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Biomedical subjects

M Ring

Publications and source records attributed to M Ring.

At least 19 recordsLinked to original sources
PubMed1996

Identification of a 5' truncated non-LTR-retrotransposon, YAKPs1, from the variegated cutworm, Peridroma saucia, using PCR.

Retrotransposable elements encode for several polypeptides that contain a number of conserved amino acid motifs, especially in the region encoding reverse transcriptase. We have used these motifs to design primers for the PCR amplification of retrotransposon DNA. These primers have allowed us to isolate a retroposon, or LINE (long interspersed nuclear element), from the pest insect, Peridroma saucia. DNA sequence analysis of this element, YAKPs1, demonstrated a high degree of homology to a number of retroposons from Drosophila melanogaster, in particular the Fw and Doc elements with homologies of up to 69%. Determination of the complete sequence of the YAKPs1 element will enable a detailed analysis of its evolutionary relatedness to other elements as well as a greater insight into its mode of action.

Amino Acid Sequence↗
PubMed1996

Locust ion transport peptide (ITP): primary structure, cDNA and expression in a baculovirus system.

Ion transport peptide (ITP) purified from locust nervous corpus cardiacum (CC) has previously been shown to stimulate salt and water reabsorption and inhibit acid secretion in the ileum of Schistocerca gregaria. We used the partial amino acid sequence of purified ITP to derive degenerate primers. These were used to amplify a cDNA from brain RNA using reverse transcription and the polymerase chain reaction (RtPCR). This sequence was extended using anchored PCR to yield a partial, 517bp cDNA clone. This cDNA encodes a putative ITP prohormone which could be cleaved at two dibasic amino acid sites to yield a 72 residue active amidated peptide. The deduced amino acid sequence from the cDNA agrees completely with the amino acid sequence and molecular mass (8564Da) derived from analysis of purified ITP. Relative to a family of crustacean hyperglycaemic hormones (CHH), all six cysteine residues and many other amino acid residues are conserved in ITP, establishing that ITP is a homologue. However, CHH, crab eyestalk and CC extracts from distantly related insects have no action, whereas CC extracts from closely related insects are active on the locust ITP assay, showing that the bioassay is selective. Insect Sf9 cells transfected with a baculovirus containing our partial cDNA secreted a potent stimulant of locust ileal transport, confirming that the peptide encoded by our ITP clone has biological activity. The mRNA for ITP is restricted to the brain and CC. Interestingly, a related mRNA is observed in other tissues which are not active on the ITP bioassay.

Amino Acid Sequence↗
PubMed1992

Automated blood component preparation with the Opti system: three years' experience.

Removal of buffy coat from the red cell preparations reduces the content of microaggregates and leukocytes and decreases transfusion side effects. However, buffy coat removal is difficult to standardize when performed manually. An automated method using a new type of plastic container system, the Optipac, and a new type of device, the Optipress, greatly improves blood component production. An initial hard centrifugation of the original whole blood provides the best results, leaving approximately 20 ml of plasma and 0.5 x 10(9) leukocytes per unit of red cells suspended in 100 ml of an additive solution (SAG-M). Improved quality and standardization of the products, reduced technician time and better working conditions for the technician are the major advantages as compared to traditional manual technique.

Blood Component Removal↗
PubMed1992

Engineering and physics in dental technology. 1.

This work is a compilation of the principles of engineering and physics that are involved in the design and construction of various types of prostheses in the dental laboratory. It is intended as a reference of scientific doctrines for dental technicians who wish to advance their knowledge and skills. This article is the first of several that will be published in Trends & Techniques during the next several issues. The article in its entirety is by no means complete--the field is too enormous to identify all the tenets that apply, and future scientific advancement will certainly add others. Some elements of biomechanics are included in this work because of the interrelationship of biomechanics to engineering.

Dental Stress Analysis↗
PubMed1991

Recombinant cytochrome c peroxidase folds properly without conformational "annealing".

Recombinant cytochrome c peroxidase isolated from Escherichia coli has recently been reported to exhibit an abnormal electronic absorption spectrum that is converted to the normal spectrum after conformational "annealing" of the recombinant enzyme by passage over a cytochrome c affinity column. The current report provides evidence that the abnormal spectrum observed in some preparations of recombinant cytochrome c peroxidase arises from the presence of contaminant, damaged forms cytochrome c peroxidase with altered spectra. Removal of these contaminant forms produces a major cytochrome c peroxidase fraction with a normal spectrum. We conclude that elution of recombinant cytochrome c peroxidase over a cytochrome c affinity column does not produce normal enzyme through conformational "annealing" but that it produces purified enzyme through removal of contaminants.

Chromatography, Affinity↗
PubMed1991

Preliminary experience with 5 and 6 French diagnostic catheters as guiding catheters for coronary angioplasty.

