Characterization of a human-specific regulator of placental corticotropin-releasing hormone

The hypothalamic hormone CRH is also expressed in the placentas of humans and higher primates and may play an important role in the regulation of labor. In choriocarcinoma cell lines, activation of cAMP-dependent pathways increases human (h)CRH reporter gene expression. A cAMP-responsive region distinct from the cAMP response element at -220 bp, has been identified between -200 and -99 bp, and a candidate transcription factor was identified in nuclear extracts of human, but not rodent, choriocarcinoma cell lines. This region, which does not contain a canonical cAMP response element (CRE), transfers protein kinase A responsiveness to a heterologous promoter. Electromobility shift assays and methylation and uracil interference studies localized factor binding to a 20-bp region from -128 to -109 bp of the hCRH promoter. This 20-bp fragment exhibited a similar shift in nuclear extracts from both human term placenta and from human JEG-3 cells. Base contacts, identified in interference studies, were confirmed as critical for binding, as a mutation of these bases abolished factor binding. Furthermore, a CRH promoter containing this mutation exhibited a diminished response to forskolin. UV cross-linking demonstrated the protein in nuclear extracts from human, but not rodent, choriocarcinoma cell lines and estimated its size as 58 kDa. Although this factor participates in cAMP-regulated gene expression, competition electrophoretic mobility assays demonstrated that the factor does not bind to a CRE. Furthermore, neither anti-CREB nor anti-ATF2 antibodies alter factor binding. These data identify this 58-kDa protein as the human-specific CRH activator previously identified as a candidate factor contributing to the species-specific expression of CRH in human placenta.

Identification of glial cell proliferation in early multiple sclerosis lesions

Multiple sclerosis (MS) is a chronic inflammatory disease of the central nervous system which leads to destruction of myelin sheaths. The patterns of cell proliferation in the early course of the disease are largely unknown. The present study used immunohistochemical identification of proliferating glial cells in stereotactic brain biopsy material of eight patients with early chronic MS. Double-labelling with the proliferation marker MIB-1 detected proliferating oligodendrocytes (MOG), astrocytes (GFAP) and microglia/macrophages (Ki-M1P). The majority of proliferating cells were macrophages/microglia when compared with oligodendrocytes (P > 0.005) or astrocytes (P > 0.0005); only a minor proportion of microglia/macrophages, however, proliferated in situ. Astrocytic and oligodendroglial proliferation was sparse to absent and showed significant variations between different patients. There were statistically significant differences when comparing the amount of proliferation between lesions of different demyelinating activity: highest numbers of proliferating cells were found in early active lesions compared with demyelinated and early remyelinated lesions (P > 0.05) or the periplaque white matter (P > 0.01). MOG-positive oligodendrocytes proliferated occasionally in the early stages of lesion formation; this proliferation occurred in four cases but was independent of the stage of the disease. Since MOG is expressed by mature oligodendrocytes, and not by immature precursors, this might suggest a potential role for the proliferation of mature surviving oligodendrocytes with subsequent remyelination.

Psychopathology following cardioverter defibrillator implantation

Previous reports have found elevated rates of psychopathology in recipients of implantable cardioverter defibrillators (ICDs). Thirty-five consecutive ICD recipients were assessed by using the Structured Clinical Interview for DSM-III-R and a semistructured questionnaire; assessments were performed within 3 days of ICD implantation (Time 1) and again 9-18 months later (Time 2). At the initial assessment, alcohol dependence in remission was the most common diagnosis, followed by mood disorders. Two cases of depression were found at follow-up assessment, but those subjects had either a lifetime history of major depression or some depressive symptoms at Time 1. No new cases of anxiety disorders were seen at Time 2. It appears that ICD recipients have rates similar to the general population at the time of implantation, and the risk for new psychopathology is largely confined to those with a lifetime history of psychopathology.

Insulin-like growth factor system and the kidney: physiology, pathophysiology, and therapeutic implications

The insulin-like growth factor (IGF) system, consisting of IGF-I and IGF-II, their binding proteins, and their receptors, is expressed in a spatial organization in the nephron, but circulating IGFs also affect the kidney. Renal and systemic IGF-I and the binding proteins are regulated by growth hormone and nutritional status. In the kidney, IGF-I dilates the resistance-regulating microvasculature, increases glomerular filtration rate, and promotes tubular phosphate and possibly sodium absorption. IGF-I contributes to compensatory renal growth in a variety of experimental models and may modestly contribute to progressive glomerular sclerosis. In chronic renal failure and the nephrotic syndrome, there are several abnormalities in the IGF system. In chronic renal failure, IGF-I increases renal function and may improve nutritional status due to its anabolic effects. IGF-I accelerates the recovery of renal function in animal models of acute renal failure, but results from clinical trials were less salutary. Several questions regarding the role of the IGF system in normal and abnormal renal biology and potential therapeutic applications in kidney diseases remain unanswered.

CD59 protects glomerular endothelial cells from immune-mediated thrombotic microangiopathy in rats

CD59 is a cell membrane-bound complement regulatory protein on glomerular cells that inhibits C5b-9 assembly and insertion. This report describes a recently developed model of immune thrombotic microangiopathy (TMA) induced by the renal artery perfusion of anti-glomerular endothelial cell (anti-GEN) antibody. To examine the role of CD59 in protecting the GEN from immune-mediated injury, rats underwent selective renal artery perfusion with F(ab')2 fragments of anti-CD59 monoclonal antibody to block CD59 activity or control mouse IgG followed by anti-GEN antibody or control goat IgG. Neutralization of CD59 in normal rats did not result in any significant functional or histologic changes. Perfusion with anti-CD59 did not change deposition of the pathogenic anti-GEN IgG used to induce the TMA model. However, neutralization of CD59 in the TMA model resulted in more C5b-9 formation in glomeruli, accompanied by increased platelet and fibrin deposition, more severe endothelial injury, and reduced renal function compared with the animals perfused with control F(ab')2 fragments. These results demonstrate directly that CD59 serves a protective role for GEN in this TMA model of rats, and confirm that C5b-9 formation has a critical pathogenic role in the mediation of the disease. CD59 may play an important role in protecting glomerular endothelium from other complement-mediated types of injury.

