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Biomedical subjects

A E Müller

Publications and source records attributed to A E Müller.

11 recordsLinked to original sources
PubMed1999

Palindromic sequences and A+T-rich DNA elements promote illegitimate recombination in Nicotiana tabacum.

Illegitimate recombination is the prevailing molecular mechanism for the integration of recombinant DNA into the genome of most eukaryotic systems and the generation of deletions by intrachromosomal recombination. We developed a ?selectable marker system to screen for intrachromosomal illegitimate recombination events in order to assess the sequence and structure-specific requirements for illegitimate recombination in tobacco. In 12 illegitimate recombination products analysed, we found that all deletion termini localise to sites of palindromic structures or to A+T-rich DNA elements. All deletion termini showed microhomologies of two to six nucleotides. In three plants, the recombination products contained filler-DNA or an inversion of an endogenous segment. Our data strongly suggest that illegitimate recombination in plants is mediated by a DNA synthesis-dependent process, and that this mechanism is promoted by DNA regions that can form palindromic structures or facilitate DNA unwinding.

Adenosine↗
PubMed1999

Aspects of social life in the fat-tailed dwarf lemur (Cheirogaleus medius): inferences from body weights and trapping data.

Body weight is an important attribute of any animal and influences its biology in many ways. In the case of the fat-tailed dwarf lemur (Cheirogaleus medius), this is of special interest because animals of this species store fat to survive extended torpor phases during the austral winter and, as a result, show extreme seasonal variation in body weight. In this paper, I present field data from a 20-month study at the Forestry Station of Ampijoroa in northwestern Madagascar on body weights of repeatedly trapped individuals combined with trapping results to investigate the general biology and notably the social life of C. medius. The most remarkable physical characteristic of wild C. medius is a dramatic weight-loss in males in September following emergence from torpor. Trapping results showed that adult males emerge from torpor earlier than females and offspring, even though food is still scarce. Early emergence from torpor puts males at an energetic disadvantage and confers no advantage in terms of access to females. Observation data from nightly follows indicate that males patrol their home range, probably to guarantee its integrity for the coming active season and to secure the food supply for their families. The high energetic costs of this strategy is argued to represent a form of paternal investment. Body weight data of repeatedly captured individuals showed that they may reach adult size and sexual maturity at 2 years of age but are not socially mature before the age of 3 years. The data presented may serve as a guide for keeping C. medius at a suitable weight in captivity.

Animals↗
PubMed1999

Nails and claws in primate evolution.

The issue of whether nails or claws were present on the digits of the last common ancestor of living primates is central to the understanding of the ecological context in which the order originated. Two lines of evidence are available, the shape (claw, nail, toilet-claw) and the histological structure (one or two horny strata). Here we review the existing data regarding the shape and histological structure of cheirideal appendages in primates and present new information from a wide range of living primates. We demonstrate the presence of a typical toilet-claw in Daubentonia madagascariensis and discuss its consequences, since the alleged lack of such structures in this species has long obscured the issue. The general view that primate nails, with the exception of those in New World primates, consist of only one layer is disproved by the presence of two distinct strata in the nails of the feet of three out of seven catarrhine species examined, as well as in Lemur catta. The combined new and old data indicate that the last common ancestor of the extant primates had lost the typical mammalian claws of its ancestors and developed nails on all pedal digits except digit II, which bore a toilet-claw. All nails as well as the toilet-claw originally consisted of two layers. We present a new hypothesis regarding the adaptational significance of these changes.

Animals↗
PubMed1999

Analysis of von Willebrand factor in platelets of patients with various forms of von Willebrand disease: is there a clinical relevance?

UNLABELLED: Besides the investigation of coagulation factor VIII:c and von Willebrand factor in plasma. vWF antigen and vWF collagen-binding activity in platelets of 24 patients with various forms of von Willebrand disease were analysed. No platelet vWF:Ag or vWF:CBA was detectable in type 3 patients (n = 4). In contrast 6 out of 7 patients with type 2 vWD had normal or increased vWF levels. Two type I patients (out of n = 13) with low von Willebrand factor in platelets had no increased bleeding tendency. In two other individuals with normal amounts of von Willebrand factor in platelets and low plasmatic vWF and factor VIII:c, more frequent bleeding episodes reflecting the low plasmatic levels were observed in a long-term follow-up. CONCLUSION: In our patients, bleeding history corresponded to plasmatic levels of FVIII:c and vWF.

Antigens↗
PubMed1995

The transformation booster sequence from Petunia hybrida is a retrotransposon derivative that binds to the nuclear scaffold.

