Surface characterization of biomedical materials by measurement of electroosmosis

This paper reviews recent studies by the authors on the surface characterization of biomedically significant materials through electroosmosis determination. The surfaces studied include transparent and nontransparent materials such as quartz, ceramics, paper, and cast polymer capillaries, slides, and particles, in both native and surface modified form. The method is nondestructive, relatively fast, mechanistically simple, automatable to varying degrees, and can be used to analyze samples under physiologically compatible conditions. New experimental and mathematical modeling approaches allow estimates to be obtained with regard to the surface density and pK of various chemical groups, as well as the thickness of polymer or other surface coatings. Surface modifications which may be characterized include, covalent alteration via radiofrequency plasma discharge or organosilane grafting, noncovalent alteration via polymer adsorption, and covalent grafting of neutral polymers, such as poly(ethylene glycol) or dextran. Results complement those from other surface analysis techniques, and correlate with physiologically significant phenomena such as protein adsorption.

Lysenin, a novel sphingomyelin-specific binding protein

Lysenin, a novel 41-kDa protein purified from coelomic fluid of the earthworm Eisenia foetida, induced erythrocyte lysis. Preincubation of lysenin with vesicles containing sphingomyelin inhibited lysenin-induced hemolysis completely, whereas vesicles containing phospholipids other than sphingomyelin showed no inhibitory activity, suggesting that lysenin bound specifically to sphingomyelin on erythrocyte membranes. The specific binding of lysenin to sphingomyelin was confirmed by enzyme-linked immunosorbent assay, TLC immunostaining, and liposome lysis assay. In these assays, lysenin bound specifically to sphingomyelin and did not show any cross-reaction with other phospholipids including sphingomyelin analogs such as sphingosine, ceramide, and sphingosylphosphorylcholine, indicating that it recognized a precise molecular structure of sphingomyelin. Kinetic analysis of the lysenin-sphingomyelin interaction by surface plasmon resonance measurements using BIAcoreTM system showed that lysenin associated with membrane surfaces composed of sphingomyelin (kon = 3.2 x 10(4) M-1 s-1) and dissociated extremely slowly (koff = 1.7 x 10(-4) s-1), giving a low dissociation constant (KD = 5.3 x 10(-9) M). Incorporation of cholesterol into the sphingomyelin membrane significantly increased the total amount of lysenin bound to the membrane, whereas it did not change the kinetic parameters of the lysenin-membrane interaction, suggesting that lysenin specifically recognized sphingomyelin and cholesterol incorporation changed the topological distribution of sphingomyelin in the membranes, thereby increasing the accessibility of sphingomyelin to lysenin. Immunofluorescence staining of fibroblasts derived from a patient with Niemann-Pick disease type A showed that lysenin stained the surfaces of the fibroblasts uniformly, whereas intense lysosomal staining was observed when the cells were permeabilized by digitonin treatment. Preincubation of lysenin with vesicles containing sphingomyelin abolished lysenin immunostaining. This study demonstrated that lysenin bound specifically to sphingomyelin on cellular membranes and should be a useful tool to probe the molecular motion and function of sphingomyelin in biological membranes.

Exposure of phosphatidylethanolamine on the surface of apoptotic cells

In the early stages of apoptosis, phosphatidylserine (PS) is translocated from the inner side of the plasma membrane to the outer layer, which allows phagocytes to recognize and engulf the apoptotic cells. In this study we have analyzed the cell surface exposure of phosphatidylethanolamine (PE) in apoptotic CTLL-2 cells, a cytotoxic T cell line, using a tetracyclic polypeptide of 19 amino acids (Ro09-0198) which specifically recognizes the structure of PE and forms a tight equimolar complex with the phospholipid. Fluorescence microscopic analysis showed that the peptide, conjugated with fluorescence-labeled streptavidin (FL-SA-Ro), bound effectively to the cell surface of cells undergoing apoptosis in response to withdrawal of interleukin-2 from the culture media, but not to nonapoptotic cells. The binding of FL-SA-Ro to apoptotic cells was not uniform and the intense staining was observed on surface blebs of apoptotic cells. The FL-SA-Ro binding was inhibited specifically by liposomes containing PE, suggesting that PE is mainly exposed on the surface blebs of apoptotic cells. The specific binding of FL-SA-Ro to the apoptotic cells was also confirmed using a flourescence-activated cell sorter and the time-dependent cell surface exposure of PE correlated well with the exposure of PS, as detected by the binding of annexin V. This study provides the first direct evidence that PE as well as PS is exposed on the cell surface during the early stages of apoptosis, resulting in the total loss of asymmetric distribution of aminophospholipids in the plasma membrane bilayer.

