Influence of vascular risk factors on executive function among an age-homogeneous elderly cohort.

The pathogenesis of executive dysfunction in geriatric depression remains uncertain although causal bidirectional relationships with depression have been discussed. Previous studies have described a potential link with 'vascular depression'. In this study, we investigate the influence of vascular risk factors and magnetic resonance imaging markers of structural brain ageing, such as increasing deep white matter hyperintensities (DWMH), on executive function in an age-homogeneous population-based study cohort. A total of 606 participants of identical age (75.8 years; standard deviation 0.45 years) took part in the baseline investigation of the Vienna Transdanube Ageing (VITA) study. Each participant underwent a full psychometric examination with standardised neuroimaging and clinical chemistry investigations. Participants were re-examined with the same protocol after exactly 30 and 60 months. Data refer to the individuals who completed the examination at baseline. In the ordinal logistic regression, fewer years of education (P < 0.0001), Trail Making Test-A (P < 0.0001), high homocysteine (P = 0.001), and depression (P < 0.0001) were significantly associated with Trail Making Test-B (TMT-B) values. A significant influence of other vascular risk factors, such as lipids, diabetes, and smoking, on executive dysfunction was not observed. A comparison of both lacunes and DWMH with respect to the TMT-B results showed no significant correlation. Our data do not support the notion that vascular pathogenesis might underlie executive dysfunction.

Gene expression profiles induced by growth factors in in vitro cultured osteoblasts.

OBJECTIVES: Effects of insulin-like growth factor 1 (IGF1), fibroblast growth factor 2 (FGF2) and bone morphogenetic protein 2 (BMP2) on the expression of genes involved in the proliferation and differentiation of osteoblasts in culture were analysed. The best sequence of growth factor addition that induces expansion of cells before their differentiation was sought. METHODS: Primary human osteoblasts in in vitro culture were treated with IGF1, BMP2 or FGF2 (10 ng/ml) for 24 hours (IGF1) or 48 hours (BMP2 and FGF2). Experiments were performed during the exponential growth phase with approximately 1e7 cells per 75 cm(2) flask. mRNA was reverse transcribed directly and analysed using RT-PCR Taqman assays. Expression levels of key genes involved in cell growth and differentiation (CDH11, TNFRSF11B, RUNX2, POSTN, ALP, WNT5A, LEF1, HSPA5, FOS, p21) were monitored using RT-PCR with gene-specific Taqman probes. RESULTS: Autocrine expression of BMP2 is stimulated by FGF2 and BMP2 itself. BMP2 and FGF2 act as proliferative factors as indicated by reduced expression of ALP and POSTN, whereas IGF1 exhibits a more subtle picture: the Wingless und Int-1 (Wnt) signalling pathway and the Smad pathway, but not p38 mitogen-activated protein (MAP) kinase signalling, were shown to be activated by IGF1, leading to proliferation and differentiation of the cells. CONCLUSIONS: For future use of autologous bone cells in the management of bony defects, new treatment options take advantage of growth factors and differentiation factors. Thus, our results might help to guide the timely application of these factors for the expansion and subsequent differentiation of osteoblastic cells in culture. Cite this article: Bone Joint Res 2014;3:236-40.

The role of memory-related gene polymorphisms, KIBRA and CLSTN2, on replicate memory assessment in the elderly.

The role of the CLSTN2 (rs6439886) and KIBRA (rs17070145) SNPs in cognitive impairment was analysed in a 75-76 years old group. Various memory assessment tests were carried out on individuals at baseline and during follow-up investigations, and biallelic genotyping was performed. No influence of the allele status of either SNPs was observed on any memory test. No increased risk of any type of late development, and cognitive impairment was associated with rs6439886 or rs17070145.

Risk factors for cerebrovascular and cardiovascular diseases beyond age 75 years.

