Fatal smothering by a domestic cat.
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Animals↗
Biomedical subjects
M D Sage
Publications and source records attributed to M D Sage.
Interrelationships of ultrastructure and function in the microvasculature of normal and ischaemic myocardium.
This paper reviews various methods involving electron microscopy that have been used to investigate the ultrastructure of the vasculature of the normal and diseased heart. Whereas scanning electron microscopy is more commonly employed to record surface topography, it can be used to examine freeze-fracture planes within the myocardium and, using heavy-metal staining and back-scattered electron imaging, to examine large 2-mu-thick resin-embedded sections through the heart. The latter technique allows the comparison of structural alterations across the wall of the heart and thus accurate definition of the transmural progression of pathological processes. Transmission electron microscopy can then be used to provide more detailed information from precisely localised regions. Human myocardium can be usefully studied up to 12 hours post-mortem provided that suitable control material is included. Intravascular tracers including low-viscosity resin and nuclear track emulsion can be used to determine whether or not particular vessels allow flow at the time of fixation, and thus changes in the pattern of flow through the microvasculature due to ischaemia and reperfusion can be quantified and defined. Particular care is required in the fixation of ischaemic tissues because oxygen dissolved in the fixative can lead to the rapid formation of oxygen-free radicals on contact with the tissue. This produces artefactual reoxygenation damage characterised by membrane disruption and cell and organelle swelling, which has previously been attributed to ischaemic injury per se. Bubbling glutaraldehyde with nitrogen substantially reduces this artefact.
Animals↗
A benign gonadal stromal tumor of the testis of spindle fibroblastic type.
Non-Leydig cell gonadal stromal tumors of the testis are rare and most are benign. Criteria for determining malignancy are poorly defined. A gonadal stromal tumor of spindle fibroblastic cells presented in a 34 year old male. The patient remains alive and well with no evidence of metastasis 3 years following surgery. Light and electron microscopical features of the tumor are described.
Adult↗
Alterations to subplasmalemmal leptomeres in adult canine myocytes during total in vitro ischemia.
Published evidence suggests that ischemia-induced cell swelling renders myocytes vulnerable to plasmalemmal disruption and consequent cell death. Alterations to the myocyte cytoskeleton may be involved in the pathogenesis of this plasmalemmal injury. One putative cytoskeletal structure in cardiac muscle that has received little consideration is the subplasmalemmal network of periodic densities with linking microfilaments termed leptomeres or leptofibrils. We demonstrate these structures in dog heart papillary muscle and describe the improvement in their definition brought about by tissue fixation at 37 degrees C in 2% glutaraldehyde with addition of 0.05 M lysine-HCl, followed by brief postfixation with osmium tetroxide. Alterations to leptomeres during ischemic injury were examined in myocardium subjected to total in vitro ischemia for 30-180 min at 37 degrees C. Leptomeres showed little morphological alteration during the first 90-120 min, after which leptomere periodic densities (striae) increased in size, from 10-20 to 50-80 nm, and were more densely stained. The leptomeres eventually (150-180 minutes) lose definition. The course of these alterations coincided with the appearance of ultrastructural evidence of irreversible ischemic injury to the myocytes.
Animals↗
Evolution of Swan-Ganz catheter-related pulmonary valve nonbacterial endocarditis.
Invasive resuscitative and supportive therapy subsequent to accidental trauma, assault, or medical mishap may create lesions that forensic pathologists must interpret. Pulmonary valve nonbacterial endocarditis sometimes complicates placement of flow-directed pulmonary artery (Swan-Ganz) catheters. We examined ten cases of endocarditis from patients dying 0-10 days after removal of a Swan-Ganz catheter, and compared the natural evolution of vegetations in critically ill patients with the reported evolution of similar vegetations in experimental animals in the Freedman model. There was wide variation in macroscopic, as well as in the light- and scanning electron-microscopic, appearances in our cases and we could not establish a direct relationship between vegetation structure and time elapsed after removal of the catheter. These findings suggest that parameters related to critical illness and species account for the differences between this disease in human and animal models.
Catheterization, Swan-Ganz↗
Cytoskeletal injury and subsarcolemmal bleb formation in dog heart during in vitro total ischemia.
