Can postoperative calcemia kinetics predict the risk of hypocalcemia for the management of parathyroid adenoma in ambulatory surgery?

INTRODUCTION

The goal of this study was to analyse the kinetics of corrected calcemia levels (Cac) after parathyroid excision and to determine the percentage of variation (ΔCa) in the initial hours after surgery, in order to entertain an early discharge.

POPULATION AND METHODS

Were included in this study, patients undergoing operation for parathyroid adenoma responsible for primary hyperparathyroidism (PHP). The Cac was measure preoperatively and four hours after surgery, and then every day until patient discharge. Group A included patients for whom the Cac was inferior to 2.2mmol/L at least once postoperatively while group B included patients for whom the Cac was always equal or superior to 2.2mmol/L. The ΔCa represented the percentage of the fall in postoperative Cac with respect to preoperative Cac.

RESULTS

Between 2010 and 2017, 156 patients fulfilled the inclusion criteria (women 80.8%, [sex ratio 1:4], median age 64 years old). Preoperative Cac was statistically significantly lower in group A compared to group B (2.67 vs. 2.82mmol/L; P<0.0001). In total, 9.6% of patients had calcium supplementation for hypocalcemia, symptomatic or not. Postoperative Cac reached its nadir value on postoperative day 2. At four hours postoperative, the risk of postoperative calcelmia falling below 2.2mmol/L appeared when the ΔCa was superior to 6% with a sensitivity of 92.9% and a negative predictive value of 97.4%.

CONCLUSION

After excision of a parathyroid adenoma for PHP, the Cac falls rapidly and reaches its nadir value on day 2. If the fall in calcemia is less than 6% four hours after surgery (vs. preoperative level), early discharge within the framework of ambulatory surgery is possible.

Double J stenting evaluation after ureteroscopy for urolithiasis

OBJECTIVES

During ureteroscopy for urolithiasis, postoperative ureteral drainage with double J stent is frequently used. It may reduce acute postoperative pain and late ureteral stenosis. Double J stent can have negative impact on life quality. After uncomplicated intervention, double J stent is not mandatory. Objective of our study was to evaluate pain and complications after ureteroscopy with or without stent.

METHODS

We retrospectively analyzed ureteroscopy performed between May 2014 and January 2017. Interventions were compared regarding ureteral drainage with double J stent or not. Our primary outcome was early postoperative pain evaluated with an oral pain scale form 1 to 10 on day one after intervention. Clinical characteristics, per- and postoperative data were collected. We also looked for risks factors of complications.

RESULTS

Three hundred and sixty-six interventions were included, 259 (70.8%) with and 107 (29.2%) without double J stent. Stone burden was higher in stented group (18.3 vs 9.4mm, P<0.0001). Patients without postoperative stents had more ureteral preparation with double J stent (78.5% vs 62.5%, P=0.0032) and had more ambulatory interventions (75.7% vs 52.5%, P<0.0001). Postoperative pain was not different (22% vs 17.75%, P=0.398). Complication rate was similar (29% vs 20.5%, P=0.1181), so was rehospitalization rate (0.8% vs 0.9%, P=1). In multivariate analysis, complications factors were unprepared ureter, experienced surgeons and access sheath.

CONCLUSION

Not stenting after ureteroscopy do not increase pain or complications. Stenting should not be used after uncomplicated interventions for centimetric stones.

LEVEL OF EVIDENCE

4.

Association between serum 25-hydroxyvitamin D concentration and severity of first-diagnosed bullous pemphigoid in older adults

BACKGROUND

Higher vitamin D status has been associated with symptom improvement and decreased risk of various autoimmune disorders. Our objective was to determine whether higher serum 25-hydroxyvitamin D (25OHD) concentration correlated with less severe first-diagnosed bullous pemphigoid (BP) in older inpatients.

METHODS

This cross-sectional study was performed from November 2012 to February 2014 among 30 consecutive older inpatients (21 women; mean ± SD, 83 ± 7 years; all Caucasian) with a de novo diagnosis of active BP recruited in the Department of Dermatology of Angers University Hospital, France. The severity of BP was graded clinically on the basis of i) the number of bullae during the first three days of hospitalization (grade 0-4, worse), and ii) the extent of the lesions (grade 0-5, worse).

