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Biomedical subjects

S Akizuki

Publications and source records attributed to S Akizuki.

At least 91 records · Page 5Linked to original sources
PubMed1987

Tensile properties of human knee joint cartilage. II. Correlations between weight bearing and tissue pathology and the kinetics of swelling.

The nonequilibrium or kinetic swelling behavior of normal, fibrillated, and osteoarthritic (OA) (removed from total knee joint replacements) human knee joint cartilage has been measured using our isometric tensile apparatus (ITA). We found that large local variations exist in the manner with which human knee joint cartilage swells, including anisotropic effects, inhomogeneities, and dependence on local biochemical composition and pathological condition. The ITA provides three convenient biomechanical parameters--peak stress (sigma p), stress relaxation (sigma R), and diffusion coefficient (D)--to quantify the kinetics of swelling. We used these parameters to quantify and differentiate the kinetic swelling behavior of normal, fibrillated, and osteoarthritic cartilage, as well as the swelling behavior of cartilage from high and low weight-bearing areas. Also, these kinetic swelling parameters correlated very well, though by varying degrees, with such biochemical measures as collagen/proteoglycan ratio, hexosamine content/wet weight, and hydroxyproline content/dry weight, providing important insight into the mechanisms and processes involved during the course of swelling. Hence, the kinetic swelling behavior of cartilage should be used to provide important information not obtainable from equilibrium swelling studies.

Body Water↗
PubMed1986

Tensile properties of human knee joint cartilage: I. Influence of ionic conditions, weight bearing, and fibrillation on the tensile modulus.

The flow-independent (intrinsic) tensile modulus of the extracellular matrix of human knee joint cartilage has been measured for normal, fibrillated, and osteoarthritic (removed from total knee joint replacements) cartilage. The modulus was determined in our isometric tensile apparatus and measured at equilibrium. We found a linear equilibrium stress-strain behavior up to approximately 15% strain. The modulus was measured for tissues from the high and low weight-bearing areas of the joint surfaces, the medial femoral condyle and lateral patello femoral groove, and from different zones (surface, subsurface, middle, and middle-deep) within the tissue. For all specimens, the intrinsic tensile modulus was always less than 30 MPa. Tissues from low weight-bearing areas (LWA) are stiffer than those from high weight-bearing areas (HWA). The tensile modulus of the ECM correlates strongly with the collagen/proteoglycan ratio; it is higher for LWA than for HWA. Osteoarthritic cartilage from total knee replacement procedures has a tensile stiffness less than 2 MPa.

Adult↗
PubMed1986

Renal oncocytoma.

Up to date only five cases of renal oncocytomas have been reported in Japan. We describe two cases of renal oncocytomas. Case 1: A 63-year-old woman, who had no urological symptoms, was pointed out of a cystic mass in the left kidney by chance. A resected kidney had a cystic tumor, which was well encapsulated and measured 6 X 7 X 8 cm. The tumor was unilocular and thick-walled cyst filled with bloody fluid. Histologically, the tumor was composed of oncocytes with eosinophilic granular cytoplasms that were packed with mitochondria. Case 2: A 70-year-old women died of malignant lymphoma and an autopsy was performed. The tumor was found in the right kidney by chance and measured 1 cm in diameter. The cut-surface of the tumor was uniform and tan-brown in color. Histologically, the tumor was composed of cells same as Case 1. We discuss the incidence of this tumor and the morphological characteristics of our cases.

Adenoma↗
PubMed1985

Infarct size limitation by the xanthine oxidase inhibitor, allopurinol, in closed-chest dogs with small infarcts.

