Intraoperative carotid evaluation

HYPOTHESIS

Intraoperative duplex scanning can identify technical defects and increase the quality of carotid artery repair.

DESIGN

We evaluated 100 consecutive carotid operations in 96 patients (60 men and 36 women) from 1995 to 1998. Spectral-derived peak systolic flow velocities (PSV) were graded (PSV < 100 cm/s, normal laminar flow; PSV 100-150 cm/s, mild or moderate flow disturbance; PSV > 150 cm/s, severe flow disturbance). Prospective criteria for intraoperative revision included PSV greater than 150 cm/s, spectral broadening, and B-mode imaging of intimal flaps or intraluminal debris. Preoperative, intraoperative, and 6-week follow-up duplex scan results were analyzed.

SETTING

All patients were evaluated and treated at a single academic institution.

INTERVENTIONS

All procedures were performed with the patient under general endotracheal anesthesia; 86% underwent shunting and 70% underwent patching.

MAIN OUTCOME MEASURE

Number and type of revisions, patency of repair, residual and recurrent stenosis, and ipsilateral neurologic events.

RESULTS

There were 33 intraoperative duplex studies with abnormal findings. Seven involved the common carotid artery and resulted in intraoperative revision of 5 intimal flaps at the site of the proximal clamp. In 11 patients, incomplete eversion endarterectomy resulted in elevated distal intimal flaps in the external carotid artery that were repaired through a separate arteriotomy. There were 15 abnormalities in the internal carotid artery prompting 5 revisions. Five studies with PSV of 100 to 150 cm/s had no defects on B-mode imaging and were observed without treatment. Five false-positive studies were attributed to increased flow velocity due to contralateral occlusive discase. At 6 weeks' follow-up, 4 of 5 repaired common carotid arteries were normal on duplex scan and 1 had a mild residual stenosis. Ten of the 11 external carotid repairs were patent and 1 was occluded. Four of the 5 internal carotid artery repairs were normal on postoperative evaluation and 1 had a mild residual stenosis. Of the 10 abnormal internal carotid arteries that were observed, 9 were normal on postoperative duplex and 1 had a mild residual stenosis. One perioperative stroke occurred in a patient with a normal, patent carotid repair.

CONCLUSIONS

Intraoperative duplex evaluation of carotid reconstruction is an efficient, sensitive tool that can detect technical lesions that will jeopardize surgical reconstruction. Interpretive judgment is required because all flow disturbances do not dictate surgical intervention. This technique enables the surgeon to maximize the quality of the arterial reconstruction during carotid artery surgery.

Functional characterization of bradykinin analogues on recombinant human bradykinin B(1) and B(2) receptors

We have examined the activity of a range of kinins on recombinant human bradykinin receptors, using a high throughput functional assay which measures intracellular Ca(2+) responses. The most potent agonist for Chinese hamster ovary (CHO) cells stably expressing recombinant human bradykinin B(1) receptors were Des-Arg(9)-bradykinin (EC(50)=7.9 nM) and Des-Arg(10)-kallidin (EC(50)=8.6 nM), while the most potent agonist for CHO cells expressing human bradykinin B(2) receptors was bradykinin (EC(50)=2.0 nM). These findings confirm the validity of the recombinant system and the microtitre plate imaging-based characterization system when compared to known agonist properties of the native receptors. The concentration-response relationship for bradykinin at bradykinin B(2) receptors was potently inhibited by [D-Arg(0),Hyp(3), beta-(2-thienyl)-Ala(5),D-Tic(7),Oic(8)]-bradykinin (Hoe140) (IC(50)=71 nM), which was 500-fold more potent against the B(2)-expressing cells than the B(1) cells. Bradykinin B(1) receptor-mediated responses activated by Des-Arg(10)-kallidin were fully antagonized by Des-Arg(9)-[Leu(8)]bradykinin (IC(50)=59 nM), Des-Arg(10)-Hoe140 (IC(50)=211 nM) and most potently by Lys-Lys-Arg-Pro-Hyp-Gly-Igl-Ser-D-Igl-Oic (B9858) (IC(50)=14 nM), none of which displayed any activity against the bradykinin B(2) receptor cell line up to 3 microM. None of the antagonists displayed partial agonism activity in these cell lines. All bradykinin B(1) and B(2) receptor antagonists tested acted in an apparently non-competitive manner that is likely to be due in part to their kinetics and to the nature of the functional assay used.

