Biomedical subjects

M Mallo

Publications and source records attributed to M Mallo.

23 records · Page 2Linked to original sources

PubMed1993

Hoxa-2 mutant mice exhibit homeotic transformation of skeletal elements derived from cranial neural crest.

Mice homozygous for a targeted mutation of the Hoxa-2 (Hox 1.11) gene are born with cleft palates and die within 24 hr of birth. Analysis of stained skeletons revealed that homozygous mutant animals contained multiple cranial skeletal defects, including a duplication of the ossification centers of the bones of the middle ear. Histological analysis suggested that this duplication resulted from the transformation of skeletal elements derived from the second branchial arch into more anterior structures, resulting in a duplication of Meckel's cartilage adjacent to the otic capsule. Skeletal elements normally derived from the second arch were absent in the mutants. These data provide direct experimental evidence for the existence of a branchial Hox code.

Abnormalities, Multiple↗

PubMed1993

Cloning and developmental expression of Grg, a mouse gene related to the groucho transcript of the Drosophila Enhancer of split complex.

Genes of the Enhancer of split complex are involved in neural-epidermal cell fate decisions during early embryogenesis in Drosophila. One of these genes, the product of the Enhancer of split m9/10 or groucho transcript, encodes a ubiquitous nuclear protein with homology at the carboxy-terminus to G-protein beta-subunits. Here we describe the cloning and RNA expression analysis of a mouse gene, designated Grg, that is homologous to just the amino-terminal region of the groucho product. Grg encodes a 197 amino acid protein that shares 53% amino acid identity with the corresponding region of the product of the Drosophila groucho gene. However, the mouse Grg protein does not contain the region homologous to G-protein beta-subunits. An analysis by in situ hybridization of the spatial and temporal localization of Grg RNA expression revealed that, while the initial pattern of Grg expression was quite restricted, by midgestation Grg RNA was ubiquitously expressed in the developing embryo. Widespread Grg RNA expression was maintained in adult mice. The implications of these results for the existence of separable functional domains of the Drosophila groucho product, and possible roles of the Grg gene during mouse development, are discussed.

Amino Acid Sequence↗

PubMed1991

Avian reovirus S1133 can replicate in mouse L cells: effect of pH and cell attachment status on viral infection.

Previous reports have suggested that avian reovirus S1133 fails to replicate in mouse L cells. In this article, we report that replication does occur under certain culture conditions. The avian reovirus was found to grow in mouse L cells at pH 6.4 and 7.2 but not at pH 8.2. Culture medium with a basic pH directly inhibited viral transcription and genome replication. As a result, viral protein synthesis was also affected. At permissive pH levels, avian reovirus grew better in monolayers than in suspension cultures of L cells because of the influence of cell attachment status on viral macromolecular synthesis. Our results not only show that avian reovirus can replicate in mouse L cells but also help to explain why it did not in previous studies.

Animals↗

PubMed1991

The stimulatory effect of actinomycin D on avian reovirus replication in L cells suggests that translational competition dictates the fate of the infection.

Indirect immunostaining of avian reovirus S1133-infected L-cell monolayers showed that most of the cells can support viral replication. However, the number of cells in which the virus was actually replicating depended on the multiplicity of virus infection. The presence of actinomycin D during infection increased viral protein synthesis, viral growth, and the number of actively infected cells at late infection times. The antibiotic elicited these effects by triggering viral replication in cells that already contained unproductive cytoplasmic virus but that would not get productively infected in the absence of the drug. From these results, we propose a model for the interaction between L cells and avian reovirus S1133 in which viral versus host mRNA competition for the translational machinery determines the fate of the virus infection.

Animals↗

PubMed1991

A comparative study of the transganglionic transport of cholera toxin-horseradish peroxidase (CT-HRP) and wheat germ agglutinin-horseradish peroxidase (WGA-HRP) in the trigeminal system of the guinea pig.

A comparative study of cholera toxin (CT) and wheat germ agglutinin (WGA) conjugated with horseradish peroxidase (HRP) was made on trigeminal central projections of the lower incisor gingiva afferent neurons in the guinea pig. Considerably more CT-HRP-labeled endings were observed in the trigeminal sensory nuclear complex (TSNC) and in the cervical spinal cord (C1-C8). The substantia gelatinosa (lamina II) of both the caudal nucleus of the TSNC and C1-C2 was the only area where WGA-HRP labeled more terminals. CT-HRP-labeled fibers and endings were traced up to C7-C8, whereas with WGA-HRP were rare caudal to C5. A comparison of the two methods currently in use, i.e. the 2-step glutaraldehyde and sodium periodate, showed that the latter yields conjugates which are more sensitive as neuroanatomical tracers.

Animals↗