Feedlot operators' and cow-calf producers' perspectives on the economic value of health-preconditioned weaner calves in South Africa.

Health preconditioning programmes have recently gained increased attention in South Africa. Uncertainty remains about whether South African feedlot operators and cow-calf producers perceive health preconditioning as an economic value-added management practice. Results indicated that most feedlot operators were willing to pay average price premiums of R0.58/kg, R0.83/kg and R1.02/kg for a basic, intermediate and comprehensive health preconditioning programme, respectively. Cow-calf producers were willing to accept average price premiums of R0.49/kg, R0.72/kg and R0.83/kg for the programmes. The findings provide information that could contribute to potential market development for health-preconditioned weaners in developing countries and could significantly aid in improving efficiency and herd health within beef industries worldwide.

Growth hormone responses to melatonin in man.

Oral administration of 1 gram of melatonin caused rapid and significant elevations of serum human growth hormone in eight out of nine normal male subjects. The mean (+/- standard error of the mean) of the peak response by growth hormone was 22.9 +/- 4.6 microunits per milliliter. The increased secretion of growth hormone may be due to interaction of melatonin with hypothalamic serotoninergic receptors.

Age influences the early events of skeletal muscle regeneration: studies of whole muscle grafts transplanted between young (8 weeks) and old (13-21 months) mice.

Injured skeletal muscle generally regenerates less efficiently with age, but little is understood about the effects of ageing on the very early inflammatory and neovascular events in the muscle repair process. This study used a total of 174 whole muscle grafts transplanted within and between young and old mice to analyse the effects of ageing on the early inflammatory response in two strains of mice (BALB/c and SJL/J). There was a very slight delay in the early inflammatory response, and in the appearance of myotubes at day 4 in BALB/c muscle grafted into an old host environment (implicating systemic events). In SJL/J mice, the initial speed of the inflammatory response was slightly delayed with old muscle grafts regardless of host age (implicating muscle-derived factors), while an old host environment transiently affected myogenesis (myotube formation). The slight delays in inflammatory and neovascular responses in old mice did not dramatically impact on the overall formation of new muscle. The neovascular response to injured young and old muscle tissue was further analysed using the corneal micropocket assay. This showed a very clear 1-2 day delay in angiogenesis induced by old versus young BALB/c muscle tissue implanted into the young rat cornea, indicating that new blood vessel formation is at least partly determined by muscle-derived factors. Taken together these results indicate that, while there are slight age-associated delays in inflammation and neovascularisation in response to injured muscle, there is no detrimental effect on myogenesis in the mouse model used in this study.

Suppression of human growth hormone secretion by melatonin and cyproheptadine.

Pituitary growth hormone (GH) release in the rat is stimulated via serotoninergic pathways and can be inhibited by treatment with compounds that act as serotonin antagonists, such as cyproheptadine or the pineal gland hormone, melatonin. To investigate a possible role for serotonin in the control of human GH release, the effects of cyproheptadine and melatonin administration on the GH responses of normal male subjects were examined. The oral administration of cyproheptadine (8-12 mg daily for 5 days) to normal subjects reduced their GH responses to both insulin-induced hypoglycemia and physical exercise to a highly significant extent. Similarly, the mean GH responses of 10 subjects to insulin-induced hypoglycemia were significantly reduced after the prior oral administration of melatonin (1 g). The data presented show that serotonin antagonism has a similar effect on GH secretion in man to that observed in the rat and provides further evidence for serotoninergic, and possibly pineal, involvement in the control of human GH secretion.

Membrane permeability of redox active metal chelators: an important element in reducing hydroxyl radical induced NAD+ depletion in neuronal cells.

