Dennis L. Miller

Medial Collateral Ligament Knee Sprains in College Football: Effectiveness of Preventive Braces

This is the second of 2 articles on a 3-year investigation of medial collateral ligament sprains of the knee to as sess the effectiveness of prophylactic knee braces in NCAA Division I college football players. Position, string, type of session, and daily brace wear were re corded. The injury rates for braced and unbraced knees were used to create an incidence density ratio. The data were stratified and simultaneously controlled for posi tion, string, and session and evaluated for their statis tical significance. The 987 Big Ten players generated 155,772 knee exposures over the study period (50% braced). Noticeable differences existed in the rates of injury for the braced and unbraced knees in almost ev ery position during practices, depending on player or nonplayer status. When the influential factors of posi tion, string, and session are considered, there is a con sistent but not statistically significant tendency for the players wearing preventive knee braces to experience a lower injury rate than for their unbraced counterparts. For starters and substitutes in the line positions, as well as the linebackers and tight ends, there was a consis tent trend toward a lower injury rate in both practices and games. The braced players in the skill positions (backs/kickers), at least during games, exhibited a higher injury rate.

Medial Collateral Ligament Knee Sprains in College Football Brace Wear Preferences and Injury Risk

In this prospective, multiinstitutional analysis of medial collateral ligament sprains in college football players, we categorized 987 previously uninjured study subjects according to frequency of wearing preventive knee braces, studied the patterns by which 47 of 100 injuries occurred to unbraced knees, and identified several ex trinsic, sport-specific risk factors shared for both braced and unbraced knees. The attendance, brace wear choice, position, string, and session of each participant were recorded daily; medial collateral ligament sprains were reported whenever tissue damage was confirmed. Both the likelihood of wearing braces and risk of injury without them was highly dependent on session (games/ practices), position group (line, linebacker/tight end, skill), and string group (players/nonplayers). Subjects wearing braces often faced a high injury risk to their unbraced knees, a finding compatible with the opinion that braces were a necessary evil, best worn when con cern over danger of injury outweighed desire for speed and agility. It is concluded that to avoid misinterpreta tions due to the confounding influence of brace wear selection bias, accurate investigation of daily brace wear patterns is required. Then, before considing the impact of preventive knee braces, a repartitioning of the data base is essential to assure that only similar groups will be compared.

The tRNAAGYSer and tRNACGYArg genes form a gene cluster in yeast mitochondrial DNA

Yeast mitochondrial DNA-pBR322 recombinant DNA molecules screened for rRNA genes were used as a source of DNA for mitochondrial tRNA gene sequence analysis. We report here the sequences of yeast mitochondrial tRNA genes coding for a tRNAAGYSer and a tRNACGYArg. The tRNAAGYSer sequence deduced from the gene is the first reported sequence of a yeast tRNAAGYSer. It is also the second yeast mitochondrial tRNASer gene to be sequenced, and demonstrates unequivocally the presence of mitochondrial encoded serine tRNA isoacceptors. The tRNACGYArg sequence deduced from the gene is the most AT-rich (82%) tRNA sequence ever reported. Whereas all the mitochondrial genes sequenced to date exist singly on the genome and are separated by long stretches of AT-rich DNA, the tRNAACYSer and tRNAcgyarg genes exist in tandem, separated by only 3 bp. This gene arrangement strongly suggests that mitochondrial tRNA genes may be transcribed into multicistronic precursors.

Translation in Escherichia coli mini-cells containing hamster mitochondrial DNA-Co1E1 - Ampr recombinant plasmids.

Hamster mitochondrial DNA is cleaved into two fragments (4.2 and 11.4 kilobase pairs of DNA (kb)) by the restriction enzyme, Eco RI. Recombinant DNA molecules formed in vitro between an Escherichia coli plasmid, Co1E1 - Ampr, and Eco RI-digested hamster mitochondrial DNA were transformed into E. coli K12. The translation products of the parent plasmid, Co1E1 - Ampr, and recombinant plasmid DNAs containing (i) the 4.2 kb mitochondrial DNA fragment and (ii) the 11.4 kb fragment were characterized on sodium dodecyl sulfate-polyacrylamide gels using bacterial mini-cell lysates. The Co1E1 - Ampr plasmid specifies at least six polypeptides whose structural genes comprise 56% of the plasmid DNA. Insertion of hamster mitochondrial DNA at the Eco RI site of the plasmid alters the relative rate of synthesis of these six polypeptides and induces the occurrence of a new band on sodium dodecyl sulfate-polyacrylamide gels which is probably not specified by the inserted mitochondrial DNA sequences.

