Maternal choline supplementation programs greater activity of the phosphatidylethanolamine N-methyltransferase (PEMT) pathway in adult Ts65Dn trisomic mice.

Maternal choline supplementation (MCS) induces lifelong cognitive benefits in the Ts65Dn mouse, a trisomic mouse model of Down syndrome and Alzheimer's disease. To gain insight into the mechanisms underlying these beneficial effects, we conducted a study to test the hypothesis that MCS alters choline metabolism in adult Ts65Dn offspring. Deuterium-labeled methyl-d9-choline was administered to adult Ts65Dn and disomic (2N) female littermates born to choline-unsupplemented or choline-supplemented Ts65Dn dams. Enrichment of d9-choline metabolites (derived from intact choline) and d3 + d6-choline metabolites [produced when choline-derived methyl groups are used by phosphatidylethanolamine N-methyltransferase (PEMT)] was measured in harvested tissues. Adult offspring (both Ts65Dn and 2N) of choline-supplemented (vs. choline-unsupplemented) dams exhibited 60% greater (P≤0.007) activity of hepatic PEMT, which functions in de novo choline synthesis and produces phosphatidylcholine (PC) enriched in docosahexaenoic acid. Higher (P<0.001) enrichment of PEMT-derived d3 and d6 metabolites was detected in liver, plasma, and brain in both genotypes but to a greater extent in the Ts65Dn adult offspring. MCS also yielded higher (P<0.05) d9 metabolite enrichments in liver, plasma, and brain. These data demonstrate that MCS exerts lasting effects on offspring choline metabolism, including up-regulation of the hepatic PEMT pathway and enhanced provision of choline and PEMT-PC to the brain.

Vacuolar pathology in the median eminence of the hypothalamus after hyponatremia.

The median eminence of the hypothalamus is an important conduit by which neurosecretory hormones from hypothalamic nuclei are delivered to the pars nervosa (neural lobe) of the pituitary en route to the bloodstream. Dilutional hyponatremia was produced in adult rats to determine the effect on the morphology of the median eminence of the hypothalamus. Hyponatremia was caused by reducing electrolyte and organic osmolyte reserves to block the excretion of water through delivery of the nephrotoxin mercuric chloride (HgCl2). Histological examination of the brain 1 day after a hyponatremic insult revealed vacuolation within the median eminence of the hypothalamus. No other lesions were found in other parts of the brain after hyponatremia. The hyponatremic lesion consisted of a band of closely packed vacuoles that crossed the floor of the third ventricle. Vacuoles associated with hyponatremia were predominantly in the subependymal, fiber, reticular, and palisade layers of the median eminence. Vacuolation was not observed in the tanycyte layer of the median eminence. This study indicates that the median eminence is a potentially vulnerable site in human hyponatremic conditions that should be evaluated further in relevant animal models.

Mitotic figures in the median eminence of the hypothalamus.

The median eminence of the hypothalamus is part of the avenue by which neurosecreted hormones from the hypothalamic nuclei reach the pars nervosa (neural lobe) of the pituitary and eventually the bloodstream. Lithium treatment and osmotic stress increases the transport of neurosecretory hormones to the pituitary in the adult rat. Specialized astrocytes termed pituicytes in the pars nervosa of the pituitary participate in the secretory process and also develop considerable mitotic activity. The present work reveals similar mitotic figures in cells within the median eminence following 3 days of lithium treatment. The location and appearance of these mitoses add to the evidence that pituicytes are present in the median eminence. Moreover, mitoses occur within the ependymal (tanycyte) layer of the median eminence. Thus, the present results suggest that the tanycyte layer may contain pituicytes, indicating that the hypothalamus possesses specialized cells for modulating neurosecretion in response to osmotic challenges.

Systemic pathology in aged mouse models of Down's syndrome and Alzheimer's disease.

