Near-infrared spectroscopy during cardiopulmonary resuscitation for pediatric cardiac arrest: A prospective, observational study.

AIM: Cerebral oxygenation (rSO2) is not routinely measured during pediatric cardiopulmonary resuscitation (CPR). We aimed to determine whether higher intra-arrest rSO2 was associated with return of spontaneous circulation (ROSC) and survival to hospital discharge. METHODS: Prospective, single-center observational study of cerebral oximetry using near-infrared spectroscopy (NIRS) during pediatric cardiac arrest from 2016 to 2020. Eligible patients had ≥30 s of rSO2 data recorded during CPR. We compared median rSO2 and percentage of rSO2 measurements above a priori thresholds for the entire event and the final five minutes of the CPR event between patients with and without ROSC and survival to discharge. RESULTS: Twenty-one patients with 23 CPR events were analyzed. ROSC was achieved in 17/23 (73.9%) events and five/21 (23.8%) patients survived to discharge. The median rSO2 was higher for events with ROSC vs. no ROSC for the overall event (62% [56%, 70%] vs. 45% [35%, 51%], p = 0.025) and for the final 5 minutes of the event (66% [55%, 72%] vs. 43% [35%, 44%], p = 0.01). Patients with ROSC had a higher percentage of measurements above 50% during the final five minutes of CPR (100% [100%, 100%] vs. 0% [0%, 29%], p = 0.01). There was no association between rSO2 and survival to discharge. CONCLUSIONS: Higher cerebral rSO2 during CPR for pediatric cardiac arrest was associated with higher rates of ROSC but not with survival to discharge.

Further characterization of embryonic tendon fibroblasts and the use of immunoferritin techniques to study collagen biosynthesis.

Morphological studies were carried out on fibroblasts from chick embryo tendons, cells which have been used in a number of recent studies on collagen biosynthesis. The cells were relatively rich in endoplasmic reticulum and contained a well-developed Golgi complex comprised of small vesicles, stacked membranes, and large vacuoles. Techniques were then devised for preparing cell fragments which were penetrated by ferritin-antibody conjuates but which retained the essential morphological features of the cells. Finally, the new procedures were employed to develop further information as to how collagen is synthesized. As reported elsewhere, preliminary studies with ferritin-labeled antibodies showed that prolyl hydroxylase was found in the endoplasmic reticulum of freshly isolated fibroblasts and that procollagen is found in both the cisternae of the endoplasmic reticulum and the large Golgi vacuoles. In the experiments described here, the cells were manipulated so that amino acids continued to be incorporated into polypeptide chains but assembly of the molecule was not completed because hydroxylation of prolyl and lysyl residues was prevented. The results indicated that these manipulations produced no change in the distribution of prolyl hydroxylase. Examination of the cells with ferritin conjugated to antibodies which reacted with protocollagen, the unhydroxylated form of procollagen, demonstrated that protocollagen was retained in the cisternae of the endoplasmic reticulum during inhibition of the prolyl and lysyl hydroxylases. Assays for prolyl hydroxylase with an immunologic technique demonstrated that although the enzyme is found within the endoplasmic reticulum, it is not secreted along with procollagen. The observations provided further evidence for a special role for prolyl hydroxylase in the control of collagen biosynthesis.

Two improved methods for preparing ferritin-protein conjugates for electron microscopy.

Two improved procedures were developed for activating ferritin so that the ferritin could be covalently linked to antibodies. One procedure involved use of a water-soluble carbodiimide and N-hydroxysuccinimide to prepare ferritin-containing activated esters. The other involved activation of the ferritin with excess glutaraldehyde. The ferritin-antibody conjugates prepared with the two procedures were shown to have a number of properties which made them suitable for locating antigenic components in cells.

Collagen synthesis: localization of prolyl hydroxylase in tendon cells detected with ferritin-labeled antibodies.

