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PubMed2000

Postnatal development of structure and arrangement of tendon cells. A scanning and transmission electron microscope study in the rat calcaneal tendon.

The postnatal development of the three-dimensional structure and arrangement of the tendon cells in the calcaneal tendon of rats from 5 to 90 days of age were examined under the scanning and the transmission electron microscope (SEM and TEM). Exposed tendon cells were seen as winged bricks with a stellate profile in a cross section. Their slender perikarya were stacked successively in rows along the long axis of the tendon. The plate-like cytoplasmic processes, which were oriented along the perikaryal long axis, extended radially and joined those of the neighboring cells in rows. Therefore, the tubular channels for collagen fascicles were lined with the chained perikarya and their processes of the tendon cells. The cell rows were usually composed of many cells in developing stages, while short rows of one or two cells were observed in the fully developed stage. The cytoplasmic processes were the primary processes in the lateral extension, and their fine branches formed the secondary processes. The secondary processes were numerous at younger stages, showing a fine meshwork due to their mutual joining in the cross sections. In advanced stages, the meshes were coarse and the secondary processes were also perforated either with grouped fenestrations or large pores. In the fully developed stage, the secondary processes were fragmented on the perikarya, while the primary processes extended in the thin delicate sheets with large perforations. The findings in the present study suggest that the tendon cells are arranged in a three-dimensional network by their mutual joining. The tendon cells of the rat calcaneal tendon may not proliferate very much after birth, but do expand their nursing area in line with normal growth by an elongation of the main primary processes and a reduction of the secondary processes and perikaryal mass. The interfascicular clefts, which were caused by an intervention of either the processes at any developmental stages or the fragmented processes at a certain level of the tendon, may also play a role in the passage of tissue fluid.

Age Factors↗

PubMed2000

Adaptive dynamics in diploid, sexual populations and the evolution of reproductive isolation.

Evolutionary branching is the process whereby an initially monomorphic population evolves to a point where it undergoes disruptive selection and splits up into two phenotypically diverging lineages. We studied evolutionary branching in three models that are ecologically identical but that have different genetic systems. The first model is clonal, the second is sexual diploid with additive genetics on a single locus and the third is like the second but with an additional locus for mate choice. Evolutionary branching occurred under exactly the same ecological circumstances in all three models. After branching the evolutionary dynamics may be qualitatively different. In particular, in the diploid, sexual models there can be multiple evolutionary outcomes whereas in the corresponding clonal model there is only one. We showed that evolutionary branching favours the evolution of (partial) assortative mating and that this in turn effectively restores the results from the clonal model by rendering the alternative outcomes unreachable except for the one that also occurs in the clonal model. The evolution of assortative mating during evolutionary branching can be interpreted as the initial phase of sympatric speciation with phenotypic divergence and partial reproductive isolation.

Adaptation, Physiological↗

PubMed2005

Cell structure of developing barbs and barbules in downfeathers of the chick: Central role of barb ridge morphogenesis for the evolution of feathers.

The present ultrastructural study shows how cells organize to form the complex structure of downfeathers in chick embryos. The embryonic epidermis of the apical part of feather filaments folds inward forming barb ridges which extend toward the base of the feather. The stratification of epidermal cells in barb ridges is maintained but the basal layer loses most of the germinal activity. New cells for the growth of feather filaments are mainly produced in its basal part. In barb ridges only the original four epidermal layers of the embryonic epidermis remain to form feathers: 1) the external periderm, 2) three-five layers of the feather sheath and barb vane ridge cells, 3) subperiderm cells, and 4) basal or cylindrical cells. Periderm, sheath, barb vane ridge and cylindrical cells synthesize only alpha-keratin. Instead, cells of the subperiderm layer synthesize a small type of beta-keratin: feather beta-keratin. At hatching, the subperiderm layer is lost in most areas of the skin of the chick (apteric and scaled), and is replaced by cells containing alpha-keratin (interfollicular-apteric epidermis), scale beta-keratin (scales), beak beta-keratin (beak), and claw beta-keratin (claws). Only in feathers, cells of the original subperiderm layer remain and give origin to barb and barbule cells. The formation of separated chains of barb and barbule cells is allowed by the presence of barb vane ridge cells that function as spacers between merging cells of barb and barbule cells. Subperiderm cells elongate and merge into a syncitium to form barbules and barbs. While barbule and barb cells accumulate feather-keratin, barb vane and cylindrical cells accumulate lipids, vesicles and little alpha-keratin. These cells eventually degenerate by necrosis leaving empty spaces and lipids between barbules and barbs. No apoptosis is necessary to explain the process of carving out of barb and barbules in feathers after dissolution of the external sheath. In fact, the retraction of blood vessels nourishing the apical part of the feather filament determines anoxia and eventually necrosis of all cells of the feather. While sheath, barb vane and cylindrical cells degenerate, the keratinized syncitium forming barbs and barbules simply remain in place to form the ramifications of feathers. The formation of barb ridges is considered as the evolutionary innovation necessary for the origin of feathers. The evolution of the morphogenetic process of barb ridge formation within epidermal tubular outgrowths of the integument of ancient archosaurians was an evolutionary novelty, a true avian and theropod characteristic. Barb ridges morphogenesis determines the contemporary formation of barb and barbule cells as a unique and inseparable process so that intermediate forms of evolving feathers with only barbs but not barbules are unlikely. Barb ridges can merge with a large ridge (rachis) or into branched ridges, a process which was at the origin of the ramogenic process from which pennaceous feathers evolved.

