Biomedical subjects
Publications and source records attributed to I L Cameron.
Experimental evidence presented suggests that [3H]TdR can be rapidly and efficiently transported from the intestine to the systemic circulation. This pathway for thymidine transport may be physiologically important since administration of cold thymidine in the drinking water enhances the utilization of a parenterally injected dose of [3H]TdR in several body tissues of the mouse.
Adult mice were pulse labeled with tritiated thymidine [3H]TdR and killed 9 hr later. A low level incorporation of [3H]TdT into the nuclear DNA of Purkinje neurons was found in autoradiographs. Enzymatic digestions with DNase and with RNase in combination with autoradiographic grain counts indicate that a portion of nuclear DNA is not stable in the Purkinje nucleus. These results are discussed in light of reports of the stable nature of DNA in Purkinje neurons of adult mice.
To demonstrate the existence of unstable or metabolic DNA in normal mammalian neurons and to study the effect of peripheral nerve injury on this metabolic DNA, adult mice were given repeated injections of high doses of 3H-thymidine (3H-T) on the day before injury to the left hypoglossal nerve. The animals were killed at intervals up to 33 days after the injections of 3H-T. Analyses of grain counts showed a low but significant elevation in the number of radioautographic grains per unit area of hypoglossal neuronal nuclei above background levels for up to 5 days after 3H-T injection. Digestion of the tissue with DNase lowered the nuclear grain counts to background levels, confirming that the DNA was indeed labelled. Although there was a loss of labelled material from the neuronal nuclei with time, there was no difference between injured and uninjured neurons at any of the intervals tested after injection of 3H-T.
Adult female Sprague Dawley rats were divided into three groups and given two daily doses of: 1) morphine (25 mg/kg at each injection), or 2) methadone (5 mg/kg), or 3) saline for nine days. Two hours before the rats were killed on day 10, they were given a double dose of the drugs. Fifteen minutes before being killed, some of the morphine-treated rats were given the opiate antagonist naloxone (2.5 mg/kg), which caused a sudden arousal in these rats. At the time of killing, the preoptic-hypothalamic region was repidly removed and frozen in liquid propane to prevent translocation of elements in cells. Frozen 4-micrometer sections were cut, freeze-dried, and electron-probed in a scanning electron microscope, and energy-dispersive x-ray spectra were collected. The characteristic peak-to-continuum ratio for all detectable elements was determined in both the nucleus and the cytoplasm of ependymal cells and neurons. The data from nine cells of each type in each rat brain were then subjected to one- and three-way analysis of variance. The results show significant differences in the distribution of elements (sodium, magnesium, phosphorus, sulfur, chlorine, potassium, and calcium) which are dependent upon: 1) subcellular localization, 2) cell type, and particularly, 3) opiate treatment. The behavioral state produced by the opiates is correlated with the effects they have on intracellular concentration of several elements, most notably, sodium.
Scanning and light microscopy reveals a selective and restrictive pattern of indigenous bacterial colonization on the tongue of rats which is accounted for by the preferred attachment of bacteria to an "intermediate soft" keratin substrate. Total intravenous feeding of rats for 10 days did not alter this colonization pattern indicating that oral intake of food is not responsible for maintenance of this pattern.
In rats bearing Morris hepatoma No. 7777, serum levels of alpha fetoprotein (AFP) increased as tumour size increased. Hepatoma-bearing females remained in dioestrus once the tumour exceeded a cross-sectional area of 12 cm2. The following changes were seen in tumour-bearing rats compared to control animals: uterine wet weight was significantly decreased, the uterine epithelial mucosa was lower, castration cells developed in the anterior pituitary, and there was a 3- to 23-fold elevation in serum oestrogen levels. We conclude that circulating oestrogen is bound to AFP in hepatoma-bearing female rats and that in this bound state it is unable to exert its normal physiological actions.
