bluuebunny/crossref_metadata_2025 huggingface dataset:
The association between melatonin production and electrophy siology of the guinea pig pineal gland
Authors: McCance I. , Partington H.C. , Coleman H.A.
Published: February 2007

Abstract: Melatonin production by isolated pineal glands from guinea pigs was examined under conditions that affect membrane potential or the firing of action potential‐like spikes. In glands from superior cervical ganglionectomized animals, depolarization resulting from increasing extracellular potassium concentration to 100 mM did not initiate melatonin production, and it delayed the response to the β‐adrenoceptor agonist orciprenaline. In glands from intact animals, melatonin production was initiated by exposure to 100 mM potassium with a time‐course similar to the response to orciprenaline. A proportion of this response was propanol resistant, suggesting that the normal control of melatonin production may involve a neurotransmitter in addition to norepinephrine. Exposure to verapamil or nifedipine, or removal of extracellular calcium, previously shown to eliminate action potential‐like spikes, did not substantially affect the increase in melatonin production induced by orciprenaline. Phenylephrine, which stimulates spiking, produced only a slight increase in melatonin production. It is concluded that the depolarization and the spiking are not closely related to the stimulation of melatonin production, but may relate principally to the secretion of a substance other than melatonin.
Melatonin‐induced T‐helper cell hematopoietic cytokines resembling both interleukin‐4 and dynorphin
Authors: Maestroni Georges J. M. , Hertens Elisabeth , Galli Paola , Conti Ario , Pedrinis Ennio
Published: February 2007

Abstract: We have reported that melatonin exerts colony stimulating activity and rescues bone marrow cells from apoptosis induced either in vivo or in vitro by cancer chemotherapy compounds. We proposed that melatonin regulates interleukin‐4 (IL‐4) production in bone marrow T‐helper cells and that IL‐4 stimulates adherent stromal cells to produce colony stimulating factors (CSF). However, in further investigations we did not find any direct evidence of the ability of melatonin to stimulate IL4. We found that besides anti‐IL4 monoclonal antibody (mAb), the opioid antagonist naltrexone also neutralized the colony stimulating activity and part of the hematopoietic protection exerted by melatonin. SDS‐PAGE and immunoblotting analysis of supernatants of bone marrow T‐helper cells incubated overnight with melatonin revealed the presence of two proteins with an apparent molecular weight of 15 and 67 kDa, which were recognized by both anti‐common opioid sequence (Tyr‐Gly‐Gly‐Phe) and anti‐lL4 mAbs. When Abs against known opioid peptides were tested, only anti‐dynorphin B Ab labeled the 67 kDa but not the 15 kDa protein. These melatonin‐induced‐opioids (MIO) were separated by gel filtration. The lower molecular weight MIO (MIO 15) seems to mediate the naltrexone‐sensitive hematopoietic effects of melatonin. Consistently, we found the presence of opioid receptors in adherent bone marrow cells. Apparently, the higher molecular weight protein, M1067, was responsible for the naltrexone‐insensitive part of the melatonin‐induced hematopoietic rescue. These melatonin‐induced T‐helper cell products which resemble both IL‐4 and dynorphin B might represent a new family of opioid peptides with hematopoietic and immune functions.
Melatonin and N‐tert‐butyl‐α‐phenylnitrone block 60‐Hz magnetic field‐induced DNA single and double strand breaks in rat brain cells
Authors: Lai Henry , Singh Narendra P.
Published: February 2007

ABSTRACT: In previous research, we have found an increase in DNA single‐and double‐strand breaks in brain cells of rats after acute exposure (two hours) to a sinusoidal 60‐Hz magnetic field. The present experiment was carried out to investigate whether treatment with melatonin and the spin‐trap compound N‐tert‐butyl‐α‐phenylnitrone (PBN) could block the effect of magnetic fields on brain cell DNA. Rats were injected with melatonin (1 mg/kg, sc) or PBN (100 mg/kg, ip) immediately before and after two hours of exposure to a 60‐Hz magnetic field at an intensity of 0.5 mT. We found that both drug treatments blocked the magnetic field‐induced DNA single‐and double‐strand breaks in brain cells, as assayed by a microgel electrophoresis method. Since melatonin and PBN are efficient free radical scavengers, these data suggest that free radicals may play a role in magnetic field‐induced DNA damage.
Effect of various acute 60 Hz magnetic field exposures on the nocturnal melatonin rise in the adult Djungarian hamster
Authors: Truong Huy , Yellon Steven M.
Published: February 2007

ABSTRACT: Acute exposure to a 1 Gauss 60 Hz magnetic field for 15 min beginning 2 hr before darkness delays and blunts the nighttime melatonin rhythm in some but not all studies. To determine whether other exposure parameters (dose, mode, or time) influence the nocturnal melatonin rise, adult Djungarian hamsters reared in long days (16L: 8D, lights off at 1000–1800 hr) were acutely exposed to a 60 Hz continuous magnetic field (15 min of 1 or 0.1 Gauss) beginning 4 hr before or 4 hr after lights off. Other hamsters were exposed to a 60 Hz intermittent magnetic field (15 or 60 min of a 1 Gauss field, 1 min on then 1 min off) between 1 and 2 hr before lights off. In sham‐exposed controls, i.e., hamsters simultaneously placed in an adjacent coil system but without current, pineal and serum melatonin concentrations increased from a low baseline (1 hr after lights off) to concentrations that were typical of the nighttime peak by 3 hr after darkness. Acute exposure to the 0.1 or 1 Gauss continuous magnetic field for 15 min at either 4 hr before or 4 hr after lights off did not disrupt the nocturnal rise in pineal or serum melatonin. Similarly, onset of the melatonin rhythm was not suppressed by intermittent magnetic field exposures compared to that in sham controls. Thus, several magnetic field exposure paradigms failed to alter the rising phase of the melatonin rhythm in pineal gland content or in circulation. These findings indicate that the biological clock mechanism that mediates photoperiodic time measurement in this seasonally breeding rodent is resistant to a variety of acute continuous or intermittent magnetic field exposures.
Influence of the light and dark phase of the cycle on the cellular proliferation in the pineal gland of the adult rat: A bromodeoxyuridine immunohistochemical study
Authors: Calvo José Luis , Boya Jesús , Carbonell Angel L. , García‐Mauriño José Enrique
Published: February 2007

