Regulation of antibody responses: the role of complement and adhesion molecules

To analyze the importance of cell surface-associated molecules in modulating the immune response by facilitating T/B cell interaction, we used the T cell-dependent antigen, bacteriophage phi X174. Taking advantage of "experiments of nature", we studied specific antibody synthesis in patients with deficiencies of complement components or of the adhesion molecule CD11/CD18 (leukocyte adhesion defect, LAD) and guinea pigs and dogs with early complement component deficiency. Following intravenous injection of bacteriophage phi X174 into normal subjects or animals, a primary response consisting of IgM, a secondary response consisting of IgM and IgG, and a tertiary, predominantly IgG response can be distinguished. Patients and guinea pigs deficient of early complement component and LAD patients responded to repeated phage immunization with depressed antibody titers, lack of or inadequate amplification, and failure to switch from IgM to IgG, suggesting a defect in generating antigen-specific memory cells. Several mechanisms have to be considered: (i) The complement portion of the antigen-antibody complement complex facilitates the accumulation and trapping of antigen in lymphoid organs, thus improving the response to Ag at low concentrations. (ii) Immune complexes preferentially bind to antigen-specific B cells, cells expressing Fc receptors, or CR2 and CR3, the receptors for C3bi. (iii) The weak binding established between the MHC-II/Ag complex and the TCR complex is strengthened through the binding of several adhesion molecule pairs. (iv) Receptor-ligand binding initiates activation signals. The concept of binding/signaling via interacting molecules is further supported by the observation that mAb 60.3, recognizing the beta chain of CD11/CD18, blocks in vitro synthesis of antibody to bacteriophage by primed PBMC.

Environmental effects on the folding of functional peptide segments from steroid hormone receptors

Recent improvements in circular dichroism (CD) instrumentation now allow investigators to obtain highly reliable and reproducible CD spectra in the far-UV range to near 180 nm. These advances, coupled with new computer software for spectral interpretation, allow accurate calculations of secondary structural content in proteins and polypeptides. CD is particularly reliable for the calculation of alpha-helical content. We have utilized these features to determine the propensity of alpha-helix formation in highly purified synthetic peptides corresponding to segments from proteins. We obtain CD spectra of the peptides in 90% 2,2,2-trifluoroethanol (90% TFE; an alpha-helix promoting solvent) and in 2 mM sodium dodecyl sulfate (2 mM SDS; a beta-sheet promoting solvent) to assess helix stability in these different chemical environments. Using this methodology, we demonstrate that a peptide corresponding to a biologically active segment of the human estrogen receptor forms a stable alpha-helix in both environments. In contrast, peptide segments of equal length from other steroid receptors are alpha-helical in TFE but not in 2 mM SDS. These results show that the conformation of a peptide is a function of both its amino acid sequence and the local chemical environment.

Calmodulin and the contractile vacuole complex in mitotic cells of Dictyostelium discoideum

In amoebae of the eukaryotic microorganism Dictyostelium discoideum, calmodulin is greatly enriched on membranes of the contractile vacuole complex, an osmoregulatory organelle. Antibodies specific for Dictyostelium calmodulin were used in the present study to immunolocalize the contractile vacuole complex in relation to the Golgi complex (detected with wheat germ agglutinin) and the microtubule organizing center (MTOC, detected with anti-tubulin antibodies). Cells were examined throughout the cell cycle. Double-staining experiments indicated that the contractile vacuole complex extended to the MTOC in interphase cells, usually, but not always, overlapping the Golgi complex. In metaphase and anaphase cells, the Golgi staining became diffuse, suggesting dispersal of Golgi membranes. In the same mitotic cells, anti-calmodulin antibodies labeled numerous small cortical vacuoles, indicating that the contractile vacuole complex had also become dispersed. When living mitotic cells were examined, the small cortical vacuoles were seen to be active, implying that all parts of the Dictyostelium contractile vacuole complex possess the ability to accumulate fluid and fuse with the plasma membrane. In contrast to observations reported for other types of cells, anti-calmodulin antibodies did not label the mitotic spindle in Dictyostelium. Despite this difference in localization, it is possible that vacuole-associated calmodulin in Dictyostelium cells and spindle-associated calmodulin in larger eukaryotic cells might perform a similar function, namely, regulating calcium levels.

