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Biomedical subjects

D P Tapper

Publications and source records attributed to D P Tapper.

13 recordsLinked to original sources

Video-assisted thoracoscopic closure of postpneumonectomy bronchopleural fistulas.

Despite improved surgical techniques and advances in medical-surgical treatment, postpneumonectomy bronchopleural fistulas remain an important cause of morbidity and a therapeutic challenge. Video-assisted thoracoscopic closure of these fistulas reinforced by transposition of bulky chest wall muscles or omentum to obliterate the residual space may lessen risks and complications of repeated thoracotomy in these often frail, debilitated, and compromised patients. We report our initial experience with video-assisted thoracoscopic debridement of the empyema cavity and closure of the postpneumonectomy bronchopleural fistula by transposing an entire pectoralis major muscle in one patient and by transposing a pedicled omentum in another patient.

Aged↗

Videothoracoscopic wedge resection for peripheral pulmonary nodules.

BACKGROUND: This study was done to evaluate the use of the endoscopic multifire linear stapler for videothoracoscopic wedge resection (VTWR) of peripheral pulmonary nodules and to define the indications, advantages, and drawbacks of this minimally invasive technique. STUDY DESIGN: A case study review of 57 consecutive video-assisted thoracic operations for wedge resection of peripheral pulmonary nodules performed upon 55 patients admitted to a community hospital from June 1991 through July 1993 is presented. RESULTS: There were 44 malignant and 13 benign lesions. Of the malignant peripheral pulmonary nodules (PPN), there were 19 adenocarcinomas, ten squamous cell carcinomas, two undifferentiated large-cell carcinomas, three bronchoalveolar carcinomas, two carcinoid tumors, one neuroendocrine tumor, and seven metastatic carcinomas. The benign nodules included five hamartomas, two granulomas, one aspergilloma, one nodular amyloidosis, one Wegener's granulomatosis, one focal pulmonary infarct, and two interstitial fibroses. Videothoracoscopic wedge resection alone was performed upon 37 patients, 17 of whom had primary carcinoma of the lung; seven had metastatic lesions, and the remainder had benign disease. Of the 17 patients with primary carcinoma of the lung who had VTWR alone, eight patients had marked impairment of pulmonary function, six had significant co-morbid disease, two had peripheral carcinoid tumors, and one had bilateral metachronous carcinomas. Videothoracoscopic wedge resections with concomitant lobectomies were performed upon 20 patients with primary carcinoma of the lung, including one patient with bilateral synchronous carcinomas. Five of the patients with nodules ranging from 2 to 3 cm in diameter were found to have metastasis to regional nodes. None of the patients who had lobectomies for peripheral carcinomas less than 2 cm in diameter had regional nodal metastases. There was no perioperative mortality and no significant morbidity. CONCLUSIONS: Videothoracoscopic wedge resection is a useful alternative to traditional transthoracic resection for suspicious, undiagnosed PPN, for low grade malignant neoplasms, such as carcinoid, for peripheral metastatic lesions, for bilateral synchronous or metachronous tumors, for the occasional clinically localized peripheral small-cell carcinoma as a surgical adjunct to chemotherapy, and for small, peripheral, T-1, N-0, M-0 bronchial carcinomas in compromised patients at high risk with marginal pulmonary reserve. The procedure is effective, minimally invasive, and has potential advantages over conventional thoracotomy, including less postoperative pain and morbidity, shorter hospitalization period and convalescence, and an earlier return to work and normal activities.

Humans↗

Detection of inspiratory resistive loads by heart-lung transplant recipients.

