Edward De Maeyer

The growth rate of two transplantable murine tumors, 3ll lung carcinoma and b16f10 melanoma, is influenced by Hyal-1, A locus determining hyaluronidase levels and polymorphism

The effect of 2 different levels of serum hyaluronidase on tumor development was studied by comparing the development of 2 transplantable tumors, the 3LL lung carcinoma and the B16F10 melanoma, in mice of the C57BL/6 and the congenic HW23 strains. The reasoning behind the study was that, in vitro, removal by hyaluronidase of the hyaluronan present in the extracellular matrix of tumor cells renders the latter more accessible to effector T cells. In the mouse, the levels and molecular forms of circulating hyaluronidase are under the influence of different alleles at the Hyal‐1 locus on chromosome 9. C57BLJ.6 mice which have the Hyal‐1b allele have only a 60,000‐kDa form of hyaluronidase in the circulation, whereas the congenic HW23 strain has, on a C57BL/6 background, the BALB/c‐derived Hyal‐1,2 allele, characterized by the presence of the 60‐, 120‐ and 140‐kDa forms and of 3 times as much enzyme activity as the CS7BL/6 strain. These 2 mouse strains that are genetically almost identical can therefore be used to compare the effect of different levels of circulating hyaluronidase on tumor development. Two different tumors were studied: the 3LL lung carcinoma and the B16F10 melanoma. After intra‐footpad inoculation, both tumors developed more slowly in the congenic Hyal‐1,2 HW23 strain, as measured by a slower rate of increase in local tumor size and by a prolonged survival time. These results are in favor of the hypothesis that the Hyal‐1,2 allele, determining higher hyaluronidase levels, enhances resistance to tumor development.

Knockout Corner: Knockout mice for monoamine oxidase A

A line of transgenic mice was isolated in which transgene integration had caused a deletion in the gene encoding monoamine oxidase A, an enzyme that degrades serotonin and norepinephrine. This has provided an animal model of MAOA deficiency in humans, a condition characterized by borderline mental retardation and impulsive aggression.

Monoamine oxidase B (MAOB)-containing structures in MAOA-deficient transgenic mice

Monoamine oxidase (MAO)-containing structures were studied for the first time in type A MAO (MAOA)-deficient transgenic mice (Tg8) derived from C3H strain, using MAO enzyme histochemistry. In this mutant line, MAOA activity was not detected in neurons of the locus coeruleus. In contrast, in their dorsal raphe neurons, we noted an intense activity of type B MAO (MAOB). Based on pharmacological MAOA suppression experiments employing a specific inhibitor (clorgyline), we confirmed that the localization of MAOB-positive structures are not different between Tg8 mutant and normal C3H line. Many of MAOB-positive structures which have not been described previously in the rat, cat and primates were described in this study. In the forebrain, MAOB-containing neurons were discriminated in the striatum, septal nuclei, major island of Calleja, diagonal band, medial forebrain bundle, ventral pallidum and amygdaloid nucleus. Stained neurons in the thalamus and hypothalamus were much more extensively distributed in the mouse than the rat. Pontine laterodorsal tegmental neurons showed MAOB activity. The present data suggest that serotonin, a preferential substrate for MAOA, can be oxidized by MAOB in MAOA-deficient Tg8 mice.

Hyal-1, a locus determining serum hyaluronidase polymorphism, on chromosome 9 in mice

Analysis of mouse serum hyaluronidase by polyacrylamide gel electrophoresis, with the substrate high-molecular-weight hyaluronan (hyaluronic acid) included in the gel performed in mice of two different strains, BALB/cBy and C57BL/6By, reveals a pattern of multiple enzyme forms specific for each genotype. In BALB/c serum, seven different forms are present, only one of which is found in C57BL/6 serum. Segregation analysis of the enzyme polymorphism in backcross progeny and in recombinant inbred and bilineal congenic lines shows that the difference is due to a single locus, which we have designated as Hyal-1. Hyal-1 is linked to the histocompatibility locus H-7, on chromosome 9.

