A glycyl radical site in the crystal structure of a class III ribonucleotide reductase

Ribonucleotide reductases catalyze the reduction of ribonucleotides to deoxyribonucleotides. Three classes have been identified, all using free-radical chemistry but based on different cofactors. Classes I and II have been shown to be evolutionarily related, whereas the origin of anaerobic class III has remained elusive. The structure of a class III enzyme suggests a common origin for the three classes but shows differences in the active site that can be understood on the basis of the radical-initiation system and source of reductive electrons, as well as a unique protein glycyl radical site. A possible evolutionary relationship between early deoxyribonucleotide metabolism and primary anaerobic metabolism is suggested.     

Modelling the hydrological regimes in acidified watersheds

Application of a hydrological model to three Canadian watersheds forms part of a verification package to test its accuracy and portability. Agreement of model results with observed data on hydrograph, groundwater flow and snowpack is reasonably good. The model results are consistent with the observed pH and with many of the episodic events that have occurred in these acidified watersheds. Contrasts have also been made on the different calibrated coefficients at several locations in these watersheds. An attempt to relate them to the geology and soil characteristics at the site has led to realistic estimation of the soil contact times.     

Long-term tillage and wheel traffic effects on a poorly drained mollic ochraqualf in northwest Ohio. 1. Soil physical properties, root distribution and grain yield of corn and soybean

Effects of 12 years of 4 tillage systems, were studied on soil bulk density, infiltration rate, penetration resistance, structural stability of aggregates, root length density, moisture release characteristics and grain yield. The objective of this study was to assess long-term effects of tillage methods and guided traffic on soil properties and crop response on a heavy-textured poorly drained soil. Tillage systems included: (A) continuous no-till for 12 years; (B) no-till for 10 years followed by plow-till for 2 years; (C) plow-till for 10 years followed by no-till for 2 years; (D) continuous plow-till for 12 years. Wheel tracks had significant effects on soil physical properties. Soil in the traffic zone (TZ) in no-till treatment had higher bulk density and penetration resistance (PR) for the upper 0–30-cm layer than plow-till treatment. The PR for the surface layer in TZ was 25–46% more than in the row zone (RZ). Mean soil bulk density in the TZ of no-till plots was about 12% more than in the RZ (1.53 vs. 1.36 g cm⁻³). Changeover from no-till to plow-till decreased PR in RZ and TZ by 50–60% while that from plow-till to no-till increased PR by 10–20%. Similar effects were observed in percent aggregation and the mean weight diameter. In no-till treatments both initial and equilibrium infiltration rates were significantly lower in TZ than RZ (27.5 vs. 6.8 cm h⁻¹ initial and 10.0 vs. 1.5 cm h⁻¹ final). There were more macropores (> 2 mm) for the TZ in no-till compared with the plow-till treatments. Fine or micropores were comparatively more numerous in the sub-soil of no-till than plow-till treatments. The median aggregate size (D₅₀) was 6.2, 4.2, 4.8 and 3.5 mm for Treatments A, B, C and D, respectively. Root length density of corn in plow-till plots was significantly more than that in no-till plots for the top 0–20-cm layer. Corn and soybean yields were greater in plow-till than no-till treatments. Grain yields in Treatment D were greater than those in Treatment A by 10% for corn and by 6% for soybean.     

Meiotic Response of In vitro Matured Canine Oocytes under Different Proteins and Heterologous Hormone Supplementation

