A.R. Rabiee, I.J. Lean Animal Reproduction Science 64 2000 199–209 203
et al. 1974 with an autoanalyzer Cobas Mira, Roch Diagnostic Systems, Switzerland using the Roch reagent Roch Diagnostic systems, NJ, USA. The uptake of cholesterol
and glucose in sheep and cows have been reported Rabiee et al., 1997a,b.The radio im- munoassay for LH used in these studies was a double antibody assay based on the method
of Scaramuzzi et al. 1970. The antiserum to LH was provided by Prof. D.R. Lindsay and Prof. G.B. Martin, Department of Animal Science and Production, University of Western
Australia. The antiserum UWA 3B was raised in rabbits, and the cross-reactivity of this antiserum with NIH bLH B5 was 100. The minimum binding of tracer in the absence of
LH was 35. Nonspecific binding was consistently below 5 of added tracer. Inter-assay and intra-assay coefficients of variation were 11.6 and 6.3, respectively.
2.6. Statistical analysis Time series methods of analysis Chatfield, 1989; Shumway, 1988 were used to an-
alyze the relationship between the uptake of glucose and cholesterol by the ovary and arterial LH. These statistical procedures were developed by Prof. Shumway, Dr. Pope and
Dr. Weber personal communication in association with the authors. The mean, linear or quadratic trends of mean values for metabolites were removed to produce series for
each cow that were approximately stationary using the time series analysis procedure of STATGRAPHICS 1989. Cross-covariances of detrended data for each cow were calcu-
lated using BMDP 1992, and cross-correlations of each variable at different lags were calculated using cross-covariance and variance at lag 0 series, with the following formula:
Cross-correlation = R
12
m √
R
11
0 × R
22
where R
12
is the cross-covariance at lag m, and R
11
and R
22
the variances at lag 0 of the two series. The cross-covariances were calculated from the following function
R
12
m, m + k = CovR
1m
, R
2m+k
where R
12
m, m + k is the cross-covariance at time m and time m + k for series R
1
and R
2
, respectively, for each cow R
1m
is the residual for series R
1
at time m after detrending to produce an approximately stationary series, and R
2m+k
the residual for series R
2
at time m + k after detrending to produce an approximately stationary series.
The cross-correlation function is used to standardize the cross-covariance coefficients, which depend on the units in which the two series are measured Chatfield, 1989. Each
lag represents a difference of 10 min. Mean cross-correlations presented in Tables 1–5 and Figs. 1–2 represent the mean cross-correlations from the six cows and nine ewes for the
two variables at each of the lags examined.
3. Results
The time series cross-correlation between each two variables are presented in a tabular form to indicate the strength of association between the uptake of metabolites by the ovary
and arterial LH concentrations. Cross-correlations between metabolites were also presented graphically to display cross-correlations for metabolites at different lags.
204 A.R. Rabiee, I.J. Lean Animal Reproduction Science 64 2000 199–209
Table 1 Cross-correlations between the uptake of glucose and cholesterol by the ovary in the luteal phase for six cows
Cow Lag
−4 −3
−2 −1
1 2
3 4
C1 0.029
−0.16 −0.01
−0.21 0.92
∗∗∗
−0.05 0.02
−0.15 0.09
C2 0.19
0.12 −0.08
0.05 0.24
0.06 0.16
−0.0004 0.07
C3 0.18
−0.06 −0.15
0.30 0.27
−0.03 −0.06
−0.03 0.21
C4 −0.13
−0.14 0.06
0.25 0.73
∗∗
0.11 0.23
0.02 −0.10
C5 0.06
−0.06 −0.03
0.21 0.44
∗
−0.05 0.22
0.04 0.02
C6 0.017
−0.03 −0.2
−0.001 0.37
−0.08 −0.10
−0.06 0.10
Mean 0.06
−0.06 −0.07
0.10 0.50
∗∗∗
−0.006 0.08
−0.03 0.07
∗
P 0.05;
∗∗
P 0.01;
∗∗∗
P 0.001.
Table 2 Cross-correlations between the uptake of glucose and cholesterol by the ovary in the follicular phase for two cows
Cow Lag
−4 −3
−2 −1
1 2
3 4
C1 −0.11
−0.14 0.12
0.08 0.81
∗∗∗
−0.31 −0.23
−0.19 −0.02
C2 −0.18
0.19 0.04
−0.10 0.94
∗∗∗
−0.10 −0.006
0.14 −0.21
Mean −0.14
0.03 0.08
−0.01 0.87
∗∗∗
−0.20 −0.12
−0.03 −0.11
∗∗∗
P 0.001.
