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Biomedical subjects

D P Roberts

Publications and source records attributed to D P Roberts.

15 recordsLinked to original sources
PubMed1988

Development of a passive device for freezing large amounts of transplantable skin at one time in a -70 degrees C mechanical refrigerator.

A simple device has been developed for the simultaneous cooling of up to 9120 cm2 of allograft skin in a flat package format. The device, named an insulated alternating-offset heat sink device, is composed of a stack of interleaved layers of 2.0-mm-thick packets of skin and 3.18-mm-thick aluminum heat sinks (each 33.0 cm long by 22.9 cm wide). Four skin packets are placed in a single layer on each heat sink plate, and the number of plates can be varied to accommodate different numbers of skin packets. Every heat sink protrudes 6.3 cm of its 33.0-cm length beyond the skin packets to make a fin for heat convection, but adjacent plates alternate the direction of their fin protrusion so that the layers of plates alternate in their 6.3-cm offset. Insulation layers of 2.54-cm-thick expanded polystyrene are placed on the exposed surfaces of the top and bottom heat sinks in the stack, and the stack is held together by rubber bands. The device is cooled in a -70 degrees C mechanical refrigerator. Maximal cooling rates of -1.8 degrees C min-1 are obtained for both 6- and 11-plate devices, and -3.0 degrees C min-1 for a 2-plate device. The exothermic temperature plateaus associated with skin cooled in these devices are 1.5-1.8 min in duration. Skin cooled by this technique maintains levels of glucose oxidation similar to those associated with skin cooled by liquid nitrogen vapor at a controlled rate of -1 degree C min-1, provided rapid warming is employed after -70 degrees C storage. The development of this device provides a method for the simple, low-cost cryopreservation of the large amounts of allograft skin obtained from a cadaveric donor.

Cell Survival↗
PubMed1988

Analysis of the Pseudomonas solanacearum polygalacturonase encoded by pglA and its involvement in phytopathogenicity.

A major endopolygalacturonase excreted by Pseudomonas solanacearum was purified to greater than 95% homogeneity and shown to have an isoelectric point of 9.0 and a subunit molecular mass of 52 kilodaltons (kDa). The gene encoding this enzyme (pglA) was isolated from a genomic library of P. solanacearum DNA based on its expression in Escherichia coli and shown to be contained on a 1.8-kilobase DNA fragment. The identity of the pglA gene product and the 52-kDa polygalacturonase was demonstrated by immunoadsorption and isoelectric focusing experiments. The cloned pglA gene was apparently expressed from its own promoter in E. coli and its product was partially secreted into the periplasm. The pglA gene was insertionally inactivated in vitro and used to mutate the chromosomal pglA gene of P. solanacearum by marker exchange mutagenesis. The resulting mutant strain was deficient in production of the 52-kDa polygalacturonase and took twice as long to wilt and kill tomato plants as the wild-type parent in plant bioassay experiments. Complementation in trans with the wild-type cloned pglA gene restored virulence to near wild-type levels. The data indicate that the pglA gene is important, but not absolutely necessary, for pathogenesis.

Escherichia coli↗
PubMed1988

Cloning of the egl gene of Pseudomonas solanacearum and analysis of its role in phytopathogenicity.

The egl gene of Pseudomonas solanacearum was cloned on a cosmid and expressed in Escherichia coli. Restriction endonuclease mapping, transposon mutagenesis, and subclone analysis showed that the egl gene was located on a 2.7-kilobase XhoI-SalI P. solanacearum DNA fragment. Immunoabsorption experiments and sodium dodecyl sulfate-polyacrylamide gel electrophoretic analysis showed that the egl gene encodes the 43-kilodalton endoglucanase that is the major excreted endoglucanase of P. solanacearum. In E. coli, the egl gene appeared to be expressed from its own promoter, but its product was restricted to the cytoplasm. The cloned egl gene was mutagenized with Tn5 and used to specifically mutate the chromosomal egl gene of P. solanacearum by site-directed mutagenesis. The resultant mutant was identical to the wild-type strain in production of extracellular polysaccharide and extracellular polygalacturonase as well as several other excreted proteins but produced at least 200-fold less endoglucanase. This mutant strain was significantly less virulent on tomato than the wild-type strain in plant bioassay experiments. Virulence of the endoglucanase-deficient strain was restored to near wild-type levels by complementation in trans with the cloned egl gene, indicating that the egl gene is important but not absolutely required for pathogenesis.

Cellulase↗
PubMed1987

Adapting personal computers for use by high-level quadriplegics.

A communication instrument has been developed for use by a quadriplegic person who is limited solely to eye motion as a control input. The instrument uses an infrared-emitting diode/phototransistor sensor mounted on the frame of a pair of eyeglasses to transform deliberate lateral eye motion into a contact-closure output form. A software program has also been developed for use with this instrument to display letters of the alphabet in a series of six lines. The lines are slowly scrolled until the desired line is reached, then stopped by a lateral eye motion. The scrolling then continues for each character in that line until the desired character is reached. Again, lateral eye movement causes the scrolling to stop and the character becomes part of a string. This process continues until a command character is selected whereby the string can be sent to a printer, spoken through a speech synthesizer, or erased.

