Some hemopoietic negative regulators

Hemopoietic negative regulators are growth inhibitory proteins or peptides of natural origin that exert their effects on cells of the blood-forming system. They are biologically defined by quantitative assay methods that exclude toxicity as a basis for their action. They act within minutes to hours, in a readily reversible and more-or-less specific manner on stem cells and progenitor cells, during S-phase to arrest DNA synthesis, or during G1 to prevent entry into DNA synthesis. Operating at picomolar to nanomolar concentrations through high-affinity receptors at their target cell surface, they oppose the action of stimulatory (or positive regulatory) growth factors. Hemopoietic negative and positive regulators acting in concert thus appear to provide a mechanism for rapid, reversible, and specific proliferative responses to changes in hemopoietic demand.     

A negative partition relation

If the continuum hypothesis is assumed, there is a graph G whose vertices form an ordered set of type ω₁²; G does not contain triangles or complete even graphs of form [[unk]₀,[unk]₀], and there is no independent subset of vertices of type ω₁².     

Luetic lymphadenopathy despite negative serology

Laboratory tests can be misleading for the diagnosis of syphilis and false-negative results are possible, but it is rare for both treponemal and non-treponemal tests to prove negative in different stages of the disease. We report on a case of luetic lymphadenopathy, diagnosed by histological examination and supported by immunohistochemical staining for Treponema pallidum, in the absence of skin lesions and positive serology. This case reminds us of how syphilis may present in many different clinical forms and that it should not be excluded only on the basis of negative serological tests. This patient's negative serology was probably due to inadequate initial antibiotic therapy. Given the current widespread use of antibiotics, greater consideration is warranted of the extent to which serological test results are modified by non-specific antibiotic therapies.     

When the negative is positive

In this issue of Blood, Hosking and colleagues report the lack of correlation between genetic variants within the MHC and the risk of ALL.     

Falsely negative cholecystography and cholangiography

Summary Three patients with symptomatic biliary calculi and normal cholecystography or cholangiography are presented. Despite the excellent diagnostic accuracy of biliary tract roentgenography, falsely negative examination results may occur, thereby creating a major diagnostic and therapeutic problem if all the available clinical data is not evaluated.Supported in part by a grant from the John A. Hartford Foundation, and by Grant TI-AM-5430-05 from the National Institute of Arthritis and Metabolic Diseases, U. S. Public Health Service.