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Biomedical subjects

G Lecatsas

Publications and source records attributed to G Lecatsas.

At least 73 records · Page 4Linked to original sources
PubMed1977

A microbiological study of gastro-enteritis in Black infants.

A survey was carried out to determine the aetiological agents responsible for acute gastro-enteritis in Black infants. Bacteriological examination of 191 patients and 178 age-matched controls showed that salmonellae and shigellae together accounted for only 15% of cases and were harboured by almost 7% of controls. Seropositive 'enteropathogenic' Escherichia coli was an important cause of diarrhoea, especially in the summer months. Enterotoxin-producing E. coli was not a significant cause of gastro-enteritis in this study. This study suggests that routine serotyping of E. coli from infantile gastro-enteritis should be continued until the relationship of serotype and enterotoxigenicity with enteropathogenicity has been established. Rotaviruses were detected by electron microscopy in 14,4% of children. The clinical features associated with the different infectious agents are described.

Black or African American↗
PubMed1977

A microbiological investigation of acute summer gastroenteritis in black South African infants.

A microbiological investigation of Black infants suffering from severe acute summer gastroenteritis revealed enteropathogenic agents in 30 out of 37 patients (81%). Enterotoxigenic bacteria were isolated from 15 patients (41%). A total of 16 enterotoxigenic strains were isolated, comprising 9 enterotoxigenic Escherichia coli strains secreting labile and stable toxin on their own and in combination, and labile-toxin secreting strains of Klebsiella pneumoniae (4), Enterobacter cloacae (2) and Proteus vulgaris (1). In the case of the latter three species, however, 6 out of the 7 strains were isolated from patients who were excreting other enteric pathogens, whereas only 2 out of 9 enterotoxigenic E. coli patients had concomitant infections with other pathogens. No invasive bacteria were isolated except for 2 shigella strains. Salmonella and shigella strains were found in four patients. No correlation was found between the enteropathogenicity of E. coli and its serotype. Rotavirus was observed by negative staining electron microscopy in only two patients (6%) but using a reverse complement fixation test rotavirus antigen was detected in the stool of 17 out of 35 patients (49%). The low EM detection rate may well be due to the patients being admitted for treatment late in the course of their illness when the degree of viral shedding has decreased below EM detectability. No significant difference in clinical presentation was noted between the various aetiological agents. Only one patient was being solely breast-fed compared to 16% of control non-diarrhoeic infants. Evidence of malnutrition was noted in over half of our patients.

Acute Disease↗
PubMed1977

Antigenic relationship between human and simian rotaviruses.

The simian rotavirus, SA 11, and the murine rotavirus, EDIM, were investigated for antigenic relatedness to the human rotavirus, by immunoelectron-microscopy. These studies led to the recognition of two types of rotavirus antibody. One agglutinated "rough" virus particles only and was group-reactive; it appears to be widely distributed in various animal species, including human infants. The second antibody agglutinated "smooth" virus particles and was more species-specific, demonstrating only a one-way cross-reaction between the simian and human viruses; it was found only in convalescent-phase human sera and in hyperimmune rabbit sera and is probably protective. The simian rotavirus is easy to propagate in primary cell culture and in cell lines and should prove useful for serodiagnosis of human gastroenteritis. It may be a candidate for immunoprophylaxis.

Animals↗
PubMed1977

Electronmicroscopical characterisation of simian papovavirus SA12.

Ultrastructural studies of simian virus SA12, growing in primary cultures of vervet monkey-kidney cells, have demonstrated a typical papovavirus capsid morphology and a diameter of 43 nm. The cytopathic nuclear characteristics, with the absence of virus crstals and elongated capsid forms, distinguish it from SV40 and the human papovaviruses. Like other papovaviruses, SA12 shows a strong affinity for cellular membranes.

Animals↗
PubMed1976

Establishment of a continuously growing cell line from primary carcinoma of the liver.

