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Biomedical subjects

K Patel

Publications and source records attributed to K Patel.

At least 217 records · Page 12Linked to original sources
PubMed1992

Effect of peroxide bleaches on resin-enamel bonds.

Human third molar teeth were divided into three groups: untreated control; enamel treated with 35% hydrogen peroxide for 2 hours; and enamel treated with 10% carbamide peroxide gel for 14 days. All teeth were ground to present a flat enamel surface, to which cylinders of light-cured composite resin were bonded. Shear bond strengths were determined for each specimen. The mean shear bond strengths of resin-enamel bonds after pretreatment with both 35% hydrogen peroxide and 10% carbamide peroxide were significantly lower than those for untreated controls. External bleaching with these materials prior to resin bonding procedures may reduce the quality of resin-enamel bonds.

Acrylates↗
PubMed1992

Neuroblastoma in the very young child: biological considerations.

Neuroblastoma is one of the childhood malignancies that frustrates both the clinical and scientist. Clearly, some forms of the disease are relatively benign and the patient can expect to be cured. However, even today, Stage 4 neuroblastoma is one of the childhood malignancies where the overall prognosis remains very poor. Despite extensive investigations into the biology of the disease, little has been gleaned about the underlying causes of the tumour and what truly separates good and poor risk disease. Fortunately, patients under the age of one with neuroblastoma often fall into the good risk group. Many people now believe that neuroblastoma is not just one disease, but several. Some forms of the tumours may, in fact, not be truly malignant. The data that has led to this conclusion and the biological characteristics that are associated with the different forms of the neuroblastoma will be reviewed. In addition, a brief outline of new studies which may identify some of the factors associated with the neuroblasts ability to metastasise will be discussed.

Biomarkers, Tumor↗
PubMed1991

A novel and rapid method for isolating sequences adjacent to rare cutting sites and their use in physical mapping.

We describe a simple PCR based technique which can be used to isolate sequences adjacent to rare cutter sites and can subsequently be employed for the construction of long range physical maps. The method involves the ligation of an adaptor to rare cutter sequences and its use as a target for forward priming in PCR. Primers to Alu repeat elements initiate synthesis of the reverse strand. Using this technique any rare cutter site which has a repeat element within amplification range can be cloned. We have isolated six unique sequences around NotI sites from an irradiation reduced hybrid containing a fragment of human chromosome 22 and are using these for physical mapping around the Ewing's sarcoma translocation breakpoint on chromosome 22.

Base Sequence↗
PubMed1991

The 200/220 kDa antigen recognized by monoclonal antibody (MAb) UJ127.11 on neural tissues and tumors is the human L1 adhesion molecule.

MAb UJ127.11, raised against 16 week human fetal brain, recognizes an antigen present primarily on normal and tumor tissues derived from the neuroectoderm. The antigen has previously been identified as a 220/240 kDa cell surface glycoprotein as determined by immunoprecipitation studies. We show here, that the 220/240 kDa antigen is the human L1 cell adhesion molecule and by Western blot analysis actually has a calculated molecular weight of between 200-220 kDa. Immunocytochemical studies with UJ127.11 and an antibody (5G3) recently utilized to isolate human L1 from brain indicate that both reagents have very similar binding profiles. The binding of radiolabelled UJ127.11 to its target antigen can be blocked by the addition of a rabbit anti-human L1 antiserum. Furthermore, sequential immunoprecipitation and Western blot analysis shows that UJ127.11 and the rabbit anti-human L1 antiserum recognize identical proteins.

Antibodies, Monoclonal↗
PubMed1991

Use of the polymerase chain reaction to analyse sequence variation within a major neutralizing epitope of glycoprotein B (gp58) in clinical isolates of human cytomegalovirus.

The heterogeneity of low passage human cytomegalovirus (HCMV) strains was determined by HindIII typing of 28 clinical isolates from transplant patients. These data have shown that, in general, each patient's strain has a unique restriction profile, usually comprising combinations of HindIII sites present in one or more of the tissue culture-adapted strains AD169, Towne and Davis. To map sequence changes in a more refined manner we performed detailed analyses of 33 low passage clinical isolates, including those aforementioned, analysing a sequence within glycoprotein B containing a major neutralizing epitope. A 149 bp sequence containing the epitope (amino acids 608 to 625) was amplified using the polymerase chain reaction, the products were cloned and their DNA sequence was determined. Comparison of the DNA and deduced amino acid sequences with those of HCMV strain AD169 revealed that there was a high degree of conservation of the epitope between the 33 clinical isolates. However 10 of the isolates possessed silent mutations and three isolates contained mutations producing amino acid changes within the neutralizing epitope. The possible functional significance of these changes is discussed.

Amino Acid Sequence↗
PubMed1991

Expression of alternative isoforms of the neural cell adhesion molecule (NCAM) on normal brain and a variety of brain tumours.

