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Try out PMC Labs and tell us what you think. Learn More. We hypothesized that a ificant portion of sexual differentiation of mouse external genitalia occurs postnatally. To establish a baseline of normal development to which genital abnormalities could be compared, we determined morphometric measurements and morphological descriptions of the postnatal period of sexual differentiation in mice from birth to 21 days postnatally.
Mice were studied by age group, including ages 0 to 1, 2 to 3, 4 to 5, 10 and 21 days. Three-dimensional reconstructions were created to visually compare differences. Morphometric measurements were made of the distal mouse external genitalia and compared across age groups, and between males and females. The morphology of male and female mouse external genitalia is similar at 0 to 1 days but undergoes dramatic changes during 21 days.
The changes include the development of mesenchymal extensions, which in males form the male urogenital mating protuberance and erectile bodies, as well as comparable structures in females. Differences in morphometric measurements in homologous males and females became pronounced during 0 to 21 Lady looking sex Baskin, serving as a baseline for recognizing the genesis of malformations of the mouse external genitalia. Male and female mouse external genitalia are similar morphologically and morphometrically at birth but achieve dramatic differences by age 21 days, suggesting that a ificant portion of sexual differentiation in the mouse occurs after birth.
We described these changes using novel, accurate morphometric measurements and 3-dimensional reconstruction. These will be useful for studying abnormal sexual development of the mouse external genitalia. Sexual differentiation of the ExG is a complex process. In humans the process of sexual differentiation of the ExG starts around week 8 of gestation and is complete by the early second trimester.
In mice ExG development begins with assembly of the ambisexual GT from embryonic days 12 to Sexual differentiation into male and female phenotypes begins at 16 days of Lady looking sex Baskin. While male and female mice can be sexed visually at birth based on the longer anogenital distance and larger size of the GT, by histological criteria the male and female ExG appear undifferentiated at birth.
We ly described the adult mouse penis, which is the end point of sexual differentiation, using morphometric measurements, histology, 3DR and scanning electron microscopy. In contrast, initial viewing of serial sections of the GT at day 0 revealed strikingly similar male and female morphology with several structures completely absent in each gender compared to day 21 of life or adulthood.
This suggests that most sexual differentiation develops after birth. We hypothesized that a ificant portion of sexual differentiation of the mouse ExG occurs postnatally. We describe the normal anatomy and morphological changes of the distal ExG in male and female mice from day 0 to 21 of life using serial histological sections, morphometric measurements, statistical analysis and 3DRs. We present our system of morphometric measurements and analysis, which Lady looking sex Baskin be used in future studies to measure and report morphometric changes related to abnormalities in mouse sexual differentiation, such as hypospadias.
The University of California-San Francisco animal care committee approved the protocol. CD-1 mice were chosen because they are outbred and a commonly used strain. Day of birth was deated as day 0. Pups were sacrificed at days 0 to 1, 2 to 3, 4 to 5, 10 and 21 of life with at least 2 litters sacrificed per age range. We measured structures of the distal ExG by counting the of consecutive serial transverse sections that contained the structure of interest.
Relational measures were obtained by counting the of Lady looking sex Baskin transverse sections from 1 point of interest to another. Only well aligned specimens were included. We defined a well aligned specimen as one in which the penile or clitoral body was a circle or ellipse in the horizontal plane, paired right and left structures appeared within 5 serial sections and all structures could be measured.
A specimen in which the penile or clitoral body was an ellipse in the vertical plane suggested that the specimen was tilted ificantly in the vertical plane, which affects the of relational measurements.
A specimen in which paired right and left structures did not appear around Lady looking sex Baskin same serial section suggests that the specimen was tilted ificantly in the horizontal plane. A digital image was obtained of each section and aligned with the section using the software. Structures of interest in the distal ExG were outlined in aligned serial sections using each section and 3DRs were generated.
Morphometric measurements were compared across age groups using 1-way ANOVA with the Bonferroni correction for multiple comparisons across groups. Select morphometric measurements were compared between males and females using the 2-tailed t test for different age groups.
Figure 1 shows a 3DR and transverse sections of the ExG of a 4 to 5-day-old male mouse to illustrate the relational measurements that were made. A critical point was to define the start of the penile urethra. This is important because there are 2 Lady looking sex Baskin lined tubes in developing and adult male ExG, namely the preputial space and urethra, which are continuous with each other at the urethral meatus.
The prepuce detaches from the penis distal by delamination of the solid preputial lamina, which has attachments to epithelia circumscribing other structures fig. The start of the penile urethra was defined as the Lady looking sex Baskin where an epithelium lined tube was completely surrounded by penile stroma in transverse section fig. The overall length of the distal penis was measured from the tip of the bifid extension of the MUMP to the point where the only epithelium remaining in the penis was urethral epithelium on transverse section fig. Ventral confluence of the prepuce was defined as the point in serial sections where preputial stroma became confluent across the ventral midline fig.
Transverse sections A to F of penis of 5-day-old CD-1 mouse in dorsal 1 and lateral 2 views, and 3DRs without prepuce elongated by factor of 3. Red lines indicate where transverse sections correspond to 3DRs.
