Functional assessment of pulmonary capillary surface area in the 2-mo-old lamb.

We recently reported that measurements of the maximal velocity of pulmonary endothelial angiotensin-converting enzyme (Vmax) in vivo provide information regarding microvascular surface area in the developing lamb. To obviate any subtle influences of development on Vmax aside from simple increases in surface area, we correlated Vmax with postmortem stereological assessments of alveolar surface area in the relatively mature lung of the 2-mo-old lamb (n = 14). We attempted to increase the range of surface area beyond its normal variability by injecting nine of the lambs with bleomycin, an antineoplastic agent with significant pulmonary toxicity in other species. Vmax, measured shortly after birth and then weekly, increased monotonically in all lambs. Despite their wide dispersion, Vmax and the stereological determinations correlated strongly at 2 mo of age, confirming that Vmax is a robust indicator of the surface area of the air-blood barrier. There was no significant difference in either measurement between the control lambs and those treated with bleomycin, suggesting that the newborn lamb is resistant to the effect of this agent.     

Electron microscopy of supercoiled pEJ4 DNA containing homopurine.homopyrimidine sequences

Supercoiled pEJ4 DNA (a derivative of pUC19 containing an insert with 60-bp-long homopurine.homopyrimidine tract from the sea urchin P. miliaris histone gene spacer) was investigated by electron microscopy using three different spreading techniques i.e., formamide and aqueous variants of the Kleinschmidt technique and protein-free benzyldimethyl-alkyl ammonium chloride (BAC) technique at different pHs. If the specimens for electron microscopy were prepared at pH 5.6 and pH 4.0 (i.e., under conditions where the homopurine.homopyrimidine tract assumes an unusual conformation) a single thick "stem" or a "denaturation bubble" in a large number of DNA molecules were observed. No such changes were found in samples prepared at neutral pH and in linearized pEJ4 DNA prepared at pH 5.6. In specimens of a control supercoiled pUC19 DNA prepared at pH 5.6 and 4.0 practically no local changes were detected. The "denaturation bubbles" were observed by BAC techniques (probably due to secondary local DNA denaturation during the specimen preparation) while the more gentle formamide technique revealed only "stems". The "stems" were almost always positioned at the sites where the curvature of supercoiled DNA molecules occurred. The results are in agreement with presence of a protonated triplex H-form in homopurine.homopyrimidine tract bringing the first evidence of curvature or kinking of the DNA molecule connected with the occurrence of the H-form in supercoiled DNA.     

MOVEMENTS OF SOUTHERN ELEPHANT SEALS AND SUBANTARCTIC FUR SEALS IN RELATION TO MARION ISLAND

Based primarily on an intensive marking/resighting program conducted at Marion Island (46°54'S, 37°45'E) in the Southern Ocean, the inter-island movements of southern elephant seals, Mirounga leonina , and fur seals Arctocephalus spp., were investigated to elucidate their little known pelagic phase. Southern elephant seals, in particular immature animals, readily move between the proximate Marion and Prince Edward islands. Some range as far afield as Iles Crozet, approximately 1,000 km distant where they haul out for the summer molt or during an autumn resting phase. The exchange of individuals between Marion Island and Iles Crozet during the return of immatures for the molt after a winter at sea, suggests overlapping of the foraging ranges of the two populations. Despite their wanderings, the majority of M. leonina from Marion Island probably feed in the proximity of the island, and relocate onto the island for breeding, molting and resting. Of the fur seals, only a few A. tropicalis were seen away from their natal island, in some cases covering distances in excess of 2,000 km. displaying a remarkable dispersal capacity.     

Free gp70 from FeLV: enrichment from cell culture fluid by ferric oxide-agarose chromatography

A new chromatographic material based on beads of macroporous crosslinked agarose containing ferric oxide particles was used for enrichment of gp70--the envelope glycoprotein of feline leukemia virus (FeLV). Free gp70 was purified from cell culture fluid in one step with a recovery of 50 to 60% and a purification of about 60 times. The described procedure is a suitable first step for the purification of gp70 from large volumes of cell culture fluid.     

Stand microclimate and physiological activity of tree leaves in an oak-hornbeam forest

Summary In an uneven-aged, multi-species oak-hornbeam forest at Báb, SW Slovakia (former IBP Forest Research Site), a series of micrometeorological and ecophysiological measurements started in 1985. The aims of the work are to improve understanding of physiological processes (photosynthesis, respiration, and transpiration) of adult trees and stand microclimate, to collect data for simulation of the canopy (stand) photosynthesis and for ecological synthesis of the functioning of the forest ecosystem. In this paper, photosynthetically active radiation (PAR), air temperature (AT) and relative humidity (RH), wind speed (WS), and CO₂ concentration ([CO₂]) in and above the forest are characterized for the fully leaved season, using diurnal courses, vertical profiles and isodiagrams (isopleths). Approximately 50% of incident PAR was absorbed by the upper 4–5 m layer of leaves and only approximately 5% or less penetrated to the forest floor. Vertical gradients of AT and RH were generally low, but large differences in diurnal ranges of AT and RH were observed between vertical levels. The upper leaf canopy greatly reduced WS, and at a height of about 14 m above the ground it was close to zero. The highest diurnal [CO₂] maximum and variations occurred at 1 m above the ground, and the lowest above the forest. In good light conditions in the forest, the entire leaf canopy (overstorey and understorey canopy) is a large sink of CO₂. At night the forest stand is a source of CO₂, the largest internal source being the soil and forest floor.     

