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Biomedical subjects

N Green

Publications and source records attributed to N Green.

At least 19 recordsLinked to original sources
PubMed1992

Mutants in three novel complementation groups inhibit membrane protein insertion into and soluble protein translocation across the endoplasmic reticulum membrane of Saccharomyces cerevisiae.

We have isolated mutants that inhibit membrane protein insertion into the ER membrane of Saccharomyces cerevisiae. The mutants were contained in three complementation groups, which we have named SEC70, SEC71, and SEC72. The mutants also inhibited the translocation of soluble proteins into the lumen of the ER, indicating that they pleiotropically affect protein transport across and insertion into the ER membrane. Surprisingly, the mutants inhibited the translocation and insertion of different proteins to drastically different degrees. We have also shown that mutations in SEC61 and SEC63, which were previously isolated as mutants inhibiting the translocation of soluble proteins, also affect the insertion of membrane proteins into the ER. Taken together our data indicate that the process of protein translocation across the ER membrane involves a much larger number of gene products than previously appreciated. Moreover, different translocation substrates appear to have different requirements for components of the cellular targeting and translocation apparatus.

Biological Transport↗
PubMed1992

Prostate cancer--the impact of irradiation on urinary outlet obstruction.

A series of 245 patients with prostate cancer treated by external irradiation was analysed to assess the impact of irradiation on urinary outlet obstruction. Prior to irradiation, obstruction was observed in 147/245 patients (60%). Irradiation either with or without hormonal therapy was as efficacious as transurethral resection of the prostate (TURP) in alleviating obstructive symptoms; 14/16 patients treated by irradiation alone responded, as did 19/19 who received hormonal therapy and irradiation and 109/112 who underwent TURP and irradiation. Following irradiation, 41/245 patients developed post-irradiation obstruction, 26/213 had post-irradiation strictures and 15/32 developed recurrent cancer. Surgical intervention was required less often for the management of recurrent obstruction caused by stricture as compared with recurrent cancer. TURP and urinary outlet obstruction acted as independent and additive variables to the development of post-irradiation stricture. Thus the avoidance of TURP in patients with obstructive symptoms reduced but did not eliminate the risk of developing a stricture.

Aged↗
PubMed1992

C-terminal sequences can inhibit the insertion of membrane proteins into the endoplasmic reticulum of Saccharomyces cerevisiae.

We have constructed three gene fusions that encode portions of a membrane protein, arginine permease, fused to a reporter domain, the cytoplasmic enzyme histidinol dehydrogenase (HD), located at the C-terminal end. These fusion proteins contain at least one of the internal signal sequences of arginine permease. When the fusion proteins were expressed in Saccharomyces cerevisiae and inserted into the endoplasmic reticulum (ER), two of the fusion proteins placed HD on the luminal side of the ER membrane, but only when a piece of DNA encoding a spacer protein segment was inserted into the fusion joint. The third fusion protein, with or without the spacer included, placed HD on the cytoplasmic side of the membrane. These results suggest that (i) sequences C-terminal to the internal signal sequence can inhibit membrane insertion and (ii) HD requires a preceding spacer segment to be translocated across the ER membrane.

Alcohol Oxidoreductases↗
PubMed1990

Prostate cancer: post-irradiation incontinence.

The experience of 272 patients with prostate cancer treated between 1976 and 1987 by external irradiation was reviewed to assess causal factors for post-irradiation incontinence and to determine measures to reduce the risk of this complication. No patient had incontinence before definitive irradiation or radical prostatectomy. Post-irradiation incontinence was observed in 19 of 272 patients (7%), including 14 with mild, 2 with moderate and 3 with severe disease. Incontinence after definitive irradiation was not significantly related to tumor stage or tumor control: 8 of 192 patients (4%) had local control and 2 of 33 (6%) had local failure. Incontinence was related to a urological operation performed in 1 of 105 patients (1%) who underwent needle biopsy and 7 of 130 (5.5%) who underwent transurethral prostatectomy before irradiation. Incontinence was more frequent, 2 of 6 patients (33%), and more severe in patients who underwent transurethral prostatectomy after irradiation. Of 31 patients 9 (29%) were incontinent after radical prostatectomy. No additional patient had incontinence after postoperative irradiation. However, 3 patients had a temporary increase in the severity of incontinence. The risk of post-irradiation incontinence may be decreased by more selective use of transurethral prostatectomy. Of 136 patients 26 (20%) underwent transurethral prostatectomy for tissue diagnosis. A needle biopsy would be the procedure of choice. A total of 29 patients with urinary outlet obstruction was treated without transurethral prostatectomy before irradiation. Ten patients with relatively mild urinary outlet obstruction were treated by irradiation alone, while 19 with more severe urinary outlet obstruction had endocrine therapy before irradiation and none of the 29 patients (0%) had post-irradiation incontinence.

