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Biomedical subjects

D L Montgomery

Publications and source records attributed to D L Montgomery.

At least 55 records · Page 3Linked to original sources
PubMed1992

Reliability and validity of three fitness tests for adults with mental handicaps.

To examine the reliability and validity of cardiovascular fitness tests, 10 untrained controls and 18 adults with mental handicaps (experimental group) completed five trials on each of four exercise protocols. VO2 max results (M +/- SD) averaged across trials were as follows: Maximal treadmill test, 27.2 +/- 6.2 for the experimental group (E) and 45.5 +/- 8.1 for the control group (C); Maximal shuttle run test, 19.7 +/- 3.4 (E) and 42.1 +/- 6.2 (C); Submax step test, 33.0 +/- 7.6 (E) and 44.5 +/- 7.6 (C); and Submax cycle ergometer test, 36.4 +/- 13.1 (E) and 42.0 +/- 7.1 (C). The four modes had similar VO2 max values across trials with intraclass correlations ranging from r = .90 to .97. To examine validity, the predictive tests were compared with the treadmill VO2 max test. Both the step and shuttle run tests correlated significantly with the treadmill test. The duration of the shuttle run test was unrelated to the exercise intensity. The stepping test is recommended over both the maximum shuttle run test and the submaximum cycling test when measuring the aerobic fitness of adults with mental handicaps.

Adult↗
PubMed1991

Blood lactate concentration following intermittent and continuous cycling tests of anaerobic capacity.

The purpose of this study was to compare the time and the magnitude of peak blood lactate concentration [La] following three 90-s cycle-ergometer tests. Intermittent all-out, continuous all-out, and continuous constant cycling tests were performed by 19 hockey players and 19 physical education students. Eight fingertip blood samples were drawn 1-11 min into recovery. [La] was similar between 3 min and 8 min of recovery for the three 90-s tests. [La] at the individual peak time was similar to that in samples taken at 1-4 min for the intermittent all-out test, 2-6 min for the continuous all-out test, and 2-4 min for the continuous constant cycling test. The intermittent and continuous all-out tests produced higher [La] at the individual peak time than did the continuous constant test. The intermittent all-out test produced an earlier peak [La] than the continuous tests. Both time and magnitude of peak [La] are dependent on the mode of testing.

Adult↗
PubMed1990

Ovine fetal telencephalic white matter necrosis.

Discrete foci of white matter necrosis were observed in the telencephalic white matter in 6 cases of spontaneous ovine abortion. All fetuses were in the third trimester of gestation and 2 of the 6 were term fetuses. The lesions were distributed randomly throughout the cerebrocortical white matter and consist of pale hypocellular plaques with a variable glial cell response and encrustation of necrotic cellular processes. A variety of additional lesions were present in the brains of the aborted fetuses. The lesions of telencephalic white matter necrosis have not been reported previously and are unlike those associated with known viral infections of the developing fetus. Based on the character of the lesions, a hypoxic-ischemic or hypotensive mechanism is suggested. The lesions are compared with a similar condition in human fetuses and neonates.

Abortion, Veterinary↗
PubMed1990

An on-site test battery to evaluate giant slalom skiing performance.

The purpose of this study was to determine if an on-site test battery would distinguish among three levels of giant slalom skiing ability. The test battery consisted of a 20-m shuttle run test, Wingate 60s cycling test, hexagonal obstacle test, high box test, double leg jumping test and vertical jump test. These tests were selected since previous studies have identified aerobic endurance, anaerobic endurance, power and agility as important components for Alpine skiers. Both construct validity and criterion related validity of the test battery were examined using data from 11 club skiers, 14 divisional level skiers, and 9 provincial level skiers. To establish construct validity, univariate F tests examined differences among the three levels of skiers. Significant (P less than 0.05) differences were found between the club skiers and the better skiers (divisional and provincial level) for the following test variables: peak power, mean power, and post-exercise lactate for a 60s Wingate cycle ergometer test, high box test, hexagonal obstacle test, double leg jumping test, and shuttle run test. Criterion related validity was established since there were significant correlations between giant slalom performance time and the hexagonal obstacle test (r = 0.82), high box test (r = -0.80), and double leg jumping (r = -0.86). These data illustrate that an on-site test battery can be used to distinguish among giant slalom Alpine skiers.

