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Biomedical subjects

Michael Horowitz

Publications and source records attributed to Michael Horowitz.

At least 55 records · Page 3Linked to original sources
PubMed2005

Hyperthermia and hypermetabolism in focal cerebral ischemia.

The reliable and reproducible creation of an animal model of focal cerebral ischemia is not easily accomplished. Using a transortibal approach, we showed that occlusion of the posterior cerebral artery (PCA), middle cerebral artery (MCA), and the contralateral anterior cerebral artery (ACA) created a large cortical and subcortical stroke in the non-human primate (NHP). Subsequently, we created the same stroke endovascularly in the NHP. Using the endovascular stroke model in the NHP, we measured brain temperature with thermocouples and cerebral blood flow (CBF) by stable xenon CT in one NHP, and CMRO2 and CBF by positron emission tomography (PET) in another NHP. Two female non-human primates (M. mulatta) weighing 7.0 and 8.0 kg, respectively, were studied under fentanyl-diazepam anesthesia with continuous monitoring of arterial blood pressure, rectal temperature, and end-tidal CO2 with intermittent blood gas measurements. Using an endovascular approach, the PCA (P2), MCA (M1), and the ICA at the bifurcation and contralateral ACA produced a large hemispheric stroke. In the right ischemic hemisphere, temperatures increased by 2 degrees C-3 degrees C. PET measurement of CBF and CMRO2 showed that CMRO2 increased in the region of the ischemic stroke. We found that both hyperthermia and hypermetabolism occur in acute stroke.

Animals↗
PubMed2005

Effect of aging on transpyloric flow, gastric emptying, and intragastric distribution in healthy humans--impact on glycemia.

The aims of this study were to evaluate (i) the relationship between transpyloric flow (TF) assessed by Doppler ultrasonography and scintigraphy, (ii) the effects of healthy aging on TF and gastric emptying (GE), and (iii) the relationship between the glycemic response to oral glucose and TF. Ten healthy "young" (7 M, 3 F) and 8 "older" (4 M, 4 F), subjects had simultaneous measurements of TF, GE, and blood glucose after a 600-ml drink (75 g glucose labeled with 20 MBq 99mTc-sulfur colloid) while seated. TF measured by ultrasound was measured during drink ingestion and for 30 min thereafter. GE was measured scintigraphically for 180 min after drink ingestion. Blood glucose was measured before the drink and at regular intervals until 180 min. During drink ingestion, TF was greater (P < 0.05) and GE faster (retention at 60 min: 70.8+/-3.3 vs. 83.8+/-4.6%; P < 0.05) in young compared to older subjects. There was no difference in fasting blood glucose between the two groups but the magnitude of the rise in blood glucose was greater in the young compared to the older subjects; (at 15 min 2.4+/-0.3 vs. 1.5+/-0.5 mmol/L; P < 0.05). In contrast, after 90 min blood glucose concentrations were higher in the older subjects. There were significant relationships between the early blood glucose concentration and both TF (e.g., at 15 min: r = 0.56, P < 0.05) and GE (e.g., at 15 min: r = -0.51, P < 0.05). In conclusion, the results of this study indicate that (i) TF is initially less, and GE slower, in older compared to young subjects; (ii) the initial glycemic response to oral glucose is related to TF; and (iii) measurements of TF by ultrasound and scintigraphy correlate significantly.

Administration, Oral↗
PubMed2005

Radiosurgery for dural arteriovenous fistulas.

