Biomedical subjects

L Larsson

Publications and source records attributed to L Larsson.

At least 55 records · Page 3Linked to original sources

PubMed2001

Effects of aging on actin sliding speed on myosin from single skeletal muscle cells of mice, rats, and humans.

The effects of aging on the mechanical properties of myosin were measured in 87 fibers from muscles of humans (n = 40), rats (n = 21), and mice (n = 26) using a single fiber in vitro motility assay. Irrespective of species, an 18-25% aging-related slowing in the speed of actin filaments was observed from 62 single fibers expressing the slow (type I) beta-myosin heavy chain isoform. The mechanisms underlying the aging-related slowing of motility speed remain unknown, but it is suggested that posttranslational modifications of myosin by oxidative stress, glycation, or nitration play an important role. The aging-related slowing in the speed of actin filaments propelled by the type I myosin was confirmed in three mammalian species with an approximately 3,400-fold difference in body size. Motility speed from human myosin was 3-fold slower than from myosin of the approximately 3,400-fold smaller mouse and approximately twofold slower when compared with the approximately 130-fold smaller rat, irrespective of age. A strong correlation was observed between the log values of actin sliding speed and body mass, suggesting that the effects of scaling is, at least in part, due to altered functional properties of the motor protein itself.

Actins↗

PubMed2001

The frequency and nature of drug administration error during anaesthesia.

We aimed to establish the frequency and nature of drug administration error in anaesthesia (a significant subset of error in medicine) at two hospitals. Anaesthetists were asked to return a study form anonymouslyfor every anaesthetic, indicating whether or not a drug administration error or pre-error (defined as any incident with potential to become an error) had occurred. Further details were sought if the response was affirmative. From 10,806 anaesthetics, 7794 study forms were returned, representing response rates of 80% from Hospital A and 57% from Hospital B (72% overall). The frequency (95% confidence intervals) of drug administration error; of any type, per anaesthetic was 0.0075 (0.006 to 0.009), of i.v. bolus errors was 0.005 (0.0035 to 0.006) and of pre-errors was 0.004 (0.003 to 0.005), with no significant difference between hospitals. Overall, one drug administration error was reported for every 133 anaesthetics. The two largest individual categories of error involved incorrect doses (20%) and substitutions (20%) with i.v. boluses of drug. Of the i.v. bolus substitutions, 69% occurred between different pharmacological classes. One patient was aware while under muscle relaxation, and two required prolonged ventilation. In addition, 47 transient physiological effects were reported, of which five required intervention. We conclude that drug administration error during anaesthesia is considerably more frequent than previously reported.

Anesthesia↗

PubMed2001

TRs have common and isoform-specific functions in regulation of the cardiac myosin heavy chain genes.

TRalpha1 and TRbeta mediate the regulatory effects of T3 and have profound effects on the cardiovascular system. We have analyzed the expression of the cardiac myosin heavy chain (MyHC) genes alpha and beta in mouse strains deficient for one or several TR genes to identify specific regulatory functions of TRalpha1 and TRbeta. The results show that TRalpha1 deficiency, which slows the heart rate, causes chronic overexpression of MyHCbeta. However, MyHCbeta was still suppressible by T3 in both TRalpha1- and TRbeta-deficient mice, indicating that either receptor can mediate repression of MyHCbeta. T3-dependent induction of the positively regulated MyHCalpha gene was similar in both TRalpha1- and TRbeta-deficient mice. The data identify a specific role for TRalpha1 in the negative regulation of MyHCbeta, whereas TRalpha1 and TRbeta appear interchangeable for hormone-dependent induction of MyHCalpha. This suggests that TR isoforms exhibit distinct specificities in the genes that they regulate within a given tissue type. Thus, dysregulation of MyHCbeta is likely to contribute to the critical role of TRalpha1 in cardiac function.

Animals↗

PubMed2001

The decrease of IGF-I, IGF-binding protein-3 and bone alkaline phosphatase isoforms during gluten challenge correlates with small intestinal inflammation in children with coeliac disease.