ABSTRACT: The cellular proliferative activity in the adult rat pineal gland was studied using bromodeoxyuridine immunohistochemistry during the light and dark phases of an artificial 12L: 12D photoperiod. The results showed statistically significant differences in the number of labeled cells between the light and dark phases, with the labeled cells being almost threefold more abundant in the light period. Minor changes were also found in the pineal gland volume between both periods. The decrease in the number of labeled cells in the dark phase of the cycle could be related to the well‐documented antimitotic action of melatonin.
Modulation of the subcellular distribution of calmodulin by melatonin in MDCK cells
Authors: Antón‐Tay Fernando , Martínez Isabel , Tovar Rosalinda , Benitez‐King Gloria
Published: February 2007

Antón‐Tay F, Martínez I, Tovar R, Benítez‐King G. Modulation of the subcellular distribution of calmodulin by melatonin in MDCK cells. J. Pineal Res. 1998; 24:35–42. © Munksgaard, Copenhagen

In this paper we describe the interaction of melatonin with calmodulin in MDCK cells. The double staining immunofluorescent method showed that calmodulin in control MDCK cells appeared as fluorescent spots at the cell periphery. In contrast, MDCK cells cultured with 10‐‐9 M melatonin for 6, 12, 24 hr or for 4 days showed that calmodulin fluorescent spots were distributed throughout the cytoplasm as well as in the nucleus. These calmodulin rearrangements were reversed 6 hr after melatonin withdrawal. Moreover, calmodulin radioimmunoassay showed that in 10‐‐9 M melatonin‐treated cells, membrane‐bound calmodulin content was increased by 78% whereas cytosolic calmodulin decreased by 60%. Simultaneous labeling of MDCK cells with specific antibodies against calmodulin and melatonin showed that not only does the indole enter the cell, but that it has the same subcellular distribution as calmodulin. Besides the early responses induced by the melatonin antagonism to calmodulin, the results suggest that the indole may also induce long‐term cellular responses by changing calmodulin concentrations in specific cellular compartments.
Sulphatoxymelatonin excretion in older people: Relationship to plasma melatonin and renal function
Authors: Basket Jonathan J. , Cockrem John F. , Antunovich Tony A.
Published: February 2007

Baskett JJ, Cockrem JF, Antunovich TA. Sulphatoxymelatonin excretion in older people: Relationship to plasma melatonin and renal function. J. Pineal Res. 1998; 24:58–61. © Munksgaard, Copenhagen

In order to validate measurement of urinary sulphatoxymelatonin as an accurate method of estimating plasma melatonin secretion in older people, we compared 24 h plasma melatonin secretion and sulphatoxymelatonin excretion with renal function in 20 subjects 62–89 years of age. There was a good correlation between plasma and urinary sulphatoxymelatonin over the same 24 h period (R2= 0.797) and no relationship between creatinine clearance and sulphatoxymelatonin excretion (R2= 0.075). The results suggest that sulphatoxymelatonin excretion estimation is a good surrogate measurement of plasma melatonin secretion in older people, at least across the range of creatinine clearance for the subjects in the study, 0.41–1.81 ml/sec.
Effect of estrogen on melatonin synthesis in female peripubertal rats
Authors: Okatani Yuji , Hayashi Kazutoshi , Watanabe Kazushi , Morioka Nobuyuki , Sagara Yusuke
Published: February 2007

Okatani Y, Hayashi K, Watanabe K, Morioka N, Sagara Y. Effect of estrogen on melatonin synthesis in female peripubertal rats. J. Pineal Res. 1998; 24:67–72. © Munksgaaard, Copenhagen

Our objective was to evaluate the effect of estrogen on the synthesis of melatonin in female rats during the peripubertal period. The level of melatonin and of N‐acetyl serotonin (NAS) and the activity of N‐acetyltransferase (NAT) and of hydroxy‐indole‐O‐methyltransferase (HIOMT) were determined in homogenates of pineal glands from peripubertal female Sprague‐Dawley rats in the mid‐dark during the daily light/dark cycle between 4 and 10 weeks of age. Ovariectomy was performed and daily administration of estradiol benzoate (E2B) was initiated at 6 weeks of age. A peak in the pineal level of melatonin and NAS and in NAT activity was observed in untreated (control) rats with intact ovaries at 6 weeks. Thereafter, HIOMT activity increased and remained unchanged. Ovariectomy at week 6 led to significant increases in the level of melatonin and of NAS and in NAT activity at week 8. At week 10, NAT activity was similar to that of control animals, but melatonin and NAS levels were slightly elevated. Ovariectomy did not affect HIOMT activity. The subcutaneous injection of a low dose (0.1 μg/day) of E2B suppressed the ovariectomy‐induced elevation of levels of melatonin and NAS and of NAT activity, similar to that seen in rats with intact ovaries. A higher dose of E2B (1.0 (μg/day) reduced the activity of NAT and HIOMT to values significantly below the control values. Results suggest that estrogen modulates the nocturnal synthesis of melatonin by the pineal gland in peripubertal female rats. The decline in melatonin synthesis during puberty may be related to an increase in the estrogen level. The inhibitory effect of estrogen in melatonin synthesis appeared to be mediated by the modulation of NAT activity.
Melatonin interaction with magnesium and zinc in the response of the striatum to sensorimotor cortical stimulation in the rat
Authors: Eseames G. , Acuna‐Castroviejo D. , Lebn J. , Vives F.
Published: February 2007

