Biomedical subjects

J B Perkins

Publications and source records attributed to J B Perkins.

36 records · Page 2Linked to original sources

PubMed1993

Optimizing high-dose therapy using pharmacokinetic principles.

The oncologic literature of the past decade contains numerous articles supporting the concept of "dose intensity." The hypothesis that greater intensity of effective drug therapy can result in higher cure rates is supported by the results obtained in bone marrow transplantation for leukemia, lymphoma, and, possibly, breast carcinoma. Stem cell infusion overcomes the first level of the dose-limiting toxicities, ie, bone marrow suppression. This predictable toxicity develops in all patients. Second organ toxicities, such as renal, hepatic, or cardiopulmonary toxicity, occur in a less predictable manner. This variation in individual patient tolerance may be related to wide variations in drug concentration between patients while receiving the same dose. This interpatient variability has been well described for many oncologic agents, but is not unique to oncologic therapy. Important but incompletely defined relationships of importance to high-dose therapy include (1) the relationship of drug dose to concentration within patient groups and for the individual patient and (2) the relationship of drug concentration, or other related parameter such as area under the concentration versus time curve, to toxicity and outcome. Assuming such relationships can be defined, the value of using improved methods to select drug doses for an individual patient to achieve therapeutic goals needs to be explored. The purpose is to optimize therapy. In the bone marrow transplantation setting, the ideal is to provide the greatest drug exposure without undo risk of life-threatening second organ toxicity. To solve these problems, we need models that predict and allow us to control therapy in a much more precise manner than is currently possible. This review examines the concept of dose intensity, defines this concept in terms of plasma drug concentrations, and reviews methods that can aid the control of therapy in the individual patient. The potential importance of this methodology to the individual patient is discussed.

Antineoplastic Agents↗

PubMed1993

Two novel high-dose treatment regimens for metastatic breast cancer--ifosfamide, carboplatin, plus etoposide and mitoxantrone plus thiotepa: outcomes and toxicities.

This report describes the results of two phase I/II dose escalation trials for the treatment of metastatic breast cancer. Successive groups of patients with metastatic breast cancer responsive to induction therapy following standard doses of chemotherapy were treated with escalating doses of ifosfamide (6,000 to 24,000 mg/m2), carboplatin (1,200 to 2,100 mg/m2), and etoposide (1,800 to 3,000 mg/m2) followed by autologous stem cell rescue. The maximum tolerated doses of these drugs were defined as ifosfamide 20,100 mg/m2, carboplatin 1,800 mg/m2, and etoposide 3,000 mg/m2. Major nonhematologic toxicity consisted of mucositis and enteritis, and the dose-limiting toxicities were central nervous system toxicity and acute renal failure. The overall treatment-related mortality rate was 4%. The event-free survival rate at 500 days for these patients was 31%. Patients with metastatic breast cancer refractory to all standard dose therapy were treated with escalating doses of mitoxantrone (45 to 105 mg/m2) and thiotepa (900 to 1,350 mg/m2) followed by autologous stem cell rescue. The maximum tolerated doses of these drugs were defined as mitoxantrone 90 mg/m2 and thiotepa 1,200 mg/m2 with mucositis and enteritis as the major nonhematologic toxicities and delayed myelosuppression as the dose-limiting toxicity. Twelve percent of the patients remain event free at 500 days and the treatment-related mortality rate for this group of heavily pretreated patients was 17%. These data suggest that patients with metastatic breast cancer may benefit from high-dose therapy and that treatment-related toxicity is tolerable.

Adult↗

PubMed1990

Streptomyces genes involved in biosynthesis of the peptide antibiotic valinomycin.

