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Biomedical subjects

M L Johnson

Publications and source records attributed to M L Johnson.

At least 199 records · Page 11Linked to original sources
PubMed1989

Natural killer lymphocyte blast crisis of chronic myelogenous leukemia.

We describe for the first time a case report documenting a chronic myelogenous leukemia (CML) patient who developed a blast crisis of natural killer (NK) lymphocytes. Many of the blasts exhibited large granular lymphocytic (LGL) morphology. Single parameter immunophenotyping results determined that the granulated as well as the agranulated blast cells were NK lymphocytes (CD45, NKH1, CD2, LEU 17, and CD16 positive; CD3, CD8, and LEU 7 negative). Dual parameter flow cytometric testing also determined that some of the blasts expressed the CD11b and CD11c markers as reported for some types of NK lymphocytes. Approximately 10% of the cells were in the S phase of the cell cycle as determined by a modified Vindelov DNA content analysis test and may theoretically reflect some of those cells expressing CD11b and CD11c. The cells did not express in vitro NK lymphocyte functional activity against a K562 target and therefore similar to other reported cases of presumably immature NK lymphocytic leukemias. The NK lymphocyte blast crisis was successfully treated with vincristine and prednisone. The patient's disease eventually relapsed and transformed to a progenitor stem cell before she died (CD45, 13, CD38, and CD34 positive). The flow cytometric immunophenotyping results contributed significantly as an important adjunct in determining the appropriate diagnosis, helping to select the type of therapy, and monitoring the patient with this unusual type of blast crisis.

Antigens, CD↗
PubMed1989

Pathophysiological features of the pulsatile secretion of biologically active luteinizing hormone in man.

The development of an in vitro bioassay of high specificity, sensitivity and precision for the measurement of low circulating concentrations of biologically active glycoprotein hormones has offered exciting new insights into the in vivo secretion and metabolic clearance of luteinizing hormone (LH) in various pathophysiological states. Moreover, the most recent combined application of the rat interstitial cell testosterone (RICT) bioassay and a novel multiple-parameter deonvolution model has allowed investigators to dissect plasma concentration profiles of bioactive LH into defined secretory bursts, which have numerically explicit amplitudes, locations in time, and durations, and are acted upon by determinable subject- and study-specific endogenous metabolic clearance rates. Here, we have: (i) reviewed the ability of the endogenous GnRH pulse signal to regulate the in vivo secretion of biologically active LH molecules as assessed in the RICT and by deconvolution mechanics; (ii) demonstrated that low-dose exogenous GnRH pulses effectively mimic spontaneous bioactive LH pulsatility; (iii) investigated the role of endogenous androgen and estrogen in modulating bioactive gonadotropin secretion in men and women; and (iv) described significant alterations in endogenous LH bioactivity in puberty and healthy aging.

Aging↗
PubMed1989

Measuring the kinetics of membrane phase transitions.

This article presents a brief review of literature on the physical chemistry of lipid phase transitions with emphasis on their kinetic properties. The theoretical foundations of perturbation techniques, and specifically the volume-perturbation technique are discussed in some detail. These are presented as a rationale for, and introduction to, a volume-perturbation kinetic calorimeter that we have constructed for measurement of the kinetics of lipid phase transitions. The instrument has been applied to study the gel-liquid crystalline phase transition in a variety of phospholipid bilayer systems. The design and implementation of the volume-perturbation calorimeter are presented along with a discussion of the techniques of data analysis. Finally, we present typical results obtained with this methodology for a multilamellar vesicle dispersion of dipalmitoylphosphatidylcholine.

Calorimetry↗
PubMed1989

Decay time distribution analysis of Yt-base in benzene-methanol mixtures.

