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Biomedical subjects

M J Tully

Publications and source records attributed to M J Tully.

5 recordsLinked to original sources
PubMed1999

A putative role for carbohydrates in sea urchin gastrulation.

Many studies have examined the effects of lectins on embryonic development. Recently, it has been shown that lectins actually enter the blastocoel of sea urchin embryos without microinjection and bind to specific cell types. The present study was performed to examine the effects of lectins on sea urchin gastrulation. Strongylocentrotus purpuratus sea urchin embryos were incubated with several lectins at concentrations from 0.01 microgram/ml to 100 micrograms/ml at 15-28 h in the presence or absence of the preferential binding sugars. The most interesting findings were that the mannose specific lectins Lens culinaris agglutinin (LcH) which binds to secondary mesenchyme cells involved in archenteron anchoring and Pisum sativum (PSA) caused exogastrulation. Wheat germ agglutinin (WGA) which binds to primary mesenchyme cells involved in skeletogenesis caused defective skeletogenesis. Our findings suggest that D-mannose-like residues (LcH and PSA specific sugar) may function in archenteron development and anchoring, while N-acetyl-D-glucosamine-like groups (WGA specific sugar) may contribute to control of primary mesenchyme positioning and function. Specific carbohydrate-containing receptors may, therefore, be of importance in specific gastrulation events.

Animals↗
PubMed1998

Accessing the embryo interior without microinjection.

For decades it has been assumed that in order to insert macromolecules into the embryo blastocoel for numerous experimental purposes, microinjection was required. Microinjection, however, can be only performed on a few embryos at a time, thus precluding many studies that could involve large populations of embryos. Laser scanning confocal microscopy, with its optical sectioning advantage, showed that fluorochrome-labeled macromolecular lectins and bovine albumin enter the blastocoel of living, swimming sea urchin embryos following a period of incubation without microinjection. A procedure is also described that shows macromolecular entry is substantially accelerated in low calcium seawater. The information gained from this study should greatly facilitate experiments on entire populations of millions of embryos at a time that require access of macromolecules to the embryo interior.

Animals↗
PubMed1980

Production of a variant of beta-lactamase II with selectively decreased cephalosporinase activity by a mutant of Bacillus cereus 569/H/9.

1. Mutants of Bacillus cereus 569/H/9 have been screened in a search for strains that synthesize variants of beta-lactamase II. 2. One of these mutants (strain 569/H/9/1) produces a beta-lactamase II-like enzyme that shows a selective decrease in cephalosporinase activity. 3. beta-Lactamase II from strain 569/H/9/1 has been purified to apparent homogeneity and its kinetic properties have been examined. This enzyme resembles the parent beta-lactamase II in its relative activity with benzylpenicillin as substrate when Zn(II) is replaced by other metal ions, but differs detectably from the parent enzyme in its isoelectric point.

Amino Acids↗