Hierarchical down-modulation of hemopoietic growth factor receptors

Granulocytes and macrophages can be produced in vitro when progenitor cells from mouse bone marrow are stimulated by any of four distinct colony stimulating factors, Multi-CSF (IL-3), GM-CSF, G-CSF, and M-CSF (CSF-1). At 0 degrees C the four CSFs do not cross-compete for binding to bone marrow cells, indicating that each has a specific cell surface receptor. However, at 21 degrees C or 37 degrees C, Multi-CSF inhibits binding of the other three CSFs and GM-CSF inhibits binding of G-CSF and M-CSF. Rather than competing directly for receptor binding, the binding of Multi-CSF, GM-CSF, or G-CSF to their own receptor induces the down-modulation (and thus activation) of other CSF receptors at 37 degrees C. The pattern and potency of down-modulation activity exhibited by each type of CSF parallels the pattern and potency of its biological activity. We propose a model in which the biological interactions of the four CSFs are explained by their ability to down-modulate and activate lineage-specific receptors.     

Elastic properties of the hind foot of the Donkey, Equus asinus

The elastic properties of the hind feet of Donkeys, and of tendons removed from the feet, have been investigated by methods similar to those used in a previous study of the forefoot. The elastic strain energy stored in the foot, during a trotting step, is calculated to be approximately the optimum which would minimize the work required of the muscles in this gait.     

Scanning and transmission electron microscopy evidence of the cytological effect of pyrrolnitrin on ‘Microsporon audouinii’ Gruby CBS 313-54 ‘in vitro’

Scanning and transmission electron microscopy showed that a ceiling quantity (1.56 mcg) of antifungal antibiotic Pyrrolnitrin caused heavy damage to dermathophyteMicrosporon audouinii Gruby CBS 313-54in vitro. Suitable preparation technique made it clear that the changes involved consisted of hyphal collapse on the edge of the culture, with loss of euplasmic organelles identity and cell autolysis. The cell wall, however, was apparently undamaged. These findings fit in with the suggestion that the mode of action of the antibiotic leads to generalised lipoproteic membranes damage. They must, however, be considered as representing the result of the terminal phase of cell distress.     

Pulsed-field gel analysis of human immunoglobulin heavy-chain constant region gene deletions reveals the extent of unmapped regions within the locus

The human immunoglobulin heavy-chain constant region gene locus is organized in three main gene groups, the physical distances of which are unknown. Different types of gene deletions, originated by unequal crossingover, have been found to encompass one or more genes in the locus. We have analyzed some of these deletions by means of pulsed-field gel electrophoresis, which allows resolution of large DNA fragments. By identifying a fragment containing two of the main gene groups and by observing the size reduction of this fragment in subjects with deletions, we were able to estimate the distance between the two groups and better locate the pseudogene in-between.     

Evaluation of two unstructured mathematical models for the penicillin G fedbatch fermentation

The mathematical model for the penicillin G fed-batch fermentation proposed by Heijnen et al. (1979) is compared with the model of Bajpai & Reuß (1980). Although the general structure of these models is similar, the difference in metabolic assumptions and specific growth and production kinetics results in a completely different behaviour towards product optimization. A detailed analysis of both models reveals some physical and biochemical shortcomings. It is shown that it is impossible to make a reliable estimation of the model parameters, only using experimental data of simple constant glucose feed rate fermentations with low initial substrate amount. However, it is demonstrated that some model parameters might be key factors in concluding whether or not altering the substrate feeding strategy has an important influence on the final amount of product.It is illustrated that feeding strategy optimization studies can be a tool in designing experiments for parameter estimation purposes.