OBJECTIVE: In children with coeliac disease, the ingestion of gluten causes small intestinal inflammation and a clinical picture of malabsorption, weight reduction and short stature. Decreased alkaline phosphatase (ALP) during gluten challenge was found in a previous study. ALP is a marker of bone formation and ALP activities are correlated with growth velocity. The aim of this study was to characterise the previously observed decrease of total ALP by investigating three specific bone ALP isoforms (bone/intestinal, B1 and B2) and three specific liver ALP isoforms (L1, L2 and L3) and, moreover, to correlate these ALP isoforms with other growth factors and growth markers. In addition, we also studied the association with possible weight changes, small intestinal mucosa inflammation, sex, age and gluten dose during gluten challenge. MATERIALS AND METHODS: Bone and liver ALP isoforms, IGF-I, IGF-binding protein (IGFBP)-3 and serum cross-linked carboxy-terminal telopeptide of type I collagen (ICTP) were measured together with change in weight and small intestinal mucosa histopathology in 54 children with earlier enteropathy who participated in a 4-week gluten challenge. RESULTS: We observed a decreased total ALP activity after 4 weeks of gluten challenge, 7.8+/-1.8 to 6.5+/-1.7 microkat/l (means +/- s.d.), which was mainly due to a reduction of the bone ALP isoforms. The sum of all three bone ALP isoforms decreased from 6.3+/-1.7 to 5.1+/-1.6 microkat/l. The decreased activities of the bone ALP isoforms correlated with the observed reductions of IGF-I (r=0.74, P<0.001), IGFBP-3 (r=0.51, P<0.001) and ICTP (r=0.57, P<0.001). The decrease of the growth factors and growth markers correlated with weight reduction, but when influences from the change in weight were adjusted for, the partial correlation of the small intestinal mucosa inflammation was significant for IGF-I (r=-0.56, P<0.001) and IGFBP-3 (r=-0.55, P<0.001). CONCLUSION: The decrease of total ALP was due to a reduction of bone ALP. The decrease of IGF-I and IGFBP-3 was independently correlated with weight change and small intestinal inflammation.

Alkaline Phosphatase↗

PubMed2001

Use of mass spectrometry for characterising microbial communities in bioaerosols.

The use of chemical marker analysis for characterising microbial communities in organic dust samples is exemplified in a comparative study of dusts collected in a home and a swine confinement building, respectively. The chemical markers studied included 3-hydroxy fatty acids (markers of endotoxin), ergosterol (marker of fungal biomass), and muramic acid (marker of peptidoglycan/bacterial biomass). Samples were hydrolysed and subjected to various chemical manipulations for rendering the markers suitable for gas chromatography-tandem mass spectrometry analysis. Considerable differences between the dust samples were revealed. Swine dust contained 46 ng/mg of ergosterol (house dust 2.1 ng/mg), 0.096 nmol/mg of endotoxin (house dust 0.020 nmol/mg), and 483 ng/mg of muramic acid (house dust 366 ng/mg). The 3-hydroxy fatty acid and muramic acid results demonstrated a much higher proportion of Gram-negative bacteria to Gram-positives in swine dust than in house dust, and ergosterol results demonstrated a much higher proportion of fungi. The different distribution of 3-hydroxy fatty acids in the 2 samples illustrated differences in their flora of Gram-negative bacteria. The described method allows accurate determination of markers even when present down to trace levels in chemically complex matrices and should be useful in evaluating the role of microorganisms in the development of occupational lung disease, e.g. in agricultural environments.

Aerosols↗

PubMed2000

New and simple procedure for the determination of muramic acid in chemically complex environments by gas chromatography-ion trap tandem mass spectrometry.

A gas chromatographic-ion trap tandem mass spectrometric method was developed for the quantification of muramic acid, a marker of bacterial peptidoglycan, in environmental and clinical specimens. Samples (bacteria, house dust and urine) were heated in methanolic hydrochloric acid overnight and extracted with hexane for removal of hydrophobic compounds. The aqueous phase was evaporated and heated in acetic anhydride and pyridine after which the product, the acetate derivative, was washed with dilute hydrochloric acid and water. The described method is both rapid and simple to apply, and produces a stable derivative. It should become widely used for measuring peptidoglycan in chemically complex environments.