Frequency-domain fluorometry was used to measure intensity decays of synthetic Yt-base in mixtures of benzene-methanol at 20 degrees C. Multiexponential analysis shows that the decay of Yt-base fluorescence in benzene and methanol can be well fitted to a single-exponential model with tau = 9.67 ns and 6.25 ns respectively. In mixtures of benzene-methanol the decays became heterogeneous, and the maximum of heterogeneity observed was in a mixture containing 6% methanol. Since we expected a distribution of Yt-base solvation states in the solvent mixtures, and because the decay times of Yt-base are sensitive to solvent, we analyzed the data in terms of decay time distributions. The goodness-of-fit for the unimodal distribution model which has two floating parameters was equivalent to that found using the double exponential model with three floating parameters. The Lorentzian distribution model appears to provide a slightly superior fit relative to the Gaussian distribution model. These results suggest that the intensity decays of solvent-sensitive fluorophores in mixed solvents are described by a distribution of decay times.

Benzene↗
PubMed1989

Resolvability of free energy changes for oxygen binding and subunit association by human hemoglobin.

Probability distributions of the free energy changes for oxygen binding, subunit association, and quaternary enhancement by human hemoglobin were obtained from Monte Carlo simulations performed on two independent sets of variable protein concentration equilibrium oxygen-binding data. Uncertainties in unliganded and fully liganded dimer to tetramer association free energy changes (0 delta G'2 and 4 delta G'2) were accounted for in the simulations. Distributions of the dimer to tetramer association free energy changes for forming singly and triply liganded tetramers (1 delta G'2 and 3 delta G'2) are well defined and quite symmetric, whereas that for forming doubly liganded tetramers (2 delta G'2) is poorly defined and highly asymmetric. The distribution of the dimer stepwise oxygen-binding free-energy change (delta g'2i) is well defined and quite symmetric as are those of the tetramer stepwise oxygen-binding free-energy changes for binding the first and last oxygens to tetramers (delta g'41 and delta g'44). Distributions of the intermediate tetramer stepwise oxygen-binding free-energy changes (delta g'42 and delta g'43) are poorly defined and highly asymmetric, but are compensatory in that their sum (delta g'4[2 + 3]) is again well defined and nearly symmetric. Distributions of the free energy changes corresponding to the tetramer product Adair oxygen binding constants (delta G'4i) are well defined and quite symmetric for i = 1, 3, 4 but not for i = 2. The distribution of delta g'44 - delta g'2i (the quaternary enhancement free energy change) is relatively narrow, nearly symmetric, and confined to the negative free-energy domain. This suggests that the quaternary enhancement free energy change (a) may be resolved with good confidence from this data and (b) is finite and negative under the conditions of these experiments. Our results also suggest two different four-state combinatorial switch models that provide accurate characterization of hemoglobin's functional behavior.

Hemoglobins↗
PubMed1989

Physiological attributes of endogenous bioactive luteinizing hormone secretory bursts in man.

The exact nature of glandular secretory events is difficult to discern in vivo, since underlying patterns of hormone release are confounded by metabolic clearance. Moreover, conventional immunoassay does not always agree with bioassay. Here, we have used the rat interstitial cell testosterone in vitro bioassay of luteinizing hormone (LH) to measure serial LH concentrations in the normal adult human male. The resultant bioactive LH time series were analyzed by a deconvolution model in which circulating hormone concentrations are controlled by the operation of four finite, nonzero, and determinable parameters: 1) the location(s); 2) the amplitude(s), and 3) the half-duration(s) of underlying secretory bursts, acted on by 4) endogenous exponential clearance kinetics. A macroscopic secretory burst was modeled in the algebraic form of a Gaussian distribution of instantaneous molecular secretory rates. The physiological implications of this model were examined by analyzing bioactive LH pulsatility in eight men sampled every 10 min for 6 h. Multiple-parameter deconvolution disclosed endogenous bioactive LH half-lives of 53 +/- 5.4 min (range 38-76 min), in agreement with earlier independent estimates of 65 +/- 4.9 (42-87) min in four LH-deficient men given a 35 micrograms iv bolus of human LH. Calculated endogenous production rates of bioactive LH (0.48 +/- 0.06 mIU.min-1.ml-1) were also in accord with values estimated previously from steady-state infusions of LH. Deconvolution further indicated that underlying bioactive LH secretory bursts had half-durations of only 12.2 +/- 1.5 min, occurred at intervals of 56 +/- 1.3 min, and achieved amplitudes of 2.1 +/- 0.26 mIU.min-1.ml-1.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1989

Amplitude modulation of a burstlike mode of cortisol secretion subserves the circadian glucocorticoid rhythm.

