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Journal of the Anatomical Society of India

Morphometric Study of Seminal Vesicles of Rat in Normal Health and Stress Conditions

Author(s): Mukerjee B and Rajan T

Vol. 55, No. 1 (2006-01 - 2006-07)

Jawaharlal Institute of Postgraduate Medical Education and Research, Pondicherry – 605 006, India.

Abstract:

Male albino rats were studied from birth to postnatal day 98. Prolonged intermittent stress was inflicted. Consequent upon stress, body weight and weight of the seminal vesicles declined. Using morphometric methods, volume of the components of the seminal vesicle were estimated. Details of the results showed that between day 42 and day 98 in normal control rats, body weight and weight of seminal vesicle increase. The height of the epithelium increase approximately three fold, nuclear diameter increase to nearly double. Absolute volume of the epithelium multiplied enormously followed by the volume of the stroma. The luminal space widen with age of the normal rats. All parameters were depressed due to prolonged stress. On withdrawal of the prolonged stress, the size of the seminal vesicles and the prolific histo-architecture tend to build up.

Key words: Rat, Seminal vesicle, Stress, Morphometry.

Introduction

In the past, morphometric studies were restricted to quantitative description of tissue structures, and therefore they are essentially subjective. In recent years, the application of morphometric and stereological techniques has increased in biomedical research and been well recognized as a new approach in morphological study as well.

In our recent paper, (Mukerjee and Rajan, 2004) we have presented the result of a morphometric study of prostate gland of rat. In sequence of the same, here we present the results of morphometric study of seminal vesicles of rats. The seminal vesicles have been studied in many ways, e.g. development and growth (Patten, 1953; Sadler, 2004; Moore and Persaud, 2003).

Research reports on the seminal vesicles have been documented in subjects like human by Riva (1967) and Brewster (1985). Among the animals, rats and mice have always been the popular choice. Rat has been used as experimental model by Moore et al (1930b), Allison and Cerley (1972) and Gottreich et al (1996). Seminal vesicle of mice was extensively studied by Cunha (1972, 1973, 1976). Later on Lung and Cunha (1981) published extensive study on seminal vesicles from neonatal period to adulthood in mice. Equally, extensive literature has accumulated on the seminal vesicles of guineapig (Al-Zuhair et al, 1975; Tse and Wong, 1980; Tam and Wong, 1991). Seminal vesicles of a few other animals like Shrew – Mathur and Goyal (1974), Ram – Ploen (1980), Deer – Chapman and Chapman (1980) and Buffalo – Abou-Elmagd et al (1992).

In this report of the present study on the seminal the epithelium, its nuclear size and the absolute volume of the epithelium, stroma and lumen of the organ in health as well as in stress state.

Material and Methods

The animals, the period of study, the appliances used for production and application of stress and the stereological method used are same as employed in our previous paper (refer, J Anat Soc India 53 (2), pp 29-34; 2004). In addition to the same here we add method of collection of seminal vesicle, and measurement of the height of epithelium, size of the nucleus and volumetric calculations of the seminal vesicles described below.

Tissue collection:

Under dissection microscope, bilaterally situated seminal vesicles excluding the ampula of vas deference and ejaculatory duct was dissected out. The dissected material was immediately weighed in mg on a sensitive digital balance without loss of seminal fluids. Paraffin sections were made and stained by haematoxyline and eosin stains. Height of the epithelium of mucosa of the seminal vesicle and diameter of the nucleus of the stained sections were measured by using an ocular micrometer scale (Fig.1).

Volume Estimation as Vvi = Pi / Pt
(Weibel and Elias, 1967)
Where:
Vvi = Volume fraction
Pi = Number of intercepting points of the reticule on the tissue component.
Pt = Total number of intercepting points in the reticule.

