Biomedical subjects

M J Cox

Publications and source records attributed to M J Cox.

At least 19 recordsLinked to original sources

PubMed2003

Serological survey of anti-group A rotavirus IgM in UK adults.

Rotaviral associated disease of infants in the UK is seasonal and infection in adults not uncommon but the relationship between these has been little explored. Adult sera collected monthly for one year from routine hospital samples were screened for the presence of anti-group A rotavirus immunoglobulin M class antibodies as a marker of recent infection. Anti-rotavirus IgM was seen in all age groups throughout the year with little obvious seasonal variation in the distribution of antibody levels. IgM concentrations and the proportion seropositive above a threshold both increased with age with high concentrations consistently observed in the elderly. Results suggest either high infection rates of rotavirus in adults, irrespective of seasonal disease incidence in infants, IgM persistence or IgM cross-reactivity. These results support recent evidence of differences between infant and adult rotavirus epidemiology and highlight the need for more extensive surveys to investigate age and time related infection and transmission of rotavirus.

Adolescent↗

PubMed2001

Nosocomial primary bloodstream infections in intensive care unit patients in a nonteaching community medical center: a 21-month prospective study.

All patients admitted to the medical and surgical intensive care units of a 500-bed nonteaching suburban hospital were followed prospectively for the occurrence of nosocomial primary bloodstream infections for 21 months. The incidence of primary bloodstream infection was 38 (1%) of 3163 patients; among patients with central venous catheters, it was 34 (4%) of 920 patients, or 4.0 infections per 1000 catheter-days. Ventilator-associated pneumonia, congestive heart failure, and each intravascular catheter inserted were independently associated with the development of a nosocomial primary bloodstream infection. Among infected patients, the crude mortality rate was 53%, and these patients had longer stays in intensive care units and the hospital than did uninfected patients. Bloodstream infection, however, was not an independent risk factor for death. The incidence, risk factors, and serious outcomes of bloodstream infections in a nonteaching community hospital were similar to those seen in tertiary-care teaching hospitals.

Adolescent↗

PubMed2001

Isolation and phenotypic characterization of Pseudomonas aeruginosa pseudorevertants containing suppressors of the catabolite repression control-defective crc-10 allele.

The amiE gene encodes an aliphatic amidase capable of converting fluoroacetamide to the toxic compound fluoroacetate and is one of many genes whose expression is subject to catabolite repression control in Pseudomonas aeruginosa. The protein product of the crc gene, Crc, is required for repression of amiE and most other genes subject to catabolite repression control in this bacterium. When grown in a carbon source such as succinate, wild-type P. aeruginosa is insensitive to fluoroacetamide (due to repression of amiE expression). In contrast, mutants harboring the crc-10 null allele cannot grow in the presence of fluoroacetamide (due to lack of repression of amiE). Selection for succinate-dependent, fluoroacetamide-resistant derivatives of the crc-10 mutant yielded three independent pseudorevertants containing suppressors that restored a degree of catabolite repression control. Synthesis of Crc protein was not reestablished in these pseudorevertants. All three suppressors of crc-10 were extragenic, and all three also suppressed a Delta crc::tetA allele. In each of the three pseudorevertants, catabolite repression control of amidase expression was restored. Catabolite repression control of mannitol dehydrogenase production was also restored in two of the three isolates. None of the suppressors restored repression of glucose-6-phosphate dehydrogenase or pyocyanin production.

Amidohydrolases↗

PubMed2001

The spherical aberration of the crystalline lens of the human eye.

The in vivo spherical aberration of the lenses of 26 subjects was estimated from the measured total aberration of the eye and that predicted from the measured shape of the anterior corneal surface. Since it was only possible to estimate the aberration contribution from the posterior corneal surface, its value led to an uncertainty in the final aberration level of the lens. For all the subjects and for a wide range of possible aberration levels at the posterior corneal surface, the spherical aberration of the relaxed lens was found to be negative.

Adult↗

PubMed2001

Fathers' participation in family research: is there a self-selection bias?

The representativeness of fathers who participate in family research was examined among 661 families. Approximately two thirds of eligible fathers participated. Mothers' and observers' reports on families of participating and non-participating fathers were compared. Participating fathers underrepresented fathers with less education, later-born children, more ambivalent marriages, partners with more traditional child-rearing beliefs, families with less optimal parenting environments, and infants who were unplanned, had more difficult temperaments, and were less healthy. Also underrepresented were ethnic minority families and working-class fathers. However, no differences were found in regard to child gender, family income, mothers' psychosocial functioning, either parent's employment experiences, or child-care arrangements. Implications for the generalizability of findings and the recruitment of fathers are discussed.

