Seasonal variations of pulsatile luteinizing hormone release in the mink (Mustela vison)

Jallageas, Monique; Mas, N.; Boissin, J.; Maurel, Daniel; Ixart, G.

doi:10.1016/0742-8413(94)00045-c

Cited by 8 publications

(7 citation statements)

References 30 publications

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“…In contrast with this, it has been previously shown in intact minks reared in natural conditions that the main parameters statistically affected during seasonal variations were pulse frequency and the correlated mean plasma LH concentration, while no significant variations in amplitude and peak length were detected (Jallageas et al, 1994b). One possibility to explain the different results obtained from intact and melatonin treated ganglionectomized mink, is that slight discrepancies in synchronization between intact animals can exist when they are maintained under natural environmental photoperiod (Jallageas et al, 1994a). Alternatively, Cagnacci et al (1991) have demonstrated that in early follicular phase women, LH pulse amplitude was augmented without a change of LH pulse frequency.…”

Section: Discussioncontrasting

confidence: 65%

“…In our present study, when ganglionectomy was performed at the onset of decreasing testicular activity, this too did not accelerate the decrease of the testes volume and plasma testosterone concentration. In particular, one month after deafferentation of the pineal, animals still had substan- tial testosterone levels, even though these were lower than the maximal levels recorded during the seasonal reproductive phase in this species (Jallageas et al, 1994a). The interesting finding emerging from examination of the temporal changes in gonadal activation following stimulation by short days or by melatonin implants, is that while photogonadal stimulation occurred 4-6 weeks after the start of exposure to short days (LD 4:20) (Maurel et al, 1991b), a longer latency of the system was observed when gonadostimulation was obtained by the insertion of melatonin implants: three months in the present experiment, and two months in a previous report (Maurel et al, 1992a).…”

Section: Discussionmentioning

confidence: 81%

“…We used a doubleantibody heterologous radioimmunoassay, previously described and validated for the mink (Jallageas et al, 1994a). Purified rabbit LH (AFP-7818-C) was used for iodination and as standard.…”

Section: Assay Proceduresmentioning

confidence: 99%

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Effects of Superior Cervical Ganglionectomy and Melatonin Replacement on Intra-hypothalamic LHRH Content and Pulsatile Luteinizing Hormone Release in the Mink

Maurel¹,

Jallageas²,

Mas³

et al. 1997

Biological Rhythm Research

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Long-term effects of subcutaneous melatonin implants on intrahypothalamic LHRH content and on pulsatile luteinizing hormone release have been investigated in ganglionectomized male mink. Animals were submitted to bilateral removal of the superior cervical ganglion in mid-April. A preliminary study revealed that plasma LH concentrations remain at a basal level throughout the year following ganglionectomy. In a second experiment, one month after ganglionectomy and transfer from the natural photoperiod environment to short daylengths (LD 4:20), melatonin pellets were subcutaneously implanted to overcome deafferentation of the pineal. Progressive effects of treatment were studied 7 days, 15 days, and one, two and three months after insertion of the melatonin implants. The intra-hypothalamic LHRH content in ganglionectomized mink was at a basal level similar to that observed during seasonally sexual quiescence, or after exposure to inhibitory long days (LD 20:4). A significant and transient elevation in LHRH content was observed already after fifteen days, and also one month after insertion of melatonin implants. This resulted in mean values similar to those observed during the breeding season, or after exposure to stimulatory short days (LD 4:20). A decrease in hypothalamic LHRH content started after two months. No pattern of pulsatile LH secretion was recorded in ganglionectomized untreated mink. A significant increase in all parameters of pulsatile LH secretion was observed fifteen days after the elevation of LHRH content induced by melatonin treatment, and maximum values were reached after two months. Pituitary activity tended to decrease after three months, characterized in particular by a significant decrease in the mean frequency of LH pulses. In addition, the increase in pulsatile characteristics of LH release occurred two months before the peripheral renewal of testicular activity. Apparently, the reproductive endocrine function in ganglionectomized mink treated with melatonin implants is restored more rapidly at the hypothalamic level than at the pituitary or testicular levels.

