[Lung resection in the elderly: some limits]

INTRODUCTION

A progressive and constant increase of mean life duration in the last century has determined the challenge of the treatment of lung cancer even in the elderly with good functional status. The aim of the present study is to evaluate the results obtained in the elderly, over seventy years old, who underwent pulmonary resection at our Division of Thoracic Surgery of Polyclinic of Bari from 1985 to 1995.

PATIENTS AND METHODS

938 patients with NSCLC have been operated on, from January 1985 to December 1995. 189 were over seventy and 19 were over eighty years old. We have performed the following surgical procedures: 21 pneumonectomies, 108 lobectomies/bi-lobectomies, 44 wedge resections, 16 staging thoracotomies.

RESULTS

Post-operative complications were as follows: atelectasis 57, air leak 37, empyema 9, broncho-pleural fistula 3, arrhythmia 103, pulmonary edema 8, cardiac ischemia 3, pulmonary embolisms 1, delirium 2, hemothorax 3, exitus 5. There were 3 deaths caused by acute myocardial ischemia, one by pulmonary embolism, one by main right bronchus broncho-pleural fistula. Two and five-year overall survival were 67.1 and 37.8, respectively.

CONCLUSION

Diagnostic and therapeutical procedures for lung cancer should be different in the elderly. In our experience, main post-operative complications were cardiovascular, consequent to the entity and duration of surgical operation and intra-operative blood leaks. The elderly require a more careful post-operative monitoring to prevent this kind of complications.

[Minimally invasive thoracic surgery versus standard surgery]

Advances in technology, with the availability of optics and minitelevision cameras and improved endoscopic instrumentation (especially endo-stapler devices), have allowed the surgeon to obtain a superior panoramic view of the thoracic cavity and an optimal surgical manuvrability. This has determined the development, besides the traditional thoracotomic approach, of minimally invasive techniques of video-assisted thoracic surgery (VATS). An auxiliary mini-thoracotomic approach and the magnification of the operating theatre, which allows the surgeon to accomplish difficult manoeuvres under diret view, have progressively extended the indications of this procedure: at first used for the treatment of pneumothorax and pleural effusions, it is now employed in biopsy or atypical resection of pulmonary nodules, lung cancer staging and diagnostic-therapeutical procedures of mediastinal diseases, major pulmonary resections (lobectomy and pneumonectomy) and lung volume reduction surgery for emphysema (LVRS). The Authors review minimally invasive techniques of video-assisted thoracic surgery (VATS), compared to the traditional surgical ones, for the treatment of various thoracic diseases.

Endothoracic nodules in patients who under-went nephrectomy for renal cell carcinoma. Results of surgical resection

AIM

A review of our experience with surgical resection of endothoracic nodules in patients who underwent nephrectomy for renal cell carcinoma (RCC) is presented, to evaluate the incidence of metastases in our series and the effectiveness and the opportunity of surgical treatment in this sort of patients.

METHODS

Between January 1988 and January 2002, 41 consecutive patients (33 men, 8 women) underwent resection for suspected endothoracic metastases from RCC; 1 more male patient for metastases from an occult renal cancer. Mean age was 62 y (range: 43-80 y). Mean time between nephrectomy and 1st pulmonary resection in 41 patients was 29 mo (range: 0-120 mo). Nineteen patients had solitary lesions, 11 multiple unilateral and 12 bilateral. Antero-lateral thoracotomy was performed in 37 patients, median sternotomy in 1, simultaneous bilateral thoracotomy (clam-shell) in 2, sterno-laparotomy in 1, thoracofrenolaparotomy in 1. Wedge excision was performed in 36 patients, lobectomy with lymphadenectomy in 5, mediastinal limphadenectomy in 1. Six patients had repeat resection for recurrent metastases.

RESULTS

Only 24 patients (57%) had histologic diagnosis of pulmonary metastases from RCC; 11 (26%) had benign lesions; 7 (17%) primary lung cancer. Mean follow-up was 25 mo (range: 1-91 mo). Overall, 4-y survival was 50%. Patients with solitary metastasis had a lower survival than those with 4 and more lesions.