OBJECTIVE: Dural arteriovenous fistulas (DAVFs) comprise 10% to 15% of all arteriovenous malformations. Recent studies have demonstrated promising results when radiosurgery is used for DAVFs. We retrospectively analyzed our patients with DAVFs who received stereotactic radiosurgery with or without embolization. METHODS: Between 1991 and 2002, 18 patients with 23 angiographically confirmed symptomatic DAVFs underwent gamma knife radiosurgery, either alone (n = 8) or in combination with embolization (n = 10). A retrospective chart review was performed to identify DAVF location, venous drainage pattern, radiosurgery dosimetry, clinical outcomes, and imaging results. The series included 9 men and 9 women with a mean age of 65 (range 50-89) years. Nine patients received particulate, coil, and/or absolute ethanol embolization before radiosurgery, and 1 patient received particulate embolization after radiosurgery. The mean duration of clinical follow-up was 43 (range 2-116) months. The mean margin radiosurgery dose was 20 (range 15-30) Gy. RESULTS: Nine patients had complete resolution of their presenting symptoms, and 9 patients had resolution of all but 1 of their presenting symptoms. Angiographic follow-up (mean 46 months) was performed on 8 patients demonstrating complete obliteration in all the cases. Seven patients evaluated by magnetic resonance angiography or computed tomography angiography showed no evidence of DAVF (4 patients) or decreased DAVF size (3 patients). After radiosurgery, 1 patient developed a temporary hemiparesis. Two permanent neurological deficits occurred after embolization before radiosurgery. No patient had an intracranial hemorrhage after treatment. CONCLUSION: Stereotactic radiosurgery provides effective long-term relief of symptoms in selected patients with DAVFs.

Aged↗
PubMed2005

New management approaches for gastroparesis.

Management of patients with gastroparesis is challenging. Although the syndrome has multiple causes and knowledge of the pathophysiology and natural history is far from complete, a number of common management principles can be applied. The relatively poor correlation between upper-gastrointestinal symptoms and disordered gastric emptying represents a major difficulty in the therapeutic approach, and evidence to support the efficacy of current management strategies is often suboptimal, especially in relation to long-term therapy. In this review, the common causes and pathophysiology of gastroparesis are summarized, the diagnostic approach considered, and the evidence to support medical and surgical therapies reviewed. These therapies include currently available prokinetic drugs, novel medical therapies, and the promising technique of gastric electrical stimulation.

Botulinum Toxins↗
PubMed2005

Intraduodenal guar attenuates the fall in blood pressure induced by glucose in healthy older adults.

OBJECTIVES: Postprandial hypotension occurs frequently in older people and may result in syncope and falls. It has recently been established that the magnitude of the fall in blood pressure is related to the rate at which glucose enters the small intestine. We addressed the hypothesis that the fall in blood pressure induced by an intraduodenal glucose infusion is influenced by the interaction of glucose with the small intestinal absorptive epithelium. METHODS: Eight healthy older participants (four male, four female, age 70.3 +/- 3.4 years) were studied on two separate occasions, in single-blind, randomized order. Participants received an intraduodenal glucose infusion (3 kcal/min) with or without guar gum (4 g) for 60 minutes (0-60 minutes), followed by 0.9% saline intraduodenally for a further 60 minutes (60-120 minutes). Blood pressure and heart rate were measured every 3 minutes. Levels of blood glucose, plasma insulin, glucagon-like peptide-1 (GLP-1), and glucose-dependant insulinotropic-polypeptide (GIP) were also determined. RESULTS: Between t = 0 and t = 30 minutes, the magnitude of the fall in systolic blood pressure (p =.03) and increase in heart rate (p =.027) were lower after guar. The blood glucose (p =.009), plasma insulin (p =.027), plasma GLP-1 (p =.018), and GIP (p <.001) responses to intraduodenal glucose were attenuated by guar. CONCLUSIONS: In healthy older participants, the magnitude of the fall in systolic blood pressure and increase in heart rate induced by intraduodenal glucose are attenuated when the exposure of glucose to the small intestinal mucosa and subsequent glucose absorption is slowed by guar.

Aged↗
PubMed2005

Effects of small intestinal and gastric glucose administration on the suppression of plasma ghrelin concentrations in healthy older men and women.