Mobilisation of intracellular Ca2+ by mGluR5 metabotropic glutamate receptor activation in neonatal rat cultured dorsal root ganglia neurones

The ability of metabotropic glutamate receptor activation to mobilise intracellular calcium was investigated in cultured dorsal root ganglion (DRG) neurones from neonatal rats using the calcium sensitive fluorescent dye Fura-2. L-glutamate (10 microM) caused sustained and oscillatory increases in intracellular calcium concentration ([Ca2+]i) in a subpopulation of cultured DRG neurones. The oscillatory responses were not blocked by combined application of the ionotropic glutamate receptor antagonists MK 801 (2 microM) and CNQX (20 microM). Oscillations in [Ca2+]i were also observed following application of the nonselective metabotropic glutamate receptor (mGluR) agonist, trans-(1S,3R)-1-aminocyclopentane-1S, 3R-dicarboxylic acid (1S,3R)-ACPD, 20 microM) and the mGluR5 agonist (RS)-2-chloro-5-hydroxyphenylglycine (CHPG, 500 microM). These responses were blocked by the selective Group I mGluR antagonist (RS)-1-aminoindan-1,5-dicarboxylic acid (AIDA) (100 microM) and Ca2+ release channel inhibitors ryanodine (100 microM) and dantrolene (10 microM). The predominantly Group II agonist (2S,2'R,3'R)-2-(2'3'-dicarboxy-cyclopropyl)glycine (DCG-IV, 100 microM) failed to produce Ca2+ transients alone but suppressed responses to CHPG. Reverse transcriptase PCR techniques, using primers specific to Group I mGluRs, revealed the presence of mGluR5 but not mGluR1 mRNA in these cells. Therefore, glutamate can cause a slowly activating and reversible mobilisation of [Ca2+]i in sensory neurones by activation of ionotropic receptors, and can induce oscillatory calcium transients by selectively activating metabotropic glutamate receptors that are likely to be of the mGluR5 subtype.

Metalloproteinase levels are decreased in symptomatic carotid plaques

BACKGROUND

Matrix metalloproteinase enzymes (MMP) have been identified in carotid atherosclerotic plaques, but their role in the development of clinical symptoms remains ill defined. We correlated the activity and levels of metalloproteinase enzymes and their inhibitors in human carotid plaques to ischemic neurologic events.

METHODS

Carotid plaques were collected at the time of endarterectomy from 23 patients with carotid stenosis. Sixteen patients were asymptomatic and 7 patients had symptoms of stroke or transient ischemic attack within 6 weeks of surgery. Protein was extracted from the plaques, proteolytic activity was determined by gelatin zymography, and pro-MMP and tissue inhibitor of metalloproteinase (TIMP) enzyme content were measured by ELISA assay. Macrophage accumulation in the plaque was determined using immunohistochemistry.

RESULTS

Plaques from symptomatic patients had decreased proteolytic activity on substrate gel zymography at the 62- and 92-kDa regions (corresponding to active MMP-2 and pro-MMP-9). A decrease in pro-MMP-9 (8.21 +/- 2.35 vs 17.42 +/- 3.14 ng, P < 0. 05) and an increase in TIMP-2 protein (12.62 +/- 0.58 vs 10.56 +/- 0. 77 ng, P < 0.05) were noted on ELISA in plaques from symptomatic patients. No difference was noted in macrophage accumulation in the plaques between the two groups.

CONCLUSIONS

Plaques from patients who present with ischemic neurologic symptoms have decreased proteolytic activity associated with decreased pro-MMP-9 and increased TIMP-2 protein levels. These data suggest that metalloproteinase enzymes are not responsible for plaque instability in the carotid circulation and may in fact promote plaque stability.

Endovascular therapy of iliac arteries: routine application of intraluminal stents does not improve clinical patency

Our objective in this study was to review our experience with endovascular therapy of iliac artery occlusive disease over the past decade, and to compare the results of angioplasty alone with the addition of endovascular stents to these procedures. This report details a retrospective analysis of clinical data on 141 consecutive patients with iliac artery occlusive disease, treated by balloon angioplasty alone, or with the addition of intraluminal stents. The procedures analyzed included 58 common iliac artery interventions (26 angioplasties and 32 stent insertions) and 83 external iliac artery procedures (43 angioplasties and 40 stent insertions). Early and continued success, and their components, are reported and compared according to published standards. While endovascular therapy of iliac artery occlusive disease is effective in relieving symptoms, clinical patency rates are lower than those reported for direct reconstruction. Primary stent placement has not enhanced clinical patency in the iliac arteries, and the selective insertion of these devices for more complicated angioplasty procedures seems warranted.

cGMP is decreased after acute ischemia in chronically ischemic canine limbs

BACKGROUND

A chronic partially ischemic state may alter the skeletal muscle response to acute ischemia and free radical formation.

METHODS

In order to investigate this hypothesis, a chronic ischemic state was established by ligating the right femoral artery of four mongrel dogs. ABIs were decreased from 1.05 +/- 0.25 preligation to 0.54 +/- 0.14 at 6 weeks (P = 0.04). At the end of 8 weeks, the hindlimb was subjected to 3 h of acute ischemia by clamping the iliac artery. The clamp was then released for 2 h of reperfusion. Plasma samples from the right iliac vein were taken during the ischemia-reperfusion period for analysis of cGMP. Tibialis anterior biopsies for Western analysis of eNOS and iNOS were taken upon completion of reperfusion. Comparisons to control dogs subjected to the acute ischemia and reperfusion without prior femoral artery ligation were made.

