Identification of initiating agents in myoglobin-induced lipid peroxidation.

Reaction of metmyoglobin with peroxides is known to involve the formation, possibly via a porphyrin radical-cation, of a ferryl (iron(IV)-oxo) species and a protein radical; there is a little information available as to which of these species initiates the damage which is observed on incubating membrane fractions with such mixtures. It is shown in this study that the initial protein radical, which is a tyrosine phenoxyl radical centered at position 103 in the protein, does not react rapidly with erythrocyte membranes. However a tyrosine peroxyl radical, formed by addition of oxygen to this species, does react rapidly, and it is concluded that this radical, together with the ferryl species, is an important initiating species in myoglobin-induced lipid peroxidation.     

Independent control of sexual and scent marking behaviors of male gerbils by cells in or near the medial preoptic area

This research studied the role of the medial preoptic area and adjacent cell populations in androgen control of scent marking and sexual behavior in male gerbils (Meriones unguiculatus). Experiment 1 replicated previous research showing that implants of testosterone propionate in or near the medial preoptic area reinstate marking behavior in castrates. Implant sites near the diagonal band of Broca or in the posterior part of the medial preoptic area, near the anterior hypothalamus, are more effective than other sites. Experiment 2 showed that medial preoptic area lesions permanently impair sexual behavior despite testosterone stimulation. Experiments 2–4 showed that lesions in or near the medial preoptic area can also disrupt scent marking; however, this behavior gradually recovered in many lesioned males, especially if they received testosterone. The data suggest that both scent marking and sexual behavior are controlled by androgens acting on cells in or near the medial preoptic area, but the cell populations involved in these two behaviors are probably not the same.     

L-serine degradation in Escherichia coli K-12: a combination of L-serine, glycine, and leucine used as a source of carbon.

Escherichia coli K-12 strain CU1008 cannot use L-serine as the sole carbon source, but it could use L-serine as an auxiliary carbon source with glucose, L-alanine, or pyruvate and could derive energy from L-serine to support oxygen uptake. CU1008 grew with L-serine if it was also provided with glycine and leucine. These may act by increasing the available activity of L-serine deaminase; other explanations are also explored.     

The distal boundary of myogenic primordia in chimeric avian limb buds and its relation to an accessible population of cartilage progenitor cells

Using chimeras consisting of chick embryos that had received substitution grafts of quail somites, we have determined the distalmost extension of the myogenic primordia in the outgrowing wing bud at 5 days of incubation. At Hamburger-Hamilton stage 25 the most distal premuscle cell is consistently 300 mum or more from the apex of the wing mesoblast. The stage 25 wing tip resembles very early whole limb buds in not having proceeded beyond the mesenchymal state or having expressed markers of terminal differentiation. However, unlike early whole limb buds it is free of a myogenic subpopulation. We therefore propose that the stage 25 wing tip is the appropriate system for in vitro and molecular studies of cartilage differentiation.     

Structural studies on lamellated osmiophilic bodies isolated from pig lung. 31P NMR results and water content

1. Lamellated osmiophilic bodies are intracellular organelles in which pulmonary surfactant is stored prior to secretion. They contain about 85% phospholipid (per dry weight) and dipalmitoyl phosphatidylcholine is a major constituent, and although their ultrastructure is uncertain it is generally supposed that they resemble liposomes. However, liposomes are stable because layers of water are interposed between the lipid bilayers whereas an essential aspect of the function of lamellated bodies is that, subsequent to their secretion, they are rapidly disrupted to form a surface-active film which covers the respiratory epithelium of the lung. 2. A new method for isolating lamellated bodies from pig lung is described which has the advantage of speed and simplicity and which results in increased yields. The homogeneity of the preparation is similar to that obtained by other methods. 3. 31P NMR spectra of lamellated bodies showed that at 40 degrees C about 95% of the phospholipid was present as extended bilayers and that about 5% was present in a phase exhibiting isotropic head group mobility (tau R less than 10(-5) s). It is suggested that this phase may be due to apolar proteins which are present both in lamellated bodies and in liposomes prepared from lipids extracted from them. 4. The internal water content of lamellated bodies has been measured gravimetrically and the hydration of the phospholipid head groups has been examined by 31P NMR. The two methods gave results in good agreement and show that there are about seven molecules of water/molecule of phospholipid. It is concluded that although the phospholipid head groups in lamellated bodies are fully hydrated, there is no zone of free water. 5. Lamellated bodies are osmotically insensitive to NaCl whereas liposomes prepared from lipids extracted from them behave like perfect osmometers. It is suggested that the osmotic insensitivity and restricted water content of lamellated bodies are important to their function and dependent upon polar proteins in the outer limiting membrane.     

A radioimmunoassay method for the rapid detection of Candida antibodies in experimental systemic candidiasis

Rabbits were employed as experimental models to evaluate a solid-phase radioimmunoassay (RIA) method for the diagnosis of systemic candidiasis. Ten rabbits were inoculated subcutaneously to mimic superficial candidiasis and were found to produce no antibodies to Candida as determined by both immunodiffusion and RIA procedures. However, 94 per cent of 18 rabbits systemically infected by intravenous injection of Candida cells were observed to produce antibody as assessed by the RIA technique. These data encourage further tests with human sera and the continued development of this RIA procedure as a useful tool in the early serodiagnosis of systemic candidiasis.     

Dissociation of absorptions of calcium and phosphate after successful cadaveric renal transplantation.

Calcium and phosphate absorptions were studied by radiotracer techniques in 30 patients after successful cadaveric renal transplantation, and results were compared with those in a group of normal subjects and in groups of patients with chronic renal failure (CRF). Both calcium and phosphate absorptions were impared in patients with CRF, including those receiving haemodialysis. Abnormalities of calcium absorption, however, seemed to occur earlier in the course of advanced renal failure than abnormalities in phosphate absorption. Calcium absorption improved dramatically after successful renal transplantation, while phosphate absorption remained the same. A dissociation between calcium and phosphate absorptions is not often seen clinically, and the mechanisms for it are unknown. Phosphate malabsorption may be a further contributing factor in the development of persistent hypophosphataemia after transplantation.