We have examined the mechanism subserving the in vivo circadian rhythm of cortisol in men. To this end, blood samples were withdrawn at 10-min intervals for 24 h in each of six men to yield well-defined profiles of episodic cortisol release. A novel multiple-parameter deconvolution model was applied to discriminate the number, amplitudes, and durations of all statistically significant underlying cortisol secretory bursts from the plasma hormone concentrations and simultaneously estimate the endogenous half-life of cortisol disappearance in each subject. These experiments disclosed randomly occurring cortisol secretory bursts at a mean frequency of 19 +/- 0.82 events per day (interpulse interval 77 +/- 4.0 min). Secretory bursts exhibited a mean half-duration (duration at half-maximal amplitude) of only 16 +/- 0.61 min indicating that 95% of daily cortisol secretion occurred in 8.2 h. Cortisol secretory burst frequency varied 2.2-fold over 24 h, whereas cortisol secretory burst amplitude varied 6.6-fold. We conclude that the nyctohemeral pattern of cortisol variation in vivo can be accounted for by an amplitude-modulated, random burstlike mode of cortisol secretion without the need to postulate a tonic mode of cortisol release.

Adult↗
PubMed1989

Biophysical modeling of sensitivity and positive accuracy of detecting episodic endocrine signals.

To investigate the nature of false-negative and false-positive errors in endocrine signal detection, we used a multiparameter convolution procedure to create random hormone secretory bursts. We observed that 1) data containing high signal frequency, amplitude, and/or duration can be analyzed at less stringent peak-detection thresholds; 2) for any given secretory burst amplitude, increasing the peak-detection threshold enhances positive accuracy but decreases sensitivity; 3) increased sampling frequency improves sensitivity but requires more stringent peak-detection thresholds; and 4) increasing noise diminishes both sensitivity and positive accuracy. We conclude that secretory properties, peak-detector thresholds, investigator-specified sampling intensity, and experimental variance all significantly influence false-positive and false-negative errors associated with the enumeration of episodic endocrine pulse signals. The present observations should offer objective principles to aid in the rational design and analysis of neuroendocrine studies of pulsatile physiological phenomena.

Computer Simulation↗
PubMed1989

In vivo biological validation and biophysical modeling of the sensitivity and positive accuracy of endocrine peak detection. I. The LH pulse signal.

The false positive (type I) and false negative (type II) errors inherent in computerized peak detection algorithms can have a major impact on the valid interpretation of physiological experiments. To objectively define the nature and extent of statistical errors associated with the identification of episodic gonadotropin (LH) peaks, we have employed two complementary approaches. First, using a general biophysical model for simulating episodic LH secretion, we have estimated optimal pulse analysis parameters that yield maximal sensitivity (probability of finding any given peak) and positive accuracy (probability that any identified peak is a true pulse) in synthetic LH series approximating those observed spontaneously in vivo. Secondly, we have estimated optimal peak detection parameters in an in vivo primate animal model, in which electrophysiological correlates of spontaneous LH pulses were documented independently by continuous electrophysiological monitoring of medial basal hypothalamus multiunit activity. These combined approaches indicate that LH time series can be analyzed for episodic LH pulsatility by an appropriately constrained, objective computerized algorithm with minimal false negative and false positive errors, i.e. with resultant high sensitivity and positive accuracy. Moreover, optimal pulse analysis parameters exhibited similar sensitivity and positive accuracy rates in both the biophysical simulations and the animal model. Thus, we suggest that the combined use of an algebraically explicit biophysical simulation model and an in vivo animal paradigm may serve to clarify the nature and extent of false negative and false positive errors in the detection of other hormone peaks as well as the gonadotropin LH.

