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Biomedical subjects

S L Loke

Publications and source records attributed to S L Loke.

At least 55 records · Page 3Linked to original sources
PubMed1990

Nasal lymphoma. A retrospective analysis of 60 cases.

Sixty cases of nasal lymphomas were reviewed. There were 42 men and 18 women. The median age was 49 years. The histologic types were low grade in four cases, intermediate grade in 33, high grade in seven, and unclassifiable in 16. Thirteen cases had features of polymorphic reticulosis. The immunophenotype was available in 18 cases and a majority of 67% of them were T-cell. Forty-one of them (68%) had clinically localized (Stage I and II) disease which often spread locally to neighboring tissues and they presented predominantly with nasal symptoms. Nasal lymphoma appeared to carry a poor prognosis. Although our patients with clinically localized disease had significantly better prognosis than those with advanced disease, the 5-year survival of Stage I and II patients was only 55%. Chemotherapy did not appear to be more effective than radiotherapy alone in preventing relapses but the patient number was too small to allow a firm conclusion to be made. Patients with advanced disease had even poorer prognosis with a 5-year survival of only 17%. Innovative therapy has to be developed for these patients.

Adolescent↗
PubMed1990

Histologic subtypes and survival of Chinese patients with non-Hodgkin's lymphomas.

The histologic subtypes and survival of 840 Chinese patients with non-Hodgkin's lymphoma (NHL) were reviewed. All cases were classified according to the Rappaport and Kiel systems and the Working Formulation (WF). A low incidence of nodular/follicular lymphomas (12%) was observed. The most common histologic subtypes were diffuse histiocytic, diffuse centroblastic, and diffuse large cell lymphomas, according to Rappaport, Kiel, and the WF, respectively. A high proportion (24%) of the cases were unclassifiable, according to Kiel, because of the precise terms of the classification. The "favorable"-prognosis NHL, according to Rappaport, or the low-grade NHL, according to Kiel and the WF, had a more indolent clinical course. However, except for the nodular mixed (Rappaport) or follicular mixed (WF) lymphomas which appeared to behave like the more aggressive NHL, a plateau was not seen in the survival curves of our patients with other kinds of favorable-prognosis or low-grade NHL, indicating the lack of curative potential of these tumors. The lymphoplasmacytoid lymphoma, according to Kiel, also appeared to have a more aggressive clinical course. A plateau was seen in most of the other survival curves of patients with the more aggressive tumors, indicating the prospect of cure. However, the prognosis of the very aggressive tumors such as the diffuse lymphoblastic and diffuse small noncleaved cell lymphomas, according to the WF, remains very poor with a median survival of less than 10 months.

Adolescent↗
PubMed1990

Tumour-specific inhibition of lymphoma growth by an antisense oligodeoxynucleotide.

In a high proportion of Burkitt lymphomas, transcription of the c-myc gene is initiated from a cryptic promoter in the first intron, creating abnormal messenger RNA molecules in which intron sequences, normally spliced out of the nascent transcripts, persist. An antisense oligodeoxynucleotide directed against these intron sequences greatly inhibited the proliferation of Burkitt lymphoma cell lines containing the abnormal transcripts (ST486 and JD38), but not that of cell lines containing normal c-myc transcripts (KK124). Flow cytometry showed a pronounced reduction in intracellular c-myc protein levels in cell lines containing aberrant myc transcripts, but no change in other cellular proteins. Control oligonucleotide did not inhibit c-myc protein expression or growth. These experiments provide evidence that antisense oligonucleotides targeted against tumour-specific, aberrant RNA species could be effective in controlling the proliferation of tumour cells without affecting normal cells.

Base Sequence↗
PubMed1990

Polymorphic reticulosis and conventional lymphomas of the nose and upper aerodigestive tract: a clinicopathologic study of 70 cases, and immunophenotypic studies of 16 cases.

Seventy patients with malignant lymphomas, including the entity known as polymorphic reticulosis (PR), involving the nose, nasal sinuses, nasopharynx, oropharynx (excluding tonsil), and larynx were studied. There were 26 cases of PR, 19 cases of lymphoma with features of PR (ML[PR]) and 25 cases of conventional lymphomas. Fourteen of the 25 conventional lymphomas were due to dissemination from distant sites. For all histologic types of primary lymphoma, the presenting symptoms were similar, and the nasal cavity was more commonly involved than the nasopharynx. Patients with PR were younger, had a higher male:female ratio, and had a better overall survival rate than patients with conventional lymphomas. Cryostat section immunohistochemistry performed on 17 samples from 16 patients showed only one B lymphoma out of 11 primary lesions; the other 10 cases and three recurrent tumors at distant sites showed phenotypic markers of T lymphocytes and natural killer cells. All three secondary tumors were of B-cell type. Of eight patients with sequential biopsies, progression to a more malignant histopathologic type was found in six. In the PR and ML[PR] biopsies, angiocentricity was detected in 11%, and angioinvasion in 22%. We could not confirm identity of PR with other angiocentric immunoproliferative lesions.

