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Biomedical subjects

T F Burks

Publications and source records attributed to T F Burks.

At least 19 recordsLinked to original sources
PubMed2006

Shock and vibration data acquisition system for off-road vehicle operator health and safety assessment.

A data acquisition software and hardware system was developed for acquiring geo-referenced shock and vibration data using National Instruments' LabView graphical programming language. This was used in conjunction with a modular data acquisition and signal conditioning system and a Differential Global Positioning System (DGPS) receiver. A prototype vehicle obstacle course, which introduced spatially varying shock events to vehicles as they traversed the course, was constructed. Obstacles consisted of both repetitious and single discrete events. A series of investigations was conducted on the obstacle course to evaluate the performance and characteristics of the DAQ system and the tractor when exposed to shock and vibration events. Spectral and time domain plots obtained from the geo-referenced data acquisition system (GDAQ) system under static, highway, and off-road obstacle course conditions were evaluated to demonstrate that the system performed as expected. The migration of experiments from laboratory to field gave confidence that this system could be used to collect shock and vibration data over a wide range of frequencies. The use of geo-referenced data records proved beneficial in isolating and extracting data segments of interest from a continuous data record.

Agriculture↗
PubMed2006

Distribution fitting and parameterization of individual operator work routine times for small dairy parlors.

A time and motion study was conducted at 13 small dairy farms with average herd sizes less than 100 cows. Parlors were configured with 3 to 6 stalls per side. A data acquisition methodology was developed using a video camera to gather work routine time data in the parlors. A computer-based data logger was used to extract individual event durations during video playback. Each parlor's video record was reviewed in the laboratory so that work routine times across all parlors and operators could be pooled to estimate typical operator performance. There were 34 operator work routine times associated with various procedures in milking parlors that were evaluated in this study. Individual times were compiled for each work routine and a data-fitting program called UNIFIT was used to fit the data to 1 of 4 data models: gamma, lognormal, Weibull, and Pearson #5. Each of 34 work routine variables was fitted, tested, and plotted to determine how well each of those models fit the actual data. Distributions for Pearson #5, lognormal, gamma, and Weibull models were best fitted to 12, 10, 8, and 4 work routine times, respectively. More common tasks such as attaching the milker, grabbing a towel, and drying the udder were more consistently executed and had smaller variances than routines in which the operator would leave the pit to go to the milk room or disassembled the milk collector after milking. One of the better fitting models was the lognormal distribution for the time to "attach milker," which had a low relative discrepancy to the P-P plot (model probability vs. data probability) of 0.019 and a moderate chi(2) test value of 0.358, thus demonstrating a good fit of the model to the data. Simulation tests were compared with observed data to validate models for work routine times and demonstrated that the models accurately predict parlor throughput in small- to medium-sized parlors.

Animals↗
PubMed2000

Measuring contributions to the research mission of medical schools.

The authors of this article, who were the members and staff of a research panel formed by the AAMC as part of its mission-based management initiative, reflect on the growing interest in quantitative information in the management of the research mission of medical schools. They note the serious limitations of any such system of measures for research, particularly its inability to represent directly the quality of the research effort. Despite these concerns, the authors acknowledge that leaders in academic medicine have always used quantitative measures in one form or another to compare performance or assess progress. Two factors appear to be driving increases in this practice: (1) the need to demonstrate to institutional stakeholders that resources are being used wisely and that the school's performance justifies continued investment in the research mission; and (2) the need to fashion an economic strategy to manage precious institutional resources, particularly research space. Given these realities, the authors offer guidelines for the proper development and use of measures to assess contributions by faculty, departments, and institutions to the research mission. They also comment on the measures most commonly used in four areas: grants and other revenue-generating activities; publications; faculty members' research reputation and contributions to the national research enterprise; and support to the general research mission of the school. The authors conclude that quantitative information can help institutional leaders in important management decisions. However, the potential for misuse is great. The key is always to regard this information as an aid to judgment, not a substitute for it.

Research↗
PubMed1997

Interactions of oxytocin and vasopressin with CRF on the rat colon.

