Adaptations during the stance phase of gait for simulated flexion contractures at the knee

Adaptations in the stance phase of gait to knee flexion contractures simulated by a knee-ankle-foot orthosis were studied in 20 healthy women (mean age: 25 +/- 3.6 years). Stride characteristics, joint postures, floor reactions, and indwelling electromyographic activity of the lower gluteus maximus, vastus lateralis, long head of the biceps femoris, and soleus muscles were measured during walking with the orthosis, with and without contracture simulation. Simulated knee flexion contracture resulted in decreased stride length and velocity and increased forefoot weight bearing and flexion posture in stance. Increases were also seen in magnitude and/or duration of flexion floor reaction torques and gluteus maximus, vastus lateralis, and soleus muscle activity. The addition of a restriction of plantar flexion resulted in a further decrease in velocity and stride length and a small increase in hip extension posture. These results show that knee flexion contractures, simulated in healthy subjects, cause a decrease in gait function with a simultaneous increase in muscular demand.

Informatics for nurse managers: integrating clinical expertise, business applications, and technology

Nurse managers must become familiar with computers, information systems, and nursing informatics in order to be competitive in the future. Knowledge and skills for identifying critical data elements, organizing the data into information, and presenting it for decision making can be learned through formal and informal education. After learning to use computers and to apply nursing informatics, nurse managers will be equipped to make more relevant, data-driven management decisions. This article describes how nurse managers can identify business applications relevant to management, learn how to use them, and put nursing informatics to work in very practical ways.

Preconditioning in isolated superfused rabbit papillary muscles

Preconditioning has only been demonstrated in arterially perfused myocardium. Our aim was to develop a model of preconditioning in isolated, superfused, isometrically contracting rabbit right ventricular papillary muscle. This would eventually allow us to evaluate isolated human muscles. Papillary muscles were suspended in an organ bath, superfused with oxygenated Tyrode solution, and field stimulated at 1 Hz. Muscles were assigned either to control or to preconditioning groups. Preconditioning was induced with 3 min of rapid pacing (3 Hz) with substrate-free hypoxic buffer and was followed by 15 min of reoxygenation with substrate. Subsequently, both groups were exposed to 45 min of substrate-free hypoxia followed by 120 min of reoxygenation with substrate. Preconditioning protected the myocardium with better recovery of developed force (50.6 +/- 6.7 vs. 27.4 +/- 4.2% of baseline developed force, P < 0.01). This effect could be blocked by 8-(p-sulfophenyl)theophylline (SPT) given during preconditioning at a dose that did not increase hypoxic damage in controls (percent developed force compared to baseline: preconditioned muscles + SPT = 30.9 +/- 2.8% and control muscles + SPT = 27.1 +/- 2.3%). In addition, pretreatment with (-)N6(2-phenylisopropyl)adenosine similarly protected the myocardium (49.5 +/- 5.5% recovery, P < 0.01). We conclude that isolated superfused muscles can be preconditioned. This preconditioning does not depend on coronary flow and involves activation of adenosine receptors.

Myocardial protection after whole body heat stress in the rabbit is dependent on metabolic substrate and is related to the amount of the inducible 70-kD heat stress protein

The aims of this study were to examine the effects of whole body heat stress and subsequent stress protein induction on glycolytic metabolism, mitochondrial metabolism, and calcium handling within the heart. The effect of heat stress on glycolytic and mitochondrial pathways was examined by measuring contractile performance in the presence of glucose and pyruvate, respectively. Calcium handling was assessed using force-interval relationships. Right ventricular papillary muscles taken from heat-stressed and control rabbit hearts were superfused with Kreb's solution containing either glucose or pyruvate and rendered hypoxic for 30 min. After reoxygenation, the greatest recovery of contractile function occurred in the heat-stressed muscles with pyruvate as substrate; there was, however, no difference in the force-interval relationship between the groups. The degree of contractile recovery was related to the content of the inducible 70-kD but not the 65-kD, heat stress protein. This study suggests that heat stress enhances the ability of rabbit papillary muscle to use pyruvate, but not glucose, after reoxygenation, and that the differences seen in contractility may be secondary to induction of the 72-kD stress protein.

