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PubMed1987

The ultrastructure of sporogony in Theileria cervi (Bettencourt et al., 1907) in salivary glands of female Amblyomma americanum (L.) ticks.

The process of sporogony of Theileria cervi in salivary glands of unfed and feeding Amblyomma americanum females that were infected as nymphs was studied by light and electron microscopy (SEM and TEM). Sporogony was observed only in granular acini type III and in cells classified as complex granular. Infected acini in salivary glands of both unfed and feeding ticks were enlarged. Some stages of parasite development were evident with light microscopy and SEM, but the specific events of sporogony could be documented only with TEM. Nuclear division was evident in unfed adults and continued throughout the developmental process. As the ticks fed, the parasite syncytium became increasingly complex and branches formed that were connected by thin processes. Sporozoites appeared to form by rapid sequential fission of the multinucleate sporont. Initially, sporozoites were oblong in shape and became rounded when mature. Rhoptries and micronemes were located at the hemisphere of the sporozoite that was opposite from the nucleus. Experimentally infected A. americanum transmitted T. cervi to susceptible fawns with a prepatent period of 14 and 20 days. This is the first ultrastructural description of sporogony in T. cervi in tick salivary glands.

Animals↗

PubMed2000

Sonic hedgehog signaling pathway in vertebrate epithelial appendage morphogenesis: perspectives in development and evolution.

Vertebrate epithelial appendages are elaborate topological transformations of flat epithelia into complex organs that either protrude out of external (integument) and internal (oral cavity, gut) epithelia, or invaginate into the surrounding mesenchyme. Although they have specific structures and diverse functions, most epithelial appendages share similar developmental stages, including induction, morphogenesis, differentiation and cycling. The roles of the SHH pathway are analyzed in exemplary organs including feather, hair, tooth, tongue papilla, lung and foregut. SHH is not essential for induction and differentiation, but is involved heavily in morphogenetic processes including cell proliferation (size regulation), branching morphogenesis, mesenchymal condensation, fate determination (segmentation), polarizing activities and so on. Through differential activation of these processes by SHH in a spatiotemporal-specific fashion, organs of different shape and size are laid down. During evolution, new links of developmental pathways may occur and novel forms of epithelial appendages may emerge, upon which evolutionary selections can act. Sites of major variations have progressed from the body plan to the limb plan to the epithelial appendage plan. With its powerful morphogenetic activities, the SHH pathway would likely continue to play a major role in the evolution of novel epithelial appendages.

Animals↗

PubMed1969

Transmission from pregnanglionic fibres in the hypogastric nerve to peripheral ganglia of male guinea-pigs.

1. Intracellular records were obtained from ganglion cells of the pelvic plexus of male guinea-pigs.2. The input resistance of cells which responded to intracellular stimulation varied from 40 to 150 MOmega. Slope resistance decreased when the membrane was hyperpolarized. Time constants varied from 5 to 200 msec. Resting membrane potentials ranged from 40 to 70 mV.3. Action potentials in response to direct stimulation were followed by a prolonged phase of after-hyperpolarization.4. A second type of cell was also impaled which did not respond to electrical stimulation. These cells had resting membrane potentials in the range 60-70 mV, input resistances of less than 20 MOmega and time constants of less than 3 msec.5. In most ganglion cells, stimulation of the hypogastric nerve evoked action potentials which were often followed by a secondary phase of depolarization indicating continuing transmitter action.6. Orthodromic responses were generally ;all-or-nothing' and could not be graded with changes in stimulus strength. The latency of orthodromic responses indicated that ganglion cells were innervated by both B and C fibres in the hypogastric nerve.7. Orthodromic responses were blocked by tubocurarine, 5 x 10(-5) g/ml., and dihydro-beta-erythroidine, 10(-5) g/ml.8. Spontaneous, excitatory post-synaptic potentials of up to 4.8 mV in amplitude were observed. The frequency of their discharge was greatly increased by repetitive stimulation of the hypogastric nerve.9. The ultrastructure of the pelvic ganglia was studied by electronmicroscopy. Two types of ganglion cell process were observed, fine (0.1 mu) branching tufts thrown up from the soma within the surrounding capsule and longer, thicker (1 mu) extracapsular processes. Synapses were found to occur most frequently between the varicose terminal segments of preganglionic axons and the small intracapsular processes.10. Similarities between the properties of the pelvic ganglia innervated by the hypogastric nerve and those of the parasympathetic division of the autonomic nervous system are discussed.