Acetic Anhydrides↗

PubMed2000

Serum isoforms of bone alkaline phosphatase increase during physical exercise in women.

Physical activity is an important factor for maintaining and probably increasing bone mass in humans. However, the mechanism by which this takes place is not completely understood. The purpose of this study was to examine the influence of physical exercise on serum alkaline phosphatase (ALP) and in particular, the bone isoforms of ALP. Six ALP isoforms were quantified by high-performance liquid chromatography: three bone (B/I, B1, and B2), and three liver ALP isoforms. In addition, serum calcium, parathyroid hormone (PTH), and other markers of bone formation and degradation, as measured by osteocalcin and cross-linked carboxyterminal telopeptide of type I collagen (ICTP), were analyzed. The study groups comprised 15 women, 8 postmenopausal (range 51-62 years) and 7 near age of peak bone mass (range 21-27 years). When the postmenopausal women exercised on an ergometer cycle until exhaustion we found significant increases in serum of bone ALP isoforms B1 and B2, and phosphate, even considering the hemoconcentration that occurred during the exercise. When the young women jogged in a moderate tempo for 40-40 minutes the levels of serum B2 and PTH increased. All changes turned towards baseline within 20 minutes after exercise. In conclusion, exercise increased serum ALP bone isoforms B1 and B2, and their responses were differentiated. As B1 and B2 are known to represent specific bone compartments, cortical and trabecular bone, the present findings may indicate different effects on bone of weight- and nonweight-bearing exercise.

Adult↗

PubMed2000

Microwaving for double indirect immunofluorescence with primary antibodies from the same species and for staining of mouse tissues with mouse monoclonal antibodies.

Many methods have been devised for double immunocytochemical staining. We now describe that moderate microwaving does not elute antibodies, but prevents their reactions with subsequently applied reagents. Thus, microwaving performed in between the first and second staining cycles permits double indirect immunofluorescence staining with antibodies raised in the same species. Moreover, microwaving also inhibits reactions with endogenous immunoglobulins present in extracellular compartments. This substantially reduces background in indirect immunostaining of mouse tissues with mouse monoclonal antibodies.

Animals↗

PubMed2000

Candida tropicalis vertebral osteomyelitis complicating epidural catheterisation with disease paralleled by elevated D-arabinitol/L-arabinitol ratios.

Deep-seated Candida infections are challenging to diagnose by noninvasive means, and new modalities are needed to improve the yield of such investigations. Reported here is a case of Candida tropicalis vertebral osteomyelitis complicating epidural catheterisation in a diabetic patient with complicated abdominal sepsis. The diagnosis was supported by detection of increased D-arabinitol/L-arabinitol ratios in urine samples, and failure of medical management was indicated by elevated D-arabinitol/L-arabinitol ratios, which later decreased to baseline with successful surgical debridement and prolonged antifungal therapy.

Aged↗

PubMed2000

Actomyosin interactions in a novel single muscle fiber in vitro motility assay.

A novel in vitro motility assay has been developed to study the actomyosin interaction, in which the molecular motor protein myosin has been extracted and immobilized directly from 2-4 mm single rat skeletal muscle fiber segments. This method study was carried out to investigate: (1) the amount of myofibrillar proteins extracted from the fiber segment; (2) the effects of temperature on the speed at which actin is propelled by fast and slow myosin; and (3) the effects of myosin isoform expression on motility speed. Approximately 80% of the myosin and myosin-associated proteins were extracted from the fiber segments. while no significant extraction was shown of the thin filament proteins. Fluorescently labeled actin filaments moved with constant speed in a bi-directional motion over the high-density myosin region in the experimental chamber, and motility speed was highly dependent on the myosin heavy chain (MyHC) isoform extracted. At 25 degrees C, significant (P < 0.001) differences in motility speed were obtained between type I (1.31 +/- 0.23 microm/s, n = 11) and IIxb (5.81 +/- 0.35 microm/s, n = 6), or llb (6.07 +/- 0.33 microm/s, n = 8) MyHC isoforms. The motility speed and maximum velocity of unloaded shortening (V0) in single fibers were well correlated, indicating that filament speed is a good molecular analogue to contractile speed at the fiber level. The effects of temperature on filament motility speed were analyzed from 10 to 35 degrees C. The Q10 values, calculated in the 10-25 degrees C temperature range, differed between slow (4.20) and fast (2.38) myosin. In conclusion, this in vitro motility assay offers a unique possibility to compare the regulatory and modulatory influence of myosin isoforms and thin filament proteins on shortening velocity, at the cellular and molecular level in the same muscle fiber.

