Search PubMed⌕ Search

Biomedical subjects

L Heller

Publications and source records attributed to L Heller.

At least 37 records · Page 2Linked to original sources
PubMed1998

Environmental determinants of infectious and parasitic diseases.

A review of the role of the environment as a determinant of infectious and parasitic diseases is presented. Historical considerations and the several environmental classifications of diseases are introduced. In a broader perspective the subject is analyzed in view of the emergence of the environmental health area, with its new paradigms. A review of epidemiological studies about environmental sanitation conditions and measures is presented, analyzing the conclusions derived from 256 studies. Finally, an epidemiological study carried out in Betim, Minas Gerais is briefly described, in order to illustrate the potentiality of this kind of study. Setting priorities of interventions regarding diarrhea control was the aim of this investigation. Conclusion about the role of this approach to optimize preventive measures for the control of infectious and parasitic diseases, of sound importance to the reality of the developing world, is stated.

Animals↗
PubMed1995

Heterotopic abdominal pregnancy following in-vitro fertilization/embryo transfer presenting as massive lower gastrointestinal bleeding.

We present a case that, as far as we know, is the first report of lower gastrointestinal haemorrhage as a complication of heterotopic pregnancy induced by artificial reproductive technology. The heterotopic abdominal pregnancy caused erosion of the intestinal wall and massive rectal bleeding, 8 weeks after in-vitro fertilization/embryo transfer. The source of the bleeding could not be identified despite comprehensive investigation including gastroscopy, ultrasonography, sigmoidoscopy, 99Tc (technetium) scanning and angiography. Tagged-erythrocyte isotope scanning revealed an abnormal concentration in the left lower quadrant, compatible with active bleeding in the area of the terminal ileum. Laparotomy disclosed a heterotopic abdominal pregnancy, causing erosion of the intestinal wall at this site. As assisted reproductive technologies become more and more common this rare complication of intestinal erosion should be kept in mind in case of lower gastrointestinal bleeding.

Abdomen↗
PubMed1995

Evaluation of boundary element methods for the EEG forward problem: effect of linear interpolation.

We implement the approach for solving the boundary integral equation for the electroencephalography (EEG) forward problem proposed by de Munck [1], in which the electric potential varies linearly across each plane triangle of the mesh. Previous solutions have assumed the potential is constant across an element. We calculate the electric potential and systematically investigate the effect of different mesh choices and dipole locations by using a three concentric sphere head model for which there is an analytic solution. Implementing the linear interpolation approximation results in errors that are approximately half those of the same mesh when the potential is assumed to be constant, and provides a reliable method for solving the problem.

Action Potentials↗
PubMed1994

Rate of weight gain of inpatients with anorexia nervosa under two behavioral contracts.

OBJECTIVE: To ascertain the rate of weight gain of inpatients with anorexia nervosa under two behavioral contracts, differing in criterion weight gain required to earn increasing privileges. DESIGN: Follow-up comparison of cohorts receiving different interventions. SETTING: Eating disorders service, operating on a general adolescent medicine unit. PATIENTS: Patients admitted consecutively who met the following criteria: (1) weight at least 15% less than that expected for age, sex, and height; (2) female gender; (3) absence of chronic medical illness; (4) hospital stay of at least 28 days. Twenty-two patients meeting these criteria were treated between July 1987 and October 1988, when contract 1 was in effect. This cohort of patients was compared with a group of 31 patients, also meeting the these criteria, who were treated between November 1988 and December 1991, when contract 2 was in effect. INTERVENTIONS: The behavioral contract, signed by the patient on admission, specifies the minimum 4-day weight gain necessary to earn increasing ward privileges, such as use of phone, frequency of visits, etc. Contracts 1 and 2 differed only in the 4-day weight gain criterion: 0.8 lb (0.36 kg) and 1.2 lb (0.55 kg), respectively. RESULTS: The results of analysis of covariance, with admission weight as the covariate, revealed a significant interaction between contract and day, such that patients receiving contract 2 gained weight more rapidly (0.36 lb/d) than those receiving contract 1 (0.20 lb/d). There was no confounding difference between groups in the use of psychotropic medication, and no complications of refeeding in either group. CONCLUSION: Increasing the 4-day criterion weight gain from 0.8 to 1.2 lb in a behavioral contracting intervention was associated with a significant increase in the rate of weight gain, without an accompanying increase in complications of refeeding. This result simultaneously: (a) provides support for the efficacy of behavioral contracting and (b) reveals malleability in the rate of gain based on the targeted gain specified in the contract.

