Pathological analysis of local delivery of paclitaxel via a polymer-coated stent

BACKGROUND

Paclitaxel can inhibit vascular smooth muscle proliferation in vitro, and early studies suggest that paclitaxel may be useful in preventing restenosis. Early and late intimal growth and local vascular pathological changes associated with paclitaxel delivered via stents have not been fully explored.

METHODS AND RESULTS

Localized drug delivery was accomplished with balloon-expandable stainless steel stents coated with a cross-linked biodegradable polymer, chondroitin sulfate and gelatin (CSG), containing various doses of paclitaxel. CSG-coated stents with paclitaxel (42.0, 20.2, 8.6, or 1.5 microgram of paclitaxel per stent), CSG-coated stents without paclitaxel, and uncoated stents (without paclitaxel or CSG) were deployed in the iliac arteries of New Zealand White rabbits, which were killed 28 days after implant. Mean neointimal thickness at stent strut sites was reduced 49% (P<0.0003) and 36% (P<0.007) with stents containing 42.0 and 20.2 microgram of paclitaxel per stent, respectively, versus CSG-coated stents without paclitaxel. However, histological findings suggested incomplete healing in the higher-dose (42.0 and 20.2 microgram) paclitaxel-containing stents consisting of persistent intimal fibrin deposition, intraintimal hemorrhage, and increased intimal and adventitial inflammation. Stents coated with CSG alone (without paclitaxel) had similar neointimal growth as uncoated stents. In a separate group of rabbits killed at 90 days, neointimal growth was no longer suppressed by CSG-coated stents containing 42.0 or 21.0 microgram of paclitaxel

CONCLUSIONS

CSG coating appears to be a promising medium for localized drug delivery. Paclitaxel polymer-coated stents reduce neointima formation but are associated with evidence of incomplete healing at 28 days. However, neointimal suppression was not maintained at 90 days.

Contractile mechanics and interaction of the right and left ventricles

The heart and lungs, together with hemoglobin, provide for the transport of oxygen from the atmosphere to the metabolizing tissue. The oxygenation of blood and the circulation of oxygenated blood are precisely synchronized so that the heart and lungs constitute an integrated cardiopulmonary unit. The functional integration of the heart and lungs is fostered by their anatomic arrangement and mechanical interaction. The cardiopulmonary unit consists of the right and left ventricles (two in-series pumps composed of cardiac muscle), which are mechanically coupled by the lungs. The factors that control cardiac muscle shortening (fiber length, afterload and myocardial contractile state) also regulate the pumping behavior of each ventricle. Because the ventricles are aligned in series a perturbation in the mechanical events of one ventricle will influence the behavior of the other ventricle. The interventricular septum and pericardium further promote the mechanical interplay between ventricles. Intrathoracic pressure (the pressure that surrounds the cardiopulmonary unit) creates an additional interaction between the ventricles as well as the heart and lungs.

Sulfatide is essential for the maintenance of CNS myelin and axon structure

Galactocerebroside (GalC) and sulfatide are abundant myelin lipids. In mice incapable of synthesizing these lipids, myelin is thin and regionally unstable and exhibits several subtle structural abnormalities. Although galactolipid-null mice have been beneficial in the analysis of galactolipid function, it has not been possible to differentiate between the functions of GalC and sulfatide with these mice alone. In the present work, we have analyzed a murine model that forms normal levels of GalC but is incapable of synthesizing sulfatide. By comparing a plethora of morphological features between the galactolipid-null and the sulfatide-null mice, we have begun to differentiate between the specific functions of these closely related lipids. The most striking difference between these two mutants is the reduction of myelin developmental abnormalities (e.g., redundant and uncompacted myelin sheaths) in young adult sulfatide-null mice as compared with the galactolipid-null animals. Although sulfatide appears to play a limited role in myelin development, this lipid is essential for myelin maintenance, as the prevalence of redundant, uncompacted, and degenerating myelin sheaths as well as deteriorating nodal/paranodal structure is increased significantly in aged sulfatide-null mice as compared with littermate wildtype mice. Finally, we show that the role played by sulfatide in CNS maintenance is not limited to the myelin sheath, as axonal caliber and circularity are normal in young adult mutant mice but are significantly altered in aged sulfatide-null animals.

