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Biomedical subjects

M Harrison

Publications and source records attributed to M Harrison.

At least 199 records · Page 11Linked to original sources
PubMed1988

Cerebral blood flow during cardiopulmonary bypass.

In a study of the cerebral consequences of cardiopulmonary bypass (CPB), we have assessed cerebral blood flow (CBF) by intra-arterial Xenon 133 clearance, utilising a Novocerebrograph 10a, before, during and immediately following CPB. All patients (n = 51), under the care of a single surgical team underwent elective coronary revascularisation using a standardised anaesthetic and surgical protocol. CBF, measured as the initial slope index (ISI), fell significantly from before (median 22.5) to on bypass (median 20) (Wilcoxon P less than 0.005) and was significantly increased in the immediate post-bypass period (median 28) compared with pre-bypass (Wilcoxon P less than 0.001). Scattergrams reveal CBF to be independent of arterial pressure (BP) but show an important relationship between arterial PaCO2 and CBF. The correlations between PaCO2 and CBF prior to bypass (r = 0.46 P less than 0.005) and post-bypass (r = 0.46 P less than 0.001) are very similar, whilst on bypass, the correlation, although remaining significant, is reduced (r = 0.31 P less than 0.02). The median values for arterial PaCO2 are low throughout the study (pre-bypass median 33 mmHg, on bypass median 28 mm Hg and post-bypass median 36 mm Hg). The maintenance of PaCO2 within the normal range of 35-45 mm Hg may minimise the risk of low CBF due to hypocarbia which could theoretically be harmful in patients known to be at risk of both short term and long term cerebral dysfunction.

Carbon Dioxide↗
PubMed1988

Changes in the self and professional images of student nurses.

This study tested hypotheses concerning the development of self-image and professional orientations among students of nursing in two Israeli schools (n = 235), one of which was religiously affiliated and the other secular. The study involved a longitudinal comparison of attitudes at the beginning of the programme of study and after 3 months, and a cross-sectional comparison of the attitudes of students in each of the 3 years of the nursing programme. Based on a review of the literature, we predicted that the student's self-image and her image of the ideal professional nurse would grow more congruent during her studies. In addition, we predicted that her image of the ideal professional and the image held by her instructor would grow more congruent. The latter hypothesis was partly supported by the panel data and strongly supported by the cross-sectional data, whereas the hypothesis concerning self-image and professional image was not supported. No support was found for two other hypotheses predicting that religious students would show a greater tendency towards the expected changes. Instead we found that the gap between the religious students' professional image and that held by their instructors was greater than it was for the secular students. Moreover, the supervisors in the religious school had different images of the profession than their secular counterparts.

Cross-Sectional Studies↗
PubMed1988

Comparison of simultaneously performed digital and film-based angiography in assessment of coronary artery disease.

This study compared digital angiography (Digital) to conventional cineangiography (Cine) for the diagnosis and quantification of coronary artery disease. Digital and Cine were obtained simultaneously under identical radiographic conditions during routine coronary arteriography. Using visual inspection and manual calipers, four independent observers identified 131 stenoses in 18 patients with multivessel coronary disease. There was no difference in interobserver variability between Digital and Cine during multiple subgroup analyses. Overall, Digital yielded significantly greater estimates of stenosis severity than did either of two separate Cine observations (p less than 0.0001; average difference, 6.25%), but the differences fell below the level of statistical significance when only the group of stenoses 50% or greater were considered. Digital and Cine correlated well for the assessment of stenosis severity (r = 0.88), but linear regression comparisons of multiple subgroups consistently indicated modest overestimation of Cine by Digital. Smaller vessels, branch vessels, and mild lesions increased the likelihood of overestimation by Digital. Digital was highly sensitive for identification of clinically relevant stenoses, but less specific and less predictive than a second observation of Cine. Our results indicate that Digital and Cine are not interchangeable imaging techniques and that potential differences must be considered when Digital is used for clinical decision making.

Angiography↗
PubMed1988

Chronic hyperdynamic sepsis in the rat: I. Characterization of the animal model.