Human heart-lung transplantation recipients (HL) are models for the effects of selective lower respiratory tract denervation. We used a series resistor to examine thresholds of inspiratory flow resistance perception among 16 HL in comparison with 15 normal control subjects (C) and 12 heart transplant recipients (H). HL and C were closely age matched. H subjects were older and had mildly reduced lung volumes compared with the other groups. The perception threshold was defined as the added resistance (delta R) detected by subjects at 50% of random, blinded presentations. These delta R were subsequently expressed as a fraction of the airway resistance of the subject and baseline resistance of the apparatus (delta R/Raw + Rapparatus), otherwise known as the Weber fraction. The mean +/- SEM Weber fractions were nearly identical for HL and C (0.32 +/- 0.05 versus 0.34 +/- 0.05, respectively). The Weber fraction of H (0.74 +/- 0.17) was significantly greater than those of both other groups (p less than 0.05 by Kruskal-Wallis test). We conclude that lower respiratory tract afferents do not play a significant role in the perception of inspiratory resistive loads. The finding of an abnormally high Weber fraction in the heart transplant population remains unexplained but may be a function of age or restrictive pulmonary defects.

Adult↗

Hypoxic coordinate regulation of mitochondrial enzymes in mammalian cells.

The effect of hypoxic exposure on various mitochondrial enzymes and on cell mitochondrial genomic content was studied in two types of mammalian cells. Hypoxia depressed the activity of six enzymes to the same degree. The kinetics of depression and of recovery during reexposure to normoxia were statistically similar for three marker enzymes. Despite the global and symmetrical decrease in enzyme activities, mitochondrial DNA remained constant. This suggests either symmetrical loss of mitochondrial enzymes from all mitochondria or complete loss of enzymes from a subpopulation of mitochondria with retention of an intact mitochondrial genome.

Aerobiosis↗

Distribution of replicating simian virus 40 DNA in intact cells and its maturation in isolated nuclei.

The maturation of replicating simian virus 40 (SV40) chromosomes into superhelical viral DNA monomers [SV40(I) DNA] was analyzed in both intact cells and isolated nuclei to investigate further the role of soluble cytosol factors in subcellular systems. Replicating intermediates [SV40(RI) DNA] were purified to avoid contamination by molecules broken at their replication forks, and the distribution of SV40(RI) DNA as a function of its extent of replication was analyzed by gel electrophoresis and electron microscopy. With virus-infected CV-1 cells, SV40(RI) DNA accumulated only when replication was 85 to 95% completed. These molecules [SV40(RI(*)) DNA] were two to three times more prevalent than an equivalent sample of early replicating DNA, consistent with a rate-limiting step in the separation of sibling chromosomes. Nuclei isolated from infected cells permitted normal maturation of SV40(RI) DNA into SV40(I) DNA when the preparation was supplemented with cytosol. However, in the absence of cytosol, the extent of DNA synthesis was diminished three- to fivefold (regardless of the addition of ribonucleotide triphosphates), with little change in the rate of synthesis during the first minute; also, the joining of Okazaki fragments to long nascent DNA was inhibited, and SV40(I) DNA was not formed. The fraction of short-nascent DNA chains that may have resulted from dUTP incorporation was insignificant in nuclei with or without cytosol. Pulse-chase experiments revealed that joining, but not initiation, of Okazaki fragments required cytosol. Cessation of DNA synthesis in nuclei without cytosol could be explained by an increased probability for cleavage of replication forks. These broken molecules masqueraded during gel electrophoresis of replicating DNA as a peak of 80% completed SV40(RI) DNA. Failure to convert SV40(RI(*)) DNA into SV40(I) DNA under these conditions could be explained by the requirement for cytosol to complete the gap-filling step in Okazaki fragment metabolism: circular monomers with their nascent DNA strands interrupted in the termination region [SV40(II(*)) DNA] accumulated with unjoined Okazaki fragments. Thus, separation of sibling chromosomes still occurred, but gaps remained in the terminal portions of their daughter DNA strands. These and other data support a central role for SV40(RI(*)) and SV40(II(*)) DNAs in the completion of viral DNA replication.

Animals↗

Altered mobility of polydeoxyribonucleotides in high resolution polyacrylamide gels due to removal of terminal phosphates.

We have compared the electrophoretic mobility of a series of polynucleotides differing solely by the presence or absence of a terminal phosphate. As expected, the effect of removal of a single terminal phosphoryl residue on electrophoretic mobility is dependent on the size of the polynucleotide and therefore is not constant. Removal of a phosphoryl residue from polynucleotides shorter than 30 nucleotides reduces the mobility the equivalent of one nucleotide. Between 30 and 50 nucleotides the reduction in mobility is approximately one-half a nucleotide, while above 50 nucleotides in size the effect of phosphate removal approaches zero.

