Unusual sequence element found at the end of an amplicon.

In a polyomavirus-transformed rat cell line, designated LPT, the polyomavirus DNA is integrated into a single chromosomal site. Treatment of LPT cells with carcinogens induces amplification of the integrated virus DNA and flanking cellular sequences. We show that the amplification is arrested within a specific cell DNA segment that maps 1.3 to 1.85 kilobases beyond one virus-cell DNA junction, defined as the left junction. We also present the sequence of an 897-base-pair fragment spanning the arrest site. This fragment contains an unusual sequence element, which consists of two contiguous components, a potential cruciform with stems of 6 base pairs and a d(G-A)27 X d(T-C)27 tract, and maps 1,497 to 1,564 nucleotides beyond the left junction. The possibility that this unusual sequence plays a role in the arrest of the amplification process is discussed.     

Sterol carrier protein 2 (non-specific lipid transfer protein) is localized in membranous fractions of Leydig cells and Sertoli cells but not in germ cells.

The cellular and subcellular distribution of sterol carrier protein 2 (SCP2; nsL-TP) was reinvestigated in rat testicular cells by Western blotting and immunocytochemistry, using the affinity purified antibody against rat liver SCP2. Western blot analysis revealed high levels of the protein in the somatic cells of the testis, e.g., Leydig and Sertoli cells whereas it could not be detected in germ cells. This cellular localization of SCP2 was confirmed by Northern blotting. Immunocytochemical techniques revealed that in Leydig cells, immunoreactive proteins were concentrated in peroxisomes. Although SCP2 was also detected in Sertoli cells, a specific subcellular localization could not be shown. SCP2 was absent from germ cells. Analysis of subcellular fractions of Leydig cells showed that SCP2 is membrane bound without detectable amounts in the cytosolic fraction. These results are at variance with data published previously which suggested that in Leydig cells a substantial amount of SCP2 was present in the cytosol and that the distribution between membranes and cytosol was regulated by luteinizing hormone. The present data raise the question in what way SCP2 is involved in cholesterol transport between membranes in steroidogenic cells but also in non-steroidogenic cells.     

Modulation of small conductance calcium-activated potassium channels in C6 glioma cells

Using the patch clamp technique, we have characterized a small conductance, calcium-activated potassium (SK) channel in the C6 glioma cell line. Elevation of cytosolic Ca²⁺ concentration ([Ca²⁺] _i ) by applications of serotonin or ionomycin induced bursts of channel openings recorded in the cell-attached configuration. These channels underlie the serotonin-induced, [Ca²⁺] _i -activated whole-cell K⁺ conductance described previously. [Ca²⁺] _i directly activated SK channels in inside-out patches with a biphasic concentration dependence. Submicromolar [Ca²⁺] _i induced bursts of channel openings with a unitary conductance of about 25 pS, similar to that of the serotonin-induced channels. Supramicromolar [Ca²⁺] _i caused prolonged openings with a unitary conductance of about 35 pS, resulting in a pronounced increase of the average current in patches exposed to [Ca²⁺] _i above 100 m. The two modes of opening reflect the activity of the same SK channel. The channel conductance depended on external K⁺ concentration with K _Dof 5 m. The channel was slightly permeable to cations other than K⁺, with a permeability ratio for K⁺Ca²⁺Na⁺ of 10.0400.030, respectively. ATP was required to maintain channel activity in outside-out patches but was not essential in inside-out patches. The modulation of SK channels in C6 cells by components in their microenvironment may be related to the role of glial cells in controlling the extracellular milieu in the CNS.The authors are grateful to Dr. M. Segal for continuous support, stimulating discussions and criticism throughout the course of this work, to Dr. I. Steinberg for helpful suggestions and to Dr. H. Jarosch, for helping with the Fortran application. N.M.'s research was supported in part by BARD, the U.S.-Israel Binational Agricultural Research and Development Fund, grant no. IS-1670-89RC.     

Rhipicephalus sanguineus: Observations on the parasitic stage on dogs in the Negev Desert of Israel

Sixteen dogs were studied for infestation with R. sanguineus in Kibbutz Ze'elim in the north-western part of the Negev Desert over a period of one year. The mean number of ticks per dog per month was 16.4. The majority of the ticks were adults: males (48.6%) and females (34.4%). The cars and abdomen of the dog were the predilection sites for the ticks. Male ticks were more abundant on the ears, whereas female ticks were more abundant on the ears and the abdomen. A strong correlation between tick numbers and the ambient temperatures was found. The mean percentage of dogs infested in the winter months was 16.6% and increased in the summer months to 34.4%. During winter, ticks were found more often on the ears and head of their hosts whereas in summer they were distributed mainly on the ears, headd and abdomen. The male: female ratio was higher in winter (2.3:1) than in summer (1.1:1).     

TNF and PGE(2) in human monocyte-derived macrophages infected with Chlamydia trachomatis

In this study levels of prostaglandin E(2) (PGE(2)), tumour necrosis factor (TNF) and interleukin-1 (IL-1) alpha in medium from monocyte derived macrophages (MdM) infected with Chlamydia trachomatis (L(2)/434/Bu or K biovars). TNF and PGE(2) were found in both cases while IL-1 alpha was not detected. Both TNF and PGE(2) levels were higher in the medium of the MdM infected with K biovars. TNF reached maximum levels 24 h postinfection, and then declined, while PGE(2) levels increased continuously during the infection time up to 96 h post-infection. Addition of dexamethasone inhibited production of TNF and PGE(2). Inhibition of PGE(2) production by indomethacin resulted in increased production of TNF, while addition of PGE(2) caused partial inhibition of TNF production from infected MdM.     

Inequalities in self rated health in the 1958 birth cohort: lifetime social circumstances or social mobility?

OBJECTIVE: To investigate explanations for social inequalities in health with respect to health related social mobility and cumulative socioeconomic circumstances over the first three decades of life. DESIGN: Longitudinal follow up. SETTING: Great Britain. SUBJECTS: Data from the 1958 birth cohort study (all children born in England, Wales, and Scotland during 3-9 March 1958) were used, from the original birth survey and from sweeps at 16, 23, and 33 years. MAIN OUTCOME MEASURES: Subjects'' own ratings of their health; social differences in self rated health at age 33. RESULTS: Social mobility varied by health status, with those reporting poor health at age 23 having higher odds of downward mobility than of staying in same social class. Men with poor health were also less likely to be upwardly mobile. Prevalence of poor health at age 33 increased with decreasing social class: from 8.5% in classes I and II to 17.7% in classes IV and V among men, and from 9.4% to 18.8% among women. These social differences remained significant after adjustment for effects of social mobility. Health inequalities attenuated when adjusted for social class at birth, at age 16, or at 23 or for self rated health at age 23. When adjusted for all these variables simultaneously, social differences in self rated health at age 33 were substantially reduced and no longer significant. CONCLUSIONS: Lifetime socioeconomic circumstances accounted for inequalities in self reported health at age 33, while social mobility did not have a major effect on health inequalities.