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Biomedical subjects

M E Mahoney

Publications and source records attributed to M E Mahoney.

32 records · Page 2Linked to original sources
PubMed1990

Implementation of an optical disk system for medical record storage.

MARS was a joint developmental effort between Maine Medical Center and Advanced Healthcare Systems, Inc. It has taken nearly three years to get the system (hardware, software, and staff) to a point where it can now meet daily production requirements. This project was truly unique, so there was no opportunity to learn from the experiences of others. The optical disk system has been an attractive solution to some of the problems experienced at Maine Medical Center. The result was worth the effort in terms of both dollars and other less quantifiable benefits that have had a positive impact on patient care.

Abstracting and Indexing↗
PubMed1988

Identification of the DNA binding domain of the phage lambda cII transcriptional activator and the direct correlation of cII protein stability with its oligomeric forms.

The bacteriophage lambda transcriptional activator protein cII is a DNA-binding protein that coordinately regulates transcription from phage promoters important for lysogenic growth. We have genetically and structurally characterized more than 80 different single amino acid substitutions in this 97-amino-acid protein. A subset of 25 of these variant proteins was utilized for detailed biochemical analysis, which allows us to define specific domains critical for sequence-selective DNA recognition, nonspecific DNA binding, and protein oligomerization. The mutation studies also demonstrated the remarkable correlation of oligomeric structure of cII protein to its stability within the bacterial host. An Escherichia coli HtpR- strain has been identified that greatly stabilizes these highly unstable cII mutants.

Amino Acid Sequence↗
PubMed1987

Mutations that affect the efficiency of translation of mRNA for the cII gene of coliphage lambda.

Starting with the lambda pRE-strain lambda ctr1 cy3008, which forms clear plaques, we have isolated two mutant strains, lambda dya2 ctr1 cy3008 and lambda dya3 ctr1 cy3008, that form plaques with very slightly turbid centers. The dya2 and dya3 mutations lie in the region of overlap between the PRE promoter and the ribosome recognition region of the cII gene, and have nucleotide alterations at positions -1 and +5 of pRE, and alterations in cII mRNA at -16 and -21 nucleotides before the initial AUG codon of the gene. Both mutations destabilize a stem structure that may be formed by cII mRNA, and dya2 also changes the sequence on cII mRNA that is complementary to the 3'-end of 16 S rRNA from 5'-UAAGGA-3' to 5'-UGAGGA-3'. --The dya2 and dya3 mutations, along with the ctr1 mutation, which destabilizes either of two alternate stem structures which may be formed by cII mRNA (these being more stable stem structures than the one affected by dya2 and dya3), were tested for their ability to reverse two cII-mutations that are characterized by inefficient translation of cII mRNA. These are cII3088, an A----G mutation four bases before the initial AUG codon, and cII3059, a GUU----GAU (Val2----Asp) second codon mutation. It was found that ctr1 completely reverses the translation defects of these two mutations, while dya2 partially reverses these translation defects. The dya3 mutation has no effect on translation efficiency under any condition tested.(ABSTRACT TRUNCATED AT 250 WORDS)

Bacteriophage lambda↗
PubMed1987

Mutations that improve the pRE promoter of coliphage lambda.

The dya5 mutation, a C----T change at position -43 of the lambda pRE promoter, results in a twofold increase in pRE activity in vivo. Smaller increases in pRE activity are found for the dya2 mutation, a T----C change at position -1 of pRE, and the dya3 mutation, an A----G change at +5 of pRE. The mutant pRE promoters retain complete dependence on cII protein for activity. These observations argue, at least for pRE-like promoters, that promoter activities are influenced by nucleotide sequences at least eight nucleotides to the 5'-side of the conventional -35 region consensus sequence, and by nucleotide sequences near the start-site of transcription. Although Hawley and McClure (1983) found A-T pairs more frequently than G-TC pairs in the region of -40 to -45 of prokaryotic promoters, other mutations that change a G-TC pair to an A-T pair at positions -41, -44 and -45 of pRE do not result in increased promoter activity. We also found that a T----C change at positions -42 results in a mild decrease in promoter activity. These observations argue that Ts at positions -42 and -43 of pRE are required for maximum promoter activity, but do not support the hypothesis that As and Ts in the -40 and -45 region generally lead to higher promoter activities.

