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At least 37 records · Page 2Linked to original sources
PubMed1991

Origins and patterning of avian outflow tract endocardium.

Outflow tract endocardium links the atrioventricular lining, which develops from cardiogenic plate mesoderm, with aortic arches, whose lining forms collectively from splanchnopleuric endothelial channels, local endothelial vesicles, and invasive angioblasts. At two discrete sites, outflow tract endocardial cells participate in morphogenetic events not within the repertoire of neighboring endocardium: they form mesenchymal precursors of endocardial cushions. The objectives of this research were to document the history of outflow tract endocardium in the avian embryo immediately prior to development of the heart, and to ascertain which, if any, aspects of this history are necessary to acquire cushion-forming potential. Paraxial and lateral mesodermal tissues from between somitomere 3 (midbrain level) and somite 5 were grafted from quail into chick embryos at 3-10 somite stages and, after 2-5 days incubation, survivors were fixed and sectioned. Tissues were stained with the Feulgen reaction to visualize the quail nuclear marker or with antibodies (monoclonal QH1 or polyclonals) that recognize quail but not chick cells. Many quail endothelial cells lose the characteristic nuclear heterochromatin marker, but they retain the species-specific epitope recognized by these antibodies. Precursors of outflow tract but not atrioventricular endocardium are present in cephalic paraxial and lateral mesoderm, with their greatest concentration at the level of the otic placode. Furthermore, the ventral movement of individual angiogenic cells is a normal antecedent to outflow tract formation. Cardiac myocytes were never derived from grafted head mesoderm. Thus, unlike the atrioventricular regions of the heart, outflow tract endocardial and myocardial precursors do not share a congruent embryonic history. The results of heterotopic transplantation, in which trunk paraxial or lateral mesoderm was grafted into the head, were identical, including the formation of cushion mesenchyme. This means that cushion positioning and inductive influences must operate locally within the developing heart tubes.

Animals↗
PubMed1985

The origin of pattern duplications in segment polarity mutants of Drosophila melanogaster.

Mutations of the segment polarity group in Drosophila melanogaster produce additional denticles with reversed polarity in every segment of the larval cuticle. We have investigated the effect of mutations in different elements of the bithorax complex on the segmental identity of these additional pattern elements. Our results suggest that they are derived, primarily, from the anterior compartment of each segment.

Animals↗
PubMed1992

Patterning in hydra cell aggregates without the sorting of cells from different axial origins.

Aggregates of Hydra cells were studied to find out how the primary centers that form new heads are generated in a system of cells in which the original pattern has been destroyed. Since cells that originate near the heads (apical cells) temporarily maintain a high level of head activation potential during aggregate formation and may contribute to pattern formation, their distribution in the aggregates was investigated. The mutual distances between labeled epithelial cells were followed by vitally staining apical cells with DAPI. The distribution was random during early regeneration stages (3, 6, 24 hr). These results show that epithelial cells originating from apical regions do not sort. That is, dynamic cell movement to generate rudiments of new heads is not necessary for head formation in aggregates. A possible explanation of the mechanism is discussed.

Animals↗
PubMed1990

Metamorphic-like changes in the nervous system of the nematode Caenorhabditis elegans.

During postembryonic development of the nematode Caenorhabditis elegans, one class of embryonic motoneurons, the DD cells, respecifies its pattern of synaptic connections. At the same time, a closely related set of postembryonic motoneurons, the VD cells, complete differentiation and assume a pattern of connections equivalent to the original pattern of the DD cells. These types of changes are reminiscent of changes observed in the nervous systems of animals as they undergo metamorphosis. The DD and VD neurons arise through different lineage mechanisms and in the adult, receive different synaptic inputs and make different outputs. The embryonic DD motoneurons are clonally related to one another; whereas the postembryonic VD motoneurons are produced by a repeated sublineage in which each stem cell generates four or five cell types in addition to the VD cells. In spite of these differences, it has been possible to identify only one gene by mutation that effects one of the two motoneuronal classes. Mutations in the gene unc-55 (unc meaning uncoordinated) cause the VD cells to become essentially identical to the DD cells; thus the unc-55 gene product appears necessary and sufficient to transform homeotically the pattern of synaptic connections of an entire class of motoneuron.

Animals↗
PubMed1990

Patterning processes in aggregates of Hydra cells visualized with the monoclonal antibody, TS19.

