Search PubMed⌕ Search

Biomedical subjects

M Schmidt

Publications and source records attributed to M Schmidt.

At least 649 records · Page 36Linked to original sources
PubMed1992

Oviduct epithelial cell co-culture of early porcine embryos.

One- to 16-cell porcine embryos were cultured in either Whittens medium supplemented with bovine serum albumin and fetal calf serum (WM) or in the same medium with porcine oviduct epithelial cell co-culture (WM-Poec). All stages of embryos cultured in WM-POEC had higher cell counts after 144-168 h of development than did embryos in WM. There was however, no significant difference in blastocyst formation rate of embryos cultured in WM-POEC over those cultured in WM. A high proportion of the embryos entering culture at the 1-2-cell were able to pass the 4-cell block stage in both WM and WM-POEC, 81% and 77%, respectively. In both media, most of the 1-2-cell embryos arrested their development at the compacted morula stage and failed to blastulate while embryos initiating culture at the 4- and 8-16-cell embryos formed blastocysts in culture at a rate of 80-90%.

Animals↗
PubMed1992

Blastomere content of cultured/frozen bovine demiembryos.

The purpose of the study was to evaluate whether a period of co-culture with bovine oviduct epithelial cells (BOEC) could improve the tolerance of bisected bovine embryos to freezing and thawing. Day 6 embryos were bisected and the resulting demiembryos were stained with Hoechst 33342 and cell counts were made by counting intact blastomere nuclei. Of these, 11 were stained as freshly manufactured demiembryos, 25 after co-culture for 24 h with BOEC and 37 stained after 24 h co-culture and freezing and thawing. The staining revealed, that there was no significant difference in cell count of demiembryos that were stained immediately after bisection, compared to those, that were co-cultured for a 24 h period. Also, the co-cultured/frozen/thawed demiembryos had a significant decrease in cell numbers compared to the non-frozen demiembryos. We conclude, that a 24 h period of co-culture with BOEC does not result in appreciable cellular proliferation in demiembryos and therefore instead of improving the survival of frozen/thawed demiembryos by giving them opportunity to multiply their cell number and thus make them more resistant to cell damage, rather compromised the viability of cryopreserved demiembryos.

Animals↗
PubMed1992

Sensory innervation of the anterior cruciate ligament. An electrophysiological study of the response properties of single identified mechanoreceptors in the cat.

In anesthetized cats, electrophysiological recordings were made from twenty-six single thick myelinated afferent fibers of the posterior articular nerve of the knee joint that had sensory endings in the anterior cruciate ligament. Most afferent fibers arising from the anterior cruciate ligament were activated by application of local pressure to discrete sites of the ligament, near the attachment to the femur. Afferent fibers from the anterior cruciate ligament did not fire when the knee was in the resting position at 30 degrees of flexion, but they were activated when the knee joint was extended and flexed and externally or internally rotated. Whereas responses were induced by movements in the working range of motion of the knee, activity was markedly increased when the joint was hyperextended and externally or internally rotated. These findings suggest that mechanoreceptors with myelinated axons provide information about tension of the anterior cruciate ligament.

Animals↗
PubMed1992

[Rapidity versus reliability: a critical analysis of the rapid diagnosis of mycobacterial infections with the polymerase chain reaction (PCR)].

In this contribution we analyzed the reliability and the diagnostic value of the results obtained by direct amplification of mycobacterial DNA from patient specimens. Presently, the PCR-method is not as sensitive as recommended culture techniques. In cases of low concentration of mycobacteria in specimens (microscopic negative!) false-negative PCR-results are not rare.

DNA, Bacterial↗
PubMed1992

Intra-abdominal lymphangioma.

Intra-abdominal lymphangiomas are rare occurrences. Of the few cases reported, most are in infants or young children. This case was in a 13-year-old boy with no previous history of problems. The etiology is probably a primary malformation of the lymphatics, which may cause blockage or inflammatory responses and subsequent enlargement of the lymphatic channels. Clinically, the patient presents with features typical of a space-occupying lesion, as in this case. This patient presented with symptoms of an obstruction or pressure from the growing mass. In diagnosis, a sonogram or CT scan is helpful. The recommended treatment is complete excision, if possible.

Abdominal Neoplasms↗
PubMed1991

Reconstitution of a heat shock effect in vitro: influence of GroE on the thermal aggregation of alpha-glucosidase from yeast.

alpha-Glucosidase from yeast is inactivated rapidly at temperatures above 42 degrees C. The thermal inactivation is accompanied by aggregation. The molecular chaperone GroEL suppresses the formation of aggregates by binding the thermally inactivated alpha-glucosidase. Spectroscopic studies suggest that GroEL binds alpha-glucosidase in an intermediately folded state. The complex between alpha-glucosidase and GroEL can be dissolved by MgATP. GroES accelerates the MgATP-dependent dissociation of the alpha-glucosidase-GroEL complex. At elevated temperatures this release leads to the formation of aggregates, while at lower temperatures native, enzymatically active molecules are formed.

