Dysmegakaryopoiesis in myelodysplastic syndromes (MDS): an immunomorphometric study of bone marrow trephine biopsy specimens.

An immunohistochemical and morphometric analysis was performed on trephine biopsy specimens of the bone marrow in 40 patients (23 men and 17 women, mean age 62 years) with different subtypes of myelodysplastic syndromes (MDS) to determine dysmegakaryopoiesis, but particularly precursor cells--that is, pro- and megakaryoblasts. In 31 of the 40 patients the numbers of megakaryocytes were increased which was associated with a predominance of smaller cell forms (micromegakaryocytes). Compared with periodic acid Schiff, immunostaining with a formalin resistant monoclonal antibody against glycoprotein IIIa (Y2/51(CD61) showed a clinically important proportion of immature elements. These could be designated pro- and megakaryoblasts by taking morphometric measurements on smears and bone marrow sections. There was a relevant increase in the number of promegakaryoblasts in 32 patients, consistent with uncontrolled expansion of the precursor pool. Seventeen repeated bone marrow biopsy specimens taken after chemotherapy largely showed a decrease in the numbers of megakaryocytes including the precursor cell population. Moreover, morphometric evaluation disclosed that micromegakaryocytes in MDS differ significantly from those in chronic myeloid leukaemia (CML) due to distinctive nuclear features and a disturbed nuclear:cytoplasmic ratio. These changes generate a more pleomorphic or atypical appearance of this cell population in MDS, compared with micromegakaryocytes in CML. It is concluded that the disproportionate increase in megakaryocyte precursors and the grossly abnormal aspects of micromegakaryocytes in MDS are characteristics of the severe defect involving haematopoiesis in this disorder.     

Mouse macrophage development in the absence of the common γ chain: defining receptor complexes responsible for IL-4 and IL-13 signaling

The common γ chain (γ_c) forms a critical component of the receptors for interleukins (IL)-2, IL-4, IL-7, IL-9, and IL-15. We analyzed γ_c-deficient mice to define a role for γ_c signaling in the development and function of the macrophage lineage. No major differences in absolute cell numbers, cell surface phenotype, or in vitro function of γ^?_c compared to γ⁺_c macrophages were observed. We therefore conclude that signaling through the γ_c chain is not essential for the differentiation of mouse macrophages. Although B and T cells require γ_c for IL-4 responses, IL-4 up-regulated major histocompatibility class II molecules and inhibited nitric oxide production from γ^?_c macrophages following stimulation with lipopolysaccharide and interferon-γ. γ^?_c macrophages could also respond to IL-13, consistent with the model of a type II IL-4 receptor α/IL-13R which can function in the absence of γ_c. Both IL-4 and IL-13 responses could be completely inhibited with the mouse IL-4 antagonist QY, suggesting that all of the observed IL-13 responses pass through the type II receptor, making it the primary signaling receptor complex for IL-13 in mouse macrophages.     

Activation and internalization of p56lck upon CD45 triggering of Jurkat cells

Relationships between CD45 and p56^Ick have been suggested by co-immunoprecipitation of both proteins and by dephosphorylation of the p56^lck regulatory site, Tyr 505, by CD45 in vitro. We investigated whether the kinase activity of p56^lck is modulated in T cells triggered via CD45. We showed that incubation of Jurkat cells with a combination of two anti-CD45 monoclonal antibodies (mAb) (MC5/2 + D3/9) induced an increase in p56^lck kinase activity, while a single mAb did not. Under these conditions, p56^lck underwent two consecutive waves of activation. This was accompanied by internalization of the kinase and by a time-dependent increased accessibility of CD45 phosphatase at the plasma membrane. Similarly, activation and internalization of p56^lck were observed using a combination of anti-CD45 (MC5/2) and anti-CD2(T11₂) mAb, suggesting that a functional complex consisting of CD45, CD2 and p56^lck was formed upon cell triggering. Taken together, these results suggests that: (i) CD45 participates in the regulation of p56^lck kinase activity in vivo and that (ii) CD45 could play a mediator role in the stimulation and endocytosis of p56^lck through the CD2 pathway.     

Release of acetylcholine in the ventral striatum is influenced by histamine receptors

To investigate whether histamine receptor ligands influence thein vivo-release of acetylcholine in the ventral striatum, this brain region was superfused with histamine receptor agonists or antagonists through a push-pull cannula and drug effects on the release of acetylcholine were investigated.