IDENTIFICATION AND SEQUENCING OF YEAST MITOCHONDRIAL tRNA GENES IN MITOCHONDRIAL DNA - pBR322 RECOMBINANTS

ABSTRACT We have cloned yeast mitochondrial DNA in the E. coli plasmid pBR322 by the poly(dA):poly(dT) tailing method and found that 62 of the 347 transformants obtained contain mitochondrial tRNA genes. In order to correlate the cloned mitochondrial tRNA genes with their gene products, we screened the recombinants with nick translated DNA isolated from petites known to carry choramphenicol (C), erythromycin (E), paramomycin (P), or oligomycin (0) markers as well as a limited subset of tRNA genes. A serine tRNA gene mapping in the OT region of the mitochondrial DNA was identified by hybridizing DNA from O 1 positive clones with [ 3 H]seryl tRNA. Other tRNA genes were identified by hybridizing [ 32 P]tRNA to Southern transfers of restriction enzyme digests of recombinant DNA molecules. Fragments selected for sequencing contained tRNA genes for two serine tRNAs, a phenylalanine tRNA, a glycine tRNA, a valine tRNA and an arginine tRNA. None of the tRNA genes appear to have intervening sequences, none have the CCA end encoded and all are surrounded by long stretches of very AT rich DNA.

Identification and Characterization of a Yeast Mitochondrial Locus Necessary for tRNA Biosynthesis

It is well established that yeast mtDNA codes for tRNAs used in mitochondrial protein synthesis. Very little is known about the expression of those tRNA genes and the processes necessary to produce functional tRNAs in mitochondria. One approach toward the elucidation of tRNA biosynthetic pathways is to analyze tRNA biosynthesis in mitochondrial mutants. Petite mutants are mtDNA deletion mutants that have lost various portions of the wild-type genome. Some petites that retain tRNA genes make tRNAs indistinguishable from wild-type tRNAs (Martin et al. 1976; Newman et al. 1980), whereas other petites that retain tRNA genes make transcripts from their tRNA genes but do not produce tRNAs (Martin et al. 1976; Martin and Underbrink-Lyon 1981). Since the ability to produce tRNA could be correlated with retention of a particular region of mtDNA, Morimoto et al. (1979) suggested that a mitochondrial locus was necessary for tRNA biosynthesis. We have now demonstrated the presence of such a locus by complementation analysis; we have located it within 2100 bp of the wild-type genome and have characterized it by restriction mapping and DNA sequencing. COMPLEMENTATION ANALYSIS OF THE tRNA SYNTHESIS LOCUS If a locus on mtDNA is necessary for tRNA synthesis, then a petite that has the locus should restore the ability to synthesize tRNA to a petite that does not make tRNA from the tRNA genes it retains. A mating procedure that allows two mitochondrial genomes to be maintained in a diploid state (Strausberg and Butow 1978) was used to test this hypothesis. Restoration...

Sequence Organization and Expression of a Plasmid DNA Molecule Found in Yeast

Most strains of baker’s yeast, Saccharomyces cerevisiae, contain closed-circular duplex DNA plasmid molecules approximately 2 μm (6,200 base pairs) in contour length. There are about 100 plasmid molecules per cell, the sum of which comprises about 2.5% of the haploid genome. The plasmid possesses a nontandem inverted repeat sequence of about 650 base pairs about which intramolecular reciprocal recombination occurs to generate two forms of sequence organization. We have identified a 750 base pair restriction enzyme fragment that contains the inverted repeat sequence and have determined its complete nucleotide sequence by Maxam/Gilbert analysis. We have also screened a bank of approximately 3,000 random yeast DNA fragments cloned in E. coli via the poly dA:T method for the presence of yeast plasmid sequences. The hope was that we would identify a cloned yeast DNA fragment which contained a boundary between the yeast plasmid sequence and a yeast chromosomal sequence. This would prove that the yeast plasmid was capable of integrating into chromosomal DNA.