A novel method for quantitative myocardial contrast echocardiography in mice

The small size of the mouse heart frequently imparts technical challenges when applying conventional in vivo imaging methods for assessing heart function. Here, we describe the use of high-frequency ultrasound imaging in conjunction with a size-tuned blood pool contrast agent for quantitatively assessing myocardial perfusion in living mice. A perflurocarbon microbubble formulation exhibiting a narrow size distribution was developed, and echogenicity was assessed at 18 MHz in vitro. Adult mice were subjected to permanent ligation of the left anterior descending artery. Ultrasound imaging was performed on day 7, and a cohort of intact mice was used as a control. Parasternal long-axis cine clips were acquired at 18 MHz before and after contrast administration. Reduced ejection fraction and increased end-systolic volume were observed in infarcted compared with control mice. In control animals, washin of the contrast agent was visible in all myocardial segments. Reduced contrast enhancement was observed in apical-posterolateral regions of all infarcted mice. A novel method for reslicing of the imaging data through the time domain provided a two-dimensional presentation of regional contrast agent washin, enabling convenient identification of locations exhibiting altered perfusion. Myocardial segments exhibiting diminished contractility were observed to have correspondingly low relative myocardial perfusion. The contrast agent formulation and methods demonstrated here provide the basis for simplifying routine in vivo estimation of infarct size in mice and may be particularly useful in longitudinal evaluation of revascularization interventions and assessment of peri-infarct ischemia. NEW & NOTEWORTHY Murine myocardial contrast echocardiography frequently suffers from poor sensitivity to contrast. Here, we formulated a novel size-tuned microbubble contrast agent and validated it for use with ultra-high-frequency ultrasound. A novel data method for evaluating myocardial perfusion based on reslicing the imaging data through the time domain is presented.

Histone deacetylase inhibitors interrupt HSP90•RASGRP1 and HSP90•CRAF interactions to upregulate BIM and circumvent drug resistance in lymphoma cells

Histone deacetylase (HDAC) inhibitors, which are approved for the treatment of cutaneous T cell lymphoma and multiple myeloma, are undergoing evaluation in other lymphoid neoplasms. How they kill susceptible cells is incompletely understood. Here we show that trichostatin A, romidepsin, and panobinostat induce apoptosis across a panel of malignant B cell lines, including lines that are intrinsically resistant to bortezomib, etoposide, cytarabine, and BH3 mimetics. Further analysis traces the pro-apoptotic effects of HDAC inhibitors to increased acetylation of the chaperone heat shock protein 90 (HSP90), causing release and degradation of the HSP90 client proteins RASGRP1 and CRAF, which in turn leads to downregulation of mitogen activated protein kinase pathway signaling and upregulation of the pro-apoptotic BCL2 family member BIM in vitro and in vivo. Importantly, these pro-apoptotic effects are mimicked by RASGRP1 siRNA or HSP90 inhibition and reversed by overexpression of constitutively active MEK1 or siRNA-mediated downregulation of BIM. Collectively, these observations not only identify a new HSP90 client protein, RASGRP1, but also delineate a complete signaling pathway from HSP90 acetylation through RASGRP1 and CRAF degradation to BIM upregulation that contributes to selective cytotoxicity of HDAC inhibitors in lymphoid malignancies.

Analysis of multigenerational families with thoracic aortic aneurysms and dissections due to TGFBR1 or TGFBR2 mutations

BACKGROUND

Mutations in the transforming growth factor beta receptor type I and II genes (TGFBR1 and TGFBR2) cause Loeys-Dietz syndrome (LDS), characterised by thoracic aortic aneurysms and dissections (TAAD), aneurysms and dissections of other arteries, craniosynostosis, cleft palate/bifid uvula, hypertelorism, congenital heart defects, arterial tortuosity, and mental retardation. TGFBR2 mutations can also cause TAAD in the absence of features of LDS in large multigenerational families, yet only sporadic LDS cases or parent-child pairs with TGFBR1 mutations have been reported to date.

METHODS

The authors identified TGFBR1 missense mutations in multigenerational families with TAAD by DNA sequencing. Clinical features of affected individuals were assessed and compared with clinical features of previously described TGFBR2 families.

RESULTS

Statistical analyses of the clinical features of the TGFBR1 cohort (n = 30) were compared with clinical features of TGFBR2 cohort (n = 77). Significant differences were identified in clinical presentation and survival based on gender in TGFBR1 families but not in TGFBR2 families. In families with TGFBR1 mutations, men died younger than women based on Kaplan-Meier survival curves. In addition, men presented with TAAD and women often presented with dissections and aneurysms of arteries other than the ascending thoracic aorta. The data also suggest that individuals with TGFBR2 mutations are more likely to dissect at aortic diameters <5.0 cm than individuals with TGFBR1 mutations.

CONCLUSION

This study is the first to demonstrate clinical differences between patients with TGFBR1 and TGFBR2 mutations. These differences are important for the clinical management and outcome of vascular diseases in these patients.

In vivo high-efficiency transcoronary gene delivery and Cre-LoxP gene switching in the adult mouse heart

High-efficiency somatic gene transfer in adult mouse heart has not yet been achieved in vivo. Here, we demonstrate high-efficiency in vivo transcoronary gene delivery to the adult murine myocardium using a catheter-based technique with recombinant adenovirus (AdV) and adeno-associated virus (AAV) vectors in normal and genetically engineered mice. The method involves immersion hypothermia followed by transient aortic and pulmonary artery occlusion with proximal intra-aortic segmental injection of cardioplegic solution containing substance P and viral vectors. Gene expression measured using a LacZ marker gene was observed throughout both ventricles. The expression efficiency of a cytoplasmic LacZ marker gene in the left ventricular myocardium was 56.4+/-14.5% (mean+/-s.d.) at 4 days with an AdV vector, and with an AAV vector it was 81.0+/-5.9% at 4 weeks. Following AAV gene transfer, no gene expression was found in kidney, brain, lung, and spleen, but there was slight expression in liver. In addition, we demonstrate temporally controlled genetic manipulation in the heart with an efficiency of 54.6+/-5.2%, by transferring an AdV vector carrying Cre recombinase in ROSA26 flox-LacZ reporter mice. Procedure-related mortality was 16% for AdV and zero for AAV transfer. Thus, this method provides efficient, relatively homogeneous gene expression in both ventricles of the adult mouse heart, and offers a novel approach for conditional gene rescue or ablation in genetically engineered mouse models.

Cardiovascular effects of fentanyl in conscious rats

The polymicrobial sepsis induced by cecal ligation and puncture (CLP) in the rat is widely used in shock research. For ethical reasons, narcotic analgesics are often administered in this model, with the potential risk of confounding effects. In conscious non-septic rats, we investigated the cardiovascular effects of a continuous i.v. infusion of fentanyl (20 microg/kg per h) administered with fluid loading (10 ml/kg per h) for 24 h, a regimen commonly applied in rat CLP. Animals were randomly allocated to receive analgesia with fluid loading (Fentanyl group), or fluid loading alone (Control). All endpoints were assessed after 24 h of infusion. At that time, Control animals had mild respiratory alkalosis, which was essentially abolished by fentanyl. Analgesia mildly elevated the plasma norepinephrine levels [median (interquartile range): Control 232 pg/ml (0-292), Fentanyl 302 pg/ml (234-676), P=0.045] but was devoid of any effect on blood pressure, heart rate, cardiac output (mean +/-SD: Control 388+/-61 ml/kg per min, Fentanyl 382+/-62 ml/kg per min, P=0.87) and indices of left ventricular function derived from high-fidelity recordings of left ventricular pressure (dP/dtmax: Control 11782+/-2324 mmHg/s, Fentanyl 12107+/-2816 mmHg/s, P=0.77). In ex vivo experiments carried out immediately after animal sacrifice, no differences were noted between the Control and Fentanyl groups in the sensitivity of endothelium-intact aortic rings to norepinephrine-induced vasoconstriction (-logEC50: Control 8.78+/-0.28, Fentanyl 8.83+/-0.26, P=0.52) or acetylcholine-induced vasodilatation (-logEC50: Control 7.00+/-0.37, Fentanyl 7.06+/-0.26+/-0.53, P=0.75). In conclusion, the present data provide no contraindication, and even some support for the ethical use of a high dose i.v. infusion of fentanyl in cardiovascular studies of conscious catheterized rats undergoing CLP or other painful procedures.

