Effect of cellular elements on pressure-velocity relationship in mice

The effect of cellular elements in the blood on peripheral vascular function in mice was evaluated using the pressure-velocity relationships in the iliac arteries of 5 wild type (WT) and 3 polycythemic (MH) mice. Pressure was obtained using a fluid filled catheter in the left iliac artery and blood velocity was measured in the right iliac artery using a 20 MHz pulsed Doppler probe. The proximal aorta was then occluded for one minute to allow flow velocity to decay to zero. The pressure-velocity relationship in the diastolic phase was determined before and after aortic occlusion. In both groups the pressure-velocity relationship was almost linear and the slopes were similar. However, the extrapolated zero-velocity intercept was significantly higher for the MH than WT mice before (55.4 +/- 4.0 vs. 36.2 +/- 4.1 mmHg, p<0.01) and after occlusion (50.7 +/- 5.5 vs. 23.8 +/- 3.1 mmHg, p<0.01). Hematocrits were 41%+/-3 in WT and 59%+/-3 in MH mice. These data show that cellular elements in the blood alter the pressure-velocity relationships in peripheral vessels of mice.

Mouse model of congenital polycythemia: Homologous replacement of murine gene by mutant human erythropoietin receptor gene

Mutations causing truncations of the cytoplasmic domain of the human erythropoietin receptor (EPOR) result in a dominantly inherited disorder-primary familial congenital polycythemia. This disorder is characterized by increased numbers of erythrocytes (polycythemia) and by in vitro hypersensitivity of erythroid precursors to erythropoietin. The consequences of EPOR truncation in nonerythroid tissues are unknown. We replaced the murine EPOR gene with a wild-type human EPOR gene and a mutant human EPOR gene that we initially identified in a patient with polycythemia. This mutation leads to an EPOR truncated after the first tyrosine residue of the intracellular domain. Mice heterozygous for this mutant allele and a wild-type human EPOR allele mimicked the human disorder. Interestingly, mice that were homozygous for the mutant human allele were severely polycythemic but viable. Our results provide a model for functional studies of EPOR-triggered signaling pathways in erythropoiesis. These animals can now be used to investigate the molecular pathophysiology of this gain-of-function EPOR mutation in erythroid tissue and in those nonerythroid tissues that express EPOR.

Molecular basis for polycythemia

This overview concentrates on familial and congenital polycythemias in the context of other polycythemic disorders, with emphasis on those with established molecular lesions. Recent advances in the regulation of erythropoiesis, as they may relate to polycythemic states, are discussed as a background for those well-defined polycythemic states wherein the molecular defect has not yet been elucidated. Primary familial congenital polycythemias and congenital and familial secondary polycythemias, including hemoglobin mutants, methemoglobinemias and congenital 2,3-bisphosphoglycerate deficiency, are discussed. The most common primary polycythemia, polycythemia vera, as well as the only likely endemic congenital secondary polycythemia, known as Chuvash polycythemia, are discussed.

Guinea pig serum erythropoietin (EPO) selectively stimulates guinea pig erythroid progenitors: human or mouse erythroid progenitors do not form erythroid burst-forming unit colonies in response to guinea pig serum EPO

Erythropoietin (EPO) is the primary regulator of mammalian erythropoiesis, providing a proliferative and differentiative signal to the early EPO-responsive erythroid progenitors, burst-forming unit-erythroid (BFU-E) and colony-forming unit-erythroid, as well as to later EPO-responsive erythroid progenitors. EPO is secreted by the kidney in response to hypoxia and anemia. There is an extensive biological crossreactivity between human EPO and the EPOs of other mammals. Necas et al. have reported that this crossreactivity may not include the guinea pig (Cavia porcelllus). Because the specificity of the guinea pig's erythropoietic responses may be of biological significance, we compared guinea pig hypoxic serum with mouse (m) and human (h) recombinant (r) EPOs for their ability to induce erythroid progenitor proliferation and differentiation in semisolid cultures. Guinea pig bone marrow mononuclear cells (BMMCs) formed BFU-E colonies in response to guinea pig hypoxic serum, rhEPO, or rmEPO in a dose-dependent fashion. Neither human nor mouse BMMCs responded to guinea pig hypoxic serum; however, guinea pig hypoxic serum exerted no inhibitory effect on human or mouse in vitro erythroid differentiation in the presence of rhEPO or rmEPO. The intensity of the EPO band on Western blotting analysis of guinea pig hypoxic serum was significantly greater than in nonhypoxic serum. This suggests that guinea pig erythropoiesis is mediated by EPO and stimulated by hypoxia in a fashion similar to that observed in human and mouse erythropoiesis. Furthermore, guinea pig EPO did not stimulate human or mouse erythroid differentiation in vitro, whereas guinea pig erythroid progenitors could be stimulated by human or mouse EPO, suggesting structural differences in guinea pig EPO and EPO receptor (EPOR) compared with human or mouse EPO and EPOR. These differences probably evolved after the guinea pig's ancestors diverged from myomorph rodents. Further characterization of the guinea pig EPO and EPOR should facilitate our understanding of the interaction between EPO and EPOR.

