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Biomedical subjects

J E Cohen

Publications and source records attributed to J E Cohen.

At least 37 records · Page 2Linked to original sources
PubMed1999

Monitoring house reinfestation by vectors of Chagas disease: a comparative trial of detection methods during a four-year follow-up.

Domestic reinfestations by triatomine bugs were monitored after application of deltamethrin and apparent elimination of Triatoma infestans in Amama and other nearby rural villages, north-west Argentina, from 1992 to 1996. The five methods used were sensor boxes, sheets of pink typing-paper, timed manual catches by a skilled three-person team aided by a flushing-out agent, collections by house-dwellers, and knockdown using insecticide fumigant canisters. In bedrooms, house-dwellers collected T. infestans significantly more frequently than the flushing-out method, but the reverse occurred in peridomestic sites. Both methods and sensor boxes revealed the frequent invasion of adult Triatoma guasayana and T. infestans, but neither T. guasayana nor Triatoma sordida colonized bedroom areas in spite of their rising abundance in nearby peridomestic sites. Sensor boxes were significantly more sensitive than the matched paper-sheets in three of five cross-sectional surveys. On average, each box recorded 2.0-3.2 times more triatomine fecal smears than each paper sheet. The frequency of dejecta in sensor boxes correlated positively with the proportion of houses where T. infestans, T. guasayana or T. sordida were captured by any method in bedroom areas. Triatomine fecal smears in sensor boxes were the earliest and most frequent sign of domiciliary infestation, followed by dwellers' collections of adult bugs. Analyzing the data prospectively, we provide a quantitative, predictive understanding of detection methods and review the validity and interpretation of the different signs of infestation obtained. The most sensitive and cost-effective combination of detection methods for vector surveillance in domestic areas was the use of sensor boxes and house-dwellers collections.

Animals↗
PubMed1999

Postcraniotomy gas-containing brain abscess: a neurosurgical emergency. Case report.

BACKGROUND: Gas-containing brain abscesses are very rare, and the majority are caused by Clostridium perfringens. We report a case of gas-containing brain abscess that required urgent surgery after a craniotomy for a brain tumor. METHODS AND RESULTS: The patient was a 53-year-old male who presented with a cerebral neoplasm. A temporal lobectomy was performed and the diagnosis of low grade glioma was confirmed. Although the surgery was uneventful the postoperative course was complicated; the patient became agitated and febrile and deteriorated to a deep coma. A computed tomography scan demonstrated gas in the temporal fossa at the lobectomy site, producing mass effect. Urgent surgical debridement and drainage was performed and C. perfringens and mixed flora were found. Antibiotics were started and the patient's condition markedly improved. He was awake and alert, followed commands adequately and was extubated; however, after a week he suffered massive gastrointestinal bleeding and died. CONCLUSIONS: Early recognition of a gas-containing brain abscess is of great interest to immediately start the appropriate treatment. Urgent surgical debridement and broad spectrum chemotherapy are major components in the management of this entity.

Brain Abscess↗
PubMed1998

Hypsographic demography: the distribution of human population by altitude.

The global distribution of the human population by elevation is quantified here. As of 1994, an estimated 1.88 x 10(9) people, or 33. 5% of the world's population, lived within 100 vertical meters of sea level, but only 15.6% of all inhabited land lies below 100 m elevation. The median person lived at an elevation of 194 m above sea level. Numbers of people decreased faster than exponentially with increasing elevation. The integrated population density (IPD, the number of people divided by the land area) within 100 vertical meters of sea level was significantly larger than that of any other range of elevations and represented far more people. A significant percentage of the low-elevation population lived at moderate population densities rather than at the highest densities of central large cities. Assessments of coastal hazards that focus only on large cities may substantially underestimate the number of people who could be affected.

Altitude↗
PubMed1998

Cooperation and self-interest: Pareto-inefficiency of Nash equilibria in finite random games.

