Biomedical subjects

Elke Zimmermann

Publications and source records attributed to Elke Zimmermann.

14 recordsLinked to original sources

PubMed2006

The ever-increasing diversity in mouse lemurs: three new species in north and northwestern Madagascar.

Mouse lemurs (Microcebus spp.) are the world's smallest primates and endemic to Madagascar. Several recent taxonomic revisions resulted in an extraordinary increase of recognized species. What still was considered as being two species at the beginning of the 20th century is currently recognized as 12 taxa. Based on fur coloration pattern, they can be divided into grayish and reddish forms. Two major models have been proposed to explain the extensive speciation events in the Malagasy fauna. The best known suggests that major rivers and mountains combine to act as effective barriers to gene flow and thereby facilitate allopatric speciation processes. A more recent model used an analysis of watersheds in the context of Quaternary climatic shifts to explain the process of explosive speciation on the island. We tested these two models by covering the areas between all major rivers (n=8) in northwestern and northern Madagascar. Mouse lemurs were systematically caught, sampled and morphometrically characterized in 25 sites (with 2-49 individuals per site and species). A complete phylogeny was constructed on the basis of the sequences of three mitochondrial loci (in total 1296 bp). The phylogenetic data revealed a previously unknown biodiversity with three new mouse lemur species among the reddish forms, each having a very small distribution, i.e., being restricted to only one Inter-River-System (IRS). Morphometric analyses underlined their distinctiveness and a brief formal species description is provided. In contrast to the reddish forms, grayish forms have a very low species diversity coupled with broad distributions that cover more than one IRS. These differences among the species are discussed as outcome of divergent colonization scenarios. Elements of both biogeographic models are combined in a new hypothesis that aims to explain the speciation process leading to the present distribution of mouse lemurs in Madagascar.

Analysis of Variance↗

PubMed2006

The role of survival for the evolution of female philopatry in a solitary forager, the grey mouse lemur (Microcebus murinus).

It is widely accepted that natal philopatry is a prerequisite for the evolution of sociality. The life-history hypothesis maintains that longevity of adults results in extended territory tenure and thus limits breeding vacancies for offspring, which makes natal philopatry more likely. Here, we tested the importance of longevity for natal philopatry in females of a basal primate, the grey mouse lemur (Microcebus murinus). This species is regarded as being solitary due to its foraging habits but while males disperse, female offspring in this species forgo dispersal and form long-term sleeping groups with their mothers. We tested whether high adult survival could be a cause for natal philopatry of female offspring. In addition, we assessed costs and benefits associated with space sharing between mothers and daughters and whether mothers actively increase survival of daughters by beqeauthal of territories, information transfer about resources or thermoregulation. Contrary to our predictions, adult females had low-survival rates. Space sharing appeared to improve survival of both, mothers and daughters. This could be a result of information transfer about sleeping sites and thermoregulatory benefits. Our results cast doubt on the idea that longevity predisposes species for social traits and provide support for benefits of philopatry.

Animals↗

PubMed2006

L-diabetes--causes, pathogenesis and therapy.

L-diabetes represents a subtype of non-autoimmunopathic and non-adipose diabetes mellitus. It is hypothesized that ATP-sensory brain centres measure the cerebral ATP concentration and announce a hypoglycaemia if the setpoint is undercut. The disease involves a decreased ATP formation in the CNS that is independent of blood glucose levels, and that leads to a "hypoglycaemia" false alarm. UGT1-polymorphisms, a sensitive sympathetic system, an IgM deficit and an increased porousity of the mucous membrane of the small intestine have been postulated in its etiology. These causative factors bring about increasing amounts of toxins and radicals which impair the ATP generation in the CNS so that through the announcement of a non-existing hypoglycaemia the release of the insulin antagonists hGH, cortisol and adrenaline is induced.

Adenosine Triphosphate↗

PubMed2006

Molecular phylogeny and taxonomic revision of the sportive lemurs (Lepilemur, Primates).