A cardiac myocyte vascular endothelial growth factor paracrine pathway is required to maintain cardiac function

The role of the cardiac myocyte as a mediator of paracrine signaling in the heart has remained unclear. To address this issue, we generated mice with cardiac myocyte-specific deletion of the vascular endothelial growth factor gene, thereby producing a cardiomyocyte-specific knockout of a secreted factor. The hearts of these mice had fewer coronary microvessels, thinned ventricular walls, depressed basal contractile function, induction of hypoxia-responsive genes involved in energy metabolism, and an abnormal response to beta-adrenergic stimulation. These findings establish the critical importance of cardiac myocyte-derived vascular endothelial growth factor in cardiac morphogenesis and determination of heart function. Further, they establish an adult murine model of hypovascular nonnecrotic cardiac contractile dysfunction.

Adult mice deficient in actinin-associated LIM-domain protein reveal a developmental pathway for right ventricular cardiomyopathy

Although cytoskeletal mutations are known causes of genetically based forms of dilated cardiomyopathy, the pathways that link these defects with cardiomyopathy are unclear. Here we report that the alpha-actinin-associated LIM protein (ALP; Alp in mice) has an essential role in the embryonic development of the right ventricular (RV) chamber during its exposure to high biomechanical workloads in utero. Disruption of the gene encoding Alp (Alp) is associated with RV chamber dilation and dysfunction, directly implicating alpha-actinin-associated proteins in the onset of cardiomyopathy. In vitro assays showed that Alp directly enhances the capacity of alpha-actinin to cross-link actin filaments, indicating that the loss of Alp function contributes to destabilization of actin anchorage sites in cardiac muscle. Alp also colocalizes at the intercalated disc with alpha-actinin and gamma-catenin, the latter being a known disease gene for human RV dysplasia. Taken together, these studies point to a novel developmental pathway for RV dilated cardiomyopathy via instability of alpha-actinin complexes.

Improvement of coronary artery endothelial dysfunction with lipid-lowering therapy: heterogeneity of segmental response and correlation with plasma-oxidized low density lipoprotein

OBJECTIVES

This study assessed coronary artery endothelial function in patients with hypercholesterolemia before and after lipid lowering, using quantitative angiography to examine the acetylcholine (Ach) response along the entire analyzable vessel.

BACKGROUND

Lipid lowering reverses endothelial dysfunction, but whether improvement occurs only in some segments and not others has not been established. Statistical correlation of improvement with specific lipid moieties remains undefined.

METHODS

Quantitative angiography was performed after Ach (10(-6), 10(-5), 10(-4) M) in 29 patients with coronary atherosclerosis before and 18 +/- 5.2 months after lipid-lowering treatment (statins, bile sequestrant resins). Standard lipid moieties and markers of oxidized low density lipoprotein (LDL) (immunoglobulin G and M autoantibody titers to malondialdehyde-LDL, E06 epitope) were measured serially.

RESULTS

Pre-treatment of the vessel diameters at control and with 10(-6)M, 10(-5) M and 10(-4) M Ach were 2.108 +/- 0.085, 2.086 +/- 0.087, 2.069 +/- 0.084 and 1.963 +/- 0.097 mm (M +/- SE), respectively, and increased at follow-up to 2.139 +/- 0.094, 2.119 +/- 0.086, 2.127 +/- 0.084 and 2.080 +/- 0.085 mm (p < 0.0001). Improvement in the most constricted and modest declination in the more dilated segments were observed. Change in the E06 and Apolipoprotein A-1 titers correlated with improved vasomotion (p = 0.027 and 0.005, respectively). The pre- and post-treatment levels of the E06 epitope, as well as the post-treatment IgM autoantibody titer to MDA-low density lipoprotein, also correlated (p < 0.028, < 0.001 and p < 0.004, respectively).

CONCLUSIONS

Drug treatment reverses endothelial dysfunction, but the effect is heterogeneous. Most coronary segments show enhancement, while others show declination of dilation, underscoring the importance of assessing the entire analyzable artery. Improvement in vasomotion correlates most significantly with markers of plasma-oxidized low-density lipoprotein.

A report of two hundred twenty cases of regional anesthesia in pediatric cardiac surgery

The use of regional anesthesia (ie, epidural, spinal, or caudal) has been reported in a few small series of children undergoing cardiac surgery, but not in larger studies. In this retrospective, descriptive study, we report the results of the use of regional anesthesia in 220 pediatric cardiac operations. We reviewed the records of children receiving a regional anesthetic for cardiothoracic surgery at Stanford Medical Center between January 1993 and February 1997. All patients were targeted for early tracheal extubation. A variety of regional techniques were used. Time to extubation, control of pain, incidence of respiratory depression and other complications, and length of hospital stay were determined. There were no deaths. Eighty-nine percent of the patients were tracheally extubated in the operating room; 4.1% of whom required reintubation within 24 h. Ninety-five percent +/-2.5% of the patients had pain scores < or =4.0 at all intervals postoperatively. Adverse effects of regional anesthesia included emesis (39%), pruritus (10%), urinary retention (7%), postoperative transient paresthesia (3%), and respiratory depression (1.8%). The incidence of peridural hematoma was zero. The rate of adverse effects was lower in the thoracic catheter epidural approach as compared with various caudal, lumbar epidural, and spinal approaches. Hospital duration of stay was not effected by the presence of regional anesthetic complications. In this study, regional anesthesia was safe and effective in the management of pediatric patients undergoing cardiac surgery.

Altered membrane proteins and permeability correlate with cardiac dysfunction in cardiomyopathic hamsters

A mutation in the delta-sarcoglycan (SG) gene with absence of delta-SG protein in the heart has been identified in the BIO14.6 cardiomyopathic (CM) hamster, but how the defective gene leads to myocardial degeneration and dysfunction is unknown. We correlated left ventricular (LV) function with increased sarcolemmal membrane permeability and investigated the LV distribution of the dystrophin-dystroglycan complex in BIO14.6 CM hamsters. On echocardiography at 5 wk of age, the CM hamsters showed a mildly enlarged diastolic dimension (LVDD) with decreased LV percent fractional shortening (%FS), and at 9 wk further enlargement of LVDD with reduction of %FS was observed. The percent area of myocardium exhibiting increased membrane permeability or membrane rupture, assessed by Evans blue dye (EBD) staining and wheat germ agglutinin, was greater at 9 than at 5 wk. In areas not stained by EBD, immunostaining of dystrophin was detected in CM hamsters at sarcolemma and T tubules, as expected, but it was also abnormally expressed at the intercalated discs; in addition, the expression of beta-dystroglycan was significantly reduced compared with control hearts. As previously described, alpha-SG was completely deficient in CM hearts compared with control hearts. In myocardial areas showing increased sarcolemmal permeability, neither dystrophin nor beta-dystroglycan could be identified by immunolabeling. Thus, together with the known loss of delta-SG and other SGs, abnormal distribution of dystrophin and reduction of beta-dystroglycan are associated with increased sarcolemmal permeability followed by cell rupture, which correlates with early progressive cardiac dysfunction in the BIO14.6 CM hamster.

Progressive cardiac dysfunction and fibrosis in the cardiomyopathic hamster and effects of growth hormone and angiotensin-converting enzyme inhibition

BACKGROUND

Growth hormone (GH) improves cardiac function in the rat with myocardial infarction, but its effects in a model of primary dilated cardiomyopathy have not been reported. GH effects were examined at early (4 months) and late (10 months) phases of disease in the cardiomyopathic (CM) hamster, and the combination of GH with chronic ACE inhibition was assessed in late-phase heart failure.

METHODS AND RESULTS

CM hamsters (CHF 147 line) at 4 months showed severe systolic left ventricular (LV) dysfunction with normal LV filling pressure, and at 10 months there was more severe systolic as well as diastolic dysfunction with increasing myocardial fibrosis. Recombinant human GH alone for 3 weeks at age 4 months increased LV wall thickness and reduced systolic wall stress without altering diastolic wall stress, whereas at 10 months, wall stress and fractional shortening did not improve. The LV dP/dt(max) was enhanced at both ages by GH, which at 4 months reflected increased contractility, but at 10 months was most likely caused by elevation of the LV filling pressure. The increasing degree of fibrosis correlated inversely with LV function but was unaffected by GH. In other CM hamsters, high-dose ACE inhibition alone (quinapril), started at 8 months and continued for 11 weeks, improved LV function and inhibited unfavorable remodeling, but the addition of GH for 3 weeks at age 10 months produced increased wall thickness with little additional functional benefit and increased the LV filling pressure and diastolic wall stress.

CONCLUSIONS

GH treatment alone improved LV dysfunction at 4 months of age in CM hamsters by increasing contractility and reducing wall stress but had few beneficial effects at 10 months in severe LV failure. After chronic ACE inhibition, addition of GH at 10 months had no additional beneficial effects and further increased LV diastolic pressure. These differing effects of GH may relate to the progressive increase of LV fibrosis in the CM hamster.

