Radiogenic initiation of thyroid cancer: a common cellular event

A transplantation system for clonogenic cells in rat thyroid was used, which allows quantitative evaluation of both the acute cytotoxicity and the late neoplastic effects of ionizing radiation at the cellular level in vivo. We have obtained direct experimental evidence that radiogenic initiation of neoplasia in vivo is a common cellular event, and that cell number influences the expression of initiation. Ten per cent of those graft sites which had received 26 clonogens surviving 5 Gy developed carcinomas, while 4 per cent of those which received 26 unirradiated clonogens developed carcinomas. By comparison, 26 per cent of the sites that were inoculated with 411 surviving irradiated clonogens developed carcinomas while none of the 38 transplant sites that received 411 unirradiated clonogens developed carcinomas. Total tumour incidence (carcinomas plus adenomas) followed the same pattern.     

Changes in binding of a 27-kilodalton chimpanzee cauda epididymal protein glycoprotein component to chimpanzee sperm

Motility patterns of caput epididymal chimpanzee sperm, caput epididymal chimpanzee sperm incubated in vitro with chimpanzee cauda epididymal fluid, and cauda epididymal chimpanzee sperm were assessed quantitatively. Sperm recovered from the caput epididymis showed no motility, whereas sperm recovered from cauda epididymis showed progressive forward motility. After incubation in cauda fluid, approximately 25% of caput epididymal sperm showed some motile activity. Electrophoretic analysis of ¹²⁵I-labeled sperm plasma membrane preparations revealed that the surface of caput epididymal sperm, incubated in cauda fluid, was modified by the appearance of a major protein-glycoprotein surface component with an apparent molecular weight of 27 kilodaltons (kD). THis 27-kD component was not detected on caput epididymal sperm incubated in buffer or in caput fluid. However, it was present in cauda fluid and on cauda epididymal sperm. Binding to caput epididymal sperm was cell specific in that chimpanzee erythrocytes incubated in cauda fluid did not bind this 27-kD cauda fluid component. Motility patterns of ejaculated chimpanzee sperm and of ejaculated chimpanzee sperm incubated in the uterus of adult female chimpanzees also were assessed quantitatively. Ejaculated sperm showed progressive forward motility, whereas in utero incubated ejaculated sperm showed hyperactivated motility typical of capacitated sperm. Electrophoretic analysis of ¹²⁵I-labeled sperm plasma membrane preparations revealed the loss of a 27-kD component from the surface of ejaculated sperm after in utero incubation. No significant change in the ¹²⁵I-distribution pattern was detectable when ejaculated sperm were incubated in buffer. These results suggest that the lumenal fluid component, which becomes adsorbed to the surface of chimpanzee sperm during maturation in the epididymis and which is removed from the surface of mature chimpanzee sperm in the female reproductive tract, affects sperm motility.     

Cell-cell recognition of host surfaces by pathogens. The adsorption of maize (Zea mays) root mucilage by surfaces of pathogenic fungi.

The adsorption of radioactive mucilage by pathogenic fungi was shown to be dependent upon time, the composition of mucilage, the type of fungal surface (conidia, hyphae, hyphal apices), fungal species, pH and bivalent cations. All fungal adhesins were inactivated by either proteinase or polysaccharase treatments. Adsorption was not inhibited by the numberous mono-, di- and oligo-saccharides that were tested individually, but it was inhibited absolutely by several polysaccharides. This suggested that adsorption of mucilage by pathogens involved conformational and ionic interactions between plant and fungal polymers but not fungal lectins bound to sugar residues of mucilage. Several fractionation schemes showed that pathogens bound only the most acidic of the variety of polymers that comprise mucilage. There was not any absolute distinction between ability to bind radioactive mucilage and type of pathogen or non-pathogen. However, there were notable differences in characteristics of adsorption between two types of pathogen. Differences were revealed by comparison of the adsorption capacities of conidia and germinant conidia and chromatography of radioactive mucilage on germinant conidia. An ectotrophic root-infecting fungus (a highly specialized pathogen) bound a greater proportion of mucilage than did a vascular-wilt fungus (of catholic host and tissue range) with more than one class of site for adsorption. In contrast with the vascular-wilt fungus, sites for adsorption on the specialized pathogen were present solely on surfaces formed by germination.     

The protein-tyrosine kinase substrate p36 is also a substrate for protein kinase C in vitro and in vivo.

p36, a major in vivo substrate of protein-tyrosine kinases, is shown to be phosphorylated at serine 25, a site very close to the major site of tyrosine phosphorylation by pp60v-src, tyrosine 23 (J. R. Glenney, Jr., and B. F. Tack, Proc. Natl. Acad. Sci. USA 82:7884-7888, 1985). We present evidence suggesting that protein kinase C mediates phosphorylation of serine 25.     

A simple sensitive radioreceptor assay for calcium antagonist drugs

A radioreceptor assay for calcium channel antagonist drugs described here is based on the ability of these drugs to affect ³H-nitrendipine binding to calcium channels. All the known calcium channel antagonists may be assayed in this manner. The assay can detect 10–100 nM (4 – 40 ng/ml) nimodipine, 10–100 nM (3.5 – 35 ng/ml) nifedipine, 3–30 μM (1.2 – 12 μm/ml) prenylamine, 0.1 – 1.0 μM (49 – 490 ng/ml) verapamil and 3–30 μM (1.2 – 12 μg/ml) diltiazem. These values cover the range of concentrations of calcium channel antagonists that are clinically important. As the radioreceptor assay detects active metabolites as well as the parent drugs, it should prove a useful adjunct in cardiovascular therapy. The method is more reproducible, simpler and less expensive than other methods such as high pressure liquid chromatography.     

ATP-dependence of 125I-insulin binding by rat soleus muscle

Muscle ATP levels were lowered by incubating rat soleus muscles under anaerobic conditions, or in the presence of 2:4-dinitrophenol (0.5 mM), EDTA (5 mM) or mannitol (400 mM). 125I-insulin binding, measured under equilibrium conditions at 25 degrees C, was reduced by 49-71% in ATP-depleted muscles. Insulin binding was also determined using two other procedures which minimized internalization of 125I-insulin: these were (a) 5 min at 25 degrees C, and (b) 24 h at 3 degrees C. Under these conditions, 125I-insulin binding was reduced by 28-55% in ATP-depleted muscles. These results confirm that in soleus muscle the effect of ATP-depletion on 125I-insulin binding is actually concerned with the binding step itself and not merely a reflection of ATP-dependent internalization of the bound hormone.     

Solubilization and partial purification of hepatic 3-hydroxy-3-methylglutaryl coenzyme A reductase

This paper describes an effective method for the solubilization of microsomal HMG-CoA reductase from rat liver. Exposing the microsomes to a freeze-thaw treatment solubilized 80% of the microsomal reductase activity. Subsequently, a 25-fold purification has led to an enzyme preparation with a specific activity of 10–14 nmoles MVA per min per mg of protein and an increased stability.