RESULTS

Sixteen participants had ≤ 5 bullae at the time of diagnosis, 8 had 6-20 bullae, 3 had 20-50 bullae, and 3 had >50 bullae. The lesions were spread over 5 cutaneous areas in 5 participants (17%). The median 25OHD concentration was 23 [IQR, 16-42] nmol/L. Serum 25OHD concentration was inversely correlated with the bullae grade (ρ = - 0.38, p = 0.04) and the lesion extension grade (ρ = - 0.50, p = 0.005).

CONCLUSIONS

Higher serum 25OHD concentration correlated with less severe BP prior to initiation of treatment among our sample of older inpatients. This result suggests that vitamin D may be involved in the pathophysiology of BP and could serve as prognostic biomarker of BP.

Short in-Frame Insertions/Deletions in the Coding Sequence of the α-Globin Gene. Consequences of the 3D Structure and Resulting Phenotypes: Hb Choisy as an Example

A small group of hemoglobin (Hb) variants result from 'in-frame' deletion/insertion (del/ins). We describe a new variant of this group (Hb Choisy), found on the α1 gene, which is the exact counterpart of a previously published deletional variant, Hb J-Biskra [codons 51-58 (or codons 52-59) (-24 bp) (-TCTGCCCAGGTTAAGGGCCACGGC); HBA1: c.157_180del (or HBA2)]. In Hb J-Biskra, the sequence Ser-Ala-Gln-Val-Lys-Gly-His-Gly located from positions α52(E1) to α59(E8) is deleted, while in Hb Choisy the same sequence (Ser-Ala-Gln-Val-Lys-Gly-His-Gly) is inserted at position α52(E1). The variant carrying the insertion appears to be less damaging than the one with the deletion. A possible explanation could be that the additional sequence is located in the C to E interhelical region, and is less disturbing to the general structure of the globin chain. This insertion/deletion (ins/del) is likely favored by the repetition, at an interval of 16 nucleotides, of an eight nucleotide sequence. Comparison of variants of this group, found in the HbVar database, shows that structural modifications resulting from insertions are frequently less damaging than that caused by deletions.

Precision of CAPILLARYS 2 for the Detection of Hemoglobin Variants Based on Their Migration Positions

OBJECTIVES

In this report, we evaluated utility of the capillary electrophoresis (CE) migration position of the CAPILLARYS 2 CE instrument.

METHODS

The precision of this x-axis number was determined on a selection of common hemoglobin (Hb) variants (Hb S, Hb C, Hb D-Punjab, Hb E, Hb Hope), and the reproducibility of this number was evaluated by comparing the results obtained by two large reference laboratories on 81 Hb variants. Additionally, the CE migration position is given for a total of 409 Hb variants.

RESULTS

The x-axis migration position showed excellent intra- and interassay precision. Comparison of Hb variants seen by both laboratories showed that 83% had a difference in migration position of 1 unit or less. Only three rare Hb variants showed a difference of more than 2 units.

CONCLUSION

In summary, the CE migration position is a reproducible value and can be used as an aid in the identification of Hb variants.

Hospitalization of HIV positive patients: Significant demand affecting all hospital sectors

BACKGROUND

In a context of the evolution of severe morbidities in patients living with HIV (PLWH), the aim of this study was to describe reasons for hospitalization and the mode of care for the patients requiring hospitalization.

METHODS

All admissions (≥24h) of PLWH to 10 hospitals in the south of Paris (COREVIH Ile-de-France Sud) between 1/1/2011 and 12/31/2011 were identified. The hospital database and the file of patients followed in the HIV referral department of each hospital were matched. Detailed clinical and biological data were collected, by returning to the individual medical records, for a random sample (65% of hospitalized patients).

