Assessment of serum total 25-hydroxyvitamin D assays for Vitamin D External Quality Assessment Scheme (DEQAS) materials distributed at ambient and frozen conditions

The Vitamin D External Quality Assessment Scheme (DEQAS) distributes human serum samples four times per year to over 1000 participants worldwide for the determination of total serum 25-hydroxyvitamin D [25(OH)D)]. These samples are stored at -40 °C prior to distribution and the participants are instructed to store the samples frozen at -20 °C or lower after receipt; however, the samples are shipped to participants at ambient conditions (i.e., no temperature control). To address the question of whether shipment at ambient conditions is sufficient for reliable performance of various 25(OH)D assays, the equivalence of DEQAS human serum samples shipped under frozen and ambient conditions was assessed. As part of a Vitamin D Standardization Program (VDSP) commutability study, two sets of the same nine DEQAS samples were shipped to participants at ambient temperature and frozen on dry ice. Twenty-eight laboratories participated in this study and provided 34 sets of results for the measurement of 25(OH)D using 20 ligand binding assays and 14 liquid chromatography-tandem mass spectrometry (LC-MS/MS) methods. Equivalence of the assay response for the frozen versus ambient DEQAS samples for each assay was evaluated using multi-level modeling, paired t-tests including a false discovery rate (FDR) approach, and ordinary least squares linear regression analysis of frozen versus ambient results. Using the paired t-test and confirmed by FDR testing, differences in the results for the ambient and frozen samples were found to be statistically significant at p < 0.05 for four assays (DiaSorin, DIAsource, Siemens, and SNIBE prototype). For all 14 LC-MS/MS assays, the differences in the results for the ambient- and frozen-shipped samples were not found to be significant at p < 0.05 indicating that these analytes were stable during shipment at ambient conditions. Even though assay results have been shown to vary considerably among different 25(OH)D assays in other studies, the results of this study also indicate that sample handling/transport conditions may influence 25(OH)D assay response for several assays.

Interlaboratory comparison of 25-hydroxyvitamin D assays: Vitamin D Standardization Program (VDSP) Intercomparison Study 2 - Part 1 liquid chromatography - tandem mass spectrometry (LC-MS/MS) assays - impact of 3-epi-25-hydroxyvitamin D3 on assay performance

An interlaboratory comparison study was conducted by the Vitamin D Standardization Program (VDSP) to assess the performance of liquid chromatography - tandem mass spectrometry (LC-MS/MS) assays used for the determination of serum total 25-hydroxyvitamin D (25(OH)D), which is the sum of 25-hydroxyvitamin D₂ (25(OH)D₂) and 25-hydroxyvitamin D₃ (25(OH)D₃). A set of 50 single-donor samples was assigned target values for concentrations of 25(OH)D₂, 25(OH)D₃, 3-epi-25-hydroxyvitamin D₃ (3-epi-25(OH)D₃), and 24R,25-dihydroxyvitamin D₃ (24R,25(OH)₂D₃) using isotope dilution liquid chromatography - tandem mass spectrometry (ID LC-MS/MS). VDSP Intercomparison Study 2 Part 1 includes results from 14 laboratories using 14 custom LC-MS/MS assays. Assay performance was evaluated using mean % bias compared to the assigned target values and using linear regression analysis of the test assay mean results and the target values. Only 53% of the LC-MS/MS assays met the VDSP criterion of mean % bias ≤ |±5%|. For the LC-MS/MS assays not meeting the ≤ |±5%| criterion, four assays had mean % bias of between 12 and 21%. Based on multivariable regression analysis using the concentrations of the four individual vitamin D metabolites in the 50 single-donor samples, the performance of several LC-MS/MS assays was found to be influenced by the presence of 3-epi-25(OH)D₃. The results of this interlaboratory study represent the most comprehensive comparison of LC-MS/MS assay performance for serum total 25(OH)D and document the significant impact of the lack of separation of 3-epi-25(OH)D₃ and 25(OH)D₃ on assay performance, particularly with regard to mean % bias.

Assessment of serum total 25-hydroxyvitamin D assay commutability of Standard Reference Materials and College of American Pathologists Accuracy-Based Vitamin D (ABVD) Scheme and Vitamin D External Quality Assessment Scheme (DEQAS) materials: Vitamin D Standardization Program (VDSP) Commutability Study 2

An interlaboratory study was conducted through the Vitamin D Standardization Program (VDSP) to assess commutability of Standard Reference Materials® (SRMs) and proficiency testing/external quality assessment (PT/EQA) samples for determination of serum total 25-hydroxyvitamin D [25(OH)D] using ligand binding assays and liquid chromatography-tandem mass spectrometry (LC-MS/MS). A set of 50 single-donor serum samples were assigned target values for 25-hydroxyvitamin D2 [25(OH)D2] and 25-hydroxyvitamin D3 [25(OH)D3] using reference measurement procedures (RMPs). SRM and PT/EQA samples evaluated included SRM 972a (four levels), SRM 2973, six College of American Pathologists (CAP) Accuracy-Based Vitamin D (ABVD) samples, and nine Vitamin D External Quality Assessment Scheme (DEQAS) samples. Results were received from 28 different laboratories using 20 ligand binding assays and 14 LC-MS/MS methods. Using the test assay results for total serum 25(OH)D (i.e., the sum of 25(OH)D2 and 25(OH)D3) determined for the single-donor samples and the RMP target values, the linear regression and 95% prediction intervals (PIs) were calculated. Using a subset of 42 samples that had concentrations of 25(OH)D2 below 30 nmol/L, one or more of the SRM and PT/EQA samples with high concentrations of 25(OH)D2 were deemed non-commutable using 5 of 11 unique ligand binding assays. SRM 972a (level 4), which has high exogenous concentration of 3-epi-25(OH)D3, was deemed non-commutable for 50% of the LC-MS/MS assays.

