Showing papers by "University of California, San Diego published in 1972"

The fluid mosaic model of the structure of cell membranes.

Abstract: A fluid mosaic model is presented for the gross organization and structure of the proteins and lipids of biological membranes. The model is consistent with the restrictions imposed by thermodynamics. In this model, the proteins that are integral to the membrane are a heterogeneous set of globular molecules, each arranged in an amphipathic structure, that is, with the ionic and highly polar groups protruding from the membrane into the aqueous phase, and the nonpolar groups largely buried in the hydrophobic interior of the membrane. These globular molecules are partially embedded in a matrix of phospholipid. The bulk of the phospholipid is organized as a discontinuous, fluid bilayer, although a small fraction of the lipid may interact specifically with the membrane proteins. The fluid mosaic structure is therefore formally analogous to a two-dimensional oriented solution of integral proteins (or lipoproteins) in the viscous phospholipid bilayer solvent. Recent experiments with a wide variety of techniqes and several different membrane systems are described, all of which abet consistent with, and add much detail to, the fluid mosaic model. It therefore seems appropriate to suggest possible mechanisms for various membrane functions and membrane-mediated phenomena in the light of the model. As examples, experimentally testable mechanisms are suggested for cell surface changes in malignant transformation, and for cooperative effects exhibited in the interactions of membranes with some specific ligands. Note added in proof: Since this article was written, we have obtained electron microscopic evidence (69) that the concanavalin A binding sites on the membranes of SV40 virus-transformed mouse fibroblasts (3T3 cells) are more clustered than the sites on the membranes of normal cells, as predicted by the hypothesis represented in Fig. 7B. T-here has also appeared a study by Taylor et al. (70) showing the remarkable effects produced on lymphocytes by the addition of antibodies directed to their surface immunoglobulin molecules. The antibodies induce a redistribution and pinocytosis of these surface immunoglobulins, so that within about 30 minutes at 37 degrees C the surface immunoglobulins are completely swept out of the membrane. These effects do not occur, however, if the bivalent antibodies are replaced by their univalent Fab fragments or if the antibody experiments are carried out at 0 degrees C instead of 37 degrees C. These and related results strongly indicate that the bivalent antibodies produce an aggregation of the surface immunoglobulin molecules in the plane of the membrane, which can occur only if the immunoglobulin molecules are free to diffuse in the membrane. This aggregation then appears to trigger off the pinocytosis of the membrane components by some unknown mechanism. Such membrane transformations may be of crucial importance in the induction of an antibody response to an antigen, as well as iv other processes of cell differentiation.

Bayesian-Based Iterative Method of Image Restoration

Abstract: An iterative method of restoring degraded images was developed by treating images, point spread functions, and degraded images as probability-frequency functions and by applying Bayes’s theorem. The method functions effectively in the presence of noise and is adaptable to computer operation.

Nonlinear Bayesian estimation using Gaussian sum approximations

Abstract: Knowledge of the probability density function of the state conditioned on all available measurement data provides the most complete possible description of the state, and from this density any of the common types of estimates (e.g., minimum variance or maximum a posteriori) can be determined. Except in the linear Gaussian case, it is extremely difficult to determine this density function. In this paper an approximation that permits the explicit calculation of the a posteriori density from the Bayesian recursion relations is discussed and applied to the solution of the nonlinear filtering problem. In particular, it is noted that a weighted sum of Gaussian probability density functions can be used to approximate arbitrarily closely another density function. This representation provides the basis for procedure that is developed and discussed.

Estimation of Infarct Size in Man and its Relation to Prognosis

Abstract: Infarct size was assessed quantitatively in 33 patients with acute myocardial infarction with a new technic based on analysis of serial serum creatine phosphokinase (CPK) changes to determine its relationship to prognosis. We have recently measured infarct size in the conscious dog with this method which takes into account CPK distribution space, fractional disappearance rate, proportion degraded in myocardium, and proportion released into the circulation, and we have validated the method by measurement of myocardial CPK depletion in the same animals. In the present study, CPK activity (determined spectrophotometrically) and isoenzyme profiles (assayed electrophoretically) were measured in patient serum samples obtained every 2 hours. Infarct size was estimated by mathematical analysis of serial CPK changes utilizing the method previously developed in the conscious dog model. CPK isoenzyme profiles demonstrated prominent anodal bands, absent from normal serum, indicating that enzyme elevations reflected C...