Action Potentials↗

PubMed1990

Peripheral development of avian trigeminal nerves.

Development of the trigeminal nerve branches was studied in stage -17 to -27 chick embryos stained with an antibody to neurofilament protein. The following findings were obtained. 1) Ectopic ganglia transiently appeared in the ectoderm of the supraorbital region and were considered as remnant ophthalmic-placode-derived ganglia. 2) Most of the cutaneous sensory branches of the maxillomandibular nerve arose from a loosely arborized mass of neurites, provisionally termed the maxillomandibular reticulum, in which the fibers intermingled in a seemingly random fashion. 3) The growth of the trigeminal branches was mainly correlated with the development of the facial processes; however, irregular communications between different groups of branches were observed, suggesting that topographical organization of the peripheral branches is not rigid in early stages. 4) From the ophthalmic nerve around stage 23, transient dorsal rami developed and were distributed in the mesenchymal space, the cavum epiptericum, and passed near the ectoderm. Their homology with the rr. tentorii in human anatomy is suggested.

Animals↗

PubMed1984

A combined scanning electron microscopy and immunofluorescence study demonstrating that the odontoblast process extends to the dentinoenamel junction in human teeth.

The extent of the odontoblast cell process has been the subject of controversy for many years. Using SEM we have examined the extent and morphology of the process on dentine surfaces of human teeth which were partially demineralized and collagenase digested. Third molars were extracted and split; the dentine surface was demineralized, digested by bacterial collagenase, fixed with glutaraldehyde, postfixed in osmium tetroxide, and prepared for SEM investigation. The SEM study revealed the presence of many processlike structures which extended from the odontoblast cell bodies up to the dentinoenamel junction (DEJ). These processes demonstrated lateral and terminal branching and some of them terminated in distended spheres. We have also applied an immunofluorescence technique at the light microscope level to these exposed dentinal surfaces to localize the intracellular microtubules. For this, a second series of third molars was processed in the same manner as for the SEM up to the fixation stage. Teeth were then fixed in periodate-lysine-paraformaldehyde, postfixed in -20 degrees C acetone, and then incubated with affinity-purified rabbit antitubulin antibodies, followed by fluorescein-conjugated goat antirabbit IgGs. Intratubular immunofluorescence labelling for tubulin was evident from the odontoblast cell bodies up to the DEJ. The presence of the tubulin-containing structures extending to the DEJ supports the hypothesis that the structures observed with the SEM are odontoblast processes and that the odontoblast processes do extend to the DEJ.

Adult↗

PubMed2005

On the conformational memory in the photodissociation of formic acid.

The photodissociation of formic acid at 248 and 193 nm was investigated by classical trajectory and RRKM calculations using an interpolated potential energy surface, iteratively constructed using the B3LYP/aug-cc-pVDZ level of calculation. Several sampling schemes in the ground electronic state were employed to explore the possibility of conformational memory in formic acid. The CO/CO2 branching ratios obtained from trajectories initiated at the cis and at the trans conformers are almost identical to each other and in very good accordance with the RRKM results. In addition, when a specific initial excitation that simulates more rigorously the internal conversion process is used, the calculated branching ratio does not vary with respect to those obtained from cis and trans initializations. This result is at odds with the idea of conformational memory in the ground state proposed recently for the interpretation of the experimental results. It was also found that the calculated CO vibrational distributions after dissociation of the parent molecule at 248 nm are in agreement with the experimental available data.