Actins↗

PubMed2000

Characterization and variability of endotoxin and 3-hydroxy fatty acids in an office building during a particle intervention study.

Air and dust samples were collected on two floors of an office building during a double-blind particle intervention study to examine spatial and temporal variability of airborne endotoxin over a period of weeks, and to characterize endotoxin activity and lipopolysaccharide (LPS) content in carpet and chair dust. Air samples were collected on multiple days within and across weeks. Dust samples were collected from carpets and chairs one day per week for three weeks. Endotoxin was measured using a Limulus assay. Dust samples were analyzed for LPS by determination of 3-hydroxy fatty acids (3-OHFAs) using gas chromatography-mass spectrometry. The geometric mean (geometric standard deviation) for 96 indoor air samples was 0.24 (1.6) EU/m3. Significant within-floor spatial variation of airborne endotoxin was found (P < 0.0001, n = 80). Temporal variability of airborne endotoxin was not significant across weeks. Mean (+/- SD) endotoxin levels in carpet dust (59 +/- 9.3 EU/mg dust, n = 12) and in chair dust (38 +/- 7.7 EU/mg dust, n = 10) were significantly different (P < 0.001). Carbon chain length-dependent differences in 3-OHFA levels by dust source and floor were found. Enhanced air filtration did not significantly affect airborne endotoxin (P = 0.62); however, total dust mass and total endotoxin in carpet dust samples increased significantly after enhanced surface cleaning (P < 0.01). These findings suggest that spatial variability, dust source, and surface cleaning may influence building occupant exposures to endotoxin.

Air Pollution, Indoor↗

PubMed2000

Determination of microbial colonisation in water-damaged buildings using chemical marker analysis by gas chromatography-mass spectrometry.

Gas chromatography-mass spectrometry was used to determine the microbial contents of building materials subjected to water damage in a laboratory experiment and of materials collected from houses affected by water during the flood in Klodzko in south-western Poland, July 1997. The samples were examined for 3-hydroxy fatty acids, markers of bacterial endotoxin, and ergosterol, marker of fungal biomass. The amounts of both 3-hydroxy fatty acids and ergosterol were higher in materials that had been exposed to water than in unexposed ones. All markers were stable in the building materials for at least 6 weeks at room temperature and could thus be used to reveal microbial contamination even when cultivation results for bacteria and fungi were negative. Direct measurement of 3-hydroxy fatty acids and ergosterol in human environments could be a useful method, e.g. in monitoring indoor air as regards presence of potentially harmful microorganisms and microbial constituents.

Air Pollution, Indoor↗

PubMed2000

Preliminary report on the results of the second phase of a round- robin endotoxin assay study using cotton dust.

In an on-going endotoxin assay study, a two-part interlaboratory endotoxin assay study has been completed. The purpose of the study was to compare the variation in assay results between different laboratories, and, if the variation was high, to see if a common protocol would reduce the variation. In both parts of the study, membrane filters laden with the same approximate amount and type of cotton dust were sent for analysis to laboratories that "routinely" perform endotoxin analyses. First, each of these laboratories performed the analysis using the methodology common to its laboratory. In the second part of the study, membrane filters with cotton dust were again sent to the same laboratories where the analyses were performed as before but with a common extraction protocol. The preliminary results from the first phase of the study have been collected and showed that intra-laboratory variations were small, but large and significant interlaboratory variation was observed. The results were reported elsewhere. The preliminary results from the second part of the study consisting of the data currently collected are presented here. Again, intra-laboratory variations were small, but, also again, large and significant inter-laboratory variation was observed. However, in this part of the study, the range between the highest and lowest average results was narrower than in the first part of the study. Influence of the assay kit type was examined. The variation within assay kit type was small but significant differences in results were observed between assay kit types. The findings suggest that endotoxin concentration in samples can be ranked within laboratories, but not necessarily between laboratories. However, some of the variation between laboratories has been reduced by a common extraction protocol which suggests the possibility of further standardization that may lead to better comparability between laboratories.

