A retrospective observational study of people with Type 1 diabetes with self-reported severe hypoglycaemia reveals high level of ambulance attendance but low levels of therapy change and specialist intervention.

AIM: To evaluate the impact of severe hypoglycaemia on NHS resources and overall glycaemic control in adults with Type 1 diabetes. METHODS: An observational, retrospective study of adults (aged ≥ 18 years) with Type 1 diabetes reporting one or more episodes of severe hypoglycaemia during the preceding 24 months in 10 NHS hospital diabetes centres in England and Wales. The primary outcome was healthcare resource utilization associated with severe hypoglycaemia. Secondary outcomes included demographic and clinical characteristics, diabetes control and pathway of care. RESULTS: Some 140 episodes of severe hypoglycaemia were reported by 85 people during the 2-year observation period. Ambulances were called in 99 of 140 (71%) episodes and Accident and Emergency attendance occurred in 26 of 140 (19%) episodes, whereas 29 of 140 (21%) episode required no immediate help from healthcare providers. Participants attended a median of 5 (range 0-58) diabetes clinic consultations during the observation period; 13% (70 of 552) of all consultations were severe hypoglycaemia-related. Of the HbA1c measurements recorded closest prior to severe hypoglycaemia (n = 119), only 7 of 119 measurements were < 48 mmol/mol (< 6.5%) and mean HbA1c was 70 (sd 19) mmol/mol (8.5%, sd 1.7%). Some 119 changes to diabetes treatment were recorded during the observation period (median/person 0;, range 0-11), of which 52 of 119 changes (44%) followed severe hypoglycaemic events. CONCLUSIONS: We observed a high level of ambulance service intervention but surprisingly low levels of hypoglycaemia follow-up, therapy change and specialist intervention in people self-reporting severe hypoglycaemia. These results suggest there may be important gaps in care pathways for people with Type 1 diabetes self-reporting severe hypoglycaemia.

Bethesda 2014: improving on a paradigm shift.

The third iteration of the Bethesda System terminology manual was recently published. This update included changes in the reporting of benign endometrial cells, and guidance for special adequacy situations and for cases in which low grade squamous intraepithelial lesions are accompanied by some cells suggesting that a high grade lesion might also be present. In addition, the manual was increased in size to include more illustrations with special studies and comparisons to histology, a greatly increased reference list, and a new chapter devoted to the modern practice of risk-based management. The third edition of the Bethesda manual is meant to serve as a primary reference for the practice of gynecologic cytology designed to provide a uniform system of reporting Worldwide for clinical, teaching, and research purposes.

Fifteen-year trends and predictors of preparation for pregnancy in women with pre-conception Type 1 and Type 2 diabetes: a population-based cohort study.

AIMS: To investigate trends in indicators of preparation for pregnancy in women with Type 1 and Type 2 diabetes and explore their predictors. METHODS: Data on 2293 pregnancies delivered during 1996-2010 by women with Type 1 (n = 1753) and Type 2 (n = 540) diabetes were obtained from the Northern Diabetes in Pregnancy Survey. Multiple logistic regression was used to analyse the relationship between potential predictors and three indicators of inadequate pregnancy preparation: non-attendance for pre-conception care; no pre-conception folate consumption; and peri-conception HbA(1c) ≥ 53 mmol/mol (≥ 7%). RESULTS: Overall, 40.3% of women with diabetes attended pre-conception care, 37.4% reported pre-conception folate consumption, and 28.2% had adequate peri-conception HbA1c . For all patients, pre-conception folate consumption improved over time, while peri-conception glucose control did not. Attendance for pre-conception care for women with Type 1 diabetes significantly declined. Residence in deprived areas, smoking and younger maternal age (for women aged < 35 years) were independently associated with all three indicators of inadequate preparation for pregnancy. Additional predictors of inadequate peri-conception HbA(1c) were: Type 1 diabetes (adjusted odds ratio 5.51, 95% CI 2.71-11.22), longer diabetes history (adjusted odds ratio 1.16, 95% CI 1.09-1.23 per year increase for those with < 15 years' diabetes duration), non-white ethnicity (adjusted odds ratio 3.13, 95% CI 1.23-7.97) and higher BMI (adjusted odds ratio 1.05, 95% CI 1.01-1.09 per 1-kg/m(2) increase). Non-attendance for pre-conception care was additionally associated with Type 2 diabetes (P = 0.003) and multiparity (P < 0.0001). CONCLUSIONS: There are socio-demographic inequalities in preparation for pregnancy among women with diabetes. Women with Type 2 diabetes were less likely to attend pre-conception care. Pre-conception services need to be designed to maximize uptake in all groups.

