Biomedical subjects
Publications and source records attributed to J Ludwig.
The injection of a dopamine D(2) receptor hammerhead ribozyme (20 microg) once daily for 5 days into the nucleus accumbens of rats resulted in an inhibition of stereotyped sniffing and locomotor activation produced by the selective dopamine D(2) receptor agonist, quinpirole (0.4 mg kg(-1) s.c.). The results suggest that ribozymes may be useful in the study of in vivo gene function in the brain.
BACKGROUND: Hemodynamic improvement is a common finding following valve replacement. However, despite a normally functioning prosthesis and normal left ventricular ejection fraction, some patients may show an abnormal hemodynamic response to exercise. METHODS: In a combined catheter/Doppler study, rest and exercise hemodynamics were evaluated in 23 patients following aortic (n = 12) (Group 1) or mitral valve (n = 11) (Group 2) replacement and compared with preoperative findings. Patient selection was based on absence of coronary artery disease and left ventricular failure as shown by preoperative angiography. Cardiac output, pulmonary artery pressure, pulmonary capillary pressure, and pulmonary resistance were measured by right heart catheterization, whereas the gradient across the valve prosthesis was determined by Doppler echocardiography. Postoperative evaluation was done at rest and during exercise. The mean follow-up was 8.2 +/- 2.2 years in Group 1 and 4.2 +/- 1 years in Group 2. RESULTS: With exercise, there was a significant rise in cardiac output in both groups. In Group 1, mean pulmonary pressure/capillary pressure decreased from 24 +/- 9/18 +/- 9 mmHg preoperatively to 18 +/- 2/12 +/- 4 mmHg postoperatively (p < 0.05), and increased to 43 +/- 12/30 +/- 8 mmHg with exercise (p < 0.05). The corresponding values for Group 2 were 36 +/- 12/24 +/- 6 mmHg preoperatively, 24 +/- 7/17 +/- 6 mmHg postoperatively (p < 0.05), and 51 +/- 2/38 +/- 4 mmHg with exercise (p < 0.05). Pulmonary vascular resistance was 109 +/- 56 dyne.s.cm-5 preoperatively, 70 +/- 39 dyne.s.cm-5 postoperatively (p < 0.05), and 70 +/- 36 dyne.s.cm-5 with exercise in Group 1. The corresponding values for Group 2 were 241 +/- 155 dyne.s.cm-5, 116 +/- 39 dyne.s.cm-5 (p < 0.05), and 104 +/- 47 dyne.s.cm-5. There was a significant increase in the gradients across the valve prosthesis in both groups, showing a significant correlation between the gradient at rest and exercise. No correlation was found between valve prosthesis gradient and pulmonary pressures. CONCLUSION: Exercise-induced pulmonary hypertension and abnormal left ventricular filling pressures seem to be a frequent finding following aortic or mitral valve replacement. Both hemodynamic abnormalities seem not to be determined by obstruction to flow across the valve prosthesis and may be concealed, showing nearly normal values at rest but a pathologic response to physical stress.
Previously, we found appreciable hepatic iron deposition in one third of our patients undergoing liver transplantation (LTx) with approximately 10% of cases having quantifiable iron in the range of that seen in hereditary hemochromatosis (HHC). The aim of this study was to compare clinical outcome in liver transplant patients with and without iron overload. We also sought to determine the prevalence of HFE mutations in liver transplant patients with iron overload. Of 456 consecutive liver transplants, 41 explants had an hepatic iron index (HII) greater than 1.9, and these cases were compared to 41 matched liver transplant recipients without increased hepatic iron. Posttransplantation complications, along with patient and graft survival were monitored. HFE gene testing was performed using DNA-based techniques. Kaplan-Meier 5-year patient survival after LTx was significantly lower in cases with hepatic iron overload compared to matched controls without iron excess (48% vs. 77%; P =.045). Fatal infections (especially fungal) were more common in patients with iron overload (24% vs. 7%; P =.03). Of the 41 patients with a liver explant HII greater than 1.9, only 4 were C282Y homozygotes. Patients with severe hepatic explant iron overload undergoing LTx have a reduced survival compared to liver transplant recipients without explant iron excess. The reduced survival was attributable mainly to fatal bacterial and fungal infections. Despite the iron overload, HFE gene mutations were uncommon in patients with hepatic explant hemosiderosis.