The relative merits of cooperation and self-interest in an ensemble of strategic interactions can be investigated by using finite random games. In finite random games, finitely many players have finite numbers of actions and independently and identically distributed (iid) random payoffs with continuous distribution functions. In each realization, players are shown the values of all payoffs and then choose their strategies simultaneously. Noncooperative self-interest is modeled by Nash equilibrium (NE). Cooperation is advantageous when a NE is Pareto-inefficient. In ordinal games, the numerical value of the payoff function gives each player's ordinal ranking of payoffs. For a fixed number of players, as the number of actions of any player increases, the conditional probability that a pure strategic profile is not pure Pareto-optimal, given that it is a pure NE, apparently increases, but is bounded above strictly below 1. In games with transferable utility, the numerical payoff values may be averaged across actions (so that mixed NEs are meaningful) and added across players. In simulations of two-player games when both players have small, equal numbers of actions, as the number of actions increases, the probability that a NE (pure and mixed) attains the cooperative maximum declines rapidly; the gain from cooperation relative to the Nash high value decreases; and the gain from cooperation relative to the Nash low value rises dramatically. In the cases studied here, with an increasing number of actions, cooperation is increasingly likely to become advantageous compared with pure self-interest, but self-interest can achieve all that cooperation could achieve in a nonnegligible fraction of cases. These results can be interpreted in terms of cooperation in societies and mutualism in biology.

Journal Article↗
PubMed1998

A novel experimental apparatus to study the impact of white noise and 1/f noise on animal populations.

This paper reports on the design and construction of a novel apparatus that allows a set of aquatic microcosms to experience complex temporal environmental fluctuations. Replicate microcosms were maintained in 18 water baths with independent environmental controls. We give results from a preliminary experiment designed to look at the effects of varying temperatures with different variance spectra (i.e. white noise or 1/f noise) on single species population dynamics. Matching time series (with identical elements, differently ordered) of environmental temperatures with different Fourier spectra were created for use as input to the apparatus using a novel spectral mimicry method. The apparatus functioned well during the course of the experiment making this an extremely useful research tool. This apparatus now provides ecologists with a means of studying how environmental variability and directional trends in this variability, are filtered and translated by real populations and micro-ecosystems.

Animals↗
PubMed1998

Rapid spontaneous resolution of acute subdural hematoma and HIV related cerebral atrophy: case report.

BACKGROUND: The natural history of a traumatic acute subdural hematoma is usually interrupted by its prompt surgical removal. Rapid spontaneous resolution within 48 hours, although infrequently reported, may be, underestimated and demonstrates a benign course of this condition. To our knowledge, this is the first case of rapid spontaneous resolution of an acute subdural hematoma in a patient with HIV encephalopathy and cerebral atrophy. METHODS AND RESULTS: This 27-year-old man, an intravenous drug user with AIDS-related complex and HIV encephalopathy, suffered an acute subdural hematoma due to head injury in a car accident. The hematoma spontaneously resolved within 12 hours, resulting in a favorable outcome with nonoperative treatment. CONCLUSIONS: AIDS related cerebral atrophy may not only have predisposed the patient to the development of an extracerebral collection, but may have also favorably influenced the spontaneous resolution of the hematoma. The mechanism of the hematoma resolution and the influence of HIV related cerebral atrophy is discussed.

AIDS Dementia Complex↗
PubMed1998

Fatal spontaneous spinal epidural hematoma following thrombolysis for myocardial infarction.

BACKGROUND: This is the first communication of a fatal spontaneous spinal epidural hematoma following thrombolysis. CLINICAL PRESENTATION: Spine pain may precede neurologic deterioration by many hours. The diagnosis can be accurately made with axial computed tomography (CT) of the involved spinal segment. TREATMENT: Emergency surgery is the treatment for this condition, but conditions such as the acute stage of a myocardial infarction or intraoperative bleeding difficulties due to iatrogenic coagulopathy, the degree of preoperative neurologic deficit, and the timing of surgery must be cautiously considered. CONCLUSIONS: Neurosurgeons will be faced with another devastating complication of thrombolytic therapy, as long as the available drugs are being used. Early clinical suspicion and availability of CT or magnetic resonance imaging for prompt diagnosis are essential to initiate appropriate medical therapy and timely surgery. New strategies must include the development of completely fibrin-specific thrombolytics and drugs that may rapidly reverse the systemic and local clotting disorder.

Aged↗
PubMed1998

Pseudotumoral chagasic meningoencephalitis as the first manifestation of acquired immunodeficiency syndrome.

BACKGROUND: Patients with AIDS frequently show secondary involvement of the brain by different infectious agents, and Chagas' disease is now recognized as a potential opportunistic infection. To our knowledge, pseudotumoral chagasic meningoencephalitis has not been previously reported as the first manifestation of AIDS. METHODS AND RESULTS: A 30-year-old Argentinian man without any risk factor for HIV infection was admitted to the hospital with an acute onset of drowsiness. A computed tomography scan showed a hypodense parietal tumor-like lesion. Open brain biopsy revealed hemorrhagic necrosis and numerous amastigotes of Trypanosoma cruzi. Nifurtimox was started, but the patient died. CONCLUSIONS: Chagas' disease can reactivate in patients with AIDS and present as a brain mass that is indistinguishable from other infectious or neoplasic processes. Our report demonstrates this entity as the first manifestation of AIDS.

