The role of the deep femoral artery as an inflow site for infrainguinal revascularization

PURPOSE

Although the deep femoral artery (DFA) is well acknowledged as an outflow vessel for inflow reconstruction, data are lacking concerning the suitability of the DFA as an inflow site for distal bypass.

METHODS

From 1986 to 1992 we performed 268 consecutive infrainguinal reversed vein bypasses, of which 56 (21%) originated from the middle or distal DFA. The indications for DFA-origin grafts included inadequate vein length, need for concomitant extended profundaplasty, and avoidance of groin scarring from previous reconstruction or infection. The surgical approach to the DFA (standard, posteromedial, or lateral) was tailored to the patient. All grafts were monitored with serial duplex scanning surveillance.

RESULTS

Primary and secondary patency rates of DFA origin grafts were 78% and 96% at 3 years. These patency rates were no different from those grafts originating from the common femoral artery (66%; 89%), the superficial femoral artery (69%; 87%), or the popliteal artery (66%; 87%). Hemodynamic failure was detected in seven DFA-origin grafts, but only one resulted from disease in the common femoral artery or DFA proximal to the origin of the vein graft.

CONCLUSIONS

Direct lateral and posteromedial approaches to the DFA were used extensively in repeat operative situations, avoiding dissection in a scarred groin and shortening the length of vein required to perform an autogenous bypass. We conclude that in appropriately selected patients, the DFA origin technique increases the versatility of lower extremity vein bypass grafting without sacrificing durability.

Worrying about waste: living close to solid waste disposal facilities in southern Ontario

As a complement to an epidemiological survey, depth interviews were used to discover the individual level impacts of living close to waste disposal facilities in southern Ontario. The paper begins by describing the nature of the sites and reporting some of the survey findings, which the depth interviews explored. Sample selection and data analysis methods are described. A by-code analysis of the material is presented, emphasizing both within- and between-site differences in type and concern (or impact). Concern varied according to type of exposure and site context. The paper ends with a discussion which relates the study's findings on non-toxic facilities to other research on psychosocial effects, lay reasoning and risk perceptions and assessments.

Modelling psychosocial effects of exposure to solid waste facilities

A parallel case study design was used to investigate psychosocial effects in populations exposed to solid waste facilities. Psychosocial effects were defined as a complex of distress, dysfunction and disability, manifested in a range of psychological, social and behavioural outcomes, as a consequence of actual or perceived environmental contamination. This paper presents the results of logistic regression analyses designed to identify determinants of psychosocial effects of exposure. The data come from an epidemiologic survey of residents (N = 696) living within a prescribed radius from each of three solid waste facilities in southern Ontario. The analytical model has three main components: external variables (e.g. individual and exposure-related variables); mediating variables (e.g. social network membership and involvement, general health status measures); and outcome variables (e.g. concern, effects and actions). Results for a series of site specific analyses show that outcome measures can be successfully explained by a combination of external and mediating factors. In general, variables from each of the three main components enter the concern-related models while the action models are clearly dominated by social network variables. Analyses using data from all three sites indicate the explanatory power of site-related characteristics. However, given the number and diversity of variables in the models, there is no support for a simple cause and effect relationship. The implication is that strategies aimed to address and alleviate psychosocial effects need to be specific to the characteristics of the populations in particular settings.

Combined coronary artery bypass and abdominal aortic aneurysmectomy: appropriate management in selected cases

Patients with aortic aneurysms frequently have concomitant coronary artery disease, which carries the potential for significantly increased perioperative morbidity. Most cases of severe surgically correctable coronary artery disease can and should be treated by a separate operation before aneurysmectomy to lower operative cardiac morbidity and enhance long-term survival. Infrequently, a patient can have both unstable coronary disease and a large symptomatic aortic aneurysm. In this situation, a single procedure combining coronary artery bypass followed by aneurysmectomy, as illustrated by this case report, is a reasonable option and should be considered in the cases of carefully selected patients.

