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At least 559 records · Page 31Linked to original sources
PubMed1982

Circadian variations in influx and efflux of the S phase in a partially synchronized cell system. Double-labelling with [3H]thymidine in the epithelium of the hamster cheek pouch.

By means of a double-labelling experiment, circadian variations in the kinetic parameters of the S phase of the hamster cheek pouch epithelium were studied. The evaluation of the experiment included a recently developed correction for deviations from the strict pulse interpretation of the labelling technique. Pronounced circadian variations were found in S phase influx and efflux; the diurnal mean of both was estimated as 0.5%/hr, when based on measurements of all nucleated epithelial cells. Variations in S phase influx seem mainly responsible for the diurnal variation in cell proliferation, although diurnal variation in DNA synthesis rate, and thus in mean transit time, was also found. The increases in LI and influx were closely correlated and related to the beginning of the dark period. A circadian variation in cell number was also observed.

Animals↗
PubMed1984

Circadian-stage dependence of methotrexate in a keratinized epithelium. An in-vivo study using flow cytometry on the hamster cheek pouch epithelium.

The partially synchronized cell system of the hamster cheek pouch epithelium shows a characteristic diurnal rhythm of cell proliferation. Bolus injections of methotrexate (Mtx) in both lethal (10 g/m2) and non-lethal (2 g/m2) doses were found to inhibit cell-cycle progression primarily by impairing the G1/S transition. The results were obtained by flow cytometric DNA analysis. The inhibitory effect of Mtx manifested itself as a relative decrease of the S fraction (drug-effector phase), and was found to be dependent both on the dose and on the time of the day it was given. A bolus injection of Mtx was given either at 1200 hr (when a minimal number of cells are in S phase) or at 0200 hr (when a maximum number of cells are in S phase). The greatest cumulative decrease in S fraction was seen when the injection was given at 1200 hr. The time between injection and the effect (seen as a decrease in S fraction) was independent of the time of the Mtx injection, but seemed instead to be related to the natural diurnal period of increasing flux from G1 to S phase (at the onset of the dark period). The main effect (the relative decrease in S fraction) was repeated during the following 24-hr period, pointing to a protracted effect of Mtx on G1 cells. G1 cells affected by the initial high Mtx plasma concentration seem to be responsible for the reduced influx into S phase in both the first and second 24-hr period. In earlier toxicological studies, the survival rate of hamsters was dependent on the time of injection and was highest after injection at 1200 hr. Thus maximum cytokinetic effect on epithelial cells was found at the time of the day when there was a minimum lethal effect on the animal.

Animals↗
PubMed1987

Iron deficiency depresses cell proliferation in hamster cheek pouch epithelium.

Iron deficiency anaemia was induced in hamsters by feeding a low iron diet coupled with weekly bleeding. To assess cell proliferation, the stathmokinetic agent vinblastine sulphate was administered and cell birth rates were calculated from cumulative mitotic indices. The rate was significantly reduced in epithelium from iron-deficient animals. The uptake of tritiated thymidine [( 3H]TdR) was also significantly reduced in these animals. Results of both stathmokinetic and labelling experiments indicate that cell production in the cheek pouch epithelium of iron-deficient animals is impaired.

Anemia, Hypochromic↗
PubMed1975

Changes of cheek pressure during swallowing following expansion of the maxillary dental arch in repaired cleft palates.

Cheek pressure during swallowing was measured on six operated complete cleft lip and palate cases (4-8 years of age) before and after expansion of buccal segments of maxillary arch. As control, seven non-cleft subjects with acceptable occlusion of the same age level were used. Before expansion, the pressures in the cleft cases were much higher than the controls. Immediately after expansion, increase in pressure was observed in cases which received rapid expansion. However, a few months after expansion, most cases showed a decrease in pressure. This is explained as being due to the adaptation of the perioral musculature to the expanded dental arch and/or the disappearance of hyperactivity of the perioral musculature during swallowing.

Amplifiers, Electronic↗
PubMed1991

Local skin flaps on the cheeks.

Local skin flap repairs on the cheek are discussed. Anatomic and special considerations are reviewed. Advancement, rotation, and transposition flaps are described.