An improved procedure was employed for linking ferritin to antibodies against prolyl hydroxylase, the enzyme that synthesizes the hydroxyproline in collagen. By electron microscopy, the enzyme was then found to be localized in cisternae of the rough endoplasmic reticulum of embryonic tendon cells; this indicates that hydroxylation of proline occurs while newly synthesized polypeptides are fed into the cisternae.

Binary Pulsar PSR 1913 + 16: Model for Its Origin.

The existing observational data for the binary pulsar PSR 1913 + 16 are sufficient to give a rather well-defined model for the system. On the basis of evolutionary considerations, the pulsar must be a neutron star near the upper mass limit of 1.2 solar masses (M.). The orbital inclination is probably high, i>/= 700, and the mass of the unseen companion probably lies close to the upper limit of the range 0.25 M. to 1.0 M.. The secondary cannot be a main sequence star and is probably a degenerate helium dwarf. At the 5.6-kiloparsec distance indicated by the dispersion measure, the magnetic dipole model gives an age of approximately 4 x 104 years, a rate of change of the pulsar period of P approximately 2 nanoseconds per day, and a surface magnetic field strength approximately (1/3) that of the Crab pulsar. The pulsar is fainter than an apparent magnitude V approximately + 26.5 and is at least approximately 80 times fainter than the Crab pulsar in the x-ray band. The companion star should be fainter than V approximately + 30, and a radio supernova remnant may be detectable near the position of the pulsar at a flux level of

Comparison of neurological outcomes following witnessed out-of-hospital ventricular fibrillation defibrillated with either biphasic or monophasic automated external defibrillators.

BACKGROUND: Biphasic waveform defibrillation results in higher rates of termination of fibrillation than monophasic waveform defibrillation but has not been shown to improve survival outcomes. OBJECTIVE: To compare the effectiveness of a biphasic automated external defibrillator (AED) with a monophasic AED for witnessed out-of-hospital cardiac arrest (OHCA) due to ventricular fibrillation (VF). METHODS: In a prospective population-based cohort study, adults with witnessed VF OHCA were treated with either monophasic or biphasic waveform AED shocks. The primary outcome measure was neurologically favourable 1-month survival, defined as a Cerebral Performance Categories score of 1 or 2. RESULTS: Of 366 adults with witnessed OHCA of presumed cardiac aetiology, 74 (20%) had VF. Termination of VF with the first shock tended to occur more frequently after biphasic AED shocks (36/44 (82%) vs 20/30 (67%), p = 0.14). Return of spontaneous circulation (ROSC) occurred more frequently after biphasic AED shocks (29/44 (66%) vs 8/30 (27%), p = 0.001). Neurologically favourable 1-month survival was also more frequent in the biphasic group (10/44 (23%) vs 1/30 (3%), p = 0.04). The median time interval from the first shock to the second shock was 67 s in the monophasic group and 24 s in the biphasic group (p = 0.001). CONCLUSIONS: Treatment with biphasic AED shocks improved the likelihood of ROSC and neurologically favourable 1-month survival after witnessed VF compared with monophasic AED shocks. In addition to waveform differences, a shorter time interval from the first shock to the second shock could account for the better outcomes with biphasic AED.

Prevention of collagen deposition following pulmonary oxygen toxicity in the rat by cis-4-hydroxy-L-proline.