Human hematopoietic progenitors express erythropoietin

Erythropoietin (EPO) is a factor essential for erythroid cell proliferation, differentiation, and survival. The production of EPO by the kidneys in response to hypoxia and anemia is well documented. To determine whether EPO is also produced by hematopoietic cells, we analyzed the expression of EPO in normal human hematopoietic progenitors and in their progeny. Undifferentiated CD34(+)lin- hematopoietic progenitors do not have detectable EPO mRNA. Differentiating CD34(+) cells that are stimulated with recombinant human EPO in serum-free liquid cultures express both EPO and EPO receptor (EPOR). Because CD34(+) cells represent a heterogeneous cell population, we analyzed individual burst-forming units-erythroid (BFU-E) and nonerythroid colony-forming unit-granulocyte-macrophage colonies for EPO mRNA. Only BFU-E colonies were positive for EPO mRNA. Lysates from pooled BFU-E colonies stained positively for EPO by immunoblotting. To further confirm the intrinsic nature of erythroid EPO, we replaced extrinsic EPO in erythroid colony cultures with EPO-mimicking peptide (EMP). We show EPO expression in the EMP-stimulated BFU-Es at both mRNA and protein levels. Stimulation of bone marrow mononuclear cells (BMMCs) with EMP upregulated EPO expression. Furthermore, we found EPO and EPOR mRNAs as well as EPO protein in K562 cells, a human erythroleukemia cell line. Stimulation of K562 cells with EMP upregulated EPO expression. We suggest that EPO of erythroid origin may have a role in the regulation of erythropoiesis.

Angiotensin II stimulates proliferation of normal early erythroid progenitors

Angiotensin II exerts a mitogenic effect in several in vitro models, but a direct effect on erythroid progenitors has not been documented. Angiotensin-converting enzyme inhibitors and losartan, an angiotensin II type 1 receptor (AT1) antagonist, ameliorate posttransplant erythrocytosis, without altering serum erythropoietin levels. We studied erythroid differentiation and the effect of angiotensin II on proliferation of erythroid progenitors by culturing CD34+ hematopoietic progenitor cells in liquid serum-free medium favoring growth of erythroid precursors. Aliquots of cells were collected every third day, and were used for RNA preparation. AT1 mRNA was detected after 6 d. In these same samples, erythroid-specific mRNA (erythropoietin receptor) was also detected. AT1 protein was detected in 7-d-old burst-forming units-erythroid colonies by Western blotting. The CD34+ cell liquid cultures were used to incubate erythroid precursors with angiotensin II from days 6-9. After incubation, cells were transferred to semisolid medium and cultured with erythropoietin. Angiotensin II increased proliferation of early erythroid progenitors, defined as increased numbers of burst-forming units-erythroid colonies. Losartan completely abolished this stimulatory effect of angiotensin II. Moreover, we observed increased numbers of erythroid progenitors in the peripheral blood of posttransplant erythrocytosis patients. Thus, activation of AT1 with angiotensin II enhances erythropoietin-stimulated erythroid proliferation in vitro. A putative defect in the angiotensin II/AT1 pathway may contribute to the pathogenesis of posttransplant erythrocytosis.