Transcriptional regulation of human placental corticotropin-releasing factor by prostaglandins and estradiol

The mechanism of labor initiation in humans has not been completely elucidated. Prostaglandins, estrogens, and corticotropin-releasing factor (CRF) have all been shown to affect uterine myocytes and enhance uterine contractility. There are also indications that these uterine regulators have additional effects on other sites involved in labor and that they may act in concert or, perhaps, by regulating each other. Therefore, we evaluated the CRF promoter for transcriptional regulation by prostaglandins and estrogens. Human placental choriocarcinoma cell lines were transfected with CRF-luciferase reporter genes and treated with prostaglandins. Prostaglandin E2 (PGE2), but not prostaglandin F2alpha (PGF2alpha), stimulated CRF-luciferase expression in choriocarcinoma cell lines via a cAMP-dependent pathway. A combination of transfections and in vitro binding studies tested for potential regulation of CRF by estrogen receptor (ER). ER neither regulated the CRF promoter nor interacted with steroid response half-sites from the CRF promoter. Our results provide a molecular regulatory link between PGE2 and CRF, two compounds that enhance uterine contractile function. Combined with the stimulation of prostaglandin release by CRF, these data support a potentially important "feed-forward" regulatory loop involving CRF and PGE2 in parturition. In contrast, we found no evidence for direct effects of estrogens or PGF2alpha on CRF transcription.

Renal microvascular injury induced by antibody to glomerular endothelial cells is mediated by C5b-9

We have recently developed a model of thrombotic microangiopathy with injury to the glomerular endothelial cell (GEN) induced by heterologous antibody to rat GEN. In addition to GEN injury rats developed glomerular platelet aggregation and fibrin deposition, acute renal failure, and acute tubular necrosis with interstitial inflammation. To study the role of complement in mediating this lesion, we induced the disease in normal complement PVG rats and measured the effects of generalized complement depletion with cobra venom factor (CVF) and of selective C6 deficiency using genetically C6 deficient PVG animals. Complement sufficient rats developed severe endothelial injury accompanied by platelet aggregation, fibrin deposition, decrease in endothelial cells assessed by antibody staining in the glomerulus, and macrophage infiltration. These changes were associated with marked reduction in renal function. These features were either absent or markedly diminished in complement depleted or C6 deficient rats. This demonstrates that C5b-9, the terminal product of activation of the complement cascade, plays an important role in the pathogenesis of this immune renal microvascular endothelial injury model. Thus, the complement system may play a pathogenic role in renal microvascular diseases such as thrombotic microangiopathy.

[Doubtful mammographic findings: the value of negative MR mammography for tumor exclusion]

PURPOSE

To determine whether the addition of MR mammography (MRM) is useful in excluding malignant lesions and how reliable negative MRM findings are.

METHODS

Amongst 694 MRM's, those originally regarded as normal were retrospectively reappraised. 239 female patients were involved. In all these patients there were clinical, sonographic and/or mammographic findings which were not entirely normal but there was no urgent indication for histological clarification. In 46 patients there were, however, histological examinations since the patients themselves insisted on it. In the remaining patients there was clinical, sonographic, mammographic and/or MRM follow-up after 12 to 18 months.

RESULTS

In 95.4% (200/239) a carcinoma could be excluded by means of MRM, in 7 patients a carcinoma in situ and in two patients an invasive carcinoma was demonstrated histologically which had not been demonstrated by MRM. Even in retrospect, no abnormality could be found.

CONCLUSION

Because of the only moderate sensitivity of MRM in the recognition of carcinoma in situ, doubtful lesions which can be localised, should be biopsied by a stereotactic method. In cases where evaluation is difficult on clinical, sonographic and mammographic findings, MRM is of value in excluding tumours, particularly in patients with increased carcinoma risk.

Transcriptional regulation of estrogen-responsive genes by non-steroidal estrogens: doisynolic and allenolic acids

Estrogen receptor (ER), a member of the nuclear receptor superfamily, exerts prominent physiological roles in both humans and other species by acting directly as a transcription factor, altering nuclear gene expression. One peculiarity of estrogenic regulation is that it is affected by a wide variety of non-steroidal compounds in addition to the natural hormone, estradiol. Doisynolic and allenolic acid compounds are non-steroidal compounds that act as potent estrogens in animal studies, yet bind to ER extremely poorly in competitive binding assays, raising the possibility of alternative molecular mechanisms for the observed estrogenic effects. In this work we demonstrate that (+/-)-Z-bisdehydrodoisynolic acid, (+/-)-Z-bisdehydrodoisynolic acid 3-methyl ether, and (-) allenolic acid can interact directly with ER. These compounds all serve as ligands for ER in mechanism-specific tissue culture-based reporter gene assays for both positive and negative gene regulation. We have also used a novel assay based on electromobility shift by ER for directly determining relative binding affinities for ER. In addition, we show cell-type-specific activity differences for (+/-)-Z-bisdehydrodoisynolic acid 3-methyl ether, supporting clinical observations indicating a higher potency of this compound in female animals than in humans.

A new model of renal microvascular endothelial injury

Although the importance of injury with consequent activation of endothelium is well-recognized in diseases affecting the glomerular endothelial cell (GEN), research on GEN injury in vivo has been hampered by the lack of adequate animal models. Here we report the establishment and characterization of a new GEN injury model in rats. This model was induced by selective renal artery perfusion with anti-GEN IgG and resulted in the severe acute renal failure with marked platelet deposition and development of a thrombotic microangiopathy involving glomeruli. Peritubular capillary endothelial cells were also damaged that was associated with severe tubular necrosis. Although the glomerular changes were severe, half of the glomeruli recovered by day 10, while interstitial changes remained throughout our observation time course. Proliferation of GEN was observed during the recovery phase. An increased expression of endothelial nitric oxide synthase in GEN was also observed, and may be an adaptive mechanism to counteract the thrombosis and ischemia. This model should be useful to investigate the pathophysiology of renal microvascular diseases and the mechanisms of GEN injury, activation and recovery in vivo.

Predictors of the progression of renal disease in the Modification of Diet in Renal Disease Study

The Modification of Diet in Renal Disease (MDRD) Study examined the effects of dietary protein restriction and strict blood pressure control on the decline in glomerular filtration rate (GFR) in 840 patients with diverse renal diseases. We describe a systematic analysis to determine baseline factors that predict the decline in GFR, or which alter the efficacy of the diet or blood pressure interventions. Univariate analysis identified 18 of 41 investigated baseline factors as significant (P < 0.05) predictors of GFR decline. In multivariate analysis, six factors--greater urine protein excretion, diagnosis of polycystic kidney disease (PKD), lower serum transferrin, higher mean arterial pressure, black race, and lower serum HDL cholesterol--independently predicted a faster decline in GFR. Together with the study interventions, these six factors accounted for 34.5% and 33.9% of the variance between patients in GFR slopes in Studies A and B, respectively, with proteinuria and PKD playing the predominant role. The mean rate of GFR decline was not significantly related to baseline GFR, suggesting an approximately linear mean GFR decline as renal disease progresses. The 41 baseline predictors were also assessed for their interactions with the diet and blood pressure interventions. A greater benefit of the low blood pressure intervention was found in patients with higher baseline urine protein. None of the 41 baseline factors were shown to predict a greater or lesser effect of dietary protein restriction.