Organization of cytokeratin intermediate filaments in basal cells of growing rat trachea

The basal cell in airway epithelium plays a major role in attachment of ciliated and nonciliated columnar cells to the basal lamina. As the airway grows in diameter and the columnar epithelium in height, the number of basal cells and the amount of tonofilaments (cytokeratin filaments) and anchoring junctions increase. In this way they maintain a constant attachment strength between the increased volume of the epithelium and the basal lamina. The purpose of this study was to determine which cytokeratins (CKs) are expressed in growing basal cells of the rat and demonstrate where they are localized in the cytoskeleton. Sprague Dawley rats 10, 30 and 90 days of age were used in this study. For light microscopy, tracheal samples were fixed in 95% alcohol or 4% formalin for 2 hr and then embedded in paraffin. For electron microscopy, the tracheal samples were placed in 20 mM EDTA in HBSS media minus Ca++ and Mg++ at pH 7.4 for 60 min to permeabilize the cells and expose the intracellular structures. Antibodies to cytokeratins 7, 8, 10, 13 and 18 did not react to basal cells at any age studied. Antibodies to CKs 5 + 8, 14, 16 + 13, and 19 gave a positive reaction with basal cells at each age studied. Immunogold particles representing antibodies to CK 14 were heavily distributed over intermediate filaments making up the cytoskeleton. Both CK 16 + 13 and 19 were also over intermediate filaments but at a much lower density.(ABSTRACT TRUNCATED AT 250 WORDS)

An adaptive current tomography using voltage sources

This paper describes the development of an adaptive electric current tomography system which contains a novel front-end analog architecture. Programmable voltage sources have been used to deliver currents into the study object and to avoid the difficulties of obtaining high quality current sources. Through inverting an admittance matrix, the system is capable of achieving a desired current drive pattern by applying a computed voltage pattern. The tomograph, operating at 9.6 kHz, comprises 32 driving electrodes and 32 voltage measurement electrodes. The study of system noise performance shows high SNR in the data acquisition which is enhanced by a digital demodulation scheme. In vitro reconstruction images have been obtained with the data collected by the tomograph.

Intra-amniotic inoculation of pigtailed macaque (Macaca nemestrina) fetuses with SIV and HIV-1

Six pregnant pigtailed macaques (Macaca nemestrina) were inoculated intra-amniotically (i.a.) with SIVMne. All became viremic and seroconverted; three viable offspring were SIV-positive and at autopsy showed disseminated viral infection; one of three abortuses had SIV-infected thymic macrophages. Three of five pregnant macaques inoculated i.v. and/or i.a. with HIV-1LAI became virus-positive, and four seroconverted, suggesting fetal-maternal transmission. One abortus had HIV-1-antigen in lymph nodes and brain; one infant, culture-positive at birth, died at age 11 days of disseminated HIV-1 infection.

Wavefront amplitude distortion and image sidelobe levels. II. In vivo experiments

For part I, see ibid., vol.40, no.6, p.747-753 (1993). In vivo measurements of the rise of the sidelobe level in a single-source image obtained through the female breast as a function of the distortion of the wavefront amplitude are described. The measured sidelobe levels are the average sidelobe floor (ASF) and the peak sidelobe level (PSL). The ASF is shown to be proportional to the variance of the modulus of the wavefront normalized to the square of its mean value, with a proportionality constant close to the value predicted by theory. The PSL similarly increases linearly. The average ratio of PSL to ASF is 5 (7 dB).

Wavefront amplitude distortion and image sidelobe levels. I. Theory and computer simulations

The quality of an imaging system is degraded by propagation anomalies that distort wavefronts propagating through the medium. Adaptive phase-deaberration algorithms compensate for phase errors in the wavefront. The algorithms suffer, however, when the wavefront is also significantly distorted. A theory which shows that the rise of image background level, which is the average sidelobe floor (ASF), in a single point-like source image is proportional to the amplitude distortion of the wavefront and inversely proportional to the effective number of array elements is derived. From the theory, the tolerance to the amplitude distortion, after the phasefront has been corrected by a deaberration algorithm, can be calculated based on the design requirement of the sidelobe floor for a given array. Computer simulations show good agreement with the theory.