BACKGROUND: The number of species within the Malagasy genus Lepilemur and their phylogenetic relationships is disputed and controversial. In order to establish their evolutionary relationships, a comparative cytogenetic and molecular study was performed. We sequenced the complete mitochondrial cytochrome b gene (1140 bp) from 68 individuals representing all eight sportive lemur species and most major populations, and compared the results with those obtained from cytogenetic studies derived from 99 specimens. RESULTS: Interspecific genetic variation, diagnostic characters and significantly supported phylogenetic relationships were obtained from the mitochondrial sequence data and are in agreement with cytogenetic information. The results confirm the distinctiveness of Lepilemur ankaranensis, L. dorsalis, L. edwardsi, L. leucopus, L. microdon, L. mustelinus, L. ruficaudatus and L. septentrionalis on species level. Additionally, within L. ruficaudatus large genetic differences were observed among different geographic populations. L. dorsalis from Sahamalaza Peninsula and from the Ambanja/Nosy Be region are paraphyletic, with the latter forming a sister group to L. ankaranensis. CONCLUSION: Our results support the classification of the eight major sportive lemur taxa as independent species. Moreover, our data indicate further cryptic speciation events within L. ruficaudatus and L. dorsalis. Based on molecular data we propose to recognize the sportive lemur populations from north of the Tsiribihina River, south of the Betsiboka River, and from the Sahamalaza Peninsula, as distinct species.

Animals↗

PubMed2006

Loud calling, spacing, and cohesiveness in a nocturnal primate, the Milne Edwards' sportive lemur (Lepilemur edwardsi).

Dispersed pair-living primates provide a unique model for illuminating the evolution of mechanisms regulating spacing and cohesiveness in permanently cohesive groups. We present for the first time data on the spatiotemporal distribution and loud-calling behavior of the Milne Edwards' sportive lemur, known to forage solitarily during the night, but to form stable male-female sleeping groups during the day. Data include radio-tracking observations of sleeping associations, and focal follows of pair partners during dispersal in the evenings and reunions in the mornings. Male-female pairs forming stable sleeping associations during the day were pair-bonded. They used sleeping sites and home ranges exclusively, and exchanged loud calls at potentially restricted resources during dispersal in the evenings and during reunion in the mornings. Direct agonistic conflicts between pairs and others were rare. The acoustic analysis of loud calls revealed nine major call types. They carry signatures for sex and pair identity, and provide the substrate for signaling and the potential for recognizing pair ownership. Thus, pairs use loud call exchanges as a vocal display for signaling territory ownership, thus limiting direct aggressive encounters between neighbors and strangers. Altogether, our findings provide the first empirical evidence for the hypothesis that loud calling has evolved as a key mechanism for regulating space use and cohesiveness in dispersed pair-living primates.

Animals↗

PubMed2006

New East-Westfalian Postoperative Therapy Concept: a telemedicine guide for the study of ambulatory rehabilitation of patients after cardiac surgery.

In-hospital rehabilitation can improve recovery of patients after surgery, but also contributes to the high costs of the German health system. A telemedicine-based rehabilitation used in the home as an alternative to in-hospital rehabilitation was evaluated in a pilot study. In an open trial, 170 patients performed a 3-month ambulatory rehabilitation after cardiac surgery. There were two groups (group 1 [n = 70] and group 2 [n = 100]). Group 1 participated in conventional in-hospital rehabilitation. Group 2 received ambulant rehabilitation using telemedicine. Physical performance, quality of life, (measured with a questionnaire), complications and costs were assessed and compared between the two groups. Maximal physical performance (MPP) was assessed at 6 and at 12 months after cardiac surgery. It was significantly increased by 46-54 watts in both study groups compared to their baseline value. Moreover, physical and psychological quality of life had increased in both study groups compared to baseline values. However, group 2 was the only group to show statistical significance in all categories. Fewer incidents of angina pectoris were reported within the study interval in group 2 compared to group 1 (p < 0.01). The total cost of rehabilitation was 58% lower in group 2 compared to group 1. Ambulatory rehabilitation using telemedicine improves physical performance, quality of life, is safe, and is inexpensive. Our data indicate that home-based rehabilitation is more effective than in-hospital rehabilitation for patients after cardiac surgery.