Rapid atrial pacing for detecting provokable demand ischemia in anesthetized patients

A stress test that can be performed intraoperatively might be valuable for cardiac risk stratification in patients needing urgent noncardiac surgery and for early evaluation of coronary reserve in patients undergoing aortocoronary bypass surgery. Therefore, we evaluated the sensitivity and safety of rapid atrial pacing combined with electrocardiography and transesophageal echocardiography for inducing and detecting provokable demand ischemia in 20 anesthetized patients with multivessel coronary artery disease. Rapid atrial pacing induced ST segment changes or new segmental wall motion abnormalities (SWMA), which were defined as evidence of induced ischemia in 15 of the 20 patients. Unexpectedly, the new SWMA normalized during the first beat after abrupt cessation of pacing in three patients who did not show any ST segment changes. Simultaneously, left ventricular preload was severely decreased during pacing and recovered to baseline immediately when pacing was abruptly discontinued. Rapid atrial pacing was safe in all patients, but the target heart rate could not be achieved because of heart block or arterial hypotension in 4 of the 20 patients. These findings raise the question of whether rapid atrial pacing is the most appropriate approach for inducing provokable demand ischemia in anesthetized patients. However, its potential usefulness for predicting adverse cardiac outcomes has not been evaluated and would require larger studies. In addition, the immediate normalization of new SWMA after abrupt cessation of pacing in some patients calls into question the validity of new SWMA as evidence of myocardial ischemia when left ventricular preload is severely decreased.

Nephrotic syndrome, renal failure, and renal malignancy: an unusual tumor-associated glomerulonephritis

The association between malignancy and glomerular disease has been appreciated for over three decades. Although the relationship between membranous glomerulonephritis or minimal-change nephrotic syndrome and carcinoma or lymphoma, respectively, are the most widely known, several other glomerular lesions have been described in patients with malignancy. In this article, a patient who presented with nephrotic syndrome, volume overload, and renal failure, who was subsequently found to have a renal mass, is described. Resection of the mass, which proved to be a renal cell carcinoma, led to resolution of proteinuria and improvement of renal function. Pathology on the noninvolved portion of the kidney revealed a membranoproliferative glomerular lesion, a lesion usually associated with lymphomas and not previously described with renal carcinoma. Although a role of tumor antigens and anti-tumor antibodies in producing glomerular immune deposits has been speculated upon, the evidence for this assertion was spotty. However, reports of remission of proteinuria after tumor treatment or removal support a role of tumor products in pathogenesis. Although the association between proteinuria and malignancy is rare, it should be kept in mind, particularly in older patients with membranous glomerulonephritis where the possibility of malignancy needs to be further evaluated.

Characterization of C3 receptors on cultured rat glomerular endothelial cells

In this study we characterized C3 receptors on cultured rat glomerular endothelial cells (GEnC), using immunochemical and molecular techniques. GEnC membrane proteins were immunoprecipitated with a polyclonal antibody directed towards mouse complement receptor 2 (CR2). This anti-MCR2 immunoprecipitated GEnC proteins of 120 and 150 kDa. By immunohistochemistry, anti-MCR2 stained GEnC in rat glomeruli in vivo. Given the presence of CR2-like proteins on GEnC, subsequent studies were done to determine whether GEnC had C3-binding proteins. GEnC proteins of 80, 200, and 300 kDa specifically bound to columns of rat C3d-Sepharose and C3b-Sepharose, illustrating that these proteins were binding to the C3d portion of C3. The 80, 200, and 300 kDa C3d-binding proteins were distinct from the 120 and 150 kDa anti-MCR2 reactive proteins, as shown by immunoabsorption studies. Next, a specific cDNA probe for rat CR2 was generated by RT-PCR. Oligonucleotides were chosen from highly conserved regions in mouse and human CR2 spanning 224 bases, with the rationale that these would also be conserved in the rat. A 224 bp PCR product was generated from both rat GEnC and rat kidney cDNA, illustrating the presence of CR2 mRNA in these tissues. By Northern analysis, the CR2 PCR product hybridized to mRNA of 2 and 5 kb from GEnC. The 5 kb transcript was also identified in rat kidney mRNA. Therefore, proteins immunologically related to mouse CR2 are present in GEnC in vitro and in vivo. C3d-binding proteins of 80, 200, and 300 kDa are also present on rat GEnC, yet these appear to be immunologically distinct from the proteins identified by anti-MCR2. Whether the GEnC CR2 mRNA transcripts of 2 and 5 kb are translated into the 80 and 200 kDa C3d-binding proteins or the 120 and 150 kDa mouse CR2-like proteins remains to be defined.

TNF-alpha regulation of C3 gene expression and protein biosynthesis in rat glomerular endothelial cells

Glomerular endothelial cells are an important site of interaction with the cellular and soluble components of inflammation. To investigate the capacity of these cells to synthesize complement they were cloned from isolated rat glomeruli. Messenger RNA (mRNA) was extracted from the cells, reverse transcribed and used as the template to identify specific gene transcripts with the polymerase chain reaction (PCR). mRNA coding for the third component of the complement cascade (C3) was detected in unstimulated endothelial cells, whereas no message for the fourth component (C4) could be demonstrated. Using a semiquantitative method of PCR, we found that the expression of C3 is up-regulated by the cytokine tumor necrosis factor-alpha (TNF-alpha), but not by the cytokines interferon-gamma (IFN-gamma) and interleukin 1 alpha (IL-1 alpha). The increase in levels of C3 mRNA occurred in a time and dose dependent manner. This increase was dependent on new protein synthesis. Production of the C3 protein was demonstrated by radiolabeling and immunoprecipitation, and this also was stimulated by TNF-alpha. In conclusion, we demonstrate the production of C3 by microvascular endothelium of glomerular origin and its stimulation by TNF-alpha. We believe that this local synthesis could have a role in the pathogenesis of disease, however, the nature of this role at present remains unclear.

