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PubMed1986

The changes in ECG ST segment and mechanical function of regional ischemic myocardium during afterload reduction in isolated dog hearts with coronary stenosis.

By measuring ECG ST segment deviation and regional mechanical dysfunction, we assessed the effects of an alteration in afterload pressure on regional myocardial ischemia due to a partial coronary occlusion of the left circumflex coronary artery (CFX). Eight isolated, perfused and paced dog hearts were loaded with an artificial arterial system which simulated the aortic input impedance of the dog arterial tree. Afterload pressure was altered by stepwise changes in peripheral resistance (Rp), while left ventricular end-diastolic pressure (LVEDP) and heart rate were kept constant. Coronary perfusion pressure (CPP) was kept equal to mean aortic pressure (AoP). ECG and myocardial systolic segment shortening (SS) were measured in both areas perfused by the CFX and the left anterior descending coronary artery (LAD). In the presence of CFX stenosis, mean AoP decreased from 96 +/- 7 to 46 +/- 7 mmHg following a decrease in Rp and cardiac output increased progressively from 465 +/- 30 to 1055 +/- 100 ml/min. In this situation, CFX coronary blood flow decreased from 75 +/- 2 to 28 +/- 6 ml/100 g/min. Epicardial ECG in the ischemic region showed two types of ST segment deviation after CFX stenosis: ST segment elevation and ST segment depression. Moreover, following afterload reduction, these individual ECG ST segment changes showed further deviations. The levels of mean AoP, below which further ST segment deviations significantly occurred, were as follows: 71 +/- 6 mmHg in ST segment elevation cases and 52 +/- 7 mmHg in ST segment depression cases. Myocardial systolic segment shortening in the ischemic region also significantly decreased following CFX stenosis (91 +/- 8% of pre-ischemic control, p less than 0.05). Then, during afterload reduction, SS in the CFX area appeared to be bimodal and it definitely decreased when mean AoP was 46 +/- 7 mmHg. To enhance the sensitivity of detection of further mechanical dysfunction throughout afterload reduction following regional myocardial ischemia, we calculated percentage values of the SS in the CFX area to the SS in the LAD area at each Rp. By this normalization, mechanical dysfunction was found when mean AoP was below 67 +/- 5 mmHg. These results suggest that reduction in afterload pressure below a certain level aggravated the regional ischemia, despite an increase in cardiac output, and to detect this change in the ischemic region during afterload reduction, ECG ST segment deviation seems to be a useful indicator.(ABSTRACT TRUNCATED AT 400 WORDS)

Animals↗
PubMed2005

ST-segment depression in lead aVR: a useful predictor of impaired myocardial reperfusion in patients with inferior acute myocardial infarction.

STUDY OBJECTIVE: During inferior acute myocardial infarction (AMI), the ECG lead aVR is frequently ignored, and therefore its clinical significance remains unclear. We examined the relation between ST-segment deviation seen in lead aVR on ECGs obtained at hospital admission and myocardial reperfusion in patients who have experienced recanalized inferior AMIs. DESIGN AND SETTING: Retrospective study. PATIENTS: A total of 225 patients with inferior AMIs in whom Thrombolysis in Myocardial Infarction grade 3 flow was achieved within 6 h after symptom onset. MEASUREMENTS AND RESULTS: Patients were classified as follows according to ST-segment deviation in lead aVR on an ECG obtained at hospital admission: group A, 103 patients with no ST-segment depression; group B, 80 patients with ST-segment depression of < or = 1.0 mm; and group C, 42 patients with ST-segment depression of > 1.0 mm. There were no differences in time from symptom onset to hospital admission or in the culprit lesion among the three groups. The degree of ST-segment elevation in leads II, III, aVF, V5, or V6, the degree of ST-segment depression in leads V1 to V4, and the sum of ST-segment deviation in these leads were lowest in group A and highest in group C. In groups A, B, and C, the incidence of impaired myocardial reperfusion, defined as myocardial blush grade 0/1, was 2%, 23%, and 67%, respectively (p < 0.001). The sensitivity and negative predictive values of ST-segment depression in lead aVR for impaired myocardial reperfusion were higher than those based on other ECG variables. Multivariate analysis showed that the degree of ST-segment depression in lead aVR was an independent predictor of impaired myocardial reperfusion (odds ratio 8.41; 95% confidence interval, 2.96 to 23.9; p < 0.001). CONCLUSIONS: We conclude that the degree of ST-segment depression in lead aVR is a useful predictor of impaired myocardial reperfusion in patients who have experienced inferior AMIs.