Bacteriophage lambda↗
PubMed1987

Cross-specificities between cII-like proteins and pRE-like promoters of lambdoid bacteriophages.

We have investigated the activation of transcription from the pRE promoters of phages lambda, 21 and P22 by the lambda and 21 cII proteins and the P22 c1 (cII-like) protein, using an in vivo system in which cII protein from a derepressed prophage activates transcription from a pRE DNA fragment on a multicopy plasmid. We find that each protein is highly specific for its own cognate pRE promoter, although measureable cross-reactions are observed. The primary recognition sequence for cII protein on lambda pRE is a pair of TTGC repeat sequences in the sequence 5'-TTGCN6TTGC-3' at the -35 region of the promoter. This same sequence is found in 21 pRE, while P22 pRE has the sequence 5'-TTGCN6TTGT-3', which is the same as that of lambda ctr1, a pRE+ variant of lambda. lambda ctr1 pRE is half as active as lambda + pRE when assayed with either the lambda cII or the P22 c1 proteins. Therefore, the single base change in the P22 repeat sequence cannot explain why the P22 c1 protein is much more active with P22 pRE than lambda pRE. The dya5 mutation, a G----A change at position -43 of pRE, makes pRE a stronger promoter when assayed with either the lambda or 21 cII proteins or the P22 c1 protein. We conclude that efficient activation of a cII-dependent promoter by a cII protein requires sequence information in addition to the TTGC repeat sequences. We do not know the characteristics of the proteins which are responsible for the specificity of each protein for its own cognate promoter.(ABSTRACT TRUNCATED AT 250 WORDS)

Bacteriophage lambda↗
PubMed1985

Failure of canine islet allografts and autografts with cyclosporine.

Intrasplenic autotransplantation of islet fragments prepared by ductal perfusion constitutes a reproducible system for islet delivery to apancreatic dogs. The animals are normoglycemic from the time of grafting, and graft failure is rare. In this study, apancreatic dogs received islet autografts (controls), autografts plus oral cyclosporine, and allografts plus oral cyclosporine. Therapeutic blood levels of cyclosporine were documented by radioimmunoassay. However, allografts and autografts ceased to function after initial normoglycemia in all animals that received cyclosporine, and four out of six autografts failed. Normoglycemia persisted in the control-autografted animals for the duration of the study. Microscopic sections of the failed grafts demonstrated meager tissue survival but no evidence of rejection by cellular infiltration.

Animals↗
PubMed1984

Mutations that alter the DNA binding site for the bacteriophage lambda cII protein and affect the translation efficiency of the cII gene.

The efficiency of translation of the cII gene of bacteriophage lambda is greatly reduced by the cII3059 mutation, a GUU----GAU (Val----Asp) change in the second cII codon. Mutations in the third and fourth codons of the cII gene, called ctr mutations, reverse this translation deficiency. Lambda cII3059 ctr-1, which has a GCA----ACA (Ala----Thr) change in the fourth cII codon, produces about half the normal level of cII activity in liquid cultures, and lambda cII3059 ctr-2 and lambda cII3059 ctr-3, which have identical CGT----CGC changes in the third codon, produce normal levels of cII activity in liquid culture. Since the cII protein of ctr-3 has the same primary sequence as that of lambda cII3059, the cII- phenotype of lambda cII3059 can be explained entirely by the deficiency of translating cII mRNA. We propose that ctr mutations increase translation efficiency by destabilizing a stable stem structure which can be formed by cII mRNA. The ctr mutations lie in an overlapping regulatory region which contains, in addition to sequence elements that influence the rate of cII translation, a region to which cII protein binds to activate transcription from the PRE promoter. The ctr-1 mutation alters the cII recognition sequence from 5'-T-T-G-C-N6T-T-G-C-3' to 5'-T-T-G-C-N6T-T-G-T-3', but has no effect on PRE activity. Since a C----T change in the first (5'-proximal) T-T-G-C sequence (to yield 5'-T-T-G-T-N6T-T-G-C) greatly lowers cII binding affinity, cII protein must not recognize the two T-T-G-C sequences in an identical manner.

Bacteriophage lambda↗
PubMed1980

Children's health care needs lack broad-based constituency.

With no consensus for action on children's behalf, the hard-won gains of the 1960s will diminish. Governmental expenditures for child health needs have steadily decreased in the face of a worsening economy. Consensus is critical to reverse this trend.

Child↗