California's male suicide rate at record high.

Breast cancer is the most commonly occurring cancer in women and, until recently surpassed by lung cancer, was the leading cause of cancer-related death in women. It is the leading cause of death in women aged 39 to 44 years. The American Cancer Society has estimated that there will be 135,000 new cases of breast cancer and 42,300 breast cancer-related deaths in 1988. It is now predicted that breast cancer will develop in one out of every ten women in the United States. Given the clinical and public health significance of breast cancer, annual screening with mammography and clinical breast examination is recommended for women aged 50 and older to reduce breast cancer mortality.     

Naltrexone prevents footshock-induced performance deficit in rats

Three experiments demonstrate that inescapable footshock delivered to unrestrained rats produces analgesia as well as performance deficits in subsequent one-way shuttle acquisition. Both the performance and the antinociceptive effects are prevented by pretreatment with as little as 0.1 mg/kg i.p. of the opiate antagonist, naltrexone. These studies suggest that both effects are mediated through opiate receptors with similar underlying naltrexone pharmacodynamics.     

Vitamin A--a pregnancy hazard alert.

Vitamin A is essential to human health, but concerns have arisen recently regarding its potential teratogenicity. Human and animal birth defects have been associated with the use of the vitamin A analogue, isotretinoin, or Accutane, for acne treatment, although the association of such defects with vitamin A itself is unclear. The federal Food and Drug Administration is evaluating the health issues surrounding vitamin A and, together with the manufacturer, has developed restrictions and label warnings to ensure the appropriate use of Accutane. We also have evaluated these issues, with concerns about the possible teratogenicity of high vitamin A intake during pregnancy. Practitioners should be familiar with the possible hazard of excessive dosages of vitamin A and its analogues. Vitamin A daily doses of higher than 8,000 IU for pregnant woman are not necessary for good health and are not recommended. Foods high in beta-carotene can provide the necessary amounts of vitamin A and, in contrast to the synthetic analogues, their use has not been associated with vitamin A toxicity or teratogenicity in humans or animals.     

A New Method for Finding Small Vertebrate Fossils: Ultraviolet Light At Night

Vertebrate fossils from many different formations fluoresce when exposed to ultraviolet (UV) light. In this paper field observations and controlled experiments in the Chadron Formation (White River Group, late Eocene) of Wyoming are used to assess the utility of searching for fossils at night using ultraviolet light. The results indicate that, especially for very small teeth and egg-shell fragments, searching with ultraviolet light at night can result in significantly more specimens than searching during daylight hours. This method has the potential to increase sample sizes for small vertebrate specimens that are often overlooked when using standard collecting techniques.     

Evidence that free polysomes are not the precursors of membrane-bound polysomes in rat liver

We tested, in rat liver, the postulate that free polysomes were precursors of membrane-bound polysomes. Three methods were used to isolate free and membrane-bound ribosomes from either post-nuclear or post-mitochondrial supernatants of rat liver. Isolation and quantitation of 28 S and 18 S rRNA allowed determination of the 40 S and 60 S subunit composition of free and membrane-bound ribosomal populations, while pulse labeling of 28 S and 18 S rRNA with [6-¹⁴C]orotic acid and inorganic [³²P]phosphate allowed assessment of relative rates of subunit renewal. Throughout the extra-nuclear compartment, 40 S and 60 S subunits were present in essentially equal numbers, but, free ribosomes contained a stoichiometric excess of 40 S subunits, while membrane-bound ribosomes contained a complementary excess of 60 S subunits. Experiments with labeled precursors showed that throughout the extra-nuclear compartment, 40 S and 60 S subunits accumulated isotopes at essentially equal rates, however, free ribosomes accumulated isotopes faster than membrane-bound ribosomes. Among free ribosomes or polysomes, 40 S subunits accumulated isotopes faster than 60 S subunits, but, this relationship was not seen among membrane-bound ribosomes. Here, 40 S subunits accumulated isotope more slowly than 60 S subunits. This distribution of labeled precursors does not support the postulate that free polysomes are precursors of membrane-bound polysomes, but, these data suggest that membrane-bound polysomes could be precursors of free polysomes.     

Synchrony between DNA synthesis and thymidine incorporation into DNA in regenerating rat liver

DNA synthesis in regenerating liver was studied to determine whether the onset of stimulated DNA synthesis preceded the onset of increased incorporation of thymidine into DNA. Thymidine incorporation into hepatic DNA was not stimulated 15 h after operation, but was stimulated after 18 h; peak stimulation occurred 30 h after operation. Thymidine kinase activity was stimulated 24 h after operation; highest kinase activity was observed at 36 h. The onset of stimulated DNA synthesis was estimated by following the incorporation of labeled aspartic acid, sodium formate, adenine or orotic acid into appropriate DNA bases, viz., thymine, adenine, adenine or cytosine, respectively. Incorporation of adenine and orotic acid was stimulated between 15 h and 18 h after operation; incorporation of aspartic acid and sodium formate was stimulated between 18 h and 21 h after operation.The incorporation of thymidine into DNA was accelerated by stress stimulus and was inhibited by hydrocortisone. Changes in thymidine kinase activity also were correspondingly accelerated or delayed. Incorporation of labeled thymidine, adenine, formate, orotic acid or thymine into appropriate DNA bases, viz., thymine, adenine, adenine, cytosine or thymine, respectively, was stimulated by stress stimulus or was inhibited by hydrocortisone.It was concluded from these data that stimulation of DNA synthesis and of thymidine incorporation into DNA was essentially synchronized in regenerating rat liver. Results from this study were compared with results from similar studies in 2 other tissues, and the limitations, attendant with using thymidine incorporation into DNA as an indicator of stimulated DNA synthesis, were discussed.     

Does phospholipase C stimulate thymide kinase activity of rat liver extracts prepared after partial hepatectomy.

Our purpose was to determine whether phospholipase C stimulated thymidine kinase activity of regenerating rat liver. We determined effects of phospholipase C upon TMP formation by rat liver extracts prepared at 0, 12, 24, 36 and 48 hr following partial hepatectomy. Data were obtained which supported these conclusions: (a) Commercial preparations of phospholipase C contained nucleoside phosphotransferase activity; (b) phospholipase C exerted no appreciable stimulatory influence upon thymidine kinase activity of regenerating rat liver; and (c), apparent stimulation of thymidine kinase was associated with linked activities of two enzymes, viz., liver extract-ATPase activity and nucleoside phosphotransferase activity.