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Biomedical subjects

T Hill

Publications and source records attributed to T Hill.

At least 73 records · Page 4Linked to original sources
PubMed1990

Silent myocardial ischemia and infarction in diabetics with peripheral vascular disease: assessment by dipyridamole thallium-201 scintigraphy.

We investigated the incidence of silent myocardial ischemia and infarction as assessed by dipyridamole thallium scintigraphy in 30 diabetic patients with peripheral vascular disease and without clinical suspicion of coronary artery disease. Seventeen patients (57%) had thallium abnormalities, with reversible thallium defects compatible with ischemia in 14 patients (47%) and evidence of prior, clinically silent myocardial infarction in 11 patients (37%). Thallium abnormalities were most frequent in patients with concomitant hypertension and cigarette smoking (p = 0.001). These results suggest that unsuspected coronary artery disease is common in this particular group of patients with diabetes mellitus.

Adult↗
PubMed1990

Antimicrobial effect of human milk on Bordetella pertussis.

It has been demonstrated that human milk, unlike bovine milk, can reduce the viability of Bordetella pertussis. This antibacterial activity was not due to the presence of antibiotics or antibodies in the human milk. Reducing the level of available iron or increasing the concentration of lysozyme in bovine milk did not induce anti-B. pertussis activity. Analysis of total fatty acids revealed that human milk contained significantly more linoleic acid than bovine milk. However, the addition of linoleic acid to bovine milk did not inhibit the growth of B. pertussis.

Animals↗
PubMed1990

Cerebral blood flow: assessment with dynamic contrast-enhanced T2*-weighted MR imaging at 1.5 T.

The authors assessed regional cerebral blood flow dynamics with magnetic resonance (MR) imaging enhanced with gadolinium diethylenetriaminepentaacetic acid (DTPA). After bolus administration of Gd-DTPA, rapid T2*-weighted gradient-echo images were acquired. Image acquisition time ranged from 2 to 3 seconds. The signal intensity (SI) of brain tissue and blood vessels markedly decreased during the first pass of contrast agent through the brain due to the local field inhomogeneity caused by the concentrated paramagnetic contrast agent. The method was used in 18 subjects with no cerebrovascular disease and 32 patients with stroke, vascular stenosis, arteriovenous malformation, and cerebral neoplasm. Comparison with intracranial angiography was performed in three patients and with single-photon emission computed tomography of blood flow in four. The change in T2* relaxation rate was approximately linearly related to the dose of contrast agent. The SI change increased as the echo time was lengthened. Regions in cerebral infarcts, metastases, and arteriovenous malformations showed different enhancement patterns than those of edema around a lesion and of normal brain tissue. Abnormal circulation times in patients with vascular stenoses were demonstrated. The method provides information about cerebral blood flow dynamics not available from conventional MR imaging and MR angiography.

Adolescent↗
PubMed1989

Predictive value of quantitative dipyridamole-thallium scintigraphy in assessing cardiovascular risk after vascular surgery in diabetes mellitus.

Cardiac complications represent a major risk to patients undergoing vascular surgery. Diabetic patients may be particularly prone to such complications due to the high incidence of concomitant coronary artery disease, the severity of which may be clinically unrecognized. Attempts to stratify groups by clinical criteria have been useful but lack the predictive value of currently used noninvasive techniques such as dipyridamole-thallium scintigraphy. One hundred one diabetic patients were evaluated with dipyridamole-thallium scintigraphy before undergoing vascular surgery. The incidence of thallium abnormalities was high (80%) and did not correlate with clinical markers of coronary disease. Even in a subgroup of patients with no overt clinical evidence of underlying heart disease, thallium abnormalities were present in 59%. Cardiovascular complications, however, occurred in only 11% of all patients. Statistically significant prediction of risk was not achieved with simple assessment of thallium results as normal or abnormal. Quantification of total number of reversible defects, as well as assessment of ischemia in the distribution of the left anterior descending coronary artery was required for optimum predictive accuracy. The prevalence of dipyridamole-thallium abnormalities in a diabetic population is much higher than that reported in nondiabetic patients and cannot be predicted by usual clinical indicators of heart disease. In addition, cardiovascular risk of vascular surgery can be optimally assessed by quantitative analysis of dipyridamole-thallium scintigraphy and identification of high- and low-risk subgroups.

Angina Pectoris↗
PubMed1989

Blood pressure response to tourniquet use in anesthetized horses.