Globally, cardiovascular diseases (CVDs) are the number one cause of all mortalities. Of these deaths, 7.6 million are due to heart attacks, and 5.7 millions are due to stroke. The Vienna Transdanube Aging Study (VITA), a population-based cohort study, enabled us to evaluate associations between the known major risk factors for cerebrovascular and CVDs and their appearance beyond age 75 years. Using a single birth cohort, age was excluded as confounding factor. In the baseline investigations in the Danube Hospital, 606 individuals took part and were examined completely at baseline. After 60 months, 508 patients were re-examined. Each participant underwent an indepth investigation with the duration of 7 h, including neuropsychological testing, as well as analyses of biochemical, clinical chemical and genetic parameters, and magnetic resonance imaging (MRI) of the brain. In the present study, only a history of cerebral and cardiovascular events at the baseline or smoking was associated significantly with the appearance of CVDs. In a multiple model both risk factors-history of cerebral and cardiovascular events at the baseline (p = 0.0003, OR 2.36, 95% CI 1.49-3.76) and smoking (p = 0.0005, OR 1.57, 95% CI 1.22-2.03)-remained significant. However, the predictive value of this assessment model was low. The rescaled r² of the model was 0.088. A significant correlation was found only between exposure to cigarette smoke or a history of previous CVDs, such as stroke or myocardial infarction. Smoking or earlier CVDs greatly increase the risk for further cerebral and cardiovascular events in persons after 75 years.

Complement factor H gene polymorphisms and Chlamydia pneumoniae infection in age-related macular degeneration.

PURPOSE: To investigate the association of the complement factor H gene (CFH)Y402H polymorphism and age-related macular degeneration (AMD) in the Austrian population (Caucasoid descent), and to determine whether there is an association between exposure to Chlamydia pneumoniae-responsible for up to 20% of community-acquired pneumoniae-and the AMD-associated CFHrisk polymorphism. METHODS: Genotypes were determined by polymerase chain reaction-restriction fragment length polymorphism analysis in 75 unrelated AMD patients and compared with 75 healthy, age-matched control subjects. C. pneumoniaeserum IgG was tested by ELISA (R&D) in both groups. The association between the CFHY402H genetic polymorphism and the disease was examined by chi (2)-test and logistic regression. RESULTS: CFH Y402H genotypefrequencies differed significantly between AMD patients and healthy controls (1277 TT, 22.7%; 1277 TC, 53.3%; and 1277 CC, 22.7% in the AMD group; 1277 TT, 48.0%; 1277 TC, 38.7%; and 1277 CC, 13.3% in the control group) showing a P-value <0.005 (OR:2.920/3.811).No association was found between a positive C. pneumoniae titre and AMD (P=0.192), nor was any association found between C. pneumoniae and the CFH Y402H polymorphism. CONCLUSIONS: Our data confirm that the CFHY402H polymorphism is a risk factor for AMD in the Austrian population with a higher frequency of the Y402 polymorphism in AMD patients. No association between preceding C. pneumoniaeinfection and diagnosed AMD was found.

Serum concentrations of retinol-binding protein 4 in women with and without gestational diabetes.