SAT-LB13 Clinical Utility of 21-Deoxycortisol in Congenital Adrenal Hyperplasia

Introduction Congenital Adrenal Hyperplasia (CAH) is most often caused by mutation of the 21-hydroxylase gene (CYP21), which results in underproduction of cortisol with overproduction of precursor steroids and their metabolites by the adrenal glands. Historically the most common biomarker used for detecting CAH in pediatric patients is 17-Hydroxyprogesterone (17OHP). Another less commonly used biomarker for 21-Hydroxylase deficiency is 21-deoxycortisol (21DOF), which increases from very low levels in normal patients to high levels in affected patients as 17OHP rises to very high levels. In this study we performed retrospective analysis of serum 21DOF concentration in specimens that had been genotyped for mutations in the CYP21A2 gene, or had been submitted to our laboratory for provocative adrenocorticotropin (ACTH / Cosyntropin) stimulation testing. Methods: Biochemical testing for 21DOF concentration was measured by LC-MS/MS. Briefly, a TX-4 HPLC system (Thermo-Fisher) with Agilent® 1100 pumps (Agilent Technologies, Inc.) and a Sciex® 5000 (Danaher) triple quadrupole mass spectrometer in positive mode atmospheric pressure chemical ionization (APCI) was used for detection in Multiple Reaction Monitoring (MRM) mode. Genetic testing was performed using the CAHDetx test, which detects the 12 most common small mutations and large gene deletions/conversions in CYP21A2. Genetic Correlations: 21DOF was quantifiable (above the LLOQ of the assay) in 4% (n=24/600) of specimens where no mutation was detected. 21-DOF was quantifiable in 42% (122/292) of specimens with 21-hydroxylase enzyme mutations as determined by the CAHDetx test. Those mutations included In2G, I172N, V281L and others. Some mutations such as Q318X did not result in a detectable increase in 21-deoxycortisol. ACTH Stimulation Response: 21-deoxycortisol was below the quantitation limit in both the baseline and stimulated samples in ~35% (52/148) of submitted samples. The 21-deoxycortisol was quantifiable in only the stimulation sample in ~45% (65/148) of ACTH stimulation submitted, and was quantifiable in both baseline and stimulated samples in the remaining ~20% (30/148) of ACTH stimulation pairings. The extent of 21-deoxycortisol increase ranged from 1.2-fold to 116-fold with a median 14-fold increase. Clinical Significance: The use of 21-deoxycortisol may be beneficial in reducing the rate of false positives in CAH diagnosis when used in concert with other steroid hormones, and may eventually reduce the need for provocative testing to confirm CAH diagnosis.

Adherence of Blood Cells to Dialyzer Membranes as a Measure of Biocompatibility

Cell adherence to plate dialyzer membranes was analysed at the end of 4 hours of dialysis. Three types of membranes were examined: Cuprophan® Hemophan® and Gambrane®, (a polycarbonate membrane). The membranes were mounted in dialyzers that contained 23 layers of one membrane type and one layer of each of the two other. Less leukocytes adhered to the Pc than to the Cu and He membranes. Transient initial complement activation during dialysis, which was considerably lower with dialysers containing mainly Pc membrane, was not correlated to adherence of cells to the membranes. Instead flow geometry is proposed as the main factor determining the adherence. Contrary to what has been earlier suggested, we think that leukocyte adherence is not a very suitable measure of membrane biocompatibility. The reason is that the influence of membrane surface-chemical factors can not be separated from mechanical factors due to the design of the device.

Individual differences in biocompatibility responses to hemodialysis

There are very few reports in the literature on individual differences in the response to dialysis treatment. We studied the influence of the individual patient, dialysis membrane quality, blood-flow (Qb) and surface area on leukocyte activation and complement generation (C3a) during 234 hemodialysis treatments using Cuprophan (CU), hemophane (HE) and polyamide (PA) dialyzers. The most common reaction was a decrease in leukocyte count and an increase in C3a after 15 minutes of treatment. Leukocyte overshoot by the end of dialysis was observed at high Qb for all three membranes but at low Qb only during CU treatments. The reaction patterns were influenced by the quality of the membrane, area and Qb. Analysis of each individual patient showed for a large number of treatments reaction patterns corresponding to those described in the literature. However, some patients reacted differently. In four patients (20%), the nadir in leukocyte count and maximum in C3a concentration was reached considerably later during CU-dialysis. Three patients were devoid of pronounced early leukocyte response but presented with the late overshoot during CU-dialysis. Three other patients reacted with an early drop in leukocyte count and a rapid increase in C3a generation during PA treatments but not during HE treatments. Three other patients reacted vice versa. A particular mode of dialysis treatment may thus be biocompatible for some patients but not necessarily for all. In the case biocompatibility is desired the individual response to the particular dialysis mode needs to be identified. The underlying mechanisms warrant further studies.

Percutaneous Nephrolithotomy through an Intercostal Approach

During a 5-year period percutaneous nephrolithotripsy through an intercostal space was performed in 56 of 231 procedures. Minimal thoracic complications were seen in 3 of 53 patients with 11th intercostal space tracts into a lower, middle, or upper pole calyx. A working sheath and a pyelostomy drainage catheter were used in all these cases. Hydro- and pneumothorax requiring treatment occurred in 2 of 3 patients with a 10th intercostal space approach into an upper pole calyx combined with improper use of the working sheath and/or the pyelostomy catheter. Review of the literature also indicates that an intercostal approach appears safe when performed via the 11th intercostal space into a lower or middle pole calyx. Thoracic complications occurred when punctures were made towards an upper pole calyx or above the 11th rib. The complications may be limited by identifying the posterior inferior lung border by fluoroscopy during puncture, and performing it under general anesthesia with controlled breath-holding. The use of a working sheath to seal the pleural opening during the procedure and an efficient pyelostomy drainage catheter to allow free drainage of urine and to tamponade the tract postoperatively are also recommended.

