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Biomedical subjects

P M Neumann

Publications and source records attributed to P M Neumann.

13 recordsLinked to original sources
PubMed2001

Exogenous ascorbic acid (vitamin C) increases resistance to salt stress and reduces lipid peroxidation.

The transition from reversible to permanent wilting, in whole tomato seedlings (Lycopersicon esculentum Mill. cv. M82) following severe salt-stress by root exposure to 300 mM NaCl, was investigated. Salinized seedlings wilted rapidly but recovered if returned to non-saline nutrient solution within 6 h. However, after 9 h of salt-treatment 100% of the seedlings remained wilted and died. Remarkably, the addition of an anti-oxidant (0.5 mM ascorbic acid) to the root medium, prior to and during salt-treatment for 9 h, facilitated the subsequent recovery and long-term survival of c. 50% of the wilted seedlings. Other organic solutes without known anti-oxidant activity were not effective. Salt-stress increased the accumulation in roots, stems and leaves, of lipid peroxidation products produced by interactions with damaging active oxygen species. Additional ascorbic acid partially inhibited this response but did not significantly reduce sodium uptake or plasma membrane leakiness.

Adaptation, Physiological↗
PubMed1991

Sodium does not compete with calcium in saturating plasma membrane sites regulating na influx in salinized maize roots.

Half maximal inhibition of sodium ((22)Na(+)) influx into maize (Zea mays L.) root segments incubated in solutions containing from 0.25 to 100 millimolar NaCl was consistently attained with external calcium activity at 0.26 +/- 0.10 millimolar. Sodium ions do not appear to compete with calcium during initial binding to sites on the plasma membrane that participate in the regulation of sodium influx under saline conditions.

Journal Article↗
PubMed1990

Does salinity reduce growth in maize root epidermal cells by inhibiting their capacity for cell wall acidification?

The reduction in growth of maize (Zea mays L.) seedling primary roots induced by salinization of the nutrient medium with 100 millimolar NaCl was accompanied by reductions in the length of the root tip elongation zone, the length of fully elongated epidermal cells, and the apparent rate of cell production: Each was partially restored when calcium levels in the salinized growth medium were increased from 0.5 to 10.0 millimolar. We investigated the possibility that the inhibition of elongation growth by salinity might be associated with an inhibition of cell wall acidification, such as that which occurs when root growth is inhibited by IAA. A qualitative assay of root surface acidification, using bromocresol purple pH indicator in agar, showed that salinized roots, with and without extra calcium, produced a zone of surface acidification which was similar to that produced by control roots. The zone of acidification began 1 to 2 millimeters behind the tip and coincided with the zone of cell elongation. The remainder of the root alkalinized its surface. Kinetics of surface acidification were assayed quantitatively by placing a flat tipped pH electrode in contact with the elongation zone. The pH at the epidermal surfaces of roots grown either with 100 millimolar NaCl (growth inhibitory), or with 10 millimolar calcium +/- NaCl (little growth inhibition), declined from 6.0 to 5.1 over 30 minutes. We conclude that NaCl did not inhibit growth by reducing the capacity of epidermal cells to acidify their walls.

Journal Article↗
PubMed1988

Salinity stress inhibits bean leaf expansion by reducing turgor, not wall extensibility.

Treatment of bean (Phaseolus vulgaris L.) seedlings with low levels of salinity (50 or 100 millimolar NaCl) decreased the rate of light-induced leaf cell expansion in the primary leaves over a 3 day period. This decrease could be due to a reduction in one or both of the primary cellular growth parameters: wall extensibility and cell turgor. Wall extensibility was assessed by the Instron technique. Salinity did not decrease extensibility and caused small increases relative to the controls after 72 hours. On the other hand, 50 millimolar NaCl caused a significant reduction in leaf bulk turgor at 24 hours; adaptive decreases in leaf osmotic potential (osmotic adjustment) were more than compensated by parallel decreases in xylem tension potential and the leaf apoplastic solute potential, resulting in a decreased leaf water potential. It is concluded that in bean seedlings, mild salinity initially affects leaf growth rate by a decrease in turgor rather than by a reduction in wall extensibility. Moreover, long-term salinization (10 days) resulted in an apparent mechanical adjustment, i.e. an increase in wall extensibility, which may help counteract reductions in turgor and maintain leaf growth rates.

