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Biomedical subjects

G Marin

Publications and source records attributed to G Marin.

At least 19 recordsLinked to original sources
PubMed1998

Influence of skull anisotropy for the forward and inverse problem in EEG: simulation studies using FEM on realistic head models.

For the sake of realism in the description of conduction from primary neural currents to scalp potentials, we investigated the influence of skull anisotropy on the forward and inverse problems in brain functional imaging with EEG. At present, all methods available for cortical imaging assume a spherical geometry, or when using realistic head shapes do not consider the anisotropy of head tissues. However, to our knowledge, no study relates the implication of this simplifying hypothesis on the spatial resolution of EEG for source imaging. In this paper, a method using finite elements in a realistic head geometry is implemented and validated. The influence of erroneous conductivity values for the head tissues is presented, and results show that the conductivities of the brain and the skull in the radial orientation are the most critical ones. In the inverse problem, this influence has been evaluated with simulations using a distributed source model with a comparison of two regularization techniques, with the isotropic model working on data sets produced by a nonisotropic model. Regularization with minimum norm priors produces source images with spurious activity, meaning that the errors in the head model totally annihilate any localization ability. But nonlinear regularization allows the accurate recovery of simultaneous spots of activity, while the restoration of very close active regions is profoundly disabled by errors in the head model. We conclude that for robust cortical source imaging with EEG, a realistic head model taking anisotropy of tissues into account should be used.

Anisotropy↗
PubMed1998

Genetic variation and bill size dimorphism in a passerine bird, the reed bunting Emberiza schoeniclus.

In passerine birds morphological differentiation in bill size within species is not commonly observed. Bill size is usually associated with a trophic niche, and strong differences in it may reflect the process of genetic differentiation and, possibly, speciation. We used both mitochondrial DNA (mtDNA) and nuclear microsatellites to study genetic variation between two subspecies of reed bunting, Emberiza schoeniclus schoeniclus and E.s. intermedia, along their distributional boundary in western Europe. These two subspecies are characterized by a high dimorphism in bill size and, although breeding populations of the two subspecies are found very close to each other in northern Italy, apparently no interbreeding occurs. The observed morphological pattern between the two subspecies may be maintained by geographically varying selective forces or, alternatively, may be the result of a long geographical separation followed by a secondary contact. MtDNA sequences of cytochrome b and ND5 (515 bp) showed little variation and did not discriminate between the two subspecies, indicating a divergence time of less than 500 000 years. The analysis of four microsatellite loci suggested a clear, although weak, degree of genetic differentiation in the large- and small-billed populations, as indicated by FST and RST values and genetic distances. The correlation between bill size and genetic distance between populations remained significant after accounting for the geographical distances between sampling localities. Altogether, these results indicate a very recent genetic differentiation between the two bill morphs and suggest that a strong selection for large bills in the southern part of the breeding range is probably involved in maintaining the geographical differentiation of this species.

Alleles↗
PubMed1997

Surgical second look in ovarian cancer: a randomized study in patients with laparoscopic complete remission--a Northeastern Oncology Cooperative Group-Ovarian Cancer Cooperative Group Study.

PURPOSE: The usefulness of extensive and repetitive surgery for patients with ovarian cancer still remains unproven (at least for some conditions). We planned an accurate prospective test of the hypothesis that patients with advanced-stage disease, after they had reached a clinical complete remission (CR), may benefit from surgical second look (SSL). PATIENTS AND METHODS: One hundred two patients in CR (as assessed by clinical findings, markers, and visualization by computed tomographic [CT] scan and laparoscopy), after initial debulking and first-line chemotherapy, were randomized to two arms, which were well balanced for predictive criteria such as age, stage at presentation, histology, grading, date of randomization, and residua after first surgery. Forty-eight patients were randomly assigned to receive follow-up evaluation only, while 54 were assigned to receive second surgery (eight of them refused). Of 46 surgical patients, 35 had negative and 11 positive surgical findings (24% clinically false-negative). RESULTS: Despite the microscopic residua found at open surgery, and the fact that the patients were then treated with second-line chemotherapy, SSL did not increase the probability of survival in this setting. In an analysis of the results according to the intention-to-treat criteria, after a 60-month follow-up period, the overall survival rates in the two groups of patients (SSL v no SSL) were 65% and 78%, respectively (P = .14). Multivariate analysis according to predictive criteria confirmed there was no significant difference between the two groups (P = .39). CONCLUSION: Our study shows the following: (1) our second-line treatment is scarcely effective; (2) SSL accurately defines complete responders to first-line chemotherapy; (3) SSL per se does not prolong survival; and (4) if confirmed, a less invasive procedure could replace SSL as a valuable method in new first-line regimens in ovarian cancer patients with clinical CR confirmed by laparoscopy.

