On refractory oxide crystals for continuous-wave tunable lasers

It is demonstrated that trapped-hole centers can be a detriment to continuous-wave tunable-laser action in irradiated oxide crystals operating in or near the visible region. Thermochemically reduced oxide crystals appear to be more promising.

Theoretical treatment of microtubules disappearing in solution

The origin of the two-phase (cap, no cap) macroscopic kinetic model of the end of a microtubule is reviewed. The model is then applied to a new theoretical problem, namely, the Mitchison-Kirschner [Mitchison, T. & Kirschner, M. W. (1984) Nature (London) 312, 237-242] experiment in which aggregated microtubules in solution spontaneously decrease in number (shorten to disappearance) while the surviving microtubules increase in length. The model fits the experiments without difficulty.

Characterization of a human interleukin 1 inhibitor

Human urine contains a specific inhibitor of interleukin 1 (IL 1) that is found in increased amounts during fever. This inhibitor was purified by using a sequence of ammonium sulfate fractionation, DEAE cellulose ion-exchange chromatography, molecular sieve chromatography on Sephacryl S-200, affinity chromatography on concanavalin A (Con A) Sepharose, and polyacrylamide gel electrophoresis. Two peaks of IL 1 inhibitory material were eluted from the polyacrylamide gels. One peak contained three proteins of 29, 32, and 67 kd, respectively, which could be visualized by silver staining. The second peak contained only a small amount of the 67 kd protein. A partially purified inhibitor fraction was found to cross-react with antisera directed against two low m.w. urine trypsin inhibitors that are cleavage products of the serum inter-alpha-trypsin inhibitor. Although these findings suggest that the urine IL 1 inhibitor may be related to the inter-alpha-trypsin inhibitor, a more exact identification will require either a homogeneous inhibitor preparation or a monospecific antiserum.

Characterization of a human interleukin 1 inhibitor

Human urine contains a specific inhibitor of interleukin 1 (IL 1) that is found in increased amounts during fever. This inhibitor was purified by using a sequence of ammonium sulfate fractionation, DEAE cellulose ion-exchange chromatography, molecular sieve chromatography on Sephacryl S-200, affinity chromatography on concanavalin A (Con A) Sepharose, and polyacrylamide gel electrophoresis. Two peaks of IL 1 inhibitory material were eluted from the polyacrylamide gels. One peak contained three proteins of 29, 32, and 67 kd, respectively, which could be visualized by silver staining. The second peak contained only a small amount of the 67 kd protein. A partially purified inhibitor fraction was found to cross-react with antisera directed against two low m.w. urine trypsin inhibitors that are cleavage products of the serum inter-alpha-trypsin inhibitor. Although these findings suggest that the urine IL 1 inhibitor may be related to the inter-alpha-trypsin inhibitor, a more exact identification will require either a homogeneous inhibitor preparation or a monospecific antiserum.

Stochastic free energy transduction

Theoretical free-energy coupling systems in which the free energy coupling intermediate (e.g., the proton) occurs only in small numbers of molecules per coupling unit are shown to exhibit a number of peculiar properties: (i) the reactions involving the intermediates do not follow conventional kinetic (or nonequilibrium thermodynamic) rate laws in terms of the average concentration or chemical potential of the intermediate, (ii) the variation of the output reaction rate with the average intermediate concentration (or apparent chemical potential) is not unequivocal but depends on whether the input reaction or the leak is varied to alter that concentration, and (iii) when the apparent free energy contained in the average concentration of the intermediate is compared with the average free energy recovered in the output reaction, apparent violations of the second law of thermodynamics can occur. These phenomena are reminiscent of experimental observations in proton-linked free-energy transducing systems that suggest a more direct coupling between electron transfer chains and H+-ATPases than only through a bulk proton gradient, delta muH. Consequently, the chemiosmotic coupling theory can account for those observations if it limits the number of free energy coupling protons per chemiosmotic coupling unit to small values.

Iron-montmorillonite: a spectral analog of Martian soil

Light absorption and reflectance by smectite clays containing various adsorbed ions were measured in the UV, VIS, and NIR ranges and compared to Martian dust and surface soil spectra. Structural iron in the octahedral sheet of smectites is responsible for a characteristic absorption feature in the UV at 240-260 nm, resulting from an O2 --> Fe3+ charge transfer that is similar to one observed in the Martian spectrum. Adsorbed iron affects, via crystal field absorptions, the reflectance of montmorillonite in the VIS and NIR (to 1.3 micrometers), causing stronger absorption and higher opacity in the wavelength range 0.4-0.6 micrometer, without developing any specific pronounced absorption feature. In both general appearance and presence of, or lack of, spectral features, the iron-montmorillonite reflectance spectra in the VIS and NIR are similar to the Martian spectra. At present, however, spectral similarity cannot be used as the sole criterion for constraining Martian mineralogy since several other minerals, other than Fe-smectites, show sufficient similitude to the Martian spectra; other properties have to be explored and combined to obtain a definitive identification.

