Effect of continuous light on the incidence of 9,10-dimethyl-1,2-benzanthracene induced mammary tumors in female Holtzman rats

Kothari, Lalita S.; Shah, Prabhaker N.; Mhatre, Molina

doi:10.1016/0304-3835(82)90012-x

Cited by 17 publications

(10 citation statements)

References 8 publications

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“…In contrast, Hamilton [ 19691 reported increased tumor incidence under similar experimental conditions. Something similar was observed by Kothari et al [1982] in rats exposed to constant light at the time of birth. However, the interpretation of these observations is complicated by the fact that, whereas in the study of Kothari et al [1982] exposure to constant light resulted in formation of almost exclusively adenocarcinomas, 93% of tumors in the study of Hamilton [1969] were fibroadenomas.…”

Section: Discussionsupporting

confidence: 80%

“…Something similar was observed by Kothari et al [1982] in rats exposed to constant light at the time of birth. However, the interpretation of these observations is complicated by the fact that, whereas in the study of Kothari et al [1982] exposure to constant light resulted in formation of almost exclusively adenocarcinomas, 93% of tumors in the study of Hamilton [1969] were fibroadenomas. It has been argued further that the observations of Kothari et al can be explained either on the basis of the stimulatory effects of light or inhibitory effects of short photoperiod or both [Blask, 19841, because the control animals were kept in short photoperiod (10 hr of light), which is stimulatory to the pineal gland.…”

Section: Discussionsupporting

confidence: 80%

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Inhibitory Effects of Superior Cervical Ganglionectomy on Dimethylbenz(a)anthracene‐Induced Mammary Tumors in the Rat

Chang¹,

Spaulding²,

Tseng³

1985

Journal of Pineal Research

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The role of the pineal in regulating the oncogenic processes was explored in Sprague-Dawley female rats by comparing incidence and growth of mammary tumors in animals subjected to superior cervical ganglionectomy (SCGx) or blinding and anosmia (BAs) with that of intact rats treated with 7-12-dimethylbenz(a)anthracene (DMBA). The surgery was performed at the age of 56 days, 1 day following the administration of the carcinogen. Growth of mammary tumors was studied, and 15 weeks later the rats were sacrificed by decapitation and the activity of the pineal hydroxyindole-O-methyltransferase (HIOMT) was determined. Carcinostatic effects of similar magnitude were present in both SCGx and BAs groups as evident from tendency toward reduced tumor incidence and decreased total tumor mass. Ganglionectomized rats developed significantly smaller numbers of tumors than intact control animals. A trend toward reduced tumor number and increased tumor regression was evident in the BAs group. Although there was no significant difference in tumor volumes among the groups, BAs animals showed a distinct trend toward smaller tumor volumes at the termination of the experiment. Despite similar carcinostatic tendencies, SCGx rats had significantly lower HIOMT activity than BAs animals. The possible existence of multiple carcinostatic mechanisms in BAs and SCGx rats is discussed.

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Section: Discussionsupporting

confidence: 80%

Section: Discussionsupporting

confidence: 80%

Inhibitory Effects of Superior Cervical Ganglionectomy on Dimethylbenz(a)anthracene‐Induced Mammary Tumors in the Rat

Chang¹,

Spaulding²,

Tseng³

1985

Journal of Pineal Research

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“…Investigation of light effects on mammary tumorigenesis in rodents began in the 1960s . For both chemically induced and spontaneous tumors, most of these studies showed an increase in tumor incidence and number by exposure to a constantly lighted environment compared with a 24‐hour alternating schedule of light and dark (eg, 24 hours of light vs 12 hours of light:12 hours of dark).…”

Section: Animal Models Of Light and Cancermentioning

confidence: 99%

“…Investigation of light effects on mammary tumorigenesis in rodents began in the 1960s. [69][70][71][72][73][74][75][76][77][78] For both chemically induced and spontaneous tumors, most of these studies showed an increase in tumor incidence and number by exposure to a constantly lighted environment compared with a 24-hour alternating schedule of light and dark (eg, 24 hours of light vs 12 hours of light:12 hours of dark). Beginning in the 1980s, researchers focused more closely on the ability of melatonin to inhibit mammary carcinogenesis and on the impact of a constant light environment in animal rooms on mammary tissue development, and major effects were reported.…”

Section: Animal Models Of Light and Cancermentioning

confidence: 99%

Breast cancer and circadian disruption from electric lighting in the modern world

