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PubMed2000

Neurohormones and catecholamines as functional components of the bone marrow microenvironment.

A variety of cytokines and growth factors exert a finely tuned control on the complex series of proliferative and differentiative events called hematopoiesis. Recent studies have shown that neuroendocrine and neural factors may also regulate hematopoiesis. In particular, besides its important immunoenhancing properties, the pineal neurohormone melatonin can also rescue hematopoiesis from the toxic effect of anti-cancer drugs via the action of T-helper cell novel opioid cytokines. In turn, these substances bind kappa-opioid receptors expressed in GM-CSF-activated macrophage-like stromal cells and seem to stimulate IL-1. Adrenergic agents can also affect hematopoiesis. We demonstrated that pre-B cells express alpha 1B-adrenoceptors (alpha 1B-AR) and that their activation by catecholamines results in suppressed myelopoiesis in vitro or protection in vivo against supralethal doses of carboplatin. Most recently, we found that alpha 1B-AR gene knockout mice show a deranged hematopoietic recovery after sublethal irradiation. Regeneration of pre-B cells (the cell type expressing alpha 1B-AR) and of erythrocytes was much faster in knockout than in wild-type mice. Most interesting, bone marrow cells can synthesize both melatonin and catecholamines. As far as melatonin is concerned, human and murine bone marrow cells contain and synthesize melatonin at a concentration that is three orders of magnitude higher than that normally found in serum. Catecholamines are also present in substantial amounts and originate both from nerve endings and bone marrow cells. These findings open interesting new perspectives and include hematology among the disciplines that would benefit from the integrative NIM approach.

Animals↗
PubMed1993

Microenvironment of respiratory neurons in the in vitro brainstem-spinal cord of neonatal rats.

1. O2-, K(+)- and pH-sensitive microelectrodes were used to measure extracellular oxygen pressure (PO2), K+ activity (aKo) and pH (pHo) in ventral regions of the medulla oblongata containing respiratory neurons in the in vitro brainstem-spinal cord preparation from 0 to 4-day-old rats. 2. The location of respiratory neurons was mapped by extracellular recordings with conventional microelectrodes, or with the reference barrel of ion-sensitive microelectrodes. The major populations of respiratory neurons were distributed in the ventrolateral reticular formation near the nucleus ambiguus at depths of 300-600 microns. In this area, aKo baseline increased from 3.2 to 3.8 mM whereas steady-state values of PO2 and pHo fell from 120 to 7 mmHg and from 6.9 to 6.7, respectively. 3. During rhythmic inspiratory discharges recorded with suction electrodes from ventral roots of spinal (C3-C5) and cranial (IX, X, XII) nerves, aKo transiently increased by up to 100 microM, and PO2 fell maximally by 0.4 mmHg. During episodes of non-rhythmic neuronal discharge, aKo increased by as much as 0.4 mM and PO2 decreased by about 10 mmHg. In contrast, no variations in pHo could be detected during such activities. 4. Activation of medullary neurons by tetanic electrical stimulation of axonal tracts in the ventrolateral column of the spinal cord at the level of the phrenic motoneuron pool produced aKo elevations of up to 5 mM, decreases of PO2 by up to 50 mmHg, and pHo increases by a maximum of 0.07 pH units. These aKo and PO2 transients were reduced by more than 80% during blockade of synaptic transmission with 5 mM manganese (Mn2+) and completely blocked by 1 microM tetrodotoxin (TTX). 5. The tissue PO2 gradient as well as activity-related decreases of PO2 were completely abolished after block of oxidative cellular metabolism by addition of 2-10 mM cyanide (CN-) to the bathing solution. 6. Inhibition of the Na(+)-K+ pump by addition of 3-50 microM ouabain (3-10 min) caused a reversible increase of aKo by 0.8-3 mM, a delayed recovery of stimulus-induced aKo elevations, and produced a disturbance of the respiratory rhythm. 7. The sensitivity of the respiratory network to oxygen depletion was tested by superfusing the neuraxis with hypoxic solutions gassed with N2 instead of O2 (5-20 min).(ABSTRACT TRUNCATED AT 400 WORDS)

Action Potentials↗
PubMed1996

Membrane potentials and microenvironment of rat dorsal vagal cells in vitro during energy depletion.

