CD200 expression in hematopoietic neoplasms: Beyond a marker for diagnosis of B-cell neoplasms

CD200 (OX-2) is expressed in myeloid cells, B cells, subsets of T cells and on other normal and neoplastic non-hematopoietic cells. It interacts with CD200R and has a suppressive effect on T cells immune mediated response. We aimed to review CD200 expression and its role in the immune evasion of non-B cell hematopoietic neoplasms. In acute myeloid leukemia, CD200 seems to be related to the worst outcome, even in diseases of good prognosis, possibly due to an immunosuppressive effect. In plasma cell myeloma studies, while some have associated CD200 expression with worst prognosis possibly due to its suppressive effect on monocyte and T cell-mediated immune response, in others CD200 appeared to be a marker of a better outcome, or even showed no impact in event-free survival (EFS). Few studies have evaluated CD200 expression in T cell neoplasms; however, it appears to be a good immunophenotypic marker for angioimmunoblastic T cell lymphoma. In conclusion, CD200 appears to be involved in the immune evasion of malignant cells, which could affect the survival of these patients.

Increased LPS levels coexist with systemic inflammation and result in monocyte activation in severe COVID-19 patients

Mucosal barrier alterations may play a role in the pathogenesis of several diseases, including COVID-19. In this study we evaluate the association between bacterial translocation markers and systemic inflammation at the earliest time-point after hospitalization and at the last 72 h of hospitalization in survivors and non-survivors COVID-19 patients. Sixty-six SARS-CoV-2 RT-PCR positive patients and nine non-COVID-19 pneumonia controls were admitted in this study. Blood samples were collected at hospital admission (T1) (Controls and COVID-19 patients) and 0-72 h before hospital discharge (T2, alive or dead) to analyze systemic cytokines and chemokines, lipopolysaccharide (LPS) concentrations and soluble CD14 (sCD14) levels. THP-1 human monocytic cell line was incubated with plasma from survivors and non-survivors COVID-19 patients and their phenotype, activation status, TLR4, and chemokine receptors were analyzed by flow cytometry. COVID-19 patients presented higher IL-6, IFN-γ, TNF-α, TGF-β1, CCL2/MCP-1, CCL4/MIP-1β, and CCL5/RANTES levels than controls. Moreover, LPS and sCD14 were higher at hospital admission in SARS-CoV-2-infected patients. Non-survivors COVID-19 patients had increased LPS levels concomitant with higher IL-6, TNF-α, CCL2/MCP-1, and CCL5/RANTES levels at T2. Increased expression of CD16 and CCR5 were identified in THP-1 cells incubated with the plasma of survivor patients obtained at T2. The incubation of THP-1 with T2 plasma of non-survivors COVID-19 leads to higher TLR4, CCR2, CCR5, CCR7, and CD69 expression. In conclusion, the coexistence of increased microbial translocation and hyperinflammation in patients with severe COVID-19 may lead to higher monocyte activation, which may be associated with worsening outcomes, such as death.

Survey on reporting of epithelial cells in urine sediment as part of external quality assessment programs in Brazilian laboratories

Introduction

Epithelial cells (ECs) are structures regularly observed during urine microscopy analysis. The correct identification of EC subtypes can be useful since renal tubular epithelial cells (RTECs) are clinically relevant. We investigate the urinary ECs report and the judgement of its clinical importance by Brazilian laboratories.

Materials and methods

A survey with four questions was made available to participants of the Urinalysis External Quality Assessment Program (EQAP) from Controllab. Laboratories composed 3 groups: (1) differentiating ECs subtypes: “squamous”, “transitional” and “RTECs”; (2) differentiating ECs subtypes: “squamous” or “non-squamous” cells; (3) without ECs subtype identification. Participants did not necessarily answer to all questions and the answers were evaluated both within the same laboratory’s category and within different categories of laboratories.

Results

A total of 1336 (94%) laboratories answered the survey; Group 1, 119/140 (85%) reported that ECs differentiation is important to the physician and 62% want to be evaluated by EQAP, while in Group 3, 455/1110 (41%) reported it is useful to them, however only 25% want be evaluated by EQAP. Group 2 laboratories 37/51 (73%) reported that the information is important, but only 13/52 (25%) are interested in an EQAP with differentiation of the 3 ECs subtypes.

Conclusion

Most of the laboratories do not differentiate ECs in the three subtypes, despite the clinical importance of RTECs. Education of laboratory staff about the clinical significance of urinary particles should be considered a key priority.

