Do peptide-induced changes in feeding occur because of changes in motivation to eat?

The usual paradigm in which peptides are tested for their effect on food intake involves measuring intake of readily available food. In the lever press apparatus, the subjects must "work" to get food. Such work has traditionally been used as a means of measuring motivation. Mice were trained to press a lever for milk reinforcement. After achieving a stable level of performance, we tested the effects of gastrin-related peptide (GRP), bombesin (BBS) and cholecystokinin octapeptide (CCK-8) on lever pressing. All three peptides suppressed lever pressing for milk reinforcement. Prefeeding mice with milk increased the suppression of lever pressing to a greater extent in peptide-treated mice than in saline-treated mice. As the duration of prefeeding increased, lever pressing decreased. When mice were required to make more lever presses to obtain milk, both saline- and CCK-8-treated mice increased their lever pressing. However, saline-treated mice pressed at a higher rate than CCK-8-treated mice. Unlike the results obtained with saline and CCK-8, administration of a known gustatory adversant, lithium chloride, suppressed lever pressing to the same degree in mice fed or not fed prior to training. The results are consistent with the hypothesis that these peptides act as satiety agents.     

Seasonal changes of thermoregulatory efficiency in Djungarian hamsters

In their natural habitat, Djungarian hamsters are faced with dramatic seasonal changes. This requires various morphological and physiological adaptations allowing cope with harsh climate and food shortage, particularly in winter. These seasonal changes are controlled by the photoperiod and can be observed also in the laboratory at room temperature. The aim of the present study was to investigate if the efficiency of thermoregulation also depends on the photoperiod. For this reason, Djungarian hamsters were transferred to short-day conditions (SDC) with 8 h light and 16 h darkness. Two-thirds of the animals were classified as responders showing the typical seasonal changes – decrease of body mass, fur change, testes regression, vagina closing. The total activity per day did not change but, the nocturnal activity was spread over the longer dark time. The body temperature decreased, and the animals showed regular daily torpor. To investigate the thermoregulatory efficiency, body temperatures were correlated with motor activity. The obtained regression coefficients describe formally the effect of motor activity on body temperature, a measure for the efficiency of thermoregulation. In SDC, the coefficients were elevated, both during rest and activity, i.e. the same amount of activity did produce a larger increase in body temperature. Under field conditions, this might be an additional mechanism to compensate the bigger in winter heat loss. Also, the high coefficients may support the increase in body temperature at the end of a torpor phase by a bout of motor activity. The results show that, seasonal changes of thermoregulatory efficiency are an effective accessory way to cope with different temperatures in hamsters’ natural environment.     

Phytochrome-induced changes of β-fructosidase activity in radish cotyledons

Summary -fructofuranosidase (E.C.3.2.1.26) activity can hardly be detected in cotyledons from dark-grown radish (Raphanus sativus) seedlings. Under continuous far-red light two waves of -fructofuranosidase activity can be observed. The first one concerns an acidic invertase which progressively disappears. This wave is followed by the appearance of a neutral invertase. Some characteristics of these two enzymes are given. Their regulation by light via phytochrome is discussed.Abbreviations -FFase -fructosidase - CH cycloheximide     

Ultrastructural changes in β-cells of pancreatic islets in α-amanitin-poisoned Mice

In mice poisoned by alpha-amanitin nuclear changes typical of this toxin were observed in beta-cells of pancreatic islets. The lesions became progressively more severe and at 48 h after toxin injection some cells were necrotic. The damage to these cells could have implications in the changes in glycogen metabolism which occur after alpha-aminitin poisoning.     

Are changes in breeding habitat responsible for recent population changes of long-distance migrant birds?

Capsule: The direction and magnitude of changes in structure of UK woodlands since the 1980s, are inconsistent with them playing a causative role in the declines of four migrant bird species in upland oak woods.

