Preparing a medical informatics research grant proposal: general principles.
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Consultants↗
Biomedical subjects
J A Mitchell
Publications and source records attributed to J A Mitchell.
Endothelin-1 and endothelin-3 release EDRF from isolated perfused arterial vessels of the rat and rabbit.
We have previously shown that porcine endothelin (ET-1) releases endothelium-derived relaxing factor (EDRF) in the rat isolated perfused mesentery. Here we show that both ET-1 (1-100 pmol) and rat endothelin (ET-3, 1-300 pmol) release EDRF in this preparation and that ET-1 releases EDRF from the luminally perfused aorta of the rabbit. Furthermore, we confirm that, as a pressor agent, ET-1 is greater than 10 times more potent than ET-3. Vasodilatations in the rat isolated perfused mesentery in response to ET-1 and ET-3 were due to the release of EDRF since they were inhibited by removal of the endothelium, methylene blue (100 microM), or hemoglobin (30 microM). ET-3 was more selective than ET-1 as a vasodilator because ET-1 induced vasodilatations were limited and in the higher doses overwhelmed by concurrent vasoconstrictions. Release of EDRF from the rabbit aorta in response to ET-1 but not to other agonists (acetylcholine, substance P, or adenosine diphosphate) was potentiated by infusion of potassium chloride (3 mM). Bay K 8644 failed to release EDRF in either system or to constrict the nondepolarized rat mesentery. Thus, both ET-1 and ET-3 release EDRF by activation of receptors or channels that differ from dihydropyridine-sensitive calcium channels.
Animals↗
Simultaneous measurement of endothelium-derived relaxing factor by bioassay and guanylate cyclase stimulation.
1. Endothelium-derived relaxing factor (EDRF) released by cultured endothelial cells (EC) from bovine aortae was measured by bioassay using pre-contracted strips of rabbit aorta and by radioimmunoassay of guanosine 3':5'-cyclic monophosphate (cyclic GMP) produced by stimulation of bovine lung soluble guanylate cyclase. 2. Bradykinin (Bk, 3 and 30 pmol) injected through a column of EC caused release of EDRF as detected by bioassay and increased cyclic GMP concentrations. Superoxide dismutase (SOD, 15 u ml-1) increased the amount of EDRF detected by the activation of soluble guanylate cyclase. 3. In the absence of endothelial cells, nitric oxide (NO, 1-2 microM), arachidonic acid (AA, 3-30 microM) or sodium nitroprusside (SNP, 1-100 microM) stimulated guanylate cyclase. Superoxide dismutase strongly increased the stimulation of guanylate cyclase induced by NO, but had little effect on the stimulation induced by SNP and no effect on the stimulation induced by AA. 4. Oxyhaemoglobin (10-300 microM) abolished the stimulation of guanylate cyclase by EDRF, NO or SNP but was much less effective as an inhibitor of AA-induced stimulation of guanylate cyclase. 5. These results demonstrate that measurement of guanylate cyclase stimulation by radioimmunoassay is a viable method for detecting EDRF release, especially useful when the drugs used interfere with bioassay tissues.
Animals↗
Size polymorphism of the erythrocyte complement receptor type 1 (CR1) in systemic lupus erythematosus induced by hydralazine.
The human erythrocyte complement receptor type 1 (CR1) is polymorphic with respect to molecular weight. Size variants with molecular weights of 190,000 (type A), 220,000 (type B) and 160,000 (type C) daltons have been detected in normal individuals (22 individuals), patients with hydralazine (Hz) lupus (n = 27), a group of Hz controls (n = 30) and the relatives of both Hz groups (27 and 11 individuals, respectively). The method of detection was SDS-polyacrylamide gel electrophoresis of erythrocyte membranes on low-percentage cross-linked gels followed by Western blotting using polyclonal rabbit anti-CR1 antibodies. In normal individuals, 77% had the A allotype and 26% carried the B allotype; amongst Hz lupus patients 67% carried the A allotype, 31% carried the B allotype, and 3% (1 individual) had the C allotype. Amongst the patients who had been on Hz but did not develop SLE, 83% carried the A allotype and 17% carried the B allotype. The AA phenotype was only found in 44% of Hz SLE patients but in 64% of normals and 70% of the Hz control group. Although not statistically significant, the results indicate a relative underrepresentation of the AA phenotype in patients with Hz-induced SLE. In addition, an equal or greater relative amount of the C allotype was detected in an Hz SLE patient with the AC phenotype. This is in contrast to lower relative amounts of the C allotype found in normal individuals with this phenotype.