Experimental Hypothyroidism Inhibits δ-Aminolevulinate Dehydratase Activity in Neonatal Rat Blood and Liver

The aim of this study was to investigate the potential relationship between hypothyroidism and δ-aminolevulinate dehydratase (δ-ALA-D) activity in rat blood and liver. Experimental hypothyroidism was induced in weanling rats by exposing their mothers to propylthiouracil (PTU) diluted in tap water (0.05% w/ v), ad libitum, during the lactational period (PTU group). Control (euthyroid) group included weanling rats whose mothers received just tap water, ad libitum, during the lactational period. Reverted-hypothyroid group (PTU + 3,3′,5-triiodo-L-thyronine [T3]) included weanling rats whose mothers were exposed to PTU similarly to those in the hypothyroid group, but pups received daily subcutaneous injections of T3(20 μg/kg, from Postnatal Days 2–20). After the treatment, serum T3levels were drastically decreased (around 70%) in the PTU group, and this phenomenon was almost reverted by exogenous T3. PTU decreased blood δ-ALA-D activity by 75%, and T3treatment prevented such phenomena. Erythrocytes and hemoglobin levels were increased by 10% in PTU-treated animals and higher increments (around 25%) were observed in these parameters when exogenous T3was coadministered. Dithiothreitol did not change blood δ-ALA-D activity of PTU-exposed animals when present in the reaction medium, suggesting no involvement of the enzyme’s essential thiol groups in PTU-induced δ-ALA-D inhibition. PTU did not affect blood δ-ALA-D activity in vitro. These results are the first to show a correlation between hypothyroidism and decreased δ-ALA-D activity and point to this enzyme as a potential molecule involved with hypothyroidism-related hematological changes.

Bright Field Microscopy to Detect Decoy Cells Due to BK Virus Infection in the Fresh and Unstained Urine Sediment in Kidney Allograft Recipients

BACKGROUND

BK virus (BKV) may reactivate in kidney allograft recipients ultimately leading to BKV nephropathy and graft loss. Decoy cells (DCs) are one of the early marks of BKV reactivation, and these can be detected in the urine sediment.

METHODS

A cohort of 102 kidney transplant patients was followed during months 3 and 6 after the transplant procedure. Urine samples were obtained to detect the presence of DC in the fresh and unstained urine sediment under bright field microscopy (BFM), in concomitance to the determination of the amount of BK viruria by qPCR.

RESULTS

Decoy cells were found in 14.7% of patients (15/102). There was a strong agreement (P < 0.001) between qualitative DC detection by two experienced analysts and by qPCR. The positive predictive value, negative predictive value, specificity, and accuracy of BFM were 80%, 75%, 97%, and 75%, respectively. Test sensitivity was 16%. The comparative method was the qPCR.

CONCLUSIONS

Despite its limited sensitivity, BFM of unstained urine sediment is an easily available, fast and cheap method to identify DCs in the population of kidney allograft recipients. The diagnostic performance of BFM on the hands of less experienced analysts deserves further investigation.

Ω3-Polyunsaturated fatty acids prevent lipoperoxidation, modulate antioxidant enzymes, and reduce lipid content but do not alter glycogen metabolism in the livers of diabetic rats fed on a high fat thermolyzed diet

Ω3-Polyunsaturated fatty acids (Ω3-PUFAs) are known to act as hypolipidaemics, but the literature is unclear about the effects that Ω3-PUFAs have on oxidative stress in obese and diabetic patients. In this study, our aim was to investigate the effects of Ω3-PUFAs on oxidative stress, including antioxidant enzyme activity and hepatic lipid and glycogen metabolism in the livers of diabetic and non-diabetic rats fed on a high fat thermolyzed diet. Rats were divided into six groups: (1) the control group (C), (2) the control diabetic group (D), (3) the high fat thermolyzed diet group (HFTD), which were fed a diet that was enriched in fat that was heated for 60 min at 180°C, (4) the high fat thermolyzed diet diabetic group (D + HFTD), (5) the high fat thermolyzed diet + Ω3 polyunsaturated fatty acid group (HFTD + Ω3), and (6) the high fat thermolyzed diet + Ω3 polyunsaturated fatty acid diabetic group (D + HFTD + Ω3). The most important finding of this study was that Ω3-PUFAs are able to reduce triglycerides, non-esterified fatty acid, lipoperoxidation levels, advanced glycation end products, SOD/CAT enzymatic ratio, and CAT immunocontent and increase SOD2 levels in the livers of diabetic rats fed with a HFTD. However, Ω3-PUFAs did not alter the observed levels of protein damage, blood glucose, or glycogen metabolism in the liver. These findings suggest that Ω3-PUFAs may represent an important auxiliary adjuvant in combating some diseases like diabetes mellitus, insulin resistance, and non-alcoholic fatty liver disease.