Aims: To investigate whether changes in woodland structure were a possible cause of population changes of four Afro-Palearctic migrants (Wood Warbler Phylloscopus sibilatrix, Tree Pipit Anthus trivialis, Pied Flycatcher Ficedula hypoleuca and Common Redstart Phoenicurus phoenicurus) in the upland oakwoods of western and northern Britain.

Methods: Bird population estimates and measures of woodland structure were recorded in two time periods 1982–85 and 2003–04 across six regions of the UK. We modelled the effect of habitat change and initial habitat state on population changes between the two time periods. The predicted effects of habitat change on populations were then compared with observed population changes across the different regions.

Results: All four species underwent population declines; there were also significant increases in ground cover and understorey cover. The number of birds in 2003–04 was influenced by habitat structure at this time in addition to showing regional differences. Change in bird numbers varied between regions and was affected by both the initial habitat state and change in habitat structure, with regional variation in the effect of habitat change. There was however no relationship between the predicted effect of change in habitat structure on population size and observed regional population changes.

Conclusions: Changes in woodland structure are unlikely to be the main driver of population change in these four migrant bird species, and large-scale factors affecting demographics in other parts of their breeding range or in their wintering areas are likely reasons for local population declines.     

β-amyloid-induced changes in calcium homeostasis in cultured hippocampal neurons of the rat

A two-wave technique of calciometry with the use of a fluorescence dye, fura-2/AM, was applied for examination of the effect of a protein, β-amyloid (the main component of senile plaques in Alzheimer’s disease), on calcium homeostasis in cultured neurons of the rat hippocampus; β-amyloid was added to the culture medium. In most neurons, the effect of β-amyloid appeared as a more than twofold increase in the basic calcium concentration, as compared with the control (153.4 ± 11.5 and 71.7 ± 5.4 nM, respectively; P < 0.05). The characteristics of calcium transients induced by application of hyperpotassium solution also changed; the amplitude of these transients decreased, and the duration of a part corresponding to calcium release from the cell (rundown of the transient) increased. The mean amplitude of calcium transients under control conditions was 447.5 ± 20.1 nM, while after incubation in the presence of β-amyloid this index dropped to 278.4 ± 22.6 nM. Under control conditions, the decline phase of calcium transients lasted, on average, 100 ± 6 sec, while after incubation of hippocampal cell cultures in the presence of β-amyloid this phase lasted 250 ± 10 sec. Therefore, an excess of β-amyloid influences significantly calcium homeostasis in the nerve cells by disturbing functions of the calcium-controlling systems, such as voltage-operated calcium channels of the plasma membrane and calcium stores of the mitochondria and endoplasmic reticulum. Neirofiziologiya/Neurophysiology, Vol. 40, No. 1, pp. 9–12, January–February, 2008.     

Developmental changes in β-subunit composition of Na,K-ATPase in the Drosophila eye

The Drosophila genome contains at least three loci for the Na,K-ATPase β-subunit; however, only the protein products of nrv1 and nrv2 have been characterized hitherto. Here, we provide evidence that nrv3 also encodes for a functional Na,K-ATPase β-subunit, as its protein product co-precipitates with the Na,K-ATPase α-subunit. Nrv3 expression in adult flies is restricted to the nervous system in which Nrv3 is enriched in selective types of sensory cells. Because Nrv3 expression is especially prominent in the compound eye, we have analyzed the subcellular and developmental distribution of Nrv3 within the visual cells and related this distribution to those of the α-subunit and of the β-subunits Nrv1 and Nrv2. Prospective visual cells express Nrv2 in the third larval instar stage and during the first half of pupal development. During the last third of pupal life, Nrv3 gradually replaces Nrv2 as the Na,K-ATPase β-subunit in the photoreceptor cells. Adult photoreceptors express Nrv3 as their major β-subunit; the visual cells R1–R6 co-express Nrv2 at a low level, whereas R7 and R8 co-express Nrv1. Notably, β-subunits do not co-distribute exactly with the α-subunit at some developmental stages, supporting the concept that the α-subunit and β-subunit can exist in the plasma membrane without being engaged in α/β heterodimers. The non-visual cells within the compound eye express almost exclusively Nrv2, which segregates together with the α-subunit to septate junctions throughout development.     

