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Biomedical subjects

C A Hart

Publications and source records attributed to C A Hart.

At least 217 records · Page 12Linked to original sources
PubMed1996

Analysis of the human serological immune response to a variable region of the attachment (G) protein of respiratory syncytial virus during primary infection.

The serum antibody responses of babies to the variable carboxy-terminal region of the attachment (G) protein of respiratory syncytial virus (RSV) have been analysed using paired acute and convalescent sera from infants experiencing their first RSV infection with viruses of known genotype. The variable 84-85 carboxy-terminal amino acids of the G protein of six recent isolates of group A RSV were expressed in Escherichia coli as fusion proteins with glutahione S-transferase. About half the infants developed antibodies which recognised these fusion proteins. The patterns of response obtained in enzyme linked immunosorbant assays and immunoblotting assays were closely related to the infecting genotype.

Acute Disease↗
PubMed1996

Regulation of neutrophil apoptosis by sodium butyrate.

Neutrophils have a very short half life because they constitutively undergo apoptosis. Granulocyte-macrophage colony-stimulating factor (GM-CSF) can delay apoptosis, but this agent also primes functions such as the respiratory burst and receptor upregulation. Here, we show that sodium butyrate, which has been shown to increase gene expression and differentiation in a variety of cell types, is more effective than GM-CSF in delaying neutrophil apoptosis. Thus, sodium butyrate preserves cell morphology and function, and butyrate-treated cells express high levels of CD16 after overnight culture. However, neither GM-CSF nor sodium butyrate appear to affect mRNA levels for CD16.

Apoptosis↗
PubMed1996

Antimicrobial peptides from Mirabilis jalapa and Amaranthus caudatus: expression, processing, localization and biological activity in transgenic tobacco.

The cDNAs encoding the seed antimicrobial peptides (AMPs) from Mirabilis jalapa (Mj-AMP2) and Amaranthus caudatus (Ac-AMP2) have previously been characterized and it was found that Mj-AMP2 and Ac-AMP2 are processed from a precursor preprotein and preproprotein, respectively [De Bolle et al., Plant Mol Biol 28:713-721 (1995) and 22:1187-1190 (1993), respectively]. In order to study the processing, sorting and biological activity of these antimicrobial peptides in transgenic tobacco, four different gene constructs were made: a Mj-AMP2 wild-type gene construct, a Mj-AMP2 mutant gene construct which was extended by a sequence encoding the barley lectin carboxyl-terminal propeptide, a known vacuolar targeting signal [Bednarek and Raikhel, Plant Cell 3: 1195-1206 (1991)]; an Ac-AMP2 wild-type gene construct; and finally, an Ac-AMP2 mutant gene construct which was truncated in order to delete the sequence encoding the genuine carboxyl-terminal propeptide. Processing and localization analysis indicated that an isoform of Ac-AMP2 with a cleaved-off carboxyl-terminal arginine was localized in the intercellular fluid fraction of plants expressing either wild-type or mutant gene constructs. Mj-AMP2 was recovered extracellularly in plants transformed with Mj-AMP2 wild-type gene construct, whereas an Mj-AMP2 isoform with a cleaved-off carboxyl-terminal arginine accumulated intracellularly in plants expressing the mutant precursor protein with the barley lectin propeptide. The in vitro antifungal activity of the AMPs purified from transgenic tobacco expressing any of the four different precursor proteins was similar to that of the authentic proteins. However, none of the transgenic plants showed enhanced resistance against infection with either Botrytis cinerea or Alternaria longipes.

Amino Acid Sequence↗
PubMed1996

Growth and propagation of normal rat intestinal epithelial cells.

A combination of mild proteolytic digestion and selective growth stimulation has been used to isolate and propagate adult rat intestinal epithelial cells with a finite life span. Growth of these cells on a variety of matrices and on mesenchymal cells has resulted in the expression of brush border enzymes including sucrase-isomaltase, aminopeptidase N, and alkaline phosphatase. Examination of the cells at the electron microscopic level has revealed that although these cells express key brush border enzymes, they do not have a fully formed brush border. These findings suggest that the expression of brush border enzymes and structural proteins represent distinct stages of enterocyte differentiation that are under separate transcriptional and temporal control.

Alkaline Phosphatase↗
PubMed1996

Studies on natural transmission of Bordetella bronchiseptica in cats.