Training and practice of cytotechnologists: a discussion forum focused on Europe.

OBJECTIVES: To discuss the role and training of cytotechnologists (CTs) in Europe, to identify areas of good practice and to provide an informed opinion to those providing guidelines for training and practice in Europe. METHODS: All members of the Editorial Advisory Board of Cytopathology were invited to take part in a 'discussion forum' for which six topics were circulated in advance concerning the roles of CTs with regard to: (1) pre-screening slides; (2) 'signing out' reports; (3) carrying out ancillary techniques; (4) supervising laboratory staff; (5) taking part in rapid on-site evaluation (ROSE) of fine needle aspirates (FNAs); and (6) whether CTs were trained specifically in cytopathology or in general histopathology. Notes of the meeting were circulated by email and a final report was agreed by 22 participants from 17 predominantly European countries. RESULTS: Training for CTs throughout Europe was variable, especially for non-gynaecological cytology, which was inconsistent with the range of activities required. The participants recommended graduate entry, preliminary training in general laboratory technology, and subsequent training to take account of the probability and, in some centres, the reality of primary cervical cancer screening changing from cytology to human papillomavirus (HPV) testing. They further recommended that CTs should perform HPV tests and take part in ROSE for FNAs, and they supported the European Federation of Cytology Societies developing guidelines for training and practice. CONCLUSION: With CT training added to a university-based education in laboratory or biomedical science, a career in cytotechnology should be an attractive option involving a diverse range of laboratory and clinically based activities.

Thyroid Bethesda reporting category, 'suspicious for papillary thyroid carcinoma', pitfalls and clues to optimize the use of this category.

OBJECTIVE: The Bethesda System of Reporting Thyroid Cytopathology classifies the indeterminate categories based on their differing risks of malignancy, as atypia of undetermined significance (AUS), follicular neoplasm/suspicious for follicular neoplasm (FLUS) and suspicious for malignancy. The vast majority of cases of the last category are suspicious for papillary thyroid carcinoma (PTC). The aim of the present study was to identify the pitfalls and clues to improve the usage of the suspicious category as well as improve its outcome of malignancy. METHODS: We reviewed the cytological features on air dried Diff-Quik® and alcohol-fixed Papanicolaou smears from 54 thyroid fine needle aspirates (FNAs) with surgical follow-up that were originally diagnosed as suspicious. Procedure data/specimen adequacy was correlated and follow-up histology reports were reviewed after our cytological review was completed. Incidental PTC that was not the target of the FNA was excluded from the calculations for correlation. RESULTS: In our cytological review, we retained a diagnosis of suspicious in 18 of the 54 cases and the remaining 36 were re-categorized as follows: 6 malignant, 10 neoplasm (which is used in our centre instead of FLUS) and 20 AUS. The reasons for overcall of suspicious cases included pseudopapillae, syncytial sheets, nuclear grooves and pinpoint nucleoli in chronic lymphocytic thyroiditis and Hürthle cell neoplasms, and intranuclear inclusions in parathyroid adenoma, hyalinizing trabecular adenoma and mesenchymal repair. The primary reasons for undercall of PTC as suspicious included cystic aspirates with minor features of PTC such as histiocytoid cells, bubblegum colloid, syncytial sheets and cellular swirls. Cases with cytoplasm similar to Hürthle cells were also noted to cause difficulty in accurate classification. CONCLUSIONS: Recognition of these pitfalls and clues can help improve diagnosis, patient treatment and consequently reduce the number of unnecessary thyroidectomies.

Endoscopic ultrasound-guided fine needle aspiration (EUS-FNA): experience of an academic centre in the USA.

