Search PubMed⌕ Search

SEARCH · Search PubMed

Results for “Segmentation”

Search indexed PubMed citations on genomics, clinical trials, systematic reviews and public health. Explore titles, authors and supplied subject terms, then open the PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 1,333 records · Page 74Linked to original sources
PubMed1981

Spatial spread of activation and background desensitization in toad rod outer segments.

1. The spread of activation and background desensitization in rods was studied by recording membrane current from single outer segments in pieces of isolated toad retina.2. Flash sensitivity changed slightly along the outer segment, falling by about 30% from base to tip.3. When only the distal half of an outer segment was in the recording pipette, illumination of the unrecorded part elicited little or no photocurrent at the recorded part, indicating that a photoisomerization does not cause activation of the entire outer segment.4. With diffuse illumination of an outer segment fully drawn into the pipette, the intensity-response relations at fixed times were invariant in form for most of the rising phase of the flash response and were considerably steeper than the Michaelis relation. The observed relation was consistent with a model in which a photoisomerization blocks all channels over a short region of the outer segment.5. With illumination restricted to a narrow transverse slit, the intensity-response relations at fixed times were much less steep, as would be expected for a very limited longitudinal spread of activation. An upper limit for the effective longitudinal diffusion coefficient of the internal transmitter was estimated to be about 3 x 10(-7) cm(2) sec(-1). This corresponds to a space constant for longitudinal spread of transmitter of about 3 mum at the time of the dim response peak.6. The time course of flash responses elicited with light positioned either on the edge or on the centre of the outer segment was very similar.7. Desensitization resulting from steady illumination by a transverse slit was also localized longitudinally. A linear desensitization parameter T, defined in Results, decayed approximately exponentially along the outer segment, on either side of the site of photoisomerization, with a space constant of about 6 mum.8. Transverse spread of desensitization was more effective than longitudinal spread.9. After turning off a dim diffuse background light, the decay of T was roughly exponential with a time constant of several seconds. From this, and the steady state space constant of 6 mum, it is estimated that the effective longitudinal diffusion coefficient for a ;desensitizing substance' would also be about 10(-7) cm(2) sec(-1).10. The restricted longitudinal spread of activation and desensitization may be explained by the barrier to diffusion presented by the stacked membranous disks in the outer segment. This baffling reduces the effective longitudinal diffusion coefficient to about 1/50 that of ordinary aqueous diffusion, but it does not significantly affect transverse spread.

Animals↗
PubMed1988

Evidence for two functionally different membrane fractions in bovine retinal rod outer segments.

1. Cyclic GMP-induced and Na+-induced Ca2+ releases from Ca2+-containing photoreceptor membrane vesicles were investigated using the Ca2+-sensitive dye Arsenazo III. Bovine photoreceptor membrane vesicles were prepared by osmotic lysis and hypotonic wash of purified rod outer segments. 2. Calcium was entrapped into these vesicles either by utilizing their passive membrane permeability ('passive' Ca2+ loading), or by activating cyclic GMP-dependent channels (cyclic GMP-stimulated Ca2+ loading), or by Na+-Ca2+ exchange (Na+-stimulated Ca2+ loading). 3. After passive Ca2+ loading, cyclic GMP released at most about 23% of the total Ca2+ which could be released with the Ca2+ ionophore A23187 (Km = 6.5 +/- 0.92 microM (6); Hill coefficient 1.68 +/- 0.19 (6]. 4. Millimolar concentrations of Na+ also induce Ca2+ releases from passively Ca2+-loaded outer segment membrane vesicles of at most 26% of the total releasable Ca2+. 5. For passively Ca2+-loaded outer segment membrane vesicles, the sum of a partial cyclic GMP-induced Ca2+ release and a consecutive saturating Na+-induced Ca2+ release, or vice versa, the sum of a partial Na+-induced Ca2+ release and a consecutive saturating cyclic GMP-induced Ca2+ release, was about 25% of the total releasable Ca2+. 6. Both cyclic GMP-induced and Na+-induced Ca2+ release was greater than 25%, up to 50% of the total releasable Ca2+ if either cyclic GMP-stimulated or Na+-stimulated Ca2+ loading of outer segment membrane vesicles was employed. 7. When the outer segment membrane vesicles were mildly sonicated in a water bath, the maximal percentages of Ca2+ releasable by both cyclic GMP and Na+ dropped, reaching final values, after a 60 s sonication period, of 2.3% for the cyclic GMP-induced Ca2+ release and 7% for the Na+-induced Ca2+ release. 8. It is concluded from these results that outer segment membrane vesicles comprise two populations of vesicles, one which contains cyclic GMP-dependent channels and Na+-Ca2+ exchanging proteins, and another one which contains neither of these proteins. 9. The sonication experiments are interpreted as suggesting that these two vesicle populations correspond to plasma and disc membranes of the rod outer segments, respectively.