Two new EPO receptor mutations: truncated EPO receptors are most frequently associated with primary familial and congenital polycythemias

Primary polycythemias are caused by an acquired or inborn mutation affecting hematopoietic/erythroid progenitors that results in an abnormal response to hematopoietic cytokines. Primary familial and congenital polycythemia (PFCP; also known as familial erythrocytosis) is characterized by elevated red blood cell mass, low serum erythropoietin (EPO) level, normal oxygen affinity of hemoglobin, and typically autosomal dominant inheritance. In this study we screened for mutations in the cytoplasmic domain of the EPO receptor (EPOR; exons 7 and 8 of the EPOR gene) in 27 unrelated subjects with primary or unidentified polycythemia. Two new EPOR mutations were found, which lead to truncation of the EPOR similarly to previously described mutations in PFCP subjects. The first is a 7-bp deletion (del5985-5991) found in a Caucasian family from Ohio. The second mutation (5967insT) was found in a Caucasian family from the Czech Republic. In both cases the EPO dose responses of the erythroid progenitors of the affected subjects were examined to confirm the diagnosis of PFCP. In one of these families, the in vitro behavior of erythroid progenitors in serum-containing cultures without the addition of EPO mimicked the behavior of polycythemia vera progenitors; however, we show that antibodies against either EPO or the EPOR distinguish the in vitro growth abnormality of polycythemia vera erythroid progenitors from that seen in this particular PFCP family. We conclude that PFCP is a disorder that appears to be associated in some families with EPOR mutations. So far, most of the described EPOR mutations (6 out of 8) associated with PFCP result in an absence of the C-terminal negative regulatory domain of the receptor.

Rapid determination of clonality by detection of two closely-linked X chromosome exonic polymorphisms using allele-specific PCR

We reported two specific, reproducible, and quantitative clonality assays based on detection of exonic polymorphisms of the X chromosome genes p55 and G6PD using rtPCR-LDR. These assays are inconvenient for screening purposes. This study sought to develop a simple, reproducible assay, practical for screening genomic DNA samples for p55/G6PD genotypes, rapid clonality determination, and to determine the linkage relationship between these closely related loci. The salient feature of ASPCR is the performance of two PCR rounds. The first generates template; the second, using one aliquot of first-round products in two reaction tubes, each containing one allele-specific primer, detects each allele. ASPCR and rtPCR-LDR produced identical p55/G6PD results in 91 normal female genomic DNAs, and in 12 clonal hematopoietic disorder cDNAs, confirming assay validity. 209 female and 207 male genomic DNA samples were analyzed for p55/G6PD genotype by ASPCR; 60% of females were heterozygous at one or both loci. G6PD and p55 allelic frequencies were significantly different among African-American men and women, but were not significantly different among Caucasian men and women. These loci were in linkage equilibrium among African Americans, but not among Caucasians. ASPCR is a rapid, sensitive, and specific method for screening large numbers of genomic DNAs, and for rapid clonality determination.

Congenital polycythemia in Chuvashia

Familial and congenital polycythemia, not due to high oxygen affinity hemoglobin or reduced 2,3-diphosphoglycerate in erythrocytes, is common in the Chuvash population of the Russian Federation. Hundreds of individuals appear to be affected in an autosomal recessive pattern. We studied six polycythemic Chuvash patients <20 years of age from unrelated families and 12 first-degree family members. Hemoglobins were markedly elevated in the index subjects (mean +/- standard deviation [SD] of 22.6 +/- 1.4 g/dL), while platelet and white blood cell counts were normal. Although performed in only three of the index subjects, serum erythropoietin concentrations determined by both radioimmune and functional assays were significantly higher in polycythemic patients compared with first-degree family members with normal hemoglobin concentrations. Southern blot analysis of the Bgl 2 erythropoietin gene polymorphism showed that one polycythemic subject was a heterozygote, suggesting the absence of linkage of polycythemia with the erythropoietin gene, assuming autosomal recessive inheritance. Polymerase chain reaction (PCR) amplification of the GGAA and GA minisatellite polymorphic regions of the erythropoietin receptor gene showed no evidence of linkage of phenotype with this gene. We conclude that Chuvash polycythemia may represent a secondary form of familial and congenital polycythemia of as yet unknown etiology. This condition is the only endemic form of familial and congenital polycythemia described.

