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PubMed1983

Neuromuscular patterns and the origin of trophic specialization in fishes.

The pattern of muscle electrical activity in the pharyngeal muscles of the mollusc-eating sunfish Lepomis microlophus is highly specialized in comparison with the pattern displayed by most other members of the sunfish family and does not change when different prey are eaten. The closest genealogical relative of this species has the specialized muscle activity pattern for crushing prey when it feeds on snails but uses the primitive sequence of muscle activity during swallowing of other prey. The ability of species that crush snails to use molluscan prey effectively is due primarily to the evolutionary transformation of the neuromuscular program controlling the trophic apparatus.

Action Potentials↗

PubMedDate not supplied

Ancient origins of axial patterning genes: Hox genes and ParaHox genes in the Cnidaria.

Among the bilaterally symmetrical, triploblastic animals (the Bilateria), a conserved set of developmental regulatory genes are known to function in patterning the anterior-posterior (AP) axis. This set includes the well-studied Hox cluster genes, and the recently described genes of the ParaHox cluster, which is believed to be the evolutionary sister of the Hox cluster (Brooke et al. 1998). The conserved role of these axial patterning genes in animals as diverse as frogs and flies is believed to reflect an underlying homology (i.e., all bilaterians derive from a common ancestor which possessed an AP axis and the developmental mechanisms responsible for patterning the axis). However, the origin and early evolution of Hox genes and ParaHox genes remain obscure. Repeated attempts have been made to reconstruct the early evolution of Hox genes by analyzing data from the triphoblastic animals, the Bilateria (Schubert et al. 1993; Zhang and Nei 1996). A more precise dating of Hox origins has been elusive due to a lack of sufficient information from outgroup taxa such as the phylum Cnidaria (corals, hydras, jellyfishes, and sea anemones). In combination with outgroup taxa, another potential source of information about Hox origins is outgroup genes (e.g., the genes of the ParaHox cluster). In this article, we present cDNA sequences of two Hox-like genes (anthox2 and anthox6) from the sea anemone, Nematostella vectensis. Phylogenetic analysis indicates that anthox2 (= Cnox2) is homologous to the GSX class of ParaHox genes, and anthox6 is homologous to the anterior class of Hox genes. Therefore, the origin of Hox genes and ParaHox genes occurred prior to the evolutionary split between the Cnidaria and the Bilateria and predated the evolution of the anterior-posterior axis of bilaterian animals. Our analysis also suggests that the central Hox class was invented in the bilaterian lineage, subsequent to their split from the Cnidaria.

Amino Acid Sequence↗

PubMed2001

Recognition of partly occluded patterns: a neural network model.

Human beings are often able to read a letter or word partly occluded by contaminating ink stains. However, if the stains are completely erased and the occluded areas of the letter are changed to white, we usually have difficulty in reading the letter. In this article I propose a hypothesis explaining why a pattern is easier to recognize when it is occluded by visible objects than by invisible opaque objects. A neural network model is constructed based on this hypothesis. The visual system extracts various visual features from the input pattern and then attempts to recognize it. If the occluding objects are not visible, the visual system will have difficulty in distinguishing which features are relevant to the original pattern and which are newly generated by the occlusion. If the occluding objects are visible, however, the visual system can easily discriminate between relevant and irrelevant features and recognize the occluded pattern correctly. The proposed model is an extended version of the neocognitron model. The activity of the feature-extracting cells whose receptive fields cover the occluding objects is suppressed in an early stage of the hierarchical network. Since the irrelevant features generated by the occlusion are thus eliminated, the model can recognize occluded patterns correctly, provided the occlusion is not so large as to prevent recognition even by human beings.

Artificial Intelligence↗

PubMed1991

[Diagnosis of periorbital diseases by means of ultrasound].

The ophthalmology was one of the first medical branches which used ultrasound in diagnostical purposes. The structure of the eye, with the large vitreous body, through which the ultrasound waves pass without attenuation, is highly appreciated in ultrasound examination, thus the diagnostical results of ocular diseases are extremely good. On the base of our rich ophthalmological experience we left the scope of the eye and the orbit, and made ultrasound examinations of the head and the face. The echograms of two patients presented original patterns: one was malignant melanoma of the skin with typical echograms performed by A and B scannings, and the other case was the Mikulicz disease with typical echograms. Original echograms of these patients can be considered as a contribution to ultrasound diagnosis of paraorbital diseases.