Exposure of rats to high oxygen tensions causes increased collagen content of lungs and alveolar enlargement in 3-6 wk. We tested whether cis-hydroxyproline, a proline analogue that inhibits collagen synthesis, could prevent the collagen accumulation and alveolar enlargement. Rats were exposed to hyperoxia for 60 h and then to room air and hyperoxia for alternate 24-h periods for 11.5 d. Treated oxygen-exposed rats received 200 mg/kg cis-hydroxyproline twice daily over the 14-d exposure period. Control rats breathed room air. Examination of lungs on day 14 showed collagen content of oxygen-exposed lungs to be 48% greater than control (P < 0.05). The collagen content of the treated oxygen-exposed lungs was -12% of control (NS). Total lung volume was 16% greater than control in oxygen-exposed rats (P < 0.05) and 8% greater than control in treated oxygen-exposed rats (NS). Morphometric studies showed alveolar size was greater than control in oxygen-exposed rats (188+/-11 [SE] vs. 143+/-6 mumul [P < 0.05]). Oxygen-exposed, treated rats had a mean alveolar volume of 150+/-7 mumul. Lung pressure-volume curves were significantly shifted to the left of control in the oxygen-exposed rats, whereas the curves of the oxygen-exposed, treated group were identical to control. These data suggest that cis-hydroxyproline prevented the accumulation of collagen in the lungs in pulmonary oxygen toxicity. In addition, there was apparent protection from airspace dilatation and decreased lung elasticity, suggesting that alveolar enlargement after oxygen toxicity is linked to the deposition in lung tissue of new connective tissue fibers.

Regulation of collagen production by the beta-adrenergic system.

The suppression of collagen production by increasing the cyclic (c) AMP content of cultured cells was examined vis-à-vis the beta-adrenergic system. Cultured human fetal lung fibroblasts incubated for 6 h with the beta-agonists isoproterenol or epinephrine produced approximately 30% less collagen per cell than in the absence of the hormones. To demonstrate that the beta-agonists were operating by their interaction with the beta-receptor to stimulate adenylate cyclase to increase the intracellular content of cAMP, d- and l-isoproterenol were incubated separately with the cultured cells. Only l-isoproterenol increased intracellular cAMP and decreased collagen production. While 20 nM l-isoproterenol was effective, the d-isomer was ineffective even at 2muM. An increase in cAMP from 40 to 73 pmol/mg protein was effective in suppressing collagen production; increasing the cAMP content to much higher levels had little additional effect on collagen production. 3-Isobutyl-1-methylxanthine, an analog of theophylline that inhibits phosphodiesterase, potentiated the effect of isoproterenol in suppressing collagen production. Further support for the concept that isoproterenol suppressed collagen production by acting through the beta-receptor was provided by the finding that only the l-isomer of propranolol, a beta-blocker, was effective in blocking both the increase in intracellular cAMP and the suppression of collagen production caused by isoproterenol. These results demonstrate that collagen production in human fibroblasts can be regulated by the beta-adrenergic system and indicate that when the cAMP content is increased beyond a threshold value, collagen production is suppressed. Since collagen production is sensitive to the small changes of cAMP content of cells brought about by beta-stimulation in cultured cells, the results point to a possibly important mechanism for the regulation of collagen production in the body.

Cell density-dependent increase in prolyl hydroxylase activity in cultured L-929 cells requires de novo protein synthesis.

Prolyl hydroxylase activity in cultured L-929 cells was found to increase when cells grew from log phase to stationary phase and when cells were harvested at the mid-log phase and replated at higher cell densities. Cycloheximide and actinomycin D inhibited the cell density-dependent increase in prolyl hydroxylase activity indicating that the increase in prolyl hydroxylase activity required de novo synthesis of protein and RNA. Prolyl hydroxylase was purified from cultured L-929 cells and antibodies against the protein were raised in rabbits. The antibodies were used to demonstrate that L-929 cells contained two forms of prolyl hydroxylase: an enzymatically active, tetrameric form consisting of two alpha and two beta polypeptide chains and an enzymatically inactive form containing immunologically cross-reacting protein. The polypeptide chains alpha, beta and cross-reacting protein were obtained by immunoadsorption. Peptide map analysis indicated that cross-reacting protein was similar if not identical to beta in primary structure, and alpha was different from both beta and cross-reacting protein. The results suggested that the prolyl hydroxylase levels in cells or tissues may be regulated by new protein and/or RNA synthesis.

Ascorbate increases the synthesis of procollagen hydroxyproline by cultured fibroblasts from chick embryo tendons without activation of prolyl hydroxyla.