Eseames G, Acuña‐Castroviejo D, León J, Vives F. Melatonin interaction with magnesium and zinc in the response of the striatum to sensorimotor cortical stimulation in the rat. J. Pineal Res. 1998; 24:123–129. © Munksgaard, Copenhagen

The sensorimotor cortex (SMCx) sends numerous projections to the striatum. These projections are excitatory and glutamate mediated. Glutamatergic receptors, specifically those of NMDA type‐receptors, are closely related to excitotoxicity. Thus, in some circumstances, an excess of Ca2+ influx through NMDA channels alters neuronal metabolism and may become lethal for the cell. Two other divalent cations, Mg2+ and Zn2+, have inhibitory effects on NMDA receptors. Magnesium ions exert a voltage‐dependent block of the NMDA calcium channel, whereas zinc ions exert a voltage‐independent NMDA block. In the present work, the effects of iontophoresis of Mg2+ and Zn2+ on the striatal response to SMCx stimulation were studied. Moreover melatonin, an indoleamine with anticonvulsant properties and inhibitory effects on the NMDA receptor, was also iontophorized alone or in combination with Mg2+ and Zn2+. Single pulse electrical stimulation of SMCx produced an excitatory response in the striatum. Iontophoresis of melatonin, Mg2+ and Zn2+ produced a potent attenuation of the excitatory response of the striatum to SMCx stimulation, although the latency of the effect of melatonin was longer than those of Mg2+ and Zn2+. When these cations were simultaneously ejected with melatonin, additive inhibitory effects were recorded. These observations suggest that the inhibitory effects produced by Mg2+ and Zn2+ and melatonin are produced via different processes, and thus the inhibitory role of melatonin on the NMDA receptor activity is exclusive of a direct action on the NMDA calcium channel.
Direct neuronal projection from the dorsal raphe nucleus to the pineal complex of the rat: A Phaseolus vulgraris‐leucoagglutinin in vivo neuronal tracing study
Authors: Møler M. , Hay‐Schmidt A.
Published: February 2007

ABSTRACT: By use of Phaseolus vulgaris‐leucoagglutinin as an anterograde in vivo tracer, a direct projection from the dorsal raphe nucleus to the pineal complex of the rat was demonstrated. The nerve fibers extended from the dorsal raphe nucleus rostrally through the mesencephalic periaqueductal grey and entered the deep pineal from both the posterior commissure and the habenular area. A dense innervation of the deep pineal and the pineal stalk was observed, but the nerve fibers were not observed to enter the superficial pineal gland. This new neural pathway might connect the visual system with the pineal complex of the rat.
Ischemia/reperfusion‐induced arrhythmias in the isolated rat heart: Prevention by melatonin
Authors: Tan Dun‐Xian , Manchester Lucien C. , Reiter Russel J. , Qi Wenbo , Kim Seok Joong , El‐Sokkary Gamal H.
Published: February 2007

Abstract: Cardiac arrhythmias during ischemia/reperfusion are believed to be related to free radicals generated in the heart especially during the period of reperfusion. Since melatonin functions as a free radical scavenger and antioxidant, the ability of this molecule to influence cardiac arrhythmias was investigated. The pineal secretory product, melatonin, reduced the incidence and severity of arrhythmias induced by ischemia/reperfusion due to ligation of the anterior descending coronary artery in the isolated rat heart. Melatonin was either infused during both the ischemia and reperfusion periods or only late in the ischemia period and throughout reperfusion. The percentage of hearts that developed cardiac arrhythmias during reperfusion as indicated by the incidence of premature ventricular contraction (PVC) and ventricular fibrillation (VF) were recorded. Melatonin either infused during both the ischemia and reperfusion periods or during essentially the period of reperfusion greatly reduced PVC and VF due to occlusion and reopening the anterior descending coronary artery. Presumably melatonin's beneficial effect in reducing cardiac arrhythmias was due in part to its free radical scavenging activity, which is greatly assisted by the rapidity with which it is taken up into cells. Previous studies have shown that vitamin C is effective in reducing the severity of cardiac arrhythmias induced by ischemia/reperfusion; thus, we also compared the efficacy of melatonin with this well‐known antioxidant. Melatonin was more potent than vitamin C in protecting against arrhythmias induced by ischemia/reperfusion. Besides melatonin's function as a broad spectrum free radical scavenger, melatonin may have also reduced cardiac arrhythmias due to its regulation of intracellular calcium levels, i.e., by preventing calcium overloading, or due to its ability to suppress sympathetic nerve function and reduce adrenergic receptor function in the myocardium. Additional studies into the mechanisms of melatonin's action in reducing cardiac arrhythmias due to ischemia/reperfusion or other causes are warranted because of the possible application of this information to humans with heart disease.
The role of granulocyte‐macrophage‐colony stimulating factor, cortisol, and melatonin in the regulation of the circadian rhythms of peripheral blood cells in healthy volunteers and patients with breast cancer
Authors: Akbulut Hakan , Icli Fikri , Büyükcelik Abdullah , Akbulut K. Gonca , Demirci Salim
Published: February 2007