Adolescent↗
PubMed1989

The application of molecular biology to the development of novel vaccines.

In summary, we have shown that yeast is the preferred host for the expression of recombinant-derived hepatitis B vaccines, and that a yeast expression system which is productive, stable and scaleable can be developed for each of the three HBV envelope proteins. The versatility of regulated and integrated yeast expression systems in the production of foreign polypeptides with biomedical utility also has been highlighted. We also have shown that careful attention to the development of recombinant clones helps to optimize the entire production process leading to highly purified products which share many biochemical properties with the plasma-derived vaccine. Furthermore, immunization with PreS2 sequences is capable of protecting chimpanzees from HBV infection. The availability of PreS2 + S and PreS1 + PreS2 + S proteins expressed in yeast now provides the opportunity for establishing the relevance of such candidate vaccines in preventing human disease, thereby highlighting the utility of molecular biology in modern vaccine development.

Animals↗
PubMed1988

Physiology of ice hockey.

Ice hockey is characterized by high intensity intermittent skating, rapid changes in velocity and duration, and frequent body contact. The typical player performs for 15 to 20 minutes of a 60-minute game. Each shift lasts from 30 to 80 seconds with 4 to 5 minutes of recovery between shifts. The intensity and duration of a particular shift determines the extent of the contribution from aerobic and anaerobic energy systems. The high intensity bursts require the hockey player to develop muscle strength, power, and anaerobic endurance. The length of the game and the need to recover quickly from each shift demands a good aerobic system. Physical characteristics of elite players show that defensemen are taller and heavier than forwards probably due to positional demands. Hockey players are mesomorphic in structure. They are relatively lean since excess mass is detrimental to their skating performance. There is a large interindividual variability in VO2 during skating. Both the aerobic and anaerobic energy systems are important during a hockey game. Peak heart rates during a shift on the ice exceed 90% of HRmax with average on-ice values of about 85% of HRmax. Blood lactate is elevated above resting values confirming the anaerobic nature of the game. Glycogen depletion studies show a preferential utilisation of glycogen from the slow twitch fibres but also significant depletion from the fast twitch fibres. Elite hockey players display a muscle fibre composition similar to untrained individuals. Physiological profiles of elite hockey teams reveal the importance of aerobic endurance, anaerobic power and endurance, muscular strength and skating speed. Training studies have attempted to improve specific components of hockey fitness. Using traditional laboratory tests, a season of hockey play shows gains in anaerobic endurance but no change in aerobic endurance. On-ice tests of hockey fitness have been recommended as an essential part of the hockey player's physiological profile. Existing training procedures may develop chronic muscular fatigue in hockey players. Lactic acidosis is associated with the onset and persistence of muscle fatigue. Muscle force output remains impaired throughout the hockey player's typical cycle of practices and games. A supplementary programme of low-intensity cycling during the competitive phase of training was unsuccessful in altering VO2max. Strength decrements during the hockey season are attributed to a lack of a specifically designed strength maintenance programmes. On-ice and off-ice training programmes should focus on the elevation of aerobic endurance, anaerobic power and endurance, muscular strength and skating speed.

Biomechanical Phenomena↗
PubMed1988

Physiology of Alpine skiing.

