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Biomedical subjects

D J Hayes

Publications and source records attributed to D J Hayes.

At least 19 recordsLinked to original sources
PubMed2004

Development and transferability of a cost-effective laparoscopic camera navigation simulator.

BACKGROUND: Laparoscopic camera navigation (LCN) is vital for the successful performance of laparoscopic operations, yet little time is spent on training. This study aimed to develop an inexpensive LCN simulator, to design a structured curriculum, and to determine the transferability of skills acquired. METHODS: In this study, 0 degrees and 30 degrees LCN simulators were developed for use on a videotrainer platform. Transferability was tested by enrolling 20 medical students in an institutional review board-approved, randomized, controlled, blinded protocol. Subjects viewed a video tutorial and were pretested in LCN on a porcine Nissen model. Procedures were videotaped and the LCN performance was scored by a blinded rater according to the number of standardized verbal cues required and the percentage of time an optimal surgical view (%OSV) was obtained. Procedure time also was recorded. Subjects were stratified and randomized. The trained group practiced on the LCN simulator until competency was demonstrated. The control group received no training. Both groups were posttested on the porcine Nissen model. RESULTS: The constructed simulators required 35 man hours for development, cost $25 per board for materials, and proved to be durable. The trained group demonstrated significant improvement in verbal cues (p = 0.001), %OSV (p < 0.001), and procedure time (p = 0.001), whereas the control group showed improvement only in verbal cues (p < 0.02). At posttesting, the training group demonstrated significantly better scores for verbal cues (2.1 vs 8.0; p = 0.02) and %OSV (64% vs 45% p = 0.01) than the control group. CONCLUSION: These data suggest that the LCN simulator is cost effective and provides trainees with skills that translate to the operating room.

Adult↗
PubMed2001

Desorption-ionization mass spectrometry using deposited nanostructured silicon films.

We present a method for desorption ionization on silicon based on novel column/void-network-deposited silicon thin films. A number of different peptides and proteins in the < or = 6000 Daltons range are analyzed by time-of-flight mass spectrometry in this demonstration of our approach. A variety of sample preparation conditions, including the use of chemical additives, surface treatments, and sample purification are used to show the potential of mass analysis using deposited column/void-network silicon films for high throughput proteomic screening.

Citric Acid↗
PubMed2001

Transcription factors in melanocyte development: distinct roles for Pax-3 and Mitf.

A transgenic mouse model was used to examine the roles of the murine transcription factors Pax-3 and Mitf in melanocyte development. Transgenic mice expressing beta-galactosidase from the dopachrome tautomerase (Dct) promoter were generated and found to express the transgene in developing melanoblasts as early as embryonic day (E) 9.5. These mice express the transgene in a pattern characteristic of endogenous Dct expression. Transgenic mice were intercrossed with two murine coat color mutants, Splotch (Sp), containing a mutation in the murine Pax3 gene, and Mitf(mi), with a mutation in the basic-helix-loop-helix-leucine zipper gene Mitf. Transgenic heterozygous mutant animals were crossed to generate transgenic embryos for analysis. Examination of beta-galactosidase-expressing melanoblasts in mutant embryos reveals that Mitf is required in vivo for survival of melanoblasts up to the migration staging area in neural crest development. Examination of Mitf(mi)/+ embryos shows that there are diminished numbers of melanoblasts in the heterozygous state early in melanocyte development, consistent with a gene dosage-dependent effect upon cell survival. However, quantification and analysis of melanoblast growth during the migratory phase suggests that melanoblasts then increase in number more rapidly in the heterozygous embryo. In contrast to Mitf(mi)/Mitf(mi) embryos, Sp/Sp embryos exhibit melanoblasts that have migrated to characteristic locations along the melanoblast migratory pathway, but are greatly reduced in number compared to control littermates. Together, these results support a model for melanocyte development whereby Pax3 is required to expand a pool of committed melanoblasts or restricted progenitor cells early in development, whereas Mitf facilitates survival of the melanoblast in a gene dosage-dependent manner within and immediately after emigration from the dorsal neural tube, and may also directly or indirectly affect the rate at which melanoblast number increases during dorsolateral pathway migration.

Animals↗
PubMed2000

Cell-density-dependent regulation of expression and glycosylation of dopachrome tautomerase/tyrosinase-related protein-2.

