Biomedical subjects

D Franceschi

Publications and source records attributed to D Franceschi.

At least 19 recordsLinked to original sources

PubMed2005

Gastric carcinoids: a temporal increase with proton pump introduction.

BACKGROUND: Recent reports have indicated a rising incidence of gastric carcinoids. This study aimed to evaluate the incidence pattern of gastric carcinoids in two large population-based cancer registries. METHODS: The Florida Cancer Data System (FCDS), Florida's statewide cancer registry, and the Surveillance, Epidemiology, and End Results (SEER) program were used. The study population was defined as all cases of gastric carcinoid identified in either database from January 1981 to December 2000. Descriptive statistics and age-adjusted incidence rates were calculated. RESULTS: There were 326 (FCDS) and 594 (SEER) cases of invasive gastric carcinoid during the 20-year study period. The mean age of the patients was 65 years (range, 21-96 years), and the male:female ratio was 1:1. The age-adjusted incidence rate in FCDS increased from 0.04 (per 100,000 age-adjusted to the 2000 U.S. standard population) to 0.18 in the year 2000. The estimated annual percentage change in incidence was 8.17 in FCDS and 9.17 in SEER (p < 0.05). A decrease in gastric cancer was noted during this same period (from 8.64 to 11.14 cases per 100,000 in FCDS and from 11.14 to 8.06 cases per 100,000 in SEER). CONCLUSIONS: This study documented a statistically significant eight- or ninefold increase in the incidence of gastric carcinoids in two large databases. The temporal increase in incidence correlates with the introduction and widespread use of proton pump inhibitors since the late 1980s. Other explanations include improved detection with wider application of upper endoscopy. Further epidemiologic studies are warranted.

Adult↗

PubMed2004

Esophageal carcinoma: current controversial topics.

Worldwide, esophageal carcinoma is a common gastrointestinal cancer with a high mortality. The incidence of adenocarcinoma of the esophagus is increasing in the western world, but squamous cell carcinoma remains dominant in the underdeveloped parts of the world. Both types of esophageal carcinoma remain equally virulent. Currently, there are no optimal preventative screening programs available and most patients present with advanced or metastatic disease. Although many options are available for improving diagnostic accuracy, a single method has not displayed significant advantages over the others. In addition, selecting a superior treatment regimen has not surfaced. Preferred resection techniques exist, but one method has not illustrated improvements in survival over the others. A lack of improved survival rates with single modality therapies has led to a multi modality approach. However, developments in neoadjuvant and adjuvant therapies have led to mixed conclusions. Collectively, past studies have not shown an optimal neoadjuvant or adjuvant regimen in terms of survival benefit. This review highlights existing staging modalities and treatment regimens for esophageal carcinoma, in an effort to illustrate the controversial nature surrounding its management.

Antineoplastic Agents↗

PubMed2001

Loss of dopamine transporters in methamphetamine abusers recovers with protracted abstinence.

Methamphetamine is a popular drug of abuse that is neurotoxic to dopamine (DA) terminals when administered to laboratory animals. Studies in methamphetamine abusers have also documented significant loss of DA transporters (used as markers of the DA terminal) that are associated with slower motor function and decreased memory. The extent to which the loss of DA transporters predisposes methamphetamine abusers to neurodegenerative disorders such as Parkinsonism is unclear and may depend in part on the degree of recovery. Here we assessed the effects of protracted abstinence on the loss of DA transporters in striatum, in methamphetamine abusers using positron emission tomography and [(11)C]d-threo-methylphenidate (DA transporter radioligand). Brain DA transporters in five methamphetamine abusers evaluated during short abstinence (<6 months) and then retested during protracted abstinence (12-17 months) showed significant increases with protracted abstinence (caudate, +19%; putamen, +16%). Although performance in some of the tests for which we observed an association with DA transporters showed some improvement, this effect was not significant. The DA transporter increases with abstinence could indicate that methamphetamine-induced DA transporter loss reflects temporary adaptive changes (i.e., downregulation), that the loss reflects DA terminal damage but that terminals can recover, or that remaining viable terminals increase synaptic arborization. Because neuropsychological tests did not improve to the same extent, this suggests that the increase of the DA transporters was not sufficient for complete function recovery. These findings have treatment implications because they suggest that protracted abstinence may reverse some of methamphetamine-induced alterations in brain DA terminals.

