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41.
Limulus ventral photoreceptors were voltage clamped to the resting (dark) potential and stimulated by a 20-ms test flash and a 1-s conditioning flash. At a constant level of adaptation, we measured the response to the test flash given in the dark (control) and the incremental response produced when the test flash occurred within the duration of the conditioning flash. The incremental response is defined as the response to the conditioning and test flashes minus the response to the conditioning flash given alone. When the test flash was presented within 100 ms after the onset of the conditioning flash we observed that: (a) for dim conditioning flashes the incremental response equaled the control response; (b) for intermediate intensity conditioning flashes the incremental response was greater than the control response (we refer to this as enhancement); (c) for high intensity conditioning flashes the incremental response nearly equaled the control response. Using 10-μm diam spots of illumnination, we stimulated two spatially separate regions of one photoreceptor. When the test flash and the conditioning flash were presented to the same region, enhancement was present; but when the flashes were applied to separate regions, enhancement was nearly absent. This result indicates that enhancement is localized to the region of illumination. We discuss mechanisms that may account for enhancement. 相似文献
42.
Andrew JS Coats 《Trials》2000,1(3):155-6
Chronic heart failure (CHF) is a common condition with a poor prognosis. It is associated with poor exercise tolerance and debilitating symptoms. These symptoms appear to be associated with pathophysiological changes that occur systemically in the patient with CHF. Exercise training in carefully selected patients has been shown to be safe and to improve exercise capacity. Many of the pathophysiological abnormalities of CHF are improved by training. Some studies have suggested a possible improvement in morbidity and mortality with training. This review analyzes the controlled clinical trials of exercise training in CHF published to date. 相似文献
43.
The success of printing technology in the electronics industry primarily depends on the availability of metal printing ink. Various types of commercially available metal ink are widely used in different industries such as the solar cell, radio frequency identification (RFID) and light emitting diode (LED) industries, with limited usage in semiconductor packaging. The use of printed ink in semiconductor IC packaging is limited by several factors such as poor electrical performance and mechanical strength. Poor adhesion of the printed metal track to the epoxy molding compound is another critical factor that has caused a decline in interest in the application of printing technology to the semiconductor industry. In this study, two different groups of adhesion promoters, based on metal and polymer groups, were used to promote adhesion between the printed ink and the epoxy molding substrate. The experimental data show that silver ink with a metal oxide adhesion promoter adheres better than silver ink with a polymer adhesion promoter. This result can be explained by the hydroxyl bonding between the metal oxide promoter and the silane grouping agent on the epoxy substrate, which contributes a greater adhesion strength compared to the polymer adhesion promoter. Hypotheses of the physical and chemical functions of both adhesion promoters are described in detail. 相似文献
44.
Elisabeth Jonas Peter C Thomson Evelyn JS Hall David McGill Mary K Lam Herman W Raadsma 《遗传、选种与进化》2011,43(1):22
Background
In sheep dairy production, total lactation performance, and length of lactation of lactation are of economic significance. A more persistent lactation has been associated with improved udder health. An extended lactation is defined by a longer period of milkability. This study is the first investigation to examine the presence of quantitative trait loci (QTL) for extended lactation and lactation persistency in sheep.Methods
An (Awassi × Merino) × Merino single-sire backcross family with 172 ewes was used to map QTL for lactation persistency and extended lactation traits on a framework map of 189 loci across all autosomes. The Wood model was fitted to data from multiple lactations to estimate parameters of ovine lactation curves, and these estimates were used to derive measures of lactation persistency and extended lactation traits of milk, protein, fat, lactose, useful yield, and somatic cell score. These derived traits were subjected to QTL analyses using maximum likelihood estimation and regression analysis.Results
Overall, one highly significant (LOD > 3.0), four significant (2.0 < LOD < 3.0) and five suggestive (1.7 < LOD < 2.0) QTL were detected across all traits in common by both mapping methods. One additional suggestive QTL was identified using maximum likelihood estimation, and four suggestive (0.01 < P < 0.05) and two significant (P < 0.01) QTL using the regression approach only. All detected QTL had effect sizes in the range of 0.48 to 0.64 SD, corresponding to QTL heritabilities of 3.1 to 8.9%. The comparison of the detected QTL with results in cattle showed conserved linkage regions. Most of the QTL identified for lactation persistency and extended lactation did not coincide. This suggests that persistency and extended lactation for the same as well as different milk yield and component traits are not controlled by the same genes.Conclusion
This study identified ten novel QTL for lactation persistency and extended lactation in sheep, but results suggest that lactation persistency and extended lactation do not have a major gene in common. These results provide a basis for further validation in extended families and other breeds as well as targeting regions for genome-wide association mapping using high-density SNP arrays. 相似文献45.
