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Biomedical subjects

J H Miller

Publications and source records attributed to J H Miller.

At least 109 records · Page 6Linked to original sources
PubMed1997

Combined macular hole and cataract surgery.

PURPOSE: Cataract often develops after macular hole surgery, necessitating cataract surgery. We report a combination of macular hole surgery and cataract surgery on four eyes of four patients. METHODS: Four eyes of four patients had a full-thickness stage III or IV macular hole and some degree of cataract. Combined cataract surgery with intraocular lens implant and macular hole surgery was associated with intravitreal perfluoropropane at 15% concentration and with face-down positioning for 21 days. RESULTS: After combined cataract and macular hole surgery, the rim of subretinal fluid resolved successfully in four eyes of four patients. Twelve months after surgery, the macular hole reopened in one eye in association with the new onset of macular pucker. Best-corrected visual acuities ranged from 20/25 to 20/100 12 months after surgery, while preoperative visual acuities with best correction were 20/70 to 20/200. CONCLUSIONS: In selected cases, a combination of cataract surgery with intraocular lens implant and macular hole surgery offers advantages. This combined approach warrants consideration.

Aged↗
PubMed1997

Epidermal growth factor and human growth hormone accelerate adaptation after massive enterectomy in an additive, nutrient-dependent, and site-specific fashion.

BACKGROUND: After massive enterectomy (ME), remnant intestine undergoes compensatory adaptation. Epidermal growth factor (EGF) and human growth hormone (hGH) have each been shown to enhance total length small intestine nutrient transport after ME. This study aims to determine the differential effects of EGF and hGH on proximal and distal small intestinal remnants after ME. METHODS: New Zealand white rabbits underwent 70% mid-jejunoileal resection. After 1 week, animals received hGH (0.2 mg/kg/day), EGF (1.5 micrograms/kg/hr), hGH + EGF, or vehicle (equal volume) for 7 days. Sodium-dependent uptake of glucose, glutamine, alanine, leucine, and arginine into brush border membrane vesicles was quantitated. Serum insulin-like growth factor-I concentrations as well as proximal and distal villus and microvillus heights were measured. IGF binding protein-3 and -4 mRNA expression was determined in full-thickness proximal and distal gut remnants. RESULTS: Concomitant hGH and EGF treatment up-regulates glucose (100%), glutamine (80%), and leucine (60%) transport in the proximal remnant; alanine (150%) and arginine (400%) transport in the distal remnant; and microvillus height (25% to 35%) both proximally and distally. Serum IGF-I levels and gross villus heights were not different among groups. CONCLUSIONS: Co-infusion of hGH and EGF accelerates intestinal adaptation after ME in an additive, nutrient-dependent, and site-specific fashion via enhanced nutrient transport as well as microvillus hypertrophy.

Alanine↗
PubMed1997

Lac repressor genetic map in real space.

Here, we present a graphic display of the phenotypes of more than 4000 single amino acid substitution mutations on the three-dimensional structure of the lac repressor tetramer bound to DNA. The genetic data and the X-ray diffraction studies contribute to define an allosteric mechanism and yield a visual demonstration of the importance of core or buried residues in protein structure.

Allosteric Site↗
PubMed1997

Robotic surgical instruments for dexterity enhancement in thoracoscopic coronary artery bypass graft.

OBJECTIVES: Endoscopically sutured vascular anastomoses are complex, time consuming, and require great dexterity. We decided to evaluate performance enhancement using a robotic device to create sutured coronary artery bypass anastomoses with endoscopic techniques in a plastic model. METHODS: Seven coronary artery bypass anastomoses were endoscopically created in a plastic model using a robotic enhancement technology (Computer Motion, Goleta, CA). Anastomoses were created with a single running suture (7-0 monofilament). Our endpoints were operative time, intraoperative incidents, stability and dexterity of the robotic system, surgeon's fatigue, and anastomotic patency. RESULTS: Operative time was 46+/-12 min (mean+/-SD). There were no intraoperative incidents. Patency was confirmed in all anastomoses. The system's stability and dexterity were high. Surgeon's fatigue was mild. CONCLUSION: The use of robotic enhancement technology leads to an efficient performance of sutured coronary artery bypass anastomoses in a plastic model. The robotic device enhances dexterity, precision, and reduces surgeon's fatigue while preserving the quality of hand suturing.

Clinical Competence↗
PubMed1997

Proliferation of mutators in A cell population.

A Lac- strain of Escherichia coli that reverts by the addition of a G to a G-G-G-G-G-G sequence was used to study the proliferation of mutators in a bacterial culture. Selection for the Lac+ phenotype, which is greatly stimulated in mismatch repair-deficient strains, results in an increase in the percentage of mutators in the selected population from less than 1 per 100,000 cells to 1 per 200 cells. All the mutators detected were deficient in the mismatch repair system. Mutagenesis results in a similar increase in the percentage of mutators. Mutagenesis combined with a single selection can result in a population of more than 50% mutators when a sample of several thousand cells is grown out and selected. Mutagenesis combined with two or more successive selections can generate a population that is 100% mutator. These experiments are discussed in relation to ideas that an early step in carcinogenesis is the creation of a mutator phenotype.

Escherichia coli↗
PubMed1996

Genomic and cDNA sequence tags of the hyperthermophilic archaeon Pyrobaculum aerophilum.