The effect of transfection of antisense cDNA for procollagen alpha 1 (IV) on stimulated proliferation in rat glomerular endothelial cells

Glomerular endothelial cells were stably transfected with a pMAMneo-Blue vector recombinant for procollagen alpha 1 (IV) cDNA in the sense (S) or antisense (AS) orientation utilizing a calcium phosphate precipitation technique. Cellular clones resistant to G418 antibiotic were selected and expanded for further analysis. Immunofluorescence microscopy demonstrated less Type IV collagen in the AS clones (1.0 +/- 0.3) than in control parent (P) and S clones (2.0 +/- 0.4) (P < 0.05). Western analysis showed that the AS clones synthesized 20 +/- 10% of the 205-kd alpha 1 (IV) chain of Type IV collagen compared with P cells (P < 0.05). As transfected clones demonstrated similar basal proliferation rates as control cells when cultured in 0.5% fetal calf serum (FCS), but failed to undergo fetal calf serum (FCS)-stimulated hyperplasia when grown on standard fibronectin-coated surfaces in 40% FCS (P < 0.05, compared with P- and S-transfected control cells). There were significant linear relationships between the presence of Type IV collagen as detected by either immunofluorescence microscopy or alpha 1 (IV) peptide chain quantitation by Western analysis and the ability of cells to undergo FCS-stimulated hyperplasia when grown on fibronectin (P < 0.05). Growth on a surface comprised of fibronectin plus Type IV collagen restored the capacity of AS transfected cells to respond to FCS stimulation (P < 0.001), but had no significant effect on the proliferative behavior of P or S cells. Measurements of AS RNA levels in these cells suggest that the inhibition of stimulated proliferation is determined by the presence of a threshold quantity of cellular AS RNA. These data demonstrate that Type IV collagen plays a critical role in conditioning glomerular endothelial cells to respond to proliferative stimuli.

Is the automatic atrial defibrillator a promising approach?

Atrial fibrillation is a common arrhythmia, accounting for more consumption of medical resources than any other arrhythmia. The impact of the disease results from the combination of a loss of atrial contraction, and atrial control over cardiac rate. Studies in animals demonstrated the basic feasibility of atrial defibrillation using electrodes passed intravenously. Subsequent studies in patients confirmed that low-energy shocks were effective in converting atrial fibrillation and were safe if delivered synchronous to the R wave in the absence of a short preceding RR interval. Preliminary experience suggests that a small implanted device might provide beneficial therapy for patients with recurring episodes of persistent, drug-refractory, atrial fibrillation.

Population pharmacokinetics of ganciclovir in newborns with congenital cytomegalovirus infections. NIAID Collaborative Antiviral Study Group

The population pharmacokinetics of ganciclovir was investigated in a group of 27 newborns with symptomatic congenital cytomegalovirus infection by nonlinear mixed-effects modeling analysis. Individual characteristics including approximated creatinine clearance from serum (ASCC) and body weight (WGE) were identified to significantly influence total clearance from plasma (CL) and the apparent total volume of distribution (V) of ganciclovir, respectively. The regression equations used to model these relationships were expressed as CL (in liters per hour) = 0.262 + (0.00271 x ASCC) and V (in liters) = 0.627 + (0.437 x WGE). By using this model, typical values of the pharmacokinetic parameter CL and V were 0.428 +/- 0.079 liters/h and 1.773 +/- 0.320 liters, respectively. Upon validation with a larger number of newborns, this model should allow for the definition of possible relationships between the pharmacokinetic disposition of ganciclovir and pharmacodynamic events in neonates.

Alteration of glomerular permeability to macromolecules induced by cross-linking of beta 1 integrin receptors

Altered glomerular epithelial cell attachment to the glomerular basement membrane is an important pathogenetic factor in increased glomerular permeability to proteins. We have previously presented evidence that antibodies reactive with integrin matrix receptors on glomerular epithelial cells inhibit adhesion of these cells and may be involved in the production of proteinuria in vivo. Therefore, we utilized intact glomeruli in an in vitro system to directly assess the effect of anti-beta 1-integrin antibody on glomerular permeability. Permeability to albumin (Palb) was calculated from the volume response of glomeruli to a transcapillary oncotic gradient. Anti-beta 1-integrin increased Palb in a dose- and time-dependent manner. Palb was increased to 0.70 +/- 0.05 whereas normal rabbit IgG had no effect (0.10 +/- 0.04). F(ab')2 fragments of antibody increased Palb to a similar degree whereas Fab fragments had no effect (0.10 +/- 0.06). Cross-linking of Fab fragments, however, with a second antibody restored their ability to increase Palb (0.60 +/- 0.09), demonstrating the importance of integrin cross-linking in producing the observed effect. Intact, F(ab')2 and Fab fragments of anti-beta 1 antibody all inhibited adhesion of glomerular epithelial cells to fibronectin, laminin, and types I and IV collagen, although the degree of inhibition by Fab fragments was significantly less on collagens. No cytotoxic effects were observed with anti-beta 1 antibody or its fragments. These results suggest that antibodies to integrin matrix receptors on glomerular cells alter cell interactions with the glomerular basement membrane and lead to increased glomerular permeability to proteins via a process that is initiated by integrin cross-linking rather than through simple interference with cell adhesion per se.

Trans-acting factors dictate the species-specific placental expression of corticotropin-releasing factor genes in choriocarcinoma cell lines

CRF, in addition to its role in the hypothalamus, demonstrates species-specific expression in the placentas of higher primates, but not rodents. Transient transfections of BeWo and JEG-3 choriocarcinoma cells, as models for human trophoblasts, demonstrate regulated expression of human (h) CRF-luciferase reporter genes, whereas little or no expression is detected in other lines, including CV-1 cells. The rodent choriocarcinoma cell line, Rcho-1, a model for rodent trophoblasts, is defective in the expression of transfected hCRF genes. The mouse CRF promoter behaves similarly to the corresponding hCRF construct. It is active in BeWo and inactive in Rcho-1 cells. The transcriptional response to cAMP contributes to the specific expression of CRF. Analyses of deleted or mutated hCRF promoters identify a key role for protein kinase A-dependent pathways. A major part, but not all, of this effect is mediated by the canonical cAMP response element conserved in mouse, rat, and human CRF promoters. Additional deletions of the human CRF promoter identify control regions that also contribute to the observed species-specific expression pattern, and each identified region binds factors in nuclear extracts derived from the appropriate cell line. These studies using human and rodent choriocarcinoma cell lines as models of placental trophoblasts demonstrate dominant effects of cellular trans-acting factors, rather than DNA sequence differences, in dictating the species-specific placental expression of CRF.

