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M Shear

Publications and source records attributed to M Shear.

At least 55 records · Page 3Linked to original sources
PubMed1978

Age-standardized incidence rates of primordial cyst (keratocyst) on the Witwatersrand.

Cases of primordial cysts derived from the records of all the hospital pathology departments and private pathology practices on the Witwatersrand, were recorded for the 10-year period 1965-74. The population at risk (1970 census) was 974,390 Whites and 1,567,280 Blacks. Age-specific morbidity rates for each sex and race were calculated, as well as age-standardized incidence rates standardized against African, World and European standard populations. The age-standardized incidence rates for primordial cysts, standardized against a World standard population, per million per year are 0.61, 0, 4.86 and 3.50 for Black males and females and White males and females, respectively. In the population at risk, primordial cysts are much more common in Whites than in Blacks, the incidence being eight times higher in White males than in Black males. The present study confirms that there is a bimodal age distribution but with a higher incidence of the cyst in the age group 50-64 years than previously suspected. This may be either because a substantial number of cases remain undiagnosed for many years or because there are two groups of primordial cyst: one which is triggered in young patients and the other in older patients.

Adolescent↗
PubMed1977

Estimation of the volumes of multinucleate giant cells.

An estimation of the volumes of three multinucleate giant cells has been attempted by measurements of the areas of enlarged tracings of serial paraffin sections which was estimated at approximately 5 mum in scanning electron-micrographs. In addition, three-dimensional models of these tracings constructed in wax were used to estimate the volumes of the same cells by means of Archimedes' Principle. The results indicate a close correlation between the estimates derived from the two procedures and suggest that the three cells measured have a volume of the order of magnitude of 50,000 to 100,000 mum(3).

Adolescent↗
PubMed1976

Agonist-specific refractoriness induced by isoproterenol. Studies with mutant cells.

The beta-adrenergic catecholamine isoproterenol produces a large, rapid, but often a transient, elevation in cellular content of cyclic AMP. We have used the S49 mouse lymphoma cell line, in which genetic variants with specific defects in the pathway of cyclic AMP generation and function have been isolated, to study the increase and subsequent decrease in cyclic AMP levels (termed refractoriness) following incubation of cells with isoproterenol. In wild type S49 cells, isoproterenol produces a peak response in the cellular content of cyclic AMP within 30 min, but the cyclic AMP level falls rapidly thereafter, approaching basal levels by 6 h. Neither inactivation of the drug nor secretion of a nonspecific inhibitor of adenylate cyclase appears to account for the refractoriness. Because isoproterenol refractory cells can still be stimulated by cholera toxin, refractoriness to isoproterenol does not represent a generalized decrease in cellular cyclic AMP response. Particulate preparations from refractory cells have a selective loss of isoproterenol-responsive adenylate cyclase activity, but their activation constants and stereoselectivity for (-)- and (+)-isoproterenol are unaltered. In addition, refractory cells have decreased specific binding of the beta-adrenergic antagonist [125I]iodohydroxybenzylpindolol. This decrease appears to represent a reduction in the number, but not the affinity, of beta-adrenergic receptor sites. Similar studies in an S49 clone that lacks the enzyme cyclic AMP-dependent protein kinase yield essentially identical findings. Because kinase-deficient cells do not induce the cyclic AMP-degrading enzyme phosphodiesterase after the cellular content of cyclic AMP is increased, induced of phosphodiesterase cannot account for refractoriness to isoproterenol. Cyclic AMP-dependent protein kinase does not appear to be required for either the decrease in beta-adrenergic receptors and isoproterenol-responsive adenylate cyclase, nor does it appear to be required for the development of refractoriness to isoproterenol. In contrast, an S49 clone lacking hormone-responsive adenylate cyclase activity but retaining beta-adrenergic receptors does not appear to lose receptors after being incubated with isoproterenol, either alone or together with dibutyryl cyclic AMP. Therefore, in this clone, receptor occupancy alone or in combination with elevated cyclic AMP levels is insufficient to cause refractoriness. Refractoriness thus appears to require intact adenylate cyclase. This suggests that adenylate cyclase may exert regulatory controls on beta-adrenergic receptors in addition to generation of cyclic AMP.

Adenylyl Cyclases↗
PubMed1976

The prediction of lymph node metastases from oral squamous carcinoma.

In an attempt to predict which cases of oral and oropharyngeal squamous carcinoma are likely to metastasize to regional lymph nodes a series of 898 cases was grouped according to site, size, grade of histological differentiation, and presence or absence of histologically confirmed regional lymph node metastases. The results were analysed by a logistic multiple regression analysis. They showed that the sites may be divided into three clusters, Cluster 1 consists of tumors of lip, floor of mouth, cheek mucosa, hard palate, and gingiva. These are not significantly different as regards metastasis rate. Cluster 2 consists of tumors of the anterior two-thirds of tongue and has a higher tendency to metastasis than those in Cluster 1. Lesions of the posterior third of tongue and oropharynx form Cluster 3 which exhibits the greatest tendency to metastasis. Sizes of primary lesions are clustered in groups of lesions less than 3 cm, those 3 to less than 4 cm, and those 4 cm or larger, in ascending tendency to metastasis. Well-differentiated and moderately differentiated tumors are not significantly different in their tendency to metastasize and may be reduced to a single cluster, whereas poorly differentiated tumors have a markedly higher metastasis rate. Using these clusters it has been possible to predict the logistically transformed probability of metastasis to a high degree of accuracy (R=0.9398). From this we conclude that if for a given tumor we know to which site, size or differentiation cluster it belongs, we can then estimate its probability of metastasising.

Carcinoma, Squamous Cell↗
PubMed1976

A case report of keratoameloblastoma.

