Gizzard

alpha-Actinins, isolated from muscle and nonmuscle sources and labeled with various fluorescent dyes, were microinjected into living PtK2 cells during interphase to observe the reformation of stress fibers following cell division. Fluorescently labeled ovalbumin and bovine serum albumin were also injected as control proteins. alpha-Actinin was incorporated into stress fibers within 5 minutes after injection and remained present in the fibers for up to 11 days. The pattern of incorporation was the same regardless of whether the alpha-actinin was isolated from muscle or nonmuscle tissues or whether it was labeled with fluorescein, Lucifer Yellow, or rhodamine dyes. In contrast, neither labeled ovalbumin nor bovine serum albumin were incorporated into stress fibers. When the injected cells entered prophase, all stress fibers disassembled, resulting in a distribution of the fluorescent alpha-actinin throughout the cytoplasm. During cytokinesis, the fluorescent alpha-actinin was concentr...

To address some concerns about the expansion of genetically engineered pharmaceutical and industrial crops to outdoor plantings and potential impacts on the human food supply, we determined whether commercial agriculture seeds of maize or corn Zea mays L., barley Hordeum vulgare L., safflower Carthamus tinctorius L. and rice Oryza sativa L. are digested or pass viably through the digestive tract, or are transported externally, by captive mallard ducks Anas platyrhynchos L., ring-necked pheasants Phasianus colchicus L., red-winged blackbirds Agelaius phoeniceus (L.) and rock pigeons Columba livia Gmelin (with the exception of whole maize seeds which were too large to feed to the blackbirds). These crop seeds, whether free-fed or force-fed, did not pass through the digestive tract of these bird species. The birds nonetheless did retain viable seeds in the esophagus/crop and gizzard for several hours. For example, after foraging for 6 h, mallards had retained an average of 228 ± 112 barley seeds and pheasants 192 ± 78 in the esophagus/crop, and their germination rates were 93 and 50%, respectively. Birds externally transported seeds away from the feeding location, but in only four instances were seeds found attached to their muddy feet or legs and in no case to feathers. Risk of such crop seeds germinating, establishing and reproducing off site after transport by a bird (externally or internally) or movement of a carcass by a predator, will depend greatly on the crop and bird species, location, environmental conditions (including soil characteristics), timing, and seed condition.

In many localities, Canada geese (Branta canadensis) have habituated to urban settings and their populations are increasing. Reproductive inhibitors contained in synthetic grit could play a role in integrated Canada goose management. We describe and quantity the physical characteristics of natural grit collected from the gizzards of Canada geese from 4 regions of the United States. The average grit sample had a weight of 14.26 g, a volume of 2.45 ml, a grit-particle count of 1,419, and a soil weight of 6.85 g. The average grit particle measured 2.02 mm long and 1.52 mm wide, and had an area of 2.05 mm2 and a roundness rating of 1.25. Synthetic grit could be patterned after our findings to most likely be retained and utilized in the gizzards of Canada geese.

We have used fluorescent analogue cytochemistry, image intensification, and digital image processing to examine the redistribution of alpha-actinin and vinculin in living cultured African green monkey kidney (BSC-1) cells treated with the phorbol ester 12-O-tetradecanoylphorbol-13-acetate (TPA). Before treatment, microinjected alpha-actinin shows characteristic distribution along stress fibers and at adhesion plaques; vinculin is localized predominantly at adhesion plaques. Soon after the addition of TPA, highly dynamic membrane ruffles begin to form. These incorporate a large amount of alpha-actinin but little vinculin. Alpha-actinin is subsequently depleted, more or less uniformly, from stress fibers. Disrupted stress fibers often fragment into aggregates and move into the perinuclear region. Careful analyses of fluorescence intensity distribution indicate that alpha-actinin is depleted more rapidly from adhesion plaques than from stress fibers. Furthermore, the depletion of alpha...

Using electron microscopy and negative staining we have studied the effect of Ca2+ on the structure of synthetic filaments of chicken gizzard smooth muscle myosin under conditions applied by Frado and Craig (1989) for demonstration of the influence of Ca2+ on the structure of synthetic filaments of scallop striated muscle myosin. The results show that Ca2+ induces the transition of compact, ordered structure of filaments with a 14.5 nm axial repeat of the myosin heads close to the filament backbone (characteristic of the relaxing conditions) to a disordered structure with randomly arranged myosin heads together with subfragments-2 (S-2) seen at a distance of up to 50 nm from the filament backbone. This order/disorder transition is much more pronounced in filaments formed of unphosphorylated myosin, since a substantial fraction of phosphorylated filaments in the relaxing solution is already disordered due to phosphorylation. Under rigor conditions some of the filaments of unphosphory...