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Biomedical subjects

A Zimmer

Publications and source records attributed to A Zimmer.

At least 91 records · Page 5Linked to original sources
PubMed1993

Tetanus toxin light chain expression in Sertoli cells of transgenic mice causes alterations of the actin cytoskeleton and disrupts spermatogenesis.

Tetanus toxin is a powerful neurotoxin known to inhibit neurotransmitter release. The tetanus toxin light chain is a metalloprotease that cleaves some members of the synaptobrevin gene family with high specificity. Here, we report the expression of a synthetic gene encoding the tetanus toxin light chain in the seminiferous epithelium of transgenic mice. Spermatogenesis was severely impaired and mature spermatozoa were completely absent. Late spermatids exhibited pleomorphic shapes and acrosomal distortions. The number of Leydig cells was greatly increased. In situ hybridization analysis revealed that the toxin acts on Sertoli cells. Affected cells exhibited an aberrant distribution of actin filaments and many cells contained large vacuoles. Our results demonstrate that tetanus toxin is active in non-neuronal cells and suggest an important function for members of the synaptobrevin gene family during the late stages of spermatogenesis.

Actins↗
PubMed1992

Induction of a RAR beta 2-lacZ transgene by retinoic acid reflects the neuromeric organization of the central nervous system.

The hormone retinoic acid (RA) has been implicated in the organization of the anteroposterior (AP) body axis. In this paper, we describe the effects of RA on the activity of the RA-inducible retinoic acid receptor-beta 2 (RAR beta 2) promoter. When transgenic embryos carrying a RAR beta 2-lacZ reporter gene were exposed to a single dose of RA between gestational days 8.5 to 10.5, lacZ expression was induced in the anterior central nervous system (CNS). Strikingly, the transgene was expressed in a segmented pattern reminiscent of that of Drosophila 'pair-rule' genes. RA treatment of midgastrulation embryos at day 7.5 disturbed the segmentation and produced severe craniofacial defects. We discuss the possibility that the entire anterior CNS is segmented and that this segmentation is reflected by the RAR beta 2-lacZ induction pattern.

Animals↗
PubMed1991

Isolation and characterization of two human H1 histone genes within clusters of core histone genes.

Two human H1 histone genes, termed H1.3 and H1.4, were isolated from two cosmid clones. The H1.4 gene is associated with an H2B gene, whereas genes coding for all four core histones are located in the vicinity of the H1.3 gene. This cluster arrangement was found both in the two cosmid clones and on overlapping bacteriophage clones isolated from an EMBL3 library. In continuation of our previous analysis of two human H1 genes, this analysis raises the number of completely sequenced H1 histone genes within clusters of core histone genes to four.

Amino Acid Sequence↗
PubMed1991

Activity of the beta-retinoic acid receptor promoter in transgenic mice.

LacZ reporter gene constructs were used to analyze the murine retinoic acid receptor beta (mRAR beta) gene promoter in transgenic mice. LacZ expression in transgenic mouse embryos with 250 bp of promoter sequences closely parallels that of RAR beta between embryonic days 8.5 and 12.5. This indicates that the -1 to -250 promoter region contains most regulatory elements required for tissue specific expression. Additional elements in the -250 to -625 region are required for high expression levels after day 12.5. Elements in the -625 to -3100 region are necessary to reproduce the RAR beta expression in the meninges and the eye mesenchyme. The expression pattern of the transgene and the endogenous RAR beta, as revealed by in situ hybridization, suggests an important role of the RAR beta in the developing nervous system.

Amino Acid Sequence↗
PubMed1991

Use of liposomes, viral capsids, and nanoparticles as DNA carriers.

We tested a variety of liposomes for parameters such as DNA binding capacity and DNase I protection of incorporated and attached DNA to elucidate their use as vehicles for DNA transfer into cells and animals. The results were compared to other potential DNA vehicles, empty viral capsids, and nanoparticles. Maximal binding capacity was achieved for positively charged nanoparticles, DNase I protection was observed for most preparations with neosome preparations being least efficient. The uptake of radiolabeled DNA by cells in culture was determined for cationic and nonionic surfactant vesicles, viral capsids, and nanoparticles. Cellular DNA uptake was best for dioleoyl-derived positively charged liposomes (N-[1-(2,3-dioleoyloxy)propyl]-N,N,N-trimethylammonium chloride; DOTMA) and the DNA could be shown to be physiologically active. The recombination rate for DNA fragments transfected in polyoma capsids in live mice was higher than for liposome mediated transfection. Homologous recombination could be observed for both DOTMA and polyoma-mediated DNA transfer.

