Search PubMed⌕ Search

Biomedical subjects

J Schmidt

Publications and source records attributed to J Schmidt.

At least 631 records · Page 35Linked to original sources
PubMed1987

In vitro induction of osteosarcomalike lesion by transformation of differentiating skeletal precursor cells with FBR murine osteosarcoma virus.

This study analyzed the transforming potential of murine viruses in organ cultures of mouse fetal condylar cartilage: Finkel-Biskis-Jinkins-Murine sarcoma virus (FBJ-MuSV) and Finkel-Biskis-Reilly-Murine sarcoma virus (FBR-MuSV). It was only the FBR-MuSV isolated from a radiation-induced osteosarcoma, that induced morphological changes as early as 24 hours following the infection. The latter manifested itself by a marked enlargement of the number of progenitor cells concomitant with an accumulation of spindle-like cells, giant cells, and pleomorphic cells along with large bone spicules and heavy mineralization of the remaining cartilage. The newly formed tissue synthesized type I collagen and revealed profound invasive characteristics. By day 7, FBR-MuSV-infected cultures acquired the appearance of an osteosarcomatouslike lesion. Electron microscopy examinations revealed that both the matrix and the osteogenic cells in the induced tumors differed markedly from that encountered in normal mammalian osseous tissue. To determine which cells within the condylar tissue served as the target for the FBR-MuSV, we used antibodies against viral P30 protein for an indirect immunoperoxidase reaction. The chondroprogenitor cells were the only ones that reacted positively for the virus-specific protein. Further, the in vitro-induced tumor was tumorigenic in syngeneic mice, hence, brought about the development of osteo-fibrosarcoma subcutaneously. By contrast to FBR-MuSV, the FBJ-MuSV did not elicit similar transformative effects in vitro. Since both viruses possess the fos oncogene, it has been suggested that the unique tumorigenic potential of the FBR-MuSV may be linked to structural alterations in the fos oncogene product.

Animals↗
PubMed1987

Neuronal transmitter sensitivity after social isolation in rats.

After 3 and 12 months of isolation rearing of rats, sensitivity of single neurons to microiontophoretically applied transmitters as well as neuronal spontaneous activity are analysed in striatum, cortex, hippocampus, locus coeruleus and nucleus raphis medialis. It is demonstrated that regulation of transmitter sensitivity, as well as spontaneous activity, depend on isolation duration, therefore showing time dynamics. Sensitivity changes of single neurons to distinct transmitters are not uniform and simultaneous in all areas but are structure specific. After 3 months of isolation an enhanced dopamine sensitivity is observed only in the striatum, whereas in the cortex the dopamine sensitivity is increased after 12 months isolation. A diminished response of single neuron activity to serotonin is demonstrable after 3 months of isolation in striatum and nucleus raphis. The observed changes are discussed in connection with biochemically and pharmacologically demonstrated changes in isolation. The complex patterns of neurobiological changes characterizing the isolation syndrome are emphasized.

Animals↗
PubMed1987

[Microangiographic findings in experimental intestinal anastomoses].

Microangiography of anastomosis at the rat colon and the pig jejunum did reveal the postoperative state of vessel regeneration. Findings for evaluation were avascular areas, dislocation and dilatation of vessels, vessel break, vessel-anastomosis to the opposite site and to adhesions as well as the complete regeneration of the vessel architecture. A suture technique leading to correct apposition of the wound edges without destroying the circulation will be followed by an almost complete regeneration of the vessel architecture.

Animals↗
PubMed1987

Quantitation of an alpha subunit splicing intermediate: evidence for transcriptional activation in the control of acetylcholine receptor expression in denervated chick skeletal muscle.

We have investigated the mechanisms responsible for the increase in acetylcholine receptor subunit mRNAs during the induction of denervation supersensitivity in skeletal muscle. Using a cRNA probe specific for exon 7 (224 nucleotides; with flanking intron sequences of 105 nucleotides on the 3' end, and of 70 nucleotides on the 5' end) of the alpha subunit of the chicken muscle acetylcholine receptor gene, we were able to quantitate the concentration of mature alpha subunit mRNA and its precursor. In 3-wk-old chicks, the concentration of alpha subunit message in leg muscle was found to be 4.0 attomoles per microgram total RNA, and to increase 40-fold within 1 wk after section of the sciatic nerve. The molar ratio of precursor/mature mRNA, which was approximately 0.023 in innervated as well as denervated muscle, transiently rose to 0.047 at the beginning of the second postoperative day when mature message content increased 20-fold; the rise in precursor level preceded the increase in mature message content. These findings suggest that an accelerated rate of transcription of the message coding for the alpha subunit causes increased message content and the stimulation of receptor synthesis characteristic of denervated muscle.

