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J C Hall

Publications and source records attributed to J C Hall.

At least 55 records · Page 3Linked to original sources
PubMed2000

Monoclonal-based ELISA for the identification of herbicidal cyclohexanedione analogues that inhibit graminaceous acetyl coenzyme-A carboxylase.

Cyclohexanediones are one of four known structural classes of herbicides that inhibit graminaceous acetyl coenzyme-A carboxylase (ACCase; EC 6.4.1.2). Five monoclonal antibodies were raised against cyclohexanediones conjugated to bovine serum albumin. Cross-reactivity studies using a homologous competitive indirect enzyme-linked immunosorbent assay (ciELISA) against 24 cyclohexanedione analogues revealed that two monoclonal antibodies (mAb A and mAb B) could segregate the analogues into active and inactive ACCase inhibitors on the basis of the analogue concentration required to inhibit 50% of antibody binding to the coating conjugate (IC(50)). Both mAb A and mAb B were also found to cross-react with various members of the indolizidinedione structural class of ACCase inhibitors in ciELISA, suggesting that both cyclohexanediones and indolizidinediones possess features recognized by monoclonal antibodies important for the inhibition of ACCase activity. In conclusion, pharmacophore-specific antibodies may be potentially valuable screening tools for the identification of new lead chemistries in a pesticide discovery program.

Acetyl-CoA Carboxylase↗
PubMed2000

Development and evaluation of an immunological approach for the identification of novel acetyl coenzyme-A carboxylase inhibitors: assay optimization and pilot screen results.

Cyclohexanediones, aryloxyphenoxypropionates, indolizidinediones, and triazinediones are four known structural classes of herbicides that inhibit acetyl coenzyme-A carboxylase (ACCase; EC 6.4.1.2). An immunological study to determine the potential of ACCase inhibitor-specific monoclonal antibodies as screening tools to identify novel lead chemistry was undertaken. Using two cyclohexanedione-specific monoclonal antibodies (mAb A and mAb B; Webb, S. R.; Hall, J. C. J. Agric. Food Chem. 2000, 48, 1210-1218) and three different cyclohexanedione hapten coating conjugates, competitive indirect enzyme-linked immunosorbent assays (ciELISA) were developed. Cross-reactivity of the monoclonal antibodies with four structural classes of ACCase inhibitors revealed that the ciELISA using mAb A and a modified cyclohexanedione hapten coating conjugate detected analogues from all four known classes of ACCase inhibitors. A pilot screen using this ciELISA format identified two novel ACCase inhibitors, demonstrating the potential for antibodies as rapid and cost-effective screening tools for identifying novel lead chemistry in pesticide discovery programs.

Acetyl-CoA Carboxylase↗
PubMed2000

Interaction of cyclohexanediones with acetyl coenzyme-A carboxylase and an artificial target-site antibody mimic: a comparative molecular field analysis.

Similarities and differences between steric and electrostatic potentials of a monoclonal-antibody-based surrogate of a herbicide target-site and its in vitro enzyme target were investigated using three-dimensional quantitative structure-activity relationship comparative molecular field analysis (3D-QSAR CoMFA). Two separate, five-component, partial least squares CoMFA models were developed to compare the interaction of cyclohexanedione herbicides with their target site, acetyl coenzyme-A carboxylase (ACCase; EC 6.4.1.2) and a cyclohexanedione pharmacophore-specific monoclonal antibody (mAb A). On the basis of CoMFA models, similarities in steric and electrostatic requirements around position 2 of the binding site for the oxime functional group of the cyclohexanedione molecule appear to be crucial for interaction of the herbicide with both ACCase and mAb A. These similarities explain the observed quantitative relationship between binding of cyclohexandedione herbicides to ACCase mAb A. Furthermore, these results support the production and use of mAb-based surrogates of pesticide targets as screening tools in pesticide discovery programs.

Acetyl-CoA Carboxylase↗
PubMed2000

Metabolism and fate of [(14)C]ethametsulfuron-methyl in rutabaga (Brassica napobrassica Mill).

The metabolism and fate of ethametsulfuron-methyl ¿methyl 2-[[[[[4-ethoxy-6-(methylamino)-1,3, 5-triazin-2-yl]amino]carbonyl]amino]sulfonyl]benzoate¿ in rutabaga were investigated. After 72 h, absorption and translocation of [(14)C]ethametsulfuron-methyl in rutabaga did not change for the duration of the study (50 days). Less than 4% of recovered radioactivity was present in the rutabaga root. Ethametsulfuron-methyl was metabolized through a proposed unstable alpha-hydroxy ethoxy intermediate that dissipated 3 days after treatment to two major metabolites, O-desethylethametsulfuron-methyl and N-desmethyl-O-desethylethametsulfuron-methyl, as determined by liquid chromatography-mass spectrometry. It was estimated that at a spray dose of 30 g of active ingredient ha(-)(1) and a harvest weight of 0.5 kg, the edible portion of the rutabaga root would contain no ethametsulfuron-methyl and approximately 1.3 ppb total of both identified metabolites. Residue analysis and toxicological assessment show that ethametsulfuron-methyl and its metabolites should pose little or no risk to consumers of rutabagas.

