Introduction 2003 2003 1999 2002 2003 1992 2004 2003 1994 2001 1998 2004 2000 1992 1983 b 1967 1965 d k 1992 q 1992 1998 2003 Materials and methods Animals 1992 Nos2 tm1Lau 1995 −/− −/− Nos2 tm1Lau +/+ +/+ Nos2 tm1Lau −/− −/− 2 Mammary gland whole mounts Pairs of inguinal mammary glands were fixed in formalin or Carnoy’s fixative, dehydrated through a graded series of ethanol solutions and defatted in xylene. Following rehydration, the mammary epithelium was stained with carmine stain (Sigma Chemical, St Louis, MO) for 30 min. After removing excess stain by washing in water, samples were dehydrated and stored in methyl salicylate (Sigma Chemical, St Louis, MO). Tumor microvascular density 2003 2 Lung metastases 2 2 +/+ −/− Statistical analysis t U +/+ −/− Results PyMT tumorigenesis is delayed in the C57Bl/6 strain 1992 1 1 Fig. 1 A P  N  N B +/+  Effects of iNOS deficiency are more apparent in the C57Bl/6 background  −/− 2003 2 2 Fig. 2 A +/+ −/− B +/+ −/−  +/+ N  −/− N  +/+ N  −/− N  PyMT tumor growth kinetics vary in FVB/N and C57Bl/6 strains  3 3 3 Fig. 3 A  N  N B +/+ −/− +/+  −/−   Deficiency in iNOS-modulated tumor growth is site specific 2003 −/− 4 −/− 4 +/+ −/− 1 Fig. 4 A −/− P B −/− P +/+ N −/− N  Table 1 Quantitative analysis of tumor microvascular density Genotype Location N 2 2 +/+ #1 9 216 ± 20 +/+ #2–5 9 176 ± 12 −/− #1 6 201 ± 11 −/− #2–5 11 189 ± 11 Data are means ± SEM 5 Fig. 5 +/+ +/+  iNOS effects on tumor metastasis  +/+ −/− 6 −/− Fig. 6 A +/+ −/− B P U +/+ N −/− N +/+ N −/− N  Discussion 2003 2001 2005 1998 1991 2002 2005 2005 1985 1998 2004 2002 2004 2006 2002 2006 −/− −/− −/− 2003 2005 2005 2001