Effects of High-Dose Vitamin D2 Versus D3 on Total and Free 25-Hydroxyvitamin D and Markers of Calcium Balance

CONTEXT

Controversy persists over: 1) how best to restore low serum 25-hydroxyvitamin D (25D) levels (vitamin D2 [D2] vs vitamin D3 [D3]); 2) how best to define vitamin D status (total [protein-bound + free] vs free 25D); and 3) how best to assess the bioactivity of free 25D.

OBJECTIVE

To assess: 1) the effects of D2 vs D3 on serum total and free 25D; and 2) whether change in intact PTH (iPTH) is more strongly associated with change in total vs free 25D.

DESIGN

Participants previously enrolled in a D2 vs D3 trial were matched for age, body mass index, and race/ethnicity. Participants received 50 000 IU of D2 or D3 twice weekly for 5 weeks, followed by a 5-week equilibration period. Biochemical assessment was performed at baseline and at 10 weeks.

SETTING AND PARTICIPANTS

Thirty-eight adults (19 D2 and 19 D3) ≥18 years of age with baseline 25D levels <30 ng/mL were recruited from an academic ambulatory osteoporosis clinic.

OUTCOME MEASURES

Serum measures were total 25D, free 25D (directly measured), 1,25-dihydroxyvitamin D, calcium, and iPTH. Urine measure was fasting calcium:creatinine ratio.

RESULTS

Baseline total (22.2 ± 3.3 vs 23.3 ± 7.2 ng/mL; P = .5) and free (5.4 ± 0.8 vs 5.3 ± 1.7 pg/mL; P = .8) 25D levels were similar between D2 and D3 groups. Increases in total (+27.6 vs +12.2 ng/mL; P = .001) and free (+3.6 vs +6.2 pg/mL; P = .02) 25D levels were greater with D3 vs D2. Percentage change in iPTH was significantly associated with change in free (but not total) 25D, without and with adjustment for supplementation regimen, change in 1,25-dihydroxyvitamin D, and change in calcium.

CONCLUSIONS

D3 increased total and free 25D levels to a greater extent than D2. Free 25D may be superior to total 25D as a marker of vitamin D bioactivity.

Analysis of film coating thickness and surface area of pharmaceutical pellets using fluorescence microscopy and image analysis

A method is presented which enables geometrical characterisation of pharmaceutical pellets and their film coating. It provides a high level of details on the single pellet level. Image analysis was used to determine the coating thickness (h) applied on the pellets and the surface area (A) of the pellet cores. Different definitions of A and h are evaluated. Hierarchical analysis of variance was used to resolve different sources contributing to the total variance. The variance within pellets and the variance between pellets were found as significant sources of variation. Special emphasis was put on evaluation of A/h due to its influence on the release rate of an active drug substance from the pellet core. The pellet images were thus used to predict variations in the release rate using a mathematical model as a link between the image data and the release rate. General aspects of image analysis are discussed. The method would be useful in calibration of near infrared spectra to h in process analytical chemistry.

Genomic cloning, structure, and regulatory elements of the 1 alpha, 25(OH)2D3 down-regulated gene for cyclic AMP-dependent protein kinase inhibitor

The cyclic AMP-dependent protein kinase inhibitor (PKI) mRNA and protein are negatively and tissue-specifically regulated in the kidney by 1 alpha, 25(OH)2D3. A 17-kb PKI clone, isolated from a chick genomic library, revealed that the PKI gene consists of two exons separated by a 4.5-kb intron. A 411-bp upstream region (constituting 93 bp upstream and 318 bp downstream from the transcriptional start site) containing a putative negative VDRE (nVDRE) fused to the luciferase gene was used for transient transfections of primary cultures of chick kidney cells. Luciferase activity was significantly down-regulated in response to 1 alpha, 25(OH)2D3. This result suggests that the promoter region containing the putative nVDRE plays a pivotal role in the negative regulation of PKI gene transcription.

Impaired regeneration in rat sciatic nerves exposed to short-term vibration

We have studied the effects of vibration on the regeneration capacity of the peripheral nerve. A rat model was used where one hind limb was subjected to vibration of defined magnitude and duration while the contralateral hind limb was not exposed to vibration. Seven days later, the sciatic nerves were transected bilaterally and cross-joined giving the following groups: group A, a proximal vibrated nerve end sutured to a non-vibrated distal nerve end; group B, a non-vibrated proximal nerve end sutured to a distal vibrated nerve end, and group C, non-vibrated proximal nerve end sutured to a non-vibrated distal nerve end. The regeneration distances were measured 3, 6 and 8 days after surgery. The control group showed a normal linear outgrowth. The outgrowth in the two experimental groups was initially not different to controls but later became significantly different, indicating a retardation of outgrowth in these groups. It is concluded that short-term exposure to vibration can impair nerve regeneration after transection and nerve repair.

Increased amounts of C3a and the terminal complement complex at high dialysis blood-flow: the relation with dialysis efficiency

To estimate the influence of blood-flow on complement generation and the relation with dialysis efficacy (KT/V) 10 patients underwent cuprophan hemodialyses for 6 h using low (200 ml/min) or high (400 ml/min) blood-flow (n = 40). Dialysis with high blood-flow compared to low induced a more rapid drop in leukocyte count and a more pronounced leukocyte rebound. Net generation of C3a (microgram/min) was also larger at all 15 measuring points during high blood-flow dialysis and there was significantly larger total generation of C3a (after 3 h p < 0.05, after 6 h p < 0.05) as compared to low blood-flow. Reaching a KT/V of 1.2-1.4 with high blood-flow induced a 40% larger total net generation of C3a and 21% more of TCC than with low blood-flow. Net generation of TCC (AU/min) was higher during the first and last parts of high blood-flow dialysis compared to low. In conclusion, increased blood-flow in order to increase dialysis efficiency (KT/V 1.2-1.4) results in larger net infusion of complement products with possible impact on immune response and complement-associated pathophysiological mechanisms.