Ambulatory Care↗

PubMed2005

[New Eastern Westfalian Postoperative Therapeutic Concept (NOPT). A telemedically guided study for ambulatory rehabilitation of patients after cardiac surgery].

BACKGROUND AND PURPOSE: In-hospital rehabilitation can improve recovery of patients after surgery, but also contributes to the high costs of the German health system. Therefore, the possibility of a telemedically monitored rehabilitation at home as an alternative to an in-hospital rehabilitation was evaluated in a pilot study. PATIENTS AND METHODS: In an open trial, 100 patients performed an ambulatory rehabilitation after heart surgery under coverage of telemedical monitoring for 3 months. 70 patients performed a regular conventional in-hospital rehabilitation for 3 weeks. Physical performance, quality of life (questionnaire), complications, and costs were assessed and compared between the two groups. RESULTS: 6 and also 12 months after surgery, maximal physical performance was significantly increased by 46-54 W in both study groups compared to their baseline value. Moreover, physical and psychological quality of life had increased in both study groups compared to baseline values. However, only in the ambulatory group all items had increased with statistical significance. Fewer insults of angina pectoris were reported during follow-up in the ambulatory group compared to the in-hospital group (p < 0.01). Total costs of the rehabilitation were 59% lower in the ambulatory group compared to the in-hospital group. CONCLUSION: An ambulatory rehabilitation improves physical performance, quality of life, and is safe and cheap. The data of this study indicate that rehabilitation at home can be established instead of an in-hospital rehabilitation for patients after heart surgery.

Adult↗

PubMed2004

First experimental evidence for female mate choice in a nocturnal primate.

Female mate choice can be hypothesised in most nocturnal primates, since females show a higher investment in their offspring than males. The aim of this experimental study was to investigate if female grey mouse lemurs perform mate choice and whether age, relatedness (to the male), or male advertisement call activity systematically influence their decisions. A two-way mate choice design was developed in which females could choose between two males. Mate choice was deduced from the time spent in proximity to the males and from mating behaviour. During oestrus 12 of 17 females participated actively in the experiment and all of them showed either a significant spatial (n = 11) or behavioural (n = 1) preference for one male. In four cases copulations were observed. The influence of age on female mate choice was not statistically significant. In the cases with copulations, however, females mostly preferred the older male. This might indicate a preference for older age as an indicator of experience, fitness, and/or status. The influence of relatedness on female mate choice could not be definitely clarified. However, results imply a mechanism of kin recognition on the basis of familiarity. In the majority of choices, females preferred the male with higher trill call activity. Since trill call activity correlates with the relative dominance status of males, these results suggest an importance of the male dominance status for female mate choice in grey mouse lemurs. Altogether our findings indicate that females use a complex of different cues to choose their mates.

Age Factors↗

PubMed2004

Social organization of the golden brown mouse lemur (Microcebus ravelobensis).

Our study provides the first data on the social organization of the golden brown mouse lemur, a nocturnal primate discovered in northwestern Madagascar in 1994. The study was carried out in two 6-month field periods during the dry season, covering time before and during the mating season. The spatial and temporal distributions of the sexes in the population were investigated by mark/recapture and radiotelemetry. Focal observations and the determination of sleeping associations provided further insights into the sociality of this solitary forager. High intra- and intersexual home-range overlaps occurred throughout the study. In general, individuals of both sexes had spatial access to more than one conspecific of the same and the opposite sex. We found no indication for spatial monopolization of females by certain males. These results suggest a dispersed multimale/multifemale system with a promiscuous mating pattern. Individuals showed temporal stability in their home range locations and interacted regularly with conspecifics. Five sleeping groups were identified during the study period: one female group and four mixed-sex groups. Even though sleeping sites were changed frequently, sleeping-group compositions remained stable over time. Thermoregulatory constraints are the most likely explanation for sleeping-group composition with members of both sexes in this species. Mixed-sex sleeping groups can be described as the basic social unit within this dispersed multimale/multifemale society.

