Clinical Pathological Conditions Research Articles

HLA-G dimers in the prolongation of kidney allograft survival.

Human leukocyte antigen-G (HLA-G) contributes to acceptance of allografts in solid organ/tissue transplantation. Most studies have determined that soluble HLA-G isoforms are systematically detected in serum/plasma of transplanted patients with significantly fewer episodes of acute and/or chronic rejection of allogeneic tissue/organ. Current models of the interactions of HLA-G and its specific receptors explain it as functioning in a monomeric form. However, in recent years, new data has revealed the ability of HLA-G to form disulfide-linked dimeric complexes with high preferential binding and functional activities. Limited data are available on the role of soluble HLA-G dimers in clinical pathological conditions. We describe here the presence of soluble HLA-G dimers in kidney transplant patients. Our study showed that a high level of HLA-G dimers in plasma and increased expression of the membrane-bound form of HLA-G on monocytes are associated with prolongation of kidney allograft survival. We also determined that the presence of soluble HLA-G dimers links to the lower levels of proinflammatory cytokines, suggesting a potential role of HLA-G dimers in controlling the accompanying inflammatory state.

Broader Aspects of Nanopharmaceutical Safety: Need for an Integrated Approach

Broader Aspects of Nanopharmaceutical Safety: Need for an Integrated Approach Nanoparticulate drug carriers and multifunctional nanoparticles are beginning to provide a range of unique therapeutic and diagnostic opportunities. However, there is an increasing concern regarding nanoparticle safety for human use, but these are not often viewed within the context of clinical dosing, administration route, and pathological conditions in question. A complex array of interrelated physicochemical and biological factors control nanoparticle pharmacokinetics, site-specific targeting, therapeutic efficacy and safety, and these have been reviewed recently. From a clinical perspective, it is imperative to identify and translate realistic opportunities offered by understanding of pathophysiological processes to the design and engineering of efficient and safe nanopharmaceuticals. Such strategies will most likely enhance benefit-to-risk ratio, as opposed to empirical approaches that tend to find forced biomedical applications for a broad range of emerging nanomaterials, which eventually contributes to increased toxicity concerns.

Development and application of polymerase chain reaction test for detection of Conidiobolus lamprauges

Conidiobolomycosis is a granulomatous disease caused by the fungus Conidiobolus spp. in humans and animals. Traditional technique for diagnosis of the disease is isolation of the agent associated with the presence of typical clinical signs and pathological conditions. The aim of this study was to describe the development of a specific polymerase chain reaction (PCR) test for Conidiobolus lamprauges to detect the fungus in clinical samples. Samples from suspected animals were collected and submitted to isolation, histopathological analysis and amplification by PCR. DNA from tissues was subjected to PCR with fungi universal primers 18S rDNA gene, and specific primers were designed based on the same gene in C. lamprauges that generated products of about 540 bp and 222 bp respectively. The culture was positive in 26.6% of clinical samples. The PCR technique for C. lamprauges showed amplification of DNA from fresh tissues (80%) and paraffin sections (44.4%). In conclusion, the PCR technique described here demonstrated a high sensitivity and specificity for detection of fungal DNA in tissue samples, providing a tool for the rapid diagnosis of C. lamprauges.

ROS-Mediated Iron Overload Injures The Hematopoiesis Of Bone Marrow By Damaging Hematopoietic Stem/Progenitor Cells In Mice