Modified technique of suction blistering for epidermal grafting in vitiligo

BACKGROUND

Suction blister epidermal grafting is a useful modality of treatment of resistant and stable vitiligo; however, it requires expensive and heavy suction apparatus. This study is an attempt to develop a cheap and small apparatus which can be assembled in the physician's own office.

PATIENTS AND METHODS

The method was tried in 22 vitiligo/leukoderma patients. The apparatus consisted of a cylindrical funnel connected with a three-way tap, and suction was given by a 50-mL syringe. The pressure inside the suction cup was retained by changing the position of lock of the three-way tap. The pressure was measured by connecting the three-way tap to a vacuum gauge. The apparatus remained adhered to the donor area because of negative pressure. The blister was formed in about 1.5 h. The roof of the blister was grafted onto the dermabraded recipient site.

RESULTS

The pigmentation was complete in 20 out of 22 patients. There were no complications.

CONCLUSIONS

The technique is inexpensive and easy and obviates the need of cumbersome and heavy equipment.

Ultrasonic backscatter system for automated on-line endocardial boundary detection: evaluation by ultrafast computed tomography

OBJECTIVES

The purpose of this study was to evaluate the accuracy of the recently developed echocardiographic on-line endocardial border detection system using ultrafast computed tomography, an independent and proved tomographic imaging modality.

BACKGROUND

The automated system for on-line endocardial border detection identifies the blood-tissue interface by acoustic quantification of the ultrasonic backscatter signal.

METHODS

Eighteen subjects were screened by conventional echocardiography and acoustic quantification. Ten of these, with high quality echocardiographic images, were also examined by ultrafast computed tomography. Comparable image planes at the midpapillary level were analyzed. Measurements of left ventricular cavity area were compared at end-diastole and end-systole and time course analyses of cavity area during the cardiac cycle were performed.

RESULTS

There was good correlation between values for left ventricular end-diastolic area (r = 0.99), end-systolic area (r = 0.93) and fractional area change (r = 0.91) using the two methods. The on-line backscatter system underestimated end-diastolic area (p < 0.001), but the negative bias was small (-1.6 cm2) and the 95% confidence intervals were narrow (-3.6 cm2 to +0.4 cm2). In contrast, the backscatter system overestimated end-systolic area (p < 0.02); the positive bias for this variable was also small (+2.6 cm2) but the confidence intervals were relatively wide (+7.9 to -2.8 cm2). The negative bias of backscatter values for cavity area was fairly constant during diastole and early systole (range -5% to -10%), but during the second half of systole, backscatter values increased progressively relative to computed tomographic values. Real time values for fractional area change measured by the backscatter system were 13% smaller than those determined by ultrafast computed tomography (p < 0.001), with wide confidence intervals (+3% to -30%). Absolute peak rates of area change during systole and diastole were lower by 39% (p < 0.001) and 41% (p < 0.01), respectively, using the on-line ultrasonic backscatter system. Time course analyses revealed the errors to be consistent with cardiac cycle-dependent alterations in gain sensitivity of the ultrasonic backscatter system.

CONCLUSIONS

The ultrasonic backscatter system is associated with cyclic cavity area measurement errors that need to be addressed if its early promise for on-line assessment of ventricular function is to be fulfilled. Incorporation of an electrocardiographically triggered time-varying gain control may improve accuracy for on-line analysis of ventricular performance.

