Liquid-based endometrial cytology: the Florence and Bari experience

Several diagnostic procedures are available to investigate the endometrium, i.e. sonography, hysteroscopy, biopsy, endometrial curettage and cytology. Among these, endometrial cytology is less commonly utilized. Although the use of cytology in the diagnosis of endometrial adenocarcinoma has already been proposed due to its low cost and simple execution, a general consensus has not been reached. The improvement of the diagnostic capacity of endometrial cytology following the introduction of a liquid-based method suggests that this test should be routinely used in endometrial diagnosis. The main advantages of this method are the reduction in confounding factors, the distribution of cells on a thin layer and the possibility to obtain more slides from the same sample. The aim of this article is to focus on the methodological procedures and diagnostic criteria in liquid-based endometrial cytology based on the experience in two Italian centres: Department of Pathology, University of Bari and Department of Human Pathology and Oncology, University of Florence. The sampling method used by the Bari authors consists in the collection of liquid for uterine distension during hysteroscopy, while the Florence group used an endometrial brush. The sensitivity and specificity at Bari were 75% and 83%, respectively, and were 94-100% and 95-100% at Florence, respectively. Endometrial cytology provided sufficient diagnostic material significantly more often than biopsy. We thus propose that endometrial cytology can be used in routine diagnosis either alone or in association with other diagnostic procedures in order to improve diagnostic accuracy.

Effect of gonadectomy on HCC development in HBV transgenic mice

BACKGROUND AND AIMS

Epidemiological data demonstrate that HCC is prevalent in men compared to women. Herein, we examined the effect of gonadectomy in a murine model that spontaneously develops HCC.

ANIMALS AND METHODS

Thirty-two male and 26 female HBV transgenic mice [Tg (Alb-1 HBV) Bri 44] underwent surgical castration or sham operation. At the 18th month, serum samples were collected and all mice were sacrificed. Liver weight and volume were evaluated, each liver was cut into 1.5-mm-thick consecutive slices and nodules were examined on freshly isolated tissue. Consecutive histological sections obtained from each liver slice were evaluated to confirm the diagnosis of HCC.

RESULTS

Sham-operated females showed a significantly lower neoplastic growth compared to sham-operated males. This difference disappeared when females underwent gonadectomy. In males, neoplastic growth was not influenced by gonadectomy. Testosterone and estradiol levels were profoundly modified by gonadectomy in both males and females. The testosterone/estradiol ratio in gonadectomized females increased 4.5-fold compared to that in sham-operated females, becoming more similar to the ratio observed in castrated and sham-operated male mice.

CONCLUSIONS

HCC growth in our experimental model was not simply influenced by the levels of testosterone or estradiol, taken singularly, but depended on their ratio.

Visual evoked potentials in infants of diabetic mothers: relations to clinical and metabolic status during pregnancy and delivery

OBJECTIVE

To evaluate Visual Evoked Potentials (VEPs) and psychomotor development of infants of diabetic mothers (IDMs) in relation to clinical and metabolic data during pregnancy and delivery.

METHODS

VEPs and psychomotor development (Brunet-Lézine) were analysed in 40 two-month-old IDMs (21 males, 19 females), 24 from mothers with type-1 diabetes, 13 gestational diabetes, and 3 type-2 diabetes. Normative VEP data were obtained from 63 age matched controls.

RESULTS

VEP latencies were significantly longer in IDMs than in controls (O1 wave IV=197.9+/-35.5 vs 155.3+/-30.3; P<0.001; O2 wave IV=200.2+/-33.8 vs 155.6+/-29.0; P<0.001). The mean developmental quotient was normal. In IDMs with type-1 diabetes delayed VEPs were related to increased weight during pregnancy (r 0.516; P 0.009), 1st trimester fasting blood glucose (r 0.458; P 0.037), insulin requirement during the 2nd (r 0.441; P 0.035) and 3rd trimester (r 0.422; P 0.039); in IDMs with gestational diabetes, VEP latency showed negative relation to Apgar scores (r -0.748; P 0.008).

CONCLUSIONS

IDMs have delayed VEPs, which may possibly be related to poor metabolic control in pre-gestational diabetes, and to delivery complications in gestational diabetes.

SIGNIFICANCE

IDMs show subtle neurophysiologic changes detectable by VEPs.