RESULTS

cGMP levels were increased in the controls at 3 h of ischemia (3539 +/- 350) and 2 h of reperfusion (2880 +/- 269). The chronic ischemia group did not develop a corresponding increase in cGMP at 3 h of ischemia (2762 +/- 251) or after 2 h of reperfusion (2102 +/- 130). Western analysis of eNOS and iNOS revealed similar levels in both groups. Analysis of eNOS revealed 0.6429 +/- 0.086 and 0.5916 +/- 0.072 (densitometric units +/- SEM) for study and control dogs, respectively. Analysis of iNOS revealed 0.3401 +/- 0.067 and 0.2475 +/- 0.066 for study and control dogs, respectively.

CONCLUSION

Previous ligation of the femoral artery resulting in chronic partial ischemia in this model demonstrated no increase in cGMP following acute ischemia that was not accompanied by a change in eNOS or iNOS levels. Nitric oxide activity is reflected by cGMP levels, which may increase in response to free radicals in the acute setting of complete ischemia.

Cholesterol, but not cigarette smoke, decreases rabbit carotid artery relaxation

The purpose of this study was to determine the physiologic effects of cigarette smoke exposure and dietary cholesterol on the availability of nitric oxide in carotid vascular rings. New Zealand white rabbits were placed in an airflow chamber for 3 hr/day over an 8-week period and were exposed to smoke from 600 cigarettes/per day added to the chamber inflow by a robotic smoke generator. New Zealand white rabbits, made hypercholesterolemic, and one group fed a normal diet, were similarly placed in the chamber without exposure to cigarette smoke. In those exposed groups, serum cotinine and cholesterol levels were consistently elevated. After the 8-week period, the carotid arteries were harvested. The vessels were cut into 3-mm rings which were suspended from pressure transducers. The rings were contracted with potassium chloride (KCl) to determine vessel integrity. One ring from each carotid was maximally contracted with 1 x 10(-3) molar norepinephrine (NE) while the experimental ring was contracted to 50% of maximum. Relaxation of the rings was achieved by adding incremental doses of acetylcholine. Our results showed that endothelial dysfunction, as measured by acetylcholine-mediated vasorelaxation, occurs in the rabbit carotid artery when exposed to high dietary cholesterol. Cigarette exposure alone in this particular vessel did not result in significant alteration in acetylcholine-mediated vasorelaxation.

Metabotropic glutamate receptor activation and intracellular cyclic ADP-ribose release Ca2+ from the same store in cultured DRG neurones

The whole cell patch clamp technique has been used to record Ca(2+)-activated cation and chloride conductances evoked by release of Ca2+ from intracellular stores of cultured neonatal dorsal root ganglion neurones. The aim of this study was to investigate metabotropic glutamate receptor (mGluR) mechanisms and evaluate a possible role for cyclic ADP-ribose as an intracellular signalling molecule. Glutamate and the metabotropic glutamate receptor agonist (1S, 3R)-ACPD-evoked transient depolarizations, Ca(2+)-activated inward currents and rises in intracellular Ca2+. The (1S, 3R)-ACPD-activated currents were insensitive to InsP3 signalling inhibitors, heparin and pentosan polysulphate. Intracellular application of ryanodine alone activated currents in this study and proved a difficult tool to use as a potential inhibitor of cyclic ADP-ribose-mediated responses. However, intracellular dantrolene did attenuate both (1S, 3R)-ACPD and cyclic ADP-ribose responses. Intracellular photo-release of cGMP and cyclic ADP-ribose mimicked the responses to mGluR receptor activation. Intracellular application of nicotinamide and W7 inhibited the responses to photo-released cGMP but did not prevent responses to mGluR activation. The cyclic ADP-ribose receptor antagonist 8-amino cyclic ADP-ribose attenuated responses to (1S, 3R)-ACPD, cGMP and cyclic ADP-ribose, but some Ca(2+)-activated inward currents were still observed in the presence of this antagonist. In conclusion, mGluR receptor activation, cGMP and cyclic ADP-ribose release Ca2+ from intracellular stores. Some evidence suggests that pharmacologically related pathways are involved.