Electrocardiography↗
PubMed1982

Segmental length changes in stimulated frog sartorius muscle during dynamic mechanical responses.

The nonuniformity of dynamic mechanical responses along the length of stimulated frog sartorius muscle was examined by recording the length changes of muscle segments by means of streak photography. During isometric force development, the central or the pelvic end segment tended to shorten due to the stretching of the other segments. In muscles showing a marked nonuniformity in the segmental length changes occurring during isometric force development, there was also a marked nonuniformity in the segmental length changes occurring during stretches or releases applied at the plateau phase of an isometric tetanus. Marked nonuniform segmental length changes were also observed during afterloaded twitches and tetani. These results indicate that great care should be taken of the muscle segmental nonuniformity in heat and X-ray diffraction studies in which measurements are made using data obtained from a limited region of muscle. During the course of slow stretches or releases applied to tetanized muscles, the tibial and segment exhibited much smaller relative lengthening or shortening than the other segments when it had been appreciably stretched by the other segments during isometric force development. This might be associated with the formation of "locked-on" cross-links in the stretched segment.

Animals↗
PubMed1993

Segmental differences in drug permeability, esterase activity and ketone reductase activity in the albino rabbit intestine.

Possible segmental differences in drug permeability as well as esterase and ketone reductase activities in the albino rabbit intestine were investigated. Beta adrenergic antagonists and timolol prodrugs spanning four orders of magnitude in distribution coefficient were used as model drugs. Drug penetration was evaluated in Ussing chambers using isolated segments of the duodenum, jejunum, ileum, ascending colon, descending colon, and rectum. Esterase and ketone reductase activities were determined in homogenates of the above segments using timolol ester prodrugs and levobunolol as substrates, respectively. The results indicate that the hydrophilic beta adrenergic antagonists atenolol and sotalol and moderately lipophilic metoprolol penetrated all intestinal segments equally well, whereas moderately lipophilic timolol and lipophilic propranolol, levobunolol and betaxolol were better absorbed from the large than from the small intestinal segments. Changes in lipophilicity exerted a more pronounced effect on the penetration of beta adrenergic antagonists in the large than the small intestinal segments. A similar pattern existed for timolol prodrugs. In addition to segmental differences in drug permeability, segmental differences in esterase and ketone reductase activities also existed. The level of esterase and ketone reductase activities in the small intestinal segments was, on average, 12 times and 5 times higher, respectively, than in the large intestinal segments. The implication of the above findings is that segmental differences in drug permeability and metabolism must be considered in the design of oral drug delivery systems.

Adrenergic beta-Antagonists↗
PubMedDate not supplied

A roentgenological evaluation of the relationship between segmental motion and malalignment in lateral bending.

OBJECTIVE: A radiographic study was undertaken to determine the relationship between static vertebral malalignment and segmental lumbar motion in lateral bending. DESIGN: Survey. SETTING: Chiropractic college student health center and private chiropractic clinic. PARTICIPANTS: 249 subjects: 114 with low back pain, 29 asymptomatic with no history and 106 asymptomatic with history. Of these, 194 were freshman volunteers and 55 were new private clinic low back pain patients. INTERVENTIONS: None. MAIN OUTCOME MEASURES: Net lumbar segmental tilt and rotation in lateral bending: corrected and uncorrected for segmental malposition with the patient standing in the upright neutral position. RESULTS: There was moderate to good negative correlation of malalignment with segmental tilt motion and segmental motion asymmetry (r = -.42 to -.89, p less than .001). Correlation of malalignment with motion from the ideal neutral segmental position of perfect alignment was modest (r = .16-.42). A large variation in segmental motion was found for all segmental malalignments. CONCLUSIONS: This study suggests that malalignment is associated with segmental tilt motion in lateral bending, although large subject variability greatly compromises predictability on an individual basis. This study also indicates that segmental malposition may complicate the palpation of active range of motion. This is because the malalignment itself may facilitate a greater arc of segmental motion in the direction of comparative restriction in movement from the ideal neutral position to the extreme of lateral flexion.

