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Cell size of mammalian myocardia is not related to physiological demand (1991)

Hamilton, N. ; Ashton, M. L. ; Ianuzzo, C. D.

Springer

Cellular and molecular life sciences 47 (1991), S. 1070-1072

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ISSN: 1420-9071

Keywords: Cell size ; cross sectional area ; myofibril ; mitochondria ; morphology

Source: Springer Online Journal Archives 1860-2000

Topics: Biology , Medicine

Notes: Abstract Morphological characteristics of myocardial ventricular myocytes have been evaluated from 5 mammalian orders with resting heart rates ranging from 51 to 475 bpm. The purpose was to determine if morphological characteristics of the myocardia are related to the functional demand imposed on the cell as represented by the resting heart rate. Cell size is a constant among mammals of different sizes which have different physiological demands. In contrast, there is more mitochondrial area and less myofibrillar area per cell in animals with rapidly beating hearts than in animals with slower heart rates. Additionally, the mean cross sectional area of individual myofibrils is 30% larger in the cow as compared to the mouse. These findings combined with our previous studies indicate that the different functional requirements of myocardia from different mammalian orders are satisfied by intracellular adaptations of both a structural and biochemical nature.

Type of Medium: Electronic Resource

URL: http://dx.doi.org/10.1007/BF01923345

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Synaptonemal complexes of normal and mutant yeast chromosomes (Saccharomyces cerevisiae) (1985)

Moens, P. B. ; Ashton, M. L.

Springer

Chromosoma 91 (1985), S. 113-120

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ISSN: 1432-0886

Source: Springer Online Journal Archives 1860-2000

Topics: Biology , Medicine

Notes: Abstract Synaptonemal complex (SC) analysis of six laboratory yeast strains showed the SC karyotypes to be repeatable within strains. Chromosomal differences were found between strains. In five of the strains, two SCs insert into the nucleolus. This represents a single bivalent with a nucleolar organizer in a medial position as is suggested by genetic data or two bivalents each with a terminal nucleolar organizer. In the first interpretation, n=16; in the second, n=17. Strain Tris has a single nucleolar SC and n=17. In strains DCx374, DCx416 and x 8366a the genetically determined rearrangements of linkage group III could not be identified. Presumably the short SC (0.33 μm) associated with linkage group III cannot accommodate an inversion loop or a translocation configuration. The strains however were found to harbour a reciprocal translocation involving the nucleolar chromosome. Trisomy for one of the longer chromosomes was observed in Tris and spo10. It is concluded that rearrangements of the medium and long but not short yeast chromosomes can be detected cytologically. — Measurements of nuclear volumes show SC length to vary with artifactually induced swelling of the nucleus. Linear regression of SC length over nuclear radius indicates that actual SC length is only about one-half the observed length. As a result the DNA packing per SC unit length is higher then previously estimated.

Type of Medium: Electronic Resource

URL: http://dx.doi.org/10.1007/BF00294054

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Neurosecretory centers from the eyestalk of Siriella armata M. Edw. (Crustacea: Mysidacea): ultrastructural variations during normal and experimentally inhibited molt cycle (1988)

Cuzin-Roudy, J. ; Ashton, M. L. ; Saleuddin, A. S. M.

Springer

Cell & tissue research 254 (1988), S. 381-391

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ISSN: 1432-0878

Keywords: X-organ ; Sinus gland ; Ultrastructure ; Cyclic activity ; Siriella armata (Crustacea)

Source: Springer Online Journal Archives 1860-2000

Topics: Biology , Medicine

Notes: Summary The ultrastructure of the medulla interna-medulla externa X-organ (MI-ME Xo)-sinus gland (SG) complex in the eyestalk of Siriella armata is described during the normal and the experimentally inhibited molt cycle. In the normal SG, four types of neurosecretory axon terminals, each containing distinguishable neurosecretory granules, can be described. Thus, type-2 granules are synthesized by G1 neurons forming the MI-ME Xo. The cell bodies and axonal endings of these cells in the sinus gland have been examined at the following molt stages: intermolt (stage C4), premolt (D0 and D2), and postmolt (A1, A2 and B). Changes in ultrastructure of the G1 cells have been monitored and correlated to inhibitions of the molt-and reproductive cycle produced by electrocauterization of the MI-ME Xo. The results obtained suggest that the neurosecretion from the G1 cells exerts a positive influence on molt and brood preparation. The occurrence of a distal group of G1 cells whose axons terminate at a different site from the SG suggests that the neural factors of the MI-ME Xo are diverse and control different physiological activities.

Type of Medium: Electronic Resource

URL: http://dx.doi.org/10.1007/BF00225810

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