The monoclonal antibody, TS19, (Heimfeld et al., 1985), labels the apical surface of ectodermal epithelial cells of tentacles and lower peduncles in Hydra. To investigate the patterning process in a tissue whose original pattern was completely destroyed, the TS19 staining pattern was examined in developing aggregates of Hydra cells. Two types of aggregates were prepared. G-aggregates were made from tissue of the gastric portion of animals and RG-aggregates from gastric tissue allowed to regenerate for 24 hr before making aggregates. G-aggregates were initially TS19-negative, and later dim and uniformly TS19-positive. Thereafter, TS19 staining broke up into brightly stained and unstained regions. The brightly staining regions developed into head or foot structures. The TS19 pattern in RG-aggregates developed differently. Since the initial aggregates contained cells of regenerating tips, they started with TS19-positive cells as well as TS19-negative cells. The numbers of brightly staining TS19-positive cells increased with time. Some patches of these cells developed into head or foot structures, while others did not. These results and a simulation using a reaction-diffusion model suggest that the changes in activation levels affected the temporal changes in the pattern of TS19 staining, and that the de novo pattern formation in hydra can be explained in terms of a process involving activation and inhibition properties.

Animals↗
PubMed1976

Structural units and the redintegrative power of picture fragments.

We suppose that line drawings are perceived and represented in memory as a hierarchy of related parts and subparts, as dictated by Gestalt laws like common direction and spatial proximity. Therefore, a figure fragment comprising a natural part of an orginally studied pattern should serve as a strong retrieval cue for redintegrating memory for the pattern, whereas an equally large fragment suggesting either no units of misleading units should lead to poorer recall. This was confirmed in an experiment in which subjects studied 33 nonsense line drawings; recall of each was tested with good, mediocre, or bad (misleading) fragments of the original patterns. Good cues had about five time more redintegrative power than bad cues. A second experiment testing multiple-choice recognition memory showed that subjects confused an originally studied pattern about four times as often with a structurally similar distractor as with a structurally dissimilar distractor (which had an equal-sized change). Thus, memory cuing by fragments and memory confusions with slightly altered distractors indicate the significant constitutents of a figure.

Adolescent↗
PubMed1968

Effect of cell moisture on the thermal inactivation rate of bacterial spores.

Thermal inactivation rates were determined for two strains of Bacillus subtilis var. niger spores after equilibration to various relative humidity (RH) levels. In these tests, small thin stainless-steel squares were each inoculated with a drop of spore suspension and equilibrated to 11, 33, or 85% RH. Following equilibration, the squares were placed on a hot plate preheated to 108, 125, 136, 164, or 192 C for various exposure times and then assayed for surviving organisms. The results revealed that spores of the A strain of B. subtilis were least resistant if preequilibrated to 11% RH and most resistant if preequilibrated to 85% RH. The same trend was obtained at all temperatures except 192 C, at which, no difference was noted, probably because the rapid kill time approaches the heat-up time of the stainless-steel square. The B strain of B. subtilis spores showed an opposite RH effect; that is, the cells preequilibrated to 11% RH were the most resistant. Because the two strains of spores were grown on different media, further studies were conducted at 136 C after subculturing the cells on different media. When the B strain was subcultured on the A strain medium, the pattern was reversed; the cells preequilibrated to low RH were then least resistant. Although it was not possible to reverse these cells to the original pattern by subculturing on the original B strain medium again, the pattern was altered to the point that there was no significant difference in heat resistance of these cells regardless of the preequilibration RH. The same result was obtained when the A strain was grown on the B strain medium; that is, the thermal resistance could not be reversed, but it was altered from the point where the low RH equilibrated cells were least resistant initially to the point where there was no significant difference in any of the cells regardless of what RH was used for preequilibration. The thermal resistance of spores seemed to be dependent on (i) the medium on which the spores are grown, (ii) the RH on which they are exposed before heating, and (iii) some genetic characteristic of the cell.

Bacillus subtilis↗
PubMed1994

External four-channel tocography during delivery.

OBJECTIVE: A four-channel tocographic technique was developed in order to improve present knowledge of spatial uterine motility. METHOD: Fifty-four women were monitored during labor. Four pressure transducers were attached in a square around the umbilicus. RESULTS: The origin of uterine contractions was generally determined to be in the upper right segment of the uterus. The rate of operative deliveries was decreased in the case of predominant upper right origin of labor. Most of the contractions with clear propagation patterns originated on the upper right side, continued to the left and then spread to the lower right part of the uterus. The highest relative intensity was also measured on the upper right side. CONCLUSION: Predominant upper right origin of labor may be important for unassisted or spontaneous delivery.