Role of motor unit number estimate electromyography in experimental canine laryngeal reinnervation

Laryngeal electromyography has been used clinically to differentiate neuromuscular pathology from other causes of vocal fold immobility such as arytenoid dislocation, tumor invasion, or cricoarytenoid joint fixation. Electromyography has also been used to predict the prognosis for nerve recovery in laryngeal paralysis. Existing electromyographic techniques either record activity with voluntary motion or study nerve conduction. In this study a new technique, motor unit number estimation, a commercially available quantitative method of electromyographic analysis, is used to study the progress of recovery of vocal fold function after recurrent laryngeal nerve injury. Four dogs underwent transection and immediate reanastomosis of selected branches of the adductor and abductor branches of the recurrent laryngeal nerve on 1 side; the opposite side served as a control. Baseline electromyographic and videolaryngoscopic studies were performed. These measures were then repeated in a longitudinal fashion every 6 weeks after denervation. The motor unit number estimation technique indicated a return of motor unit numbers with time, along with estimates of their size. This was consistent with the expected progress of laryngeal reinnervation. These data and their predictive value for nerve recovery will be discussed.

Comparison of nerve banking techniques in delayed laryngeal reinnervation

Successful laryngeal transplantation will require adequate reinnervation of the larynx to allow phonation, coordinated swallowing, and respiration. A delay between laryngectomy and transplantation would be necessary in oncology patients because of the need for immunosuppression. In these patients, reinnervation of the donor organ would require "banking" and recovery of dormant recipient recurrent laryngeal nerves (RLNs). This pilot study was undertaken to compare the effectiveness of RLN storage using 1 of 2 techniques: 1) inserting the nerve into a muscle pocket or 2) anastomosing the proximal RLN stump to the ansa cervicalis. Six months following nerve transection and "banking," the proximal anterior branch of the RLN was reanastomosed to the distal anterior segment and the posterior branch was anastomosed directly to the posterior cricoarytenoid muscle. Tensionometry, image analysis, and electromyographic data were collected 1 year later. Results show reinnervation of adductors and abductors with both techniques. Banking of the RLN branches during total laryngectomy is effective and should permit delayed physiological reinnervation following laryngeal transplantation.

The internalization of posterior subcapsular cataracts (PSCs) in Royal College of Surgeons (RCS) rats. I. Morphological characterization

PURPOSE

To document lens ultrastructure during and after internalization of posterior subcapsular cataracts (PSCs) in Royal College of Surgeons (RCS) rats, a model for human autosomal retinal degenerative disease.

METHODS

RCS rat lenses at 2, 2.5, 3, 4, 6, 9, 12, and 15 months old were enucleated and fixed. For light and transmission electron microscopy (TEM), lenses were embedded in epoxy and sectioned along the visual axis. For scanning electron microscopy, lenses were dissected to expose the posterior fibers in concentric growth shells down to the internalized PSC plaques.

RESULTS

Overgrowth of the plaque began between 8 and 9 weeks postnatal and proceeded from the periphery to the posterior pole. This is in contrast to PSC formation which begins centrally and enlarges radially between 4-6 weeks postnatal. Peripheral-to-central overgrowth resulted in the formation of a convexo-concave, disk-shaped suture plane oriented parallel to the capsule. The initial fibers overlying the plaque were extremely flattened at their posterior ends. However, by 3 months postnatal, fiber ultrastructure was relatively normal and displayed only minor morphological irregularities. These temporal and structural changes were used to create 3-dimensional computer assisted-drawing (3D-CAD) reconstructions and animations. TEM examination of plaques revealed scattered fiber defects such as membrane whorls, globular aggregates and intracellular voids in both the internalized plaques and the initial overgrowth. The internalized PSC plaques had comparable morphology in all animals, regardless of age. Specifically, the posterior segments of fibers were enlarged and curved abnormally toward the capsule.

CONCLUSIONS

PSC plaques are not internalized and broken down in the classical cell biological sense (i. e. via lysosomal degradation). Rather the plaques retain their structure indefinitely as lens growth proceeds (albeit not entirely normally). This demonstrates that the lens has a restricted ability to respond to growth defects and effect a limited recovery after PSC formation.

The internalization of posterior subcapsular cataracts (PSCs) in Royal College of Surgeons (RCS) rats. II. The inter-relationship of optical quality and structure as a function of age

PURPOSE

The Royal College of Surgeons (RCS) rat is an animal model for human retinal degenerative disease and posterior subcapsular cataracts (PSCs). The purpose of this study was to correlate the structure and optical quality of RCS lenses with PSCs as a function of their internalization, with normal, non-cataractous, age-matched control lenses.

METHODS

Correlative light (LM), scanning electron microscopic (SEM), three-dimensional computer assisted drawings (3D-CADs) and low power helium-neon laser scan analysis were used to examine the structure and function of lenses.

RESULTS

The optical properties (average focal length variability; sharpness of focus) of RCS rat lenses are quantitatively compromised by PSCs. Correlative LM and SEM analysis of RCS lenses at various stages of PSC internalization (1.5, 3, 6, 9, 12 and 15 months of age), revealed that the sutures formed by additional fiber growth were progressively more abnormal. During PSC internalization, two to nine small suture branches were formed and arranged in modified line to multiple y configurations rather than the normal three branch y sutures. These temporal changes were also chronicled in animated 3D-CAD videos derived from lens reconstructions based on LM and SEM micrographs from the selected time points stated above. However, laser scan analysis also revealed that as the PSCs of RCS rat lenses were progressively internalized, there was a steady improvement in total sharpness of focus that reached normal levels by 12 months of age. The correlation of laser scan and structural data from specific regions of lenses revealed the following: 1. The abnormal posterior sutures of RCS rats with internalized PSCs effect a greater reduction in optical quality than normal posterior sutures of age-matched controls; 2. However, the resulting abnormal suture plane area was cumulatively similar to that of age-matched controls; 3. Thus, total optical quality was similar between RCS lenses with internalized PSCs and age-matched controls by 12 months of age.

CONCLUSIONS

The results of this study show that RCS lenses with internalized PSCs can appear grossly, and indeed optically perform, at levels comparable to aged lenses. These findings are consistent with clinical observations of spontaneous recovery from PSC. The results suggest that human PSCs that occur as a consequence of retinal degenerative disease could also be the result of abnormal posterior suture growth. If this is proven to be the case, such PSCs may have some capacity for repair or recovery thereby obviating their surgical removal.

Outcomes after single injection caudal epidural versus continuous infusion epidural via caudal approach for postoperative analgesia in infants and children undergoing patent ductus arteriosus ligation

Adequate postoperative analgesia enhances deep breathing and minimizes respiratory complications after thoracotomy. This study compares postoperative outcomes after single injection caudal epidural vs continuous infusion epidural via caudal approach for postoperative analgesia in infants and children undergoing thoracotomy for patent ductus arteriosus (PDA) ligation. A retrospective chart review was performed for 27 children who had undergone PDA ligation. The children were divided into three groups. We compared patient demographics, surgical duration, anaesthesia duration, length of ICU stay, incidence of emesis requiring treatment, time required to establish regular oral intake, requirement for supplemental intravenous opioids during the first postoperative day, and length of hospital stay. For paediatric patients undergoing PDA ligation, postoperative analgesia with continuous infusion epidural via caudal approach produced shorter ICU stay, less occurrence of postoperative emesis, earlier oral intake, elimination of intravenous opioid supplementation, and shorter hospital stay compared with single injection caudal epidural techniques.

The utility of an in-hospital observation period after discontinuing intravenous antibiotics

PURPOSE

To determine whether observing patients overnight in the hospital after intravenous antibiotics have been discontinued is a useful way to identify important clinical events.

SUBJECTS AND METHODS

We performed a retrospective chart review of patients admitted during a 6-month period to a tertiary care teaching hospital with a primary diagnosis of either pneumonia, urinary tract infection, or cellulitis who were treated with intravenous antibiotics. Charts were abstracted for patient characteristics, including comorbid illnesses and laboratory values, as well as for evidence of recurrent infection or other adverse events.

RESULTS

Of the 374 patients in the study, 63 (17%) were discharged on the day intravenous antibiotics were discontinued. These patients were 10 years younger (P = 0.0009) and had fewer comorbid illnesses (P = 0.02) than those who were observed in the hospital. Recurrent infection was noted in 3 (1%; 95% confidence interval 0.2% to 3%) of the 308 patients who were observed. A mild adverse antibiotic reaction was also noted in three observed patients. The readmission rate to the same institution for recurrent infection was 3% for patients with an observation period and 2% for patients without an observation period (P = 0.70).

