Individual behavior differences related to induced tumor growth in the female Syrian hamster: two studies.

The relationship of individual behavioral differences to induced tumor growth and to Natural Killer (NK) cell activity was investigated in the Syrian hamster in the context of a long-term natural stressor (group social interaction). In the first sub-experiment, 90-day-old females had blood drawn for NK cell assays. Animals were then placed in groups of ten, and two samples of behavior were obtained on videotape. All hamsters were injected midback subcutaneously with malignant melanoma, developed tumors, and were sacrificed 35 days later. Eight reliable behaviors were coded from the videotapes and were factor analyzed, yielding two factors: "Activation" and "Inactivity." The first factor of "Activation" was correlated p less than .06, two-tailed) with autopsy tumor size. The experiment was repeated using females aged 210 days. Factor analysis generated two factors virtually identical to those previously found. The factor of "Activation" was again correlated with autopsy tumor size (p less than .05, one-tailed). For older animals only, the second factor of "Inactivity/dominance" was associated with higher NK cell activity for one of the two samples. A second study was conducted in order to replicate the factor structure of the first two sub-experiments, as well as the relationships of behavioral variables to tumor outcome variables. However, the design differed mainly in taking four rather than two samples of behavior; and in using as an outcome measure time to detection of palpable tumor, rather than autopsy tumor size. The factor analysis derived very similar factors. The second factor of "Inactivity" was correlated significantly (p less than .007, two-tailed) with tumor latency, which is congruent with the previous results. Overall, the results showed that: (a) individual behaviors in hamsters can be rated reliably, and cluster repeatedly across independent studies into certain patterns; and (b) the pattern interpreted as "Activation" was associated with poorer tumor outcome relative to the pattern of "Inactivity-(dominance)."

Stress-behavior interactions in hamster tumor growth.

The aim of this study was to investigate the effects of a mechanical stressor and individual behavior differences (separately and in combination) on tumor development in the female Syrian hamster. Studies by other investigators have documented the tumor-enhancing effects of such mechanical stressors as rotational stress. Previous studies by our group found that both size of tumor and time to tumor detection were significantly related to a dimension we call "activation." Eighty 100-day old female Syrian hamsters were placed in circular plexiglas environments in groups of 10. Nineteen days after introduction to the cages, a stress condition was imposed on half the animals (four cages). This consisted of shaking each cage of animals three times a week for three 10-minute intervals. Each group's behavior was videotaped in multiple samples to document pre- and poststress behaviors. Twelve days after the stress condition was initiated, each animal was injected subcutaneously midback with one melanoma tumor fraction. Animals were palpated every three days to determine time to detection of tumor. The videotaped behavior samples were coded for behaviors associated with "activation," inactivity, and interaction. Factor analysis resulted in basically the same first factor of activation found in our previous studies. Hamsters in the nonstressed groups had a significantly longer time to tumor development than those in the stressed groups (22.5 days vs. 12.6 days, p less than 0.005). While no prestress behaviors were associated significantly with time to tumor detection, the poststress activation factor was significantly correlated with longer time to tumor development in the stressed group (r = .61, p less than 0.0001). These results suggest that while the stress condition is more powerful than prestress individual behaviors in affecting the outcome variable, stress appears to interact with the individual behaviors related to "activation" to mitigate the negative effects of stress on tumor growth.

Silicon-containing granules of rat liver, kidney and spleen mitochondria. Electron probe X-ray microanalysis.

Isolated rat liver mitochondria containing granule aggregates (25-75 nm in diameter) and small (5-10 nm) electron opaque granules were examined by electron probe X-ray microanalysis. The granule aggregates gave an intense Si signal, while the small granules gave both Si and P signals. Isolated mitochondria of rat liver, spleen and kidney, subjected to detergent solubilization and differential centrifugation, produced two granule fractions: (1) a 10,000 g fraction consisting predominantly of granule aggregates (25--75 nm) composed of smaller granules (5--10 nm in diameter), and (2) a 10,000--30,000 g fraction of non-aggregated small granules (5-10 nm). Thin sections of isolated granule aggregates gave Si X-ray signals similar to those obtained from in situ granules. In addition S, Cl, Mg, Cr and Fe X-ray signals were observed. Cr occurred only in the large kidney granules, while Fe occurred in both fractions of the spleen and kidney granules. The presence of Si in the granules was confirmed by chemical analysis of the isolated granules and in vivo radiolabeling of the granules with 31Si and 68Ge. Contamination within the electron microscope was eliminated by a liquid nitrogen anticontamination device.