A substantial portion of patients with inherited blood disorders such as beta thalassemia, or bone marrow failure syndromes such as aplastic anemia(AA), myelodysplastic syndromes(MDS) require frequent transfusions of red blood cells. Frequent blood transfusions may lead to the excess of plasma non-transferrin -bound iron(NTBI) and iron overload occurs, which will significantly injure bone marrow (BM) function as well as induce organ dysfunctions such as liver cirrhosis, diabetes and cardiac diseases. However, the exact mechanism behind this effect remains elusive and ideal treatment needs to be explored. In our preliminary studies, we have demonstrated free iron catalyzes oxidative damage to hematopoietic cells/ mesenchymal stem cells in vitro and suppresses hematopoiesis in iron overload patients (Zhao et al.,blood, 2010 abstract; Lu et al.,blood,2012 abstract; Lu et al., Eur J Haematol, 2013). Here we observed the hematopoiesis inhibitory effects of iron overload on the basis of estabalished iron overload mice model and preliminarily disscussed the mechanism.In this study, we first established an iron overload mice model by administering different doses(12.5mg/ml,25mg/ml,50mg/ml) iron dextran by intraperitoneal injection every three days for four weeks. To confirm the efficacy of the mice model, the BM, hepatic and splenic iron deposits were observed by morphological study and the labile iron pool level (LIP) of bone marrow mononuclear cells(BMMNCs) was detected using the calcein-AM fluorescent dye. It was found that iron deposits in BM cells of iron overload mice, liver and spleen were markedly increased and the BMMNCs LIP level was much higher than that of normal control mice. The above results showed that the iron-overloaded mice model has been established successfully.Next we observed whether iron overload (25mg/ml) could affect the hematopoiesis of BM. The colony-forming cell assay was performed by culturing BMMNCs in MethoCult M3434 methylcellulose medium to evaluate hematopoietic progenitor cells(HPCs) proliferation function. The competitive repopulation assay and single-cell colony cultures of sorted hematopoietic stem cells (HSCs,CD34-Lin- sca1+c-kit+cells,LSK+)were used to validate HSCs function.The counts of BMMNCs have no significant difference. However, It was found that hematopoietic colony-forming unit (CFU-E, BFU-E, CFU-GM and CFU-mix) was much lower than that of normal control(P<0.05)(Fig.1). Notely, the number of LSK+ cells (*103/femur) was decreased significantly in iron overload mouse (26.43±3.28) compared with normal control(40.12±5.21) and the single-cell colony formation(/60wells) was reduced significantly in iron overload mouse(28.54±3.33) compared with normal control(47.93±4.82) (P<0.05). The long-term and multilineage engraftment capability of the iron-overloaded HSCs was weaken after transplantation.We then explored the possible mechanism of this inhibitory effects. Our previous studies have shown that iron overload could elevated reactive oxygen species (ROS) levels of mesenchymal stem cells and HSCs in vitro. Similarly, the intracellular ROS levels were analyzed by a flow cytometer. It was found that ROS level in iron overload BM was increased by 3.32 folds in erythroid cells, 1.51 folds in granulocytes and 4.80 folds in LSK+ cells,respectively. And also, the expression of p53, p38MAPK and p16Ink4a mRNA remained significantly elevated, which indicated that ROS related signal pathway was involved in the deficient hematopoiesis of iron overload BM.In addition, we also observed the effects of iron overload on the mice with deficient hematopoiesis exposed to 4Gy total body irradiation(TBI), which was more similar to clinical pathological conditions such as AA or MDS. It was found that BM damage caused by iron overload was aggravated in pathological conditions (primary findings were not shown).In conclusion, our study confirmed that iron overload injures the hematopoiesis of BM by enhancing oxidative stress in mice, which would be helpful to further study on the mechanism and would provide an experimental basis to find new therapeutic targets for the treatment of iron overload in patients with hematopoietic dysfunction. [Display omitted] Disclosures:No relevant conflicts of interest to declare.

A Very Unusual Thyroid Tumor: A Nodule with Mature Fat Papillary Hyperplasia and Focal Atypia

Fat-containing lesions of the thyroid are rare, encompassing several clinical-pathological conditions such adenolipomas, thyrolipomatosis and lipomotous tissue in case of amyloidosis. Furthermore, cases of papillary thyroid carcinoma have been identified in association with thyrolipomatosis. We report a case of 51 years old man referred to surgery for a multinodular goiter, showing multiple cystic and hemorrhagic nodules of up to 3 cm. One of these lesions showed features of papillary hyperplasia with focal cytological atypia and mature fat. Here, we describe and discuss the histological and immunophenotypical features of this rare lesion.

Cell therapy of peripheral arterial disease: from experimental findings to clinical trials.

