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L Haynes

Publications and source records attributed to L Haynes.

34 records · Page 2Linked to original sources
PubMed1992

Nutrition in dystrophic epidermolysis bullosa.

In dystrophic epidermolysis bullosa (EB), a combination of diminished food intake and increased nutritional requirements commonly leads to malnourishment. Adequate nutrition in these patients could provide many benefits, including improved growth, accelerated healing, decreased susceptibility to infection, and enhanced well-being. We assessed nutrition status of children with dystrophic EB, and evaluated the benefits of nutritional advice in those who were considered malnourished. The majority of patients had inadequate intakes of a wide spectrum of nutrients, including those who appeared to be relatively mildly affected. We were unable to secure persisting substantial improvements in dietary intake despite thorough counseling. Adequate nutrition in patients with dystrophic EB depends on active nutritional support starting from birth. The need for more invasive techniques of nourishment, such as nasogastric and gastrostomy feeding, may have to be considered earlier than is currently the case.

Body Height↗
PubMed1991

Beta-endorphin C-terminal peptide evokes arachidonic acid release from cortical neurones.

The release of free [3H]arachidonic acid and its metabolites (AAM) from mouse embryo cortical neurones cultured in serum-free medium stimulated by beta-endorphin C-terminal dipeptide (glycl-L-glutamine, Gly-Gln) was investigated. Gly-Gln but not the related dipeptide, glycyl-glutamic acid, caused a 2-fold elevation of AAM release which was blocked in the absence of extracellular calcium, in the presence of 5 mM magnesium and by the phospholipase A2 (PLA2) inhibitor, mepacrine. Other proopiomelanocortin (POMC) peptides did not elicit AAM release. The response to Gly-Gln was unaffected by D-amino-2-phospho-5-valeric acid (AP5) and 7-chlorokynurenic acid (7-ClKY), antagonists respectively at the ligand and allosteric glycine binding sites of the NMDA glutamate receptor subtype. However, it was inhibited in a dose-dependent manner by antagonists at the phencyclidine (PCP) and sigma sites. The results suggest that Gly-Gln causes AAM release by activating PLA2 through the mediation of a PCP/sigma-like receptor.

Animals↗
PubMed1991

Shark spontaneous cytotoxicity: characterization of the regulatory cell.

Down regulation of shark macrophage-mediated spontaneous cytotoxicity is evident in vitro when animals are maintained at environmental temperatures greater than 26 degrees C. Previous work has shown that inhibition of spontaneous killing is mediated by viable, glass nonadherent, nonphagocytic cells which are sensitive to alterations in environmental temperature. The current report further characterizes the regulatory cell population. Glass nonadherent leukocytes were enriched for regulatory activity by density gradient centrifugation, and the majority of activity sedimented to 34% iso-osmotic Percoll. Two morphologically distinct cells are found in this fraction, lymphocyte-like cells and granulocytes. The 34% fraction was further separated by adherence to SIg-coated dishes, and the ability to inhibit spontaneous killing partitioned with the SIg- subset. In addition, fractionation of cells bearing Fc receptors (FcR) for shark Ig showed the regulator to be devoid of FcR. Sequential depletion of cells expressing SIg and FcR confirmed these data. Inhibition by allogeneic cells indicated that histocompatibility between the cytotoxic effector and the regulator is not a requirement for expression of activity. Thus, down regulation of spontaneous cytotoxicity is mediated by nonadherent, nonphagocytic, SIg-, FcR-cells which are not MHC restricted. The lymphoid or granulocytic lineage of the regulatory cell is discussed.

Animals↗
PubMed1990

A monoclonal antibody against the human IL-2 receptor binds to paraformaldehyde-fixed but not viable frog (Xenopus) splenocytes.

Others have reported that a monoclonal anti-human IL-2 receptor antibody (anti-CD25) specifically binds a membrane receptor on Xenopus laevis PHA-induced and paraformaldehyde-fixed splenic blasts. In this paper, we present evidence suggesting that this binding is an artifact of membrane damage. Specifically, significant binding of anti-CD25 could only be achieved if the lymphoblasts were acid-washed and/or paraformaldehyde-fixed prior to being incubated with the fluoresceinated antibody. For example, in a representative experiment 95% of paraformaldehyde-fixed blasts, about 19% of acid-washed but not fixed blasts, but fewer than 2% of viable (untreated) blasts were positive for the CD25 epitope. Paraformaldehyde is known to alter membrane permeability. The DNA dye propidium iodide (PI) was used to demonstrate that the acid washing procedure also causes membranes to become permeable. Flow cytometric analyses of acid-washed PHA-induced splenic blasts doubly stained with the anti-CD25 antibody and PI showed that only 1.5% of the cells that were positive for CD25 did not stain with PI. Additionally, the anti-CD25 antibody, which immunoprecipitated a molecule from human lymphoblasts of between 50 and 60 kDa, did not immunoprecipitate any surface molecules from 125I-labeled Xenopus splenic blasts. Since binding of anti-CD25 to Xenopus splenic blasts appears to occur only after membrane damage, the antibody may be recognizing a cross-reactive internal epitope that is not involved in ligand binding on the cell surface.