OBJECTIVES: Endoscopic ultrasound-guided fine needle aspiration (EUS-FNA) has become widely accepted as an effective modality for obtaining tissue for primary diagnosis and staging. We have been using EUS-FNA since July 2001 and herein we summarize our experience over a 5-year period. METHODS: A computer-based search for in-house EUS-FNA was performed in the pathology database from July 2001 to October 2006. To calculate the sensitivity, specificity and accuracy of EUS-FNA, the cytology diagnosis was compared with the surgical follow-up. RESULTS: A total of 951 EUS-FNAs were performed during the study period and included 279 pancreatic solid lesions, 186 pancreatic cyst lesions, 249 lymph node aspirations, 111 gastrointestinal (GI) tract submucosal lesions, and 126 miscellaneous lesions. EUS-FNA had a very high sensitivity and accuracy for solid pancreatic lesions (94.7 and 97.7%, respectively), low sensitivity and accuracy but high specificity (47, 64.8 and 95%, respectively) for cystic lesions. Cyst fluid carcinoembryonic (CEA) levels were significantly higher in mucinous neoplasms than non-neoplastic cysts. EUS-FNA also had very high sensitivity and specificity for detecting metastatic carcinoma in lymph nodes (95 and 100%, respectively). GI submucosal spindle cell tumours were further classified with immunohistochemical stains performed either on a cell block or a core biopsy obtained via EUS guidance. CONCLUSIONS: EUS-FNA has a very high sensitivity and accuracy for pancreatic solid lesions, but the sensitivity for cystic lesions is generally low. Cyst fluid chemical analysis for CEA is helpful, but the overlap between mucinous neoplasm and non-neoplastic cysts is significant. Recognizing GI contamination is important and immunohistochemical stains are useful for GI submucosal spindle cell lesions.

Perinucleolar compartment prevalence has an independent prognostic value for breast cancer.

The perinucleolar compartment (PNC) is a multicomponent nuclear structure enriched with RNAs transcribed by RNA pol III and RNA binding proteins. Studies in cultured cells showed an association between PNC and transformed phenotype. To evaluate the relationship between structure and malignancy in vivo, we examined PNC prevalence (the percentage of cells containing at least one PNC) in normal and cancerous paraffin-embedded breast tissues using immunohistochemistry against a PNC-associated protein. Five hundred nuclei in the most active area of each sample were scored for PNC prevalence. The results show that PNC prevalence significantly correlates with the progression of breast cancer (by the criteria of staging). PNC prevalence in primary tumors, lymph nodes, and distant metastases shows a stepwise increase from a median of 23% in primary tumors to approximately 100% in distant metastases. In addition, univariate and multivariate (controlling for tumor size and grade) analyses show that early-stage patients with invasive ductal carcinomas containing a higher PNC prevalence have a significantly poorer prognosis. These findings link PNC prevalence with the progression of breast cancer in vivo and suggest that PNC-containing cells have metastatic advantages. These findings also show the potential of PNC prevalence as a prognostic marker for breast cancer.

Structural preferences of phosphatidylinositol and phosphatidylinositol-phosphatidylethanolamine model membranes. Influence of Ca2+ and Mg2+.

The structural preferences of soya phosphatidylinositol in isolation and in mixtures with soya phosphatidylethanolamine, and the influence of Ca2+ and Mg2+ on these preferences, have been examined employing 31P-NMR and freeze-fracture techniques. It is shown that phosphatidylinositol assumes the bilayer organization on hydration both in the presence and absence of Ca2+ and Mg2+. In mixed systems with (HII phase) phosphatidylethanolamine, phosphatidylinositol induces lipidic particle structure at low (less than 10 mol%) concentrations and bilayer structure at higher levels. In systems containing 15 or 20 mol% phosphatidylinositol, Ca2+ (but not Mg2+) can induce HII phase structure. The results indicate that phosphatidylinositol is a more effective agent than other acidic phospholipids for stabilizing bilayer structure, particularly when high levels of divalent cations are present. These findings are discussed in terms of functional roles of phosphatidylinositol and mechanisms whereby Ca2+ induces structural reorganizations in mixed systems containing acidic phospholipids and phosphatidylethanolamine.

Phosphatidic acid as a calcium ionophore in large unilamellar vesicle systems.

The ionophoretic capabilities of dioleoylphosphatidic acid (DOPA) for transporting calcium across phospholipid bilayers have been investigated. Calcium uptake by large unilamellar vesicles is shown to depend on the presence of DOPA. This uptake is sensitive to the nature and concentration of calcium chelators in the vesicle interior, indicating that accumulation results from DOPA-mediated translocation of calcium across the membrane. Further, it is shown that characteristics of DOPA-mediated Ca2+ uptake are similar to those observed for the fungal calcium ionophore, A23187.