In previous studies a two-step hypothesis explaining the mechanism of lethal ischemic injury to cardiac myocytes has been advanced. It proposes that damage to the myocyte cytoskeleton precedes, and predisposes the cell to, mechanical injury induced by cell swelling or by ischemic contracture. This study quantitated the prevalence of breakage of the major cytoskeletal attachment between the plasmalemma and peripheral myofibers as a function of the duration (0-180 minutes) of in vitro total ischemia in dog heart papillary muscle. Breakages of Z-band, plasmalemmal attachment complexes were few before 120 minutes of ischemia, but thereafter became more prevalent; the transition between the initial rate of appearance of the breaks and the later fast rates coincided with the appearance of severe cell swelling, ischemic contracture, and ultrastructural criteria of irreversible ischemic injury. Z-band, plasmalemmal attachment complex breakage and cell swelling resulted in formation of subsarcolemmal blebs. Two major bleb types have been discerned on ultrastructural appearance using as the criteria the preservation of integrity of the plasma-lemma and subplasmalemmal leptomeres. The identification of two types of blebs suggests two independent mechanisms of injury, the first directed at Z-band attachments, and the second at the cytoskeletal structures of A- and I-band regions of the plasmalemma.
Animals↗
Myocyte swelling and plasmalemmal integrity during early experimental myocardial ischemia in vivo.
Using scanning and transmission electron microscopy, the structure of myocytes early in the phase of irreversible injury induced by 40 minutes of severe regional ischemia has been investigated, paying particular attention to the effects of cell swelling on the SEM appearance of the myocytes. Swollen myocytes showed an increased space beneath the plasmalemma and between organelles. True subsarcolemmal blebs were not seen and the attachment complexes between the Z-band and the underlying myofibrils remained intact. The proportion of the PS face of the plasmalemma which appeared "en face" (0.70%, SD:1.22 vs 5.01%, SD:3.72) in freeze-fracture faces of ischemic tissue was increased significantly. The increase may be due to swelling of the cell in the subplasmalemmal space or may be mediated through structurally unapparent alterations in the cytoskeleton. The PS face showed frequent longitudinal shifts in the alignment of Z band - plasmalemmal attachment between adjacent myofibers. T-tubule ostia, caveolae and junctional SR were demonstrable on the PS face. With standard preparative methods and instrumentation, no discrete fibrillar network associated with Z band attachment or subjacent to the plasmalemma was detected and there was no direct structural evidence of cytoskeletal alteration as a result of ischemic injury. Osmium-ligand preparation of tissue samples resulted in less damage induced by the electron beam, but did not allow significantly better resolution.
Animals↗
Deaths from trauma in Auckland: a one year study.
We report a one year prospective study of all deaths from trauma in the Auckland region. Data was collected on the circumstances of death from coroner's, police and hospital records. All cases had autopsies and the injuries were scored using the abbreviated injury scale (AIS) system. The group of 236 had a median age of 27 years and 73% were under the age of 45. Seventy-two percent were male. Blunt trauma, predominantly the result of road crashes, accounted for 89% of the fatalities. Most deaths occurred at the site of injury and only 37% survived to reach hospital. Cases were audited if death occurred without a critical or unsurvivable injury. Thirteen cases were considered to be potentially salvageable if medical treatment had been optimal. The implications for the organisation of prehospital and inhospital trauma care are discussed.
Accidents, Traffic↗
Coronary arterial abnormalities in pulmonary atresia with intact ventricular septum.
The incidence and severity of abnormalities of the coronary arteries were evaluated in 35 necropsy patients with pulmonary atresia and an intact ventricular septum. Right ventricular to coronary artery fistulous connections were found in more than 60% of the cases. All patients with fistulous connections had histologic abnormalities of the coronary arteries. In 50% the lesions were mild, with medial and intimal thickening producing up to moderate luminal stenosis. In 50% there was loss of normal arterial wall structure and severe narrowing or obliteration of the arterial lumen. The coronary arterial fistulas and histologic abnormalities were prevalent in those with underdevelopment of the tricuspid valve and right ventricular cavity but were not found in patients with a normal or dilated tricuspid valve anulus. The coronary arterial abnormalities were found in more than 80% of patients with a tricuspid valve/mitral valve ratio less than 1. A single coronary artery occurred in 6 patients (17%) of this series. In 80% of those with 1 coronary artery arising from the other, the aberrantly arising coronary artery crossed anteriorly to the pulmonary artery and could be at risk in surgical attempts to reconstruct the right ventricular outflow. Aortography is recommended if the coronary arteries are not clearly delineated on ventricular cineangiocardiography.
Coronary Vessel Anomalies↗
Microvascular function at the margins of early experimental myocardial infarcts in isolated rabbit hearts.
