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121.
Kou Kubota 《Biochemical and biophysical research communications》1982,105(2):688-697
A growing organism that produces antibiotic peptide was incubated with L-(U-14C)serine for labeling linear gramicidin. Linear gramicidin was isolated by a simple chromatographic method from tyrothricin (mixture of linear gramicidin and tyrocidine) applied to a column of basic aluminum oxide. The hydrolysate of labeled linear gramicidin on thin layer chromatography showed that L-(U-14C)serine was one of a precursor of ethanolamine moiety by autoradiography. L-(3-14C)serine generated formic acid in the presence of tetrahydrofolic acid by an enzyme fraction prepared with ammonium sulfate, and further formed ethanolamine binding to the protein. Formylvaline was biosynthesized by it with tetrahydrofolic acid and ATP, and subsequently released from the protein. 相似文献
122.
Natural convection from leaves at realistic Grashof numbers 总被引:4,自引:2,他引:2
Abstract. The boundary layer resistance of model leaves was measured in still air, at a range of leaf-to-air temperature differences. The results were compared to those calculated from standard formulae for natural convection. The agreement between observed and calculated was only satisfactory when Grashof numbers exceeded about 105. At the lower Grashof numbers, which often prevail in nature, the observed rates of heat transfer considerably exceeded those calculated. 相似文献
123.
Formation of the perinuclear theca in spermatozoa of diverse mammalian species: relationship of the manchette and multiple band polypeptides 总被引:1,自引:0,他引:1
The perinuclear theca is a novel cytoskeletal consisting of a densely layered lamina that surrounds the nucleus of mammalian sperm. Using antibodies specific for the multiple band polypeptides present in the perinuclear theca of bull sperm, we show that a heterogeneous group of immunological related proteins are present in the sperm heads of other mammals with greatly different morphologies, including guinea pig, hamster, rat, and mouse. In none of the species were identical groups of immunoreactive polypeptides found, although immunoreactive proteins of molecular weights 65,000 to 80,000 were present in the sperm heads of all species examined. Immunoreactive proteins less than Mr 55,000 were prominent in rat sperm heads and mouse sperm: guinea pig, hamster, and rat sperm heads and mouse sperm had one band in common at approximately Mr 50,000. Different immunoreactive proteins were present in isolated sperm tails. The perinuclear theca first appeared in the subacrosomal space of round to elongating spermatids. Later, with the caudal movement of the manchette, the postacrosomal segment of the perinuclear theca was deposited in a cephalad to caudal direction along the sperm nucleus. Concomitantly, the cytoplasmic space between the nuclear envelope and the plasma membrane narrowed such that only the theca occupied this portion of the sperm head. Immunoreactivity accompanied the ultrastructural appearance of the subacrosomal layer and the postacrosomal segment. The periods of spermiogenesis, in which sub- and post-acrosomal components of the perinuclear theca are formed and the morphogenesis of sperm organelles with which these elements are associated, suggest that components of this cytoskeletal structure function to join the acrosome and the postacrosomal plasma membrane to the nucleus. 相似文献
124.
This paper describes a joint study of the structure and nonlinear optical properties of vacuum evaporated thin films of copper phthalocyanine (CuPc for brevity). Film thickness ranges from 50 to 500 nm. The anisotropic paramagnetic resonance of Cu++ ions reveals that the Pc rings lie almost parallel to the substrate plane with however a large angular distribution (30° FWHM). Third harmonic optical generation measurements performed at 1.064 m and 1.907 m fundamental wavelengths give respectively an average value of the cubic susceptibility (3)(-3,)=(4±0.4)·10–12 e.s.u. and (2.1+-0.2) · 10-12 These values, although significantly higher than for a common ionic crystal, are about one order of magnitude lower than in conjugated 1-D systems, which shows that the 2-D -electron delocalization is less profitable than the 1-D one. Besides third harmonic, we have also observed second harmonic generation. Its polarization dependence is characteristic of a quadratic susceptibility enhanced in one direction, almost perpendicular to the substrate, withd
eff comprised between 30 and 60 · 10-9 e.s.u. The possible origins ofd
eff are discussed. 相似文献
125.
K. C. Katsirdakis K. A. Roubelakis-Angelakis 《In vitro cellular & developmental biology. Plant》1992,28(2):90-96
Summary To identify possible reasons that may contribute to recalcitrance in plant protoplasts, the time course of new cell wall deposition
was studied by scanning electron microscopy in protoplasts of a recalcitrant species, the grapevine. Results showed that microfibrils
were developed after 2 days of culture, that complete cell wall formation occurred on Day 6 to 7 of protoplast culture, and
its ultrastructural appearance was identical to that of grapevine leaf-derived callus cells. In addition, a comparative study
was undertaken on [U-14C]glucose uptake and incorporation in ethanol-soluble, cellulosic, and noncellulosic polysaccharide fractions in protoplasts
of grapevine and of a readily regenerating species, tobacco, during culture. There was a significantly higher [U-14C]glucose uptake by tobacco than by grapevine protoplasts. The label distribution in the ethanol-soluble, cellulosic, and
noncellulosic fractions of newly synthesized cell walls differed quantitatively between the two species. In particular, the
labeled glucose incorporated in the noncellulosic cell wall fraction was threefold greater in tobacco than in grapevine protoplasts.
Differences were also revealed in the monosaccharide composition of this fraction between the two species. Addition of dimethyl
sulfoxide to the culture medium resulted in a dramatic increase in [U-14C]glucose uptake by grapevine protoplasts, whereas it exhibited a limited effect in tobacco protoplasts. It showed no effect
on the ultrastructural characteristics of new cell wall nor on the incorporation rate of labeled glucose in the cellulosic
and noncellulosic cell wall fractions. 相似文献
126.