Silicon in rat liver organelles: electron probe microanalysis.

Electron probe microanalysis of unfixed freeze-substituted rat liver tissue embedded in Spurr's low viscosity epoxy resin demonstrated the occurrence of Si as well as P, S, and Cl in the nucleus, nucleolus, mitochondria, and rough endoplasmic reticulum. Chemical analysis confirmed that the Si in the organelles did not originate from instrumental contaminants. This suggests that Si may be involved in the biochemistry of these subcellular organelles.

Evaluation of silicon and germanium retention in rat tissues and diatoms during cell and organelle preparation for electron probe microanalysis.

Chemical, radiochemical and x-ray microanalysis assays were used to define parameters of silicon (Si) retention during preparation og biologic samples (rat liver, spleen, kidney, lung, diatoms and cell organelles) for x-ray microanalysis, Due to its longer half-life 68-Fe was used in some cases to trace SI. Leaching of Si from cells and organelles by the aqueous preparation media was overcome by use of the freeze-substitution process. Cells were treated with 30% glycerol hypertonic sucrose medium to reduce ice damage. Embedment in Spurr's low viscosity epoxy resin medium caused no apparent Si loss. A semiquantitative evaluation showed 0.5 x 10-8 to 0.3 x 10-17 g detectable Si in isolated rat liver mitochondria in thin sections, which is within the instrument's range of detection. This study indicateds that the presence of Si in the mitochondria is not the rsult of contamination.

Similarity in uptake and retention of trace amounts of 31 silicon and 68 germanium in rat tissues and cell organelles.

Uptake of Si and Ge (chemical analogue of Si) in rat tissues was compared to establish their subcellular localization and determine if Ge could be used to trace Si in situ. 31Si and 68Ge were found in tissues and in cell organelles after injection of 31Si (OH) 4 or 68Ge (OH) 4. Accumulation of 31Si and 68Ge in the tissues increased for 30 minutes, declined rapidly about 30 minutes and then was gradually but steadily depleted. Simultaneous double labelling with 31Si and 68Ge produced concomitant accumulation and release of both isotopes. After a single IP injection, some 68Ge remained in the spleen and kidney for up to 20 days. The 31Si and 68Ge concentration in the tissues and cell organelles increased linearly with the amount administered (31Si, 10-4 to 10-2 g/kg body wt and 68Ge, 10-9 to 10-3 g/kg body wt). Thus, substitution of 68Ge for 31Si can extend the limit of detection of Si by at least 5 orders of magnitude. Both 31Si and 68Ge were water extractable (47%-74% and 38%-89%, respectively) from liver cell organelles; 45%-81% 31Si and 66%-90% 68Ge were extractable in 10% TCA, while only 10%-59% of either isotope were extractable in organic solvents (acetone, chloroform, ethanol). A small percentage of Si may be bound or polymerized.

A Lack of Specificity for Ethylene-induced Mitochondrial Changes.

A critical evaluation was made of the hypothesis that the primary mode of action of ethylene in inducing physiological responses is by changing the permeability of cell organelles. The parameter investigated was the evaluation of the influence of ethylene and other gases on mitochondrial oxidation and swelling. Spectrometric evidence demonstrated that mitochondria prepared with good respiratory control can be induced to swell more rapidly with ethylene and other aliphatic gases (ethane, propene, propane, I-butene) in test solutions of 0.125 m KCl. The fact that saturated as well as unsaturated hydrocarbon gases elicited similar changes provides evidence that ethylene does not directly alter membrane permeability as its mechanism of action.

Utilization of model membranes in a test for the mechanism of ethylene action.

Reversible alteration of the surface tension of thin films of lipids, proteins and mixtures of both resulted when the thin films were treated with ethylene and other aliphatic gases. This effect appeared to be a nonspecific surface effect related to the molecular size of the gases. Ethylene produced no change which would ascribe to it any specific properties in this test system. The conductivity of an egg lecithin-cholesterol bilayer membrane separating two electrolytes was unaffected by all the test gases (including ethylene), but chloroform vapors markedly altered the conductivity in a reversible manner. In each of the test systems empoloyed, there was no specificity exhibited by ethylene, either qualitatively or quantitatively, indicating the mechanism of ethylene action cannot be explained as a simple physical effect on membranes.