Chemical Phenomena↗

Mechanism of replication of human mitochondrial DNA. Localization of the 5' ends of nascent daughter strands.

Human mitochondrial DNA contains two physically separate and distinct origins of DNA replication. The initiation of each strand (heavy and light) occurs at a unique site and elongation proceeds unidirectionally. Animal mitochondrial DNA is novel in that short nascent strands are maintained at one origin (D-loop) in a significant percentage of the molecules. In the case of human mitochondrial DNA, there are three distinct D-loop heavy strands differing in length at the 5' end. We report here the localization of the 5' ends of nascent daughter heavy strands originating from the D-loop region. Analyses of the map positions of 5' ends relative to known restriction endonuclease cleavage sites and 5' end nucleotides indicate that the points of initiation of D-loop synthesis and actual daughter strands are the same. In contrast, the second origin is located two-thirds of the way around the genome where light strand synthesis is presumably initiated on a single-stranded template. Mapping of 5' ends of daughter light strands at this origin relative to known restriction endonuclease cleavage sites reveals two distinct points of initiation separated by 37 nucleotides. This origin is in the same relative genomic position and shows a high degree of DNA sequence homology to that of mouse mitochondrial DNA. In both cases, the DNA region within and immediately flanking the origin of DNA replication contains five tightly clustered tRNA genes. A major portion of the pronounced DNA template secondary structure at this origin includes the known tDNA sequences.

Carcinoma↗

Preferred DNA sites are involved in the arrest and initiation of DNA synthesis during replication of SV40 DNA.

Previous analysis of simian virus 40 (SV40) DNA replication revealed a 2-4 fold excess of DNA molecules that were 90 +/- 2% replicated, demonstrating that replication forks accumulate near the termination site. To determine whether replication is arrested at specific DNA sites, forks were located on the SV40 genome by specifically 32P labelling 3' ends of nascent DNA on purified replicating SV40 DNA, isolating the longest 32P-DNA chains, annealing them to SV40 DNA and then digesting them with a restriction endonuclease that cut near the terminatin site. 32P-DNA fragments of several discrete lengths were released, demonstrating that replication forks on native chromosomes were arrested at preferred sites on the DNA. Most forks were arrested when bidirectional DNA replication was 91% completed, and the two forks were separated by about 470 bp of unreplicated DNA centered at the expected termination site. Forks were also arrested at other locations such that the center of the termination region defined by DNA arrest sites varied by +/- 450 bp. Electron microscopic analysis of replicating DNA suggested that such variation may result from asynchronous arrival of some replication forks. Analysis of 5' end-labeled nascent DNA demonstrated that initiation of Okazaki fragments was also promoted at preferred DNA sites (about 100-120 per genome). Thus specific DNA sequences appear to be utilized throughout DNA replication, not just at the origin.

Base Sequence↗

Maturation of replicating simian virus 40 DNA molecules in isolated nuclei by continued bidirectional replication to the normal termination region.

Mature SV40 DNA synthesized for different periods of time either in isolated nuclei or in intact cells was highly purified and then digested with restriction endonucleases in order to relate the time of synthesis of newly replicated viral DNA to its location in the genome. Replication in nuclei supplemented with a cytosol fraction from uninfected cells was a faithful continuation of the bidirectional process observed in intact cells, but did not exhibit significant initiation of new replicons. SV40 DNA replication in cells at 37 degrees C proceeded at about 145 nucleotides/min per replication fork. In the absence of cytosol, when DNA synthesis was limited and joining of Okazaki fragments was retarded, bidirectional SV40 DNA replication continued into the normal region where separation yeilded circular duplex DNA molecules containing one or more interruptions in the nascent DNA strands. In the presence of cytosol, this type of viral DNA was shown to be a precursor of covalently closed, superhelical SV40 DNA, the mature from of viral DNA.

Animals↗