AIDS-Related Opportunistic Infections↗
PubMed1998

Prolactin levels in the cerebrospinal fluid of patients with HIV infection and AIDS.

The objective of this study was to assess the levels of prolactin (PRL) in cerebrospinal fluid (CSF) of HIV-infected patients with regard to nonHIV-infected patients, and to assess the levels of prolactin in the CSF of HIV-infected patients with and without neurological HIV-involvement. Seventeen HIV-infected patients with different degrees of immunological and neurological involvement were studied. A second group of six HIV-seronegative patients with varying clinical conditions requiring lumbar punctures were included as controls. CSF was collected from patients and controls. Patients were studied neurologically and neuropsychologically, and computed tomography of the brain were performed. They were staged according to CDC clinical classification for HIV infection, and on the basis of tomographic findings into one of five stages. An additional classification for neurological involvement in AIDS was used. CD4+ cell counts, CSF studies, serum-prolactin levels and CSF-prolactin levels were performed as principal laboratory tests. CSF PRL concentrations were significantly higher in the HIV-infected group (n = 17) than the nonHIV infected control group (n = 6) (mean +/- s.d.; 5.77 +/- 2.22 vs. 3.53 +/- 0.69 x 10(-6) g l-1, respectively; p = 0.009, Mann-Whitney U-test). Moreover, even CSF-PRL concentration was higher in HIV-infected patients without cognitive impairment (stage 0 of the clinical classification), (n = 12) in comparison with nonHIV infected controls (n = 6) (mean +/- s.d.; 5.51 +/- 2.31 vs. 3.53 +/- 0.69 x 10(-1) g l-1, respectively; p = 0.028, Mann-Whitney U-test). There was a good correlation between serum and CSF-PRL levels in HIV-infected patients when measured by the Spearman Rank Test (rs = 0.773; p = 0.005). PRL raised serum levels were found in 4 out of 13 patients (30.73%). We conclude that higher levels of CSF-PRL are more frequently found in HIV-infected patients in comparison to uninfected controls. High levels of circulating PRL were also found in HIV-infected patients corroborating results from other work. A good correlation coefficient was found between circulating and CSF-PRL levels in HIV-infected patients, suggesting that disruption of the blood-brain barrier might account for a possible pathogenic mechanism.

AIDS Dementia Complex↗
PubMed1998

Central neurocytoma with symptomatic paraventricular cyst: case report.

This is the first report of the occurrence of a central neurocytoma and a symptomatic paraventricular cyst; this entity may have particular surgical implications. A 37-year-old male was admitted with a four month history of dizziness and gait instability. He subsequently developed increasing weakness of his left arm and leg. An unenhanced computed tomography scan revealed a hyperdense mass in the right lateral ventricle with a paraventricular cystic lesion in the frontoparietal white matter. MR images showed the origin and extent of the lesion more completely. A frontoparietal craniotomy with a transfrontal transcystic approach allowed resection of the tumor. Intraventricular tumors continue to present a major challenge for neurosurgeons because of their depth and the important surrounding structures. We report the use of a well-known neurosurgical strategy, the transcystic approach, for gross removal of a neurocytoma located in the ventricles.

Adult↗
PubMed1998

Influence of humans and domestic animals on the household prevalence of Trypanosoma cruzi in Triatoma infestans populations in northwest Argentina.

In three rural villages of northwest Argentina, the overall proportion of domiciliary Triatoma infestans infected with Trypanosoma cruzi was 49% among 1,316 bugs individually examined for infection in March and October 1992). Most of the variation among individual households in the proportion of infected triatomines was explained by variations among houses in the proportion of bugs that fed on dogs or cats, the prevalence of infected dogs or cats, and the proportion of bugs that fed on humans, according to a logistic multiple regression analysis. The effects of human infection rates on bug infection rates were not statistically significant. After adjusting for the effects of other predictors, the presence of chickens in bedroom areas had negative and significant effects on the proportion of infected Triatoma infestans, and positive and significant effects on the number of T. cruzi-infected triatomines collected per person-hr per house. Dog or cat infection rates and the proportion of bugs that fed on dogs or cats and on chickens explained 80% of the total variance of infected-bug numbers in a linear multiple regression model. This is the first study to use detailed field data to show that variations in triatomine infection rates depend on bug host feeding patterns and dog or cat infection rates, while the presence of chickens in bedroom areas exerts opposite effects on the proportion and number of infected triatomines. Domestic animals play a crucial role in the domiciliary transmission of T. cruzi.

