Pattern formation in an immobilized bienzyme system. A morphogenetic model

Experimental and theoretical studies of a reaction-diffusion model of two immobilized enzymes participating in the cellular acid-base metabolism, namely glutaminase and urease, are presented. The system shows an unstable steady state at pH 6.0, where any perturbation will drive the system towards a more alkaline or more acidic pH, owing to the autocatalytic behaviour with respect to pH exhibited by both enzymes. When diffusion is coupled to reaction by means of immobilization, different patterns of the internal pH profile appear across the membrane. If the bienzymic membrane is subjected to a perturbation at its boundaries, of the same amplitude but in opposite directions, the internal pH evolves through an asymmetric pattern to attain a nearly symmetric distribution of pH. The pH value at the final steady state is more acidic or more alkaline than the initial state according to the initial and boundary conditions. The final nearly symmetric state is attained more rapidly when less enzyme is immobilized (1.8 x 10(-4) M.s-1 as against 3.3 x 10(-4) M.s-1 of total enzyme activity in the membrane volume). The experimental results agree rather well qualitatively with numerical predictions of the model equations.

Tomography for reconstructing continuous fields from ill-posed multidirectional interferometric data

A computational tomographic technique has been developed to accurately reconstruct continuous flow fields of a simple shape from severely limited interferometric data. The algorithm is based on iterative reconstruction of the complementary field, the difference between the field to be reconstructed and its estimate. Its advantages lie in the treatment of various ill-posed problems in a unified manner and ease of incorporation of a priori information, even an approximate field shape. In principle it can utilize only available data. Test results demonstrated stable convergence and potential for substantial error reduction with a proper field estimate.

Clinical application of autogenous mandibular bone grafts. Analysis of 166 cases

Of the 166 patients receiving autogenous mandibular bone grafts during 1972-1987, 55 were used for repair of mandibular bone defect, 67 for correction of maxillofacial malformation and 44 for reconstruction of temporo-mandibular joint. Follow-up showed that 155 patients had satisfactory results after operation.

Genetic analysis of olfactory behavior in Drosophila: a new screen yields the ota mutants

A simple means of measuring Drosophila olfactory response is described, and the behavior which it measures is characterized. The assay was used to screen for X-linked mutants defective in olfactory function. Six ota mutants were isolated and characterized (ota = olfactory trap abnormal). Four of the mutants were found to be abnormal in another chemosensory behavior as well. Two of the mutant phenotypes extend to include another sensory system: they are defective in visual system physiology. All were normal, however, in a test of giant fiber system physiology. Two of the mutations are dominant, and the recessive mutations define two complementation groups. Mutations representing each complementation group, as well as one of the dominant mutations, were mapped. For the mutants with defective visual system physiology, the visual defects were shown to cosegregate with olfactory phenotypes.

Effects of atmospheric turbulence on photodetector arrays

In this paper we study quantitatively the effects of atmospheric turbulence on the measurement sensitivity of a quadrant detecting array, along with the measurement variance induced by atmospheric turbulence. Our results show that the stronger the turbulence strength, the lower the measurement sensitivity, and the larger the measurement variance. This agrees with the experimental phenomena we have observed up to now. In addition, the measurement sensitivity in the X direction could be affected by the deviation of light spots in the Y direction due to the existence of gaps between the quadrant elements. Such effects still exist for the measurement variance even when there are no gaps at all. This effect is analyzed quantitatively.

[24-hour ambulatory blood pressure monitoring in normal and hypertensive subjects]

24-hour ambulatory blood pressures (BP) of 172 normal subjects and 167 hypertensive patients recorded by automatic ambulatory monitoring device (A method) and standard mercury sphygmomanometer (B method) were studied. The results show: (1) 66% of normal subjects and 78% hypertensive patients have an evident circadian rhythm BP during 24-hours, BP readings during sleep and noon time are lower. (2) There is no significant difference between times at work and at home readings (P greater than 0.05), but the mean BP during sleeping time is the lowest (P less than 0.01). (3) The correlative coefficient of 24-hour average BP and casual clinic BP is low (r = 0.38-0.74). (4) The validity and accuracy of ambulatory BP monitoring by A and B methods were compared.

