Food preference of young rhesus monkeys fed marginally zinc deficient diets

Zinc deprivation has been shown to produce hypogeusia in rhesus monkeys but the possible consequences of altered taste sensitivity for food preference and selection is not known. We studied 13 rhesus monkeys (2.5 to 3 years of age) for food preference in a structured choice situation. These animals were fed two levels of dietary zinc: marginally zinc deprived (fed 4 μg zinc/g diet from conception and throughout development;N=6), or control (fed a 100 μg zinc/g diet throughout the study;N=7). Preference for familiar vs unfamiliar food items, order of food preferences, persistence in retrieval of preferred and nonpreferred foods, and preference under four deprivation periods were examined. Animals were offered a choice of two food items, both containing minimal zinc levels, and food choice and latency of choice were measured. Results indicate that animals fed the marginal zinc diets had reduced preference for unfamiliar foods relative to controls and different patterns of food preference. These results may be relevant to maintenance of appropriate food selection in marginally zinc deprived populations.     

Differences in the mineral contents between falx cerebri and tentorium cerebelli

A study was performed to determine the effect of zinc deficiency on the zinc concentration of the retina, lens, and the retinal pigment epithelium and choroid. Weanling, male Sprague-Dawley rats were fed ad libitum modified AIN-93 diets containing 3 mg zinc/kg diet (−Zn; n=10) for 6 wk. Control animals were pair-fed (+ZnPF; n=10) or fed ad libitum (+ZnAL; n=10) diets containing 100 mg zinc/kg diet. At 6 wk, plasma and tibia zinc were measured by flame atomic absorption spectrophotometry to confirm zinc deficiency. The zinc concentration of ocular tissues was measured by inductively coupled plasma-mass spectrometry. Mean (±SEM) lens zinc concentration was significantly depressed in the zinc-deficient group as compared to that of pair-fed or ad libitum-fed controls, suggesting that the role of zinc in cataract formation should be investigated. The zinc concentration of total neural retina was preserved in zinc deficiency. Previously reported deterioration of retinal function in zinc deficiency may be the result of a decline in the zinc concentration of a specific cell layer of the retina that cannot be detected on gross analysis of the entire retina. This work was presented in part at Experimental Biology 98, April 1998, San Francisco, CA [P. G. Paterson, B. H. Grahn, and J. S. Fabe, Retinal and lens zinc concentration in the zinc-deficient rat. FASEB J. 12, A521 (1998)].     

Zinc supplementation to protein-deficient diet in CO-exposed mice decreased fetal mortality and malformtion

In developing countries, diet during pregnancy is frequently low in both protein and zinc contents and exposure to CO is common because of environmental pollution and smoking. This study was conducted to evaluate whether zinc supplementation ameliorates fetal mortality and malformations in protein-deficient, CO-exposed mice. Pregnant mice of the CD-1 strain were maintained on 17% (reference) or 9% protein diets mixed with deficient, normal, or supplemental zinc throughout gestation. The dams in each dietary group were exposed to air (control) or 500 ppm CO in air in environmental chambers from gestation days 7–18. As compared to the control group (normal protein, normal zinc), the incidence of fetal mortality was 66.8% and 57.2% higher, respectively, and malformation incidence was 74.4% and 72.4% higher (0 and 500 ppm CO, respectively) in mice fed both deficient protein-zinc diets. However, the highest malformation rate was observed in the group with normal protein, deficient zinc (96% mortality in both 500 and 0 ppm CO, as compared to the reference group, p<0.0001). The fetal mortality rate was −3.5% (0 ppm CO) and 25.4% (500 ppm CO) lower in zinc-supplemented, protein-deficient groups compared to the control group. There was a significant negative association between fetal zinc concentrations and fetal malformations (p≤0.001). The result of this study might be relevant to populations that are exposed to CO and or consume marginal zinc and protein diets during gestation.     

