Control of feeding during saline consumption and fluid deprivation in hamsters

Cellular dehydration induced by water deprivation or hypertonic saline injection reduces feeding in a variety of species. Normal feeding in rats is maintained during isotonic saline consumption by increasing the intake of saline compared to the usual intake of water. Hamsters do not show the spontaneous preference for isotonic saline noted in rats, even after adrenalectomy. In the present investigation, feeding by hamsters was depressed during both isotonic and hypertonic saline consumption compared to the usual feeding with water. Saline intakes did not exceed water intakes under similar conditions. When fluid intakes were elevated by prior fluid deprivation, feeding rates increased at all concentrations of saline after a delay proportional to the osmolality of the solution. Positive 24-hr sodium balances were always associated with saline consumption. Water and hypertonic saline injections reduced feeding, and the fluid loads were excreted very slowly. When hamsters were fluid deprived prior to injections, saline totally suppressed feeding, while water increased feeding compared to sham injected controls. It is concluded that cellular dehydration produces a reduction of feeding in hamsters drinking isotonic or hypertonic saline. Reduced feeding with isotonic saline consumption results from the failure of hamsters to increase their ad lib intake of that solution. The prolonged retention of both sodium and fluid after saline consumption or injection suggests that further saline intake may be inhibited by an expansion of the extracellular space.     

Feeding and locomotion responses to centrally injected nociceptin/orphanin FQ in chicks

Nociceptin/orphanin FQ (N/OFQ), the endogenous ligand of the opioid receptor-like receptor or nociceptin receptor (NOP), has been shown to induce feeding, locomotion, anti-stress and anxiolytic effects in rodents after central nervous system injection. In this study, the effect of intracerebroventricular (icv) injection of N/OFQ on feeding and locomotion behavior was evaluated in male broiler-type chickens. The icv injection of N/OFQ caused a moderate but significant increase in feed intake similar to the classical opioid peptides in rats. It also increased feed pecking frequency and feeding time 1 h after injection. Stepping, wing flapping and preening were not affected by N/OFQ. These results suggest that N/OFQ can act within the central nervous system of chickens to increase feed intake.     

Opiate induced feeding is not dependent on the hippocampus

It has been shown that spreading depression of the hippocampus can elicit feeding, and that several opioid peptides elicit spreading depression when injected into the hippocampus. To determine whether such depression is the primary mechanism by which opiates induce feeding, we tested the feeding effects of naloxone, an opiate antagonist, and butorphanol tartrate, a kappa-sigma agonist, on feeding in rats with and without hippocampal lesions. Naloxone tended to reduce intake approximately equally in the two groups. Similarly, the doses of butorphanol that increased intake in sham rats were equally effective in lesioned rats. It was concluded that the hippocampus is not the major structure mediating opiate-induced feeding.     

Copy number variation burden does not predict severity of neurodevelopmental phenotype in children with a sex chromosome trisomy

Sex chromosome trisomies (SCTs) (XXX, XXY, and XYY karyotypes) are associated with an elevated risk of neurodevelopmental disorders. The range of severity of the phenotype is substantial. We considered whether this variable outcome was related to the presence of copy number variants (CNVs)—stretches of duplicated or deleted DNA. A sample of 125 children with an SCT were compared with 181 children of normal karyotype who had been given the same assessments. First, we compared the groups on measures of overall CNV burden: number of CNVs, total span of CNVs, and likely functional impact (probability of loss‐of‐function intolerance, pLI, summed over CNVs). Differences between groups were small relative to within‐group variance and not statistically significant on overall test. Next, we considered whether a measure of general neurodevelopmental impairment was predicted by pLI summed score, SCT versus comparison group, or the interaction between them. There was a substantial effect of SCT/comparison status but the pLI score was not predictive of outcomes in either group. We conclude that variable presence of CNVs is not a likely explanation for the wide phenotypic variation in children with SCTs. We discuss methodological challenges of testing whether CNVs are implicated in causing neurodevelopmental problems.     

遗传性果糖不耐受症

遗传性果糖不耐受症（HFI）是一种罕见的、由于先天性醛缩酶B缺陷导致的果糖代谢病。为常染色体隐性遗传性疾病。特征是摄取果糖、蔗糖或山梨醇后发生严重的低血糖。若不及时终止此类食物，会导致肝肾功能损伤及生长发育障碍。本病诊断比较困难，治疗主要以对症治疗和饮食控制为主。本文就遗传性果糖不耐受症的临床生化特征、诊治方法及醛缩酶B损伤的分子学基础进行综述，为临床早期发现、早期诊断、早期治疗遗传性果糖不耐受症提供参考。     

Neuropeptides TRH and cyclo(His-Pro) share neuromodulatory,but not stimulatory,action on hypothalamic neurons in vitro: implication for the regulation of feeding

Summary Electrical activity of neurons in rat hypothalamic ventromedial nucleus was recorded in tissue slices, to investigate central neural mechanisms underlying reduction of food intake caused by TRH and its metabolite, cyclo(His-Pro) [cHP]. Application of TRH had two actions: stimulation of neuronal activity, which was desensitized on closely repeated applications; and modulation of neuronal responses to neurotransmitters, even in the absence of the stimulatory action. The neuromodulatory but not the direct stimulatory action could also be achieved by cHP. The neuromodulatory action is more likely to be a neural mechanism underlying the inhibition of feeding, while other biological functions, unique to TRH, may depend on direct stimulation. In this way, TRH could achieve different biological results through different modes of action on hypothalamic neurons.     

