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J B Jones

Publications and source records attributed to J B Jones.

At least 145 records · Page 8Linked to original sources
PubMed1979

Circular dichroism and magnetic circular dichroism of nitrogenase proteins.

Circular dichroism (CD) and magnetic circular dichroism (MCD) spectra of nitrogenase components (MoFe protein and Fe protein) from Azotobacter vinelandii (Av) and Klebsiella pneumoniae (Kp) have been obtained in the near infrared-visible-near ultraviolet spectral region. Previously, visible CD was reported to be absent or barely detectable in nitrogenase proteins; MCD spectra have not been reported. The chiroptical spectra can be measured in solution at room temperature, an advantage relative to spectroscopic methods requiring cryogenic sample temperatures. Absorption spectra were also obtained. The CD and MCD are markedly more structured, and thus interpretively more useful, than the corresponding absorption spectra. The dithionite-reduced MoFe proteins (Av1, Kp1) have nearly identical CD and MCD, demonstrating identical numbers and types of metal centers in similar protein environments. The CD and MCD cannot be explained solely in terms of contributions from known 4-Fe or 2-Fe clusters; the near-infrared MCD is inconsistent with the presence of known 4-Fe clusters. CD and MCD spectra of Lauth's violet-oxidized Kp1 are also reported. The reduced Fe proteins (Av2, Kp2) have similar CD and MCD, again indicating significant conservation of chromophore environment. The spectra clearly demonstrate the presence of a reduced bacterial ferredoxin-like (C(3-)) 4-Fe cluster. No obvious evidence of additional chromophores is observed. CD, MCD, and absorption spectra of Av1-oxidized Av2 are reported. The absorption spectrum shows the expected shoulder near 390 nm. The CD and MCD are characteristic of a C(2-) 4-Fe cluster; in particular, the diagnostic near-infrared MCD peak is observed at approximately 8300 cm(-1). The CD of Av2 oxidized in the presence and absence of MgATP are radically different, providing the first direct evidence for MgATP interaction with Fe protein in this oxidation state.

Azotobacter↗
PubMed1979

Some immunological and haematological aspects of human cyclic neutropenia.

In addition to standard peripheral blood cell counts, sequential studies have been made of changes in the T-lymphocyte population and in the serum titres of the presumptive humoral regulators of haematopoiesis, Colony Stimulating Activity (CSA) and Erythroid Stimulating Activity (ESA), in a young woman with cyclic neutropenia (CN). In addition, serum immunoglobulins, C3 and total complement levels and serum protein concentrations were determined on several occasions during the study. Similar tests were done concomitantly on a haematologically normal, age and sex-matched control. Cell counts on peripheral blood from the subject with CN demonstrated a clearly defined periodicity in neutrophil and monocyte concentrations and equivocal fluctuations in reticulocyte numbers. There was no evidence of periodicity in the lymphocyte concentrations and the T-lymphocyte population appeared functionally normal. Spontaneous incorporation of tritiated thymidine into peripheral blood cells showed a highly significant correlation with the monocyte count, suggesting that these cells were responsible for the radioisotope uptake. CSA titres were elevated on all occasions tested and showed no evidence of periodicity. ESA showed some evidence of cycling with elevated levels being observed during the periods of neutropenia. Serum complement levels were within the normal range but all classes of immunoglobulins were elevated and albumin levels were depressed.

Adult↗
PubMed1979

The in vitro growth of erythroid colonies from dog bone marrow.

Enriched methyl cellulose media together with either human urinary erythropoietin or serum collected from phlebotomized dogs exposed to hypoxia was used in the study of the erythroid colony forming (CFU-E) capacity of dog marrow. The dog serum erythropoietin was found to be more efficient in stimulating CFU-E than comparable concentrations of human urinary erythropoietin. Numbers of CFU-E were directly related to the culture concentration of the stimulating serum and to the number of cells per plate. Sheep plasma erythropoietin was also found to be effective in stimulating CFU-E growth. The system described is chemically better defined and produced more consistent results than has been reported for the plasma clot method.

