Some rumen ciliates have endosymbiotic methanogens

Abstract Most of the small ciliate protozoa, including Dasytricha ruminantium and Entodinium spp. living in the rumen of sheep, were found to have intracellular bacteria. These bacteria were not present in digestive vacuoles. They showed characteristic coenzyme F₄₂₀ autofluorescence and they were detected with a rhodamine-labelled Archaea-specific oligonucleotide probe. The measured volume percent of autofluorescing bacteria (1%) was close to the total volume of intracellular bacteria estimated from TEM stereology. Thus it is likely that all of the bacteria living in the cytoplasm of these ciliates were endosymbiotic methanogens, using H₂ evolved by the host ciliate to form methane. Intracellular methanogens appear to be much more numerous than those attached to the external cell surface of ciliates.     

Short-range and long-range guidance by Slit and its Robo receptors: a combinatorial code of Robo receptors controls lateral position

Slit is secreted by midline glia in Drosophila and functions as a short-range repellent to control midline crossing. Although most Slit stays near the midline, some diffuses laterally, functioning as a long-range chemorepellent. Here we show that a combinatorial code of Robo receptors controls lateral position in the CNS by responding to this presumptive Slit gradient. Medial axons express only Robo, intermediate axons express Robo3 and Robo, while lateral axons express Robo2, Robo3, and Robo. Removal of robo2 or robo3 causes lateral axons to extend medially; ectopic expression of Robo2 or Robo3 on medial axons drives them laterally. Precise topography of longitudinal pathways appears to be controlled by a combination of long-range guidance (the Robo code determining region) and short-range guidance (discrete local cues determining specific location within a region).     

Reversal of sexual dimorphism in splenic T lymphocyte responses after trauma-hemorrhage with aging

Previous studies have demonstrated that hemorrhagic shockproduces immunodepression in young male mice, whereas theimmunoresponsivness in young proestrus female mice is enhanced undersuch conditions. This sexually dimorphic immune response to hemorrhageappears to be related to high estrogen and testosterone levels infemales and males, respectively. Nonetheless, it is unknown what impact the age-related decline in the sex steroid levels has on the immune response after hemorrhage. To study this, young (2-3 mo) and aged (18-19 mo) male and female CBA/J NIA mice were subjected tolaparotomy (i.e., soft tissue trauma) and hemorrhage (35 ± 5 mmHg for90 min and fluid resuscitation) or sham operation. Twenty-four hours later, splenocyte responses were assessed in vitro. Splenic T lymphocyte responses [i.e., proliferation, interleukin-2 (IL-2) and interferon- (IFN-) release] were depressed in youngmales and enhanced in young females after trauma-hemorrhage. Incontrast, in the aged male and female groups these parameters ofsplenocyte function were reversed after trauma-hemorrhage (i.e.,increased proliferation and IL-2 release in aged males compared withsuppressed proliferation and IFN- release in aged females).Furthermore, the release of the immunosuppressive cytokine IL-10inversely correlated with the age- and gender-related changes insplenocyte responses after trauma-hemorrhage. Thus the sexuallydimorphic immune response in young males and females totrauma-hemorrhage appears to reverse as sex hormone levels decline with age.

     

Counting error in the line-intercept method of measuring root length

The line-intercept method is widely used to estimate the length of roots washed from soil samples. Human error in root length estimates has not been quantified and is needed for error analysis and specification of training/testing requirements for new workers. Nine or ten individuals counted four samples of roots on each of five days. One sample was counted on each of the days to test day-to-day variation. A coefficient of variation of 10% was typically obtained for estimates of the length of a single sample by the counters. An uncertainty of about 7% resulted from differences in how a sample was arranged on the grid and how the counters varied as a group from day-to-day. Certain individuals tended to yield estimates appreciably higher or lower than the entire group, so new workers must be adequately evaluated.     

Role of neutrophils in lung vascular injury and edema after premature birth in lambs

Carlton, David P., Kurt H. Albertine, Soo Chul Cho, MennoLont, and Richard D. Bland. Role of neutrophils in lung vascular injury and edema after premature birth in lambs. J. Appl. Physiol. 83(4): 1307-1317, 1997.Toinvestigate the role of neutrophils in the pathogenesis of respiratorydistress after premature birth, we assessed the relationship betweencirculating neutrophil concentration and neutrophil accumulation in thelung, lung lymph and pleural liquid flow, and extravascular lungwater in 10 chronically catheterized preterm lambs (127 ± 1 days gestation) that were mechanically ventilated for 8 h afterbirth. Circulating neutrophil concentration transiently decreasedwithin 2 h after birth and then returned to prenatal values by 6-8h. The decrease in circulating neutrophil concentration was relateddirectly to the accumulation of neutrophils in the air spaces, drainageof liquid and protein from the lung 6-8 h after delivery, andpostmortem extravascular lung water. In additional studies, weintravenously administered mechlorethamine to 5 fetal lambs to reducecirculating neutrophils before delivery (neutrophil concentrationbefore birth: 9 ± 11 cells/µl). Compared with control lambs,neutrophil-depleted lambs had significantly less drainage of liquid(7.8 ± 5.9 vs. 2.6 ± 1.9 ml/h, respectively) and protein (116 ± 74 vs. 42 ± 27 mg/h, respectively) from the lung 6-8 hafter birth and significantly less extravascular lung water atpostmortem (6.5 ± 0.8 vs. 4.8 0.6 g/g dry lung,respectively). Thus neutrophils contribute to thepathogenesis of respiratory distress after premature birth byincreasing lung vascular protein permeability and promoting lung edema.

     

Ethanol Perturbs Glycosylation and Inhibits Hypersecretion in Trichoderma reesei

The effects of ethanol and phenylethanol on the growth of and glycoprotein secretion by Trichoderma reesei were studied. Low levels (1.5%, vol/vol) of ethanol perturbed the glycosylation process, as shown by alterations in the isoelectric profile of the secreted proteins and a reduction in the rate of incorporation of mannose into oligosaccharides. In addition to these effects on posttranslational modification, ethanol drastically lowered the protein secretion level of a hypersecretory strain.