Gelatin Foam Research Articles

Predictive Value of Intraosseous Venography before Percutaneous Vertebroplasty

Percutaneous vertebroplasty is a novel approach for treating patients with painful vertebral body compression fractures. The use of intraosseous venography before the percutaneous injection of polymethylmethacrylate (PMMA) is not universally accepted. The purpose of this study was to determine if intraosseous venography predicts PMMA flow characteristics when injected into a vertebral body. One hundred thirty-five intraosseous venograms were obtained during 96 vertebroplasty procedures (39 thoracic, 57 lumbar) in 61 patients (49 women, 12 men; age, 36-94 y) over a 32-month period. All venograms were obtained by injecting water-soluble contrast material through the vertebroplasty needle that had been placed percutaneously via a transpedicular approach. The venograms were retrospectively reviewed by the authors and compared in a blinded fashion with the subsequent final vertebroplasty result. Several venographic patterns were observed: bilateral or unilateral marrow blush with or without venous filling, direct venous filling, leakage of contrast material through an endplate or cortical defect, and stasis within the marrow space. Venograms that demonstrated a bilateral marrow blush predicted flow of PMMA across the midline to adequately fill the contralateral hemivertebrae 95% of the time (40 of 42 cases). A unilateral marrow blush predicted the necessity of a second puncture 97% of the time (32 of 33 cases). Intraosseous venography predicted PMMA entering endplate/cortical defects in all cases (22 of 22) and venous structures in 29% (22 of 75) of cases. Direct venous filling was observed during two vertebroplasty procedures and gelatin foam embolization was performed before PMMA instillation. Stasis of contrast material in the marrow space was observed in 15 cases. Overall, in 83% (80 of 96) of the vertebroplasty procedures, intraosseous venography was believed to predict the flow characteristics of PMMA. Intraosseous venography provides useful information in predicting PMMA flow characteristics within the vertebral body and in predicting potential undesirable sites of cement deposition, such as through cortical defects and within venous structures.

Easy Sellar Reconstruction in Endoscopic Endonasal Transsphenoidal Surgery with Polyester-Silicone Dural Substitute and Fibrin Glue: Technical Note

To describe a simple method of sellar reconstruction after endoscopic endonasal transsphenoidal surgery that will allow rapid watertight closure of the sellar floor. A bent sheet of a polyester-silicone dural substitute, fashioned for this purpose with scissors, is introduced into the sella after removal of the lesion. Because of the consistency of the sheet, it opens spontaneously and becomes stuck. Autologous fat tissue or gelatin foam is positioned thereafter, followed by another layer of the dural substitute; a film of fibrin glue completes the sealing. Fifteen patients underwent this method and no postoperative cerebrospinal leak or other complication was experienced. This easy method of sellar reconstruction represents an effective and fast possibility to perform the final step of the endoscopic transsphenoidal procedure, which otherwise may cause maneuverability problems in the limited space of one nostril.

This month in J Lab Clin Med: Issue highlights for April 2001

This month in J Lab Clin Med: Issue highlights for April 2001

Management of hemorrhage during laparoscopy.

Bleeding can be a complication of laparoscopic procedures commonly performed by urologists, such as pelvic node dissection and nephrectomy, and is often difficult to manage. Hemorrhage also can occur as a result of Veress needle or trocar placement, and there are specific strategies for the management of these injuries. Laparoscopic clip appliers, laparoscopic staplers, laparoscopic suturing, various energy sources (monopolar and bipolar electrocautery, laser, ultrasonic dissectors, and argon beam coagulators), and topical agents (gelatin foam, cellulose, collagen, and fibrin sealant) can be used to obtain hemostasis. Converting to laparotomy to obtain hemostasis may be necessary in some cases. Proper patient selection is important for lowering the risk of hemorrhage.

Sellar reconstruction with resorbable vicryl patches, gelatin foam, and fibrin glue in transsphenoidal surgery: a 10-year experience with 376 patients.