A second mammalian gene for the ether-à-go-go (eag) potassium channel has been cloned from the rat, and its predicted protein sequence is 70% identical to that of rat ether-à-go-go1 with a further 10% conservatively replaced residues. The rat eag2 mRNA was predominantly expressed in neural tissue and was not detected in adult skeletal, cardiac, or smooth muscle. Within the brain, its distribution overlaps that of rat ether-à-go-go1 in specific regions within the cortex and olfactory bulb, but was differentially distributed in other locations, being scanty within the cerebellum, and most notably present in the thalamus, inferior colliculus, and certain brainstem nuclei. Heterologous expression of rat eag2 in HEK-293 cells gave rise to a voltage-gated, noninactivating potassium current, active at the cells' resting potential and blocked by low nanomolar concentrations of cytosolic calcium. Thus, in neurones, this current is likely to impart a modulation in membrane conductance, which is sensitively responsive to resting internal calcium, and levels of electrical activity.
Primary biliary cirrhosis is the prototype of the small-duct biliary diseases which are characterized by damage or destruction of interlobular and proximal septal bile ducts. Autoimmune cholangitis differs serologically from primary biliary cirrhosis but, by current consensus, has the same pathological features. The histological findings in primary biliary cirrhosis and the staging criteria of that disease are well described and at this point can be applied to autoimmune cholangitis also. Diagnostic difficulties arise either because other small-duct biliary diseases are not considered or because tell-tale histological signs, particularly ductopenia, are not recognized. Review of all small-duct biliary diseases suggests that interlobular and adjacent septal bile ducts (1st and 2nd generation ducts) represent an immunosensitive portion of the biliary tree. Comparative studies of these unique segments may have important implications for our understanding of primary biliary cirrhosis and autoimmune cholangitis and possibly for future treatment options for these conditions.
OBJECTIVE: Cholestasis may result from diverse etiologies. We review chronic cholestatic disorders involving small intrahepatic bile ducts in the adult ambulatory care setting. Specifically, we discuss variant forms of primary biliary cirrhosis (PBC) and primary sclerosing cholangitis (PSC) as well as other conditions that may present diagnostic and therapeutic difficulties. METHODS: We conducted a MEDLINE search of the literature (1981-1997) and reviewed the experiences at the Mayo Clinic. All articles were selected that discussed antimitochondrial antibody (AMA)-negative PBC, small-duct PSC (formerly pericholangitis), and idiopathic adulthood ductopenia. RESULTS: The most common chronic cholestatic liver diseases affecting adults are PBC and PSC. Patients without the hallmarks of either syndrome are diagnosed according to their clinical and histological characteristics. Autoimmune cholangitis is diagnosed if clinical and histological features are compatible with PBC but autoantibodies other than AMA are present. Isolated small duct PSC is diagnosed if patients have inflammatory bowel disease, biopsy features compatible with PSC, but a normal cholangiogram. If ductopenia (absence of interlobular bile ducts in small portal tracts) is found histologically in the absence of PSC, inflammatory bowel disease, and other specific cholestatic syndromes such as drug reaction or sarcoidosis, the most likely diagnosis is idiopathic adulthood ductopenia. CONCLUSIONS: Based on these definitions, an algorithm for diagnosis and therapy in patients with laboratory evidence of chronic cholestasis may be constructed, pending results of further investigations into the etiopathogenesis of these syndromes.
