Luteolysis during two stages of the estrous cycle: subsequent endocrine profiles associated with radiotelemetrically detected estrus in heifers.

Our objective was to correlate hormonal changes with the timing and onset of estrus in heifers before and after luteolysis was induced with PGF2 alpha at two stages of the estrous cycle: d 6 to 9 (early; n = 10) or d 14 to 15 (late; n = 10). Blood was collected at intervals of 2 or 12 h to quantify serum concentrations of progesterone, estradiol-17 beta, and LH while heifers were observed visually for estrus and monitored for standing activity by pressure-sensitive, radiotelemetric devices. Although the concentrations of estradiol-17 beta that were associated with the putative appearance of the first dominant follicle declined before luteolysis was induced early in the cycle, some heifers that were given PGF2 alpha were in estrus as early as 35 h. Compared with heifers treated late in the estrous cycle, heifers that were treated early in the cycle produced less progesterone before PGF2 alpha treatment and had greater peak concentrations of estradiol-17 beta at estrus. In addition, heifers that were treated early in the cycle had shorter intervals from PGF2 alpha treatment to estrus, to peak estradiol-17 beta, and to peak LH and to initiation of estrus after the peak in estradiol-17 beta than did heifers treated later in the cycle. The increase in estradiol-17 beta associated with the putative first-wave follicle of the subsequent cycle and the duration of that cycle in early cycle heifers was less than after late cycle luteolysis. Results indicated that greater concentrations of estradiol-17 beta during estrus may be related to the durations of previous cycles and less progesterone exposure before luteolysis. The onset of estrus corresponded closely to, but preceded, the preovulatory LH surge by approximately 3 h.

Fertility in estrus-cycling and noncycling virgin heifers and suckled beef cows after induced ovulation.

A procedure was developed to either induce or synchronize ovulation in heifers and suckled cows. Beef females were assigned to two breeding programs: 1) two injections of prostaglandin F2alpha (PGF2alpha) given 14 d apart to synchronize estrus (PGF2alpha control; n = 179), with inseminations 12 to 16 h after detected estrus or at 80 h in the absence of estrus, or 2) two injections of PGF2alpha (d -14 and 0) plus 100 microg of GnRH on d -7 when 6 mg of norgestomet was implanted (PGF2alpha/NORG/GnRH treatment; n = 173). Implants were removed 24 h after the second PGF2alpha injection (d +1) and females were inseminated 12 to 16 h after detected estrus until 54 h after PGF2alpha. The remaining cattle were given a second 100-microg GnRH injection 54 h after PGF2alpha and inseminated 18 to 20 h later. Percentages of noncycling females with subsequently elevated progesterone (P4) on d 0 or +1 were not different between treatment groups (20.4 vs 25%), but conception rate was greater (P < .05) in noncycling treated females than in noncycling controls (55 vs 12.8%). Conception rates in cycling (59.2%) and noncycling (62.2%) treated females were similar to those in cycling controls (56.2%) but greater (P = .06) than those in noncycling controls (26.5%). Conception rates in treated females inseminated 12 to 16 h after detected estrus (63.1%) or at one fixed time (58.3%) were similar to those in controls inseminated 12 to 16 h after detected estrus (68.7%). This treatment procedure produced fertility after one timed insemination that was equal to controls inseminated after detected estrus and induced equally fertile ovulations in noncycling heifers and cows.

Restricting calf presence without suckling compared with weaning prolongs postpartum anovulation in beef cattle.

To determine how continued presence of a calf affected duration of postpartum anovulation, 23 udder-intact cows and their calves were assigned to three treatments on d 4 to 9 postpartum (experimental d 0). The treatments were 1) calf present with unlimited contact with its dam (n = 8), 2) calf restricted to noninguinal contact with its dam (n = 8), and 3) calf weaned from its dam (n = 7). Calves in the calf-present and calf-restricted treatments were weaned after 5 wk. Based on daily measurements of blood progesterone, days to first ovulation after onset of treatments were 35.4 +/- 2.2, 22.5 +/- 2.2, and 14.3 +/- 2.2 for the calf-present, calf-restricted, and calf-weaned treatments, respectively; each one differed (P < .01) from the others. Mean concentrations of LH were greater (P < .05) in the calf-restricted treatment and tended (P = .13) to be greater in the calf-weaned treatment than in the calf-present treatment on d 7 after the onset of treatments. On d 7 and 21, calves in the calf-present and calf-restricted (calves could not suckle) treatments were returned to their dams after overnight separation. Blood samples were collected to assess changes in cortisol, ACTH, prolactin, and oxytocin. No treatment effects were detected on d 7, but on d 21, the calf-present and calf-restricted cows had a greater (P < .05) increase in cortisol after calf return than the calf-weaned cows (calves were not returned), whereas prolactin was increased (P < .05) after calf return in the calf-present cows only. We conclude that calf presence is associated with an increase in cortisol and calf presence without suckling is one factor that delays the onset of first postpartum ovulation in beef cows.

A phosphatidylinositol 4,5-bisphosphate-sensitive casein kinase I alpha associates with synaptic vesicles and phosphorylates a subset of vesicle proteins.

