Comparison of a New Intranasal Naloxone Formulation to Intramuscular Naloxone: Results from Hypothesis-generating Small Clinical Studies.

Easy-to-use naloxone formulations are needed to help address the opioid overdose epidemic. The pharmacokinetics of i.v., i.m., and a new i.n. naloxone formulation (2 mg) were compared in six healthy volunteers. Relative to i.m. naloxone, geometric mean (90% confidence interval [CI]) absolute bioavailability of i.n. naloxone was modestly lower (55%; 90% CI, 43-70% vs. 41%; 90% CI, 27-62%), whereas average (±SE) mean absorption time was substantially shorter (74 ± 8.8 vs. 6.7 ± 4.9 min). The opioid-attenuating effects of i.n. naloxone were compared with i.m. naloxone (2 mg) after administration of oral alfentanil (4 mg) to a separate group of six healthy volunteers pretreated with 240 mL of water or grapefruit juice. The i.m. and i.n. naloxone attenuated miosis by similar extents after water (40 ± 15 vs. 41 ± 21 h*%) and grapefruit juice (49 ± 18 vs. 50 ± 22 h*%) pretreatment. Results merit further testing of this new naloxone formulation.

UNEXPECTED PRESENCE OF SOLUTE-FREE ZONES AT METAL-WATER INTERFACES.

Solute-free zones, termed "exclusion zones" are routinely seen next to hydrophilic surfaces in aqueous solution. Here we report similar zones next to various metals. The largest, approximately 200 µm in width, was found adjacent to zinc. Other reactive metals, including aluminum, tin, lead, and tungsten exhibited distinct but smaller exclusion zones, while precious metals such as platinum and gold did not produce any. Electrical potential measurements showed positive potentials within the exclusion zones, while pH measurements revealed an abundance of OH- groups in the aqueous regions beyond the exclusion zones. A correspondence was found between exclusion-zone size and the respective metal's position within the galvanic series. The presence of these interfacial exclusion zones is unexpected, and may shed new light on electrochemical processes taking place at metal interfaces.

Origin of microbial life hypothesis: a gel cytoplasm lacking a bilayer membrane, with infrared radiation producing exclusion zone (EZ) water, hydrogen as an energy source and thermosynthesis for bioenergetics.

The hypothesis is proposed that pre-biotic bacterial cell(s) and the first cells capable of growth/division did not require a cytoplasmic membrane. A gel-like microscopic structure less than a cubic micrometer may have had a dual role as both an ancient pre-cytoplasm and a boundary layer to the higher-entropy external environment. The gel pre-cytoplasm exposed to radiant energy, especially in the infrared (IR) region of the EM spectrum resulted in the production of an exclusion zone (EZ) with a charge differential (-100 to -200 mV) and boundary that may have been a possible location for the latter organization of the first cytoplasmic membrane. Pre-biotic cells and then-living cells may have used hydrogen as the universal energy source, and thermosynthesis in their bioenergetic processes. These components will be discussed as to how they are interconnected, and their hypothesized roles in the origin of life.

[Mechanical characteristics of synthetic polyelectrolyte gel as a physical model of the cytoskeleton].

A physical model of the cytoskeleton based on synthetic polyelectrolyte hydrogel of polymethacrylic acid has been proposed. From the physicochemical point of view, the structures of polyelectrolyte gel and the cytoskeleton show a high degree of similarity. It was shown that polyelectrolyte gel can shorten and produce mechanical stress in response to changes in the composition of the surrounding solution. The mechanical properties of the model gel were evaluated: Young modulus (2-6 kPa), stress relaxation time (0.1-1 s), and apparent viscosity (0.3-3 kPa x s). The viscoelastic properties of the gel depend on the degree of its swelling. It has been demonstrated that the mechanical properties of gels of polymethacrylic acid are close to those of biological objects.

EFFECT OF PARTICLE DIAMETER ON EXCLUSION-ZONE SIZE.