Absorption↗
PubMed2000

Metabolism-based resistance of a wild mustard (Sinapis arvensis L.) biotype to ethametsulfuron-methyl.

Under controlled-environment conditions, ethametsulfuron-methyl doses that inhibited growth by 50% (ED(50)) were >100 and <1 g of active ingredient (ai) ha(-)(1) for ethametsulfuron-methyl-resistant (R) and -susceptible (S) wild mustard, respectively. There were no differences between the two biotypes with regard to absorption and translocation of the herbicide. Three days after treatment, approximately 90, 5, and 2% of the applied [(14)C]ethametsulfuron-methyl was found in the treated leaf, foliage, and roots of each biotype, respectively. Acetolactate synthase extracted from the two biotypes was equally sensitive to both ethametsulfuron-methyl and chlorsulfuron. These results indicate that resistance was not due to differences in the target site, absorption, or translocation. However, ethametsulfuron-methyl was metabolized more rapidly in the R than the S biotype. Approximately 82, 73, 42, 30, and 17% of the recovered radioactivity remained as ethametsulfuron-methyl in R wild mustard 3, 6, 18, 48, and 72 h after treatment, respectively. Conversely, 84, 79, 85, and 73% of the (14)C was ethametsulfuron-methyl in the S biotype 12, 24, 48, and 72 h after treatment, respectively. On the basis of these results, it is proposed that resistance is due to enhanced metabolism of ethametsulfuron-methyl in the R biotype.

Absorption↗
PubMed2000

A newly uncovered phenotype associated with the fruitless gene of Drosophila melanogaster: aggression-like head interactions between mutant males.

Male sexual behavior is regulated by the sex-determination hierarchy (SDH) in Drosophila melanogaster. The fruitless (fru) gene, one of the regulatory factors functioning downstream of other SDH factors, plays a prominent role in male sexual behavior. Here we demonstrate that fru mutations cause a previously unappreciated behavioral anomaly: high levels of head-to-head interactions between mutant males. These apparent confrontations between males are exhibited by all of the homozygous-viable fru mutants (expressing the effects of a given allele, among the four tested). Mutant dissatisfaction (dsf) males also exhibit this behavior at higher-than-normal levels, but it was barely displayed by doublesex or intersex mutants. For fru, a social component is involved in the head-interaction phenotype, while increasing age is a modifying factor for the behavior of dsf males. We suggest that head-to-head interactions, especially those performed by fru males, are instances of putative aggression analogous to those exhibited by wild-type males and that head interactions are, to an extent, operationally separable from courtship behavior.

Aggression↗
PubMed2000

Acquiring surgical skills.

BACKGROUND: Technical competence is the bedrock of surgery, yet it has only recently been viewed as a valid area for either critical evaluation or formal teaching. METHODS: This review examines the teaching of surgical skills. The core is derived from a literature search of the Medline computer database. RESULTS AND CONCLUSION: The impetus for surgical change has generally related to the introduction of new technology. Advances initially allowed for open operation within the main body cavities; more recently minimal access surgery has appeared. The latter was introduced in an inappropriate manner, which has led to the evolution of teaching of technical skills away from an apprenticeship-based activity towards more formal skill-based training programmes. There is now a need for a solid theoretical base for the teaching of manual skills that accommodates concepts of surgical competence.

Clinical Competence↗
PubMed2000

Branched-chain amino acids.

The branched-chain amino acids (BCAA), isoleucine, leucine and valine, are unique in that they are principally metabolized extrahepatically in the skeletal muscle. This observation led to the investigation of these nutrients in a number of clinical scenarios. By far the most intensively studied applications for BCAA have been in patients with liver failure and/or patients in catabolic disease states. However, the resulting studies have not demonstrated a clear clinical benefit for BCAA nutritional supplements. In patients with liver failure, the BCAA did improve nitrogen retention and protein synthesis, but their effect on patient outcome was less clear. Similarly, in critically ill septic patients, BCAA did not improve either survival or morbidity. The BCAA are important nutrients, and it seems that any specific benefits associated with their use will be based upon a greater understanding of the underlying cellular biology. Potential areas of further research may include the combination of BCAA supplements with other anabolic factors (e.g. growth hormone) in managing patients with catabolic disease states.

Amino Acids, Branched-Chain↗
PubMed2000

Antibiotic prophylaxis for patients undergoing breast surgery.