There is substantial evidence implicating increased production of the hydroxyl radical and oxidative stress in the pathogenesis of neurodegenerative diseases such as Alzheimer's disease (AD). Significant amounts of hydroxyl radicals will be produced in the presence of hydrogen peroxide and redox active iron via Fenton chemistry. Increased iron levels within the cytoplasm of vulnerable neurons suggest that this may also be an important site of oxidative activity. We investigated the likelihood that intracellular, rather than extracellular chelation of ferrous or ferric iron may be more effective in reducing hydroxyl radical induced cell damage and preserving NAD(+) levels and cell viability. Using intracellular NAD(H) measurements as an indicator of cell viability we found that membrane permeable ferrous chelators were most efficient in preserving cellular NAD(+) levels. Hydrophilic, ferrous or ferric chelators and lipophilic ferric chelators were essentially ineffective in preventing cellular NAD(+) depletion when added at physiological concentrations. We propose that lipophilic ferrous chelators, due to their actions inside the cell, are effective agents for moderating neuronal damage in conditions such as AD where intracellular oxidative stress plays a significant role in disease pathology.

Application of Targeted Mass Spectrometry for the Quantification of Sirtuins in the Central Nervous System.

Sirtuin proteins have a variety of intracellular targets, thereby regulating multiple biological pathways including neurodegeneration. However, relatively little is currently known about the role or expression of the 7 mammalian sirtuins in the central nervous system. Western blotting, PCR and ELISA are the main techniques currently used to measure sirtuin levels. To achieve sufficient sensitivity and selectivity in a multiplex-format, a targeted mass spectrometric assay was developed and validated for the quantification of all seven mammalian sirtuins (SIRT1-7). Quantification of all peptides was by multiple reaction monitoring (MRM) using three mass transitions per protein-specific peptide, two specific peptides for each sirtuin and a stable isotope labelled internal standard. The assay was applied to a variety of samples including cultured brain cells, mammalian brain tissue, CSF and plasma. All sirtuin peptides were detected in the human brain, with SIRT2 being the most abundant. Sirtuins were also detected in human CSF and plasma, and guinea pig and mouse tissues. In conclusion, we have successfully applied MRM mass spectrometry for the detection and quantification of sirtuin proteins in the central nervous system, paving the way for more quantitative and functional studies.

Tolbutamide increases hypothalamic serotonin activity in the rat.

Sulfonylureas are potent hypoglycemic agents; however, their mechanism of action remains incompletely understood. Recent data indicate that hypothalamic norepinephrine (NE) plays a major role in mediating the central neural regulation of blood glucose. We therefore examined whether the sulfonylurea tolbutamide might lower serum glucose via an effect on hypothalamic NE neuronal activity, and compared the effects with those of 2-deoxyglucose-induced neuroglycopenia and of chronic insulin administration. Serum glucose levels fell and serum insulin levels rose 10, 20, and 30 min after acute tolbutamide injection. Serum glucose concentrations were reduced after chronic tolbutamide administered in drinking water, but serum insulin did not change. Hypothalamic NE neuronal activity was increased 10 min after tolbutamide administration, but not at the later times, nor during chronic tolbutamide administration. However, consistent with a rise in serotonin (5-HT) neuronal activity, hypothalamic 5-hydroxyindoleacetic acid (5-HIAA) and the 5-HIAA/5-HT ratio rose 30 min after acute tolbutamide and during chronic tolbutamide administration. This rise was not due to neuroglycopenia per se, since hypothalamic NE neuronal activity was increased and hypothalamic 5-HT neuronal activity was reduced after 2-deoxyglucose-induced neuroglycopenia. Furthermore, the effect of chronic tolbutamide contrasted with that of chronic insulin administration where hypothalamic NE neuronal activity was increased, while hypothalamic 5-HT neuronal activity was unchanged. We conclude that tolbutamide does not lower serum glucose via a direct effect on hypothalamic NE neuronal activity; however, we note that tolbutamide specifically increases hypothalamic 5-HT neuronal activity.(ABSTRACT TRUNCATED AT 250 WORDS)

Effect of d-fenfluramine on basal glucose turnover and fat-feeding-induced insulin resistance in rats.