The expression of the dopachrome tautomerase gene (Dct) and its protein product, tyrosinase-related protein-2, was studied in the cultured, phorbol-ester-dependent murine melanocyte cell line melan-a. Increased cell density was found to stimulate Dct expression both in cells stably transfected with a Dct promoter-lacZ construct and endogenously in nontransfected cells. Increased Dct expression under these conditions corresponds to increased tyrosinase-related protein-2 production. Tyrosinase-related protein-2 was found to exist in two distinct glycoforms with different endoglycosidase sensitivities. Density-dependent expression of tyrosinase-related protein-2 was independent of time of cell growth, cell proliferation, and soluble factors, implying that cell-cell contact is the important determinant governing increased Dct expression under these conditions. Tyrp1 gene expression and tyrosinase-related protein-1 production were also induced under similar conditions. The results show that cell-cell contact between melanocytes induces a coordinated response at both transcriptional and nontranscriptional levels that induces production of the tyrosinase-related proteins that have a significant role in melanization.

Animals↗
PubMed1998

Novel bisphosphonate inhibitors of phosphoglycerate kinase.

A series of novel, conformationally-restrained bisphosphonate analogues of 1,3-bisphosphoglyceric acid 1 have been synthesised and evaluated as inhibitors of 3-PGK. They are competitive inhibitors of the human enzyme and, especially for certain alpha-halophosphonic acid analogues, both Ki and IC50 values extend into the submicromolar range.

Diphosphonates↗
PubMed1997

Efflux of 6-deoxy-D-glucose from Plasmodium falciparum-infected erythrocytes via two saturable carriers.

Glucose transport in human erythrocytes infected with the malaria parasite, Plasmodium falciparum, has been studied using 6-deoxy-D-glucose (6DOG) as a non-metabolised glucose analogue. Inhibition studies using cytochalasin B, a powerful inhibitor of the erythrocyte glucose transporter, GLUT1, indicate that in the infected red blood cell (IRBC), glucose is transported via a saturable carrier. However, inhibition is not as complete as in the uninfected erythrocyte. The synergistic inhibition effect of 6DOG entry by niflumic acid, an inhibitor of the non-specific malaria-induced pore, in the presence of cytochalasin B suggests that some glucose may also enter the infected erythrocytes through the pore, if entry via the carrier is blocked. The time course of 6DOG efflux from infected erythrocytes in the presence of cytochalasin B did not follow simple first-order kinetics. To elucidate the kinetic mechanism of 6DOG efflux from the infected erythrocytes, the concentration dependence of efflux was determined. Eight two-compartment kinetic models were simulated, involving first-order pore diffusion and carrier-mediated saturable diffusion in two systems, one ductless and one assuming the existence of a parasitophorous duct. The only two models showing reasonable fits to the efflux data each involve two saturable carriers. It is likely that one of the saturable carriers is associated with the parasite itself. Evidence that the parasite carrier has different inhibitor sensitivities from that of GLUT1 is presented.

Animals↗
PubMed1995

A colorimetric method for the determination of lipoxygenase activity suitable for use in a high throughput assay format.

A rapid and sensitive method for measuring the activity of lipoxygenase is described. The assay is based on the principle that under acidic conditions a lipid hydroperoxide can oxidize Fe2+ to Fe3+ which then oxidizes xylenol orange to form a product that absorbs strongly in the visible region (see Z-Y. Jiang, A. C. S. Woollard, and S. P. Wolff, Lipids 26, 853-856, 1991). This methodology was modified to measure lipoxygenase activity and the system was optimized using platelet 12-lipoxygenase. This assay is suitable for use in a 96-well microtiter plate and may be utilized as a high throughput screen for the identification of novel lipoxygenase inhibitors.

12-Hydroxy-5,8,10,14-eicosatetraenoic Acid↗
PubMed1995

A comparison of preferences for pork sandwiches produced from animals with and without somatotropin administration.

Experimental auction markets were designed and used to investigate consumer preferences for sandwiches produced with meat from pigs treated with porcine somatotropin. A second-price, sealed-bid auction procedure was used to determine willingness to pay to exchange a pork loin sandwich with leaner meat from pigs treated with somatotropin for a similar sandwich with meat from untreated pigs. The research was conducted using a sample of 114 undergraduate students in Iowa, Arkansas, Massachusetts, and California. At the end of the experiment 33 of 58 subjects would not bid to change their leaner pork for typical pork, whereas 15 of 56 subjects would not bid to change their typical pork for leaner pork. The results suggest a preference for leaner meat from the treated pigs, but also the potential for niche markets for meat and meat products from untreated pigs.

Animals↗
PubMed1994

Consumer acceptability of milk from cows treated with bovine somatotropin.

