Dinucleotide repeat in the human mitochondrial D-loop.
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Base Sequence↗
Biomedical subjects
L G Mitchell
Publications and source records attributed to L G Mitchell.
Thrombin inhibition is impaired in plasma of sick neonates.
The sick neonate may develop spontaneous or catheter-related thromboses, which must in part reflect poor regulation of the formation and activities of the coagulation enzyme, thrombin. We hypothesized that the balance between the generation and inhibition of thrombin may differ in sick neonates compared with healthy neonates. Fifty neonates with respiratory failure requiring mechanical ventilation and 40 healthy neonates were studied on d 1 of life. All neonates had normal coagulation screening tests and a platelet count greater than 150 x 10(9)/L. Plasma pools from neonates with similar gestational age (GA), birth weight, and health status were prepared. Eight plasma pools from 40 healthy neonates of GA 30-38 wk were compared with six plasma pools from 30 sick neonates of GA 30-38 wk. An additional four plasma pools prepared from 20 sick neonates of GA less than 30 wk were studied. Thrombin generation was measured by amidolysis of a chromogenic substrate, S2238, after defibrination, contact activation, and recalcification of the test plasmas. The contributions of antithrombin III, heparin cofactor II, and alpha 2-macroglobulin as inhibitors of 125I-thrombin were quantitated by SDS-PAGE followed by autoradiography and densitometry. Thrombin generation was similar for both healthy and sick neonates of GA 30-38 wk. However, the inhibition of thrombin was impaired in plasma from sick neonates of GA 30-38 wk compared with plasma from healthy neonates of GA 30-38 wk (4.37 +/- 0.22 versus 5.21 +/- 0.21 nmol; p less than 0.05).(ABSTRACT TRUNCATED AT 250 WORDS)
Antithrombin III↗
A lifetime of retinal light exposure does not appear to increase mitochondrial mutations.
Recently, there have been a number of reports of an accumulation of mutations in the mitochondrial (mt) genome with age. Such mutations may be due in part to the mt oxidative metabolic pathways which provide most of the cell's energy, but also generate free radicals. In addition, the mt genome in some tissues, such as the retina, may also accumulate mutations from the effects of ultraviolet light. To obtain information concerning the possible accumulation of retinal mt mutations with age, we cloned retinal mt DNA from a 71-year-old person. Thirty-two kilobases of sequence from 83 independently isolated clones representing two regions, a coding and a noncoding region, of the mt genome were obtained. Three polymorphisms between these sequences and the standard 'Anderson sequence' were discovered. Only one heteroplasmic mutation was found. These results confirm the low somatic mutation rate found in prior studies utilizing different types of human tissues. In addition, these results suggest that there is little if any accumulated damage to the mt DNA of the retina during normal aging.
Aged↗
Affinity generation of single-stranded DNA for dideoxy sequencing following the polymerase chain reaction.
A method to rapidly generate single stranded DNA for dideoxy sequencing following the polymerase chain reaction is described. By incorporating biotin in one of the amplification primers, we are able to physically separate the two DNA strands produced in the polymerase chain reaction. After amplification, the mixture is passed through a column containing streptavidin agarose. The strand produced by the biotinylated primer is bound in this matrix. The unbiotinylated strand is eluted with 0.2 N NaOH and sequenced by the dideoxy method. This method was utilized to sequence mitochondrial DNA from crude genomic DNA and to determine the sequences of four clones containing human mitochondrial DNA as a test of its accuracy. The use of biotin-facilitated separation permitted us to amplify and sequence DNA samples in a single day.
Autoradiography↗
Use of image analysis to quantitate changes in form of mitochondrial DNA after x-irradiation.
In order to develop a sensitive method that can reliably assess the amount of previous genotoxic exposure, we examined whether relative loss of the supercoiled form of mitochondrial DNA in tissue culture cells could retrospectively reflect exposure to x-irradiation of 375,750, and 1500 roentgens. Five routines of a graphic analysis program named IMAGE developed for the Apple Macintosh II computer were used to densitometrically quantitate the relative amounts of supercoiled and nicked-circular forms of mitochondrial DNA blotted onto nitrocellulose. After x-irradiation, there were dose-dependent losses of supercoiled relative to nicked-circular DNA forms. Further developments in the methodology to evaluate changes in form of mitochondrial DNA should increase the sensitivity and reliability of the dosimetry. The IMAGE program is useful for a wide variety of studies in molecular biology, and is available at no charge.
Animals↗
The effect of hypoxia on platelet survival and site of sequestration in the newborn rabbit.
