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101.
Avise JC; Shapira JF; Daniel SW; Aquadro CF; Lansman RA 《Molecular biology and evolution》1983,1(1):38-56
We address the problem of the possible significance of biological
speciation to the magnitude and pattern of divergence of asexually
transmitted characters in bisexual species. The empirical data for this
report consist of restriction endonuclease site variability in maternally
transmitted mitochondrial DNA (mtDNA) isolated from 82 samples of
Peromyscus polionotus and P. leucopus collected from major portions of the
respective species' ranges. Data are analyzed together with previously
published information on P. maniculatus, a sibling species to polionotus.
Maps of restriction sites indicate that all of the variation observed can
be reasonably attributed to base substitutions leading to loss or gain of
particular recognition sites. Magnitude of mtDNA sequence divergence within
polionotus (maximum approximately equal to 2%) is roughly comparable to
that observed within any of five previously identified mtDNA assemblages in
maniculatus. Sequence divergence within leucopus (maximum approximately
equal to 4%) is somewhat greater than that within polionotus. Consideration
of probable evolutionary links among mtDNA restriction site maps allowed
estimation of matriarchal phylogenies within polionotus and leucopus.
Clustering algorithms and qualitative Wagner procedures were used to
generate phenograms and parsimony networks, respectively, for the
between-species comparisons. Three simple graphical models are presented to
illustrate some conceivable relationships of mtDNA differentiation to
speciation. In theoretical case I, each of two reproductively defined
species (A and B) is monophyletic in matriarchal genealogy; the common
female ancestor of either species can either predate or postdate the
speciation. In case II, neither species is monophyletic in matriarchal
genotype. In case III, species B is monophyletic but forms a subclade
within A which is thus paraphyletic with respect to B. The empirical
results for mtDNA in maniculatus and polionotus appear to conform closely
to case III. These theoretical and empirical considerations raise a number
of questions about the general relationship of the speciation process to
the evolution of uniparentally transmitted traits. Some of these
considerations are presented, and it is suggested that the distribution
patterns of mtDNA sequence variation within and among extant species should
be of considerable relevance to the particular demographies of speciation.
相似文献
102.
M W Aarnoudse H B Lamberts F Dijk J Vos A J de Vries 《Virchows Archiv. B, Cell pathology including molecular pathology》1984,47(3):211-216
Previous experiments have shown that local irradiation of the carotid arteries of hypercholesterolemic rabbits results in the development of atheromatosis in the irradiated areas of the arteries. The process starts with the adherence of monocytes to the endothelial layer, their entrance into the subendothelial space, and their subsequent transformation into lipophages (foam cells). Prevention of this type of plaque formation can be achieved by prednisolone (in a lower concentration than previously used) (Vos et al. 1981) and by VP16-213 (Vepesid). Differential blood cell counts demonstrated that the animals subjected to treatment with prednisolone developed a moderate relative lymphocytopenia, whereas treatment with Vepesid resulted in a severe monocytopenia. Since prednisolone treatment only partially prevented plaque formation, whereas Vepesid seemed to fully inhibit the development of plaques, we conclude that although a role of the lymphocyte in the process of plaque formation cannot be excluded, the monocyte seems to play a crucial role in the pathogenesis of radiation-induced atheromatosis. 相似文献
103.
104.
L van Bree J Commandeur B Lamberts M Cornelissen M van Roon H Laterveer J de Vries 《Journal of biochemical toxicology》1990,5(1):57-63
The effects of pretreatment with symmetrically dihalogenated biphenyls (DXBs, X-F, Cl(C), Br(B) and I) on rat liver drug metabolism enzymes were investigated. 4,4'-DFB, -DCB, and -DBB as well as 2,2'-DFB appeared to be inducers of microsomal cytochrome P-450-linked monoxygenases (N-demethylases of aminopyrine and ethylmorphine). However, no structure-induction relationship was found. 4,4'-DXBs also induced a cytochrome P-448-linked mono-oxygenase (ethoxyresorufin O-deethylase), and their order of induction potential seemed to parallel the increase of the size of the halogen substituent. Therefore, 4,4'-DXB's may be categorized as mixed-type inducers, the cytochrome P-450 component being the more pronounced. Data on the cytochrome P-448 induction by dihalogenated biphenyls with only para substituents may be considered as a refinement of the previously described structure-activity relationship in this respect. All of the DXBs except 3,3'-DCB and 4,4'-DIB, enhanced, like phenobarbital, the activity of UDP-glucuronyltransferase toward 4-hydroxybiphenyl. Only 4,4'-DFB was able to induce the activity of glutathione S-transferase toward 1,2-epoxy-3-(p-nitrophenoxy)propane. Studies after 4,4'-DBB-treatment revealed, like phenobarbital, a preferential induction of ethylmorphine N-demethylase on rough endoplasmic reticulum-derived microsomes, whereas UDP-glucuronyltransferase activity toward 4-hydroxybiphenyl was induced to a larger extent on smooth endoplasmic reticulum microsomes, suggesting a dissimilar enzyme induction in microsomal subfractions. 相似文献
105.