Adult↗

PubMed2001

Evidence that L-deprenyl treatment for one week does not inhibit MAO A or the dopamine transporter in the human brain.

In this study, we investigated whether treatment with L-deprenyl, a selective monoamine oxidase B (MAO B) inhibitor, also inhibits MAO A or the dopamine transporter in the human brain. Six normal volunteers (age 46+/-6 yrs) had two PET sessions, one at baseline and one following L-deprenyl (10 mg/day) for 1 week. Each session included one scan with [11C]clorgyline (to assess MAO A) and one scan 2 hours later with [11C]cocaine (to assess dopamine transporter availability). A 3-compartment model was used to compare the plasma-to-brain transfer constant, K1 (a function of blood flow) and lambdak3 (a kinetic term proportional to brain MAO A) before and after treatment. Dopamine transporter availability was measured as the ratio of distribution volumes of the striatum to cerebellum (DVR) which is equal to Bmax/KD +1. L-Deprenyl treatment for 1 week did not affect either brain MAO A activity or dopamine transporter availability. There was a non-significant trend for an increase in K1 after L-deprenyl. These results confirm that L-deprenyl after one week of treatment at doses typically used clinically is selective for MAO B and that it does not produce a measurable affect on the dopamine transporter, suggesting that MAO A inhibition and dopamine transporter blockade do not contribute to its pharmacological effects.

Adult↗

PubMed2001

Influence of Hispanic ethnicity on outcome after resection of carcinoma of the head of the pancreas.

BACKGROUND: Poor outcomes in Hispanic patients have been reported for tumors at a number of sites. The authors sought to determine whether a similar phenomenon occurs in Hispanics after the resection of solid epithelial tumors of the head of the pancreas. METHODS: Between 1983-1995, 273 patients with noncystic epithelial carcinoma of the head of the pancreas were evaluated. Resection was accomplished in 104 patients (38%); these patients were the focus of the current retrospective review. Of the patients who underwent resection, 26 (25%) were Hispanic and 78 (75%) were non-Hispanic. RESULTS: Although Hispanic patients tended to present at a significantly younger age and their serum bilirubin level was significantly higher, no other differences in clinical characteristics were observed. After resection, Hispanic patients had a median survival of only 11.4 months, whereas the non-Hispanic group had a median survival of 21.7 months (P = 0.009). Hispanic ethnicity, as well as age > 74 years and jaundice at the time of presentation also were found to be significant prognostic factors on multivariate analysis. Hispanic patients did not present with more advanced disease and no delays in assessment by a physician or in proceeding to surgery were observed. Furthermore, the rate of resection was the same in Hispanic patients and non-Hispanic patients. Long-term survival after palliative bypass was similarly worse in the Hispanic subgroup. CONCLUSIONS: Hispanic patients treated at the study center appeared to have a diminished survival after resection of a tumor of the head of the pancreas. No treatment-related factors were identified that could explain this discrepancy in outcome.

Aged↗

PubMed2001

Breast carcinoma presents a decade earlier in Mexican women than in women in the United States or European countries.