JS Agerholm O Andersen MB Almskou C Bendixen J Arnbjerg GP Aamand US Nielsen F Panitz AH Petersen 《Acta veterinaria Scandinavica》2004,45(3):133
To investigate the congenital complex vertebral malformation syndrome (CVM) in Holstein calves, two breeding studies were
performed including 262 and 363 cows, respectively. Cows were selected from the Danish Cattle Database based on pedigree and
insemination records. Selected cows were progeny of sires with an established heterozygous CVM genotype and pregnant after
insemination with semen from another sire with heterozygous CVM genotype. Following calving the breeders should state, if
the calf was normal and was requested to submit dead calves for necropsy. In both studies, significantly fewer CVM affected
calves than expected were obtained; a finding probably reflecting extensive intrauterine mortality in CVM affected foetuses.
The findings illustrate increased intrauterine mortality as a major potential bias in observational studies of inherited disorders. 相似文献
46.
Differential expression of miRNAs and their target genes in senescing leaves and siliques: insights from deep sequencing of small RNAs and cleaved target RNAs 下载免费PDF全文
SHAWN R. THATCHER SHAUL BURD CHRISTOPHER WRIGHT AMNON LERS PAMELA J. GREEN 《Plant, cell & environment》2015,38(1):188-200
MicroRNAs (miRNAs) are a class of small RNAs, which typically function by guiding cleavage of target mRNAs. They are known to play roles in a variety of plant processes including development, responses to environmental stresses and senescence. To identify senescence regulation of miRNAs in Arabidopsis thaliana, eight small RNA libraries were constructed and sequenced at four different stages of development and senescence from both leaves and siliques, resulting in more than 200 million genome‐matched sequences. Parallel analysis of RNA ends libraries, which enable the large‐scale examination of miRNA‐guided cleavage products, were constructed and sequenced, resulting in over 750 million genome‐matched sequences. These large datasets led to the identification a new senescence‐inducible small RNA locus, as well as new regulation of known miRNAs and their target genes during senescence, many of which have established roles in nutrient responsiveness and cell structural integrity. In keeping with remobilization of nutrients thought to occur during senescence, many miRNAs and targets had opposite expression pattern changes between leaf and silique tissues during the progression of senescence. Taken together, these findings highlight the integral role that miRNAs may play in the remobilization of resources and alteration of cellular structure that is known to occur in senescence. 相似文献
47.
A characteristic feature of the sperm P1 protamines of eutherian mammals is
the constant presence of six to nine cysteine residues per molecule. During
spermiogenesis these residues become oxidized to form a three-dimensional
network of disulfide bridges between, and within, protamine molecules in
the sperm chromatin. This covalent cross linking strongly stabilizes
eutherian sperm nuclei. In contrast, protamines sequenced from teleost
fish, birds, monotremes, and marsupials all lack cysteine residues and
their sperm nuclei, without the stabilizing cross links, are easily
decondensed in vitro. We have now found that one genus of tiny, shrewlike
dasyurid marsupials, the Planigales, possess P1 protamines containing five
to six cysteine residues. These residues appear to have evolved since the
divergence of Planigales from other members of the family Dasyuridae, such
as the marsupial mouse, Sminthopsis crassicaudata. We believe this
constitutes a case of convergent evolution in a subfamily of dasyurid
marsupials toward the cysteine-rich eutherian form of sperm protamine P1.
相似文献
48.
49.
The ability of particular cell surface glycoproteins to recycle and become
exposed to individual Golgi enzymes has been demonstrated. This study was
designed to determine whether endocytic trafficking includes significant
reentry into the overall oligosaccharide processing pathway. The Lec1
mutant of Chinese hamster ovary (CHO) cells lack N -
acetylglucosaminyltransferase I (GlcNAc-TI) activity resulting in surface
expression of incompletely processed Man5GlcNAc2 N -linked
oligosaccharides. An oligosaccharide tracer was created by exoglycosylation
of cell surface glycoproteins with purified porcine GlcNAc-TI and
UDP-[3H]GlcNAc. Upon reculturing, all cell surface glycoproteins that
acquired [3H]GlcNAc were acted upon by intracellular mannosidase II, the
next enzyme in the Golgi processing pathway of complex N -linked
oligosaccharides (t1/2= 3-4 h). That all radiolabeled cell surface
glycoproteins were included in this endocytic pathway indicates a common
intracellular compartment into which endocytosed cell surface glycoproteins
return. Significantly, no evidence was found for continued oligosaccharide
processing consistent with transit through the latter cisternae of the
Golgi apparatus. These data indicate that, although recycling plasma
membrane glycoproteins can be reexposed to individual Golgi-derived
enzymes, significant reentry into the overall contiguous processing pathway
is not evident.
相似文献
50.