Adolescent↗
PubMed2006

[Influence factors of adjacent segment degeneration after instrumented lumbar fusion].

OBJECTIVE: To investigate the influence factors of adjacent segment degeneration (ASD) after instrumented lumbar fusion. METHODS: Thirty-three patients who had undergone an instrumented lumbar fusion from March 1998 to May 2002 were reviewed. The incidence, age, position, radiographic characteristics and clinical manifestations of ASD were studied. Then the relations between "floating fusion" and ASD were compared, the range of fusion and ASD and investigated the incidences of different adjacent segments. RESULTS: The mean follow-up period for the patients was 4 years and 7 months (24 - 82 months). Adjacent segment degeneration mainly occurred in patients older than 60. Ten patients (10%) were found to have radiographic characteristics of ASD. Nine of the ten patients had ASD at cranial segments. Using "floating fusion" or not did not show difference in the risk of ASD. There was a trend of more ASDs after long-segment fusion than short-segment fusion. As an adjacent segment, L(2)/L(3) had a high risk of ASD, while L(5)/S(1) had a much lower risk. CONCLUSIONS: The cranial segment has a higher degeneration risk than the caudal segment. If L(2)/L(3) has degenerative appearance and has chance to be the adjacent segment, we'd better fuse it. If there is no evidence of obvious degeneration, L(5)/S(1) should not be fused. During instrumented lumbar fusion, long-segment fusion should be avoided if possible.

Adult↗
PubMed1989

Peripheral target choice by homologous neurons during embryogenesis of the medicinal leech. I. Segment-specific preferences of Retzius cells.

A pair of large serotonergic neurons, the Retzius (Rz) cells, is found in each segment of the leech nervous system. Most Rz cells innervate the body wall of their own segment as well as adjacent anterior and posterior segments. Rz cells in segments 5 and 6 [Rz (5,6)] instead innervate the reproductive tissue found only in those segments. Rz cells from adjacent segments [Rz (4,7)] provide the serotonergic innervation of the body wall of segments 5 and 6. During embryogenesis, the body wall and the reproductive tissue are apparently available to both Rz (5,6) and Rz (4,7), yet these neurons choose different targets. We asked how Rz (5,6) and Rz (4,7) choose their respective peripheral targets in the reproductive segments by ablating either the reproductive tissue or specific Rz cells. Ablation of the reproductive tissue caused Rz (5,6) to innervate body wall, although not as proficiently as did standard Rz cells, suggesting a preference of Rz (5,6) for reproductive tissue. Ablation of those Rz cells that would normally innervate the body wall of segments 5 and 6 did not cause Rz (5,6) to innervate body wall, ruling out competition for this target. When Rz (5,6) were ablated, Rz (4,7) innervated the body wall of segments 5 and 6 normally and did not innervate reproductive tissue. Thus, competition did not act in the choice of target by Rz (4,7) either. These results suggest that during normal development, Rz (5,6) and Rz (4,7) choose their targets independently of one another rather than competing for the available targets and that these cells have segment-specific target preferences.

Animals↗
PubMed1985

Analysis of the terminal sequences of the genome segments of four orbiviruses.