Closure of the sella turcica after transsphenoidal surgery is mainly accomplished with autologous muscle fascia and fat or muscle; this requires a second surgical incision. The authors review the results of using resorbable vicryl patches, gelatin foam, and fibrin glue for sellar reconstruction. A review was conducted of 376 consecutive patients who underwent surgery for pituitary adenomas, cysts, or subdiaphragmatic craniopharyngiomas in the sella turcica that the senior author (R.W.S.) had performed or directly supervised over the last 10 years. The sellar reconstruction was performed with a commercially available, synthetic absorbable patch composed of polyglactin 910/poly-p-dioxanone, gelatin foam, and fibrin glue. The patch is essentially resorbed in 2 to 3 months and replaced by fibrous collagen tissue. There were 117 small, 112 medium-sized, and 147 large lesions. The overall nonendocrine postoperative morbidity rate was 2.8%, and included visual deterioration, meningitis, secondary epistaxis, nasal septum complication, and cerebrospinal fluid (CSF) leakage. Two patients with macroadenomas needed reoperation for persistent CSF leakage, which comprised 0.5% of the whole series or 0.8% of the 259 patients with medium-sized or large lesions. There was no mortality and no morbidity related to the implanted material, and in particular no delayed empty sella syndrome. Closure of the sella turcica with a synthetic absorbable vicryl patch, gelatin foam, and fibrin glue after transsphenoidal surgery is safe and very effective in preventing postoperative CSF fistulas. The use of this technique obviates the need for a second surgical incision and shortens the operating time. Because of the progressive resorption of the substitute material, the interpretation of postoperative magnetic resonance studies was not significantly hindered.

Use of a Collagen Plug Device to Seal a Subclavian Artery Puncture Secondary to Intraarterial Dialysis Catheter Placement

O SCVIR, 1999 THE role of endovascular therapies for the treatment of traumatic arterial lesions has expanded in recent years. In the past, percutaneous treatment of such lesions was limited to arteries that could be embolized with coils, gelatin foam, or other agents. Traumatic pseudoaneurysms may be amenable to coil embolization or, more recently, in the common femoral artery region, to ultrasoundguided compressive occlusion. The advent of covered endovascular stent grafts has expanded the role of the interventional radiologist to treat arterial injuries, especially in locations that are more difficult to approach surgically. However, one of the limitations of this technique includes the occlusion of vital branch vessels by the covered stent. Recently, two collagen plug devices have been marketed to seal arterial puncture sites after arteriography and intervention (1,2). We report our experience in a patient with a dialysis catheter placed within the subclavian artery in which a collagen plug device was used to seal the arterial puncture site.

Finlepsin-retard in clinic of borderline states : V. Ya. Semke, M.M. Aksyonov, I.E. Kupriyanova, A.V. Semke. Mental Health Research Institute, Sosnovy bor, Tomsk, 6340146, Russia

Epistaxis is an important emergency that can sometimes be life threatening without effective intervention. Persistent and recurrent bleeding can lead to aspiration, hypotension, hypoxia, or even severe and mortal cardiovascular complications. Providing prompt hemostasis is important, and the hemostatic method used must be easily and locally applicable, efficient, and inexpensive.The aim of this study was to assess the hemostatic efficacy of Ankaferd Blood Stopper (ABS) in an experimental epistaxis model and to determine the histopathologic alterations with topical ABS application.Twenty-eight New Zealand rabbits were evaluated in 4 study groups. Topical ABS, gelatin foam (GF), adrenalin + lidocaine (AL), and serum physiologic as negative control (C) were applied to the animals for controlling epistaxis. The bleeding was generated with a standard mucosal incision in all groups. Cotton pieces soaked with ABS, AL, C, and GF were applied to the nasal bleeding area. Time of hemostasis was recorded. Tissue samples were obtained after hemostasis for histopathologic examination. The samples were stained with hematoxylin and eosin (HE) and phosphotungstic acid hematoxylin (PTAH) and were examined under a light microscope. In this experimental study, the observers were blind to ABS, AL, and C but not to GF, because of its solid nature.Median durations required for hemostasis in ABS, AL, GF, and C groups were recorded as 30, 90, 90, and 210 seconds, respectively. The time until termination of bleeding in the ABS group was significantly shorter than that in the AL, GF, and C groups (P = 0.002, P = 0.002, and P = 0.001, respectively). On histopathologic evaluation, after staining with HE, minimal fibrin at the incision edges and a few extravasated erythrocytes were observed in the C, AL, and GF groups. In the ABS group, a dark amorphous material surrounded by fibrin, filling the space between the edges of incisions, was noticed. Fibrin was determined in the C, GF, and AL groups with PTAH stain and in the positive control group. In the ABS group, it was observed that the amorphous substance surrounded by fibrin seen in the HE sections was not stained with PTAH.Topical nasal ABS application controlled epistaxis faster than C, GF, and AL in this animal bleeding model. The bleeding model used here might fail to replicate the type of injury that would be likely to result in life-threatening bleeding in humans, which should be considered a limitation of the present study. The histopathologic findings in the nasal incision area suggest that ABS might affect global hemostasis by inducing a unique protein network formation, potentially representing a different mechanism of action among conventional antihemorrhagic applications.

