Dynamics of cardiorespiratory function in Standardbred horses during different intensities of constant-load exercise

Summary Six Standardbred horses were used to evaluate the time course of pulmonary gas exchange, ventilation, heart rate (HR) and acid base balance during different intensities of constant-load treadmill exercise. Horses were exercised at approximately 50%, 75% and 100% maximum oxygen uptake ( max) for 5 min and measurements taken every 30 s throughout exercise. At all work rates, the minute ventilation, respiratory frequency and tidal volume reached steady state values by 60 s of exercise. At 100% max, the oxygen consumption ( ) increased to mean values of approximately 130 ml/kg·min, which represents a 40-fold increase above resting . At the low and moderate work rates, showed no significant change from 30 s to 300 s of exercise. At the high work rate, the mean at 30 s was 80% of the value at 300 s. The HR showed no significant change over time at the moderate work rate but differing responses at the low and high work rates. At the low work rate, the mean HR decreased from 188 beats/min at 30 s to 172 beats/min at 300 s exercise, whereas at the high work rate the mean HR increased from 204 beats/min at 30 s to 221 beats/min at 300 s exercise. No changes in acid base status occurred during exercise at the low work rate. At the moderate work rate, a mild metabolic acidosis occurred which was nonprogressive with time, whereas the high work rate resulted in a progressive metabolic acidosis with a base deficit of 16 mmol/l by 300 s exercise. It is concluded that the kinetics of gas exchange during exercise are more rapid in the horse than in man, despite the relatively greater change in in the horse when going from rest to high intensity exercise.Symbols and abbreviations E minute ventilation - V _T tidal volume - oxygen uptake - carbon dioxide output - oxygen pulse - ventilatory equivalent for oxygen - ventilatory equivalent for carbon dioxide - R respiratory exchange ratio - HR heart rate - SBC standard bicarbonate - STPD standard temperature and pressure dry - BTPS body temperature and pressure saturated - arterial oxygen content - arteriovenous oxygen content difference - Rf respiratory frequency     

Development and analysis of pectic screening media for use in the detection of pectinase mutants

Summary Two solid pectic media were devised for mutually exclusive detection of extracellular polygalacturonase and pectin lyase produced by fungi including the vascular parasite of tomato Verticillium albo-atrum. These media allowed detection of pectinase-defective mutants. Polygalacturonase detection medium contains non-methylated polygalacturonan (sodium polypectate) is buffered at pH 5.0 (Na citrate, 0.05 M) and is calcium-free. In contrast pectin lyase medium contains polymethylgalacturonan (pectin), is buffered at pH 8.0 (HEPES, 0.05 M) and contains calciumrich agar. When glucose was added to the media for selection of catabolite-resistant mutants, enzyme synthesis was still evident, whereas in comparable conditions in liquid culture production was almost completely repressed. This apparent discrepancy is discussed in terms of the influence of basal synthesis, colony biomass and accumulation of oligouronides which repress induced synthesis and activity.Abbreviations CR catabolite repression - CTAB cetyltrimethyl ammoniumbromide - GALA galacturonic acid - NAPP sodium polypectate - PG polygalacturonase - PL pectin lyase - TBA thiobarbituric acid - UGALA unsaturated galacturonic acid     

Distribution of the Glucose-1,6-Bisphosphate System in Brain and Retina

The distribution of glucose-1,6-bisphosphate (G16P2) synthase was measured in more than 70 regions of mouse brain, and nine layers of monkey retina. Activities in gray areas varied as much as 10-fold, in a hierarchical manner, from highest in telencephalon, especially the limbic system, to lowest in cerebellum, medulla, and spinal cord. The synthase levels were significantly correlated among different regions with G16P2 itself, as well as with previously published levels of a brain specific IMP-dependent G16P2 phosphatase. In contrast, neither G16P2 nor either its synthase or phosphatase correlated positively with phosphoglucomutase, and in all regions the G16P2 levels greatly exceeded requirements for activation of this mutase. This strengthens the view that G16P2 has some function besides serving as coenzyme for phosphoglucomutase. However, attempts to correlate the "G16P2 system," as defined by the three coordinately related elements, synthase, phosphatase, and G16P2, with other enzymes of carbohydrate metabolism, or with regional data of Sokoloff et al. [J. Neurochem. 28, 897-916 (1977)] for glucose consumption, were unsuccessful. This leaves open the possibility that brain G16P2 might serve as a phosphate donor for specific nonmetabolic effector proteins.     

