Variability in the ratio of mutant to wildtype myosin heavy chain present in the soleus muscle of patients with familial hypertrophic cardiomyopathy. A new approach for the quantification of mutant to wildtype protein

The ratio of mutant to wildtype myosin heavy chain (beta-isoform, beta-MHC) in the soleus muscle of patients with familial hypertrophic cardiomyopathy was determined by a combination of HPLC, mass spectrometry and capillary zone electrophoresis. In two patients, one with a Val 606 Met mutation and another with a Gly 584 Arg mutation, the fraction of mutant beta-MHC was only 12+/-6% and 23+/-0.7% of total beta-MHC, respectively. These results demonstrate the necessity to determine the ratio of mutant to wildtype protein for the interpretation of functional studies on biopsy material from heterozygous patients with an inherited disease.

A single-fiber in vitro motility assay. In vitro sliding velocity of F-actin vs. unloaded shortening velocity in skinned muscle fibers

We describe an approach that allows us to form a micro in vitro motility assay with as little myosin as can be retrieved from a short (approximately 10 mm) segment of a single skinned skeletal muscle fiber (diameter some 100 microm). Myosin is directly extracted from the single fiber segment by a high ionic strength solution in the presence of MgATP, and the extracted myosin is immediately applied to a miniaturized flow cell that has been pretreated with BSA. The observed sliding velocities of fluorescently labeled F-actin are essentially identical with those reported in the literature. Since at the single fiber level most muscle fibers contain only a single myosin heavy chain isoform this approach allows us to determine without additional purification steps, the sliding velocity driven by myosins with different heavy chain isoforms. In addition, this approach can be used to directly correlate under identical experimental conditions unloaded shortening velocity measured in segments of skinned muscle fibers with the in vitro sliding velocity of fluorescently labeled F-actin by extraction of myosin from the same skinned fibers. Such direct correlation was performed with different myosin heavy chain isoforms as well as at different temperatures and ionic strengths. Under all conditions studied, unloaded shortening velocity was 4- to 8-fold faster than sliding velocity in the motility assay even at high temperature (22 degrees C) and ionic strengths >50 mM. This suggests that sliding velocity in the motility assay is limited by additional factors beyond those thought to limit velocity of unloaded shortening in muscle fibers. One such factor might be unspecific ionic interactions between F-actin and the substrate in the motility assay resulting in somewhat higher sensitivity for ionic strength of sliding velocity in the motility assay. This might become of special relevance when using in vitro sliding velocity in assessing functional consequences of mutations involving charged residues of actin or myosin.

Toxicity of adjuvant high-dose interferon-alpha-2b in patients with cutaneous melanoma at high risk of recurrence

Interferon-alpha-2b (INF-alpha-2b) has been approved by the FDA as adjuvant treatment for patients with melanoma at high risk of recurrence. INF-alpha-2b is administered at 20 MU/m2/day IV, 5 days per week for 4 weeks, and then 10 MU/m2/day SC, three times weekly for 48 weeks. We investigated the toxicity of this protocol in 30 patients between June 1996 and February 1998. An intensive toxicity evaluation program was developed to monitor side effects. During both induction and maintenance phases, 60% of patients required a dose delay and/or reduction. Twenty percent were unable to complete the treatment plan, and 53% tolerated at least 80% of the scheduled dose. The frequently reported toxicity during induction included constitutional symptoms, myelosuppression, and hepatotoxicity. All were reversible on cessation of treatment or dose modification. During maintenance, toxicity included thyroid dysfunction, hypertriglyceridemia, retinopathy and a combination of mood disturbances, memory loss, cognitive slowing and impaired executive function. Administration of high-dose INF-alpha-2b is feasible, with close patient monitoring.

Expression of the apoptosis-related oncogenes bcl-2, bax, and p53 in Merkel cell carcinoma: can they predict treatment response and clinical outcome?