Redistribution of phosphatidylethanolamine at the cleavage furrow of dividing cells during cytokinesis

Ro09-0198 is a tetracyclic polypeptide of 19 amino acids that recognizes strictly the structure of phosphatidylethanolamine (PE) and forms a tight equimolar complex with PE on biological membranes. Using the cyclic peptide coupled with fluorescence-labeled streptavidin, we have analyzed the cell surface localization of PE in dividing Chinese hamster ovary cells. We found that PE was exposed on the cell surface specifically at the cleavage furrow during the late telophase of cytokinesis. PE was exposed on the cell surface only during the late telophase and no alteration in the distribution of the plasma membrane-bound cyclic peptide was observed during the cytokinesis, suggesting that the surface exposure of PE reflects the enhanced scrambling of PE at the cleavage furrow. Furthermore, cell surface immobilization of PE induced by adding the cyclic peptide coupled with streptavidin to prometaphase cells effectively blocked the cytokinesis at late telophase. The peptide-streptavidin complex treatment had no effect on furrowing, rearrangement of microtubules, and nuclear reconstitution, but specifically inhibited both actin filament disassembly at the cleavage furrow and subsequent membrane fusion. These results suggest that the redistribution of the plasma membrane phospholipids is a crucial step for cytokinesis and the cell surface PE may play a pivotal role in mediating a coordinate movement between the contractile ring and plasma membrane to achieve successful cell division.

MR imaging evaluation of the spine with titanium alloy pedicular screw fixation

We studied the cases of 60 patients who underwent magnetic resonance (MR) imaging evaluation after fixation with the titanium alloy pedicular screw system. Spine stabilization was required in the thoracic and lumbar region for various spinal disorders. The images were evaluated for the spinal and adjacent tissues. These pedicular screw systems were imaged safely and caused no particular clinical problems. The localized signal void artifacts were seen around the implants. This artifact did not interfere with the diagnosis for another disease. The spinal cord and dura mater appeared in midsagittal and in axial images except for regions lying close to the implants. After surgery MR imaging revealed the decompressed or the deformed spinal cord. However, the prognosis of spinal disorder could not be revealed by the intensity grade of MR imaging because of the distortion in the spinal cord.

Brain ischemia decreases phosphatidylcholine-phospholipase D but not phosphatidylinositol-phospholipase C in rats

BACKGROUND AND PURPOSE

Phosphatidylcholine (PC)-phospholipase D (PLD) is an important intracellular signaling pathway in response to a variety of agonists, but little is known about the effects of brain ischemia on the PC-PLD system. We thus have examined the effects of global cerebral ischemia on PLD in rats.

METHODS

We have examined the effects of global ischemia (decapitation or four-vessel occlusion) on PLD and PLC activity in the membrane fraction of rat brains. We measured the PLD and PLC activity in detergent-mixed micelle assay systems using 3H-labeled exogenous substrate.

RESULTS

The results demonstrate that basal PLD activity showed a gradual decrease with increased duration (5 to 30 minutes) of ischemia by decapitation in the hippocampus; after 30 minutes of ischemia, PLD activity was significantly decreased compared with the control. Lineweaver-Burk plots showed that the apparent Vmax value of PLD in ischemia was one half of that in the control without changes in Km value. Ischemia by decapitation significantly decreased PLD activity in the brain stem as well as the hippocampus, whereas in four-vessel occlusion study, ischemia significantly decreased PLD activity in the hippocampus but not in the brain stem. Lowered temperature (30 degrees C and 22 degrees C) during ischemic incubation did not reverse the ischemia-induced PLD activity decrease. In contrast to PLD, ischemia by decapitation had no effect on basal phosphatidylinositol-phospholipase C activity or the amount of phospholipase C beta 1 in the membrane fractions from 30-minute ischemic hippocampus by immunoblots probed with the antibody.

CONCLUSIONS

These results suggest that PC-PLD is one of the target enzymes of ischemia; its decrease may cause a perturbation of PC hydrolysis and/or disorders of intracellular transduction of signals or choline metabolism for acetylcholine formation in brain.

Coronary vasospasm following subarachnoid hemorrhage as a cause of stunned myocardium. Case report

A patient with subarachnoid hemorrhage was found to have electrocardiographic abnormalities resembling an acute myocardial infarction as well as left ventriculographic findings of cardiac dysfunction. These cardiac abnormalities resolved following surgical clipping of the aneurysm and the patient recovered well from the operation. She died 2 months later from cancer and a postmortem examination at that time revealed no evidence of myocardial necrosis. In this report, the authors discuss coronary vasospasm and reversible postischemic "stunned myocardium," a condition that has not been considered previously in relation to subarachnoid hemorrhage.

