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Biomedical subjects

D W White

Publications and source records attributed to D W White.

At least 55 records · Page 3Linked to original sources
PubMed1994

Expression of the pea albumin 1 gene in transgenic white clover and tobacco.

In order to improve the quality of pasture protein for ruminant animal nutrition, we are introducing genes encoding rumen-protected proteins, rich in essential amino acids, into white clover (Trifolium repens L.). We have introduced a chimaeric gene transcribed from the 35S CaMV promoter, and encoding the pea albumin 1 (PA1) protein, rich in sulphur amino acids, into the white clover genotype WR8 by Agrobacterium-mediated transformation. A transgenic plant with high levels of PA1 mRNA was crossed with a commercial genotype from cv. Regal Ladino and both the parent and progeny plants were analyzed for expression and accumulation of PA1 gene products. Steady-state mRNA levels and transcript sizes in transgenic parent and progeny were comparable. The abundance and stability of the PA1 protein in transgenic white clover plants was examined by immunoselection of in vivo [35S]Na2SO4-labelled plant proteins. Evidence is presented here, that the 11 kDa PA1 proprotein precursor is processed correctly in petiole tissues of newly regenerated white clover plantlets but only the 6 kDa PA1a subunit accumulates in leaflets of tissue-culture-grown and older glasshouse-grown clover plants. Attempts to enhance PA1 abundance by altering its subcellular target in transgenic tobacco plants suggest that the endomembrane system is a relatively stable environment compared with the cytoplasm or chloroplast, for the accumulation of PA1, despite its low abundance there (< 0.001% total cell protein).

Albumins↗
PubMed1994

Identification of sulphur-rich proteins which resist rumen degradation and are hydrolysed rapidly by intestinal proteases.

Several proteins with high proportions of S-containing essential amino acids were incubated in sheep rumen fluid in vitro and their rate of digestion was examined by sodium dodecyl sulphate-polyacrylamide-gel electrophoresis. The S-rich proteins rice prolamin (10 kDa), maize zein (10 kDa) and the 3.2 kDa pumpkin (Cucurbita maxima L.) trypsin inhibitor-1 (CMTI-1) were highly resistant to rumen fluid degradation, relative to control proteins of known degradation rate (casein, bovine serum albumin (BSA) and pea (Pisum sativum) albumin-1 (PA1)). Comparison of PA1 and a recombinant N-terminal epitope-tagged PA1 indicated that addition of the epitope caused a slight increase in resistance to rumen degradation. The proteins were also incubated with a mixture of trypsin (EC 3.4.21.4) and chymotrypsin (EC 3.4.21.1). PA1, BSA and casein were hydrolysed less rapidly than rice prolamin, maize zein and CMTI-1. Digestion by these intestinal proteases appeared to be complete. Thus, the prolamin, zein and CMTI-1 proteins are suitable candidates for expression as foreign proteins in pasture plants to increase throughput and uptake of essential amino acids in sheep.

Amino Acids, Essential↗
PubMed1994

Posttranslational modification of an isoinhibitor from the potato proteinase inhibitor II gene family in transgenic tobacco yields a peptide with homology to potato chymotrypsin inhibitor I.

A member of the potato proteinase inhibitor II (PPI-II) gene family under the control of the cauliflower mosaic virus 35S promoter has been introduced into tobacco (Nicotiana tabacum). Purification of the PPI-II protein that accumulates in transgenic tobacco has confirmed that the N-terminal signal sequence is removed and that the inhibitor accumulates as a protein of the expected size (21 kD). However, a smaller peptide of approximately 5.4 kD has also been identified as a foreign gene product in transgenic tobacco plants. This peptide is recognized by an anti-PPI-II antibody, inhibits the serine proteinase chymotrypsin, and is not observed in nontransgenic tobacco. Furthermore, amino acid sequencing demonstrates that the peptide is identical to a lower molecular weight chymotrypsin inhibitor found in potato tubers and designated as potato chymotrypsin inhibitor I (PCI-I). Together, these data confirm that, as postulated to occur in potato, PCI-I does arise from the full-length PPI-II protein by posttranslational processing. The use of transgenic tobacco represents an ideal system with which to determine the precise mechanism by which this protein modification occurs.

Amino Acid Sequence↗
PubMed1994

Immobilization of Escherichia coli expressing the lux genes of Xenorhabdus luminescens.

The luxCDABE operon of Xenorhabdus luminescens was cloned into pUC18 to make pLITE27. Expression of the lux genes from the lac promoter resulted in strong constitutive light emission by Escherichia coli DH5 carrying the recombinant lux plasmid, pLITE27. When strain DH5(pLITE27) was immobilized with sodium alginate-CaCl2, the embedded cells retained their luminescence up to 2 weeks under appropriate storage conditions.

Cloning, Molecular↗
PubMed1994

Inclusion of women and minorities in occupational cancer epidemiologic research.