Chemotherapy and radiation therapy act predominantly through the induction of apoptosis in malignancies. Merkel cell carcinoma, an aggressive malignancy with prominent apoptosis, has proved to be sensitive to both modes to a certain degree. We used immunohistochemical methods to examine 25 Merkel cell carcinomas and 8 of their lymph node metastases to assess the status of the antiapoptotic gene bcl-2 and 2 proapoptotic genes, wild-type p53 and bax. All tumors showed prominent bax immunopositivity; 76% were positive for bcl-2, and only 28% were positive for p53, the latter presumably reflecting mutated p53. No statistically significant relationship was found between tumor immunopositivity and therapy response or survival. The widespread bax immunopositivity and the apparently low rate of p53 mutations, as suggested by the low rate of p53 immunopositivity, may be related to the presence of prominent apoptosis in Merkel cell carcinoma. The finding of bcl-2 immunopositivity in 76% of the tumors suggests that some of the tumor cells may be resistant to apoptosis-inducing agents.

Thrombophilia-associated pregnancy wastage

OBJECTIVE

To critically review the literature regarding inherited thrombophilia and recurrent fetal loss.

DESIGN

English-language literature review.

PATIENT(S)

Women who experienced repeated pregnancy wastage.

INTERVENTION(S)

Aspirin, glucocorticoids, heparin, and IV immunoglobulin for the prevention of miscarriage.

MAIN OUTCOME MEASURE(S)

Live birth, miscarriage, preeclampsia, and pregnancy loss.

RESULT(S)

Recurrent fetal loss and other placental vascular pathologies of pregnancy have long been associated with antiphospholipid syndrome, an acquired autoimmune thrombophilic state. The number of known heritable thrombophilic disorders has grown rapidly in recent years with the identification of activated protein C resistance, factor V Leiden mutation, and hyperhomocysteinemia as major causes of thrombosis. Data accumulated over the past 2 years suggest that heritable thrombophilia is associated with an increased risk of fetal loss and preeclampsia. The present review discusses potential pathogenetic mechanisms for this association and evaluates reported therapeutic regimens for the prevention of fetal loss in women with thrombophilia.

CONCLUSION(S)

Placental thrombosis may be the final common pathophysiologic pathway in most women with habitual abortions and repeated pregnancy wastage. Prophylactic antithrombotic therapy is indicated in women with heritable thrombophilia and antiphospholipid syndrome and probably is more effective than the previously used modalities of prednisone, aspirin, and IV immunoglobulin.

Thin filament activation probed by fluorescence of N-((2-(iodoacetoxy)ethyl)-N-methyl)amino-7-nitrobenz-2-oxa-1,3-diazole-labeled troponin I incorporated into skinned fibers of rabbit psoas muscle

A method is described for the exchange of native troponin of single rabbit psoas muscle fibers for externally applied troponin complexes without detectable impairment of functional properties of the skinned fibers. This approach is used to exchange native troponin for rabbit skeletal troponin with a fluorescent label (N-((2-(iodoacetoxy)ethyl)-N-methyl)amino-7-nitrobenz-2-oxa-1, 3-diazole, IANBD) on Cys(133) of the troponin I subunit. IANBD-labeled troponin I has previously been used in solution studies as an indicator for the state of activation of reconstituted actin filaments (. Proc. Natl. Acad. Sci. USA. 77:7209-7213). In the skinned fibers, the fluorescence of this probe is unaffected when cross-bridges in their weak binding states attach to actin filaments but decreases either upon the addition of Ca(2+) or when cross-bridges in their strong binding states attach to actin. Maximum reduction is observed when Ca(2+) is raised to saturating concentrations. Additional attachment of cross-bridges in strong binding states gives no further reduction of fluorescence. Attachment of cross-bridges in strong binding states alone (low Ca(2+) concentration) gives only about half of the maximum reduction seen with the addition of calcium. This illustrates that fluorescence of IANBD-labeled troponin I can be used to evaluate thin filament activation, as previously introduced for solution studies. In addition, at nonsaturating Ca(2+) concentrations IANBD fluorescence can be used for straightforward classification of states of the myosin head as weak binding (nonactivating) and strong binding (activating), irrespective of ionic strength or other experimental conditions. Furthermore, the approach presented here not only can be used as a means of exchanging native skeletal troponin and its subunits for a variety of fluorescently labeled or mutant troponin subunits, but also allows the exchange of native skeletal troponin for cardiac troponin.

