Studies on the physiological and structural characteristics of rat intestinal mucosa. Mitochondrial structural changes during amino acid absorption

Sections from mucosal strips and rings of rat jejunum were studied with the light microscope and the electron microscope before and after incubation in a modified Krebs bicarbonate Ringer. Various additions were made to the incubation medium, and their effects on both the structure and the respiratory activity of the mucosal tissue were noted. In those cases in which an amino acid mixture was added, there was a pronounced increase in the rate of respiration. When strips of intestine were used, the presence of the amino acid mixture more than doubled the rate of oxygen consumption. Along with the increased levels of respiration there was a sharp rise in the percentage of mitochondria assuming a condensed ultrastructural conformation. The amino acid mixture did not cause the condensation of jejunal mitochondria if glucose was included in the incubation medium or if 2,4-dinitrophenol was present. The evidence suggests that a high proportion of the jejunal mitochondria assumes a condensed conformation in response to an increased energy demand. Apparently glucose can prevent the amino acid mixture from increasing the energy drain on the oxidative processes in these cells. Although a high rate of respiration was obtained in the presence of dinitrophenol, the studies indicated that mitochondrial condensation was only associated with a high rate of coupled oxidative phosphorylation.

ER-annulate lamellar associations of mucosal epithelial cells of the rat jejunum

Mucosal cells of the rat jejunum vary greatly in the relative abundance and kind of endoplasmic reticulum (ER). Many cells have few rough surfaced cisternal ER elements; these cells frequently are located in basal villous regions and generally are less differentiated than those near apices. Profiles of rough ER cisternae were often encountered in stacks of 3-4 parallel units in apical cells. A number of differentiating basal cells were found to contain ER-annulate lamellar associations arranged similarly to the ER stacks of apical cells. The annulate lamellae of this complex resemble those described for other rapidly differentiating or embryonic cells and may be derived from the nuclear envelope. They could be involved in the formation of the ER.

Genomic variant representation in a Chlamydia population is dynamic and adaptive with dependence on in vitro and in vivo passage

We have previously shown that Chlamydia muridarum has multiple genomic variants that concomitantly vary in their in vitro and in vivo phenotype. Herein, we used real-time polymerase chain reaction-based genotyping assays to query plaque-cloned isolates of C. muridarum for the frequency of eight selected polymorphisms. These strains had no history of passage in vivo since their original isolation from laboratory mice. There was significant variance in the frequency of two of the eight polymorphisms assessed with the remaining exhibiting a low rate of variance. To determine if any of these polymorphisms were more favorable for in vivo conditions, we blindly passaged non-clonal C. muridarum three times at 7-day intervals through the urogenital tract of mice. Seven of the eight polymorphisms varied in frequency following in vivo passage and four of these varied between C. muridarum strains. Selected isolates displayed variable growth rates and cytopathic effect in vitro. We conclude that multiple genotypic variants are present within the existing known C. muridarum strains and that the frequency of these variants changes upon introduction into the mouse host. These findings lend support to the concept that genotypic proportional representation in a chlamydial population is dynamic and adaptive.

Sodium hypochlorite as a tissue solubilizing agent compatible with liquid scintillation counting

The use of hypochlorite to prepare biological samples, containing incorporated radiolabeled molecules, for liquid scintillation counting was investigated. Hypochlorite both solubilized and decolorized a variety of animal tissues, but fat aggregates, cartilagenous tissue, and plant material resisted digestion. Although hypochlorite induced chemiluminescence, addition of acidified stannous chloride to the counting cocktail alleviated the spurious counts. The reported procedure, modified to suit particular experiments, may be applicable in a variety of situations where quantitation of biologically incorporated radiolabeled molecules is desired.

Gender-specific effects of HIV protease inhibitors on body mass in mice

Protease inhibitors, as part of highly active anti-retroviral therapy (HAART), have significantly increased the lifespan of human immunodeficiency virus (HIV) infected patients. Several deleterious side effects including dyslipidemia and lipodystrophy, however, have been observed with HAART. Women are at a higher risk of developing adipose tissue alterations and these alterations have different characteristics as compared to men. We have previously demonstrated that in mice the HIV protease inhibitor, ritonavir, caused a reduction in weight gain in females, but had no effect on male mice. In the present study, we examined the potential causes of this difference in weight gain. Low-density lipoprotein receptor (LDL-R) null mice or wild-type C57BL/6 mice, were administered 15 mug/ml ritonavir or vehicle (0.01% ethanol) in the drinking water for 6 weeks. The percent of total body weight gained during the treatment period was measured and confirmed that female LDL-R gained significantly less weight with ritonavir treatment than males. In wild type mice, however, there was no effect of ritonavir treatment in either sex. Despite the weight loss in LDL-R null mice, ritonavir increased food intake, but no difference was observed in gonadal fat weight. Serum leptin levels were significantly lower in females. Ritonavir further suppressed leptin levels in (p < 0.05). Ritonavir did not alter serum adiponectin levels in either gender. To determine the source of these differences, female mice were ovariectomized remove the gonadal sex hormones. Ovariectomy prevented the weight loss induced by ritonavir (p < 0.05). Furthermore, leptin levels were no longer suppressed by ritonavir (p < 0.05). This study demonstrates that gonadal factors in females influence the hormonal control of weight gain changes induced by HIV protease inhibitors in an environment of elevated cholesterol.