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At least 73 records · Page 4Linked to original sources
PubMed2006

The testing of classical pulse concepts in Chinese medicine: left- and right-hand pulse strength discrepancy between males and females and its clinical implications.

OBJECTIVES AND DESIGN: The use of the radial pulse as a diagnostic tool is an important part of the Chinese medicine (CM) clinical evaluation. This study reports the findings of an investigation into inter-arm pulse strength differences in subjects and the relationship to traditional pulse claims relating to gender. METHOD: Using a standardized pulse taking procedure and concrete operational definitions, two pulse assessors with a demonstrated high level of inter-rater agreement each assessed the overall left and right pulse strength and rated their findings on a standardized pulse form. RESULTS: The overall percentage of inter-rater agreement for manual assessment of dominant hand was 86% (based on a cohort of 65 subjects). In relation to the three possible choices regarding dominant side (right, neither, left) the right-hand side was most commonly selected as relatively strongest of the two regardless of gender (60% of males and 71% of females). Analysis of the data using Chi-square (II) found the observed frequencies for an assessor's rating of dominant hand in males were significantly different to those expected according to CM theory. CONCLUSIONS: The CM assumption of gender-related pulse-strength differences in left and right hand pulses was not supported within this study.

Adult↗
PubMed2002

[Representation of the pulse wave of blood pressure by the series of impulses of the pulse-rhythmic neurons in the nucleus tractus solitarii].

Baroreceptor afferent fibers from the aortic arch and carotid sinus project to the nucleus of solitary tract in the medulla. The aim of this study was to define the relation between the activity of neurons in this nucleus and changes of the blood pressure in the aorta during the pulse wave. Impulses of 74 pulse-rhythmic neurons, i.e. neurons discharging in bursts of impulses synchronously with the pulse wave, were recorded in acute experiments on 30 rabbits. Impulse histograms triggered by the R wave of the ECG and the averaged pulse wave over 250 consecutive R-R intervals were compared. These post-R histograms showed a close correlation of impulse activity with the pulse wave for most (74%) neurons. The beginning of the burst of impulses corresponded to the beginning of the pulse wave and the highest frequency of discharges coincided with the steepest rise in blood pressure of the pulse wave. The similarity of the histograms to the pulse wave shows that the pulse-rhythmic neurons integrate mostly the afferent input received from the arterial baroreceptors.

Afferent Pathways↗
PubMed1996

Antifungal pulse therapy for onychomycosis. A pharmacokinetic and pharmacodynamic investigation of monthly cycles of 1-week pulse therapy with itraconazole.

BACKGROUND AND DESIGN: In the treatment of onychomycosis, oral therapies have generally been given as a continuous-dosing regimen. For example, the suggested dose of itraconazole for the treatment of onychomycosis has thus far been 200 mg/d for 3 months. Based on the advances in our understanding of the pharmacokinetics of itraconazole, we investigated the efficacy and nail kinetics of intermittent pulse-dosing therapy with oral itraconazole in patients who were suffering from onychomycosis. Fifty patients with confirmed onychomycosis of the toenails, predominantly Trichophyton rubrum, were recruited and randomly assigned to three (n = 25) or four (n = 25) pulses of 1-week itraconazole therapy (200 mg twice daily for each month). Clinical and mycological evaluation of the infected toenails, and determination of the drug levels in the distal nail ends of the fingernails and toenails, were performed at the end of each month up to month 6 and then every 2 months up to 1 year. RESULTS: In the three-pulse treatment group, the mean concentration of itraconazole in the distal ends of the toenails ranged from 67 (month 1) to 471 (month 6) ng/g, and in the distal ends of the fingernails, it ranged from 103 (month 1) to 424 (month 6) ng/g. At month 11, the drug was still present in the distal ends of the toenails at an average concentration of 186 ng/g. The highest individual concentrations of 1064 and 1166 ng/g were reached at month 6 for toenails and fingernails, respectively. At end-point follow-up, toenails in 84% of the patients were clinically cured with a negative potassium hydroxide preparation and culture in 72% and 80% of the patients, respectively. In the four-pulse treatment group, the mean concentration of itraconazole in the distal ends of the toenails ranged from 32 (month 1) to 623 (month 8) ng/g, and in the distal ends of the fingernails, it ranged from 42 (month 1) to 380 (month 6) ng/g. The highest individual concentrations of 1549 and 946 ng/g were reached at month 7 for toenails and at month 9 for fingernails, respectively. At month 12, the drug was still present in the distal ends of the toenails at an average concentration of 196 ng/g. At end-point follow-up, toenails in 76% of the patients were clinically cured with a negative potassium hydroxide preparation and culture in 72% and 80% of the patients, respectively. There were no significant intergroup differences between the three- and four-pulse treatment groups for the primary efficacy parameters. The drug was well tolerated with no significant side effects in either patient group. CONCLUSIONS: Following pulse therapy with itraconazole (400 mg/d given for 1 week each month for 3 to 4 months), the drug has been detected in the distal ends of nails after the first pulse, and it has reached therapeutic concentrations with further therapy. After stopping the last pulse, the drug remains in the nail plate at levels above 300 ng/g for several months. Clinical cure rates between 76% and 84% and negative mycological examination findings between 72% and 80%, respectively, were observed in toenail onychomycosis. The data suggest that pulse therapy with itraconazole is an effective and safe treatment option for onychomycosis.