Ultrastructural correlates in the cerebellum of the biochemical effects of lithium on gene expression : S. Sidiropoulou-Skokou, S. Havaki and M.R. Issidorides. Neurobiology Research Institute, Theodor Theohari Cozzika Foundation, and Department of Psychiatry, University of Athens, Eginition Hospital, Greece

Epistaxis is an important emergency that can sometimes be life threatening without effective intervention. Persistent and recurrent bleeding can lead to aspiration, hypotension, hypoxia, or even severe and mortal cardiovascular complications. Providing prompt hemostasis is important, and the hemostatic method used must be easily and locally applicable, efficient, and inexpensive.The aim of this study was to assess the hemostatic efficacy of Ankaferd Blood Stopper (ABS) in an experimental epistaxis model and to determine the histopathologic alterations with topical ABS application.Twenty-eight New Zealand rabbits were evaluated in 4 study groups. Topical ABS, gelatin foam (GF), adrenalin + lidocaine (AL), and serum physiologic as negative control (C) were applied to the animals for controlling epistaxis. The bleeding was generated with a standard mucosal incision in all groups. Cotton pieces soaked with ABS, AL, C, and GF were applied to the nasal bleeding area. Time of hemostasis was recorded. Tissue samples were obtained after hemostasis for histopathologic examination. The samples were stained with hematoxylin and eosin (HE) and phosphotungstic acid hematoxylin (PTAH) and were examined under a light microscope. In this experimental study, the observers were blind to ABS, AL, and C but not to GF, because of its solid nature.Median durations required for hemostasis in ABS, AL, GF, and C groups were recorded as 30, 90, 90, and 210 seconds, respectively. The time until termination of bleeding in the ABS group was significantly shorter than that in the AL, GF, and C groups (P = 0.002, P = 0.002, and P = 0.001, respectively). On histopathologic evaluation, after staining with HE, minimal fibrin at the incision edges and a few extravasated erythrocytes were observed in the C, AL, and GF groups. In the ABS group, a dark amorphous material surrounded by fibrin, filling the space between the edges of incisions, was noticed. Fibrin was determined in the C, GF, and AL groups with PTAH stain and in the positive control group. In the ABS group, it was observed that the amorphous substance surrounded by fibrin seen in the HE sections was not stained with PTAH.Topical nasal ABS application controlled epistaxis faster than C, GF, and AL in this animal bleeding model. The bleeding model used here might fail to replicate the type of injury that would be likely to result in life-threatening bleeding in humans, which should be considered a limitation of the present study. The histopathologic findings in the nasal incision area suggest that ABS might affect global hemostasis by inducing a unique protein network formation, potentially representing a different mechanism of action among conventional antihemorrhagic applications.

