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M F Brown

Publications and source records attributed to M F Brown.

At least 109 records · Page 6Linked to original sources
PubMed1985

Class II determinants recognized by TNP-specific cloned human T cell lines.

Cloned human T lymphocyte lines were generated against trinitrophenyl (TNP)-modified autologous cells from four different individuals. By examining the reactivity patterns of 58 of these T cell clones (TLC) on panels of HLA-typed antigen presenting cells and employing monoclonal antibodies (MoAb) for inhibition studies, we have demonstrated that TNP may be recognized in the context of different DR and DP associated determinants. We did not identify any TLC restricted by determinants associated uniquely with DQ. Determinants associated with the expression of DR1,2,4,5, and 7 as well as the supertypic specificities DRw52 (MT2) and DRw53 (MT3) functioned as restriction elements. In addition, at least two antigenically distinct regions of the DP4 molecule appeared to function in the presentation of TNP. One TNP-specific TLC recognized a determinant associated with the expression of DP4 while another recognized TNP in the context of a highly nonpolymorphic determinant on DP which was expressed on all stimulators tested. Monoclonal antibody blocking studies suggest that these two determinants lie on different portions of the DP molecule. These studies demonstrated that both polymorphic and relatively nonpolymorphic restriction determinants on DR and DP may function in the presentation of conventional antigen to autologous lymphocytes.

Antibodies, Monoclonal↗
PubMed1985

Flexible memory processing by rats: use of prospective and retrospective information in the radial maze.

Four experiments investigated the content of the memory used by rats in mediating retention intervals interpolated during performance in a 12-arm radial maze. The delay occurred following either the 2nd, 4th, 6th, 8th, or 10th choice. A 15-min delay had the greatest disruptive effect when interpolated in the middle of the choice sequence and less of an effect when it occurred either earlier or later. This pattern of results was obtained when either a free- or forced-choice procedure was used prior to the delay and regardless of whether postdelay testing consisted of completion of the maze or two-alternative forced-choice tests. Assuming that the disruptive effect of a delay is a function of memory load, this implies that the rats used information about previously visited arms (retrospective memory) following an earlier interpolated delay but information about anticipated choices (prospective memory) following a delay interpolated late in the choice sequence. There appeared to be a recency effect only in the early and middle delay conditions. This provides converging evidence for the dual-code hypothesis. No evidence for prospective memory was obtained following a 60-min delay.

Animals↗
PubMed1984

14N NMR of lipid bilayers: effects of ions and anesthetics.

The interaction of divalent and trivalent metal cations, ferricyanide, a lipophilic ion (tetraphenylborate), and a local anesthetic (tetracaine) with the phosphocholine head group of egg lecithin was investigated by using wide-line 14N and 31P NMR. Measurements of the 14N quadrupolar splittings in the presence of a variety of perturbing agents demonstrated that the 14N NMR technique can be used to directly monitor ion or anesthetic binding. The 14N quadrupolar splitting (delta nu Q) is a measure of the order parameter of the C beta-N bond segment, and changes in delta nu Q as large as 3.5 kHz were observed. Moreover, a comparison of the changes in the quadrupolar splittings induced by the binding of ions or anesthetics provided a sensitive method of discriminating between these perturbing agents in their ability to alter the orientational order of the C beta-N bond segment of the phosphocholine moiety. Without exception, addition of metal ions or anesthetics always resulted in a decrease of the 14N delta nu Q. This reduction reflects a change in the average orientation or degree of motional averaging at the C beta-N bond segment position. In the case of metal ion binding, the strength of the interaction increased with the charge of the metal ion in the order Ca2+ less than Ln3+, in agreement with a previous 2H NMR study [Akutsu, H., & Seelig, J. (1981) Biochemistry 20, 7366-7373].(ABSTRACT TRUNCATED AT 250 WORDS)

Anions↗
PubMed1984

Cloned human T cells synthesize Ia molecules and can function as antigen presenting cells.

TNP-specific proliferative cloned human T cell lines were investigated for their synthesis and cell surface expression of HLA-DR molecules and for their capacity to function as antigen presenting cells. Utilizing radioactive amino acid precursors for metabolic labeling, these studies demonstrated endogenous synthesis of HLA-DR molecules by cloned T cells, which by two-dimensional gel electrophoresis were similar to HLA-DR molecules expressed by B cells and monocytes. Moreover, when TNP-modified, the irradiated cloned T cells functioned very effectively to stimulate TNP-specific proliferation by cloned responders; when unmodified they were potent stimulators of allogeneic mixed leukocyte responses. Thus, for haptens covalently attached to cell membrane proteins and for allogeneic HLA antigens, Ia+ cloned T cells can function as effectively for antigen presentation and T cell activation as other Ia+ populations to which such properties have been ascribed.

Antigen-Presenting Cells↗
PubMed1984

Cellular requirements for induction of human primary proliferative responses to trinitrophenyl-modified cells.