Animals↗
PubMed1989

The nature of the gonadotropin-releasing hormone stimulus-luteinizing hormone secretory response of human gonadotrophs in vivo.

To examine the stimulus-secretion response of human pituitary gonadotrophs in vivo, we applied a new multiple parameter deconvolution technique to analyze (1) exogenous GnRH-stimulated LH secretory responses in 10 men with isolated hypogonadotropic hypogonadism (IHH), and (2) endogenous and exogenous GnRH-stimulated LH secretory responses in 8 normal men. The GnRH-deficient men were given 4 bolus doses of synthetic GnRH (7.5, 25, 75, and 250 ng/kg) iv at 2-h intervals in randomized order after long term pulsatile GnRH administration. The normal men were studied by sampling blood at 10-min intervals for 12 h basally and after 2 consecutive 10-micrograms iv GnRH doses. The serum LH peaks in both groups were subjected to quantitative deconvolution to resolve underlying LH secretory and clearance rates simultaneously. Such analyses revealed that exogenous GnRH-induced LH secretory episodes in GnRH-deficient men with IHH could be modeled as algebraically Gaussian distributions of instantaneous LH secretory rates with a mean half-duration of 14 +/- 2 min. The simultaneously resolved half-life of endogenous LH disappearance was 71 +/- 5 min. The log dose-response relationship for GnRH dose vs. maximal LH secretory rate or vs. calculated mass of LH released per secretory burst was linear. In contrast, varying GnRH doses did not alter the duration of LH secretory bursts, the half-time of LH disappearance, or the latency of LH secretory bursts after iv GnRH injections (viz. 7.6 min). Deconvolution analysis of the spontaneous (endogenous GnRH-stimulated) LH peaks in normal men revealed a mean half-duration of secretory bursts of 9.9 +/- 1.5 min, and a mean half-time of endogenous LH disappearance of 76 +/- 5 min. These values were not significantly different from those in the GnRH-treated normal or GnRH-deficient men. In summary, deconvolution analysis of LH release in men with IHH revealed a significant linear relationship between iv doses of pulsed GnRH and computer-resolved LH secretory rate and/or the mass of LH released per secretory event. In contrast, varying doses of GnRH did not alter the lag time between the GnRH stimulus and the LH secretory burst, the duration of LH secretion, or the calculated half-life of the LH released. We conclude that GnRH exerts dose-dependent effects on specific attributes of the secretory response of human gonadotrophs in vivo.

Adult↗
PubMed1989

Circadian, ultradian, and episodic release of beta-endorphin in men, and its temporal coupling with cortisol.