The hyperthermophilic archaeum, Pyrobaculum aerophilum, grows optimally at 100 degrees C with a doubling time of 180 min. It is a member of the phylogenetically ancient Thermoproteales order, but differs significantly from all other members by its facultatively aerobic metabolism. Due to its simple cultivation requirements and its nearly 100% plating efficiency, it was chosen as a model organism for studying the genome organization of hyperthermophilic ancient archaea. By a G+C content of the DNA of 52 mol%, sequence analysis was easily possible. At least some of the mRNA of P. aerophilum carried poly-A tails facilitating the construction of a cDNA library. 245 sequence tags of a poly-A primed cDNA library and 55 sequence tags from a 1-2 kb Sau3AI-fragment containing genomic library were analyzed and the corresponding amino acid sequences compared with protein sequences from databases. Fourteen percent of the cDNA and >9% of genomic DNA sequence tags revealed significant similarities to proteins in the databases. Matches were obtained to proteins from archaeal, bacterial and eukaryal sources. Some sequences showed greatest similarity to eukaryal rather than to bacterial versions of proteins, other matches were found to proteins which had previously only been found in eukaryotes.

Archaea↗
PubMed1996

Finding new mutator strains of Escherichia coli--a review.

Mutations in the lacZ gene were constructed that allowed the detection of mutators that caused specific transversion mutations. This allowed the detection of two new mutator genes, mut Y and mut M, which are involved in the repair of the 8-oxodguanine (8oxodG) lesion.

8-Hydroxy-2'-Deoxyguanosine↗
PubMed1996

Substrate specificity of Escherichia coli MutY protein.

The MutY protein of Escherichia coli removes mismatched deoxyadenine residues from DNA. In this study, duplex oligodeoxynucleotides containing modified bases are used as model substrates for this enzyme. In contrast to a recent report [Lu, A.-L., et al. (1995) J. Biol. Chem. 270, 23582], dA:8-oxo-dG appears to be the preferred natural substrate for MutY, as evidenced by the specificity constants (kcat/Km) for dA:8-oxo-dG and dA:dG of 39 600 x 10(-6) and 383 x 10(-6) (min-1 nM-1), respectively. kcat for the duplex containing dA:dG was highest at lower pH; the rate of cleavage for the duplex containing dA:8-oxo-dG was unaffected over a pH range of 5.5-8.0. The presence of an 8-oxo function in dG increased significantly the rate of removal of dA from all substrates tested. Replacement of dA by rA reduced the specificity constant of dA:8-oxo-dG to 294 x 10(-6) (min-1 nM-1), whereas replacement of dA by 2'-O-methyladenosine virtually abolished enzymatic activity. Modifications of the dG moiety generally were better tolerated than those of dA; however, introduction of a methyl ether at the 6 position of dG produced a noncleavable substrate and replacement of dG by 2'-O-methylguanosine generated a substrate with a low specificity constant. Rates of cleavage of duplexes containing dA:dC and dA:tetrahydrofuran were three orders of magnitude lower than the reference substrate. Duplexes containing a carbocyclic analog of dA were not cleaved. A model is proposed to explain the recognition of DNA substrates by MutY and the catalytic properties of this enzyme.

DNA↗
PubMed1996

Mutator tRNAs are encoded by the Escherichia coli mutator genes mutA and mutC: a novel pathway for mutagenesis.

We have previously described the mutator alleles mutA and mutC, which map at 95 minutes and 42 minutes, respectively, on the Escherichia coli genetic map and which stimulate transversions; the A.T-->T.A and G.C-->T.A substitutions are the most prominent. In this study we show that both mutA and mutC result from changes in the anticodon in one of four copies of the same glycine tRNA, at either the glyV or the glyW locus. This change results in a tRNA that inserts glycine at aspartic acid codons. In view of previous studies of missense suppressor tRNAs, the mistranslation of aspartic acid codons is assumed to occur at approximately 1-2%. We postulate that the mutator tRNA effect is exerted by generating a mutator polymerase and suggest that the epsilon subunit of DNA polymerase, which provides a proofreading function, is the most likely target. The implications of these findings for the contribution of mistranslation to observed spontaneous mutation rates in wild-type strains, as well as other cellular phenomena such as aging, are discussed.

Alleles↗
PubMed1996

Hyperlucent lung secondary to homocystinuria.

At 23 months of age, one of a pair of monozygotic twins with radiographic unilateral hyperlucent lung was evaluated by radionuclide ventilation/perfusion pulmonary studies, which revealed a ventilation/perfusion mismatch of an entire lung. This twin died, and autopsy revealed pulmonary arterial thrombosis and histological changes compatible with homocystinuria, which was subsequently shown to be present in the surviving twin as well. A ventilation/perfusion lung scan of the surviving twin revealed multiple ventilation/perfusion mismatched defects, suggestive of pulmonary embolism. The presenting manifestation of homocystinuria in these patients was the pulmonary thrombotic disease. Neither twin had any other stigmata of homocystinuria at the time of initial presentation.

Diseases in Twins↗
PubMed1996

Malrotation discovered during routine radionuclide gastric emptying study.

In infants with recurrent vomiting, and especially bilious vomiting, the algorithmic approach is to perform conventional barium upper gastrointestinal radiography to rule out malrotation and midgut volvulus, which are surgical emergencies. However, children with protracted vomiting and failure to thrive are candidates for medical treatment. These children are often evaluated by radionuclide gastric emptying studies to assess gastric emptying. Three patients are presented in whom the radionuclide gastric emptying study revealed the presence of a malrotation anomaly which had been undetected by antecedent barium gastrointestinal radiographic studies.

Barium Sulfate↗
PubMed1996

Pulmonary gallium-67 uptake in diffuse pulmonary calcinosis.

Diffuse pulmonary uptake of both technetium-99m- labeled methylene diphosphonate (99(m)Tc-MDP) and gallium (67Ga) citrate was noted in a patient with chronic renal failure and indicated the presence of pulmonary calcinosis. The uptake of 67Ga could be misinterpreted to represent abnormal uptake due to an opportunistic infection.

Adolescent↗