Effects of sigma ligands on rat cerebellar Purkinje neuron firing: an iontophoretic study

The electrophysiological responses of rat cerebellar Purkinje neurons to selective sigma ligands applied iontophoretically was examined in urethane anesthetized male Sprague-Dawley rats. 1,3-Di-o-tolylguanidine (DTG), dextrallorphan (DEX), (+)-pentazocine((+)-PENT), (+)-3-(3-Hydroxyphenyl)-N-propylpiperidine ((+)-3-PPP), and the novel diamine BD1008, were ejected from multibarrel pipettes onto individual Purkinje cells. In some neurons, cell firing was inhibited following ejections of all compounds. These inhibitory effects were dose dependent and occurred without changes in spike amplitude or duration, thus ruling out local anesthetic effects as a mechanism. (+)-3-PPP and DEX increased firing rate in 27% and 14% (n = 15, n = 14, respectively) of cells studied. The results of this study indicate that sigma ligands significantly alter the spontaneous firing of Purkinje neurons, consistent with previous work suggesting motor effects of sigma ligands via the rubro-cerebellar circuitry.

Antinociceptive actions of cannabinoids following intraventricular administration in rats

Intraventricular administration of 5 or 20 micrograms of the cannabinoids WIN55,212-2 and CP-55,940 markedly reduced rat's responses to noxious thermal stimuli in the tail-flick test; no significant effect was found at 1 micrograms. The dose-response curves were steep and monotonic, the onset was rapid, and the effect lasted about an hour at the highest dose. In contrast to their antinociceptive actions, WIN55,212-2 and CP-55,940 failed to alter the latency of righting reflexes at the highest dose, suggesting that motor impairment did not cause the decreased responsiveness to the thermal stimulus. Finally, an assessment of the biodistribution of intraventricularly administered [3H]WIN55,212-2 in brain and spinal cord at the time of maximal antinociception revealed that the drug was confined to the brain. The levels of [3H]WIN55,212-2 found in S3-S4, the location of the spinal mechanisms for tail-flick, were below the limit of detectability. Together, these findings provide direct evidence that the antinociceptive effects of cannabinoids are mediated, at least in part, by their actions in the brain.

Global myocardial ischemia protects the myocardium from subsequent regional ischemia

Many investigators use in vitro models of global ischemia to examine the effects of preconditioning, often with recovery of contractile function as the end-point. Such models are relevant to myocardial protection during cardiac surgery. However, there is still debate as to whether preconditioning preserves ventricular contraction secondary to limitation of infarction or by a direct effect on stunning. Since infarct size is the original end-point against which protection by preconditioning is measured, our aims were, first, to validate global ischemic preconditioning by measuring infarct size after subsequent regional ischemia and, second, to correlate limitation of infarct size with mechanical function. After stabilization, seven isolated buffer perfused rabbit hearts were subjected to 5 minutes of global "no-flow" ischemia followed by 10 minutes of reperfusion ("global preconditioning"). Seven control hearts were allowed to stabilize for an additional 15 minutes at constant flow. Subsequently, regional ischemia was induced in both groups for 45 minutes followed by 2 hours of reperfusion. Left ventricular and coronary perfusion pressures were measured throughout. Myocardial infarct size was measured using triphenyltetrazolium staining and expressed as a percentage of the area at risk outlined with fluorescent microspheres. The ratio of infarct to risk zone was reduced from 47.6 +/- 7.3% in control hearts to 16.4 +/- 5.4% (p = 0.005) in preconditioned hearts, confirming the efficacy of global preconditioning. In addition, preconditioning led to a better preservation of systolic function, which correlated significantly with limitation of infarct size (r = 0.75, p = 0.002). Global preconditioning may account for the successful use of cross-clamp fibrillation during cardiac surgery.

Sigma binding parameters in developing rats predict behavioral efficacy of a sigma ligand

The relationship between sigma binding and the behavioral efficacy of a selective sigma ligand was examined in rats of varying ages (30, 45, 60, 75, 90, and 150 days old). Scatchard analyses of the binding of the sigma radioligand [3H]1,3-di-o-tolylguanidine ([3H]DTG) to brain membranes revealed significant age-related differences in binding to both crude synaptosomal and microsomal fractions. The functional significance of these developmental changes in sigma ligand binding was studied by determining the postural effects of rubral microinjections of DTG in age-matched littermates of rats used in the binding studies. The degree of dystonia produced by a single dose of DTG was significantly correlated with the amount of [3H]DTG bound to rat brain synaptosomal membranes at low but not at high concentrations. No significant correlation between binding to the microsomal fraction and drug efficacy was observed. These experimental results were in good agreement with predicted amounts bound as estimated from a Scatchard analysis of the data. The results suggest that sigma binding sites found in brain synaptosomal membranes are functional receptors involved in the control of movement and posture.

