The fifth freedom

Women in developing countries suffer considerable morbidity and mortality due to inability to control their own fertility and lack of access to family planning services. Over 500,000 deaths each year are related to pregnancy. Two thirds of these maternal deaths could be prevented by providing contraception to those women who wish to use it in developing countries. There is no tenable ethical defence of cultural and religious behaviour which denies a women a choice as to whether she will undertake a pregnancy or not. Implementaion of the principles of the programme of action from the 1994 Cairo Population Conference would, through empowering women to control their own fertility, have a huge impact on maternal health in the developing world. [Kincaid-Smith is president of the World Medical Association].     

Time-dependent changes of calcium influx and efflux rates in rabbit skeletal muscle sarcoplasmic reticulum

Unfractionated and low buoyant density sarcoplasmic reticulum vesicles released calcium spontaneously after ATP- or acetyl phosphate-supported calcium uptake when internal Ca²⁺ was stabilized by the use of 50 mM phosphate as calcium-precipitating anion. This spontaneous calcium release could not be attributed to falling Ca²⁺ concentration outside the vesicles (Ca₀²⁺), substrate depletion, ADP accumulation, nonspecific membrane deterioration or the attainment of a high vesicular calcium content. Instead, spontaneous calcium release was directly proportional to Ca₀²⁺ at the time that calcium content was maximal. A causal relationship between high Ca₀²⁺ and spontaneous calcium release was suggested by the finding that elevation of Ca₀²⁺ from less than 1 μM to 3–5 μM increased the rate and extent of calcium release.The spontaneous calcium release was due both to acceleration of calcium efflux and slowing of calcium influx that was not accompanied by a significant change in the rate of ATP hydrolysis. Neither reversal of the transmembrane KCl gradient nor incubation with cation and proton ionophores abolished the spontaneous calcium release. The persistence of calcium release under conditions where the membrane was permeable to both anions and cations makes it unlikely that this phenomenon is due to a changing transmembrane potential.     

Location of the origin of replication for the 7.5-kbChlamydia trachomatis plasmid

The hypothetical origin of replication for the 7.5-kb plasmid common toChlamydia trachomatis is believed to be in a region of the plasmid that contains four 22-bp tandem repeats preceded by an A-T-rich region. To test this hypothesis, replication of plasmid DNA in metabolically active reticulate bodies of the Lymphogranuloma venereum biovar ofC. trachomatis was examined by electron microscopy. The results presented show that the origin of replication appears to be near the tandem repeats of pCHL2. In addition, replication of the 7.5-kb plasmid is unidirectional, and the copy number during replication is 7–10. The evidence presented suggests thatC. trachomatis has a homologue to theEscherichia coli dnaA gene and that this homologue might be involved in replication of theC. trachomatis 7.5-kb plasmid.     

Discriminant analysis on cells from developing squamous cancer of the respiratory tract

Cytologic preparations made from the tracheobronchial tree taken by the Schreiber catheter have been scanned by three color microphotometry. The digitized cell images were processed by the analytical cytodiagnostic programs of the TICAS system. Cells were sorted into two control groups and five groups of increasing atypia ranging from normal epithelium to invasive squamous cell carcinoma. Standard statistical tests, including Wilk's Lambda, Rao's V, and the Kruskal-Wallis tests are performed on these subsets of cell image features. This study demonstrates that discriminant analyses permit differentiation between normal cells and those from marked atypia or carcinoma and that the classification achieves a high degree of agreement with visual assignment.     

Freeze-fracture study of the junctional complexes of human and rabbit thyroid follicles

Summary Zonulae occludentes, gap junctions and desmosomes have been demonstrated in replicas of freeze-fractured follicular cells of normal human and rabbit thyroid glands. The zonulae occludentes between the human follicular cells are composed of two to eight strands, which completely separate the intercellular space from the follicular lumen. Four to twelve or more strands are visible between the follicular cells of the rabbit thyroid gland.In the meshes of the zonulae occludentes as well as below them, gap junctions are present. They are numerous on the fracture faces of the human follicular cell membranes, but infrequent in those of the rabbit.Aggregates of particles related to desmosomes are found in the deeper meshes of the zonulae occludentes or close to them.     

The glomeruli of the human and the rat kidney studied by freeze-fracturing

Glomeruli isolated from rat and human kidneys were studied using the freeze-fracture technique. Discontinuous zonulae occludentes and gap junctions were found in the replicas of the split plasma membrane of the endothelial cells. A diaphragm across the endothelial pores was not demonstrated. The central layer of the basement membrane, corresponding to the lamina densa described in thin sections, revealed a coarse substructure. A slit membrane between the pedicles of the podocytes was not detectable; however, its position was indicated by the different texture of the replica, which abruptly changed at the transition of the basement membrane to the primary urinary space. Furthermore, at the level of the slit membrane arrays of particles were present within the cleaved membrane of the pedicles, probably representing the attachment points of the slit membrane. Isolated strands of a zonula occludens as well as gap junctions were seen on the split plasma membrane of the podocytes. The mesangial cells could be identified by their contiguity to the endothelial cells and by their numerous gap junctions.     

Thyrotropin-releasing hormone inreases prolactin mRNA activity in the cytoplasm of GH-cells as measured by translation in a wheat germ cell-free system

A wheat germ embryo extract was used to translate cytoplasmic RNA isolated from rat pituitary tumor cells (GH-cells). This RNA directed the synthesis of a radioactive product which was precipitated with antiserum specific for rat prolactin. The molecular weight of this immunoprecipitated product was 24,500 as determined by electrophoresis in denaturing gels. Prolactin secreted by intact GH-cells had a molecular weight identical to standard pituitary prolactin, reported to be about 22,500. Our finding that a larger form of prolactin is made by the wheat germ system is similar to results recently described by Maurer, Stone and Gorski (J. Biol. Chem., in press). Thyrotropin-releasing hormone (TRH) stimulates prolactin synthesis in GH-cells, and cytoplasmic RNA isolated from cells treated with TRH directed the synthesis in wheat germ extracts of larger amounts of prolactin than RNA isolated from control cells. The increase in translatable cytoplasmic mRNA for prolactin corresponded to the increase in prolactin synthesis which suggests that the increase in prolactin synthesis in TRH-treated cells is a result of the accumulation of cytoplasmic mRNA for prolactin.