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M L Johnson

Publications and source records attributed to M L Johnson.

At least 235 records · Page 13Linked to original sources
PubMed1988

Health effects of sunlight exposure in the United States. Results from the first National Health and Nutrition Examination Survey, 1971-1974.

The dermatologic component of the first National Health and Nutrition Examination Survey (N = 20,637), conducted from 1971 through 1974, documented the deleterious effect of ultraviolet radiation on selected skin and eye conditions. Actinic skin damage was more frequent in white men with high as compared with low sunlight exposure, 36.7% vs 23.3%, respectively. Among white women, the corresponding figures were 34.1% vs 18.6%, respectively. Actinic damage was found more often in individuals with light eye color. Basal cell epitheliomas were found in 11.3% of white men aged 65 to 74 years who had severely actinic-damaged skin as compared with 1.0% of those with undamaged skin. Sunlight exposure was positively associated with localized hypomelanism, localized hypermelanism, seborrheic keratoses, senile lentigines, freckles, acne rosacea, spider nevi, varicose veins, venus star, dry skin, wrinkled skin, pterygia, arcus senilis, and a variety of minor oral lesions of the tongue, palate, and buccal mucosa. These findings suggest that a large number of dermatologic conditions, which may in part result from overexposure to sunlight, may be preventable.

Adolescent↗
PubMed1987

Interaction of trans-parinaric acid with phosphatidylcholine bilayers: comparison with the effect of other fluorophores.

The effect of the fluorophore trans-parinaric acid on the structure of lipid bilayer was studied and compared with the effect of other 'perturbants'. These include commonly used fluorophores (diphenylhexatriene, heptadecylhydroxycoumarin, cis-parinaric acid and two fatty acids, palmitic and oleic acids). Differential scanning calorimetry (DSC) and proton nuclear magnetic resonance techniques were used to evaluate structural changes in the lipid bilayers. The thermodynamic parameters of dipalmitoylphosphatidylcholine multilamellar vesicles obtained from the DSC thermograms suggest that trans-parinaric acid differs from the other 'perturbants'. trans-Parinaric acid has the most pronounced impact on the Tm, the width (delta T1/2) and the index of asymmetry of the main gel to liquid crystalline phase transition without any effect on its transition, delta H. The presence of trans-parinaric acid in the lipid bilayer of dimyristoylphosphatidylcholine small unilamellar vesicles influences the chemical shift difference between the choline protons of phosphatidylcholine molecules present in the two leaflets of the vesicle bilayer (delta delta H). This suggests that trans-parinaric acid affects the head group packing in the bilayer. Its main effect is abolishing the major alterations in head group packing that occur through the phase transition. The above data indicate that trans-parinaric acid is concentrated in the gel phase domains, whereby it stabilizes the phase separation between the gel and liquid crystalline phases, probably by affecting lipid molecules present in the boundary regions between these two domain types.

1,2-Dipalmitoylphosphatidylcholine↗
PubMed1987

Diffusion coefficients of quenchers in proteins from transient effects in the intensity decays.

We used 2-GHz frequency-domain fluorometry to examine the intensity decays of N-acetyl-L-tryptophamide (NATA) and the protein staphylococcal nuclease in the presence and absence of quenching by oxygen or acrylamide. When analyzed with a multiexponential model, the decays of NATA and nuclease both become more heterogeneous in the presence of quenching. We attribute the increased complexity to transient effects in quenching or equivalently a time-dependent rate constant for quenching. The frequency-domain data were analyzed using the Smoluchowski model (exp(-t/tau-2b square root t)) and the radiation model, which is known to correct some flaws in the more approximate Smoluchowski model. The radiation model provides improved fits to the data, as evidenced by average 10-fold decreases in chi R2. The radiation model also provides an estimate of the sum of the diffusion coefficients and the specific rate constant for quenching. The apparent diffusion coefficients for acrylamide and oxygen in nuclease, as seen by its single tryptophan (residue 140) are 15- and 11-fold lower than in water, respectively. The apparent values of the oxygen diffusion coefficient in water, as seen by NATA, are 2- to 3-fold larger than expected from earlier steady-state measurements. The ability to recover the detailed form of the intensity decays by the frequency-domain method should allow comparison of experimental results with calculated trajectories of quenchers in proteins.

Acrylamide↗
PubMed1987

Analysis of fluorescence decay kinetics measured in the frequency domain using distributions of decay times.

