Biomedical subjects

T Gomez

Publications and source records attributed to T Gomez.

14 recordsLinked to original sources

PubMed2003

von Kármán-Howarth relationship for helical magnetohydrodynamic flows.

We derive an exact equation for homogeneous isotropic magnetohydrodynamic (MHD) turbulent flows with nonzero helicity; this result is of the same nature as the classical von Kármán-Howarth (VKH-HM) formulation for the kinetic energy of turbulent fluids. Helical MHD is relevant to the astrophysical flows such as in the solar corona, or the interstellar medium, and in the dynamo problem. The derivation involves the new writing of the general form of tensors for that case, for either vectors or (pseudo)axial vectors. It is shown that, for general third-order tensors, four generating functions are needed when taking into account the nonmirror invariance of helical fluids, instead of two as in the fully isotropic case. The new equation obtained, denoted by VKH-HM, links the dissipation of magnetic helicity to the third-order correlations involving combinations of the components of the velocity, the magnetic field, and the magnetic potential. Finally, in the long-time and nonresistive limit, this relationship leads to a linear scaling with separation of the third-order tensor, correlating the two normal components of the electromotive force and of the magnetic potential.

Journal Article↗

PubMed2000

Exact relationship for third-order structure functions in helical flows

An exact law for turbulent flows is written for third-order structure functions taking into account the invariance of helicity, a law akin to the so-called "4/5 law" of Kolmogorov. Here, the flow is assumed to be homogeneous, incompressible and isotropic but not invariant under reflectional symmetry. Our result is consistent with the derivation by O. Chkhetiani [JETP Lett. 10, 808, (1996)] of the von Karman-Howarth equation in the helical case, leading to a linear scaling relation for the third-order velocity correlation function. The alternative relation of the Kolmogorov type we derive here is written in terms of mixed structure functions involving combinations of differences of all components for both the velocity and vorticity fields. This relationship could prove to be a stringent test for the measuring of vorticity in the laboratory, and provide a supplementary tool for the study of the properties of helical flows.

Journal Article↗

PubMed1999

Lessons from a large outbreak of Escherichia coli O157:H7 infections: insights into the infectious dose and method of widespread contamination of hamburger patties.

Between November 1992 and February 1993, a large outbreak of Escherichia coli O157:H7 infections occurred in the western USA and was associated with eating ground beef patties at restaurants of one fast-food chain. Restaurants that were epidemiologically linked with cases served patties produced on two consecutive dates; cultures of recalled ground beef patties produced on those dates yielded E. coli O157:H7 strains indistinguishable from those isolated from patients, confirming the vehicle of illness. Seventy-six ground beef patty samples were cultured quantitatively for E. coli O157:H7. The median most probable number of organisms was 1.5 per gram (range, < 0.3-15) or 67.5 organisms per patty (range, < 13.5-675). Correlation of the presence of E. coli O157:H7 with other bacterial indicators yielded a significant association between coliform count and the presence of E. coli O157:H7 (P = 0.04). A meat traceback to investigate possible sources of contamination revealed cattle were probably initially colonized with E. coli O157:H7, and that their slaughter caused surface contamination of meat, which once combined with meat from other sources, resulted in a large number of contaminated ground beef patties. Microbiological testing of meat from lots consumed by persons who became ill was suggestive of an infectious dose for E. coli O157:H7 of fewer than 700 organisms. These findings present a strong argument for enforcing zero tolerance for this organism in processed food and for markedly decreasing contamination of raw ground beef. Process controls that incorporate microbiological testing of meat may assist these efforts.

Animals↗

PubMed1997

Clinical features and outcomes of HIV-related cytomegalovirus pneumonia.

