Ventilatory parameters such as tidal volume, minute ventilation (VE), and inspiratory flow rate decrease in 24- vs. 12-month-old male and female rats. Differences between male and female values are maintained with age. Ventilatory response male and female rats exhibit to hypercapnia is altered by a decrease of the intercept, but not the slope value. The pattern of breathing exhibited by young females and males in response to hypercapnia (i.e. an increase of VT and f) is different than that noted in old males and females (i.e. an increase in VT only). In contrast, the ventilatory response both of slope and intercept male rats show by 24 months is decreased compared to the 12-month value; but the slope value is actually increased in the older vs. younger female rats in response to hypoxia.
This review examines and evaluates the literature on the ability of inorganic arsenic compounds to cause cancer in humans and laboratory animals. The epidemiological data that supports the position that inorganic arsenical derivatives are carcinogenic in humans is convincing and difficult to deny because of their consistency. These data are from studies of different occupational exposures such as smelter and pesticide workers, as well as from studies of drinking water, wines and medicinal tonics that contained or were contaminated with inorganic compounds of arsenic. Indeed, positive dose-response relationships between cancer incidence or mortality with many inorganic arsenical substances have been shown. Despite the presence of data which confuse the interpretation and evaluation of epidemiological data, associated neoplasms of the lungs, skin and gastrointestinal systems have been observed as a result of exposure to inorganic arsenic compounds.The mechanism of carcinogenicity of inorganic arsenical substances in humans is unknown. Inorganic arsenic compounds are not carcinogenic in laboratory animals by most routes of administration. However, further studies (subchronic, chronic, carcinogenic) using intratracheal and other conventional routes in other animal species would appear to be warranted. Moreso, especially since there is no evidence that organic arsenic compounds are carcinogenic in numerous mammalian species. Inorganic derivatives of arsenic are not mutagenic but may be teraiogenic. This latter conclusion is dependent on the method of administration and size of the dose, as well as on the species of animal used for the study.
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