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Biomedical subjects

C E Smith

Publications and source records attributed to C E Smith.

At least 289 records · Page 16Linked to original sources
PubMed1980

Cell turnover in the odontogenic organ of the rat incisor as visualized by graphic reconstructions following a single injection of 3H-thymidine.

Turnover of cells within the odontogenic organ was studied in three dimensions by preparing serial sections of incisors from young male rats killed at various times following a single intraperitoneal injection of 1 muCi/g body weight of 3H-thymidine. Radioautographs showed that at 1 hour after injection labeled cells were present in all cell layers throughout the entire depth of the odontogenic organ. They were encountered frequently within the inner dental epithelium and stratum intermedium but appeared less abundant within the stellate reticulum and outer dental epithelium. With time, the frequency of labeled cells in each layer declined progressively, and more rapidly at the anterior and labial side of the odontogenic organ than toward its posterior and lingual side. Hence labeled cells were observed over the longest time interval in regions where cell layers were in closest proximity to the opening of the apical foramen, that is, near the apical and cervical loops. By 32 days after injection, numerous labeled cells could still be identified within the outer dental epithelium and stellate reticulum near the apical loop (bulbous part of the odontogenic organ) and the outer dental epithelium near the cervical loops ("U"-shaped part of the odontogenic organ). These findings support the hypothesis that cells originate within the bulbous part of the odontogenic organ and migrate anteriorly through the "U"-shaped and root sheath parts of the odontogenic organ during renewal of the incisor. It appears that individual stem cell compartments may be maintained for surface (outer/inner dental epithelium) and intermediate layers (stellate reticulum/stratum intermedium) in the odontogenic epithelium.

Animals↗
PubMed1980

[3H]2-amino-6,7-dihydroxy-1,2,3,4-tetrahydronaphthalen (ADTN). Regional distribution and in vivo binding after acute and chronic drug treatment.

The regional distribution and in vivo binding of the dopamine analog 2-amino-6,7-dihydroxy-1,2,3,4-tetrahydronaphthalen (ADTN) was studied in the brain. The highest density of binding sites was in the striatum, with virtually no binding in the cerebellum. The binding of [3H]ADTN reflects an occupation of specific dopamine sites because the binding was diminished by the simultaneous administration of the dopamine antagonist haloperidol or the dopamine precursor L-3,4-dihydroxyphenylalanine (L-dopa). Chronic administration of haloperidol or L-dopa prior to assaying for in vivo binding resulted in an increase in the number of sites for [3H]ADTN which correlates to the increase observed in in vitro assays following long-term treatment with these agents. The subcellular distribution of in vivo labeled ADTN sites in the caudate nucleus indicate a high density of specific binding sites in the microsomal fraction, P3. Overall, these data demonstrate that the aminotetralins, such as ADTN, which bind with high affinity to the dopamine receptor in the caudate nucleus in vitro and in vivo, can provide precise information on the topography of this receptor.

Animals↗
PubMed1980

Ultrastructural localization of nicotinamide adenine dinucleotide phosphatase (NADPase) activity to the intermediate saccules of the Golgi apparatus in rat incisor ameloblasts.

Cytochemical evidence for the existence of a Golgi-associated phosphatase activity that hydrolyzes nicotinamide adenine dinucleotide phosphate (NADP) at acid pH in rat incisor ameloblasts was obtained by incubating sections from glutaraldehyde-fixed teeth in a medium containing NADP as substrate and lead ions as capture agent. Following incubation for 1 hr at 37 degrees C and pH 5.0, the Golgi saccules situated between those at the cis (immature) and trans (mature) faces of the ameloblast Golgi apparatus were marked by reaction product with the heaviest deposit in the middle saccule. Reaction product was otherwise seen in trace amounts only over some elements of the GERL system as well as a few lysosomal dense bodies and immature secretory granules. Control experiments established that the selective staining of intermediate Golgi saccules at pH 5.0 could only be duplicated by using substrates that resembled the complete NADP molecule, and not just the portion containing the adenosine 2'-monophosphate group. As well, no deposits of reaction product were seen within the Golgi saccules of ameloblasts incubated at pH 5.0 with nictoinamide adenine dinucleotide (NAD) as the substrate or that were incubated at pH 7.2 or pH 9.0 with NADP as the substrate. It was concluded that a specific, acid-NADPase activity is present in the intermediate Golgi saccules of secretory ameloblasts. Preliminary observations on other cells suggest that the localization of NADPase activity to Golgi saccules may constitute a general phenomenon.

Ameloblasts↗
PubMed1980

Effect of glutaraldehyde and decalcifying agents on acid phosphomonoester hydrolase activity in the enamel organ of the rat incisor: a biochemical study comparing enamel organ with liver.

