Mutation analysis in patients with Wilson disease: identification of 4 novel mutations. Mutation in brief no. 250. Online

In order to obtain novel mutations in the recently discovered Wilson disease gene, we screened 5 unrelated German individuals for mutations in the 21 exons and their flanking intronic sequences. We detected 9 mutations affecting the Wilson disease gene. Four of those, designated 802-808delTGTAAGT, 2008-2013delTATATG, Cys985Thr, and Ile1148Thr have not yet been reported. One patient had a homozygous mutation whereas the remaining four subjects were compound heterozygous. Therefore these data confirm, that mutations causing Wilson disease are frequently found in affected subjects and they are very heterogenous.

Improvement of acute and chronic renal dysfunction in liver transplant patients after substitution of calcineurin inhibitors by mycophenolate mofetil

BACKGROUND

Renal dysfunction caused by treatment with the calcineurin inhibitors (CNI) is a major problem in the long-term course after liver transplantation.

PATIENTS

In 22 liver graft recipients with renal dysfunction and stable graft function between 3 weeks and 12 years after transplantation, CNI were substituted by MMF at a final dose of 1.5-3 g/day between October 1996 and October 1998.

METHODS

In a prospective non-randomized study, the development of renal function, the side effects of MMF medication, and the stability of liver function were analyzed for a mean follow-up of 15 months. Results. (1) MMF was withdrawn in four patients for major side effects between 1 and 7 months after study entry; eight patients had minor side effects. (2) Six months after study entry, renal function had improved in 17 of the 22 study patients; mean serum creatinine +/-SD (micromol/L) was 201+/-77 at entry and 153+/-65 after 3 months (P<0.001). (3) Improvement occurred in 11 of 15 patients with creatinine elevation > or =12 months and in 6 of 6 patients with creatinine elevation < or =6 months. (4) One patient developed transient liver dysfunction and a second required retransplantation for progressive cholestasis but without signs of rejection.

CONCLUSIONS

In patients who undergo liver transplantation, substitution of CNI by MMF leads to improvement of acute as well as chronic renal dysfunction in most cases. Side effects of MMF may be limiting in some patients, and the immunological consequences remain to be studied.

Allosteric regulation of neuronal nitric oxide synthase by tetrahydrobiopterin and suppression of auto-damaging superoxide

The underlying mechanisms regulating the activity of the family of homodimeric nitric oxide synthases (NOSs) and, in particular, the requirement for (6R)-5,6,7,8-tetrahydro-L-biopterin (H(4)Bip) are not fully understood. Here we have investigated possible allosteric and stabilizing effects of H(4)Bip on neuronal NOS (NOS-I) during the conversion of substrate, L-arginine, into L-citrulline and nitric oxide. Indeed, in kinetic studies dual allosteric interactions between L-arginine and H(4)Bip activated recombinant human NOS-I to increase L-arginine turnover. Consistent with this was the observation that H(4)Bip, but not the pterin-based NOS inhibitor 2-amino-4,6-dioxo-3,4,5,6,8,8a,9,10-octahydrooxazolo[1, 2-f]-pteridine (PHS-32), caused an L-arginine-dependent increase in the haem Soret band, indicating an increase in substrate binding to recombinant human NOS-I. Conversely, L-arginine was observed to increase in a concentration-dependent manner H(4)Bip binding to pig brain NOS-I. Secondly, we investigated the stabilization of NOS quaternary structure by H(4)Bip in relation to uncoupled catalysis. Under catalytic assay conditions and in the absence of H(4)Bip, dimeric recombinant human NOS-I dissociated into inactive monomers. Monomerization was related to the uncoupling of reductive oxygen activation, because it was inhibited by both superoxide dismutase and the inhibitor N(omega)-nitro-L-arginine. Importantly, H(4)Bip was found to react chemically with superoxide (O(2)(-.)) and enzyme-bound H(4)Bip was consumed under O(2)(-.)-generating conditions in the absence of substrate. These results suggest that H(4)Bip allosterically activates NOS-I and stabilizes quaternary structure by a novel mechanism involving the direct interception of auto-damaging O(2)(-.).

Electron-paramagnetic resonance spectroscopy using N-methyl-D-glucamine dithiocarbamate iron cannot discriminate between nitric oxide and nitroxyl: implications for the detection of reaction products for nitric oxide synthase

Purified neuronal nitric oxide synthase (NOS) does not produce nitric oxide (NO) unless high concentrations of superoxide dismutase (SOD) are added, suggesting that nitroxyl (NO(-)) or a related molecule is the principal reaction product of NOS, which is SOD-dependently converted to NO. This hypothesis was questioned by experiments using electron paramagnetic resonance spectroscopy and iron N-methyl-D-glucamine dithiocarbamate (Fe-MGD) as a trap for NO. Although NOS and the NO donor S-nitroso-N-acetyl-penicillamine produced an electron paramagnetic resonance signal, the NO(-) donor, Angeli's salt (AS) did not. AS is a labile compound that rapidly hydrolyzes to nitrite, and important positive control experiments showing that AS was intact were lacking. On reinvestigating this crucial experiment, we find identical MGD(2)-Fe-NO complexes both from S-nitroso-N-acetyl-penicillamine and AS but not from nitrite. Moreover, the yield of MGD(2)-Fe-NO complex from AS was stoichiometric even in the absence of SOD. Thus, MGD(2)-Fe directly detects NO(-), and any conclusions drawn from MGD(2)-Fe-NO complexes with respect to the nature of the primary NOS product (NO, NO(-), or a related N-oxide) are invalid. Thus, NOS may form NO(-) or related N-oxides instead of NO.

Endothelial nitric-oxide synthase (type III) is activated and becomes calcium independent upon phosphorylation by cyclic nucleotide-dependent protein kinases

Endothelial nitric-oxide synthase (NOS-III) is defined as being strictly dependent on Ca(2+)/calmodulin (CaM) for activity, although NO release from endothelial cells has been reported to also occur at intracellular free Ca(2+) levels that are substimulatory for the purified enzyme. We demonstrate here that NOS-III, but neither NOS-I nor -II, is rapidly and strongly activated and phosphorylated on both Ser and Thr in the presence of cGMP-dependent protein kinase II (cGK II) and the catalytic subunit of cAMP-dependent protein kinase (cAK) in vitro. Phosphopeptide analysis by mass spectrometry identified Ser(1177), as well as Ser(633) which is situated in a recently defined CaM autoinhibitory domain within the flavin-binding region of human NOS-III. Phosphoamino acid analysis identified a putative phosphorylation site at Thr(495) in the CaM-binding domain. Importantly, both cAK and cGK phosphorylation of NOS-III in vitro caused a highly reproducible partial (10-20%) NOS-III activation which was independent of Ca(2+)/CaM, and as much as a 4-fold increase in V(max) in the presence of Ca(2+)/CaM. cAK stimulation in intact endothelial cells also increased both Ca(2+/)CaM-independent and -dependent activation of NOS-III. These data collectively provide new evidence for cAK and cGK stimulation of both Ca(2+)/CaM-independent and -dependent NOS-III activity, and suggest possible cross-talk between the NO and prostaglandin I(2) pathways and a positive feedback mechanism for NO/cGMP signaling.

Evidence against a role of physiological concentrations of estrogen in post-myocardial infarction remodeling

OBJECTIVES

The purpose of this study was to examine whether endogenous estrogen deficiency induced by ovariectomy affects chronic left ventricular dysfunction post-myocardial infarction (MI).

