Use of endovascular stents for the treatment of abdominal aortic aneurysm

The conventional open surgical repair of abdominal aortic aneurysms is a well-established and durable procedure. However, as with all other major abdominal surgical operations, there are associated morbidities. Both mortality and morbidity increase significantly with advanced patient age and associated comorbid conditions. Endovascular aortic stent-grafts offer a significantly less invasive alternative to conventional open-surgical repair. Patients previously considered unsuitable for open repair can often receive treatment for aneurysms with endovascular techniques. The US Food and Drug Administration has recently approved two endovascular stent-graft devices for use within the United States.

Proliferation and differentiation of fetal liver epithelial progenitor cells after transplantation into adult rat liver

To identify cells that have the ability to proliferate and differentiate into all epithelial components of the liver lobule, we isolated fetal liver epithelial cells (FLEC) from ED 14 Fischer (F) 344 rats and transplanted these cells in conjunction with two-thirds partial hepatectomy into the liver of normal and retrorsine (Rs) treated syngeneic dipeptidyl peptidase IV mutant (DPPIV(-)) F344 rats. Using dual label immunohistochemistry/in situ hybridization, three subpopulations of FLEC were identified: cells expressing both alpha-fetoprotein (AFP) and albumin, but not CK-19; cells expressing CK-19, but not AFP or albumin, and cells expressing AFP, albumin, and cytokeratins-19 (CK-19). Proliferation, differentiation, and expansion of transplanted FLEC differed significantly in the two models. In normal liver, 1 to 2 weeks after transplantation, mainly cells with a single phenotype, hepatocytic (expressing AFP and albumin) or bile ductular (expressing only CK-19), had proliferated. In Rs-treated rats, in which the proliferative capacity of endogenous hepatocytes is impaired, transplanted cells showed mainly a dual phenotype (expressing both AFP/albumin and CK-19). One month after transplantation, DPPIV(+) FLEC engrafted into the parenchyma exhibited an hepatocytic phenotype and generated new hepatic cord structures. FLEC, localized in the vicinity of bile ducts, exhibited a biliary epithelial phenotype and formed new bile duct structures or were incorporated into pre-existing bile ducts. In the absence of a proliferative stimulus, ED 14 FLEC did not proliferate or differentiate. Our results demonstrate that 14-day fetal liver contains lineage committed (unipotential) and uncommitted (bipotential) progenitor cells exerting different repopulating capacities, which are affected by the proliferative status of the recipient liver and the host site within the liver where the transplanted cells become engrafted. These findings have important implications in future studies directed toward liver repopulation and ex vivo gene therapy.

A comparison of EGF and MAb 528 labeled with 111In for imaging human breast cancer

Our objective was to compare 111In-labeled human epidermal growth factor (hEGF), a 53-amino acid peptide with anti-epidermal growth factor receptor (EGFR) monoclonal antibody (MAb) 528 (IgG2a) for imaging EGFR-positive breast cancer.

METHODS

hEGF and MAb 528 were derivatized with diethylenetriamine pentaacetic acid (DTPA) and labeled with 111In acetate. Receptor binding assays were conducted in vitro against MDA-MB-468 human breast cancer cells. Biodistribution and tumor imaging studies were conducted after intravenous injection of the radiopharmaceuticals in athymic mice bearing subcutaneous MCF-7, MDA-MB-231, or MDA-MB-468 human breast cancer xenografts or in severe combined immunodeficiency mice implanted with a breast cancer metastasis (JW-97 cells). MCF-7, MDA-MB-231, JW-97, and MDA-MB-468 cells expressed 1.5 x 10(4), 1.3 x 10(5), 2.7 x 10(5), and 1.3 x 106 EGFR/cell, respectively in vitro.

