Metabolism of exogenous galactosylceramide in the twitcher mouse brain

The in vivo metabolism of galactosylceramide (gal-cer) in normal mice and in twitcher mice, a model of human GLD, was examined following intracerebral administration of gal-cer containing [1-¹⁴C]stearic acid. In normal mice, gal-cer was hydrolyzed to ceramide within 6 hours and ceramide was hydrolyzed to sphingosine and fatty acid. Most of the released fatty acid was immediately incorporated into other lipids. About 75% of injected gal-cer was hydrolyzed 80 hours after the injection, while in the twitcher mouse, only 17% of gal-cer was hydrolyzed. These results show that degradation of gal-cer is impaired in the twitcher mouse brain, but contradict to the fact that there was no evidence of any accumulation of gal-cer in the brain. This discrepancy may be due to the different sorting routes of biosynthesized and exogenously-administered gal-cer in the mouse brain. Most of the biosynthesized gal-cer is incorporated into myelin, while the injected gal-cer is incorporated into lysosomes.     

Concentrations of essential elements after repeated administrations of tin and selenium

To study effects of simultaneous administration of tin (Sn) and selenium (Se) on concentrations of several essential elements, mice were injected with either SnCl2 (ip) or Na2SeO3 (sc), alone or both compounds at a daily dose of 5 mumol/kg each for 12 consecutive days. Mice were sacrificed at 20 h after the last injection and concentrations of Sn, Se, Na, Ca, Zn, P, Fe, K, and Mg in the liver, kidney, spleen, pancreas, testis, seminal vesicle, lung, femoral muscle, and femoral bone were determined. In the control mice, Sn and Se concentrations were the highest in bone (0.69 micrograms Sn and 6.93 micrograms Se/g dry wt). Administered Sn was found to accumulate in all organs except the testis. Among the essential elements determined, Na was the most affected in terms of concentration in the organs and Mg was the least affected element in these organs. Among the organs tested, each elemental concentration in the pancreas was most affected. Simultaneous injections of Sn and Se appeared to keep the correlation coefficients between elements similar to those found in the control mice.     

小鼠巨核系祖细胞增殖,分化特性的研究

小鼠骨髓细胞经7d培养后进行细胞形态学观察,可见不同发育阶段的巨核细胞及不同大小的巨核细胞集落。通过计数每个集落中的细胞数,可确定相应祖细胞的有丝分裂能力。结果表明,具有不同有丝分裂能力的祖细胞的体外增殖动力学有所不同。祖细胞的数量与其有丝分裂次数呈负相关(r=-0.986)。进行0、1、2和3次有丝分裂的祖细胞的阿糖胞苷自杀率分别为48.9,58.7,48.0和41.2％;放射敏感性的D_O值(Gy)分别为1.71,1.24,1.03和0.77,D_O值的大小与有丝分裂次数呈负相关(r=-0.958)。经3Gy全身照射后CFU-Meg与CFU-GM的恢复动态过程具有不同特点。     

Serum-free culture of enriched mouse anterior and ventral prostatic epithelial cells in collagen gel

Summary Sustained growth of mouse ventral and anterior prostatic epithelial cells embedded within collagen gel matrix was achieved in a serum-free medium composed of Dulbecco's modified Eagle's medium and Ham's F12 medium, 1∶1 (vol/vol), supplemented with bovine serum albumin fraction V, epidermal growth factor, transferrin, cholera toxin, prolactin, 5α-dihydrotestosterone, cortisol, putrescine, fibroblast growth factor, and a trace element mixture. Three-dimensional growth of prostatic epithelial cells occurred inside the collagen gel matrix. This serum-free medium allowed cell growth greater than sevenfold over 10 d in culture. Tissue recombination and cell culture techniques were integrated to demonstrate that cultured cells retained prostatic characteristics. Following 10 d of culture, epithelial colonies from mouse ventral and anterior prostatic epithelial cell cultures were isolated and combined with rat fetal urogenital sinus mesenchyme and grown for 4 wk under the renal capsule of intact athymic male mice. These tissue recombinants showed distinctive prostatic histologic characteristic (alveoli and ducts lined with cuboidal or columnar epithelium surrounded by stroma). When histologic sections of recombinants were stained with the Hoechst 33258, epithelial cells of mouse origin were distinguishable from stromal cells of rat origin. Aided by grants CA-05388 and CA-09041 from the National Institutes of Health, Bethesda, MD, and by M. A. R. C. fellowship GM08730 to T. T.     