Thrombocytopenia occurs frequently in sick neonates that have experienced perinatal asphyxia. This study investigated the effect of one component of asphyxia, hypoxia, on platelet lifespan and site of sequestration. 111Indium oxine platelet survivals with scintigraphic imaging were performed in newborn and adult rabbits exposed to room air (normoxia) or following exposure to a 15 minute, severe hypoxic insult (FIO2 = 0.05). Platelet survivals in normoxic adults (n = 27) and newborn rabbits (n = 11) were similar (60 +/- 3.9 hr vs 64 +/- 8.0 hr, m +/- SEM). Inhalation of 5% oxygen for 15 minutes was not associated with an acidemia and did not produce thrombocytopenia but significantly shortened the platelet survival to 34 +/- 3 hr in the adult (n = 18) and 38 +/- 3 hr in the newborn rabbit (n = 7). Postmortem measurement of the sites of 111In-platelet accumulation showed that under normoxic conditions the platelets accumulated in the liver and spleen (23 +/- 4.3% and 8 +/- 1.0% of the total body counts) in the adult with even greater accumulation in the liver (58 +/- 6.8%) and spleen (19 +/- 4.9%) of the newborn (p less than 0.001). The latter observation was likely due to the relatively increased size of the liver and spleen in the newborn compared to the adult. Hypoxia did not alter the site of platelet sequestration in adults or newborns. Our results suggest that the newborn has the same platelet survival as the adult and that acute, severe hypoxia significantly shortens the survival of platelets in both groups. Although the sites of sequestration are qualitatively the same in the newborn, there is greater sequestration in the liver and spleen when compared to the adult.
Animals↗
Pancreatic infections of Myxobolus osburni Herrick (Myxozoa: Myxosporea) in the pumpkinseed, Lepomis gibbosus (Linnaeus) in Iowa.
Cysts of Myxobolus osburni occurred throughout the pancreas in 119 of 150 (79.3%) pumpkinseed (Lepomis gibbosus) from West Lake Okoboji, northwest Iowa during the summer, 1980. None of 341 bluegill (Lepomis macrochirus) were infected. Lobate cysts (up to 3 mm diameters) adjacent to the gall bladder contained sporulating plasmodia and mature spore masses. Inflammatory responses in the infected pancreas included engorged blood vessels, endocrine cell nuclei pyknosis, leukocyte (mostly lymphocyte) infiltration, fibroblast proliferation, dark pigment deposition and fibrosis. Host reaction was most pronounced in pancreas containing unencapsulated spore aggregates. Spore variability and plasmodial structure are also described.
Animals↗
On the relationship between computed tomography numbers and specific gravity.
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Chemical Phenomena↗
Scanning electron microscopy of spores of the myxosporidans Chloromyxum trijugum Kudo and Chloromyxum catostomi Kudo.
Spores of Chloromyxum trijugum Kudo from Lepomis macrochirus Rafinesque and Chloromyxum catostomi Kudo from Notropis dorsalis (Agassiz) were obtained from infected gall bladders, glass-bead sonicated, and examined by scanning electron microscopy. Valves of C trijugum spores each have a thick ridge running parallel to the sutural ridge. Uncapped cnidocyst pores open into the extrasutural ridges. A pyriform structure of unknown function was observed at the posterior surface in some spores. Spore valves of C catostomi are sculptured with ridged striations running in various parallel and converging patterns over the entire surface. Cnidocyst pores open into ridges adjacent to the sutural plane. Glass bead sonication was found effective in polar filament extrusion. Discharged filaments were twisted along the long axis and partially coated with mucoid globules.
Animals↗
Serial measurements of CT attenuation and specific gravity in experimental cerebral edema.
Vasogenic cerebral edema was induced cryogenically in rhesus monkeys. Serial scans in both axial and coronal planes were used to study the onset, peak, and regression of edema. Progression of edema, predominantly involving the white matter, was analyzed from the postmortem distribution of a blood/brain barrier indicator (Evans blue) injected at surgery. Specific gravity was measured in fresh, unfixed specimens from both the edematous and normal hemispheres and correlated with corresponding CT attenuation values obtained before death. The drop in specific gravity closely corresponded to the decrease in CT attenuation.
Animals↗
Epizootiology and histopathology of Chloromyxum trijugum (Myxospora: Myxosporida) in centrarchid fishes from Iowa.
The gall bladder parasite, Chloromyxum trijugum, shows marked host specificity within the sunfish family Centrarchidae. During 1977-78 80% of 230 bluegills (lepomis macrochirus) in Iowa were infected. Prevalence in green sunfish (L. cyanellus) was lower (17%); one of 2 specimens of the hybrid L. macrochirus x L. cyanellus was infected; orangespotted sunfish (L. humilis) and hybrids (L. humilis x L. macrochirus) were not infected. Intensity of infection in bluegills varied throughout the year. Prevalence of free-floating plasmodia in bluegill gall bladders was highest (100%) during winter and spring months, and decreased to 40-50% during summer and fall. Prevalence of attached plasmodia may remain 80-100% throughout the year. Sporulation and plasmotomy were observed year-round. Plasmodia were attached to underlying epithelial cells by pseudopodia-like projections and were associated with various stages of breakdown in the mucosal layer.
Animals↗
Myxosporidan infections in some fishes of Iowa.
A survey of 617 specimens of fishes representing 8 families in Iowa revealed coelozoic infections by Chloromyxum catostomi, Chloromyxum triijugum, and Myxidium macrocapsulare and histozoic infections by Henneguya exilis and Myxobolus spp. The trophozoite of M. macrocapsulare is described. Descriptive notes supplementary to previous literature are provided for 3 coelozoic species.
Animals↗