Specificity in the synergism between retinoic acid and EGF on the growth of adult human skin fibroblasts

Vitamin A (retinol) and five retinoids were tested for their ability to enhance epidermal growth factor (EGF) stimulation of adult human skin fibroblast growth in vitro. The retinoids utilized in this study were RO-1-5488 (all-trans-retinoic acid), RO-4-3780 (13-cis-retinoic acid), RO-10-9359, RO-10-1670, and RO-21-6583. Retinol and each retinoid were capable of stimulating fibroblast growth alone (0-86%), while 13-cis and all-trans-retinoic acid were the most potent in potentiating the EGF promotion of fibroblast growth. Other growth factors tested in addition to EGF were nerve growth factor (NGF), fibroblast growth factor (FGF), and thrombin. While EGF and FGF stimulated fibroblast growth to the same degree (2.3-fold), only growth stimulated by EGF was potentiated by retinoic acid. Since retinoic acid might enhance the EGF stimulation of cell growth by increasing either EGF receptor number or binding affinity, the binding of 125I-labeled EGF was carried out in the presence of retinoic acid and the data were subjected to a Scatchard-type analysis. No change in EGF receptor number or affinity was seen in the presence of retinoic acid. The data indicate a specific interaction between retinoid acid and EGF which results in the potentiation of the EGF-stimulated cell growth. Furthermore, the mechanism of this interaction does not seem to involve the initial binding of EGF to its plasma membrane receptor or the available number of EGF receptors located on the cell surface.     

Radiotherapy in small cell cancer of the lung treated with combination chemotherapy: a controlled trial.

Three hundred and seventy one patients with extensive or limited small cell cancer of the lung took part in a randomised trial to evaluate irradiation of the primary tumour in patients treated with combination chemotherapy. They were randomly allocated to treatment either with chemotherapy alone (198) or with both chemotherapy and radiotherapy (173). All 371 initially received 12 weeks of chemotherapy after which they were categorised according to response. Only those with stable or responding disease continued with their allotted treatment. Thus 144 received chemotherapy alone and 135 received both chemotherapy and radiotherapy. The design of the study permitted analysis of the effect of radiotherapy according to initial extent of disease and quality of early response to chemotherapy. Radiotherapy (40 Gy (4000 rad), one fraction a day over 20 days) did not improve the survival of patients in any category of initial extent of disease or early response to chemotherapy and was not effective in preventing local relapse.     

Localization of a unique DNA sequence to band p16 of human chromosome 4

Southern blot analysis of DNA from human-rodent cell hybrids and in situ hybridization to metaphase chromosomes allowed the assignment of a unique human DNA sequence associated with satellite DNA to band p16 of human chromosome 4.     

Spatial pattern in the organic layer and tree growth: A case study from regenerating Picea mariana stands prone to paludification

Questions: 1. How does the spatial structure of the organic layer affect tree sapling physiology? 2. Are the organic layer and Picea mariana height growth spatially structured at different scales? 3. Does microtopography influence the accumulation of organic matter and does organic layer thickness affect height growth? Locations: Picea mariana forests, northwestern Quebec, Canada. Methods: We assessed the spatial pattern of each variable in one wildfire site and one harvest site using semivariograms and correlograms. We measured the cross‐correlation between relative elevation and organic layer thickness, and between organic layer thickness and growth using cross‐correlograms. Results: Picea mariana height growth was autocorrelated to a greater extent in the wildfire site (103 m) than in the harvest site (43 m). The spatial structure of organic layer thickness was similar in both sites. Deeper depressions in the harvest site, as illustrated by spatial variance in relative elevation at short distances (ca. 50 m), and by high autocorrelation values, increased the accumulation of organic matter within 20 m. Conclusions: The interaction between microtopography and organic matter accumulation led to paludification and poor growth of Picea mariana at the harvest site. Paludification at the wildfire site was independent of microtopography and was probably a result of stand development.     

Stage-specific hypermutability of the regA locus of Volvox, a gene regulating the germ-soma dichotomy

Mutation at the regA locus confers on somatic cells of Volvox (which otherwise undergo programmed death) ability to redifferentiate as reproductive cells. Stable mutations at the regA locus, but not at other loci, were induced at high frequency when embryos at one particular stage were exposed to either UV irradiation, novobiocin, nalidixic acid, bleomycin, 4-hydroxyaminoquinoline-1-oxide, 5-bromodeoxyuridine, or 5-fluorouracil. All treatments led to some mutations that were not expressed until the second generation after treatment. The sensitive period was after somatic and reproductive cells of the next generation had been set apart, but before they had undergone cytodifferentiation. Hypermutability occurs in presumptive reproductive cells (in which regA is normally not expressed) somewhat before regA normally acts in somatic cells. We postulate that hypermutability of regA in the reproductive cells at this time reflects a change of state that the locus undergoes as it is inactivated.