Search PubMed⌕ Search

Biomedical subjects

I L Cameron

Publications and source records attributed to I L Cameron.

At least 127 records · Page 7Linked to original sources
PubMed1981

Observations on electron probe x-ray microanalysis compared to other methods for measuring intracellular elemental concentration.

Electron probe X-ray microanalysis provides the capability of accurately measuring the concentration of a number of elements at the subcellular level in tissues which are appropriately prepared using cryofixative procedures. This preview compares quantitative data obtained by the authors, using X-ray microanalysis, with quantitative data obtained in other laboratories using routine chemical procedures such as flame photometry, atomic absorption spectrophotometry, titrimetry, and ion-selective electrodes. Results are compared for cells in whole tissue, for cells in suspension (erythrocytes), and for subcellular analysis. Subcellular elemental data obtained after cell fractionation and isolation and after cryomicrodissection are considered. Agreements and differences between the results obtained by the different methods of analysis as compared to microprobe are discussed and the sources of the differences are explored. The biological significance of microprobe concentration data itself is limited without additional information regarding the state of the elements, such as oxidation state, ionic activity, degree of binding, etc. In this regard, the supplementation of subcellular elemental concentration with ionic activity and flux data for the large amphibian oocyte is presented as an example of how measurement of multiple parameters can be used to explain the maintenance of subcellular concentration gradients.

Animals↗
PubMed1981

X-ray microanalysis of electrolyte content of normal, preneoplastic, and neoplastic mouse mammary tissue.

Intracellular sodium, chlorine, and potassium concentrations (mmol/kg dry weight) were determined by electron probe X-ray microanalysis of individual epithelial cells in freeze-dried 2-micrometer sections of mouse mammary tissue which were cut at -30 degrees. A model system was utilized in order to compare elemental content of cells from normal pregnant mammary tissue and preneoplastic and neoplastic mammary tissues from female BALB/cCrlMed mice. Animals were killed by cervical dislocation, and tissue was rapidly frozen in liquid propane. Normal mammary glands were obtained from primiparous mice at 16 to 17 days of gestation. Tissue from the hyperplastic alveolar nodule line D1 was removed from donor mice 12 to 16 weeks after transplantation into the cleared mammary fat pad. All mammary adenocarcinomas, D1T, were primary tumors which developed in mice with transplants of nodule line D1. Data were collected from five animals (10 cells/animal) in each of the three groups. It was found that the electrolyte content of cells of preneoplastic tissue was the same as that of the normal mammary tissue but was significantly elevated in neoplastic tissue (162, 130, and 48% increases for sodium, chlorine, and potassium, respectively). Thus, an increase in electrolyte content seems to be associated with the transformation to a neoplastic state and not associated with conversion to the preneoplastic state.

Adenocarcinoma↗
PubMed1980

Intracellular concentration of elements in normal and dystrophic skeletal muscles of the chicken.

In this study, the intracellular concentrations of six elements (mmole/kg dry weight) were directly measured in the muscle fibers of pectoralis major muscles of eight week old, genetically dystrophic and normal chickens by the X-ray microanalysis technique. The extent of muscle degeneration was evaluated by morphometric measurements of muscle fiber diameter and other histological changes. A significant increase in the concentration of intracellular sodium and chlorine was evident in dystrophic muscles. The concentration of intracellular sodium was 127.0 +/- 35.0 in the muscle fibers of dystrophic chicks compared to 65.7 +/- 16.5 in normal controls. The concentration of chlorine was 90.5 +/- 27.5 and 54.1 +/- 5.5 in the muscle fibers of dystrophic and normal chicks respectively. The intracellular concentrations of potassium, magnesium, phosphorous, and sulfur remained unchanged in the dystrophic condition. Morphometric studies revealed that the dystrophic pectoralis muscles contain fewer but thicker fibers per unit area compared to normal pectoralis muscles. The importance of these findings are discussed in relation to the results of earlier investigations.