Animals↗
PubMed1998

Household prevalence of seropositivity for Trypanosoma cruzi in three rural villages in northwest Argentina: environmental, demographic, and entomologic associations.

Environmental, demographic, and entomologic variables were analyzed by logistic multiple regression analysis for their association with the likelihood of being seropositive for Trypanosoma cruzi in three highly infested rural villages of northwest Argentina. The prevalence of seropositivity for T. cruzi, as determined by the composite results of three serologic tests, was 34% among 338 persons in 1992. The strongest positive predictors of the adjusted odds of being infected were the household number of dogs, the density of T. cruzi-infected Triatoma infestans in bedroom areas, and each person's age. Dwellers from houses with roofs made completely or partly with a grass called simbol, or which used insecticides rudimentarily and nonsystematically, had a significantly lower odds of being seropositive for T. cruzi than residents from other types of dwellings. The adjusted odds of infection also increased with the number of T. cruzi-infected dogs or cats and the presence of chickens in bedroom areas. No significant effects on the adjusted odds of infection of a community-wide deltamethrin spraying carried out in one of the villages seven years before were detected. Socioeconomic indicators, such as domiciliary area, and numbers of corrals and livestock, were inversely related to being infected. Our study identified several manageable variables suitable for control actions, most of them not examined before in univariate or multivariate analyses. Environmental management based on low-cost housing with appropriate local materials and removal of domestic animals from domiciliary areas have a crucial role to play in the control of Chagas' disease in rural areas.

Adolescent↗
PubMed1998

Short report. How provincial and territorial legislators view tobacco and tobacco control: findings from a Canadian study.

We report on legislators' attitudes and experiences regarding tobacco and tobacco control using findings from a 1996/97 telephone survey of provincial and territorial legislators in Canada. Across all jurisdictions, legislators showed support for a number of tobacco control policies and for a major government role in implementing programs and policies to discourage youth from smoking. Further, substantial numbers of legislators indicated they did not have enough tobacco-related contact with medical and non-profit health organizations. These findings can guide the activities of health agencies, researchers and advocates in support of effective strategies to reduce the public health impact of tobacco use in Canada.

Attitude to Health↗
PubMed1998

Factors limiting the domestic density of Triatoma infestans in north-west Argentina: a longitudinal study.

Reported are the environmental and demographic risk factors associated with the domestic infestation and density of Triatoma infestans in three heavily infested rural villages in Santiago del Estero Province, Argentina. In a one-factor unadjusted analysis, the number of T. infestans captured per person-hour was associated significantly and negatively with the use of domestic insecticides by householders, type of thatch used in the roofs and the age of the house; and positively with the following: degree of cracking of the indoor walls and presence of hens nesting indoors. In one model, using multiple linear regression and a backward stepwise elimination procedure, most of the variation in the overall abundance of T. infestans was explained by insecticide use and the presence of hens nesting indoors; in another model using the same procedure it was explained by insecticide use, bug density in 1988 and previous spraying with deltamethrin in 1985. Variations in bug density per capture stratum (household goods, beds, walls and roof) were explained by the bug density in other strata and by one or two of the following risk factors: hens nesting indoors, type of roof, presence of cracks in the walls and number of people living in the house. Bug density might be locally controlled by the availability of refuges in the roofs and walls, by the presence of hens nesting indoors and by the use of domestic insecticides. Certain local materials, such as a grass known as simbol, could be successfully used in rural housing improvement programmes aimed at reducing the availability of refuges for insects in the roof.

Adult↗
PubMed1998

[Empirical anti-toxoplasma therapy in cerebral AIDS and Chagas disease. Presentation of 2 cases, review of the literature and proposal of an algorithm].

Trypanosoma cruzi is the responsible agent of Chagas disease and is endemic in extended areas of South and Central America. There are many previous reports indicating that T. cruzi frequently involves the central nervous system in AIDS patients. Here, we present two cases illustrating that neurological involvement caused by T. cruzi frequently shows a clinical picture similar to that caused by Toxoplasma gondil. Since in neurological Chagas disease early treatment has been associated with a better outcome and considering that the diagnosis is easily reached by the detection of the agent in the cerebrospinal fluid, we propose a new algorithm for the management of AIDS patients presenting neurological focal lesions in endemic areas for T. cruzi.

AIDS-Related Opportunistic Infections↗