The "blue-toe" syndrome as a harbinger of impending infrainguinal vein graft failure: a report of three cases

Spontaneous "blue-toe" syndrome classically results from distal lower extremity microembolization of intraluminal atheromatous debris from a proximal source to the digital end arteries. During a 6-year period, 274 consecutive infrainguinal reversed vein arterial reconstructions were performed; in three patients (1.1% incidence), atypical distal microembolization originating from focal preocclusive intraluminal vein graft stenoses was identified. Sudden, spontaneous onset of ipsilateral blue-toe syndrome occurred at intervals of 4 to 11 months. Subsequent duplex scans and arteriography demonstrated patent grafts with high-grade, hemodynamically significant focal proximal short-segment sclerotic vein graft stenosis (n = 1) and midgraft valvular weblike stenoses (n = 2) with luminal irregularity. No other associated tandem lesions in the proximal or distal arterial tree were noted that would account for the microembolic phenomenon. The stenotic vein segments were excised with interposition vein graft replacement (n = 1) or with primary end-to-end reanastomoses (n = 2), resulting in complete resolution of the distal microembolic events without need for amputation. Histologic examination of these graft lesions demonstrated significant focal myointimal hyperplasia with adherent platelet aggregates and organized thrombus. The clinical presentation of distal lower extremity cutaneous digital ischemia consistent with microembolization developing ipsilateral to a previously placed vein conduit arterial bypass may signify a "failing" graft with a source from a preocclusive lesion. This finding should prompt aggressive evaluation and immediate revision to maintain assisted primary graft patency and prevention of tissue loss.

A reevaluation of intraarterial thrombolytic therapy for acute lower extremity ischemia

PURPOSE

This study was performed to clarify the role of intraarterial thrombolytic therapy (IATT) in the management of acute lower extremity ischemia.

METHODS

A retrospective review of 77 patients undergoing 84 courses of high-dose regional urokinase IATT from July 1981 to June 1991 was performed. The group included patients with acute thrombosis of lower extremity bypass grafts (n = 48) or native arteries (n = 36), presenting with ischemic but viable limbs, minimal or no motor dysfunction, and an absence of muscle rigor or compartment syndrome. The data were then examined individually by site of thrombosis to evaluate patient selection for IATT.

RESULTS

Complete lysis, complications (either distal thromboembolism or bleeding), and early limb loss occurred in 59.5%, 11%, and 6% of infusions, respectively. IATT precluded the need for operative intervention in 49% of acutely ischemic limbs. When surgery was required, successful IATT precisely localized responsible lesions and reduced the magnitude of operation. A subset of 13 patients were identified in whom either no intrinsic abnormality or poor runoff were evident after lysis and were treated with anticoagulation alone.

CONCLUSIONS

These data show IATT to be especially suitable for thrombosis of native iliac or femoropopliteal arteries and infrainguinal vein grafts. IATT serves primarily as an adjunct in management of acute lower extremity ischemia. After successful IATT, subsequent therapy can be tailored to the anatomic cause of thrombosis.

5-Aza-2'-deoxycytidine: cell differentiation and DNA methylation

5-Azacytidine (5-aza-CR) and 5-aza-2'-deoxycytidine (5-aza-CdR), analogs of cytidine modified in position 5, were originally developed as antitumor agents, and have been useful in the treatment of both childhood and adult leukemias. These agents are cytotoxic per se, but also induce differentiation in several experimental systems, most notably the induction of muscle, adipocytes, and chondrocytes in cultures of drug-treated mouse embryo fibroblasts. The mechanisms underlying this drug-induced differentiation have been difficult to unravel, a fact which limits the rational design of differentiation therapy as a modulator of cancer using these agents. Induction of new developmental pathways in cultured cells involves stable, heritable changes, presumably of an epigenetic nature. Our early studies demonstrated that changes in methylation of cytosine in DNA occurred concurrently with changes in developmental potential, and that the presence of 5-azacytosine in DNA interfered with the action of DNA methyltransferase. Since DNA methylation is believed to be involved at some level in the regulation of gene expression, the hypothesis was developed that changes in methylation allowed the expression of new genes whose activity initiated new pathways of differentiation. The characterization of this drug-induced system of differentiation has therefore opened the way to identifying genes directly involved in the initiation or modification of pathways of differentiation. The first of these was MyoD, a member of a family of myogenic determination genes. Expression of MyoD in myogenic cell lines has been correlated with loss of methylation at specific sites in the genome, but the critical events leading to expression of MyoD and muscle differentiation are poorly understood. Recent developments in understanding this mechanism are discussed.

