Free and polymerized tubulin in cultured bone cells and Chinese hamster ovary cells: the influence of cold and hormones

A low pH method of liposome-membrane fusion (Schneider et al., 1980, Proc. Natl. Acad. Sci. U. S. A. 77:442) was used to enrich the mitochondrial inner membrane lipid bilayer 30-700% with exogenous phospholipid and cholesterol. By varying the phospholipid-to- cholesterol ratio of the liposomes it was possible to incorporate specific amounts of cholesterol (up to 44 mol %) into the inner membrane bilayer in a controlled fashion. The membrane surface area increased proportionally to the increase in total membrane bilayer lipid. Inner membrane enriched with phospholipid only, or with phospholipid plus cholesterol up to 20 mol %, showed randomly distributed intramembrane particles (integral proteins) in the membrane plane, and the average distance between intramembrane particles increased proportionally to the amount of newly incorporated lipid. Membranes containing between 20 and 27 mol % cholesterol exhibited small clusters of intramembrane particles while cholesterol contents above 27 mol % resulted in larger aggregations of intramembrane particles. In phospholipid-enriched membranes with randomly dispersed intramembrane particles, electron transfer activities from NADH- and succinate-dehydrogenase to cytochrome c decreased proportionally to the increase in distance between the particles. In contrast, these electron- transfer activities increased with decreasing distances between intramembrane particles brought about by cholesterol incorporation. These results indicate that (a) catalytically interacting redox components in the mitochondrial inner membrane such as the dehydrogenase complexes, ubiquinone, and heme proteins are independent, laterally diffusible components; (b) the average distance between these redox components is effected by the available surface area of the membrane lipid bilayer; and (c) the distance over which redox components diffuse before collision and electron transfer mediates the rate of such transfer.     

High density lipoprotein particle size distribution in subjects with obstructive jaundice

High density lipoproteins (HDL) from 14 patients with obstructive jaundice were examined by gradient gel electrophoresis to determine the effect of obstruction on particle size distribution. HDL from 7 of these patients were fractionated by gel permeation chromatography and further characterized by electron microscopy, SDS gel electrophoresis, apolipoprotein A-I and apolipoprotein A-II immunoturbidimetry, and analysis of chemical composition. In addition, lecithin:cholesterol acyltransferase (LCAT) activity was measured and correlated with plasma apolipoprotein A-I concentration and particle size distribution. HDL were abnormal in all patients regardless of severity, cause, or duration of obstruction. The major HDL subfraction in normal subjects, HDL3a (radius 4.1-4.3 nm) was either absent or considerably diminished, and HDL2b (radius 5.3 nm) was also frequently absent. Very small particles comparable in size to normal HDL3c (radius 3.8 nm) were prominent. In patients with a bilirubin concentration greater than 250 mumol/l, normal HDL had totally disappeared and were replaced by large discoidal particles of radius 8.5 nm and small spherical particles of radius 3.6-3.7 nm. Both populations of particles were markedly depleted of cholesteryl ester and enriched in free cholesterol and phospholipid. The discoidal particles were rich in apolipoproteins E, A-I, A-II, and C, while the small spherical particles contained predominantly apolipoprotein A-I. LCAT activity was diminished in all subjects to 8-54% of normal, and was strongly positively correlated (r = 0.91 P less than 0.05) with plasma apolipoprotein A-I levels.     

The acute effect of 30 min of moderate exercise on high density lipoprotein cholesterol in untrained middle-aged men

Fifteen middle-aged, untrained (defined as no regular exercise) men (mean age 49.9 years, range 42-67) cycled on a cycle ergometer at 50 rpm for 30 min at an intensity producing 60% predicted maximum heart rate [(fc,max), where fc,max = 220 - age]. Total cholesterol (TC), high-density lipoprotein cholesterol (HDL-C), low-density lipoprotein cholesterol (LDL-C) and triglyceride (Tg) concentrations were measured from fasting fingertip capillary blood samples collected at rest, after 15 and 30 min of exercise, and at 15 min post-exercise. The mean HDL-C level increased significantly from the resting level of 0.85 mmol.l-1 to 0.97 mmol.l-1 (P < 0.05) after 15 min of exercise, increased further to 1.08 mmol.l-1 (P < 0.01) after 30 min of exercise and remained elevated at 1.07 mmol.l-1 (P < 0.01) at 15 min post-exercise. These increases represented changes above the mean resting level of 14.1%, 27.1% and 25.9% respectively. The HDL-C/LDL-C ratio increased significantly from a resting ratio of 0.20 to 0.26 after 30 min of exercise (P < 0.01) and to 0.24 at 15 min post-exercise (P < 0.05). The mean Tg level increased significantly from a resting level of 0.88 mmol.l-1 to 1.05 mmol.l-1 after 15 min, and to 1.06 mmol.l-1 after 30 min of exercise (P < 0.05 at each time). The TC/HDL-C ratio decreased significantly (P = 0.05) after 30 min of exercise and at 15 min post-exercise by 18.8% and 14%, respectively. No significant changes were observed in the levels of TC or LDL-C over time.(ABSTRACT TRUNCATED AT 250 WORDS)     

