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Biomedical subjects

M A Eaton

Publications and source records attributed to M A Eaton.

At least 19 recordsLinked to original sources
PubMed2000

Incidental splenic injury during abdominal vascular surgery: a case-controlled analysis.

BACKGROUND: The small but finite risk of postsplenectomy sepsis is generally regarded as a firm indication for splenic preservation after iatrogenic injury, especially in the young. But splenectomy may be preferable in patients who sustain splenic injuries during vascular operations because of the potential for continued bleeding associated with anticoagulation. The purpose of this study was to determine the perioperative morbidity of incidental splenectomy among patients undergoing abdominal vascular operations. STUDY DESIGN: We studied 17 patients who underwent incidental splenectomy at the time of abdominal vascular operations. Complete data collected on each subject included preoperative and postoperative blood counts, operative indications and details, transfusion requirements, length of hospital stay, and outcomes. Using age- and gender-matched case controls undergoing identical vascular operations from the same period, we evaluated the complication rate and outcomes of patients who underwent splenectomy for iatrogenic injuries of the spleen, versus those who did not sustain splenic injuries. RESULTS: The estimated prevalence of iatrogenic splenic injury during the study period was 0.5%. Mean operative time, estimated blood loss, and duration of mechanical ventilation tended to be greater in the splenectomy patients, but the differences did not achieve statistical significance. Splenorrhaphy was attempted in seven patients, but continued bleeding mandated spleen removal in all cases. Splenectomy patients had a higher transfusion requirement (p = 0.03) and a longer mean length of stay (p = 0.03) than controls. Compared with controls, there was a higher prevalence of infectious complications in the splenectomy patients (p = 0.015), but there was no difference in the prevalence of thromboembolic complications between groups. Two of the splenectomy patients died in the postoperative period from multisystem organ failure, and one died of a missed splenic injury. CONCLUSIONS: These data suggest that incidental splenectomy during abdominal vascular operations is associated with increased postoperative infectious complications and prolonged hospitalization.

Aged↗
PubMed1999

The regiochemical distribution of positive charges along cholesterol polyamine carbamates plays significant roles in modulating DNA binding affinity and lipofection.

We have quantified the effects of the regiochemical distribution of positive charges along the polyamine moiety in lipopolyamines for DNA molecular recognition. High affinity binding leads to charge neutralisation, DNA condensation and ultimately to lipofection. Binding affinities for calf thymus DNA were determined using an ethidium bromide displacement assay and condensation was detected by changes in turbidity using light scattering. The in vitro transfection competence of cholesterol polyamine carbamates was measured in CHO cells. In the design of DNA condensing and transfecting agents for non-viral gene therapy, the interrelationship of ammonium ions, not just their number, must be considered.

Animals↗
PubMed1998

Intracardiac iron distribution in newborn guinea pigs following isolated and combined fetal hypoxemia and fetal iron deficiency.

Myocardial iron deficiency complicates chronic intrauterine hypoxemia during diabetic pregnancies. To understand the effect of both conditions during fetal life on intracardiac iron prioritization, we measured heart myoglobin, cytochrome c, and elemental iron concentrations in six iron-deficient, hypoxic, five iron-sufficient, hypoxic, six iron-deficient, normoxic, and six iron-sufficient, normoxic newborn guinea pigs. The iron-deficient, hypoxic group had lower heart iron (p = 0.03) but higher myoglobin concentration (p < 0.0001) when compared with the iron-sufficient, normoxic group. The percentage of iron incorporated into myoglobin was higher than control in the iron-deficient, hypoxic group (23.2+/-7.2% vs. 5.2+/-0.8%; p < 0.001) and increased as total heart iron decreased (r = 0.97; p < 0.001). In contrast, heart cytochrome c concentration was lower than control in the iron-deficient, hypoxic group (p = 0.01), with equal percentages of heart iron incorporated into cytochrome c. This intracellular prioritization of myocardial iron to myoglobin and away from cytochrome c following combined fetal hypoxemia and iron deficiency may represent an adaptive mechanism to preserve myocardial tissue oxygenation, although at the expense of oxidative phosphorylative capability.

Animals↗
PubMed1994

Placental transferrin receptor in diabetic pregnancies with increased fetal iron demand.