Air Pollution, Indoor↗

PubMed2000

Investigation of the concentration of bacteria and their cell envelope components in indoor air in two elementary schools.

Bacterial cell envelope components are widely distributed in airborne dust, where they act as inflammatory agents causing respiratory symptoms. Measurements of these agents and other environmental factors are assessed in two elementary schools in a southeastern city in the United States. Muramic acid (MA) was used as a marker for bacterial peptidoglycan (PG), and 3-hydroxy fatty acids (3-OH FAs) were used as markers for Gram-negative bacterial lipopolysaccharide (LPS). Culturable bacteria were collected using an Andersen sampler with three different culture media. In addition, temperature (T), relative humidity (RH), and CO2 were continuously monitored. Concentrations of airborne MA and 3-OH FAs were correlated with total suspended particulate (TSP) levels. Outdoor MA (mean = 0.78-1.15 ng/m3) and 3-OH FA levels (mean = 2.19-2.18 ng/m3) were similar at the two schools. Indoor concentrations of airborne MA and 3-OH FAs differed significantly between schools (MA: 1.44 vs. 2.84 ng/m3; 3-OH FAs: 2.96 vs. 4.57 ng/m3). Although indoor MA levels were low, they were significantly related to teachers' perception of the severity of indoor air quality (IAQ) problems in their classrooms. Concentrations of CO2 correlated significantly with all bacteria measurements. Because CO2 levels were related to the number of occupants and the ventilation rates, these findings are consistent with the hypothesis that the children and teachers are sources of bacterial contamination. Many culturable bacteria present in indoor air are opportunistic organisms that can be infectious for compromised individuals, while both culturable and nonculturable bacterial remnants act as environmental toxins for both healthy and compromised individuals. Measuring the "total bacteria load" would be most accurate in assessing the biotoxicity of indoor air. Chemical analysis of MA and 3-OH FAs, when coupled with the conventional culture method, provides complementary information for assessing biocontamination of indoor air.

Air Microbiology↗

PubMed2000

Acute quadriplegia and loss of muscle myosin in patients treated with nondepolarizing neuromuscular blocking agents and corticosteroids: mechanisms at the cellular and molecular levels.

OBJECTIVE: Long-term treatment with nondepolarizing neuromuscular blocking agents and corticosteroids in the intensive care unit is not benign, and an increasing number of patients with acute quadriplegic myopathy have been reported with increased use of these drugs. The purpose of this study was to investigate the mechanisms underlying acute quadriplegic myopathy. DESIGN: Percutaneous muscle biopsy samples were obtained, and electrophysiologic examinations were performed during the acute phase and during recovery in patients with acute quadriplegic myopathy. Regulation of muscle contraction and myofibrillar protein synthesis was studied using cell physiologic techniques, ultrasensitive electrophoresis, in situ hybridization, and histopathologic techniques. SETTING: All patients were seen in the intensive care unit of different university hospitals. PATIENTS: All patients were critically ill with sepsis. They had been given massive doses of corticosteroids in combination with variable doses of neuromuscular blocking agents. All patients developed paralysis of spinal nerve-innervated muscles. On the other hand, cranial nerve-innervated muscle and sensory and cognitive functions were well maintained after discontinuation of treatment with neuromuscular blocking agents. INTERVENTION: Muscle biopsy samples were obtained and electrophysiologic examinations were performed in all patients. MEASUREMENTS AND MAIN RESULTS: The major observations in patients with acute quadriplegic myopathy were, as follows: a) a general decrease in myofibrillar protein content; b) specific but highly variable partial or complete loss of myosin and myosin-associated proteins; c) very low thick-filament/thin-filament protein ratios; d) absence of myosin messenger RNA; and e) a dramatically impaired muscle cell force-generating capacity in the acute phase of acute quadriplegic myopathy. During clinical improvement, normal expression of myosin messenger RNAs, reexpression of thick-filament proteins, and increased specific tension were observed. CONCLUSIONS: Acute quadriplegic myopathy is associated with a specific decrease in thick-filament proteins related to an altered transcription rate. Although the decreased content of thick-filament proteins is important for prolonged muscle weakness, it is not the primary cause of muscle paralysis in the acute stage, during which impaired muscle membrane excitability probably plays a more significant role. Several factors contribute to this condition, but the action of corticosteroids seems to be the predominant one, along with potentiation by neuromuscular blocking agents, immobilization, and probably also concurrent sepsis.

