Biomedical subjects

S Zullo

Publications and source records attributed to S Zullo.

6 recordsLinked to original sources

PubMed1996

Long-circulating bacteriophage as antibacterial agents.

The increased prevalence of multidrug-resistant bacterial pathogens motivated us to attempt to enhance the therapeutic efficacy of bacteriophages. The therapeutic application of phages as antibacterial agents was impeded by several factors: (i) the failure to recognize the relatively narrow host range of phages; (ii) the presence of toxins in crude phage lysates; and (iii) a lack of appreciation for the capacity of mammalian host defense systems, particularly the organs of the reticuloendothelial system, to remove phage particles from the circulatory system. In our studies involving bacteremic mice, the problem of the narrow host range of phage was dealt with by using selected bacterial strains and virulent phage specific for them. Toxin levels were diminished by purifying phage preparations. To reduce phage elimination by the host defense system, we developed a serial-passage technique in mice to select for phage mutants able to remain in the circulatory system for longer periods of time. By this approach we isolated long-circulating mutants of Escherichia coli phage lambda and of Salmonella typhimurium phage P22. We demonstrated that the long-circulating lambda mutants also have greater capability as antibacterial agents than the corresponding parental strain in animals infected with lethal doses of bacteria. Comparison of the parental and mutant lambda capsid proteins revealed that the relevant mutation altered the major phage head protein E. The use of toxin-free, bacteria-specific phage strains, combined with the serial-passage technique, may provide insights for developing phage into therapeutically effective antibacterial agents.

Animals↗

PubMed1996

Possible relationship between conditions associated with chronic hypoxia and brain mitochondrial DNA deletions.

The brain relies heavily on aerobic metabolism which requires functional mitochondria. Mitochondria are subcellular organelles with their own genome which codes for 13 essential protein subunits. By employing PCR assays to examine brain tissue from 43 age-comparable individuals (between ages 34 and 73), we found a correlation between mitochondrial DNA deletion mutations, mtDNA4977 deletions, and conditions associated with chronic hypoxia. In prior studies, utilizing only 6 to 12 clinical samples, mtDNA4977 deletions were reported to increase in specific regions of the brain with aging. However, we found 12-fold and 5-fold higher levels of mtDNA4977 deletions in the putamen and the superior frontal gyrus of the cortex, respectively, from individuals who had conditions associated with chronic hypoxia when compared with individuals without evidence of such conditions. These findings suggest that chronic hypoxia should be more closely examined in the pathophysiology of central nervous system diseases.

Base Sequence↗

PubMed1996

A World Wide Web (WWW) server database engine for an organelle database, MitoDat.

We describe a simple database search engine "dbEngine" which may be used to quickly create a searchable database on a World Wide Web (WWW) server. Data may be prepared from spreadsheet programs (such as Excel, etc.) or from tables exported from relationship database systems. This Common Gateway Interface (CGI-BIN) program is used with a WWW server such as available commercially, or from National Center for Supercomputer Algorithms (NCSA) or CERN. Its capabilities include: (i) searching records by combinations of terms connected with ANDs or ORs; (ii) returning search results as hypertext links to other WWW database servers; (iii) mapping lists of literature reference identifiers to the full references; (iv) creating bidirectional hypertext links between pictures and the database. DbEngine has been used to support the MitoDat database (Mendelian and non-Mendelian inheritance associated with the Mitochondrion) on the WWW.

Computer Communication Networks↗

PubMed1995

Rat karyotyping by fluorescence in situ hybridization (FISH): localization of oncogene c-raf to 4q42, retinoblastoma antioncogene to 15q12, and mitochondrial D-loop-like sequences to the Y chromosome.

Fluorescence in situ hybridization (FISH) has been used to karyotype the rat genome with long interspersed repetitive elements (LINEs). Two-color FISH experiments were used to localize the rat c-raf oncogene to 4q42 and the rat retinoblastoma anti-oncogene to 15q12. In addition, sequences similar to the rat mitochondrial origin of replication (D-loop-like sequences) have been found to be concentrated among repetitive element sequences on the Y chromosome. This report extends hybridization-based karyotype technology to the rat, thus facilitating the application of FISH to rat gene mapping.

Animals↗

PubMed1993

Eliminating mitochondrial DNA competition for nuclear DNA primers.

Mitochondrial DNA (mtDNA) sequences were synthesized with nuclear DNA (nucDNA) sequence-tagged site (STS) primers by mismatch priming in three independent studies of the human nuclear genome. Mismatch primer binding sites on the mtDNA were identified with from 6- to 10-bp identity at the 3' ends of the primers. In two of three cases, single-stranded mtDNA copies were gel-isolated with intended nucDNA PCR products. During routine screening of the STSs, the radiolabeled gel-isolated products hybridized to polymorphic mtDNA restriction fragments. Intense signals after overnight exposure of radiolabeled PCR probes on Southern blots suggest contaminating mtDNA PCR products. The theoretical annealing temperatures of the mismatches were well below the annealing temperatures of the PCR primers, demonstrating annealing reactions driven by the molar surplus of the primers, that is, mass action. The probability that two primers (either one of a pair or both), designed to amplify nucDNA, will bind to and amplify mtDNA may be as high as 1 in 64, assuming that an identical match with only the 3' hexanucleotide is sufficient for amplification. To circumvent this problem we have developed OLIGFIND, a program that has identified the 104 of 4096 possible hexamers that are not present in human mtDNA. Our results suggest that time could be saved by designing STS primers with one of these 104 hexamers at the 3' end. OLIGFIND can also evaluate primer 3' ends for potential PCR products from mtDNA.

Base Sequence↗

PubMed1991

Mitochondrial D-loop sequences are integrated in the rat nuclear genome.

We have cloned two fragments of rat nuclear DNA (nucDNA), 3.3 x 10(3) nucleotide-pairs (knp) and 9.1 knp, that contain a 0.5 knp section sharing 80% sequence identity with the mitochondrial DNA (mtDNA) heavy strand origin of replication (D-loop) nascent strand and 88% identity with each other. The light and heavy strand promoters of the D-loop region are not present in either clone, thus they likely do not function as replication origins in the nuclear genome. The nucDNA sequences surrounding the mtDNA-like sequences are not mitochondrial, thus the mtDNA-like sequences are demonstrably covalently linked in the nuclear genome. Indeed, the surrounding nuclear sequences of each clone also share 88% identity. This sequence arrangement strongly suggests an initial insertion of mtDNA into nucDNA with subsequent amplification of an encompassing region of nucDNA. Divergence calculations suggest that the mtDNA insertion occurred around 13.6 million years ago (MYA) with the subsequent separation occurring around 6.5 MYA. The mtDNA-like sequences of the nuclear clones hybridize strongly to a number of different BamHI-PstI restriction fragments, suggesting either repeated integration and/or frequent mutational events producing new restriction enzyme sites. It is not yet known if one or more of the uncloned D-loop-like sequences are associated with promoters, which would suggest possible function. The 3.3 knp nucDNA fragment is present in low copy number. In contrast, the 9.1 knp nucDNA fragment appears to be moderately repeated. The elements do not appear to be tandemly repeated. The nucDNA clones contain remnants of rat long interspersed repetitive element (LINE) sequences; in addition the 9.1 knp fragment contains sequences with similarity to portions of viral reverse transcriptase and RNaseH genes. Until now, all mtDNA-like sequences found in the nuclear genome have been coding sequences. This is the first confirmation by sequence analysis of a portion of the mtDNA control region in the nuclear genome.

Amino Acid Sequence↗