Intravenous infusion of iloprost in arterial occlusive disease: dose-dependent effects on skin microcirculation

Transcutaneous oxygen pressure (tcPo2), laser Doppler flux and capillary microscopy have been used to examine the forefoot skin in 5 healthy men and 8 patients with severe peripheral arterial occlusive disease in order to evaluate the dose dependent effects of iloprost on skin microcirculation. Iloprost was infused IV starting at 0.0625 ng.kg-1.min-1 and doubling the dose every 15 min up to 2 ng.kg-1.min-1. While tcPo2 at an electrode core temperature of 44 degrees C decreased in both patients and controls, there was a significant dose dependent increase in tcPo2 (37 degrees C) in the controls from 0.25 ng.kg-1.min-1. In the patients the reaction was variable: it was decreased in two and increased in 6, with a maximum either at 0.25-0.5 ng.kg-1.min-1 (n = 3) or at the highest dose (1.0 or 2.0 ng.kg-1.min-1; n = 3). Mean laser Doppler flux in both groups was increased, although the reaction was not consistent in the patients. Density of forefoot skin capillaries was reduced in 3 patients, and in the others the flow velocity was very low. During infusion of iloprost, both an increase in capillary density and blood cell velocity were observed. The effects were of variable intensity and occurred at varying doses, some appeared early and diminished as the dose was increased, and others were found only at 2 ng.kg-1.min-1. Adverse effects were numerous, extending from harmless skin flushing to mental changes and a quickly reversible attack of angina pectoris.(ABSTRACT TRUNCATED AT 250 WORDS)

[Hemodynamic effects of intermittent intra-arterial infusion treatment with prostaglandin E1 in peripheral arterial occlusive disease]

14 femoral arteries of twelve patients with peripheral arterial occlusive disease (Fontaine stage II: n = 4, stage III/IV: n = 10) were investigated before, immediately after a series of 26 (ten to 52) intraarterial infusions with prostaglandin E1, and 30 weeks later. Using combined B-mode and pulsed Doppler (duplex) ultrasound blood flow measurements were performed in the common femoral, the superficial femoral, and the deep femoral artery. There was a significant decrease of resting blood flow volume in the common femoral artery after therapy (418.5----362.2 [p less than 0.01]----324.5 ml/min [p less than 0.05]) in the group of patients treated successfully. The peak flow (maximum value of blood flow volume during reactive hyperaemia) in the common femoral artery increased significantly after therapy (597.3----779.1 [p less than 0.05]----843.7 ml/min). The increase of peak flow correlated well with clinical improvement. Other parameters (blood flow velocities, pulse rise time, pulse decrease time, pulsatility index) changed without correlation to clinical outcome. The increase of peak flow after therapy might be caused by an improved collateral circulation, and the decrease of resting blood flow might be due to metabolic effects of prostaglandin E1 (improved oxygen utilization).

A phosphoglycerate kinase-like molecule localized to glycosomal microbodies: evidence that the topogenic signal is not at the C-terminus

The phosphoglycerate kinase (PGK) gene complex of Trypanosoma brucei contains three tandemly linked related genes. One gene encodes a cytoplasmic PGK, while another encodes a PGK isozyme localized to glycosomal microbodies. In this communication, we report that the third gene in this complex encodes a 56-kDa molecule which is also localized to the glycosomal core. DNA sequence analysis indicates that this gene contains multiple substitutions and a large insertion in the amino domain, but that it is very similar to the other PGK isozymes in the carboxy domain. The C-terminal tripeptide is identical to that of the cytoplasmic isozyme, and only one conservative change occurs in the last 25 amino acids. The encoded protein, p56, thus contrasts with the many peroxisomal microbody proteins in which the C-terminal tripeptide contains sufficient information for targeting to peroxisomes. Multiple mechanisms may exist for targeting proteins to the protein cores of microbody organelles. Comparisons of the DNA sequences of several alleles suggest that homologous recombination plays a role in the generation of allelic diversity.

Alterations of the nailfold capillary morphology associated with Raynaud phenomenon in patients with systemic lupus erythematosus

Quantitative analysis of nailfold capillary morphology was performed in age and sex matched groups of 29 patients with systemic lupus erythematosus (SLE) presenting Raynaud phenomenon (RP), 29 RP negative patients with SLE with the same duration of the disease, and 29 healthy controls. Percentages of tortuous, meandering and bushy capillaries were significantly increased in both groups of patients without influence of RP. Capillary density was lower, mean diameters of the capillary loops were higher in patients, especially when RP was present (at the venular branch in microns, mean +/- SD: controls: 15.0 +/- 2.0, RP negative patients with SLE: 17.6 +/- 3.6, RP positive patients with SLE: 20.5 +/- 6.3). In a subgroup of 13 patients with frequent Raynaud's attacks (more than 1/week), diameters were still higher (22.1 +/- 7.1, p to controls less than 0.0005; p to RP negative patients less than 0.05). In patients with SLE, the prevalence of RP seems not to be associated with the increased number of abnormal capillaries but with capillary enlargement, correlating with the frequency of attacks.

