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Biomedical subjects

J H Wilson

Publications and source records attributed to J H Wilson.

At least 163 records · Page 9Linked to original sources
PubMed1991

Oligonucleotide capture during end joining in mammalian cells.

Extra nucleotides (termed filler DNA) are found at about 10% of the junctions of the genetic rearrangements that arise by illegitimate recombination in mammalian cells. Such filler DNAs could arise by the joining of oligonucleotide fragments to broken ends prior to end joining. We tested this possibility by microinjecting mixtures of defined oligonucleotides with SV40 genomes that were linearized in the intron for T antigen, a site where incorporation of extra nucleotides does not impair viability. Using an injection ratio of 1000 oligonucleotides per DNA end, we screened viable genomes for incorporation of single-stranded and double-stranded oligonucleotides with varying degrees of complementarity to the ends of the linear SV40 molecules. Genomes from 510 independent plaques were screened by restriction digestion to identify those that had picked up a restriction site unique to the injected oligonucleotides. Double-stranded oligonucleotides that were fully complementary to the SV40 ends were readily incorporated, but uptake of the other oligonucleotides was not detected by restriction analysis. Nucleotide sequences of junctions from 12 genomes derived from co-injection of noncomplementary oligonucleotides revealed two with filler DNA, but neither could be assigned unambiguously to the injected oligonucleotides.

Animals↗
PubMed1991

Calcium and phosphorus requirement of swine from weaning to market weight: II. Development of response curves for bone criteria and comparison of bending and shear bone testing.

Three trials involving 251 crossbred pigs were conducted to establish response surfaces for effects of Ca/P levels (70, 85, 100, 115 and 130% of NRC [1979] estimated requirements) and time (weaning to market) on bone criteria and to compare bending and shear bone testing. Nine replicates, each consisting of five pigs, were used over the three trials. One pig per replicate was slaughtered every 4 wk following the start of the trials. Third metacarpals and metatarsals (3M) and fourth metacarpals and metatarsals (4M) were collected at slaughter; the bone length, bending or shear stress, and dry, fat-free ash percentage (DFF%) were determined. Most bone criteria increased (P less than .01) at a decreasing rate (P less than .05) in response to increasing dietary Ca/P intake and increased linearly (P less than .01) with time on test, although bone length and stress increased at a decreasing rate with time on test. Asymptotic models relating continuous effects of total Ca + P intake ratio (CAP; expressed as a percentage of NRC) and number of days on test before slaughter to bone measurements were fit to least squares slaughter time by diet means. Bone length and DFF% reached 98% maximum at or near 100% the NRC estimated CAP level; however, to reach 98% of maximum bone shear and breaking stress higher CAP levels were required. Shear testing of bones was more desirable than bend testing as a method of determining bone strength due to reduced variability, better discrimination of Ca/P and time effects and ease of calculation.

Animals↗
PubMed1991

Photodynamic therapy for gastrointestinal tumors.

Photodynamic therapy is based on the administration of a compound that is preferentially accumulated by a tumor and which causes tumor destruction after exposure to light of a specific wavelength. The photosensitizers most commonly used in treating tumors of the gastrointestinal tract are porphyrins--hematoporphyrin derivative and dihematoporphyrin ether. These compounds have been used with success to produce reduction in tumor size of esophageal, gastric, and colorectal cancers. In some instances long-lasting complete remission have been observed after photodynamic therapy. New developments include photosensitizers that react to light of a longer wavelength, which is able to penetrate tissue to a greater depth, the use of 5-aminolevulinic acid, which is preferentially converted to porphyrin in malignant cells, and combination of photodynamic therapy with thermic laser, radiotherapy, or chemotherapy.

Colorectal Neoplasms↗
PubMed1991

Tetralogy of Fallot and segmental uterine aplasia in a three-year-old Morgan filly.

A 3-year-old Morgan filly was presented to the University of Florida, Veterinary Medical Teaching Hospital, for heart murmur, poor growth, and progressive exercise intolerance. Thoracic radiographs, cardiac ultrasound, cardiac catheterization, and differential blood gases were utilized to tentatively diagnose tetralogy of Fallot. Postmortem examination confirmed tetralogy of Fallot and additionally revealed segmental uterine aplasia.

Animals↗
PubMed1991

Prognostic implications of the localization of carcinoma in the head of the pancreas.

