SCA6 is caused by moderate CAG expansion in the alpha1A-voltage-dependent calcium channel gene

Recently, moderate (CAG)>20 repeat expansions in the alpha1A-voltage-dependent calcium channel gene (CACNL1A4) have been identified in a previously unmapped type of SCA which has been named SCA6. We investigated the (CAG)n repeat length of the CACNL1A4 gene in 733 patients with sporadic ataxia and in 46 German families with dominantly inherited SCA which do not harbor the SCA1, SCA2, or MJD1/SCA3 mutation, respectively. The SCA6 (CAG)n expansion was identified in 32 patients most frequently with late manifestation of the disease. The (CAG)n stretch of the affected allele varied between 22 and 28 trinucleotide units and is therefore the shortest trinucleotide repeat expansion causing spinocerebellar ataxia. The (CAG)n repeat length is inversely correlated with the age at onset. In 11 parental transmissions of the expanded allele no repeat instability has been observed. Repeat instability was also not found for the normal allele investigating 431 meioses in the CEPH families. Analyzing 248 apparently healthy octogenerians revealed one allele of 18 repeats which is the longest normal CAG repeat in the CACNL1A4 gene reported. The SCA6 mutation causes the disease in approximately 10% of autosomal dominant SCA in Germany. Most importantly, the trinucleotide expansion was observed in four ataxia patients without obvious family history of the disease which necessitates a search for the SCA6 (CAG)n expansion even in sporadic patients.

Effects of ultra-purified polymerized bovine hemoglobin on the microcirculation of striated skin muscle in the hamster

Since the beginning of this century, the development of hemoglobin based oxygen carriers has been propagated for replacement of the oxygen carrying properties of red blood cells. A breakthrough has been impeded by problems related to the hemoglobin molecule itself and the ingredients of the solution, resulting in nephrotoxic side effects, limited intravascular half-life, vasoconstrictor potential and potential catalysis of oxygen free radical formation. Using intravital fluorescence microscopy and the dorsal skin fold chamber model of the awake Syrian golden hamster, the microcirculatory changes occurring in the thin striated skin muscle were quantitatively analyzed before and after administration of an ultrapurified polymerized bovine hemoglobin solution (U-PBHb) under the following experimental conditions: (1) Hypervolemic infusion of U-PBHb at approximately 10% of calculated blood volume, (2) isovolemic exchange transfusion with U-PBHBb by replacing approximately 50% of calculated blood volume and (3) severe hemorrhagic shock by acute bleeding of approximately 50% of calculated blood volume to a MAP of 35 +/- 5 mm Hg for 45 min followed by resuscitation with U-PBHb. Control animals received equivalent treatment with vehicle solution, dextran 60 (M(r) 60,000 D) or Ringer's lactate. The microcirculation was found unchanged after both hypervolemic infusion and isovolemic exchange transfusion with respect to perfusion quality and leukocyte/ endothelium interaction while a decrease of functional capillary density by approximately 25% was observed after exchange transfusion with U-PBHb. After hemorrhagic shock, microvascular perfusion was most efficiently restored by U-PBHb without evidence of arteriolar vasoconstriction or activation of leukocyte/endothelial cell interactions during reperfusion. These data indicate, the U-PBHb exerts no unwanted side effects on the microcirculation either under non-ischemic or post-ischemic conditions. The microcirculatory findings post-resuscitation let U-PBHb appear as a safe resuscitation fluid which is superior to the commonly used resuscitation fluids, Ringer's lactate and dextran 60.

The human S3a ribosomal protein: sequence, location and cell-free transcription of the functional gene

The intron-containing gene encoding human ribosomal protein S3a (hRPS3a) was isolated by utilizing a PCR-based strategy to detect a gene-specific intron which was subsequently used as a probe for cloning of the entire gene. The hRPS3a gene is composed of six exons and five introns spanning 5013 bp. As described for other hRP-encoding genes, the promoter lacks a canonical TATA sequence and a defined CAAT box. Primer extension experiments, as well as cell-free transcription, revealed that a cytosine functions as the major transcription start point in a polypyrimidine region, but a guanosine at position -1 was also able to initiate transcription. Hybridization analysis of chromosomal DNA from a panel of human-rodent somatic cell hybrids revealed that hRPS3a is encoded by a single locus in the human genome, present on chromosome 4.

Tissue protection by anti-ischemic drugs

Ischemia followed by reperfusion is associated with typical microvascular disturbances characterized by capillary perfusion break-down (no-reflow), accumulation and adhesion of leukocytes to the microvascular endothelium (reflow-paradox) and impairment of endothelial barrier function, indicating the onset of cellular and/or organ dysfunction. Therapeutic approaches aiming at the prevention of microvascular failure elicited by ischemia/reperfusion, have to be devided into measures interfering with 1) the insult induced during the ischemic period and its consequences from cellular energy depletion and 2) the microvascular disturbances induced during the reperfusion/reoxygenation period. Using various microcirculation models in hamster and/or mouse allowing for chronic visualization of the microcirculation in striated muscle and skin, different therapeutic strategies have been investigated in our laboratory to protect the tissue from the manifestation of postischemic microvascular disturbances. The results are discussed with respect to the potential mode of action of the various therapeutic strategies performed.

