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Biomedical subjects

M H Rodriguez

Publications and source records attributed to M H Rodriguez.

18 recordsLinked to original sources
PubMed1992

Gonotrophic cycle and survivorship of Anopheles albimanus (Diptera: Culicidae) in southern Mexico.

The length of the gonotrophic cycle of Anopheles albimanus was estimated by 12 mark-release-recapture studies conducted in corrals in southern Mexico from 1987 to 1990. The initial set of three mark-release studies indicated that the gonotrophic cycle takes at least 4 d based on the day when gravid mosquitoes were first recaptured. However, in later experiments, mosquitoes recaptured seeking hosts at 48 h after release were in Sella's and Christophers' stages I and II, but parity rates had nearly doubled, indicating that eggs may have developed in less than 48 h and that mosquitoes returned to refeed immediately following oviposition. Two gonotrophic cycles probably exist, one of 48 h dominated by parous mosquitoes and one of 4 d comprised of nulliparous, pregravid mosquitoes. Daily survivorship was estimated by regression from the decrease in the daily recapture rate (0.46-0.68) was less than that estimated by the parity rates (0.67-0.69), with no important differences found between wet and dry seasons. Estimates of the probability of a mosquito living long enough to transmit malaria were 2% (range, 1.8-2.5%).

Animals↗
PubMed1992

Scanning electron microscopic observations of Anopheles albimanus (Diptera: Culicidae) eggs.

To investigate the existence of subspecies of Anopheles albimanus Wiedeman in southern Mexico, the egg morphology of specimens obtained from several field populations and from insectary-adapted colonies of uniform pupal phenotype was examined. Scanning electron microscopic observations have shown that the eggs of An. albimanus are polymorphic in respect to the size and shape of their floats, but not in their ornamentation. Four types of eggs were found. Differences in the proportion of the various morphological types were statistically significant, although proportions of egg types were variable among individuals within the same population. These observations are suggestive of distinctive populations and warrant further studies using more sensitive methods to investigate sibling species in An. albimanus sensu lato.

Animals↗
PubMed1992

Scanning electron microscopy of egg hatching of Anopheles albimanus (Diptera: Culicidae).

Scanning electron and light microscopic observations showed that egg hatching in Anopheles albimanus Wiedemann is aided by a chisel-shaped spine. This hatching tooth is surrounded by a thin flexible membrane fixed to a groove in the head of the larvae. Increased intracranial pressure may force the spine against the egg shell until a fissure is produced. Further opening of the egg is achieved by movements of the head and the entire body of the larva.

Animals↗
PubMed1992

Tests for the existence of genetic determination or conditioning in host selection by Anopheles albimanus (Diptera: Culicidae).

The existence of sympatric populations within Anopheles albimanus Wiedemann with specific host preferences and the question of whether host selection has a genetic basis or is a learned characteristic were investigated. Progeny of wild females collected from corrals or human bait were reared in an insectary. F1 females were fed on a cow or on a human host, allowed to oviposit, and then were released in an experimental hut divided into three compartments. The side rooms occupied by two human or one calf baits were connected by a "funnel-like" cone with the central room in which mosquitoes were released. Females were released at 2000 hours and recaptured the next morning at 0600 hours. A fixed proportion of mosquitoes selected either host (approximately 65% cow and 35% human), irrespective of their parental origin or source of the first blood meal. The data indicate that the existence of cryptic populations with anthropophilic habits is unlikely and that a "learned" host selection also may be ruled out.

Animals↗
PubMed1992

Circumsporozoite genotyping of global isolates of Plasmodium vivax from dried blood specimens.