Histamine, the H₁ receptor agonist 2-thiazolyl-ethylamine and the H₃ receptor antagonist thioperamide enhanced acetylcholine release, while the H₃ receptor agonist (R)-α-methylhistamine was ineffective. The results indicate that H₁ receptors and H₃ receptors modulate acetylcholine release.

The thioperamide-induced increase of acetylcholine release might be exerted via H₃-receptors located on cholinergic terminals. Alternatively, thioperamide might enhance acetylcholine release by incresing endogenous histamine release via H₃ autoreceptors.

It is concluded that, via stimulation of striatal H₁- and H₃ receptors, histaminergic neurons are involved in the regulation of cholinergic neuronal activity in the ventral striatum.

     

Electrode Positioning for Reliable Telemetry ECG Recordings During Social Stress in Unrestrained Rats

We describe a surgical procedure for optimizing the location of telemetry ECG leads in rats. The new location was aimed at obtaining an accurate representation of ECG features throughout the cardiac cycle by limiting the voltage instability usually observed during intense somatomotor activity and improving the signal-to-noise ratio. The two electrodes (wire loops) were fixed on the dorsal surface of the xiphoid process and in the anterior mediastinum close to the right atrium. The implantation procedure was fast, little invasive, and allowed animals to completely recover from intervention. The performance of the “improved” location (IL, n = 10) with respect to two subcutaneous (SC) positionings (“conventional positioning,” CSP, n = 5; “updated location,” USL, n = 5) was evaluated by comparing ECGs obtained in baseline, stress and recovery conditions and during different behavioral activities (immobility and grooming). The resident-intruder test (emotional/physical challenge) was chosen as experimental stress paradigm. The noise level of ECGs obtained from IL rats was lower than in CSP and USL animals, in all recording conditions. Percentages of correctly recognized beats (CRBs) over the total number of beats (TBs) were significantly higher in IL rats than in CSP and USL animals, both in baseline conditions (99% vs. 11% and 40%) and situations involving high somatomotor activity (stress: 97%, 5% and 16%; recovery: 97%, 7%, and 15%) (p < 0.01). The performance of IL as compared to CSP and USL was also better when percentages during grooming and immobility were considered (grooming: 93% vs. 4% and 23%; immobility: 97%, 6%, and 33%; p < 0.01).     

Calcitonin gene products and the kidney

Summary Calcitonin gene-related peptide (CGRP) is localized in capsaicin-sensitive nerve fibres in the kidney and urogenital tract whereas calcitonin reaches the kidney through the general circulation. Systemic infusion of CGRP and perfusion of isolated rat kidney reduces vascular resistance, and increases renal blood flow and glomerular filtration. CGRP stimulates renin secretion in vivo and in vitro and inhibits contraction of isolated rat mesangial cells by angiotensin II. Calcitonin does not affect vascular resistance, renal blood flow and glomerular filtration, and is less potent in stimulating renin secretion, and does not alter contraction of isolated rat mesangial cells by angiotensin II. CGRP also exerts renal tubular effects brought about probably through interaction with calcitonin receptors. To this end, increased excretion of sodium and chloride, and stimulation of urinary flow are less pronounced with CGRP than with calcitonin. Calcitonin, moreover, stimulates the fractional urinary excretion of calcium and phosphate.     

Molecular orientation of ultrahigh molecular weight polyethylene induced by various sliding motions

Wear and wear debris of ultrahigh molecular weight polyethylene (UHMWPE) in joint replacements have been recognized as one of the major contributors to the failure of orthopedic implants. The detailed wear mechanism of polyethylene under biomechanic motions is not well understood. In simulation wear bench tests, it was found that unidirectional sliding produces the least amount of wear, reciprocating motion increases wear significantly, and cross-shear motion (similar to hip and knee joint motion in the human body) produces the highest amount of wear. Conventional wear theories are inadequate to explain this observation. This study utilizes resonant absorption of linearly polarized soft X-rays at a synchrotron radiation beam line to measure the molecular orientation of a UHMWPE surface layer subjected to different wear motions. Carbon-K-edge partial-electron-yield X-ray absorption measurements were done on the worn UHMWPE samples. X-ray absorption measurements show conclusively that the molecular chains of UHMWPE align preferentially parallel to the direction of sliding. Examination under various wear motions showed that unidirectional shear produced the maximum chain orientation, whereas cross-shear wear motions produced the least amount of orientation. When polymeric chains align, the surface layer tends to be more brittle and hard, thus resisting wear. When they do not align, loose chains may be subjected to both Mode I and Mode II fracture, hence increasing the wear rate. This molecular alignment observation may offer an explanation of why different wear motions have different wear characteristics.