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Biomedical subjects

A Rivero

Publications and source records attributed to A Rivero.

At least 19 recordsLinked to original sources
PubMed2003

The energetic budget of Anopheles stephensi infected with Plasmodium chabaudi: is energy depletion a mechanism for virulence?

Evidence continues to accumulate showing that the malaria parasites (Plasmodium spp.) reduce the survival and fecundity of their mosquito vectors (Anopheles spp.). Our ability to identify the possible epidemiological and evolutionary consequences of these parasite-induced fitness reductions has been hampered by a poor understanding of the physiological basis of these shifts. Here, we explore whether the reductions in fecundity and longevity are the result of a parasite-mediated depletion or reallocation of the energetic resources of the mosquito. Mosquitoes infected with Plasmodium chabaudi were expected to have less energetic resources than uninfected mosquitoes, and energy levels were predicted to be lowest in mosquitoes infected with the most virulent parasite genotypes. Not only was there no evidence of a parasite-mediated reduction in the overall energetic budget of mosquitoes, but Plasmodium was actually associated with increased levels of glucose, a key insect nutritional and energetic resource. The data strongly suggest the existence of an increase in sugar feeding in mosquitoes infected with Plasmodium. We suggest different adaptive explanations for an enhanced sugar uptake in infected mosquitoes and call for more studies to investigate the physiological role of glucose in the Plasmodium-mosquito interaction.

Adaptation, Physiological↗
PubMed2003

The influence of malaria parasite genetic diversity and anaemia on mosquito feeding and fecundity.

Studies of invertebrate-parasite interactions frequently report that infection reduces host fecundity. The extent of the reduction is likely to be determined by a wide range of host and parasite factors. We conducted a laboratory experiment to evaluate the role of parasite genetics and infection genetic diversity on the fecundity of mosquitoes carrying malaria parasites. The malaria vector Anopheles stephensi was infected with either of 2 different genotypes of the rodent malaria parasite Plasmodium chabaudi, or by a mixture of both. Mixed genotype infections reduced mosquito fecundity by 20%, significantly more than either of the 2 single genotype infections. Mixed genotype infections were associated with high gametocyte densities and anaemia in mice, both of which were correlated with reduced bloodmeal size in mosquitoes. Bloodmeal size was the most important predictor of mosquito fecundity; the presence and number of parasites had no direct effect. Parasite density influenced the propensity of mosquitoes to feed on infected mice, with a higher percentage of mosquitoes taking a meal as asexual parasite and gametocyte density increased. Thus mosquitoes may preferentially feed on hosts who will most impair their fecundity.

Anemia↗
PubMed2002

Usefulness of sputum culture for diagnosis of bacterial pneumonia in HIV-infected patients.

The use of sputum culture in immunocompetent patients with community-acquired pneumonia is controversial. The usefulness of this technique in HIV-infected patients has not been evaluated. A prospective, observational, multicenter, hospital-based study of bacterial community-acquired pneumonia was carried out to analyze the value of sputum culture in HIV-infected patients. Only good-quality sputum samples were cultured. Altogether, 355 cases of bacterial community-acquired pneumonia were included. An etiological diagnosis was obtained in 190 (53.5%) cases. Sputum was cultured in 313 (88.1%) cases, being diagnostic in 108 (34.5%). The microorganism identified in sputum culture was the same as that identified in sterile samples in 26 of 27 (96.3%) cases in which both cultures were diagnostic. The microbiologic findings in sputum and bronchoscopic cultures were concordant in seven of eight (87.5%) cases in which both were positive. These results suggest that sputum culture is a useful technique, given its availability and ease of performance and its good correlation with culture of sterile samples.

AIDS-Related Opportunistic Infections↗
PubMed2002

[Nocardiosis in patients with HIV infection].