Gene Therapy for Human Genetic Disease

Abstract: In our view, gene therapy may ameliorate some human genetic diseases in the future. For this reason, we believe that research directed at the development of techniques for gene therapy should continue. For the foreseeable future, however, we oppose any further attempts at gene therapy in human patients because (i) our understanding of such basic processes as gene regulation and genetic recombination in human cells is inadequate; (ii) our understanding of the details of the relation between the molecular defect and the disease state is rudimentary for essentially all genetic diseases; and (iii) we have no information on the short-range and long-term side effects of gene therapy. We therefore propose that a sustained effort be made to formulate a complete set of ethicoscientific criteria to guide the development and clinical application of gene therapy techniques. Such an endeavor could go a long way toward ensuring that gene therapy is used in humans only in those instances where it will prove beneficial, and toward preventing its misuse through premature application. Two recent papers have provided new demonstrations of directed genetic modification of mammalian cells. Munyon et al. (44) restored the ability to synthesize the enzyme thymidine kinase to thymidine kinase-deficient mouse cells by infection with ultraviolet-irradiated herpes simplex virus. In their experiments the DNA from herpes simplex virus, which contains a gene coding for thymidine kinase, may have formed a hereditable association with the mouse cells. Merril et al. (45) reported that treatment of fibroblasts from patients with galactosemia with exogenous DNA caused increased activity of a missing enzyme, alpha-D-galactose-l-phosphate uridyltransferase. They also provided some evidence that the change persisted after subculturing the treated cells. If this latter report can be confirmed, the feasibility of directed genetic modification of human cells would be clearly demonstrated, considerably enhancing the technical prospects for gene therapy.

On one-dimensional finite-strain beam theory: the plane problem

Abstract: The paper formulates a one-dimensional large-strain beam theory for plane deformations of plane beams, with rigorous consistency of dynamics and kinematics via application of the principle of virtual work. This formulation is complemented by considerations on how to obtain constitutive equations, and applied to the problem of buckling of circular rings, including the effects of axial normal strain and transverse shearing strain.

Segmental aneuploidy and the genetic gross structure of the drosophila genome

Abstract: By combining elements of two Y-autosome translocations with displaced autosomal breakpoints, it is possible to produce zygotes heterozygous for a deficiency for the region between the breakpoints, and also, as a complementary product, zygotes carrying a duplication for precisely the same region. A set of Y-autosome translocations with appropriately positioned breakpoints, therefore, can in principle be used to generate a non-overlapping set of deficiencies and duplications for the entire autosomal complement.-Using this method, we have succeeded in examining segmental aneuploids for 85% of chromosomes 2 and 3 in order to assess the effects of aneuploidy and to determine the number and location of dosage-sensitive loci in the Drosophila genome (Figure 5). Combining our data with previously reported results on the synthesis of Drosophila aneuploids (see Lindsley and Grell 1968), the following generalities emerge.-1. The X chromosome contains no triplo-lethal loci, few or no haplo-lethal loci, at least seven Minute loci, one hyperploid-sensitive locus, and one locus that is both triplo-abnormal and haplo-abnormal. 2. Chromosome 2 contains no triplo-lethal loci, few or no haplo-lethal loci, at least 17 Minute loci, and at least four other haplo-abnormal loci. 3. Chromosome 3 contains one triplo-lethal locus that is also haplo-lethal, few or no other haplo-lethal loci, at least 16 Minute loci, and at least six other haplo-abnormal loci. 4. Chromosome 4 contains no triplo-lethal loci, no haplo-lethal loci, one Minute locus, and no other haplo-abnormal loci.-Thus, the Drosophila genome contains 57 loci, aneuploidy for which leads to a recognizable effect on the organism: one of these is triplo-lethal and haplo-lethal, one is triplo-abnormal and haplo-abnormal, one is hyperploid-sensitive, ten are haplo-abnormal, 41 are Minutes, and three are either haplo-lethals or Minutes. Because of the paucity of aneuploid-lethal loci, it may be concluded that the deleterious effects of aneuploidy are mostly the consequence of the additive effects of genes that are slightly sensitive to abnormal dosage. Moreover, except for the single triplo-lethal locus, the effects of hyperploidy are much less pronounced than those of the corresponding hypoploidy.

