Inhibition of endothelial cell proliferation by type beta-transforming growth factor: interactions with acidic and basic fibroblast growth factors

TGF beta is a potent (ED50 approximately 10(-11) M) inhibitor of the proliferative activities of both acidic and basic FGF on vascular and capillary endothelial cells in vitro. The inhibition of cell growth is dose-dependent and characteristic of a non-competitive interaction. The results demonstrate that TGF beta and FGF can interact at the cellular level to modulate growth and suggest that many of the biological activities of FGF observed in vitro and in vivo (ie angiogenesis, cell growth, cell differentiation) may be regulated by the presence of TGF beta and related proteins (ie inhibin) in the local cellular milieu. The possible identity of TGF beta with the inhibitors of endothelial cell growth detected in in vitro assays of crude extracts is discussed.     

Fibroblast growth factor in the human placenta

Fibroblast growth factor (FGF) has been purified 333,000-fold from human placenta by a combination of salt precipitation, cation-exchange chromatography, and Heparin-Sepharose affinity chromatography. Molecular weight (15-16 kDaltons), amino acid composition, bioactivity and immunological crossreactivity with bovine pituitary FGF indicate that the mitogens from the two species are closely related molecules.     

Evidence for related virulence sequences in plasmids of Salmonella dublin and Salmonella typhimurium

Transposon-insertion mutants were prepared from virulent field isolates of Salmonella dublin and Salmonella typhimurium. Detailed restriction-enzyme mapping of the single sites of TnA insertion in two mutants (M51 and M173) of S. dublin that showed diminished virulence in a mouse assay indicated that these sites were about 5 kbp apart on the approximately 70 kbp plasmid harboured by the isolate. A Tn10-insertion mutant (M242) of S. typhimurium that showed diminished virulence was also identified. A single copy of Tn10 was inserted into the approximately 90 kbp plasmid harboured by this isolate. Hybridization studies indicated that homology existed between the region encompassing the sites of TnA insertion in M51 and M173 and that encompassing the site of Tn10 insertion in M242. Restriction mapping indicated that the two regions were very similar and could even be identical and, if so, the Tn10 insertion in M242 could be mapped to a point 1.5 kbp from the TnA insertion in M51 and 6.5 kbp from that in M173. It appeared that the maximal extent of the putative similarity/identity was between 13 and 23 kbp. It is proposed that this stretch of high homology could represent a virulence sequence that has been conserved during the evolutionary divergence of the two Salmonella serotypes.     

Congenital malformations associated with anencephaly in liveborn and stillborn infants

Records from the population-based British Columbia Health Surveillance Registry were examined, and a total of 456 infants with anencephaly (181 liveborns, 275 stillborns) were identified. Registry records list up to four congenital malformations per individual, and the records of the study cohort were reviewed for the presence of additional malformations. A total of 12.7% of infants (14.4% liveborns, 11.6% stillborns) had congenital malformations in addition to anencephaly. The frequencies of specific congenital malformations (e.g., talipes, cleft lip and/or palate, omphalocele) in infants with anencephaly were compared with the frequencies of these malformations in the general population of liveborns. In addition, the types of additional congenital malformations in liveborn anencephalics compared to stillborns were looked at. The similarity suggests that it is not just the presence of these additional congenital malformations that leads to death in utero. The data provide further evidence for etiological heterogeneity in neural tube defects.     

Radioimmunoassay for fibroblast growth factor (FGF): release by the bovine anterior pituitary in vitro

A radioimmunoassay (RIA) was developed to measure fibroblast growth factor (FGF) using antiserum generated against a synthetic replicate of [Tyr¹⁰]FGF(1–10). The antisera, previously shown to be capable of inhibiting the biological action of FGF on bovine aortic arch endothelial cells in vitro [1], are highly specific for the amino-terminus of FGF. In the RIA, the antisera recognize the decapeptide antigen [Tyr¹⁰]FGF(1–10) and the intact mitogen on an equimolar basis and show less than 0.01% cross-reactivity with N-acetyl-[Tyr¹⁰]FGF(1–10).

Bovine adenohypophysial cells maintained in primary monolayer culture release and ir-FGF which is indistinguishable from the intact mitogen in as much as it is retained on heparin-Sepharose affinity columns and shows a dose-dependent and parallel displacement in RIA. The release of ir-FGF by the bovine adenohypophysis can be increased with forskolin (10⁻⁵ M) or KCl (50 mM). Preincubation of pituitary cells with 17β-estradiol has no measurable effects on basal ir-FGF, but increases the release after KCl treatment 2–3-fold. These results show that ir-FGF can be released by the bovine adenohypophysis in vitro and lend credence to the hypothesis that FGF plays a physiological role in the homeostatic mechanisms regulating mesoderm-derived cell growth.     

Chemical modification of nucleic acids. Methylation of calf thymus DNA investigated by mass spectrometry and liquid chromatography

Mass spectrometry provides an extremely sensitive method for the identification and quantification of modified nucleosides and hence for determining chemical modifications of nucleic acids. When mass spectrometry is used in conjunction with a new high-performance liquid chromatographic system capable of separating 15 methylated and naturally occurring nucleosides, this allows the quantification of products of in vitro DNA methylation. With synthetic (2H3)methyl-labeled methylnucleosides as internal references, the distribution of methylated products formed when calf thymus DNA was reacted with N-methyl-N-nitrosourea(MeNU) was determined. Five modified products, 1-methyldeoxyadenosine(m1dA), 3-methyldeoxycytidine(m3dC), 7-methyldeoxyguanosine(m7dG), 3-methylthymidine(m3T) and O4-methylthymidine(m4T) were detected and the relative distributions were measured. The ability of mass spectrometry/mass spectrometry (tandem mass spectrometry) to increase specificity and sensitivity in this determination is demonstrated and its application to in vivo studies is suggested.     

Effect of enucleation of the corpus luteum at different stages of the luteal phase of the human menstrual cycle on subsequent follicular development

To investigate the mechanism of suppression of follicular development during the luteal phase of the human menstrual cycle, the corpus luteum was enucleated surgically from 10 women at various times after ovulation. In the 24 h after CL enucleation there was an immediate and rapid fall in the concentration of oestradiol and progesterone and a temporary decline in the concentration of FSH and LH. Within 3 days, however, all 10 women showed evidence of renewed follicular activity as indicated by a progressive rise in the concentration of oestradiol. This rise was preceded by a rise in the concentration of FSH and LH, and ovulation, as indicated by a mid-cycle surge in LH and rise in the concentration of plasma progesterone, occurred 16-19 days after enucleation. There was no significant difference in the time to ovulation following enucleation at different times of the luteal phase. The post-operative follicular phase, measured from the time of enucleation, was 3 days longer than that observed pre-operatively from the first day of menstrual bleeding. In the follicular phase of post-operative cycles the concentration of FSH was higher and that of oestradiol lower than the corresponding values before surgery. These results indicate that the absence of healthy antral follicles in the luteal phase of the cycle is due to the inhibitory effects of the corpus luteum. The fact that, after CL enucleation, emergence of the dominant follicle was always preceded by a rise in the concentration of FSH and LH suggests that suppression of gonadotrophins by ovarian steroids secreted by the corpus luteum is responsible for the inhibition of follicular development during the luteal phase of the cycle.