Animals↗

PubMed1997

Triple-helical DNA as a reversible block of the branch point in a partially symmetrical DNA four-arm junction.

DNA branch migration is a fundamental process in genetic recombination. A new model system has been developed for studying branch migration in a small synthetic four-arm junction. A mathematical method for describing branch-point movement by discrete steps in such junctions is also presented. The key to our experimental system is the ability to fix the location of the branch point during the assembly of the junction with a reversible block. The block is provided by a short oligonucleotide that forms triplex DNA adjacent to the initial location branch point at low pH. Raising the pH causes the triplex strand to dissociate, making the branch point free to migrate. Once mobile, the branch point can run off the end of the junction. The time-course for this runoff is consistent with a random walk of the branch point. If it is assumed that one migration step moves the branch point one base-pair, the time-course gives a rate constant for one step of 1.4 second-1 at 37 degrees C in 10 mM MgCl2, 50 mM NaCl. These values are consistent with other measurements of non-enzymatic branch migration. We have also monitored the spread of the branch points directly with T4 endonuclease VII. Using EcoRI restriction endonuclease, we have shown that the binding of this protein to the arms of the junction essentially blocks branch migration through the binding site. In these experiments Ca2+ replaces Mg2+, and the enzyme does not cleave the DNA. In vivo there must be a special process to get branch points to migrate past bound proteins.

DNA↗

PubMed1988

Unusual branch point selection involved in splicing of the alternatively processed Calcitonin/CGRP-I pre-mRNA.

To study splice site selection in alternative RNA processing we used the human Calcitonin/CGRP-I (CALC-I) gene. Expression of the CALC-I gene in thyroid C-cells results predominantly in calcitonin (CT) mRNA (containing exons 1 to 4) whereas CGRP-I mRNA (containing exons 1,2,3,5 and 6) is the exclusive product in particular nerve cells. We previously reported that a model precursor RNA containing the exon 3 to exon 5 region is predominantly processed into CGRP-I mRNA in vitro using nuclear extracts of three different cell types. To study CT specific processing in Hela cell nuclear extracts we have used precursor RNAs corresponding to the exon 3 to exon 4 region containing only CT specific processing signals. The results revealed the usage of a uridine residue 23 nucleotides upstream of the 3' splice site as the major site of lariat formation in CT specific splicing. The implications of this finding for the alternative, tissue specific processing of the CALC-I pre-mRNA and for branch point selection in general are discussed.

Calcitonin↗

PubMed2002

Branch-specific migration cues in the Drosophila tracheal system.

The Drosophila tracheal system forms by highly stereotyped migration of the tracheal cells, generating an elaborate network of interconnected tubes supplying oxygen to all tissues. A major guiding system in the migration process of all branches is the dynamic and localized expression of Branchless (Bnl), an FGF-like molecule. Bnl triggers the activation of the FGF receptor Breathless (Btl) locally in all tracheal cells. Is this the only guiding cue, or do additional local signals provide distinct inputs to each branch? Several recent papers identify such local signals, relying on contacts with specific cell types and with the matrix encountered by the migrating tracheal branches. In particular, the paper by Boube et al(1) demonstrates a role for PS integrins in promoting migration of a specific tracheal branch.

Animals↗

PubMed2004

Ultrasound-guided lumbar facet nerve block: accuracy of a new technique confirmed by computed tomography.