Animals↗
PubMed1992

Calcium homeostasis in the outer segments of retinal rods from the tiger salamander.

1. The processes regulating intracellular calcium in the outer segments of salamander rods have been investigated. The main preparation used was the isolated rod loaded with the Ca(2+)-sensitive photoprotein aequorin, from which outer segment membrane current and free [Ca2+]i could be recorded simultaneously. Two other preparations were also used: outer segment membrane current was recorded from intact, isolated rods using a suction pipette, and from detached outer segments using a whole-cell pipette. 2. Measurements of free intracellular [Ca2+] in Ringer solution were obtained from two aequorin-loaded rods. Mean [Ca2+]i in darkness was 0.41 microM, and after a bright flash [Ca2+]i fell to below detectable levels ( < 0.3 microM). No release of intracellular Ca2+ by a bright flash of light could be detected ( < 0.2 microM). 3. Application of the phosphodiesterase inhibitor 3-isobutyl-1-methylxanthine (IBMX) caused an increase in the size of the light-sensitive current and a rise in [Ca2+]i, but application of IBMX either when the light-sensitive channels had been closed by a bright light or in the absence of external Ca2+ caused no detectable rise in [Ca2+]i. It is concluded that IBMX increases [Ca2+]i by opening light-sensitive channels, and does not release Ca2+ from stores within the outer segment. 4. Removal of external Na+ caused a rise in [Ca2+]i to around 2 microM and completely suppressed the light-sensitive current. 5. The Na(+)-Ca2+, K+ exchange current in aequorin-loaded rods was activated in first-order manner by internal free calcium, with a mean Michaelis constant, KCa, of 1.6 microM. 6. The KCa of the Na(+)-Ca2+, K+ exchange was increased by elevating internal [Na+]. 7. The Michaelis relation between [Ca2+]i and the activity of the Na(+)-Ca2+, K+ exchange was used to calculate the change in [Ca2+]i occurring during the response to a bright light. In aequorin-loaded rods in Ringer solution the mean change in free [Ca2+]i after a bright flash was 0.34 microM. In these rods 10% of the dark current was carried by Ca2+. 8. Most of the calcium entering the outer segment was taken up rapidly and reversibly by buffer systems. The time constant of equilibration between free and rapidly bound Ca2+ was less than 20 ms. No slow component of calcium uptake was detected. 9. Two components of calcium buffering could be distinguished in the outer segments of aequorin-loaded rods.(ABSTRACT TRUNCATED AT 400 WORDS)

1-Methyl-3-isobutylxanthine↗
PubMed2003

Magnetic resonance imaging analysis of anterior and posterior eye segment displacement during ocular gaze shifts.

PURPOSE: To determine the relationship between movements of the posterior and anterior eye segments during arbitrary gaze shifts and to obtain information for monitoring fixation during radiotherapy for ocular diseases. METHODS: We examined eye movements of ten emmetropic volunteers in a 1.5 T magnetic resonance system. Using a T2-weighted ultrafast turbo-spin echo sequence (UTSE), the eyes were examined within 21 seconds. Sagittal and transversal eye slices were obtained in five passages in five gaze directions (straight ahead, 15 degrees above, 15 degrees below, 15 degrees right and 15 degrees left of the primary position). Displacement of the posterior eye segment was analyzed in relation to the movement of the anterior segment in all directions. RESULTS: The relationship between the movements of the anterior and posterior eye segment was 1:0.8 (+/- 0.06 SD) during horizontal gaze shifts and 1:1.16 (+/- 0.11 SD) during vertical gaze shifts. CONCLUSIONS: Magnetic resonance imaging showed that the relationship between anterior and posterior eye segments was different during horizontal and vertical eye movements, indicating the presence of more than one center of rotation. Compared to the anterior eye segment, there was less displacement of the posterior eye segment during horizontal eye movements and more displacement during vertical eye movements.

