Scanning tunneling microscopy: a unique tool in the study of chirality, dynamics, and reactivity in physisorbed organic monolayers.

Scanning tunneling microscopy (STM) is applied to study organic monolayers, physisorbed at the liquid-graphite interface. Due to the very local nature of the probing, the structure of these adlayers has been imaged with very high detail. The high resolution allowed us to investigate the effect of molecular chirality on the monolayer formation and provided a unique way to study chemical reactions at the liquid-graphite interface. Making use of a fast scanning mode, dynamic processes in these adlayers have been visualized.

Prognostic scores for use in African meningococcal epidemics.

Current WHO guidelines for the case management of meningococcal infections during epidemics in developing countries often cannot be applied, largely because of the limited health resources in such countries. Several scoring scales based on clinical and laboratory features in numerous combinations have been developed for the management of meningococcal infections in developed countries, and these have facilitated early identification of patients with fulminant disease and thus early intervention and reduction in mortality. Unfortunately such scoring scales are not appropriate for use in developing countries. We identified hypotension, tachycardia, tachypnoea, delay in capillary refill time, coma, absence of neck stiffness and petechiae and/or purpura as simple prognostic factors of meningococcal disease. Two scores were developed: score I, which includes all seven prognostic factors, had a sensitivity and specificity of 80% and 94%, respectively. Score II, which excluded hypotension, had a sensitivity and specificity of 73.3% and 89.7%, respectively. Quick and simple scoring scales are therefore not only applicable but useful for the case management of patients in meningococcal epidemics in developing countries.

Spatialization and greater generosity in the stochastic Prisoner's Dilemma.

The iterated Prisoner's Dilemma has become the standard model for the evolution of cooperative behavior within a community of egoistic agents, frequently cited for implications in both sociology and biology. Due primarily to the work of Axelrod (1980a, 1980b, 1984, 1985), a strategy of tit for tat (TFT) has established a reputation as being particularly robust. Nowak and Sigmund (1992) have shown, however, that in a world of stochastic error or imperfect communication, it is not TFT that finally triumphs in an ecological model based on population percentages (Axelrod and Hamilton 1981), but 'generous tit for tat' (GTFT), which repays cooperation with a probability of cooperation approaching 1 but forgives defection with a probability of 1/3. In this paper, we consider a spatialized instantiation of the stochastic Prisoner's Dilemma, using two-dimensional cellular automata (Wolfram, 1984, 1986; Gutowitz, 1990) to model the spatial dynamics of populations of competing strategies. The surprising result is that in the spatial model it is not GTFT but still more generous strategies that are favored. The optimal strategy within this spatial ecology appears to be a form of 'bending over backwards', which returns cooperation for defection with a probability of 2/3--a rate twice as generous as GTFT.

The effect of on-site extracorporeal membrane oxygenation on the therapy choice and outcomes of neonates with persistent pulmonary hypertension.

The effect of on-site extracorporeal membrane oxygenation (OS-ECMO) and selection criteria on the utilization rate of this technology is unknown. We retrospectively studied 55 neonates who were admitted to Arkansas Children's Hospital from 1985 to 1993. We compared the ECMO utilization, mortality, and morbidity rates for outborn neonates with moderate and severe persistent pulmonary hypertension (PPHN) before and after the establishment of an ECMO program with guidelines for its use at our institution. The rate of ECMO use was three times higher and the mortality rate was 13 times lower in the period after OS-ECMO compared with the period when ECMO was available only at other institutions. No differences were observed in the morbidity rates between the two periods. Physician decisions to initiate ECMO involved more than guidelines, since 37% of the increased ECMO use was not associated with use of the guidelines. Possible reasons for noncompliance with the guidelines are discussed. Neonates who had received medical therapy only and who had an oxygenation index > or = 30 and < 40 had no mortality. Our findings suggest that the need for ECMO in this group of neonates is low.

Hyperbaric oxygen therapy.

Hyperbaric oxygen therapy involves intermittent inhalation of 100% oxygen under a pressure greater than 1 atm. Despite over a century of use in medical settings, hyperbaric oxygen remains a controversial therapy. The last 20 years have seen a clarification of the mechanism of action of hyperbaric therapy and a greater understanding of its potential benefit. However, despite the substantial evidence that hyperbaric oxygen may have a therapeutic effect in certain carefully defined disease states, many practitioners remain unaware of these findings or are concerned about using hyperbaric therapy because of the controversy it has engendered. This review examines the indications currently considered appropriate for hyperbaric oxygen and briefly evaluates animal and clinical data substantiating these indications. Areas in which the mechanism of action of hyperbaric oxygen is still not well understood, as well as possible new areas of applications, are discussed.