Humans↗

PubMedDate not supplied

[Anatomo-radiological study of the origin of the arteria ascendens, a colic branch of the ileocolic artery].

With the inadequate anatomic revision observed in the literature, the authors tried to establish the most frequent origin patterns of the arteria ascendens, colic branch of the ileocolic artery. The search consisted of one hundred cases and it was possible to distinguish four fundamental types of vascular origin. The absence of studies in radiological anatomy made this contribution very important for the knowledge of the arterial disposition in the modern diagnostic procedures of the region.

Adolescent↗

PubMed1979

Vascular supply of the testis of the camel (Camelus dromedarius).

The origin, pattern of distribution and the length of the convoluted part of the testicular artery were examined by blunt dissection and by the preparation of arterial casts with vinylite. The testicular artery originates from the abdominal aorta just cranial to its bifurcation and forms compact coils and reveals a tortuous course in the region of the pampiniform plexus and along the attached border. The artery divides at the caudal extremity of the testis into 2--4 branches. The epididymal artery, which is a branch of the testicular artery, was seen to anastomose with the deferential artery, but no anastomosis occurs between these arteries and the testicular artery. The convoluted part of the testicular artery was 20 cm in length, but when unravelled totalled 240 cm. This is not affected by seasonal variations. The possible significance of these results was discussed and compared with similar findings of other mammals.

Animals↗

PubMed1992

Establishment and maintenance of stable spatial patterns in lacZ fusion transformants of Polysphondylium pallidum.

Polysphondylium pallidum cells were transformed with a construct containing the Dictyostelium discoideum ecmA promoter fused to a lacZ reporter gene. Two stably transformed lines, one in which beta-galactosidase (beta-gal) is expressed in apical cells of the fruiting body (p63/2.1), and one in which it is expressed in basal cells (p63/D), have enabled us to infer how cells move during aggregation and culmination. Several types of cell movement proposed to occur during slime mold culmination, such as random cell mixing and global cell circulation, can be ruled out on the basis of our observations. Cells of the two transformant lines express beta-gal very early in development. In both cases, stained cells are randomly scattered in a starving population. By mid to late aggregation, characteristic spatial patterns emerge. Marked cells of p63/2.1 are found predominantly at tips of tight aggregates; those of p63/D accumulate at the periphery. These patterns are conserved throughout culmination, showing that marked cells maintain their relative positions within the multicellular mass following aggregation. Neither the apical nor the basal pattern appears to be regulated within the primary sorogen by de novo gene expression or by cell sorting as whorls are formed. However, marked cells within a whorl re-establish the original pattern in secondary sorogens. This must be achieved by cell migration, since beta-gal is not re-expressed.

Cell Movement↗

PubMed2001

Phenotypic and genotypic characterization of antibiotic-resistant Propionibacterium acnes isolated from acne patients attending dermatology clinics in Europe, the U.S.A., Japan and Australia.

