David R. Gross

Induction of Alzheimer-like β-Amyloid Immunoreactivity in the Brains of Rabbits with Dietary Cholesterol

beta-amyloid and ALZ-50 immunocytochemical reactivity were determined in the brains of rabbits fed either a control or 2% cholesterol diet. Control rabbits demonstrated no accumulation of intracellular immunolabeled beta-amyloid within 3 min after death. In animals fed the experimental diet for 4, 6, and 8 weeks (postmortem interval < 3 min), there was an increasingly mild-to-moderate-to-severe accumulation of intracellular immunolabeled beta-amyloid. Whether or not beta-amyloid is causally linked to processes leading to dementia, it is related in some way to the prime cause of human death; heart disease. Hypercholesterolemic rabbits may provide an animal model to study altered beta-APP metabolism leading to Alzheimer-like beta-amyloid accumulation xe03and extracellular deposition in brain.

Minimally Invasive Coronary Artery Bypass Grafting: A New Method Using an Anterior Mediastinotomy

The benefit of internal mammary artery (IMA) grafting as a long‐lasting intervention for coronary artery disease is well recognized. However, largely because they are less invasive, catheter based alternatives are frequently chosen, particularly to treat single or double vessel disease. To retain the advantages of the IMA graft, and to offset the invasiveness of conventional coronary artery bypass grafting, we developed a new minimally invasive method using an anterior mediastinotomy for treating left anterior descending (LAD) or right coronary artery disease, or both. Feasibility studies using 16 pigs and a human cadaver led to approval by the Institutional Review Board for use of this procedure to treat six patients (four men, two women; mean age, 63.8 ± 13.6 [SD] yrs) who granted informed consent. Pedicle dissection of the IMA, using video assisted thoracoscopy if necessary, was made through a 2‐to 3‐inch horizontal anterior mediastinotomy. The underlying LAD artery was grafted during femoral vessel cardiopulmonary bypass, with cooling to 30°C, induced ventricular fibrillation, and left ventricular venting if required. Transesophageal echocardiography performed after bypass showed that two patients maintained normal wall motion and four had improvement from the original impairment. One patient suffered a recurrence of angina 4 weeks after the procedure; recatheterization showed an acutely angled IMA, subsequently corrected by balloon angioplasty. The results of follow‐up dobutamine echocardiographic stress tests were negative in all patients. With this minimally invasive approach, the procedure should provide the benefits of IMA grafting with shorter hospital stay, more rapid recovery, and less overall cost.

Increased density of cortical apolipoprotein E immunoreactive neurons in rabbit brain after dietary administration of cholesterol.

Rabbits were fed 2% cholesterol diet for 4, 6 and 8 weeks or control diet for 6 weeks. Frontal cortex and hippocampal formation were stained with apolipoprotein E (Apo-E) antibody using standard immunocytochemical methods. The number of neurons expressing the Apo-E epitope and the intensity of Apo-E immunoreactivity increased with increasing time on the cholesterol diet. Because Apo-E chaperones cholesterol in the brain, the data may suggest that elevated circulating levels of cholesterol eventually cause increased cerebral levels.

Nω-nitro-L-arginine blocks the second phase but not the first phase of the endothelium-dependent relaxations induced by substance P in isolated rings of pig carotid artery

Summary: Endothelium‐dependent relaxations can be evoked by a variety of stimuli, among them substance P (SP), which is found in sensory nerve fibers supplying the adventitia‐media junction of most muscular arteries. This study determined the role of endothelium‐derived nitric oxide as a mediator of endothelium‐dependent relaxations to SP in isolated rings of the pig carotid artery suspended in organ chambers for isometric tension recording. SP (10−12‐10−7 M) caused concentration‐dependent relaxations of arteries precontracted with norepinephrine (10−7 M). The relaxations were characterized by a partially transient relaxation (phase 1) and a sustained relaxation of the artery (phase 2). The inhibitor of nitric oxide formation, N&ohgr;‐nitro‐L‐arginine (l‐NNA) methyl ester caused a gradual increase in tension, the phase I response at 3 × 10−10 to 3 × 10−7 M SP was shifted to the right, but the maximal relaxation was comparable in the presence of l‐NNA. However, the sustained relaxation after addition of substance P (phase II) was lost and tension in the presence of l‐NNA returned to a level above that induced by l‐NNA and norepinephrine (10−9 M). These results suggest that the endothelium‐dependent relaxations to SP, particularly the prolonged relaxation (phase II), are due to de novo synthesis of nitric oxide and hence fully abolished by a specific inhibitor.

Effectiveness of Community Health Workers in Providing Outreach and Education for Colorectal Cancer Screening in Appalachian Kentucky

The purpose of this study was to examine the effectiveness of a community health worker (CHW)–delivered cancer education program designed to increase knowledge and awareness of colorectal cancer screening options. The study population was an extremely vulnerable and medically underserved geographic region in Appalachian Kentucky. CHWs enrolled participants in face-to-face visits, obtained informed consent, and administered a baseline assessment of knowledge of colorectal cancer risks and the benefits of screening and screening history. An educational intervention was then provided and participants were re-contacted 6 months later when a posttest was administered. The mean score of the 637 participants increased from 4.27 at baseline to 4.57 at follow-up (p < .001). Participants who reported asking their health care provider about colorectal cancer screening increased from 27.6% at baseline to 34.1% at follow-up (p = .013). Results suggest that CHWs were very effective at maintaining the study population; no loss to follow-up occurred. The results also showed increased knowledge and awareness about colorectal cancer screening education. Implications for social work practice, policy and research are discussed.