CONCLUSIONS

Observing patients overnight in the hospital after discontinuing intravenous antibiotics is a common clinical practice. There was an extremely low incidence of adverse events during the observation period, and the events that did occur would have been discovered in an outpatient setting. In-hospital observation after discontinuing intravenous antibiotics is unnecessary for most patients with pneumonia, urinary tract infection, or cellulitis and greatly increases health-care costs.

Thermodynamics of ligand binding and catalysis in human liver medium-chain acyl-CoA dehydrogenase: comparative studies involving normal and 3'-dephosphorylated C8-CoAs and wild-type and Asn191 --> Ala (N191A) mutant enzymes

Following our demonstration that the terminal 3'-phosphate group of acyl-CoA substrates (which is confined to the exterior of the protein structure, and is fully exposed to the outside solvent environment) exhibits a functional role in the recombinant human liver medium-chain acyl-CoA dehydrogenase (MCAD)-catalyzed reaction [Peterson, K. L., and Srivastava, D. K. (1997) Biochem. J. 325, 751-760], we became interested in delineating its thermodynamic contribution in stabilizing the "ground" and "transition" state structures during enzyme catalysis. Since the 3'-phosphate group of the coenzyme A thiolester has the potential to form a hydrogen bond with the side chain group of Asn-191, these studies were performed utilizing both normal and 3'-dephosphorylated forms of octanoyl-CoA and octenoyl-CoA (cumulatively referred to as C8-CoA) as the physiological substrate and product of the enzyme, respectively, as well as utilizing wild-type and Asn191 --> Ala (N191A) site-specific mutant enzymes. The experimental data revealed that the enthalpic contribution of the 3'-phosphate group was similar in both ground and transition states, and was primarily derived from the London-van der Waals interactions (between the 3'-phosphate group of C8-CoA and the surrounding protein moiety), rather than from the potential hydrogen bonding. The temperature dependence of DeltaH degrees for the binding of octenoyl-CoA and 3'-dephosphooctenoyl-CoA revealed that the deletion of the 3'-phosphate group from octenoyl-CoA increased the magnitude of the heat capacity changes (DeltaCp degrees) from -0.53 to -0.59 kcal mol-1 K-1. Although the latter effect could be attributed to an increase in the relative hydrophobicity of the ligand, the experimentally observed DeltaCp degrees's (for either of the ligands) could not be predicted on the basis of the changes in the solvent-accessible surface areas of the enzyme and ligand species. These coupled with the fact that the DeltaCp degrees for the binding of octenoyl-CoA to pig kidney MCAD (which is believed to be structurally identical to human liver MCAD) is only -0.37 kcal mol-1 K-1 [Srivastava, D. K., Wang, S., and Peterson, K. L. (1997) Biochemistry 36, 6359-6366] prompt us to question the reliability of predicting the DeltaCp degrees values of the enzyme-ligand complexes from their X-ray crystallographic data. Arguments are presented that certain intrinisic limitations of the crystallographic data preclude kinetic and thermodynamic predictions about the enzyme-ligand complexes and enzyme catalysis.

Quantitative angiography of coronary artery dimensions 24 hours after rotational atherectomy

Rotational atherectomy results in platelet activation and heat generation, which may impact artery size immediately after treatment. In addition, arteries treated with balloon angioplasty may exhibit recoil within 24 hours. In this study, arteries treated with rotational atherectomy, with and without adjunctive balloon angioplasty, were analyzed by quantitative coronary angiography to determine the effect of rotational atherectomy on the dynamic behavior of the arterial wall within 24 hours after the procedure. Quantitative coronary angiography was performed at a core laboratory. Coronary angiogram acquisitions were preceded by intracoronary nitroglycerin injections and were repeated using identical angles of projection. Proximal and distal reference vessel diameters were 2.55 +/- 0.60 and 2.28 +/- 0.51 mm, respectively, and did not change from pre- to postprocedure. Both were larger the following day increasing to 2.72 +/- 0.65 and 2.52 +/- 0.52 mm, respectively, (p <0.001). Minimum luminal diameter (MLD) increased from 0.70 +/- 0.28 mm before to 1.49 +/- 0.34 mm after the procedure and to 1.72 +/- 0.37 mm at 24-hour follow-up (p <0.001). Subset analysis of patients treated with rotational atherectomy alone or rotational atherectomy with adjunctive balloon angioplasty revealed that the increase in luminal diameters occurred in both subsets. Patients treated with adjunctive angioplasty had a smaller initial MLD, a larger postprocedure MLD, and no difference in MLD at 24-hour follow-up compared with stand-alone rotational atherectomy. Subset analysis of 100 patients who had 6-month follow-up angiography revealed that both a calculated acute gain and chronic late loss, based on a 24-hour film, differed significantly from values using a film acquired immediately after the procedure. However, the slope of the linear regression between acute gain and chronic late loss did not differ. Coronary arteries treated with rotational atherectomy with or without adjunctive balloon angioplasty increase significantly in size during the first 24 hours after the procedure. This phenomenon has implications for the calculation of absolute gain and chronic late loss, but not for the linear relation between the 2 quantitative outcomes.

Discriminatory influence of Glu-376-->Asp mutation in medium-chain acyl-CoA dehydrogenase on the binding of selected CoA-ligands: spectroscopic, thermodynamic, kinetic, and model building studies

We investigated the influence of Glu-376-->Asp (E376D) mutation on the UV/visible spectral, thermodynamic, and kinetic properties for the interaction of structurally different types of CoA-ligands (viz., octenoyl-CoA, acetoacetyl-CoA, and indoleacryloyl-CoA) to human liver medium-chain acyl-CoA dehydrogenase (MCAD). Whereas the E376D mutation had minimal/negligible effect on the above properties for the binding of octenoyl-CoA to the enzyme, it had pronounced effects (albeit in opposite directions) for the binding of acetoacetyl-CoA and indoleacryloyl-CoA to the enzyme. In the case of acetoacetyl-CoA, the spectrum of the enzyme-ligand complex (in the charge-transfer region; lambdamax = 545 nm) was 1.8-fold more pronounced, and the DeltaH degrees value for the binding of acetoacetyl-CoA to the enzyme was 5.6 kcal/mol more favorable with wild-type as compared to the E376D mutant enzyme. The kinetic data revealed that the above effects were related to an increase in the dissociation "off-rate" of acetoacetyl-CoA from the enzyme-acetoacetyl-CoA complex. In contrast, in the case of IACoA, the resultant UV/visible spectrum of the enzyme-IACoA complex (lambdamax = 416 nm) was 2.7-fold less pronounced, and the DeltaH degrees value of the enzyme-IACoA complex was 6.4 kcal/mol less favorable with the wild-type than the E376D mutant enzyme. The latter effects were supported by the fact that the above mutation impaired the dissociation "off-rate" of IACoA from the enzyme-IACoA complex by 5.7-fold. Molecular model building studies revealed that the discriminatory influence of the E376D mutation on the spectral, thermodynamic, and kinetic properties of the enzyme-ligand complexes is due to ligand-specific changes in the spatial relationship between the FAD and CoA-ligands at the enzyme site. Arguments are presented that the "void" created by excision of a methylene group from Glu-376 (upon Glu-376-->Asp mutation) is adjusted differently upon interaction with structurally different types of CoA-ligands.

Objective measures of laryngeal function after reinnervation of the anterior and posterior recurrent laryngeal nerve branches

Previous research indicates that separate reinnervation of the anterior and posterior branches of the recurrent laryngeal nerve (RLN) can provide purposeful motion of the larynx, even after transplantation. This canine study was undertaken to better determine the results of RLN reinnervation after nerve transection distal to its bifurcation. This approximates ideal conditions for transplantation, because potential rejection and nerve branch mismatch are eliminated. Eight months after nerve repair, video, electromyographic, mechanical, and histologic data were collected on four canines. Results show return of appropriate motion without synkinesis, including purposeful abduction on endotracheal tube occlusion. Abductory function was weaker on the reinnervated side, but adduction was equal or stronger on the reinnervated vocal cord. These results indicate that this method of RLN reinnervation produces consistent, strong physiologic motion in the denervated larynx.

