Electron microscopy of lysosome-rich fractions from rat thymus isolated by density-gradient centrifugation before and after whole-body x-irradiation

Impact of CNS Diseases on Drug Delivery to Brain Extracellular and Intracellular Target Sites in Human: A "WHAT-IF" Simulation Study

The blood-brain barrier (BBB) is equipped with unique physical and functional processes that control central nervous system (CNS) drug transport and the resulting concentration-time profiles (PK). In CNS diseases, the altered BBB and CNS pathophysiology may affect the CNS PK at the drug target sites in the brain extracellular fluid (brainECF) and intracellular fluid (brainICF) that may result in changes in CNS drug effects. Here, we used our human CNS physiologically-based PK model (LeiCNS-PK3.0) to investigate the impact of altered cerebral blood flow (CBF), tight junction paracellular pore radius (pararadius), brainECF volume, and pH of brainECF (pHECF) and of brainICF (pHICF) on brainECF and brainICF PK for 46 small drugs with distinct physicochemical properties. LeiCNS-PK3.0 simulations showed a drug-dependent effect of the pathophysiological changes on the rate and extent of BBB transport and on brainECF and brainICF PK. Altered pararadius, pHECF, and pHICF affected both the rate and extent of BBB drug transport, whereas changes in CBF and brainECF volume modestly affected the rate of BBB drug transport. While the focus is often on BBB paracellular and active transport processes, this study indicates that also changes in pH should be considered for their important implications on brainECF and brainICF target site PK.

Characterization of two independent, exposure-time dependent paclitaxel-resistant human ovarian carcinoma cell lines

This experiment was conducted to address the question of whether acquired paclitaxel resistance is dependent upon whether it is given as a single brief exposure or as a long-term exposure. PX2 and PX24 were established from 2008 human ovarian cancer cells by 2-h single exposure or 24-h continuous exposure to paclitaxel. PX2 acquired paclitaxel resistance faster than PX24 by twofold. Drug resistant pattern was exposure-time dependent. In 2-h exposure, PX2 showed 53.86 ± 4.96 (mean ± standard deviation [SD]) fold paclitaxel resistance while PX24 showed 9.51 ± 1.01 fold resistance (P = 0.002). In 24-h exposure, PX2 showed 2.31 ± 0.3 fold paclitaxel resistance while PX24 showed 28.17 ± 0.98 fold resistance (P = 0.040). PX2 and PX24 acquired cross-resistance to docetaxel and SN38 and the resistance degrees were significantly higher in PX2 than PX24. They displayed approximately twofold cisplatin collateral sensitivity. PX24 also displayed sensitivity to other platinum drugs, oxaliplatin and ZD0473, whereas PX2 acquired significant resistance to both of them. Although differential tubulin-isotype expressions were noted among 2008, PX2 and PX24, they were not significant. In electron microscopy, prominent, densely stained lysosomes were observed more in the resistant cells than 2008. Two independent, exposure-time dependent paclitaxel-resistant human ovarian carcinoma cell lines were established. Understanding the characteristics of the differential resistance pattern could be clinically beneficial for the selection of second line chemotherapy for relapsed ovarian cancer.

LYSOSOMAL FRACTIONS FROM TRANSITIONAL EPITHELIUM

Histochemical data suggested that the so called lipoid granules of transitional epithelium in some species are equivalent to lysosomes. Scrapings of bovine and canine transitional epithelium were subjected to differential centrifugation to confirm this identification biochemically. Fractions of rat liver, the classic source of lysosomes, were also prepared by the same methods to compare with the fractions obtained from urinary epithelium. In contrast to rat liver, uroepithelial fractions with a high relative specific activity for hydrolases were sedimented before the heavy mitochondria. Microscopically, these fractions contained the highest proportion of lipoid granules. The size and sedimentation characteristics of lysosomes from transitional epithelium more closely resembled those of lysosomes derived from rat kidney than those isolated from liver.

Lysosomes in lymphoid tissue. I. The measurement of hydrolytic activities in whole homogenates

Methods have been developed for the quantitative assay of cytochrome oxidase, esterase, and 11 acid hydrolases in rat-spleen homogenates. These methods seem to be applicable also to other lymphoid tissues. Preliminary studies, extended to nine of the acid hydrolases, indicate that these enzymes occur in partly latent and sedimentable form and that they can be unmasked and rendered soluble by some of the treatments that liberate the enzymes from rat-liver lysosomes. The spleen particles appear to be very sensitive to mechanical injury, a property which necessitates special precautions in homogenizing the tissue. Agglutination of spleen particles takes place to a larger extent in 0.25 M sucrose than in 0.15 M KCl.

