Inhibition of iron absorption by omeprazole in rat model

Since gastric acid is an important luminal factor in the absorption of non-heme iron, the effect of omeprazole on the absorption of iron in a rat model was studied. Iron absorption studies were performed on rats on a normal diet (N = 42) and rats fed an iron-deficient diet (N = 43) for three weeks. Rats were orally dosed with 40 mumol/kg of omeprazole or placebo daily for two days prior to iron absorption studies. Rats were orally dosed with 1 mmol of ferrous chloride, ferric chloride or food iron (dietary suspension) containing 11 micrograms of iron and labeled with 1 microCi of 59Fe. Omeprazole-treated rats on the normal diet had no significant reduction in the absorption of ferric, ferrous, or food iron. In the rats on the iron-deficient diet, the absorption of ferrous iron decreased from 76 +/- 7.5% (mean +/- SE) in control rats to 38 +/- 8.5% in the omeprazole-treated rats (P less than 0.003) and the absorption of food iron decreased from 65 +/- 7.5% in control rats to 37 +/- 6.5% in the omeprazole-treated rats (P less than 0.016). There was no significant reduction in the absorption of ferric iron. Omeprazole therapy is unlikely to be associated with significant iron malabsorption in normal patients but may reduce iron absorption in pathological states associated with increased iron absorption such as iron deficiency.

Pattern-specific contrast threshold elevation

Visual channels are defined psychophysically; stimuli that interact share information in the same channel, and those that do not interact are processed in different channels. Channels are often investigated by means of adaptation to one stimulus, testing contrast threshold elevation with one (or more) others. Much recent work has tested the tuning of channels for orientation and spatial frequency, using simple line gratings. This study examined the pattern-specificity of such adaptation, testing the hypothesis that the fundamental operators of the Lie Transformation Group Theory of Neuropsychology (LTG/NP) define psychophysical channels. In Experiment I the three basic pattern pairs of LTG/NP were used as adaptation and test stimuli in a conventional contrast threshold-elevation experiment. Threshold elevation was pattern-specific, thus supporting the hypothesis. In subsequent experiments various 'fractured' patterns, and patterns generated by combinations of Lie operators were used both for adaptation and test. The results were mixed; some supported the original hypothesis, but many did not. Relations between local contour orientations in adaptation and test patterns could explain some results, but not all. The hypothesis that adaptation occurs to the oriented spatial-frequency components of the test patterns, on the other hand, gave a good fit to the data. It is concluded that there is pattern-specificity in contrast threshold elevation, but it is a form of specificity that can be explained without recourse to a model of geometrical pattern processing, at least for the simple patterns used here.

Independent orientation-selective mechanisms for the cardinal directions of colour space

Simultaneous, oppositely tilted, aftereffects were obtained for pairs of equiluminant gratings (e.g. magenta/cyan vs purple/greenish-yellow) and pairs of equiluminant and luminant gratings (e.g. magenta/cyan vs dark-grey/light-grey, or purple/greenish-yellow vs dark-grey/light-grey). Maximum aftereffects occurred for gratings whose colours were modulated along the principle axes of the colour space of Krauskopf, Williams and Heeley (1982): an axis of short-wavelength cone activation (B-cone axis), the difference between long- and medium-wavelength cone activation (R-G cone axis), and an axis of a contrast ratio of long-, medium- and short-wavelength cone activation (R + G + B cone axis). The results indicate that selectivity for orientation occurs independently in at least two chromatic channels and one achromatic channel.

Safe application of a 13-Gy split dose total body irradiation schedule prior to bone marrow transplantation

Two conditioning regimens for bone marrow transplantation for patients with acute lymphoblastic leukaemia were compared. Both regimens (VVRAPID and VVRAPID-X) incorporated the same cytotoxic chemotherapy but differed in the radiation dose; VVRAPID employed a single fraction of 10.5 Gy and VVRAPID-X employed 10.5 Gy followed 4 days later by a further dose of 2.5 Gy. The 13-Gy split-fraction schedule was well tolerated with no significant increase in infection or requirement for blood products. An increase in gastrointestinal toxicity occurred but responded to increased oral anti-diarrhoeal agents. Overall survival and relapse rates did not differ significantly between the two groups. There was a trend for the 13-Gy schedule to reduce the graft failure rate following T cell-depleted bone marrow transplants.