Circadian feeding and drinking rhythms in the rat under complete and skeleton photoperiods

Feeding and drinking rhythms were studied in rats maintained under 24-hr light-dark (LD) cycles with various photoperiods, under two-pulse (2P) and one-pulse (1P) skeleton photoperiods, and under constant dark (DD). Rhythmic waveforms were similar under complete LD cycles and corresponding skeleton photoperiods, indicating that these rhythms mainly reflect the entrainment of underlying circadian pacemakers. Little or no role was found for masking effects of light on circadian feeding and drinking waveforms. Entrainment was found to depend mainly on the timing of the dawn light signal, whether it was a 15-min light pulse or a dark-to-light transition initiating a complete photoperiod. Furthermore, the use of 1P schedules revealed that a dawn signal was sufficient for entrainment. These results closely match those obtained for motor activity measures in other nocturnal rodent species, and generally conform to the predictions of Pittendrigh's nonparametric theory of entrainment. Furthermore, the close correspondence of the two rhythms during entrainment, phase-jumps, and free-running (DD) conditions indicates that they are controlled by common circadian pacemakers.     

Genetic obestiy: estrogenic influences on the body weight and food intake of lean and obese adult Zucker (fa/fa) rats

The effects of chronic estrogen withdrawal and subsequent hormone replacement on the feeding and body weight of adult lean and genetically obese Zucker rats were investigated. Following confirmation of a delay in the vaginal canalization of the fatty rat, subgroups of each genotype received either ovariectomy or sham surgery (Experiment 1). One hundred days later all subjects were injected subcutaneously (SC) with 1.0 microgram of estradiol benzoate (EB) daily for 16 treatment days (Experiment 2A). A second series of daily 2.0 microgram EB injections was administered intraperitoneally (IP) for 1 week (Experiment 2B). The first experiment revealed that ovariectomy produced overeating and similar weight gains in both genotypes. In the second experiment, SC hormone treatment completely reversed ovarian obesity in lean animals but failed to alter the food intake or weight gain of fatty rats. IP administration of EB depressed the feeding of fatty and lean animals to a comparable degree but a reduction in weight gain was observed only in the lean rats. These findings are discussed in light of current theories of estrogenic modulation of energy balance.     

Self-selecting albino rats exhibit differential preferences for pure macronutrient diets: Characterization of three subpopulations

Analyses of natural feeding behavior in albino male Sprague-Dawley rats demonstrate that, when allowed to self-select from pure macronutrient diets (protein, carbohydrate and fat), these rats of the same genetic strain can be categorized into 3 subpopulations according to either their 24-h or their 12-h nocturnal patterns of nutrient intake. A majority of the animals (HC for high carbohydrate, 50% of the total population) consumed a diet rich in carbohydrate relative to protein or fat, while a smaller population of rats (HF, 30%) preferred the fat diet, and an even smaller population (HP, 20%) chose a high-protein diet. These 3 subpopulations, after a few weeks of maintenance on the diets, differed in their body weight, with the HF rats having a higher body weight than the HP animals, who tended to weigh more than the lightest HC rats. Whereas all subgroups exhibited a similar bimodal distribution of feeding during the nocturnal cycle, with peaks during the early and late dark periods, they were distinguishable on the basis of their nutrient consumption during specific phases of the dark cycle. This difference was most apparent in the early dark phase, when the 3 subgroups exhibited exaggerated preferences for the specific nutrient that was generally preferred over the 24-h cycle. This is in contrast to the middle dark phase, when diet preferences were attenuated or lost, and the late dark phase, when most rats were similar in showing an increased preference for protein and fat and a decreased preference for carbohydrate. The HF group was further distinguished by an unusually strong burst of feeding during the first 2 h of the dark period and an extra peak of feeding in the middle dark period (7th h), both of which were relatively high in fat content.     

CATs and HATs: the SLC7 family of amino acid transporters

The SLC7 family is divided into two subgroups, the cationic amino acid transporters (the CAT family, SLC7A1–4) and the glycoprotein-associated amino acid transporters (the gpaAT family, SLC7A5–11), also called light chains or catalytic chains of the hetero(di)meric amino acid transporters (HAT). The associated glycoproteins (heavy chains) 4F2hc (CD98) or rBAT (D2, NBAT) form the SLC3 family. Members of the CAT family transport essentially cationic amino acids by facilitated diffusion with differential trans-stimulation by intracellular substrates. In some cells, they may regulate the rate of NO synthesis by controlling the uptake of l-arginine as the substrate for nitric oxide synthase (NOS). The heterodimeric amino acid transporters are, in contrast, quite diverse in terms of substrate selectivity and function (mostly) as obligatory exchangers. Their selectivity ranges from large neutral amino acids (system L) to small neutral amino acids (ala, ser, cys-preferring, system asc), negatively charged amino acid (system x_c^–) and cationic amino acids plus neutral amino acids (system y⁺L and b^0,+-like). Cotransport of Na⁺ is observed only for the y⁺L transporters when they carry neutral amino acids. Mutations in b^0,+-like and y⁺L transporters lead to the hereditary diseases cystinuria and lysinuric protein intolerance (LPI), respectively.