Adaptive changes in bacteria: a consequence of nonlinear transitions in chromosome topology?

Adaptive changes in bacteria are generally considered to result from random mutations selected by the environment. This interpretation is challenged by the non-randomness of genomic changes observed following ageing or starvation in bacterial colonies. A theory of adaptive targeting of sequences for enzymes involved in DNA transactions is proposed here. It is assumed that the sudden leakage of cAMP consecutive to starvation induces a rapid drop in the ATP/ADP ratio that inactivates the homeostasis in control of the level of DNA supercoiling. This phase change enables the emergence of local modifications in chromosome topology in relation to the missing metabolites, a first stage in expression of an adaptive status in which DNA transactions are induced. The nonlinear perspective proposed here is homologous to that already suggested for adaptation of pluricellular organisms during their development. In both cases, phases of robustness in regulation networks for genetic expression are interspaced by critical periods of breakdown of the homeostatic regulations during which, through isolation of nodes from a whole network, specific changes with adaptive value may locally occur.     

Developmental changes in functional expression and β-adrenergic regulation of If in the heart of mouse embryo

The hyperpolarization-activated current (If) plays an important role in determining the spontaneousrate of cardiac pacemaker cells. The automatic rhythmicity also exists in working cells of embryonic heart,therefore we studied developmental changes in functional expression and β-adrenergic regulation of If inembryonic mouse heart. The expression of If is high in early developmental stage (EDS) (10.5 d after coitus)ventricular myocytes, low in intermediate developmental stage (IDS) (13.5 d) atrial or ventricular myocytesand even lower in late developmental stage (LDS) (16.5 d) atrial or ventricular myocytes, indicating thatthese cells of the EDS embryonic heart have some properties of pacemaker cells. β-adrenergic agonistisoproterenol (ISO) stimulates If in LDS but not in EDS cardiomyocytes, indicating that theβ-adrenergicregulation of If is not mature in EDS embryonic heart. But forskolin (a direct activator of adenylate cyclase)and 8-Br-cAMP (a membrane-permeable analogue of cAMP) increase the amplitude of If in EDS cells,indicating that adenylate cyclase and cAMP function fairly well at early stage of development. Furthermore,the results demonstrate that If is modulated by phosphorylation via cAMP dependent PKA both in EDSand LDS cells.     

Developmental changes in functional expression and β-adrenergic regula-tion of If in the heart of mouse embryo

The hyperpolarization-activated current (If) plays an important role in determining the spontaneous rate of cardiac pacemaker cells. The automatic rhythmicity also exists in working cells of embryonic heart,therefore we studied developmental changes in functional expression and β-adrenergic regulation of If in embryonic mouse heart. The expression of If is high in early developmental stage (EDS) (10.5 d after coitus) ventricular myocytes, low in intermediate developmental stage (IDS) (13.5 d) atrial or ventricular myocytes and even lower in late developmental stage (LDS) (16.5 d) atrial or ventricular myocytes, indicating that these cells of the EDS embryonic heart have some properties of pacemaker cells, β-adrenergic agonist isoproterenol (ISO) stimulates If in LDS but not in EDS cardiomyocytes, indicating that the β-adrenergic regulation of If is not mature in EDS embryonic heart. But forskolin (a direct activator of adenylate cyclase) and 8-Br-cAMP (a membrane-permeable analogue of cAMP) increase the amplitude of If in EDS cells,indicating that adenylate cyclase and cAMP function fairly well at early stage of development. Furthermore,the results demonstrate that If is modulated by phosphorylation via cAMP dependent PKA both in EDS and LDS cells.     

