Intrinsic PEEP monitored in the ventilated ARDS patient with a mathematical method.

Under mechanical volume-controlled ventilation, the intensive care patient can develop intrinsic positive end-expiratory pressure (iPEEP); that is, the passive expiration is terminated by the following inspiration before the alveolar pressure comes to its physical equilibrium value. We present a mathematical method to estimate this alveolar dynamic iPEEP breath by breath, without the need of a maneuver. We tested it in paralyzed patients ventilated for adult respiratory distress syndrome after multiple trauma and/or sepsis, and we compared the results obtained with the new mathematical method with those from the occlusion method introduced by Pepe and Marini. The results agreed well (median difference of 0.8 mbar in 201 investigations in 12 patients). However, the mathematically determined values, representing dynamic iPEEP, are systematically slightly smaller than those measured by the occlusion maneuver. A variation of expiratory time suggests that this difference might be due to mechanical time-constant inhomogeneity, viscoelastic processes, or other mechanisms showing time dependence.     

Hydrophobic surfaces of tubulin probed by time-resolved and steady-state fluorescence of nile red

Binding of Nile Red to tubulin enhances and blue-shifts fluorescence emission to about 623 nm with a "shoulder" around 665 nm. Binding is reversible and saturable with an apparent Kd of approximately 0.6 microM. Nile Red does not alter tubulin polymerization, and polymerization in 2-(N-morpholino)ethanesulfonic acid (Mes) buffer does not alter the spectrum of the Nile Red-tubulin complex. In contrast, polymerization in glutamate buffer results in a red shift, reduction of intensity, and a decrease in lifetime, suggesting an increase in "polarity" of the binding environment. Lifetimes of 4.5 and 0.6 ns fluorescence in Mes buffer are associated with the 623-nm peak and the 665-nm shoulder, respectively. Indirect excitation spectra for these components are distinct and the 4.5-ns component exhibits tryptophan to Nile Red energy transfer. Acrylamide quenching yields linear Stern-Volmer plots with unchanged lifetimes, indicating static quenching. Apparent quenching constants are wavelength-dependent; global analysis reveals a quenchable component corresponding to the 4.5 ns component and an "unquenchable" component superposing the 0.6-ns spectrum. Analysis of anisotropy decay required an "associative" model which yielded rotational correlation times of greater than 50 ns for the 4.5-ns lifetime and 0.3 ns for the 0.6-ns lifetime. Dilution of tubulin in Mes results in an apparent red shift of emission without lifetime changes, due only to loss of the 623-nm component. These data are reconciled in terms of a model with two binding sites on the tubulin dimer. The more "nonpolar" site is located in a region of subunit-subunit contact which accounts for the fluorescence changes upon dilution; this permits estimation of a subunit dissociation constant of 1 microM.     

Cleavage of spermidine as the first step in deoxyhypusine synthesis. The role of NAD

The biosynthesis of deoxyhypusine (N-(4-aminobutyl)lysine) occurs by the transfer of the 4-aminobutyl moiety of spermidine to a specific lysine residue in a precursor of eukaryotic translation initiation factor 4D (eIF-4D). Deoxyhypusine synthase, the enzyme that catalyzes this reaction, was purified approximately 700-fold from rat testis. The Km values for the substrates, spermidine, the eIF-4-D precursor protein, and NAD+, were estimated as approximately 1, 0.08, and 30 microM, respectively. After incubation of partially purified enzyme with [1,8-3H]spermidine, NAD+, and the eIF-4D precursor, equal amounts of radioactivity were found in free 1,3-diaminopropane and in protein-bound deoxyhypusine. However, when the protein substrate (eIF-4D precursor) was omitted, radioactivity was found in 1,3-diaminopropane and in delta 1-pyrroline in nearly equal quantities, providing evidence that the cleavage of spermidine occurs, albeit at a slower rate, in the absence of the eIF-4D precursor. That NAD+, which is required for this reaction, functions as the hydrogen acceptor was demonstrated by the fact that radioactivity from spermidine labeled with 3H at position 5 is found in NADH as well as in delta 1-pyrroline. Transfer of this hydrogen from spermidine to the re face of the nicotinamide ring of NAD+, as determined by the use of dehydrogenases of known stereospecificity, defines the first step of deoxyhypusine synthesis as a pro-R, or A, stereospecific dehydrogenation. Based on these findings, an enzyme mechanism involving imine intermediate formation is proposed.     

Transport of particulate organic material between salt marsh and estuary

Summary The macrophyte production and the transport of particulate organic matter between march and adjacent estuary have been investigated for a 30 ha salt marsh along the Oosterschelde estuary, The Netherlands.The primary production of macrophytes, measured with Smalley's method, was 837–1030 g dry organic matter.m^–2.year^–1. Measurements of amounts of particulate organic matter transported through one of the main tidal creeks in the salt march resulted in a net import. On average 31% of the material brought in by the flood settled in the marsh. The majority of this material is smaller than 63 m. On the other hand large floating material is exported during storm tides, although the quantity seems to be smaller than that of the suspended material imported.The differences between various marshes with regard to export and import of organic matter are explained in terms of marsh level, primary production, turbulent diffusion, sinking and resuspension of particulate matter and biotic transformations.     

