Functional antagonism of the Polycomb-Group genes eed and Bmi1 in hemopoietic cell proliferation

The murine Polycomb-Group (PcG) proteins Eed and Bmi1 govern axial patterning during embryonic development by segment-specific repression of Hox gene expression. The two proteins engage in distinct multimeric complexes that are thought to use a common molecular mechanism to render the regulatory regions of Hox and other downstream target genes inaccessible to transcriptional activators. Beyond axial patterning, Bmi1 is also involved in hemopoiesis because a loss-of-function allele causes a profound decrease in bone marrow progenitor cells. Here, evidence is presented that is consistent with an antagonistic function of eed and Bmi1 in hemopoietic cell proliferation. Heterozygosity for an eed null allele causes marked myelo- and lymphoproliferative defects, indicating that eed is involved in the negative regulation of the pool size of lymphoid and myeloid progenitor cells. This antiproliferative function of eed does not appear to be mediated by Hox genes or the tumor suppressor locus p16(INK4a)/p19(ARF) because expression of these genes was not altered in eed mutants. Intercross experiments between eed and Bmi1 mutant mice revealed that Bmi1 is epistatic to eed in the control of primitive bone marrow cell proliferation. However, the genetic interaction between the two genes is cell-type specific as the presence of one or two mutant alleles of eed trans-complements the Bmi1-deficiency in pre-B bone marrow cells. These studies thus suggest that hemopoietic cell proliferation is regulated by the relative contribution of repressive (Eed-containing) and enhancing (Bmi1-containing) PcG gene complexes.

Mice lacking skeletal muscle actin show reduced muscle strength and growth deficits and die during the neonatal period

All four of the muscle actins (skeletal, cardiac, vascular, and enteric) in higher vertebrates show distinct expression patterns and display highly conserved amino acid sequences. While it is hypothesized that each of the muscle isoactins is specifically adapted to its respective tissue and that the minor variations among them have developmental and/or physiological relevance, the exact functional and developmental significance of these proteins remains largely unknown. In order to begin to assess these issues, we disrupted the skeletal actin gene by homologous recombination. All mice lacking skeletal actin die in the early neonatal period (day 1 to 9). These null animals appear normal at birth and can breathe, walk, and suckle, but within 4 days, they show a markedly lower body weight than normal littermates and many develop scoliosis. Null mice show a loss of glycogen and reduced brown fat that is consistent with malnutrition leading to death. Newborn skeletal muscles from null mice are similar to those of wild-type mice in size, fiber type, and ultrastructural organization. At birth, both hemizygous and homozygous null animals show an increase in cardiac and vascular actin mRNA in skeletal muscle, with no skeletal actin mRNA present in null mice. Adult hemizygous animals show an increased level of skeletal actin mRNA in hind limb muscle but no overt phenotype. Extensor digitorum longus (EDL) muscle isolated from skeletal-actin-deficient mice at day 2 to 3 showed a marked reduction in force production compared to that of control littermates, and EDL muscle from hemizygous animals displayed an intermediate force generation. Thus, while increases in cardiac and vascular smooth-muscle actin can partially compensate for the lack of skeletal actin in null mice, this is not sufficient to support adequate skeletal muscle growth and/or function.

Evidence for the local production and utilization of immune reactants in rheumatoid arthritis

Immunoglobulins, including rheumatoid factors, are produced by the rheumatoid synovial membrane. A significant contribution of the synovial membrane to the total IgG and IgM detected in the synovial fluid has been documented. The present study was designed to examine the contribution of the synovial membrane to the rheumatoid factors detected in the synovial fluid. Analysis of the data demonstrated that the synovial membrane was the source of a significant component of the total synovial fluid IgA rheumatoid factor and IgM rheumatoid factor. While some fluids possessed extremely elevated concentrations of the IgG rheumatoid factor, the data suggested that IgG rheumatoid factor was preferentially reduced, relative to total IgG, by the rheumatoid inflammatory process. These observations suggest a potentially important role for IgG rheumatoid factor in rheumatoid synovitis.

Why is there no carbonic anhydrase activity available to fish plasma?

Carbonic anhydrase (CA) is absent from the plasma of vertebrates. In vitro, CA in fish plasma will short-circuit the effect of catecholamines, which is to increase red blood cell (RBC) pH and volume, both of which enhance the affinity of hemoglobin for O2. CA was infused into trout for a period of 6 h and injected after 48 h, during which the animal was submitted to deep hypoxia (PO2=30­35 mmHg; 4.0­4.7 kPa). O2 content, lactate content, catecholamine levels, hematocrit, hemoglobin concentration and pHi were similar to those in the saline-infused control group. In contrast, cell volume was significantly higher and pHe, total CO2 content and organic phosphate levels were significantly lower than in the control group. The concentration of CA was not high enough completely to short-circuit the increase in pHi and red blood cell volume caused by catecholamines. The lower pHe in the CA-infused animals could enhance the activity of the Na+/H+ pump, which would keep the nucleotide triphosphate levels low. pH is a balance between acid loading at the muscle and acid excretion at the gills or the kidneys; we cannot distinguish between which of these resulted in a decrease of plasma pH. In conclusion, CA in plasma did not cause the expected reduction in blood oxygen content but did have a marked effect on plasma total CO2 content.