Abstract: The circulating blood cells show highly reproducible circadian rhythms. However, the factors that regulate these rhythms are not well understood. In the current study, we examined the diurnal variations of peripheral blood cells (white blood cells, neutrophils, lymphocytes), granulocyte‐macrophage‐colony stimulating factor (GM‐CSF), and melatonin levels, and considered the role of melatonin on these rhythms in healthy volunteers and in patients with early breast cancer. Fourteen premenopausal patients with early stage breast cancer (T2, N1 tumors) and 10 premenopausal healthy volunteers were included in the study. Blood samples were taken every 4 hr for a period of 24 hr. Peripheral blood cells were counted by automated analyser and also from peripheral blood films. GM‐CSF levels were measured by ELISA and melatonin levels by radioimmunoassay (RIA). Serum melatonin, cortisol, and GM‐CSF levels, and peripheral blood cell counts showed significant circadian rhythms in healthy volunteers. Except for GM‐CSF, these circadian rhythms were found not to be suppressed in early breast cancer patients. While there were significant correlations of serum GM‐CSF and cortisol levels with peripheral blood cell counts in healthy volunteers, only lymphocyte counts were found to be significantly correlated with serum GM‐CSF and cortisol levels in patients with breast cancer. Serum melatonin levels were found to be significantly correlated with lymphocyte counts in both groups. Our results suggest that peripheral blood cells show significant circadian rhythms in both healthy volunteers and in patients with stage II (T2, N1) breast cancer, and GM‐CSF, cortisol, and melatonin may have a role in the regulation of peripheral blood cell counts.
Long‐term exposure of hypothalamic explants to melatonin alters the release of gonadotrophin releasing hormone and the density of melatonin binding sites in the pars tuberalis of the male mink (Mustela vison)
Authors: Messager S. , Caillol M. , Martinet L.
Published: February 2007

Abstract: To investigate the action of melatonin on the reproductive system, the effect of prolonged versus short‐term exposure to melatonin on the release of gonadotrophin releasing hormone (GnRH) was examined in hypothalamic explants of male mink sacrificed in July, September or November. Mediobasal hypothalamic (MBH) explants including the pars tuberalis (PT) were incubated for 1 night with or without melatonin (10−8 M) for 8 hr or 16 hr and the release of GnRH was then measured. The next day, the explants were incubated further but in a melatonin free buffer, and the release of GnRH was measured with increasing time. Half of the July and September explants had melatonin binding sites quantified by autoradiography. In November, a 16‐hr exposure to melatonin induced a significant increase in the release of GnRH during the night, compared with control or 8‐hr melatonin exposure. This increase persisted for at least 45 min after the withdrawal of melatonin, suggesting a stimulatory effect of melatonin on the synthesis of GnRH; this effect was apparent in July, September and November. In September, the density of melatonin binding in the PT was significantly lower in the explants incubated for 16 hr with melatonin, compared with those incubated for 8 hr. Thus, in vitro, a long exposure to melatonin, mimicking a single long night, stimulates the release and synthesis of GnRH in parallel with a decrease in the density of melatonin binding in the PT. These effects seem to depend heavily on the duration of exposure to melatonin.
Correlation between the circadian rhythm of melatonin, phagocytosis, and superoxide anion levels in ring dove heterophils
Authors: Rodriguez A. B. , Marchena J. M. , Nogales G. , Durán J. , Barriga C.
Published: February 2007

Abstract:A functional role for melatonin is its relationship to circadian timing mechanisms. In addition, there has recently been assumed to be a functional connection between the pineal gland and the immune system in mammals and birds, with some findings showing melatonin to be a free radical scavenger and general antioxidant. The present study investigates the possible relationship between the circadian rhythm of melatonin and the ingestion capacity as well as superoxide anion levels of ring dove (Streptopelia risoria) heterophils. In birds, heterophils, with their ability to ingest and kill different antigens, play a central role in the host defence mechanism. All determinations were made during 24 hr periods at 2 hr intervals. Radioimmunoassay showed an increase of melatonin serum levels during the dark period (from 20:00 to 07:00 hr) with a maximum at 04:00 hr, and a significant decline during the hours of light with a minimum at 16:00 hr. Similary, the phagocytic index was enhanced during the night, with the maximum at ∼04:00 hr and the minimum at ∼18:00 hr. The same was the case in relation to phagocytic percentage. However, the superoxide anion levels were lower during darkness (minimum at 04:00 hr) and higher during the light period (maximum at 14:00 hr). In conclusion, our findings show that one pineal‐mediated effect on the immune system may be a direct action of melatonin on phagocytosis and the phagocytic biochemical process, and that this neurohormone might act as an antioxidant.
Melatonin protects against ischemia and reperfusion‐induced oxidative lipid and DNA damage in fetal rat brain
Authors: Wakatsuki Akihiko , Okatani Yuji , Lzumiya Chiaki , Lkenoue Nobuo
Published: February 2007