Disseminated Mycobacterium avium-intracellulare infection and red cell hypoplasia in patients with the acquired immune deficiency syndrome

During a period of 14 months in 1985 and 1986, infection with Mycobacterium avium-intracellulare (MAI) complex was diagnosed in 10 of 76 patients with Human Immunodeficiency Virus (HIV)-associated infection. In eight of the 10 patients, the infection was disseminated. All eight patients were anaemic. A bone marrow aspirate and/or trephine biopsy performed in six of them revealed evidence of red cell hypoplasia. MAI was cultured from all six samples of bone marrow. The strains of MAI isolated were resistant to conventional antituberculous drugs but were susceptible in vitro to ansamycin, ethionamide and cycloserine. None of the eight patients responded clinically to antituberculous therapy. The eight anaemic patients had pronounced constitutional symptoms. We suggest that severe anaemia and constitutional symptoms in patients with HIV-associated disease should prompt a search for evidence of disseminated MAI infection.

An evaluation of the Cell-Dyn 1000

The Cell-Dyn 1000 is a new eight parameter fully automatic cell counter. This was evaluated following the ICSH guidelines. Scientific evaluation was generally satisfactory, largely conforming to the manufacturer's specifications. A number of potential microbiological safety hazards were noted; many could be overcome by minor modifications. Throughput and start-up/close-down times were acceptable. However, the reliability of the tested machine was felt to be less than satisfactory although this may be corrected by further minor machine modifications.

Recombination by resolvase is inhibited by lac repressor simultaneously binding operators between res sites

The Tn3 resolvase requires that the two recombination (res) sites be aligned as direct repeats on the same molecule for efficient recombination to occur. To test whether resolvase must contact the DNA between res sites as predicted by tracking models, we have determined the sensitivity of recombination to protein diffusion blockades. Recombination between two res sites is unaffected either by lac repressor or bacteriophage T7 RNA polymerase being bound between them. Yet recombination is inhibited by lac repressor if the res site is bounded by a lac operator on both sides. We demonstrate that lac repressor will bind to more than one DNA site under the conditions used to assay recombination. This result suggests that lac repressor can inhibit resolvase by forming a DNA loop that isolates a res site topologically. These results do not support a tracking model for resolvase but suggest that the structure and topology of the DNA substrate is important in the formation of a synapse between res sites.

Quantification of Ca2+-activated K+ channels under hormonal control in pig pancreas acinar cells

Ca2+- and voltage-activated K+ channels are found in many electrically excitable cells and have an important role in regulating electrical activity. Recently, the large K+ channel has been found in the baso-lateral plasma membranes of salivary gland acinar cells, where it may be important in the regulation of salt transport. Using patch-clamp methods to record single-channel currents from excised fragments of baso-lateral acinar cell membranes in combination with current recordings from isolated single acinar cells and two- and three-cell clusters, we have now for the first time characterized the K+ channels quantitatively. In pig pancreatic acini there are 25-60 K+ channels per cell with a maximal single channel conductance of about 200 pS. We have quantified the relationship between internal ionized Ca2+ concentration [( Ca2+]i) membrane potential and open-state probability (p) of the K+ channel. By comparing curves obtained from excised patches relating membrane potential to p, at different levels of [Ca2+]i, with similar curves obtained from intact cells, [Ca2+]i in resting acinar cells was found to be between 10(-8) and 10(-7) M. In microelectrode experiments acetylcholine (ACh), gastrin-cholecystokinin (CCK) as well as bombesin peptides evoked Ca2+-dependent opening of the K+ conductance pathway, resulting in membrane hyperpolarization. The large K+ channel, which is under strict dual control by internal Ca2+ and voltage, may provide a crucial link between hormone-evoked increase in internal Ca2+ concentration and the resulting NaCl-rich fluid secretion.

Complete suppression of haemoglobin A synthesis in haemoglobin D Los Angeles--beta thalassaemia

A family study is reported in which all three siblings were shown to be doubly heterozygous for haemoglobin D Los Angeles and beta thalassaemia, which resulted in a complete suppression of haemoglobin A synthesis. This demonstrates the effects of genetic interaction which occur when the genes for haemoglobin D Los Angeles and beta thalassaemia are both transmitted to the offspring. The importance of family studies in the investigation of haemoglobin abnormalities is stressed.

Necrotizing arteritis with giant cells associated with haemolytic anaemia

Necrotizing arteritis with giant cells, involving the aorta, pulmonary and coronary arteries, and coronary, splenic, and renal arterioles was found at necropsy in a 74-year-old male who had died with severe haemolytic anaemia associated with cold haemagglutinins. The clinical and pathological features of this case are shared by well-recognized forms of necrotizing angiitis, in particular giant cell arteritis, but do not conform satisfactorily with any of these disorders. Cold agglutinin haemolytic anaemia in this instance suggests the possibility of an autoimmune aetiology.