OBJECTIVE: To know the characteristics of nocardiosis in HIV infected patients. PATIENTS AND METHODS: Retrospective analysis of HIV infected patients with a concomitant Nocardia spp. infection in nine Andalusian hospitals. RESULTS: Eighteen cases of nocardiosis were studied. Seventeen patients were males and the mean age was 33.1 years. The risk behaviour for acquiring HIV infection was parenteral drug use in 15 patients (83.3%) and seven of them were active users when acquiring nocardiosis. The mean CD4 lymphocyte count was 66.3 106/l. The nocardiosis was manifested as disseminated disease in eight patients, only pulmonary disease in four cases, lymphocutaneous or soft-tissue nocardiosis in five, and pericarditis in the remaining patient. In the ten cases with pulmonary involvement, the chest X-ray revealed an alveolar, interstitial, and mixed pattern in five, three, and two patients, respectively. Most patients were treated with cotrimoxazole, with good clinical and microbiological responses in 88.8% of them. Some surgical procedures were required in six patients. Eight patients died, three on account of nocardiosis and five on account of other causes. There were three relapses. CONCLUSIONS: Nocardia spp. infection is rare among patients with AIDS and occurs in immunosuppressed patients and drug users. The pulmonary, cutaneous, and soft-tissue were the most commonly observed forms in our series. Despite the high frequency of disseminated infection, the response to th

Adult↗
PubMed2002

Pre-emptive oral ganciclovir can reduce the risk of cytomegalovirus disease in liver transplant recipients.

A cohort of 65 liver transplant recipients was prospectively monitored with qualitative polymerase chain reaction (PCR) in plasma. The first 25 patients did not receive prophylaxis. From a consecutive group of 40 recipients, 11 high-risk patients donor CMV-seropositive/receptor CMV-seronegative (D+/R-), persistent CMV replication) received pre-emptive oral ganciclovir (1000 mg three times daily), when a marker of risk was identified, until day 90. The overall incidence of cytomegalovirus (CMV) disease at six months was 20% (five of 25 patients) in the non-prophylaxis group and 2.5% (one of 40 patients) in the group treated with pre-emptive oral ganciclovir (relative risk, 0.11; 95% confidence interval; 0.01-0.96; P = 0.04). The PCR sensitivity for detecting CMV disease was 80%, the specificity was 90%, and the positive and negative predictive values were 66% and 95%, respectively. Adverse events, graft rejection and survival were similar between groups. We conclude that pre-emptive oral ganciclovir in high-risk patients can reduce the risk of CMV disease.

Antiviral Agents↗
PubMed2001

Allograft rejection predicts the occurrence of late-onset cytomegalovirus (CMV) disease among CMV-mismatched solid organ transplant patients receiving prophylaxis with oral ganciclovir.

The natural history of cytomegalovirus (CMV) disease associated with solid organ transplantation has been modified as a result of the widespread use of antiviral prophylaxis. Anecdotal reports have indicated a reduction of CMV disease at the expense of its later occurrence after completion of ganciclovir prophylaxis. The present study investigated the occurrence of CMV disease and its risk factors among 37 liver and kidney transplant recipients with CMV D+/R- status who received oral ganciclovir during the first 100 days posttransplantation. CMV disease occurred in 9 patients (24.3%) at a median of 144 days posttransplantation (range, 95-190 days). Allograft rejection was found to be strongly associated with the occurrence of late-onset CMV disease (risk ratio, 6.6; 95% confidence interval, 1.4-32.1; P=.02). Thus, CMV D+/R- solid organ transplant recipients receiving 3 months of oral ganciclovir who develop allograft rejection during the period of antiviral prophylaxis may benefit from extended and/or enhanced antiviral prophylaxis to prevent late-onset CMV disease.

Administration, Oral↗
PubMed2001

Failure of a short-term prednisone regimen to prevent nevirapine-associated rash: a double-blind placebo-controlled trial: the GESIDA 09/99 study.

