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S Parks

Publications and source records attributed to S Parks.

At least 37 records · Page 2Linked to original sources
PubMed1992

Secretion and localized transcription suggest a role in positional signaling for products of the segmentation gene hedgehog.

The segment polarity genes engrailed and wingless are expressed in neighboring stripes of cells on opposite sides of the Drosophila parasegment boundary. Each gene is mutually required for maintenance of the other's expression; continued expression of both also requires several other segment polarity genes. We show here that one such gene, hedgehog, encodes a protein targeted to the secretory pathway and is expressed coincidently with engrailed in embryos and in imaginal discs; maintenance of the hedgehog expression pattern is itself dependent upon other segment polarity genes including engrailed and wingless. Expression of hedgehog thus functions in, and is sensitive to, positional signaling. These properties are consistent with the non-cell autonomous requirement for hedgehog in cuticular patterning and in maintenance of wingless expression.

Amino Acid Sequence↗
PubMed1991

The Drosophila gastrulation gene concertina encodes a G alpha-like protein.

Gastrulation is a complex process requiring the coordination of cell shape changes and cell movements. In Drosophila, gastrulation begins immediately upon cellularization of the blastoderm stage embryo with the formation of the ventral furrow and posterior midgut. Cells that form both of these invaginations change their shape via apical constriction. Embryos from mothers homozygous for mutations in the concertina (cta) gene begin furrow formation by forming a zone of tightly apposed cells, constrict some cells, and then fail to constrict enough cells to form an organized groove. The cta gene has been cloned, and sequence analysis suggests that it encodes an alpha subunit of a G protein. G proteins have a role in cell-cell communication as mediators of signals between membrane-bound receptors and intracellular effectors. The phenotype of embryos from homozygous cta mothers suggests that the cta gene plays a role in a signal transduction pathway used during gastrulation.

Amino Acid Sequence↗
PubMed1991

Gastrulation in Drosophila: the formation of the ventral furrow and posterior midgut invaginations.

The ventral furrow and posterior midgut invaginations bring mesodermal and endodermal precursor cells into the interior of the Drosophila embryo during gastrulation. Both invaginations proceed through a similar sequence of rapid cell shape changes, which include apical flattening, constriction of the apical diameter, cell elongation and subsequent shortening. Based on the time course of apical constriction in the ventral furrow and posterior midgut, we identify two phases in this process: first, a slow stochastic phase in which some individual cells begin to constrict and, second, a rapid phase in which the remaining unconstricted cells constrict. Mutations in the concertina or folded gastrulation genes appear to block the transition to the second phase in both the ventral furrow and the posterior midgut invaginations.

Animals↗
PubMed1986

Replication and expression of an X-linked cluster of Drosophila chorion genes.

Two 80- to 100-kb chromosomal replicons containing clustered chorion genes amplify in the ovarian follicle cells during the final 22 hr of Drosophila oogenesis. We have studied the relationship between amplification and transcription within one of these domains, located at 7E10-7F3,4 on the X chromosome. A tandem cluster of six genes, encoding chorion structural proteins s36-1, s38-1, and four putative minor chorion protein mRNAs, was mapped in the central 18 kb of the amplified domain, a region showing the highest levels of amplification. The regions both proximal and distal to this gene cluster, where lower levels of amplification occur, were also transcribed in ovary, but mRNAs produced specifically during choriogenesis were not detected. Thus, differences in amplification do not appear to modulate differential RNA accumulation. Instead, the gradient of amplification observed in egg chamber DNA may simply reflect the mechanism of amplification. In the female sterile mutation, In(1)ocelliless, a chromosomal rearrangement separates the central gene cluster into two parts, only one of which retains the capacity to amplify. Genes located within the unamplified portion of the ocelliless chromosome were expressed at the appropriate time during oogenesis, but at a 5- to 10-fold reduced level of RNA per gene. Thus neither cluster integrity nor amplification are required for the normal developmental program of gene expression within the cluster.

Animals↗
PubMed1986

Storage and transportation of lymphoid tissue for immunophenotyping.

Immunoperoxidase staining of frozen sections is a cost-effective technic for immunophenotyping cells of lymphoid tissue. Because this procedure is not performed in many institutions, a simple method to transport fresh tissue to centers performing these studies is required. Tissues in saline at refrigerator temperature may be successfully transported. In addition, in order to minimize laboratory expenses, lymphoid tissue can be kept refrigerated in saline until permanent sections are examined and immunodiagnostic procedures become necessary. In this study reproducible immunophenotyping of 12 samples of lymphoid tissue stored up to seven days was achieved.

Antibodies, Monoclonal↗
PubMed1980

Lipogranulomatosis of the genitalia caused by topical application of "baby oil".

A case is reported of lipogranulomatosis of the genitalia caused by topical application of "baby oil". To our knowledge this is the first such case reported in the English literature. The chemical nature of the lipid in question was analyzed by sophisticated procedures, including gas liquid chromatography, thin layer chromatography and mass spectrometry. After the etiologic agent was defined retrospective questioning of the patient confirmed the diagnosis.

Administration, Topical↗