Cellular requirements for induction of primary proliferative responses by human T cells to trinitrophenylated autologous stimulators have been characterized. Substantial proliferative responses were observed with each of the Ia+ stimulator populations tested. Nevertheless, major differences in the hapten specificity of such responses were observed. Thus purified macrophages/monocytes (M phi) when TNP-modified induced responses that were relatively modest in absolute magnitude, but were highly hapten specific. This reflected the very limited capacity of purified M phi to induce proliferation when unmodified, i.e., an autologous mixed leukocyte response (AMLR). In contrast, unmodified M phi-depleted B plus null cells were potent stimulators of AMLR, but hapten modification did not significantly enhance the responses induced by these cells. Moreover, when M phi were added to B plus null cell stimulators AMLR responses were reduced and, with TNP-modified stimulators, hapten-specific responses were restored. The data thus suggest that M phi may have important roles in induction of primary T cell responses to conventional antigens but function largely as regulators rather than stimulators of AMLR. Finally, we have introduced a novel antigen-presenting cell population, the irradiated Ia+ TNP-specific cloned T cell. The possibility that such cells may utilize autostimulatory positive feedback circuits for activation of naive T cells and in interactions between subpopulations of hapten-reactive T cells is discussed.

Clone Cells↗
PubMed1983

Lipid bilayer dynamics and rhodopsin-lipid interactions: new approach using high-resolution solid-state 13C NMR.

High-resolution, solid-state 13C NMR spectra have been obtained for unsonicated multilamellar dispersions of 1,2-dilauryl-sn-glycero-3-phosphocholine (DLPC), recombinant membranes containing DLPC and rhodopsin, and native retinal rod disk membranes. The roles of 1H dipolar decoupling, 1H-13C cross-polarization, and magic-angle sample spinning have been investigated. Rotating-frame 13C relaxation times have been measured and are discussed in terms of lipid bilayer dynamics and rhodopsin-lipid interactions.

Fatty Acids, Unsaturated↗
PubMed1983

Antigen presentation to human T lymphocytes. II. Requirements for Mac-120+ macrophages and responsiveness to interleukin 2.

To investigate mechanisms by which antigen, macrophages, and interleukin 2 (IL2) participate in the induction of secondary T-cell proliferative responses, trinitrophenyl (TNP) was presented in three distinct modes: (i) TNP-modified peripheral blood mononuclear cells (TNP-PBMC), (ii) TNP-PBMC cell sonicates, and (iii) TNP-ovalbumin (TNP-OVA). Stimulators were depleted of Mac-120+ macrophages using Mac-120 monoclonal antibody plus complement. TNP-Mac-120 macrophages stimulated primed T cells nearly as well as TNP-unfractionated macrophages (which were about 40% Mac-120+). In contrast, although greater than 70% DR+, Mac-120- macrophages plus either TNP-OVA or TNP-PBMC sonicate elicited minimal responses compared to unfractionated macrophages plus antigen. After 21-28 days of in vitro priming, macrophage-depleted T cells were not stimulated to proliferate by either IL2 alone or sonicates alone. IL2 plus TNP-PBMC sonicates, however, stimulated significant proliferation. Furthermore, this response was considerably greater than that to IL2 plus either TNP-T cell sonicates or TNP-mouse spleen sonicates. Thus, the Mac-120+ macrophage population may have an important antigen-presenting and/or accessory function in the stimulation of primed T cells by soluble or particulate antigen, although it is unnecessary for responses to intact TNP-Ia+ PBMC. In addition, the data suggest that Ia+ sonicates alone may suffice for induction of IL2 responsiveness, but not for endogenous IL2 production and subsequent proliferation by primed T cells.

Antigens, Surface↗
PubMed1983

New view of lipid bilayer dynamics from 2H and 13C NMR relaxation time measurements.

Natural abundance 13C spin-lattice (T1) relaxation time measurements are reported for unilamellar vesicles of 1,2-dipalmitoylphosphatidylcholine (1,2-dipalmitoyl-sn-glycero-3-phosphocholine), in the liquid crystalline phase, at magnetic field strengths of 1.40, 1.87, 2.35, 4.23, 7.05, 8.45, and 11.7 tesla (resonance frequencies of 15.0, 20.0, 25.1, 45.3, 75.5, 90.5, and 126 MHz, respectively), and the results are compared to previous 2H T1 studies of multilamellar dispersions. For both the 13C and 2H T1 studies, a dramatic frequency dependence of the relaxation was observed. At superconducting magnetic field strengths (4.23-11.7 tesla), plots of the 13C T1(-1) relaxation rates as a function of acyl chain segment position clearly reveal the characteristic "plateau" signature of the liquid crystalline phase, as found previously from 2H NMR studies. The dependence of T1(1) on ordering, determined previously from 2H NMR, and the T1(-1) dependence on frequency, determined from both 13C and 2H NMR studies, suggest that a unified picture of the bilayer molecular dynamics can be provided by a simple relaxation law of the form T1(-1) approximately equal to A tau f + BS2C-H omega -1/2(0). In the above expression, A and B are constants, SC-H (= SC-D) is the bond segmental order parameter, and omega 0 is the nuclear Larmor frequency. The first (A) term includes contributions from fast, local segmental motions characterized by the effective correlation time tau f, whereas the second (B) term describes slower, collective fluctuations in the local ordering. The value of tau f approximately equal to 10(-11) sec, obtained by extrapolating T1(-1) to infinite frequency, suggests that the segmental microviscosity of the bilayer hydrocarbon region does not differ appreciably from that of the equivalent n-paraffinic liquids of similar chain length.