The RNA sequences of the terminal regions of the genome segments of 4 different orbiviruses were analysed. In 3 of these [bluetongue virus (BTV) types 1 and 20 and Ibaraki virus, a member of the epizootic hemorrhagic disease (EHD) serogroup], 1 strand of all of the genome segments analysed ends in 3'CAAUUU...5' while the other strand ends in 3'CAUUCA...5'. These conserved sequences are identical to those reported for BTV types 10 and 11. The 3' terminal sequences of segments 3 and 10 of the BTV 1 genome (including the conserved regions) were confirmed by the detection of exactly complementary sequences at the 5' termini of the ssRNA strands of opposite polarity. This also confirmed for these dsRNA segments (and by analogy for all of the genome segments of these viruses) that the dsRNA molecules are fully base-paired end to end. Using in vitro synthesised mRNA of BTV 1 in annealing experiments with the separated ssRNAs from the individual genome segments, it was shown that in each case the strand ending in 3'CAUUCA...5' is of the same polarity as the mRNA (+ve), while the strand ending in 3'CAAUUU...5' is of the opposite (-ve) polarity. The 4th virus analysed (Tilligerry, a member of the Eubenangee serogroup) only had 5 conserved bases at the 3' termini of 1 strand of each genome segment (3'CAU-CA...5') and 3 conserved bases at the 3' termini of the other strand (3'CA--U...5'). Considerable sequence homology was found in the near-terminal nonconserved regions of comparable genome segments, particularly between the different BTV types. There was little evidence however for absolute conservation of "segment specific" sequences in these regions of the RNA, as reported for rotaviruses. The percentage of sequence homology found in the terminal regions of the genome segments between members of the BTV, EHD and Eubenangee serogroups examined correlates with the serological interrelationships between these groups of viruses. The conserved terminal sequences and sequence homology in these regions of the RNA are discussed as to their role in virus replication and their significance to the reassortment of genome segments between different viruses during dual infections.

Base Sequence↗
PubMed1984

Morphological and experimental studies of the somitomeric organization of the segmental plate in snapping turtle embryos.

The segmental plate mesoderm of snapping turtle embryos (Chelydra serpentina) was examined with stereoscanning electron microscopy imaging. A metameric pattern was detected along the entire length of the segmental plates. This pattern consisted of a tandem sequence of mesodermal units, called somitomeres. Each somitomere was oval to cubic in shape and the processes of the constituent mesodermal cells tended to be arranged in concentric rings about the centre of the somitomere. Several experiments from a previous study (Packard, 1980b) of snapping turtle segmental plates were repeated, but, instead of culturing the explants and observing the numbers of somites that formed, the explants were fixed immediately for scanning electron microscopy and the number of somitomeres was counted. The segmental plates were found to contain an average of 6.5 +/- 0.7 somitomeres, which is almost identical to the average number of somites formed by such segmental plates when cultured (6.6 +/- 1.2). Furthermore, the number of somitomeres was identical in right and left explants removed from the same embryo, and the number of somitomeres was consistent regardless of the length of the segmental plate. Both of these observations are identical to those made previously for somite formation in culture. This association between numbers of somitomeres and somites strongly suggests that one gives rise to the other. Finally, it was demonstrated that for each somite formed by a segmental plate in culture, the segmental plate contained one less somitomere. This showed in a direct manner that turtle somitomeres become somites. It was concluded that the segmental plate mesoderm of snapping turtle embryos is already segmented, and that the 'segmentation' seen under a dissecting microscope is actually the final stage of somitomere differentiation into an epithelial somite.

Animals↗
PubMed1978

Induced segmental reorganization in sabellid worms.

Processes of regeneration and reorganization are analyzed in two sabellid polychaetes. Abdominal pieces of Branchiomma nigromaculata, during head regeneration, ordinarily reorganize only a fraction of the number of segments typical of the thorax. In pieces transected in the vertical plane, but obliquely with regard to the main axis of the worm, the extent of reorganization is greatly enhanced. The same number of segments transform on the right and left sides, the surviving damaged segments transforming on one side and a corresponding number of more posterior, undamaged segments transforming on the other. Reorganization is shown, in abdominal pieces of Sabella melanostigma, to involve destruction and inversed dorso-ventral reconstitution of all parapodial structures in the segments affected, the conversion of intestine to thoracic stomach, and the invasion of previously abdominal segments by a pair of large nephridia which grow posteriorly after being formed in the basal portion of the head blastema. All three events exhibit a time-graded character, staring soonest at the anterior end and progressively later posteriorly, and apparently independently of one another. Abdominal type segments are formed only from the anterior region of the caudal, prepygidal zone of growth, successively, never by transformation. The dorso-ventrality of abdominal segments is the inverse of the thoracic, with the antero-posterior polarity unchanged, in all circumstances. Only during posterior regeneration from thoracic segments are thoracic segments produced from the posterior zone of growth, but only two or three are thus formed, the zone of growth then changing to the production of abdominal segments. It is concluded that the feature of sabellid-serpulid organization is the complete inversion of the dorso-ventrality of the posterior zone of growth as the result of emancipation from the generally dominating dorsal field emanating from the anterior end.