OBJECTIVE: Ghrelin is a peptide hormone secreted primarily from the gastric mucosa. It plays a role in energy balance by stimulating appetite, thereby increasing food intake and enhancing weight gain and fat mass deposition. Plasma ghrelin concentrations increase with fasting and are suppressed by nutrient intake. The aim of this study was to examine in humans the relative contributions of small intestinal and gastric nutrient exposure to postprandial suppression of ghrelin, to determine whether gastric exposure is necessary for ghrelin suppression. PATIENTS: Twelve healthy older (age range 65-85 years) men (n = 7) and women (n = 5) were studied. DESIGN: On three separate days, equivolaemic (315 ml) intragastric (IG) and intraduodenal (ID) carbohydrate solutions (both 300 kcal) or intragastric water (control) were infused over 150 min. MEASUREMENTS: Food intake was quantified at a buffet meal offered immediately following each 150-min infusion. Blood ghrelin, cholecystokinin and glucose concentrations were measured. RESULTS: There was a 25% suppression of mean plasma ghrelin concentrations following ID glucose (ID 2016 vs. control 2686 ng/l, P < 0.0001) and a 19% suppression following IG glucose (IG 2181 vs. control 2686 ng/l, P < 0.0001), with ghrelin concentrations slightly (7.6%) and nonsignificantly lower after ID than after IG glucose infusions (P = 0.2). There was no difference between the treatments for the amount of food consumed at the buffet meal (P = 0.88). CONCLUSIONS: Although the primary source of ghrelin is the gastric mucosa, these results suggest that small intestinal nutrient exposure is sufficient for food-induced plasma ghrelin suppression in humans, and that gastric nutrient exposure is not necessary for suppression.

Aged↗
PubMed2005

Relationship between fasting serum glucose, age, body mass index and serum 25 hydroxyvitamin D in postmenopausal women.

OBJECTIVE: Because it has been reported that vitamin D, given to mother or infant, can prevent type I diabetes in children, that diabetes is more common in adults with low serum vitamin D and that insulin secretion and action are related to vitamin D levels in healthy young adults we examined the relationship between serum vitamin D metabolites and fasting serum glucose in patients attending our outpatient clinics. DESIGN: Retrospective examination of convenience sample of postmenopausal women attending our osteoporosis clinics. PATIENTS: A total of 753 postmenopausal women attending a university hospital outpatient clinic and not on any treatment known to affect glucose metabolism. MEASUREMENTS: Body weight and height, serum 25-hydroxyvitamin D [25(OH)D], serum 1,25-dihydroxyvitamin D [1,25(OH)2D], serum PTH and fasting serum glucose. RESULTS: On simple correlation fasting serum glucose was a positive function of age (P < 0.05), weight (P < 0.001) and body mass index (BMI) (P < 0.001) and a negative function of serum 25(OH)D (P < 0.001), but it was not significantly related to either serum 1,25(OH)2D, PTH or creatinine. When fasting serum glucose was regressed simultaneously on age, BMI and 25(OH)D, glucose was still an inverse function of 25(OH)D (P = 0.006). CONCLUSIONS: Fasting serum glucose increased as 25(OH)D levels fell throughout the range of serum 25(OH)D measured but the greatest increase was observed in those with 25(OH)D below 40 nmol/l.

Adult↗
PubMed2005

Emergent basilar artery and bilateral posterior cerebral artery angioplasty, urokinase thrombolysis, and stenting for acute basilar artery occlusion secondary to diagnostic cardiac catheterization: case presentation.

This case presentation describes the use of emergent neurointerventional procedures to revascularize a patient who developed a symptomatic stroke during coronary artery angiography. Rapid identification of a neurologic deficit in the coronary angiography suite and notification of a skilled neurointerventionalist permit for early revascularization and improved patient outcomes.

Acute Disease↗
PubMed2005

Endovascular management of ventricular catheter-induced anterior cerebral artery false aneurysm: technical case report.