The development of the RISK tool for fall prevention

The authors tailored a 26-item risk assessment tool (RAT) for falls based on a literature review and an analysis of causative factors of falls that had occurred over a 3-month period at the Olin E. Teague VA Medical Center, an 1,100-bed acute medical-surgical, psychiatric, and extended care facility in Temple, TX. The RAT was completed by nursing staff on 10 patient units (four medical, four surgical, and two nursing home units) for all admissions during the period. A 25% sample of the completed RATs was randomly selected (n = 208). Pearson's correlation coefficient was used to identify factors that would most likely predict falls from the RATs of the randomly selected group and of the patients who fell (n = 78). Only 4 of the 26 items were statistically related to falls. Based on findings from this study, the RAT was shortened to the four items and called the RISK (Reassessment Is Safe "Kare") tool.

Microbody phosphoglycerate kinase of Trypanosoma brucei: expression and complementation in Escherichia coli

In the primitive eukaryotic parasite, Trypanosoma brucei, most of the enzymes of glycolysis are located within microbody organelles called glycosomes. Proteins destined for the glycosome are synthesized on free ribosomes and post-translationally translocated into the organelle. The gene, gPGK, encoding the glycosomal isozyme of phosphoglycerate kinase (gPGK), was cloned adjacent to a T7 promoter and cotransformed with a plasmid encoding T7 RNA polymerase into Escherichia coli Pgk-cells. Functional complementation occurred, but only after the creation of a ribosome-binding site by mutagenesis. This represents the first example of complementation of an E. coli mutant with a gene encoding a microbody protein. Enzymatically active recombinant gPGK was purified to near homogeneity by ion exchange chromatography from highly expressing E. coli. The recombinant protein will aid in studies of glycosomal biogenesis.

[Duplex sonography: accuracy, reproducibility and possibilities for error. Checking quantitative flow measurements against an in vitro model]

Using a pulsatile model of tubes, duplex-sonographic measurements of flow were compared with actual flow. The correlation coefficient between actual and duplex-sonographically obtained flow was 0.975, mean percentage deviation being -18.1% (P less than 0.0001). The obvious scatter (margin of error -69.2 to +50%) is to be explained by the simulation closely imitating a real situation: the transducer was hand-held and tubes were placed in muscle or fat tissue. Accuracy was increased by multiple measurements, especially when taking into account only the maximal value of any series of measurements. Vessel diameter was easy to measure accurately (mean error less than 0.01% [-18.7 to +9.4%]). Repeated measurements of flow velocity had only a small scatter (coefficient of variance 0.064). In muscle or fat the Doppler signal was attenuated and the error the greater the deeper the level at which measurements were made. Low flow (common in patients with obstructive vascular disease) can also cause faulty results.

Skin microcirculation and regional peripheral resistance in patients with chronic renal anaemia treated with recombinant human erythropoietin

Skin microcirculation and regional peripheral resistance were studied in 14 patients with renal anaemia during therapy with recombinant human erythropoietin. Haematocrit was raised from 20.0 to 31.3% after 10-12 weeks of treatment and remained stable over another period of 12 weeks. Antihypertensive treatment had to be intensified in five patients. Regional calf blood flow decreased significantly; accordingly, calculated peripheral vascular resistance was increased by more than 100%. However, transcutaneous oxygen pressure (37 degrees C and 44 degrees C) increased significantly. The pathological vasoconstrictor response of skin capillaries was not influenced. There were no significant differences of any parameter between the patients requiring reinforced antihypertensive therapy and those with stable blood pressure. In conclusion skin oxygenation may be improved by erythropoietin treatment to a large extent despite an increase in calculated total limb vascular resistance.

Skin surface oxygen pressure fields during administration of prostaglandin E1 in patients with arterial occlusive disease

Prostaglandin E1 is offered as a new therapeutic agent in the treatment of severe peripheral arterial occlusive disease. Especially when treating patients with ulcers or gangrene, the oxygen tension of the skin should improve during PGE1 administration. The new technique of assessing skin surface oxygen pressure histograms allows study of the skin microcirculation in vivo. Oxygen histograms were determined on the forefeet of 19 patients with different degrees of disease and different occlusion levels before and during a single intraarterial infusion of PGE1 at a dosage of 1.5 ng/kg body weight/min. Only 9 patients showed improvement during the infusion period. Skin oxygen pressure was increased to a large extent only in patients assumed to suffer from diabetic microangiopathy. The effect of a long-term therapy with PGE1 on skin microcirculation remains to be settled.

The inactivation of rhodanese by nitrite and inhibition by other anions in vitro

Cyanide detoxification in mammals occurs, in part, by sulfur transfer by rhodanese to form the less toxic thiocyanate. Thiosulfate and nitrite are often used in combination for the treatment of cyanide intoxication. This report shows that nitrite can inhibit the rate of sulfur transfer by rhodanese in vitro. Nitrate, chloride, sulfate, and acetate were also examined as inhibitors. Inhibition by nitrite appeared to be more complex than for the other anions tested. Closer examination showed that nitrite can inactivate the sulfur-free rhodanese. Our observation leads to the suggestion that, in vivo, either rhodanese is maintained in its more stable sulfur-substituted form or cellular compartmentalization prevents inactivation by nitrite.