An improved procedure was developed to extract prolyl hydroxylase from tendon cells of chick embryos with detergent, and improved assays were developed for both the activity of the enzyme and the amount of enzyme protein. Freshly isolated tendon cells were found to contain approx. 100 mug of enzyme protein per 10(8) cells and 40-50% of the enzyme protein was active. When the cells were cultured, they were found to contain the same amount of enzyme protein but only 15-20% of the enzyme protein was active. Gel filtration of cell extracts indicated that the active form of prolyl hydroxylase in freshly isolated tendon cells and incultured tendon cells had the same apparent size and the same activity per mug of immunoreactive protein as enzyme which was shown to be a tetramer. The inactive form was found to have about the same apparent size as subunits of the enzyme. When freshly isolated cells were incubated for 2 h in the presence of 40 mug per ml of ascorbate, there was a slight increase in the rate of hydroxyproline synthesis. In cultured cells, ascorbate at a concentration of 40 mug per ml caused a 2-fold increase in the rate of hydroxyproline synthesis within 30 min. However, ascorbate did not icrease the activity of prolyl hydroxylase in extracts from either cell system. Therefore it appears that the influence of ascorbate on synthesis of procollagen hydroxyproline by the cells studied here must be ascribed to a cofactor effect on the hydroxylation reaction similar to that observed with purified enzyme, and it does not involve "activation" of inactive enzyme protein to active enzyme as has been observed in cultures of L-929 and 3T6 mouse fibroblasts.

Endothelin-1 vasoconstriction during swine cardiopulmonary resuscitation improves coronary perfusion pressures but worsens postresuscitation outcome.

BACKGROUND: Vasoconstriction during cardiopulmonary resuscitation (CPR) improves coronary perfusion pressure (CPP) and thereby outcome. The combination of endothelin-1 (ET-1) plus epinephrine improved CPP during CPR compared with epinephrine alone in a canine cardiac arrest model. The effect of the combination on outcome variables, such as successful resuscitation and survival, has not been investigated. METHODS AND RESULTS: Twenty-seven swine were randomly provided with 1 mg epinephrine (Epi group) or 1 mg epinephrine plus 0.1 mg ET-1 (ET-1 group) during a prolonged ventricular fibrillatory cardiac arrest. ET-1 resulted in substantially superior aortic relaxation pressure and CPP during CPR. These hemodynamic improvements tended to increase initial rates of restoration of spontaneous circulation (8 of 10 versus 8 of 17, P=0.12). However, continued intense vasoconstriction from ET-1 led to higher aortic diastolic pressure and very narrow pulse pressure after resuscitation. The mean pulse pressure 1 hour after resuscitation was 7+/-8 mm Hg with ET-1 versus 24+/-1 mm Hg with Epi, P<0.01. Most importantly, the postresuscitation mortality was dramatically higher in the ET-1 group (6 of 8 versus 0 of 8 in the Epi group, P<0.01). CONCLUSIONS: These data establish that administration of ET-1 during CPR can result in worse postresuscitation outcome. The intense vasoconstriction from ET-1 improved CPP during CPR but had detrimental effects in the postresuscitation period.

"Bystander" chest compressions and assisted ventilation independently improve outcome from piglet asphyxial pulseless "cardiac arrest".