Aged↗
PubMed1998

Simple two-pulse detection scheme in pulsed EPR for studying low-frequency nuclear coherences

A microwave two-pulse sequence with a weak and long 180 degrees first pulse and a hard 90 degrees second pulse is employed to detect nuclear coherences in pulsed EPR. The coherences created by the first pulse are transferred after an evolution period T into an observable FID by the second pulse. The free induction is measured at some fixed delay after the second pulse; it is modulated when T is varied. As the second pulse may be switched on immediately after the first pulse, the nuclear coherences may be detected immediately as they start to freely oscillate, without loss of information within the instrumental dead time. The method is demonstrated for a sample of the radical cation of 15N-labeled bacteriochlorophyll a. Copyright 1998 Academic Press.

Journal Article↗
PubMed2001

A Q-band pulse EPR/ENDOR spectrometer and the implementation of advanced one- and two-dimensional pulse EPR methodology.

A versatile high-power pulse Q-band EPR spectrometer operating at 34.5--35.5 GHz and in a temperature range of 4--300 K is described. The spectrometer allows one to perform one- and two-dimensional multifrequency pulse EPR and pulse ENDOR experiments, as well as continuous wave experiments. It is equipped with two microwave sources and four microwave channels to generate pulse sequences with different amplitudes, phases, and carrier frequencies. A microwave pulse power of up to 100 W is available. Two channels form radiofrequency pulses with adjustable phases for ENDOR experiments. The spectrometer performance is demonstrated by single crystal pulse ENDOR experiments on a copper complex. A HYSCORE experiment demonstrates that the advantages of high-field EPR and correlation spectroscopy can be combined and exploited at Q-band. Furthermore, we illustrate how this combination can be used in cases where the HYSCORE experiment is no longer effective at 35 GHz because of the shallow modulation depth. Even in cases where the echo modulation is virtually absent in the HYSCORE experiment at Q-band, matched microwave pulses allow one to get HYSCORE spectra with a signal-to-noise ratio as good as at X-band. Finally, it is shown that the high microwave power, the short pulses, and the broad resonator bandwidth make the spectrometer well suited to Fourier transform EPR experiments.

Journal Article↗
PubMed1989

Twin pulse facilitation in dependence on pulse duration and calcium concentration at motor nerve terminals of crayfish and frogs.

Phasic release from motor-nerve terminals of crayfish and frogs was elicited and recorded by means of a macro-patch-clamp electrode through which the terminal was depolarized in graded pulses. The tip of the electrode was perfused and the Ca concentration around the terminal, Cae, was controlled independent from that in the superfusion of the muscle, Cab. Release increased with pulse duration with a double-logarithmic slope of 5 to 9 in crayfish and frogs, which represents a form of "early facilitation" (Katz and Miledi 1968). In crayfish, this relation was shifted to longer pulse durations on lowering Cae, while in frogs, in addition, the saturation level of release was suppressed at low Cae. Responses to twin pulses with intervals of 7-10 ms showed facilitation, Fd. When pulse duration of the twin pulses was increased, starting from about 0.5 ms, Fd increased to a maximum, but declined for longer pulses which elicited release approaching the saturation range. On lowering Cae, the maximum of Fd, Fd, increased in amplitude and was shifted to larger pulse durations. Also reduction of Cab increased Fd. The effects of pulse duration and of Cae and Cab on Fd are predicted by the residual Ca theory of facilitation, if it is assumed that changes of Cae produce corresponding changes in Ca inflow during depolarization, and if the resting intracellular Ca concentration is influenced by the extracellular Ca concentration. The large values of early facilitation can not be explained by the residual Ca theory of facilitation and may indicate the action of another depolarization dependent factor which joins in the control of release.