RESULTS

111In-DTPA-hEGF and 111In-DTPA-MAb 528 bound with high affinity to MDA-MB-468 cells (Ka of 7.5 x 10(8) and 1.2 x 10(8) L/mol, respectively). 111In-DTPA-hEGF was eliminated rapidly from the blood with < 0.2% injected dose/g (%ID/g) circulating at 72 h after injection, whereas 111In-DTPA-MAb 528 was cleared more slowly (3%ID/g in the blood at 72 h). Maximum localization of 111In-DTPA-hEGF in MDA-MB-468 tumors (2.2 %ID/g) was 10-fold lower than with 111In-DTPA-MAb 528 (21.6 %ID/g). There was high uptake in the liver and kidneys for both radiopharmaceuticals. Tumor-to-blood ratios were greater for 111In-labeled hEGF than for MAb 528 (12:1 versus 6:1), but all other tumor-to-normal tissue ratios were higher for MAb 528. MDA-MB-468 and JW-97 tumors were imaged successfully with both radiopharmaceuticals, but tumors were more easily visualized using 111In-labeled MAb 528. There was no direct quantitative relationship between EGFR expression on breast cancer cell lines in vitro, and tumor uptake of the radiopharmaceuticals in vivo, but control studies showed that tumor uptake was receptor mediated.

CONCLUSION

Our results suggest that the tumor uptake in vivo of receptor-binding radiopharmaceuticals is controlled to a greater extent by their elimination rate from the blood than by the level of receptor expression on the cancer cells. Radiolabeled anti-EGFR MAbs would be more effective for tumor imaging in cancer patients than peptide-based radiopharmaceuticals such as hEGF, because they exhibit higher tumor uptake at only moderately lower tumor-to-blood ratios.

111In-labeled EGF is selectively radiotoxic to human breast cancer cells overexpressing EGFR

Our objective was to determine whether the internalization and nuclear translocation of human epidermal growth factor (hEGF) after binding to its cell surface receptor (EGFR) could be exploited to deliver the Auger electron emitter 111In into EGFR-positive breast cancer cells for targeted radiotherapy.

METHODS

hEGF was derivatized with diethylenetriamine pentaacetic acid (DTPA) and radiolabeled with 111In-acetate. The internalization of 111In-DTPA-hEGF by MDA-MB-468 breast cancer cells (1.3x10(6) EGFRs/cell) was determined by displacement of surface-bound radioactivity by an acid wash. The radioactivity in the cell nucleus and chromatin, isolated by differential centrifugation, was measured. The effect on the growth rate of MDA-MB-468 or MCF-7 (1.5x10(4) EGFRs/cell) cells was determined after treatment in vitro with 111In-DTPA-hEGF, unlabeled DTPA-hEGF, or 111In-DTPA. The surviving fraction of MDA-MB-468 or MCF-7 cells treated in vitro with 111In-DTPA-hEGF was determined in a clonogenic assay. The radiotoxicity in vivo against normal hepatocytes or renal tubular cells was evaluated by measuring alanine aminotransferase (ALT) or creatinine levels in mice administered high amounts of 111In-DTPA-hEGF (equivalent to human doses up to 14,208 MBq) and by light and electron microscopy of the tissues.

RESULTS

Approximately 70% of 111In-DTPA-hEGF was internalized by MDA-MB-468 cells within 15 min at 37 degrees C and up to 15% was translocated to the nucleus within 24 h. Chromatin contained 10% of internalized radioactivity. The growth rate of MDA-MB-468 cells was decreased 3-fold by treatment with 111In-DTPA-hEGF (45-60 mBq/cell). Treatment with unlabeled DTPA-hEGF caused a 1.5-fold decrease in growth rate, whereas treatment with 111In-DTPA had no effect. Targeting of MDA-MB-468 cells with up to 130 mBq/cell of 111In-DTPA-hEGF resulted in a 2-logarithm decrease in their surviving fraction. No decrease in the growth rate or surviving fraction of MCF-7 cells was evident. There was no evidence of hepatotoxicity or renal toxicity in mice administered high amounts of 111In-DTPA-hEGF. Radiation dosimetry estimates suggest that the radiation dose to an MDA-MB-468 cell targeted with 111In-DTPA-hEGF could be as high as 25 Gy with up to 19 Gy delivered to the cell nucleus.

