Methods for detecting local intestinal ischemic anaerobic metabolic acidosis by PCO2

Rozenfeld, Ranna A., Michael K. Dishart, Tor IngeTønnessen, and Robert Schlichtig. Methods for detecting localintestinal ischemic anaerobic metabolic acidosis byPCO₂. J. Appl. Physiol. 81(4): 1834-1842, 1996.Gut ischemia isoften assessed by computing an imaginary tissue interstitial pH fromarterial plasma HCO₃ and thePCO₂ in a saline-filled balloontonometer after equilibration with tissuePCO₂ (Pti_CO2).Pti_CO2 mayalternatively be assumed equal to venous PCO₂(Pv_CO2) in that region of gut. The ideais that as blood flow decreases, gutPti_CO2 andPv_CO2 will increase to the maximumaerobic value, i.e., maximum respiratoryPv_CO2(Pv_CO2 rmax). Above a "critical" anaerobic threshold, lactate(La) generation, bytitration of tissue HCO₃, should raisePti_CO2abovePv_CO2 rmax.During progressive selective whole intestinal flow reduction insix pentobarbital-anesthetized pigs, we usedPCO₂ electrodes to test thehypotheses that criticalPti_CO2is achieved earlier in mucosa than in serosa and thatPv_CO2 rmax,computed using an in vitro model, predicts criticalPti_CO2. Wedefined criticalPti_CO2 as theinflection ofPti_CO2-Pv_CO2vs. O₂ delivery(O₂)plots. CriticalO₂for O₂ uptake was 12.55 ± 2 ml ^· kg^{1 ·} min¹.Critical Pti_CO2 for mucosaand serosa was achieved at similar whole intestineO₂(13.90 ± 5 and 13.36 ± 5 ml ^· kg^{1 ·} min¹,P = NS). CriticalPti_CO2 (129 ± 24 and 96 ± 21 Torr) exceeded Pv_CO2 rmax(62 ± 3 Torr). During ischemia,La excretion into portalvenous blood was matched by K⁺excretion, causing Pv_CO2 to increaseonly slightly, despitePti_CO2 risingto 380 ± 46 (mucosa) and 280 ± 38 (serosa) Torr. These resultssuggest that mucosa and serosa become dysoxic simultaneously, thatischemic dysoxic gut is essentially unperfused, and that in vitropredictedPv_CO2 rmaxunderestimates criticalPti_CO2.

     

Urinary Pyrophosphate in Normal Subjects and in Stone Formers

The urinary excretion of inorganic pyrophosphate was determined in nine normal subjects and also in eight patients with recurrent calcium-containing renal stones during varied levels of phosphate intake. The excretion of pyrophosphate and orthophosphate is virtually the same in the two groups at all levels of phosphate intake. It appears unlikely that a consistently reduced urinary excretion of pyrophosphate is a factor in the formation of urinary calculi. Pyrophosphate excretion rose and calcium excretion fell with increasing phosphate intake; this might be expected to have a beneficial effect in patients with recurrent calcium stones.     

Zur Herkunft und Struktur der Plasmafilamente in Assimilatleitbahnen

Zusammenfassung Für die den Stoffleitbahnen eigenen fädigen Strukturen wird die Bezeichnung Plasmafilamente vorgeschlagen.Wie erste Untersuchungen zur Differenzierung der Siebelemente zeigen, entstehen die Plasmafilamente bei Dioscorea direkt im Cytoplasma. Ihre Verbreitungsweise und ihr Feinbau in frühesten Differenzierungsstadien lassen vermuten, daß sie unmittelbar aus dem Grundplasma hervorgehen. Das Netzwerk der Plasmafilamente ist stets durchsetzt von Elementen des ER und zu keiner Zeit von einer Membran umgeben.Das Einzelfilament hat bei Dioscorea, Primula, Cuscuta und Cucumis eine unbestimmte Länge und einen Durchmesser von 120–150 Å. Im Querschnitt zeigt es den Aufbau aus einem osmiophilen Ring mit einem elektronenlichten Binnenraum. Dem entsprechen in der Längsaufsicht zwei äußere kontrastreiche und eine innere kontrastarme Schicht.Der Aussagewert der Filamentfeinstruktur wird unter Berücksichtigung ähnlicher Strukturen und ihrer Bedeutungen in der tierischen und pflanzlichen Zelle diskutiert.

