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1.
Populations of the Australian sleepy lizard, Tiliqua rugosa, near Mt. Mary, South Australia carry natural infestations of two tick species Aponomma hydrosauri and Amblyomma limbatum. In field experiments at two sites, 18 km apart, lizards with experimentally increased tick loads had smaller home ranges,
moved shorter distances in a day, and were found basking more but moving less often than lizards from which ticks were experimentally
removed. The results were consistent for adult lizards in two years, and for sub-adults in a third year. Laboratory trials
showed that juvenile lizards that had tick infestations had lower sprint speeds than uninfested siblings, and that adults
with tick infestations had less endurance than those that were uninfested. The results contrast with those of a previous survey
that showed that lizards with high tick loads had greater body size and remained longer at a site, but indicate that there
may be a balance, for lizards, between the fitness advantages in occupying habitats with high-quality resources, and the costs
from parasites that also prefer those habitats.
Received: 02 March 1999 / Accepted: 07 October 1999 相似文献
2.
Abstract Vitronectin, a serum and extracellular matrix protein involved in immunological reactions, interacts with Helicobacter pylori strains. Of the 20 H. pylori strains tested three strains bound more than 50% of the vitronectin added, five strains bound 25–40%, nine strains bound 10–20% and three strains bound 5–8% vitronectin. Two strains, one with high- and one with low-binding properties, were selected for further characterization of 125 I-vitronectin binding. Binding to the urea-activated 125 I-labelled vitronectin was fast, saturable and reversible when an excess of unlabelled vitronectin was added to the bacteria with bound 125 I-vitronectin. The binding was heat- and protease-sensitive, suggesting that the binding was mediated by bacterial cell-surface proteins. Since components such as fetuin and orosomucoid but not asialofetuin inhibited the binding, sialic-acid specific proteins, related to H. pylori sialic-acid specific haemagglutinins, were probably involved. 相似文献
3.
The serine carboxylesterase from horse serum was characterized by amino acid composition, peptide mapping, molecular and subunit weights, and sequencing of the amino acids around the essential serine residue at the active site. A protocol was developed for using reversed-phase high-performance liquid chromatography as the final step to obtain homogeneous preparations of horse serum carboxylesterase. Amounts sufficient for determining the amino acid composition and for peptide maps were obtained from a partially purified starting material which contained approximately 55% carboxylesterase. The amino acid composition, like the subunit weight (70,800 +/- 1400), was similar to the corresponding values reported for other serine carboxylesterases. However, the amino acid sequence of the tryptic digest fragment containing the essential nucleophilic seryl residue differed significantly from the corresponding sequences of other mammalian serine carboxylesterases. 相似文献
4.
Use of procainamide gels in the purification of human and horse serum cholinesterases 总被引:2,自引:0,他引:2 下载免费PDF全文
Two large-scale methods based primarily on the use of procainamide-Sepharose gels were developed for the purification of horse and human serum non-specific cholinesterases. With method I, the procainamide-Sepharose 4B gel was used in the first step to handle large volumes of serum. With method II, the procainamide-Sepharose 4B gel was used in the final step to obtain pure enzyme. Although both methods gave electrophoretically pure cholinesterase preparations in good yields, they were significantly more efficient at purifying the horse enzyme than the human enzyme. To study this problem, the relative binding of human and horse cholinesterases to procainamide-, methylacridinium (MAC)-, m-trimethylammoniophenyl (m-PTA)- and p-trimethylammoniophenyl (p-PTA)-Sepharose 4B gels were measured, by using two approaches. In one, binding was measured by a procedure involving equilibration of pure cholinesterase in a small volume of diluted gel slurry (4%, v/v). A partially purified preparation of Electrophorus acetylcholinesterase was included. Pure human cholinesterase bound consistently more tightly to each of the gels than did horse cholinesterase, and the acetylcholinesterase appeared to bind the gels 10-100 times more tightly than did the non-specific cholinesterases. The order of binding for the cholinesterases, beginning with the tightest, was: procainamide-Sepharose 4B, MAC-Sepharose 4B, p-PTA-Sepharose 4B and m-PTA-Sepharose 4B. For the acetylcholinesterase the order was: MAC-Sepharose 4B, procainamide-Sepharose 4B, p-PTA-Sepharose 4B and m-PTA-Sepharose 4B. The second approach involved passing native sera or partially purified sera fractions through 1 ml test columns of each of the four affinity gels to determine their retention capacity for the cholinesterases. With these impure samples, the MAC-Sepharose 4B gels proved superior to the procainamide-Sepharose 4B gels at retaining human cholinesterase, but the opposite was true for the horse cholinesterase. 相似文献
5.
