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Biomedical subjects

T Hill

Publications and source records attributed to T Hill.

At least 19 recordsLinked to original sources
PubMed1997

Hidden covariation detection: a fundamental and ubiquitous phenomenon.

H. Hendrickx, J. De Houwer, F. Baeyens, P. Eelen, and E. Van Avermaet (1997) reported a series of (mostly unsuccessful) studies on nonconscious hidden covariation detection (HCD); for example, they reported that out of 3 attempts to replicate P. Lewicki et al.'s studies, only 1 produced the expected results. They concluded that HCD may be not as general and robust as the previous research suggested, and they considered boundary conditions. In this article, the authors discuss a number of weaknesses of H. Hendrickx et al.'s experiments (and systematic deviations from the original methodology) that are potentially responsible for the lack of the expected results and discuss missing facts in their arguments (e.g., they failed to mention any published replications of the HCD studies from other than the present authors' laboratories). It is argued that when all evidence is considered, the proper conclusion is that nonconscious processing of covariations is not only general and robust but also a ubiquitous phenomenon mediating a variety of processes of acquisition of information.

Humans↗
PubMed1997

Gestational herpes simplex virus hepatitis.

Hepatitis due to herpes simplex virus (HSV) is unusual in healthy individuals. To date, only 56 cases of HSV hepatitis in adult patients have been reported, including 21 pregnant patients. We describe a 25-year-old white woman in her 30th week of gestation who had progressive acute hepatitis. Histologic examination of the liver biopsy specimen showed diffuse microabscesses involving more than 50% of the hepatic parenchyma, with multiple hepatocytes containing Cowdry type A and ground-glass nuclear inclusions. The diagnosis of herpes hepatitis was confirmed by positive immunoreactivity to HSV antibodies in the tissue sections. Intravenous acyclovir therapy was immediately initiated, and the patient's condition improved dramatically. She then had a normal baby at term. Subsequently, the patient had a second pregnancy and an uncomplicated vaginal delivery without recurrence of the disease. Even though alterations of the humoral and cell-mediated immunity occur during pregnancy, herpes hepatitis is rare in pregnant women. Since the prompt administration of antiviral drugs is a lifesaving measure, we recommend including HSV hepatitis in the differential diagnosis of acute hepatitis in pregnancy.

Acute Disease↗
PubMed1996

Regional cerebral blood flow changes after light therapy in seasonal affective disorder.

There is considerable evidence to indicate that depressive disorders may be associated with changes in regional cerebral blood flow (rCBF), and that successful treatment may reverse these changes. We studied patients with seasonal affective disorder (SAD) using 99Tcm-hexamethylpropylene amine oxime (99TCm-HMPAO) single photon emission tomography (SPET) to examine the effect of light therapy on rCBF. Ten depressed patients (8 females, 2 males) with a mean (+/- S.D.) age of 33.5 +/- 11.3 years underwent 99TCm-HMPAO SPET studies before and after light therapy. The treatment response was evaluated using the Structured Interview Guide for the Hamilton Depression Rating Scale-Seasonal Affective Disorders Version (SIGH-SAD). A patient was considered responsive to light therapy if the post-treatment SIGH-SAD score was reduced by 60% or more in comparison to the pre-treatment score (responders, n = 5; non-responders, n = 5). Pre- and post-treatment SIGH-SAD scores and SPET data were compared in each patient. An improvement in depressive symptoms after light therapy was associated with an increase in rCBF in the frontal and cingulate regions as well as the thalamus. Such changes were not seen in non-responsive subjects.

Adult↗
PubMed1996

Routine perioperative dipyridamole 201Tl imaging in diabetic patients undergoing vascular surgery.