PURPOSE: To evaluate the efficacy of fabric-covered endoprostheses for percutaneous repair of traumatic iliac artery lesions. METHODS: Among 47 patients treated for catheter-induced iliac artery injuries, 20 (42%) patients (13 men; mean age 58 +/- 10 years, range 41-76) presented with acute (n = 7) or subacute (n = 13) lesions considered inappropriate for bare stent implantation (17 dissecting aneurysms, 2 perforations, and 1 traumatic arteriovenous fistula). The self-expanding Cragg EndoPro System I or Passager devices were deployed percutaneously to exclude the defects. RESULTS: Immediate exclusion of the lesion was achieved in all 20 cases; there were no major procedural complications. However, within 24 hours after implantation, fever (n = 11, 55%) and elevations in white blood cell count (n = 10, 50%) and C-reactive protein (n = 13, 65%) were seen in the majority of patients, which prolonged hospitalization in this group (8.4 versus 4.2 days). During a median 21-month follow-up (range 5-31), 2 angiographically documented restenoses at the outlet of the endografts were treated successfully with balloon angioplasty, achieving primary and secondary patency rates of 87% and 100%, respectively. CONCLUSIONS: Early model stent-grafts provided a safe and effective endovascular treatment for iliac perforations and large arterial dissections, showing a high mid-term patency rate. However, postimplantation syndrome appears to occur frequently with this type of Dacron-covered nitinol device.
Many diseases are closely tied to deficient or subnormal metabolic and secretory cell functions. Milder forms of these diseases can be managed by a variety of treatments. However, it is often extremely difficult or even impossible to imitate the moment-to-moment fine regulation and the complex roles of the hormone, factor or enzyme that is not sufficiently produced by the body. Immunoisolated transplantation is one of the most promising approaches to overcome the limitations of current treatments. Non-autologous (transformed) cell lines and allogeneic and xenogeneic cells/tissues that release the therapeutic substances are enclosed in immunoprotective microcapsules. The microcapsules avoid a lifetime of immunosuppressive therapy while excluding an immune response in the host. Research in this direction has shown the feasibility of microcapsules based on hydrogels (particularly of alginate) for transplantation of non-autologous cells and tissue fragments. Numerous technical accomplishments of the immunoisolation method have recently made possible the first successful long-term clinical applications. However, realizing the potential of immunoisolated therapy requires the use of several factors that have received limited attention in the past but are important for the formulation of hydrogel-based immunoisolation systems that are highly versatile, potentially economical and can gain medical approval.
Voltage-dependent K+ channels open when depolarizing the membrane voltage. Among the different alpha-subunits, the time course of current activation spreads over a wide range. The structural basis underlying this diversity is not known. We constructed multiple chimeras between two voltage-dependent K+ channels, the rapidly activating Kv1.2 and the slowly activating Kv2.1, and we focused on the C-terminal half of the core region. The general strategy was to substitute parts of Kv2.1 by corresponding parts of Kv1.2 and to test for an acceleration of activation. We identified three regions which contribute to the determination of the activation kinetics: the S5-pore linker, the deep pore, and the S4-segment.
Inward-rectifier K(+) channels of the ROMK (K(ir)1.1) subtype are responsible for K(+) secretion and control of NaCl absorption in the kidney. A hallmark of these channels is their gating by intracellular pH in the neutral range. Here we show that a lysine residue close to TM1, identified previously as a structural element required for pH-induced gating, is protonated at neutral pH and that this protonation drives pH gating in ROMK and other K(ir) channels. Such anomalous titration of this lysine residue (Lys-80 in K(ir)1.1) is accomplished by the tertiary structure of the K(ir) protein: two arginines in the distant N and C termini of the same subunit (Arg-41 and Arg-311 in K(ir)1.1) are located in close spatial proximity to the lysine allowing for electrostatic interactions that shift its pK(a) into the neutral pH range. Structural disturbance of this triad as a result from a number of point mutations found in patients with antenatal Bartter syndrome shifts the pK(a) of the lysine residue off the neutral pH range and results in channels permanently inactivated under physiological conditions. Thus, the results provide molecular understanding for normal pH gating of K(ir) channels as well as for the channel defects found in patients with antenatal Bartter syndrome.