Between 1974 and 1989, 411 patients with pathologically and anatomically proven carcinoma of the head of the pancreas underwent endoscopic retrograde cholangiopancreatography (ERCP). According to the localization of the tumor, these patients were divided into those with a cranially, centrally (periductally), caudally, or indeterminately localized tumor. In cranially localized tumors, extrahepatic metastases and vessel invasion were absent or resectable in 53% and 46%, respectively. The tumor was resectable in 41% of cases. If a patient with a cranially localized tumor could not be operated curatively for secondary reasons, the prognosis was better than for tumors with another localization. If there was unresectable vessel invasion and the tumor was not resectable, the 0% survival rate was reached at 33 months. Of the curatively operated patients, 26% were alive at 36 months after the start of complaints. Of the centrally or periductally localized tumors, there were no liver metastases in 73%. Extrahepatic metastases and vessel invasion were absent or resectable in 57% and 53%, respectively. The tumor was resectable in 48% of cases. If there was unresectable vessel invasion or the tumor was unresectable, the 0% survival rate was reached after 18 months. These tumors have maximal chances at curative resection. Of the curatively operated patients, 31% were alive at 36 months after the start of complaints. In caudally localized tumors, there were liver metastases in 59%, unresectable other abdominal metastases in 93%, unresectable vessel invasion in 91%, and the tumor was unresectable in 96%. In patients with an unresectable vessel invasion or an unresectable tumor, the 0% survival rate was reached after 33 months; 3% of these patients were operated curatively. Indeterminately localized tumors had liver metastases in 77%, unresectable extrahepatic metastases in 90%, unresectable vessel invasion in 95%, and the tumor was unresectable in 91%. Only one of the 44 patients (2%) could be operated curatively.

Carcinoma↗
PubMed1991

Iron and uroporphyrin in hepatocytes of inbred mice in experimental porphyria: a biochemical and morphological study.

UNLABELLED: Hexachlorobenzene-induced porphyria is iron dependent and characterized by the decreased activity of uroporphyrinogen decarboxylase and the accumulation of porphyrins in the liver. To examine the relationship between iron and porphyrins in liver tissue, we performed a biochemical and morphological (histological, ultrastructural and morphometrical) study in the livers of C57BL/10 mice. Mice were treated with hexachlorobenzene, iron dextran or the combination of hexachlorobenzene and iron dextran. An accumulation of porphyrins and an increased total iron content were found not only in the livers of mice treated with hexachlorobenzene and iron dextran but also in mice treated with iron dextran alone. In contrast, the amount of porphyrins was only slightly increased in the livers of mice treated with hexachlorobenzene alone. Needle-like structures, representing uroporphyrin crystals, were observed, histologically and ultrastructurally, in hepatocytes of mice treated with hexachlorobenzene and iron dextran and with iron dextran alone. Uroporphyrin crystals and ferritin iron were found in the same hepatocyte. A single uroporphyrin crystal, surrounded by ferritin iron, was observed in a hepatocyte of a mouse treated with hexachlorobenzene alone. Both in the livers of mice treated with hexachlorobenzene and iron dextran and in the livers of mice treated with iron dextran alone, morphometrical analysis showed that an increased area fraction of uroporphyrin crystals was associated with an increased area fraction of ferritin iron in hepatocytes. CONCLUSIONS: In C57BL/10 mice, experimental porphyria can be induced by iron overload alone; uroporphyrin crystals and ferritin iron are located in the same hepatocyte; and the morphological co-occurrence of uroporphyrin crystals and ferritin iron in hepatocytes suggests a role for iron (as ferritin) in the pathogenesis of porphyria.

Animals↗
PubMed1990

A novel selection system for recombinational and mutational events within an intron of a eucaryotic gene.

In order to identify a poison sequence that might be useful in studying illegitimate recombination of mammalian cell chromosomes, several DNA segments were tested for their ability to interfere with gene expression when placed in an intron. A tRNA gene and its flanking sequences (267 bp) were shown to inhibit SV40 plaque formation 100-fold, when inserted into the intron in the T-antigen gene. Similarly, when the same DNA segment was placed in the second intron of the adenosine phosphoribosyl transferase (APRT) gene from CHO cells, it inhibited transformation of APRT-CHO cells 500-fold. These two tests indicated that the 267-bp DNA segment contained a poison sequence. The poison sequence did not affect replication since the replication of poisoned SV40 genomes was complemented by viable SV40 genomes and poisoned APRT genes were stably integrated into cell chromosomes. Cleavage of the poison sequence in the SV40 T-antigen intron by restriction enzymes indicated that the tRNA structural sequences and the 5' flanking sequences were not required for inhibition of SV40 plaque formation. Sequence analysis of viable mutant SV40, which arose after transfection of poisoned genomes, localized the poison sequence to a 35 bp segment immediately 3' of the tRNA structural sequences.

Adenine Phosphoribosyltransferase↗
PubMed1990

Gene targeting in normal and amplified cell lines.