Class III β‐Tubulin isotype (β III) in the adrenal medulla: III. Differential expression of neuronal and glial antigens identifies two distinct populations of neuronal and glial‐like (sustentacular) cells in the PC12 rat pheochromocytoma cell line maintained in a gelfoam matrix system

Background The rat PC12 pheochromocytoma cell line provides an established system for the study of neuronal differentiation. To our knowledge, glial differentiation has not been reported in this cell line. Methods We have studied, by immunohistochemistry and immunoblotting, the presence of neuronal cytoskeletal antigens [class III β-tubulin isotype (β III), microtubule associated proteins MAP2, MAP1B and tau, and different neurofilament (NF) protein components], and synaptophysin in comparison with the glial fibrillary acidic protein (GFAP) and S-100 protein in the PC12 cell line. In three different experiments, PC12 cells were maintained in a three-dimensional gelatin foam (Gelfoam) matrix system for up to 34 days with and without treatment with 1 mM dibutyryl cyclic (dc)AMP. Immunohistochemistry was performed on explants ranging from 2 to 32 days-in vitro, which were fixed in either Bouin's solution, 70% ethanol, or 10% neutral-buffered formalin and embedded in paraffin. Immunoblotting was performed on Gelfoam explants with a panel of antibodies against all aforementioned neuronal and glial markers. Additional immunoblot experiments using anti-GFAP and anti-β III monoclonal antibodies in cell suspensions and homogenates from PC12 monolayer cultures were carried out to compare growth conditions in relation to the expression of these proteins. Results β III and MAP2 were demonstrated by immunohistochemistry and immunoblotting of PC12 explants maintained for up to 32 days in Gelfoam matrices with and without treatment with dcAMP. Intense filamentous and granular β III staining of PC12 cells was observed in dcAMP-treated cultures concomitant with neuronal morphologic alterations (neuritogenesis and ganglionic phenotype). In untreated cultures, β III staining was present in less differentiated cells, as well in cells undergoing neuritic development. The neuronal phenotype of PC12 cells was confirmed by staining for MAP2, tau, and NF proteins, as well as for synaptophysin. The presence of β III, MAP2, MAP1B, tau, and NF proteins was confirmed by immunoblotting. Clusters of GFAP-positive and S-100 protein-positive spindle cells, phenotypically distinct from the chromaffin-like or neuronal cells, were demonstrated in Gelfoam explants at 5–30 days in vitro. In 30-day-old cultures treated with dcAMP, there was strong filamentous GFAP and diffuse S-100 protein staining in an increased number of sustentacular-like PC12 cells. GFAP staining was corroborated by immunoblotting of explants maintained under identical conditions in vitro. In contrast, immunoblots performed on homogenates from PC12 suspension and monolayer cultures were GFAP-negative. Conclusions Neuronal and glial-like, presumed sustentacular, phenotypes were demonstrated in PC12 cells grown in Gelfoam matrices with and without treatment with dcAMP for up to 34 days. To our knowledge, the occurrence of glial differentiation in the PC12 line is a hitherto unreported finding. Adult rat medullary sustentacular cells are known to express S-100 and GFA proteins (Suzuki and Kachi, Kaibogaku Zasshi—J Anat 70(2): 130–139, 1995), and the organ culture system employed in our study may well have favored this direction of differentiation. Anat. Rec. 250:351–365, 1998. © 1998 Wiley-Liss, Inc.

Class III β-Tubulin isotype (β III) in the adrenal medulla: III. Differential expression of neuronal and glial antigens identifies two distinct populations of neuronal and glial-like (sustentacular) cells in the PC12 rat pheochromocytoma cell line maintained in a gelfoam matrix system