The present study was designed to evaluate the ability of allopurinol to limit infarct size following permanent coronary occlusion in the greyhound. Coronary occlusion was produced by injecting 2.5 mm plastic beads into the coronary artery of the closed chest dog. Non-perfused myocardium, the area at risk, was visualised by autoradiography of 141Cerium labelled microspheres which were infused immediately following coronary embolization. The treated dogs (n = 12) received 400 mg of allopurinol orally one day before surgery. A 25 mg . kg-1 bolus was administered (iv) immediately before occlusion, and repeated every 8 h. 11 dogs served as controls. After 24 h, the dogs were killed and the hearts were sliced into 5.0 mm transverse sections. The infarcted myocardium was visualised by triphenyl tetrazolium chloride staining. The percentage of the risk zone which evolved to infarct was calculated. This percentage was 18.1 +/- 3.95% in the allopurinol group vs 58.4 +/- 2.81% in the control group (p less than 0.001). We conclude that allopurinol is a potent drug for the limitation of infarct size in the dog with permanent coronary occlusion.

Allopurinol↗
PubMed1985

Influence of nitroglycerin on collateral blood flow during acute ischaemia in the dog.

To investigate the effects of nitroglycerin on collateral blood flow 10 open chest dogs underwent coronary occlusion followed by nitroglycerin infusion (80 to 300 micrograms . min-1) to lower mean systemic blood pressure by 20 mmHg, followed by phenylephrine infusion (10 to 40 micrograms . min-1) to restore blood pressure to the pre-nitroglycerin level. Myocardial blood flow was measured with microspheres. The contribution of overlapping normal zone tissue in the ischaemic zone was evaluated with the balloon perfusion technique. Collateral flow was measured with microspheres in the most ischaemic tissue. In addition "load line" analysis was used to calculate collateral flow from retrograde flow. Nitroglycerin lowered blood flow to non-ischaemic tissue, and tended to lower blood flow to ischaemic tissue. Phenylephrine restored blood flow to the value after coronary occlusion. Load line analysis data was similar to data on myocardial blood flow from the microspheres. Collateral resistance changed little during the experiment. Th effects of nitroglycerin on collateral blood flow are, thus, minimal. While it is possible that under special circumstances there may be some decrease in collateral resistance, the bulk of data from this study and others do not support the idea that systemic infusion of nitroglycerin in the setting of an acute myocardial infarction will affect collateral flow.

Animals↗
PubMed1985

Discrepancy between microsphere and diffusible tracer estimates of perfusion to ischemic myocardium.

This study critically tests the ability of microspheres to accurately measure perfusion to ischemic myocardium. The left anterior descending coronary artery was cannulated and perfused with arterial blood. The perfusion line was clamped, and a sidearm between the clamp and the cannula was opened to the atmosphere, allowing blood to flow retrograde from the distal segment of the artery. Measurement of regional blood flow during retrograde flow diversion with 15-micron microspheres revealed essentially zero flow to the perfused segment (0.005 ml X min-1 X g-1). Measurements under the same conditions by either 86Rb uptake or 133Xe washout revealed that an appreciable perfusion of the tissue persisted during retrograde flow diversion (0.043 and 0.11 ml X min-1 X g-1, respectively, for the 2 methods). Thus we have identified a condition during which microspheres indicate zero flow to the tissue but diffusible tracers can both be washed in and washed out at a brisk rate. We conclude that with simple occlusion there is a hidden component of perfusion to an ischemic zone that cannot be measured by microspheres, causing them to underestimate flow by about 25% in that condition.

Animals↗
PubMed1984

Variable effects of intracoronary nitroglycerin on myocardial blood flow and segmental shortening according to dose and degree of coronary occlusion.