Adult↗
PubMed1993

Characterization of calpain II in the retina and photoreceptor outer segments.

Calpain II was purified to apparent homogeneity from bovine neural retinas. It was found to be biochemically similar to brain calpain II, purified by the same procedure, with respect to: subunit mobility in SDS-polyacrylamide gel electrophoresis; Ca2+ sensitivity; inhibition by calpeptin and other cysteine protease inhibitors; and optimal pH. Semithin cryosections were immuno-labeled with antibodies specific for the catalytic subunit of calpain II. Calpain II was detected in most layers of the retina, with the most pronounced label present in the plexiform layers (synaptic regions) and the photoreceptor outer segments. In dark-adapted retinas, the label was distributed throughout the outer segments. In light-adapted retinas, outer segment labeling was concentrated in the connecting cilium, and the inner segments were labeled. A partially pure preparation of calpain II from isolated rod outer segments was found to have the same biochemical characteristics as calpain II prepared in the same way from the whole retina. The enzyme was distributed fairly evenly between the cytosolic and cytoskeletal fractions of isolated rod outer segments. Immunoblots of the rod outer segment cytoskeleton were used to determine the susceptibility of known components of the actin-based cytoskeleton to proteolysis by calpain II in vitro. Actin was not proteolyzed at all, alpha-actinin was only slowly degraded, but myosin II heavy chain was rapidly proteolyzed. Actin filaments have been shown previously to be associated with myosin II and alpha-actinin in a small domain within the connecting cilium, where they play an essential role in the morphogenesis of new disk membranes. The localization of calpain II in the connecting cilium after light exposure, combined with the in vitro proteolysis of myosin II, suggests that calpain II could be involved in light-dependent regulation of disk membrane morphogenesis by proteolysis of myosin II.

Animals↗
PubMedDate not supplied

Longitudinal diffusion of a polar tracer in the outer segments of rod photoreceptors from different species.

Vertebrate rod photoreceptors are the ultimate light sensors, as they can detect a single photon. In darkness, rods maintain a high concentration of the intracellular messenger cyclic guanosine monophosphate (cGMP), which binds to and keeps open cationic channels on the plasma membrane of the outer segment. Absorption of a photon by the visual pigment of the rod, rhodopsin, initiates a biochemical amplification cascade that leads to a reduction in the concentration of cGMP and closure of the channels, thereby converting the incoming light to an electrical signal. Because the absorption of a photon and the ensuing reactions are localized events, the magnitude of the response of the rod to a single photon depends on the spread of the decrease in the cGMP concentration along the length of the outer segment. The longitudinal diffusion of cGMP depends on the structural parameters of the rod outer segment, specifically the area and the volume available for diffusion. To characterize the effect of rod outer segment cytoarchitecture on diffusion, we have used fluorescence recovery after photobleaching (FRAP) and examined the mobility of a fluorescent polar tracer, calcein, in the rod outer segments from three species with different outer segment structures: frog (Rana pipiens), mouse (Mus musculus domesticus) and gecko (Gekko gekko). We found that the diffusion coefficient is similar for all three species, in the order of 8-17 microm(2) s(-1), in broad agreement with the predictions by Holcman and Korenbrot (Biophys. J. 2004:86;2566-2582) based on the known cytoarchitecture of rod outer segments. Consequently, the results also support their prediction that the longitudinal spread of light excitation in rods is similar across species.

Animals↗
PubMed2000

Chemical changes in the photoreceptor outer segments due to iron induced oxidative stress: analysis by Fourier transform infrared (FT-IR) microspectroscopy.