We have identified genes from Streptomyces levoris A-9 involved in the biosynthesis of the peptide antibiotic valinomycin. Two segments of chromosomal DNA were recovered from genomic libraries, constructed by using the low-copy-number plasmid pIJ922, by complementation of valinomycin-deficient (vlm) mutants of S. levoris A-9. One set of plasmids restored valinomycin production to only one mutant, that carrying vlm-1, whereas a second set of plasmids restored productivity to seven vlm mutants, those carrying vlm-2 through vlm-8. Additional complementation studies using subcloned restriction enzyme fragments showed that the vlm-1+ gene was contained within a 2.5-kilobase (kb) DNA region, whereas alleles vlm-2+ through vlm-8+ were contained in a 12-kb region, representing at least three genes. Physical mapping experiments based on the isolation of cosmid clones showed that the two vlm loci were 50 to 70 kb apart. Southern hybridization experiments demonstrated that the vlm-2+ gene cluster was highly conserved among other valinomycin-producing Streptomyces strains, whereas the vlm-1+ gene was ubiquitous among Streptomyces species tested. Increasing the copy number of the vlm-2+ gene cluster in S. levoris A-9 by the introduction of low-copy-number recombinant plasmids resulted in a concomitant increase in the level of valinomycin production.

Alleles↗

PubMed1987

Hypersensitivity reaction following chloramphenicol administration in a patient with typhoid fever.

Hypersensitivity reactions due to chloramphenicol are rarely reported in the literature. We present a case report of a patient with typhoid fever who experienced a hypersensitivity reaction subsequent to the infusion of chloramphenicol sodium succinate. The patient had previously reacted similarly to ampicillin infusion. A brief review of reported cases of chloramphenicol hypersensitivity in the English-language literature, as well as possible alternative explanations in this case, are provided.

Adult↗

PubMed1986

Construction and properties of Tn917-lac, a transposon derivative that mediates transcriptional gene fusions in Bacillus subtilis.

A derivative of Tn917 was constructed, referred to as Tn917-lac, which is capable of generating fusions that connect the transcripts of Bacillus subtilis chromosomal genes to the coding sequence of the lacZ gene of Escherichia coli. Two independent insertions of Tn917-lac into the gltA gene and one insertion into the trpE gene (in the trpEDCFBA operon) of B. subtilis were studied in detail, and the results confirmed that Tn917-lac-mediated transcriptional fusions produce levels of beta-galactosidase that reflect accurately the regulated expression of interrupted genes. To facilitate these studies, a procedure was developed that permits the analysis of Tn917-lac-mediated fusions in partial diploids where insertional mutations are complemented by an intact copy of the interrupted genes. Tn917 is known to function efficiently in bacteria representing three quite different Gram-positive genera (Streptococcus, Bacillus, and Staphylococcus) and is known to display a relatively high degree of randomness in its insertions into bacterial genomes, making it likely that Tn917-lac will be useful for the identification and study of many kinds of regulated genes in a wide range of Gram-positive species.

Bacillus subtilis↗

PubMed1984

A novel method for the rapid cloning in Escherichia coli of Bacillus subtilis chromosomal DNA adjacent to Tn917 insertions.

A rapid and general procedure has been devised for the pBR322-mediated cloning in Escherichia coli of Bacillus subtilis chromosomal DNA extending in a specified direction from any Tn917 insertion. Derivatives of Tn917 have been constructed that contain a pBR322-derived replicon, together with a chloramphenicol-resistance (Cmr) gene of Gram-positive origin (selectable in B. subtilis), inserted by ligation in two orientations into a SalI restriction site located near the center of the transposon. When linearized plasmid DNA carrying such derivatives was used to transform to Cmr B. subtilis bacteria already containing a chromosomal insertion of Tn917, the pBR322 sequences efficiently became integrated into the chromosomal copy of the transposon by homologous recombination. It was then possible to clone chromosomal sequences adjacent to either transposon insertion junction into E. coli, using a selection for ampicillin-resistance, by transforming CaCl2-treated cells with small amounts of insert-containing DNA that had been digested with various restriction enzymes and then ligated at a dilute concentration. Because pBR322 sequences may be inserted by recombination in either orientation with respect to the transposon arms, a single restriction enzyme (such as EcoRI or SphI) that has a unique recognition site in pBR322 DNA may be used to separately clone chromosomal DNA extending in either direction from the site of any transposon insertion. A family of clones generated from the region of an insertional spo mutation (spoIIH::Tn917) was used in Southern hybridization experiments to verify that cloned material isolated with this procedure accurately reflected the arrangement of sequences present in the chromosome. Strategies are discussed for taking advantage of certain properties inherent in the structure of clones generated in this way to facilitate the identification and study of promoters of insertionally mutated genes.