Systemic treatment of venous leg ulcers with high doses of pentoxifylline: efficacy in a randomized, placebo-controlled trial

Several small studies have indicated that the systemic administration of pentoxifylline may accelerate healing of venous leg ulcers. The goal of this study was to further evaluate these findings in a larger scale placebo controlled trial and to explore the effect of the dose of pentoxifylline on healing. The study used a prospective, randomized, double-blind, parallel group placebo controlled design in a multicenter outpatient setting. Patients with one or more venous ulcer were enrolled, with all patients receiving standardized compression bandaging for treatment for their ulcers. Patients were also randomized to receive either pentoxifylline 400 mg, pentoxifylline 800 mg (two 400 mg tablets), or placebo tablets three times a day for up to 24 weeks. The main outcome measure was time to complete healing of all leg ulcers, using life table analysis. The study was completed as planned in 131 patients. Patients receiving 800 mg three times a day of pentoxifylline healed faster than placebo (p = 0.043, Wilcoxon test). The median time to complete healing was 100, 83, and 71 days for placebo, pentoxifylline 400 mg, and pentoxifylline 800 mg three times a day, respectively. Over half of all patients were ulcer free at week 16 (placebo) and at week 12 in both pentoxifylline groups. Whereas the placebo group had only achieved complete healing in half of the cases by week 16, all of the subjects remaining in the group receiving the high dose of pentoxifylline had healed completely. Treatment with pentoxifylline was well tolerated with similar drop-out rates in all three treatment groups. Complete wound closure occurred at least 4 weeks earlier in the majority of patients treated with pentoxifylline by comparison to placebo. A higher dose of pentoxifylline (800 mg three times a day) was more effective than the lower dose. We conclude that pentoxifylline is effective in accelerating healing of leg ulcers.

Airborne particulates in the OR environment

Intraoperative sampling of airborne particulates is rarely performed in the OR environment because of technical difficulties associated with sampling methodologies and because of the common belief that airborne contamination is infrequently associated with surgical site infections (SSIs). In this study, investigators recovered non-viable (i.e., lint) and viable (i.e., microorganisms) particulates during vascular surgery using a personal cascade impactor sampling device. The predominant nonviable particulates recovered during intraoperative sampling were wood pulp fibers from disposable gowns and drapes. Several potential nosocomial pathogens (e.g., Staphylococcus aureus, Staphylococcus epidermidis) and other drug-resistant isolates frequently were recovered from an area adjacent to the surgical field. The widespread presence of airborne particulates during surgery suggests that further studies are warranted to assess the role these particles may play in the development of SSIs or in dissemination of nosocomial pathogens within the OR and hospital environment.

Ascorbic acid prevents cigarette smoke injury to endothelium-dependent arterial relaxation

BACKGROUND

Arterial endothelium-dependent acetylcholine relaxation is impaired by smoking, and this injury may be mediated by oxygen free radicals. The purpose of this study was to examine the effect of ascorbic acid (AA) treatment on this injury.

MATERIALS AND METHODS

New Zealand White rabbits (n = 6, each group) were placed in a 240-ft3 airflow chamber for 3 h per day, 5 days per week over an 8-week period. Animals were divided into four groups and fed rabbit chow and water or rabbit chow and AA (250 ml/kg)-supplemented water. The control-smoke rabbit group and the ascorbic acid-smoke rabbit group were exposed to mainstream cigarette smoke from a robotic smoke generator for the 3-h period, while the control-no smoke rabbit group and ascorbic acid-no smoke rabbit group were similarly placed in the chamber without smoke. At the end of 8 weeks, rabbits were sacrificed and segments of their superficial femoral arteries were suspended from tension transducers and the maximal contraction was determined. The remaining rings were contracted to 50% of the maximum and relaxation was determined by adding acetylcholine. Groups were compared using one-way ANOVA.

RESULTS

Rings from control-smoke (5.13 +/- 0.21 g) and AA-smoke rabbits (6. 24 +/- 0.46 g) exhibited increased mean contraction to KCl (P < 0. 05) compared to control-no smoke rabbits (3.86 +/- 0.40 g). Acetylcholine-dependent relaxation was significantly reduced in the rings from the control-smoke rabbits compared to control-no smoke rabbits (acetylcholine, 5 x 10(-7) M: 24.7 +/- 2.7% versus 55.3 +/- 8.0%; acetylcholine, 7 x 10(-7) M: 27.5 +/- 2.3% versus 56.3 +/- 9. 2%). The AA-smoke group (acetylcholine, 5 x 10(-7) M: 61.8 +/- 12. 4%; 7 x 10(-7) M: 67.9 +/- 11.4%) had significantly increased relaxation compared to the control-smoke group (P < 0.05). There was no statistical difference in the mean percentage ring relaxation between the control-no smoke, AA-no smoke, and AA-smoke groups.

CONCLUSIONS

Ascorbic acid protected the artery from cigarette smoke-induced endothelial injury.

Women have increased risk of perioperative myocardial infarction and higher long-term mortality rates after lower extremity arterial bypass grafting

PURPOSE

The purpose of this study was to determine the effect of gender on the immediate and long-term postoperative morbidity, mortality, and patency rates for infrainguinal autogenous vein bypass grafts.

METHODS

Data were abstracted for consecutive patients who were followed in a prospective surveillance protocol after undergoing infrainguinal autogenous vein bypass grafting during the years 1988 to 1994. There were 165 grafts constructed in 148 patients (101 in 87 men, and 64 in 61 women). Gender differences were analyzed with Student t test or chi2 test for risk factors, indications for reconstruction, and complications. The patency rates and the long-term survival rates were compared by means of life-table analysis. Eagle criteria and long-term survival rates were compared with multivariate analysis.