Two fatal cases of diarrhoea in horses associated with larvae of the small strongyles

Detailed pathological examinations of two horses with subacute fatal diarrhoea suggested an association between the diarrhoea and damage to the colonic and caecal mucosae caused by large numbers of cyathostome larvae (larval cyathostomiasis). The affected animals deteriorated rapidly, and died after a short illness.

Effects of dietary variations on plasma concentrations of oral flukicides in sheep

Groups of parasite-free lambs which were either housed and fed hay and concentrates or were grazing on pasture were dosed with the oral flukicides rafoxanide and triclabendazole and subsequent plasma concentrations monitored. Peak plasma concentrations and areas under curves (AUC) of both chemicals were significantly reduced in the grazing compared with the housed lambs. In order to investigate the observation similar groups of lambs were dosed orally with chromium EDTA and faecal throughput estimated. It was observed that the rate of throughput was greater in the grazing lambs, leading to the conclusion that the differences in plasma concentrations of the flukicides was caused by a reduction in their absorption in the grazing lambs. The implications on flukicide efficacy and dose rates are discussed.

The characteristics and anatomic distribution of lesions that cause reversed vein graft failure: a five-year prospective study

PURPOSE

The cause of vein graft failure in the intermediate postoperative period (3 to 18 months) has not been well defined. To delineate the incidence, characteristics, and anatomic distribution of lesions that cause graft failure in this critical interval, 227 consecutive infrainguinal reversed vein grafts (IRVGs) constructed at a single institution from July 1986 to December 1991 were prospectively entered into a duplex scan surveillance protocol.

METHODS

Duplex surveillance with arteriographic confirmation identified 29 patent, hemodynamically failing IRVGs during a mean follow-up of 22 months (range 1 to 64 months). An additional 18 grafts thrombosed before detection of any underlying abnormality; thrombolytic therapy and repeat operation uncovered the cause of occlusion in 12 of these grafts. The cause of graft failure (failing as well as failed) was therefore clear in 41 (87.2%) of 47 instances.

RESULTS

The causes of failure were intrinsic graft stenosis (n = 28; 59.6%), inflow failure (n = 6; 12.8%), outflow failure (n = 4; 8.5%), muscle entrapment (n = 2; 4.3%), and hypercoagulable state (n = 2; 4.3%). The most common intrinsic graft lesion was focal intimal hyperplasia (18 lesions in 16 grafts) in the juxtaanastomotic position, occurring solely in the vein graft itself. It occurred with equal frequency immediately distal to the proximal anastomosis or proximal to the distal anastomosis. Only rarely (n = 5) did this involve the juxtaanastomotic artery. Focal midgraft valvular stenoses (n = 6) and diffuse myointimal hyperplasia (n = 4) were also detected. The peak incidence of graft failure was 4 to 12 months after operation (70% within 12 months, 80% within 18 months).

CONCLUSIONS

We conclude that duplex surveillance of IRVGs is warranted by the 21% incidence of potentially remediable graft failure. A significant portion of these failures occur during the intermediate postoperative period (3 to 18 months), usually as a result of focal intrinsic vein graft lesions. With reversed vein conduits, these lesions arise predominantly in the vein graft itself, in the juxtaanastomotic position.