Down's syndrome (DS) in humans is caused by trisomy of chromosome 21 (HSA 21). DS patients have a variety of pathologies, including mental retardation and an unusually high incidence of leukemia or lymphoma such as megakaryocytic leukemia. Individuals with DS develop the characteristic neuropathological hallmarks of Alzheimer's disease (AD) in early adulthood, generally by the fourth decade of life. There are several mouse models of DS that have a segmental trisomy of mouse chromosome 16 (MMU 16) with triplicated genes orthologous to HSA 21. These mice display neurodegeneration similar to DS. Although brain pathology in DS models is known, little information is available about other organs. We studied the extraneural pathology in aged DS mice (Ts65Dn, Ts2 and Ts1Cje aged 8 to 24 months) as well as other mouse models of neurodegeneration, including presenilin (PS), amyloid-beta precursor protein (APP), and tau (hTau and JNPL) transgenic mice. An increased incidence of peripheral amyloidosis, positive for amyloid A (AA) but not amyloid-beta peptide (A beta), was found in APP over-expressing and tauopathic mice as compared to non-transgenic (ntg) littermates or to DS mouse models. A higher incidence of lymphoma was found in the DS models, including Ts1Cje that is trisomic for a small segment of MMU 16 not including the App gene, but not in the APP over-expressing mice, suggesting that high APP expression is not the cause of lymphoma in DS. The occurrence of lymphomas in mouse DS models is of interest in relation to the increased incidence of malignant conditions in human DS.

Different inflammatory reactions to vitamin D3 among the lateral, third and fourth ventricular choroid plexuses of the rat.

The four choroid plexuses in the brain ventricles are not identical, but differences among them have rarely been studied. The present work concerns the inflammatory and hemorrhagic choroid plexitis produced in Lewis rats by a single gavage of cholecalciferol (vitamin D(3)) or related steroids with vitamin D activity. Plexitis was very severe in the fourth ventricular plexus, somewhat less severe in the lateral ventricular plexuses, and almost absent in the third ventricular plexus. These findings were compared to the scanty data from the literature on differences among the plexuses.

Lithium increases gastrointestinal tract weight of male or female rats but it increases body weight only in females.

Lithium treatment of patients and laboratory animals causes increased body weight but no single organ or system has been found responsible. In the present work, we showed that lithium increased the weight of the female rat's gastrointestinal (GI) tract including its contents. The weight gain of the female rat GI tract was the same order of magnitude as the weight gain of the whole body of the females. All three parts of the GI tract (stomach, small intestine, colon) participated in the weight gain. Lithium treatment of male rats also increased GI tract weight, but lithium did not increase their overall body weight because of loss of weight at other sites.

A procedure for inducing sustained hyperlipemia in rats by administration of a surfactant.

Tyloxapol (Triton WR 1339) is a non-ionic detergent that inhibits lipoprotein lipase and thereby raises levels of serum lipids. It is used frequently for acute studies on lipids in rats but not for subacute or chronic studies. In the present work, we found that tyloxapol must be injected intravenously three times each week in order to have high and sustained levels of serum cholesterol and triglycerides for 1, 2, or 3 weeks. These results make it possible to extend the use of tyloxapol into chronic studies of hyperlipemia and vascular disease.

Lithium increases body weight of rats: relation to thymolysis.

Lithium treatment of patients and laboratory animals causes increased body weight. Lithium also elevates the plasma corticosterone levels of rats. Our purpose was to correlate the gain of body weight with the effects of lithium on the thymus gland, the organ most susceptible to stress and to elevated corticosterone levels. Toward this end, it was also necessary to establish a reliable and reproducible model by use of an inbred strain of rats. Female rats of the inbred Lewis strain were injected subcutaneously with lithium chloride or saline for an 18-day period. Necropsies were performed one day after the last treatment or at intervals during the treatment period. Lithium increased body weight gain compared to controls in all the experiments on Lewis rats. Contrary to the body as a whole, lithium caused loss of weight of the thymus gland. The spleen lost less weight than the thymus. Both lithium and nonspecific stress elevate plasma corticosterone and cause thymolysis. Mild nonspecific stress is known to cause increased weight gain in rats as well as in humans. Our data suggest that lithium acts like nonspecific stress to increase weight gain as a consequence of elevated glucocorticoids, manifested in our experiments by thymolysis. This mechanism has not been proposed previously.

