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Biomedical subjects

K Kendrick

Publications and source records attributed to K Kendrick.

At least 37 records · Page 2Linked to original sources
PubMed1995

Effect of intensity and energy expenditure on postexercise insulin responses in women.

The purposes of the study were to compare insulin responses after rest and exercise of two different intensities and equal total energy expenditure and to examine these responses in normoglycemic women. Twenty-four untrained women (age 23.4 +/- 0.9 yr) completed three randomly assigned treatments over the course of a 3- to 4-wk period: rest, 40% maximal oxygen consumption x 87 min (Low), and 70% maximal oxygen consumption x 50 min (High). Total energy expenditure was 1,821 +/- 61 and 1,692 +/- 59 kJ, heart rate was 119 +/- 2 and 163 +/- 2 beats/min, and oxygen consumption was 17.1 and 27.2 ml.kg-1.min-1 for Low and High, respectively. Fifteen to 17 h posttreatment and 12 h postprandial, each subject drank a 75-g glucose solution (oral glucose tolerance test). Blood samples were drawn before and at 30, 60, 90, 120, and 150 min after ingestion and were analyzed for glucose and insulin. Glucose areas and responses at the same time points across treatments were similar. Area under the insulin curve was significantly lower (P < 0.05) after High (51,864 +/- 3,780 pM x min) compared with rest (61,009 +/- 4,425 pM x min), but Low (59,191 +/- 5,307 pM x min) was not different from either rest or High. The insulin level at the 120-min time point was significantly (P < 0.01) lower after High (290.8 pM) compared with rest (391.7 pM). On the basis of these results, exercise-related changes in insulin responses are more dependent on exercise intensity than on energy expenditure in untrained women.

Adolescent↗
PubMed1994

Simultaneous in vivo measurements of HbO2 saturation and PCr kinetics after exercise in normal humans.

Simultaneous measurements of phosphocreatine (PCr) and oxyhemoglobin (HbO2) saturation were made during recovery from exercise in calf muscles of five male subjects. PCr was measured using magnetic resonance spectroscopy in a 2.0-T 78-cm-bore magnet with a 9-cm-diam surface coil. Relative HbO2 saturation was measured as the difference in absorption of 750- and 850-nm light with use of near-infrared spectroscopy. The light source and detectors were 3 cm apart. Exercise consisted of isokinetic plantar flexion in a supine position. Two 5-min submaximal protocols were performed with PCr depletion to 60% of resting values and with pH values of > 7.0. Then two 1-min protocols of rapid plantar flexion were performed to deplete PCr values to 5-20% of resting values with pH values of < 6.8. Areas of PCr peaks (every 8 s) and HbO2 saturation (every 1 s) were fit to a monoexponential function, and a time constant was calculated. The PCr time constant was larger after maximal exercise (68.3 +/- 10.5 s) than after submaximal exercise (36.0 +/- 6.5 s), which is consistent with the effects of low pH on PCr recovery. HbO2 resaturation approximated submaximal PCr recovery and was not different between maximal (29.4 +/- 5.5 s) and submaximal (27.6 +/- 6.0 s) exercise. We conclude that magnetic resonance spectroscopy measurements of PCr recovery and near-infrared spectroscopy measurements of recovery of HbO2 saturation provide similar information as long as muscle pH remains near 7.0.

Adult↗
PubMed1994

Validation of near-infrared spectroscopy in humans.