106.
Lloyd G. Simonson Robert W. Gaugler Burton L. Lamberts David A. Reiher 《Biochimica et Biophysica Acta (BBA)/General Subjects》1982,715(2):189-195
An endo-1, 3-α-D-glucanase (EC 3.2.1.59) was purified from cell-free culture supernatants of Pseudomonas NRRL-B-12324. The enzyme was purified 8.7-fold to a specific activity of 78.1 U/mg of protein. The enzyme was inducible and had an isolectric point of 4.6 and a Km of 80.0 mM in terms of anhydroglucose units. Two distinct peaks of activity were resolved by gel filtration with two different supporting media, whereas only one peak of activity was resolved by isoelectricfocusing. The two peaks were assigned molecular weight values of 67 400 and 279 000. The pH optimum was near 5.0 and the temperature optimum was near 56°C. Additional gel filtration data indicated that the enzyme functions as an endohydrolase. 相似文献
107.
Somatostatin receptors in normal and tumoral tissue 总被引:3,自引:0,他引:3
Somatostatin receptors have been visualized with autoradiography and characterised biochemically in various somatostatin target tissues, such as brain, pituitary, pancreas and gastrointestinal tract, where they are likely to mediate the somatostatin actions. With the same methods, somatostatin receptors have been detected also in tumors originating from somatostatin target tissues: high receptor incidence is found in GH-producing pituitary adenomas as well as in some hormone-producing gastrointestinal tumors. These tumors are often highly responsive to somatostatin analogs in vivo. Among brain tumors, meningiomas usually contain a high density of receptors, suggesting a novel function for somatostatin in the human meninges. Among other human tumors tested, prostate, ovarian and endometrial carcinomas were free of receptors whereas 3 out of 39 mammary tumors contained somatostatin receptors. 相似文献
108.
109.
S W Lamberts R Angement A van der Heijden J W Wladimiroff W H Hackeng F H de Jong 《Hormone research》1987,27(4):195-199
The course of plasma beta-endorphin/beta-lipotropin, cortisol and prolactin (PRL) levels was followed from 0.5 till 5 h after normal delivery in 13 healthy women. Six subjects who did not want to breast-feed their child received 2.5 mg bromocriptine orally 1 h after delivery. After 3 h the effect of the intravenous administration of 200 micrograms thyrotropin-releasing hormone (TRH) was also measured. Elevated plasma beta-endorphin and cortisol levels decreased after delivery in a (log) linear fashion which was not influenced by bromocriptine. TRH elicited a significant short-lived identical increase in plasma beta-endorphin/beta-lipotropin concentrations in the control and the bromocriptine-treated subjects. TRH similarly delayed the rapid decline in plasma cortisol levels in both groups of women. Basal and TRH-induced PRL levels were rapidly suppressed by bromocriptine. These studies show the presence of a paradoxical increase of beta-endorphin/beta-lipotropin and cortisol levels in response to TRH occurring shortly after delivery in normal women. This response cannot be mediated by the placenta. The absence of an inhibiting effect of bromocriptine on basal and TRH-induced beta-endorphin and cortisol release does not lend support to the hypothesis of the presence of a functionally active intermediate pituitary lobe in man early in puerperium. 相似文献
110.
S W Lamberts 《Hormone research》1988,29(2-3):118-120
Experience with SMS 201-995 (Sandostatin), a somatostatin analog, in the treatment of endocrine active gastrointestinal tumors is reviewed. Best immediate results were obtained in vipomas and insulinomas but a scape phenomenon was frequently observed. A positive and persistent effect was recorded in a case of nesidioblastosis. It was striking that good clinical control could be obtained in some instances despite insufficient suppression of hormone secretion by the tumor. This finding suggests peripheral actions of somatostatin and SMS independently of its primary effect on hormone release. 相似文献