Targeted recombination in mammalian cells is rare compared with non-homologous integration. In Saccharomyces cerevisiae the reverse is true. Differences in targeting efficiency could arise because a target of unique DNA is 200 times more dilute in mammalian genomes than it is in yeast. We tested this possibility by measuring gene targeting in normal CHO cells with two copies of the dihydrofolate reductase (DHFR) gene and in amplified CHOC 400 cells, which carry 800 copies. If the concentration of the target gene is critical, amplified cells should show an enhanced frequency of targeted recombination relative to non-homologous integration. Using a positive/negative selection protocol, we demonstrated that the efficiency of targeting into DHFR genes is indistinguishable in normal and amplified CHO cells. As targeting does not depend on the number of targets, the search for homology is not a rate-limiting step in the mammalian pathway of gene targeting. Thus, the difference in genome size is not the basis for the different outcomes of targeting experiments in S. cerevisiae and mammals.

Animals↗
PubMed1990

Targeted gene replacement at the endogenous APRT locus in CHO cells.

We demonstrate the feasibility of targeted gene replacement at an endogenous, chromosomal gene locus in cultured mammalian cells, employing a two-step strategy similar to an approach routinely used for genetic manipulation in yeast. Utilizing an APRT+ recombinant generated by targeted integration of plasmid sequences (including a functional copy of the gpt gene) at the CHO APRT locus, we have been able to select gpt- "pop-out" recombinants that have arisen by intrachromosomal recombination between APRT direct repeats at the targeted integration site. Reciprocal exchanges leading to "pop-out" of integrated plasmid/gpt gene sequences occur at a rate of approximately 6.3 x 10(-6) per cell generation. Depending on the site of crossover, such "pop-out" events result in either replacement or restoration of the original APRT target gene sequence.

Adenine↗
PubMed1990

Significance of thromboxane A2 and prostaglandin I2 in acute necrotizing pancreatitis in rats.

Plasma thromboxane concentrations were found to be significantly elevated in acute necrotizing pancreatitis in rats, whereas prostaglandin I2 levels were not. The significance of these alterations was investigated. Pancreatitis was induced by injecting 5% sodium taurocholate into the pancreatic duct. Iloprost (ZK 36374, a stable analog of prostaglandin I2, 25 ng/kg body weight) decreased the mortality rate from 100% to 50%. When treatment with iloprost was combined with simultaneous administration of either Sibelium (flunarizine R 14,950, 0.2 mg/kg body weight) or dazmegrel (UK 38,485, 50 mg/kg body weight) an additional decrease in the mortality rate was recorded. Dazmegrel is a selective thromboxane A2 synthetase inhibitor and flunarizine (a calcium entry blocker) also inhibits the effects of elevated thromboxane A2 levels. With flunarizine and iloprost the mortality rate was 40% (P less than 0.05); with dazmegrel and iloprost it was 10% (P less than 0.01). The results of the present study suggest that thromboxane A2 and prostaglandin I2 play a role in the course of acute necrotizing pancreatitis.

Acute Disease↗
PubMed1990

Severe hemolysis after incomplete mitral valve repair.

We report 2 cases of severe intravascular hemolysis after mitral valve repair using a Duran annuloplasty ring. In both patients residual mitral regurgitation was present, hemolysis was severe enough to warrant a second operation, and hemolysis ceased immediately after the second operation. We believe that a high-velocity regurgitant jet directed toward the cloth-covered annuloplasty ring was responsible for the hemolysis in both patients.

Adult↗
PubMed1990

Phenprocoumon-induced hepatitis mimicking non-A, non-B hepatitis.

A 58-year-old man presented with jaundice 6 months after aortic valve replacement. Although non-A, non-B hepatitis was initially suspected, the final diagnosis of phenprocoumon (Marcoumar)-induced hepatitis progressing to cirrhosis was based on recurrence of jaundice after re-exposure to the drug, improvement after withdrawal and centrilobular necrosis with eosinophilic infiltration in the liver biopsy. Antibodies to hepatitis C virus were absent. The aortic valve was replaced by a bioprosthesis to eliminate the need for life-long anticoagulation.

Antibodies, Viral↗
PubMed1990

Clinical evaluation of an automatic sensitivity adjustment feature in a dual chamber pacemaker.

The clinical evaluation of a new automatic sensitivity adjustment feature in the Cosmos II, Model #284-05 is described. This feature, designed to maintain a 2:1 safety margin for sensing intrinsic signals, was activated by way of special programmer software in ten patients at two centers. While the feature worked satisfactorily in some cases, it did not perform as expected, and undersensing in both chambers was observed. This may have been due to biasing the adjustment toward maximum rather than minimum electrograms. This study suggested that electrograms may vary by more than 100% which underscores the importance of this feature, and reinforces the need for continued development.

Algorithms↗