The use of starter cultures to produce ‘Pito’, a Nigerian fermented alcoholic beverage

Pito a traditional Nigerian alcoholic beverage was brewed in the laboratory with pure cultures of Lactobacillus plantarum in combination with Saccharomyces cerevisiae and Pediococcus halophilus in combination with Candida tropicalis isolated from a local brew. The pH, colour, titrable acidity, alcohol content, specific gravity, taste and flavour of Pito produced by this method compared favourably with that produced by the traditional method. The method achieved a reduced fermentation time and an improved production process. It is recommended that Pito be produced with Lactobacillus plantarum in combination with Saccharomyces cerevisiae.     

Alternative pathway activities in aged potato tuber slices measured by three methods

To find a simple and reliable oxygen electrode-based method to estimate the values of alternative pathway activity (V _alt) and its contribution to total respiration V _alt/V _t) in aged potato (Solanum tuberosum L.) tuber slices, we compared conventional hydroxamate-inhibiting method, improved hydroxamate-inhibiting method with 2,6-dichlorophenol indophenol (DCPIP), and the oxygen isotope discrimination (OID) method. The values of V _alt and V _alt/V _t obtained with an improved hydroxamate-inhibiting method with DCPIP in 12-h- and 24-h-aged slices were about twice higher than those with the conventional hydroxamate-inhibiting method. Only a relatively small difference in the values of V _alt and V _alt/V _t obtained by the OID method and the improved hydroxamate-inhibiting method with DCPIP in 12-h and 24-h-aged slices was observed. These results indicated that the improved hydroxamate-inhibiting method with DCPIP could be considered as a new, simple, and reliable technique for the noninvasive assay of the AP activity.From Fiziologiya Rastenii, Vol. 52, No. 2, 2005, pp. 311–315.Original English Text Copyright © 2005 by Hou, Zhou, Kong, Liang, Zhang.This article was submitted by the authors in English.This revised version was published online in April 2005 with a corrected cover date.     

A posteriori time-varying filtering of averaged evoked potentials

The problem of estimating an unknown transient signal, given an ensemble of waveforms, in which this signal appears as a nonrandom component in the presence of additive noise is considered. This problem is solved by generalizing the method of a posteriori Wiener filtering. In the new method, the ensemble average is filtered by a time-varying system which is based on estimated time-varying power spectra of signal and noise. The nature of this system, and the computational procedures involved, are discussed in detail. A software package for time-varying filtering is briefly described. Application of the method is illustrated by a simulation example, which also provides a comparison to time-invariant a posteriori Wiener filtering.     

Cloning and characterization of the alkaline phosphatase positive regulator gene (phoB) of Escherichia coli

Summary The positive regulator gene (phoB) for alkaline phosphatase of Escherichia coli was cloned into the EcoRI site of pBR322 from the E. coli chromosome by a shotgun method. phoB was then constructed in vitro by replacing the C fragment of gtC by the phoB chromosomal fragment obtained from the hybrid plasmid. When the phoB mutant was lysogenized by phoB, the lysogen became PhoB⁺. The integration site of the phage was identified by P1 phage transduction to be around phoB site on the chromosome. From these results, we conclude that the cloned gene is phoB and not a gene which suppresses phenotypically phoB mutation when it is in a multi-copy state. The restriction map was constructed. Based on this information, several PhoB deletion plasmids and smaller PhoB⁺ plasmids were constructed in vitro. By examining PhoB phenotype when these plasmids were introduced into phoB mutant, we could define the phoB gene locus in 2 kb on the restriction map of the cloned chromosomal fragment. Cells carrying the multi-copy phoB gene produced alkaline phosphatase qualitatively under normal phosphate regulation. The phoB gene product was identified by the maxicell method as a protein with a molecular weight of approximately 31,000 daltons.     