Transplacental and nonplacental clearances of diphenhydramine in the chronically instrumented pregnant sheep

Pharmacokinetic studies of the histamine H1-receptor antagonist diphenhydramine were conducted in eight chronically instrumented pregnant sheep at 126-138 days of gestation. Diphenhydramine was administered by simultaneous intravenous bolus injection and infusion to steady state given 48 h apart, to the ewe and the fetus on separate occasions. Average steady-state drug concentration in plasma after maternal infusion was 212.1 +/- 67.8 ng/mL in the mother and 36.3 +/- 14.4 ng/mL in the fetus, resulting in a fetal-to-maternal concentration ratio of 0.19 +/- 0.10. Following fetal infusions, maternal and fetal steady-state drug concentrations were 31.1 +/- 11.6 and 447.6 +/- 185.2 ng/mL, respectively. The free fraction of diphenhydramine determined in the fetus (0.277 +/- 0.087) was significantly greater than that in the mother (0.141 +/- 0.079). Transplacental and nonplacental clearances were calculated at steady state according to a general two-compartment open model, with drug elimination occurring from both compartments. The total fetal clearance (472.7 +/- 215.7 mL/min) was relatively small compared with the total maternal clearance (3426.1 +/- 905.8 mL/min). The transplacental clearance from fetus to mother (264.4 +/- 138.7 mL/min) was approximately threefold higher than that from mother to fetus (82.4 +/- 40.5 mL/min). Maternal nonplacental clearance (3343.8 +/- 890.7 mL/min) accounted for 97.8 +/- 1.1% of the maternal total clearance, whereas fetal nonplacental clearance (208.4 +/- 80.4 mL/min) accounted for 45.1 +/- 4.7% of the fetal total clearance. It is concluded that in the fetus both the transplacental and nonplacental pathways are important for drug elimination.

The characteristics and anatomic distribution of lesions that cause reversed vein graft failure: a five-year prospective study

PURPOSE

The cause of vein graft failure in the intermediate postoperative period (3 to 18 months) has not been well defined. To delineate the incidence, characteristics, and anatomic distribution of lesions that cause graft failure in this critical interval, 227 consecutive infrainguinal reversed vein grafts (IRVGs) constructed at a single institution from July 1986 to December 1991 were prospectively entered into a duplex scan surveillance protocol.

METHODS

Duplex surveillance with arteriographic confirmation identified 29 patent, hemodynamically failing IRVGs during a mean follow-up of 22 months (range 1 to 64 months). An additional 18 grafts thrombosed before detection of any underlying abnormality; thrombolytic therapy and repeat operation uncovered the cause of occlusion in 12 of these grafts. The cause of graft failure (failing as well as failed) was therefore clear in 41 (87.2%) of 47 instances.

RESULTS

The causes of failure were intrinsic graft stenosis (n = 28; 59.6%), inflow failure (n = 6; 12.8%), outflow failure (n = 4; 8.5%), muscle entrapment (n = 2; 4.3%), and hypercoagulable state (n = 2; 4.3%). The most common intrinsic graft lesion was focal intimal hyperplasia (18 lesions in 16 grafts) in the juxtaanastomotic position, occurring solely in the vein graft itself. It occurred with equal frequency immediately distal to the proximal anastomosis or proximal to the distal anastomosis. Only rarely (n = 5) did this involve the juxtaanastomotic artery. Focal midgraft valvular stenoses (n = 6) and diffuse myointimal hyperplasia (n = 4) were also detected. The peak incidence of graft failure was 4 to 12 months after operation (70% within 12 months, 80% within 18 months).

CONCLUSIONS

We conclude that duplex surveillance of IRVGs is warranted by the 21% incidence of potentially remediable graft failure. A significant portion of these failures occur during the intermediate postoperative period (3 to 18 months), usually as a result of focal intrinsic vein graft lesions. With reversed vein conduits, these lesions arise predominantly in the vein graft itself, in the juxtaanastomotic position.

Proximal anastomotic failure following infrarenal aortic reconstruction: late development of true aneurysms, pseudoaneurysms, and occlusive disease

