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PubMed2002

Pathophysiology of bacterial meningitis: mechanism(s) of neuronal injury.

No bacterial disease has undergone a more dramatic change in epidemiology during the past decade than acute bacterial meningitis. This review describes the changing epidemiology and considers some important recent observations that contribute to our understanding of the pathogenesis and pathophysiology of meningitis. The major focus is on the mechanisms of neuronal injury and the pathophysiologic concepts responsible for death and neurologic sequelae. In recent years, experimental studies have amplified our understanding of the substantial body of evidence that now implicates cytokines and chemokines, proteolytic enzymes, and oxidants in the inflammatory cascade leading to tissue destruction in bacterial meningitis. The molecular mechanisms responsible for oxidant-induced neuronal injury in meningitis are explored in some depth. Genetic targeting and/or pharmacologic blockade of the implicated pathways may be a future strategy for therapeutic adjunctive measures to improve outcome and may hold substantial promise, in concert with antimicrobial agents, in humans with acute bacterial meningitis.

Adolescent↗
PubMed1997

Prospective study of histoplasmosis in patients infected with human immunodeficiency virus: incidence, risk factors, and pathophysiology.

Histoplasmosis is a common opportunistic infection in patients with human immunodeficiency virus (HIV) infection who reside in areas where Histoplasma capsulatum is endemic. We undertook a prospective study of a cohort of 304 HIV-Infected patients in Kansas City from October 1990 through March 1993 to define the incidence-specific risk factors, and pathophysiology of histoplasmosis. The annual incidence of histoplasmosis was 4.7%; 74% of the patients with histoplasmosis were symptomatic (all of whom had disseminated disease). A history of exposure to chicken coops, a positive baseline serology for complement-fixing antibodies to Histoplasma mycelium antigen, and a baseline CD4+ lymphocyte count of < 150/microL were associated with an increased risk for histoplasmosis. Histoplasmin reactivity and the presence of pulmonary calcifications were not useful markers for patients at high risk. Symptomatic infection occurred in 9.9% of patients with evidence of prior exposure to H. capsulatum, in 4.0% of patients without documented prior exposure, and in 3.0% of patients who were anergic; these findings suggest that the pathophysiology of histoplasmosis in patients with AIDS involves reactivation of latent infection in some cases and dissemination of exogenously acquired infection in other cases.

AIDS-Related Opportunistic Infections↗
PubMed1996

Sensory pathophysiology in chronic acquired demyelinating neuropathy.

Pathophysiological changes in sensory fibres in chronic acquired demyelinating neuropathy (CADP) are poorly understood, and it is not known to what extent sensory loss may be due to axonal loss or to conduction block. Motor and sensory nerve condition were studied in 18 patients with CADP to delineate abnormalities in the compound sensory action potential (CSAP) recorded proximally along the limb. To distinguish small CSAPs from noise, near-nerve needle electrodes and electronic averaging were used. In all, 58 motor and 78 sensory nerves in the upper and lower limbs were studied, and in 29 nerves, motor and sensory conduction was compared over the same proximal and distal segments of the upper limbs. The proximal/distal amplitude ratio (P/D ratio) of the compound muscle action potential (CMAP) was reduced in 76% of the nerves compared with only 21% of the CSAPs. The amplitudes of CMAPs evoked and of CSAPs recorded distally were reduced to the same extent. The prolongation of the distal motor latency (DML) was linearly related to the reduction in amplitude of the CMAP whereas reduction of the distal sensory conduction velocity (SCVd) mainly occurred if the amplitude of the CSAP was reduced more than 70%. The proximal motor nerve conduction velocity (MCVp) was reduced by 40-50%, twice as much as the reduction in distal MCV (MCVd) (calculated from the reciprocal DML), and related to the reduction in the P/D ratio of the CMAP. The proximal SCV (SCVp) decreased approximately 20%, similar to the reduction in SCVd and out of proportion to the marked reduction of the MCVp. The results suggest different pathophysiological changes in sensory and motor fibres in CADP. Thus, nerve fibre loss could account for most of the abnormal parameters in sensory conduction, whereas demyelination was the dominating cause of motor nerve dysfunction.

Action Potentials↗
PubMed1994

Putative pathophysiological interactions of cytokines and phagocytic cells in severe human falciparum malaria.