A panel of monoclonal antibodies, including a reagent designated ERIC-1, have been characterized as binding to the human neural cell adhesion molecule (NCAM). These monoclonal antibodies bind in a relatively uniform manner to a variety of normal and neoplastic tissues arising from the neuroectoderm. However, multiple forms of the protein are known to arise from the differential splicing of exons within the NCAM gene located on chromosome 11 at q23. On human adult brain, four isoforms of 180, 170, 145 and 120 kDa have been identified. Here, we report the identification of another NCAM isoform of 95 kDa that is apparent on tissues following either N-glycanase or neuraminidase treatment to remove carbohydrate and sialic acid residues from the molecule respectively. NCAM expression is further complicated by differential post-translational modification of the molecule which is developmentally regulated. In general, fetal NCAM is more heavily polysialylated than the adult forms of the molecule. Human fetal brain has been shown to express the heavily sialylated embryonic form of NCAM, but following neuraminidase digestion, a similar pattern of NCAM expression is seen to that in adult brain. A variety of human brain tumours examined also show different patterns of NCAM expression, despite their uniform staining with monoclonal antibodies. The significance of these observations for designing new molecular and immunological approaches to the diagnosis of a variety of primary tumours is reviewed.

Adult↗
PubMed1991

Expression of neural cell adhesion molecule (NCAM) isoforms in neuroblastoma.

A comparative study on the expression of the neural cell adhesion molecule (NCAM) in human neuroblastoma cell lines and tissues was undertaken. NCAMs are a family of closely related cell surface glycoproteins involved in cell-cell interactions. Using antibodies that recognise distinct epitopes on NCAM, their presence was shown in neuroblastoma, but these studies do not yield any information on the specific NCAM isoforms associated with the tumour. Western and Northern blot analyses were therefore carried out to characterise the NCAM isoforms in this neuroectodermal tumour. Western blot studies using the monoclonal antibody ERIC-1 showed that all human neuroblastoma cell lines tested expressed the 140 and 120 kilodalton isoforms of NCAM in their desialo state. Some of the cell lines also expressed NCAM-180. The data are corroborated by Northern blotting where a transcript of 7.4 kilobase pairs was identified only in lines expressing NCAM-180; the 6.7 and 5.4 kilobase pair transcripts coding for 140 and 120 kilodalton isoforms, respectively, were present in all the cell lines tested. The NCAM isoforms identified in neuroblastoma were also different from those found in adult and fetal brain tissue, suggesting that aberrations are expressed in the molecule during tumorigenesis.

Antibodies, Monoclonal↗
PubMed1991

Predictors of improvement in the 12-minute walking distance following a six-week outpatient pulmonary rehabilitation program.

We evaluated the relationship of clinical characteristics, pulmonary function, and exercise test data to the degree of improvement in the 12-minute walking distance (12MD) in 50 ambulatory outpatients completing a six-week pulmonary rehabilitation program. The 12MD increased by 27.7 +/- 32.5 percent, or 462 +/- 427 ft, by the end of the program. There were no significant relationships between improvement in the 12MD and age, sex, oxygen requirement, arterial blood gas levels, and pulmonary function; however, patients with a greater ventilatory reserve (1-[VEmax/MVV] x 100) had more improvement in their 12MD, both with respect to distance and percentage of increase over baseline. Additionally, patients with a lower peak oxygen consumption (VO2) and peak oxygen pulse (O2P) showed greater percentage of improvement in their 12MD. The magnitude of the initial 12MD was inversely related to its improvement, both with regard to distance (r = -0.43; r2 = 0.18; p less than 0.003) and percentage of increase (r = -0.71; r2 = 0.51; p less than 0.0001). Using stepwise regression, the combination of smaller initial 12MD and greater FEV1 was significantly predictive of improvement in the 12MD. Patients with poor performance on either a 12MD or maximal exercise test are not necessarily poor candidates for a pulmonary rehabilitation program.

Ambulatory Care↗
PubMed1991

Diagnosis and follow-up of children with Wilms' tumor: correlative study of ultrasound and computed tomography. Report of eighteen cases.

A retrospective study of 18 children with Wilms' tumor was performed to compare the efficacy of ultrasound (US) and computed tomography (CT) for the diagnosis, staging, and follow-up evaluation of these patients. US and CT were found to be complementary to one another in evaluation of Wilms' tumor. In one patient, CT was more accurate than US in determining the organ of origin of a very large tumor. US is superior to CT for the evaluation of thrombosis in IVC. It can define whether or not the thrombus is attached to the wall of the IVC. This finding has a major impact on the management of the patient.

Adolescent↗
PubMed1991

Expression of the cluster 1 antigen (neural cell adhesion molecule) in neuroectodermal tumours.

