Luteinizing hormone secretion patterns in boys at the onset of puberty measured using a highly sensitive immunoradiometric assay.

Pulsatile LH secretion was studied in 3 prepubertal and 11 early pubertal boys by measuring plasma LH concentrations at 10-min intervals from 1200-1800 h and from 2400-0600 h using an immunoradiometric assay with a lower limit of detection of 0.10 IU/L. Plasma testosterone (T) was measured hourly. In the prepubertal boys plasma LH was not detectable during the daytime but at night 20- to 300-min periods of detectable, but low (less than 0.5 IU/L) plasma LH values occurred. A discrete episodic LH pattern was discernible, and the median number of pulses was 2 during the 6-h nocturnal sampling periods. Plasma T was not detectable (less than 1.0 nmol/L). In the pubertal boys most daytime plasma LH values were greater than 0.3 IU/L, with periods of values of 0.1-0.3 IU/L and short periods of undetectable levels as well. At night definite pulses, up to 4.7 IU/L, were found in all boys. The median number of pulses was 4 during the 6-h nocturnal sampling period. Plasma T was detectable at night in 5 of these 11 boys. The results strongly suggest that at the onset of puberty prepubertal boys (G1) have no LH secretion during the day but intermittent gonadotrophic activity during the night. In early puberty LH secretion increases in amplitude as well as frequency to a clear pulsatile pattern during the night, sometimes with pulses during the day as well.

Luteinizing hormone release after two injections of synthetic luteinizing hormone releasing hormone in the ewe.

Anoestrous ewes were given two injections of 30 mug synthetic luteinizing hormone releasing hormone (LH-RH) separated by one of the following intervals: 1-5, 3, 6, 12 or 24 h. The first injection caused an increase in the plasma LH concentration in each animal. The response to the second injection was dependent on the interval between the injections. When the second injection was administered 1-5 h after the first it caused a further increase in the LH concentration to maximal levels which were significantly greater than those induced in the other anoestrous groups. When the second injection was administered 3 h after the first, there was no significant difference between the responses to the two injections although the time to reach the maximal LH concentration was shorter and the height of the LH peak was greater in each animal following the second injection. When the second injection was administered 6, 12 or 24 h after the first, the LH response was significantly less, in terms of height and area of the induced peak, than following the first injection. The LH response to the second injection was particularly low in the 12 and 24 h groups. Two injections of 30 mug synthetic LH-RH were also administered at 1-5 h intervals to ewes on either day 10 of the oestrous cycle or at onset of oestrus. The pattern of LH responses in all these animals was similar to that observed in anoestrous ewes injected at 1-5 h intervals. The total LH release, as assessed in terms of the induced peaks, was significantly greater in the onset of oestrus group than in the day 10 group or any of the anoestrous groups. Presumably the sensitization-desensitization sequence of the pituitary gland to LH-RH which has been demonstrated, together with the effects of sex steroid hormones, must play an important part in the development and decay of the natural preovulatory LH peak.

Leteinizing hormone and luteinizing hormone releasing hormone-like immunoreactivity in the jugular venous blood of sheep at various stages of the oestrous cycle.

Luteinizing hormone and LH-RH-like immunoreactivity were measured in the jugular venous plasma of Clun Forest ewes at various stages of the oestrous cycle. Blood samples were collected through jugular venous cannulae every 2 h for at least 20 days from three ewes during the breeding season. The ewes were checked twice daily for oestrus using a vasectomized ram. Plasma LH peaks of apparent height 112-192 ng NIH-LH-S17 equivalents/ml were detected at oestrus with basal levels of 2-15 ng/ml during most of the remainder of the 17-day oestrous cycle. Peaks of LH-RH-like immunoreactivity occurred at various times of the cycle. The apparent maximal level of these peaks was 220 pg/ml compared with basal levels of less than 10 pg/ml. Further ewes (two for each group) were sampled at 4 min intervals for 12 h, (1) from onset of oestrus, (2) 36-48 h after onset of oestrus or (3) on day 10 of the oestrous cycle. In the ewes sampled at oestrus, peaks of LH-RH-like immunoreactivity were detected before, during and after the preovulatory LH peak. Those detected after the LH peak were unassociated with any further increases in the plasma LH level. In the ewes sampled 36-48 h after onset of oestrus and on day 10 of the cycle, several peaks of LH-RH-like immunoreactivity unassociated with any increases in the LH level were detected. These peaks, and those detected at oestrus, had durations of only one or two samples, and in some cases reached levels of several ng/ml compared with basal levels of less than 10 pg/ml. The significance of these results is discussed.

Plasma LH concentrations after single or double injections of synthetic LH-RH in dairy cows.

