Hydrolyses of alpha- and beta-cellobiosyl fluorides by Cel6A (cellobiohydrolase II) of Trichoderma reesei and Humicola insolens

We have measured the hydrolyses of alpha- and beta-cellobiosyl fluorides by the Cel6A [cellobiohydrolase II (CBHII)] enzymes of Humicola insolens and Trichoderma reesei, which have essentially identical crystal structures [Varrot, Hastrup, Schülein and Davies (1999) Biochem. J. 337, 297-304]. The beta-fluoride is hydrolysed according to Michaelis-Menten kinetics by both enzymes. When the approximately 2.0% of beta-fluoride which is an inevitable contaminant in all preparations of the alpha-fluoride is hydrolysed by Cel7A (CBHI) of T. reesei before initial-rate measurements are made, both Cel6A enzymes show a sigmoidal dependence of rate on substrate concentration, as well as activation by cellobiose. These kinetics are consistent with the classic Hehre resynthesis-hydrolysis mechanism for glycosidase-catalysed hydrolysis of the 'wrong' glycosyl fluoride for both enzymes. The Michaelis-Menten kinetics of alpha-cellobiosyl fluoride hydrolysis by the T. reesei enzyme, and its inhibition by cellobiose, previously reported [Konstantinidis, Marsden and Sinnott (1993) Biochem. J. 291, 883-888] are withdrawn. (1)H NMR monitoring of the hydrolysis of alpha-cellobiosyl fluoride by both enzymes reveals that in neither case is alpha-cellobiosyl fluoride released into solution in detectable quantities, but instead it appears to be hydrolysed in the enzyme active site as soon as it is formed.

Clinical evaluation of contrast-enhanced color Doppler sonography in the differential diagnosis of liver tumors

PURPOSE

We investigated the value of contrast-enhanced color Doppler sonography in the differential diagnosis of liver tumors.

METHODS

We prospectively examined 105 focal liver lesions in 100 patients by real-time gray-scale sonography, color Doppler sonography, and contrast-enhanced color Doppler sonography with galactose-based microbubbles (SH U 508A; Levovist). The final diagnoses of the liver lesions as confirmed by pathology or additional imaging techniques were 31 metastases, 25 hemangiomas, 19 hepatocellular carcinomas, 19 focal nodular hyperplasias, 2 cholangiocellular carcinomas, and 9 other lesions.

RESULTS

Vascularity could be detected in 43 (41%) of the 105 lesions by conventional color Doppler sonography compared to 67 (64%) by contrast-enhanced color Doppler sonography. Contrast-enhanced color Doppler sonography identified moderate or extensive vascularity in all 19 focal nodular hyperplasias, moderate or extensive vascularity in 16 hepatocellular carcinomas and both cholangiocellular carcinomas, and no or minor vascularity in all but 3 hemangioma. The combination of gray-scale, conventional color Doppler, and contrast-enhanced color Doppler sonography led to the correct diagnosis in 81% of cases (85 of 105), compared to 57% (60/105) for gray-scale and conventional color Doppler sonography and 31% (33/105) for gray-scale sonography alone.

CONCLUSIONS

Contrast-enhanced color Doppler sonography improves the detection of tumor vascularity and is useful in the differential diagnosis of liver lesions.

Macroscopic spectral imaging and gene expression analysis of the early stages of melanoma

BACKGROUND

The stages of melanocytic progression are defined as atypical (dysplastic) nevus, melanoma in situ, melanoma in the radial growth phase (RGP), melanoma in the vertical growth phase (VGP), and melanoma in the metastatic growth phase (MGP). Melanoma in situ and RGP melanoma often develop in contiguous association with atypical nevi. This frequently poses a problem with respect to their early detection. Furthermore, unlike cells obtained from VGP and MGP melanomas, cells derived from melanoma in situ and RGP melanoma do not proliferate in vitro. Thus, compared to the late stages of the disease, less information is available regarding genes expressed in the early stages.

MATERIALS AND METHODS

To determine whether spectral imaging, a recently developed optical imaging technique, can detect melanoma in situ and RGP melanoma arising in melanoma precursor lesions, atypical nevi in patients with a clinical history of melanoma were subjected to noninvasive macroscopic spectral imaging. To determine at what stage in the progression pathway of melanoma genes having important biological functions in VGP and MGP melanomas are activated and expressed, lesions of melanoma in situ were analyzed by immunohistochemistry and in situ hybridization for expression of some of these known molecular and immunologic markers.