Interferometric tomography of continuous fields with incomplete projections

Interferometric tomography in the presence of an opaque object has been investigated. In principle the developed iterative algorithm does not need to augment the missing information. It is based on the successive reconstruction of the difference field, the difference between the object field to be reconstructed and its estimate, in the defined region only. The application of the algorithm results in stable convergence.

Double-strand breaks at an initiation site for meiotic gene conversion

It has been proposed that the initiation of meiotic recombination involves either single-strand or double-strand breaks in DNA. It is difficult to distinguish between these on the basis of genetic evidence because they give rise to similar predictions. All models invoke initiation at specific sites to explain polarity, which is a gradient in gene conversion frequency from one end of a gene to the other. In the accompanying paper we describe the localization of an initiation site for gene conversion to the promoter region of the ARG4 gene of the yeast Saccharomyces cerevisiae. Here, we show that a double-strand break appears at the ARG4 recombination initiation site at the time of recombination, and that the broken DNA molecules end in long single-stranded tails.

Characterization of the larval olfactory response in Drosophila and its genetic basis

Drosophila larvae are attracted to a wide variety of chemical stimuli. The olfactory response to ethyl acetate, a powerful attractant, was found to be surprisingly well conserved across a variety of different wild-type strains. Strain differences are documented, however, both in attraction to ethyl acetate and in another chemosensory behavior: avoidance of an aversive stimulus. As a means of analyzing the extent of genetic heterogeneity within strains, one wild-type population, Canton-S, was screened for variant X chromosomes. An enrichment procedure was characterized and used to make the screening more efficient. Lines homozygous for individual X chromosomes were established, and all were found to exhibit a strong olfactory response, although evidence was found for variation among them. The olfactory response was found to be conserved through an extended period of larval development, including the final period during which larvae leave the culture medium in preparation for metamorphosis. The results are discussed in terms of the genetic basis of the response and the use of single-gene mutations as a means of dissecting olfactory system function.

Radiographic image sequence coding using two-stage adaptive vector quantization

A two-stage adaptive vector quantization scheme for radiographic image sequence coding is introduced. Each frame in the sequence is first decomposed into a set of vectors, corresponding to nonoverlapping spatially contiguous block of pixels. A codebook is generated using a training set of vectors drawn from the sequence. Each vector is then encoded by the label representing the closest codeword of the codebook, and the label values in a frame label map memory at both ends of the communication channel. The changes occurring in the radiographic image sequences can be categorized into two types: those due to body motion and those due to the injected contrast dye material. In the second scheme proposed, encoding is performed in two stages. In the first stage, the labels of corresponding vectors from consecutive frames are compared and the frame label map memory is replenished (updated). This stage is sufficient to tack the changes caused by patient motions but not due to the injected contrast dye material. The resulting residual error vectors after the first stage coding are calculated for the latter changes and are further encoded by a second codebook, which is updated on a frame-to-frame basis.

New Pseudoguaianolides from Ambrosia maritima

The investigation of the aerial parts of two collections of AMBROSIA MARITIMA afforded in addition to known pseudoguaianolides nine new ones including two nor-sesquiterpene lactones and two dimeric lactones. The structures were elucidated by highfield (1)H-NMR spectroscopy.

Further Sesquiterpene Lactones from Eupatorium altissimum

A reinvestigation of the aerial parts of EUPATORIUM ALTISSIMUM afforded, in addition to several, previously isolated sesquiterpene lactones, five new ones. The structures of these were elucidated by highfield (1)H-NMR spectroscopy.

Organization and evolution of D region class I genes in the mouse major histocompatibility complex

Chromosome walking has been used to study the organization of the class I genes in the D and Qa regions of the MHC of the BALB/c mouse and in the D region of the AKR mouse. Five and eight class I genes are found in the D and Qa regions of the BALB/c mouse, respectively, while the AKR mouse contains only a single class I D region gene that has been identified by transfection as the Dk gene. Restriction map homologies and crosshybridization experiments suggest that the multiple class I genes in the D region of the BALB/c mouse have been generated by unequal crossing-over involving class I genes from the Qa region. The expanded D region of BALB/c and other H-2d haplotype mouse strains appears to be metastable, since evidence for gene contraction in the Dd region has been found in two mutant strains. Thus the D region and also the Qa region class I genes are in a dynamic state, evolving by gene expansion and contraction.