Lysosomes in lymphoid tissue. III. Influence of various treatments of the animals on the distribution of acid hydrolases

The density-distribution patterns of various enzymes and of labeled materials have been determined by isopycnic centrifugation in a sucrose-0.2 M KCl gradient on homogenates of lymphoid tissues from rats injected with Triton WR-1339, (14)C-labeled dextran, (51)Cr-labeled erythrocytes, and cortisol. The results confirm and extend the conclusion, derived from previous investigations on normal animals, that the lysosomes of lymphoid tissues form two and possibly three, distinct populations. The evidence indicates that the L(19) population belongs to macrophages and the L(15) group to lymphocytes. The L(30) population appears to be associated with a special type of phagocyte with a high capacity for dextran storage. All three populations seem to contribute to the activities found in soluble form in homogenates of normal lymphoid tissues.

The ultrastructure of male germ cells in rats x-irradiated at birth

A histological and ultrastructural study was made of the testes of rats, aged 1 to 15 days, which had received partial-body X-irradiation (ca. 100 r) on the day of birth. Nineteen serially sectioned testes were subjected to a quantitative analysis including counts of germ cells and measurements of nuclear volume. The type, position and general form of germ cells, together with the incidence of various organelles, was assessed semi-quantitatively from 533 electron micrographs of irradiated (370) and normal (163) tissues. Exposure to 100 r at birth has no marked effect on the total population of germ cells during the first 5 days. The transformation of gonocytes into transitional cells is not affected. Subsequently, the treated testes differ from those of coeval controls by the almost complete absence of germinal mitoses and, consequently, of spermatogonia type A. Many of the transitional cells grow into irregularly-shaped giant cells, usually with a highly lobed nucleus and enlarged nucleoli. Although some cells show condensation of chromatin which may indicate the onset of mitotic prophase, the majority appear to degenerate at interphase. By 10 days, the testes contain only a fraction of the original population of germ cells. No significant changes are detectable in the ultrastructure of germ cells up to 4 days after irradiation. The treatment only induces the sporadic appearance of two minor features (pinocytotic vesicles containing electron-dense material; peripheral granular bodies with some internal organization) which are normally absent from corresponding cells in the controls. Electron micrographs of giant transitional cells confirmed the cytological observations of irregularity of nuclear outline and nucleolar enlargement. The nucleoli are frequently irregular in shape and contain material of two distinct electron densities. In general, the organelles of giant transitional cells are normal and healthy in appearance. With advancing age, an increasing proportion of germ cells show degenerative changes leading to pyknosis. Dead cells appear to be engulfed by neighbouring somatic cells. In both normal and irradiated testes, the simple form of Golgi apparatus in the gonocyte changes to a more complex type in the transitional cells. The persistence of giant cells is associated with a tendency for the Golgi apparatus to revert to the simple type, or to disperse into a number of small simple units. The most striking feature is the relatively high incidence of centrioles, suggesting that radiation-induced mitotic inhibition and gigantism may be accompanied by endomitosis. Irradiation does not markedly affect the appearance and incidence of A- and B-bodies (Franchi & Mandl 1964). These organelles tend, however, to persist over a longer period in irradiated than in untreated young rats.

Lysosomes: some pathologic implications

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THE EVOLUTION OF LYSOSOMES IN HYPOXIC LIVER PARENCHYMA AS SEEN WITH THE ELECTRON MICROSCOPE

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CONCERNING THE INFLUENCE OF HEAD IRRADIATION ON THE DEVELOPMENT OF RADIATION DAMAGE IN THE RAT THYMUS

Early radiation damage in rat thymocytes has been assessed at 4 hours and 24 hours following varying doses of whole body irradiation and compared with the effects produced by a dose of 1000 rads to the head only of the animal. The indirect dose to the shielded thymus in these head irradiation experiments was found to be 22 rads. The criteria employed to assess the radiation damage were: changes in wet weight, DNA content, pyknosis, Cr51uptake, supernatant NADase alkaline RNAase and soluble RNA and nucleotide content of the thymus. No radiation damage beyond what could be expected from scattered irradiation was produced in the thymus by head irradiation only. Adrenalectomized and hypophysectomized animals showed no difference in their response to whole body irradiation as compared to unoperated controls. It is concluded that the adenohypophysis response of irradiation is not involved in the death or damage of thymocytes following low doses of whole body irradiation.