Adult↗
PubMed1986

Requirement for two or more Erwinia carotovora subsp. carotovora pectolytic gene products for maceration of potato tuber tissue by Escherichia coli.

Several genes encoding enzymes capable of degrading plant cell wall components have been cloned from Erwinia carotovora subsp. carotovora EC14. Plasmids containing cloned EC14 DNA mediate the production of endo-pectate lyases, exo-pectate lyase, endo-polygalacturonase, and cellulase(s). Escherichia coli strains containing one of these plasmids or combinations of two plasmids were tested for their ability to macerate potato tuber slices. Only one E. coli strain, containing two plasmids that encode endo-pectate lyases, exo-pectate lyase, and endo-polygalacturonase, caused limited maceration. The pectolytic proteins associated with one of these plasmids, pDR1, have been described previously (D. P. Roberts, P. M. Berman, C. Allen, V. K. Stromberg, G. H. Lacy, and M. S. Mount, Can. J. Plant Pathol. 8:17-27, 1986) and include two secreted endo-pectate lyases. The second plasmid, pDR30, contains a 2.1-kilobase EC14 DNA insert that mediates the production of an exo-pectate lyase and an endo-polygalacturonase. These enzymes are similar in physicochemical properties to those produced by EC14. Our results suggest that the concerted activities of endo-pectate lyases with endo-polygalacturonase or exo-pectate lyase or both cause maceration.

Cell Wall↗
PubMed1980

Holography.

Explore the source record for details and available documents.

Forecasting↗
PubMed1976

Oral carbenicillin treatment of uncomplicated gonorrhea in men and women.

In a prospective controlled study of 290 men and women with uncomplicated gonorrhea, carbenicillin was shown to be less than 90% effective. Positive cultures were the basis for initial diagnosis and therapeutic failure in both sexes. Carbenicillin was evaluated in three different schedules: 5gm p.o., 10 gm p.o, and 2gm IM Plus 5GM p.o. The three schedules were equally effective. Eleven of 20 failures in women occurred in infection of the rectum. MICs of carbenicillin ranged from 0.025% to 1.0 mug/ml with a mean of 0.29 mug/ml.

Administration, Oral↗
PubMed1972

Treatment of gonorrhea with spectinomycin hydrochloride: comparison with standard penicillin schedules.

Spectinomycin hydrochloride, a new parenteral antibiotic prepared from Streptomyces spectabilis, was compared with standard U.S. Public Health Service-recommended dosages of aqueous procaine penicillin G in the treatment of uncomplicated gonorrhea in 353 men and 314 women. Of the 314 women, 130 had a pretreatment positive rectal culture. All diagnoses were proven by culture on Thayer-Martin selective medium. Minimal inhibitory concentrations of both drugs were determined. Single doses of 2 and 4 g of spectinomycin were compared with 2.4 million units of procaine penicillin in males and with both 2.4 and 4.8 million units of procaine penicillin in females. Both spectinomycin schedules, 2.4 million units of penicillin in males and 4.8 million units of penicillin in females, resulted in cure rates in excess of 90%. There were no failures at the rectal site only in those women with positive rectal cultures. There was no advantage to using the larger amount of spectinomycin in either sex.

Antibiotics, Antineoplastic↗
PubMedDate not supplied

A model for evaluating tissue donation seminars: implications for skin banks.

Educational seminars on tissue donation are costly in terms of time, effort, and resources, for both the planners and the participants. Although long-term outcomes from these projects cannot always be practically assessed, specific short-term conclusions can be drawn and degrees of success measured. An ideal evaluation technique needs to address issues such as identification of participant interests, levels of existing participant knowledge, and participant reaction to presented materials. Assessment in these areas allows for subsequent modifications intended to produce more effective and interesting seminars. Such an evaluation technique has been developed, and it is presented here in the context of its application to an educational seminar on the topic of organ and tissue procurement with special reference to skin banking.

Analysis of Variance↗
PubMedDate not supplied

Reduced bacteria on transplantable allograft skin after preparation with chlorhexidine gluconate, povidone-iodine, and isopropanol.

A comparison was made of the residual microbiologic contamination on transplantable allograft skin for burn wound coverage taken from cadaver donors prepared by two different protocols. One group was prepared with povidone-iodine, detergent, and 70% isopropanol; the other was prepared with these agents and 4% chlorhexidine gluconate (CG). The skin from each of the donor bodies was removed from independently prepared body areas. Without CG, 13.7% of donor body areas were contaminated; with CG, only 5.6% were contaminated. The number of gram-positive bacterial species isolated from skin after CG preparation was dramatically reduced. The gram-positive bacterial contamination rate dropped from 12.1% to 2.2% of donor body areas, a drop of 82%. With CG, 12 of the 15 contaminant species were eliminated; and we saw a general reduction in the total number of contaminated body areas, a specific and pronounced reduction in gram-positive bacteria, and an increase from 86.3% to 94.4% in the amount of skin obtained from donor cadavers that tested negative for bacterial contamination.

1-Propanol↗