Functional capillary density: an indicator of tissue perfusion?

Functional capillary density (FCD) is one of the parameters obtained by intravital microscopy using epi-illumination of the tissue surface or trans-illumination of thin tissue layers. FCD, defined as the length of red cell-perfused capillaries per observation area (cm-1), has been used as an indicator of the quality of tissue perfusion in various animal models. Quantitative analysis of FCD in randomly selected regions of the tissue is performed by means of a computer-assisted video analysis system which allows calculation of the length of RBC-perfused capillaries. Basically, two different mathematical approaches can be employed: the first approach is based on the addition of the distances between two neighboring points (pixels) on the video screen (Pythagorean principle). The second approach uses the superimposition of a grid system that allows estimation of the capillary length by counting the number of intersections between the capillaries and the grid lines (stereological approach). The immanent error has been calculated in our laboratory to be +/- 1% with the Pythagorean and +/- 5% with the stereological method. Beside these systematic errors of computerized measurement, the individual (user-dependent) errors occurring during recognition and redrawing of the capillaries on the video image with use of a digitizing tablet are in the range of +/- 10% (intraindividual) and +/- 70% (interindividual) for the recognition and +/- 3% (interindividual) for the redrawing procedure. Our studies indicate that the errors resulting from the use of a computer-assisted calculation (Pythagorean or stereological approach) or the user-assisted redrawing of the capillaries are negligible when compared to the errors made during recognition of the capillaries on the video screen. The methods are applied for assessment of FCD in two different microcirculation models of skin muscle and pancreas yielding highly reproducible, user-independent results under physiologic conditions and the pathophysiologic conditions of ischemia-reperfusion.

Microcirculatory models of ischaemia-reperfusion in skin and striated muscle

Intravital microscopy is used for analysis of the microcirculation in various organs, e.g. mesentery, intestine, heart, liver and lung, requiring either exteriorization or in situ visualization techniques in anaesthetized animals. In contrast, the implantation of transparent chambers has been employed to allow chronic observation of the microcirculation in intact, non-anaesthetized animals. This paper reports results with two transparent chamber models: the skin-fold chamber model in the hamster and the mouse. An overview is provided of the technical development of the chamber technique and of the various experimental studies that have been performed using these models in ischaemia-reperfusion of striated muscle. Particular emphasis is given to a description of the methods used to induce ischaemia and reperfusion, namely pressure-induced or tourniquet-induced ischaemia. While the former allows simulation of the pathophysiological situation in compartment syndromes, the latter provides an appropriate simulation of the clinical situation in vascular, transplantation and reconstructive surgery. Future possibilities for these microcirculation models in research into the pathophysiology of ischemia-reperfusion are outlined, and potential therapeutic measures to preserve postischaemic tissue are discussed.

Role of Mac-1 and ICAM-1 in ischemia-reperfusion injury in a microcirculation model of BALB/C mice

The leukocyte beta 2-integrin Mac-1 (CD11b/CD18) and its endothelial ligand intercellular adhesion molecule 1 (ICAM-1) are involved in leukocyte adhesion to and macromolecular leakage from postcapillary venules during inflammatory reactions. Both events are also encountered after ischemia-reperfusion of striated muscle, suggesting a central role of both adhesion proteins in reperfusion injury. Using intravital fluorescence microscopy and a microcirculation model in awake BALB/C mice, we investigated the effects of monoclonal antibodies (MAb) and Fab fragments to Mac-1 and MAb to ICAM-1 on leukocyte-endothelium interaction and macromolecular leakage of fluorescein isothiocyanate-dextran (1.5 x 10(5) mol wt) in striated skin muscle after 3 h of ischemia followed by reperfusion. We demonstrated that administration of MAb and Fab to Mac-1 before reperfusion was as effective as administration of MAb to ICAM-1, which was found to be significantly upregulated in the postischemic tissue by immunohistochemical analysis, in preventing postischemic leukocyte adhesion to and macromolecular leakage from postcapillary venules, whereas postischemic leukocyte rolling was not affected after MAb administration. Postischemic capillary perfusion was efficiently preserved in animals treated with anti-Mac-1 and anti-ICAM-1 MAb compared with animals receiving the isotype-matched control antibodies.(ABSTRACT TRUNCATED AT 250 WORDS)

Leukocyte rolling in venules of striated muscle and skin is mediated by P-selectin, not by L-selectin

