Spectroscopic observations of a sample of dwarf spirals galaxies.
  I.Oxygen abundances
  The oxygen abundances for four dwarf spiral galaxies have been determined
using long-slit spectroscopy. The abundances of these galaxies have not
previously reported in the literature. Several HII regions were detected in
each galaxy. The electronic temperature method could be used only in one region
because of the lack of the auroral lines of oxygen or sulfur. Therefore, four
different semi empirical methods were used in the abundance determinations and
a weighted-average abundance is obtained. The abundances of three of the
galaxies are sub solar for all the regions, one of them having a very low
metallicity. Only three HII regions in the fourth galaxy show slightly over
solar abundances. Three of the HII regions might have a PN embedded. A
comparison with the oxygen abundances among different types of late-type
galaxies (BCG, LSBG, dI, Sm) is made. The conclusion is that all of them show
the same range in metallicity. Also, the log(N/O) is similar, showing a
secondary behaviour for abundances larger than 8.2 dex in spite of the
morphological type of the mother galaxy.