Blood pressure during anesthesia and surgery was compared for 2 groups of horses. Group A, consisting of 23 horses, had a tourniquet placed on the distal portion of a limb. The other group of 20 horses (group B) had surgery of comparable nature and duration as did group-A horses, but a tourniquet was not used. There was a statistical difference (P less than 0.05) in the peak systolic arterial blood pressure between the groups; group-A horses had a mean (+/- SEM) peak of 151 +/- 6 mm of Hg and group-B horses had a peak of 118 +/- 4 mm of Hg. In addition, group-A horses had immediate decrease in blood pressure, coincident with tourniquet deflation. The blood pressure decrease of 23 +/- 3 mm of Hg represented 16% of immediate predeflation blood pressure. Comparable blood pressure decrease was not observed at the end of surgery in group-B horses. Significant difference was not found when other factors that could affect blood pressure were considered. These factors included preanesthetic medication, anesthetic agents, mode of ventilation, pretourniquet inflation blood pressure, and duration of tourniquet inflation. Significant (P less than 0.05) difference in peak blood pressure was observed when the tourniquet was placed on the dependent, compared with the uppermost, limb, with changes more pronounced when the tourniquet was placed on the dependent limb. Tourniquet placement was associated with hypertension, and tourniquet deflation was associated with blood pressure decrease in these anesthetized horses.

Analysis of Variance↗
PubMed1989

Elevated phosphoglycerate kinase mRNA but not protein in monomorphic Trypanosoma brucei: implications for stage-regulation and post-transcriptional control.

Phosphoglycerate kinase (PGK) is present in high levels in the glycosomes of bloodstream stage Trypanosoma brucei, but is virtually absent in procyclic stage glycosomes. Glycosomes isolated from slender and stumpy stage bloodforms show similar levels of PGK, although levels are slightly lower in stumpy forms. Lower levels of glycosomal PGK transcripts are observed in stumpy form RNA, paralleling the decrease in glycosomal PGK activity. Monomorphic strains and pleiomorphic strains show similar glycosomal PGK activity, but monomorphic strains have much higher levels of the glycosomal PGK transcript. In three separate cases, predominantly monomorphic strains derived from highly pleiomorphic strains showed increased levels of glycosomal PGK (gPGK) mRNA. gPGK synthesis rates in monomorphic and pleiomorphic strains were similar, and no significant differences in turnover were observed. These data suggest the possibility of translational control of gPGK protein levels in trypanosome bloodforms. The data also indicate that the metabolism of gPGK mRNA in highly passaged laboratory strains is altered, and counsel caution when attributing differences in transcript levels to stage-specific regulation.

Animals↗
PubMed1989

Central hemodynamic assessment of normal term pregnancy.

Ten carefully screened primiparous patients between 36 and 38 weeks' gestation underwent pulmonary artery catheterization, arterial line placement, and central hemodynamic assessment in the left lateral recumbent position. Studies were repeated in the same patients between 11 and 13 weeks post partum. Compared with the nonpregnant state, there was a significant fall in systemic vascular resistance, pulmonary vascular resistance, colloid oncotic pressure, and colloid oncotic pressure-pulmonary capillary wedge pressure gradient by the late phase of the third trimester (p less than 0.05). Pregnancy was associated with a significant rise in cardiac output and pulse in all patients (p less than 0.05). There was no significant change in pulmonary capillary wedge pressure, central venous pressure, left ventricular stroke work index, or mean arterial pressure. Normally the late phase of the third trimester is not associated with hyperdynamic left ventricular function as assessed by the left ventricular stroke work index/pulmonary capillary wedge pressure ratio.

Adult↗
PubMed1989

Localization by hand-held gamma probe of tumor labeled with antibody "cocktail".

Five groups (n = 4) of congenitally athymic female nude mice bearing subcutaneous implants of CX-1 and/or SW-1116 tumor in the hind limbs received iodine-125 radio-labeled monoclonal antibodies (MoAbs) B72.3 (two groups), 17-1A (two groups), and cocktail (one group) (iodogen method, 50 microCi/10 micrograms/mouse). Daily probe counts were made in duplicate with a hand-held detector over each tumor site and the front leg (background) for 21 days. Animals were sacrificed and appropriate well counts were obtained. All the single MoAb preparations localized well in both tumor cell lines. Uptake of monoclonal antibody 17-1A was similar in the two tumor cell lines, with counts initially high and slowly decreasing over the 21-day period. Tumor/background ratios continued to increase over time, indicating that both tumor lines have similar antigenic expression for the monoclonal antibody 17-1A. This was not the case for monoclonal antibody B72.3, which showed a preferential uptake by the CX-1 tumor, with higher initial counts and prolonged binding of the antibody, giving rise to higher tumor/background ratios. The mixture of monoclonal antibodies B72.3 and 17-1A markedly improved the uptake by the CX-1 tumor cell line but not that by the SW-1116 cell line, where the effect was negative when compared to the uptake of the single MoAb preparations. The use of a monoclonal antibody mixture can enhance targeting of some tumor sites. Due to the heterogeneity of tumor cell lines, even within the same animal, different mixtures of monoclonal antibodies are needed to increase the targeting of tumor.

