A method to calculate tissue impedance through a standard bipolar pacing lead.

UNLABELLED: The transthoracic impedance (T) and its variations may be estimated through the measurement of the electrical impedance between the can and the right ventricular coil of a defibrillation lead. This method may allow the monitoring of fluid overload before a heart failure attack. Aim of this study was to validate in vitro a method to calculate T in case of a standard bipolar pacing lead, by performing 3 measurements: standard unipolar impedance from the tip (Zuni-tip); unipolar impedance from the ring (Zuni-ring); standard bipolar impedance (Zbip). The formula we used is derived from the standard equivalent circuit of a pacing system: [Formula: see text] T represents the tissue impedance between the can and the electrodes of the lead. To validate the method we used a saline solution and 3 different pacing leads manufactured by Vitatron (Vitatron BV, Arnhem, The Netherlands): Impulse II (high impedance lead), Crystalline ActFix (screw-in lead), Brilliant S+ (VDD single-lead). The measured values of the saline solution impedance were compared to the values calculated through the formula. RESULTS: The calculated impedance of the solution, evaluated through the proposed formula, is reliable independently of the electrode used and highly correlated to the corresponding measured values (R>0.9). CONCLUSION: Tissue impedance may be calculated from standard unipolar and bipolar impedance measurements with a standard bipolar pacing lead.

Seasonal variation in the incidence of deep vein thrombosis in patients with deficiency of protein C or protein S.

An attempt was made to identify circaseptanal or seasonal variation of deep vein thrombosis (DVT) in a population with protein C or protein S deficit. Forty-four patients with DVT and protein C or protein S deficit were studied for 1 year. A significant circannual rhythm was found for the total population that peaked during winter. There was also a significant falling circaseptanal rhythm on Fridays. These observations may optimize an adequate and precise anticoagulant therapy in patients with protein C or protein S deficits.

Molecular definition of Xq common-deleted region in patients affected by premature ovarian failure.

High-resolution cytogenetic analysis of a large number of women with premature ovarian failure (POF) identified six patients carrying different Xq chromosome rearrangements. The patients (one familial and five sporadic cases) were negative for Turner's stigmata and experienced a variable onset of menopause. Microsatellite analysis and fluorescent in situ hybridization (FISH) were used to define the origin and precise extension of the Xq anomalies. All of the patients had a Xq chromosome deletion as the common chromosomal abnormality, which was the only event in three cases and was associated with partial Xp or 9p trisomies in the remaining three. Two of the Xq chromosome deletions were terminal with breakpoints at Xq26.2 and Xq21.2, and one interstitial with breakpoints at Xq23 and Xq28. In all three cases, the del(X)s retained Xp and Xq specific telomeric sequences. One patient carries a psu dic(X) with the deletion at Xq22.2 or Xq22.3; the other two [carrying (X;X) and (X;9) unbalanced translocations, respectively] showed terminal deletions with the breakpoint at Xq22 within the DIAPH2 gene. Furthermore, the rearranged X chromosomes were almost totally inactivated, and the extent of the Xq deletions did not correlate with the timing of POF. In agreement with previous results, these findings suggest that the deletion of a restricted Xq region may be responsible for the POF phenotype. Our analysis indicates that this region extends from approximately Xq26.2 (between markers DXS8074 and HIGMI) to Xq28 (between markers DXS 1113 and ALD) and covers approximately 22 Mb of DNA. These data may provide a starting point for the identification of the gene(s) responsible for ovarian development and folliculogenesis.

Premature ovarian failure.

Secondary amenorrhoea with elevated gonadotrophins occurring under the age of 40 (premature ovarian failure (POF)), and at the age between 41 and 44 years (early menopause (EM)), respectively, affects 1-2% and 5% of women in the general population. Objective of this study was to evaluate the prevalence of familial cases of POF and EM and to assess the clinical and genetic characteristics of these patients. One hundred and sixty women with idiopathic secondary amenorrhoea before the age of 45 and serum follicle-stimulating hormone (FSH) levels greater than or equal to 40 IU/l were included in the study. Tests performed on patients included complete medical history, pedigree's analysis, clinical pelvic examination, gonadotrophins and thyroid assessment, chromosomal analysis. The 160 patients included in the study showed idiopathic POF (n=130) or EM (n=30). Following pedigree assessment, we were able to identify an incidence of familial cases of 28.5% in the POF group (n=37) and of 50% in the EM group (n=15). POF and EM condition were often present in the same family. There were no differences between POF and EM patients and between familial and sporadic cases regarding age at menarche, personal history, gynaecological history, weight, height and diet habits. There was a statistically significant difference between sporadic and familial cases in age at POF onset: 32.0+/-7.3 years (12-40) compared to 35. 0+/-5.8 (18-40), respectively (P<0.05). The POF and EM families identified showed two or more affected females and transmission through either maternal or paternal relatives; in four families both maternal and paternal transmission was observed. This study suggests that idiopathic POF and EM conditions, differing only in age of menopause onset, may represent a variable expression of the same genetic disease. The different age of menopause onset in these patients may be explained by genetic heterogeneity and/or by different environmental factors. Our results indicate a high rate of familial transmission of the condition. Pedigree's analysis suggests an autosomal or an X-linked dominant sex-limited pattern of inheritance for POF and EM.