Oxidative stress is thought to be an important pathogenic mechanism in many diseases of the retina. The purpose of this study was to investigate the chemical changes that are present in the photoreceptor outer segments of the retina following exposure to oxidative stress. Fourier transform infrared (FT-IR) microspectroscopy enables the characterization and semi-quantitation of chemical functional groups in microscopic regions of tissue sections. This technique was used to evaluate the chemical changes in the outer segments following exposure to ferrous sulfate, which promotes oxidative tissue damage. A reduction of C=C-H and C=O functional groups was observed in the outer segments of iron-injected eyes compared to vehicle-injected eyes at 3 days following injection, which is prior to major histological changes that occur by 7 days. These functional groups are found in docosahexaenoic acid (DHA), which is present at a high concentration in the outer segments. DHA contains a series of six cis-conjugated double bonds, which are vulnerable to free radical attack, and the reduction of these unsaturation group absorptions suggests that DHA was degraded and/or removed from the outer segments. An unexpected finding was that several other chemical functional groups increased in concentration over time in the outer segments of vehicle-injected eyes compared to non-injected eyes. These increases generally did not include C=C-H or C=O, which suggests that either DHA was being degraded while other organic molecules were being concentrated, or that production of DHA failed to be upregulated in vehicle-injected eyes. In summary, there was a loss of both C=C-H and C=O functional group concentrations in the outer segments of iron-injected eyes, and there was an increased concentration of several other chemical functional groups following trauma induced by vehicle injection.

Animals↗
PubMed1990

Incorporation of squalene into rod outer segments.

We have reported previously that squalene is the major radiolabeled nonsaponifiable lipid product derived from [3H]acetate in short term incubations of frog retinas (Keller, R. K., Fliesler, S. J., and Nellis, S. W. (1988) J. Biol. Chem. 263, 2250-2254). In the present study, we demonstrate that newly synthesized squalene is incorporated into rod outer segments under similar in vitro conditions. We show further that squalene is an endogenous constituent of frog rod outer segment membranes; its concentration is approximately 9.5 nmol/mumol of phospholipid or about 9% of the level of cholesterol. Pulse-chase experiments with radiolabeled precursors revealed no metabolism of outer segment squalene to sterols in up to 20 h of chase. Taken together with our previous absolute rate studies (Keller, R. K., Fliesler, S. J., and Nellis, S. W. (1988) J. Biol. Chem. 263, 2250-2254), these results suggest that most, if not all, of the squalene synthesized by the frog retina is transported to rod outer segments. Synthesis of protein is not required for squalene transport since puromycin had no effect on squalene incorporation into outer segments. Conversely, inhibition of isoprenoid synthesis with mevinolin had no effect on the incorporation of opsin into the outer segment. These latter results support the conclusion that the de novo synthesis and subsequent intracellular trafficking of opsin and isoprenoid lipids destined for the outer segment occur via independent mechanisms.

Acetates↗
PubMedDate not supplied

[Outer segments of the retinal photoreceptors of vertebrates: the ultrastructure, development and renewal of the disks].

The external photoreceptor segments in the retina of vertebrates have been studied already more than 100 years; the intensity of these studies increased markedly during the recent 20 years due to the introduction of autoradiography and electron microscopy. These methods allowed to study the ultrastructure of external segments of the rods and cones in many vertebrate species, its development in ontogenesis, the renewal of external segments and the dependence of renewal on the diurnal rhythm of illumination. All these data have never been summed up and discussed. This review provides a general picture of studies of different aspects of the ultrastructure of external segments; the models of formation of the external segments' discs proposed by several authors are considered; the necessity of continuation and widening of comparative studies of the ultrastructure of external photoreceptor segments in different vertebrates is founded. The most important conclusions concern the differences between the rods and the cones during renewal of the membranes discs of external segments.

Animals↗
PubMed1996

Development and maintenance of outer segments by isolated chick embryo photoreceptor cells in culture.