Temperature-dependent laser Doppler fluxmetry in healthy and patients with peripheral arterial occlusive disease

Laser Doppler flux (LDF) was determined at the forefoot in 17 healthy volunteers and 16 patients with mild peripheral arterial occlusive disease. LDF was assessed simultaneously by two probes, one was unheated and the other was run with a probe holder temperature of 37 degrees C. During occlusion of the venous circulation a decrease between 43 and 61% was recorded in both groups and at both temperatures. When the leg was elevated there was an increase of about 60% in unheated skin; at 37 degrees C LDF was impaired significantly in patients. During leg dependency LDF decreased in 15 of the volunteers by 44 and 50% which is the result of the physiological vasoconstrictor response. In patients there was a decrease in unheated skin in 12 cases, in heated skin only in 8 cases. When pure oxygen was inhaled, LDF was unchanged in probands, but increased in patients when measured at 37 degrees C. Reactive hyperaemia flow was about three times higher in unheated skin than in heated skin. Reproducibility was best during leg elevation and was more reliable for measurements at 37 degrees C. Rhythmical variations had a frequency of about 4 cycles/min in healthy subjects and 2.6 cycles/min in patients. As a rule, in both groups frequencies at 37 degrees C were higher as compared with unheated skin. Patients had lower frequencies than probands at both temperatures. During intraarterial application of two differently acting drugs quite different reactions of LDF could be recorded. Measurements of LDF at 37 degrees C made differences between patients with PAOD and healthy volunteers more obvious. Moreover, vasomotional changes in skin blood flow could better be studied at this temperature.

Properties of an Escherichia coli rhodanese

A rhodanese enzyme of less than 20,000 molecular weight has been purified from Escherichia coli. The enzyme is accessible to substrates upon addition of whole cells to standard assay mixtures. This rhodanese has a Stokes radius of 17 A which for a globular protein corresponds to a molecular weight close to 14,000. It undergoes autoxidation to a polymeric form which is probably an inert dimer. Enzyme inactivated by oxidation can be reactivated by millimolar concentrations of cysteine. Steady-state initial velocity measurements indicate that the enzyme catalyzes the transfer of sulfane sulfur by way of a double displacement mechanism with formation of a covalent enzyme-sulfur intermediate. The turnover number for the enzyme-catalyzed reaction, with thiosulfate as donor substrate and cyanide ion as the sulfur acceptor, is 260 s-1. This value corresponds to a catalytic efficiency 60% of that measured for a previously characterized bovine liver enzyme of more than twice the molecular weight. Furthermore, KmCN is 24 mM which is 2 orders of magnitude higher than the value observed previously for the bovine enzyme. Evidence from chemical inactivation studies implicates an essential sulfhydryl group in the enzyme activity. It is proposed that this group is the site of substrate-sulfur binding in the obligatory enzyme-sulfur intermediate. Furthermore, a cationic site important for binding of the donor thiosulfate is tentatively identified from anion inhibition studies. Tests of alternate acceptor substrates indicate that the physiological dithiol, dihydrolipoate, is a more efficient acceptor than cyanide ion for the enzyme-bound sulfur. Of possibly greater physiological significance, it has been found that the enzyme catalyzes the formation of iron-sulfur centers. Other work indicates the E. coli rhodanese is subject to catabolite repression and suggests a physiological role for the enzyme in aerobic energy metabolism.

The inhibition of cytochrome oxidase by diaminomaleonitrile

Diaminomaleonitrile, a tetramer of cyanide, was examined as a possible antagonist to cyanide inhibition of cytochrome oxidase (EC 1.9.3.1). This compound was found to inhibit cytochrome oxidase in vitro; however, despite their structural similarities, diaminomaleonitrile and cyanide inhibit cytochrome oxidase by different mechanisms and bind to the enzyme at different sites. Diaminomaleonitrile inhibition of cytochrome oxidase is described in terms of a partially competitive mechanism. Biological oxidation of diaminomaleonitrile may lead to the formation of cyanide.

Comparison of Laser-Doppler-Flux and tcPO2 in healthy probands and patients with arterial ischemia

Transcutaneous PO2 (tcPO2) and Laser-Doppler-Flux (LDF) were compared on the dorsum of the foot in 20 healthy probands and 35 patients with peripheral arterial occlusive disease at clinical stage II b or IV. The probes were kept at a temperature of 37 degrees C. Using different procedures, we brought about dynamic changes and compared the reaction of the two signals. Venous occlusion resulted in a decrease of both signals to a similar extent in both groups. During leg dependency both signals decreased in the probands suggesting a normal vasoconstrictor response. In most of the patients an increase was observed, but some showed a decrease even at clinical stage IV. LDF had a stronger tendency towards a decrease. On leg elevation, LDF slightly increased in probands and decreased in patients. Here, the tendency towards a decrease was higher for tcPO2. After arterial occlusion reactive hyperemia was more pronounced in probands. Differences between tcPO2 and LDF seem to be mainly due to the different capillary systems contributing to the signal.