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P Renner

Publications and source records attributed to P Renner.

18 recordsLinked to original sources
PubMed2001

C3-chiral tripodal amido complexes.

A comprehensive study into the coordination chemistry of two C3-chiral tripodal amido ligands has been carried out. The amido ligands contain a trisilylmethane backbone and chiral peripheral substituents. The amine precursors. HC(SiMe2NH[(S)-1-phenylethyl]]3 (1) and HC[SiMe2NH[(R)-1-indanyl]]3 (2) were found to be in equilibrium in solution with the cyclic diamines HC[SiMe2N[(S)-1-phenylethyl]2](SiMe2NH-[(S)-1-phenylethyl]] (3) and HC[SiMe2NH[(R)-1-indanyl]][SiMe2NH[(R)-1-indanyl]) (4), which are generated upon ejection of one molecule of the chiral primary amine. Reaction of these equilibrium mixtures with three molar equivalents of butyllithium instantaneously gave the trilithium triamides HC[SiMe2N(Li)[(S)-1-phenylethyl]]3 (5) and HC[SiMe2N(Li)[(R)-1-indanyl]]3 (6), both of which were characterised by an X-ray diffraction study. Both lithium compounds possess a central heteroadamantane core, in which the two-coordinate Li atoms are additionally weakly solvated by the three aryl groups of the chiral peripheral substituents, the Li-C contacts being in the range of 2.65-2.73 A. Reaction of 5 and 6 with [TiCl4(thf)2] and ZrCl4 gave the corresponding amido complexes [TiCl-[HC[SiMe2N[(S)-1-phenylethyl]]3]] (7), [TiCl(HC[SiMe2N[(R)-1-indanyl]]3]] (8), [ZrCl[HC[SiMe2N[(S)-1-phenylethyl]]3]] (9) and [ZrCl[HC[SiMe2N[(R)-1-indanyl]]3]] (10), respectively. Of these, compound 7 was structurally characterised by X-ray structure analysis and was shown to possess a C3-symmetrical arrangement of the tripod ligand. The chiral anionic dinuclear complex [Li-(OEt2)4][Zr2Cl3[HC[SiMe2N[(S)-1-phenylethyl]]3]2] (11) was isolated from reaction mixtures leading to 9. An X-ray diffraction study established its dimeric structure, in which the chiral amido ligands cap the two metal centres, which are linked through three symmetrically arranged, bridging chloro ligands. Reaction of 9 and 10 with a series of alkyl Grignard and alkyllithium reagents yielded the corresponding alkylzirconium complexes. X-ray structure analyses of [Zr(CH3)[HC[SiMe2N[(S)-1-phenylethyl]]3]] (12) and [Zr(CH3)-[HC[SiMe2N)[(R)-1-indanyl]]3]] (20) established their detailed molecular arrangements. While the reaction of 12 with the aryl ketones PhC(O)R (R = CH = CHPh, iPr, Et) gave the corresponding C-O insertion products, which contain an additional chiral centre in the alkoxy group, with low stereoselectivity (0-40% de). The corresponding conversions with several aryl aldehydes yielded the alkoxo complexes with high stereoselectivity. Upon hydrolysis, the chiral alcohols were isolated and shown to have enantiomeric excesses between 68 and 82%. High stereodiscrimination was also observed in the insertion reactions of several chiral ketones and aldehydes. However, this was shown to originate primarily from the chirality of the substrate. In analogous experiments with carbonyl compounds, the ethyl- and butyl-zirconium analogues of 12 did not undergo CO insertion into the metal-alkyl bond. Instead, beta-elimination and formal insertion into the metal-hydride bond occurred. It was found that the elimination of the alkene was induced by

Journal Article↗
PubMed2000

Implicit and explicit memory in autism: is autism an amnesic disorder?

Medial temporal lobe amnesic disorder is characterized by an impairment in explicit memory (e.g., remembering a shopping list) and intact implicit memory (e.g., a woman seems familiar although you cannot remember having met her before). This study examined whether children with high-functioning autism have this same dissociation between explicit and implicit memory abilities. Children with autism and normal development participated in three memory tasks: one implicit task (perceptual identification) and two explicit tasks (recognition and recall). Children with autism showed intact implicit and explicit memory abilities. However, they did not show the typical pattern of recalling more items from both the beginning and end of a list and instead only recalled items from the end of the list. These results do not support the theory that high-functioning autism is a type of medial temporal lobe amnesia. However, these findings suggest that persons with autism use different organizational strategies during encoding or retrieval of items from memory.

