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Biomedical subjects

R E Bird

Publications and source records attributed to R E Bird.

At least 37 records · Page 2Linked to original sources
PubMed1991

Single chain antibody variable regions.

The use of antibodies or antibody fragments for targeting tumors (either for tumor imaging or as carriers for drugs or toxins), has encountered problems of clearance, and non-specific or inefficient binding in clinical trials. A novel approach, linking two antibody variable fragments (Fvs), with a short peptide to generate a continuous polypeptide chain, may be able to overcome some of these problems. Since these single chain antibody variable regions (scFvs), are transcribed from constructed 'genes', large-scale production in, for example, E. coli, should be straightforward.

Animals↗
PubMed1989

Low-cost screening mammography: report on finances and review of 21,716 consecutive cases.

A review of the results of 21,716 mammograms obtained at a low-cost screening center is presented, along with a report on the finances of that center. A total of 142 cancers were discovered, 12 of which gave false-negative results at mammography. The sensitivity was 91.5% and the specificity 90%. The positive predictive value for lesions categorized as "suspicious for malignancy" was 54%. Thirty-one percent of the cancers were "minimal," in other words, in situ or less than 1 cm in diameter and with no tumor-positive lymph nodes. An average of 42 examinations were performed each day at a cost of +28 each. Nonphysician expenses were +16 for each examination, leaving +12 per examination as professional revenue. This project demonstrates that high-quality, low-cost screening mammography can be provided if the volume is adequate and if there is sufficient attention to detail.

Breast Neoplasms↗
PubMed1988

Single-chain antigen-binding proteins.

Single-chain antigen-binding proteins are novel recombinant polypeptides, composed of an antibody variable light-chain amino acid sequence (VL) tethered to a variable heavy-chain sequence (VH) by a designed peptide that links the carboxyl terminus of the VL sequence to the amino terminus of the VH sequence. These proteins have the same specificities and affinities for their antigens as the monoclonal antibodies whose VL and VH sequences were used to construct the recombinant genes that were expressed in Escherichia coli. Three of these proteins, one derived from the sequence for a monoclonal antibody to growth hormone and two derived from the sequences of two different monoclonal antibodies to fluorescein, were designed, constructed, synthesized, purified, and assayed. These proteins are expected to have significant advantages over monoclonal antibodies in a number of applications.

Amino Acid Sequence↗
PubMed1988

Synthesis of biologically active deletion mutants of human factor VIII:C.

The recent cloning and sequence analysis of human factor VIII:C (antihaemophilic factor) revealed a domain structure for the protein which can be presented as A1-A2-B-A3-C1-C2. In this report we describe the construction of two altered factor VIII:C cDNAs coding for molecules in which a part (amino acids 816 to 1598) or all of the B domain (amino acids 741 to 1689) was removed. In the latter mutant a new thrombin cleavage site has been created, which does not exist in wild-type factor VIII:C. The mutated cDNAs were cloned into eucaryotic expression vectors based on regulatory sequences of the virus SV40 and transfected into two different mammalian cell lines. Both truncated recombinant factor VIII:C molecules were secreted into the culture medium, showed full biological activity and could be activated by thrombin.

Amino Acid Sequence↗
PubMed1986

How to initiate and operate a low-cost screening mammography center.

An in-depth "how-to" report on initiating and operating a low-cost screening mammography facility is presented. It is based on a successful program of this type in Charlotte, North Carolina, and includes information on feasibility determination, financial analysis, site selection and preparation, equipment, public relations, promotion, and operational details. The authors believe that use of such a model, with modification as necessary, should result in a successful program and a valuable community service.

Ambulatory Care Facilities↗
PubMed1983

Ectopic pro-opiolipomelanocortin: sequence of cDNA coding for beta-melanocyte-stimulating hormone and beta-endorphin.

A recombinant bacterial plasmid, pMS1, was constructed that contains 318 nucleotides complementary to a portion of pro-opiolipomelanocortin (proOLMC) messenger RNA from an ectopic adrenocorticotropin-producing tumor. The cloned complementary DNA insert, which contains the sequence that codes for all of the beta-melanocyte-stimulating hormone and beta-endorphin portions of proOLMC, as well as the 3' nontranslated section, is identical to the genomic sequence. Hybridization of tumor proOLMC complementary DNA to RNA subjected to electrophoresis and transferred to a nitrocellulose filter revealed two proOLMC messenger RNA species in the tumor polyadenylated RNA, but only one in pituitary polyadenylated RNA. At least one of the tumor proOLMC messenger RNA's is similar, if not identical, to human pituitary proOLMC messenger RNA.

Amino Acid Sequence↗
PubMed1983

Accumulation of ColE1 early replicative intermediates catalyzed by extracts of Escherichia coli dnaG mutant strains.

To investigate the events occurring at the replication forks during DNA synthesis, we studied the replication of plasmid ColE1 DNA in vivo and in vitro, using strains of Escherichia coli carrying either the dnaG3(Ts) or dnaG308(Ts) mutation. Extracts of both mutant strains supported in vitro DNA synthesis, but the amount of [3H]TMP incorporated into DNA was always less for mutant extracts than for extracts of revertant strains, which were able to grow at 42 degrees C. Sucrose gradient analysis, Southern blot analysis, and electron microscopy showed that mutant extracts synthesize a large number of early replicative intermediates containing one or two (one on each template strand) fragments at the origin of replication and some completed molecules, either open circles or covalently closed circles. The revertant extracts synthesized more completed molecules although the fraction of templates used was about the same, 0.27 for mutant extracts and 0.21 for revertant extracts. Our results show that a mutation in dnaG causes a block in the synthesis of both leading and lagging strands after initiation, which results in the accumulation of early replicative intermediates. The average size of the newly replicated region in the early replicative intermediates is 730 bases as measured from electron micrographs of early replicative intermediates. We conclude that the DnaG protein functions in lagging strand synthesis and may be necessary for the continuation of leading strand synthesis as well.

