Biomedical subjects

S M Lim

Publications and source records attributed to S M Lim.

At least 19 recordsLinked to original sources

PubMed1992

Morphometric analysis of nucleolar organizer regions in benign and malignant peritoneal effusions using backscattered electron microscopy.

Nucleolar organizer regions are loops of DNA associated with silver-stainable proteins (AgNORs). In general, malignant cells have more and larger AgNORs than benign cells. An inconsistent argyrophilic method and difficulties in objectively evaluating AgNORs account for some of the reluctance to utilize AgNOR staining as a diagnostic tool to differentiate benign and malignant lesions. Sections from paraffin-embedded cell blocks of 10 cases of benign and malignant peritoneal effusions were stained with a modified AgNOR method. Backscattered electron imaging in the scanning electron microscope, together with image analysis, was used to evaluate more objectively a number of AgNOR parameters and to determine which measurement was the most reliable discriminant of the two types of fluids. One hundred nuclei per case were identified and imaged. In contrast to benign nuclei, AgNORs in malignant nuclei were more numerous (P less than 0.0001) and larger (P less than 0.0001). A cut-off mean AgNOR area of 1.1 microns 2 (P less than 0.0001) correctly categorized all malignant (greater than 1.1 microns 2) and benign (less than or equal to 1.1 micron 2) cases. This system's objectivity and specificity could be used to enhance the cytological interpretation of effusions, where the separation of reactive mesothelial cells and malignant cells is extremely difficult.

Adenocarcinoma↗

PubMed1992

Immunofluorescent localization of pig complement component 3, regardless of the presence or absence of detectable immunoglobulins, in hyperacutely rejected heart xenografts.

Rabbit heart xenografts transplanted into the neck of newborn pigs were all hyperacutely rejected within two hours regardless of the presence or absence of detectable endogenous immunoglobulins (Ig). Cryostat tissue sections were prepared from the rejected rabbit hearts and incubated with sheep polyclonal antibodies against pig complement component 3 (C3), pig IgG and pig IgM. Specific immunoreaction was visualized by fluorescein-conjugated antibodies to sheep IgG. C3 was localized mainly on the surfaces of vascular endothelial as well as myocardial cells, and the localization was not dependent upon the presence of pig immunoglobulins within the same tissue. Both pig IgG and IgM were detected only in the heart xenografts transplanted into suckled pigs, whereas no trace of immunoglobulin was found in those transplanted into circulating antibody-free presuckled pigs. Treatment with cobra venom factor (which inhibits complement activity) prior to transplantation prolonged xenograft survival and completely abolished C3 immunostaining. The results provide new evidence at the histochemical level that the alternative pathway of complement is involved in hyperacute xenograft rejection of the species combination (rabbit to pig) used in this study.

Animals↗

PubMed1992

Discordant xenograft rejection in an antibody-free model.

Newborn pigs prevented from suckling colostrum were shown to have less than 0.05 micrograms/ml total immunoglobulin present in their serum. Rabbit heart xenografts transplanted heterotopically into the neck of such pigs were hyperacutely rejected, with a mean survival time of 92 +/- 14 min (mean +/- SD). Pigs which had been allowed to suckle and whose serum contained 10-15 mg/ml maternal immunoglobulin hyperacutely rejected rabbit heart xenografts in 109 +/- 62 min. Histological studies showed no Ig binding but complement component 3 (C3) binding to rabbit hearts placed in immunoglobulin-negative pigs. Prolongation of rabbit heart xenograft survival was achieved by administering cobra venom factor (1 mg/kg) to the pigs pretransplant. These data show hyperacute xenograft rejection in the absence of antibody and suggest that its cause is activation of complement by the alternative pathway.

Animals↗

PubMed1992

Cloning and characterization of pathogenicity genes from Xanthomonas campestris pv. glycines.

Nonpathogenic mutants of Xanthomonas campestris pv. glycines 8ra were generated with N-methyl-N-nitro-N'-nitrosoguanidine to identify and characterize pathogenicity genes of the bacterium. A total of 16 nonpathogenic mutants were isolated from 2,000 colonies. One mutant, NP1, was chosen for further study. NP1 did not multiply in soybean cotyledons. A genomic library of strain 8ra was constructed in the cosmid pLAFR3, and the cosmids were tested for complementation in NP1. One cosmid clone, pIH1, which contained a 31-kb insert, complemented mutant NP1. A restriction map of pIH1 was constructed, and deletion analyses identified a 10-kb HindIII fragment that restored pathogenicity to NP1. Southern hybridization analysis indicated that DNA sequences in the 10-kb HindIII fragment are conserved among other X. campestris pathovars tested. Three regions responsible for restoring pathogenicity have been identified by Tn3-HoHo1 mutagenesis. A 2.7-kb ClaI fragment was sequenced, and two possible open reading frames (ORF1 and ORF2) were found. Results indicated that ORF2 but not ORF1 may be expressed in Escherichia coli and in X. campestris pv. glycines. The carboxy terminus of the potential polypeptide encoded by ORF2 has an amino acid sequence similar to that of the gamma subunit of oxaloacetate decarboxylase, which is involved in sodium ion transport in Klebsiella pneumoniae.

Amino Acid Sequence↗

PubMed1992

A descriptive study of emergencies admitted to a surgical department.

A study was undertaken to evaluate the pattern of emergency admissions and their management by the surgical firm in a medium size (700 beds) general hospital. Over a three month period, 258 patients were admitted to one surgical team that was on take every third day. All patients were entered into a protocol that was updated daily by a registrar. In four (13.3%) of the 30 days on take, patients had to be referred to a nearby hospital due to shortage of emergency beds. The accuracy of diagnosis by the Accident and Emergency (A&E) resident, surgical resident and surgical team were 75.7, 77.2 and 88.4% respectively. The mean delay before attendance by an intern after admission was 47 (SD +/- 29) mins. Forty-four (17%) of these admissions were probably unnecessary. A further 22 (8.5%) patients had to be referred to other disciplines, indicating an initial wrong diagnosis. A substantial number of investigations were unnecessarily done on an emergency basis. Ninety-three (36.0%) patients required surgery. The median duration of hospital stay was three days. The overall morbidity was 4.2% and mortality 1.2%. The study was valuable in revealing the deficiencies in the existing emergency service; leading to new proposals to achieve our ultimate aim of providing high quality patient care.

Adult↗

PubMed1992