Two pregnant specific-pathogen-free (SPF) cats, from a colony endemically infected with Bordetella bronchiseptica, were housed under barrier conditions in the latter stages of pregnancy in order to study the possible transmission of the organism to their kittens. Both queens had antibody titres to Bordetella bronchiseptica of 1 in 320 at the start of the experiment but did not shed Bordetella bronchiseptica until 9 days and 6 weeks after parturition, respectively. Five of the nine kittens had detectable maternally-derived-antibody to Bordetella bronchiseptica which declined to < or = 1 in 40 by two weeks of age. Kittens were weaned at 12 weeks of age. No Bordetella bronchiseptica was isolated from any of the kittens and none seroconverted over this time. At 15 1/2 weeks of age, half of each litter were housed separately and inoculated intra-nasally with 10(8) colony-forming-units B. bronchiseptica. Mild signs of upper respiratory tract disease were seen and the organism was isolated for 19 weeks following inoculation when the experiment ended. Seroconversion occurred at 4 weeks postinoculation. Oral treatment of two clinically-recovered kittens with doxycycline once a day did not eliminate shedding.

Animals↗
PubMed1996

The occurrence of hepatitis B and C viruses in Pakistani patients with chronic liver disease and hepatocellular carcinoma.

To study the occurrence of hepatitis B virus (HBV) and hepatitis C virus (HCV) in patients with chronic liver disease (CLD) and hepatocellular carcinoma (HCC) in Pakistan, blood samples from 105 sequential patients with biopsy-proven CLD (n = 82) and HCC (n = 23) were tested for HBV and HCV markers. Of the 105, 87 (83%) had evidence of hepatitis B exposure, 58 (55%) were positive for hepatitis B surface antigen (HBsAg), 23 (22%) had hepatitis C antibodies and 25 (24%) had detectable HCV RNA. Significantly more patients with HCC had evidence of HBV exposure in the absence of HCV markers (49/82 vs. 20/23, odds ratio 4.49, 95% CI 1.17-25.16). The proportion of patients positive for HBsAg with no HCV markers was also significantly higher in the HCC group (34/82 vs. 18/23, odds ratio 5.08, 95% CI 1.59-18.96). There were more patients with only HCV markers in the CLD group than the HCC group but the difference was not statistically significant (19/82 vs. 1/23, odds ratio 6.63, 95% CI 0.93-288.01). A modified non-isotopic restriction fragment length polymorphism study on PCR products was used to investigate the epidemiology of HCV genotypes in Pakistan. Due to depletion of the initial samples, a second series of specimens collected one year afterwards was used. Fifteen out of 40 samples had amplifiable product and all were identified as type 3. A commercial serological typing method on the same samples also confirmed that type 3 was the predominant HCV genotype in Pakistan.

Adolescent↗
PubMed1996

Sodium butyrate delays neutrophil apoptosis: role of protein biosynthesis in neutrophil survival.

Sodium butyrate, which directly affects chromatin structure and function in many cells, is as effective as granulocyte-macrophage colony-stimulating factor (GM-CSF) in delaying apoptosis in human neutrophils. Both butyrate and GM-CSF preserved the ability of neutrophils cultured for 22 h in vitro to generate reactive oxidants and express receptors such as CD16. They also delayed apoptotic morphology and DNA fragmentation, and stimulated de novo biosynthesis: newly-labelled polypeptides detected by 2D-polyacrylamide gel electrophoresis after treatment with GM-CSF and butyrate were very similar. Cycloheximide abrogated the effects of both GM-CSF and butyrate. Exposure to butyrate for 1 h did not prime oxidant production and did not up-regulate expression of CD11b. Hence, unlike GM-CSF, butyrate does not stimulate translocation of granules to the plasma membrane. These data suggest that active gene expression is involved in the regulation of neutrophil apoptosis and changes in chromatin structure and function may control apopotosis in these cells.

Apoptosis↗
PubMed1996

Placental transfer and maternally acquired neonatal IgG immunity in human immunodeficiency virus infection.

Transplacental transfer of specific IgG antibodies was studied in 46 pairs of human immunodeficiency virus type 1 (HIV-1)-seropositive women and their neonates and in 53 pairs of healthy HIV-seronegative mothers and their newborns. Neonatal and maternal sera were assessed by nephelometry for total levels of serum IgG and by ELISA for IgG antibodies to herpes simplex virus (HSV), varicella-zoster virus (VZV), measles virus, tetanus toxoid, streptolysin O, and Streptococcus pneumoniae capsular antigens. Placental transfer of IgG antibodies to VZV, tetanus toxoid, measles, streptolysin O, and S. pneumoniae was decreased by maternal HIV infection. Maternal levels of total IgG had an independent effect on transfer of antibodies to HSV, VZV, measles, and S. pneumoniae. Neonatal antibody levels to tetanus toxoid, measles, and S. pneumoniae were significantly lower in the HIV group. Both maternal hypergammaglobulinemia and maternal HIV infection may contribute to these low antibody levels at birth and thus lead to early infection in this high-risk population.

Antibodies, Bacterial↗
PubMed1996

Multi-drug resistant non-typhi salmonellae in Kenya.