Journal Article↗

PubMedDate not supplied

Radiologic spectrum of intraductal papillary mucinous tumor of the pancreas.

"Intraductal papillary mucinous tumor" is now the preferred term to describe a spectrum of proliferation of the pancreatic ductal epithelium. The tumor produces an excessive amount of mucin and results in progressive dilation of the main pancreatic duct or cystic dilation of the branch ducts, depending on the location of the tumor. This tumor is small and localized in a segment of the main pancreatic duct or in branch ducts, particularly in the branch ducts of the uncinate process, but it may also be diffuse, involving a wide area of the pancreatic ducts. Excessive mucin may impede the pancreatic duct flow and, in turn, produce symptoms of chronic pancreatitis. The following findings are seen on imaging studies: lobulated multicystic dilatation of the branch ducts, diffuse dilatation of the main pancreatic duct, intraductal papillary tumors, elongated or globlike mucous plugs in the dilated ducts, and bulging of the papilla into the duodenal lumen. The diagnosis is suggested at ultrasonography, computed tomography, or magnetic resonance cholangiopancreatography. Endoscopic retrograde cholangiopancreatography is the imaging modality of choice for the diagnosis, because it depicts the communication between the cystically dilated branch ducts and the diffusely dilated main pancreatic duct, as well as intraductal papillary tumor and mucous plugs.

Adenocarcinoma, Mucinous↗

PubMed2005

Holliday junction dynamics and branch migration: single-molecule analysis.

The Holliday junction (HJ) is a central intermediate in various genetic processes including homologous and site-specific recombination and DNA replication. Branch migration allows the exchange between homologous DNA regions, but the detailed mechanism for this key step of DNA recombination is unidentified. Here, we report direct real-time detection of branch migration in individual molecules. Using appropriately designed HJ constructs we were able to follow junction branch migration at the single-molecule level. Branch migration is detected as a stepwise random process with the overall kinetics dependent on Mg2+ concentration. We developed a theoretical approach to analyze the mechanism of HJ branch migration. The data show steps in which the junction flips between conformations favorable to branch migration and conformations unfavorable to it. In the favorable conformation (the extended HJ geometry), the branch can migrate over several base pairs detected, usually as a single large step. Mg2+ cations stabilize folded conformations and stall branch migration for a period considerably longer than the hopping step. The conformational flip and the variable base pair hopping step provide insights into the regulatory mechanism of genetic processes involving HJs.

Base Sequence↗

PubMed1994

Lamina propria macrophages involved in cell death (apoptosis) of enterocytes in the small intestine of rats.

In the rat small intestine, apoptotic enterocytes are exfoliated at the villus tip as a whole cell, in contrast to guinea pig enterocytes which are phagocytosed by macrophages in their cell body and shed off only in their apical cortex. While macrophages gather in the lamina propria of the intestinal villi in both species, their functions seem to differ. Unlike the guinea pig, lamina propria macrophages observed in the rat small intestine did not show morphological signs of phagocytosis, revealing few cellular elements in their phagosomes. At the "shoulder" of the villus, i.e., a certain distance proximal to the villus tip, subepithelial macrophages extended a thick process deep into the epithelium; their branched terminals penetrated the cytoplasm of enterocytes, resulting in the formation of excavated spaces in the cell body. Processes of macrophages frequently reached close to the brush border. At the shoulder of the villus, a few effete cells showed typical apoptotic signs and appeared to be pushed out into the lumen; still, the shedding of apoptotic enterocytes was recognized mainly at the very top of the villus, where no intraepithelial processes of macrophages could be seen. The present findings indicate that in the rat, lamina propria macrophages do not engulf aged enterocytes, but are involved in inducing their apoptosis.

Acid Phosphatase↗

PubMed2002

Tumor necrosis factor inhibits neurite outgrowth and branching of hippocampal neurons by a rho-dependent mechanism.