Erythrocyte Membrane↗
Regulation of lymphocyte proliferation in contact sensitivity: homeostatic mechanisms and a possible explanation of antigenic competition.
Epicutaneous exposure of mice to the contact sensitizing chemicals 4-ethoxymethylene-2-phenyl-oxazol-5-one (oxazolone) and 2,4,6-trinitrochlorobenzene (picryl chloride) causes an inhibition of proliferative responses induced following subsequent topical challenge. The effects on lymphocyte proliferation comprise both transient antigen non-specific and more persistent hapten-specific mechanisms. Pretreatment of mice with one chemical 5 days prior to sensitization with a second, at which time antigen non-specific influences on proliferative responses are manifest, results in depression of contact sensitization as measured by changes in ear thickness following challenge. If, however, the period between pretreatment and sensitization is extended the inhibition of contact sensitization disappears in parallel with a decline in the antigen non-specific depression of lymph node cell proliferation. These data reveal that there exist two homeostatic mechanisms which control proliferation in response to challenge with at least some antigens, and that the extent of lymphocyte proliferation directly influences the degree of contact sensitization achieved. Moreover these results demonstrate that, in some instances at least, competition between antigens may be a function of immunoregulatory influences on lymphocyte proliferation.
Animals↗
CR1 polymorphism in hydralazine-induced systemic lupus erythematosus: DNA restriction fragment length polymorphism.
The contribution of genetic factors in the reduction in erythrocyte CR1 levels observed in hydralazine (Hz) induced systemic lupus erythematosus (SLE) was investigated by determining the frequency of a HindIII restriction fragment length polymorphism (RFLP) in the CR1 gene. This RFLP is associated with quantitative erythrocyte CR1 expression. Individuals who have developed SLE as a reaction to Hz therapy, consanguinous relatives of the Hz-SLE patients, controls who had been treated with Hz without any adverse reaction, and the consanguinous relatives of these controls were included in this study. No difference was found in the frequency of occurrence of the alleles associated with CR1 expression between the Hz-SLE patients and the control groups (P greater than 0.2). Individuals from the Hz-SLE group who were homozygous for the 7.4 kb 'high expressor' allele had lower mean levels of erythrocytes CR1 (564 +/- 65) than the corresponding homozygous subgroups within the Hz-SLE relative group (774 +/- 46), the Hz control group (756 +/- 80) and the Hz control relatives group (825 +/- 66). In addition, 50% of the Hz-SLE patients in the 'high expressor' subgroup who had less than 500 CR1 per erythrocyte had elevated levels of circulating immune complexes. This study suggests that individuals who are genetically low expressors of erythrocyte CR1 are not predisposed to developing SLE in response to Hz therapy, and that in a subgroup of genetically 'high expressors', low CR1 levels are associated with elevated levels of circulatory immune complexes.
Alleles↗
Teaching human genetics in biochemistry by computer literature searching.
We describe a new user-intense-learning experience that incorporates the teaching of clinical and research applications of human genetics in biochemistry while training first-year medical students to develop skills in computer access to the literature. Human genetics was incorporated into the biochemistry curriculum by providing each student with experience in on-line literature searching in MEDLINE, using Grateful Med, in order to write an abstract about a specific inherited biochemical disorder. We stressed the need for the students to obtain current information in order to understand and interpret the rapidly changing field of human genetics. We taught the students that the most efficient method of obtaining such information was by searching the medical literature via computer.