Female↗
PubMed1996

Evaluation of patch testing in patients with chronic vulvar symptoms.

The Dermogynaecology Clinic was established at the Mercy Hospital for Women in 1989. Since its inception, 700 patients have been investigated and 15% were clinically diagnosed as having contact dermatitis. Primary irritant dermatitis was regarded as the common cause but to investigate the place of contact allergy 50 patients were patch tested to a standard battery, medicaments, preservatives, corticosteroids and miscellaneous allergens. Twenty-one patients (42%) had a total of 44 positive tests. The most common positive reactions were to nickel (22%), cobalt (6%), fragrances (12%), caine mix (6%) and ethylenediamine (8%). Medicaments and fragrances were regarded as important allergens. Corticosteroid and imidazole allergy was not a problem in this series of patients.

Adult↗
PubMed1996

Pulmonary valvular stenosis associated with Takayasu's Disease. Favorable response to corticosteroids. A case report.

The authors describe the first reported case of type IV Takayasu's arteritis with pulmonary valve stenosis. After thirty months under corticosteroid therapy the disappearance of the pulmonary valve stenosis signs was observed in the patient. In the same patient coarctation of the aorta, aortic insufficiency, stenosis of both pulmonary arteries, and left coronary artery stenosis were observed. This case illustrates the extensive cardiovascular involvement that can occur in Takayasu's arteritis and suggests that pulmonary valvular stenosis could be secondary to the same inflammatory process.

Adult↗
PubMed1995

Hepatocellular carcinoma and cirrhosis in 746 patients: long-term results of percutaneous ethanol injection.

PURPOSE: To define indications for percutaneous ethanol injection (PEI) in patients with hepatocellular carcinoma (HCC) and cirrhosis. MATERIALS AND METHODS: Survival rates were determined in 746 patients who had undergone PEI (567 men, 179 women; mean age, 64.3 years; mean follow-up, 36 months). RESULTS: In patients with Child A (n = 293), B (n = 149), or C (n = 20) cirrhosis and single HCCs 5 cm or smaller, the 3-5 year survival rate was 47%-79%, 29%-63%, and 0%-12%, respectively. In patients with Child A cirrhosis, it was 36%-68% for multiple HCCs (n = 121), 30%-53% for single HCCs larger than 5 cm (n = 28), and 0%-16% for advanced HCC (n = 16). Treatment was associated with a 1.7% rate of severe complications and a 0.1% mortality rate. CONCLUSION: PEI proved safe, effective, and repeatable and had a low cost. Survival after PEI was comparable to that after surgery, probably because of a balancing between greater radicality of surgery and absence of early mortality and liver damage of PEI.

Administration, Cutaneous↗
PubMed1995

[Cardiac lipoma of the septum with systemic and pulmonary emboli].

Cardiac lipoma is an uncommon tumor and is rarely a source of either lung or systemic emboli. A 46-year-old woman hospitalized because of left hemiplegia is presented. CT scan revealed a right temporo-parietal infarction. Chest x-ray showed a left lower lobe infiltrate. Pulmonary perfusion-ventilation scan indicated "high probability" of pulmonary embolism. Because brain and lung emboli are often associated, an echocardiogram was made and a 2 x 2 cm mass in the apical septum was found, confirmed by transesophageal echocardiogram. At operation a septal lipoma was resected. When pulmonary emboli occurs in association with systemic emboli, lipoma of the septum, although very rare, should be considered.

Cerebral Infarction↗
PubMed1994

Thyroid function and attention-deficit hyperactivity disorder.

OBJECTIVE: To examine thyroid indices in a community referred sample of boys with attention-deficit hyperactivity disorder (ADHD) for evidence of generalized resistance to thyroid hormone (GRTH). METHOD: TSH, T3, and T4 values were gathered prospectively in 53 physician, school, and/or parent referred ADHD subjects, and in 41 age and gender-matched normal controls. RESULTS: None were in the range suggestive of global or pituitary thyroid hormone resistance. CONCLUSIONS: GRTH is rare, and thyroid function should not be measured routinely in nonfamilial ADHD.

Attention Deficit Disorder with Hyperactivity↗
PubMed1994

The effects of estrogen priming and puberty on the growth hormone response to standardized treadmill exercise and arginine-insulin in normal girls and boys.

