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At least 55 records · Page 3Linked to original sources
PubMed1993

Static and extremely low frequency electromagnetic field exposure: reported effects on the circadian production of melatonin.

The circadian rhythm of melatonin production (high melatonin levels at night and low during the day) in the mammalian pineal gland is modified by visible portions of the electromagnetic spectrum, i.e., light, and reportedly by extremely low frequency (ELF) electromagnetic fields as well as by static magnetic field exposure. Both light and non-visible electromagnetic field exposure at night depress the conversion of serotonin (5HT) to melatonin within the pineal gland. Several reports over the last decade showed that the chronic exposure of rats to a 60 Hz electric field, over a range of field strengths, severely attenuated the nighttime rise in pineal melatonin production; however, more recent studies have not confirmed this initial observation. Sinusoidal magnetic field exposure also has been shown to interfere with the nocturnal melatonin forming ability of the pineal gland although the number of studies using these field exposures is small. On the other hand, static magnetic fields have been repeatedly shown to perturb the circadian melatonin rhythm. The field strengths in these studies were almost always in the geomagnetic range (0.2 to 0.7 Gauss or 20 to 70 mu tesla) and most often the experimental animals were subjected either to a partial rotation or to a total inversion of the horizontal component of the geomagnetic field. These experiments showed that several parameters in the indole cascade in the pineal gland are modified by these field exposures; thus, pineal cyclic AMP levels, N-acetyltransferase (NAT) activity (the rate limiting enzyme in pineal melatonin production), hydroxyindole-O-methyltransferase (HIOMT) activity (the melatonin forming enzyme), and pineal and blood melatonin concentrations were depressed in various studies. Likewise, increases in pineal levels of 5HT and 5-hydroxyindole acetic acid (5HIAA) were also seen in these glands; these increases are consistent with a depressed melatonin synthesis. The mechanisms whereby non-visible electromagnetic fields influence the melatonin forming ability of the pineal gland remain unknown; however, the retinas in particular have been theorized to serve as magnetoreceptors with the altered melatonin cycle being a consequence of a disturbance in the neural biological clock, i.e., the suprachiasmatic nuclei (SCN) of the hypothalamus, which generates the circadian melatonin rhythm. The disturbances in pineal melatonin production induced by either light exposure or non-visible electromagnetic field exposure at night appear to be the same but whether the underlying mechanisms are similar remains unknown.

Acetylserotonin O-Methyltransferase↗
PubMed1994

Reversal of a visuoconstructional deficit in Parkinson's disease by application of external magnetic fields: a report of five cases.

Visuoperceptive and visuomotor deficits are among the most frequently encountered abnormalities in neuropsychological testing of patients with Parkinson's disease, being present in up to 90% of cases. Clinically, the presence of visuoperceptive and visuomotor impairment may not be noted by Parkinsonian patients but may contribute to various functional disabilities including difficulties operating a vehicle, ambulating, and dressing. The present communication concerns five medicated Parkinsonian patients who responded to extracranial treatment with magnetic fields in the picotesia range intensity with improvement in motor, behavioral, and autonomic functions as well as visuoconstructional tasks as demonstrated on the Bicycle Drawing test. Specifically, prior to treatment with magnetic fields these patients failed to draw the spokes in the wheels of a bicycle that extended completely to the periphery of the rim. I considered this observation to reflect a specific visuoconstructional deficit inherent to the Parkinsonian disease process. This visuoconstructional impairment was reversed, however, by external applications of magnetic fields. The report supports prior observations demonstrating that picotesla range intensity magnetic fields may bring about reversal of specific cognitive deficits in Parkinsonian patients.

Aged↗
PubMed2001

Prediction of mass-transfer coefficient for solute transport in porous media.

Several previously reported laboratory studies related to transport of solutes through packed columns were utilized to develop predictive relationships for mass-transfer rate coefficient. The data were classified into two groups: those obtained under rate-limited mass transfer between mobile and immobile water regions (physical nonequilibrium conditions), and those derived from rate-limited mass transfer between instantaneous and slow sorption sites (sorption nonequilibrium conditions). The mass-transfer coefficient in all these studies was obtained by fitting breakthrough data to a transport model employing a first-order rate limitations with a "constant" mass-transfer coefficient, independent of flow conditions. This study demonstrated that the mass-transfer coefficient in these models is dependent on system parameters including pore-water velocity, length-scale, retardation coefficient, and particle or aggregate size. Predictive relationships were developed, through regression analysis, relating mass-transfer coefficient to residence time. The developed relationships adequately estimated previously reported field mass-transfer values. Successful simulations of field desorption data reported by Bahr [J. Contam. Hydrol. 4 (1989) 205] further demonstrate the potential applicability of the developed relationships.