In vitro development of one-cell embryos from outbred mice: Influence of culture medium composition

Summary One-cell embryos from outbred mice (CF1, CD-1, and Dub:ICR) were cultured in various modifications of egg culture medium (ECM). The best development was observed in medium in which inorganic salts of modified T6 medium (mT6) replaced those of ECM. In this modification (TE), 66% of one-cell CF1 embryos developed into blastocysts, comared to 46 and 43% for ECM and mT6, respectively. Moreover, the cell numbers of blastocysts developing in TE (74.9±3.3) were higher than the cell numbers of those developing in ECM (55.1±2.4). The culture requirements of embryos varied between different stocks of mice: Fewer CF1 embryos developed to the blastocyst stage than either Dub:ICR embryos (90%) or CD-1 embryos (84%). Lowering the osmolarity of the medium from 300 to 280 mOsm, increasing the concentration of KC1 from 1.42 to 25 mM, or omitting lactate from the medium during Day 1 of culture did not further improve development of embryos, in contrast to previous reports. However, the time at which embryos were transferred to outgrowth medium influenced their postblastocyst development. The best development was observed when embryos were transferred on Day 4 of culture at the late morula-early blastocyst stage. This work was supported by the Office of Health and Environmental Research, U.S. Department of Energy, Washington, DC, contract DE-AC03-76-SF01012.     

Radical Cations in Aromatic Hydrocarbon Carcinogenesis

Most carcinogens, including polycyclic aromatic hydrocarbons (PAH), require metabolic activation to produce the ultimate electrophilic species that bind covalently with cellular macromolecules to trigger the cancer process. Metabolic activation of PAH can be understood in terms of two main pathways: one-electron oxidation to yield reactive intermediate radical cations and monooxygenation to produce bay-region diol epoxides. The reason we have postulated that one-electron oxidation plays an important role in the activation of PAH derives from certain common characteristics of the radical cation chemistry of the most potent carcinogenic PAH. Two main features common to these PAH are: 1) a relatively low ionization potential, which allows easy metabolic removal of one electron, and 2) charge localization in the PAH radical cation that renders this intermediate specifically and efficiently reactive toward nucleophiles. Equally important, cytochrome P-450 and mammalian peroxidases catalyze one-electron oxidation. This mechanism plays a role in the binding of PAH to DNA. Chemical, biochemical and biological evidence will be presented supporting the important role of one-electron oxidation in the activation of PAH leading to initiation of cancer.     

EPISTASIS AS A SOURCE OF INCREASED ADDITIVE GENETIC VARIANCE AT POPULATION BOTTLENECKS

The role of epistasis in evolution and speciation has remained controversial. We use a new parameterization of physiological epistasis to examine the effects of epistasis on levels of additive genetic variance during a population bottleneck. We found that all forms of epistasis increase average additive genetic variance in finite populations derived from initial populations with intermediate allele frequencies. Average additive variance continues to increase over many generations, especially at larger population sizes (N = 32 to 64). Additive-by-additive epistasis is the most potent source of additive genetic variance in this situation, whereas dominance-by-dominance epistasis contributes smaller amounts of additive genetic variance. With additive-by-dominance epistasis, additive genetic variance decreases at a relatively high rate immediately after a population bottleneck, rebounding to higher levels after several generations. Empirical examples of epistasis for murine adult body weight based on measured genotypes are provided illustrating the varying effects of epistasis on additive genetic variance during population bottlenecks.     

Rhombomere formation and hind-brain crest cell migration from prorhombomeric origins in mouse embryos

Prior to rhombomere development, structures called prorhombomeres appear in the mammalian hindbrain. This study clarifies the developmental relationship between prorhombomeres and their descendent rhombomeres and hindbrain crest cells in mouse embryos by focal dye injections at various levels of prorhombomere A (proRhA), proRhB, and proRhC, as well as at their boundaries. ProRhA gives rise to two rhombomeres, rhombomeres 1 and 2 (r1 and r2), as well as to crest cells that migrate into the first pharyngeal arch, including the trigeminal ganglion. ProRhB develops into r3 and r4 and produces crest cells populating the second arch and acousticofacial ganglion. The anterior portion of proRhC gives rise to r5 and r6 and to crest cells migrating into the third pharyngeal arch and the IXth ganglion; its posterior portion develops into r7 and releases crest cells into the fourth pharyngeal arch region as well as the Xth ganglion. These results suggest that the boundaries between prorhombomeres serve as lineage restrictions for both hind-brain neuroepithelial cells and for segmental origins of crest cell populations in mouse embryos. The Hox code of the mouse head can be schematized in a much simpler way based on this prorhombomeric organization of the hind-brain, suggesting that prorhombomeres primarily underlie mammalian hind-brain segmentation.     

Human aging brain disorders: Role of antioxidant enzymes

In order to investigate the role of two free radical detoxificant enzymes in patients with aging brain disorders, superoxide dismutase (SOD) and catalase (CAT) activities have been measured in blood from male and female human patients of different ages with several types of aging brain disorders. When compared with activities in the normal population, we have detected: 1) SOD and CAT activities are decreased in patients with Parkinson disease. 2) SOD activity seems to be normal and CAT activity is decreased in patients with dementia. 3) In the patients with stroke, SOD activity is normal, while CAT activity is decreased. SOD activity was measured in red blood cells using the Minami and Yoshikawa method. CAT activity was measured in hemolysates by the method of Aebi. We can conclude that SOD and CAT activities in patients with Parkinson disease are decreased.