Convergent evolution of cysteine residues in sperm protamines of one genus of marsupials, the Planigales

A characteristic feature of the sperm P1 protamines of eutherian mammals is the constant presence of six to nine cysteine residues per molecule. During spermiogenesis these residues become oxidized to form a three-dimensional network of disulfide bridges between, and within, protamine molecules in the sperm chromatin. This covalent cross linking strongly stabilizes eutherian sperm nuclei. In contrast, protamines sequenced from teleost fish, birds, monotremes, and marsupials all lack cysteine residues and their sperm nuclei, without the stabilizing cross links, are easily decondensed in vitro. We have now found that one genus of tiny, shrewlike dasyurid marsupials, the Planigales, possess P1 protamines containing five to six cysteine residues. These residues appear to have evolved since the divergence of Planigales from other members of the family Dasyuridae, such as the marsupial mouse, Sminthopsis crassicaudata. We believe this constitutes a case of convergent evolution in a subfamily of dasyurid marsupials toward the cysteine-rich eutherian form of sperm protamine P1.      

Evidence for independent recruitment of zeta-crystallin/quinone reductase (CRYZ) as a crystallin in camelids and hystricomorph rodents

Zeta-crystallin/quinone reductase (CRYZ) is an NADPH oxidoreductase expressed at very high levels in the lenses of two groups of mammals: camelids and some hystricomorph rodents. It is also expressed at very low levels in all other species tested. Comparative analysis of the mechanisms mediating the high expression of this enzyme/crystallin in the lens of the Ilama (Lama guanacoe) and the guinea pig (Cavia porcellus) provided evidence for independent recruitment of this enzyme as a lens crystallin in both species and allowed us to elucidate for the first time the mechanism of lens recruitment of an enzyme- crystallin. The data presented here show that in both species such recruitment most likely occurred through the generation of new lens promoters from nonfunctional intron sequences by the accumulation of point mutations and/or small deletions and insertions. These results further support the idea that recruitment of CRYZ resulted from an adaptive process in which the high expression of CRYZ in the lens provides some selective advantage rather than from a purely neutral evolutionary process.      

Functional changes in human leukemic cell line HL-60. A model for myeloid differentiation

Polar solvents induce terminal differentiation in the human promyelocytic leukemia cell line HL-60. The present studies describe the functional changes that accompany the morphologic progression from promyelocytes to bands and poly-morphonuclear leukocytes (PMN) over 9 d of culture in 1.3 percent dimethylsulfoxide (DMSO). As the HL-60 cells mature, the rate of O(2-) production increase 18-fold, with a progressive shortening of the lag time required for activation. Hexosemonophosphate shunt activity rises concomitantly. Ingestin of paraffin oil droplets opsonized with complement or Ig increases 10-fold over 9 d in DMSO. Latex ingestion per cell by each morphologic type does not change significantly, but total latex ingestion by groups of cells increases with the rise in the proportion of mature cells with greater ingestion capacities. Degranulation, as measured by release of β-glucuronidase, lysozyme, and peroxidase, reaches maximum after 3-6 d in DMSO, then declines. HL-60 cells contain no detectable lactoferrin, suggesting that their secondary granules are absent or defective. However, they kill staphylococci by day 6 in DMSO. Morphologically immature cells (days 1-3 in DMSO) are capable of O(2-) generation, hexosemonophosphate shunt activity, ingestion, degranulation, and bacterial killing. Maximal performance of each function by cells incubated in DMSO for longer periods of time is 50-100 percent that of normal PMN. DMSO- induced differentiation of HL-60 cells is a promising model for myeloid development.     

Enhancement and phototransduction in the ventral eye of limulus

Limulus ventral photoreceptors were voltage clamped to the resting (dark) potential and stimulated by a 20-ms test flash and a 1-s conditioning flash. At a constant level of adaptation, we measured the response to the test flash given in the dark (control) and the incremental response produced when the test flash occurred within the duration of the conditioning flash. The incremental response is defined as the response to the conditioning and test flashes minus the response to the conditioning flash given alone. When the test flash was presented within 100 ms after the onset of the conditioning flash we observed that: (a) for dim conditioning flashes the incremental response equaled the control response; (b) for intermediate intensity conditioning flashes the incremental response was greater than the control response (we refer to this as enhancement); (c) for high intensity conditioning flashes the incremental response nearly equaled the control response. Using 10-μm diam spots of illumnination, we stimulated two spatially separate regions of one photoreceptor. When the test flash and the conditioning flash were presented to the same region, enhancement was present; but when the flashes were applied to separate regions, enhancement was nearly absent. This result indicates that enhancement is localized to the region of illumination. We discuss mechanisms that may account for enhancement.     