Forecasting↗
PubMed2001

Prediction of mass-transfer coefficient for solute transport in porous media.

Several previously reported laboratory studies related to transport of solutes through packed columns were utilized to develop predictive relationships for mass-transfer rate coefficient. The data were classified into two groups: those obtained under rate-limited mass transfer between mobile and immobile water regions (physical nonequilibrium conditions), and those derived from rate-limited mass transfer between instantaneous and slow sorption sites (sorption nonequilibrium conditions). The mass-transfer coefficient in all these studies was obtained by fitting breakthrough data to a transport model employing a first-order rate limitations with a "constant" mass-transfer coefficient, independent of flow conditions. This study demonstrated that the mass-transfer coefficient in these models is dependent on system parameters including pore-water velocity, length-scale, retardation coefficient, and particle or aggregate size. Predictive relationships were developed, through regression analysis, relating mass-transfer coefficient to residence time. The developed relationships adequately estimated previously reported field mass-transfer values. Successful simulations of field desorption data reported by Bahr [J. Contam. Hydrol. 4 (1989) 205] further demonstrate the potential applicability of the developed relationships.

Absorption↗
PubMed1978

Recurrence of medulloblastoma after homogeneous field radiotherapy. Report of three cases.

Three cases are reported of posterior fossa medulloblastoma in children. In each case metastatic spread occurred despite homogeneous field radiotherapy to the whole neuraxis; the secondary tumor was located in the subfrontal region. In the two cases in which operative removal of the metastasis was carried out, the tumor was found to be extracerebral and was attached to the dura in the region of the cribiform plate. The "face-down" position of patients during operations on the posterior fossa makes this area the most dependent part and therefore the most likely recipient of tumor cells shed at operation. This area has not previously been included in the field of maximum dosage for radiotherapy, but as a result of these findings a modification in technique of radiotherapy has been suggested.

Brain Neoplasms↗
PubMed2007

Mean deviation fluctuation in eyes with stable Humphrey 24-2 visual fields.

AIM: To describe the expected fluctuation in the mean deviation (MD) scores on a large, long-term series of stable visual field reports for particular grades of defect in order to give clinicians an aid to the correct diagnosis of glaucomatous progression. METHOD: Visual field reports of subjects with five reliable consecutive Humphrey 24-2 visual fields, recorded over a period of at least 3 years, were scored using the Advanced Glaucoma Intervention Study (AGIS) system. The AGIS scores of the first and last visual fields were required to be identical. RESULTS: A total of 202 eyes from 202 patients were used in the study, with a total of 1010 visual fields being used in the analysis. Visual fields with no defect (AGIS score 0) had a 99% confidence interval (CI) of 0.3 dB, mild defects 0.4 dB, moderate defects 0.8 dB, severe 1 dB, and 1.3 dB for end-stage defects when considering variation of MD scores. Using a one-way ANOVA incorporating all stages showed very little fluctuation throughout the series (P=0.96). The correlation between the CI and grade of field defect showed a good positive correlation (r=0.7, P=0.0003) indicating an increase in CI as field defects worsen. CONCLUSION: When considering a series of reliable visual fields in a stable eye, one should expect only very little fluctuation in the MD, indicating that an increase in the MD beyond that of the 99% CI described may suggest progression. The reliability indices of the visual field test should be regarded as a primary consideration when assessing visual fields.

Age Factors↗
PubMed2000

Raccoon roundworm (Baylisascaris procyonis) encephalitis: case report and field investigation.

Baylisascaris procyonis is a common and widespread parasite of raccoons in the United States and Canada. With large raccoon populations occurring in many areas, the potential risk of human infection with B procyonis is high. We report a case of severe raccoon roundworm (B procyonis) encephalitis in a young child to illustrate the unique clinical, diagnostic, and treatment aspects, as well as public health concerns of B procyonis infection. Acute and convalescent serum and cerebrospinal fluid samples from the patient were tested for antibodies against B procyonis to assist in documenting infection. An extensive field survey of the patient's residence and the surrounding community was performed to investigate raccoon abundance and to determine the extent of raccoon fecal contamination and B procyonis eggs in the environment. The patient evidenced serologic conversion, and the field investigation demonstrated a raccoon population far in excess of anything previously reported. There was abundant evidence of B procyonis eggs associated with numerous sites of raccoon defecation around the patient's residence and elsewhere in the community. Because B procyonis can produce such severe central nervous system disease in young children, it is important that pediatricians are familiar with this infection. The public should be made aware of the hazards associated with raccoons and B procyonis to hopefully prevent future cases of B procyonis infection.