Pulsatile patterns of gonadotropin release in subjects with and without ovarian function.

Abstract: Minute-to-minute fluctuations of serum LH and FSH concentrations resembling a pulsatile pattern were demonstrated in both pre- and post-menopausal women A pulsatile pattern of LH but not FSH was seen during the menstrual cycle These appear to follow a varying frequency and magnitude according to the different phases of the cycle; a periodicity of 1–2 hr was seen during the early follicular phase, early luteal phase and midcycle surge while a periodicity of 4 hr was seen in the mid- and late-luteal phase During the late follicular phase only “minor oscillations” were noted A greater net increase of circulating LH was found in pulses during the midcycle surge which was more than double that seen during other phases of the cycle In contrast, post-menopausal subjects had pulses of both gonadotropins These were usually coincident, however, a minor asynchrony between LH and FSH patterns was discernible The frequency of pulses in the postmenopausal subjects was the same as in the follicular phase and midc

Precordial S-T segment elevation mapping: An atraumatic method for assessing alterations in the extent of myocardial ischemic injury

Abstract: A noninvasive technique for evaluating the extent of myocardial ischemic injury after experimental coronary artery occlusion was devised and applied to study alterations in the extent of injury produced by hemodynamic and pharmacologic interventions. The technique was then extended to the assessment of myocardial ischemic injury in patients with acute myocardial infarction. In 7 closed chest dogs, electrocardiograms were recorded from 15 sites on the chest wall before and after intermittent occlusions of the left anterior descending coronary artery. There was no S-T segment elevation before the occlusion; 15 minutes after occlusion the sum of S-T segment elevations (ΣS-T) averaged 15.0 ± 3.0 mm (SEM, 1 mm deflection = 0.1 mv), and an average of 4.2 ± 0.6 sites exhibited elevations exceeding 0.1 mv (NS-T). Occlusions occurring during administration of isoproterenol (0.25 μg/kg per min) increased ΣS-T to 51.0 ± 9.0 mm and NS-T to 10.6 ± 0.9, whereas occlusions occurring after administration of propranolol (1 mg/kg) decreased ΣS-T to 3.0 ± 1.5 mm and NS-T to 0.2 ± 0.2. In 8 dogs the extent of ischemic injury, manifested by S-T segment changes, was decreased by propranolol and norepinephrine and increased by hemorrhagic hypotension and isoproterenol, applied up to 6 hours after occlusion. Reproducible S-T segment maps, using 35 surface electrodes, were obtained in 19 patients with acute myocardial infarction. In 15 patients studied serially, ΣS-T decreased from 54.25 ± 7.00 to 38.50 ± 6.30 mm and NS-T from 18.7 ± 2.5 to 12.3 ± 2.8, respectively, during a 24 hour period. However, in 3 patients in whom ventricular fibrillation, arterial hypotension and further ischemic pain occurred, ΣS-T and NS-T increased whereas in another patient propranolol decreased ΣS-T and NS-T. Thus, precordial mapping, both in dogs and patients, shows changes parallel to those measured by the epicardial technique and should provide a useful clinical tool for determining acute changes in the extent of ischemic injury.

Melting on Fault Planes During Large Earthquakes

Abstract: Summary For simple models of the movement on a fault during an earthquake the temperature on the fault plane is shown to reach the melting temperature for short periods if the slip is sufficiently large. The displacement required to produce melting depends on the magnitude of the regional stress and also on the friction stress. If both stresses are one kilobar melting can occur for displacements as small as one millimetre. If, however, both stresses are ten bars melting is impossible for any observed displacement. It is estimated that the width of the melted zone could be between 2 mm and lcm. Melting on fault planes during earthquakes is not in disagreement with geological and geophysical observations, and suggests a new explanation for some mylonites. Melting may be important because the molten film rock formed on the fault may act as a lubricant and in the case of large earthquakes allow the release of almost all the elastic strain in the region of the shock. This would provide an important constraint in estimating the state of stress along a fault.

