Vagotomy in the rat reduces meal size of diets containing fat

This study was designed to examine the possibility that the presence of rat in a diet is responsible for preventing the small post vagotomy meals that occur with chemically defined low fat liquid diets but not with lab chow diets. Rats were thoroughly adapted to four liquid diets varying in fat content from virtually 0 to 30 g per 100 ml. They were then subjected to an operation designed to destroy the vagus nerves. All animals who were shown in post mortem tests to have suffered vagal damage also showed reduced meal sizes on all the diets. The meal sizes of animals for whom there was no evidence of vagal damage were normal. It was concluded that bulk rather than fat content is responsible for preventing the reduced post vagotomy meals.     

DHA-enriched phospholipid diets modulate age-related alterations in rat hippocampus

Our previous work on rat hippocampus showed that a loss of docosahexaenoic acid (DHA) occurs in the fatty acid composition of phosphatidylethanolamine (PE), plasmenylethanolamine (PmE) and phosphatidylserine (PS) with increasing age. The present study investigated whether a DHA-enriched phospholipid dietary supplement could restore DHA levels and cholinergic activity. Male rats were fed a balanced diet containing both linoleic and alpha-linolenic acids until the age of 2, 18 and 21 months. From 18 to 21 months, one subgroup received a diet supplemented with DHA-enriched phospholipids from egg yolk (E-PL), and another a diet with DHA-enriched phospholipids from pig brain (B-PL). Compared to the control diet, the E-PL diet restored the proportion of polyunsaturated fatty acids (PUFAs: 22:6n-3 and 20:4n-6) in PE and PmE, while enhancing spontaneous and evoked-acetylcholine (Ach) release. The B-PL diet had no effect on PUFAs, but increased basal extracellular levels of Ach in 21-month-old rats as compared to the age-matched control. Our results show that supplementation with DHA-enriched egg PL can enhance Ach release and correct PUFA composition.     

Comparison of three bioassays for rat interferon

Compared to the well-characterized murine and human interferons, few studies have been conducted on rat interferons. In the present study, we compared three rat interferon bioassays: a plaque-reduction method, a hemagglutination yield-reduction method, and a method involving reduction in viral cytopathic effect. These methods were evaluated in order to better assay rat interferons and thus facilitate investigations to determine the antiviral, antitumor, and immunoregulatory role of interferon in existing rat model systems. Each method has certain desirable characteristics; the choice of bioassay depends on the specific application required. Overall, the reduction in viral cytopathic effect bioassay combines most of the desired features of a rat interferon bioassay including sensitivity, precision, convenience, rapidity, and economy.     

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.     

The effects of varying sodium diets on haemodynamics and fluid balance in the spontaneously hypertensive rat

Spontaneously hypertensive rats (SHR) were given either 'low' (LNa; 0.5 mmol Na 100 g-1 food), 'control' (CNa; 12 mmol) or 'very high' (vHNa; 120 mmol) sodium diets from 5 to 13-14 weeks of age, to explore how these 240-fold variations in Na intake affected body weight, cardiac, renal and adrenal weights, overall water-electrolyte equilibrium and haemodynamic balance during rest, mental stress and blood loss. Body growth was retarded both in vHNa and LNa SHR presumably reflecting disturbed appetite due to the greatly altered dietary Na contents. Compared with CNa SHR, both cardiac and renal weights 100 g-1 body wt were slightly increased in vHNa and decreased in LNa SHR, with opposite changes of adrenal weights. Total body water, haematocrit and plasma Na-K levels were largely equal in the three groups. Furthermore, cardiac output (CO), stroke volume (SV) and central blood volume (CBV) did not differ significantly between groups; if anything, CO and SV were higher and CBV lower in vHNa and LNa SHR than in CNa SHR. However, while mean arterial pressure (MAP) was only marginally elevated in vHNa compared with CNa SHR, both MAP and total peripheral resistance (TPR) were lowered about 15% in LNa SHR with signs of increased sympathetic activity to the heart also during rest. Despite an apparently normal volume and cardiac output balance in LNa SHR, the latter changes suggest a disturbed neuro-hormonal cardiovascular control.(ABSTRACT TRUNCATED AT 250 WORDS)     