BACKGROUND: In Mexico, breast carcinoma is the second most frequent malignancy, representing 10.6% of all cases and 16.4% of all cancers in women, with an increase in breast carcinoma mortality rates from 3.6 per 100,000 women in 1985 to 6 per 100,000 women in 1994. Most of the tumors are diagnosed in advanced stages with little chance of cure. METHODS: To determine the age of patients in Mexico at presentation of breast carcinoma, the authors analyzed the cases registered from 1993 to 1996 from the database of the Histopathological Registry of Malignant Neoplasms in Mexico. RESULTS: There were 29,075 cases of breast carcinoma. The median age of Mexican women with breast carcinoma is 51 years, and 45.5% of all breast carcinomas develop before patients reach age 50 years. The most frequently affected age group is that of 40-49 years (29.5%), whereas the groups from 30 to 39 and from 60 to 69 years of age have a similar percentage (14%) of frequency. This contrasts with women from the United States, as well as with women from European countries, where the median age at presentation is 63 years, and only one-fourth of the patients are younger than 50 years of age, and three-fourths are postmenopausal. Similar to Mexico, in Venezuela and in Japan nearly one-half of women with breast carcinoma are younger than 50 years of age, and this resembles rates in many Latin American countries. CONCLUSIONS: It is necessary to change the guidelines of breast carcinoma screening in Mexican women, to increase the possibility of early diagnosis and better survival.

Adult↗

PubMed2001

Therapeutic doses of oral methylphenidate significantly increase extracellular dopamine in the human brain.

Methylphenidate (Ritalin) is the most commonly prescribed psychoactive drug in children for the treatment of attention deficit hyperactivity disorder (ADHD), yet the mechanisms responsible for its therapeutic effects are poorly understood. Whereas methylphenidate blocks the dopamine transporter (main mechanism for removal of extracellular dopamine), it is unclear whether at doses used therapeutically it significantly changes extracellular dopamine (DA) concentration. Here we used positron emission tomography and [(11)C]raclopride (D2 receptor radioligand that competes with endogenous DA for binding to the receptor) to evaluate whether oral methylphenidate changes extracellular DA in the human brain in 11 healthy controls. We showed that oral methylphenidate (average dose 0.8 +/- 0.11 mg/kg) significantly increased extracellular DA in brain, as evidenced by a significant reduction in B(max)/K(d) (measure of D2 receptor availability) in striatum (20 +/- 12%; p < 0.0005). These results provide direct evidence that oral methylphenidate at doses within the therapeutic range significantly increases extracellular DA in human brain. This result coupled with recent findings of increased dopamine transporters in ADHD patients (which is expected to result in reductions in extracellular DA) provides a mechanistic framework for the therapeutic efficacy of methylphenidate. The increase in DA caused by the blockade of dopamine transporters by methylphenidate predominantly reflects an amplification of spontaneously released DA, which in turn is responsive to environmental stimulation. Because DA decreases background firing rates and increases signal-to-noise in target neurons, we postulate that the amplification of weak DA signals in subjects with ADHD by methylphenidate would enhance task-specific signaling, improving attention and decreasing distractibility. Alternatively methylphenidate-induced increases in DA, a neurotransmitter involved with motivation and reward, could enhance the salience of the task facilitating the "interest that it elicits" and thus improving performance.

Administration, Oral↗

PubMed2001

Diminished benefit from resection of cancer of the head of the pancreas in patients of advanced age.

BACKGROUND AND OBJECTIVES: The incidence of pancreatic cancer is increasing, and an increasing proportion of these patients is older than 65 years. The benefits of resection in the geriatric population, in whom major comorbidity is more likely, are poorly defined. The authors sought to determine the relative benefits of resection of cancer of the head of the pancreas in different age groups, with particular emphasis on the geriatric population. METHODS: Between 1983 and 1995, 273 patients presented to the University of Miami for evaluation of noncystic epithelial cancer of the head of the pancreas. Resection was performed in 104 patients, and these patients are the subject of this retrospective review. Mean length of follow-up for surviving patients was 37 +/- 24 months. Outcomes were compared in patients < 65 years old (group 1, n = 38), 65-74 years old (group 2, n = 47), and > 74 years old (group 3, n = 19). RESULTS: Total pancreatectomy was performed in 12 patients and pancreaticoduodenectomy was performed in 92 patients. The overall complication rate was similar in all groups, but major morbidity was highest in group 3 (P = 0.05). Median survival for patients in group 2 was 25.1 months. Survival was significantly shorter in patients from groups 1 and 3 (median survivals 12.4 months and 11.4 months, respectively; P = 0.02). Following control for Hispanic ethnicity, which was also a significant prognostic factor on univariate analysis, only the oldest age group had a significantly shorter survival than the other two groups. Age > 74 years and Hispanic ethnicity remained significant after multivariate analysis. CONCLUSIONS: Long-term survival after resection is truncated in older patients. This finding and the observation that the major complication rate is higher in the older subgroup emphasize the need to evaluate critically whether older patients should be submitted to radical resection.