CONTEXT: The cost of treating gunshot injuries imposes a financial burden on society. Estimates of such costs are relevant to evaluation of gun violence reduction programs and may help guide reimbursement policies. OBJECTIVES: To develop reliable US estimates of the medical costs of treating gunshot injuries and to present national estimates for the sources of payment for treating these injuries. DESIGN AND SETTING: Cost analysis using E-coded discharge data from hospitals in Maryland for 1994-1995 and New York for 1994 and from emergency departments in South Carolina for 1997. Other sources of data included the National Electronic Injury Surveillance System for 1994 incidence of nonfatal gun injuries, the National Spinal Cord Injury Statistical Center database for 1988-1992 estimates of lifetime medical costs of gun injuries, and the 1994 Vital Statistics census for incidence of fatal gun injuries. MAIN OUTCOME MEASURES: Estimated national acute-care and follow-up treatment costs and payment sources for gunshot injuries. RESULTS: At a mean medical cost per injury of about $17000, the 134445 (95% confidence interval [CI], 109465-159425) gunshot injuries in the United States in 1994 produced $2.3 billion (95% CI, $2.1 billion-$2.5 billion) in lifetime medical costs (in 1994 dollars, using a 3% real discount rate), of which $1.1 billion (49%) was paid by US taxpayers. Gunshot injuries due to assaults accounted for 74% of total costs. CONCLUSIONS: Gunshot injury costs represent a substantial burden to the medical care system. Nearly half this cost is borne by US taxpayers.
Cyclic nucleotide-gated (CNG) channels play an important role in Ca2+ signaling in many cells. CNG channels from various tissues differ profoundly in their Ca2+ permeation properties. Using the voltage-dependent Ca2+ blockage of monovalent current in wild-type channels, chimeric constructs and point mutants, we have identified structural elements that determine the distinctively different interaction of Ca2+ with CNG channels from rod and cone photoreceptors and olfactory neurons. Segments S5 and S6 and the extracellular linkers flanking the pore region are the only structural elements that account for the differences between channels. Ca2+ blockage is strongly modulated by external pH. The different pH dependence of blockage suggests that the pKa of intrapore glutamates and their protonation pattern differ among channels. The results support the hypothesis that the S5-pore-S6 module, by providing a characteristic electrostatic environment, determines the protonation state of pore glutamates and thereby controls Ca2+ affinity and permeation in each channel type.
Recurrence of primary sclerosing cholangitis (PSC) following liver transplantation has been suggested; however, it has not been fully defined because of numerous complicating factors and the lack of diagnostic criteria. In the present study, we investigated the recurrence of PSC by developing strict criteria and applying them to a large cohort of PSC patients who underwent liver transplantation. Between March 1985 and June 1996, 150 PSC patients underwent liver transplantation at the Mayo Clinic; mean follow up was 55 months. The incidence of nonanastomotic biliary strictures and hepatic histologic findings suggestive of PSC were compared between patients transplanted for PSC and a non-PSC transplant control group. Our definition of recurrent PSC was based on characteristic cholangiographic and histologic findings that occur in nontransplant PSC patients. By using strict criteria, 30 patients with other known causes of posttransplant nonanastomotic biliary strictures were excluded leaving 120 patients for analysis of recurrence of PSC. We found evidence of PSC recurrence after liver transplantation in 24 patients (20%). Of these, 22 out of 24 patients showed characteristic features of PSC on cholangiography and 11 out of 24 had compatible hepatic histologic abnormalities with a mean time to diagnosis of 360 and 1,350 days, respectively. Both cholangiographic and hepatic histologic findings suggestive of PSC recurrence were seen in nine patients. The higher incidence and later onset of nonanastomotic biliary strictures in patients with PSC compared with a non-PSC control group is supportive of the fact that PSC does recur following liver transplantation. We were unable to identify specific clinical risk factors for recurrent PSC, and the overall patient and graft survival in patients with recurrent PSC was similar to those without evidence of recurrence. Our observations provide convincing evidence that PSC frequently recurs in the hepatic allograft using strict inclusion and exclusion criteria.
The decision about operative or non-operative treatment of herniated lumbar discs has to be based on the results of clinical and neurological examination. Results of imaging techniques as CT or MRI are secondary. Various percutaneous endoscopic or open techniques have been described. The most appropriate technique is determined by the anatomical situation of the dislocated lumbar disc tissue. Intradiscal percutaneous therapies such as percutaneous nucleotomy and laser decompression are possible, but they revealed poor results in prospective randomized and controlled studies. Chemonucleolysis remains as an effective intradiscal technique at the time, but is afflicted with side effects and complications. Endoscopic transforaminal or interlaminary techniques are still experimental. Whenever open surgery is necessary, microsurgical techniques are preferred. If a certain technique is to be applied, there has to be the correct indication, technical support for and experience in using the choosen method.