The severe disease and high mortality associated with Plasmodium falciparum infection have traditionally been attributed solely to parasitic virulence factors, but more recent evidence suggests that the host's immunologic response may also contribute to the pathophysiology of the disease in humans. This response would be expected to be proportionate--in intensity and nature--to the antigenic load created by the sequestration of parasites in the microvasculature and to be directed against the sites of maximal parasitization; thus the immunologic response could potentially contribute to the pathophysiology of both survival and fatal outcome in severe infection. Cytokines appear to play a pivotal role in the activation of the immune response in human falciparum malaria, and their levels correlate with disease severity. The putative mechanisms by which cytokines may mediate both beneficial and deleterious effects by activating phagocytic cells in severe falciparum malaria are discussed.

Cytokines↗
PubMed1993

Cation conduction in the calcium release channel of the cardiac sarcoplasmic reticulum under physiological and pathophysiological conditions.

OBJECTIVE: The aim was to perform a theoretical and experimental study of the possible variations in Ca2+ current through the open cardiac sarcoplasmic reticular Ca2+ release channel under the ionic conditions associated with physiological and pathophysiological states. METHODS: The sheep cardiac sarcoplasmic reticular Ca2+ release channel was purified and reconstituted into planar phospholipid bilayers for study under voltage clamp conditions. Single channel current-voltage relationships were measured under putative physiological conditions with 1, 5, and 10 mM intraluminal Ca2+. The mathematics of a computer model based on Eyring rate theory were extended to include the interactions of three permeant ions. RESULTS: A model used previously to describe ionic conduction under simpler ionic conditions was able to predict the interaction of Ca2+, Mg2+, and K+ in the probable physiological range over the voltage range of interest. The predicted Ca2+ current under ionic conditions proposed to occur at the end of diastole is sensitive to relatively small changes in holding potential which suggests the need for adequate charge compensation across the sarcoplasmic reticular membrane. Theoretically, it was predicted that variations in intraluminal Ca2+, such as may occur in Ca2+ overload and other conditions, and variations in cytosolic Mg2+, which may occur in myocardial stunning, may significantly affect Ca2+ flux through the open Ca2+ release channel. CONCLUSIONS: Variations in permeant ion concentration such as may occur in physiological and pathophysiological states may significantly affect the quantity of Ca2+ released from the cardiac sarcoplasmic reticulum.

Animals↗
PubMed1993

Pathophysiological and biochemical characterisation of an avian model of dilated cardiomyopathy: comparison to findings in human dilated cardiomyopathy.

OBJECTIVE: With the recent availability of human myocardium, many animal models have been shown to be unsuitable as models of human heart failure. The aim of this study was to describe the pathophysiological changes in a model of dilated cardiomyopathy in turkey poults and to compare them to results obtained from failing human hearts. METHODS: After receiving furazolidone for 2-3 weeks, animals developed cardiomyopathy (Fz-DCM) and were studied at the whole heart and isolated muscle level. Myofibrillar ATPase activity and noradrenaline turnover were determined in tissue homogenates in failing and non-failing control hearts. RESULTS: Fz-DCM animals had greater heart weights, heart weight/body weight ratios, and end diastolic volumes. Fractional shortening of the left ventricle and systolic blood pressures were reduced (p < 0.01) in myopathic animals. Isolated perfused hearts had lower peak developed pressures (p < 0.01). Isolated muscle preparations showed no significant differences in peak twitch forces between control and Fz-DCM muscles at a 1 Hz stimulation rate. The relationship between force and frequency of stimulation was positive in control muscles up to 1.7 Hz, whereas in Fz-DCM muscles the relationship was sharply negative above 1 Hz. Time to 80% relaxation was markedly slower in the Fz-DCM muscles. Although [Ca2+]o responsiveness was similar for Fz-DCM and normal animals, responsiveness to isoprenaline was significantly reduced in Fz-DCM hearts. Cardiomyopathic animals displayed diminished noradrenaline content in the left ventricle. Fractional noradrenaline turnover was higher (p < 0.05) in the cardiomyopathic birds. In skinned fibre preparations from control and Fz-DCM hearts calcium activations were similar. Maximum myofibrillar ATPase activities were, however, significantly lower in myopathic animals and myofibrillar protein content was reduced by 25%. CONCLUSIONS: In this model of dilated cardiomyopathy: (1) relaxation is markedly prolonged; (2) the response to beta adrenergic stimulation is diminished; (3) Mg-ATPase activities and myofibrillar protein content are reduced; and (4) sympathetic activity in the heart is markedly increased with depletion of noradrenaline stores. Furthermore, a reduction in tissue noradrenaline content per se is a misleading index of the dynamic state of cardiac noradrenaline stores. With its similarities to human cardiomyopathy, this model promises to provide new insights into the pathophysiology and progression of dilated cardiomyopathy.

