Mutants of Aspergillus nidulans with increased resistance to the alkylating agent, N-methyl-N'-nitro-N-nitrosoguanidine

The isolation and characterisation of mutants of Aspergillus nidulans showing resistance to MNNG is described. Such isolates were stable through prolonged subculture in the absence of the selective agent, and resistance segregated as an allele of a single gene in meiotic and mitotic analysis. MNNG-resistant strains showed an increase in resistance to EMS and UV irradiation but no cross-resistance to MMS was detected. Possible mechanisms of resistance to alkylating agents are discussed.     

Analytical errors in measuring radioactivity in cell proteins and their effect on estimates of protein turnover in L cells.

Previous studies from this laboratory on protein turnover in 3H-labelled L-cell cultures have shown recovery of total 3H at the end of a 3-day experiment to be always significantly in excess of the 3H recovered at the beginning of the experiment. In this study we have critically reviewed a number of possible sources for this error in measuring radioactivity in cell proteins. 3H-labelled proteins, when dissolved in 0.3 M-NaOH and counted for radioactivity in a liquid-scintillation spectrometer, showed losses of 30-40% of the radioactivity; neither external or internal standardization compensated for this loss. Hydrolysis of these proteins with either Pronase or concentrated HCl significantly increased the measured radioactivity. In addition, approx. 5-10% of the cell protein is left on the plastic culture dish when cells are recovered in phosphate-buffered saline. To aggravate this latter loss further, this surface-adherent protein, after pulse labelling, contains proteins of high radioactivity that turn over rapidly and make a major contribution to the accumulating radioactivity in the medium. These combined errors can account for up to 60% of the total radioactivity in the cell culture. Similar analytical errors have been found in studies of other cell cultures. The effect of these analytical errors on estimates of protein turnover in cell cultures is discussed.     

Nanosecond fluctuations of the molecular backbone of collagen in hard and soft tissues: a carbon-13 nuclear magnetic resonance relaxation study

We have determined the amplitude of nanosecond fluctuations of the collagen azimuthal orientation in intact tissues and reconstituted fibers from an analysis of 13C NMR relaxation data. We have labeled intact rat calvaria and tibia collagen (mineralized and cross-linked), intact rat tail tendon and demineralized bone collagen (cross-linked), and reconstituted lathyritic (non-cross-linked) chick calvaria collagen with [2-13C]glycine. This label was chosen because one-third of the amino acid residues in collagen are glycine and because the 1H-13C dipolar coupling is the dominant relaxation mechanism. Spin-lattice relaxation times (T1) and nuclear Overhauser enhancements were measured at 15.09 and 62.98 MHz at 22 and -35 degrees C. The measured NMR parameters have been analyzed by using a dynamic model in which the azimuthal orientation of the molecule fluctuates as a consequence of reorientation about the axis of the triple helix. We have shown that if root mean square fluctuations in the azimuthal orientations are small, gamma rms much less than 1 rad, the correlation function decays with a single correlation time tau and T1 depends only upon tau and gamma rms and not the detailed model of motion. Our analysis shows that, at 22 degrees C, tau is in the 1-5-ns range for all samples and gamma rms is 10 degrees, 9 degrees, and 5.5 degrees for the non-cross-linked, cross-linked, and mineralized samples, respectively. At -35 degrees C, gamma rms is less than 3 degrees for all samples. These results show that mineral and low temperature significantly restrict the amplitude of nanosecond motions of the collagen backbone.(ABSTRACT TRUNCATED AT 250 WORDS)     

Humoral antibodies to the antigens related to the structural protein antigens of the mammary cancer virus (MTV) in breast cancer patients and in healthy donors

Indirect radioimmunoassay and immunoperoxidase studies provided further evidence of human serum reactivity with murine mammary tumor virus (MMTV) structural proteins. Examination of over 400 human sera from breast cancer (BC) patients and controls has shown that the incidence of antibodies which react with MMTV structural proteins was significantly higher in BC patients (50%) than in patients with carcinomas of other organs (3%) or normal women (3%). However, the percentage of subjects immune to MMTV was higher in pregnant women (10%) as compared with normal subjects. All the women with BC of the first clinical stage had antibodies to MMTV. The percentage of immune donors was lower among patients with BC of the later stages (IIa, 90%, IIb, 76%, III, 27%, IV, 0%). Thus, a good agreement has been demonstrated between the first stages of BC and expression of antibodies to MMTV.     

Structural changes in cardiac vessels in experimental patent ductus arteriosus

In 43 puppies an experimental arterial duct was produced. The animals were observed for 1--2 months and then killed. Their hearts were separately weighed, and their vessels were studied by means of a complex histomicrometry method. In the puppies with the artificially produced arterial duct, hypertrophy of both cardiac ventricles was gradually developing, combined with thickening medial tunica of the coronary arteries at all levels of their branching. Simultaneously, the oblique-longitudinal musculature of the vascular walls grew stronger. In the distributing arteries it occurred at the expense of the muscular fasciculi situated in adventitia, in the resistance arteries--at the expense of the fasciculi situated in intima. The hypertrophic-hyperplastic changes noted in the vessels of the coronary system were connected with cardiac hypertrophy and with disorders of coronary hemodynamics.     

Q fever urban cases in Romania

Q fever urban sporadic cases in Romania in the 1981-87 period are reviewed as concerns their incidence, seasonality and epidemiological data. Urban cases represented 76.8% as against 23.2% rural cases from the 134 Q fever sporadic cases detected in this period. Cases were distributed throughout all months with peaks during April (18.4% of cases) and June (19.4%). Infections were not related to contact with livestock or domestic birds or with raw milk drinking. Cases could not be identified as Q fever occupational ones. 36.7% of patients were working in nonalimentary industry and only 12.6% were involved in meat industry, veterinary or human medical practices. New studies concerning unusual sources of urban infection such as dogs, cats or urban street pigeons are emphasized.     

A new restriction fragment length polymorphism in the haptoglobin gene region

Summary Direct gene analysis of the haptoglobin gene region was carried out by Southern blotting using an Hp cDNA as probe. Two types of polymorphism were observed: one due to intragenic duplication, is characterized by a constant fragment length difference of 1700bp observed with several enzymes and by complete correspondence with the protein molecular weight polymorphism; the second type, due to point mutation, was represented by two additional restriction sites for Eco RI and Pst I, with a frequency comparable to that of other genes. These two mutations segregated together in families, suggesting that the recently described Hp related gene is closely linked to the Hp gene. Moreover, they were completely associated with each other. The evolutionary significance of this finding is discussed.     

Optimal administration of dual screening tests for detecting a characteristic with special reference to low prevalence diseases.

We consider the problem of deciding optimally whether a characteristic exists based on one or two screening tests. We discuss the relative merits of giving either one or two tests, including the order in which they might be given, as well as their costs. Operating in the Bayesian mode, we derive posterior distributions for the accuracies of the tests and the prevalence of the characteristic. Applications to detecting rare conditions, such as the AIDS virus, are discussed.