In the summer of 1992, morbidity and mortality in juvenile double-crested cormorants (Phalacrocorax auritus; DCC) attributable to Newcastle disease virus (NDV) was observed for the first time in seven northern USA states and one Canadian province, and recurred in three western Canadian provinces. Based on clinical signs and laboratory diagnostic findings, DCC mortality from NDV occurred in 59 of the 63 nesting colonies and two of three non-colony sites investigated. An estimate of in excess of 20,000 DCC died, with mortality rates ranging from < 1 to 37% in Great Lakes colonies to 20 to 92% in Minnesota (USA) and North and South Dakota (USA) colonies. Sick juvenile white pelicans (Pelecanus erythrorhynchos) exhibiting signs similar to sick cormorants, and dead pelicans were observed in Minnesota and North Dakota. Mortality rates in pelican colonies were as high as in the adjacent cormorant colonies, but no cause for the mortality of an estimated 5,000 pelicans was determined. No evidence of NDV was found in other species nesting in proximity to affected cormorants. Although the source of the NDV infection is unknown in cormorants, the simultaneous onset of the epizootics in juvenile birds over a wide geographic area implies that the virus was acquired by adults prior to migration and was carried back to nest sites, exposing susceptible nestlings. The possible transmission of this virus from free-ranging wild birds to domestic poultry is a concern. Based on repeated epizootics in cormorants since 1990, NDV seems to be established in DCC.
1. Screening of rat cortex cDNA resulted in cloning of two complete and one partial orthologue of the Drosophila ether-à-go-go-like K+ channel (elk). 2. Northern blot and reverse transcriptase-polymerase chain reaction (RT-PCR) analysis revealed predominant expression of rat elk mRNAs in brain. Each rat elk mRNA showed a distinct, but overlapping expression pattern in different rat brain areas. 3. Transient transfection of Chinese hamster ovary (CHO) cells with rat elk1 or rat elk2 cDNA gave rise to voltage-activated K+ channels with novel properties. 4. RELK1 channels mediated slowly activating sustained potassium currents. The threshold for activation was at -90 mV. Currents were insensitive to tetraethylammonium (TEA) and 4-aminopyridine (4-AP), but were blocked by micromolar concentrations of Ba2+. RELK1 activation kinetics were not dependent on prepulse potential like REAG-mediated currents. 5. RELK2 channels produced currents with a fast inactivation component and HERG-like tail currents. RELK2 currents were not sensitive to the HERG channel blocker E4031.
In this paper, we show that an adenosine to inosine mutation at position 15.1 changes the substrate specificity of the hammerhead ribozyme from N16.2U16.1H17to N16.2C16.1H17(H represents A, C or U). This result extends the hammerhead cleavage triplet definition from N16.2U16.1H17to the more general N16.2Y16.1H17. Comparison of cleavage rates using I15.1ribozymes for NCH triplets and standard A15.1 ribozymes for NUH triplets under single turnover conditions shows similar or slightly enhanced levels of reactivity for the I15. 1-containing structures. The effect of I15.1 substitution was also tested in nuclease-resistant 2'- O -alkyl substituted derivatives (oligozymes), showing a similar level of activity for the NUH and NCH cleaving structures. The availability of NCH triplets that can be targeted without loss of efficiency increases the flexibility of ribozyme targeting strategies. This was demonstrated by an efficient cleavage of an HCV transcript at a previously inaccessible GCA site in codon 2.
Vacuolar proton-translocating ATPase (holoATPase and free membrane sector) was isolated from bovine chromaffin granules by blue native polyacrylamide gel electrophoresis. A 5-fold excess of membrane sector over holoenzyme was determined in isolated chromaffin granule membranes. M9.2, a novel extremely hydrophobic 9.2-kDa protein comprising 80 amino acids, was detected in the membrane sector. It shows sequence and structural similarity to Vma21p, a yeast protein required for assembly of vacuolar ATPase. A second membrane sector-associated protein (M8-9) was identified and characterized by amino-terminal protein sequencing.