Informed consent in emergency research. Prehospital thrombolytic therapy for acute myocardial infarction.

Can the conscious patient in the midst of a medical emergency provide adequate informed consent for a clinical research protocol? Adequate consent is crucial to the ethical conduct of clinical trials, including those performed in emergency settings. We examine the problem of emergency informed consent. As an illustrative case, we discuss a pilot trial of prehospital thrombolytic therapy for myocardial infarction. Federal regulations for clinical research do not provide clear guidelines on emergency research in the conscious patient. Clinical investigators currently approach emergency consent in four ways: (1) avoid such research, (2) omit the consent process, (3) obtain deferred consent, or (4) obtain customary consent. We suggest a fifth alternative, two-step consent, which permits the conduct of emergency research while protecting the rights of the emergency research subjects. Such a process may serve as an alternative solution for future studies faced with the problem of informed consent in emergencies.

KIE: The problem of informed consent to research in emergency care is examined, using as an example a pilot trial of prehospital administration of thrombolytic therapy for acute myocardial infarction. Current federal regulations governing emergency care research are reviewed, along with four ways in which investigators currently approach emergency consent. The authors' use of a two-step process to resolve the problem of emergency consent is described. This approach allows the conduct of emergency research while protecting the rights of research subjects, and may offer a solution to the the ethical conduct of other studies faced with the problem of consent to emergency care.

Evaluation of patients for the need of thrombolytic therapy in the prehospital setting.

Maximum benefit from thrombolytic therapy in acute myocardial infarction is obtained with early therapy. The earliest possible time to treat is during the initial evaluation of the patient in the home or ambulance, which requires accurate diagnosis of acute myocardial infarction in the prehospital setting. In our study, paramedics evaluated patients who had chest pain with a 12-lead ECG transmitted by cellular telephone and a checklist for inclusion and exclusion criteria for thrombolytic therapy. This information was transmitted to a hospital-based telemetry physician who diagnosed or excluded acute myocardial infarction and made a mock decision to withhold or administer a thrombolytic agent. Forty-eight patients with chest pain were evaluated. Six were diagnosed as having overt acute myocardial infarction by the hospital-based telemetry physician. All six patients had the diagnosis substantiated by both ECG and enzyme studies on hospital admission. Based on the data supplied by paramedics, two of these six patients were considered eligible for thrombolytic therapy by the physician. Hospital evaluation confirmed the prehospital decision to treat with a thrombolytic agent. In addition, all other patients were appropriately diagnosed as ineligible. Prehospital ECG diagnosis resulted in two patients going directly to the catheterization lab, thereby bypassing the emergency department. Overt acute myocardial infarction can be accurately identified by a prehospital-acquired 12-lead ECG transmitted to a hospital-based physician. Our study demonstrates that in conjunction with specially trained paramedics, the hospital physician can decide whether to administer thrombolytic therapy to such patients in the prehospital setting.

Cellular telephone transmission of 12-lead electrocardiograms from ambulance to hospital.

Currently, only single-lead, serial telemetry rhythm strips can be transmitted from ambulances. Triage of patients with chest pain and administration of thrombolytic therapy in ambulances is limited by the lack of specific electrocardiographic (ECG) diagnosis. A new technique is described using cellular telephone transmission of simultaneous 12-lead ECGs from ambulance to hospital to overcome this limitation. A portable 12-lead ECG installed in an ambulance was connected via modern link to a cellular telephone and digitized ECG information was transmitted to an ECG device in the hospital emergency room. Paramedics in the field placed adhesive patch electrodes and attached ECG wires. Field ECGs from 23 patients were compared with corresponding transmitted ECGs. There were no differences in heart rate, PR interval, QRS duration, QT interval or R- and T-wave axes. Baseline and transmitted ECGs had identical morphologic characteristics. Differences in R-wave amplitude in 5 transmitted tracings compared with hospital-recorded ECGs resulted in computer diagnosis of left ventricular hypertrophy by voltage, possibly due to differences in patient position. Twelve-lead ECGs can be easily transmitted from a moving ambulance using cellular telephones. This allows diagnosis before hospital arrival, improves prehospital triage of patients and may facilitate prehospital therapy with lidocaine or streptokinase. In addition, the cellular telephone link can convey both verbal and digitized information and thus improve on current telemetry systems.

Effect of spontaneous sighs on arterial oxygenation during isoflurane anesthesia in humans.