Adolescent↗
PubMed1992

Saccharomyces cerevisiae sec59 cells are deficient in dolichol kinase activity.

The temperature-sensitive Saccharomyces cerevisiae mutant sec59 accumulates inactive and incompletely glycosylated protein precursors in its endoplasmic reticulum at the restrictive temperature. O-mannosylation and glycosyl phosphatidylinositol membrane anchoring of protein are also abolished, consistent with a deficiency in dolichyl phosphate mannose. Membranes prepared from sec59 cells that had been shifted to the restrictive temperature, however, made normal amounts of dolichyl phosphate mannose when exogenous dolichyl phosphate was supplied, but dolichyl phosphate mannose synthesis was severely depressed in the absence of exogenous dolichyl phosphate. Quantitative measurements of dolichyl phosphate in sec59 cells showed that the levels were decreased to 48% of wild type at the permissive temperature and to less than 10% at the restrictive temperature. Assays of enzymes from the dolichyl phosphate synthetic pathway, cis-prenyltransferase and dolichyl pyrophosphate phosphatase, gave wild-type levels. However, dolichol kinase activity was greatly decreased. When sec59 cells were transformed with a plasmid that overexpresses the wild-type gene, dolichol kinase activity increased 10-fold over wild-type levels. These results strongly suggest that the sec59 gene encodes dolichol kinase.

Dimethylallyltranstransferase↗
PubMed1992

Brain stimulation using electromagnetic sources: theoretical aspects.

We prove that, at the frequencies generally proposed for extracranial stimulation of the brain, it is not possible, using any superposition of external current sources, to produce a three-dimensional local maximum of the electric field strength inside the brain. The maximum always occurs on a boundary where the conductivity jumps in value. Nevertheless, it may be possible to achieve greater two-dimensional focusing and shaping of the electric field than is currently available. Towards this goal we have used the reciprocity theorem to present a uniform treatment of the electric field inside a conducting medium produced by a variety of sources: an external magnetic dipole (current loop), an external electric dipole (linear antenna), and surface and depth electrodes. This formulation makes use of the lead fields from magneto- and electroencephalography. For the special case of a system with spherically symmetric conductivity, we derive a simple analytic formula for the electric field due to an external magnetic dipole. This formula is independent of the conductivity profile and therefore embraces spherical models with any number of shells. This explains the "insensitivity" to the skull's conductivity that has been described in numerical studies. We also present analytic formulas for the electric field due to an electric dipole, and also surface and depth electrodes, for the case of a sphere of constant conductivity.

Biophysical Phenomena↗
PubMed1992

An open trial of vacuum penile tumescence: constriction therapy for neurological impotence.

Sexual dysfunction is a frequent result of traumatic and non traumatic neurological disorders, including spinal cord injury, stroke, traumatic brain injury and autonomic neuropathy (for example, as may be seen in patients with diabetes mellitus). Although many methods have been suggested for the treatment of some of these problems in male patients, most are invasive and have a substantial morbidity. This is the report of a pilot trial of vacuum tumescence constriction therapy for 30 patients with chronic neurological impotence. Seventeen of these patients, following sexual counselling and training, decided to purchase such a device. At follow up, a mean of 21 months, over 50% of those who had purchased the device were still actively using it. The frequency of coitus increased from 0.3/wk to 1.5/wk (t = -5.7; p less than 0.0001). No significant morbidity was reported by patients. Vacuum tumescence constriction therapy shows promise as a noninvasive method for the treatment of neurological impotence.