Cheek↗
PubMed1994

Combining flaps. Medical canthal/lateral nasal root reconstruction utilizing glabellar "fan" and cheek rotation flaps--an O-to-Z variation.

An increased use of multiple flaps applied to single reconstructive problems is encouraged. Removal of a basal cell carcinoma involving the medial canthus and adjacent lateral nasal root skin resulted in significant defect. When a glabellar "fan" flap failed to provide adequate tissue for canthal reconstruction without undue distortion, a preplanned medial cheek rotation flap followed sequentially in the repair process. The basic principles of an O-to-Z flap reconstruction were therefore fulfilled by conjoining two different flap design applications.

Basal Cell Carcinoma↗
PubMed1976

Long-term organ culture of hamster cheek pouch mucosa.

Explants of cheek pouch mucosa from 12- to 48-hour-old hamsters have been maintained in organ culture for up to 49 days with excellent preservation of tissue integrity and relationships. The technique uses gelatin sponge matrix in Leighton tubes with Eagle's Minimum Essential Medium (M.E.M.) supplemented with 10% calf serum and antibiotics.

Animals↗
PubMed1977

Changes in vitamin A conditioned hamster cheek pouch epithelium on exposure to commercial shell lime (calcium hydroxide) and tobacco. I-Optical histopathology.

Epidemiologically a high incidence of oral cancer and addiction to tobacco, singly or in combination with other ingredients of the betel quid, are closely correlated. Attempts at the induction of malignancy in laboratory animals on exposure to these ingredients have hitherto failed. Studies are reported on cheek pouch epithelium of 152 Syrian golden hamsters exposed to commercial shell lime (calcium hydroxide) and tobacco, singly and in combination, with parallel conditioning by Vitamin A palmitate. The abnormal changes found especially in lime and lime-plus-tobacco treated epithelia are massive hyperplasia, keratinization anomalies, marked edema and dysplasia. The most significant findings are (1) greater epithelial alteration caused by lime, lime plus vitamin A, tobacco plus vitamin A, lime plus tobacco and lime plus tobacco and vitamin A, than by tobacco alone; (2) increasing epithelial dysplasia in response to longer periods of exposure to the test substances; and (3) enhancement of tissue changes in the presence of vitamin A.

Animals↗
PubMed1980

The effect of DMBA on hamster cheek pouch mucosa in vitro.

Neonatal hamster cheek pouch mucosa was treated with DMBA for three h either before being explanted or after 7 days in vitro. The epithelium of the treated cultures exhibited dysplasic changes, most marked at 21 to 28 days in vitro. These changes were not seen in the explants maintained for 35 to 49 days in vitro indicating a return to an apparently normal morphology. Examination of the ultrastructure of DMBA treated and untreated explants showed changes consistent with those described in similar tissues in vivo. The epithelium of the carcinogen treated tissue exhibited widened intercellular spaces, tortuous cell membranes, an irregular and discontinuous basal lamina and pseudopodia of the basal cells extending into the underlying mesenchyme. Similar changes have been described in inflamed epithelium, in some other experimental preparations, and in premalignant lesions in vitro, both in animals and man.

9,10-Dimethyl-1,2-benzanthracene↗
PubMed1980

Stereological analysis of hamster cheek pouch epithelium after one application of DMBA or turpentine.

Both cheek pouches of two groups of five male hamsters were treated with one application of either 50% turpentine in liquid paraffin (TLP50) or a 0.5% solution of dimethylbenz(alpha)anthracene in liquid paraffin (DMBA); animals were killed 48 h later. Five untreated animals served as controls. Mucosal specimens were removed from each pouch, fixed in normal-acetic-alcohol and processed for light microscopy. Sections were cut at 4 micrometer and stained with haematoxylin and eosin. A systematic random sampling method was used to obtain sections for sterological analysis. Grids for point and intersect counting were superimposed on the projection screen of an automatic sampling microscope. Results showed that the epithelial nuclear-cytoplasmic ratio, nuclear density, nuclear diameter and surface area interface ratios were similar for the experimental groups and, with the exception of the last parameter, differed significantly from controls. The volume proportion of TLP50-treated epithelium was significantly larger than that of DMBA-treated epithelium. Derived values for the average nuclear volume in both experimental groups were almost twice that of controls; the cytoplasmic volumes were more than doubled. At 48 h the epithelial response to a single application of TLP50 or DMBA was essentially similar except that TLP50 probably induced greater hyperplasia.