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On the plasmatic filaments in assimilate conducting cells, their development and fine structure

Summary Taking into account the literature on the so-called sieve-tube slime (mictoplasm, slime strands) and regarding its fine structure more in detail the term plasmatic filament (Plasmafilament) is proposed and will be used in this paper to characterize the individual exceedingly fine subunit of the plasmatic network (or slime) in sieve elements. Up to now plasmatic filaments have mostly been erroneously called fibrils. The dimension of a fibrill has now been defined anew and differentiated from its subunit plasmatic filament.In the first part of these investigations some aspects of the development of plasmatic filaments and their spreading over the total lumen of Dioscorea sieve elements will be reported.Previous to the first appearance of filaments the later sieve element abounds in plasmatic components, the groundplasm being extremely rich in ribosomes (Fig. 1). The difference between young sieve elements and the neighbouring parenchyma cells is nearly imperceptible apart from a slight variation in ribosome density. Plastids are very useful in distinguishing these two cell types from each other. The development of osmiophilic inclusions that characterize sieve-element plastids in Dioscorea has already been initiated in these very young cells.The earliest stages in the formation of plasmatic filaments that up to now have been revealed in Dioscorea show masses of filaments, some short and granular in appearance (Fig. 2: *), some already elngated and filamentous (Fig. 2: F). After expanding over the entire cell those filaments still look like having their origin directly in groundplasm (Fig. 5). Elements of the ER-system and many ribosomes cross the plasmatic filaments during all developmental stages of their network, which is at no time surrounded by any membrane.In sieve elements of Dioscorea, Primula, Cuscuta and Cucumis our investigations furthermore yielded some detail on the filament substructure. A cross-sectioned plasmatic filament is composed of an osmiophilic outer ring with a light centre (Fig. 11) corresponding in a longitudinal view to two deeply contrasted outer layers and an inner one without any contrast (Fig. 8). An individual filament has an overall diameter of 120–150 Å and an up to now indeterminable length that exceeds at least several microns.The real nature of these fine structures will be discussed in relation to similar structures and their meaning in plant and animal cells.

     

Vinblastine-induced precipitation of phloem proteinsin vitro

Summary Purified proteins from sieve tubes ofCucurbita maxima were precipitated with vinblastine and the precipitates were analyzed with the electron microscope. Filaments (35–40 Å in diameter) and tubular structures (160 Å in width) were observed in negatively stained preparations. The predominant structures of the negatively stained and of the thin sectioned material, however, were membrane-like sheets (100–120 Å in width) which showed the typical unit membrane aspect.Dedicated to Professor Dr. W.Schumacher on his 70th birthday.The investigations were supported by the Deutsche Forschungsgemeinschaft.     

9α-homo-9,11-epoxy-5,13-prostadienoic acid analogues: Specific stable agonist (SQ 26,538) and antagonist (SQ 26,536) of the human platelet thromboxane receptor

A newly synthesized 9α-homo-9,11-epoxy-5,13-prostadienoic acid analogue, SQ 26,536, (8(R)9(S)11(R)12(S)-9α-homo-9,11-epoxy-5(Z), 13(E)-15S-hydroxyprostadienoic acid) inhibited arachidonic acid (AA)-induced platelet aggregation with an I₅₀ value of 1.7 μ . SQ 26,536 did not inhibit prostaglandin (PG) synthetase activity of bovine seminal vesicle microsomes or thromboxane (Tx) synthetase activity of lysed human blood platelets. SQ 26,536 also inhibited platelet aggregation induced by epinephrine (secondary phase), 9,11-azoPGH₂ and collagen but did not inhibit the primary phase of epinephrine-induced aggregation or ADP-induced platelet aggregation. SQ 26,538 (8(R)9(S)11(R)12(S)-9α-homo-9-, 11-epoxy-5(Z),13(E)-15R-hydroxyprostadienoic acid), a 15-epimer of SQ 26,536, induced platelet aggregation with an A₅₀ value of 2.5 μ . SQ 26,536 competitively inhibited SQ 26,538-induced platelet aggregation with a K_i value of 3 μ . Neither indomethacin, a PG synthetase inhibitor, nor SQ 80,338 (1-(3-phenyl-2-propenyl)-1H-imidazole), a Tx synthetase inhibitor, inhibited SQ 26,538- or 9,11-azoPGH₂-induced platelet aggregation. These data indicate that SQ 26,536 and SQ 26,538 are stable antagonist and agonist, respectively, of the human blood platelet thromboxane receptor.     