Phase changes at the end of a microtubule with a GTP cap

Examination of Monte Carlo kinetic simulations, based on a realistic set of microscopic rate constants that apply to the end of a microtubule with a GTP cap, suggests that the end of a microtubule alternates between two quasimacroscopic phases. In one phase, the microtubule end has a GTP cap that fluctuates in size; in the other phase, the GTP cap has been lost. These repeated phase changes take place at any given tubulin concentration in a wide range of concentrations. While in the first phase, the microtubule grows slowly; while in the second phase, it shortens rapidly and may disappear completely. These results are closely related to the recent experimental work of Mitchison and Kirschner [Mitchison, T. & Kirschner, M.W. (1984) Nature (London), in press].

Interference of GTP hydrolysis in the mechanism of microtubule assembly: an experimental study

This paper reports an experimental study of the interference of GTP hydrolysis in the mechanism of microtubule assembly, following the model and theory previously published [Hill, T. L. & Carlier, M.-F. (1983) Proc. Natl. Acad. Sci. USA 80, 7234-7238]. Results from dilution experiments show that microtubules depolymerize faster below the critical concentration than expected with a reversible polymerization model. The experimental plot of flux versus tubulin concentration exhibits a slope discontinuity at the critical concentration, in agreement with the theory. Theoretical points calculated by the Monte Carlo method can be fitted qualitatively to the data. A consequence of this peculiar dynamic behavior of microtubules is that the ratio of tubulin dissociation and association rate constants measured, respectively, below and above the critical concentration does not yield the true value of the critical concentration. It is emphasized that the presence of GTP at microtubule ends is necessary to maintain the stability of the polymer.

Use of Monte Carlo calculations in the study of microtubule subunit kinetics

GTP-tubulin forms a cap on microtubule ends during aggregation. The bulk of the microtubule is GDP-tubulin. This complicates the usual simple kinetic theory of subunit exchange at microtubule ends to such an extent that Monte Carlo calculations are needed to handle the complications, except in special cases. The Monte Carlo method is introduced here, for this problem, and illustrated with steady-state and transient examples. Monte Carlo transients are needed to simulate dilution experiments. Preliminary results (with M. F. Carlier) have been obtained applying these theoretical procedures to experimental data.

Acute infectious torticollis

Acute torticollis has occurred in epidemics in eastern and northern China since 1975, but has not yet been reported in other countries. A general account of this disease, including its terminology, epidemiology, clinical features, laboratory findings, diagnosis, differential diagnosis, and treatment, is presented. The etiology, though highly suggestive of a virus infection, remains to be determined.

Immunosuppression in plasmacytoma: induction of suppressor cells

Immunosuppression in BALB/c mice with plasmacytomas (PC) is, at least in part, due to increased suppressor activity of splenic adherent cells. A PC subcellular fraction rich in intracisternal A particles, previously shown to have an immunosuppressive effect in normal BALB/c mice, is now shown to exert this effect through the development of splenic suppressor cells. The splenic suppressor cells induced with this subcellular fraction were found to be radioresistant adherent macrophages that suppressed the immune response of normal splenic cells to sheep erythrocytes through a diffusible factor, but did not influence their polyclonal IgM secretion ater LPS stimulation in vitro. These characteristics are identical to those of the naturally occurring suppressor macrophages in mice with PC. Whether the induction of suppressor cells is due to the intracisternal A particles themselves or a factor co-purified with them, remains to be established.

The mode of action of splenic suppressor cells in murine plasmacytoma

Polyclonal IgM secretion after LPS stimulation and antigen-dependent antibody production by splenic cells of BALB/c mice with plasmacytoma were found to be markedly reduced. The former occurred without mediation of suppressor cells, probably as the result of a quantitative reduction of mitogen-responsive B lymphocytes. On the other hand, the reduction in the generation of antibodies to sheep erythrocytes in vitro, as determined by the number of PFC, was found to be dependent on the activity of suppressor cells which had the functional characteristics of macrophages. The targets of these suppressor cells were found to be normal macrophages, B and T lymphocytes which were all independently suppressed. A diffusible factor appeared to be responsible for the suppressive effect of the suppressor macrophages interfering mainly with those early stages of the immune response involving antigen-triggered B cell activation.

