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Biomedical subjects

J Schmidt

Publications and source records attributed to J Schmidt.

At least 595 records · Page 33Linked to original sources
PubMed1988

Amplification of endogenous proviral MuLV sequences in radiation-induced osteosarcomas.

The endogenous ecotropic provirus of BALB/c mice was found to be amplified in 17 out of 29 radiation-induced osteosarcomas. In contrast, 19 clonal cell lines established from bone-marrow cells of a tumor-bearing mouse, which were used as controls, did not reveal newly acquired ecotropic proviruses. Ecotropic viral RNA was expressed in tumors that showed reintegrated proviruses. DNA probes from 2 tumors, derived from cellular sequences flanking the newly integrated proviruses, did not detect DNA rearrangements in any of the other tumors. The possible role of activated endogenous retroviruses in the development of radiation-induced osteosarcomas is discussed.

Animals↗
PubMed1988

Transmembrane orientation and receptor-like structure of the Rhizobium meliloti common nodulation protein NodC.

The 46.8-kd NodC protein of Rhizobium meliloti is a membrane protein, essential for nodule formation. Gene fusions of nodC to a portion of the lambda cI repressor gene were used to define the membrane-anchor domain which is necessary for membrane insertion of the NodC protein into the membrane. The transmembrane orientation of NodC was confirmed by surface-specific radiolabeling and proteolysis experiments. A highly hydrophobic transmembrane-anchor domain was found near the carboxyl terminus, separating a large extracellular domain which contains an unusual cysteine-rich cluster from a short putative intracellular domain. Cross-linking studies showed that the NodC protein exists in the membrane probably as a dimer. The domain structure of the NodC protein shows striking similiarities with cell surface receptors. In nodules of various legumes a truncated form of the NodC protein was detected. The processed NodC was associated with the bacteroids and the amount of this protein increased during nodule development.

Journal Article↗
PubMed1988

Expression of glycoconjugates on normally developing and immunologically impaired Hymenolepis diminuta.

The carbohydrates on the surface of Hymenolepis diminuta were analyzed with gold-labelled lectins, and it was found that the surface coat of the anterior body differs from that of the strobila in its lectin-binding properties. Binding sites for lectins from Abrus precatorius (APA), Arachis hypogaea (PNA), Glycine max (SBA) and for wheat germ agglutinin (WGA) and succinylated WGA were located on the scolex and strobilation zone. Lectin-gold particles attached mainly to the electron-dense spines. The surface coat may therefore expose sugar residues of the N-acetylglucosamine and galactose types. In contrast, the strobila had few binding sites for the above-mentioned lectins but bound concanavalin A (ConA). Lectins from Dolichos biflorus (DBA) and Ulex europaeus (UEA-I) were not bound to H. diminuta. In juvenile worms from rats, the extension of the WGA- and SBA-positive region of the strobilation zone increased in length with the development of the worms. Lectin binding in juveniles from mice was similar when the mice had been immunosuppressed with cortisone. After the onset of the immune defense against H. diminuta in nontreated mice, a moderate expression of lectin-binding substance also occurred on the strobila. Destrobilated worms were entirely covered with the N-acetylglucosamine- and galactose-containing glycoconjugates, and it is suggested that these worm remnants correspond to the lectin-binding part of normal, growing juveniles. The presence of the carbohydrates is discussed with respect to the relative resistance of the scolex-strobilation zone of H. diminuta to immune rejection.

Animals↗
PubMed1988

Effect of an aldose reductase inhibitor, AL-1576, on the development of UV-B and X-ray cataract.

The effect of an aldose reductase inhibitor, AL-1576, on the development of UV-B and X-ray-induced cataract was studied with 100 female Brown-Norway rats. Histological studies were made with 32 eyes. A new histological procedure enabled detailed information on UV or X-ray-induced impairment on the lens, as well as on the potential efficiency of anticataract drugs. No definite effect of the aldose reductase inhibitor, AL-1576, on the development of UV or X-ray-induced cataract could be found. It may be concluded that AL-1576 cannot prevent damage caused by irradiation, like that of other oxidative influences. Disadvantageous effects of AL-1576 on the lens could be excluded.

