The infrared dichroism of transmembrane helical polypeptides

Polarized attenuated total internal reflectance techniques were applied to study the infrared dichroism of the amide I transition moment in two membrane-bound peptides that are known to form oriented transmembrane helices: gramicidin A in a supported phospholipid monolayer and Ac-Lys2-Leu24-Lys2-amide (L24) in oriented multibilayers. These studies were performed to test the ability of these techniques to determine the orientation of these peptides, to verify the value of optical parameters used to calculate electric field strengths, to examine the common assumptions regarding the amide I transition moment orientation, and to ascertain the effect of surface imperfections on molecular disorder. The two peptides exhibit marked differences in the shape and frequency of their amide I absorption bands. Yet both peptides are highly ordered and oriented with their helical axes perpendicular to the membrane surface. In the alpha-helix formed by L24, there is evidence for a mode with type E1 symmetry contributing to amide I, and the amide I transition moment must be more closely aligned with the peptide C=O (< 34 degrees) than earlier studies have suggested. These results indicate that long-standing assumptions about the orientation of amide I in a peptide require some revision, but that in general, infrared spectroscopy yields reliable information about the orientation of membrane-bound helical peptides.     

Agreement between rectal and tympanic membrane temperatures in marathon runners

STUDY OBJECTIVE: To determine the agreement between rectal temperature and infrared tympanic membrane temperatures in marathon runners presenting to a field hospital at the finish line. METHODS: The subjects of this prospective, blinded, controlled study were runners 18 years or older who were triaged to the acute care medical area at the finish line for suspected hypothermia, hyperthermia, dehydration, or altered mental status. Rectal and tympanic temperatures were measured simultaneously in all subjects for whom rectal temperature measurement had been deemed necessary and recorded on separate data cards. RESULTS: Of the 239 runners treated in the acute care medical area, 37 required rectal temperature measurement and were enrolled in the study. The mean rectal temperature was 38.45 degrees +/- 1.20 degrees C (range, 35.9 degrees to 41.5 degrees C). The mean tympanic membrane temperature was 37.81 degrees +/- 95 degrees C (range, 36.3 degrees to 40.4 degrees C). Pearson's correlation coefficient revealed a moderate correlation (r = .6902, P = .00023). The mean temperature difference between the two thermometers, mean rectal minus mean tympanic membrane, was .64 degrees C (95% confidence interval, .35 degrees to .93 degrees C). Sixty-Two percent of the tympanic membrane readings were within 1 degree C of their rectal counterparts. Agreement ranged from 1.16 degrees (+2 SD) to -2.95 degrees (-2 SD). The 95% confidence interval was 1.67 degrees to -2.95 degrees C. CONCLUSION: We were able to demonstrate only a moderate correlation between the two thermometer readings, with a wide spread between the limits of agreement. This spread could be clinically significant and therefore limits the usefulness of tympanic temperature in the marathon race setting. Because of the potentially large and clinically significant differences in rectal and tympanic temperatures and the limitations inherent in our study, we cannot endorse the use of tympanic temperature in the setting of a marathon event.     

Use of pentastarch solution in the treatment of patients with hemorrhagic hypovolemia: randomized phase II study in the emergency room

The weeping fig, Ficus benjamina (Fb), is a relatively common indoor allergen. Many cases of perennial allergic rhinoconjunctivitis and allergic asthma caused by Fb hypersensitivity are not detected. These patients typically have proven sensitization to housedust mites and do not improve after avoidance of exposure (encasing) and specific immunotherapy. The number of Fb sensitizations is increasing in Germany, which can partly be explained by the cross-reactivity between Hevea brasiliensis (Hb) latex and Fb and the rapidly increasing number of mostly occupational latex allergies. But Fb itself is a potential sensitizer which is widely spread as ornamental plant in homes and offices. As relevant indoor allergen Fb ranks third after housedust mites and pets but before molds among our allergy patients. For diagnosis, prick-tests with Fb-latex seem to be more sensitive than in vitro-methods (RAST, CAPRAST). Fb plants should not be kept in the homes of atopic individuals or persons with latex (Hb) allergy.     

Biphasic insulin secretion during intravenous glucose tolerance test promotes optimal interstitial insulin profile

We examined the hindlimb lymph insulin profile during simulated intravenous glucose tolerance tests (IVGTTs) in anesthetized dogs to test the following hypotheses: 1) the biphasic insulin response to intravenous glucose can be seen as a priming bolus and a secondary infusion that effect a rapid stepwise increase in the interstitial insulin concentration and 2) the activation of glucose utilization (rate of glucose uptake [Rd]) during an IVGTT is more similar to the dynamics of the interstitial insulin profile than that of the arterial plasma. Three insulin profiles were infused: a normal biphasic pattern, a second phase infusion only, and a biphasic pattern with a fourfold greater first phase and a normal second phase. During the normal biphasic infusion, lymph insulin quickly reached and maintained a steady-state concentration (10 min, 26.42 +/- 0.86 microU/ml). With second phase only, it took lymph insulin 35 min to reach a steady state of lower concentration (13.13 +/- 0.46 microU/ml) than the normal. And with a fourfold greater first phase, lymph insulin plateaued quickly (16 min, 140.87 +/- 1.68 microU/ml), but for a shorter duration than the normal. For each profile, the time course of activation of Rd did not follow the time course of insulin in the plasma, but was more similar to that of insulin in the interstitial fluid. These results show that the biphasic response allows interstitial insulin to rapidly reach and maintain a steady state beneficial to activation and maintenance of glucose utilization.     