Tissue microenvironment and the genetic control of hair pigment patterns in mice

This study was conducted to assess microenvironmental variability within integumental tissue of genetically identical mice with respect to a specific cellular response: cyclic synthesis of yellow and black pigment by hair bulb melanocytes. Crosses were performed within and between inbred strains of mice that were isogenic with the exception of a single gene substitution at the agouti locus. Agouti locus genes included the A^vy, A^w, A, a^td, a^t, a^x, a^m, and a alleles. The pigment patterns of dorsal, flank, and ventral hairs of the first and third hair generations and of hairs growing in special integumentary areas such as the pinna, tail, and hind foot were studied. It was found that the amount of yellow pigment synthesized by hair bulb melanocytes within genetically identical mice is both agedependent and conditioned by the integumentary environment. Furthermore, the special integumentary regions produce hairs with a variety of pigment patterns in which the distribution and relative amounts of black and yellow pigments do not necessarily conform to dominance relationships expected among agouti locus alleles as judged by their effects on the pigmentation of the dorsal pelage. We conclude that within genetically uniform integumental tissues, microenvironmental differences occur and are reflected as alterations in the metabolic pattern of differentiated cells.     

The formation of carbon monoxide during peroxidation of microsomal lipids

The evolution of carbon monoxide during lipid peroxidation has been demonstrated in microsomal membranes. The formation of carbon monoxide was dependent on the peroxidation process, but independent of the initiators (NADPH-ADP x Fe(+3) or Ascorbate-Fe(+3)) used. Contrary to published results, the carbon monoxide does not result from heme catabolism. Carbon monoxide was generated during the peroxidation of isolated phospholipids, indicating that carbon monoxide may form directly during the peroxidative degradation of unsaturated fatty acids.     

Mapping of neurons in the gravity receptor system of the octopus statocyst by iontophoretic cobalt staining

Summary The presence of uni-, bi- and multipolar neurons beneath the hair cell epithelium of the Octopus gravity receptor system has been demonstrated by iontophoretic cobalt staining. Counts give an average number of 1,940 neurons per macula. Whether the hair cells are primary of secondary sensory cells is discussed.This work was supported by grant Wo 160/3 of the Deutsche Forschungsgemeinschaft (DFG) to H.G.W. Thanks are due to the Director and staff of the Zoological Station in Naples for their hospitality and help     

The induction of chromatid deletions in accord with the breakage-and-reunion hypothesis.

In the present experiments it has been possible to study large numbers of X-ray induced chromatid deletions, or breads, in Chinese hamster chromosomes and to discern whether or not a sister chromatid exchange also occurs at the point of breadage. Chromatid deletions are only infrequently associated with a sister chromatid exchange. This is contrary to the expectations derived from the exchange hypothesis of Revell. Pn the basis of this hypothesis, in which chromatid deletions are considered to be incomplete exchanges that occur in the necks of little loops in the chromosomes, 40% of the chromatid breaks are expected to be associated with sister chromatid exchanges. The present data are in accord with the conclusions drawn from the earlier autoradiographic experiments of HEDDLE AND BODYCOTE, and show that chromatide breaks can be accounted for on the basis of the breakage-and reunion hypothesis, with the majority being simple breaks and some being incomplete exchanges between two such breaks.     

Acentrosomal spindle assembly and maintenance in Caenorhabditis elegans oocytes requires a kinesin-12 nonmotor microtubule interaction domain

During the meiotic divisions in oocytes, microtubules are sorted and organized by motor proteins to generate a bipolar spindle in the absence of centrosomes. In most organisms, kinesin-5 family members crosslink and slide microtubules to generate outward force that promotes acentrosomal spindle bipolarity. However, the mechanistic basis for how other kinesin families act on acentrosomal spindles has not been explored. We investigated this question in Caenorhabditis elegans oocytes, where kinesin-5 is not required to generate outward force and the kinesin-12 family motor KLP-18 instead performs this function. Here we use a combination of in vitro biochemical assays and in vivo mutant analysis to provide insight into the mechanism by which KLP-18 promotes acentrosomal spindle assembly. We identify a microtubule binding site on the C-terminal stalk of KLP-18 and demonstrate that a direct interaction between the KLP-18 stalk and its adaptor protein MESP-1 activates nonmotor microtubule binding. We also provide evidence that this C-terminal domain is required for KLP-18 activity during spindle assembly and show that KLP-18 is continuously required to maintain spindle bipolarity. This study thus provides new insight into the construction and maintenance of the oocyte acentrosomal spindle as well as into kinesin-12 mechanism and regulation.     

若尔盖人-狼冲突现状与管理研究

大中型食肉动物肇事事件导致人类与野生动物关系恶化,给生物多样性保护工作带来巨大的挑战。若尔盖湿地是我国三大湿地之一,湿地、草原分布广泛,生物多样性丰富,畜牧业发达,但近年来狼(Canis lupus)捕杀牲畜的肇事事件时有发生。为了解若尔盖野生狼肇事件的空间分布以及牧民对人-狼冲突管理的看法,本研究于2022年对若尔盖县13个乡镇83个行政村进行走访调查。结果表明：(1)多数受访者(66.0%)认为在过去5年内,若尔盖县野生狼数量有所增加;(2)狼肇事事件具有明显的空间分异性,最严重的是包座乡。包座乡临近山区,该区域牧场面积广阔、牧民饲养牲畜数量多等原因导致该镇发生狼肇事事件较多;(3)对于狼肇事,绝大多数牧民(85.0%)更希望采取经济补偿或者驱赶措施,只有少数牧民(9.4%)希望采取捕杀的措施;(4)影响牧民对狼肇事管理措施的偏好因子中,受教育程度、年龄、民族以及被杀牲畜数量有显著影响。建议加强狼种群监测管理,采取措施减少狼捕杀牲畜,优化补偿机制,缓解当地牧民与狼之间的矛盾。本研究为当前若尔盖县野生动物保护和管理决策提供了依据,对其他地区大型食肉动物与当地居民冲突管理具有借鉴意义。