In response to injury and inflammation of the CNS, brain cells including microglia and astrocytes secrete tumor necrosis factor-alpha (TNF). This pro-inflammatory cytokine has been implicated in both neuronal cell death and survival. We now provide evidence that TNF affects the formation of neurites. Neurons cultured on astrocytic glial cells exhibited reduced outgrowth and branching of neurites after addition of recombinant TNF or prestimulation of glial cells to secrete TNF. This effect was absent in neurons of TNF receptor-deficient mice cultured on prestimulated glia of wild-type mice and was reverted by blocking TNF with soluble TNF receptor IgG fusion protein. TNF activated in neurons the small GTPase RhoA. By inactivating Rho with C3 transferase, the inhibitory effect of TNF on neurite outgrowth and branching was abolished. These results suggest that glia-derived TNF, as part of an injury or inflammatory process, can inhibit neurite elongation and branching during development and regeneration.

ADP Ribose Transferases↗

PubMed2000

Functional significance of MMP-9 in tumor necrosis factor-induced proliferation and branching morphogenesis of mammary epithelial cells.

Tissue remodeling is a key process involved in normal mammary gland development, with matrix metalloproteinases (MMPs) playing an important role in this process. Our laboratory has demonstrated that tumor necrosis factor (TNF) stimulates branching morphogenesis of mammary epithelial cells (MEC) within a reconstituted basement membrane. Studies were therefore undertaken to determine whether MMPs might mediate the effects of TNF. Using a primary culture model in which rat MEC grow three-dimensionally within a reconstituted basement membrane, we found that TNF stimulated secretion of MMP-9 but not MMP-2. To determine whether MMP-9 was involved in TNF-induced proliferation and branching morphogenesis, we used a peptide containing the prodomain sequence of MMPs and two MMP inhibitors. Both the prodomain peptide (5 x 10(-4)-10(-3) M), as well as BB-94 (10(-8)-10(-5) M) and CGS 27023A (10(-6)-10(-5) M), inhibited TNF-induced proliferation and branching morphogenesis in a concentration-dependent manner. Finally, to verify the specific requirement for MMP-9, we demonstrated that an MMP-9 neutralizing antibody blocked TNF-induced proliferation and branching morphogenesis. Together, these data suggest that TNF-regulated MMP-9 may play a role in the controlled invasion of the fad pad that occurs during normal mammary gland development and that misregulation of MMP-9 may contribute to the invasiveness of breast cancer.

Animals↗

PubMed2003

Branched filaments no fungus, ovoid bodies no bacteria: Two unusual cases of mycetoma.

We describe a 58-year-old man presenting with necrotizing panniculitis of the lower right leg and a 64-year-old woman with a clinically similar lesion combined with pustular eruptions and subsequent ulceration on the forehead. In the first patient, Giemsa staining showed small ovoid bodies and Grocott staining revealed hyphae. Histology from the process on the forehead showed branched filaments in the periodic acid-Schiff (PAS) staining. In the first case, Madurella mycetomatis, a fungus, was the pathogenic agent, whereas in the other case white colonies of filamentous organisms resembling fungi could be cultivated that turned out to be the bacterium Nocardia brasiliensis. Since the initial clinical appearance of these two forms of mycetoma were almost identical and histopathologic findings were inconclusive, only sophisticated microbiologic work-up of material from lesional skin led to the correct diagnosis. In times of global tourism, these unusual cases impressively document the necessity to become more familiar with mycetoma to make accurate therapeutic decisions with effective results, possibly saving a limb.

Antifungal Agents↗

PubMed1996

Genetic control of epithelial tube fusion during Drosophila tracheal development.