Biochemistry↗
Interferon gamma induces synthesis of complement alternative pathway proteins by human endothelial cells in culture.
Human umbilical vein endothelial cells grown in vitro under standard conditions contain a high level of mRNA specific for the complement regulatory factors H and I. An additional 1.8-kb mRNA encoding a truncated form of factor H is also present. IFN-gamma stimulation of the cells causes a 6-7 fold increase in both factor H mRNA species, and a greater than 10-fold increase in factor I mRNA. IL-1 and LPS slightly suppressed factor H mRNA, while TNF had no effect. mRNA for factor B is also detectable in IFN-gamma-stimulated cells, but messengers for C1q, C4bp, and CR3 beta chain were not found. Secretion of factor H protein was also stimulated by IFN-gamma. The presence of mRNA for factors H, B, and I, together with C3 secretion, demonstrated by others, suggests that endothelial cells can assemble the complete alternative complement pathway. Endothelial cell complement may be involved in leukocyte-endothelium interactions mediated by leukocyte C3 receptors.
Blotting, Northern↗
Learning in rats with caudate-putamen lesions: unimpaired classical conditioning and beneficial effects of redundant stimulus cues on instrumental and spatial learning deficits.
The effects of caudate-putamen lesions in the rat on conditioning were investigated in three experiments. In Experiment 1, rats with lesions were impaired on a spatial task that required learning to make the correct position response, but no deficit was obtained when the alternatives were differentiated by salient visual cues. Performance remained good even when the visual cues were removed. A classical conditioned suppression paradigm was used in Experiment 2, and caudate-putamen lesions were found not to impair acquisition of suppression or overshadowing. In Experiment 3 we revealed poor instrumental learning in subjects with lesions as retarded acquisition of lever-press responding and depressed variable interval response rates. When a light stimulus was present together with reinforced responses, response rates were depressed in the control group (which suggested an overshadowing phenomenon) but were potentiated in the group with lesions. The results showed that caudate-putamen lesions did not produce a general deficit in association formation. There was disruption of learning about responses but not stimuli and, moreover, it was found that redundant stimulus cues aided response learning. It appears that for normal subjects, the salience or associability of the response cues may largely determine the influence of stimuli presented during instrumental conditioning.
Animals↗
Implantation-induced changes in uterine arylamidase localization in the rabbit, rat, hamster and guinea-pig.
Localization of uterine arylamidase activity varied between species: arylamidase was found primarily in the apical aspect of uterine epithelial cells in the rabbit, hamster and non-pregnant rat; only moderate staining was observed in these animals in the endometrial stroma. By contrast, arylamidase localization was primarily stromal in the guinea-pig at all stages studied while the luminal epithelium was devoid of reactivity. In all species, uterine enzyme activity increased before implantation but decreased in the vicinity of the blastocyst once implantation had begun. A generalized increase over the entire length of the uterus was seen during the preimplantation phase in the uterine epithelium of the rabbit and in the endometrial stroma of the guinea-pig. Increase in stromal activity appeared to indicate predecidual transformations which were embryo-dependent (i.e. localized to the implantation site) in the rat, or embryo-independent (i.e. occurring throughout the uterus) in the guinea-pig. A subsequent decrease in enzyme activity occurred in the vicinity of the implanting embryo irrespective of the cell type involved (epithelium in the rabbit, stroma/decidua in the rat and guinea-pig). Since arylamidases of the type studied here are integrated membrane proteins, the uniformity of changes observed in different species may reflect profound changes in membrane properties of endometrial cells as an element of the implantation reaction.
Aminopeptidases↗
Caudate-putamen lesions in the rat may impair or potentiate maze learning depending upon availability of stimulus cues and relevance of response cues.
