Demetrios A. Rigas

Hemoglobin Portland 1: A New Human Hemoglobin Unique in Structure

A new hemoglobin (Hb), Portland 1, has been found in a newborn infant having multiple congenital anomalies and complex autosomal chromosomal mosaicism. The new hemoglobin has a unique tetrameric structure (molecular weight, 66,000) composed of two pairs of different types of chains, neither of which is α, γ2x2. The x-chain of Hb Portland 1 may be a new type of hemoglobin chain, but the available evidence suggests that it may be identical with the ε chain. We suggest that Hb Portland 1 is an embryonic hemoglobin that persisted until after birth in relatively large amounts in this patient.

Genetics of haemoglobin H.

Additional studies are reported on the first family reported with haemoglobin H disease. These include the finding of a second fast minor haemoglobin in two of the subjects with haemoglobin H. This component does not have the alkaline resistance or ultra‐violet spectrum of foetal haemoglobin and is slower than Barts haemoglobin on electrophoresis at pH 8‐6; it is, therefore, not Barts haemoglobin. Another sibling has been studied and has thalassaemia trait. The current literature and hypotheses to explain the inheritance of haemoglobin H disease are reviewed.

Biphasic toxicity of diethyldithiocarbamate, a metal chelator, to T lymphocytes and polymorphonuclear granulocytes: Reversal by zinc and copper

Abstract A new type of toxicity biphasically dependent on concentration was observed with diethyldithiocarbamate, a metal chelator utilized in medicine. As judged by cell survival and [ 3 H]Urd incorporation, diethyldithiocarbamate was maximally toxic to T lymphocytes and polymorphonuclears at 2.5×10 −5 M (first phase) and at higher than 2.5×10 −3 M (second phase), but was not toxic at intermediate concentrations around 2.5×10 −4 M. The response of chelator treated T lymphocytes to phytohemagglutinin was also biphasic. The first toxic phase was partially reversed by 2.5×10 −5 M ZnCl 2 , while the second phase was partially reversed by 10 −2 M CuCl 2 . This suggests that inhibition of Zn-metalloenzymes in the first phase and of Cu-metalloenzymes in the second may play a crucial role in the mechanism of toxicity. The second toxic phase may be in part due to the observed inhibition of superoxide dismutase rendering the cells susceptible to oxygen toxicity, like obligate anaerobes.

Biphasic radiosensitization of human lymphocytes by diethyldithiocarbamate: possible involvement of superoxide dismutase.

A biphasic radiosensitization of human lymphocytes by diethyldithiocarbamate (DDC), a metal chelator, was observed. The first phase occurred at 10(-5) M and the second at 10(-3) MDDC. The biphasic radiosensitization coincided with the previously reported biphasic toxicity of DDC. Inhibition of superoxide dismutase (SOD) occurred only in the second phase, suggesting that it may be a contributing cause of this phase. The mechanism of the first radiosensitization phase is not known. The radiation survival curves indicated the presence of at least two lymphocyte populations differing in their radiosensitivity and representing 40 per cent and 60 per cent of the cells. Both cell populations were biphasically radiosensitized by DDC.

Determinants of resistance to radiation injury in blood granulocytes from normal donors and from patients with myeloproliferative disorders

Dose-dependent injury to human blood granulocytes was measured within 2 hr of x irradiation, as changes in net /sup 22/Na influx and phagocytosing O/sub 2/ consumption. Among samples from normal donors and patients with chronic myeloproliferative diseases, samples from 10 to 12 patients with chronic granulocytic leukemia exhibited increased sensitivity to injury by radiation. Selected granulocyte constituents which may contribute to inactivation of oxidant and free-radical products of radiation-activated H/sub 2/O were also measured. These included glutathione and ascorbate contents; superoxide dismutase, catalase, glutathione proxidase, and glutathione reductase activities; and capacity to take up and reduce dehydroascorbate. Catalase activity was irregularly higher in radiation-sensitive than in radiation-resistant granulocytes (P = < 0.05). Dehydroascorbate uptake and reduction was consistently low in radiation-sensitive cells (P = < 0.001). We propose that cell capacity to maintain ascorbate in reduced form against oxidant and free-radical stress is a part of mechanisms which determine resistance to injury by ionizing radiation in human granulocytes.

Kinetics of isotope incorporation into the desoxyribonucleic acid (DNA) of tissues: Life span and generation time of cells

The dynamics of cell multiplication and differentiation in tissues in asteady state and the kinetics of isotope incorporation into the DNA have been theoretically analyzed. Equations have been derived, with the aid of which thegeneration time, thelife span, and the distribution or rate of death of the cells can be obtained if the tissue is in asteady state, i.e., if the number of cells is maintained constant by constant, equal rates of cell division and cell death and if the mean DNA content per cell is also constant. An equation has also been derived which gives thegeneration time in the case of logarithmic multiplication of cells.

A nomogram for radioactivity counting statistics

Abstract A nomogram with expandable range has been developed for determining counting times, fractional errors, confidence levels, factors of merit, and for optimizing spectrometer settings in radioactivity counting. A special plastic ruler (nomogram reader) has been constructed which facilitates the use of this and other nomograms and graphs.

Cryoglobulinemia: Rationale of treatment of a case based on unusual properties of the cryoprotein

Abstract The studies of a forty-eight year old man who has a cryoglobulin with unique properties are presented herein. The cryoglobulin polymerizes to form a gel which interferes with the blood clotting test systems, causes increased blood viscosity, and slows peripheral circulation. The mechanism of these effects is related to hydrogen bond formation, which can be prevented in vivo and in vitro by basic organic amines. The protein has a long turnover time with a half-time of 18.8 days. It is related immunologically to gamma globulin but also has a specific immunologic reaction. Nitrogen balance studies showed a decrease in the concentration of cryoglobulin when the patient was in negative nitrogen balance. Removal of the abnormal protein by plasmapheresis resulted in lowering of the concentration from 9.5 to 4 to 5 gm. per cent and correction or improvement of all abnormal clinical and laboratory findings.

ISOTOPE INCORPORATION INTO THE DNA AND ITS USE IN STUDIES OF LEUKOKINETICS

The incorporation of various radioisotopes into the deoxyribonucleic acid (DNA) of cells has been frequently used in recent years in studies of the lifespan and of the movement of mammalian cells from one compartment to another, particularly of the leucocytes. These studies have been based on the well-supported observations that the mean DNA content of cells is constant in each species; that the DNA of resting cells is metabolically inert; that new DNA is synthesized only when a cell prepares to divide, at which time it doubles in amount; and that DNA breakdown occurs only when a cell dies. However, it is not easy to determine the lifespan of the cells simply by pulse-labeling the DNA and following the disappearance of labeled cells by autoradiography. This is because the labeled DNA is divided equally among the daughter cells at the time of cell division and, as a result, every generation of cells that is formed following the incorporation of the radioisotope into the DNA will be labeled. The amount of labeled DNA per cell in subsequent generations will decrease exponentially if the isotope is no longer available to the cells because of dilution with newly synthesized unlabeled DNA. The problem is further complicated by the fact that cell division, cell movement from compartment to compartment, and cell death are stochastic processes, i.e., the generation time, the time spent in each compartment, and the lifespan vary to a certain extent among otherwise identical cells. Information is thus needed not only of the mean generation time, mean time spent in a certain compartment and mean lifespan of the cells, but also of the distribution functions of these parameters. For this reason, the kinetics of isotope incorporation into the DNA cannot be described by differential equations unless certain assumptions are made in regard to these unknown distribution functions. However, it is highly desirable to avoid such assumptions, as they may lead to results of questionable validity.