Dysfunctional DC subsets in RCC patients: ex vivo correction to yield an effective anti-cancer vaccine

Dendritic cells (DCs) are potent antigen-presenting cells responsible for the activation and functional polarization of specific T cells. In patients with renal cell carcinoma (RCC) and other cancers, coordinate DC and T cell defects have been reported. In particular, DC and T cell functional subsets that are not conducive to tumor clearance are hypothesized to predominate in patients with advanced-stage disease. Two major peripheral blood DC subsets have been identified in humans: myeloid dendritic cells (mDCs) and plasmacytoid dendritic cells (pDCs) that are believed to mediate contrasting effects on cancer immunity. Given the lack of information regarding DC subsets in patients with RCC, in the present study we have investigated the comparative frequencies and activation states of mDC and pDC in peripheral blood, cancer tissues and lymph nodes of patients with RCC using flow cytometry and immunohistochemistry. Three monoclonal antibodies (mAbs) reactive against specific DC subsets (BDCA-2 or BDCA-4 for pDC and BDCA-1 and BDCA-3 which represent two distinct subsets of mDC, mDC1 and mDC2, respectively) were employed. We observed a significant reduction of both DC subsets in the peripheral blood of patients as compared to normal donors. Similarly, both mDC and pDC were recruited in large numbers into RCC tumor tissues, where they displayed an immature phenotype (DC-LAMP(-)) and appeared unable to differentiate into mature DC (CD83(+)) that were competent to migrate to draining lymph nodes. However, we were readily able to generate ex vivo mDC from RCC patients. These DC stimulated robust anti-tumor CTL in vitro and would be envisioned for use in DC-based vaccines applied in patients with RCC whose existing immune system is judged dysfunctional, anergic or prone to undergo apoptosis.

Perinatal outcomes associated with the use of glargine during pregnancy

AIMS

Insulin glargine (IG), with its non-peaking action profile, might be useful in diabetic pregnancy. However, data on its safety are limited and its use during pregnancy is not recommended. This study focused on the effects of IG on perinatal outcome, particularly to estimate the rate of congenital anomalies and birthweight.

METHODS

This retrospective study included women with pre-gestational diabetes who used IG before (at least 1 month) and during pregnancy. For all women we recorded data regarding maternal glycaemic control and pregnancy outcome. We also compared women treated with IG throughout pregnancy and women who stopped taking IG at an earlier stage.

RESULTS

From 27 centres, 107 Type 1 diabetic pregnancies were identified. IG was started 10.3 +/- 6.9 months before conception and in 57.4% of cases was stopped during the first trimester; 42.6% of women continued using it until the end of pregnancy. There were six abortions (four spontaneous and two induced) and five newborns (4.9%) with congenital anomalies. Glycaemic control, birthweight and the prevalence of macrosomia and neonatal morbidity were similar in women who used IG for the full term compared with those who stopped IG earlier during pregnancy.

CONCLUSIONS

This study, although limited, suggests that IG is safe and effective; the rate of congenital malformations was within the range expected for diabetic pregnancies treated with more traditional forms of insulin. IG used throughout pregnancy did not seem to influence birthweight or increase adverse outcomes.

[Mucinous gastric adenocarcinoma and duodenal somato-statinoma. Case report]

The Authors present a rare association of gastric adenocarcinoma and somatostatin-producing duodenal carcinoid. The pre-operative abdominal CT scan revealed the gastric lesions and a duodenal polypoid lesion, giving an important indication to perform a subtotal gastrectomy and a duodenal resection. The definitive diagnosis was possible with histological examination.

Outcome of pregnancy in type 1 diabetic patients treated with insulin lispro or regular insulin: an Italian experience

Some studies have shown that fetal outcome observed in patients using insulin lispro is much the same as in pregnant women using regular insulin. This study aims to analyze the Italian data emerging from a multinational, multicenter, retrospective study on mothers with type 1 diabetes mellitus before pregnancy, comparing those treated with insulin lispro for at least 3 months before and 3 months after conception with those treated with regular insulin. The data collected on pregnant women with diabetes attending 15 Italian centers from 1998 to 2001 included: HbA1c at conception and during the first and third trimesters, frequency of severe hypoglycemic episodes, spontaneous abortions, mode and time of delivery, fetal malformations and mortality. Seventy-two diabetic pregnancies treated with lispro and 298 treated with regular insulin were analyzed, revealing a trend towards fewer hypoglycemic episodes in the former, who also had a significantly greater reduction in HbA1c during the first trimester. The rate of congenital malformations was similar in the offspring of the two groups of women treated with insulin lispro or regular insulin. These findings suggest that insulin lispro could be useful for the treatment of hyperglycemia in type 1 diabetic pregnant women.