The largest convex patches: A boundary-based method for obtaining object parts

The importance of boundaries for shape decomposition into component parts has been discussed from different points of view by Koenderink and van Doorn (1982), and by Hoffman and Richards (1984). The former define part boundaries as parabolic contours, whereas the latter propose that part boundaries should be defined by contours of negative minima (or maxima) of principal curvature. In this article, building on aspects of both approaches, we develop a new method for shape decomposition. This method relies exclusively on global properties of the surface which are fully characterized by local surface properties. We propose that a useful parcellation of shapes into parts can be obtained by decomposing the shape boundary into the largest convex surface patches and the smallest nonconvex surface patches. The essential computational steps of this method are the following: (i) build initial parts from the largest locally convex patches, (ii) consider an initial part as a constituent part if it is essentially convex, and (iii) obtain the remaining constituent parts by merging adjacent initial parts generated by the largest locally convex and the smallest nonconvex patches of nearly the same sizes. The method is illustrated on both smooth and continuous shapes. We show that the decomposition of shapes into the largest convex patches aims to maximize the thingness in an object, and to minimize its non-thingness. The method is conducive to a natural parcellation of shapes into constituent parts useful for recognition and for inferring function.     

A new method for analysis of heart rate variability: counting statistics of 1/f fluctuations

1/f fluctuations in heart rate are usually measured by spectral analysis using Fast Fourier Transform. Here, we introduce a new method based on counting the number of QRS complexes in time intervals t of various length. For a 1/f ^b spectrum the variance of counts in t follows a power-law as gDt ^1+b. This method is applied to analyze long term fluctuations in heart rate variability in 10 healthy men. The results show periods of 1/f fluctuations with interpolated periods of white noise during night hours.     

Fuzzy self-tuning PI controller for bioreactors

A fuzzy self-tuned PI controller for regulation of a nonlinear bioreactor is presented. The basic idea is to parameterize Ziegler-Nichols like tuning formula by two parameters and and then to use an on-line fuzzy inference mechanism to tune the PI controller parameters k _c and _I . The fuzzy self-tuning method takes the process output error as input and the tuning parameters and as outputs. Simulation studies on the nonlinear bioreactor model equations show that the present method is superior to that of fixed parameters conventional PI controller (based on transfer function) for both servo and regulatory problems. The present fuzzy logic controller is robust to process parameters uncertainties and to changes in magnitude and direction of the disturbances.     

Indigogenic methods for glycosidases

Summary The indigogenic method for -D-galactosidase of Pearson et al. (1963) with 4-Cl-5-Br-3-indolyl--D-galactoside was tested and evaluated.The acid -D-galactosidase is not firmly associated with structures and escapes from cryostat sections prepared in the usual manner into incubation solutions. This leakage cannot be prevented by a short postfixation of these sections in cold acetone or Baker's formol-calcium chloride. The leakage is negligible from frozen sections prepared from tissue blocks fixed 12–24 h in cold Baker's solution or in 3% buffered glutaraldehyde (the latter fixation is preferred). Even if this fixation causes about 70–80% inactivation of acid -D-galactosidase it is a prerequisite for studies concerned with its localization. The brush border -D-galactosidase of enterocytes is more firmly structurally bound. Since its activity against 4-Cl-5-Br-3-indolyl--D-galactoside cannot be proved after overnight fixation in cold aldehyde fixatives its demonstration is to be performed in sections prepared from specimens fixed in cold Baker's solution for 2 h at the most, or in cold microtome sections.The localization obtained with the original method is not correct. The addition of horseradish peroxidase did not result in any improvement of the localization because the employed samples of this peroxidase contained a concomitant -D-galactosidase activity.A striking improvement of the localization was achieved by a mixture of ferri- and ferrocyanide which causes a 40–75% inhibition of acid -D-galactosidase when used in concentrations of 1 · 10^–3 M to 1 · 10^–2 M.A new medium was devised consisting of 0,1 M citrate phosphate buffer pH 3,5–5,5, 8 · 10^–4M 4-Cl-5-Br-3-indolyL--D-galactoside, and 3,1 · 10^–3M potassium ferri- and ferrocyanide. This medium enabled to achieve a very good correlation with biochemical studies and to localize acid and neutral -D-galactosidases in situ.The acid enzyme was demonstrated first of all in lysosomes of many cells. Its activity is inhibited by galactonolactone, lactose and p-chloromercuribenzoate. The nature of the diffuse extralysosomal staining cannot be decided at present. The distribution pattern of this enzyme in many animal organs is given.The neutral -D-galactosidase (lactase) was localized by the improved method in the brush border of differentiated rat, human and monkey enterocytes and is inhibited by galactonolactone, lactose, gluconolactone, and cellobiose. In patients with celiac sprue this activity is very much reduced or absent. It is restituted after a gluten-free diet.Our revised method proved also very useful in processing zymograms and immunoprecipitation lines of -D-galactosidase(s) with homologous antisera obtained by Ouchterlony's technic and by immunoelectrophoresis.     