Aldehyde Reductase↗
PubMed1988

In vitro chemosensitivity testing of renal cell cancer. Short-term culture technique.

In an attempt to solve the problem of chemosensitivity testing of renal cell carcinoma in vitro, a modified short-term culture technique was developed. The kinetic study of hypernephroma cells and normal renal cells showed that the uptake of H3-uridine and H3-thymidine is at its maximum after eighty hours. The effect of doxorubicin, cisplatinum, vinblastine, and mitomycin C in different concentrations was tested. Tumors generally showed more resistance than sensitivity. Some tumors showed sensitivity to one or more drugs, but no one drug was persistently effective in all tumors. Our short-term culture technique solved the discrepancy between cell kinetics and test duration found in the Volm test and the problem of nongrowth in the clonogenic assay.

Carcinoma, Renal Cell↗
PubMed1988

Effect of lectins on KK-47 bladder cancer cell line.

The effect of three lectins, Ricinus communis agglutinin (RCA II), concanavalin agglutinin (ConA), and wheat germ agglutinin (WGA), on KK-47 bladder cancer cell line was studied, RCA II showed effective inhibition of H3-uridine and H3-thymidine uptake by KK-47. ConA showed a stimulatory effect in all three concentrations used. WGA also showed stimulatory effect, but it was less pronounced than ConA.

Carcinoma↗
PubMed1988

Endogenous murine leukemia viruses: frequency of radiation-activation and novel pathogenic effects of viral isolates.

Female C57BL/6 and BALB/c mice were injected i.p. with 0.06 microCi/kg or 0.5 microCi/kg of the short-lived alpha-emitting radionuclide 224radium at 3-day intervals. Infectious N-ecotropic XC+, and xenotropic C-type retroviruses were activated in several tissues in both strains. In C57BL/6 mice the activation of ecotropic and xenotropic virus was dose-dependent as observed 4 weeks after the start of irradiation. In BALB/c mice a few animals showed activation of ecotropic virus after four weeks of irradiation. The expression of xenotropic virus was similar in irradiated mice and controls. Viral antigen, indicative for viraemia, was not detected in irradiated or control animals. Antiviral antibodies were found in both control and irradiated mice but higher titers were found in the irradiated mice. Bone tissue-derived N-tropic XC+ virus isolates were found to be non-oncogenic in newborn mice of the parental strain. In contrast, the same virus isolates induced a novel pattern of disease, such as osteopetrosis and osteomas together with malignant lymphomas in NMRI mice. The data indicate that the pattern of endogenous murine leukemia virus activation by internal alpha-irradiation is dependent on the dose rate, and on the genetics of the mouse strain.

Animals↗
PubMed1988

Acetylcholine receptor synthesis rate and levels of receptor subunit messenger RNAs in chick muscle.

Levels of mRNAs specific for the alpha-, gamma- and delta-subunit of the nicotinic acetylcholine receptor were measured in chick skeletal muscle by solution hybridization, using a genomic DNA probe containing the intramembrane segments M2 and M3 of the alpha-subunit and probes comprising exons 2-6 and exons 4-8, respectively, of the gamma- and delta-subunit. In the innervated calf musculature of adult chickens, receptor-specific messages were detected in approx. 100-fold excess over the amount required to account for the observed synthesis rate. Within 1 week after section of the sciatic nerve, alpha-, gamma- and delta-subunit message levels rose 112-, 42- and 24-fold, respectively, while receptor expression rate increased about 150-fold. The rise in message levels preceded the denervation-induced increase in receptor concentration. In differentiating myogenic cells all three messages were found in excess over the amounts required for the observed rate of receptor synthesis. Treatment of differentiated myotubes with drugs that change receptor synthesis rate selectively affects alpha-subunit mRNA. In all situations in vitro and in vivo the alpha-subunit mRNA was found to reach final levels faster, and to be from 3 to over 30 times more abundant, than the other messages. These observations corroborate earlier evidence for a regulatory mechanism in which the supply of mRNA determines acetylcholine receptor synthesis rate. They also suggest that receptor expression is not simply proportional to acetylcholine receptor subunit mRNA concentrations, but rather is controlled, to a considerable extent, by the efficiency with which the receptor-specific mRNAs and/or the subunits they code for are subsequently utilized.