Effect of adenosine deaminase on cardiac interstitial adenosine

Adenosine deaminase was infused into isolated perfused guinea pig hearts to determine its effect on myocardial adenosine levels. The enzyme was administered during constant coronary flow perfusion at 6.11 +/- 0.36 ml.min-1.g-1. Venous adenosine was measured in samples of pulmonary artery effluent; epicardial and endocardial adenosine were measured with the porous nylon disk technique. Infusion of adenosine deaminase at 2.4 and 4.8 U/ml produced adenosine deaminase activity of 0.92 +/- 0.09 and 2.33 +/- 0.15 U/ml, respectively, in epicardial fluid and 1.93 +/- 0.28 and 4.84 +/- 0.47 U/ml, respectively, in endocardial fluid. Aortic pressure was unchanged by infusion of adenosine deaminase at both infusion rates. Adenosine deaminase (data from both infusion rates pooled) reduced epicardial adenosine from 0.327 +/- 0.028 to 0.139 +/- 0.022 microM, endocardial adenosine from 4.61 +/- 0.42 to 1.64 +/- 0.20 microM, and venous adenosine from 0.017 +/- 0.02 to 0.003 +/- 0.001 microM. The data indicate that infused adenosine deaminase reaches the epicardial and endocardial interstitial fluid (ISF) compartments. The absence of any effect on coronary pressure suggests that adenosine may not be involved in resting basal coronary tone. The presence of significant residual adenosine despite adenosine deaminase infusion indicates that adenosine production in the unstressed isolated guinea pig heart exceeds the degradative capacity of infused adenosine deaminase. Previous studies in which it was assumed that almost all of the endogenous adenosine is inactivated by the infusion of adenosine deaminase should be reevaluated in light of these observations.

Morphologic changes in basal cells during repair of tracheal epithelium

Basal cells are differentiated with respect to junctional adhesion mechanisms and play a role in attachment of columnar epithelium to the basal lamina. Although much is known about nonciliated and ciliated cell differentiation during the repair process after injury, little is known about the basal cell. We studied the morphology of basal cells and quantitated junctional adhesion structures during repair of tracheal epithelium exposed to toxic cotton smoke. Ten adult ewes were given a smoke injury to a portion of the upper cervical trachea and were killed at 4, 6, 8, 10, and 18 days after injury for morphometric studies. At 4 days, there was a stratified reparative epithelium over the basal lamina, which was two to four cells in depth. The basal cells were identified by their hemidesmosome (HD) attachment to the basal lamina. Basal cells were about 69% larger than controls and flattened rather than columnar. The amount of HD attachment was 192% greater than controls. In contrast, volume density of cytokeratin filaments had decreased about 47%. Basal cells had returned to normal numbers and size and a columnar shape by day 18. The amount of desmosome (D) and HD attachment and volume density of cytokeratins had also reached control levels by day 18. These data indicate that morphology of basal cells changes during the initial stages of reparative regeneration but returns to normal by 18 days. Morphologic changes appear to reflect changes in size of the cell associated with cell division rather than differentiation of recently divided basal cells.

Freezing preservation of the mammalian cardiac explant. VI. Effect of thawing rate on functional recovery

This study investigated the effect of thawing rate on the preservation of frozen isolated rat hearts. The hearts were flushed with a hyperosmotic cardioplegic solution, CP-14/EtOH (1.15 Osm/kg), frozen at a rate of 0.18 degree C/hr for 6 h to -3.2 degrees C. Thereafter, the hearts were thawed at rates ranging from 0.08 to 1.1 degrees C/min for 1 to 14 min until the heart temperature reached -2.1 degrees C, the melting point (MP) of the flush solution; then they were held at -1 degree C for 11 to 24 min so that the total thaw time was 25 min. Post-thaw function was assessed by working reperfusion and expressed as percentage of unstored control function. Cardiac output (CO) and other hemodynamic performance showed biphasic responses to the thaw rate. At 0.08 degree C/min rate, CO recovered to 29.1 +/- 4.1 ml/min (40.8 +/- 5.8% of control). Thawing at 0.13 degree C/min enhanced the recovery of CO to 60.5 +/- 4.9%. Between 0.13 and 0.34 degree C/min, recovery was statistically insignificant. Faster thawing at 0.59 and 1.1 degrees C/min caused progressively less recovery. Overall, 0.13 degree C/min offered the highest recovery. In conclusion, function in slowly frozen heart is intimately affected by the thawing rate; there was an optimal intermediate thawing rate and both too slow and too fast thawing were detrimental.