Imaging of myocardial infarction using a 64-slice MDCT scanner: correlation between infarcted region and status of territory-dependent coronary artery

PURPOSE

This study was performed to evaluate the ability of 64-slice multidetector computed tomography (MDCT) to detect previous myocardial infarctions (MIs) in patients referred for the assessment of the coronary arteries. In patients with regional changes of left ventricular wall myocardial density, the territory-dependent coronary vessel status was examined.

MATERIALS AND METHODS

We retrospectively assessed 202 consecutive patients referred for 64-slice MDCT of the coronary arteries. In all cases, detailed, clinical, serological and electrocardiograph (ECG) data were collected to identify patients with a previous diagnosis of MI. An initial qualitative evaluation of MDCT images was performed in all patients to identify areas of suspected myocardial necrosis, which were defined as regions of lower density within normally enhanced left ventricular myocardium. Thereafter, in all patients with suspected MIs, attenuation values and left ventricular wall thickness were also measured at the level of the normal myocardium and within the hypodense regions. Each MI was also assigned to the distribution territory of a coronary vessel, and morphological data were combined with MDCT angiographic findings.

RESULTS

After clinical assessment, MI was found in 27 patients (six acute).; 64-slice MDCT was able to detect the presence of MI in 24/27 cases, showing sensitivity and specificity of 89% and 95%, respectively, and an overall diagnostic accuracy of 95%. Quantitative analysis showed a significant difference (p<0.01) between attenuation values of normal vs. infarcted myocardium (124.5+/-19 HU vs. 56.1+/-23 HU, respectively); wall thinning was exclusively observed in chronic MIs (p<0.01). In 23/24 detected cases, analysis of territory-dependent arteries showed findings compatible with presence of MI.

CONCLUSIONS

The presence of MI is well depicted with retrospective 64-slice MDCT. The main advantage of 64-slice MDCT is that it allows to evaluate and relate the status of a vessel and its dependent myocardial region in a single exam.

Imaging the whole body atherosclerosis: high resolution magnetic resonance angiography using blood-pool agent. Initial clinical experience

AIM

Recently whole-body 3D MR angiography (MRA) with blood-pool contrast agent has become available. The purpose of this study was to introduce and evaluate this technique to demonstrate arterial steno-occlusive involvement in systemic atherosclerosis and to compare blood-pool enhanced MRA results with those of CT angiography (CTA) as reference modality.

METHODS

Twenty patients with clinically and US documented carotid occlusive disease underwent whole-body MRA on a 1.5 T scanner and CTA on a 64-MDCT unit. Ten milliliters of a blood-pool agent (MS-235 Gadofosveset Trisodium, VASOVIST, Schering, Berlin, Germany) were administered intravenously and four 3-D MRA stations were acquired successively through automatic table moving. Images were reviewed by two observers. Overall image quality of each arterial segment was assessed and rated for both MRA and CTA examinations; MRA sensitivity, MRA specificity interobserver and intermodality agreement were calculated.

RESULTS

Whole-body MRA with blood-pool contrast agent was well tolerated by all patients. It yielded a detailed display of the arterial system with a short examination time. In 14 out of 20 patients there was extensive involvement of the arterial bed by steno-occlusive atherosclerotic disease; for the identification and characterization of vessel damage in the various vascular districts MRA sensitivity was 92-100%, MRA specificity was 95-100%; in 2 cases MRA underestimated the degree of peripheral vessel stenosis. Interobserver agreement calculated with K value was 0.63, intermodality agreement with CTA was 93% (P<0.01).

CONCLUSION

The whole-body MRA technique is a valuable tool for comprehensive evaluation of arterial steno-occlusive involvement in systemic arterial atherosclerosis; there is a good agreement between blood-pool enhanced MRA results and CTA, used as modality of reference.