AIMS/HYPOTHESIS: Pregnancy is characterised by temporarily increased insulin resistance. Gestational diabetes occurs when pancreatic beta cell function is unable to compensate for this insulin resistance. Retinol-binding protein 4 (RBP4) could be related to insulin resistance. We hypothesised that RBP4 is elevated in gestational diabetes. METHODS: Serum RBP4, transthyretin and retinol were cross-sectionally measured in 42 women with gestational diabetes and 45 pregnant controls. Of these, 20 women with and 22 without gestational diabetes were included in an additional longitudinal study. RBP4 was determined by enzyme immunometric assay (EIA) and western blot. RESULTS: Women with gestational diabetes had lower RBP4 EIA and western blot levels than controls (median 6.8 [interquartile range, 3.9-14.3] vs 11.3 [7.8-19.9] microg/ml, p < 0.001 and 25.1 [21.7-29.6] vs 26.6 [23.5-32.2] microg/ml, p = 0.026). Transthyretin and the RBP4:transthyretin molar ratio were comparable between the groups. Serum retinol was lower (p < 0.001) and the RBP4 Western blot level: retinol molar ratio was higher in women with gestational diabetes (p = 0.044). RBP4 was not associated with the glucose or homeostasis model assessment of insulin resistance (HOMA-IR), but in gestational diabetes the RBP4:retinol molar ratio correlated with blood glucose and negatively with 2 h post-load insulin. The RBP4:transthyretin ratio correlated with HOMA-IR and fasting insulin in controls. In women with gestational diabetes RBP4 EIA and western blot levels increased after delivery. Retinol increased in both groups, while transthyretin and the RBP4:transthyretin ratio were not altered after parturition. CONCLUSIONS/INTERPRETATION: RBP4 measured by two different techniques is not elevated, but the RBP4:retinol molar ratio is higher and correlates with fasting blood glucose in women with gestational diabetes. Thus, the RBP4:retinol ratio and the RBP4:transthyretin ratio are more informative than RBP4 levels alone when assessing insulin-glucose homeostasis during pregnancy.

AB0 system and D(Rh o) antigen frequencies in left ventricular hypertrabeculation/noncompaction in relation to cardiac and neuromuscular findings.

BACKGROUND: Left ventricular hypertrabeculation/noncompaction (LVHT) is a cardiac abnormality with suspected genetic background, characterized by trabeculations and intertrabecular recesses. Aim of the study in LVHT patients was to assess the AB0 system and D(Rh(o)) antigen frequencies, to look for an association between the prevalence of cardiac and neuromuscular abnormalities and to compare distribution of the AB0 system and D(Rh(o)) antigen frequencies with the Austrian general population. METHODS AND RESULTS: In 77/102 LVHT patients (75%) information about blood group could be obtained. There were no differences in the prevalence of clinical, electrocardiographic and echocardiographic findings and neuromuscular disorders between the AB0 blood groups. When comparing 67 LVHT patients who were D(Rh(o)) antigen positive with 10 patients who were D(Rh(o)) antigen negative, no differences could be found. Among LVHT patients, 0 D(Rh(o)) antigen positive was the most frequent (39%) followed by A D(Rh(o)) antigen positive (34%). In the Austrian general population A D(Rh(o)) antigen positive was the most frequent (33%) followed by 0 D(Rh(o)) antigen positive (30%). CONCLUSION: This study shows that LVHT patients do not differ according the blood groups, and that the distribution of blood groups is only minimally different between LVHT patients and the general Austrian population.

Adiponectin concentrations increase during acute FFA elevation in humans treated with rosiglitazone.

The adipocytokine adiponectin is released by adipocytes upon activation of the peroxisome proliferator-activated receptor gamma (PPAR gamma). PPAR gamma has binding sites for thiazolidinediones and free fatty acids (FFAs). To evaluate if adiponectin serum concentrations are synergistically regulated by FFAs and thiazolidinediones IN VIVO plasma FFAs were acutely elevated in healthy subjects pre-treated with rosiglitazone or placebo. Sixteen healthy male subjects (23-37 years) were included in this double-blind, randomized, placebo-controlled parallel-group study. Rosiglitazone 8 mg or placebo was administered daily for 21 days. On the last day plasma FFA concentrations were increased by an intravenous triglyceride/heparin infusion. Blood for determination of adiponectin, C-reactive protein (CRP), leptin, resistin, FFAs, glucose, and insulin was drawn at baseline and on day 21 before and after 5 hours of triglyceride/heparin infusion. Adiponectin concentrations increased and FFA levels decreased in subjects receiving rosiglitazone (all p<0.05 VS. baseline). Lipid infusion significantly increased FFA plasma concentrations, with an attenuated elevation in rosiglitazone-treated subjects. However, adiponectin concentrations were only increased in subjects on rosiglitazone (p=0.018 VS. before lipid infusion), but not in controls. Leptin increased during lipid infusion in subjects receiving placebo but not in those on rosiglitazone. CRP and resistin were not affected by rosiglitazone or FFAs. The acute increase in circulating adiponectin concentrations during acutely elevated FFA depends on PPAR gamma activation in healthy subjects.

