Interactions of surfactin,a biosurfactant fromBacillus subtilis,with inorganic cations

Summary The properties of surfactin, a biosurfactant lipopeptide, were highly modified in the presence of inorganic cations. The micellization of surfactin was favoured by monovalent and, especially by divalent cations with a modification of the molecular area at the air-water interface. Haemolysis of erythrocytes by surfactin was enhanced by low concentrations of divalent cations with an increase of the binding of the lipopeptide to membrane. Inorganic ions induced conformational rearrangements probably due to ion-surfactin associations which modify the surface-active properties.     

Activation of lignin and manganese peroxidase excretion in Phanerochaete chrysosporium by fungal extracts

Summary Lignin (LiP) and manganese peroxidase (MnP) excretion by Phanerochaete chrysosporium INA-12 was significantly increased in response to fungal extract supplementation. LiP and MnP production was increased 1.7- and 1.8-fold, respectively, with fungal extracts from agitated pellet cultures of strain INA-12, namely fungal extracts P₆ and P₄. In cultures supplemented with a fungal extract harvested from static cultures of strain INA-12 (fungal extract S₄), LiP and MnP production was increased 1.8- and 1.6-fold, respectively. Succinate dehydrogenase activity, a mitochondrial marker, was significantly enhanced (2.7-fold) in cultures with the addition of fungal extracts. Correspondence to: M. Asther     

Production of Cell Wall-Degrading Enzymes by the Phytopathogenic Fungus Sclerotinia sclerotiorum

The range of polysaccharide-degrading enzymes and glycosidases formed by the phytopathogenic fungus Sclerotinia sclerotiorum was monitored following growth on 16 carbohydrate substrates. Endo- and exoenzymes capable of degrading cellulosic, hemicellulosic, and pectinolytic polysaccharides were secreted. Pectinolytic activities were produced constitutively on all of the substrates tested. Cellulolytic enzymes were not induced in simple sugar (i.e., glucose or xylose) media. Polysaccharide growth substrates and cellulase inducers increased all of the enzyme activities tested. Gel filtration analysis revealed the appearance of new molecular forms of pectinase, β-xylosidase, and cellobiosidase during induction on pectin and carboxymethyl cellulose media.     

Increase of IGF I binding to erythrocyte receptors during the TRH-test: correlation between IGF I binding and thyroid hormone values

The effects of TRH on insulin-like growth factor I receptors were investigated on erythrocytes from 7 GH-deficient children having plasma GH levels less than 10 ng/ml during two provocation tests. Intravenous injection of synthetic TRH (0.2 mg/m2) was followed by a marked increase of IGF I binding on erythrocytes, from 3.9% +/- 0.3% to 5.9% +/- 0.3% (P less than 0.005) after 1 hour and 7.3% +/- 0.4% (P less than 0.005) after 2 hours. The IGF I binding variations were due to an increase in both the receptor affinity and the number of sites. The levels of plasma GH, IGF I, T3, T4, free T4, TSH and prolactin having been determined during the TRH test at 0, 1 hour, and 2 hours after the injection, the increase in the IGF I binding to erythrocytes at the same time correlated with the rise of thyroid hormones: triiodothyronine T3 (P less than 0.001) and thyroxine T4 (P less than 0.005) and not with the level of the other hormones. These findings suggest that thyroid hormones play a role in the regulation of insulin-like growth factor I receptors.     

Identification of a membrane glycoprotein overexpressed in murine lymphoma sublines resistant to cis-diamminedichloroplatinum(II)

A series of murine thymic lymphoma cell sublines was selected in vitro for resistance to cis-diamminedichloroplatinum(II) (CDDP). The level of CDDP resistance correlated with reduced drug accumulation in these cells. A rabbit antiserum was raised against the plasma membrane of a CDDP-resistant subline and used in Western blot analyses. Increased expression of a surface antigen of approximately 200 kDa was observed and found to correlate with the degree of resistance. Further biochemical and immunological studies demonstrated that this is a plasma membrane glycoprotein. However, it is different from the multidrug resistance-associated P-glycoprotein with a molecular weight of about 170,000. We have called this unique CDDP resistance-associated membrane protein CPR-200.     

Hybridization of a mouse T-cell lymphocyte line (HB1) with a polyoma virus-transformed mouse fibroblast line

The establishment of permanent T-lymphocyte cell lines by transformation with DNA viruses has not yet been achieved. This paper reports the successful transfer of polyoma virus genome into T-lymphocyte cells by somatic hybridization. A T-lymphocyte clone, HB₁, derived from (DBA/ 2J×AKR) spleen cells, isolated in vitro by cloning in semi-solid agar, was fused with a polyoma (Py) virus-transformed fibroblast C3HPy, clone 1. The authenticity of the hybrid C3H/HB was established by chromosome and histocompatibility antigen studies. This initial population and the various clones retained T-lymphocyte characteristics such as morphological appearance, growth properties (suspension culture) and differentiation antigen (Thy 1–2). The hybrid cell line and the various clones presented all the characteristics of Py transformation. Namely, they carried the Py genome originating from the fibroblastic parent and maintained Py virus tumour-associated antigens (TSTA, TSSA and T antigens). In most respects, this hybrid population resembled the C3HPy/C11 parent and exhibited the same tumorigenicity.     

Stochastic prey-predator relationships: A random evolution approach

The formalism and results of the theory of random evolutions are used to establish and investigate a model for two randomly interacting populations. The asymptotic stability of the expected solution is studied and contrasted to that of the associated deterministic system.     

Choline acetyl transferase activity in chick embryo neuroretinas during development in ovo and in monolayer cultures

The specific activity of the enzyme choline acetyl transferase (CAT) in chick neuroretinas was investigated during in ovo development and in monolayer cultures. The enzyme activity was barely detectable on the 6th day of incubation but increased markedly between the 7th and 11th days. The activity increased sharply between the 15th and 17th days and then slowly until hatching. When cell suspensions from 6- to 7-day neuroretinas were cultured as monolayers, CAT specific activity increased rapidly. After 4–5 days in culture, the activity of the enzyme was identical to that found in the neuroretina on the 11th day of incubation. Cells from 9-day neuroretinas also differentiate in monolayer cultures, but with a more irregular pattern. These data show that cholinergic neurons from chick embryo neuroretina differentiate in monolayer cultures without a lag and at the same rate as in vivo.