Aromatization of Androstenedione by the Anterior Hypothalamus of Adult Male and Female Rats

Abstract: Homogenates of fresh tissue from adult male and female rats were incubated with appropriate co-factors and androstenedione-3H for one hour at 37° C. Extraction and identification of reaction products demonstrated the aromatization of androstenedione to estrone by anterior hypothalamus but not by posterior hypothalamus, anterior pituitary gland or frontal cortex. This finding confirms and expands the previous preliminary report of aromatization by human fetal hypothalamus to include adults of both sexes in a second species, the rat. Further localization of this reaction is consistent with concepts derived from experimental evidence which indicate central aromatization of androgens to be involved in sexual differentiation of the brain, initiation and maintenance of sexual behavior, control of gonadotropin secretion and “peripheral conversion” of circulating androgens to estrogens. (Endocrinology 90: 295, 1972)

Dynamics of spermiogenesis in Drosophila melanogaster. I. Individualization process.

Abstract: A morphogenetic process that transforms spermatids from a syncytial state to a state in which each spermatid is invested in its own membrane, is initiated at the head region of the spermatid bundle and traverses through the entire length of the bundle in the testis of Drosophila melanogaster. This process not only eliminates the syncytial bridges between spermatids but also removes unneeded organelles and the excess parts of the nuclear membrane, nucleoplasm and cytoplasm. It also brings about structural modifications to flagellar elements. The propagation of this process is seen as the caudal movement of a fusiform swelling of the spermatid bundle, 100 μ or more in length. Spermatids are individualized in the basal half of the swelling, whereas they remain syncytial in the apical half. The swelling increases its volume as it accumulates cytoplasmic debris while traversing the sperm bundle, from about 15 μ in maximum diameter in the basal testicular region to as large as 30 μ at the apical end where it becomes a bag of wastes. A variation of the process in a mutant stock which is known to inactivate up to half of the products of meiosis is briefly described. The morphological change of interspermatid bridges prior to the individualization is also reported.

Effect of growth conditions on the formation of the relaxation complex of supercoiled ColE1 deoxyribonucleic acid and protein in Escherichia coli.

Abstract: Colicinogenic factor E1 (ColE1) is present in Escherichia coli strain JC411 (ColE1) cells to the extent of about 24 copies per cell. This number does not appear to vary in situations which give rise to twofold differences in the amount of chromosomal deoxyribonucleic acid (DNA) present per cell. If cells are grown in the absence of glucose, approximately 80% of the ColE1 molecules can be isolated as strand-specific DNA-protein relaxation complexes. When glucose is present in the medium, only about 30% of the plasmid molecules can be isolated as relaxation complexes. Medium shift experiments in which glucose was removed from the medium indicate that within 15 min after the shift the majority (>60%) of the plasmid can be isolated as relaxation complex. This rapid shift to the complexed state is accompanied by a two- to threefold increase in the rate of plasmid replication. The burst of replication and the shift to the complexed state are both inhibited by the presence of chloramphenicol. Inhibition of protein synthesis in log cultures by the addition of chloramphenicol or amino acid starvation allows ColE1 DNA to continue replicating long after chromosomal replication has ceased. Under these conditions, noncomplexed plasmid DNA accumulates while the amount of DNA that can be isolated in the complexed state remains constant at the level that existed prior to treatment. In the presence of chloramphenicol, there appears to be a random dissociation and association of ColE1 DNA and “relaxation protein” during or between rounds of replication.