Corticotropin-releasing factor (CRF), a primary mediator of stress responses, produces changes in the gastrointestinal tract identical to those induced by stress. CRF is tenfold more potent in females than in males, but gonadectomy reverses this difference. We postulated that positive modulators of CRF, such as oxytocin (OT) and vasopressin (AVP), may act in females to potentiate effects of CRF and thus could account for the gender-related differences in colonic sensitivity to CRF and stress. Given with CRF, neither OT, peripheral AVP, nor central AVP increased colonic transit any more than CRF alone, suggesting that OT and AVP do not potentiate CRF's actions in the colon. These data indicate that endogenous OT and AVP do not directly affect colonic transit, and that OT and AVP do not account for the gender-related differences in the effects of stress and CRF on colonic transit.

Animals↗
PubMed1997

Cholecystokinin-induced antinociception is not blocked by CCK-A or CCK-B receptor antagonists.

To determine the relative importance of CCK-A, CCK-B, and opioid receptors in mediating the antinociceptive actions of cholecystokinin, we evaluated the actions of selective agonists and antagonists in the mouse hot plate assay. The agonists used were CCK (1-30 nmol i.c.v.), a CCK-A receptor agonist (SNF9019; 0.3-10 nmol i.c.v.), and a CCK-B receptor agonist (SNF9007; 0.3-10 nmol i.c.v.). The antagonists used were the CCK-A receptor antagonist, L364,718 (12.5 nmol i.c.v.), CCK-B receptor antagonist, L365,260 (2.5-25 nmol i.c.v.), and the nonselective opioid receptor antagonist naloxone (1 mg/kg s.c.). CCK and its receptor-selective analogues, SNF9019 and SNF9007, resulted in antinociception that was blocked by naloxone, but was not antagonized by L364,718 or L365,260. In contrast, in positive control experiments, the inhibitory effects of CCK, SNF9019, and SNF9007 on gastrointestinal propulsion in mice were antagonized by identical i.c.v. doses of L364,718 and L365,260. We conclude that centrally administered CCK produces antinociception in the mouse hot plate assay via opioid receptors, but independent of CCK-A or CCK-B receptors. It is necessary to speculate that other CCK receptors, not antagonized by currently available selective antagonists, may exist.

Analgesia↗
PubMed1997

Morphine tolerance and dependence in the rat intestine in vivo.

There has been no previous demonstration of opioid tolerance and dependence with respect to the propulsive and contractile activities of the gut in vivo. In the experiments described herein, morphine was administered continuously (1 mg/kg/hr s.c., 72 hr) and/or by bolus injection (2 mg/kg) and intestinal motility and transit were evaluated in unanesthetized rats. Tolerance in intestinal motility (contractions) and propulsion (transit) was measured in two ways, i.e., by measuring the time required for motility and propulsion to return to control values and by measuring the loss of effectiveness of bolus morphine administered to animals receiving continuous infusion of the opiate. The dose of morphine chosen for continuous administration (1 mg/kg/hr s.c. via Alzet minipumps) was based on the dose at which morphine inhibited intestinal propulsion by 50%. Morphine (1 mg/kg/hr) decreased the frequency of contractions in, and propulsion along, the small bowel and colon and produced mild antinociception. The frequency of duodenal and colonic contractions returned to normal within 13 to 16 hr. After 24 hr of morphine treatment, the inhibitory effects of bolus doses of morphine on motility and transit were diminished; the effects were eventually lost (48 hr). Similarly, the antinociceptive effects of bolus doses of morphine were diminished by 18 hr and lost by 24 hr. Naloxone (0.1 mg/kg s.c.) given to morphine-tolerant animals (72 hr) resulted in an increase in the frequency and amplitude of contractions in the colon, an increase in the propulsive activity of the small intestine and colon and diarrhea. These results provide direct demonstration of opioid tolerance and dependence of contractile and propulsive activity in the rat intestine in vivo.

Animals↗
PubMed1996

Inhibition of adenylyl cyclase activity by the cholecystokinin analog SNF 9007 in neuroblastoma x glioma NG108-15 hybrid cells.

