Estrogen receptor distribution in enucleated breast cancer cell lines.

The intracellular location of estrogen receptors in hormone-responsive cells has been studied with a number of techniques which indicate that the unoccupied receptors are nuclear and not cytoplasmic proteins. We used cell enucleation of two human breast cancer-derived cell lines, MCF-7 and T47D, to determine whether the unoccupied receptors were also nuclear in these cells and to determine whether the weak estrogen phenol red, present in nearly all tissue culture media, affected the distribution of the receptors seen with this technique. Nucleoplasts prepared from the breast cancer cells contained most of the estrogen receptors that were present in whole cells. The cytoplast fraction, which contained some contaminating whole cells, also contained some receptors. However, incubating cells with estradiol before enucleation did not translocate any receptors out of the cytoplast fraction (to the nucleoplasts). The unoccupied receptors appeared to be almost exclusively nuclear in these cells. The same results were obtained with either radioligand binding or enzyme-linked immunoassay used to measure estrogen receptor, and the distribution of receptors was unaffected by the presence of the pH indicator phenol red. In addition, we observed changes in the estrogen receptor content of incubated cytoplasts that were consistent with receptor synthesis, and this may prove to be a useful model system to characterize receptor synthesis and degradation.

Dense fibers protect mammalian sperm against damage.

The relative tensile strengths of the sperm of seven mammalian species and sea urchins have been measured by determining the minimum shear necessary to kill them (assayed by lack of motility) when they are suspended in a viscous fluid. In general, long sperm are killed by smaller shears than short sperm. However, the longer sperm are not as fragile as would be expected from theoretical predictions. Their additional tensile strength correlates well with the size of their dense fibers; a theory that includes the dense fiber contributions accurately predicts the sperm tensile strength for most of the species in which this has been measured. This added strength may be necessary to protect sperm from shear forces encountered during epididymal transport and especially during ejaculation, as these forces are strong enough to kill long sperm if they are not strengthened.

Detection of chlamydiosis in a shipment of pet birds, leading to recognition of an outbreak of clinically mild psittacosis in humans.

Avian chlamydiosis was detected in a shipment of > 700 pet birds from a Florida bird distributor that were sold to nine Atlanta-area pet stores in August 1995. Respiratory illness among persons who had recently acquired birds from this shipment was reported to local public health officials. The attack rate of acute respiratory illness was 10.7% among persons in households exposed to birds from the implicated flock vs. 1.8% among control households (odds ratio, 6.60; 95% confidence interval, 1.39-31.2). Illness and serological evidence of infection in the absence of symptoms were more common among persons in households with recently purchased birds that were sick or that had died and among persons who had had direct contact with the birds. Clinical psittacosis or serological evidence of Chlamydia psittaci infection was found in 30.7% of households with birds from the infected flock. Mild illnesses and asymptomatic infections in exposed persons were unusual features of this outbreak.