Propionyl-L-carnitine

Propionyl-L-carnitine stimulates energy production in ischaemic muscles by increasing citric acid cycle flux and stimulating pyruvate dehydrogenase activity. The free radical scavenging activity of the drug may also be beneficial. Propionyl-L-carnitine improves coagulative fibrinolytic homeostasis in vasal endothelium and positively affects blood viscosity. Improvements in maximum walking distance (MWD) correlated positively with increased mitochondrial oxidative adenosine triphosphate (ATP) synthesis in a study in patients with peripheral arterial disease. Oral propionyl-L-carnitine 1 to 3 g/day significantly improved mean MWD compared with placebo in patients with peripheral arterial obstructive disease (Fontaine Leriche stage II) in double-blind multicentre phase III studies (mean improvements ranged from 21 to 50% with placebo and from 33 to 73% with propionyl-L-carnitine). In one phase III study, propionyl-L-carnitine 1 to 3 g/day significantly improved mean MWD (measured by treadmill) compared with placebo (by 73 vs 46% after 24 weeks) in patients with intermittent claudication. Oral propionyl-L-carnitine therapy was associated with significant improvements in quality of life compared with placebo in patients with a baseline MWD < 250m. Propionyl-L-carnitine appears to be well tolerated, showing a similar incidence of adverse events to that reported in placebo recipients.     

Corticomotoneuronal contribution to the fractionation of muscle activity during precision grip in the monkey

1. During independent finger movements, the intrinsic muscles of the hand show a fractionated pattern of activity in which the timing and amplitude of electromyographic (EMG) activity varies considerably from one muscle to another. It has been suggested that, in the macaque monkey, corticomotoneuronal (CM) cells that produce postspike facilitation (PSF) of EMG in these muscles contribute to this fractionation. To test this hypothesis, we have investigated the relationship between the pattern of PSF exerted by a CM cell and the pattern of activity shown by the cell and by its target muscles. 2. The activity of 15 identified CM cells was recorded from two monkeys that performed a precision grip task. Spike-triggered averaging of rectified EMG during the hold period of this task showed that each cell produced PSF in at least two intrinsic hand muscles. 3. Segments of data were selected from the initial movement period of the task in which the EMG activity in one target muscle was substantially greater than that of the other, and the mean firing rate of each CM cell was determined for these periods. 4. CM cells showed bursts of activity in the movement period. Most of them (13/15) had a significantly (P < 0.001) higher firing rate when one of its target muscles was more active than the other. For nine of these cells (identified as set A), this muscle was the one receiving the larger PSF. In four cases (set B), the reverse was true. Two cells (set C), which produced PSF of equal size in their target muscles, showed no change in firing rate across the periods of fractionated EMG activity. 5. All set A and set B cells fired at significantly (P < 0.001) higher rates during the movement period, in association with fractionation of EMG activity, than in the hold period, in which a cocontracted pattern of muscle activity was observed. 6. There were pronounced differences in the strength of PSF exerted by the CM cells on their target muscles during the fractionation periods. One CM cell exerted PSF of a muscle during one period of fractionation, but postspike suppression of the same muscle during the other period. 7. It is suggested that changes in the firing rate of a CM cell and in the degree of facilitation it exerts could both contribute to the fractionation of activity in its target muscles. Cells of set A appear to be specifically recruited in a manner that directly reflects the pattern of facilitation they exert on the sampled target muscles. These results may explain why the CM system is so important for the performance of relatively independent finger movements.     

Distribution of iatrogenic retinal breaks in macular hole surgery

BACKGROUND: Intraoperative peripheral iatrogenic retinal breaks can be a serious complication of vitreous surgery. This study was undertaken to determine whether vitreous surgical techniques used for macular hole surgery were associated with a different incidence or distribution of retinal breaks. METHODS: The authors prospectively evaluated a series of 181 consecutive eyes undergoing macular hole surgery. Contemporaneous reporting of intraoperative and postoperative retinal breaks and postoperative retinal detachments was performed. Comparison was made to historic controls of two case series of patients undergoing vitreous surgery for other indications. RESULTS: Of 181 eyes, 10 (5.5%) had 15 intraoperative retinal breaks. Of the 15 breaks, 3 (20%) were in the quadrant near the surgeon's right-hand sclerotomy, 9 (60%) were in the two inferior quadrants, and 11 (73%) were in the two temporal quadrants. By comparison to previously reported case series, tears in our series were less likely to be near the right-hand sclerotomy (P = 0.00055) and more likely to occur in the two inferior retinal quadrants (P = 0.00015) and two temporal retinal quadrants (P = 0.0042). Two patients (1.1%) of 181 had postoperative retinal detachments. CONCLUSIONS: Patients undergoing vitreous surgery for macular hole have a similar incidence but different location of iatrogenic retinal breaks when compared with patients undergoing pars plana vitrectomy for other indications. These breaks are not distributed near sclerotomy sites and tend to be in the inferior and temporal retina. This establishes the need for greater intraoperative surveillance in these areas.     

Type 2 diabetes: patient education and home blood glucose monitoring. 3

Successful treatment of type 2 diabetes requires the interaction of the patient, his or her family, and a variety of healthcare professionals. Education is the most powerful tool doctors have to convince patients, especially those who are asymptomatic, of the serious complications that can result from uncontrolled diabetes. Home blood glucose monitoring is a key to the doctor-patient partnership. Physicians may have to consider a patient's cultural and dietary customs in developing a manageable program of weight loss, diet, and physical activity, the most effective forms of treatment. Referrals should be made to local diabetes organizations with patient support programs, when available. Patient empowerment and education are key to effective management.