Association between idiopathic premature ovarian failure and fragile X premutation.

A total of 106 women affected by premature ovarian failure (POF) were evaluated for fragile X (FRAXA) premutation. The POF patients were classified as having a familial condition (33 women), at least one relative with early menopause (12 women), or a sporadic condition (61 women). The FRAXA premutation was only detected in patients with familial (four out of 33) or sporadic POF (two out of 61). In general, the results obtained indicated that the prevalence [six out of 106, 6%, 95% confidence interval (CI) 3-11%] of FRAXA premutation is significantly higher in women affected by POF than expected (P = 1.24x10(-3)), suggesting a phenotype consequence of the premutation alleles. This relationship is more convincingly derived from the observation in two analysed pedigrees of a co-segregation between FRAXA and POF. These findings suggest a possible involvement of premutated alleles in ovarian failure, and indicate the utility of POF families screening for FRAXA premutation in order to prevent the transmission of mental retardation syndrome.

Clinical features and anti-neural reactivity in neuropathy associated with IgG monoclonal gammopathy of undetermined significance.

Neuropathy has been frequently reported in patients with IgG monoclonal gammopathy of undetermined significance (MGUS) but it is still unclear whether this association has clinical or pathogenetic relevance. In order to clarify the possible role of IgG MGUS in the neuropathy we correlated the clinical and electrophysiological features of the neuropathy with the duration and anti-neural activity of the M-protein in 17 patients with neuropathy and IgG MGUS. Ten patients (59%) had a chronic demyelinating neuropathy clinically indistinguishable from chronic inflammatory demyelinating polyneuropathy (CIDP) while 7 (41%) had a predominantly sensory axonal or mixed neuropathy. In 80% of patients in the CIDP-like and 28% in the sensory group the IgG M-protein became manifest several months to years after onset of the neuropathy. Antibodies to one or more neural antigens (including tubulin, a 35KD P0-like nerve myelin glycoprotein, GD1a, GM1 and chondrotin sulfate C) were found in 40% of patients with CIDP-like and 43% with sensory neuropathy but also in 37% patients with IgG MGUS without neuropathy. Neuropathy associated with IgG MGUS is probably less heterogeneous than previously considered suggesting that this association may not be merely casual. The evidence for primary pathogenetic role of IgG M-proteins in the neuropathy remains however elusive.

Expression of glycosylated recombinant human myelin-associated glycoprotein on a neuroblastoma cell line and its reactivity with HNK-1 but not human anti-MAG antibodies.

A correctly glycosylated myelin-associated glycoprotein (MAG) must express the carbohydrate epitope HNK-1, which is the target antigen for IgM antibodies in some patients with neuropathy. We transfected a human MAG cDNA clone into the neuroblastoma cell line SK-N-SH and verified by immunoblot the expression of the HNK-1 epitope on the recombinant molecule. By the same method and by indirect immunofluorescence we did not find any reactivity of human anti-MAG IgM antibodies with glycosylated recombinant MAG and transfected neuroblastoma cells. These findings suggest that the mere presence of the HNK-1 epitope is probably not sufficient for MAG to be recognized by human antibodies and that other factors such as the concentration or fine structure of this epitope in MAG, which mostly depend on the cellular context, may be also critical for this reactivity.

Anti-MAG and anti-SGPG antibodies in neuropathy.

We compared the binding of human antibodies from patients with neuropathy to the myelin-associated glycoprotein (MAG), to its cross-reactive glycolipid sulfoglucuronyl paragloboside (SGPG), and to sections of peripheral nerve. Titers were correlated with the clinical presentation and results of electrophysiological and pathological studies. Most patients had a predominantly sensory or sensorimotor demyelinating neuropathy and highly elevated antibodies to both MAG and SGPG, but 2 had highly elevated antibodies to MAG alone, and 1 to SGPG alone. Two patients had predominantly motor neuropathy and highly elevated antibodies to SGPG which reacted with MAG by Western blot but not by enzyme-linked immunosorbent assay. One patient had amyotrophic lateral sclerosis and antibodies to SGPG but not to MAG. These studies indicate that the neuropathic syndrome associated with anti-MAG or -SGPG antibodies are more heterogeneous than previously suspected, and that although most of the antibodies react with both MAG and SGPG, some may react with MAG or SGPG alone.

