Ketogenic regulation by certain metabolites in rumen epithelium

In experiments with rumen epithelium incubated in vitro in the presence of butyrate, the ketogenic effect of glucose was shared by epimeric monosaccharides but not by non-metabolizable analogues. 14C from glucose was not incorporated into ketone bodies. Malate increased ketogenesis from butyrate and decreased its oxidation, pyruvate and NH4+ had the opposite effect, and malonate inhibited both processes. The ketogenic effect of glucose was also effective with isovalerate maintaining the high proportion of acetoacetate which is characteristic of this substrate. Rumen epithelium transformed added acetoacetate into 3-hydroxybutyrate. It is concluded that reducing equivalents produced from glucose and other metabolizable substrates are responsible regulators of ketogenesis from butyrate. The results are discussed in view of the functional role of ruminal ketogenesis.     

Feeding of Sagitta enflata and vertical distribution of chaetognaths in relation to low oxygen concentrations

Zooplankton samples were collected in Mejillones Bay, northernChile (23°00'15'S, 70°26'43'W ). Sampling was conductedat 4 h intervals, for 24 h during three seasons, austral spring(October 2000), summer ( January 2001) and winter (August 2001)at three different strata (0–25, 25–50 and 50–100m). Five species of chaetognaths were collected. Sagitta enflatawas the most abundant species, representing up to 65% of allchaetognaths in total numbers, followed by Sagitta bierii, makingup 34% of the total abundance of chaetognaths. S. enflata wasdistributed mainly above the Oxygen Minimum Zone, while S. bieriiremained below this zone. Feeding rates were relatively constantwithin the upper layer (0–25 m depth), for each samplingdate, averaging 1.2 prey S. enflata day^–1, and decreasingwith depth. Gut content analyses demonstrated that predationwas principally focused on small copepods (<1500 µm),with greatest feeding activity occurring at night. The dailypredation impact on the total standing stock of small copepodsvaried seasonally between 6% in spring and 0.4% in winter. Thispercentage may represent a negligible impact on the entire copepodcommunity, but it is relevant at the species or genus level,since S. enflata removed more than 20% of the standing stockof Centropages brachiatus and Corycaeus sp. Thus, during someperiods of the year, chaetognaths may strongly influence theabundance and size distribution of copepods in coastal upwellingecosystems.     

L1 (LINE-1) retrotransposable elements provide a "fossil" record of the phylogenetic history of murid rodents

The single most difficult problem in phylogenetic analysis is decidingwhether a shared taxonomic character is due to common ancestry or one thatappeared independently due to convergence, parallelism, or reversion to anancestral state. Mammalian L1 retrotransposons undergo periodicamplifications in which multiple copies of the elements are interspersed inthe genome. Because these elements apparently are transmitted only byinheritance and are retained in the genome, a shared L1 amplification eventcan only be an inherited ancestral character. We propose that L1amplification events can be an excellent tool for analyzing mammalianevolution and demonstrate here how we addressed several refractory problemsin rodent systematics using L1 DNA as a taxonomic character.     

Metabolism of D(-)lactic acid in rats given high intragastral doses

In rats given D[u-14C]-labelled DL-lactate with 3.8-13.4 mmol D-lactate per kg 0.75 by stomach tube, the exhalation of CO2 produced from and the renal excretion of D-lactate and metabolites were measured. Exhalation of D-lactate-C accounted for 45-30% of the dosage given with a decreasing proportion at higher doses. The renal excretion of D-lactate averaged 0.9% and that of metabolites from D-lactate 2.4% of the doses given. The fraction of unrecovered D-lactate accounted for about 54-68% of the doses given and increased with doses. The time course of D-lactate oxidation indicated a maximum rate of about 1.5 mmol C per kg 0.75 in 1 hr which was reached at 1 hr after infusion at the earliest and extended up to 8 hr if high doses were given.     

Some model based considerations on observing generation times for communicable diseases

The generation time of an infectious disease is usually defined as the time from the moment one person becomes infected until that person infects another person. The concept is similar to “generation gap” in demography, with new infections replacing births in a population. Originally applied to diseases such as measles where at least the first generations are clearly discernible, the concept has recently been extended to other diseases, such as influenza, where time order of infections is usually much less apparent.By formulating the relevant statistical questions within a simple yet basic mathematical model for infection spread, it is possible to derive theoretical properties of observations in various situations e.g. in “isolation”, in households, or during large outbreaks. In each case, it is shown that the sampling distribution of observations depends on a number of factors, usually not considered in the literature and that must be taken into account in order to achieve unbiased inference about the generation time distribution. Some implications of these findings for statistical inference methods in epidemic spread models are discussed.     

The role of the chaetognath Sagitta gazellae in the vertical carbon flux of the Southern Ocean

Chaetognaths are among the most abundant predators in the Southern Ocean and are potentially important components in the biological carbon pump due to the production of large, fast-sinking fecal pellets. In situ S. gazellae abundance, fecal pellet production, sinking rates, carbon content, and vertical carbon fluxes were measured at the Lazarev Sea between December 2005 and January 2006. Sagitta gazellae produce fecal pellets that sink at speeds of 33–600 m day⁻¹ and have carbon contents of 0.01–0.8 mg C pellet⁻¹. Vertical carbon flux was later compared with the total carbon flux measured at 360 m depth at the study area. Rough estimates using published seasonal abundance of S. gazellae indicate that, at 360 m depth in the Lazarev Sea, this specie may contribute 12 and 5% of the total vertical carbon flux in winter (ice-covered) and summer (ice-free), respectively. Thus, the role of chaetognaths in the downward transport of organic matter may be far more important than previously thought.     

Production of alkaline protease with Bacillus licheniformis in a controlled fed-batch process

Summary A production method for alkaline serine protease with Bacillus licheniformis in a synthetic medium was developed. Employing closed-loop control of oxygen, nitrogen and carbon source the pO₂ was held at 5%, the ammonium concentration kept below 1 mM and the glycerol concentration was maintained between 20 and 100 mM. Protease production was monitored by flow injection analysis. Thus, in a fed-batch procedure production could be increased 4.6-fold in comparison to an uncontrolled batch process.Offprint requests to: G. Bierbaum     

Incidence of symptoms and AIDS in 146 Swedish haemophiliacs and blood transfusion recipients infected with human immunodeficiency virus.

The times from infection with the human immuno-deficiency virus (HIV) to the onset of the first clinical symptom and the development of AIDS were studied prospectively in 98 haemophiliacs and 48 blood transfusion recipients infected with the virus. Patients were followed up for a median of 61 months after infection, the dates of infection being either known exactly or estimated from the interval between the last negative and first positive HIV antibody test result. The rate of progression to AIDS was significantly higher for the transfusion recipients than for the haemophiliacs. The difference in time to the occurrence of the first clinical symptom was less pronounced between the two groups, though pointing in the same direction. The results suggest that on average roughly half of all patients positive for HIV will develop some clinical sign or symptom within five to six years after infection.