Animals↗
PubMed1997

On the involvement of a tonic dopamine D2-autoinhibition in the regulation of pulse-to-pulse-evoked dopamine release in the rat striatum in vivo.

The dopamine overflow evoked by trains of electrical stimulation pulses applied to the ascending dopaminergic pathway was measured with continuous amperometry in the striatum of anesthetised rats. As previously observed in in vitro studies, a pulse by pulse analysis showed a fall in dopamine overflow evoked by pulses 2 to 6, compared to the response evoked by pulse 1. However, in contrast with in vitro findings, the present in vivo data showed that the dopamine receptor antagonist haloperidol i) completely reverses the fall in dopamine overflow between pulse 1 and subsequent pulses, ii) enhances the dopamine overflow elicited by pulse 1. These results suggest that in vivo, both basal and pulse-evoked dopamine overflow results in stimulation of dopamine D2-type autoreceptors and therefore in regulation of dopamine release.

Animals↗
PubMed2005

Plant N capture from pulses: effects of pulse size, growth rate, and other soil resources.

In arid ecosystems, the ability to rapidly capture nitrogen (N) from brief pulses is expected to influence plant growth, survival, and competitive ability. Theory and data suggest that N capture from pulses should depend on plant growth rate and availability of other limiting resources. Theory also predicts trade-offs in plant stress tolerance and ability to capture N from different size pulses. We injected K15NO3, to simulate small and large N pulses at three different times during the growing season into soil around the co-dominant Great Basin species Sarcobatus vermiculatus, Chrysothamnus nauseosus ssp. consimilis, and Distichlis spicata. Soils were amended with water and P in a partial factorial design. As predicted, all study species showed a comparable decline in N capture from large pulses through the season as growth rates slowed. Surprisingly, however, water and P availability differentially influenced the ability of these species to capture N from pulses. Distichlis N capture increased up to tenfold with water addition while Chrysothamnus N capture increased up to threefold with P addition. Sarcobatus N capture was not affected by water or P availability. Opposite to our prediction, Sarcobatus, the most stress tolerant species, captured less N from small pulses but more N from large pulses relative to the other species. These observations suggest that variation in N pulse timing and size can interact with variable soil water and P supply to determine how N is partitioned among co-existing Great Basin species.

California↗
PubMed1997

Pulsed low dose rate brachytherapy in a rat model: dependence of late rectal injury on radiation pulse size.

PURPOSE: Clinical protocols utilizing pulsed low dose rate brachytherapy (PDR) to replace traditional continuous low dose rate brachytherapy (CLDR) employ irradiation in individual pulses given at intervals of a few hours. A critical factor in determining whether PDR will produce equivalent or greater late-occurring normal tissue toxicity is the dose per pulse. A rat rectal model was used to determine the role of pulse size in modifying dose effectiveness in producing late-occurring toxicity. METHODS AND MATERIALS: A rat model in which the rectum is irradiated with 192Ir sources was used in conjunction with an intracavitary applicator. A section of rectum 1.3 cm in length was irradiated with either 0.75 Gy/h CLDR or one of five schemes of PDR. The schemes applied 0.375, 0.75, 1.5, 3.0, or 6.0 Gy pulses at 0.5, 1.0, 2.0, 4.0, or 8.0 h intervals, respectively. Rats were observed for up to 300 days after completion of irradiation for rectal obstruction. Rectal specimens were taken at the time of sacrifice for obstruction or at the end of follow-up and analyzed histologically for injury. RESULTS: Effectiveness of irradiation was analyzed by calculating the ED50 for incidence of obstruction and severe histological injury. The ED50 for obstruction after treatment with CLDR and pulse sizes of 0.375, 0.75, and 1.5 Gy were 70.5, 68.0, 68.6, and 68.8 Gy, respectively. These values were not significantly different. Compared to CLDR, the ED50 for obstruction after pulse sizes of 3.0 and 6.0 Gy were significantly different at 60.9 and 46.3 Gy, respectively. The relative changes in ED50 for the different radiation schemes in producing ulceration, fibrosis, and vascular sclerosis injury were similar to that observed for obstruction. The endpoints of colitis cystica profunda and atypical epithelial regeneration varied less with increasing pulse size. CONCLUSIONS: We have demonstrated that for late rat rectal injury, dose responses to PDR pulse sizes up to 1.5 Gy at 2-h intervals are not distinguishable from that seen with CLDR at a dose rate of 0.75 Gy/h.