Red arrows A to D indicate preputial space not shown on 3DRs. Yellow double arrows A to F indicate prepuce stroma not shown on 3DRs. Orange arrows and outlines indicate penile urethra E and F. Black arrows indicate where penile stroma completely surround epithelial tube, indicating penile urethra E. Blue outlines indicate central penile body B to F. Figure 2 shows a day-old CD-1 mouse penis with an intact prepuce. The overlying 3DRs are approximately to scale and show the relationship between the prepuce and penis. Note how prepuce extends distal to MUMP tip so that most elevation on perineum is prepuce.
At age 10 days ventral confluence of preputial is distal to MUMP tip. Composite provides reasonably accurate representation of relative position of developing penis to hair bearing elevation in perineum, which is prepuce. The table lists measurements of the developing mouse penis by age category. Penile length increased ificantly from days 0 to 21 fig.
Morphogenesis of the Lady looking sex Baskin male ExG was characterized in part by the development of 3 paired mesenchymal extensions of the central penile mesenchyma, including paired distal mesenchymal extensions from the bifid MUMP tip, paired lateral mesenchymal extensions form the MUMP corpus cavernosum and paired ventral mesenchymal extensions that formed the corpus cavernosum urethrae. The length of these 3 paired extensions increased ificantly from day 0 to 21 see Table. Relational measurements of interest included the distance from the MUMP tip to the ventral mesenchymal extension tip, to the lateral mesenchymal extension tip, to the beginning of the urethra and to the ventral preputial confluence see table.
The relational measurement that changed the most from day 0 to 21 was the point of ventral preputial confluence in relation to the MUMP tip. Ventral preputial fusion was proximal to the MUMP tip at day 0 to 1 and quite distal to the MUMP tip by day 21, as denoted by negative values see table. An additional measurement made at day 21 but not at earlier time points was the length of the ventral cleft in the MUMP ridge. Figure 3 shows the development of the ExG of male CD-1 mice from birth to 10 days, as represented by 3DRs with the prepuce removed.
In contrast, figure 2 shows the prepuce. Morphological changes in the distal male mouse ExG were characterized by an overall increase in the length of all parameters and the development of the 3 paired mesenchymal extensions fig. The MUMP ridge ventral cleft was not discernible at earlier ages. Red lines indicate where 3DRs correspond to transverse sections. Note lateral 1 and ventral 2 3DR views. Semitransparent penile body and CCG demonstrate Lady looking sex Baskin and lateral mesenchymal structures and extensions, and distal tips of ventral mesenchymal extensions proximal to ventral stromal confluence of MUMP ridge 3.
Red arrow indicates preputial space A and B. Double yellow arrows denote preputial stroma A to D. Blue outlines indicate central penile mesenchyma B to D. Orange outlines and arrow indicate penile urethra C and D. The fully formed clitoral body was defined as the point where a U-shaped clitoral epithelial lamina was fully formed and, therefore, not connected to any other epithelia fig.
The FUMP was defined as a midline distal mesenchymal structure with a bifid tip extending distal to the fully formed Lady looking sex Baskin body, appearing homologous to the MUMP fig. The start of the female urethra was Lady looking sex Baskin as the point where the urethral epithelial tube was completely surrounded by stroma and not attached to other epithelial Lady looking sex Baskin fig.
The ventral confluence of the female prepuce was defined as the point in transverse section where stroma were confluent across the ventral preputial midline. Dorsal 1 and lateral 2 3DRs elongated by factor of 3 without prepuce, and transverse sections A to F demonstrate morphometric measurements in day-old CD-1 female mouse. Red arrows indicate preputial space A to D. Yellow double arrows indicate preputial stroma A to F shown in 3DRs. Orange outlines and arrows indicate urethral stroma and urethra D to F.
Black arrows indicate point where urethral epithelium is not in contact with other epithelium, indicating start of female urethra E. The table lists ExG measurements of female CD-1 mice by age category. The distal ExG in female CD-1 mice did not change as dramatically as in males in overall length from day 0 to As in males, the development of the distal ExG in females was characterized by 3 paired mesenchymal extensions of the central clitoral mesenchyma, including paired distal extensions of the FUMP, paired lateral mesenchymal extensions and paired ventral mesenchymal extensions.
The length of these 3 paired mesenchymal extensions increased ificantly from day 0 to 21 see table. The relational measurement with the most dramatic change from day 0 to 21 was the point of ventral preputial confluence across in relation to the FUMP tip, while the ventral preputial confluence was proximal to the FUMP tip at day 0 to 1 and then distal to the FUMP tip by day 21 see table. Figure 3 shows the development of the distal ExG in female CD-1 mice from age 0 to 10 days as 3DRs with the preputial skin and stroma removed.
The male and female murine ExG were most similar in appearance at day 0 to 1, as shown by 3DRs fig. The smallest difference between males and females was seen at day 0 to 1.
Figure 6 shows how morphometric measurements evolved with time in male and female mice. In general, male and female ExG measurements and 3DR appearance were most similar in the youngest age group at day 0 to 1.Lady looking sex Baskin
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