Adolescent↗
PubMed2000

Performance-based measures in autism: implications for diagnosis, early detection, and identification of cognitive profiles.

Provides a critical review of performance-based assessment measures in autism. Currently, performance-based measures of autism are being explored in two domains: structured play sessions and cognitive-neuropsychological assessments. Structured play sessions are designed to elicit the behavioral symptoms associated with autism to provide a consistent and valid means of early detection and diagnosis of autism across different evaluators and settings. These structured play sessions provide a supplement to diagnostic instruments based on parental report. Cognitive-neuropsychological tasks have been used to identify possible underlying cognitive impairments in autism including executive function, theory of mind, selective attention, and abstraction. Currently, cognitive tasks are useful in treatment planning but are inappropriate for diagnostic purposes. Important goals for the future will be to integrate parent-report diagnostic interviews and structured play observations and to identify a profile of cognitive impairments that are specific to pervasive developmental disorders that can be incorporated into diagnostic protocols.

Autistic Disorder↗
PubMed1999

Resistance of enterococci to heat and chemical agents.

Within the framework of the standardisation efforts on disinfectant testing on the European level the test germ Enterococcus hirae ATCC 10541 has been included for some time in the test requirements whereas the test strain Enterococcus faecium, which has frequently been used up to now, has been largely ignored. We compared the thermal and the chemical resistance of both test germ species. In the quantitative suspension test with active ingredients from the group of aldehydes, phenols, quaternaries and oxidizing agents with the exception of peracetic acid, no significant differences were determined between the two strains. In the case of the studies on thermal resistance at 65 degrees C and 68 degrees C, Enterococcus faecium ATCC 6057, by contrast, proved to be far more resistant than Enterococcus hirae ATCC 10541. According to these results, priority should be given to Enterococcus faecium over Enterococcus hirae as the test germ for chemical and also chemothermal disinfection.

Benzalkonium Compounds↗
PubMed1998

[Effect of protamine on the microbicidal efficacy of formaldehyde].

Testing the ability of commercial compounds to provide an effective disinfection of instruments requires test conditions that are close to reality which includes the proper selection of the material used to contaminate the test objects. The adhesion of the material must be strong enough to keep it attached to the test object during and after insertion into the disinfectant solution. Its characteristics should come as close as possible to those of the contaminations encountered in practice. The guideline for instrument disinfectants published by the Robert Koch-Institute recommends the use of coagulated blood. Accordingly, heparinized sheep blood is mixed with the test germs, and protamin is added to initiate coagulation. In the present investigation we compared this contamination procedure with a second one, in which coagulation was achieved by adding a CaCl2 solution to citrate blood. We also included agarose as an almost inert contaminant in our experiments. The results showed that protamine is able to increase the microbicidal efficacy of formaldehyde on staphylococci significantly. When these test germs were embedded either in citrat blood or in agarose, it took about twice the disinfectant concentrations to achieve the same microbicidal effects as with protamine blood (Fig. 1). Remarkably, the results obtained with citrate blood were the same as those with agarose, regardless of the differences in material between the two contaminants. It should also be noted that the microbicidal effect of the formaldehyde proved to be almost independent from the amount of contaminant per test area, hence, from the thickness of the layer. When M. terrae was employed as test germ, the results obtained with protamine blood and citrate blood, respectively, as contaminants were identical (Fig. 2). The same was true for the other test germs investigated, except for E. faecium (Fig. 3). The addition of even very small amounts of protamine to the embedding compound, agarose led to a substantially increased efficacy of the formaldehyde against staphylococci (Fig. 4). This effect was especially distinct in suspension (Fig. 5). Whenever the efficacy of formaldehyde-containing disinfectants is to be tested and evaluated, one should be aware of this synergism between protamine and formaldehyde. In these cases, it is advised to employ other contaminating agents, such as coagulated blood prepared by addition of CaCl2 to citrate blood.

Animals↗
PubMed1992

Do NMDA receptor antagonists protect against MPTP-toxicity? Biochemical and immunocytochemical analyses in black mice.