There is evidence that fenfluramine improves insulin action independently of its anorectic and weight-loss-inducing properties. Chronic d-fenfluramine also reduces hypothalamic noradrenergic tone, which correlates highly with hepatic glucose output. We report that chronic d-fenfluramine (5 mg.kg-1.day-1) ameliorates insulin resistance induced by high-fat feeding. Insulin action was assessed in adult male rats at basal insulin levels and at hyperinsulinemia (approximately 140 mU/L with the euglycemic clamp technique). Hepatic glucose production, peripheral glucose disposal, and individual tissue glucose metabolism were determined from bolus injections of [3H]-2-deoxyglucose and [14C]glucose. Food intake was matched between groups. Basal glucose turnover was reduced 28% (P less than .05) in fat-fed rats receiving d-fenfluramine (fat + fen). The glucose infusion rate to maintain euglycemia was 22.0 +/- 1.1 mg.kg-1.min-1 in the high-carbohydrate-fed rats, 8.2 +/- 1.0 in fat-fed rats, and 15.1 +/- 0.5 in the fat + fen group. Peripheral glucose disposal, reflecting measured skeletal muscle changes, was reduced by fat feeding (from 23.5 +/- 1.0 to 13.8 +/- 0.6 mg.kg-1.min-1) but was improved by d-fenfluramine (16.9 +/- 0.5, P less than .05 vs. fat fed). Impaired suppression of hepatic glucose output by insulin, caused by fat feeding, was totally reversed by d-fenfluramine. Thus, d-fenfluramine counteracted diet-induced insulin resistance, with the predominant effect on the liver. We hypothesize that d-fenfluramine improves insulin action by reducing hypothalamic noradrenergic tone, which in turn reduces the neural drive to hepatic glucose output and improves the hepatic response to insulin.

Quinolinic acid promotes albumin deposition in Purkinje cell, astrocytic activation and lipid peroxidation in fetal brain.

In high concentrations or after prolonged exposure, the N-methyl-D-aspartate receptor agonist quinolinic acid (QUIN) induces lipid peroxidation, oxidative stress, and cell death in the adult brain, and after i.c.v. injection induces seizures and increases blood-brain barrier permeability. As QUIN is substantially increased in plasma and brain of fetal sheep after endotoxin treatment or maternal tryptophan loading, we examined the effects of increasing plasma QUIN concentrations on the brain of late gestation fetal sheep. Continuous fetal infusion of QUIN (0.1 mmol/h i.v.; n=4) for 12 h increased plasma QUIN concentrations from 22.3+/-6.0-210.8+/-31.4 microM; the infusion of vehicle [normal saline] had no effect on QUIN concentrations (n=4). At 24 h after QUIN infusion glial fibrillary acidic protein immunoreactivity was significantly increased in cerebral gray matter and the granule cell layer of cerebellum, and the lipid peroxide product 4-hydroxynonenal-immunoreactivity and albumin-immunoreactivity were present throughout the cytoplasm of cerebellar Purkinje cells. Extravasation of albumin into the brain was not observed, indicating the cerebral microvasculature with respect to permeability to plasma proteins was normal at the time of analysis. We suggest that increased glial fibrillary acidic protein and 4-hydroxynonenal result from oxidative stress induced by QUIN, and that the increased intracellular albumin in cerebellar Purkinje cells may be an adaptive response.

Steroid estrogens in ocean sediments.

This paper gives results from a study measuring the abundance of steroid hormones in ocean sediments in the proximity of a deep ocean sewage outfall. The outfall is discharge point for an enhanced primary sewage treatment plant and sediment samples were taken adjacent and 7 km from the outfall. All samples contained steroid estrogens at nanogram per gram levels with higher concentrations at the 7 km sampling site. The concentration of estrone ranged from (0.16-1.17 ng/g), 17beta-estradiol (0.22-2.48 ng/g) and the synthetic 17alpha-ethinylestradiol (<0.05-0.5 ng/g). The values detected correspond with estimates based on the proportion of estrogens sorbed to particles in the effluent and the expected proportion of particles originating from sewage in the ocean sediments. The results suggest that estrogens associated with the particulate fraction aggregate on contact with high ionic strength seawater and settle to the seafloor after discharge through deep ocean outfalls.