Influence of excision of a methylene group from Glu-376 (Glu376-->Asp mutation) in the medium chain acyl-CoA dehydrogenase-catalyzed reaction

The human liver medium chain acyl-CoA dehydrogenase (MCAD)-catalyzed reaction proceeds via abstraction of an alpha-proton from the acyl-CoA substrates by the carboxyl group of Glu-376. By using the methods of site-directed mutagenesis, we replaced Glu-376 by Asp (E376D mutation), expressed the wild-type and mutant enzymes in Escherichia coli, purified them to homogeneity, and compared their kinetic properties. The steady-state kinetic data revealed that the E376D mutation impaired (by about 15-20-fold) the turnover rate of the enzyme as well as its inactivation by 2-octynoyl-CoA. There was no selective solvent deuterium isotope effect on enzyme catalysis. These results lead to the suggestion that the carboxyl group of Asp-376 does not serve as efficient catalytic base as the carboxyl group of Glu-376. The E376D mutation impaired the octanoyl-CoA-dependent reductive half-reaction such that the rate-limiting step of enzyme catalysis shifted from the product dissociation step (in the case of the wild-type enzyme) to the flavin reduction step, and abolished the previously noted kinetic and thermodynamic correspondences between the octanoyl-CoA-dependent reductive half-reaction and the enzyme-octenoyl-CoA interaction [Kumar, N. R., and Srivastava, D. K. (1994) Biochemistry 33, 8833-8841]. Arguments are presented that the Glu-376-->Asp mutation results in uncoupling between the proton transfer and protein conformational change steps during enzyme catalysis.

Force-frequency effect is a powerful determinant of myocardial contractility in the mouse

The effects of heart rate (HR) on myocardial contractility in the mouse heart in situ were first investigated in open-chest mice (n = 7) by left ventricular (LV) catheter-tip micromanometry. HR was first slowed with a sinus node inhibitor (zatebradine), and atrial pacing to progressively increase the HR caused a positive inotropic response (assessed by maximum positive first derivative of LV pressure, LV dP/dtmax) up to a HR of 282 beats/min with the onset of a descending limb of the force-frequency relation (FFR) at 332 beats/min. beta-Adrenergic receptor stimulation (dobutamine) shifted upward and significantly steepened the positive FFR and increased HR at the onset of the descending limb to 402 beats/min. HR and LV dP/dtmax were then studied in closed-chest mice without pacing during recovery from anesthesia (n = 7), and during rest and intermittent physical activity the FFR was linear and positive up to 600 beats/min. HR was then progressively slowed with zatebradine, and the points at rest and during activity fell on the same linear relation. Thus we conclude the following: 1) in the open-chest anesthetized mouse, a positive FFR was amplified by beta-adrenergic receptor stimulation, and 20 in the mouse recovering from anesthesia the sinus node rate remained a critical determinant of myocardial contractility, without a descending limb of the FFR.

Functional role of a distal (3'-phosphate) group of CoA in the recombinant human liver medium-chain acyl-CoA dehydrogenase-catalysed reaction

The X-ray crystallographic structure of medium-chain acyl-CoA dehydrogenase (MCAD)-octenoyl-CoA complex reveals that the 3'-phosphate group of CoA is confined to the exterior of the protein structure [approx. 15 A (1.5 nm) away from the enzyme active site], and is fully exposed to the outside solvent environment. To ascertain whether such a distal (3'-phosphate) fragment of CoA plays any significant role in the enzyme catalysis, we investigated the recombinant human liver MCAD (HMCAD)-catalysed reaction by using normal (phospho) and 3'-phosphate-truncated (dephospho) forms of octanoyl-CoA and butyryl-CoA substrates. The steady-state kinetic data revealed that deletion of the 3'-phosphate group from octanoyl-CoA substrate increased the turnover rate of the enzyme to about one-quarter, whereas that from butyryl-CoA substrate decreased the turnover rate of the enzyme to about one-fifth; the Km values of both these substrates were increased by 5-10-fold on deletion of the 3'-phosphate group from the corresponding acyl-CoA substrates. The transient kinetics for the reductive half-reaction, oxidative half-reaction and the dissociation 'off-rate' (of the reaction product from the oxidized enzyme site) were all found to be affected by deletions of the 3'-phosphate group from octanoyl-CoA and butyryl-CoA substrates. A cumulative account of these results reveals that, although the 3'-phosphate group of acyl-CoA substrates might seem 'useless' on the basis of the structural data, it has an essential functional role during HMCAD catalysis.

The C1q-binding cell membrane proteins cC1q-R and gC1q-R are released from activated cells: subcellular distribution and immunochemical characterization

Two types of widely coexpressed cell surface C1q-binding proteins (C1q-R): a 60-kDa calreticulin-homolog which binds to the collagen-like "stalk" of C1q and a 33-kDa protein with affinity for the globular "heads" of the molecule, have been described. In this report, we show that the two molecules are also secreted by Raji cells and peripheral blood lymphocytes and can be isolated in soluble form from serum-free culture supernatant by HPLC purification using a Mono-Q column. The two purified soluble proteins had immunochemical and physical characteristics similar to their membrane counterparts in that both bound to intact C1q and to their respective C1q ligands, cC1q and gC1q. In addition, N-terminal amino acid sequence analyses of the soluble cC1q-R and gC1q-R were found to be identical to the reported sequences of the respective membrane-isolated proteins. Ligand blot analyses using biotinylated membrane or soluble cC1q-R and gC1q-R showed that both bind to the denatured and nondenatured A-chain and moderately to the C-chain of C1q. Moreover, like their membrane counterparts, the soluble proteins were found to inhibit serum C1q hemolytic activity. Although cC1q-R was released when both peripheral blood lymphocytes and Raji cells were incubated in phosphate-buffered saline for 1 hr under tissue culture conditions, gC1q-R was releasable only from Raji cells, suggesting that perhaps activation or transformation leading to immortalization is required for gC1q-R release. Subcellular fractionation of Raji cells and analyses by enzyme-linked immunosorbent assay and Western blotting showed that the two molecules are present in the cytosolic fractions as well as on the membrane. The data suggest that soluble forms of both C1q-binding molecules are released from cells and that these molecules may play important roles in vivo as regulators of complement activation.

Rhinocerebral mucormycosis: evolution of the disease and treatment options

Rhinocerebral mucormycosis is recognized as a potentially aggressive and commonly fatal fungal infection. The classic presentation is involvement of nasal mucosa with invasion of the paranasal sinuses and orbit. Mucormycosis is most commonly seen in association with diabetic ketoacidosis, but disease demographics have changed with the onset of AIDS and the advent of powerful immunosuppressive drugs. Treatment includes aggressive debridement, systemic antifungal therapy, and control of underlying comorbid factors. Although surgical intervention remains essential, advances in medical therapy have permitted a more limited surgical approach to minimize functional loss without compromising survival. We present the UCLA experience with rhinocerebral mucormycosis from 1955 to 1995, with emphasis on the evolution of disease presentation and alternative treatment options.

Isothermal titration microcalorimetric studies for the binding of octenoyl-CoA to medium chain acyl-CoA dehydrogenase

We investigated the binding of octenoyl-CoA to pig kidney medium chain acyl-CoA dehydrogenase (MCAD) by isothermal titration microcalorimetry under a variety of experimental conditions. At 25 degrees C in 50 mM phosphate buffer at pH 7.6 (ionic strength of 175 mM), the binding is characterized by the stoichiometry (n) of 0.89 mole of octenoyl-CoA/(mole of MCAD subunit), delta G = -8.75 kcal/mol, delta H = -10.3 kcal/mol, and delta S = -5.3 cal mol(-1) K(-1), suggesting that formation of MCAD-octenoyl-CoA is enthalpically driven. By employing buffers with various ionization enthalpies, we discerned that formation of the MCAD-octenoyl-CoA complex, at pH 7.6, accompanies abstraction (consumption) of 0.52 +/- 0.15 proton/(MCAD subunit) from the buffer media. We studied the effects of pH, ionic strength, and temperature on the thermodynamics of MCAD-octenoyl-CoA interaction. Whereas the ionic strength does not significantly influence the above interaction, the pH of the buffer media exhibits a pronounced effect. The pH dependence of the association constant of MCAD +octenoyl-CoA <==> MCAD-octenoyl-CoA yields a pKa for the free enzyme of 6.2. Among thermodynamic parameters, whereas delta G remains invariant as a function of temperature, delta H and deltaS(standard) both decrease with an increase in temperature. At temperatures of < 25 degrees C, delta G is dominated by favorable entropic contributions. As the temperature increases, the entropic contributions progressively decrease, attain a value of zero at 23.8 degrees C, and then becomes unfavorable. During this transition, the enthalpic contributions become progressively favorable, resulting in an enthalpy-entropy compensation. The temperature dependence of delta H yields the heat capacity change (delta Cp(0)) of -0.37 +/- 0.05 kcal mol(-1) K(-1), attesting to the fact that the binding of octenoyl-CoA to MCAD is primarily dominated by the hydrophobic forces. The thermodynamic data presented herein are rationalized in light of structural-functional relationships in MCAD catalysis.

