THREE-DIMENSIONAL DISTRIBUTION OF BASEMENT MEMBRANE COMPONENTS IN DYSTROPHIC RECESSIVE EPIDERMOLYSIS BULLOSA

Absent or defective collagen VII at the dermo-epidermal junction is the hallmark of dystrophic recessive epidermolysis bullosa. Little is known of the alterations of other collagenous and non-collagenous components of the basement membrane; it is likely that their assembly may be disturbed by the lack of collagen VII molecules. The spatial relationship of collagen IV and laminin has been studied, both in bullous and in non-bullous areas. Skin biopsies from five patients affected by severe dystrophic recessive epidermolysis bullosa were rapidly frozen and freeze-dried. Collagen IV and laminin were labelled with specific monoclonal antibodies and FITC- or TRITC-conjugated secondary antibodies. Sections were observed with conventional light/fluorescence microscopy and with confocal laser scanning microscopy. Collagen IV and laminin were not co-localized: the former displayed a split image, being present at the floor and the roof of the blister, while the latter was confined to the roof. Confocal microscopy also allowed three-dimensional (3D) reconstruction of the dermo-epidermal junction from a series of optical sections, with viewing of the reconstructed specimen from a sequence of angles. By this procedure, laminin exhibits an irregular, coarsely granular distribution, both in affected and in apparently non-affected areas, while collagen IV appears as a homogeneous sheet. These results show that freeze-drying is the technique of choice for high-resolution immunofluorescence of skin samples and suggest that in dystrophic recessive epidermolysis bullosa, a complex disruption of the extracellular matrix assembly exists even before blister formation, probably due to the lack of collagen VII.     

LONG-TERM SURVIVAL OF PATIENTS WITH HIV-RELATED SYSTEMIC NON-HODGKIN'S LYMPHOMAS

Background: the overall outcome of patients with HIV-related non-Hodgkin's lymphomas (HIV–NHL) is poor because of the adverse clinico-pathological features of HIV–NHL and of the underlying HIV infection. However, the experience of physicians in the management of HIV–NHL has increased, in particular in the use of intensive chemotherapy regimens, leading to an improvement in the prognosis of some of these neoplasms. Because some patients with AIDS may survive up to 5 years, it is possible to evaluate the long-term efficacy of the treatment of patients with HIV–NHL. In the general population, aggressive NHL, that are those occurring in HIV patients, may be considered cured after 2 years of lasting complete remission (CR) after chemotherapy. Patients and methods: we reviewed our monoinstitutional case-series of 73 HIV-infected patients with systemic NHL, observed between April 1985 and February 1993. Two groups of patients were arbitrarily identified, the first one (group A) including patients with a CR lasting for at least 2 years (N=13) and the other including all remaining patients (group B) (N=60). Results: the 13 patients of group A differed significantly from the other patients in terms of higher CD4+ cell count and performance status (PS) at the time of diagnosis of NHL. There was no significant difference in the histological subtypes of the HIV–NHLs. The overall survival of the 73 patients was 8 months. In a separate analysis on all patients, age less than 30 years, PS less or equal to 1, a CD4+ cell count equal to or higher than 100/mm³ and the absence of B symptoms were significantly associated with a longer survival. The median survival in patients of group A was 42 months, however none of these patients relapsed during a median observation time of 42 months (range, 24–90). Conclusions: long-term survival and possibly cure can be obtained in some patients with HIV–NHL, in particular in those with a better PS and a less advanced immune dysfunction. In fact some of these patients are alive without evidence of disease 4 to 7 years after therapy, and others died of causes related to underlying HIV infection, in particular opportunistic infections, rather than relapse of NHL.     

MOLECULAR ABNORMALITIES OF THE p53 PATHWAY IN DEDIFFERENTIATED LIPOSARCOMA

Dedifferentiated liposarcoma represents a distinct subtype of liposarcoma and is characterized by the presence of abrupt transition from well-differentiated liposarcoma to high-grade pleomorphic sarcoma (mostly MFH-like). A key role for p53 in tumour progression of this subset of liposarcomas has been suggested on the basis of p53 immunopositivity. A series of 14 dedifferentiated liposarcomas has been investigated by analysing the p53 gene and protein together with the p53-related molecules p21^Waf1 and mdm2, to verify whether the p53 pathway is involved in the development and progression of this tumour type. The results indicate that the p53 gene is rarely involved in dedifferentiated liposarcoma (7 per cent of cases analysed) and that low percentages of p53 immunopositivity are still compatible with integrity of the p53 gene. This concept is also supported by the observed preservation of p21^Waf1 immunoreactivity in all but the p53-mutated cases. By contrast, mdm2 overexpression emerges as the most frequent abnormality in dedifferentiated liposarcoma (57 and 78 per cent of cases in well-differentiated and high-grade areas, respectively). © 1997 by John Wiley & Sons, Ltd.     