Stevens

Brainard²,

Blask

et al. 2013

CA A Cancer J Clinicians

269

201

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Breast cancer is the leading cause of cancer death among women worldwide and there is only limited explanation of why. Risk is highest in the most industrialized countries but also rising rapidly in the developing world. Known risk factors account for only a portion of the incidence in the high risk populations, and there has been considerable speculation, and many false leads, on other possibly major determinants of risk such as dietary fat. A hallmark of industrialization is the increasing use of electricity to light the night, both within the home and without. It has only recently become clear that this evolutionarily new, and thereby unnatural exposure can disrupt human circadian rhythmicity, of which three salient features are melatonin production, sleep, and the circadian clock. A convergence of research in cells, rodents, and humans suggests that the health consequences of circadian disruption may be substantial. An innovative experimental model has shown that light at night markedly increases growth of human breast cancer xenografts in rats. In humans, the theory that light exposure at night increases breast cancer risk leads to specific predictions that are being tested epidemiologically: evidence has accumulated on risk in shift workers, risk in blind women, and impact of sleep duration on risk. If electric light at night does explain a portion of the breast cancer burden then there are practical interventions that can be implemented, including more selective use of light, and adoption of recent advances in lighting technology and application.

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“…The influence of the pineal gland on the development of DMBA-induced mammary tumors in rodents has been studied usually in albino rats, in experiments that modified the levels of pineal function through manipulations such as: exposure to various photoperiods [Aubert et al, 1980;Bartsch and Bartsch, 1981;Hamilton, 1969;Kothari et al, 1982Kothari et al, , 1984Shah et al, 19841; surgical removal of the gland [Aubert et al, 1980;Kothari et al, 1984;Sinchez-Barcelo et al, 1988;Tamarkin et al, 1981, 19851; superior cervical ganglionectomy [ Chang et al, 1985, 19861; administration of pineal extracts [Dilman et al, 1979;Lapin and Ebels, 19761; or administration of melatonin, either in vivo [Aubert et al, 1980;Bartsch and Bartsch, 1981; Kothari, 1987;Shah et al, 1984;Tamarkin et al, 1981; Wrba et al, 19861 or in vitro [Blask and Hill, 19861. The parameters most frequently studied are the latency time of tumor appearance, their incidence, the number and size of tumors, and their rate of growth.…”

Section: Introductionmentioning

confidence: 99%

Histopathologic Features of DMBA‐Induced Mammary Tumors in Blind‐Underfed, Blind‐Anosmic, and Blind Cold‐Exposed Rats: Influence of the Pineal Gland

Cos

Garijo

Corral

et al. 1989

Journal of Pineal Research

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The influence of the pineal gland on the histopathologic changes induced in mammary glands by 7, 12-dimethylbenz(a)-anthracene (DMBA) has been studied. To achieve the maximum expression of pineal action in animals, 28-day-old female Sprague-Dawley rats were subjected to one of the following treatments: blindness + olfactory bulbectomy (BA), blindness + underfeeding (BU), or blindness + cold exposure (BC). Half of the rats in each group were also pinealectomized. Animals that were intact or only pinealectomized served as controls. Each animal received a single intragastrical dose of DMBA (20 mg) 4 weeks after performing the treatments mentioned above. At 28 weeks of age animals were sacrificed, and mammary tumors as well as mammary glands without macroscopic lesions were collected. Animals of the BU group failed to develop any tumors throughout the 20-week control period. In the remaining groups, tumors were found; the relation between number of adenocarcinomas (AC) and fibroadenomas was similar, always with a greater incidence of ACs. Some ACs showed areas with changes in the ductal epithelium that are considered signs of tumoral regression; pinealectomized animals had the lowest incidence of ACs with signs of regression. Ductule hyperplasia, considered as a premalignant lesion, was more frequent in pinealectomized rats than in controls and in animals with enhanced pineal function (BA, BU, and BC). Some nontumoral mammary glands showed dysplastic lesions; these lesions were less frequent in BU rats than in controls. We conclude that suppression of pineal function sensitizes the ductule cells to the initiation of neoplastic processes and hinders the development of regressive changes.

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Effect of continuous light on the incidence of 9,10-dimethyl-1,2-benzanthracene induced mammary tumors in female Holtzman rats

Cited by 17 publications

References 8 publications

Inhibitory Effects of Superior Cervical Ganglionectomy on Dimethylbenz(a)anthracene‐Induced Mammary Tumors in the Rat

Inhibitory Effects of Superior Cervical Ganglionectomy on Dimethylbenz(a)anthracene‐Induced Mammary Tumors in the Rat

Breast cancer and circadian disruption from electric lighting in the modern world

Histopathologic Features of DMBA‐Induced Mammary Tumors in Blind‐Underfed, Blind‐Anosmic, and Blind Cold‐Exposed Rats: Influence of the Pineal Gland

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