1. Brainstem slices were taken from mature rats. In the dorsal vagal nucleus (DVNX), membrane potentials (Em) of neurons (DVNs) and glia, as well as extracellular oxygen, K+ and pH (Po2, aKo, pHo), were analysed during metabolic disturbances. 2. Postsynaptic potentials of DVNs, elicited by repetitive electrical stimulation of the solitary tract (TS), led to a secondary glial depolarization of up to 25 mV, a fall in Po2 of up to 150 mmHg, a rise in extracellular aKo of up to 9 mM, and a fall in pHo of about 0.2 pH units. 3. Hypoxic superfusates produced tissue anoxia, leading to an aKo increase of less than 2 mM and a pHo fall of 0.24 +/- 0.04 pH units (mean +/- S.D.). Glucose-free solution evoked, after a delay of more than 8 min, a slow rise in aKo of 1.9 +/- 0.8 mM, accompanied by a mean increase in pHo of 0.24 +/- 0.13 pH units. After pre-incubation in glucose-free solution, anoxia elevated aKo by up to 15 mM, whereas the anoxia-induced pHo decrease was completely blocked. 4. In 45 of 118 DVNs, anoxia elicited a persistent hyperpolarization of 15.6 +/- 5.0 mV. In the remaining DVNs, anoxic exposure either did not produce a change in Em (37%) or led to a depolarization of less than 10 mV (25%). A stable depolarization of 9 +/- 3.8 mV was detected in glial cells during anoxia. Similar responses were revealed in oxygenated glucose-free solution after a delay of 12-60 min. 5. The metabolism-related hyperpolarizations were blocked by 100-500 microM tolbutamide or 20-100 microM glibenclamide, leading to recovery of spontaneous (0.5-6 Hz) spike discharge. In these cells, 400-500 microM diazoxide evoked hyperpolarizations and blockade of spontaneous activity. 6. In DVNs and glial cells, a progressive depolarization of up to 40 mV in amplitude developed during anoxic exposure after pre-incubation in glucose-free solution. 7. The results show that oxygen or glucose depletion does not impair the viability of DVNX cells. The contribution of neuronal ATP-sensitive K+ (KATP) channels to this tolerance is discussed.

Animals↗
PubMed2003

Cyanobacterial ecotypes in different optical microenvironments of a 68 degrees C hot spring mat community revealed by 16S-23S rRNA internal transcribed spacer region variation.

We examined the population of unicellular cyanobacteria (Synechococcus) in the upper 3-mm vertical interval of a 68 degrees C region of a microbial mat in a hot spring effluent channel (Yellowstone National Park, Wyoming). Fluorescence microscopy and microsensor measurements of O(2) and oxygenic photosynthesis demonstrated the existence of physiologically distinct Synechococcus populations at different depths along a light gradient quantified by scalar irradiance microprobes. Molecular methods were used to evaluate whether physiologically distinct populations could be correlated with genetically distinct populations over the vertical interval. We were unable to identify patterns in genetic variation in Synechococcus 16S rRNA sequences that correlate with different vertically distributed populations. However, patterns of variation at the internal transcribed spacer locus separating 16S and 23S rRNA genes suggested the existence of closely related but genetically distinct populations corresponding to different functional populations occurring at different depths.

Base Sequence↗
PubMed2005

Algal species and light microenvironment in a low-pH, geothermal microbial mat community.

Unicellular algae are the predominant microbial mat-forming phototrophs in the extreme environments of acidic geothermal springs. The ecology of these algae is not well known because concepts of species composition are inferred from cultivated isolates and microscopic observations, methods known to provide incomplete and inaccurate assessments of species in situ. We used sequence analysis of 18S rRNA genes PCR amplified from mat samples from different seasons and different temperatures along a thermal gradient to identify algae in an often-studied acidic (pH 2.7) geothermal creek in Yellowstone National Park. Fiber-optic microprobes were used to show that light for algal photosynthesis is attenuated to < 1% over the 1-mm surface interval of the mat. Three algal sequences were detected, and each was present year-round. A Cyanidioschyzon merolae sequence was predominant at temperatures of > or = 49 degrees C. A Chlorella protothecoides var. acidicola sequence and a Paradoxia multisita-like sequence were predominant at temperatures of < or = 39 degrees C.

Chlorella↗
PubMed1996

Staphylocidal action of thrombin-induced platelet microbicidal protein is influenced by microenvironment and target cell growth phase.