Steroid estrogens in primary and tertiary wastewater treatment plants.

The concentrations of two natural estrogens (estrone (E1) and Estradiol (E2)) and one synthetic progestin (Ethinylestradiol (EE2)) were measured for different unit operations in an advanced sewage treatment plant and in a large coastal enhanced primary sewage treatment plant. The average influent concentration to both plants was similar: 55 and 53 ng/L for E1 and 22 and 12 ng/L for E2 for the advanced and enhanced primary STPs, respectively. The activated sludge process at the advanced STP removed up to 85% and 96% of E1 and E2, respectively. The enhanced primary sewage treatment plant was mostly ineffective at removing the steroids with only 14% of E1 and 5% of E2 being removed during the treatment process. EE2 was not been detected during the study period in the influent or effluent of either STP. The difference in the observed removal between the two plants is primarily linked to plant performance but the extent to which removal of steroid estrogens is due to bacterial metabolism (i.e. the advanced STP) rather than adsorption to the bacterial biomass remains unclear. The poor removal observed for the coastal enhanced primary STP may have implications for the receiving environment in terms of a greater potential for abnormal reproductive systems in marine animals, particularly if discharges are into large bays or harbours where flushing is limited.

Hypothalamic monoamine control of stress-induced adrenocorticotropin release in the rat.

Despite evidence that ACTH release after stress is under excitatory hypothalamic control, a stimulatory role for any of the monoamine neurotransmitters is yet to be clearly demonstrated. In the present investigation computerized gas chromatography/mass spectrometry was used to assess the neuronal activities of hypothalamic dopamine, norepinephrine (NE), and serotonin (5-HT) in rats after stress-induced ACTH release. Medial basal hypothalamic NE neuronal activity as assessed by the ratio of 3,4-dihydroxyphenylethyleneglycol (DHPG) to NE. (DHPG/NE) was elevated (P less than 0.0005) within 2 min after a 3-min cold water swim stress. Ether stress also caused a marked elevation in NE activity (P less than 0.0025). A highly significant positive correlation between the ratio of hypothalamic DHPG/NE and serum corticosterone was found over a large population of normal and stressed rats. Consistent with this relationship between hypothalamic NE neuronal activity and ACTH release being a causal one were the findings that 1) adrenalectomized rats exhibited markedly elevated hypothalamic DHPG/NE ratio and serum ACTH (both P less than 0.0005) together with serum corticosterone levels reduced to about 3% of control levels (P less than 0.0005), and 2) the administration to rats of the alpha-blocker yohimbine or the antianxiety agent diazepam resulted in significant changes in hypothalamic NE activity, together with parallel changes in ACTH secretion. In hypothyroid rats, which have elevated hypothalamic 5-HT activity, and in normal gentled rats, stress caused a significant reduction in hypothalamic 5-HT activity. High hypothalamic activity of dopamine or 5-HT in hypothyroid rats did not significantly affect basal ACTH levels nor prevent the responses to either cold water swim or ether stress, and both stresses resulted in elevated hypothalamic DHPG/NE, serum ACTH, and serum corticosterone (all P less than 0.005) in these animals. From these data it is concluded that NE is an excitatory hypothalamic monoamine for ACTH release in stress and that hypothalamic 5-HT activity is reduced after stress.

Hyperinsulinemia suppresses glucose utilization in specific brain regions: in vivo studies using the euglycemic clamp in the rat.