Adenosine Triphosphate↗
PubMed1991

Central projections of Limulus photoreceptor cells revealed by a photoreceptor-specific monoclonal antibody.

Studies of lateral, median, and ventral eyes of the chelicerate arthropod Limulus polyphemus (the common American horseshoe crab) are providing important basic information about mechanisms for information processing in the peripheral visual system and for the modulation of visual responses by light and circadian rhythms. The processing of visual information in Limulus brain is less well understood in part because the specific central projections of the various classes of visual neurons are not known. This study describes a mouse monoclonal antibody, 3C6A3, which binds to Limulus photoreceptor cell bodies, their axons, and terminals, but not to any other cell type in the central nervous system. This antibody, and intracellular injection of biocytin, are used to demonstrate the central projections of each type of photoreceptor. Our main conclusions are that: 1) the photoreceptors (retinular cells) of the lateral eye project only to the lamina; 2) the photoreceptors of the lateral rudimentary eye project to both the lamina and medulla; 3) the photoreceptors of the median ocellus project only to the ocellar ganglion; and 4) the photoreceptors of the rudimentary median (endoparietal) eye project to the ocellar ganglion and also into the optic tract. These results, along with previous studies, allow us to infer the projections of the secondary cells. The eccentric cells of the lateral eye project to the lamina, medulla, optic tract, and ocellar ganglion. The arhabdomeral cells of the median ocellus project through the ocellar ganglion and to optic tract to the medulla.

Afferent Pathways↗
PubMed1991

Amplification and sequencing of mRNA encoding acidic fibroblast growth factor (aFGF) from porcine heart.

Progredient stenosis of coronary arteries can induce angiogenic processes, which are probably regulated by polypeptide growth factors like aFGF. Using applications of reverse transcription-polymerase chain reaction, we amplified and sequenced an mRNA encoding aFGF in the porcine myocardium. A DNA fragment of expected size encoding aFGF was amplified with human and bovine aFGF specific oligonucleotide primers in porcine heart. Identity of amplified PCR product to aFGF sequence was confirmed by internal reamplification, Southern hybridization and sequencing of asymmetrically amplified PCR products. The nucleotide sequence analysis of porcine aFGF revealed a homology of 94% to the human and 92% to the bovine cDNA sequences respectively. The amino acid sequence was homologous to the known sequences except for three alterations in the human and thirteen in the bovine aFGF sequences.

Amino Acid Sequence↗
PubMed1991

Anti-Xa clotting activities in different hepatic-triglyceride lipase preparations from post-heparin plasma.

Two different preparations of hepatic triglyceride lipase (HTGL) with comparable lipolytic activities, purified from post-heparin human plasma, were assessed for their anti-Xa activities by two clotting and one chromogenic method. Preparation 1, prepared by heparin affinity followed by ion exchange chromatography, did not contain antithrombin III and exhibited no anti-Xa activity in any of the assay systems. Preparation 2, prepared by two consecutive heparin affinity chromatography steps, was active in all three assay systems, and was shown to contain antithrombin III (AT III). Addition of purified AT III to preparation 1 did not result in the anti-factor Xa activity of preparation 2, and monoclonal antibodies to AT III did not antagonize the activity of preparation 2. These results show that the anti-Xa activity of some HTGL preparations is neither due to the lipase itself nor to the content of AT III, but suggest, that it could be due to contamination with another protein, which binds to heparin sepharose columns but is removed during ion exchange chromatography. Most likely the effect is due to the extrinsic pathway inhibitor (EPI), also called lipoprotein-associated coagulation inhibitor (LACI), which has recently been shown to be released by heparin.

Antibodies↗
PubMed1991

GroE facilitates refolding of citrate synthase by suppressing aggregation.

The molecular chaperone GroE facilitates correct protein folding in vivo and in vitro. The mode of action of GroE was investigated by using refolding of citrate synthase as a model system. In vitro denaturation of this dimeric protein is almost irreversible, since the refolding polypeptide chains aggregate rapidly, as shown directly by a strong, concentration-dependent increase in light scattering. The yields of reactivated citrate synthase were strongly increased upon addition of GroE and MgATP. GroE inhibits aggregation reactions that compete with correct protein folding, as indicated by specific suppression of light scattering. GroEL rapidly forms a complex with unfolded or partially folded citrate synthase molecules. In this complex the refolding protein is protected from aggregation. Addition of GroES and ATP hydrolysis is required to release the polypeptide chain bound to GroEL and to allow further folding to its final, active state.