Steady-state kinetics of the overall oxidative phosphorylation reaction in heart mitochondria. Determination of the coupling relationships between the respiratory reactions and miscellaneous observations concerning rate-limiting steps

The linear sequence of steps involved in the oxidation of extramitochondrial succinate by O₂ in bovine heart mitochondria was examined by a steady-state kinetic method to determine whether or not freely diffusible intermediates occur between the various inhibitor-sensitive steps. The kinetic method is based on the facts (1) that if two inhibitor-sensitive steps within a sequence are linked by a freely diffusible intermediate, inhibition of one will make the other less rate limiting in the overall reaction and thus will increase the amount of inhibitor of the other step required for half-maximal inhibition of the overall reaction, and (2) that if the two steps are not linked in this manner, inhibition of one will make the other more rate limiting and thus will decrease the amount of inhibitor of the other required for half-maximal inhibition. These two types of coupling relationships between steps were designated as sequential and fixed, respectively. The results indicate the existence of freely diffusible intermediates (sequential coupling relationships) between the succinate transport and succinate dehydrogenase reactions, between the succinate dehydrogenase and cytochromebc ₁ reactions, and between the cytochromesbc ₁ andaa ₃ reactions. Uncoupling respiration from phosphorylation results in the coupling relationship between thebc ₁ andaa ₃ reactions becoming partially fixed. This change is accompanied by marked decreases in the degrees to which thebc ₁ andaa ₃ reactions limit the overall reaction and appears to account for the large uncoupler-induced releases of inhibition at the levels of thebc ₁ andaa ₃ reactions observed previously by others. It is suggested that cytochromec is the freely diffusible intermediate between thebc ₁ andaa ₃ reactions and that the uncoupler-induced changes occur as a result of formation of functional and highly efficient supercomplexes between cytochromec and the cytochromesbc ₁ andaa ₃ complexes.     

Determination of thermodynamic functions from scanning calorimetry data. II. For the system that includes self-dissociation / association process

The basic relations between the molar fractions and the scanning calorimetry data for the system that includes self-dissociation/association process such as are presented, where m_i is the stoichiometric coefficient of the ith state A_i. The relations are described for each state j as where f_j(T) is the molar fraction function of state j and ΔH_j(T) is the difference enthalpy function of the system referred to the state j, which can be obtained by scanning calorimetry; R is the gas constant; and T is the absolute temperature. By these relations, scanning calorimetry data can be deconvoluted in order to determine the thermodynamic functions by means of single and double deconvolution. The concentration dependence of the data is analyzed by a method presented in this paper. The nonlinear least squares fitting method for the determination of the functions is discussed. For an example of the application of this method to the actual scanning calorimetry data, thermodynamic data of multistate thermal transition of Vibrio parahaemolyticus hemolysin are analyzed.     

Further genetic variation at the esterase loci of Drosophila virilis

Reexamination of the electrophoretic mobilities of esterases encoded by the Est- and the Est- alleles of Drosophila virilis was carried out in detail using both thin-layer agar gel and polyacrylamide slab gel electrophoresis. Many allelic products with fine differences in their electrophoretic mobilities were found and designated by a new system. Some esterases separable by the agar gel method were indistinguishable using the polyacrylamide gel method. But the polyacrylamide gel method uncovered two multiband homozygotes, ^(d).77 and ^(d)1.28. Some allelic frequencies on the basis of the new designation were estimated in two natural populations. As a result, it is proposed that the total scope of allelic variation at the two esterase loci of Drosophila virilis is composed of discrete distribution patterns of gene frequencies, each histogram of which shows a bell-shaped pattern.     

