Characterization of ferritin in murine erythroleukaemia cells

Murine erythroleukaemic cells were studied to determine whether different isoferritins have different functions. The cells were labelled with radioactive iron and the pattern of isoferritins was analysed by chromatofocussing. No change was found after iron-loading the cells but after inducing erythroid differentiation with dimethyl sulphoxide (DMSO), iron was incorporated into both more basic and more acidic isoferritins. This was compared to ferritin subunit synthesis; DMSO induced the synthesis of a third, minor subunit whereas iron-loading had no effect. The fate of murine erythroleukaemic cell ferritin iron was followed after incubations in iron-deficient medium containing DMSO; some, but not all, of the ferritin iron was mobilized and used for haem synthesis, and the remaining iron was found amongst the more basic isoferritins. Finally, sequential radioactive iron labels were used to demonstrate that the movement of iron from ferritin to haem was compatible with the 'last-in-first-out' principle, but this could not be related to different isoferritins. These results show firstly that DMSO changes the pattern of isoferritins and ferritin subunits in murine erythroleukaemic cells. Secondly, iron associated with more basic isoferritins seems to be less easily mobilized for haem synthesis. These results support the concept that different isoferritins have different functions.     

The effects of salts and amino group modification on the iron binding domains of transferrin

The origins of the effects of salts on the properties of the iron binding sites of transferrin have been investigated. The chaotropically distinct salts NaCl and NaClO4 each induce characteristic changes in the EPR lineshapes of the N- and C-terminal Fe3+ binding domains, respectively. To a good approximation the perturbed EPR spectrum of diferric transferrin in the presence of salts is the sum of the EPR spectra of the N- and C-terminal monoferric proteins. Acetylation of amino groups causes spectral and kinetic changes in the protein similar to those induced by NaClO4. Thus, both acetylation and NaClO4 cause a loss of structure in the g' = 4.3 EPR signal of the N-terminal domain, and both retard iron removal from this domain. In contrast, iron removal from the C-terminal domain is accelerated by acetylation or the presence of NaClO4. These observations are ascribed to charge effects of lysine residues which are probably in the vicinity of the iron binding sites.     

Active immunization of intact mares against gonadotropin-releasing hormone: differential effects on secretion of luteinizing hormone and follicle-stimulating hormone

Five lighthorse mares were actively immunized against gonadotropin releasing hormone (GnRH) to determine the relative importance of this hypothalamic hormone in the secretion of luteinizing hormone (LH) and follicle-stimulating hormone (FSH). Five mares immunized against the conjugation protein served as controls. Mares were initially immunized in November and received secondary immunizations 4 wk later, and then at 6-wk intervals until ovariectomy in June. All mares immunized against GnRH exhibited an increase (p less than 0.01) in the binding of tritiated GnRH by plasma, an indication that antibodies against this hormone had been elicited. Concentrations of LH, FSH and progesterone in weekly blood samples were lower (p less than 0.05) in GnRH-immunized mares than in controls after approximately 4 mo of immunization. However, the LH concentrations were affected to a greater degree than were FSH concentrations. All five control mares exhibited normal cycles of estrus and diestrus in spring, whereas no GnRH-immunized mare exhibited cyclic displays of estrus up to ovariectomy. All mares were injected intravenously with a GnRH analog (which cross-reacted less than 0.1% with the anti-GnRH antibodies) in May, after all control mares had displayed normal estrous cycles, to characterize the response of LH and FSH in these mares; two days later, the mares were injected with GnRH. The LH response to the analog, which was assessed by net area under the curve, was lower (p less than 0.01) by approximately 99% in mares immunized against GnRH than in control mares. In contrast, the FSH response to the analog was similar for both groups.(ABSTRACT TRUNCATED AT 250 WORDS)     

Substrate concentration control by dialysis in fermentations of Escherichia coli

A substrate control system based upon dialysis culture techniques has been developed. In fermentations of Escherichia coli where phosphate or sulfate concentrations were controlled, the relation between the apparent specific growth rate, mu, and the phosphate concentration followed Monod kinetics, while the relation between mu and sulfate showed a sharp optimun. The pH of fermentations of E. coli was controlled by dialysis culture techniques without the fluctuations in pH associated with control by direct addition of acid or base.     

