UCP1 mRNA does not produce heat

Because of the possible role of brown adipose tissue and UCP1 in metabolic regulation, even in adult humans, there is presently considerable interest in quantifying, from in-vitro data, the thermogenic capacities of brown and brite/beige adipose tissues. An important issue is therefore to establish which parameters are the most adequate for this. A particularly important issue is the relevance of UCP1 mRNA levels as estimates of the degree of recruitment and of the thermogenic capacity resulting from differences in physiological conditions and from experimental manipulations. By solely following UCP1 mRNA levels in brown adipose tissue, the conclusion would be made that the tissue's highest activation occurs after only 6 h in the cold and then successively decreases to being only some 50% elevated after 1 month in the cold. However, measurement of total UCP1 protein levels per depot ("mouse") reveals that the maximal thermogenic capacity estimated in this way is reached first after 1 month but represents an approx. 10-fold increase in thermogenic capacity. Since this in-vitro measure correlates quantitatively and temporally with the acquisition of nonshivering thermogenesis, this must be considered the most physiologically relevant parameter. Similarly, observations that cold acclimation barely increases UCP1 mRNA levels in classical brown adipose tissue but leads to a 200-fold increase in UCP1 mRNA levels in brite/beige adipose tissue depots may overemphasise the physiological significance of these depots, as the high fold-increases are due to very low initial levels, and the UCP1 mRNA levels reached are at least an order of magnitude lower than in brown adipose tissue; furthermore, based on total UCP1 protein amounts, the brite/beige depots attain only about 10% of the thermogenic capacity of the classical brown adipose tissue depots. Consequently, inadequate conclusions may be reached if UCP1 mRNA levels are used as a proxy for the metabolic significance of recruited versus non-recruited brown adipose tissue and for estimating the metabolic significance of brown versus brite/beige adipose tissues. This article is part of a Special Issue entitled Brown and White Fat: From Signaling to Disease.     

GSM phone signal does not produce subjective symptoms

The influence of pulsed radiofrequency (RF) electromagnetic fields of digital GSM mobile phones (902 MHz, 217 Hz pulse modulation) on subjective symptoms or sensations in healthy subjects were studied in two single-blind experiments. The duration of the RF exposure was about 60 min in Experiment 1 and 30 min in Experiment 2. Each subject rated symptoms or sensations in the beginning of the experimental session and at the end of both the exposure and the nonexposure conditions. The symptoms rated were headache, dizziness, fatigue, itching or tingling of the skin, redness on the skin, and sensations of warmth on the skin. The results did not reveal any differences between exposure and non-exposure conditions, suggesting that a 30-60 min exposure to this RF field does not produce subjective symptoms in humans.     

Chromium picolinate does not produce chromosome damage in CHO cells

Chromium picolinate (CrPic, Chromax) is a dietary supplement that has been commercially available for the past two decades. CrPic has potential benefits for reducing insulin dependence in diabetics by increasing sensitivity of insulin receptors and in stimulating insulin binding. In this study, CrPic was tested for its ability to produce chromosomal aberrations in vitro using Chinese hamster ovary K1 (CHO) cells. CHO cells were exposed to a range of cytotoxic to non-cytotoxic concentrations of CrPic for 4 or 20h in the absence of metabolic (S9) activation or for 4h in the presence of S9 activation. CrPic was solubilized with dimethyl sulfoxide (DMSO) to attain the highest possible solubility for maximizing the test doses. Cells were treated with 96.25, 192.5, 385 or 770 microg/mL of CrPic for 4 h in the presence of S9 activation, and for 4 or 20 h in the absence of S9 activation. A distinct precipitate of CrPic was evident in the cell culture medium at 770 microg/mL, which was the highest dose tested. Results showed no statistically significant increases in structural or numerical chromosome aberrations were produced at any test dose level with CrPic in 4-h treatments up to a precipitating dose of 770 microg/mL in either the presence or absence of S9 activation. Additionally no aberrations were observed up to 385 microg/mL (the maximum analyzable dose) following treatment for 20 h in the absence of S9 activation. The percentage of cells with structural or numerical aberrations in CrPic treated cultures was not statistically different (p>0.05) from that quantified in controls at any dose level. The absence of significant differences from control levels demonstrates that CrPic did not induce structural or numerical chromosome aberrations up to doses that were insoluble in the culture medium.     