N-succinyldioleoylphosphatidylethanolamine: structural preferences in pure and mixed model membranes.

The structural preferences of the pH-sensitive phospholipid, N-succinyldioleoylphosphatidylethanolamine (N-succinyl-DOPE), have been examined alone and in mixtures with DOPE by 31P-NMR, fluorescence energy transfer, and freeze-fracture techniques. The basic polymorphic behavior of pure N-succinyl-DOPE and DOPE/N-succinyl-DOPE lipid systems and the influence of calcium and pH were investigated. It is shown that, similar to other negatively charged acidic phospholipids, N-succinyl-DOPE adopts the bilayer organization upon hydration. This structure is maintained at both pH 7.4 and 4.0 in the presence or absence of calcium. In the mixed lipid system, N-succinyl-DOPE can stabilize the non-bilayer lipid, DOPE, into a bilayer structure at both pH 7.4 and 4.0 at more than 10 mol% N-succinyl-DOPE, although a narrow 31P-NMR lineshape is observed at acidic pH values. This corresponds to the presence of smaller vesicles as shown by quasi-elastic light scattering measurements. Addition of equimolar calcium (with respect to N-succinyl-DOPE) to the DOPE/N-succinyl-DOPE systems induces the hexagonal HII phase at both pH values. In unilamellar systems with similar lipid composition the addition of Ca2+ results in membrane fusion as indicated by fluorescence energy-transfer experiments. These findings are discussed with regard to the molecular mechanism of the bilayer to hexagonal HII phase transition and membrane fusion and the utility of N-succinyl-DOPE containing pH-sensitive vesicles as drug-delivery vehicles.

Structural properties of phospholipids in the rat liver inner mitochondrial membrane.

1. The 31P-NMR characteristics of intact rat liver mitochondria, mitoplasts and isolated inner mitochondrial membranes, as well as mitochondrial phosphatidylethanolamine and phosphatidylcholine, have been examined. 2. Rat liver mitochondrial phosphatidylethanolamine hydrated in excess aqueous buffer undergoes a bilayer-to-hyexagonal (HII) polymorphic phase transition as the temperature is increased through 10 degrees C, and thus prefers the HII arrangement at 37 degrees C. Rat liver mitochondiral phosphatidylcholine, on the other hand, adopts the bilayer phase at 37 degrees C. 3. Total inner mitochondrial membrane lipids. dispersed in an excess of aqueous buffer, exhibit 31P-NMR spectra consistent with a bilayer arrangment for the majority of the endogeneous phospholipids; the remainer exhibit spectra consistent with structure allowing isotropic motional averaging. Addition of Ca2+ results in hexagonal (HII) phase formation for a portion of the phospholipids, as well as formation of 'lipidic particles' as detected by freeze-fracture techniques. 4. Preparations of inner mitochondrial membrane at 4 and 37 degrees C exhibit 31P-NMR spectra consistent with a bilayer arrangement of the large majority of the endogenous phospholipids which are detected. Approx. 10% of the signal intensity has characteristics indicating isotropic motional averaging processes. Addition of Ca2+ results in an increase in the size of this component, which can become the domiant spectral feature. 5. Intact mitochondria, at 4 degrees C, exhibit 31P-NMR spectra arising from both phospholid and small water-soluble molecules (ADP, Pi, etc.). The phospholipid spectrum is characteristic of a bilayer arrangement. At 37 degrees C the phospholipids again give spectra consistent with a bilayer; however, the labile nature of these systems is reflected by increased isotropic motion at longer (at least 30 min) incubation times. 6. It is suggested that the uncoupling action of high Ca2+ concentrations on intact mitochondria may be related to a Ca2+-induced disruption of the integrity of the inner mitochondrial phospholipid bilayer. Further, the possibility that non-bilayer lipid structures such as inverted micelles occur in the inner mitochondrial membrane cannot be excluded.

Liposomes with entrapped doxorubicin exhibit extended blood residence times.

