Biomedical subjects
J C Hall
Publications and source records attributed to J C Hall.
Inhibition of ACCase220 and ACCase240 isozymes from sethoxydim-resistant and -susceptible maize hybrids.
Acetyl-coenzyme A carboxylase (ACCase) isozymes were separated from cyclohexanedione-resistant and -susceptible maize. ACCase240 from resistant maize was 3.7-, >77-, and 12.8-fold more resistant to inhibition by clethodim, sethoxydim, and tralkoxydim, respectively, than ACCase240 from susceptible maize. The resistant ACCase240 preparation had 3.0-fold more protein and 14.5-fold lower specific activity than susceptible ACCase240. Resistant ACCase240 has a V(max) 5.5-fold lower than that of susceptible ACCase240, whereas apparent K(m) values were similar. ACCase220 from resistant maize was >25- and 7.2-fold more resistant to inhibition by sethoxydim and tralkoxydim, respectively, than susceptible ACCase220 but was inhibited to the same extent by clethodim. In summary, sethoxydim-resistant corn has an altered herbicide-resistant ACCase220 isozyme and increased expression of a less efficient, herbicide-resistant ACCase240 isozyme. However, to what extent alteration of both isozymes contributes to sethoxydim resistance is not clear.
Development of an enzyme-linked immunosorbent assay for the detection of glyphosate.
A competitive indirect enzyme-linked immunosorbent assay (CI-ELISA) was developed to quantitate the herbicide glyphosate [N-(phosphonomethyl)glycine] in water. The ELISA has a detection limit of 7.6 microg mL(-1) and a linear working range of 10-1000 microg mL(-1) with an IC(50) value of 154 microg mL(-1). The glyphosate polyclonal antisera did not cross-react with a number of other herbicides tested but did cross-react with the glyphosate metabolite aminomethylphosphonic acid and a structurally related herbicide, glyphosine [(N,N-bis(phosphonomethyl)glycine]. The assay was used to estimate, quantitatively with accuracy and precision, glyphosate concentrations in water samples. Water samples were analyzed directly, and no sample preparation was required. To improve detection limits, water samples were concentrated prior to analysis, resulting in the increase of the detection limits by 100-fold. After the sample preconcentration step, the detection limit improved to 0.076 microg mL(-1) with an IC(50) value of 1.54 microg mL(-1), and a linear working range was 0.1-10 microg mL(-1). Glyphosate concentrations determined by ELISA correlated well with those determined by high-pressure liquid chromatography (r(2) = 0.99). This assay contributes to reducing the costs associated with conventional residue analysis techniques for the quantitation of glyphosate in water.
Single-versus multiple-dose antimicrobial prophylaxis for major surgery: comment.
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Monitoring wound infection after surgery: the quest for useful information at a reasonable cost.
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Nutritional strategies to reduce the risk of osteoporosis.
Osteoporosis is a risk for as many as 28 million Americans, with the risk being higher in women than men. Osteoporosis is frequently not diagnosed until a fracture occurs. Early screening and detection are critical to prevent fractures and subsequent debilitation. Proper nutrition and exercise are vital to preventing and treating osteoporosis.
Degradation of 2,4-dinitrophenol and selected nitroaromatic compounds by Sphingomonas sp. UG30.
Sphingomonas strain UG30 mineralizes both p-nitrophenol (PNP) and pentachlorophenol (PCP). Our current studies showed that UG30 oxidatively metabolized certain other p-substituted nitrophenols, i.e., p-nitrocatechol, 2,4-dinitrophenol (2,4-DNP), and 4,6-dinitrocresol with liberation of nitrite. 2,6-DNP, o- or m-nitrophenol, picric acid, or the herbicide dinoseb were not metabolized. Studies using 14C-labelled 2,4-DNP indicated that in glucose-glutamate broth cultures of UG30, greater than 90% of 103 microM 2,4-DNP was transformed to other compounds, while 8-19% of the 2,4-DNP was mineralized within 5 days. A significant portion (20-50%) of the 2,4-DNP was metabolized to highly polar metabolite(s) with one major unidentified metabolite accumulating from 5 to 25% of the initial radioactivity. The amounts of 2,4-DNP mineralized and converted to polar metabolites was affected by glutamate concentration in the medium. Nitrophenolic compounds metabolized by UG30 were also suitable substrates for the UG30 PCP-4-monooxygenase (pcpB gene expressed in Escherichia coli) which is likely central to degradation of these compounds. The wide substrate range of UG30 could render this strain useful in bioremediation of some chemically contaminated soils.
CRY, a Drosophila clock and light-regulated cryptochrome, is a major contributor to circadian rhythm resetting and photosensitivity.
Light is a major environmental signal for circadian rhythms. We have identified and analyzed cry, a novel Drosophila cryptochrome gene. All characterized family members are directly photosensitive and include plant blue light photoreceptors. We show that cry transcription is under circadian regulation, influenced by the Drosophila clock genes period, timeless, Clock, and cycle. We also show that cry protein levels are dramatically affected by light exposure. Importantly, circadian photosensitivity is increased in a cry-overexpressing strain. These physiological and genetic data therefore link a specific photoreceptor molecule to circadian rhythmicity. Taken together with the data in the accompanying paper, we propose that CRY is a major Drosophila photoreceptor dedicated to the resetting of circadian rhythms.
The cryb mutation identifies cryptochrome as a circadian photoreceptor in Drosophila.