Adenocarcinoma↗
PubMed1989

Self-perpetuating development of encoding biases in person perception.

It was hypothesized that encoding (interpretive) biases may develop in a self-perpetuating manner through biased, self-supportive encoding (even in the absence of any objectively supportive evidence). This process was investigated in 3 experiments with different stimulus materials (matrices of digits, silhouettes of persons, descriptions of personal problems). In the learning phase of each study, Ss nonconsciously acquired some encoding bias. In the testing phase, Ss' encoding of new material was predictably biased, and, consistent with the self-perpetuation hypothesis, the strength of the bias gradually increased over the segments of the material, even though the material did not contain any evidence supportive of the bias. Given the ambiguity of many (particularly social) stimuli, the self-perpetuation process may play a ubiquitous role in the development of interpretive categories and other individually differentiated cognitive dispositions.

Affect↗
PubMed1989

On the status of nonconscious processes in human cognition: comment on Reber.

Two issues are discussed. The first one pertains to the generality of the nonconscious learning processes and their somewhat paradoxical status in cognitive psychology. We argue that the ability of the human cognitive system to nonconsciously acquire complex knowledge structures is one of its elementary and indispensable properties. Moreover, the existence of this ability constitutes one of the necessary metatheoretical assumptions of contemporary cognitive psychology. Nevertheless, the contemporary cognitive psychology literature often implies that it is only one of many controversial and unusual phenomena. The second issue pertains to the distinction between the so-called primitive unconscious and the sophisticated unconscious as proposed by Reber (1989).

Concept Formation↗
PubMed1989

Self-perpetuating development of encoding biases.

The process of encoding new information involves the imposition of preexisting interpretive categories on newly encountered stimuli, even if the categories do not match perfectly those stimuli. We hypothesized that such encoding of stimuli as supportive of preexisting encoding dispositions may become a source of a perceiver's subjective experiences that support these dispositions. Through this nonconsciously operating mechanism, encoding rules may gradually develop in a self-perpetuating manner, even in the absence of any objectively supportive evidence. Results demonstrated this self-perpetuating process in three studies involving different stimulus materials and experimental tasks (matrix-scanning paradigm and two "intuitive judgment" tasks). The self-perpetuating development of encoding biases is discussed as one of the elementary mechanisms involved in the development of interpretive categories and other individually differentiated cognitive dispositions.

Adult↗
PubMed1989

Circulating calcium modulates adrenaline induced cyclic adenosine monophosphate production.

Inotropic support of the failing myocardium may combine calcium with adrenaline in an attempt to augment the haemodynamic actions of each drug. We have previously shown, however, that calcium blunts adrenaline induced increases in blood pressure and cardiac output in animals and man. The mechanisms by which calcium may interfere with the haemodynamic actions of adrenaline are not well understood. Adrenaline is known to stimulate adenylate cyclase and increase levels of cellular cyclic adenosine monophosphate (cAMP), a crucial second messenger in cell regulation. We evaluated the effect of increased circulating calcium levels on adrenaline stimulated cAMP production in laboratory animals. Calcium infusion in rats nearly doubled the circulating ionised calcium concentration, from 1.27 (SEM 0.03) mM to 2.3(0.18) mM. Adrenaline infusion significantly increased plasma cAMP in saline infused control animals, from 26(6) pmol.ml-1 to 98(22) pmol.ml-1, whereas there was no increase in cAMP plasma levels in the calcium infused rats. The apparent inhibition of adenylate cyclase by calcium may participate in a negative feedback system which helps protect cells from harmful intracellular calcium overload.

Animals↗
PubMed1989

The effect of the organophosphate trichlorfon on the neuromuscular blocking activity of atracurium in halothane-anesthetized horses.

To determine whether cholinesterase inhibition by an organophosphate would influence atracurium's neuromuscular blockade, six horses were anesthetized and paralyzed with atracurium (total of five injections per horse) on experimental Day 1, then were given trichlorfon (64 mg/kg per os) 6 days later. On Day 7, horses were anesthetized and paralyzed in the same manner as on experimental Day 1. Blood was taken to measure serum cholinesterase activity prior to anesthesia on Days 1 and 7. No significant difference was noted in atracurium's neuromuscular blocking activity between the 2 experimental days (P less than 0.05), despite Day 7 cholinesterase activity that was 16% of pre-trichlorfon values. For atracurium Injections 1 and 2-5, 85 and 43 micrograms/kg of atracurium, respectively, were required to produce a 95-99% reduction in hoof twitch. The time from injection to maximum twitch reduction was approximately 9 min after Injection 1 and 5 min after subsequent injections. Time from injection to maximum twitch reduction was significantly longer for Injection 1 than Injections 2-5 on both experimental days. The time from maximum twitch reduction until 10% recovery was approximately 8 min, with no significant difference between experimental days. The time for twitch recovery from 10 to 75% was approximately 17 min for all injections. Antagonism of atracurium with edrophonium caused the twitch height to return to pre-atracurium strength in approximately 7 min. Edrophonium caused a significant increase in arterial blood pressure. Heart rate change was variable after edrophonium.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1989