OBJECTIVE: To describe the characteristics and outcomes of HIV-infected patients with biopsy-proven cytomegalovirus (CMV) pneumonia. DESIGN: Retrospective study. SETTING: A 900-bed acute facility in New York City. PATIENTS: Eighteen HIV-infected patients with pathologically confirmed CMV inclusions in lung tissue without other pathogens and 36 control patients with biopsy-proven Pneumocystis carinii pneumonia (PCP) selected for comparisons by computer-generated random sequential numbers. MAIN OUTCOME MEASURES: Demographic, clinical, laboratory, radiological findings, and in-hospital mortality. RESULTS: Eighteen HIV-infected patients were found to have CMV lung infection alone. Pathologic findings were pneumonitis (n = 11); pneumonitis and pulmonary vasculitis (n = 1); and CMV inclusions alone (n = 6). All presented with respiratory symptoms (cough or dyspnea), 89% had fever, 83% had radiological abnormalities, and 56% had severe hypoxemia. The pulmonary presentation was similar except for higher lactate dehydrogenase (median, 449 versus 329 IU/l; P = 0.03) and presence of pleural effusions (33 versus 0%; P = 0.001) in CMV patients. Multivariate analysis showed that CD4 counts < or = 12 x 10(6)/l (odds ratio; 9.2; P = 0.029) and extrapulmonary CMV (odds ratio, 20.4; P = 0.039) were independently associated with CMV pneumonia. Seventeen patients received specific anti-CMV therapy for a mean of 22 +/- 13 days. In-hospital mortality was higher in patients with CMV pneumonia (odds ratio, 11.9; P = 0.002). The median time from admission to death was 31 days. CONCLUSIONS: CMV lung infection was seen in severely immunosuppressed HIV-positive patients and associated with clinical pneumonitis with high early mortality. Although the clinical features resemble PCP, the presence of extrapulmonary CMV disease should suggest the diagnosis of CMV pneumonia.

AIDS-Related Opportunistic Infections↗

PubMed1997

Epidemiology and control of egg-associated Salmonella enteritidis in the United States of America.

The isolation rate for Salmonella enterica serotype Enteritidis (SE) in humans in the United States of America (USA) increased from 1,207 sporadic isolates identified in 1976 (0.6 isolates/100,000 population) to 10,201 identified in 1995 (4.0/100,000 population). The proportion of reported Salmonella isolates which were SE increased from 5% to 25% during the same time period. In 1990, 1994, and 1995, SE was the most commonly reported reported Salmonella serotype in the USA. Much of this increase has been associated with the consumption of contaminated shell eggs. An examination of the results of a United States Department of Agriculture (USDA) survey of spent hens at slaughter and unpasteurised liquid egg at breaker plants (liquid egg processors) in 1991 and 1995 reveals an increase in the prevalence of SE isolates overall and in most regions of the USA. SE phage type 4 (pt 4), the predominant SE phage type in other parts of the world, has emerged in the egg industry in the western USA concurrent with a sharp increase in the number of sporadic human SE pt 4 isolates in California and Utah. Research on the molecular structure and virulence of SE pt 4 isolates from the USA as compared with isolates from other parts of the world (human and poultry) should be a priority. A comparison of DNA from pt 4 isolates from the USA and Europe may provide information about the potential threat to public health and poultry in the USA from this phage type. Some regional success in the reduction of human illness as a result of SE control efforts is apparent. The Pennsylvania Egg Quality Assurance Program has shown progress in reducing SE infection in participating flocks. At a national level, however, neither the incidence of human illness due to SE nor the prevalence of SE in flocks and unpasteurised liquid eggs have decreased significantly, despite the implementation of the USDA 'trace back' regulation from 1990 to 1995, and intensified efforts to educate food handlers and to enforce safe food handling practices. More effort is needed to control SE at every stage of the egg continuum, from production through to consumption. A risk-reduction approach, with barriers to the introduction and multiplication of the pathogen throughout the farm-to-table continuum, is the most practical method for reducing human illness from SE in shell eggs at present. An effective long-term solution will require interdisciplinary efforts involving government, industry, consumers, and academics. Interventions should be developed and evaluated in compliance with the potential for reducing the risk to human health and cost-effectiveness.

Animal Husbandry↗

PubMed1996

Multizone versus monozone in the treatment of high and moderate myopia with an excimer laser.