Rabbit liver class III alcohol dehydrogenase: a cathodic isoform with formaldehyde dehydrogenase activity

Electrophoresis of rabbit liver homogenate on starch gel followed by activity staining revealed multiple forms of alcohol dehydrogenase (ADH) which, based on their electrophoretic mobilities, had been tentatively labeled as class "I," class "II," and class "III" ADHs. The class II enzyme has now been purified to homogeneity by ion exchange and affinity chromatography and, except for an isoelectric point of 7.7, closely resembles human class III ADH. It is a homodimer of molecular weight near 80,000 with a similar amino acid composition and comparable kinetic parameters for the oxidation of primary alcohols. Like the rat, human, and Escherichia coli class III ADHs, the rabbit enzyme is a glutathione-dependent formaldehyde dehydrogenase, and catalyzes the oxidation of S-hydroxymethylglutathione and the hemithiolacetal of 8-thiooctanoic acid. Ethanol up to 3 M does not saturate the enzyme, whereas longer chain primary alcohols exhibit Michaelis-Menten kinetics.

On complement net generation in fast hemodialysis: are high blood flow rates bioincompatible?

Arterial and venous concentrations of complement (C3a) and leukocyte count were determined in 17 patients during 201 hemodialysis sessions by 12 different treatment modes executed in random order using cuprophan, hemophan, or polyamide membranes with small or large membrane areas and high blood flow (Qb) (400 mL/min) for 2 hours or low Qb (200 mL/min) for 4 hours. With all membrane types, the number of leukocytes was significantly higher after 120 minutes of dialysis and by the end of treatment at high Qb compared with low Qb. C3a concentrations (microgram/mL) in the arterial and venous blood lines were significantly higher during cuprophan dialysis compared with hemophan and polyamide dialyses (P < 0.001). In addition, the net generation of C3a (microgram/min) was significantly higher during hemodialysis with cuprophan compared with hemophan and polyamide (P < 0.001). After 2 hours at high Qb for each of the three membranes, the net generation of C3a was significantly higher compared with low Qb (P < 0.05 for all comparisons). Possible reasons for the increase in the net generation of C3a (microgram/min) at high Qb are less protein deposition on the membrane at high Qb or the fact that the protein coat is stripped off in the dialyzer, thereby recreating a less biocompatible surface. Hemodialysis at high Qb may thus be less biocompatible than dialysis at low Qb.

Predegeneration enhances regeneration into acellular nerve grafts

In the present study, we determined the regeneration rate and the initial delay in rat sciatic nerve grafts first made hypercellular by predegeneration then acellular by freeze-thawing. 7-day predegenerated nerve pieces from the distal nerve stump on the right side were made acellular by repeated freeze-thawing and inserted as grafts into a 10-mm long freshly created defect on the left contralateral side. Freshly made (no predegeneration period) acellular nerve grafts were used as controls. Both types of grafts supported outgrowth of regenerating axons as demonstrated by the sensory pinch test. However, the predegenerated acellular nerve grafts had a significantly shorter initial delay period (2.7 days) as compared with freshly made acellular nerve grafts (9.5 days). The initial delay period for predegenerated acellular nerve grafts was similar to that for fresh cellular nerve grafts but significantly longer than that for predegenerated cellular nerve grafts [24]. The rate of regeneration appeared independent of the type of grafts used. We suggest that modifications of the basal lamina and/or factors produced during the predegeneration period by non-neuronal cells survive the freeze-thawing cycle and account for the decrease in the initial delay period.

Pre-degenerated nerve grafts enhance regeneration by shortening the initial delay period

In the present study we tested how nerve grafts with different pre-degeneration periods (1-28 days) influenced the early regenerative response in the rat sciatic nerve. The sciatic nerve on the right side was crushed and after 1-28 days of pre-degeneration, a 10 mm segment was used as an autologous nerve graft and transposed to a freshly made 10 mm long nerve defect on the left side. The regeneration distance was measured by the sensory pinch test 2-10 days after nerve repair. A newly developed mathematical model was used to calculate regeneration rates and initial delay periods from the measured regeneration distances. Pre-degenerated nerve grafts improved nerve regeneration by decreasing the initial delay period as compared to fresh nerve grafts without affecting the regeneration rate. Only one day of pre-degeneration was sufficient to reduce the initial delay period from 3.6 days to 1.7 days. The maximal effect on the initial delay period was achieved after 3 days of pre-degeneration. The initial delay period at later pre-degeneration intervals (7-14 days) was about 1 day. The effect persisted for at least 28 days of pre-degeneration. The regeneration rate was 1.5 mm/day for fresh nerve grafts and between 1.8-2.1 mm/day for pre-degenerated grafts. The results suggest that the effects of pre-degeneration are not only due to the increased cell proliferation in the graft, but that also trophic and/or inflammatory mechanisms may be of importance. Grafts pre-degenerated by crush may have clinical implications since they are easy to perform if an elective nerve grafting procedure is planned.