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Unfixed frozen-dried and uncoated tissue sections of the mouse duodenum were placed on carbon planchets and analyzed in a scanning electron microscope fitted with energy dispersive X-ray equipment. Computer analysis of the X-ray spectra allowed elemental microanalysis of the nucleus, cytoplasm, and mitotic chromatin regions in the cryptal and villus enterocytes. The peak to continuum ratio of S, Cl, K, and Ca were higher in mitotic chromatin than any of the other sites measured. The redistribution of Ca at mitosis is postulated to help explain both chromosome condensation and assembly of the mitotic spindle apparatus.
delta1-tetrahydrocannabinol (THC) elicited a dose-dependent (1, 5, 10 mg/kg) depression of the immune response, of immature mice, stimulated with sheep red blood cells. The impairment of humoral immunity was specific for THC but not for cannabidiol at 25 mg/kg or cannabinol at 25 mg/kg. The mice were given four daily doses (i.p.) of either drug or vehicle (Tween 80-propylene glycol in 1% saline) or a single injection (i.p.) of sheep red blood cells in addition to four daily doses (i.p.) of drug or vehicle. Suppression of the antigenic response by THC was reflected as a reduction of splenic weight, reduction in the number of splenic antibody-forming cells, lowered hemagglutination titer and reduction in the percentage of splenic white pulp of total spleen volume.
The chromatin fibres of the male gamete nucleus of Dasypus novemcinctus contain fibrils. Measurements indicate that the chromatin fibre diameter and the number of fibrils within the fibre increase, whereas the diameter of the fibrils decreases during spermiogenesis. It is suggested that the fibrils represent a DNA-protein complex. It is further suggested that the increased fibre diameter, and the increased number of fibrils correlates with the formation of larger fibres during the condensation of the spermatid nucleus, whereas the decrease in fibril diameter is correlated with the replacement of histones with new low molecular weight acid-soluble proteins.
Cells of different types from different species were investigated to determine if there are significant variations between chromatin fibre measurements in electron micrographs of thin sections. A larger chromatin fibre of 20 plus nm is seen in both condensed chromatin and dispersed chromatin and contains an irregularly folded or coiled fibril of 2.1 to 3.7 nm. In all cell types the larger fibre of dispersed chromatin was significantly thicker than the larger fibre of condensed chromatin. Numerous significant differences were also found between chromatin measurements of the different species. The ultrastructural differences may help explain the functional differences already known to exist between dispersed and condensed chromatin.
Studies on the growth sequence of follicles in mature mice four to six months old were conducted by giving the three injections of 16 muCi tritiated thymidine (3H-T)/gm body weight at four hour intervals over a period of eight hours. Subsequent radioautographic analysis on ovaries obtaine d 1,3,5,9, and 17 days after the last injection showed an overall follicle growth time of 17 to 19 days. The duration of the different follicle stage times were also estimated from radioautographic data. Intense 3H-T incorporation was noted in the developing antra and zona pellucida of follicles of animals sarcrificed on e and three days after treatment suggesting that these areas serve as precursor storage sites during development. Oocytes of follicles in early antrum formation also showed juxtanucleolar 3H-T incorporation concomitantly with rapid and massive oocyte and follicular growth. The findings further indicate that the earliest follicular cells surrounding the oocyte originate at some distance from the developing primordial follicle.
Mice were injected three times over an 8-hour period with a total of 48 muci 3H-T/gm of body weight and were sacrificed 1, 3, 5, 9 and 17 days afterwards. Radioautographs of the ovaries showed significantly higher grain counts in oocytes of follicles that are in the antrum formation stage. The radioautographic visualization of DNase digestible 3H-thymidine incorporation into the juxtanucleolar region in oocytes of mature mice occurs in association with ooctye growth in follicles that are in the antrum formation stage. The scheduled disappearance of this juxtanucleolar oocyte DNA and its label during later oocyte growth suggests a degradation or dispersion of this labeled DNA prior to ovulation.
Young BUF rats of similar ages were inoculated with the transplantable Morris hepatoma No. 7777. At 4 weeks after inoculation, 1 group was given total iv (parenteral) feeding at high caloric and nutritional levels for 2 weeks. Such total iv feeding (hyperalimentation) of rats stimulated a more rapid tumor growth in the host. In addition, the tumors from rats fed parenterally for 2 weeks had higher mitotic activity and larger areas of necrosis, which indicate that iv feeding caused the tumor to undergo faster cell turnover with greater cell production and cell loss. Analysis of organ weights showed that parenteral feeding caused atrophy of the intestines, whereas spleen weights of the hepatoma-bearing rats fed iv were greater than those of the orally fed hepatoma-bearing rats.
The synthesis of the nuclear acidic proteins in immature and mature avian erythroid cells was compared. Synthesis of these proteins was found to occur in both types of cells. However, there are quantitative and qualitative differences in incorporation of labelled amino acids into the electrophoretic patterns of these proteins. There was an overall decline in the specific activity of the proteins as erythrocyte maturation proceeds. In particular, one protein band of molecular weight 81,000 is predominantly synthesizied in the immature cells but not in the mature cells.