bluuebunny/crossref_metadata_2025_split huggingface dataset:
Why don't producers adopt best management practices? An analysis of the beef cattle industry
Authors: Gillespie Jeffrey , Kim Seon‐Ae , Paudel Krishna 
Published: February 2007

AbstractCattle producers were surveyed to determine their adoption rates and reasons for non‐adoption of 16 best management practices. Potential reasons for non‐adoption included unfamiliarity, non‐applicability, high cost, still considering adoption, and preference not to adopt. The two most commonly cited reasons for non‐adoption were unfamiliarity and non‐applicability of the practice. Results highlight the importance of educational efforts in encouraging adoption, as well as farm type and financial situation of the farmer.
Effects of Melatonin and Control Injections on Pineal Serotonin and Norepinephrine: Afternoon Injections Lower Serotonin Levels Thirty‐Six Percent at Light‐Dark Transition
Authors: Catalá M. Dolores , Du Ji‐zeng , Quay W.B. , Timiras P.S. 
Published: February 2007

Pineal weight and serotonin (5‐HT) and norepinephrine (NE) contents were studied in male Sprague‐Dawley rats that were maintained under controlled light:dark conditions (LD 14:10; lights on 0700‐2100) and that received daily subcutaneous injections of either melatonin (20 μg in 0.1 ml per animal) or the same volume (0.1 ml) of vehicle alone, at one of two times (0800‐0900 or 1800‐1900). Animals were sacrificied at four times (1000, 1400, 2000, or 2300) on the day after the last of the 7 consecutive d of injection. Pineal glands were quickly weighed and then frozen for 5‐HT and NE assay by the Maickel and Miller extraction and fluorescence methods.Pineal NE content showed differences related to time of day, in confirmation of early work. But no effects attributable specifically to melatonin were found. Melatonin also failed to affect pineal 5‐HT content significantly. But injection of either melatonin or vehicle at 1800‐1900 led to a reduction in 5‐HT content averaging 36% when sampled at either 2000 or 2300, and in comparison with animals injected at 0800‐0900. It is suggested that a stresslike or zeitgeberlike effect of injections within a critical period at the end of the daily light phase can cause an earlier‐than‐normal daily fall in pineal 5‐HT content.
The Influence of Various Irradiances of Artificial Light, Twilight, and Moonlight on the Suppression of Pineal Melatonin Content in the Syrian Hamster
Authors: Brainard George C. , Richardson Bruce A. , Hurlbut Edward C. , Steinlechner Stephan , Matthews Susan A. , Reiter Rüssel J. 
Published: February 2007

The purpose of the present studies using artificial light was to determine how the timing and duration of exposure influence the light‐induced suppression of pineal melatonin levels in hamsters. An 8‐min exposure to 0.186 μW/cm2 of cool white fluorescent light caused a continued depression of pineal melatonin even when animals were returned to darkness. In addition, the pineal gland does not appear to change its sensitivity to light throughout the night. A 20‐min exposure to 0.019 μW/cm2 of cool white fluorescent light did not significantly suppress pineal melatonin during any time of the melatonin peak, whereas a 20‐min exposure to 0.186 μW/cm2was capable of always suppressing melatonin. Furthermore, increasing the duration of 0.019‐μW/cm2 exposure to 30, 60, 120, or 180 min does not increase the capacity of this irradiance to depress melatonin.Similar to artifical light, natural light has a variable capacity for suppressing nocturnal levels of pineal melatonin. Twilight irradiances of 0.138 μW/cm2 or less did not suppress nocturnal melatonin whereas twilight irradiances of 3.0 μW/cm2 or greater did suppress pineal melatonin. A few animals did have lower melatonin after a 40‐min exposure to full moonlight during July (0.045 μW/cm2) or January (0.240 μW/cm2). However, pineal melatonin levels remained high in the majority of animals exposed to full moonlight.
Melatonin Rhythms in Quail: Regulation by Photoperiod and Circadian Pacemakers
Authors: Underwood Herbert , Siopes Thomas 
Published: February 2007