Adenosine Triphosphatases↗
PubMed1989

Pathophysiological mechanisms of ventricular tachyarrhythmias.

The pathophysiological background for ventricular tachyarrhythmias based on experimental and clinical evidence is presented. Sudden cardiac death may occur as the first manifestation of coronary artery disease without antecedent complaints or it may occur in patients with a previous myocardial infarction. In the latter situation, a circumscribed area of cardiac tissue may be responsible for the genesis and maintenance of a ventricular tachyarrhythmia which may be called the 'arrhythmogenic substrate'. This zone of electrically abnormal ventricular myocardium is usually located at the border of a previous myocardial infarction, and is characterized by islands of relatively viable muscle alternating with areas of necrosis and, later, fibrosis. The consequent fragmentation of the propagating electromotive forces leads to the development of high-frequency components that can be recorded directly or non-invasively using signal-averaging techniques. These signals have been called ventricular late potentials. The 'arrhythmogenic substrate' may be present permanently or may rise acutely and be present only transiently in the case of extensive ischaemia or acute myocardial infarction. In the setting of a chronic 'arrhythmogenic substrate', this electrically abnormal tissue may be triggered by spontaneously occurring ventricular ectopic beats or salvoes or by programmed ventricular stimulation, as well as by transient episodes of ischaemic causing spontaneous arrhythmias. These trigger factors modify the 'arrhythmogenic substrate' in such a way that ventricular tachyarrhythmias are sustained. It is apparent that sudden cardiac death is due to a wide spectrum of pathophysiological mechanisms which may be interrelated. There is obviously no single parameter that helps the clinician to predict the propensity for sudden cardiac death in the individual patient.

Coronary Disease↗
PubMed1997

The pathophysiology of ovarian hyperstimulation syndrome--views and ideas.

Ovarian hyperstimulation syndrome (OHSS) is a serious complication affecting ovulation induction. Its most severe manifestation takes the form of massive ovarian enlargement and multiple cysts, haemoconcentration and third-space accumulation of fluid. The full-blown clinical syndrome may be complicated by renal failure and oliguria, hypovolaemic shock, thromboembolic episodes, adult respiratory distress syndrome (ARDS), and death. Although the pathophysiology of this syndrome has not been completely elucidated, it seems likely that the increased capillary permeability triggered by the release of vasoactive substance secreted by the ovaries under human chorionic gonadotrophin (HCG) stimulation plays a key role in this syndrome. Several factors such as histamine, serotonin, prostaglandins, prolactin, and a variety of other substances have been implicated in this process in the past. At present, factors belonging to the renin-angiotensin system, cytokines including the interleukins, tumour necrosis factor alpha, endothelin-1 and vascular endothelial growth factor (VEGF) are thought to be involved in triggering increased vascular permeability after ovulation induction treatment. This manuscript summarizes the current knowledge of the pathophysiology of ovarian hyperstimulation syndrome with emphasis on the correlation of the various factors with the clinical phenomena of this iatrogenic syndrome.

Adult↗
PubMed2004

Increased erythrocyte aggregation in ovarian hyperstimulation syndrome: a possible contributing factor in the pathophysiology of this disease.