In this study, we have investigated the expression of the neural cell adhesion molecule (NCAM) in the human brain, primary brain tumours and neuroblastoma. Adult brain was found to express discrete isoforms of 180, 170, 140 and 120 kDa, which on neuraminidase treatment resolved into bands of 180, 170, 140, 120 and 95 kDa. Primary brain tumours such as Schwannoma and medulloblastoma expressed embryonic NCAM characterised by a high level of glycosylation, whereas other tumours, e.g. astrocytoma, meningioma, glioma and oligodendroglioma expressed adult NCAM. Post-neuraminidase treatment, differential expression of the 180, 170, 140, 120 and 95 kDa isoforms were noted in these various tumour types. On the other hand, neuroblastoma cell lines were found to express only embryonic NCAM, which after neuraminidase treatment resulted in differential presence of only 180, 140 and 120 kDa proteins.

Astrocytoma↗
PubMed1991

The expression of small cell lung cancer related antigens in foetal lung and kidney.

The presence and distribution of antigens recognised by the antibodies submitted to the Second International Workshop on Small Cell Lung Cancer Antigens has been mapped on human foetal lung and kidney using a streptavidin immunoperoxidase technique on frozen tissue sections. Thirteen of the antibodies showed no staining at all on these tissues and five showed staining of all structures in all tissues of equal intensity. The staining patterns of the remaining antibodies could be divided into several groups. All the cluster 1 antibodies recognising the neural cell adhesion molecule (NCAM) gave a distinctive staining pattern in both tissues. The cluster 2 antibodies and several groups of unclustered antibodies gave varying pure epithelial patterns of staining. The cluster w4 and 5 antibodies gave an interesting staining pattern which included some of the distinctive features of the cluster 1 pattern plus some epithelial expression. Various less distinctive patterns were also observed. Serial sections of foetal lung which had been stained with NCC-LU-246 (cluster 1), anti-desmin, and anti-neurofilament antibodies were also studied to attempt to determine the nature of the cells expressing NCAM in the foetal lung.

Antibodies, Monoclonal↗
PubMed1991

Retinoic acid and alpha-difluoromethylornithine induce different expression of neural-specific cell adhesion molecules in differentiating neuroblastoma cells.

Human neuroblastoma cells SK-N-BE(2) can be induced to differentiate towards a neuronal phenotype by retinoic acid (RA) or a schwannian/glial phenotype by alpha-difluoromethylornithine (DFMO), producing differential binding of 14 antibodies (MAbs). RA induced the expression of the neural cell adhesion molecule, NCAM (also confirmed by northern blot); whereas DFMO enhanced the binding of MAbs UJ181.4, UJ127.11 which recognise an identical protein doublet of 220-240 kDa, thought to be the L1 protein(s). The data presented demonstrate that neuroblastoma cells differentiate toward separate phenotypes associated with a specific induction of two different adhesion molecules, NCAM on neuronal cells and L1 on schwannian/glial cells.

Antibodies, Monoclonal↗
PubMed1990

Hormone and cytotoxic drug responsiveness of cultured human breast cancer cells resistant to specific hormones.

Attempts have been made to develop sublines of MCF-7 cells resistant to the growth-inhibitory actions of medroxyprogesterone acetate (MPA), dexamethasone (DEX), anti-oestrogens or high-dose oestradiol (E2) by prolonged exposure to high hormone concentrations. While high degrees of resistance to MPA, DEX and E2 were achieved, cells remained anti-oestrogen-sensitive after prolonged treatment with 4 microM tamoxifen (TAM) or the anti-oestrogen LY 117018 (LY). Cells resistant to DEX were also resistant to MPA, while cells resistant to high-dose E2 remained sensitive to TAM. Cells resistant to MPA and E2 appeared to be less responsive to cytotoxic drugs than wild-type cells, while resistance to DEX was associated with increased sensitivity. The responses of tumours to cytotoxic drugs may be affected by prior endocrine therapy.

Breast Neoplasms↗
PubMed1990

Chemical pathways of peptide degradation. II. Kinetics of deamidation of an asparaginyl residue in a model hexapeptide.

Deamidation of Asn residues is a major chemical pathway of degradation of peptides and proteins. To understand better the external factors that influence deamidation, we studied the degradation of the hexapeptide Val-Tyr-Pro-Asn-Gly-Ala, a fragment of adrenocorticotropic hormone, by HPLC. The deamidation of this model peptide showed marked dependence on pH, temperature, and buffer composition. In the pH range 5 to 12, the peptide deamidated exclusively via a cyclic imide intermediate with the formation of both the Asp- and the isoAsp-hexapeptides. Buffer catalysis was also observed in the pH range of 7 to 11. However, at acidic pH's, the pathway of deamidation involved direct hydrolysis of the amide side chain of Asn residue to produce only the Asp-hexapeptide.

Amides↗