Animals↗
PubMed1980

Intracellular concentration of potassium and other elements in vaginal epithelial cells stimulated by estradiol administration.

Electron probe x-ray microanalysis was used to measure cytoplasmic elemental content (in mmoles/kg dry weight) of the basal layer of cells of the vaginal epithelium of ovariectomized rats. Measurements were made both before estradiol injection and at 2 hr, 17 hr, and 24 hr after estradiol administration. Mitotic figures first appeared in the basal cell layer at 24 hr. During the course of the study significant time-dependent differences were seen in the content of all elements mesured. A pattern of change in cytoplasmic content was seen for Na, P, S, and Cl; all of which decrease significantly by 17 hr and then return to approximately the nonstimulated concentration by 24 hr. On the other hand K, and to a lesser extent Mg, show an early and continued increase in cytoplasmic content after estadiol injection. Thus, the marked increase in the intracytoplasmic content of K in the estradiol treated cells suggests that K, or the ratio of Na to K, may be directly or indirectly involved in growth stimulation.

Animals↗
PubMed1980

Changes in proliferation and surface morphology in the rat ileum in response to total parenteral nutrition.

To find out how the ileum adapts to total parenteral feeding, two experiments were performed. In the first experiment rats were given total intravenous feeding for 10 days. The animals were injected with tritiated thymidine (1 muCi/g body weight) 1 hour before being killed. Portions of the ileum were used for (1) radioautography, (2) analysis of the tissue DNA content, (3) specific activity of the DNA, and (4) scanning electron microscopy. The DNA content of ileum was decreased 72% while the specific activity of DNA was increased 289% in the i.v. fed rats. In the second experiment rats were given total intravenous feeding for 10 days. The animal were injected with colchicine (1 mg/kg body weight) 3 hours before being killed. The number of labelled cell nuclei per ileal crypt section was significantly decreased by parenteral feeding as was the number of colchicine collected metaphase figures. Light microscopy revealed the crypt and the villus height to be shorter and the number of goblet cells per unit surface area to be increased in parenterally fed rats as compared to those fed solid food orally. Enterocytes of the exfoliative zone from the ileal villi of rats fed solid food showed three distinct types of surface architecture whereas those from i.v. fed rats all possessed abundant microvilli. No bacteria were seen in ilea of i.v. fed animals but many were seen embedded in enterocytes from orally fed rats. Because the amount of DNA per cell is known to be constant, we concluded that the overall number of cells in the lieum decreased about 72% in the i.v. fed rats and that cell proliferation in the crypts, although significantly deceased, was still supporting an epithelial renewal process.

Animals↗
PubMed1980

Evaluation of a preparative method for x-ray microanalysis of soft tissues.

We have adapted the cryopreparative methods designed for the radioautography of diffusible substances (Stumpf and Roth, 1966, 1967) to produce freeze-fried sections of soft tissues for electron probe microanalysis. This report concerns the evaluation of these methods for use with X-ray microanalysis with particular reference to: (1) the preservation of cellular morphology, (2) the introduction of structural artefact by ice crystal formation, (3) the preservation of natural elemental distributions under experimental conditions where known quantities of diffusible elements are present, (4) the effects of ice crystal formation upon possible artefactual elemental redistributions, (5) the effect of section thickness on elemental quantitation, and (6) the effect of tissue excision on element translocation. Freeze-dried sections were prepared from mouse pancreas and from 20% (w/v) solutions of bovine serum albumin (BSA) and gelatin containing known amounts of inorganic salts and were analysed in a scanning electron microscope fitted with energy dispersive X-ray detecting equipment. With the preparative methods used, the morphology of pancreatic acinar cells was well preserved. Acinar cell boundaries, nuclear boundaries, chromatin, nucleoli, ergastoplasm and zymogen granules were readily discernible. Ice crystals were present within sections of BSA, but 70% had a cut surface area < 1 micrometer2 and over 90% had a cut surface area of < 2 micrometer2. Characteristic peak-to-continuum ratios of elements in the BSA sections remained constant over an order of magnitude change in magnification. Elemental redistributions were not detected until the magnification was such that the analysed area fell totally within the confines of a single ice crystal. No differences in elemental peak-to-continuum values were obtained between 2 and 4 micrometer sections of the gelatin-salt solution. Tissue excision did not cause element translocations when compared to tissues frozen in situ. We conclude that this method is valid for preparing tissues for microanalysis under our conditions (analysis of nuclear, cytoplasmic, and secretory compartments) and is limiting only when analyses are conducted at very high magnifications.