Mitochondrial redox state as a potential detector of liver dysoxia in vivo

Dysoxia canbe defined as ATP flux decreasing in proportion toO₂ availability with preserved ATPdemand. Hepatic venous -hydroxybutyrate-to-acetoacetate ratio(-OHB/AcAc) estimates liver mitochondrial NADH/NAD and may detectthe onset of dysoxia. During partial dysoxia (as opposed to anoxia),however, flow may be adequate in some liver regions, diluting effluentfrom dysoxic regions, thereby rendering venous -OHB/AcAc unreliable.To address this concern, we estimated tissue ATP whilegradually reducing liver blood flow of swine to zero in a nuclearmagnetic resonance spectrometer. ATP flux decreasing withO₂ availability was taken asO₂ uptake(O₂) decreasing inproportion to O₂ delivery(O₂);and preserved ATP demand was taken as increasingP_i/ATP.O₂, tissueP_i/ATP, and venous -OHB/AcAcwere plotted againstO₂to identify critical inflection points. Tissue dysoxia required meanO₂for the group to be critical for bothO₂ and forP_i/ATP. CriticalO₂values for O₂ andP_i/ATP of 4.07 ± 1.07 and 2.39 ± 1.18 (SE) ml · 100 g¹ · min¹,respectively, were not statistically significantly different but notclearly the same, suggesting the possibility that dysoxia might havecommenced after O₂ begandecreasing, i.e., that there could have been"O₂ conformity." CriticalO₂for venous -OHB/AcAc was 2.44 ± 0.46 ml · 100 g¹ · min¹(P = NS), nearly the same as that forP_i/ATP, supporting venous -OHB/AcAc as a detector of dysoxia. All issues considered, tissue mitochondrial redox state seems to be an appropriate detector ofdysoxia in liver.

     

Carbon stock changes and carbon sequestration potential of Flemish cropland soils

Evaluations of soil organic carbon (SOC) stocks are often based on assigning a carbon density to each one of a number of ecosystems or soil classes considered, using data from soil profiles within these categories. A better approach, in which the use of classification methods by which extrapolation of SOC data to larger areas is avoided, can only be used if enough data are available at a sufficiently small scale. Over 190 000 SOC measurements (0–24 cm) have been made in the Flemish cropland (the Northern part of Belgium) in the 1989–2000 period. These SOC data were grouped into 3‐year periods and as means plus standard deviation per (part of) community (polygons). This large dataset was used to calculate SOC stocks and their evolution with time, without data extrapolation. Using a detailed soil map, larger spatial groups of polygons were created based on soil texture and spatial location. Linear regression analysis showed that in the entire study area, SOC stocks had decreased or at best had remained stable. In total, a yearly decrease of 354 kton OC yr^?1 was calculated, which corresponds with a net CO₂ emission of 1238 kton CO₂ yr^?1. Specific regions with a high carbon sequestration potential were identified, based on SOC losses during the 1989–2000 period and the mean 1999 SOC content, compared to the average SOC content of soils in Flanders with a similar soil texture. When restoring the SOC stocks to their 1990 level, we estimated the carbon sequestration potential of the Flemish cropland soils to be some 300 kton CO₂ yr^?1 at best, which corresponds to a 40‐year restoration period. In conclusion, we can say that in regions where agricultural production is very intense, carbon sequestration in the cropland may make only a very modest contribution to a country's effort to reduce greenhouse gas emissions.     

Rol genes alter hormonal requirements for protoplast growth and modify the expression of an auxin responsive promoter

Summary Growth characteristics of tobacco protoplasts containing rolA linked to its own promoter, or the rolB, or rolC genes of Agrobacterium rhizogenes linked to the Cauliflower Mosaic Virus 35S RNA promoter were compared with those from untransformed plants. RolA protoplasts require auxin and cytokinin for callus formation. Protoplasts overexpressing rolB and C form callus in the absence of exogenously applied auxin and cytokinin, respectively. Long term callus growth requires auxin, but the requirement for cytokinin is not critical. Optimal transient expression of an auxin responsive promoter element occurred at lower external levels of auxin in rolB and rolC protoplasts compared with untransformed protoplasts. Addition of putrescine was required for auxin responsive transient gene expression in rolA protoplasts suggesting that polyamines, or their products affect gene expression in rolA plants.Abbreviations T-DNA transferred DNA - TL-DNA left transferred DNA - NAA naphthalene acetic acid - PEG polyethylene glycol - GUS glucuronidase - CaMV cauliflower mosaic virus