Kinetics of thin filament activation probed by fluorescence of N-((2-(iodoacetoxy)ethyl)-N-methyl)amino-7-nitrobenz-2-oxa-1,3-diazole-labeled troponin I incorporated into skinned fibers of rabbit psoas muscle: implications for regulation of muscle contraction

Making use of troponin with fluorescently labeled troponin I subunit (N-((2-(iodoacetoxy)ethyl)-N-methyl)amino-7-nitrobenz-2-oxa-1, 3-diazole-troponin I, IANBD-TnI) that had previously been described in solution studies as a probe for thin filament activation (. Proc. Natl. Acad. Sci. 77:7209-7213), we present a new approach that allows the kinetics of thin filament activation to be studied in skinned muscle fibers. After the exchange of native troponin for fluorescently labeled troponin, the fluorescence intensity is sensitive to both changes in calcium concentration and actin attachment of cross-bridges in their strong binding states (. Biophys. J. 77:000-000). Imposing rapid changes in the fraction of strongly attached cross-bridges, e.g., by switching from isometric contraction to high-speed shortening, causes changes in thin filament activation at fixed Ca(2+) concentrations that can be followed by recording fluorescence intensity. Upon changing to high-speed shortening we observed small (<20%) changes in fluorescence that became faster at higher Ca(2+) concentrations. At all Ca(2+) concentrations, these changes are more than 10-fold faster than force redevelopment subsequent to the period of unloaded shortening. We interpret this as an indication that equilibration among different states of the thin filament is rapid and becomes faster as Ca(2+) is raised. Fast equilibration suggests that the rate constant of force redevelopment is not limited by changes in the activation level of thin filaments induced by the isotonic contraction before force redevelopment. Instead, our modeling shows that, in agreement with our previous proposal for the regulation of muscle contraction, a rapid and Ca(2+)-dependent equilibration among different states of the thin filament can fully account for the Ca(2+) dependence of force redevelopment and the fluorescence changes described in this study.

Prospective evaluation of hemostatic system activation and thrombin potential in healthy pregnant women with and without factor V Leiden

Normal pregnancy is associated with alterations of the hemostatic system towards a hypercoagulable state and an increased risk of venous thromboembolism. The risk of venous thrombosis is higher in pregnant women with factor V Leiden (FVL) than in those with wildtype factor V. Routine laboratory assays are not useful to detect hypercoagulable conditions. A prospective and systematic evaluation of hemostatic system activation in women with and without FVL during an uncomplicated pregnancy employing more sensitive markers of hypercoagulability, such as prothrombin fragment 1+2 (F1+2), thrombin-antithrombin complex (TAT), D-Dimer, or the endogenous thrombin potential (ETP), an indicator of the plasma's potential to generate thrombin, has not been performed. We prospectively followed 113 pregnant women with (n = 11) and without (n = 102) FVL and measured F1+2. TAT, D-Dimer and the ETP at the 12th, 22nd and 34th gestational week as well as 3 months after delivery (baseline) in each subject. None of the women developed clinical signs of venous thromboembolism during pregnancy or postpartum. Pregnant women with and without FVL exhibited substantial activation of the coagulation and fibrinolytic system as indicated by a gradual increase of F1+2, TAT and D-Dimer throughout uncomplicated pregnancy up to levels similar to those found in acute thromboembolic events (p < 0.0001 by analysis of variance for each parameters). Levels of F1+2 and TAT were comparable between women with and without FVL, but levels of D-Dimer were significantly higher in women with FVL than in those without the mutation (p = 0.0005). The ETP remained unchanged in both women with and without FVL at all timepoints. Our data demonstrate a substantial coagulation and fibrinolytic system activation in healthy women with and without FVL during uncomplicated pregnancy. An elevated F1+2, TAT or D-Dimer level during pregnancy is not necessarily indicative for an acute thromboembolic event. The normal ETP in both women with and without FVL suggests that the capacity of the plasma to generate thrombin after in vitro activation of the clotting system is not affected by pregnancy. Higher levels of D-Dimer in women with FVL than in women with wildtype factor V at baseline as well as during pregnancy indicate increased fibrinolytic system activation in carriers of the mutation.

High prevalence of activated protein C resistance due to factor V leiden mutation in cases of intrauterine fetal death

OBJECTIVE

To test a possible association between activated protein C resistance and intrauterine fetal death.

METHODS

The activated protein C anticoagulant activity and factor V R506Q mutation were assessed in 14 nonpregnant women with a history of intrauterine fetal death and 14 healthy controls.

