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1.
Goats and some sheep synthesize a juvenile hemoglobin, Hb C (alpha 2 beta
C2), at birth and produce this hemoglobin exclusively during severe anemia.
Sheep that synthesize this juvenile hemoglobin are of the A haplotype.
Other sheep, belonging to a separate group, the B haplotype, do not
synthesize hemoglobin C and during anemia continue to produce their adult
hemoglobin. To understand the basis for this difference we have determined
the structural organization of the beta- globin locus of B-type sheep by
constructing and isolating overlapping genomic clones. These clones have
allowed us to establish the linkage map 5' epsilon I-epsilon II-psi beta
I-beta B-epsilon III-epsilon IV- psi beta II-beta F3' in this haplotype.
Thus, B sheep lack four genes, including the BC gene, and have only eight
genes, compared with the 12 found in the goat globin locus. The goat
beta-globin locus is as follows: 5' epsilon I-epsilon II-psi beta X-beta
C-epsilon III-epsilon IV-psi beta Z-beta A-epsilon V-epsilon VI-psi beta
Y-beta F3'. Southern blot analysis of A-type sheep reveals that these
animals have a beta- globin locus similar to that of goat, i.e., 12 globin
genes. Thus, the beta-globin locus of B-haplotype sheep resembles that of
cows and may have retained the duplicated locus of the ancestor of cows and
sheep. Alternatively, the B-sheep locus arrangement may be the result of a
deletion of a four-gene set from the triplicated locus.
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2.
The sensitivity to tobacco rattle virus of nine potato cultivars and 24 potato clones from the potato breeding programme at SCRI was assessed in a glasshouse pot test and in field trials for two consecutive years. The results and analyses presented indicate that the pot test gives an accurate and reliable estimate of sensitivity to tobacco rattle virus. Methods of assessing severity of expression of disease symptoms were examined. The advantages of such a glasshouse pot test and its application are discussed. 相似文献
3.
Entrance of water into human red cells under an osmotic pressure gradient 总被引:7,自引:17,他引:7
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A new technique to determine the rate of water passage through the membrane of the human erythrocyte under an osmotic gradient has been developed. It utilizes a rapid mixing apparatus of the Hartridge-Roughton type which permits measurements at short intervals after the reaction has begun. This is coupled with a light-scattering device of new design which permits the determination of very small changes in volume of the cells without disturbing them. With this technique it was possible to measure the change in volume of freshly drawn human erythrocytes after about 50, 100, 155, and 215 msec. of exposure to anisotonic media. The experimental curves were compared with theoretical curves derived from accepted equations for the process and a permeability coefficient of 0.23 ± 0.03 (cm.4/osm., sec.) was obtained. 相似文献
4.
Whole human blood is incubated for periods of ½ to 3 hours with K42 at 37°C. At the close of this period, called pre-incubation, the plasma is removed from the cells and the cells, now become radioactive, are again incubated in a mixture of plasma and buffer for periods of up to 10 additional hours. The time course of the K42 activity of the incubating medium is followed. Characteristically, after 2 hours of pre-incubation, the activity in the medium rises to a peak about 1 and ½ hours after resuspension, and then falls slowly until at 10 hours it is very close to its initial value at the beginning of the resuspension interval. This transient rise in K42 activity in the medium is taken to indicate that the red cell does not consist of a single uniform K compartment, but contains at least two compartments. Thus one cellular compartment contains a reservoir of high specific activity K which provides the specific activity gradient necessary to drive the K42 content of the medium to its transient peak. Experiments with Na indicate that its behavior in this respect is unlike that of K. The experimental data are matched to a simple model system which is capable of theoretical analysis with the aid of an analogue computer. The model system, whose characteristics agree fairly well with those observed experimentally on red cell suspensions, comprises two intracellular compartments, one containing 2.35 m.eq. K/liter blood, and the other 44.1 m.eq. K/liter blood. The plasma K content is 2.64 m.eq./liter blood. The flux between plasma and the smaller intracellular compartment is 0.65 m.eq. K/liter blood hour; that between the smaller and the larger intracellular compartment, 1.77 m.eq. K/liter blood hour; and that between the larger intracellular compartment and the plasma is 0.34 m.eq. K/liter blood hour. 相似文献
5.
Calcrete aquifers from the Yilgarn region of arid central Western Australia contain an assemblage of obligate groundwater invertebrate species that are each endemic to single aquifers. Fine-scale phylogeographic and population genetic analyses of three sympatric and independently derived species of amphipod (Chiltoniidae) were carried out to determine whether there were common patterns of population genetic structure or evidence for past geographic isolation of populations within a single calcrete aquifer. Genetic diversity in amphipod mitochondrial DNA (cytochrome c oxidase subunit I gene) and allozymes were examined across a 3.5 km2 region of the Sturt Meadows calcrete, which contains a grid of 115 bore holes (=wells). Stygobiont amphipods were found to have high levels of mitochondrial haplotype diversity coupled with low nucleotide diversity. Mitochondrial phylogeographic structuring was found between haplogroups for one of the chiltoniid species, which also showed population structuring for nuclear markers. Signatures of population expansion in two of the three species, match previous findings for diving beetles at the same site, indicating that the system is dynamic. We propose isolation of populations in refugia within the calcrete, followed by expansion events, as the most likely source of intraspecific genetic diversity, due to changes in water level influencing gene flow across the calcrete. 相似文献
6.