The impact of TCM‐199 supplemented with different proteins and heterologous hormones on the in vitro maturation (IVM) rate of bitch oocytes was evaluated by nuclear staining under fluorescence microscopy. Oocytes were recovered by slicing of ovaries from bitches presented at various stages of oestrous cycle to ovariohysterectomy. The basic culture medium was TCM‐199 supplemented with 25 mM Hepes/l, with 10% heat‐inactivated oestrous cow serum (ECS), 50 μg/ml gentamicin, 2.2 mg/ml sodium bicarbonate and 22‐μg/ml pyruvic acid, 1.0‐μg/ml oestradiol (E 8875; Sigma), 0.5‐μg/ml follicle‐stimulating hormone (FSH) (Folltropin‐V; Vetrepharm Inc., Ontario, Canada) and 0.03 IU/ml human gonadotropin (hCG) (Profasi HP; Serono, Aubonne, Switzerland). Oocytes were distributed randomly between basic culture medium (control) and the corresponding experimental treatment. Hormone treatments were: oocytes cultured in; (1) medium without FSH, (2) control medium supplemented with 20 μg/ml oestradiol, or (3) medium supplemented with 1 μg/ml human somatotropin (hST; Humatrope, Lilly, Saint Cloud, France). The second experiment consisted of oocytes cultured in medium supplemented with 0.4% (w/v) bovine serum albumin (BSA, fraction V; Gibco Grand Island, NY, USA) instead of ECS, or oocytes cultured in medium with 10% inactivated oestrous bitch serum (EBS) instead of ECS. Oocytes were cultured in 100 μl droplets (up to 25 oocytes per drop) under mineral oil at 37°C in a 100% humidified atmosphere containing 5% CO₂ in air. After 72 h of IVM, the highest rates (p < 0.05) of meiotic resumption were achieved with the 0.4% BSA supplementation. A positive influence on the metaphase II (MII) acquisition rate was observed with hST supplement. Oocytes cultured with 10% EBS supplementation did not develop to the MII stage. The results in this study show that the protein and hormone supplements to TCM‐199 culture medium tested did not promote the final steps of IVM of bitch oocytes.     

Cowdria ruminantium: stability and preservation of the organism

Blood collected in either sodium heparin or disodium edetate vacutainers from febrile goats infected with 4 isolates of Cowdria ruminantium and cryopreserved with 10% dimethyl sulphoxide at -70 degrees C and -196 degrees C was an effective stabilate to initiate heartwater infections in goats. A homogenized pool of whole Amblyomma variegatum ticks in Snyder's buffer, maintained at -196 degrees C, was used to infect a goat with C. ruminantium. Liver and spleen collected from Swiss mice infected with the Kwanyanga isolate of C. ruminantium were homogenized in Snyder's buffer, maintained at -196 degrees C and were used to initiate infections in mice. Fresh blood collected from febrile goats and maintained at 4 degrees C for as long as 72 h was infectious to mice. Neutrophils separated from blood of C. ruminantium infected goats and maintained in modified RPMI medium at 37 degrees C for 68 h were infectious for a goat. Similarly neutrophils from a 2nd infected goat maintained for 96 h at 37 degrees C were infectious for mice.     

Factors influencing the quantity and quality of colostrum in the cow

It is well established that the survival of newborn calves is dependent on their absorbing adequate amounts of maternal immunoglobulin from colostrum. The level of immunity is influenced by the time of feeding after birth and the quantity and quality of the available colostrum. Several factors affect either the quantity or quality of colostrum. The yield of colostrum varies with breed but perhaps more significantly with age, heifers giving much less colostrum than cows. Poor nutrition during winter months causes a marked drop in colostral quantity and often in the early spring a large number of suckler cows give insufficient colostrum to protect their calves from disease. Colostral quality in terms of immunoglobulin concentration is unaffected by yield but varies considerably between individual cows.Much of the present evidence is equivocal and there are many subjects for further research. A detailed study should be carried out, particularly in beef cattle, to establish which breed has the highest yield of colostrum. More research should be directed to establish the minimum plane of nutrition necessary to maintain colostrum quantity and quality.