CONCLUSION

111In-DTPA-hEGF is a promising novel radiopharmaceutical for targeted Auger electron radiotherapy of advanced, hormone-resistant breast cancer.

Primary Gianturco stent placement for inferior vena cava abnormalities following liver transplantation

PURPOSE

To determine the efficacy of primary Gianturco stent placement for patients with inferior vena caval (IVC) abnormalities following liver transplantation.

MATERIALS AND METHODS

From August 1996 through March 1999, nine adult patients developed significant IVC abnormalities following liver transplantation. Patients were referred for vena cavography on the basis of abnormal clinical findings, laboratory values, liver biopsy results, Doppler findings, or a combination. Those patients demonstrating a significant caval or hepatic venous gradient were treated with primary Gianturco stent placement. Patients were followed clinically (nine patients), with duplex ultrasound (nine patients), vena cavography (four patients), and biopsy (seven patients).

RESULTS

Original pressure gradients ranged from 3 to 14 mm Hg, with a mean of 9 mm Hg. Gradients were reduced to 3 mm Hg or less in all nine patients; presenting signs and symptoms either resolved or improved in eight of nine patients. The ninth patient required repeated transplantation 2 days later. A second patient died 433 days after stent placement of recurrent hepatitis C. Another initially improved following caval stent placement, but underwent repeated transplantation 7 days later due to hepatic necrosis from hepatic arterial thrombosis. Follow-up for the remaining six patients has averaged 491 days, with no clinical, venographic, or ultrasound evidence for recurrent caval stenosis.

CONCLUSIONS

Intermediate term results suggest that primary Gianturco stent placement for IVC stenosis, compression, or torsion resulting after liver transplantation is safe and effective.

Human serum induces apoptosis of xenogenic cardiomyocytes in vivo and in vitro

Discordant xenotransplantation is complicated by delayed xenograft rejection (DXR). Previous studies have demonstrated that anti-apoptotic genes are protective against DXR. This study examines the hypothesis that apoptosis plays a role in human anti-xenograft responses. C57BL/6 mice and NOD SCID mice were given a single intravenous injection of either a lethal dose (LD, survival < 30 min) or a sublethal dose (SLD) of human serum, and isolated pig and mouse rod-shaped cardiomyocytes were exposed to human serum in vitro. In situ detection of apoptotic cells in mouse hearts was assessed using a terminal deoxynucleotidyl transferase-mediated dUTP nicked-end labeling assay. Mice transfused with human serum had approximately a 10-fold increased percentage of apoptotic cells after SLD 18 h post-injection compared with animals given saline, and a fourfold increase over LD. Administration of cobra venom factor (CVF) decomplemented SLD 18 h did not significantly (P > 0.05) alter the percentage apoptosis. The addition of 20 mM Gal-alpha-1,3-Gal to SLD 18 h significantly (P < 0.05) reduced percentage apoptosis to levels comparable to saline treated control animals. In vitro using mouse and pig cardiomyocytes demonstrated parallel results as in vivo experiments. Human serum induces apoptosis of cardiomyocytes in immunocompetent and immunoincompetent mice in vivo, as well as mouse and pig cardiomyocytes in vitro. Further, this apoptotic response can be inhibited by the addition of Gal-alpha-1,3-Gal without affecting the capacity of the serum to cause HAR. These results demonstrate that a putative human serum factor induces a delayed apoptotic injury of xenograft tissues, and supports the hypothesis that apoptosis may be an important mediator of DXR.

Resource requirements for interventional radiologic management of long-term ambulatory hemodialysis patients

OBJECTIVE

The purpose of this study was to determine how many and what type of procedures a vascular and interventional radiology service should provide for patients at ambulatory-patient dialysis centers and to determine the necessary resource requirements. These data may provide a realistic starting point for those engaged in the planning and provision of contractual services to dialysis centers.

MATERIALS AND METHODS

Patient records at three dialysis centers for a recent 3-year period were examined, and demographic and clinical data were recorded. Records were cross-correlated with records from the vascular and interventional radiology service that had contractually provided all dialysis-related procedures. These data generated a monthly procedure volume and case mix per 100 dialysis patients. Facility usage times for 121 dialysis-related procedures were obtained prospectively and used to calculate the expected resources needed to service the dialysis patients.