The blood residence time of liposomes with entrapped doxorubicin is shown to be significantly longer than for identically prepared empty liposomes. Liposomal doxorubicin systems with a drug-to-lipid ratio of 0.2 (w/w) were administered at a dose of 100 mg lipid/kg. Both doxorubicin and liposomal lipid were quantified in order to assess in vivo stability and blood residence times. For empty vesicles composed of phosphatidylcholine (PC)/cholesterol (55:45, mole ratio) and sized through filters of 100 nm pore size, 15-25% of the administered lipid dose was recovered in the blood 24 h after i.v. injection. The percentage of the dose retained in the circulation at 24 h increased 2-3-fold when the liposomes contain entrapped doxorubicin. For 100 nm distearoyl PC/chol liposomal doxorubicin systems, as much as 80% of the injected dose of lipid and drug remain within the blood compartment 24 h after i.v. administration.

Synergistic effect of stem cell factor with interleukin-3 or granulocyte-macrophage colony-stimulating factor on the proliferation of murine primitive hematopoietic progenitors.

We examined the effect of recombinant murine stem cell factor (SCF) on murine primitive hematopoietic stem cells in vivo. Marrow cells from 5-fluorouracil (5-FU)-treated male CBA/J mice were transplanted into lethally irradiated female littermates. Immediately after marrow transplant, the mice received SCF, interleukin-3 (IL-3), and granulocyte-macrophage colony-stimulating factor (GM-CSF) alone or in combination daily for 6 days. Day-12 colony-forming units-spleen (CFU-S) and marrow-derived colony-forming units-granulocyte/macrophage (CFU-GM) were assessed. Bone marrow cells from primary transplant recipients were transplanted into a secondary group of lethally irradiated mice, and the number of spleen colonies arising after 12 days' engraftment was determined as pre-CFU-S. SCF alone did not increase spleen colony formation in either primary or secondary recipients. In contrast, treatment of primary recipients with SCF and GM-CSF or IL-3 or with all three cytokines resulted in a synergistic increase of CFU-S in secondary recipients, indicating increased pre-CFU-S levels. The cytokine combinations also produced synergistic increases of CFU-GM in primary recipient marrow. Evaluation of spleen colonies in secondary recipients by PCR amplification of the Y-chromosome sex-determining region indicated that about 80% were of donor (male) origin. We conclude that SCF with IL-3 and/or GM-CSF increases pre-CFU-S proliferation.

Optimizing the CD34+ and CD34+Thy-1+ stem cell content of peripheral blood collections.

We have previously described a sensitive and specific CD34 enumeration assay and report here a prospective analysis of 25 myeloma patients undergoing PBSC mobilization using this assay to determine the optimal days for collection of CD34+ and CD34+Thy-1+ cells after chemotherapy and growth factor mobilization. Correlations between frequency of peripheral blood CD34+ cells, circulating white blood cell (WBC) count, apheresis CD34+ cell count, nucleated cell count (NCC), and numbers of apheresis colony-forming units granulocyte/macrophage (CFU-GM) were determined. To assess levels of the more primitive subsets of CD34+ cells in the PBSC collections, coexpression of the Thy-1 antigen (CDw90) on CD34+ cells was also assessed. Marked heterogeneity was noted between patients with apheresis samples containing a median NCC of 4.2 x 10(8)/kg (range 1.3-8.1), median CFU-GM 17 x 10(4)/kg (range 0.15-32 x 10(4)/kg), and median CD34+ cell count of 1.39 x 10(6)/kg (range 0.02-6.6). The frequency of CD34+ cells in PBSC collections coexpressing Thy-1 was also heterogenous (6.2-50% of CD34+ cells), median 21.6%, mean 24.7 +/- 2%. The apheresis CD34+ cell count correlated with the peripheral blood CD34+ cell percentage (r = 0.71, p < 0.0001) but only weakly with the peripheral WBC. Apheresis CD34+Thy-1+ cell numbers correlated strongly with the circulating CD34+ cell numbers (r = 0.80), but no correlation was noted between these candidate stem cells and the peripheral WBC. In contrast, apheresis CFU-GM levels correlated most strongly with the peripheral WBC count (r = 0.61, p < 0.0001). The apheresis CD34+ cell count correlated with apheresis CFU-GM (r = 0.75, p < 0.0001) but not with the apheresis NCC. Apheresis CD34+Thy-1+ counts significantly correlated only with the apheresis CD34+ cell count and not with the apheresis CFU-GM or NCC. A higher percentage of circulating and apheresis CD34+ cells expressing Thy-1 were found on day 1 of collection, and the percentage of CD34+ cells expressing Thy-1 decreased on each subsequent day of measurement: median of 22% day 1 vs. 16.6% day 4, p = 0.04. This study therefore confirms that accurate quantitation of circulating CD34+ cells best predicts the optimal day for apheresis collection of CD34+ and CD34+Thy-1+ cells and is superior to the WBC count in this regard. Furthermore, the candidate stem cell (CD34+Thy-1+) subset is most prevalent during the earliest phases of CD34+ cell mobilization.