Pyridoxine (vitamin B6) neurotoxicity: enhancement by protein-deficient diet.

Large doses of pyridoxine cause injury to the primary sensory neurons in trigeminal and dorsal root ganglia of animals and patients subjected to megavitamin therapy. The increased hazard to subjects with reduced renal excretory function has been explored previously. In the present work, the neurotoxicity of pyridoxine for rats was found to be increased by dietary protein deficiency. A mere 3 or 7 days of pretreatment with either of two protein-deficient diets were sufficient to accelerate and intensify the clinical neurological signs and histological lesions from pyridoxine injections. These results are caused, at least in part, by loss of body weight, decreased protein binding in serum and decreased consumption of water and decreased volume of urine, which reduce the urinary losses of the toxicant. The vitamers related to pyridoxine (pyridoxal, pyridoxamine) and the coenzyme (pyridoxal 5-phosphate) did not cause clinical signs or lesions similar to those produced by pyridoxine even when injected in maximum tolerated doses. Neither a protein-deficient diet nor bilateral nephrectomy changed the results with the vitamers.

Metallic tin is an adjuvant for anaphylaxis in rats.

Metallic tin powder is known to have an adjuvant-like property, by which it increases the levels of natural antibodies and induced hemagglutinins, and it enhances the induction of allergic encephalomyelitis in rats. In the present work, metallic tin is shown to be an adjuvant for a different immunologic process, anaphylactic sensitization. The new data support the notion that metallic tin causes polyclonal B-cell activation with proliferation of plasma cells.

Hydropic degeneration of the anterior pituitary gland (adenohypophysis) in uremic rats.

We observed hydropic degeneration of the anterior pituitary in rats made uremic by nephrotoxic chemicals, especially when the uremic rats were given a pure carbohydrate diet beforehand. The hydropic degeneration caused loss of nuclear and cytoplasmic content of many or most anterior pituitary cells. It was readily visible in paraffin sections by light microscopy. It was exaggerated when water was injected after the nephrotoxin and it was greatly reduced if saline was injected after the nephrotoxin. Low serum sodium levels in affected rats and the response to saline injection suggested that the mechanism for development of hydropic degeneration of the anterior pituitary gland involved hyponatremia. Depletion of total body sodium probably accounts for the enhancement of hydropic degeneration by the pure carbohydrate diet. Morphologic lesions of the anterior pituitary related to hyponatremia and uremia have not been described previously.

A method for peripheral chromatolysis in neurons of trigeminal and dorsal root ganglia, produced in rats by lithium.

In classical chromatolysis, Nissl bodies are initially lost centrally with subsequent progression to the periphery of the neuron. Peripheral chromatolysis has the opposite pattern; it is less common and more difficult to produce. We describe a new method for producing peripheral chromatolysis in neurons of trigeminal ganglia and dorsal root ganglia that requires only injection of large doses of lithium chloride (LiCl) for two, three or four consecutive daily doses. This method may be useful for elucidating the intraneuronal mechanisms that control the location and structure of the Nissl bodies.

A model for perinephric fluid accumulation in uremic rats with toxic nephrosis.

Severe edema developed around the kidneys of rats after several days of uremia induced by large intravenous doses of mercuric chloride. Edema was prevented when the kidney was removed or had its hilum ligated, or when rats were deprived of fluid intake. The edema fluid had a very low protein content. These facts suggested that the edema was derived from the kidneys, probably from the glomerular filtrate, and that the edema depended on some degree of remaining renal function. Increased permeability of the necrotic proximal tubules and obstruction by casts in the collecting tubules may have been involved. Histologic study suggested that the fluid diffused through the intact renal capsule. These experiments provide a model for perinephric (perirenal) fluid accumulation in certain human diseases and in certain intoxications of grazing animals.