Result

The weight of the seminal vesicle is the combined weight of the organ and the secretion contained in it (Table I; Fig.2)(Fig.2 Unavailable). Between day 42 and day 98 there is 44.87 times increase in the weight of the seminal vesicle of healthy rats, out of which only 16.37 times rise in weight is between day 42 and day 70. Thus, it appears that the weight of the seminal vesicle increase rapidly when the rats presumably have achieved sexual maturity. On the other hand, during the same period, condition gained 15.63 times. After day 70, the increase of the weight of seminal vesicle expedite in both groups but the increase was significantly less in the stressed rats.

The mucosal epithelium is essentially columnar but at place where mucosal folds are compressed some portions of the epithelium was pseudostratified columnar. The nucleus of the epithelium of healthy as well as stressed rats was neatly spherical with smooth periphery. The height of the epithelium gradually increased it was remarkable after day 56 in normal healthy rats. Increase in epithelial height was slower in stressed rats. Concurrent with the total height of the epithelial cells the diameter of the nuclei of the epithelial cells were proportionate and uniform in all stages of the study.

D = mean diameter (Ám) of the nucleus of the cell L = Length of the nucleus (μm) B = Breadth of the nucleus (μm)

Table I. Weight of Seminal Vesicle (mg ▒ SD) of Albino Rat in Normal and Under Stress Conditions

Age (days) Weight Normal (Cont.) Stressed (Exp.)
42 5.34 ± 1.51 4.82 ± 0.86
49 8.88 ± 1.58 7.28 ± 1.56*
56 39.00 ± 9.37 33.71 ± 12.67*
63 60.42 ± 1.11 46.41 ± 10.11***
70 87.47 ± 13.15 75.47 ± 14.72***
77 127.30 ± 9.86 105.52 ± 11.54**
84 197.26 ± 11.50 180.62 ± 33.39***
91 232.73 ± 14.58 188.93 ± 14.93***
98 239.73 ± 21.77 209.36 ± 37.26***
* P < 0.05; ** P < 0.01; *** P < 0.001

Table II. Height of the Epithelial Cells and their Nuclear Diameter (mm) in Seminal Vesicles of Rat

Age
(Days)
Height of
Epithelial Cells
Nuclear Diameter of
Epithelial Cells
Normal
(Cont.)
Stressed
(Exp.)
Normal
(Cont.)
Stressed
(Exp.)
42 6.4 ± 0.66 5.1 ± 0.66** 3.05 ± 0.30 2.56 ± 0.38**
56 8.66 ± 0.63 6.2 ± 1.22*** 3.91 ± 0.32 3.55 ± 0.40**
70 12.26 ± 0.58 8.93 ± 0.98*** 4.58 ± 0.22 4.03 ± 0.42**
84 15.2 ± 0.66 11.26 ± 1.80*** 5.38 ± 0.39 4.33 ± 0.54***
98 17.2 ± 0.67 12.9 ± 1.46*** 5.61 ± 0.36 5.05 ± 0.35**
** P < 0.01; *** P < 0.001

Absolute volume of the epithelium of the seminal vesicle of healthy rats is 0.75 ▒ 0.24 cumm at about puberty. It increase more than 50 times by day 70 and keeps increasing due to proliferation of the epithelial cells; it is more than five times less prolific in the rats under stress.

The stroma consisted of smooth muscle fibers. It becomes denser with sexual maturity in healthy adult rats. It is significantly scanty in stressed rats even after achieving sexual maturity.

On day 42 postnatal the seminal vesicles of rat were tubular structures. The lumen of the tubules were compact with a narrow opening lined by pseudostratified columnar epithelium. By day 70, the lumen became wider. The cells lining surface of the epithelium around the lumen were generally columnar except at acute folds where there were pseudostratified in appearance. The volume of the lumen enlarged 121.43 times between day 42 and day 98 in normal healthy rats but in the rats under chronic stress it enlarged only 41.03 times (Table III; Fig.4).