The hemodynamic tracking system: a method of data management and guide for cardiovascular therapy

In the operating room or intensive care unit, multiple measurements of circulatory function are almost mandatory in patients with significant cardiovascular disease. Use in these areas requires that the information must be easily organized, rapidly obtained, and inexpensive. A hemodynamic tracking system that meets these criteria is described. This system incorporates a hand-held programmable calculator (cost = $210 to $300) to derive variables computed from standard cardiovascular measurements. The time required to obtain a set of measurements (including thermodilution cardiac output determinations in duplicate), key the numbers into the calculator, and obtain the derived indices is 4 minutes. Two patients, who had acute mitral insufficiency and whose clinical management differed substantially are presented to illustrate the use of data obtained from the hemodynamic tracking system.

Cross-bridge model of muscle contraction. Quantitative analysis

We recently presented, in a qualitative manner, a cross-bridge model of muscle contraction which was based on a biochemical kinetic cycle for the actomyosin ATPase activity. This cross-bridge model consisted of two cross-bridge states detached from actin and two cross-bridge states attached to actin. In the present paper, we attempt to fit this model quantitatively to both biochemical and physiological data. We find that the resulting complete cross-bridge model is able to account reasonably well for both the isometric transient data observed when a muscle is subjected to a sudden change in length and for the relationship between the velocity of muscle contraction in vivo and the actomyosin ATPase activity in vitro. This model also illustrates the interrelationship between biochemical and physiological data necessary for the development of a complete cross-bridge model of muscle contraction.

Differences in vitro between fibroblast-like cells from cornea, heart, and skin of embryonic chicks

Populations of fibroblast-like cells of corneal stroma, heart ventricle, and back skin of day-14 embryonic chicks were grown in vitro as primary and secondary cultures and were found to differ from one another by several criteria. Such cells were obtained from tissues either directly (cornea) by dissection or indirectly (heart and skin) by the rapid adhesion of the fibroblast-like cells to glass and plastic substrata. Individual fibroblast-like cells of cornea and heart were distinguishable from one another during their first 24–48 h in vitro. The morphologies of the individual cels of these 2 populations became indistinguishable during logarithmic growth, although each could be distinguished from individual fibroblast-like cells of skin. When the cultures reached saturation, corneal cells formed a monolayer of randomly oriented polygonal cells; skin cells formed a monolayer of long, narrow, ragged cells in parallel arrays with occasional double-layering; and heart cells formed multilayers of criss-crossed cells whose broad, smooth outlines were in parallel array in each layer. Saturation densities of the 3 fibroblast-like populations were different: heart greater than skin greater than cornea. By 3 methods of assay the cells were found to be differentially sensitive to treatment with trypsin and EDTA, and to EDTA alone, heart cells consistently being the least sensitive. Taken together, these data suggest that fibroblast-like cell populations isolated from different tissues of a single organism are different from one another and thus may behave differently from one another during in vitro studies.

Peripheral blood B-lymphocyte abnormalities associated with hyperthyroidism of Graves' disease

Proportions of peripheral blood thymus-derived T lymphocytes (T cells) and bone-marrow-derived B-lymphocytes (B cells) were studied in twelve hyperthyroid patients and ninety-nine non-hyperthyroid control subjects including thirty-nine healthy individuals and sixty patients with various disorders. All hyperthyroid patients had Graves' disease and eight were untreated. The sheep erythrocyte (E)-rosetting technique was employed for enumeration of T cells and the immunofluorescent technique was used for identification of lymphocytes with surface immunoglobulins (SIg), a marker for B cells. The results showed that hyperthyroid patients had higher percentages of lymphocytes stainable for SIg, whereas their T-cell proportions were the same as our control values. In addition, approximately half or more of the fluorescein stainable lymphocytes reacted with each of the five antisera against individual heavy chain determinants, including the epsilon chain, indicating the presence of more than three Ig determinants on the same cell. The fluorescein-stainable cells did not form E rosettes. Blocking of the Fc receptor on lymphocytes by incubating the patients' cells with heat-aggregated human IgG or heated goat anti-bovine serum albumin (anti-BSA) failed to abolish the subsequent fluorescent staining of the cells. Incubation of patients' lymphocytes with non-fluorescent anti-epsilon inhibited the subsequent staining of cells with fluoresceinated anti-epsilon but not staining with fluoresceinated anti-mu or anti-gamma. Thus, the study revealed B-cell abnormalities associated with hyperthyroidism, manifested by the simultaneous presence of multiple Ig classes, including IgE, on a single B cell. Results of studies of incubation of the patients' plasmas with lymphocytes from health individuals and studies of SIg by overnight culture of the patients' lymphocytes with or without prior trypsinization suggested that the SIg was generated endogenously by the cell on which it resided.