Bacillus subtilis↗

PubMed1984

A physical and functional analysis of Tn917, a Streptococcus transposon in the Tn3 family that functions in Bacillus.

The erythromycin-resistance (Emr)-conferring transposon Tn917, first isolated in the genus Streptococcus, has in previous work been shown to function efficiently in the spore-forming species Bacillus subtilis, where it has been developed as a tool for identifying and studying sporulation genes. In the present work, a physical analysis of Tn917 was undertaken, including detailed restriction mapping, chemical DNA sequencing, heteroduplex studies, and Southern hybridization analysis, as a first step in understanding the genetic organization of this useful insertion element. The location and transcriptional orientation of the transposon-borne erm gene (the gene responsible for the Emr phenotype) have been determined, and a partial sequence of DNA 5' to the coding sequence of this gene indicates that its inducibility is probably the result of "translational attenuation," a mechanism known to be responsible for the regulation of at least two other gram-positive erm genes. Restriction mapping and heteroduplex analysis have revealed extensive homology between Tn917 and the Staphylococcus transposon Tn551, throughout virtually their entire lengths, and DNA sequencing studies have revealed a remarkably high degree of sequence correspondence within the terminal inverted repeats of Tn917, Tn551 and the gram-negative transposon Tn3. Tn917 was also shown to generate a 5-bp duplication upon insertion, as do Tn3 and Tn551 (and all of the other Tn3-related elements studied thus far), strengthening the conclusion that these three transposons are members of a highly dispersed family of related insertion elements which populate both gram-positive and gram-negative genera.

Bacillus↗

PubMed1984

Construction of a cloning site near one end of Tn917 into which foreign DNA may be inserted without affecting transposition in Bacillus subtilis or expression of the transposon-borne erm gene.

A 1.3-kb restriction fragment carrying a cat gene derived from Staphylococcus aureus was inserted by ligation in both possible orientations into a HpaI restriction site located less than 300 bp from one end of Tn917. The resulting transposon derivatives were unimpaired in their ability to make and resolve transpositions into the chromosome of Bacillus subtilis and they displayed no detectable defect in expression of the inducible erm gene carried by the transposon. This demonstrates that the HpaI site itself, and perhaps the entire 250- to 300-bp region between the HpaI site and the nearest transposon terminal inverted repeat consists of nonessential DNA, and is there fore available to be modified or used as a cloning site with the expectation that the resulting transposon derivatives should be capable of normal transposition activity. To facilitate such manipulations, the HpaI site was "replaced" by a 24-bp DNA segment which contains a BamHI site flanked on either side by SmaI sites; these BamHI and SmaI sites are unique to the transposon. Several of the plasmid constructions undertaken in the course of this work illustrate ways in which homologous recombination may be used in conjunction with ligation in B. subtilis (and other bacteria, such as Streptococcus pneumoniae, which have similar mechanisms for DNA uptake during competence) to facilitate significantly the recovery of certain kinds of recombinant molecules.

Bacillus subtilis↗

PubMed1983

Genetic transposition and insertional mutagenesis in Bacillus subtilis with Streptococcus faecalis transposon Tn917.

The Streptococcus faecalis transposon Tn917 was introduced into Bacillus subtilis by transformation of competent cells with the plasmid pAM alpha 1::Tn917 and was tested for transposition activity by selection for insertions into the temperate phage SP beta. Insertions were obtained at a frequency indicating relatively efficient movement of the element, and Southern hybridization analysis of a particular insertion confirmed it to be the result of a genuine transposition event. A restriction fragment from pAM alpha 1::Tn917 containing the transposon sequences was ligated into a temperature-sensitive plasmid (pBD95), and transpositions into the B. subtilis chromosome were selected by requiring the transposon drug resistance to be maintained at temperatures nonpermissive for plasmid replication. Insertions have been recovered at many chromosomal sites, including ones that produced auxotrophy of different kinds and ones that produced various different sporulation-defective phenotypes, indicating good prospects for the use of Tn917 as a tool for insertional mutagenesis in B. subtilis.