PURPOSE: To investigate the capacity of isolated chick embryo photoreceptors to develop and maintain outer-segment processes in dissociated cell cultures, in the absence of pigment epithelial and glial cells. METHODS: Cells were obtained from the retinas of embryonic day (ED) 17 chick embryos, after the onset of outer-segment formation in vivo. After 5 to 12-minute incubation in Ca++ and Mg++-free Hank's balanced salt solution, neural retinas were freed from other optical tissues, including the pigment epithelium. Retinal cell suspensions were prepared by repeated pipetting after mild trypsinization and were grown in serum-containing medium on a polyornithine-coated substratum. Cell differentiation was evaluated using phase-contrast and transmission electron microscopes and by autoradiographic analysis of the uptake of putative amino acid neurotransmitters, lectin cytochemical analysis, and immunocytochemical analysis with rod and cone-specific antibodies. Cells isolated from ED 8 retinas, before the onset of outer-segment formation in vivo, were also studied. RESULTS: At culture onset, ED 17 cells appeared morphologically undifferentiated and devoid of processes; differentiated features could be detected after 24 to 48 hours in vitro. Photoreceptor cells were the most abundant cell type after 6 days in vitro, followed by nonphotoreceptor multipolar neurons and morphologically undifferentiated cells. Autoradiographic analysis showed extensive Na+ -dependent uptake of (2,3,4-(3)H)gamma- aminobutyric acid in nonphotoreceptor neurons, whereas photoreceptors were labeled predominantly with 3H-glutamate. Most of the photoreceptors were labeled with fluorescent peanut lectin and with a sheep polyclonal antibody against bovine rhodopsin. Subsets of photoreceptors, on the other hand, were immunoreactive with cone- or rod-specific monoclonal antibodies COS-1, OS-2, 50-1B11, or Rho-4D2. Approximately 50% to 65% of the photoreceptors positive with these monoclonal antibodies showed a remarkable polarization of immunoreactive materials, which accumulated predominantly, or even exclusively, in an outer-segment-like apical process. When viewed on the transmission electron microscope, these outer-segment-like processes appeared as distal expansions of the photoreceptor cilium and contained disc-like membranous profiles. Outer-segment-like processes also could be detected using the electron microscope and by immunocytochemical analysis of cultures of ED 8 retinal cells. CONCLUSIONS: After undergoing morphologic dedifferentiation as a result of tissue dissociation, isolated retinal photoreceptors, grown in the absence of contact-mediated cell interactions and of pigment epithelial and glial cells, can regenerate and maintain a highly polarized pattern of structural and molecular organization, including the formation of outer-segment-like processes. The cultures provide an experimental system for the investigation of cellular and molecular mechanisms regulating further development and maturation of these photoreceptor structures.

Animals↗
PubMed2000

Isolated resection of segment 8 for liver tumors: a new approach for anatomical segmentectomy.

HYPOTHESIS: Isolated resection of segment 8 (the right anterosuperior liver segment) is one of the most difficult hepatectomies to perform because of the location of segment 8, the relation between section 8 and the main intrahepatic vessels, and the absence of any anatomical landmarks. The few reports that deal with isolated resection of section 8 generally describe the use of a deep wedge transparenchymal transection. DESIGN: Original surgical technique. PATIENTS AND METHODS: The proposed technique is based on the extraparenchymal isolation and temporary clamping of the right anterior artery and portal branches, causing ischemic demarcation on the liver surface, which corresponds to the anatomical borders of the right paramedian segments (5 and 8). The liver is widely transected along the main hepatic fissure; then the pedicles of segment 8 are selectively ligated inside the parenchyma, and the resection is accomplished. This technique was used in 10 patients: 5 with hepatocellular carcinoma on cirrhosis and 5 with liver metastases. RESULTS: The mean operation time was 253 minutes. Intraoperative blood loss was minimal in all cases, and 7 patients did not require blood transfusion. Slight complications developed in 3 patients, and there was no operative death. The mean hospital stay was 9.3 days. CONCLUSIONS: This operative procedure is safe and ensures a complete anatomical resection of segment 8. The wide opening of the liver parenchyma facilitates hemostasis and makes it possible to obtain a correct resection margin. This technique is recommended for limited metastatic lesions located in segment 8 or for hepatocellular carcinoma arising in a cirrhotic liver.