It has been suggested that insulin acts centrally by altering brain glucose uptake. Previous studies of the effect of insulin on brain glucose metabolism have been difficult to interpret due to lack of steady state conditions for glucose and/or insulin. To determine whether insulin per se alters brain glucose metabolism, we measured glucose utilization rates, using the deoxyglucose method, in the medial basal hypothalamus, locus coeruleus, and motor cortex of conscious, unrestrained rats undergoing 2-h euglycemic clamps (blood glucose, 4.1 +/- 0.1 mmol/liter) at increasing insulin infusion rates. Plateau insulin levels were 29 +/- 5 mU/liter (controls) and 48 +/- 4, 146 +/- 8, 670 +/- 40, and 7560 +/- 410 mU/liter (clamped). Glucose utilization rates in the medial basal hypothalamus fell significantly from 60 +/- 4 mumol/100 g X min (controls) to 46 +/- 3, 39 +/- 2, 35 +/- 2, and 39 +/- 3 mumol/100 g X min in respective insulin-infused animals (P less than 0.01 vs. controls). Similar falls of up to 39% and 48% were seen in the locus coeruleus and motor cortex, respectively. A significant inverse correlation was found between the glucose utilization rate in each brain region and the log plasma insulin level. The reduction in glucose utilization rate was associated with marked increases in serum corticosterone levels (995 +/- 157 vs. 91 +/- 31 nmol/liter in controls, P less than 0.001). Serum potassium was significantly lower in clamped animals (5.2 +/- 0.3 to 5.9 +/- 0.3 mmol/liter) than in controls (7.0 +/- 0.4 mmol/liter, P less than 0.01). However, the inverse correlation between regional brain glucose utilization and log plasma insulin was independent of changes in serum potassium, while there was no independent correlation with serum potassium. The data reveal reduced glucose utilization in specific brain regions in the presence of insulin levels both equal to and above those found in the postabsorptive state and support a direct effect of insulin in suppressing regional brain glucose utilization.

Rapid bidirectional effects of insulin on hypothalamic noradrenergic and serotoninergic neuronal activity in the rat: role in glucose homeostasis.

Glucose release from the liver is mediated by hypothalamic norepinephrine (NE) neuronal activity, but glucose itself (or a metabolite of it) exerts negative feedback effects on central NE activity. The aim of the present study was to investigate a possible role for insulin in these central glucose homeostatic mechanisms. Computerized gas chromatography-mass spectrometry was used to assess the neuronal activities of hypothalamic NE and serotonin [5-hydroxytryptamine (5-HT)] in rats after acute insulin (2 U/kg) administration. Medial basal hypothalamic NE neuronal activity was assessed by the ratio of 3,4-dihydroxyphenylethyleneglycol to NE. The ratio was suppressed (P less than 0.005) 10 min after insulin administration but rose again to be significantly higher (P less than 0.05) than in saline controls by 30 min and at 45 min post insulin was highly significantly elevated. Hypothalamic 5-HT neuronal activity was assessed by the ratio of 5-hydroxyindoleacetic acid to 5-HT and showed effects opposite to those on NE and was elevated (P less than 0.0005) 10 min post insulin. Significant changes in serum corticosterone and GH levels also occurred after insulin administration, and the changes in these two hormones were positively associated with the changes in hypothalamic neuronal activities of NE and 5-HT, respectively. Serum glucagon levels were found to be significantly elevated in association with the secondary rise in hypothalamic NE activity but did not fall in the 10 min postinsulin phase thus indicating stimulation of pancreatic glucagon release by central NE neuronal pathways. The hypothalamic NE and 5-HT neural responses to a bolus dose of insulin were unaffected by feeding or fasting. These results and evidence that brain glucose utilization is reduced in the immediate postinsulin period suggest that the rapid effects of insulin on hypothalamic NE and 5-HT neuronal activities is a direct one not mediated by stimulation of brain glucose uptake.

The stimulation of human prolactin secretion by 3-Iodo-L-tyrosine.