Metabolism of high density lipoproteins by the perfused rabbit liver

The role of the liver in the catabolism of high density lipoproteins (HDL) was examined in isolated perfused rabbit livers. Using 125I-labeled rabbit HDL the disappearance of labeled apolipoproteins from the perfusate was biphasic with 7% of the label removed after 20 min and a further 6% between 20 and 90 min. In contrast, with HDL labeled with [3H]cholesteryl esters 35% of label had been removed after 90 min. The effect of liver perfusion on HDL size and composition was further studied by recirculating rabbit HDL for 120 min. In control experiments HDL was incubated at 37 degrees C for 120 min with nonperfused media and with media that had been liver perfused. The added HDL was predominantly particles of 4.8-4.9-mm radius, and incubation with nonperfused and preperfused media produced no significant change in size. However, liver perfusion resulted in particles predominantly 4.2-4.3-mm radius. Hepatic perfusion also significantly reduced HDL cholesteryl ester composition as a percentage of lipoproteins mass from 13.3 +/- 2.2% in control incubations to 10.7 +/- 3.1% (p less than 0.001), and cholesteryl ester:protein mass ratio was reduced from 0.31 +/- 0.06 in control to 0.24 +/- 0.10 (p less than 0.001) after 120 min of liver perfusion. Thus interaction of rabbit HDL with rabbit liver results in smaller HDL particles significantly depleted of core cholesteryl esters.     

Histologic assessment of nerve regeneration in the rat

This study reports the degree of spontaneous regeneration that will occur in the sciatic nerve of a rat 5 months after complete resection of the nerve. In 30 animals, the sciatic nerve was excised. Histological assessment at 5 months revealed evidence of regeneration for a variable distance (mean 23.7 mm +/- 6.4 mm). Histological sections were studied at 1-cm intervals along the length of the nerve. Evidence of compartmentation with "minifascicle" formation was noted. The orientation of the nerve fibers was parallel to the long axis of the nerve. This study assessing spontaneous regeneration is meant to serve as a control for other studies evaluating the effect of factors that may influence nerve regeneration in the rat model.     

Complex maxillary fractures: role of buttress reconstruction and immediate bone grafts

Between 1978 and 1984, 558 patients with complex facial fractures have been treated. One hundred and seventy-one of these patients have had complex Le Fort fractures of the maxilla. In this group of patients, the importance of direct anatomic reconstruction of the anterior maxillary buttresses has been assessed. Complete exposure of the injured buttresses will facilitate assessment of the exact fracture pattern. Direct fixation of the medial and lateral maxillary buttresses on each side, in combination with immediate bone-graft reinforcement or replacement of comminuted or missing buttresses, will facilitate the reconstruction of even the most severely injured maxilla in one stage. This approach is combined with similar reconstructive techniques in other areas of the craniofacial skeleton. Associated mandibular fractures are managed with rigid internal fixation utilizing A-O techniques. The use of these techniques dramatically facilitates airway management and simplifies the treatment of the edentulous patient, the patient with bilateral condylar neck fractures, and those patients with sagittal splitting of the maxilla and palate. The use of both internal craniofacial suspension wires and external craniofacial suspension devices has become largely unnecessary, and reconstruction of even the most complex injuries in one stage with minimal complications and secondary deformities is made possible.     