The age-adjusted prevalence of peripheral arterial disease in the US population was estimated to approach 12% in 1985, and as the population ages, the overall population having peripheral arterial disease is predicted to rise. The clinical consequences of occlusive peripheral arterial disease include intermittent claudication, that is, pain with walking, and critical limb ischemia (CLI), which includes pain at rest and loss of tissue integrity in the distal limbs, which may ultimately lead to amputation of a portion of the lower extremity. The risk factors for CLI are similar to those linked to coronary artery disease and include advanced age, smoking, diabetes mellitus, hyperlipidemia, and hypertension. The worldwide incidence of CLI was estimated to be 500 to 1000 cases per million people per year in 1991. The prognosis is poor for CLI subjects with advanced limb disease. One study of >400 such subjects in the United Kingdom found that 25% required amputation and 20% (including some subjects who had required amputation) died within 1 year. In the United States, ≈280 lower-limb amputations for ischemic disease are performed per million people each year. The first objective in treating CLI is to increase blood circulation to the affected limb. Theoretically, increased blood flow could be achieved by increasing the number of vessels that supply the ischemic tissue with blood. The use of pharmacological agents to induce new blood vessel growth for the treatment or prevention of pathological clinical conditions has been called therapeutic angiogenesis. Since the identification of the endothelial progenitor cell in 1997 by Asahara and Isner, the field of cell-based therapies for peripheral arterial disease has been in a state of continuous evolution. Here, we review the current state of that field.

Molecular mechanisms of endothelial to mesenchymal cell transition (EndoMT) in experimentally induced fibrotic diseases

Several recent studies have demonstrated that endothelial to mesenchymal transition (EndoMT), a newly recognized type of cellular transdifferentiation may be an important source of myofibroblasts during the development of experimentally induced pulmonary, cardiac and kidney fibrosis. EndoMT is a complex biological process induced by members of the transforming growth factor (TGF-β) family of regulatory polypeptides in which endothelial cells adopt a mesenchymal or myofibroblastic phenotype acquiring motile and contractile properties and initiating expression of mesenchymal cell products such as α smooth muscle actin (α-SMA) and type I collagen. Although these experimental studies provide compelling evidence for the participation of EndoMT in the development of experimentally-induced fibrotic processes the precise role of EndoMT in the pathogenesis of human fibrotic disorders requires confirmation and validation from studies of human clinical pathologic conditions. Such confirmation should lead to a change in the paradigm of the origin of profibrogenic myofibroblasts involved in human fibrotic diseases. Further understanding of the molecular mechanisms and the regulatory pathways involved in EndoMT may lead to the development of novel therapeutic approaches for the incurable and often devastating fibrotic disorders.

Synergistic effects of amyloid peptides and lead on human neuroblastoma cells

Aggregated amyloid peptides (AP), major components of senile plaques, have been considered to play a very important and crucial role in the development and neuro-pathogenesis of Alzheimer’s disease (AD). In the present in vitro, study the synergistic effects of Pb2+, a heavy metal, and AP on the human neuroblastoma SH-SY5Y cells were investigated. The cells treated with Pb2+ (0.01–10 μM) alone exhibited a significant decrease in viability and IC50 was 5 μM. A similar decrease in viability was also observed when the cells were exposed to AP, Aβ1–40 (20–120 μM) and Aβ25-35 (2.5–15 μM) for 48 hrs. The IC50 values were 60 μM and 7.5 μM for Aβ1–40 and Aβ25–35 respectively. To assess the synergistic effects the cells were exposed to IC50 of both AP and Pb2+, which resulted in further reduction of the viability. The study was extended to determine the lactate dehydrogenase (LDH) release to assess the cytotoxic effects, 8-isoprostane for extent of oxidative damage, COX 1 and 2 for inflammation related changes, p53 protein for DNA damage and protein kinases A and C for signal transduction. The data suggest that the toxic effects of AP were most potent in the presence of Pb2+, resulting in an aggravated clinical pathological condition. This could be attributed to the oxidative stress, inflammation neuronal apoptosis and an alteration in the activities of the signaling enzymes.

False-positive BNP results caused by human antimouse antibodies (HAMAs) interference: a case report

A 61-year-old man was seen for sustained high serum B-type natriuretic peptide (BNP) level prior to admission. During the past 3 months, the serum BNP of the patient were measured...

The function and structure of the cerebrospinal fluid outflow system.

This review traces the development of our understanding of the anatomy and physiological properties of the two systems responsible for the drainage of cerebrospinal fluid (CSF) into the systemic circulation. The roles of the cranial and spinal arachnoid villi (AV) and the lymphatic outflow systems are evaluated as to the dominance of one over the other in various species and degree of animal maturation. The functional capabilities of the total CSF drainage system are presented, with evidence that the duality of the system is supported by the changes in fluid outflow dynamics in human and sub-human primates in hydrocephalus. The review also reconciles the relative importance and alterations of each of the outflow systems in a variety of clinical pathological conditions.

