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Biomedical subjects

R B Simpson

Publications and source records attributed to R B Simpson.

At least 55 records · Page 3Linked to original sources
PubMed1982

DNA from the A6S/2 crown gall tumor contains scrambled Ti-plasmid sequences near its junctions with plant DNA.

The A6S/2 tumor incited on tobacco by Agrobacterium tumefaciens harboring the octopine-type A6 Ti plasmid contains one insert of Ti-plasmid sequences (the T DNA). This 13 kb insert is derived from a colinear sequence in the Ti plasmid (the T region) and becomes attached to plant DNA in the nucleus of the host cell. We have determined the DNA sequence encompassing the left end of the T region of the A6 Ti plasmid and the corresponding portion of the A6S/2 T DNA. The two sequences are identical for at least 806 bp. To the left of the divergence point, the tumor contains five partially overlapping sequences that are direct or inverted repeats of sequences to the right of the divergence point. The Ti plasmid contains only the right member of each of these repeats. We have also performed heteroduplex studies that indicate that this T DNA has a 520 bp inverted repeat of an internal sequence at the right end near its junction with plant DNA. The repeated sequences near the ends of the T DNA resemble the repeats of adenovirus type 12 sequences found near its junction with host DNA. We discuss data suggesting that the 23 bp to the immediate right of the divergence point of the A6 left junction form a site important in some step in the transfer of T-region DNA from the bacteria to the plant.

Base Sequence↗
PubMed1982

Glucose-nonfermenting Gram-negative bacilli associated with clinical veterinary specimens.

Glucose-nonfermenting gram-negative bacilli (NFB) have been recognized recently as opportunistic pathogens of humans. With few exceptions, strains of NFB have not been considered important enough to be identified when isolated from animals. In this study, all NFB isolated during a 1-year period in a clinical veterinary microbiology laboratory were identified to determine their prevalence. Of the 347 strains of NFB obtained, the most common species were Pseudomonas aeruginosa, Acinetobacter calcoaceticus, Bordetella bronchiseptica, and Pseudomonas pseudoalcaligenes. Of all clinical veterinary specimens submitted for cultures, 10% contained nonfermenters.

Acinetobacter↗
PubMed1982

Effects of washing on the bacterial flora of the stallion's penis.

Six stallions were subjected to extensive cleansing of the penis and prepuce with water, Ivory Soap and water, or Betadine surgical scrub and water. The stallions were all washed for 14 days, and then allowed 14 days respite. This pattern of washing and resting was repeated consecutively. Swabs were taken from all 7 stallions twice weekly and semen was collected once a week for bacteriological examination. All forms of cleansing altered the bacterial flora of the stallion's penis; the Ivory Soap tended to encourage the replacement of the normal flora with coliform organisms, while Betadine favoured the growth of Pseudomonas aeruginosa and Klebsiella spp. This experiment showed that the systematic washing of a stallion's penis will cause the normal flora to be replaced with pathogens and potential pathogens.

Animals↗
PubMed1982

Hypnosis in dental education: a survey of U.S. dental schools, 1980.

This paper reports the results of a 1980 survey of the teaching of hypnosis in U.S. dental schools. Responses were received from 60 dental schools. Information was obtained on hypnosis education in both the predoctoral and postdoctoral curriculums, including what is being taught, how hypnosis education is structured in the curriculum, who is teaching hypnosis, the number of students receiving hypnosis education, and attitudes and policies about hypnosis education. Results of this survey were compared to previous surveys by Parrish (1973) and Scott (1977, for the United Kingdom). The survey reveals a gradual increase in the number of U.S. dental schools teaching hypnosis.

Curriculum↗
PubMed1982

Influence of bacterial products on the motility of stallion spermatozoa.