Gestational and postnatal low protein diet alters insulin sensitivity in female rats

Nutrition during pregnancy and lactation can program an offspring's metabolism with regard to glucose and lipid homeostasis. A suboptimal environment during fetal, neonatal and infant development is associated with impaired glucose tolerance, type 2 diabetes and insulin resistance in later adult life. However, studies on the effects of a low protein diet imposed from the beginning of gestation until adulthood are scarce. This study's objective was to investigate the effects of a low protein diet imposed from the gestational period until 4 months of age on the parameters of glucose tolerance and insulin responsiveness in Wistar rats. The rats were divided into a low protein diet group and a control group and received a diet with either 7% or 25% protein, respectively. After birth, the rats received the same diet as their mothers, until 4 months of age. In the low protein diet group it was observed that: (i) the hepatic glycogen concentration and hepatic glycogen synthesis from glycerol were significantly greater than in the control group; (ii) the disposal of 2-deoxyglucose in soleum skeletal muscle slices was 29.8% higher than in the control group; (iii) there was both a higher glucose tolerance in the glucose tolerance test; and (iv) a higher insulin responsiveness in than in the control group. The results suggest that the low protein diet animals show higher glucose tolerance and insulin responsiveness relative to normally nourished rats. These findings were supported by the higher hepatic glycogen synthesis and the higher disposal of 2-deoxyglucose in soleum skeletal muscle found in the low protein diet rats.

Ketogenic diet-fed rats have increased fat mass and phosphoenolpyruvate carboxykinase activity

The ketogenic diet (KD), characterized by high fat and low carbohydrate and protein contents, has been proposed to be beneficial in children with epilepsy disorders not helped by conventional anti-epileptic drug treatment. Weight loss and inadequate growth is an important drawback of this diet and metabolic causes are not well characterized. The aim of this study was to examine body weight variation during KD feeding for 6 wk of Wistar rats; fat mass and adipocyte cytosolic phosphoenolpyruvate carboxykinase (PEPCK) activity were also observed. PEPCK activity was determined based on the [H(14)CO(3) (-)]-oxaloacetate exchange reaction. KD-fed rats gained weight at a less rapid rate than normal-fed rats, but with a significant increment in fat mass. The fat mass/body weight ratio already differed between ketogenic and control rats after the first week of treatment, and was 2.4 x higher in ketogenic rats. The visceral lipogenesis was supported by an increment in adipocyte PEPCK, aiming to provide glycerol 3-phosphate to triacylglycerol synthesis and this fat accumulation was accompanied by glucose intolerance. These data contribute to our understanding of the metabolic effects of the KD in adipose tissue and liver and suggest some potential risks of this diet, particularly visceral fat accumulation.

Different effect of high fat diet and physical exercise in the hippocampal signaling

Obesity is an epidemic disease that may affect brain function. The present study examined the effect of high fat diet (HF) and physical exercise on peripheral tissue and hippocampal signaling. CF-1 mice (n = 4, per cage) were divided into groups receiving high fat (HF) or control (CD) diets for 5 months, with or without voluntary exercise. Serum triacylglycerol, total cholesterol, HDLc, liver triacylglycerol and glycogen concentrations were evaluated (n = 6). Also, the phosphorylation state of the AKT --> ERK 1/2 --> CREB pathway (AKT, pAKTser473, ERK 1/2, pERK 1/2, CREB and pCREB, n = 4-6) was analyzed in the hippocampus. HF diet caused an increase in AKT phosphorylation at ser473 (P < 0.05), while exercise increased the phosphorylation of ERK 1/2 (P < 0.05) and CREB (P < 0.05). As expected, exercise reversed some of the harmful effects of HF, i.e., increased liver deposition of fat (P < 0.05) and fat gain in the abdominal region (P < 0.05). In conclusion, the effects of exercise and HF diet on brain signaling appear to affect the hippocampal AKT --> ERK 1/2 --> CREB pathway in independent ways: HF intake caused increased phosphorylation of AKTser473, while exercise increased ERK 1/2 --> CREB signaling. The physiological relevance of these findings in brain function remains to be elucidated.