An evaluation of a rinse procedure using sodium bicarbonate and hydrogen peroxide on the recovery of bacteria from broiler carcasses

A patent entitled "Reduction of Bacteria Count on Poultry Being Processed into Food at a Poultry Processing Plant" (U.S. Patent No. 4,683,618) claimed that a three-step rinse process using sodium bicarbonate and hydrogen peroxide solutions would remove bacteria from the surface of broiler carcasses. In three replicate trials, 40 broilers were obtained postchill from a commercial processing plant. Broilers (n = 20) were treated according to the patent by spraying the inside and outside surfaces of each carcass with a 2% NaHCO3 solution for 5 s and rinsing with water, repeating, spraying with a 3% H2O2 solution for 5 s, and rinsing a final time with water. Controls (n = 20) were treated identically except that in each of the rinse steps tap water was used in place of the test solutions. Whole carcass rinses were conducted and total aerobic plate counts (TPC) and impedance detection times (DT) were determined after 1 h and 7 days at 4 C. The NaHCO3 + H2O2 treatment resulted in no significant difference in TPC at 1 h post-treatment but did result in lower TPC after 7 days and greater DT at both 1 h and 7 days. The procedure was effective in reducing the recovery of bacteria at 7 days post-treatment by .3 log10 but was not effective in removing the bacteria to the extent implied in the patient. Based on previous studies using H2O2, these results are not unexpected, but commercial applicability remains questionable based on actual reduction levels.

Nurses' perceptions of patients' feelings about breast surgery

This qualitative study was designed to gain insight into nurses' perceptions of patients' feelings and needs with specific reference to breast surgery. A grounded theory approach was adopted, based on in-depth, unstructured interviews with eight trained nurses working on surgical wards in a district general hospital. It emerged that the informants believed breast surgery patients to be very vulnerable and to be suffering from extreme stress and trauma. Patients were thought to lack knowledge regarding their treatment and condition. The nurses thought it to be their moral and professional duty to act as advocates for the patient and the family. Imposed restrictions on their advocacy role were found to cause a sense of frustration and powerlessness which appeared to be compounded by the nurses' perceived lack of counselling skills and the absence of a readily available counsellor or specialist nurse. Recommendations for improvements in the care of patients undergoing breast surgery are based upon these findings.

The difference between disability and impairment: A distinction worth making

American employers pay far too much for workplace disability. In part, disability expenditures continue to increase because key decision-makers in work organizations do not understand the difference between impairment and disability. Impairment is a medical issue. Disability is a non-medical concept; a vocational issue. Disability can be managed like any other vocational problem. Managing disability in the workplace is a function of employer commitment and planned team effort. Managing disability can save employers substantial costs.

Attenuation by heat stress of a submaximal calcium paradox in the rabbit heart

Heat stress limits the injury associated with myocardial ischaemia and reperfusion, an effect previously attributed to enhanced endogenous anti-oxidant activity. We examined the influence of heat stress on the calcium paradox, an injury in which oxidant stress is not thought to play a major role. Twenty-four hours following sham or true heat stress, rabbits were re-anaesthetized and hearts either removed for stress protein analysis (n = 8), or Langendorff-perfused (n = 20) and subjected to a calcium paradox. Ten minutes following calcium repletion (Ca2+ = 1.3 mM), left ventricular developed pressure was better preserved in heat stress vs control hearts (38.3 +/- 5.0 vs 18.8 +/- 4.1 mmHg, respectively, P = 0.003) whilst contracture, measured by left ventricular end-diastolic pressure, was diminished (21.6 +/- 4.7 vs 39.9 +/- 5.2 mmHg, respectively, P = 0.02). Creatine phosphokinase release at 1 min was less in heat stress vs control hearts (10.6 +/- 8.6 vs 86.4 +/- 33.7 U/min/g, respectively, P = 0.01). The myocardial content of the 72 kDa stress protein was elevated eight-fold in heat stress vs control hearts (2.8 +/- 0.2 vs 0.4 +/- 0.1 U, respectively, P = 0.01). This study suggests that some portion of the stress protein response represents a form of cardiac adaptation capable of limiting myocyte injury independent of antioxidant mechanisms.

Cardiac stress protein elevation 24 hours after brief ischemia or heat stress is associated with resistance to myocardial infarction

BACKGROUND

To test the hypothesis that the heat shock response is associated with myocardial salvage, the heat stress protein (HSP) content of cardiac tissue was increased by either ischemic or thermal stress.