BACKGROUND: Bystander cardiopulmonary resuscitation (CPR) without assisted ventilation may be as effective as CPR with assisted ventilation for ventricular fibrillatory cardiac arrests. However, chest compressions alone or ventilation alone is not effective for complete asphyxial cardiac arrests (loss of aortic pulsations). The objective of this investigation was to determine whether these techniques can independently improve outcome at an earlier stage of the asphyxial process. METHODS AND RESULTS: After induction of anesthesia, 40 piglets (11.5+/-0.3 kg) underwent endotracheal tube clamping (6.8+/-0.3 minutes) until simulated pulselessness, defined as aortic systolic pressure <50 mm Hg. For the 8-minute "bystander CPR" period, animals were randomly assigned to chest compressions and assisted ventilation (CC+V), chest compressions only (CC), assisted ventilation only (V), or no bystander CPR (control group). Return of spontaneous circulation occurred during the first 2 minutes of bystander CPR in 10 of 10 CC+V piglets, 6 of 10 V piglets, 4 of 10 CC piglets, and none of the controls (CC+V or V versus controls, P<0.01; CC+V versus CC and V combined, P=0.01). During the first minute of CPR, arterial and mixed venous blood gases were superior in the 3 experimental groups compared with the controls. Twenty-four-hour survival was similarly superior in the 3 experimental groups compared with the controls (8 of 10, 6 of 10, 5 of 10, and 0 of 10, P<0.05 each). CONCLUSIONS: Bystander CPR with CC+V improves outcome in the early stages of apparent pulseless asphyxial cardiac arrest. In addition, this study establishes that bystander CPR with CC or V can independently improve outcome.

Adverse hemodynamic effects of interrupting chest compressions for rescue breathing during cardiopulmonary resuscitation for ventricular fibrillation cardiac arrest.

BACKGROUND: Despite improving arterial oxygen saturation and pH, bystander cardiopulmonary resuscitation (CPR) with chest compressions plus rescue breathing (CC+RB) has not improved survival from ventricular fibrillation (VF) compared with chest compressions alone (CC) in numerous animal models and 2 clinical investigations. METHODS AND RESULTS: After 3 minutes of untreated VF, 14 swine (32+/-1 kg) were randomly assigned to receive CC+RB or CC for 12 minutes, followed by advanced cardiac life support. All 14 animals survived 24 hours, 13 with good neurological outcome. For the CC+RB group, the aortic relaxation pressures routinely decreased during the 2 rescue breaths. Therefore, the mean coronary perfusion pressure of the first 2 compressions in each compression cycle was lower than those of the final 2 compressions (14+/-1 versus 21+/-2 mm Hg, P<0.001). During each minute of CPR, the number of chest compressions was also lower in the CC+RB group (62+/-1 versus 92+/-1 compressions, P<0.001). Consequently, the integrated coronary perfusion pressure was lower with CC+RB during each minute of CPR (P<0.05 for the first 8 minutes). Moreover, at 2 to 5 minutes of CPR, the median left ventricular blood flow by fluorescent microsphere technique was 60 mL. 100 g(-1). min(-1) with CC+RB versus 96 mL. 100 g(-1). min(-1) with CC, P<0.05. Because the arterial oxygen saturation was higher with CC+RB, the left ventricular myocardial oxygen delivery did not differ. CONCLUSIONS: Interrupting chest compressions for rescue breathing can adversely affect hemodynamics during CPR for VF.

Myocardial dysfunction after resuscitation from cardiac arrest: an example of global myocardial stunning.

