Camille François

Comparitive study of the milk fat globule membrane and the mouse mammary tumour virus prepared from the milk of an infected strain of Swiss albino mice

Abstract Milk fat globule membranes and mammary tumour virus particles ( d = 1.17 g/cm 3 ) have been obtained from the milk of a Swiss albino mice strain. Comparitive biochemistry shows that these two structures differ significantly in the phospholipid, polypeptide and glycopolypeptide patterns and enzymatic activities. However, the lipid profile and the morphology of both structures suggest a filiation with the plasma membrane. Density fractions obtained from the crude virus preparation have been thoroughly investigated. The results suggest that most of these fractions represent degraded virus and/or atypical virus assembly.

Peroral infection of suckling mice with milk-borne mouse mammary tumour virus: uptake of the main viral antigens by the gut.

Persistence of mouse mammary tumour virus (MMTV) components in the digestive tract of suckling mice was investigated by immunoperoxidase staining of the main viral antigens and micro-immunoenzyme assays of gp52 and p28; these latter assays were also performed after ingestion of milk enriched in viral antigens using Cr2O3 as a marker for the alimentary bolus migration. When compared to the ingested antigens, the amounts of gp52 and p28 decreased during transit, p28 being more rapidly digested than gp52. The antigens were, however, destroyed to a much larger extent in the gut of the adult than in that of the newborn mouse. A fraction of the marker remained for a long time in the stomach; a prolonged retention was also observed with gp52 and especially with p28. Significant amounts of viral antigens were detected in the intestinal walls: both p28 and gp52 were found in the duodenum and small intestine. Moreover, the four viral antigens gp52, gp36, p28 and p8 were clearly observed in very large supranuclear vacuoles inside the epithelial cells of the distal part of the gut. Total particles can reach the intestine; the viral material could then be either destroyed or taken up in the epithelial cells by endocytosis, so that the intestinal epithelium might serve as a portal of entry for MMTV in the suckling mouse.

Distribution of Mouse Mammary Tumour Virus Antigens in RIII Mice as Detected by Immunofluorescence on Tissue Sections and by Immunoassays in Sera and Organ Extracts

Organs of RIII mice at various physiological stages were tested for mouse mammary tumour virus (MMTV) antigen expression. Indirect immunofluorescence was used with three monospecific antisera to localize one envelope glycoprotein, gp47, and two core proteins, p28 and p8. These virus-specific antigens gave characteristic fluorescent patterns in the mammary tissues and were also detected in thymus and salivary gland sections of some mice. The amounts of antigens gp47 and p28 were measured by immunoassay in sera and organ extracts of corresponding samples of mice. Sera of mice of both sexes contained virus antigens from the suckling age onwards. Although ingested virus could be traced in suckling mice, weanlings were characterized by the absence of virus expression except in lymph nodes. This location points to the possible role of lymphoid tissue in producing the antigens of the blood and in disseminating the infection. In adult animals, virus antigens were present in salivary glands, digestive tract, lymph nodes, male genital organs and female mammary glands. Antigen expression, even found in the mammary glands of virgin mice, was strikingly increased by pregnancy, lactation and (or) ageing, the highest values being found in mammary tumours. The results for milk-borne MMTV infection in RIII mice are compared with those obtained previously in Swiss albino mice.

Detection of virus antigens in Swiss albino mice infected by milk-borne mouse mammary tumour virus: the effect of age, sex and reproductive status. I. Localization by immunofluorescence of four antigens in mammary tissues and other organs.

