Metabolic Activity of Fatty Acid-Oxidizing Bacteria and the Contribution of Acetate, Propionate, Butyrate, and CO2 to Methanogenesis in Cattle Waste at 40 and 60°C

The quantitative contribution of fatty acids and CO₂ to methanogenesis was studied by using stirred, 3-liter bench-top digestors fed on a semicontinuous basis with cattle waste. The fermentations were carried out at 40 and 60°C under identical loading conditions (6 g of volatile solids per liter of reactor volume per day, 10-day retention time). In the thermophilic digestor, acetate turnover increased from a prefeeding level of 16 μM/min to a peak (49 μM/min) 1 h after feeding and then gradually decreased. Acetate turnover in the mesophilic digestor increased from 15 to 40 μM/min. Propionate turnover ranged from 2 to 5.2 and 1.5 to 4.5 μM/min in the thermophilic and mesophilic digestors, respectively. Butyrate turnover (0.7 to 1.2 μM/min) was similar in both digestors. The proportion of CH₄ produced via the methyl group of acetate varied with time after feeding and ranged from 72 to 75% in the mesophilic digestor and 75 to 86% in the thermophilic digestor. The contribution from CO₂ reduction was 24 to 29% and 19 to 27%, respectively. Propionate and butyrate turnover accounted for 20% of the total CH₄ produced. Acetate synthesis from CO₂ was greatest shortly after feeding and was higher in the thermophilic digestor (0.5 to 2.4 μM/min) than the mesophilic digestor (0.3 to 0.5 μM/min). Counts of fatty acid-degrading bacteria were related to their turnover activity.     

Reversible high temperature exchange of carbonate and hydroxyl ions in tooth enamel and synthetic hydroxyapatite

Parallel experiments on human tooth enamel with sp.g. >2.95 and synthetic hydroxyapatite have been carried out to study the substitution of CO ₃ ^2– for OH^–, produced at 1000°C in dry CO₂, with the complementary use of neutron diffraction, x-ray diffraction, infrared spectroscopy and thermochemical techniques. It was verified that the substitution (i) is CO ₃ ^2– 2(OH^– and is completely reversible on specimen exposure to H₂O vapor at 1000°C, (ii) takes place with the carbon atom on or near the hexad axis, (ii) places one CO ₃ ^2– group per unit cell in an ordered fashion and so changes the space group fromP6 ₃/m to one without a screw axis, (iii) was consistent, by its incompleteness, with the occurrence of substitution of O^2– for 2(OH^–) in 25 to 40% of the unit cells, (iv) produced similar marked changes in the neutron powder diffraction patterns of both tooth enamel and hydroxyapatite, and (v) took place at a site where only a minor portion of the CO ₃ ^2– in normal untreated human tooth enamel occurs. From comparative Rietveld analysis results from x-ray and neutron powder diffraction patterns it is suggested that the carbon atom of this A-site CO ₃ ^2– is near 0,0,0.12 and the CO ₃ ^2– plane makes an angle of 18° with thec direction.On being heated at 400°C in H₂O vapor, tooth enamel retained much of its CO ₃ ^2– but its a lattice parameter changed from 9.445(3) Å to 9.420(1) Å, essentially that of hydroxyapatite. After once being heated at high temperatures, tooth enamel and hydroxyaptite showed similar responses to various treatments, including carbonation. After heating, more -Ca₃(PO₄)₂ was found in the tooth enamel specimen. Comparative weight change, IR, and other data for tooth enamel and hydroxyapatite heated in He, then in CO₂, and then in H₂O vapor showed a 20% or more deficiency of structural OH^– in the untreated tooth enamel.     