RESULTS

The present study demonstrates the capability of noninvasive spectral imaging to detect melanoma in situ and RGP melanoma that arise in contiguous association with atypical nevi. Furthermore, the study provides evidence that genes and antigens expressed in VGP and MGP melanoma are also expressed in melanoma in situ.

CONCLUSIONS

Because of the dark and variegated pigmentation of atypical nevi, melanoma in situ and RGP melanoma that arise in these melanoma precursor lesions are often difficult to recognize and thus frequently go unnoticed. The application of new optical screening techniques for early detection of melanoma and the identification of genes expressed in the early stages of melanoma development are two important avenues in the pursuit of melanoma prevention. The investigations presented here document that macroscopic spectral imaging has the potential to detect melanoma in its early stage of development and that genes essential for the proliferation and cell adhesion of VGP and MGP melanoma are already expressed in melanoma in situ.

A missense mutation in myosin VIIA prevents aminoglycoside accumulation in early postnatal cochlear hair cells

Myosin VIIA is expressed by sensory hair cells in the inner ear and proximal tubule cells in the kidney, the two primary targets of aminoglycoside antibiotics. Using cochlear cultures prepared from early postnatal Myo7a6J mice with a missense mutation in the head region of the myosin VIIA molecule we show that this myosin is required for aminoglycoside accumulation in cochlear hair cells. Hair cells in homozygous mutant Myo7a6J cochlear cultures have disorganized hair bundles, but are otherwise morphologically normal and transduce. However, and in contrast to hair cells from heterozygous Myo7a6J cultures, the homozygous Myo7a6J hair cells do not accumulate [3H]gentamicin and do not exhibit an ototoxic response on exposure to aminoglycoside. Possible roles for myosin VIIA in the process of aminoglycoside accumulation are discussed.

Allergen-specific immune deviation from a TH2 to a TH1 response induced by dendritic cells and collagen type I

BACKGROUND

Atopy and IgE production are associated with enhanced allergen-specific T(H)2 responses. Therefore a causative treatment may result from the deviation of this T(H)2-dominated immune response toward a T(H)1 response.

OBJECTIVE

This study was carried out to analyze whether dendritic cells, the most potent antigen-presenting cells that are also known to induce antigen-specific T(H)1 responses, are suitable for therapy of atopic diseases by shifting the allergen-specific T(H)2 response toward a T(H)1 response.

METHODS

Monocyte-derived dendritic cells were used to present allergens in vitro to autologous CD4(+) T cells of allergic persons. Because collagen type I activates dendritic cells and enhances the secretion of IL-12, we performed allergen presentation assays also in the presence of collagen type I.

RESULTS

After stimulation with allergen-pulsed dendritic cells the production of IFN-gamma as well as that of IL-4 and IL-5 by CD4(+) T cells was enhanced. In the presence of collagen type I, however, a significant shift toward a T(H)1 response with increased production of IFN-gamma and a decreased production of IL-5 could be observed. When T cells were stimulated directly with anti-CD3 and anti-CD28 in the absence of antigen-presenting cells, it was demonstrated that collagen type I also exerted a direct effect on T cells, increasing their IFN-gamma production.

CONCLUSION

These data indicate that collagen type I influences dendritic cells as well as T cells in a way that a shift in cytokine production results in a T(H)1 response even in already-sensitized atopic individuals.

Auxin-induced K+ channel expression represents an essential step in coleoptile growth and gravitropism

Auxin-induced growth of coleoptiles depends on the presence of potassium and is suppressed by K+ channel blockers. To evaluate the role of K+ channels in auxin-mediated growth, we isolated and functionally expressed ZMK1 and ZMK2 (Zea mays K+ channel 1 and 2), two potassium channels from maize coleoptiles. In growth experiments, the time course of auxin-induced expression of ZMK1 coincided with the kinetics of coleoptile elongation. Upon gravistimulation of maize seedlings, ZMK1 expression followed the gravitropic-induced auxin redistribution. K+ channel expression increased even before a bending of the coleoptile was observed. The transcript level of ZMK2, expressed in vascular tissue, was not affected by auxin. In patch-clamp studies on coleoptile protoplasts, auxin increased K+ channel density while leaving channel properties unaffected. Thus, we conclude that coleoptile growth depends on the transcriptional up-regulation of ZMK1, an inwardly rectifying K+ channel expressed in the nonvascular tissue of this organ.