RESULTS

The three centers provided 5795 hemodialysis-months to 386 patients. Of the 386 patients over the 36-month period, 101 died and 92 transferred from the centers. Three hundred and sixteen patients required 1580 interventional procedures. Monthly procedure volume per 100 dialysis patients averaged 27.1 procedures. Observed procedure times were used to calculate expected room-time hours required to service the monthly procedural volume and case mix per 100 dialysis patients.

CONCLUSION

On average, 500 ambulatory dialysis patients will require the full-time use of an interventional suite and the services of a full-time technologist, nurse, and physician to provide necessary dialysis-related procedures. If resources cannot accommodate this volume, the quality and timeliness of care for these patients is jeopardized.

Hepatitis C prevalence and risk factors in the northern Alberta dialysis population

Hepatitis C virus (HCV) is an emerging global public health issue with particular relevance in multiply transfused renal dialysis patients. This cross-sectional study evaluated the prevalence and risk factors for HCV infection among renal dialysis patients in northern Alberta, Canada. Ninety-two percent of eligible patients (n = 336) provided informed consent to participate. Participants were interviewed to gather risk factor information and, using multiple logistic regression analysis with exact inference, a predictive model for HCV infection in this population was developed. The prevalence of HCV infection in the population was 6.5%, and all positive patients had at least one identifiable risk factor. The multivariate analysis showed that the risk of HCV infection was greater for those in the 18-55 years age category (odds ratio (OR) = 4.9, 95% confidence interval (CI) 1.2-27.9), patients who had been on dialysis > 5 years (OR = 3.7, 95% CI 1.2-12.0), and patients who had > or = 2 high risk life-style behaviors (OR = 5.0, 95% CI 1.5-16.7). Transfusion prior to 1990 was marginally associated with HCV status (OR = 4.0, 95% CI 0.96-16.3). This study documented previously unreported life-style risk factors for HCV infection in patients with renal failure, confirmed the expected decline in transfusion-acquired HCV infection in this population, and provided evidence against nosocomial transmission of HCV.

Substance P fragments and striatal endogenous dopamine outflow: interaction with substance P

Accumulating evidence shows that N- and C-terminal substance P fragments have significant biological activity. Substance P(1-9) and substance P(6-11) have been reported to be major substance P metabolites in rat striatum. We investigated the effects of these fragments on endogenous dopamine outflow in rat striatal slices. Substance P-(1-9) and substance P-(6-11) induced a significant increase in dopamine outflow at 0.1 and 1 nM. The effects of substance P-(6-11) (1 nM) were reversed by the tachykinin NK1 antagonist WIN 51,708 (17beta-hydroxy-17alpha-ethynyl-5alpha-androstano[3,2- b]pyrimido[1,2-a]benzimidazole) (2.5 nM), whereas the effects of substance P-(1-9) were not modified by the antagonist. Substance P-(1-9) and substance P-(6-11) (1 nM) did not increase the dopamine overflow induced by 25 mM KCI. The effects of the two fragments were reversed by the muscarinic antagonist atropine (1 microM) but not by nicotinic antagonists dihydro-beta-erythroidine (0.5 microM) and pempidine (10 microM). The co-incubation of tissue with substance P and each fragment in a 1/1 or 10/1 ratio of substance P to metabolite revealed a negative interaction between parent and fragments. A similar pattern was observed when substance P was co-administered with the active fragments substance P(1-4), substance P(1-7), substance P(5-11) and substance P(8-11). The data show that substance P-(1-9) and substance P-(6-11) have modulatory effects similar to substance P. However, the presence of active substance P metabolites does not appear to amplify the signal mediated by the parent peptide.

The role of T cells in polyethylene particulate induced inflammation

OBJECTIVE

To investigate the role of T lymphocytes in ultra-high molecular weight polyethylene (UHMWPE) induced inflammation in joint arthroplasty.