Adult↗

PubMed2001

Venomous snake husbandry in Thailand.

A captive breeding program for venomous Thai snakes was established at the Queen Saovabha Memorial Institute at Bangkok, Thailand. This was necessary to secure a stable, healthy, and species-confirmed source of snake venom for antivenom production. In 1994, wild-caught specimens were collected, sexed, quarantined, and housed appropriately. All data in this report, with the exclusion of Table 6, were collected from 1994 to 1997. Two species were bred successfully in captivity to date during this study period. Although captive breeding has not yet been achieved with all species and subspecies, our early success was encouraging.

Animal Husbandry↗

PubMed1999

Modeling the impact of subclinical measles transmission in vaccinated populations with waning immunity.

An increasing body of evidence suggests that a substantial proportion of individuals who respond to measles vaccine display an antibody boost accompanied by mild or no symptoms on exposure to wild virus. It is unknown whether this emerging class of individuals can support transmission. The epidemiologic consequences of vaccinated individuals able to transmit virus are investigated using a mathematical model. Parameters for this model are estimated using regression analysis on a Canadian serologic data set. The authors confirm that neutralizing antibodies are decaying significantly in absence of circulating virus. Based on a protective threshold plaque reduction neutralization (PRN) titer of 120, the authors estimate the mean duration of vaccine-induced protection in absence of reexposure to be 25 years (95% confidence interval (CI) 18, 48). After long-term absence of circulating virus, the mathematical model predicts that 80% (95% CI 65, 91) of all seroconverted vaccinees have titers below the protective threshold. In this case, elimination of measles virus cannot be achieved by a single-dose routine vaccination strategy if the basic reproduction number in vaccinated individuals exceeds 1.24 (95% CI 1.10, 1.53). For this reason, there is a need to establish the intensity and duration of infectiousness in vaccinated individuals.

Adolescent↗

PubMed1999

Failure of glove hole detection device for synthetic gloves.

Holes in latex gloves can be reliably detected by commercially available electronic devices. The purpose of this study was to compare the performance of an electronic glove hole detection device using latex gloves to that of neoprene, vinyl, and nitrile latex-free gloves. The electronic hole detection device accurately detected holes in the latex gloves during the 2-h study. In contrast, the latex-free gloves were immediately conductive of electricity in the absence of holes. Consequently, electronic glove hole detection devices cannot be reliably used with latex-free gloves.

Electronics↗

PubMed1999

The effect of surround luminance on measurements of contrast sensitivity.

We investigated how the luminance of an immediate surround to a visual target affects the measurement of contrast sensitivity. We examined four young, healthy, subjects under typical lighting conditions for each test but varied the surround luminance systematically by controlling a backlit surround. The effect of varying the surround on contrast sensitivity measurements made with a Pelli-Robson chart was minimal. The only statistically significant difference was between measurements made with a 900 cd.m-2 surround compared to those made with 5.6, 9, or 30 cd.m-2 surrounds when tested at a viewing distance of 4 m. The higher luminance surround produced higher levels of contrast sensitivity. The effect of the surround luminance was greater when measuring contrast sensitivity to sinewave gratings using a method of constant stimuli. Optimum performance was found using a surround luminance of 9 cd.m-2 (20% of the mean target luminance). Statistically, a wide range of surround luminances (3-30 cd.m-2, or 7-67% mean target luminance) gave similar levels of visual performance, but higher luminance surrounds led to reduced contrast sensitivity. Possible reasons for the difference in the effect of the surround depending upon the test are discussed. Ophthalmic practitioners using contrast sensitivity measurements with letter charts probably need not make special efforts to illuminate the test surround appropriately. However, practitioners using sinewave gratings, especially computer generated sinewave gratings, to measure contrast sensitivity, may have their measurements affected by inappropriately lit task surrounds.

Adolescent↗

PubMed1999

Malaria transmission and naturally acquired immunity to PfEMP-1.