Abstract: To investigate whether melatonin reduces the susceptibility of the fetal rat brain to oxidative damage of lipids and DNA, we created a model of fetal ischemia/reperfusion using rats at day 19 of pregnancy. Fetal ischemia was induced by bilateral occlusion of the utero‐ovarian artery for 20 min. Reperfusion was achieved by releasing the occlusion and restoring the circulation for 30 min. A sham operation was performed in control rats. Melatonin (10 mg/kg) or vehicle was injected intraperitoneally 60 min prior to the occlusion. We measured the concentration of thiobarbituric acid reactive substances (TBARS) in fetal brain homogenates, as well as the levels of deoxyguanosine (dG) and 8‐hydroxydeoxyguanosine (8‐OHdG) in DNA extracted from those homogenates. lschemia for 20 min did not significantly alter the levels of dG, 8‐OHdG, and TBARS. Subsequent reperfusion, however, led to a significant reduction in the dG level (P < 0.05) and to significant increases in the levels of 8‐OHdG (P < 0.05) and TBARS (P < 0.05), and in the 8‐OHdG/dG ratio (P < 0.005). Melatonin administration prior to ischemia significantly reduced the ischemia/reperfusion‐induced increases in the levels of 8‐OHdG (14.33 ± 6.52 5.15 ± 3.28 pmol/mg of DNA, P < 0.001) and TBARS (11.61 ± 3.85–4.73 ± 3.80 nmol/mg of protein, P < 0.001) as well as in the 8‐OHdG/dG ratio (7.19 ± 2.49–1.61 ± 0.98, P < 0.001). Furthermore, melatonin significantly increased the dG level (210.19 ± 49.02–299.33 ± 65.08 nmol/mg of DNA, P < 0.05). Results indicate that melatonin administration to the pregnant rat may prevent the ischemia/reperfusion‐induced oxidative lipid and DNA damage in fetal rat brain
Pharmacological aspects of N‐acetyl‐5‐methoxytryptamine (melatonin) and 6‐methoxy‐ 1,2,3,4‐tetrahydro‐β‐carboline (pinoline) as antioxidants: Reduction of oxidative damage in brain region homogenates
Authors: Pless Gitte , Frederiksen Tina J. P. , Garcia Joaquin J. , Reiter Russel J.
Published: February 2007

Abstract: Oxygen consumption is a necessity for all aerobic organisms, but oxygen is also a toxic molecule that leads to the generation of free radicals. The brain consumes a high percentage of the oxygen inhaled (18.5%), and it contains large amounts of unsaturated fatty acids, which makes it highly susceptible to lipid peroxidation. Melatonin (N‐acetyl‐5‐methoxytryptamine), the main secretory product of the pineal gland, is a free radical scavenger that was found to protect against lipid peroxidation in many experimental models. Another compound found in the pineal gland is pinoline (6‐methoxy‐1,2,3,4‐tetrahydro‐β‐carboline). Pinoline is structurally related to melatonin. Evidence suggests that pinoline may have an antioxidant capacity similar to that of melatonin. In this study, the ability of pinoline to protect against H2O2‐induced lipid peroxidation of different rat brain homogenates (frontal cortex, striatum, cerebellum, hippocampus, and hypothalamus) was investigated. The degree of lipid peroxidation was assessed by estimating the levels of thiobarbituric acid reactive substances, malondialdehyde (MDA) and 4‐hydroxyalkenals (4‐HDA). Pinoline's antioxidant capacity was compared with that of melatonin. Both melatonin and pinoline reduced the level of MDA and 4‐HDA in a dose‐dependent manner in all brain regions tested. To compare the antioxidant capacities, percent‐inhibition curves were created, and the IC50 values were calculated. The IC50 values for melatonin were higher in all brain regions than were those for pinoline. The IC50 values for melatonin in the five different brain regions ranged from 0.16mM‐0.66 mM, and for pinoline, they ranged from 0.04 mM‐0.13 mM. The possibility of synergistic interactions between melatonin and pinoline were also determined using the method of Berenbaum. Little evidence for either synergistic, additive, or antagonistic interactions between melatonin and pinoline was found.
Biochemical characterization of recombinant serotonin N‐acetyltransferase
Authors: Zhan‐Poe Xinyi , Craft Cheryl M.
Published: February 2007

Abstract: Pineal and retinal melatonin synthesis is controlled by the enzymatic activity of arylalkylamine N‐acetyltransferase (AA‐NAT, EC 2. 3. 1. 87), which is regulated by light/dark signals and circadian factors. This enzyme converts serotonin to N‐acetylserotonin by the transfer of an acetyl group from acetyl coenzyme A. Endogenous AA‐NAT instability during routine purification has made enzyme characterization difficult, but now a stable recombinant protein for AA‐NAT has been synthesized to investigate the intrinsic biochemical properties of AA‐NAT from a rat pineal cDNA encoding a 205 amino acid. 23 kilodalton protein, by using a glutathione‐S‐transferase (GST) fusion protein system. Recombinant GST‐AA‐NAT showed substrate specificity for arylalkylamines and stability at 4°C; however, the enzyme activity was reduced by 40% upon preincubation at 37°C for 2 hr. GST‐AA‐NAT is preferentially phosphorylated by either cyclic AMP‐ or cyclic GMP‐dependent kinases in vitro, but no detrimental effect was observed on AA‐NAT enzymatic activity. Among the metal cations tested in this study, Ca2+, Mn2+, Mn2+, Fe2 ‐, and Co2+ showed little or no inhibitory potency, while either 1 mM Zn2+ or 0.1 mM Cu2+ nearly abolished the enzymatic activity. GST‐AA‐NAT enzyme activity is also inhibited by reagents that are known biochemically to modify thiol groups (N‐ethylmaleimide, NEM) and histidine residues (p‐chloromercuribenzoate, NBS and diethyl pyrocarbonate, DEPC), suggesting the presence of essential cysteine and histidine moieties. Moreover, preincubation of acetyl CoA completely protects the recombinant AA‐NAT from inactivation by NEM and DEPC, indicating that specific cysteine and histidine residues may be at the acetylation site. The conclusion is that the biochemical properties of rat recombinant AA‐NAT is similar to the endogenous pineal and retinal AA‐NAT with respect to the sensitivity to temperature, metal cations, as well as the thiol modification reagents. These data also suggest that the phosphorylation status of the AA‐NAT does not affect enzymatic activity directly, and histidine residues are potentially important residues required for high catalytic activity.
Melatonin and other antioxidants prolong the postmortem activity of the outer hair cells of the organ of Corti: Its relation to the type of death
Authors: Lopez‐Gonzalez Miguel A. , Guerrero Juan M. , Rojas Francisco , Osuna Carmen , Delgado Francisco
Published: February 2007