Metabolic Activity of Fatty Acid-Oxidizing Bacteria and the Contribution of Acetate, Propionate, Butyrate, and CO(2) to Methanogenesis in Cattle Waste at 40 and 60 degrees C

The quantitative contribution of fatty acids and CO(2) to methanogenesis was studied by using stirred, 3-liter bench-top digestors fed on a semicontinuous basis with cattle waste. The fermentations were carried out at 40 and 60 degrees C under identical loading conditions (6 g of volatile solids per liter of reactor volume per day, 10-day retention time). In the thermophilic digestor, acetate turnover increased from a prefeeding level of 16 muM/min to a peak (49 muM/min) 1 h after feeding and then gradually decreased. Acetate turnover in the mesophilic digestor increased from 15 to 40 muM/min. Propionate turnover ranged from 2 to 5.2 and 1.5 to 4.5 muM/min in the thermophilic and mesophilic digestors, respectively. Butyrate turnover (0.7 to 1.2 muM/min) was similar in both digestors. The proportion of CH(4) produced via the methyl group of acetate varied with time after feeding and ranged from 72 to 75% in the mesophilic digestor and 75 to 86% in the thermophilic digestor. The contribution from CO(2) reduction was 24 to 29% and 19 to 27%, respectively. Propionate and butyrate turnover accounted for 20% of the total CH(4) produced. Acetate synthesis from CO(2) was greatest shortly after feeding and was higher in the thermophilic digestor (0.5 to 2.4 muM/min) than the mesophilic digestor (0.3 to 0.5 muM/min). Counts of fatty acid-degrading bacteria were related to their turnover activity.     

Evidence that Cellulolysis by an Anaerobic Ruminal Fungus Is Catabolite Regulated by Glucose, Cellobiose, and Soluble Starch

A Piromyces-like ruminal fungus was used to study preferential carbohydrate utilization of [U-¹⁴C]cellulose, both alone and in combination with several soluble sugars. For cells grown on cellulose alone, cellulolytic activity was immediate and, initially, greater than that observed in the presence of added carbohydrate. Cellulolytic activity remained minimal in cultures containing cellulose plus glucose or cellobiose until the soluble sugar was depleted. Soluble starch also regulated cellulose activity but to a lesser extent. The results presented suggest that some fungal cellulases are susceptible to catabolite regulatory mechanisms.     

Identification of several cyclosporine binding proteins in lymphoid and non-lymphoid cells in vivo.

The immunosuppressant cyclosporine A (CSA) has been shown to bind to the ubiquitous cellular protein, cyclophilin, and to inhibit its rotamase activity. In the present study, 3H-cyclosporine diazirine analogue was used to photolabel viable human cells of lymphoid and fibroblast origin in order to identify the intracellular targets for the drug. While cyclophilin was strongly labeled in situ, additional minor cyclosporine-protein complexes of 25, 40, 46 and 60 kDa were identified in the T cell leukemia cell line Jurkat. These proteins bound specifically, since only active CSA but not inactive CSH or FK506 competed for binding. Photolabeling of MRC5 cells, a CSA resistant human fibroblast cell line, revealed a 25 kDa complex as the major product, while the 46 and 60 kDa bands were not detectable and cyclophilin labeling was only faint, even though both MRC5 and Jurkat cells contain similar cyclophilin concentrations. Thus, our data suggest that the intracellular targets of CSA and/or the accessibility to cyclophilin varies considerably in drug sensitive and resistant cell types, which may contribute to explaining the lymphocyte selectivity of the drug.     

Contractions of holothurian muscles

Summary In response to quick stretch, contraction is elicited in longitudinal retractor muscles of five tested species of holothurians, and in the pharyngeal retractor ofCucumaria. The effects of amplitude of stretch and rate of stretch are additive. Rates of contraction and repetitiveness of response, and spontaneous rhythmicity (especially in muscles ofLeptosynapta), correlate with mode of life.Contractile responses to stretch are abolished by anesthesia with procaine or magnesium. Responses are enhanced by physostigmine or prostigmine, blocked by d-tubocurarine. Responses to electric shocks persist after block of responses to stretch and after block of spontaneous activity by anesthesia, by cholinergic blockers or by Na replacement. Responses to both stretch and shock are abolished by reducing calcium or by agents which block Ca-conductance.It is postulated (1) that quick stretch stimulates the terminals of cholinergic nerves, (2) that conduction in these nerve fibers is by Na but is TTX resistant, (3) that the nerve endings activate conductance increase for Ca⁺⁺ in muscle fibers which initiate contractions.No muscle potentials were recorded by suction or pressure electrodes and no nexal junctions were observed between muscle fibers. The muscles were well innervated and synaptic endings and some neural somata were seen in the nerve bundles.Thanks are due to Dennis Willows, director and to staff, University of Washington Laboratories, Friday Harbor; to C.L. Singla of the University of Victoria for preparing and examining electron micrographs; to J.L.S. Cobb for commenting on electron micrographs; to Richard Meiss for designing and constructing ramp stretching device. C. Ladd Prosser was supported by NIH grant 5-R01 AM 12768-10 and George O. Mackie by grant no. A 1427, Nat. Sci. and Eng. Res. Council of Canada.     