We investigated whether excitatory amino acids acting at the N-methyl-D-aspartate (NMDA) subtype of the L-glutamate receptor contribute to the dopaminergic neurotoxicity induced by systemic administration of the Parkinson's syndrome-inducing toxin 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP) in C57Bl/6 mice. The MPTP-regimen chosen (30-40 mg/kg body weight subcutaneously) resulted a 60-70% depletion of striatal dopamine (DA) content and a 20% reduction of tyrosine hydroxylase immunoreactive (TH-IR) cells in the substantia nigra pars compacta 20 days after administration. Repeated systemic coadministration of the non-competitive NMDA receptor antagonist MK-801 or of the novel competitive NMDA receptor antagonist CGP 40116 did not protect against MPTP-induced striatal DA depletion 20 days after toxin administration. Additionally, no short-term protective effects of MK-801 on striatal DA content were observed 24, 48, and 96 h, respectively, after exposure to MPTP. A slight and non-significant attenuation (approximately 10%) of the MPTP-induced decrease in the number of nigral TH-IR cells was observed after MK-801- and CGP 40116-treatment. We conclude that neurotoxicity of systemically administered MPTP is not substantially antagonized by NMDA receptor antagonists in mice.

1-Methyl-4-phenyl-1,2,3,6-tetrahydropyridine↗
PubMed1992

Postsynaptic contribution to long-term potentiation revealed by the analysis of miniature synaptic currents.

Miniature excitatory synaptic currents were recorded from CA1 pyramidal cells in hippocampal slices to study the site of the persistent change in synaptic efficacy during long-term potentiation. Induction of long-term potentiation produced a large increase in the amplitude of these currents. Such a change in amplitude suggests an increase in postsynaptic transmitter sensitivity.

6-Cyano-7-nitroquinoxaline-2,3-dione↗
PubMed1992

The competitive NMDA antagonist CGP40.116 enhances L-dopa response in MPTP-treated marmosets.

Experiments in MPTP-treated non-human primates testing potential antiparkinsonian action have shown both, beneficial and adverse effects of gutamate receptor antagonists. To investigate this matter further, the novel competitive NMDA antagonist CGP40.116 was administered systemically to three adult MPTP-treated marmosets. When coadministered subcutaneously with a subthreshold dose of L-DOPA, 2 mg/kg, CGP40.116 25-250 micrograms/kg, increased locomotor activity. However, when administered alone, CGP40.116 had no effect on locomotor activity.

1-Methyl-4-phenyl-1,2,3,6-tetrahydropyridine↗
PubMed1991

Multiple peaks and low bioavailability of furosemide correlate with the volume of fluid ingested.

Two different single dose cross-over bioavailability studies were performed comparing a new oral furosemide preparation (test preparation = preparation A) with a marketed standard with a marketed standard preparation (reference preparation = preparation B). Test and reference preparation contained 40 mg of furosemide each. Into both studies, 18 healthy male volunteers were included; 4 volunteers participated in both studies. In study 1, the volunteers ingested the tested preparations together with 300 ml of an electrolyte solution in order to substitute volume and electrolyte deficits. Additional 200 ml were given 30 min post dose, 500 ml during the next 30 min and 1000 ml during the second hour after drug intake. In study 2, the tested preparations were ingested together with 200 ml of water without any additional volume substitution. The plasma concentration curves of study 1 showed a double peaking with a first maximum of furosemide levels at 1 h and a second peak at 3 h and 4 h, respectively, on average. The concentration-time curves of study 2 showed a single peak 1 h p.a. in the mean for both preparations. The relative bioavailability of preparation A was about 67% in study 1 compared to study 2. Preparation B showed a relative bioavailability of 59% in study 1 compared to study 2.

Adult↗
PubMed1988

Strain-specific development of the mossy fiber system in organotypic cultures of the mouse hippocampus.

The postnatal development of the hippocampus of the inbred mice strains BALB/c, C57BL/6, and DBA/2 was studied in organotypic explant cultures using the roller-tube technique. In vivo, mice exhibit strain-specific mossy fiber distribution patterns. As a main result we found, that after cultivation of 3-4 weeks, similar strain-specific patterns became apparent in vitro, as visualized by a modified Timm staining. From this experiment we can conclude that a postnatal extrinsic influence cannot be the cause of the strain-specific hippocampal features.