OBJECTIVE AND IMPORTANCE: We describe the case of a 3.3-kg infant who developed an anterior cerebral artery pseudoaneurysm after ventricular catheter placement. The lesion was treated with endovascular vessel sacrifice. CLINICAL PRESENTATION: A 3.3-kg infant with a myelomeningocele underwent repair and ventricular catheter insertion for hydrocephalus. During shunt insertion, intracerebral arterial bleeding was encountered. Subsequent arteriography demonstrated an anterior cerebral artery pseudoaneurysm. TECHNIQUE: Via a transfemoral artery approach, the aneurysm and feeding vessel were catheterized with a microcatheter and wire. The aneurysm and vessel were then sacrificed with detachable platinum coils. CONCLUSION: Arterial injury is uncommon after ventricular catheter placement. When it does occur, however, an unstable pseudoaneurysm may form. Endovascular techniques can be used to remedy this problem, thus at times obviating the need for a standard craniotomy, which can be particularly difficult in a newborn.

Angiography↗
PubMed2005

Periprocedural morbidity and mortality associated with endovascular treatment of intracranial aneurysms.

BACKGROUND AND PURPOSE: Despite experience and technological improvements, endovascular treatment of intracranial aneurysms still has inherent risks. We evaluated cerebral complications associated with this treatment. METHODS: From October 1998 to October 2002, 180 consecutive patients underwent 131 procedures for 118 ruptured aneurysms and 79 procedures for 72 unruptured aneurysms. We retrospectively reviewed their records and images to evaluate their morbidity and mortality. RESULTS: Thirty-seven (17.6%) procedure-related complications occurred: 27 and six with initial embolization of ruptured and unruptured aneurysms, respectively, and four with re-treatment. Complications included 22 cerebral thromboembolisms, nine intraprocedural aneurysm perforations, two coil migrations, two parent vessel injuries, one postprocedural aneurysm rupture, and one cranial nerve palsy. Fourteen complications had no neurologic consequence. Three caused transient neurologic morbidity; 10, persistent neurologic morbidity; and 10, death. Procedure-related neurologic morbidity and mortality rates, respectively, were as follows: overall, 4.8% and 4.8%; ruptured aneurysms, 5.9% and 7.6%; unruptured aneurysms, 1.4% and 1.4%; and re-treated aneurysms, 10% and 0%. Combined procedure-related morbidity and mortality rates for ruptured, unruptured, and re-treated aneurysms were 13.5%, 2.8%, and 10%, respectively. Nonprocedural complications attributable to subarachnoid hemorrhage in 118 patients with ruptured aneurysm were early rebleeding before coil placement (0.9%), symptomatic vasospasm (5.9%), and shunt-dependent hydrocephalus (5.9%); mortality from complications of subarachnoid hemorrhage itself was 11.9%. CONCLUSION: Procedural morbidity and mortality rates were highest in ruptured aneurysms and lowest in unruptured aneurysms. Morbidity rates were highest in re-treated aneurysms and lowest in unruptured aneurysms. No procedural mortality occurred with re-treated aneurysms. The main cause of morbidity and mortality was thromboembolism.

Adult↗
PubMed2004

Effects of intraduodenal fatty acids on appetite, antropyloroduodenal motility, and plasma CCK and GLP-1 in humans vary with their chain length.

The gastrointestinal effects of intraluminal fats may be critically dependent on the chain length of fatty acids released during lipolysis. We postulated that intraduodenal administration of lauric acid (12 carbon atoms; C12) would suppress appetite, modulate antropyloroduodenal pressure waves (PWs), and stimulate the release of cholecystokinin (CCK) and glucagon-like peptide-1 (GLP-1) more than an identical dose of decanoic acid (10 carbon atoms; C10). Eight healthy males (19-47 yr old) were studied on three occasions in a double-blind, randomized fashion. Appetite perceptions, antropyloroduodenal PWs, and plasma CCK and GLP-1 concentrations were measured during a 90-min intraduodenal infusion of 1) C12, 2) C10, or 3) control (rate: 2 ml/min, 0.375 kcal/min for C12/C10). Energy intake at a buffet meal, immediately after completion of the infusion, was also quantified. C12, but not C10, suppressed appetite perceptions (P < 0.001) and energy intake (control: 4,604 +/- 464 kJ, C10: 4,109 +/- 588 kJ, and C12: 1,747 +/- 632 kJ; P < 0.001, C12 vs. control/C10). C12, but not C10, also induced nausea (P < 0.001). C12 stimulated basal pyloric pressures and isolated pyloric PWs and suppressed antral and duodenal PWs compared with control (P < 0.05 for all). C10 transiently stimulated isolated pyloric PWs (P = 0.001) and had no effect on antral PWs but markedly stimulated duodenal PWs (P = 0.004). C12 and C10 increased plasma CCK (P < 0.001), but the effect of C12 was substantially greater (P = 0.001); C12 stimulated GLP-1 (P < 0.05), whereas C10 did not. In conclusion, there are major differences in the effects of intraduodenal C12 and C10, administered at 0.375 kcal/min, on appetite, energy intake, antropyloroduodenal PWs, and gut hormone release in humans.