Enamel organs were dissected from the labial surface of unfixed and glutaraldehyde-fixed rat incisors and assayed biochemically at pH 5.0 for acid phosphomonoester hydrolase activity using cytidine 5'-monophosphate (5'-CMP), beta-glycerophosphate (beta GP), phosphorylcholine (PC), and phosphoserine (PS) as substrates. Whole homogenates from unfixed enamel organs showed substantial enzyme activity toward 5'-CMP and beta GP, but 1/4 and 1/8 less activity toward PC and PS, respectively. Perfusion fixation with 2% glutaraldehyde resulted in a net loss of 80% of the enzyme activity toward each substrate. Lineweaver-Burk plots revealed that the fixative depressed the rate of hydrolysis of substrate (decrease in Vmax) and it also lowered the affinity of enzymes for substrate (increase in KM). Hence, fixed tissue generally required two or three times as much substrate to saturate the enzymes, but less substrate was hydrolyzed, as compared to unfixed tissue. Decalcification of fixed incisors with either formic citric acid, ethylenediaminetetraacetic acid (EDTA), or ethyleneglycoltetacetic acid (EGTA) did not further alter enzyme activity in the enamel organ as determined by Lineweaver-Burk plots, However, EDTA and EGTA were found to increase the susceptibility of fixed enzymes to inhibition by lead ions. This chelator-enhanced lead inhibition was greatest following decalcification with EGTA and using PC as substrate. Similar results were obtained for liver.

Acid Phosphatase↗
PubMed1979

Stress-induced cortisol release in hypothalamic hypoadrenalism.

A 52-year-old woman experienced hypoadrenalism (mean 8 AM plasma cortisol level, 3.7 microgram/dL) after hypothalamic surgery and radiotherapy for craniopharyngioma. Despite low plasma adrenocorticotropic hormone levels (less than 25 pg/mL), absent diurnal variation of the plasma cortisol level, and subnormal urinary 17-hydroxycorticosteroid response to metyrapone, she had normal plasma cortisol responses to insulin-induced hypoglycemia and to administration of vasopressin or synthetic adrenocorticotropic hormone. Stress-induced cortical release may be preserved despite notable abnormalities in regulation of cortisol secretion by diurnal and feedback-mediated mechanisms.

17-Hydroxycorticosteroids↗
PubMed1979

Potential antiinflammatory compounds. 3. Compounds derived from acenaphthene and indan.

Compounds having acenaphthene and indan as their parent nuclei were synthesized for antiinflammatory testing. Compounds which showed activity were 1-phenyl-5-acenaphthenylacetic acid and its alpha-methyl derivative (carrageenan rat paw edema) and the same alpha-methylacenaphthenylacetic acid and 2-(4-chlorobenzylidene)-3-oxo-5-indanacetic acid and its alpha-methyl derivative (rat adjuvant arthritis). None of the compounds was more active than the control compounds phenylbutazone and indomethacin.

Acenaphthenes↗
PubMed1979

Ameloblasts: secretory and resorptive functions.

The sequence of steps which an ameloblast passes through in forming enamel appears remarkably similar in amphibian and man. Despite considerable improvements in understanding the early events in the life cycle that lead to the intracellular synthesis and secretion of enamel matrix by the cell, little is known about the cell's functional role at later stages of the life cycle when the extracellular enamel matrix undergoes classical maturation in becoming fully mineralized.

Ameloblasts↗
PubMed1979

Hydrocortisone and the antibody response in mice. II. Correlations between serum and antibody and PFC in thymus, spleen, marrow and lymph nodes.

The discovery that corticosteroids can alter leucocyte distribution implies that suppression of PFC in the spleen is not necessarily indicative of suppression of the antibody response as a whole. Therefore we have examined IgM and IgG serum antibodies and PFC in the thymus, spleen, femoral marrow, popliteal, thoracic and mesenteric lymph nodes of mice given a single injection of hydrocortisone acetate at various times relative to primary immunization with SRBC. Contrary to certain reports, there was close correlation between suppression of serum antibody and of splenic PFC, from which it was predicted and verified that few PFC could be detected elsewhere. In our hands, therefore, splenic PFC measurements did give an accurate indication of suppression overall. The characteristics of suppression suggest some of the underlying causes, and these are discussed.

Animals↗
PubMed1979

Hydrocortisone and the antibody response in mice. I. Correlations between serum cortisol levels and cell numbers in thymus, spleen, marrow and lymph nodes.

Mice injected with a single well tolerated dose of hydrocortisone acetate were observed over 2--3 weeks for serum cortisol levels and for cell depletion in thymus, spleen, femoral marrow, mesenteric, inguinal and popliteal lymph nodes. Serum cortisol peaked within 24 h and declined to normal after 4 days. Total marrow cell numbers were relatively unaffected, but in all other tissues studied, cell depletion was severe and prolonged. B lymphocytes were affected more severely than T lymphocytes. There was a transient increase in the percentage of marrow T lymphocytes but otherwise little change. The percentage of node T lymphocytes increased while that of B lymphocytes decreased. The percentage of spleen B lymphocytes was reduced severely but transiently during the period of serum cortisol elevation. Spleen T lymphocyte percentages rose steadily between the fourth and seventh days after treatment, then returned to normal. Representatives of most types of lymphoid tissue were studied. As cell losses in any one were not compensated by gains in any other, most were probably due to destruction rather than redistribution. The slow rates of recovery were also more consistent with regeneration than with reappearance after redistribution.

Animals↗