The rat PC12 pheochromocytoma cell line provides an established system for the study of neuronal differentiation. To our knowledge, glial differentiation has not been reported in this cell line. We have studied, by immunohistochemistry and immunoblotting, the presence of neuronal cytoskeletal antigens [class III beta-tubulin isotype (beta III), microtubule associated proteins MAP2, MAP1B and tau, and different neurofilament (NF) protein components], and synaptophysin in comparison with the glial fibrillary acidic protein (GFAP) and S-100 protein in the PC12 cell line. In three different experiments, PC12 cells were maintained in a three-dimensional gelatin foam (Gelfoam) matrix system for up to 34 days with and without treatment with 1 mM dibutyryl cyclic (dc)AMP. Immunohistochemistry was performed on explants ranging from 2 to 32 days-in vitro, which were fixed in either Bouin's solution, 70% ethanol, or 10% neutral-buffered formalin and embedded in paraffin. Immunoblotting was performed on Gelfoam explants with a panel of antibodies against all aforementioned neuronal and glial markers. Additional immunoblot experiments using anti-GFAP and anti-beta III monoclonal antibodies in cell suspensions and homogenates from PC12 monolayer cultures were carried out to compare growth conditions in relation to the expression of these proteins. Beta III and MAP2 were demonstrated by immunohistochemistry and immunoblotting of PC12 explants maintained for up to 32 days in Gelfoam matrices with and without treatment with dcAMP. Intense filamentous and granular beta III staining of PC12 cells was observed in dcAMP-treated cultures concomitant with neuronal morphologic alterations (neuritogenesis and ganglionic phenotype). In untreated cultures, beta III staining was present in less differentiated cells, as well in cells undergoing neuritic development. The neuronal phenotype of PC12 cells was confirmed by staining for MAP2, tau, and NF proteins, as well as for synaptophysin. The presence of beta III, MAP2, MAP1B, tau, and NF proteins was confirmed by immunoblotting. Clusters of GFAP-positive and S-100 protein-positive spindle cells, phenotypically distinct from the chromaffin-like or neuronal cells, were demonstrated in Gelfoam explants at 5-30 days in vitro. In 30-day-old cultures treated with dcAMP, there was strong filamentous GFAP and diffuse S-100 protein staining in an increased number of sustentacular-like PC12 cells. GFAP staining was corroborated by immunoblotting of explants maintained under identical conditions in vitro. In contrast, immunoblots performed on homogenates from PC12 suspension and monolayer cultures were GFAP-negative. Neuronal and glial-like, presumed sustentacular, phenotypes were demonstrated in PC12 cells grown in Gelfoam matrices with and without treatment with dcAMP for up to 34 days. To our knowledge, the occurrence of glial differentiation in the PC12 line is a hitherto unreported finding. Adult rat medullary sustentacular cells are known to express S-100 and GFA proteins (Suzuki and Kachi, Kaibogaku Zasshi-Anat 70(2): 130-139, 1995), and the organ culture system employed in our study may well have favored this direction of differentiation.

Percussive foraging : Stimuli for prey location by aye-ayes (Daubentonia madagascariensis)

Aye-ayes (Daubentonia madagascariensis) use the thin middle finger to tap on wood in search of subsurface cavities containing insect larvae. When a cavity is located, they gnaw away wood until the prey can be extracted. Previous researchers suggested that acoustical cues reveal cavity location. We designed five studies to identify the cavity features that provide acoustical cues. When cavities were backfilled with gelatin or acoustical foam, excavation was still successful, suggesting that the reverberation of sound in air-filled cavities is not necessary for detection. Moreover, when the density of cavity content was varied, there was no difference in excavation frequency. On the other hand, a one-dimensional break in the subsurface wood was an effective stimulus for excavation. These studies suggest that a simple interface beneath the surface is sufficient to elicit excavation and that neither prey nor cavity nor even small air pockets are necessary to elicit the behavior. These results raise provocative questions as to how the aye-aye manages to forage efficiently.

5665144 Method and apparatus utilizing hydrocarbon pollutants from glycol dehydrators : Hill D Jeffre; Wiggins E Tod Edmond, OK, United States

Calcium phosphate whiskers have been suggested to be effective as the reinforcement in improving mechanical properties of composite biomaterials. Therefore, composite scaffolds of varying compositions were prepared by freeze drying of gelatin foams containing increasing amounts of calcium phosphate whiskers/fibrous spherulites, up to 50 wt%. The whiskers were attempted to synthesize in acidic solutions under thermal conditions using two different methods: aging of a highly crystalline beta-tricalcium phosphate powder in H2O2 solution, and the precipitation−hydrolysis method using aqueous solutions of calcium and phosphate ions in HNO3 solution and urea as an additive. The morphology and phase analysis of the whiskers were studied by scanning electron microscopy (SEM) and X-ray diffractometry (XRD), respectively. The results proved that the whiskers could not be obtained by first method at an appropriate period, but using the second method, a mixed plate-like and long whiskers, and fibrous spherulites could be formed. The XRD patterns revealed the biphasic mixture of octacalcium phosphate (OCP) and dicalcium phosphate anhydrate (DCPA). The composite scaffolds containing whiskers obtained by freeze drying were characterized by SEM, Fourier transform infrared spectroscopy and compressive mechanical test. Scaffolds with interconnective pores in a range of 150–350 μm and porosity of 65–74%, as well as homogenous dispersion of the whiskers could be produced which indicates their potential to use in bone tissue engineering applications. The prepared scaffolds showed the compressive yield strength of 4.3−6.2 MPa and Young modulus of 28−38 MPa. In the view of mechanical and microstructural features, the composite of 25 wt% calcium phosphate phase was introduced as the optimal composite for bone tissue engineering.

