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Biomedical subjects

A Ewert

Publications and source records attributed to A Ewert.

At least 37 records · Page 2Linked to original sources
PubMed1985

Perturbation of lymphatic endothelial cells in experimental Brugia malayi infections.

Infection with filarial nematodes induces lymphatic dysfunction in many individuals in endemic areas. The present morphometric study describes changes in lymphatic endothelial cells of Brugia-infected cats. Transmission electron microscopy revealed a decrease in the number of cytoplasmic vesicles in endothelial cells from lymphatic vessels harboring filarial nematodes (4.9 vesicles per micron 2 cytoplasm) when compared with similar cells from the contralateral uninfected control vessels (9.0 vesicles per micron 2). The size of the vesicles and their location within the cytoplasm was not changed. Irregular large vacuoles, often containing degenerating organelles, were common in endothelial cells lining Brugia-infected lymphatic vessels. These studies suggest that damage of cells by living or dead worms or worm products may have a direct effect on the endothelial lining of lymphatic vessels. This may compromise the efficiency of vessels that collect and transport edematous fluid in affected limbs.

Animals↗
PubMed1985

Use of 99mTc-sulfur colloid to assess lymphatic dysfunction in filarial infection.

Investigations of lymphatic dysfunction in animals infected with filarial parasites has been hampered by a paucity of techniques to measure efficiency of lymphatic drainage. In this study a 99mTc-sulfur colloid technique was used to assess the efficiency of lymphatic drainage in Patas monkeys infected with filarial nematodes. In all 15 uninfected hind limbs there was rapid and consistent appearance of labeled colloid in the primary lymph node (popliteal) and subsequently in the secondary nodes (abdomino-pelvic) in 11 of 15 limbs. In contrast, in all eight limbs tested 1-9 months after infection there was reduced rate of migration of the colloid and initial appearance in the abdomino-pelvic region: subsequent accumulation was seen in the popliteal region in only four of the limbs. This data indicated that lymphatic vessels were blocked and that collateral vessels channeled the colloid to the secondary lymph nodes. The lymph flow patterns demonstrated by the isotope technique were supported at autopsy.

Animals↗
PubMed1984

Collagen metabolism in experimental filariasis.

Chronic lymphatic filariasis is accompanied by edema and fibrosis. In order to assess the latter response, the tissue content of collagen was measured in the skin and lymphatic vessels of normal and affected limbs of cats infected by Brugia malayi. Collagen content, expressed per gram wet weight of tissue, was increased in the infected limbs for both kinds of tissues. Moreover, the proportion of acetic acid soluble to total collagen was increased. The degree of crosslinking in soluble collagen was assessed by acrylamide gel electrophoresis and shown to be decreased in infected tissues. These data suggest an increased rate of collagen metabolism in Brugia malayi-infected tissues and provide data for future studies evaluating the efficacy of treatment in chronic experimental filariasis.

Animals↗
PubMed1984

Thrombus formation in lymphatic vessels associated with Brugia malayi.

Lymph thrombi within affected afferent lymphatic vessels of cats infected with Brugia malayi were examined by scanning electron microscopy. Thrombi were made up of alternating layers of fibrin strands and cells, many of which were intact erythrocytes. The endothelial lining of the vessel wall near the site of thrombus attachment showed transition from normal endothelial cells to a flattened syncytium in which individual endothelial cells could not be distinguished. Imprints of cells, including erythrocytes, were visible in the vessel wall at the point of thrombus attachment. Damage to the endothelial lining may be a factor in the initiation of thrombus formation.

Animals↗
PubMed1983

Effects of selected cholinergic and anticholinergic drugs on Brugia malayi (Nematoda).

1. Several drugs were tested as inhibitors of the body movements of adult Brugia malayi. 2. Atropine, carbachol, DDNS (a fluorescent acetylcholine analog), diethylcarbamazine, and physostigmine caused significant reduction in motor activity. 3. Glutamate, hexamethonium, muscarine, norepinephrine, serotonin and d-tubocurarine had no effect. Three novel phosphonium compounds were tested as inhibitors of Brugia and vertebrate acetylcholinesterase. 4. Two of these produced preferential inhibition of the enzyme from Brugia.