We describe the theoretical and practical aspects of analyzing complex fluorescence decay kinetics using continuous distributions of decay times. Our analysis uses frequency-domain data, provides for global analysis of multiple data sets and includes the possibility of excited-state processes. Simulated data were used to estimate the types of distributions which can be reasonably recovered from the measurements. Additionally, we describe a variety of distributions recovered from experimental data. For mixtures of one, two or three exponentially decaying fluorophores we recovered narrow lifetime distributions, which are essentially identical to a multiexponential decay. Similarly, a two-state excited-state reaction also yielded a narrow distribution with negative preexponential factors. The presence of time-dependent spectral relaxation of labeled lipids results in a wide distribution of decay times, which becomes narrower for faster relaxation rates at higher temperatures. Hence, the decay-time distributions appear to be sensitive to the dynamics of the environment surrounding the fluorophore. Additionally, distributions of decay times were observed to result from transient effects in collisional quenching, from energy transfer in the presence of a range of donor-to-acceptor distances, and for several single-tryptophan proteins.

Energy Transfer↗
PubMed1987

Enhanced resolution of fluorescence anisotropy decays by simultaneous analysis of progressively quenched samples. Applications to anisotropic rotations and to protein dynamics.

Enhanced resolution of rapid and complex anisotropy decays was obtained by measurement and analysis of data from progressively quenched samples. Collisional quenching by acrylamide was used to vary the mean decay time of indole or of the tryptophan fluorescence from melittin. Anisotropy decays were obtained from the frequency-response of the polarized emission at frequencies from 4 to 2,000 MHz. Quenching increases the fraction of the total emission, which occurs on the subnanosecond timescale, and thereby provides increased information on picosecond rotational motions or local motions in proteins. For monoexponential subnanosecond anisotropy decays, enhanced resolution is obtained by measurement of the most highly quenched samples. For complex anisotropy decays, such as those due to both local motions and overall protein rotational diffusion, superior resolution is obtained by simultaneous analysis of data from quenched and unquenched samples. We demonstrate that measurement of quenched samples greatly reduces the uncertainty of the 50-ps correlation time of indole in water at 20 degrees C, and allows resolution of the anisotropic rotation of indole with correlation times of 140 and 720 ps. The method was applied to melittin in the monomeric and tetrameric forms. With increased quenching, the anisotropy data showed decreasing contributions from overall protein rotation and increased contribution from picosecond tryptophan motions. The tryptophan residues in both the monomeric and the tetrameric forms of melittin displayed substantial local motions with correlation times near 0.16 and 0.06 ns, respectively. The amplitude of the local motion is twofold less in the tetramer. These highly resolved anisotropy decays should be valuable for comparison with molecular dynamics simulations of melittin.

Acrylamide↗
PubMed1987

The pituitary gland secretes in bursts: appraising the nature of glandular secretory impulses by simultaneous multiple-parameter deconvolution of plasma hormone concentrations.

To investigate patterns of endogenous hormone release, we have proposed a biophysical model in which measured hormone concentrations at any given instant reflect the operation of a suitable cumulation function (secretory input) convolved with an appropriate elimination mechanism (metabolic clearance). The cumulation function underlying a macroscopic hormone secretory burst can be represented by a random (Gaussian) distribution of instantaneous molecular secretory rates, which are centered with some finite and determinable standard deviation about a particular moment in time. The hormone elimination mechanism is described by a mono- or biexponential clearance function. The resultant convolution integral is solved by iterative nonlinear least-squares parameter estimation, in which all plasma hormone concentrations and their variances are considered simultaneously. Experiments with human endocrine time series revealed that the spontaneous secretory patterns of any of multiple distinct anterior pituitary hormones (luteinizing hormone, follicle-stimulating hormone, growth hormone, prolactin, thyrotropin, and adrenocorticotropic hormone) can be described effectively by this parsimonious model. In addition, endogenous hormone disappearance rates determined by deconvolution agreed well with those reported earlier that were determined after exogenous hormone injections. Moreover, this model predicted that durations of underlying secretory impulses are extremely brief; i.e., the standard deviations of the Gaussian distributions of instantaneous secretory rates range from 4.5 min (luteinizing hormone) to 16 min (growth hormone) compared to plasma hormone concentration peaks of 90-140 min in duration. Accordingly, we conclude that observed physiological patterns of fluctuating plasma hormone concentrations can be accounted for by distinct, highly delimited, random bursts of hormone release separated by intervals of secretory quiescence.

Adrenocorticotropic Hormone↗
PubMed1987

Impact of intensive venous sampling on characterization of pulsatile GH release.