RESULTS

Four women in the study group were heterozygotes for the factor V mutation and none of the controls. The mean activated protein C activity of the study group was statistically significantly lower than that of the controls (P = 0.013).

CONCLUSION

Resistance to activated protein C activity may be of etiologic importance in some cases of intrauterine fetal death.

Visual disturbances and pathologic ocular findings in primary antiphospholipid syndrome

OBJECTIVE

To delineate the features and prevalence of the systemic and ophthalmic involvement of primary antiphospholipid syndrome (PAS).

DESIGN

Prospective case series.

PARTICIPANTS

A total of 39 consecutive patients with PAS.

METHODS

During an 18-month period, the medical records of all patients with PAS who attended a clinic for thrombosis and hemostasis were reviewed on arrival. The patients were then referred to a retinal clinic and examined prospectively. The first 20 consecutive patients underwent retinal fluoroangiography.

MAIN OUTCOME MEASURES

The prevalence of the various organs affected by the disease was noted in the group, as well as the prevalence and type of ophthalmic involvement.

RESULTS

The most common forms of systemic involvement were fetal loss in 11 female patients (46%), central nervous system involvement in 17 patients (44%), and venous thrombosis in 16 patients (41%). Ophthalmic findings were as follows: 13 patients (33%) were symptomatic, and 12 of them complained of visual disturbances. In 10 (83%) of these 12 patients, the visual symptoms were transient, and 7 of them were nonocular in nature. Pathologic signs on ophthalmic examination were found in 5 of the 39 patients (13%), two of whom had intraocular pathologic findings related to PAS, and these were in the form of mild retinopathy. Of the 36 patients who were either asymptomatic or had transient visual disturbances, pathologic ocular findings were detected in only 2 (6%). Routine retinal fluoroangiography did not reveal any additional information that could not otherwise have been detected by funduscopy.

CONCLUSIONS

Ocular involvement in PAS is uncommon. Transient visual disturbances are common, although most of them are related to central nervous system rather than ocular ischemia. Pathologic ophthalmic findings are unlikely to be found in asymptomatic patients or in patients with transient visual disturbances. Routine retinal fluoroangiography performed on patients with PAS is unproductive.

Thrombophilic polymorphisms are common in women with fetal loss without apparent cause

An association between fetal loss and thrombophilia has recently been described but has not been yet fully elucidated. We have evaluated prospectively the prevalence of the three common thrombophilic polymorphisms (TP) factor V G1691A (Leiden), thermolabile-methylenetetrahydrofolate reductase (TL-MTHFR) C677T and factor II G20210A mutations, in 76 women with fetal loss (> or =3 in first, > or =2 in second, > or =1 in third trimester) without apparent cause and 106 controls without fetal loss. Thirty seven out of 76 (49%) of the women in the fetal loss group had at least one TP compared to only 23/106 (22%) in the control group (p = 0.0001 ). Factor V-Leiden was more common in the fetal loss group 24/76 (32%) compared to the control group 11/106 (10%) (OR = 4.0, 95% CI: 1.8-8.8, p <0.001). Five of the 76 patients (7%) were homozygous for factor V-Leiden compared to none of the controls (p = 0.012). A trend, albeit no statistically significant difference was found between women with fetal loss and control groups regarding factor II G20210A (8% vs. 4% respectively, OR = 2.2, 95% CI: 0.6-8.0, p = 0.23) and MTHFR C677T (18% vs. 10% respectively, OR = 1.95, 95% CI: 0.83-4.6, p = 0.12). Combined TP were documented in 6/76 (8%) patients compared to 1/106 (1%) in controls (OR = 9.0, 95% CI: 1.1-76, p = 0.02). Second or third trimester fetal loss were more common cause of pregnancy termination in 37 patients with TP compared to 39 patients without TP (57/158 (36%) vs. 23/135 (17%) respectively, (p = 0.0004). Thrombophilic polymorphisms are common in women with fetal loss without apparent cause and are associated with late pregnancy wastage. Combinations of TP increase the risk for fetal loss.

