Reverse pharmacology of orexin: from an orphan GPCR to integrative physiology

Orexins, which were initially identified as endogenous peptide ligands for two orphan G-protein coupled receptors (GPCRs), have been shown to have an important role in the regulation of energy homeostasis. Furthermore, the discovery of orexin deficiency in narcolepsy patients indicated that orexins are highly important factors for the sleep/wakefulness regulation. The efferent and afferent systems of orexin-producing neurons suggest interactions between these cells and arousal centers in the brainstem as well as important feeding centers in the hypothalamus. Electrophysiological studies have shown that orexin neurons are regulated by humoral factors, including leptin, glucose, and ghrelin as well as monoamines and acetylcholin. Thus, orexin neurons have functional interactions with hypothalamic feeding pathways and monoaminergic/cholinergic centers to provide a link between peripheral energy balance and the CNS mechanisms that coordinate sleep/wakefulness states and motivated behavior such as food seeking.     

Behavioural versus physiological mediation of life history under predation risk

Predator-generated variation in prey energy intake remains the dominant explanation of adaptive response to predation risk in prey life history, morphology and physiology across a wide range of taxa. This "behavioural hypothesis" suggest that chemical or visual signals of predation risk reduce prey energy intake leading to a life history characterized by a small size and late age at maturity. However, size-selective predation can induce either smaller size-early age or large size-late age life history. The alternative "physiological hypothesis" suggests that size-selective cues decouple the relationship between energy and life history, acting instead directly on development. Here we use a series of experiments in a fish-daphnid predator-prey system to ask whether size-selective predator cues induce a physiological mediation of development, overshadowing behaviourally based changes in food intake. We found fish chemical cues reduce the net energy intake in Daphnia magna, suggesting a behaviourally mediated reduction in energy. Experimental manipulation of food levels show further that reductions in food lead to later but smaller size at maturity. However, in line with the physiological hypothesis, we show that D. magna matures earlier and at a smaller size when exposed to fish predation cues. Furthermore, our data shows that they do this by increasing their development rate (earlier maturity) for a given growth rate, resulting in a smaller size at maturity. Our data, from a classic size-selective predation system, indicate that predator-induced changes in this system are driven by physiological mediation of development rather than behavioural mediation of energy intake.     

Effect of Acute and Chronic Administration of Methylphenidate on Mitochondrial Respiratory Chain in the Brain of Young Rats

Methylphenidate is commonly used for the treatment of attention deficit/hyperactivity disorder. There are still few works regarding the effects of methylphenidate on brain energy metabolism. Thus, in the present study we evaluated the effect of chronic administration of methylphenidate on the activities of mitochondrial respiratory chain complexes I and III in the brain of young rats. The effect of acute administration of methylphenidate on mitochondrial respiratory chain complexes I, II, III and IV in the brain of young rats was also investigated. For acute administration, a single injection of methylphenidate was given to rats on postnatal day 25. For chronic administration, methylphenidate injections were given starting at postnatal day 25 once daily for 28 days. Our results showed that complexes I and III were not affected by chronic administration of methylphenidate. Moreover, the acute administration of methylphenidate decreased complex I activity in cerebellum and prefrontal cortex, whereas complexes II, III and IV were not altered.     

Plasmic degradation of bovine fibrinogen and non-crosslinked fibrins in solution and in gel form.

1. Analysis of degradation processes of bovine fibrinogen by bovine plasmin using sodium dodecyl sulfate-polyacrylamide gel electrophoresis and a study on the mode of changes of the properties related to clotting of digestion products as a function of time were performed. Gross features and patterns very similar to those which had been reported with human fibrinogen-plasmin systems were obtained. 2. Based on the molecular size of the degradation products and the mode of appearance and disappearance of the degradation products, the processes could tentatively be divided into three stages: stage 1, where fibrinogen (mol. wt 370 000) was degraded to produce fragments X1 (330 000) and X2 (290 000); stage 2, fragment X2 was degraded with appearance of Y (210 000) and D1 (140 000); stage 3, appearance of fragments D1, D2 (110 000), and D3 (100 000) sequentially and E (68 000) with concomitant disappearance of Y. 3. A microseparation method, which is a combination of dansylation and sodium dodecylsulfate-polyacrylamide gel electrophoresis, was devised to analyze the events of stage 1 in detail, and a molecular model for the process was proposed. 4. The plasmic degradation processes of bovine non-cross-linked fibrins in solution and in gel form were compared with that of fibrinogen and it was found that the state of the substrates, fibrins, could cause differences in the degradation patterns. With the former substrate, essentially the same sodium dodecyl sulfate-polyacrylamide gel electrophoretic patterns as those with fibrinogen were obtained. With the latter substrate, however, a distinct difference in the mode of degradation of beta chains was observed.     