Loss of striatal mu1 opiate binding by substantia nigra lesions in the rat

Opiate receptors have been identified within the striatum and some have been localized presynaptically to nigrostriatal neurons. Using unilateral ablative lesions of the substantia nigra, we examined binding in the ipsilateral and contralateral striata. Lesions significantly lowered both 3H[D-Ala2,MePhe4,Gly(ol)5]enkephalin (DAGO) and 3H[D-Ala2,Leu5]enkephalin (DADL) binding. The inclusion of competitors in these assays revealed a decrease in both mu1 and mu2 receptors. Mu1 binding was slightly more sensitive to the lesioning than mu2 binding. Selective mu1 and mu2 binding assays supported these observations. No change in delta binding was observed in the lesioned striata. These studies raise the possibility that both mu1 and mu2, but not delta, receptors are localized presynaptically on nigrostriatal neurons.     

Correlations between carbon isotope ratio and microhabitat in desert plants

Summary Water is usually considered to be the key limiting factor for growth of desert plants, yet there is little information available of the water-use efficiency of species within a desert community. Leaf carbon isotope ratios, an indicator of long-term intercellular carbon dioxide concentrations and thus of water-use efficiency in C₃ plants, were measured on species occurring within a Sonoran Desert community, consisting of wash, transition and slope microhabitats. Along a soil moisture gradient from the relatively wetter wash to the relatively drier slope, leaf carbon isotope ratios increased in all species, indicating that water-use efficiency increased as soil water availability decreased. Leaf carbon isotope ratios of long-lived perennials were substantially more positive than in short-lived perennials, even though plants were growing adjacent to each other. Leaf carbon isotope ratio and leaf duration (evergreen versus deciduous) were not correlated with each other. The results are discussed in terms of how the efficiency of water use may affect community structure and composition.     

Influence of food size and food quantity on the feeding of the mussel Dreissena polymorpha

Summary In common with many other suspension feeders, the freshwater mussel Dreissena polymorpha has a maximum filtration rate at low food concentrations and a maximum ingestion rate at high food concentrations. These high rates, which reflect the potential maximum food uptake of the animal, are called the filtration capacity and the ingestion capacity respectively. The ingestion capacity was attained without forming pseudofaeces with Chlamydomonas reinhardii as food. The incipient limiting level could be calculated as the quotient of these two values. A decrease of the filtration rate at high food concentrations was correlated with changes in pumping activity, which showed more frequent interruptions, or a lower level of water transport. Dreissena can filter out particles of diameter greater than 0.7 m from the water. Retention reaches a plateau at about 5 m particle diameter. Scanning electron micrographs of the arrangement of the cilia on the gill filaments are given.     

Ig isotypes produced by EBV-transformed B cells as a function of age and tissue distribution

EBV can transform human B cells giving rise to lymphoblastoid cell lines that produce and secrete Ig. Herein B cells from various tissues of newborns and adults were transformed by EBV and their Ig products were analyzed with isotype-specific mAb. Although IgG- and IgA-bearing B cells were present in the newborn, EBV transformed IgM-producing cells almost exclusively in both newborn blood and breast milk. IgM-secreting cells were derived from IgM+ B cells and IgM- pre-B cells present in neonatal blood, but only from IgM+ cells in adult blood. Whereas in adults most EBV-transformed cells produced IgM, producers of IgG and of IgA were present in frequencies that varied according to the tissue source. Precursors of IgG-producing cells were relatively abundant in blood, spleen, and tonsil, and relatively infrequent in bone marrow and appendix. EBV-inducible IgA producers were relatively concentrated in the appendix and to a lesser extent in tonsils and blood. Differences in the subclass composition of EBV-transformed populations of IgG- and IgA-producers were also observed for the various adult lymphoid tissues. IgG1-producing cells predominated in most tissues, and precursors of IgG2 were largely confined to the circulation. Whereas IgA1-producing cells were predominant in all tissues, a marked enrichment in IgA2-producers was observed in the appendix. These results indicate a remarkable heterogeneity in the isotype distribution pattern of EBV-transformable B cells that is determined both by developmental age and tissue localization. We propose that EBV selectively transforms primed B cells, the isotype commitment of which varies according to tissue origin and age.     