The profile of melatonin in the eyes, pineal, and blood of Japanese quail was assessed in birds held under LD 16:8 and LD 6: 18 photoperiods. Melatonin levels in all three tissues showed a robust daily rhythm with higher levels occurring at night. The amplitude of the rhythm was depressed and its duration lengthened on LD 6: 18 relative to LD 16:8. The blood melatonin rhythm precisely reflected the rhythms shown by the pineal and eyes, supporting the idea that the blood rhythm is a result of melatonin secretion by both the eyes and pineal.The ocular melatonin rhythm continued after sectioning of the optic nerve, was reentrainable to a shift in the phase of the LD cycle, and persisted for at least 2 days in constant darkness. It was concluded that either (1) an intraocular circadian clock drives the ocular melatonin rhythm, or (2) an extraocular clock drives the ocular melatonin rhythm via a route other than the efferent innervation (which enters the eye via the optic tract).
Melatonin Lowers Plasma Prolactin Levels in Female Red Deer (Cervus elaphus)
Authors: Adam Clare L. , Atkinson Terence , Moir Carol E. 
Published: February 2007

The aim of the study was to determine the effect of exogenous melatonin treatment on circulating prolactin levels in red deer. Melatonin was administered from 12 June 1984 (day 1) to lactating and non‐lactating hinds in the feed daily at 1600 h, and to non‐lactating hinds by a subcutaneous implant. Average concentrations (ng/ml) of prolactin in plasma taken serially over 15‐h periods were significantly higher for untreated hinds than for melatonin‐treated animals on day 15 whether lactating (66–133 v. 23–28, P<0.05) or non‐lactating (28–174 v. 8–13, P< 0.01), remained higher on day 36 (lactating: 41–152 v. 15–21, P< 0.05; non‐lactating: 21–50 v. 1–7, P<0.001) but had decreased to similar levels on day 72 (lactating: 5–24 v. 7–17; non‐lactating: 2–9 v. 0–4).The advanced reduction in plasma prolactin for all melatonin‐treated hinds was associated with an advanced onset of seasonal breeding activity.
[3H] Melatonin Binding in Membrane and Cytosol Fractions From Rat and Calf Brain
Authors: Niles Lennard P. 
Published: February 2007

The binding characteristics of the tritiated pineal hormone, [3H] melatonin, were studied in brain tissues using in vitro binding techniques. In synaptosomal membranes prepared from rat hippocampus and subjected to preincubation at 37°C and multiple washings, high‐affinity binding of [3H] melatonin significantly exceeds that previously reported for membrane or cytosol fractions from mammalian brain. Scatchard analysis of saturation binding data indicates that binding affinities are similar in membrane (Kd= 15 nM) and cytosol (Kd=11 nM) preparations. However, binding is about sevenfold greater in membranes than in cytosol prepared by centrifugation of homogenates at 104,000g for 60 min. Specific binding is also present in both particulate and soluble fractions from calf brain.Inhibition experiments, in rat hippocampal membranes, indicate that norepinephrine is the most potent inhibitor of about 55% of total binding. Serotonin also exhibited high affinity for about 25% of total binding, suggesting that [3H] melatonin labels both adrenergic and serotonergic sites in this brain region.Further studies are required to characterize the serotonergic and adrenergic sites labelled by [3H] melatonin and to determine whether these sites are functionally important receptors for melatonin.
Interactive Effects of Stress and Photoperiod History on Gonadal Condition in Male Syrian Hamsters
Authors: Rusak Benjamin 
Published: February 2007

A study of the effects of melatonin injections given to male Syrian hamsters (Mesocricetus auratus) late in the light phase in a 14L:10D photoperiod included control, oil‐injected hamsters that had been transferred from a 16L:8D photoperiod. Many oil‐injected hamsters underwent gonadal regression under these conditions. A literature review indicated that endocrine effects of‘control’injections are fairly common but that they might depend on previous photoperiodic history. A second study found that hamsters born and raised in 16L:8D had larger testes at 150 days of age than those raised in 14L:10D. Transfer from 16L:8D to 14L: 10D caused some unhandled hamsters to show gonadal regression while transfer to 14L:10D combined with daily oil injections caused most hamsters to undergo gonadal regression. Injections in animals maintained in 14L:10D throughout the study did not cause gonadal regression.These results indicate that stress effects can confound interpretation of drug treatments that require daily injections. They also demonstrate that the endocrine system of male Syrian hamsters distinguishes two photoperiods that are longer than the critical daylength (12.5 h). The effects of shortening daylengths may be potentiated by environmental stressors; together these may trigger gonadal regression at variable annual phases in anticipation of the critical daylength.
Subneuronal Fate of Intracerebroventricular Injected 3H‐Melatonin
Authors: Anton‐Tay Fernando , Forray Carlos , Ortega‐Corona Bertha G. 
Published: February 2007

