Browsing by Author "Wilkens, Jerrel L."

Now showing 1 - 13 of 13
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    Electrophysiology of neurosecretory cells of the fleshfly: Sarcophage bullata
    (1975) Bruce, Iain Charles; Wilkens, Jerrel L.
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    Histological organization of the intestine in the crayfish Procambarus clarkii
    (Blackwell Publishing, 2004-04) To, Terence H.; Brenner, Tracy L.; Cavey, Michael J.; Wilkens, Jerrel L.; Biological Sciences; Faculty of Science; University of Calgary
    Six longitudinal ridges span the length of the intestine in the crayfish Procambarus clarkii . A simple columnar epithelium with tetralaminar cuticle lines the lumen. Folds of the epithelium overlie a dense irregular connective tissue packed with mixed acinar (alveolar) glands. Mucous secretions are probably involved with formation and lubrication of faecal strings; neither the nature nor the role of the serous secretions is immediately apparent. Aggregations of cells with large cytoplasmic vacuoles, called bladder cells, appear in the subepithelial connective tissue near the tops of the intestinal ridges. The bladder cells are suitably positioned to bolster the integrity of the ridges. Striated muscle of the intestine occurs in inner longitudinal and outer circular layers. The inner longitudinal layer consists of six strips, with one strip associated with the base of each intestinal ridge. The outer circular layer is essentially complete, but there are periodic apertures in this layer on the left and right sides of the intestine, providing nerves and haemolymph vessels with access to the interior of the gut. Based on histological features, and consistent with reports on other crayfish, we conclude that the intestine of P. clarkii has a proctodeal (ectodermal) origin.
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    Microscopic anatomy of the thin-walled vessels leaving the heart of the lobster Homarus americanus: anterior lateral arteries
    (Blackwell Publishing, Inc., 2006) Cavey, Michael J.; Chan, Kincaid S.; Wilkens, Jerrel L.; Biological Sciences; Faculty of Science; University of Calgary
    The anterior lateral arteries are paired vessels leaving the anterior end of the lobster (Homarus americanus) heart and proceeding to the antennae and eyestalks, the stomach and hepatopancreas, the gonads, and the thoracic and branchial muscles. These vessels have a trilaminar organization, consisting of a tunica interna with elastic fibrils, a tunica intermedia represented by a bilayered cell mass, and a tunica externa with collagen fibrils. In the tunica intermedia, cells flanking the tunica interna (light cells) show less affinity for basic dyes and electron stains than those flanking the tunica externa (dark cells). Each light cell exhibits an irregularly shaped stress fiber (a bundle of closely packed microfilaments) in the region adjoining the tunica interna. Collectively, these bundles have a circumferential or slightly oblique orientation relative to the lumen of the vessel. The role of the stress fibers is unresolved. If they are static structures, they might contribute to the non-linear elasticity shown by lobster arteries. If they generate force, and small bundles of microfilaments do diverge from the stress fibers to enter filamentous mats applied to the plasmalemmata, a coordinated contraction of the cells might reduce the luminal diameter and, thus, retard the flow of hemolymph. Coordination of contraction would have to occur in the absence of nerves and without the benefit of communicating (gap) junctions between the light and dark cells.
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    Muscle physiology and ecology of the Brachiopod Terbratalia transversa
    (1979) Eshleman, William Phillip; Wilkens, Jerrel L.
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    Neural and horomonal control of gill ventilation in the shore crab, Carcinus maenas
    (1983) Mercier, Alfred Joffre; Wilkens, Jerrel L.
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    Ornate Setae on the Branchial Flabella ("Grill Rakers") of the Green Shore Crab Carcinus maenas (Crustacea: Decapoda)
    (Blackwell Publishing, 1992) Cavey, Michael J.; Modi, Eech; Wilkens, Jerrel L.; Biological Sciences; Faculty of Science; University of Calgary
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    The Role of suspensory ligaments in modifying cardiac output in crustaceans
    (1988) Volk, Emily Lisa; Wilkens, Jerrel L.
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    VASCULAR PERIPHERAL RESISTANCE AND COMPLIANCE IN THE LOBSTER HOMARUS AMERICANUS
    (Blackwell Publishing, Inc., 1996-10-24) Cavey, Michael J.; Wilkens, Jerrel L.; Davidson, Glen W.; Biological Sciences; Faculty of Science; University of Calgary
    The peripheral resistance to flow through each arterial bed (in actuality, the entire pathway from the heart back to the pericardial sinus) and the mechanical properties of the seven arteries leaving the lobster heart are measured and compared. Resistance is inversely proportional to artery radius and, for each pathway, the resistance falls non-linearly as flow rate increases. The resistance of the hepatic arterial system is lower than that predicted on the basis of its radius. Body-part posture and movement may affect the resistance to perfusion of that region. The total vascular resistance placed on the heart when each artery is perfused at a rate typical of in vivo flow rates is approximately 1.93 kPa s ml−1. All vessels exhibit adluminal layers of fibrils and are relatively compliant at pressures at or below heart systolic pressure. Arteries become stiffer at pressures greater than peak systolic pressure and at radii greater than twice the unpressurized radius. The dorsal abdominal artery possesses striated muscle in the lateral walls. This artery remains compliant over the entire range of hemolymph pressures expected in lobsters. These trends are illustrated when the incremental modulus of elasticity is compared among arteries. All arteries should function as Windkessels to damp the pulsatile pressures and flows generated by the heart. The dorsal abdominal artery may also actively regulate its flow.