METHOD

We address the role of T cells in wear induced inflammation by injecting the knee joints of both immune competent rats and mice and severe combined immunodeficient (SCID) mice with UHMWPE. Histological and immunohistochemical analysis of the synovial tissues was compared. Interaction between human T cells and UHMWPE particles was examined in vitro using T cell activation assays.

RESULTS

Histological and immunohistochemical analysis of the knees of the immune competent animals showed significant UHMWPE induced inflammation. In contrast, the tissue in the SCID mice knee joints showed very little inflammatory response to UHMWPE despite phagocytosis of the particulate. Since the SCID mice have no functional T or B lymphocytes, it is highly likely that the lack of inflammation in knee joints may be due to the absence of mouse T cells, as the infiltration of T cells into the joint tissue may enhance the inflammatory response to UHMWPE particles. T cell activation assays showed that T cells were not directly activated by UHMWPE particles and the nature of the interaction was not revealed from these experiments.

CONCLUSIONS

Although T cells are not directly involved in UHMWPE particle induced inflammation, as shown by the T cell activation assays, the histological data from the mice studies clearly show differences in the amplitude of inflammation from animals with and without functional T cells. Our studies suggest that the T cells may enhance the inflammatory response due to a bystander effect. Since the macrophages upon ingestion of UHMWPE particles release several cytokines including tumor necrosis factor-alpha, interleukin 1, and IL-6, it is possible that T cells in the vicinity of these macrophages may become attracted to the knee joint and activated due to cytokine release.

Effect of high hydrostatic pressure on Pacific whiting surimi

The effects of high hydrostatic pressure (HHP) on gel strength, microbial numbers, proteolytic activity, color and pH of Pacific whiting surimi gels were investigated. Strong gels without the use of protease inhibitors were formed with HHP treatments from 1-4 kBars. Gel strength was not affected by holding time. Total plate counts showed that destruction of vegetative cells was accomplished with 4 kBar. Proteolytic activity was diminished but not eliminated with pressure treatments. The color of the surimi gels treated were translucent while the heat-treated gels were opaque. The pH was increased slightly with HHP treatment. HHP was an effective processing method for making high quality surimi gels from Pacific whiting.

Macrophage phagocytosis of polyethylene particulate in vitro

In this study, an in vitro model has been developed to examine the interactions of macrophages with ultrahigh molecular-weight polyethylene (UHMWPE) and high-density polyethylene (HDPE) particles. Polyethylene particles are the major constituent of the material debris formed as a result of orthopedic implant wear. However, the study of polyethylene particle interactions with cells has been limited. UHMWPE (18-20 microns) and HDPE (4-10 microns) were suspended in soluble collagen type I and subsequently solidified on glass coverslips. The particle chemistry was characterized by Fourier transform infra-red spectroscopy (FT-IR) and X-ray photoelectron spectroscopy (XPS). Mouse cell line macrophages (IC-21) were established on the collagen-particle substrata and maintained for up to 24 h. The response of the cells to the particles was examined by light and transmission electron microscopy (LM and TEM), as well as by scanning electron microscopy (SEM), and compared to cells on control collagen surfaces without particles. Histological analysis of the samples revealed that the macrophages surrounded larger particles (18-20 microns) and the cells appeared to be attached to the surface of the particles, and the smaller particles (4-10 microns) had been phagocytosed within 2 h. Inflammatory cytokines (TNF-alpha, IL-1 alpha, IL-1 beta, and IL-6), lysosomal enzymes (beta-galactosidase and hexosaminidase), and prostaglandin E2 were released into the medium, and IL-1 alpha, IL-1 beta, PGE2, beta-galactosidase, and hexosaminidase levels were significantly increased over collagen control values. The results demonstrate active phagochemotaxis by macrophages for wear particulates and validate this model as a means of studying the specific in vitro interactions of polyethylene with cells.

Physiologic human T-cell responses to OKT3 in the human peripheral blood lymphocyte-severe combined immunodeficiency mouse model

BACKGROUND

Our goal was to study physiologic responses of human T lymphocytes to OKT3 in the human peripheral blood lymphocyte-severe combined immunodeficiency (hu-PBL-SCID) mouse model.