Peptidase mutants of Salmonella typhimurium

Six peptidase activities have been distinguished electrophoretically in cell extracts of Salmonella typhimurium with the aid of a histochemical stain. The activities can also be partially separated by chromatography on diethylaminoethyl-cellulose. These peptidases show overlapping substrate specificities. Mutants (pepN) of the parent strain leu-485 lacking one of these enzymes (peptidase N) were obtained by screening for colonies that do not hydrolyze the chromogenic substrate l-alanyl-beta-naphthylamide. The absence of this broad-specificity peptidase in leu-485 pepN(-) mutants allowed the selection of mutants unable to use l-leucyl-l-alaninamide as a leucine source. These mutants (leu-485 pepN(-)pepA(-)) lack a broad-specificity peptidase (peptidase A) similar to aminopeptidase I previously described in Escherichia coli. Mutants (pepD) lacking a dipeptidase (peptidase D) have been isolated from a leu-485 pepN(-)pepA(-) parent by penicillin selection for mutants unable to use l-leucyl-l-glycine as a leucine source. Mutants (pepB) lacking a fourth peptidase (peptidase B) have been isolated from a leu-485 pepN(-)pepA(-)pepD(-) strain by penicillin selection for failure to utilize l-leucyl-l-leucine as a source of leucine. Single recombinants were obtained by transduction for each of the peptidases missing in a leu-485 pepN(-)pepA(-)pepD(-)pepB(-) strain. The growth response of these recombinants to leucine peptides shows that all of these peptidases can function in the catabolism of peptides and that they display overlapping substrate specificities in vivo.     

Clinical nerve reconstruction with a bioabsorbable polyglycolic acid tube

Microneurosurgical techniques to reconstruct nerve gaps with nerve grafts frequently fail to achieve excellent functional results and create donor-site morbidity. In the present study, 15 patients had gaps of 0.5 to 3.0 cm (mean 1.7 cm) in digital nerves reconstructed by one surgeon with a bioabsorbable polyglycolic acid (PGA) tube. A final evaluation of sensibility was done by a second surgeon at a mean postoperative interval of 22.4 months (range 11 to 32 months). These were all secondary reconstructions. The evaluation included a digital nerve block with local anesthetic for the intact (not reconstructed) digital nerve. Excellent functional sensation (moving two-point discrimination less than or equal to 3 mm and/or static two-point discrimination less than or equal to 6 mm) was present in 33 percent and good functional sensation (moving two-point discrimination of 4 to 7 mm and/or static two-point discrimination of 7 to 15 mm) in 53 percent of the digital nerve reconstructions. One patient with poor sensory recovery and one with no recovery were judged as functional failures (14 percent). Absence of pain at the site of reconstruction was judged by the patient to be excellent in 40 percent, good in 33 percent, and poor in 27 percent. We conclude that reconstruction of nerve gaps of up to 3.0 cm with a bioabsorbable PGA tube gives clinical results at least comparable to the classic nerve graft technique while avoiding donor-site morbidity.     

Resistance and aerobic training in older men: effects on VO2 peak and the capillary supply to skeletal muscle

Hepple, R. T., S. L. M. Mackinnon, J. M. Goodman, S. G. Thomas, and M. J. Plyley. Resistance and aerobic training in oldermen: effects onO_{2 peak} and thecapillary supply to skeletal muscle. J. Appl.Physiol. 82(4): 1305-1310, 1997.Both aerobic training (AT) and resistance training (RT) may increase aerobic power(O_{2 peak}) in theolder population; however, the role of changes in the capillary supplyin this response has not been evaluated. Twenty healthymen (age 65-74 yr) engaged in either 9 wk of lower body RTfollowed by 9 wk of AT on a cycle ergometer (RTAT group) or 18 wk of AT on a cycle ergometer (ATAT group). RT was performedthree times per week and consisted of three sets of four exercises at6-12 repetitions maximum. AT was performed threetimes per week for 30 min at 60-70% heart ratereserve. O_{2 peak} was increasedafter both RT and AT (P < 0.05).Biopsies (vastus lateralis) revealed that the number of capillaries per fiber perimeter length was increased after both AT and RT(P < 0.05), paralleling the changesin O_{2 peak}, whereascapillary density was increased only after AT(P < 0.01). These results, and thefinding of a significant correlation between the change in capillarysupply and O_{2 peak}(r = 0.52), suggest the possibility that similar mechanisms may be involved in the increase ofO_{2 peak} afterhigh-intensity RT and AT in the older population.