The fate of 3H‐melatonin after its intracerebroventricular administration was studied both in different brain regions and in subcellular fractions. The rate of disappearance of 3H‐melatonin from the brain was found to be multiphasic. Forty‐eight h after a 3H‐melatonin injection, radioactivity was still present in the brain. Nonlinear regression analysis of the data confirmed a very rapid half‐life component and (t½= 3.04 min) a slower one (t½= 36 min). We also found a much slower component (t½= 24 h), however. Considerable metabolism of melatonin was detected since only 36.5% of administered radioactivity remained as melatonin at 45 min. The subcellular distribution of the radioactivity present in the brain at all times studied showed that a major proportion of the radioactivity remained in the cytosol and respectively decreasing proportions in the 900g pellet, mitochondrial pellet, and the microsomes.The radioactivity remaining in the cytosol at 45 min was found to coelute with a macromolecule that was resolved by gel filtration and could be displaced by previous melatonin administration. Purified nuclei retained 0.71% of the radioactivity at 45 min; of this total, 73% was KC1 extractable. Our data suggest the presence of a binding site in the cytosol and in the nucleus. The presence of 3H‐melatonin up to 48 h after its administration may account for melatonin's long‐term effects on brain function.
Rapid and Simple Synthesis for the Sulphate Esters of 6‐Hydroxy‐Melatonin and N‐Acetyl‐Serotonin
Authors: Leone A. M. , Francis P. L. , McKenzie‐Gray B. 
Published: February 2007

Melatonin is metabolised by hydroxylation at the 6 position and to a variable extent by demethylation. Both metabolites so formed are excreted as sulphate and, to a lesser extent, glucuronide conjugates. To authenticate these metabolites which we had earlier isolated from urine, we wished to have synthetic samples. Since we also required them as standards we needed them as powders. A review of the literature showed that there were only two published methods, of which only one gave rise to 6‐sulphatoxy‐melatonin (SaMT) as a solid.The other metabolite, N‐acetyl‐serotonin‐sulphate (SNAS), has not been previously made, and we here describe some of its chemical properties. Our method modifies a published method taking into account the results given in a recent paper describing the sulphation of the thyroid hormones, T3 and T4. Hydroxy‐melatonin is thus reacted with a complex formed from dimethylformamide and chlorosulphonic acid. The reaction is of interest since it is rapid, easy, and produces pure powdered material in excellent yield.
Daily Melatonin Injections Have Only Minor Effects on Gonadotropins of Intact or Castrated Male Rats Kept Under Constant or Periodic Light
Authors: Porkka‐Heiskanen T. , Laakso M. L. , Stenberg D. , Johansson G. 
Published: February 2007

Daily Melatonin Injections Have Only Minor Effects on Gonadotropins of Intact or Castrated Male Rats Kept Under Constant or Periodic LightIntact and castrated adult male Wistar rats were kept under constant or periodic (lights on 0600 and off 1800 h) light for 1 wk. During the study they received melatonin or saline injections daily either at 0900 or 1600 h. After each experiment, serum samples and the adenohypophyses were collected between 1000 and 1100 h and the gonadotropin concentrations were measured radioimmunologically. We had previously found changes in light sensitivity of the hypothalamo‐pituitary axis of castrated rats and hypothesized that this axis could also involve changes in sensitivity to exogenous melatonin. However, the results of the present study do not support the hypothesis.
Effects of Short‐Day Photoperiods and of N‐(2,4‐Dinitrophenyl)‐5‐Methoxytryptamine, a Putative Melatonin Antagonist, on Melatonin Synthesis in the Harderian Gland of the Syrian Hamster, Mesocricetus auratus
Authors: Buzzell Gerald R. , Menendez‐Pelaez Armando , Troiani Maureen E. , McNeill M. Evelyn , Reiter Russel J. 
Published: February 2007