Why there are so few gametocytes (the transmission stage of malaria) in the blood of humans infected with Plasmodium spp. is intriguing. This may be due either to reproductive restraint by the parasite or to unidentified gametocyte-specific immune-mediated clearance mechanisms. We propose another mechanism, a cross-stage immunity to Plasmodium falciparum erythrocyte membrane protein 1 (PfEMP-1). This molecule is expressed on the surface of the erythrocyte infected with either trophozoite or early gametocyte parasites. Immunoglobulin G antibodies to PfEMP-1, expressed on both life cycle stages, were measured in residents from an area where malaria is endemic, Papua New Guinea. Anti-PfEMP-1 prevalence increased with age, mirroring the decline in both the prevalence and the density of asexual and transmission stages in erythrocytes. These data led us to propose that immunity to PfEMP-1 may influence malaria transmission by regulation of the production of gametocytes. This regulation may be achieved in two ways: (i) by controlling asexual proliferation and density and (ii) by affecting gametocyte maturation.

Adolescent↗

PubMed1999

Effect of aging on the monochromatic aberrations of the human eye.

We measured the contrast sensitivity (CS) of a group of older subjects through natural pupils and compared the results with those from a group of younger subjects. We also measured each subject's monochromatic ocular wave-front aberrations using a crossed-cylinder aberroscope and calculated their modulation transfer functions (MTF's) and root-mean-squared (RMS) wave-front aberrations for fixed pupil diameters of 4 mm and 6 mm and for a natural pupil diameter. The CS at a natural pupil diameter and the MTF computed for a fixed pupil diameter were found to be significantly poorer for the older group than for the younger group. However, the older group showed very similar MTF's and significantly smaller RMS wave-front aberrations compared with the younger group at their natural pupil diameters, owing to the effects of age-related miosis. These results suggest that although monochromatic ocular wave-front aberrations for a given pupil size increase with age, the reduction in CS with age is not due to this increase.

Adult↗

PubMed1998

Seroepidemiological study of respiratory syncytial virus in São Paulo state, Brazil.

Transmission of respiratory syncytial virus is thought to be highly seasonal based on reported clinical cases, although transmission resulting in mild disease in all age groups has been little studied. This has been investigated in a seroepidemiological survey using sera from São Paulo, Brazil. Seroprevalence was found to increase rapidly with age, reaching over 90% by three years of age. This is typical of viral infections, which produce life-long immunity following primary infection. One-hundred percent seropositivity was attained by five years of age and maintained throughout adulthood, whereas mean antibody titers continued to increase with age. The mean duration of maternal antibodies was estimated to be 3.3 months with antibody decay demonstrated in paired samples from infants. The results are discussed in relation to possible mechanisms generating such a profile.

Adolescent↗

PubMed1998

Seroepidemiology of group A rotavirus in suburban São Paulo, Brazil.

Age-specific patterns of rotavirus infection were investigated using a randomly selected and representative sample of sera from a suburban community of São Paulo, Brazil screened for class-specific antibodies to group A rotavirus. Age-serology of anti-rotavirus IgG showed primary infection predominant in young infants with a median age of around 18 months consistent with IgM serology suggesting highest rates of recent infection between ages 4 and 48 months. Anti-rotavirus serum IgA prevalence increased gradually with age. Paired samples from infants, collected 1 month apart, indicated high exposure rates with seroconversion occurring in several infants during the reported low transmission season. Between 5 and 10% of adults had elevated IgM levels indicative of recent infection and, potentially, of an important contribution adults may play to rotavirus transmission. Further understanding of the dynamics of rotavirus transmission within populations, at group and serotype level, would benefit the design and monitoring of future immunization programmes.

Adolescent↗

PubMed1998

Infection with group C rotavirus in a suburban community in Brazil.

Group C rotaviruses are associated with sporadic outbreaks of gastroenteritis worldwide. Age-specific seroprevalence of group C rotavirus antibodies was investigated in sera, randomly collected and representative of a suburban community in Brazil which had previously been screened for group A rotavirus antibodies. Antibody prevalence to group C rotavirus was low in children under 5 years and increased slowly with age to 36% seropositivity in adults, reflecting continuous exposure to primary infection in all age groups. This suggests a higher incidence of infection than disease might predict. Adult antibody prevalence was similar to that in other geographical settings. No obvious patterns of infection with group A and group C rotavirus were found within individuals, which suggests independent transmission. However, further epidemiological studies are required to understand group C rotavirus dynamics and possible interactions with group A rotavirus transmission and immunity.

Adolescent↗

PubMed1998

A compassionate response toward providing. Nutrition and hydration in vulnerable populations.