A continuously growing cell line has been established from autopsy material taken from a primary liver carcinoma, a cancer which has a high incidence in Southern Africa. The cell line was initiated from multifocal areas of outgrowth in the primary culture, and adaptation to in vitro conditions was completed after 18 months. The cells resemble hepatocytes in culture, have a doubling time of 35-40 hours and a plating efficiency of 40-50%. No virus particles have been found in the cells by ultrastructural examination. The isozyme pattern and the karyology of the cells are human. The chromosome pattern is heteroploid (mean number 56) and there are marker chromosomes.

Adult↗
PubMed1976

Development of a new human polyoma virus strain (MG).

A polyoma virus isolated from the urine of a renal transplant patient has been grown on primary human foetal fibroblasts and its pattern of replication studied by thin section electron microscopy. Virus replication is characterized by the appearance of spherical, crystalline arrays in the nucleoplasm which differ from the nuclear virus crystals found in cells infected by the human polyoma virus prototypes JC and BK. A serological study has substantiated differences between the prototypes and the MG isolate. The affinity of MG and other polyoma viruses for the cell membrane suggests a possible basis for the demyelinating effect seen in cases of polyoma-associated progressive multifocal leucoencephalopathy.

Antigens, Viral↗
PubMed1976

Hepatitis B surface antigen produced by a human hepatoma cell line.

The human hepatoma cell line, PLC/PRF/5, was shown to produce hepatitis B surface antigen (HBsAg). Immunologically reactive material was present in the supernatant tissue culture medium in significant amounts, and was associated with spherical particles approximately 20 nm in diameter. The rate of antigen production by the cells was estimated at 500 ng/day/10(6) cells by reference to a purified HBsAg standard. All immunological activity was neutralized by specific antibody and the subtype was ad. The studies reported here broaden the scope of investigations on both the in vitro production of HBsAg and the association between this antigen and primary liver cancer.

Carcinoma, Hepatocellular↗
PubMed1976

Experimental techniques in the determination of aetiology of acute infantile gastroenteritis.

Techniques used in the research laboratory for the microbiological diagnosis of infantile gastroenteritis are described. These techniques are in essence experimental models of the three pathogenetic mechanisms of bacterial diarrhoea. From the clinical bacteriological standpoint, although there is little difficulty with the identification of enteropathic bacteria such as Salmonella and Shigella, the differentiation of enteropathic strains of Escherichia coli from commensal strains is not possible with present routine bacteriological procedures. Possible adaptations of these experimental techniques to the routine laboratory are discussed. At present, negative-staining electron microscopy is the only way in which reoviruslike particles, the most important viral pathogen in infantile gastroenteritis, may be detected. Because of its relative simplicity this examination is strongly recommended in all cases of infantile gastroenteritis.

Adenoviridae↗
PubMed1975

Absence of hepatitis B antigens from feces and sewage as a result of enzymatic destruction.

Hepatitis B surface antigen (HBs Ag) was not detected in sewage by means of a sensitive affinity chromatography method combined with radioimmunoassay. The antigen was also absent from the feces and urine of 23 patients with HBs Ag antigenemia; this observation indicates that HBs Ag is rarely discharged into sewage. The absence of HBs Ag from feces is ascribed to antagonists of an enzymatic nature or to carboxypeptidase A, which destroys the antigen. Antagonists with similar effects were produced by three species of Pseudomonas but were not produced by various other bacteria. HBs Ag was also destroyed by two subtilisin enzymes. When hepatitis B sera were incubated with these enzymes or with the antagonists, small spherical particles, tubules, and the coats of Dane particles disappeared first, and Dane cores disappeared later. Although sewage or activated sludge did not affect the stability of HBs Ag, the results indicate that even Dane cores are not excreted in feces and that sewage plays a negligible role in the spread of HBs Ag, Dane cores, and viral hepatitis type B.

Bacteriological Techniques↗