Biomedical subjects

T Hill

Publications and source records attributed to T Hill.

At least 55 records · Page 3Linked to original sources

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↗

PubMed1994

Report of first year's operation of an ortho-geriatric service.

An ortho-geriatric service operated by Bundoora Extended Care Centre and Preston and Northcote Community Hospital was established in 1991 to improve rehabilitative care and discharge planning of elderly hip fracture patients. 123 patients were treated during the first year of the service's operation. There was a 25 per cent reduction in the acute hospital length of stay, an increased proportion of patients discharged home and a decreased need for post-acute rehabilitation in comparison to figures for 1989, leading to a substantial reduction in the total number of bed-days occupied in the hospital system as a whole by hip fracture patients. An ortho-geriatric service is an effective means of helping to improve both patient and hospital centred outcomes for a condition which will be seen ever more commonly in the future.

Aged↗

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↗

PubMed1993

Neuromuscular blockade by use of atracurium in anesthetized llamas.

Anesthesia was induced in 8 healthy llamas by administration of guaifenesin and ketamine, and was maintained with halothane in oxygen. On 2 separate experimental days, atracurium was given to induce 95 to 99% reduction of evoked hind limb digital extensor tension (twitch). For the first part of the study, atracurium was given IV as repeat boluses, with muscle twitch strength being allowed to return without intervention to 75% of baseline after each bolus before the subsequent bolus was given. A total of 5 bolus doses of atracurium was given. For the first bolus, 0.15 mg/kg of body weight IV, and for subsequent boluses, 0.08 mg/kg, induced desired relaxation. Onset of relaxation was slightly more rapid for repeat, compared with initial, bolus. Duration of relaxation and recovery time were similar to initial and repeat doses. Maximal twitch reduction was observed in 4 +/- 0.2 minutes (mean +/- SEM). Duration from maximal twitch reduction to 10% recovery was 6.3 +/- 0.4 minutes. Twitch recovery from 10 to 50% of baseline took 11.6 +/- 0.6 minutes. Twitch recovery from 10 to 75% recovery took 19.5 +/- 1.1 minutes. Recovery from 10% twitch to 50% fade took 12.8 +/- 0.5 minutes. Fade at 50% recovery of twitch was 39 +/- 0.02%. Significant (P < 0.05) animal-to-animal variation was observed in twitch recovery times. For the second part of the study, atracurium was initially given IV as a 0.15-mg/kg bolus, followed by infusion for 1 to 2 hours.(ABSTRACT TRUNCATED AT 250 WORDS)

Analysis of Variance↗

PubMed1992

Muscle fatigue measured with evoked muscle vibrations.

Skeletal muscle vibrates laterally during voluntary and evoked muscle contractions. We hypothesized that the vibration amplitude from evoked muscle twitches is directly related to evoked twitch force from fatiguing muscle. To test the hypothesis, vibrations produced by evoked muscle twitches were recorded during short (5-second) rest periods as the muscle was intermittently exercised with voluntary contractions. Trials were performed at 30%, 50%, and 70% of maximal voluntary contraction. Evoked muscle twitches eliminated the problems of motivation and tremor that complicate sound and vibration measurements during voluntary contractions. Results from the first dorsal interosseus hand muscle in 11 normal adult volunteers revealed that the vibration amplitude is highly correlated (r2 = 0.93, at 70% MVC, r2 = 0.97, at 50% MVC; r2 = 0.85, at 30% MVC) with force. Both potentiation and reduction of force with exercise were accompanied by parallel changes in vibration amplitude, as measured with an accelerometer. Compound muscle action potentials did not increase with exercise-induced twitch potentiation, and did not correlate as highly with force during fatigue.

Action Potentials↗

PubMed1992

Nonconscious acquisition of information.

The authors review and summarize evidence for the process of acquisition of information outside of conscious awareness (covariations, nonconscious indirect and interactive inferences, self-perpetuation of procedural knowledge). Data indicate that as compared with consciously controlled cognition, the nonconscious information-acquisition processes are not only much faster but are also structurally more sophisticated, in that they are capable of efficient processing of multidimensional and interactive relations between variables. Those mechanisms of nonconscious acquisition of information provide a major channel for the development of procedural knowledge that is indispensable for such important aspects of cognitive functioning as encoding and interpretation of stimuli and the triggering of emotional reactions.

Algorithms↗

PubMed1992

Part I. Reconstruction after total mandibulectomy with free cranial and microvascular iliac crest grafts as preparation for implants.