Effects in chicks of arsenic,arginine, and zinc and their interaction on body weight,plasma uric acid,plasma urea,and kidney arginase activity

The interaction among arsenic, zinc, and arginine was studied in chicks using two fully crossed, three-way, two-by-two-by-two experiments. Arsenic at levels of 0 and 2 μg/g zinc at levels of 2.5 (zinc-deficient) and 25 (zinc-adequate) μg/g, and arginine at levels of 0 and 16 mg/g were supplemented to the diet. After 28 d in both experiments, growth was depressed in chicks fed diets either supplemented with arginine or deficient in zinc. Arsenic deprivation depressed growth of chicks fed diets containing the basal level of arginine and 25 μg supplemental Zn/g. Arsenic deprivation had little or no effect on growth of zinc-deprived chicks fed diets containing the basal level of arginine, or in zinc-deprived or zinc-adequate chicks fed supplemental arginine. Zinc-deficiency elevated urea in plasma and arginase activity in kidney. Those elevations, however, were more marked in arsenic-supplemented than in arsenic-deprived chicks. Also, plasma urea and kidney arginase activity were markedly elevated in chicks fed supplemental arginine; the elevations were more marked in zinc-deficient chicks. These findings support the concept that arsenic has a physiological role, associated with zinc, that can influence arginine metabolism in the chick.     

Expression of P2X6, a purinergic receptor subunit,is affected by dietary zinc deficiency in rat hippocampus

The purpose of these experiments was to determine whether dietary zinc depletion affected protein expression in the hippocampus. Eleven weanling Sprague-Dawley male rats (21 d) were fed the AIN-93G diet containing 1.5 ppm zinc and supplemented with 30 ppm of zinc in the drinking water. After 1 wk, the rats were randomly divided into three groups: control (n=3), pair fed (n=3), and zinc restricted (n=5). All groups consumed the same diet. The zinc-restricted group consumed water containing no zinc. The rats were sacrificed 3 wk later. Chelatable zinc levels in the hippocampus, as measured by N-(6-methoxy-8-quinolyl)-para-toluenesulfonamide (TSQ) staining, were significantly reduced in the zinc-restricted group. Analysis of hippocampal protein expression by two-dimensional electrophoresis (2DE) revealed increased expression of the P2X₆ purinergic receptor in the zinc-restricted rats, as determined by MALDI mass spectrometry (MS) and database analysis. The data provided evidence for the dual effects of dietary zinc deficiency on the hippocampus, reducing ionic zinc levels and stimulating protein expression. The role the P2X₆ receptor plays in the physiological response of the hippocampus to zinc depletion remains to be determined.     

Relative and combined effects of ethanol and protein deficiency on some hair trace elements

This study was performed in order to analyze the relative and combined effects of ethanol and protein deficiency on hair copper, zinc, manganese, and iron content in four groups of seven animals each which were pair-fed during 8 wk with (1) a nutritionally adequate diet, (2) a 36% (as energy) ethanol-containing isocaloric diet, (3) a 2% protein, isocaloric diet, and (4) a 36% ethanol, 2% protein isocaloric diet, respectively, following the Lieber-DeCarli model, and to analyze the relationship between hair copper, zinc, manganese, and iron content, and the liver and muscle content of these elements. Although there was a trend to higher levels of all the elements analyzed in the the hair of the low-protein fed animals, differences were statistically significant regarding copper and manganese, effects being solely attributable to the low protein diet, not to ethanol. Moreover, hair copper was significantly, inversely related with final weight and weight loss. There were significant relationship between liver zinc and muscle zinc (r=0.57, p=0.002), but not between liver or muscle zinc and hair zinc; no correlations were observed between muscle copper and hair copper, nor between liver manganese and hair manganese. An inverse, statistically significant correlation was observed between liver copper and hair copper (r=−0.39, p<0.05).     

Normal growth rate in rats is recovered after a period of zinc deficiency by restoration of zinc supply by means of a zinc-fortified Petit Suisse cheese

Fortification of a Petit Suisse cheese with zinc sulfate and zinc gluconate stabilized with glycine was used as a tool to overcome zinc-deficiency effects on total-body growth and skeletal growth. Animals were divided in 4 groups of 10 rats: basal (B), control (C), depletion-repletion 1 (DR1), and depletion-repletion 2 (DR2). These four groups were fed with four diets: basal (2 ppm Zn), control (30 ppm Zn), DR1, and DR2; they received a basal diet for 14 d and a control diet for the other 14 d of the experiment, using zinc sulfate for DR1 and zinc gluconate stabilized with glycine for DR2. After 28 d of the experiment, total-body weight and weight gain of the control and DR1 and DR2 animals were not statistically different (p<0.05), Femur weight and femur zinc content of DR1 and DR2 did not achieve the values of control animals (p<0.05), but they were higher than that of basal animals. Our results show that restoration of dietary zinc levels by means of food fortification normalized weight gain, as an indicator of total-body growth, and presented a trend to normalize bone weight, as a marker of skeletal growth, in young rats and independently of the zinc source used.     