CONCLUSION

The evidence of pulmonary nodules in patients submitted to nephrectomy for RCC is not necessarily indicative of metastatic disease. Pulmonary resection for RCC metastases, even bilateral and recurrent, may help prolong survival in selected patients.

Dietary intake of calcium, magnesium and phosphorus in an elderly population using duplicate diet sampling vs food composition tables

The aim of this study was to estimate the dietary intake of calcium, magnesium and phosphorus in the elderly institutionalised population using duplicate diet sampling and to establish any related difference with the results obtained using food composition tables. The study was carried out on a sample group of 112 subjects in Granada (Spain). 1-week food duplicate samples offered by the elderly were studied. Calcium and magnesium were determined by AAS and phosphorus was determined by spectrophotometry. Anova showed significant differences (p<0.05) in all the minerals analyzed. These results suggest that the use of food composition tables is not suitable to evaluate the calcium, magnesium and phosphorus in nutritional trials. Moreover, the results show clearly that it is essential to consider these differences to establish the adequate intakes of calcium, magnesium and phosphorus for the elderly population in relation to the mineral bone status.

[Anesthesia induction with sevoflurane in adult patients with predictive signs of difficult intubation]

OBJECTIVE

This work was carried out to study induction with sevoflurane in adult patients with predictive signs of difficult intubation.

STUDY DESIGN

Randomised prospective study.

PATIENTS AND METHODS

The study had two parts. Part I: 15 patients without predictive signs of difficult intubation but with a cervical collar. Eight patients were anaesthetised with propofol 3 mg.kg-1 and fentanyl 2 micrograms.kg-1, seven with sevoflurane 8%. Part II: 20 patients with predictive signs of difficult intubation anaesthetised with sevoflurane 8%.

RESULTS

In part I, all patients were intubated, the time for intubation was longer with sevoflurane, 6 vs 4 min. They were apneic only in the propofol group. After intubation, 7 cases of coughing (4 severe) occurred in the propofol group and 3 moderate coughing in the sevoflurane group. In part II, one patient experienced considerable agitation after oral airway insertion and was excluded. Other patients were intubated with sevoflurane. Seven patients were intubated with a bougie, three patients through an intubating LMA and one patient with a rigid bronchoscope. The other patients were intubated with a Macintosh blade. The mean time for intubation was 10 +/- 7 min and end tidal sevoflurane concentration after intubation was 4 +/- 0.6%. After intubation, 7 cases of coughing (3 severe) occurred but no desaturation < 95%. No significant haemodynamic variations occurred.

CONCLUSION

Induction with sevoflurane 8% allowed tracheal intubation without major incidents. All patients breathed spontaneously. Sevoflurane can be recommended for induction in cases of predictive difficult intubation.

Thermal and structural behavior of anhydrous milk fat. 2. Crystalline forms obtained by slow cooling

The crystallization behavior of milk fat has been examined on slow cooling at 0.1 degrees C/min from 50 to -15 degrees C, to determine the variations of triacylglycerol organizations as a function of temperature. The experiments have been conducted with an instrument allowing coupled X-ray diffraction (XRD) at both small and wide angles and high-sensitivity differential scanning calorimetry (DSC) recordings from the same sample by taking advantage of the high-energy flux of a synchrotron. On slow cooling, milk fat triacylglycerols sequentially crystallize in four different lamellar structures with double-chain length of 41.5, 48.3, and 39.2 A and a triple-chain length of 62.2 A stackings. Simultaneous wide-angle XRD has shown that initial nucleation occurs in a packing of beta' type at about 24 degrees C. For temperature < 13 degrees C, triacylglycerols crystallize in an hexagonal subcell of alpha type, leading to the coexistence of the beta' + alpha polymorphic forms, which is recorded until -15 degrees C. Thermal analysis allowed to correlate the formation of the different crystalline species monitored by XRDT (XRD as a function of temperature) to the exothermal events recorded simultaneously by differential scanning calorimetry. The evolution of the species formed during crystallization was also monitored on heating at 2 degrees C/min. The absence of polymorphic evolution on heating, as well as the high final melting point observed, about 40 to 41 degrees C, confirmed that cooling at 0.1 degrees C/min leads to quasi equilibrium.