Effects of chewing gum on responses to routine painful procedures in children

In infants, sweet taste and sucking on a pacifier both have analgesic effects. Animal studies suggest that sweet taste may involve opioids, while rhythmic oral movements, as with a pacifier, increase the release of serotonin, which is involved in the gating of nociceptive afferents. The present study was designed to see if these effects produce an analgesic effect in children. Two studies were performed, during blood draws in a pediatric test center in 7- to 12-year-old children, and during vaccination at school in 9- to 11-year-old children. Using unsweetened or sweetened chewing gum, there were four groups: control, sweet, chew, and sweet plus chew. Overall, there was no effect of either sweet taste or chewing on pain responses. However, in boys sweet taste tended to increase pain ratings, but only in conjunction with chewing, while in girls sweet taste tended to decrease pain ratings in conjunction with chewing and increased them in the absence of chewing. Ratings of pain intensity and affective state were correlated. Affective state before the painful stimulus was related to pain response in the girls and in the boys in the test center, but not in the schools. In the schools, the presence of peers may have influenced the ratings.

Differential effects of therapeutic regimens on specific classes of rheumatoid factor

This study was performed to define further the relationship of circulating IgM and IgG rheumatoid factor to the articular manifestations of rheumatoid arthritis. Patients with substantial clinical improvement (greater than 55%) or no improvement or worsening were chosen for study. Patients were further selected to include those treated with non-steroidal anti-inflammatory drugs (NSAIDs) alone, or NSAIDs plus D-penicillamine or gold. Significant reductions of IgM (p less than 0.001) and IgG (p less than 0.005) rheumatoid factor were seen only in those treated with gold who improved clinically. These observations suggest that in patients experiencing comparable degrees of clinical improvement the simultaneous alterations of circulating IgG and IgM rheumatoid factor observed are dependent upon the therapeutic regimen employed.

Adenosine receptor blockade and hypoxia-tolerance in rainbow trout and Pacific hagfish. I. Effects on anaerobic metabolism

The physiological properties of adenosine may be essential in the control of energy metabolism for the survival of animals exposed to oxygen shortages. Accordingly, we tested the hypothesis that adenosine modulates metabolic regulation in rainbow trout and Pacific hagfish exposed to acute hypoxia. Treatment of hypoxic rainbow trout (PwO2=3.33 or 4.00 kPa) with the adenosine receptor (AR) blocker theophylline was associated with greater increases in plasma [lactate], more rapid and pronounced metabolic acidosis, higher tissue [lactate], and lower heart creatine charge and glycogen content than in the hypoxic controls. The recruitment of anaerobic metabolism in hypoxic trout treated with enprofylline, an AR blocker with very weak affinity, was intermediate to that of the hypoxic theophylline-injected and control groups. In hagfish, plasma [lactate] increased following exposure to a PwO2 of 1.33 kPa but did not increase following exposure to 3.33 kPa and, like plasma acidosis, it was greatest in the animals treated with theophylline. These findings indicate that AR blockade results in a more rapid and pronounced recruitment of anaerobic metabolism following acute hypoxic exposure, and while rainbow trout and Pacific hagfish show marked differences in their responses to hypoxia, adenosine appears to play an important protective role in both species.

cAMP dependent actin phosphorylation in developing rat lung and type II epithelial cells

Cyclic adenosine monophosphate (cAMP) increased in vitro phosphorylation of protein of 43,000 daltons in cytosolic fractions of rat lung and type II epithelial cells. The phosphoprotein was identified as 32P-actin by means of migration in one- and two-dimensional SDS-polyacrylamide gel electrophoresis and by phosphopeptide mapping followed by immunoperoxidase staining of peptides with anti-actin monoclonal antibody. Phosphorylation of actin in lung and type II cell cytosol was entirely cAMP dependent and the phosphorylated amino acid was identified as 32P-serine. Actin phosphorylation increased during the perinatal period of development, was barely detectable between 17 and 20 days gestation, increased prior to birth, and increased dramatically during the first week of life. Actin was the major substrate of cAMP-dependent protein kinase in lung cytosol from postnatal rats. Changes in actin phosphorylation that occur during development were not due to changes in cytosolic actin content or cAMP-dependent protein kinase activity but appeared to be related to the presence of factors inhibiting cAMP-dependent actin phosphorylation in fetal lung cytosol. Actin was also the major cAMP-dependent phosphoprotein identified in cytosolic fractions of purified type II epithelial cells. cAMP-dependent phosphorylation of pulmonary actin is developmentally regulated, occurring in association with other aspects of type II epithelial cell maturation during the perinatal period.