Developmental effects and mineral interactions in rats fed textured vegetable protein

The teratogenic effects of feeding a diet based on textured vegetable protein to Long-Evans rats were studied along with maternal and fetal mineral interactions and their relationship to diet composition. Pregnant rats were fed purified diets containing 18% protein as casein (CAS), textured vegetable protein (TVP, from defatted soy flour) with 18 mg Zn/kg, or TVP diet with 100 mg Zn/kg. A fourth group was fed diet NIH-31. The animals received their diets throughout pregnancy and were sacrificed on day 20 of gestation. Fetuses were examined for developmental effects, and mineral levels were determined in maternal and fetal tissues by inductively coupled argon plasma-atomic emission spectrometry. Females fed the casein diet or diet NIH-31 had normal weight gains throughout pregnancy and their progeny exhibited normal development. The animals on the TVP-containing diet with 18 mg Zn/kg had decreased food consumption and body weights, and their fetuses exhibited developmental anomalies as well as reductions in size and weight. These developmental alterations may be the result of decreased zinc levels in the fetal tissues, caused by reduced bioavailability of the trace element in the maternal diet. Significant increases in tissue iron accompanied the low zinc levels. No developmental effects were found in animals receiving the high Zn-TVP diet, and mineral data from these animals were not significantly different from the casein group.     

The Effect of Peripheral Administration of Zinc on Food Intake in Rats Fed Zn-adequate or Zn-deficient Diets

Zinc deficiency induces a striking reduction of food intake in animals. To elucidate the mechanisms for this effect, two studies were connectedly conducted to determine the effects of peripheral administration of zinc on food intake in rats fed the zinc-adequate or zinc-deficient diets for a 3-week period. In study 1, two groups of male Sprague-Dawley rats were provided diets made either adequate (ZA; 38.89 mg/kg) or deficient (ZD; 3.30 mg/kg) in zinc. In study 2, after feeding for 3 weeks, both ZA and ZD groups received intraperitoneal (IP) injection of zinc solution with three levels (0.5, 1.0, and 2.0 mug zinc/g body weight, respectively) and cumulative food intake at 0.5, 1, 2, 4, and 24 h, and plasma hormones concentrations were measured. The results in study 1 showed rats fed the ZD diets revealed symptoms of zinc deficiency, such as sparse and coarse hair, poor appetite, susceptibility to surroundings, lethargy, and small movements. Zinc concentrations in serum, femur, and skeletal muscle of rats fed the ZD diets declined by 26.58% (P < 0.01), 27.32% (P < 0.01), and 24.22% (P < 0.05), respectively, as compared with ZA control group. These findings demonstrated that rat models with zinc deficiency and zinc adequacy had been fully established. The results in study 2 showed that IP administration of zinc in both ZA and ZD rats did not influence food intake at each time points (P > 0.05), although zinc deficiency suppressed food intake. Plasma neuropeptide Y (NPY) was higher, but insulin and glucagon were lower in response to zinc deficiency or zinc administration by contrast with their respective controls (P < 0.05). Leptin, T3, and T4 concentrations were uniformly decreased (P < 0.05) in rats fed the ZD diets in contrast to ZA diets; however, no differences (P > 0.05) were observed during zinc injection. Calcitonin gene-related peptide was unaffected (P > 0.05) by either zinc deficiency or zinc administration. The present studies suggested that zinc administration did not affect short-term food intake in rats even in the zinc-deficient ones; the reduced food intake induced by zinc deficiency was fprobably associated with the depression in thyroid hormones. The results also indicated that NPY and insulin varied conversely during the control of food intake.     

Evidence for dietary essentiality of lithium in the rat

The purpose of this study was to determine the dietary essentiality of lithium (Li) in rats. In three experiments, two types of diets were fed during growth, reproduction, and lactation. In the first experiment, dams were maintained on a corn-based diet containing 2 ng or 500 ng (controls) Li/g through five successive periods of pregnancy and lactation. The offspring of dams fed the low-Li diet had significantly lower weaning weights (p=0.011), and the percent weaned was lower (p=0.094) than that of controls. In the second experiment, rats were maintained through three generations on a rice-based diet containing 0.6 ng Li/g, or the control (500 ng/g) diet. There was a significant effect of Li level on litter size (p=0.017) and litter wt at birth (p=0.006) in the third generation. The overall effect through three generations on litter wt at birth approaches statistical significance (p=0.086). In the third experiment, third-generation rats were continued on the respective rice-based diets with three levels of dietary sodium, the normal level, one-half, and four times that level. The litter size and birth wt were significantly lower (p=0.0030 and 0.0038, respectively) among the low-Li dams that consumed the normal and high-sodium levels compared to those that consumed the low-sodium diets. The interaction of Li and sodium as regards litter wt at birth approached significance (p=0.083). Various tissues of the rats in the third experiment were analyzed for Li. It seems likely that Li exerts an essential nutrient role for the rat. Contribution of the Missouri Agricultural Experiment Station, Journal Series No. 11,327.     