Family outbreak of gastroenteritis due to Yersinia enterocolitica serotype 0:3 from well water

Yersinia enterocolitica serotype 0:3, biotype 4, has been isolated from two family members with diarrhea and from the well used as a source of their drinking water.     

Inhibition of phorbol ester stimulated superoxide production by 1-oleoyl-2-acetyl-sn-glycerol (OAG); fact or artefact?

OAG-stimulated superoxide (O2) production by HL-60 granulocytes showed enantiomeric specificity but reached a maximum of only 5% of that produced by either phorbol myristate acetate (PMA) or phorbol dibutyrate (PDBu). At 10-100 microM, OAG displaced specifically-bound [3H]PDBu from intact HL-60 cells by only 25%, suggesting limited cell penetration. OAG (10-100 microM) also inhibited PDBu-stimulated O2 production by 25%; this inhibition was enantiomerically specific. However, at a lower concentration (3 microM), both enantiomers of OAG fully blocked O2 production stimulated by PMA (0.5 microM). This inhibition is probably artefactual, due to the hydrophobic PMA physically associating with OAG in the extracellular fluid.     

Structural aspects and orientation mechanism of mitochondrial F1 adenosinetriphosphatase. Evidence for a negative electric birefringence due to a permanent moment perpendicular to the long axes of the particle

The electric birefringence technique was used to investigate the steady-state birefringence, the orientational relaxation time, and the orientation mechanism of pig heart mitochondrial F1 adenosine-5'-triphosphatase (F1-ATPase). The electrooptical properties of this enzyme in solution were studied as functions of pH, protein concentration, and applied electric field. The F1-ATPase exhibits a surprising negative electric birefringence with a specific Kerr constant of -1.5 X 10(-3) esu cgs. The field-independent relaxation time was found to be 0.65 +/- 0.05 microseconds, corresponding to a rotational diffusion constant of 2.55 X 10(5) s-1. The overall size and shape of F1-ATPase have been calculated from both translational and rotational diffusion constants. The enzyme may be assumed to be an oblate ellipsoid of revolution with dimensions of about 170 X 170 X 70 A. The orientation mechanism of F1-ATPase was analyzed by fitting experimental birefringence rising curves with theoretical rising functions. The ratio of the permanent to induced dipole moment is found to be very high; therefore, the birefringence of F1-ATPase is due to a strong permanent dipole moment in a direction perpendicular to the long axes of the particle. These particular electric properties can be explained by the oligomeric structure of the protein and seem likely to play a role in its mechanism of functioning.     

Mathematical model for human myeloma relating growth kinetics and drug resistance

We present a computer-based mathematical model that can simulate characteristic features of the clinical time course of human myeloma. It asserts that therapy resistance in myeloma cells is an inherited trait associated with the longer inter-mitotic times of some cells and that the strength of this trait affects tumour growth characteristics. These kinetic differences within the malignant cell clone may also influence therapeutic efficacy. In the model, the same total therapy, administered in different time-dose fractions, could be 'curative' or 'minimally effective' depending on kinetic properties. For example, as others have shown, in myeloma pulsed intermittent therapy is often more effective than low dose continuous therapy. According to our model this finding is compatible with a high coefficient of inheritability of resistance from one cell generation to the next. The model also suggests that if there are subclones of varying resistance, a therapy must have some effect on each of them if it is to be employed in a curative fashion. While many aspects of the model are not yet clinically testable, exploration of its concepts might increase knowledge about fundamental neoplastic mechanisms.     

Long-term hyperalgesia in rats induced by neonatal administration of vasopressin antiserum

Vasopressin antiserum was given to two day old rats and the nociceptive thresholds were evaluated three months later. The rats were hypersensitive to pain when electrical current, but not heat, was used as the noxious stimulus. These animals were also insensitive to cold-water swim, a non-opioid form of stress analgesia. The vasopressin content in the pituitary or in the hypothalamus was not however modified by the neonatal treatment. The present results suggest a physiological role for vasopressin in non-opioid pain inhibitory systems.