Bacterial Proteins↗
PubMed1981

Homology between Escherichia coli plasmids ColE1 and p15A.

The location and extent of the homology between plasmids ColE1 and p15A were determined by analysis of heteroduplexes formed between them as well as with a related plasmid, pBR322, and by hybridization of radioactive deoxyribonucleic acids to restriction fragments of p15A and ColE1. The homology between the plasmids contained the entire region of ColE1 required for its replication as well as an additional 400 base pairs downstream from the origin of replication. This region on p15A, which was 980 +/- 43 base pairs, started at 0.1 of the molecular length from one end formed by cleavage with the restriction endonuclease BglI and extended to 0.54 of the molecular length from the same end. Restriction cleavage maps for the enzymes BglI, HpaI, HaeII, HaeIII, and HincII are also presented.

Base Sequence↗
PubMed1979

Cell specific antiserum to chromosome scaffold proteins.

Antiserum has been raised to a chromosomal protein fraction specific for Hela cells. The immunoactivity is located in the transcriptionally inactive regions of log phase chromatin. Digestion of metaphase chromosomes results in the purification of the immunoactivity in the scaffold region of the chromosomes. Extensive nuclease digestion of the scaffolds results in loss of activity. The data suggest that some of the proteins in the scaffold area are both tight binding and cell specific and may therefore play a sophisticated role in gene expression.

Cell Cycle↗
PubMed1977

Origin of replication of colicin E1 plasmid DNA.

Cleavage maps of colicin E1 plasmid DNA and its smaller derivative, pNT1 DNA, were constructed by using restriction endonucleases. The nucleotide sequence of a region that contains the orgin of replication was determined. The site of the nucleotide from which DNA replication is initiated was determined with 6S L-fragments, the DNA fragment first made on colicin E1 plasmid DNA. The fragments were labeled with [gamma-32P]ATP and polynucleotide 5'-hydroxyl-kinase (ATP:5'-dephosphopolynucleotide 5'-phosphotransferase, EC 2.7.1.78) at the 5'-OH groups which were uncovered by alkali treatment. The site is one of three consecutive nucleotides, dA, dA, and dC, located at a unique position. One or a few rA residues were found to be attached to some of the DNA molecules. The transition from the primer RNA to DNA occurs in a region consisting of a segment of five A residues. Both sides of this segment are rich in G and C.

Base Sequence↗
PubMed1976

Suppression of an Escherichia coli dnaA mutation by the integrated R factor R.100.1: Change of chromosome replication origin in synchronized cultures.

We have followed, by deoxyribonucleic acid-deoxyribonucleic acid hybridization, the order of replication of three chromosomal markers during a synchronous round of replication in three strains of Escherichia coli carrying a dnaAts mutation: one strain in which the F-like R factor R.100.1 was established as a plasmid and two strains in which the dnaA mutation was suppressed by the integration of R.100.1 into the chromosome. In the R+ strain at 30C, replication of the plasmid took place simultaneously with the initiation of chromosome replication at the normal origin. In the integratively suppressed Hfr strains, at 42.5 C, chromosome replication was initiated preferentially from the integrated plasmid; little or no initiation occurred at the normal origin. Similar results were obtained for the one strain tested at 30 C. For both Hfr strains at 42.5 C, the data suggest that at least part of the population replicated bidirectionally. This conclusion had been confirmed using an autoradiographic procedure. Both types of experiment indicate a wide variation in the rate of travel of individual replication forks within the population.

Cell Division↗
PubMed1974

Size distribution and molecular polarity of newly replicated DNA in Escherichia coli.

Newly synthesized DNA, in E. coli lysogenic for the phage lambda, was labeled by short pulses of [(3)H]-thymidine, isolated, and separated on the basis of size by alkaline sucrose density gradient centrifugation. The molecular polarity of this DNA was determined by hybridization with each of the separated strands of lambda DNA. The results show that, in the 3' to 5' direction, replication proceeds by synthesis of short chains that are subsequently joined to long DNA. This is true for both a polA(+) and a polA(-) strain. (The polA locus codes for DNA polymerase I.) In the 5' to 3' direction, replication proceeds continuously, by addition of nucleotides to long DNA, for the polA(+) strain. In the polA(-) strain, however, replication in the 5' to 3' direction is also discontinuous, but the discontinuities are 1-40 times less frequent than in the other direction.

Centrifugation, Density Gradient↗
PubMed1974

More precise mapping of the replication origin in Escherichia coli K-12.

The origin of replication in Escherichia coli K-12 was mapped by determining the rate of marker replication during a synchronous round of replication. Four isogenic strains were made lysogenic for lambdaind(-) and for phage Mu-1, with Mu-1 integrated into a different chromosomal location in each strain. Cultures were starved for amino acids to allow completion of chromosome replication cycles and then starved for thymine in the presence of amino acids, and a synchronous cycle of replication was initiated by the addition of thymine. Samples were exposed to radioactive thymidine at intervals, deoxyribonucleic acid was extracted, and the rate of marker replication was determined by deoxyribonucleic acid-deoxyribonucleic acid hybridization to filters containing Mu-1, lambda, and E. coli deoxyribonucleic acid. The results confirm that the origin of replication is near ilv. The travel times of the replication forks, calculated from the data obtained for cultures with doubling times of approximately 40 and 61 min, are 40 and 52 min, respectively.

Amino Acids↗