Animals↗
PubMed1988

NMDA receptors activate the arachidonic acid cascade system in striatal neurons.

Receptors for excitatory amino-acid transmitters on nerve cells fall into two main categories associated with non-selective cationic channels, the NMDA (N-methyl-D-aspartate) and non-NMDA (kainate and quisqualate) receptors. Special properties of NMDA receptors such as their voltage-dependent blockade by Mg2+ (refs 3, 4) and their permeability to Na+, K+ as well as to Ca2+ (refs 5, 6), have led to the suggestion that these receptors are important in plasticity during development and learning. They have been implicated in long-term potentiation (LTP), a model for the study of the cellular mechanisms of learning. We report here that glutamate and NMDA, acting at typical NMDA receptors, stimulate the release of arachidonic acid (as well as 11- and 12-hydroxyeicosatetraenoic acids from striatal neurons probably by stimulation of a Ca2+-dependent phospholipase A2. Kainate and quisqualate, as well as K+-induced depolarization were ineffective. Our results provide direct evidence in favour of the hypothesis, that arachidonic acid derivatives, produced by activation of the postsynaptic cell, could be messengers that cross the synaptic cleft to modify the presynaptic functions known to be altered during LTP. In addition, we suggest that NMDA receptors are the postsynaptic receptors which trigger the synthesis of these putative transynaptic messengers.

Arachidonic Acid↗
PubMed1988

Fc receptor for shark IgM.

Fc receptors for shark IgM have been demonstrated on shark leukocytes. Measurement of receptor binding required treatment of leukocytes with Cytochalasin D to inhibit phagocytosis. EA rosetting assays were carried out using human erythrocytes coated with shark anti-human antibody. Binding to shark leukocytes was demonstrated to be specific to shark IgM in that affinity purified shark IgM and purified Fc5 mu fragments could block rosette formation, but not shark transferrin, bovine serum albumin or fetal bovine serum. The binding was shown to be saturable and reversible, characteristic of receptor-ligand interaction. Further, it was shown that affinity purified, radioiodinated IgM could also bind Cytochalasin D-treated shark leukocytes in a manner analogous to rosetting. We conclude that Fc receptors appeared early in evolution, and that previous difficulties in demonstrating the Fc mu receptor resulted from non-specific binding associated with phagocytosis.

Animals↗
PubMed1986

Macrophage-like effector of spontaneous cytotoxicity from the shark.

The effector of spontaneous cytotoxicity from shark peripheral blood has been shown to be a macrophage-like cell. Effector cells are isolated by centrifugation over Lymphocyte Separation Medium, adherence to glass, Percoll density gradient centrifugation and adherence to fibronectin sequentially. Effector cells are adherent to glass, sediment to densities of 1.048-1.052 g/ml and are adherent to fibronectin. The isolated effectors represent less than 1% of the peripheral blood leukocytes, and exhibit potent cytotoxic capability, both spontaneous and in the presence of phytohemagglutinin. In addition, the activity of these cells is resistant to 3000 rads gamma irradiation. Although nurse sharks have natural antibody to trinitrophenol, spontaneously cytotoxic cells are incapable of killing trinitrophenol modified targets indicating that natural antibody is not required for reactivity, and that natural antibody and spontaneous effectors do not have the same repertoire. However, cold target inhibition studies showed that these effector cells can recognize four of five human lymphomyeloid targets. It is concluded that the spontaneous, extracellular killing by the macrophage-like effector most closely resembles that of activated mammalian tumoricidal macrophages with the exception that they do not appear to require in vitro activation.

Animals↗
PubMed1982

The role of the conjugated carbonyl of cytochalasin A in contractility inhibitions.

A study of the mechanism of action of cytochalasin A (CA) in relation to its structural features and to its selective inhibition of certain contractile processes has been initiated. Quantitative structure-function analyses with several CA-related cytochalasins - including synthetic 21,22-dihydro-CA (DHCA), the 22-beta mercaptoethanol CA-adduct, (CA-2ME), and the 22-dithiothreitol CA-adduct (CA-DTT) - have been carried out in a temperature sensitive gel-sol extract from Ehrlich ascites tumor cells. Each drug congener was purified to homogeneity by HPLC prior to biological testing. The undiminished inhibitory indices of DHCA and CA-2ME (ID50 congruent to 3.7 x 10(-7) M) overrules the prior circumstantial evidence accumulated for the obligatory electrophilic interaction of this drug, at its alpha-beta-unsaturated ketone region, with presumptive receptor nucleophiles.