Abstract: The outer hair cells of the organ of Corti transform sound into electrical signals, beginning the nervous auditive process. These cells produce acoustic emissions when working routinely, known as otoacoustic emissions. Otoacoustic emissions (OAEs) are recorded from the hearing duct through a probe which incorporates a sound source and a sensitive microphone. On the other hand, the cochlea produces oxygen‐derived free radicals and nitric oxide, in addition, melatonin is present in the cochlea. The authors have studied the influence of melatonin or an antioxidant mixture (alpha‐tocopherol acid succinate, ascorbic acid, glutathione, and N‐acetylcysteine) on the postmortem activity of the outer hair cells of the organ of Corti of the rat, measuring distortion product otoacoustic emissions. Control rats showed postmortem distortion product otoacoustic emissions for about 2 min when sacrificed by decapitation, and for about 3 min when sacrificed by chloroform inhalation. Melatonin prolonged the postmortem activity 3.5 times when the animals were sacrificed by decapitation, and 7 times when animals were sacrificed by chloroform inhalation. Similar results were obtained with the antioxidant mixture. Results show that melatonin and other antioxidants have, in general, a protective role on the postmortem activity of the outer hair cells of the organ of Corti.
Estimation of frequently sampled nocturnal melatonin production in humans by deconvolution analysis: Evidence for episodic or ultradian secretion
Authors: Geoffriau Martine , Claustrat Bruno , Veldhuis Johannes
Published: February 2007

Abstract: In order to investigate nocturnal melatonin production and clearance rates, we applied deconvolution analysis to plasma melatonin concentration time series obtained every 20 min for 12 hr from 20:00 h to 08:00 h in two groups of healthy subjects at rest (group 1, 12 male subjects, 22–26 yr; group 2, ten female subjects, 31–42 yr). The estimated melatonin production rate from group 1 (0.55 ± 0.21 μ/kg/night) was significantly higher than that of group 2 (0.26 ± 0.19 μg/kg/night), as well as the mass of melatonin released per burst (275 ± 110 vs. 145 ± 130 pg/mL for groups 1 and 2, respectively), the amplitude of secretory bursts (7.8 ± 3.2 vs. 4.7 ± 3.5 pg/mL/min), and the pulsatile melatonin production rate (2.76 ± 1.14 vs. 1.27 ± 0.97 ng/mL/night). These differences could reflect alterations related to age and/or gender. No differences were observed between the two groups in the secretory burst half‐duration and frequency and the interburst interval. Melatonin production rates, as estimated by deconvolution analysis, are in agreement with other independent estimates, especially the isotopic method, and disclose an ultradian rhythmicity.
EFFECT OF TEMPERATURE AND WATER CONCENTRATION DURING PROCESSING ON FOOD QUALITY
Authors: THIJSSEN H. A. C. , KERKHOF P. J. A. M.
Published: February 2007

Water content and temperature during food processing have a pronounced influence on the rates of those changes in food properties which are the object of the process such as reduction in water content or sterilization. However, they also strongly influence adverse side effects such as browning, loss of nutrients or shrinking. When the effects of temperature and water concentration on the process rates of the desired and adverse processes are known, the processes can be optimized. An example of the optimization procedure is given for the spray drying of heat‐labile aroma containing liquid foods. Both temperature and moisture content of the droplets change with time in spray‐drying. In a second example a new and simple calculation method is introduced for the optimization of quality retention in the sterilization of packed foods.
A REVIEW OF FUNDAMENTAL AND ENGINEERING ASPECTS OF EXTRUSION OF BIOPOLYMERS IN A SINGLE‐SCREW EXTRUDER
Authors: BRUIN S. , VAN ZUILICHEM D. J. , STOLP W.
Published: February 2007

A review of fundamental and engineering aspects of extrusion in a single‐screw is given. Attention is focussed on flow patterns, flow rates, residence time distributions and power consumption as a function of extruder design and screw rotation speed. The relationship for these engineering variables in extrusion of a purely Newtonian liquid and a power law liquid are reviewed. Where possible these relationships are compared with experimental results from the literature (corn‐grits) and with our own measurements on biopolymers (corn‐grits, defatted soy flour, modified di‐amylopectin).
DESIGN AND MODELING OF A CAPILLARY FOOD EXTRUDER
Authors: MORGAN RONNIE G. , SUTER DWAYNE A. , SWEAT VINCENT E.
Published: February 2007

A simple capillary ram food extruder was designed, constructed and mathematically modeled. The mathematical model was developed from a group of meaningful dimensionless parameters derived from a dimensional analysis of the extruder. This approach to modeling greatly reduced the number of experiments required to determine the model equation constants.

Commercial defatted soy flour was used to conduct tests for validating the model. Flour moisture content, die length and die diameter were varied with all other variables remaining constant. Pressure loss through the extruder was the measured variable.

