Biomedical subjects

I Montgomery

Publications and source records attributed to I Montgomery.

At least 19 recordsLinked to original sources

PubMed1998

Lactic acid efflux from white skeletal muscle is catalyzed by the monocarboxylate transporter isoform MCT3.

The newly cloned proton-linked monocarboxylate transporter MCT3 was shown by Western blotting and immunofluorescence confocal microscopy to be expressed in all muscle fibers. In contrast, MCT1 is expressed most abundantly in oxidative fibers but is almost totally absent in fast-twitch glycolytic fibers. Thus MCT3 appears to be the major MCT isoform responsible for efflux of glycolytically derived lactic acid from white skeletal muscle. MCT3 is also expressed in several other tissues requiring rapid lactic acid efflux. The expression of both MCT3 and MCT1 was decreased by 40-60% 3 weeks after denervation of rat hind limb muscles, whereas chronic stimulation of the muscles for 7 days increased expression of MCT1 2-3-fold but had no effect on MCT3 expression. The kinetics and substrate and inhibitor specificities of monocarboxylate transport into cell lines expressing only MCT3 or MCT1 have been determined. Differences in the properties of MCT1 and MCT3 are relatively modest, suggesting that the significance of the two isoforms may be related to their regulation rather than their intrinsic properties.

Animals↗

PubMed1996

Quantitative skeletal muscle histochemistry of four east African ruminants.

A quantitative histochemical study was made of superficial thigh muscle specimens (semimembranosus and some vastus lateralis) from topi, hartebeest, wildebeest and waterbuck (species listed in order of increasing size). Fibres were largest (up to 120 microns diameter) in waterbuck but smallest (maximum approximately 90 microns) in wildebeest. Type 2B fibres, most of them large, highly glycolytic and weakly aerobic, constituted approximately 75% of the cross-section of topi specimens and approximately 83% of the others, greater area fractions than in other large herbivores. Type 1 fibres, highly aerobic but weakly glycolytic, occupied only 2-3.5% of the area fractions, very low figures, even for these superficial sites. Type 2A fibres occupied > 20% areas in topi, approximately 15% in the other species. In waterbuck they were never more than moderately aerobic, but quite highly glycolytic; elsewhere their characteristic metabolic profiles were close to those of type 1 fibres. The 2B fractions indicate that glycolytic metabolism predominates over lipolytic in all 4 species. Mean enzymic capacities were compared semiquantitatively between species on the basis of wide-area photometric readings. Much the greatest difference was in aerobic (succinate dehydrogenase) capacities: the mean reading in topi was x 2.6 that in waterbuck, but wildebeest capacity came close to that of topi. These latter are the 2 most active species. Readings for the force-generating enzyme, actomyosin ATPase, were slightly weaker in the heavier species. This could be predicted on allometric grounds, but mass considerations appear to be overridden by behavioural differences in relation to metabolism.

Africa, Eastern↗

PubMed1993

Dose dependent effects of alcohol on visual evoked potentials.

The effects of various alcohol doses on components of the visual evoked potential were investigated. Using a repeated measures, Latin square design, five alcohol dose conditions were administered to ten male subjects: 0.00 (placebo); 0.28; 0.36; 0.54 and 0.72 g/kg total body weight. EEG responses to a reversing checker board stimulus were measured in a standard oddball paradigm. In the alcohol conditions, latencies of the P1 and P2 components of the VEP were unaffected. However, reaction time, and the latencies of N2 and P3 displayed significant dose related increases with increasing blood alcohol levels. Further, RMS power of the P3 complex was reduced by higher alcohol doses, as was the N2-P3 amplitude difference at central and parietal sites. It is concluded that the latency and power of the endogenous components of the VEP are altered by alcohol, without effects being seen in earlier components.

Adolescent↗

PubMed1993

Investigation of stimulus-secretion coupling in equine sweat gland epithelia using cell culture techniques.