Physiological profiles of elite Alpine skiers reveal the importance of muscular strength, anaerobic power, anaerobic endurance, aerobic endurance, coordination, agility, balance, and flexibility. On-hill snow training and dryland training programmes should focus on the elevation of these fitness components. Physical characteristics of elite skiers reveal an average height and body mass. Today, successful skiers are taller and heavier than their predecessors. Slalom skiers tend to be leaner than skiers in other events while the downhill racers are the heaviest. Elite skiers have strong legs when peak torque is measured during isometric and isokinetic conditions involving knee extension, which may be a specific adaptation since the skier is in a crouched position for a prolonged period when racing. Leg strength correlates significantly with performance in the downhill and giant slalom events. The glycolytic contribution in the slalom and giant slalom events is about 40% of the total energy cost. Following a race, blood lactate concentration averages 9 to 13 mmol/L. A muscle lactate concentration of 24 mmol/kg wet muscle tissue has been reported. Elite skiers have higher lactate values than advanced or novice skiers. The aerobic demands of competitive Alpine skiing may approach (90 to 95%) of the athlete's maximal aerobic power. Maximal heart rate is achieved during the latter part of the race. Elite skiers have a high VO2max. This may reflect their training programme and not the actual demands of the sport. When turning, muscular activity acts to impede blood flow and oxygen delivery. As a consequence, anaerobic metabolism is increased. Glycogen studies show significant utilisation from both slow and fast twitch muscle fibres. Skilled and unskilled skiers differ with respect to glycogen utilisation. Skilled skiers have greater glycogen depletion in the slow twitch fibres compared to unskilled skiers. Muscle glycogen decreases by about 32 mmol/kg wet muscle tissue following a day of ski training. Glycogen depletion may contribute to the injury pattern which peaks toward the end of the ski day. The risk of injury has been estimated at 17 injuries per 1000 skier days. When the severity criterion was an injury causing the skier to miss 3 days of skiing or visit a physician, the risk was 2 injuries per 1000 skier-days.(ABSTRACT TRUNCATED AT 400 WORDS)

Exercise↗
PubMed1988

The effects of two physical fitness programs designed for mentally retarded adults.

The purpose of this study was to design a systematic program of fitness training that enhances physical fitness of mentally retarded adults in sheltered workshops. The first phase of the study was a six-month program conducted by physical education graduate students while the second phase was four months in duration and led by workshop employees. Instructors followed a manual containing 48 lesson plans that were specifically prepared for mentally retarded participants. The physical fitness programs were evaluated using the Canadian Standardized Test of Fitness. MANOVA results revealed that both the six-month and four-month programs increased the physical fitness of the mentally retarded workers, although cardiovascular endurance improved only as a function of the four-month program.

Adult↗
PubMed1987

A mild method for the preparation of disulfide-linked hybrids of immunoglobulin light chains.

A method is described for the hybridization of immunoglobulin light chains (Bence-Jones proteins) from different patients. The interchain half-cystine residues in the light chains from one subject are converted into mixed disulfides with 2,2'-dithiodipyridine. In the Bence-Jones dimer from a second patient the interchain disulfide bond is reduced with dithiothreitol. A covalently linked hybrid molecule is produced by the reaction of the mixed disulfide with the reduced thiol. In favorable cases the mild treatment yields heterodimers which can be crystallized for X-ray diffraction studies. The procedure can also be employed for converting a monomer into a covalent dimer. The engineered dimer of one kappa chain (Jen) crystallizes in the same space group as an aggregate of monomers, but the unit cell is only one-third as large.

Bence Jones Protein↗
PubMed1987

Regulated overproduction of the GAL4 gene product greatly increases expression from galactose-inducible promoters on multi-copy expression vectors in yeast.