Adult↗
PubMed2004

Relationships of ratings of appetite to food intake in healthy older men and women.

The aim of this study was to determine how rated appetite relates to the amount eaten in a meal in healthy older people. On two study days, 32 healthy older men (n = 16) and women (n = 16) aged 65-85 years, recruited by advertisement, consumed a standardised breakfast and 4 h later were offered lunch from which they could eat freely. Foods eaten at lunch were weighed and energy intake calculated from nutrient composition data. Appetite was assessed at baseline and at 30-min intervals between meals by line ratings of hunger, fullness, nausea and how much could be eaten. The optimum time for correlations both among appetite ratings and between appetite and lunch intake was just before the lunch. Mean coefficients of repeatability (21-38 mm) and correlation coefficients (0.67-0.71) at that point in time were similar to those reported previously in young adults. Thus, in older and well as young adults, the size of a meal is most closely related to rated appetite just before the meal.

Aged↗
PubMed2004

Giant cell tumor of the skull: a case report and review of the literature.

BACKGROUND: Giant cell tumors are benign lesions that typically occur at the epiphyses of long bones that typically present with pain or swelling. Most data on giant cell tumors in the skull consist of case reports, and many large series of giant cell tumors have no examples in the skull. METHODS: We report a case of giant cell tumor of the skull and review the literature on these lesions. RESULTS: A 24-year-old woman presented with localized tenderness and mild swelling over the left inferior parietal and occipital bones. She was neurologically intact with a nonmobile, tender, palpable mass over the left subocciptal area. A computed tomography (CT) scan showed a radiolucent, expansile, lytic lesion involving the left occipital bone. The patient underwent a left occipital craniectomy with resection of the bone and epidural mass. Permanent histopathologic sections and immunostains revealed a giant cell tumor. CONCLUSIONS: Giant cell tumors are generally benign, locally aggressive lesions for which surgical excision is the treatment of choice. This report contributes to the scarce literature on these tumors in the skull.

Adult↗
PubMed2004

Blood pressure responses in healthy older people to 50 g carbohydrate drinks with differing glycaemic effects.

The aim of the present study was to determine the effects on blood pressure response of 50 g carbohydrate drinks with differing glycaemic effects in ten healthy elderly subjects (age > 65 years; randomized crossover design). Systolic (SBP), diastolic (DBP) and mean arterial (MAP) blood pressure, heart rate and plasma glucose levels were determined following ingestion of equal volumes (379 ml) of water and 50 g carbohydrate drinks with differing reported glycaemic indices (GI) (surrogate marker for glycaemic effect): (1) low-GI: Apple & Cherry Juice; (2) intermediate-GI: Fanta Orange; (3) high-glucose. Glucose (SBP and DBP P < 0.001; MAP P = 0.005) and Fanta Orange (SBP P = 0.005; DBP and MAP P < 0.001) ingestion caused a significant decrease in BP whilst blood pressure increased (SBP P = 0.008; MAP P = 0.005) from baseline following Apple & Cherry Juice ingestion. Water had no significant effect on postprandial blood pressure. Fanta Orange and Apple & Cherry Juice caused similar (P = 0.679) glycaemic effects, which were significantly greater than water, but lower than glucose (P < 0.001). There was no significant correlation between the glycaemic effect of the carbohydrate drinks and there was no change in blood pressure from baseline (SBP r - 0.123, P = 0.509; DBP r - 0.051, P = 0.784; MAP r - 0.069, P = 0.712). Apple & Cherry Juice and Fanta Orange had similar glycaemic effects, but differing effects on blood pressure. Therefore, it is unlikely that the glycaemic effect of a drink can be used to predict the subsequent cardiovascular response.