When sweat glands isolated from samples of horse skin were explanted and cultured under favourable conditions, they could exhibit cellular outgrowth. This growth could be maintained for 2-4 weeks and these primary cultures were then disaggregated and the resultant cell suspensions used to initiate epithelial cell lines. Secretion from intact equine sweat glands is regulated by beta 2-adrenoceptors and appears to be mediated by cyclic AMP, but there is evidence that calcium may also play a role. Adrenaline could increase the cyclic AMP content of the cultured cells and this response was mediated by beta 2-adrenoceptors. Adrenaline was also able to evoke a small increase in intracellular free calcium ([Ca2+]i) but the pharmacology of this response remains obscure. Adrenaline thus activates at least two potentially important second-messenger signalling pathways which have the capacity to interact, because adrenaline-evoked cyclic AMP formation was inhibited if [Ca2+]i was raised with ionomycin. The chloride permeability of mammalian epithelial cells characteristically rises during secretion, and adrenaline could increase chloride permeability in the cultured epithelia but the cells did not contain cyclic-AMP-dependent chloride channels and so this response was mediated by [Ca2+]i.

Animals↗

PubMed1992

Differences in the axon composition of nerves supplying the rat knee joint following intra-articular injection of capsaicin.

This study was used to examine the ultrastructure of articular nerves supplying the medial aspect of the rat knee joint following injection of capsaicin into the synovial cavity. One week after the intra-articular injection of 0.2 ml of 1% capsaicin solution there was significant reduction in the number of unmyelinated fibres. Two weeks post-injection this appeared to recover and by 4 weeks post-injection no further changes were observed. Myelinated fibres were unaffected by capsaicin injection. This procedure provides an effective means of producing short-term degeneration of unmyelinated fibres innervating the knee joint.

Animals↗

PubMed1991

Myasthenia gravis in Jamaica. Clinical, immunological and genetic studies.

Clinical, immunological and genetic parameters were studied in 73 Jamaican patients with myasthenia gravis (MG). The reported bimodal clinical distribution of females with early onset of disease and males with late onset was not observed. The female to male ratio was 2:1. The most frequent manifestations of disease were ptosis (84.9%), general muscle weakness (68.5%), bulbar symptoms (41.1%) and diplopia (32.9%). Unusual presenting features such as unilateral ptosis, recurrent chest infection and stumbling while walking resulted in diagnosis being missed in 5.8% of cases. The sensitivity of radioimmunoassay in detecting acetylcholine receptor antibody (AchR-Ab) in sera from a subgroup of 35 MG patients was 71.4% whilst that of the ELISA was only 14.2%. There was no correlation between concentration of AchR-Ab and severity of disease. Similarly, there was no association between HLA-type, thymic pathology and course of disease. HLTV-I could not be implicated in the pathogenesis of this disease. There was a paucity of other associated autoimmune conditions among MG patients. Thymectomy was an important therapeutic modality in that improvement was observed in 22 cases and remission in 11.

Adolescent↗

PubMed1990

The effect of afternoon body heating on body temperature and slow wave sleep.

Recent evidence suggests that body temperature at sleep onset affects the subsequent level of slow wave sleep. According to one hypothesis, the actual temperature is the critical factor determining the relationship. An alternative proposal is that it is the rate of fall of body temperature following sleep onset. These hypotheses were tested by measuring rectal temperature and sleep, following late afternoon passive heating in a warm bath and during a control condition. Passive heating increased rectal temperature, which then returned rapidly toward the control level. However, immediately before lights out rectal temperature was still higher in the passive heating condition, a difference that continued throughout the night. Following passive heating the amount of slow wave sleep was higher in the early part of the night. These results support the hypothesis that body temperature at sleep onset and the amount of slow wave sleep are positively related.

Adult↗

PubMed1989

Effects of season and lower ambient temperature on the structure of the sweat glands in anhidrotic horses.