Individual differences in biocompatibility responses to hemodialysis

There are very few reports in the literature on individual differences in the response to dialysis treatment. We studied the influence of the individual patient, dialysis membrane quality, blood-flow (Qb) and surface area on leukocyte activation and complement generation (C3a) during 234 hemodialysis treatments using Cuprophan (CU), hemophane (HE) and polyamide (PA) dialyzers. The most common reaction was a decrease in leukocyte count and an increase in C3a after 15-minutes of treatment. Leukocyte overshoot by the end of dialysis was observed at high Qb for all three membranes but at low Qb only during CU treatments. The reaction patterns were influenced by the quality of the membrane, area and Qb. Analysis of each individual patient showed for a large number of treatments reaction patterns corresponding to those described in the literature. However, some patients reacted differently. In four patients (20%), the nadir in leukocyte count and maximum in C3a concentration was reached considerably later during CU-dialysis. Three patients were devoid of pronounced early leukocyte response but presented with the late overshoot during CU-dialysis. Three other patients reacted with an early drop in leukocyte count and a rapid increase in C3a generation during PA treatments but not during HE treatments. Three other patients reacted vice versa. A particular mode of dialysis treatment may thus be biocompatible for some patients but not necessarily for all. In the case biocompatibility is desired the individual response to the particular dialysis mode needs to be identified. The underlying mechanisms warrant further studies.

Morphological, biochemical, and molecular changes in endothelial cells after alpha-particle irradiation

The response of cultured bovine aortic endothelial (BAE) cells after exposure to alpha-particle radiation from chelated 212Bi has been evaluated. The results suggest that even relatively high doses of alpha-particle radiation from 212Bi (20-72 Gy) cause only minor acute changes in the morphology of BAE cells (light and electron microscopy) under conditions of confluent monolayer growth. Significant morphological changes can be detected in cells that detach from the monolayer, though it is unclear whether these changes represent a genuine response to irradiation or reflect the causes or effects of monolayer detachment with the consequent loss of intercellular biochemical communication. After alpha-particle irradiation (20-40 Gy) angiotensin-converting-enzyme activity was not detectable in the monolayer culture medium but was significantly decreased within the cell monolayer. Neutral-elution-assay data demonstrated that DNA double-strand-break (DSB) damage occurred in these cells and that about 35% of the DSBs were repairable.

Basic features of class-I alcohol dehydrogenase: variable and constant segments coordinated by inter-class and intra-class variability. Conclusions from characterization of the alligator enzyme

The enzymatic and structural properties of alligator liver alcohol dehydrogenase have been determined. Aliphatic and alicyclic alcohols serve as substrates for this first reptilian form of the enzyme characterized, with Km values decreasing rapidly from methanol to hexanol, as for the human class I enzymes, and a Km of 1.2 mM for ethanol at pH 9.9. The N-terminus of the 374-residue protein chain is acetyl-blocked. The enzyme is related in descending order to class I > III > V > II of the structurally characterized mammalian alcohol dehydrogenases. This observation is compatible with the presence of a I/III ancestral line. Differences of the enzyme classes exceed those of the species, suggesting an early origin of the classes. Within its enzyme class, the reptilian protein is most closely related to the avian form (82% residue identities), and is closer to the human than to the amphibian form (76%, versus 69%, respectively). This establishes class I alcohol dehydrogenase as an enzyme having fairly constant rate of change during much of vertebrate evolution, approximately 10% residue differences/100 million years of separation between pairs compared. Residues interacting with the substrate and coenzyme are largely conserved. In the alligator enzyme, there are only four replacements in the substrate pocket compared with the human class I gamma subunit, and those are not known to have functional roles. These properties account for the kinetic parameters, and suggest distinct metabolic functions for the class I enzyme in vertebrates. Comparisons of the enzymes of the different vertebrate lines reveal that segment patterns are characteristic features of the class I enzymes. Three segments are 'variable', while two are 'constant', and both these types of segment are identical with those of the classes. There is extensive variability in close proximity to the active site of the enzyme and this appears to constitute a fundamental property of class I liver alcohol dehydrogenases in general.

The influence of predegeneration on regeneration through peripheral nerve grafts in the rat

Nerve regeneration through predegenerated (PNG) or fresh (FNG) autografts in either fresh or delayed recipient nerve beds were studied in the rat sciatic nerve. Grafts 10 mm in length were excised either immediately or following a 7-day period of predegeneration. They were sutured into gaps on the contralateral side which were either freshly made or had been made 7 days previously. The early recovery (10 days at 2-day intervals) was evaluated by the sensory pinch test to measure the rate of regeneration and the delay period. The PNG group had an improvement in axonal regeneration as evidenced by a reduced delay period, a reduced number of regeneration failures, and less variability in regeneration distances compared to the FNG group. Conditioning the host site blocked some of the delay reduction in the PNG group, but had no effect on regeneration rate or delay in the FNG group. The presence of axons in the graft was confirmed by immunocytochemistry for neurofilament protein and by electron microscopy. The results suggest that proliferated cells, primarily Schwann cells, promote regeneration through the suture line and graft into the distal segment.

A mathematical model for regeneration rate and initial delay following surgical repair of peripheral nerves

A mathematical model is presented by which the regeneration rate and initial delay for peripheral nerve regeneration can be calculated from sensory pinch test data following surgical repair of peripheral nerves. The model is based on the assumption that experimental variations in regeneration distances between animals is due to the initial delay period--the time period before the regenerating fibers cross the suture line whereas the rate of regeneration is constant. This model which accounts for all observed data including 'regenerating failures' showed that nerve fibers in the rat sciatic nerve repaired with a fresh nerve graft regenerated at a rate of 1.5 mm/day after an initial delay of 3.6 days.

Role of arginine 115 in fatty acid activation and formaldehyde dehydrogenase activity of human class III alcohol dehydrogenase

Modification of class III alcohol dehydrogenase (chi chi-ADH) with phenylglyoxal eliminates fatty acid activation by pentanoate and octanoate and concomitantly increases specific activity toward ethanol and 3-methylcrotyl alcohol 2-3-fold. In contrast, chemical modification decreases activity toward S-(hydroxymethyl)glutathione (FDH activity) and 12-hydroxydodecanoic acid by increasing Km, pointing to a role for arginine in binding anionic substrates. Modification with [7-14C]phenylglyoxal indicates that only one arginine residue per subunit is modified. Sequence analysis of tryptic peptides indicates that Arg-115 is modified. Site-directed mutation of this residue to alanine eliminates both fatty acid activation and FDH activity, thus confirming the identity of the modified residue and its function. These results account in part for the unique specificity of chi chi-ADH relative to other human ADH isozymes.