Bacillus subtilis↗

PubMed1983

Streptococcus plasmid pAM alpha 1 is a composite of two separable replicons, one of which is closely related to Bacillus plasmid pBC16.

A tetracycline resistance plasmid of Streptococcus faecalis, pAM alpha 1, is shown to contain two independent sets of replication functions, separated from each other on either side by short (300- to 400-base-pair) sequences of homology. The homologous sequences are oriented as direct repeats and therefore permit the dissociation of pAM alpha 1 into its component replicons, referred to here as pAM alpha 1 delta 1 and pAM alpha 1 delta 2, as the reciprocal products of a simple intramolecular recombination. pAM alpha 1 delta 1 is a 4.6-kilobase plasmid which carries the tet gene, and pAM alpha 1 delta 2 is a 5.1-kilobase plasmid which carries no known selectable marker. pAM alpha 1 delta 1 is shown to replicate efficiently in Bacillus subtilis and to confer tetracycline resistance on Bacillus hosts. We demonstrate by restriction mapping analysis that pAM alpha 1 delta 1 is virtually identical to a 4.6-kilobase tetracycline resistance plasmid of Bacillus cereus, pBC16, which is known to show extensive homology to plasmid isolates from Staphylococcus species (such as pUB110), as well as from other Bacillus species. The pAM alpha 1 delta 1-pBC16-pUB110 replicon thus exists naturally in at least three different gram-positive genera, indicating that these plasmids have a high degree of interspecific functional adaptability and supporting the view that plasmid DNA is commonly exchanged among many species of gram-positive bacteria in their natural environments.

Bacillus↗

PubMed1983

Transfection of Bacillus subtilis protoplasts by bacteriophage phi do7 DNA.

DNA from the Bacillus subtilis temperate bacteriophage phi do7 was found to efficiently transfect B. subtilis protoplasts; protoplast transfection was more efficient than competent cell transfection by a magnitude of 10(3). Unlike competent cell transfection, protoplast transfection did not require primary recombination, suggesting that phi do7 DNA enters the protoplast as double-stranded molecules.

Bacillus subtilis↗

PubMed1980

Physical mapping of Bacillus subtilis phage rho14 cloning vehicles: heteroduplex and restriction enzyme analyses.

Four deletion mutants of temperate Bacillus subtilis bacteriophage rho14 have been examined utilizing restriction enzyme and DNA heteroduplex methods. This has allowed the orientation and mapping of the deletions on the rho14 physical map. A continuous 15% of the genome contains functions not essential for bacteriophage viability. A 7% subsection of this region contains phage immunity functions. The deletions were found to range in size from about 2.2-3.3 kilobases. In addition, the deletion mutants retain a single Sal I restriction site, which is currently being used as a cloning site for recombinant DNA. We have located the Sal I site to be 400 basepairs from the immunity region. Thus, the clear- and turbid-plaque deletion mutants are all capable of being utilized as molecular cloning vehicles for Bacillus subtilis.

Bacillus subtilis↗

PubMed1978

Restriction endonuclease mapping of bacteriophage phi105 and closely related temperate Bacillus subtilis bacteriophages rho10 and rho14.

Cleavage maps of the three similar Bacillus subtilis temperate bacteriophages, phi105, rho10, and rho14, were constructed by partial digestion analysis utilizing the restriction endonuclease EcoRI. Comparison of the topography of these maps indicates that all phage DNAs posses cohesive ends and a number of EcoRI restriction sites; the fragments are conserved, and the estimated base substitution/nucleotide divergence between these phages is 0.03 to 0.07 based on conserved fragments or between 0.03 and 0.11 based on conserved cleavage sites. These lines of evidence indicate that phi105, rho10, and rho14 are closely related. Double-enzyme digestion analysis reveals that rho14 DNA has unique SalGI and BglII restriction sites and phi105 DNA has a unique SalGI restriction site, making these phages possible cloning vectors for B. subtilis.

Bacillus subtilis↗

PubMed1970