The analysis of PIK3CA mutations in gastric carcinoma and metanalysis of literature suggest that exon-selectivity is a signature of cancer type.

BackgroundPIK3CA is one of the genes most frequently mutated in human cancers and it is a potential target for personalized therapy. The aim of this study was to assess the frequency and type of PIK3CA mutations in gastric carcinoma and compare them with their clinical pathological correlates.MethodsWe analysed 264 gastric cancers, including 39 with microsatellite instability (MSI), for mutations in the two PIK3CA hotspots in exons 9 and 20 by direct sequencing of DNA obtained from microdissected cancer cells.ResultsThe cases harbouring mutations were 42 (16%). All were heterozygous missense single base substitutions; the most common was H1047R (26/42; 62%) in exon 20 and the second was Q546K (4/42; 9.5%) in exon 9. All the mutated MSI cases (8/39) carried the H1047R mutation. No other association between PI3KCA mutations and their clinical pathological covariates was found. A metanalysis of the mutations occurring in the same regions presented in 27 publications showed that ratio between exon 20 and exon 9 prevalences was 0.6 (95% CI: 0.5 -0.8) for colon, 1.6 (95% CI: 1.1 -2.3) for breast, 2.7 (95% CI: 1.6 -4.9) for gastric and 4.1 (95% CI: 1.9 -10.3) for endometrial cancer.ConclusionsThe overall prevalence of PIK3CA mutations implies an important role for PIK3CA in gastric cancer. The lack of association with any clinical-pathological condition suggests that mutations in PIK3CA occur early in the development of cancer. The metanalysis showed that exon-selectivity is an important signature of cancer type reflecting different contexts in which tumours arise.

Trisomy 21- affected placentas highlight prerequisite factors for human trophoblast fusion and differentiation

Trophoblastic cell fusion is one essential step of the human trophoblast differentiation pathway and is a multifactorial and dynamic process finely regulated and still poorly known. Disturbances of syncytiotrophoblast formation are observed in numerous pathological clinical conditions such as preeclampsia, intrauterine growth retardation and trisomy 21. In this review, we summarize current knowledge of the different membrane proteins directly involved in trophoblastic cell fusion, which we identified by using the physiological model of primary culture of villous trophoblastic cells. Connexin 43 and gap junctional intercellular communication point to the role of molecular exchanges through connexin channels preceding membrane fusion. Zona occludens-1, which can interact with connexin 43, is also directly involved in trophoblast fusion. The recently identified fusogenic membrane retroviral envelop glycoproteins syncytin 1 (encoded by the HERV-W gene) and syncytin 2 (encoded by the FRD gene) and their receptors are major factors involved in human placental development . We describe the increasing number of factors promoting or inhibiting trophoblast fusion and differentiation and emphasize the role of human chorionic gonadotropin (hCG) and its receptor. Indeed, in trisomy 21 the dynamic process leading to membrane fusion is impaired due to an abnormal hCG signaling. This abnormal trophoblast fusion and differentiation in trisomy 21-affected placenta is reversible in vitro. Trisomy 21 trophoblastic cell culture may therefore be useful to identify the possible large number of prerequisite factors involved in trophoblast fusion, the limiting step of trophoblast differentiation.

Altered Chemokine Receptor Expression in Papillary Thyroid Cancer

Papillary thyroid cancer (PTC), the most prevalent type of differentiated thyroid carcinoma, displays a strikingly high frequency of lymph node metastasis (LNM). Recent data suggest that chemokines can play an important role in promoting tumor progression and metastatic migration of tumor cells. Here we have evaluated whether PTC tissues express a different pattern of chemokine receptors and if the expression of these receptors correlates with LNM. We assessed by immunohistochemistry and flow cytometry the expression of the chemokine receptors CCR3, CCR7, and CXCR4 in tumor and nonmalignant thyroid tissues from patients suffering from PTC. Expression of these receptors in PTC was correlated with the clinical pathological condition of PTC. Our data show a significant enhancement of CCR3 (2.5 times higher, p = 0.038) and CXCR4 (1.7 times higher, p = 0.02) expression in PTC tissues as determined by immunohistochemical staining, and of CCR3 (3.5 times higher, p < 0.002) in the plasma membrane as determined by flow cytometric analyses, compared to controls. In addition, while CCR3 (100%) and CXCR4 (90%) were present in both tumor and control thyroid tissues, expression of CCR7 was scarcely detected in PTC cells (5-10%) and not found in control cells. CXCR4 expression correlated with the classical variant of PTC (p < 0.035) and extranodal extension (p < 0.010) in patients with LNM. Our data support the notion that CCR3, CCR7, and CXCR4 are increasingly expressed in tumor cells from PTC and that CXCR4 expression in PTC could be a potential marker for enhanced tumor aggressiveness.