Distal anastomotic failure of aortic reconstructions attributable to femoral pseudoaneurysm or outflow stenosis has been well described, but little is known about proximal aortic anastomotic graft failure. A retrospective review was performed between January 1987 and March 1992 to characterize the presentation and management of proximal aortic anastomotic failure. Of 329 consecutive aortic reconstructive operations during this period, 11 (3.3%) were performed to correct complications arising at or adjacent to the proximal anastomosis of an aortic prosthesis. These included anastomotic pseudoaneurysm (n = 6), true aneurysmal dilatation of the residual infrarenal or suprarenal aorta (n = 4), and stenosis of the residual infrarenal aorta (n = 1). The 11 patients had undergone prior infrarenal aortic reconstruction for either aneurysmal (n = 5) or occlusive (n = 6) disease an average of 120 months (range 36 to 175 months) before detection of proximal para-anastomotic graft failure. Eighty-two percent (n = 9) of the proximal lesions were asymptomatic and were discovered incidentally during unrelated medical evaluations. Excluding the six pseudoaneurysms, four of the remaining five lesions developed in a relatively long segment of residual infrarenal aorta, including aneurysm above the graft (n = 2), aneurysm below a proximal end-to-side anastomosis (n = 1), and progressive proximal aortic atherosclerosis (n = 1). Tube graft replacement of the proximal lesions was the most frequently performed operation (n = 7); renal artery reimplantation or bypass was necessary in five cases (45%). Although there was no operative mortality, significant surgical morbidity occurred in three patients (27%). Proximal aortic graft complications tended to be asymptomatic and difficult to repair.(ABSTRACT TRUNCATED AT 250 WORDS)

Contribution of routine intraoperative completion arteriography to early infrainguinal bypass patency

To determine the clinical utility of routine intraoperative completion arteriography, we prospectively evaluated 214 consecutive infrainguinal bypass grafts (209 reversed-vein and 5 polytetrafluoroethylene grafts) performed from July 1987 to August 1991. Visual inspection, pulse palpation, and continuous-wave Doppler examination were performed in all cases. At least 1 completion arteriogram was obtained in 213 cases (99%). The bypasses were to the popliteal artery in 130 cases and to the tibial or pedal arteries in 84 cases. Graft patency was confirmed at 30 days in all patients by ankle-brachial index determinations (greater than 0.2 increase) and duplex scan-derived peak-systolic flow velocities (greater than 45 cm/s). Significant technical problems requiring revision were identified in 18 grafts (8%), including 6% of popliteal grafts and 12% of tibial/pedal grafts. Only three of these problems were suspected by pulse palpation or continuous-wave Doppler examination. The intraoperative angiographic findings leading to revision included distal anastomotic stenoses (n = 6), distal arterial disease requiring sequential bypass (n = 4), mid-graft valvular or branch ligature stenoses (n = 4), distal arterial thrombosis (n = 2), and graft kink or twist (n = 2). Thirty-day primary patency was 99% (129 of 130) for femoropopliteal grafts and 93% (78 of 84) for femorodistal grafts. Secondary patency was 100% (130 of 130) and 96% (81 of 84), respectively. Primary patency was 89% (16 of 18) for those grafts that required intraoperative revision based on arteriographic findings. We conclude that routine completion arteriography is an excellent method of ensuring the intraoperative technical adequacy of infrainguinal bypass. The test is easy to perform, reproducible, and should be considered the "gold standard" for intraoperative bypass assessment. Prior to adopting angioscopy or duplex scanning for intraoperative surveillance, randomized, controlled validation studies against angiography should be performed.

Validation of a survey instrument to measure the extent to which physician and dentist office environments discourage smoking

The health professional's office environment has been identified as one of the potential influences on smoking behaviour of patients. This study compared characteristics of office smoking policies and environments of 30 physicians and 30 dentists using both telephone survey and site visit. The site visit was considered the 'gold standard'. The sequence of interview presentation was randomly reversed for half the physicians and half the dentists to control for order effects. Kappa estimates and two-way Analysis of Variance were used on categorical and continuous variables, respectively. The results show there was a high agreement between the two modes of surveying. Physicians and dentists do not differ in level of agreement and in the consistency of responses obtained by telephone and site visit. We conclude that a telephone survey is a valid method to obtain smoking-related information from health professional offices.