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Section: Discussioncontrasting

confidence: 65%

Section: Discussionmentioning

confidence: 81%

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Effects of Superior Cervical Ganglionectomy and Melatonin Replacement on Intra-hypothalamic LHRH Content and Pulsatile Luteinizing Hormone Release in the Mink

Maurel¹,

Jallageas²,

Mas³

et al. 1997

Biological Rhythm Research

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“…The presence of a nocturnal peak in plasma Lh seems to be critical to launch gametogenesis in pre-pubertal male European sea bass, a situation that may resemble, in certain aspects, the Lh pattern described in pre-pubertal humans by Wu (1995). In mammals, such as the mink (Mustela vison), the lowest values of amplitude, frequency and mean Lh secretion occur during the months of quiescence (Jallageas et al, 1994). Thus it can be hypothesized that similar to mammals, in fish and particularly in European sea bass, nocturnal surges of Lh could prove to be more important as puberty approaches.…”

Section: Only Delays the Phase Of The Rhythmsmentioning

confidence: 98%

Updating control of puberty in male European sea bass: A holistic approach

Carrillo

Espigares

Felip

et al. 2015

General and Comparative Endocrinology

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“…In response to natural mating, and based on a low frequency sampling programme, elevated LH within a few hours after mating were reported, lasting at least 24 h [42]. Pulsatile LH release has only been described for males in various stages of reproductive activity or quiescence [24].…”

Section: Introductionmentioning

confidence: 99%

LH release in mink (Mustela vison). Pattern of the LH surge and effect of metabolic status

Tauson¹,

Fink²,

Forsberg

et al. 2000

Reprod. Nutr. Dev.

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-The mink is a seasonal breeder with induced ovulation and delayed implantation. Reproductive processes are strongly influenced by energy supply and body condition. Items for which there is paucity or complete lack of data were the main objectives of this study: the temporal relationship between copulation and the pre-ovulatory LH surge and the influence of energy supply on LH release. A total of 30 yearling female mink with a well defined metabolic status was used. Twelve females kept in the laboratory were measured in six consecutive one-week balance periods each including the measurement of heat production by means of indirect calorimetry, and 18 females were kept under conventional farm conditions. The animals were fed so as to maintain energy balance (CON), flush fed by 2 weeks food restriction followed by 2 weeks refeeding (FLUSH), or kept in a negative energy balance (NEG). Plasma concentrations of the thyroid hormones, IGF-1 and insulin were determined weekly (n = 12), or 1 week after change in energy supply to the FLUSH group (n = 18). On the day of mating, blood samples for LH and oestradiol-17β (E 2 ) were taken before and immediately after mating and then 4, 8, 12, 24, 30 and 48 h thereafter. Frequent blood samplings, each lasting 60 min, were taken during the LH surge from two other females surgically fitted with venous access ports. Peak concentrations of LH were recorded on the first sampling, an average 16 min after mating. The concentrations remained elevated for 12 h, but almost decreased to basal values 24 h after mating. Plasma E 2 was high before mating and peak values were attained 4 h after mating after which it decreased. Energy supply had no significant influence on LH and E 2 , but there was a tendency for a more sluggish LH release in NEG animals. The lack of response in FLUSH animals was explained by these animals having a lower intake of metabolisable energy than CON animals, the total intake not being significantly different from the NEG group. Plasma concentrations of thyroid Reprod. Nutr. Dev. 40 (2000) 229-247 229

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Seasonal variations of pulsatile luteinizing hormone release in the mink (Mustela vison)

Cited by 8 publications

References 30 publications

Effects of Superior Cervical Ganglionectomy and Melatonin Replacement on Intra-hypothalamic LHRH Content and Pulsatile Luteinizing Hormone Release in the Mink

Effects of Superior Cervical Ganglionectomy and Melatonin Replacement on Intra-hypothalamic LHRH Content and Pulsatile Luteinizing Hormone Release in the Mink

Updating control of puberty in male European sea bass: A holistic approach

LH release in mink (Mustela vison). Pattern of the LH surge and effect of metabolic status

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