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Animals↗
AI/LEARN: an interactive videodisk system for teaching medical concepts and reasoning.
This paper describes AI/LEARN, an educational videodisk system designed to teach clinical observational skills and reasoning in medicine. The AI/LEARN system uses a learning conditions approach to teaching. To teach visual concepts, we use the principle of exemplar/nonexemplar pairs and immediate feedback. To teach If-Then problem solving we use the format of minicases with delayed feedback. The software to operate the system has been custom developed and is domain independent. The result is a prototype of a new authoring package for videodisk teaching which operates on IBM compatible microcomputers. The medical domain selected for this prototype system was rheumatic diseases; the knowledge used to teach reasoning skills is derived from the knowledge base of an expert system: AI/RHEUM.
Computer Systems↗
AI/LEARN network. The use of computer-generated graphics to augment the educational utility of a knowledge-based diagnostic system (AI/RHEUM).
AI/LEARN Network is an educational package that enhances a knowledge-based diagnostic system called AI/RHEUM. This paper describes a microcomputer-based graphical representation of the knowledge base and discusses graphical representation of knowledge.
Artificial Intelligence↗
The behavioral and toxicological effects of testosterone pellet implantation.
Forty gonadally intact male Wistar rats, 200-225 g, were utilized to study the behavioral and physiological effects of testosterone (T) pellet administration. T was administered via pellets (10, 25, 50, and 100 mg) implanted subcutaneously in the dorsal region of the neck. Fifty mg lactate pellets were utilized as the control. T plasma levels were determined using RIA procedures on days 30, 60, and 90 after pellet implantation. T (50 and 100 mg) resulted in plasma concentrations significantly greater than controls. T (100 mg) and lactate control groups were subjected to a competition situation utilizing an estrogen-primed female as the goal object. Subjects were exposed to the test procedure prior to the implantation of the pellets. T resulted in previously defined losers becoming winners in the competition situation on days 30, 60, and 90 post-implantation. T implantation did not significantly affect muricidal behavior as compared to lactate controls. On day 90, the subjects were sacrificed, and the organ/body-weight ratios determined for the heart, liver, testes, and skeletal muscles of the left shoulder girdle. T (100 mg) resulted in a decrease in the testes/body-weight ratio as compared to controls, while the liver/body-weight ratio was increased in this group T (100 mg) also resulted in an increase in the activity of serum enzyme glutamic-oxaloacetic transaminase (SGOT) on day 90 post-implantation. Food intake and body weight were monitored throughout the course of the study. However, no significant differences from controls were noted.
Aggression↗
The effects of d-amphetamine on food competition in male rats.
Male Wistar rats were tested in 3 competitive situations to determine the effects of d-amphetamine (AMP) on competitive behavior. Subjects were initially tested in a fixed-pair food competition paradigm. Based on the percentage of pellets obtained, a winner and loser were defined for each pair. AMP (2.0 and 4.0 mg/kg) was then administered to one or both members of pair, and the effects of the drug on the defined winners and losers were determined. AMP did not significantly alter the percentage of pellets obtained by losers except when only the winners were administered AMP (4.0 mg/kg). Subjects were then tested in a round-robin competition paradigm in which each subject was paired with every other subject. The animals were ranked according to the percentage of pellets obtained out of a possible 450 pellets. AMP (2.0 mg/kg) decreased pellet acquisition in higher ranking subjects, whereas pellet acquisition was increased in lower ranking subjects. The effects of AMP were also evaluated in a "worker-parasite" paradigm. Subjects were individually conditioned to press a lever using an FI schedule for presentation of a food pellet. When the lever was located on the wall opposite the food hopper, a worker and parasite were defined for each pair. The worker was the subject that made the most responses on the lever while obtaining fewer reinforcements. Subjects that were defined as winners in the fixed pair food competition emerged as the workers in this situation. AMP (0.8 mg/kg) given concurrently to both subjects resulted in a reversal of roles; the parasites now emitted the majority of responses and obtained less pellets. The data indicate that AMP has a differential effect on participants in competitive situations when all subjects in the situation are treated.