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Kurzfassung Die Tatsache, dass die Lebensfähigkeit neugeborener Kälber von der Aufnahme von genügend mütterlichen Immunoglobinen aus dem Kolostrum abhängt, ist wohlbekannt. Das Immunitätsniveau wird von der Säugezeit nach der Geburt und von der Menge und Qualität des verfügbaren Kolostrums beeinflusst. Mehrere Faktoren wirken entweder auf die Menge oder die Qualität des Kolostrums ein. Die Menge variiert mit der Rasse, aber vielleicht noch wichtiger mit dem Alter, da Färsen viel weniger Kolostrum geben als Kühe. Unzureichende Fütterung während der Wintermonate verursacht einen starken Fall der Kolostralleistung; in den ersten Frühjahrstagen gibt eine grosse Anzahl von Ammenkühen oft nicht genug Kolostrum, um die Widerstandsfähigkeit ihrer Kälber gegen Krankheiten zu sichern. Im Sinne von Immunoglobulinkonzentration wird die Qualität des Kolostrums nicht von seiner Menge beeinflusst, doch variiert sie beträchtlich zwischen einzelnen Kühen.Viele gegenwärtige Resultate sind zweideutig und viele Probleme müssen noch bearbeitet werden. Es bedarf auch einer vertieften Studie, insbesondere bei Fleischrindern, um festzustellen, welche Rasse die höchste Kolostralleistung hat. Man müsste auch Untersuchungen anstellen, um das minimale Fütterungsniveau fur die Erhaltung der Qualität und der Menge des Kolostrums zu ermitteln.

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Resume Le fait que la survie des veaux nouveau-nés dépend de leur pouvoir d'absorber une quantité adéquate d'immoglobulines maternelles par le colostrum, est bien établi. Le niveau d'immunité est influencé par le temps de la tétée après la naissance, et par la quantité ainsi que la qualité du colostrum disponible. La production de colostrum varie, selon la race, mais peut-être l'âge est plus significatif, puisque les génisses donnent beaucoup moins de colostrum que les vaches. Une alimentation de qualité inférieure pendant les mois d'hiver cause une baisse importante de la quantité de colostrum, et souvent, beaucoup de vaches nourrices donnent trop peu de colostrum, aux premiers jours du printemps, pour protéger leurs veaux contre les maladies. La qualité du colostrum n'est pas effectée par le niveau de production, en termes de concentration d'immunoglobulines, mais elle varie considérablement entre les individus.L'évidence actuelle est équivoque, et beaucoup de sujets demandent encore des recherches. Il faudrait une étude approfondie pour établir la race à production de colostrum la plus élevée, surtout chez les bovins de boucherie. Il faudrait aussi des recherches plus poussées pour établir le niveau minimum nutritionnel nécéssaire pour maintenir la quantité et la qualité du colostrum.

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Riassunto E'un fatto ben accertato che la sopravvivenza dei vitelli neonati dipende dall'assorbimento di una adeguata quantità di immunoglobuline materne attraverso il colostro. Il livello immunitario è a sua volta influenzato dal momento in cui si ha la poppata dopo la nascita e dalla quantità e qualità del colostro fornito. Svariati fattori influiscono sia sulla quantità che sulla qualità del colostro. La produzione di questo varia infatti a seconda della razza, ma varia forse anche in misura maggiore in rapporto all' età; le giovenche, infatti, producono molto meno colostro delle bovine di età superiore. Un apporto alimentare insufficiente durante i mesi invernali causa una notevole caduta della quantità di colostro e spasso, all'inizio della primavera, un gran numero di bovine in lattazione ne producono in quantità non sufficiente ai fini della protezione dei vitelli contro le malattie. La qualità del colostro in termini di concentrazione di immunoglobuline non viene influenzata dal livello di produzione, ma varia in modo considerevole da bovina a bovina.Gran parte dei dati oggi disponibili è oggetto di dubbio, ed esistono molti campi da sottoporre ad ulteriori indagini. Sarebbe necessario eseguire uno studio dettagliato, specie nelle bovine da carne, per stabilire quale razza ha la più alta produzione di colostro. Altre ricerche andrebbero indirizzate a stabilire il valore minimo alimentare necessario per il mantenimento del livello quanti-qualitativo del colostro.