Zinc deficiency inhibits the direct growth effect of growth hormone on the tibia of hypophysectomized rats

The effect of zinc deficiency on the direct-growth effect of growth hormone (GH) on tibia growth in hypophysectomized rats was studied. There were three dietary groups. Zinc deficient (ZD) group (0.9 mg/kg diet), control (C) group (66 mg/kg diet) and zinc adequate pair fed (PF) group (66 mg zinc/kg diet). All rats in each group received local infusion of recombinant human-growth hormone (hGH) (1 Μg/d), except for half of the animals in the control group, which were sham-treated, receiving vehicle infusion only. The substances were infused continuously for 13 d by osmotic minipumps through a catheter implanted into the right femoral artery. Food intake was lower and body weight loss was greater in ZD, and PF animals compared with C animals (p < 0.001). Tissuezinc concentration and plasma alkaline-phosphatase activity were decreased (p < 0.05) by dietary-zinc deficiency. GH infusion increased the tibial-epiphyseal width of the treated right limb, but not of the noninfused left limb in C and PF animals. However, in ZD rats, no difference was found between the infused and the noninfused limbs. These results demonstrate that zinc deficiency inhibits the direct-growth effect of GH on long-bone growth.     

Zinc nutritional status in obese children and adolescents

Studies in animals and humans have corroborated that zinc (Zn) metabolism is altered in obesity. The present work intends to evaluate the Zn nutritional status in obese children and adolescents by the determination of some biochemical parameters and analyses of the diets. The investigation was carried out in a group of obese children and adolescents (n=23) and compared to a control group (n=21), both between 7 and 14 yr of age. A software analyzed diet information from 3-d food records. Body composition was evaluated by body mass index, bioelectrical impedance, and skinfold measurements. Zinc nutritional status was evaluated by Zn determination in plasma, erythrocyte, and 24-h urine, by atomic absorption spectrophotometry (γ=213.9 nm). Diets consumed by both groups had marginal concentrations of zinc. Zinc concentrations in plasma and erythrocytes were significantly lower in the obese group. Urinary zinc excretion was significantly higher in the same group. The results allowed one to conclude that zinc nutritional status in obese individuals is altered.     

Effects of natural winter pasture and commercial pellet on the ultrastructure of small intestinal epithelium in reindeer

Segments of small intestine (duodenum, jejunum and ileum) from slaughtered reindeer (Rangifer tarandus tarandus) grazing natural winter pastures (n=3) and reindeer fed commercially available pellets (RF-80) in winter (n=5) were collected and immediately fixed in McDowells fixative. Transmission electron microscopy was employed to investigate the ultrastructural features of the epithelium and lamina propria along the small intestine and to relate these to the different diets. Major differences in ultrastructural features were observed between the small intestinal enterocytes of reindeer fed the two diets. Enterocytes in reindeer fed the natural diet displayed a normal appearance with a dense cytoplasm and distinct microvilli. In contrast, reindeer fed the commercial diet showed damaged enterocytes amongst the normal cells. Abnormal changes included disintegration and loss of microvilli, cytoplasmic swelling, loss of membrane integrity and increases in the width of intercellular spaces, especially in the jejunum. The transport and holding of animals was supported by a grant from the Reindeer Husbandry Research Fund.     