Animals↗

PubMed2003

[Peer-education workshop on research during medical studies. Results of a survey among participants].

BACKGROUND AND OBJECTIVE: Physicians in Germany are conferred the title "Doctor of medicine" (MD) upon successful completion of a dissertation. There is no course in the German medical curriculum that enables students to pursue original research. CONCEPT AND METHODS: We sought to address this lack of adequate preparation through a student-organized, hands-on workshop, which was problem- and, in part, computer-based. The workshop lasted 16 h (over the course of a weekend). The chronological sequence of a dissertation served as the main structure of this peer-education approach and was supported by a 30-page handout. The following topics were addressed: (1) Search for a dissertation, (2) Legal regulations, (3) Literature research and statistics, (4) Scientific writing, (5) Practical work, and (6) Review of the dissertation. The participants gained knowledge about and started working with the appropriate computer applications for these issues. So far, 60 students participated in four workshops. Evaluations were collected through an anonymous questionnaire at the end of the workshops. RESULTS: 56 students responded (93%). 98% of the respondents would definitely recommend other students to participate in the workshop. None of them recommend against taking the class. Students' opinion about their own skills in pursuing a dissertation before and at the end of the workshop (range: 1 = very good to 5 = unsatisfying) was 3.4 +/- 0.8 and 1.8 +/- 0.5, respectively ( p < 0.001). No student believed that his skills did not improve. 88% of the respondents wanted the workshop to continue being optional. CONCLUSIONS: This peer-education approach is cost-efficient, enjoys high acceptance by students, and improves research skills among participants.

Academic Dissertations as Topic↗

PubMed2003

Seasonal changes in general activity, body mass and reproduction of two small nocturnal primates: a comparison of the golden brown mouse lemur ( Microcebus ravelobensis) in Northwestern Madagascar and the brown mouse lemur ( Microcebus rufus) in Eastern Madagascar.

To investigate for the first time the relationship between contrasting patterns of seasonal changes of the environment and activity, body mass and reproduction for small nocturnal primates in nature, we compared a population of golden brown mouse lemur ( Microcebus ravelobensis) in a dry deciduous forest of northwestern Madagascar and of the brown mouse lemur ( Microcebus rufus) in an evergreen rain forest of eastern Madagascar. Both species live under similar photoperiodic conditions. Golden brown mouse lemurs (GBML) were active during the whole period (May to December) irrespective of changing environmental conditions. In contrast, a part of the population of brown mouse lemurs (BML) showed prolonged seasonal torpor, related to body mass during periods of short day length and low ambient temperatures. Differences between species might be due to differences in ambient temperature and food supply. Body weight and tail thickness (adipose tissue reserve) did not show prominent differences between short and long photoperiods in GBML, whereas both differ significantly in BML, suggesting species-specific differences in the photoperiodically driven control of metabolism. Both species showed a seasonal reproduction. The rate of growth and size of the testes were similar and preceded estrous onset in both species suggesting a photoperiodic control of reproduction in males. The estrous onset in females occurred earlier in GBML than in BML. Estrous females were observed over at least 4 months in the former, but in only 1 month in the latter species. Intraspecific variation of estrous onset in GBML may be explained by body mass. Interspecific variation of female reproduction indicates species-specific differences in the control of reproduction. Thus, environmentally related differences in annual rhythms between closely related small nocturnal lemurs emerged that allow them to cope with contrasting patterns of seasonal changes in their habitats.