BACKGROUND AND OBJECTIVE: Numerous modifications have been proposed to photorefractive keratectomy (PRK) in the treatment of myopia in excess of 6.00 diopters (D). One of the techniques employed in an attempt to achieve better refractive results and to avoid, above all, the appearance of an intense haze, is the technique known as multizone. PATIENTS AND METHODS: We have attempted, in a prospective study, to compare the refractive results and the complications of monozone and multizone techniques for the treatment of moderate and high myopia. We performed 139 monozone PRKs and 30 multizone PRKs with a one-year follow-up. RESULTS: We did not find statistically significant differences between the two groups either in the degree of correction obtained nor in the final visual acuity. A statistically significant difference was found only in the number of cases with severe haze (greater than 3) which proved more frequent in the monozone group. CONCLUSION: Our results suggest the techniques are comparable in predictability and effectiveness. However, the incidence of severe haze was lower in the multizone group, which may render its use preferable in the treatment of myopias in excess of 6.00 D.

Corneal Opacity↗

PubMed1991

[3H]-flunitrazepam binding after morphine treatment and under abstinence syndrome.

Chronic morphine treatment produced increases in [3H]-flunitrazepam binding in some hippocampal areas of the rat brain. The differences in binding were statistically significant in some cases. Both morphine-dependent and morphine-deprived (abstinence syndrome) animals showed an identical response in binding, which confirms a real, although small, increase in benzodiazepine binding sites in the hippocampus after morphine treatment, that is not affected by a naloxone-induced abstinence syndrome under the conditions studied. These findings support the hypothesis of a morphine-induced up-regulation of benzodiazepine binding sites in the hippocampus. A possible different response in benzodiazepine binding sites 1 and 2 could explain the different findings reported in the literature. Our data suggest that the detected increase in benzodiazepine binding would be mainly due to type 2 binding sites, since the hippocampus has a higher density of this type of benzodiazepine binding sites.

Animals↗

PubMed1991

Normative database for trunk range of motion, strength, velocity, and endurance with the Isostation B-200 Lumbar Dynamometer.

A review of related literature and trends was used to develop a protocol for testing range of motion, isometric strength, velocity, endurance, and consistency of effort in the low-back pain (LBP) population by the use of the triaxial, Isostation B-200 Lumbar Dynamometer. Eighty-five men and 83 women with no history of LBP for the past 6 months volunteered for the study. Relationships between demographic and test measures were calculated by the use of the Pearson r correlation analysis and ANOVA. Body weight, age, and gender all showed strong (P less than .001), positive relationships to various test measures. The normative database is reported in terms of descriptive statistics allowing comparison of future test results within the normal distribution and corrected for significant demographic features.

Adult↗

PubMed1990

Structural analysis of the regulatory region of the human corticotropin releasing hormone gene.

A DNA fragment containing the human corticotropin releasing hormone (CRH) gene, along with 9 kb of upstream and 4 kb of downstream sequences, was isolated from a human genomic DNA library. Nucleotide sequence analysis of the proximal 918 nucleotides 5' flanking the putative major mRNA start site of the human gene and comparison to the 866 nucleotide long homologous ovine sequence, revealed that this region of the CRH gene consists of two distinct areas with different degrees of homology, varying from 72% to 94%. The putative functional features of the human sequence were identified. Many, but not all, features were conserved in the ovine sequence. The highly conserved nature of the regulatory region of this gene makes it a good candidate for tracing possible related genetic defects of the hypothalamic-pituitary-adrenal (HPA) axis.

Animals↗

PubMed1990

Semitendinosus repair augmentation of acute anterior cruciate ligament rupture.

The semitendinosus tendon has been used since 1980 by the senior author (J.P.M) to augment anterior cruciate ligament repair surgery in cases of acute rupture. There are two major criticisms of this technique: first, the semitendinosus tendon lacks adequate tensile strength functionally to replace the normal anterior cruciate ligament; and second, the semitendinosus is an important hamstring muscle, the loss of which has the potential to weaken the dynamic control of the knee. Objective measurement of success or failure of this procedure is provided by KT1000 arthrometer laxity testing for static recovery of stability, and by Cybex isokinetic dynamometer testing of peak torque and fatigue index to evaluate muscular rehabilitation. Thirty-seven patients were examined using these techniques in a standardized protocol at least two years after surgery. Results show excellent return of static stability and near-normal recovery of strength and endurance of quadriceps and hamstring muscles.