The transformation booster sequence (TBS) from Petunia hybrida enhances transformation frequencies in P. hybrida, Nicotiana tabacum and Zea mays. TBS also stimulates homologous inter- and intramolecular recombination in P. hybrida, the molecular basis for this stimulation is not known. We investigated whether TBS contains sequence elements that might contribute to the stimulation of recombination and whether its recombinogenic potential reflects a biological function of TBS. We identified a scaffold attachment region (SAR) within TBS and analysed its distribution in the genome and its homologies to other genomic sequences. A 516 bp subfragment of TBS binds to the nuclear scaffold. The sequence of the TBS-SAR fragment shows strong homologies to retroviral elements from plants, suggesting that TBS is an inactive derivative of a retrovirus that still promotes DNA recombination.

Base Sequence↗
PubMed1991

Bronchial neuroendocrine (carcinoid) tumor causing unilateral left-sided carcinoid heart disease.

A female patient suffering from a bronchial neuroendocrine tumor with unilateral left-sided carcinoid heart disease is reported. Repeated x-ray films of the chest showed a slowly growing lung tumor in the left lower lobe. The patient refused any diagnostic or therapeutic procedure to define the type of the tumor. During the follow-up of 24 years she developed severe mitral and moderate to severe aortic insufficiency, both invasively quantified by thermodilution techniques. During surgery for double valve replacement the patient died from left ventricular heart failure. Necropsy revealed the typical pattern of a bronchial neuroendocrine tumor without metastases. Examination of the heart disclosed the characteristic deposits of fibrous tissue on the cusps of both the mitral and the aortic valves whereas the right heart showed no abnormalities. Review of the literature suggests the unilateral left-sided carcinoid heart disease to be a very rare finding, its pathogenesis remains to be elucidated.

Aged↗
PubMed1981

Design of the mammalian respiratory system. IV Morphometric estimation of pulmonary diffusing capacity; critical evaluation of new sampling method.

The quality of morphometric data obtained by stereological methods depends on the sampling scheme adopted. In the light of recent advances in sampling theory for stereology a sampling strategy has been developed which differs significantly from that used in previous studies. It operates with a cascade of four sampling levels and adopts the principle of A-weighted sampling, a method that should eliminate bias and possibly yield smaller variances. This method is described and discussed in detail. When compared with the old simpler sampling approach it is found that the new method (1) is at least as efficient and (2) that the estimates of morphometric parameters obtained by this method are similar to the data generated by the old method.

Animals↗
PubMed1981

Comparison of two subsampling methods for electron microscopic morphometry.

The purpose of the present paper is twofold. Firstly, to compare the accuracy per unit cost achieved by two different methods of subsampling micrographs from sections of a material for stereology when the sections cannot be analysed as a whole at the required magnification. Secondly, to illustrate, by means of real data, the application of some of the methods and formulae proposed in the companion paper (Cruz-Orive & Weibel, 1981) for estimating ratios at the electron microscopic level. The final estimates of a same ratio obtained by either subsampling method (namely systematic (SQ) and systematic area-weighted quadrats (SAWQ)) agreed in the mean and they were about equally precise. The former fact indicates that the new SAWQ method is at least as reliable as the SQ method as far as bias is concerned. The latter result is a consequence of the well-known fact that subsampling is relatively unimportant in two-stage sampling. Yet, SAWQ subsampling enjoys definite practical advantages over other subsampling methods in certain situations.

Anatomy↗
PubMed1976

[Possible role of immune-phenomena in the pathogenesis of rheumatoid arthritis (author's transl)].

The R.A. is accompanied by a variety of different immune-phenomena. These are not restricted to the well known and diagnostically exploited IgM-rheumatoid factors in serum, but involve also rheumatoid factors of the Ig-classes G and A, which, at least partially are produced by lymphoid cells, which infiltrate the synovial membranes. These cellular infiltrations consist of macrophages, B and T lymphocytes, the latter being in excess. There is now good evidence that locally deposited, complement activating immune-complexes participate in the inflammatory lesions of the R.A.-joints by inducing the release of hydrolases from phagocytic cells. This event is also mediated by lymphokines and complement factors. Is is suggested that the pathogenicity of the immunoreactions occuring within the synovial tissue and fluid is a quantitative rather than a qualitative problem. In contrast to other tissues, the anatomy of the joint may favour the local accumulation of the immune-complexes. Moreover abundant immuno-reactions may be provided by a defective T-cell mediated control. Thus there is strong indication that immune-phenomena play an important role in the pathogenesis of R.A. This does not exclude the significance of metaboltic disturbances of the connective tissues for this disease.

Antigen-Antibody Complex↗
PubMed1976

[On the mode of action of antirheumatic drugs (author's transl)].

Since the etiology of rheumatoid arthritis presently is mostly unknown, the therapeutical efforts are focussed on attempts to influence the pathogeneic events occurring in this disease. Among the discussed pathogenic mechanisms aberration of immunereactions seem to play an important role. The drugs mainly used for basical treatment of rheumatoid arthritis are cytostatics, D-penicillamine, gold salts and chloroquine. The clinical experiences with these drugs and their mode of action are reviewed.

Antibiotics, Antineoplastic↗