BACKGROUND: Propionibacterium acnes is the target of antimicrobial treatments for acne vulgaris. Acquired resistance to erythromycin, clindamycin and tetracyclines has been reported in strains from diverse geographical loci, but the molecular basis of resistance, via mutations in genes encoding 23S and 16S rRNA, respectively, has so far only been elucidated for isolates from the U.K. OBJECTIVES: To determine whether similar or different resistance mechanisms occur in resistant P. acnes isolates from outside the U.K. METHODS: The phenotypes and genotypes of 73 antibiotic-resistant strains of P. acnes obtained from the skin of acne patients in the U.K., U.S.A., France, Germany, Australia and Japan were compared. Antibiotic susceptibilities were determined by minimum inhibitory concentration (MIC) measurements, and polymerase chain reaction and DNA sequencing were used to identify mutations in genes encoding rRNA. RESULTS: Most erythromycin-resistant isolates (MIC(90) > or = 512 microg mL(-1)) were cross-resistant to clindamycin but at a much lower level (MIC(90) > or = 64 microg mL(-1)). As in the U.K., resistance to erythromycin was associated with point mutations in 23S rRNA in 49 of 58 strains. An A-->G transition at Escherichia coli equivalent base 2058 was present in 24 strains. This gave a unique cross-resistance phenotype against a panel of macrolide, lincosamide and type B streptogramin antibiotics. Two further point mutations (at E. coli equivalent bases 2057 and 2059) were identified (in three and 22 isolates, respectively) and these were also associated with specific cross-resistance patterns originally identified in isolates from the U.K. However, nine of 10 erythromycin resistant-strains from Germany did not exhibit any of the three base mutations identified and, in six cases, cross-resistance patterns were atypical. Consistent with previous U.K. data, 34 of 38 tetracycline-resistant strains carried a base mutation at E. coli 16S rRNA equivalent base 1058. Tetracycline-resistant isolates displayed varying degrees of cross-resistance to doxycycline and minocycline, but isolates from the U.S.A. had higher MICs for minocycline (4--16 microg mL(-1)) than isolates from other countries and, in particular, Australia. All the P. acnes isolates resistant to one or more of the commonly used antiacne antibiotics were sensitive to penicillin, fusidic acid, chloramphenicol and the fluoroquinolone, nadifloxacin. All but one isolate (from the U.K.) were sensitive to trimethoprim. CONCLUSIONS: This study shows that 23S and 16S mutations identified in the U.K. conferring antibiotic resistance in P. acnes are distributed widely. However, resistant strains were isolated in which mutations could not be identified, suggesting that as yet uncharacterized resistance mechanisms have evolved. This is the first report of high-level resistance to minocycline and is of concern as these strains are predicted to be clinically resistant and are unlikely to remain confined to the U.S.A. Epidemiological studies are urgently required to monitor how resistant strains are selected, how they spread and to ascertain whether the prevalence of resistance correlates with antibiotic usage patterns in the different countries.

Acne Vulgaris↗

PubMed1999

Spontaneous changes in Drosophila melanogaster transposable elements and their effects on fitness.

Twenty-eight spontaneous alterations modifying the hybridization banding pattern of six families of transposable elements (297, Foldback, copia, jockey, P and hobo) have been fixed in a set of mutation-accumulation lines of Drosophila melanogaster. Their effect on fitness has been studied by competition with the original pattern. Most alterations affecting transposable elements were shown to be rearrangements with no detectable effect on fitness, showing that spontaneous transposable element mutations mainly generate minor fitness mutations.

Animals↗

PubMed1995

Multiplicity of N-terminal structures of medium-chain alcohol dehydrogenases. Mass-spectrometric analysis of plant, lower vertebrate and higher vertebrate class I, II, and III forms of the enzyme.

Ten different alcohol dehydrogenases, representing several classes of the enzyme and a wide spread of organisms, were analyzed for patterns of N-terminal structures utilizing a combination of conventional and mass spectrometric peptide analysis. Results show all forms to be N-terminally acetylated and allow comparisons of now 40 such alcohol dehydrogenases covering a large span of forms and origins. Patterns illustrate roles of acetylation in proteins in general, define special importance of the class I N-terminal acetylation, and distinguish separate acetylated structures for all classes, as well as a common alcohol dehydrogenase motif.

Acetylation↗

PubMed1982

Mammographic parenchymal patterns. Risk indicator for breast cancer?

Mammographic parenchymal patterns, originally presented as a new risk factor for breast cancer, have been prospectively studied in a large (27,157 examinations) consecutive screening population. Although there is a significantly higher risk of breast cancer in the so-called dysplastic breasts (P2 and DY pattern groups), the classification is of little practical value, as more than 72% of the cancers in the prevalent population were found in the so-called low-risk breasts (N1 and P1 pattern groups). A similar trend occurred at repeated screening of younger women, in which most of the "incident" cancers were found in the "low-risk" breasts. These patterns should not be used to influence patient management or screening programs.

Adult↗

PubMed1976

Molecular information structures in the brain.