Abdomen↗
PubMed1976

Total synthesis of the structural gene for the precursor of a tyrosine suppressor transfer RNA from Escherichia coli. 9. Enzymatic joining of chemically synthesized deoxyribopolynucleotide segments corresponding to nucleotide sequence 57-94.

The DNA duplexes representing nucleotide sequences 61-89 and 57-94 have been synthesized, isolated pure, and fully characterized. Synthesis of the duplex with the nucleotide sequence 61-89 involved the DNA ligase-catalyzed joining of chemically synthesized deoxyoligonucleotide segments 14 to 18 shown in Fig. 1A, while for the longer duplex (sequences 57-94) seven deoxyribooligonucleotides (segments 13 to 19, Fig. 1B) were used in one-step enzymatic joining. The joining of the short tetranucleotide (segment 16) to the segment 17 required the presence of the adjacent segment 14, even if the latter did not contain a 5'-phosphate group, to allow its joining to segment 16. However, in the synthesis of both of the DNA duplexes, the yields were comparatively low (30 to 40%) and could not be significantly increased although a variety of conditions was tried. The main cause in both cases evidently was the sluggish joining of segment 14 to 16 and of segment 16 to segment 17. Although the original plan for the total synthesis of this part of the gene for the tRNA precursor involved the DNA duplex consisting of segments 14 to 18, this duplex could not be quantitatively phosphorylated at the two 5'-OH ends for subsequent joining to the adjoining parts of the gene. The DNA duplex consisting of segments 13 to 19, which possesses both terminal 5'-OH groups at protruding single-stranded ends, was readily phosphorylated and used successfully in the total synthesis of the gene as described in an accompanying paper.

Base Sequence↗
PubMed1994

Segmental patterning of rat and chicken sympathetic preganglionic neurons: correlation between soma position and axon projection pathway.

The segmental organization of midthoracic rat and chicken sympathetic preganglionic neurons was examined by retrograde labeling in vivo and in vitro. The results demonstrate that individual sympathetic preganglionic neurons project only rostrally or caudally within the sympathetic chain, even though the spinal segment in which they reside provides innervation to both rostral and caudal ganglia. In addition, there is both a segmental and an intrasegmental pattern in the thoracic sympathetic column, in which the position of preganglionic neurons is related to the direction they project in the sympathetic chain. Thoracic sympathetic preganglionic neurons are organized into discrete segmental units, each of which exhibits an internal rostrocaudal polarity with respect to the direction of axon projection in the sympathetic chain. The rostrocaudal bias of this internal polarity is graded from segment to segment along the longitudinal axis. Since there is minimal overlap between thoracic segments, the transition from one segment to another entails a sharp change in the pathway choice of the preganglionic neurons. The organization of the preganglionic projections thus includes (1) segmental periodicity, (2) intrasegmental gradients of neuronal identity, and (3) an axial gradient of segment identity. The significance of these findings is twofold. First, they suggest a functional organization that may be related to the specificity of sympathetic reflex action. Second, they reveal a cellular organization that suggests an underlying segmental pattern in the developing spinal cord.

Amidines↗
PubMed1993

Heavy chain joining region segments of the channel catfish. Genomic organization and phylogenetic implications.

The JH locus of the channel catfish has been characterized to determine the organization and structural diversity of JH segments. These analyses indicate that there are a total of nine JH segments tightly clustered within a region spanning about 2.2 kb. The JH locus is closely linked to the CH 1 domain of the expressed catfish H chain; the distance between the CH proximal JH segment (JH9) and the CH 1 domain is about 1.8 kb. Each JH segment has an upstream recombination sequence, which includes a T-rich nonamer, a 22- to 24-bp spacer, and a phylogenetically conserved heptamer. Each JH segment also has an open reading frame that encodes the conserved framework region 4 tryptophan (Trp-103) and terminates with a RNA donor splice site. The catfish JH locus contains an internal repetitive sequence region characterized by a short (183-188 bp) repeat that occurs sequentially five times. Strong sequence homology as well as the unified length of the repeated sequences indicate that JH segments JH3-JH7 probably arose as the result of a series of homologous but unequal crossover events. Sequence alignments of the duplicated JH segments indicates that there is diversity within the 5-11 nucleotides located immediately downstream from the heptamer, an observation which indicates that closely related JH segments can serve to enhance CDR3 diversity in the expressed H chain. Comparisons of the genomic JH sequences with different cDNA clones indicate that each JH segment is probably functional and that junctional diversity serves an important role in the generation of CDR3 diversity. In addition, single base differences observed in comparisons of JH-encoded regions indicate that there is probably somatic mutation or allelic variation of genomic JH segments. These studies suggest that the characteristic structure and organizational pattern of JH segments in higher vertebrates may have evolved early in vertebrate phylogeny at the level of the bony fish.