During development of tubular networks such as the mammalian vascular system, the kidney and the Drosophila tracheal system, epithelial tubes must fuse to each other to form a continuous network. Little is known of the cellular mechanisms or molecular control of epithelial tube fusion. We describe the cellular dynamics of a tracheal fusion event in Drosophila and identify a gene regulatory hierarchy that controls this extraordinary process. A tracheal cell located at the developing fusion point expresses a sequence of specific markers as it grows out and contacts a similar cell from another tube; the two cells adhere and form an intercellular junction, and they become doughnut-shaped cells with the lumen passing through them. The early fusion marker Fusion-1 is identified as the escargot gene. It lies near the top of the regulatory hierarchy, activating the expression of later fusion markers and repressing genes that promote branching. Ectopic expression of escargot activates the fusion process and suppresses branching throughout the tracheal system, leading to ectopic tracheal connections that resemble certain arteriovenous malformations in humans. This establishes a simple genetic system to study fusion of epithelial tubes.

Animals↗

PubMed1990

Isolation and characterization of a complementary DNA clone coding for the E1 beta subunit of the bovine branched-chain alpha-ketoacid dehydrogenase complex: complete amino acid sequence of the precursor protein and its proteolytic processing.

A 1.7-kb cDNA clone encoding the entire precursor of the E1 beta subunit of the branched-chain alpha-ketoacid dehydrogenase (BCKDH) complex was isolated from a bovine liver cDNA library by screening with a mixture of synthetic oligonucleotide probes corresponding to the C-terminal five-residue sequence of the mature E1 beta subunit. A partial amino acid sequence was determined by Edman degradation of the intact subunit and the peptides generated by cleavage at the lysyl bonds. Nucleotide sequence analysis revealed that the isolated cDNA clone contained the 5'-untranslated sequence of 186 nucleotides, the translated sequence of 1176 nucleotides, and the 3'-untranslated sequence of 306 nucleotides with a poly(A) tail. A type AATAAA polyadenylation signal was located 17 nucleotides upstream of the start of a poly(A) tail. Comparison of the amino acid sequence predicted from the nucleotide sequence of the cDNA insert of the clone with the partial amino acid sequence of the mature BCKDH E1 beta subunit showed that the cDNA insert encodes for a 342 amino acid subunit with Mr 37,745 and that the subunit is synthesized as the precursor with a leader sequence of 50 amino acids and processed at the N-terminus. Northern blot analysis using the cDNA insert as a probe showed the presence of a 1.8-1.9-kb mRNA in bovine liver, suggesting that the insert covers nearly a full length of mRNA. Alignment of the deduced amino acid sequence of bovine BCKDH E1 beta with that of the human pyruvate dehydrogenase (PDH) complex E1 beta subunit revealed a high degree of sequence homology throughout the two enzymes.(ABSTRACT TRUNCATED AT 250 WORDS)

3-Methyl-2-Oxobutanoate Dehydrogenase (Lipoamide)↗

PubMed1980

Anatomic arrangement of the hepatic veins in the goat.

In gross anatomic and angiographic examinations of the hepatic veins of 15 goats, the following were seen: (i) The middle hepatic vein was formed by the contribution of two main branches, one branch coming from the quadrate lobe and the other branch from the right lobe. (ii) There were two right hepatic veins, one of them running along the caudate process and the other formed by branches coming from the dorsal part of the right lobe. (iii) The entrance of the middle hepatic vein, as well as the entrance of the left hepatic vein into the caudal vena cava were partly covered by valvelike membranous flaps.

Animals↗

PubMed1980

Studies on the activation and inactivation of the branched chain alpha-keto acid dehydrogenase in the perfused rat heart.