The prevalence and global distribution of two circumsporozoite (CS) genotypes of Plasmodium vivax (VK210 and VK247) were determined by genetic analysis of isolates from 234 malaria-infected patients. Whole blood specimens were collected on filter paper from patients infected with malaria in Thailand, Mexico, Papua New Guinea, Peru, Afghanistan (Pakistan), India, and western Africa and from 50 asymptomatic smear-negative controls. Following extraction of DNA from the filter paper samples, the CS gene was amplified by the polymerase chain reaction and genotyped by using oligoprobes specific for the VK210 and VK247 repeat epitopes. The sensitivity of genotyping from a single blood dot was 95.2%. The VK247 CS genotype was identified in the blood of patients from all seven study areas and was the predominant form present in samples from Thailand (83%) and Papua New Guinea (90%). In contrast, VK247 DNA was present in only 9% of isolates from Mexico. Individuals infected with both genotypes simultaneously were identified in all study areas except Mexico and were particularly common in Thailand (58%) and Papua New Guinea (60%). These findings indicate that the VK247 genotype of P. vivax is widely distributed but that its prevalence varies geographically. In addition, we conclude that use of samples of whole blood on filter paper is a practical and sensitive method for determining the genotypes of large numbers of malaria isolates collected in field settings.

Amino Acid Sequence↗
PubMed1992

Serologic and genetic characterization of Plasmodium vivax from whole blood-impregnated filter paper discs.

The presence in the New World of a variant strain of Plasmodium vivax (VK247) containing a unique circumsporozoite (CS) repeat domain was determined by the detection of antibodies to the variant CS protein and by genetic analysis of the CS gene from field isolates. Whole blood specimens were collected on filter paper from patients infected with P. vivax in Mexico and Peru. Plasmodium vivax DNA was eluted from filter paper samples and the CS gene was amplified by the polymerase chain reaction (PCR) and analyzed for the presence of VK247 or VK210 DNA by oligoprobe hybridization. Sera eluted from a companion filter paper sample were screened for antibodies reactive with the predominant and variant repeat peptides by enzyme-linked immunosorbent assays (ELISA) and with sporozoites by the immunofluorescent antibody (IFA) test. All 24 patients were positive by PCR and oligoprobe hybridization for either VK210 (16 of 24), VK247 (3 of 24), or both (5 of 24). Mixed infections were common (5 of 7) in Peru, but were not observed in the Mexican isolates (0 of 17). All three VK247 infections from Mexico occurred in residents of the foothills above Tapachula (P = 0.02). Of patients with smear-positive P. vivax infection, 42% (10 of 24) had detectable antibodies eluted from dried blood dots that were reactive with the CS protein by IFA or ELISA. These findings establish the widespread distribution of the P. vivax variant CS protein in the New World and indicate that dried blood filter paper samples represent a valuable source of material for the serologic and molecular analysis of plasmodial infections.

Animals↗
PubMed1991

Comparative use of bendiocarb and DDT to control Anopheles pseudopunctipennis in a malarious area of Mexico.

The state of Sinaloa has one of the highest and most persistent malaria transmission levels in Mexico. Due to this situation, with resistance of the vector Anopheles pseudopunctipennis Theobald to DDT, the carbamate insecticide bendiocarb was evaluated as an alternative to DDT for residual house-spraying in village-scale trials during 1985-87. Application rates of the active ingredient per square metre of sprayable surface (ai/m2) were 0.4 g bendiocarb 80% wettable powder (80WP) and 2 g DDT 75% WP. Both insecticides failed to control mosquito populations. Human-bait mosquito densities were not altered as a result of insecticide spraying and human-bait collected mosquito mortality rates were low, suggesting little pre-biting insecticide contact due to avoidance or insufficient resting time indoors. Lower densities of indoor-resting mosquitoes were observed with DDT as opposed to bendiocarb treated houses. Anopheline mortality was higher (98-100%) when exposed for 1 h to 1% bendiocarb in standard WHO susceptibility tests and wall bioassays. Mortality-rates of 15-48% due to 1 h exposure to 4% DDT indicated that this insecticide may continue to be partially effective. House curtain and mark-recapture mosquito studies indicated that DDT produced higher excito-repellency than bendiocarb, as reflected by more mosquito landings but lower feeding rates, shorter resting period and earlier exit time from DDT sprayed houses. In the absence of insecticide, more than 50% of blood-fed An.pseudopunctipennis females exited from houses within 2-4 h of release, showing exophilic behaviour. The outdoor/indoor density ratio indicated that the majority were exophagic. These behavioural characteristics limit the usefulness of any residual insecticide against An.pseudopunctipennis.

Aerosols↗
PubMed1989

Uterine rupture: are intrauterine pressure catheters useful in the diagnosis?