Cardiac and noncardiac, particularly neuromuscular, disease with troponin-T positivity.

OBJECTIVES: Although elevated cardiac troponin T is caused by myocardial damage in the vast majority of the cases (primary cardiac causes), noncardiac disease with secondary damage to the myocardium (secondary cardiac causes) is being increasingly recognised. The present study aimed to retrospectively evaluate the frequency of primary cardiac and secondary cardiac causes of troponin-T positivity, in particular how often troponin-T positivity is associated with neuromuscular disorders. RESULTS: Of 16,944 troponin-T determinations in a secondary centre between April 2004 and April 2005, troponin T was positive in 1408 of them (8.3%). Of these, 622 were included for evaluation. Troponin-T positivity was associated with elevated creatine kinase in 54.5% and with creatinine >2 mg/dl (177 micromol/l) in 16.6% of the tests. The most frequent primary cardiac causes of troponin-T positivity were myocardial ischaemia (59%), atrial fibrillation (23%), and heart failure (22%). The most frequent secondary cardiac causes of troponin-T positivity were renal insufficiency (22%), chronic obstructive lung disease (10%), and acute stroke (4%). There was one cause for troponin-T positivity in 249 cases and more than one in 373 cases. A neurologist saw patients with troponin-T positivity in 9.5% of the cases. Troponin-T positivity was associated with a neuromuscular disorder in 6.3% of the cases. Causes of troponin-I positivity were also frequently causes of troponin-T positivity. CONCLUSIONS: Ischaemic heart disease is the most frequent cause of troponin-T positivity, followed by heart failure and renal insufficiency. Many causes previously described to be only responsible for troponin-I positivity also cause troponin-T elevation. Troponin-T positivity is frequently associated with neuromuscular disorders, most likely due to cardiac involvement of these conditions.

Positive troponin-T in noncompaction is associated with neuromuscular disorders and poor outcome.

OBJECTIVES: Though cardiac troponin-T may be positive in hypertrophic and dilated cardiomyopathy, it is not known how often troponin-T is positive in left ventricular hypertrabeculation/ noncompaction (LVHT), an unclassified cardiomyopathy. This retrospective study aimed to assess how often troponin-T is positive in LVHT, is associated with elevated CK, is attributable to cardiac or extra-cardiac causes, in particular neuromuscular disorders (NMDs), or if it is a predictor of poor survival. RESULTS: Among 100 patients, detected over a period of 11 years, troponin-T was determined at least once in 71 (71%) of them. Troponin-T was determined once in 36 patients, twice in 8 cases, three times in 11 patients, and more than three times in 16 cases. Troponin- T was positive at least once in 12 patients (17%). Forty-five of the 71 patients suffered from a NMD (63%). Troponin-T positivity was associated with elevated CK in 6 cases. Troponin-T-positivity was attributable to acute myocardial ischemia in a single case, to chronic renal failure in 5 cases, to dilated cardiomyopathy in 4 cases, to atrial fibrillation in 3 cases, to heart failure in 4 cases, and to NMD in 10 cases. Troponin-T positivity in LVHT patients with NMD was assumed to be due to cardiac involvement in the disease. Among the 22 patients who died during the observational period troponin was determined in 16 and was positive in 4 (25%). CONCLUSIONS: Troponin-T is positive in 17% of the patients with LVHT. Most of these patients suffer from a NMD. Troponin-T positivity in LVHT predicts the presence of NMD and poor survival.

Improved metabolic control decreases platelet activation markers in patients with type-2 diabetes.