BACKGROUND: Many theories regarding the pathophysiology leading to ovarian hyperstimulation syndrome (OHSS) have been proposed and tested. Increased erythrocyte aggregation is associated with capillary slow flow and tissue hypoxaemia. We performed this study in order to assess the degree of erythrocyte aggregation in the peripheral blood of individuals with OHSS and undergoing controlled ovarian stimulation (COH). METHODS: Twenty women with severe OHSS, 20 women undergoing COH under IVF protocol, and 20 healthy matched controls were recruited for this prospective study. Blood samples were drawn for determination of erythrocyte aggregation as well as haematological indices. The percentage of slide covered by the cells ('erythrocyte percentage': EP) was determined using a simple slide test and image analysis. Lower EP values correspond to higher degrees of aggregation. RESULTS: The respective measures of EP were 59.2 +/- 3.0, 42.0 +/- 3.0 and 35.0 +/- 2.4% micro m for the controls, women with COH and OHSS (P < 0.01 between controls and the two stimulation groups). CONCLUSIONS: The degree of erythrocyte aggregation is enhanced in the peripheral venous blood of patients with both COH and OHSS. This finding, known to cause capillary leak, may contribute to the pathophysiology of the OHSS.

Capillaries↗
PubMedDate not supplied

The pathophysiology of varicoceles in the light of current molecular and genetic information.

Varicoceles are a common cause of male infertility, but despite data being obtained from animal models and human studies the pathophysiology remains unclear. Recently, molecular and genetic information has been reported on men with varicoceles which may shed new light onto the causes of decreased semen parameters and poor sperm function. Here, a number of studies are reviewed in an attempt to develop a working hypothesis for the relationship of varicoceles and infertility. New studies on testicular tissue of men with varicoceles have demonstrated increased apoptosis among developing germ cells, which may be the cause of oligospermia. Other studies with semen have shown increased levels of reactive oxygen species (ROS) in association with poor sperm motility. Recent studies of morphologically abnormal spermatozoa have demonstrated disruption of the sperm head actin by cadmium, a cation reported to be present in high concentrations among some men with varicoceles. Finally, microdeletions of the alpha-1 subunit of the sperm calcium channels in a proportion of men with varicoceles suggests a genetic defect leading to abnormal acrosomal function. The intent of this review was to explain the pathophysiology of varicoceles, and the findings seem to support a 'co-factor' hypothesis. In order for varicoceles to be associated with infertility, they exist as 'co-factors' along with other molecular/genetic problems.

Acrosome Reaction↗
PubMed2006

Animal models of type 2 diabetes: clinical presentation and pathophysiological relevance to the human condition.

The prevalence of diabetes throughout the world has increased dramatically over the recent past, and the trend will continue for the foreseeable future. One of the major concerns associated with diabetes relates to the development of micro- and macrovascular complications, which contribute greatly to the morbidity and mortality associated with the disease. Progression of the disease from prediabetic state to overt diabetes and the development of complications occur over many years. Assessment of interventions designed to delay or prevent disease progression or complications in humans also takes years and requires tremendous resources. To better study both the pathogenesis and potential therapeutic agents, appropriate animal models of type 2 diabetes (T2D) mellitus are needed. However, for an animal model to have relevance to the study of diabetes, either the characteristics of the animal model should mirror the pathophysiology and natural history of diabetes or the model should develop complications of diabetes with an etiology similar to that of the human condition. There appears to be no single animal model that encompasses all of these characteristics, but there are many that provide very similar characteristics in one or more aspects of T2D in humans. Use of the appropriate animal model based on these similarities can provide much needed data on pathophysiological mechanisms operative in human T2D.

Animals↗
PubMed2001

Anaemia in end-stage renal disease: pathophysiological considerations.

Anaemia is a frequent complication of many diseases but the mechanisms that link reduced blood oxygen content to the long-term consequences of anaemia are incompletely understood. The maintenance of oxygen supply to the tissues during anaemia involves complex cardiovascular adaptations, including an increase in cardiac output, reduced peripheral resistance and increased oxygen extraction from haemoglobin (Hb). In addition, hypoxia-inducible factors are associated with the transcriptional activation of genes involved in adaptive mechanisms that increase oxygen delivery and provide alternative metabolic pathways. The complex pathophysiology of chronic kidney disease alters the adaptations to anaemia in uraemic patients. The increased cardiac output induced by anaemia is associated with left ventricular hypertrophy and cardiac disease in renal patients. Alterations in endothelial cell function, common in renal disease, may diminish endothelium-induced vasodilatation, increase the risk of atherosclerosis and impair angiogenesis. Many potential reasons for erythropoietin-induced hypertension in uraemic patients have been postulated, including increased blood viscosity as haematocrit rises, a reversal of hypoxic vasodilatation, increased blood volume that is not compensated by haemodialysis, ultrafiltration and impaired nitric oxide synthesis, preventing vascular relaxation in response to increased blood viscosity. In view of this impaired vascular reactivity, rapid increases in haematocrit should be avoided during epoetin treatment. As the interaction between anaemia and uraemia is very complex, it is not possible to derive the optimal Hb concentration for individual patients by using simple physiological or pathophysiological models and there is a need for good randomized controlled clinical trials to address this issue.