A survey of published epidemiologic studies from eight journals during 1971 to 1990 was conducted to assess the proportion and characteristics of occupational cancer studies that have included women and minorities. A total of 1233 reports included 562 (46%) with subjects limited to white men. The remaining 671 (54%) had subjects from other race-gender groups. Thirty-five percent included white women, but only 14% presented any analyses of white women specifically and only 7% presented more than five risk estimates. The proportions with analyses of nonwhite women (any = 2%; detailed = 1%) or men (any = 7%; detailed = 3%) were also small. Studies with detailed analyses of women and minorities tended to use weaker methodologies (ie, proportionate mortality or cross-sectional design) than the studies of white men and were less able to provide convincing data on the occupational cancer risks of women and minorities.

Epidemiologic Methods↗
PubMed1993

Nopaline causes a conformational change in the NocR regulatory protein-nocR promoter complex of Agrobacterium tumefaciens Ti plasmid pTiT37.

The nocR gene of Agrobacterium tumefaciens Ti plasmid pTiT37 is the regulatory gene of the nopaline catabolism (noc) operon of pTiT37. We have cloned and sequenced nocR, which encodes a DNA-binding protein. The deduced amino acid sequence is similar to those of members of the LysR family of prokaryotic activator proteins. Gel retardation experiments demonstrated that the NocR protein binds to the nocR promoter in both the presence and absence of nopaline. The increased mobility of the complex and alterations in the DNase I footprints revealed a nopaline-induced conformational change in the NocR-DNA complex. Sequence analysis of the NocR binding site indicated the presence immediately downstream of the -10 sequence of the nocR promoter of a 12 bp putative operator overlapping a consensus gyrase recognition sequence and an 18 bp long alternating purine-pyrimidine sequence. These results suggest that nopaline-induced alterations in the NocR protein-nocR promoter complex might control gene expression in the noc operon.

Agrobacterium tumefaciens↗
PubMed1993

Temperature-sensitive transforming mutants of the v-rel oncogene.

By making site-directed mutations in the avian retroviral oncogene v-rel, we created two temperature-sensitive (ts) transforming mutants; these changes were analogous to mutations previously shown to confer a ts function onto the Dorsal protein of Drosophila melanogaster. Chicken spleen cells infected with the ts v-rel mutants formed colonies in agar at 36.5 degrees C but not at 41.5 degrees C. In addition, spleen cells derived from the ts v-rel-transformed colonies could be propagated in liquid culture at 36.5 degrees C but rapidly senesced at 41.5 degrees C. Both mutant v-Rel proteins were also ts for DNA binding in vitro. These mutants may be valuable for identifying genes directly regulated by v-rel.

Amino Acid Sequence↗
PubMed1992

Directed evolution of a protein: selection of potent neutrophil elastase inhibitors displayed on M13 fusion phage.

Inhibitors of human neutrophil elastase were engineered by designing and producing a library of phage-displayed protease inhibitory domains derived from wild-type bovine pancreatic trypsin inhibitor and fractionating the library for binding to the target protease. The affinity of one of the engineered variants for human neutrophil elastase (Kd = 1.0 pM) is 3.6 x 10(6)-fold higher than that of the parental protein and exceeds the highest affinity reported for any reversible human neutrophil elastase inhibitor by 50-fold. Thus the display phage method has allowed us to obtain protein derivatives that exhibit greatly increased affinity for a predetermined target. The technology can be applied to design high-affinity proteins for a wide variety of target molecules.

Amino Acid Sequence↗
PubMed1992

A simple method for the preparation of single-stranded polydeoxynucleotides of desired length.

A method for the preparation of homogeneous, single-stranded polydeoxynucleotides of desired length up to 800 bases is described. The procedure entails 1) generation of double-stranded DNA of desired length by PCR using a pair of primers of which one is biotinylated and the other is either unlabeled or fluorescently labeled, 2) isolation of PCR products by agarose slab gel electrophoresis, 3) recovery of desired product by electroelution, 4) binding of the product to streptavidin-coated magnetic beads and is followed by 5) duplex denaturation and removal of the unbound single strand that is either unlabeled or fluorescently labeled. Final product characteristics were determined by capillary gel electrophoresis with fluorescence detection. Up to microgram quantities of homogeneous single-stranded DNA of a desired length were obtained. These can be used as single-stranded size standards in capillary gel electrophoresis experiments as well as in other techniques requiring such standards.

Base Sequence↗
PubMed1991

Continuous electrical stimulation as a helpful adjunct during intraoperative facial nerve monitoring.

Routine intraoperative monitoring of facial function has been used since 1985. An adaptor has been developed for continuous stimulation (SACS) to be used with the new WR-S8, Monitor/Stimulation The SACS allows the microsurgical instruments and air drills to be electrified and to function as probe tips during surgical dissection. The new WR-S8 Monitor/Stimulator has an ultrasensitive strain gauge that detects facial movement before it is palpable. The remote probe allows an assistant to adjust the current easily. The routine use of facial nerve monitoring with SACS has decreased surgical time, has helped prevent iatrogenic injuries, and has improved our ability to save the facial nerve during otologic and neuro-otologic surgery.