9,10-Dimethyl-1,2-benzanthracene↗
PubMed1988

In vivo effects of Sn-1,2-dioctanoylglycerol, TPA and A23187 on hamster cheek pouch epithelium.

Cheek pouches of male Syrian golden hamsters were topically treated with a single dose of TPA (.5 microgram), calcium ionophore A23187 (75 micrograms) or Sn-1,2-dioctanoylglycerol (DiC8) (500 micrograms) dissolved in 0.25 ml acetone. Acetone-treated animals served as controls. After 48 h the mitotic index for the control group was 1.1 +/- 0.1 per 1 mm of the basement membrane length. All the test congeners exhibited higher mitotic indices than controls: TPA (4.8 +/- 0.4), A23187 (3.9 +/- 0.3), DiC8 (2.1 +/- 0.2). All groups exhibited an increase in the epithelial thickness manifested by cellular hyperplasia. The treatment of the pouches with the anti-inflammatory agent fluocinolone acetonide inhibited the mitogenic and hyperplasiogenic affects on the epithelium induced by the various test chemicals. These studies indicate a possible role of calcium-phospholipid dependent protein kinase (protein kinase C) in the mediation of oral epithelial cell proliferation.

Animals↗
PubMed1989

Cytokeratins in hamster cheek pouch epithelium during DMBA-induced carcinogenesis.

The pattern of keratin expression in hamster cheek pouch epithelium during 15-wk of DMBA-induced carcinogenesis was studied. The sequential changes in cytokeratins of premalignant and malignant tissues and comparative investigation of normal epithelial tissues were examined during a weekly sequential DMBA-induced chemical carcinogenesis. Keratin polypeptides of normal pouch epithelium appear in a molecular weight range of 43-67 kd and 5-6 proteins can be identified. The disappearance of high molecular weight keratin (61-67 kd) was observed from the 6-wk DMBA-treated premalignant group to the 15-wk DMBA-treated malignant group. An additional keratin polypeptide was noted initially on the 11th-wk-DMBA-treated group and remained to the 15th-wk-DMBA treated group.

9,10-Dimethyl-1,2-benzanthracene↗
PubMed1989

Iron deficiency reduces cytochrome concentrations of mitochondria isolated from hamster cheek pouch epithelium.

The effects of iron deficiency on the aerobic pathway of energy metabolism were studied using mitochondria isolated from epithelial cells from the hamster cheek pouch. A statistically significant reduction in the concentrations of cytochromes aa3, b and c (P less than 0.05), a reduction (P = 0.064) in cytochrome cl and altered cytochrome ratios were found in the mitochondria of iron deficient compared to normal animals. State 4 respiration was demonstrated in the mitochondria of both normal and iron deficient animals but state 3 respiration could not be demonstrated; this suggests uncoupling of oxidative phosphorylation which may be an artefact associated with the separation of epithelium from its connective tissue. Nevertheless we conclude that the reduction in cytochrome concentration is a real effect of iron deficiency which may explain, at least in part, the reduction of both energy production and cell proliferation seen in oral epithelia under these conditions.

Animals↗
PubMed1993

Liposarcoma of the cheek: report of a case.

Liposarcomas of the head and neck region are rare. Those originating in the buccal mucosa cause special diagnostic and therapeutic difficulties. In this report, a predominantly well-differentiated liposarcoma of the cheek in a 32-yr-old man is reported. The tumor continued to grow slowly over a period of 3 yr before definitive diagnosis was established. Radical maxillectomy was performed with total excision of the tumor. Recommendations for earlier and correct diagnosis and treatment of this rare neoplasm are discussed.

Adult↗
PubMed1996

Scanning electron microscopy of dimethylbenzanthracene (DMBA)-treated hamster cheek pouch.

