Mass–length ratio of fibrin fibers from gel permeation and light scattering

Mass–length ratios of fibers in fibrin gels were obtained from measurements of the angular dependence of the intensity of light scattered by dilute gels and from the permeability of more concentrated gels. The permeability was determined by measuring the forced flow of buffer through a short column of gel held in a glass tube. The results obtained with the two methods are consistent. At high pH and high ionic strength the mass–length ratio is found to be that calculated for a protofibril, i.e., a double strand of fibrin molecules laid end to end at a separation of 450 Å. This same value is found under conditions where the polymerized fibrin is not gelled (pH 10.25) and where it is just gelled (pH 10.0). At pH 7.4, ionic strength 0.35, the fibers are found to have a higher mass–length ratio, the average fiber consisting of some three protofibrils associated laterally. At pH 7.4 and low ionic strength (0.10 M) the fibers are up to a hundred times more massive.     

Root length and diameter measurement using NIH Image: application of the line-intercept principle for diameter estimation

The objective of this study was to develop an image analysis algorithm for estimating the length versus diameter distribution of washed root samples. Image analysis was performed using a Macintosh computer and the public domain NIH Image program. After an appropriate binary image of roots was obtained, the image was processed to get the thinned image to calculate the length of the roots. The edge pixel of the binary image was then deleted and root length was calculated again. This `edge deletion–length calculation' cycle was repeated until no root pixel was left in the image. Repeated edge deletion removed one pixel layer from around the periphery of root objects in each iteration. The number of edge deletions, which is equivalent to the intercept length, can be used to estimate the root diameter. We used the vertical or horizontal intercept length, whichever was shorter. The accuracy of diameter estimation due to orientation of objects varied from 89.1 to 126.0%. Branching root systems consist of several orders of laterals, and as the root branches to a higher order, the diameter of the roots becomes smaller. Therefore, edge deletions eliminate sequentially from the highest order roots, which have the smallest diameter, to the lowest order roots, which have the widest diameter. Thus, the length and diameter of each root order can be calculated by the proposed method. For verification, images of copper wire of 0.23, 0.50, and 1.0 mm diameter were analyzed. The results showed reasonable agreement with the expected distribution of length versus diameter for randomly oriented objects, and consequently the wire length of each diameter could be estimated. The proposed method was tested for primary and secondary roots of water-cultured rice (Oryza sativa L.), and it was proven that the method can provide accurate length and diameter measurements for each root order.     

Accurate root length and diameter measurement using NIH Image: use of Pythagorean distance for diameter estimation

This report describes an image analysis algorithm to estimate the length versus diameter of washed root samples accurately. Image analysis was performed using a Macintosh computer and the public domain NIH Image program. The binary image of the roots was processed to get the thinned image to calculate the length of the roots. The pixels of the root in a binary image were then stripped off from around the periphery based on the pixel's Pythagorean distance from the nearest background pixel. The length of the remaining root in each stripping off process was calculated after the image was thinned. Images (300 dpi) of copper wire of 0.23, 0.5, 1.0 mm diameter were analyzed for verification of the usefulness of the procedure. The results showed that more than 93% of the wires in each diameter wire were calculated to be in diameter classes including the true diameter and its adjoining classes: 93.6% of the wires of 0.23 mm diameter appeared in the 0.098–0.38 mm diameter classes, 96.19% of the wires of 0.5 mm diameter appeared in the 0.38–0.61 mm diameter classes, and 96.17% of the wires of 1 mm diameter appeared in the 0.85–1.08 mm diameter classes. The proposed method was tested for primary and secondary roots of water-cultured rice (Oryza sativa L.) and it was proven that the method could provide accurate length and diameter measurements for each root order. In addition, it was found that the method could provide the lengths of the thick primary, thin primary, and secondary roots. The effectiveness of applying sharpening for the grayscale image before making the binary image is also discussed.     

Utilization of mass–energy balance regularities in the analysis of continuous-culture data

Material and energy balances for continuous-culture processes are described based on the facts that the heat of reaction per electron transferred to oxygen for a wide variety of organic molecules, the number of available electrons per carbon atom in biomass, and the weight fraction carbon in biomass are relatively constant. Energy requirements for growth and maintenance are investigated and related to the biomass energetic yield. The consistency of experimental data is examined using material and energy balances and the regularities identified above. When extracellular products are absent, the consistency of yield models containing separate terms for growth and maintenance may be investigated using organic substrate consumption, biomass production, oxygen consumption (or heat evolution), and carbon dioxide evolution rate data for a series of dilution rates. The consistency of continuous-culture data in the published literature is examined.     