Particles and solutes are excluded from the vicinity of hydrophilic surfaces, leaving large microsphere-free regions known as exclusion zones (EZs). Prior work had indicated that EZs could extend to distances of up to several hundred micrometers from the nucleating surface. These observations were made on large, extended surfaces, leaving open the question whether EZ size might depend on the characteristic dimension of the excluding surface. We placed one or few ion-exchange-resin beads whose diameters varied from 15 µm to 300 µm in cuvettes. The beads were suffused with aqueous microsphere suspensions for observing the surfaces' exclusionary behavior. Results showed a direct relation between bead size and EZ size over the full range of bead diameter, implying a similar relation for smaller particles or molecules, perhaps extending beyond the resolution of the light microscope.

WATER, ENERGY AND LIFE: FRESH VIEWS FROM THE WATER'S EDGE.

Recent observations have shown an unexpected feature of water adjacent to hydrophilic surfaces: the presence of wide interfacial zone that excludes solutes. The exclusion zone is charged, while the water beyond is oppositely charged, yielding a battery-like feature. The battery is powered by absorbed radiant energy. Implications of this energetic feature are discussed. It appears that the presence of this 'exclusion zone' may play an important role in the behavior of aqueous systems.

[Mechanoelectric potentials in synthetic hydrogels: possible relation to cytoskeleton].

Mechanical and electrical properties of a synthetic polyelectrolyte hydrogel considered as a model of the cytoskeletal gel were studied. Hydrogels were synthesized from polymethacrylic acid by radical polymerization in aqueous solution. The electrical charge was introduced into the gel network by partial neutralization of monomer acids with magnesium (hydro)oxides. Through the use of a motor, triangular longitudinal (axial) deformations were applied to gel samples. Simultaneously, the electrochemical (Donnan) potential of the gel was measured using conventional microelectrodes. We found that: (1) the Young modulus of the gel was 0.53 kPa; (2) at a given deformation velocity, the extent of gel deformation closely correlates with the gel potential; and (3) at the same level of gel deformation, the lower the deformation velocity, the higher the relative change of gel potential. These findings show a striking similarity to the data obtained in living cells, particularly in cardiac myocytes. A hypothesis involving the deformation-induced solvent migration from the gel to the surrounding solution is considered. It is concluded that the physicochemical features of the cytoskeletal gel may play a role in determining the mechanoelectric properties of excited cells.

[The relationship between the mechanical and electrical properties of a synthetic hydrogel chosen as an experimental model of cytoskeleton].

A correlation between the electrochemical (Donnan) potential and volume swelling has been studied for synthetic polyelectrolyte hydrogels considered as models of cytoskeleton gel-forming biopolymers. Hydrogels based on polyacrylic and polymethacrylic acids with varying network density have been synthesized by radical polymerization in water solution. Electric charge was introduced into the gel network by partial neutralization of acidic monomers by alkali and alkali-earth (hydr)oxides. The electrochemical (Donnan) potential of synthetic gels was measured by a conventional microelectrode technique used in studies of cell potential. It was shown that the negative electric potential became lower as the equilibrium swelling degree decreased for a large number of anionic gels with varying electric charge and network density, i.e., the content of water in the gel decreased. It was shown that the abrupt phase transition of hydrogel structure from a swollen to a contracted state under the influence of K+/Ca2+ ionic exchange is accompanied by a similar decrease in absolute values of the Donnan potential of the gel. A kinetic study showed that volume changes went prior to the decrease in electric potential. This suggests that the volume phase transition in gel structure is the major cause for the electric response. A similarity was shown between the swelling/collapse phase transition in the gel and volume changes in cytoskeleton beneath the cell membrane. Based on the universal properties of synthetic and biopolymer hydrogels, a possible swelling-induced mechanism of cell electrical potential regulation is proposed.

Efficient inhibition of bursts by bursts in the auditory system of crickets.