The usefulness of the intrauterine pressure catheter in the diagnosis of uterine rupture was assessed by review of 76 cases of uterine rupture, 39 of which were monitored with an intrauterine pressure catheter. The classic description of a loss of intrauterine pressure or cessation of labor was not observed in any of the patients. However, an increase in baseline intrauterine pressure was observed in four patients with an intrauterine pressure catheter. The increase in pressure was associated with severe variable decelerations such that by itself the intrauterine pressure catheter added little to the diagnosis of uterine rupture.

Adult↗
PubMed1989

Ultrasound evaluation of the postdate pregnancy.

In summary, ultrasound plays an important role in the evaluation of the postterm pregnancy, and its use should be considered in the following situations: 1) estimation of fetal weight in the potentially macrosomic infant before vaginal delivery is attempted; 2) frequent evaluation for oligohydramnios using the amniotic fluid index for the expectant management of the postdate pregnancy; 3) placental evaluation prior to elective induction of labor in a poorly dated pregnancy; and 4) evaluation of the postterm fetus for possible congenital abnormalities.

Female↗
PubMed1989

Twice a cesarean, always a cesarean?

The cesarean delivery rate has quadrupled during the past two decades, resulting in considerable attention focused on alternatives to cesarean birth. One option, vaginal birth after one previous cesarean, has come to be recognized as an acceptable alternative to routine elective repeat cesarean delivery. The purpose of this report was to evaluate whether women with two previous cesareans can safely undergo a trial of labor. Between July 1, 1982 and June 30, 1986, data were collected prospectively on all women with previous cesareans. Those with a known classical incision or a medical or obstetric contraindication to a trial of labor were excluded from an attempted vaginal delivery. During this period, 67,784 patients were delivered, of whom 6250 (9.2%) had had a previous cesarean. Of the 6250 previous-cesarean patients, 1088 (17.4%) had had two previous cesareans; of these, 501 (46%) underwent a trial of labor and 346 (69%) delivered vaginally. Whereas the overall rate of uterine dehiscence was 3%, the rate in those women who attempted a vaginal delivery was 1.8%, versus 4.6% in those who did not. Overall, oxytocin was used in 284 (57%) and was associated with a dehiscence rate of 2.1%, versus 1.4% in the no-oxytocin group. Successful vaginal delivery was related significantly to the use of oxytocin and to a previous vaginal delivery. Trial of labor in patients with two previous cesareans appears to be a reasonable consideration.

Cesarean Section↗
PubMed1988

Calcium/creatinine ratio and microalbuminuria in the prediction of preeclampsia.

Eighty-eight normotensive gravid women between 24 and 34 weeks of gestation underwent urine evaluation for the presence of microalbuminuria and urinary calcium excretion (calcium/creatinine ratio). Preeclampsia subsequently developed in 83% of patients with a high level of microalbuminuria (greater than or equal to 11 micrograms/ml) and a low calcium/creatinine ratio (less than or equal to 0.04). Conversely, 94% of women who did not demonstrate high microalbuminuria and a low calcium/creatinine ratio remained normotensive at the time of delivery. These results suggest that changes in renal function are present in gravid women who are otherwise free of symptoms in whom preeclampsia will eventually develop. Testing for microalbuminuria and a calcium/creatinine ratio may be a useful screening tool in predicting the subsequent development of preeclampsia.

Albuminuria↗
PubMed1988

The use of transvaginal sonography for evaluation of postmenopausal ovarian size and morphology.

Ultrasonic evaluation has been suggested as a possible screening tool for early changes in ovarian morphology. This study uses transvaginal sonography to evaluate the ovaries in postmenopausal women who were scheduled for gynecologic surgery unrelated to adnexal disease. The findings of ultrasonic ovarian examination are compared with the findings at surgery and the pathologic evaluation of the ovaries. Nine (17.3%) abnormal ovaries were identified by ultrasonography and at surgery and were confirmed at pathologic examination. Among the abnormal ovaries there were one malignancy (10%) and two neoplasms with known malignant potential (20%). One ovary that was identified to have microscopic areas of Brenner tumor cells at pathologic examination was described as normal by both ultrasound and surgical evaluation. The sensitivity (90%) and specificity (100%) of vaginal sonography were the same as that of gross examination of the ovary at the time of surgery. We conclude that vaginal sonography is a reliable tool in the detection of early abnormalities in the postmenopausal ovary.

