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Biomedical subjects

J Wolff

Publications and source records attributed to J Wolff.

At least 163 records · Page 9Linked to original sources
PubMed1986

Proteolysis of tubulin and the substructure of the tubulin dimer.

The alpha and beta subunits of tubulin each have a single highly reactive site for a variety of proteases that divides each subunit into two unequal regions. The position of cleavage is not the same for alpha and beta, since alpha is consistently cleaved into about 38- and 14-kDa pieces, while beta is cleaved into about 34- and 21-kDa pieces. The larger fragment is amino-terminal in both subunits as shown: by size reduction of the smaller fragment by subtilisin (which cleaves at the extreme carboxyl-terminal end), but no change in size of the larger fragment; by the charge/mass ratios of the proteolytic fragments; and by sequence analysis which locates trypsin cleavage after residue 339 (alpha) and chymotrypsin cleavage after residue 281 (beta). Since this cleavage pattern of the alpha and beta subunits is found for very different proteases, we suggest that it is determined by structural features of the tubulin molecule. The two pieces of each subunit remain associated following cleavage. While both cleavage sites are exposed in the free dimer, assembly of dimers into microtubules or sheets protects the internal site against cleavage. By contrast, the carboxyl-terminal subtilisin-sensitive sites remain exposed. Based on these results we propose a model for the substructure of the tubulin dimer that accommodates internal cleavage in the dimer but not the polymer, access to the COOH termini in both forms, and the orientation of the dimer in the polymer.

Animals↗
PubMed1986

B ring regulation of colchicine binding kinetics and fluorescence.

Several properties of the colchicine-tubulin interaction such as association rate, reversibility, and the promotion of drug fluorescence have been related to the B ring of colchicine. The B ring itself retards the binding rate, and substitution at C-7 leads to further binding rate decreases that appear to be related to both substituent bulk and the presence of a N-acyl group. Thus, the decreasing order of binding rates is 2-methoxy-5-(2',3',4'-trimethoxyphenyl)tropone greater than deacetamidocolchicine greater than deacetylcolchicine greater than or equal to colcemid greater than colchicine greater than N-benzoyldeacetylcolchicine, etc. The apparent irreversibility of the binding seems more closely related to the presence of an N-acyl group rather than the bulk of the substituent at C-7. Substitution at C-7 also affects the tropolone fluorophore. Thus, amines (deacetylcholchicine, colcemid, or N-methylcolcemid) fluoresce poorly in the presence of tubulin, whereas substitution of the amino group with an acyl group enhances fluorescence. The presence of an N-acyl group at C-7 is essential for enhanced fluorescence. We conclude that, in addition to A- and the C-ring portion of the molecule, the B ring of colchicine is a third determinant recognized by the binding site on tubulin.

Animals↗
PubMed1986

Epidural buprenorphine for postoperative analgesia. A controlled comparison with epidural morphine.

In a double-blind controlled study, epidural buprenorphine 0.3 mg was compared with 4 mg of epidural morphine for postoperative pain relief the first 24 hours after major orthopaedic surgery. The degree of analgesia was equal and satisfactory in both groups. Duration of action was 620 minutes with buprenorphine and 580 minutes with morphine, which was not significantly different. The only serious side effects were recorded in the morphine group, with two patients complaining of pruritus and five of urinary retention. In conclusion, epidural buprenorphine did not offer any advantages in preference to morphine for postoperative pain relief following orthopaedic surgery.

Adolescent↗
PubMed1986

Ro 15-1788 for postoperative recovery. A randomised clinical trial in patients undergoing minor surgical procedures under midazolam anaesthesia.

In a double-blind randomised study, 100 women who underwent induced abortion under midazolam anaesthesia were given the benzodiazepine antagonist Ro 15-1788 or placebo after termination of anaesthesia. Recovery was assessed by means of a modified Steward coma scale. Following incremental doses of Ro 15-1788, 56% of the patients were fully awake within 3 minutes and 92% after 5 minutes, which was significant compared to the placebo group. The median duration of amnesia was 91 minutes after Ro 15-1788 compared to 121 minutes in the placebo group (p less than 0.001). The median dose of Ro 15-1788 was 0.4 mg. A slight positive correlation between total dose of Ro 15-1788 and total amount of midazolam was found. Nausea and/or vomiting were found to be more frequent in the Ro 15-1788 group, but otherwise we found no differences between groups with regard to either side effects or cardiorespiratory function. Ro 15-1788 is evidently an effective antagonist to the sedation induced by midazolam.

Abortion, Induced↗
PubMed1986

[Results of functional aftercare following surgically treated ruptures of the outer ligaments. A comparative study of aftercare by a lower leg walking cast or the Dr. Spring special shoe].