Acetylcholinesterase↗
PubMed1983

Effect of diethylcarbamazine citrate on Brugia malayi infections in cats following daily, weekly, or monthly administration.

Cats with patent infections of Brugia malayi were treated by intraperitoneal injection of diethylcarbamazine citrate (DEC) for 6 consecutive days, weekly for 6 consecutive weeks or monthly for 3 months. Each cat received a total of 100 mg DEC per kg. At necropsy 7 months after infection, no living worms were recovered from any of eight cats treated weekly and only one of nine cats treated daily had a single living Brugia. Five of nine cats treated monthly and six of eight untreated controls had one or more living worms. Cats treated weekly showed a larger decline in microfilariae than those of the other treated groups. The mean microfilariae level of untreated controls increased 2-fold. At necropsy, gross appearance of regional lymphatics in daily and weekly treated cats resembled those of uninfected controls more closely than those in cats treated monthly or untreated. Differences in degree of histological changes between groups of infected cats were not apparent. Weekly administration of DEC appeared to be the most effective regimen; monthly treatment was less effective.

Animals↗
PubMed1983

Efficacy of oral and transepidermal application of diethylcarbamazine citrate in Brugia malayi infected cats.

This experimental study showed that daily oral administration of DEC at levels of 5 to 15 mg/kg/day with food for 3 weeks decreased the level of both developing and adult B. malayi in infected cats. There were no adverse reactions due to the medication. Topical application of 5% DEC in skin cream or in mineral oil appears to be effective in killing developing B. malayi in cats.

Administration, Oral↗
PubMed1982

Experimental necrotic dermatosis induced by group G streptococci in mice.

Self healing necrotic lesions were produced on the backs of laboratory mice by injecting group G streptococci into the skin. The incidence and severity of necrotic dermatosis was dose related. When 1 x 10(1) colony forming units (cfu) were injected subcutaneously, lesions developed on three of 16 mice 4 days post inoculation. Injection of 1 x 10(3) cfu produced lesions on five of 16 mice and 1 x 10(5) cfu produced lesions on seven of 15 mice 3 days post inoculation. An inoculation of 1 x 10(7) cfu produced lesions on all of 16 mice 2 days post inoculation. Lesions produced by the 1 x 10(1) inoculum were smaller and had healed by the 15th day post inoculation, whereas lesions produced by the 1 x 10(7) inoculum persisted until the 24th day post inoculation. No mortality could be attributed to experimental design and all lesions healed without the use of medication or antibiotics.

Animals↗
PubMed1981

Microfilariae of Mansonella ozzardi in human skin biopsies.

Microfilariae of Mansonella ozzardi were seen in specimens of skin taken by biopsy from 4 of 6 subjects previously shown to be positive for microfilariae in the blood. While most of the microfilariae were confined to small blood vessels in the papillary and superficial reticular dermis, some were in perivascular spaces and a few were noted in the dermal interstitium. There was no microscopic evidence that the minimal cutaneous disease seen could be directly attributed to the microfilariae.

Adult↗
PubMed1980

A parasitologic survey for Mansonella ozzardi in the Comisaría del Vaupés, Colombia.

The prevalence of Mansonella ozzardi in the Comisaría del Vaupés of eastern Colombia was investigated as part of an extensive study of human filariasis in Colombia. Three hundred and forty-seven individuals from various parts of Vaupés were examined. The overall infection rate for M. ozzardi was 49%, but the distribution of the parasite was not uniform throughout the Comisaría. Microfilariae were found in both venous blood samples and ski biopsies of infected individuals. The rate of infection was 55% for males and 42% for females, and infection ratenerally low, with 88% of the positive films having less than 50 microfilariae.

Adolescent↗
PubMed1980

Reappearance of Sporothrix schenckii lesions after administration of Solu-Medrol R to infected cats.