The effect of sampling intensity on quantitative properties of pulsatile growth hormone (GH) release was tested using an objective, statistically based pulse detection algorithm (Cluster). Seven normal young men had blood withdrawn at 5-min intervals for 24 h. The number of GH peaks/24 h (mean +/- SE) detected in the 5-min series (5.93 +/- 0.66) was significantly greater than the number of peaks documented in the constituent 10-min (3.45 +/- 0.28), 15-min (2.79 +/- 0.31), 20-min (2.86 +/- 0.64), 30-min (2.5 +/- 0.36), 45-min (2.21 +/- 0.21), and 60-min (1.93 +/- 0.23) series. The increased number of peaks detected with 5-min sampling reflected high-frequency pulsatile GH release occurring within the major GH secretory episodes. Both the mean widths and areas associated with peaks identified in the 5-min series were smaller than those documented with less intensive sampling. Peak amplitude did not change with sampling intensity. These data suggest that the major secretory episodes of GH release in normal young men encompass high-frequency GH secretory activity. That these high-frequency GH secretory events have not previously been described probably reflects the relatively infrequent sampling paradigms (e.g., every 20-30 min) commonly used in the past.

Adult↗
PubMed1987

Appraising the nature of luteinizing hormone secretory events in men.

We have appraised the nature of spontaneous luteinizing hormone (LH) secretory events in normal men by analyzing immunoactive LH concentrations in blood samples withdrawn at 5-min intervals for 24 h in eight healthy individuals. A novel discrete deconvolution algorithm was applied to determine apparent instantaneous LH secretory rates from these LH concentration series. These analyses unmasked unique attributes of spontaneous LH secretory events, which were represented as delimited momentary augmentations in endogenous LH secretory rates interspersed among intervals of relative secretory quiescence. For three different peak-detection thresholds (P = 0.02, = 0.01, and = 0.005), the frequency of LH secretory episodes was significantly greater than that of LH "pulses" judged from concentration data alone. Moreover, the total mass of LH released within discrete secretory episodes could account for approximately 90% of LH secreted during the day. This model of distinct, short-lived, burst-like secretion of LH has important implications for further investigations of the neuroendocrine regulation of gonadotropin secretion in humans.

Adult↗
PubMed1987

Augmentation of growth hormone secretion during puberty: evidence for a pulse amplitude-modulated phenomenon.

The augmentation of GH secretion that occurs during puberty has been attributed to changes in sex steroid levels that enhance the frequency and amplitude of GH pulses. To investigate the specific GH pulse characteristics responsible for such augmentation we analyzed the serum GH concentration profiles of 10 boys in Tanner stages I-II of sexual development (group A; aged 10 5/12-15 1/12 yr) and compared their GH pulse characteristics with those of 5 boys at Tanner stages IV-V of development (group B; aged 14 8/12-15 1/12 yr). We also reanalyzed previously reported data from 5 prepubertal boys (group C; aged 13 6/12-15 5/12 yr) before and after 10 weeks of treatment with testosterone enanthate (100 mg/4 weeks, im). Using a pulse detection algorithm that constrains the false positive pulse detection rate to less than 5% (Cluster), we found that group B boys had a significantly higher mean serum GH pulse amplitude compared to group A boys (17.1 +/- 2.6 vs. 8.6 +/- 1.7 ng/mL; P = 0.012), but both groups had the same mean GH pulse frequency (group B, 5.4 +/- 0.5 pulses/24 h vs. group A, 5.5 +/- 0.4 pulses/24 h; P greater than 0.05). Similar changes were found in group C boys before and after testosterone therapy; there was no significant change in GH pulse frequency (6.6 +/- 0.9 before vs. 7.6 +/- 0.5 pulses/24 h after treatment; P greater than 0.05), but there was a significant increase in the GH pulse amplitude after therapy (6.8 +/- 1.6 before vs. 15.4 +/- 2.4 ng/mL after treatment; P = 0.04). When the 24-h GH concentration profiles were analyzed using a mathematically distinct method for the estimation of pulse amplitudes, namely the Fourier expansion time series, we confirmed a significant increase in GH pulse amplitude with later stages of puberty and androgen treatment. We conclude that the augmentation in GH secretion that occurs during either spontaneous puberty or exogenous testosterone therapy is an amplitude-modulated phenomenon, relatively independent of changes in pulse frequency. Such an effect may be secondary to the action of sex steroid hormones modulating either the responsivity of somatotrophs to endogenous GH-releasing hormone, the amount of GH-releasing hormone secreted, or the tonic inhibitory tone of somatostatin.