Stable transduction of recombinant adeno-associated virus into hematopoietic stem cells from normal and sickle cell patients

Stable introduction of genes into human hematopoietic stem cells with self-renewing potential is a necessary requirement for gene therapy strategies. We have developed an adeno-associated virus (AAV) vector and a partial packaging cell line that produces recombinant AAV at a titer of 10(8) transducing particles per milliliter. A high-titer viral stock containing the CMV/lacZ gene was used to transfer lacZ sequences into CD34+ Lin-Thy+ hematopoietic stem cells purified from normal and homozygous sickle cell patients. After infection, the cells were cultured in two ways. In the first set of experiments, the cell were expanded 300-fold in liquid culture for 21 days and plated in methylcellulose. Burst-forming units-erythroid (BFU-E) and colony-forming units-granulocyte/macrophage (CFU-GM) were then analyzed for lacZ sequences. In the second set of experiments, infected cells were cultured for 6 weeks under conditions that maintain long-term culture-initiating cells (LTC-IC). Progenitors were plated in methylcellulose, and BFU-E were analyzed for lacZ DNA. Stable transduction of lacZ sequences was observed in 25% of the colonies in both sets of experiments. These results demonstrate for the first time that LTC-IC can be transduced stably with a recombinant AAV vector. The results suggest that AAV may be a useful vector for genetic therapy of sickle cell disease and other hematopoietic disorders.

Clonal stability of blood cell lineages indicated by X-chromosomal transcriptional polymorphism

The idea that stem cells oscillate between a state of activity and dormancy, thereby giving rise to differentiating progeny either randomly or in orderly clonal succession, has important implications for understanding normal hematopoiesis and blood cell dyscrasias. The degree of clonal stability in individuals also has practical implications for the evaluation of clonal lymphomyeloproliferative diseases. To evaluate the clonality pattern of the different types of blood cells as a function of time we have validated the applicability, sensitivity, and reproducibility of a thermostable ligase reaction to detect transcripts of the G6PD allele on the active X-chromosome in normal heterozygous females. While the ratio of the two X-chromosome-derived allelic transcripts varied widely among hemopoietic tissues in a given individual, this allelic ratio was virtually identical in all types of mature myeloid and lymphoid cells. Longitudinal studies indicated constancy of the G6PD allelic ratio in blood cells over a 912-d period of observation in healthy females. The individual variability observed in this allelic ratio suggests that the progeny of a relatively small number of original embryonic hemopoietic stem cells, approximately eight, contribute to the sustained production of all types of blood cells in healthy individuals.

A novel clonality assay based on transcriptional polymorphism of X chromosome gene p55

The clonal nature of cell populations in malignant and myeloproliferative disorders can be determined in female subjects by random-inactivation assays of the X chromosome. Assays utilizing either expression of the G6PD isozymes or DNA-methylation differences between the active and inactive X chromosomes have significant short-comings. We developed a test based on nucleotide #1311 exonic polymorphism of G6PD that allows detection of clonality by determining the transcriptional polymorphism of the active X chromosome using a reverse transcription-polymerase chain reaction-ligase detection reaction (rtPCR-LDR). Since only 18% of females in the United States are informative (heterozygous) for this chromosome with this assay, we searched for other exonic X chromosome polymorphisms. Concentrating on a discrepancy (G or T at cDNA #358) of published sequences of ubiquitously expressed gene, palmitoylated membrane protein for p55, we confirmed this conservative polymorphism at the cDNA level. To detect the genotype of this polymorphism, we established the intron/exon boundary of the first 5' exons and determined the whole sequence of the second intron. We found that the polymorphic site is at the third exon, nine nucleotides downstream from the 294-bp second intron. This close proximity to the intron necessitated the development of a separate PCR-LDR reaction with oligonucleotides for cDNA and genomic DNA. Furthermore, we determined that the p55 gene is subject to X chromosome inactivation. Based on these observations, we developed a novel p55 clonality assay that is reproducible, quantitative, and very sensitive. Screening of 37 randomly selected healthy females of Caucasian, African-American, and Asian origin revealed that 38% of females are informative when this assay is used. We demonstrate a multiple crossover between the G6PD and the p55 polymorphisms (separated by approximately 200 kb), suggesting that these two polymorphisms are in linkage disequilibrium; thus, approximately 50% of female subjects are informative for clonality studies using the two assays.

