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2.
The isolation of spirochaetes from the rat caecum 总被引:1,自引:1,他引:0
Spirochaetes indigenous to the conventional rat caecum were cultivated on agar medium using selective isolation techniques. The 27 axenic isolates represented four morphological types of spirochaetes differing in cell size, cell coiling pattern and number of protoplasmic flagella. 相似文献
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A COMPARISON OF FEEDING MECHANISMS IN MICROPHAGOUS, HERBIVOROUS, INTERTIDAL, PROSOBRANCHS IN RELATION TO RESOURCE PARTITIONING 总被引:2,自引:0,他引:2
HAWKINS S. J.; WATSON D. C.; HILL A. S.; HARDING S. P.; KYRIAKIDES M. A.; HUTCHINSON S.; NORTON T. A. 《Journal of Molluscan Studies》1989,55(2):151-165
Several microphagous grazers co-exist on British rocky shores.The nature of the microbial film which is their prime food sourceis outlined. The radula morphology, hardness, and feeding mechanismsof rhipidoglossan trochids (Gibbula, Monodonta) taenioglossanLittorina, and docoglossan Patella have been compared. Docoglossanscan penetrate hard substrates deeply, taenioglossans can onlypenetrate softer substrates, and rhipidoglossans appear to primarilybrush the surface. A preliminary study found some differencesin diet. Whether feeding mechanisms allow partitioning of themicrofloral film and whether this allows continuing co-existenceof intertidal grazers is discussed. 相似文献
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DAVID P. FOX BRUCE F. HILL DONALD M. SPOON GEORGE B. CHAPMAN 《The Journal of eukaryotic microbiology》1988,35(1):4-12
ABSTRACT. A sessile, tentacle-bearing protozoon, Heliophrya sp. (Suctoria, Ciliata), reproduces asexually by evaginative budding to form a ciliated swarmer, which begins metamorphosis to the adult form within 30 min of its release from the parent cell. Morphological features of embryogenesis were investigated using transmission and scanning electron microscopy and found to correspond, with certain exceptions, to the few previous reports concerning evaginative budding in suctorians. Following invagination of a portion of the pellicle to form an embryonic cavity within the parent cell, numerous kinetosomes, apparently formed de novo, organize into rows which surround the embryonic cavity and eventually develop cilia that project into the cavity. When the cavity is complete, its walls are extruded through an opening in the parent cell surface. Parent cell cytoplasm streams into the incipient swarmer, thus supplying it with at least the minimum requirement of all cytoplasmic organelles. The ciliated swarmer remains attached to its parent cell for several minutes before it detaches. A complete pellicle is formed in both parent and swarmer prior to detachment. The numerous mitochondria underlying the parent cell pellicle in the vicinity of the attachment area suggest that cross wall formation is an energy-dependent process. 相似文献
7.
A revised infrageneric classification of Nothofagus (Fagaceae) 总被引:1,自引:0,他引:1
ROBERT S. HILL F.L.S JENNIFER READ 《Botanical journal of the Linnean Society. Linnean Society of London》1991,105(1):37-72
HILL, R. S. & READ, J., 1991. A revised infrageneric classification of Nothofagus (Fagaceae). An examination of cupule morphology, leaf architecture and cuticular morphology of Nothofagus species demonstrates that the existing infrageneric classifications are inaccurate. Four subgenera are proposed, based on these characteristics as well as other morphological information. This analysis indicates that the traditional pollen groupings of Nothofagus closely reflect the infrageneric taxonomy. It is hypothesized that deciduousness is primitive in Nothofagus , and the evergreen habit has arisen more than once, and therefore the deciduous or evergreen habit is invalid as a primary taxonomic character. 相似文献
8.