Adolescent↗
PubMed1987

Preferential release of bioactive luteinizing hormone in response to endogenous and low dose exogenous gonadotropin-releasing hormone pulses in man.

We used the rat interstitial cell testosterone (RICT) bioassay to assess biological LH activity secreted in response to endogenous and low dose exogenous GnRH pulses in normal men. The absence of nonspecific plasma effects in the LH bioassay was demonstrated by the finding of undetectable levels of LH bioactivity despite low but measurable immunoactivity in 10 hypogonadotropic men. Moreover, bolus injections of human LH in 6 hypogonadotropic men defined a curvilinear relationship between plasma bioactive and immunoactive LH concentrations, in which the extrapolated concentration of plasma bioactive LH at a zero dose of immunoactive LH was indistinguishable from zero. Zero bioactive LH intercepts were also found when physiological bio- and immunoactive LH concentrations derived from 7 intensively sampled normal men were subjected to linear regression using 2-dimensional error fitting. In these men, exogenous low dose (10 micrograms) iv GnRH administration resulted in preferential release of bioactive LH, with a consequent significant increase in the median plasma bio- to immunoactive (bioimmuno) LH ratio. This pattern mimicked that of endogenous LH pulsatility, in which median intrapulse bio:immuno LH ratios were significantly higher than median interpulse ratios in the same individuals (P = 0.006). Increases in spontaneous plasma bio:immuno LH ratios were not attributable to spurious rises in bioactive LH concentrations associated with decreases in serum immunoactive LH levels. Rather, sample cross-correlation analyses demonstrated positive correlations between bio- and immunoactive LH at lags of 0-40 min, indicating that both hormones increased or decreased concomitantly. These results demonstrate that LH is secreted physiologically in pulses of increased biological activity, presumably reflecting the release of a functionally compartmentalized LH pool relatively enriched in biologically active hormone. Accordingly, evaluation of the plasma bio:immuno LH ratio can provide a useful and sensitive index of qualitative changes in the LH molecule in response to endogenous (spontaneous) and exogenous GnRH stimulation.

Adult↗
PubMed1987

Operating characteristics of the male hypothalamo-pituitary-gonadal axis: pulsatile release of testosterone and follicle-stimulating hormone and their temporal coupling with luteinizing hormone.

To appraise the physiological pattern(s) of episodic testosterone and FSH release in man, we withdrew blood samples at 10-min intervals for 24-36 h in a total of 15 normal men. We subjected the resulting FSH (15 men) and testosterone (5 men) time series to 3 statistically based and mathematically independent procedures for detecting hormone pulsatility, viz. Cluster analysis, the Detect program, and Fourier transformation. The Cluster technique disclosed discrete testosterone and FSH peaks occurring at mean (+/- SEM) interpulse intervals of 112 +/- 14 and 85 +/- 3.4 min, respectively. These values were not significantly different from the mean LH interpulse interval of 95 +/- 11 min. The average durations of the testosterone and FSH pulsations were 90 +/- 11 and 59 +/- 3 min, respectively. The mean testosterone pulse amplitude reached a maximal value of 910 +/- 92 ng/dL (31.5 +/- 3.2 nmol/L), which represented a mean increase of 242 +/- 26 ng/dL (8.4 +/- 0.9 nmol/L) above the preceding nadir. FSH pulses had a maximum of 7.2 +/- 0.3 IU/L, and an incremental amplitude of 1.3 +/- 0.1 IU/L. An independent pulse detection procedure. Detect, yielded a testosterone pulse frequency of 12.3 +/- 0.8 pulses/day [P = NS vs. Cluster program (13 +/- 1.9 pulses/day)]. The Cluster and Detect estimates of FSH pulse frequency were also similar, viz. 16 +/- 1.9 and 16 +/- 0.6 pulses/day. Further analysis by Fourier transformation revealed significant circadian periodicities for serum testosterone, FSH, and LH, which had mean nyctohemeral amplitudes of 185 ng/dL (6.4 nmol/L), 0.38 IU/L, and 1.3 IU/L, respectively. Cross-correlation analyses disclosed significantly positive uncorrected cross-correlations between LH and testosterone that were maximal at a testosterone lag of 60 min (range, 50-70 min). To eliminate high intrinsic autocorrelations within the testosterone and LH time series, stepwise autoregressive fitting was employed. The resulting partial cross-correlation matrices indicated that LH concentrations at any given instant were significantly positively correlated to testosterone concentrations lagged by 10 and 20 min. Similarly, contemporaneous LH and FSH concentrations were significantly positively correlated (r = 0.40-0.89; P less than 0.001). Moreover, autoregressive modeling disclosed significantly positive partial cross-correlations between LH and FSH at a FSH lag of 10 min. In summary, we have identified significant pulsatile as well as circadian (24-h) patterns of testosterone and FSH release in normal men.(ABSTRACT TRUNCATED AT 400 WORDS)

