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M L Johnson

Publications and source records attributed to M L Johnson.

At least 415 records · Page 23Linked to original sources
PubMed1965

Some properties of the lactic dehydrogenase agent of mice.

The lactic dehydrogenase agent was obtained in quantities sufficient for purification studies by growing the virus in Ehrlich ascites tumor-bearing mice. A rapid method of titration of the agent is described. Subsequent to the standard procedure of concentration of virus by treatment with hyaluronidase and centrifugation, lipids were removed by extraction with PE, without major loss of infectivity. Electron microscopic sections of purified preparations contained particles consisting of a dense inner ring of about 25 mmicro and a less dense ring extending to about 50 mmicro. The particles occur frequently in single-membraned vesicles of varying size, and occasionally in large double-membraned bodies. The purified LDH agent did not stimulate the formation of neutralizing antibodies in rabbits and guinea pigs. The crude LDH agent was found to be a low interferon producer. Increased interferon, produced by secondary inoculation with Newcastle disease virus temporarily decreased the titer of the LDH agent. The results of others regarding the nature and the size of the LDH agent are interpreted in regard to the findings presented, and the role of interferon in permanently LDH agent infected mice is discussed.

Animals↗
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Child factor in measurement dependability.

A primary consideration in longitudinal growth studies is the identification of growth from error components. While previous research has considered matters of measurement accuracy and reproducibility in detail, few reports have investigated the errors of measurement due to aspects of the physiology and cooperation of the child. The present study directly assesses this source of measurement undependability for the first time. Investigation of total measurement error variance in 925 recumbent length replicates taken over stasis intervals in growth identifies that between 60% and 70% of total measurement unreliability is due to a child factor undependability. Individual differences are significant and longitudinal growth analyses should consider two to three times the technical error of measurement statistic as a reasonable estimate of the total unreliability for any single measurement of an infant's recumbent length. These results raise issues regarding analytic methods as applied to serial growth data.

Analysis of Variance↗
PubMedDate not supplied

Pulsatile secretion of gonadotropins and prolactin in male marathon runners. Relation to the endogenous opiate system.

We tested the hypothesis that sustained, strenuous physical training alters the neuroendocrine regulation of pulsatile gonadotropin and/or prolactin secretion in men. Blood was sampled at 20-minute intervals over 8 hours in five endurance-trained men after a 10-15 mile run in the middle of the active training season, and in 11 nonendurance trained normal controls. In these two groups, basal patterns of physiologically pulsatile secretion of LH, FSH, and prolactin (PRL) were not significantly different in relation to the following parameters: mean serum concentration of each of the three hormones (N = 25 samples); areas under the hormone concentration vs. time curves; fractional, incremental, and absolute pulse amplitudes; and pulse frequency, or periodicity. To test for enhanced suppressive effects of endogenous opiates in trained male marathon runners, subjects were administered the potent opiate-receptor antagonist, naltrexone (1 mg/kg). This antagonist significantly stimulated pulsatile LH secretion by increasing mean serum LH values from 10.94 to 13.58 mIU/ml (P = 0.007); area under the LH concentration vs. time curve increased from 5370 to 6510 mIU/ml X 8 hours (P = 0.05) and, pulse frequency rose from 2.8 to 4.9 pulses/8 hours (P = 0.006). Naltrexone also enhanced pulse frequency of FSH secretion from 3.4 to 5.4 pulses/8 hours (P = 0.009), but did not alter serum prolactin concentrations. None of these responses differed significantly from those in normal sedentary controls.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMedDate not supplied

Spectrum of the pulsatile characteristics of LH release in normal men.