BACKGROUND: Lumbar facet nerve (medial branch) blocks are often used to diagnose facet joint-mediated pain. The authors recently described a new ultrasound-guided methodology. The current study determines its accuracy using computed tomography scan controls. METHODS: Fifty bilateral ultrasound-guided approaches to the lumbar facet nerves were performed in five embalmed cadavers. The target point was the groove at the cephalad margin of the transverse (or costal) process L1-L5 (medial branch T12-L4) adjacent to the superior articular process. Axial transverse computed tomography scans, with and without 1 ml contrast dye, followed to evaluate needle positions and spread of contrast medium. RESULTS: Forty-five of 50 needle tips were located at the exact target point. The remaining 5 were within 5 mm of the target. In 47 of 50 cases, the applied contrast dye reached the groove where the nerve is located, corresponding to a simulated block success rate of 94% (95% confidence interval, 84-98%). Seven of 50 cases showed paraforaminal spread, 5 of 50 showed epidural spread, and 2 of 50 showed intravascular spread. Despite the aberrant distribution, all of these approaches were successful, as indicated by contrast dye at the target point. Abnormal contrast spread was equally distributed among all lumbar levels. Contrast traces along the needle channels were frequently observed. CONCLUSIONS: : The computed tomography scans confirm that our ultrasound technique for lumbar facet nerve block is highly accurate for the target at all five lumbar transverse processes (medial branches T12-L4). Aberrant contrast medium spread is comparable to that of the classic fluoroscopy-guided method.

Aged↗

PubMed2001

A computational model of dendrite elongation and branching based on MAP2 phosphorylation.

We introduce a new computational model of dendritic development in neurons. In contrast to previous models, our model explicitly includes cellular mechanisms involved in dendritic development. It is based on recent experimental data which indicates that the phosphorylation state of microtubule-associated protein 2 (MAP2) may play a key role in controlling dendritic elongation and branching (Audesirk et al., 1997). Dephosphorylated MAP2 favours elongation by promoting microtubule polymerization and bundling, whilst branching is more likely to occur when MAP2 is phosphorylated and microtubules are spaced apart. In the model, the rate of elongation and branching is directly determined by the ratio of phosphorylated to dephosphorylated MAP2. This is regulated by calmodulin-dependent protein kinase II (CaMKII) and calcineurin, which are both dependent on the intracellular calcium concentration. Results from computer simulations of the model suggest that the wide variety of branching patterns observed among different cell types may be generated by the same underlying mechanisms and that elongation and branching are not necessarily independent processes. The model predicts how the branching pattern will change following manipulations with calcium, CaMKII and MAP2 phosphorylation.

Animals↗

PubMed1998

The significance of the morphology of the dorsal pancreatic artery in determining the presence of the accessory right hepatic artery passing behind the portal vein.

The dorsal pancreatic artery (DP) and an accessory right hepatic artery (AcRH) passing behind the portal vein were investigated in 98 Japanese specimens. The dorsal pancreatic artery was identified in 87 specimens (88.8%). This artery has been found to yield the following 6 branches: (1) an inferior pancreatic artery (left branch, 83.9%); (2) a right branch-1 that serves as the prepancreatic arcade in front of the pancreas (77.0%); (3) an uncinate branch that distributes to the uncinate process (60.9%); (4) a head branch that distributes from the dorsal side of the pancreas to the head of the pancreas (newly defined in the present study, 60.9%); (5) a right branch-4 that distributes superior to the dorsal part of the pancreatic neck (39.1%); and (6) a right branch-5 that communicates with the posterior pancreaticoduodenal arcade (21.8%). In some cases, the above six branches are formed separately, i.e., two (18.4%) or three (5.7%) dorsal pancreatic arteries are present. The parent artery of the DP was the superior mesenteric artery (SM; 55.0%), accounting for 45.0% of the entire celiac trunk. An accessory right hepatic artery was identified in 18 specimens (18.4%). In cases where the AcRH originated from the entire celiac trunk (5 specimens, 27.8%), it always formed a common trunk with the DP. On the other hand, when the AcRH derived from the SM (13 specimens, 72.2%), it formed a common trunk with the DP 6 of the specimens (33.3%), independent branching was observed in 6 specimens (33.3%). And a common trunk with the inferior pancreaticoduodenal artery was observed in one specimen (5.6%). The dorsal pancreatic artery was considered to supply not only the AcRH but also other pathways that form more complicated variations such as an accessory middle colic artery.

Aged↗

PubMed2003

Neuronal processing delays are compensated in the sensorimotor branch of the visual system.

