Until recently, the presence of sponge spicules in ancient ceramics has only been reported from South America. Current technological studies of Neolithic pottery from Sudan and Iron Age pottery from ...Mali provide evidence that sponge spicules are also a distinctive inclusion of some African ceramics. In this study, new data concerning the presence and quantitative variability of sponge spicules in West African Iron Age pottery from sites along the Niger River are discussed. Additionally, we discuss the potential archaeological insights offered by the study of sponge inclusions in pottery, and we consider methods for assessing whether or not these spicules were intentionally added as temper to vessels.
Negatively stained enzyme‐avidin complexes, seen at different stages of the titration of the biotin‐binding sites on avidin with chicken liver pyruvate carboxylase, have been studied using electron ...microscopy. Formation of linear, unbranched polymers of the enzyme‐avidin complex is seen to occur when the ratio of avidin to enzyme is between 2:1 and 1:2; beyond these limits only single enzyme tetramers are visible. The single avidin molecules observed seem to have a cuboid structure. The orientation and dimensions of the enzyme tetramers within the polymers indicate that the tetrahedron‐like structure, observed in the single molecules, has been prserved. From the structure of the polymers and the observation of single enzyme‐avidin complexes, we deduce that the biotin groups on the enzyme are located on the external faces of each subunit close to, and probably within 3 nm of, the intersubunit junction.
The reaction pathway catalysed by pyruvate carboxylase was re-examined by using two independent experimental approaches not previously applied to this enzyme. To avoid the variable stoicheiometry ...associated with oxaloacetate formation, the reaction rate was measured by following release of Pi. Initial velocities, when plotted as a function of varying concentrations of either MgATP2- or HCO3-, at fixed concentrations of pyruvate, gave in double-reciprocal-form families of straight intersecting lines. Further, when the reaction velocity was determined as a function of varying MgATP2- concentrations by using pyruvate, 3-fluoropyruvate and 2-oxobutyrate as alternative carboxyl-acceptor substrates, the slopes of the double-reciprocal plots were significantly different. Both results support a sequential reaction pathway.
The first case of breast implant-associated anaplastic large cell lymphoma (breast implant ALCL) was described by John Keech and the late Brevator Creech in 1997. In the following 2 decades, much ...research has led to acceptance of breast implant ALCL as a specific clinicopathologic entity, a process that we bring up to life through the memories of 6 persons who were involved in this progress, although we acknowledge that many others also have contributed to the current state of the art of this disease. Dr. Keech recalls the events that led him and Creech to first report the disease. Ahmet Dogan and colleagues at the Mayo Clinic described a series of 4 patients with breast implant ALCL, and led to increased awareness of breast implant ALCL in the pathology community. Daphne de Jong and colleagues in the Netherlands were the first to provide epidemiologic evidence to support the association between breast implants and ALCL. Garry Brody was one of the first investigators to collect a large number of patients with the disease, present the spectrum of clinical findings, and alert the community of plastic surgeons. Roberto Miranda and L. Jeffrey Medeiros and colleagues studied the pathologic findings of a large number of cases of breast implant ALCL, and published the findings in 2 impactful studies in the medical oncology literature. The recognition and acceptance of this disease by surgeons, epidemiologists, and medical oncologists, working together, has led to subsequent studies on the pathogenesis and optimal therapy of this disease.
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