Animals↗
PubMed1988

Binding sites for [3H]-acetylcholine and 125I-alpha-bungarotoxin in the optic ganglion of Loligo pealii.

1. In the optic ganglion of Loligo pealii, binding sites for [3H]-acetylcholine (KD: 5.2 x 10(-7) M; Bmax: 1.7 x 10(-11) mol/g tissue) and 125I-alpha-bungarotoxin (KD: 3.3 x 10(-9) M; Bmax: 9.7 x 10(-11) mol/g tissue) were observed. 2. Both sites are blocked by nicotinic compounds, but differ significantly in their affinity for individual ligands, with the acetylcholine site preferentially binding agonists, and the toxin site, antagonists. 3. The acetylcholine site is substantially more thermolabile than the toxin site. 4. A partial separation of the two binding activities is accomplished by sucrose density centrifugation. 5. These observations and a comparison with other tissues (Torpedo californica electroplaque; chick optic lobe; rat brain) suggest the presence, in the squid, of more than one kind of neuronal nicotinic receptor.

Animals↗
PubMed1988

A cell type-specific enhancer drives expression of the chick muscle acetylcholine receptor alpha-subunit gene.

The regulation of acetylcholine receptor alpha-subunit gene expression was analyzed by transient expression assays. Using rabbit beta-globin cDNA as a reporter gene, we have confirmed that the 5'-flanking sequence of the chicken acetylcholine receptor alpha-subunit gene directs specific expression in differentiated C2C12 cells, a mouse muscle cell line, but not in undifferentiated C2C12 cells and mouse 3T3 fibroblasts. Testing chimeric plasmids containing Bal31 deletion mutants of the alpha-subunit gene upstream sequence, we found the -116 to -81 region of the alpha-subunit to be responsible for tissue- and stage-specific expression. This 36 bp fragment stimulates the activity of both alpha-subunit and SV40 promoters in a distance- and orientation-independent manner, thus fulfilling the criteria of an enhancer.

Animals↗
PubMed1988

Rhizobium meliloti nodA and nodB genes are involved in generating compounds that stimulate mitosis of plant cells.

The nodB gene of Rhizobium meliloti encodes a 23.8-kDa protein that is conserved in several Rhizobium species. Monospecific polyclonal antibodies against NodB were used to localize this protein in the cytosol of R. meliloti and Escherichia coli cells containing nodABC genes. In comparison to the NodA and NodC proteins, NodB is synthesized in a disproportionately low amount. The NodA and NodB proteins are involved in generating small, heat-stable compounds that stimulate the mitosis of various plant protoplasts. Our experiments suggest that NodC is not involved in the synthesis of the factors. On the basis of their properties, we speculate that the factors are cytokinin-like substances.

Journal Article↗
PubMed1988

Nitrendipine treatment in so-called therapy-resistant arterial hypertension; effect as monotherapy and in combination with propranolol on blood pressure, heart rate, other hemodynamic parameters, plasma renin activity, and catecholamines.

Twenty-three patients [mean age 49.7 +/- 5.6 years (WHO II-III)] with severe hypertension and not responding to previous drug treatment were included in the study to evaluate the effect of nitrendipine (NTP) as monotherapy and also in combination with propranolol (PRO). After a control period of 10 days, NTP was started with 20 mg twice a day and titrated to the maximal dosage of 2 X 40 mg/day. After 1 week of NTP treatment, PRO was added in increasing dosage to a maximal 2 X 100 mg/day. NTP lowered systolic and diastolic blood pressure (BP) significantly (supine BP from 182/119 +/- 19/9 to 157/98 +/- 16/9 mm Hg). After combination with PRO, systolic BP was decreased additionally (supine BP from 157/98 +/- 16/9 to 150/97 +/- 19/9 mm Hg). Plasma norepinephrine (NE) was increased by NTP (from 1.82 +/- 0.78 to 2.38 +/- 1.08 nmol/l, p less than 0.01) and remained elevated during PRO treatment (2.76 +/- 1.10 nmol/l). Plasma renin activity (PRA) showed no significant changes by NTP. Additional effect of PRO on BP correlated significantly with NE and PRA after the NTP period. Plasma epinephrine and dopamine beta-hydroxylase remained unchanged. NTP decreased systemic resistance, calculated from isotope dilution technique (p less than 0.05); after combination with PRO no additional significant changes were registered. Nitrendipine is an effective alternative in so-called therapy-resistant hypertension.