Primary familial polycythemia: a frameshift mutation in the erythropoietin receptor gene and increased sensitivity of erythroid progenitors to erythropoietin

Primary familial and congenital polycythemia (PFCP) is characterized by erythrocytosis with normal arterial PO2, blood P50, and serum erythropoietin (EPO) levels. In two PFCP families EPO receptor (EPOR) polymorphisms cosegregated with PFCP. A heterozygous insertion of G at EPOR nucleotide 5975 was identified in genomic DNA from polycythemic members of family no. 2. 5974insG shifts the reading frame at codon 430, predicting amino acid substitutions and truncation of the last 64 amino acids. Wild-type and mutant EPOR transcripts were detected in erythroid progenitors from affected individuals. Burst-forming units-erythroid from patients exhibited increased colony size and sensitivity to EPO. Transfected Ba/F3 cells expressing EPOR 5974insG exhibited increased EPO sensitivity compared with cells expressing wild-type EPOR. The functional effect of this EPOR mutation was directly compared with the other C-terminal mutations reported in unrelated PFCP families by expression in Ba/F3 cells. The transfected cells with another primary polycythemia associated EPOR mutant construct (G6002A) also exhibited increased sensitivity to EPO.

Anti-erythropoietin (EPO) receptor monoclonal antibodies distinguish EPO-dependent and EPO-independent erythroid progenitors in polycythemia vera

Erythroid progenitor cells isolated from patients with polycythemia vera (PV) proliferate and differentiate in methylcellulose in the absence of exogenous erythropoietin (EPO). To investigate the potential role of the erythropoietin receptor (EPO-R) in the pathogenesis of PV, we cultured bone marrow-derived or peripheral blood-derived erythroid progenitors in the presence of neutralizing monoclonal antibodies (MoAbs) specific for EPO or EPO-R. Mononuclear cells were obtained from 9 healthy adults and 9 PV patients by Ficoll-Hypaque gradients and cultured with or without EPO in methylcellulose for 12 days under standard or serum-free conditions. Neutralizing anti-EPO and anti-EPO-R MoAbs, added to cultures at day 0, caused dose-dependent growth inhibition of all normal burst-forming units-erythroid (BFU-E) derived from health adult controls. The MoAbs had no effect on the growth of nonerythroid progenitor cells under the same culture conditions. In contrast, neutralizing antibodies distinguished two classes of BFU-E derived from PV patients. Class I BFU-E from PV patients were EPO-dependent. These progenitors, like those derived from healthy adults, had normal EPO dose-dependent growth characteristics and showed a normal period of EPO requirement in vitro that extended 6 days after the initiation of culture. These results indicate that EPO exerts its critical effect early during erythroid differentiation; the addition of neutralizing antibodies to normal progenitors after 6 days had no effect on the subsequent size or maturation of the colonies. Class II BFU-E from PV patients were EPO-independent. They proliferated and differentiated even in the presence of high concentrations of neutralizing anti-EPO or anti-EPO-R MoAbs. We conclude that the class II BFU-E from PV patients are independent of free EPO.

Mutation in the negative regulatory element of the erythropoietin receptor gene in a case of sporadic primary polycythemia

A 42-year-old Caucasian male with sporadic primary polycythemia has been followed by us for 13 years. During the time of observation, his hemoglobin had been stable, and he has never had an elevated white count or platelet count or any other stigmata of polycythemia vera (PV). Both of his parents, his three children, and all siblings have been hematologically normal. The in vitro culture of erythroid progenitors revealed an absence of autonomous erythropoietin (Epo)-independent erythroid colonies but demonstrated a marked increase in the sensitivity of erythroid progenitors to Epo. We have undertaken a study designed to determine whether a mutation in the Epo receptor (Epo-R) gene could cause the polycythemia phenotype seen in either dominant or recessive primary polycythemia described by us and others, or in polycythemia vera. We have sequenced the cytoplasmic positive and negative regulatory domains of the Epo-R genomic DNA, and a transversion of C to T in nucleotide 6148 was found in one of the patient's chromosomes. This mutation is located in the negative regulatory domain and results in a change from proline to serine (P488S). We have subsequently analyzed more than 40 chromosomes from unrelated normal subjects, as well as autosomal dominant, recessive, and sporadic primary polycythemia and polycythemia vera subjects. In no instance was the same or any other mutation in the Epo-R found. To determine if this Epo-R mutation is a cause of increased sensitivity of erythroid progenitors to erythropoietin, Ba/F3 cells (interleukin-3-dependent murine lymphoid line) were transfected with normal and mutated Epo-R cDNA, rendering the transfected cells viable and able to proliferate in Epo. Transfectants with wild-type and mutant Epo-R cDNA exhibited no difference in the presence of Epo. More recently, we were able to obtain DNA from the seven family members of the propositus and found that the nonpolycythemic mother and one of the siblings have the same Epo-R mutation. We conclude that this first described mutation of Epo-R encountered in humans does not appear on its own to explain the polycythemia phenotype; however, the possibility that it may interact with some other acquired or congenital abnormality in generating the polycythemia phenotype cannot be excluded.