Transcriptional regulation of the KEL gene and Kell protein expression in erythroid and non-erythroid cells

The Kell blood-group antigen was originally reported to be a protein expressed in erythroid tissue only. Transcriptional analysis of the KEL promoter activity in human erythroleukaemia K562 and epithelial HeLa cells by electrophoretic mobility-shift and supershift assays, chloramphenicol acetyltransferase assays, co-transfection studies and site-directed mutagenesis provided the following results: (i) the KEL promoter exhibits a strong transcriptional activity in K562 cells and, unexpectedly, a basal non-erythroid activity in HeLa cells, (ii) up-regulation of the 5' distal promoter activity occurs only in the erythroid context, and (iii) two motifs localized in the exon 1 region, which bind the Sp1/Sp3 and the human GATA-1/Ku70/80 factors, were required for down-regulation of the promoter activity, but inhibition of the promoter activity by the repressing factors in HeLa cells was incomplete. KEL expression in HeLa cells was performed further by primer-extension analysis, which revealed the presence of a low amount of Kell transcript correlating with basal expression of the Kell protein in these cells, as shown by immunopurification and Western-blot analysis. DNA sequencing of the transcript revealed a sequence identical to that obtained from erythroid tissue. In human tissues, KEL expression was investigated by dot-blot analysis and revealed high levels of Kell mRNAs, particularly in brain tissues, testis and lymphoid tissues. Moreover, most tissues analysed exhibited low levels of Kell transcripts. The Kell protein was also detected by immunohistochemistry in the Sertoli cells of the testis and in lymphoid tissues like spleen and tonsil, specifically localized in the follicular dendritic cells. Altogether, the results indicated that KEL expression is not restricted to erythroid tissue.

Thermal and Structural Behavior of Milk Fat. 1. Unstable Species of Anhydrous Milk Fat

The thermal and structural behavior of anhydrous milk fat (AMF) was studied by a technique that allowed simultaneous time-resolved synchrotron X-ray diffraction as a function of temperature (XRDT) and high sensitivity differential scanning calorimetry (DSC) to be carried out in the same apparatus from the same sample. In this paper (the first of a series), the less stable crystalline structures made by triacylglycerols (TG) of bulk AMF after its liquid quenching down to -8 degrees C are addressed The coexistence of two lamellar structures characterized by sharp long spacing reflections corresponding to well-defined 3L (70 A) and 2L (47 A) longitudinal stackings but broad short spacing lines related to poorly ordered hexagonal (alpha) lateral packing is shown for the first time, The bilayered structure was very unstable, since it disappeared during a 20-min isothermal recording. Simultaneous DSC and X-ray monitoring of AMF heating in the range -8, +50 degrees C at a rate of 2 degrees C/min allows the same sample to be followed on the evolution of these unstable forms to more stable varieties. The 3L stacking transforms into a new 2L crystalline structure characterized by broad LS reflections corresponding to a ill-defined 2L (37 A) longitudinal stacking but a more compact orthorhombic (beta') lateral packing. A delimitation of the domains of existence of the crystalline structures resulted from the comparison of detailed analysis of the evolutions of positions, intensities, and widths of X-ray peaks as a function of temperature to microcalorimetry recording.