The inward transport of potassium by separated dog erythrocytes has been studied at concentrations of potassium in the medium from 2.9 to 25.0 m.eq./liter and at 38.0 and 33.0 degrees C. At the physiological concentration of external potassium (4.06 m.eq./liter medium), the inward potassium flux is 0.11 m.eq./liter cells hour and the glucose consumption is 2.0 mM/liter cells hour. The dependence of potassium influx on extracellular potassium concentration is given by the following equation, K influx (m.eq./liter cells hour) = 0.028 [K](amb.) - 0.003 in which [K](amb.) refers to the potassium concentration in the medium. In a single 93 hour experiment, 94 per cent of the intracellular potassium was exchanged at an apparently uniform rate. The average apparent activation energy for the process is 7,750 calories +/- 2,000 calories/mol and there is some indication that the apparent activation energy of inward K transport decreases with increasing external K concentration. 相似文献
7.
Holger?J?SchünemannEmail author Brydon?JB?Grant Paola?Muti Susan?E?McCann Deepa?Kudalkar Malathi?Ram Tom?Nochajski Marcia?Russell Maurizio?Trevisan 《BMC pulmonary medicine》2002,2(1):3
Background
Lung function is a strong predictor of cardiovascular and all-cause mortality. Previous studies suggest that alcohol exposure may be linked to impaired pulmonary function through oxidant-antioxidant mechanisms. Alcohol may be an important source of oxidants; however, wine contains several antioxidants. In this study we analyzed the relation of beverage specific alcohol intake with forced expiratory volume in one second (FEV1) and forced vital capacity (FVC) in a random sample of 1555 residents of Western New York, USA. 相似文献8.
Kuliszewski MA Kutryk MJ Sandhu R Fitchett D Stewart DJ 《International journal of cardiovascular interventions》2000,3(3):167-172
BACKGROUND: The NOGA (Biosense Webster, Markham, ON, Canada) injection catheter is an innovative navigational device that provides an ideal platform for intra-myocardial injection material. However, injection through a long (1.91 m), narrow (27G) nitinol needle could result in deterioration in the integrity and functionality of DNA. METHODS: To test this possibility, DNA in plasmid form (pcDNA3.1) containing the Lac Z transgene (250 micro l) was passed through the NOGA needle using a hand-held 1 cc syringe at a gentle hand injection pressure (43 +/- 3 PSI, 3.0 +/- 0.2 kg/cm(2)) or at maximal manual pressure (90 +/- 6 PSI, 6.3 +/- 0.4 kg/cm(2)), either once or 20 times. This DNA, compared to DNA not passed through the NOGA needle (control), was then used to transfect primary cultures of rat skin fibroblasts (FB) from Fisher 344 rats and the cells were subsequently stained for beta galactosidase (betagal). RESULTS: Transfection efficiency was significantly reduced by passing the DNA through the needle at both 43 +/- 3 PSI (78 +/- 4% of control, n = 10, P < 0.05 versus control) and 90 +/- 6 PSI (66 +/- 4 % of control, n = 10, P < 0.01 versus control, P < 0.02 versus 43 +/- 3 PSI). Passage of the DNA through the NOGA needle 20 times resulted in a transfection efficiency of only 5 +/- 1% of control (n = 20, P < 0.1 x 10(-11) versus control). Capillary Electrophoresis revealed that the reduction in transfection efficiency was due to a conformational change in the DNA from predominantly supercoiled to nicked and linearized DNA. Transfection efficiency as compared with control decreased as the concentration of the DNA solution which was passed through the needle was increased from 0.3 micro g/ micro l to 2.4 micro g/ micro l. Recovery experiments confirmed that the reduction in transfection efficiency was not due to loss of DNA by binding to the NOGA needle. CONCLUSION: These results suggest that DNA is susceptible to shear forces when injected through the NOGA needle even at nominal clinical injection pressures, suggesting that careful and controlled injections will be required to achieve optimal gene integrity and expression. 相似文献
9.
Phylogenetic relationships were determined for 76 partial P-element
sequences from 14 species of the melanogaster species group within the
Drosophila subgenus Sophophora. These results are examined in the context
of the phylogeny of the species from which the sequences were isolated.
Sequences from the P-element family fall into distinct subfamilies, or
clades, which are often characteristic for particular species subgroups.
When examined locally among closely related species, the evolution of P
elements is characterized by vertical transmission, whereby the P-element
phylogeny traces the species phylogeny. On a broader scale, however, the
P-element phylogeny is not congruent with the species phylogeny. One
feature of P-element evolution in the melanogaster group is the presence of
more than one P-element subfamily, differing by as much as 36%, in the
genomes of some species. Thus, P elements from several individual species
are not monophyletic, and a likely explanation for the incongruence between
P-element and species phylogenies is provided by the comparison of
paralogous sequences. In certain instances, horizontal transfer seems to be
a valid alternative explanation for lack of congruence between species and
P-element phylogenies. The canonical P-element subfamily, which represents
the active, autonomous transposable element, is restricted to D.
melanogaster. Thus, its origin clearly lies outside of the melanogaster
species group, consistent with the earlier conclusion of recent horizontal
transfer.
相似文献
10.