This paper presents a theory of memory and memory mediated learning based on the manipulation of macromolecular conformations. The main features of the theory are: 1) the brain contains primary and reference neurons; 2) inputs from the external environment produce particular patterns of primary firing; 3) the firing of a primary neuron sensitizes certain of its dendrites; 4) the sensitized primaries are loaded by the reference neuron active at the time and in such a way that they fire when called by this reference neuron, thus reconstructing the original pattern of primary activity. The reference neurons may also be loaded by primaries, thus making it possible for the reconstruction process to be initiated by some feature of the initial input. Each reference neuron loads and calls at most one primary pattern of activity, thereby preventing superposition of memories. If the primaries are loadable by sequences of impulses, this makes it possible to increase the connectivity among the various types of neurons by using party-line organization. The loading and calling processes themselves are mediated by call molecules. These are allosteric enzymes, located in the dendrites of primary and reference neurons, whose states are set either by an impulse or sequence of impulses and which catalyze events leading to impulse formation whenever this input recurs. The call molecules are capable of duplicating their setting (or conformation) using either intra- or interneuronal potentials, thereby ensuring stability of the memory trace. The theory allows for general powers of memory manipulation (by rememorization), for the construction of time ordered, content ordered, and associative data structures, and for computation with global representations of the environment. It makes a large number of testable predictions, provides a natural interpretation for the structure of the cerebral cortex, and accounts for: resistance to cooling, differential effects of chemical agents on short and long term memory, distributed character of memory, accessibility of memories by stimulation of specific brain loci, and also the details of classical conditioning and instrumental learning.

Association Learning↗

PubMed1983

Fourier analysis of ground reaction forces in normals and patients with knee joint disease.

Fourier analysis was performed on the ground reaction force patterns during gait in 26 normals and 10 patients with knee joint disease prior to total knee replacement. A method was developed to determine the essential number of harmonics for each force component, based on data sampling rate and the level of accuracy required in reconstructing the original patterns. The criteria used to select the level of accuracy depend upon the type of analysis to be performed. Only the first two to four harmonics, plus the constant term, were found to be the dominating coefficients in describing each of the reaction force patterns, and they are subsequently used as the key parameters in differentiating normals and patients with knee joint disease. The advantages of this method and its implication to objective gait analysis in biomechanics are discussed.

Adult↗

PubMedDate not supplied

Colour but not form patterns combine between the eyes.

PURPOSE: A visual pattern was broken into patches, some of which were shown to one eye and the remainder of which were shown to the other eye. Our aim was to find the conditions under which the subject could combine the information given to the two eyes separately to reconstruct the original pattern. METHODS: One green and four red patches were presented to one eye. Five patches were presented to the other eye at corresponding locations but with red substituted for green and green for red. RESULTS: When the chromatic contrasts were appropriately adjusted, subjects saw five patches of a single colour for most of the viewing time. Intermixed horizontal and vertical gratings did not separate into coherent percepts in the same way. CONCLUSIONS: This result indicates cooperation between the responses to colour patches presented to different eyes, a finding that may be of use in testing for normal binocular vision.

Color Perception↗

PubMed1996

Regularity of spectral pattern and its effects on the perceptual fusion of harmonics.

A single even harmonic added to an odd-harmonic complex may be judged as perceptually more salient than the odd harmonics themselves (Roberts & Bregman, 1991). It is proposed that this effect occurs because the even harmonic is inconsistent with the regular spectral pattern formed by the odd-harmonic complex (the base). Therefore, a reduction in the regularity of the base spectrum should reduce the even-odd difference. Spectral regularity was reduced either by removing base components, or by including components in the base that were inconsistent with its original pattern. Subjects listened to (primarily) harmonic complex tones and rated the clarity of one of the harmonics, cued by a preceding pure tone. Both removing components from the base and including extraneous components in the base reduced the even-odd difference. The results suggest that it is easier to segregate a harmonic from a periodic complex tone when it does not form part of the regular pattern of spectral spacing defined by the other harmonics.

Attention↗

PubMed1998

A model neuron with activity-dependent conductances regulated by multiple calcium sensors.