Age
(Days)
Absolute volume of Epithelium Absolute volume of Stroma Absolute volume of Lumen
Normal (Cont.) Stressed (Exp.) Normal (Cont.) Stressed (Exp.) Normal (Cont.) Stressed (Exp.)
42 0.75 ± 0.24 0.62 ± 0.28** 3.06 ± 1.39 2.70 ± 1.36 1.22 ± 0.39 1.79 ± 1.24***
56 4.17 ± 0.83 3.34 ± 1.18*** 4.83 ± 1.26 4.60 ± 1.15 3.12 ± 1.41 4.61 ± 1.19***
70 53.18 ± 7.36 9.79 ± 2.80*** 28.68 ± 6.58 7.80 ± 2.36*** 40.93 ± 11.44 15.08 ± 3.01***
84 150.62 ± 16.78 40.48 ±10.39*** 76.20 ± 14.25 29.89 ± 9.86*** 69.67 ± 18.76 39.43 ± 11.81***
98 171.67 ± 24.14 70.65 ±11.31*** 90.2 ± 13.45 62.07 ± 12.06*** 146.95 ± 25.48 73.45 ± 14.45***
** P < 0.01; *** P < 0.001

Discussion

Morphometry by light microscopy is best performed when the organ has reasonably developed to a sizable dimension. The seminal vesicles in rats as well as mice develop as lateral outgrowths from the caudal end of each mesonephric duct (Moore and Persaud, 2003; Sadlar, 2004). In mouse, morphogenesis of the seminal vesicle begins approximately on the 15th day of gestation (vaginal plug – day 0) (Lung and Cunha, 1981). After 17th day, buried in the surrounding mesenchyme behind the developing bladder, tips of the seminal vesicle forming cane-like structure make there appearance, but these tiny structures could not be handled for light morphometric study. In the current literature (Gray’s Anatomy, 2005) it is stated that the seminal vesicles develop slowly until the onset of puberty. In perspective of the same, the present work spanning 8 weeks(day 42 to day 98) stands feasible. In morphology and quantitative morphometry size of the organ may play much role as we find notable variation in size of the seasonally breeding animals (Chapman and Chapman, 1980; Siwela and Tam, 1984).

We have confined our study in a specific season so that the seasonal alteration may not effect the hormonal status of the animal. However, in any season, the androgenic activity resulting on the volumetric morphometry relates to important difference on testis and accessory sex organs in males (Amuller et al, 1985; Amuller, 1989; Amuller et al, 1998; Gattreich et al, 1996). Action of androgen in the architectural development of the seminal vesicle (Cunha, 1972; Cunha, 1973; Lung and Cunha, 1981) proves supportive to the findings of the present study. As for the absolute volume of each component of the mucosa of seminal vesicle, our findings substantiates many of the earlier reported documents (Dean, 1963; Dean 1964; Dean and Wurzelmann, 1965; Cunha, 1976). Present observations indicate that till day 56 the structural components of the seminal vesicles in rats are dormant but thereon a spert occurs indicating sexual maturity of the rat.

Due to variability in the epithelial shape, in this work, the epithelial height was measured at place where the epithelial cells stand erect on the basement membrane. Huand Tam and Wong (1992) reported that in guineapig the epithelium accounts for 9.6% of the total volume of the organ. Observations of the present study show that in active young adulthood of rat up to day 56, the epithelium to stroma ratio is almost similar in both, normal and stressed rats. Later on, due to rapid proliferation of the epithelium and stroma, the difference between the absolute volume of the epithelium and stroma becomes much greater. In humans, the volumetric quantity of the epithelium and muscular tissue increase with age upto 45 years, then degenerative changes begin (Brewester, 1985). Seminal vesicles of rat have very thin lamina propria. At any point of time it is only 1% or less of the total volume of the organ (Tam and Wong, 1991). The seminal vesicles are relatively solid with little lumen up to day 42 or puberty but with age the lumen widens remarkably. Tse and Wong (1980) recorded that in a well grown healthy guinea pig the lumen accounts 70% of the total area. In summary of the present study, it can be concluded that consequential effect of prolonged stress through the pre-weaning and post-weaning period of laboratory rats, the weight of seminal vesicles and the histological features of the mucosa were severely effected.

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