The role of belowground competition and plastic biomass allocation in altering plant mass–density relationships

Metabolic scaling theory (MST) predicts a ‘universal scaling law’ for plant mass–density relationships, but empirical observations are more variable. Possible explanations of this variability include plasticity in biomass allocation between the above‐ and belowground compartment and different modes of competition, which can be asymmetric or symmetric. Although complex interactions of these factors are likely to occur, so far the majority of modelling and empirical studies has focussed on mono‐factorial explanations. We here present a generic individual‐based model, which allows exploring the plant mass–density relationship in realistic settings by representing plasticity of biomass allocation and different modes of competition in the above‐ and belowground compartment. Plants grew according to an ontogenetic growth model derived from MST. To evaluate the behavior of the simulated plants related to the allocation patterns and to validate model predictions, we conducted greenhouse experiments with tree seedlings. The model reproduced empirical patterns both at the individual and population level. Without belowground resource limitation, aboveground processes dominated and the slopes of mass–density relationships followed the predictions of MST. In contrast, resource limitation led to an increased allocation of biomass to belowground parts of the plants. The subsequent dominance of symmetric belowground competition caused significantly shallower slopes of the mass–density relationship, even though the growth of individual plants followed MST. We conclude that changes in biomass allocation induced by belowground resource limitation explain the deviations from the mass–density relationship predicted by MST. Taking into account the plasticity of biomass allocation and its linkage to the above‐ and belowground competition is critical for fully representing plant communities, in particular for correctly predicting their response of carbon storage and sequestration to changing environmental conditions.     

The diameters of frozen-hydrated chromatin fibers increase with DNA linker length: evidence in support of variable diameter models for chromatin

The diameters of chromatin fibers from Thyone briareus (sea cucumber) sperm (DNA linker length, n = 87 bp) and Necturus maculosus (mudpuppy) erythrocytes (n = 48 bp) were investigated. Soluble fibers were frozen into vitrified aqueous solutions of physiological ionic strength (124 mM), imaged by cryo-EM, and measured interactively using quantitative computer image-processing techniques. Frozen-hydrated Thyone and Necturus fibers had significantly different mean diameters of 43.5 nm (SD = 4.2 nm; SEM = 0.61 nm) and 32.0 nm (SD = 3.0 nm; SEM = 0.36 nm), respectively. Evaluation of previously published EM data shows that the diameters of chromatin from a large number of sources are proportional to linker length. In addition, the inherent variability in fiber diameter suggests a relationship between fiber structure and the heterogeneity of linker length. The cryo-EM data were in quantitative agreement with space-filling double-helical crossed-linker models of Thyone and Necturus chromatin. The data, however, do not support solenoid or twisted-ribbon models for chromatin that specify a constant 30 nm diameter. To reconcile the concept of solenoidal packing with the data, we propose a variable-diameter solid-solenoid model with a fiber diameter that increases with linker length. In principle, each of the variable diameter models for chromatin can be reconciled with local variations in linker length.     

Concentration of protein in fibrin fibers and fibrinogen polymers determined by refractive index matching

We have used refractive index matching to determine the concentration of protein in the fibers in fibrin clots and of needlelike crystals of native fibrinogen. Our results are in agreement with those of Carr and Hermans [(1978) Macromolecules 11 , 46–50], as determined by light scattering—namely, that protein makes up about 20% of the volume of the fiber. However, we have found that the protein concentration is strongly dependent on ionic strength. An increase in ionic strength caused a substantial drop in the protein concentration. In a buffer containing 100 mM NaCl, the protein concentration was 26.6–29.8 g of protein per 100 cm³ of polymer, and at 200 mM NaCl it was reduced to 22.1–23.1 g/100 cm³.     