RESULTS

The mean follow-up period was 36 months (39 months for men, and 32 months for women), with a range of 6 to 123 months for the total follow-up period. The two groups did not differ in age at the time of operation (66.6 +/- 1.2 years for men, and 66.7 +/- 1.5 years for women) or in history of diabetes (48% for men, and 56% for women). The risks were similar for hypertension (48% for men vs 45% women), preoperative myocardial infarction (23% for men vs 26% for women), and previous coronary artery bypass grafting (9% for men vs 8% for women). The thallium stress scintigraphy results showed a diagnosis of proportionately more preoperative defects in men (reversible, 34% vs 18%, P <.05; overall, 75% vs 43%, P <.05). The 30-day limb loss rates (0.9% for men, and 0% for women) and mortality rates (2.2% for men, and 5% for women) were similar. Women had statistically more perioperative myocardial infarctions than did men (6 of 61, 9.8% vs 2 of 101, 2%; P <.05), as was documented with electrocardiography and cardiac isoenzymes. Two of these women died within a 30-day postoperative period. The 3-year primary patency rate was 85% for the men and 88% for the women, and the primary assisted patency rate was 97% for the men and 97% for the women. The secondary patency rate was 98% for the men and 97% for the women. The limb salvage rate was slightly higher for the men than for the women (93% vs 87%), although this was not statistically significant. The 5-year survival rate for women was statistically less than for men, with life-table analysis (58% for men vs 42% for women; P <.05).

CONCLUSION

After distal bypass grafting, men and women have similar rates of patency and limb salvage, but women have a higher incidence rate of perioperative myocardial infarction and a decreased 5-year survival rate. These data suggest that women have unrecognized cardiac disease that affects them adversely in the perioperative period and the long term when compared with men who undergo the same operation.

Health-related quality of life and functional outcome following arterial reconstruction for limb salvage

Vascular surgery outcomes have traditionally been measured by limb salvage and graft patency. However, as health care resources are rationed, the patient's functional outcome and quality of life will require assessment. The in situ saphenous vein graft has proven successful in achieving long-term limb salvage for patients with critical ischemia, with the expectation of preserving a life-style and sense of well-being that would be lost with limb amputation. This study was conducted to measure functional capacity and quality of life in these patients. Seventy patients with successful in situ saphenous vein bypass grafts constructed for limb-threatening ischemia, followed for a mean of 45.6 months in a surveillance program with normal graft flow characteristics, were compared with a group of age and gender-matched controls with normal limb pressures and no history of vascular occlusive disease. A questionnaire was designed from standardized health status scales and administered to the two groups to assess symptoms, health perceptions, physical functioning and life quality. When comparing the groups of revascularized and control patients, symptoms and perceptions about their health were similar. However, the revascularized patients had significantly decreased functional capacity in their ability to walk various distances (P< or =0.005), perform household tasks (P< or =0.001) and bathe (P< or =0.001). The patient group with vascular grafts functioned as well as the controls only in activities of dressing and using the toilet. Indicators of life quality that rate independence and mobility, including the ability to procure groceries (P< or = 0.001), prepare meals (P< or =0.005) participate in social activities (P< or =0.001) and drive an automobile (P< or =0.01), were also significantly limited in the patients with successful vascular reconstructions. Although achieving long-term limb salvage and graft patency, the patients in this group of successful vascular reconstructions retain functional disabilities that require significant care. Despite these physical handicaps, these patients have a remarkably similar sense of well-being and lack of somatic complaints compared with the control group. This medical outcome study identifies the functional capacity and lifetime needs for vascular surgery patients that will provide useful data for those responsible for allocating health care resources.

Catheter-directed thrombolysis for lower extremity deep venous thrombosis: report of a national multicenter registry

PURPOSE

To evaluate catheter-directed thrombolysis for treatment of symptomatic lower extremity deep venous thrombosis (DVT).

MATERIALS AND METHODS

From a registry of patients (n = 473) with symptomatic lower limb DVT, results of 312 urokinase infusions in 303 limbs of 287 patients (137 male and 150 female patients; mean age, 47.5 years) were analyzed. DVT symptoms were acute (< or = 10 days) in 188 (66%) patients, chronic (> 10 days) in 45 (16%), and acute and chronic in 54 (19%). A history of DVT existed in 90 (31%). Lysis grades were calculated by using venographic results.