Tailoring treatment for classical Kaposi's sarcoma: comprehensive clinical guidelines

Classical Kaposi's sarcoma (CKS) is a rare indolent proliferative disease which is particularly prevalent among Jews of Ashkenazi and Mediterranean origin. To define guidelines for its comprehensive management, we conducted a retrospective analysis of 123 patients, focusing mainly on treatment modalities. The CKS-related mortality was 4% (5 patients). Of the 39 patients for whom observation only was the primary approach, 15 (38%) remained progression-free for 1-83 months (median, 4 months). Twenty-nine of the 52 (56%) patients who underwent surgery as the primary approach remained recurrence-free for 1-162 months (median, 15 months). Radiotherapy achieved an objective response in 74 courses (85%), including 50 (58%) complete responses. Symptomatic relief was reported in 95% of the patients. Vinblastine (27 series) achieved an objective response in 73% of series, including 22% complete responses. Multivariate analysis of time to progression with observation alone identified immunosuppression as the only significant independent factor that predicted disease progression. Our study suggests that observation alone may be sufficient for immunocompetent asymptomatic patients; symptomatic resectable lesions are suitable for simple excision; and more advanced disease or unresectable lesions require radiotherapy. If disease is extensive or the other approaches fail, chemotherapy is appropriate. Tailoring the treatment for CKS is an integrative process, requiring good understanding of the role of each available modality in the different clinical disease settings.

Safety of low-molecular-weight heparin in pregnancy: a systematic review

Unfractionated heparin (UFH) remains the anticoagulant of choice during pregnancy. Low-molecular-weight heparins (LMWH) are an attractive alternative to UFH due to their logistic advantages and their association with a lower incidence of osteoporosis and HIT. We reviewed all published clinical reports concerning the use of LMWH during pregnancy. In addition, participants of an international interest group contributed a cohort of pregnant women treated with LMWH. Pregnancies were divided into two groups; those with and those without maternal comorbid conditions. The number of adverse fetal outcomes and the occurrence of maternal complications were evaluated in the two groups. In the group of women with comorbid conditions (n = 290), 13.4% of the pregnancies were associated with an adverse fetal outcome. In contrast, in the group of women without comorbid conditions (n = 196), 3.1% were associated with an adverse outcome, which is comparable to that seen in the normal population. We conclude that LMWH appear to be a safe alternative to unfractionated heparin as an anticoagulant during pregnancy.

Sarcomeric binding pattern of exogenously added intact caldesmon and its C-terminal 20-kDa fragment in skinned fibers of skeletal muscle

Intact caldesmon and particularly the actin-binding C-terminal fragment (20-kDa) of caldesmon have been shown in skeletal muscle fibers to selectively displace low affinity, weakly bound cross-bridges from actin without significantly altering the actin attachment of force producing, strong binding cross-bridges (Brenner et al., 1991; Kraft et al., 1995a). However, the sarcomeric distribution and the specific binding of externally added caldesmon to the myofilaments of skeletal muscle fibers was not known. It was e.g., unclear whether caldesmon binds along actin in a manner similar to tropomyosin or whether it also binds to myosin. In this study, we determined the binding pattern of exogenously added intact caldesmon and its C-terminal 20-kDa fragment, respectively, in MgATP-relaxed rabbit skeletal muscle fibers using electron (EM) and confocal fluorescence microscopy (CFM). EM showed that similar to what has been demonstrated earlier for smooth muscle thin filaments (Lehman et al., 1989), intact caldesmon binds periodically every 38 nm along the thin filaments. CFM revealed that rhodamine-labeled intact caldesmon and the 20-kDa caldesmon fragment bind along nearly the entire length of the thin filaments. A portion of the I-band near the Z-line appears unlabeled, both when equilibrated at normal and long sarcomere lengths. The width of the unlabeled region seems to depend on ionic strength. The 20-kDa C-terminal caldesmon fragment binds in essentially the same pattern as intact caldesmon. This indicates that the high fluorescence intensity in the overlap region seen with intact caldesmon does not depend on caldesmon binding to myosin. X-ray diffraction was used to monitor the effects of filament lattice. Intact caldesmon at > 0.3 mg/ml induced disorder in the myofilament lattice. No such disordering was observed, however, when fibers were equilibrated with up to 0.8 mg/ml of the 20-kDa caldesmon fragment.