Recommendations on treatment for IPF

Patient management in Idiopathic Pulmonary Fibrosis (IPF) is largely based on societal guidelines and recommendations. A recent update by the American Thoracic Society (ATS), European Respiratory Society (ERS), Japanese Respiratory Society (JRS) and Latin American Thoracic Association (ALAT) provided updated guidance on the diagnosis and management of IPF, along with recommendations on pharmacologic and non-pharmacologic approaches to patient management. The treatment guidance is based on GRADE criteria, which rates the quality of evidence according to previously published methodology. Here we discuss how to interpret the recent guideline updates and the implications of this guidance for clinical practice. In addition we discuss the assessment and recommendations for a number of pharmacological agents that have been the focus of clinical trials over the past years. Although no single pharmacological agent was recommended by the guidelines committee, we discuss how since then, more recent data have resulted in the approval of pirfenidone in Europe, and preliminary negative findings regarding the safety of a triple therapy regimen consisting of prednisone, azathioprine and N-acetylcysteine have raised the question of whether it is no longer a treatment option. As clinicians, we must interpret the available guidance and recommendations as we consider each individual patient and as we discuss the available clinical data and the patient’s own preferences in our approach to the management of this disease.     

Understanding Miro GTPases: Implications in the Treatment of Neurodegenerative Disorders

The Miro GTPases represent an unusual subgroup of the Ras superfamily and have recently emerged as important mediators of mitochondrial dynamics and for maintaining neuronal health. It is now well-established that these enzymes act as essential components of a Ca²⁺-sensitive motor complex, facilitating the transport of mitochondria along microtubules in several cell types, including dopaminergic neurons. The Miros appear to be critical for both anterograde and retrograde mitochondrial transport in axons and dendrites, both of which are considered essential for neuronal health. Furthermore, the Miros may be significantly involved in the development of several serious pathological processes, including the development of neurodegenerative and psychiatric disorders. In this review, we discuss the molecular structure and known mitochondrial functions of the Miro GTPases in humans and other organisms, in the context of neurodegenerative disease. Finally, we consider the potential human Miros hold as novel therapeutic targets for the treatment of such disease.     

Effect of lard and corn oil intake on serum lipids in young men

An experimental diet with lard (30 g/day for 7 days) and corn oil (30 g/day for 7 days) on high carbohydrate (basal diet) was given to four healthy Japanese young men and the effect of diets containing different fat on serum lipids was examined. Serum total cholesterol was increased significantly from a basal diet of 106 +/- 23 to 141 +/- 26 mg/dl on lard diet, and then decreased significantly (p less than 0.05) to 111 +/- 22 mg/dl on corn oil diet. Serum triglycerides increased significantly (p less than 0.01) from 66 +/- 38 to 173 +/- 32 mg/dl on basal diet. Serum HDL-cholesterol was decreased significantly (p less than 0.01) from 41.9 +/- 1.6 to 31.2 +/- 3.8 mg/dl on lard diet and increased significantly (p less than 0.05) to 41.9 +/- 4.6 mg/dl on corn oil diet. Serum HDL-cholesterol fraction was decreased significantly (p less than 0.01) from 41.6 +/- 4.9 to 28.1 +/- 3.2% on basal diets, but increased significantly (p less than 0.05) to 44.3 +/- 3.1% on lard diet, and then decreased to 36.3 +/- 2.5% on corn oil diet. Serum HDL phospholipid fraction decreased significantly (p less than 0.05) from 62.5 +/- 6.7 to 50.7 +/- 1.8% on basal diet and increased significantly (p less than 0.05) to 60.4 +/- 1.0% on lard and corn oil diet. Serum phospholipids did not change by experimental diets. It is concluded that lard and corn oil have different and specific roles in lipid metabolism.     

ARHGAP18, a GTPase-activating protein for RhoA, controls cell shape, spreading, and motility

Rho GTPases are molecular switches that transmit biochemical signals in response to extracellular stimuli to elicit changes in the actin cytoskeleton. Rho GTPases cycle between an active, GTP-bound state and an inactive, GDP-bound state. These states are regulated by two distinct families of proteins-guanine nucleotide exchange factors and GTPase-activating proteins (GAPs). We studied the role of a previously uncharacterized GAP, ARHGAP18 (MacGAP). Overexpression of ARHGAP18 suppressed the activity of RhoA and disrupted stress fiber formation. Conversely, silencing of ARHGAP18 by small interfering RNA transfection-enhanced stress fiber formation and induced rounding of cells. We examined the role of ARHGAP18 in cell spreading and migration. Immunofluorescence analysis revealed that ARHGAP18 was localized to the leading edge during cell spreading and migration. ARHGAP18-knockdown cells showed impaired spreading, premature formation of stress fibers, and sustained activation of RhoA upon cell attachment. In addition, knockdown and overexpression of ARHGAP18 resulted in the inhibition and promotion of cell migration, respectively. Furthermore, ARHGAP18 was required for the polarization of cells for migration. Our results define ARHGAP18 as one of the crucial factors for the regulation of RhoA for the control of cell shape, spreading, and migration.     

Surface enlargement in the rumen of free-ranging muskoxen (<Emphasis Type="Italic">Ovibos moschatus</Emphasis>)

The intraruminal papillation pattern indicates the degree of rumen contents stratification and is related to the feeding niche of a ruminant. Muskoxen (Ovibos moschatus) display a variety of morphophysiological adaptations typical for grazers. We investigated the intraruminal papillation of 22 free-ranging muskoxen from five different months by comparing the surface enlargement factor both between seasons and between individual rumen regions. The seasonal pattern of rumen papillation indicated a distinct seasonality in food quality. The intraruminal papillation indicated a moderate degree of rumen contents stratification typical for intermediate feeders. The nutritional ecology of muskoxen is characterised by specific morphophysiological adaptations to a grass-dominated diet that nevertheless allow extensive seasonal use of browse forage.