Histological studies of the sweat glands of anhidrotic horses in the Hong Kong summer and under conditions of reduced thermal stress, both natural and controlled, were undertaken to determine if glandular regeneration occurs. Clinical data were collected for comparison with the histological results in each instance. Horses were assigned to one of three categories on the basis of the resulting change in the number of thin glandular profiles in a cooler environment. Group 1, which was classed as normal, had a low initial value, which was maintained. Group 2, typical of mild and moderately affected animals, had a high initial value, which fell markedly after as little as six weeks in the cool environment. Animals in Group 3, classed as severely affected, had a high initial value which remained high even after prolonged exposure to the cool environment. Light microscopical examination of the sweat glands in the heat, and after six weeks in a cool environment, provided a means of predicting the degree of anhidrotic severity and the potential for recovery in a cool climate. This was superior to clinical observation, although a diagnostic test based on glandular function is still required.

Animals↗

PubMed1989

Effect of sleep and circadian cycle on sleep period energy expenditure.

Energy expenditure is lower during sleep than relaxed wakefulness. However, there is disagreement as to the particular metabolic changes that produce the difference. The present study assessed the contribution of sleep, circadian cycle, and the specific dynamic action effect of the evening meal to the sleep period fall in metabolic rate. Five subjects were tested for a total of nine nights under three conditions in a repeated-measures design. Subjects were confined to bed throughout their usual sleep period but were instructed to go to sleep 0, 3, or 6 h after their usual time for lights out. O2 consumption was measured in all conditions for the 0.5 h before and after each of the times for lights out and then throughout the sleep period after lights out. The results demonstrated that changes in energy expenditure during the sleep period are a function of both sleep and circadian cycle. In this study, the contribution of the two components was approximately equal. However, the effect of sleep was rapid asymptoting within 15 min of sleep onset, whereas that of circadian cycle was constant over the assessment period.

Adult↗

PubMed1988

Effects of stimulation on the ultrastructure and Na, K, Cl composition of the fundus of the rat plantar sweat gland.

Initial stimulation of the rat plantar sweat gland with pilocarpine caused a variable degree of distension of the apical membrane of the secretory cell. This appeared to be a process of filtration of secretory cell cytoplasm through the apical terminal web. Further stimulation resulted in luminal dilatation, cytoplasmic depletion, and morbidity of some cells. These morphological changes in the footpad gland, which thus can no longer be considered as eccrine, were accompanied by a fall in potassium and a rise in sodium concentration within the secretory cells. The mode of secretion induced by pharmacological stimulation was fundamentally the same as that in the glands of species responsive to thermal stimulation.

Animals↗

PubMed1988

The effects of thermally-induced activity in vivo upon the ultrastructure and Na, K and Cl composition of the epithelial cells of sweat glands from patients with cystic fibrosis.

The secretory cells of the fundus of sweat glands from cystic fibrosis (CF) patients had higher Na and Cl contents and showed more granule depletion, cellular disruption and dilated intercellular canaliculi than normal. The cells of the coiled duct also had higher cytoplasmic levels of Na and Cl but were structurally normal. Thermal stimulation produced ultrastructural changes in the CF fundus comparable to normal, including further dilatation of the basolateral clefts, but did not induce the marked changes in the coiled duct which normally occur. The elevated Na and fall in K in the fundus and raised Na and Cl in the coiled duct upon activation, were not observed in the CF glands in which no significant changes were detected.

Chlorides↗

PubMed1988

The effect of exercise on sleep: the negative view.

Theories of sleep typically view sleep as having a compensatory relationship to wakefulness. This hypothesis leads to the prediction that physical exercise will cause both sleep duration and the amount of slow wave sleep (SWS) to be higher on the following night. Three previous reviews of the literature, while not agreeing in detail, have generally supported the hypothesis. It is argued that, in two of these reviews in particular, the extent of the positive evidence was overstated. Consistent with this interpretation the subsequent literature is also negative with regard to the hypothesis. Further, physical fitness, which occurs as a result of long periods of physical training, is not consistently associated with either longer sleep durations, or higher levels of SWS. While there is some evidence that exercise may have indirect effects on sleep under a limited range of circumstances, there is no evidence to support the hypothesis that physical exercise directly causes, or is reliably associated with, longer sleep durations or higher levels of SWS.

Exercise↗

PubMed1988

Physical exercise and sleep: the effect of the age and sex of the subjects and type of exercise.