OBJECTIVES: This study investigated the effect of prolonged cardiac arrest and subsequent cardiopulmonary resuscitation on left ventricular systolic and diastolic function. BACKGROUND: Cardiac arrest from ventricular fibrillation results in cessation of forward blood flow, including myocardial blood flow. During cardiopulmonary resuscitation, myocardial blood flow remains suboptimal. Once the heart is defibrillated and successful resuscitation achieved, reversible myocardial dysfunction, or "stunning," may occur. The magnitude and time course of myocardial stunning from cardiac arrest is unknown. METHODS: Twenty-eight domestic swine (26 +/- 1 kg) were studied with both invasive and noninvasive measurements of ventricular function before and after 10 or 15 min of untreated cardiac arrest. Contrast left ventriculograms, ventricular pressures, cardiac output, isovolumetric relaxation time (tau) and transthoracic Doppler-echocardiographic studies were obtained. RESULTS: Twenty-three of 28 animals were successfully resuscitated and postresuscitation data obtained. Left ventricular ejection fraction showed a significant reduction 30 min after resuscitation (p < 0.05). Regional wall motion analysis revealed diffuse, global left ventricular systolic dysfunction. Left ventricular end-diastolic pressure increased significantly in the postresuscitation period (p < 0.05). Isovolumetric relaxation time (tau) was significantly increased over baseline by 2 h after resuscitation (p < 0.05). Similar findings were noted with the Doppler-echocardiographic analysis, including a reduction in fractional shortening (p < 0.05), a reduction in mitral valve deceleration time (p < 0.05) and an increase in left ventricular isovolumetric relaxation time at 5 h after resuscitation (p < 0.05> By 24 h, these invasive and noninvasive variables of systolic and diastolic left ventricular function had begun to improve. At 48 h, all measures of left ventricular function had returned to baseline levels. CONCLUSIONS: Myocardial systolic and diastolic dysfunction is severe after 10 to 15 min of untreated cardiac arrest and successful resuscitation. Full recovery of this postresuscitation myocardial stunning is seen by 48 h in this experimental model of ventricular fibrillation cardiac arrest.

Dobutamine stress echocardiography: a sensitive indicator of diminished myocardial function in asymptomatic doxorubicin-treated long-term survivors of childhood cancer.

Doxorubicin is an effective anticancer chemotherapeutic agent known to cause acute and chronic cardiomyopathy. To develop a more sensitive echocardiographic screening test for cardiac damage due to doxorubicin, a cohort study was performed using dobutamine infusion to differentiate asymptomatic long-term survivors of childhood cancer treated with doxorubicin from healthy control subjects. Echocardiographic data from the experimental group of 21 patients (mean age 16 +/- 5 years) treated from 1.6 to 14.3 years (median 5.3) before this study with 27 to 532 mg/m2 of doxorubicin (mean 196) were compared with echocardiographic data from 12 normal age-matched control subjects. Graded dobutamine infusions of 0.5, 2.5, 5 and 10 micrograms/kg per min were administered. Echocardiographic Doppler studies were performed before infusion and after 15 min of infusion at each rate. Dobutamine infusion at 10 micrograms/kg per min was discontinued after six studies secondary to a 50% incidence rate of adverse symptoms. The most important findings were that compared with values in control subjects, end-systolic left ventricular posterior wall dimension and percent of left ventricular posterior wall thickening in doxorubicin-treated patients were decreased at baseline study and these findings were more clearly delineated with dobutamine stimulation. End-systolic left ventricular posterior wall dimension at baseline for the doxorubicin-treated group was 11 +/- 1.9 mm versus 13.1 +/- 1.5 mm for control subjects (p less than 0.01). End-systolic left ventricular posterior wall dimension at the 5-micrograms/kg per min dobutamine infusion for the doxorubicin-treated group was 14.1 +/- 2.4 mm versus 19.3 +/- 2.6 mm for control subjects (p less than 0.01).(ABSTRACT TRUNCATED AT 250 WORDS)

Structural brain deficits in schizophrenia. Identification by computed tomographic scan density measurements.

Research has suggested the presence of brain damage as a cause or concomitant of chronic schizophrenia. The most recent research in this area has been the identification of abnormalities in schizophrenia by computed tomographic (CT) scans. A study was done to investigate localized changes in CT scan density numbers in the brains of schizophrenic patients, as opposed to the brains in normal control subjects. Twenty-four normal subjects and 23 schizophrenic patients were tested with CT scans. Density measurements in each area of the brain (left, right, anterior and posterior) were compared to three separate CT scan levels. Of six measurements of anterior left-hemisphere density, it was found that five showed lower density in schizophrenic brains, as compared with normal brains. Of the remaining 18 measurements that evaluated other areas of the brain, only three differentiated between schizophrenic patients and normal subjects. The results support the hypothesis that there are primary structural deficits in some schizophrenic patients, and these deficits are centered in and around the anterior area of the left (dominant) hemisphere. The results also demonstrated further implications.

