exhibiting this pattern of staining reflect that either these fibers may have been innervated by collaterals of skeletomotor axons that originally innervated type I extrafusal fibers or that fibers innervated by only fusimotor neurons express patterns of staining for mATPase similar to extrafusal fibers in the absence of sensory innervation. Sensory innervation may also influence the reestablishment of multiple sites of motor endings on regenerated intrafusal fibers. Those regenerated fibers innervated by afferents had more motor endings than did regenerated fibers devoid of sensory innervation. Differences in size, morphology, and patterns of staining for mATPase and numbers of motor endings between fibers innervated by afferents and fibers devoid of sensory innervation reflect that afferents can influence the differentiation of muscle cells and the reestablishment of motor innervation other than during the late prenatal/early postnatal period when muscle spindles form and differentiate in rats.     

The electric conductance of seedling stems and the water content of spruce and pine seedlings in the course of desiccation

The dependence of electric conductance (admittance) of the stem on seedling water content (on the relative water content related to dry matter, or on the water saturation deficit, respectively) was followed in spruce and pine seedlings. The dependence was statistically highly significant and strong:r = 0.80 when individual plants were evaluated andr = 0.97 when mean values of twenty-seedlmg sets were taken into account. Electric conductance values can be used as a substitute) for water content determinations in plant tissues under defined conditions, although tho exact interpretation, especially of absolute values of those quantities with regard to their capacity component, remains to be offered.     

The properties of exo-1.4-alpha-D-glucosidase (E.C.3.2.1.3) covalently bound to mycelium

Summary The values of K_m, E_a, and K_i (for product inhibition) of glucoamylase covalently bound to the waste mycelium were determined as 7.9mM, 71.4 kJ/mol, and 3.2 M resp. using maltose as the substrate. The bound enzyme is not subject to diffusion limitation in the range of the concentration used.