Adaptation, Physiological↗
PubMed1988

Pathophysiology of anovulation.

Anovulatory disorders are physiological during puberty, postpartum period and just before the menopause. In pathology, they are one of the earliest symptoms of different diseases: functional or organic hypothalamic diseases, pituitary destruction or inappropriate feedback by the peripheral hormones and, obviously, primary ovarian insufficiency. Their real interest lies in their pathophysiology. Functional hypothalamic disorders are defined as the inability to liberate GnRH in a physiological way. The role of endogenous opioids, as essential factors of gonadotrophin regulation will be discussed. Hyperprolactinaemias, which represent 20% of the anovulations, have an antigonadotrophic effect at the hypothalamic level, but the very mechanism of the inhibitory effect of prolactin on GnRH is still open to discussion. Although polycystic ovarian disease is one of the most common endocrine abnormalities in women, its pathophysiology remains far from fully understood. The relative parts played by hypothalamic disturbances and by abnormal feedback of gonadal steroids will be discussed.

Anovulation↗
PubMed1991

Pathophysiology of polycystic ovarian disease: new insights.

The incidence of polycystic ovarian disease (PCOD) varies from 0.6 to 92%, depending on the parameters analysed, PCOD has been reported to appear in association with Cushing's Syndrome, adrenal hyperplasia, hypothyroidism, adrenal and ovarian tumours and some genetic abnormalities. The controversy regarding the pathophysiological mechanism underlying the disease still persists. Critical evaluation of old data, assessment of new findings concerning the possible role of insulin, growth factors and their binding proteins, and extrapolation of neuroendocrinological experiments enabled the construction of a concise hypothesis of the pathophysiology of PCOD. According to this hypothesis, PCOD is a multifactorial disease. The sequence of events finally leading to clinical manifestation of the disease (hyperandrogenism, abnormal luteinizing hormone pulsatility pattern and ovulation disturbances) may originate in different organs or be triggered by different mechanisms. It may stem from the adrenals, the hypothalamus or higher central nervous system centres, or from the ovary itself; it may originate from excess of fat tissue usually combined with hyperinsulinism; or may be the result of a net increase in active growth factors. Each of the above disturbances probably appears early in life, much before the clinical signs of the disease are evident. Predisposing factors such as gestational diabetes of the mother, childhood obesity, borderline adrenal hyperplasia and late menarche have to be looked for as early as possible in order to prevent the late consequences of the disease, such as increased risk of infertility, endometrial and breast cancer and cardiovascular disease.

Female↗
PubMed2006

Pathophysiology and clinical consequences of Raynaud's phenomenon related to systemic sclerosis.

According to the so-called vascular hypothesis, Raynaud's phenomenon (RP) is one initial event in the pathophysiological cascade leading to sclerosis in systemic sclerosis (SSc). It is characterized by recurrent, reversible spasms of small arterioles and digital arteries, usually triggered by cold and emotional stress. Clinical signs of RP are a sudden pallor of single digits of fingers followed by reactive hyperaemia and in severe cases also by cyanosis. Besides imbalances between vasoconstrictive and vasodilatory processes, structural alterations of the involved vessels are fundamental to secondary RP in SSc. The latter is the reason why secondary RP in SSc, in contrast to primary RP, often leads to ischaemia and re-perfusion injuries. New insights into the pathophysiology of RP feature a special role for alpha2c-adrenoreceptors, Rho-kinase signalling pathways and soluble mediators. They have resulted in promising therapeutic options, including antagonism of endothelin receptors, inhibition of phosphodiesterases or selective blockade of alpha2c-adrenoreceptors. They should also have a positive impact on the course of SSc in general.

Fibrosis↗
PubMed1994

Impaired attention, genetics, and the pathophysiology of schizophrenia.