Substance P induces biphasic endothelium-dependent relaxations in pig and rabbit carotid arteries

Careful handling and preparation of freshly harvested vessels from 22 pigs and 12 rabbits revealed a two-phase vasorelaxation response to cumulative doses of substance P (SP). A rapid, transient relaxation was observed during the cumulative dose-response and a new plateau of equilibrium was seen following an increase in developed force after the last dose of SP. The phase 2 response is also produced by submaximal doses of SP and is not altered by pretreatment of the rings with Indomethacin. Acetylcholine (ACh) caused an endothelium-dependent relaxation but without evidence of a phase 2 plateau. N omega-Nitro-L-Arginine (L-NNA) and N omega-Nitro-L-Arginine Methylester (L-NAME) pretreatment resulted in a shift to the right in the phase 1 response to SP and a complete blockade of phase 2. Methylene blue caused nearly complete block of both phases. Nitroglycerin caused a dose-dependent and prolonged vasorelaxation with no phase 2.

Normal Cardiovascular Parameters from Intact, Awake Animals

In this chapter resting baseline cardiovascular parameter values for the most commonly used species of animal models are tabulated. Sophistication in collecting data from previously instrumented animals has made more of this information available. Only fairly recent publications are used, based upon a greater level of confidence in the reliability of the measurements obtained.

Skeletal muscle microcirculatory response to rat α-calcitonin gene-related peptide

We used in vivo video microscopy to determine the effect of increasing doses of rat alpha-calcitonin gene-related peptide (rCGRP) on rat cremaster muscle arterioles in the presence or absence of the nitric oxide synthase inhibitor N-omega-nitro-L-arginine (L-NNA). Male Sprague-Dawley rats (118-148 g) were anaesthetized with pentobarbital, and neurovascularly intact cremaster muscles were imaged. Changes in the diameter, erythrocyte velocity and volume flow in second-(A2), third-(A3), and fourth-(A4) order arterioles were determined. To produce uniform arteriolar tone, the cremaster preparation was challenged with norepinephrine (NE: 10(-7) M). L-NNA (10(-4) M), which was shown to inhibit acetylcholine-(ACh: 10(-6) M) induced arteriolar dilations, was added to 16 of the preparations. Preparations were then challenged by adding cumulative log concentrations of rCGRP (10(-12)-10-7) M; n = 16) or an equivalent volume of vehicle (n = 19) to the bath. Following rCGRP challenge, arterioles were maximally dilated with 10(-5) M nitroprusside (NP). rCGRP caused significant dose-dependent increases in erythrocyte velocity and volume flow in A2 arterioles, and in diameter, velocity, and volume flow in A3 and A4 arterioles, by 10(-8) M, when compared with vehicle-treated controls. L-NNA had no significant effect on rCGRP-induced responses. These data indicate that rCGRP causes dose-dependent dilation of skeletal muscle resistance arterioles at a concentration similar to that observed in larger vessels. This dilation does not appear to be dependent on the vascular production of nitric oxide from L-arginine.

Development of a minimally invasive technique for coronary revascularization in a porcine model.

BACKGROUND This porcine model was designed to develop a minimally invasive method for internal mammary artery (IMA) grafting using an anterior mediastinal approach and without routine use of cardiopulmonary bypass. METHODS Assessment was made of IMA mobilization through a small parasternal incision, the feasibility of coronary artery grafting with cardiopulmonary bypass using this approach, and conditions for off-pump bypass grafting. RESULTS In group 1, 6 pigs underwent IMA mobilization through a 5-cm horizontal midparasternal incision. Of the 2 group 2 pigs, 1 underwent IMA grafting to the left anterior descending coronary artery and the other, bilateral IMA grafting to the left anterior descending and right coronary arteries using femoral-vessel cardiopulmonary bypass. In group 3, 4 of 10 pigs had successful off-pump grafting during retrograde regional coronary venous perfusion of arterial blood. Retrograde coronary venous perfusion could not be established in the other 6 pigs, and attempts at off-pump grafting failed. CONCLUSIONS The study demonstrates that coronary artery grafting with the IMA by this minimally invasive off-pump method is feasible, although it draws attention to areas of concern and potential methods of correction. The model provides a realistic and important learning platform for the surgical issues involved with this minimally invasive technique.

Coronary vascular and myocardial effects of substance P in hypercholesterolemic rabbits

Age-matched male New Zealand white rabbits (n = 16) were allocated to two groups: group 1 (n = 8) received a standard rabbit diet; group 2 (n = 8) received a 2% cholesterol-enriched diet. After 8 weeks of prescribed diet, hearts were excised and placed on a constant perfusion pressure Langendorff-type apparatus. Coronary flow, left ventricular pressure, and isovolumic dP/dt were continuously measured. Baseline recordings were made and then a single 5 nmol bolus dose of substance P was delivered into the coronary perfusate. Mean serum cholesterol levels in group 1 were 53 +/- 17 (SEM) mg.dl-1, in group 2 1438 +/- 143 mg.dl-1. In group 1, the injection of substance P caused mean coronary flow to increase 39 +/- 6%, mean coronary vascular resistance to decrease 28 +/- 3%, and mean dP/dt to increase 11 +/- 4%. In group 2, coronary flow increased 57 +/- 13%, coronary vascular resistance decreased 33 +/- 5%, and dP/dt increased 17 +/- 4%. Within groups, values changed significantly from baseline but these changes were not significantly different between groups. The duration of coronary flow response was 113 +/- 20 s in group 1 and 63 +/- 8 s in group 2. Substance P is a potent dilator of coronary resistance vessels and has positive inotropic effects in the rabbit. High levels of cholesterol exposure do not alter the magnitude of substance P-induced vasodilation, but the duration of the response is shortened.