Humans↗
PubMed1990

Translocation of bcl-2 gene in non-Hodgkin's lymphomas in Hong Kong Chinese.

The close association between translocation of the proto-oncogene bcl-2 and follicular lymphomas has been well established in Caucasian patients and the de-regulation of bcl-2 has been implicated in follicular lymphomagenesis. Similar molecular structural alterations have also been detected in diffuse lymphomas with a previous history of a follicular pattern as well as in a smaller proportion of de novo diffuse lymphomas. There is a lower incidence of follicular lymphomas in Chinese. In order to investigate further this phenomenon, we used bcl-2 translocation as a genetic marker of follicular lymphomas, to study 31 cases of B cell non-Hodgkin's lymphomas in Chinese patients by Southern blot analysis. Eight out of 16 cases of follicular lymphomas showed bcl-2 translocation with involvement of the major breakpoint region (MBR). Six of these cases utilized breakpoints within the 4.3 kb HindIII fragment, while in two cases the breakpoints were more dispersed, but still within the BamHI fragment. An additional case of follicular lymphoma showed translocation of bcl-2 gene with involvement of the minor cluster region (mcr), making a total of nine out of 16. None of the 15 cases of diffuse lymphomas showed similar molecular structural alterations. These data show that bcl-2 translocation is present in 57% of follicular lymphomas in Chinese patients, and support the notion that bcl-2 translocation is a consistent marker for follicular lymphomas irrespective of ethnic differences. As the translocation is not detected in the diffuse lymphomas, there is no evidence to suggest that the low incidence of follicular lymphomas in Chinese patients is due to a greater tendency for follicular tumours to progress rapidly and present as diffuse lymphomas.

Blotting, Southern↗
PubMed1990

Human papillomavirus in oesophageal squamous cell carcinoma.

Thirty seven cases of oesophageal squamous cell carcinoma were studied by applying DNA slot blot analysis and in situ hybridisation using type specific probes for HPV 6, 11, 16 and 18. Cases of condyloma accuminata, cervical carcinoma, and laryngeal papilloma were used as controls. Blocks including areas of invasive carcinoma, intraepithelial neoplasia, and normal epithelium were studied in each case. No HPV genome was detectable in any of the oesophageal cases. It is concluded that these types of HPV do not have an association with oesophageal squamous cell carcinoma.

Carcinoma, Squamous Cell↗
PubMed1990

Localisation of CD10 to biliary canaliculi by immunoelectron microscopical examination.

Common acute lymphoblastic leukaemia antigen (CALLA) was first characterised in lymphoid leukaemic cells. The antigen is present in different stages of lymphoid cell differentiation as well as in subsets of myeloid cells, and further studies have also shown its presence in non-lymphoid tissues. The recent cloning and sequencing of the gene permitted deduction of its amino acid sequence which is identical with the human membrane-associated enzyme, neutral endopeptidase. Strong immunostaining for CALLA was detected in the human liver with a canalicular pattern. Immunoelectron microscopy also confirmed that the antigen was localised only in the area of the bile canaliculi. Although the function of neutral endopeptidase in the canaliculi is unknown, this antigen may prove useful in the study of biliary function and diseases.

Antigens, CD↗
PubMed1989

Characterization of oligonucleotide transport into living cells.

Addition of antisense oligonucleotides to cell cultures has been used to specifically inhibit gene expression. We have investigated the mechanism by which oligonucleotides enter living cells. These compounds are taken up by cells in a saturable, size-dependent manner compatible with receptor-mediated endocytosis. Polynucleotides of any length are competitive inhibitors of oligomer transport, providing they possess a 5'-phosphate moiety. Using oligo(dT)-cellulose for affinity purification, we have identified an 80-kDa surface protein that may mediate transport. Knowledge of the oligonucleotide transport mechanism should facilitate the design of more effective synthetic antisense oligomers as potential clinical agents.

Acridine Orange↗
PubMed1989

Improved silver technique for showing nucleolar organiser regions in paraffin wax sections.

An improved technique for the demonstration of nucleolar organiser regions (NORs) was devised. It has the advantage that any non-specific background deposits which mimic the NOR dots formed during staining are trapped by the celloidin film. The specificity of the silver staining is also increased by the postfixation treatment of sections in an acetic acid-ethanol mixture. Moreover, it is economical because of the low silver content and small volume of the incubation solution used.

Humans↗
PubMed1988

Phosphorothioate and normal oligodeoxyribonucleotides with 5'-linked acridine: characterization and preliminary kinetics of cellular uptake.