The Harderian glands of Syrian hamsters contain melatonin and the enzymes N‐acetyltransferase (NAT) and hydroxyindole‐O‐methyltransferase (HIOMT) which synthesize melatonin from serotonin. Because the Harderian glands share this metabolic pathway with the pineal gland, we examined the effects of short‐day photoperiods, which stimulate pineal‐mediated gonadal regression, and N‐(2,4‐dinitrophenyl)‐5‐methoxytryptamine (ML‐23), which has been described as a melatonin antagonist, on melatonin synthesis in the Harderian glands of the hamster.Harderian glands of male hamsters kept in short days had reduced NAT activity and melatonin concentration, but HIOMT activity was unchanged from that of longday controls. In males kept in short days, ML‐23 restored melatonin concentrations to levels seen in long days but did not affect the short‐day induced reduction in NAT activity. ML‐23 had no effect upon NAT or HIOMT activity or melatonin concentration in male hamsters kept on long days.Harderian glands of female hamsters kept on short days had reduced melatonin concentrations, but NAT and HIOMT activities similar to those of long‐day controls. ML‐23 had no effect on Harderian NAT or HIOMT activities or melatonin concentration in females kept in short days. However, in females kept in long days, ML‐23 treatment led to increased NAT activity and decreased melatonin concentrations.We conclude from these results that short‐day photoperiods alter some aspects of melatonin synthesis in hamster Harderian glands and that these effects differ in males and females. ML‐23 does not usually prevent the effects of short days on Harderian melatonin synthesis, suggesting that it is not a melatonin antagonist in the Syrian hamster.
Plasma melatonin in the Adelie penguin (Pygoscelis adeliae) under continuous daylight in Antarctica
Authors: Cockrem J.F. 
Published: February 2007

Cockrem JF, Plasma melatonin in the Adelie penguin (Pygoscelis adeliae) under continuous daylight in Antarctica. J. Pineal Res. 199 1 10:2‐8.Abstract:Circadian rhythms of melatonin secretion in birds are influenced by daylength and light intensity. Daily patterns of melatonin secretion were examined in Adelie penguins (Pygoscelis adeliae) under natural continuous daylight at Cape Bird, Antarctica (77$S). Although daylight is continuous during the Antarctic summer there was a marked daily cycle of light intensity. However, there was no relationship between mean plasma melatonin levels and time of day in groups of 2–10 penguins sampled at 2–3 h intervals in November, December, or January. Mean melatonin levels over 24 h in groups of birds from which single samples were collected, or in groups of birds sampled repeatedly through cannulae, were low (12.4 ± 1.2 pg/ml‐28.8 ± 4.4 pg/ml for 4 sampling periods; n = 22‐163). Levels in individual birds were, however, quite variable and ranged from 5.0–68.1 pg/ml. Some birds had periods of increased melatonin levels that tended to occur during the time of day when light intensity was least. One bird had a clear low amplitude melatonin rhythm with a peak during the time of least light intensity. These results, the first for any bird under a natural photoperiod, indicate that melatonin secretion is inhibited by natural continuous daylight, but that it is not abolished.
Human nocturnal blood melatonin and liver acetylation status
Authors: Smith John A. , Helliwell Philip S. , Isdale Amanda , Astbury Carol , Padwick David J. , Bird Howard A. 
Published: February 2007

Smith JA, Helliwell PS, Isdale A, Astbury C, Padwick DJ, Bird HA. Human nocturnal blood melatonin and liver acetylation status. J. Pineal Res 199 1 : 10: 14‐1 7.Abstract:The human dark phase melatonin concentrations exhibit a wide range of values. In an attempt to explain this variation, we measured 2250–2305 h melatonin levels by radioimmune assay in eleven fast and eleven slow acetylator phenotypes. No statistical difference between the two groups existed, suggesting therefore that such variations are not due to acetylator status. The study revealed a negative relationship between body weight or area and nocturnal melatonin concentration. No correlation was found between dark phase melatonin levels and age, anxiety, depression, or sleep rating.
Effect of dose and time of melatonin injections on the diurnal rhythm of immunity in chicken
Authors: Skwarlo‐Sońta Krystyna , Thaela Mary‐Jane , Gluchowska Boźena , Stȩpień Diana , Jagura Monika 
Published: February 2007