METHODS

SCID mice were pretreated with anti-asialo-GM1 (alpha-ASGM1) and radiation, then engrafted with human peripheral blood lymphocytes (PBLs). Seven to 14 days after engraftment, when most human T cells in the spleen of these mice are CD3+/CD4+ and CD3+/CD8+, mice were treated with OKT3 or control antibody. Mice were killed for histopathologic examination, for flow cytometric assessment of the engrafted human lymphocytes, and for analysis of human tumor necrosis factor-alpha serum levels.

RESULTS

Intravenous injection of 5 microg of OKT3 resulted in early antigenic modulation of engrafted human T lymphocytes, with the emergence of CD3-/CD4+ and CD3-/CD8+ cells in the spleen of hu-PBL-SCID mice. There was an increase in the serum concentration of human tumor necrosis factor-alpha within 4 hr after OKT3 injection, suggesting early T-cell activation. Antigenic modulation and activation of the human lymphocytes in the spleen was followed by their depletion within 24 hr. This human T-cell response to OKT3 in hu-PBL-SCID mice is analogous to the response in humans treated with OKT3 and in BALB/c mice injected with an anti-murine CD3 monoclonal antibody. Graft-versus-host disease in the mice was abrogated by OKT3 treatment, and OKT3-treated mice lived longer than controls. Histopathologic studies showed clearance of lymphocytic infiltration in the liver and lungs of OKT3-treated mice.

CONCLUSIONS

These findings provide further evidence of functional human immune T cells in the hu-PBL-SCID mouse. This model may have useful applications in the study of transplantation immunology.

Interventional procedures in the AIDS patient

The detection and characterization of radiologic abnormalities in the AIDS population are frequently adequate to suggest which opportunistic infection or malignancy is affecting the patient. In addition, tissue sampling for more specific diagnosis and therapeutic interventions is often guided by the results of the imaging studies. This article discusses the various diagnostic and therapeutic options that may be applicable to the AIDS patient.

Murine antibody responses to the verotoxin 1 B subunit: demonstration of major histocompatibility complex dependence and an immunodominant epitope involving phenylalanine 30

Structurally conserved verotoxin 1 (VT1) mutant derivatives, showing reduced receptor binding and cytotoxicity, may serve as natural toxoids to protect against VT-mediated disease. In this study, the antibody responses to the wild-type VT1 B subunit, a B-subunit mutant (Phe30Ala B), and the corresponding holotoxin (Phe30Ala HT) were examined in three inbred mouse strains. BALB/c (H-2d) and CBA (H-2k) mice produced strong antibody responses to both wild-type and mutant B subunits. VT1 B-raised sera reacted more strongly with VT1 B than with Phe30Ala B in enzyme-linked immunosorbent assays, while Phe30Ala B-raised sera reacted equally with VT1 B and Phe30Ala B. C57BL/6 (H-2b) and congenic BALB/c (BALB x B [H-2b]) mice produced no detectable antibody response to either VT1 B or Phe30Ala B. However, an anti-VT1 B antibody response was detected in H-2b mice immunized with biologically active Phe30Ala HT. Based on these observations, we conclude that the VT1 B subunit possesses a B-cell immunodominant epitope formed partly by phenylalanine 30 and that the B-subunit antibody response is dependent on the H-2 haplotype of the mouse strain. Our results also support a potential role for the A subunit in providing the T-cell help necessary to overcome a deficient B-subunit antibody response in H-2b mice.

Endoscopic sclerotherapy compared with percutaneous transjugular intrahepatic portosystemic shunt after initial sclerotherapy in patients with acute variceal hemorrhage. A randomized, controlled trial

BACKGROUND

Hemorrhage from esophageal varices remains a substantial management problem. Endoscopic sclerotherapy was preferred for more than a decade, but fluoroscopically placed intrahepatic portosystemic stents have recently been used with increasing frequency.