Association of calmodulin and an unconventional myosin with the contractile vacuole complex of Dictyostelium discoideum

mAbs specific for calmodulin were used to examine the distribution of calmodulin in vegetative Dictyostelium cells. Indirect immunofluorescence indicated that calmodulin was greatly enriched at the periphery of phase lucent vacuoles. The presence of these vacuoles in newly germinated (non-feeding) as well as growing cells, and the response of the vacuoles to changes in the osmotic environment, identified them as contractile vacuoles, osmoregulatory organelles. No evidence was found for an association of calmodulin with endosomes or lysosomes, nor was calmodulin enriched along cytoskeletal filaments. When membranes from Dictyostelium cells were fractionated on equilibrium sucrose density gradients, calmodulin cofractionated with alkaline phosphatase, a cytochemical marker for contractile vacuole membranes, at a density of 1.156 g/ml. Several high molecular weight calmodulin-binding proteins were enriched in the same region of the gradient. One of the calmodulin-binding polypeptides (molecular mass approximately 150 kD) cross-reacted with an antiserum specific for Acanthamoeba myosin IC. By indirect immunofluorescence, this protein was also enriched on contractile vacuole membranes. These results suggest that a calmodulin-binding unconventional myosin is associated with contractile vacuoles in Dictyostelium; similar proteins in yeast and mammalian cells have been implicated in vesicle movement.

Isolation and mode of action of rabbit corticostatic (antiadrenocorticotropin) peptides

Corticostatic peptides are a family of arginine-rich cysteine-rich peptides that inhibit ACTH-stimulated corticosterone (B) production in rat adrenal cell suspensions. In this communication we describe a new method for the facile isolation and purification of these basic peptides from rabbit adult lung. We then describe the isolation and sequences of the four rabbit peptides, CSI, CSII, CSIII, and CSIV, and compare their biological activities in the ACTH (150 pg/ml) inhibition assay. CSI is by far the most potent of the four peptides. Using CSI as a model, we then studied its effects on the proximal and distal parts of the pathway leading to the generation of cAMP. CSI had no effect on (Bu)2cAMP action on forskolin or cholera toxin in their ability to mimic ACTH and increase B production in rat adrenal cells, nor did CSI have any effect on the stimulation of B production by pertussis toxin. Endogenous cAMP stimulated by ACTH decreased after the addition of CSI, which pointed to the inhibition of ACTH binding to explain the mode of action of this corticostatin. Displacement of the specific binding of labeled ACTH by CSI and the ACTH antagonist ACTH-(6-24) was determined, and indeed, CSI did displace ACTH from its binding site. The question of what portion of the ACTH molecule was involved in the action of CSI was answered by studying ACTH-(1-13) acetyl amide (alpha MSH) and ACTH-(1-18) amide. CSI had no effect on alpha MSH stimulation of B production, but did lower the production of B stimulated by ACTH-(1-18) amide. Therefore, CSI must act on ACTH-(14-18), which is part of the so-called address region of ACTH, which is -Gly14-Lys15-Lys16-Arg17-Arg18-, the very basic part of the molecule. These results indicate that CSI acts by competing with ACTH for its binding receptor on the adrenal cell and that this competition is confined to amino acids 14-18 of the molecule when it is bound to the receptor.

Compressibility of M3C60 Fullerene Superconductors: Relation Between Tc and Lattice Parameter

X-ray diffraction and diamond anvil techniques were used to measure the isothermal compressibility of K(3)C(60) and Rb(3)C(60), the superconducting, binary alkali-metal intercalation compounds of solid buckminsterfullerene. These results, combined with the pressure dependence of the superconducting onset temperature T(c) measured by other groups, establish a universal first-order relation between T(c) and the lattice parameter a over a broad range, between 13.9 and 14.5 angstroms. A small secondorder intercalate-specific effect was observed that appears to rule out the participation of intercalate-fullerene optic modes in the pairing interaction.