Injection of low-viscosity resin was used to identify in situ functional blood vessels at the margins of developing regional myocardial infarcts. The ventral interventricular branch (VIB) of the left coronary artery was occluded for 0-240 min in 20 isolated perfused rabbit hearts. After perfusion fixation with glutaraldehyde, resin was injected into the coronary arteries--that injected into the VIB contained dispersed lead dioxide and that injected into the remainder of the heart contained Fat Red 7B dye. This allowed macroscopic and microscopic identification of functional blood vessels. Following transmural freeze fracture, left ventricles were examined using back-scattered electron imaging in a scanning electron microscope. Close to 60% of capillaries in nonischemic myocardium allowed the passage of resin. Thirty minutes of ischemia produced a hyperemic increase to 80%-90% in the proportion of filled vessels. After 60 min, however, a severe reperfusion defect corresponding to the "no-reflow" phenomenon had developed, with virtually all vessels collapsed and less than 10% functional. Among the structurally normal myocytes adjacent to the infarct margin there was a significant reduction (to 30%-40%) in the proportion of functional capillaries. This was due to groups of dilated vessels which were not accessible to arterial supply. Although these marginal "low-flow" regions were of small volume at any one point in time, they seem likely to contribute to the progression of ischemic necrosis, and are probably nonfunctional due to the compression of their venous drainage traversing the infarct.
Animals↗
Ultrastructural alterations to myocytes and associated microvascular functional changes at lateral margins of developing experimental myocardial infarcts.
Knowledge of the temporal and spatial patterns of development of irreversible injury at the margins of regional myocardial infarcts is a prerequisite for assessment of interventions aimed at preventing the transition from reversible to irreversible injury of myocytes. Regional ischaemia was modelled in 20 isolated rabbit hearts by ligation of the ventral interventricular branch of the left coronary artery for 0-240 min prior to perfusion fixation of the entire heart. Transmural blocks of fixed myocardium spanning the margins of the ischaemic region were cryofractured, freeze-dried, and fracture faces up to 1 cm2 examined by scanning electron microscopy (SEM). Evidence of irreversible injury was seen in the subendocardium by 60 min, with extension to epicardium by 120 min. No progression was seen at lateral margins, which showed a cell-to-cell demarcation of morphologically normal areas and severely injured myocardium. A very narrow discontinuous zone (less than or equal to 150 microns wide) at lateral margins showed less severe changes. Provided this zone does not advance with time, ischaemic myocardium potentially "salvageable" by reperfusion appears confined to the subepicardial zone in rabbit hearts. The advantages of SEM in assessing the extent of ischaemic injury are compared with those of previously utilised morphologic methods.
Acrylic Resins↗
Fatal postpartum coronary artery dissection. A light- and electron-microscope study.
A case report of fatal spontaneous dissection of the distal left circumflex coronary artery in a 37-year-old postpartum female is presented. Samples of arterial wall from this patient and from six other postpartum females who died of unrelated causes were examined by light (LM), scanning electron (SEM), and transmission electron (TEM) microscopy. Morphological changes to explain the recognized predisposition of this cohort to coronary artery dissection were sought. The origin of the dissection was demonstrated by serial LM sections to be in midmedia with no intimal extension. The predominant plane of dissection was the junction of media and adventitia. Sarcolemmal blebbing and accumulation of amorphous intercellular material were demonstrated at the dissection site by SEM but were not seen elsewhere in the affected heart or in any of the six control hearts. These changes could not be distinguished by TEM from prolonged ischemic injury. There was no accumulation of eosinophilic leukocytes in the vessel wall or adventitia, and adventitial mast cells were not consistently more frequent than in the controls. No increase of stainable intramural mucopolysaccharides was seen in the fatal case. The results indicated no generalized arterial change in postpartum coronary arteries to account for the increased frequency of dissection. A focal degenerative process remains the most likely possibility.
Adult↗
Test and teach. Number fifty-four. Diagnosis: Myxoglobulosis occurring in a retention cyst type mucocele of the appendix.
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Appendix↗
Scanning electron microscopy of heart muscle freeze-dried from dimethylsulfoxide for simultaneous demonstration of cell morphology and microvascular function.
Scanning electron microscopy was used to examine cryofracture surfaces of ventricular myocardium from glutaraldehyde fixed rat and rabbit hearts subjected to intravascular injection of polymerizing acrylic resin. This allowed simultaneous observation of morphological features of cardiac muscle cells and the functional state of their associated small blood vessels. Because the resin injected to identify capillaries accessible to flow might be soluble in commonly used tissue dehydrating agents, alternative preparation methods using the cryoprotectants dimethylsulfoxide (DMSO) and glycerol were investigated. Provided a high performance backscattered electron detector and simple environmental cell were used to abolish specimen charging and circumvent potential instrument contamination, immersion in 2.82 M DMSO for 12 hr prior to cryofracture and freeze-drying gave the best results. The SEM appearance of specimens dehydrated in this way differed little from that of specimens prepared by ethanol dehydration and freeze-drying or by acetone dehydration and critical-point drying. Tissue shrinkage was 26.5 +/- 9.4%, comparable to that found after standard methods using solvent dehydration and critical-point drying.
