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1.
This study has demonstrated that aneurysms occur in about 50 percent of the rat femoral arteries subjected to microvascular anastomosis. These aneurysms are consistent histologically--being characterized by medial necrosis, loss of elastic lamellae, and subintimal hyperplasia. Mechanical trauma is implicated as a factor in their pathogenesis, though further study in necessary to define the exact etiology. 相似文献
2.
Attila Virág 《Journal of morphology》2012,273(12):1406-1423
The chequered pattern (often called Schreger pattern), which can be seen by unaided eye on transverse profiles of several proboscidean tusks and which can be emphasized by the spreading pattern of the cracks or by mineral discoloration, is an autapomorph feature of the clade Elephantoidea. The pattern differs among proboscidean taxa; therefore, it allows the coarse differentiation of elephants, mammoths, and some other basal groups. Such identification methods could facilitate efforts concerned with protection of the remaining elephant populations through ivory trade restrictions, since the tooth dentine from extinct Mammuthusprimigenius and from extant Loxodontaafricana and Elephasmaximus are the most common raw materials of the ivory carvings. The aim of this study was to show the internal structure of proboscidean ivory and to revise the existing theories on the aforementioned pattern of the elephantoids with reflections on the events which lead to the development of this microstructure. Thin sections and natural crack surfaces with various orientations of M.primigenius, Elephasantiquus, Prodeinotherium, and Deinotherium tusk fragments were used to produce a three‐dimensional model which explains the features on all profiles. The “phase shift” model is introduced, which assumes a sinusoid undulation of the dentinal tubules in radial profiles in the case of elephantoids. The model was confirmed by photomicrographs, scanning electron microscopic images, interpretation of natural crack surfaces, and radial displacement analysis of the dentinal tubules. The latter proved that the adjacent waves are not in the same phase. Several new nondestructive distinguishing methods are described here on the basis of the correlation between some microscopic and macroscopic features related to the Schreger pattern. J. Morphol. 2012. © 2012 Wiley Periodicals, Inc. 相似文献
3.
Uranium-series dating of coral samples from raised marine terrace deposits between 1.5 and 10 m above sea level in the La Paz Peninsula area, Baja California Sur, yielded ages between 123 ka and 138 ka that are in agreement with previously reported results. The stratigraphy and ages of marine units near the El Coyote Arroyo indicate the presence of two high stands of the sea during the last interglacial or oxygen isotope substage 5e at about 140 ka and 123 ka. Accepting 5 m for the sea level during the last interglacial transgression, we calculate average uplift rates for the marine terraces of about 70 mm/ka and 40 mm/ka. These slow rates of uplift indicate a relative stability of the La Paz peninsula area for the past 140 000 years. In contrast, areas of Baja California affected by major faultf experienced higher rates of uplift. Rockwell et al. (1987) reported vertical uplift rates of 180 to 300 mm/ka at Punta Banda within the Aqua Blanea fault zone in northern Baja California. 相似文献
4.
Rapid hydrophobic grid membrane filter-enzyme-labeled antibody procedure for identification and enumeration of Escherichia coli O157 in foods 总被引:2,自引:0,他引:2
E C Todd R A Szabo P Peterkin A N Sharpe L Parrington D Bundle M A Gidney M B Perry 《Applied and environmental microbiology》1988,54(10):2536-2540
An O-antigen-specific monoclonal antibody, labeled by horseradish peroxidase-protein A, was used in a hydrophobic grid membrane filter-enzyme-labeled antibody method for rapid detection of Escherichia coli O157 in foods. The method yielded presumptive identification within 24 h and recovered, on average, 95% of E. coli O157:H7 artificially inoculated into comminuted beef, veal, pork, chicken giblets, and chicken carcass washings. In food samples from two outbreaks involving E. coli O157:H7, the organism was isolated at levels of up to 10(3)/g. The lower limit of sensitivity was 10 E. coli O157 per g of meat. Specific typing for E. coli O157:H7 can be achieved through staining with labeled H7 antiserum or tube agglutination. 相似文献
5.
Molecular genotypes of the human T cell receptor gamma-chain 总被引:2,自引:0,他引:2
New RFLP of the human TCR gamma-chain defined by a single restriction enzyme (PvuII) are described. They define three alleles and allow haplotype assignments within families. They occur at a high frequency within the population studied and are useful for studies on disease associations with the gamma-chain genes. The PvuII sites flank the C gamma 2 gene. A polymorphic site maps to an area 0.5 kb downstream of C gamma 2-exon III. The second RFLP appears to be the result of a 3-kb insertion giving rise to differences in the number of copies of exon II in the C gamma 2 gene. 相似文献
6.
