No description available.

Considerable progress has been made in determining the factors in the environment which are responsible for the control of seasonal breeding in mammals and birds. There is less information available about how these factors produce their physiological effects. Light has been shown to be very important in the control of vole breeding seasons. Temperature may also have some effect. How these factors act is not known. As part of an attempt to understand how the breeding season of the vole is controlled, an investigation of some of its endocrine organs has been undertaken. Animals have been collected from the field in mid-summer (at the height of the breeding season) and in mid-winter (during the non-breeding period). A total of 174 adult field animals has been studied. As an approximate indication of the reproductive and endocrinological state of the animals, measurements have been made of the weights of their bodies, adrenals, thyroids, gonads and also certain accessory organs (the uteri of females in winter and the seminal vesicles and ventral prostates of males in both summer and winter). From the examination of this data it is clear that there are considerable endocrine changes with season. Furthermore, within both winter and summer populations reproductive sub-groups which show endocrine differences can be recognized. More detailed study of these endocrine differences has involved the use of cytological and histological methods. Because of the trophic control which the adenohypophysis exercises over the other endocrine organs, it may be presumed to be important in bringing about seasonal changes. It has, therefore, received particular study. The adenohypophyses of field animals have been examined by the methods of cytology, histochemistry and bioassay. In order to identify the cells responsible for the production of gonadotrophin and thyrotrophin, the pituitary function of laboratory bred animals has been altered by castration and the administration of goitrogens. In the adenohypophysis of the vole five cell types have been recognized. Oval basophils which are periodic acid-Schiff (PAS) positive and aldehyde fuchsin (AF) negative. They react to castration by degranulation and the subsequent formation of colloid filled castration cells. They are considered to secrete gonadotrophins. In field animals it has been found that the gonadotrophin producing cells (gonadotrophs) of winter animals are markedly different from those of summer animals. The gonadotrophin content of the pituitaries of male voles in winter and in summer has been studied by means of bioassay. In the summer the vole pituitary contains well granulated gonadotrophs and gonadotrophic hormone can be detected. In winter the gonadotrophs are vesiculated and no gonadotrophic hormone can be detected. This indicates that the granulated gonadotrophs contain hormone, but that the vesiculated cells are depleted of active gonadotrophic principles. Angular basophils which are PAS positive and AF positive. They react to the administration of goitrogen by the formation of colloid filled thyroidectomy cells. They are considered to secrete thyrotrophin. They show no marked changes with season, as would be anticipated from the lack of marked change in the thyroid itself. Round acidophils which show no marked change with season. This study provides no indication as to their function. A second type of acidophil which is numerous and well developed only in females which are pregnant or show signs of mammary development. It is suggested that they may be the source of prolactin. The adenohypophysis also contains a few large cells with poor staining qualities. They do not show any marked changes with season or in response to either castration or the administration of goitrogens. Their function is not known. The gonads were, in general, found to exhibit the expected seasonal change in activity. Sexually inactive males in winter may be divided into two groups on the basis of the structure of the tunica albuginea. It is suggested that these two groups represent, respectively, regressed males, which were sexually active in the preceding summer, and inhibited males, which were born late in the season and have never been sexually active. Similarly, on the basis of uterine weight, female voles in winter can be divided into two groups, parous and non-parous. The pituitary cytology of regressed and inhibited males, parous and non-parous females in winter is similar. In one winter collection the males show considerable evidence of being sexually active. This suggests the operation of a factor or factors other than light and temperature in the control of vole breeding seasons. These males were distinguished from the males in other winters by differences in pituitary cytology. The study of the pituitary suggests that gonadal changes at the end of the breeding season are secondary to changes in the pituitary. The alternative possibility, that the gonads are not competent to respond to pituitary hormones, was tested experimentally. Commercial gonadotrophins were injected into winter field animals and into laboratory bred animals whose sexual development had been inhibited by maintaining them on short days in the cold. The results suggest that the gonads of such animals are able to respond to gonadotrophins. The adrenal has been found to undergo marked changes in weight with season. In summer there is also a sex difference in adrenal weight. These weight changes can be correlated with striking histological differences in the inner regions of the adrenal cortex. In winter voles the adrenal cortex possesses a juxtamedullary zone. It is similar in cytological appearance to the X zone of mice and the two zones are seemingly homologous. The zone is present in all winter field voles, whether regressed or inhibited males, parous or non-parous females. The zone is small or absent in the adrenals of sexually active males. It must, therefore, be formed secondarily in the adrenals of regressed males. It also reappears in a similar, though not identical, form in males after castration. The zone can also disappear from females, but is present in an especially well developed form in all pregnant and lactating animals. Multipara and primipara differ in the details of the structure of the juxtamedullary zone. These changes are clearly related to sexual activity, but their significance is not known. The epithelium lining the ventral prostate is the site of marked stimulation in winter field males and in castrated laboratory animals. It is possible that the adrenal is the source of the hormone responsible for this stimulation. The zona glomerulosa and zona fasciculata of the adrenal cortex also show cytological and histological change with season. Their structure in the winter males which may have been sexually active suggests that these changes are not primarily related to sexual activity. The principal conclusions which can be drawn from this study are: That in the vole there is functional differentiation of adenohypophyseal cells. Two cell, types have been recognized which are clearly related to the production and secretion of gonadotrophic and thyrotrophic hormones, respectively. A third cell type is probably the source of prolactin. There is no evidence available on the function of the other two cell types which have been recognized. That the cessation of breeding in winter in the vole is apparently brought about by a cessation of both the synthesis and the secretion of gonadotrophin. That there are striking changes in the juxtamedullary region of the vole adrenal which appear to be related to sexual activity.