Animals↗
PubMed1989

Production of chimaeric mice containing embryonic stem (ES) cells carrying a homoeobox Hox 1.1 allele mutated by homologous recombination.

Several mouse gene families related to Drosophila developmental control genes and containing a homoeobox, a paired box or a finger domain, have been cloned and structurally analysed. On the basis of structural similarities to the Drosophila genes and of their spatially and temporally restricted expression patterns during mouse embryogenesis, it has been proposed that these mammalian genes also are involved in the control of development. To elucidate the function of homoeobox genes by genetic means, mouse mutants must be generated. We have developed a technique for mutagenesis in vivo and have used it to mutate the homoeobox Hox 1.1 gene. In vivo mutagenesis was achieved through homologous recombination between an endogenous Hox 1.1 allele and a microinjected mutated gene in pluripotent embryonic stem (ES) cells. Mutant cells were identified by means of the polymerase chain reaction (PCR) and mutant clones were used to generate chimaeric mice. Because the homologous recombination event is formally a gene conversion event and no selection is required to screen for cells carrying the mutated allele, in vivo mutagenesis allows specific alterations in the target sequence to be made without the introduction of any other sequences.

Animals↗
PubMed1989

[Selected properties of lactose-fermenting and non-fermenting Salmonella agona strains isolated from specimens from hospitalized infants].

The aim of this study was to compare some of the properties of 28 lactose-positive and 28 lactose-negative Salmonella agona strains isolated from faeces of infants hospitalized in the same hospital. Some of biochemical properties, sensitivity to 14 antibiotics and chemotherapeutic agents and sensitivity to bacteriophages used for typing of this Salmonella genus were tested. Results of biochemical examinations revealed that lactose-fermenting strains retain the remaining of Salmonella of subspecies I. Two biochemical features are of particular importance: the ability to ferment lactose on all lactose containing media and a lack of the ability to produce H2S on Kligler medium. These two features differentiate lactose-fermenting strains of Salmonella from non-lactose fermenting ones. Antibiotic sensitivity pattern differed between lactose-positive and lactose-negative strains. Lactose-positive strains showed higher degree of resistance than lactose-negative strains. The differences in resistance were seen in the case of chloramphenicol, doxycycline, gentamicin and tetracycline. Both lactose-positive and lactose-negative strains were sensitive to colistin, neomycin, nitrofurantoin and nalidixic acid. They were resistant to ampicillin, cloxacillin, rifampicin, streptomycin, sulfatiazol and biseptol. Bacteriophage typing revealed that all lactose-negative strains isolated in this study from clinical samples belonged to the same phage pattern V. Lactose-positive strains belonged to two phage types VB and XI. Type VB prevailed.

Anti-Bacterial Agents↗
PubMed1987

The murine homeo box gene product, Hox 1.1 protein, is growth-controlled and associated with chromatin.

In order to gain insight into the function of the Hox 1.1 gene, we studied the expression of the murine homeo box gene product, the Hox 1.1 protein. Monoclonal antibodies were raised against synthetic peptides of the Hox 1.1 protein to study the localization and expression pattern of this protein under various culture conditions. By means of indirect immunofluorescence we localized the Hox 1.1 protein to the nucleus in differentiated F9 and NIH 3T3 cells. During mitosis the protein was found to be associated with chromatin. Confluent NIH 3T3 cells harbored little if any Hox 1.1 protein. After "wounding" the cells in this confluent monolayer, we observed an induction of the expression of the Hox 1.1 protein. However, addition of insulin to F9 and contact-inhibited NIH 3T3 cells led to an increase of the Hox 1.1 RNA and protein expression. Thus, the induction of the Hox 1.1 protein is associated not only with the differentiation of embryonal carcinoma (EC) cells, but may also correlate with stages of cell growth.

Amino Acid Sequence↗
PubMed1986

Redistribution of nuclear lamins in mitotic cells.