Botulinum neurotoxin injection after total laryngectomy

BACKGROUND

One of several causes of tracheoesophageal puncture (TEP) speech failure after total laryngectomy is disturbance in relaxation of the pharyngoesophageal (PE) segment. We introduce the use of chemical denervation of the PE segment through botulinum neurotoxin (Botox) injection to improve TEP speech.

METHODS

An analysis was performed on eight patients who received Botox injections for TEP speech problems after total laryngectomy at the University of Iowa between June 4, 1991 and August 8, 1994. Retrospective chart review identified the evolution of pretreatment evaluation and injection technique which became standardized in April 1992. Prospective evaluation of results was recorded by a single speech pathologist who subjectively identified the response to Botox in all patients and recorded pressure readings at the tracheostoma site during speech in 6 patients.

RESULTS

Seven of the eight patients were noted to have improved TEP speech following injection. Five of these seven patients experienced substantially improved speech, three of whom had no ability to produce speech prior to the Botox injection.

CONCLUSION

Botox injection is a safe and effective method of improving TEP speech in selected patients with disturbed relaxation of pharyngoesophageal segment.

The influence of coronary collateral flow on the assessment of myocardial perfusion by videodensitometry

OBJECTIVES

Coronary collateral flow often mitigates the effects of coronary artery obstruction and has a significant impact on the prognosis of patients with coronary artery disease. In the presence of variable degrees of coronary collateral flow, digital radiographic assessment of myocardial blood flow has not been quantitatively validated.

METHODS

A distal coronary arterial collateral path was created into the left anterior descending coronary artery (LAD) bed in 8 anesthetized pigs. Both LAD and collateral paths were pump-perfused and corresponding flows measured. A number of commonly used digital indices and parametric images of myocardial perfusion were then extracted from the sequence of images filmed before and during the injection of contrast. Data were acquired at 5 levels of total flow (LAD flow + collateral flow): 100, 85, 70, 55 and 40% of maximally vasodilated, baseline flow. At each level of total flow, data were acquired at 4 levels of collateral flow ratios (collateral flow/total flow): 0, 10, 25 and 50%.

RESULTS

Regional percent segment shortening, reflecting myocardial blood flow, decreased as total flow fell, and remained unaltered when coronary collateral ratio alone was altered without change in total flow. On the other hand, linear regression between total flow and digital indices at 10, 25 and 50% coronary collateral flow ratios, compared with 0%, showed a successive and significant downward displacement, documenting an underestimation of flow by all digital indices in the presence of collateral flow.

CONCLUSIONS

In the absence of a collateral pathway and during maximal coronary vasodilation with adenosine, digital radiographic indices of myocardial perfusion, based upon indicator dilution theory, show a relatively good correlation with regional transmural myocardial blood flow. However, due to underestimation of total transmural blood flow, these indices have limited utility when myocardial perfusion is provided in part by a collateral pathway. The effect is probably related to an alteration in the regional vascular volume into which iodinated contrast is injected.

Subglottic paraganglioma

Paragangliomas are uncommon neuroendocrine tumors. In the head and neck region they are most commonly associated with the carotid body, vagus nerve, jugulotympanic paraganglia, and occasionally the superior and inferior laryngeal paraganglia. Laryngeal paragangliomas and subglottic paragangliomas are rare. There have been nine reported cases in the English literature of subglottic paragangliomas. We present a case of this unusual lesion and discuss histologic characteristics and surgical treatment.

Transthoracic echocardiography in models of cardiac disease in the mouse

BACKGROUND

Transthoracic echocardiography (M-mode and Doppler) offers a noninvasive approach for in vivo evaluation of the mouse heart. The present study examines its usefulness for assessing the morphological/functional phenotype of the left ventricle (LV) in several transgenic and surgical murine models of cardiac disease.

METHODS AND RESULTS

Observations were made in 83 intact, anesthetized mice. In mice with a surgical arteriovenous fistula, volume overload and LV dilation were detected. In normal mice, echocardiographic indexes of increased contractility (dobutamine) were confirmed by LV dP/dtmax. In transgenic mice with overexpression of the beta 2-adrenergic receptor, heart rate and mean velocity of circumferential fiber shortening were increased, indicating enhanced contractility. In colony screening of transgenic mice overexpressing the H-ras gene, 45% had increased LV wall thickness (> 0.9 mm), and those showing a striking increase were selected for breeding. In mice with LV hypertrophy (aortic constriction) and normal mice, the actual LV mass determined by echocardiography correlated well (r = .93), and 95% confidence limits were determined. The maximum intraobserver and interobserver coefficients of variation for M-mode data were 0.03 +/- 0.29 mm (+/- 2 SD), < 10% for LV internal dimensions but 27% to 30% for wall thickness.

CONCLUSIONS

These studies provide the first application of transthoracic echocardiography for morphological/functional characterization of the cardiac phenotype in transgenic and surgical murine models, including (1) high reliability for detecting LV chamber dilation and function; (2) reliability (and its limits) for determining abnormal LV wall thickness and LV mass; (3) identification of marked, sometimes asymmetrical, hypertrophy in a transgenic model of hypertrophic cardiomyopathy; and (4) usefulness for transgenic colony screening to identify markedly abnormal phenotypes.

Atheroma morphology and distribution in proximal left anterior descending coronary artery: in vivo observations

OBJECTIVES

This study sought to examine, in vivo, the shape and position of atheroma in the proximal left anterior descending coronary artery.

BACKGROUND

The prevalence, shape and location of atheromas involving the proximal left anterior descending artery have implications regarding the role of disturbed shear forces in the genesis of atherosclerosis. However, no data are available regarding in vivo findings or advanced disease.

METHODS

Forty-two consecutive high quality intravascular ultrasound images were examined from patients with atherosclerotic disease in the proximal left anterior descending artery just distal to the left main bifurcation. Lesion percent area stenosis and maximal, minimal and flow divider intimal-medial thickness were measured at the region immediately after the circumflex takeoff. The angle formed by the midpoint of the flow divider, the human center of gravity and the maximal plaque thickness were determined.

RESULTS

Eccentricity of vessel wall atheroma was observed such that the maximal wall thickness (1.42 +/- 0.50 mm [mean +/- SD]) differed significantly from minimal wall thickness (0.17 +/- 0.098 mm). Further, the region of vessel wall manifesting maximal thickness was greater than the flow divider thickness (0.26 +/- 0.16 mm). Maximal plaque thickness spared the region of the flow divider in 100% of cases and was positioned at a mean angle of 193 +/- 49 degrees from the center of the flow divider. Eccentric morphology was maintained across the 24% to 80% range of area stenosis.

CONCLUSIONS

Atheromas in the very proximal left anterior descending artery are located opposite the circumflex takeoff, spare the flow divider and maintain eccentricity across a wide range of vessel stenoses. These in vivo morphologic data support the potential role of fluid dynamic mechanical factors in atherogenesis and have implications regarding the success of catheter-based interventional procedures at the site.

Recombinant human liver medium-chain acyl-CoA dehydrogenase: purification, characterization, and the mechanism of interactions with functionally diverse C8-CoA molecules

We offer a large scale purification procedure for the recombinant human liver medium-chain acyl-CoA dehydrogenase (HMCAD). This procedure routinely yield 100-150 mg of homogeneous preparation of the enzyme from 80 L of the Escherichia coli host cells. A comparative investigation of kinetic properties of the human liver and pig kidney enzymes revealed that, except for a few minor differences, both of these enzymes are nearly identical. We undertook detailed kinetic and thermodynamic investigations for the interaction of HMCAD-FAD with three C8-CoA molecules (viz., octanoyl-CoA, 2-octenoyl-CoA, and 2-octynoyl-CoA), which differ with respect to the extent of unsaturation of the alpha-beta carbon center; octanoyl-CoA and 2-octenoyl-CoA serve as the substrate and product of the enzyme, respectively, whereas 2-octynoyl-CoA is known to inactivate the enzyme. Our experimental results demonstrate that all three C8-CoA molecules first interact with HMCAD-FAD to form corresponding Michaelis complexes, followed by two subsequent isomerization reactions. The latter accompany either subtle changes in the electronic structures of the individual components (in case of 2-octenoyl-CoA and 2-octynoyl-CoA ligands), or a near-complete reduction of the enzyme-bound flavin (in case of octanoyl-CoA). The rate and equilibrium constants intrinsic to the above microscopic steps exhibit marked similarity with different C8-CoA molecules. However, the electronic structural changes accompanying the 2-octynoyl-CoA-dependent inactivation of enzyme is 3-4 orders of magnitude slower than the above isomerization reactions. Hence, the octanoyl-CoA-dependent reductive half-reaction and the 2-octynoyl-CoA-dependent covalent modification of the enzyme occur during entirely different microscopic steps. Arguments are presented that the origin of the above difference lies in the protein conformation-dependent orientation of Glu-376 in the vicinity of the C8-CoA binding site.