5665149 Anti-corrosion pigment and use thereof : Gotzmann Karl; Dorn Karlheinz; Numl agerl Hans-Dieter; Guml obelbecker Sieghard Budenheim, Germany assigned to Chemische Fabrik Budenheim

Calcium phosphate whiskers have been suggested to be effective as the reinforcement in improving mechanical properties of composite biomaterials. Therefore, composite scaffolds of varying compositions were prepared by freeze drying of gelatin foams containing increasing amounts of calcium phosphate whiskers/fibrous spherulites, up to 50 wt%. The whiskers were attempted to synthesize in acidic solutions under thermal conditions using two different methods: aging of a highly crystalline beta-tricalcium phosphate powder in H2O2 solution, and the precipitation−hydrolysis method using aqueous solutions of calcium and phosphate ions in HNO3 solution and urea as an additive. The morphology and phase analysis of the whiskers were studied by scanning electron microscopy (SEM) and X-ray diffractometry (XRD), respectively. The results proved that the whiskers could not be obtained by first method at an appropriate period, but using the second method, a mixed plate-like and long whiskers, and fibrous spherulites could be formed. The XRD patterns revealed the biphasic mixture of octacalcium phosphate (OCP) and dicalcium phosphate anhydrate (DCPA). The composite scaffolds containing whiskers obtained by freeze drying were characterized by SEM, Fourier transform infrared spectroscopy and compressive mechanical test. Scaffolds with interconnective pores in a range of 150–350 μm and porosity of 65–74%, as well as homogenous dispersion of the whiskers could be produced which indicates their potential to use in bone tissue engineering applications. The prepared scaffolds showed the compressive yield strength of 4.3−6.2 MPa and Young modulus of 28−38 MPa. In the view of mechanical and microstructural features, the composite of 25 wt% calcium phosphate phase was introduced as the optimal composite for bone tissue engineering.

Transarterial oily chemoembolization for the treatment of hepatocellular carcinoma: A multivariate analysis of prognostic factors

A total of 84 patients with hepatocellular carcinoma and cirrhosis were analyzed retrospectively to investigate prognostic factors. All patients received transarterial oily chemoembolization as the only anticancer therapy. The follow-up range was 1 to 39 mo (median, 9.5 mo). The overall actuarial survival rates at 12, 24 and 30 mo were 62%, 31% and 24%, respectively. According to univariate analysis, variables significantly associated with survival were age, Child-Pugh grade, total serum bilirubin, Okuda stage, tumor size, degree of labeling of the tumor with Lipiodol, gelatin foam use, changes with treatment in tumor size and changes with treatment in alpha-fetoprotein concentration. Two multivariate analyses were performed. When pretreatment and treatment variables were considered, parameters with independent prognostic value were age, Child-Pugh grade, total serum bilirubin, tumor size and degree of Lipiodol labeling of the tumor. When follow-up variables were also considered, we (a) confirmed the prognostic significance of all these parameters (age, Child-Pugh grade, total serum bilirubin, tumor size) and (b) found the independent prognostic value of the change in tumor size (or change in alpha-fetoprotein concentration). Both models yielded different risk coefficients for each class of each variable. Two simple prognostic indexes, based on these coefficients, are proposed: an "initial" index (including pretreatment and treatment variables) and a "follow-up" index (also including follow-up variables). According to the two indexes, the patients were classified into three groups with different prognoses: good (93% and 100% actuarial survival at 1 yr for the initial and follow-up indexes, respectively), intermediate (65% and 53%, respectively) and poor (27% for both indexes).