Impaired attention is commonly observed among schizophrenia patients and those at genetic risk for the disease. This article reviews over 40 studies that used various versions of the Continuous Performance Test (CPT) as the primary measure of attention. These studies of normal subjects, affected patients, and various at-risk populations demonstrate that the CPT is a psychometrically sound procedure that consistently discriminates affected patients from controls. Sufficiently difficult versions of this task have also demonstrated that impaired attention is (1) evident in schizophrenia patients regardless of clinical state, (2) detectable before illness onset, (3) apparently heritable, (4) specific--in terms of distinct profile patterns--to schizophrenia, and (5) predictive of later behavioral disturbances in susceptible individuals. Selected studies are also discussed that examine the role of attentional deficit in the pathophysiology of schizophrenia and its potential consequences for personality development. With respect to pathophysiology, preliminary data suggest that subcortical brain dysfunction has an important role in the attentional deficits tapped by the CPT. With respect to personality, an association between chronically impaired attention and deficient social skills has been found. It is concluded that the CPT is a cost-effective measure of the attentional deficit commonly found in affected schizophrenia subjects and those at risk for the disorder, and is therefore a potentially valuable screening device for preventive intervention programs.

Attention↗
PubMed2006

Spatial working memory as a cognitive endophenotype of schizophrenia: assessing risk for pathophysiological dysfunction.

Research suggests that first-degree relatives and individuals with schizophrenia spectrum personality disorders (SSPD) may represent nonpenetrant carriers of the genetic diathesis for schizophrenia. This study examined visuospatial working memory (SWM) as a cognitive endophenotype of schizophrenia by expanding the concept of risk for pathophysiological dysfunction beyond overt psychosis. Risk was thus defined by familial status and the presence or absence of SSPD. SWM was assessed in the following groups, in order of decreasing likelihood of genetic vulnerability: 23 patients with schizophrenia, 17 SSPD relatives of patients with schizophrenia, 23 non-SSPD relatives of patients with schizophrenia, 14 SSPD community members with no family history of psychosis, and 36 non-SSPD community members. SWM performance during a computer task was quantified by A-Prime. Relative risk ratios for SWM deficits were compared among the groups. Compared with community non-SSPD volunteers, relative risk (RR) of SWM deficits was significantly elevated in patients with schizophrenia (RR = 3.76, p = .002) and SSPD family members (RR = 2.97, p = .027), but not in the family non-SSPD (RR = 1.88, p = .241) or community SSPD (RR = 1.03, p = .971) groups. The pattern of SWM performance deficits reflected the proposed model of latent genetic liability, upholding SWM as a viable cognitive endophenotype. The results underscore the importance of including both familial liability and the schizophrenia spectrum when considering risk for schizophrenia and schizophrenia-related traits. This is particularly relevant for research efforts to identify pathophysiological components of the disease.

Adult↗
PubMed2006

An updated physiologically based pharmacokinetic model for hexachlorobenzene: incorporation of pathophysiological states following partial hepatectomy and hexachlorobenzene treatment.

Physiologically based pharmacokinetic (PBPK) modeling is generally used for describing xenobiotic disposition in animals and humans with normal physiological conditions. We describe here an updated PBPK model for hexachlorobenzene (HCB) in male F344 rats with the incorporation of pathophysiological conditions. Two more features contribute to the distinctness of this model from the earlier published versions. This model took erythrocyte binding into account, and a particular elimination process of HCB, the plasma-to-gastrointestinal (GI) lumen passive diffusion (i.e., exsorption), was incorporated. Our PBPK model was developed using data mined from multiple pharmacokinetic studies in the literature, and then modified to simulate HCB disposition under the conditions of our integrated pharmacokinetics/liver foci bioassay. This model included plasma, erythrocytes, liver, fat, rapidly and slowly perfused compartments, and GI lumen. To account for the distinct characteristics of HCB absorption, the GI lumen was split into an upper and a lower part. HCB was eliminated through liver metabolism and the exsorption process. The pathophysiological changes after partial hepatectomy, such as alterations in the liver and body weights and fat volume, were incorporated in our model. With adjustment of the transluminal diffusion-related parameters, the model adequately described the data from the literature and our bioassay. Our PBPK model simulation suggests that HCB absorption and exsorption processes depend on exposure conditions; different exposure conditions dictate different absorption and exsorption rates. This model forms a foundation for our further exploration of the quantitative relationship between HCB exposure and development of preneoplastic liver foci.

Animals↗