BACKGROUND

Epidemiologic findings suggest that mortality of postmenopausal women is increased after MI, but the underlying mechanisms are unknown.

METHODS

Rats were either not ovariectomized (non-OVX), ovariectomized (OVX) or ovariectomized and treated with subcutaneous 17-beta-estradiol (E2) pellets (OVX + E2). Two weeks later, animals were sham-operated (Sham) or left coronary artery ligated (MI). Eight weeks later, in vivo echocardiographic and hemodynamic measurements were performed. Thereafter, hearts were isolated and perfused isovolumically.

RESULTS

Mean infarct size was similar among the three MI groups. Ovariectomy decreased serum E2 levels (11 +/- 4 vs. 49 +/- 11 pg/ml in non-OVX, p < 0.01) and increased body weight. These changes were reversed by E2 replacement. The degree of cardiac hypertrophy was similar for all groups post-MI. Left ventricular diameters were increased post-MI (8.9 +/- 0.4 in non-OVX + MI vs. 6.7 +/- 0.2 mm in non-OVX + Sham hearts, p < 0.0001), but OVX or OVX + E2 replacement did not alter left ventricular diameters in post-MI and Sham hearts. Left ventricular fractional shortening was severely impaired post-MI (19 +/- 2% vs. 50 +/- 3 in non-OVX + Sham hearts, p < 0.0001) with no influence of hormonal status. Left ventricular end-diastolic pressure, measured in vivo, was increased in all MI groups without significant differences between groups. Pressure-volume curves, obtained in perfused hearts, demonstrated a right and downward shift with reduced maximum left ventricular developed pressure post-MI (75 +/- 6 vs. 108 +/- 3 mm Hg in non-OVX + Sham hearts, p < 0.001) and were also unaffected by either OVX or E2 replacement.

CONCLUSIONS

Chronic endogenous estrogen deficiency does not have major effects on the development of cardiac hypertrophy, dysfunction and dilation post-MI.

Inhibition of neuronal nitric oxide synthase by 4-amino pteridine derivatives: structure-activity relationship of antagonists of (6R)-5,6,7,8-tetrahydrobiopterin cofactor

The family of nitric oxide synthases (NOS) catalyzes the conversion of L-arginine to L-citrulline and nitric oxide (NO), an important cellular messenger molecule which has been implicated in the pathophysiology of septic shock and inflammatory and neurodegenerative disease states. NOS can be maximally activated by the ubiquitous cofactor, (6R)-5,6,7,8-tetrahydrobiopterin (H(4)Bip), and antagonists of H(4)Bip may be of therapeutic importance to inhibit pathologically high NO formation. The 4-amino substituted analogue of H(4)Bip was reported to be a potent NOS inhibitor. Therefore, we developed a series of novel 4-amino pteridine derivatives, anti-pterins, to pharmacologically target the neuronal isoform of nitric oxide synthase (NOS-I). To functionally characterize the pterin/anti-pterin interaction and establish a structure-activity relationship (SAR), we systematically altered the substituents in the 2-, 4-, 5-, 6-, and 7-position of the pteridine nucleus. Varying the substitution pattern in the 2-, 5-, and 7-position resulted in no significant inhibitory effect on enzyme activity. In contrast, bulky substituents in the 6-position, such as phenyl, markedly increased the inhibitory potency of the reduced 4-amino-5,6,7,8-tetrahydropteridines, possibly as a consequence of hydrophobic interactions within NOS-I. However, this was not the case for the aromatic 4-amino pteridines. Interestingly, chemical modification of the 4-amino substituent by dialkyl/diaralkylation together with 6-arylation of the aromatic 2,4-diamino pteridine resulted in potent and efficacious inhibitors of NOS-I, suggesting possible hydrophilic and hydrophobic interactions within NOS-I. This SAR agrees with (a) the recently published crystal structure of the oxygenase domain of the inducible NOS isoform (NOS-II) and (b) the comparative molecular field analysis of selected NOS-I inhibitors, which resulted in a 3D-QSAR model of the pterin binding site interactions. Further optimization should be possible when the full length structure of NOS-I becomes available.

Biochemical and functional characterization of nitric oxide synthase III gene transfer using a replication-deficient adenoviral vector

Nitric oxide (NO) produced in endothelial cells has been implicated in the regulation of blood pressure, regional blood flow, inhibition of platelet aggregation, and endothelial and vascular smooth muscle cell proliferation. In a variety of cardiovascular disease states, such as atherosclerosis, arterial hypertension, and restenosis, expression of endothelial NO synthase (NOS-III) and endothelial NO production appear to be altered. Thus, NOS-III is an attractive target for cardiovascular gene therapy for which adenoviral vectors are one of the most effective vector systems. Therefore, a recombinant adenoviral vector expressing NOS-III (adenovirus type 5 [Ad5] cytomegalovirus [CMV] NOSIII) was constructed and biochemically and pharmacologically characterized both in vitro and in intact cells. Ad5CMVNOSIII-derived recombinant NOS-III was successfully expressed, as shown by immunoprecipitation and immunocytochemistry, and biologically active, as shown by functional assays in human primary umbilical vein and EA.hy926 endothelial cells, as well as 293 human embryonic kidney and Chinese hamster ovary cells. The Km values for NADPH and L-arginine and the Ka for tetrahydrobiopterin as well as the enzyme's dependency on other cofactors were similar to recombinant reference enzyme and literature values. NOS-III expression levels correlated linearly with the multiplicity of infection with Ad5CMVNOSIII and lasted for at least 8 days. NOS-III transfection inhibited endothelial cell proliferation. In conclusion, adenovirus-mediated gene transfer of Ad5CMVNOSIII to vascular and nonvascular cells resulted in the dose-dependent expression of intact, physiologically regulated, and functionally active NOS-III.

Downregulation of soluble guanylyl cyclase in young and aging spontaneously hypertensive rats

Endothelial dysfunction, as observed in hypertension and atherosclerosis, is associated with a reduction in the bioavailability of endothelium-derived nitric oxide (NO). We tested the hypothesis that alterations in the soluble guanylyl cyclase (sGC) pathway may also contribute to the pathogenesis of hypertension. Therefore, we investigated the expression and activity of sGC in young (6 weeks) and aging (17 months) spontaneously hypertensive (SHR) and normotensive Wistar-Kyoto rats (WKY). Endothelium-independent relaxation of aortic rings in response to the sGC activator YC-1 was attenuated in SHR, and expression of both alpha(1) and beta(1) subunits of heterodimeric sGC and the basal contents of cGMP were reduced specifically in SHR aorta. Moreover, mRNA expression of the cGMP receptor and effector protein cGMP-dependent protein kinase type Ialpha (cGKIalpha) was also reduced. Interestingly, downregulation of both sGC and cGKIalpha expression was observed in young, ie, normotensive SHR, whereas impairment of the endothelium-independent relaxation was found only in aging SHR. Accordingly, similar cGMP levels were reached in response to YC-1 in young SHR and young WKY, suggesting a compensatory increased sensitivity or effectiveness of the sGC pathway in young SHR. In aging SHR, however, increased sensitivity to YC-1 no longer compensated for the impairment of endothelium-independent relaxation, suggesting that other mechanisms were involved. In fact, endothelium-independent relaxations were partially restored by superoxide dismutase, suggesting a pathophysiological role of superoxide production, particularly at later disease stages. Thus, tissue-specific downregulation of components of the sGC/cGMP pathway is an early event in the pathogenesis of hypertension.