6.
M. G. Brook G. Chan I. Yap P. Karayiannis A. M. Lever M. Jacyna J. Main H. C. Thomas 《BMJ (Clinical research ed.)》1989,299(6700):652-656
OBJECTIVE--To confirm the findings of pilot studies that interferon alfa is an effective treatment of Europid men with chronic hepatitis B virus infection. DESIGN--Randomised controlled trial of three months treatment with interferon alfa followed by 12 months of observation. SETTING--Outpatient clinic of a tertiary referral centre. PATIENTS--37 Treated men (six anti-HIV positive) and 34 untreated men (nine anti-HIV positive) who met the criteria for the trial. Four controls failed to complete follow up. INTERVENTIONS--The treated group received subcutaneous injections of 5-10 MU interferon alfa/m2 daily for five days, then 10 MU/m2 thrice weekly for 11 weeks. Follow up continued at monthly intervals for 12 months. Untreated controls were monitored over the same period. MAIN OUTCOME MEASURE--Hepatitis B e antigen and hepatitis B virus DNA state after 15 months of observation. RESULTS--12 Of the 37 treated patients cleared hepatitis B e antigen and hepatitis B virus DNA, whereas only one of 30 untreated controls seroconverted over the same period--an increased response rate of 29% (95% confidence interval 13% to 45%). The life table estimate of response at 15 months was 35% in treated patients, an increase of 32% above controls (95% confidence interval 16% to 48%). The response rates in groups by predictive pretreatment variables were 12 of 31 anti-HIV negative patients (excess response 34%; 95% confidence interval 14% to 54%), 12 of 26 with chronic active hepatitis before treatment (excess response 46%; 27% to 65%), and 12 of 21 with a pretreatment serum aspartate aminotransferase activity greater than 70 IU/l (excess response 46%; 16% to 76%). The combination of these factors predicted response with a sensitivity of 100% and a specificity of 80%. Four of the 12 responders, who had all been infected for less than two years, also lost hepatitis B surface antigen. Treatment was well tolerated. CONCLUSIONS--Interferon alfa is effective in the treatment of a proportion of Europid men with chronic hepatitis B virus infection, who might be identified before treatment. Additional strategies are required to improve the rate of response. 相似文献
7.
We have broadly defined the DNA regions regulating esterase6 activity in
several life stages and tissue types of D. melanogaster using P-
element-mediated transformation of constructs that contain the esterase6
coding region and deletions or substitutions in 5' or 3' flanking DNA.
Hemolymph is a conserved ancestral site of EST6 activity in Drosophila and
the primary sequences regulating its activity lie between -171 and -25 bp
relative to the translation initiation site: deletion of these sequences
decrease activity approximately 20-fold. Hemolymph activity is also
modulated by four other DNA regions, three of which lie 5' and one of which
lies 3' of the coding region. Of these, two have positive and two have
negative effects, each of approximately twofold. Esterase6 activity is
present also in two male reproductive tract tissues; the ejaculatory bulb,
which is another ancestral activity site, and the ejaculatory duct, which
is a recently acquired site within the melanogaster species subgroup.
