Colonic hemorrhage produced in mice by a unique vero cell cytotoxin from an Escherichia coli strain that causes hemorrhagic colitis

A Vero cell cytotoxin that produces colonic lesions and subsequent colonic hemorrhage in mice has been purified from a strain of Escherichia coli O157:H7 that causes hemorrhagic colitis in humans. This toxin is different in physicochemical properties from the Shiga-like toxin previously associated with this organism and may be responsible for the unique diffuse mucosal hemorrhage in the colon of individuals with E. coli O157:H7 infections.     

Novobiocin modulates colchicine sensitivity in parental and multidrug-resistant B16 melanoma cells

The effect of the antibiotic agent novobiocin on the sensitivity of melanoma cells to colchicine and vinblastine was examined in drug-sensitive and drug-resistant B16 melanoma cells. A cell line COL/R was selected for colchicine resistance. The COL/R cell line (resistant to 80 ng/ml colchicine) was found to possess the multidrug-resistant (MDR) phenotype. The cells were shown to be cross-resistant to vinblastine and Adriamycin and to overexpress P glycoprotein. P glycoprotein activity was assessed by using the rhodamine 123 accumulation test. Rhodamine accumulation was markedly decreased in COL/R cells as compared to the parental B16 cells. Verapamil reversed drug resistance and increased rhodamine accumulation in COL/R cells. Novobiocin in combination with colchicine or vinblastine synergistically inhibited the proliferation of parental B16 cells. In COL/R cells, novobiocin markedly decreased colchicine resistance and increased rhodamine accumulation. These data show that novobiocin incrases the sensitivity of both parental and MDR melanoma cells to microtubule-disrupting cytotoxic drugs.Abbreviation PGP P glycoprotein     

Testing hypotheses of aging in long-lived painted turtles (Chrysemys picta)

For 38 of the past 50 years, Painted Turtles were studied on the University of Michigan's E.S. George Reserve in southeastern Michigan. We compared age specific body sizes, reproductive traits and survival of Painted Turtles ranging from 9 to 61 years of age to test contrasting predictions of the Relative Reproductive Rate and Senescence Hypotheses of aging. Indeterminate growth (i.e. continued body growth of adults) was important in increasing reproductive output of older turtles; however, growth rate of the oldest age-group was reduced compared to that of younger adults. Although clutch size and among year reproductive frequency did not increase with age, within year reproductive frequency (production of second clutches), egg size, and hatchling size did. Nest predation rates and the proportion of surviving nests that produced hatchlings were similar among age groups, and embryo mortality in nests was not related to age. Survivorship of males was less than that of females, and survivorship of the oldest group of females was not statistically different from that of a younger group of females. No decline in reproductive output or survivorship was detected in the oldest females as predicted by the Senescence Hypothesis. Thus, the majority of data on reproductive traits and survivorship support the Relative Reproductive Rate Hypothesis. We also compared Painted Turtles to Blanding's Turtles, another species studied on the E.S. George Reserve. That Painted Turtles exhibit indeterminate growth whereas Blanding's Turtles do not, appears to be a primary mechanism for some differences between species in the relationships between reproductive traits and age. An important mechanism for increasing reproductive output in both species was increased reproductive frequency in older females. Painted Turtles also increased offspring quality (egg and hatchling size) with age, whereas Blanding's Turtles did not. Compared to younger individuals, there was no reduction in survivorship in the oldest Painted Turtles and survivorship increased in the oldest Blanding's Turtles.     

The effect of aloe emodin on the proliferation of a new merkel carcinoma cell line.

A free-floating cell line has been established from a metastatic lesion of a Merkel cell carcinoma (MCC) patient. The cell line was characterized by immunocytochemical reactions with antibodies against the epithelial and neuroendocrine antigens: cytokeratin 20, neuron-specific enolase, chromogranin A, neurofilament protein, synaptophysin, and calcitonin. Karyotype analysis of the MCC cells showed deletion in chromosomes 3 and 7, loss of chromosome 10, and several translocations in other chromosomes. No mutation was detected in the TP53 gene, after analyzing the complete coding region. Growth factors such as basic fibroblast growth factor, transforming growth factor-beta, and nerve and epidermal growth factors had no effect on the proliferation of the cells. The differentiation-inducing agents sodium butyrate and dimethyl sulfoxide, especially the former, markedly inhibited the proliferation of the MCC cells. Aloe emodin, a natural constituent of aloe vera leaves, significantly inhibited the growth of MCC cells. Aloe emodin has been reported to be nontoxic for normal cells but to possess specific toxicity for neuroectodermal tumor cells. Differentiation-inducing agents, and aloe emodin, merit further investigation as potential agents for treating MCC.