Certain phosphorothioate oligodeoxynucleotide (S-oligo) analogs, unlike their normal congeners, have been found to exhibit significant anti-HIV activity [Matsukura et al., Proc. Natl. Acad. Sci. USA 84 (1987) 7706-7710]. Here we report melting temperatures (Tm) of a series of S-oligos compared with those of the corresponding normal oligomers. The Tm's for AT base pairs of S-oligos are significantly depressed relative to normal oligos, while GC-containing S-oligos show much less Tm depression. The Tm's of S-dT oligomers with poly(rA) are reduced relative to the duplexes with normal dA oligomers. These results provide a rational basis for the S-d(CG) sequences as anti-message inhibitors of gene expression. We also describe an automated synthesis of 5'-acridine linked oligothymidylates using phosphoramidite-linked acridine. During this synthesis we noted the replacement of thiophenol for the 6-chloro substituent on acridine. We have measured the Tm's of the compounds with 3 and 5 methylene groups linked to normal and phosphorothioate dTn (with n = 3-40) on duplex formation with the equivalent dAn, and have found small increases of Tm for the 5-methylene-linked acridine derivative. We have monitored the uptake of these fluorescently labeled oligos into HL60 cells, and found that the shorter oligos are more rapidly taken up than the longer, and the normal oligos faster than the S-oligos. The temperature dependence of the cellular uptake suggests an energy-dependent process, and a possible membrane receptor for oligos. These results have significance for the potential use of such compounds as inhibitors of gene expression.

Acridines↗
PubMed1988

c-myc protein in normal tissue. Effects of fixation on its apparent subcellular distribution.

The c-myc protein is thought to be a DNA-associated nuclear protein. However, immunohistochemical studies on normal or tumor tissues have shown conflicting findings on its subcellular distribution. By using various fixation procedures on cytospin preparations of HL60 cells, the authors found the subcellular distribution of the c-myc protein to be dependent on the method of fixation. When studying mouse tissues in frozen sections using a biotinylated monoclonal antibody against the c-myc protein, they found the protein to be widely distributed in various normal adult mouse tissues, in most cases localized to the nucleus. However, when these tissues were studied after formalin fixation and paraffin embedding, a loss of nuclear staining was observed concurrent with the appearance of c-myc protein immunoreactivity in the cytoplasm. It is concluded that immunohistochemical studies on the expression of this oncogene should take into consideration the effects of fixation when its subcellular distribution is being examined.

Animals↗
PubMed1987

Non-Hodgkin's lymphoma as a cause of hypoadrenalism.

Non-Hodgkin's lymphoma which presents as adrenocortical insufficiency is rare, however, it should be a well-recognised entity because, in addition to specific chemotherapy or radiotherapy, it needs hormonal replacement. We report a patient with diffuse histiocytic lymphoma, who had remission for seven years and relapsed with Addisonian crisis.

Adrenal Gland Neoplasms↗
PubMed1987

Peripheral T cell lymphoma.

Thirty-one Chinese patients with peripheral T cell lymphoma (PTCL) were reviewed. Using the modified Japanese Lymphoma Group classification, there were nine (29%) of the pleomorphic type, 16 (52%) immunoblastic lymphadenopathy (IBL)-like, two (7%) T-zone lymphoma, and one (3%) Lennert's lymphoepithelioid type. Three (9%) were not classifiable. All were positive for T11 (E rosette receptor antigen). Fifty-four percent (15 of 28) were positive predominantly for T4 (helper T cell) and 46% (13/28) for T8 (suppressor T cell). The median age of the patients was 57 years. They usually presented with advanced disease, and while extranodal involvement was common, CNS disease was not seen. The IBL-like type was associated with a positive Coombs' test and polyclonal hypergammaglobulinemia. Five of the nine pleomorphic type were checked for antibody to HTLV-I virus and all were negative. PTCL was associated with poor prognosis, which was not influenced by the histologic subtypes and the T4/T8 phenotypes. The complete response rate of 13 consecutive patients who received the BACOP (bleomycin, doxorubicin, cyclophosphamide, vincristine, and prednisone) L17M regimen was significantly better than the 16 historic controls who received other less-intensive regiments, 84% v 19% (P less than .01). The relapse rate was also significantly lower, 9% v 100% (P less than .001). There appeared to be an improvement in the disease-free survival (DFS) (80% v 0% at 18 months), as well as the overall survival (60% v 36% at 18 months), but the differences did not reach statistical significance due to small sample sizes.

Adult↗
PubMed1987

Localized amyloidosis of the ureter.

An unusual case of localized amyloidosis of the ureter is described. Suspicion of the condition was first raised during operation when a frozen section was examined. An unnecessary nephrectomy was thus spared. It is a rare condition and awareness of the entity is required to recognise it clinically, radiologically or pathologically. The pathogenesis of localized amyloidosis is briefly discussed.

Aged↗