Melatonin does not produce sedation in rats: A chronobiological study

ABSTRACT

Background: Melatonin has been associated with a wide variety of cellular, neuroendocrine, and neurophysiological processes. Clinical studies have reported the use of melatonin as an agent that exerts sedative-hypnotic effects. However, evidence of the sedative-hypnotic effects of different doses of melatonin is inconsistent, and available data regarding its night/day-time sedative effects are limited. The purpose of this study was to evaluate the effects of melatonin administered at different times of day on the magnitude of the sedative-hypnotic activity of different melatonin doses (5, 10, 30, and 50 mg/kg) in rats.

Methods: Sedation was assessed in Wistar rats behaviorally, using rota-rod, spontaneous locomotor activity, and fixed-bar tests at different times of day (ZT4, ZT10, ZT16, and ZT22).

Results: Our results showed that, compared to trazodone, acute and chronic dosing of ≤5 mg melatonin produced mild, transient sedative effects, mainly in the light period. Nevertheless, doses of ≥10 mg/kg did not cause sustained sedative effects.

Conclusion: These results suggest that melatonin may be used for sedation induction, mainly in preoperative patients.     

When maladaptive gene flow does not increase selection

Populations receiving high maladaptive gene flow are expected to experience strong directional selection—because gene flow pulls mean phenotypes away from local fitness peaks. We tested this prediction by means of a large and replicated mark‐recapture study of threespine stickleback (Gasterosteus aculeatus) in two stream populations. One of the populations (outlet) experiences high gene flow from the lake population and its morphology is correspondingly poorly adapted. The other population (inlet) experiences very low gene flow from the lake population and its morphology is correspondingly well adapted. Contrary to the above prediction, selection was not stronger in the outlet than in the inlet, a result that forced us to consider potential reasons for why maladaptive gene flow might not increase selection. Of particular interest, we show by means of a simple population genetic model that maladaptive gene flow can—under reasonable conditions—decrease the strength of directional selection. This outcome occurs when immigrants decrease mean fitness in the resident population, which decreases the strength of selection against maladapted phenotypes. We argue that this previously unrecognized effect of gene flow deserves further attention in theoretical and empirical studies.     

Cell migration: neurons go with the flow

Cilia lining the surfaces of the brain ventricles may be responsible for the graded distribution of chemorepellents that drive the directed migration of neurons.     

Vacuolar ethylene formation does not depend on membrane potential

Enzymatic synthesis of ethylene in the vacuole is assumed to require membrane integrity. The possibility that this reflects dependence on the vacuolar membrane potential was investigated. Vacuoles were released from protoplasts isolated from leaves of Vicia faba L. cv. Cyprus. The dependence of the ethylene-forming activity on tonoplast integrity was re-examined by immobilization of the vacuoles in a cross-linked polymeric matrix and subsequent permeabilization of the tonoplast with toluene, a pore-forming reagent. The relationship between the vacuolar ethylene formation and the membrane potential of free vacuoles was investigated by following the uptake of thiocyanate using permeabilized, depolarized and hyperpolarized vacuoles. Toluene and the proton conductor carbonyl cyanide m -chlorophenylhydrazone (CCCP) caused loss of ethylene-forming activity and depolarized the vacuolar membrane potential. However, depolarization of the membrane potential with choline chloride and hyperpolarization by ATP did not affect ethylene biosynthesis. These conflicting results lead to the conclusion that vacuolar ethylene biosynthesis is not dependent on the vacuolar membrane potential. The possibility that the inhibition of ethylene biosynthesis by toluene and CCCP may result from direct hydrophobic interactions between these compounds and hydrophobic components of the ethylene-forming enzyme is discussed.     

Monensin does not prevent recycling of plasma membrane glycoconjugates

Plasma membrane glycoconjugates, internalized during fluid-phase pinocytosis in the macrophage cell line, P388D1, were found to be rapidly recycled to the cell surface, also in the case where the cells had been treated with 25 microM monensin for 80 min which resulted in a reduction of the pinocytotic uptake rate to 30%. The result is discussed in terms of the intracellular pathway of internalized membrane.     

Circulating neuropeptide Y does not produce pulmonary hypertension during massive sympathetic activation.