Aged↗
PubMed2004

Energy intake and appetite are related to antral area in healthy young and older subjects.

BACKGROUND: Gastric distension reduces food intake, and antral, rather than proximal, gastric distension may be the dominant mechanism in the induction of appetite-related sensations. Healthy aging is associated with reduced appetite. OBJECTIVE: We examined the effects of different energy preloads on appetite, plasma cholecystokinin, antral area, and subsequent energy intake in healthy older and young subjects. DESIGN: On 3 separate days, 12 young and 12 older subjects consumed 400 mL of a drink containing either 0 kcal (water), 250 kcal, or 750 kcal 70 min before a buffet-style meal. RESULTS: Hunger was less in the older than in the young subjects (P < 0.001). Both nutrient preloads reduced hunger and increased fullness more than did water (P < 0.02), and older subjects were more full than were the young (P < 0.05). Antral area was greater after the nutrient preloads than after water (P = 0.001) and greater in the older than in the young subjects (P = 0.005). In both groups, food intake was suppressed in an energy-dependent manner (P = 0.008). Plasma cholecystokinin was greater in the older than in the young subjects (P = 0.003). Immediately before the meal, hunger (r = -0.59) and energy intake (r = -0.90) were inversely related and fullness (r = 0.66) was directly related to antral area (all: P < 0.001). Antral area, but not plasma cholecystokinin, was a predictor of subsequent energy intake. CONCLUSION: In healthy young and older subjects, the suppression of subsequent energy intake by a liquid preload is nutrient dependent and comparable, and both satiation and satiety are related to antral area and (presumably) antral distension.

Adolescent↗
PubMed2004

Effect of age on calcium absorption in postmenopausal women.

BACKGROUND: It is assumed that calcium absorption decreases with age, but this is not well documented. We report a study that addresses this issue. OBJECTIVE: The aim was to establish the extent and timing of any age-related change in calcium absorption in postmenopausal women. DESIGN: We measured radiocalcium absorption (alpha) in 262 healthy postmenopausal women aged 40-87 y. We also measured the serum vitamin D metabolites, parathyroid hormone (PTH), and other biochemical variables. RESULTS: Radiocalcium absorption decreased with age (P = 0.018); it was 28% lower in the 25 women aged >75 y than in the rest (P < 0.001). It was significantly related to serum 1,25-dihydroxyvitamin D [1,25(OH)(2)D] in the whole set and in both the younger and older subsets, but it was not related to either 25-dihydroxyvitamin D [25(OH)D] or PTH or to any other measured variable. No decrease in 1,25(OH)(2)D was seen with age to account for the decrease in calcium absorption, so radiocalcium absorption corrected for serum 1,25(OH)(2)D decreased significantly after age 75 y. On multivariate analysis, the serum 1,25(OH)(2)D concentration was a positive function of 25(OH)D (P < 0.001), albumin (P = 0.010), and PTH (P = 0.012) and a negative function of serum creatinine (P = 0.003). PTH was a negative function of calculated ionized calcium (P = 0.004) and 25(OH)D (P = 0.009) and a positive function of weight (P = 0.011) and age (P = 0.028). CONCLUSIONS: A late age-related decrease in calcium absorption is seen in postmenopausal women in addition to the decline that occurs at menopause. This decrease could be due to a decline in either the active calcium transport or diffusion component of the calcium absorption system.

Adult↗