Familial and congenital polycythemia in three unrelated families

Three families with polycythemia inherited through apparently different modes are described. Secondary causes of polycythemia were ruled out. Erythropoietin (EPO) levels were normal or low, even after phlebotomy. In vitro erythroid colony growth in standard assay cultures containing EPO was normal; however, in the absence of added EPO, a few progenitors from most of the affected individuals were able to generate recognizable colonies of mature erythroblasts, although these were smaller and proportionately less numerous than seen in polycythemia vera (PV). To search for EPO-receptor changes as a possible pathophysiologic mechanism, we examined, by Southern blot analysis, genomic DNA samples from affected and nonaffected family members, as well as three patients with PV. Two different probes, derived from the human EPO-receptor, were used. We found no evidence for chromosomal rearrangements or gene amplification in hereditary polycythemia or PV patients. Further, no nucleotide sequences were found that were homologous to the Friend spleen focus-forming virus glycoprotein gp55, which has been shown to bind to and activate the murine EPO-receptor. Functional studies examining number and binding affinity of the EPO-receptor on erythroid progenitors from three hereditary polycythemia patients demonstrated no abnormalities. We conclude that the mechanism(s) for the erythrocytosis in familial and congenital polycythemia and in PV may not involve the EPO-receptor and, therefore, may result from alterations of postreceptor responses.

Immunological studies in focal epilepsy

Serum immunoglobulins, T-lymphocyte subsets and HLA investigations were carried out in 24 patients with focal, mainly temporal lobe, epilepsy and in 30 of their first degree relatives. The mean serum level of IgA was significantly decreased in the epileptic probands compared with controls. In the relatives, there was a significant decrease in mean IgM levels. The epileptic group had significantly fewer circulating T4 "helper" lymphocytes (absolute and percent) and an increased percentage of T8 "cytotoxic"/"suppressor" lymphocytes than the controls. The effect of antiepileptic drug treatment on these results is discussed. The frequencies of 63 HLA specificities determined were not significantly different in probands compared with controls. Among 5 of the most commonly occurring haplotypes there was a lower frequency of the haplotype A1,B8 in epileptic probands, which is in accordance with an earlier study on benign focal epilepsy in children. The immunological findings support the possibility that focal epilepsy may be linked to a genetically dependent immune dysregulation. The latter may contribute to the variability underlying the multifactorial inheritance of the epilepsies.

B-lymphocyte colony formation in chronic lymphocytic leukemia

A semisolid culture system for B-cell colony formation is described. The system includes pretreatment of B-cells by neuraminidase-galactose oxidase and help of mitomycin-treated T-cells. With this assay system, colony-forming B-cell precursors were detected in all eight patients we studied with B-cell chronic lymphocytic leukemia. These patients' own T-cell helper effect was less than that of normal T-cells.

Bone marrow cultures in dysmyelopoietic syndrome: diagnostic and prognostic evaluation

Thirty-four patients with a probable clinical diagnosis of dysmyelopoietic syndrome (DMPS) were studied to assess the in vitro growth pattern of their hemopoietic progenitors, i.e. burst-forming unit erythroid (BFU-E) and colony-forming unit myeloid (CFU-C) progenitor cells. Twenty-one patients had DMPS confirmed by final diagnosis and were classified according to the French-American-British (FAB) recommendations. Our results indicate that the normal colony growth of hemopoietic progenitors in vitro excludes DMPS and other preleukemic conditions. In addition, within the DMPS group a low number of CFU-C (11 colonies or fewer) was a highly significant indicator for the development of acute leukemia. Analysis of the limited number of cytogenetic results in the DMPS patients did not reach statistical significance in relation to the development of acute leukemia.