METHODS AND RESULTS

Rabbits were divided into four groups. Ischemic pretreatment (n = 15) comprised four 5-minute episodes of coronary ligation separated by 10 minutes of reperfusion. The corresponding control group (n = 21) underwent surgical preparation without coronary ligation. Thermal pretreatment (n = 16) involved whole-body temperature elevation to 42 degrees C for 15 minutes; corresponding controls (n = 15) were treated with anesthetic alone. Twenty-four hours later, hearts were removed for HSP estimation or infarct size assessment after a 30-minute coronary ligation. Myocardial HSP72 content assessed by Western blotting was elevated by both ischemic and thermal pretreatments (2.5 +/- 0.2 units, n = 4, and 2.8 +/- 0.3 units, n = 4, mean +/- SEM; P = NS, respectively) compared with the corresponding control groups (1.0 +/- 0.3, n = 4, P < or = .01 and 0.3 +/- 0.1, n = 4, P < or = .01, respectively). HSP60 was preferentially elevated by ischemic pretreatment. After a 30-minute coronary occlusion and 120 minutes of reperfusion, ischemic and thermal pretreatments limited infarct size as a percentage of the volume at risk by 28.8 +/- 5.2% vs 52.0 +/- 5.2%, P < or = .01 and 32.8 +/- 3.8% vs 56.9 +/- 6.5%, P < or = .01, respectively.

CONCLUSIONS

Myocardial stress protein induced by either sublethal thermal or ischemic injury is associated with myocardial salvage. Our findings suggest that stress protein elevation, rather than the nonspecific effects of thermal or ischemic stress, may be responsible for the myocardial protection seen in this model. Our observations may have important implications regarding myocardial adaptation to brief periods of ischemia.

Carboxy-terminal deletion analysis of oat phytochrome A reveals the presence of separate domains required for structure and biological activity

A series of seven carboxy-terminal deletion mutants of oat phytochrome A were stably expressed in transgenic tobacco to localize phytochrome domains involved in chromophore attachment, spectral integrity, photoreversibility between the red light (Pr)- and far-red light (Pfr)-absorbing forms, dimerization, and biological activity. Amino acids necessary for chromophore attachment in vivo were localized to the amino-terminal 398 residues because mutant proteins this small had covalently bound chromophore. Deletion mutants from the carboxy terminus to residue 653 were spectrally indistinguishable from the full-length chromoprotein. In contrast, further truncation to residue 399 resulted in a chromoprotein with a bleached Pfr absorbance spectrum, Pr and Pfr absorbance maxima shifted toward shorter wavelengths, and reduced Pfr to Pr phototransformation efficiency. Thus, residues between 399 ad 652 are required for spectral integrity but are not essential for chromophore attachment. The sequence(s) between residues 919 and 1093 appears to be necessary for dimerization. Carboxy-terminal mutants containing this region behaved as dimers under nondenaturing conditions in vitro, whereas truncations without this region behaved as monomers. None of the plants expressing high levels of deletion mutants lacking the 35 carboxy-terminal amino acids displayed the light-exaggerated phenotype characteristic of plants expressing biologically active phytochrome A, even when the truncated phytochromes were expressed at levels 6- to 15-fold greater than that effective for the full-length chromoprotein. Collectively, these data show that the phytochrome protein contains several separable carboxy-terminal domains required for structure/function and identify a domain within 35 residues of the carboxy terminus that is critical for the biological activity of the photoreceptor in vivo.

A single five minute period of rapid atrial pacing fails to limit infarct size in the in situ rabbit heart

OBJECTIVE

Rapid pacing has been shown to precondition the dog heart against ischaemic dysrhythmia. The aim of this study was to determine whether rapid pacing could also limit infarct size.

METHODS

Rabbits (n = 5) were rapidly paced via the left atrium at 420-480 beats.min-1. Five min of rapid pacing and 10 min of recovery in sinus rhythm were followed by 45 min of regional ischaemia and 120 min of reperfusion. Control rabbits (n = 9) were treated identically without prior rapid pacing. Infarct size was determined in both groups using tetrazolium and expressed as a percentage of the area at risk demarcated by fluorescent microspheres. In a separate series of experiments, rapidly paced Langendorff perfused rabbit hearts (n = 9) were used to determine coronary flow under perfusion conditions designed to simulate the in vivo situation during rapid pacing.