Amino Acid Sequence↗
PubMed1996

Short segment Barrett's esophagus: clinical and histological features, associated endoscopic findings, and association with gastric intestinal metaplasia.

OBJECTIVES: To prospectively determine the clinical features, associated esophageal endoscopic lesions, associated gastric intestinal metaplasia, and prevalence of dysplasia and adenocarcinoma of short segment Barrett's. METHODS: All patients undergoing upper endoscopy over a 5-month period were scrutinized for endoscopic features suggestive of short segment Barrett's, and, if present, multiple biopsies were obtained from the suspicious areas. Prevalence of gastric intestinal metaplasia was determined by obtaining biopsies from the antrum, body, and cardia. RESULTS: Two hundred thirty seven patients were examined. Short segment Barrett's was suspected in only 42 patients, and traditional Barrett's was noted in 45 patients. Short segment Barrett's was confirmed by biopsy in 48%. Clinical presentation of short segment Barrett's was that of typical or complicated gastroesophageal reflux disease in 53%. A hiatal hernia was the most common associated esophageal endoscopic finding; however, none of the endoscopic findings differed significantly from findings of patients who did not have short segment Barrett's. Diagnosis of short segment Barrett's required histological analysis. A significant difference was noted in the prevalence of intestinal metaplasia between the esophagus and stomach in patients with Barrett's. No dysplasia or adenocarcinoma was detected in patients with short segment Barrett's. CONCLUSIONS: Short segment Barrett's is a frequent finding in patients undergoing upper endoscopy. All patients with short tongues or patches of red mucosa lying less than 2 cm above the esophagogastric junction should be biopsied to exclude short segment Barrett's. Large scale endoscopic and histological surveillance studies along with long-term follow-up are required to clarify short segment Barrett's prevalence and cancer risk.

Adenocarcinoma↗
PubMed1997

Comparison of the effects of the interposition of 'narrow' cycloperistaltic v. antiperistaltic segments on fluid perfusion through isolated loops of jejunum.

Experimental studies in dogs showed a delaying action of the cycloperistaltic (C-P) segment when interposed in isolated loops of jejunum ('narrow' C-P segments) and between stomach and duodenum after Billroth I gastrectomies ('wide' C-P segments). This study was designed to establish whether there were any differences in the delaying action on the passage of perfused fluids between isolated loops of jejunum with C-P and antiperistaltic (A-P) segments interposed. The latter is the surgical technique that is currently considered the gold standard for such actions. Two isolated segments of jejunum with the ends exteriorised as jejunostomies (Thiry-Vella (T-V) loops) were created in each of 4 dogs. Towards the end of one, a C-P segment with a diameter 70% that of the jejunum ('narrow' C-P segment) was interposed. Towards the end of the other, a reversed A-P segment was interposed. Fluid containing 14C-labelled polyethylene glycol was infused at a rate of 4 ml/min through all the 8 loops (4 dogs) for 1 hour (6 experiments per dog). Descriptive statistics (means and standard errors) show that no obvious differences in volume of output, absorption and pooling existed between T-V loops with 'narrow' C-P and A-P segments. The delaying effect in the passage of fluids of the C-P segment, shown in previous experiments, does not appear to be superior to that of the A-P segment. This statement is made with some reservation as the number of animals involved was relatively small and analytical statistics could not be used.

Animals↗
PubMed1994

Insulin stimulation of retinal outer segment uptake by cultured human retinal pigment epithelial cells determined by a flow cytometric method.