To determine the effects of puberty and estrogen priming on the GH response to standardized treadmill exercise and arginine-insulin in normal boys and girls, we performed tests in 84 normal children (41 girls and 43 boys) representing all stages of puberty. A subset of the prepubertal children received the tests twice, with or without the administration of ethinyl estradiol (40 micrograms/m2 daily) for 2 days before the tests. The peak GH response to the three tests increased significantly with pubertal stage (r = 0.57; P < 0.0001), but did not differ between boys and girls at the same stage. With advancing puberty, the percentage of normal children who failed to attain a GH level greater than 7 micrograms/L during any of the three tests declined from 61% at pubertal stage 1 to 44% at stage 2, 11% at stage 3, and 0% at stages 4 and 5. Administration of estrogen to the prepubertal subjects raised the normal range for the peak GH response to the three tests from 1.9-20.3 to 7.2-40.5 micrograms/L. We conclude that both puberty and estrogen administration significantly increase the peak GH response to exercise, arginine, or insulin in normal subjects. Moreover, the conventional criterion that the peak GH response to three stimulation tests should exceed 7 micrograms/L was applicable in our study only to subjects who had attained pubertal stage 4 or 5 or who had received estrogen administration.

Adolescent↗
PubMed1993

[Ring-valve abscess--a diagnostic challenge].

Infective endocarditis is a life-threatening disease which may be complicated by ring-valve abscess. Since this complication increases morbidity and mortality early diagnosis is important. Pericardial effusion complicating infective endocarditis is uncommon and should raise suspicion of the presence of an abscess. We describe 2 patients admitted for infective endocarditis and pericarditis. In both, ring-valve abscess was suspected on clinical grounds. At surgery there was pathological confirmation of the diagnosis. Both patients underwent successful aortic valve replacement with complete recovery. Controlled trials are providing increasing evidence for the superiority of transesophageal echocardiography in detecting valvular vegetations. Moreover, it is the most accurate means of detecting ring-valve abscess in cases of infective endocarditis. In view of these advantages, we propose the use of transesophageal echocardiography in every case of infective endocarditis.

Abscess↗
PubMed1993

Endocrine profile of catch-up growth in the cynomolgus monkey.

We studied catch-up growth following withdrawal of glucocorticoid administration in seven intact prepubertal cynomolgus monkeys. To reduce stress during blood sampling, a vascular access port was implanted subcutaneously in each animal for the duration of the study. After a baseline observation period of 50 weeks, the monkeys received injections of dexamethasone at a dose of 100 micrograms.kg-1.day-1 for 15 weeks. Growth velocity was monitored every 3 weeks by measuring lower leg length and body weight. Spontaneous serum growth hormone (GH) concentrations and GH levels after insulin and L-dopa stimulation, as well as serum insulin-like growth factor I (IGF-I) and plasma thyrotropin, triiodothyronine and thyroxine, were measured during the study. Differences between animals were analyzed by repeated measures analysis of variance and Student's paired t-test. Mean +/- SEM growth velocity (mm/3 weeks) decreased from 0.90 +/- 0.08 during the baseline period to 0.29 +/- 0.07 (p < 0.001) during the period of growth retardation, and increased to 1.23 +/- 0.2 (p < 0.001) during the period of catch-up growth. Spontaneous GH and peak GH levels following insulin did not show any significant variation during the study. Peak GH during the L-dopa test decreased from 15.4 +/- 3.2 micrograms/l during the baseline period to 6.2 +/- 2.4 micrograms/l during the period of growth retardation (p < 0.05), and increased to 23.0 +/- 5.9 micrograms/l during the period of catch-up growth (p < 0.05).(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1993

New joint imaging tools in osteoarthritis. I--Validation and preliminary experience with GGGS treatment.

In the pathology of joints, the main aim is an early diagnosis. In osteoarthritis (OA), where laboratory support is particularly poor, traditional radiology is informative only when the pathologic process is so advanced that prevention is difficult, either by changing life habits or by treating with chondroprotective drugs. Therefore an ideal diagnostic imaging tool should be sensitive, specific, reproducible and not invasive. In our opinion, Nuclear Magnetic Resonance (NMR) has all these characteristics and in particular can show meaningful pictures of cartilage and subchondral bone. We therefore compared NMR and traditional radiology to the gross pathology shown by arthroscopy at an early stage of OA, before and after treatment with glycosamino-glucuron-glycan-sulphate (GGGS) or placebo. Our results suggest that NMR is quite meaningful and can detect early OA joint modifications. With this technique the placebo-treated OA patients showed a natural increase in their pathologic picture, while the GGGS-treated patients seemed to experience a retardation in the progression of the disease.

Aged↗
PubMed1992

Percutaneous ethanol injection in the treatment of hepatocellular carcinoma in cirrhosis. A study on 207 patients.