Bystander Effects

Bystander Effects

Is the quantity of circulatory cell-free DNA in human plasma and serum samples associated with gender, age and frequency of blood donations?

Circulatory cell-free DNA (cf-DNA) is increased in a variety of clinical pathologic conditions; therefore, these markers could be widely used as markers for detecting and monitoring several disorders. To better understand the biology of this molecule, we analysed the relationship between the level of circulatory cf-DNA and physiological parameters such as gender, age and frequency of blood donations. Paired plasma and serum samples were obtained from 87 blood donors and 50 healthy adults who had never donated blood. Cf-DNA was extracted from plasma and serum samples using the MagNA Pure LC Instrument. Quantity determination of circulatory cf-DNA was performed by TaqMan real-time PCR for the ubiquitous GAPDH gene. Our data showed that the concentration of cf-DNA in serum was about eightfold higher than that in plasma. Regarding the level of these circulatory species, no significant differences were observed between the age-matched men and women and gender-matched, different-age cohorts, except in women who were older than 60 years of age. Frequent blood donations did not increase the circulatory species. Circulatory cf-DNA in plasma and serum samples is not correlated with human gender and human age except in women who are older than 60 years of age. Frequent blood donation did not affect the quantity of circulatory cf-DNA. The explanation for the latter most likely is the short half-life time of free fetal DNA in maternal circulation.

Debate Forum: Levocarnitine Therapy Is Rational and Justified in Selected Dialysis Patients

Carnitine is a metabolic cofactor which is essential for normal fatty acid metabolism. Patients with chronic kidney disease on dialysis have been shown both to suffer from disordered fatty acid metabolism and to have a significant deficiency in plasma and tissue carnitine. Aberrant fatty acid metabolism has been associated with a number of cellular abnormalities such as increased mitochondrial permeability (a promoter of apoptosis), insulin resistance, and enhanced generation of free radicals. These cellular abnormalities have, in turn, been correlated with pathological clinical conditions common in dialysis patients including cardiomyopathy with attendant hypotension and resistance to the therapeutic effect of recombinant human erythropoietin (EPO). In 1999, the Food and Drug Administration approved levocarnitine injection for the prevention and treatment of carnitine deficiency in patients on dialysis based on documentation of free plasma carnitine levels in dialysis patients similar to other serious carnitine deficiency states for which treatment was required. Data analysis performed by expert panels convened by both the American Association of Kidney Patients and, subsequently, the National Kidney Foundation recommended a trial of levocarnitine therapy for specific subsets of dialysis patients including those with EPO resistance, dialysis-related hypotension, cardiomyopathy and muscle weakness. In 2003, the Centers for Medicare and Medicaid services convened a Medical Advisory Committee which established reimbursement on a national level for carnitine-deficient dialysis patients who had either dialysis-related hypotension or EPO resistance. Recently, a correlation between reductions in hospitalization rates of dialysis patients receiving levocarnitine therapy has been demonstrated in a large retrospective study. Despite data-based recommendations and national reimbursement, only a small minority of dialysis patients have been prescribed a therapeutic trial of levocarnitine. Whereas the reasons for the reluctance of nephrologists to prescribe this therapeutic trial are unclear, possible explanations include a lack of appreciation of the pivotal role played by carnitine in cellular metabolism and the strength of evidence for a substantial deficiency of carnitine in dialysis patients, an underestimation of the prognostic import of EPO resistance and dialysis-related hypotension, inadequate dissemination of the clinical trial data supporting the use of levocarnitine in dialysis patients, and the heterogeneous clinical response of dialysis patients to levocarnitine therapy. Difficulties in documenting both initial eligibility and evidence of improvement as a result of therapy may also be a contributing factor. This paper discusses the biological role of carnitine and its particular relevance to dialysis patients. Clinical trial data concerning an effect of therapy on EPO resistance and dialysis-related hypotension are summarized along with a discussion of the logic behind the use of levocarnitine in dialysis. Finally, the difficulties posed by a reimbursement policy based on clinical as opposed to laboratory endpoints and a heterogeneous response to therapy are addressed.