Effect of Glucose-Insulin-Potassium Infusion on Myocardial Infarction following Experimental Coronary Artery Occlusion

Abstract: The effects of glucose-insulin-potassium (GIK) infusion and glucose (G) infusion started 30 min after experimental coronary occlusion and the combination of GIK and propranolol (P) started 3 hours after coronary occlusion on the development of myocardial infarction were studied in 37 dogs. Fifteen minutes after the coronary occlusion, epicardial electrocardiograms were recorded at 10-15 sites; 24 hours later transmural specimens were obtained from the same sites for determination of myocardial creatine phosphokinase (CPK) activity and the evaluation of morphologic changes. In the control group (normal saline infusion) the relationship between S-T-segment elevation (mv) 15 min after occlusion and CPK activity (IU/mg of protein) 24 hours later was: log CPK = –0.064 S-T + 1.24; r = 0.81. In the GIK group, the infusion was begun 15 min following epicardial mapping, and sites with the same S-T-segment elevations showed less CPK depression than did the control group: log CPK = –0.022 S-T + 1.25. The G group als...

Alkaline phosphatase activity in subtropical Central North Pacific waters using a sensitive fluorometric method

Abstract: This paper describes a fluorometric method for assaying low levels of the enzyme alkaline phosphatase in seawater. The assay is based on the hydrolysis of the monophosphate ester bond of 3-0-methylfluorescein phosphate. This enzyme is synthesized by many microorganisms when phosphate becomes limiting. Alkaline phosphatase activity was detected in phytoplankton from the nutrient-impoverished surface waters of the subtropical Central North Pacific Ocean. The presence of naturally occurring phosphatase suggests that phosphorus may be limiting to phytoplankton growth in these waters. The phytoplankton in water samples lacking enzyme activity at the time of collection produced phosphatase within 1 to 2 days of incubation at in situ temperatures.

The Effects of Solid Earth Deformation on Global Ocean Tides

Abstract: Summary Laplace's Tidal Equations (LTE) are modified to allow for the yielding of the solid Earth to tide generating forces and to the weight of the oceanic tidal column as well as for oceanic gravitational self-attraction A realistic cotidal-corange chart for the global M2 tide is used to show that the first effect is the order of the astronomical potential itself while the second and third are roughly one order of magnitude smaller However, the later potential perturbations produce order one effects in the computed tide because they are much richer in high spherical harmonics than is the astronomical potential The existence of an appreciable solid Earth tide significantly modifies the usual expressions for stored tidal energy, for tidal energy flux and for the rate of working on the oceans by tide generating bodies An unexpectedly high value of Q(∼ 34) is found for the global M2 tide

Inhibitory and stimulatory effects of concanavalin A on the response of mouse spleen cell suspensions to antigen. I. Characterization of the inhibitory cell activity.

Abstract: The presence of concanavalin A (Con A) inhibits the immune response of mouse spleen cell suspensions to erythrocyte antigens, stimulates the incorporation of tritiated thymidine, and increases cell recovery. Con A also restores the depressed response of cell preparations treated to remove thymus-derived cells. The dose-response curve for all four effects shows peak activity at 2 µg/ml. The depressed in vitro response of spleen cell suspensions from adult thymectomized, irradiated, bone marrow-restored mice is also restored by Con A. Here the dose-response curve is quite different with activity over a much wider range of concentration. The restoration of thymus-derived cell-depleted cultures by Con A is inhibited by the addition of untreated, unirradiated, mouse spleen cell suspensions, but is not inhibited by untreated, irradiated cells. Small numbers of spleen cells that have been preincubated with Con A and washed will inhibit the response of fresh, untreated cells to antigen. If the mouse spleen cell suspensions are incubated for 24 hr before the addition of Con A, the response to antigen is no longer inhibited but is stimulated instead. The data are compatible with the hypothesis that there are at least two cell targets for the action of Con A. One cell, that mediates the inhibitor effect, is a short-lived, radiosensitive, thymus-derived cell. The other cell, that mediates the stimulating effect, cannot be identified from the data presented here but may also be of thymus origin on the basis of studies by other investigators.