本文综述了外生菌根的形态学和解剖学特征,评价了这些特征用于外生菌根分类的价值,同时指出各种类型的形态学特征和解剖学特征与其营养吸收的关系。这些特征包括了菌根的颜色类型及变化、形状及分枝方式、外伸菌丝的多少及特征、根状菌索有无及分化、菌核有无及特征、菌套内外表面的菌丝排列及分化,菌套的切面特征,丹宁层厚度及分化、哈氏网的菌丝排列及厚度等。较详细阐述了100多年来,人们为外生菌根分类所作出的种种努力,并对各种分类方式作了简单的评价。 相似文献
127.
Using immunofluorescence and cytofluorimetric scanning (CFS), we investigated the short-term (1-7 days) influence of lower thoracic spinal cord transection on lumbar motor neurons. The content of calcitonin gene-related peptide- (CGRP) like immunoreactivity (LI), chromogranin A (Chr A) -LI, vasoactive intestinal polypeptide (VIP)-LI, Syn I-LI, and synaptophysin (p38)-LI in motor perikarya, and the anterograde and retrograde axonal transport of these substances in the sciatic nerve, were studied in nerve crush (6 h) experiments. During the week after transection, CGRP-LI in perikarya decreased, whereas Chr A-LI increased. VIP-LI, co-localized with Chr A-LI in motor perikarya, did not change after transection. The antero- and retrograde transport of CGRP-LI in the sciatic nerve, occurring in both motor and sensory axons, appeared unchanged in cytofluorimetric scanning (CFS) graphs, but the microscopical picture clearly showed that large motor axons had a decreased content of CGRP-LI at 3 and 7 days posttransection, whereas thinner axons were unchanged in fluorescence intensity. The anterograde transport of Chr A-LI, present in both motor and postganglionic adrenergic axons, was decreased 1 and 3 days after lesion, but returned to control by day 7. There was a marked decrease in anterograde transport of VIP-LI, present mainly in postganglionic sympathetic axons, at day 3, but at 7 days transport was normal. The amounts of transported p38, the synaptic vesicle marker, were in the normal range during the whole period. Syn I-LI accumulation anterogradely was somewhat decreased at 3 and 7 days posttransection, and at 1 day the retrograde accumulation was significantly increased. The results suggest that removal of supraspinal input to intact lower motor neurons causes alterations in metabolism and axonal transport of organelle-associated substances, partly probably related to the complex pattern of transmitter leakage from degenerating, descending nerve terminals. These alterations appear to take place also in postganglionic sympathetic neurons in the sciatic nerve, that originate in the lumbar sympathetic chain. © 1992 John Wiley & Sons, Inc. 相似文献
128.
Four protozoan epizooites are found attached to the gills of Gammarus pulex collected from Rutland Water. The suctorian, Dendrocometes paradoxus, and the peritrichs, Epistylis sp. and Lagenophrys sp., are relatively abundant, but the chonotrich, Spirochona gemmipara is only occasionally found. SEM studies of various aspects of these protozoa are described. SEM has been useful in distinguishing between the two species of Lagenophrys found on Gammarus. L. ampulla is found on the gills and L. nassa is found on the limbs. The two species are distinguished by the differences in the structure of the loricastome. The relationship between the epizooites and their host is discussed briefly. 相似文献
129.
Michael G. Gabridge Marlene J. Bright Helen R. Richards 《In vitro cellular & developmental biology. Plant》1982,18(1):55-62
Summary Cell monolayer cultures were prepared from hamster tracheal explants by a collagenase exposure and subsequent incubation in
Waymouth’s MAB 87/3 medium. The epithelial outgrowth occurred on glass cover slips. Cilia on the monolayers continued to beat
normally after the “parent” explant was removed. Monolayer cultures infected withMycoplasma pneumoniae had significant amounts of attachment. A morphological analysis of the attachment was conducted with scanning electron microscopy.
Clusters, cocci, and filaments ofM. pneumoniae all attached to the epithelial cells, but the filaments were especially common. Mycoplasmas were seen in association with
both ciliated and nonciliated cell membranes. On ciliated cells, mycoplasmas were on the ciliary strands and on the cell membrane.
When located immediately adjacent to or in between cilia, mycoplasmas were oriented vertically with the constricted attachment
tip oriented down toward the host cell membrane. When located more than a micron away from the ciliary fibers, mycoplasmas
lay horizontally along the epithelial cell membrane. The photographic data suggest that clusters or “sperules” of mycoplasmas
may liberate individual mycoplasmas that attach to the cell membrane. It appears that the receptor sites forM. pneumoniae are rather uniformly distributed along the ciliated cell membrane, and are not restricted to the interciliary areas.
Electron microscopy was done with the cooperation of Dr. R. Macleod and the staff of the Center for Electron Microscopy at
the University of Illinois. Critical editorial review was provided by C. Dayton.
This investigation was supported in part by grants to M. G. G. from the National Institute of Allergy and Infectious Diseases
(AI 12559) and the National Heart, Lung, and Blood Institute (HL 23806), Bethesda, Maryland. 相似文献
130.
This study examines the types of structural information that can be gained by utilizing the scanning electron microscope (SEM) and a cryofracture technique to examine the host-parasite interaction. Roots of tomato, Lycopersicon esculentum cv. Marglobe, were cultured aseptically and inoculated with the root-knot nematode, Meloidogyne incognita. Twenty-four hours to four weeks after inoculation, developing galls were removed from the cultures and processed for SEM observation. The cryofracture technique was used to reveal internal structural features within the developing galls. The results illustrate structural details concerning penetration of the roots, differentiation of syncytia, and development of the nematodes beginning with the second-stage larvae and ending with adult egg-laying females. 相似文献