Mate choice by wild and mass‐reared females of the Mediterranean fruit fly

The sterile insect technique (SIT) is used to control Mediterranean fruit fly, Ceratitis capitata (Wiedemann), but its effectiveness is limited by low sexual competitiveness of mass‐reared males. This study investigated whether wild and mass‐reared [from a temperature sensitive lethal (tsl) genetic sexing strain] females display similar mate preferences and thus exert similar selective forces on the evolution of male courtship behaviour. Wild females preferred wild males over tsl males, whereas tsl females mated indiscriminately. The probability that mounting resulted in copulation was related to the duration of pre‐mount courtship for wild females, and wild males performed longer courtships than tsl males. Copulation occurred independently of courtship duration in tsl females. Counter to the aim of the SIT, female choice by tsl females appears to promote the evolution of male behaviour disfavoured by wild females.     

Effect of master mixes on the measurement of telomere length by qPCR

Molecular Biology Reports - Alterations in telomere length (TL) have been associated with several diseases and a method based on qPCR, the Monochrome Multiplex Real-Time Quantitative PCR (MMQPCR)...     

Reproductive constraints,not environmental conditions,shape the ontogeny of sex‐specific mass–size allometry in roe deer

In polygynous mammals, sex‐specific patterns of body growth are linked to divergent selection pressures on male and female body size, resulting in sexual dimorphism (SD). For males, reproductive success is generally linked to body size, hence, males should prioritise early growth. For females, reproductive success is linked to resource availability, so they may adopt a more conservative growth tactic. Using longitudinal monitoring of known‐age animals in two contrasting populations and an allometric approach to disentangle the relative contribution of structural size and physiological condition to SD, we addressed these issues in the weakly polygynous roe deer. Despite very different environmental conditions, we found remarkably similar patterns in the two populations in the mass–size allometric relationship at each life history stage, suggesting that relative allocation to structural size and physiological condition is highly constrained. SD in structural size (indexed by hind foot length) involved sex‐specific growth trajectories governed by a single mass–size allometric relationship during the juvenile stage, such that males were both bigger and heavier than females. In contrast, SD in physiological condition (indexed by the allometric relationship between body mass and hind foot length, expressed as body mass for a given body size) developed markedly during the sub‐adult stage in relation to sex differences in the timing of first reproduction. Among adults, males were heavier for a given size than females, suggesting that, relative to females, males express a capital breeder tactic, accumulating fat reserves to offset reproductive costs. By the senescent stage, SD in physiological condition had disappeared, with both sexes governed by a single allometric relationship, suggesting more rapid senescence in males than females. Individuals born into poor cohorts were generally lighter for a given size, indicating growth priority for skeletal size over physiological condition in both sexes. However, sex differences in cohort effects among sub‐adults resulted in lower size‐specific SD in poor cohorts, indicating that body condition of sub‐adult females is buffered against environmental harshness. We conclude that sex‐differences in reproductive tactics impose constraints on the ontogeny of SD in roe deer, leading to sex‐specific trajectories in structural size and physiological condition.     

The effect of prefixation on the diameter of chromosome fibers isolated by the Langmuir trough-critical point method

The effect of prefixation on the diameter of chromosome fibers isolated by the Langmuir trough-critical point method has been investigated in several species of plants and animals. In barley, fibers isolated from endosperm without prefixation have an average diameter of between 240 and 250 A, and are similar in dimensions and structure to the chromosome fibers isolated from animals by this method. Chromosome fibers from other tissues of the same plant are smaller in diameter when isolated without prefixation, approximating 200 A. After prefixation in 2% buffered formalin, isolated fibers from the three barley tissues studied are reduced in diameter, to approximately 120-130 A for endosperm and leaflet and to 140 A for root tip. Chromosome fibers isolated from newt erythrocytes also show a significantly reduced diameter after formalin prefixation, to approximately 120 A.     

Length–weight and length–length relationships of fish species from the Chi River,northeastern Thailand

The relationships of total length (TL), fork length (FL) and standard length (SL) are presented for four fish species and the relationships between TL and wet weight for 23 fish species from the Chi River in northeastern Thailand. All length–length relationships were linear (r² > 0.95). Slope (b) of the length–weight relationships showed values between 2.5073 and 3.4896.     