Experimental auction markets were used to investigate the acceptability to undergraduate students of milk from cows treated with bST. The auction market was used to elicit willingness of participants to pay to exchange "bST milk" for "normal" milk when given repeated market participation. The results suggest that more than 60% of participants would purchase milk from cows treated with bST at economically feasible discounts.

Animals↗
PubMed1992

Treatment of experimental NADH ubiquinone reductase deficiency with menadione.

Chronic administration of diphenylene iodonium (DPI) to rats has been shown to model the characteristics of mitochondrial myopathy. Using this model the efficacy of menadione therapy has been assessed. Menadione treatment of rats injected with DPI was associated with improved weight gain and increased survival rate. This was accompanied by an improvement in muscle function as judged by analysis of isometric twitch tension of the gastrocnemius muscle (1 Hz for 20 min). The decline in phosphocreatine (PCr) levels in the gastrocnemius muscle during stimulation and delayed recovery in PCr after stimulation were similar in the menadione treated and untreated models. Menadione treatment of the DPI model resulted in a resting intramuscular pH significantly lower than control or untreated DPI rats, but a similar decline in intramuscular pH to the DPI rats during stimulation. The changes in metabolite levels were broadly similar in both the menadione treated and untreated DPI models following stimulation, although the changes, except for increased lactate concentration, were generally less marked in the menadione-treated DPI model.

Adenosine Diphosphate↗
PubMed1991

Applications of piezoelectric fluid jetting devices to neuroscience research.

Piezoelectric pumps or "jets" are used in industry for precise dispensing of small volumes of fluids. In the present work we have tested the feasibility of using these piezoelectric devices for dispensing fluids in neurobiological research. In one experiment, 70 picoliter (pl) droplets of histochemical reagent were jetted onto discrete targets of frozen tissue sections, and qualitative and quantitative histochemical studies were done on the small (170 microns diameter) circle of tissue wet by the droplets. In the second experiment, 70 pl droplets of neuroactive drugs were jetted onto brain tissue slices while recording single neurons extracellularly in vitro, and the effects of the drugs were found to vary systematically as a function of the number of drops and the distance between drop application and the recorded neuron. The results indicate that piezoelectric jets could have wide application for dispensing fluids in neurobiological research.

Administration, Topical↗
PubMed1991

Alterations in cysteine proteinase content of rat lung associated with development of Pneumocystis carinii infection.

The rate of hydrolysis of three cysteine-type proteinase substrates, N-benzyloxycarbonyl-Arg-Arg-4-methyl-7-coumarylamide (AMC) (cathepsin B), Arg-AMC (cathepsin H), and N-benzyloxycarbonyl-Phe-Arg-AMC (cathepsin L), were determined in rat lung throughout the time course of the induction of Pneumocystis carinii infection by immunosuppression. Cathepsin B-like and cathepsin L-like activities fell below control values initially, but from week 8 of the immunosuppressive treatment significant increases above the control were noted. Cathepsin H-like activity was greater than control levels from week 3, and by week 12 it was 7,600% of the mean control value. When compared with the relative degree of infection, as assessed from the number of cysts present in lung impression smears, cathepsin B-like and cathepsin L-like activities were significantly increased only at heavy parasite burdens while cathepsin H-like activity displayed a close correlation with parasite number (r = 0.884; P less than 0.001). Activity was detected in lysates of purified P. carinii with all three substrates. Treatment of heavily infected animals with co-trimoxazole cleared the lungs of P. carinii, and this was accompanied by a marked reduction in proteinase activity, in particular, cathepsin H-like activity, which fell from 108- to 3-fold the mean control value following drug treatment. Analysis of cathepsin H isozyme patterns by fluorography following isoelectric focusing revealed differences between treated and control lung samples. In the immunosuppressed group, there was a time-dependent increase in the intensity of some of the bands observed in the controls and an appearance of several novel bands which corresponded to bands observed in lysates of P. carinii. It is likely, therefore, that the increased proteinase activity observed in the treated group is due, at least in part, to isozymes from P. carinii; consequently, cathepsin H-like activity might be of use diagnostically in the identification of P. carinii infection and in the estimation of parasite burden.

Animals↗
PubMed1990

The effect of two novel analogues of antimycin A on oxygen consumption and survival of filarial nematodes in vitro.