This study investigates the mechanism by which insulin stimulates phagocytosis in cultured human retinal pigment epithelium, using a flow cytometric assay of retinal outer segment uptake. RPE cells were isolated from adult human donors and grown in culture. Retinal outer segments were isolated from fresh bovine eyes and covalently labeled with the fluorescent dye carboxy-SNAFL-2. Retinal outer segment binding and uptake was quantified by direct visualization and the increase in cellular fluorescence measured using a flow cytometer and the methods compared. Uptake measured by flow cytometry was further characterized by concentration, time, temperature and serum stimulation, and shown to be comparable to other published methods. Uptake of retinal outer segments was acutely stimulated by insulin in the absence or presence of serum with half maximal stimulation occurring between 0.1 and 1.0 microgram ml-1. Theophylline, forskolin and cholera toxin all reduced retinal outer segment uptake by RPE cells, but had no effect upon insulin stimulation. Measurements of cAMP showed that insulin did not change intracellular cAMP concentration compared to controls in the absence or presence of added retinal outer segments. One hundred nanomolar okadaic acid also inhibited retinal outer segment uptake but not insulin-stimulated uptake, nor did 100 microM genistein have an effect upon insulin-stimulated uptake. Preincubation of RPE cells with 25 microM ZnCl2 overnight stimulated retinal outer segment uptake and appeared to inhibit the insulin stimulation. Preincubation of the cells in 25 mM glucose overnight also increased the uptake of retinal outer segments over control and reduced the effect of insulin. We conclude that insulin stimulates retinal outer segment phagocytosis by an as yet unknown process which may involve specific tyrosine phosphatases.

Cells, Cultured↗
PubMed1987

Anterior segment ischemia after recession of various recti. An experimental study.

In 40 normal adult cynomolgus monkey eyes, recession of various recti in different combinations was done to evaluate their effects on the anterior segment. These procedures were done as primary, secondary, tertiary, and fourth procedures (each separated by several weeks or months), ultimately involving all four recti in the eyes. In 11 eyes, posterior ciliary arteries (PCAs) were occluded to determine its effects on the anterior segment. All eyes were examined by slit lamp, color photography, and fluorescein angiography of the anterior segment, and tonometry, before surgery and serially thereafter during the follow-up period. These studies showed that recession of two or three recti simultaneously in different combinations produced no serious permanent anterior segment changes, although initially in some of the eyes there was transient mild-to-moderate anterior segment ischemia. Recession of four recti simultaneously as a primary procedure produced serious permanent ocular and anterior segment changes; however, when this was done as a secondary or tertiary procedure after previous recessions of three or four recti, anterior segment changes were much fewer and milder than when it was a primary procedure. Occlusion of all the posterior ciliary arteries in itself produced no important changes in the anterior segment, but when combined with simultaneous recession of both the horizontal recti, it produced serious anterior segment changes. In the light of these findings, the pattern of arterial blood supply of the anterior segment is discussed.

Animals↗
PubMed1996

Segment inertial properties of primates: new techniques for laboratory and field studies of locomotion.

Studies of the dynamics of locomotor performances depend on knowledge of the distribution of body mass within and between limb segments. However, these data are difficult to derive. Segment mass properties have generally been estimated by modelling limbs as truncated cones, but this approach fails to take into account that some segments are of elliptical, not circular, cross section; and further, the profiles of real segments are generally curved. Thus, they are more appropriately modelled as solids of revolution, described by the rotation in space of convex or concave curves, and the possibility of an elliptical cross section needs to be taken into account. In this project we have set out to develop a general geometric model which can take these factors into account, and permit segment inertial properties to be derived from cadavers by segmentation, and from living individuals using linear external measurements. We present a model which may be described by up to four parameters, depending on the profile and serial cross section (circular or ellipsoidal) of the individual segments. The parameters are obtained from cadavers using a simplified complex-pendulum technique, and from intact specimens by calculation from measurements of segment diameters and lengths. From the parameters, the center of mass, moments of interia, and radii of gyration may be derived, using simultaneous equations. Inertial properties of the body segments of four Pan troglodytes and a single Pongo were determined, and contrasted to comparable findings for humans. Using our approach, the mass distribution characteristics of any individual or species may be represented by a rigid-link segment model or "android." If this is made to move according to motion functions derived from a real performance of the individual represented, we show that recordings of resulting ground reaction forces may be quite closely simulated by predictive dynamic modelling.

Animals↗