Adult↗

PubMed1988

The role of aldosterone in water and electrolyte transport across the colonic epithelium of the lizard, Gallotia galloti.

1. The effects of D-aldosterone on the electrical properties and ionic transport have been analysed (in vitro) in the colonic epithelium of the lizard, Gallotia galloti. 2. The injection of 30 g of D-aldosterone induced a significant rise of plasma aldosterone concentration, sustained for 4 hr after administration. 3. Intraperitoneal injections of D-aldosterone caused a slight reduction of transmural potential difference (PD) and short-circuit current (Isc). 4. Net absorption of Na+ across the colon from aldosterone-treated lizards did not increase when compared to colon from normal lizards. Cl- absorption was increased in treated lizards. 5. Addition of mucosal barium to treated tissues brought about a sustained increase of PD and Isc. 6. The absorption of fluid in normal lizards was reversed to fluid secretion in treated lizards. 7. The effects of D-aldosterone on lizard colon are compared with those reported for the colon of mammals and birds.

Aldosterone↗

PubMed1988

The prophylactic effect of diphenylhidantoin in the kindling effect on reptiles (Gallotia galloti).

1. Lizards Gallotia galloti received daily 3 mg/kg body wt of diphenylhidantoin (DPH) over a period of 15 days and at the same time the animals were kindled. 2. The progression of the kindling effect was evaluated by counting the number of spontaneous epileptiform potentials, the duration of afterdischarges and the duration of electroencephalographic spontaneous seizures. 3. The diphenylhidantoin treated group, relative to controls presented: (a) significant reduction in the duration of afterdischarges and spontaneous electroencephalographic seizures; and (b) increased frequency of the spontaneous epileptiform potentials.

Animals↗

PubMed1986

Electrical properties of a Na+-dependent phenylalanine transport in lizard (Lacerta galloti) duodenum.

The unidirectional transepithelial fluxes of L-phenylalanine across lizard duodenum were determined in flux chambers. Phenylalanine was preferentially transferred from the mucosal to the serosal fluid. This transport was accompanied by an accumulation of substrate from the mucosal medium into the tissue to a similar level and against a concentration gradient. There was no net movement of phenylalanine when the sodium was substituted by choline. The influx of L-phenylalanine into the epithelial cells of lizard duodenum was examined by incubating slices of intestine in radioactively-labelled solutions of the substrate for 2 min. The steady-state uptake was assessed after similar incubations lasting 45 min. Phenylalanine influx obeys the Michaelis-Menten equation with a Km of 5.1 and is dependent on the presence of sodium ions in the incubation medium. Phenylalanine has been used to induce changes in short-circuit current (delta Isc) across intestine. delta Isc was a hyperbolic function of amino acid concentration characterized by the parameters Jm (maximum change in delta Isc) and Km (concentration needed to attain an delta Isc equal to half the Jm). delta Isc determined Km constants showed good agreement with values obtained from direct measurements of phenylalanine uptake into tissue.

Animals↗

PubMedDate not supplied

High prevalence of calcified silent neurocysticercosis in a rural village of Mexico.

Human neurocysticercosis (NC) is a parasitic disease caused by TAENIA SOLIUM when its larvae lodge in the central nervous system. NC prevalence estimates are obscured by the variable and often asymptomatic clinical picture. While infection depends on exposure, severity is possibly related with various host factors (immunity, genes and gender). This epidemiological study of cranial CT scans in an endemic rural community found that 9.1% of apparently healthy subjects had calcified lesions and were completely asymptomatic. Silent NC cases did not correlate with the exposure factors tested but showed family aggregation and higher rates of positive serology. Thus, NC prevalence may be higher than currently considered and host-related factors appear to be involved in infection and pathogenesis.

Adolescent↗