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Biomedical subjects

K Thomas

Publications and source records attributed to K Thomas.

At least 271 records · Page 15Linked to original sources
PubMed1986

The application of flow cytophotometry in measurements of cell adhesion.

A common approach to the study of cell substrate interactions is the measurement of the attachment of cells to different substrates or to cultured cell layers. The evaluation of attachment is made either by scintillation counting of previously labelled adhering cells, or by light microscopy using the criterion of cell shape, sometimes refined by automatic image analysis. These methods have many drawbacks. This paper suggests the use of fluorescence-activated flow cytophotometry, (FC) which yields direct counts of the non-adhering cells. These "free" cells are removed after completion of the adhesion experiment from the microtitre plate wells. An internal standard, in the form of fluorescent polystyrene beads is added, allowing evaluation of the percentage of cells adhering to the well walls. Flow cytophotometry then produces data based on the analysis of large populations of cells. Unequivocal discrimination is obtained between the counted cells and counted fluorescent beads eliminating counting errors. The results can be processed on line by computer. A suspension of mouse splenocytes was used for the evaluation of the overall error of the method arising from inaccuracies in pipetting, interference of glutaraldehyde with ethidium bromide (EB) staining and instrumental error. Each adhesion experiment was terminated by staining and post-fixation and it was established that this introduces no change in cell counting, in comparison with the original unfixed cells. Prefixation, however, quenches the EB staining and would interfere with the counting procedure. The overall standard error of the technique was found to be 5%-10%.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1986

V.S.O. in Gambia.

Explore the source record for details and available documents.

Community Health Nursing↗
PubMed1986

Loss of adrenergic innervation in induced rabbit hydrosalpinx.

Ligation of the proximal and distal ends of the rabbit oviducts was used to induce hydrosalpinges. The adrenergic innervation of the induced hydrosalpinx was studied. Depletion of adrenergic innervation in rabbit hydrosalpinges was found. Our findings suggest that not only mucosal changes, but also loss of adrenergic nerves must be taken into account as factors in the pathology of hydrosalpinx.

Animals↗
PubMed1986

Substance P in human hypothalamus.

The undecapeptide substance P (SP) is found in widely dispersed areas of the brain. Recently, in experimental animals, a role for SP as a presumptive neuromodulator of endocrine responses has been described. Part of this role appears to be expressed at the level of the hypothalamo-pituitary axis. The distribution of SP in human hypothalamus and pituitary stalk has rarely been examined. In this study the distribution of SP was determined using radio-immunoassay and immunohistochemical methods in 7 regions of hypothalamus and the pituitary stalk in 21 autopsy samples. The SP content was greatest in the pituitary stalk (16.7 +/- 2.9 ng/mg protein) and the mediobasal hypothalamus at the level of the tuber cinereum. (8.3 +/- 1.1 ng/mg protein) compared with all other regions (range 3.7 to 6.0 ng/mg protein). Histochemical studies in 7 cases showed a dense innervation of the pituitary stalk portal vessels by substance P-containing nerve terminals. The pituitary stalk, mediobasal and lateral hypothalamus had the highest number of SP-containing neuronal perikarya. The SP content was not affected by age, sex or delay from death to freezing of tissue. The distribution of SP supports the view that the peptide is a neuromodulator of hypothalamo-pituitary endocrine function in man.

Adult↗
PubMed1985

Brain-derived acidic fibroblast growth factor: complete amino acid sequence and homologies.

Bovine brain-derived acidic fibroblast growth factor (aFGF) is a protein mitogen originally identified in partially purified preparations of whole brain. The protein was purified to homogeneity and shown to be a potent vascular endothelial cell mitogen in culture and angiogenic substance in vivo. The homology of aFGF to human interleukin-1 beta was inferred from partial sequence data. The complete amino acid sequence of aFGF has now been determined and observed to be similar to both basic FGF and interleukin-1's. A neuropeptide-like sequence, flanked by basic dipeptides, was observed within the aFGF sequence.

Amino Acid Sequence↗
PubMed1985

Disinfection of gastrointestinal fibrescopes: an evaluation of the Pauldrach Endocleaner, and various chemical agents.