Calcium Chloride↗
PubMed1987

Sequential leaf senescence and correlatively controlled increases in xylem flow resistance.

In bean, Phaseolus vulgaris L. (Contender), the directly measured hydraulic resistance of the xylem pathway between roots and primary leaf pulvinal junctions increased rapidly and progressively from 21 to 28 days after planting. These increases in xylem resistance (+390%) were specifically located in the pulvinal junction of the primary leaf. Moreover, they occurred just prior to the onset of primary leaf yellowing. Developmental increases in xylem hydraulic flow resistance and stomatal resistance, as well as subsequent primary leaf yellowing, were completely prevented by detopping the shoots above the primary leaves at 21 days. Thus, the onset of these senescence-associated symptoms was correlatively controlled. In short-term investigations of the mechanisms involved, flow between petiole and cut tip of excised leaves was rapidly reduced by infiltration of 20 picomoles of soluble dextran into the xylem. Moreover, imbibition of approximately 120 picomoles of dextran by excised leaves increased stomatal resistances. A programmed secretion of hormonal concentrations of similar polysaccharides into specific xylem sections in vivo might provide a mechanism for regulating the partitioning of essential xylem supplies between leaves, thus inducing sequential leaf senescence.

Journal Article↗
PubMed1986

Comparative Phloem mobility of nickel in nonsenescent plants.

(63)Ni was applied to nonsenescent source leaves and found to be transported to sink tissues in pea (Pisum sativum L.) and geranium plants (Pelargonium zonale L.). The comparative mobilities (percent tracer transported out of source leaf /% (86)Rb transported) for (63)Ni in peas was 2.12 and in geranium 0.25. The value for the phloem mobile (86)Rb was 1.00. By contrast, the comparative mobility of (45)Ca, which is relatively immobile in the phloem, was low (0.05 in peas, 0.00 in geranium). Interruption of the phloem pathway between source and sink leaves by steam girdling almost completely inhibited (63)Ni accumulation in the sink leaves of both species. We conclude that Ni is transported from nonsenescent source leaves to sink tissues via the phloem of leguminous and nonleguminous plants.

Journal Article↗
PubMed1984

Identity of immune cells in graft-versus-host disease of the skin. Analysis using monoclonal antibodies by indirect immunofluorescence.

The cellular infiltrate in skin biopsies of 9 patients with graft-versus-host disease (GVHD) has been characterized with the use of monoclonal antibodies by indirect immunofluorescence. Most infiltrating cells in dermis reacted with monoclonal antibodies which recognize T-cell antigens. A mean of 45% of all dermal cells were T11-reactive, while a smaller proportion of cells were identified by another "pan" antibody, OKT3. In all but two instances the proportion of dermal cells reactive with OKT8 exceeded the proportion reactive with OKT4. Anti-Tac, which identifies activated T cells, reacted with a variable proportion of cells. Monocytes and null cells (OKM1+) were frequently observed but were less numerous than T-lymphocytes. Infiltrates were sparsely populated with OKT6-reactive cells, and there was no difference between the number of intraepidermal cells reactive with this antibody in study subjects and normal controls. Few cells reactive with Leu 7 (large granular lymphocytes) or with anti-B-cell reagents were seen. These findings may have clinical implications for use of monoclonal antibodies for prophylaxis and treatment of GVHD.

Adolescent↗
PubMed1983

Characterization of leaf senescence and pod development in soybean explants.