The effect of unilateral internal carotid arterial occlusion upon contralateral duplex study: criteria for accurate interpretation

To determine the influence of unilateral internal carotid arterial occlusion (ICO) on Doppler frequency spectral analysis (DFSA) of the patent contralateral carotid artery, a retrospective review of 154 patients between July 1987 and December 1991 with angiographically confirmed ICO was performed, correlating duplex and arteriographic findings in a blinded fashion. Biplane arteriograms and bilateral carotid artery duplex studies that used a 5.0 MHz Doppler probe with a 1.5 mm3 sample volume at a 60 degree angle of insonation were performed on all patients. Each carotid artery was categorized by the severity of stenosis as quantified by arteriography: 1% to 15% (n = 41); 16% to 49% (n = 48), 50% to 79% (n = 21), 80% to 99% (n = 34), and bilateral occlusion (n = 10). DFSA peak systolic frequencies were commonly exaggerated in the presence of contralateral ICO and use of standard criteria for DFSA interpretation overestimated bifurcation stenoses in 43 of 89 lesions (48.3%) when determining nonhemodynamically significant lesions (less than 50% diameter reduction) with a sensitivity of only 57.3% and specificity of 96.9%. Conversely, prediction of hemodynamically significant lesions (greater than 50% diameter reduction) with standard criteria had 96.9% sensitivity but only 57.3% specificity. Modification of these criteria to account for the velocity increase or "jet effect" in the ipsilateral carotid artery system increased the sensitivity and specificity to 97.8% in predicting nonhemodynamically and hemodynamically significant stenoses respectively. A Doppler frequency spectrum with a peak systolic frequency (PSF) greater than 4.0 kHz and end-diastolic frequency (EDF) less than 5 kHz with an "open window" distinguished lesions with less than 50% diameter reduction.(ABSTRACT TRUNCATED AT 250 WORDS)

Metabolic effects of ritodrine in the fetal lamb

Ritodrine infusion to fetal lambs causes numerous metabolic perturbations including hypoxemia. To investigate these changes further and to elucidate a mechanism for the development of hypoxemia, ritodrine was infused at rate of 2.6 micrograms/min into nine chronically catheterized fetal lambs for 8, 12 or 24 hr. Plasma levels of ritodrine (20.0 +/- 2.7 ng/ml) were within the range of those reported in human fetuses exposed to ritodrine tocolysis. Fetal arterial glucose levels nearly doubled (0.72 +/- 0.07 to 1.29 +/- 0.18 mM), whereas lactate levels rose more than 5-fold (1.54 +/- 0.11 to 8.67 +/- 1.12 mM), with the latter change leading to a decline in fetal arterial pH from 7.370 +/- 0.004 to 7.273 +/- 0.033. Fetal oxygen consumption (VO2) rose from 342 +/- 35 to 407 +/- 30 mumol/min.kg via an increase in fetal fractional O2 extraction (32.0 +/- 1.1 to 49.0 +/- 1.7%). The rise in fetal O2 extraction contributed to concurrent declines in fetal arterial PO2 (21.9 +/- 0.6 to 17.0 +/- 0.5 mm Hg) and O2 content (3.7 +/- 0.2 to 2.1 +/- 0.1 mM). Umbilical venous PO2 and O2 content also fell resulting in a decline in fetal O2 delivery (DO2) from 1115 +/- 97 to 838 +/- 68 mumol/min.kg. The rise in fetal VO2 was reflected by a similar rise uterine VO2 (not significant), with the latter being accompanied by a significant increase in uterine O2 extraction and decrease in uterine venous PO2 and O2 content, perhaps contributing to the fall in fetal DO2. In conclusion, fetal hypoxemia during the infusion of ritodrine results from an increase in fetal VO2 that is not compensated for by a similar increase in umbilical or uterine DO2. These metabolic effects may put the fetus at risk, particularly in situations in which fetal DO2 is already reduced, as may occur in compromised pregnancies.