Effects of dietary protein restriction on the progression of advanced renal disease in the Modification of Diet in Renal Disease Study

Patients with advanced renal disease randomized to the very low-protein diet group in the Modification of Diet in Renal Disease (MDRD) Study had a marginally (P = 0.066) slower mean glomerular filtration rate (GFR) decline compared with patients randomized to the low-protein diet group. The objective of these secondary analyses was to determine the relationship between achieved, in addition to prescribed, dietary protein intake and the progression of advanced renal disease. A randomized controlled trial was conducted in patients with chronic renal diseases of diverse etiology. The average follow-up was 2.2 years. Fifteen university hospital outpatient nephrology practices participated in the study, which comprised 255 patients aged 18 to 70 years with a baseline GFR 13 to 24 mL/min/1.73 m2 who participated in MDRD Study B. Patients with diabetes requiring insulin were excluded. The patients were given a low-protein (0.58 g/kg/d) or very low-protein (0.28 g/kg/d) diet supplemented with keto acids-amino acids (0.28 g/kg/d). Outcomes were measured by comparisons of protein intake from food or from food and supplement between randomized groups, and correlations of protein intake with rate of decline in GFR and time to renal failure or death. Comparison of the randomized groups showed that total protein intake from food and supplement was lower (P < 0.001) among patients randomized to the very low-protein diet (0.66 g/kg/d) compared with protein intake from food only in patients randomized to the low-protein diet (0.73 g/kg/d). In correlational analyses, we combined patients assigned to both diets and controlled for baseline factors associated with a faster progression of renal disease. A 0.2 g/kg/d lower achieved total protein intake (including food and supplement) was associated with a 1.15 mL/min/yr slower mean decline in GFR (P = 0.011), equivalent to 29% of the mean GFR decline. After adjusting for achieved total protein intake, no independent effect of prescription of the keto acid-amino acid supplement to slow the GFR decline could be detected. If the GFR decline is extrapolated until renal failure, a patient with a 29% reduction in the rate of GFR decline would experience a 41% prolongation in the time to renal failure. Additional analyses confirmed a longer time to renal failure in patients with lower total protein intake. In conclusion, these secondary analyses of the MDRD Study suggest that a lower protein intake, but not the keto acid-amino acid supplement, retards the progression of advanced renal disease. In patients with GFR less than 25 mL/min/1.73 m2, we suggest a prescribed dietary protein intake of 0.6 g/kg/d.

Blood pressure control, proteinuria, and the progression of renal disease. The Modification of Diet in Renal Disease Study

OBJECTIVE

To examine the relations among proteinuria, prescribed and achieved blood pressure, and decline in glomerular filtration rate in the Modification of Diet in Renal Disease Study.

DESIGN

2 randomized trials in patients with chronic renal diseases of diverse cause.

SETTING

15 outpatient nephrology practices at university hospitals.

PATIENTS

840 patients, of whom 585 were in study A (glomerular filtration rate, 25 to 55 mliters/min.1.73 m2) and 255 were in study B (glomerular filtration rate, 13 to 24 mliters/min.1.73 m2). Diabetic patients who required insulin were excluded.

INTERVENTIONS

Patients were randomly assigned to a usual blood pressure goal (target mean arterial pressure, < or = 107 mm Hg for patients < or = 60 years of age and < or = 113 mm Hg for patients > or = 61 years of age) or a low blood pressure goal (target mean arterial pressure, < or = 92 mm Hg for patients < or = 60 years of age and < or = 98 mm Hg for patients > or = 61 years of age).

MAIN OUTCOME MEASURES

Rate of decline in glomerular filtration rate and change in proteinuria during follow-up.

RESULTS

The low blood pressure goal had a greater beneficial effect in persons with higher baseline proteinuria in both study A (P = 0.02) and study B (P = 0.01). Glomerular filtration rate declined faster in patients with higher achieved blood pressure during follow-up in both study A (r = -0.20; P < 0.001) and study B (r = -0.34; P < 0.001), and these correlations were stronger in persons with higher baseline proteinuria (P < 0.001 in study A; P < 0.01 in study B). In study A, the association between decline in glomerular filtration rate and achieved follow-up blood pressure was nonlinear (P = 0.011) and was stronger at higher mean arterial pressure. In both studies, the low blood pressure goal significantly reduced proteinuria during the first 4 months after randomization. This, in turn, correlated with a slower subsequent decline in glomerular filtration rate.

CONCLUSIONS

Our study supports the concept that proteinuria is an independent risk factor for the progression of renal disease. For patients with proteinuria of more than 1 g/d, we suggest a target blood pressure of less than 92 mm Hg (125/75 mm Hg). For patients with proteinuria of 0.25 to 1.0 g/d, a target mean arterial pressure of less than 98 mm Hg (about 130/80 mm Hg) may be advisable. The extent to which lowering blood pressure reduces proteinuria may be a measure of the effectiveness of this therapy in slowing the progression of renal disease.

Integrated case studies and medical decision making: a novel, computer-assisted bridge from the basic sciences to the clinics

This article describes a novel course that was designed to bridge the gap between the basic science years and clinical experiences in medical school by using information science and computer technology as major components of problem-based learning (PBL) sessions. The course, Integrated Case Studies and Medical Decision Making, was first given to second-year students at the University of Pittsburgh School of Medicine in the spring of 1994. It consists of 13 PBL exercises, each of which explores a clinical case. The cases, including images and gated access to information, are housed on a computer. Using one of 16 networked terminals in specially designed small-group rooms, groups of nine students progress through the cases with a faculty facilitator. The responses of students and faculty to the initial year of the course were favorable. In comparison with traditional PBL sessions, enhanced quality of and access to images and accountability for accessing case information in sequential fashion were cited as major strengths of the course. Juxtaposition of basic science and clinical material and utility in reviewing for the United States Medical Licensing Examination were also cited as strengths. The diversity of the basic science material involved in completing the cases drew overwhelming enthusiasm from students and facilitators alike. In conclusion, the course successfully employs computer and information science technology, which will be of increasing importance to future physicians. The course also serves as an effective bridge to the clinical years of medical school and as a study adjunct for the USMLE.

The undergraduate medical curriculum: centralized versus departmentalized

The authors describe the advantages and disadvantages of central governance of the undergraduate medical curriculum as contrasted with traditional departmental approaches, based upon their school's experience with a new centrally governed curriculum during the preceding four years. Central governance has more advantages, but also more costs, compared with traditional departmental approaches. Central governance does what it was intended to do: it provides rational and integrative mechanisms for ensuring a broad general education in medicine focusing on the doctor-patient relationship. It also provides an effective mechanism for dealing with "turf" and time issues in the curriculum while allowing for and encouraging changes and providing mechanisms for evaluating those changes. However, as the allocation of resources and rewards remains more departmentally than centrally based, a major challenge of central governance has been to help faculty resolve a "conflict of loyalty" (the sense of serving two masters) between school and department, particularly in the evaluation and reward of teaching. On balance, central governance provides a powerful means of introducing broad-based reforms into all elements of the undergraduate medical curriculum, but it requires ongoing collaboration with faculty and chairs to assist them in negotiating competing pressures and priorities as they strive to become excellent teachers.