Augmented fetal hemoglobin synthesis during diabetic pregnancy increases fetal iron demand. To study the effect of increased fetal iron demand on placental transferrin receptor (TR), we utilized a monoclonal antibody to localize placental TR immunoreactivity and 125I-labeled transferrin to study TR binding characteristics in 10 placentas from poorly controlled diabetic mothers with increased fetal iron demand and 10 placentas from nondiabetic mothers. The infants born to the diabetics had higher cord serum C-peptide, erythropoietin, and hemoglobin concentrations, indicating fetal hyperinsulinemia and hypoxia, with augmented erythropoiesis and iron demand. TR immunoreactivity was localized to the syncytiotrophoblast in both groups, was greater in the diabetic group, and was inversely correlated with fetal storage iron (r = -0.75; P < 0.001). Scatchard analysis of 125I transferrin binding data confirmed greater receptor number (Bmax 17.9 +/- 2.2 vs. 12.6 +/- 1.3 pM/mg protein, P = 0.05), but reduced binding affinity [dissociation constant (Kd) 7.6 +/- 0.9 vs. 5.4 +/- 0.4 nM/l, P = 0.03] in the diabetic group. The TR staining intensity, Bmax, and Kd were each correlated with cord C-peptide, suggesting either a primary or secondary role for fetal hyperinsulinemia in TR expression. This study provides in vivo evidence that fetal factors, such as iron demand or hyperinsulinemia, influence regulation of placental TR in humans. The increase in placental syncytiotrophoblastic TR expression associated with reduced cord serum ferritin concentration suggests that the fetus utilizes both increased placental iron transport and mobilization of fetal iron stores to support augmented fetal erythropoiesis.

Erythropoiesis↗
PubMed1992

Iron deficiency of liver, heart, and brain in newborn infants of diabetic mothers.

Infants of diabetic mothers frequently have polycythemia, elevated serum erythropoietin concentrations, and decreased serum iron and ferritin concentrations, likely representing a redistribution of fetal iron into erythrocytes to support augmented fetal hemoglobin synthesis. We hypothesized that fetal liver, heart, and brain iron concentrations are also reduced in these infants. After obtaining autopsy tissue from infants who had died before 7 days of age, we measured liver, heart, and brain iron concentrations using atomic absorption spectrophotometry. Seven infants of diabetic mothers and seven gestational age-matched control infants were studied. All infants of diabetic mothers had pancreatic islet cell hyperplasia, indicating fetal hyperglycemia and hyperinsulinemia. Liver iron concentrations in the infants of diabetic mothers were 6.6% of control values (489.0 +/- 154.4 vs 7379.7 +/- 1473.8 micrograms/gm dry tissue weight (mean +/- SEM); p less than 0.001), heart iron concentrations were 43.9% of control values (124.7 +/- 20.5 vs 284.1 +/- 34.8 micrograms/gm dry tissue weight; p less than 0.002), and brain iron concentrations were 60.6% of control values (106.1 +/- 13.7 vs 175.2 +/- 10.7 micrograms/gm dry tissue weight; p less than 0.003). Heart and brain iron concentrations were directly correlated with liver iron concentrations (r = 0.80 for both; p less than 0.001) and indicated that hepatic iron was greater than 75% depleted before heart and brain iron reduction. We conclude that severely affected infants of diabetic mothers have reduced liver, heart, and brain iron concentrations. The role of tissue iron deficiency in the genesis of the abnormal clinical findings in these infants deserves further consideration.

Brain Chemistry↗
PubMed1986

Reovirus infection in adult mice: the virus hemagglutinin determines the site of intestinal disease.

Reovirus type 1, strain Lang, and type 3, strain Dearing, induced site-specific intestinal lesions in the adult mouse after intravenous inoculation. Reovirus type 1 caused inflammation and epithelial changes such as loss of nuclear polarity, villus blunting and crypt hyperplasia restricted to the ileum. In contrast, reovirus type 3 induced duodenitis, jejunitis, and ulcerative colitis. In the duodenum and jejunum, the epithelial cells appeared normal, but hemorrhage and inflammation in the lamina propria was present. In the colon, superficial ulceration, crypt abscesses, and intraluminal hemorrhage was observed. Segregation analysis using reassortant clones derived from reoviruses 1 and 3, suggested the viral hemagglutinin, encoded by genome segment S1, to be the major viral determinant of site specific intestinal disease following intravenous inoculation.

Animals↗
PubMed1986

Reovirus type 1 is secreted into the bile.

Reovirus type 1, known to be a cause of systemic and intestinal disease in mice, is secreted into the bile of adult A/J mice after viremia. Virus found in the bile in concentrations higher than those in blood may indicate that reovirus type 1 is actively transported into the bile. The transport of virus was independent of levels of virus-specific immunoglobulin A antibody. Modifications of the virus that occurred during transport did not discernibly affect the infectivity of the virus. Entry of virus into the bile may be an important mechanism by which an enteric virus that produces systemic disease reenters the intestine for transmission.

Animals↗
PubMed1984

Synthesis and biophysical studies of short oligodeoxynucleotides with novel modifications: a possible approach to the problem of mixed base oligodeoxynucleotide synthesis.

The syntheses of 1,2-dideoxy-D-ribofuranose and 1,2-dideoxy-1-phenyl-beta-D-ribofuranose are described. Oligodeoxynucleotides containing these analogues have been synthesised and hybridized to their complementary strands. Hypochromicity studies have shown that these duplices are less stable than either the totally complementary duplex or those containing A.C and G.T mismatches.