Animals↗

PubMed2003

Species-specific usage of sleeping sites in two sympatric mouse lemur species (Microcebus murinus and M. ravelobensis) in northwestern Madagascar.

We investigated the sleeping site ecology of two sympatric mouse lemur species (Microcebus murinus and M. ravelobensis) in northwestern Madagascar during the second half of the dry season with respect to the type, quality, and usage pattern of the sleeping sites, as well as to social sleeping habits and response to potential threats. The type and quality of the sleeping sites differed between the two species. M. murinus used protected wooden shelters (tree holes) more frequently than M. ravelobensis, and M. ravelobensis used a broader variety of less protected sites (e.g., branches, lianas, and leaves) than M. murinus. Whereas male M. murinus usually slept alone, and female M. murinus mostly slept in groups, both sexes of M. ravelobensis slept in mixed-sex sleeping groups. M. murinus relied on crypsis in their sleeping sites, whereas M. ravelobensis regularly showed a flight response to the approach of an observer. This behavioral difference could indicate an adaptation to a higher predation risk in less protected sleeping sites. Whereas female M. murinus showed a high site fidelity, male M. murinus and both sexes of M. ravelobensis frequently changed their sleeping sites, which may also be interpreted as an antipredator strategy. The results are discussed with respect to three possible ecological explanations: interspecies competition, restricted resource availability, and niche differentiation. The latter is the most likely explanation for these interspecific differences.

Animals↗

PubMed2003

Pair-specific usage of sleeping sites and their implications for social organization in a nocturnal Malagasy primate, the Milne Edwards' sportive lemur (Lepilemur edwardsi).

Safe sleeping sites may be a limited resource crucial for survival. In order to investigate their potential significance for social organization in nocturnal primates, we analyzed the spatial distribution of daily sleeping sites, their characteristics, their usage, and sleeping group compositions in the nocturnal Milne Edwards' sportive lemur during a 6-month field study in the dry deciduous forest of northwestern Madagascar. Sexes did not differ either in body size or in body mass. Sleeping sites were used almost exclusively by adult male-female pairs. Individuals showed a high sleeping-site fidelity limited to 2-3 different sleeping sites in close vicinity during the whole study period. Most females showed a higher fidelity to one distinct sleeping site than their male partners. Sleeping groups consisted of one adult male and one adult female and remained stable in composition over the whole study period. Exclusive pair-specific usage of sleeping sites suggests sleeping site related territoriality of male-female pairs, perhaps influenced by inter- and intrasexual resource competition. Results give first insights into the distribution patterns and social organization of this species. They imply dispersed monogamy for the Milne Edwards' sportive lemur, with sleeping sites as a potentially restricted and defendable resource.

Animals↗

PubMed2002

Characterization and phylogenetic relationship of prosimian MHC class I genes.

MHC class I cDNA sequences from the most divergent primate group of extant primates compared to human, the suborder Strepsirrhini (prosimians), are described. The sequences are derived from the gray mouse lemur (Microcebus murinus) and the ring-tailed lemur (Lemur catta), which are members of the malagasy Lemuriformes, as well as from the pygmy slow loris (Nycticebus pygmaeus), a prosimian from East Asia. The M. murinus sequences have been analyzed in detail. Analysis of the expression level, G/C content, and synonymous vs. nonsynonymous substitution rates in the peptide-binding region codons suggests that these cDNA clones represent classical class I (class Ia) genes. According to Southern blot analysis, the genome of the gray mouse lemur might contain about 10 class I genes. In gene tree analysis, the strepsirrhine class Ia genes described here cluster significantly separately from the known class I genes of Catarrhini (humans, apes, Old World monkeys) and Platyrrhini (New World monkeys) species, suggesting that the class I loci of Simiiformes arose by gene duplications which occurred after the divergence of prosimians.

Amino Acid Sequence↗