Moving objects change their position until signals from the photoreceptors arrive in the visual cortex. Nonetheless, motor responses to moving objects are accurate and do not lag behind the real-world position. The questions are how and where neural delays are compensated for. It was suggested that compensation is achieved within the visual system by extrapolating the position of moving objects. A visual illusion supports this idea: when a briefly flashed object is presented in the same position as a moving object, it appears to lag behind. However, moving objects do not appear ahead of their final or reversal points. We investigated a situation where participants localized the final position of a moving stimulus. Visual perception and short-term memory of the final target position were accurate, but reaching movements were directed toward future positions of the target beyond the vanishing point. Our results show that neuronal latencies are not compensated for at early stages of visual processing, but at a late stage when retinotopic information is transformed into egocentric space used for motor responses. The sensorimotor system extrapolates the position of moving targets to allow for precise localization of moving targets despite neuronal latencies.

Humans↗

PubMed1978

Distribution of myosin and the glial fibrillary acidic protein (GFA protein) in rat spinal cord and in the human frontal cortex as revealed by immunofluorescence microscopy.

The glial fibrillary acidic (GFA) protein and myosin were localized in rat spinal cord and human frontal cortex using specific antibodies against GFA protein from human spinal cord and highly purified smooth myosin from chicken gizzard by means of an indirect immunofluorescence microscopical approach. A strong GFA protein and myosin immunoreactivity was found in astrocytes of the white and grey matter and in the external glial limitans membrane. The very fine branches of astrocytic processes stained with anti-GFA protein, but not with anti-myosin. Similar results were obtained with the human frontal cortex, where myosin antibodies failed to reveal the very fine branches of protoplasmic astrocytes. As a whole, staining with the GFA protein antiserum was more crisp than with the myosin antibody.

Animals↗

PubMed2003

Excitation energy transfer in branched dendritic macromolecules at low (4 k) temperatures.

To understand the mode of energy transport in branched dendritic macromolecules, the optical excitation of a dendritic core (A-DSB) at low temperature (4.2 K) was investigated. Fluorescence depolarization measurements were utilized to probe the energy-transfer processes in the branching center at several different temperatures. We found that the anisotropy decay shows an interesting trend at low temperature where depolarization times decreased and the residual anisotropy value also decreased with decreasing temperature. The very fast anisotropy decay suggests a coherent mechanism of energy transport in these systems at low temperature. The contribution of inhomogeneous broadening is suggested as an important factor in the temperature dependence of the anisotropy decay and residual value. The change in inhomogeneous linewidth is responsible for this type of anisotropy behavior.

Journal Article↗

PubMed1991

[Electronic data processing in the hospital: current status, options, "branch packets", customer-specific software and users' needs].

Data management in hospitals used to be the data management of the hospital-management in the last 15 years, not however the data management the doctors performed. The acceptance for electronic means slowly rising more software is used in the clinics today but still by the doctors privately. Software specialists have registered the growing market available for their products. That is why the danger to accept even unusuable software rises every day, as unexperienced software-beginners as doctors mostly are often relied on offers without being told about their dignity and usefulness.

Electronic Data Processing↗

PubMed1985

Enkephalin neurons in the guinea pig proximal colon: an immunocytochemical study using an antiserum to methionine-enkephalin-Arg6-Gly7-Leu8.

The distribution and structure of the neurons containing opioid peptide-like immunoreactivity (enkephalin neurons) in the antimesenteric border of the guinea pig proximal colon were immunocytochemically investigated using an antiserum for methionine-enkephalin-Arg6-Gly7-Leu8 (R-0171). Whole-mount preparations of the different layers of the intestine perfusion-fixed with Bouin's fluid were immunostained by peroxidase-antiperoxidase techniques. Immunopositive nerve fibers were apparent in the longitudinal muscle layer, myenteric plexus, circular muscle layer and submucosa. Immunopositive perikarya of the ganglionic cells were found in the myenteric plexus. A Golgi-type panoramic view was obtained in the intensely-immunostained enkephalin neurons. Distinct immunoreactivity was shown in the many Dogiel type 1 neurons, characterized by short broad processes (winglets or alulae) and one long axon-like process, as well as a few type 2, characterized by several tapering processes, and type 3 neurons, characterized by dendrite-like processes. Many twig-like processes originated from the free margin of the winglet of the enkephalin neurons (wing-ramuli). A part of them entered the intramuscular fasciculus, while the rest remained inside the ganglion. There were transitional forms between these wing-ramuli and the tapering processes of the type 2 neurons or the dendrite-like processes of the type 3 neurons. The axon-like processes sent out branches (axon-ramuli) along their courses or into the intramuscular fasciculus. At the origin of these axon-ramuli, there was a nodulous or humped swelling of the axon-like process (nodulus or crista). In the myenteric ganglion, the axon-ramuli formed varicose terminals. In the guinea pig proximal colon, many axon-like processes of the enkephalin neurons ran in the oral direction. This polarity of neuronic processes may have a functional significance in the neuronal control of the antiperistalsis.