To assess the spectrum of LH pulse characteristics in normal men, blood samples from 36 individuals were drawn at 20-minute intervals for 8 hours. The subsequent immunoactive LH concentrations were analyzed by computer algorithms to delineate the frequency and amplitude characteristics of pulsatile LH secretion. The absolute range for LH pulse frequency estimated by a modified threshold method was 1-6 pulses/8 hr, with a mean (+/- SEM) of 3.36 +/- 0.17 (median -3)pulses/8 hr. The distribution differed significantly from a Gaussian pattern. The mean LH pulse amplitude expressed as a percent increase above nadir was 92.1 +/- 6.1 (median-91.5%). When LH pulse amplitude was defined as an increment (mIU/ml) above nadir, the mean value was 5.13 +/- 0.4 (median -4.8) mIU/ml. These two expressions of amplitude were positively correlated (P less than 0.01), while the incremental (mIU/ml) pulse amplitude correlated inversely with pulse frequency (P less than 0.01). To examine the influence of more intensified rates of venous sampling on the spectrum of LH pulse properties, blood was sampled at 4-minute intervals for 8 hours in a subgroup of 13 men. Under these conditions, estimated LH pulse frequency was significantly higher, with a mean of 10.31 +/- 1.87 (median -9) pulses/8 hr compared with 20-minute sampling in the same individuals (P less than 0.001). Although the estimates of LH pulse frequency at 4-minute and 20-minute sampling intervals were significantly correlated (P less than 0.01), the dispersion of the LH pulse frequency estimates was considerably larger at more rapid rates of sampling. There was an absolute range of 2-20 pulses/8 hr for the 4-minute sampling, and 1-6 pulses/8 hr for the 20-minute sampling in the same individuals. This increase in LH pulse frequency and the broader dispersion of the range of frequencies estimated at 4-minute compared with 20-minute sampling intervals were confirmed using either another pulse detection algorithm, or separate criteria designed to adjust false-positive error rates in relation to sampling intensity. It was concluded that eugonadal men exhibit a broad spectrum of pulsatile LH characteristics, and the range of LH pulse attributes is even greater at more intensive rates of venous sampling. The results of this study in normal men demonstrate that a wider dispersion of physiologic LH pulse characteristics must be recognized in man.(ABSTRACT TRUNCATED AT 400 WORDS)

Adult↗
PubMedDate not supplied

Physiologic attributes of the luteinizing hormone pulse signal in the human. Cross-validation studies in men.

The performance of two new statistically based, independently formulated, endocrine peak detection methodologies (Cluster and Detect) were tested on the same large set of physiologic LH pulsations. Serum LH concentrations were determined in blood samples withdrawn at 5-minute intervals for 24 hours in eight healthy young men. The subsequent comprehensive LH time series were subjected to Cluster and Detect analysis, each constrained to an alpha level of 0.01 or 0.05. Under both circumstances, computer estimates of physiologic LH pulse frequency by the two separate algorithms were statistically indistinguishable. Moreover, the two distinct methodologies were concordant not only in relation to the original 5-minute sampling series but also with respect to the constituent 10-, 15-, 20-, 30-, and 45-minute sampling data. The cross-validation of these two mathematically independent methodologies has permitted delineation of the detailed spectrum of spontaneous LH pulse properties within individual men and among different males under basal physiologic conditions.

Adult↗
PubMedDate not supplied

Alterations in the pulsatile properties of gonadotropin secretion in alcoholic men.

The functional characteristics of the hypothalamic-pituitary-testicular axis were examined quantitatively in 10 chronic alcoholic men without hepatic dysfunction or clinical nutritional deficiencies. Spontaneous gonadotropin pulsatility was analyzed in blood sampled every 20 minutes over a 24-hour period 3 to 16 days after abstinence from alcohol and again 29 to 39 days later. The numbers of LH and FSH pulses per 24 hours were normal in these alcoholic men compared with controls. However, we found increased mean 24-hour concentrations of immunoactive LH (P = 0.012) and FSH (P = 0.018), increased peak heights for LH (P = 0.035) and FSH (P = 0.004), decreased fractional LH (P = 0.002) and FSH (P = 0.044) pulse amplitudes and increased interpulse valley mean LH (P = 0.010) and FSH (P = 0.018) concentrations. Serum levels of total testosterone, total estradiol and estrone were normal, whereas concentrations of free testosterone and free estradiol were increased. Pituitary release of LH and FSH was normal in response to low (5-micrograms) and high (95-micrograms) doses of GnRH given intravenously. The present observations indicate that in chronically alcoholic men, acute abstinence from ethanol is associated with elevated circulating concentrations of immunoactive gonadotropins in the presence of intact spontaneous gonadotropin pulsatility, preserved pituitary responsiveness to exogenous GnRH, and increased concentrations of free testosterone and free estradiol. Such findings are consistent with alterations in the endogenous feedback actions of sex steroid hormones in this setting.

Adult↗
PubMedDate not supplied

24-hour pulsatile and circadian patterns of cortisol secretion in alcoholic men.