The nuclear lamins are directed from the cytoplasm to chromosomes as part of the maturation pathway of the interphase nucleoskeleton. In mitosis, the three polypeptides lamin A, B and C were found in the cytoplasm from prophase until anaphase and shifted to chromosomal surfaces at telophase (Ely, D'Arcy and Jost, 1978; Gerace, Blum and Blobel, 1978). We show here that early events in nucleoskeleton formation could be regulated by extracellular pH. When exponentially growing tissue culture cells and cells arrested in mitosis were exposed to different extracellular pH values, three patterns of distribution of lamins were observed in mitotic cells: exclusively cytoplasmic distribution of mitotic lamins at low pH (6.8 to 7.3); a premature association of a lamin subfraction with metaphase chromosomes at intermediate pH 7.5; a more prominent relocation of lamins onto chromosomes in metaphase and in disorganized metaphase at pH 8.0. Reassembly of lamins occurred at telomeric ends of mitotic chromosomes followed by a lateral fusion to form a nuclear cage. Using immunogold localization, we show that pH-induced, premature, partial deposition of lamins onto condensed chromosomes may occur prior to the formation of the bilamellar nuclear envelope. These results suggest that the pH-induced redistribution of lamins acts to trigger early events of mitosis to interphase transition.

Cell Cycle↗
PubMed1983

Microsomal epoxide hydrolase in different rat strains.

Epoxide hydrolase activity was determined in hepatic microsomes of adult males of 22 rat strains. The specific activity varied between 4.3 and 12.7 nmole styrene glycol/mg protein per min. The enzyme in F344, DA and Sprague--Dawley rats, strains with low, high and intermediate activity, respectively, was studied in more detail. No differences in substrate specificity and pH-dependence of the activity were observed between the strains with high and low activity, and immunoprecipitation by antibodies raised against microsomal epoxide hydrolase purified from Sprague--Dawley rats showed that the amounts of enzyme protein in microsomes from DA and F344 rats correlated with the activities. These results indicate quantitative rather than qualitative differences in epoxide hydrolase. The enzyme activity was inherited in an autosomal and codominant manner. The hepatic activity in females (about 78% of that in males) and, with the limitation that only few situations were studied, the trans-stilbene oxide-induced activity were under the same genetic control as the basal hepatic activity in males. In contrast, some extrahepatic tissues showed strain differences in epoxide hydrolase activity which contrasted with those found in liver. Hence, the enzyme activity in one tissue cannot serve as a reliable guide to the relative activity in another tissue, unless a specific correlation between the two tissues has been established. Although the strain differences in activity were not very large in themselves, in combination with inter-individual variation, sex differences and effects of the enzyme inducer transstilbene oxide they led to a 20-fold variation in hepatic epoxide hydrolase activity among the rats investigated in the present study.

Animals↗
PubMed1981

Fully automated high-performance liquid chromatography. A new chromatograph for pharmacokinetic drug monitoring by direct injection of body fluids.

A new fully automated high-performance liquid chromatography is described which detects drugs from directly injected plasma (urine, saliva) without sample pretreatment. The apparatus consists of a programmable automatic sampling unit, which is connected via two alternating working pre-columns to an analytical column ("alternating pre-column sample enrichment"). The new device is able to operate with directly injected body fluids like an auto-analyzer and is especially useful for pharmacokinetic and clinical studies, where drug concentrations have to be determined from plasma, urine or saliva.

Body Fluids↗
PubMed1981

[Pharmacokinetics of AR-L 115 BS in rabbits and dogs].