Animals↗
PubMed1987

Presynaptic effects of the pardaxins, polypeptides isolated from the gland secretion of the flatfish Pardachirus marmoratus.

The effects of the two toxic proteins Pardaxin I and II isolated from the gland secretion of the flatfish Pardachirus marmoratus on frog neuromuscular transmission have been investigated and compared to those of the gland secretion. Pardaxin I and II showed pre- but not postsynaptic neurotoxic effects. They increased the frequency of the spontaneous release of transmitter quanta in a dose-dependent and temperature-influenced way up to more than 100 times control values. At the same time the quantal content of the evoked end-plate potentials was greatly elevated. Pardaxin I was about 5 times more effective than Pardaxin II, and both were roughly in the same range of efficacy as the original gland secretion (w/v). The glycosteroids isolated from the same gland secretion were relatively ineffective in promoting neurotransmitter release; however, at high doses they had postsynaptic effects, as shown by a diminution of the amplitude of the evoked end-plate potentials. They did not reinforce the effect of the Pardaxins. At higher doses both the Pardaxins and the gland secretion induced depolarization of postsynaptic membranes, muscle cell contractions which could not be blocked by (+)-tubocurarine or by tetrodotoxin, and eventually also physical disruption of muscle cells. No effects on nerve conductance were observed. Pore-forming activity of the Pardaxins has already been demonstrated. It is suggested that their presynaptic effects are a result of a possible affinity to the nerve terminals, of their hydrophobicity and mainly of this pore-forming activity. These toxins might be valuable tools in neuroscience research.

Animals↗
PubMed1987

[Extra-corporal shock wave lithotripsy using the HM3 Dornier lithotripter with a modified shock wave generator. Initial clinical reports of experiences].

We report on the clinical application of a modified shock-wave generator for the Dornier Lithotripter HM 3. Stone fragmentation, complication rate, and frequency of auxiliary measures were unchanged in comparison to the former generator. The new shock-wave generator led to markedly reduced patient discomfort during treatment, with the result that more than 50% of all ESWLs could be done with sedation only or without any medication.

Analgesia↗
PubMed1986

[Gas in the pancreas: value of computed tomography].

Intrapancreatic gas in acute pancreatitis is generally due to infection with gas-forming organisms. CT provides evidence of pancreatitis, its extent and complications. The demonstration of gas in an inflamed pancreas indicates abscess formation and is an indication for surgical intervention. A review of our own patients has shown abscess formation in six out of seven patients with gas in the pancreas. The differential diagnosis of gas collections in the region of the pancreas is discussed and illustrated by examples.

Abscess↗
PubMed1986

Expression of X-linked phosphoglycerate kinase in early mouse embryos homozygous at the Xce locus.

The expression of maternally derived X-chromosomal Pgk-1 alleles was investigated in oocytes and early embryos of mice carrying different alleles (Xcea, Xcec) of the X-chromosome controlling element (Xce) locus. Pgk-1 allelic expression was determined by measuring their gene products using Cellogel electrophoresis and a sensitive fluorimetric enzyme assay. In addition to the already existing mouse strain of the genotypes Pgk-1a Xcec and Pgk-1b Xcea, a new line was bred carrying the combination Pgk-1b Xcec. The X chromosomes carrying the combinations Pgk-1a Xcec and Pgk-1b Xcec were of feral origin, whereas Pgk-1b Xcea was derived from a laboratory line. Our results using Xcec homozygous females confirm that maternal Pgk-1 is already expressed on day 4 of embryogenesis, thus substantiating data previously obtained using Xcea/Xcec heterozygous females. This finding also demonstrates that the timing of reactivation of maternal Pgk-1 is not influenced by the Xce locus. Furthermore, we found that oocytes from Xcec homozygous females have a balanced PGK-1 A/PGK-1 B allozyme ratio (50:50), whereas in oocytes obtained from Xcea/Xcec heterozygotes, the PGK-1 allozyme ratio is about 60:40. In tissues of adult Xce homozygous females, the PGK-1 allozymes are also balanced, whereas in Xcea/Xcec heterozygous females, the ratio is about 35:65. In addition to the relative activity of the PGK-1 allozymes, we also measured the absolute activity of PGK-1 in oocytes obtained from three types of Xce homozygous females.(ABSTRACT TRUNCATED AT 250 WORDS)

Alleles↗