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1.
2.
Indirect evidence suggests that legumes can adjust rapidly theresistance of their root nodules to O2 diffusion. Here we describeexperiments using O2 specific micro-electrodes and dark fieldmicroscopy to study directly the operation of this diffusionbarrier. The O2 concentration sensed by the electrode decreasedsharply in the region of the inner cortex and was less than1.0 mmol m3 throughout the infected tissue in nodulesof both pea (Pisum sativum) and french bean (Phaseolus vulgaris).In a number of experiments the ambient O2 concentration wasincreased to 40% while the electrode tip was just inside theinner cortex. In 13 out of 21 cases the O2 concentration atthis position either remained low and unchanged or increasedirreversibly to near ambient values. In the remaining casesthe O2 concentration increased after 1 to 2.5 min and then decreasedto its former value. These results are ascribed to an increasein resistance of the barrier in response to increased O2 fluxinto the nodule. It was shown microscopically that air spacesboth at the boundary between the infected zone and the innercortex, and within the infected zone started to disappear 3min after nodules were exposed to high ambient O2 concentrationsand had disappeared completely after 8 min. These spaces werenot changed by exposure of the nodule for 10 min to either N2or air. Key words: Oxygen, root nodules, air spaces 相似文献
3.
Evolution of the 28S ribosomal RNA gene in anurans: regions of variability and their phylogenetic implications 总被引:1,自引:0,他引:1
Fifteen restriction sites were mapped to the 28S ribosomal RNA gene of
individuals representing 54 species of frogs, two species of salamanders, a
caecilian, and a lungfish. Eight of these sites were present in all species
examined, and two were found in all but one species. Alignment of these
conserved restriction sites revealed, among anuran 28S rRNA genes, five
regions of major length variation that correspond to four of 12 previously
identified divergent domains of this gene. One of the divergent domains
(DD8) consists of two regions of length variation separated by a short
segment that is conserved at least throughout tetrapods. Most of the
insertions, deletions, and restriction-site variations identified in the
28S gene will require sequence-level analysis for a detailed reconstruction
of their history. However, an insertion in DD9 that is coextensive with
frogs in the suborder Neobatrachia, a BstEII site that is limited to
representatives of two leptodactylid subfamilies, and a deletion in DD10
that is found only in three ranoid genera are probably synapomorphies.
相似文献
4.
Summary Innervation of the ascidian branchial basket and other structures is demonstrated by staining for cholinesterase. Cholinesterase activity is not restricted to synaptic sites but is present throughout the neurons. Primary and secondary axonal bundles form a bilaterally symmetric innervation pattern around the large dorsal visceral nerve. These bundles continue to split into progressively smaller bundles as they course throughout the basket. Axons are suspended in a fibrous matrix and run within the blood sinuses on the atrial side of the basket. Stigmatal ciliated cells of the branchial basket are innervated by highly branched distal portions of neurons, whose cell bodies are located in the ganglion. Synaptic boutons, containing electron-lucent vesicles, are found at nearly all stigmatal ciliated cells. NiCl2backfills of the visceral nerve reveal a distinct population of central neurons, some of which presumably control ciliary arrest. 相似文献
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6.
A simplified technique of laparoscopy was developed for ovarian observation in the riverine buffalo, through a right paralumbar incision. The technique differed from previously described ones in that it involved only a single puncture and required no abdominal insufflation. A Hopkins 0 degrees forward viewing endoscope (5.5 mm x 500 mm) in combination with an endoscope sheath having a built-in instrument channel, and a long flexible forceps (630 mm) were used. Of the 23 observation attempts on 13 buffalo, 21 successful observations were conducted. Laparoscopies were performed using a combination of Xylazine, local infiltration and epidural anesthesia in a standing position. Six repeated observations were made within a 21-day period on 1 buffalo, with no postoperative complications. Observation of both left and right ovaries was possible through the same puncture. The technique was useful in buffalo to confirm ovarian structures which could not be determined with certainty through palpation per rectum. Our results suggest that the single puncture laparoscopy technique can be safely used for repeated ovarian examination in the water buffalo. 相似文献
7.
Rice seedlings accumulate stainable amounts of the 104 and 90 kDa polypeptides in response to high temperature stress. We have purified and raised highly specific polyclonal antisera against both of these polypeptides. In western blotting experiments, we find that these proteins are accumulated to different extents in rice seedlings subjected to salinity (NaCl), water stress, low-temperature stress and exogenous abscisic acid application. These proteins also accumulated when rice seedlings grown in pots under natural conditions were subjected to water stress by withholding watering. Seedlings of Triticum aestivum, Sorghum bicolor, Pisum sativum, Zea mays, Brassica juncea and mycelium of Neurospora crassa showed accumulation of the immunological homologues of both the 104 and the 90 kDa polypeptides, in response to high-temperature stress. We have earlier shown that shoots of rice seedlings exposed to heat shock accumulate a 110 kDa polypeptide which is an immunological homologue of the yeast HSP 104 (Singla and Grover, Plant Mol Biol 22: 1177–1180, 1993). Employing anti-rice HSP 104 antibodies and anti-yeast HSP 104 antibodies together, we provide evidence that rice HSP 104 is different from the earlier characterized rice HSP 110. 相似文献
8.
Dr. C. L. Singla 《Cell and tissue research》1978,188(2):317-327
Aglantha digitale swims in two ways: a slow rhythmical swim typical of hydromedusae in general and a sudden rapid movement that appears to be an escape response. The swimming musculature is an extremely well developed striated circular muscle layer that possesses a sarcoplasmic reticulum. The nervous system of this species can be divided into three units: an inner nerve ring and an outer nerve ring, which are joined by unusually large transmesogleal pathways, a group of giant axons that extends over the surface of the swimming muscle, and the radial canal. Well developed ciliated sensory cells are located on the exumbrellar surface of the margin. Consideration of these properties of the organisation of this species suggests that normal slow swimming is controlled by a mechanism similar to that found in other medusae, while the escape response is the result of the action of the giant axons. 相似文献
9.
Water buffalo (Murrah) oocytes were collected from ovaries obtained from a local slaughterhouse. They were classified according to the character of the cumulus cells under a stereomicroscope and then cultured in 25 mM Hepes buffered tissue culture medium-199 (TCM-199) supplemented with 5% estrous water buffalo serum in an atmosphere containing 5% CO(2) in air at 39 degrees C. After 20 to 24 hours of in vitro maturation, the oocytes were cultured at 38.5 degrees C in TCM-199 supplemented with 1% estrous water buffalo serum and in an atmosphere containing 5% CO(2) in air. Oocytes with compact and dense cumulus cells cleaved significantly further (P<0.01, 67.3%, 33 49 ) than those with fair, partially denuded oocytes with thin cumulus layers (27.5%, 25 91 ) or small remnants of cumulus cells and poor naked oocytes (3 100 ). A substantial variation in fertilization and developmental rates (16.0 to 43.8%) was observed among 4 different bulls. Late morulae were transferred nonsurgically into 14 buffalo recipients on Day 6 or 7 of their estrous cycle. One recipient was diagnosed to be pregnant by palpation per rectum on Day 60 and delivered a calf in October 1991. 相似文献
10.