We tested the possibility that neuropeptide Y (NPY) may contribute to the pulmonary hypertension that occurs after massive sympathetic activation produced by intracisternal veratrine administration in the chloralose-anesthetized dog. In six dogs, veratrine caused arterial NPY-like immunoreactivity (NPY-LI) to rise from 873 +/- 150 (SE) pg/ml to peak values of 3,780 +/- 666 pg/ml by 60-120 min. (In 3 animals, adrenalectomy significantly reduced the increases in NPY-LI.) In five additional dogs, we infused porcine NPY for 30 min in doses that increased arterial NPY-LI to 8,354 +/- 1,514 pg/ml and observed only minor changes in pulmonary hemodynamics. In three isolated perfused canine left lower lung lobe (LLL) preparations, increasing doses of NPY were administered, producing levels of plasma NPY-LI, at the highest dose, that exceeded those observed after veratrine administration by three orders of magnitude. No changes in LLL arterial or double-occlusion capillary pressures were observed at any dose. Similarly, no changes in LLL hemodynamics were observed in three additional lobes when NPY was administered while norepinephrine was being infused. We conclude that it is unlikely that NPY plays a role as a circulating vasoactive agent in producing the pulmonary hypertension and edema that occur in this model.     

Increased gravitational stress does not alter maximum expiratory flow

We measured maximum expiratory flow-volume (MEFV) curves in six seated subjects during normal (+1 Gz) and increased (+2 and +3 Gz) gravitational stress. Full MEFV curves, initiated at total lung capacity, were recorded, as were partial MEFV curves, initiated at approximately 60% of the vital capacity. Data were acquired in all subjects breathing air at +1 and +2 Gz; results were available for three subjects breathing 80% He-20% O2 at +1 and +2 Gz, and in two subjects, results were obtained at +3 Gz. Changes in gravitational stress were not associated with changes of either full or partial MEFV curves. The known increase in differences of regional lung volume and recoil caused by increased gravitational stress did not influence maximum expiratory flow. Though increased gravitational stress probably changed regional emptying sequences little during full MEFV maneuvers, substantial changes of emptying sequence were expected during partial maneuvers. It is possible that such changes in emptying sequence occurred but were not associated with changes in maximum flow because the latter was determined by choking in central airways common to all regions.     

Peroxisomal membrane protein import does not require Pex17p

Of the approximately 20 proteins required for peroxisome biogenesis, only four have been implicated in the process of peroxisomal membrane protein (PMP) import: Pex3p, Pex16p, Pex17p, and Pex19p. To improve our understanding of the role that Pex17p plays in PMP import, we examined the behavior of PMPs in a Pichia pastoris pex17 mutant. Relative to wild-type cells, pex17 cells appeared to have a mild reduction in PMP stability and slightly aberrant PMP behavior in subcellular fractionation experiments. However, we also found that the behavior of PMPs in the pex17 mutant was indistinguishable from PMP behavior in a pex5 mutant, which has no defect in PMP import, and was far different from PMP behavior in a pex3 mutant, which has a bona fide defect in PMP import. Furthermore, we found that a pex14 mutant, which has no defect in PMP import, lacks detectable levels of Pex17p. Based on these and other results, we propose that Pex17p acts primarily in the matrix protein import pathway and does not play an important role in PMP import.     

Colicin V-treated Escherichia coli does not generate membrane potential.

Colicin V-treated Escherichia coli was inhibited in its capacity to carry out active transport of proline and was unable to generate a membrane potential. Colicin V also prevented membrane potential formation by isolated cytoplasmic membrane vesicles. We conclude that a primary effect of this colicin involves the cytoplasmic membrane as a target.     

Extended exposure to a discriminated,limited-hold temporal schedule does not produce stimulus control

Four rats were exposed to two different stimuli (either lights or tones), each stimulus being correlated with independent probabilities of water delivery in a temporally defined schedule. The schedule consisted of a 60 s T cycle with 30 s t(D) and t(-) successive subcycles; t(D) was correlated with a probability of water delivery of 1.0 and t(-) was correlated with a probability of water delivery of 0.0. The schedule was maintained during 180 sessions and extended for 25 extra sessions omitting the stimulus in t(-). The four rats showed low frequencies of responding, response frequency being slightly higher in t(-) than in t(D). The percentage of lost reinforcers was independent of response frequency. The rats which lost less reinforcers were those which obtained more water deliveries during the first 15 cycles of each session. These results show that stimulus control does not develop in limited-hold temporal schedules, and that response-reinforcer effectiveness may depend on the initial contact with reinforcers in the first cycles of the session.