Extensive sequence homology between IgA receptor and M proteins in Streptococcus pyogenes

Many strains of Streptococcus pyogenes are known to express a receptor for IgA. The complete nucleotide sequence of the gene for such a receptor, protein Arp4, has been determined. The deduced amino acid sequence of 386 residues includes a signal sequence of 41 amino acids and a putative membrane anchor region, both of which are homologous to similar regions in other streptococcal surface proteins. The processed form of the IgA receptor has a length of 345 amino acids and a calculated molecular weight of 39544. The N-terminal sequence of the processed form is different from that previously found for a similar IgA receptor isolated from a S. pyogenes strain of type M60. The sequence of protein Arp4 shows extensive homology to the C-terminal half of streptococcal M proteins, but not to the streptococcal IgG receptor protein G or staphlyococcal protein A. Apart from the membrane anchor, this homology includes a sequence of 119 amino acid residues containing three repeated units and a 54-residue sequence without repeats. The protein expressed in Escherichia coli is found in the periplasmic space, in which it constitutes the major protein. Protein Arp4 is the first example of a surface protein that has both immunoglobulin-binding capacity and structural features characteristic of M proteins.     

Resistance to H-2-restricted but not to allo-H2-specific graft and cytotoxic T lymphocyte responses in lymphoma mutant

The lymphoma mutant RMA-S escaped graft rejection after transplantation over a minor histocompatibility barrier, whereas it was rejected in H-2 allogeneic mice. The parental control line was rejected in both situations. The mutant, which had been selected against MHC class I molecules retained 5 to 10% of the wild-type H-2Db, Kb, and beta 2-microglobulin expression on the cell surface. It remained sensitive to allo-H-2b CTL in vitro, but was completely resistant to minor histocompatibility antigen-specific, H-2b-restricted CTL. It was equally resistant to other H-2b-restricted responses against internally derived Ag, such as tumor-specific CTL or a CTL clone specific for the influenza virus nucleoprotein. The results indicate a target cell defect that selectively abolishes the sensitivity to H-2-restricted CTL directed against internally processed Ag. This appears sufficient to shift the transplantation response over a minor histocompatibility Ag barrier from rejection to acceptance. There are two possible explanations for the results: 1) a block in the MHC class I-directed pathway for internal Ag processing, and 2) subthreshold H-2/Ag ligand density in relation to triggering requirements of restricted CTL. Regardless of the type of defect, the results demonstrate a difference between allo-H-2-specific and H-2-restricted CTL recognition at the level of the target cell.     

A novel functional cell surface dimer (Kp43) expressed by natural killer cells and T cell receptor-gamma/delta+ T lymphocytes. I. Inhibition of the IL-2-dependent proliferation by anti-Kp43 monoclonal antibody.

In the present study we describe a novel functional cell surface molecule, designated as Kp43, which is expressed among leukocytes by NK cells, TCR-gamma/delta + T lymphocytes, and some CD8+ CD56+TCR-alpha/beta + T cell clones. The Kp43 Ag is a 70-kDa disulfide-linked dimer, which migrates in SDS-PAGE under reducing conditions as a single 43-kDa band. Two-color immunofluorescence staining of fresh PBL revealed that only a fraction of CD16+, and of TCR-gamma/delta + T lymphocytes expressed the Ag. The analysis of TCR-alpha/beta + T cell clones showed that a small proportion (2 out of 20) weakly expressed Kp43 together with the CD8 and CD56 molecules. By immunoperoxidase staining of different tissues the anti-Kp43, reactivity was detected exclusively in lymphoid organs, where a minority of scattered cells was stained, and in some liver sinusoidal cells. Essentially all NK cells acquired Kp43 when stimulated with a B lymphoblastoid cell line. By contrast, the pattern of distribution of Kp43 remained stable upon in vitro culture of T-gamma/delta lymphocytes, thus delineating two subsets according to its expression. In lymphokine-activated killer populations, obtained by culturing either PBL or NK cells with high concentration of IL-2, most CD16+ and CD56+ cells became Kp43+. The Kp43-specific mAb inhibited the IL-2-dependent proliferative response of cultured NK and TCR-gamma/delta + T cells without affecting their non-MHC-restricted cytotoxicity. The partial inhibitory effect, which was mediated as well by pepsin digested F(ab')2 fragments, was lost upon reduction to Fab. The anti-Kp43 mAb did not interfere with the specific binding of IL-2 to its surface receptors. Altogether the data point out that the Kp43 dimer is involved in the regulation of the IL-2-dependent proliferative response of NK cells and a subset of TCR-gamma/delta + T lymphocytes.     

Mixed infection of Rickettsiella phytoseiuli and Coxiella burnetii in Dermacentor reticulatus female ticks: electron microscope study

Mixed infection of Rickettsiella phytoseiuli and Coxiella burnetii was investigated in hemolymph and organs of experimentally infected females of Dermacentor reticulatus ticks. Following intracoelomic infection, both agents, with the exception of Gene's organ, multiplied well in the cells of the tick host's organs. Two out of six developmental stages of R. phytoseiuli, i.e., crystal-forming and small dark particles, in dual infection with C. burnetii revealed marked morphological alterations. C. burnetii in the presence of R. phytoseiuli penetrated into the cortical layer of the synganglion and into the alveoli of the second and third type of salivary glands, but did not occur in the single infection.