Characteristics of vascular hydraulic load in patients with heart failure

Aortic input impedance and hydraulic power were derived from simultaneous catheter recordings of ascending aortic pressure and velocity in eight normal subjects and 11 age-matched subjects with clinical heart failure secondary to idiopathic congestive cardiomyopathy. Resting data revealed the characteristic depression of cardiac output and elevation of systemic vascular resistance in patients with heart failure. The pulsatile component of vascular hydraulic load, characteristic impedance (Zc), was similar in both groups (Zc normal: 85 +/- 30 dyne-sec-cm-5; Zc cardiomyopathy: 93 +/- 33 dyne-sec-cm-5). The oscillatory fraction of aortic input power in patients with heart failure (14 +/- 4%) was also similar to that of normal subjects (11 +/- 2%). The transition from rest to exercise in patients with heart failure was marked by a decrease in the steady component of arterial hydraulic load, although characteristic impedance did not change. A similar qualitative response occurred in normal subjects, although the systemic vascular resistance during exercise remained above normal in patients with heart failure. The modulus of the first harmonic of impedance significantly decreased during exercise in normal subjects but did not change significantly in patients with heart failure. Furthermore, the modulus of the first harmonic of the reflection coefficient decreased significantly during exercise in normal subjects but did not change in patients with heart failure in spite of systemic vasodilation. Exercise appears to impose no additional increase in vascular hydraulic load on the ejecting left ventricle. The similar aortic characteristic impedances in patients with heart failure and in normal subjects, at rest and during exercise, are consistent with a constant oscillatory fraction of input power.

Neointimal responses 3 months after (32)P beta-emitting stent placement

PURPOSE

Studies have shown a potential benefit of brachytherapy in preventing restenosis. However, the effects of intravascular radiation on arterial healing have not been well-established. The purpose of this study was to explore the histologic changes following placement of beta-emitting radioactive stents in arteries focusing on intimal responses and endothelialization.

METHODS AND MATERIALS

3.0-mm beta-emitting (32)P stents (6-microCi and 24-microCi) were placed in rabbit iliac arteries with nonradioactive stents serving as controls. Animals were euthanized at 3 months and histologic assessment, morphometry, and analysis of endothelialization were performed.

RESULTS

The lumen areas of 24-microCi stents (4.24 +/- 0.22 mm(2), p < 0.0007) and 6-microCi stents (4.23 +/- 0.49 mm(2), p < 0.01) were larger than control stents (3.64 +/- 0.44 mm(2)). The mean lumen percent stenosis was 11. 4 +/- 3.0% in the 24-microCi stents (p < 0.007 vs. 6-microCi stents and p < 0.0001 vs. control stents), 18.7 +/- 6.4% in the 6-microCi stents (p < 0.02 vs. control stents), and 25.0 +/- 4.9% in control stents. Neointimal area was least in the 24-microCi stent (54.2% smaller than controls and 42.7% smaller than 6-microCi); the neointimal area of the 6-microCi stents was 20.0% less than controls. The control stent neointima consisted of smooth muscle cells in a proteoglycan and collagen matrix. In contrast, the intima of radioactive stents showed persistent fibrin thrombus with nonconfluent areas of matrix. Actin-positive intimal cell density was reduced with radioactive stenting, but intimal cell proliferation was increased. Evans blue staining, an indicator of increased endothelial permeability, was present on 86 +/- 9% of the stented segment of 6-microCi stents vs. 10 +/- 11% in controls (p < 0.0001). Scanning electron microscopy demonstrated endothelialization of 97 +/- 8% of the intimal surface of control stents; in contrast, the midportion of the 6-microCi stents remained nonendothelialized, and only 33 +/- 15% (p < 0.0001) of the entire stent surface was endothelialized.

CONCLUSIONS

(32)P beta-emitting stents reduce neointimal growth, but healing is incomplete with poor endothelialization at 3 months. Longer-term studies with complete arterial healing are needed to determine whether there is sustained neointimal inhibition by stent-delivered brachytherapy.

Experience with ureteroscopy in children

OBJECTIVE

To present our experience of ureteroscopic procedures in children using miniaturized instrumentation.

PATIENTS AND METHODS

Fourteen children aged between 13 months and 14 years underwent 20 ureteroscopic procedures. Semi-rigid 7.2 F and flexible 9.5 F ureteroscopes were used in a retrograde and an antegrade fashion. Eighteen ureteroscopies were performed retrogradely and two antegradely. Of the 20 ureteroscopic procedures, 18 were for stone disease, one for haematuria of unknown origin and one for removal of a migrated stent. The average size of the stone was 12.9 x 6.6 mm.

