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Biomedical subjects

J B Robertson

Publications and source records attributed to J B Robertson.

At least 19 recordsLinked to original sources
PubMed2000

Genome organization and phylogenetic distribution of a novel family of ancient murine endogenous proviruses with evidence for transposition-mediated proliferation.

A new family of murine endogenous proviruses (VL6.0) is described here. The intact provirus is near 6 kb in length and shows a genomic organization of 5' LTR, gag, pol, env, and 3' LTR. The primer binding site (PBS) is that of a tRNA(gly). The lack of functional open reading frames and occurrence of significant gaps in most, if not all, members of this group show it to be ancient. Our estimate of copy number per haploid genome is 30+. Members of this group have been isolated from Mus musculus domesticus, M. m. casteneus, M. m. hortulanus, M. caroli, and M. spretus. The occurrence of these sequences throughout such diverse members of the genus Mus may indicate that the date of the original infection predated the divergence of the extant Mus lineages at around 2.5 million years ago. Analysis of gap (deletion/insertion) patterns indicates that these sequences may have proliferated within the Mus genome by a mechanism of reverse transcriptase-mediated transposition. As yet, there are no closely related murine retroviruses described. The closest mammalian retrovirus based on sequence similarity is from the miniature swine (Sus scrofa).

Amino Acid Sequence↗
PubMed2000

Smooth muscle myosin heavy chains are developmentally regulated in the rabbit bladder.

PURPOSE: In smooth muscle (SM), myosin heavy chain (MHC) is expressed predominantly as two isoforms, SM1 and SM2, which are encoded by a single gene and expressed by alternative splicing mechanisms. Although functional differences of these isoforms are unknown, changes in SM1/SM2 ratio have been reported in various pathophysiologic conditions. We analyzed MHC composition of bladder detrusor SM from rabbits of different ages to determine whether SM1 and SM2 isoform expressions are developmentally regulated. MATERIALS AND METHODS: Rabbit bladders on the -11, -4, 1, 7, 14, 21, and 90th days of life were analyzed for SM MHC isoform expression at protein and mRNA levels. Porous sodium dodecyl sulfate polyacrylamide gel electrophoresis (SDS-PAGE), S1 protection assay, and histological analysis were employed. RESULTS: The predominant MHC isoform in fetal and neonatal bladders was SM1. In the third postnatal week, the SM1/SM2 ratio decreased from 2.3 to 1.0. A stable SM1/SM2 ratio of 0.6 was observed in the adult animal. Although expression of SM1 mRNA was 2.6-fold greater than that of SM2 in the fetus, the relative amount of SM2 mRNA increased rapidly after birth and remained the predominant isoform throughout adult life. Developmental changes in relative amounts of SM1 and SM2 protein in bladder tissues were virtually identical to those of SM1 and SM2 mRNA. SM cell growth and disappearance of primitive mesenchyme from the bladder occurred concomitantly with the MHC isoform shift. CONCLUSIONS: The parallel temporal course of MHC mRNA and protein isoform levels suggests detrusor SM MHC expression may be developmentally regulated at the mRNA level.

Animals↗
PubMed1997

Natural protection of spring and well drinking water against surface microbial contamination. I. Hydrogeological parameters.

The fate and transport of microbes in groundwater are controlled by physicochemical characteristics of the microbe and of the groundwater/aquifer media. Key characteristics of the microbe include size, inactivation (die-off) rate, and surface electrostatic properties. Key properties of the groundwater/aquifer system include flow velocity, aquifer grain (or pore) size, porosity, solid organic carbon content, temperature, pH, and other chemical characteristics of water and mineral composition. Because of size and surface electrical properties, viruses are much more mobile in groundwater than Cryptosporidium and Giardia (which are about 100 times or more larger than viruses). The inactivation or die-off rate is usually the most important factor governing how far microbes can migrate in significant numbers in groundwater. Typical half-lives of microbes in groundwater range from a few hours to a few weeks. Examples of maximum reported migration distances of microbes in groundwater include: bacteria, 600 m in a sandy aquifer: viruses, 1000 to 1600 m in channeled limestones and 250 to 408 m in glacial silt-sand aquifers; Cryptosporidium and Giardia, no confirmed reports found of significant migration distances. Investigations by the EPA have indicated that distances of 210 to 325 m away from septic tanks are necessary to achieve with high confidence an 11 order of magnitude reduction in virus concentrations.

Animals↗
PubMed1994

Epidermal growth factor receptors in human breast carcinoma cells: a potential selective target for transforming growth factor alpha-Pseudomonas exotoxin 40 fusion protein.