OBJECTIVES: Rash is the most frequent adverse event associated with nevirapine. The use of prednisone has been controversial in this setting. A double-blind placebo-controlled study was performed to evaluate its efficacy in nevirapine-induced rash prevention. DESIGN: Multicentered, randomized, double-blind, placebo-controlled clinical trial with prednisone (30 mg/day x 2 weeks). INCLUSION CRITERIA: HIV-1 infection; CD4 count >200 cells/mm3; plasma viral load (PVL) <5 log10 copies/ml; nevirapine (200 mg/day x 2 weeks, followed by 200 mg twice daily) plus stavudine and didanosine. Clinical follow-up was performed at 15, 30, and 60 days and thereafter every 2 months. RESULTS: In all, 75 evaluable patients were enrolled (39 prednisone/36 placebo). Median baseline CD4 + cell count was 390 cells/mm3 and PVL, 20,200 copies/ml. Overall, nine cases of rash (12.5%) were detected, seven (18%) in the prednisone group and two (5.5%) in the placebo group (odds ratio [OR], 3.85; 95% confidence interval [CI], 0.65-29.3; p =.11). Incidence of moderate-to-severe rashes leading to nevirapine withdrawal was 13.5% (5 of 37) in the prednisone group and 3% (1 of 35) in the placebo group ( p =.2). Median time to rash in both groups was 16 days. Adverse events that motivated withdrawal of therapy appeared in 6 patients from the prednisone group (15.4%) and 3 from the placebo group (8.3%) ( p =.3). CONCLUSION: Short-term prednisone administration does not prevent nevirapine rash, but might even increase its incidence.

Adult↗
PubMed2001

Lifetime allocation of juvenile and adult nutritional resources to egg production in a holometabolous insect.

In holometabolous insects reproductive success is strongly determined by the nutritional resources available to the females. In addition to nutrients derived from adult feeding, resources for egg production may come from the limited reserves accumulated during the larval stages. The pattern of allocation of these larval reserves to egg production is expected to be strongly linked to the nutritional ecology of the adult. We investigate the temporal pattern of allocation of larval reserves to reproduction in a host-feeding parasitoid wasp. As predicted by the dynamics of allocation of an adult meal, larval reserves are the main source of nutrients for four or five days after emergence. However, despite the high frequency of host feeding and the high nutrient content of a haemolymph meal, which we predicted would lead to larval reserves being conserved in the event of host deprivation, larval reserves contribute to egg production throughout the lifetime of the female. We propose several mechanistic and adaptive explanations for our results, including the possible existence of a limiting or key nutrient for egg production of exclusively larval origin. We make further predictions concerning the pattern of allocation of larval resources in parasitoids with different adult nutritional requirements.

Animal Nutritional Physiological Phenomena↗
PubMed2001

Comparative quantitation of cytomegalovirus (CMV) DNA in solid organ transplant recipients with CMV infection by using two high-throughput automated systems.

Cytomegalovirus (CMV) DNA quantitation in clinical specimens is progressively becoming a cornerstone in the diagnosis and management of CMV infection in the immunocompromised host. We evaluated two automated and reproducible PCR tests, the LightCycler (Roche Molecular Biochemicals, Indianapolis, Ind.) and the COBAS AMPLICOR CMV Monitor (Roche Diagnostics, Pleasanton, Calif.), for the detection of CMV DNA in blood samples from transplant recipients with CMV infection as determined by shell vial culture. Following a log transformation analysis, the mean CMV DNA in plasma (PL), whole blood (WB), peripheral blood leukocytes (PBL), and peripheral blood mononuclear cells (PBMC) using the LightCycler was 6.79 copies per ml, 7.23 copies per ml, 6.38 copies per 2 x 10(6) cells, and 6.27 copies per 2 x 10(6) cells, respectively. This compares to 7.86 copies per ml, 8.37 copies per ml, 7.59 copies per 2 x 10(6) cells, and 7.44 copies per 2 x 10(6) cells, respectively, using COBAS AMPLICOR CMV Monitor. While higher CMV DNA levels were observed for the various blood compartments analyzed using COBAS AMPLICOR CMV Monitor, a high degree of correlation was evident between the two automated systems (jackknife correlation r = PL 0.77 [95% confidence interval (CI); 0.64, 0.90], WB 0.77 [95% CI; 0.62, 0.92], PBL 0.77 [95% CI; 0.67, 0.88], and PBMC 0.81 [95% CI; 0.72, 0.89], all P < 0.001). Therefore, we conclude that either automated diagnostic system is accurate for CMV DNA quantitation.

Adult↗
PubMed2001

Focal stiff-person syndrome.