Beta 2-microglobulin generation and removal in long slow and short fast hemodialysis

We studied the influence of different modes of hemodialysis (HD) on plasma levels of beta 2-microglobulin (P-beta 2-m) and its correlation to changes in leukocyte count, complement activation (C3a), and elastase generation. The influence of dialyzer membrane, membrane surface area, duration of treatment, and blood flow was analyzed with respect to post-HD levels of P-beta 2-m. Twenty patients underwent 12 modes of bicarbonate hemodialysis in random order (n = 252) using three different membranes (Cuprophan [CU], hemophan [HE], or polyamide [PA], two dialyzer areas, and fast (400 mL/min) or slow (200 mL/min) blood flow (Qb) for 2 or 4 hours, respectively. All dialysate was collected and beta 2-m was analyzed (D-beta 2-m). After correction for hemoconcentration, P-beta 2-m concentrations were found to have decreased significantly during treatment with all three membranes (CU, 0.9 +/- 0.3 mg/L, P = 0.002; HE, 1.2 +/- 0.3 mg/L, P < 0.001; and PA, 8.3 +/- 0.3 mg/L, P < 0.001). Elimination of P-beta 2-m was influenced by type of membrane (P < 0.001) and ultrafiltration volume (P = 0.0019) but not by membrane area or Qb. The largest reduction in P-beta 2-m (-10.4 mg/L) was achieved by the following treatment combination: PA membrane, large dialyzer area, and low Qb for 4 hours. P-beta 2-m decreased more during PA dialysis at low Qb for 4 hours (-9.9 +/- 0.5 mg/L) than during high Qb for 2 hours (-6.8 +/- 0.5 mg/L, P < 0.001).(ABSTRACT TRUNCATED AT 250 WORDS)

Mutation of Arg-115 of human class III alcohol dehydrogenase: a binding site required for formaldehyde dehydrogenase activity and fatty acid activation

The origin of the fatty acid activation and formaldehyde dehydrogenase activity that distinguishes human class III alcohol dehydrogenase (alcohol:NAD+ oxidoreductase, EC 1.1.1.1) from all other alcohol dehydrogenases has been examined by site-directed mutagenesis of its Arg-115 residue. The Ala- and Asp-115 mutant proteins were expressed in Escherichia coli and purified by affinity chromatography and ion-exchange HPLC. The activities of the recombinant native and mutant enzymes toward ethanol are essentially identical, but mutagenesis greatly decreases the kcat/Km values for glutathione-dependent formaldehyde oxidation. The catalytic efficiency for the Asp variant is < 0.1% that of the unmutated enzyme, due to both a higher Km and a lower kcat value. As with the native enzyme, neither mutant can oxidize methanol, be saturated by ethanol, or be inhibited by 4-methylpyrazole; i.e., they retain these class III characteristics. In contrast, however, their activation by fatty acids, another characteristic unique to class III alcohol dehydrogenase, is markedly attenuated. The Ala mutant is activated only slightly, but the Asp mutant is not activated at all. The results strongly indicate that Arg-115 in class III alcohol dehydrogenase is a component of the binding site for activating fatty acids and is critical for the binding of S-hydroxymethylglutathione in glutathione-dependent formaldehyde dehydrogenase activity.

A synthetic peptide encompassing the binding site of the second zinc atom (the 'structural' zinc) of alcohol dehydrogenase

A 23-residue peptide was synthesized that incorporates the loop which binds the structural zinc atom of mammalian alcohol dehydrogenases and contributes, in part, to subunit interactions in the native enzyme. Neither the amino acid composition nor the sequence of the peptide resemble those of zinc fingers. The reduced peptide stoichiometrically binds zinc or cobalt to form stable complexes with a dissociation constant of the peptide/CO2+ complex of 2.1 microM at pH 7.5. EDTA disrupts the complex. The absorption and magnetic circular dichroic spectra of the cobalt-peptide are indicative of a tetrahedral coordination geometry, and are similar to those of the cobalt-substituted structural site of horse and human (beta 1 beta 1) liver alcohol dehydrogenases. Consequently, the synthetic peptide can serve as a model for the metal-binding segment of alcohol dehydrogenase and for studies of fundamental problems concerning protein/metal interactions.

Purification, characterization, and partial sequence of the glutathione-dependent formaldehyde dehydrogenase from Escherichia coli: a class III alcohol dehydrogenase

The glutathione-dependent formaldehyde dehydrogenase from Escherichia coli has been purified to homogeneity and characterized. It is a 83,000-kDa homodimer containing 4 g-atom of zinc per dimer with a specific activity of 60 units/mg toward S-(hydroxymethyl)glutathione and NAD+ as substrates. Its isoelectric point, 4.4, is consistent with both its amino acid composition and chromatographic behavior on DEAE HPLC. The N-terminus is unblocked, and 47 residues from the N-terminus were sequenced. A computer search of the Swiss-Prot protein sequence data bank shows that the N-terminal sequence, [sequence; see text], is homologous with the mammalian class III alcohol dehydrogenases with 27 identities when compared to the human enzyme. Like the human, rat, and rabbit enzymes, it has high formaldehyde dehydrogenase activity in the presence of glutathione and catalyzes the oxidation of normal alcohols (ethanol, octanol, 12-hydroxydodecanoate) in a reaction that is not GSH-dependent. In addition, hemithiolacetals other than those formed from GSH, including omega-thiol fatty acids, also are substrates. The wide distribution and high degree of similarity of this enzyme to the plant and animal alcohol dehydrogenases suggest that the E. coli enzyme is closely related to the ancestor of the plant and animal dimeric zinc alcohol dehydrogenases.

