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R Maschler

Publications and source records attributed to R Maschler.

26 records · Page 2Linked to original sources
PubMed1977

A lymphocyte chalone assay using lymphocyte colony growth in agar capillaries.

Using a recently developed method of culturing T-lymphocyte colonies in agar-containing capillary tubes, the capacity of three different lymphoid extracts with lymphocyte chalone (LC) activity to inhibit colony growth was demonstrated. Sephadex fractions from a calf spleen extract were tested on the colony growth of granulocytic cells and PHA-stimulated T-lymphocytes as well as on the in vitro uptake of 3H-thymidine by bone marrow and ConA- and LPS-stimulated mouse spleen cells. The data strongly suggest that it is only the combination of several different assay systems applied to the same fractions that permits a clear-cut determination of a specific lymphocyte proliferation inhibitor like LC.

Agar↗
PubMed1977

In vitro culture of lymphocyte colonies in agar capillary tubes after PHA-stimulation.

Human peripheral lymphocytes were stimulated with phytohemagglutinin (PHA) in liquid culture, suspended in agar and incubated in glass capillary tubes. Compact colonies of lymphocytes were found growing along the tube bottom in a buffer film, while compact clusters and rare diffuse colonies were observed inside the agar. Several parameters affecting the clonal growth were studied and optimized: PHA-dose, agar concentration, gel length (volume), quantity and density of seeded cells per capillary and gel length. Colony yield mainly depends on the seeded-cell density with a sharp optimum at 2 X 10(5) cells/ml irrespective of gel length; higher cell densities reduce the colony yield, suggesting that colony growth is the result of both stimulatory and inhibitory factors produced by cooperating cells. Following the daily clonal growth was only possible with undisturbed tubes; the number of colonies steadily increased from day 2 until day 7. Densitometric colony scanning is possible, yet problematic. Colony yield (plating efficiency is 10--50-fold higher in agar capillaries than in the usual Petri dishes. An additional advantage is that the capillaries provide a basis for a simple and reliable assay system for determining regulatory factors of lymphocyte proliferation (including chalones).

Agar↗
PubMed1974

Function of individual 30S subunit proteins of Escherichia coli. Effect of specific immunoglobulin fragments (Fab) on activities of ribosomal decoding sites.

Specific anti-30S protein immunoglobulin G fragments (Fab) were used to determine the contribution of each of the 30S ribosomal proteins to: (1) polyphenylalanine synthesis, (2) initiation factor-dependent binding of fMet-tRNA, (3) T-factor-dependent binding of phenylalanyl-tRNA, and (4) fixation of radioactive dihydrostreptomycin. Twenty of the 21 possible antibodies (antibody against S17 excepted) were used. In conditions where all the 30S proteins were accessible to Fabs, all of these monovalent antibodies strongly inhibited polyphenylalanine synthesis in vitro. Antibodies against S4, S6, S7, S12, S15, and S16, however, showed a weaker effect.30S proteins can be classified into four categories by their contributions to the function of sites "A" and "P": class I appears nonessential for tRNA positioning at either site (S4, S7, S15, and S16); class II includes proteins whose role in initiation is critical (S2, S5, S6, S12, and S13); class III (S8, S9, S11, and S18) corresponds to proteins whose blockade prevents internal (elongation factor Tudependent) positioning; and class IV includes entities that are essential for activities of both "A" and "P" sites (S1, S3, S10, S14, S19, S20, and S21). Dihydrostreptomycin fixation to the 30S or 70S ribosomes was inhibited by antibodies against S1, S10, S11, S18, S19, S20, and S21, but only weakly by the anti-S12 (Str A protein) Fab. The significance of these results is discussed in relation to 30S protein function, heterogeneity, and topography.

Antigen-Antibody Reactions↗
PubMedDate not supplied

The influence of spermine, spermidine and various sera on T-lymphocyte and granulocyte colony growth in vitro.

Using T-lymphocyte (T-LC) and granulocyte colony (GC) assays with truly proliferating cells, the dose-response relationships of spermine and spermidine, fetal calf (FCS), calf (CS), horse (HS) and human AB serum (ABS), and of the polyamines in the presence of selected does of the sera were analyzed. In contrast to earlier observations using [3H]thymidine uptake masurements it was found that the polyamines as well as the sera themselves inhibit T-LC and GC growth in the presence of autologous HS and ABS, respectively. The polyamines also inhibit in the presence of additional HS and ABS, yet most effectively with added FCS and CS. Thus the previously reported species-specificity of the serum-dependent polyamine inhibition has here been shown to be more quantitative than qualitative. These studies stress the significance of assays utilizing truly dividing cells and broad dose-response relationship in order to assess specific biological effects in vitro.

Animals↗
PubMedDate not supplied

Lymphocyte chalone from calf thymus: problems of large scale extraction and assay.

Large scale extraction and assay of the lymphocyte chalone (LC), the natural lymphocyte proliferation inhibitor, require optimized, reproducible and standardizable methods. To this end we compared the effects on LC yield of storing thymus at different temperatures after collection from calves: Both quick freezing on solid CO2 and slow freezing at -50 degrees C led to a 30% loss of LC yield relative to that from unfrozen tissue kept at O degrees C. Moreover we found that the apparent decrease or total loss of LC activity upon storage of a purified LC fraction may result from an occasional lack of LC-responsiveness of human blood lymphocytes depending on the donor's physiological state, in spite of normal PHA reactivity. This suggested the use of LC-responsive, cryopreserved lymphocytes, the advantages of which are documented and discussed in detail.

Animals↗
PubMedDate not supplied

Elucidation of the different effects of polyamines and other naturally-occurring inhibitors of cell proliferation (chalones) on T-lymphocyte and granulocyte colony growth in vitro.

Using T-lymphocyte and granulocyte colony assays with truly proliferating cells the effects of the polyamine spermine and of other naturally-occurring inhibitors of cell proliferation have been differentiated. It has been confirmed that spermine, in the presence of fetal calf serum, is a potent inhibitor of cell proliferation. This inhibition could be reversed by the addition of either 3-hydroxybenzyl-oxyamine or 4-bromo-3-hydroxybenzyl-oxyamine, both of which are inhibitors of the polyamine oxidase. In comparison, fractions isolated from calf thymus were shown to inhibit lymphocyte, but not granulocyte colony growth, indicating their tissue specificity and lymphocyte chalone activity. Further this inhibition was not reversed by polyamine oxidase inhibitors demonstrating that polyamines were not the inhibitory principles in this preparation.

Animals↗