Age Factors↗

PubMed2001

Non-MAO A binding of clorgyline in white matter in human brain.

Clorgyline is an irreversible inhibitor of monoamine oxidase (MAO A) which has been labeled with carbon-11 (C-11) and used to measure human brain MAO A with positron emission tomography (PET). In this study we compared [11C]clorgyline and deuterium-substituted [11C]clorgyline ([11C]clorgyline-D2) to better understand the molecular link between [11C]clorgyline binding and MAO A. In PET studies of five normal healthy volunteers scanned with [11C]clorgyline and [11C]clorgyline-D2 2 h apart, deuterium substitution generally produced the expected reductions in the brain uptake of [11C]clorgyline. However, the reduction was not uniform with the C-11 binding in white matter being significantly less sensitive to deuterium substitution than other brain regions. The percentages of the total binding attributable to MAO A is largest for the thalamus and smallest for the white matter and this is clearly seen in PET images with [11C]clorgyline-D2. Thus deuterium-substituted [11C]clorgyline selectively reduces the MAO A binding component of clorgyline in the human brain revealing non-MAO A binding which is most apparent in the white matter. The characterization of the non-MAO A binding component of this widely used MAO A inhibitor merits further investigation.

Adult↗

PubMed2001

Low level of brain dopamine D2 receptors in methamphetamine abusers: association with metabolism in the orbitofrontal cortex.

OBJECTIVE: The role of dopamine in the addictive process (loss of control and compulsive drug intake) is poorly understood. A consistent finding in drug-addicted subjects is a lower level of dopamine D2 receptors. In cocaine abusers, low levels of D2 receptors are associated with a lower level of metabolism in the orbitofrontal cortex. Because the orbitofrontal cortex is associated with compulsive behaviors, its disruption may contribute to compulsive drug intake in addicted subjects. This study explored whether a similar association occurs in methamphetamine abusers. METHOD: Fifteen methamphetamine abusers and 20 non-drug-abusing comparison subjects were studied with positron emission tomography (PET) and [11C]raclopride to assess the availability of dopamine D2 receptors and with [18F]fluorodeoxyglucose to assess regional brain glucose metabolism, a marker of brain function. RESULTS: Methamphetamine abusers had a significantly lower level of D2 receptor availability than comparison subjects (a difference of 16% in the caudate and 10% in the putamen). D2 receptor availability was associated with metabolic rate in the orbitofrontal cortex in abusers and in comparison subjects. CONCLUSIONS: Lower levels of dopamine D2 receptor availability have been previously reported in cocaine abusers, alcoholics, and heroine abusers. This study extends this finding to methamphetamine abusers. The association between level of dopamine D2 receptors and metabolism in the orbitofrontal cortex in methamphetamine abusers, which replicates previous findings in cocaine abusers, suggests that D2 receptor-mediated dysregulation of the orbitofrontal cortex could underlie a common mechanism for loss of control and compulsive drug intake in drug-addicted subjects.

Adult↗

PubMed2001

Association of dopamine transporter reduction with psychomotor impairment in methamphetamine abusers.