The effects of two novel analogues of antimycin A (BWA466C and BWA728C) on filarial oxygen consumption, energy generation and survival were investigated in vitro. For comparison, incubations were performed with a range of mitochondrial respiration inhibitors. All compounds tested (rotenone, antimycin A, KCN, oligomycin, CCCP, rafoxanide, BWA466C and BWA728C) inhibited oxygen uptake. The two analogues were less potent than antimycin A at impairing respiration of either filariae or beef heart submitochondrial particles. However, the two compounds affected motility and were lethal in vitro. Although the analogues affected oxygen uptake similarly to antimycin A itself, the levels of ATP were significantly lower than those noted in the presence of antimycin A. Glucose consumption and lactate output were markedly reduced by BWA466C and BWA728C. Glucose transport (measured as 2-deoxy-[2,6-3H]glucose) was reduced after treatment with BWA728C. It is likely that a combination of the effects on glucose transport and inhibition of oxidative pathways of carbohydrate metabolism may lead to worm death in vitro.

Adenine Nucleotides↗
PubMed1990

An investigation of fructose utilization in Acanthocheilonema viteae.

The capacity of Acanthocheilonema viteae to metabolize fructose was investigated in vitro. In common with other filarial species A. viteae oxidized fructose to lactate but its rate of consumption was only 40% of the glucose-containing control value. Fructose was not incorporated into glycogen. Release of 14CO2 from [U-14C]fructose was not detected in the presence of glucose and was about 40% of the glucose-containing value under conditions where fructose was the sole hexose substrate. Fructose consumption and lactate excretion increased in proportion to the external concentration of fructose. However, worm viability was not maintained in fructose over a 120 h in vitro incubation. In the presence of fructose, protein synthesis (measured incorporation of [35S]methionine into acid-insoluble material) was reduced compared to the glucose-containing control group; but was significantly greater than the value obtained under glucose-free conditions.

Animals↗
PubMed1990

Glucose transport in Acanthocheilonema viteae.

The uptake of glucose by Acanthocheilonema viteae was studied in vitro. The process was selective for the D-isomer and saturatable with a Km of 2 mM. The rate of glucose transport/utilization was inhibited by 2-deoxyglucose, mannose, 5-thioglucose and dipyridamole but, unlike mammalian systems, was not impaired by cytochalasin B, phloretin, phloridzin, 3-O-methylglucose and 4,6-ethylideneglucose. A potential chemotherapeutic advantage of selectively inhibiting filarial glucose transport exists for the following reasons. (1) The glucose transporter present in A. viteae was shown to be different from the one present in some mammalian systems. (2) Incubation under glucose-free conditions led to glycogen depletion, loss of motility and worm death. (3) Worms maintained in vitro for more than 18 h without glucose did not survive when implanted into gerbils.

Animals↗
PubMed1988

A 31P-NMR study of the acute effects of altered beta-adrenoceptor stimulation on the bioenergetics of skeletal muscle during contraction.

The effects of acute administration of a beta-adrenoceptor agonist (isoprenaline) or antagonist (propranolol) on skeletal muscle contraction and metabolism in the rat have been studied in vivo using 31P-nuclear magnetic resonance spectroscopy and conventional metabolite analysis. In resting muscle, isoprenaline caused a three-fold increase in cyclic AMP concentration, whereas propranolol decreased cyclic AMP concentration by 40%. Isometric contraction of gastrocnemius muscle at a frequency of 4 Hz was caused by supramaximal sciatic nerve stimulation. Altered beta-adrenoceptor stimulation had no effect on contractile performance at any time during the 30 min stimulation period. During the initial stimulation period (0-4 min) intracellular pH decreased to significantly lower values in the isoprenaline-treated animals (6.24 +/- 0.03) compared to either the control (6.44 +/- 0.08) or propranolol-treated (6.42 +/- 0.08) groups. During the subsequent stimulation period (after 15-30 min stimulation at 4 Hz), pH recovered in all experimental groups to values greater than 6.90 and phosphocreatine concentration achieved a constant level at 35-40% of resting values. Calculation of free ADP concentrations using 31P-NMR determined metabolite concentrations and the creatine phosphokinase equilibrium showed that at similar tension development, [ADP]free varied between the three experimental groups; with the lowest (47 +/- 4 microM) and highest (73 +/- 4 microM) values being calculated for the beta-adrenoceptor agonist- and antagonist-treated groups respectively. Upon termination of stimulation, recovery of phosphocreatine concentration to pre-stimulation values was rapid and similar in all experimental groups. However, gastrocnemius muscle ATP concentration, determined by 31P-NMR and analysis of freeze-clamped muscle, was lower in the isoprenaline-treated group. This study has shown that although altered beta-adrenoceptor stimulation had no effect on contractile performance, significant changes in muscle metabolism were observed in vivo; these effects are discussed with respect to the role of beta-adrenoceptors in skeletal muscle.

Adenine Nucleotides↗