In interphase cells, alpha-casein kinase I (alpha-CKI) is found associated with cytosolic vesicular structures, the centrosome, and within the nucleus. To identify the specific vesicular structures with which alpha-CKI is associated, established cell lines and primary rat neurons were immunofluorescently labeled with an antibody raised to alpha-CKI. In nonneuronal cells, alpha-CKI colocalizes with vesicular structures which align with microtubules and are partially coincident with both Golgi and endoplasmic reticulum markers. In neurons, alpha-CKI colocalizes with synaptic vesicle markers. When synaptic vesicles were purified from rat brain, they were highly enriched in a CKI, based on activity and immunoreactivity. The synaptic vesicle-associated CKI is an extrinsic kinase and was eluted from synaptic vesicles and purified. This purified CKI has properties most similar to alpha-CKI. When the activities of casein kinase I or II were specifically inhibited on isolated synaptic vesicles, CKI was shown to phosphorylate a specific subset of vesicle proteins, one of which was identified as the synaptic vesicle-specific protein SV2. As with alpha-CKI, the synaptic vesicle CKI is inhibited by phosphatidylinositol 4,5-bisphosphate (PIP2). However, synthesis of PIP2 was detected only in plasma membrane-containing fractions. Therefore, PIP2 may spatially regulate CKI. Since PIP2 synthesis is required for secretion, this inhibition of CKI may be important for the regulation of secretion.

Mechanism underlying the absence of ischemic changes on the exercise electrocardiogram in patients with abnormal exercise thallium-201 imaging and coronary artery disease.

Patients with coronary artery disease may have reversible abnormalities on a thallium myocardial perfusion study without simultaneous ischemic changes on the exercise electrocardiogram, but the mechanisms responsible for this disparity have not been fully elucidated. A group of 37 patients with angiographically demonstrated coronary artery disease and abnormal thallium perfusion imaging were divided into two groups on the basis of their exercise electrocardiographic ST segment response. Thirteen patients (Group A) had no significant electrocardiographic changes with exercise, while 24 patients (Group B) had ST changes consistent with ischemia during the test. There were no significant differences in clinical or angiographic characteristics between the two groups. Stress test results showed a similar mean duration of exercise in the two groups (6.2 +/- 1.8 versus 6.7 +/- 2.5 min, p = NS), but the patients in Group A achieved a significantly lower mean maximal heart rate (117 +/- 26 versus 132 +/- 21 beats/min, p less than 0.05) and mean maximal double product (19,650 +/- 5116 versus 22,650 +/- 4871, p less than 0.05). There was no consistent pattern of thallium perfusion abnormality noted in Group A to suggest that a particular region of electrically silent myocardium was responsible for ischemia in the absence of electrocardiographic changes. These results suggest that exercise thallium-electrocardiogram discordance is mediated by the level of myocardial workload achieved. An abnormal perfusion scan accompanying an exercise electrocardiogram which does not demonstrate any ischemic ST change may occur when there is sufficient increase in myocardial oxygen demand to result in differential augmentation of myocardial blood flow, but insufficient imbalance of supply and demand to result in signs of ischemia on the surface electrocardiogram.

Response to thyrotropin releasing hormone: an objective criterion for the adequacy of thyrotropin suppression therapy.

Most serum thyrotropin (TSH) assays do not adequately discriminate between normal values and absent TSH. We therefore evaluated the TSH response to thyrotropin releasing hormone (TRH) as a criterion for the adequacy of TSH suppression therapy. Twenty-six outpatients with various thyroid disorders (cancer, 10; nodules, 9; miscellaneous, 4; hypothyroidism after 131I therapy for Graves' disease, 3) were studied. Using the frequent sampling technique (samples every 20 min) in two normal volunteers and one untreated patient who was TRH-responsive, we first confirmed the observation that TSH secretion occurred episodically throughout the 24-h period. In contrast, serum TSH was undetectable (less than 0.6 micronU/ml) throughout the 24-h period in 5 patients on TSH suppression therapy who were TRH-unresponsive and one who had a minimal response to TRH. Thus, TRH-unresponsive patients did not secrete measurable amounts of TSH throughout the 24-h period. To suppress TSH secretion, all patients were treated with L-thyroxine (T4) at doses which resulted in undetectable TSH values in random plasma samples. TRH tests were carried out only when random TSH concentrations were less than 0.6 micronU/ml. Seven of the twenty-six patients (27%) including two with thyroid cancer were TRH-responsive indicating a potential for TSH secretion. In these seven, the T4 dose was adjusted until they were TRH-unresponsive. The mean change in T4 dose of these 7 patients was 20+/-10 (SD) microng/day and this resulted in a mean increase of 1.5+/-1.1 microng/dl for T4 and 20+/-20 ng/dl for T3. For all patients, the mean T4 dose required for TSH suppression was 172+/-53 microng/day or 2.6+/-0.8 microng per day per kg body weight. Twenty-three of 26 patients required between 100-200 microng/day and the remaining 3, 250-300 microng/day. The T4 dose required to suppress TSH resulted in normal serum concentrations of T4. 9.1+/-2.0 MICRONG/DL, AND T3, 136.7+/-33.6 NG/DL. These T4 doses did not produce a rapid heart rate, either awake or asleep, arrhythmias, or electrocardiographic abnormalties as assessed by 24-h Holter monitor tracings in 11 patients. Our results thus show that the T4 dose which results in an unresponsive TRH test ensures that serum TSH will remain undetectable (less than 0.6 micronU/ml) throughout the 24-h period. An unresponsive TRH test, therefore, appears to be a very useful and reliable index of TSH suppression.