OBJECTIVE: To assess the utility of dipyridamole thallium testing in symptomatic and asymptomatic patients with diabetes undergoing vascular surgery. RESEARCH DESIGN AND METHODS: Dipyridamole 201Tl myocardial scintigraphy was performed preoperatively in 93 consecutive patients with diabetes undergoing peripheral vascular procedures. The utility of clinical and thallium variables in predicting cardiovascular complications was assessed. RESULTS: Two groups of patients were identified: group A (36 patients) without clinical evidence of cardiac disease and group B (57 patients) with clinical evidence of cardiac disease. Dipyridamole thallium scans were abnormal in 21 of 36 (58%) of group A patients compared with 53 of 57 (93%) of group B patients (P < 0.0001). Compared with group B patients with perfusion defects, group A patients with perfusion abnormalities tended to have fewer defects per scan (2.7 +/- 1.5 vs. 3.6 +/- 1.9, P = 0.05). No perioperative cardiac complications occurred in group A patients while perioperative cardiac complications occurred in 9 of 57 (16%, 95% CI 7-28%) group B patients (P = 0.01). For the entire study population, the complication rate was 10%. CONCLUSIONS: Diabetic individuals without clinical markers for coronary artery disease appear to be at low risk for adverse postoperative cardiac events after vascular surgery. Preoperative myocardial perfusion imaging may add little to cardiovascular risk assessment in this subgroup of patients with diabetes.

Aged↗
PubMed1995

Three genes and two isozymes: gene conversion and the compartmentalization and expression of the phosphoglycerate kinases of Trypanosoma (Nannomonas) congolense.

The glycosome, a microbody organelle found only in kinetoplastid protozoa, compartmentalizes the first six enzymes of glycolysis. In order to better understand the regulation and targeting of glycolytic enzymes in trypanosomes, we have cloned and analyzed the three genes of the phosphoglycerate kinase (PGK) complex of Trypanosoma (Nannomonas) congolense. The organization of the genes within the complex is similar to that of Trypanosoma brucei brucei. The nucleotide and amino-acid sequences, including those of the novel high-molecular-weight 56PGK, show substantial cross-species similarity. However, the two downstream genes, c1PGK and c2PGK, encode identical isozymes in T. congolense, while they encode distinct glycosomal and cytoplasmic isozymes in T. brucei. Western analysis also indicated that there are only two isozymes in T. congolense and that these are constitutively expressed. Differential digitonin solubilization of the trypanosomes indicated that 56PGK is primarily localized to the glycosome, as expected, and that c1/c2PGK is cytoplasmic. Northern analysis demonstrates that while 56PGK is constitutively expressed, c1PGK and c2PGK mRNAs are differentially expressed in the T. congolense developmental stages. This work demonstrates that T. congolense has only one PGK isozyme, 56PGK, that is predominantly localized in glycosomes.

Amino Acid Sequence↗
PubMed1995

The percutaneous absorption of hydroquinone (HQ) through rat and human skin in vitro.

Because of the potential for human contact with photographic developer solutions containing hydroquinone (HQ), the rates of percutaneous absorption of HQ through human stratum corneum and full-thickness rat skin have been measured in vitro using 5% aqueous solutions of HQ as the donor solutions. The studies were performed using infinite doses of aqueous solutions containing 14C-labeled HQ in Franz-type diffusion cells. The measured absorption rate (mean +/- S.D.) of HQ through human stratum corneum was 0.52 +/- 0.13 micrograms/cm2/h, while that for full-thickness rat skin was 1.1 +/- 0.65 micrograms/cm2/h. The ratio (rat/human) of the permeability constants (Kp) was 2.4. Using the definitions suggested by Marzulli et al. (1969) Toxicol. Appl. Pharmacol. Suppl. 3, 76-83, HQ would be classified as 'slow' with respect to its absorption through human stratum corneum.

Animals↗
PubMed1995

Somatostatin receptor imaging of neuroendocrine tumors with indium-111 pentetreotide (Octreoscan).