The mathematical model fit the observed data accurately. It is proposed that once all experimental constants are determined, the general model may be used to determine rheological and thermodynamic data for doughs during extrusion processes. These data may then be used to develop certain rheological material functions.
RETENTION OF SPARINGLY SOLUBLE VOLATILE COMPOUNDS DURING THE FREEZE DRYING OF MODEL SOLUTIONS
Authors: SMYRL T. G. , LeMAGUER MARC
Published: February 2007

The retentions of terpenic essential oil components (carvone, pulegone and piperitone) and non‐terpenic essential oil components (eugenol and m‐anisaldehyde) were measured during the freeze drying of model aqueous solutions. Model solutions contained sucrose, glucose, sodium chloride or gum arabic which are all common food components. The percent retentions of these slightly soluble flavoring compounds were found to increase with increased initial solids concentration, decreased initial volatile content, increased sample thickness, increased freezing rate and the absence of an additional sparingly soluble volatile.
BREAKAGE OF RICE DURING MILLING — COMPARISON AMONG DIFFERENT SHELLERS1
Authors: SWAMY Y. M. INDUDHARA , BHATTACHARYA K. R.
Published: February 2007

A medium‐long, semislender variety of paddy was shelled using four types of shellers (rubber roll, centrifugal, disc under‐runner, McGill) followed by pearling with a McGill miller. Grain breakage during shelling was the least in the rubber roll. But the less the breakage during shelling, the more it was during pearling. As a result, the rubber roll gave considerable advantage after low and medium degrees of milling, but only a marginal advantage at high milling. Total rice breakage was equal to or less than the content of defective grains in the original paddy depending on the sheller.
TEMPERATURE DISTRUBITIONS AND LIQUID‐SIDE HEAT TRANSFER COEFFICIENTS IN MODEL LIQUID FOODS IN CANS UNDERGOING FLAME STERILIZATION HEATING
Authors: MERSON R. L. , LEONARD S. J. , MEJIA ERNESTO , HEIL J.
Published: February 2007

Heat transfer studies were performed with clay suspensions and sugar solutions in 303 × 406 cans heated singly in a flame process simulator. Experimental results show that the can wall temperature does not reach excessive temperatures and that the temperature distribution throughout the can is uniform. The slowest heating point was on the axis near the end of the can but this temperature lagged the center temperature by less than 3°C even with adverse heating conditions (i.e., no head space).

The liquid‐side heat transfer coefficient in 60% sucrose solution at 30 rpm was measured to be 466 ± 34 W/m2K based on the cylindrical area of the can. Rotational speed had only a small effect on heating rate in the range of 10 to 120 rpm.
EFFECT OF DEFORMATION RATE AND MOISTURE CONTENT ON RICE GRAIN STIFFNESS1
Authors: CHATTOPADHYAY P. K. , HAMANN D. D. , HAMMERLE J. R.
Published: February 2007

Grains of brown rice, paddy variety IR‐8, were subjected to two types of uniaxial compressive loading, constant displacement rate and sinusoidally varying stress, to determine behavior over a wide range of time scale. Grains from four different moisture level groups were used.

With a time decrease from 120 to 1.6 × 10−4s the relaxation modulus increased 15, 25, 16 and 20 fold at respective moisture contents of 12, 17, 22 and 27%. A master relaxation curve for each moisture content is presented. Understanding the viscoelastic behavior of brown rice as a function at time and moisture content is basic to the solution of stress‐strain analysis problems.
THERMAL CONDUCTIVITY AND DIFFUSIVITY OF SHELLED CORN AND GRAIN
Authors: KUSTERMANN MARTIN , SCHERER REINHOLD , KUTZBACH HEINZ DIETER
Published: February 2007

Increasing energy costs have stressed the importance of calculation of heat and mass transfer in a grain bulk in order to be able to optimize drying facilities. Therefore values for the thermal conductivity and diffusivity of grain and especially shelled corn were determined. The investigations were carried out for single kernels as well as for grain and corn in bulk. Thermal conductivity and diffusivity were found to be mainly dependent on moisture content. Regression analyses showed a good correlation between moisture content and thermal conductivity or diffusivity, respectively.
THE THERMAL PROPERTIES OF FROZEN INVERT SUGAR SOLUTIONS
Authors: KEPPELER R. A. , ARBOLEDA JOSE R.
Published: February 2007

The thermal conductivity, thermal diffusivity, apparent heat capacity and density of frozen invert sugar solutions were found for 40, 50, 60 and 95% sugar inversion, each in concentrations from 2 to 35%, between ‐40°C and 3.9°C at 2.78°C temperature intervals. The apparatus and instrumentation used was identical with that reported by Keppeler and Boose (1970).
HYDROGEN IONS PROFILES, APPARENT MOBILITY AND DISAPPEARANCE DURING COOKING OF MEAT EMULSION—2. CYLINDRICAL GEOMETRY
Authors: MITTAL GAURI S. , BLAISDELL JOHN L.
Published: February 2007

The modeling techniques developed in the first part of this series were applied to describe the hydrogen ion profiles in meat emulsion in cylindrical shape during thermal processing at temperatures >58°C. The model was verified with experimental data collected at various processing conditions and the compositions of the product. An increase of 0.27 to 0.50 pH units was recorded in the processed product. The values of reaction rate constant varied between 0.88 to 2.90 1/h and the diffusivity of H+ was constant at 0.2E‐5 m2/h.
A NEW EMPIRICAL MODEL TO SIMULATE TRANSIENT SHEAR STRESS GROWTH IN SEMI‐SOLID FOODS1
Authors: MASON PHILLIP L. , BISTANY KAREN L. , PUOTI MARIA G. , KOKINI JOZEF L.
Published: February 2007

A family of models has been developed which has the ability to simulate transient shear stress growth in foods. The models can be written as follows:

Three relaxation terms (seven parameters) are necessary to stimulate transient shear stress growth for stick butter, tub margarine and peanut butter at shear rates of 10 s−1 and 100 s−1.