The secretory pattern of three stomach preparations in the rat

1. In conscious rats provided with a gastric fistula, or a Pavlov pouch, or a Heidenhain pouch, the secretion of acid and pepsin was studied in the interdigestive state and in response to hog gastrin II. In Pavlov pouches and in Heidenhain pouches the responses to 2-deoxy-D-glucose and to food were established, as were also the responses to gastrin pentapeptide and methacholine in Heidenhain pouches.2. Interdigestive secretion of acid and pepsin is substantial in the gastric fistula and the Pavlov pouch preparation, whereas in the Heidenhain pouch acid secretion is low or scanty, and the ratio pepsin/acid output is higher than in the innervated preparations.3. Feeding evoked secretion of acid and pepsin in the Heidenhain and Pavlov pouches; the increase in pepsin secretion lasted much longer in the Heidenhain than in the Pavlov pouch.4. Methacholine, infused in a threshold dose, augmented the acid output in response to food in the Heidenhain pouch, but did not affect the pepsin output.5. Gastrin II (hog) evoked graded acid responses in the three stomach preparations, and the innervated preparations were more sensitive to gastrin II than the denervated one, whereas stimulation of pepsin secretion was apparent only in the Heidenhain pouch.6. Methacholine, on infusion, in the Heidenhain pouch, gave a maximal acid secretory response, greater than twice that obtained by gastrin, and produced strong stimulation of pepsin.7. Methacholine, infused in a threshold dose, accentuated the acid secretory response to graded doses of gastrin.8. 2-deoxy-D-glucose stimulated acid and pepsin secretion consistently in the Pavlov pouch, whereas in the Heidenhain pouch the response was scanty or absent.9. A large dose of gastrin pentapeptide injected intravenously while a background secretion was maintained by gastrin II, produced in the Heidenhain pouch triphasic changes in the sequence: stimulation, inhibition, stimulation.     

Dietary self-selection of protein-unbalanced diets supplemented with three essential amino acids in Nile tilapia

Animals do not eat whatever food item they encounter, but choose different foods that best match their requirements. Fish exhibit such "nutritional wisdom" and adapt their feeding behaviour and food intake according to their needs and the nutritional properties of diets. In this paper, we tested the ability of Nile tilapia to select between diets with a balanced or unbalanced composition of essential amino acids. To this end, three different diets were prepared: a gelatine based diet (D(1)), a gelatine diet supplemented with three essential amino acids (EAA, l-tryptophane, l-methionine, l-threonine) (D(2)), and a diet containing only cellulose and the three crystalline EAA (D(3)). In addition, the putative role of both orosensorial factors (using pellets vs capsules) and social interactions (single vs groups of ten fish) was investigated. To this end, a total of 68 male tilapia of about 141±48 g (mean±S.D.) were challenged, individually or in groups, to select between D(1)vs D(2) using pellets dispensed by self-feeders (exp. 1). In another experiment (exp. 2), 11 individual fish were challenged to select encapsulated diets with non flavour or smell proprieties (D(1)vs D(2)), and in exp. 3 fish were challenged to self-supplementation in EAA (D(1)vs D(3)). The results showed the ability of tilapia to avoid the EAA-deficient diet, choosing 82.2% D(2) in the case of individual fish, and 80.8% D(2) in the case of fish groups. Dietary selection was not directly driven by the orosensorial characteristics of food, since tilapia sustained a higher preference for D(2) when fed with encapsulated diets. Finally, in exp. 3 tilapia self-supplemented the EAA deficiency by selecting a synchronised combination of D(1) and D(3) that matched their nutritional requirements. These findings highlighted the capacity of fish to make dietary selection based on the EAA content, which should be considered when discussing food intake regulation mechanisms, and diet formulation and supplementation with EAA.     

The use of three esterase kits to measure plasma cholesterol concentration in the rat and three other species

Three enzymatic methods for the determination of cholesterol and its esters were applied to plasma samples obtained from normocholesterolaemic rats, dogs, rabbits and man. A major difference was observed for rat plasma values, where the results obtained with a microbial esterase for the hydrolysis of cholesteryl esters were much lower than those obtained with mammalian esterases. This difference was greater for rats than for the other three species studied and is probably related to the plasma distribution of lipoproteins in the rat.     

Studies of the effects of high fat diets on cognitive function in a rat model

This research summarises a research program that is concerned with the effects of high fat diets on cognitive function in rats. The diets selected accurately represent current upper limits of human fat consumption in western societies. Rats fed with diets high in saturated or unsaturated fat for 3 months, were severely impaired on a range of learning and memory tasks. Related studies showed that these effects were modulated by concentration of fat, environmental influences, and treatment with glucose. More work is needed to identify the neurobiological mechanisms underlying this impairment but saturated fatty acid intake, as well as insulin resistance and glucose intolerance may be important factors. In demonstrating a clear relationship between obesity and cognitive impairment, this research has important implications for aging. Older adults are particularly vulnerable to the adverse effects of dietary fat and the present results underscore the importance of evidence that seniors with marginal levels of nutrient intake often perform poorly on tests of cognitive function, and are at increased risk for various forms of dementia.     