Changes of brainstem auditory evoked responses (BAERs) in a brain stem ischemic model using embolization technique in cats, a preliminary study

In order to evaluate brain stem dysfunction related to ischemic process, the authors monitored the Brainstem Auditory Evoked Responses (BAERs) with time in a brain stem ischemic model. 19 adult mongrel cats were divided into two groups: embolization (n = 14) and sham operated control (n = 5). Embolization was done by injecting cylindrical silicone embolus to the right vertebral artery. Each successful embolization of the basilar artery was then confirmed by vertebral angiography. BAERs were monitored before embolization and then 5-10 min, 15 min, 30 min, 60 min, 3 hr and 6 hr after embolization. The presence of ischemic lesion caused by embolization was confirmed by injecting 2% Evans blue solution 30 min before sacrificing the animals. Leakage of the dye was observed. In embolized animals, significant (Student t test, p less than 0.05) delay of interpeak latencies of waves 1-3, 3-5, and 1-5 was observed 15 min after embolization. This delay became more significant (p less than 0.01) 30 min after embolization. These results provide evidence for the usefulness of BAERs monitoring which can be used to complement other diagnostic methods for patients with vertebrobasilar insufficiency and/or infarction.

An investigation of vascular anatomy and microvascular architecture of the brainstem in cats

The vascular anatomy and microvascular architecture of the vertebrobasilar system, especially within the brainstem, was investigated in cats. The main branches of the basilar artery were observed and the inner diameters of these vessels were measured on vertebral angiograms. The three-dimensional microvascular architecture was constructed using molded vascular models. The arterial anastomoses between the arteries inside the brainstem were studied using contact microangiograms. The paramedian branch penetrated into the brainstem in a retrograde fashion from the cranial basilar artery, and in an anterograde fashion from the caudal basilar artery. Arterial anastomoses were noted between the circumferential arteries. The frequency of arterial anastomoses was higher and diameters of the anastomotic vessels were larger in the ventrolateral region of the brainstem than in the ventromedial region. Regarding the perforating arteries, the arterial anastomoses were present outside the brainstem. No arterial anastomoses were found inside the brainstem.

[A case of epidural hematoma occurring on the opposite site of craniotomy after clipping surgery performed on internal carotid giant aneurysm]

Postoperative epidural hematomas remote from the operating field are sometimes seen as a complication after ventricle drainage, ventricle-peritoneal shunt or suboccipital craniotomy. Reported here is a very rare case of epidural hematoma which occurred on the opposite site of craniotomy after clipping surgery performed on internal carotid giant aneurysm. A 43-year-old woman was admitted to our hospital because of progressive visual disturbance in her right eye for twelve months. Precise examinations of her right eye revealed deterioration of visual acuity (0.02) right temporal-hemianopsia and an optic disc atrophy. A computed tomography scan (CT) showed a suprasellar round mass which was homogeneously well enhanced. Right carotid angiogram disclosed a large internal carotid artery aneurysm directed supramedially. The aneurysm was explored in June 1988. The neck was clipped with Sugita's ring clips through right frontotemporal craniotomy. The patient recovered fully and extubation was performed soon after the operation. Neurological examinations revealed no abnormal findings. Two days after the operation, she gradually developed impairment of consciousness and nausea. CT scan showed mass effect caused by epidural hematoma over the left temporoparietal region contralateral to the craniotomy site. Evacuation of the hematoma was carried out urgently. She had a good clinical course and postoperative angiogram demonstrated disappearance of the giant aneurysm. She was discharged and returned home without new neurological deficits. We review literature, and discuss presumptive pathogenesis responsible for such unexpected postoperative epidural hematomas.

[Metastatic malignant lymphoma of the skull with extradural and extracranial extension. Case report]

A 72-year-old male was hospitalized because of a steadily growing mass (4 x 4 x 2 cm) in the frontal region, noticed following head injury. Six months earlier, he had declined treatment for malignant lymphoma (small non-cleaved cell type), discovered upon evaluation of a subcutaneous mass in his forearm. Neurological examination on admission was negative. Plain skull films revealed a large, osteolytic lesion with an irregular margin. Bone scintigraphy disclosed no uptake other than in the frontal bone. Computed tomography (CT) showed a large, homogeneously enhanced mass with both extradural and extracranial extension, which had destroyed the left frontal bone. The skull tumor was totally resected, and the diagnosis was malignant lymphoma, large cell, immunoblastic and plasmacytoid type. Postoperative combined chemotherapy with vincristine, cyclophosphamide, prednisolone, and adriamycin resulted in the complete disappearance of liver metastases. The patient was readmitted 2 months later, however, because of headache and gradually progressive impairment of consciousness. A CT scan disclosed brain metastasis in the paraventricular region. Radiation therapy (20 Gy) was administered but no further treatment was given. Skull metastasis is not uncommon in cases of malignant lymphoma, but a large mass with both extradural and extracranial extension is rare. Although aggressive chemotherapy was effective, prophylactic irradiation of the brain should have been considered in this case.