RESULTS

A total of 3013 hospitalizations (1489 patients) were recorded in 2011. The estimated rate of hospitalized patients was about 8% among the 10105 PLWH routinely managed in COREVIH Ile-de-France Sud in 2011. The majority (58.5%) of these hospitalizations occurred in a unit other than the HIV referral unit. Non-AIDS-defining infections were the main reason for admission (16.4%), followed by HIV-related diseases (15.6%), hepatic/gastrointestinal diseases (12.0%), and cardiovascular diseases (10.3%). The median length of stay was 5 days overall (IQR: 2-11), it was longer among patients admitted to a referral HIV care unit than to another ward. HIV infection had been diagnosed >10 years previously in 61.4% of these hospitalized patients. They often had associated comorbidities (coinfection HCV/HVB 40.5%, smoking 45.8%; hypertension 33.4%, dyslipidemia 28.8%, diabetes 14.8%). Subjects over 60 years old accounted for 15% of hospitalized patients, most of them were virologically controlled under HIV treatment, and cardiovascular diseases were their leading reason for admission.

CONCLUSION

Needs for hospitalization among PLWH remain important, with a wide variety in causes of admission, involving all hospital departments. It is essential to prevent comorbidities to reduce these hospitalizations, and to maintain a link between the management of PLWH, that becomes rightly, increasing ambulatory, and recourse to specialized inpatient services.

[Study of the reproducibility of the sterilization process and proposal of an sterilizer requalification protocol]

Unlike EN 554, and since the publication of ISO 17665-1 standard, the user of autoclaves may use methods other than those indicated in the guidelines. Outsourcing the requalification of sterilizers by an external service provider and after observing from the previous requalification reports that the thermometric data seemed reproducible, we decided to propose and validate a validation method for the reproducibility of the sterilization process. This is to exempt from the study of the repeatability of the EN 554 standard in future requalifications. Reproducibility was studied with the sensors of the sterilization service and from the production cycles. This study was carried out in three parts. First, we checked whether our sensors were reliable. Then we evaluated the sterilization process fidelity of each sterilizer. Finally, we compared our measurements performed by the service sensors with the measurements performed by the service provider during the requalifications of the previous years. This work leads us to describe a new protocol of requalification of our sterilizers.

Hb Olivet (HBA1: C.40G > A; p.Ala14Thr), a Novel Silent Hemoglobin Variant in Two Families of Distinct Origin

We report two families, members of which are carriers of a novel hemoglobin (Hb) variant that was named Hb Olivet [α13(A11)Ala→Thr (α1) (GCC > ACC); HBA1: c.40G > A; p.Ala14Thr]. The analysis of these cases allowed a clear description of this anomaly that behaves as a silent Hb. In the first family, of Portuguese ethnicity living in France, the proband, a 24-year-old male and his 57-year-old mother, both appeared to be carriers. The son presented with borderline mean corpuscular volume (MCV), while the mother was normocytic and normochromic. Hemoglobin separation on capillary electrophoresis (CE) was normal, while a slightly asymmetric peak was observed on high performance liquid chromatography (HPLC). In a second family, originally from Surinam but living in The Netherlands, the proband, a 6-year-old girl, showed a mild microcytosis at low ferritin levels. The abnormal Hb was inherited from the mother who was clearly iron depleted, was not present in the sister and brother of the proband. The microcytic hypochromic anemia was only shown in two out of a total of four carriers. It therefore seems likely that iron depletion is causative as two carriers are completely normal. Characterization and genotype/phenotype correlation are briefly described.

Hb Savaria [α49(CE7)Ser→Arg; HBA2: c.150C > A]: A New Case and Complete Description

Hb Savaria [α49(CE7)Ser→Arg; HBA2: c.150C > A] is a rare hemoglobin (Hb) variant, initially described in Eastern Europe but present worldwide. It belongs to that class of variants which can be confused with Hb S [β6(A3)Glu→Val; HBB: c.20A > T] by automated protein analysis and thus needs special tests for proper identification. Because it could arise from different nucleotide substitutions and according to the rules of the Human Genome Variation Society (HGVS) nomenclature, three 'Hb Savaria' variants are possible. In the case reported here it resulted from the HBA2: c.148A > C change.