Persistent Yersinia enterocolitica infection in three rat strains

Yersinia enterocoliticamay persist for prolonged periods of time in humans sometimes resulting in the development of reactive arthritis. To elucidate factors predisposing for persistence we developed animal models. In Lewis and Fischer rats, viable bacteria could be demonstrated for prolonged time and abscesses could be found in the liver, spleen and lungs. Splenic abscesses were observed for more than 20 weeks.Yersinia enterocoliticapersisted in Lewis and Fischer rats, but only Lewis rats developed reactive arthritis. In Brown Norway rats abscesses developed early during infection but in contrast to the other strains disappeared after 3 weeks. Culture of homogenized abscess-containing tissue of all three rat strains yieldedYersiniae. Immunofluorescence studies of the abscesses showed diffuse staining inside the abscesses only, indicating the presence ofYersinia enterocoliticaantigen. Brown Norway rats, in contrast to Lewis and Fischer rats, developed a different serological reaction pattern againstYersinia enterocoliticaantigens and this correlated with the disappearance of the abscesses.     

Neural organization of spindles in three hindlimb muscles of the rat

The neuroanatomical organization of the dynamic (bag₁) and static (bag₂ and chain) intrafusal systems was compared by light and electron microscopy of serial sections among 71 poles of muscle spindle in soleus (SOL), extensor digitorum longus (EDL), and lumbrical (LUM) muscles in the rat. Eighty-four percent of 195 fusi-motor (γ) axons to the spindles innervated either the dynamic bag₁ fiber or the static bag₂ and/or chain fibers. Sixteen percent of the γ axons coin-nervated the dynamic and static intrafusal fibers. Some of these nonselective axons were branches of efferents that also gave rise to axons selective to either the dynamic or static types of intrafusal fibers in one or more spindles. Thus activation of individual stem γ efferents might not have a purely dynamic or purely static effect on the integrated afferent outflow from spindles of a hind-limb muscle in the rat. In addition, primary afferents in all muscles had terminations that cross-innervated the dynamic bag₁ and static bag₂ and/or chain intrafusal fibers in individual spindles, an arrangement that may enhance the mixed dynamic/static behavior of afferents when different intrafusal fibers are activated concurrently. Spindles of the slow SOL and fast EDL muscles had similar features, whereas differences were observed in the organization of the proximal (SOL and EDL) and distal (LUM) muscles. Spindles in LUM muscles had fewer static intrafusal fibers, a higher ratio of dynamic to static γ axons, and a higher incidence of skeletofusimotor (β) innervation to intrafusal fibers than spindles in the SOL or EDL muscles. Thus, the relative contribution of dynamic and static systems to muscle afferent outflow may differ among spindles located in different segments of the rat hindlimb. However, the dynamic and static intrafusal systems of spindle were less sharply demarcated in each of the three hindlimb rat muscles than in the cat tenuissimus muscle.     

Cytogenetic characterization of three human and three rat medullary thyroid carcinoma cell lines

Medullary thyroid carcinoma (MTC) is a neuroendocrine tumor of the thyroid C-cells. MTC may arise as a sporadic tumor or as a component of one of three autosomal dominant familial cancer syndromes, MEN 2A, MEN 2B, or familial MTC. Recent studies have identified mutations of the RET protooncogene in the proximal long arm of chromosome 10, which are thought to be causative for these syndromes. To facilitate the search for other genes involved in the development of MTC, we characterized cytogenetically three human MTC cell lines and three rat MTC cell lines. The human cell lines studied were TT and RO-H85-1, previously reported, and an uncharacterized cell line, MZ-CRC-1, derived from a malignant pleural effusion from a patient with metastatic MTC. The rat MTC cell lines characterized were CA-77, 6–23C₆, and 44-2. Cytogenetic abnormalities present in the human and rat cell lines were compared with 13 reported cytogenetic studies of human MTC tumors and three other cytogenetically analyzed MTC cell lines. The human 9q/rat 3 and human 3p/rat 15 chromosomes were affected in six of the comparable cell lines and tumors. These findings suggest human chromosome regions 9q and 3p may contain genes involved in the pathogenesis of MTC.     

Chronic vascular catheterization in the rat: Comparison of three techniques

Rats were implanted with an indwelling vascular cannula in the jugular vein, femoral artery or carotid artery, and evaluated for postsurgical weight changes and cannula patency. Complete details for surgical methods and materials are presented for each procedure. Over a 14 day period, the carotid artery procedure produced the most profound weight loss, while the jugular vein implantation was followed by minimal changes in body weight. Weight loss was intermediate for the femoral artery group. Body weight had returned to, or was above presurgical weight at 2, 4 and 6 days postsurgery for the jugular, femoral and carotid catheterizations, respectively. By 14 days following implantation 83%, 67% and 50% of the femoral, carotid and jugular cannulas, respectively, were patent. We conclude that for long-term sampling of blood in the rat, the femoral artery catheterization procedure is preferable in terms of patency and postsurgical weight loss.