In 10 of 34 adult cats infected with Sporothrix schenckii, demonstrable lesions healed spontaneously in 31 to 88 days after inoculation of the organism. None of 5 untreated cats developed additional visible lesions during the period of observation, nor were they positive for S. schenckii by culture at necropsy. Five animals were treated with Solu-Medrol R to determine if the apparent clinical cure was also accompanied by a mycological cure. Lesions reappeared at, or near, the site of the original lesions in 3 of the 5 treated cats from 4 to 6 months after the initial lesions healed. Fungi were cultured both from the regional lymph node and from exudate of the skin lesions. Thus, it appears that viable S. schenckii may be sequestered in tissues for at least 6 months without showing clinical evidence of their presence. Moreover, apparently "healed" lesions may be reactivated and progress to typical demonstrable skin lesions following immuno-suppression.

Animals↗
PubMed1980

Chronic infection of cats with Brugia malayi and streptococcus.

An elephantoid condition was seen in the affected limbs of 5 of 6 cats at necropsy 12 to 18 months after initial infection with Brugia malayi. Repeated infection with Brugia and exposure to an opportunistic streptococcus appeared to enhance the production and persistence of edematous and fibrotic tissues surrounding the affected lymphatics.

Animals↗
PubMed1979

Onchocerciasis focus in Colombia: follow-up study after 12 years.

This study is a follow-up of a 1965 investigation of the only known focus of Onchocerca volvulus in Colombia. In the first phase of the current study, 254 persons were examined. Of the 19 individuals found to be infected with O. volvulus, the youngest was a 16-year-old male. Among those included in the 1965 study, 22 were examined again for microfilariae. Two were positive in both studies, 4 were positive in 1965 but negative in 1977 and the remaining 16 were negative on both occasions. The prevalence of infection, based on identification of microfilariae in skin snips, was lower in the current study (7.5%) than the 15.1% recorded 12 years earlier. However, a 50% response to the Mazzotti test (administration of oral diethylcarbamazine) among a limited number of people upstream from the previously identified endemic area suggests that infection with O. volvulus may be quite widespread.

Adolescent↗
PubMed1979

Effect of diethylcarbamazine citrate on fourth stage and adult Brugia malayi in cats.

Sixty-three experimental and 58 control cats were infected with Brugia malayi so that the developing and adult worms localized in the regional lymphatics of the hind legs. At 20 days after infection when Brugia were in the 4th larval stage, and at 8 weeks when worms were young adults, cats were divided into groups to test the efficacy of diethylcarbamazine citrate (DEC) at various dosage levels. At 100 mg total DEC/kg no 4th-stage larvae were seen in 5 cats compared with a mean of 20.4 living larvae in each of 5 controls. At this level of DEC, 2 of 5 cats had 1 and 2 adult worms while 4 of 4 controls had a mean of 23.2 living adult worms. At 50 and 25 mg/kg there was a substantial reduction of both 4th stage and adult worms when compared to controls. At 10 mg/kg, 4 of 6 cats had 4th-stage larvae but at a lower level (mean = 7.0) than in 6 controls (mean = 23.2). No reduction of either 4th-stage larvae or adult worms was seen at 1 mg/kg. This study establishes the efficacy of DEC against 4th-stage and adult Brugia malayi in cats, although considerably higher levels of the drug were required than the level previously determined to kill 3rd-stage larvae. It appears that the cat-B. malayi model will be an effective method to compare the efficacy of drugs against adult lymphatic-dwelling filariae.

Animals↗
PubMed1977

Lymphatic patterns of cats infected with Brugia malayi and streptococcus.

Approximately 50% of the hind legs of cats infected with Brugia malayi and insulted with a beta haemolytic streptococcus became elephantoid in appearance after four to six weeks. This condition was found to be reversible. Collateral lymphatic vessels were seen by lymphography in most of the Brugia-streptococcus-infected legs. The popliteal draining systems in two of three cats, which harboured no worms, appeared normal by lymphography at 18 weeks.

Animals↗