Animals↗
PubMed1987

Failure to detect hydrogen-sulphide production in lactose/sucrose-fermenting Enterobacteriaceae, using triple sugar iron agar.

Triple Sugar Iron agar failed to detect hydrogen sulphide in 44 out of 69 hydrogen-sulphide producing strains of Enterobacteriaceae, which at the same time fermented lactose and/or sucrose. The species involved were Salmonella typhi, Salmonella enteritidis, Citrobacter freundii, Escherichia coli, and Proteus vulgaris. By contrast, no false-negative reactions were observed in 74 strains, which fermented neither lactose nor sucrose. Failure to detect hydrogen sulphide was probably due to acidification of the medium following the fermentation of carbohydrates. A medium without carbohydrates is preferable in diagnostic situations where hydrogen-sulphide detection is of great importance.

Citrobacter↗
PubMed1987

Double-antibody sandwich enzyme-linked immunosorbent assay for rapid detection of toxin-producing Corynebacterium diphtheriae.

An enzyme-linked immunosorbent assay for determining the toxigenicity of Corynebacterium diphtheriae is presented. The assay uses hyperimmune horse diphtheria antitoxin as a capture antibody and mouse monoclonal diphtheria antitoxin as a detecting antibody. Growth of bacteria and capture of diphtheria toxin by antitoxin are carried out in one step. Toxin produced by as little as 100 toxin-producing corynebacteria is detectable, corresponding to a sensitivity of 10 ng of diphtheria toxin per ml. Demonstration of toxin after incubation of the bacteria for 4.75 h, as well as after 18 h, was in accordance with the modified Elek gel diffusion method and the guinea pig inoculation test. However, heavy inocula incubated overnight produced significantly lower optical density than did diluted inocula; thus, the higher optical density was used as an indicator of toxin production. A decrease in optical density was also seen by shortening the incubation time. For laboratory safety, ethanol was added to the microtiter plate wells before washing out of the bacteria. This resulted in a further decrease in optical density. Using 4.75-h incubation time gave a single false-negative result. No false-positive results were ever seen. Incubation for 18 h is suitable for large-scale screening, and 4.75 h of incubation is suitable for rapid identification of toxin-producing C. diphtheriae.

Corynebacterium diphtheriae↗
PubMed1987

Retrovirus-induced osteopetrosis in mice. Effects of viral infection on osteogenic differentiation in skeletoblast cell cultures.

Newborn female strain NMRI mice were injected with a mouse retrovirus (OA MuLV) known to induce osteopetrosis. Primary skeletoblast cell cultures were established from humeri and calvaria of 3-day-old, 7-day-old, and 28-day-old animals. Infectious ecotropic MuLV was found in all humerus cultures from infected animals and in 7-day and 28-day calvaria cell cultures. Levels of alkaline phosphatase activity were markedly higher in cultures of calvaria and humeri from infected mice than in those from controls. In vitro infection of undifferentiated periosteal cells was followed by a decrease in cell growth and an increase in alkaline phosphatase activity. In contrast, differentiated osteoblast-like cells were barely susceptible to OA MuLV infection, and the virus did not influence their cell growth or differentiation. Electron-microscopic studies of skeletal tissue from infected old osteopetrotic mice showed virus particles associated with and budding from osteocytes and accumulated in devitalized osteocyte lacunae. The results indicate that progenitor cells of the osteoblastic lineage represent the target cells for OA MuLV in bone tissue, that virus infection induces an increase in osteoblastic activity, and that infected cells produce virus until full development of the disease.

Animals↗
PubMed1987

The influence of long-term treatment with haloperidol on neuronal activity and sensitivity in several brain structures of the rat.