Animals↗
PubMed1979

The growth and differentiation of transitional epithelium in vitro.

The development of rat transitional epithelial cells grown on conventional non-permeable surfaces was compared with development on permeable collagen supports. On glass or plastic surfaces, cells grew as expanding nomolayer sheets. Once confluent, growth continued with a bilayer being formed in most areas and apical cells being continuously sloughed off. Although most cells were interconnected by desmosomes, and junctional complexes were formed, no other indications of differentiation were observed. After 2-3 wk of growth, division stopped and cel death ensued. In contrast, single-cell suspensions plated on collagen-coated nylon disks reassociated into multicellular islands and commenced growth. Mitoses were confined to the basal cells in contact with the permeable substrate. The islands developed into epithelial trilayers, tapering to monolayers along spreading edges. Once the islands were confluent, stratification was completed and appeared similar to that observed in vivo. Germinal cells formed a basal lamina, and the upper layer was composed of large, flattened cells with an unusually thick asymmetrical plasma membrane on the apical surface. Electron microscopic and radioactive tracers demonstrated "leaky" zonulae occludentes with a restricted permeability to small molecules. The movement of urea was retarded in comparison to water. Unlike the slow turnover of adult epithelium in vivo, maturation and sloughing of apical cells were measurable. Transfer of cells could be effected and growth maintained for up to 4 mo. These results may indicate the necessity of a nutrient-permeable growth surface for the polarized differentiation of adult transitional epithelium.

Animals↗
PubMedDate not supplied

Immune system activation associated with a naturally occurring infection in Xenopus laevis.

Immune system activation correlated with a naturally occurring infection has been found in the South African clawed frog Xenopus laevis. The microorganism thought to be the cause of this infection is coccobacilloid and approximately 1 micron in diameter. Since this microorganism does not grow on conventional bacterial media and it has been observed intracellularly, it may be an obligate intracellular bacterium. It has been found in Xenopus peripheral blood and in highly vascularized organs such as the spleen and liver. Splenomegaly is the only pathology thus far described for infected frogs; infection is not associated with increased morbidity or mortality. This infection has been found in all outbred frogs examined in shipments from one South African and three separate North American vendors, and has been transmitted to animals bred and raised in our laboratory. This infection has a profound effect on the immune system of Xenopus. Significant numbers of splenocytes from infected individuals exhibit morphology commonly associated with activated T lymphocytes. There is constitutive production of T-cell growth factor (TCGF) and both IgM and IgY. Freshly harvested splenocytes from infected animals proliferate in response to a TCGF-containing supernatant, indicating that they express receptors for TCGF, a trait exclusively exhibited by activated lymphocytes. These splenocytes also show an increase in the activation marker recognized by the monoclonal antibody FJ17.

Animals↗
PubMedDate not supplied

Cyclic GMP-sensitive conductance in outer segment membrane of catfish cones.

A cyclic GMP-sensitive conductance has recently been observed with patch-clamp recording in excised inside-out patches of plasma membrane from frog and toad rod outer segments. This conductance has properties suggesting that it is probably the light-sensitive conductance involved in visual transduction. We now report a similar conductance in the outer segment membrane of catfish cones. Cyclic GMP showed positive cooperativity in opening this conductance, with a Hill coefficient of 1.6-3.0 and a half-saturating cGMP concentration of 35-70 microM. Cyclic AMP at 1 mM, or changing Ca concentration (in the presence of Mg), had little effect on the conductance. In physiological solutions the cGMP-induced current had a reversal potential near +10 mV; the current amplitude increased roughly exponentially with membrane potential in both depolarizing and hyperpolarizing directions. Our results suggest that cGMP is also the internal transmitter for phototransduction in cones.

Animals↗
PubMedDate not supplied

Constipation in epidermolysis bullosa: successful treatment with a liquid fiber-containing formula.

In epidermolysis bullosa (EB), chronic constipation, painful defecation, and fecal impaction frequently contribute to malnutrition and growth failure. Standard treatments for constipation, such as increased intake of conventional dietary fiber and fluids and/or the use of laxatives and stool softeners, are largely unsuccessful. We evaluated by questionnaire the use of a fiber-containing liquid formula (Enrich) in 20 chronically constipated children with dystrophic EB. All derived substantial improvement in constipation when taking 250 to 750 ml Enrich per day. We recommend that such a fiber-containing food be prescribed for chronic constipation in EB. In cases of fecal impaction, this should be preceded by bowel cleansing.

Adolescent↗