Somatostatin, a naturally occurring 14-amino acid peptide, can be thought of as an anti-growth hormone and functional down-regulator of sensitive tissue. Most neuroendocrine tumors seem to possess somatostatin receptors in sufficient abundance to allow successful scintigraphic imaging with radiolabeled somatostatin congeners. Several of these, including Indium-III-DTPA Pentetreotide (Octreoscan [Mallinckrodt Medical, St. Louis, MO]), which was approved for clinical use by the Food and Drug Administration in June 1994, have been of considerable value in scintigraphically identifying various neuroendocrine tumors. The Octreoscan compares favorably with other imaging modalities. The success of somatostatin receptor imaging in evaluating patients with suspected neuroendocrine tumors, including identifying otherwise radiographically occult lesions, has resulted in ranking somatostatin receptor imaging as the prime imaging procedure in patients with suspected neuroendocrine tumors at The Ohio State University.

Humans↗
PubMed1995

Prospective evaluation of viable myocardium by quantitative dipyridamole-thallium-201 scintigraphy and radionuclide ventriculography.

Improvement of myocardial function is a major goal of coronary revascularization. Considerable interest remains in the preoperative identification of viable myocardium. We examined 26 consecutive patients with left ventricular dysfunction undergoing coronary artery bypass grafting. Serial dipyridamole-thallium imaging and radionuclide ventriculography was performed preoperatively and postoperatively. The relationship between preoperative and postoperative thallium perfusion and segmental wall motion was analyzed. The mean preoperative ejection fraction was 32 +/- 9 (21 to 51%) and increased to 41 +/- 12 (17 to 67%) postoperatively (p > 0.01). Seventy-seven percent of patients improved their global ejection fraction postoperatively by > 5%. Thallium perfusion improved postoperatively in 84% of reversible defects vs 63% of partially reversible defects and 35% of fixed defects. Segments with either reversible or partially reversible thallium defects showed an improved postoperative wall motion in 71% and 68%, respectively. Postoperative wall motion improved in 43% of fixed defects. Overall, 67% of hypokinetic segments showed improved postoperative wall motion while only 29% of akinetic or dyskinetic segments improved postoperatively. Preoperative thallium redistribution coupled with preserved wall motion was predictive of improvement in wall motion was predictive of improvement in wall motion postoperatively and indirectly indicates myocardial viability. However, 43% of fixed defects also showed improved postoperative wall motion. A significant improvement in global ejection fraction was found and could be predicted by a linear regression analysis utilizing clinical and thallium parameters.

Aged↗
PubMed1994

Measurement of nuclear DNA modification by 32P-postlabeling in the kidneys of male and female Fischer 344 rats after multiple gavage doses of hydroquinone.

Oral administration of hydroquinone (HQ) to male Fischer 344 (F344) rats results in dose-related kidney toxicity beginning with mild enzymuria by 1 week, significant cell proliferation by 6 weeks, and nephropathy and an increase in the incidence of renal tubule adenomas after 2 years. Female F344 rats, B6C3F1 mice, Sprague-Dawley rats, dogs, and humans are resistant to the renal toxicity of HQ associated with repeated exposure. To determine the potential of HQ to induce covalent DNA adducts in the kidney, male and female F344 rats were given 0, 2.5, 25, or 50 mg/kg HQ by gavage for 6 weeks, and nuclear DNA isolated from kidneys was analyzed by the 32P-postlabeling assay. At 50 mg/kg, males, but not females, showed an increase in the rate of excretion of N-acetyl-beta-D-glucosaminidase, indicative of proximal tubular damage. Analysis of nuclear DNA preparations by the postlabeling assay showed that HQ does not produce covalent DNA adducts in the kidneys of male and female rats. The assay's lower limit of detection is 1 adduct in 10(9) to 10(10) DNA nucleotides. No treatment-related increases in background radioactivity levels on the chromatograms were seen at locations corresponding to the major in vitro adducts of HQ and p-benzoquinone. HQ treatment, however, resulted in the reduction of the levels of certain endogenous adducts (I-compounds), the biological significance of which is unknown.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1994

The contribution of immunization to economic development.