Pulsatile and circadian patterns of cortisol secretion during acute (3 to 16 days) and chronic (29 to 39 days) abstinence were examined in alcoholic men with no clinical or laboratory evidence of hepatic dysfunction or nutritional deficiencies. Mean and integrated 24-hour serum concentrations of cortisol determined by sampling the blood every 20 minutes over a 24-hour period were increased in six out of 10 alcoholic subjects during acute abstinence when compared with normal controls. Sustained abstinence in seven subjects with follow-up studies caused significant decreases in the mean maximal cortisol peak amplitude (13 +/- 1.0 SEM acutely vs. 10.3 +/- 0.52 micrograms/dl follow-up; P = 0.01), mean 24-hour serum cortisol concentrations (10.9 micrograms/dl +/- 1.2 vs. 8.5 micrograms/dl +/- 0.26; P = 0.047), interpulse valley mean (9.3 micrograms/dl +/- 0.88 vs. 6.5 micrograms/dl +/- 0.34; P = 0.007), and valley nadir (7.9 micrograms/dl +/- 0.69 vs. 5.4 micrograms/dl +/- 0.30; P = 0.0036) concentrations. Cortisol pulse frequency was normal. Although circadian cortisol rhythmicity was maintained in alcoholics, the timing of the circadian acrophase was delayed significantly (P = 0.006) during acute abstinence (1022 [clocktime] +/- 34 min) as compared with normal controls (0743 [clocktime] +/- 34 min), and the amplitude of circadian cortisol rhythms exceeded normal in five of 10 alcoholics. Analysis of data in one alcoholic subject by a new multiparameter deconvolution method demonstrated increases in secretory burst amplitude (0.64 microgram/dl +/- 0.08 SD), mass of cortisol released per burst (9.8 micrograms/dl +/- 1.2 SD), and daily endogenous cortisol production rate (22 mg +/- 2.4 SD) during acute abstinence. These values were statistically different when compared with seven normal controls and the subjects' values during sustained abstinence (P less than 0.02). In conclusion, the results of the present study suggest increased daily production of cortisol as a possible mechanism underlying the elevated serum cortisol concentrations in chronic alcoholics during acute abstinence. This abnormality is shown to be reversible with sustained abstinence from alcohol.

Adult↗
PubMedDate not supplied

Effects of opioid receptor blockade on luteinizing hormone (LH) pulses and interpulse LH concentrations in normal women during the early phase of the menstrual cycle.

To determine the role of endogenous opioid peptides in regulating pulsatile luteinizing hormone (LH) release in the early follicular phase of the menstrual cycle of eumenorrheic women, we evaluated serum LH concentrations in blood collected every 10 min for 12 h in 27 women each studied during two menstrual cycles: (1) without pretreatment and (2) following oral administration of naltrexone, a mu opiate receptor blocking agent, at a dose of 1.0 mg/kg. Pulsatile LH release was assessed by the CLUSTER algorithm. The mean (+/- SE) integrated serum LH concentration (IU/L/min) increased following the administration of naltrexone (4715 +/- 298) in comparison to the control day (3997 +/- 381; p = 0.0008). The mean number of LH pulses (/12 h) detected on the naltrexone day (10.3 +/- 0.3) was higher than on the control day (8.9 +/- 0.4; p = 0.0068). Mean maximal LH peak height (IU/L) was greater on the naltrexone (7.8 +/- 0.5) vs control (6.7 +/- 0.5) days (p = 0.0064) as was the interpulse valley mean serum LH concentration (IU/L; 6.3 +/- 0.4 vs 5.0 +/- 0.4; p = 0.0013). No difference was noted in the mean incremental LH pulse amplitude (IU/L; 1.9 +/- 0.1 vs 2.1 +/- 0.1; p = 0.13), or peak duration (min; 40 +/- 1.8 vs 45.0 +/- 2.4; p = 0.06). Mean LH peak area (IU/L/min) was greater on the control (45.0 +/- 2.4) vs naltrexone (40 +/- 1.8) days (p = 0.0475).(ABSTRACT TRUNCATED AT 250 WORDS)

Administration, Oral↗
PubMedDate not supplied

Evaluation of a heparin assay method using a fluorogenic synthetic peptide substrate for thrombin.

