By late 18 th or early 19 th century, albino rats became the most commonly used experimental animals in numerous biomedical researches, as they have been recognized as the preeminent model mammalian system. But, the precise correlation between age of laboratory rats and human is still a subject of debate. A number of studies have tried to detect these correlations in various ways, But, have not successfully provided any proper association. Thus, the current review attempts to compare rat and human age at different phases of their life. The overall findings indicate that rats grow rapidly during their childhood and become sexually mature at about the sixth week, but attain social maturity months later.
Sep 09, AGE DETERMINATION OF A LABORATORY RAT: COMMON METHODS. Numerous methods have been investigated in several studies to correlate the ages of small mammals with that of a human, i.e. using the weight of the eye lens, growth of molar teeth, counting of endosteal layers in the tibia, musculoskeletal growth along with the closure and Cited by: Simran 23 Age Equivalent Dating Private Escorts Navi, Mumbai. Hi! Age Equivalent Dating I am ready to have some fun! My name is Simran. I am 23 years old. People call me cute with chubby cheeks and trust me I smell like a rose Age Equivalent Dating always¦. I am bold and beautiful with a sense of humor and full of energy/ For many kids, 16 seems to be an appropriate age, but it may be entirely suitable for a mature year-old to go on a date, or to make your immature year-old wait a year or two. You can also.
For example, we all count Feb. However, there are two ways to calculate the age from Feb. If thinking Feb. If thinking both Feb. Both calculation results are reasonable. Similar situations exist for dates like Apr.
The confusion comes from the uneven number of days in different months. In our calculation, we used the former method. Date of Birth Age at the Date of. Financial Fitness and Health Math Other. During the fertile period in a female's life in most species, mating usually only occurs when a female is fecund at the time of ovulation in spontaneous ovulators or when primed to ovulate in reflex ovulators.
But, this integration of behavior and physiology can break down during aging in female rats. Most aging female rodent exhibits periods of persistent estrus constant sexual receptivity that are associated with tonic blood titers of estrogen and low levels of progesterone. Because the tonic estrogen secretion stimulates cornification of the vaginal epithelium, this state is also referred to as persistent vaginal cornification. This is the most common state of acyclicity in laboratory rats.
Similarly, the traditional marker of reproductive senescence in women is menopause, characterized by loss of menstrual or fertility cycles at midlife. Thus, during reproductive senescence, If the periods of post-senescence to death are compared, the following is found: Female rats live an average of days after senescence and female humans live an average of 10, days after senescence.
Thus, in the aged phase, Thus, the findings of this review suggest that although rats are indispensable elements of biomedical research,[ 3536373839404142 ] they are not a miniature form of humans;[ 1819 ] differences in anatomy, physiology, development and biological phenomena must be taken into consideration when analyzing the results of any research in rats when age is a crucial factor [ Table 2 ]. Special care should be taken when the intention is to produce correlation with human life.
It is important for a researcher to understand that the relative ages are different depending upon the stage of life; therefore, one has to determine the relevant age under investigation and what factors are being analyzed. For this, special attention is needed to verify the phase in days of the animal and its correlation with age in years of humans. Source of Support: Nil.
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Conflict of Interest: None declared. National Center for Biotechnology InformationU. Int J Prev Med.
Pallav Sengupta. Author information Article notes Copyright and License information Disclaimer. Correspondence to: Dr. E-mail: ni. Received Sep 9; Accepted Nov This is an open-access article distributed under the terms of the Creative Commons Attribution-Noncommercial-Share Alike 3.
This article has been cited by other articles in PMC. Abstract By late 18 th or early 19 th century, albino rats became the most commonly used experimental animals in numerous biomedical researches, as they have been recognized as the preeminent model mammalian system.
Keywords: Adult, human age, laboratory rat, physiology, puberty, rat age. Weight of eye lens: A useful measure Several studies have been performed using the weight of the eye lens in an attempt to use the development and growth of the lens throughout the mammalian life as an indicator that could help correlate the ages of different species. Teeth: A test of age Some researchers have developed methods to determine the ages of smaller mammals by using the growth of molar teeth, mostly by the molar ageing method or the crown method.
Counting endosteal layers in tibia Although many age determination techniques have been developed, the most widely used method in vertebrates involves a technique of counting endosteal layers in the tibia that allows to accurately determine the age of the experimental animals. Musculoskeletal examination: Epiphyseal closure Because dental development is minimal in fetal animals, most estimates of age rely on bone formation, especially long bone lengths, and also other bones such as the assessment of the development of the ilium and the petrous portion of the temporal.
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Open in a separate window. Figure 1. Correlation of body weight with different phases of postnatal days. Figure 2. Variations in body weight of male rats throughout the lifespan.
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Reproductive senescence: The rat is no longer sexually active! Post senescence: When the rat is aged! Table 2 Rat's age in human years. Sengupta P. Environmental and occupational exposure of metals and their role in male reproductive functions. Drug Chem Toxicol. Alves MJ, Colli W. Animal experimentation: A controversy about the scientific work. Choices criteria and current animal specimens.
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