Synthesis,metabolic stability and chemotactic activity of peptide T and its analogues

Acquired immunodeficiency syndrome (AIDS) is initiated by the attachment of the human immunodeficiency virus (HIV) to a surface glycoprotein CD₄ present on T₄ helper/inducer lymphocytes, monocytes/macrophages and other cells. A simple octapeptide (H-Ala-Ser-Thr-Thr-Thr-Asn-Tyr-Thr-OH, peptide T) seems to inhibit HIV infectivity and to activate human monocyte chemotaxis. In order to study in vitro metabolic stability and structure-activity relationships, peptide T and a number of analogues were prepared and tested on human monocytes by chemotactic assay. Peptide T and the shorter fragments T(3-8)-OH and T(4–8)-OH displayed potent bioactivity (maximal chemotactic activity in the range 10^-11-10^-10M). The C-terminal heptapeptide showed a reduction of potency, while further truncations at N-terminus of T(4–8)-OH abolished the biological action. In the octapeptide series, whereas the α-amino butyric acid (Abu) substitution for Thr⁴ was well tolerated, the same “slight” structural change at Thr⁵ or Thr⁸ was very detrimental. Finally, [d -Asn⁶]T(1-8)-OH analogue has low chemotactic activity. All these results indicate that i) the C-terminal pentapeptide is the minimum sequence required for bioactivity, ii) residues 5 to 8 appear to play a crucial biological role, iii) peptide T chemotaxis is mediated, at least in part, through the polar properties of Thr side chains at the critical positions 5 and 8, while the Thr⁴ does not interfere with biological characteristics of peptides. With regard to the enzymic degradation, the in vitro experiments showed the susceptibility of peptide T to rapid metabolism by human or rat plasma (T1/2 = 5.2 min), rat brain (T1/2 = 2.1 min) and kidney (T1/2 = 0.4 min) enzymes. The main metabolic product appears to be the C-terminal heptapeptide, which retains, in turn, a low enzymatic stability.     

Image Integration-Guided Catheter Ablation of Atrial Fibrillation: A Prospective Randomized Study

Background: Several studies have provided details of left atrial anatomy by means of the image integration techniques, particularly focusing on the atypical patterns of the pulmonary veins.
Objective: To compare, in a prospective, randomized fashion, the conventional method of pulmonary vein disconnection and the image integration-guided approach.
Methods: Two hundred and ninety consecutive patients (290 patients, mean age 55 ± 11 years) with drug-refractory paroxysmal or persistent atrial fibrillation were enrolled in the study and were divided into two treatment groups: group 1 (145 patients) undergoing an imaging integration-guided (CartoMerge TM) ablation; group 2 (145 patients) treated by a conventional radiofrequency catheter ablation procedure. The arrhythmia was refractory to at least two antiarrhythmic drugs (IC, amiodarone).
Results: Electrical disconnection of all identified pulmonary veins was obtained in all patients of both groups. Bidirectional block of the cavotricuspid isthmus was achieved in 34 group 1 patients and in 40 group 2 patients. Left mitral isthmus ablation was attempted in 52 group 1 patients and in 56 group 2 patients. At a mean follow-up of 14 ± 12 months, the atrial fibrillation-free survival rate was significantly higher in group 1 patients compared with group 2 patients (88% vs 69%, P = 0.017). The analysis for the subset of patients with previously ineffective ablation (98 patients: 52 group 1 patients and 46 group 2 patients) showed a significantly lower recurrence rate in group 1 versus group 2 (19% vs 48%, P < 0.01).
Conclusions: Our data indicate a superior efficacy of the image-integration guided catheter ablation of atrial fibrillation over the long term.     