Comparison of Ultrasound and Cineangiographic Measurements of the Mean Rate of Circumferential Fiber Shortening in Man

Abstract: It has been shown that cineangiographic measurement of the mean rate of circumferential fiber shortening (mean VCF) at the minor left ventricular equator is a reliable method for evaluating the mechanics of cardiac performance. Since fiber shortening can be derived from the echocardiogram, we sought to validate the measurement of mean VCF by this noninvasive technic in patients studied by both methods. In 15 patients considered to have normal left ventricular function, the average mean VCF determined by ultrasound was 1.29 ± 0.23 circumferences/sec, while in the 13 patients with reduced left ventricular performance this value was 0.75 ± 0.16 circumferences/sec ( P < 0.001). Values of mean VCF by the two technics were similar and separated normal from abnormal ventricular function in 27 of 28 patients. The average mean velocity of posterior wall motion was 4.7 ± 1.1 cm/sec in normal patients and 3.9 ± 1.3 cm/sec in abnormals, but posterior wall velocities did not correlate well with either ultrasound or cineangiographic determinations of mean VCF. Ejection fraction calculated from ultrasound measurements correlated significantly with the ejection fraction calculated by cineangiography (r = 0.83, P < 0.0001). The ejection fraction and mean V CF , as determined by ultrasound in the 28 patients, correlated well (r = 0.92, P < 0.0001), but there were six discordant points. From these studies we conclude that the ultrasound determination of mean VCF is a valid method for distinguishing normal from abnormal myocardial performance of the left ventricle. These data also support the use of ultrasound in determining ejection fraction. Estimation of posterior wall velocity, although perhaps useful in the serial study of the same patient, seems limited in its ability to assess cardiac performance accurately.

The Uptake of Urea by Natural Populations of Marine PHYTOPLANKTON1

Abstract: Nitrogen-15 isotopes were used to study the uptake of nitrate, ammonium, and urea by natural phytoplankton populations in 36 samples collected at nine stations off the coast of southern California. The percentage of the total phytoplankton nitrogen productivity accounted for by urea varied from 60% and for the entire study averaged 28%. The percentage of total available nitrogenous nutrient (ambient nitrate, ammonium, and urea plus the 15N additions) utilized per day varied among the stations from a minimum of 5% at station 4 (12 km off San Diego) to a maximum of 46% at station 19 (off White Point). The average C:N uptake ratio was 12.4.

Principles and methods of low-frequency electric and magnetic measurements using an rf-biased point-contact superconducting device

Abstract: A comprehensive study has been made of some low-frequency electric and magnetic measurements which can be made using an rf-biased point-contact superconducting device of the symmetric two-hole type introduced by Zimmerman. Section 1 begins with a qualitative description of the phenomena which are observed and utilized in making the measurements. In Section 2 a semiquantitative and semiempirical analysis is made of the weakly superconducting system as it interacts with the rf field. Reasonable agreement between the analysis and experiment is obtained, thereby establishing a basis for optimization of conditions for measurement. Empirical data are also given as needed on coupling-coil characteristics. In Section 3 noise in the measuring system is discussed and the characteristics of the flux-locked loop used in the measurements introduced. It is shown that the total observed noise may be divided into at least three parts: one intrinsic to the sensor, one which reflects voltage noise in the amplifier, and one coupled into the instrument by the measuring circuit. The noise power spectra of the first two are shown to be comparable in an actual system. Below 100 Hz the spectrum, relative to the square of the flux quantum, is white and estimated by 10−8 Hz−1. In Section 4 the characteristics are discussed of a dc voltmeter using a flux-locked loop and having a relatively high input impedance and good noise figure. An experimental study of noise is presented. A particular case with subpicovolt sensitivity limited by Johnson noise is discussed. In Section 5 low-frequency ac measurements of resistance, self-inductance, and mutual inductance are discussed using a novel bridge circuit and the superconducting sensor in a flux-locked loop as null detector. The noise characteristics are described and studied experimentally. Extreme sensitivity is achieved, both in resistance and inductance. A 1 µω resistor may be measured with a precision of 1 part in 105 with subpicowatt power dissipation. Measurements of the mutual inductance due to a 1.6-mg crystal of CMN are described in which the crystal temperature was reduced to the millidegree region. In Section 6 measurements of static magnetization are discussed and the ideas applied to measurement of temperature using milligram quantities of CMN. Measurements using a pair of thermometers, one inside and the other outside the mixing chamber of a dilution refrigerator, are presented. In Section 7 the concept of a device-noise temperature is introduced and shown to be in the microdegree region. A very simple Johnson noise thermometer is then described. Measurements with this thermometer in the mixing chamber of a dilution refrigerator were carried out to 12 mK, the effective device temperature being measured to be +0.8±1.3mK. A qualitative experimental estimate places the actual device temperature well below 1 mdeg. In appendices a technical discussion of the flux-locked loop and of noise is given.