Hepatitis C virus seroprevalence in adults in Africa: a systematic review and meta-analysis

With the introduction of more efficient treatments for hepatitis C virus (HCV), improved epidemiological information is required at the country level to allow evidence-based policymaking for elaboration of national strategies and HCV resources planning. We present a systematic review with meta-analysis of HCV seroprevalence data in adults in African countries. We conducted a systematic review of all HCV seroprevalence estimates reported in African countries from 2000 to 2014 in MEDLINE, AJOL and grey literature. We assessed studies performed in the general population and among blood donors, pregnant women and HIV-positive patients. A meta-regression analysis was used to provide adjusted estimates of HCV seroprevalence in the general adult population in each country, accounting for the heterogeneity in sample age structure and population types in the included studies. We identified 775 national-level estimations, among which 184 were included. Estimates of HCV seroprevalence were produced for 38 countries, in addition to the results from nationwide representative surveys available in Egypt and Libya. Next to Egypt, which clearly stands out, the highest levels of seroprevalence were found in Middle Africa (e.g. Cameroon, Gabon and Angola) and some West African countries (e.g. Burkina Faso, Benin), and the largest absolute numbers of infected adults were found in Nigeria, Ethiopia and Democratic Republic of Congo. This study exposes the diversity of HCV epidemiology among African countries. Egypt and several countries of West and Middle Africa present a HCV burden that will require strong governmental commitment to promote efficient preventive and curative interventions.

The two-year outcome of the I-Stop TOMS™ transobturator sling in the treatment of male stress urinary incontinence in a single centre and prediction of outcome

PURPOSE

The aim of this study was to present the results of the 2 year outcome of I-Stop TOMS™ transobturator sling for post-prostatectomy (UIPP) minor to moderate male urinary incontinence treatment.

MATERIALS AND METHODS

A prospective, single center study, including 26 patients with minor to moderate IUPP and operated on using a suburethral sling (MS) TOMS™ (four arms) was performed. UIPP assessment was made preoperatively and 1 year postoperatively, using validated questionnaires (SF36 and ICIQ), number of pads daily, and the 24 hours Pad-test (LPT). Telephone follow-up evaluation was performed in 21 patients over a 2 years period following surgery.

RESULTS

Radical prostatectomy was performed 48.4 months earlier and average patient age was 67.3 years. Preoperatively, the mean number of pads used daily was 2.3 with an average weight loss of 207.1grams at LPT. At 1 year, ICIQ and SF36 scores significantly improved. Weight loss in the LPT as well as the number of pads significantly decreased (P<0.05). At 1 year, 13 patients were cured, 12 were improved, one reached improvement criteria, and 96.2% using a pad daily maximum. With more than a 2 year follow-up, 10/21 patients were dry, nine improved and two failed, and 90.5% using 0 to 1 pad per day.

CONCLUSIONS

The transobturator TOMS™ male sling is a simple and well-tolerated procedure permitting a significant improvement of UIPP, with 50% of patients achieving complete continence at 1 year postoperatively, these good results continued beyond 2 years.

LEVEL OF EVIDENCE

4.

Pitfalls in the genetic diagnosis of Hb S

Patients homozygous for Hb S need to be properly identified to start as early as possible a treatment that should avoid complications. For prevention and genetic counseling, carriers of Hb S have to be screened. Hb S is easily detected by several analytical systems, but other variants, usually harmless, may behave as Hb S, leading to false positive diagnosis. Some interactions may also cause difficulties in the qualitative or quantitative interpretation of a chromatography or electrophoresis profile. These problems may result from several causes among which the simultaneous presence of an α chain variant leading to the formation of tetramers having both an α and a β chain modified, the presence of a second mutation within the Hb S allele, the existence of a compound heterozygous state leading to some "Hb S trait with dominantly transmitted sickle cell disease (SCD)", and the presence of thalassemic allele affecting the intracellular proportion of Hb S. In case of any "dominant Hb S trait" a thorough Hb study is always required. This work reports some of the difficulties observed by us, or reported in the literature, and propose how to avoid them and reach a correct diagnosis.