The effect of the cholecystokininB (CCKB) receptor-selective cholecystokinin octapeptide (CCK-8) analog SNF 9007 on forskolin-stimulated adenylyl cyclase activity in NG108-15 hybrid cells was measured. The activity of SNF 9007 was compared to the delta opioid agonists D-Pen2-D-Pen5-enkephalin (DPDPE, delta 1 receptor-selective) and Tyr-D-Ala-Phe-Glu-Val-Val-Gly-NH2, (D-Ala2-deltorphin II, delta 2-receptor-selective) because SNF 9007 binds with moderate affinity to delta opioid receptors. SNF 9007 inhibited forskolin-stimulated adenylyl cyclase activity with efficacy similar to DPDPE. IC50 determinations showed that D-Ala2-deltorphin II was the most potent, followed by DPDPE, then SNF 9007 (IC50 values = 0.013, 0.21 and 4.8 microM, respectively). CCK-8 had no effect on adenylyl cyclase activity. The delta 1 receptor-selective antagonist 7-benzylidenenaltrexone hydrochloride (BNTX, 10 nM) had no effect on the activity of any of these agonists, but the delta 2 receptor-selective antagonist naltriben methanesulfonate (NTB, 10 nM) increased IC50 values of all the agonists. Combinations of BNTX and NTB (10 nM each) increased the D-Ala2-deltorphin II IC50 value 12-fold, the DPDPE IC50 value 18-fold and the SNF 9007 IC50 value 26-fold. The effect of the combined delta antagonists on SNF 9007 activity was different from the effect on DPDPE or D-Ala2-deltorphin II activity. These data suggest that the interaction of the CCK-8 analog SNF 9007 with opioid receptors in NG108-15 hybrid cells is different from the interaction of opioid peptides with these receptors.

Adenylyl Cyclase Inhibitors↗
PubMed1995

In vitro brainstem-gastric preparation with intact vagi for study of primary visceral afferent input to dorsal vagal complex in caudal medulla.

An in vitro neonatal rat preparation, consisting of the isolated caudal brainstem and stomach joined by the intact vagi, was developed using Sprague-Dawley rats. The animals were 0 to 4 days of age. This preparation provided an opportunity to investigate the extracellular and intracellular responses of neurons in the nucleus tractus solitarius (NTS) of the brainstem to electrical stimulation of subdiaphragmatic vagal fibers. The dorsal and ventral vagal branches were electrically stimulated at the point of the common subdiaphragmatic vagal trunk. The isolated preparation was superfused in a recording chamber at 28 degrees C with a modified Krebs solution, equilibrated with 95% O2 and 5% CO2. Suction microelectrodes, for electrical stimulation, were positioned on the common vagal trunk just below the diaphragm to evaluate extracellular and intracellular evoked responses in NTS. A total of 204 subdiaphragmatic vagally-evoked (SDVe) brainstem unitary responses in the NTS were recorded. The mean latency of the extracellular SDVe brainstem responses was 89 +/- 12.9 ms (mean +/- SD). The peripheral gastric effects of CCK-8 on SDVe unitary responses in NTS neurons were evaluated. The peptide caused a significant increase in the excitability of these NTS neurons which was blocked by the CCKA receptor antagonist L-364,718. Neurons in the NTS and the dorsal motor nucleus of the vagus which showed excitatory responses to vagal stimulation were filled with Lucifer Yellow to evaluate their morphology.

Afferent Pathways↗
PubMed1994

Pharmacology in the new era of higher education: view from the USA.

We are witnessing great changes in higher education in the USA, with profound implications for all of the biomedical sciences, including pharmacology. Higher education from 1950 to approximately 1980 witnessed expansion of scientific knowledge and expertise, increased numbers of health professional schools, more revenues for support of education and research, creation of new research institutes and growth of academic departments. We have now entered into a new era characterized by continuing expansion of knowledge, but with static or diminishing sizes and possibly numbers of schools and institutes, shrinkage of revenues, substitution of expertise and consolidation of departments. There have been many worthwhile scientific advances that should lead to new directions in education and research, but there are few resources available for supporting these new educational and research ventures. This article by Thomas Burks is adapted from the annual Croker Lecture, which was delivered at the 1994 meeting of the American Society for Pharmacology and Experimental Therapeutics.