A new rhythm mutation was isolated based on its elimination of per-controlled luciferase cycling. Levels of period or timeless clock gene products in the mutant are flat in daily light-dark cycles or constant darkness (although PER and TIM oscillate normally in temperature cycles). Consistent with the fact that light normally suppresses TIM, cryb is an apparent null mutation in a gene encoding Drosophila's version of the blue light receptor cryptochrome. Behaviorally, cryb exhibits poor synchronization to light-dark cycles in genetic backgrounds that cause external blindness or demand several hours of daily rhythm resets, and it shows no response to brief light pulses. cryb flies are rhythmic in constant darkness, correlating with robust PER and TIM cycling in certain pacemaker neurons.
A mutant Drosophila homolog of mammalian Clock disrupts circadian rhythms and transcription of period and timeless.
We report the identification, characterization, and cloning of a novel Drosophila circadian rhythm gene, dClock. The mutant, initially called Jrk, manifests dominant effects: heterozygous flies have a period alteration and half are arrhythmic, while homozygous flies are uniformly arrhythmic. Furthermore, these flies express low levels of the two clock proteins, PERIOD (PER) and TIMELESS (TIM), due to low per and tim transcription. Mapping and cloning of the Jrk gene indicates that it encodes the Drosophila homolog of mouse Clock. The mutant phenotype results from a premature stop codon that eliminates much of the putative activation domain of this bHLH-PAS transcription factor, thus explaining the dominant features of Jrk. The remarkable sequence conservation strongly supports common clock components present in the common ancestor of Drosophila and mammals.
CYCLE is a second bHLH-PAS clock protein essential for circadian rhythmicity and transcription of Drosophila period and timeless.
We report the identification, characterization, and cloning of another novel Drosophila clock gene, cycle (cyc). Homozygous cyc flies are completely arrhythmic. Heterozygous cyc/+ flies are rhythmic but have altered periods, indicating that the cyc locus has a dosage effect on period. The molecular circadian phenotype of homozygous cyc flies is like homozygous Clk flies presented in the accompanying paper: mutant flies have little or no transcription of the per and tim genes. Cloning of the gene indicates that it also encodes a bHLH-PAS transcription factor and is a Drosophila homolog of the human protein BMAL1. cyc is a nonsense mutation, consistent with its strong loss-of-function phenotype. We propose that the CYC:CLK heterodimer binds to per and tim E boxes and makes a major contribution to the circadian transcription of Drosophila clock genes.
Quantitation of glutaminase mRNA in enterocytes using competitive RT-PCR.
The concentration of mRNA within the intestinal mucosa is usually measured by either Northern blot analysis or semi-quantitative reverse transcription polymerase chain reaction (RT-PCR). However, these methods are limited by a lack of valid internal controls, low sensitivity, and large differences in the concentration of the internal control and target gene. The authors present an alternative method using competitive RT-PCR to measure glutaminase mRNA in isolated enterocytes.
Duration of antimicrobial prophylaxis in vascular surgery.
BACKGROUND: This randomized clinical trial compares the incidence of wound infection after vascular surgery in patients who received prophylaxis using the same antibiotic as either a single-dose or a multiple-dose regimen (until the lines/drain tubes were removed, but not for more than 5 days). METHODS: Each of the 302 patients who entered the study received ticarcillin 3.0 g/clavulanate 0.1 g (Timentin) intravenously immediately after the induction of anesthesia. Patients randomized to the multiple-dose group received an average of 14.3 doses (range 9 to 20). RESULTS: The incidence of wound infections was 18% (28 of 153) for patients in the single-dose group and 10% (15 of 149) for patients in the multiple-dose group (P = 0.04; relative risk estimate = 2.00, 95% confidence interval = -1.02 to 3.92). CONCLUSIONS: A multiple-dose antibiotic regimen, rather than single-dose therapy, provides optimal prophylaxis against wound infection for patients undergoing vascular surgery.
The pathobiology of peritonitis.
The peritoneum is more than a mechanical covering that allows for the easy gliding of opposed peritoneal surfaces. The peritoneal mesothelial cells facilitate the action of powerful innate immune mechanisms. In addition, the peritoneal-associated lymphoid tissues contain unique cells that may play a crucial role in the localization of intraperitoneal infection. A clearer understanding of the molecular and cellular events underlying peritoneal functions in both the unstimulated and stimulated state will aid future treatment of peritonitis.
Genetics of biological rhythms in drosophila.
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Evidence that the TIM light response is relevant to light-induced phase shifts in Drosophila melanogaster.
Light is a major environmental signal for the entrainment of circadian rhythms. In Drosophila melanogaster, recent experiments suggest that photic information is transduced to the clock through the timeless gene product, TIM. We provide genetic and spectral evidence supporting the relevance of TIM light responses to clock resetting. A missense mutant TIM, TIM-SL, exhibits greater sensitivity to light in both TIM protein disappearance and locomotor activity phase shifting assays. We show that the wavelength dependence of light-induced decreases in TIM levels and that of light-mediated phase shifting are virtually identical. Analysis of dose response of TIM disappearance in a variety of mutant genotypes suggests cell-autonomous light responses that are largely independent of the canonical visual transduction pathway.
The time of presentation of wound infection after cardiac surgery.
Clinical experience indicates that many wound infections present relatively late after cardiac surgery. Hence, timing may be an important issue in using this outcome as a clinical indicator. A database of 1000 patients who underwent cardiac surgery was accessed to ascertain baseline characteristics, the type of surgery, and the time of presentation of wound infections. The overall incidence of wound infection was 5.9% (59/1000). Only 36% (21/59) of the wound infections presented while the patient was in hospital. Diabetics were more likely to have a late presentation of a wound infection (the median time of presentation of wound infections (more than 17 days), i.e. 10/29 (33.4%) versus 98/971 (10.1%), Fisher's exact test P < 0.01). Wound infection can only be regarded as a reliable clinical indicator after cardiac surgery if patients are reviewed with care for 6 weeks after surgery.