There is no doubt that primary suturing of the ruptured ankle ligament gives the best results regarding joint stability. However, there are differing views concerning the follow-up treatment. In particular, there are controversial opinions about the value of a special shoe by Dr. Spring during the rehabilitation phase. During the period April 1984 to July 1985 100 patients with rupture of the fibular ligament were treated operatively, 50 of whom were treated post-operatively with 14-day lying plaster of Paris followed by a further 14 days with the special shoe from Dr. Spring and 50 with a lower leg walking plaster of Paris. The results were compared over a period of 8 weeks, using objective criteria. The subjective impressions followed after at least 6 months. After 8 weeks the mobility of the joint in dorsalflexion and pronation is similar in both groups; in plantar flexion and supination better mobility was seen after the plaster of Paris treatment. There was no significant difference in the duration of unfitness for work. Subjectively, there was a reduced tendency to swelling after the plaster of Paris treatment.

Adolescent↗
PubMed1986

Effects of acetate and bicarbonate dialysis on cardiac performance, transmural myocardial perfusion and acid-base balance.

The effects of acetate and bicarbonate dialysis on cardiac performance, myocardial oxygen balance and acid-base balance were evaluated in 7 patients with end-stage renal failure. During acetate dialysis cardiac output increased and was significantly higher than during bicarbonate dialysis (p less than 0.05). Systemic vascular resistance was significantly lower during acetate than during bicarbonate dialysis (p less than 0.05). The myocardial oxygen balance estimated from the supply/demand ratio (DPTI/SPTI) was significantly reduced after acetate dialysis and significantly lower than during bicarbonate dialysis (p less than 0.05). After 90 min acetate dialysis DPTI/SPTI dropped to its lowest value as a result of an excess of myocardial oxygen demand (SPTI) over myocardial oxygen supply (DPTI), signifying transient hypoperfusion of the subendocardium which did not occur during bicarbonate dialysis. Acidosis was more adequately corrected with bicarbonate dialysis, and there was no change in pCO2 which was significantly higher than during acetate dialysis (p less than 0.05). During bicarbonate dialysis a stable hemodynamic circulation and well balanced acid-base values were seen. Acetate dialysis leads to improvement in left ventricular performance, but at the expense of myocardial oxygen balance, which falls to marginal safety levels in uremic patients.

Acetates↗
PubMed1985

Tubulin, hybrid dimers, and tubulin S. Stepwise charge reduction and polymerization.

Limited proteolysis of rat brain tubulin (alpha beta) by subtilisin cleaves a 1-2-kDa fragment from the carboxyl-terminal ends of both the alpha and beta subunits with a corresponding loss in negative charge of the proteins. The beta subunit is split much more rapidly (and exclusively at 5 degrees C), yielding a protein with cleaved beta and intact alpha subunit, called alpha beta s, which is of intermediate charge. Further proteolysis cleaves the carboxyl terminus of the alpha subunit leading, irreversibly, to the doubly cleaved product, named tubulin S, with a composition alpha s beta s. Both cleavage products are polymerization-competent and their polymers are resistant to 1 mM Ca2+- and 0.24 M NaCl-induced depolymerization. The two polymers differ in that the alpha beta s polymer is stable to cold, GDP, and podophyllotoxin, whereas tubulin S polymer is disassembled by these agents; moreover, alpha beta s forms ring-shaped polymers, whereas alpha s beta s forms filaments associated into bundles and sheets. Tubulin S co-polymerizes with native tubulin yielding a mixed product of intermediate stability. The presence of low mole fractions of tubulin S leads to a marked reduction in the critical concentration for polymerization of the mixture.

Animals↗
PubMed1985

Microtubule-associated adenylate cyclase.

Twice-cycled bovine brain or rat brain microtubule protein contains an adenylate cyclase activity that passes 0.2 micron filters, is activated 2-7-fold by 30 microM forskolin, shows modest stimulation by fluoride (especially in the presence of added AI3+), but is virtually insensitive to added guanine nucleotides. The activity is insensitive to various hormones or Ca2+/calmodulin. The adenylate cyclase is active with both Mg2+ and Mn2+ but activity is less in the presence of Mg2+ than with Mn2+. The cyclase is inhibited by agonists of the adenosine P site. It is proposed that the catalytic unit of adenylate cyclase and probably small quantities of the guanine nucleotide regulatory protein, Ns, are cycled along with microtubules.

Adenylyl Cyclases↗
PubMed1985

Tubulin subunit carboxyl termini determine polymerization efficiency.