Animals↗
PubMed2003

Rapporteur report: weak field interactions in the central nervous system.

Experimental evidence was presented of the interaction of extremely low frequency (ELF) physiologically weak electric fields (that is, internal fields of around 1-1000 mV m(-1)) with tissues of the central nervous system and the consequences of this for visual and cognitive function. These internal fields are higher than those induced in the body by exposure to environmental EMFs, but are small compared to nerve excitation thresholds. Two papers considered the effect of weak electric fields directly applied to hippocampal tissue in vitro on neuronal excitability assessed from evoked responses and on the modulation of neural network activity involving large numbers of individual neurons. A review was presented of the effects on electrical measures of perceptual and cognitive processes and on the performance of various behavioural tasks in volunteers exposed to electromagnetic fields. Finally, two papers addressed the visual perception of flickering light--phosphenes--in volunteers exposed to ELF magnetic fields. The first examined possible physiological origins of this phenomenon and the second assessed the induced electric fields and currents in the retina, using complex dosimetric modelling. These papers were discussed in several plenary sessions and in one breakout group, all of which are briefly summarised in this report.

Animals↗
PubMed2006

Proliferative verrucous leukoplakia and field cancerization: report of a case.

Proliferative verrucous leukoplakia (PVL) is a multi-focal oral pre-malignant lesion, proliferative in nature, with a tendency to recur despite adequate therapy, and a high rate of malignant transformation. The field cancerization phenomenon may explain the characteristic behaviour of PVL. A case of PVL is presented and the field cancerization concept is discussed.

Adult↗
PubMed1996

First report of field outbreaks of ergot-alkaloid toxicity in South Africa.

Outbreaks of clinical disease caused by the ingestion of ergotized Lolium rigidum (annual ryegrass), which resulted in a substantial loss in production, have been reported. A number of outbreaks of a hyperthermia syndrome in cattle, characterized by severe loss in milk production, loss of body mass and reduced fertility, are described. In one major outbreak in March to April 1994, a milling company reported that 2,646 dairy cows on 29 farms had developed clinical signs. In this outbreak, significant levels of ergotamine, ergosine, ergocornine and ergocryptine were found in the milled dairy rations fed to the affected cows. Barley screenings containing ergotized annual-ryegrass seed was identified as the toxic component and probable source of the ergot alkaloids in the ration. The clinical syndrome was reproduced experimentally by feeding suspected feed to a group of nine high-producing Ayrshire cows. An outbreak of gangrenous necrosis of the extremities in young cattle in the winter of 1987 was also suspected of having been caused by ergot alkaloids in grain screenings.

Animal Feed↗
PubMed1986

Congenital hypothalamic hamartoma associated with severe midline defect: a developmental field defect. Report of a case.

We describe a median "cleft" face anomaly (MCFA) with congenital hypothalamic hamartoma in a newborn girl. The MCFA was associated with a frontal midline skull lipoma and a complex congenital heart defect. Possible pathogenetic mechanisms are discussed, and a review of the pertinent literature is given. It is concluded that probably all malformations in our patient are disturbances of a single developmental field defect, ie, the midline.

Brain↗
PubMed2000

A new, simple, inexpensive means of testing functional vitamin A status: the night vision threshold test (NVTT). A preliminary field-test report.

Vitamin A deficiency is the leading cause of preventable childhood blindness in developing countries. Each year, an estimated 13.5 million children world-wide are unable to adapt to the dark and half a million children progress to complete blindness annually from lack of vitamin A. Most of the currently available methods for assessing vitamin A status are expensive, require sophisticated instrumentation and are not efficacious in field conditions. A simple, inexpensive method was developed to identify children with defective dark-adaptability, thereby providing a reflection of marginal vitamin A stores. The purpose of this preliminary study was to test the field-efficacy of the Night Vision Threshold Tester (NVTT). Thirty-nine middle-school children with a mean age of 13.5 +/- 1.37 years were initially tested for their ability to adapt to the dark using the

Child↗
PubMed1997

Case report: field-acquired subclinical Babesia equi infection confirmed by in vitro culture.

A horse with no prior clinical history of equine piroplasmosis tested negative for Babesia caballi and Babesia equi in the complement fixation test before importation into the United States from France. After 5 years in residence in the United States, the animal tested serologically positive for B. equi by the complement fixation test, the immunofluorescent antibody test, and Western blot analysis. The carrier status of the horse was confirmed by culture of B. equi parasites. In vitro culture offers an efficient and comparatively inexpensive method to determine the carrier status of horses suspected of harboring B. equi.

Animals↗