Skwado‐Solita K, Thaela M‐J, GXuchowska B, Stepien D, Jagura M. Effect of dose and time of melatonin injections on the diurnal rhythm of immunity in chicken. J Pineal Res 1991: 10:3&35.Abstract:The effect of daily melatonin injections on the diurnal rhythm of immune parameters was examined in White Leghorn cockerels, kept from hatching in L:D 12:12 conditions. Subcutaneous injections of melatonin were made at the beginning of darkness or 4 h earlier for four weeks starting from one week of life. The melatonin dosage in one group was raised (10, 13, 16, and 20 ng per bird daily, respectively) during four consecutive weeks. The two other doses were 10 and 500 times higher and were increased every week as well. Control birds received equivalent injections of vehicle. Three‐week‐old chickens were immunized ip with sheep red blood cells and reimmunized one week later. Five‐week‐old birds were sacrificed during a 24 h period every 4 h. The existence of the diurnal rhythm was evaluated by cosinor analysis. The diurnal rhythm of total white blood cells and serum agglutinins was more dependent on the time of melatonin injections than on the hormone used. The effect of melatonin injections on the level of immune parameters examined was also dependent on the time of sample collection. Results obtained indicate the participation of pineal gland in the regulation of the diurnal rhythm of the examined indices of avian immune system function that exhibit diurnal changes in sensitivity to exogenous melatonin.
Effects of melatonin on the cell cycle kinetics and “estrogen‐rescue” of MCF‐7 human breast cancer cells in culture
Authors: Cos Samuel , Blask David E. , Lemus‐Wilson Athena , Hill Anna B. 
Published: February 2007

Cos S, Blask DE, Lemus‐Wilson A, Hill AB. Effects of melatonin on the cell cycle kinetics and “estrogen‐rescue of MCF‐7 human breast cancer cells in culture. J Pineal Res 1991:10:3642.Abstract:Melatonin has been shown to have a direct inhibitory action on the proliferation of estrogen‐responsive MCF‐7 human breast cancer cells in culture. In the present study, we examined by flow cytometry whether this inhibitory effect might be exerted on the G1 phase of the cell cycle, thus causing a transition delay into the S phase. In order to further verify this hypothesis we tested the ability of estradiol to “rescue” MCF‐7 cells from melatonin inhibition, and the potential of this indoleamine to block the ability of estradiol to rescue the cells from tamoxifen inhibition. Following five days of incubation, melatonin (10‐9M) increased the fraction of cells in G1 of the cell cycle while simultaneously causing a 50% reduction in the proportion of cells in S phase. The antiproliferative effect of melatonin (11‐5M) was prevented by the simultaneous treatment of the cells with estradiol (10‐8M) in clonogenic soft agar culture, or reversed by the addition of estradiol to cells previously incubated with and inhibited by melatonin (10‐9M) in monolayer culture. Additionally, melatonin blocked the estrogen‐rescue of tamoxifen‐inhibited cells in both types of culture systems. These results support the hypothesis that the antiproliferative effect of melatonin, like tamoxifen, is cell cycle specific by causing a G1‐S transition delay. These results also indicate an important interaction of melatonin with estrogen‐mediated mechanisms of MCF‐7 cell proliferation.
Chronic administration of sublethal doses of carbaryl increases pineal N‐acetyltransferase and hydroxyindole‐O‐methyltransferase activities and serum melatonin levels
Authors: Attia Ahmed M. , Reiter Russel J. , Withyachumnarnkul Boonsirm , Mostafa Mostafa H. , Soliman Salah A. , El‐sebae Abdel‐Khalek H. 
Published: February 2007

Attia AM, Reiter RJ, Withyachumnarnkul B, Mostafa MH, Soliman SA, El‐sebae A.‐K.H. Chronic administration of sublethal doses of carbaryl increases pineal N‐acetyltransferase and hydroxy‐0‐ rnethyltransferase activities and serum melatonin levels. J Pineal Res 1 99 1 1 0149‐54.Abstract:The purpose of this study was to examine the effects of chronic administration of sublethal doses of carbaryl on pineal melatonin synthesis. N‐methyl 1‐naphthylcarbamate (carbaryl) (8.33 mg/kg B.W. daily) was administered orally to adult male albino rats for 6 successive days. Nocturnal (0100) N‐acetyltransferase and hydroxyindole‐0‐methyltransferase activities were increased (roughly 75% and 60%, respectively) by carbaryl administration; likewise, carbaryl augmented serum melatonin levels at 2300. Pineal tryptophan, 5‐hydroxytryptophan, serotonin, and 5‐hydroxindole acetic acid levels were unaffected at all three time points. The results indicate that the carbamate pesticide, i.e., carbaryl, modifies pineal melatonin synthesis in vivo.