RESULTS

Iliofemoral DVT (n = 221 [71%]) and femoral-popliteal DVT (n = 79 [25%]) were treated with urokinase infusions (mean, 7.8 million i.u.) for a mean of 53.4 hours. After thrombolysis, 99 iliac and five femoral vein lesions were treated with stents. Grade III (complete) lysis was achieved in 96 (31%) infusions; grade II (50%-99% lysis), in 162 (52%); and grade I (< 50% lysis), in 54 (17%). For acute thrombosis, grade III lysis occurred in 34% of cases of acute and in 19% of cases of chronic DVT (P < .01). Major bleeding complications occurred in 54 (11%) patients, most often at the puncture site. Six patients (1%) developed pulmonary emboli. Two deaths (< 1%) were attributed to pulmonary embolism and intracranial hemorrhage. At 1 year, the primary patency rate was 60%. Lysis grade was predictive of 1-year patency rate (grade III, 79%; grade II, 58%; grade I, 32%; P < .001).

CONCLUSION

Catheter-directed thrombolysis is safe and effective. These data can guide patient selection for this therapeutic technique.

Age-related cognitive deficits, impaired long-term potentiation and reduction in synaptic marker density in mice lacking the beta-amyloid precursor protein

Mutations in the beta-amyloid precursor protein are strongly associated with some cases of familial Alzheimer's disease. The normal physiological role of beta-amyloid precursor protein in the brain was evaluated in a cross-sectional analysis of mice deficient in beta-amyloid precursor protein. Compared with wild-type control mice the beta-amyloid precursor protein-null mice developed age-dependent deficits in cognitive function and also had impairments in long-term potentiation. In addition, the brains of the beta-amyloid precursor protein-null mice had marked reactive gliosis in many areas, especially in the cortex and hippocampus. A subpopulation of mice (n = 15) died prematurely (between three and 18 months of age). Analysis of another six mice from the same population that were showing weight loss and hypolocomotor activity exhibited a marked reactive gliosis as detected by immunoreactivity for glial fibrillary acidic protein and a profound loss of immunoreactivities for the presynaptic terminal vesicle marker proteins synaptophysin and synapsin and the dendritic marker microtubule-associated protein-2 in many brain areas, but most predominantly in the cortex and hippocampus. These results suggest that normal beta-amyloid precursor protein may serve an essential role in the maintenance of synaptic function during ageing. A compromise of this function of the beta-amyloid precursor protein may contribute to the progression of the memory decline and the neurodegenerative changes seen in Alzheimer's disease.

Mechanisms contributing to the deficits in hippocampal synaptic plasticity in mice lacking amyloid precursor protein

Abnormal processing of amyloid precursor protein (APP), in particular the generation of beta-amyloid (Abeta) peptides, has been implicated in the pathogenesis of Alzheimer's disease. This study examined the consequences of deleting the APP gene on hippocampal synaptic plasticity, and upon the biophysical properties of morphologically identified neurones in APP-null mice. The hippocampus of APP-null mice had a characteristic increase in gliosis throughout the CA1 region and a disruption of staining for the dendritic marker MAP2 and the presynaptic marker synaptophysin. The disruption of MAP2 staining was associated with a significant reduction in overall dendritic length and projection depth of biocytin labeled CA1 neurones. In two groups of APP-null mice that were examined at 8-12 months, and 20-24 months of age, there was an impairment in the formation of long-term potentiation (LTP) in the CA1 region compared to isogenic age matched controls. This LTP deficit was not associated with an alteration in the amplitude of EPSPs at low stimulus frequencies (0.033 Hz) or facilitation during a 100 Hz stimulus train, but was associated with a reduction in post-tetanic potentiation. Paired-pulse depression of GABA-mediated inhibitory post-synaptic currents was also attenuated in APP-null mice. These data demonstrate that the impaired synaptic plasticity in APP deficient mice is associated with abnormal neuronal morphology and synaptic function within the hippocampus.

Cigarette smoke impairs endothelium-dependent relaxation in rabbit superficial femoral veins

BACKGROUND

The use of autogenous vein for arterial reconstruction provides the optimal conduit for limb salvage. Cigarette smoking is a risk factor for vascular disease and may adversely affect graft patency and limb preservation rates of extremities reconstructed with autogenous vein. This study was performed in order to determine the effects of cigarette smoke on venous endothelium-dependent relaxation which is mediated by nitric oxide.

MATERIALS AND METHODS

New Zealand white rabbits were exposed to cigarette smoke in a 240-ft3 air-flow chamber for 3 h per day, 5 days per week, for 8 weeks. A control group was treated similarly without infusion of smoke into the chamber. Elevated serum cotinine and carboxyhemoglobin levels comparable to those of chronic smokers were observed in the experimental group. After 8 weeks, the superficial femoral veins were explanted, cut into 3-mm segments, and studied in organ chambers.