Sterile filtrates were prepared from equine isolates of Klebsiella pneumoniae (genitalium), Proteus mirabilis, Pseudomonas aeruginosa, Escherichia coli, Streptococcus zooepidemicus, Streptococcus equisimilis, Actinobacillus equuli, and Corynebacterium equi and mixed individually with extended stallion semen. When diluted in the extended semen the filtrates represented bacterial populations of 0.5 x 10(6), 1 x 10(6), 2 x 10(6) and 4 x 10(6) cells/ml. pH values were recorded for each filtrate. Specimens were monitored for percentage motile spermatozoa at 30-min intervals until they reached 10% or less for 2 consecutive observations. All specimens were maintained at 25 degrees C in a water bath. Ten specimens were examined from each of 5 clinically normal stallions. The major reduction in percentage motile spermatozoa as compared to the control sample occurred before the first observation. From this point the rate of deterioration in motility in the filtrates approximated that of the control. The differences detected between the filtrates and control in percentage motile sperm cells were all statistically significant at P less than 0.01.

Animals↗
PubMed1981

Revertant seedlings from crown gall tumors retain a portion of the bacterial Ti plasmid DNA sequences.

BT37 is a crown gall teratoma incited on tobacco by Agrobacterium tumefaciens containing pTi-T37, a nopaline-type Ti plasmid. Treatment of this cloned tumor tissue with kinetin at 1 mg/liter results in the formation of relatively normal-appearing shoots. These shoots can be induced to root and set viable seed. In contrast to BT37 tissue, the derived tissues are not phytohormone independent and do not produce nopaline. The reverted plants, like normal tobacco plants, are susceptible to infection by A. tumefaciens. This loss of tumorous traits is accompanied by the loss of most of the Ti plasmid sequences (T-DNA) found in BT37 DNA. Southern blot analysis indicates that the revertant tissues have lost the central portion of the T-DNA, which contains the "common DNA" sequences, a highly conserved region of the Ti plasmid that has been found to be incorporated into all tumors studied. Thus, these sequences appear necessary for oncogenicity and tumor maintenance and their loss is probably directly related to tumor reversal. The reverted plants as well as the plants obtained from seed, however, do retain sequences homologous to the ends of the T-DNA present in the parental teratoma. The persistence of foreign DNA sequences during the process of meiosis and seed formation has important implications for the possibility of the genetic engineering of plants.

Journal Article↗
PubMed1980

Interaction of the cAMP receptor protein with the lac promoter.

The cyclic AMP receptor protein (CRP) stimulates transcription of the lactose operon by binding to the lac promoter. I have identified those 5-positions of thymines in the promoter that lie close to bound CRP. Although ultraviolet irradiation of DNA with 5-bromouracil substituted in place of thymine normally cleaves the DNA at the bromouracils, a protein bound to the DNA can perturb these cleavages at those locations at which the protein lies close to the bromine. The contacts inferred from this photochemical probe and the results of nucleolytic attack of this complex by exonuclease III support a model where the cyclic AMP receptor protein binds to the promoter making symmetrical contacts with one face of the double helix and then stimulates transcription through contacts with RNA polymerase.

Binding Sites↗
PubMed1980

E. coli RNA polymerase interacts homologously with two different promoters.

We present and review experiments that identify points of close approach of the RNA polymerase to two promoters, lac UV5 and T7 A3. We identify the contacts to the phosphates along the DNA backbone, to the N7s of guanines in the major groove and the N3s of adenines in the minor groove, and to the methyl groups of thymines. These contacts to the two promoters are strikingly homologous in space, as shown on three-dimensional models, and identify major regions of interactions lying on one side of the DNA molecule (at -35 and -16), as well as further areas extending through the Pribnow box. Both promoters are unwound similarly by the polymerase, across a region of about twelve bases extending from the middle of the Pribnow box to just beyond the RNA start site. We discuss the areas of interaction in the context of promoter homologies and promoter mutations. The disposition of the contacts in space suggests a model for the pathway along which the RNA polymerase binds to promoters.

Adenine↗
PubMed1979

Zoonotic diseases in psittacine birds: apparent increased occurrence of chlamydiosis (psittacosis), salmonellosis, and giardiasis.