Regional cerebral blood flow in schizophrenics. Tests using the xenon Xe 133 inhalation method.

Measurements of intrahemispheric and bilateral regional cerebral blood flow (CBF) for gray and white matter were compared in 29 schizophrenic patients and 22 normal controls, using the xenon Xe 133 inhalation method. Results showed significantly lower CBF values for all brain regions in the schizophrenic group, and post hoc comparisons showed relatively greater reduced gray-matter CBF values in the anterior areas of the brain. There was also a left-hemisphere frontal loss similar to that reported previously, although it was in the context of a generalized loss in anterior functioning. Interhemispheric comparison within both groups showed no differences between homologous regions for gray matter, and greater white-matter CBF values in the right hemisphere than in the left hemisphere. The findings support a hypothesis of a bilateral anterior deficit in schizophrenia.

Chemotactic activity of collagen-like polypeptides for human peripheral blood neutrophils.

Damage to interstitial connective tissue is associated with the rapid accumulation of monocytes and neutrophils at the site of injury. To study the role of collagen fragments in neutrophil migration, we analyzed the chemotactic properties of peptide fragments of bovine collagen digested with bacterial collagenase or cyanogen bromide and small molecular weight synthetic polypeptides containing proline (Pro), hydroxyproline (Hyp), and glycine (Gly), the major amino acids that comprise collagen. Using the Boyden chamber and under agarose techniques, we found that collagen fragments were as potent in inducing chemotaxis in neutrophils as the bacterial-derived peptide f-met-leu-phe. The synthetic polytripeptides (Pro-Pro-Gly)5 and (Pro-Hyp-Gly)5 were found to be equipotent in inducing chemotaxis, producing a maximal induction of chemotaxis at 5-10 nM. This suggests that Hyp, the unique imino acid found in collagen, is not required for chemotactic activity. Increasing the length of the synthetic tripeptide from 5 to 10 subunits decreased its chemotactic activity, while the single tripeptide subunit (Pro-Hyp-Gly)1 was the least active peptide, inducing a maximal response at 100 nM. To study the structural requirements for chemotaxis, Pro-Hyp-Gly tripeptides were synthesized with modifications at the N and C terminals ends. Addition of a methyl group to the carboxyl of Gly to form an ester enhanced the chemotactic activity of the peptide by 50%, while substitutions on the amino terminus with an acetyl group decreased the chemotactic activity by 50%. Substitution on the amino terminus with a Boc group decreased the chemotactic activity by 100%. These results indicate that there are specific structural requirements for chemotaxis induced by peptides having a collagen-like sequence of amino acids.

Bystander cardiopulmonary resuscitation. Concerns about mouth-to-mouth contact.

BACKGROUND: Bystander cardiopulmonary resuscitation (CPR) is performed on only a small percentage of patients who suffer cardiac arrest. We conducted a study to elucidate attitudes toward and potential obstacles to performance of bystander CPR. METHODS: Attitude survey of 975 people on the University Heart Center, University of Arizona, Tucson, mailing list. Participants were asked about their willingness to perform CPR under four conditions, with varying relationships (stranger vs relative or friend) and CPR techniques (chest compressions plus mouth-to-mouth ventilation [CC+V] vs chest compressions alone [CC]). RESULTS: Participants rated willingness to perform CPR and concern about disease transmission. Both relationship and CPR technique affected willingness to respond. Only 15% would "definitely" provide CC+V with strangers compared with 68% who would "definitely" perform CC. Even with relatives or friends, only 74% would "definitely" provide CC+V compared with 88% who would "definitely" provide CC. Eighty-two percent of participants were at least "moderately" concerned about disease transmission. CONCLUSION: Concerns regarding mouth-to-mouth ventilation appear to create substantial barriers to performance of bystander CPR. Intensified educational efforts and investigations of new approaches to bystander CPR are warranted.