Acute uremia produced in rats by nephrotoxic chemicals is alleviated by protein deficient diet.

Rats injected with mercuric chloride develop an acute renal tubular necrosis with uremia, which is frequently lethal. Pretreatment for 3 or 7 days with a protein-free diet reduces the mortality, the clinical signs (tremor), and the severity of renal tubular necrosis, and ameliorates the uremic chemical findings in the serum. Similar results followed injection of a nephrotoxic amino acid, D-serine, after pretreatment with a protein-free diet. Indirect evidence suggests that induction of metallothionein may be involved, at least in the experiments with mercury. Acute uremia produced by nephrotoxic chemicals may be useful for further studies of the role of nutrition in uremia, while avoiding the surgical procedures and prolonged observations required for the "remnant kidney" models.

Choroidal bodies: a new structure in the fourth ventricular choroid plexus of the rat and mouse.

Histologic study of the caudal end of the fourth ventricular choroid plexus of the rat and mouse revealed 1-4 small, discrete collections of cells that differed from the surrounding choroidal epithelial cells in appearance. They did not occur in other parts of the choroid plexuses. These choroidal bodies were not affected by a chemical toxin that caused hydropic degeneration of all the epithelial cells in the choroid plexuses. The function, if any, of the choroidal bodies is unknown. They were present in all rats that were studied by serial sections.

Acute uremia in rats: feeding sucrose overnight is preferable to starvation.

Some experiments on uremia in rats may require an overnight fast in order to empty the gastrointestinal tract, or for other reasons. Previous investigation of normal rats showed that an overnight fast is not completely innocuous and that feeding pure sucrose is a valuable alternative. In the present study, anephric uremic rats were fasted or fed sucrose for 20 h. Sucrose feeding resulted in lower serum urea values and less loss of liver weight. Therefore, feeding sucrose overnight is preferable to starvation in uremic rats, as in normal rats.

Malnutrition interferes with the unique lymphadenopathy induced in Lewis rats by metallic tin.

Metallic tin powder injected into Lewis rats caused marked enlargement of draining lymph nodes with prominent hyperplasia of plasma cells. A low level of dietary protein (8%) or deficiency of choline interfered with the cellular proliferation and reduced the size of the nodes by nearly one-third compared to a normal protein diet (20%). A high level of protein in the diet (50%) did not augment the effect of metallic tin powder beyond that achieved by a level usually considered adequate (20%).

An Alternative to Overnight Withholding of Food from Rats.

Withholding of food overnight has been used for numerous experimental purposes, including to reduce errors of intraperitoneal injections by diminishing the size and weight of the gastrointestinal tract, to prepare for gavage or surgery, or to avoid the effects food in the gastrointestinal tract might exert on drugs or nutrients. However, withholding food overnight causes undesirable side effects including loss of body and hepatic weight and decreases in blood glucose concentrations. Withholding food from rats housed on bedding can also lead to ingestion of bedding. Providing rats with commercially available sucrose cubes overnight ameliorated these undesirable effects while still reducing the size of the gastrointestinal tract. Rats housed in cages without access to bedding had an additional reduction in weight of the gastrointestinal tract. Analysis of our results indicated that providing sucrose cubes overnight and reducing access to bedding was an effective alternative to overnight withholding of all food.

Rathke's pouch during autoimmune inflammation of the rat pituitary.

Allergic adenohypophysitis was produced in rats by injection of anterior lobe tissue, Freund's adjuvant, and pertussis vaccine. In addition to the inflammatory changes in the parenchyma, fluid and inflammatory cells were found in the lumen of Rathke's pouch. The cells entered the lumen through small ulcers of the lining of the anterior wall of the pouch. Pituitaries with inflammation were increased in size and weight. The enlargement was caused mostly by dilation of Rathke's pouch with fluid and cells.