Noninvasive imaging of the coronary arteries using a 64-row multidetector CT scanner: initial clinical experience and radiation dose concerns

PURPOSE

We present our initial clinical experience with a recently introduced 64-detector computed tomography (64-MDCT) scanner that makes use of a periodic motion of the focal spot in the longitudinal direction (z-flying focal spot), which enables it to reach a final spatial resolution of 0.4 x 0.4 x 0.4 mm(3) and a temporal resolution of 83 ms.

MATERIALS AND METHODS

A total of 114 patients (108 men, six women; age range 36-77 years, mean 63.1 years) underwent retrospective electrocardiogram (ECG)-gated examination of the coronary arteries using a 64-MDCT scanner (Somatom Sensation 64, Siemens Medical Solutions, Germany). Acquisition parameters were the following: collimation 64 x 0.6 mm, 800 quality reference milliampere second (mAs), 120 kVp, 0.33-s gantry rotation time and pitch 0.2. Images were acquired in all cases after i.v. administration of 80 ml of contrast agent (Iomeron 400 mgI/dl, Bracco, Italy) + 30 ml of saline at 4 /s and delay time determined using a bolus triggering technique. Oral betablockers were administered to patients with heart rate (HR) >75 bpm. To reduce radiation exposure, an automatic exposure control system was applied in all cases to adapt tube current to patient size and anatomic shape (CARE Dose 4D, Siemens Medical Solutions, Germany). The optimal temporal window for raw data reconstruction was chosen from an initial preview of images reconstructed with different phase settings (range 0%-95% RR interval with 5% gap) at a selected anatomical level in the mid part of the right coronary artery. CT dose index volume and effective dose were quantified in all patients using dedicated software.

RESULTS

Mean HR recorded during image acquisition was 65.6+/-19.2 bmp (range: 44-96 bmp), and beta-blockers were administered to 16/114 patients (14.0%). Technical adequacy was achieved in all patients but two (2/114; 1.7%). In patients with HR <60 bmp, the best reconstruction intervals were identified in the end-systolic (30%-35% of the RR interval) and end-diastolic (60%-65% of the RR interval) phases; with faster HR (>80 bmp), high image quality was observed in end-systole (30%-35% of the RR interval). Mean CT dose index (CTDI) volume was 36.53+/-8.30 mGy per patient. In comparison with a conventional examination with fixed mAs, the use of the CARE Dose 4D system provided a 33.3% CTDI volume reduction (p<0.001). Mean effective dose was 9.5+/-3.4 millisievert (mSv) per patient (range 7.1-17.7).

CONCLUSIONS

The 64-MDCT scanner diagnostic performance for coronary CT angiography is further improved with better spatial and temporal resolution and faster scan times; besides, initial clinical results are promising. The use of dose-reducing acquisition techniques is mandatory to limit radiation exposure to the patient.

Multidetector–row CT angiography of renal artery stenosis in 50 consecutive patients: prospective interobserver comparison with DSA

PURPOSE

The purpose of this study was to establish the diagnostic value of multidetector-row computed tomography (MDCT) angiography compared with digital subtraction angiography (DSA) for detection and quantification of both main and accessory renal artery stenosis in patients with secondary hypertension.

MATERIALS AND METHODS

Fifty consecutive patients scheduled for DSA were considered candidates for MDCT angiography. In all patients, MDCT angiography of the abdominal aorta was performed before DSA. For the purpose of interpretation, the arteries were separately interpreted either with DSA or MDCT angiography in order to provide qualitative and quantitative information. For qualitative evaluation, one experienced reader graded the opacification of renal arteries as excellent, good or poor; for quantitative evaluation, MDCT and DSA were independently evaluated for the number of renal arteries and the presence, location and degree of stenosis in random order by three readers. On the basis of consensus readings, calculations of sensitivity, specificity, accuracy, positive predictive value (PPV) and negative predictive value (NPV) for detection of degree of stenosis were made by using DSA findings as the standard of reference. Interobserver variability was also assessed.