The pharmacokinetics of 2-[(2-methoxy-4-methylsulfinyl) phenyl]-1H-imidazo[4,5-b]pyridine (AR-L 115 BS) were investigated in the rabbit and the dog. The rabbits were dosed with 1 mg/kg 14C-AR-L 115 BS i.v. or p.o and the dogs with 1 mg/kg i.v. or 5 mg/kg p.o. following i.v. administration the blood levels in the two investigated species are described by a 3-exponential decline, during which the preponderant amount of radioactivity is eliminated in the first two phases. The half-lives are 0.25 h and 6 h in the rabbit and 0.2 h and 0.6 in the dog. Following oral administration the radioactivity is absorbed rapidly and quantitatively. Blood level peaks occur after 1 h p.a. amounting to 0.07--0.1 microgram Eq/ml in the rabbit (1 mg/kg) and 2.7 +/- 0.3 micrograms Eq/ml in the dog (5 mg/kg). The elimination behaviour is comparable to that after i.v. dosing. The plasma radioactivity in the dog is not protein bound. On average the urinary excretion amounts to 45% (i.v) and 40% (p.o.) in the rabbit, with a further 52% (both application routes) in the faeces up to 144 h p.a. In the dog the mean urinary excretion is 24% (i.v.) and 29% (p.o.). Faecal elimination is 63% (i.v.) and 56% (p.o.) up to 96 h p.a.

Administration, Oral↗
PubMed1981

The absorption, metabolism and excretion of (14C)-AR-L 115 BS in the baboon.

(14C)-Labelled 2-[(2-methoxy-4-methylsulfinyl)phenyl]-1H-imidazo[4,5-b]pyridine (AR-L 115 BS) (base) was administered to male baboons by the p.o. (10 mg . kg-1 by capsule) and i.v. (2 mg.kg-1) routes. Comparison of routes and extent of excretion suggests the importance of biliary elimination and indicates that an oral dose of (14C)-AR-L 115 BS is almost quantitatively absorbed. Thus in 5 days, after the oral dose, a mean of 42% was excreted in the urine and 38% in faeces. Similarly in 0--5 days after the i.v. dose, a mean of 49% was excreted in urine and 31% in faeces. Substantial elimination of administered radioactivity was observed in the 0--24 h period: 52% following p.o. administration and 60% following i.v. administration. Plasma levels of total radioactivity peaked at 6 micrograms equiv.ml-1 4 h following an oral dose. The concentration of unchanged AR-L 115 BS at this time was ca. 4 micrograms . ml-1. 4 h following the lower i.v. dose, plasma concentrations of ca. 0.5 micrograms equiv.ml-1 were observed and were associated with ca. 0.2 micrograms . ml-1 unchanged drug. Two phases of elimination of total radioactivity from plasma after the i.v. dose could be distinguished with t1/2 ca. 2 h and ca. 48 h. An estimated late phase t1/2 of 48 h was also observed following the oral dose. Although less polar metabolites (chromatographically identical to the synthetic compounds AR-L 114 Cl (hydrochloride) and AR-L 113 Cl) were observed in the plasma at 4 h, the urine and faeces contained some polar metabolites which appeared to be neither glucuronide nor sulphate conjugates. The lower i.v. dose was apparently more extensively metabolised than the higher oral dose.

Administration, Oral↗
PubMed1981

[AR-L 115 BS, comparison of human metabolite pattern and biotransformation with other species].

Following oral administration of 14C labelled 2-[(2-methoxy-4-methylsulfinyl)phenyl]-1H-imidazo[4,5-b]pyridine (AR-L 115 BS) to the rat, rabbit, dog, rhesus monkey, baboon and man the metabolic pattern in plasma and urine was compared and human urinary metabolites were isolated. None of the animal species investigated shows a metabolic pattern identical to that of man. The plasma of rat, dog and rabbit shows wide variation of metabolites with high amounts of two unpolar metabolites of AR-L 115 BS (sulfoxide), namely M0/2 identical with AR-L 114 BS (sulfone with regard to AR-L 115 BS) and M0/1 identical with AR-L 113 BS (sulfide). In comparison to man the urines of the animals show higher amounts of the sulfone (AR-L 114 BS) and the sulfide (AR-L 113 BS). A main pathway of the metabolism of the pyrido-imidazole of the AR-L 115 BS-type is the oxidative pyridine-ring cleavage leading to N-acetylated 5-aminoimidazoles. Further metabolites are characterised by a hydroxyl group in the 6-position of the pyrido-imidazole moiety. Besides the oxidation of tthe sulfoxide function to the sulfone we could also observe the thioether (sulfide) not only of the parent compound itself but also of some of the metabolites in the series of the AR-L 115 BS-biotransformation. The identification of the human urinary metabolites, was carried out by means of TLC, HPLC, UV-, MS- and NMR-spectroscopy.

Administration, Oral↗