Glycosaminoglycan synthesis by mammary tumor spheroids

Multicellular aggregates of tumorigenic mouse mammary epithelial cells contain a hyaluronate-rich matrix, both at the aggregate periphery and within the growing spheroid. It is proposed that the establishment of a hyaluronaterich matrix is essential to spheroid growth in vitro, and that the spheroid is a good model system for analysis of this aspect of early tumor development.     

Fast Atom Bombardment-High Field Magnet Mass Spectrometry of 6000 Dalton polypeptides

Using a combination of Fast Atom Bombardment lonisation and High Field Magnet — Mass Spectrometry we demonstrate here the ability to observe, for the first time, the accurate molecular weights of polypeptides or other important bioorganic substances up to 6000 Dalton in size. This claim is substantiated with data on intact unreduced Insulin and on the intact sweet protein Monellin, which consists of three polypeptide chains.     

Expression of GTP-binding proteins and prostaglandin E2 receptors during human T cell activation.

GTP-binding proteins (G-proteins) are a family of closely related, yet structurally distinct signal transducing proteins. In this study the presence and relative abundance of several G-proteins and of their corresponding mRNAs were measured in resting and activated human T lymphocytes. We found that T lymphocytes contain RNA coding for Gs, Gi2, and Gi3. No Gi1- and Go-specific RNA could be detected. Membrane fractions of resting and activated lymphocytes were studied in immunoblot experiments. Again, Gs, Gi2, and Gi3, but not Gi1 and Go, were detected. Upon mitogenic activation, a relative increase in mRNA for Gs and Gi3, but not for Gi2 could be demonstrated in Northern blot experiments. Immunoblotting indicated an increase in Gs and Gi3 density in membrane fractions of T cells as well. Paralleling the increase in Gs, we found that activated T cells produce five to seven times more cAMP per cell in response to prostaglandin E2 (PGE2) than resting lymphocytes. Finally, PGE2 binding studies showed that the number of receptors for this hormone increased from 435 +/- 322 to 1035 +/- 357 per cell following in vitro stimulation. We propose that in vitro T cell activation is paralleled by an increase in sensitivity to PGE2-induced cAMP generation. This sensitization is accompanied by both an increase in cell surface PGE2 receptor numbers as well as by increased expression of the signal transducing protein Gs and may physiologically be important for limiting an immune response.     

The lysis of Gram-negative Alcaligenes eutrophus by enzymes from Cytophaga

Summary The use of Cytophaga lysing enzymes was investigated for the liberation of poly--hydroxybutyrate (PHB) granules from the Gram-negative bacterium Alcaligenes eutrophus. Complete cell lysis was approached within a 60 minute period. Contrary to previous findings for the lysis of Gram-negative bacteria, prior removal of the outer membrane was not essential for enzymic lysis. The destabilisation of the outer membrane by the removal of divalent cations resulted in no significant improvement in the disruption process.     

The notion of minimum distance or why rare species are clumped

Summary The prevalence of statistical clumping in natural populations can sometimes obscure mutual avoidance behavior and the adaptive role of spacing out among population members. The problem is particularly severe in rare species where the inverse square relationship between expected nearest neighbor distance and population density demands mean distances between individuals be excessively large to maintain randomness or overdispersion. Realistically, individuals dispersing from a central nucleus might be expected to establish a minimum distance from neighbors to obtain a substantial gain in fitness but further dispersal would be undesirable due to increasing costs and decreasing gains. The result would be higher clumping at low densities. Data on clumping of rare species in an oak-cynipid gall wasp complex are interpreted in the context of the minimum distance notion, and the influence of parasitism on cynipid host population dispersion is discussed.     

Fast atom bombardment: A new mass spectrometric method for peptide sequence analysis

We have studied a selection of peptides using a new mass spectrometric ionisation technique - fast atom bombardment (FAB). We define the fragmentation pathways observed and comment on the utility in sequence analysis. A simple acetylation experiment is shown to aid rapid sequence assignment.     

Interaction of DNA with a porphyrin ligand: evidence for intercalation.

The porphyrin photosensitizer, meso-Tetra (4-N-methylpyridyl) porphine tetraperchlorate binds to calf thymus DNA by intercalation and by external electrostatic association. This was concluded from the results of measruements involving Scatchard analysis, viscometry, thermal denaturation, and circular dichroism.     

Electrokinetic study of the reactions of peritoneal macrophages and eosinophils with IgG immune complexes

Electrophoretic light scattering (laser Doppler electrophoresis) has been employed to study the effects of guinea pig IgG immune complexes on the electrophoretic mobility distributions of guinea pig resident peritoneal cells. The resident population of cells is composed of macrophages (approximately 75%) and eosinophils (approximately 25%). These cells were separated according to the well-established method of Boyum. Populations of resident macrophages, eosinophils, and the unfractionated samples were incubated with soluble immune complexes, antigen alone, or antibody alone. The mean mobility of the resident macrophages decreased approximately 60% when incubated in the presence of immune complexes, although no effect could be discerned in the presence of antigen or antibody alone. The width of the resulting macrophage mobility distribution was larger than that of the control distributions, with a broad shoulder on the high-mobility side, indicating a heterogeneous response of the macrophages to the immune complexes. Eosinophils react in two distinct fashions. One population of eosinophils is present near the control experiments. The second population reacts in a manner very similar to that of macrophages. This suggest that at least two populations of eosinophils are present in the unstimulated guinea pig peritoneal cavity. Results that are intermediate between these two cases are found when unfractionated samples are studied.     

A radioimmunoassay for the Gm(b0) allotype of human immunoglobulins

A radioimmunoassay for the human allotype Gm(b⁰) which provides a sensitive and quantitative measurement of the level of this IgG3 genetic marker has been developed. The assay system can detect 15 nanograms of Gm(b⁰) IgG3 protein and is not inhibited by immunoglobulins of other allotypes and isotypes. Using this assay, good correlation was found between IgG3 and Gm(b⁰) levels in homozygous Gm(f, b⁰) sera and gene dosage effects could be confirmed. The correlation between Gm(b⁰) levels and IgG3 in Negroid Gm(a, b⁰) sera was not as good. This reduced correlation has been attributed to antigen differences in the IgG3 Gm markers characteristic of some Negroid Gm(a, b⁰) sera.