Oral administration of a single 1 g dose of MIT to 10 normal male and female subjects resulted in a rise in serum prolactin in each subject. The mean peak level of serum prolactin attained by the 10 subjects was 36.3 plus or minus 7.9 ng/ml which was highly significantly elevated (P smaller than 0.0005) above the mean basal level of 5.3 plus or minus 1.0 ng/ml. While there was no significant difference between the basal serum prolactin levels of male and female subjects, the mean peak level attained by male subjects following MIT (18.8 plus or minus 3.3 ng/ml) was significantly less (P smaller than 0.0025) than that recorded for the female group (62.5 plus or minus 9.1). Serum levels of growth hormone (GH), thyroid-stimulating hormone (TSH), luteinizing hormone (LH), triiodothyronine (T3), thyroxine (T4) and cortisol were not significantly altered following MIT administration. The complete absence of side effects due to MIT make it a suitable drug for the acute clinical assessment of pituitary prolactin reserve.

Prolactin secretion by metoclopramide in man.

Six men and nine women were given intravenous injections of 2.5 mg of metoclopramide to assess its potential as a stimulus to prolactin release. Following the administration of metoclopramide, there was prompt increase in serum prolactin to a peak response of 38.2 +/- 3.9 ng/ml in men and 103 +/- 10.2 ng/ml in women. The prolactin response to metoclopramide in men was compared with the response to 400 mug of TRH in 10 men. The peak response after TRH was 22.4 +/- 2.2 ng/ml, which was significantly less than that observed after metoclopramide. Pretreatment with 500 mg of L-dopa suppressed the prolactin response to metoclopramide in 6 men to a mean response of 16.3 +/- 4.3 ng/ml. We have concluded that metoclopramide is a safe, reliable, and potent stimulus of prolactin secretion and exerts this effect by blocking dopamine receptors in the hypothalamus and decreasing prolactin inhibiting factor. It is free of side effects and is a useful alternative to chlorpromazine.

Dopamine infusion studies in patients with pathological hyperprolactinemia: evidence of normal prolactin suppressibility but abnormal dopamine metabolism.

The cause of pathological hyperprolactinemia (PHP) is not known, although it has been postulated that lactotroph refractoriness to dopamine (DA) is an important factor. We, therefore, studied PRL suppressibility in response to iv DA administered in a dose designed to achieve peripheral plasma DA concentrations in the range reported in rat pituitary portal plasma. Nine normal subjects and 14 patients (8 with probable microadenomas and 6 with macroadenomas) with PHP were studied during a 4-h infusion of 0.5 micrograms/kg X min DA. Serum PRL levels decreased in normal subjects to 18 +/- 3% (mean +/- SEM) of initial basal levels, not significantly different from the fall to 22 +/- 2% of basal levels found in patients with PHP. Maximal PRL suppression in patients with probable microadenomas (21 +/- 2%) was not significantly different from that in those with macroadenomas (22.8 +/- 2.0%). Upon cessation of DA infusion, there was a rapid rebound in PRL release, which was significantly greater (P less than 0.05) in patients (155 +/- 15%) than in normal subjects (118 +/- 13%). Plasma DA levels were measured by gas chromatography/mass spectroscopy and were significantly higher (P less than 0.05) in patients than in normal subjects during the infusion. The MCR for DA in normal subjects (12.5 +/- 2.8 liters/kg X h) was significantly greater (P less than 0.005) than that in patients (6.2 +/- 0.5 liters/kg X h). The data show that the release of PRL in patients with PHP is not refractory to physiological concentrations of DA, but that there is an abnormality of peripheral DA metabolism in these patients. We conclude that the development of PHP is unlikely to be due to insensitivity of lactotrophs to endogenous DA and that patients with PHP have a systemic disturbance of DA metabolism.

Effect of the anesthetic agent propofol on hormonal responses to ECT.