Cleavage of tubulin by subtilisin removes a small (Mr less than 2000) fragment from the C-terminal end of both alpha and beta subunits. The resulting protein is much reduced in negative charge. The cleaved, less acidic protein retains its competence to polymerize in a GTP-dependent and cold-, GDP-, and podophyllotoxin-sensitive manner and assembles into sheets or bundles of twisted filaments. The critical concentration for polymerization of the cleaved protein is about 50-fold lower than that for intact tubulin. It is proposed that the C termini of the subunits normally impede polymerization.

Adenosine Diphosphate↗
PubMed1985

Intestinal obstruction due to peritoneal adhesions as a complication of peritoneal dialysis for neonatal hyperammonemia.

A male infant with ornithine transcarbamylase deficiency developed massive neonatal hyperammonemia and was treated with peritoneal dialysis. He later developed intestinal obstruction due to peritoneal bands which originated at the site of the previous peritoneal catheter. In this infant the blood concentration of ammonia could not be lowered below 1000 micrograms/dl using peritoneal dialysis, while treatment with sodium benzoate led to control within 24 h. In view of the possibility of this and other complications of peritoneal dialysis, pharmacologic therapy of neonatal hyperammonemia should be considered as an initial modality of treatment.

Ammonia↗
PubMed1985

B-lymphocyte associated differentiation antigen expression by 'non-B, non-T' acute lymphoblastic leukemia.

We investigated the neoplastic cells obtained from 37 cases of 'non-B, non-T' (SIg-E-) acute lymphoblastic leukemia (ALL) for their expression of 13 distinct monoclonal antibody defined B lymphocyte associated differentiation antigens. We correlated the expression of these B cell antigens with terminal deoxynucleotidyl transferase (TdT), HLA-DR antigen, common ALL antigen (cALLa), and cytoplasmic mu heavy chain (Cu) expression by these neoplastic cells. In this way, we were able to describe a hierarchy of B lymphocyte associated differentiation antigens as well as the marked phenotypic heterogeneity of 'non-B, non-T' ALL. TdT and HLA-DR are expressed throughout the stages of B cell differentiation represented by 'non-B, non-T' ALL. The earliest B cell antigen appears to be Leu 12 (B4) followed by BA-2 and then BL2. OKB2, BL1 and BA-1 are acquired next, followed by B1, BL3, cALLa and Cu. BL7 appears just prior to SIg. OKB1, OKB4, OKB7 and BL4 appear at or after the time of SIg expression and hence are not expressed by 'non-B, non-T' ALL cells. This developmental hierarchy is supported by the results of phorbol ester (TPA) induction studies. Thus, cases of 'non-B, non-T' ALL constitute a useful model for probing the hierarchal expression of B cell antigens and delineating the B cell developmental pathway(s).

Antibodies, Monoclonal↗
PubMed1985

Effect of tamoxifen on the receptor-positive T61 and the receptor-negative T60 human breast carcinomas grown in nude mice.

A study was made of the in vivo effect of the anti-oestrogen tamoxifen on the growth and cell cycle kinetics of the oestrogen and progesterone receptor-positive T61 human breast carcinoma and of the oestrogen and progesterone receptor-negative T60 human breast carcinoma grown in nude mice. The T61 tumour was exposed to single doses of 0.1, 1.0, 5 or 10 mg tamoxifen, resulting in serum concentrations 1 day after treatment ranging from less than 27 to 134 nM. The T60 tumour was exposed to a single dose of 1.0 mg tamoxifen. The effect on the tumour growth curves was determined according to a transformed Gompertz function, and the effect on the cell cycle distributions was estimated by flow cytometric DNA analysis on tumour tissue obtained by fine-needle aspirations at intervals after the treatment. The results showed that in the T61 tumour, tamoxifen induced a dose-related growth inhibition, whereas it had no concomitant effect on the cell cycle distribution of the tumour. The treatment had no effect on the T60 tumour. The results indicate that tamoxifen is unsuitable as a synchronizing agent in human breast tumours with responses to the drug similar to those of the T61 and T60 breast tumours.

Animals↗
PubMed1985

Effect of acetate and bicarbonate dialysis on cardiac performance and transmural myocardial perfusion in patients with renal failure.

The object of the present study was to assess the haemodynamic changes measured by impedance cardiography during acetate and bicarbonate dialysis in uraemic patients without cardiovascular diseases. It was demonstrated that the cardiac output increased significantly after 60 minutes during acetate dialysis compared with bicarbonate dialysis while the peripheral resistance decreased significantly during acetate dialysis. As estimated by the diastolic systolic pressure time index ratio myocardial perfusion fell significantly following acetate dialysis as compared to bicarbonate dialysis. It is concluded that the work of the heart increases during acetate dialysis. This involves risk of myocardial hypoperfusion. It is therefore recommended that bicarbonate dialysis is the choice for patients with unstable circulation and/or ischaemic heart disease.

