Hyperammonaemia and lactic acidosis in a patient with pyruvate dehydrogenase deficiency

A patient who presented in the newborn period with severe lactic acidosis and hyperammonaemia has been shown to have a specific defect in the pyruvate dehydrogenase complex. The secondary inhibition of ureagenesis in this patient appears to be due to a functional deficiency of carbamyl phosphate synthetase.

An effect of CO2 on the maximum safe direct decompression to 1 bar from oxygen-nitrogen saturation

An investigation into the maximum safe decompression step from oxygen nitrogen saturation to 1 bar was carried out with and without the presence of 0.02 bar carbon dioxide. The series, Islander 1, involved 13 teams of 5, fully informed, male volunteers carrying out simulated dives. One group of 6 teams carried out dives in an atmosphere of 0.4 bar oxygen, balance nitrogen (O2-N2); another group of 7 teams used an atmosphere of 0.38 bar oxygen, 0.02 bar carbon dioxide, balance nitrogen (O2-N2-CO2). The dives consisted of a 48-h stay at 1.7 or 1.8 bar to saturate the tissues, followed by decompression to 1 bar air at 0.5 bar/min. Two decompression parameters were studied; the incidence of decompression sickness (DCS) in the 24 h postdecompression, and the incidence and grade of venous gas emboli (VGE) in the first 6 h postdecompression. The grade of VGE was assessed using the Kisman-Masurel scoring system which produces a bubble grade with the subject at rest and after movement. No significant difference was found in the incidence of DCS between the two groups. Twenty subjects were decompressed from 1.7 bar using each mixture, without signs or symptoms of DCS. However, after decompression from 1.8 bar there were 2 cases of DCS in 10 subjects in the O2-N2 group and 2 cases in 15 subjects in the O2-N2-CO2 group. The incidence of detectable VGE was always lower in the O2-N2-CO2 group at both saturation pressures; at 1.7 bar the VGE incidence was lower by 40% (P less than 0.05) at rest and by 55% (P less than 0.001) after movement. At 1.8 bar the reduction was 3% (NS) at rest and 30% (NS) after movement. The results indicate that decompression from 1.8 bar to 1 bar, with or without the presence of 0.02 bar carbon dioxide, is likely to produce more than 5% DCS.

Inhibition of phorbol ester stimulated interleukin 2 production by copper(II) complexes

Superoxide dismutase mimetic copper(II) complexes, such as copper(II)(3,5-diisopropylsalicylate)2 (CuDIPS), inhibit phorbol ester stimulated tumor promotion in mouse skin. Therefore, CuDIPS was tested as a potential inhibitor of another effect of phorbol esters, induction of interleukin 2 (IL2) synthesis, in the mouse thymoma cell line EL4. CuDIPS inhibited phorbol ester induced IL2 production in a concentration dependent manner with a 50% inhibitory concentration of about 10 microM. However, the ligand 3,5-diisopropylsalicylic acid also inhibited the induction of IL2 by phorbol esters (50% inhibitory concentration, 15 microM). Since the superoxide dismutase mimetic activity of CuDIPS is not stable in the presence of ethylenediaminetetraacetic acid, the effects of CuDIPS could be due to the free ligand and not to the intact metallocomplex. Consequently, a series of extremely stable copper(II) macrocyclic compounds was synthesized, and the reduction potential, superoxide dismutase mimetic activity, and ability to inhibit phorbol ester induced IL2 production were determined for each. Of the copper(II) macrocyclic complexes studied, only the most potent superoxide dismutase mimetic compound was found to inhibit phorbol ester induced IL2 production. Copper(II) complexes had to be added no later than 4 following phorbol ester administration to be effective inhibitors of the IL response, suggesting that these compounds act subsequent to the binding of phorbol esters but prior to the transcription of IL2 messenger RNA. Adherence of EL4 cells to substrate in response to phorbol esters was unaffected by copper(II) compounds. In summary, copper(II) compounds with appropriate reduction potentials can act within a defined time period to inhibit some, but not all, of the effects of phorbol esters on EL4 cells.

Avian medullary bone in organ culture: effects of vitamin D metabolites on collagen synthesis

A new organ culture system for the study of bone metabolism has been developed using chicken medullary bone. The presence of viable bone cells in culture was demonstrated by histological and histochemical techniques. Incorporation of 3H-proline into collagenase-digestible protein (CDP) and noncollagen protein (NCP) was determined using purified bacterial collagenase. Collagen accounted for approximately 10-15% of the total protein labeled. The addition of 1,25-dihydroxycholecalciferol (1,25(OH)2D3) resulted in a dose-dependent inhibition of 3H-proline incorporation into CDP at doses from 10(-10)M to 10(-7)M, with maximal suppression reaching 30% of control. The effect was specific for collagen, since 3H-proline incorporation into NCP was unaffected. Hydroxyproline analysis of bone explants and culture medium revealed a 1,25(OH)2D3-induced decrease in the 3H-hydroxyproline content of the system (bone + medium), suggesting that the effect of 1,25(OH)2D3 is due to inhibition of collagen synthesis rather than enhanced collagen degradation, impaired incorporation of collagen into bone matrix, or bone resorption. Medullary bone collagen synthesis was not affected by 24,25(OH)2D3, either alone or in combination with 1,25(OH)2D3. Structure-activity studies of vitamin D metabolites showed that 1,25(OH)2D3 and 1,24,25(OH)3D3 were the most potent metabolites tested, followed by 1-alpha(OH)D3. 25(OH)D3 and 24,25(OH)2D3 had no effect at concentrations as high as 10(-7)M. These results indicate a possible role for vitamin D in the regulation of medullary bone formation during the reproductive cycle of the egg-laying hen, and suggest the potential utility of medullary bone as an in vitro model for the study of bone formation.

Clathrin light chains and secretory vesicle binding proteins are distinct

Recently, several groups have initiated studies on cytosolic proteins that bind to isolated secretory vesicle membranes in the presence of Ca2+ in order to identify proteins that may regulate exocytosis. Two major chromaffin granule binding proteins, of molecular weights 32,000 (32K) and 34,000 (34K), were reported to have the same mobility on one-dimensional SDS gels as clathrin-associated light chains from the adrenal medulla, and the 34K granule binding protein the same one-dimensional peptide map as the 34K clathrin light chain. These observations support the hypothesis that Ca2+-dependent recruitment of soluble light chains to the vesicle membrane may nucleate the assembly of a clathrin coat and initiate endocytosis. Here we report that two-dimensional peptide maps of the clathrin light chains and of all chromaffin granule membrane binding proteins in the 30K range are distinct, and therefore fail to support this hypothesis. It has also been suggested that some or all of the vesicle binding proteins require calmodulin for their interaction with the membrane. However, we find that antagonism of calmodulin by trifluoperazine does not prevent the association of the other cytosolic proteins with the chromaffin granule membrane.

Enzymatic diagnosis of the mucopolysaccharidoses: experience of 96 cases diagnosed in a five-year period

We assessed lysosomal exohydrolase activities in homogenates of cultured skin fibroblasts and peripheral blood leucocytes of approximately 550 patients referred from throughout Australasia and suspected of having a mucopolysaccharidosis. Of these, 96 patients from 80 families were diagnosed as being homozygous deficient for a particular lysosomal enzyme activity. Clinical phenotype varied considerably within each of the enzyme-deficient states. This did not correlate with the level of "residual" enzyme activity in leucocyte or fibroblast homogenates. It was not always possible to discriminate heterozygotes from normal controls by enzyme assay of leucocyte or fibroblast homogenates in this study of a large number of mucopolysaccharidoses Type II by means of a single hair root assay system.