Role of intraaortic balloon pump counterpulsation in high risk coronary rotational atherectomy

OBJECTIVES

This study sought to evaluate the role of intraaortic balloon pump counterpulsation in preventing hemodynamic instability and promoting a successful outcome during percutaneous transluminal coronary rotational atherectomy in high risk patients.

BACKGROUND

The application of rotational atherectomy has widened to include patients with complex lesions and left ventricular dysfunction. Although intraaortic balloon pumping has been successfully used to provide hemodynamic support during balloon angioplasty, its role in high risk rotational atherectomy has not yet been defined.

METHODS

In a retrospective review of 159 consecutive high risk patients who underwent rotational atherectomy, 28 had an intraaortic balloon pump placed electively before the procedure (Group 1) whereas 131 did not (Group 2).

RESULTS

Group 1 was older and more likely to have multivessel disease and left ventricular dysfunction. Augmented diastolic pressure was maintained > 90 mm Hg in all Group 1 patients, and significant procedure-related hypotension was encountered in nine Group 2 patients, requiring an emergency intraaortic balloon pump in five. Procedural success was achieved in all 28 patients in Group 1 and in 118 in Group 2 (p = 0.07). Slow flow occurred in 18% and 17% of Group 1 and 2 patients, respectively. Among patients with slow flow, non-Q wave myocardial infarction occurred only in Group 2 (0% vs. 27%). On multivariate analysis, elective intraaortic balloon pump placement was the only variable to correlate with a successful procedure uncomplicated by hypotension (p < 0.05). Hospital stay and vascular complications were similar in both groups.

CONCLUSIONS

Elective placement of an intraaortic balloon pump before coronary rotational atherectomy in selected high risk patients promotes both procedural hemodynamic stability and a successful outcome.

Quantitative structure-activity relationships in carboquinones and benzodiazepines using counter-propagation neural networks

Counter-propagation neural networks are used to model and predict activities of carboquinones and of benzodiazepines from physicochemical parameters. For carboquinones, networks with one hidden layer processing element (PE) for each compound achieved significantly better training set RMSE values than corresponding back-propagation and multiregression results and test set RMSE values as good or slightly worse than back-propagation. Test set results improved by 10-15% using networks with fewer hidden layer PEs than carboquinones; the smallest test set RMSE values are between 0 and 10% better than back-propagation values, about 1.3 times greater than corresponding training set values, and occur when there are about as many competitive layer PEs as there are compounds in the data set. Training set RMSE values increase with decreasing number of competitive layer PEs and approach those of test sets. Both counter-propagation and back-propagation networks, however, have worse predictive capability than multiregression. For benzodiazepines, networks with one hidden layer PE for each compound achieved significantly better training set RMSE values than back-propagation and multiregression results and test set RMSE values slightly worse than back-propagation. Test set results improved by 10-15% using fewer hidden layer PEs than benzodiazepines; the smallest test set RMSE values are 0-10% better than back-propagation values, about 1.3 times greater than training set values, and occur when there are about half as many competitive layer PEs as there are compounds in the data set. Training set RMSE values increase with decreasing number of competitive layer PEs and approach those of test sets. Counter-propagation, back-propagation, and multiregression all have similar predictive capabilities.

Detection of cocaine and its polar transformation products and metabolites in human urine

This paper describes a method for the analysis of thermal degradation compounds generated from cocaine during the smoking process, together with chemical and enzymatic biotransformation products which, by virtue of their polarity, are not recovered by existing analytical procedures. The method employs cation exchange solid phase extraction coupled with gas chromatography/mass spectrometry. Compounds identified in urine from subjects of cocaine-related death included cocaine, benzoylecgonine, ecgonine methyl ester and ecgonine, which were measured quantitatively, and ecgonidine, ecgonidine methyl ester, ecgonine ethyl ester, ethyl benzoylecgonine, norcocaine, benzoylnorecgonine, cinnamoylcocaine, and cinnamoylecgonine. The concentrations of ecgonine (0-104 micrograms/ml) and ecgonine methyl ester (0-177 micrograms/ml) were substantial and averaged about one tenth the concentrations of benzoylecgonine (0-1074 micrograms/ml) and cocaine (0-1221 micrograms/ml). These and several of the other compounds identified will be valuable markers for cocaine use, in degraded samples and for indicating the route of administration.

An atypical case of fragile X syndrome caused by a deletion that includes the FMR1 gene

Fragile X syndrome is the most common form of inherited mental retardation and results from the transcriptional inactivation of the FMR1 gene. In the vast majority of cases, this is caused by the expansion of an unstable CGG repeat in the first exon of the FMR1 gene. We describe here a phenotypically atypical case of fragile X syndrome, caused by a deletion that includes the entire FMR1 gene and > or = 9.0 Mb of flanking DNA. The proband, RK, was a 6-year-old mentally retarded male with obesity and anal atresia. A diagnosis of fragile X syndrome was established by the failure of RK's DNA to hybridize to a 558-bp PstI-XhoI fragment (pfxa3) specific for the 5'-end of the FMR1 gene. The analysis of flanking markers in the interval from Xq26.3-q28 indicated a deletion extending from between 160-500 kb distal and 9.0 Mb proximal to the FMR1 gene. High-resolution chromosome banding confirmed a deletion with breakpoints in Xq26.3 and Xq27.3. This deletion was maternally transmitted and arose as a new mutation on the grandpaternal X chromosome. The maternal transmission of the deletion was confirmed by FISH using a 34-kb cosmid (c31.4) containing most of the FMR1 gene. These results indicated that RK carried a deletion of the FMR1 region with the most proximal breakpoint described to date. This patient's unusual clinical presentation may indicate the presence of genes located in the deleted interval proximal to the FMR1 locus that are able to modify the fragile X syndrome phenotype.

"Dehydrogenase" and "oxidase" reactions of medium-chain fatty acyl-CoA dehydrogenase utilizing chromogenic substrates: role of the 3',5'-adenosine diphosphate moiety of the coenzyme A thioester in catalysis

We undertook a comparative investigation of the medium-chain fatty acyl-CoA dehydrogenase (MCAD)-catalyzed reaction utilizing indole-, furyl-, and 4-(dimethylamino)phenyl-substituted propionyl- and acryloyl-CoAs as potential substrate/product pairs. All these propionyl-CoA derivatives undergo MCAD-catalyzed conversion into their corresponding acryloyl-CoAs via both "dehydrogenase" (in the presence of "organic" electron acceptors) and "oxidase" (buffer-dissolved oxygen serving as the electron acceptor) pathways [Johnson, J. K., Wang, Z. X., & Srivastava, D. K. (1992) Biochemistry 31, 10564-10575]. The steady-state kinetic parameters for the enzyme utilizing these substrates reveal that the KmS (for the CoA substrates) and kcatS for the dehydrogenase reaction are at least an order of magnitude higher than those for the oxidase reaction. As with the CoA substrates, the enzyme catalyzes the conversion of indolepropionyl pantetheine phosphate (IPPP) into indoleacryloyl pantetheine phosphate (IAPP) via these two pathways. However, with IPPP as substrate, the Km (for IPPP) and kcat values of the dehydrogenase and oxidase reactions are the same. These, coupled with the spectral changes of the enzyme-product complexes as well as the binding affinities of the enzyme-substrate/product complexes, lead to the following conclusions: (1) The aromatic/heterocyclic group-containing substrates are converted into their corresponding products via both the dehydrogenase and the oxidase pathways. (2) The 3',5'-ADP moiety of the CoA thioester provides a significant fraction of the total binding energy in stabilizing the enzyme-substrate/product complexes.(ABSTRACT TRUNCATED AT 250 WORDS)

Heterogeneity of vasomotor response to acetylcholine along the human coronary artery

OBJECTIVES

In view of the segmental occurrence of coronary atherosclerosis, we postulated that acetylcholine may cause heterogeneous vasomotion, depending on the extent of vessel analyzed, criteria for change in vessel caliber and dose of drug administered.

BACKGROUND

Previous studies have reported that acetylcholine causes constriction of atherosclerotic arteries. This dysfunction of endothelium-dependent dilation may be seen without angiographically detectable disease.

METHODS

We developed algorithms to quantitate the dimensions of a single coronary artery over virtually its entire length during a control state and during graded doses of intracoronary acetylcholine. On the basis of triplicate control angiograms, the limit of detection of a change from control diameter was 0.31 mm (> or = 2 SD).