Animals↗
PubMed1979

Evidence that the fetal mouse liver cell assay detects erythroid regulatory factors (ERF) not measured with a standard in vivo assay.

A simplified modification of the fetal mouse liver cell (FMLC) assay has been used to investigate the relationship between in vivo and in vitro detectable Erythroid Regulatory Factors (ERF) in the serum of dogs exposed to hypoxia. The results suggest that the FMLC assay is a useful technique for following changes in serum ERF. However, the data obtained cannot be directly equated with the in vivo erythrocythemic mouse assay unless a correction factor is applied. This is necessary because the in vitro assay, in general, detects 50% more ERF than does the standard mouse assay.

Animals↗
PubMed1978

Evidence for the existence of an agent in the serum of the cyclic hematopoietic dog which influences hemoglobin synthesis.

Serum samples collected through the cycle of a cyclic hematopoietic (CH) dog under reduced atmospheric conditions, were assayed for their ability to affect hemoglobin synthesis by normal canine bone marrow. Varying levels of hemoglobin synthesis in the presence of different serum samples suggest an agent cycles in the serum of CH dogs which influences hemoglobin synthesis.

Animals↗
PubMed1978

A reappraisal of the reaction of butyryl-coenzyme A dehydrogenase with phenylmercuric acetate. Evidence that de-greening involves a reaction of the tightly bound thioester.

Phenylmercuric acetate reversibly de-greens butyryl-CoA dehydrogenase from Megasphaera elsdenii, abolishing the absorption band at 710nm. The view that this is a result of modification of a protein thiol group is re-examined in the light of the following new observations. (i) After treatment with phenylmercuric acetate, the enzyme's ability to be re-greened by addition of thiols was not decreased by gel filtration or precipitation with (NH(4))(2)SO(4). (ii) Phenylmercuric acetate caused the same extent of de-greening whether added in a few large amounts or many small ones. The overall time taken for de-greening was, however, greatly extended when many small additions were made. (iii) In Tris/acetate buffer, pH7.5, 3.5mol of phenylmercuric acetate/mol of enzyme subunit was required for complete de-greening, compared with only 2.5mol/mol in phosphate buffer, pH7. (iv) None of the groups that react with phenylmercuric acetate is accessible to iodoacetate or iodoacetamide. (v) On a molar basis dithiothreitol, mercaptoethanol and CoA are equally effective in re-greening the enzyme. (vi) Provided that phenylmercuric acetate is not present in excess, the de-greened enzyme forms normal and stable complexes with crotonyl-CoA and acetoacetyl-CoA. (vii) When a small excess of phenylmercuric acetate is present, full stable development of the enzyme-acetoacetyl-CoA complex requires addition of several mol of acetoacetyl-CoA/mol of enzyme subunit. (viii) The ability of de-greened enzyme to be immediately re-greened by an excess of thiol declines with time, more rapidly at pH6 than at pH7 or 8, but at all three pH values the instantaneous re-greening was followed by a slow phase of further increase in A(710). This further recovery was most extensive and most rapid at pH8. These findings are reminiscent of the previously described reversible decline in the re-greening capacity of a protein-free acid extract of green butyryl-CoA dehydrogenase. It is concluded that the likely cause of de-greening is chemical modification of the tightly bound thioester rather than a protein thiol group. The reversibility would be explained if the thioester exists on the surface of the enzyme in equilibrium with free CoA and a lactone, or if the acyl group is readily and reversibly transferred from the thiol of CoA to a protein side chain.

Acyl Coenzyme A↗
PubMed1978

Oral anticoagulants controlled by the British comparative thromboplastin versus low-dose heparin in prophylaxis of deep vein thrombosis.