Education, Pharmacy↗
PubMed1994

The essential role of integrative biomedical sciences in protecting and contributing to the health and well-being of our nation.

The biomedical sciences in the United States are currently experiencing the effects of an increased emphasis on in vitro models of biological and disease processes. Advances in cellular and subcellular biology have been a driving force in the funding of new research, the training of new scientists, and new drug discovery and development. The importance of new findings at the cellular and subcellular levels is not disputed. However, the corresponding decline in funding and training opportunities for biologically relevant investigations at the level of the intact animal (including humans; hereafter designated as integrative biology) is a serious threat to continued biomedical advances. The lack of resources for integrative biology has far-reaching negative consequences in 1) the development and utilization of whole animal models of disease and dysfunction; 2) assessing the relevancy of in vitro studies to physiological mechanisms; 3) the evaluation of the scientific merit of whole animal investigations and their relevancy to the nation's scientific imperatives; 4) the instruction of young scientists in the technology and especially in the methods of integrative biology, including how to develop appropriate experimental hypotheses; 5) the instruction of graduate, medical, dental, pharmacy, and nursing students in drug and disease processes in the intact human; and 6) the ability of the pharmaceutical manufacturers, the FDA, the EPA and academia to hire scientists who can develop drugs and evaluate the effects of exogenous agents on the intact animal. These negative consequences can be alleviated in a variety of ways. These include 1) increasing the availability of funding for research in integrative biology, 2) increasing the opportunities for training in integrative biology, and 3) instituting grant reviews of integrative biomedical research by peers in integrative biomedical sciences. These measures can revitalize integrative biomedical research, help ensure the continued advancement of biomedical understanding, and consequently contribute to the alleviation of human suffering.

Animals↗
PubMed1994

SNF9007: a novel analgesic that acts simultaneously at delta 1, delta 2 and mu opioid receptors.

Intracerebroventricular administration of the synthetic cholecystokinin analog SNF9007 (Asp-Tyr-D-Phe-Gly-Trp-[NMe]-Nle-Asp-Phe-NH2) produced antinociception in the mouse hot-plate and warm water tail-flick tests. The mechanisms of its analgesic actions were assessed by administering antagonists selective for CCK (cholecystokinin octapeptide, sulfated)-A and CCK-B receptors, as well as specific antagonists for the mu opioid receptor (D-Phe-Cys-Tyr-D-Trp-Arg-Thr-Pen-Thr-NH2, 1 microgram i.c.v.), the delta-1 opioid receptor [D-Ala2-Leu5,Cys6]enkephalin, 4.57 nmol i.c.v., 24 hr pretreatment), the delta-2 opioid receptor (naltrindole benzofuran, 25 pmol i.c.v.) and the kappa opioid receptor (nor-binaltorphimine, 10 mg/kg s.c.). The antinociceptive activity of SNF9007 was not a result of the activation of CCK receptors, as treatment with either CCK-A or CCK-B receptor antagonist was ineffective in blocking SNF9007 antinociception. Nor-binaltorphimine and naltrindole benzofuran were completely ineffective in blocking SNF9007 antinociception when administered alone or in combination. However, co-administration of delta-1 or delta-2 opioid receptor antagonists with the mu opioid receptor antagonist D-Phe-Cys-Tyr-D-Trp-Arg-Thr-Pen-Thr-NH2 resulted in a dramatic reduction in analgesic responses to SNF9007. Furthermore, the co-administration of mu+delta-1 + delta-2 opioid receptor antagonists resulted in an even greater inhibition of SNF9007 antinociception (> 10-fold shift). We conclude that SNF9007 acts simultaneously at brain delta-1, delta-2 and mu opioid receptors to induce antinociceptive effects in mice.

Amino Acid Sequence↗