Effect of 2-deoxy-D-glucose on aminoacids metabolism in rats' cerebral cortex slices

We studied the effect of different concentrations of 2-deoxy-D-glucose on the L-[U-14C]leucine, L-[1-14C]leucine and [1-14C]glycine metabolism in slices of cerebral cortex of 10-day-old rats. 2-deoxy-D-glucose since 0.5 mM concentration has inhibited significantly the protein synthesis from L-[U-14C]leucine and from [1-14C]glycine in relation to the medium containing only Krebs Ringer bicarbonate. Potassium 8.0 mM in incubation medium did not stimulate the protein synthesis compared to the medium containing 2.7 mM, and at 50 mM diminishes more than 2.5 times the protein synthesis compared to the other concentration. Only at the concentration of 5.0 mM, 2-deoxy-D-glucose inhibited the CO2 production and lipid synthesis from L-[U-14C] leucine. This compound did not inhibit either CO2 production, or lipid synthesis from [1-14C]glycine. Lactate at 10 mM and glucose 5.0 mM did not revert the inhibitory effect of 2-deoxy-D-glucose on the protein synthesis from L-[U-14C]leucine. 2-deoxy-D-glucose at 2.0 mM did not show any effect either on CO2 production, or on lipid synthesis from L-[U-14C]lactate 10 mM and glucose 5.0 mM.

Hematological changes in rats chronically exposed to oral aluminum

This study was aimed to investigate the effects of the long-term oral exposure to aluminum sulfate on hematological parameters in rats. For this purpose, 24 adult female Wistar rats were divided in three groups with 8 animals each (control, citrate, and citrate plus aluminum groups). Rats from control and citrate groups had free access to tap water and to a sodium citrate solution (35 mM), respectively. Rats from citrate plus aluminum group received, as unique source of liquid, an aluminum sulfate solution (30 mM) diluted in the above-mentioned sodium citrate solution, ad libitum. After the treatment period (18 months), aluminum-exposed rats showed a significant decrease in the number of red blood cells, blood hemoglobin concentration and hematocrit when compared to rats from the control group. Serum iron levels were also significantly lower in citrate plus aluminum group, whereas total iron binding capacity did not change after citrate plus aluminum exposure. Erythrocyte thiobarbituric acid-reactive substances (TBARS) and nonprotein thiols (NPSH) levels, erythrocyte osmotic fragility and hepatic delta-aminolevulinic acid dehydratase (delta-ALA-D) activity did not change after treatment with citrate plus aluminum. Conversely, aluminum exposure increased delta-ALA-D activity in bone marrow. The present results indicate that long-term oral exposure to low doses of aluminum sulfate promotes alterations on erythrocyte parameters in rats, probably as a consequence of alterations in the iron status. In addition, although the details of the underlying mechanism remain unclear, our study reports, for the first time, a stimulatory effect of chronic aluminum exposure on bone marrow delta-ALA-D activity.

Increased locomotor response to amphetamine, but not other psychostimulants, in adult mice submitted to a low-protein diet

Protein malnutrition results in a variety of brain dysfunctions, ultimately affecting cognitive functions. The effects of protein malnutrition in brain response to psychostimulants have been less studied in adult animals. We therefore aimed to study the response to psychoactive drugs on the locomotor activity (a behavior paradigm) of adult protein malnourished mice. Two-month-old mice were divided in two groups: (a) low-protein group (LP), which received 6% of protein diet, and (b) a control group that received a 25% of protein diet. After 3 months, they were tested for locomotor activity after an i.p. injection of one of psychoactive drugs: D-amphetamine (5.0 mg/kg), apomorphine (2.0 mg/kg), dizocilpine (0.25 mg/kg), or caffeine (30 mg/kg). Mice submitted to the LP diet presented prolonged induction of hyperlocomotion caused by amphetamine (about 350% between 90 and 180 min post drug injection as compared with well-nourished mice, p<0.01) but presented unaltered response to apomorphine, caffeine, and dizocilpine. These data point to altered catecholamine metabolism induced by protein restriction in adult mice. The results are discussed based on previous works, presenting theoretical hypotheses about the possible mechanisms involved in the present findings.

Effects of Undernutrition on Glycine Metabolism in the Cerebellum of Rats

Undernutrition is a worldwide problem affecting millions of unborn and young children during the most vulnerable stages of brain development. Total restriction of protein during the perinatal period of life can alter the development of the mammalian fetus and have marked repercussions on development of the central nervous system (CNS). The brain is vulnerable to undernutrition with altered morphologic and biochemical maturation, leading to impaired functions. The focus of this study is to investigate [U-14C]glycine metabolism in undernourished rats submitted to pre- and postnatal protein deprivation (diet: 8% protein with and without addition of L-methionine; control group: 25% protein). Although undernutrition produced a reduction in cerebellar weight and alterations in the DNA concentration, the present study shows that glycine metabolism in this structure is partially protected because the undernourished group with L-methionine did not show modifications in glycine metabolism at all ages studied. However, L-methionine deficiency alters glycine metabolism at 7 and 21 days, but in the adult age both undernourished groups presented no differences in oxidation to CO2, conversion to lipids and incorporation into protein from glycine, compared to the control group.