The cDNA cloning and molecular evolution of reptile and pigeon lactate dehydrogenase isozymes

The cDNAs encoding lactate dehydrogenase isozymes LDH-A (muscle) and LDH-B (heart) from alligator and turtle and LDH-A, LDH-B, and LDH-C (testis) from pigeon were cloned and sequenced. The evolutionary relationships among vertebrate LDH isozymes were analyzed. Contrary to the traditional belief that the turtle lineage branched off before the divergence between the lizard/alligator and bird lineages, the turtle lineage was found to be clustered with either the alligator lineage or the alligator-bird clade, while the lizard lineage was found to have branched off before the divergence between the alligator/turtle and bird lineages. The pigeon testicular LDH-C isozyme was evidently duplicated from LDH-B (heart), so it is not orthologous to the mammalian testicular LDH-C isozymes.      

Runoff losses of Pseudomonas aureofaciens (lacZY) from soil

Abstract: Leaching of genetically modified microorganisms (GMMs) through soil profiles is generally not a significant concern, since GMMs typically remain near the soil surface following application. The presence of high numbers of GMMs at the soil surface, however, suggests that losses via runoff may occur. Traditional methods of plating nonlabeled bacteria lack precision and are thus seldom used to monitor runoff losses. To examine whether lac ZY, a common genetic marker, could be used to evaluate bacterial runoff from soil, a lac ZY⁺ strain of Pseudomonas aureofaciens 3732 RN-L11 was used at three different pH levels, with and without wheat ( Triticum aestivum L.) cover in a greenhouse experiment. Twelve times over a 245 day period, soils were subjected to simulated rainfall of 84 mm h⁻¹ for a 15 min duration. Runoff losses and survival were quantified at each time. Pseudomonas aureofaciens survived for the longest period at a soil pH of 7; survival was reduced at lower pHs. The number of cells in runoff were usually related to the number of cells surviving in the soil. When high soil populations were present, runoff losses often exceeded 10¹⁰ cfu event⁻¹. When the soil population declined to low or undetectable levels, the runoff contained fewer organisms. Runoff losses of 10⁸ cfu event⁻¹, however, were observed during one runoff event even when the soil population was below the detection limit. This study indicates that lac ZY is an effective marker, and that runoff of GMMs may be an important mechanism for movement to nontarget environments.     

Neointimal formation in two apolipoprotein E-deficient mouse strains with different atherosclerosis susceptibility

C57BL/6 (B6) and C3H/HeJ (C3H) are two commonly used mouse strains that differ markedly in atherosclerosis susceptibility. In this study, we determined plaque formation after removal of the endothelium in the two strains carrying the mutant apolipoprotein E gene (apoE(-/-)). At 10 weeks of age, male B6.apoE(-/-) and C3H.apoE(-/-) mice underwent endothelial denudation of the left common carotid artery. Two weeks after injury, B6.apoE(-/-) mice developed significantly larger neointimal lesions in the vessel than their C3H.apoE(-/-) counterparts, although they had comparable plasma cholesterol levels on a chow diet. Feeding of a Western diet aggravated lesion formation in both strains, but the increase was more dramatic in B6.apoE(-/-) mice than in C3H.apoE(-/-) mice. Immunohistochemical and histological analyses demonstrated the presence of macrophage foam cells in neointimal lesions. We then compared neointimal growth in F1 mice reconstituted with bone marrow from B6.apoE(-/-) and C3H.apoE(-/-) mice. No significant lesions were observed 2 weeks after endothelial denudation in the mice reconstituted with bone marrow from either donor. Thus, these data indicate that foam cell formation contributes to neointimal growth in the hyperlipidemic apoE(-/-) model and that neither endothelial cells nor blood cells alone explain the dramatic difference between B6 and C3H mice in plaque formation.