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Dive into the research topics where M.T.J. van der Meer is active.

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Featured researches published by M.T.J. van der Meer.


Laboratory Animals | 2001

Use of score sheets for welfare assessment of transgenic mice

M.T.J. van der Meer; A. Rolls; V. Baumans; Berend Olivier; L.F.M. van Zutphen

The use of transgenic mice has increased dramatically in recent years and continues to increase further. However, because transgenesis may alter a balanced genotype and produce unpredictable effects, careful monitoring of health and welfare of the transgenic animal is advised. The present study assessed the feasibility of the use of score sheets for monitoring transgenic mice, as part of daily routine, in a transgenic unit. The score sheets used were based on parameters which are sensitive and easy to determine. The score sheets were used by two animal technicians and a thorough evaluation showed that the score sheets, as described in this paper, are useful for routine monitoring in a transgenic unit and may result in the early detection of animal welfare problems. However, notwithstanding the limited number of parameters included and the restricted age-span covered by the screening, the monitoring system was considered to be time consuming. Large-scale implementation of such a scoring system during the first weeks of life would increase daily care time by at least 15-20 min for an average litter of 4-6 pups. Nevertheless, the use of score sheets seems to be a prerequisite for monitoring the animals welfare in the course of producing transgenic lines.


Paleoceanography | 2010

Sensitivity of Red Sea circulation to monsoonal variability during the Holocene: An integrated data and modeling study

E. Biton; Hezi Gildor; G. Trommer; Michael Siccha; Michal Kucera; M.T.J. van der Meer; Stefan Schouten

Received 20 October 2009; revised 6 March 2010; accepted 30 June 2010; published 4 November 2010. [1] We used an oceanic general circulation model to evaluate the sensitivity of the hydrography and circulation of the Red Sea in response to reduced sea level and modified atmospheric conditions during the Holocene. With Holocene sea level close to the modern level, the Red Sea was sensitive to changes in atmospheric conditions, and it only shows a relatively mild response to sea level change. Changes in the monsoon system influence the exchange flow through the Strait of Bab el Mandab, the meridional overturning circulation of the Red Sea, and its hydrography. Forced by humid conditions the (modeled) Red Sea temperature increased by ∼1.5°C, while when arid conditions were imposed, the temperature decreased by ∼2.5°C. Similar heating and cooling events during the early and late Holocene are seen in a sea surface temperature record from the northern Red Sea (derived from the temperature sensitive TEX86 molecular biomarker), which suggests that humid conditions prevailed during the early Holocene and more arid conditions prevailed during the late Holocene. The gradual decline in Red Sea temperature between these two time periods suggests a gradual decline in the summer monsoon strength. This monsoon trend and the resulting changes in the Red Sea circulation are supported by the distribution of crenarchaea fossil lipids in Red Sea sediments from this period. Monsoon‐ driven changes in the exchange flow through the Strait of Bab el Mandab affected the crenarchaea population structure, and therefore, their molecular fossil distribution in the sediments of the Red Sea potentially provides an index for the summer monsoon strength during the Holocene.


Organic Geochemistry | 1999

All-cis hentriaconta-9,15,22-triene in microbial mats formed by the phototrophic prokaryote Chloroflexus

M.T.J. van der Meer; Stefan Schouten; David M. Ward; Jan A. J. Geenevasen; Jaap S. Sinninghe Damsté

All-cis hentriaconta-9,15,22-triene (I) has been isolated from Chloroflexus mats, Yellowstone National Park (USA), and identified by GC-(HR)MS analysis of I and its hydrogenated and DMDS-derivatized products and by 1H and 13C NMR spectroscopy.


Geobiology | 2013

Comparison of intact polar lipid with microbial community composition of vent deposits of the Rainbow and Lucky Strike hydrothermal fields.

Robert A. Gibson; M.T.J. van der Meer; Ellen C. Hopmans; Anna-Louise Reysenbach; Stefan Schouten; J.S. Sinninghe Damsté

The intact polar lipid (IPL) composition of twelve hydrothermal vent deposits from the Rainbow (RHF) and Lucky Strike hydrothermal fields (LSHF) has been investigated in order to assess its utility as a proxy for microbial community composition associated with deep-sea hydrothermal locations. Gene-based culture-independent surveys of the microbial populations of the same vent deposits have shown that microbial populations are different in the two locations and appear to be controlled by the geochemical and geological processes that drive hydrothermal circulation. Large differences in the IPL composition between these two sites are evident. In the ultramafic-hosted RHF, mainly archaeal-IPLs were identified, including those known to be produced by hyperthermophilic Euryarchaeota. More specifically, polyglycosyl derivatives of archaeol and macrocyclic archaeol indicate the presence of hyperthermophilic methanogenic archaea in the vent deposits, which are related to members of the Methanocaldococcaceae or Methanococcaceae. In contrast, bacterial IPLs dominate IPL distributions from LSHF, suggesting that bacteria are more predominant at LSHF than at RHF. Bacterial Diacyl glycerol (DAG) IPLs containing phosphocholine, phosphoethanolamine or phosphoglycerol head groups were identified at both vent fields. In some vent deposits from LSHF ornithine lipids and IPLs containing phosphoaminopentanetetrol head groups were also observed. By comparison with previously characterized bacterial communities at the sites, it is likely the DAG-IPLs observed derive from Epsilon- and Gammaproteobacteria. Variation in the relative amounts of archaeal versus bacterial IPLs appears to indicate differences in the microbial community between vent sites. Overall, IPL distributions appear to be consistent with gene-based surveys.