Biologic activity of synthetic analogues of C5a anaphylatoxin

The C activation fragment C5a is the most potent plasma-derived chemotactic factor known. This humoral factor induces both neutrophil and macrophage activation at low nanomolar concentrations. We have synthesized a series of C-terminal C5a analogues that exhibit all of the characteristic biologic activities of C5a. These peptides apparently contain the effector site for C5a receptor-mediated cellular activation, but express only a fraction of the potency of intact C5a. We have demonstrated the following in vitro activities for these C5a peptides: 1) ileal (guinea pig) contraction; 2) platelet (guinea pig) activation; and 3) neutrophil (human) polarization and chemotaxis. The effect of C5a peptides in vivo was evaluated by measuring enhancement in vascular permeability. Although potencies of the most effective synthetic C5a analogues were on the order of 0.01 to 0.1% that of the natural factor, our biologic data confirm that the C5a peptides are full agonists of the intact factor and may be useful substitutes for intact C5a. Furthermore, our results indicate that elongation of the C5a analogues from 10 to 19 residues in length contributes little toward enhancing or decreasing potency of the synthetic C5a analogues. Replacement of residues in the effector region by D-amino acids or by introduction of a cyclic group to reduce flexibility of the backbone decreased potency of the analogues. Substitution of His 67 by Phe in the decapeptide C5a 65-74 resulted in a significant increase in potency of the C5a analogue. The marked enhancement in potency from replacing His 67 by Phe in analogue C5a peptides identifies an important hydrophobic subsite. We conclude that site-specific amino acid modifications in or near the C-terminal effector site sequence can diminish or optimize potency of the model C5a peptides. However, there apparently are subsites on folded C5a, from regions other than the C-terminal portion of the molecule, that contribute significant receptor interactions. These subsites must be identified and incorporated into C5a model peptide designs before expression of full potency by synthetic analogues of this factor will be realized.

Biologic activity of synthetic analogues of C5a anaphylatoxin

The C activation fragment C5a is the most potent plasma-derived chemotactic factor known. This humoral factor induces both neutrophil and macrophage activation at low nanomolar concentrations. We have synthesized a series of C-terminal C5a analogues that exhibit all of the characteristic biologic activities of C5a. These peptides apparently contain the effector site for C5a receptor-mediated cellular activation, but express only a fraction of the potency of intact C5a. We have demonstrated the following in vitro activities for these C5a peptides: 1) ileal (guinea pig) contraction; 2) platelet (guinea pig) activation; and 3) neutrophil (human) polarization and chemotaxis. The effect of C5a peptides in vivo was evaluated by measuring enhancement in vascular permeability. Although potencies of the most effective synthetic C5a analogues were on the order of 0.01 to 0.1% that of the natural factor, our biologic data confirm that the C5a peptides are full agonists of the intact factor and may be useful substitutes for intact C5a. Furthermore, our results indicate that elongation of the C5a analogues from 10 to 19 residues in length contributes little toward enhancing or decreasing potency of the synthetic C5a analogues. Replacement of residues in the effector region by D-amino acids or by introduction of a cyclic group to reduce flexibility of the backbone decreased potency of the analogues. Substitution of His 67 by Phe in the decapeptide C5a 65-74 resulted in a significant increase in potency of the C5a analogue. The marked enhancement in potency from replacing His 67 by Phe in analogue C5a peptides identifies an important hydrophobic subsite. We conclude that site-specific amino acid modifications in or near the C-terminal effector site sequence can diminish or optimize potency of the model C5a peptides. However, there apparently are subsites on folded C5a, from regions other than the C-terminal portion of the molecule, that contribute significant receptor interactions. These subsites must be identified and incorporated into C5a model peptide designs before expression of full potency by synthetic analogues of this factor will be realized.

Diminished arachidonic acid metabolite release by bovine alveolar macrophages exposed to surface-modified silica

Modification of the silica surface has been shown to reduce its cytotoxicity in vitro and its fibrogenic activity in vivo. We have shown silica to be a potent stimulator of arachidonic acid (AA) metabolism in bovine alveolar macrophages (BAM). To determine the effect of surface-modified silica on AA metabolism in BAM, we exposed BAM in vitro to silica treated with aluminum lactate or polyvinylpyridine-N-oxide (PVPNO). BAM were prelabeled with [3H]AA and incubated with 3 and 5 mg of silica. Unmodified silica at these doses elicited maximal AA metabolite release from BAM. AA metabolites were analyzed by high performance liquid chromatography. Lactate dehydrogenase release was quantitated to determine the cytotoxicity of treated and untreated silica on BAM. Treating silica with aluminum lactate or PVPNO significantly (P less than or equal to 0.05) reduced 5-lipoxygenase metabolite release and significantly (P less than or equal to 0.05) increased cyclooxygenase metabolite release. These changes in AA metabolite release were accompanied by a significant (P less than or equal to 0.05) reduction in the cytotoxicities of the treated silicas compared with untreated silica. Our results suggest that the reduced inflammatory and fibrogenic activity of surface-modified silica may in part be due to reduced AA metabolite release from exposed macrophages.