The indirect immunofluorescence technique was used to investigate the expression of virus antigens in a Swiss albino mouse strain infected by mouse mammary tumour virus (MMTV). The antisera used were monospecific for: the glycopolypeptides gp160 and gp47, and the internal polypeptides p28 and p8. In mice infected with milk-borne MMTV, all four antigens were detected in the mammary gland during the first pregnancy and then throughout life, and in mammary tumours. Antigen gp160, located at the secretory border of all glandular cells, is shared by the plasma membrane of the mammary cell, whether virus-producing or not, and by the virus envelope, as shown by the use of absorbed antisera. The other three antigens are virus-specific. Anti-p47 serum stained the secretory border of cells whereas the fluorescence related to p28 and p8 consisted of a few large intracytoplasmic spots. The specific antibodies for p28 and p8 were only absorbed by disrupted virions, confirming that these polypeptides are internal antigens. With serial sections of glands from pregnant and old female mice, the alveoli stained with anti-p28 or anti-p8 serum were found to react also with anti-gp47 serum. However, during lactation, the presence of p28 and p8 could not be detected in the alveoli stained with anti-gp47 serum. Thus, infected alveoli express virus antigens differently. In the mammary glands of all mice studied, some alveoli did not display any staining when the latter three antisera were used. The specific antigenic pattern, maintained in differentiated mammary tumours, became a diffuse and unlocalized staining after transformation into the undifferentiated state. With the exception of the kidney, where gp47 was found in the glomeruli, all other organs of the mouse did not stain with any of the antisera. The presence of gp47 in the glomeruli, probably related to immune-complex deposits, increases with the age of the mouse and is most noticeable in tumour-bearing females. In mice free of milk-borne MMTV, examined during the first week of lactation, antigen gp47 could not be detected. Internal antigens p28 and p8 were detected in nearly all mammary cells as numerous small cytoplasmic dots. This suggests a limited expression of an endogenous virus genome; this expression would be modified when milk-borne virus is produced.

Natural infection of Swiss mice with mouse mammary tumor virus (MMTV): viral expression in milk and transmission of infection.

SummaryQuantitative determinations of gp52, the main envelope glycoprotein, and p28, the main core protein, of MMTV, have been performed in about 1000 individual samples of milk of breeding females from our colony of MMTV-infected Swiss mice, a line characterized by a moderate incidence of mammary tumors. A computer analysis of the results showed: 1— an important individual variation, ranging from 0 to 120µg per ml of milk for p28, and from 0 to 320 µg per ml of milk for gp52; 2— a variation of the release of both antigens during a single lactation, with a maximum on the 7–8th day of nursing; 3— an increase of the release of both antigens with parity up to the 6th lactation, followed by a marked decrease during later lactations; 4— a higher degree of infection in the offspring of 2nd and 3rd litters. The possible dependence of viral expression and transmission of infection upon factors such as cyclic activity of the mammary gland and progressive immunization of mice against MMTV is analyzed. The status of our laboratory line of MMTV infected Swiss mice is discussed in comparison with high and low tumor incidence strains.

Detection of Virus Antigens in Swiss Albino Mice Infected by Milk-borne Mouse Mammary Tumour Virus: the Effect of Age, Sex and Reproductive Status. II. Radioimmunoassay of Two Virus Components, gp47 and p28 in Serum and Organ Extracts

Extracts of various organs, mammary tumours and sera from milk-borne MMTV infected Swiss albino mice of different age, sex and physiological conditions were tested by radioimmunoassay for the presence of gp47, the main envelope polypeptide, and p28, the main core protein of the virus. Except in brain, ovaries and testes, both antigens were found in all organs of old animals and of females after the onset of their first pregnancy. Antigens were not present in organs of weanlings or in whole foetuses. Higher values were found in mammary glands, mammary tumours, epididymis and seminal vesicles. These organs also harboured a greater amount of gp47 than p28. The serum generally contained gp47 but rarely p28. This indicates that gp47 is not virion-bound in blood. Pregnancy, lactation and especially the presence of mammary tumours increased the concentration of gp47 in serum. The results do not allow localization of target organs of MMTV infection in the interval between ingestion of the virus by the suckling mouse and the first pregnancy. Moreover, results obtained with one group of mice devoid of exogenous virus show that, as endogenous MMTV genome expresses p28, it might account for part of the p28 detected exogenous MMTV-infected mice.