OBJECTIVE: Methamphetamine is a popular and highly addictive drug of abuse that has raised concerns because it has been shown in laboratory animals to be neurotoxic to dopamine terminals. The authors evaluated if similar changes occur in humans and assessed if they were functionally significant. METHOD: Positron emission tomography scans following administration of [(11)C]d-threo-methylphenidate (a dopamine transporter ligand) measured dopamine transporter levels (a marker of dopamine cell terminals) in the brains of 15 detoxified methamphetamine abusers and 18 comparison subjects. Neuropsychological tests were also performed to assess motor and cognitive function. RESULTS: Methamphetamine abusers showed significant dopamine transporter reduction in the striatum (mean differences of 27.8% in the caudate and 21.1% in the putamen) relative to the comparison subjects; this reduction was evident even in abusers who had been detoxified for at least 11 months. Dopamine transporter reduction was associated with motor slowing and memory impairment. CONCLUSIONS: These results provide evidence that methamphetamine at dose levels taken by human abusers of the drug leads to dopamine transporter reduction that is associated with motor and cognitive impairment. These results emphasize the urgency of alerting clinicians and the public of the long-term changes that methamphetamine can induce in the human brain.

Adult↗

PubMed2001

Higher cortical and lower subcortical metabolism in detoxified methamphetamine abusers.

OBJECTIVE: Methamphetamine has raised concerns because it may be neurotoxic to the human brain. Although prior work has focused primarily on the effects of methamphetamine on dopamine cells, there is evidence that other neuronal types are affected. The authors measured regional brain glucose metabolism, which serves as a marker of brain function, to assess if there is evidence of functional changes in methamphetamine abusers in regions other than those innervated by dopamine cells. METHOD: Fifteen detoxified methamphetamine abusers and 21 comparison subjects underwent positron emission tomography following administration of [(18)F]fluorodeoxyglucose. RESULTS: Whole brain metabolism in the methamphetamine abusers was 14% higher than that of comparison subjects; the differences were most accentuated in the parietal cortex (20%). After normalization for whole brain metabolism, methamphetamine abusers exhibited significantly lower metabolism in the thalamus (17% difference) and striatum (where the differences were larger for the caudate [12%] than for the putamen [6%]). Statistical parametric mapping analyses corroborated these findings, revealing higher metabolism in the parietal cortex and lower metabolism in the thalamus and striatum of methamphetamine abusers. CONCLUSIONS: The fact that the parietal cortex is a region devoid of any significant dopaminergic innervation suggests that the higher metabolism seen in this region in the methamphetamine abusers is the result of methamphetamine effects in circuits other than those modulated by dopamine. In addition, the lower metabolism in the striatum and thalamus (major outputs of dopamine signals into the cortex) is likely to reflect the functional consequence of methamphetamine in dopaminergic circuits. These results provide evidence that, in humans, methamphetamine abuse results in changes in function of dopamine- and nondopamine-innervated brain regions.

Adult↗

PubMed2001

Benign and solid tumors of the liver: relationship to sex, age, size of tumors, and outcome.

From 1983 through 1997, our center diagnosed 130 cases of benign neoplasms: 27 with focal nodular hyperplasia (FNH), 25 with hepatic adenoma, 71 with cavernous hemangioma, and seven with mixed tumors of different diagnoses. Most often these lesions were seen in females [female-to-male ratio (f/m): 5.5/1]. Hepatic adenomas and mixed tumors were seen exclusively in females and FNH predominantly in females (f/m: 26/1). Hemangiomas, however, were not uncommon in men (f/m: 52/19) relative to the other tumors (P < 0.001). Furthermore patients with hemangioma were older (mean age: 49 years) whereas patients with hepatic adenoma, FNH, and mixed tumors were often younger (mean age: 33, 35, and 44 years respectively; P < 0.004). Oral contraceptive steroid use was related by 21 of 25 patients (84%) with hepatic adenoma, 22 of 26 (85%) females with FNH, five of seven (71%) females with mixed tumors, and 10 of 52 (19%) patients with hemangioma. Ninety-five of the 130 patients (73%) had one or more symptoms. There was no statistically significant correlation between symptoms and the size of the lesion, the final diagnosis, and whether there were solitary or multiple masses. Three of 25 (12%) with hepatic adenoma presented with rupture, and one of 27 (4%) with FNH had such a consequence. None of the hemangiomas presented with rupture or progressed to such a state. One patient with hepatic adenoma (4%) had a focus of malignancy. Surgical removal of benign tumors was performed in 82 of 130 patients (63%), and there was one operative mortality (1.2%) in a patient who had a caudate lobe FNH. The types of surgical procedures included segmentectomy (62%), lobectomy (34%), and trisegmentectomy (4%). In two of 84 patients who had undergone laparotomy resection was not technically possible. Resection is recommended in all cases of hepatic adenoma because of fear of rupture or associated focus of malignancy. FNH was not observed to undergo a malignant transformation and will rarely rupture. Surgery is only recommended for symptomatic hemangioma, and size of the lesion is not a criterion for excision.