Acetone↗
Fatal injuries to bicycle riders in Auckland.
Twenty bicycle riders were fatally injured in Auckland between 1974 and 1984. Eighteen were male and nine aged under 15 years. The age distribution of fatalities corresponds closely to the known age distribution of the cycling population. Few differences in pattern of injury were demonstrable between younger (under 15 years) and older riders. Sixteen died of fatal injury to multiple organ systems. Fourteen had fatal injury to brain, including four with no other significant organ injury. Fatal cardiopulmonary trauma was seen in seven riders and fatal abdominal trauma in seven. Cervical and high thoracic fracture dislocation with cord injury were seen in seven riders. Compared to the population base, incidence of fatalities is low, and no recent significant increase is detected.
Adolescent↗
The development and progression of myocyte injury at the margins of experimental myocardial infarcts.
Distinct differences in the extent and progression of the lateral and epicardial boundaries of evolving regional infarcts were demonstrated in isolated rabbit hearts. Ischemia was produced by interrupting (0-240 minutes) flow in the ventral interventricular branch of the left coronary artery, whilst the remainder of the heart was continuously perfused with oxygenated Krebs-Henseleit bicarbonate buffer. Perfusion fixed blocks were freeze-fractured then examined using back-scattered electron imaging in a scanning electron microscope. Control myocytes showed relatively smooth, continuous internal fracture faces. After 30 min of ischemia myocytes showed evidence of mild, probably reversible, injury in the form of prominence of pits and channels. Severe injury, characterized by separation of organelles and prominent intracellular spaces, developed after 60 or more min of ischemia, first in the subendocardial two thirds, and after 120 min across the full thickness of the ventricular wall. At the lateral margins of infarcts there was a distinct cell-to-cell boundary between control and severely injured myocytes, with only a few scattered mildly injured cells within 30 mu of the infarct. Although transmural progression of necrosis provides the potential for recovery of the external aspect of the myocardium in the ischemic zone by reperfusion, corresponding regions of salvageable myocytes at lateral infarct margins are very narrow.
Animals↗
Cardiac performance of isolated beating hearts obtained from rats anesthetized by three different agents.
Two functional performance parameters (heart rate and coronary flow rate) of three groups of six isolated beating hearts obtained from rats anesthetized by inhalation of diethyl ether in air, injection intraperitoneally of sodium pentobarbital (60mg/kg) or intravenously of alphaxalone/alphadolone (15mg/kg) were compared. Differences were small, but alphaxalone-alphadolone showed lowest stable mean coronary flow rate and diethyl ether the widest variation between animals. No significant difference in function was found between ether and pentobarbital, currently the two most widely used methods. But, pentobarbital showed higher stable functional performance and least variation between animals. We conclude that pentobarbital is the most useful of these three agents for obtaining hearts for perfusion as isolated beating organs, and that alphaxalone-alphadolone is clearly less suitable.
Anesthesia↗
Morphological identification of functional capillaries in the myocardium.
This study used acrylic resin as an intravascular marker to demonstrate functional myocardial capillaries after fixation by perfusion. Eight rat hearts were excised and allowed to function as isolated organs perfused with oxygenated Krebs-Henseleit buffer (37 degrees C, 10 kPa) for 10 min. Four were fixed by perfusion (4 min) with 2.5% glutaraldehyde at the same temperature and pressure and then immersion fixed (24 hr). The other four hearts were perfused with 0.2% procaine HCl for 30 sec just prior to similar fixation. Polymerizing low viscosity acrylic resin was injected at 10 kPa pressure into the fixed vascular beds and allowed to cure, then transmural blocks of left ventricular myocardium were prepared for scanning electron microscopy. Total initial coronary flow of fixative after procaine treatment was significantly increased, while in untreated hearts the initial fixative flow rate was closely similar to that of oxygenated buffer. The pattern of capillary perfusion was assessed, and the percentage of capillary profiles filled by acrylic resin were calculated. Following procaine treatment, 95.2% of capillaries appeared functional, whereas without procaine arrest, only 62.0% of capillaries allowed the passage of resin. This study indicates that perfusion fixation with glutaraldehyde stabilizes myocardial structure so that the proportion of functional capillary pathways remains closely similar to that in the beating heart and so that such functional capillaries can be identified in morphological preparations by using a low viscosity intraluminal resin marker.
Acrylic Resins↗