Reproducibility of irritant patch test reactions to sodium lauryl sulfate in a double-blind placebo-controlled randomized study using clinical scoring. Results from a study group of the German Contact Dermatitis Research Group (Deutsche Kontaktallergie-Gruppe, DKG)

Reading of doubtful patch test reactions can be improved by comparing them to defined negative, allergic and irritant controls. For the latter, an irritant patch test is needed that gives sufficiently reproducible results. In our double-blind, placebo-controlled, randomized study, we have analysed the synchronous reproducibility of patch tests with 0%, 0.0625%, 0.125%, 0.25%, 0.5% and 1.0% sodium lauryl sulfate (SLS). Tests and readings were done according to ESCD guidelines. 139 patients (75 women, 64 men) 18 to 77 years old were tested. The % of positive patients as well as the % of reproducible positive reactions increased with rising concentrations of SLS to a maximum of approximately 90% and 85%, respectively, with 1% SLS. Time courses of reactions were also related to the concentration of SLS: with 1% SLS, plateau-type time courses were most common (65%), followed by decrescendo- (23%) and crescendo-type reactions (12%). With 1% SLS, very similar mild to moderate reactions were obtained on days 2 and 3. The reaction threshold and reproducibility of tests were not related to age and sex of patients or to their own assessment of skin irritability. We conclude that 1% SLS is appropriate for an irritant patch test that gives sufficiently reproducible results.

Evolution of the HOXB6 intergenic region: motif conservation at the lateral plate mesoderm (LPM) enhancer element

This study reports the results of a comparative sequencing study in higher primates, focusing on the intergenic region located between HOXB6 and HOXB7. We have examined an 832 bp. region, encompassing a putative Lateral Plate Mesoderm (LPM) enhancer element in a variety of anthropoid apes. The interspecific comparisons reveal extensive substitutions occurring within this region, with a marked bias in favor of C-->T transitions within the enhancer element. The pattern of these substitutions suggests that the LPM enhancer region is subject to specific sequence and compositional constraints that are only revealed through comparative sequencing. These constraints produce an enhancer signature, the CpG microisland, which may be useful in identifying additional regulatory elements located within the HOX complexes. J. Exp. Zool. (Mol. Dev. Evol.) 285:170-176, 1999.

Percutaneous ethanol injection and radio-frequency ablation for the treatment of nonresectable colorectal liver metastases - techniques and results

BACKGROUND

Percutaneous ethanol injection (PEI) and radio-frequency (RF) ablation are possible palliative treatment modalities for patients with non-resectable liver metastases of colorectal carcinomas. The different techniques are explained and reviewed.

RESULTS

PEI did not show promising results for the treatment of liver metastases. RF results were more encouraging; some studies showed improved mean survival times for patients when a complete necrosis of the metastases could be achieved. The maximum diameter of the necrotic area possible in a single session is about 5 cm.

CONCLUSION

PEI and RF are palliative last-line treatment strategies for patients with non-resectable liver metastases and should only be applied if chemotherapy is not sufficient or not possible. The long-term efficacy of RF ablation in this group of patients has to be evaluated.

Improved glycemic control reduces the impact of weight gain on cardiovascular risk factors in type 1 diabetes. The Epidemiology of Diabetes Complications Study

OBJECTIVE

To assess the prevalence and incidence of being overweight in type 1 diabetes, to identify factors associated with weight gain and improved glycemic control, and to examine relationships among weight gain, glycemic control, and cardiovascular risk factors.

RESEARCH DESIGN AND METHODS

The prevalence and incidence of being overweight in the Pittsburgh Epidemiology of Diabetes Complications (EDC) cohort (n = 441) were compared with the general population (National Health and Nutrition Examination Survey [NHANES]). Factors associated with weight gain and improved glycemic control were identified, and relationships among weight gain, glycemic control, and cardiovascular risk factors were examined over a 6.9 +/- 2.2-year period.

RESULTS

At baseline, the prevalence of being overweight (BMI > 27.8 kg/m2 for men and > 27.3 kg/m2 for women) was 10.4 and 11.4%, respectively, and was lower than the age- and sex-specific estimate for the general population (P < 0.05). The incidence of being overweight was comparable in men (12.6%) and women (11.8%) and did not differ from the general population (P = 0.98). Weight gain correlated with improvements in HbA1c (r = -0.21, P < 0.001). Patients with the highest baseline HbA1c levels gained the most weight and had the greatest improvement in glycemic control. A lower baseline BMI was also associated with a greater improvement in glycemic control. Weight gain favorably influenced the lipid profile in the setting of improved glycemic control, but adversely influenced the lipid profile in the absence of improved glycemic control. Weight change was directly associated with blood pressure change, but the incidence of hypertension was more strongly influenced by the development of nephropathy.