High-level, galactose-inducible expression originating from GAL promoters in Saccharomyces cerevisiae is mediated by highly specific interactions between the GAL4-coded protein and nucleotide sequences. The potential utility of recombinant GAL promoter/foreign gene constructions for the regulatable and high-level expression of foreign proteins in yeast is well recognized. However, the utility of this system is limited severely in the case of multiple copies of such constructions due to the very low level of the GAL4-coded protein and to the loss of inducibility which occurs if levels of the GAL4 protein are amplified constitutively. To surmount these limitations, we have constructed a novel yeast strain which overproduces the GAL4 protein in a regulated fashion. This 'integrant' strain contains an integrated copy of a hybrid gene consisting of the galactose-inducible GAL10 promoter fused to the GAL4 structural gene. In the absence of galactose, the integrant strain and the isogenic 'non-integrant' parental strain show only a basal level of transcription from the constitutively active chromosomal GAL4 gene. However, following the addition of galactose to the culture medium, the 'integrant' strain synthesizes at least 20-fold more GAL4 mRNA and substantially more GAL4 protein than the 'non-integrant' strain. A high-copy-number expression vector containing the GAL10 promoter and alpha mating factor pre-pro leader fused to the structural gene for Epstein-Barr virus gp350 was introduced into both types of cells. The resulting transformed 'integrant' cells produced approximately five-fold more gp350 mRNA and ten-fold more gp350-related proteins than the transformed 'non-integrant' cells following galactose induction. This 'integrant' strain should prove generally useful for the maximal, regulated expression in yeast of structural genes driven by a galactose-inducible promoter.

DNA, Recombinant↗
PubMed1986

Unusually high-level expression of a foreign gene (hepatitis B virus core antigen) in Saccharomyces cerevisiae.

As a model system for the study of factors affecting gene expression, hepatitis B virus core antigen (HBcAg) has been expressed in the yeast Saccharomyces cerevisiae. The singularly high levels of expression achieved are approx. 40% of the soluble yeast protein. The HBcAg polypeptides are present as 28-nm particles which are morphologically indistinguishable from HBcAg particles in human plasma and are highly immunogenic in mice. The plasmid construction employed to achieve these very high levels of expression utilizes the constitutively active yeast promoter from the GAP491 gene which is fused in a way that all non-translated sequences flanking the HBcAg coding region are yeast-derived. Hybrid constructions containing 3'-nontranslated viral DNA (yeast 5') or 5'-nontranslated viral DNA (yeast 3') as well as a construction with both 5'- and 3'-nontranslated viral DNA also have been made. A comparison of these constructions for levels of HBcAg expression indicates that the strongest contributor to the high levels of protein is the presence of 5'-flanking sequences which are yeast-derived; secondarily, a significant improvement can be achieved if the 3'-flanking sequences also are yeast-derived. The high abundance of HBcAg in the highest producer is explicable in part on the basis of the very high stability in yeast cells of HBcAg polypeptides. Analysis of the HBcAg coding sequence reveals a very low index of codon bias for S. cerevisiae, largely discounting codon usage as a contributor to the high level of protein obtained.

Genes↗
PubMed1986

Sequences required for delivery and localization of the ADP/ATP translocator to the mitochondrial inner membrane.

The ADP/ATP translocator, a transmembrane protein of the mitochondrial inner membrane, is coded in Saccharomyces cerevisiae by the nuclear gene PET9. DNA sequence analysis of the PET9 gene showed that it encoded a protein of 309 amino acids which exhibited a high degree of homology with mitochondrial translocator proteins from other sources. This mitochondrial precursor, in contrast to many others, does not contain a transient presequence which has been shown to direct the posttranslational localization of proteins in the organelle. Gene fusions between the PET9 gene and the gene encoding beta-galactosidase (lacZ) were constructed to define the location of sequences necessary for the mitochondrial delivery of the ADP/ATP translocator protein in vivo. These studies reveal that the information to target the hybrid molecule to the mitochondria is present within the first 115 residues of the protein. In addition, these studies suggest that the "import information" of the amino-terminal region of the ADP/ATP translocator precursor is twofold. In addition to providing targeting function of the precursor to the organelle, these amino-terminal sequences act to prevent membrane-anchoring sequences located between residues 78 and 98 from stopping import at the outer mitochondrial membrane. These results are discussed in light of the function of distinct protein elements at the amino terminus of mitochondrially destined precursors in both organelle delivery and correct membrane localization.

Amino Acid Sequence↗
PubMed1984

Hereditary striatonigral and cerebello-olivary degeneration of the Kerry Blue Terrier. II. Ultrastructural lesions in the caudate nucleus and cerebellar cortex.