Animals↗
PubMed1998

Pulse frequency in pulsed brachytherapy based on tissue repair kinetics.

PURPOSE: Investigation of normal tissue sparing in pulsed brachytherapy (PB) relative to continuous low-dose rate irradiation (CLDR) by adjusting pulse frequency based on tissue repair characteristics. METHOD: Using the linear quadratic model, the relative effectiveness (RE) of a 20 Gy boost was calculated for tissue with an alpha/beta ratio ranging from 2 to 10 Gy and a half-time of sublethal damage repair between 0.1 and 3 h. The boost dose was considered to be delivered either in a number of pulses varying from 2 to 25, or continuously at a dose rate of 0.50, 0.80, or 1.20 Gy/h. RESULTS: The RE of 20 Gy was found to be identical for PB in 25 pulses of 0.80 Gy each h and CLDR delivered at 0.80 Gy/h for any alpha/beta value and for a repair half-time > 0.75 h. When normal tissue repair half-times are assumed to be longer than tumor repair half-times, normal tissue sparing can be obtained, within the restriction of a fixed overall treatment time, with higher dose per pulse and longer period time (time elapsed between start of pulse n and start of pulse n + 1). An optimum relative normal tissue sparing larger than 10% was found with 4 pulses of 5 Gy every 8 h. Hence, a therapeutic gain might be obtained when changing from CLDR to PB by adjusting the physical dose in such a way that the biological dose on the tumor is maintained. The normal tissue-sparing phenomenon can be explained by an increase in RE with longer period time for tissue with high alpha/beta ratio and fast or intermediate repair half-time, and the RE for tissue with low alpha/beta ratio and long repair half-time remains almost constant. CONCLUSION: Within the benchmark of the LQ model, advantage in normal tissue-sparing is expected when matching the pulse frequency to the repair kinetics of the normal tissue exposed. A period time longer than 1 h may lead to a reduction of late normal tissue complications. This theoretical advantage emphasizes the need for better knowledge of human tissue-repair kinetics.

Animals↗
PubMed2002

Evaluation of a long-pulsed Nd:YAG laser at different parameters: an analysis of both fluence and pulse duration.

BACKGROUND: Effective hair removal continues to pose a challenge to the physician. The use of lasers represents a significant advance in epilation, but still requires further refinement. The long-pulsed Nd:YAG laser may offer advantages over other systems because of its significant depth of penetration and minimal absorption by epidermal melanin, but ideal parameters need to be determined. OBJECTIVE: To evaluate the efficacy of a long-pulsed Nd:YAG laser system and determine the optimal parameters for hair removal. METHODS: Twenty-two subjects were treated with a cryogen spray-cooled long-pulsed Nd:YAG laser. Four adjacent sites were assigned to each subject, where the following sets of parameters were utilized: 50 J/cm2 with a 25-msec pulse duration, 60 J/cm2 with a 50-msec pulse duration, 80 J/cm2 with a 50-msec pulse duration, and control. Hair counts were obtained immediately, 1 week, 1 month, and 3 months after treatment, and multivariate regression analysis was used to determine the significance of hair reduction. Acute reactions and adverse events were also evaluated. RESULTS: Treatment at all three sets of parameters resulted in significant mean hair reductions immediately, at 1 week, and at 1 month (P <.001). At 3 months, the higher settings of 60 J/cm2 and 50 msec and 80 J/cm2 and 50 msec were statistically significant for reduced mean hair counts (P =.014, P =.042, respectively), while the lowest setting at 50 J/cm2 and 25 msec was not significant (P =.079). Patient and physician assessments suggested optimal hair reduction at the highest fluence (80 J/cm2) and longest pulse duration (50 msec). The most common acute reactions were pain during treatment, erythema, and perifollicular edema, all of which were more severe with higher fluences. CONCLUSION: The long-pulsed Nd:YAG laser is a safe and effective method of hair removal. Increased fluence (60-80 J/cm2) and longer pulse duration (50 msec) settings were generally correlated with reduced hair counts and improved clinical outcome.

Adult↗
PubMed2001

Single-blind, randomized, prospective study of sequential itraconazole and terbinafine pulse compared with terbinafine pulse for the treatment of toenail onychomycosis.