Adult↗
PubMed1991

Individuality of DNA denaturation patterns in human sperm as measured by the sperm chromatin structure assay.

Eight monthly semen samples from 45 men not known to be exposed to industrial toxicants were measured by the flow cytometric sperm chromatin structure assay (SCSA). This assay determines susceptibility of sperm DNA to in situ, acid-induced denaturation and is quantitated by the metachromatic shift of acridine orange fluorescence from green (native DNA) to red (denatured DNA). The observed green versus red fluorescence scattergram (cytogram) patterns were generally unique between donors and homogeneous within a donor over time. Within a donor, the cytogram patterns were the same whether intact sperm cells or detached nuclei were measured. For some individuals the cytogram patterns differed for some months and then returned to the original pattern. Intraclass correlations for mean and standard deviation of alpha t [alpha t = red/(red + green) fluorescence] were higher (.67 to .90) than any classically measured semen variables, suggesting that SCSA results within an individual were more consistent than other measures. Furthermore, average within-donor CV of alpha t parameters expressed as a percent of any given individual's means was around 10%, which is significantly lower than those derived from common semen measures. The SCSA is an objective, technically sound, biologically stable, sensitive, and feasible measure of semen quality.

Chromatin↗
PubMed1989

Memory and age differences in spatial manipulation ability.

Young and old adults were asked, in 3 experiments, to make decisions about the identity of line segment patterns after either adding or subtracting line segments from the original pattern. On some of the trials, the line segments from the initial display were presented again in the second display to minimize the necessity of remembering early information during the processing of later information. Although this manipulation presumably reduced the importance of memory in the tasks, it had little effect on the magnitude of the age differences in any of the experiments. Because the 2 groups were equivalent in accuracy of simple recognition judgments, but older adults were less accurate when the same types of decisions were required in the context of an ongoing task, the results suggested that older adults may be impaired in the ability to retain information while simultaneously processing the same or other information.

Adolescent↗
PubMedDate not supplied

[Significance of the site of uterine contraction for labor progress and duration of pregnancy].

A four-channel topographic technique was developed in order to improve information about spatial uterine motility. 54 women were monitored during delivery. Four pressure transducers were attached in a square around the umbilicus. Most frequently the origin of labour could be determined in the upper right segment of the uterus. The rate of operative deliveries was decreased in case of predominant upper right origin of labour. The majority of contractions with clear propagation patterns originated at the upper right site, continued to the left and then to the lower right part of the uterus. The highest relative intensity was also measured at the upper right site. Predominant upper right origin of labour may be important for undisturbed delivery. The probability of a preterm delivery is increased in case of an upper right origin of labour.

Adult↗
PubMed1995

Is transposed skin transformed in major head and neck mucosal reconstruction?

We used histological and histochemical methods to investigate the possible changes with time in skin transposed into the oropharynx and oral cavity of patients whose surgical wounds were reconstructed with the classic pectoralis major flap. We found histological evidence that skin morphology was maintained (keratinization with reduced, but the desquamating layer, hair follicles, sweat and sebaceous glands were identifiable), and noted an intense inflammatory reaction in the dermis. Histochemical studies confirmed the progressive flattening of the basal interdigitations between the epithelium and dermis, and the gradual reconstruction of the basement membrane. Although skin-mucosa continuity developed fairly quickly without scar reactions, the two epithelia maintained their original patterns of keratin production, i.e., their textural peculiarities. We propose an original method for the transposition of muscular flaps implanted with autologous culture of keratinocytes, an approach developed in an attempt to ensure more satisfactory rehabilitation of the removed mucosal structures.

Carcinoma↗
PubMed1989

On the visual orientation of random dot Moiré patterns.

We studied the orientation perception of dot patterns with Moiré effect. The Moiré effect was achieved by rotating the original patterns over small angles. When the angle was increased the effect disappeared while the characteristics of orientation estimation remained unchanged. For relatively small angles the subjects performance can be described by a model based on the concept of least squared distance axis. For large angles of rotation this model has began to be insufficient and a more refined model is proposed here.

Adult↗