Activity Cycles↗
PubMed1986

Analysis of the order of free energy couplings between ligand binding and subunit assembly in human hemoglobin.

The concept of free energy couplings has been extensively used in studies of the ligand-linked subunit assembly of oligomeric proteins such as human hemoglobin A [cf. Ackers, G. K. (1980) Biophys. J. 32, 331-346]. Recently, the concept of "order" of free energy couplings has been introduced as a description of the number of protein subunits that must be liganded to effect changes in intersubunit interactions [Weber, G. (1984) Proc. Natl. Acad. Sci. U.S.A. 81, 7098-7102]. That report utilized the concept of order of free energy couplings to analyze a set of previously published equilibrium constants derived from data pertaining to the chemical equilibrium between oxygen and stripped hemoglobin A [Mills, F. C., Johnson, M. L., & Ackers, G. K. (1976) Biochemistry 15, 5350-5362]. The Weber report claims to have "unequivocally" demonstrated that the coupling between oxygenation and subunit assembly in hemoglobin A is "first order". In the present report, it is demonstrated that free energy couplings of both the first and second order are capable of describing the original oxygen binding data.

Hemoglobin A↗
PubMed1986

Use of the temporary soft-tissue expander in posttraumatic alopecia.

Use of temporary soft-tissue expansion in five patients with posttraumatic alopecia and one patient with congenital alopecia is presented. Indications, operative technique, results, and complications are discussed. It is recommended that transpositional and free scalp flaps be expanded prior to transfer, and it is shown that to achieve greater expansion secondarily, the expanders can be reinserted and the scalp reexpanded as needed. The expansion technique provides a quantity of tissue of similar color, texture, and hair-bearing qualities for reconstruction of adjacent defects and makes secondary reconstruction of donor sites unnecessary. After a minimum follow-up of at least 1 year in each case presented, we have determined that the method is safe, simple, and reliable and provides excellent aesthetic results and high patient acceptance and satisfaction.

Adolescent↗
PubMed1986

Cluster analysis: a simple, versatile, and robust algorithm for endocrine pulse detection.

Endocrine signaling provides one critical means of physiological communication within an organism. Many endocrine signals exhibit an episodic or pulsatile configuration. In an effort to provide a versatile and statistically based algorithm for investigating the regulation of endocrine pulse signals, we have formulated a computerized algorithm in which a pulse is defined as a statistically significant increase in a "cluster" of hormone values followed by a statistically significant decrease in a second cluster of values. The increase or decrease is judged in relation to the actual experimental error expressed by the replicates in the presumptive nadir and peak data clusters. The program permits the operator to specify the cluster sizes of test peaks and pre- and postpeak nadirs. This method is largely insensitive to unstable base-line hormone concentrations and is not adversely affected by varying pulse amplitudes, widths, or configurations within the endocrine series. In addition, the simple statistical basis for this algorithm renders it minimally dependent on explicit or a priori assumptions about rates of hormone secretion or disappearance. The program has been validated for false-positive errors against a wide range of intraseries coefficients of variation (4-52%). We have illustrated its performance for profiles of luteinizing hormone, follicle-stimulating hormone, growth hormone, prolactin, adrenocorticotropic hormone, and cortisol and compared these episodic patterns with those of stable serum constituents (total serum protein and calcium), which do not exhibit pulsatile fluctuation.

Adrenocorticotropic Hormone↗
PubMed1986

Sex-related differences in GH secretion in rat using reverse hemolytic plaque assay.