Autosomal dominant polycythemia

Two families with polycythemia inherited as an autosomal dominant trait are described. Serial hemoglobin determinations in multiple family members and RBC volume measurements in selected affected subjects documented their polycythemia. Measurements of arterial p02s, p50s, and blood oxygen affinity were normal in all affected individuals from each family who were tested. Erythropoietin (EPO) levels were low in affected individuals from family 1 and normal in affected members of family 2. Stimulation of in vitro CFU-E colony growth by low levels of EPO was significantly increased in subjects from family 1, but normal in those affected from family 2. We conclude that although the inheritance pattern for the polycythemia in both of these families appeared to be the same, the biologic defect leading to the disorder in each of these unique families was different. The precise mechanism of the increased EPO sensitivity noted in affected subjects from family 1 awaits elucidation.

Abnormalities of T-lymphocyte subsets in epileptic patients

This study concerns the distribution of T-cell subsets as determined by specific monoclonal antibodies in 50 individuals with complex partial seizures (31) and primary generalized tonic-clonic seizures (19), and in 30 healthy controls. The epileptic group had significantly fewer circulating T4 "helper" lymphocytes and significantly greater number of T8 "suppressor" lymphocytes than the controls. The T4/T8 ratio was consistently significantly lower in the epileptic group. There was no relation between lymphocyte subsets or T4/T8 ratio and antiepileptic medication. The results suggest a derangement of cell-mediated immunity in individuals with epilepsy.

Measurements of red blood cell methotrexate concentrations and lymphocyte subsets during therapy of rheumatoid arthritis

Nine patients with rheumatoid arthritis were treated with low dose oral weekly methotrexate for 6 months. Successful therapy was not associated with changes in concentrations of total circulating lymphocytes nor with alterations of T lymphocytes in the helper-inducer, OKT4, or cytotoxic-suppressor, OKT8, subpopulations. Concentrations of methotrexate in circulating erythrocytes stabilized by 1 month of therapy and this measurement did not correlate with clinical efficacy or methotrexate toxicity in the long-term patient assessments.

Low serum vitamin B12 in Alzheimer-type dementia

Serum vitamin B12 levels (as determined by radio-immunoassay) were measured in 20 subjects aged 65 years and over with Alzheimer-type dementia, 20 age-matched subjects with non-Alzheimer type dementia and 20 age-matched subjects with no dementia. Serum vitamin B12 levels were significantly lower and serum vitamin B12 deficiency was significantly more frequent in subjects with Alzheimer-type dementia and were independent of age, sex, haematological abnormality or serum folate.

Persistent generalized lymphadenopathy in homosexual men: clinical, pathological and immunologic characteristics

Eighteen homosexual men who had had lymphadenopathy in two or more extrainguinal sites for more than 5 months but had no evidence of other illnesses or infections were studied. All had extreme malaise, and 90% had additional symptoms (fever, night sweats, weight loss or gastrointestinal dysfunction). They were compared with 10 healthy homosexual and 10 healthy heterosexual male controls. The mean numbers of circulating T8 (suppressor) lymphocytes were increased equally in the two homosexual groups, but the mean number of T4 (helper) lymphocytes was decreased only in the group with lymphadenopathy. The response to testing for recall anergy was diminished in both homosexual groups but was significantly lower in the group with lymphadenopathy. The serum immunoglobulin and complement concentrations and the numbers of circulating B lymphocytes were normal in each group. Seven of nine lymph node biopsy specimens showed characteristic hyperplasia and confluence of follicles. Thus, idiopathic persistent, generalized lymphadenopathy in homosexual men without opportunistic infections or malignant diseases appears to be a distinct syndrome; it may also be related to the acquired immune deficiency syndrome.