BACKGROUND: Cardiovascular disease is associated with platelet dysfunction in patients with diabetes. Hyperglycaemia is known as an independent risk factor for micro- and macrovascular complications, and improvement of metabolic control has shown beneficial effects on diabetic late complications. Our study attempts to clarify the effect of improved metabolic control on platelet activation markers in patients with type-2 diabetes. MATERIALS AND METHODS: Thirty patients were studied at baseline and 3 months after improvement of metabolic control and compared with an age-matched nondiabetic control group. Platelet activation markers (CD31, CD36, CD49b, CD62P and CD63) were assessed by flow cytometry analysis. RESULTS: Significantly more activated platelets were detected in patients with diabetes compared with controls. After 3 months' improvement of metabolic control, a significant decline of all platelet activation markers except CD36 was noted. Furthermore a significant correlation between CD62P, CD63 and HbA(1c) levels was observed. CONCLUSIONS: We conclude therefore that improvement of metabolic control has a beneficial effect on platelet activation. This may have an implication in the pathogenesis of vascular disease in patients with type-2 diabetes.

Low levels of Sex-Hormone-Binding Globulin predict insulin requirement in patients with gestational diabetes mellitus.

Low Sex-Hormone-Binding Globulin (SHBG) levels--indicating a state of hyperandrogenicity--are associated with a higher risk for the development of non-insulin dependent diabetes (NIDDM) in women and are accepted as a marker of muscular insulin resistance. To analyze whether low SHBG values are also present in patients with gestational diabetes, we investigated levels of SHBG in 42 patients with gestational diabetes mellitus (GDM) in comparison with 48 pregnant women with normal glucose tolerance (NGT). Beside maternal parameters like body-mass index (BMI), HbA1c, fasting, 1- and 2-hour blood glucose and insulin concentrations, parameters of the new-borns (head-circumference, body weight, height and sex) were recorded. Maternal and neonatal variables were then related to SHBG levels. Both groups showed no differences in BMI, height, weight or age of gestation. Patients with GDM revealed significantly lower levels of SHBG than pregnant women with NGT(512 +/- 249 nmol/l vs. 643 +/- 137 nmol/l; p < 0.01). In patients with severe GDM and insulin therapy significantly lower levels of SHBG than in those with dietary treatment only were found (223 +/- 210 nmol/l vs. 592 +/- 102 nmol/l; p < 0.001). SHBG was inversely correlated to BMI (r = - 0.30; p < 0.01), 1-hour (r = - 0.20; p < 0.05) and 2-hour blood glucose levels (r = - 0.30; p <0.01). In summary, we found significantly lower levels of SHBG in patients with GDM, especially in those who developed severe GDM and required insulin therapy during the last months of pregnancy.

Severe factor XI deficiency caused by compound heterozygosity for the type III mutation and a novel insertion in exon 9 (codons 324/325 +G).

We investigated a 42-year-old Caucasian woman with severe factor XI deficiency and her family members. Restriction enzyme analysis and DNA sequencing revealed compound heterozygosity in the patient for the known type III mutation, which is a Phe283Leu amino acid substitution in the fourth apple domain causing impaired dimerization and secretion, and for a novel frameshift mutation in exon 9 (codons 324/325 +G), leading to premature termination with lack of parts of the fourth apple domain and the downstream serine protease domain.

Possible causes of symptoms in suspected coronary heart disease but normal angiograms.