Introduction Previous studies on the glandular odontogenic cyst (GOC) have largely focused on the application of immunohistochemistry for determining how the GOC lining epithelium compares with that of other odontogenic cysts. Studies on the histochemical composition of the mucous cells in the GOC are, however, lacking. This study therefore aimed to determine the mucin phenotype of the mucous cells in the GOC and compared these findings with the mucous cells in the epithelial linings of other odontogenic cysts and with normal salivary gland mucous acinar cells. Materials and Methods Twenty-seven cases made up of 10 GOCs, 9 dentigerous cysts (DC) with mucous cells and 8 radicular/residual radicular cysts (RC) with mucous cells were stained using the combined alcian blue pH 2.5-PAS (AB-PAS) histochemical technique. AB-PAS allows for differentiation between acidic- (type I mucous cells), neutral- (type II mucous cells) and mixed mucin-containing cells (type III mucous cells). Submandibular, sublingual and palatal salivary gland tissue was also subjected to AB-PAS staining. The odontogenic cysts and salivary glands were evaluated for the frequency of type I, II and III mucous cells in these tissues. Results There were significant differences between the level of type I, type II and type III mucous cells within each of the three cyst types; GOC (p=0.006), DC (p=0.0004), RC (p=0.0017). There were no significant differences in the cell counts for each mucous cell type between the 3 cyst types;type I mucous cells (p=0.54); type II mucous cells (p=0.73) and type III mucous cells (p=0.97).All 3 odontogenic cysts showed a predominance of type III mucous cells and this mirrored the mucin phenotype of the submandibular and sublingual salivary glands. Conclusion The mucin phenotype of the GOC is shared by DC and RC with mucous metaplasia. The overlapping mucin phenotypes of the different odontogenic cysts unfortunately does not support the use of the AB-PAS stain as a potential histochemical marker to distinguish between the GOC and other odontogenic cysts with mucous metaplasia. Similarities in the mucin phenotype between odontogenic cysts, submandibular and sublingual salivary glands may suggest a common ectodermal histogenetic origin for the mucous cells in odontogenic cysts and major salivary glands.

No description available.

This study investigated some functional and biochemical characteristics of a bacteriolytic protein in the salivary glands of adult Aedes aecupti. A method for the isolation of this protein from other mosquito salivary gland components is also described. Based on some of its biochemical properties, this bacteriolytic protein can be classified as a lysozyme. This protein is strongly-linked to mosquito sugarfeeding activity because there is a statistically significant (P < 0.05) increase in the levels of lytic activity six hours before mosquitoes start to sugar feed. By its bacteriolytic action, it may function as a protective mechanism against bacteria-contaminated sugar meals. Preliminary work suggests that mosquitoes exposed to lyophilized Micrococcus lysodeikticus in their sugar meal respond by increasing the lytic activity in their salivary glands. The levels of bacteriolytic activity are apparently not affected by bloodfeeding. In the absence of feeding, as in teneral and bloodfed mosquitoes, salivary bacteriolytic activity increases to a maximum, then levels off. This suggests a regulation of the synthesis of this salivary protein that is independent of the feeding state of the adult mosquito. A combination of centrifugation, polyacrylamide gel electrophoresis (non-denaturing and denaturing), cation exchange chromatography and gel filtration, was used to isolate the protein from other mosquito salivary gland components. This salivary protein is lysozyme-like in several aspects: 1) it lyses bacterial cell walls of M. lysodeikticus, 2) it is a basic protein with a pI between 7.47 and 8.89, 3) it is thermostable at low pH, and loses its activity at high pH, and 4) it is composed of one polypeptide chain. Its molecular weight is twice that of hen egg white lysozyme. This salivary bacteriolytic protein is the first insect exocrine lysozyme to be characterized. / Graduation date: 1992

Thesis (M. Sc.)--University of Hong Kong, 1969. / Typewritten.

published_or_final_version / Dentistry / Master / Master of Dental Surgery

published_or_final_version / Anatomy / Master / Master of Philosophy

No description available.

No description available.