Immunization received intensive support during the 1980s in light of its demonstrable value, relatively low cost, and established infrastructure. The goal of universal childhood immunization was achieved in 1990 on the basis of a strategy of expanding coverage, technological improvements, and social mobilization. Although its impact is difficult to quantify precisely, the Expanded Programme on Immunization (EPI) has had significant positive effects on national and household economies as a result of the reduction of morbidity and mortality. It also has contributed to the development of the managerial and operational capacity of health systems and to the generation of widespread social and political support for health actions through a variety of different mechanisms. Priorities for the next decade include attention to policies to ensure the maintenance of high levels of coverage, continued technical development, and further strengthening of EPI planning and management.

Child Health Services↗
PubMed1994

Nonconscious indirect inferences in encoding.

Indirect (transitive) inference (i.e., if A is related to B, and B is related to C, then C is related to A) is a ubiquitous component of thinking and reasoning. This research demonstrates that a mechanism at least functionally similar to drawing indirect inferences can also be observed in unintentional processes of encoding. The 2 studies followed the same design and used modified versions of procedures tested in previous research on nonconscious information processing (P. Lewicki, T. Hill, & M. Czyzewska, 1992). In the first learning phase, Ss acquired an encoding algorithm relating Variables A and B. In the second learning phase, Variable A was removed from the material and replaced with Variable C, allowing Ss to acquire the second encoding algorithm (relating B and C). Consistent with the original studies, Ss were not aware that there were any consistencies in the material. In the testing phase material, Variable B was removed, and Ss were asked to make intuitive judgments regarding Variable A. The data from both experiments confirmed the expectation that Ss would implicitly draw indirect inferences (A on the basis of C). This process is discussed as one of the mechanisms that may trigger the development of various components of procedural knowledge.

Brain↗
PubMed1994

Measured energy expenditure in mechanically ventilated very low birth weight infants.

Forty-nine calorimetric studies were performed on 24 very low birth weight infants with respiratory distress syndrome on mechanical ventilation during the first seven postnatal days. Mean resting energy expenditure for the entire study was 59 +/- 21 kilocalories/kg daily, with a respiratory quotient of 0.93 +/- 0.1, reflecting the predominance of carbohydrate calories. A comparison of mean energy intake with mean resting energy expenditure showed a mean caloric deficit of 31 kcal/k daily during the first 4 postnatal days, followed by 3 days where resting energy expenditure was met by equivalent caloric intake. Wide variation was noted in resting energy expenditure.

Energy Metabolism↗
PubMed1994

Interaction of gentamycin and atracurium in anaesthetised horses.

Evoked hind limb digital extensor tension (hoof twitch) was maintained at 40% of baseline for 1 h by atracurium infusion in 7 horses anaesthetised with halothane. After 1 h, atracurium was discontinued and hoof twitch allowed to recover to 75%. Atracurium was again given by infusion to maintain 40% twitch for a second hour, then 2 mg gentamycin/kg bwt were given i.v. Atracurium infusion was continued for a third hour, and then hoof twitch was again allowed to recover spontaneously to 75%. Gentamycin reduced twitch strength from 40 +/- 1% (mean +/- sem) to 29 +/- 4% within 7.0 +/- 1.5 min (P = 0.02). Twitch gradually returned to pre-gentamycin strength over the course of the next hour. Recovery of hoof twitch from 50% to 75% took 7.7 +/- 0.7 min for atracurium alone and 11.5 +/- 2.7 min for atracurium plus gentamycin (P = 0.03). Recovery from 50% twitch to 75% fade recovery took 13.8 +/- 0.8 min for atracurium alone and 13.7 +/- 1.2 min for atracurium plus gentamycin. At 75% recovery of fade, hoof twitch was 87 +/- 3% for atracurium alone and 82 +/- 4% for atracurium plus gentamycin. Reversal of the block with edrophonium and subsequent recovery of the horses from anaesthesia were uneventful. It was concluded that, although gentamycin did augment the neuromuscular blockade of atracurium, the effect was minimal.

Anesthetics, Inhalation↗
PubMed1994

Detection of myocardial ischemia: value of combined myocardial perfusion and cineangiographic MR imaging.