Transthoracic DC Shock May Represent a Serious Hazard in Pacemaker Dependent Patients

External defibrillation is widely used for the termination of various atrial and ventricular tachyarrhythmias, including pacemaker patients. Our study was intended to evaluate the effects of DC shocks in 36 patients with unipolar pacemakers implanted in the right pectoral region (25 DDD, 10 VVI, 3 AAI). The shocks were delivered with paddles on the anterior surface of the thorax, as far as possible away from the pacemaker. The pacing output was programmed at 0.5 msec and 5 V (25 patients), 4 V (1 patient), and 2.5 V (10 patients). Transient loss of capture occurred in 18 patients (50%). These patients, compared with those without capture failure, received higher peak and cumulative shock energies, respectively, 216 ± 99 versus 123 ± 50 joules (P < 0.002) and 352 ± 62 versus 147 ± 98 joules (P < 0.004) and had a lower pacemaker pulse amplitude (4.0 ± 1.2 vs 4.6 ± 1.0 V, P = 0.11). Failure to capture lasted from 5 seconds to 30 minutes (mean 157 sec). In 15 patients the ventricular stimulation threshold was measured before and serially after cardioversion. A six-fold threshold increase was observed 3 minutes after the shock (P < 0.004) with gradual recovery to nearly baseline values at 24 hours. Transient sensing failure occurred in 7 of the 17 patients in whom it could be evaluated (41%). Furthermore, three cases of shock induced pacemaker malfunctions were observed requiring replacement of the stimulator in two patients. In conclusion, the incidence of loss of capture in pacemaker patients subjected to electrical cardioversion/defibrillation is high. The phenomenon is due to an abrupt rise in stimulation threshold, caused by the electrical shock, and may represent a serious hazard in pacemaker dependent patients. The risk of pacing failure could be reduced by utilizing low shock energies when possible, and by programming the pacemaker at its maximal output before cardioversion.     

Impairment of daytime cerebrovascular reactivity in patients with obstructive sleep apnoea syndrome

Several studies have demonstrated a clear association between snoring, sleep apnoea and increased risk of stroke. However, the possible role of sleep apnoea in the pathophysiogenetic mechanisms of cerebrovascular disease is still unknown. Our aim in this study was to investigate cerebral haemodynamic changes during the waking state in eight patients with sleep apnoea syndrome (OSAS) by means of transcranial Doppler (TCD). In particular, we studied cerebral vascular reactivity (CVR) to hypercapnia calculated by means of the breath holding index (BHI). The investigation was performed in the early morning, soon after awakening, and in the late afternoon. Data were compared with those of eight healthy subjects matched for age and vascular risk factors. OSAS patients showed significantly lower BHI values with respect to controls both in the morning (0.56 vs. 1.36; P < 0.0001) and in the afternoon (1.12 vs. 1.53; P < 0.0001). In patients, BHI values in the afternoon were significantly higher than in the morning ( P < 0.0001). These data demonstrate a diminished vasodilator reserve in OSAS patients, particularly evident in the morning. This reduction of the possibility of cerebral vessels to adapt functionally in response to stimulation could be linked to hyposensitivity of cerebrovascular chemoreceptors after the continuous stress caused by nocturnal hypercapnia.     

Steroid-Eluting Electrodes Prevent Chronic Pacing Threshold Rise in the Atrial Chamher After Oral Propafenone Administration

The aim of the study was to evaluate chronic atrial pacing threshold increase after oral propafenone therapy. Fifty patients affected by advanced AV block and sick sinus syndrome were studied at least 6 months after pacemaker implantation, before and after oral propafenone therapy (450–900 mg/day based on body weight). The patients were subdivided into three groups as to the type of electrode implanted, all three unipolar: group I (20 patients) Medtronic CapSure 4003, group II (13 patients) Medtronic Target Tip 4011, group III (17 patients) Medtronic 4057 screw-in leads. In all cases, Medtronic unipolar pacemakers were implanted with the same noninvasive autothreshold measurement method. Propafenone and 5-OH-propafenone blood levels were measured 3–5 hours after drug administration. The pacing autothreshold was measured at 0.8, 1.6, and 2.5 V by reducing the pulse width. After propafenone. groups II and III showed a statistically significant threshold rise (P ranging from < 0.01 to <0.05), whereas no significant difference was found in group I. Propafenone and 5-OH-propafenone blood levels did not show any significant difference among the three groups. Strength-durution curves were drawn for the three groups before und after propafenone: at baseline the curves shifted to the left with the steep part above the knee, clearly favoring CapSure over the other two groups. After propafenone, the curves shifted to the right, with the flat part progressively more evident in groups II and III. In the atrial chamber, steroid-eluting leads prevented threshold increase after propafenone therapy, in contrast with a significant threshold rise with conventional porous and screw-in leads.