Aged↗
PubMed1987

Normative childhood EMG gait patterns.

The population characteristics of the linear envelopes of the electromyograms measured from seven lower extremity muscles in children were studied during locomotion. The variability and changes in pattern with respect to walking speed and age were investigated using statistical properties and analysis of variance of the envelopes. All muscles studied showed changes in their patterns that were associated with different walking speeds. Some changes concerned the relative intensity of existing phases of activity whereas others concerned the existence of additional phases of activity. The most remarkable trend was that all envelopes tended to have more consistent patterns as speed increased. With regard to age, within the span of 4-11 years, only the two thigh muscles studied demonstrated appreciable differences.

Age Factors↗
PubMed1987

Ca2+-activated K+ channels in cultured medullary thick ascending limb cells.

The conductive properties of a clone of medullary thick ascending limb (MTAL) cells (GRB-MAL1) were assessed using conventional microelectrodes and the patch clamp technique. The apical cell membrane potential (Va) of MTAL cells was -46 +/- 3 mV. Addition of Ba2+ (1 mM) to the apical solution induced a 22 +/- 2 mV depolarization of Va, whereas furosemide hyperpolarized Va by -5 +/- 1 mV. In the cell-attached patch configuration, the most frequently occurring channel had a single channel conductance of 121 +/- 5 pS and carried outward current. In excised patches, current movement was down the electrochemical K+ gradient. Fluctuations were activated by depolarization of Va and by increasing Ca2+ concentration on the intracellular face. Micromolar amounts of Ba2+ on the intracellular face of the membrane inhibited channel activity. We conclude that cultures of MTAL cells GRB-MAL1 retain at least two of the properties of the mature phenotype, namely, an apical K+ conductance and a sensitivity to loop diuretics; the most frequently occurring channel in the apical cell membrane is a Ca2+-activated, maxi-K+ channel; and, finally Ca2+-activated K+ channels may play a role in generating the apical K+ conductance in cultured MTAL cells.

Animals↗
PubMed1987

Blocking agents of Ca2+-activated K+ channels in cultured medullary thick ascending limb cells.

Ca2+-activated K+ channels with estimated single channel conductances of 127 +/- 2 pS were identified in the apical cell membrane of clone A3 of cultured medullary thick ascending limb (MTAL) cells. Both Ba2+ and the scorpion toxin, charybdotoxin (CTX), are slow blockers of the channels. An application of 0.1 microM Ba2+ to the intracellular face caused a 50% reduction in fractional open time (fv). Ba2+ block is both concentration and voltage dependent. Concentrations of CTX as low as 2 nM in the extracellular solution caused a significant reduction in fv. Tetraethylammonium (TEA) and quinine are fast blockers of Ca2+-activated K+ channels in MTAL cells. TEA, 400 microM, in the extracellular solution caused a voltage-dependent reduction in channel amplitude, whereas it takes 10 mM in the intracellular solution to reduce channel amplitude by 30%. Micromolar amounts of quinine applied to the intracellular face caused the channels to flicker rapidly between open and blocked states. These results suggest that K+ channels in MTAL cells are homologous to those found in muscle cells, and that these blocking agents may be used to probe the nature of K+ conductances in several nephron segments.

Animals↗
PubMed1987

High NaCl induces stable changes in phenotype and karyotype of renal cells in culture.

Extracellular fluid in the renal medulla normally is hyperosmotic. To test adaptation to such an environment, a continuous line of rabbit renal inner medullary epithelial cells (GRB-PAP1), which had been established in isosmotic medium, was switched to a medium containing high NaCl. The origin of these cells is described. When the osmolality was raised from 300 to 600 mosmol/kg by adding NaCl, cells eventually survived and proliferated, but unexpectedly, they underwent major changes in phenotype and karyotype that persisted during proliferation in isosmotic or hyperosmotic medium for at least 7 months. The threshold concentration for the changes was approximately 500 mosmol/kg. Cells of a typical strain (PAP-HT25) that formed in hyperosmotic medium were much larger and more often multinucleated than were GRB-PAP1. GRB-PAP1 cells were near diploid; PAP-HT25 cells were polyploid. The changes, since they occurred in most clones, were due to adaptation of the majority of cells and not to selection of a minority of cells already having these characteristics. Cloning efficiency was higher for GRB-PAP1 than PAP-HT25 in isosmotic medium, but the reverse occurred in hyperosmotic medium. Thus exposure to the hyperosmotic medium induced greater ability to clone in it. We suggest that these changes may involve persistent alterations in gene regulation, possibly like those previously reported in chicken embryo fibroblast cells after hyperosmotic NaCl (Cell 30: 131-139, 1982).