Complement regulation in the rat glomerulus: Crry and CD59 regulate complement in glomerular mesangial and endothelial cells

The complement regulators, decay accelerating factor, membrane cofactor protein, and CD59 are present in human glomeruli. Crry is the rodent analogue to the former two proteins. In this study, we examined complement regulation in cultured rat glomerular endothelial cells (GEnC) and mesangial cells (MES). Immunoprecipitation of 125I-labeled membrane proteins and Western blotting studies were performed with anti-Crry and anti-CD59. In both GEnC and MES, Crry was present as 53, 65, and 78 kD proteins. The 20 kD CD59 was apparent in GEnC. CD59 was also present in MES, but in relatively smaller quantities. By Northern analyses, 1.8 kb CD59 mRNA was present in GEnC as well as in RNA from isolated rat glomeruli. mRNA for Crry was present in both GEnC and MES as 2.2 kb species. The functional significance of these proteins was evaluated next. Anti-Thy 1.1 IgG was used to activate the complement classical pathway in MES. To inhibit the function of the complement regulators, anti-CD59 and/or anti-Crry F(ab')2 antibodies were added with anti-Thy 1.1. Inhibition of Crry function led to enhanced cytotoxicity, while there was no effect when CD59 function was inhibited. The complement alternative pathway was studied by adding complement in Mg-EGTA buffer. Inhibition of Crry led to productive alternative pathway activation, which was accentuated by anti-CD59 when Crry was incompletely inhibited. Alternative pathway regulation was also evaluated in GEnC. Inhibition of CD59 function alone had no effect in GEnC, while inhibition of Crry led to significant cytotoxicity from alternative pathway activation. Under conditions in which Crry was inactive, inhibition of CD59 further enhanced cytotoxicity. Therefore, Crry is present in both GEnC and MES and restricts the complement alternative pathway in both cell types. Crry also regulates the classical pathway in MES. CD59 is present and functionally active in GEnC, while it appears to have a minor role in MES.

[Vaso-occlusive crises in sickle-cell anemia]

HISTORY AND FINDINGS

Severe pain suddenly occurred in the shaft of the right thigh in a 21-year-old patient of Turkish descent with known homozygotic sickle cell anaemia. He also had marked scleral jaundice and anaemia (haemoglobin 9.1 g/dl). An X-ray film of the lower leg pointed to a bone infarct. Type of pain, partial pressure of oxygen in blood (70 mm Hg), concentration of lactate dehydrogenase and the bilirubin level (4,5 mg/dl) as signs of haemolysis, as well as the fall in haemoglobin, indicated a vascular occlusive crisis in sickle cell anaemia.

TREATMENT AND COURSE

The symptoms regressed within 8 days of the patient receiving fluids, analgesics and oxygenation by nasal tube. A few weeks later he developed a fever, productive cough and severe pain in joints and abdomen. Blood p02 was 54 mm Hg. Pneumonia in the right lung base was the cause of this renewed life-threatening crisis, which was again associated with haemolysis. Klebsiella having been found in sputum he was treated with cefotaxim (1 g twice daily intravenously) and oxygen insufflation via nasal tube (7 l/min). His condition quickly improved.

CONCLUSIONS

In patients with sickle cell anaemia it is important (1) to regard crises as potentially life-threatening conditions, (2) to detect and treat infections as possible causes early and (3) to provide sufficient oxygen insufflation quickly, especially in pulmonary infections.

Estrogenic activity of RU 486 (mifepristone) in rat uterus and cultured uterine myocytes

OBJECTIVE

Our purpose was to determine whether RU 486 (mifepristone) has direct estrogenic activity in uterine myocytes.

STUDY DESIGN

Ovariectomized adult rats were treated with RU 486, and its effect on uterine oxytocin receptor concentration, as a marker of estrogenic activity, was measured. Results were compared with the induction by RU 486 of an estrogen-responsive reporter gene in a cultured Syrian hamster uterine myocyte cell line.

RESULTS

Baseline oxytocin receptor concentration was 58.8 +/- 7.2 fmol/mg protein (mean +/- SEM) and increased to 227 +/- 49 fmol/mg with 17 beta-estradiol (2.5 micrograms/kg) and to 145 +/- 18 fmol/mg after RU 486 (5 mg/kg) treatment, an effect that was inhibited by the antiestrogen ICI 182,780 (1.5 mg/kg). In the cultured Syrian hamster uterine myocyte cell line cells RU 486 (10(-6) mol/L) caused a 2.17 +/- 0.17-fold increase in the expression of the reporter gene versus 113.0 +/- 7.4-fold with 17 beta-estradiol (10(-8) mol/L). The estrogenic activity of RU 486 was dependent on the presence of both estrogen receptor and the promoter's estrogen response element.

CONCLUSION

RU 486 has a weak estrogen-like activity in uterine myocytes. This activity may partly explain the therapeutic effects of RU 486 on this target organ.

Crinkling of epicardial defibrillator patches. A common and serious problem

The durability and reliability of the implantable cardioverter-defibrillator epicardial patch systems have not been reported. In 128 consecutive patients such systems manufactured by Cardiac Pacemakers, Inc. (St. Paul, Minn.) or Medtronic, Inc. (Minneapolis, Minn.) were implanted with 100% follow-up to investigate the rate of patch crinkling and its consequences. A total of 122 patients survived the operation (operative mortality, 6 patients: 4.7%). Ninety-four patients received Cardiac Pacemakers, Inc. AICD patches and 28 received Medtronic PCD patches. Patients had chest x-ray studies every 3 to 6 months and function of the defibrillator was checked every 3 months. Late mortality occurred in 17 patients (13%) leaving a total of 105 long-term survivors (82%) to the present. Among 122 survivors, severe crinkling of the patches occurred in 48 patients--33 in the Cardiac Pacemakers, Inc. AICD group (36%) and 15 in the PCD group (54%)--within 2 years of the implant. Crinkling of patches caused not only malfunction of the system, but also cardiac pain in three patients. Crinkling occurred as early as 2 months after implant and progressed throughout the period of observation. Fourteen patients later required implant of an additional transvenous defibrillator because of failure of the epicardial system. The percentage of transvenous implantable cardioverter-defibrillator systems needed was higher for the Medtronic group (28%) than for the Cardiac Pacemakers, Inc. AICD group (6.3%). Both systems have shown an unacceptably high rate of patch crinkling that occurs in a relatively short time. There is no difference whether a thoracotomy or midline sternotomy is used or whether the patches are implanted intrapericardially or extrapericardially. The quest should continue for a better patch system design.