BACKGROUND: In patients with suspected coronary heart disease and normal angiography, the causes of cardiac symptoms frequently remain undetermined. A correct diagnosis is desirable, however, since some of the underlying disorders may be curable, treatable, influence prognosis, or induce screening of the relatives. HYPOTHESIS: In such patients, the prevalence of arterial hypertension, hemochromatosis, hypothyroidism, hypoparathyroidism, tachycardiomyopathy, amyloidosis, and neuromuscular disorders as a possible cause for their symptoms and the seroprevalence of micro-organisms, known to cause myocardial damage, were assessed. METHODS: Consecutive patients with normal coronary angiograms were invited for two visits comprising clinical history and investigation, electrocardiograms, blood tests, and echocardiography. Patients were investigated neurologically if unexplained anginal chest pain or creatine kinase elevation persisted or if echocardiography showed isolated left ventricular abnormal trabeculations. RESULTS: In 71 patients (31 women, 40 men, mean age 60 years), the most common cause for cardiac symptoms was hypertension (66%), followed by neuromuscular disorders (13%), tachycardiomyopathy (9%), hypothyroidism (4%), and hemochromatosis (3%). The seroprevalence for Chlamydia species was 90%, Helicobacter pylori 70%, Chlamydia pneumoniae 63%, Borrelia burgdorferi sensu lato 15%, and Rickettsia conorii 10%. No possible cause was found in 24% of the patients. CONCLUSIONS: In patients with suspected coronary heart disease and normal angiograms, hypertension, neuromuscular disorders, tachycardiomyopathy, hypothyroidism, and hemochromatosis should be considered as possible causes.

A serine/alanine polymorphism in the nucleotide-binding fold-2 of the sulphonylurea receptor-1 (S1369A) is associated with enhanced glucose-induced insulin secretion during pregnancy.

The sulphonylurea receptor-1 (SUR-1) regulates glucose-induced insulin secretion by controlling K+-ATP channel activity of the pancreatic beta-cell membrane. In this study, we investigated the putative role of a T/G-polymorphism (exon 33, codon 1369; S1369A) in the adenosine diphosphate-sensing nucleotide-binding fold-2 (NBF-2) of the SUR-1 on glucose-induced insulin secretion during an oral glucose tolerance test in pregnant women (PW; n=182). Compared to PW with the T/T genotype, statistically significant elevated C-peptide concentrations were found 60 min after glucose intake in PW with the T/G and G/G genotype (T/T 9.0+/-0.4 ng/ml vs T/G 10.8+/-0.4 ng/ml or G/G 10.8+/-0.7 ng/ml, p=0.01). Furthermore, compared to PW with T/T genotype the deltaC-peptide (60/0 min) was significantly enhanced in PW with T/G or G/G genotype (T/T 6.7+/-0.3 vs T/G 8.9+/-0.4 or G/G 8.9+/-0.7, p=0.0009). A significant correlation of C-peptide concentrations with blood glucose (BG) 60 min after glucose intake was only found in PW with the T/T genotype (r=0.6, p<0.0004). Similarly, a significant correlation of insulin concentrations with BG 60 min after glucose intake was observed in PW with T/T genotype (r=0.5, p<0.0001) and T/G genotype (r=0.24, p<0.03) but not in PW with G/G genotype (r=0.01, p=0.9). From our data we conclude that in PW with the alanine substitution in the NBF-2 region, the insulin response of the pancreatic beta-cell after glucose intake is enhanced and does not correlate with actual BG levels.

Relative hypoleptinaemia in women with mild gestational diabetes mellitus.

AIMS: There is increasing evidence suggesting that leptin plays a major role in the regulation of energy homeostasis, as well as in the neuroendocrine and reproductive systems. Leptin is synthesized in the human placenta. The aim of this study was to relate serum leptin levels during pregnancy to glucose tolerance, body mass index (BMI) and specific metabolic variables, such as specific insulin and proinsulin. METHODS: A 2-h 75 g oral glucose tolerance test was performed in 221 pregnant women at 22-29 weeks of gestation (median 25th week). Serum leptin was measured using a radioimmunoassay. In 49 women, sequential leptin measurements were performed (during pregnancy and post partum (median 5 months)). RESULTS: During pregnancy serum leptin was significantly related to body weight (r = 0.49), BMI (r = 0.51), fasting immunoreactive insulin (r = 0.46), specific insulin (r = 0.43) and proinsulin (r = 0.29) (all P-values <0.0001). In women with mild gestational diabetes (GDM, n = 55), leptin levels were lower compared to women with normal glucose tolerance (n = 166) after adjusting for BMI and fasting insulin (26.9 vs. 19.4 ng/ml, P = 0.0001). Leptin was significantly higher during pregnancy compared to post partum (mean +/- SE: 24.3+/-1.5 vs. 19.6+/-1.6 ng/ml, P = 0.0003), even after adjustment for changes in BMI and changes in fasting insulin (P = 0.013). CONCLUSIONS: Leptin levels are elevated in pregnancy. Women with mild GDM presented with relative hypoleptinaemia compared to women with normal glucose tolerance.