Aged↗
PubMed1988

Distribution of a macaque immunosuppressive type D retrovirus in neural, lymphoid, and salivary tissues.

Simian acquired immune deficiency syndrome (SAIDS) in rhesus macaques (Macaca mulatta) at the California Primate Research Center is caused by a type D retrovirus designated SAIDS retrovirus serotype 1 (SRV-1). This syndrome is characterized by profound immunosuppression and death associated with opportunistic infections. Neurologic signs and lesions have not been described as part of this syndrome. The distribution of SRV-1 in the salivary glands, lymph nodes, spleens, thymuses, and brains of eight virus-infected rhesus macaques was examined by immunohistochemistry. Electron microscopy, in situ RNA hybridization, and Southern blot hybridization were also performed on selected tissues to detect viral particles, RNA, and DNA, respectively. In seven of eight SRV-1-infected animals, the transmembrane envelope glycoprotein (gp20) of SRV-1 was present in three or more tissues, but never in the brain. In the remaining animal, no viral antigen was detected in any tissue. In this same group of animals, viral nucleic acid was detected in the lymph nodes of six of six animals by Southern blot hybridization, in the salivary glands of two of five animals by both Southern blot and in situ hybridizations, and, surprisingly, in the brains of three of three animals by Southern blot and of three of five animals by in situ hybridization, including the one animal in which viral gp20 was undetectable. None of these animals had neurologic signs or lesions. The detection of viral nucleic acid in the absence of viral antigen in the brain suggests latent SRV-1 infection of the central nervous system.

Acquired Immunodeficiency Syndrome↗
PubMed1987

Glycoprotein recognition mediates attachment of Plasmodium chabaudi to mouse erythrocytes.

The interaction between Plasmodium falciparum merozoites and human erythrocytes is mediated by specific parasite proteins and sialoglycoproteins (SGPs) on the surface of the host cell. To investigate whether a similar mechanism functions in rodent malaria, a series of experiments was performed to identify the proteins involved in the interaction of Plasmodium chabaudi parasites and mouse erythrocytes. Labeled parasite proteins incubated with purified mouse SGP bound specifically to glycoprotein 2.1. Two parasite proteins (72 and 126 kilodaltons [kDa]) were coprecipitated with antibody directed to mouse erythrocyte membrane proteins. The lower band (72 kDa) as well as a band of 105 kDa were also observed to bind to N-acetyl-D-galactosamine affinity columns, suggesting a carbohydrate component in the binding of these parasites to erythrocytes. These experiments indicate that P. chabaudi possesses specific proteins which recognized SGP on the surface of murine erythrocytes in a manner similar to that of the merozoites of P. falciparum. Thus P. chabaudi in mice may provide an in vivo model of the human parasite for testing ways to inhibit merozoite recognition and invasion of host cells.

Animals↗
PubMedDate not supplied

A protein on Plasmodium falciparum-infected erythrocytes functions as a transferrin receptor.

Several observations suggest that iron is essential for the development of malaria parasites but there is evidence that the parasites in erythrocytes do not obtain iron from haemoglobin. The total haemin level in parasitized erythrocytes does not vary during parasite development, indicating that the iron-containing moiety of haemoglobin is not detectably metabolized. Although parasite proteases can degrade the protein part of haemoglobin in red cells, no parasite enzymes that degrade haemin have been identified. In mammalian cells, haemin is degraded to carbon monoxide and bilirubin by the enzyme haeme oxygenase. This enzyme has not been found in malaria parasites. In fact haemin has been found to be toxic to parasite carbohydrate metabolism. Thus, iron apparently cannot be liberated from haemin and instead is sequestered in infected red cells as haemozoin, the characteristic pigment associated with malarial infection. If iron bound to transferrin is the source of ferric ions for malaria parasites within mature erythrocytes, then the parasite must synthesize its own transferrin receptor and localize it on the surface of the infected cell, because the receptors for transferrin are lost during erythrocyte maturation. Our results here suggest that Plasmodium falciparum synthesizes its own transferrin receptors enabling it to take up iron from transferrin by receptor-mediated endocytosis.

Erythrocyte Membrane↗