Excised soybean (Glycine max [L.] Merrill) cv Anoka leaf discs tend to remain green even after the corresponding intact leaves have turned yello on fruiting plants. We have found that explants which include a leaf along with a stem segment (below the node) and one or more pods (maintained on distilled H(2)O) show similar but accelerated leaf yellowing and abscission compared with intact plants. In podded explants excised at pre-podfill, the leaves begin to yellow after 16 days, whereas those excised at late podfill begin to yellow after only 6 days. Although stomatal resistances remain low during the first light period after excision, they subsequently increase to levels above those in leaves of intact plants. Explants taken at mid to late podfill with one or more pods per node behave like intact plants in that pod load does not affect the time lag to leaf yellowing. Explant leaf yellowing and abscission are delayed by removal of the pods or seeds or by incubation in complete mineral nutrient solution or in 4.6 micromolar zeatin. Like chorophyll breakdown, protein loss is accelerated in the explants, but minerals or especially zeatin can retard the loss. Pods on explants show rates and patterns of color change (green to yellow to brown) similar to those of pods on intact plants. These changes start earlier in explants on water than in intact plants, but they can be delayed by adding zeatin. Seed dry weight increased in explants, almost as much as in intact plants. Explants appear to be good analogs of the corresponding parts of the intact plant, and they should prove useful for analyzing pod development and mechanisms of foliar senescence. Moreover, our data suggest that the flux of minerals and cytokinin from the roots could influence foliar senescence in soybeans, but increased stomatal resistance does not seem to cause foliar senescence.

Journal Article↗
PubMed1981

Gelatin-based sprayable foam as a skin substitute.

Physical and antimicrobial properties of a newly developed gelatin based spray-on foam bandage for use on skin wounds have been evaluated. The aqueous foam is sprayed from aerosol containers and effectively covers and washes uneven wound surfaces. The foam dries to form an adherent and stable three-dimensional matrix which diminishes evaporative water losses. The foam possesses antimicrobial activity against gram-positive, gram-negative, and fungal contaminants.

Aerosols↗
PubMed1975

Foliar Iron Spray Potentiates Growth of Seedlings on Iron-free Media.

Growth of bean (Phaseolus vulgaris cv. ;Brittle Wax') seedlings in iron-free media caused large reductions in root size and dye reduction capacity. Shoot growth was also severely retarded and the classical symptoms of chlorosis were observed. A single prophylactic spray of FeSO(4), applied to the primary leaves of 7-day seedlings, enabled subsequent growth to equal that obtained when iron was continuously supplied to the roots over a 12-day period, although chlorophyll levels were lower. By adding a silicone-based surfactant to FeSO(4) spray solutions, the burn damage normally caused to seedlings by such sprays was largely eliminated and the irreversible adsorption of iron increased. Foliar spray of an iron chelate (ferric ethylenediaminedi (o-hydroxyphenylacetic acid)) were less effective than those of FeSO(4).

Journal Article↗
PubMed1974

Senescence of attached bean leaves accelerated by sprays of silicone oil antitranspirants.

During an investigation into the use of oil emulsions in foliar sprays, it was found that silicone oil emulsions accelerated the senescence of the primary leaves of bean (Phaseolus vulgaris) plants. It was shown that accelerated senescence was not a result of the reduced transpiration rates found in silicone-sprayed leaves. Furthermore, the silicone oil emulsions did not induce leakiness in plant cell membranes. The senescence-enhancing effect seems to be connected with the ability of the silicone oil emulsions to penetrate into the leaf interior.

Journal Article↗
PubMedDate not supplied

Hospital control and multidrug-resistant pulmonary tuberculosis in female patients, Lima, Peru.

We examined the prevalence of tuberculosis (TB), rate of multidrug-resistant (MDR) TB, and characteristics of TB on a female general medicine ward in Peru. Of 250 patients, 40 (16%) were positive by sputum culture and 27 (11%) by smear, and 8 (3%) had MDRTB. Thirteen (33%) of 40 culture-positive patients had not been suspected of having TB on admission. Six (46%) of 13 patients whose TB was unsuspected on admission had MDRTB, compared with 2 (7%) of 27 suspected cases (p = 0.009). Five (63%) of 8 MDRTB patients were smear positive and therefore highly infective. In developing countries, hospital control, a simple method of reducing the spread of MDRTB, is neglected.

Adolescent↗