An improved model of recurrent herpetic eye disease in mice.

Mice were passively immunized with serum containing antibodies to herpes simplex virus type 1 (HSV-1) before inoculation on the cornea with HSV-1 strain McKrae. After such immunization most mice survived and most had normal eyes. When primary infection had subsided, mice with normal eyes were selected and treated with cyclophosphamide, dexamethasone and UV irradiation of the inoculated eye or UV irradiation alone, to reactivate latent virus. After either treatment mice developed signs of recurrent infection (virus in eyewashings and recurrent corneal and/or lid disease). The incidence of such signs was 17/33 (52%) in mice receiving immunosuppressive drugs and UV irradiation and 19/32 (59%) in mice given UV irradiation alone. In mice treated with either stimulus dendritic or geographic ulceration of the cornea was seen. These closely resembled the herpetic lesions seen in humans. There was good correlation between the pattern and distribution of recurrent corneal disease and the distribution of cells containing virus antigens in corneal epithelial sheets. Again, as in humans, the induction of recurrent infection was found to correlate poorly with a rise in the level of serum neutralizing antibody. In mice treated with UV irradiation alone corneal ulcers healed and the eyes returned to normal. By contrast, in mice given immunosuppressive drugs and UV irradiation, the ulceration became more severe and the eyes became opaque and vascularized. The use of passive immunization has greatly improved our previously reported model of recurrent herpetic eye disease since it has increased the incidence of mice suitable for the induction of recurrent infection and has increased the incidence of such infection.

Animals↗
PubMed1989

Effects of atracurium administered by continuous intravenous infusion in halothane-anesthetized horses.

Atracurium (0.4 mg/ml in isotonic NaCl solution) was administered by IV infusion to 7 healthy adult horses for 2 hours. Over the 2-hour period, a 95 to 99% reduction of train-of-four hoof-twitch response was maintained by 0.17 +/- 0.01 mg of atracurium/kg of body weight/h, for a total of 161 +/- 6 mg of atracurium (mean +/- SEM) for horses 1 to 4, 6, and 7. Horse 5, a mare in estrus, required 0.49 mg of atracurium/kg/h to maintain comparable relaxation. Hoof-twitch recovery time from 10 to 75% of baseline strength was 19.8 +/- 2.5 minutes for all horses. The 10 to 75% recovery time for horse 5 was 18 minutes. Recovery time from discontinuation of halothane until standing was 86 +/- 14 minutes (range, 55 to 165 minutes). Horse 5 had a 165-minute recovery. Regarding recovery from anesthesia, 3 recoveries were rated as excellent, 1 recovery good, and 2 recoveries as fair. Horse 5 laid quietly until she stood with 1 strong, smooth effort.

Anesthesia Recovery Period↗
PubMed1988

Neural spread of herpes simplex virus to the eye of the mouse: microbiological aspects and effect on the blink reflex.

This paper reports the microbiological aspects of zosteriform spread of herpes simplex virus (HSV) to the eye in the NIH strain of inbred mouse. Microbiological data support the concept of true zosteriform spread of herpes simplex virus from the inoculation site on the snout to the trigeminal ganglion, and thence to the eye. Following zosteriform spread of HSV to the eye, there is a frequent bacterial superinfection and this is associated with a typical clinical picture. Treatment of the mice with intensive systemic and topical antibiotics is able to alter the frequency with which this type of keratitis is seen.

Animals↗
PubMed1988

Pulmonary veno-occlusive disease associated with severe reduction of single-breath carbon monoxide diffusing capacity.

A 49-year-old woman presented with pulmonary hypertension, profound arterial hypoxemia, and a single-breath carbon monoxide diffusing capacity (DLCO) which was 17% of predicted. History, physical examination, and chest roentgenograms did not suggest the presence of parenchymal pulmonary disease. Spirometry and lung volume measurements were within normal limits. Pulmonary veno-occlusive disease was diagnosed by lung biopsy. This case illustrates the severe reduction of DLCO which can be associated with pulmonary veno-occlusive disease.

Carbon Monoxide↗