Activities in these tissues are at least in part independently regulated:
activity in the ejaculatory bulb is conferred by sequences between -273 and
-172 bp (threefold decrease when deleted), while activity in the
ejaculatory duct is conferred by more distal sequences between -844 and
-614 bp (fourfold decrease when deleted). The reproductive tract activity
is further modulated by two additional DNA regions, one in 5' DNA (-613 to
-284 bp; threefold decrease when deleted) and the other in 3' DNA (+1860 to
+2731 bp; threefold decrease when deleted) that probably overlaps the
adjacent esteraseP gene. Collating these data with previous studies
suggests that expression of EST6 in the ancestral sites is mainly regulated
by conserved proximal sequences while more variable distal sequences
regulate expression in the acquired ejaculatory duct site.
相似文献
8.
The snare web is used as a medium for communication betweenindividuals within colonies of social spiders and has thereforebeen suggested as necessary for the evolution of sociality inthe Araneae. The social spider Diaea socialis (Thomisidae) isan exception because it does not build a snare web. Experimentsdemonstrate that silk attracts all spiders and that a chemicaldeposited onto the silk attracts adult female spiders, suggestingthat the group living of this species is mediated by a pheromone.The pheromone attracts spiders differentially: females are notattracted to juvenile silk, and it repels gravid females. Thepheromone appears to be stable but volatile, is ether-soluble,and retains its viability after dissolution. Molecular-ionicmasses for 7-8 different compounds were found in the range 220281atomic units; the pheromone may be one or a combination of severalof these. 相似文献
9.
Litman GW; Rast JP; Shamblott MJ; Haire RN; Hulst M; Roess W; Litman RT; Hinds- Frey KR; Zilch A; Amemiya CT 《Molecular biology and evolution》1993,10(1):60-72
Immunoglobulins are encoded by a large multigene system that undergoes
somatic rearrangement and additional genetic change during the development
of immunoglobulin-producing cells. Inducible antibody and antibody-like
responses are found in all vertebrates. However, immunoglobulin possessing
disulfide-bonded heavy and light chains and domain-type organization has
been described only in representatives of the jawed vertebrates. High
degrees of nucleotide and predicted amino acid sequence identity are
evident when the segmental elements that constitute the immunoglobulin gene
loci in phylogenetically divergent vertebrates are compared. However, the
organization of gene loci and the manner in which the independent elements
recombine (and diversify) vary markedly among different taxa. One striking
pattern of gene organization is the "cluster type" that appears to be
restricted to the chondrichthyes (cartilaginous fishes) and limits
segmental rearrangement to closely linked elements. This type of gene
organization is associated with both heavy- and light-chain gene loci. In
some cases, the clusters are "joined" or "partially joined" in the germ
line, in effect predetermining or partially predetermining, respectively,
the encoded specificities (the assumption being that these are expressed)
of the individual loci. By relating the sequences of transcribed gene
products to their respective germ-line genes, it is evident that, in some
cases, joined-type genes are expressed. This raises a question about the
existence and/or nature of allelic exclusion in these species. The
extensive variation in gene organization found throughout the vertebrate
species may relate directly to the role of intersegmental
(V<==>D<==>J) distances in the commitment of the individual
antibody-producing cell to a particular genetic specificity. Thus, the
evolution of this locus, perhaps more so than that of others, may reflect
the interrelationships between genetic organization and function.
相似文献
10.
J D Wilson J Y Bullock D C Sutherland C Main K P O'Brien 《BMJ (Clinical research ed.)》1978,1(6104):14-16
Antinuclear antibodies (ANA) were found in 54 (7.0%) out of 767 treated hypertensive patients compared with 59 (2.4%) out of 2470 healthy controls. Inclusion of a non-practolol beta-blocker in the treatment regimen did not significantly affect the incidence of ANA. ANA was found in significantly more patients being treated with methyldopa (13.0%) than patients receiving other hypotensive agents (3.8%). Non-practolol beta-blockers in combination with methyldopa did not increase the incidence of ANA further. 相似文献