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Biomedical subjects

M Pollock

Publications and source records attributed to M Pollock.

At least 19 recordsLinked to original sources

Exercise training-induced alterations in skeletal muscle oxidative and antioxidant enzyme activity in senescent rats.

Limited data exist concerning exercise training-induced alterations in skeletal muscle oxidative and antioxidant enzyme activity in senescent animals. Therefore, the purpose of this study was twofold: 1) to examine the exercise training-induced changes in oxidative and antioxidant enzyme activity in skeletal muscle of old rats; and 2) to critically analyze the relationship between oxidative and antioxidant enzyme activities in skeletal muscle in both trained and untrained senescent rats. Female Fischer-344 rats (approximately 24-mo-old) were divided into 1) exercised trained (ET; n = 10) and 2) sedentary (S; n = 6) groups. The ET rats performed a 10-week training program of treadmill exercise (approximately 60 min, 5 days/wk). Training significantly (p less than 0.05) improved VO2max (delta 22.8%) in the ET rats above their age-matched controls. Further, the ET group had significantly elevated (p less than 0.05) activities of succinate dehydrogenase (SDH) in the soleus and red gastrocnemius (RG) muscles as well as greater (p less than 0.05) 3-hydroxyacyl-CoA dehydrogenase (HADH) activity in the RG when compared to the S group. However, training did not alter (p greater than 0.05) HADH activity within the white gastrocnemius (WG) or soleus muscles. Activity of the antioxidant enzyme, glutathione peroxidase (GPX) was higher (p less than 0.05) in the soleus and RG in ET rats when compared to the S rats; in contrast, training did not alter (p less than 0.05) GPX activity in the WG. Finally, the correlation coefficients between SDH and GPX activities (combined ET and S groups) for the RG, WG, and soleus muscles were r = .73, .17 and .36, respectively.(ABSTRACT TRUNCATED AT 250 WORDS)

3-Hydroxyacyl CoA Dehydrogenases

Sensory nerve pathology in amyotrophic lateral sclerosis.

A detailed morphometric study was performed on sural nerve biopsies to determine the consistency of sensory nerve pathology in amyotrophic lateral sclerosis (ALS) and to seek a correlation between the severity of peripheral nerve pathology and disease duration. Nerve biopsies from patients with ALS consistently showed evidence of early axonal atrophy, increased remyelination and a shift in the diameter distributions curve towards smaller fiber diameters. Importantly, the severity of sensory nerve pathology in ALS patients correlated with disease duration. The peripheral nerve sodium pump concentration of patients was not reduced. It is concluded that an ingravescent dorsal root ganglion neuronopathy is seen in the incipient stages of ALS, preferentially affecting the largest neurons and resulting in turn in progressive axonal atrophy, secondary demyelination-remyelination and finally in nerve fiber degeneration. Etiologically, a parallel involvement of motor and sensory neurons suggests a more widespread metabolic disturbance in ALS than simply "sick" motor neurons.

Adult

An intragenic suppressor of a calmodulin mutation in Paramecium: genetic and biochemical characterization.

We describe a suppressor of the calmodulin mutant cam1 in Paramecium tetraurelia. The cam1 mutant, which has a SER----PHE change at residue 101 of the third calcium-binding domain, inhibits the activity of the Ca(2+)-dependent K+ current and causes exaggerated behavioral responses to most stimuli. An enrichment scheme, based on an increased sensitivity to Ba2+ in cam1 cells, was used to isolate suppressors. One such suppressor, designated cam101, restores both the activity of the Ca(2+)-dependent K+ current and behavioral responses of the cells. We show that the cam101 mutant is an intragenic suppressor of cam1, based on genetic and microinjection data. The cam101 calmodulin is shown to be similar to wild-type calmodulin in terms of its ability to stimulate calmodulin-dependent phosphodiesterase at low concentrations of free calcium. However, the cam101 calmodulin has a reduced affinity for a monoclonal antibody to wild-type Paramecium calmodulin, as does the parental cam1 calmodulin, and a different mobility on acid-urea gels relative to both wild-type and cam1 calmodulin. We have been able to demonstrate that the isolation of intragenic suppressors of a calmodulin mutation is possible, which allows for the further genetic analysis of structure-function relationships in the calmodulin molecule.

Animals

Benign hereditary cerebellar ataxia with extensive thermoanalgesia.

A New Zealand family with 3 members affected by late onset hereditary cerebellar ataxia is reported, distinguished by the development of near global thermoanalgesia. Because proprioception and autonomic function were preserved, and ataxia only slowly worsened, this proved to be a benign syndrome. The pattern of sensory loss indicated a 'length-dependent' neuropathy. Evaluation of sural nerve biopsy revealed a marked loss of axons, especially of those with diameters 1-7 microns and 0.2-1.5 microns. It therefore seemed likely that impairment of pain and temperature in the syndrome resulted from a loss of primary sensory afferents. It is concluded that this family represents a previously unrecognized variant and that the spectrum of hereditary ataxias needs to be widened to include an associated severe but selective loss of pain and temperature sensation.

Aged

Identical twins with papilloedema and cranial nerve palsies.

Central nervous system involvement has not been reported previously as a manifestation of sarcoidosis in monozygotic twins. Twin sisters developed multiple cranial nerve palsies and papilloedema within a two month period. Clinical features and the course of their diseases were remarkably similar.

Adult

The analysis of collagen in glutaraldehyde-fixed, osmicated peripheral nerve.

Glutaraldehyde fixation and osmication of rat sciatic nerve and human sural nerve did not appreciably alter the apparent weight of collagen in nerve fasciculi as determined by hydroxyproline analysis of hydrolysed samples. The collagen content of autopsied peripheral nerve is unaltered at least up to 24 h after death. The mean endoneurial weight of collagen per fascicle in rat sciatic nerve was 123 mug (all results expressed for 1 cm length). In human sural nerve the mean weight was 57 mug and the mean fascicular volume 1.75 mm3. Human endoneurial collagen fibrils gave a unimodal distribution of diameters with a peak at 40 nm.

Animals

Peripheral nerve abnormality in multiple sclerosis.

Biopsy specimens of sural nerve from 10 patients with multiple sclerosis (MS), of whom only 1 was severely disabled, were assessed by morphometric techniques and compared to nerves from age-matched controls. The frequency of abnormal teased fibers was increased in MS nerve, with many internodes showing at least a 50% reduction in myelin thickness. Myelinated nerve fiber densities were not significantly different in MS and control nerves. Regression analysis of axonal area on number of myelin lamellae indicated a generalized reduction of myelin lamellae in this disorder. It is suggested that peripheral myelin may be involved in multiple sclerosis.

Axons

The important role of fitness determination and stress testing in predicting coronary incidence.

The question of whether there is some effect of status of cardiorespiratory fitness and exercise ECG abnormalities on occurrence of CHD other than their effect on the risk factors of serum cholesterol, blood pressure, glucose, and smoking seems to have been answered in the affirmative by this study. The relative prognostic importance of the measures considered here, the role of exercise, and the interrelationships between fitness, exercise, other risk factors, and CHD provide many interesting hypotheses for continued study. A future investigation will involve a large prospective study in which the risk function to be derived would include stress ECG and treadmill performance as predictor variables. The retrospective approach reported in this paper had certain limitations. It did, however, permit demonstration of new results because, essentially for the first time, all of the important risk factors are measured in the study population and can be evaluated simultaneously.

Adult