Nitric oxide synthase-containing projections to the ventrobasal thalamus in the rat

Microiontophoretic studies of thalamic neurons suggests that nitric oxide (NO) plays an important role in mediating somatosensory transmission. The thalamus contains few nitric oxide synthase (NOS)-immunoreactive neurons; thus, the major source of thalamic NO is presumably from NOS-positive axons of extrathalamic origin. The cells of origin of these putative NOS-containing pathways to the ventrobasal thalamus were investigated in rats by combining retrograde tracing with immunocytochemistry for NOS. The location and morphology of double-labeled neurons was compared with that of single-labeled neurons. The most significant sources of NOS-containing afferents to the thalamus were found to be the pedunculopontine (PPN) and laterodorsal tegmental (LDT) nuclei. NOS-immunoreactive neurons in these cholinergic nuclei project bilaterally to the thalamus, most strongly ipsilaterally. The thalamus appears to be a major target of PPN, since even selective thalamic injections result in retrograde labeling of at least one third of its NOS-immunoreactive neurons. A significant number of NOS-negative neurons in both the PPN and LDT also project to the thalamus. Minor sources of NOS-containing thalamic afferents include the lateral hypothalamus, the dorsal, median and pontine raphe nuclei, the parabrachial nuclei, and the pontomedullary reticular formation. In all these structures, NOS-negative thalamopetal neurons greatly outnumber the NOS-positive ones. Ascending sensory pathways to the thalamus, including those from the sensory trigeminal nuclei, the dorsal column nuclei, and the spinal cord, as well as the auditory and vestibular centers, arise exclusively from NOS-negative neurons. The major NOS-positive projections are implicated in affective and alerting systems, supporting that NO may act to modulate attentiveness in thalamic relay nuclei.

Intravenous administration of recombinant adenoviruses causes thrombocytopenia, anemia and erythroblastosis in rabbits

BACKGROUND

Recombinant adenoviruses are highly efficient gene transfer vehicles but their administration to mammals is accompanied by a strong inflammatory response. The present study reports additional side effects observed during adenoviral gene transfer studies in rabbits.

METHODS

Hematological and serological parameters, the course of viremia and the organ distribution were analyzed after in vivo administration of E1-deleted adenoviruses in rabbits.

RESULTS

The systemic administration of a therapeutic dose of 5 x 10(11) infectious particles/kg (infusion time 20 min) led to an average reduction of 80-90% in the platelet count within 48 h. Full recovery took 10-14 days. Virus administration induced a strong but transient erythroblastosis (peaking 24 h after administration) which settled 48 h later. Normochromic anemia occurred over the next 10 days with hemoglobin levels dropping by about 40% to reach the lowest level 10 days after administration and taking two months for full recovery. Dose-dependent thrombocytopenia was also found in mice, but neither erythroblastosis nor anemia was observed (in equivalent doses). The hematological findings did not improve after local injection via the portal vein. Local and systemic administration led to a comparable course of viremia. Only minor differences were found in the biodistribution of viruses between local and systemic administration. Large amounts of viral DNA and transgene expression were found in the lungs, the kidneys and the ovaries, even after local administration via the portal vein.

CONCLUSIONS

Local intravenous injection via the portal vein does not prevent systemic spread of viral vectors and the occurrence of vector-related side effects. The hematological changes observed in rabbits suggest the need for careful monitoring of hematological and rheological parameters in clinical trials.

Tetrahydrobiopterin inhibits monomerization and is consumed during catalysis in neuronal NO synthase

The biosynthesis of nitric oxide (NO) is catalyzed by homodimeric NO synthases (NOS). For unknown reasons, all NOS co-purify with substoichiometric amounts of (6R)-5,6,7,8-tetrahydrobiopterin (H(4)Bip) and require additional H(4)Bip for maximal activity. We examined the effects of H(4)Bip and pterin-derived inhibitors (anti-pterins) on purified neuronal NOS-I quaternary structure and H(4)Bip content. During L-arginine turnover, NOS-I dimers time dependently dissociated into inactive monomers, paralleled by a loss of enzyme-associated pterin. Dimer dissociation was inhibited when saturating levels of H(4)Bip were added during catalysis. Similar results were obtained with pterin-free NOS-I expressed in Escherichia coli. This stabilizing effect of H(4)Bip was mimicked by the anti-pterin 2-amino-4,6-dioxo-3,4,5,6,8,8a,9, 10-octahydro-oxazolo[1,2f]-pteridine (PHS-32), which also displaced NOS-associated H(4)Bip in a competitive manner. Surprisingly, H(4)Bip not only dissociated from NOS during catalysis, but was only partially recovered in the solute (50.0 +/- 16.5% of control at 20 min). NOS-associated H(4)Bip appeared to react with a NOS catalysis product to a derivative distinct from dihydrobiopterin or biopterin. Under identical conditions, reagent H(4)Bip was chemically stable and fully recovered (95.5 +/- 3.4% of control). A similar loss of both reagent and enzyme-bound H(4)Bip and dimer content was observed by NO generated from spermine NONOate. In conclusion, we propose a role for H(4)Bip as a dimer-stabilizing factor of neuronal NOS during catalysis, possibly by interfering with enzyme destabilizing products.

Attitudes of patients before and after transplantation towards various allografts

BACKGROUND

The presence of an allogeneic graft inside the body may have psychological impact on transplant patients. It was the aim of this study to evaluate the attitude of patients before and after different types of organ transplantation towards organ allografts.

METHODS

A total of 1,049 patients (722 patients after and 327 patients on the waiting list for either kidney, liver, heart, or lung transplantation) under care of a single transplant center were studied using a questionnaire with blinded analysis of the data. Mental condition of the patients, their attitude towards the allograft and its donor, emotional stress caused by a graft, and correlation of the attitudes with clinical and demographic parameters were analyzed.

RESULTS

The self-reported mental condition of the patients was markedly and consistently better after organ transplantation; 27% of patients before and 60% after transplantation were in good mental condition. Sixty-two percent of transplant patients considered the graft as their own organ, 37% regarded it as a foreign organ now belonging to their body, and 1% considered it as a foreign body; among waiting list patients, 40%, 55%, and 5% assumed they would perceive their graft accordingly. The graft caused considerable emotional stress for 2% of transplant patients, whereas for 70% it did not cause any stress; the latter was assumed by 47% of patients before transplantation. Eleven percent of transplant patients frequently think about the origin of their graft, and 30% would like to have information about their donor. Knowledge about different religion, opposite sex, homosexuality, suicidal death, and age above 65 years of their donor would be of moderate or major concern for 0%, 3%, 21%, 24%, and 38% of the patients, respectively.

CONCLUSIONS

The comprehensive survey shows that transplant patients incorporate their graft well into their body image. Emotional stress caused by the graft is very low and is generally less than assumed before transplantation. Knowledge about certain characteristics of the donor may cause increased concerns in some patients.