In the "WHO histological typing of odontogenic tumors, jaw cysts and allied lesions", the authors recognize five distinct histologic types of ameloblastoma. A further histologic variant, the keratoameloblastoma, was first described by PINDBORG. A second case of a keratoameloblastoma is reported. This lesion occurred in the maxilla of a 28-year-old Caucasian male.

Adult↗
PubMed1976

Root resorption by ameloblastomas and cysts of the jaws.

Radiographs of 122 cases of a series of nonmalignant simple jaw cysts and ameloblastomas were examined and the frequency of resorption of adjacent tooth roots compared. The ameloblastomas proved to have a root resorptive potential far greater than the cystic lesions considered. Certain statistically significant differences were observed in the root resorption related to the cystic lesions. The dentigerous cyst showed a tendency to resorb roots (55%), whereas in this study no resorption was observed in primordial cysts. These differences may aid the clinician in the preoperative differential diagnosis. It is suggested that the capacity of the dentigerous cyst for root resorption may be the result of its origin from the dental follicle, which is associated with resorption of the roots of primary teeth during normal tooth succession.

Ameloblastoma↗
PubMed1976

Granular cell peripheral odontogenic fibroma.

A case of a peripheral odontogenic fibroma which contained aggregates of large granular cells is reported. These granular cells are similar to those previously described in the granular cell myoblastoma, congenital epulis and the granular cell ameloblastic fibroma. Deep extensions of the basal layer of overlying gingival epithelium, in double-strand fashion, are frequently observed in peripheral odontogenic fibromas. These strands closely resemble those seen in the tumor itself. On this basis, and as similar basal cell prolongations are seen in otherjaw lesions, it is postulated that residual ectomesenchymal influence may be responsible for inducing the basal cell proliferations in a similar manner to that which occurs during early embryonic dental development. This, it is suggested, might possibly be the histogenesis of the odontogenic epithelial strands in the peripheral odontogenic fibroma.

Adult↗
PubMed1975

Microscopic features of the lateral periodontal cyst.

The lateral periodontal cyst is of developmental odontogenic origin and must be differentiated from the gingival cyst of adults, a primordial cyst in a lateral periodontal position, and a cyst of inflammatory origin. This paper is based on a histologic study of five cases. Four were in the mandibular premolar region and one in the lateral incisor-canine region of the maxilla. The cysts are lined by a thin non-keratinized epithelium which resembles the reduced enamel epithelium. Many of them arecharacterized by the presence of localized plaque-like thickenings of their epithelial linings, consisting of fusiform or large swollen, edematous cells. These epithelial thickenings appear to result from a localized proiferation of basal cells. The lateral periodontal cyst may arise initially as a dentigerous cyst which develops by expansion of the follicle along the lateral surface of the crown and comes to lie on the lateral aspect of the root if tooth eruption is normal. Alternatively, it may arise from the cell rests of Malassez.

Epithelial Cells↗
PubMed1975

Histochemically demonstrable changes in amylase activity in submaxillary salivary glands of puberal male mice following castration.

The sexual dimorphism in mouse submaxillary glands is well documented. The main difference is seen in the granular convoluted tubules (G.C.T.) which in the adult male are large and in the adult female are small and fewer. Previous studies have shown that amylase is localized histochemically to these G.C.T.'s; that following castration there is a histological reduction in size and number of the G.C.T.'s and a roughly 50 per cent decrease in amylase activity demonstrable biochemically. In the present study 74 male mice aged 60 days were divided in six groups. The animals were fasted overnight. Under general anaesthesia, the submaxillary glands on the left side were removed and frozen in liquid nitrogen for subsequent histochemistry. The animals were then castrated and returned to their cages. At periods of 2, 4, 6, 8, 10 and 12 weeks later, the other submaxillary gland was removed under the same conditions, and the animals were then killed. Fresh frozen cryostat sections of both glands were subjected to the starch substrate film technique for the histochemical demonstration of amylase. Adjacent sections were stained with HE. The 2-week animals showed a slight but define reduction in size and number of G.C.T.'s and a parallel reduction in amylase activity. This was more pronounced by 4 and 6 weeks. In the 4-week animals, however, the changes were not consistent, being more pronounced in some animals than in others. This same phenomenon was observed in the 6-, 8- and 10-week animals, in some of whom there was considerable G.C.T. atrophy in the submaxillaries and in others very much less. In many of the 12-week animals there was very little evidence of G.C.T. atrophy. These findings confirmed other studies which suggested that there may be some regeneration of G.C.T's, possibly as a result of influence of other endocrine glands such as thyroid, adrenal and pituitary.

Amylases↗
PubMed1974

A histological comparison of the giant cells in the central giant cell granuloma of the jaws and the giant cell tumor of long bone.

A histological comparison has been made of the giant cells in 10 cases which had been diagnosed as central giant cell granuloma of the jaws and 10 cases diagnosed as giant cell tumor of long bone. The numbers of nuclei in each of 50 giant cells were counted in the 20 lesions. The giant cells were measured in order to compare their sizes in the respective lesions. It was found that the giant cells of the jaw lesions contained significantly fewer nuclei than those of the lesions in other bones. Secondly it was found that cells in the lesions of long bone have significantly larger dimensions than those in the jaw lesions. There was, however, an area of overlap. It was concluded that these data supported the view that giant cell tumor and giant cell granuloma are distinct entities. Some giant cell lesions of long bones are, however, morphologically indistinguishable from lesions of the jaws; and conversely giant cell lesions of the jaws are indistinguishable from some giant cell lesions of the long bones. It seems possible, therefore, that some jaw lesions are giant cell tumors and that some giant cell lesions outside the jaws are giant cell granulomas.

Bone Neoplasms↗