Animals↗
Changes in intraconceptus pressure in the rabbit during days 7-10 of pregnancy.
The present study established the magnitude of and temporal changes in the pressure within in situ rabbit conceptuses during early pregnancy. At the 7th, 8th, 9th, or 10th day post coitum (dpc), animals were anesthetized, and the number and dimensions of implantation sites were recorded. Conceptus pressure was measured by the servo-nulling method employing a glass micropipette. The mean number of sites was 6/cornu; spacing appeared normal. Implantation dome volume increased from 7 through 10 dpc: 0.2 +/- 0.03; 0.5 +/- 0.1; 1.6 +/- 0.2, and 2.7 +/- 0.9 cm3, respectively (Day 7 vs. 8, 9 and 10, p less than 0.01). Intraconceptus pressure declined between 7 and 10 dpc: 6.3 +/- 0.4; 5.7 +/- 0.4; 4.5 +/- 0.9, and 3.9 +/- 0.7 mm Hg, respectively (Day 7 vs. 10, p less than 0.05). Pressure fluctuated; the frequency of change in pressure varied between 7 and 8 dpc (4.2 +/- 3.0 to 2.3 +/- 3.5 peaks/min). The amplitude of fluctuation did not vary significantly between 7 and 10 dpc (2.6 +/- 0.3; 0.79 +/- 0.8 mm Hg, respectively). Simultaneous measurement of pressure within the conceptus and within the adjacent uterine lumen indicated that alterations in luminal pressure only occasionally influenced pressure within the conceptus. The decline in conceptus pressure suggests that the uterine wall becomes progressively more compliant as blastocyst cavity/yolk sac fluid accumulates within the conceptus. Conceptus expansion resulting from internal pressure may enhance conceptus-uterine metabolic exchange by facilitating apposition of conceptus-uterine surfaces and by increasing the ratio of conceptus surface to cytoplasmic mass.
Animals↗
Depression of lymph node cell proliferation induced by oxazolone.
The influence of topical exposure to two sensitizing chemical on draining lymph node cell proliferative responses in BALB/c mice has been examined. Conventional contact sensitization with 4-ethoxymethylene-2-phenyloxazol-5-one (oxazolone) has been shown to induce a rapid and systemic suppression of subsequent proliferative responses to topically applied chemical which can be adoptively transferred to recipient mice with immune lymph node cells. In contrast to some previous reports in which such suppression was found to be largely antigen-specific in nature, we report that, at least initially, the inhibition of lymphocyte proliferation induced by skin sensitization is hapten-non-specific. The relevance of this phenomenon to the regulation of contact sensitization is discussed.
Animals↗
Reduction of hyperinsulinemia and insulin resistance by opiate receptor blockade in the polycystic ovary syndrome with acanthosis nigricans.
We previously reported that circulating beta-endorphin levels are increased in obese hirsute women and that plasma immunoreactive insulin (IRI) levels are increased in proportion to the degree of hyperandrogenism in women with the polycystic ovary (PCO) syndrome. We, therefore, tested the hypothesis that endogenous opiates are at least partially responsible for the hyperinsulinemia and insulin resistance in this syndrome. In the first study, acute naloxone administration significantly reduced the plasma IRI response and IRI/glucose ratio in three euglycemic obese women with PCO and acanthosis nigricans (AN) and marked insulin resistance, but did not alter the glucose response. Naloxone had no effect on these parameters in the normal weight control subjects. In the second study, nalmefene, a new, orally active opiate antagonist, reduced IRI and the IRI/glucose ratio in four women with PCO-AN and marked hyperinsulinemia in a randomized, double blind, crossover protocol. We conclude that endogenous opiates are at least partially responsible for the hyperinsulinemia and insulin resistance in PCO-AN.
Acanthosis Nigricans↗