Trp64Arg polymorphism of the beta3-adrenergic receptor gene in pregnancy: association with mild gestational diabetes mellitus.

A missense mutation of the beta3-adrenergic receptor gene (Trp64Arg) has been associated with obesity and increased capacity to gain weight in nonpregnant populations. Furthermore, the mutation is a potential modifying factor in the etiology of impaired glucose tolerance and type 2 diabetes. We studied the relation of the beta3-adrenergic receptor genotype to glucose tolerance during pregnancy, a state of physiological insulin resistance. In 179 pregnant women (mean age, 28.5 +/- 0.4 yr), a 2-h oral glucose tolerance test was performed between gestational weeks 20 and 31. The beta3-adrenergic receptor genotype was assessed using restriction fragment length polymorphism. The frequency of the Arg64 allele was 9.15%. In women with mild gestational diabetes (n = 70), as defined by 60 min postload glucose values, the Trp64Arg genotype was more frequent than in women with normal glucose tolerance (n = 109; 26% vs. 11%; P = 0.01). Furthermore, the Trp64Arg polymorphism was associated with increased weight gain during pregnancy (baseline to gestational weeks 20-31) and increased postload glucose, insulin, and C peptide values during the oral glucose tolerance test. The results of the present study extend current knowledge about the association of the Trp64Arg beta3-adrenergic receptor polymorphism with glucose tolerance to a pregnant population. The association with mild gestational diabetes suggests that the impact of the polymorphism may be clinically important during pregnancy, a state of physiological insulin resistance.

Self-renewal, maturation, and differentiation of the rat myelomonocytic hematopoietic stem cell.

Hematopoiesis is viewed as a differentiating system emanating from a pluripotent hematopoietic stem cell capable of both self-renewal and differentiation. By identifying and characterizing a novel and highly specific in vitro mitogenic response to the N-acetyl glucosamyl/sialic acid specific, stem cell-binding lectin wheat germ agglutinin (WGA), we demonstrate the existance of a rare (0.1%), plastic adherent precursor in rat bone marrow capable of proliferation (two to seven divisions) in response to WGA. Stimulated cells possess a lineage (lin)low/- immunophenotype and immature blastoid morphology (WGA blasts). A subsequent proliferative response to stem cell factor (SCF), the ligand for the proto-oncogene receptor tyrosine kinase c-kit, is characterized by an initial maturation in immunophenotype and subsequent self-renewal of cells (SCF blasts) without differentiation for at least 50 generations. Although granulocyte colony-stimulating factor (G-CSF), interleukin (IL) -6, IL-7, and IL-11 synergize with SCF to increase blast colony formation, cytokines such as granulocyte-macrophage CSF or IL-3 are without significant effect. At all time points in culture, however, cells rapidly differentiate to mature neutrophils with dexamethasone or to mainly monocytes/macrophages in the presence of 1alpha,25-dihydroxyvitamin D3, characterized by cell morphology and cytochemistry. Removal of SCF during blast maturation, self-renewal, or induction of differentiation phases results in apoptotic cell death. Data indicate a pivotal role for SCF/c-kit interaction during antigenic maturation, self-renewal, and apoptotic protection of these lineage-restricted progenitors during non-CSF-mediated induction of differentiation. This approach provides a source of many normal, proliferating myelomonocytic precursor cells, and introduces possible clinical applications of ex vivo expanded myeloid stem cells.