A Model of the Peripheral Auditory System Responding to Low-Frequency Tones

A model of the peripheral auditory system responding to low-frequency tone stimulation is given. The model is of the type previously introduced by Weiss (1966). It includes three interconnected parts: a linear model of the ear's mechanical system, a model of the cochlear transducer, and a stochastic model of an auditory nerve fiber. The output of the model accurately mimics many characteristics of the output of some auditory nerve neurons responding to sinusoidal stimuli but is unable to successfully match all reported aspects of data obtained from other of these neurons. Characteristics of the model neurons are discussed.     

Surface Antigens of Smooth Brucellae

Surface antigens of smooth brucellae were extracted by ether-water, phenol-water, trichloroacetic acid, and saline and examined by immunoelectrophoresis and gel diffusion with antisera from infected and immunized rabbits. Ether-water extracts of Brucella melitensis contained a lipopolysaccharide protein component, which was specific for the surface of smooth brucellae and was correlated with the M agglutinogen of Wilson and Miles, a polysaccharide protein component devoid of lipid which was not restricted to the surface of smooth brucellae and was not correlated with the smooth agglutinogen (component 1), and several protein components which were associated with internal antigens of rough and smooth brucellae. Immunoelectrophoretic analysis of ether-water extracts of B. abortus revealed only two components, a lipopolysaccharide protein component, which was correlated with the A agglutinogen, and component 1. Component 1 from B. melitensis and B. abortus showed identity in gel diffusion tests, whereas component M from B. melitensis and component A from B. abortus showed partial identity with unabsorbed antisera and no cross-reactions with monospecific sera. Attempts to prepare monospecific sera directly by immunization of rabbits with cell walls or ether-water extracts were unsuccessful. Absorption of antisera with heavy fraction of ether-water extracts did not always result in monospecific sera. It was concluded (as has been described before) that the A and M antigens are present on a single antigenic complex, in different proportions depending upon the species and biotype, and that this component is a lipopolysaccharide protein complex of high molecular weight that diffuses poorly through agar gel. Components 1, A, and M were also demonstrated in trichloroacetic acid and phenol-water extracts. With all extracts, B. melitensis antigen showed greater diffusibility in agar than B. abortus antigens. After mild acid hydrolysis, B. abortus ether-water extract was able to diffuse more readily.     

Golgi apparatus mediated polysaccharide secretion by outer root cap cells of Zea mays

Summary In the outer cap cells of roots of Zea mays, secretion is accompanied by hypertrophy of dictyosome cisternae with formation of large secretory vesicles. Vesicle contents are subsequently released from the protoplast by fusion of the vesicle membrane with the plasma membrane. The secreted material, a highly hydrated polysaccharide, was localized intracellularly by the periodic acid-Schiff reaction. Under appropriate conditions, the product moves outward through the cell wall after discharge from the protoplast, and appears as a droplet adhering to the root tip. Under conditions where the secretory product accumulates at the inner wall surfaces, no external droplet is formed.The secretory activity has an active phase that is sensitive to metabolic inhibitors and influenced by temperature (Q₁₀>2), and a passive phase that is independent of temperature, insensitive to metabolic inhibitors but sensitive to osmotic agents. The active phase is characterized by a temperature-independent periodicity (3 hours). Sucrose supplied to the growth medium increases the amount of polysaccharide secreted. Polysaccharide synthesis, segregation into vesicles, and discharge from the protoplast are assumed to require active metabolism; the step involving extrusion of polysaccharide through the cell wall region appears to be a passive process influenced by the degree of hydration of the polysaccharide and by cell turgor.Purdue University Agricultural Experiment Station Journal Paper No. 2967; Charles F. Kettering Research Laboratory Contribution No. 261.     

EXTRUSION OF NUCLEOLI FROM PRONUCLEI OF THE RAT

Electron microscope observations of osmium tetroxide-fixed rat eggs indicate that small nucleoli are extruded from pronuclei in a sharply demarcated time period after sperm penetration. Approximately 4½ hours after sperm penetration, fine fibrous material aggregated in distinct loci along the inner surface of the nuclear envelope and condensed into small, dense bodies. The term tertiary nucleolus or extrusion body is used to designate the forming bodies. The small tertiary nucleoli form distinct protrusions from the pronuclei during the following developmental period and finally bud off into the cytoplasm, carrying with them a small portion of the double nuclear envelope. The extrusion bodies can be observed only in the vicinity of the pronuclei and have not been seen near the cell membrane. The fate of the tertiary nucleoli is not known; apparently they transform or disappear after they have passed into the cytoplasm. Eleven hours after sperm penetration, tertiary nucleoli are not present near the nuclear membrane and the extrusion activity has apparently ceased. Large and small nucleoli react similarly to cytochemical reagents: they are Feulgen negative; they are positive to the Millon, Sakaguchi, brom-phenol blue, and PAS reactions. Azure B stain combined with nuclease extraction indicates the presence of small amounts of RNA in the nucleoli.