Strategy for identification by mass spectrometry of a new human hemoglobin variant with two mutations in Cis in the beta-globin chain: Hb S-Clichy [beta6(A3)Glu-->Val; beta8(A5)Lys-->Thr]

Hemoglobinopathies are the most frequent genetic diseases in the world. Among them, the Hb S variant [beta6(A3)Glu-->Val], which, in the homozygous state, produces a severe disease known as sickle cell anemia with polymerization of Hb S inside red blood cells under hypoxic conditions. Additional mutations, in cis or in trans of the beta(S)-globin chain, may inhibit or enhance the polymerization process. We describe here a new hemoglobin (Hb) variant (Hb S-Clichy) which carries the beta(S)-globin chain and an additional mutation beta8(A5)Lys-->Thr. The variant was detected by routine electrophoretic techniques and cation exchange liquid chromatography (CE-LC). Globin chain separation by reversed phase LC (RP-LC) showed normal and abnormal beta chains, confirming that the additional abnormality was located in cis to Hb S. Electrospray ionization mass spectrometry (ESI-MS) gave a 57 Da mass decrease for the abnormal globin chain. The abnormal chain was isolated and submitted to trypsin digestion. Normal peptides betaT-1 and betaT-2 were not observed on the matrix-assisted laser desorption-time of flight (MALDI-TOF) mass spectrum but a new peptide betaT-1,2 was detected. Nano LC-ESI-MS/MS of the new peptide showed that the glutamic acid at codon 6 was replaced by a valine residue, and the lysine at codon 8 was replaced by a threonine residue, as confirmed by DNA sequencing. This example demonstrates that in a population where Hb S is present, every unidentified Hb needs to be clearly characterized to prevent major sickle cell syndromes. In addition, the identification of these variants must be considered in newborn screening for sickle cell disease, using either classical biochemical methods or MS techniques.

Neonatal screening for sickle cell disease in France

BACKGROUND

As a result of population growth in African-Caribbean regions of overseas France, and now immigration essentially from North and sub-Saharan Africa to mainland France, neonatal screening for sickle cell disease (SCD) has been performed in France since 1985 in Guadalupe and dependencies, as a universal test. After several pilot studies, screening was gradually extended to mainland France in 1996. Since 2000, the test has been performed at national level for all newborns defined as being "at risk" for SCD based on ethnic origin.

METHODS

A dry blood sample is obtained by heel stick and analysed by isoelectric focusing as a first-line method, followed by either high-performance liquid chromatography or acid agar electrophoresis for confirmation, whenever a variant haemoglobin is observed on isoelectric focusing.

RESULTS

In 2007, 28.45% of all newborns in mainland France were screened for SCD. Since 1996, a total of 3,890 newborns have been found to have SCD, and they have been followed up by reference paediatricians.

CONCLUSION

Although screening for SCD at birth in France is not universal, it appears that missed babies are relatively infrequent. Despite obvious sociological problems inherent to the at-risk population, the follow-up of SCD babies is rather successful. Due to the birth prevalence of SCD in France, especially in comparison with other common genetic diseases, screening all newborns regardless of ethnic origin is an issue that is being addressed.

Hb Gerland [alpha 55(E4)Val-->Ala]: a mutation found on the alpha1-globin gene

The Hb Gerland [alpha 55(E4)Val-->Ala] mutation has been described in the alpha2-globin gene. We report here the same mutation in the paralogous alpha1-globin gene. This variant was found in a healthy 18-month-old boy of Chinese origin. Abnormal hemoglobin (Hb) fractions were visible on isoelectric focusing (IEF) and cation exchange high performance liquid chromatography (HPLC), with elution patterns differing from one system to another. Direct sequencing of the alpha-globin genes revealed a GTT>GCT (Val-->Ala) transversion at codon 55 of the alpha1-globin gene. We propose to name the variant encoded by the alpha1-globin gene Hb Gerland [A1], and the variant that is encoded by the alpha2-globin gene Hb Gerland [A2].

