A microcomputer program for evaluating sampling error: an application to stereological methods for electron microscopy.

In situations where there is a need to minimize sampling error or sample size, the coefficient of variation (CV) may be used to evaluate sampling error as a function of the number of observations or subjects in a sample. For example, CV is useful for estimating the minimum number of electron micrographs (Nmin) required to obtain a representative field sample for stereological analysis. To facilitate the determination of Nmin, we have written a program (COEFficient) for DOS microcomputers which calculates CVs. COEF assists the user in reducing error to that which solely reflects biological variability, thereby minimizing the time and cost of subsequent analyses.

Hemorrhage and the products of fibrinogen digestion after intracoronary administration of streptokinase.

Hemorrhage was prospectively identified in 26 of 116 consecutive patients (23%) who were receiving intracoronary streptokinase for occlusive coronary thrombi producing infarction. Bleeding was not influenced by the dose of streptokinase or the method of cardiac catheterization. Before treatment, prothrombin time and partial thromboplastin time were normal in both bleeders and nonbleeders. Fibrinogen levels measured by bioassay after streptokinase (mean +/- SEM) were 62 +/- 29 mg/dl in patients with major bleeding, 111 +/- 26 mg/dl in patients with minor bleeding, and 109 +/- 13 mg/dl in nonbleeders (p = NS). The regression slope b calculated from poststreptokinase fibrinogen time-concentration data in 71 patients was 4.7 mg/dl/hr. However, mean fibrinogen concentrations calculated at sequential 5 hr intervals revealed no net regeneration for the first 20 hr after thrombolysis. The apparent fibrinogen regeneration rate was less than normal (31 mg/kg/day) for more than 10 hr but subsequently increased to 94 +/- 10 mg/kg/day by the second day. The initial apparent latency of fibrinogen regeneration paralleled the sharp rise in fibrinogen degradation products, which began to decline after 20 hr of treatment but remained elevated well into the second day. Because of their anticoagulant effects, these products may interfere with the fibrinogen assay, causing spuriously low results. Thus, whether the early delay in fibrinogen regeneration is real or simply a reflection of the effects of fibrinogen degradation products on the bioassay, it signals the time for caution in initiating systemic heparin therapy.

Silkmoth chorion proteins: sequence analysis of the products of a multigene family.

Five polypeptide components have been isolated from the eggshell (chorions) of a silkmoth. Two are homogeneous on sodium dodecyl sulfate and isoelectric focusing gels, and three contain predominantly two proteins each. Amino acid analyses show that all five components are similar to each other. These proteins have been sequenced from the amino terminus. Homogeneous components yielded single sequences; heterogeneous components yielded two residues at some positions, consistent with their containing two major electrophoretic components. Striking similarities are apparent among all these sequences. These similarities can be increased dramatically by separating each of the three protein mixtures into two sequences and introducing a small number of gaps or insertions. This is due in part to bringing into register a portion that contains short repeating subunits found in all sequences. All proteins are also characterized by a region of high cysteine content near the amino terminus followed by a longer low-cysteine region. The data suggest that these proteins share a common evolutionary origin and are encoded by a multigene family.

Immunoglobulin allotypes of rabbit kappa chains: polymorphism of a control mechanism regulating closely linked duplicated genes?

The amino acid sequence of the constant (CK) region from the kappa immunoglobulin chains of a b9 rabbit is compared with the CK sequences, taken from the literature, of a b4 rabbit. These CK regions differ by 33% of their amino acid sequences and by three sequence insertions or deletions (sequence gaps). These extensive differences together with other published observations suggest that the b9 and b4 CK genes may not be simple alleles, but rather they may be encoded by closely linked CK genes present in every rabbit whose expression is regulated by a polymorphic control mechanism.