I was asked in class if glycolytic oscillations have been observed "in vivo"
(that is, in real living cells, instead of just in a test-tube that contains
the same chemicals), and I said I'd look into some references.
Here are two papers (selected from many) that report on this phenomenon;
I included some quotes from their abstracts too.

Nature 402, 320 - 322 (1999)
Sustained oscillations in living cells
by Sune Danø, Preben Graae Sørensen, and Finn Hynne

"Glycolytic oscillations in yeast have been studied for many years simply by
adding a glucose pulse to a suspension of cells and measuring the resulting
transient oscillations of NADH [1-12]. Here we show, using a suspension of
yeast cells, that living cells can be kept in a well defined oscillating state
indefinitely when starved cells, glucose and cyanide are pumped into a cuvette
with outflow of surplus liquid.  Our results show that the transitions between
stationary and oscillatory behaviour are uniquely described mathematically by
the Hopf bifurcation..."

Am J Physiol. 1992 Jun;262(6 Pt 1):E800-5.
Oscillations of lactate released from islets of Langerhans: evidence for
oscillatory glycolysis in beta-cells
Chou HF, Berman N, Ipp E.

"Oscillations in the glycolytic process have been demonstrated in a number of
different biological systems. However, their presence has never been
demonstrated in insulin-secreting beta-cells....
...
In conclusion, sustained oscillations in lactate released from islets of
Langerhans suggest that the glycolytic process in beta-cells also
oscillates...."

While on the topic: you may want to look at:
  http://bill.srnr.arizona.edu/classes/496yGLYCOL.HTM
for a good introduction, several experimental graphs, and lots of references