Hb Barika [alpha42(C7)Tyr-->His (alpha2)] leads to an alpha+ -Thalassemia-like syndrome

In human deoxyhemoglobin (deoxyHb), the hydrogen bond between Aspbeta99(G1) and Tyralpha42(C7), located in the alpha1beta2 interface, is crucial for the stability of the T structure. All the variants that could arise from a single point mutation affecting codon beta99 have already been observed, leading always to erythrocytosis. Conversely, up to now, Hb Barika is the only example found in a patient in whom the alpha42 is mutated. From a biochemical point of view, for theoretical reasons, this substitution has already been extensively studied on recombinant hemoglobin (rHb). In the patient, Hb Barika is expressed at a level lower than expected for an alpha2 gene variant and leads to an alpha+-thalassemic-like syndrome.

Hb Montfermeil [β 130(H8) Tyr→Cys]: suggests a key role for the interaction between helix A and H in oxygen affinity of the hemoglobin molecule

Hb Montfermeil [beta130(H8) Tyr-->Cys] is a high oxygen affinity variant causing erythrocytosis. The cysteine replacement is buried in the inside of the beta chain where it alters the interactions between helix A and H, with a further effect on helix E. This position has already been proposed to contribute to the difference in oxygen affinity between human and bovine hemoglobins. Three dimensional structural considerations and comparison of the functional behavior of other variants suggest that this region is an important determinant of the intrinsic oxygen affinity of the hemoglobin molecule.

Evaluation of the Bio-Rad VARIANT™ II HbA 2/HbA 1C Dual Program for measurement of hemoglobin concentrations and detection of variants

In this work data obtained on the VARIANT™ II hemoglobin analyzer using the Dual Kit elution system were compared to those obtained with the β-Thalassemia Short Program. Since many laboratories still use an earlier model of the hemoglobin analyzer, the Variant™ 1, these data were also compared to those obtained with the latter instrument. Our study is divided into two parts. The first is an evaluation of the precision of the VARIANT™ II for determining the levels of hemoglobin (Hb)A

Short insertion in a hemoglobin chain: Hb Esch, an unstable alpha1 variant with duplication of the sequence Ala65-Leu-Thr-Asn68

Hemoglobin (Hb) Esch, is an alpha1 variant, expressed at less than 5%, resulting from the duplication of the 12 nucleotides corresponding to CD65 through 68. The effect of this insertion is the repetition of the sequence Ala-Leu-Thr-Asn, which corresponds to the last turn of helix E. In this variant the presence of a one-turn elongated helix E causes instability and increased ligand affinity. Hb Esch was characterized by DNA sequencing and confirmed by electrospray mass spectrometry. Functional studies were performed by flash photolysis measurements on a fraction isolated by flatbed isoelectric focusing, which was enriched in the abnormal hemoglobin. Similar to other alpha chain variants due to short insertion (or deletion), Hb Esch probably results from a slipped mispairing mechanism. The stability of such modified proteins depends upon the region which is added or deleted and usually is more stable when involving a flexible loop or complete helix turn(s) near by.

Globin chain analysis by reversed phase high performance liquid chromatography: recent developments

Reversed phase high performance liquid chromatography of globin chains is an important additional tool in the study of hemoglobin abnormalities. Using a technique modified from that of Leone et al.,[1] we report here the relative chromatographic behavior of about 200 different hemoglobin variants. This method provides an additional dimension in the presumptive characterization of hemoglobin variants. It was also found to be of special value for measuring the expression of neutral variants, such as thalassemic or unstable hemoglobins, and to identify neutral mutations associated with another variant, resulting in unusual hematological presentations.

Hb O-Tibesti [beta121(GH4)Glu-->Lys; beta11(A8)Val-->Ile], a hemoglobin variant carrying in the same beta chain the substitutions of Hb O-Arab and Hb Hamilton, found in combination with Hb S [beta6(A3)Glu-->Val]

Hb O-Tibesti, carries in the same chain the substitution of Hb O-Arab [beta121(GH4)Glu-->Lys] and that of Hb Hamilton [beta11(A8)Val-->Ile]. Hb O-Tibesti may be distinguished from Hb O-Arab by polyacrylamide gel electrophoresis in the presence of urea and Triton-X100, and by reversed phase high performance liquid chromatography. It was found in a compound heterozygous condition with Hb S [beta6(A3)Glu-->Val] in a child of Chad-Sudanese descent, suffering from a sickle cell syndrome. Compared to the classical description of the Hb S/Hb O-Arab association, the additional Hb Hamilton mutation does not seem to modify the clinical presentation.