Enzymoimmunoassay of the main core protein (p28) of mouse mammary tumour virus (MMTV)

Abstract An enzymoimmunoassay was developed to detect p28, the main core protein of mouse mammary tumour virus. It is an ELISA test (enzyme-linked immunosorbent assay) using polystyrene tube as solid phase. The method was assessed according to two techniques: the one-step technique in which tubes coated with anti-p28 antibodies are incubated only once after simultaneous addition of both antigen (sample or standard) and enzymatic tracer (anti-p28 antibodies conjugated to glucose oxidase); and the two-step technique in which coated tubes are incubated first with antigen, then, after washing, submitted to a second incubation with the enzymatic tracer. In both techniques, after the last incubation, tubes are washed and submitted to enzymic detection. The dose-response curves of the reaction are investigated and appear as different according to the technique used. As regards sensitivity, precision, accuracy and reproducibility, these methods were equal to competition radioimmunoassay and the results obtained by enzymoimmunoassay and radioimmunoassay for a series of tissue extracts are closely related. The advantages of the enzymoimmunoassay over radioimmunoassay are simplicity, speed, absence of radioactive material and stability of the tracer.

Activité oxydasique de l'oxydoréductase de la xanthine, spécifique de la classe des mammifères

Abstract In every species other than mammals xanthine oxidoreductase behaves as a dehydrogenase, never as an oxidase. In three mammalian species, the enzyme acts intracellularly as a dehydrogenase, but its class-specific ambivalence allows its extracellular conversion into an oxidase.

Mouse mammary tumor virus (MMTV) infection in SWISS and RIII mice Correlation between resistance to exogenous infection and anti-MMTV serum response

SummaryHost-virus relationships were examined in mice from the two mouse mammary tumor virus (MMTV)-infected strains SWISS MB+ and RIII, which harbour the same MMTV variant, and from the derived sublines Swiss MB-and RIIIf, which were freed of milk-borne MMTV by foster-nursing. These two strains are not phylogenetically related, the SWISS strain bearing the endogenousMtv-3 locus in its DNA. In RIII and SWISS MB+ mice, the incidence of early mammary tumors, which was of 96% and 8%, respectively, was correlated to the level of MMTV expression in milk. In the SWISS MB-line, a non-coordinate expression of the provirus associated with theMtv-3 locus was observed in the mammary glands, the salivary glands and the spleen. This expression was not tumorigenic and was characterized by the presence of the p28gag antigen and the absence of the gp52env antigen, except, however, in mammary glands of elder mice where traces of gp52 were found. In the mammary glands of SWISS MB+ mice, the expression of theMtv-3 locus was masked by large amounts of antigens resulting from exogenous virus expression. RIIIf mice were MMTV-negative.Viral antigens coexisted with anti-MMTV antibodies in the serum of infected and tumor-bearing mice, but not in the form of immune complexes as verified by a method that allowed to detect specific antigen-containing-soluble immune complexes. An anti-MMTV serum reactivity was also detected in SWISS MB-and RIIIf mice. However, the serum response was higher in the two SWISS lines than in the two RIII lines. Except in tumor-bearing mice, the anti-MMTV response was not significantly modified by the presence of exogenous virus and thus resulted essentially from exposure to endogenous MMTV expression. In experimental infection studies, RIII mice were more susceptible to MMTV infection than SWISS mice. The correlation between resistance to MMTV infection and serum response to endogenous MMTV expression, suggests that the non-tumorigenic expression of an endogenous provirus can protect at least partially, against exogenous MMTV infection.

The earliest evidence for modern-style plate tectonics recorded by HP–LT metamorphism in the Paleoproterozoic of the Democratic Republic of the Congo

Knowing which geodynamic regimes characterised the early Earth is a fundamental question. This implies to determine when and how modern plate tectonics began. Today, the tectonic regime is dominated by mobile-lid tectonics including deep and cold subduction. However, in the early Earth (4.5 to 2 Ga) stagnant-lid tectonics may also have occurred. The study of high pressure–low temperature (HP–LT) metamorphic rocks is important, because these rocks are only produced in present-day subduction settings. Here, we characterize the oldest known HP–LT eclogite worldwide (2089 ± 13 Ma; 17–23 kbar/500–550 °C), discovered in the Democratic Republic of the Congo. We provide evidence that the mafic protolith of the eclogite formed at 2216 ± 26 Ma in a rift-type basin, and was then subducted to mantle depths (>55 km) before being exhumed during a complete Wilson cycle lasting ca. 130 Ma. Our results indicate the operation of modern mobile-lid plate tectonics at 2.2–2.1 Ga.