Cytoplasmic gel and water relations of axon

Summary A previous method of measuring the swelling pressure ( _g ) of the cytoplasmic gel of the giant axon ofLoligo vulgaris was refined. The estimates of _g made with the improved method were consistent with those made with the earlier method. In these methods the activity of the solvent in the gel is measured by increasing the activity of the solvent in the internal phase of the gel by application of hydrostatic pressure to the gel directly. Comparable values for the activity of the solvent in the gel were obtained also by an alternate method, in which the deswelling of the gel is measured upon decreasing the activity of the solvent in the external phase by addition of a nonpenetrating high mol wt polymer (i.e., Ficoll).Additional support was obtained for the earlier suggestion that _g contributes to the swelling and shrinkage pattern of the whole axon. In part, the new evidence involved two consecutivedirect measurements of intraxonal pressure. The first measurement was that of a mixed pressure composed of _g and _m ( _m being the effective osmotic pressure due to the intra-extraxonal gradient in the activity of mobile solutes). The subsequent measurement was that of _g alone. The latter measurement was made feasible by destroying the axolemma, thereby eliminating the contribution of _m . An estimate of _m was obtained by subtracting _g from the total pressure measured initially. The _m determined by the above method was two orders of magnitude smaller than the theoretical osmotic pressure. This is consistent with the _m determined previously, where osmotic intra-extraxonal filtration coefficients were compared to the hydrostatic. The mixed pressure experiments lend credence to the idea that the substantial contribution of _g to the water relations of the whole axon is due to _g being of the same order of magnitude as _m .The degree of free swelling of axoplasmic gels was studied as a function of pH, salt concentration, and hydration radius of the anion of the salt used. The swelling increased with an increase in the reciprocal of the hydration radius, a decrease in salt concentration, and at pH below or above 4.5.The nature of the constraints to the free swelling of axoplasm in axons immersed in seawater was studied. With the seawater employed, these constraints appeared to be due more to the retractive forces of the sheath than to _m .     

N-banding in polytene chromosomes of Chironomus and Drosophila

The N-banding patterns of the polytene chromosomes of Drosophila melanogaster, Chironomus melanotus, Ch. th. thummi and Ch. th. thummi x Ch. th. piger were studied. In Chironomus the polytene N-banding patterns correspond to the polytene puffing patterns. This is revealed by comparison of the puffing and N-banding patterns of identical chromosomes. Size and staining intensity of the N-bands reflect the size of the puffs as shown by puff induction. There is no evidence that the N-bands are also located in Chironomus heterochromatin or are restricted to the nucleolar organizer regions. In Drosophila the -heterochromatin is strongly N-positive, whereas the -heterochromatin, as well as the Chironomus heterochromatin is not N-banded. Contrary to Chironomus, the puffs in Drosophila polytene chromosomes do not give rise selectively to well stained N-bands. — The N-banding method is interpreted to stain specifically non-histone protein which is (1) accumulated in genetically active chromosome regions and (2) present in a specific type of heterochromatin (-heterochromatin of Drosophila).     

Comparison of lethal mutations of Drosophila melanogaster with D. simulans when detected by the attached-X method

The purpose of this study was to evaluate the attached-X method compared with the standard Basc method, and, using this method, to find out whether the observed differences in genetic polymorphisms are related to differences in lethal mutation rates in D. melanogaster and D. simulans. When EMS-treated Drosophila melanogaster males are mated to untreated attached-X females, a decrease in the progeny sex ratio (/+) is observed due to the induced lethal mutations on the X chromosome. The decrease in the frequency of male progeny were shown as the attached-X index. The expected male number is calculated from the control sex ratio. The difference between the expected and the observed male numbers, expressed as the ratio to the expected male number, defines the attached-X index. The index values for various EMS concentrations were compared to the lethal frequencies obtained by the standard Basc method for the same EMS treatments, and gave a highly positive correlation (=0.993, p<0.01, d.f.=2), thus providing an alternative method for evaluation of possible mutagens. The attached-X method was applied to D. simulans, of which natural populations are known to have relatively low genetic variation, and frequencies of the EMS-induced X chromosome lethal mutations were estimated and compared with those in D. melanogaster. The results indicate that D. melanogaster is slightly more sensitive in the sperm and spermatogonial stages, but less susceptible in the spermatid stage when compared with D. simulans. Since the spermatid stage occupies a relatively short period in spermatogenesis, a higher mutability of D. simulans during this stage probably does not make a significant contribution to the genetic variability of this species.     