RESULTS

Access using miniaturized ureteroscopes was successful in all patients. Dilatation was required only in 1 of 20 procedures. The management of stone disease in 10 of 13 children was straightforward and a single ureteroscopy was required to clear the ureters. In three of 13 children with stone disease the problems were more complex and nine ureteroscopies were undertaken to render the ureters stone free. Complications were stricture at the site of stone impaction (one patient), retention of urine due to a stone fragment in the urethra (one patient), haematuria (one patient) and migrated stent requiring ureteroscopy (one patient).

CONCLUSION

In the hands of an experienced surgeon ureteroscopy can be used with equal success in children as in adults to treat calculus disease.

Arterial mechanical properties in dilated cardiomyopathy. Aging and the response to nitroprusside

The effects of aging on arterial mechanical properties and the response to nitroprusside were examined in 25 patients with dilated cardiomyopathy. High-fidelity pressures were recorded with a multisensor catheter. Pulse wave velocity was determined between two sensors in the thoracic aorta. Arterial compliance was determined by an analysis of the diastolic waveform and cardiac output. At baseline, despite a similar systemic vascular resistance, the pulsatile load (e.g., arterial compliance) and wave transmission characteristics (e.g., pulse wave velocity) were altered with aging. Arterial compliance was reduced in older (greater than 50 yr, n = 8) versus younger (less than 35 yr, n = 8) patients (0.51 +/- 0.17 vs. 1.33 +/- 0.63 ml/mmHg, P less than 0.01) and intermediate in those 35-50 yr of age (n = 9, 0.72 +/- 0.40 ml/mmHg). There was a positive correlation between age and pulse wave velocity (r = +0.90). Nitroprusside infusion decreased resistance, increased arterial compliance, and lowered pulse wave velocity in all groups. Yet, advancing age was associated with a greater fall in wave velocity for a given fall in aortic pressure. The slope (K) of the relation between pulse wave velocity and aortic diastolic pressure progressively increased with age (0.01 +/- 0.03, 0.06 +/- 0.02, and 0.09 +/- 0.03 m/s-mmHg). Multiple linear regression analysis revealed a significant relation between K and age. These data demonstrate that in older patients with dilated cardiomyopathy the left ventricle is coupled to an arterial circulation that has a greater pulsatile load, despite a similar steady load. Furthermore, these age-related changes in the arterial system affect the hemodynamic response to pharmacologically-induced vasodilatation.

The holmium: YAG laser for ureteric stones

OBJECTIVE

To assess the efficacy of the pulsed holmium: YAG laser for the fragmentation of ureteric stones.

PATIENTS AND METHODS

One hundred patients (72 males and 28 females, age range 14 months-85 years) underwent 114 ureteroscopic procedures using either a 7.2 F semi-rigid or 9.5 F flexible ureteroscope. A holmium: YAG laser (Sunrise Technologies. Fremont, Ca, USA) was used for laser lithotripsy at a maximum energy of 1.0 J/pulse at 5 Hz. Most of the stones (46%) were located in the upper third of the ureter. The mean size of the stones was 9 x 8 mm and the mean duration of the procedure was 73 min (including anaesthesia) with a mean hospital stay of 2.7 days.

RESULTS

All the stones were accessed successfully using miniaturized endoscopes either retrogradely or antegradely. The holmium laser effectively fragmented all types of stones. Total clearance of all stones fragments was achieved in 87% of cases, with the best results obtained for stones in the lower third of the ureter (96%). The complications attributed directly to the laser included three strictures and three perforations of the ureteric wall.

CONCLUSION

The holmium: YAG laser was effective in fragmenting ureteric stones irrespective of their hardness. However, it has the potential to damage the ureteric wall and must be used with caution.

Late arterial responses (6 and 12 months) after (32)P beta-emitting stent placement: sustained intimal suppression with incomplete healing

BACKGROUND

Three-month studies of stent-delivered brachytherapy in the rabbit model show reduced neointimal growth. However, intimal healing is delayed, raising the possibility that intimal inhibition is merely delayed rather than prevented. The purpose of this study was to explore the long-term histological changes after placement of beta-emitting radioactive stents in normal rabbit iliac arteries.