Blood Pressure↗
PubMed1988

Induction of 33-kD and 60-kD Peroxidases during Ethylene-Induced Senescence of Cucumber Cotyledons.

Ethylene enhanced the senescence of cucumber (Cucumis sativus L. cv ;Poinsett 76') cotyledons. The effect of 10 microliters per liter ethylene was inhibited by 1 millimolar silver thiosulfate, an inhibitor of ethylene action. An increase in proteins with molecular weights of 33 to 30 kilodaltons and lower molecular weights (25, 23, 20, 16, 12, and 10 kilodaltons) were observed in sodium dodecyl sulfate-polyacrylamide gel electrophoresis gels after ethylene enhanced senescence. The measurement of DNase and RNase activity in gels indicated that these new proteins were not nucleases. Two proteins from ethylene-treated cotyledons were purified on the basis of their association with a red chromaphore and subsequently were identified as peroxidases. The molecular weights and isoelectric points (pI) of two of these peroxidases were 33 kilodaltons (cationic, pI = 8.9) and 60 kilodaltons (anionic, pI = 4.0). The observation that [(35)S]Na(2)SO(4) was incorporated into these proteins during ethylene-enhanced senescence suggests that these peroxidases represent newly synthesized proteins. Antibodies to the 33-kilodalton peroxidase precipitated two in vitro translation products from RNA isolated from ethylene-treated but not from control cucumber seedlings. This indicates that the increase in 33-kilodalton peroxidase activity represents de novo protein synthesis. Both forms of peroxidase degraded chlorophyll in vitro, which is consistent with the hypothesis that peroxidases have catabolic or scavenging functions in senescent tissues.

Journal Article↗
PubMed1988

Establishment and characterization of osteogenic cell lines from a spontaneous murine osteosarcoma.

Five clonal cell lines were established from a spontaneous BALB/c mouse osteosarcoma, and characterized. Four of these lines showed some similarities in morphology, in vitro growth properties, production of collagenous and noncollagenous extracellular matrix proteins and osteogenic differentiation. The cells formed colonies with characteristic differences in size and morphology in soft agar, and osteogenic sarcomas and metastases in syngeneic mice after transplantation. Ultrastructurally, cells in the transplant tumours showed marked osteogenic features. There were no osteoclast-like cells. The fifth cell line had somewhat different characteristics. All five lines expressed infectious endogenous murine leukemia viruses. Increased c-myc protoon-cogene expression was found in one cell line and c-fos expression at different levels in all lines. There was only very low expression of c-Ha-ras and no expression of c-Ki-ras and c-sis. DNA analysis showed the presence of newly acquired proviral genomes integrated at different sites in the cellular DNA. The results show that distinct osteogenic neoplastic subclones can be obtained from a primary mouse osteosarcoma. Although the clones exhibited an appreciable morphological, functional, and molecular diversity they retained the basic pathogenic properties of the tumour from which they were derived.

Alkaline Phosphatase↗
PubMed1988

Perinatal risk factors and first-year vocalizations: influence on preschool language and motor performance.

Spontaneous vocalizations of nine children with neonatal risk factors were systematically tape-recorded during the first year of life, as were those of 20 randomly chosen children without such risk factors. All the children were also given a battery of tests measuring language, speech, intelligence and motor function at six years. Cumulated tape-recordings for the periods six to 11 months and six to 14 months showed the infants with risk factors to have a significant reduction in various reduplicated syllables and consonants during the first year compared to those without risk factors. At six years, six of the nine at-risk children had an abnormal language test, as did two of the 20 without neonatal risk factors. Children with abnormal language tests performed significantly more poorly on various motor tasks; they also had had significantly fewer reduplications and consonants during infant vocalizations than the children with normal language tests. Perinatal risk factors may delay the production of prelinguistic sounds, and analysis of vocalizations might help to identify children who are at risk for later language disorders.

Apgar Score↗