CONCLUSIONS

The prevalence of being overweight in type 1 diabetes remains lower than that in the general population. Moderate weight gain did not adversely affect the cardiovascular risk profile in the setting of improved glycemic control.

The significance of high levels of lipoprotein (a) compared with established risk factors in premature coronary artery disease: differences between men and women

It was shown in a series of studies that increased lipoprotein (a) concentration is a strong and independent risk factor for coronary artery disease. The goal of this study was to determine the significance of elevated lipoprotein (a) levels for the existence and the early manifestation of coronary artery disease by systematically recording cardiovascular risk factors in diagnostic coronary angiographies in a larger group of patients, whereby particular attention was paid to sex-specific differences. In 1011 consecutive patients who underwent coronary angiography (731 men, 280 women, mean age 59 +/- 10 years), fasting blood samples were taken immediately before the angiographies to determine the levels of cholesterol, low density lipoprotein-, high density lipoprotein-cholesterol, triglycerides and lipoprotein (a). In addition, further risk factors were qualitatively recorded. The data evaluation was carried out using the SPSSx software package univariately and multivariately with stepwise discriminant analysis. In 231 patients (144 men, 87 women) either no or only discrete coronary findings appeared, while in 780 cases (587 men, 193 women) coronary artery disease with stenoses > 50% were found. Women with coronary artery disease were significantly older than men and demonstrated higher lipoprotein levels. Women as well as men with coronary artery disease differed from healthy controls by having higher levels of lipoprotein (a) and other lipoproteins, lipoprotein (a) having the smallest error probability (P < 0.0005). The early manifestation of coronary artery disease (below the 18th age percentile) in men (< 50 years) was connected with significantly higher levels of cholesterol, triglycerides and lipoprotein (a), which emphasized their atherogenic significance in the general view. The most striking finding was that in young women (< 53 years), compared to older women with coronary artery disease--corresponding to the age-determined prevalence--significantly lower concentrations of cholesterol, triglycerides and lipoprotein (a) were found. Possible explanations include later manifestation of coronary artery disease, a steeper increase of the lipids with age, particularly of lipoprotein (a), but also a different valence of the risk factors in women.

Gap junctions and connexin expression in the inner ear

Several different recessive mutations in the connexin26 (Cx26; beta 2) gene have been associated with non-syndromic hereditary deafness. This suggests gap junctions are important to cochlear function. Numerous large gap junctions are present between adjacent supporting cells in both the vestibular and auditory sensory epithelia of the mature inner ear. In vestibular organs, Cx26 is highly expressed, but antibodies of Cx32 (beta 1) also label the supporting cells. In the organ of Corti of the cochlea, Cx26 is the predominant connexin isoform; neither Cx32 nor Cx43 (alpha 1) can be detected by immunohistochemistry. One role for gap junctions between supporting cells may be to provide a pathway for the rapid removal of ions away from the region of the sensory cells during transduction in order to maintain sensitivity. In the cochlea gap junctions are also associated with the basal cells of the stria vascularis, an ion-transporting epithelium that maintains a positive electrical potential in the potassium-rich endolymph fluid which bathes the apical surfaces of the sensory 'hair' cells and which is crucial for auditory transduction. Gap junctions are present between fibrocytes in the spiral ligament that underlies the stria vascularis, and between these fibrocytes and strial basal cells. During cochlear development, the initial formation and subsequent increase in size and number of gap junctions in the stria vascularis coincides with the initial generation and rise of the endocochlear potential. This and other evidence suggests that one role of gap junctions in the cochlea is to provide a pathway for passage of ions to maintain endolymph and, thus, auditory acuity. Mutations to Cx26 could, therefore, disrupt this ion circulation, resulting in deafness.

[Color doppler ultrasonographic detection of focal thyroid nodules]

AIM

To determine if colour Doppler sonography is a sensitive tool to detect solitary hot thyroid nodules.

METHODS

All patients evaluated in our ultrasound laboratory during study period also underwent thyroid sonography. If one or more nodules with a diameter of at least 8 mm were present, thyroid scientigraphy was performed. Hyperperfusion within the nodule compared to the surrounding tissue indicated autonomy according to the study protocol.

RESULTS

1010 patients were screened. 385 had one or more nodules, 309 of them with a diameter of more than 8 mm. Among these patients a hot nodule was proved with scintigraphy in 120 cases. 116 of these 120 patients were correctly identified with colour Doppler sonography.

CONCLUSION

Colour Doppler sonography is a reliable method to detect solitary hot or hyperperfused thyroid nodules and to identify a risk group of patients prior to the administration of x-ray contrast media.

