Intracellular Cl regulates Na-K-Cl cotransport activity in human trabecular meshwork cells

The trabecular meshwork (TM) of the eye plays a central role inmodulating intraocular pressure by regulating aqueous humor outflow,although the mechanisms are largely unknown. We and others have shownpreviously that aqueous humor outflow facility is modulated byconditions that alter TM cell volume. We have also shown that theNa-K-Cl cotransport system is a primary regulator of TM cell volume andthat its activity appears to be coordinated with net efflux pathways tomaintain steady-state volume. However, the cellular mechanisms thatregulate cotransport activity and cell volume in TM cells have yet tobe elucidated. The present study was conducted to investigate thehypothesis that intracellular Cl concentration([Cl]_i) acts toregulate TM cell Na-K-Cl cotransport activity, as has been shownpreviously for some other cell types. We demonstrate here that thehuman TM cell Na-K-Cl cotransporter is highly sensitive to changes in[Cl]_i. Our findingsreveal a marked stimulation of Na-K-Cl cotransport activity, assessedas ouabain-insensitive, bumetanide-sensitive K influx, in TM cells following preincubation of cells with Cl-free medium as a means ofreducing [Cl]_i. Incontrast, preincubation of cells with media containing elevated Kconcentrations as a means of increasing [Cl]_i results ininhibition of Na-K-Cl cotransport activity. The effects of reducing[Cl]_i, as well aselevating [Cl]_i, onNa-K-Cl cotransport activity are concentration dependent. Furthermore, the stimulatory effect of reduced[Cl]_i is additive withcell-shrinkage-induced stimulation of the cotransporter. Our studiesalso show that TM cell Na-K-Cl cotransport activity is altered by avariety of Cl channel modulators, presumably through changes in[Cl]_i. These findingssupport the hypothesis that regulation of Na-K-Cl cotransport activity,and thus cell volume, by[Cl]_i may participatein modulating outflow facility across the TM.

     

New markers and map sequences inNeurospora crassa,with a description of mapping by duplication coverage,and of multiple translocation stocks for testing linkage

Thirty previously unmapped markers have been located; 13 are at newly designated loci. Numerous sequences for previously mapped genes have also been determined. A revised map of linkage group I is presented. The order from conventional mapping has been confirmed by testing recessive markers in IL for coverage by duplications. Assignment of new mutants to linkage groups is greatly facilitated by using gene-tagged multiple translocation strains for linkage detection; these “alcoy” tester strains and procedures for using them are described. Recent mapping data of other workers are compiled. Distal markers are now known for all but one of the 14 chromosome arms, but extensive map segments are still devoid of markers.     

Immunological cross-reactions among gadidae parvalbumins

Antisera raised against apparently homogeneous whiting parvalbumin III have been found to recognize two non cross-reacting molecular species of parvalbumins. Aliquots of these antisera have been separately absorbed with two distinct parvalbumins from a near-related fish species, namely haddock parvalbumins II and III, and also with the homologous antigen. The immunochemical reactivities of absorbed and non-absorbed antisera toward parvalbumins from nine Gadidae species have been systematically explored by immunoelectrophoresis. The observed cross-reactions lead to distinguish two groups among Gadidae parvalbumins. So far this discrimination can be correlated with differences in amino-acid compositions, peptide maps and sequences which are known to characterize several protein members from each of the two groups. Using the same anti-whiting antisera, a tenuous common antigenic reactivity is shown between Gadidae and some Cyprinidae parvalbumins.     

Positive regulation of normal and tumoral mammary epithelial cell proliferation by fibroblasts in coculture

Summary In the mammary gland, mesenchymal-epithelial interactions are of paramount importance during normal and tumoral developments. We have studied the paracrine growth regulation of a variety of breast epithelial cells in coculture with normal or pathological breast fibroblasts. Two models of coculture were used in which the two cell types were seeded and grown, either together in microchamber slides or separated by a microporous membrane. Under these two conditions, all fibroblasts were shown to stimulate the proliferation of the hormono-responsive breast carcinoma MCF-7 cell line, suggesting that cell contacts were not indispensable for the paracrine stimulation of MCF-7 cell growth by fibroblasts. Moreover, in the Transwell coculture system, the proliferation of a variety of other breast carcinoma cells (MDA-MB231, T47D, and BT-20) was also stimulated by fibroblasts. However, the amplitude of the proliferative response seemed to be dependent on the carcinoma cell line considered. Moreover, the proliferative response of normal mammary epithelial cells to the presence of fibroblasts was shown to be significantly higher than the tumor cell response. The nature of the tissue of fibroblast origin, normal or pathological, did not influence the growth response of the epithelial cells. In this study, we thus demonstrate that fibroblasts are able to stimulate the proliferation of normal and carcinoma cells through paracrine exchange mechanisms. We also conclude that the target epithelial cell phenotype will essentially determine the extent of the proliferative response.     

Exercise ECG changes in normal women

Submaximal and/or maximal exercise was carried out by 357 women without a history of cardiovascular disease, using a bicycle ergometer and/or treadmill while monitored by a bipolar ECG lead CM₅. In 40- to 60-year-old women the incidence of an ischemic ECG pattern during or after exercise ranged from 20 to 50%. Because clinical coronary disease can be expected in less than 10% of normal women followed for 16 years, most of these ECG changes were not considered to be due to occult coronary disease. At the present time exercise ECG changes in women cannot be used with any reliability as an aid in the diagnosis of chest pain or in screening normal female populations for coronary heart disease.