Genome-wide analysis of the chalcone synthase superfamily genes of Physcomitrella patens.

Enzymes of the chalcone synthase (CHS) superfamily catalyze the production of a variety of secondary metabolites in bacteria, fungi and plants. Some of these metabolites have played important roles during the early evolution of land plants by providing protection from various environmental assaults including UV irradiation. The genome of the moss, Physcomitrella patens, contains at least 17 putative CHS superfamily genes. Three of these genes (PpCHS2b, PpCHS3 and PpCHS5) exist in multiple copies and all have corresponding ESTs. PpCHS11 and probably also PpCHS9 encode non-CHS enzymes, while PpCHS10 appears to be an ortholog of plant genes encoding anther-specific CHS-like enzymes. It was inferred from the genomic locations of genes comprising it that the moss CHS superfamily expanded through tandem and segmental duplication events. Inferred exon-intron architectures and results from phylogenetic analysis of representative CHS superfamily genes of P. patens and other plants showed that intron gain and loss occurred several times during evolution of this gene superfamily. A high proportion of P. patens CHS genes (7 of 14 genes for which the full sequence is known and probably 3 additional genes) are intronless, prompting speculation that CHS gene duplication via retrotransposition has occurred at least twice in the moss lineage. Analyses of sequence similarities, catalytic motifs and EST data indicated that a surprisingly large number (as many as 13) of the moss CHS superfamily genes probably encode active CHS. EST distribution data and different light responsiveness observed with selected genes provide evidence for their differential regulation. Observed diversity within the moss CHS superfamily and amenability to gene manipulation make Physcomitrella a highly suitable model system for studying expansion and functional diversification of the plant CHS superfamily of genes.

Zidovudine-related anemia with reticulocytosis.

In patients infected with human immunodeficiency virus (HIV), zidovudine has been known to cause a severe hypoproliferative anemia that resolves promptly when the drug is stopped. Some patients, however, may come to medical attention after having stopped taking the drug for 1-2 weeks and may already be in the recovery phase and present with severe anemia, normoblastemia, and reticulocytosis. These features can be mistaken for hemolytic disease, as shown by our experience with three such patients.

Hemoglobin S-C disease revisited: clinical study of 106 adults.

We describe the clinical features of S-C hemoglobin disease in 106 adults seen during the years 1972-2000 and followed for a mean period of 6.8 years (range 1-27 years). The median age of the patients was 50 years. Common clinical features were pain crisis (65%), avascular necrosis of the hip (23%), proliferative sickle retinopathy (34%), and splenic infarction/splenic sequestration syndrome (19%). Acute splenic sequestration crisis occurred in 10 patients and was the presenting feature in two. Obesity (19.8%), essential hypertension (20.7%), and type-2 diabetes mellitus (10.3%) were common. The frequent occurrence of these co-morbidities among patients with hemoglobin S-C disease has not been reported previously.

Parvovirus B19-related anemia in HIV-infected patients.

Persistent infection with parvovirus B19 (B19) is an important treatable cause of anemia in HIV-infected patients. B19 has a tropism for erythroid progenitors and causes pure red cell aplasia (PRCA). The failure to produce neutralizing antibodies to the virus following B19 infection in immunodeficient persons may result in persistent viremia and chronic PRCA (B19-PRCA). The seroprevalence rates for B19 in unselected persons with HIV infection are high, similar to those seen in the general population. Reports of B19-related anemia in HIV infected patients, however, are infrequent. A partial explanation may be that B19-PRCA is predominantly a complication associated with advanced immunodeficiency. The condition is probably underdiagnosed as well. The finding of an unexplained normocytic anemia with absent reticulocytes, in an afebrile HIV-infected patient without renal dysfunction suggests a diagnosis of B19-PRCA. The diagnosis is established when the following criteria are met: (1) bone marrow biopsy showing PRCA, (2) serum or bone marrow positivity for B19 DNA by PCR or dot-blot hybridization, and (C) no alternate explanation for the PRCA. Serological methods are unreliable for the diagnosis because these patients often lack IgM and IgG antibodies to B19. Nearly all patients with B19-PRCA respond to treatment with intravenous immunoglobulin (IVIg) with a rise in the hemoglobin to levels appropriate for the clinical condition of the patient. An alternative explanation for the anemia must be sought in patients not responding to IVIg. Most patients with CD4+ T-lymphocyte counts of < or = 100 cells/mm3 relapse to anemia, usually within 6 months of IVIg therapy. Such patients must be retreated with IVIg 2 g/kg given over 2 to 5 days. The routine use of maintenance IVIg 0.4 g/kg q 4wk may be considered in these patients to prevent relapse.