The effects of intracoronary nitroglycerin were determined in 21 open-chest dogs. Six dogs with severe stenosis (25 mm Hg diastolic perfusion pressure) and nine dogs with moderate stenosis (40 mm Hg) received a 12 micrograms bolus followed by 44 micrograms/min intracoronary nitroglycerin. In addition, six dogs with moderate stenosis (40 mm Hg) received 5 micrograms followed by 5 micrograms/min nitroglycerin. Myocardial blood flow was measured with radioactive microspheres and segment shortening with ultrasonic crystals. At 40 mm Hg, high-dose but not low-dose nitroglycerin raised epicardial blood flow, while at 25 mm Hg nitroglycerin had no effect. Subendocardial blood flow was not affected in any group. Partial occlusion resulted in a decrease in segment shortening in the 25 mm Hg group but not at 40 mm Hg. High-dose nitroglycerin had no effect on shortening at either level of occlusion. Thus, in the presence of coronary vascular reserve, high-dose nitroglycerin may overcome coronary autoregulation. A dose equivalent to one that simulates the amount of nitroglycerin delivered to the coronary circulation by a systemic infusion did not affect myocardial blood flow. In addition, even a large dose of nitroglycerin did not affect segment shortening.

Animals↗
PubMed1984

Contrasting incidence, inducibility, and transmural sites of origin of ventricular arrhythmias during acute coronary occlusion and reperfusion.

The incidence, inducibility, and sites of origin of ventricular arrhythmias were studied in 16 open-chest dogs. The dogs were placed on cardiopulmonary bypass. Electrograms from ischemic endocardium and epicardium and normal epicardium were recorded with bipolar composite electrodes. Burst pacing was used to induce arrhythmias. Dogs were studied in the control state, 15 minutes after left anterior descending coronary artery occlusion, and during reperfusion performed after 20 minutes of occlusion. Ventricular fibrillation was seen more commonly (in 8 of 14 dogs) during reperfusion than during occlusion (in 4 of 13 dogs). Continuous fragmented electrical activity was first recorded on the ischemic zone epicardium in six of eight episodes during occlusion arrhythmias and on the endocardium in 25 of 33 episodes during reperfusion. These data may relate to the effects of varying degrees of ischemia and reperfusion on conduction characteristics of the respective layers.

Animals↗
PubMed1984

Entrapment neuropathy caused by tophaceous gout.

Entrapment neuropathy associated with gout is a rare occurrence. We report two cases of entrapment neuropathy of ulnar tunnel syndrome and carpal tunnel syndrome caused by gouty tophi. Problems related to its mechanism and treatment are discussed.

Aged↗
PubMed1984

Influence of nifedipine on collateral blood flow during acute ischemia in the dog.

Vasodilators have been found effective in increasing blood flow in the lateral border surrounding a central zone of infarction, but any change in blood flow to this border zone may be to the normal tissue in this zone, rather than to the ischemic tissue. In this study of the effects of nifedipine on collateral blood flow, 31 open chest dogs underwent coronary occlusion followed by nifedipine infusion, either 3 or 1 microgram/kg per min. A balloon perfusion microsphere labeling device was used to separate the influence of normally perfused tissue overlapping with ischemic tissue in the lateral border zone. Nifedipine increased blood flow in the border zone, but this increase could be accounted for by the effect of nifedipine on admixed normal tissue. In the central ischemic zone, nifedipine administration resulted in a decrease in collateral blood flow. Thus, to fully understand the effect of a vasodilator on ischemic zone blood flow, it is necessary to account for flow in overlapping normal tissue.

Animals↗
PubMed1984

Ultrastructure of the spleens in childhood ITP with special reference to the foamy cells.

We examined the spleens from four patients with childhood ITP. Numerous foamy cells were investigated in two cases, moderate number in one case, and a few in one case. PAP method using anti-human platelet antibody demonstrated the platelet antigen in the cytoplasms of these foamy cells, which were granular or reticular. Electron microscopically, many platelets in various stages of intracellular digestion from intact-appearing forms to myelin-like materials, were disclosed. Enzyme cytochemical electron microscopy revealed localization of acid phosphatase activity around the degrading platelets and vacuolated inclusions, but rarely in the myelin-like materials. We suggest that the mechanism of formation of the foamy cells in ITP is as follows; macrophages phagocytize many platelets, exhaust their lysosomal enzyme, and can not digest the engulfed platelets completely. Thus the partially degraded platelets remain as myelin-like materials in the cytoplasm of macrophages, which have foamy appearance in light microscopy.