[A case report of advanced malignant mixed germ cell tumor of parasellar origin indicating marked efficacy of a salvage combined chemotherapy of CDDP and etoposide and subsequent chemotherapy using oral etoposide]

A case of a 13-year-old boy with malignant mixed germ cell tumor of parasellar origin was reported. After partial removal of the tumor, combined chemotherapy (using cisplatin, vinblastine and bleomycin: PVB therapy) and irradiation were performed, and the tumor was reduced to under one tenth. In spite of PVB maintenance chemotherapy, it became refractory later. The patient was then treated with both CDDP 20 mg/m2 daily for 5 days and etoposide 100 mg/m2 for 1, 3, 5 days. After this one course, the tumor was diminished. Oral etoposide was administered at our outpatient department, and the boy was free of disease for six months.

Anterior inferior cerebellar artery aneurysm at the internal auditory meatus--case report

The authors present a case of a ruptured anterior inferior cerebellar artery aneurysm at the right internal auditory meatus, the incidence of which is thought to be very rare. The patient experienced sudden onset of headache, vomiting, and right tinnitus. Moderate right peripheral facial paresis, hearing disturbance and diplopia appeared 2 weeks after the onset. These signs and symptoms improved to some extent after successful clipping of the aneurysmal neck.

Aneurysm of the anterior inferior cerebellar artery at the internal auditory meatus: case report and review of the literature

The authors present a case of a ruptured aneurysm of the anterior inferior cerebellar artery at the right internal auditory meatus, of which incidence is thought to be very rare. The patient experienced a sudden onset of headache, vomiting and tinnitus in the right side. Moderate peripheral facial palsy and hearing disturbance in the right appeared 2 weeks after the onset with diplopia. These symptoms improved to some extent after the successful neck clipping of this aneurysm.

[A case of primary intrasellar malignant germ cell tumor]

A case of a 13-year-old boy with a primary, intrasellar malignant germ cell tumor is reported. An immunohistochemical study revealed that the serum HCG and AFP levels were highly elevated and that the tumor contained elements of seminoma, choriocarcinoma, a yolk sac tumor, and an embryonal carcinoma. After operation, combined chemotherapy (cisplatin, vinblastine and bleomycin, i.e. PVB therapy) and irradiation were performed in hope of achieving the radiosensitizing effect of cisplatin. As a result, partial remission was obtained. Although PVB therapy is considered effective, combined radio-chemotherapy, as was done in this case, is thought to be better method for treating an intracranial, malignant germ cell tumor.

Mesangial bridges. A mode of progression in diabetic glomerulosclerosis

Electron microscopic examination of the renal biopsy material obtained from a 35-year-old diabetic patient revealed subdivisions of glomerular capillaries into several branches by dendritic mesangial projections built between the mesangium and peripheral loop, a similar process which was described as mesangial bridges in a chronic phase of masugi nephritis. In comparison with those in experimental animals, mesangial bridges in the present case appeared rather solid with matrix formation, most presumably depending on long duration of the disease state in the diabetic patient. This process may represent a more complicated type of lesion invariably accompanying the nodule formation and is assumed to be an irreversible lesion ultimately undergoing segmental obliteration of glomerular capillaries.

Heterotransplantation of human urinary bladder cancers in nude mice

Thirty-one human urinary bladder cancers were transplanted subcutaneously into congenitally athymic nude mice. Subcutaneous growth was obtained in eight at the initial transplantation. Only one of these eight successful transplants, which was derived from squamous cell carcinoma, has been serially transplanted successfully and was characterized by high thromboplastic and low fibrinolytic activities which were virtually constant throughout the serial passages. This strain will provide a useful model system for studying anticancer therapies.

Heterotransplantation of human upper urinary tract tumors in nude mice

Eight human upper urinary tract tumors were transplanted subcutaneously into congenitally athymic nude mice. Subcutaneous growth was obtained in three (NKPP 1, NKPP 2, and NKPU 1) at initial transplantation and they were all serially passaged up to 29, 28, and 5 passages, respectively. Their histologic appearances were similar to those of the originals. These established strains with high transplantability and differing degrees of thromboplastic and fibrinolytic activities will provide a useful model system for studying anticancer therapies and biological characteristics of upper urinary tract tumors.