Sensitive detection and enumeration of CD34+ cells in peripheral and cord blood by flow cytometry.

Peripheral blood stem cell autografts are increasingly used to reconstitute hematopoiesis after intensive, potentially marrow-ablative therapy. Assessment of autograft adequacy by enumeration of hematopoietic progenitors in colony-forming assays is handicapped by lack of reproducibility and prolonged assay time. Alternative approaches of graft assessment by flow-cytometric enumeration of stem/progenitor cells bearing the CD34 antigen can be hampered by low specificity and sensitivity. Here, we report a rapid and reliable multiparameter flow-cytometric approach to accurately enumerate CD34+ cells in peripheral blood (PB) mononuclear cells (MNCs). Total nucleated white blood cells (WBCs) are quantified by staining with fluorescein isothiocyanate (FITC)-conjugated CD45 antibody. Simultaneous staining by phycoerythrin (PE)-conjugated CD34 antibody defines an approximate number for the CD34+ progenitor/stem cell subfraction. When starting CD34+ cell numbers are low (0.01-0.5%), other nonspecifically stained leukocytes make accurate enumeration impossible. However, when the CD34+ fraction is analyzed for CD45 expression vs. side scatter (granularity), true CD34+ blast cells form a discrete cluster exhibiting low-density CD45 expression and low side-scatter characteristics. Cells within this "blast region" can be readily distinguished from lymphocytes, monocytes, granulocytes, and other events that can contaminate the CD34+ population. Here, we used this sensitive procedure to enumerate CD34+ cells in steady-state PB samples (0.03-0.09%), normal bone marrow (BM) aspirates, and umbilical cord blood collections (0.33-1.98%). This approach thus provides a means to analyze CD34+ cells in specimens from patients who have been extensively treated with chemotherapy and those undergoing PB stem cell mobilization with cytokines. Additionally, it is useful for assessment of CD34+ cells in a variety of clinical samples exhibiting perturbations of the hematopoietic progenitor/stem cell compartments.

Identification of CD34+ subsets after glycoprotease selection: engraftment of CD34+Thy-1+Lin- stem cells in fetal sheep.

Epitopes on the CD34 molecule detected by some CD34 antibodies can be cleaved by a unique glycoprotease from Pasteurella haemolytica, which cleaves only glycoproteins rich in O-linked glycans. A method to isolate CD34+ cells from adult bone marrow was developed subsequently, in which CD34+ cells were isolated in high purity and yield following immunomagnetic bead selection and detachment with the glycoprotease. Using a variety of other cell-surface markers shown here to be insensitive to glycoprotease, committed progenitors of T lymphoid, B lymphoid, monomyeloid, megakaryoblastic, or erythroid lineages could be identified. Significantly, candidate hematopoietic stem cells (HSC) that are contained within a CD34+Lin- (CD2-, CD14-, CD15-, CD16-, CD19-) (or CD34+CD38-) subset expressing the Thy-1 antigen (CDw90), c-kit receptor (CD117), and CDw109 but lacking expression of CD71 and HLA-DR antigens also were detected. Functionally distinct subsets of glycoprotease-selected CD34+ cells were identified and subfractionated using flow cytometry and fluorescence-activated cell sorting (FACS). These subsets included candidate HSCs expressing the CD34+Thy-1+Lin- phenotype, which were sorted from a CD34+ fraction of a mobilized peripheral blood (MPB) sample. In a fetal sheep model, when CD34+Thy-1+Lin- cells were injected intraperitoneally, they were capable of homing to the marrow, where they generated long-term multilineage hematopoiesis and maintained human CD34+ cells, indicating that candidate HSC subsets of CD34+ cells selected with this highly specific enzyme were capable of engraftment in vivo. The ability to identify and purify virtually any phenotypically defined subset of glycoprotease-selected CD34+ stem/progenitor cells should facilitate the study of hematopoiesis in vitro and in animal models in vivo as well as the development of novel genetic techniques for the correction of specific blood cell disorders in humans.