Intracellular mechanisms of L-selectin induced capping

Leucocyte adhesion to endothelial cells is a tightly regulated process involving selectins, integrins and immunoglobulin-like proteins. Cell adhesion and communication are controlled by membrane dynamics like receptor capping. Capping of surface receptors is an ubiquitous mechanism but still not well understood. Employing immunofluorescence techniques, we demonstrate that L-selectin triggering results in receptor capping of the L-selectin molecules in lymphocytes. Using pharmacological inhibitors and genetic deficient cell lines we show that this process involves intracellular signalling molecules. L-Selectin capping seems to be independent on activation of p56lck-kinase, but requires the neutral sphingomyelinase, small G proteins and the cytoskeleton. Therefore, capping of L-selectin upon stimulation might play an important role in the very early phase of lymphocyte trafficking.

Prognostic factors for local control of early glottic cancer: the Rabin Medical Center retrospective study on 207 patients

PURPOSE

Different radiation therapy schedules and devices have been used over the last 20 years at Rabin Medical Center in patients with early glottic cancer. The aim of the present retrospective analysis was to identify the subgroup of patients at high risk of failure of radiation treatment.

MATERIALS AND METHODS

Between 1974 and 1994, 207 patients with squamous cell carcinoma of the glottis, 182 Stage T1 and 25 Stage T2, underwent definitive radiation therapy. During this period, treatment was administered with different radiation devices (60Co or 6-MV X ray), using different dose/fraction protocols (1.8 or 2 Gy per day, 5 or 6 fractions per week), total doses (42-77.4 Gy), overall radiation times, and delays. These treatment variables, in addition to certain patient and tumor characteristics, were correlated with local control at a median follow-up of 57 months (range 18-265 months).

RESULTS

The 5-year local control rates for T1 and T2 tumors were 88% and 73%, respectively. Univariate analysis showed that smoking, diabetes mellitus, anterior commissure involvement, T stage, and extension of tumor to one third or more of the vocal cord were highly significantly correlated with decreased local control. None of the treatment variables, including dosage at which complete tumor regression was noted, were found to be predictive. By multivariate analysis, only anterior commissure involvement was found to be highly significant (risk ratio 1.9, 95% CI 1.2-3.0, p = 0.027), and T stage was borderline significant (risk ratio 1.6, 95% CI 1.0-2.5, p = 0.054).

CONCLUSION

This study suggests that only two tumor characteristics are predictive of local failure of early glottic cancer: anterior commissure involvement and T stage. Treatment variables apparently do not influence local control.

The effect of thin filament activation on the attachment of weak binding cross-bridges: A two-dimensional x-ray diffraction study on single muscle fibers

To study possible structural changes in weak cross-bridge attachment to actin upon activation of the thin filament, two-dimensional (2D) x-ray diffraction patterns of skinned fibers from rabbit psoas muscle were recorded at low and high calcium concentration in the presence of saturating concentrations of MgATPgammaS, a nucleotide analog for weak binding states. We also studied 2D x-ray diffraction patterns recorded under relaxing conditions at an ionic strength above and below 50 mM, because it had been proposed from solution studies that reducing ionic strength below 50 mM also induces activation of the thin filament. For this project a novel preparation had to be established that allows recording of 2D x-ray diffraction patterns from single muscle fibers instead of natural fiber bundles. This was required to minimize substrate depletion or product accumulation within the fibers. When the calcium concentration was raised, the diffraction patterns recorded with MgATPgammaS revealed small changes in meridional reflections and layer line intensities that could be attributed in part to the effects of calcium binding to the thin filament (increase in I380, decrease in first actin layer line intensity, increase in I59) and in part to small structural changes of weakly attached cross-bridges (e.g., increase in I143 and I72). Calcium-induced small-scale structural rearrangements of cross-bridges weakly attached to actin in the presence of MgATPgammaS are consistent with our previous observation of reduced rate constants for attachment and detachment of cross-bridges with MgATPgammaS at high calcium. Yet, no evidence was found that weakly attached cross-bridges change their mode of attachment toward a stereospecific conformation when the actin filament is activated by adding calcium. Similarly, reducing ionic strength to less than 50 mM does not induce a transition from nonstereospecific to stereospecific attachment.

Budd-Chiari syndrome associated with factor V leiden mutation: a report of 6 patients

Budd-Chiari syndrome is characterized by hepatic venous outflow obstruction. Although myeloproliferative disorders are usually responsible for this severe thrombotic disorder, deficiency or dysfunction of the natural anticoagulants can be involved. Resistance to activated protein C caused by factor V Leiden mutation has been recently identified as a major cause of thrombophilia. We report 6 patients with Budd-Chiari syndrome associated with factor V Leiden mutation combined with another acquired thrombophilic state (myeloproliferative disorder and lupus anticoagulant in 3 cases) and without another thrombophilic disorder in the other 3 cases. We conclude that factor V Leiden mutation should be evaluated in any case of hepatic vein occlusion because the prevalence of this mutation in the general population is high.