G. Akoev G. N. Andrianov T. Szabo B. Bromm 《Journal of comparative physiology. A, Neuroethology, sensory, neural, and behavioral physiology》1991,168(6):639-646
Summary Dissected ampullae of Lorenzini of the skate (Raja clavata) were studied with the aim of determining the synaptic transmitter between electroreceptor cell and afferent fibre. Resting activity and stimulus-evoked activity in response to electrical pulses were recorded in single afferent units at constant perfusion with normal and test solutions containing different putative neurotransmitters. Presynaptic transmitter release was blocked by Mg2+ (up to 50 mM) to investigate the effects of the test substances upon the postsynaptic membrane. l-Glutamate (l-GLU) and l-aspartate (l-ASP), both at concentrations between 10-7 and 10-3
M, enlarged strongly resting and stimulus-evoked discharge frequency in the afferent fibre. If transmission was blocked by high Mg2+, resting discharge frequency could be restored by l-GLU or l-ASP. The glutamate agonists quisqualate (10-8–105
M) and N-methyl-D-aspartate (10-5–10-3
M) enlarged spontaneous activity in the afferent fiber. The same was found for kainic acid (10-9–10-5
M). Taurine at concentrations between 10-5 and 10-3
M caused a concentration-dependent decrease in afferent activity. The same was found for gammaaminobutyric acid (GABA; 10-5–10-4
M), and for the catecholamines adrenaline and noradrenaline, both in concentrations between 10-5 and 10-3
M. Serotonine (10-5–10-3
M) and dopamine (10-5-10-3
M) had no effect on resting or evoked activity in the Lorenzinian ampulla afferents. Acetylcholine (ACh; 10-4
M) enlarged discharge frequency in those units with initial rates lower than 22–25 Hz, but diminished discharge frequency in fibres with initial activity higher than 25 Hz. When synaptic transmission was blocked by high Mg2+ solution, perfusion with additional ACh did not restore resting activity in the afferent fibre. The results suggest that the most probable transmitter in the afferent synapse of the ampullae of Lorenzini is l-GLU or l-ASP, or a substance of similar nature.Abbreviations
ACh
acetylcholine
-
GABA
gamma aminobutyric acid
-
KA
kainic acid
-
l-ASP
l-aspartate
-
l-GLU
l-glutamate
-
NMDA
N-methyl-D-aspartate
-
Q
quisqualate
-
n.s.
normal solution 相似文献
7.
L Szabo D G Mottershead F J Ballard J C Wallace 《Biochemical and biophysical research communications》1988,151(1):207-214
The insulin-like growth factor binding protein (BP) secreted by bovine kidney (MDBK) cells has been purified by affinity chromatography on a rat IGF-2 Sepharose column. Purified BP migrated as a single band of Mr 40,000 upon SDS polyacrylamide gel electrophoresis. An N-terminal sequence of 53 residues was obtained which was very similar up to residue 21 to the corresponding rat BRL-3A BP sequence. In competitive binding experiments with bovine IGF-1 and IGF-2, and recombinant human IGF-1, BP had a similar affinity for these ligand when IGF-1 tracer was used, but a higher affinity for IGF-2 with IGF-2 as radioligand. The N-terminal destripeptide truncated form of bovine IGF-1, which has enhanced biological activity, was found to have a markedly reduced affinity for BP compared to intact IGF-1. The increased bioactivity of destripeptide IGF-1 can be explained by this reduced affinity for BP. 相似文献
8.
A series of murine erythroleukemia cell (MELC) variants was generated by selection for the ability to grow in increasing concentrations of the folate antagonist methotrexate (MTX). Growth of the parental MELC strain DS-19 was completely inhibited by 0.1 microM MTX. We isolated cells able to grow in 5, 40, 200, 400, and 800 microM MTX. Growth rates and yields were essentially the same in the presence or absence of the selective dose of MTX for all variants. MTX resistance was not the result of a transport defect. Dihydrofolate reductase (DHFR) from our variants and DS-19 was inhibited to the same extent by MTX. Variants had increased dihydrofolate reductase activities. The specific activity of DHFR was proportional to the selective concentration of MTX employed to isolate a given variant. DNA dot blotting established that the cloned variant (MR400-3) had a 160-fold increase in DHFR gene copy number relative to the parental strain (DS-19). Hybridization studies performed in situ established the presence of amplified DHFR genes on the chromosomes of the MTX-resistant but not the MTX-sensitive (parental) cells. Quantitation of DHFR mRNA by cytoplasmic dot blotting established that the amplified DHFR gene expression was proportional to gene copy number. Thus, MTX resistance was due to amplification of the DHFR gene. The variants retained the ability to be induced to differentiate in response to dimethyl sulfoxide and hexamethylenebis(acetamide) as evaluated by the criteria of globin mRNA accumulation, hemoglobin accumulation, cell volume decreases, and terminal cell division.(ABSTRACT TRUNCATED AT 250 WORDS) 相似文献
9.
Integration and excision of pMC7105 in Pseudomonas syringae pv. phaseolicola: involvement of repetitive sequences. 总被引:13,自引:7,他引:6 下载免费PDF全文
The site for integration of pMC7105 into the chromosome of Pseudomonas syringae pv. phaseolicola has been mapped to a 2.6-kilobase-pair (kb) Bg/II-EcoRI fragment on this 150-kb indigenous plasmid. Selected excision plasmids resulting from imprecise excision of pMC7105 were used to identify one of the plasmid-chromosome juncture fragments and to characterize the mechanism of recombination from the chromosome. A 14.2-kb BamHI plasmid-chromosome juncture fragment has been identified in pEX8060 (234 kb), an excision plasmid which carries approximately 90 kb of chromosomal sequences to the left of the site of integration. This fragment contains a portion of the 2.6-kb Bg/II-EcoRI fragment as well as chromosomal sequences. Blot hybridization with a probe made from selected fragments of pMC7105 revealed three distinct repetitive sequences, RS-I, RS-II, and RS-III, on this plasmid. The 2.6-kb fragment, to which the site of integration maps, also contains RS-II. Five copies of RS-II are present in pMC7105, and more than 20 copies are present in the chromosome. Eight small excision plasmids were shown to result from recombination among fragments of pMC7105 that contain common repetitive sequences. The results indicate that integration and excision of pMC7105 occur through general recombination at homologous repetitive sequences. 相似文献
10.