At small times the model tends to:

which simulates the stress growth part of the curve. At long times the models tend to the power‐law. The series of relaxation terms allows for the introduction of several time scales in the relaxation behavior of each food.
THE EFFECTS of GAS INJECTION ON the EFFICIENCY of THERMAL ENERGY UTILIZATION IN SPRAY DRYING1
Authors: ROMERO‐FERRER D. E. , AMUNDSON C. H. , HILL C. G.
Published: February 2007

Factorial experimental designs were used to study the effects of gas injection on the efficiency of thermal energy utilization in evaporation by spray drying. Both the main effect and the interactions of this variable with feed pressure, feed concentration, nozzle size, and drying temperature were investigated. the use of gas injection led to a decrease in the thermal energy required for evaporation. the magnitude of this effect was larger at the lower levels of feed pressure, feed concentration, and drying temperature. However, this does not imply that spray drying is more energy efficient than such alternative modes of water removal as multi‐effect evaporation and reverse osmosis.
CALCULATION of an APPROXIMATE COOLING CURVE FOR COOKED ROAST BEEF1
Authors: NOLAN E. J.
Published: February 2007

On June 1, 1983, the Food Safety and Inspection Service of the U.S. Department of Agriculture issued a final regulation regarding cooking and cooling requirements for roast beef. This regulation includes a specification of the time that the cooked roast may be exposed to temperatures in the range 120°F (332K) and 55°F (285.93K), no more than 6h, and that chilling must continue until the center temperature reaches 40°F (277.6K) before packaging. the purpose of this work was to suggest means by which processors may estimate these temperature limits. Several measured temperature profiles at the center of the roasts were obtained from beef processors, h was found that the measured temperatures obtained during the cooling of cooked roasts by ice water, may be predicted satisfactorily by methods described in this paper. Cooling with cold air introduces a boundary layer resistance to heat transfer and possibly also mass transfer because of potential evaporation of water. However, in this latter case further investigation is needed to determine its effect on the cooling of moist food products; the use of heat transfer considerations alone gave reasonable agreement with measurement in this particular instance. It appears that ice water velocities should be kept in excess of about 0.076 m/s to ensure that minimal surface resistance to heat transfer occurs during cooling; ice water velocities in the order of 0.15 m/s seem to lead to excellent cooling conditions.
CONCENTRATION of ORANGE JUICE BY REVERSE OSMOSIS
Authors: MEDINA BENJAMIN G. , GARCIA ALBERT
Published: February 2007

Orange juice was concentrated by RO up to 50% hydraulic recovery with a polyamide membrane. Permeate fluxes and solute recoveries were determined at transmembrane pressures of 6.21 and 4.14 MPa. Pectinase treatment was required to prevent fouling and to allow Cleaning in Place procedures. Enzymatic treatment did not affect permeate flux or solute recoveries. Overall recovery of sugars, organic acids, and flavor‐volatile components was approximately 93%.
A FINITE ELEMENT METHOD to MODEL STEAM INFUSION HEAT TRANSFER to A FREE FALLING FILM
Authors: McCARTHY KATHRYN L. , MERSON RICHARD L.
Published: February 2007

This work is a theoretical and experimental analysis of heat transfer to a free falling film of homogeneous fluid food. Fluid falls vertically in a thin film through a stagnant steam environment. the thermal energy equation governing the steady state heat transfer is solved numerically by a finite element method. the Froude number and the Peclet number characterize the fluid flow and heat transfer. Water was used as the experimental test fluid in the steam infusion unit. Average fluid temperatures measured as a function of position compare well with model predictions. the model was incorporation into a kinetic model to predict the extent of microbial destruction expected with the time/temperature treatment.
A SIMPLIFIED ANALYTICAL MODEL FOR FREEZING TIME CALCULATION IN BRICK‐SHAPED FOODS
Authors: ILICALI COŞKAN
Published: February 2007

A simplified analytical model for the freezing time prediction of brick‐shaped foodstuffs was developed. It was assumed in the model that the solution to the unsteady, one‐dimensional heat conduction equation with constant thermophysical properties was valid during cooling and freezing for each of the three directions of the brick‐shaped food. Cooling and freezing times were calculated by superposition of the solutions of the unsteady, one‐dimensional heat conduction equation with constant thermophysical properties for each direction. the latent heat effects were incorporated into an effective thermal diffusivity term. the predictions of the model were compared to the available experimental data on freezing of two‐ and three‐dimensional bricks and to the experimental data obtained in this research for the freezing of ground beef and mashed potato bricks. Mean errors varying between ‐6.3% and 2.3%, and standard deviations from the mean being between 6.6% and 14.0% were obtained for the data sets considered.
APPARENT CONCENTRATION: A METHOD to PREDICT the FLOW PROPERTIES of VISCOUS FOODS FOR PROCESS APPLICATIONS
Authors: HÄRRÖD MAGNUS
Published: February 2007

Compared with traditional methods, the prediction of flow properties of starch pastes is greatly improved with the new apparent concentration method proposed in this study. the new method considers the effects on the flow properties of minor variations in the preparation procedure and the composition of the product. the deviations with the new method range from ± 10% for high‐viscosity pastes down to ‐30% for low‐viscosity pastes. the deviations are mainly due to the time dependency of the shear stress, as these effects are considerable for starch pastes, but have not been considered in the modelling in this work. Successful use of the apparent concentration method requires a reference model with known parameter values, a simple rheological measurement on the actual product, and appropriate calculations. the simple measurement can be performed on‐line or in the laboratory. A special residual analysis was developed to make it possible to split up the differences between observed and predicted values and attribute the parts to the following factors: measuring instrument, changes in the sample during the measuring process, model, parameter values, and the concentration used in the prediction. This residual analysis made it possible to identify the weakest link in the predictions.