The soluble guanylyl cyclase inhibitor 1H-[1,2,4]oxadiazolo[4,3,-a] quinoxalin-1-one is a nonselective heme protein inhibitor of nitric oxide synthase and other cytochrome P-450 enzymes involved in nitric oxide donor bioactivation

Soluble guanylyl cyclase (sGC) is an important effector for nitric oxide (NO). It acts by increasing intracellular cyclic GMP (cGMP) levels to mediate numerous biological functions. Recently, 1H-[1,2, 4]oxadiazolo[4,3,-a]quinoxalin-1-one (ODQ) was identified as a novel and selective inhibitor of this enzyme. Therefore, ODQ may represent an important pharmacological tool for differentiating cGMP-mediated from cGMP-independent effects of NO. In the present study, we examined the inhibitory action of ODQ both functionally and biochemically. In phenylephrine-preconstricted, endothelium-intact, isolated aortic rings from the rat, ODQ, in a concentration-dependent manner, increased contractile tone and inhibited relaxations to authentic NO with maximal effects at 3 microM. Pretreatment of vascular rings with ODQ induced a parallel, 2-log-order shift to the right of the concentration-response curves (CRCs) to histamine, ATP, NO, the NO-donors S-nitrosoglutathione, S-nitroso-N-acetyl-D,L-penicillamine, and spermine NONOate [N-[4-[1-(3-amino propyl)-2-hydroxy-2-nitroso hydrazino]butyl]-1, 3-propane diamine], and the direct sGC-stimulant [3-(5'-hydroxymethyl-2'furyl)-1-benzyl indazole] YC-1 but did not affect relaxations induced by papaverine and atriopeptin II. Moreover, the rightward shift of the CRCs to Angeli's salt, peroxynitrite, and linsidomine was similar to that of NO. These results suggested that ODQ is specific for sGC. Furthermore, they indicate that NO can cause vasorelaxation independent of cGMP. Three interesting exceptions were observed to the otherwise rather uniform inhibitory effect of ODQ: the responses to acetylcholine, glycerol trinitrate, and sodium nitroprusside. The latter two agents are known to require metabolic activation, possibly by cytochrome P-450-type proteins. The 3- to 5-log-order rightward shift of their CRCs suggests that, in addition to sGC, ODQ may interfere with heme proteins involved in the bioactivation of these NO donors and the mechanism of vasorelaxation mediated by acetylcholine. In support of this notion, ODQ inhibited hepatic microsomal NO production from both glycerol trinitrate and sodium nitroprusside as well as NO synthase activity in aortic homogenates. The latter effect seemed to require biotransformation of ODQ. Collectively, these data reveal that ODQ interferes with various heme protein-dependent processes in vascular and hepatic tissue and lacks specificity for sGC.

Inosine(15.1) hammerhead ribozymes for targeting the transthyretin-30 mutation

The most common cause of hereditary amyloidosis (HA) is the val30met mutation in the transthyretin protein (TTR-met30). The mutation is caused by a mononucleic substitution from G to A (GUC to AUC) in the transthyretin gene resulting in the exchange for the amino acids valine to methionine in the corresponding protein sequence. The aim of our work was the development of a specific cleavage of TTR-30 mRNA using hammerhead ribozymes. We chemically modified nuclease stable hammerhead ribozymes to target the TTR-30 mRNA with high specificity. The exchange of adenosine(15.1) with inosine(15.1) in the catalytic core of the hammerhead ribozyme resulted in a change of the cleavable target sequence from N(16.2)U(16.1)H(17) to N(16. 2)C(16.1)H(17) without loss in ribozymal activity (Nucleic Acids Res. 26, 2279-2285, 1998). This modification allowed a specific cleavage of the TTR-30 mutation ("gCC Gug" to "gCC Aug"). In vitro experiments with TTR-30 mRNA demonstrated that the RNase stable inosine(15.1) hammerhead ribozyme cleaved the TTR-30 mRNA with 100% specificity and with a velocity of 0.23 min(-1), whereas no cleavage occured in the wildtype mRNA of TTR. In conclusion, the development of this NCH specific hammerhead ribozyme represents a promising tool for future in vivo therapeutic application for TTR-met30 induced hereditary amyloidosis.

Homodimerization of soluble guanylyl cyclase subunits. Dimerization analysis using a glutathione s-transferase affinity tag

Soluble guanylyl cyclase (sGC) is an alpha/beta-heterodimeric hemoprotein that, upon interaction with the intercellular messenger molecule NO, generates cGMP. Although the related family of particulate guanylyl cyclases (pGCs) forms active homodimeric complexes, it is not known whether homodimerization of sGC subunits occurs. We report here the expression in Sf9 cells of glutathione S-transferase-tagged recombinant human sGCalpha1 and beta1 subunits, applying a novel and rapid purification method based on GSH-Sepharose affinity chromatography. Surprisingly, in intact Sf9 cells, both homodimeric GSTalpha/alpha and GSTbeta/beta complexes were formed that were catalytically inactive. Upon coexpression of the respective complementary subunits, GSTalpha/beta or GSTbeta/alpha heterodimers were preferentially formed, whereas homodimers were still detectable. When subunits were mixed after expression, e.g. GSTbeta and beta or GSTalpha and beta, no dimerization was observed. In conclusion, our data suggest the previously unrecognized possibility of a physiological equilibrium between homo- and heterodimeric sGC complexes.

Autoinhibition of neuronal nitric oxide synthase: distinct effects of reactive nitrogen and oxygen species on enzyme activity

Nitric oxide (NO) synthases (NOSs), which catalyse the oxidation of L-arginine to L-citrulline and an oxide of nitrogen, possibly NO or nitroxyl (NO-), are subject to autoinhibition by a mechanism that has yet to be fully elucidated. In the present study we investigated the actions of NO and other NOS-derived products as possible autoregulators of enzyme activity. With the use of purified NOS-I, L-arginine turnover was found to operate initially at Vmax (0-15 min, phase I) although, despite the presence of excess substrate and cofactors, prolonged catalysis (15-90 min, phase II) was associated with a rapid decline in L-arginine turnover. Taken together, these observations suggested that one or more NOS products inactivate NOS. Indeed, exogenously applied reactive nitrogen oxide species (RNSs) decreased Vmax during phase I, although with different potencies (NO->NO> ONOO-) and efficacies (NO>NO-=ONOO-). The NO scavengers oxyhaemoglobin (HbO2; 100 microM) and 1H-imidazol-1 - yloxy - 2 - (4-carboxyphenyl) - 4,5 - dihydro - 4,4,5,5 - tetramethyl - 3 -oxide (CPTIO; 10 microM) and the ONOO- scavenger GSH (7 mM) had no effect on NOS activity during phase I, except for an endogenous autoinhibitory influence of NO and ONOO-. However, superoxide dismutase (SOD; 300 units/ml), which is thought either to increase the half-life of NO or to convert NO- to NO, lowered Vmax in an NO-dependent manner because this effect was selectively antagonized by HbO2 (100 microM). This latter observation demonstrated the requirement of SOD to reveal endogenous NO-mediated autoinhibition. Importantly, during phase II of catalysis, NOS became uncoupled and began to form H2O2 because catalase, which metabolizes H2O2, increased enzyme activity. Consistent with this, exogenous H2O2 also inhibited NOS activity during phase I. Thus during catalysis NOS is subject to complex autoinhibition by both enzyme-derived RNS and H2O2, differentially affecting enzyme activity.