The Pauldrach Endocleaner was evaluated for the disinfection of gastrointestinal fibrescopes, and found to be a convenient, relatively inexpensive machine for use in endoscopy clinics. An experimental procedure was designed, for use with the endocleaner, which allowed application of an inoculum of Pseudomonas aeruginosa to a Fujinon OX52 endoscope and its subsequent quantitation before and after disinfection procedures. Using aldehyde based disinfectants ('Cidex', 'Kohrsolin' and 'Gigasept') it was possible to achieve a 99.999% reduction in the recovery of viable Ps. aeruginosa with a minimum exposure time of 20 min 'Dettox ABC' and buffered hypochlorite (100 ppm) were less effective achieving an approximately 99% reduction with a minimum exposure time of 30 min. Following apparently adequate disinfection and irrespective of the disinfectant used, the endoscope was found to be heavily contaminated with Ps. aeruginosa when examined after overnight storage at room temperature thus emphasising the need for meticulous disinfection of instruments prior to use in a day's list.

Disinfectants↗
PubMed1985

Cyclic changes in ciliation, cell height, and mitotic activity in human tubal epithelium during reproductive life.

The percentage of ciliated cells, the height, and the mitotic index of human oviductal epithelium were studied during the menstrual cycle and under progestogens. A total of 141 fallopian tubes were examined. During the menstrual cycle, a process of ciliation and deciliation was observed. Maximal ciliation was attained around the time of ovulation, particularly in the fimbria where significant differences were noted. Deciliation was observed under progestogen therapy, but this progestogen effect was easily reversible. The decrease of epithelial height observed after ovulation was also found after progestogen therapy. Cyclic mitotic activity was noted during the menstrual cycle. Estrogens influence the mitotic activity of tubal epithelium, whereas endogenous progesterone and progestogens inhibit this estrogenic effect.

Cell Cycle↗
PubMed1985

Ovulation instantaneously modifies women's peritoneal fluid characteristics: a demonstration from an in vitro fertilization program.

Concentrations of P and E2 were measured in serum and PF obtained from 34 laparoscopies performed in 18 patients for oocyte retrieval in an in vitro fertilization program. Samples from group A (28 patients who had not ovulated at laparoscopy) and group B (6 patients who had ovulated very shortly before laparoscopy) were compared. No difference was observed in serum steroid levels between the two groups; however, group B showed a 100-times increase in E2 concentration and a 200-times increase in P concentration measured in the PF. In conclusion, we can postulate that this sudden and large increase in PF steroids after ovulation is initially solely dependent on the mechanic rupture of the follicle and not on its luteinization.

Ascitic Fluid↗
PubMed1985

Control of myogenic differentiation by fibroblast growth factor is mediated by position in the G1 phase of the cell cycle.

We have used the expression of the muscle form of creatine phosphokinase (M-CPK) to assay myogenic differentiation in the cloned muscle cell line BC3Hl. BC3Hl cells express M-CPK when arrested in the G0 portion of the cell cycle. Addition of the anionic form of brain fibroblast growth factor (B-FGF) rapidly represses synthesis of M-CPK with a half-time of 7 h. Even though B-FGF is not mitogenic for the cells, it causes quiescent BC3Hl cells to exit from the G0 portion of the cell cycle, and to accumulate at a new restriction point approximately 4 to 6 h in the G1 portion of the cell cycle. The repression of M-CPK synthesis by B-FGF is reversible upon removal of B-FGF, and cells which have re-initiated expression of M-CPK have also returned to the G0 portion of the cell cycle. The primary control of M-CPK expression by B-FGF appears to be at the level of gene transcription. We conclude that arrest of cells at G0 but not at other positions in the G1 phase of the cell cycle provides permissive conditions for the expression of muscle-specific proteins, and that defined polypeptide growth factors, in this case B-FGF, are important in the control of the expression of muscle-specific proteins.

Cell Cycle↗
PubMed1985

Isolation of Acanthamoeba culbertsoni from a patient with meningitis.