High Extracellular K+Levels Stimulate Acetate Oxidation in Brain Slices from Well and Malnourished Rats

We investigated the effect of high (12, 20, and 50 mM) extracellular K+ concentrations ([K+]0) on [U-14C] acetate oxidation to CO2 in cerebral cortex slices of control and perinatal malnourished rats. High [K+]o increased the acetate oxidation, compared with a medium containing 2.7 mM [K+]0. By investigating the mechanisms involved in this stimulation, it was shown that (i) ouabain (1 mM) and monensin (10 microM) prevented this increase; (ii) in a medium with physiological [K+]0 (2.7 mM), the decreasing of [Na+]0 stimulated acetate oxidation. These results suggest that the stimulatory effect of [K+]0 on acetate oxidation was due to the decreasing of Na1 levels. Considering that malnutrition could alter the activity of Na+,K(+)-ATPase and/or other pertinent proteins, its effect on acetate oxidation was investigated. The malnutrition, which altered the body and cerebral weight of rats, did not modify the acetate oxidation in any protocol.

Characterization of imido [8-(3)H] guanosine 5'-triphosphate binding sites to rat brain membranes

Besides their well-defined intracellular roles in transmembrane signals transduction, guanine derivatives play important roles by acting from the outside of neural cell membranes. These roles are mediated by two different pool sites in cell membranes: G proteins, which bind to specific (GDP and GTP) intracellular guanine derivatives, and sites that bind to extracellular guanine derivatives. In this study we investigated some methodological characteristics of both guanine derivatives binding sites (intracellular and extracellular) in rat brain neural membranes. By investigating the binding of a poorly hydrolyzed GTP analogue and the adenylate cyclase activity in neural membranes, we observed some distinctiveness of guanine derivatives binding sites: stability to washing procedures (extracellular) and modulation of adenylate cyclase activity (intracellular). These results allow dealing with each site separately, which could be useful for discriminating the roles of extracellular and intracellular guanine derivatives in the central nervous system.

In vitro effects of D-2-hydroxyglutaric acid on glutamate binding, uptake and release in cerebral cortex of rats

Neurological dysfunction is common in patients with D-2-hydroxyglutaric aciduria (DHGA). However, the mechanisms underlying the neuropathology of this disorder are far from understood. In the present study, we investigated the in vitro effects of D-2-hydroxyglutaric acid (DGA) at various concentrations (0.1-1.0 mM) on various parameters of the glutamatergic system, namely the basal and potassium-induced release of L-[3H]glutamate by synaptosomal preparations, Na(+)-dependent L-[3H]glutamate uptake by synaptosomal preparations and Na(+)-independent L-[3H]glutamate uptake by synaptic vesicles, as well as of Na(+)-independent and dependent L-[3H]glutamate binding to synaptic plasma membranes from cerebral cortex of male adult Wistar rats. We observed that DGA significantly increased synaptosomal L-[3H]glutamate uptake, without altering the other parameters. Although these findings do not support a direct excitotoxic action for DGA since the metabolite did not affect important parameters of the main neurotransmission system, they do not exclude a direct action of DGA on NMDA or other glutamate receptors. More comprehensive studies are therefore necessary to evaluate the exact role of DGA on neurotransmission.

Serum and liver lipids in rats and chicks fed with diets containing different oils

OBJECTIVES

Because dietary fat composition is determinant for serum cholesterol level, which is related to cardiovascular disease, we evaluated the effects of diets containing saturated (coconut oil) or polyunsaturated fatty acids (soybean oil) supplemented or not with dietary cholesterol on serum and liver lipid composition in two animal species.

METHODS

Male Wistar rats (21 d old) were assigned to one of seven groups and fed with commercial diet or diets containing 5% or 20% soybean oil or 20% coconut oil with or without 1% cholesterol. Chicks were assigned to one of four groups and fed with diets containing 15% soybean oil or 15% coconut oil with or without 1% cholesterol.

RESULTS

In rats, the accumulations of hepatic cholesterol and triacylglycerols were higher in the group fed 20% soybean oil and 1% cholesterol than in the group fed 20% coconut fat and 1% cholesterol. The highest serum levels of cholesterol and triacylglycerols were observed in the group fed coconut oil and cholesterol, compared with the group fed soybean oil and cholesterol. Triacylglycerol, high-density lipoprotein, and total cholesterol serum levels increased with diet containing coconut oil and cholesterol. In chicks, the highest hepatic cholesterol accumulation occurred in the group fed 15% coconut fat and 1% cholesterol. Total and high-density lipoprotein cholesterol levels increased with diet containing coconut oil and cholesterol, although none of these diets modified serum triacylglycerol levels.

CONCLUSIONS

The type of experimental animal model and the diet composition influence lipid metabolism.