Some groups of patients undergoing clean surgery benefit from the provision of antibiotic prophylaxis against wound infection. Breast surgery may belong to this category because several substantial studies have reported that it is accompanied by an unacceptably high rate of wound infection. However, only two clinical trials have addressed this issue and both produced equivocal results. Resolution of this problem is important because, aside from the usual advantages obtained by preventing such complications, wound infection diminishes the proportion of patients with breast cancer who start adjuvant regimens within an optimum time after surgery.

Antibiotic Prophylaxis↗
PubMed2000

Aberrant splicing and altered spatial expression patterns in fruitless mutants of Drosophila melanogaster.

The fruitless (fru) gene functions in Drosophila males to establish the potential for male sexual behaviors. fru encodes a complex set of sex-specific and sex-nonspecific mRNAs through the use of multiple promoters and alternative pre-mRNA processing. The male-specific transcripts produced from the distal (P1) fru promoter are believed to be responsible for its role in specifying sexual behavior and are only expressed in a small fraction of central nervous system (CNS) cells. To understand the molecular etiology of fruitless mutant phenotypes, we compared wild-type and mutant transcription patterns. These experiments revealed that the fru(2), fru(3), fru(4), and fru(sat) mutations, which are due to P-element inserts, alter the pattern of sex-specific and sex-nonspecific fru RNAs. These changes arise in part from the P-element insertions containing splice acceptor sites that create alternative processing pathways. In situ hybridization revealed no alterations in the locations of cells expressing the P1-fru-promoter-derived transcripts in fru(2), fru(3), fru(4), and fru(sat) pharate adults. For the fru(1) mutant (which is due to an inversion breakpoint near the P1 promoter), Northern analyses revealed no significant changes in fru transcript patterns. However, in situ hybridization revealed anomalies in the level and distribution of P1-derived transcripts: in fru(1) males, fewer P1-expressing neurons are found in regions of the dorsal lateral protocerebrum and abdominal ganglion compared to wild-type males. In other regions of the CNS, expression of these transcripts appears normal in fru(1) males. The loss of fruitless expression in these regions likely accounts for the striking courtship abnormalities exhibited by fru(1) males. Thus, we suggest that the mutant phenotypes in fru(2), fru(3), fru(4), and fru(sat) animals are due to a failure to appropriately splice P1 transcripts, whereas the mutant phenotype of fru(1) animals is due to the reduction or absence of P1 transcripts within specific regions of the CNS.

Amino Acid Sequence↗
PubMed2000

Involvement of the period gene in developmental time-memory: effect of the perShort mutation on phase shifts induced by light pulses delivered to Drosophila larvae.

Phases of circadian locomotor activity rhythms of adult Drosophila reared in constant darkness have been shown to be set by a light stimulus delivered as early as the first-instar larval stage. This implies that a circadian clock functions continuously throughout postembryonic development. The clock genes period (per) and timeless (tim) are expressed cyclically in the larval central nervous system of Drosophila, and daily oscillations of per expression persist throughout metamorphosis in a group of cells, which gives rise to the pacemaker cells underlying locomotor activity rhythms of adults. Therefore, PER and TIM cyclings in these neurons may be responsible for the phenomenon of "larval time-memory." In the absence of any evidence for the involvement of these genes in such a developmental clock, and because circadian-pacemaker functions are underanalyzed in terms of the functions during development, the authors tested the time-memory of a fast-clock period mutant. They show that dark-reared perS mutant individuals as well as wild-type flies can be entrained as larvae and that a brief light pulse given to such entrained larvae can induce phase shifts in animals of either genotype. However, the direction and magnitude of phase shifts were different between wild type and perS, suggesting that a clock under the control of period gene participates in the regulation of developmental time-memory. The authors show that the relevant clock can be entrained by two light input pathways, one involving the phospholipase C encoded by the norpA gene, the other mediated by the blue-light receptor cryptochrome. Phase shifts of molecular oscillations during the larval stage were smaller than those measured by adult behavior, suggesting molecularly transient responses during development.

Animals↗
PubMed2000

Molecular and behavioral analysis of sex-linked courtship song variation in a natural population of Drosophila melanogaster.

Genes controlling the "lovesong" in Drosophila are particularly interesting under a evolutionary point of view as they could be involved in the reproductive isolation between closely related species and, as a consequence, in the speciation process. We carried out a survey of sex-linked molecular and behavioral courtship song variation in 27 lines derived from a natural population of Drosophila melanogaster in Italy. We sequenced a 983 bp fragment of cacophony(cac), a calcium channel gene controlling aspects of the courtship song. The same region was also sequenced in a D. simulans strain. Only 5 non-coding sites were polymorphic among the D. melanogaster lines, and no amino acid substitutions were found between the two species. Statistical tests applied to the data did not reveal any significant deviations from a neutral model. Using the same lines we also carried out an analysis of three different song parameters which are known to be affected by the cac(S) song mutation: interpulse-interval (IPI), pulse amplitude (PA) and cycles per pulse (CPP). We found significant differences among the lines in IPI and PA, and for the latter a significant association with one of the polymorphic sites of cac.