OBJECTIVE

To compare sclerotherapy with transjugular intrahepatic portosystemic shunt (TIPS) in patients with bleeding from esophageal varices.

DESIGN

Randomized, controlled clinical trial.

SETTING

Three teaching hospitals.

PATIENTS

49 adults hospitalized with acute variceal hemorrhage from November 1991 to December 1995: 25 assigned to sclerotherapy and 24 assigned to TIPS.

INTERVENTION

Patients assigned to repeated sclerotherapy had the procedure weekly. In those assigned to TIPS, an expandable mesh stent was fluoroscopically placed between an intrahepatic portal vein and an adjacent hepatic vein.

MEASUREMENTS

Pretreatment measures included demographic and laboratory data. Postrandomization data included index hospitalization survival, duration of follow-up, successful obliteration of varices, rebleeding from varices, number of variceal rebleeding events, total days of hospitalization for variceal bleeding, blood transfusion requirements after randomization, prevalence of encephalopathy, and total health care costs.

RESULTS

Mean follow-up (+/-SE) was 567 +/- 104 days in the sclerotherapy group and 575 +/- 109 days in the TIPS group. Varices were obliterated more reliably by TIPS than by sclerotherapy (P < 0.001). Patients having TIPS were significantly less likely to rebleed from esophageal varices than patients receiving sclerotherapy (3 of 24 compared with 12 of 25; P = 0.012). No other follow-up measures differed significantly between groups. A trend toward improved survival, which was not statistically significant, was noted in the TIPS group (hazard ratio, 0.53 [95% CI, 0.18 to 1.5]).

CONCLUSIONS

In obliterating varices and reducing rebleeding events from esophageal varies, TIPS was more effective than sclerotherapy. However, TIPS did not decrease morbidity after randomization or improve health care costs. It seemed to produce better survival, but the increase in survival was not statistically significant.

Oral delivery of antibodies. Future pharmacokinetic trends

Antibodies have been investigated as specific targeting agents for cancer diagnosis and therapy, to inactivate toxic substances including drugs and also as passive immunotherapy for neoplastic or infectious diseases. In most cases the antibodies were administered systemically by the intravenous route. More recently, however, there has been increasing interest in the oral administration of antibodies for localised treatment of infections or other conditions in the gastrointestinal tract. The normal physiological handling of ingested proteins is degradation by proteases in the stomach and intestine into small peptides or amino acids which are subsequently absorbed. Proteolytic enzymes involved in the degradation of orally administered immunoglobulins include pepsin, trypsin, chymotrypsin, carboxypeptidase and elastase. These enzymes initially degrade the antibodies to F(ab')2. Fab and Fc fragments. The F(ab')2 and Fab fragments, however, retain some of their neutralising activity locally in the gastrointestinal tract. Various approaches are possible to increase the stability of orally administered antibodies against proteolysis, including formulation in liposomes, coating with polymers and genetic engineering of resistant forms. The clinical application of orally administered antibodies includes the treatment and prevention of gastrointestinal infections caused by enteric pathogens such as rotavirus, Escherichia coli or Vibrio cholerae in susceptible individuals including those with immunodeficiency diseases and patients with bone marrow transplants. There is also a suggestion that such agents may be useful in preventing chemotherapy-induced gastrointestinal mucositis. Future opportunities for research include the design of oral dosage forms of antibodies which resist proteolysis and can deliver a greater fraction of immunoreactive antibody locally in the gastrointestinal tract for the treatment of infections or perhaps even to allow the absorption of antibodies for the treatment or prevention of systemic conditions.