Membrane channels are subject to a wide variety of regulatory mechanisms that can be affected by activity. We present a model of a stomatogastric ganglion (STG) neuron in which several Ca2+-dependent pathways are used to regulate the maximal conductances of membrane currents in an activity-dependent manner. Unlike previous models of this type, the regulation and modification of maximal conductances by electrical activity is unconstrained. The model has seven voltage-dependent membrane currents and uses three Ca2+ sensors acting on different time scales. Starting from random initial conditions over a given range, the model sets the maximal conductances for its active membrane currents to values that produce a predefined target pattern of activity approximately 90% of the time. In these models, the same pattern of electrical activity can be produced by a range of maximal conductances, and this range is compared with voltage-clamp data from the lateral pyloric neuron of the STG. If the electrical activity of the model neuron is perturbed, the maximal conductances adjust to restore the original pattern of activity. When the perturbation is removed, the activity pattern is again restored after a transient adjustment period, but the conductances may not return to their initial values. The model suggests that neurons may regulate their conductances to maintain fixed patterns of electrical activity, rather than fixed maximal conductances, and that the regulation process requires feedback systems capable of reacting to changes of electrical activity on a number of different time scales.

Action Potentials↗

PubMed1991

The intrasession repeatability of pattern electroretinograms and the effects of digital filtering.

Transient pattern electroretinograms were recorded in 12 normal young volunteers with the use of 12' and 30' checkerboard stimuli and 1 c/deg and 2.5 c/deg vertical gratings. The intrasession repeatability of pattern electroretinograms was determined by employing alternative statistics to the frequently used correlation coefficients. Comparisons were made with the repeatability of cone electroretinograms elicited by ganzfeld stimulation. The coefficient of repeatability was substantially lower (better) for pattern electroretinogram b-wave implicit times than for a-wave implicit times and b-wave amplitudes, the latter having high coefficients of repeatability. Cone electroretinograms had better repeatability with respect to all three parameters. Digital filtering using a bandpass of 1-40 Hz was applied to the original pattern electroretinograms recorded with a bandpass of 1-250 Hz. Although peak definition was generally enhanced, repeatability did not show marked improvement. Differences between broadband analogue-filtered pattern electroretinograms and the same responses with high-frequency noise removed by digital filtering need to be taken into account. The coefficient of repeatability statistic appears to facilitate the assessment of pattern electroretinograms and permits the comparison of the repeatability of both implicit time and amplitude parameters irrespective of absolute values. The implications of the relatively poor repeatability of pattern electroretinogram b-wave amplitudes for clinical applications need to be considered.

Adult↗

PubMed1997

Monitoring expenditure in relation to epidemiological and demographical characteristics of AIDS in South East England.

In the UK, over 70% of AIDS, including new cases, is located in a few Districts in central London where the distribution of previously occurring and new cases is essentially confined to the original risk groups of homosexual/bisexual men, drug addicts of both sexes, and some of their sexual partners and consorts. But control policy is still based on the assumption that HIV has already spread from persons in these risk groups into the general population, and that it will spread hereafter at an increased rate because of heterosexual transmission to cause a widespread epidemic of AIDS. The basis and implications of this policy were investigated in the South East region adjacent to London. Analysis of demographic and epidemiological data shows that, with one exception, there is very little extension of AIDS from affected Districts in London to the surrounding region or even to the suburban fringe. Where AIDS is prevalent, as in this exception, the distribution follows the same, original pattern which relates essentially to risks arising from life-styles. There is no significant association between the prevalence or spread of AIDS and conventional markers of deprivation, economic and social disadvantage. Allocations of personnel, services and expenditure, assessed from returns required under the AIDS Control Act of 1987 and official registration data, continue to follow the original policy assumptions. They are therefore unrelated to the numbers of existing and new cases, disproportionate and unrealistic. Claims that this widespread excess of effort is justified by the fact that AIDS has not spread to the general population are falsified by the continuation of cases almost exclusively in risk groups. There is nothing in the data required under the Act or in registrations in this main locus of AIDS in the UK to suggest any change in this or to justify continuation of current expenditure and redundant activities. There is no evidence in these data that ethnic variations in the resident populations of Districts are associated with variations in the prevalence of AIDS. However, the larger figures available in some of the national data do indicate a disproportionate increase in some minority ethnic groups. Further detail about risks factors in these groups are required and, meanwhile, effort and expenditure should be re-orientated toward treatment, contact tracing and other public health measures for more effective containment of the continuing spread of AIDS in all the high risk groups.

Acquired Immunodeficiency Syndrome↗