METHODS AND RESULTS

Three-millimeter beta-emitting (32)P stents (6, 24, and 48 microCi) were placed in normal rabbit iliac arteries with nonradioactive stents as controls. Animals were euthanatized at 6 and 12 months, and histological assessment, morphometry, and analysis of endothelialization were performed. Morphometric measurements demonstrated a >50% reduction in intimal growth and percent lumen stenosis within 24- and 48-microCi stents versus control nonradioactive stents at both 6 and 12 months. However, the 24- and 48-microCi stents also showed delayed healing of the intimal surface, characterized by persistent fibrin thrombus with nonconfluent areas of matrix, incomplete endothelialization, and increased intimal cellular proliferation. Stent edge stenosis was present at 12 months in the 24- and 48-microCi stent groups, characterized by both intimal thickening and negative arterial remodeling.

CONCLUSIONS

Inhibition of intimal growth is maintained 6 and 12 months after (32)P beta-emitting stent placement. However, delayed arterial healing, incomplete endothelialization, and edge effects are present.

Organ Donation and Transplantation—The Chennai Experience in India

Tamil Nadu has been at the forefront of medical care in the country. It was the first state in the country that started a living kidney transplant program. It is also the first state to successfully start the cadaver programme after the passing of the "Transplantation of Human Organ Act" of 1994 and in the last 5 years has formed a network between hospitals for organ sharing. From the year 2000 to 2006 an organ sharing network was started in Tamil Nadu and the facilitator of this programme has been a non-government organization called MOHAN (acronym for Multi Organ Harvesting Aid Network) Foundation. The organs shared during the period number over 460 organs in two regions (both Tamil Nadu and Hyderabad). In Tamil Nadu the shared organs have included 166 Kidneys, 24 livers, 6 hearts, and 180 eyes. In 2003 sharing network was initiated by MOHAN in Hyderabad and to some extent the Tamil Nadu model was duplicated. with some success and 96 cadaver organs have been transplanted in the last 3 years. There are many advantages of organ sharing including the cost economics. At present there is a large pool of brain dead patients who could become potential organ donors in the major cities in India. Their organs are not being utilized for various support logistics. A multi-pronged strategy is required for the long term success of this program. These years in Tamil Nadu have been the years of learning, un-learning and relearning and the program today has matured slowly into what can perhaps be evolved as an Indian model. In all these years there have been various difficulties in its implementation and some of the key elements for the success of the program is the need to educate our own medical fraternity and seek their cooperation. The program requires trained counselors to be able to work in the intensive cares. The government's support is pivotal if this program to provide benefit to the common man. MOHAN Foundation has accumulated considerable experience to be able to evolve a model to take this program to the national level and more so as it recently has been granted 100% tax exemption on all donations to form a countrywide network for organ sharing.

Proportionate reversible decreases in systolic function and myocardial oxygen consumption after modest reductions in coronary flow: hibernation versus stunning

OBJECTIVES

This study sought to determine whether modest short-term reductions in coronary flow can produce subsequent proportionate reductions in myocardial function and O2 consumption compatible with myocardial hibernation.

BACKGROUND

Acute studies indicate that myocardial energy utilization can be downregulated during moderate flow reduction. Whether this apparently beneficial adjustment persists into the reperfusion period is unsettled because most postischemic contractile dysfunction has been presumed to represent stunned or irreversibly injured myocardium.

METHODS

Responses of regional myocardial function and O2 consumption were assessed in chronically instrumented dogs after approximately 50% reductions in flow for 2 h (n = 8) or repeated 2-min total coronary occlusions (n = 6).

RESULTS

When unrestricted perfusion was restored after sustained partial occlusions, regional function and O2 consumption stabilized at proportionate, systematically decreased levels ([mean +/- SEM] 80 +/- 3.1% and 81 +/- 5.1% of control values, both p < 0.05) and then returned to control values within 24 h. Similar proportionate reductions occurred after as few as five cycles of brief total occlusion (79 +/- 5.1% and 83 +/- 1.6% of control values, both again p < 0.05); these persisted with additional occlusions and then returned to baseline values within 3 h. The absence of irreversible injury was documented histologically in both series. Sham animals (n = 5) showed no changes in regional function or O2 consumption throughout similar experimental periods.