Stiff-person syndrome (SPS) is a disorder of motor function characterized by rigidity of axial musculature and fluctuating painful spasms, which are often induced by startle or emotional stimuli. Neurophysiological studies have demonstrated the presence of continuous motor unit activity in muscle at rest, with abnormally enhanced extereoceptive reflexes. Although criteria for the diagnosis of SPS were proposed, several variants of this syndrome have been described before. In this communication, we report the case of a patient with a focal form of SPS. A 39-year-old woman developed progressive instability in her gait, spasms and stiffness restricted to both legs. The electromyographic examination showed continuous motor unit activity of the affected muscles at rest. Moreover, high anti-GAD antibodies titers were found in CSF and serum. Clinical symptoms, electrophysiological and immunological profiles suggest a focal form of SPS. Clinical and immunological findings indicate that SPS is a heterogeneous disease, suggesting the need to redefine its diagnostic criteria. Definition of the range of clinical expression and immunological profiles could be important for the clinical management of these patients.

Adult↗
PubMed2001

[Multifocal motor neuropathy. Immediate response to intravenous immunoglobulin].

Multifocal motor neuropathy, a rare insidious immune-mediated disorder, features muscular weakness and atrophy, as well as areflexia, due to nerve conduction block and is often associated with the presence of anti-GM1 antibody. We report a patient with a nine-year history of progressive upper limb weakness, misdiagnosed as amyotrophic lateral sclerosis, who responded within hours to intravenous immunoglobulin treatment with full recovery of muscle strength. This case highlights the need to search for conduction block in patients with lower motor neuron involvement.

Amyotrophic Lateral Sclerosis↗
PubMed2000

High rate of tuberculosis reinfection during a nosocomial outbreak of multidrug-resistant tuberculosis caused by Mycobacterium bovis strain B.

We present a study of a nosocomial outbreak of multidrug-resistant tuberculosis caused by Mycobacterium bovis in 31 patients, 30 of whom were infected with human immunodeficiency virus; all 31 died of progressive tuberculosis. All M. bovis strains had identical spoligotyping patterns and showed resistance to 12 antituberculosis drugs. Reinfection was suggested in 11 cases and confirmed in 4 by molecular typing methods. The causative strain was named "B strain."

AIDS-Related Opportunistic Infections↗
PubMed2000

Periodic limb movements in syringomyelia and syringobulbia.

Twenty-six patients with syringomyelia were studied with polysomnography to determine the frequency of periodic limb movements (PLM) and its relationship to the presence of a Chiari anomaly, the severity of corticospinal tract involvement, and localization of the syrinx. Sixteen patients showed PLM in stages I and II of non-REM sleep and three PLM also while awake. There were no statistically significant differences in overall disability, corticospinal signs, presence of an associated Chiari anomaly, and disease duration between patients with and without PLM, although there was a trend for patients with PLM to have more severe disease. There was preservation of the lumbosacral enlargement of the spinal cord by the syrinx in all patients with PLM. The latency delay between lower and upper limb muscles was suggestive of conduction along propriospinal pathways. Syringomyelia may lead to an abnormal state of spinal hyperexcitability favoring the appearance of PLM. Detailed magnetic resonance image studies of patients with different localizations of the syrinx cavities may help to determine which tracts are involved in the production of PLM.

Adolescent↗
PubMed2000

Acoustic signalling in a wolf spider: can signal characteristics predict male quality?

While there has been considerable interest in female choice for male sexual signals, there have been few studies of the underlying information that different aspects of the signal calls convey. Such studies, however, are essential to understand the significance of signals as honest handicaps, arbitrary Fisherian traits and/or in species recognition. We studied the somewhat exceptional system of audible drumming in the wolf spider Hygrolycosa rubrofasciata. We estimated the repeatabilities of signal components, the levels of between-male variance, the symmetry of the signal, the correlations between different aspects of drumming and their correlations with body weight. While in other taxa the frequency of audible signals may convey honest information of male size, in this species signal frequency was not related to male size and had a low repeatability. The pulse rate within each drum was highly repeatable but had a relatively small between-male coefficient of variation. In previous studies on this species, these traits were not important for male mating success. Among the traits directionally preferred by females, signal volume had considerable repeatability. Signal length was repeatable with high variability between males. In one population, signal length and volume were positively correlated with the rate at which males produced the drumming signals, a trait essential for male mating success. Thus, while signal length may reliably indicate male quality, other signal characteristics such as peak frequency and symmetry were not repeatable or were static and not related to any other male traits. Copyright 2000 The Association for the Study of Animal Behaviour.

Journal Article↗