A young Ecuadorian girl underwent a total mandibulectomy due to infected fibrous dysplasia. In the subsequent 16 years, she was unable to speak intelligibly or masticate, surviving on liquids alone. After referral to the United States, the patient underwent six major surgical procedures that reconstructed her mandible from cranial and microvascular iliac crest grafts. The reconstruction improved her appearance and prepared her for insertion of dental implants and the eventual construction of a prosthetic device. These resulted in both functional and esthetic benefits.

Adult↗

PubMed1992

Part II. Mandibular reconstruction: combined intra-oral and in vitro placement of osseointegrated implants into a free and vascularized bone graft.

A 28-year-old Hispanic girl underwent a complete mandibular reconstruction many years following full mandibulectomy for fibrous dysplasia. Because of infectious complications, both free cranial and microvascular iliac crest grafts were used. The patient had osseointegrated implants placed directly into the grafted mandible. Osseointegrated implants were also placed into a segment of free iliac crest bone, in vitro, and then grafted laterally onto the reconstructed mandible. Prosthetic reconstruction was then carried out to restore the patient to normal function, health, comfort, and esthetics.

Adult↗

PubMed1992

The risk of severity of limb injuries in racing thoroughbred horses.

A retrospective study was carried out to identify factors which predisposed Thoroughbred horses to severe injuries, as compared to less severe injuries, while racing on New York Racing Association (NYRA) tracks during the period of January 1986 to June 1988. A severe injury was defined as an injury which led to humane destruction of the horse. A less severe injury was defined as a horse which didn't race within 6 months following a muscular, ligament, tendon, or skeletal injury on the racetrack. The data were obtained from the Horse Identification Department records kept by the Chief Examining Veterinarian of NYRA and included 55 severely injured horses and 245 less severely injured horses. Multiple logistic regression analysis was used to identify factors associated with the risk of severe injuries compared to less severe injuries in those horses. There was a significant association between track and the risk of severe injury (horses raced on Belmont and Saratoga were more likely to develop a severe injury compared to horses raced on Aqueduct Main). The track surface was also associated with the risk of severe injury (horses raced on a firm turf had a significantly lower risk of severe injury associated with the track was significantly modified by the track condition (horses raced at Belmont when it was muddy had a significantly increased risk compared to Aqueduct dirt). Horses were more likely to experience severe injury in the early part of the race (less than or equal to 6 furlongs) than the latter part of the race (greater than 6 furlongs). The risk of severe injury decreased with the age of the horse.

Age Factors↗

PubMed1991

Effect of tumor necrosis factor-alpha on the proliferation of leukemic cells from children with B-cell precursor-acute lymphoblastic leukemia (BCP-ALL): studies of primary leukemic cells and BCP-ALL cell lines.

The effect of recombinant tumor necrosis factor-alpha (rTNF-alpha) on the primary leukemic blasts and leukemic cell lines derived from children with B-cell precursor acute lymphoblastic leukemia (BCP-ALL) was studied. The proliferation of leukemic cells from the bone marrow of 11 of 13 patients (seven at diagnosis, four in relapse) and from the 697 (BCP-ALL) cell line was significantly inhibited by rTNF-alpha at the lowest dose tested (0.1 ng/mL), as measured by 3H-TdR uptake. The degree of inhibition was variable, ranging from 17% to 78%. Furthermore, a dose-dependent inhibitory effect was observed, with approximately 70% mean inhibition of DNA synthesis detected when cells from 12 of 13 patients were incubated with 100 ng/mL of rTNF-alpha for 3 days. In contrast, rTNF-alpha did not inhibit another BCP-ALL cell line (EU-1/ALL) established recently in our laboratory. Studies indicated that the TNF-alpha gene was expressed by the primary leukemic blasts of one TNF-resistant case in his third relapse and by EU-1 cells. Also, TNF-alpha protein was detected by Western blot analysis and enzyme-linked immunoabsorbent assay in the supernatant of EU-1 cells; this is the first report of TNF production by a BCP-ALL cell lines. The production of TNF-alpha mRNA and protein was not detected in the 697 cell line and in the primary leukemic blasts from six patients (four at diagnosis, two in relapse) whose leukemic cells were inhibited by TNF. The partially purified TNF-alpha obtained from the EU-1 cell line also suppressed the proliferation of TNF-sensitive primary leukemic cells, and this inhibitory activity was abolished by an anti-TNF-alpha specific antibody. Our results demonstrate that TNF-alpha is an inhibitor of in vitro proliferation of BCP-ALL cells from most patients. The TNF-resistant leukemic cells from a few patients and the EU-1 cell line express TNF mRNA, suggesting that the induction of TNF gene expression is associated with the development of TNF resistance.

