Aspects of the Life History of Three Catostomids Native to the Upper Colorado River Basin

The distribution, abundance and life history were studied for three catostomids -- the razorback sucker (Xyrauchen texanus), the flannel-mouth sucker (Catostomus latipinnis), and the bluehead sucker (Catostomus discobolus) -- all native to the upper Colorado River basin. The razorback sucker has declined in abundance due to man\u27s impact upon the system and it has been recommended that this species be listed as \u27\u27threatened on the U. S. Department of the Interior\u27s list of Threatened or Endangered species [Personal corrmunication, G. C. Kobetich, U. S. Fish and Wildlife Service, Las Vegas, Nevada]. During this investigation, razorback suckers were found in relatively large concentrations at the mouth of the Yampa River and in a flooded gravel pit connected to the Colorado River near Grand Junction, Colorado. Flannelmouth and bluehead suckers were collected in large numbers throughout the study area. Razorback and flannelmouth suckers spawned in April and May, when water temperatures were between 6 and 15 C. Bluehead suckers spawned later (June and early July) when water temperatures exceeded 15 C. It can be inferred from this study that razorback suckers made a spawning migration, but the data are insufficient to draw any conclusions about the pervasiveness of this phenomenon. There was no evidence that flannelmouth or bluehead suckers made a spawning migration. Fecundity of razorback suckers was variable and ranged from 24,490 for a fish 529 mm in total length (TL) to 76,576 eggs for a fish 485 mm TL. The youngest razorback sucker that was collected during this study was age IV; all razorback suckers were mature. Flannelmouth suckers first matured at age IV and most fish were mature by age VII. Flannelmouth sucker fecundity ranged from 4,000 eggs (450 mm TL) to 40,000 eggs (500 mm TL). Bluehead suckers produced as few as 4,000 (340 mm TL) and as many as 20,000 eggs (430 mm TL). Bluehead and flannelmouth suckers from the Colorado River produced significantly greater numbers of eggs than fish of equivalent lengths from the Green and Yampa Rivers. Razorback and flannelrnouth suckers collected in 1974-76 attained a maximum age of nine years. Razorback suckers from the Colorado River were significantly longer than fish of the same age from the Green and Yampa Rivers. Flannelmouth suckers from the Colorado River were significantly heavier than fish of equivalent lengths from the Green and Yampa Rivers. The differences in fecundity and growth rates for fish from the two locations can probably be attributed to differences in temperature between the rivers

Journalism Education: a Survey of CIty Editors' Attitudes

This study determined attitudes held by metropolitan city editors in Texas toward current journalism instruction in colleges and universities. An open-ended questionnaire was mailed to city editors of newspapers in Texas with circulation over 50,000

Transport into mitochondria and intramitochondrial sorting of the Fe/S protein of ubiquinol-cytochrome c reductase

The Fe/S protein of complex III is encoded by a nuclear gene, synthesized in the cytoplasm as a precursor with a 32 residue amino-terminal extension, and transported to the outer surface of the inner mitochondrial membrane. Our data suggest the following transport pathway. First, the precursor is translocated via translocation contact sites into the matrix. There, cleavage to an intermediate containing an eight residue extension occurs. The intermediate is then redirected across the inner membrane, processed to the mature subunit, and assembled into complex III. We suggest that the folding and membrane-translocation pathway in the endosymbiotic ancestor of mitochondria has been conserved during evolution of eukaryotic cells; transfer of the gene for Fe/S protein to the nucleus has led to addition of the presequence, which routes the precursor back to its “ancestral” assembly pathway

Apocytochrome c

The cytochrome c import pathway differs markedly from the general route taken by the majority of other imported proteins, which is characterized by the import involvement of namely, surface receptors, the general insertion protein (GIP), contact sites and by the requirement of a membrane potential (Δψ). Unique features of both the cytochrome c precursor (apocytochrome c) and of the mechanism that transports it into mitochondria, have contributed to the evolution of a distinct import pathway that is not shared by any other mitochondrial protein analysed thus far. The cytochrome c pathway is particularly unique because i) apocytochrome c appears to have spontaneous membrane insertion-activity; ii) cytochrome c heme lyase seems to act as a specific binding site in lieu of a surface receptor and; iii) covalent heme addition and the associated refolding of the polypeptide appears to provide the free energy for the translocation of the cytochrome c polypeptide across the outer mitochondrial membrane

Successive translocation into and out of the mitochondrial matrix

We investigated the import and sorting pathways of cytochrome b2 and cytochrome c1, which are functionally located in the intermembrane space of mitochondria. Both proteins are synthesized on cytoplasmic ribosomes as larger precursors and are processed in mitochondria in two steps upon import. The precursors are first translocated across both mitochondrial membranes via contact sites into the matrix. Processing by the matrix peptidase leads to intermediate-sized forms, which are subsequently redirected across the inner membrane. The second proteolytic processing occurs in the intermembrane space. We conclude that the hydrophobic stretches in the presequences of the intermediate-sized forms do not stop transfer across the inner membrane, but rather act as transport signals to direct export from the matrix into the intermembrane space

Mitochondrial Protein Import

The role of nucleoside triphosphates (NTPs) in mitochondrial protein import was investigated with the precursors of N. crassa ADP/ATP carrier, F1-ATPase subunit β, F0-ATPase subunit 9, and fusion proteins between subunit 9 and mouse dihydrofolate reductase. NTPs were necessary for the initial interaction of precursors with the mitochondria and for the completion of translocation of precursors from the mitochondrial surface into the mitochondria. Higher levels of NTPs were required for the latter reactions as compared with the early stages of import. Import of precursors having identical presequences but different mature protein parts required different levels of NTPs. The sensitivity of precursors in reticulocyte lysate to proteases was decreased by removal of NTPs and increased by their readdition. We suggest that the hydrolysis of NTPs is involved in modulating the folding state of precursors in the cytosol, thereby conferring import competence

Mitochondrial precursor proteins are imported through a hydrophilic membrane environment

We have analyzed how translocation intermediates of imported mitochondrial precursor proteins, which span contact sites, interact with the mitochondrial membranes. F1-ATPase subunit β(F1β) was trapped at contact sites by importing it into Neurospora mitochondria in the presence of low levels of nucleoside triphosphates. This F1β translocation intermediate could be extracted from the membranes by treatment with protein denaturants such as alkaline pH or urea. By performing import at low temperatures, the ADP/ATP carrier was accumulated in contact sites of Neurospora mitochondria and cytochrome b2 in contact sites of yeast mitochondria. These translocation intermediates were also extractable from the membranes at alkaline pH. Thus, translocation of precursor proteins across mitochondrial membranes seems to occur through an environment which is accessible to aqueous perturbants. We propose that proteinaceous structures are essential components of a translocation apparatus present in contact sites