Effects of L-2-hydroxyglutaric acid on various parameters of the glutamatergic system in cerebral cortex of rats

L-2-Hydroxyglutaric acid (LGA) accumulates and is the biochemical hallmark of the neurometabolic disorder L-2-hydroxyglutaric aciduria (LHGA). Although this disease is predominantly characterized by severe neurological findings and pronounced cerebral atrophy, the pathomechanisms of brain injury are virtually unknown. In the present study, we investigated the effect of LGA (0.1-1 mM) on various parameters of the glutamatergic system, namely the basal and potassium-induced release of L-[3H]glutamate by synaptosomal preparations, Na(+)-dependent L-[3H]glutamate uptake by synaptosomal preparations and Na(+)-independent L-[3H]glutamate uptake by synaptic vesicles, as well as of L-[3H]glutamate binding to synaptic plasma membranes from cerebral cortex of male adult Wistar rats. We observed that LGA significantly increased L-[3H]glutamate uptake into synaptosomes and synaptic vesicles, without altering synaptosomal glutamate release and glutamate binding to synaptic plasma membranes. Although more comprehensive studies are necessary to evaluate the exact role of LGA on neurotransmission, our findings do not support a direct excitotoxic action for LGA. Therefore, other abnormalities should be searched for to explain neurodegeneration of LHGA.

Effects of undernutrition on glutamatergic parameters in rat brain

Early restriction of nutrients during the perinatal period has marked repercussions on CNS ontogeny, leading to impaired functions. This study investigated the effects of pre- and postnatal (up to 75 days) undernutrition (diet: 8% protein; normonourished group: 25% protein) on some glutamatergic and behavioral parameters of rats. Undernutrition reduced: (i) seizures caused by ICV quinolinic acid (QA) administration; (ii) Na-independent [3H]glutamate binding in cell plasma membranes of cerebral cortex, and (ii) basal [3H]glutamate release from synaptosomal preparation. Behavioral parameters related to locomotion, anxiety, or memory were not affected. These results indicate that our model of undernutrition decreased the sensitivity to QA as convulsing agent and point to some putative glutamatergic parameters involved in this effect.

Ontogenetic study of the effects of energetic nutrients on amino acid metabolism of rat cerebral cortex

We studied the effect of various energetic nutrients on metabolism of L-[U-14C]leucine and [1-14C]glycine in cerebral cortex of rats at different ages. At gestational age, glucose and lactate stimulated protein synthesis from L-[U-14C]leucine and [1-14C]glycine and from L-[U-14C]leucine, respectively; glucose, beta-OH-butyrate and lactate stimulated lipid synthesis from L-[U-14C]leucine. At 10 days of age, glucose, mannose, and fructose stimulated protein synthesis, and glucose and mannose stimulated oxidation to CO2 as well as lipid synthesis from L-[U-14C]leucine. In adult rats, glucose, mannose, and fructose stimulated protein synthesis from L-[U-14C]leucine and [1-14C]glycine; glutamine also markedly decreased the oxidation of L-[U-14C]leucine and [1-14C]glycine in 10-day-old and adult rats.

Effect of undernutrition on GMP-PNP binding and adenylate cyclase activity from rat brain

1. Undernutrition is an insult that affects brain development and functioning. Considering that signaling through metabotropic receptors/G proteins is critical for normal synaptic transmission and contributes to CNS development and synaptic plasticity, the present study investigated the effects of pre- and postnatal protein deprivation (diet: 8% protein; normonourished group: 25% protein) on brain signal transduction by G proteins. 2. Undernutrition decreased the [3H] GMP-PNP binding to G proteins and AC activity, in neural plasma synaptic membranes of 21- and 75-day-old rats. This effect was less pronounced or even absent in old rats. 3. Ontogenetically, the dietary treatment effect might be interpreted as a retarded development associated with protein malnutrition.

Exposure to ebselen changes glutamate uptake and release by rat brain synaptosomes

We investigated effects of Ebselen, diphenyl diselenide (PhSe)2 and diphenyl ditelluride (PhTe)2 on [3H]glutamate uptake and release by brain synaptosomes. Ebselen after acute exposure inhibited K+-stimulated [3H]glutamate release by brain synaptosomes. (PhSe)2 and (PhTe)2 did not change [3H]glutamate release by brain synaptosomes. Ebselen, (PhSe)2 and (PhTe)2 had no significantly effects on [3H]glutamate uptake after acute exposure. In vitro, Ebselen (100 microM) inhibited [3H]glutamate release and uptake. (PhSe)2 had no significant effect, while (PhTe)2 (100 microM) inhibited [3H]glutamate uptake by brain synaptosomes. In vitro, (PhSe)2, (PhTe)2 and Ebselen caused a significant inhibition of [3H]glutamate uptake by brain synaptic vesicles in vitro. The results demonstrated that organochalcogenides have a rather complex effect on glutamate homeostasis depending on the compound and the schedule of exposition. We propose that the neuroprotective action of Ebselen can be related, in addition to its glutathione peroxidase-like and antilipoperoxidative activity, to a direct interaction with the glutamatergic system by reducing K+-evoked glutamate release.