Student evaluations of teachers.

Abstract: Rodin and Rodin point out that there are two ways of judging teaching through students—ascertaining how much students have learned and obtaining student evaluations of teacher effectiveness. Some commonly accepted notions regarding student evaluations are challenged in this article, which comments on the results obtained in a number of studies. The authors suggest that “students are less than perfect judges of teaching effectiveness”—at least if teaching effectiveness is measured by how much students learn. This paper, reprinted from Science, helps to set the stage for the remaining articles in this issue.

Variation of pituitary responsiveness to synthetic LRF during different phases of the menstrual cycle.

Abstract: Synthetic. LRF (IV 150 μg dose) elicited a prompt increase in circulating LH during all phases of the cycle studied. The maximal response was found during preovulatory phase and the minimal response was seen during the early follicular phase. A change in LRF responsiveness with greater and more sustained LH release from the early to the late follicular phase was observed. The response during luteal phase was significantly greater than responses in both the early and the late follicular phases. A concomitant but a much smaller response in the rise of serum FSH levels was observed. These data indicate that the sensitivity of pituitary gonadotrophs to LRF is preferentially increased for LH release during the late follicular phase of the cycle and that a maximal pituitary responsiveness to LRF appears to occur at the midcycle.

Serum enzyme determinations in the diagnosis and assessment of myocardial infarction.

Abstract: DIAGNOSTIC ENZYMOLOGY has grown exponentially since elevated serum amylase was first associated with pancreatitis in 19081 and Karmen, Wroblewski, LaDue, and their associates demonstrated in 1954 that SGOT* and LDH activity in serum increased following myocardial infarction.2 Following Markert's elucidation of the nature of LDH isoenzymes3 their importance in differential diagnosis was emphasized.4 Serum CPK elevations following myocardial infarction were first reported by Dreyfus and his coworkers5 in 1960, and soon confirmed by Hess and MacDonald.6 Determination of SGOT, LDH, and CPK activity rapidly became cornerstones in the laboratory diagnosis of acute myocardial infarction in man. Activity of many enzymes including aldolase, malic dehydrogenase, isomerase, and ICD may increase following myocardial infarction.7 Serum GGT, a lysosomal enzyme, exhibits increased activity late, reaching a peak within 8 days and returning to normal approximately 1 month following the initial insult.8 SPK contrary to CPK is not elevated following intramuscular injections,9 while serum GAPDH elevation may precede increases in conventional enzymes and aid detection of extension of myocardial necrosis.10 However, since SGOT, LDH, and CPK determinations have become established criteria in the laboratory diagnosis of acute myocardial

Nonlinear Frequency Shift of an Electron Plasma Wave

Abstract: The shift in the complex frequency of a large-amplitude electron plasma wave is formulated in terms of a new subtraction procedure which reproduces the damping coefficient of Mazitov and of O'Neil directly from Poisson's equation. A time-dependent frequency shift is obtained which produces a phase shift that should be amenable to experimental observation. The results are interpretated in terms of simultaneous conservation of momentum and energy in the wave frame.

Petroleum Hydrocarbons: Uptake and Discharge by the Marine Mussel Mytilus edulis

Abstract: The common marine mussel Mytilus edulis has been observed to rapidly take up mineral oil, [ 14 C] heptadecane, 1,2,3,4-tetrahydronaphthalene, [ 14 C] toluene, [ 14 C] naphthalene, and [ 3 C] 3,4-benzopyrene from seawater solution. This species of mussel did not metabolize any of these compounds, and transfer of the mussel to fresh seawater, after exposure to the hydrocarbon in solution, resulted in the discharge of most of the hydrocarbon, although significant amounts remained (between 1 and 400 micrograms per mussel). The nontoxic paraffinic hydrocarbons mineral oil and heptadecane were taken up (10 milligrams per mussel) to a much greater extent than the aromatic hydrocarbons (2 to 20 micro-grams per mussel).