We describe a new rat model of chronic hyperdynamic sepsis. After control values for weight gain, and food and water intake of each animal were obtained over a 5-day period, male Sprague-Dawley rats weighing 370-425 g were anesthetized, catheterized to allow chronic cardiac-output measurements, and a sterile subcutaneous cavity was formed over the flank area. The animals were allowed a 3-4 day postoperative recovery period. Body weight, food and water intake, and cardiac output were measured daily. Frequent blood samples were withdrawn for bacterial cultures and white cell counts (WBC). On the third and, in some cases, the fourth postoperative day, the subcutaneous cavity was inoculated with 10(9) colony-forming units of Escherichia coli and Bacteroides fragilis. The resulting sepsis was characterized by loss of body weight in spite of normal food and water intake, increased cardiac output, increased WBC, intermittent bacteremia, decreased muscle mass, and decreased cross-sectional area of skeletal muscle myofibrils. Two levels of septic response emerged--moderate and severe. Based on the above-mentioned measurements, it was possible to categorize all long-term septic animals into these two groups. Both groups exhibited cardiac-output, body-weight, and WBC data significantly different from sham controls. Repeated inoculations of the subcutaneous abscess initiated on the third postoperative day resulted in moderate sepsis with no long-term mortality, severe sepsis with 23% mortality over a 3-week period, or a 100% mortality within 4 days, depending on the virulence of the E. coli organisms used. The new model is ideally suited for pathophysiologic studies of sustained, hyperdynamic sepsis.

Animals↗
PubMed1987

Ultrastructural, histochemical, and freeze-fracture evaluation of multilamellated structures in human pulmonary alveolar proteinosis.

Ultrastructural, histochemical, and freeze-fracture studies of material recovered by bronchoalveolar lavage from patients with pulmonary alveolar proteinosis revealed four types (A, B, C, and D) of multilamellated structures (MS). Type A, the major component, consisted of concentric, trilaminar structures which were composed of two electron-dense layers and a central lucent layer (5.7-7.5 nm in overall width) alternating with wider (25-30 nm) electron-lucent intervening layers. Type B MS were formed by concentric lamellae with a 5-5.3-nm periodicity. Type C MS were composed of wavy, electron-dense lamellae with a 4-4.5-nm periodicity. Type D MS were conglomerated masses of intricately arranged double or triple electron-dense layers (7.5-13.5 nm wide) alternating with wider (30-40-nm) electron-lucent layers. The electron-dense lamellae of type A, type C, and type D MS were stained with ruthenium red, the Thiéry method, and concanavalin A, indicating the presence of carbohydrate components. Freeze-fracture studies revealed smooth inner and outer surfaces in type A MS, with the fracture planes passing through the central parts of the trilaminar structures; the intervening layers contained 10-nm particles, which probably are proteins. Type B MS had smooth surfaces, and type C MS had slightly particulate surfaces; while type D MS showed tubular or polygonal structures, 350 nm wide, with rows of particles 7-8 nm in diameter. It is concluded that type A and type D MS contain proteins and carbohydrates, probably in the form of glycoproteins, as well as phospholipids, and are related to tubular myelin. Type B and type C MS are considered to contain mainly phospholipids; type C MS are also considered to contain carbohydrates and to be related to lamellar bodies of type II alveolar epithelial cells.

Adult↗
PubMed1987

Pain: advances and issues in critical care.

The milieu of the critical care unit is stressful for both the patient and health care professionals. As such, it has the potential to increase pain perception in patients, and decrease the nurse's awareness of pain relief needs of the patient. Several physical and pharmacologic methods of pain relief were discussed in this article. Nontechnologic analgesia such as hypnosis and relaxation were introduced as adjuncts or alternatives to more familiar methods of pain relief. Although critically ill patients are not always able to express their discomfort, it is the responsibility of the nurse to recognize the potential for pain, and plan treatment accordingly. This article suggests several strategies for dealing with pain in critically ill patients.

Analgesics↗
PubMed1987

Hypnosis as an intervention for pain control.

The use of formal hypnosis and/or positive, comforting suggestions to patients for control of pain, fear, and anxiety is simple and effective. In addition, it is easy to learn and teach to patients. Spiegel states that hypnosis, a group of techniques long associated with fantasies of loss of control, is ironically very helpful in actually enhancing patients' sense of control. The clinicians daring to become proficient in the use of hypnotic trance must begin with a conscious effort to abandon all negative suggestions such as "Do you have pain?"; "How much do you hurt?"; and "Move your bad leg." Simultaneously, a conscious effort is made to increase the use of the following positive suggestions: "How comfortable are you going to be tonight?" "Your hand feels so soft and warm"; "It is important to move this leg." These communication skills are best learned from clinicians skilled in hypnotherapeutic techniques. Simultaneously, it is important to become familiar with the works of Erikson and Barber. The American Society of Clinical Hypnosis will provide information about the national organizations and state hypnosis societies that offer approved workshops, conferences, and training opportunities. Hypnosis as analgesia surely provides rest, relaxation, and comfort for patients without the negative side effects of other analgesics. In addition, the ultimate benefit of hypnotic analgesia lies in enabling patients to potentiate their inner strength, resulting in improved self-esteem and self-control.