Animals↗
PubMed1991

Duplications of the X chromosome in males: evidence that most parts of the X chromosome can be active in two copies.

We have analysed two duplications of the X chromosome in male patients using chromosome replication and DNA methylation patterns as determinants of the functional status of the duplicated segments. In both cases, the large duplicated regions, Xq12-q22 and Xq26.3-qter, were not inactivated. A review of previously reported male cases revealed that these duplications were also not subject to inactivation. Taken together, the examined duplications cover almost the entire X chromosome except the pericentromeric region and Xq25-26. Thus, most regions of the X chromosome can be present in two functional copies without lethal consequences.

Blotting, Southern↗
PubMed1991

Characterization of recA genes and recA mutants of Rhizobium meliloti and Rhizobium leguminosarum biovar viciae.

DNA fragments carrying the recA genes of Rhizobium meliloti and Rhizobium leguminosarum biovar viciae were isolated by complementing a UV-sensitive recA- Escherichia coli strain. Sequence analysis revealed that the coding region of the R. meliloti recA gene consists of 1044 bp coding for 348 amino acids whereas the coding region of the R. leguminosarum bv. viciae recA gene has 1053 bp specifying 351 amino acids. The R. meliloti and R. leguminosarum bv. viciae recA genes show 84.8% homology at the DNA sequence level and of 90.1% at the amino acid sequence level. recA- mutant strains of both Rhizobium species were constructed by inserting a gentamicin resistance cassette into the respective recA gene. The resulting recA mutants exhibited an increased sensitivity to UV irradiation, were impaired in their ability to perform homologous recombination and showed a slightly reduced growth rate when compared with the respective wild-type strains. The Rhizobium recA strains did not have altered symbiotic nitrogen fixation capacity. Therefore, they represent ideal candidates for release experiments with impaired strains.

Amino Acid Sequence↗
PubMed1991

Transcriptional and translational regulation of the expression of the l(2)gl tumor suppressor gene of Drosophila melanogaster.

By structural, biochemical and molecular genetic analyses, we have investigated the different mechanisms that control the expression of the lethal(2) giant larvae gene, a tumor suppressor gene of Drosophila melanogaster. Transcription of the l(2)gl gene is controlled by two highly identical promoters that result from the duplication of the 2.8 kb proximal portion of the gene. These two repeats are 96% homologous. Reverse genetic analysis has shown that each promoter can drive gene expression. In addition to the promoters, both repeats express two or three exons according to the pattern of splicing. The most distal exon in the second repeat is required because it contains the ATG initiating codon at the beginning of the open reading frame. The 3' untranslated region appears to contain motifs that specifically destabilize the transcript. Deletion of this region results in the formation of more stable mRNAs. The l(2)gl gene is characterized by an unusual codon usage that may reflect an enhanced translation efficiency by moderating the strength of pairing between codons and anticodons and may therefore increase the expressivity of this gene. Analysis of the spatio-temporal expression of the l(2)gl transcripts and proteins has shown that transcripts and proteins are produced ubiquitously during early embryogenesis, at a time when expression of the gene is required for preventing tumorigenesis. In the second half of embryogenesis, l(2)gl expression becomes restricted to tissues that do not show any phenotypic alteration in mutant animals. The l(2)gl protein exhibits two distinct intracellular localizations. It is preferentially found free in the cytoplasm but can become associated with the inner face of the plasma membrane where it is restricted to domains facing contiguous cells. In particular, the l(2)gl protein is absent from the basal and apical domains of the plasma membrane. The aim of the current research is directed towards understanding the functional relevance of the l(2)gl protein binding to the plasma membrane and its role in the control of cell proliferation and differentiation.

Animals↗
PubMed1991

Mediation of visual responses in the nucleus of the optic tract in cats and rats by excitatory amino acid receptors.

The contribution of excitatory amino acid receptors to visual responses of directional selective neurons in the nucleus of the optic tract (NOT) was examined in anesthetized cats and rats by iontophoretic application of glutamate (GLU), quisqualate (QQL), N-methyl-D-aspartate (NMDA), 6-cyano-7-nitroquinoxaline-2,3-dione (CNQX), 6,7-dinitroquinoxaline-2,3-dione (DNQX) and 2-amino-5-phosphonovalerate (APV). Spontaneous and visually evoked NOT cell activities were increased by GLU, QQL and NMDA. CNQX and DNQX decreased activities predominantly during stimulus movement in the preferred direction, while APV decreased activities to preferred and non-preferred directed stimulus movement. Spontaneous activities were suppressed only following APV application. The results were similar in both species. Furthermore, the effects were similar during binocular stimulation and during monocular stimulation of either eye in the cat. The results indicate a functional role of both non-NMDA and NMDA receptors for the transfer of visual input to directional selective NOT cells in cat and rat.

2-Amino-5-phosphonovalerate↗