Evidence for a reversible process resulting in stable activated and inactivated states of the mitochondrial branched chain alpha-keto acid dehydrogenase complex in isolated perfused rat heart is presented. The inactivation process is mediated by pyruvate infusion, while activation (up to 18-fold) is facilitated by branched chain alpha-keto acid substrates. The low activity state of the branched chain complex characteristic of freshly excised rat hearts could be maintained by infusion of either pyruvate or glucose. Activation of the complex in the perfused rat heart was achieved slowly by substrate-free perfusion, while rapid activation was accomplished by infusion of branched chain alpha-keto acids. The fully activated enzyme complex resulting from branched chain alpha-keto acid infusion subsequently could be inactivated maximally by infusion of pyruvate alone or intermediate degrees of inactivation could be produced by certain ratios of co-infused pyruvate and branched chain alpha-keto acid. alpha-Ketoisocaproate was an order of magnitude more effective than alpha-keto isovalerate either in preventing inactivation or in stimulating the opposing activation process when co-infused with pyruvate. The mitochondrial pyruvate transport inhibitor, alpha-cyanocinnamate, effectively prevented inactivation of the complex by infused pyruvate. Differential changes in the activation states of the branched chain alpha-keto acid dehydrogenase and pyruvate dehydrogenase complexes were evident when the two complexes were compared in apparently similar flux-inhibited (via octanoate infusion) and flux-stimulated (via dichloroacetate infusion) metabolic conditions. The differential effect of pyruvate concentration on the activity states of the two complexes was also well-defined. The results of the present study suggest distinct systems for the regulation of the activity of the two multienzyme complexes of interest. While our results argue neither for nor against an inactivation of the branched chain alpha-keto acid dehydrogenase complex by a protein kinase, the regulatory properties of such an intramitochondrial protein kinase may not be similar to the pyruvate dehydrogenase kinase. The mechanistic nature of the suggested novel regulatory system concerned with the pyruvate-mediated inactivation of the branched chain alpha-keto acid activation cannot be inferred at the present time.

3-Methyl-2-Oxobutanoate Dehydrogenase (Lipoamide)↗

PubMed1999

Steroid hormone enhancement of neurite outgrowth in identified insect motor neurons involves specific effects on growth cone form and function.

Dramatic reorganization of dendrites and axonal terminals is a hallmark of neuronal remodeling during metamorphosis in the hawkmoth, Manduca sexta. The dendritic and axonal arbors of leg motor neurons regress in late larval stages, then regrow during adult development. Ecdysteroids, the insect steroids that trigger metamorphosis, control both regression and outgrowth in vivo and stimulate neuritic growth in cultured pupal leg motor neurons. To identify subcellular targets of ecdysteroid action in these neurons, we examined the dynamic and structural features of branching and their modulation by ecdysteroids in vitro. Delayed treatment of pupal leg motor neurons with ecdysteroid led to a robust enhancement of neuritic branch accumulation accompanied by a subtle effect on total neuritic length. Repeated imaging revealed that branch formation occurred almost exclusively at the growth cone; interstitial branching was extremely rare. Ecdysteroid treatment significantly enhanced both the formation and retention of branches at the growth cone. Branches formed via two distinct processes: engorgement (of fine protrusions) and condensation (of lamellae) with the relative contributions of these mechanisms being unaltered by ecdysteroid. Confocal imaging of the cytoskeleton demonstrated that growth cones consisted of microtubule-based domains fringed by actin-based filopodia. Treated growth cones were larger and displayed increased numbers of microtubule-based branches, whereas filopodial density was unaffected. These findings indicate that ecdysteroid enhances neuritic branching by altering growth cone structure and function, and suggest that hormonal modulation of cytoskeletal interactions contributes significantly to neuritic remodeling during metamorphosis.

Animals↗

PubMed1993

In vitro protein splicing of purified precursor and the identification of a branched intermediate.

Protein splicing is a posttranslational processing event in which an internal polypeptide is excised from a protein precursor and the terminal polypeptides are then ligated together, resulting in the production of two proteins. This report presents direct evidence for protein splicing by demonstrating in vitro splicing of purified precursor that accumulated when the protein splicing element from Pyrococcus DNA polymerase was cloned into a foreign gene. In vitro splicing was temperature and pH dependent. A slowly migrating species exhibited kinetic properties of a splicing intermediate and was shown to be a branched molecule by N-terminal sequencing. The precursor and slowly migrating species were interconvertible in response to pH shifts.

Amino Acid Sequence↗