Utilization of energy nutrients by cerebellar slices

We performed an ontogenetic study about the utilization of glycine, glutamine, beta-hydroxybutyrate and glycerol as energy nutrients by rat cerebellum slices. Production of CO2 from glycerol and glutamine increased with the animals' age and glutamine was the most used nutrient for CO2 production. In adult age, glutamine oxidation to CO2 was 15 to 35 times higher than all other nutrients studied. CO2 production from glycine decreased markedly with age and 10 day-old rats showed an oxidation 7.5 times higher than that of adult rats. At fetal age and at 10 postnatal days, glycine oxidation to CO2 was only 2 times lower than glutamine oxidation to CO2. Lipid synthesis from beta-hydroxybutyrate was highest in adult rats. We did not observe any difference in the utilization of beta-hydroxybutyrate between slices of cerebral cortex and cerebellum at the ages of 10 days and adult. The main nutrients used for lipid synthesis were glycerol and beta-hydroxybutyrate.

A ketogenic diet increases protein phosphorylation in brain slices of rats

Ketogenic diets have been used to treat seizure disorders of children and recently it was shown to increase the drug-induced seizure threshold in rats. Protein phosphorylation is a major regulatory mechanism of signal transduction that has been implicated in modulating neuronal excitability. We investigated the basal protein phosphorylation in microslices from different brain regions (hippocampus, cerebral cortex and cerebellum) of young rats fed a ketogenic diet, and we evaluated the effect of this diet on weight development and health of these rats based on serum biochemistry. Thirty-day-old rats consumed ad libitum ketogenic (high fat) or control diets for 8 wk. Rats consuming the high fat diet had ketonemia without signs of undernutrition or illness. Microslices were incubated in media containing (32)P-phosphate, and (32)P-phosphoprotein content was analyzed by one- or two-dimensional electrophoresis followed by autoradiography. Basal protein phosphorylation was greater in brain slices from ketogenic rats. Different increments of synapsin I, GAP-43 and GFAP phosphorylation were observed in two-dimensional autoradiography. A ketogenic diet induced metabolic changes affecting the basal status of protein phosphorylation. This change could affect the mechanisms of signal transduction in neural cells involved in the increase in the seizure threshold.

Effects of methylmalonic and propionic acids on glutamate uptake by synaptosomes and synaptic vesicles and on glutamate release by synaptosomes from cerebral cortex of rats

Neurological dysfunction is common in patients with methylmalonic and propionic acidemias. However, the mechanisms underlying the neuropathology of these disorders are far from understood. In the present study we investigated the in vitro effects of methylmalonic (MMA) and propionic (PA) acids at various concentrations (1 microM-5 mM) on three parameters of the glutamatergic system, namely the basal and potassium-induced release of L-[3H]glutamate by synaptosomes, Na+-dependent L-[3H]glutamate uptake by synaptosomes and Na+-independent L-[3H]glutamate uptake by synaptic vesicles from cerebral cortex of male adult Wistar rats. The results showed that MMA significantly increased potassium-induced but not basal L-[3H]glutamate release from synaptosomes with no alteration in synaptosomal L-[3H]glutamate uptake. A significant reduction of L-[3H]glutamate incorporation into vesicles caused by MMA was also detected. In contrast, PA had no effect on these parameters. These findings indicate that MMA alters the glutamatergic system. Although additional studies are necessary to evaluate the importance of these observations for the neuropathology of methylmalonic acidemia, it is possible that the effects elicited by MMA may lead to excessive glutamate concentrations at the synaptic cleft, a fact that may explain previous in vivo and in vitro findings associating MMA with excitotoxicity.