Trimethyloxonium modification of single batrachotoxin-activated sodium channels in planar bilayers. Changes in unit conductance and in block by saxitoxin and calcium 总被引:13,自引:9,他引:4
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Single batrachotoxin-activated sodium channels from rat brain were modified by trimethyloxonium (TMO) after incorporation in planar lipid bilayers. TMO modification eliminated saxitoxin (STX) sensitivity, reduced the single channel conductance by 37%, and reduced calcium block of inward sodium currents. These effects always occurred concomitantly, in an all-or-none fashion. Calcium and STX protected sodium channels from TMO modification with potencies similar to their affinities for block. Calcium inhibited STX binding to rat brain membrane vesicles and relieved toxin block of channels in bilayers, apparently by competing with STX for the toxin binding site. These results suggest that toxins, permeant cations, and blocking cations can interact with a common site on the sodium channel near the extracellular surface. It is likely that permeant cations transiently bind to this superficial site, as the first of several steps in passing inward through the channel. 相似文献
9.
ABSTRACT. Since May 1979, 190 rodents in the family Sciuridae, representing three genera and nine species, have been collected in the western United States and northern Mexico and examined for coccidia; 71 (37%) had coccidian oocysts in their feces. These included 2 of 12 (17%) Eutamias canipes; 7 of 12 (58%) E. dorsalis; 18 of 50 (36%) E. merriami; 33 of 96 (34%) E. obscurus; 3 of 4 (75%) E. townsendii; 3 of 9 (33%) Sciurus aberti; 1 of 1 S. griseus; 1 of 1 Tamiasciurus hudsonicus mogollonensis; and 3 of 5 (60%) T. mearnsi. The following coccidians were identified from infected rodents: Eimeria cochisensis n. sp. and Eimeria dorsalis n. sp. from E. canipes; E. cochisensis, E. dorsalis, and E. tamiasciuri from E. dorsalis; E. dorsalis and E. tamiasciuri from E. merriami; E. cochisensis, E. dorsalis, E. tamiasciuri, and E. wisconsinensis from E. obscurus; E. cochisensis and E. dorsalis from E. townsendii; E. ontarioensis and E. tamiasciuri from S. aberti; E. tamiasciuri from S. griseus; E. tamiasciuri and E. toddi from T. h. mogollonensis; and E. tamiasciuri from T. mearnsi. Sporulated oocysts of Eimeria dorsalis n. sp. were ovoid, 21.9 × 16.8 (17–24 × 14–20) μm with sporocysts ovoid, 11.5 × 6.9 (10–14 × 6–8) μm. Sporulated oocysts of Eimeria cochisensis n. sp. were spheroid to subspheroid, 16.7 × 15.3 (15–18 × 14–17) μm, with sporocysts ovoid, 8.4 × 5.6 (6–11 × 4–7) μm. Fifty-five of 71 (77%) infected hosts had oocysts of only one eimerian species in their feces at the time they were examined. One eimerian, E. tamiasciuri, was found in seven of nine host species in three genera. A list is provided of all eimerians (22, including the species described here) that have been described in the literature from Eutamias, Sciurus, and Tamiasciurus spp. 相似文献
10.
The effect of spring temperature on first egg date, laying period and last clutch date was studied in the Mallard and Tufted Duck. Seasonal clutch size and egg size trends were also examined. In years When Mallard laid early, Tufted Duck also did so. The first Mallard clutch was started earlier and laying period was longer in years with a high mean February temperature. The last clutch was started later in years with a high mean June temperature. In Tufted Duck the laying period increased and the last clutch was started later in years with high mean April temperatures.
Mean hatching date of Mallard clutches was later in years when the date of peak chironomid emergence was late.
In both species, clutch size declined through the season. Egg volume was not related to clutch size in either species, but egg volume in the Tufted Duck declined through the season. No difference in Tufted Duck egg size existed between sites, but the significance of egg size on duckling survival is discussed. Genetic factors related to individual consistency in egg size in Mallard may have obscured egg volume trends during the season because of renesting. 相似文献
Mean hatching date of Mallard clutches was later in years when the date of peak chironomid emergence was late.
In both species, clutch size declined through the season. Egg volume was not related to clutch size in either species, but egg volume in the Tufted Duck declined through the season. No difference in Tufted Duck egg size existed between sites, but the significance of egg size on duckling survival is discussed. Genetic factors related to individual consistency in egg size in Mallard may have obscured egg volume trends during the season because of renesting. 相似文献