To test the hypothesis that the folli cle -stimulating hor-mone(FSH)threshold in patients with elevated FSH levels in the early follicular phase(EFP)is higher than in con-trols.Pilot study.Academic hospital.Six patien...To test the hypothesis that the folli cle -stimulating hor-mone(FSH)threshold in patients with elevated FSH levels in the early follicular phase(EFP)is higher than in con-trols.Pilot study.Academic hospital.Six patients with elevated EFP FSH(>10IU /L)and 13controls.Treat-ment with a GnRH agonist in the midlut eal phase before IV administration of recombinant FSH w as started in an ul-tra -low -dose step -up protocol.The FSH threshold was determined by the mean of FSH levels o f the above threshold value and the below thresh old value.Follicle -stimulating hormone threshold,FSH screening value,E 2,number of follicles.The FSH threshold in the elevated EFP FSH group was 6.75IU /L and was significantly higher than the FSH threshold of the controls(4.65IU /L).The FSH screening value on day 3was 12.0I U /L in the pa-tient group and 5.0IU /L in the contro ls.Estradiolwas significantly lower on the day that t he largest follicle was 18mm in the elevated EFP FSH group compared with controls(277vs.491pmol /L,respectively)-.On the day of hCG administration,the number of sm aller(10-13mm)follicles was equal but the number of larger(>14mm)follicles was higher in the control g roup compared with the elevated FSH group.In the contro l group,the basal FSH levels correlated highly with th e FSH threshold levels(r =0.8),but in the patients with elevated EFP FSH this correlation was absent.In normal wo men,basal FSH day 3values represent the ovarian thresh old for FSH.In womenwith elevated day 3FSH,the FSH threshold is higher but not as high as basal FSH values.We postulate that the FSH threshold in patients with elevated EFP FSH is higher be-cause of intraovarian factors.Basa l FSH overshoots the threshold,probably because of the l imited feedback by the ovary.展开更多
Motoneurons in the spinal cord have intrinsic voltage dependent persistent in ward currents (PICs; e.g. persistent calcium currents) that amplify synaptic inp uts by three to five fold in addition to providing a susta...Motoneurons in the spinal cord have intrinsic voltage dependent persistent in ward currents (PICs; e.g. persistent calcium currents) that amplify synaptic inp uts by three to five fold in addition to providing a sustained excitatory driv e that allows motoneurons to fire repetitively following a brief synaptic excita tion. In this study, we examined whether prolonged involuntary muscle spasms in subjects with long term injury to the spinal cord are mediated by the activatio n of PICs in the motoneuron. To examine this in the human, we used a paired moto r unit analysis technique where the firing frequency of one motor unit of the pa ir (control unit) was used to estimate the synaptic drive to the motoneuron pool , including the drive to a second higher threshold motor unit of the pair (test unit). The degree to which a motoneuron PIC helped to sustain the discharge of a test motor unit (self sustained firing) was determined from the reduction in control unit firing at de recruitment (△F) compared with recruitment of the te st unit. This △F value corresponds to the reduction in synaptic drive needed to counteract the intrinsic PIC and, thus, was used an indirect measure of this cu rrent. In the nine motor unit pairs studied, the average estimated synaptic driv e, or control unit firing rate, required to recruit a test motor unit at the ons et of a muscle spasm was significantly higher (by 43%) than the estimated synap tic drive during derecruitment at the end of a muscle spasm. This indicated that a motoneuron PIC, and associated self sustained firing, facilitated the firing of the test units during the prolonged muscle spasms. In addition, in all subje cts tested (seven out of seven), we observed that following a muscle spasm or vo luntary contraction, spontaneous and self sustained firing of motor units could continue for many seconds, even minutes, at very low discharge rates (average 5.2 ±.1.6 Hz) with extremely low spike to spike variability (coefficient of v ariation = 5.4 ±.1.6%). Moreover, increases 展开更多
文摘To test the hypothesis that the folli cle -stimulating hor-mone(FSH)threshold in patients with elevated FSH levels in the early follicular phase(EFP)is higher than in con-trols.Pilot study.Academic hospital.Six patients with elevated EFP FSH(>10IU /L)and 13controls.Treat-ment with a GnRH agonist in the midlut eal phase before IV administration of recombinant FSH w as started in an ul-tra -low -dose step -up protocol.The FSH threshold was determined by the mean of FSH levels o f the above threshold value and the below thresh old value.Follicle -stimulating hormone threshold,FSH screening value,E 2,number of follicles.The FSH threshold in the elevated EFP FSH group was 6.75IU /L and was significantly higher than the FSH threshold of the controls(4.65IU /L).The FSH screening value on day 3was 12.0I U /L in the pa-tient group and 5.0IU /L in the contro ls.Estradiolwas significantly lower on the day that t he largest follicle was 18mm in the elevated EFP FSH group compared with controls(277vs.491pmol /L,respectively)-.On the day of hCG administration,the number of sm aller(10-13mm)follicles was equal but the number of larger(>14mm)follicles was higher in the control g roup compared with the elevated FSH group.In the contro l group,the basal FSH levels correlated highly with th e FSH threshold levels(r =0.8),but in the patients with elevated EFP FSH this correlation was absent.In normal wo men,basal FSH day 3values represent the ovarian thresh old for FSH.In womenwith elevated day 3FSH,the FSH threshold is higher but not as high as basal FSH values.We postulate that the FSH threshold in patients with elevated EFP FSH is higher be-cause of intraovarian factors.Basa l FSH overshoots the threshold,probably because of the l imited feedback by the ovary.
文摘Motoneurons in the spinal cord have intrinsic voltage dependent persistent in ward currents (PICs; e.g. persistent calcium currents) that amplify synaptic inp uts by three to five fold in addition to providing a sustained excitatory driv e that allows motoneurons to fire repetitively following a brief synaptic excita tion. In this study, we examined whether prolonged involuntary muscle spasms in subjects with long term injury to the spinal cord are mediated by the activatio n of PICs in the motoneuron. To examine this in the human, we used a paired moto r unit analysis technique where the firing frequency of one motor unit of the pa ir (control unit) was used to estimate the synaptic drive to the motoneuron pool , including the drive to a second higher threshold motor unit of the pair (test unit). The degree to which a motoneuron PIC helped to sustain the discharge of a test motor unit (self sustained firing) was determined from the reduction in control unit firing at de recruitment (△F) compared with recruitment of the te st unit. This △F value corresponds to the reduction in synaptic drive needed to counteract the intrinsic PIC and, thus, was used an indirect measure of this cu rrent. In the nine motor unit pairs studied, the average estimated synaptic driv e, or control unit firing rate, required to recruit a test motor unit at the ons et of a muscle spasm was significantly higher (by 43%) than the estimated synap tic drive during derecruitment at the end of a muscle spasm. This indicated that a motoneuron PIC, and associated self sustained firing, facilitated the firing of the test units during the prolonged muscle spasms. In addition, in all subje cts tested (seven out of seven), we observed that following a muscle spasm or vo luntary contraction, spontaneous and self sustained firing of motor units could continue for many seconds, even minutes, at very low discharge rates (average 5.2 ±.1.6 Hz) with extremely low spike to spike variability (coefficient of v ariation = 5.4 ±.1.6%). Moreover, increases