Near-infrared (NIR) spectroscopy is a noninvasive technique that uses the differential absorption properties of hemoglobin to evaluate skeletal muscle oxygenation. Oxygenated and deoxygenated hemoglobin absorb light equally at 800 nm, whereas at 760 nm absorption is primarily from deoxygenated hemoglobin. Therefore, monitoring these two wavelengths provides an index of deoxygenation. To investigate whether venous oxygen saturation and absorption between 760 and 800 nm (760-800 nm absorption) are correlated, both were measured during forearm exercise. Significant correlations were observed in all subjects (r = 0.92 +/- 0.07; P < 0.05). The contribution of skin flow to the changes in 760-800 nm absorption was investigated by simultaneous measurement of skin flow by laser flow Doppler and NIR recordings during hot water immersion. Changes in skin flow but not 760-800 nm absorption were noted. Intra-arterial infusions of nitroprusside and norepinephrine were performed to study the effect of alteration of muscle perfusion on 760-800 nm absorption. Limb flow was measured with venous plethysmography. Percent oxygenation increased with nitroprusside and decreased with norepinephrine. Finally, the contribution of myoglobin to the 760-800 nm absorption was assessed by using 1H-magnetic resonance spectroscopy. At peak exercise, percent NIR deoxygenation during exercise was 80 +/- 7%, but only one subject exhibited a small deoxygenated myoglobin signal. In conclusion, 760-800 nm absorption is 1) closely correlated with venous oxygen saturation, 2) minimally affected by skin blood flow, 3) altered by changes in limb perfusion, and 4) primarily derived from deoxygenated hemoglobin and not myoglobin.

Absorption↗
PubMed1994

In vivo magnetic resonance spectroscopy measurement of deoxymyoglobin during exercise in patients with heart failure. Demonstration of abnormal muscle metabolism despite adequate oxygenation.

BACKGROUND: Skeletal muscle metabolic abnormalities have been described in patients with heart failure that are independent of total limb perfusion, histochemical changes, and muscle mass. However, these skeletal muscle metabolic abnormalities may result from tissue hypoxia caused by maldistribution of flow. Myoglobin is an O2 binding protein that can indirectly assess tissue hypoxia. METHODS AND RESULTS: In vivo measurement of deoxymyoglobin was performed by use of proton (1H) magnetic resonance spectroscopy in 16 heart failure (HF) (left ventricular ejection fraction = 20 +/- 6%; VO2 = 14.5 +/- 5.1 mL/kg per minute) and 7 healthy (Nl) subjects. Simultaneous phosphorus (31P) magnetic resonance spectroscopy and near-infrared spectroscopy also were obtained to examine muscle metabolism and oxygenation. Supine calf plantarflexion was performed every 4 seconds. Incremental steady-state work was performed. A second exercise protocol studied rapid incremental (RAMP) exercise with plantarflexion every 2 seconds. Arterial occlusion at end exercise provided physiological calibration for myoglobin and hemoglobin signals. With steady-state exercise, the work slope, ie, inorganic phosphorus to phosphocreatine ratios versus work, was significantly greater in patients with heart failure (Nl: 0.18 +/- 0.08; HF: 0.40 +/- 0.32 W-1; P < .05). Intracellular pH was reduced significantly at end exercise in patients but not healthy subjects. Despite these metabolic abnormalities, muscle oxygenation derived from 760- to 850-nm absorption was comparable in both groups throughout exercise. The relation of inorganic phosphorus/phosphocreatine (P1/PCr) ratio and muscle oxygenation was shifted upward in patients with heart failure such that at the same muscle oxygenation, Pi/PCr ratio in these patients was increased. No deoxymyoglobin signals were observed at rest. At maximal exercise, 4 of the healthy subjects and 3 of the patients exhibited deoxymyoglobin (P = NS). With RAMP exercise, the work slope was again significantly greater in patients with heart failure (Nl: 0.21 +/- 0.10; HF: 0.57 +/- 0.32 W-1; P < .05). Intracellular pH again was significantly decreased at end exercise in patients but not healthy subjects. Five of the healthy subjects and 3 of the heart failure patients had deoxymyoglobin signal (P = NS). With arterial occlusion, deoxymyoglobin was seen in all subjects. CONCLUSION: Abnormal skeletal muscle metabolism in patients with heart failure usually occurs in the absence of myoglobin deoxygenation, suggesting that the abnormalities are not a result of cellular hypoxia during exercise with minimal cardiovascular stress.