Animals↗
PubMed1986

Influence of antigen structure on the activation and induction of unresponsiveness in cloned human T lymphocytes.

Using cloned human helper T lymphocytes reactive with a 24 amino acid peptide (p20) of the carboxyl terminal of the HA-1 molecule of influenza haemagglutinin we have investigated the influence of antigen structure on the activation and in the induction of antigen specific unresponsiveness of T cells. For this analysis stereoisomers and structural isomers of p20 have been constructed. P20 in the form of a single loop created by a disulphide based between residue 306 and an additional cysteine at position 330 was able to activate the helper T cells in the presence of accessory cells but unable to induce tolerance. This result suggested that critical residues were prevented from direct interaction with the T-cell receptor and/or the MHC Class II determinants and required processing to expose them. The enantiomer (D-p20) and the inverted sequence (retro-L-p20) which have non complementary side chain topography as compared to the parent peptide neither activated nor tolerized the T cells. Furthermore the retro-D-p20 isomer which has the same side chain topography as L-p20 but with a reversal of amino and carboxyl acid groups also failed to stimulate or tolerize. Therefore T-cell antigen recognition is not determined by side chains alone. The results presented suggest that structure of extrinsic antigen influences T-cell antigen recognition.

Epitopes↗
PubMed1986

Long-term survival following bony metastases from basal cell carcinoma. Report of a case.

A patient with recurrent basal cell carcinoma developed cervical-vertebral and epidural metastases. He received palliative irradiation and had a durable remission for three years. With relapse, he underwent a laminectomy and chemotherapy and remained asymptomatic at 54 months following the diagnosis of bony metastases. To our knowledge, he is the longest reported survivor with bony metastases and is illustrative of the potential survival advantage from palliative therapy.

Basal Cell Carcinoma↗
PubMed1985

Prostate cancer: experience with definitive irradiation in the aged.

When considering therapeutic options for localized prostate cancer, stage and grade of disease have been the most important determinants. In the elderly, the nominal age has assumed increasing importance in the final decision. A balanced judgment must be reached between the patient's normal life expectancy and the rapidity with which the cancer may be expected to express its malignant potential. By careful attention to patient selection and the details of treatment, definitive irradiation can improve quality of life and survival. Of 63 patients aged seventy-three to ninety years referred for irradiation, 56 were found medically suitable for definitive treatment. A review of our experience is presented.

Adenocarcinoma↗
PubMed1985

The experience with definitive irradiation of clinically limited squamous cell cancer of the trachea.

Squamous cell cancer of the trachea is an uncommon malignancy infrequently cured by either surgery or irradiation. Failure to control the primary tumor has been the most common cause for death. Our experience in three patients with small squamous cell cancer of the trachea treated by definitive irradiation is encouraging. The primary tumor was controlled in each patient. Histologic confirmation of tumor sterilization was observed in two. One patient remains alive and well at 54 months; one patient developed an epidural metastases at 16 months and subsequently died; and the third patient developed a separate primary lung cancer at 48 months. Two patients developed significant radiation complications.

Adult↗
PubMed1985

Differentiated lines of cells from rabbit renal medullary thick ascending limbs grown on amnion.

Previously we grew differentiated primary epithelial tissue cultures from rabbit renal medullary thick ascending limbs but were unable to subculture them into lines. Now, following the use of amnion as a support during the initial passages, two cell lines have grown from single fragments of medullary thick ascending limbs. Cells have now been in culture past 12 passages over more than 2 yr. On confluence they formed morphologically differentiated epithelial monolayers with polarization of the cells visible on electron microscopy. They had apical zonula occludens and microvilli, lateral cellular interdigitations, and basal membranes flat against the support. "Domes" often were visible when the epithelia formed on dishes, indicative of salt and water transport. Other functional differentiation in some passages of one line or the other included presence of Tamm-Horsfall protein (demonstrated by immunofluorescence) or transepithelial voltage oriented apical surface positive. Both the Tamm-Horsfall protein and the voltage are normally expressed by intact medullary thick ascending limbs and are characteristic of this particular nephron segment.

Amnion↗
PubMed1984

The transfer of strontium-90 and caesium-137 to milk in a dairy herd grazing near a major nuclear installation.