RESULTS

No difference in contractile response to KCl (80 mM) (control, 0.10 +/- 0.06; smoke, 0.17 +/- 0.04) or norepinephrine (EC50) (control, 0.78 +/- 0.18; smoke, 0.87 +/- 0.11) was seen. A significant decrease in relaxation was noted with all doses of acetylcholine (M) (control, 10(-8) - 50.35 +/- 8.37, 3 x 10(-8) - 71.20 +/- 9.05, 10(-7) - 88.32 +/- 13.72, 3 x 10(-7) - 92. 86 +/- 13.69; and smoke, 10(-8) - 8.25 +/- 1.83*, 3 x 10(-8) - 19.11 +/- 5.11*, 10(-7) - 31.84 +/- 7.90*, 3 x 10(-7) - 39.74 +/- 8.65*; *P < 0.05). Both control and smoke veins relaxed completely with sodium nitroprusside.

CONCLUSIONS

Superficial femoral veins, when exposed to cigarette smoke, demonstrated a significant decrease in endothelium-dependent relaxation in response to acetylcholine without smooth muscle injury. This loss of vasomotor tone could be detrimental over time in veins which have been placed as arterial conduits.

Transgenic animals relevant to Alzheimer's disease

This article reviews the functional studies that have been carried out on transgenic and knockout animals that are relevant to Alzheimer's disease (AD). The discussion focuses upon the functional characterisation of these strains, particularly upon factors that affect synaptic processes that are thought to contribute to memory formation, including hippocampal long-term potentiation. We examine the use of transgenes associated with amyloid precursor protein and presenilin-1, their mutations linked to early onset familial AD, and the recent attempts to establish double transgenic strains that have an AD-like pathology which occurs with a more rapid onset. The development of new transgenic strains relevant to Alzheimer's disease has rapidly outpaced their characterisation for functional deficits in synaptic plasticity. To date most studies have focused on those transgenes linked to the minority of familial early onset rather than late-onset sporadic AD cases, and have focused on those changes linked to the induction of the early-phase of hippocampal long-term potentiation. Future studies will need to address the question of whether the development of AD pathology can be reversed or at least halted and this will be aided by the use of conditional transgenics in which genes linked to AD can either be switched on or off later in development. Furthermore, it remains to be resolved whether the deficits in synaptic function are specific to the hippocampus and whether deficits affect late-phase long-term potentiation. Nonetheless, the recent advances in genome sciences and the development of transgenic technology have provided a unique opportunity to study how genes associated with human cognitive dysfunction alter synaptic transmission between neurones in the mammalian brain.

Tissue inhibitor of metalloproteinase-1 is increased in the saphenofemoral junction of patients with varices in the leg

PURPOSE

The goal of the present study was to examine the role of matrix metalloproteinase (MMP) activity in the development of varicose changes in the superficial veins of the lower extremity.

METHODS

Normal-caliber vein segments from the saphenofemoral junction were harvested from patients undergoing saphenous vein ligation for varices and from patients undergoing infrainguinal bypass graft procedures. The activity and quantity of MMPs and their inhibitors (tissue inhibitors of metalloproteinases [TIMPs]) in the vein segments were compared. Vein segments were obtained from 13 patients. Seven patients had varicose disease in the leg, including 6 women and 1 man (average age, 48 years). Six patients had no evidence of varicose disease, including 2 women and 4 men (average age, 59 years). Proteolytic activity was determined with substrate gel zymography, and enzyme content was determined with Western immunoblotting using monoclonal antibodies directed against MMP-2, MMP-3, MMP-9, TIMP-1, TIMP-2, and alpha2-macroglobulin. Signals were quantified by scanning densitometry and normalized to a positive control (densitometric index [DI]). Immunohistochemistry was performed for enzyme localization.

RESULTS

Zymography did not detect a difference between groups at loci consistent with the major MMPs; however, a small but significant decrease in proteolytic activity was noted in veins from patients with varices. TIMP-1 is increased in vein segments from patients with varices (DI 0.8 +/- 0.1 vs 0.2 +/- 0.05, P < .05) while MMP-2 levels were decreased (DI 1.5 +/- 0.3 vs 0.5 +/- 0.1, P < .05). Immunohistochemistry localized MMPs to the adventitia of the vein wall.

CONCLUSION

A decrease in proteolytic activity may be responsible for the histological and structural alterations leading to varicose degeneration of superficial lower extremity veins.

Human D2 and D4 dopamine receptors couple through betagamma G-protein subunits to inwardly rectifying K+ channels (GIRK1) in a Xenopus oocyte expression system: selective antagonism by L-741,626 and L-745,870 respectively

To examine the effects of a novel selective D4 receptor ligand, L-745,870 (3-[4-(4-chlorophenyl)piperazin-1-yl]methyl-1H-pyrrolo[2,3-b]pyrid ine), on human dopamine receptor function, the ability of this ligand to antagonise G-protein gated inwardly rectifying K+ (GIRK/Kir3) currents activated by cloned human D2 and D4 receptors expressed in Xenopus oocytes was examined using voltage-clamp recording. Its effects were also contrasted with that of a selective D2 receptor antagonist L-741,626. L-745,870 had no detectable agonist activity on human D4 receptors and selectively blocked currents activated by D4 but not D2 receptors. The role of G-protein subunits in dopamine receptor modulation of GIRK currents was also examined by co-expression of beta1 and/or gamma2 subunits on spontaneously active and receptor-activated currents. Currents activated by both D2 and D4 receptors were occluded by direct activation of GIRK currents following co-transfection with the cDNA encoding G-protein betagamma subunits. These data demonstrate that L-745,870 and L-741,626 act as antagonists on human D4 and D2 receptors respectively, and that activation of GIRK channels by these dopamine receptors can be disrupted by direct stimulation of K+ currents by G-protein betagamma subunits.