Epidermal growth factor (EGF) receptors are expressed in high levels by some poor prognosis breast tumors. We have examined the cytotoxic effect of the tumor growth factor alpha (TGF alpha)-delta Cys-Pseudomonas exotoxin (PE40) recombinant fusion protein on normal and tumorigenic human breast epithelial cells in vitro and in vivo. The MDA-468, MDA-231, BT-20, and MCF-7ADR estrogen receptor-negative, EGF receptor-rich breast cancer lines were exquisitely sensitive in vitro to TGF alpha-delta Cys-PE40 with a 50% inhibitory concentration of < or = 0.02 nM. The estrogen receptor-positive, low EGF receptor MCF-7, ZR75-1, and T47D cells were less sensitive to the fusion toxin with a 50% inhibitory concentration of > 0.2 nM. The nontumorigenic cell lines 184, 184A1, and 184B5 were relatively resistant to TGF alpha-delta Cys-PE40 despite exhibiting high levels of EGF receptors. Continuous i.p. administration of TGF alpha-delta Cys-PE40 via an osmotic minipump at a dose of 0.4 microgram/g/day over 7 days inhibited MDA-468, MA-231, and BT-20 but not MCF-7 tumor growth in female athymic mice. Host tissue toxicity was not observed with this dose of TGF alpha-delta Cys-PE40. Mixed MDA-468/MCF-7 tumors were established in nude mice after coinoculation of both cell types in estrogen-supplemented animals. EGF receptor immunohistochemistry and immunoblot procedures indicated that TGF alpha-PE40 eliminated the MDA-468 cells while sparing the adjacent MCF-7 cells. By immunoblot, EGF receptors were consistently more abundant in tumor tissue than in adjacent nontumor tissue from the same mastectomy specimen (n = 7). These data support the notion that EGF receptors can be selectively targeted in human breast cancer cells for the delivery of antitumor agents. Further clinical studies with TGF alpha-delta Cys-PE40 and other chimeric toxins using the same cellular target will address this possibility.

Animals↗
PubMed1994

Relative biological effectiveness and microdosimetry of a mixed energy field of protons up to 200 MeV.

We have studied radiation effects utilizing the new 250 MeV Synchrotron at Loma Linda University Medical Center. In this paper we present the data collected for the survival of Chinese hamster lung (V79) cells, that were irradiated with a beam of mixed energy protons up to 200 MeV. The RBE for protons, when compared to 60Co gamma rays, ranged from a low of 1.2 at the high energy portion of the field to 1.3+ at the low energy portion of the field. These results are consistent with the measured lineal energy (microdosimetric) spectra.

Animals↗
PubMed1994

Suboptimal treatment results with the Therasonics lithotriptor.

From July 1988 to August 1991, 174 stone treatments were attempted on 112 stones in 86 patients using a Therasonics lithotriptor. Mean stone diameter was 13 mm. (range 4 to 60). The success rate (defined as no debris or fragments less than 4 mm. in an asymptomatic patient) was 49% and the retreatment rate was 63%. Subjects reported moderate to severe pain during 70 treatment sessions (42%) despite sedation with parenteral narcotics (50 to 100 mg. meperidine and 50 mg. hydroxyzine intramuscularly). One patient had perirenal bleeding requiring a 7-unit blood transfusion. Of the treatments 24 (13%) were aborted, 10 due to pain and 13 because of inability of the operator to position the patient or localize the stone. These results appear to be inferior to those reported with alternative lithotriptors. Modifications that have been made in the Therasonics system may improve stone localization and treatment results.

Adult↗
PubMed1993

Paraquat uptake in the cultured gastrointestinal epithelial cell line, IEC-6.

Although the major target organ of paraquat toxicity is the lung, the primary route of absorption of the herbicide is across the gastrointestinal epithelium. Thus, uptake of paraquat was investigated in the rat duodenal crypt cell line, IEC-6. The herbicide was toxic; as measured by cell number, the LD50 was 75 microM. Using 2 microM [14C]paraquat as tracer, uptake of the herbicide was found to be slow but linear over 24 hr at 37 degrees C. No accumulation was observed at 4 degrees C. Inhibition studies showed paraquat inhibited both putrescine and spermidine uptake after only a 15-min incubation. The Km for putrescine was increased when incubated in the presence of paraquat whereas Vmax was not changed, suggesting a competitive mode of inhibition. In the reverse situation, putrescine also inhibited paraquat uptake (IC50 10 microM). Paraquat uptake was reduced in a dose-dependent manner by the putative calmodulin antagonist W-7, but was not affected by KN-62, a Ca2+/calmodulin kinase II specific inhibitor. These results provide evidence that paraquat uptake occurs through the polyamine transport system in IEC-6 cells. Furthermore, this process is modulated by intracellular events involving a major signaling protein, Ca2+/calmodulin.