A heparin assay method based on thrombin cleavage of a fluorogenic synthetic peptide has been evaluated in normal subjects, in patients with chronic renal disease on hemodialysis, and in patients with other disorders. The method has satisfactory accuracy, sensitivity, and reproducibility. In contrast to methods commonly used to monitor heparin therapy, it measures heparin directly and is uninfluenced by patient variables such as low antithrombin III. The method may provide valuable information in selected clinical settings such as cardiopulmonary bypass and in patients with chronic renal disease who receive heparin during hemodialysis or prior to surgery.

Cardiopulmonary Bypass↗
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Teaching children to resolve conflicts cooperatively.

Managing conflicts with and among children can be stressful and time-consuming for caregivers. Children and parents can learn to resolve differences in a cooperative way that allows each person to feel good about the process and the outcome. This article describes one cooperative conflict resolution process and suggests available resources.

Child↗
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Mixed distribution analysis identifies saltation and stasis growth.

A maximum likelihood method of mixed distribution analysis is investigated for its utility as a method for the identification of saltation and stasis in longitudinal growth data. Daily infant growth data that have been previously identified to follow a saltatory growth process are employed. This is a novel application of the finite mixed distribution analysis (MDA), a method designed to objectively identify the presence of one or more Gaussian populations. The null hypothesis is that a single Gaussian distribution best describes the incremental growth data. This would be compatible with smooth, slowly varying daily growth patterns. This study explores whether or not two distinctive populations are evident in incremental saltatory growth data, as postulated by the saltation and stasis observations. The analysis is important in providing a growth model-independent test for the presence of saltation and stasis by a separate statistical assessment with none of the saltatory algorithm assumptions. The finite mixed distribution analysis identifies that each individual's incremental growth data is statistically best described as a mixture consisting of two components, or two populations of increments (chi-square, p < 0.05). For each individual, one of these populations is centred about a zero increment, and is compatible with the previous evidence of stasis intervals. The second population of data points is characterized by unique distributions for each individual, compatible with the previous observation that infants grow by unique patterns of growth saltations in both amplitude and frequency. The percentage of data points that fall within each of the two unique finite mixture distributions (FMDs) is similar to the proportions of discrete saltation and stasis intervals previously identified by the saltation and stasis method. Thus, the FMD analysis lends support to the nature of growth as a saltatory process characterized by two states in the daily growth of these infants. By contrast with the saltatory algorithm, which is applied to the original serial growth measurements, the mixed distribution analysis employs increments removed from their time relationships. The lack of time series sequence information precludes the mixed distribution method from reconstructing specific temporal patterns of saltatory growth. The present analysis reiterates that individual growth patterns are statistically unique and cannot be reconstructed or identified from group data.

Biometry↗
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The use of regularity as estimated by approximate entropy to distinguish saltatory growth.

A nonlinear dynamics metric, approximate entropy (ApEn), is investigated as a diagnostic method for distinguishing between mathematical models, and the underlying mechanistic hypotheses that purport to describe the same time series experimental observations. ApEn measures the occurrence of pattern regularity within a time series, and is used here to investigate growth patterns in daily length growth. The notion investigated is that ApEn distributions for competing time series patterns expressed as mathematical formulations can be modelled by Monte Carlo and bootstrap methods and compared to the ApEn values for an original experimental data series. If the ApEn values for the different models do not overlap, then it is expected that ApEn can be utilized to distinguish these models and hypotheses, and to provide statistical assessment for the underlying biological patterns in experimental data. The conclusion is that the ApEn metric is successful as a time series diagnostic tool. It is a model-independent statistic that clearly differentiates saltatory growth from slowly varying continuous models of growth and serves to further document the saltatory nature of growth. This is a unique application of approximate entropy, illustrating the broad applicability of ApEn to biological time series, with the specific example of discriminating a saltatory growth process in longitudinal growth data. Future investigations of regularity in longitudinal time series in human biology with ApEn statistics are suggested.

Data Interpretation, Statistical↗
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A case study of daily growth during adolescence: a single spurt or changes in the dynamics of saltatory growth?

Standing height of one adolescent male was measured daily between the ages of 12.83 and 13.95 years on 328 days out of 389 consecutive days according to standard techniques for maximal stature measurement. The serial growth data were analysed by a modification of techniques developed to identify patterns in serial hormone data. The entire growth in height during this interval occurred during 12 non-periodic saltatory episodes with amplitude of 0.92 +/- 0.09 cm (SEM) in < or = 24 h separated by 3-100 days of no significant growth. The proposition that adolescent growth is characterized by a change in the dynamics of growth saltus amplitude and/or frequency is suggested.

Adolescent↗