Immunological and hematological response in experimental Toxocara canis-infected pigs

The relationship between the immunological and hematological response to infection was studied in pigs inoculated experimentally with Toxocara canis. Two groups of four pigs were infected with doses of 1000 and 2000 infective eggs, respectively. Two uninfected animals were used as negative controls. Blood samples were collected from each pig once a week. Serological examination by ELISA to determine antibody levels against T. canis L2/L3 excretory-secretory (ES) antigens showed values higher than the positive cut-off point (1:32) for both the infected groups. These values increased from day 7 p.i. and remained high during the experimental period until day 56. Significant differences were recorded for the two inoculating doses (p</=0.01) from day 14 to 42 p.i. Western blots run on day 7 p.i. with serum from the 2000 eggs group showed two polypeptide bands of 70 and 55kDa. These same bands were observed for both infected groups from day 15 p.i. until the end of the experiment. Eosinophil counts were significantly higher (p</=0.05) for both inoculated groups between weeks 2 and 7 p.i. as compared with the control group. No significant changes were observed for other blood parameters. The pig is a useful animal model since T. canis induces an early immunological response and ELISA can detect the presence of these antibodies against T. canis L(2)/L(3) ES antigens in animals inoculated with low doses of Toxocara eggs.

The Composition of the Milk Fat Globule Surface Alters the Structural Characteristics of the Coagulum

The effects of the composition of a fat globule surface in reconstituted milks on the properties of rennet-induced coagulums were studied by rheological measurements and by front-face fluorescence spectroscopy in combination with a multivariate statistical method to investigate, at a molecular level, the evolution of the structure during the milk coagulation process. Reconstituted milks used in this study were prepared from different fat-in-water emulsions stabilized by whole skim-milk proteins, beta-casein, or beta-lactoglobulin. Coagulation of milk reconstituted with natural fat globules was also investigated. The study showed that the fat droplet/water interface influences the rheological properties (G' modulus) of the reconstituted milks during the coagulation process. The tryptophan fluorescence emission spectra of proteins were recorded during the kinetics of coagulation. The results of the principal component analysis performed on the spectral data showed a discrimination in the different systems investigated. It was shown that the fluorescence properties of protein tryptophans and, consequently, the structures of the protein networks were different for the investigated systems. The development of fluorescence transfer between protein tryptophans and fat-globule vitamin A during the coagulation kinetics agreed with the interactions between the protein network and fat globules. Copyright 2001 Academic Press.

An association study of bipolar mood disorder (type I) with the 5-HTTLPR serotonin transporter polymorphism in a human population isolate from Colombia

The short variant of a functional length polymorphism in the promoter region of the serotonin transporter has been associated with several behavioural and psychiatric traits, including bipolar mood disorder. The same short allele has also been implicated as a modifier of the bipolar phenotype. Here we evaluate the etiologic/modifier role of this polymorphism in a case (N=103) / control (N=112) sample for bipolar mood disorder (type I) collected from an isolated South American population. We did not detect an association between bipolar disorder and the 5-HTT promoter polymorphism in this sample. However, an excess of the short allele was seen in younger cases and in cases with psychotic symptoms. When combined with data from the literature, the increased frequency of the short allele in patients with psychotic symptoms was statistically significant.

Bulk dynamics for interfacial growth models

We study the influence of the bulk dynamics of a growing cluster of particles on the properties of its interface. First, we define a general bulk growth model by means of a continuum Master equation for the evolution of the bulk density field. This general model just considers an arbitrary addition of particles (though it can be easily generalized to consider subtraction) with no other physical restriction. The corresponding Langevin equation for this bulk density field is derived where the influence of the bulk dynamics is explicitly shown. Finally, when a well-defined interface is assumed for the growing cluster, the Langevin equation for the height field of this interface for some particular bulk dynamics is written. In particular, we obtain the celebrated Kardar-Parisi-Zhang equation. A Monte Carlo simulation illustrates the theoretical results.