In crickets, auditory information about ultrasound is carried bilaterally to the brain by the AN2 neurons. The ON1 neuron provides contralateral inhibitory input to AN2, thereby enhancing bilateral contrast between the left and right AN2s, an important cue for sound localization. We examine how the structures of the spike trains of these neurons affect this inhibitory interaction. As previously shown for AN2, ON1 responds to salient peaks in stimulus amplitude with bursts of spikes. Spike bursts, but not isolated spikes, reliably signal the occurrence of specific features of the stimulus. ON1 and AN2 burst at similar times relative to the amplitude envelope of the stimulus, and bursts are more tightly time-locked to stimulus feature than the isolated spikes. As a consequence, spikes that, in the absence of contralateral inhibition, would occur within AN2 bursts are more likely to be preceded by spikes in ON1 (mainly also in bursts) than are isolated AN2 spikes. This leads to a large decrease in the burst rate of the inhibited AN2. We conclude that the match in coding properties of ON1 and AN2 allows contralateral inhibition to be most efficient for those portions of the response that carry the behaviourally relevant information, i.e. for bursts.

Revitalizing science in a risk-averse culture: reflections on the syndrome and prescriptions for its cure.

This paper considers problems with the scientific culture and granting systems, the most important of which is an aversion to risk. Grant awards tend to be "safe" rather than bold. This discourages the fresh approaches that may bring important breakthroughs. The paper then suggests remedies that could restore the scientific enterprise to one that is friendlier to fresh thinking.

Differential temporal coding of rhythmically diverse acoustic signals by a single interneuron.

The omega neuron 1 (ON1) of the cricket Teleogryllus oceanicus responds to conspecific signals (4.5 kHz) and to the ultrasonic echolocation sounds used by hunting, insectivorous bats. These signals differ in temporal structure as well as in carrier frequency. We show that ON1's temporal coding properties vary with carrier frequency, allowing it to encode both of these behaviorally important signals. Information-transfer functions show that coding of 4.5 kHz is limited to the range of amplitude-modulation components that occur in cricket songs (<32 Hz), whereas coding of 30-kHz stimuli extends to the higher pulse rates that occur in bat sounds ( approximately 100 Hz). Nonlinear coding contributes to the information content of ON1's spike train, particularly for 30-kHz stimuli with high intensities and large modulation depths. Phase locking to sinusoidal amplitude envelopes also extends to higher AM frequencies for ultrasound stimuli. ON1s frequency-specific behavior cannot be ascribed to differences in the shapes of information-transfer functions of low- and high-frequency-tuned receptor neurons, both of which are tuned more broadly to AM frequencies than ON1. Coding properties are nearly unaffected by contralateral deafferentation. ON1's role in auditory processing is to increase binaural contrast through contralateral inhibition. We hypothesize that its frequency-specific temporal coding properties optimize binaural contrast for sounds with both the spectral and temporal features of behaviorally relevant signals.

'Minimum average risk' as a new peak-detection algorithm applied to myofibrillar dynamics.

We present a new peak-detection algorithm based on the method of 'minimum average risk' proposed by Kolmogorov and developed for signal processing in various fields. In this method, translations of features within a signal scan are quantified by minimizing the integrated pointwise product of each scan relative to the first derivative of the immediately previous scan. We have adapted this method for use in a new algorithm to monitor dynamic changes of sarcomere length in single myofibrillar sarcomeres of striated muscles, but the algorithm can also be used more generally for peak localization. We find that this method results in sub-nanometer precision and higher signal-to-noise ratio than current methods. At an equal noise level, the RMS deviation of the minimum average risk algorithm was 1.3 times lower than that of the center of mass method with modeled data and 3-4 times lower with actual data.

Sensory cues for sound localization in the cricket Teleogryllus oceanicus: interaural difference in response strength versus interaural latency difference.

Two potential sensory cues for sound location are interaural difference in response strength (firing rate and/or spike count) and in response latency of auditory receptor neurons. Previous experiments showed that these two cues are affected differently by intense prior stimulation; the difference in response strength declines and may even reverse in sign, but the difference in latency is unaffected. Here, I use an intense, constant tone to disrupt localization cues generated by a subsequent train of sound pulses. Recordings from the auditory nerve confirm that tone stimulation reduces, and sometimes reverses, the interaural difference in response strength to subsequent sound pulses, but that it enhances the interaural latency difference. If sound location is determined mainly from latency comparison, then behavioral responses to a pulse train following tone stimulation should be normal, but if the main cue for sound location is interaural difference in response strength, then post-tone behavioral responses should sometimes be misdirected. Initial phonotactic responses to the post-tone pulse train were frequently directed away from, rather than towards, the sound source, indicating that the dominant sensory cue for sound location is interaural difference in response strength.

