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Biomedical subjects

T Steiner

Publications and source records attributed to T Steiner.

At least 109 records · Page 6Linked to original sources
PubMed1987

Antenna organization in green photosynthetic bacteria. 2. Excitation transfer in detached and membrane-bound chlorosomes from Chloroflexus aurantiacus.

The photosynthetic antenna of Chloroflexus aurantiacus includes bacteriochlorophyll (BChl) C740 and BChl a792, both of which occur in chlorosomes, and B808-866 (containing BChl a808 and BChl a866), which is membrane-located (subscripts refer to near-infrared absorption maxima in vivo). BChl a792 is thought to mediate excitation transfer from BChl c740 to BChl a808. Lifetimes of fluorescence from BChl c740 and BChl a792 were measured in isolated and membrane-bound chlorosomes in order to study energy transfer from these pigments. In both preparations, the lifetime of BChl c740 fluorescence was at or below the instrumental limit of temporal resolution (about 30-50 ps), implying extremely fast excitation transfer from this pigment. Attempts to disrupt excitation transfer from BChl c740, either by conversion of part of this pigment to a monomeric form absorbing at 671 nm or by partial destruction of BChl a792 by oxidation with K3Fe(CN)6, had no discernible effects on the lifetime of BChl c740 fluorescence. Most (usually greater than 90%) of the fluorescence from BChl a792 decayed with a lifetime of 93 +/- 21 ps in membrane-attached chlorosomes and 155 +/- 22 ps in isolated chlorosomes at room temperature. Assuming that the only difference between these preparations is the occurrence of excitation transfer from BChl a792 to B808-866, a 41% efficiency was calculated for this process. This value is lower than the 60% efficiency of excitation transfer from BChl c740 to B808-866 determined by comparison of fluorescence excitation and absorption spectra of membranes with attached chlorosomes and compares even less favorably with the 100% efficiency of excitation transfer found in whole cells by the same method.(ABSTRACT TRUNCATED AT 250 WORDS)

Bacteria↗
PubMed1986

Triiodothyronine increases responsiveness of cultured rat bone cells to parathyroid hormone.

Osteoblast-like cells prepared from calvaria of newborn rats and grown in culture for 1 week show markedly increased ornithine decarboxylase (ODC) activity upon exposure to parathyroid hormone (PTH) for 4 h. Triiodothyronine (T3) increases ODC activity of the cultures in long-term experiments but does not stimulate cell replication. Moreover, PTH responsiveness is enhanced by T3. Thus, T3 acts directly on bone cells, and the clinical observation of bone sensitization to PTH by thyroid hormones is confirmed at the cellular level.

Animals↗
PubMed1985

Comparison of in vivo effects of insulin-like growth factors I and II and of growth hormone in hypophysectomized rats.

Pure human IGF I (43 and 103 micrograms/day) and IGF II (131 micrograms/day) were infused into hypophysectomized rats during 6 days by means of sc implanted minipumps. Their effects on several growth indices were compared with those of various doses of sc infused human growth hormone. Growth hormone infusion produced a dose-dependent rise of endogenous rat IGF from 39 (without growth hormone) to 86 microU equivalents/ml (with 400 mU hGH/day) as determined by a competitive protein binding assay with a human IGF standard. In rats receiving the two doses of IGF I, total serum IGF levels rose to 83 and 99 microU equivalents/ml, respectively, in those receiving the IGF II dose the total serum IGF level rose to 146 microU equivalents/ml. These increases corresponded to steady state levels of 168 and 286 ng/ml of immunoreactive insulin-like growth factor (IR-IGF) I and 320 ng/ml of IR-IGF II. IGF I, but not IGF II led to an increase in body weight similar to that induced by the low doses of hGH (12.5 and 25 mU, respectively). The rise of endogenous rat IGF as well as the infused human IGF I and II caused a widening of the tibial epiphysis and an increase of the [3H]thymidine incorporation into costal cartilage. With respect to these two indices IGF II was clearly less potent that IGF I. When expressed in microU equivalents of the protein binding assay, endogenous rat IGF induced by hGH appeared to be relatively more effective than infused human IGF I or II.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1984

Insulin-like growth factor I supports differentiation of cultured osteoblast-like cells.