The presence, frequency, and volume of spontaneous sighs was evaluated in 21 (ASA 1-2) supine patients aged 44 +/- 15.2 (SD) yr, during isoflurane-nitrous oxide anesthesia. Before induction the inspiratory capacity of each patient was determined. After induction of anesthesia and tracheal intubation patients breathed spontaneously except for three manual inflations to each patient's predetermined inspiratory capacity at the beginning and end of surgery. Arterial blood gas tensions were measured before and 5 min after each set of mechanical deep breaths and each hour during surgery, the mean duration of which was 2 +/- 0.09 hr. Spontaneous sighs occurred in 13 of 21 patients. The average frequency was 6 +/- 4 sighs/hr. At FIO2 = 0.5, nonsighing patients had an initial PaO2 of 229 +/- 59 mm Hg and sighers had an initial PaO2 of 162 +/- 57 mm Hg (P less than 0.05). Arterial oxygen did not change in sighing patients during the course of surgery, while in nonsighing patients the PaO2 decreased from the initial value of 229 +/- 60 mm Hg to 170 +/- 63 mm Hg (P less than 0.05). Mechanical deep breaths administered at the end of surgery produced no improvement in oxygenation in either sighers or nonsighers. The presence or absence of sighs did not correlate with PaO2 or PACO2. Though the results suggest that spontaneous sighs in some patients may function to help maintain arterial oxygenation, all patients maintained their PaO2 while breathing spontaneously under general anesthesia in the supine position.

Two uncommon radiographic signs of an anterior neonatal pneumothorax. Correlated with clinical finding.

An anterior pneumothorax in a supine neonate is difficult to diagnose. A correlation was sought between radiographic signs of an anterior pneumothorax and clinical data to facilitate the radiographic diagnosis. A total of 817 consecutive admissions to two regional nurseries were reviewed, and infants with pneumothoraces were identified. Nineteen percent of these neonates had anterior pneumothoraces with Medial Stripe and Large Hyperlucent Hemithorax signs observed on the chest radiographs. The Medial Stripe sign was not associated with any distinguishing clinical features that would assist the physician in the interpretation of the radiograph. The Large Hyperlucent Hemithorax sign was noted predominantly on the left side in near-term infants who were breathing spontaneously. It was concluded that there are specific clinical variables associated with a Large Hyperlucent Hemithorax sign of an anterior pneumothorax in a supine neonate.

A differential effect of thyroxine and glucocorticoids on fetal brain and heart insulin receptor.

We investigated the effect of thyroxine (T4), glucocorticoids, and T4 + glucocorticoids on the maturation of fetal rabbit brain and heart insulin receptors. Five doses of T4 over 10 days (50 micrograms/kg body weight per dose) were administered to the mother; significant amounts crossed the placenta (fetal serum free T4 = 0.75 +/- 0.08 versus a control of 0.21 +/- 0.02 ng/dl, p less than 0.02) and increased the specific binding of [125I]insulin to 30-day-old fetal heart membranes from a control of 3.6 +/- 0.74% per 100 micrograms protein to 5.8 +/- 0.19% (p less than 0.05). Curvilinear Scatchard plots revealed an increase in receptor number X 10(7) micrograms protein-1 from 137 +/- 4 to 244 +/- 39 (p less than 0.05) with no change in receptor affinity. No appreciable alteration by T4 in the [125I]insulin-specific binding and receptor number of 30-day fetal brains was noted. Fetal heart glycogen content was decreased and there was a small increase in plasma glucose concentration in the T4-treated group (each p less than 0.02). Betamethasone at 0.17 mg/kg did not affect the specific binding of [125I]insulin to 27-day fetal heart or brain plasma membranes, although a decrease in heart glycogen content and an increase in plasma glucose concentration were observed (each p less than 0.02). Also T4 + betamethasone did not alter the [125I]insulin binding to 27-day fetal heart or brain plasma membranes, but resulted in an additive effect (a marked depletion) on cardiac glycogen (p less than 0.001).(ABSTRACT TRUNCATED AT 250 WORDS)

Change in auditory asymmetry with amobarbital: evidence of cerebral pharmacological asymmetry?

Eleven right-handed subjects were administered a dichotic listening test to assess cerebral hemispheric dominance, both under a drug-free condition and following systemic injection of the barbiturate, amobarbital. The finding of increased right ear advantage during the drug period reflects increased left cerebral dominance, and suggests that amobarbital may have an asymmetric, pharmacological effect on the two cerebral hemispheres.

Fossil deep-sea channel on the aleutian abyssal plain.

The discovery of a leveed deep-sea channel whose axial gradient reverses near the Aleutian trench supports the hypothesis that the downbowing of the trench interrupted the turbidity current processes that constructed the Aleutian abyssal plain.