Analysis of temporal patterns of communication signals.

Temporal pattern is a crucial feature of communication signals, and neurons in the brains of many animals respond selectively to behaviorally relevant temporal features of sensory stimuli. Many aspects of neural function contribute to this selectivity, including membrane biophysics, channel properties, synaptic physiology and network structure.

Phase transitions and molecular motion in the cell.

The cytoplasm exhibits all of the signature characteristics of a gel. The thesis put forth here is that the cytoplasm's gel-like character is central to the generation of biological movement. In artificial gels, a common vehicle for generating movement is the polymer-gel phase-transition. By undergoing phase-transition, gels produce motion of both solvent and solutes. It is argued that cells do the same. Three examples are given: the secretory system, the muscle contraction system and the biological streaming system. In each case it is shown that the characteristic motions may be created as proteins and water undergo transition from an expanded, hydrated state to a contracted, dehydrated state--or the reverse. These changes shift solutes and solvent in a characteristic way that depends on the respective organelle's structure. Phase-transitions are simple, powerful mechanisms that may be responsible for many, if not all, biological motions.

Nonstationary disposition of valproic acid during prolonged intravenous infusion: contributions of unbound clearance and protein binding.

Circadian variations in disposition have been observed for a variety of agents, including anticonvulsants. Valproic acid (VPA), an anticonvulsant used to control generalized and partial seizures, has exhibited diurnal oscillations in steady-state concentrations during long-term administration to humans and non-human primates. The present study was conducted to assess potential diurnal changes in the disposition of VPA during prolonged i.v. infusion in rats. Animals, maintained on a strict 12-h per day light cycle, were equipped with venous cannulae and an arterial microdialysis probe. VPA was administered as a 50-mg/kg loading dose followed by a 42 mg/kg/h infusion for 70 h. Blood and microdialysate samples were obtained at timed intervals after establishment of steady-state throughout two complete light/dark cycles; and total (serum) and unbound (microdialysate) VPA was determined by gas chromatography. Modest oscillations (6-7 h period) in total and unbound VPA were observed; clearance and binding parameters were not different between light and dark periods. However, unbound clearance increased, and unbound fraction decreased, with time over the course of the infusion. These results suggest that time-dependent changes in VPA disposition occur in rats, although oscillations in steady-state concentrations do not appear to be diurnal in nature.

Effect of mdr1a P-glycoprotein gene disruption, gender, and substrate concentration on brain uptake of selected compounds.

PURPOSE: This study assessed the influence of mdr1a P-glycoprotein (P-gp) gene disruption, gender and concentration on initial brain uptake clearance (Clup) of morphine, quinidine and verapamil. METHODS: Clup of radiolabeled substrates was determined in P-gp-competent and deficient [mdr1a(-/-)] mice by in situ brain perfusion. Brain:plasma distribution of substrates after i.v. administration was determined in both strains. RESULTS: Genetic disruption of mdr1a P-gp resulted in 1.3-, 6.6- and 14-fold increases in Clup for morphine, verapamil and quinidine, respectively. With the exception of small differences for verapamil, gender did not affect Clup. Saturable transport of verapamil and quinidine was observed only in P-gp-competent mice, with apparent IC50 values for efflux of 8.6 +/- 2.3 microM and 36 +/- 2 microM, respectively. Verapamil Clup was approximately 50% higher in mdr1a(+/-) vs. mdr1a(+/+) mice; no such difference was observed for quinidine. In P-gp-competent mice, uptake of verapamil and quinidine was unaffected by organic vehicles. Plasma decreased VER Clup to a greater extent in the presence of P-gp. The influence of P-gp in situ was lower than, but correlated with, the effect in vivo. CONCLUSIONS: P-gp decreases Clup of morphine, verapamil and quinidine in situ with little or no influence of gender, but this effect cannot fully account for the effects of P-gp in vivo. P-gp is the only saturable transport mechanism for verapamil and quinidine at the murine blood-brain barrier. The influence of protein binding on Clup may be enhanced by P-gp-mediated efflux.