Rat calvaria cells grown in culture for one week had properties of osteoblasts: a high content in alkaline phosphatase and a marked cyclic AMP response to parathyroid hormone (PTH). In short-term experiments, insulin-like growth factor I (IGF I) stimulated the incorporation of [14C] glucose into glycogen. When IGF I was present in the medium during 6 days the cell number increased slightly and there was a substantial, disproportionate rise in alkaline phosphatase activity of the cultures. Thus, IGF I stimulates growth, and in addition, and in contrast to other growth factors, mainly enhances differentiation of osteoblasts.

Alkaline Phosphatase↗
PubMed1984

Oxidoreduction sites and relationships of spiroplasmas with insect cells in culture.

We have previously shown that Spiroplasma citri oxidoreduction sites, as revealed by the reduction of potassium tellurite into electron-dense tellurium crystals detectable by electron microscopy, were located at the blunt end of the organisms. The time of incubation of S. citri in potassium tellurite had no influence on the labeling. We have investigated the presence and location of oxidoreduction sites for other spiroplasmas such as the corn stunt spiroplasma (CSS), 277F, B88, BNR1 and PPS1. For all of these strains (except CSS, which is similar to S. citri), the location of oxidoreduction sites was affected by the time of incubation in potassium tellurite, and could be observed in different locations of the helix. 277F showed first labeling at the blunt end and a second, strong labeling at the tapered end. The other strains showed labeling all along the helix, but labeling at the blunt end generally appeared first. When Drosophila (Dm-1) cell cultures were infected with S. citri or 277F, the organisms adsorbed to the cells. Observation of infected cells by electron microscopy revealed that S. citri attached to the cells by the blunt end, while 277F attached either by the blunt end or the tapered one. The infection of leafhopper cell cultures (AS-2) with S. citri has been followed by transmission electron microscopy after incorporation of tritiated thymidine in the organism, and an immunocytochemical method has been developed to locate the organisms inside the cells.

Animals↗
PubMed1983

Preferential enhancement of myoblast differentiation by insulin-like growth factors (IGF I and IGF II) in primary cultures of chicken embryonic cells.

Cells prepared from the body walls of chicken embryos were plated in the absence of serum. Insulin-like growth factors (IGFs) barely stimulated cell replication, but preferentially enhanced the differentiation of muscle cells. Myoblast fusion was favoured in the presence of IGF (or insulin). Concomitantly, acetylcholinesterase activity increased. IGF I and IGF II were equipotent and active in low physiological concentrations, in contrast to insulin, which was known for a long time to exert such effects at pharmacological concentrations.

Acetylcholine↗
PubMed1983

Insulin-like growth factors stimulate synthesis of nucleic acids and glycogen in cultured calvaria cells.

A (sub)population of cells obtained from newborn rat calvaria by (sequential) collagenase digestion is grown to confluence in serum-containing medium. These cells are osteoblast-like with respect to high alkaline phosphatase activity and marked responsiveness (cAMP) to parathormone. Insulin-like growth factors (IGFs) enhance net incorporation of the labeled precursors thymidine, uridine, and glucose into the respective macromolecules DNA, RNA, and glycogen. Human IGF I is five times as potent as IGF II in evoking these anabolic responses in cultured rat calvaria cells. In contrast to insulin, the factors are effective in concentrations in which they are present in serum.

Alkaline Phosphatase↗
PubMed1983

Mycoplasmal infection of insect cell cultures.