Effects of diet on plasma concentrations of oral anthelmintics for cattle and sheep

Groups of parasite-free lambs and calves which were either housed and fed hay and concentrates or were grazing on pasture were dosed separately with the oral anthelmintics fenbendazole and ivermectin (lambs only). The plasma concentrations of the drugs and their major metabolites were monitored during the period of their metabolism and excretion. The peak plasma concentrations and the availability of the drugs, as estimated by the areas under the plasma concentration-time curves, were significantly less in the grazing animals. When similar groups of lambs were dosed orally with the inert marker chromium EDTA, which has a particle size similar to the anthelmintics, it was observed that a higher percentage of chromium was excreted by the grazing lambs during the first 40 hours after dosing, suggesting that the extent of absorption in the grazing animals was less than in the housed animals.

Inhibition of invasion and metastasis in cells transfected with an inhibitor of metalloproteinases

The balance between levels of metalloproteinases and their corresponding inhibitors is a critical factor in tumor invasion and metastasis. Down-regulation of the activity of these proteases was achieved by transfection of invasive and metastatic rat cells with the complementary DNA for metalloproteinase inhibitor/tissue inhibitor of metalloproteinase 2 (MI/TIMP-2), a novel inhibitor of metalloproteinases recently described. (Y. A. DeClerck et al., J. Biol. Chem., 264: 17445-17453, 1989; W. G. Stetler-Stevenson et al., J. Biol. Chem., 264: 17374-17378, 1989). Secretion of functional MI/TIMP-2 protein in stably transfected cells resulted in a marked decrease in metalloproteinase activity. Partial suppression of the formation of lung colonies after i.v. injection in nude mice was observed in a transfected clone expressing high levels of MI/TIMP-2. Production of MI/TIMP-2 in four clones markedly reduced tumor growth rate in vivo after s.c. injection and completely suppressed local tissue invasion. Thus, down-regulation of metalloproteinase activity has a striking effect on local invasion and partially suppresses hematogenous metastasis.

Elimination of apolipoprotein B48 formation in rat hepatoma cell lines transfected with mutant human apolipoprotein B cDNA constructs

Rat hepatoma McA-RH7777 cell lines transfected with full-length human apolipoprotein (apo) B constructs produce mostly human apoB48 and only small amounts of apoB100, as a result of mRNA editing at codon 2153 (C to U conversion at nucleotide 6666). To abolish the formation of apoB48 and increase the yield of apoB100 and other forms of apoB longer than apoB48, site-specific mutations were introduced at or near the site of apoB mRNA editing. Among four mutations examined, only that in which codon 2153 was converted from CAA (Gln) to CTA (Leu) effectively precluded the formation of apoB48. In this mutant, a stop codon would not be generated even if the C to U conversion occurred. The three other mutations were introduced to disrupt the proposed stem-loop structure encompassing the editing site. Changes made in the third positions of five codons on the 5' side of the edited base or of four codons 3' of the edited base failed to eliminate the production of a protein with the approximate size of apoB48. A construct in which codon 2153 was changed from CAA to GAT (Asp) also failed to eliminate the production of a protein the size of apoB48. Analysis of the region between nucleotides 6200 and 6900 of the cDNA did not detect any prevalent alternate editing sites. Immunoblot analysis using polyclonal antibodies raised against synthetic peptides of human apoB100 indicated that the carboxyl terminus of the apoB48-like proteins probably resides between amino acid residues 2068 and 2129 of apoB100. These results provide some insight into the mechanism of apoB mRNA editing and will facilitate further studies on apoB-containing lipoproteins.