Effect of rapid correction of hyponatremia on the blood-brain barrier of rats

Brain demyelination sometimes follows rapid correction of hyponatremia, especially if the hyponatremia is chronic. During correction brain water decreases and the brain shrinks. The present study examined whether such shrinkage might be sufficient to disrupt the tight junctions of the blood-brain barrier. Barrier intactness was evaluated using magnetic resonance imaging and intravenous gadolinium contrast administration. Hypertonic saline infusion rapidly increased the plasma sodium concentration and caused barrier disruption more frequently in chronic than in acute hyponatremic rats. Similar increases in plasma sodium concentration did not disrupt the barrier in normonatremic rats. The disruption appeared to be due to altered plasma osmolality since infusion of hypertonic mannitol, which raised plasma osmolality without changing the plasma sodium concentration, disrupted the barrier in hyponatremic but not normonatremic rats. Moreover, the osmotic threshold for barrier disruption was lowest in chronic hyponatremia, intermediate in acute hyponatremia, and highest in normonatremia. The greater susceptibility to osmotic disruption in chronic hyponatremia suggests that blood-brain barrier disruption may play a significant role in causing the demyelination sometimes found following too rapid correction of hyponatremia, possibly through exposure of oligodendrocytes to plasma macromolecules such as complement.

Differential positive and negative transcriptional regulation by tamoxifen

Tamoxifen, a nonsteroidal antiestrogen and breast cancer chemotherapeutic, exhibits both estrogen agonist and antagonist properties. Rat GC3 cells grown under estrogen-free conditions were analyzed for the expression of model luciferase reporter genes, either positively or negatively regulated by estrogens. Expression assays adding tamoxifen alone or in combination with 17 beta-estradiol were performed to determine agonist or antagonist activities. In rat GC3 cells, tamoxifen acts as an estrogen antagonist for gene activation, but as an agonist for repression. Regulation by tamoxifen is mediated by estrogen receptor (ER), not via nonreceptor tamoxifen effects. Evaluation of human ER shows that although the wild-type receptor behaves similarly to the rat receptor, the Gly400 to Val400 mutant receptor does not. Tamoxifen, an effective agonist for gene repression with rat and wild-type receptor, shows no agonist activity using this mutated Val400 receptor. Yet, 17 beta-estradiol and clomiphene, another mixed agonist/antagonist, are effective agonists for gene repression with all three receptors. In this model system, tamoxifen functions as antagonist or agonist, depending on whether the ER acts to activate or repress its gene target. In other systems regulated by estrogens, functional analyses of ER action might also serve to predict the agonist or antagonist activity of tamoxifen.

Multiple-sensor systems for physiologic cardiac pacing

PURPOSE

To review the status of artificial sensors in cardiac pacemakers and the rationale for developing pacing systems that use multiple sensors.

DATA SOURCES

Journal articles published between 1982 and 1993 indexed in MEDLINE using the keywords pacemakers, sensors, and rate-adaptive, as well as abstracts and articles in the authors' personal files.

STUDY SELECTION

Articles describing clinical experience with or clinical evaluation of cardiac pacing systems using multiple artificial sensors.

DATA SYNTHESIS

Artificial sensors were created to adjust pacing rate reliably in response to changes in levels of physical exertion for patients with sinoatrial disease in whom exercise heart rate response is inadequate (for example, chronotropic incompetence in sinoatrial disease). To achieve this, various artificial sensors were developed and many reports confirm improved exertional tolerance. More recently, sensors have assumed a greater role in cardiac pacemakers. For example, sensors are used to permit automatic adjustment of certain programmable pacemaker settings, such as the atrioventricular interval. In the future, they may also be used to maximize pacemaker longevity by automatically optimizing energy output (voltage, pulse width). No single sensor is ideal for all potential applications, and investigators have advocated using two or more sensors. Several pacemakers that use multiple sensors with different but complementary operating characteristics are already commercially available outside the United States. Although preliminary findings are encouraging, additional clinical experience with these pacemakers is needed to determine their ultimate role in clinical practice.

CONCLUSION

Simultaneous use of multiple complementary artificial sensors may permit development of cardiac pacemakers that operate more physiologically yet require less specialized medical follow-up.

Structure-function relationships associated with extracellular matrix alterations in diabetic glomerulopathy

Proteinuria and progressive renal insufficiency are the primary manifestations of diabetic nephropathy. Accumulating evidence suggests that these clinical features can be linked, at least in part, to pathologic changes in the glomerular extracellular matrix. Most evidence suggests that glomerular basement membrane thickening and mesangial matrix expansion consist of at least three elements. These are (1) an accumulation of normal extracellular components; (2) an increase in the novel peptide chains of the normal components of Type IV collagen; and (3) an increase in matrix elements not normally expressed in the glomerulus. The pathogenetic features underlying these changes include increased synthesis and decreased degradation of matrix. Abnormal physico-chemical interactions among these matrix elements likely contribute to alterations in three-dimensional structure, leading to proteinuria and loss of glomerular basement membrane filtering surface area. Many of these changes may be explained in whole or in part by direct or secondary effects of hyperglycemia, as well as by hemodynamic changes.

T cell epitope analysis with peptides simultaneously synthesized on cellulose membranes: fine mapping of two DQ dependent epitopes

Several MHC class II restricted, CD4+ human T cell clones from three donors were induced with soluble matrix protein of influenza virus. The epitopes recognized by these clones were mapped using a complete set of overlapping 15-mer peptides synthesized with the newly developed SPOT method which allows the simple simultaneous synthesis of numerous peptides on cellulose membranes. Fine analysis of two clones by truncation of the stimulatory peptide by single subsequent amino acids from either the NH2- or the COOH-terminus revealed the minimal stimulatory determinants of two DQ dependent T cell epitopes.

Brain buffering is restored in hyponatremic rats by correcting their plasma sodium concentration

Previous studies from this laboratory showed that both acute and chronic hyponatremia impaired active brain buffering. These studies were performed to determine whether correcting the plasma sodium restored normal buffering in hyponatremic rats. Acute (1- and 2-day) and chronic (7- and 14-day) hyponatremia was induced in male Sprague-Dawley rats by constant desmopressin administration combined with a liquid diet. Plasma sodium was corrected by stopping desmopressin for 6 h, substituting solid chow, and allowing free access to water. Studies were performed 24 h later. Uncorrected hyponatremic rats who continued to receive desmopressin and liquid diet served as controls. Brain pH was determined by [31P]NMR in rats anesthetized with N2O and paralyzed with pancuronium. Brain buffering was determined by the response to CO2 loading. Resting brain pH was the same in corrected and uncorrected rats, but the two groups responded differently to CO2 loading. Thus, 55 min after ventilation with 20% CO2, corrected rat brain pH was 0.13 pH units higher than in uncorrected rats despite statistically similar changes in CO2 tension and arterial pH in both groups. Moreover, 15 min into recovery from CO2 exposure, brain pH in corrected rats overshot resting pH by 0.07, whereas no overshoot occurred in uncorrected rats. Buffering in corrected rats was identical to that shown previously in normonatremic rats. The complete restoration of late-phase buffering achieved by normalizing the plasma sodium of hyponatremic rats indicates that at least some portion of active hydrogen ion transport is sodium dependent in the brain.