Propofol is a new anesthetic induction agent that reduces electroconvulsive therapy (ECT) seizure duration. To indirectly investigate the effect of propofol on ECT-induced acute central neurotransmitter changes, we studied neuroendocrine responses in 25 primary depressed subjects treated with ECT under either propofol or thiopentone anesthesia. Blood samples were taken prior to ECT, and then at regular intervals for 2 hr. Only the prolactin response correlated significantly with seizure duration (r = 0.52, p less than 0.01). Subjects given propofol had significantly reduced adrenocorticotropin (ACTH) (p less than 0.01) and cortisol (p less than 0.05) responses compared to thiopentone, which were independent of seizure duration. There was a trend towards a reduction in the prolactin response with propofol compared to thiopentone, but this was dependent upon the diminished seizure duration. The results indicate that propofol affects endocrine responses to ECT by two distinct mechanisms: decreasing prolactin by reducing the seizure duration and decreasing ACTH and cortisol by another process, possibly via a reduction in central noradrenergic activation.

Measurements of protein carbonyls, ortho- and meta-tyrosine and oxidative phosphorylation complex activity in mitochondria from young and old rats.

Mitochondrial bioenergetic function is often reported to decline with age and the accumulation of oxidative damage is thought to contribute. However, there are considerable uncertainties about the amount and significance of mitochondrial oxidative damage in aging. We hypothesized that, as radical production in mitochondria is greater than the rest of the cell, protein oxidative damage should accumulate more in mitochondria than the cytoplasm, and that this relative accumulation should increase with age. To test these hypotheses we measured the accumulation of three markers of protein oxidative damage in liver, brain, and heart from young and old rats. Ortho- and meta-tyrosine levels in protein hydrolysates were measured by a gas chromatography/mass spectrometry assay, and protein carbonyl content was determined by ELISA. Using these assays we found no evidence for increased protein oxidative damage in mitochondria relative to the cytosol. Most increases found in protein oxidative damage on aging were modest for all three tissues and there was no consistent pattern of increased oxidative damage in mitochondrial proteins on aging. Mitochondrial oxidative phosphorylation complex activities were also assessed revealing 39-42% decreases in F0F1--ATP synthase activity in liver and heart on aging, but not in other oxidative phosphorylation complexes. These findings have implications for the contribution of mitochondrial oxidative damage and dysfunction to aging.

Quinolinic acid production by macrophages stimulated with IFN-gamma, TNF-alpha, and IFN-alpha.

Quinolinic acid (QUIN) has been associated with several inflammatory neurologic disorders, including AIDS dementia complex (ADC). Recent studies suggest that activation of macrophages with either HIV-1 or interferon-gamma (IFN-gamma) can lead to QUIN production. However, the importance of other cytokines, especially those related to the macrophage and that are especially important in ADC pathogenesis, remains unclear. We, therefore, sought to determine the role of tumor necrosis factor-alpha (TNF-alpha) and IFN-alpha in the production of QUIN. Primary human macrophages were stimulated with two different concentrations of these cytokines alone, in combination with each other, and with IFN-gamma. QUIN concentrations in the supernatants were then measured by mass spectrometry at 24, 48, and 72 hs. Results at 72 h showed significant increases in QUIN production in the cells stimulated with IFN-gamma (10297 +/- 170 nmol/L) and also in those stimulated with IFN-alpha (3600 +/- 113 nmol/L), whereas TNF-alpha-stimulated macrophages produced low levels of QUIN (1108 +/- 23 nmol/L). Macrophages stimulated with the cytokine combinations TNF-alpha and IFN-gamma, IFN-alpha, and IFN-gamma, and TNF-alpha and IFN-alpha also resulted in increases in QUIN production (11471 +/- 77.6 nmol/L, 16656 +/- 184 nmol/L, and 3369 +/- 120.5 nmol/L, respectively). The increases in QUIN production in all of the cytokine treatments approached or exceeded in vivo concentrations of QUIN that have been shown to be neurotoxic. These data further support a role for QUIN in cytokine-mediated neuronal death in inflammatory disorders of the brain, especially ADC.