RESULTS

Rapid pacing caused a fall in systolic pressure from 91.4(SEM 4.5) to 47.0(5.9) mm Hg (p < 0.01) and diastolic pressure from 67.2(2.9) to 23.6(3.2) mm Hg (p < 0.01). Both recovered within 30 s of cessation of pacing. During rapid pacing the action potential duration shortened from 192(13) to 128(5) ms (p = 0.01) and developed electrical alternans (n = 4). Following rapid pacing the ECG showed either ST depression or T wave inversion (n = 4). Despite these profound changes, rapid pacing did not reduce infarct size v control [52.7(4.6)% v 60.8(9.1)% of the area at risk, respectively]. The in vitro experiments estimated that rapid pacing would result in a reduction in coronary flow to 44% of that in sinus rhythm without a significant rise in lactate efflux.

CONCLUSIONS

In our model, pretreatment with rapid pacing fails to reduce infarct size. The most likely reason for this is that rapid pacing at a rate of 480 beats.min-1 does not cause myocardial ischaemia of sufficient severity to trigger the preconditioning response.

Purification of aspartate aminotransferase from Thermus aquaticus

A method is described for the purification of the enzyme aspartate aminotransferase from the thermophile Thermus aquaticus. The enzyme has been characterized with respect to its molecular weight on SDS PAGE and by amino acid analysis. Attempts to obtain N-terminal sequence data was unsuccessful, presumably due to a blocked N-terminus. The purified enzyme has been shown to be highly thermostable, having a half life of inactivation of about 6 hours at 100 degrees C, and to have a temperature optimum greater than 95 degrees C.

Increases in rat striatal extracellular dopamine and vacuous chewing produced by two sigma receptor ligands

The present studies were carried out to analyze the neurochemical and behavioral effects of peripheral sigma ligand administration in the rat. Based upon previous studies which showed an increase in turning behavior following unilateral intranigral administration of sigma ligands, we determined the effects of two sigma ligands, 1,3-di-o-tolylguanidine (DTG) and (+)-pentazocine, on extracellular dopamine levels in the rat striatum. Dopamine levels were monitored via microdialysis in awake freely moving animals following i.p. injection of the ligands. Both DTG (1 and 3 mg/kg) and (+)-pentazocine (10 mg/kg) produced a significant (30-50%) increase in extracellular dopamine. Given the relatively high concentration of sigma receptors in brain nuclei involved in facial and mouth movements, we have also determined the effects of the two sigma ligands on facial movements. Both ligands produced a significant increase in vacuous chewing movements, suggesting that studies on the consequences of sigma receptor activation may have relevance to animal models of human dystonia and/or dyskinesia.

False aneurysm of the pulmonary artery associated with cardiac catheterisation

A false aneurysm of the pulmonary artery developed in a 59 year old woman as a complication of right-sided cardiac catheterisation. This rare, life-threatening condition was successfully treated with coil embolisation of the feeding artery. Cardiologists and intensive care doctors should be aware of the possibility of the formation of false aneurysms of the pulmonary artery after Swan-Ganz and other right heart catheterisation. Appropriate therapy could be life-saving.

A comparison of (-)-deoxybenzomorphans devoid of opiate activity with their dextrorotatory phenolic counterparts suggests role of sigma 2 receptors in motor function

Three novel benzomorphans, (+)-N-benzylnormetazocine, (-)-deoxy-N-benzylnormetazocine, and (-)-deoxypentazocine were tested for their ability to produce circling behavior in rats following intranigral microinjections. Dose studies revealed the following rank order of potency: (-)-deoxypentazocine > (-)-deoxy-N-benzylnormetazocine > (+)-N-benzylnormetazocine. This rank order approximates that for affinities for sigma 2 receptors but not sigma 1 receptors. It is very unlikely that the effects of the (-)-deoxybenzomorphans were mediated by opiate receptors for the following reasons: (1) consistent with the known requirement for the phenolic hydroxyl group for opiate activity, both (-)-deoxy compounds showed very low affinity for opiate receptors; (2) naloxone (4 micrograms) co-administered with (-)-deoxy-N-benzylnormetazocine failed to reduce its efficacy; (3) both (-)-deoxy compounds failed to produce marked analgesic effects in the tail flick test following systemic injections of 20 mg/kg s.c. These finding suggest that sigma 2 receptors mediate the motor effects of sigma ligands in rats.

High-throughput microtiter plate-based chromogenic assays for glycosidase inhibitors

Rapid microtiter plate-based colorimetric assays have been developed that allow the screening of large numbers of samples for the presence of inhibitors of alpha-glucosidase, alpha-amylase, and beta-galactosidase. The assays are particularly useful for screening large numbers of microbial culture filtrates.