1-(5-Isoquinolinesulfonyl)-2-Methylpiperazine↗
PubMed1992

Oxidation of nitrotoluenes by toluene dioxygenase: evidence for a monooxygenase reaction.

Pseudomonas putida F1 and Pseudomonas sp. strain JS150 initiate toluene degradation by incorporating molecular oxygen into the aromatic nucleus to form cis-1,2-dihydroxy-3-methylcyclohexa-3,5-diene. When toluene-grown cells were incubated with 2- and 3-nitrotoluene, the major products identified were 2- and 3-nitrobenzyl alcohol, respectively. The same cells oxidized 4-nitrotoluene to 2-methyl-5-nitrophenol and 3-methyl-6-nitrocatechol. Escherichia coli JM109(pDTG601), which contains the toluene dioxygenase genes from P. putida F1 under the control of the tac promoter, oxidized the isomeric nitrotoluenes to the same metabolites as those formed by P. putida F1 and Pseudomonas sp. strain JS150. These results extend the range of substrates known to be oxidized by this versatile enzyme and demonstrate for the first time that toluene dioxygenase can oxidize an aromatic methyl substituent.

Biodegradation, Environmental↗
PubMed1991

Methods for dietary fiber, neutral detergent fiber, and nonstarch polysaccharides in relation to animal nutrition.

There is a need to standardize the NDF procedure. Procedures have varied because of the use of different amylases in attempts to remove starch interference. The original Bacillus subtilis enzyme Type IIIA (XIA) no longer is available and has been replaced by a less effective enzyme. For fiber work, a new enzyme has received AOAC approval and is rapidly displacing other amylases in analytical work. This enzyme is available from Sigma (Number A3306; Sigma Chemical Co., St. Louis, MO). The original publications for NDF and ADF (43, 53) and the Agricultural Handbook 379 (14) are obsolete and of historical interest only. Up to date procedures should be followed. Triethylene glycol has replaced 2-ethoxyethanol because of reported toxicity. Considerable development in regard to fiber methods has occurred over the past 5 yr because of a redefinition of dietary fiber for man and monogastric animals that includes lignin and all polysaccharides resistant to mammalian digestive enzymes. In addition to NDF, new improved methods for total dietary fiber and nonstarch polysaccharides including pectin and beta-glucans now are available. The latter are also of interest in rumen fermentation. Unlike starch, their fermentations are like that of cellulose but faster and yield no lactic acid. Physical and biological properties of carbohydrate fractions are more important than their intrinsic composition.

Animal Feed↗
PubMed1990

Analysis of foodstuffs for dietary fiber by the urea enzymatic dialysis method.

Total dietary fiber (TDF) values for cereal grains, fruits, vegetables, processed foods, and purified or semi-purified dietary fiber products were determined by a new method using 8M urea and enzymes (urea enzymatic dialysis, UED, method). The results are compared with the official AOAC procedure. Soluble and insoluble dietary fiber were determined for several of these foodstuffs and compared with the NDF values. Crude protein and ash contamination was usually lower with the UED method compared with the AOAC method, particularly for samples that formed gels during ethanol precipitation. Urea and the heat stable amylase were effective in removing starch even at relatively low temperatures of the assay (50 degrees C). The new assay is relatively economical in use of equipment, enzymes, and reagents. Studies are currently in progress to minimize the assay time for the UED method while further improving its flexibility and robustness. The results of the studies will be discussed.

Amylases↗
PubMed1989

AbrB, a regulator of gene expression in Bacillus, interacts with the transcription initiation regions of a sporulation gene and an antibiotic biosynthesis gene.

The abrB gene of Bacillus subtilis is believed to encode a repressor that controls the expression of genes involved in starvation-induced processes such as sporulation and the production of antibiotics and degradative enzymes. Two such genes, spoVG, a sporulation gene of B. subtilis, and tycA, which encodes tyrocidine synthetase I of the tyrocidine biosynthetic pathway in Bacillus brevis, are negatively regulated by abrB in B. subtilis. To examine the role of abrB in the repression of gene transcription, the AbrB protein was purified and then tested for its ability to bind to spoVG and tycA promoter DNA. In a gel mobility shift experiment, AbrB was found to bind to a DNA fragment containing the sequence from -95 to +61 of spoVG. AbrB protein exhibited reduced affinity for DNA of two mutant forms of the spoVG promoter that had been shown to be insensitive to abrB-dependent repression in vivo. These studies showed that an upstream A + T-rich sequence from -37 to -95 was required for optimal AbrB binding. AbrB protein was also observed to bind to the tycA gene within a region between the transcription start site and the tycA coding sequence as well as to a region containing the putative tycA promoter. These findings reinforce the hypothesis that AbrB represses gene expression through its direct interaction with the transcription initiation regions of genes under its control.