Multiple mechanisms are involved in the acute vasodilatory effect of 17beta-estradiol in the isolated perfused rat heart

The purpose of this study was to define the dose-dependent effects of 17beta-estradiol on coronary flow and cardiac function in isolated rat hearts and to identify the mechanisms involved in its vasodilator action. Hearts from female and male Wistar rats were perfused at constant pressure (100 mm Hg). Stereoisomer specificity and the mechanism of vasodilation by 17beta-estradiol were examined in female rat hearts. Function was measured by a left ventricular (LV) balloon and coronary flow (CF) with an ultrasonic flowmeter. 17Beta-estradiol at 10(-6), 5 x 10(-6), and 10(-5) M increased CF in female hearts by 5 +/- 2, 27 +/- 4 (p < 0.05 vs. baseline), and 40 +/- 4% (p < 0.05 vs. baseline), respectively. The effect of 17beta-estradiol in hearts from male rats was similar but less pronounced compared with females [deltaCF 8 +/- 3, 19 +/- 3 (p < 0.05 vs. baseline)] and 25 +/- 7% (p < 0.05 vs. baseline; p < 0.05 vs. female 17beta-estradiol). Maximum vasodilation by the stereoisomer 17alpha-estradiol was significantly smaller [deltaCF 5 +/- 3, 4 +/- 3 (p < 0.05 vs. female 17beta-estradiol) and 14 +/- 1% (p < 0.05 vs. baseline; p < 0.05 vs. female 17beta-estradiol)] for 10(-6), 5 x 10(-6), and 10(-5) M. Pretreatment with the NO-synthesis inhibitor Nomega-methyl-L-arginine (10(-4) M) had no effect on the maximal vasodilator response to 17beta-estradiol (10(-5) M) [deltaCF 36 +/- 6% (p < 0.05 vs. baseline)]. When hearts were pretreated with the prostaglandin-synthesis inhibitor diclofenac (10(-6) M), the maximal vasodilator effect of 17beta-estradiol was partially attenuated [deltaCF 12 +/- 7% (p < 0.05 vs. female 17beta-estradiol)]. Similarly, pretreatment with the K+ATP-blocker glibenclamide (10(-6) M) partially inhibited the maximal vasodilator effect of 17beta-estradiol [deltaCF 22 +/- 6% (p < 0.05 vs. baseline; p < 0.05 vs. female 17beta-estradiol)]. Pretreatment with the Ca2+ channel antagonist nifedipine (7.2 x 10(-8) M) completely blocked the vasodilator effect. In isolated perfused rat hearts, 17beta-estradiol induced marked acute coronary vasodilation; this effect is in part gender specific, and in female hearts, largely stereoisomer specific. The dilator effect is mediated predominantly by calcium channel blockade, but prostaglandin release and K+ATP channel activation also are involved. In the isolated perfused rat heart, NO production does not contribute to the acute vasodilator effect of 17beta-estradiol.

Cytotoxic versus genotoxic effects of nitric oxide (NO)

The pathobiochemistry of endogenous reactive nitrogen species includes functions in inflammation and carcinogenesis. Genotoxicity has been suggested to play a major role. Two donor compounds, spermine NONOate, which can release authentic nitric oxide (NO), and 3-Morpholino-sydnonimine hydrochloride (SIN-1), which generates NO together with superoxide, possibly yielding peroxynitrite (ONOO-), were investigated in L5178Y mouse lymphoma cells for cytotoxic and genotoxic effects. As demonstrated by cell growth, 'micronucleus' and 'comet' assays NO, with and without concomitant superoxide formation, did not induce significant genotoxicity at concentrations with low cytotoxicity. Therefore, at least for the three tested parameters and the chosen time window, the pronounced cytotoxicity exhibited by NO and its oxidative metabolites most likely outweighs any genotoxic potential.

ABL amplification in a patient with lymphoid blast crisis of chronic myelogenous leukaemia

Although chronic phase myelogenous leukaemia (CML) is characterised by the Philadelphia (Ph) chromosome leading to a fusion of the BCR and ABL genes, additional genetic alterations involved in blast crisis are poorly understood. We report an at least 15-fold amplification of the ABL oncogene in a 29-year-old male patient with a variant Ph-positive t(19;22)(p13;q11.2) CML who presented in lymphoid blast crisis. Our finding suggests that an amplification of the ABL oncogene might play a part in the appearance of an aggressive phenotype in some cases of CML.

Familial Amyloidotic Polyneuropathy: domino liver transplantation

BACKGROUND/AIMS

The primary cause of Familial Amyloidotic Polyneuropathy is a variant transthyretin gene on chromosome 18. Progressive polyneuropathy followed by fatal cardiac and renal failure commonly manifest during middle age. Within 10 years after onset of clinical symptoms, affected individuals usually die due to malnutrition or heart failure. Currently, liver transplantation is the only available therapeutic option.

METHODS

We performed liver transplantation in two patients with Familial Amyloidotic Polyneuropathy carrying the transthyretin-30 mutant. Two patients aged more than 50 years received the two explanted amyloidotic livers. This procedure is called Domino liver transplantation. We report the outcome in the studied subjects and analyze the metabolic consequences of this procedure.

RESULTS

We determined the serum half-life of transthyretin-30 as 2.25 days using daily monitoring of transthyretin-30 levels. An affected amyloidotic patient had an increased serum concentration of lipoprotein(a) of 78 mg/dl before transplantation. The tumor patient, who received the organ from this affected patient, developed an almost identical serum concentration of lipoprotein(a) after liver transplantation, confirming the liver as the primary site of synthesis of this lipoprotein.

CONCLUSION

Once Domino liver transplantation has been performed, the impact of the liver-dependent metabolism of specific proteins of interest can be studied.

Anti-pterins as tools to characterize the function of tetrahydrobiopterin in NO synthase

Nitric oxide synthases (NOS) are homodimeric enzymes that NADPH-dependently convert L-arginine to nitric oxide and L-citrulline. Interestingly, all NOS also require (6R)-5,6,7, 8-tetrahydro-L-biopterin (H4Bip) for maximal activity although the mechanism is not fully understood. Basal NOS activity, i.e. that in the absence of exogenous H4Bip, has been attributed to enzyme-associated H4Bip. To elucidate further H4Bip function in purified NOS, we developed two types of pterin-based NOS inhibitors, termed anti-pterins. In contrast to type II anti-pterins, type I anti-pterins specifically displaced enzyme-associated H4Bip and inhibited H4Bip-stimulated NOS activity in a fully competitive manner but, surprisingly, had no effect on basal NOS activity. Moreover, for a number of different NOS preparations basal activity (percent of Vmax) was frequently higher than the percentage of pterin saturation and was not affected by preincubation of enzyme with H4Bip. Thus, basal NOS activity appeared to be independent of enzyme-associated H4Bip. The lack of intrinsic 4a-pterincarbinolamine dehydratase activity argued against classical H4Bip redox cycling in NOS. Rather, H4Bip was required for both maximal activity and stability of NOS by binding to the oxygenase/dimerization domain and preventing monomerization and inactivation during L-arginine turnover. Since anti-pterins were also effective in intact cells, they may become useful in modulating states of pathologically high nitric oxide formation.

[Xanthoma disseminatum with marked mucocutaneous involvement]

HISTORY AND CLINICAL FINDINGS

When aged 23 years, a now 36-year-old man was first diagnosed as having xanthomas on the upper arms and shoulders. Xanthomas then progressed, affecting both the skin and the laryngo-pharyngeal mucosa. They were so marked that several laser-surgical interventions for their removal in the phayngo-laryngeal tract were necessary to ensure unimpaired breathing. There were also extensive confluent symmetrical cutaneous xanthomas over the upper and lower arms, the face, neck and trunk. Xanthomas and scars in the pharynx and larynx necessitated marked nasal breathing.