Animals↗
PubMed1980

Cellular potentials of normal and cancerous fibroblasts and hepatocytes.

Several lines of investigation point to differences in electrical properties between normal and cancerous cells. Several tumor lines have low-resting membrane potentials. A few comparisons have been made between normal and tumor cells within the same tissue cell type. This study compares the cellular or transmembrane potential of hepatocytes and fibroblasts in both normal and tumor cells. High-impedance micropipets were used to record intracellularly in vivo in Buffalo rat hepatocytes and Morris 7777 hepatoma cells, as well as A/J mouse corneal fibroblasts and poorly differentiated fibrosarcoma cells. Rat hepatocytes had a mean membrane potential of -37.1 +/- 4.3 (S.D.) mV compared to -19.8 +/- 7.1 mV in the hepatoma cells. Mouse corneal fibroblasts measured -42.5 +/- 5.4 mV, while cells of mouse fibrosarcoma were -14.3 +/- 5.4 mV. The membrane potentials of the tumor cells were lower in both instances than in their normal counterpart (statistically significant at p = 0.001 for both tissue cell types). This supports the notion that lower cellular or membrane potentials may play a significant role in the altered physiology of the tumor cell.

Animals↗
PubMed1980

Concentration of calcium and other elements at a subcellular level in the lactating epithelium of rat.

Unfixed, freeze-dried and uncoated sections of lactating mammary tissue from rat were analysed for element concentration using a scanning electron microscope fitted with energy-dispersive X-ray analytical equipment. The subcellular concentration (mmol/kg dry weight) of calcium and several other elements (Na, Mg, P, S, Cl and K) was measured in: the basal-lateral cytoplasm, the nucleus, the apical cytoplasm, and the alveolar lumen in the lactating epithelium. The element concentration data was correlated to the ultrastructural features of the microprobed areas. Ca was concentrated, 4- to 5-fold, in the apical cytoplasm in comparison to other parts of the cell. The lumen contents show a 10-fold increase over the apical cytoplasm. The apical cytoplasm includes the Golgi apparatus and secretory vacuoles containing dense granules or casein micelles. The latter are numerous in the lumen. Because most of the CA in milk is known to be bound to the casein micelles, our data support the idea that Ca is sequestered in the golgi region, and transported within the secretory vacuoles to the plasma membrane for exocytosis to the lumen.

Animals↗
PubMed1979

Chromatin substructure: an electron microscopic study of thin-sectioned chromatin subjected to sequential protein extraction and water swelling procedures.