It is not known whether enhanced growth hormone (GH)-releasing factor (GRF)-stimulated GH release observed in the male reflects differences in somatotrope numbers and/or secretory response to GRF. We addressed this question by using the hemolytic plaque assay which allows quantification of hormone secretion by single pituitary cells. Time-course studies and GRF-GH concentration-response relationships (0.01, 0.1, 1, 10, 100, 1,000 nM GRF) in age-matched male and diestrous day 2 female rats were compared by quantitating the percent of GH plaque-forming cells, and measuring the plaque areas. The male pituitary contained a greater percent (P less than 0.05) of somatotropes (% of plaque-forming cells 45 +/- 2 vs. 27 +/- 4% in the female; mean +/- SE). GRF induced a greater concentration-dependent increase in plaque areas in the male. Maximal responses were attained at 10 nM GRF in both sexes. However, mean maximal plaque area was significantly greater (P less than 0.001) and the EC50 was significantly lower (P less than 0.05) in the male (0.25 +/- 0.09 vs. 1.78 +/- 0.64 nM in the female). The data suggest that the greater percent of somatotropes in the male and greater secretory capacity and sensitivity to GRF may contribute to sex-related differences in GH secretion in the rat.

Animals↗
PubMed1986

Appraising endocrine pulse signals at low circulating hormone concentrations: use of regional coefficients of variation in the experimental series to analyze pulsatile luteinizing hormone release.

We have developed a regional dual-threshold method for detecting endocrine pulses at variably low hormone concentrations such as those that occur in the pediatric age group. This algorithm uses the local intra-series coefficient of variation to test for a significant increase and decrease (peak or pulse) in the experimental series. The method is unique in combining the following considerations: 1) use of internal measurement error present in the actual sample replicates (rather than that estimated from external standards); 2) an ability to accommodate a wide range of nonuniformity in intraassay coefficients of variation; 3) utilization of both upstroke and downstroke threshold criteria; and 4) adaptability to specify a physiologically relevant proximity of the postpeak nadir to the center of the peak. We have validated the behavior of this method in relation to false-positive rates for various program parameters and have illustrated the application of this new regional dual-threshold method to luteinizing hormone pulse detection in pubertal boys who have relative hypogonadotropism, which renders reliable luteinizing hormone pulse detection particularly difficult.

Adolescent↗
PubMed1986

Physiological properties of the luteinizing hormone pulse signal: impact of intensive and extended venous sampling paradigms on its characterization in healthy men and women.

The pulsatile nature of the gonadotropin signal is a critical determinant of physiological activation of the gonadal axis. Nonetheless, major uncertainties exist regarding the exact patterns of LH secretion that constitute normal physiological profiles in man. To assess possible bases for the discrepancies in the literature, we sampled blood at 5-min intervals for 24 h in eight normal men and eight normal women in the early follicular phase of the menstrual cycle. The constituent 5-, 10-, 15-, and 20-min immunoactive LH series and the consituent 6-, 12-, or 24-h sampling durations provided ranges of sampling intensities and durations for analysis of significant LH pulses. A technique for minimizing the influence of false positive immunoassay errors on peak detection was used to aid in estimating apparent true positive LH pulse frequency. Nonlinear curve fitting of the relationship between sampling intensity and apparent true positive LH pulse frequency revealed a stable pulse frequency estimate at intensive rates of venous sampling, with values of 19.5 +/- 1.9 (+/- SEM) pulses/24 h (periodicity, 73.8 +/- 6.5 min/pulse) in men and 20.6 +/- 3.6 pulses/24 h (periodicity, 70.0 +/- 10 min/pulse) in women. Further analyses indicated that sampling every 3.1 and 2.0 min for 24 h would be required to capture 90% of the LH pulses in men and women, respectively. Moreover, even with a 5-min sampling rate, the statistical counting errors of the LH pulse frequency estimates varied markedly with sampling duration; for example, in men sampled in 6-, 12-, and 24-hr sessions, the values were, respectively, 49%, 35%, and 24% of the observed pulse frequencies. Similar variations were found in women. Counting errors were 30-50% higher for conventional 20-min sampling rates than for 5-min sampling intervals. Measured interpulse intervals varied widely from 10-330 min (median, 60 min; n = 131 LH pulses) in men and from 10-340 min (median, 65 min; n = 125 LH pulses) in women. In addition, absolute LH pulse amplitudes varied from 1-28 mIU/ml (median, 4.1 mIU/ml) in men and from 1-24 mIU/ml (median, 3.6 mIU/ml) in women. These estimates were associated with a median number of points identified within each pulse of 6.0 in men and 4.0 in women. In summary, the present exhaustive sampling studies demonstrate for the first time stable estimates of physiological LH pulsations in normal men and women, and document broad ranges of normal LH pulse amplitudes and interpulse intervals.(ABSTRACT TRUNCATED AT 400 WORDS)

Adult↗