RESULTS

With regard to qualitative analysis, arterial enhancement was considered excellent in 39 patients and good in 11. For quantitative analysis, 73 arteries were classified as normal with DSA. Although 72 of these were also classified as normal with CT angiography, one was overestimated by one grade; at DSA, 16 arteries were classified as moderately stenotic; in two arteries, there was an overestimation of one grade. Perfect correlation was achieved for the diagnosis of occlusion. In two patients, all three readers detected multiple severe stenoses on both modalities, with a "string-of-beads" appearance typical of fibromuscular dysplasia. Accessory arteries were correctly identified as such by all three readers on either DSA or MDCT. Levels of sensitivity, specificity and accuracy regarding degree of stenosis were 100%, 98.6% and 96.9%, respectively, with PPV and NPV of 97.6% and 100%, respectively. When we considered significant arterial stenosis (50%-100% luminal narrowing), sensitivity, specificity and accuracy were 100%, 97.3% and 97.8%, respectively, with a PPV and NPV of 98.2% and 97.8%, respectively. For all observers, interobserver agreement was almost perfect (k=0.81-1) for both MDCT and DSA, with a k value between 0.82 and 0.95.

CONCLUSIONS

MDCT angiography is very accurate and robust, even for the assessment of renal artery stenosis, and has the potential to become a viable substitute, in most cases, for diagnostic catheter-based DSA.

Volumetric evaluation of therapy response in patients with lung metastases. Preliminary results with a computer system (CAD) and comparison with unidimensional measurements

PURPOSE

The aim of this study was to assess the efficacy of a Computer-Aided Detection (CAD) system in the identification of lung metastases and to compare the volumetric CAD measurements with unidimensional observer measurements in the evaluation of treatment response in oncology patients.

MATERIALS AND METHODS

Two observers (A and B) evaluated nine patients undergoing lung computed tomography (CT) just before and immediately after treatment with chemotherapy. Multislice CT scans were performed before and after the injection of contrast material with a high-resolution protocol (collimation 4x1 mm, 100 mAs, 120 kV). Response Evaluation Criteria in Solid Tumours (RECIST) criteria were used to consider the disease as stable, increased or decreased. Subsequently, target lesions (most significant lesions identified before and after chemotherapy) were evaluated with a computerised system (CAD) to establish volumetric measurements. Observers' unidimensional measurements and CAD volumetric measurements were analysed for comparison.

RESULTS

Twenty-four nodules (diameter: 5-18 mm in the first study and 4-20 mm in the follow-up study) were included. Observers agreed in the assessment of therapy response in 21 nodules: eight were considered to have increased in size, and 13 were judged stable. Observer and CAD measurements disagreed in three nodules: two were considered stable by radiologists and increased by CAD; one was considered increased by radiologists and stable by CAD.As regards patient response, radiologists disagreed in two cases. CAD and observers did not agree in one case.

CONCLUSIONS

Our preliminary data suggest that volumetric measurements can modify the diagnostic and therapeutic evaluation of oncology patients under chemotherapy.CAD volumetric measurements allow an easy and objective evaluation, reducing interobserver variability in the evaluation of chemotherapy response.

A lower level of entropy in circadian rhythm of the sinus R-R intervals suggests a prevalence of the cardiac sympathetic regulation in early physiological pregnancy

The study estimates the unpredictable disorder (chaos) within the 24 h pattern of sinus R-R intervals (SRRI) in clinically healthy pregnant women (CHPW) and clinically healthy non-pregnant women (CHNPW), in order to evaluate the early gestational changes in neurovegetative cardiac pacing. SRRI were provided by the 24-h Holter ECG of 10 CHPW and 10 CHNPW. SRRI were investigated by descriptive conventional statistics by means of the Time and Frequency Domain Analysis, and subsequently, in their chaotic component by means of entropy analysis. Both the SRRI and entropy were tested via the Cosinor method to better decipher whether or not the periodic disorder in heart rate variability is modified in pregnancy as a result of a gestational tonic resetting of the cardiac sympatho-vagal regulation. Cosinor analysis documented that the circadian rhythm of both the SRRI and entropy were preserved in CHNPW and CHPW. However, the circadian rhythm of SRRI and entropy in CHPW exhibited a significantly decreased 24 h mean. Via the analysis of the rhythmicity of entropy, this study has documented that the chaos in the 24 h pattern of SRRI is less prominent in CHPW than in CHNPW. Such a reduction of level in the deterministic periodic chaos of heart rate variability provides evidence that, in early pregnancy, a tonic elevation of the sympathetic activity regulates cardiac pacing.