With the reduction in profile of balloon dilation catheters, until recently, it has been the internal dimensions and performance of the guiding catheter that has mandated the use of 7, 8 or 9 French (F) systems for the performance of percutaneous transluminal coronary angioplasty (PTCA). A new 5F catheter design (Sherwood Medical Co., St. Louis, MO) provided a large inner lumen (0.4") permitting use of 0.20-0.22" fixed-wire PTCA balloon catheters with good coronary visualization. Potential advantages include reduced coronary artery ostial trauma and catheter induced damping and enhanced patient comfort. We report our initial experience in 14 patients undergoing PTCA with a 5 and 6F guide/fixed-wire system. Mean age was 63 +/- 10 (43-78 years). PTCA indications: Cardiogenic shock (1), post-myocardial infarction angina pectoris (2), grade III angina (5) and unstable angina pectoris (6). Vessel attempted: Left anterior descending (3), circumflex (4), obtuse marginal (2), diagonal (1), right coronary artery (3), and internal thoracic artery (1). Twelve patients had femoral approach; two brachial approach. The USCI Probe (USCI Division, Billerica, MA) was used in 8 lesions and SCIMED ACE (SCIMED Life Systems, Maplegrove, MN) catheter in 7 lesions. Successful 5 or 6F guide/fixed-wire dilations reduced the stenosis (77 +/- 14 to 37 +/- 30%) and were successfully performed in 79% (11/14). One 5F patient required 8F guiding catheter and was dilated with 2.0 fixed-wire balloon. A second failed 5F PTCA could not be dilated with any larger conventional system. A third total occlusion could not be crossed with a guidewire or fixed wire balloon. No patient had a complication.(ABSTRACT TRUNCATED AT 250 WORDS)

Angioplasty, Balloon, Coronary↗
PubMed1990

Multiple replacements establish the importance of tyrosine-503 in beta-galactosidase (Escherichia coli).

Tyr-503 of beta-galactosidase was specifically replaced with Phe, His, Cys, and Lys using site-directed mutagenesis. The normal enzyme and the substituted enzymes were purified. The activities of each of the substituted enzymes with o-nitrophenyl-beta-D-galactopyranoside (ONPG) and p-nitrophenyl-beta-D-galactopyronoside (PNPG) were very low and Y503K-beta-galactosidase was essentially inactive, showing that Tyr-503 is important for activity. The stability (including tetrameric stability) of the enzymes at 4 and 25 degrees C was essentially the same as that of the wild-type enzyme and the cleavage patterns on sodium dodecyl sulfate gels after protease action were unchanged. These studies thus indicate that Tyr-503 has no noticeable influence on stability under normal conditions. The substitutions for Tyr-503 had some small effects on the binding of both substrate and inhibitor. However, both kappa 2 (glycosidic bond cleavage rate) and kappa 3 (hydrolysis rate constant) were dramatically reduced. Each substitution except that of Lys (which can be explained by electrostatic effects) gave decreases in kappa 2 and kappa 3 of roughly the same magnitude regardless of whether the substitutions were conservative or not. This strongly implies that the changes in rate were not due to conformational changes as it is very unlikely that there would be such similar decreases in the values of kappa 2 and kappa 3 for amino acids with such different structures and chemical properties if the changes in rate were due to conformational differences. The data suggest that one possible role of Tyr-503 is as a general acid/base catalyst. Profiles of the kinetic data of the enzymes as functions of pH supported the suggestion that Tyr-503 normally acts as a general acid and base catalyst. When Tyr-503 was substituted by His, a small amount of base catalytic activity seemed to be restored. The strongest evidence that Tyr-503 acts as an acid catalyst came from studies with isoquinolinium-beta-D-galactopyranoside as the substrate. The kappa cat(s) of Y503F-beta-galactosidase and of Y503C-beta-galactosidase decreased by about an order of magnitude while the rate decreases were about 3 orders of magnitude with ONPG and PNPG. The breakdown of isoquinolinium-beta-D-galactopyranoside cannot be catalyzed by acids.

Base Sequence↗
PubMed1989

Laboratory procedures for the one-clasp removable partial denture.

The lateral rotational path of insertion for removable partial dentures in the Kennedy class II category is generally limited to situations where the dentulous side has been restored with fixed restorations that provide a lingual undercut. The rigid lingual plate is first inserted horizontally into the undercut, followed by a lateral rotation to seat the edentulous side. No alterations of properly designed fixed restorations are necessary. This article discusses the technical procedures in detail.

Dental Abutments↗
PubMed1988

Site-directed mutagenic replacement of glu-461 with gln in beta-galactosidase (E. coli): evidence that glu-461 is important for activity.

Glutamic acid 461 of beta-galactosidase (E. coli) was replaced by gln using site-directed mutagenesis. Kinetic studies on the purified Q461-beta-galactosidase showed that it had less than 0.4% of the wild-type activity (with ONPG as substrate), confirming other studies which have suggested that the negative charge on glu-461 is important for activity. The Km values did not increase, indicating that binding of the substrate was not decreased by this change. Thermal denaturation studies showed Q461-beta-galactosidase to be somewhat more susceptible to heat denaturation than the wild-type enzyme.

Escherichia coli↗
PubMed1988

Site-directed mutagenesis of beta-galactosidase (E. coli) reveals that tyr-503 is essential for activity.

By using the technique of site-directed mutagenesis we have succeeded in replacing tyr-503 of beta-galactosidase (E. coli) with a phe. A study of the kinetic and stability properties of this mutant enzyme (F-503 beta-galactosidase) showed that the loss in activity upon this change is due to the loss of a catalytic group (rather than a detrimental change in the enzyme's overall structure or a change in the enzyme's binding capacity). This confirms previous suggestions that this tyr residue is involved in catalysis.

Cloning, Molecular↗