OBJECTIVE: Efficacy and safety of sequential pulse therapy with itraconazole and terbinafine were compared with pulse terbinafine alone in the treatment of toenail onychomycosis. METHODS: This was a 72-week prospective, single-blind, randomized, multicenter, comparative, parallel group, nonindustry-sponsored trial. A total of 190 patients were recruited from 3 outpatient dermatology offices in North America. Patients were at least 18 years old and had a clinical and mycologic diagnosis of dermatophyte toenail onychomycosis. Patients were randomly assigned to receive sequential pulse therapy (IIT) with 2 pulses of itraconazole followed by 1 or 2 pulses of terbinafine (itraconazole pulse is 200 mg twice daily for 1 week and terbinafine pulse is 250 mg twice daily for 1 week) versus 3 or 4 pulses of terbinafine (TTT). Main outcome measures at week 72 evaluated mycologic cure rate (negative light microscopy and culture), clinical cure (nail appears completely or totally normal), complete cure (clinical and mycologic cure), and effective therapy (mycologic cure and clinical response with at least 5 mm of new, uninvolved nail growth). RESULTS: At week 72, in the IIT versus TTT groups, the mycologic cure rate was 54 of 75 (72.0%) versus 44 of 90 (48.9%), clinical cure rate was 42 of 75 (56.0%) versus 35 of 90 (38.9%), effective therapy 49 of 75 (65.3%) versus 41 of 90 (45.6%), and complete cure 39 of 75 (52.0%) versus 29 of 90 (32.2%), respectively. Both regimens were well tolerated with no new adverse effects being identified. The rate of permanent discontinuation of therapy because of adverse effects was 2 of 81 (2.5%) with IIT and 2 of 95 (2.1%) with TTT. Each of the adverse effects normalized over time. The number of patients who reported an adverse effect in the 2 groups was 12 of 81 (14.8%) versus 22 of 95 (23.2%), respectively. All these adverse effects were reversible and mild to moderate in severity. CONCLUSION: Sequential pulse therapy with itraconazole and terbinafine is effective and safe for the treatment of dermatophyte toenail onychomycosis.

Adult↗
PubMed1999

Pulsed carbon dioxide and long pulse 10-ms erbium-YAG laser resurfacing: a comparative clinical and histologic study.

BACKGROUND: The recent introduction of pulsed erbium-YAG laser technology has been accompanied by relatively few clinical studies with widely varying claims regarding postoperative healing, clinical side-effects and efficacy. We evaluated a new long (10 ms) pulsed erbium-YAG laser in order to determine safety and clinical efficacy in comparison with a pulsed carbon dioxide laser. OBJECTIVE: Our objective was to comparatively evaluate a pulsed CO2 and long-pulsed erbium-YAG laser with regard to clinical side-effects, postoperative healing and efficacy in the reduction of rhytids. METHODS: Bilateral periocular or perioral sites were treated using a pulsed CO2 (UltraPulse) laser on one side and long-pulsed erbium-YAG laser (CO3) on the opposite side. Histologic specimens were also studied in order to compare tissue effects of both lasers. RESULTS: Results showed equivalent postoperative healing and lack of complications. In addition, the long-pulsed erbium-YAG laser showed significant efficacy in the treatment of mild and moderate rhytids. CONCLUSION: The long-pulsed (10 ms) erbium-YAG laser appears to be of significant benefit in the treatment of facial rhytids. Tissue studies show a greater degree of thermal damage in the dermis when compared to traditional 350 microseconds erbium-YAG lasers which may underlie the beneficial effects of this laser in the treatment of aging skin.

Adult↗
PubMed2001

Epithelial damage thresholds for multiple-pulse exposures to 80 ns pulses of CO2 laser radiation.

Corneal epithelial damage thresholds for exposures to 80 ns pulses of 10.6 microm infrared radiation produced by a CO2-TEA laser were investigated. Thresholds were determined for sequences of 1, 2, 8, 32, 128, and 1,024 pulses at pulse repetition frequencies of 10 and 16 Hz. Threshold damage is correlated by an empirical power law of the form EDth = CN(-alpha) in which EDth, is the threshold radiant exposure per pulse, and N is the number of pulses. The constants C and alpha are similar for the two pulse repetition frequencies. For the combined data set, C = 2,955 J m(-2) pulse(-1) (295.5 mJ cm(-2) pulse(-1) and alpha = 0.178. This value of the constant C is within 5% of the measured damage threshold for a single 80 ns pulse exposure. Temperature calculations reveal that the maximum temperature increase on the beam axis, 10 microm beneath the anterior tear surface, resulting from the different threshold exposures is constant to within +/-10% of the mean values. This result is consistent with a critical temperature damage model. Damage threshold measurements on cooled corneas indicate that the damage mechanism indeed has a substantial thermal component.

