Oncogenes and human breast cancer.

The role of oncogenes in breast tumorigenesis is unclear. Alterations and/or amplification of several oncogene sequences have been observed in primary human breast tumors, in breast tumor cell lines, and in mammary tumors in model systems. In principle, such alterations could be sites of primary lesions for human breast cancer, causes of tumor progression or metastasis, or simply secondary lesions of highly aberrant tumor genomes. The present study tested genetic linkage of breast cancer susceptibility to nine oncogenes in 12 extended families including 87 affected individuals. Lod scores for close linkage of each candidate sequence to breast cancer were -19.6 for HRAS, -12.3 for KRAS2, -1.0 for NRAS, -6.0 for MYC, -6.1 for MYB, -8.2 for ERBA2, -7.9 for INT2, and -5.1 for RAF1. Regions of chromosome 11p associated with tumor homozygosity and the region of 3p carrying the gene for Von Hippel-Lindau disease could also be excluded from linkage to human breast cancer. The 5-kb allele of the MOS oncogene, previously proposed to be associated with breast cancer, was absent in these families, suggesting that polymorphism at this locus is not associated with inherited susceptibility. These results strongly suggest that oncogenes are not the sites of primary alterations leading to breast cancer. On the other hand, alterations in one or more of these sequences may be associated with tumor progression.     

Blood glucose discrimination training in insulin-dependent diabetes mellitus (IDDM) patients

Self-management of insulin-dependent diabetes mellitus (IDDM) is dependent on a negative feedback loop of blood glucose (BG) fluctuations, which in turn directs treatment decisions to maintain normal BG. Although this feedback is typically accomplished by self-monitoring of blood glucose (SMBG), SMBG has limitations, and patients often rely on what their BG "feels" like. Two studies were performed to evaluate whether patients could learn to more accurately "feel"/discriminate their BG on the basis of internal cues or internal plus external BG cues. In Study I, BG Awareness Training significantly improved pre- to posttreatment BG estimation accuracy, relative to a control group. Study II replicated BG Awareness Training efficacy in improving BG estimation accuracy. Improvement in estimation accuracy was related only to initial accuracy; those who were initially less accurate improved the most. This improvement was represented in a 31% reduction in dangerous BG estimation errors and a 9% increase in accurate estimates. Resulting estimations were, however, still significantly less accurate than SMBG at the end of training.     

Distribution of the Glucose-1,6-Bisphosphate System in Brain and Retina

The distribution of glucose-1,6-bisphosphate (G16P2) synthase was measured in more than 70 regions of mouse brain, and nine layers of monkey retina. Activities in gray areas varied as much as 10-fold, in a hierarchical manner, from highest in telencephalon, especially the limbic system, to lowest in cerebellum, medulla, and spinal cord. The synthase levels were significantly correlated among different regions with G16P2 itself, as well as with previously published levels of a brain specific IMP-dependent G16P2 phosphatase. In contrast, neither G16P2 nor either its synthase or phosphatase correlated positively with phosphoglucomutase, and in all regions the G16P2 levels greatly exceeded requirements for activation of this mutase. This strengthens the view that G16P2 has some function besides serving as coenzyme for phosphoglucomutase. However, attempts to correlate the "G16P2 system," as defined by the three coordinately related elements, synthase, phosphatase, and G16P2, with other enzymes of carbohydrate metabolism, or with regional data of Sokoloff et al. [J. Neurochem. 28, 897-916 (1977)] for glucose consumption, were unsuccessful. This leaves open the possibility that brain G16P2 might serve as a phosphate donor for specific nonmetabolic effector proteins.     

Alternate mRNA splicing is required for synthesis of adeno-associated virus VP1 capsid protein.

Fine-structure mapping of the capsid-specific mRNAs from adeno-associated virus (AAV) revealed an alternate splicing pattern in these RNAs. S1 nuclease and primer extension analyses showed that splicing of these mRNAs occurs at acceptor sites at nucleotide 2228 (major splice) or 2201 (minor splice). Both splice acceptors were ligated to the same 55-nucleotide leader in mature mRNAs. Both species were present in equal amounts in mRNA derived from AAV plasmid-transfected cells. However, when adenovirus infection accompanied the DNA transfection, the major splice predominated over the minor splice. Using cDNA clones of both the major and minor spliced mRNAs, we demonstrated that the largest AAV capsid protein, VP1, was derived from the minor spliced mRNA. The other capsid proteins, VP2 and VP3, came predominantly from the major spliced mRNA. These results, which describe the previously undetected minor splice, provide a mechanism for the production of all three AAV virion proteins.     

Blood glucose discrimination training in insulin-dependent diabetes mellitus (IDDM) patients

Self-management of insulin-dependent diabetes mellitus (IDDM) is dependent on a negative feedback loop of blood glucose (BG) fluctuations, which in turn directs treatment decisions to maintain normal BG. Although this feedback is typically accomplished by self-monitoring of blood glucose (SMBG), SMBG has limitations, and patients often rely on what their BG feels like. Two studies were performed to evaluate whether patients could learn to more accurately feel/discriminate their BG on the basis of internal cues or internal plus external BG cues. In Study I, BG Awareness Training significantly improved pre- to posttreatment BG estimation accuracy, relative to a control group. Study II replicated BG Awareness Training efficacy in improving BG estimation accuracy. Improvement in estimation accuracy was related only to initial accuracy; those who were initially less accurate improved the most. This improvement was represented in a 31% reduction in dangerous BG estimation errors and a 9% increase in accurate estimates. Resulting estimations were, however, still significantly less accurate than SMBG at the end of training.This research was supported by NIH grants AM282880, AM24177, AM22125, and RR00847 and by the Ames Company. The authors express their appreciation for the contribution made by trainers Leslie Butterfield and Linda Zimbelman, by the nursing staff at the University of Virginia's Clinical Research Center and the Diabetes and Nutrition Unit, and by Dr. James May from the Medical College of Virginia in soliciting subjects. We would also like to thank Andrea Snyder for her assistance.     

Lipopolysaccharide-induced NF-kappa B activation in mouse 70Z/3 pre-B lymphocytes is inhibited by mevinolin and 5''-methylthioadenosine: roles of protein isoprenylation and carboxyl methylation reactions.

We show that both the lipopolysaccharide (LPS)-induced activation of NF-kappa DNA binding and kappa gene expression are blocked by treating murine pre-B lymphocyte 70Z/3 cells with 5'-methylthioadenosine (MTA), an inhibitor of several S-adenosylmethionine-dependent methylation reactions. We further show that the LPS-induced incorporation of radioactivity from [methyl-3H]methionine into methyl ester-like linkages on a group of membrane polypeptides is also inhibited by MTA treatment, suggesting the involvement of protein methylation reactions in the LPS signal transduction pathway. We also find that NF-kappa B and kappa gene activation in LPS-treated 70Z/3 cells is blocked by mevinolin, an inhibitor that prevents protein isoprenylation. Interestingly, mevinolin-treated cells also exhibited a marked reduction in the methylation of membrane proteins. Neither MTA nor mevinolin significantly inhibited NF-kappa B activation by phorbol myristate acetate, suggesting that these agents act early in signal transduction. These results provide the first evidence that carboxyl methylated and/or isoprenylated proteins play an essential role in the LPS-signaling pathway.