Animals↗

PubMed1981

Reassociation rate limited displacement of DNA strands by branch migration.

Large branched DNA structures are constructed by two-step reassociation of separated complementary strands from restriction fragments of different lengths. The displacement of DNA strands initially annealed to longer complementary DNA sequences, a process mediated by branch migration, is very rapid and has thus far been followed only under conditions which are second order, DNA reassociation rate limiting. The average lifetime of branched DNA leading to displacement of 1.6 Kb strands is estimated to be less than 10 seconds under conditions of DNA reassociation, Tm-25 degrees C. Several DNA-binding drugs, including intercalating dyes, have been tested to determine their influence, if any, on the kinetics of DNA strand displacements by branch migration. Only actinomycin D was found to have significant effect under the conditions we have described. The kinetics of the strand displacement in the presence of low concentrations of actinomycin D remain second order and slower rate of strand displacement must be attributed to decreased rate of reassociation of DNA strands to form the branched intermediates. Consideration is given to the potential manipulation of DNA structures at site-directed branches and the limitations due to rapid strand displacements. The feasibility of constructing sufficiently large branched DNA regions to approach first order, branch migration rate limiting kinetics is also discussed.

Adenoviruses, Human↗

PubMed1975

Morphogenesis in Micrasterias. II. Patterns of morphogenesis.

The final form of the polar lobe and lateral wings of developing semicells of M. rotata results from combined action of three growth processes: tip growth, branching and lobe broadening. Tip growth unaccompanied by branching or broadening occurs during normal development in M. radiata, but is observed only under abnormal conditions (e.g. raised temperature) in M. rotata. When branching and broadening do occur, they occur together and for this reason may be causally related. Autoradiograms demonstrate that specific patterns of cell wall incorporation can be associated with each of the three processes in M. rotata. Autoradiographic patterns found in the polar lobe differ from those found in wings. The growing polar lobe also responds to laser irradiation differently from the wings; lasings occasionally cause duplication of the polar lobe.

Autoradiography↗

PubMed1994

Prolonged exposure of human chondrocytes to ascorbic acid modifies cellular behavior in an agarose gel.

Using an agarose gel culture system, the response of adult human chondrocytes to prolonged exposure of ascorbic acid was evaluated using histochemical, immunocytochemical and morphological techniques. The response of these cells to ascorbic acid was different from those previously reported in the literature. Many chondrocytes branched within the agarose gel with continued exposure to ascorbic acid while other chondrocytes maintained a round configuration typical of chondrocytes in vivo. Fibronectin and type I collagen were closely associated with the cell processes of the branching cells. Type II collagen and an alcian blue-staining matrix were associated with the rounded cells but not with the branched cells. These data suggest that the chondrocytes are able to express both dedifferentiated and redifferentiated phenotypes with ascorbic acid under these culture conditions. In addition, human chondrocytes were cultured in a collagen gel and began branching within 1 hour of culture. It is possible that an accumulation of type I collagen in the pericellular matrix of ascorbic acid treated cultures may enhance and explain the branching seen in these cultures. Studies by others have indicated that ascorbic acid may enhance, reduce, and/or modify the cartilage matrices produced by chondrocytes. These controversial reports in the literature are presumably due to variations between species and the culture methods employed.

Ascorbic Acid↗

PubMed1990

Architecture of the medial smooth muscle of the arterial vessels in the normal human brain: a scanning electron-microscopic study.

The architecture of the medial smooth muscle of arterial vessels in normal human brains was investigated using scanning electron microscopy. We could divide the arterial vessels into four subdivisions according to the number of the circular muscle cells. The arteries (greater than 100 microns in diameter) had 4-20 layers of circular smooth muscle cells; individual circular muscle cells were spindle-shaped and occasionally had branches at their ends. Multidirectional muscle cells were observed in the medio-adventitial border only at the branching sites in large arteries (greater than 300 microns), but at both branching and non-branching sites in the small arteries (100-300 microns). The nonterminal arterioles (30-100 microns) had 2-3 layers of circular muscle cells; most of the circular muscle cells had nodular or rod-like processes at their branched ends. Multidirectional muscle cells were most frequently observed in the medio-adventitial border in this subdivision at both branching and non-branching sites. The terminal arterioles (10-30 microns) had a single layer of circular muscle cells. Multipolar (stellate in appearance) smooth muscle cells were mainly seen in the medio-adventitial border at branching sites. The precapillary arterioles (7-10 microns) had a single layer of branched muscle cells; individual muscle cells had 2-4 circular branches on both sides of the central bulges.

Adolescent↗