Anti-alpha- and beta-tubulin IgM antibodies in dysimmune neuropathies.

An increased frequency of serum IgM antibodies to beta-tubulin has been found by ELISA in patients with chronic inflammatory demyelinating polyneuropathy (CIDP) and the Guillain-Barré syndrome (GBS). We used an immunoblot technique to compare the frequency, titer and specificity of anti-tubulin IgM antibodies in 207 patients with different neuropathies, 109 with other neurological disease (OND) and 110 non-neurological controls. High titers of serum anti-tubulin IgM antibodies (> 1:1600) were present in 2 patients with CIDP (10.5%), 1 with multifocal motor neuropathy (MMN) (11%), 1 with GBS (1.8%), two with IgM monoclonal gammopathy, one with (1.3%) and one without neuropathy (2.1%), and in two with OND (1.8%). Even if the relative binding to alpha- and beta-tubulin differed among positive patients, in all IgM bound to both tubulin subunits. All positive patients had a similarly intense IgM reactivity with tubulin by ELISA that showed high anti-tubulin IgM in 4 additional CIDP patients (total positive by ELISA 30%) and in 7 of 23 normal subjects (30%). Even if high anti-tubulin IgM were slightly more frequent by immunoblot in chronic dysimmune neuropathies than in other diseases, possibly reflecting a secondary response to neural damage during an ongoing immune response, their relatively low frequency in these diseases does not seem to justify their measurement for diagnostic application.

Frequency and clinical correlates of anti-neural IgM antibodies in neuropathy associated with IgM monoclonal gammopathy.

We studied the frequency and clinical correlates of different IgM specificities in 75 patients with neuropathy associated with IgM monoclonal gammopathy. Patients were tested for IgM reactivity with the myelin-associated glycoprotein, P0, neurofilaments, and tubulin by immunoblot; with GM1, asialo-GM1, GM2, GD1a, GD1b, sulfatide, and chondroitin sulfate C by enzyme-linked immunosorbent assay; and with brain and nerve glycolipids by overlay high-performance thin-layer chromatography. Forty-two patients (56%) had high titers of IgM antibodies to MAG; 4 (5%), to sulfatide (1 also to myelin-associated glycoprotein); 4 (5%), to the 200-kd neurofilament (2 also to myelin-associated protein); and 1 each, to GD1b and chondroitin sulfate C. No reactivity was found in 26 patients (35%). More patients with anti-myelin-associated glycoprotein IgM (62%) than with unknown IgM reactivity (31%) had a predominantly sensory neuropathy (p < 0.025). Nerve conduction findings were consistent with a demyelinating neuropathy in 77% of patients reactive to myelin-associated glycoprotein and 24% with unknown reactivity (p < 0.0001) and the mean conduction velocity of peroneal nerve was lower in the former group (22.9 m/sec) than in the latter group (39.6 m/sec) (p < 0.000001). Patients with anti-sulfatide IgM had a sensorimotor neuropathy with morphological evidence of demyelination while anti-neurofilament IgM was not associated with homogeneous findings. Patients with anti-GD1b or anti-chondroitin sulfate C IgM had a predominantly motor impairment. The frequent occurrence of anti-neural IgM antibodies in neuropathy associated with IgM gammopathy, and their frequent, though not constant association with similar neuropathy features, support their possible pathogenetic role in the neuropathy.

Serum IgG antibodies to a 35-kDa P0-related glycoprotein in motor neuron disease.

Using an immunoblot technique we found a significantly higher frequency of serum IgG antibodies to a 35-kDa peripheral nerve myelin glycoprotein in patients with motor neuron disease (MND) (39% of 70) than in patients with neuropathy (13% of 61), other neurological disease (9% of 32) and normal subjects (5% of 20) (P < 0.005 in all cases), but not with multiple sclerosis (MS) (20% of 30) or non-neural immune diseases (25% of 32). Most positive patients had antibody titers of 1:200 or 1:2000 while higher titers were only found in seven patients with MND, one with chronic inflammatory demyelinating neuropathy, two with MS, two with non-neural immune diseases and one with stroke. The reacting protein had a higher molecular mass than P0 and was only faintly bound by an anti-P0 antiserum, but had the same N-terminal amino acid sequence of P0. The difference in molecular mass between P0 and the 35-kDa protein and the IgG reactivity of one patient's IgG with the 35-kDa protein persisted after its deglycosylation and dephosphorylation. Although there is no evidence that these antibodies are pathogenic, their frequent occurrence in MND and other immune-mediated conditions supports the hypothesis of an activation of the immune system in MND.