Determination of human serum alcohol dehydrogenase using isozyme-specific fluorescent substrates

Both class I and class II alcohol dehydrogenase (ADH) activities are present in human serum. The contribution of each class can be measured using two class-specific, fluorogenic substrates, 4-methoxy-1-naphthaldehyde and 6-methoxy-2-naphthaldehyde. The former is highly selective for class I isozymes, especially those containing alpha or gamma subunits, whereas class II (pi) ADH preferentially reduces the latter. Selective inhibition of class I ADH by 4-methylpyrazole further increases the specificity. Specificity, accuracy, and precision of the assay for serum measurements have been determined. The activity of class I ADH in normal human serum is below the limit of detection of this method, i.e., less than 1.0 nM/min. The activity of class II ADH in normal individuals is 15 +/- 5 nM/min. In some patients values as high as 2100 nM/min are observed for class I, but in all instances, the amount of class II found was higher than that of class I ADH.

Adherence of blood cells to dialyzer membranes as a measure of biocompatibility

Cell adherence to plate dialyzer membranes was analyzed at the end of 4 hours of dialysis. Three types of membranes were examined: Cuprophan Hemophan and Gambrane, (a polycarbonate membrane). The membranes were mounted in dialyzers that contained 23 layers of one membrane type and one layer of each of the two other. Less leukocytes adhered to the Pc than to the Cu and He membranes. Transient initial complement activation during dialysis, which was considerably lower with dialysers containing mainly Pc membrane, was not correlated to adherence of cells to the membranes. Instead flow geometry is proposed as the main factor determining the adherence. Contrary to what has been earlier suggested, we think that leukocyte adherence is not a very suitable measure of membrane biocompatibility. The reason is that the influence of membrane surface-chemical factors can not be separated from mechanical factors due to the design of the device.

Human liver class III alcohol and glutathione dependent formaldehyde dehydrogenase are the same enzyme

Human liver class III alcohol dehydrogenase (chi chi-ADH) and glutathione dependent formaldehyde dehydrogenase are the same enzyme. The enzyme, chi chi-ADH, exhibits a kcat of 200 min-1 and a km of 4 microM for the oxidation of formaldehyde, but only in the presence of GSH. In the absence of GSH the enzyme is essentially inactive toward formaldehyde but very active toward long chain alcohols. Thus, as in the rat (Koivusalo, M., Baumann, M., and Uotila, L. (1989) FEBS Letters 257, 105-109), the class III alcohol dehydrogenase and the GSH dependent formaldehyde dehydrogenase are identical enzymes. S-Hydroxymethyl derivatives of 8-thiooctanoate and lipoate are also very active substrates. The activity is specific for class III alcohol dehydrogenase; neither the class I and II nor the horse EE, ES, and SS isozymes oxidize hemithiolacetals. o-Phenanthroline competitively inhibits both activities and the two substrate types compete with each other.

Hydrophobic anion activation of human liver chi chi alcohol dehydrogenase

Class III alcohol dehydrogenase (chi chi-ADH) from human liver binds both ethanol and acetaldehyde so poorly that their Km values cannot be determined, even at ethanol concentrations up to 3 M. However, long-chain carboxylates, e.g., pentanoate, octanoate, deoxycholate, and other anions, substantially enhance the binding of ethanol and other substrates and hence the activity of class III ADH up to 30-fold. Thus, in the presence of 1 mM octanoate, ethanol displays Michaelis-Menten kinetics. The degree of activation depends on the size both of the substrate and of the activator; generally, longer, negatively charged activators result in greater activation. At pH 10, the activator binds to the E-NAD+ form of the enzyme to potentiate substrate binding. Pentanoate activates methylcrotyl alcohol oxidation and methylcrotyl aldehyde reduction 14- and 30-fold, respectively. Such enhancements of both oxidation and reduction are specific for class III ADH; neither class I nor class II shows this effect. The implications as to the nature of the physiological substrate(s) of class III ADH are discussed in light of the recent finding that this ADH and glutathione-dependent formaldehyde dehydrogenase are identical. A new rapid purification procedure for chi chi-ADH is presented.

Oxidation and reduction of 4-hydroxyalkenals catalyzed by isozymes of human alcohol dehydrogenase

4-Hydroxyalkenals, natural cytotoxic products of lipid peroxidation, are substrates for human alcohol dehydrogenases (ADH). Class I and II ADHs reduce aliphatic 4-hydroxyalkenals with chain lengths of from 5 to 15 carbons at pH 7 with kcat and Km values comparable to simple aliphatic aldehydes of the same chain length. Class II is particularly effective in the reduction with kcat values as high as 3300 min-1 for 4-hydroxyundecenal. Class III ADH is essentially inactive toward all of these substrates. The class I and II isozymes also catalyze the oxidation of the 4-hydroxy group at pH 10. However, during the reaction, an NAD(+)-dependent irreversible partial inactivation of the alpha beta 1 isozyme is observed which is attributed, with the aid of computer graphics modeling, to selective modification of the alpha subunit. Both ethanol and 1,10-phenanthroline, known to compete with conventional substrates, instantaneously, reversibly, and competitively inhibit 4-hydroxyalkenal reduction and oxidation, indicating that 4-hydroxyalkenals bind at the same site as do conventional substates. The fact that the class II enzyme pi pi-ADH so far is found only in the liver and that the 4-hydroxyalkenals are the best substrates known for this isozyme suggest that it may play a significant role in cellular defenses in the conversion of the cytotoxic aldehydes to the less reactive alcohols.