Leukocyte rolling in post-capillary venules is mediated by adhesion molecules of the selectin family expressed on both leukocytes (L-selectin) and endothelial cells (E- and P-selectin). With the use of intravital fluorescence microscopy, the effects of antibodies against these selectins were analyzed in the skinfold chamber model of BALB/c mice and the ear model of homozygous hairless mice (hr/hr) that permit chronic observation of striated muscle and skin microcirculation in awake animals, respectively. Mice were injected intravenously with monoclonal antibodies (MAb) to murine L-selectin and E-selectin and affinity-purified polyclonal antibodies to P-selectin. The antibodies, which are known to block cell adhesion, were tested by immunoprecipitation to selectively bind to L-, E-, or P-selectin. Leukocyte rolling was a constant finding in both microcirculation models in the absence of inflammatory stimuli. In both models, injection of anti-P-selectin antibodies completely prevented baseline leukocyte rolling over an observation period of 2 h (P < 0.01 vs. baseline), while no effects were seen after administration of either anti-L-selectin or anti-E-selectin MAb. Treatment with the isotype-matched control antibodies did not affect leukocyte rolling in either model. We conclude that leukocyte rolling in postcapillary venules of murine striated muscle and skin is a physiological process mediated via P-selectin, whereas L- and E-selectin appear not to play a significant role under these circumstances.

Comparative efficacy of azelastine nasal spray and terfenadine in seasonal and perennial rhinitis

The efficacy and tolerability of intranasal azelastine (0.14 mg/nostril twice daily) and oral terfenadine (60 mg twice daily) were compared under double-blind conditions in two 6-week, multicenter, parallel-group studies, including 167 patients suffering from seasonal and 52 patients suffering from perennial allergic rhinitis. In both studies, patients were symptomatic on entry and showed significant improvement on both treatments within the first 8 d of therapy, showing little further improvement with continued treatment. Symptoms most pronounced on entry--nasal itching, rhinorrhea, sneezing, and nasal obstruction--responded best to treatment (response rates 80-90%). Objective signs such as mucosal swelling and conjunctivitis improved in a manner parallel to symptoms. In perennial rhinitis, azelastine showed a trend to a superior relief of rhinorrhea and nasal obstruction, whereas terfenadine showed a trend toward better control of sneezing and nasal itchiness. No clinically relevant or statistically significant differences between treatments could be identified. The incidence of adverse effects of possible causal relationship to therapy was low. The most frequent effects in azelastine-treated patients were related to application site disorders, e.g., nasal irritation. Results indicate that with the dose used azelastine nasal spray is an effective treatment for both seasonal and perennial allergic rhinitis.

Diaspirin crosslinked hemoglobin: evaluation of effects on the microcirculation of striated muscle

Hemoglobin-based oxygen carriers such as diaspirin-crosslinked hemoglobin (DCLHb) have been proposed for blood substitution due to their plasma expansion and oxygen transport capacity. This study investigates the effects of DCLHb on the microcirculation of striated muscle after moderate topload infusion and isovolemic exchange transfusion in awake hamsters. The skinfold chamber model in hamsters and intravital fluorescence microscopy were used for analysis of vessel diameter, red blood cell velocity (RBCV), leukocyte sticking to the microvascular endothelium, and macromolecular leakage in striated skin muscle. In each animal, arteriolar and postcapillary vessel segments were chosen and sequentially recorded on videotape (baseline). Animals were subjected to either topload infusion (10% of blood volume) or isovolemic exchange transfusion (hct 30%) of DCLHb followed by measurements at 10, 30, and 60 min thereafter. In vivo visualization of plasma and leukocytes was performed using FITC-dextran 150,000 and rhodamine 6G, respectively. No significant changes of vessel diameter and RBCV were observed after topload infusion or isovolemic exchange transfusion with DCLHb, either in postcapillary venules or in arterioles when compared with baseline values. Leukocyte sticking and macromolecular leakage were not found enhanced after administration of DCLHb. We conclude that the introduction of DCLHb-bound oxygen into the tissue does neither stimulate leukocyte adhesion nor impair endothelial integrity.

Dorsal skinfold chamber technique for intravital microscopy in nude mice

For many years, observation chambers, implanted in various animal species and in man, have been used for intravital microscopy of the microcirculation in granulation tissue, preformed tissue, or of the microvascularization of tissue implants. We describe herein a skinfold chamber model for the intravital microscopic investigation of striated skin muscle in immunoincompetent, nude mice over a minimum period of 2 weeks. Using fluorescent markers for contrast enhancement of plasma (fluorescein isothiocyanate-dextran) and leukocytes (acridine orange), the presented model allows the quantitative analysis of 1) the microhemodynamic parameters microvessel diameter and red blood cell velocity in arterioles (16 to 50 mu diameter), capillaries (4 to 9 mu diameter), and post-capillary venules (19 to 60 mu diameter), 2) leukocyte/endothelium interaction in these vessel segments, 3) functional capillary density and intercapillary distance, and 4) endothelial cell integrity. These parameters can be assessed in the microcirculation of the striated muscle tissue under normal or pathological conditions, as well as in the microcirculation of transplanted xenogeneic (human) neoplastic and non-neoplastic tissue grafts.