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Econometric methods for assessing the degree of market power typically rely on a maintained hypothesis of price‐taking behavior on one side of the market or the other. In the analysis of bilateral oligopoly, however, one would like to leave open the question of whether buyers or sellers (or both) behave competitively while allowing for the possible exercise of market power on either side. In this paper, we address the problem of measuring market power in bilateral oligopoly. This requires that we first distinguish among three candidate equilibrium concepts: bilateral price‐taking, seller price‐taking, and buyer price‐taking. Choosing among them comes down to a test of nonnested, nonlinear, simultaneous equation models. Our application to the U.S. wholesale market for beef, characterized by high degrees of concentration among both sellers (beef packers) and buyers (primarily retail grocery chains), reveals seller price‐taking among the three candidates to be the most consistent with the data. In particular, the hypothesis of price‐taking conduct on both sides of the market can be rejected. This is a conclusion that would not have been reached had we considered monopoly conduct by sellers as the only alternative to perfect competition.

The three-dimensional structure of the Saccharomyces cerevisiefatty acid synthase was computed from electron microscopy of stain images. The barrel-shaped structure (point group symmetry 32) has major and minor axes of ∼245 × 220 Å, respectively, and consists of two different subunits organized in an α6β6complex (Mr= 2.5 × 106). Two sets of three β subunits form triangle-shaped caps that enclose the ends of the barrel. The wall of the barrel appears to consist of three N-shaped α subunit pairs each with an over and underlying arch-shaped β subunit. Inside the molecule there are three major interconnected cavities that are tilted ∼20° with respect to its major axis. An axle-shaped structure extends the length of the cavity on the 3-fold axis and is connected to the two ends of the barrel. The cavities are partially divided on the equator of the molecule by three spokes that extend from the axle on the 2-fold axis to the exterior wall. We propose that these six cavities constitute the six equivalent sites of fatty acid synthesis resulting in an extraordinary structure-function relationship with the 42 catalytic sites involved in fatty acid synthesis inside the molecule. The six cavities each have two funnel-shaped openings (∼20 Å in diameter) which may serve to permit the diffusion of substrates and products in and out of these functional units. The subunits appear to be arranged in a manner that affords extensive intermolecular interactions contributing to the stability of this macromolecular complex.

The Z band in skeletal muscle has two distinct structural states —a relaxed (small square or ss) form and a maximally activated (basket weave or bw) form. We have examined by electron microscopy and optical diffraction Z lattice forms and dimensions and A band spacings in relaxed, tetanized, stretched, and stretched‐and‐tetanized rat soleus muscle. We have tested the independent contributions of passive load, active tension, and sarcomere length to Z band state. As the A band spacing decreased with increasing load and increasing sarcomere length in the untetanized muscles, the Z lattice remained in the ss form and the Z spacing changed only slightly. Computer‐enhanced images from digitized electron micrographs showed that the ss Z lattice resisted deformation regardless of load or method of stretching. In contrast, when the muscle was tetanized at sarcomere lengths of up to 2.7 μm, the Z lattice assumed the bw form and the Z spacing was increased by 20%. Regardless of lattice form, Z spacing did not vary significantly with sarcomere length. Images from freeze‐substituted preparations showed both lattice forms comparable to those in images from glutaraldehyde‐fixed muscles. Thus, Z band state appears to be a function of the presence (or absence) of active tension. Our previous three‐dimensional model is compatible with these observations and with the substructures revealed by computer‐enhanced images of both lattice forms.—Goldstein, M. A.; Michael, L. H.; Schroeter, J. P.; Sass, R. L. Z band dynamics as a function of sarcomere length and the contractile state of muscle. FASEB J.1: 133‐142; 1987.

Dihydrolipoamide acyltransferase (E2), a catalytic and structural component of the three functional classes of multienzyme complexes that catalyze the oxidative decarboxylation of α-keto acids, forms the central core to which the other components attach. We have determined the structures of the truncated 60-mer core dihydrolipoamide acetyltransferase (tE2) of the Saccharomyces cerevisiaepyruvate dehydrogenase complex and complexes of the tE2core associated with a truncated binding protein (tBP), intact binding protein (BP), and the BP associated with its dihydrolipoamide dehydrogenase (BP·;E3). The tE2core is a pentagonal dodecahedron consisting of 20 cone-shaped trimers interconnected by 30 bridges. Previous studies have given rise to the generally accepted belief that the other components are bound on the outside of the E2scaffold. However, this investigation shows that the 12 large openings in the tE2core permit the entrance of tBP, BP, and BP·;E3into a large central cavity where the BP component apparently binds near the tip of the tE2trimer. The bone-shaped E3molecule is anchored inside the central cavity through its interaction with BP. One end of E3has its catalytic site within the surface of the scaffold for interaction with other external catalytic domains. Though tE2has 60 potential binding sites, it binds only about 30 copies of tBP, 15 of BP, and 12 of BP·;E3. Thus, E2is unusual in that the stoichiometry and arrangement of the tBP, BP, and E3·;BP components are determined by the geometric constraints of the underlying scaffold.

Dihydrohpoamide acetyl transferase (E2), a catalytic and structural component of a multienzyme complex that catalyzes the oxidative decarboxylation of pyruvate, forms the central core to which the other components are bound. We have utilized protein engineering and 3-D electron microscopy to study the structural organization of the largest multienzyme complex known (Mr ∼ 107). The structures of the truncated 60-mer core (tE2) and complexes of the tE2associated with a binding protein (BP), and the BP associated with its dihydrohpoamide dehydrogenase (BP'E3) and the intact E2associated with BP and the pyruvate dehydrogenase (E1) were determined (Figs. 1 and 2). The tE2core is a pentagonal dodecahedron consisting of 20 cone-shaped trimers interconnected by 30 bridges.Previous studies have given rise to the generally accepted belief that BP and BP'E3components are bound on the outside of the E2scaffold and that E1is similarly bound to the core in variable positions by flexible tethers.

The article offers the authors view on the risk of settling for Health Insurance Portability and Accountability Act (HIPAA) compliance in the U.S. They mention the confirmation of the Department of Health and Human Services on the lack of training as the cause of such problem. They also note myths that can jeopardize organizations and customers which involve a check-the-box approach, goal as a regulatory compliance and training underestimation.