A field investigation of the transfer of artificially produced radionuclides in the pasture--cow--milk pathway has been made at a farm close to the nuclear fuel reprocessing installation at Sellafield on the north-west coast of England. This paper reports results from analyses of samples collected during 1981, reports transfers coefficients for 90Sr and 137Cs from various types of feed to milk, and discusses factors that affect the transfer of these radionuclides. It is shown that during 1981 a large proportion of the 90Sr and 137Cs consumed by cattle grazing near Sellafield was derived from activity deposited in previous years. Transfer coefficients to milk, Fm, have been derived which are within the ranges of those observed in tracer and fallout studies. There are significant seasonal changes in transfer. For 90Sr, values of Fm between 9 X 10(-4)d 1(-1) and 4 X 10(-3)d 1(-1) have been obtained. It is concluded that this large range arises because daily intakes of 90Sr by the herd during the winter months are lower (by a factor of about 3) than intakes during the summer months and that the concentration of 90Sr in milk is not in equilibrium with intake, that is, the concentration of 90Sr in milk is maintained both by recent intakes and by remobilisation of activity that has been accumulated in bone from earlier intakes. For 137Cs, values of Fm between 3 X 10(-3)d 1(-1) and 9 X 10(-3)d 1(-1) have been obtained. It is concluded that this range most probably occurs because during the summer months, when the cows are grazing, a substantial proportion of the 137Cs intake is associated with soil on the surface of herbage and that, in this form, the 137Cs is less available for uptake from the digestive tract of the cows.

Animals↗
PubMed1984

Inhibition of T cell proliferation by antibodies to synthetic peptides.

While T cell proliferation to antigen in the presence of antigen-presenting cells is well known to be readily inhibited by antibodies directed against Class II major histocompatibility complex (MHC) (Ia/HLA-DR) products, it has not been possible to inhibit proliferation by antibodies directed against the antigen. Because of the implications of these observations for targets of T cell recognition, this phenomenon was reinvestigated using human T cell clones, recognizing a small (24 amino acid) synthetic peptide (termed p20) derived from the influenza hemagglutinin-1 molecule. It was found that proliferation of clones to p20 was inhibited efficiently (less than 90%), using p20 as antigen, and rabbit anti-p20. Inhibition was possible either by coculturing p20 antigen and antibody to p20 with cloned T cells and antigen-presenting (E-) cells, or by pulsing antigen-presenting cells with antigen prior to a brief incubation with antibody before washing the E- cells and using them to stimulate cloned T cells. These results do not indicate why previous attempts had failed, but in view of the different techniques available now (cloned T cells, small synthetic polypeptides, and antibody raised against polypeptide) we investigated the influence of these parameters. It was found that, using cloned T cells, the form of the antigen was of importance, as antibody inhibition of the response to hemagglutinin or whole influenza A was much less apparent. These differences were interpreted as being due to greater access of anti-p20 to p20 than to hemagglutinin or influenza. If uncloned T cell lines were used, inhibition was also much harder to detect. This was interpreted as masking of inhibition of the response of some clones in the line by interleukin 2-induced recruitment.

Animals↗
PubMed1984

Direct evaluation of antigen binding to human T lymphocyte clones: involvement of major histocompatibility complex products in antigen binding.

Cloned human helper T lymphocytes reactive with a defined peptide (p20; residues 306-329) of the HA-1 molecule of influenza virus hemagglutinin were analyzed for their capacity to specifically bind peptide antigen. Three different methods of analyzing antigen binding to T cell receptors were compared. One method involved the binding of radiolabeled T cells to antigen-pulsed populations of sheep erythrocyte rosette-negative (E-) cells (B cells and monocytes). The binding was antigen specific, in that only E- cells pulsed with the appropriate antigen bound the treated T cells, and was inhibitable by free peptide. Furthermore, antigen binding was major histocompatibility complex-restricted in that only E- cells histocompatible at the HLA-D region locus bound the T cells, and monoclonal antibody of the relevant specificity was able to inhibit the binding. Secondly, it was demonstrated that tritiated T cells could bind to insolubilized antigen (p20) in the absence of E- cells. The binding was inhibited by anti-class II antibody suggesting that the interaction of antigen with the T cells involves recognition of T cell major histocompatibility complex class II determinants. Finally, radiolabeled peptides were also used to detect binding to the appropriate clones in the absence of presenting cells. This binding was specific, inhibitable by the appropriate unlabeled peptide and temperature dependent. These studies demonstrate that the process of antigen binding to receptors is analyzable and should in turn facilitate the analysis of the mechanism of T cell activation.

Antigen-Presenting Cells↗