     

High-Frequency Jet Ventilation in Anesthetized, Paralyzed Dogs and Cats Via Transtracheal and and Endotracheal Tube Routes

The ability of the SAV 6 high-frequency jet ventilator to effectively ventilate three anesthetized, paralyzed cats (3.2–4.2 kg), two small dogs (7.2 and 10.0 kg), six medium-sized dogs (20.5–25.0 kg), and three large dogs (36.0–43.0 kg) via a 14-gauge (dogs) or a 16-gauge (cats) catheter placed percutaneously into the trachea via the cricothyroid membrane or into a preplaced endotracheal tube was evaluated. The lowest driving pressure within the range of 0.25 to 2.0 kg/cm² (1 kg/cm²= 14.2 psi) and the highest cycle rate within the range of 60 to 240 per minute that would generate a PaCO₂ of 30 ± 3 mm Hg were determined.
All animals could be ventilated to a PaC0₂ of 30 ± 3 mm Hg by the endotracheal tube and transtracheal route, except the largest dogs, which couid be ventilated to an average PaC0₂ of 36 mm Hg by the transtracheal route. The transtracheal route consistently required higher driving pressures and lower cycle rates than did the endotracheal tube route. Cats could be ventilated with a driving pressure of 0.25 kg/cm²; small dogs could be ventilated with 0.5 to 1.0 kg/cm₂; medium-sized dogs with 1.0 to 1.5 kg/cm²; and large dogs with 1.5 to 2.0 kg/cm².
The SAV 6 high-frequency jet ventilator can effectively ventilate cats and dogs (7.2–43.0 kg) via a transtracheal catheter and an endotracheal tube.     

The development of Cowdria ruminantium in neutrophils

The sequential development of C. ruminantium (Kwanyanga and Kümm isolates) was followed in caprine leukocyte cultures by light microscopy, direct immunofluorescent microscopy (DFA), indirect immunoflourescent microscopy (IFA) and transmission electron microscopy (TEM). During the febrile response, one to several small cocci, large ring forms or rods were observed in neutrophils in blood smears and cytopreparations of neutrophil fractions using Diff Quik stain, Giemsa stain, DFA and TEM. One to several C. ruminantium colonies were seen in up to 35% of neutrophils maintained in vitro for 18 h to 5 days. The organisms were located in neutrophil phagosomes by TEM and were enveloped by two trilamellar unit membranes. Initially, C. ruminantium was tightly enclosed within phagosomes. At 20 h of incubation, organisms were frequently observed undergoing binary fission within enlarged phagosomal vacuoles. At later time periods, neutrophils harboured fully formed colonies (morula) containing numerous organisms. An occasional C. ruminantium-infected macrophage (Kümm isolate), and an occasional infected eosinophil (Kümm and Kwanyanga isolate) were found.     

Persistence of colonies of Anaplasma marginale in overwintering Dermacentor variabilis

Dermacentor variabilis were infected as nymphs with Anaplasma marginale by allowing the ticks to feed on a single infected donor calf. Two weeks after molting to the adult stage, the ticks were allotted into 1 of 3 groups and were allowed to overwinter at room temperature (25 C) in the laboratory (group 1), cold storage (4.5 C) in the laboratory (group 2), or outdoors in leaf litter (group 3). Persistence of A marginale was assessed by determining density of colonies (number of colonies/0.1 mm2 of gut tissue examined) in tick gut specimens at 3, 5, 7, 9, and 12 months after molting to the adult stage. Colonies of A marginale were found in all groups at every density evaluation period. Highest colony densities were observed uniformly in specimens collected at month 7 (May); densities decreased at month 9 and were lowest at month 12. Statistical analysis indicated that ticks subjected to cold storage and to outdoor conditions had similar colony densities of A marginale; the density curve in these 2 groups indicated significant quadratic effects over time, with peak densities in May. Mean colony density in ticks kept at room temperature fit a different quadratic equation. The morphologic data indicated that A marginale overwinters in Dermacentor variabilis, and that increasing numbers of organisms are found from January to May.     

Observations on the Ultrastructural Appearance of Endocrine Cells of the Small Intestine of the Calf

The endocrine cells of the small intestine of neonatal calves are described, with the aid of transmission and scanning electron microscopy. It is demonstrated that endocrine cells have long microvilli, and are organized into two populations, similar to those of other species.