Mycelia and spent fermentation broth of Beauveria bassiana incorporated into synthetic diets affect mortality,growth and development of larval Helicoverpa zea (Lepidoptera: Noctuidae)

Beauveria bassiana endophytically colonises corn (Zea mays) reducing tunneling from European corn borer (Ostrinia nubilalis). Endophytic colonisation of other plants by B. bassiana has been reported, and potentially, may reduce insect feeding on these plants. We evaluated the effects on larval growth and development, and mortality of different rates of dried, ground mycelia and water-soluble metabolites from fermentation broth culture of different isolates of B. bassiana incorporated into a synthetic diet and fed to neonate bollworm, Helicoverpa zea larvae. Development was delayed, weights of larvae were lower, and mortality was high for larvae fed the highest rates (1.0 and 5.0%, w/v) of mycelia incorporated diet compared to control. Insects fed diets containing mycelia of B. bassiana isolate 11-98 had the greatest mortality. Mortality was 100% for larvae fed 5% (w/v) mycelia incorporated diet of isolate 11-98, and 61% for isolate 3-00. For insects fed low rates (0.1 to 0.5%, w/v) of mycelia incorporated diet, mortality was lower, approximately 5% for isolate 11-98, and 5 to 14% for isolate 3-00. At the 0.1% (w/v) rate of mycelia incorporated diet, development occurred at an accelerated rate, compared to fungus-free controls, indicating increased nutrition in the lowest rate fungal diet. Mortality was low for all larvae fed diets containing spent fermentation broth of B. bassiana; however, development was delayed. Insects fed the highest rate (0.5%, v/v) of spent fermentation broth-amended diet had lower pupal weights, and a greater number of days to pupation than insects fed the lowest (0.1%, v/v) rate. Insects fed the 5% (v/v) rate of spent fermentation broth of isolates 11-98 and 3-00 had the longest days to pupation.     

Effects of marginal zinc deficiency on microtubule polymerization in the developing rat brain

One of the possible mechanisms that has been proposed to underlie the deleterious effects of zinc deficiency on brain development is an impairment in the normal formation of the cytoskeletal network. In the current study, in vivo microtubule polymerization was characterized in brain supernatant fluids, from 20-d-old pups whose dams were fed diets containing control (50 micrograms zinc/g) or marginal levels of zinc (10 micrograms zinc/g) throughout pregnancy and lactation. Pup brain and body weights were similar between the groups; however, plasma zinc concentrations were lower (27%) in pups fed the marginal zinc diet than in controls. Tubulin concentrations in 100,000 g brain supernates were similar between the groups; however, tubulin polymerization in the brain supernates was significantly lower in pups fed the marginal zinc diet compared to controls. Primarily, the early events of polymerization were affected; the lag period of the reaction was doubled, and the initial velocity was slower (26%) in supernates from pups fed the marginal zinc diet than in controls. These findings support the idea that some of the negative effects of marginal zinc deficiency on brain development and function may be mediated by an alteration in microtubule formation.     

Activities of liver microsomal fatty acid desaturases in zinc-deficient rats force-fed diets with a coconut oil/safflower oil mixture of linseed oil

The present study was conducted to investigate the effect of zinc deficiency on fatty acid desaturation in rats fed two different types of dietary fat, a mixture of coconut oil and safflower oil (7∶1, w/w, “coconut oil diet”) or linseed oil (“linseed oil diet”). In order to ensure an adequate food intake, all rats were force-fed by gastric tube. Zinc deficiency caused statistical significant reducion of Δ9-desaturase activity in liver microsomes of rats fed coconut oil diet and tendencial reduction (p<0.15) in rats fed linseed oil diet compared with control rats fed diets with the same type of fat. In agreement with this effect, zinc deficiency in the rats fed both types of dietary fat increased the ratio between total saturated and total monounsaturated fatty in liver phospholipids and liver microsomes. Zinc deficient rats on the coconut oil diet had unchanged Δ6-desaturase activity with linoleic acid as substrate and lowered activity with α-linolenic acid as substrate. In contrast, zinc deficient rats on the linseed oil diet had increased Δ6-desaturase activity with linoleic acid as substrate and unchanged activity with α-linolenic acid. Because linoleic acid is the main substrate for Δ6-desaturase in the rats fed coconut oil diet, and α-linolenic acid is the main substrate in the rats fed linseed oil diet, it is concluded that in vivo Δ6-desaturation was not changed by zinc deficiency in the rats fed both types of dietary fat. Activity of Δ5-desaturase was also not changed by zinc deficiency in the rats fed both dietary fats. Levels of fatty acids in liver phospholipids and microsomes derived by Δ4-, Δ5-, and Δ6-desaturation were not consistently changed by zinc deficiency in the rats fed both types of dietary fat. Thus, the enzyme studies and also fatty acid composition data of liver phospholipids and microsomes indicate that zinc deficiency does not considerably disturb desaturation of linoleic and α-linolenic acid. Therefore, it is suggested that similarities between deficiencies of zinc and essential fatty acids described in literature are not due to disturbed desaturation of linoleic acid in zinc deficiency. The present study also indicates that zinc deficiency enhances incorporation of eicosapentaenoic acid into phosphatidylcholine of rats fed diets with large amounts ofn-3 polyunsaturated fatty acids.     