Thrombin-induced platelet microbicidal protein (tPMP) is a small, cationic peptide released from rabbit platelets following exposure to thrombin in vitro. This peptide exerts potent in vitro microbicidal activity against a broad spectrum of bloodstream pathogens, including Staphylococcus aureus. It is known that the microbicidal actions of other cationic antimicrobial peptides (e.g., neutrophil defensins) are influenced by environmental factors and target cell growth phase. However, whether these parameters affect tPMP microbicidal activity has not been studied. Thus, we assessed the in vitro bactericidal activity of tPMP against two tPMP-susceptible strains, Bacillus subtilis ATCC 6633 and S. aureus 502A, in various target cell growth phases or under various microenvironmental conditions. The conditions studied included differing bacterial growth phase (logarithmic versus stationary), temperature (range, 4 to 42 degrees C), pH (range, 4.5 to 8.5), cationicity (range, 0.1 mM to 2 M), anionicity (range, 0.08 to 5 microM), and neutral carbohydrates ranging in molecular weight (MW) from 180 to 37,700 (range, 50 to 500 mM) as well as rabbit platelet-free plasma and serum. tPMP staphylocidal activity was greater against logarithmic- than stationary-phase cells. tPMP bactericidal activity against both B. subtilis and S. aureus was directly correlated with temperature and pH, with microbicidal activity exhibited near the physiological range (37 to 42 degrees C and pH 7.2 to 8.5, respectively). The presence of cations (Na+, K+, Ca2+, and Mg2+) decreased tPMP bactericidal activity in a time- and concentration-dependent manner, with complete inhibition at monovalent or divalent cation concentrations of > or = 250 or > or = 10 mM, respectively. Staphylocidal activity of tPMP was also inhibited by the polyanions polyanetholsulfonic acid and polyaspartic acid, at 0.1 and 0.4 microM, respectively. Coincident exposure with low-MW carbohydrates (glucose, sucrose, and melezitose) did not affect tPMP staphylocidal activity. However, higher-MW carbohydrates (raffinose and dextrans) decreased tPMP activity in a manner directly proportional to their concentration and MW. Solute-mediated inhibition of tPMP bactericidal activity was independent of solute osmolality but directly related to the duration of tPMP-solute coexposure. tPMP enhanced the staphylocidal activities of platelet-free plasma and heat-inactivated serum, while the activity of normal serum was not affected. These collective observations suggest that tPMP retains antimicrobial activities under physiological conditions which are likely to be relevant to host defense in vivo.

Animals↗
PubMed1992

Behavioral analysis of Vibrio parahaemolyticus variants in high- and low-viscosity microenvironments by use of digital image processing.

Digital image analysis and light microscopy were used to study and quantify the growth and behavior of two variants and selected flagellar mutants of Vibrio parahaemolyticus in glass flow cells under high- and low-viscosity conditions. The observations showed a series of surface-associated behaviors, including attachment, microcolony formation, migration, chemotactic movements, and aggregation, indicating a substantial degree of adaptive flexibility and multicellular behavior during growth of V. parahaemolyticus at interfaces.

Bacterial Adhesion↗
PubMed2000

Cutaneous microenvironment of human immunodeficiency virus (HIV)-seropositive and HIV-seronegative individuals, with special reference to Staphylococcus aureus colonization.

A cross-sectional quantitative study of cutaneous bacterial and yeast flora at seven body sites in 99 human immunodeficiency virus-seropositive and 50 seronegative military personnel was performed. Statistically significant differences in carriage rates were only observed for Staphylococcus aureus on the foreheads of seropositive individuals. Seronegative individuals demonstrated staphylococcal carriage rates 1.3 to 2 times as great as those of historical controls (defined as healthy individuals not receiving any medications) at five of six body sites. We conclude that seropositive military personnel do not exhibit statistically significant elevations in densities and carriage rates of the microorganisms examined (except Staphylococcus aureus), relative to seronegative individuals. Seropositive individuals may be predisposed to staphylococcal carriage. The elevated staphylococcal carriage rates of military personnel undergoing basic training warrants a formal evaluation of the impact of training exercises on cutaneous flora. The information gained may serve to limit the spread of infection during training exercises and battlefield conditions.

Adolescent↗
PubMed1982

Sterile microenvironment in prevention of wound infection.

A prospective controlled trial was carried out to assess the effect of using a wound isolator on reducing postoperative infection. A total of 291 patients undergoing hip pinning for fractures of the neck of femur entered the trial and were allocated at random to have their wound contained in a wound isolator (study group) or dressed with a standard gamma-irradiated adhesive dressing (control group). The bacteriological flora of the patient was monitored before, during, and after operation and that of the ward before and after. No significant difference was found in the flora of the wards in which the patients were nursed. On several occasions the source of the infective organism was traced to the ward but never to the theatre. The isolator prevented direct contamination and airborne cross-infection of the wound and appreciably reduced the rate of infection.

Air Microbiology↗