INVESTIGATIONS

There was no laboratory evidence of abnormal lipid metabolism. The concentrations of cholesterol, triglycerides, lipoprotein (a), apolipoprotein A-1, apolipoprotein B, apolipoprotein E phenotype and steroles were all normal. The biochemical composition of LDL, VLDL and HDL particle was also unremarkable. Histological examination of resected xanthomas revealed dense infiltrations of the interstitial spaces by foam-cell histiocytes with multiple lipid vacuoles, typical of xanthoma disseminatum.

TREATMENT AND COURSE

Neither probucol nor cholesterol synthesis enzyme inhibitors nor glucocorticoid medication influenced the xanthomas. The only effective treatment was removal of the most unsightly or obstructing lesions. But the sars left removal in the mucocutaneous regions caused obstruction in the laryngopharyngeal tract.

CONCLUSION

The cause of xanthoma disseminatum remains unknown. Skeletal muscle can also be extensively infiltrated. This case shows similarities to Erdheim-Chester disease, another are xanthomatous condition.

Lipid parameters predicting liver function in patients with cirrhosis and after liver transplantation

BACKGROUND/AIMS

The liver plays a central role in the production and metabolism of lipoproteins, regulating their synthesis and degradation. The protein content of the lipoproteins are the so-called apolipoproteins. Some of the apolipoproteins serve as cofactors for enzymatic reactions, as ligands for interaction with specific receptors, and as structural proteins. Apolipoprotein B (apoB) is the primary structural component of the atherogenic low density lipoprotein (LDL) particles and has a specific binding region for interacting with the LDL-receptor. In contrast, apolipoprotein A-I (apoA-I) represents the primary protein content of the high density lipoprotein (HDL) particles, which interacts with the putative HDL-receptor, and stimulates the enzymatic reaction of lecithin-cholesterol acyltransferase (LCAT) resulting in esterified cholesterol, which is the essential step in the process of reverse cholesterol transport.

METHODOLOGY

We studied lipid parameters in arterial and hepatic venous serum samples from 52 patients with cirrhosis and from 16 patients in the clinically stable long-term course after liver transplantation. Splanchnic blood flow was measured (indocyanine-green steady-state infusion) and hepatic extraction/production rates were calculated. To assess the influence of the clinical stage of established cirrhosis, the quantitated parameters were statistically analyzed.

RESULTS

In cirrhosis, apolipoprotein A-I levels are decreased depending on the clinical stage (p<0.01). This parameter showed excellent correlations to liver function tests. Triglycerides (TG) (p<0.05) and cholesterol (Chol) (p<0.05) were reduced as well, whereas apolipoprotein B levels did not change. In cirrhosis, hepatic production of both cholesterol and triglycerides were decreased (p<0.05 each), as well as hepatic extraction of free fatty acids (FFA) (p<0.01). Except for cholestatic liver disease with raised serum cholesterol (p<0.05) and apolipoprotein B levels (p<0.001), the etiology of cirrhosis had no impact on the observed serum lipid alterations.

CONCLUSIONS

The serum concentrations of the determined lipid parameters depend primarily on liver function. Decreased liver function was associated with reduced extraction of free fatty acids and reduced cholesterol and triglyceride synthesis. Liver transplantation restored the lipid abnormalities to normal. Finally, apolipoprotein A-I served as an excellent parameter for predicting liver function in the studied patients.

Distribution of nitric oxide synthase and nitric oxide-receptive, cyclic GMP-producing structures in the rat brain

The structures capable of synthesizing cyclic GMP in response to nitric oxide in the rat brain were compared relative to the anatomical localization of neuronal nitric oxide synthase. In order to do this, we used brain slices incubated in vitro, where cyclic GMP-synthesis was stimulated using sodium nitroprusside as a nitric oxide-donor compound, in the presence of the phosphodiesterase inhibitor isobutylmethylxanthine. Nitric oxide-stimulated cyclic GMP synthesis was found in cells and fibers, but was especially prominent in varicose fibers throughout the rat brain. Fibers containing the nitric oxide-stimulated cyclic GMP production were present in virtually every area of the rat brain although there were large regional variations in the density of the fiber networks. When compared with the localization of nitric oxide synthase, it was observed that although nitric oxide-responsive and the nitric oxide-producing structures were found in similar locations in general this distribution was complementary. Only occasionally was nitric oxide-mediated cyclic GMP synthesis observed in structures which also contained nitric oxide synthase. We conclude that the nitric oxide-responsive soluble guanylyl cyclase and nitric oxide synthase are usually juxtaposed at very short distances in the rat brain. These findings very strongly support the proposed role of nitric oxide as an endogenous activator of the soluble guanylyl cyclase in the central nervous system and convincingly demonstrate the presence of the nitric oxide-cyclic GMP signal transduction pathway in virtually every area of the rat brain.

Outcome of 22 successful pregnancies after liver transplantation

To evaluate course and outcome of pregnancies in liver transplanted patients and to provide a brief summary on the development of these children, 22 pregnancies and 23 children (1 month-99 months old) of 16 patients who had been liver transplanted at our institution (mean interval from transplantation to pregnancy 43.1 months) were reviewed. Standard immunosuppressive regimen during pregnancy consisted of cyclosporine A (CyA), tacrolimus (FK), azathioprine (Aza) and/or a low-dose steroid therapy. CyA and FK whole blood trough levels were monitored on a routinely basis to keep therapeutic range (CyA 80-150 ng/mL; FK 4-8 ng/mL). No patient had a graft loss and there were no lethal complications. Beside de novo hypertension (n = 3) and preeclampsia (n = 3) problems during pregnancy included one steroid-sensitive rejection at 36 wk gestation, one case of tacrolimus toxicity at 24 wk with complete reconstitution, and one case of de novo choledocholithiasis with recurrent cholangitis. Three cases of infections occurred. In total, 23 children, including one set of twins, were born. Terms of gestation (mean = 38.1 wk, +/- 2.2 SD), deliveries (spontaneous n = 13, cesarean section n = 7, forceps n = 1, vacuum extraction (VE) n = 1) and birth weights (2876 g, +/- 589.3 SD) were typical. Three pregnancies were preterm, one being a twin pregnancy. Neither congenital malformations nor unusual infections were seen in the children. Postnatal follow-up revealed appropriate physical growth to date. Psychological development seems to be adequate. Our data indicate that successful pregnancies after liver transplantation (LTX) under careful management by transplant specialists, obstetricians and perinatalogists have a good outcome. So far, neither pre- nor postnatal child development appear to be influenced by maternal immunosuppressive therapy during pregnancy.

Human soluble guanylate cyclase: functional expression and revised isoenzyme family

Soluble guanylate cyclase (sGC), a heterodimeric (alpha/beta) haem protein that converts GTP to the second messenger cGMP, functions as the receptor for nitric oxide (NO) and nitrovasodilator drugs. Three distinct cDNA species of each subunit (alpha1-alpha3, beta1-beta3) have been reported from various species. From human sources, none of these have been expressed as functionally active enzyme. Here we describe the expression of human alpha/beta heterodimeric sGC in Sf9 cells yielding active recombinant enzyme that was stimulated by the nitrovasodilator sodium nitroprusside or the NO-independent activator 3-(5'-hydroxymethyl-2'-furyl)-1-benzylindazole (YC-1). At the protein level, both alpha and beta subunits were detected in human tissues, suggesting co-expression also in vivo. Moreover, resequencing of the human cDNA clones [originally termed alpha3 and beta3; Giuili, Scholl, Bulle and Guellaen (1992) FEBS Lett. 304, 83-88] revealed several sequencing errors in human alpha3; correction of these eliminated major regions of divergence from rat and bovine alpha1. As human beta3 also displays more than 98% similarity to rat and bovine beta1 at the amino acid level, alpha3 and beta3 represent the human homologues of rat and bovine alpha1 and beta1, and the isoenzyme family is decreased to two isoforms for each subunit (alpha1, alpha2; beta1, beta2). Having access to the human key enzyme of NO signalling will now permit the study of novel sGC-modulating compounds with therapeutic potential.