Hepatic Arterial Chemoembolization for Metastatic Endocrine Tumors

In patients with hepatic metastases from endocrine tumors, the safety and effectiveness of chemoembolization with ethiodized oil was determined and compared with those of embolization with particulate matter alone. Twenty patients with hepatic islet cell or carcinoid tumor metastases were treated with selective hepatic artery injection of doxorubicin and iopamidol emulsified in ethiodized oil, followed by gelatin foam powder embolization. In 16 patients with hormonally active tumors, hormone secretion decreased 90% (range, 69%-98%) in 10 days, with relief of symptoms in all patients. Average tumor size decrease was 84%; average hospitalization was 8 days. Seventeen patients are alive 6-27 months after embolization, and all are asymptomatic. Three patients died within 1 year after embolization of progressive disease outside the liver. Chemoembolization with doxorubicin emulsified in ethiodized oil and iopamidol is effective in the treatment of hepatic metastases from endocrine tumors. This technique appears to result in less morbidity than particulate embolization alone.

The effect of gas bubbles on the production of ultrasound hyperthermia at 0.75 MHz: a phantom study.

Transparent phantoms, made of bovine hide gelatine, have been constructed in order to study the consequences of the occurrence of cavitation in tissues. Gas pockets of about resonant size, physically introduced into the gel, lead to a mean temperature rise of 41 +/- 15 degrees C in 1 min, when the gel of concentration 11.4% (w/v) is sonicated in the continuous-wave (cw) mode at 1 W cm-2 (spatial average) and 0.75 MHz. Nyborg (1965) has shown that gas bubbles in a sound field can act as acoustic amplifiers and the observations reported here may be connected with this feature. A layer of gelatine foam was also used to introduce gas into the gel and in this case the temperature rise was about 12 +/- 5 degrees C under similar conditions. Without gaseous inclusions, the mean temperature rise in gel in 1 min was 2.3 +/- 0.2 degree C. At a gel/air interface, the rise per unit intensity per minute was 4.4 degrees C. It is concluded that in clinical situations, cavitation (or degassing due to supersaturation), when it does occur, is likely to be an undesirable consequence of ultrasound treatment. This finding, of large temperature rises in proximity to gas bubbles, is in broad agreement with the report by Hynynen (1991) of an excess temperature elevation of 60 degrees C in dogs' muscle in vivo during a 1 s pulse at 250 W cm-2 and 0.56 MHz. Other studies, by ter Haar and Daniels (1981) and Daniels and ter Haar (1986), of sonicated animal tissues in vivo, have found thresholds for bubble inception but no consequent temperature rise greater than 0.3 degrees C was observed.

Pituitary adenomas: findings of postoperative MR imaging.

Preoperative and postoperative magnetic resonance (MR) images obtained in 25 patients with pituitary macroadenomas (1.1-5.2 cm in diameter) were evaluated to determine normal (physiologic) and abnormal findings after transsphenoidal or subfrontal surgery. With a 1.5-T unit, T1-weighted sagittal and coronal images were obtained before and after administration of gadopentetate dimeglumine. The physiologic changes after surgery included resorption of packing material and sphenoid sinus opacifications, reexpansion of the pituitary gland, and lowering of the optic chiasm. Implanted gelatin foam appeared as an endosellar, circularly enhancing mass that was seen on follow-up studies to have decreased in size. Muscle-and-fat implants appeared as areas of high signal intensity. In 14 patients, residual tumors were found in the suprasellar (n = 4), retrosellar (n = 3), parasellar (n = 8), and/or endosellar (n = 3) space. Residual tumors were differentiated from implant materials by means of location, characteristic signal intensity, and enhancing pattern, which were identical to those of the corresponding preoperative adenoma in 13 cases (93%). Preoperative studies and clinical information are helpful in the evaluation of postoperative MR imaging examinations.