The aim of the present study was to describe changes which could be regarded as a result of neoplastic rather than inflammatory processes. Fifty-five weeks after 6 weeks of DMBA application to the cheek pouches of 5 male hamsters there were 4 types of lesion: larger ulcerated sessile; smaller non-ulcerated sessile; non-ulcerated pedunculated; conical projections. These and the rest of the pouches were examined by scanning electron and light microscopy. The interlesional mucosa, non-ulcerated sessile lesions and conical projections were covered by flat polygonal cells with either a honeycomb surface pattern of interconnecting microridges, or microridges arranged into more parallel lines. Cell imprints and boundaries were formed by linear ridges, grooves or both. Pedunculated lesions had flat smooth-surfaced cells and cells with a honeycomb surface pattern. None of these lesions were carcinomas by light microscopy but the ulcerated sessile lesions were. The appearance of the cells on the ulcerated lesions varied: flat, with a variable number of short microvilli that were often knob-like, isolated short microridges, or both; plump, giving a cobblestone appearance with surfaces that were smooth, covered by microvilli, short microridges or both. Such appearances have been described as characteristic for dysplastic and malignant stratified squamous epithelium in a number of sites. Further study of both experimental and naturally occurring mucosal disease is needed to validate this.

9,10-Dimethyl-1,2-benzanthracene↗
PubMed2004

Increased expression of cyclooxygenase (COX)-2 in DMBA-induced hamster cheek pouch carcinogenesis and chemopreventive effect of a selective COX-2 inhibitor celecoxib.

BACKGROUND: In recent years, overexpression of cyclooxygenase (COX)-2 protein and mRNA has been reported in various cancer tissues. Therefore, it has been suggested that COX-2 is related to carcinogenesis. METHODS: Hamsters were treated by painting a buccal pouch with a 0.5% DMBA solution dissolved in acetone. Basal diet or diets containing 150, 500 and 1500 ppm of celecoxib, a selective COX-2 inhibitor, were given ad libitum to hamsters, and tumor development was observed. RESULTS: Immunohistochemical and Western blot analyses revealed that COX-2 expression was increased toward the carcinogenesis. Although all hamsters developed squamous cell carcinoma, the onset of tumor formation was delayed in a dose-dependent manner. Also, tumor growth was retarded and survived animals were increased in the group of celecoxib treatment. Histologically, administration of celecoxib increased the apoptotic cells in the tumor parenchyma and significantly inhibited the angiogenesis in the stroma. CONCLUSIONS: The COX-2 expression was increased during hamster cheek pouch chemical carcinogenesis. Administration of celecoxib demonstrated the chemopreventive potential against the carcinogenesis.

9,10-Dimethyl-1,2-benzanthracene↗
PubMed1985

Electrical resistance of arterioles and venules in the hamster cheek pouch.

The electrical resistance of the vascular endothelium was determined on single microvessels in the hamster cheek pouch in order to obtain information about this variable in a mammalian preparation. So far, the technique has only been applied to frog microvessels. The technique consists of injection of current into the vascular lumen via a microelectrode and recording of the ensuing intravascular potential distribution by a second microelectrode. Cable theory was used for the analysis. The average diameter of the vessels under study was 41 micron for arterioles and 28 micron for venules. The average resistance of the vessel wall at 37 degrees C was 19 omega cm2 and 3.3 omega cm2, respectively. For the venules this is somewhat lower than what has been recorded on muscle capillaries (Olesen & Crone 1983) in the frog at room temperature, whilst the values on arterioles are rather similar. The calculated sodium permeabilities, PNa+, were for arterioles 4 X 10(-5) cm X s-1 and for venules 23 X 10(-5) cm X s-1. The high permeability values for arterioles and venules indicate that the vascular exchange function may not be limited to capillaries only.

Action Potentials↗
PubMedDate not supplied

Prevention of habitual cheek biting: a case report.

Oral and peri-oral structures can be traumatized by self-injurious behavior (SIB). Various articles have described prostheses used to prevent SIB-related injuries to the oral tissues of patients who have developmental or medical problems, such as psychological problems, congenital syndromes or mental retardation; however, reports of oral SIB in individuals unaffected by the above conditions are scarce. This case report describes the use of a removable prosthesis to prevent a stress-induced cheek biting habit in 15-year-old girl who did not have any of the commonly related conditions. The report discusses the importance of designing a prosthesis that protects tissues, while considering injury severity and the patient's healthas well as her ability to cooperate with treatment.

Adolescent↗