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Biomedical subjects

J Perera

Publications and source records attributed to J Perera.

10 recordsLinked to original sources
PubMed1992

Effects of transcutaneous needle stimulation on the immune response in rabbits.

Studies in the field of neuroimmunomodulation have shown that endorphins such as methionine-encephalin may have an immunomodulatory role. This study was undertaken to test whether transcutaneous needle stimulation, which is known to release such peptides from the central neurones, has an effect on immune response in rabbits. Twelve healthy rabbits, in three similar subgroups, were exposed to pathogenic Escherichia coli and their immune response was studied under different experimental conditions. Our results show that needle stimulation causes a reversal of stress induced suppression of antibody production. Further studies are necessary to evaluate any therapeutic uses these observations may have in humans.

Animals↗
PubMed1992

Methicillin resistant Staphylococcus aureus.

Out of 308 isolates of Staphylococcus aureus isolated from specimens processed at the Department of Microbiology, Faculty of Medicine, Colombo 66 (21.5%) were resistant to methicillin. A significantly higher proportion of methicillin resistant Staphylococcus aureus (MRSA) were isolated from special care units, namely the Premature Baby Unit (PBU) and the Plastic Surgery Unit (PSU) when compared with other general medical and surgical units. Most of these strains were also resistant to many other antibiotics. The patients with MRSA infections had a longer mean hospital stay when compared to patients with methicillin sensitive Staphylococcus aureus (MSSA) infections. MRSA strains are as virulent as MSSA strains and these infections are mainly nosocomial.

Female↗
PubMed1991

Class II-restricted presentation of an endogenously derived immunodominant T-cell determinant of hen egg lysozyme.

An in vitro model was used to investigate the potential for different structural forms of endogenous antigen to be processed and presented by major histocompatibility complex class II molecules. For this purpose the class II-restricted presentation of an immunodominant epitope of hen egg lysozyme [HEL-(46-61)] was studied in class II-positive B-lymphoma cells (M12.C3) transfected with genes encoding HEL molecules either (i) secreted in high (hi) or low (lo) amounts as soluble antigen [sHEL(hi/lo)], (ii) localized within the endoplasmic reticulum (ER)/salvage compartment (ER-HEL), or (iii) anchored on the cell surface as an integral membrane protein (mHEL). The corresponding sHEL, ER-HEL, and mHEL gene products were expressed as predicted except that HEL determinants accumulated in the culture supernatant as well as on the cell membrane of mHEL-transfected cells. Class II-positive cells endogenously expressing all three forms of HEL antigen constitutively presented the immunodominant HEL-(46-61) determinant with differential efficiency (mHEL, sHEL greater than ERHEL) to a class II-restricted T hybridoma. A second T hybridoma recognized endogenous HEL-(46-61) determinants constitutively presented on sHEL(hi) and mHEL transfectants but not on sHEL(lo) or ERHEL transfectants. The formation of HEL-(46-61)/I-Ak complexes in the ERHEL and sHEL(lo) transfectants was therefore limiting. Mixing experiments with different antigen-presenting cells indicated that the HEL-(46-61) determinant was derived from endogenous antigen rather than by reuptake of shed or secreted HEL determinants. We conclude that MHC class II molecules can present some antigenic determinants derived from endogenous proteins that are sequestered in the ER/salvage compartment as well as distally transported in the form of secretory or membrane antigens.

Animals↗
PubMed1991

Distribution of oxidizing bacterial activities and characterization of bioleaching-related microorganisms in a uranium mineral heap.

The occurrence and activity of bioleaching-related microorganisms are highest at 0.25 m under the surface of a uranium mineral heap, and decrease at points deeper than 1 m inside the heap. Thiobacillus ferrooxidans, Th. acidophilus, Th. thiooxidans and Leptospirillum ferrooxidans have been found and isolated from different sites inside the heap. Other mesophilic iron- or sulphur-oxidizing bacteria and some moderate thermophile have also been isolated from deep (1 m and 4 m) sites and characterized. Several fungi and some yeasts are present in this bioleaching habitat.

Bacteria↗
PubMed1991

Comparison of quantitative analytical methods in evaluating acidophilic iron- and sulphur-oxidizing microorganisms liquid cultures.