Aged↗
PubMed1994

Gaze discrimination in patients with schizophrenia: preliminary report.

The authors administered a gaze discrimination task to 24 patients with chronic schizophrenia and 25 subjects with no psychiatric history. Each subject was shown slides and asked, "Is the person in the slide looking directly at you?" Patients with schizophrenia were more likely than comparison subjects to perceive the person in the slide as looking at them when the person was looking away. Because there is evidence that gaze discrimination performance involves the superior temporal sulcus region of the brain and this region has been implicated in theories about the pathogenesis of schizophrenia, further study of the gaze discrimination task seems indicated.

Adult↗
PubMed1994

Building bridges: teaching ward-based ethics.

Ethics has traditionally been taught in the 'ivory towers' of academia. Recent developments and reforms in nurse education have given ethics a prominent position in most curricula. However, the vast majority of ethics teaching continues to take place in academic departments. This approach fuels the practitioner's views that nursing is a pragmatic activity whilst ethics is a cognitive endeavour; such perspectives entrench ethics firmly in the traditional gap between theory and practice. The focus of this paper presents an argument that the teaching of ethics must be versed in clinical reality if bridges are ever to be built and the theory-practice gap crossed.

Bioethical Issues↗
PubMed1994

An advocate for whom--doctor or patient? How far can a nurse be a patient's advocate?

1. Nursing has always placed a great deal of emphasis on safeguarding patients' interests. 2. The role of advocate is presented as a key means by which nurses can represent the patient's 'best interests'. 3. Healthcare is so laden down by issues of power and politics that it raises doubts about whether nurses are actually in a position to act as the patient's advocate.

Empathy↗
PubMed1994

A freedom to choose. The ethics of informed consent.

1. It is difficult to know how much information should be given to patients to help them give an informed consent. 2. Informed consent provides an avenue for the expression of the ethical themes of autonomy, respect for persons and truth. 3. Informed consent acknowledges patients' intrinsic right to decide what happens to their bodies.

Aged↗
PubMed1988

Striatal grafts in rats with unilateral neostriatal lesions--II. In vivo monitoring of GABA release in globus pallidus and substantia nigra.

GABA release was recorded in vivo by push-pull perfusion from the globus pallidus and substantia nigra of control rats, rats with unilateral ibotenic acid lesions of the neostriatum, and rats with embryonic striatal tissue grafts implanted in the lesioned striatum. The lesions reduced baseline levels of GABA release to 5% of control levels in the globus pallidus and to 13% of control levels in the substantia nigra pars reticulata. GABA release was substantially restored in both the globus pallidus and substantia nigra of the grafted rats, to 34 and 60%, respectively. Peripheral injection of the dopaminergic stimulant methamphetamine induced a short (lasting approximately 20 min) 4-5 fold increase in GABA release in the intact globus pallidus and a longer (lasting longer than 80 min) increase in the substantia nigra. The stimulatory effect of methamphetamine on GABA release was completely abolished in both sites by the strial lesions, suggesting that the effect was mediated via a direct or indirect dopaminergic action on striatal output neurons. The grafts reinstated methamphetamine-induced stimulation of GABA release in striatal output targets to a level (as a proportion of baseline) that was similar to that seen in the control rats. The results support the view that activation of the dopaminergic inputs to the striatum is functionally excitatory on the major striatal output projections to the globus pallidus and substantia nigra pars reticulata. The results also support the hypothesis that striatal grafts have the capacity to become functionally incorporated by reciprocal graft-host connections into the neural circuitry of the host brain.

Animals↗
PubMedDate not supplied

Understanding ethics in nursing practice.

Ethics has traditionally been viewed as an abstract subject confined to the ivory towers of academia. This article challenges that view and describes how ethics can offer nurses a framework for analysing difficult situations at the interface of practice.

Adult↗