Blotting, Western↗

PubMed1991

Acquisition of iron from transferrin by Bordetella pertussis.

It has been demonstrated that under iron-restricted conditions Bordetella pertussis can take up iron from human transferrin within 30 min of exposure. B. pertussis utilizes two mechanisms for acquiring iron from human transferrin, a direct contact method and a siderophore mediated system. Both systems are shown to result in bacterial internalization of iron from transferrin. However, direct contact between B. pertussis and transferrin provides far more effective iron uptake than siderophore activity alone.

Biological Transport↗

PubMed1991

Risk factors associated with injuries in thoroughbred horses.

A case-control study was conducted on Thoroughbred horses to identify factors associated with the risk of breakdown on racetracks. A total of 310 cases (breakdowns) were identified from the Horse Identification Department records kept by the chief examining veterinarian of New York Racing Association. For each case, two control horses were selected randomly from the Daily Racing Form Inc. records. Multiple logistic regression analysis was used to identify and quantify the risk of factors associated with breakdown, while simultaneously controlling for the effect of other putative factors. Factors associated with risk of breakdown were: track (horses raced on Saratoga racetrack were at a lesser risk of breakdown), track composition/condition (turf tracks had a lower risk compared to dirt), number of seasons in race, racing in a later race, number of starts per year, the total number of starts, season (summer had a higher risk than winter or spring) and age of the horse.

Animals↗

PubMed1990

Atracurium administration, as an infusion, to induce neuromuscular blockade in clinically normal and temporarily immune-suppressed cats.

Atracurium besylate, a nondepolarizing neuromuscular blocking agent, was administered by infusion to 10 cats that were anesthetized with isoflurane and oxygen to allow transplantation of a myocutaneous flap. Five of the cats were given cyclosporine (20 mg/kg of body weight, PO q 12 h in divided doses) for 2 days prior to anesthesia, and prednisolone (0.25 mg/kg, PO) on the morning of surgery. The other 5 cats were not given either drug. Neuromuscular blockade was assessed, using the train-of-four stimulation, and throughout surgery, the infusion rate was adjusted to maintain the first-twitch response (T1) at 90 to 95% depression from baseline. At completion of surgery, atracurium was discontinued, and the infusion rate and the time for recovery (the time for the train-of-four ratio to increase from 50 to 75%) were recorded. Once the train-of-four ratio had been stable for 10 minutes, edrophonium (0.5 mg/kg), a cholinesterase inhibitor, was administered IV, and neuromuscular blockade was monitored for another 10 minutes. Mean (+/- SD) duration of the atracurium infusion was 302.1 +/- 70.5 minutes for the control group and was 323.9 +/- 61.7 minutes for the cats given cyclosporine and prednisolone. In the cats of the control group, the infusion rate required to induce 90 to 95% T1 depression from baseline was 3.7 +/- 0.7 micrograms/kg/min. This rate was not significantly different from that of 2.8 +/- 1.2 micrograms/kg/min in cats given cyclosporine and prednisolone. Significant difference in recovery time was not evident between the control group and the treated group (6.4 +/- 4.5 minutes vs 6.2 +/- 2.5 minutes).(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗

PubMed1990

Microbody phosphoglycerate kinase of Trypanosoma brucei: expression and complementation in Escherichia coli.

In the primitive eukaryotic parasite, Trypanosoma brucei, most of the enzymes of glycolysis are located within microbody organelles called glycosomes. Proteins destined for the glycosome are synthesized on free ribosomes and post-translationally translocated into the organelle. The gene, gPGK, encoding the glycosomal isozyme of phosphoglycerate kinase (gPGK), was cloned adjacent to a T7 promoter and cotransformed with a plasmid encoding T7 RNA polymerase into Escherichia coli Pgk-cells. Functional complementation occurred, but only after the creation of a ribosome-binding site by mutagenesis. This represents the first example of complementation of an E. coli mutant with a gene encoding a microbody protein. Enzymatically active recombinant gPGK was purified to near homogeneity by ion exchange chromatography from highly expressing E. coli. The recombinant protein will aid in studies of glycosomal biogenesis.

Animals↗