Adenoma, Liver Cell↗

PubMed2001

Neoadjuvant therapy for esophageal cancer: standard of care or elusive myth?

Although surgical resection as the sole treatment modality for esophageal carcinoma has historically been associated with poor survival rates, improvements have recently been reported using varied neoadjuvant chemo-radiation protocols. This study evaluates the outcome of patients undergoing surgery for esophageal carcinoma at the University of Miami/Jackson Memorial Hospital between July 1991 and June 1996. Seventy-two patients underwent esophageal resection; 51 males and 21 females with a median age of 62.5 years (range = 42-82). Histology was equally distributed between adenocarcinoma (36 patients; 50%) and squamous cell carcinoma (36 patients; 50%). Pathological stage distribution consisted of 6 stage 0 (8%), 10 stage I (14%), 23 stage II (32%), 31 stage III (43%), and 2 stage IV (3%) lesions. Patients were divided into three groups according to the type of preoperative treatment; Group 1 (n = 44); surgery alone; Group 2 (n = 18); neoadjuvant 5-fluorouracil based chemotherapy, and Group 3 (n = 9); neoadjuvant 5-fluorouracil based chemotherapy in conjunction with external beam radiation (XRT). One patient received preoperative XRT alone. All survivors were followed for a minimum of 1 year and statistical analysis was performed using Kaplan-Meier curves, log-rank, and chi-square tests. In the 28 patients receiving any form of neoadjuvant therapy only one patient had a pathological complete response (CR) (3.5%). The overall 5 year and median survival rates were 18 per cent and 20.5 months (range = 0-73), respectively. Individual treatment group survival rates at 5 years were 28% for Group 1; 21% for Group 2; and 0% for Group 3, showing no survival difference between Groups 1 and 2; Group 3 fared significantly worse than the other two, probably as a result of the high operative mortality in this group. These results indicate that surgical resection continues to be an important treatment modality for esophageal carcinoma. Neoadjuvant chemotherapy in our experience failed to improve these survival rates and pre-operative chemoradiation was associated with a high perioperative mortality rate. Chemotherapy regimens with higher CRs may further improve these survival rates.

Adenocarcinoma↗

PubMed2000

Effects of route of administration on cocaine induced dopamine transporter blockade in the human brain.

The route of administration influences the reinforcing effects of cocaine. Here we assessed whether there were differences in the efficacy of cocaine to block the dopamine transporters (major target for cocaine's reinforcing effects), as a function of route of administration. Positron emission tomography and [11C]cocaine, a dopamine transporter radioligand, were used to compare the levels of dopamine transporter blockade induced by intravenous, smoked and intranasal cocaine in 32 current cocaine abusers. In parallel, the temporal course for the self-reports of "high" were obtained. Cocaine significantly blocked dopamine transporters. The levels of blockade were comparable across all routes of administration and a dose effect was observed for intravenous and intranasal cocaine but not for smoked cocaine. For equivalent levels of cocaine in plasma and DAT blockade, smoked cocaine induced significantly greater self reports of "high" than intranasal cocaine and showed a trend for a greater effect than intravenous cocaine. The time to reach peak subjective was significantly faster for smoked (1.4+/-0.5 min) than for intravenous cocaine (3.1+/-0.9 min), which was faster than intranasal cocaine (14.6+/-8 min). Differences in the reinforcing effects of cocaine as a function of the route of administration are not due to differences in the efficacy of cocaine to block the dopamine transporters. The faster time course for the subjective effects for smoked than intravenous and for intravenous than for intranasal cocaine highlights the importance of the speed of cocaine's delivery into the brain on its reinforcing effects.