beta-Endorphin and ACTH derive from a common peptide precursor. Although much is known about the physiological patterns of ACTH release, neither the minute to minute regulation of beta-endorphin secretion nor its temporal relationship to cortisol has been characterized. As an initial step to defining the regulation of beta-endorphin release in man, we studied the circadian periodicity, ultradian rhythmicity, and episodic pulsatility of serum beta-endorphin concentrations in seven normal men. Blood sampling was conducted at 10-min intervals for 24 h, and the subsequent serum samples were assayed by a two-site immunoradiometric assay. Computerized analysis of the subsequent beta-endorphin time series revealed a mean beta-endorphin pulse frequency of 13 +/- 1 (+/- SE) peaks/24 h, corresponding to an interpulse interval of 100 +/- 7 min. The mean maximal peak height of beta-endorphin pulses was 31 +/- 3 pg/mL (9.0 +/- 0.8 pmol/L), which represented an incremental increase of 11 +/- 1 pg/mL 3.2 +/- 0.4 pmol/L; 63 +/- 13%) above the preceding nadir. The average beta-endorphin peak exhibited a duration of 68 +/- 6 min. Fourier analysis revealed a significant circadian amplitude of 6 +/- 1 pg/mL (1.6 +/- 0.4 pmol/L; 23% of the 24-h mean concentration), with an acrophase (time of maximum value) at 1043 h (+/- 40 min). Spectral analysis also disclosed beta-endorphin rhythms with mean periodicities of 29 +/- 4, 42 +/- 4, and 61 +/- 5 min. Gel filtration chromatography confirmed that serum beta-endorphin peaks contained significantly more immunoactive beta-endorphin [62 pg/mL (18 pmol/L)] than did the flanking nadirs [16 and 18 pg/mL (4.6 and 5.2 pmol/L)]. Auto- and cross-correlation analyses of serum beta-endorphin and cortisol concentrations followed by autoregressive modeling disclosed that all seven men had significant positive cross-correlations between serum beta-endorphin and cortisol considered simultaneously or when cortisol lagged beta-endorphin by 10 min. A negative cross-correlation was found in five of the seven men when cortisol was considered to lead beta-endorphin by 20 or 30 minutes. We conclude that beta-endorphin is released physiologically in a pulsatile manner with circadian and ultradian rhythmicity and a close temporal coupling to cortisol.

Adult↗
PubMed1989

Carnivora: the primary structure of the Pacific Walrus (Odobenus rosmarus divergens, Pinnipedia) hemoglobin.

The primary structure of the alpha- and beta-chains of the hemoglobin from the Pacific Walrus (Odobenus rosmarus divergens, Pinnipedia) is presented. Sequence analysis revealed only one hemoglobin component whereas two bands were found in polyacrylamide gel electrophoresis. The globin chains were separated by high-performance liquid chromatography and the sequences determined by automatic liquid- and gas-phase sequencing of the chains and their tryptic peptides. The alpha-chains show 20 and the beta-chains 12 exchanges compared to the corresponding human chains. In the alpha-chains one heme- and two alpha 1/beta 1-contacts were exchanged whereas in the beta-chains one alpha 1/beta 1-, one alpha 1/beta 2-and one heme-contact are substituted. Compared to Harbour Seal (Phoca vitulina) the Walrus hemoglobin shows 9 amino-acid replacements in the alpha-chains and 5 in the beta-chains. The relation between Pinnipedia and Arctoidea is discussed.

Amino Acid Sequence↗
PubMed1989

Surgical management of brain metastases: how aggressive should we be?

Treatment of cancer metastatic to the brain is dictated by both the need to achieve immediate short-term palliation and the desire for durable symptom-free remission. Surgical resection of brain metastases makes available tissue for diagnosis and experimental study, permits prompt relief of neurological signs and symptoms secondary to tumor mass effect, enhances the potential for sustained local tumor control in those patients with solitary disease, and allows greater therapeutic flexibility by obviating the need for cranial radiation in some situations and by expanding patient access to alternative experimental protocols or systemic chemotherapy.

Brain Neoplasms↗
PubMed1989

Aging of the United States population. The dermatologic implications.

Clearly in the near and later future the older patient will augment significantly the burden of dermatologic disease and the consequent need for care. Increasing in numerical strength, those 65 years and older, carrying along the common problems prevalent in every adult age group, will, by living longer, have new problems related to wear, tear, and actinic exposure as well as pharmacologically induced problems arising from needed therapy for other conditions. The predictable challenge to our specialty is formidable.

Age Factors↗
PubMed1988

Distance distributions in proteins recovered by using frequency-domain fluorometry. Applications to troponin I and its complex with troponin C.