Altered zincergic innervation of the developing primary somatosensory cortex in monoamine oxidase-A knockout mice

Genetic inactivation of monoamine oxidase-A (MAO-A) significantly elevates levels of serotonin (5-HT) during early development and causes a disruption in the compartmented organization of thalamocortical axon terminals in layer 4 of the somatosensory cortex. In order to determine whether corticocortical innervation of the primary somatosensory cortex is also affected by this mutation, we examined the distribution of zinc-containing axon terminals (terminals known to originate from within the cortex) in the developing somatosensory cortex of MAO-A knockout mice, at postnatal days (PD) 3, 5, 6, 8, 10, 12, 15, 28, and 60. In layer 4 of wild-type mice, histochemical staining for zinc respected barrel-specific compartments at all ages beyond PD 5. By contrast, zinc staining in MAO-A knockout mice did not exhibit signs of barrel compartmentation at any age. Across cortical layers, substantial developmental changes in the distribution of zinc-containing terminals were observed in wild-type mice up until PD 12, at which time the mature lamina-specific pattern of zinc staining was achieved. Similar changes were observed in the somatosensory cortex of MAO-A knockout mice, except that its developmental time course was significantly compressed, with zincergic innervation achieving a mature appearance by PD 8. These results provide evidence that an excess of monoamines, most likely 5-HT, dramatically perturbs the columnar organization of intracortical zincergic afferents in layer 4 and significantly accelerates the appearance of a mature laminar pattern of zinc-containing corticocortical terminals.

An interferon analogue, |Ala30,32,33| HuIFN-α2, acting as a HuIFN-α2 antagonist on bovine cells

Abstract We have studied the biological and receptor binding properties of a human α2-interferon (HuIFN-α2) analogue, [Ala30,32,33] HuIFN-α2, which is shown in the accompanying paper(1) to be biologically inactive on homologous cells. Here we demonstrate that this analogue is also devoid of biological activity on bovine MDBK cells. However, whereas the analogue did not inhibit the binding of radiolabeled HuIFN-α2 to WISH cells, it did compete for binding to receptors on the bovine cells. This behavior suggested that [Ala30,32,33] HuIFN-α2 could act as an antagonist of HuIFN-α2 on bovine cells and indeed coaddition of the analogue and native HuIFN-α2 to MDBK cells competitively inhibited both the antiviral and antiproliferative activity of HuIFN-α2.

Linkage analysis of the murine mos proto-oncogene on chromosome 4

A linkage analysis of the murine Mos gene, which codes for the c-mos proto-oncogene, was performed in 88 backcross progeny of an interspecies cross of laboratory mice and Mus spretus. Linkage was tested for four different genes on mouse chromosome 4: Aco-1, Mup-1, b, and Ifb. The gene order (from centromere) with intervening percentage recombination is Mos-15.9 (+/- 3.9)-Aco-1-5.6 (+/- 2.4)-Mup-1-3.4 (+/- 1.9)-b-5.6 (+/- 2.4)-Ifb. These results confirm the previous assignment of Mos to chromosome 4 on the basis of segregation in somatic cell hybrids (D. Swan et al., 1982, J. Virol. 44: 752-754) and show furthermore that Mos and the Ifa/Ifb clusters are not tightly linked as a group of intronless genes, but are separated by a map distance of 30.6 +/- 4.9 recombination units. The linkage data obtained in the present study place Mos in a region compatible with the physical map (D. W. Threadgill and J. E. Womack, 1988, Genomics 3: 82-86).

Electron-microscopic study of MAOB-containing structures in the nucleus accumbens shell: using MAOA-deficient transgenic mice

MAOB-containing structures in the nucleus accumbens were ultrastructurally studied for the first time, using MAOA-deficient transgenic mice and MAO enzyme histochemistry. Among the striatal structures, the nucleus accumbens, and in particular its dorsal shell, showed the strongest MAOB activity. MAOB-active cell bodies were embedded in a dense MAOB-active fiber plexus. MAOB-positive terminals formed axo-dendritic synapses which were exclusively of the asymmetric type. It is suggested that dopamine in the nucleus accumbens shell is transported into MAOB-positive fibers where it is degraded by MAOB.

Isotopic labeling of mouse interferon by incorporation of radioactive amino acids during synthesis.

Mouse interferon produced by C-243 cells induced with Newcastle disease virus was isotopically labeled by adding either [35S]methionine or a 14C-labeled amino acid mixture to the culture medium. A method combining butyric acid and theophylline treatment and resulting in high interferon yields was used. Following purification by two-step affinity chromatography on poly(U) and antibody columns, the resulting material was analyzed on SDS-PAGE. The migration pattern of radioactivity and interferon coincided well and autoradiography revealed three major bands at migration distances corresponding, respectively, to 35, 28, and 22 K. Interferon represented 3.8% of all [35S]methionine-labeled proteins and 2.6% of all 14C-amino acid-labeled proteins released into the medium.