Physiology & Behavior | 2001

Behavioral and physiological effects of biotechnology procedures used for gene targeting in mice

M.T.J. van der Meer; V. Baumans; Berend Olivier; Cas Kruitwagen; J. E. van Dijk; L.F.M. van Zutphen

The effects of gene-targeting procedures on the behavior and physiological development of (chimeric) mice have been investigated. We used six groups of mice, each of them undergoing specific aspects of the biotechnological procedure, including electroporation, microinjection, and/or blastocyst culture. Changes in behavior and physiological development of the progeny (age 4-30 weeks) were investigated. Besides increased body weights, no significant difference between the six treatment groups and untreated C57BL/6 controls could be attributed to the biotechnology procedures. Therefore, we conclude that these procedures per se do not induce significant discomfort for the offspring. Differences in behavior, observed for the two groups of chimeric mice [one derived from electroporated embryonic stem (ES) cells and the other from nonelectroporated ES cells] when compared to the other (nonchimeric) groups, are, at least partly, due to the genetic background of the 129/Ola strain from which the ES cells are derived rather than to the biotechnological manipulations of the ES cells and/or blastocysts. The occurrence of hermaphrodites (8%) and some other gross pathologies observed in both groups of chimeric animals seem to indicate that developmental problems may occur when cells from different origin are simultaneously contributing to the development of one individual. This implies that during the production of gene-targeted mice, health and welfare of chimeric animals must be carefully monitored.


Fems Microbiology Letters | 2015

Comparison of the effect of salinity on the D/H ratio of fatty acids of heterotrophic and photoautotrophic microorganisms

Sandra M Heinzelmann; David Chivall; D. M'boule; Daniëlle Sinke-Schoen; Laura Villanueva; J.S. Sinninghe Damsté; Stefan Schouten; M.T.J. van der Meer

The core metabolism of microorganisms has a major influence on the hydrogen isotopic composition of their fatty acids. Heterotrophic microorganisms produce fatty acids with a deuterium to hydrogen (D/H) ratio either slightly depleted or enriched in D compared to the growth water, while photo- and chemoautotrophic microorganisms produce fatty acids which are heavily depleted in D. However, besides metabolism other biochemical and environmental factors (i.e. biosynthetic pathways, growth phase and temperature) have been shown to affect the D/H ratio of fatty acids, and it is necessary to evaluate the magnitude of these effects compared to that of metabolism. Here, we show that the effect of salinity on the D/H ratio of fatty acids depends on the core metabolism of the microorganism. While fatty acids of the photoautotroph Isochrysis galbana become more enriched in D with increasing salinity (enrichment of 30-40‰ over a range of 25 salinity units), no effect of salinity on the D/H ratio of fatty acids of the heterotrophic Pseudomonas str. LFY10 was observed ((ε)lipid/water of the C16:0 fatty acid of ~120‰ over a range of 10 salinity units). This can likely be explained by the relative contributions of different H and nicotinamide adenine dinucleotide phosphate sources during fatty acid biosynthesis.


Archive | 1997

Welfare Aspects of Transgenic Animals

L.F.M. van Zutphen; M.T.J. van der Meer

What do you do to start reading welfare aspects of transgenic animals? Searching the book that you love to read first or find an interesting book that will make you want to read? Everybody has difference with their reason of reading a book. Actuary, reading habit must be from earlier. Many people may be love to read, but not a book. Its not fault. Someone will be bored to open the thick book with small words to read. In more, this is the real condition. So do happen probably with this welfare aspects of transgenic animals.


Archive | 1997

Use of Transgenic Animals and Welfare Implications

M.T.J. van der Meer; L.F.M. van Zutphen

This paper presents the results of a literature survey and an inquiry intended to gain insight into the extent of use of transgenic animals in EU-Member States and into the potential effects of transgenesis on the health and welfare of the animals. Screening of the Medline database revealed data for quantifying research with transgenic animals and for estimating the number of institutes working with these animal models. Questionnaires have been sent to the national contact points (NCPs, i.e. governmental representatives for legislative issues on animal protection) of the EU-Member States. From the responses to the questionnaires and the information available in the literature, the conclusion could be reached that the degree of suffering caused by the experimental procedures and insertional mutations is, in general, less severe than the welfare problems caused by the direct effect of the expression of the transgene. However, only very few data are presently available to substantiate this conclusion. Further research is necessary to identify and quantify indicators of discomfort in the animals involved in the process of transgenesis. A proposal is made for the development of a model protocol, to be used as a standard operating procedure for evaluating adverse effects in the process of producing transgenic animals.


Biogeosciences | 2009

Assessment of soil n -alkane δ D and branched tetraether membrane lipid distributions as tools for paleoelevation reconstruction

Francien Peterse; M.T.J. van der Meer; Stefan Schouten; G. Jia; Jort Ossebaar; Jord Blokker; J.S. Sinninghe Damsté


Climate of The Past | 2013

Salinity changes in the Agulhas leakage area recorded by stable hydrogen isotopes of C 37 alkenones during Termination I and II

S. Kasper; M.T.J. van der Meer; Anchelique Mets; Ralph Zahn; J.S. Sinninghe Damsté; Stefan Schouten

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Stefan Schouten

Delft University of Technology

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G. Trommer

University of Tübingen

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E. Biton

Weizmann Institute of Science

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Hezi Gildor

Hebrew University of Jerusalem

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Albert Benthien

Alfred Wegener Institute for Polar and Marine Research

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