The influence of long-term haloperidol pretreatment on neuronal spontaneous activity and transmitter sensitivity was investigated in prefrontal cortex, hippocampus and locus coeruleus. The changes are different in all areas as well as in the transmission systems involved. In particular cases, analogies exist between haloperidol- and isolation-induced changes, reflecting a comparable dopaminergic supersensitivity.

Action Potentials↗
PubMed1987

Antibodies to interleukin-1 raised with synthetic peptides: identification of external sites and analysis of interleukin-1 synthesis in stimulated human peripheral blood monocytes.

Rabbit antibodies against peptides corresponding to amino acids 1-18, 45-65 and 71-90 of mature human interleukin-1 beta (IL-1 beta) precipitated 125I-labelled IL-1 beta, showing that these sites are accessible to antibody and located externally. Immunoprecipitation of 35S-methionine-labelled LPS-stimulated human peripheral blood monocytes followed by SDS-PAGE revealed the expected major bands of molecular weights 35,000 and 17,500. The 35,000 protein was found in the cell lysate and extracellularly in the medium, but the 17,500 protein was exclusively in the medium. A previously undescribed 31,000 band was also detected in the medium. These results are most simply explained by the hypothesis that the 35,000 IL-1 beta precursor is released from the cell and processed extracellularly to the 17,500 mature form. The 31,000 molecule may represent a processing intermediate.

Animals↗
PubMed1987

The influence of social isolation, hypoxia and immobilization on potassium-stimulated dopamine release from telencephalon slices of mice.

Dopamine release from mice telencephalon slices was investigated following immobilization or hypobaric hypoxia exposure during periods of social isolation of different length which itself affects dopamine release in a characteristic manner. Isolation initially results in a decreasing release, which is compensated at the end by adaptive processes. The decrease of dopamine release induced by immobilization is highly dependent on the foregoing isolation. On the other hand, a hypoxia-induced decrease of release always dominates the results. Adaptive processes in consequence of social isolation are supposed to be important in relation to immobilization effects but not to hypoxia-induced changes.

Adaptation, Physiological↗
PubMed1987

Changes in seizure susceptibility in rats following chronic administration of pentylenetetrazol.

Repeated administration of pentylenetetrazol (PTZ) once every 48 h in behaviourally active threshold and suprathreshold doses induces a marked enhancement of seizure behaviour (kindling phenomenon). In contrast, PTZ in initially subconvulsive doses failed to elicit convulsions more complex than stage 1 seizures. With 40 mg/kg PTZ i.p. kindled rats show in the fully kindled state a marked shift of the dose-response curve for PTZ-seizures to the left. The mean stage 4 dose of PTZ is 40 mg/kg in kindled and 75 mg/kg in non-kindled rats.

Animals↗
PubMed1987

Inhibition of stimulated dopamine release from striatum slices after hemorrhagic shock in the rat. Protective effect of piracetam.

The antihypoxic effect of piracetam was studied using a hemorrhagic shock model in the rat. Different shock severity was achieved by bleeding of 35% or 50% of estimated blood volume (EBV). Hemorrhagic shock caused an inhibition of K+ induced dopamine release from striatum slices in proportion to the magnitude of hemorrhage, reflecting the degree of membrane damage in dopaminergic transmission structures. Piracetam was effective in preventing the post-hemorrhagic changes in moderate shock and accelerated restitution of post-hemorrhagic release inhibition in severe shock.

Animals↗
PubMed1986

Organization, structure and symbiotic function of Rhizobium meliloti nodulation genes determining host specificity for alfalfa.

In R. meliloti we have identified four nodulation genes determining plant host-range specificity and have designated them hsnABC and D. The genes code for 9.7, 41.7, 26.7, and 28.6 kd proteins, respectively, and are organized into two transcriptional units. Mutations in these genes affect nodulation of their natural plant hosts Medicago sativa and Melilotus albus to different extents and hsnD mutants have an altered host-range. These Nod- mutations are not complementable by nodulation genes of other Rhizobium species such as R. leguminosarum. The hsn genes determine plant-specific infection through root hairs: hsnD is required for host-specific root hair curling and nodule initiation while the hsnABC genes control infection thread growth from the root hairs.

Bacterial Proteins↗