Between September 1977 and November 1978, chlamydiosis (psittacoisis) was diagnosed in 52 of 128 parrots, 5 of 12 cockatiels, 2 of 5 cockatoos, 3 of 6 macaws, 1 of 22 conures, 2 of 18 lovebirds, and 6 of 76 parakeets; 2 lories and 1 lorikeet were chlamydiosis negative. Two cases of human chlamydiosis were associated with two submissions of parrots subsequently found to have active infection. Twenty parrots (including 13 that were chlamydiosis positive), 2 cockatiels, 1 macaw, 1 lorie, and 1 parakeet yielded salmonella organisms, of which 16 were identified as Salmonella typhimurium, 8 as untypeable monophasic salmonellae of serogroup B, and 1 as S arizonae. Three S typhimurium from parrots that had been treated with chlortetracycline for chlamydiosis were resistant to tetracyclines, streptomycin, and sulfonamides; another isolate was found to be resistant to chloramphenicol only. Severe giardiasis was diagnosed in parakeets originating from six aviaries.

Animals↗
PubMed1979

The molecular topography of RNA polymerase-promoter interaction.

Ultraviolet irradiation forms covalent crosslinks between E. coli RNA polymerase and the lac UV5 promoter substituted with bromouracil in the place of thymine. I have determined the polymerase subunit and the base within the promoter sequence that are joined to each other in two such crosslinks. The sigma and beta subunits of RNA polymerase, respectively, are crosslinked to the third base upstream (-3) and the second base downstream (+3) from the starting point of transcription (+1). Both bases are on the nontemplate strand of the promoter DNA. The location of the beta subunit suggests that it forms at least part of the catalytic site of the enzyme. The disposition of sigma suggests that this subunit plays a direct role in unwinding the DNA at the promoter. The sigma crosslink is close to the "Pribnow Box," which is centered about 10 bases upstream from the RNA start site, contains a striking homology between promoters and is the locus of many promoter mutations.

Base Sequence↗
PubMed1979

Contacts between Escherichia coli RNA polymerase and thymines in the lac UV5 promoter.

I have identified those 5 positions of thymines in the lac UV5 promoter that lie close to bound Escherichia coli RNA polymerase (nucleosidetriphosphate:RNA nucleotidyltransferase, EC 2.7.7.6). Although ultraviolet irradiation of DNA with 5-bromouracil substituted in place of thymine normally cleaves the DNA at the bromouracils, a protein bound to the DNA can perturb these cleavages at those locations at which the protein lies close to the bromine. In the lac promoter most of these contacts lie in three regions. Four contacts lie in the region where transcription initiates; four lie in the "Pribnow box," which is located about 10 base pairs upstream from the initiation site; and three more lie in the "-35 region," located about 35 base pairs upstream from the initiation site. The "Pribnow box" and the "-35 region" are regions whose sequences are partially conserved between promoters and in which most promoter mutations are located; thus, contacts in these two regions probably represent sites of sequence-specific recognition by RNA polymerase.

Base Sequence↗
PubMed1978

Mutual expectations in the process of joining a dental health group.

Productivity can be seriously affected when new persons join an existing group and little or no attention is given to the process by which that person becomes a member of the group practice. Parallels can be drawn between organizational management and the functioning of the dental team. Observations were made of three clinicians who attempted to join an existing dental delivery group. There are some predictable phases through which the joiner passes to acceptance or lack of acceptance in an existing group. Recommendations for groups to consider before either hiring or training members of a dental health group are given.

Cooperative Behavior↗
PubMed1975

Control of microflora in stallion semen with a semen extender.

Sterile equipment was used to collect ten ejaculates from each of ten normal stallions and quantitative and qualitative bacterial counts were made within 15 min after collection. The mean bacterial population in undiluted semen was found to be 573,000 +/- 374,000 organisms/ml. The bacterial content of semen diluted with two parts sterile physiological saline, or with two parts of a cream-gelatin extender, was measured within 15 min after collection and again after 2 hr at 25 degrees C. The number of bacteria was slightly increased in the saline after 2 hr, but 1 93% and 99% reduction occurred in the extended semen within 15 min and after 2 hr at room temperature.

Animals↗