Milked Friesian dairy cows were given 1 or 2 i.v. injections of synthetic LH-RH. The second of 2 injections of LH-RH given 1.5 h apart induced a significantly greater release of LH than did the first. The response to this injection was also significantly greater than that caused by injections given 6 h apart. There was no significant difference between the LH responses to the two injections given 6 h apart. The total LH release produced by the two injections of 100 microgram synthetic LH-RH given 1.5 h apart was significantly greater than that produced by single injection of 200 microgram synthetic LH-RH. It is concluded that there is a short-term increase in the responsiveness of the bovine pituitary gland to LH-RH after an initial LH-RH stimulus.

Short-term relationships between plasma LH, FSH and progesterone concentrations in post-partum dairy cows and the effect of Gn-RH injection.

Jugular venous blood samples were obtained from 7 dairy cows every 10 min for 10-19 h during the early- or mid-luteal phase of the oestrous cycle, and each cow was given 1 or 2 i.v. injections of 100 micrograms synthetic Gn-RH. Four of these cows were also sampled in a different cycle with no treatment being administered. Peaks of plasma LH, FHS and progesterone were detected in each animal in the absence of treatment; those of LH and progesterone often occurred in parallel. Injection of Gn-RH was always followed by a significant increase in plasma LH and progesterone concentrations and in most cases by a significant FSH increase. There was a significant temporal relationship between the peaks of all 3 hormones. A further 8 cows were sampled during the first 10 days post partum when the mean plasma progesterone concentration was low. An i.v. injection of 200 micrograms synthetic Gn-RH was given to each animal and this resulted in a significant increase in plasma LH and FSH concentrations, but in only one cow was the Gn-RH injection followed by a significant increase in plasma progesterone concentration. The LH response to Gn-RH injection was significantly less in cows injected on or before Day 5 post partum than in cows injected on Days 7-10 post partum.

Differential release of LH and FSH in cyclic mares in response to synthetic Gn-RH.

Mares at different stages of the oestrous cycle were given a single intravenous injection of 0.5 mg synthetic Gn-RH. The mean area of the induced LH peak was significantly less at mid-cycle (Day 10-11) than at any other time. The mean height of the LH peak above preinjection concentration was greater at late oestrus and early cycle (Day 5-6) than at mid-cycle and early oestrus. There were no significant different in mean FSH responses. The LH:FSH ratio for both height and area of induced peaks was significantly less at mid-cycle than at other times of injection. These results suggest that one releasing hormone could cause the release of both FSH and LH in the normal cyclic mare.

Identification of an antigenic subtype of eastern equine encephalitis virus isolated from a human.

Eastern equine encephalitis (EEE) virus was isolated from the cerebrospinal fluid of a 6-year-old male who had clinically diagnosed aseptic meningitis and subsequently died. Several standard serologic tests that use polyclonal antibody and indirect immunofluorescence and hemagglutination inhibition tests that use monoclonal antibody provided evidence that the isolate was an antigenic subtype of prototype North American EEE virus. We believe that this is the first evidence of an antigenic subtype of EEE virus.

Plasma progesterone and LH concentrations in ewes after injection of an analogue of prostaglandin F-2alpha.

Plasma progesterone and LH concentrations were monitored throughout a natural oestrous cycle in 12 Clun Forest ewes and compared to those following treatment with a single i.m. injection of 100 microng ICI 80,996, an analogoue of prostaglandin F-2alpha, given during the luteal phase of the cycle. After injection of the analogue there was a high degree of synchrony in the return of oestrus (440 +/- 1-9 h; mean +/- S.E.M.) and the timing of the LH peak (48-5 +/- 2-0 h) from injection. There were no significant differences in the plasma progesterone concentrations or in the height and duration of the preovulatory LH peak between control and treatment cycles. The technique offers the possibility of controlled ovulation in the ewe.

Progesterone levels following treatment of seasonally anoestrous ewes with synthetic LH-releasing hormone.

Plasma progesterone determinations were carried out on blood samples collected daily from Clun Forest ewes during the normal oestrous cycle and also after administration of LH-releasing hormone (LH-RH) during seasonal anoestrus. Levels of plasma progesterone at oestrus ranged from 0.1 to 0.5 ng/ml and luteal phase levels from 3 to 6 ng/ml. Levels found during seasonal anoestrus were within the range of those observed as oestrus. Following treatment with LH-RH, there was in increase in the plasma LH level in a-l cases and ovulation occurred in twenty-three out of twenty-seven treated ewes. In the animals which ovulated, the plasma progesterone concentration either remained basal (eighteen animals) or rose to a lower level (2 ng/ml is greater than) than that found during the luteal phase of the cycle.