Channel-mediated high-affinity K+ uptake into guard cells from Arabidopsis

Potassium uptake by higher plants is the result of high- or low-affinity transport accomplished by different sets of transporters. Although K+ channels were thought to mediate low-affinity uptake only, the molecular mechanism of the high-affinity, proton-dependent K+ uptake system is still scant. Taking advantage of the high-current resolution of the patch-clamp technique when applied to the small Arabidopsis thaliana guard cells densely packed with voltage-dependent K+ channels, we could directly record channels working in the concentration range of high-affinity K+ uptake systems. Here we show that the K+ channel KAT1 expressed in Arabidopsis guard cells and yeast is capable of mediating potassium uptake from media containing as little as 10 microM of external K+. Upon reduction of the external K+ content to the micromolar level the voltage dependence of the channel remained unaffected, indicating that this channel type represents a voltage sensor rather than a K+-sensing valve. This behavior results in K+ release through K+ uptake channels whenever the Nernst potential is negative to the activation threshold of the channel. In contrast to the H+-coupled K+ symport shown to account for high-affinity K+ uptake in roots, pH-dependent K+ uptake into guard cells is a result of a shift in the voltage dependence of the K+ channel. We conclude that plant K+ channels activated by acid pH may play an essential role in K+ uptake even from dilute solutions.

Absorbable fasteners for the fixation of ankle fractures

Bioabsorbable materials have been used for the treatment of fractures for more than a century. We reviewed the results of a combined series of 30 ankle fractures from Bad Hersfeld, Germany, and Louisville, Kentucky, using initially polyglycolide and more recently poly-L-lactide screws and rods. The results were comparable to treatment with metal screws. The advantage of bioabsorbable implants is they do not need operations to take them out. There was a low incidence of reaction around the screw heads, which was reduced further with the use of the newer self-reinforced poly-L-lactate screws. The technique for use of plastics is different than the methods for placement of metal screws. Bioabsorbables will have an increasing role in fracture fixation in the future.

On the accuracy of a new displacement instrumentation for rotary tablet presses

The Portable Press Analyzer (PPA; Puuman Oy, Finland), a commercially available instrumentation for rotary tablet presses, was tested for accuracy of determination of force and displacement. The calibration of the force transducers (strain gauges) was tested under a static condition. The calibration of the displacement transducers (plastic film potentiometer) was compared for static and dynamic recordings. Force measurement was found precise (deviation < 1.1%) after alterations in the calibration procedure. Displacement measurement was affected by punch tilting and the application of the transducers. If tilting of punches was not considered, the deviation of displacement measurement from the true value (using steel tablets as a reference) was found up to 110 microns. By modifying the original PPA system by supplementing additional displacement transducers in the adjacent turret positions of the punches and adding a custom electronic device (Tilting Compensation Device), the accuracy of distance measurement was improved to 18.1 microns (+/- 3.64). Furthermore, machine and tooling deformation were recorded and found different under static and dynamic conditions. Correction of punch displacement for elastic deformation therefore should preferably be made from dynamic recordings.

Detection of increased tyrosine phosphorylation in murine Langerhans cells after stimulation with contact sensitizers

The signalling pathways in epidermal Langerhans cells (LC) during activation by contact sensitizers are poorly understood. Recently, we have described an increased phosphorylation of tyrosine residues in human MHC class II-positive cells in vitro following stimulation with contact sensitizers. In the study reported here the formation of phosphotyrosine (p-tyr) in murine epidermal LC upon stimulation with contact sensitizers was examined. By the use of a flow cytometric technique a significant increase in p-tyr was demonstrated in LC stimulated in vitro with the strong contact sensitizers TNCB (2,4,6-trinitro-chlorobenzene) and MCI/MI (5-chloro-2-methylisothiazolinone plus 2-methylisothiazolinone) but not after treatment with the irritants sodium lauryl sulphate or benzoic acid. The protein tyrosine kinase inhibitors genistein and tyrphostin A9, but not tyrphostin AG 1288, were able to block this process significantly. Similar results were obtained using the LC-like dendritic cell line XS52. In addition, Western blot analysis on XS52 cells revealed a selective phosphorylation of two protein bands with a molecular weight between 50 and 60 kDa following stimulation with TNCB. These results demonstrate that contact sensitizers induce an increased phosphorylation of tyrosine residues in murine LC and can be used as the basis for in vivo studies using inhibitors for signal transduction pathways for prevention of primary sensitization to contact sensitizers.