Acetates↗
PubMed1984

Immobilization-dependent fluorescence of colchicine.

Colchicine fluoresces when bound to tubulin but not in water, dioxane, or benzene. The basis of the fluorescence has now been investigated. Colchicine fluoresces in higher alcohols and shows a blue shift as a function of chain length. Glycerol produces a higher fluorescence efficiency and a further blue shift. Plots of 1/fluorescence versus T/eta yield straight lines for both alcohols and glycerol/water mixtures. Fluorescence in glycerol/dimethyl sulfoxide mixtures, in which the dielectric constant remains unchanged, varies as a function of solvent viscosity. Even highly nonpolar solvents such as dioxane require a threshold viscosity for fluorescence to occur. When solvent polarity was decreased at constant viscosity, there was also an enhancement of colchicine fluorescence, but this effect appeared to be smaller than that obtained with increasing viscosity. Immobilization by covalent attachment of desacetylcolchicine to thyroglobulin, serum albumin, or lysozyme also promotes fluorescence from the drug. By contrast, the highly rigid analogue of colchicine, imerubine, fluoresces in water and is unaffected by viscosity changes. We concluded that a major contribution to colchicine fluorescence stems from immobilization of colchicine in the site and that this response to immobilization depends, in part, on the partially flexible nature of the drug. Since certain other flexible molecules such as auramine O, reduced flavines, and diarylalkanes also require increased viscosity or binding to macromolecules to fluoresce at room temperature, we propose that immobilization-enhanced fluorescence may be more common than heretofore believed.

Animals↗
PubMed1984

The use of iodine as a thyroidal blocking agent in the event of a reactor accident. Report of the Environmental Hazards Committee of the American Thyroid Association.

In the event of a nuclear reactor accident, radioactive materials could be released into the environment: radioisotopes of iodine could constitute a major component of such a release. Upon such exposure, radioiodines could enter the body and accumulate in an unprotected thyroid gland where they would remain for varying periods of time. A number of methods have been proposed to protect those at risk of exposure. Administration of thyroid-blocking agents (such as potassium iodide) to exposed populations could be effective, but their use has raised a number of questions since there are considerable gaps in the scientific information available about the possible effects of low-level radiation from radioiodine. In addition, there are only limited data available about potential toxic side effects of potassium iodide distributed widely to large, unsupervised populations. Concern about these issues led the American Thyroid Association to appoint a committee of its members with special interest and competence in these areas to review the problems in detail and develop an advisory statement on the questions at issue for those to whom this matter might be of concern.

Accidents↗
PubMed1984

The calmodulin-binding domain on microtubule-associated protein 2.

Microtubule-associated protein 2 (MAP2) binds calmodulin with a stoichiometry approaching 1-1.5 mol of calmodulin/mol of MAP2 in the presence of calcium ion. The calmodulin-binding domain(s) of MAP2 were probed by cross-linking 125I-calmodulin with partially digested MAP2, by limited digestion of the preformed 125I-calmodulin-MAP2 adduct, and by cross-linking 125I-calmodulin with the projection- and assembly-promoting portions of MAP2. Cross-linking 125I-calmodulin with partially digested MAP2 resulted in radioactive adducts of approximately 300, approximately 235, approximately 205, approximately 58, and approximately 40 kDa. The radioactive adducts with smaller molecular mass became prominent with increasing time of digestion concomitant with loss of those with higher molecular size. Limited chymotryptic digestion of preformed 125I-calmodulin-MAP2 adducts also produced a approximately 58-kDa radioactive band followed later by a approximately 40-kDa band. Brief chymotryptic digestion and subsequent centrifugation of microtubules preformed with pure tubulin and MAP2 permitted separation of microtubule-bound MAP2 fragments (molecular mass = approximately 215, approximately 180, and approximately 36 kDa) from unbound fragments (molecular mass = approximately 240, approximately 180, and approximately 140 kDa). 125I-Calmodulin cross-linked only with the microtubule-bound MAP2 fragments (forming mainly the approximately 58-kDa adduct) and not with unbound MAP2 fragments. Since the apparent molecular size of calmodulin is approximately 21 kDa on these sodium dodecyl sulfate-polyacrylamide gels, the results indicate that partial digestion of MAP2 by chymotrypsin produces a approximately 37-kDa fragment which can be further degraded to a approximately 20-kDa fragment. The approximately 37-kDa fragment that is labeled corresponds to the previously identified assembly-promoting fragment that attaches to the microtubule.

Animals↗