Humans↗
PubMed1986

Structural relationship between tRNALys2 and tRNALys4 from mouse lymphoma cells.

Mouse lymphoma cells have three major isoaccepting lysine tRNAs. Two of these isoacceptors, tRNALys2 and tRNALys4, were sequenced by rapid gel or chromatogram readout methods. They have the same primary sequence but differ in two modified nucleotides. tRNALys4 has an unmodified uridine replacing one dihydrouridine and an unidentified nucleotide, t6A*, replacing t6A. This unidentified nucleotide is not a hypomodified form of t6A. Thus, tRNALys4 is not a simple precursor of tRNALys2. Both tRNAs have an unidentified nucleotide, U**, in the third position of the anticodon. Also, partial sequences of minor homologs of tRNALys2 and tRNALys4 were obtained. The distinctions between tRNALys2 and tRNALys4 may be part of significant cellular roles as illustrated by the differential effects of these isoacceptors on the synthesis by lysyl-tRNA synthetase of diadenosine-5',5'''-P1,P4-tetraphosphate, a putative signal in DNA replication.

Animals↗
PubMed1986

Metallurgical analysis of failed Björk-Shiley cardiac valve prostheses.

An investigation into the mechanisms of failure of current Björk-Shiley cardiac valve prostheses is reported. Two failed valves, one apparently unfailed but defective valve, and one unused valve, were examined by scanning electron microscopy and metallographic section. In the first two valves (removed 12 and 23 months after implantation) fracture was associated with the welds joining the short strut to the valve ring. The fracture surfaces in all cases were heavily faceted and showed branching cracks. Extensive wear had occurred on one fracture surface in the first case, suggesting that one leg of the short strut had failed before the other, though this had been clinically undetectable. The third valve was removed owing to failure of the suturing (24 months after implantation) but one leg of the short strut was found to be completely fractured. The other leg showed extensive cracking and porosity in the weld region. A metallographic section taken through the weld region of the fourth (unused) valve illustrated several sizable defects directly attributable to the welding process. It is suggested that the valves failed by fatigue and that these problems could be overcome if the complete valve cage were machined as a single piece.

Aged↗
PubMed1986

Basal temporal language area demonstrated by electrical stimulation.

We report on a 38-year-old patient with intractable complex partial seizures originating in the dominant left medial temporal region. In the work-up for seizure surgery, arrays of subdural electrodes were placed, and electrical stimulation revealed marked language interference in a 2 X 2-cm area in the left basal temporal fusiform gyrus (3.5 to 5.5 cm posterior to the temporal tip). Complete receptive and expressive aphasia, inability to repeat, agraphia, and alexia were elicited, but visual memory was preserved, and no constructional apraxia was noted. Stimulation of the basal temporal gyrus at lower stimulus intensities produced a relatively selective and severe anomia.

Adult↗
PubMed1986

Electrical stimulation of Wernicke's area interferes with comprehension.

Arrays of subdural electrodes were placed over the lateral convexity of the dominant hemisphere for propositional language in four patients with epilepsy as part of an evaluation prior to cortical resections. Stimulation was performed over several days. When we stimulated the posterior temporal language area, reading and comprehension of complex verbal information were impaired, but comprehension of nonverbal and simple verbal data was not affected. Impairment produced by stimulation seemed to be due to language comprehension difficulties, rather than impaired praxis or initial word storage.

Adolescent↗
PubMed1985

Mitochondrial redox responses to cerebral ischaemia produced by four-vessel occlusion in the rat.

Changes in reduction/oxidation (redox) ratios of the initial and terminal members of the mitochondrial respiratory chain (nicotine adenine dinucleotide and cytochrome a,a3) were measured by fluorometry and reflection spectrophotometry in rat cerebral cortex. Three patterns of responses were observed during the transition to global ischaemia produced by electrocoagulation of the vertebral arteries and carotid artery ligation. Most often, arterial occlusion was accompanied by shifts towards reduction of the mitochondrial components followed by partial reoxidation and then further reduction. Less frequently, ischaemia produced reductive shifts of the respiratory chain reactants that rapidly reached maximal values. In some rats, however, arterial, occlusion produced mitochondrial reduction followed by partial or complete reoxidation. ECoG remained suppressed, despite mitochondrial reoxidation, in approximately 1/3 of the latter animals. This study demonstrates that responses to 4-vessel occlusion can vary greatly among animals and suggests that monitoring of signals of ischaemic insult, such as mitochondrial redox status, may offer advantages for assessment of the consequences of ischaemic insult.

Anesthesia, General↗