Cellular signalling properties in microcircuits

Molecules and cells are the signalling elements in microcircuits. Recent studies have uncovered bewildering diversity in postsynaptic signalling properties in all areas of the vertebrate nervous system. Major effort is now being invested in establishing the specialized signalling properties at the cellular and molecular levels in microcircuits in specific brain regions. This review is part of the TINS Microcircuits Special Feature.     

20 Hz membrane potential oscillations are driven by synaptic inputs in collision-detecting neurons in the frog optic tectum

Although the firing patterns of collision-detecting neurons have been described in detail in several species, the mechanisms generating responses in these neurons to visual objects on a collision course remain largely unknown. This is partly due to the limited number of intracellular recordings from such neurons, particularly in vertebrate species. By employing patch recordings in a novel integrated frog eye-tectum preparation we tested the hypothesis that OFF retinal ganglion cells were driving the responses to visual objects on a collision course in the frog optic tectum neurons. We found that the majority (22/26) of neurons in layer 6 responding to visual stimuli fitted the definition of η class collision-detectors: they readily responded to a looming stimulus imitating collision but not a receding stimulus (spike count difference ∼10 times) and the spike firing rate peaked after the stimulus visual angle reached a threshold value of ∼20–45°. In the majority of these neurons (15/22) a slow frequency oscillation (f = ∼20 Hz) of the neuronal membrane potential could be detected in the responses to a simulated collision stimulus, as well as to turning off the lights. Since OFF retinal ganglion cells could produce such oscillations, our observations are in agreement with the hypothesis that ‘collision’ responses in the frog optic tectum neurons are driven by synaptic inputs from OFF retinal ganglion cells.     

Comparison of non-surgical methods for the treatment of deep partial thickness skin burns of the hand

This paper describes a randomized, controlled, parallel-group, single-center clinical trial designed to compare non surgical treatment methods of deep partial thickness skin burns of the hand.All patients were scanned with the Laser Doppler Imaging device to determine the depth of the burn wound. Viable keratinocytes sites were determined according to the established Perfusion Units (PU) measurement system. The trial enrolled 87 patients with hand burn wounds in the section of 260–600 PU.Hand burn patients were divided into the following four groups: treated with hydrocolloid dressings; treated with mechanical debridement of monofilament polyester fibers pad and then applying silver sulfadiazine; treated with gauze dressings containing enzymatic collagenase preparation. The fourth group of patients was treated with silver sulfadiazine and gauze dressings. This group was considered as the control group. The wound healing status was assessed after 3, 7, 14 and 21 days. Burn scars and injured extremity function were assessed after six months according to the Vancouver Scar Scale and Disabilities of the Arm, Shoulder and Hand Outcome Measure.The fastest epithelialization of hand burn wounds was observed in the patients group treated with hydrocolloid dressings (15, 7 days, p < 0,05). The patients of this group also had less scars and a better hand function.     

Physicochemical characterization of native glycyl-l-histidyl-l-lysine tripeptide for wound healing and anti-aging: a preformulation study for dermal delivery

This study investigates the physicochemical properties of glycyl-histidyl-lysine-copper (GHK-Cu) to support the development of a formulation for effective topical delivery. The solubility and distribution coefficients (log D) were investigated using conventional methods and GHK concentrations were quantified with a validated stability-indicating reversed phase high performance liquid chromatography (RP-HPLC) method. In addition, the stability of GHK-Cu under stressed conditions and the compatibility with some potential formulation components were assessed. The peptide was susceptible to hydrolytic cleavage under basic and oxidative stressors and to a lesser extent acidic stress with first-order degradation profiles. Surprisingly, the peptide was stable in water and in pH (4.5–7.4) buffers for at least two weeks at 60 °C. The HPLC in conjunction with mass spectrometry identified three key degradation products, one of which was the constituent amino acid histidine. The distribution coefficients in octanol-phosphate buffered saline indicated the highly hydrophilic nature of GHK-Cu with log D values between ?2.38 and ?2.49 at pH range of 4.5–7.4. Furthermore, GHK-Cu was compatible with Span 60 based niosomes but less stable in the presence of the negatively charged lipid dicetyl phosphate. In summary, the preformulation studies provided information useful to deliver the GHK-Cu complex by carrier.     

Effects of forearm vs. leg submersion in work tolerance time in a hot environment while wearing firefighter protective clothing

This study compared physiological responses and total work tolerance time following forearm submersion (FS) or leg submersion (LS) in cool water, after performing work in a hot environment while wearing fire fighting protective clothing (FPC). Participants walked at 3.5 mph on a treadmill in a hot environment (WBGT 32.8 ± 0.9°C) until a rectal temperature (T(rec)) of 38.5°C was reached. Participants were then subjected to one of two peripheral cooling interventions, in a counterbalanced order. Forearms or lower legs were submerged in water (16.9 ± 0.8°C) for a total of 20 min, followed by a work tolerance trial. Results indicated no significant difference (p = 0.052) between work tolerance time (LS = 21.36 ± 5.35 min vs. FS = 16.27 ± 5.56 min). Similarly, there was no significant difference for T(rec) (p = 0.65), heart rate (HR) (p = 0.79), mean skin temperature (T(sk)) (p = 0.68), and rating of perceived exertion (RPE) (p = 0.54). However, LS ratings of thermal comfort (RTC) at Minute 14 (p = 0.03) were significantly lower for LS (10 ± 1) vs. FS (12 ± 1). Results indicate little difference between FS and LS for physiological measures. Despite a lack of statistical significance a 5-min (24%) increase was found during the work tolerance time following LS.