Wiskott-Aldrich syndrome: cellular impairments and their implication for carrier detection

A family in which two male siblings were affected with Wiskott-Aldrich syndrome (WAS) was studied using G-6-PD isoenzymes as an X-linked marker in order to investigate the nature of cellular abnormalities. Isolated peripheral blood cell types from the doubly heterozygous mother of the affected males seemingly failed to express the G-6-PD allele in cis position with the WAS allele while her cultured skin fibroblasts expressed both G-6-PD alleles. Additionally, a histogram analysis of platelet size revealed a single population of abnormally small platelets in the affected propositus, whereas the heterozygous mother had no appreciable small platelet subpopulation. In vitro culture of hemopoietic progenitor cells of the heterozygous mother showed that the majority of progenitor cells did not express the WAS allele. However, a small number of cells expressing the G-6-PD type linked with the WAS allele were detected. The proportion of the latter progenitors was significantly higher among more primitive progenitors (those giving rise to later appearing colonies). This observation suggests that selection against cells expressing the Wiskott-Aldrich defect takes place in the hemopoietic system of the heterozygous female and offers a possible means of carrier detection in some women. Linkage studies in this family revealed one example of probable recombination between the loci for WAS and G-6-PD among three informative subjects, suggesting that these two loci may not be closely linked on the X-chromosome.

Polycythemia vera. The in vitro response of normal and abnormal stem cell lines to erythropoietin

Bone marrow cells from two glucose-6-phosphate dehydrogenase (G-6-PD) heterozygotes with polycythemia vera were cultured to determine whether progenitors which wre not of the polycythemia vera clone were present, and, if present, which cell lines contributed to the increase in erythroid colonies observed in response to added erythropoietin (ESF). To accomplish this, the G-6-PD isoenzyme activity of individual erythroid colonies was determined. All of the erythroid colonies analyzed in cultures without added ESF, contained the G-6-PD isoenzyme type characteristic of the abnormal clone. With higher ESF concentrations in the culture, however, there was an increase in the colonies that were not of the polycythemia vera clone. Analysis of the ratio of the various types of colonies indicated that normal and polycythemia vera cells are capable of responding to ESF in vitro. In selected patients, this technique permits analysis of the ratios of normal to abnormal cells during the course of the disease, in response to therapy and during late complications, such as myelofibrosis or leukemic transformation.

Human erythroid colony formation in vitro: evidence for clonal origin

Human marrow cells, suspended in methylcellulose medium containing erythropoietin, give rise to discrete colonies of hemoglobin synthesizing cells. The presumption that such colonies originate from single progenitor cells has been tested directly in females with X-chromosome inactivation mosaicism using glucose-6-phosphate dehydrogenase (G-6-PD) as a marker. When individual colonies were grown from marrow cells obtained from two black females heterozygous for G-6-PD, only one or the other isoenzyme type was observed, but not both. These results are most consistent with the interpretation that human erythroid colonies arise from single cells.

Polycythemia vera: stem-cell and probable clonal origin of the disease

Two women with polycythemia vera and heterozygosity (GdB/GdA) at the X-chromosome-linked locus for glucose-6-phosphate dehydrogenase were studied to determine the nature of the cellular origin of their polycythemia. In contrast to unaffected tissue, such as skin fibroblasts, which consisted of both B and A types, the glucose-6-phosphate dehydrogenase of the patients' erythrocytes, granulocytes and platelets was only of Type A. These results provide direct evidence for the stem-cell nature of polycythemia vera and strongly imply a clonal origin for this disease. The fact that no descendants of the presumed normal stem cells were found in circulation suggests that bone-marrow proliferation in this disorder is influenced by local (intramarrow) regulatory factors.

Comparison of the transfer RNA complements of chick embryos and their supporting membranes

The transfer RNA complement of 5- to 6-day chick embryos was compared with that of the associated membranes by chromatography of preparations of aminoacyl-tRNAs on columns of benzoylated diethyl-aminoethylcellulose. Profiles of all aminoacyl-tRNAs were determined under conditions selected for emphasis on the region containing a component believed to play a role in regulating onset of rapid hemoglobin synthesis in the blood islands of young blastodiscs. Differences in profile were observed only for alanyl- and glutamyl-tRNAs. A marked quantitative change in the distribution of components in the complement of glutamyl-tRNAs was in the converse direction of that required for increase in content of putative regulator and was not further investigated.Small reproducible differences in the profiles of alanyl-tRNAs were further investigated and were shown to be due to a marked increase in the content of a distinct minor component of the alanyl-tRNA complement of the membranes relative to that of the embryo.