Exercise has generally been held to result in an increase in slow wave sleep (SWS) and sleep duration. We report the results of three experiments which assessed the effects of exercise on the sleep of young fit women as compared to young fit men; fit older men (aged 41 years) as compared to fit younger men (aged 22 years); and the effects of power exercise on the sleep of a group of trained power lifters. In each experiment physically fit subjects had their sleep assessed following both late afternoon exercise and no exercise conditions. In none of the experiments did exercise result in an increase in SWS or sleep duration. Instead the tendency was for exercise to affect sleep adversely.

Adult↗

PubMed1987

Effects of topically-applied antiperspirant on sweat gland function.

In subjects exposed to a hot environment, short-term topical pretreatment with aluminium zirconium tetrachlorhydrate delayed the onset of visible sweating although it failed to prevent the response. The delay was considered most probably to be due to the occlusive action, in the duct within the upper epidermis, of aluminium-containing conglomerates, which disappear after continuous sweating. However, microanalytical evidence indicated that ionic transport within the fundus secretory cells was also modified.

Administration, Topical↗

PubMed1986

Do asthmatics suffer bronchoconstriction during rapid eye movement sleep?

Many patients with asthma are troubled by nocturnal wheeze. The cause of this symptom is unknown, but sleep is an important factor. A study was carried out to determine whether nocturnal bronchoconstriction is related to any specific stage of sleep. Eight asthmatics with nocturnal wheeze and eight control subjects performed forced expiratory manoeuvres immediately after being woken from rapid eye movement (REM) or non-REM sleep, wakings being timed to differentiate temporal effects from those related to the stage of sleep. The control subjects showed no significant temporal bronchoconstriction or bronchoconstriction related to the stage of sleep. All patients showed bronchoconstriction overnight, the mean peak expiratory flow rate falling from 410 (SEM 50) 1/min before sleep to 186 (49)1/min after sleep. After the patients had been woken from REM sleep the forced expiratory volume in one second was on average 300 ml lower (p less than 0.02) and peak expiratory flow rate 45 1/min lower (p less than 0.03) than after they had been woken from non-REM sleep. As wakenings from REM sleep were 21(8) minutes later in the night than those from non-REM sleep multivariate analysis was performed to differentiate temporal effects from those related to the stage of sleep. This showed that the overnight decreases in forced expiratory volume in one second and peak expiratory flow rate were significantly related both to time and to REM sleep. This study suggests that asthmatics may suffer bronchoconstriction during REM sleep.

Adolescent↗

PubMed1986

Passage of lanthanum through the intercellular spaces of the sebaceous gland.

Lanthanum introduced intradermally into cattle, sheep, goats, ponies and rats penetrated into the sebum through the intercellular spaces of the sebaceous gland. It is concluded that the sebaceous gland is permeable to the passage of small molecules outwards and probably in some circumstances inwards. Since the constituents of sebum are not all produced by necrosis it is likely that the sebaceous gland is not a simple holocrine gland.

Animals↗

PubMed1985

Comparative studies of the ultrastructure of the sebaceous gland.

Three-dimensional reconstructions and ultrastructural evidence on the sebaceous glands of man and domestic animals indicate that sebum is produced from a column of developing and degenerating cell populations derived from peripheral progenitor cells at the base of the lobe in a manner analogous to hair growth. The remainder of the peripheral cells apparently have no direct involvement with sebocyte production; those towards the neck of the gland contribute keratin to the secretory product.

Adult↗

PubMed1985

The effects of thermal stimulation on the ultrastructure of the human atrichial sweat gland. II. The duct.

The duct of the human atrichial sweat gland, after thermal stimulation, exhibited increased cytoplasmic vesiculation, particularly of the luminal cells, a widening of the intercellular spaces, and the presence of particulate matter in the lumen. The luminal cells of the coiled zone also displayed varying degrees of apical disruption, most probably due to filtration of cell fluid through the terminal web of microfilaments. This zone seems to have a secretory as well as an absorptive role. Specialized junctions (intercellular bridges, gap junctions and tight junctions) were found amongst the basal and luminal cells of the wall of the ascending duct.

Cytoplasm↗