das Mutation in bacteriophage T4D does not suppress an amber mutation in T4 gene 59.

Mutations termed das were isolated originally (Hercules and Wiberg, 1971) as partial suppressors of mutants in phage T4 genes 46 and 47. Since mutants in genes 46, 47, and 59 exhibit both an early arrest of phage DNA synthesis and the loss of this arrest in the presence of chloramphenicol or of mutations of T4 genes 33 and 55, we asked whether a das mutation can also suppress a gene 59 mutant. We find that it cannot--either at the level of phage production or DNA synthesis.     

Electroejaculation and semen analysis in the La Plata three‐banded armadillo (Tolypeutes matacus)

The objectives of this study were to: 1) develop an electroejaculation procedure for collecting semen from the La Plata three‐banded armadillo (Tolypeutes matacus), and 2) characterize basal reproductive traits, including sperm concentration, motility, morphology, acrosomal status, and viability. Three male armadillos were each electroejaculated on one to five occasions. Fluid containing spermatozoa was recovered during each attempt, and high proportions (>75%) of morphologically normal spermatozoa were seen in all analyzed samples. Two fluorescent stains (FITC‐PNA and Hoechst 33258) appeared to be effective for assessing acrosomal status and viability, respectively, in this species. Sperm concentration and motility were usually low, and urine contamination was a persistent problem—possibly due to anesthesia, unique reproductive anatomy, and/or improper probe placement. Poor sperm recovery, urine contamination, and sensitivity of spermatozoa to culture medium must be addressed before electroejaculation can be used routinely in the La Plata three‐banded armadillo. Zoo Biol 21:481–487, 2002. © 2002 Wiley‐Liss, Inc.     

The evolutionary origin of proinsulin: Amino acid sequence homology with the trypsin-related serine proteases detected and evaluated by new statistical methods

Proinsulins and pancreatic serine proteases were analyzed for possible amino acid sequence similarity, using an adapted version of the nucleotide sequence alignment technique of Sankoff (1972). The technique allowed us to determine simultaneously the statistical significance of both the sequence alignment and the number of gaps necessary to achieve that alignment. In the course of this work, it was realized that a rigorous analysis required non-parametric statistics.For the B-chain (amino-terminal) of insulin a highly significant gap-free sequence alignment with the serine proteases was found. For the A-chain (carboxy-terminal) of insulin a sequence alignment of modest statistical significance with two gaps could be obtained, while the search for a corresponding alignment for the C-peptide remained unsuccessful. Presumably the rapid evolution of the C-peptide has obscured its origin. Reconstruction of ancestral sequences was of no help. In contrast to the amino acid sequences, three-dimensional structures of the two protein families are quite different.Considering current histophysiological understanding of ontogeny and phylogeny of exocrine and endocrine pancreas, the observed sequence similarity of proinsulins and serine proteases was interpreted to mean that the two protein families have diverged from a common genetic ancestor. Moreoever, from the organismic distribution of these proteins it was concluded that at least one serine protease existed first, and that proinsulin was generated after duplication of a serine protease gene and subsequent drastic modification, such as a large deletion. Thus proinsulin, basically an anabolic hormone, is derived from a serine protease, an enzyme involved in digestion. This constitutes a refinement of a similar proposal by Steiner et al. (1973).The emergence of proinsulin seems to have occurred after coelenterates diverged, and possibly before most other major animal phyla diverged from the line leading to vertebrates, i.e. 520 to 700 million years ago. The evolution of proinsulin seems to have paralleled the evolution of endocrine cells. Homology of the secreted products of endocrine and exocrine cells was most readily reconciled with a common embryological and phylogenetic origin of the two cell types, as considered by Pictet & Rutter (1972).