Analysis of the chaotic component of the sinusal R-R intervals as a tool for detecting a silent cardiac dysautonomia in type 2 diabetes mellitus

This study explores the heart rate (HR) variability (V) in order to detect whether the chaotic component of the sinusal R-R intervals (SRRI) can be interpreted as an early indicator of a silent cardiac neurovegetative dysautonomia in apparently uncomplicated Type 2 diabetic patients (DP). The SRRI were provided by the 24-h Holter ECG of 10 Type 2 DP (5 M and 5 F, mean age = 41 +/- 5 years). Control data were obtained by the 24-h Holter ECG of 10 clinically healthy subjects (CHS, 5 M and 5 F, mean age = 38 +/- 6 years). The chaotic component of HRV was investigated via the correlation dimension (CD) analysis (A) of the SRRI, performed per each hour of the ECG recording. The hourly-qualified series of SRRI, HR and CD index (I) were, in turn, analyzed via methods of conventional statistics and chronobiology, the latter ones for assessing the circadian rhythm (CR). The CDI CR was found to peak during the night in CHS, and to be unphysiologically rotated to the diurnal hours of the day in Type 2 DP. The diurnal inversion of the CDI CR in Type 2 DP suggests that the chaotic component of HRV shows an abnormal rhythnic pattern over the day-night period. Considering that the investigated Type 2 DP were lacking of documentable signs of cardiac neuropathy, it is hypothesized that the diurnal phase of shift CDI CR might be a potential indicator of a silent autonomic cardiac dysfunction in Type 2 DP. Such a hypothesis waits for further confirmations.

Coherent control of stimulated emission inside one-dimensional photonic crystals

In this paper, the quasinormal mode (QNM) theory is applied to discuss the quantum problem of an atom embedded inside a one-dimensional (1D) photonic band gap (PBG) cavity pumped by two counterpropagating laser beams. The e.m. field is quantized in terms of the QNMs in the 1D PBG and the atom modeled as a two-level system is assumed to be weakly coupled to just one of the QNMs. The main result of the paper is that the decay time depends on the position of the dipole inside the cavity, and can be controlled by the phase difference of the two laser beams.

Contraception in diabetic women: an Italian study

Over 1 year, a survey on contraception and obstetric history was performed on a cohort of 667 Caucasian fertile diabetic women (446, type 1 and 201, type 2) living in Italy.

RESULTS

Of these women, 30.4% used hormonal contraceptives, 12.0% intra-uterine device (IUD), 10.7% declared they used no contraception, 47.0% only utilised barrier and/or natural methods. However, irrespective of their previous contraceptive strategy, 7.2% of all the studied population was surgically sterilized during caesarean section.

HORMONAL CONTRACEPTION

Of these women, 60.4% was prescribed by a gynaecologist, 11.2% by a diabetologist, 15% by both of them and 13.4% by others. The proportion using oral contraception was similar among types 1 and 2 women (29.4% versus 27.8%, chi(2) = ns).

SMOKING HABITS

Of women taking hormonal contraception, 30.0% were smokers.

EDUCATIONAL LEVEL

University graduates (37.1%), high school leaves (32.2%), secondary school (28.2%) and primary school leaves (15.5%) used oral contraceptives (OC).

OBSTETRIC HISTORY

The mean number of deliveries was 1.14 +/- 1.1, of miscarriages was 1.3 +/- 0.7 and of induced abortions 0.17 +/- 0.5. Planning of at least one pregnancy was reported in 29.4% of patients.

Second quantization and atomic spontaneous emission inside one-dimensional photonic crystals via a quasinormal-modes approach

An extension of the second quantization scheme based on the quasinormal-modes theory to one-dimensional photonic band gap (PBG) structures is discussed. Such structures, treated as double open optical cavities, are studied as part of a compound closed system including the electromagnetic radiative external bath. The electromagnetic field inside the photonic crystal is successfully represented by a new class of modes called quasinormal modes. Starting from this representation we introduce the Feynman's propagator to calculate the decay rate of a dipole inside a PBG structure, related to the density of modes, in the presence of the vacuum fluctuations outside the one-dimensional cavity.

Reactivity models of 1-N-vinyluracil and synthesis of a new class of potential antiviral agents by the use of 1,3-dipolar cycloaddition reactions

By the use of a convergent approach based on 1,3-dipolar cycloaddition reactions between N-protected formylnitrones generated in situ and 1-N-vinyluracil, a new class of 4'-aza-analogues of 2',3'-dideoxynucleosides is synthesized. Competitive reaction for the endocyclic bond of uracil also brings to a new isoxazolidine derivative fused with the pyrimidine nucleus.