Investigation on the carcinogenic effects of coal tar pitch in rat respiratory tract by intratracheal instillations

The effects of coal tar pitch (CTP) on the tracheobronchial mucosa of Wistar rats were studied. Three groups of animals received 10 weekly intratracheal instillations of CTP at the cumulative doses of 6.48, 136.56 and 200 mg respectively. The control group of rats received 10 weekly intratracheal instillations of charcoal powder at a cumulative dose of 20 mg. The study in which the animals were killed serially revealed that CTP had conspicuous damage on the respiratory system of rats, especially on the bronchiolo-alveolar areas. The lesions induced by CTP ranged from hyperplastic, metaplastic and dysplastic changes to extensive cancers. These lesions were usually multifocal, and were more severe in the rats receiving higher dosages of CTP. The deposition of CTP particles within or adjacent to these lesions could be readily identified. Lung cancers occurred in 12.5% (4/32) and 25% (10/40) of the rats treated with 136.56 and 200 mg of CTP, whereas no tumors were found in control rats and the rats that received 6.48 mg of CTP. The overall cancer incidence significantly related to the cumulative dose of CTP. The histological types of lung cancers consisted of squamous cell carcinomas (10 out of the 14 lung cancers), adenocarcinoma (1/14), and combined squamous and adenocarcinomas (3/14). The development of CTP-induced rat lung cancers appears to derive from the hyperplasias of bronchiolo-alveolar epithelium, and processing stages of squamous metaplasias and/or dysplasias to carcinomas. The present results confirmed the carcinogenic effects of CTP on the respiratory system of rats, and provided experimental evidence for human lung carcinogenesis, particularly in those occupationally exposed to coal tars or tar products.

X-Ray Diffraction Evidence for Nonstoichiometric Rubidium-C 60 Intercalation Compounds

Powder x-ray diffraction at 300 K on equilibrated samples of several nominal compositions chi in Rb(chi)C(60) is reported. In addition to the face-centered cubic (fcc) (chi = 3, superconducting), body-centered tetragonal (chi = 4), and body-centered cubic (bcc) (chi = 6) stoichiometric phases, direct evidence for a dilute fcc doped phase, 0 x c </= 1, and for a substoichiometric bcc phase, chi approximately 5, is presented. In contrast, chi = 3 and chi = 4 appear to be line phases with nearly zero solubility of Rb vacancies and interstitials at 300 K. These results are summarized in a provisional binary phase diagram.

The role of oxygen free radicals in myocardial ischemia/reperfusion injury

A series of experiments have been done to investigate the role of oxygen free radicals in ischemia/reperfusion injury. The following results were found: Myocardial MDA content increased significantly after post-ischemic reperfusion in vivo and in vitro. A blockade of the xanthine oxidase pathway for free radical generation could provide effective protection against ischemia/reperfusion injury. Exogenous reactive oxygen intermediates H2O2, .OH and O2- could induce changes in the contractility and electrophysiological properties of myocardial cells similar to those seen in ischemia/reperfusion. An outburst of free radical generation was detected by ESR spectroscopy at low temperature (-173 degrees C) and with the spin trapping technique during the very early phase of reperfusion. The authors emphasize the important role of free radicals in the pathogenesis of myocardial ischemia/reperfusion injury.

[An approach to removing stains and remineralization of dental fluorosis]

341 mottled teeth were bleached with 4% and 18% hydrochloric acid; the mixture of 36% hydrochloric acid, 30% hydrogen peroxide and anesthetic ether; and 30% hydrogen peroxide warmed by infra-red ray lamp. The effects were evaluated clinically. The extracted mottled and normal teeth were treated with the methods mentioned above. The decolouration effects, the structural changes of tooth surface, and the remineralization were examined by scanning electronmicroscopy and polaroid microscopy. The results showed: all of the four methods had the decolouration effects; the decolouration effect was better in the teeth with higher mineralization and the pigmentation existed more superficially; complete decolouration was 94.8% and lightened cases were 5.2%. The mechanism of decolouration seemed to be the dissolution of tooth superficial layer containing pigment. The decalcified tooth surface might be recalcified by the treatment of recalcification solution, or by saliva itself.

Maternal-fetal transmission of SIV in macaques: disseminated adenovirus infection in an offspring with congenital SIV infection

To develop a nonhuman primate model for maternal-fetal transmission of HIV infection, we have inoculated pregnant Macaca nemestrina with uncloned SIVMne. Three animals inoculated during the third trimester delivered healthy infants. One of the three infants, a male born 31 days after the mother was inoculated with SIV, became virus-positive but failed to produce SIV-specific antibody and died with overt simian immunodeficiency and disseminated adenovirus (SV20) infection at age six and one-half months. SIV and adenovirus antigen could be demonstrated by immunohistochemical methods in multiple organ systems.