Twenty-five cell cultures of three insect orders from eight laboratories were tested for mycoplasmal infection. Acholeplasma laidlawii was detected in one culture, an incidence of 4.0%. A. laidlawii, Mycoplasma orale, M. arginini, but not M. hyorhinis, could establish infections of drosophila Dm-1 cell cultures at 25 degrees C. In prospective studies, drosophila Dm-1 cultures were intentionally infected with broth-propagated A. laidlawii and M. hyorhinis. M. hyorhinis did not grow and was eliminated from the Dm-1 cultures during consecutive passages. A. laidlawii grew without obvious cytopathic effects during six weekly passages; titers of over 10(7) CFU/ml were recorded at Passages 2 and 5 (p2 and p5). Minimal cell culture infectious doses were also determined during these studies. 0.1 milliliter cell samples were inoculated into Leighton tubes containing either fresh M1A culture medium or 3T6 indicator cells in McCoy's 5a medium. After 4 d of incubation at 25 and 37 degrees C, respectively, the cover slips were stained by DNA fluorochrome Hoechst 33258 (A. laidlawii) or by specific fluorescein-conjugated antiserum (M. hyorhinis). At p2 with both mycoplasma species, the procedure using M1A medium and incubation at 25 degrees C without 3T6 cells was inferior to indicator cells. In five of six experiments at least a two-log higher titer of mycoplasmas was needed to be detected with M1A and 25 degrees C. At p5 no difference could be found. Uridine phosphorylase assays of Dm-1 cultures infected with A. laidlawii, M. hyorhinis, M. orale, and M. arginini gave clearly positive results only with A. laidlawii. The ratio of incorporated uridine to incorporated uracil method yielded false positives with two drosophila cell lines. Suggestions for assay of mycoplasmas in invertebrate cell cultures are given.

Acholeplasma↗
PubMed1983

[Detection and early treatment of mental disorders in early childhood].

Neurotic and psychosomatic developmental disorders and the rare psychoses in early childhood should be recognized and treated at an early age. This paper shows some characteristic features of treatment, as nonverbal communication, frequent organic-functional symptoms, family systems that are just being built up, risk of competitive situations towards the parents (especially the mother), problems of the indication of transfer from the paediatrician to the psychotherapist. Because of its institutional concept the psychotherapeutic day-clinic is especially qualified for intensive and early treatment of problems due to age and development.

Child Guidance Clinics↗
PubMed1982

Parathormone promotes glycogen formation from [14C]glucose in cultured osteoblast-like cells.

Parathyroid hormone stimulates [U-14C]glucose incorporation into glycogen of cultured osteoblast-like calvaria cells. This effect is detectable only several hours after the addition of PTH and it is mimicked by dibutyryl cyclic AMP. In contrast to insulin (in pharmacological concentrations), PTH enhances glycogen formation only in calvaria cells, but not in fibroblasts. Insulin-like growth factor I in physiological concentrations promotes glycogen-synthesis shortly after addition.

Animals↗
PubMed1982

Cultivation and partial characterization of spiroplasmas in cell cultures.

Spiroplasmas were propagated in the Drosophila melanogaster cell line Dm-1. Spiroplasma citri and unidentified strains (corn shunt organism, 277F [tick isolate], powder puff, BNR-1, honey bee, and OBMG) grew to 10(8) to 10(9) colony-forming units per ml and could be passaged. Cytopathic effect (CPE) varied with the infecting spiroplasma. The honey bee isolate killed Dm-1 within 2 to 4 days and produced CPE in four mammalian cells tested. At 25 degrees C, suckling mouse cataract agent produced no CPE in Dm-1 cells. Dm-1 cells did not support growth of the spiroplasmal sex ratio organism. Spiroplasmas could be detected in the cell cultures by agar inoculation, dark-field microscopy, scanning electron microscopy, and DNA fluorescent staining. The uridine phosphorylase test showed significant levels of conversion of [14C]uridine to [14C]uracil for all but some plant isolates: S. citri, corn shunt organism, lettuce, cactus, and powder puff strains, the first mycoplasmas to lack the enzyme. Primary isolations of corn shunt organism from infected corn plants were made in Dm-1 and I-XII cultures. The course of corn stunt organism infection of Dm-1 was monitored for three passages. The use of agarose and Dienes staining of the colonies improved growth and colony counting of corn stunt organism. The number of viable infected DM-1 cells decreased from 1.2 x 10(7) at passage 1 to 7.0 x 10(6) at passage 2 and 3 x 10(5) at passage 3.

Animals↗