Relationship between birthweight and blood pressure in childhood

Studies have shown an inverse relationship between birthweight and blood pressure in later life. The objective of this study is to analyze the relationship between birthweight and blood pressure in childhood in a North American-based population. Data on 2,958 births with follow-up at 7 years of age from the Providence, RI, cohort of the Collaborative Perinatal Project of the National Institute of Neurological Diseases and Stroke were retrospectively analyzed using univariate and multivariate analytic methods. Bivariate analysis of the total cohort showed a direct relationship between follow-up weight at age 7 years and birthweight (r = 0.24; P < 0.001) and follow-up weight with systolic (SBP) and diastolic blood pressure (DBP; r = 0.33; P < 0.001 and r = 0.22; P < 0.001, respectively). On multivariate analysis, follow-up weight and height were the strongest predictors of SBP and DBP. There was also a significant inverse relationship between birthweight and SBP. A cohort of term infants (n = 2,561) was subdivided into birthweight-for-gestational-age groupings to further evaluate the effects of birthweight on blood pressure. Small-for-gestational-age (SGA) infants were markedly smaller at age 7 years than those large-for-gestational-age (LGA; 21 +/- 4 kg v 26 +/- 4 kg; P < 0.01). Despite the direct association between follow-up weight and blood pressure, the mean blood pressure did not differ between SGA (103/58 mm Hg) and LGA patients (103/59 mm Hg). To assess whether birthweight was an independent predictor of blood pressure, blood pressures were predicted using linear regression equations. For every 1-kg decrease in birthweight in term infants, SBP at 7 years increased by 1.3 mm Hg and DBP by 0.6 mm Hg. In conclusion, controlling for weight and height in term infants at 7 years of age has an inverse linear effect on blood pressure. This suggests that birthweight in relation to gestation may be a contributor to the multifactorial cause of essential hypertension.

X-ray diffraction studies of the cross-bridge intermediate states

Two dimensional x-ray diffraction was obtained from skinned rabbit psoas muscle fibers. The goal is to correlate structures of the cross-bridge population with various intermediate states in the cross-bridge cycle by using nucleotides and their analogs. It was found that in a relaxed muscle in ATP containing solutions, cross-bridges are distributed in three populations in equilibrium: those detached from actin and ordered on the myosin helix, those that are detached and disordered, and those weakly attached to actin in random orientations. The distribution among the three populations is highly dependent on temperature. Those that are detached and yet ordered in a helical structure surrounding the myosin backbone are very likely in the M.ADP.Pi state, supporting an earlier suggestion by Wray (1987). It was also found that the attached cross-bridges with bound MgADP are structurally distinct from those without nucleotide, in agreement with one of our earlier findings by osmotic compression (Xu et al., 1993). Another finding of interest is that the analog AMP-PNP was found to be an ATP analog, rather than an ADP analog as it has been reported previously by many research groups.

Fluorescence of NBD-labelled troponin-I as a probe for the kinetics of thin filament activation in skeletal muscle fibers

Using fluorescence of NBD-labelled troponin I incorporated into skinned fibers of the rabbit psoas muscle by chasing native troponin by troponin with the NBD-labelled TnI subunit we attempted to study kinetics of thin filament activation at different Ca(++)-concentrations. Since fluorescence of NBD-labelled TnI is sensitive to both, changes in Ca++, and strong cross-bridge attachment, we were able to induce changes thin filament activation by rapidly dropping the fraction of strongly attached cross-bridges to very low levels, e.g. by switching from isometric to isotonic contraction conditions. At any [Ca++], the time course of the resulting changes in fluorescence of NBD-labelled TnI was found at least an order of magnitude faster than the time course of force redevelopment subsequent to the period of isotonic contraction. Modelling shows that with the kinetics of thin filament activation derived from these studies, common kinetic schemes of the actomyosin ATPase predict regulation to act via changes in cross-bridge cycling kinetics, as we had previously proposed.