Effects of hypoxia on rainbow trout (Oncorhynchus mykiss): intraerythrocytic phosphates

Intraerythrocytic levels of guanosine and adenosine phosphates were estimated in normoxic and hypoxic rainbow trout after intra-arterial injection with either saline or carbonic anhydrase. A significant reduction of the total pool of adenosine and guanosine was observed in hypoxic animals. Similarly, a decrease in both ATP and GTP levels occurred in hypoxic animals injected either with saline or with carbonic anhydrase. Interestingly, there was a highly significant relationship between ATP and GTP levels, indicating that they are under similar control. In addition, a significant positive relationship between nucleoside triphosphate (NTP) and Mg2+ levels was observed. It is possible that the availability of ATP and GTP to hemoglobin (Hb) may be proportionally smaller than their intraerythrocytic absolute levels. No clear relationship between intraerythrocytic NTP levels and plasma carbonic anhydrase infusion was observed, despite the significant effect of carbonic anhydrase on acid­base balance. There was a significant relationship between red blood cell pH and [NTP]:[Hb] in fish exposed to hypoxia for 48 h. No such relationship existed during the first 6 h of hypoxic exposure. Possible mechanisms accounting for the reduction in NTP levels during the initial phases of hypoxia are discussed.

Ecological strategies of (pl)ants: Towards a world-wide worker economic spectrum for ants

Current global challenges call for a rigorously predictive ecology. Our understanding of ecological strategies, imputed through suites of measurable functional traits, comes from decades of work that largely focussed on plants. However, a key question is whether plant ecological strategies resemble those of other organisms.Among animals, ants have long been recognised to possess similarities with plants: as (largely) central place foragers. For example, individual ant workers play similar foraging roles to plant leaves and roots and are similarly expendable. Frameworks that aim to understand plant ecological strategies through key functional traits, such as the 'leaf economics spectrum', offer the potential for significant parallels with ant ecological strategies.Here, we explore these parallels across several proposed ecological strategy dimensions, including an 'economic spectrum', propagule size-number trade-offs, apparency-defence trade-offs, resource acquisition trade-offs and stress-tolerance trade-offs. We also highlight where ecological strategies may differ between plants and ants. Furthermore, we consider how these strategies play out among the different modules of eusocial organisms, where selective forces act on the worker and reproductive castes, as well as the colony.Finally, we suggest future directions for ecological strategy research, including highlighting the availability of data and traits that may be more difficult to measure, but should receive more attention in future to better understand the ecological strategies of ants. The unique biology of eusocial organisms provides an unrivalled opportunity to bridge the gap in our understanding of ecological strategies in plants and animals and we hope that this perspective will ignite further interest. Read the free Plain Language Summary for this article on the Journal blog.

The Cotton Effects of Conjugated Homoannular Dienes. I. The Non-generality of the Rule of Moscowitz

The non-generality of the diene rule of Moscowitz, relating the helicity of a non-planar conjugated homoannular diene to the sign of its Cotton effect, is discussed. We report the preparation of 3β-bromoacetoxy-16α-ethyl-162-cyano-162,21-cyclo-5α-pregna-17,21-diene, the X-ray crystallographic analysis of which confirms, as reported by Ahmed and Pollard, the stereochemistry which we previously assigned to the parent alcohol and acetate. We also report the synthesis of the methyl ketonic analogues of these dienonitriles and show that their sodium borohydride reduction product still has a Cotton effect in contradiction to the diene rule. The implications of these and other experiments are discussed.

Gamma/delta T cell receptor positive T cells in the inflammatory joint: lack of association with response to soluble antigens

In patients with inflammatory synovitis, the proliferative response by lymphocytes from synovial fluid to soluble mycobacterial antigens is enhanced relative to those from peripheral blood. Earlier studies suggested that gamma/delta T cell receptor positive (TCR+) T lymphocytes may significantly contribute to the mycobacterial-specific synovial fluid response. We therefore examined the relationship of the T cell proliferative response to Mycobacterium tuberculosis antigens and the presence of gamma/delta TCR+ T cells employing several monoclonal antibodies. No consistent increase of gamma/delta TCR+ T cells was noted in inflammatory synovial fluids or tissues. Nonetheless, lymphocytes from the majority of the synovial fluids proliferated vigorously in response to water-soluble M. tuberculosis antigens. There was no relationship between the percentage of gamma/delta TCR+ T lymphocytes and the intensity of the proliferative response. In contrast, stimulation with whole mycobacterial organisms was capable of enriching the gamma/delta TCR+ cell population obtained from the peripheral blood of tuberculosis skin test positive normal controls and from some inflammatory synovial fluids. These observations do not support a role for mycobacteria reactive gamma/delta TCR+ synovial T lymphocytes in response to soluble mycobacterial antigens or in the local pathogenesis of inflammatory synovitis.