In 207 cirrhotic patient carriers of hepatocellular carcinoma (HCC), percutaneous ethanol injection (PEI) was administered with ultrasound guidance. The patients were classified as Child's Class A, 136; B, 54; and C, 17. Their mean age was 63.5 years, and the male-female ratio was 3.5:1. There was a single HCC less than 5 cm in diameter in 162 patients; 45 had more than one HCC. The follow-up ranged from 5 to 71 months (mean, 25 months). No noteworthy complications occurred during or after 2485 treatments. The 1-year, 2-year, and 3-year survival percentages (by the Kaplan-Meier method) for the patients with one HCC were 90%, 80%, and 63%, respectively. The corresponding percentages by Child's class were 97%, 92%, and 76% for Class A; 88%, 68%, and 42% for B; and 40%, 0%, and 0% for C. The 1-year, 2-year and 3-year survival rates for patients with more than one HCC were 90%, 67%, and 31% respectively. These results were similar to those found by others and showed that PEI was a safe, reproducible, easy-to-do, and low-cost therapeutic technique. In terms of survival, these PEI results were better than the published results of no treatment and equivalent to those of surgery. In uncontrolled series, bias can play an important role. Therefore, additional trials would be useful.

Aged↗
PubMed1992

Predictors of condom accessibility among Hispanics in San Francisco.

Ready access to condoms can be an important means of slowing the spread of sexually transmitted diseases and human immunodeficiency virus. We identified the factors associated with keeping or carrying condoms in a random-digit dialing survey of 522 Hispanic adults aged 18 to 65 years in San Francisco. Overall, more Hispanic men reported having condoms than Hispanic women (55.2% vs 23.8%). Hispanic men also reported much higher levels of risky sexual behavior than Hispanic women. Condom promotion efforts with Hispanics will require different approaches for each gender.

Adolescent↗
PubMed1991

Growth hormone (GH) responses to the hexapeptide GH-releasing peptide and GH-releasing hormone (GHRH) in the cynomolgus macaque: evidence for non-GHRH-mediated responses.

GH-releasing peptide (GHRP; His-D-Trp-Ala-Trp-D-Phe-Lys-NH2), a hexapeptide derived from enkephalin, has been shown to have GH-releasing activity in man and several animal species. To characterize the GHRP dose-response curve and compare it with that of GH-releasing hormone [GHRH-(1-44)NH2], six unanesthetized young adult cynomolgus macaques were tested with a range of iv doses of GHRP or GHRH in random order. Animals were fitted with vests and tethers. Blood samples were obtained before and at 15-min intervals after the administration of drugs. Doses ranged from 0.03-3 mg/kg for GHRP and from 1-30 micrograms/kg for GHRH. The dose-response curves for the two peptides were not parallel. GHRP had lower potency, but evoked a much higher peak GH response than GHRH (greater than 55 vs. 12 micrograms/L). Because one of the proposed mechanisms of action of GHRP is the inhibition of somatostatin (SS), we tested the effects of propranolol, which inhibits SS, on the GH responses to GHRH and GHRP. Propranolol was given at a dose of 14 micrograms/kg, iv, 10 min before the injection of saline, GHRH (10 micrograms/kg), or GHRP (1 mg/kg). GH responses to propranolol alone did not differ from those to placebo (peak, 6 +/- 2 vs. 8 +/- 2 micrograms/L). However, propranolol pretreatment doubled the GH responses to both GHRH and GHRP compared with those to GHRH or GHRP alone 28 +/- 5 micrograms/L vs. 14 +/- 5 (P less than 0.05) and 54 +/- 2 vs. 25 +/- 6 micrograms/L (P less than 0.001), respectively]. These results show that GHRP causes a potent dose-dependent release of GH in this primate species. Since GHRP can produce a greater maximal GH response than GHRH, mechanisms other than release of endogenous GHRH must be involved.

Animals↗
PubMed1991

Preoperative and postoperative evaluations by means of three-dimensional computed tomography in cases of Chiari osteotomy.

Three-dimensional computed tomography was employed to investigate the changes of pelvic and hip morphology in nine adult cases of congenital hip dysplasia. Six cases were treated with Chiari pelvic osteotomy and were reexamined postoperatively using the same technique. This new method clearly showed a number of important anatomic features that were not easy to detect with conventional roentgenography. Information provided by three-dimensional computed tomography imaging is useful in selecting the appropriate type of surgical treatment and in evaluating the results of Chiari pelvic osteotomy.

Adolescent↗
PubMed1990

Saccade-related responses of centrifugal neurons projecting to the chicken retina.

Centrifugal projections to several sensory systems modulate the afferent activity during active behaviors. To see whether such modulation occurred in the visual system, we recorded the activity of isthmo-optic neurons in awake chickens during eye movements. We find that the discharge of all isthmo-optic neurons tends to stop during saccades, although every neuron does not pause for every saccade. The pause begins at approximately the same time as the saccade, and pause duration is correlated with saccade duration. Pausing during saccades occurs in both dark and light suggesting that it is motoric rather that visual in origin. In addition, we find that the spontaneous activity of isthmo-optic neurons increases in darkness. We discuss the significance of the saccadic modulation of isthmo-optic activity in terms of possible functions of the centrifugal projection in modulation of ganglion cell activity.

Animals↗