High affinity, selective neurokinin 2 and neurokinin 3 receptor antagonists from a common structural template

High affinity, selective hNK2 or hNK3 ligands can be prepared from the common template 1 in a few simple chemical operations. The hNK3 ligands 3 antagonise the calcium mobilisation caused by activation of hNK3 receptors expressed in CHO cells as measured using fura-2 microspectrofluorimetry.

The group I mGlu receptor agonist DHPG induces a novel form of LTD in the CA1 region of the hippocampus

The group I specific metabotropic glutamate (mGlu) receptor agonist (RS)-3,5-dihydroxyphenylglycine (DHPG) (100 microM, 10 min) induced long-term depression (LTD) of synaptic transmission in the CA1 region of adult rat hippocampal slices, measured using a grease-gap recording technique. In "normal" (1 mM Mg2+-containing) medium, LTD (measured 30 min after washout of DHPG) was small (13+/-3%), but LTD was enhanced if DHPG was applied when the tissue was made hyperexcitable, either by omitting Mg2+ from the perfusate (35+/-3%) or by adding the GABA(A) receptor antagonist picrotoxin (29+/-2%). The N-methyl-D-aspartate (NMDA) receptor antagonist AP5 (100 microM) substantially reduced the generation of DHPG-induced LTD in Mg2+-free medium, but had little effect on LTD induced in the presence of picrotoxin. In Mg2+-free medium, the threshold concentration of DHPG required to induce LTD was between 1 and 3 microM. Neither agonists specific for group II (100 nM DCG-IV or 1 microM LY354740) or group III (10 microM L-AP4) mGlu receptors or a combined group I and II agonist (30-100 microM (1S,3R)-ACPD) induced LTD. However, an agonist (1 mM CHPG) which activates mGlu5 but not mGlu1 receptors did induce LTD. Surprisingly, DHPG-induced LTD was reversed by mGlu receptor antagonists, applied hours after washout of DHPG. DHPG-induced LTD did not occlude with LTD induced by synaptic activation (1200 stimuli delivered at 2 Hz), in Mg2+-free medium. These data show that activation of group I mGlu receptors (probably mGlu5) can induce LTD and that this mGlu receptor-mediated LTD may, or may not, require activation of NMDA receptors, depending on the experimental conditions.

Expression of B1 and B2 bradykinin receptor mRNA and their functional roles in sympathetic ganglia and sensory dorsal root ganglia neurones from wild-type and B2 receptor knockout mice

Bradykinin has been implicated in nociception and inflammation. To examine the relative significance of B1 and B2 bradykinin receptor subtypes in sympathetic and sensory ganglia, the electrophysiological effects of bradykinin analogues and the expression of receptor subtype mRNA were examined in wild-type and "B2 knockout" mice from which the B2 receptor gene had been deleted. In wild-type mice the B2 receptor agonist bradykinin depolarized superior cervical ganglia (SCG) and activated inward currents in dorsal root ganglia (DRG) neurones. Responses to the B1 receptor agonist, [des-Arg10]-kallidin, were seen only in SCG that had been pre-treated with interleukins and the peptidase inhibitor captopril, but not in DRG neurones. The up-regulation of responses to [des-Arg10]-kallidin and substance P were blocked by indomethacin and, thus, were dependent upon cyclo-oxygenase activity. The effects of bradykinin were abolished in SCG and DRG's from B2 knockout mice and this was correlated with the absence of B2 receptor mRNA in ganglia from these animals. However, despite the presence of B1 receptor mRNA in interleukin treated SCG from B2 knockout mice, no depolarizing effects of the B1 receptor agonist [des-Arg10]-kallidin were observed. The successful elimination of bradykinin responses and B2 mRNA in sympathetic and sensory ganglia from B2 knockout mice, confirms that B2 receptors are the predominant functional bradykinin receptor subtype in these tissues and that B1 receptor mRNA is expressed in both sympathetic and sensory ganglia from these animals.

Schizophrenia and L-745,870, a novel dopamine D4 receptor antagonist

The discovery of a novel high-affinity and selective dopamine D4 receptor antagonist, L-745,870, and the results of clinical trials with this compound are reviewed. Despite several lines of evidence which suggest that a selective D4 receptor antagonist may be an effective antipsychotic agent with a lower propensity to induce extrapyramidal side-effects, L-745,870 was ineffective as an antipsychotic in humans.