Adult↗
PubMed1992

Noninvasive treatment for erectile dysfunction in the neurogenically disabled population.

Erectile dysfunction is the most prevalent sexual dysfunction in neurogenically disabled men. Studies of rehabilitation patients indicate that the restoration of sexual functioning is considered an important priority. This article reports on a pilot study of vacuum tumescence constriction therapy as a noninvasive method for use by a population with traumatic or nontraumatic neurologic disorders such as spinal cord injury, stroke, multiple sclerosis, and diabetes mellitus. Of the 30 patients who participated in the study, 17 purchased the device and over 50% of them reported using the device on a long-term basis. Frequency of coitus increased from 0.3/wk to 1.5/wk. Included in the study are methods used by patients to integrate the device into their sex life, the role of the patient's partner in the decision to purchase the device, and the rate of partner satisfaction. There were no reports of substantial morbidity. Thus, this method shows promise as a noninvasive treatment for men who are moderately to severely neurogenically disabled.

Equipment and Supplies↗
PubMed1990

Return current in encephalography. Variational principles.

The encephalographic problem of finding the electric potential V and the return current associated with any assumed primary current, Jp, is put in the form of a variational principle. With Jp and the conductivity specified, the correct V is one which makes an integral quantity P[V] a maximum. The terms in P[V] are related to the rates at which work is done by the electric field on the primary and return currents. It is shown that there is a unique solution for the electric field, and it satisfies the conservation of energy; this condition can serve as a check on any numerical solution. With the conductivity a different constant in different regions, the variational principle is recast in terms of the charge density on the surfaces of discontinuity. An iteration-variation method for finding the solution is outlined, and possible computational advantages over other approaches are discussed.

Brain↗
PubMed1990

Transverse myelitis associated with mycoplasma pneumoniae: case report.

Acute transverse myelitis (ATM) is a disorder of the spinal region of the central nervous system. In the present case, the clinical course showed ATM associated with mycoplasma pneumoniae (MP) and little recovery; the girl was left with a flaccid paraplegia, and thus differed from other cases in the literature which all reported complete or near-complete recovery.

Adolescent↗
PubMed1987

Allergen-specific leukocyte adherence inhibition (LAI) assay: sensitivity, specificity and mechanism.

An allergen-specific tube leukocyte adherence inhibition (LAI) assay has been developed in order to study the mechanism by which leukocytes lose their normal property of adherence to glass. Peripheral blood leukocytes (PBL) from 27 individuals allergic to Dermatophagoides farinae (DF), 10 with seasonal rhinitis not induced by DF and 49 non-allergic healthy volunteers were challenged in vitro with DF and a non-relevant allergen, Artemisia vulgaris (AV) and then assayed for the ability to adhere to glass tubes. Challenge by DF, but not by AV, resulted in loss of adherence by PBL from patients allergic to DF, but not in those of normal controls. The specific LAI response was dose-dependent and occurred only when a critical dose of 0.5 X 10(3) was employed. Following in vitro challenge with DF, radio-immunoassay using an antiserum to LTC4 detected immunoreactive material in supernatants of PBL from DF-allergic individuals. When highly enriched mononuclear cells from non-allergic individuals were armed with cytophilic allergen-specific IgE and challenged with the specific allergen, they lost the property of glass adherence and released a substance that was immunoreactive with LTC4. The results suggest that the chain of events leading to the LAI response in PBL from allergic individuals involves primary recognition of the allergen by specific IgE antibodies bound to receptors on mononuclear cells. The cells are thus triggered to synthesize cysteinyl-containing leukotrienes which mediate the LAI phenomenon. The results suggest that this assay may be used to study allergen-antibody interaction and the subsequent events leading to the clinical picture of atopic diseases.

Allergens↗