Adult↗
PubMed1986

Segmental hepatic resection utilizing the ultrasonic dissector.

Hepatic resection continues to become a more widely accepted therapeutic modality, with increased use as improved imaging modalities more precisely define the nature and extent of various liver abnormalities. The surgical anatomy of the liver indicates that there are eight segments with single or multiple segmental resections able to be performed. The use of the ultrasonic dissector facilitates the performance of transparenchymatous segmental resection without obtaining vascular inflow or outflow control. This report describes the segmental anatomy of the liver and the use of the ultrasonic dissector. Thirteen patients have undergone segmental hepatic resection with the ultrasonic dissector. Five patients had cirrhosis. Mean +/- 1 SD operative time required for segmental resection was 128 +/- 57 minutes, and blood loss was 830 +/- 623 mL. Utilization of the ultrasonic dissector to perform segmental hepatic resection may increase our versatility in the management of various hepatic and biliary tract diseases.

Adult↗
PubMed1999

An alternative model for the transmembrane segments of the yeast H+-ATPase.

An alternative topological model for the yeast plasma membrane H(+)-ATPase from K. lactis was deduced by joint prediction, using 11 algorithms for the prediction of transmembrane segments complemented with hydrophobic moment analysis. Similarly to the model currently used in the literature, this alternative model contains 10 transmembrane segments, four in the N-half and six in the C-half of the protein. However, the distribution of the membrane-associated segments on the C-half of the enzyme differs in both models. Nine of the 10 transmembrane segments are highly hydrophobic with low hydrophobic moments, and are probably involved in structural roles. The fifth transmembrane segment is, on the other hand, less hydrophobic, with the highest hydrophobic moment, suggesting that this segment might have a dynamic role in the coupling of the hydrolysis of ATP with the translocation of protons across the membrane. The alignment of the Ca(2+)-ATPase, the Na(+)/K(+)-ATPase and the H(+)-ATPase sequences showed that these proteins have the same topology in the N-half, but important differences were found at the C-half of the enzymes. In contrast with the mammalian ATPases, the fifth transmembrane segment in the H(+)-ATPase appears early in the sequence, giving rise to a shorter cytoplasmic central loop. This alternative model will be useful in the designing of site-directed mutagenesis experiments and contains information for the fitting of the amino acid sequence into the transmembrane region of the three-dimensional model of the ATPase.

Algorithms↗
PubMed1992

Relationship between gallbladder carcinoma and the segmental type of adenomyomatosis of the gallbladder.

Specimens from 3197 consecutive and unselected cholecystectomies performed during a 6-year period were studied. Adenomyomatosis of the gallbladder was defined as a lesion characterized by a thickened wall that consisted of Rokitansky-Aschoff sinuses surrounded by proliferated fibromuscular tissue. Adenomyomatosis was found in 279 specimens and classified as one of three types: segmental, fundal, or diffuse. Segmental adenomyomatosis was found in 188 specimens; gallbladder cancer (GBC) developed in 12 (6.4%) of the patients with segmental type adenomyomatosis. GBC developed in the mucosa of the fundal compartment distal to the annular stricture of the segmental type adenomyomatosis in all 12 of these patients. Conversely, GBC developed in 93 (3.1%) of the other 3009 patients (those with fundal alone, diffuse, or no adenomyomatosis). The prevalence of GBC in patients with segmental adenomyomatosis was significantly (P less than 0.025) higher than that of patients without segmental adenomyomatosis. Clinicians should be aware that segmental adenomyomatosis often coexists with GBC.

Adenoma↗
PubMed1978

Masses, centers-of-gravity, and moments-of-inertia of the body segments of the rhesus monkey (Macaca mulatta).