Chronotherapy with 5-fluorouracil and folinic acid in advanced colorectal carcinoma. Results of a chronopharmacologic phase I trial

BACKGROUND

Chronotherapy with antineoplastic drugs is a rather new strategy of reducing cytotoxic side effects. Because the circadian timing of 5-fluorouracil (5-FU) was reported to result in a higher efficacy and lower toxicity, the authors conducted a chronopharmacologic Phase I trial with 5-FU and folinic acid (FA).

METHODS

Eight patients with advanced colorectal cancer received 5-FU (initial dose of 500 mg/m2/day) and FA (20 mg/m2/day) as a continuous intravenous infusion over 5 consecutive days. Using a portable, ambulatory drug delivery system, 75% of the daily dose of 5-FU and FA were given from Oh00-7h00, and the remaining 25% from 7h00-24h00. Treatment courses were repeated after 28 days. Dose escalations of 250 mg/m2/day of 5-FU and 10 mg/m2/day of FA per course were performed in the absence of any toxicity greater than WHO (World Health Organization) grade 2.

RESULTS

Dose-limiting toxicity WHO grade 3 was observed at a dose of 750 mg/m2/day of 5-FU and 30 mg/m2/day of FA in five, and 1000 mg/m2/day of 5-FU and 40 mg/m2/day of FA in two patients, respectively. One patient tolerated 1000 mg/m2/day of 5-FU and 40 mg/m2/day of FA, but the treatment was stopped before further dose escalation because of rapid disease progression. Mucositis was the dose-limiting toxicity in seven patients and diarrhea in two. Disease stabilization occurred in three patients and disease progression in five. Compared with conventional Phase I/II trials using a 5-day infusion regimen, the maximal tolerated dose of 5-FU and FA was slightly higher but significantly lower than in a chronotherapeutic trial that used a different, sinusoidal mode of drug application.

CONCLUSION

Based on these results, the authors feel justified to caution that the circadian timing of 5-FU plus FA may not always allow the safe application of high dose levels. Future Phase I/II studies need to define whether specific drug delivery systems or schedules are necessary for chronotherapy with 5-FU and FA in patients with colorectal carcinoma.

Positive inotropic effects of the beta 2-adrenoceptor agonist terbutaline in the human heart: effects of long-term beta 1-adrenoceptor antagonist treatment

OBJECTIVES

This study was conducted to determine whether activation of cardiac beta 2-adrenoceptors increases contractility in humans and whether this is affected by long-term beta 1-adrenoceptor antagonist treatment.

BACKGROUND

Coexistence of beta 1- and beta 2-adrenoceptors in the human heart is generally accepted. The functional importance of cardiac beta 2-adrenoceptors for increases in contractility in humans, however, has not been completely established.

METHODS

We studied 1) the beta-adrenoceptor subtype mediating positive inotropic effects of the beta 2-adrenoceptor agonist terbutaline in vitro (on right atrial and left ventricular preparations from nonfailing human hearts) and increases in contractility (by measurement of systolic time intervals) in vivo in seven healthy male volunteers; and 2) in vivo whether long-term treatment of volunteers with the beta 1-adrenoceptor antagonist bisoprolol affects terbutaline-induced increases in contractility.

RESULTS

In vitro terbutaline caused a concentration-dependent increase in atrial and ventricular adenylate cyclase activity and force of contraction. Terbutaline effects were antagonized only by the beta 2-adrenoceptor antagonist ICI 118,551, indicating that they were mediated by beta 2-adrenoceptor stimulation. In vivo intravenous infusions of terbutaline (dose range 25 to 300 ng/kg body weight per min for 15 min) dose dependently increased heart rate and shortened the pre-ejection period and heart rate-corrected electromechanical systole (QS2) time. These effects are mediated predominantly by beta 2-adrenoceptor stimulation because they were only marginally affected by the beta 1-adrenoceptor antagonist bisoprolol (1 x 10 mg orally), either given 2 h before infusion or long term for 3 weeks.

CONCLUSIONS

Stimulation of cardiac beta 2-adrenoceptors in humans causes not only in vitro but also in vivo positive inotropic effects. Long-term beta 1-adrenoceptor antagonist treatment does not considerably affect beta 2-adrenoceptor-mediated in vivo increases in contractility. Thus, it may be possible to treat patients with chronic heart failure and long-term beta 1-adrenoceptor antagonist therapy with beta 2-adrenoceptor agonists if immediate inotropic support is needed.

Perfusion imaging of the rat kidney with MR

PURPOSE

To develop a technique for measurement of regional renal perfusion with magnetic resonance (MR) imaging.

MATERIALS AND METHODS

Quantitative renal perfusion images in rats were obtained by measurement of the reduction in kidney MR image signal intensity after steady state magnetic labeling of arterial blood in the suprarenal aorta. Labeling was achieved with adiabatic fast passage inversion of arterial water.

RESULTS

Cortical renal blood flow was 4.9 mL/g/min +/- 0.15 (12 rats), which correlated well with previous measurements obtained with other techniques. Serial perfusion images obtained every 5 minutes during intravenous infusion of either acetylcholine or angiotensin II showed that one increased and the other decreased renal blood flow, respectively, also correlating with previous measurements.

CONCLUSION

Quantitative measurement of cortical renal blood flow can be obtained with proton MR imaging techniques, with use of endogenous arterial water as a tracer. This technique should be readily applicable to measurement of renal perfusion in humans.

Integrin matrix receptors in renal injury

Integrins play a major role in cell-matrix interactions. They alter cellular functions upon binding to matrix proteins or following cross linking and can in turn be regulated by other stimuli acting on the cell. In the kidney integrins may help regulate cellular proliferation and matrix turnover during renal injury, effects which could play an important role in the pathogenesis of glomerulosclerosis and the resultant loss of renal function. Alterations in cell adhesiveness may contribute to tubular epithelial cell sloughing and tubular obstruction in acute renal failure and may play a role in alterations of glomerular capillary wall permeability, leading to proteinuria. Adhesion molecules on GEC may be important targets of antibodies in several models of proteinuric renal disease and areas of GEC detachment from the GBM may be involved in the development of glomerulosclerosis. Since integrins are major links between the ECM and cells, better understanding of their function in the normal kidney and during injury is of importance to a better understanding of the pathogenesis of renal disease.