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Biomedical subjects

P W Mayer

Publications and source records attributed to P W Mayer.

6 recordsLinked to original sources
PubMed1985

Somatomedin synthesis by a subclone of Buffalo rat liver cells. Influence of divalent cations on rIGF-II release.

Previous studies have provided evidence that biosynthesis and secretion of somatomedin (SM) is not only hormone dependent, but also modulated by nutritional factors. Little is known, however, about the role of divalent cations in these processes. A subclone of Buffalo rat liver (BRL) cells, known to secrete rat insulin-like growth factor-II (rIGF-II) into serum-free medium, was used to define the influence of Ca2+, Mg2+ and Zn2+ on this function. The secretion of rIGF-II by subclone BRL-3SC appears to be quite stable in minimal essential medium (MEM) over a wide range in Ca2+ concentrations (0.18-3.0 mM) but is reduced to only 8% of controls in the absence of Ca2+ (P less than 0.01). Reducing, and even eliminating, the extracellular concentration of Mg2+ alone caused no change in basal rIGF-II release, while simultaneously decreasing Mg2+ and Ca2+ results in a marked drop in the secretion of this SM, reaching a nadir of 38% of controls in the absence of Mg2+ (P less than 0.001). A Mg2+ concentration of 10 mM, or 25 times 'normal', did not alter the basal secretion of rIGF-II. Eliminating the trace amount (0.8 nM) of Zn2+ in MEM by chelation with EDTA decreased rIGF-II secretion to 62% of control levels (P less than 0.01), while increasing the concentration of this cation to 3 mM did not alter the basal release of this SM. Decreased rIGF-II release in the presence of EGTA and EDTA is not due to irreversible cell damage since the secretion of this SM was restored to normal during subsequent reincubation in MEM alone.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1983

Somatomedin synthesis by a subclone of Buffalo rat liver cells: characterization and evidence for immediate secretion of de novo synthesized hormone.

Previous studies have reported that cultured Buffalo rat liver (BRL-3A) cells synthesize and release a somatomedin called multiplication-stimulating activity, a major component of which is rat insulin-like growth factor-II (rIGF-II). We have isolated a subclone of hepatocytes (BRL-3SC) from these cells, which release rIGF-II into serum-free medium at a similar but considerably more uniform rate than BRL-3A cells, and have described their morphology and defined some of the conditions regulating the rate of synthesis and secretion of rIGF-II. Time-course experiments indicate that after a 2-h lag, rIGF-II is released at a nearly constant rate of 70 microU insulin-like activity/ml . 24 h for 5 days. These cells demonstrate considerable resistance to variations in environmental pH, with extremes of pH 6.8-8.0 in the initial culture medium causing a negligible effect on rIGF-II release. We found no evidence for the existence of an appreciable amount of intracellular rIGF-II, consistent with the lack of secretion granules in these cells. Moreover, at concentrations not causing irreversible cell damage, inhibitors of protein synthesis, cycloheximide and actinomycin D, produced 87% and 76% reductions, respectively, in rIGF-II release in 24 h, and inhibitors of oxidative phosphorylation, dinitrophenol and sodium azide, reduced rIGF-II release by 72% and 78%, respectively. We conclude from these studies that BRL-3A cells, and particularly those of the subclone BRL-3SC herein described, may provide an excellent model for investigations of somatomedin synthesis and release and that such studies are facilitated by the fact that rIGF-II released into serum-free medium appears to be the immediate product of de novo peptide synthesis.

Animals↗
PubMedDate not supplied

Neck motion in the high school football player. Observations and suggestions for diminishing stresses on the neck.

In a group of 40 high school athletes (height: 166.37 to 189.57 cm, average, 174.40 cm; neck circumference: 35.56 to 41.91 cm, average, 39.12 cm), the neck motions were studied in flexion and extension, clinically, radiographically, and cineoradiographically. Flexion ranged from 34 to 84 degrees (average 72 degrees) and extension from 21 to 64 degrees (average 45 degrees) without helmet and shoulder pads. In well-fitting equipment flexion ranged from 36 to 86 degrees (average 73 degrees) and extension from 12 to 56 degrees(average 34 degrees). No correlation was determined between the size of the athlete's neck and the range of motion. The size of the athlete's neck was important in the determination of maximum stresses in the neck. The helmets impinged on the shoulder pads or interscapular region; this impingement diminished tension on the anterior portion of the cervical spine in extension. The face masks impinged on the shoulder pads in flexion of the neck; this impingement diminished stress on the posterior musculature. Proper fitting equipment, conditioning neck exercises, and changes in the rules of the game so that abuse of the head and neck is not encouraged are some of the aspects that may reduce the risk of injury to the cervical region in football players.

Adolescent↗
PubMedDate not supplied

Nonunion treatment with pulsed electromagnetic fields.

Noninvasive, pulsed electromagnetic field treatment, when properly employed, was effective in securing healing of ununited fractures in 64.4% of 149 patients. The effectiveness of this modality can be ascertained after three months of intensive use in more than 85% of patients, thus enabling the clinician to decide to terminate treatment, continue electrostimulation, or abandon it in favor of another treatment modality. The success of treatment is dependent upon certain variables. Anatomic location of the nonunion is important. Higher healing rates were noted in the tibia than in the femur or humerus. In some conditions, combined electrostimulation and bone grafting was more effective than either measure alone. Young patients healed more rapidly than older patients. Electrostimulation is more effective when instituted within two years of the original fracture than when started at longer intervals after the injury. Infection, either quiescent or actively draining, does not seem to affect the overall results. Of greatest importance is patient adherence to the treatment protocol as outlined, with emphasis placed on adequate immobilization of the fracture and absolute nonweight-bearing during treatment. Considering these factors and in light of the very rare frequency of short-term side effects, the use of pulsed electromagnetic fields appears to be a reasonable choice of treatment in the management of ununited fractures.

Adolescent↗