OBJECTIVE: Established noninvasive methods for assessing myocardial ischemia have limitations that might be overcome by MR imaging. We investigated MR myocardial perfusion imaging and MR ventriculography, before and after dipyridamole-induced stress, to determine whether the superior spatial and temporal resolution of MR imaging has advantages for the evaluation of myocardial ischemia. SUBJECTS AND METHODS: Eighteen patients with symptoms suggestive of myocardial ischemia were examined by use of MR perfusion imaging and MR cineangiography before and during dipyridamole-induced stress. Multiplanar gradient-echo MR cineangiography and cardiac gated fast low-angle shot (turbo-FLASH) MR imaging during injection of gadopentetate dimeglumine were used. Results were compared with findings from perfusion scintigraphy and coronary arteriography. RESULTS: The accuracy of the combination MR technique for detecting myocardial ischemia was similar to that of scintigraphy. No significant difference was found between the MR technique and scintigraphy for detecting segments of myocardium supplied by stenosed coronary arteries (> 70% reduction in diameter, as determined by coronary arteriography). The sensitivity of the combination MR technique for angiographically detecting significant coronary artery narrowing was 92%, and the specificity was 100%. For scintigraphy, the sensitivity was also 92% and the specificity was 100%. CONCLUSION: Initial results indicate that a combination of stress MR myocardial perfusion imaging and MR ventriculography is feasible and that this technique can detect myocardial ischemia with an accuracy similar to that of scintigraphy. This technique may make more complete noninvasive assessment of myocardial ischemia possible.

Adult↗
PubMed1993

Application of an immortalized human endothelial cell line to the leucocyte:endothelial adherence assay.

This report shows that an immortalized endothelial cell line (EA.hy 926) is able to substitute for secondary cultures of human umbilical vein endothelial cells (HUVEC) in the leucocyte:endothelial adherence assay. Enriched preparations of blood polymorphonuclear leucocytes, monocytes and resting and activated lymphocytes exhibited similar adherence characteristics to HUVEC and the EA.hy 926 cells. Cytokines such as tumour necrosis factor (TNF) act on endothelial cells to increase their adhesiveness for leucocytes and in this study there was no difference between TNF-treated HUVEC and EA.hy 926 cells in supporting the enhanced binding of leucocytes. The adherence promoting effect of TNF-treated EA.hy 926 cells appears to be dependent upon their endothelial properties since TNF treatment of A549 cells, the permanent human cell line used to generate the hybrid EA.hy 926 cells did not augment lymphocyte attachment. Monoclonal antibodies against CD11a and CD18 inhibited the binding of lymphocytes to untreated and TNF-treated HUVEC and EA.hy 926 cells and ICAM-1 expression was increased on both monolayers following treatment with TNF. The availability of a hybrid endothelial cell line whose adhesive properties are similar to those of recently isolated endothelial cells should benefit the study of factors that govern leucocyte-endothelial cell interactions and be advantageous to the longitudinal investigation of leucocyte adherence under static conditions.

Antigens, CD↗
PubMed1993

Protection against ocular and cutaneous infection with herpes simplex virus type 1 by intragastric immunization with live virus.

Intragastric administration of live herpes simplex virus type 1 (HSV-1) was assessed for the induction of humoral immune responses and for protection against ocular and cutaneous challenge with virus. Mice showed no clinical abnormalities following intragastric inoculation with three different strains of virus (Miyama + GC, SC16, and P2C6, a thymidine kinase-defective mutant). Replication of virus was not detected in the oesophagus, superior cervical ganglia or coeliac ganglia of such animals and latent infection was not detected in these ganglia at later times after inoculation. Induction of a mucosal immune response was indicated by the presence of antibody (mainly IgG or IgA)-secreting cells in Peyer's patches. Intragastric immunization gave protection to some extent against ocular challenge and to a greater extent against cutaneous challenge with HSV-1. Following the latter challenge, particularly after intragastric immunization with strains SC16 and Miyama, the establishment of latency was almost completely prevented.

Administration, Oral↗