Percutaneous nephrolithotomy through an intercostal approach

During a 5-year period percutaneous nephrolithotripsy through an intercostal space was performed in 56 of 231 procedures. Minimal thoracic complications were seen in 3 of 53 patients with 11th intercostal space tracts into a lower, middle, or upper pole calyx. A working sheath and a pyelostomy drainage catheter were used in all these cases. Hydro- and pneumothorax requiring treatment occurred in 2 of 3 patients with a 10th intercostal space approach into an upper pole calyx combined with improper use of the working sheath and/or the pyelostomy catheter. Review of the literature also indicates that an intercostal approach appears safe when performed via the 11th intercostal space into a lower or middle pole calyx. Thoracic complications occurred when punctures were made towards an upper pole calyx or above the 11th rib. The complications may be limited by identifying the posterior inferior lung border by fluoroscopy during puncture, and performing it under general anesthesia with controlled breath-holding. The use of a working sheath to seal the pleural opening during the procedure and an efficient pyelostomy drainage catheter to allow free drainage of urine and to tamponade the tract postoperatively are also recommended.

Human class III alcohol dehydrogenase/glutathione-dependent formaldehyde dehydrogenase

The class III human liver alcohol dehydrogenase, identical to glutathione-dependent formaldehyde dehydrogenase, separates electrophoretically into a major anodic form (chi 1) of known structure, and at least one minor, also anodic but a slightly faster migrating form (chi 2). The primary structure of the minor form isolated by ion-exchange chromatography has now been determined. Results reveal an amino acid sequence identical to that of the major form, suggesting that the two derive from the same translation product, with the minor form modified chemically in a manner not detectable by sequence analysis. This pattern resembles that for the classical alcohol dehydrogenase (class I). Hence, the chi 1/chi 2 multiplicity does not add further primary forms to the complex alcohol dehydrogenase system but shows the presence of modified forms also in class III.

Avian alcohol dehydrogenase: the chicken liver enzyme. Primary structure, cDNA-cloning, and relationships to other alcohol dehydrogenases

The major ethanol-active form of chicken liver alcohol dehydrogenase was characterized. The primary structure was determined by peptide analysis and, to a large part, was also deduced by cDNA analysis of a near full-length cDNA clone. The latter was detected by screening of a chicken liver cDNA library with antibodies raised against the purified dehydrogenase. The structure shows that the avian enzyme exhibits characteristics of the complex mammalian alcohol dehydrogenase system, tracing its origin and divergence, and allowing functional correlations. The chicken protein analyzed proves to be a class I alcohol dehydrogenase, with 74% residue identity to gamma chains of the human enzyme, a Km for ethanol of 0.5 mM and a Ki for 4-methyl pyrazole of 2.5 microM. Relationships to the other two classes are non-identical; residue exchanges towards the human classes increase in the order I less than III less than II, and human/chicken differences are less than inter-class differences. Consequently, the origins of the classes are more distant than the avian/mammalian separation. They reflect duplicatory events separated in time, and the lines that lead to present-day classes I and II deviate early. Integrated with the data for the quail enzyme, the structure of the chicken protein shows that within the avian enzymes the degree of variation is comparable to that within the mammalian class I enzymes, which are more variable than the class III forms. The coenzyme-binding and substrate-binding residues of this chicken alcohol dehydrogenase are largely identical to those in the mammalian class I counterparts. However, the subunit-interacting areas are more variable and suggest some relationships of the avian enzyme with both class I and III mammalian forms. One of the residues, Gly260 (mammalian class I numbering system), previously considered characteristic of all alcohol dehydrogenases, is replaced by Gln.

Comparison of three classes of human liver alcohol dehydrogenase. Emphasis on different substrate binding pockets

Conformational models of the three characterized classes of mammalian liver alcohol dehydrogenase were constructed using computer graphics based on the known three-dimensional structure of the E subunit of the horse enzyme (class I) and the primary structures of the three human enzyme classes. This correlates the substrate-binding pockets of the class I subunits (alpha, beta and gamma in the human enzyme) with those of the class II and III subunits (pi and chi, respectively) for three enzymes that differ in substrate specificity, inhibition pattern and many other properties. The substrate-binding sites exhibit pronounced differences in both shape and properties. Comparing human class I subunits with those of class II and III subunits there are no less than 8 and 10 replacements, respectively, out of 11 residues in the substrate pocket, while in the human class I isozyme variants, only 1-3 of these 11 positions differ. A single residue, Val294, is conserved throughout. The liver alcohol dehydrogenases, with different substrate-specificity pockets, resemble the patterns of other enzyme families such as the pancreatic serine proteases. The inner part of the substrate cleft in the class II and III enzymes is smaller than in the horse class I enzyme, because both Ser48 and Phe93 are replaced by larger residues, Thr and Tyr, respectively. In class II, the residues in the substrate pocket are larger in about half of the positions. It is rich in aromatic residues, four Phe and one Tyr, making the substrate site distinctly smaller than in the class I subunits. In class III, the inner part of the substrate cleft is narrow but the outer part considerably wider and more polar than in the class I and II enzymes. In addition, Ser (or Thr) and Tyr in class II and III instead of His51 may influence proton abstraction/donation at the active site.

Fast atom bombardment mass spectrometry and chemical analysis in determinations of acyl-blocked protein structures

Peptide generation and fast atom bombardment mass spectrometry in combination with conventional chemical analysis was used to identify the blocking group and establish the N-terminal structure of six different proteins at the nanomole level. In this manner, the first terminal structures of three non-mammalian alcohol dehydrogenases were determined, demonstrating the presence of N-terminal acetylation in these piscine, amphibian, and avian enzymes. Similarly, two different yeast glucose-6-phosphate dehydrogenases and a minor variant of a human alcohol dehydrogenase were found to be acetylated. The exact end location of C-terminal structures was also established. Together, the analyses permit the definition of terminal regions and blocking groups, thus facilitating the delineation of remaining structures.