Table 3 Cross-correlations between the uptake of glucose and cholesterol uptakes by the ovary at different stages of the
estrus cycle for nine ewes
a
Sheep Lag
−4 −3
−2 −1
1 2
3 4
S1 −0.0008
0.11 0.009
0.11 0.60
∗∗
0.45
∗
0.26 −0.002
0.09 S2
−0.04 −0.07
0.40 −0.15
0.80
∗∗∗
−0.03 0.16
0.03 −0.01
S3 0.0
−0.04 0.02
−0.34 0.95
∗∗∗
−0.24 −0.05
−0.01 −0.004
S4 −0.07
0.18 0.01
0.10 0.52
∗
−0.16 −0.07
0.17 −0.15
S5 −0.12
−0.07 −0.10
0.06 0.96
∗∗∗
0.15 0.05
−0.04 −0.08
S6 0.07
−0.07 −0.21
−0.23 0.81
∗∗∗
−0.12 −0.21
−0.007 0.10
S7 0.02
−0.06 0.28
−0.60
∗∗
0.96
∗∗∗
−0.46
∗
0.17 −0.20
0.02 S8
−0.11 −0.16
0.21 −0.28
0.95
∗∗∗
−0.47
∗
0.17 −0.17
−0.08 S9
0.03 −0.02
−0.09 0.26
0.70
∗∗
0.29 −0.07
0.11 0.10
Mean −0.03
−0.02 0.06
−0.12 0.81
∗∗∗
−0.07 0.05
0.0001 −0.002
a
S1 and S2 were in proestrus, S3 and S4 in oestrus, S5–S8 in diestrus, and S9 had no luteal or follicular structure.
∗
P 0.05;
∗∗
P 0.01;
∗∗∗
P 0.001.
A.R. Rabiee, I.J. Lean Animal Reproduction Science 64 2000 199–209 205
Table 4 Cross-correlations between transovarian uptake of glucose and arterial LH in the luteal phase for six cows
Cow Lag
−4 −3
−2 −1
1 2
3 4
C1 0.13
0.03 −0.28
−0.20 0.46
∗
0.10 −0.09
−0.08 0.004
C2 0.05
0.02 −0.19
−0.20 −0.39
0.13 0.007
−0.25 0.14
C3 −0.04
−0.09 −0.09
0.17 0.26
−0.13 0.09
0.26 −0.17
C4 0.10
0.05 0.06
0.20 0.22
0.01 −0.15
0.15 −0.18
C5 −0.04
−0.004 −0.23
0.14 0.50
∗
0.03 0.21
0.10 0.04
C6 −0.02
−0.09 0.18
0.37 −0.23
0.21 0.21
0.16 0.12
Mean 0.03
−0.008 −0.09
0.08 0.14
0.06 0.04
0.06 −0.007
∗
P 0.05.
Table 5 Cross-correlations between transovarian uptake of cholesterol and arterial LH in the luteal phase for six cows
Cow Lag
−4 −3
−2 −1
1 2
3 4
C1 0.09
−0.009 −0.20
0.02 0.38
0.007 −0.04
−0.09 −0.05
C2 0.001
0.05 −0.21
−0.02 −0.33
−0.21 −0.14
−0.07 −0.04
C3 0.02
−0.19 0.15
0.19 0.02
−0.07 0.12
0.0 0.02
C4 0.0
0.22 0.21
0.36 −0.12
−0.17 0.09
−0.34 0.10
C5 0.02
0.03 −0.29
−0.10 0.58
∗∗
0.29 0.10
0.03 −0.01
C6 −0.11
−0.17 −0.09
0.02 0.04
0.03 0.14
0.11 0.16
Mean 0.005
−0.01 −0.07
0.08 0.09
−0.02 0.04
−0.06 0.03
∗∗
P 0.01.
Fig. 1. Mean cross-correlation between the uptake of glucose and cholesterol in the luteal phase for six cows.
206 A.R. Rabiee, I.J. Lean Animal Reproduction Science 64 2000 199–209
Fig. 2. Mean cross-correlation between the uptake of glucose and cholesterol at different stages of the estrus cycle for all ewes.
Correlations between the uptake of metabolites were examined for individual cows and sheep. Cross-correlations between glucose and cholesterol uptakes by the ovary and arterial
LH in individual ewes and cows at different stages of the oestrous cycle are given in Ta- bles 1–3. Mean cross-correlations MCC between cholesterol and glucose uptakes by the
ovary were significant at lag 0 in cattle in the luteal and follicular phases MCC = 0.5 and 0.87, P 0.01 and 0.001, respectively; Fig. 1, and in sheep MCC = 0.81, P 0.001;
Fig. 2. Although, three cows did not have significant cross-correlations between the uptake glucose and cholesterol, these correlations were consistently significant for all sheep. There
was some evidence of negative feedback in sheep, as significant negative cross-correlations between glucose and cholesterol at lags −1 and +1 were observed.
Table 4 shows cross-correlations between glucose and arterial LH for all cows. There was no significant difference between mean cross-correlations for glucose uptake and arterial
LH at lag 0 MCC = 0.14, P = 0.13, but cross-correlations were significant for two cows at lag 0. Cross-correlations between cholesterol uptake and arterial LH are presented
in Table 5. Mean cross-correlations between cholesterol uptake and arterial LH were not significant MCC = 0.096, P 0.2, but were significant in one cow only at lag 0. There
was no similar data available for the sheep to assess these relationships.
4. Discussion