Different quantitative methods to evaluate cell concentrations in acidophilic iron- and sulphur-oxidizing microorganisms liquid cultures have been compared with the "most probable number of viable germs" procedure. Plating and colony counting on recently developed solid media give good results when used with pure bacterial cultures, but plating efficiency decreases with natural mixed cultures.

Bacteriological Techniques↗
PubMed1990

Cutaneous leishmaniasis in Sri Lanka. An imported disease linked to the Middle East and African employment boom.

Cutaneous leishmaniasis acquired by two Sri Lankan nationals while they were employed in Iraq and Northern Nigeria respectively constitutes examples of an imported disease related to the 'Middle East and African employment boom'. In both cases the diagnoses were confirmed by demonstrating the parasites in smears from the lesions and in tissue sections, and by culturing the parasites in vitro. Since leishmaniasis, neither visceral nor cutaneous is prevalent in Sri Lanka the risks of 'introduced' diseases is discussed here in the context of these two cases.

Adult↗
PubMed1990

Cryptosporidiosis--oocyst shedding and infection in household contacts.

The incidence of cryptosporidiosis in children with acute diarrhoea when compared with age-matched controls was 6.1% in a paediatric unit. Studies were made on eight immunocompetent children with cryptosporidiosis to determine the period of oocyst shedding after cessation of diarrhoea. The majority (75%) shed oocysts for less than ten days after cessation of diarrhoea. There was considerable variation among patients, some eliminating oocysts more quickly than others. This was not related to the severity or duration of diarrhoea. The sucrose floatation technique was found to be more sensitive than direct smear for detecting small numbers of oocysts present at the end of the shedding period. Studies on household contacts showed infection in 43%, which suggests a subclinical infection or a transient carrier state, and confirms the occurrence of person to person transmission.

Animals↗
PubMed1989

Expression, cloning and cDNA sequence of a fibroblast serum-regulated gene encoding a putative actin-associated protein (p27).

A cDNA clone for a basic putative actin microfilament-associated protein, p27, highly induced in serum-stimulated NIH 3T3 cells, has been isolated by polyclonal antibodies and sequenced. p27 mRNA is a 1.2-kb molecule which is very low in resting NIH 3T3 cells but can be induced at least 100 times after 8 h of fetal calf serum stimulation. In contrast to other inducible mRNAs, p27 mRNA is stable, and its levels can be superinduced by cycloheximide mainly by prolonging transcription. The lack of expression of this messenger in mouse tissues, as well as in all cell lines so far tested, suggests that p27 may be an fibroblast-specific protein. One major open reading frame found in p27 cDNA codes for a 201 amino acid polypeptide not related to any previously described actin-binding protein. Interestingly, it shows alternative hydrophilic and hydrophobic domains of amino acids symmetrically arranged from the middle of the protein. The coordinate induction of p27 and actin mRNAs suggest that p27 may be involved in the cytoskeletal rearrangements induced early in cell growth and proliferation.

Amino Acid Sequence↗
PubMed1988

Complexity of the early genetic response to growth factors in mouse fibroblasts.

Genes whose expression is growth factor regulated are likely to be important components in the mechanisms controlling cell proliferation and differentiation. With the aim of identifying some of those genes, a lambda cDNA library was prepared with poly(A)+ RNA from quiescent NIH 3T3 cells stimulated with serum for 4 h in the presence of cycloheximide. Differential screening of approximately 200,000 recombinant phage plaques revealed 2,540 clones that cross hybridized preferentially with [32P]cDNA derived from RNA of stimulated cells rather than with cDNA derived from nonstimulated cells. Cross hybridization of these clones identified 82 independent sequences, including c-fos and c-myc. Seventy-one clones were further studied. Analysis of the changes in transcription and mRNA levels after serum stimulation demonstrated that the kinetics and extent of the induction vary dramatically between the different genes. Cycloheximide in all cases superinduced the mRNA levels by two mechanisms, inhibiting the shutoff of transcription and prolonging the half-lives of the mRNAs. Our results showed that induction of proliferation is accompanied by the onset of a complex genetic program.

Animals↗