Deoxyribose↗
PubMed1984

A rapid deprotection procedure for phosphotriester DNA synthesis.

An equimolar solution of aldoxime and tetramethylguanidine at 70 degrees C removes both the base and phosphate protection from oligonucleotides prepared by solid phase phosphate triester technology. The rate of cleavage from the succinyl linkage commonly used for solid phase synthesis is also increased. The method is simpler, faster and more easily automated than existing methods.

Chemical Phenomena↗
PubMed1983

Isolation and characterisation of cDNA clones for the A alpha- and gamma-chains of human fibrinogen.

cDNA clones coding for the A alpha- and gamma-chains of human fibrinogen have been isolated from an adult liver cDNA library. Clones were identified by hybridisation with mixtures of synthetic oligonucleotides 17 bases long, predicted using amino acid sequence data for each chain. The cDNA insert sizes are 1,950bp for A alpha-fibrinogen and 950bp for gamma-fibrinogen. The clones do not show any cross-hybridisation. Each cDNA hybridises to a unique sequence in the human genome. In adult human liver, Northern blots give an estimated messenger RNA size of 2.6kb for A alpha-fibrinogen and 1.8kb for gamma-fibrinogen.

Adult↗
PubMed1982

Improvements to solid phase phosphotriester synthesis of deoxyoligonucleotides.

A solution of benzenesulphonic acid (3%, w/v) in a dimethylformamide and dichloromethane mixture (9:1, v/v) is shown to be a very effective reagent for the detritylation of deoxyoligonucleotides attached to a solid support. The levels of depurination with this reagent were lower than those observed with other reagents such as trichloroacetic acid. Coupling reactions are described using above ambient temperatures with no detectable increase in side products. Both procedures have been successfully incorporated into an automated system, which can compete with the rate of synthesis by the phosphite approach.

Benzenesulfonates↗
PubMed1982

Chemical synthesis and cloning of a gene for human beta-urogastrone.

A DNA duplex coding for the 53 amino acids of human beta-urogastrone has been synthesised. Computer assisted design of the gene included restriction endonuclease sites for plasmid insertion, a termination codon and two triplets coding for lysine at the 5'-end of the structural gene. The synthesis involved preparation of 23 oligodeoxyribonucleotides by phosphotriester procedures coupled to rapid HPLC techniques. The gene was constructed in two halves by enzymatic ligation of the oligonucleotides and cloned into a specially constructed chimeric plasmid vector. Escherichia coli K12 MRC8 was transformed by the plasmid and clones containing the full gene sequence were isolated and characterised.

Amino Acid Sequence↗
PubMed1982

Molecular cloning and nucleotide sequence of cDNA coding for calf preprochymosin.

DNA complementary to calf stomach mRNA has been synthesised and inserted into the Pst1 site of pAT153 by G-C tailing. Clones containing sequences coding for prochymosin were recognised by colony hybridisation with cDNA extended from a chemically synthesised oligodeoxynucleotide primer, the sequence of which was predicted from the published amino acid sequence of calf prochymosin. Two clones were identified which together contained a complete copy of prochymosin mRNA. The nucleotide sequence is in substantial agreement with the reported amino acid sequence of prochymosin and shows that this protein has a mol.wt. of 40431 and chymosin a mol.wt. of 35612. The sequence also indicates that prochymosin is synthesised as a precursor molecule, preprochymosin, having a 16 amino acid hydrophobic leader sequence analogous to that reported for other secreted proteins.

Amino Acid Sequence↗
PubMed1980

The amino-terminal sequence of human fibroblast interferon as deduced from reverse transcripts obtained using synthetic oligonucleotide primers.

From recently published data on the amino-terminal structures of human and mouse interferons, we have predicted and synthesised an oligonucleotide capable of priming specifically the reverse transcription of human fibroblast interferon mRNA present within a total mRNA population. From these transcripts we determined the sequence of the 5'-terminus of the mRNA and identified a putative pre-peptide signal sequence. This enabled us to predict the sequence of another primer capable of directing the synthesis of interferon double-stranded cDNA corresponding to the entire coding region of the mRNA. Further sequencing studies also enabled us to establish the identity of 47 consecutive amino acids beginning with the methionine residue at the amino-terminus of the mature protein.

Amino Acid Sequence↗
PubMed1974

Purification of polynucleotide phosphorylase by affinity chromatography and some properties of the purified enzymes.

A method is described for the preparation of p-aminophenyl oligo(dT)-Sepharose. This matrix has been used for the purification of polynucleotide phosphorylase from both E.coli and B.stearothermophilus. The effects of temperature and pH on the binding of the different enzymes to the matrix have been investigated. B.stearothermophilus isolated by affinity chromatography may be useful in selectively removing the polyA tract on the 3'-end of mRNA's.

Bacillus↗