A case of amoebic meningitis, presumably primary, was encountered in the Christian Medical College Hospital, Vellore, South India, in November 1983. The patient, a 40-year-old man, had cerebrospinal fluid rhinorrhea before the meningitis developed. Acanthamoeba culbertsoni was repeatedly demonstrated in and cultured from the cerebrospinal fluid. The patient responded dramatically to a combination therapy of penicillin and chloramphenicol.

Adult↗
PubMed1985

Nonreciprocal exchanges of information between DNA duplexes coinjected into mammalian cell nuclei.

We have examined the mechanism of homologous recombination between plasmid molecules coinjected into cultured mammalian cells. Cell lines containing recombinant DNA molecules were obtained by selecting for the reconstruction of a functional Neor gene from two plasmids that bear different amber mutations in the Neor gene. In addition, these plasmids contain restriction-length polymorphisms within and near the Neor gene. These polymorphisms did not confer a selectable phenotype but were used to identify and categorize selected and nonselected recombinant DNA molecules. The striking conclusion from this analysis is that the predominant mechanism for the exchange of information between coinjected plasmid molecules over short distances (i.e., less than 1 kilobase) proceeds via nonreciprocal homologous recombination. The frequency of homologous recombination between coinjected plasmid molecules in cultured mammalian cells is extremely high, approaching unity. We demonstrate that this high frequency requires neither a high input of plasmid molecules per cell nor a localized high concentration of plasmid DNA within the nucleus. Thus, it appears that plasmid molecules, once introduced into the nucleus, have no difficulty seeking each other out and participating in homologous recombination even in the presence of a vast excess of host DNA sequences. Finally, we show that most of the homologous recombination events occur within a 1-h interval after the introduction of plasmid DNA into the cell nucleus.

Animals↗
PubMed1985

Efficient correction of mismatched bases in plasmid heteroduplexes injected into cultured mammalian cell nuclei.

Heteroduplexes were prepared from two plasmids, pRH4-14/TK and pRH5-8/TK, containing different amber mutations in the neomycin resistance gene (Neor). The Neor gene was engineered to be expressed in both bacterial and mammalian cells. A functional Neor gene conferred kanamycin resistance to bacteria and resistance to the drug G418 to mammalian cells. In addition, the plasmids contained restriction site polymorphisms which did not confer a selectable phenotype but were used to follow the pattern of correction of mismatched bases in the heteroduplexes. In a direct comparison of the efficiency of transforming mouse LMtk- cells to G418r, the injection of heteroduplexes of pRH4-14/TK-pRH5-8/TK was 10-fold more efficient than the coinjection of pRH4-14/TK and pRH5-8/TK linear plasmid DNA. In fact, injection of 5 to 10 molecules of heteroduplex DNA per cell was as efficient in transforming LMtk- cells to G418r as the injection of 5 to 10 molecules of linear plasmid DNA per cell containing a wild-type Neor gene. To determine the pattern of mismatch repair of the injected heteroduplexes, plasmids were "rescued" from the G418r cell lines. From this analysis we conclude that the generation of wild-type Neor genes from heteroduplex DNA proceeds directly by correction of the mismatched bases, rather than by alternative mechanisms such as recombination between the injected heteroduplexes. Our finding that a cell can efficiently correct mismatched bases when confronted with preformed heteroduplexes suggests that this experimental protocol could be used to study a wide range of DNA repair mechanisms in cultured mammalian cells.

Animals↗
PubMed1984

Management of pain in sickle cell disease using biofeedback therapy: a preliminary study.

Fifteen patients with a history of painful episodes of sickle cell disease were given training in progressive relaxation, thermal biofeedback, cognitive strategies, and self-hypnosis to help them develop self-management skills to relieve pain. Results show a 38.5% reduction in the number of emergency room visits, a 31% reduction in the number of hospitalizations, and a 50% reduction in the inpatient stay during the 6 months since the beginning of therapy compared to 6 months prior to therapy. Analgesic intake was reduced by 29% for those who were using it regularly. This is a preliminary study, and the results are considered only as suggestive of the potential use of biofeedback therapy and behavioral management in alleviating painful episodes in sickle cell disease.

Adult↗