A 22-amino-acid peptide restores DNA-binding activity to dimerization-defective mutants of the estrogen receptor.

We have identified residues within the estrogen receptor that are required for dimerization and high-affinity DNA binding. A 22-amino-acid peptide encompassing these residues was sufficient to restore DNA-binding activity to a mutant receptor lacking most of the hormone-binding domain. Point mutagenesis of the fusion protein confirmed that this sequence continued to mediate dimerization in a manner similar to that within the native receptor, although its position relative to the DNA-binding domain was appreciably altered.     

Metal-dependent binding of a nuclear factor to the rat metallothionein-I promoter.

Genomic footprinting studies in vivo and experiments using synthetic metal regulatory elements (MREs) in vitro suggest protein binding to the MREs of the mouse and rat metallothionein I (MT-I) genes. Using gel-retardation assays of promoter fragments, we observe a cadmium-dependent binding factor for the rat MT-I promoter in rat hepatoma cells. This factor is present in extracts from both uninduced and cadmium-induced cells, but requires the presence of cadmium to bind to the promoter. The formation of a cadmium-dependent complex is competed by an oligonucleotide containing two MREs. This competition is lost when when one of the MREs is mutated, indicating a requirement for at least two MREs for binding of this factor. The cadmium-dependent factor dissociates more rapidly from the MT-I promoter than does a factor that binds to a consensus Sp1 site present on the same DNA fragment. UV crosslinking analysis using nuclear extracts from cadmium induced cells, in the presence of an oligonucleotide probe containing both 5-bromodeoxyuridine and 32P-deoxycytidine, identifies a 39 kDalton protein associated with the metal inducible complex.     

Phase I study of combination recombinant interleukin-2 and interferon gamma in patients with advanced malignancies

A phase I trial of interleukin-2 and interferon gamma combination treatment in patients with advanced malignancies was performed based on preclinical in vitro and in vivo data which demonstrated synergistic antitumor effect. The toxicities, immune parameters, and tumor responses are described. The clinical and biologic maximal tolerated doses were extrapolated from these data.     

Expression of ACh-activated channels and sodium channels by messenger RNAs from innervated and denervated muscle

Xenopus oocytes were used to express polyadenylated messenger RNAs (mRNAs) encoding acetylcholine receptors and voltage-activated sodium channels from innervated and denervated skeletal muscles of cat and rat. Oocytes injected with mRNA from denervated muscle acquired high sensitivity to acetylcholine, whereas those injected with mRNA from innervated muscle showed virtually no response. Hence the amount of translationally active mRNA encoding acetylcholine receptors appears to be very low in normally innervated muscle, but increases greatly after denervation. Conversely, voltage-activated sodium currents induced by mRNA from innervated muscle were about three times larger than those from denervated muscle; this result suggests that innervated muscle contains more mRNA coding for sodium channels. The sodium current induced by mRNA from denervated muscle was relatively more resistant to block by tetrodotoxin. Thus a proportion of the sodium channels in denervated muscle may be encoded by mRNAs different from those encoding the normal channels.     

Lack of differentiation following mouse serum treatment of cultured chick limb myoblasts

This investigation was conducted to assess the effects of mouse serum on chick skeletal muscle cell differentiation. In light of earlier findings of altered membrane phospholipid metabolism following mouse serum treatment of Friend erythroleukemic and chick chondrogenic cells, it was of interest to determine whether similar changes would modulate the fusion of mononucleated myoblasts, which is necessary for the formation of multinucleated skeletal muscle fibers. When mouse serum is added to low density cultures of enriched chick myoblasts shortly following cell attachment to the substratum, fusion is inhibited and neutral lipid accumulation ensues. There is an early inhibitory effect on DNA synthesis but not on protein synthesis. There is no increase in the uptake of 2-deoxyglucose following insulin stimulation of the cells, which suggests that while the cells are accumulating large amounts of lipid, they are not being converted into typical adipocytes. Finally, even in cultures of mouse serum-treated cells that undergo significant fusion, one observes thinner myotubes that do not spontaneously contract as do those of control cultures, as well as a disorganization of fluorescently stained actin and myosin myofilaments. These findings demonstrate that mouse serum acts in a dose-dependent manner, is not cytotoxic to the cells, but is capable of modulating normal developmental events of myoblasts as reported for other cell and tissue types.     

Taking care of patients--does it matter whether the physician is a woman?

Researchers have recently begun to compare male and female physicians'' attitudes toward patients, medical knowledge, and practice styles. Although women start medical school with more "humanistic views," the conservative effect of medical socialization on both male and female students attenuates these differences. While some studies suggested that men are more scientifically knowledgeable, recent studies showed no significant differences in physicians'' medical knowledge. Male and female physicians also had comparable diagnostic and therapeutic behavior. In the intimate world of physicians and patients, however, there were notable differences. Women physicians seemed better able to communicate sensitivity and caring to patients, which may account for the common perception that women are more caring and empathic physicians. Medical educators may wish to study more closely female physicians'' communication styles to identify these behaviors and inculcate them into all physicians.     

Intergeneric rosettes: sequestered surface recognition among human periodontal bacteria

The human oral bacteria, Streptococcus sanguis and Bacteroides loescheii, when mixed in equal numbers in vitro, formed large settling coaggregates. As the relative number of each cell type was changed, coaggregates became smaller until at cell-type ratios of 10 to 1, rosettes formed. Rosettes consisting of a streptococcal cell in the center surrounded by bacteroides cells exhibited surface recognition properties of only the bacteroides, which coaggregated with many other cell types such as Actinomyces naeslundii, and formed large settling multigeneric aggregates. The ecological significance of these results derives from the following: (i) the direct demonstration that intergeneric coaggregates can protect the central cell from or prevent its access to other cells in the environment, and (ii) the potential for these effects to occur during bacterial succession of various cell types observed in progressively more severe stages of human periodontal disease.     

Measurement of exchange of trace metals between the body and its surroundings with the use of trace methodology

Application of general tracer theory to the problem of estimating fluxes of tracee between the gastrointestinal tract and the body proper, from observations of the movement of tracer, shows that a number of assumptions must be fulfilled. Two specific sets of assumptions are discussed and, in both cases, measurement of tracer fluxes yields information on the integrated absorption of the tracee.