Electron microscopic observations and measurements were made on thin-sectioned chromatin fibers and fibrils obtained from nuclei of mature chicken erythrocytes. The nuclei were isolated in low ionic strength gum arabic and octanol then extracted sequentially with (1) 0.14 M NaCl, (2) 0.25 N HCl, (3) buffer saturated phenol, (4) hot 5% SDS and 0.14 M 2-mercaptoethanol and, (5) 0.4 N NaOH. The amount of nuclear protein removed at each of the first four extraction steps was 1, 86, 3 and 11% of the total, respectively. Each extract was characterized by electrophoretic profiles. At each extraction the chromatin was fixed by adding large quantities of a mixture of equal volumes of sodium cacodylate buffered 8% (w/v) glutaraldehyde (pH 6.8) and 2% OsO4 (w/v), directly into (1) an aliquot of the chromatin in extraction fluid, and (2) an aliquot of the chromatin after water washing and swelling. Three size classes of chromatin structure were seen in thin sections prepared for high resolution transmission electron microscopy and stained with uranyl acetate and lead citrate. A thick fiber of about 25 + nm diameter was the predominant large fiber seen in freshly isolated nuclei or in nuclei after salt extraction. This 25 + nm fiber has a substructure consisting of 3.2-5.2 nm diameter fibrils. After water swelling of such freshly isolated or salt extracted nuclei a fiber of about 10 nm diameter was the predominant large fiber instead of the 25 nm diameter fiber. The HCl extraction step which is known to remove histones, caused the disappearance of both the 25 nm and the 10 nm fibers. High magnification (600,000 x) micrographs of the chromatin at all procedural steps, except the last NaOH step, reveal the fibril to be omnipresent. This fibril tends to decrease somewhat in diameter during the protein extraction steps to a 2.5 nm diameter fibril after the hot SDS extraction. A fibril of 2.5 nm diameter is expected of naked double helical DNA stained with a positive stain. The NaOH, which is known to denature DNA, completely destroyed the remaining fibril. We inerpret our results to indicate that the larger chromatin fiber seen in micrographs of thin-sectioned chromatin has a fibrillar substructure which probably represents a double coil of native DNA which may have a thin protein coating of its own. The latter fibril may in turn be wrapped around a hydrophobic histone domain, perhaps reflected in the 10 nm diameter fiber which is seen upon swelling of the chromatin. This 10 nm diameter fiber is thought to be further packaged by folding into the 25 + nm diameter chromatin fiber most frequently reported in thin sections of eukaryotic cell nuclei in situ.

Animals↗
PubMed1979

Electron probe microanalysis of elemental composition of mouse cardiac myocytes during post-natal maturation.

Elemental concentrations in the cytoplasm and nucleus of t tests post-natal mouse myocytes were measured at 2, 4, 8, 16, 32 days and in adults using electron probe X-ray microanalysis. Using an analysis of variance test, significant age dependent changes were found in intracellular potassium, sulfur, phosphorus, and chlorine concentrations (mg/kg dry weight), while sodium and magnesium concentrations did not show significant changes. The application of t tests following linear regression analyses (age versus concentration for each element) did, however, give a significant slope for cytoplasmic sodium, potassium, sulfur, and phosphorus values. The findings correspond closely with an emission spectroscopy-titrimetric study of whole heart ventricle of the same developmental period (Hazelwood and Nichols, '70).

Aging↗
PubMed1979

An X-ray microanalysis survey of the concentration of elements in the cytoplasm of different mammalian cell types.

Electron probe energy dispersive X-ray microanalysis was performed on freeze-dried tissue sections. The dry weight concentration of elements (mmole/kg dry weight) was measured in the cytoplasm of several cell types from adult mice and rats. This comparative investigation showed: (1) That the energy dispersive X-ray spectrum of element concentration from the cytoplasm of a specific cell type allows one to distinguish this specific cell type from other cell types with considerable accuracy. (2) That there is a relationship between the concentration of the various elements and the ultrastructural features of the cytoplasmic regions being analyzed. For example, areas rich in ribosomes are also rich in P, K and Mg. (3) These data support the idea that K is directly involved in the control of protein synthesis. The catalog of element concentrations in the cytoplasm of 13 cell types from both mice and rats should be of value to others who seek to answer various questions about these cell types.

Animals↗
PubMed1979

The pineal gland of the gerbil, Meriones unguiculatus. II. Morphometric analysis over a 24-hour period.