Ethical guidelines provide a valuable first step in thinking about a new model of caring--one that brings together an enhanced model of patient autonomy, a clearer understanding of the moral (as opposed to merely biologic) meaning of life and death, a consistent concern for human life, and a recovery of the gerontological nurse practitioner's role as advocate, counselor, educator, and healer of the human spirit. Instead of creating a slippery slope, the emerging consensus will place decisions to withhold or withdraw fluids and nutrition on even firmer ethical, legal, and moral ground. Even in cases involving severe and enduring illness, disability, and "helplessness," society's focus must be on life. By its very nature, every human life, without reference to its condition, has a value that no one rightfully can deny or measure. Recognition of that truth is the cornerstone on which American law is built. Society's acceptance of that fundamental principle explains why, from time immemorial, society through law has extended its protection to all, including, especially, its weakest and most vulnerable members (Brophy v. New England Sinai Hospital., Inc., 1986).

Advance Directives↗

PubMed1998

Venomous snakebite in Thailand. I: Medically important snakes.

Thailand has an abundance of venomous snakes. Among the neurotoxic family Elapidae, there are three species of the genus Naja (cobras), three of the genus Bungarus (kraits), and the king cobra of the genus Ophiophagus. Other Elapidae snakes in Thailand include sea snakes and Asian coral snakes of the genus Calliophis. They have potent venoms but rarely bite humans. Tissue and hemotoxic snakes are represented by family Viperidae, subfamilies Viperinae and Crotalinae. They remain an occupational hazard for farmers and rubber tappers, causing serious morbidity but only rare deaths, since competent treatment is now widely available throughout Thailand. Purified equine antivenin is manufactured locally for the monocled and Siamese spitting cobras (Naja kaouthia and N. siamensis), king cobra (Ophiophagus hannah), banded krait (Bungarus fasciatus), most green pit vipers (Trimeresurus sp.), Malayan pit viper (Calloselasma rhodostoma), and the Siamese Russell's viper (Daboia russelli siamensis).

Animals↗

PubMed1998

Venomous snakebite in Thailand. II: Clinical experience.

We reviewed a total of 2,525 snakebite patients in Bangkok. Of these, 1,415 were bitten by venomous snakes, 91 by neurotoxic snakes of genus Naja or Bungarus and 1,324 by snakes of family Viperidae or Crotalidae. Seventy-one percent of bites were on the lower extremity. There were two fatal cobra bites; both patients were dead on arrival at the hospital. Bites from vipers caused morbidity but no deaths. Species-specific antivenins are effective in reversing respiratory failure from cobra bites and coagulopathies from bites by Viperidae and Crotalidae snakes. However, early respiratory and wound care will save lives even in the absence of specific cobra and krait antivenin. Care of a snakebite victim should consist of immobilization and bandaging of the bitten limb with elastic bandages during transport to the hospital, early surgical debridement of necrotic tissue, appropriate infusion of antivenin, aggressive respiratory support, management of shock and infection, and peritoneal dialysis or hemodialysis. Incision of bite wounds, suctioning, application of ice, and tourniquets are of no proven value and may be dangerous. All snakebite victims in southeast Asia should survive if they receive early competent care.

Adult↗

PubMed1998

Cross immunity and vaccination against multiple microparasite strains.

We explore the equilibrium properties of a series of compartmental, ODE models describing the interaction between different strains of pathogen. The interaction is conceptualized as acting through shared antigens: infection and recovery from one strain leaves the host with a primed immune response against subsequent strains. The models consider the effect of this priming on susceptibility (the ability to be infected) and transmission (the ability to infect) in an SIR model. In these models, the specific past history of infection is encapsulated in different susceptible compartments within the model. In a third, SIS, model, specific past history is not included, but strains have differential abilities to infect previously infected hosts. Equilibrium results include criteria for the coexistence of strains. For the SIR models, the region of coexistence defined by parameters shrinks as the effect of strains on each other (increased antigenic similarity) increases. For the SIS model, coexistence depends critically on the rate at which complete susceptibility is recovered following infection, and coexisting strains must have differential abilities to infect completely and partially susceptible hosts. Interestingly, this model provides analogies to commensalism (the first species gains from the presence of the second; the second neither gains nor loses from the interaction) and symbiosis (the presence of both species benefits the other). Additionally, we show that the maximum number of coexisting strains is two in this model. The effect of vaccination depends on the initial strain structure, the ability of vaccination to mount protection to both strains and the coverage. Vaccination may allow a previously excluded strain to coexist or exist alone, and may allow a previously rarer strain to become more common with the possibility of increasing incidence of disease. We discuss the dynamics of these models, compare model results to observed patterns and consider additional model structures. The importance of these results to specific multi-strain pathogens, in particular rotavirus, is considered.

Animals↗