Adolescent↗
PubMed1984

Malignant cystosarcoma phyllodes of prostate.

A case of malignant cystosarcoma phyllodes of the prostate is reported in a 45-year-old male. This tumor was composed of benign columnar or squamous cystic folds and sarcomatous stroma including rhabdomyomatous elements. The prostatic origin of the tumor was clearly proved by the unlabeled immunoperoxidase method.

Autoantibodies↗
PubMed1984

The role of vascular capacitance in the coronary arteries.

When the left coronary artery was perfused with nonpulsatile pressure, the onset of diastole was accompanied by a capacitance overshoot in flow with an exponential decay back to a steady state. Time constant for that decay ranged from 55 msec when tone was present to 105 msec with maximal dilation. Since the transient resulted from a fall in tissue pressure, this represents an estimation of intramural arterial capacitance only. Transients in perfusion pressure, which would also affect epicardial arteries, yielded similar time constants. We concluded that most of the coronary capacitance resides in the small intramural vessels. Analysis of transients yielded a value for capacitance of between 0.01 and 0.05 ml/mm Hg per 100 g. We then used the data from the transients to construct coronary pressure flow curves which were free of any back flow from capacitance. When coronary tone was present, the curves indicated that flow ceased at 30 mm Hg. With maximal dilation, flow ceased at only 18 mm Hg. Long diastoles in those same hearts indicated that flow ceased at about 10 mm Hg higher pressure. Although capacitance causes critical closing pressure as determined by a long diastole to be artifactually high, critical closing pressure is still appreciable in the heart, and tone dependent. Finally, three computer models were built, one of which included only small vessel capacitances, the second, only vascular waterfalls, and the third, both of the above. Only model 3 was capable of reproducing the flow patterns which were actually seen.

Animals↗
PubMed1984

Serous papillary cystadenocarcinoma associated with alpha-fetoprotein production.

A 74-year-old woman with a right ovarian tumor had a high level of the serum tumor marker alpha-fetoprotein (AFP). After combination chemotherapy, the serum AFP level decreased significantly. Histopathologic study of surgically excised tumor tissue revealed a serous papillary cystadenocarcinoma. By the indirect immunoperoxidase technique, the AFP was stained in the cytoplasm of the differentiated tumor cells, showing papillary or tubular structures. Serial sections showed that the cells containing PAS-positive substances did not correspond to those producing AFP.

Aged↗
PubMed1984

Foamy cells associated with platelet phagocytosis.

In order to gain an insight into the mechanism for the formation of foamy cells (macrophages with foamy cytoplasm) frequently seen in spleens affected by idiopathic thrombocytopenic purpura (ITP), these cells were experimentally induced in mice by subcutaneous injection of platelets with or without accompanied administration of corticosteroid. The light- and electron-microscopic features of experimentally reproduced foamy cells were essentially similar to those seen in the spleens of ITP patients. Corticosteroid had no significant effect on the formation of foamy cells. Most macrophages with foamy cytoplasm contained various amounts of phospholipids, which were derived from platelet membranes. By electron microscopy, myelinlike materials were frequently demonstrated in the cytoplasm of foamy cells. Although lysosomal enzyme activity was revealed in the macrophages that contained morphologically recognizable platelets, there was no demonstrable activity in the cells that contained myelinlike materials. From these results, the following conclusion has been suggested as the mechanism for the formation of foamy cells. Under the state of accelerated phagocytosis of platelets by the macrophages, such as in ITP, the amount of ingested platelet membranes is beyond the capacity of lysosomal digestion. Thus, the incompletely degraded membrane constituents, especially membrane-derived phospholipids, remain in the macrophages, and they are most responsible for the foamy appearance of these macrophages.

Animals↗