CONCLUSIONS

Moderate decreases in coronary flow or repeated brief coronary occlusions can be followed by proportionate reversible reductions in regional systolic function and O2 consumption compatible with the traditional definition of myocardial hibernation. These findings emphasize the complexity of myocardial responses to flow restriction and call attention to limitations in characterizing reversibly hypocontractile myocardium as simply hibernating or stunned.

Risk of malignant progression in Barrett's esophagus indefinite for dysplasia

Barrett's esophagus is a well-recognized risk factor for esophageal adenocarcinoma. The natural history of Barrett's esophagus classified as ‘indefinite for dysplasia’ (IND) is poorly characterized. The aim of this study is to characterize the natural history of IND by determining the rate of neoplastic progression and identifying risk factors for progression. Patients from the University of Pennsylvania Health System pathology database and Barrett's esophagus registry with a diagnosis of IND between 2000 and 2014 were identified. Exclusion criteria included: (1) prior diagnosis of low-grade dysplasia (LGD), high-grade dysplasia (HGD), or esophageal adenocarcinoma (EAC); (2) presence of LGD, HGD, or EAC at the time of diagnosis of IND; and (3) lack of follow-up endoscopy after diagnosis. Patients with neoplastic progression were classified as having either prevalent disease (LGD, HGD, or EAC on surveillance biopsy within 12 months of IND diagnosis) or incident disease (LGD, HGD, or EAC on surveillance biopsy >12 months after IND diagnosis). One hundred six patients were eligible for analysis. Of 87 patients with follow-up endoscopy and biopsies within 1 year of IND diagnosis, 7 (8%) had prevalent disease (2 LGD, 4 HGD, 1 EAC). The prevalence of LGD was 2.3%, HGD was 4.6%, and EAC was 1.1%. Importantly, four of the seven prevalent (2 LGD, 2 HGD) cases were found to have dysplasia within 6 months of IND diagnosis. No demographic or endoscopic characteristics studied were associated with prevalent disease. Of the 106 IND patients, there were 66 patients without prevalent dysplasia with >1-year follow-up. Three (4.5%) progressed (1 to LGD after 12 months, 2 to HGD after 16.5 and 28 months), yielding an incidence rate for any dysplasia of 1.4 cases/100 person-years and HGD/EAC of 0.9/100 person-years. Risk factors for incident disease were smoking (p = 0.02) and Barrett's esophagus segment length (p = 0.03). IND is associated with considerable risk of prevalent dysplasia, especially within the first 6 months after diagnosis. However, the incidence of HGD/EAC is low and similar to previous studies of IND. These data suggest that IND patients should have repeat endoscopy within 6 months with careful surveillance protocols. Longer BE length and smoking history may help predict which patients are more likely to develop dysplasia, and therefore identify patients who may warrant even closer monitoring.

Imaging spectrum of adverse events of immune checkpoint inhibitors

Immune checkpoint inhibitors (ICIs), a form of immunotherapy, are increasingly used for a variety of malignancies and have been linked to numerous treatment-related side effects known as immune-related adverse events (irAEs). IrAEs can affect multiple organ systems and are important to recognise in order to avoid misinterpretation as progressive tumour and to ensure appropriate management. In this pictorial review, we will briefly discuss radiological response criteria of immunotherapy and describe the imaging appearances of the wide spectrum of these ICI-associated toxicities.

Renal aspergillosis giving rise to obstructive uropathy and recurrent anuric renal failure

A sixty-year-old previously healthy male patient presented with anuric renal failure of sudden onset. He was detected to have Aspergillus fumigatus fungal balls in the renal pelvis, ureters and bladder which were removed and his renal function improved. He was treated with itraconazole and sent home. Three weeks later he again presented with anuria and renal failure. He had recurrence of the obstruction with the same fungus. The fungal ball was removed, a double 'J' stenting was performed and he was treated with amphotericin B and itraconazole. Hence we report a previously healthy patient with no evidence of immunosuppression presenting an obstructive anuric renal failure due to isolated renal aspergillosis.