Carbon Isotopes↗
PubMed1983

A comparison of the regulatory effects of human monocytes, pulmonary alveolar macrophages (PAMs) and spleen macrophages upon lymphocyte responses.

Human monocytes, pulmonary alveolar macrophages (PAMs) and spleen macrophages were concentrated by immobilization on cold insoluble globulins. These cell preparations were 90 +/- 3%, 95 +/- 1% and 83 +/- 3% esterase rich, respectively, 87 +/- 4%, 95 +/- 3% and 66 +/- 11% phagocytic and 78 +/- 3%, 79 +/- 9% and 68 +/- 5% reactive with OKM1 monoclonal antibody. Spleen macrophages differed from the other two cell preparations in that significantly fewer reacted with 61D3 or 63D2 monoclonal antibodies. Monocytes and PAMs promoted the mixed leucocyte response by autologous lymphocytes when added at low concentrations, but suppressed this response at high concentrations. Spleen macrophages only promoted the mixed leucocyte reaction but were required in much higher numbers than either monocytes or PAMs for optimal promotion. Likewise, the added presence of monocytes or PAMs in high numbers suppressed Ig synthesis stimulated with pokeweed mitogen, while spleen macrophages were not suppressive in this system. This study shows that the distribution of macrophages that differ in their regulatory effects upon lymphocyte responses varies in different tissues. The human spleen is deficient in macrophage related suppression.

Adult↗
PubMed1982

Carotid artery injuries.

One-hundred twenty-nine patients with carotid artery injuries were analyzed to compare the results of revascularization with those of ligation or occlusion. In patients who present with central neurologic deficit short of coma (Grades 1 to 4), revascularization is clearly the operative method of choice. Revascularization in patients with preoperative coma (Grade 5) is also indicated when ischemia has only been present for a short period of time before surgery. Controlling cerebral edema and minimizing infarct size in patients with severe deficits may be essential to optimize the chance of recovery of these patients.

Adolescent↗
PubMed1980

Renovascular trauma.

One hundred fifty-four patients with renovascular injuries were analyzed to gain insight into the mortality, morbidity and indications for immediate nephrectomy versus arterial revascularization. Arterial revascularization is seldom indicated in patients with a normal contralateral kidney who have multiple associated injuries, hilar injuries, long segmental arterial injuries or prolonged renal ischemia. An attempt at renal artery revascularization is justified with bilateral injuries, when only one kidney is present or when a solitary artery injury can be repaired by simple lateral arteriorrhaphy.

Adolescent↗
PubMed1980

Morphological comparison of isolates of Phakopsora pachyrhizi from different areas of the world.

Isolates of Phakopsora pachyrhizi from Australia, Indian, the Philippines, Taiwan, and Puerto Rico were compared with respect to morphology and development of "Wayne" soybean. The most extensive comparisons were made between the Puerto Rican and Taiwanese isolates; these were indistinguishable in their prepenetration, penetration, and early colonization phases. Examination of uredia of all isolates by light and scanning electron microscopy (SEM) revealed no differences in uredial morphology. All isolates were indistinguishable with respect to uredospore size, shape, and apparently the number and distribution of uredospore germ pores. The only difference observed was the appearance of germ pores; germ pores of the Puerto Rican isolate were easier to see by means of SEM than those of the four Eastern Hemisphere isolates, suggesting that the Puerto Rican isolate may have thinner germ pore plugs. This difference is not sufficient to consider the isolates as taxonomically distinct.

Australia↗
PubMed1979

Histidyl and tyrosyl residue ionization studies of subtilisin Novo.

The low field portion of the 360 MHz 1H nuclear magnetic resonance spectrum of phenylmethanesulfonyl-subtilisin Novo (EC 3.4.21.14) has been studied as a function of pH. Analysis of the pH-induced chemical shift changes occurring between 6 to 7 ppm revealed five classes of ionizable residues with pK values (uncorrected) of 10.3, 10.7, 10.7, 10.8, and 11.0. With a single exception the titration curves can be fit by assuming a simple proton ionization equilibrium. Four classes of low intensity broad resonances, assigned to the histidyl residues, are observed between 8 and 9 ppm. Uncorrected pK values of 5.4, 5.7, 6.0, and 6.4 were determined for the residues comprising each of these classes. The spectral data are consistent with protonation of one or more histidyl residues upon acid induced denaturation of the protein. These results are compared with those of analogues studies performed by the use of other techniques.

Chemical Phenomena↗