In the Black Jack story 'Tetsu of the Yamanote Main Line', there is an inspector called Tomobiki which is an part of Tokyo in the Nerima area in Urusei Yatsura. The Urusei Yatsura manga ran 1978–87 and the the Black Jack manga ran 1973-83 so its conceivable.
The manga story can be read here http://www.mangafox.com/manga/black_jack/v04/c007/1.html and the exact page with the reference can be found here http://www.mangafox.com/manga/black_jack/v04/c007/13.html.
SonicDaMan:
Hmm.. it's hard to say. It could just be a coincidence.
cata:
I think a reference is mainly images and sometimes with dialog. I don't think names have to be a reference, and I'll show you why. How many Sakura do you know?
I know:
Sakura Haruno - Naruto/Naruto Shippuuden Sakura - Urusei Yatsura Sakura - CardCaptor Sakura (and some other supporter characters that appear in 1-2 episodes)
That's just an example and if you go to www.myanimelist.com and type "Sakura" on "Characters" it will appear a huge list and it doesn't mean that all those Sakuras exist because they're a refference to the first Sakura.
Kroptik:
Sakura is also the main male (yes, MALE) character of Bokusatsu Tenshi Dokuro-chan. It's his last/family name though. :P
SonicDaMan:
I've been to a sushi restaurant called "Sakura" lol