Journal Article↗
PubMed1990

Molecular cloning of the C-terminal domain of Escherichia coli D-mannitol permease: expression, phosphorylation, and complementation with C-terminal permease deletion proteins.

We have subcloned a portion of the Escherichia coli mtlA gene encoding the hydrophilic, C-terminal domain of the mannitol-specific enzyme II (mannitol permease; molecular mass, 68 kilodaltons [kDa]) of the phosphoenolpyruvate-dependent carbohydrate phosphotransferase system. This mtlA fragment, encoding residues 379 to 637 (residue 637 = C terminus), was cloned in frame into the expression vector pCQV2 immediately downstream from the lambda pr promoter of the vector, which also encodes a temperature-sensitive lambda repressor. E. coli cells carrying a chromosomal deletion in mtlA (strain LGS322) and harboring this recombinant plasmid, pDW1, expressed a 28-kDa protein cross-reacting with antipermease antibody when grown at 42 degrees C but not when grown at 32 degrees C. This protein was relatively stable and could be phosphorylated in vitro by the general phospho-carrier protein of the phosphotransferase system, phospho-HPr. Thus, this fragment of the permease, when expressed in the absence of the hydrophobic, membrane-bound N-terminal domain, can apparently fold into a conformation resembling that of the C-terminal domain of the intact permease. When transformed into LGS322 cells harboring plasmid pGJ9-delta 137, which encodes a C-terminally truncated and inactive permease (residues 1 to ca. 480; molecular mass, 51 kDa), pDW1 conferred a mannitol-positive phenotype to this strain when grown at 42 degrees C but not when grown at 32 degrees C. This strain also exhibited phosphoenolpyruvate-dependent mannitol phosphorylation activity only when grown at the higher temperature. In contrast, pDW1 could not complement a plasmid encoding the complementary N-terminal part of the permease (residues 1 to 377). The pathway of phosphorylation of mannitol by the combined protein products of pGJ9-delta 137 and pDPW1 was also investigated by using N-ethylmaleimide to inactivate the second phosphorylation sites of these permease fragments (proposed to be Cys-384). These results are discussed with respect to the domain structure of the permease and its mechanism of transport and phosphorylation.

Chromosome Deletion↗
PubMed1990

Wide surgical exposure for singular neurectomy in the treatment of benign positional vertigo.

Since 1972, singular neurectomy has been performed on 58 patients who had classical benign positional vertigo. The procedure is done under general anesthesia; a wide postauricular exposure is made and the external auditory canal is maximally enlarged until the vertical portion of the facial nerve is identified. This gives an excellent view of the round window niche. Our results indicate vertigo was completely cured in 80% of the cases and improved in 17%. There has been no incidence of total hearing loss in the last 49 cases and only 3 of 49 patients (6%) had sensorineural loss. Although singular neurectomy can be mastered, it will remain a procedure done by few surgeons. The wide exposure technique is safer for preservation of cochlear function and the posterior ampullary nerve is easier to find than using the transmeatal approach as described by Gacek.

Adult↗
PubMed1987

Interaction between magnetic fields and metallic ossicular prostheses.

A selection of commonly used metal ossicular prostheses were tested to see if they were attracted by the 5000-gauss magnetic field of a magnetic resonance imager. None of the prostheses tested was attracted by the magnetic field. Using a model system, it was found that some of the metal objects perturbed the magnetic field, thus affecting the image produced by the scanner. Therefore, while metal implants may be safe in a powerful magnetic field, they can alter the field, resulting in abnormal images.

Electromagnetic Fields↗
PubMed1984

Cancer mortality patterns by work category in three Texas oil refineries.

A previous proportionate mortality ratio analysis revealed elevated mortality from brain tumors, stomach cancer, leukemia, and other cancers among OCAW members employed in three Texas oil refineries. In order to evaluate these findings, complete work histories of cases and a matched set of controls who died from other causes of death were obtained from company personnel records. Work histories were summarized by classifying each job title and department entry into one of several broad work categories of refinery unit operations. A worker was considered "exposed" to a work category if he was known to have worked at least 1 day in the category 15 or more years prior to his death. Maximum likelihood estimates of the relative risk for brain tumor, stomach cancer, and leukemia were calculated by work category using a procedure for matched case-control data. No strong associations for brain tumor risk were seen with any work categories. A slight association for leukemia was seen among workers in the Treating category, which included unit operations that reduce the level of aromatic and sulfur constituents of petroleum products and combine them with additives to improve their quality. Stomach cancer risk was elevated among maintenance workers and workers exposed to lubricating oils and paraffin wax processing.

Brain Neoplasms↗