Developmental changes in functional expression andβ-adrenergic regulation of I_f in the heart of mouse embryo

The hyperpolarization-activated current (If) plays an important role in determining the spontaneous rate of cardiac pacemaker cells. The automatic rhythmicity also exists in working cells of embryonic heart, therefore we studied developmental changes in functional expression and β-adrenergic regulation of Iy in embryonic mouse heart. The expression of If is high in early developmental stage (EDS) (10.5 d after coitus) ventricular myocytes, low in intermediate developmental stage (IDS) (13.5 d) atrial or ventricular myocytes and even lower in late developmental stage (LDS) (16.5 d) atrial or ventricular myocytes, indicating that these cells of the EDS embryonic heart have some properties of pacemaker cells.β-adrenergic agonist isoproterenol (ISO) stimulates If in LDS but not in EDS cardiomyocytes, indicating that the β-adrenergic regulation of If is not mature in EDS embryonic heart. But forskolin (a direct activator of adenylate cyclase) and 8-Br-cAMP (a membrane-permeable analogue of cAMP) increase t     

Thermal denaturation and structural changes of α-helical proteins in keratins

To gain insight into the thermal stability of intermediate filaments and matrix in the biological composite structure of α-keratins, the thermal denaturation performance of human hair fibers was investigated by Modulated Differential Scanning Calorimetry (MDSC) in the dry and the wet state. Denaturation enthalpy ΔH(D) in water was found to be independent of heating rate (11.5J/g) and to be approximately double as high as in the dry state (5.2J/g). The lower enthalpy (dry) and its dependency on heating rate are attributed to effects of pyrolysis. The stepwise change of reversing heat capacity ΔC(p) marks the denaturation process as a classic two-stage transition. The increase of ΔC(p) with heating rate reflects a continuous shift of the nature of the denaturation of the α-helical material, first, into random coil and then towards random β-materials for lower heating rates. Denaturation temperatures follow Arrhenius relationships with heating rate, yielding activation energies of 416kJ/mol (dry) and 263kJ/mol (wet), respectively. A decrease of activation energy (wet) for high heating rates supports the hypothesis of systematic changes of the pathway of denaturation.     

Does endothelin-1 participate in the exercise-induced changes of blood flow distribution of muscles in humans?

Maeda, Seiji, Takashi Miyauchi, Michiko Sakane, MakotoSaito, Shinichi Maki, Katsutoshi Goto, and Mitsuo Matsuda. Does endothelin-1 participate in the exercise-induced changes of blood flowdistribution of muscles in humans? J. Appl.Physiol. 82(4): 1107-1111, 1997.Endothelin-1(ET-1) is an endothelium-derived potent vasoconstrictor peptide thatpotentiates contractions to norepinephrine in human vessels. Wepreviously reported that the circulating plasma concentration of ET-1is significantly increased after exercise (S. Maeda, T. Miyauchi, K. Goto, and M. Matsuda. J. Appl.Physiol. 77: 1399-1402, 1994). Tostudy the roles of ET-1 during and after exercise, we investigatedwhether endurance exercise affects the production of ET-1 in thecirculation of working muscles and nonworking muscles. Male athletesperformed one-leg cycle ergometer exercise of 30-min duration atintensity of 110% of their individual ventilatory threshold. Plasmaconcentrations of ET-1 in both sides of femoral veins (veins in theworking leg and nonworking leg) and in the femoral artery (artery inthe nonworking leg) were measured before and afterexercise. The plasma ET-1 concentration in the femoralvein in the nonworking leg was significantly increased after exercise,whereas that in femoral vein in the working leg was not changed. Thearteriovenous difference in ET-1 concentration was significantlyincreased after exercise in the circulation of the nonworking leg butnot of the working leg, which suggests that the production of ET-1 wasincreased in the circulation of the nonworking leg by exercise. Thepresent study also demonstrated that the plasma norepinephrineconcentrations were elevated by exercise in the femoral veins of boththe working and nonworking legs, suggesting that the sympathetic nerveactivity was augmented in both legs during exercise. Therefore, thepresent study demonstrates the possibility that the increase inproduction of ET-1 in nonworking muscles may cause vasoconstriction andhence decrease blood flow in nonworking muscles through its directvasoconstrictive action or through an indirect effect of ET-1 toenhance vasoconstrictions to norepinephrine and that these responsesmay be helpful in increasing blood flow in workingmuscles. We propose that endogenous ET-1 contributes tothe exercise-induced redistribution of blood flow in muscles.