Determination of sevoflurane alveolar concentration for tracheal intubation with remifentanil, and no muscle relaxant

The sevoflurane alveolar concentration needed for tracheal intubation with remifentanil was studied in 26 adult patients premedicated with 100 mg hydroxyzine. Anaesthesia was induced with sevoflurane in oxygen. The concentration was determined by Dixon's up-and-down method. The first patient was tested at 4.5%. One minute after obtaining the preselected value, remifentanil 1 microg.kg-1 was injected for 60 s followed by an infusion of 0.25 microg.kg-1. min-1. Ventilation was then manually assisted for 2 min and tracheal intubation was attempted. Tracheal intubation conditions and responses to intubation were noted. Heart rate and mean arterial pressure were recorded before induction, before remifentanil injection, and before and 3 min after tracheal intubation. The concentration for acceptable intubating conditions was 2.5 +/- 0.7%. From logistic regression, ED50 and ED95 were 2.0% (95% CI 1.3-2.5) and 3.2% (95% CI 2.6-5.6), respectively. With sevoflurane 2.5%, heart rate and mean arterial pressure decreased by 18% and 15%, respectively, after remifentanil administration and increased slightly after tracheal intubation.

[Lower pole pedicle in a series of 84 pyelo-ureteral junction syndromes surgically treated in children]

OBJECTIVE

To evaluate the involvement and consequences of the lower pole pedicle (LPP) associated with ureteropelvic junction syndrome.

MATERIAL AND METHOD

Retrospective study in 81 children presenting a total of 84 ureteropelvic junction syndromes operated consecutively between 1994 and 1998. Urinary tract ultrasound and cystography were systematically performed. Renal scintigraphy (DTPA or MAG 3) was performed in 80 children. Preoperative intravenous urography was performed in 60 children. LPP was considered to be present when its participation in the obstruction was confirmed intraoperatively (Anderson Hynes technique with uncrossing of the vascular pedicle).

RESULTS

Group I: a LPP was revealed in 24 kidneys (28.5% of cases), 17 left kidneys and 7 right kidneys, in 14 boys and 10 girls, with a mean age of 4 years (range: 2 months-14 years). Group II: 60 kidneys without LPP (71.5% of cases), 32 left kidneys and 28 right kidneys, in 40 boys and 17 girls, with a mean age of 2 years (range: 1 month-15 years). The most frequent presenting complaint was recurrent low back pain in 58% of cases in group I (14/24) and 5% of cases in group II (3/60). The mean age at diagnosis was 6 years. Hydronephrosis was detected by antenatal ultrasound in 33% of cases in group I (8/24) and in 72% of cases in group II (43/60). Kidney function in group I was greater than 40% in 19 patients, between 20 and 39% in 2 patients and less than 20% in 2 patients. These results were not influenced by age at diagnosis and were not significantly different from those observed in group II. Renal malrotation was observed in 2 cases in group I and in 12 cases in group II. Histology of the junction revealed nonspecific fibrosis in the same percentage of cases (91%) in the two groups. The mean follow-up was 15 months (range: 2 months-5 years). No surgical failure was observed.

CONCLUSION

Ureteropelvic junction syndrome associated with a LPP appears to present later with recurrent low back pain in older children. It does not worsen the functional prognosis of the affected kidney. LPP can be visualized by duplex ultrasound. It may act as an inducer of obstruction by aggravating a pre-existing abnormality of the ureteropelvic junction. When LPP is associated with isolated dilatation of the pyelocaliceal cavities, the risk of subsequent decompensation requires closer ultrasound surveillance, until puberty.