Peripheral neuropathy in monoclonal gammopathy of undetermined significance: prevalence and immunopathogenetic studies.

In an unselected series of patients with monoclonal gammopathy of undetermined significance (MGUS) we found neuropathy in 2 of 34 patients with IgG (6%), 2 of 14 with IgA (14%), and 8 of 26 with IgM MGUS (31%). The neuropathy was subclinical in 6 patients (1 IgG, 1 IgA, and 4 IgM). Patients with IgG or IgA MGUS had a prominent motor impairment with electrophysiologic and morphologic findings suggestive of predominant axonal degeneration. No deposit of the M-protein in sural nerve and no reactivity of the M-protein with nerve was detected in these patients. Patients with IgM MGUS had a prominent sensory impairment with evidence of predominant demyelination. In 6 of these patients the M-protein reacted with the myelin-associated glycoprotein (MAG). The higher prevalence of neuropathy in patients with IgM MGUS may be related to the frequent reactivity of IgM M-proteins with MAG.

Complement-mediated demyelination in patients with IgM monoclonal gammopathy and polyneuropathy.

We investigated the role of complement in the pathogenesis of the demyelinating polyneuropathy that occurs in some patients with IgM monoclonal gammopathy. Seven patients with chronic sensorimotor polyneuropathy and IgM monoclonal gammopathy were examined. In six patients, the monoclonal protein recognized an epitope shared by myelin-associated glycoprotein and two peripheral-nerve glycolipids, whereas in one patient, IgM bound to an unidentified myelin antigen. Direct and indirect immunofluorescence and immunoperoxidase assays showed colocalization along the myelin sheaths of peripheral-nerve fibers of monoclonal protein with complement components C1q, C3d, and C5. In addition, terminal-complement complex that was not associated with S protein was detected in myelin sheaths. It appeared that alterations in myelin geometry caused by the separation of myelin lamellae corresponded to sites at which terminal-complement complex was deposited. We conclude that demyelination in polyneuropathy associated with IgM monoclonal gammopathy may be mediated by complement.

Anti-myelin-associated glycoprotein IgM antibody titers in neuropathy associated with macroglobulinemia.

Twenty-seven patients with neuropathy and IgM monoclonal gammopathy were tested for antigen specificity of the M-protein and for anti-myelin-associated glycoprotein (MAG) IgM levels by immunoblot. In 16 patients (59.2%) the M-protein reacted with MAG and with cross-reactive glycoconjugates. Anti-MAG IgM titers in these patients ranged between 1:12,800 and 1:100,000. A fainter IgM reactivity with MAG and related glycoconjugates was detected in 3 additional patients with neuropathy, but also in 8 of 24 patients with IgM M-protein without neuropathy (33.3%). This reactivity was not due to the M-protein and corresponded to antibody titers of 1:400 or less in all but 1 patient with a titer of 1:3,200. Low titers of anti-MAG IgM (1:200 or less) were also detected in 17 of 101 control patients without IgM M-proteins (16.8%), while 1 patient with neuropathy of unknown cause had anti-MAG IgMK titers of 1:25,600. In 1 patient with neuropathy and IgM M-protein that was not anti-MAG, the M-protein bound to other antigens in nerve, while in 6, other possible causes or mechanisms for the neuropathy were found. In this study, high titers of anti-MAG IgM antibodies were always associated with neuropathy. The presence of low levels of anti-MAG IgM in a significant proportion of controls suggests that monoclonal expansion of naturally occurring B-cell clones secreting anti-MAG IgM may be responsible for the high incidence of this antigen specificity of the M-protein.

Visual evoked potentials in patients with neuropathy and macroglobulinemia.

Visual evoked potentials were studied in 11 patients with neuropathy and macroglobulinemia. The P100 latency was increased bilaterally in 5 of the 6 patients whose IgM M-proteins reacted with myelin-associated glycoprotein (MAG) and in 1 of the other patients. In patients whose M-protein bound to MAG, abnormal visual evoked potentials correlated with the presence of the M-protein in the cerebrospinal fluid. Subclinical involvement of the central nervous system is frequent in patients with neuropathy and anti-MAG M-proteins and may be due to the binding of M-proteins to central nervous system myelin.