Telomere length measurement by fluorescence in situ hybridization and flow cytometry: tips and pitfalls

BACKGROUND: Telomeres containing noncoding DNA repeats at the end of the chromosomes are essential for chromosomal stability and are implicated in regulating the replication and senescence of cells. The gradual loss of telomere repeats in cells has been linked to aging and tumor development and methods to measure telomere length are of increasing interest. At least three methods for measuring the length of telomere repeats have been described: Southern blot analysis and quantitative fluorescence in situ hybridization using either digital fluorescence microscopy (Q-FISH) or flow cytometry (flow-FISH). Both Southern blot analysis and Q-FISH have specific limitations and are time-consuming, whereas the flow-FISH technique requires relatively few cells (10(5)) and can be completed in a single day. A further advantage of the flow-FISH method is that data on the telomere length from individual cells and subsets of cells (lymphocytes and granulocytes) can be acquired from the same sample. In order to obtain accurate and reproducible results using the flow-FISH technique, we systematically explored the influence of various steps in the protocol on telomere length values and established an acceptable range for the most critical parameters. METHODS: Isolated leukocytes from whole blood are denatured by heat and 70%/75% formamide, then hybridized with or without a telomere-specific fluorescein isothiocyante (FITC)-conjugated peptide nucleic acid probe (PNA). Unbound telomere PNA is washed away, the DNA is counterstained, and telomere fluorescence is measured on a flow cytometer using an argon ion laser (488 nm) to excite FITC. For each sample, duplicates of telomere PNA-stained and unstained tubes are analyzed. RESULTS: Cell counts and flow-FISH telomere length measurements were performed on leukocytes and thymocytes of humans and other species. Leukocyte suspensions were prepared by two red blood cell lysis steps with ammonium chloride. Optimal denaturation of DNA was achieved by heating at 85-87 degrees C for 15 min in a solution containing 70%/75% formamide. Hybridization was performed at room temperature with a 0.3 microg/ml telomere-PNA probe for at least 60-90 min. Unbound telomere-PNA probe was diluted at least 4,000-40,000 times with wash steps containing 70%/75% formamide at room temperature. LDS 751 and DAPI were suitable as DNA counterstains as they did not show significant interference with telomere length measurement. CONCLUSIONS: The use of flow-FISH for telomere length measurements in nucleated blood cells requires tight adherence to an optimized protocol. The method described here can be used to determine rapidly the telomere length in subsets of nucleated blood cells.     

Length–weight and length–length relationships for 10 species of scorpionfishes (Scorpaenidae) on the south coast of Korea

The relationships are given between total length and wet weight, and between total length and standard length for 10 scorpionfishes from the south coast of Korea.     

Blocking calcium-dependent potassium in permeability of skeletal muscle fibers in the frog by a sodium-free medium

In voltage-clamped frog muscle fibres, the total or partial substitution of NaCl by LiCl does not alter the calcium-dependent slow outward potassium current. In contrast, an equimolar substitution of NaCl by choline-Cl (+atropine) or trisCl induces a rapid and reversible blockage of the current.     

The effect of mass‐rearing on death‐feigning behaviour in the sweet potato weevil (Coleoptera: Brentidae)

The aim of our study was to examine the effect of mass‐rearing, in which there is no exposure to predators, on antipredator traits of insects for improving sterile insect technique programs. The duration of death‐feigning (antipredator behaviour) in sweet potato weevil Cylas formicarius (Summers) (Coleoptera: Brentidae) after mass‐rearing for 71 generations were compared with those in wild strain. There was no significant difference in the duration of death‐feigning between wild and mass‐reared strains. This indicated that the death‐feigning behaviour of mass‐reared strain was maintained for 71 generations even in the absence of predators. We discuss the reasons why death‐feigning behaviour is maintained after mass‐rearing.     

Gas chromatography–combustion–isotope ratio mass spectrometry analysis of 19-norsteroids: application to the detection of a nandrolone metabolite in urine

Determination of whether the major metabolite of nandrolone in urine, 19-norandrosterone (19-NA), is exogenous or endogenous in origin is one of the most exciting challenges for antidoping laboratories. Gas chromatography–combustion–isotope ratio mass spectrometry (GC–C–IRMS) can be used to differentiate these two origins by carbon isotopic ratio analysis. A complete method for purification of 19-NA in urine has been established. Acetylated ketosteroids, and in particular 19-NA, are isolated from the urine matrix before analysis after hydrolysis and purification of urine by reversed-phase and normal solid-phase extraction. The limit of detection for 19-NA was about 60 ng with recoveries of 54–60%. Evidence of exogenous administration of 19-NA may be established from isotope ratio determination from the ¹³C/¹²C ratios of several synthetic 19-norsteroids compared to those obtained for endogenous steroids.