Abnormal hemoglobins: laboratory methods

Laboratory methods allowing the detection and characterization of hemoglobin variants are reviewed. Protein chemistry techniques such as isoelectrofocusing, electrophoreses under various experimental conditions, cation exchange and reversed phase high performance liquid chromatography, are the most frequently used for the detection of variants. When associated with a few additional data they may lead to a presumptive diagnosis. DNA studies are also developed in many laboratories. Final identification of a variant may be achieved either by molecular biology techniques or by protein sequence analysis in which mass spectrometry now occupies a key position.

Hb Mont Saint Aignan [beta128(H6)Ala-->Pro]: a new unstable variant leading to chronic microcytic anemia

Hb Mont Saint-Aignan [beta128(H6)Ala-->Pro] is a mildly unstable variant, associated with hemolytic anemia, marked microcytosis and increased alpha/beta biosynthetic ratio (1.55 versus 1.1 +/- 0.1 in the control). The abnormal chain was isolated by selective precipitation with isopropanol and the structural modification determined by protein chemistry methods (reversed phase high performance liquid chromatography and mass spectrometry). Possible mechanisms underlying the beta(+)-thalassemia-like expression of this variant are discussed.

Hb Ernz [beta123(H1)Thr-->Asn] and Hb Renert [beta133(H11)Val-->Ala]: two new neutral variants revealed by reversed phase high performance liquid chromatography analysis

Analysis of globin chains by reversed phase high performance liquid chromatography, used as an additional tool for characterizing hemoglobin variants, has led to the discovery of a new class of variants that display only differences in hydrophobicity. Two such variants are here described. Hb Ernz was found in a man of Italian origin who was polycythemic, and in two of his three daughters who were hematologically normal. Hb Renert, a slightly unstable variant, was found in a man from Cape Verde who also carried Hb S and presented with chronic hemolysis. The structural abnormalities were characterized by protein structure methods involving reversed phase high performance liquid chromatographic separations of globins and peptides, followed by mass spectrometry studies (electrospray, ion trap, tandem mass spectrometry).

Signaling specificities of fibroblast growth factor receptors in early Xenopus embryo

Formation of mesoderm and posterior structures in early Xenopus embryos is dependent on fibroblast growth factor (FGF) signaling. Although several FGF receptors (FGFRs) are expressed in the early embryo, their respective role in these processes remains poorly understood. We provide evidence that FGFR-1 and FGFR-4 signals elicit distinct responses both in naive and neuralized ectodermal cells. We show that naive ectodermal cells expressing a constitutively active chimeric torso-FGFR-1 (t-R1) are converted into mesoderm in a Ras-dependent manner, while those expressing torso-FGFR-4 (t-R4) differentiate into epidermis without significant activation of Erk-1. In neuralized ectoderm, expression of t-R4 causes the up-regulation of the midbrain markers En-2 and Wnt-1, but not of the hindbrain nor the spinal cord markers Krox20 and Hoxb9. Mutation of tyr(776) in the phospholipase C-(gamma) binding consensus sequence YLDL of t-R4 completely abolishes En-2 and Wnt-1 induction. In contrast to t-R4, platelet derived growth factor (PDGF)-dependent FGFR-1 activation in neuralized ectodermal cells expressing a chimeric PDGFR-FGFR-1 receptor results in the expression of Krox20 and Hoxb9. A similar effect is observed when an inducible form of oncogenic Raf is expressed, therefore implicating FGFR-1 and Raf in the transduction of FGF-caudalizing signals in neural tissue. Our results suggest that FGFR-1 and FGFR-4 transduce distinct signals in embryonic cells, and mainly differ in their ability to activate the Ras/MAPK pathway.