Human osteoblasts survive and deposit new bone when human bone is implanted in SCID mouse

We describe the first successful engraftment of viable human bone that maintains human osteoblast function and deposits new bone after implantation into pretreated SCID (Hu-bone-SCID) mice. The pretreatment consists of radiation before bone implantation and subsequent administration of antiasialo GM1 antisera every 7 days to deplete mouse macrophage and natural killer (NK) cell activity. The implanted bone samples were analyzed at various times up to 8 weeks. Comparison of pre- and post-implanted human specimens in untreated and pretreated SCID mice showed that while specimens underwent resorption and necrosis in untreated SCID mice, the structure of the implanted bone was preserved in the pretreated Hu-bone-SCID mice. In addition, histochemistry and histomorphometric analysis combined with tetracycline labeling showed that new bone formed in in the implants in the pretreated SCID mice. That the new bone resulted from the activity of the implanted human bone cells rather than from induction of differentiation of host mesenchymal cells into mouse osteoblasts was shown by immunohistochemical analysis with two different monoclonal antibodies (mAb), one mAb recognizing human HLA class II antigens and one recognizing human osteoblasts and osteocytes. Donor variability was observed in the implanted bone; however, bone from the same donor maintained its characteristics in all Hu-bone-SCID mice, and striking quantitative differences were seen in bone implanted from young (4-9 years) vs. adult (67-82 years) individuals. This model will be useful to investigate and compare endogenous osteoblast activity in different bone samples without the variables of isolating cells and examining them in vitro.

Problems of delivery of monoclonal antibodies. Pharmaceutical and pharmacokinetic solutions

Monoclonal antibodies to tumour-associated antigens have great theoretical potential for the specific targeting of radioactivity and anti-neoplastic agents to tumours. The clinical success of monoclonal antibody-based cancer diagnosis and therapy depends, however, on solving a number of pharmacokinetic delivery problems. These include: (i) slow elimination of monoclonal antibodies from the blood and poor vascular permeability; (ii) low and heterogeneous tumour uptake; (iii) cross-reactivity with normal tissues; (iv) metabolism of monoclonal antibody conjugates; and (v) immunogenicity of murine forms in humans. As a result of extensive pharmaceutical and pharmacokinetic research conducted over the past 10 to 15 years, several potential solutions to these delivery problems have been identified. Blood concentrations of antibody conjugates may be reduced through regional administration, the use of antibody fragments, interventional strategies and various pre-targeting techniques. Tumour uptake may be increased through administration of higher doses, or the use of agents to increase tumour vascular permeability. Tumour retention of antibody conjugates may be improved by inhibition of metabolism, by using more stable linkage chemistry. Alternatively, normal tissue retention may be decreased through the use of metabolisable chemical linkages inserted between the antibody and conjugated moiety. Very small antigen-binding fragments and peptides that exhibit improved tumour penetration and more rapid elimination from the blood and normal tissues have been prepared by genetic engineering techniques. Chimeric (mouse/human) and human monoclonal antibodies have been developed to circumvent the problem of immunogenicity. Future research will continue to be focused on improvements in the design of monoclonal antibodies for tumour targeting, with the ultimate goal of finally uncovering the 'magic bullet' envisioned by Paul Ehrlich almost a century ago.

Human primary immune response in SCID mice engrafted with human peripheral blood lymphocytes

Severe combined immune deficient (SCID) mice were engrafted with human peripheral blood lymphocytes (Hu-PBLs) after treatment with anti-asialo GM-1 antiserum and radiation. This pretreatment facilitates high level of Hu-PBL engraftment in the SCID mice spleen. The next day, the Hu-PBL-SCID mice were immunized with either keyhole limpet hemocyanin (KLH), or carbohydrate Ag STn (AcNeu-alpha 2-alpha 6-Gal NAc-0) conjugated to KLH or protein of circumsporozoite malaria parasite (CSP), in a mixture of complete and incomplete Freund's adjuvant (1:10 v/v). The mice were bled 14 to 16 days after immunization, and the sera analyzed for STn-, KLH-, and CSP-specific human IgG and IgM Abs. The results showed that the immunized animals had a significantly higher titer of Ag-specific human IgG and IgM Abs compared to the control Hu-PBL-SCID mice. No significant Ab cross-reactions were detected between sera from KLH-, STn-, and CSP-vaccinated Hu-PBL-SCID mice. Depletion of either human CD4+ or CD8+ cells, in Hu-PBL-SCID mice, showed that CD4+ cells were essential for the primary immune response, but depletion of CD8+ cells had no influence on the titer of Ag-specific human IgG and IgM Abs.