Animals↗
PubMed1993

Effects of nifedipine and ryanodine on adrenergic neurogenic contractions of rat vas deferens: evidence for a pulse-to-pulse change in Ca2+ sources.

1. The effects of nifedipine and ryanodine on the adrenergic component of neurogenic contractions of the rat isolated vas deferens were studied in an attempt to identify the sources of Ca2+ mediating the contraction. The tissue was electrically stimulated by single pulses or pairs of widely spaced pulses. The purinergic component of contraction was suppressed by the presence of 300 microM suramin. 2. In Mg(2+)-free medium, nifedipine (0.01-10 microM) reduced the first and, to a greater extent, the second twitch elicited by two pulses 3 s apart. This pattern of inhibition was observed both in the absence of rauwolscine (when twitch 2 was smaller than twitch 1) and in the presence of 0.1 microM rauwolscine (when, due to interruption of prejunctional alpha 2-adrenoceptor-mediated autoinhibition, twitch 2 was of similar height to twitch 1). Nifedipine reduced only twitch 2 but not twitch 1 in medium containing 1.2 mM Mg2+. 3. Single pulses of increasing current strength elicited increasing contraction. Nifedipine reduced contractions by about the same absolute extent at all current strengths, so that the relative contribution of the nifedipine-sensitive component decreased with increasing current strength. 4. When the pulse interval in a pair was increased from 5 to 60 s, the inhibition by nifedipine of the second twitch was most marked at an interval of 5 s and declined as the interval increased. 5. In contrast to nifedipine, 20 microM ryanodine reduced the first twitch of a pair to a greater extent than a second twitch 5 s later, so that twitch 2 became greater than twitch 1. The inhibition by ryanodine of twitch 2 increased with increasing pulse interval.6. In vasa deferentia preincubated with [3H]-noradrenaline, I microM nifedipine and 20 microM ryanodine did not change the electrically evoked overflow of tritium, whereas 10 microM nifedipine increased it.7. It is concluded that, when the sympathetic axons of the vas deferens are stimulated by a single pulse(or the first pulse of a pair) in Mg2+-free medium, both Ca2+ mobilization inside the smooth muscle cells and Ca2+ entry contribute to the ensuing adrenergic contraction. The relative contribution of Ca2+ entry is small at maximal stimulus strength but increases with decreasing stimulus strength. When a second pulse follows the first after an appropriate interval, a switch of Ca2+ sources occurs: intracellular Ca2+mobilization is decreased during twitch 2, whereas Ca2+ entry is increased.

Animals↗
PubMed2003

Pulse picking by phase-coherent additive pulse generation in an external cavity.

We have implemented a simple method for generating an "amplified" phase-coherent light pulse in which a pulse train of phase-coherent, equidistant input light pulses from a mode-locked Ti:sapphire laser is coupled into a ring cavity resonator whose length is matched to the mode-locked pulse repetition frequency at 82 MHz. Pulses are thus coherently superimposed and added inside the buildup cavity and form an intense pulse that is switched out from the cavity via a fast acousto-optic modulator. The method thus provides a pulse train at a reduced and controlled repetition frequency and with higher pulse energies than the original mode-locked pulses.

Journal Article↗
PubMed1985

GnRH pulse frequency determines LH pulse amplitude by altering the amount of releasable LH in the pituitary glands of ewes.

We have measured the size of the releasable pools of LH and FSH in the pituitary glands of ovariectomized ewes in which the pituitary was isolated surgically from the hypothalamus. The ewes were given GnRH pulses (250 ng) every hour (N = 3) or every 2 h (N = 3) for 1 week and then given a high dose GnRH infusion (0.5 micrograms/min) for 4 h. Blood samples were collected to characterize the LH and FSH responses to the GnRH pulses and infusion. The LH, but not FSH, responses to the individual GnRH pulses were pulsatile and the amplitudes of the LH pulses were greater in the sheep receiving pulses every 2 h. The sheep receiving hourly pulses showed lower LH responses to the high-dose infusions than did the sheep receiving pulses every 2 h. These data indicate a relationship between the amplitude of LH pulses and the size of the releasable pool of LH in the pituitary gland. As the frequency of GnRH pulses is decreased the amplitude of the LH responses is increased in direct proportion to the size of the releasable LH pool.

Animals↗