WHIM syndrome: a genetic disorder of leukocyte trafficking.

WHIM syndrome (the association of warts, hypogammaglobulinemia, recurrent bacterial infections, and 'myelokathexis') is a rare congenital form of neutropenia associated with an unusual immune disorder involving hypogammaglonulinemia and abnormal susceptibility to warts. In this review, we describe the clinical, laboratory and genetic features of WHIM syndrome. The identification of chemokine receptor CXCR4 as the causative gene of WHIM syndrome yields new interest in the study of this disease as a model for the comprehension of CXCR4 biology in humans and highlights the importance of the chemokine network for inducing effective immune responses and governing leukocyte trafficking. CXCR4 participates in several biological processes (bone marrow hematopoiesis, cardiogenesis, angiogenesis, neurogenesis) and is implicated in different clinical pathologic conditions (WHIM, HIV infection, tumor metastatization, autoimmunity). Pharmacologic agents that modulate CXCR4 expression/function are already available and promise a wide range of future clinical applications.

Total iron-binding capacity and serum transferrin determination under the influence of several clinical conditions

In this study TIBC and serum-transferrin concentrations were determined by immunochemical turbidimetry, immunochemical nephelometry and radial immunodiffusion under normal and pathological clinical conditions. A total of 246 (123 male/123 female) patients were included [iron deficiency: 60 (18/42), iron overload: 56 (39/17), chronic inflammation: 47 (23/24), undefined diseases: 35 (16/19), healthy volunteers 48 (27/21)]. The data show that determination of TIBC from conversion of transferrin values using a constant factor results in significantly higher values compared to conversion with a function of first degree. For clinical practice the influence of different diseases is negligible. This study indicates that it is not possible to develop a universal algorithm for the conversion of transferrin values into TIBC.

Structure and Function of Hemidesmosomes: More Than Simple Adhesion Complexes

The attachment of cells to the extracellular matrix is of crucial importance in the maintenance of tissue structure and integrity. In stratified epithelia such as in skin as well as in other complex epithelia multiprotein complexes called hemidesmosomes are involved in promoting the adhesion of epithelial cells to the underlying basement membrane. In the past few years our understanding of the role of hemidesmosomes has improved considerably. Their importance has become apparent in clinical conditions, in which absence or defects of hemidesmosomal proteins result in devastating blistering diseases of the skin. Molecular genetic studies have increased our knowledge of the function of the various components of hemidesmosomes and enabled the characterization of protein-protein interactions involved in their assembly. It has become clear that the alpha6beta4 integrin, a major component of hemidesmosomes, is able to transduce signals from the extracellular matrix to the interior of the cell, that critically modulate the organization of the cytoskeleton, proliferation, apoptosis, and differentiation. Nevertheless, our knowledge of the mechanisms regulating the functional state of hemidesmosomes and, hence, the dynamics of cell adhesion, a process of crucial importance in development, wound healing or tumor invasion, remains limited. The aims of this review are to highlight the recent progresses of our knowledge on the organization and assembly of hemidesmosomes, their involvement in signaling pathways as well as their participation in clinical pathologic conditions.

Mathematical pressure volume models of the cerebrospinal fluid

Numerous mathematical models have emerged in the medical literature over the past two decades attempting to characterize the pressure and volume dynamics of the central nervous system compartment. These models have been used to study the behavior of this compartment under such pathological clinical conditions as hydrocephalus, head injury and brain edema. The number of different approaches has led to considerable confusion regarding the validity, accuracy or appropriateness of the various models. In this paper we review the mathematical basis for these models in a simplified fashion, leaving the mathematical details to appendices. We show that most previous models are in fact particular cases of a single basic differential equation describing the evolution in time of the cerebrospinal fluid pressure (CFS). Central to this approach is the hypothesis that the rate of change of CSF volume with respect to pressure is a measure of the compliance of the brain tissue which as a consequence leads to particular models depending on the form of the compliance function. All such models in fact give essentially no information on the behavior of the brain itself. More recent models (solved numerically using the Finite Element Method) have begun to address this issue but have difficulties due to the lack of information about the mechanical properties of the brain. Suggestions are made on how development of models which account for these mechanical properties might be developed.