Effect of olive oil- and corn oil-enriched diets on the tissue mineral content in mice

The mineral content (zinc, iron, magnesium, and calcium) in the liver, spleen, and thymus of male Balb/C mice was analyzed. Animals were fed, over 21 d, diets enriched with corn oil (FCO diet) or olive oil (FOO diet) (5% addition to standard pellet, w/w). Olive oil with predominant oleic acid (C18:1, n-9) had a quite different composition than corn oil, in which linoleic acid (C18:2, n-6) prevails. The zinc and magnesium tissue concentrations were not changed in either group. The calcium concentration in liver as well as the calcium concentration in spleen increased in mice fed both the FCO and FOO diets. Furthermore, mice fed both the FOO and FCO diets had increased spleen iron concentration. Mice fed the FCO diet had increased thymus calcium concentration compared to controls. The results show the effect of diets with unsaturated, particularly polyunsaturated fatty acids, on the calcium and iron concentration in some organs.     

Megaloblastic anemia and the requirement for folic acid in the cebus monkey (Cebus albifrons)

To study the development of folic acid deficiency, nine 3-year-old cebus monkeys (Cebus albifrons) were fed purified diets containing varying amounts of added folic acid. Monkeys fed the diet without added vitamin stopped growing and then lost weight. Macrocytic anemia and leukopenia developed, and megaloblastic changes were observed in precursors of both erythrocytes and leukocytes in the bone marrow. Urinary excretion of formiminoglutamic acid was increased significantly in these animals compared with controls. Repletion of deficient animals with injections of folic acid caused a rapid weight increase and reversed the hematological and biochemical abnormalities. It was estimated that the minimal folic acid requirement for adequate growth and normal hematological parameters was between 45 and 75 μg/kg body weight/day. To allow for needs above the minimal requirement, purified diets for cebus monkeys should be formulated to provide at least 150 μg of folic acid/kg body weight/day.     

Modulations in the biotransformation of tobacco extract and N′-nitrosonornicotine under differential dietary protein status

The modulation of the phase I and phase II biotransformation enzymes upon treatment with tobacco extract (TE) and N'-nitrosonornicotine (NNN) was investigated using male Sprague-Dawley rats fed differential protein diets. It was observed that the animals fed a low protein diet showed an overall decrease in the basal levels of hepatic and pulmonary phase I and II enzymes. TE and NNN significantly decreased the detoxifying system in the low-proteinfed animals. Animals fed 20% protein, however, showed significant increases in glutathione and glutathione S-transferase upon treatment. Furthermore, TE and NNN treatment brought about a significant depletion in the hepatic pool of vitamin A with a concomitant increase in the vitamin C levels.     

Low Tryptophan and Protein in the Diet During Development Increase the Susceptibility to Convulsions in Adult Rats

Tryptophan (TRY) is the precursor for serotonin (5-HT) synthesis. Common maize has low protein content with low concentration of TRY and lysine. A diet based on two strains of corn differing in their TRY content were given to adult female rats, prior mating, during pregnancy and lactation. Same diets were offered to their male offspring after weaning until reaching 60-days old. The pattern and severity of the convulsive phenomenon induced by monosodium glutamate (MSG) in a well established model of Status epilepticus were evaluated in comparison with data from animals of two control groups: (a) rats fed a hypoproteic (8% protein) diet, and (b) rats fed a normal Purina chow diet (23% protein). Significant increased susceptibility to convulsions was observed in both groups of rats fed the corn-based diets. However, the animals fed the common corn-based diet (8–9% protein; 0.058% TRY) showed a higher susceptibility to convulsions than what was registered in animals fed a Quality Protein Maize (QPM)-based diet (8–9% protein; 0.1% TRY). It is concluded that low TRY concentration in the diet during development, produces lower rate of brain 5-HT synthesis, affecting development and maturation of GABAergic inhibitory cortical interneurons, with alteration of cortical excitability, contributing in part, to the increased susceptibility to convulsions, as shown in the experiments here reported. Special issue article in honor of Dr. Ricardo Tapia.