The effects of mechanical stretching on fetal rat lung cell prostacyclin production

A model system was used to determine the effect of stretch on prostacyclin (PGI) production by organotypic fetal rat lung cultures grown on gelatin foam in vitro, measured by RIA of 6-keto-PGF1 α (6KF) in the culture medium. The stretching apparatus was programmable for stretch of varying frequency and duration. The effective stimuli for PGI production were: continuous pulsatile stretch> intermittent pulsatile stretch> permanent stretch (p<0.05). The rate of PGI production was greatest in the first 15min of pulsatile stretch and was associated with a 70% increase in cAMP production (p < 0.05). When the effect of magnitude of stretch was compared (15% vs 28% extension), there was a significant increase with a maximum in the 28% stretch group double that of the 15% stretch group (p<0.01). PGI production in response to pulsatile stretching was inhibited by indomethacin but not by pretreatment with cortisol. These results suggest that the production of PGI by lung cells may be significantly affected by the frequency and magnitude of pulsatile stretching.

Analyses of T-cell differentiation from hemopoietic stem cells in the G0 phase by an in vitro method.

Using differential radiation sensitivity of components of mouse embryonal thymus, an in vitro method for studying T-cell differentiation from hemopoietic stem cells (HSCs) in the G0 phase was established. Intrathymic T-cell precursors present in embryonal thymus were found to be quite radioresistant (up to 20 Gy), and consequently 25-Gy-irradiated embryonal thymic lobes were used. Thymic lobes (25-Gy irradiated) taken from mouse fetuses (gestation day 15) were placed in Millipore-HA culture plates supported on squares of gelatin foam sponge in 24-well culture plates in which neonatal thymus stromal cells were cultured. HSCs (10(5) cells per well) in the G0 phase were added to these thymic lobes and cocultured at 37 degrees C in a 5% CO2/95% air incubator. Half the culture medium was changed every week. After 3 weeks, a large number of colonies had formed. Immunohistochemical studies and fluorescence-activated cell sorter analyses revealed that the colonizing cells regularly develop and exhibit surface markers characteristic of T cells (Thy-1, IL-2R, L3T4, Lyt-2, etc.). In situ hybridization analyses revealed that mRNA expression for T-cell receptor (TCR) beta chains occurred within colonizing cells. Using a monoclonal antibody (F23.1), expression of TCR beta-chain variable domain (V beta 8) on the surface of these developing T cells was demonstrated. These cells responded to interleukin 2 and/or anti-CD3 monoclonal antibody, indicating functional T cells. This method will be useful in studying T-cell differentiation pathways from pluripotent HSCs and in clarifying the mechanisms involved in negative and positive selection of T cells within the thymus.

Arteriovenous fistulas complicating biopsy of renal allografts: treatment of bleeding with superselective embolization.

The use of superselective embolization was assessed as a treatment for bleeding from postbiopsy arteriovenous fistulas (AVFs) in renal transplants. AVFs commonly occur after biopsy procedures in renal transplants, but severe bleeding is rare. Transcatheter embolization can be used to control bleeding, but unless it is sufficiently selective, the procedure results in loss of significant amounts of renal parenchyma. During a 4-year period, embolization procedures were attempted in seven patients 30-65 years old. All had AVFs shown on arteriography. Five patients underwent embolization; occlusion occurred only in the branch supplying the AVF. In one patient with three large AVFs, two were found to have occluded the day after embolization was attempted. In another, an AVF occluded when superselective catheter position was achieved but before embolization. Catheter manipulation in these cases may have precipitated occlusion. In five cases, coaxial embolization techniques were used. Embolization materials consisted of coils in three cases: 0.038 in. (0.97 mm) in one case, 0.025 in. (0.64 mm) in one case, 0.018 in. (0.46 mm) in one case; 0.038 in. (0.97 mm) coils and gelatin foam particles in one case; and localized contrast extravasation in one case. Serum creatinine level was measured before and after embolization in all patients, and radionuclide studies were undertaken in three cases. In all patients, bleeding was effectively controlled. None of the patients showed an increase in serum creatinine level after embolization, and in four, significant improvement was seen. Nuclear medicine studies showed no loss of renal function and a dramatic improvement in one patient. No complications due to the procedure were seen. Our experience suggests that superselective embolization with coaxial catheter techniques is an effective method of treating bleeding from postbiopsy AVFs in renal transplants with minimal loss of renal parenchyma.