Localization of nitric oxide synthase, NADPH diaphorase and soluble guanylyl cyclase in adult rabbit retina

Nitric oxide (NO) acts as a neuronal messenger which activates soluble guanylyl cyclase (SGC) in neighboring cells and produces a wide range of physiological effects in the central nervous system (CNS). Using immunocytochemical and histochemical stains, we have characterized the NO/SGC system in the rabbit retina and to a lesser extent, in monkey retina. Based on staining patterns observed with an antibody to nitric oxide synthase (NOS) type I and a histochemical marker for NADPH diaphorase, a metabolic intermediate required for NOS activity, three major classes of neurons appear to generate NO in the rabbit retina. These include two subclasses of sparsely distributed wide field amacrine cells, rod and cone photoreceptors, and a subpopulation of ganglion cells. Equivalent cell populations were labeled in monkey retina. An antibody to SGC (tested only in rabbit retina), labeled large arrays of cone photoreceptors in the outer nuclear layer, both amacrine and bipolar cells in the inner nuclear layer (INL), as well as populations of neurons in the ganglion cell layer. These data suggest that the ability to generate NO is restricted to relatively few neurons in the inner retina and to photoreceptor cells in the outer retina; while presumptive target cells, containing pools of SGC, are widespread and form contiguous fields across the inner and outer nuclear layers (ONL) as well as the ganglion cell layer.

Upregulated synthesis of both apolipoprotein A-I and apolipoprotein B in familial hyperalphalipoproteinemia and hyperbetalipoproteinemia

A family was identified with vertical transmission through three generations with simultaneous increases of apolipoprotein A-I (apoA-I), apolipoprotein B (apoB), low-density lipoprotein (LDL)-cholesterol, and high-density lipoprotein (HDL)-cholesterol, which we have designated familial hyperalphalipoproteinemia and hyperbetalipoproteinemia (HA/HBL). Affected patients develop xanthomas and coronary artery disease (CAD). HA/HBL apoA-I and LDL-apoB were isolated and characterized. The in vivo kinetics of radiolabeled apoA-I and LDL-apoB were evaluated in two HA/HBL probands and three controls. Structural and metabolic characterization showed normal apoA-I and LDL-apoB. The kinetics of metabolism of HA/HBL apoA-I in the HA/HBL subjects showed that elevated apoA-I levels were solely due to an increased synthesis rate (15.2 to 17.6 mg/kg/d v 11.1 to 11.4 mg/kg/d) with a normal apoA-I residence time in plasma (4.2 to 5.4 days v 5.1 to 5.3 days). The elevation of LDL-apoB levels resulted from both an increased synthetic rate (16.6 to 22.9 mg/kg/d v 12.3 to 13.8 mg/kg/d) and a prolonged residence time (3.3 to 3.8 days v 1.4 to 1.9 days). In addition, we evaluated another HA/HBL proband of an unrelated family with HA/HBL to confirm the kinetic data. LDL-receptor binding studies of HA/HBL fibroblasts showed normal binding, uptake, and degradation of LDL isolated from a normolipemic control. The serum concentration of the cholesterol ester transfer protein (CETP) was normal in the studied probands. An apoB 3500 and apoB 3531 mutant, respectively, was ruled out by polymerase chain reaction (PCR). In conclusion, the site of the molecular defect in HA/HBL subjects may be involved in the coordinate regulation of metabolism for both LDL and HDL.

Translocation (3;5)(p26;q13) in a patient with chronic T-cell lymphoproliferative disorder

A 67-year-old patient with large granular lymphocyte (LGL) leukemia is described. At fluorescence-activated cell sorting (FACS) analysis of the peripheral blood, the lymphocytes were positive for CD3, CD4, CD5, CD29, CD45RA, CD57, and TCR alpha/beta and negative for CD7, CD8, CD16, CD56, CD19, CD22, and TCR gamma/delta. Bone marrow histology and immunohistochemistry did not reveal any lymphocyte infiltration. Cytogenetic examination of peripheral blood cultures showed a clone with the karyotype 46,XY,t(3;5)(p26;q13). Molecular analysis revealed rearrangement of the gamma-T-cell-receptor chain. The region 3p25-3p26 which harbors the von Hippel-Lindau tumor suppressor gene and the RAF1 oncogene has been rearranged in a few cases of T-cell leukemia. The translocation in this case has not yet been described and may reflect an alternative mechanism in the pathogenesis of these disorders.

Apolipoprotein A-I induced amyloidosis

Amyloidosis is characterized by extracellular deposits of protein fibrils with a high content of beta-sheets in secondary structure. The protein forms together with proteoglycans amyloid fibrils causing organ damage and serious morbidity. Intact apolipoprotein A-I (apoA-I) is an important protein in lipid metabolism regulating the synthesis and catabolism of high density lipoproteins (HDL). Usually, apoA-I is not associated with amyloidosis. However, four naturally occurring mutant forms of apoA-I are known so far resulting in amyloidosis. The most important feature of all variants is the very similar formation of N-terminal fragments which were found in the amyloid deposits (residues 1-83 to 1-94). The new insights in the understanding of the association of apoA-I with HDL, its metabolism, and its hypothesized structural findings may explain a common mechanism for the genesis of apoA-I induced amyloidosis. Here we summarized the specific features of all known amyloidogenic variants of apoA-I and speculate about its metabolic pathway, which may have general implications for the metabolism of apoA-I.

Renal toxicity of the neuron-blocking and mitochondriotropic agent m-iodobenzylguanidine

meta-Iodobenzylguanidine (MIBG) is a multipotent drug used in its radiolabeled form as a tumor-seeking radiopharmaceutical in the diagnosis and treatment of pheochromocytoma and neuroblastoma. Nonradiolabeled MIBG has also proved to be effective in the palliation of carcinoid syndromes and, on a predosing schedule, in enhancing the relative tumor uptake of a subsequent [131I]-MIBG dose in tumors of neuroadrenergic origin. In addition, MIBG is under investigation as an inhibitor of mitochondrial respiration and, as such, for its use in tumor-specific acidification. In this report we describe the side effects of nonradiolabeled MIBG on kidney function in mice. High doses of MIBG (40 mg/kg) reduced renal blood perfusion as measured by 86Rb distribution by 50%, which could be antagonized by the bioamine receptor blockers prazosin and cyproheptadine. MIBG also induced reversible renal damage as evidenced from a decrease in [51Cr]-ethylenediaminetetraacetic acid (EDTA) clearance and from histological damage, which was most pronounced in the distal tubuli. These effects were unrelated to reduced perfusion, however, and could not be antagonized by bioamine receptor blockers, Ca2+-channel blockers, or diuretics. Clearance effects of MIBG were mimicked by N-nitro-L-arginine methyl ester (L-NAME), a known inhibitor of nitric oxide synthase (NOS), and MIBG itself (100 microM) also inhibited NOS in vitro, suggesting that NOS inhibition by MIBG may have contributed to the observed reduction in renal clearance. The MIBG analog benzylguanidine (BG), which is equipotent in terms of mitochondrial inhibition, did not affect renal clearance, thus excluding mitochondrial inhibition as the main mechanism of MIBG-induced damage. MIBG, however, was much more cytotoxic than BG to kidney tubular cells in primary cultures. Although the renal effects of high-dose MIBG were reversible, alterations in the pharmacokinetics of concomitant medications by a temporary reduction in renal function should be taken into account in its clinical application.