Administration, Inhalation↗

PubMed2000

Cocaine abusers show a blunted response to alcohol intoxication in limbic brain regions.

UNLABELLED: Cocaine and alcohol are frequently used simultaneously and this combination is associated with enhanced toxicity. We recently showed that active cocaine abusers have a markedly enhanced sensitivity to benzodiazepines. Because both benzodiazepines and alcohol facilitate GABAergic neurotransmission we questioned whether cocaine abusers would also have an enhanced sensitivity to alcohol that could contribute to the toxicity. In this study we compared the effects of alcohol (0.75 g/kg) on regional brain glucose metabolism between cocaine abusers (n = 9) and controls (n = 10) using PET and FDG. Alcohol significantly decreased whole brain metabolism and this effect was greater in controls (26+/-6%) than in abusers (17+/-10%) even though they had equivalent levels of alcohol in plasma. Analysis of the regional measures showed that cocaine abusers had a blunted response to alcohol in limbic regions, cingulate gyrus, medial frontal and orbitofrontal cortices. CONCLUSIONS: The blunted response to alcohol in cocaine abusers contrasts with their enhanced sensitivity to benzodiazepines suggesting that targets other than GABA-benzodiazepine receptors are involved in the blunted sensitivity to alcohol and that the toxicity from combined cocaine-alcohol use is not due to an enhanced sensitivity to alcohol in cocaine abusers. The blunted response to alcohol in limbic regions and in cortical regions connected to limbic areas could result from a decreased sensitivity of reward circuits in cocaine abusers.

Adult↗

PubMed2000

Evidence that gingko biloba extract does not inhibit MAO A and B in living human brain.

Extracts of Ginkgo biloba have been reported to reversibly inhibit both monoamine oxidase (MAO) A and B in rat brain in vitro leading to speculation that MAO inhibition may contribute to some of its central nervous system effects. Here we have used positron emission tomography (PET) to measure the effects of Ginkgo biloba on human brain MAO A and B in 10 subjects treated for 1 month with 120 mg/day of the Ginkgo biloba extract EGb 761, using [11C]clorgyline and [11C]L-deprenyl-D2 to measure MAO A and B respectively. A three-compartment model was used to calculate the plasma to brain transfer constant K1 which is related to blood flow, and lambdak3, a model term which is a function of the concentration of catalytically active MAO molecules. Ginkgo biloba administration did not produce significant changes in brain MAO A or MAO B suggesting that mechanisms other than MAO inhibition need to be considered as mediating some of its CNS effects.

Adult↗

PubMed2000

Resting brain metabolic activity in a 4 tesla magnetic field.

MRI is a major tool for mapping brain function; thus it is important to assess potential effects on brain neuronal activity attributable to the requisite static magnetic field. This study used positron emission tomography (PET) and (18)F-deoxyglucose ((18)FDG) to measure brain glucose metabolism (a measure of brain function) in 12 subjects while their heads were in a 4 T MRI field during the (18)FDG uptake period. The results were compared with those obtained when the subjects were in the earth's field (PET scanner), and when they were in a simulated MRI environment in the PET instrument that imitated the restricted visual field of the MRI experiment. Whole-brain metabolism, as well as metabolism in occipital cortex and posterior cingulate gyrus, was lower in the real (4 T) and simulated (0 T) MRI environments compared with the PET. This suggests that the metabolic differences are due mainly to the visual field differences characteristic of the MRI and PET instruments. We conclude that a static magnetic field of 4 T does not in itself affect this fairly sensitive measure of brain activity.

Adult↗