The British comparative thromboplastin (BCT) was used to monitor the effectiveness of oral anticoagulants in preventing deep vein thrombosis (DVT) in patients undergoing major gynaecological surgery. All patients were screened for DVT with the use of the (125)I-fibrinogen scan.One hundred and forty-five patients aged 40 years or more were randomised into three groups. Group 1 received oral anticoagulant (nicoumalone) treatment, stabilised over five days before surgery and continuing into the second postoperative week. The other patients served as two contrast groups and were managed on a double-blind basis. Group 2 received a subcutaneous low-dose regimen of heparin calcium. Group 3 received subcutaneous saline. Eleven of 48 patients in the saline group, three of 49 patients in the heparin group, and three of 48 patients in the oral anticoagulant group developed DVT as judged by (125)I-fibrinogen scanning. The incidences in groups 1 and 2 were significantly lower than in the saline group. The falls in haemoglobin concentration and incidence of haemorrhage were similar in all three groups.The study showed that oral anticoagulant prophylaxis stabilised preoperatively and low-dose heparin were equally effective in preventing deep vein thrombosis in a moderate-risk group. Immediate preoperative prothrombin ratios of 2.0-2.5 and postoperative ratios of 2.0-4.0 with the BCT gave adequate protection without increased haemorrhagic risk.

Acenocoumarol↗
PubMed1978

The cyclic hematopoietic dog: a model for spontaneous secondary amyloidosis. A morphologic study.

Spontaneous amyloidosis was found in dogs affected with hereditary cyclic hematopoiesis (CH dogs). Early perifollicular deposits of amyloid were observed in the spleens of 15-week-old CH dogs. By the 24th week, amyloid deposits were also found in the liver, kidneys, pancreas, adrenals, and small intestine; the incidence of the condition rose to more than 90%. The visceral involvement and the histologic characteristics of amyloid deposition closely resemble those of the secondary form in humans. A transient lymphoid hypoplasia was noted in the spleens of neonates and pups. This abnormality did not appear to be related to exogenous conditions. In young adult dogs, the initial hypoplastic characteristics were replaced by enlarged marginal zones in the follicles of the spleen, composed of pyroninophilic cells and, in a later stage, of PAS-positive cells. These cellular changes preceded the amyloid deposition. Due to the characteristic cyclic neutropenia of the hereditarily transmitted hematologic syndrome, most CH dogs experience episodes of infectious diseases, although the episodes of infection may be separated by long periods of relatively good health. This may provide the underlying antigenic stimulation which triggers the process of amyloid deposition. However, the lag period for the onset of amyloidosis is extremely short and the type of infections is not considered a predisposing factor for amyloid deposition. It is possible that a peculiar sensitivity of the lymphoid system in the CH dog would facilitate the development of widespread amyloidosis. Since the sequence of splenic lymphoid hypoplasia, follicular activation, and amyloid deposition associated with age are consistently repeated, the CH dog may be a suitable animal model for the study of the pathogenesis of secondary form of amyloidosis in humans.

Age Factors↗
PubMed1978

Erythroid colony formation in vitro from the marrow of dogs with cyclic hematopoiesis: interrelationship of progenitor cells.

Committed erythroid progenitor cells (Colony Forming Units-Erythroid, CFU-E) have been studied in canine cyclic hematopoiesis (CH) utilizing a semi-solid methyl cellulose culture system. Erythroid colonies were stimulated by the addition of a standard volume of serum from normal dogs that had been phlebotomized and subjected to hypoxia. CFU-E fluctuated over the cycle in dogs with CH from concentrations 4--5 times normal during the periods of peripheral blood neutropenia to less than one tenth of normal during the phases of elevated peripheral blood neutrophil counts. In spite of these marked fluctuations there was no change in the proliferation rate of the CFU-E as estimated by the tritiated thymidine (3H-TdR) suicide technique. Failure to demonstrate a change in the CFU-E proliferation rate may be related to the relative maturity of these cells with the fluctuations in number resulting from a 'feed-in' from more immature cells. The results show that CFU-E fluctuate in the same phase as committed granulocytic progenitor cells (CFU-C). Our current knowledge of the interrelationships of marrow progenitor cells and events in the peripheral blood of dogs with CH is briefly reviewed and some additional questions, raised by recent studies regarding the pathogenesis of this disease, are discussed.

Animals↗