Diphenyl diselenide and diphenyl ditelluride affect the rat glutamatergic system in vitro and in vivo

The aim of this study was to investigate the possible involvement of the glutamatergic system in the toxicity of organochalcogens, since this is an important neurotransmitter system for signal transduction and neural function. The results indicated that 100 microM diphenyl diselenide (PhSe)(2) and diphenyl ditelluride (PhTe)(2) inhibit by 50 and 70% (P<0.05), respectively, [(3)H]glutamate binding in vitro. Acute administration of 25 micromol/kg (PhSe)(2) or 3 micromol/kg (PhTe)(2) caused a significant reduction in [(3)H]glutamate (30%, P<0.05) or [(3)H]MK-801 binding (30%, P<0.05) to rat synaptic membranes. These results suggest that (PhSe)(2) and (PhTe)(2) affect, in a rather complex way, the glutamatergic system after acute in vivo exposure in rats. In vitro, total [(3)H]GMP-PNP binding was inhibited about 40% at 100 microM (PhSe)(2) and (PhTe)(2). Acute exposure in vivo to (PhSe)(2) decreased the stable [(3)H]GMP-PNP binding to 25% and (PhTe)(2) to 68% of the control value (P<0.05, for both compounds). Simultaneously, the unstable binding of [(3)H]GMP-PNP was decreased about 30 and 50% (P<0.05, for both compounds) after exposure to (PhSe)(2) and (PhTe)(2), respectively. GMP-PNP stimulated adenylate cyclase (AC) activity significantly in control animals. (PhSe)(2)- and (PhTe)(2)-treated animals increased the basal activity of this enzyme, but GMP-PNP stimulation was totally abolished. These results suggest that the toxic effects of organochalcogens could result from action at different levels of neural signal transduction pathways, possibly involving other neurotransmitters besides the glutamatergic system.

Glycine, serine, and leucine metabolism in different regions of rat central nervous system

We have investigated the glycine, serine and leucine metabolism in slices of various rat brain regions of 14-day-old or adult rats, using [1-14C]glycine, [2-14C]glycine, L-[3-14C]serine and L-[U-14C]leucine. We showed that the [1-14C]glycine oxidation to CO2 in all regions studied occurs almost exclusively through its cleavage system (GCS) in brains of both 14-day-old and adults rats. In 14-day-old rats, the highest oxidation of [1-14C]glycine was in cerebellum and the lowest in medulla oblongata. In these animals, the L-[U-14C]leucine oxidation was lower than the [1-14C]glycine oxidation, except in medulla oblongata where both oxidations were the same. Serine was the amino acid that showed lowest oxidation to CO2 in all structure studied. In adult rats brains, the highest oxidation of [1-14C]glycine was in cerebral cortex and the lowest in medulla oblongata. We have not seen difference in the lipid synthesis from both glycine labeled, neither in 14-day-old rats nor in adult ones, indicating that the lipids formed from glycine were not neutral. Lipid synthesis from serine was significantly high than lipid synthesis and from all other amino acids studied in all studied structures. Protein synthesis from L-[U-14C]leucine was significantly higher than that from glycine in all regions and ages studied.

Study of developmental changes on hexoses metabolism in rat cerebral cortex

We have studied the developmental changes of glucose, mannose, fructose and galactose metabolism in rat cerebral cortex. As the animals aged, glucose, mannose and fructose oxidation to CO2 increased, whereas galactose oxidation decreased. Lipid synthesis from glucose and fructose also increased with age, that from mannose decreased and galactose did not change. Cytochalasin B, a potent non-competitive inhibitor of sodium-independent glucose transport, significantly impaired glucose, mannose and galactose metabolism, but had no effect on fructose metabolism. Both galactose or fructose did not change, whereas mannose declined the glucose metabolism. Glucose decreased fructose, galactose and mannose metabolism. Our results show that besides glucose, the metabolism of mannose, galactose and fructose present developmental changes from fetal to adult age, and reinforce the literature data indicating that mannose and galactose are transported by glucose carriers, while fructose is not.

Undernutrition decreases serine palmitoyltransferase activity in developing rat hypothalamus

BACKGROUND/AIMS

Undernutrition reduces the hypothalamic ganglioside concentration. This may be attributed to some modifications in the contents of precursors of sphingolipid biosynthesis in undernourished rats. The present study evaluated the serine palmitoyl transferase activity (SPT; EC 2.3.1.50) during the development of the rat hypothalamus. This work also shows the L-[3-(14)C]serine metabolic labeling of hypothalamic sphingolipids in normal and undernourished rats at weaning.

METHODS

The SPT activity was determined in microsomal fractions obtained from the hypothalamus of normal rats (diet: 25% protein) and pre- and postnatally undernourished rats (diet: 8% protein since pregnancy) at 21 days of gestational age and at 7, 14, and 21 days of postnatal life.

RESULTS

The enzymatic activity was lower in the hypothalamus of undernourished than in the hypothalamus of control rats since the 7th postnatal day. Incorporation of the precursor L-[3-(14)C]serine into sphingolipid fraction was lower in the hypothalamus of undernourished rats than in the hypothalamus of control rats on the 21st postnatal day which coincided with the age of the highest difference in SPT activity between normal and undernourished rats.

CONCLUSION

These results indicate that undernutrition reduces the biosynthesis of the main sphingolipids during the period of brain growth spurt.