Thermal and Structural Behavior of Milk Fat

The thermal and structural properties of unstable varieties of triacylglycerols (TGs) crystallizing in milk fat globules of cream are examined in the range -8- +50 degrees C using a new instrument allowing simultaneously time-resolved synchrotron X-ray diffraction at both wide and small angles as a function of temperature (XRDT) and high sensitivity differential scanning calorimetry (DSC). Small angle X-ray diffraction shows that the unstable alpha form first formed by cream quenching to -8 degrees C corresponds in fact to two different lamellar phases corresponding to 2L (47 Å) and 3L (70.4 Å) arrangements of TGs. The bilayered structure is very unstable since it disappears during the course of a 20-min isothermal conditioning at -8 degrees C. On fast heating, the crystalline evolution of cream TGs demonstrates the monotropic character of their polymorphism. The structural and thermal behaviors of cream which are compared to that of its anhydrous milk fat isolated from the cream (C. Lopez et al., J. Dairy Sci., submitted) show that the crystallization occurring in emulsion droplets is similar to bulk. However, the comparison of XRD peak widths indicates that the TG crystallization is more disordered in emulsion. This disorder is attributed to the constraints due to the interface curvature in emulsion droplets. Copyright 2000 Academic Press.

Kikuchi-Fujimoto necrotizing lymphadenitis associated with cutaneous lupus erythematosus: a case report

Histiocytic necrotizing lymphadenitis or Kikuchi-Fujimoto disease is a rare entity, and even more rarely, it is associated with other diseases. In a few cases, the condition is associated with cutaneous lupus erythematosus (CLE). Histiocytic necrotizing lymphadenitis predominantly affects young women, who present with solitary or multiple cervical lymphadenopathy accompanied by symptoms such as fever, weight loss, sweating, or, in exceptional cases, hepatosplenomegaly. Laboratory examinations show normal or nonspecific results. The disease is of unknown origin, although a viral origin has been suggested, with the suspected agents including Epstein-Barr virus, herpesvirus type 6, and cytomegalovirus (CMV). Although the first and most of the more recent cases have been reported in Oriental patients, the disease has a wide geographic distribution. The clinical evolution is favorable, with spontaneous remission in less than 4 months in almost all cases. We present a case of a 37-year-old woman from Peru who presented with cervical adenopathies on two occasions. Biopsy of a lymph node revealed a histopathologic picture compatible with Kikuchi-Fujimoto histiocytic necrotizing lymphadenitis. The adenopathy disappeared in a few months. A year later, she presented with a maculopapular rash in the nasal and malar regions. The results of the skin biopsy and immunofluorescence examination were compatible with chronic CLE. The results of the serology testing for CMV were positive. Treatment with chloroquine was initiated, with almost complete recovery by 5 months. No manifestations of systemic lupus erythematosus have occurred since. The epidemiologic, clinical, and anatomopathologic aspects as well as the differential diagnosis of this entity are reviewed.

Quantitative analysis of XG blood group and CD99 antigens on human red cells

CD99, the product of the MIC2 gene, exhibits an erythroid-specific quantitative polymorphism co-regulated with the Xga blood group polymorphism. The co-expression of X-linked MIC2 and XG genes is presumably controlled at the transcriptional level by a single XGR locus in the pseudoautosomal region of sexual chromosomes. This locus is composed of two alleles, XGR(low) and XGR(high), which determine low or high CD99 levels (CD99-L, CD99-H) and the Xg(a-)/ Xg(a+) status. To test this hypothesis, the phenotypic relationship between Xga and CD99 antigens on human RBCs was investigated by quantitative flow cytometry using NBL-1 (anti-Xga) and 12E7 (anti-CD99) monoclonal antibodies and semi-quantitative estimate of membrane proteins and RNA by Western blot and Northern blot, respectively. The antibody binding capacity of RBCs, which is an estimation of the antigen density, was determined for 118 blood donors including 60 males and 58 females. Xg(a+) RBCs, which all belong to the group of CD99-H expressors, carry 159+/-13 and 960+/-50 copies of Xga and CD99 molecules/cell, respectively. Xg(a-) RBCs have no Xga antigen, but are subdivided into CD99-H (all male) and CD99-L expressors carrying 747+/-28 and 200+/-22 CD99 copies/cell, respectively, with identical CD99 levels between CD99-L males and females. However, among males, the CD99 expression was higher in Xg(a+) than in Xg(a-)/CD99-H individuals (P<0.01). In addition, CD99-H expressors in Xg(a+) males could be clearly subdivided into two categories, high and super high expressors, which are presumably heterozygous and homozygous for the XGR(high) allele, which fits the above hypothesis. This was not the case for Xg(a+) females where CD99-H subcategories were not found. Quantitative differences were confirmed by Western blot analysis of red cell membrane preparations from individuals of different Xga and CD99 phenotypes and by Northern blot analysis showing that the reticulocytes from CD99-L individuals expressed a reduced level of MIC2 transcripts compared to CD99-H donors. These findings further support the hypothesis of a single genetic control of CD99 and Xga expression by the XGR locus.