Local arterial responses to 32P beta-emitting stents

PURPOSE

32P beta-emitting stents reduce neointimal growth in rabbit iliac arteries for at least 12 months after deployment but are associated with incomplete healing. The aim of this study was to quantitate arterial cellularity, with emphasis on the inflammatory response following radioactive stenting.

METHODS

32P beta-emitting stents were placed in rabbit iliac arteries and analyzed at 3 months (6 and 24 microCi), and 6 and 12 months (6, 24, and 48 microCi). Arterial cellular proliferation and cell densities of smooth muscle cells (SMC), mononuclear cells (macrophages and lymphocytes), and neutrophils (PMN) were determined.

RESULTS

Total intimal cell density was greatest in control stents at all three time points, composed mostly of SMCs. SMC density associated with radioactive stents increased from 3 to 12 months but was significantly less than control nonradioactive stents. There was a 4-fold increase in cellular proliferation in the 24 and 48 microCi group vs. control stents. In the media, SMC density of radioactive stent groups was significantly reduced vs. control stents at all three time points, for all three activities. At 3, 6 and 12 months, there was a dose-dependent increase in intimal inflammatory cell density, which consisted mostly of macrophages. For 6-microCi stents inflammation peaked at 3 months and decreased thereafter. Inflammation for 24-microCi stents peaked at 6 months and then decreased at 12 months. Inflammation associated with 48-microCi stents remained high at 6 and 12 months. Focal atherosclerotic change was seen in 11% of stents in the 24-microCi group, and 37% and 50% in the 48-microCi group at 6 and 12 months, respectively.

CONCLUSION

Intimal SMC density remains suppressed out to 12 months after placement of 32P beta-emitting stents. However, inflammation and cell proliferation remain increased and may potentially result in greater neointimal formation over time.

Three-dimensional myocardial and ventricular shape: a surface representation

To date, a detailed three-dimensional (3D) analysis of cardiac shape and size has not been available. Accordingly, we developed a method for such an analysis using sectioned hearts and a computer-based 3D description of the epi- and endocardial surfaces of the left and right ventricles (LV and RV) and the interventricular septum. The accuracy of this analysis as a function of section thickness (hs) was evaluated and reference axes for the LV, RV, and myocardium determined in eight canine hearts. After diastolic arrest, the RV, LV, and their atria were fixed in formaldehyde solution at pressures of 6 and 12 cmH2O, respectively. The hearts were then cast (plastic or gelatin) and sectioned, and the surfaces were digitized. We found that 1) accurate 3D computer reconstructions and computed volumes of the LV, RV, and myocardium were obtained then hs less than or equal to 5 mm, 2) the apex-to-base circumference and cross-sectional area relations could be approximated provided hs less than 10 mm, and 3) the section centers of gravity for the LV, RV, and myocardium defined three distinct vertical lines. Thus, an accurate description of 3D configuration is obtainable by a 5-mm section thickness. The centers of gravity provide a set of geometrical references for the study of shape in normal and diseased hearts.

Theta and gamma rhythmic coding through two spike output modes in the hippocampus during spatial navigation

Hippocampal CA1 neurons generate single spikes and stereotyped bursts of spikes. However, it is unclear how individual neurons dynamically switch between these output modes and whether these two spiking outputs relay distinct information. We performed extracellular recordings in spatially navigating rats and cellular voltage imaging and optogenetics in awake mice. We found that spike bursts are preferentially linked to cellular and network theta rhythms (3-12 Hz) and encode an animal's position via theta phase precession, particularly as animals are entering a place field. In contrast, single spikes exhibit additional coupling to gamma rhythms (30-100 Hz), particularly as animals leave a place field. Biophysical modeling suggests that intracellular properties alone are sufficient to explain the observed input frequency-dependent spike coding. Thus, hippocampal neurons regulate the generation of bursts and single spikes according to frequency-specific network and intracellular dynamics, suggesting that these spiking modes perform distinct computations to support spatial behavior.