Plasma phenylalanine: Tyrosine ratios during high-dose methotrexate-citrovorum “rescue”

We have measured phenylalanine and tyrosine in the plasma of patients with osteogenic sarcoma undergoing chemotherapy with high-dose methotrexate (HDMTX) citrovorum factor rescue (CFR). During 14 treatments in six different patients, the phenylalanine to tyrosine ratio (PHE/TYR) at 21 to 38 hours was elevated over pretreatment levels. The observed increase in plasma phenylalanine is attributed to inhibition by MTX of the phenylalanine hydroxylase system of the liver, which is not folate-dependent and thus is not corrected by administration of CF. A post-infusion increase in PHE/TYR of 571% after 22 hours in one patient and of 410% after 30 hours in another were associated with marked MTX toxicity. The greatest increase in PHE/TYR seen in a patient who did not experience toxicity was was 249% in 21 hours. Thus, in this group of patients, there appears to be a correlation between evidence of clinical MTX toxicity and the magnitude of the percentage increase in PHE/TYR in the plasma, which indicates inhibition of a liver enzyme and thus reflects the intracellular concentration of MTX.     

Plasma cell tumors in HIV-positive patients: report of a case and review of the literature

Plasma cell tumors show an increased incidence in HIV-positive patients. The cases reported in the literature suggest that plasma cell tumors occur in a younger age group than that encountered in the general population. Pathologically, many of these tumors show a plasmablastic morphology. Plasma cell tumors in HIV-positive patients may present at unusual sites and progress rapidly to involve multiple sites, including the soft tissues and viscera. The prognosis is generally poor. These features may be related to a combination of factors, including immunodeficiency, oncogenic viruses, and altered cytokine milieu in these patients. A case of plasma cell tumor in an HIV-positive patient is presented.     

Thrombospondin-1 mimetic peptide ABT-898 affects neovascularization and survival of human endometriotic lesions in a mouse model

Endometriosis is a common cause of pelvic pain and infertility in women, and a common indication for hysterectomy, yet the disease remains poorly diagnosed and ineffectively treated. Because endometriotic lesions require new blood supply for survival, inhibiting angiogenesis could provide a novel therapeutic strategy. ABT-898 mimics the antiangiogenic properties of thrombospondin-1, so we hypothesized that ABT-898 will prevent neovascularization of human endometriotic lesions and that ABT-898 treatment will not affect reproductive outcomes in a mouse model. Endometriosis was induced in BALB/c-Rag2(-/-)Il2rg(-/-) mice by surgical implantation of human endometrial fragments in the peritoneal cavity. Mice received daily injections of ABT-898 for 21 days. Flow cytometry was performed to measure circulating endothelial progenitor cells in peripheral blood. Cytokines were measured in plasma samples. Half of the ABT-898-treated and control mice were euthanized to assess neovascularization of endometriotic lesions, using CD31(+) immunofluorescence. The remaining mice were mated and euthanized at gestation day 12. Endometriotic lesions increased circulating endothelial progenitor cells 13 days after engraftment, relative to baseline. Endometriotic lesions from ABT-898-treated mice exhibited reduced neovascularization, compared with controls, and lesions had fewer CD31(+) microvessels. Chronic treatment with ABT-898 did not lead to any fetal anomalies or affect litter size at gestation day 12, compared with controls. Our results suggest that ABT-898 inhibits neovascularization of human endometriotic lesions without affecting mouse fecundity.     

Computed radiography image artifacts revisited

OBJECTIVE: Computed radiography (CR) has provided a ready cost-effective transition from screen film to digital radiography and a convenient entrance to PACS. This article revisits artifacts encountered in CR systems. These artifacts may obscure abnormalities, mimic a clinical entity, or hamper image quality. CONCLUSION: With the new-generation CR systems, software- and hardware-related artifacts have decreased, making operator errors more evident. The purpose of this study is to establish the current trend of CR artifacts and the new facets in identifying and resolving problems quickly that will help prevent future occurrences. This article also brings to light the importance of constant review required of this extensively studied topic to avoid diagnostic misadventures.     

In Search of Drug Targets for Mycobacterium tuberculosis

Mycobacterium tuberculosis is the etiological agent for tuberculosis in humans. The studies related to survival of this pathogen in the human host and development of drugs against reveal that the organism uses a complex physiology to adapt to the host environment. Many studies were targeted to key enzymes that allow this pathogen to either survive or remain latent within the host. Most of the models, which address the survival of pathogen, have evaluated limited dissolved oxygen and prevailing stress conditions. Hence, the truncated citric acid cycle, with the glyoxylate shunt was suggested as an option for survival of the pathogen and pathogenesis. We propose that the precursors to support this pathway could also be generated via enzymatic conversion involving poly-beta-hydroxybutyrate (PHB). We have used available genome sequence data and analyzed for the possible enzymatic conversions that can generate glyoxylate, acetyl CoA, and other enolases that can also be useful for various fatty acid transformations. The enzymes for accumulation and further hydrolysis of PHB were examined in sequence data analysis. The target enzymes were searched for in the genome using identified conserved domains. Using M. tuberculosis H37Rv as a model bacterium a supportive pathway has been envisaged and integrated with glyoxylate cycle to provide a complete option to pathogen for sustainable consumption of available carbon source(s). The study proposes that the enzymes of PHB synthesis and hydrolysis are possible targets for drug design, and that this should be considered when evaluating isocitrate lyase and malate synthase as targets.