Chronic pure red cell aplasia caused by parvovirus B19 in AIDS: use of intravenous immunoglobulin--a report of eight patients.

The optimal management of chronic pure red cell aplasia caused by parvovirus B19 (B19-PRCA) in patients with AIDS is unclear. Our purpose was to determine the effects of intravenous immunoglobulin (IVIg) in the treatment of B19-PRCA in patients with AIDS. The patients were eight adults with AIDS admitted during the period 1993-1997. A diagnosis of B19-PRCA was made if all the following criteria were met: 1. Bone marrow biopsy finding of pure red cell aplasia; 2. Detection of parvovirus B19 DNA in serum; and 3. No alternative explanation for PRCA. Initial (induction) therapy was with IVIg 1 g/kg daily for 1-2 days. Relapses were treated with IVIg 1 g/kg for 2 days. Maintenance therapy with IVIg 0.4-1.0 g/kg q 4 weeks was given to those patients who developed a second or subsequent relapse. The patients were followed for a mean of 27 months (range 8-38 months). All patients responded to initial therapy with IVIg. Six patients with CD4 counts < 80 cells/mm3 relapsed. The response was short lived in two patients with a CD4 count < 80 cells/mm3 who were given a single infusion of IVIg 1 g/kg as initial therapy. Four patients were given regular maintenance IVIg therapy following a second or subsequent relapse and remain in remission. Two patients whose CD4 counts were > 300 cells/mm3 remain in continuous unmaintained remission from B19-PRCA for over 8 and 11 months, respectively, following induction therapy with IVIg. AIDS patients with B19-PRCA respond well to therapy with IVIg 2 g/kg given over 2 days. Most patients with CD4 counts of < or = 80 cells/mm3 suffer relapse within six months necessitating retreatment with IVIg; maintenance therapy with IVIg 0.4 g/kg q 4 weeks is effective in preventing relapse of B19-PRCA, and may be cost effective. Routine maintenance therapy is probably not indicated in patients with CD4 counts over 300 cells/mm3. Prospective studies are needed to confirm these findings.

Novel cytomorphology of the giant proerythroblasts of parvovirus B19 infection.

The morphology of the giant proerythroblasts (GPE) in air-dried and Wright-Giemsa-stained smears of bone marrow in 16 patients with pure red cell aplasia (PRCA) caused by parvovirus B19 infection is described. B19 infection was diagnosed by the presence of the virus or viral DNA and/or IgM antibodies. Twelve patients had chronic hemolytic anemia and aplastic crisis and 4 patients had AIDS with chronic PRCA. In patients with chronic hemolytic anemia and aplastic crisis, GPE were not detectable in bone marrow biopsies that showed any degree of recovery of erythropoiesis. The GPE morphology was quite variable. The early (basophilic) GPE measured 25 to 35 microm in diameter, had a narrow rim of intensely blue and often vacuolated cytoplasm with pseudopodia, round nuclei with compact uncondensed chromatin, and an indistinct and inclusion-like purple-colored tinctorial change. The "intermediate" and "late" GPE measured 25 to 45 microm in diameter and showed cytoplasmic swelling, gradual loss of cytoplasmic basophilia, and fraying of the cytoplasm with focal rupture; the nuclei showed an increase in volume, a highly uncondensed and coarse sieve-like chromatin, and 1 to 3 prominent, pale to moderate purple inclusion-like nucleoli or inclusions. Bare nuclei similar in size and chromatin pattern to those of the GPE were present in proximity to the GPE and may have arisen from the GPE by dissolution of the cytoplasm. The glassy intranuclear inclusions with central clearing, the so-called lantern cells described in formalin-fixed tissues of patients with B19 infection, were absent in all cases. These findings suggest that direct toxic cell injury rather than apoptosis may be involved in the pathogenesis of erythroid aplasia in B19 infection.

Red cell aplasia caused by parvovirus B19 in AIDS: use of i.v. immunoglobulin.

We describe the case of a 34-year-old man with AIDS who developed severe anemia due to chronic pure red cell aplasia (PRCA) caused by parvovirus B19. Following initial treatment with an infusion of intravenous immunoglobulin (IVIg), 1 g/kg, PRCA resolved, but there was a recurrence of severe anemia in 3 months. Retreatment with 2 g/kg IVIg over 2 days resulted in normalization of hemoglobin and a significantly longer remission duration. Two doses of 0.4 g/kg IVIg q 4 wk failed to prevent a relapse of PRCA in our patient. The dose and schedule of IVIg in the treatment of PRCA caused by parvovirus B19 in AIDS requires further definition.