BP-3 alloantigen. A cell surface glycoprotein that marks early B lineage cells and mature myeloid lineage cells in mice

To explore the cell surface molecules expressed on pre-B cells we have produced a panel of alloantibodies against transformed pre-B cells from BALB/c mice by immunizing a wild mouse, Mus spretus. One of these antibodies, BP-3, recognized glycoproteins of Mr 38,000 to 48,000 on pre-B cells transformed either by the Abelson murine leukemia virus or an erb B oncogene construct. Removal of N-linked oligosaccharides from the BP-3 Ag revealed a single core protein of Mr 32,000. The Ag was expressed by bone marrow cells in all but one (A/J) of the inbred mouse strains tested and in wild mice of biochemical groups Mus-1 and Mus-2. Analysis of the tissue distribution revealed expression of the BP-3 reactive molecule on normal pre-B and B cells in the bone marrow, 35% of B cells in the circulation, 30% of the B cells in the spleen, and less than or equal to 20% of B cells in lymph nodes, peritoneal cavity, and Peyer's patches. The subpopulation of BP-3+ B cells in bone marrow and peripheral tissues displayed an immature phenotype (IgM IgD +/- ). Examination of a panel of transformed B lineage cells confirmed the early stage-specific expression of the BP-3 alloantigen. In addition, a myeloid cell line and normal myeloid cells were found to express the BP-3 alloantigen. In contrast to B lineage cells, the level of BP-3 expression increased as a function of myeloid cell differentiation. Myeloid cells in the bone marrow expressed relatively little Ag, whereas circulating neutrophils and peritoneal macrophages expressed relatively high levels of the BP-3 alloantigen with Mr 38,000, 41,000, and 46,000. The data suggest that this variably glycosylated cell surface protein could play different roles in the differentiation of B lineage and myeloid lineage cells. The BP-3 alloantigen appears to be a useful marker for virgin B cells that have recently migrated from the bone marrow to the periphery.     

CR2 ligands modulate human B cell activation

A considerable body of evidence from this and other laboratories indicates that complement receptor type 2 (CR2) modulates B cell activation and growth. In the present studies we have examined the effects of three different types of CR2 ligands, i.e., monomeric, aggregated, and latex-bound C3dg; mAb to different CR2 epitopes; and UV-inactivated, non-transforming EBV (EBVUV) for their actions on highly purified, high density resting tonsil B cells. Although none of these ligands induced B cells to enter the cell cycle or synergized with either anti-mu or low m.w. B cell growth factor in triggering B cell mitogenesis, aggregated C3dg, latex-bound C3dg, the OKB7 anti-CR2 mAb, and EBVUV-enhanced thymidine incorporation by phorbol ester-activated tonsil B cells. Such enhancement was not T cell or monocyte dependent. The major action of the CR2 ligands thus seems to be to enhance the transition of B cells activated by certain stimuli from the G1 to the S phase of the cell cycle. In contrast to the action of aggregated and latex-bound C3dg, monomeric C3dg was inhibitory for phorbol ester and aggregated C3dg-induced B cell activation. The HB-5 anti-CR2 mAb, which reacts with a different epitope on CR2 from that of OKB7, did not synergize with PMA in B cell activation. These data provide additional evidence for a role for the CR2 in the control of B cell growth and provide a useful model for studying the CR2-mediated signals that affect the growth of B cells.