     

Physical changes of β-sitosterol crystals in oily suspensions during heating

The aim of this research was to describe the thermal behavior of β-sitosterol crystals in oil-suspensions with a focus on the role of water during heating. The suspensions were prepared by recrystallization in order to achieve a microcrystalline particle size. The structural changes together with the mechanical properties of the suspensions during heating were studied by using variable temperature X-ray powder diffractometry (VT-XRPD), differential scanning calorimetry (DSC), and dynamic mechanical analysis (DMA). Hydrated β-sitosterol crystals in an oil-suspension, dehydrated, despite the composition of the suspensions, at low temperatures. At high β-sitosterol concentration, the monohydrate crystal form changed partially to a hemihydrated form, and when only a small amount of water was initially incorporated, the hemihydrate crystal form dehydrated to a mostly anhydrate crystal form. The released water, which was immiscible in the surrounding oil, caused the recrystallization of hydrated β-sitosterol during cooling. This procedure indicated a reversible dehydration process. Structural and thermal analysis of β-sitosterol crystals in suspensions, together with mechanical analysis made it possible to understand various physical changes during heating. Published: October 19, 2005     

Post-translational processing of β-d-xylanases and changes in extractability of arabinoxylans during wheat germination

Endo-1,4-β-d-xylanase (EC 3.2.1.8, β-d-xylanase) activity, and arabinoxylan (AX) level and extractability were monitored for the first time simultaneously in wheat kernels (Triticum aestivum cv. Glasgow) up to 24 days post-imbibition (DPI), both in the absence and presence of added gibberellic acid (GA). Roughly three different stages (early, intermediate and late) can be discriminated. Addition of GA resulted in a faster increase of water extractable arabinoxylan (WEAX) level in the early stage (up to 3–4 DPI). This increase was not accompanied by the discernible presence of homologues of the barley X-I β-d-xylanase as established by immunodetection. This suggests that other, yet unidentified β-d-xylanases operate in this early time window. The intermediate stage (up to 13 DPI) was characterized by the presence of unprocessed 67 kDa X-I like β-d-xylanase, which was much more abundant in the presence of GA. The occurrence of higher levels of the unprocessed enzyme was related with higher β-d-xylanase activities and a further increase in WEAX level, pointing to in vivo activity of the unprocessed 67 kDa β-d-xylanase. During the late stage (up to 24 DPI) gradual processing of the 67 kDa β-d-xylanase occurred and was associated with a drastic increase in β-d-xylanase activity. Up to 120-fold higher activity was recorded at 24 DPI, with approx. 85% thereof originating from the kernel remnants. The WEAX level decreased during the late stage, suggesting that the β-d-xylanase is processed into more active forms to achieve extensive AX breakdown.     

Age-Dependent changes of mineral contents in men and women’s calcanei

To elucidate age-related change of mineral contents in human bones, the mineral content and density of human calcanei were determined by inductively coupled plasma atomic emission spectrometry and dual-energy X-ray absorptiometry. Calcanei were removed from 27 subjects (17 men and 10 women) who died in the age range from 40–98 yr old. Both the inductively coupled plasma emission spectrometry and dual-energy X-ray absorptiometry indicated that there were agedependent decreases of the mineral contents and density in the men’s calcaneus in the age range from 40–98 yr, but not in the women’s calcaneus in the age range from 42–87 yr. It was also found that the calcanean masses of the men and women remained constant within the same age range until 98 yr.