The blocking effect of l-cis-diltiazem on the light-sensitive current of isolated rods of the tiger salamander

The effect of the organic compound l-cis-diltiazem on the light-sensitive current of isolated rods of the tiger salamander was analysed by rapidly changing the extracellular medium using the method of Hodgkin et al. (1985). Addition to the extracellular medium of small amounts of l-cis-diltiazem rapidly inhibits the photocurrent. Complete suppression of the current was observed with 1 mM l-cis-diltiazem. Half blockage of the photocurrent occurred with about 150 M l-cis-diltiazem. The blocking effect of l-cis-diltiazem was enhanced by light and by a reduction of extracellular Na. A concentration of l-cis-diltiazem of 140 M, which suppresses one third of the photocurrent, was able to completely suppress the photocurrent carried by Ba. It is suggested that l-cis-diltiazem blocks the light-sensitive channel, possibly competing with cyclic guanosine-3-5-monophosphate (cGMP) for an internal regulatory site.     

Microradiographic determination of lead in mineralized tissues

Summary A dichromatic contact microradiographic method is presented for quantitative microanalysis of lead in mineralized tissues utilizing the L absorption edges of lead. Sections of mineralized tissue with a thickness of about 100 are exposed to filtered molybdenum K and copper K radiation. Quantitative localization of lead is possible within small areas of the order of 50 ² with an accuracy of 25 · 10^–12g lead. The method has been applied to studies of long term accumulation of lead in bone tissue.     

Sea anemone collagen: Further evidence for the existence of only oneα-chain type

Summary Collagen from an inferior invertebrate, namely from the sea anemoneActinia equina L., appears to consist of three identical subunits (-chains). New evidence for this situation is reported on the basis of preparative-scale experiments.No fractionation of sea anemone collagen was obtained by CM-cellulose chromatography which is the method of choice for the isolation of vertebrate collagen subunits. On the other hand, the-component (mol. wt., 95.000) could be isolated by gel chromatography. It was homogenous when investigated by polyacrylamide gel electrophoresis (in the presence of sodium dodecyl sulphate) and by ion exchange chromatography on CM-cellulose. The amino acid composition of the-component was identical with that of unfractionated collagen.Divergent evolution of the collagen molecule appears likely since vertebrate collagen molecules are made up of different-chain types.     

Orientation of the porphyrin ring in artificial chlorophyll membranes

Summary A sensitive photometric method is described by which the dichroism of lipid bilayer membranes in aqueous phase can be measured. The method is applied to black films with incorporated chlorophylla andb. With chlorophylla a relatively large dichroism is found in the Soret band and a much weaker dichroism in the red band. From the experimental data, the angles _B and _R between the blue and red transition moments and the membrane can be obtained. _B and _R are then used to calculate the angle of the porphyrin ring with respect to the membrane surface. For chlorophylla and three different lipids, values of between 44 and 49° are found.     

Development of a new method for testing strength of cells against fluid shear stress

A new method for testing the strength of cells against fluid shear stress by using a long capillary column was proposed. The trajectories of cells in the column were simulated by introducing the Brownian motion model. The Brownian motion was performed by the generation of random numbers. The mean exposure time to shear stress and the mean shear stress acting on the surface of cells were discussed by the result of computer simulation. The mean shear stress acting on the surface of cells flowing in the capillary column was estimated as 4/3-fold of the shear stress at the column wall provided that the ratio of the cell radius to the column radius does not exceed 0.08. The effectiveness of this new method for testing the strength of cells against fluid shear stress was shown.List of Symbols a m radius of cell - c constant - E distribution function - L m length of capillary column - M number of division - N number of division - p probability - Q m³/s flow rate - R m radius of capillary column - r m radial position - t s time - T s exposure time - T _m s mean exposure time - T ₀ s mean residence time - m/s axial velocity - u _m m/s cross-sectional flow velocity - z m axial position - s^–1 shear rate - _w s^–1 shear rate at wall - Pa s viscosity - spherical coordinate - spherical coordinate - Pa shear stress - _m Pa mean shear stress - _w Pa shear stress at wall