Segmental parameters (mass, center-of-gravity, and moment-of-inertia) are necessary for biomechanical analyses of a species' locomotor behavior. Seven male and eight female adult rhesus monkey cadavers were dismembered in order to determine segmental parameters. Mean values for the segment masses and moments-of-inertia are presented for males and females, separately and together. Statistical tests revealed significant differences between the sexes for these parameters. Regression equations for predicting segment masses and moments-on-inertia were developed for the sexes separately and pooled. For most segments the male and female equations did not differ significantly in slope or y-intercept. The center-of-gravity for each segment is presented as a mean percentage of the distance between the proximal and distal joint centers. The regression equations and center-of-gravity locations presented here permit biomechanical investigations of rhesus monkey locomotion without the necessity of subsequent sacrifice. The segmental parameter values determined for the rhesus monkey are compared with available data for other primate and mammalian species and the biomechanical and adaptive implications of such comparisons are discussed.

Animals↗
PubMed1977

Segmental dearterialization in penetrating renal trauma.

Refractory renal haemorrhage following low velocity penetrating trauma has conventionally been treated by nephrectomy or partial nephrectomy. Anatomical studies have demonstrated that the renal artery branches are end-arteries, each branch supplying a renal segment, with no collateral artery supply between segments. Life-threatening haemorrhage is arterial, and usually issues from a single segmental artery easily demonstrable by renal angiography. Fourteen patients had various segmental arteries ligated to control haemorrhage. Associated visceral injuries were present in 4 patients. Preoperative selective renal arteriography was possible in 13 patients and demonstrated the bleeding site in all cases. Segmental dearterialization produced haemostasis in 12 of the 14 patients. One patient required nephrectomy and one patient ligation of a second segmental artery to control bleeding. All the patients survived the operative procedure. Supine renin levels were normal on the fourteenth postoperative day and no patient developed hypertension during the follow-up period of 9-24 months. Segmental renal dearterialization by open operation is a simple and effective technique of controlling refractory renal haemorrhage with maximum preservation of renal parenchyma.

Adolescent↗
PubMed2003

Segmental nature of the porcine liver and its potential as a model for experimental partial hepatectomy.

BACKGROUND: In-depth knowledge of pig liver anatomy allows potential research into segmental liver resections and hepatic regeneration, as well as liver transplantation techniques. The segmental anatomy, however, remains largely unknown. This study aimed to delineate the segmental anatomy of the porcine liver in comparison with that of the human. METHODS: The segmental anatomy of the porcine liver was determined using acrylic injection casting of ex vivo pig livers, allowing the arterial, venous and biliary supply to be visualized directly. This was correlated using multi-slice computed tomography (CT) and three-dimensional reconstructions. RESULTS: Although the external morphology of the porcine liver differs from that of the human, the segmental anatomy is remarkably similar in term of its vascularity and biliary tree. CONCLUSION: Acrylic casting of the porcine liver accurately delineates the vascular and biliary anatomy, and is a useful tool for performing experimental liver surgery. The similarities between porcine and human segmental anatomy allow domestic swine to be used as a comparable model. Three-dimensional CT reconstructions can also accurately visualize the anatomy and may be used to perform virtual surgery, or to assess segmental volumes.

Animals↗
PubMed1979

Evaluation of segmental left ventricular wall motion by equilibrium gated radionuclide ventriculography.

The ability of equilibrium gated radionuclide ventriculography to detect segmental left ventricular (LV) wall motion abnormalities was determined in 26 patients undergoing cardiac catheterization. Multiple gated studies obtained in 30 degrees right anterior oblique and 45 degrees left anterior oblique projections, played back in a movie format, were compared to the corresponding LV ventriculograms. The LV wall in the two projections was divided into eight segments. Each segment was graded as normal, hypokinetic, akinetic, dyskinetic, or indeterminate. Thirteen percent of the segments in the gated images were indeterminate; 24 out of 27 of these were proximal or distal inferior wall segments. There was exact agreement in 86% of the remaining segments. The sensitivity of the radionuclide technique for detecting normal versus any abnormal wall motion was 71%, with a specificity of 99%. Equilibrium gated ventriculography is an excellent noninvasive technique for evaluating segmental LV wall motion. It is least reliable in assessing the proximal inferior wall and interventricular septum.

Adult↗