By means of morphometric analytical procedures, a diurnal rhythm in the cellular volume of gerbil pinealocytes was determined. This rhythm has been attributed primarily to a change in the cytoplasmic volume of the pinealocytes which is low during the daylight hours and increases to reach a peak during the middle of the dark period. At the ultrastructural level, six cytoplasmic components of the pinealocytes were found to exhibit a rhythm: free cytoplasm, smooth endoplasmic reticulum (SER), rough endoplasmic reticulum (RER) and ribosomes, secretory vesicles, microtubules, and mitochondria. The presumptive secretory vesicles and the microtubules reached a peak in volume one hour before lights-off. It is suggested that lights-on and lights-off both signal a decrease in size and/or number of the secretory vesicles. The SER and RER/ribosomes reached their peak volume one hour after lights-off which is interpreted as indicating a peak in indoleamine synthesis and protein synthesis, respectively. The volume of free cytoplasm exhibits two peaks; one occurs one hour before lights-off while the second peak occurs in the middle of the dark phase. It is suggested that, although part of the secretory product of the pinealocyte may be present in dense-cored vesicles, other locations could include the free cytoplasm and clear secretory vesicles.

Animals↗
PubMed1979

Element concentration changes in mitotically active and postmitotic enterocytes. An x-ray microanalysis study.

Unfixed freeze-dried and uncoated tissue sections of the mouse duodenum were suspended across a hole in a carbon planchet and analyzed in a scanning electron microscope fitted with energy-dispersive x-ray analytical equipment. Computer analysis of the x-ray spectra allowed elemental microanalysis of the nucleus, cytoplasm, and late anaphase-early telophase chromatin regions in the cryptal and villus enterocytes. Elemental concentrations (mmol/kg dry wt) were measured for Na, Mg, P, S, Cl, K, and Ca. None of the elements were compartmentalized preferentially in either the nucleus or the cytoplasm of interphase enterocytes of crypts or in postmitotic enterocytes of villi. In contrast, Ca, S, and Cl are detectable in significantly higher concentrations in mitotic chromatin of dividing enterocytes of the crypt as compared to surrounding mitotic cytoplasm, but Na, Mg, and P are in lower concentrations in the mitotic chromatin as compared to mitotic cytoplasm. Interphase enterocytes of crypts have higher concentrations of Mg, P, and K, and lower concentrations of Na than do postmitotic enterocytes of villi.

Animals↗
PubMed1979

Tumor-host responses to various nutritional feeding procedures in rats.

Parenteral and enteral nutrition are being used as adjuncts to cancer therapy. A liquid diet formulation containing a 27% solution of glucose and 3.9% crystalline amino acids with electrolytes and vitamins was given continuously for a week via parenteral (iv), and via intragastric (ig) routes and also was given ad libitum via the oral or per os (po) route to groups of Buffalo rats with and without a Morris No. 7777 transplantable hepatoma to find out how these feeding procedures affect tumor-host interactions. Other groups of rats with and without the hepatoma were given solid food ad libitum. The following parameters were examined: mortality, carcass and organ weights, body and tumor growth, nitrogen balance, energy intake, fluid balance, urinalysis, hematology values, and serum protein levels. The results are considered with respect to the influence of the tumor on the host and the influence of the feeding procedure on the animal with and without a tumor. The presence of the hepatoma was associated with: higher mortality, a decrease in carcass mass, leucocytosis, anemia, a decrease in serum IgG, transferrin and albumin, and an increase in serum alpha fetoprotein. The iv and ig feeding procedures alone resulted in some mortality which was exacerbated by the presence of the tumor. Mortality was especially high in the tumorous rats on the ig feeding procedure. The degree of positive nitrogen balance and carcass mass was similar in non-tumorous rats fed the same liquid diet formula when given iv, ig, or po. Tumorous rats fed the liquid diet ad libitum showed anorexia and a significantly lower nitrogen balance. The iv and ig feeding of tumorous rats at a level which was well above those of the tumorous rats given solid or liquid diet ad libitum maintained the same degree of positive nitrogen balance as non-tumorous rats. Even though the iv feeding of tumorous rats maintained about the same degree of positive nitrogen balance as non-tumorous rats, these tumorous rats still suffered loss of carcass mass. It appears that the large rapidly growing hepatoma has priority for available nutrition over the host. It is further suggested that the rapidly growing hepatoma places an ever increasing demand on the available nutrients. Thus, a point is eventually reached where even supplemental nutritional support can no longer meet the needs of the growing hepatoma and the host.

Animals↗