We used resonance energy transfer to examine the distribution of distances between two sites on troponin I (TnI). The donor (D) was the single tryptophan residue at site 158 (Trp 158), and the acceptor (A) was cysteine 133 (Cys 133) which was labeled with N-(iodoacetyl)-N'-(1-sulfo-5-naphthyl)ethylenediamine (IE). A distribution of D-A distances results in a distribution of donor decay times, which were resolved by using frequency-domain fluorometry. In the native state we recovered a relatively narrow distribution of D-A distances. The widths of the distance distributions were found to increase progressively and dramatically with increasing concentrations of guanidine hydrochloride. Binding of calcium-free troponin C (TnC) to troponin I did not alter the distance distribution. Addition of Ca2+ to the TnI.TnC complex resulted in a sharper distance distribution and protected against the guanidine hydrochloride induced increase in the width of the distance distribution. Additionally, the same distance distributions were recovered for native and denatured TnI when the Forster distance for energy transfer was decreased by acrylamide quenching. These results demonstrate that distance distributions can be recovered with good accuracy, to the extent of revealing modest changes due to binding of other components. This technique should have widespread applications in studies of protein folding.

Fluorometry↗
PubMed1988

Three-state combinatorial switch models as applied to the binding of oxygen by human hemoglobin.

We have generated a series of all 6561 unique, discrete three-state combinatorial switch models to describe the partitioning of the cooperative oxygen-binding free change among the 10 variously ligated forms of human hemoglobin tetramers. These models were inspired by the experimental observation of Smith and Ackers that the cooperative free energy of the intersubunit contact regions of the 10 possible ligated forms of human hemoglobin tetramers can be represented by a particular distribution of three distinct energy levels [Smith, F. R., & Ackers, G. K. (1985) Proc. Natl. Acad. Sci. U.S.A. 82, 5347-5351]. A statistical thermodynamic formulation accounting for both dimer-tetramer equilibria and ligand binding properties of hemoglobin solutions as a function of oxygen and protein concentrations was utilized to exhaustively test these thermodynamic models. In this series of models each of the 10 ligated forms of the hemoglobin tetramer can exist in one, and only one, of three possible energy levels; i.e., each ligated form was assumed to be associated with a discrete energy state. This series of models includes all possible ways that the 10 ligation states of hemoglobin can be distributed into three distinct cooperative energy levels. The mathematical models, as presented here, do not permit equilibria between energy states to exist for any of the 10 unique ligated forms of hemoglobin tetramers. These models were analyzed by nonlinear least-squares estimation of the free energy parameters characteristic of this statistical thermodynamic development.(ABSTRACT TRUNCATED AT 250 WORDS)

Hemoglobins↗
PubMed1988

Description of the molecular mechanism of cooperativity in human hemoglobin cannot be limited to a first-order free energy coupling concept.

Studies of the linkage between ligand binding and subunit assembly of oligomeric proteins have extensively used the concept of free energy coupling. The "order" of these free energy couplings was introduced [Weber, G. (1984) Proc. Natl. Acad. Sci. U.S.A. 81, 7098-7102] as the number of subunits that must be liganded to alter specific intersubunit interactions. This concept dictates that the ligation of fewer subunits has no effect, but once the order number of subunits becomes ligated, the specific intersubunit interaction energy between those particular subunits is completely eliminated. Weber's report claims that the free energy coupling between oxygen binding and the dimer-tetramer subunit assembly in stripped human hemoglobin A is "first order". This conclusion is based on the analysis of a set of previously published equilibrium constants [Mills, F. C., Johnson, M. L., & Ackers, G. K. (1976) Biochemistry 15, 5350-5362]. I subsequently reported that the original experimental data, from which the equilibrium constants were derived, are consistent with both the first-order and "second-order" free energy coupling concepts [Johnson, M. L. (1986) Biochemistry 25, 791-797]. I also demonstrated that more precise recent experimental data [Chu, A. H., Turner, B. W., & Ackers, G. K. (1984) Biochemistry, 23, 604-617] are consistent with both the first-order and second-order free energy coupling concepts. A recent article [Weber, G. (1987) Biochemistry 26, 331-332] disagrees that the oxygen-binding data for human hemoglobin A are consistent with a second-order model.(ABSTRACT TRUNCATED AT 250 WORDS)

Hemoglobin A↗