Two methods of plasmid characterization, restriction digest patterns and incompatibility grouping, were used to study self-transmissible multi-drug resistance among non-typhi salmonellae (NTS). Resistance to ampicillin and other commonly applied beta-lactams was evaluated by iso-electric focusing and disc inactivation. Of the NTS isolated from blood, 75% were Salmonella typhimurium but those included several different phage types. Over 47% of isolates were resistant to three or more of the readily available drugs including ampicillin, cefuroxime, chloramphenicol, co-trimoxazole, streptomycin and tetracycline. Self-transferable resistance plasmids (c. 100 kb) were essentially of incompatibility group incFIIA, but their restriction fragment patterns revealed a diversity in relatedness. More than half of parent strains and their transconjugants produced beta-lactamases which co-electrophoresed with TEM-1 and OXA-1. This study has observed a disturbingly high prevalence of transmissible multi-drug resistance among NTS which are an important cause of morbidity in HIV-1 seropositive individuals.

Ampicillin Resistance↗
PubMed1996

Expression of Aeromonas caviae bla genes in Escherichia coli.

An isolate of Aeromonas caviae 035 carried a 55.5 kb self-transferable plasmid. Transfer of the plasmid to Escherichia coli K12 resulted in the expression of a TEM-like beta-lactamase that was not expressed in parental A. caviae. The bla gene sequence was detectable by DNA hybridization and PCR amplification of the plasmid when extracted from parental A. caviae or from E. coli K12 transconjugants. Sequence analysis of the bla genes revealed in each case an 858 bp open reading frame, differing from the TEM-1 sequence by five nucleotide substitutions. Only one of these resulted in amino acid substitution (at position 162 serine-->arginine). The sequence most closely resembles that of TEM-12.

Aeromonas↗
PubMed1996

Lactobacillus GG and acute diarrhoea in young children in the tropics.

A prospective, placebo controlled, triple blind clinical trial was undertaken in Thailand to determine the effect of Lactobacillus GG on recovery from acute diarrhoea in children. Thirty-nine children (mean age = 8 months) were enrolled and following rehydration received either oral Lactobacillus GG (n = 20) as a freeze-dried preparation or placebo (n = 19) twice daily for 2 days. The clinical characteristics of the study groups were similar. There was no significant difference overall in clinical response detected between the study groups. When only those with acute non-bloody diarrhoea (n = 26) were considered, the mean duration of diarrhoea was significantly shorter in the lactobacillus group (1.9 days) than in the placebo group (3.3 days) (P < 0.055). Stool frequency was less on the second day in the lactobacillus group (P < 0.05). The results suggest that Lactobacillus GG accelerates recovery from acute watery diarrhoea in young children in a tropical setting.

Acute Disease↗
PubMed1996

Flagellin gene and protein variation amongst clinical isolates of Pseudomonas aeruginosa.

Flagellin gene sequences from 64 clinical isolates of the opportunistic pathogen Pseudomonas aeruginosa were amplified by PCR and subjected to RFLP analysis by using seven restriction enzymes to digest the amplified products. Using this approach the isolates were assigned to one of 13 groups. The method was rapid, reproducible and applicable to all isolates. In contrast, serotyping failed to satisfactorily resolve 49% of the strains tested. The vast majority of clinical isolates generated amplified products of 1.02 kb (type a) or 1.25 kb (type b). Electron microscopical analysis revealed evidence fax some. flagellar structural variation between P. aeruginosa strains. This study provides further evidence that the flagellin gene is a widely applicable and useful genetic marker for studying genetic variation within populations of closely related bacteria.

Base Sequence↗
PubMed1996

Sputum induction for the diagnosis of tuberculosis.

Confirmation of tuberculosis in young children is difficult as they seldom expectorate sputum. Gastric aspirates are invasive and stressful and like laryngeal swabs are seldom smear positive. Induction of sputum by nebulised hypertonic saline (3%) was attempted in 30 Malawian children aged 3-15 years and was successful in 29. Four sputa were smear positive and Mycobacterium tuberculosis was cultured from three of them. A further four sputa were culture positive though smear negative. In all, the diagnosis of tuberculosis was confirmed in eight (28%) of 29 children. The presence of polymorphonuclear cells in the specimen was indicative of sputum, in contrast to epithelial cells which originate from saliva. A predominance of polymorphonuclear cells in specimens was more common in older children and these specimens were more likely to be smear positive or culture positive. Sputum induction is a useful method for the confirmation of tuberculosis and is possible in young children.

Adolescent↗
PubMed1996

Proinflammatory and anti-inflammatory cytokines in meningococcal disease.

Interleukin-10 (IL-10), an anti-inflammatory cytokine, was measured in 131 children with meningococcal disease. IL-10 concentrations were significantly higher in children who died and correlated positively with proinflammatory cytokines. Children who die from meningococcal disease have high IL-10 concentrations, which do not suppress proinflammatory cytokines.

Adolescent↗