Morphological stabilization of capsules of group B streptococci, types Ia, Ib, II, and III, with specific antibody.

Antibody prepared to the type-specific capsular polysaccharides of group B streptococci was used to demonstrate a stabilizing effect on the capsular glycocalyx. This permitted visualization by electron microscopy of the size of the capsule relative to the rest of the bacterial cell, and clear differences in the dimensions of untreated and antibody-treated capsular material were noted. Antibodies produced against group B streptococci types Ia, Ib, II, and III were used to demonstrate morphologically that the organization and extent of the capsular glycocalyx more closely resembles its natural state on stabilization by reaction with specific antibody.     

Studies on the receptors mediating responses of osteoblasts to thrombin

The serine protease thrombin stimulates proliferation in osteoblasts, but decreases alkaline phosphatase (ALP) activity, a marker of osteoblast differentiation. Three thrombin receptors have been identified, protease activated receptor (PAR)-1, PAR-3 and PAR-4; we have previously demonstrated that mouse osteoblasts express PAR-1 and PAR-4. The effect of thrombin on osteoblast proliferation and differentiation was studied to determine which of the thrombin receptors is responsible for the primary effects of thrombin. Primary mouse calvarial osteoblasts from PAR-1-null and wild-type mice, and synthetic peptides that specifically activate PAR-1 (TFFLR-NH2) and PAR-4 (AYPGKF-NH2) were used. Both the PAR-1-activating peptide and thrombin stimulated incorporation of 5-bromo-2'-deoxyuridine (two to four-fold, P < 0.001) and reduced alkaline phosphatase activity (approximately three-fold, P < 0.05) in cells from wild-type mice. The PAR-4-activating peptide, however, had no effect on either alkaline phosphatase activity or proliferation in these cells. Neither thrombin nor PAR-4-activating peptide was able to affect osteoblast proliferation or alkaline phosphatase activity in cells isolated from PAR-1-null mice. The results demonstrate that thrombin stimulates proliferation and inhibits differentiation of osteoblasts through activation of PAR-1. No other thrombin receptor appears to be involved in these effects.     

How close to a pendulum is human upper limb movement during walking?

The aim of this work was to investigate how close to pendulum-like behaviour the periodic motion of the human upper limb (or upper extremity) is, during normal walking at a comfortable speed of locomotion. Twenty-five healthy young persons (males and females) participated in the experiment. Biomechanical testing was undertaken (mass and centre of mass of each segment of the total upper extremity). Participants were walking on a treadmill with a standardised velocity of 1.1 ms(-1) (comfortable speed for all of them). A video analysis system with Silicon software was used to measure the different angles of the arm and forearm. The theoretical period of motion and maximal angular velocity were computed for the centre of mass of the total upper limb from the measured phases of the arm swing and associated positional potential energies. Actual measured periods of motion, in comparison, represented a level of similarity to a lightly damped simple pendulum. Using this assumption, the "damping factor" was calculated from the ratio between theoretical and measured values. A vast majority of people exhibited an actual angular velocity exceeding the expected theoretical angular velocity calculated for a virtual pendulum of similar mass and length characteristics. This may be due to muscle forces that are contributing to the motion of the upper limb during walking rather than simple gravity force acting alone. The observed positional potential energy of the dominant limb was greater than that of the non-dominant limb for the vast majority of participants.