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Biomedical subjects

F K Ng

Publications and source records attributed to F K Ng.

6 recordsLinked to original sources
PubMed2001

Adsorption of colostral antibodies against classical swine fever, persistence of maternal antibodies, and effect on response to vaccination in baby pigs.

OBJECTIVE: To determine kinetics of antibody absorption, persistence of antibody concentrations, and influence of titers on vaccination of baby pigs with a vaccine against classical swine fever (CSF). ANIMALS: 15 sows and their litters. PROCEDURE: Farrowings were supervised. Initial time of suckling was recorded. In the first experiment, blood samples were collected at farrowing, 2 and 4 hours after suckling, and hourly until 10 hours after initial suckling. Samples were assayed for CSF antibodies, using a serum neutralizing (SN) test. A second experiment included 33 baby pigs vaccinated as follows: 10 prior to ingestion of colostrum, 18 between 1 and 4 hours after ingestion of colostrum, and 5 at 12 hours after ingestion of colostrum. Fourteen pigs were vaccinated when 7 weeks old, and 15 pigs were not vaccinated. At 10 weeks of age, pigs were challenge-exposed with virulent CSF virus. Blood samples were collected and assayed for CSF antibodies and p125 antigen and p125 antibodies. RESULTS: CSF antibodies were detected in pigs beginning 2 hours after suckling. Colostral antibodies persisted for > 7 weeks (half-life, 79 days). Vaccination of pigs before suckling provided effective protection from severe disease after challenge-exposure. However, vaccination of neonates with antibody titers was not effective, because 19 of 23 (82%) pigs succumbed after challenge-exposure. All pigs vaccinated when 7 weeks old resisted challenge-exposure, whereas all unvaccinated control pigs succumbed. CONCLUSIONS AND CLINICAL RELEVANCE: Vaccination before ingestion of colostrum conferred good protection against CSF in baby pigs. Vaccination of 7-week-old pigs that had decreasing concentrations of passively acquired antibodies was efficacious.

Adsorption↗
PubMed1994

Vaccination of maternally immune pigs with a live Aujeszky's disease vaccine by coarse spray and other routes.

33 ten weeks old passively immune weaners were inoculated with live, attenuated Aujeszky's disease (AD) vaccine, according to four different vaccination protocols: (groups A/A2) 3 x coarse spray vaccination at 10, 11 and 13 weeks of age, (groups B/B2) 1 x coarse spray at 10 weeks of age followed by 1 x intramuscularly at 13 weeks, (C) 1 x intranasal instillation at 10 weeks of age, and (groups D/D2) 2 x intramuscularly at 10 and 13 weeks of age. A further 10 weaners were included as unvaccinated controls (E/E2). Spray vaccination was technically simple to perform but on average, 20% of subjects were reluctant to expose themselves to the spray. Clinical reactions were absent apart from mild fever in one pig from group B. Weight gains between 10 and 17 weeks of age were slightly lower in group A and group B weaners, compared to control unvaccinated pigs and pigs vaccinated by other routes. Virus neutralising (VN) antibody response was extremely uneven between individuals in groups A and B. Group D pigs vaccinated 2 x intramuscularly showed a 3 week lag in developing high levels of antibody but the intramuscular route, as well vaccination by intransal instillation, proved to be the most dependable technique for inducing uniformly high levels of VN antibody. Challenge with virulent ADV at 17 weeks of age resulted in death from Aujeszky's disease of all five control pigs. One pig in group A which had no VN antibody, also died. All other pigs were protected against death.(ABSTRACT TRUNCATED AT 250 WORDS)

Administration, Inhalation↗
PubMed1985

A scanning and transmission electron microscopic examination of Rickettsia tsutsugamushi-infected human endothelial, MRC-5, and L-929 cells.

Monolayers of primary human endothelial cells were infected with the Karp strain of Rickettsia tsutsugamushi and examined by scanning and transmission electron microscopy. The results were compared with those obtained with similarly infected L-929 and MRC-5 cells and with uninfected cells of all three types. The rickettsiae grew to slightly higher titers in the human endothelial cells. Transmission electron microscopy revealed significant changes in the host cell organelles; a reduction in ribosome-coated endoplasmic reticulum and in Golgi activity, swelling of mitochondria, and an increase in vacuolation within the cytoplasm. Since human endothelial cells are known to retain their in vivo structural and functional qualities when cultured in vitro, it is likely that these effects are similar to those which occur during the infectious process in human scrub typhus.

Animals↗
PubMed1985

Pathology of toxic death in mice following intravenous injection of Rickettsia tsutsugamushi strain gilliam: examination by light and scanning electron microscopy.

The pathologic manifestations of the toxic death elicited by the iv injection of mice with Rickettsia tsutsugamushi strain Gilliam were examined by light and scanning electron microscopic techniques to ascertain the cause of death. Light microscopic examinations of hematoxylin and eosin-stained sections of organs suggested the presence of fluid in the lungs; this was confirmed by an increase in the weight of the lungs of moribund mice. Scanning electron microscopy of blood cells demonstrated a marked crenation of erythrocytes from these mice. Death appears to be the result of shock brought on by vascular collapse secondary to plasma leakage.

Animals↗
PubMed1984

Factors affecting the lethality of Campylobacter fetus subspecies jejuni in mice.

Intraperitoneal injection of Campylobacter fetus ss. jejuni into HAM/1CR mice was lethal, but viable counts of bacteria from whole body homogenates, organs and blood indicated that death was not due to sustained bacterial multiplication. Heat-killed organisms (5 X 10(9) cfu) injected into 7-day-old mice caused death within 24 h and this was shown to be due to endotoxin. Both ferric iron and heterologous lipopolysaccharide enhanced virulence; the LD50 was lowered from 1.8 X 10(9) cfu to 2.7 X 10(7) cfu when both were used. Three-day-old or adult animals survived challenge with Campylobacter fetus without clinical symptoms when challenged orally or by intravenous or intraperitoneal routes.

Aging↗