The character and progression of ultrastructural lesions in the caudate nucleus and cerebellar cortex were studied in four Kerry Blue Terriers afflicted with a hereditary neurodegenerative disease. In the caudate nucleus, the initial lesion was mitochondrial hypertrophy in dendrites of intrinsic neurons. Degeneration of these neurons became widespread while axons of passage and terminal boutons were spared. During the final stages, there was severe disruption of the neuropil with loss of both neurons and glia. A narrow zone bordering the lateral ventricles, however, remained unaffected. In the cerebellar cortex, the lesions involved principally Purkinje cells and progressed through a pattern of degeneration comparable to that involving intrinsic neurons of the caudate nucleus. In the later stages, there was astroglial scarring of the molecular layer. In contrast to the caudate nucleus, there was no disruption of the neuropil with loss of structure in the cerebellum. The fact that progression of lesions during the early stages of the disease in both the caudate nucleus and cerebellar cortex was similar suggested a common mechanism for the neurodegeneration .

Animals↗
PubMed1984

Glucose represses transcription of Saccharomyces cerevisiae nuclear genes that encode mitochondrial components.

By Northern blot hybridization analysis, we demonstrated that the steady-state levels of mRNAs specifying the alpha subunit of ATPase, the beta subunit of ATPase, and the ATP/ADP translocator are all reduced in cells grown in glucose-rich medium. The extent to which glucose represses the levels of alpha, beta, and translocator mRNAs varies from strain to strain, from 2.5- to 7-fold. Furthermore, by hybridization experiments with an excess of DNA, we showed that glucose represses the rates of synthesis of these mRNAs. The kinetics of repression and depression of transcription were also studied. Finally, a mutant was characterized which appears to be defective in depression of transcription of the genes encoding the alpha and beta ATPase subunits as well as the ATP/ADP translocator.

Adenosine Triphosphatases↗
PubMed1983

Hereditary striatonigral and cerebello-olivary degeneration of the Kerry blue terrier. I. Gross and light microscopic central nervous system lesions.

The character and progression of gross and light microscopic central nervous system lesions associated with a hereditary neurodegenerative disease with juvenile onset are described in ten affected Kerry blue terriers. The central nervous system lesions were progressive and, although there was some variability, followed a relatively well-defined temporal course. Degeneration of Purkinje cells in the cerebellar cortex was evident at the onset of clinical signs (approximately 4.5 months of age). After two weeks to one month of clinical illness, retrograde transsynaptic neuronal degeneration occurred in the olivary nucleus. Degeneration of both large and small neurons in the caudate nucleus began approximately two to three months after the onset of clinical signs, and by seven to eight months of clinical illness, the caudate nucleus was reduced to numerous microcystic cavities and almost was devoid of neurons except for a narrow subependymal zone and the tail of the nucleus. Neuronal depletion in the pars reticularis of the substantia nigra, which was evident after five to seven months of clinical illness, was attributed to an anterograde transsynaptic mechanism of neuronal degeneration. The disease in the Kerry blue terrier is compared with similar neurodegenerative diseases in man. The pathogenesis may involve altered neurotransmitter systems in the cerebellar cortex and caudate nucleus.

Animals↗
PubMed1983

Brain damage in the epileptic beagle dog.

Brain lesions associated with seizures in an epilepsy-prone colony of beagle dogs were studied in 68 dogs which died as a result of the disorder. Approximately 48.5% of the dogs had a relatively specific pattern of acute brain damage on microscopic examination. In all affected areas, there was a triad of lesions consisting of perineuronal and perivascular astrocytic swelling, perineuronal basophilic incrustations, and ischemic cell change in neurons. The most common areas of involvement were the cerebral cortex, basal nuclei, claustrum, amygdala, septal nuclei, dorsal thalamic nuclei, isthmus of the pyriform lobe, and hippocampus. The cerebellum was affected only rarely. In addition, intraneuronal inclusions identical to Lafora's bodies found in myoclonus epilepsy of man were detected in thalamic nuclei of six dogs.

Animals↗