Delayed low density lipoprotein (LDL) catabolism despite a functional intact LDL-apolipoprotein B particle and LDL-receptor in a subject with clinical homozygous familial hypercholesterolemia

We identified a 38-yr-old male patient with the clinical expression of homozygous familial hypercholesterolemia presenting as severe coronary artery disease, tendon and skin xanthomas, arcus lipoides, and joint pain. The genetic trait seems to be autosomal recessive. Interestingly, serum concentrations of cholesterol responded well to diet and statins. We had no evidence of an abnormal low density lipoprotein (LDL)-apolipoprotein B (apoB) particle, which was isolated from the patient using the U937 proliferation assay as a functional test of the LDL-binding capacity. The apoB 3500 and apoB 3531 defects were ruled out by PCR. In addition, we found no evidence for a defect within the LDL-receptor by skin fibroblast analysis, linkage analysis, single-strand conformational polymorphism and Southern blot screening across the entire LDL-receptor gene. The in vivo kinetics of radioiodinated LDL-apoB were evaluated in the proband and three normal controls, subsequently. The LDL-apoB isolated from the patient showed a normal catabolism, confirming an intact LDL particle. In contrast the fractional catabolic rate (d-1) of autologous LDL in the subject and the normal controls revealed a remarkable delayed catabolism of the patient's LDL (0.15 vs. 0.33-0.43 d-1). In addition, the elevation of LDL-cholesterol in the patient resulted from an increased production rate with 22.8 mg/kg per day vs. 12.7-15.7 mg/kg per day. These data indicate that there is another catabolic defect beyond the apoB and LDL-receptor gene causing familial hypercholesterolemia.

Low molecular weight heparin-induced skin necrosis occurring distant from injection sites and without thrombocytopenia

In this paper we report a case of 76-year-old white male patient with skin necrosis induced by subcutaneous prophylactic administration of low-molecular-weight heparin (LMWH). Skin necrosis occurred distant from heparin injection sites and without concomitant thrombocytopenia. This is the first reported case presenting these clinical findings.

In vivo kinetics as a sensitive method for testing physiologically intact human recombinant apolipoprotein A-I: comparison of three different expression systems

In order to assess the structural and functional integrity of recombinant human apoA-I, we expressed apoA-I using three different expression systems: Baculovirus transfected Spodoptera frugiperda (Sf9) cells, stably transfected Chinese hamster ovary (CHO) cells, and transformed Escherichia coli (E. coli). Purified apoA-I from the three expression systems was radioiodinated and their catabolism was compared in normolipemic rabbits. The kinetic turnover studies of radiolabelled apoA-I in normolipemic rabbits revealed that highly purified recombinant apoA-I had an identical decay curve compared to native apoA-I, regardless whether it was purified from Sf9 cells, CHO cells, or E. coli. We also determined the association of the three recombinant apoA-I forms with both rabbit and human HDL. All three recombinant apoA-I forms were associated with HDL2 and HDL3 after injection into the rabbits and after incubation with human serum using both a Superose 6 column separation system and density gradient ultracentrifugation. The addition of the pro-segment or the addition of methionine at the amino-terminal end of apoA-I did not alter its metabolism and association to HDL. In conclusion, all studied expression systems are capable of producing high levels of physiologically intact recombinant human apoA-I. The aminoterminal addition of the prosegment of apoA-I or methionine did not alter the in vivo metabolism of apoA-I or its association to HDL.

Erdheim-Chester disease: low low-density lipoprotein levels due to rapid catabolism

We have identified a 44-year-old patient with symmetrically excessive xanthomatosis, called Erdheim-Chester disease (ECD), and simultaneously decreased levels of low-density lipoprotein (LDL) cholesterol. Clinically, this patient presents lipoidgranulomatosis of numerous long and flat bones with involvement of the liver, spleen, pericardium, pleura, thyroid, skin, conjunctiva, and gingiva. However, the patient does not have any signs of atherosclerosis. So far, the underlying defect has not been elucidated. We performed a LDL-apolipoprotein B (apoB) kinetic study in the ECD patient and a normal control to determine the etiology of the low LDL level in ECD. LDL was isolated from both subjects, radioiodinated with either 131I or 125I, and injected simultaneously into the ECD patient and the normal control. Normal and ECD LDL was catabolized at the same rate after injection into the control subject (fractional catabolic rate [FCR], 0.43/d and 0.46/d, respectively). Therefore, LDL isolated from an ECD subject is metabolically normal. In contrast, autologous LDL injected into the ECD subject showed a markedly increased catabolism (FCR, 0.69/d) compared with that in the control subject (FCR, 0.43/d). This is the first report about increased catabolism of LDL cholesterol in a patient.

Expression and purification of recombinant human apolipoprotein A-I in Chinese hamster ovary cells

The expression of apolipoprotein A-I (apoA-I) has been shown to be very difficult due to its amphiphilic character, autoaggregation, and degradation. We have expressed apoA-I using CHO cells, Baculovirus, and Escherichia coli [Schmidt et al., J. Biol. Chem. (1995) 270, 469-475]. Here we report about optimized conditions for the expression of proapoA-I in CHO cells, testing various serum-free media. We were able to yield apoA-I expression up to 80 micrograms/ml, by far the highest ever reported. However, immunoblot analysis revealed degraded apoA-I. The best apoA-I expression testing various conditions was about 20-30 micrograms/ml without any evidence of degradation. Interestingly, the apoA-I expression resulted in reproducible apoA-I fragments of 26 and 14 kDa. These fragments are consistent with already reported in vivo findings, in which carboxy-terminal proteolysis was suggested. The use of the protease inhibitors pepstatin and chymostatin, both carboxy-peptidase inhibitors, did result in contrast to other studied protease inhibitors in increased apoA-I yield. Therefore, limited carboxy-terminal proteolysis contributes to the degradation of CHO cell-secreted apoA-I. In addition, we evaluated various purification methods for the preparative isolation of recombinant apoA-I. In our hands we obtained the best recovery and no degradation with reversed-phase chromatography using a FPLC system.

Perspectives of liver cell transplantation: a review

Liver-directed somatic gene therapy may be performed using the techniques of in vivo gene therapy, liver cell transplantation (HcTx) including ex vivo gene therapy, and liver transplantation, respectively (1). Liver transplantation has become a routine surgical technique in correcting liver disease. The usage of HcTx and in vivo gene therapy has increased and may replace liver transplantation, at least to some extent, in the future. HcTx involves the transplantation of healthy, intact hepatocytes with metabolic properties which are deficient in the recipient. Among its different applications, this concept may be used for the correction of inborn errors of liver disease and acute liver failure. The advantage of HcTx is that for successful gene therapy, the underlying primary defect does not require detailed characterization. In addition, HcTx is currently being-tested for ex vivo gene therapy. In this form of therapy, hepatocytes are isolated after surgical liver resection. The hepatocytes are ex vivo genetically modified, e.g. using retroviral vectors, and the selected modified cells are subsequently re-injected. Herein, we report the historical development, current status and perspectives of the concept of HcTx.