Analysis of Variance↗
PubMed2000

Malnutrition: role of the TwoCal HN Med Pass program.

Malnutrition is common in older adults and is associated with poor outcomes. The causes and outcomes of malnutrition are discussed, and the TwoCal HN Med Pass program, designed to overcome poor dietary intake, is described. Benefits of the program, role of the pharmacist, identification of candidates for the TwoCal HN Med Pass program, and health care team roles and responsibilities are reviewed.

Aged↗
PubMed1999

A pdf neuropeptide gene mutation and ablation of PDF neurons each cause severe abnormalities of behavioral circadian rhythms in Drosophila.

The mechanisms by which circadian pacemaker systems transmit timing information to control behavior are largely unknown. Here, we define two critical features of that mechanism in Drosophila. We first describe animals mutant for the pdf neuropeptide gene, which is expressed by most of the candidate pacemakers (LNv neurons). Next, we describe animals in which pdf neurons were selectively ablated. Both sets of animals produced similar behavioral phenotypes. Both sets entrained to light, but both were largely arrhythmic under constant conditions. A minority of each pdf variant exhibited weak to moderate free-running rhythmicity. These results confirm the assignment of LNv neurons as the principal circadian pacemakers controlling daily locomotion in Drosophila. They also implicate PDF as the principal circadian transmitter.

Animals↗
PubMed1999

GABAergic inhibition shapes frequency tuning and modifies response properties in the auditory midbrain of the leopard frog.

The functional role of GABAergic inhibition in shaping the frequency tuning of 96 neurons in the torus semicircularis of the leopard frog, Rana pipiens, was studied using microiontophoresis of the GABAA receptor antagonist, bicuculline methiodide. Bicuculline application abolished, or reduced in size, the inhibitory tuning curves of 72 neurons. In each case, there was a concommitant broadening of the excitatory tuning curve such that frequency-intensity combinations that were inhibitory under control conditions, became excitatory during disinhibition with bicuculline methiodide. These effects were observed irrespective of the excitatory tuning curve configuration prior to bicuculline methiodide application. Results indicate an important role for GABA-mediated inhibition in shaping the frequency selectivity of neurons in the torus semicircularis of the leopard frog. Bicuculline application also affected several other response properties of neurons in the leopard frog torus. Disinhibition with bicuculline methiodide increased both the spontaneous firing rate (18 cells) and stimulus-evoked discharge rate (81 cells) of torus neurons, decreased the minimum excitatory threshold for 18 cells, and altered the temporal discharge pattern of 47 neurons. Additional roles for GABAergic inhibition in monaural signal analysis are discussed.

Acoustic Stimulation↗
PubMed1999

Sound duration selectivity in the pallid bat inferior colliculus.

Neurons selective for sound duration have been reported in the auditory midbrain and cortex of several specialized vertebrate species that process behaviorally relevant signals of stereotypic duration. This study examines duration selectivity in the inferior colliculus (IC) of the pallid bat to determine if this selectivity is limited to regions that serve echolocation, or if it extends to low-frequency regions that serve passive listening. It also focuses on the temporal response properties of duration-selective neurons to elucidate mechanisms that may underlie the creation of this selectivity. Of 140 neurons tested, 36% were selective for short durations of </=7 ms, and acted as short-pass or bandpass duration filters. Sixteen percent, termed long duration neurons, differed in that they required minimum sound durations of 5-50 ms before responding, and all acted as long-pass duration filters. Short duration neurons were equally common in the high-frequency region serving echolocation and the lateral low-frequency region that serves passive listening, indicating that selectivity for short duration sounds was not associated only with the specialized function of echolocation. Long duration neurons were most common in the medial low-frequency region IC. Selectivity for short and long duration sounds was therefore not uniformly distributed across the IC. Analyses of the temporal response properties of short duration neurons, and the application of bicuculline to block gamma-aminobutyric acid-A receptors, were used to infer the synaptic interactions that underlie the creation of duration selectivity, the role of inhibition in its creation, and whether a coincidence mechanism proposed by Casseday et al. (Science 264 (1994) 847-850) is consistent with the behavior of the duration-selective neurons recorded in the pallid bat IC. Present results suggest that while some neurons do behave in a manner that is consistent with the coincidence mechanism, the behaviors of others suggest that more than one mechanism may create a selectivity for short duration sounds.

Animals↗