Mesigyna once-a-month combined injectable contraceptive: experience in Latin America

A phase III clinical study was carried out among 534 fertile Latin American women to evaluate cycle control, side effects, and contraceptive efficacy of a once-a-month combined injectable, Mesigyna, consisting of 50 mg norethisterone enanthate and 5 mg estradiol valerate. The pregnancy rate at 1 year was 0 per 100 woman-years for a total experience of 4688 woman-months. The overall discontinuation rate at one year was 17.9%. Discontinuation rate for bleeding problems was 5.1%. The Colombian women had a significant increase (p <0.001) in bleeding problems compared to other countries. The discontinuation rate for amenorrhea was 1.1%. There were no significant differences between the groups regarding discontinuation for other medical or non-medical reasons. Mean weight gain after one year of use was 1.02 kg. Mesigyna is an appropiate once-a-month injectable contraceptive for Latin American women since it is highly effective and its perception of normal menstrual bleeding is of importance in the Latin American population.

Multifractal structure of chaotically advected chemical fields

The structure of the concentration field of a decaying substance produced by chemical sources and advected by a smooth incompressible two-dimensional flow is investigated. We focus our attention on the nonuniformities of the Holder exponent of the resulting filamental chemical field. They appear most evidently in the case of open flows where irregularities of the field exhibit strong spatial intermittency as they are restricted to a fractal manifold. Nonuniformities of the Holder exponent of the chemical field in closed flows appears as a consequence of the nonuniform stretching of the fluid elements. We study how this affects the scaling exponents of the structure functions, displaying anomalous scaling, and relate the scaling exponents to the distribution of local Lyapunov exponents of the advection dynamics. Theoretical predictions are compared with numerical experiments.

A study of the coregulation and tissue specificity of XG and MIC2 gene expression in eukaryotic cells

CD99, the product of the MIC2 gene, exhibits an erythroid-specific quantitative polymorphism coregulated with the polymorphism of the XG blood group gene. As a preliminary study of this phenomenon, human XG and CD99 recombinant proteins were expressed in murine RAG cells and analyzed by flow cytometry. Both proteins were expressed independently and at a similar level in single and double transfectants. Immunoprecipitation and Western blot analysis, using the murine monoclonal antibodies NBL-1 and 12E7, revealed species of 26 kd (XG) and 32 kd (CD99), respectively. A putative 28-kd intracellular precursor of CD99 was also detected, as was a 26-kd species after neuraminidase treatment of CD99-expressing cells. No evidence of association or complex formation between XG and CD99 proteins could be proven, either on transfected RAG cells or on human erythrocytes. These results were confirmed using somatic hybrids between single transfectants. These findings suggest that the phenotypic relationship between XG and CD99 is mostly regulated at the transcriptional level, but they do not formally exclude some posttranscriptional effect. Studies on the tissue specificity of XG expression showed that surface expression of the XG protein could not be restored in somatic hybrids between B-lymphoblastoid cell lines from Xg(a+) persons and fibroblasts (RAG) or erythroid (MEL) cells. RT-PCR analysis of the transcripts revealed the existence of an XG mRNA in each cell line, suggesting that the tissue-specific regulation of cell surface XG expression occurs either at a quantitative transcriptional level or is a posttranscriptional event. By Northern blot analysis, XG transcripts were detected in erythroid tissues and several nonerythroid tissues. (Blood. 2000;95:1819-1826)