RESULTS

Analysis of multiple segments (each 5.6 +/- 1.1 [mean +/- SD] mm) along a single coronary artery revealed a heterogeneous response to acetylcholine in 27 of 31 patients at the 10(-4) mol/liter dose and in 29 of 31 patients when responses at 10(-6), 10(-5) and 10(-4) mol/liter doses were combined; in this latter analysis, constriction and dilation in the same vessel occurred in 45% of the patients. With acetylcholine, most of 349 segments demonstrated no change, but the greatest frequency of vasoconstriction (24.6%) and vasodilation (6.9%) was seen at the 10(-4) mol/liter dose. Inducible vasomotion was observed as far distally as 7.3 cm from the site of acetylcholine infusion.

CONCLUSIONS

Response to intracoronary acetylcholine with mild coronary disease is heterogeneous; disparate dimensional responses may occur in different segments of the same vessel. Inclusion of all analyzable regions of a coronary artery and the use of a reproducibility limit for quantitative angiography are optimal for assessment of segmental coronary vasomotion.

Analysis of ketorolac in postmortem blood

This paper describes analytical methods using high-performance liquid chromatography and gas chromatography-mass spectrometry (GC-MS) for the isolation of the nonsteroidal anti-inflammatory drug, ketorolac. The drug is isolated from postmortem blood using a batched solid-phase extraction method on Amberlite XAD-2 resin. Derivatization of ketorolac using diazopropane was necessary prior to GC-MS analysis. The methods were applied in the investigation of a death occurring shortly after the administration of an intramuscular injection of ketorolac tromethamine. Death was attributed to an adverse reaction to the drug, resulting in anaphylaxis and cardiac arrest.

The interrelationship of lens anatomy and optical quality. II. Primate lenses

We have quantified the influence of lens sutural anatomy on optical quality (focal length variability, i.e. spherical aberration) in adult monkeys (Macaque nemestrina). Adult lenses (n = 6) were initially scanned by a low-power helium-neon laser beam that was passed at a series of acute angles to, and/or directly through, lens sutures. Optical analysis showed that while the 'star' sutures of primate lenses exerted a quantifiable negative effect on focal length variability, this detrimental effect was far less significant than that attributable to 'line' and 'Y' sutures in non-primate lenses. Correlative morphological and 3-D computer-assisted drawing (CAD) analysis of the laser-scanned lenses areas, as well as of variably aged lenses (n = 30), revealed that primates have a more complex lens architecture than non-primates. Non-primate lenses feature suture planes, aligned along the visual axis that are responsible for a significant quantifiable increase in spherical aberration. Primate lenses are characterized by an absence of continuous suture planes aligned along the visual axis. Rather, 3-D-CADs of primate lenses demonstrate that distinct generations of progressively more complex sutures are produced as a function of development, growth, and age. In succession, 'Y' sutures (three branches) are formed throughout embryonic development, 'simple star' sutures (three-six branches) evolve after birth and through infancy, 'star' sutures (six-nine branches) are made in young adult lenses and, finally, 'complex star' sutures (nine-15 branches) are laid down from middle through old age. In view of the fact that slit-lamp evaluation of cataractous lenses often reveals abnormally thin zones of discontinuity, it is significant to note that the temporal development of the zones of discontinuity in normal human lenses is essentially identical to the progressive iteration of offset monkey lens sutures. In conclusion, these studies describe a specific structural aspect of lenses that adversely influences optical quality, and relates it to the most commonly employed clinical technique to identify and monitor the progress of cataracts.

The interrelationship of lens anatomy and optical quality. I. Non-primate lenses

We have quantified the influence of 'Y' sutures on lens optical quality (spherical aberration, i.e. focal length variability) as a function of age. Young (n = 6) and old (group 1, n = 5; and group 2, n = 4) bovine lenses were initially scanned by a low-power (2 mW) helium-neon laser beam passed either through or at a series of acute angles to suture branches. In all lenses, focal length variability was least when the beam was passed through areas of the lens devoid of sutures and greatest when passed through sutures. In older lenses, variability was also significantly increased in all locations though to a greater degree at sutures. Correlative morphological analysis by scanning electron microscopic (SEM) and three dimensional (3-D) computer-assisted drawings (CADs) revealed the following: (1) young lenses had uniformly hexagonal fibers arranged in parallel radial cell columns (RCCs), while old lenses had nonuniformly hexagonal fibers arranged in variably parallel RCCs; (2) the irregularly-sized and -shaped ends of young fibers overlapped within growth shells to form complementary anterior and posterior symmetrical 'Y' suture patterns, while larger and more irregularly-shaped ends of older lenses overlapped to form asymmetrical 'Y' patterns; and (3) the identical suture patterns in successive shells of young lenses resulted in inverted triangular suture planes extending from the embryonic nucleus to the lens periphery, while the progressively wider and more serpentine suture branches of old lenses resulted in inverted pyramidal suture planes with narrow apices oriented towards the embryonic nucleus and broad irregular bases oriented toward the lens periphery. Thus, there is a significant interrelationship between lens optical quality and structure that varies as a function of age. These results extend and confirm the results of our earlier studies on lenses with simpler 'line' sutures and preface our studies of primate lenses with more complex 'star' sutures. All of these studies show that lens sutural anatomy should be considered when evaluating the optical quality of normal and pathological lenses.

Physiology of the native heart and Thermo Cardiosystems left ventricular assist device complex at rest and during exercise: implications for chronic support

Studies of patients supported with a left ventricular assist device have considered determinants of acute survival emphasizing the role of right heart function. In patients with refractory heart failure awaiting heart transplantation, chronic left ventricular assist device implantation may provide an opportunity for rehabilitation before surgery if hemodynamics are adequate at rest and during activities of daily life. For the assessment of the efficacy of the left ventricular assist device in this setting, four patients in whom the HeartMate pneumatic left ventricular assist device had been implanted were tested during graded supine bicycle exercise with Doppler echocardiography interrogation and central hemodynamic measurements. Patients with left ventricular assist device increased total left ventricular-left ventricular assist device complex output with exercise as Fick cardiac output increased from 5.7 +/- 1.5 to 8.6 +/- 3.1 L/min (mean +/- standard deviation). In two patients, peak left ventricular assist device rate and output were either present at the start of exercise or reached at mid-exercise and were associated with abrupt increases in left ventricular filling pressures (pulmonary capillary wedge pressure = 9 to 27 mm Hg and 12 to 24 mm Hg, respectively). During exercise, left ventricular end-diastolic size and pressure increased as right ventricular dimensions decreased or remained the same (patients 1, 3, and 4: 1.7 to 1.8 cm, 4.7 to 3.9 cm, and 2.6 to 1.8 cm, respectively) despite increased right atrial filling pressures, implying a decrease in functional right ventricular diastolic compliance. Although the left ventricular assist device functioned as a series pump at rest, Fick cardiac output exceeded left ventricular assist device output during exercise consistent with parallel ejection of the left ventricle through the native aortic valve. During exercise, residual left ventricular function may contribute to the hemodynamic response by (1) active filling of the left ventricular assist device to reduce filling time and to overcome left ventricular assist device inflow cannula impedance, (2) augmentation of total cardiac output with parallel ejection out of the native aortic valve, or (3) reduction of ventricular interaction-related changes in functional right ventricular diastolic compliance. When residual left ventricular function is sufficient, hemodynamics with exercise may be limited by peak left ventricular assist device rate. Although right ventricular function may affect acute postoperative survival, residual left ventricular function and peak left ventricular assist device rate may be important determinants of exercise performance during chronic implantation. A preliminary model of factors affecting the "left ventricular-left ventricular assist device complex" performance at rest and during exercise is presented.

Comparison of aerodynamic and electroglottographic parameters in evaluating clinically relevant voicing patterns

The purpose of the present study was to identify one or more aerodynamic or electroglottographic measures that distinguish among voicing patterns that are clinically relevant for nodule pathogenesis and regression: a presumably pathogenic pattern (pressed voice), a neutral pattern (normal voice), and two presumably therapeutic patterns (resonant voice and breathy voice). Trained subjects with normal voices produced several tokens of each voice type on sustained vowels /a/, /i/, and /u/. For each token, maximum flow declination rate, alternating current flow, and minimum flow were obtained from inverse-filtered airflow signals, and closed quotient and closing time were obtained from electroglottographic signals. The results indicate that for /a/ and /i/ (but not for /u/), the closed quotient provides a sensitive tool for distinguishing the voice types in physiologically interpretable directions. Further, post-hoc analyses confirmed a direct relationship between the closed quotient and videoscopic ratings of laryngeal adduction, which previous work links to nodule pathogenesis and regression.