Amino Acid Sequence↗
PubMed1988

Development of a validation test for self-reported abstinence from smokeless tobacco products: preliminary results.

Using X-ray fluorescence spectrometry, 11 heavy elements at concentrations that are easily detectable have been identified in smokeless tobacco products. These concentrations were found to increase in cheek epithelium samples of the user after exposure to smokeless tobacco. This feasibility study suggests that the level of strontium in the cheek epithelium could be a valid measure of recent smokeless tobacco use. It also demonstrates that strontium levels become undetectable within several days of smokeless tobacco cessation. This absence of strontium could validate a self-report of abstinence from smokeless tobacco. Finally, the X-ray spectrum of heavy metal content of cheek epithelium from smokeless tobacco users could itself provide a visual stimulus to further motivate the user to terminate the use of smokeless tobacco products.

Cheek↗
PubMed1988

Comparison of the effects of psyllium and wheat bran on gastrointestinal transit time and stool characteristics.

Gastrointestinal transit time, frequency of defecation, stool weight, and stool consistency were studied in 12 subjects who were each given fiber supplements containing wheat bran, psyllium gum, a combination of wheat bran and psyllium gum, or a low-fiber control for 2 weeks. Gastrointestinal transit time was measured using four different markers: plastic pellets, chromium mordanted bran, cobalt-ethylenediamine-tetraacetic acid, and terbium oxide. The wet weight and dry weight of stools were measured, and a questionnaire accessed subjects' perceptions of the consistency of their stools. Fiber supplementation decreased transit time and increased the daily number of defecations and the wet weight and dry weight of stools. Bran had a greater effect on transit time than psyllium. Psyllium had a greater effect on the amount of water found in the stools and the total stool weight. On the days that stools were passed, 50% of the daily stool ratings were scored as "hard" when subjects received the control supplement. Less than 10% of the ratings were scored as "hard" when subjects received the high-fiber supplements. The type of marker used did not significantly affect the transit time measured.

Adult↗
PubMed1987

Effect of psyllium gum and wheat bran on spontaneous energy intake.

Energy intake, fecal energy output, and gastrointestinal symptoms were measured in 12 females who consumed either approximately 23 g/d supplementary fiber or a 4 g/d fiber control. Fiber supplements were crackers containing psyllium gum, wheat bran, or a combination of the two fiber sources. After 1 wk on the control cracker, subjects consumed the three high-fiber crackers and the control cracker for 2-wk periods in a balanced design. Gum and combination supplements gave increased bloating and flatulence. Increase in abdominal pain was reported with gum supplement. Mean daily fecal energy was 96 kcal/d with control crackers and was increased by 63 kcal with high-fiber crackers. Gum and combination supplements significantly decreased intake of digestible energy by 153 and 115 kcal/d, respectively. This suppression was not dependent upon fiber intolerance. Wheat bran supplement had no effect on energy intake.

Adult↗
PubMed1987

Mean transit time measurement by analysis of a single stool after ingestion of multicolored plastic pellets.

Mean transit time (MTT) was measured in 12 females and served as a standard to evaluate the validity of different methods of estimating transit by analysis of a single stool (SST). Each subject consumed three different fiber supplements and a low-fiber control for 14-d periods. On days 4-8 of each period, subjects were given 20 plastic pallets, which varied in color each day. SST was calculated using from two to five sets of colored pellets and different criteria for designation of the stool to be analyzed were compared. Results indicate that the following modifications in the SST method originally proposed by Cummings and Wiggins will result in improved prediction of MTT: 1) Increase the days of dosing from 3 to 6.2) Collect for study the first stool passed 3 h after the last dosing. 3) Include all pellets identified in the selected stool in the SST calculation.

Defecation↗
PubMed1987

The care of elderly patients by elderly physicians.

To examine the content of care that elderly patients receive from physicians greater than or equal to 65 years of age, data from the 1981 National Ambulatory Medical Care Survey were analyzed. Compared to physicians aged 35 to 54 years, elderly physicians devoted a larger proportion of their practices to the care of elderly patients. In caring for these patients, elderly physicians spent more time per visit than did younger physicians and were more likely to conduct general examinations and provide counseling. In contrast, elderly physicians were less likely to perform mental status or vision examinations. Elderly physicians were also less likely to provide telephone follow-up for those patients greater than or equal to 75 years of age and more likely to discharge patients greater than or equal to 65 years of age without any specific follow-up planned. These data suggest that the content of care for elderly patients may differ substantially depending upon the physician's age.

Aged↗