Acute Disease↗

PubMed2000

A population-based study on motor performance and white matter lesions in older women.

OBJECTIVE: To investigate the relationship between motor performance and white matter lesions (WMLs) on computed tomography (CT) of the brain in older women. DESIGN: Cross-sectional study. SETTING: Population-based study in Göteborg, Sweden. PARTICIPANTS: A total of 248 women aged 70, 74, and 78 years. MEASUREMENTS: Motor performance was measured by a Postural-Locomotion-Manual (PLM) test using an optoelectronic technique. WMLs on CT scans were rated as no, mild, moderate, or severe. RESULTS: White matter lesions were associated with impaired mobility of the lower extremities, that is, prolonged locomotion phase in the PLM test. This association was also present after controlling for age, hypertension, coronary heart disease, stroke, diabetes mellitus, chronic bronchitis, intermittent claudication, and smoking. CONCLUSIONS: Cerebral white matter lesions may contribute to motor impairments in older adults.

Activities of Daily Living↗

PubMed2000

Urine D-arabinitol/L-arabinitol ratio in diagnosis of invasive candidiasis in newborn infants.

Infants treated in neonatal intensive care units suffer an increased risk for invasive candidiasis, but the diagnosis is sometimes difficult. D-arabinitol is a metabolite of most pathogenic Candida species. An elevated urine D-arabinitol/L-arabinitol (DA/LA) ratio is a sensitive sign of invasive candidiasis in children with cancer, but the method has not been previously evaluated for newborn infants. We therefore enrolled 117 infants in a neonatal intensive care unit, and 411 urine samples were obtained on filter paper. The DA/LA ratio was measured by gas chromatography-mass spectrometry. For 81 infants with no suspicion of superficial or invasive candidiasis, the urine DA/LA ratio was 2.7 +/- 0.7 (mean +/- standard deviation [SD]). The upper cutoff level was set at 4.8 (mean plus 3 SD). Of 22 infants with mucocutaneous candidiasis and not given systemic antifungal treatment, two had elevated DA/LA ratios, which normalized after removal of intravascular catheters. Eight other infants were given empiric antifungal treatment but had negative cultures; five of these had repeatedly elevated DA/LA ratios. Six infants with culture-positive invasive candidiasis all had one or more samples with elevated ratios. For seven infants, three with suspected and four with confirmed invasive candidiasis (for which follow-up samples were available), ratios normalized during antifungal treatment. In conclusion, urine DA/LA ratio determination is a rapid test and can be used for newborns. It is possibly more sensitive than fungal blood cultures in the diagnosis of invasive candidiasis and can also be used for monitoring the effect of antifungal treatment.

Candidiasis↗

PubMed2000

Effects of thyroid hormone receptor gene disruption on myosin isoform expression in mouse skeletal muscles.

Skeletal muscle is known to be a target for the active metabolite of thyroid hormone, i.e., 3,5,3'-triiodothyronine (T(3)). T(3) acts by repressing or activating genes coding for different myosin heavy chain (MHC) isoforms via T(3) receptors (TRs). The diverse function of T(3) is presumed to be mediated by TR-alpha(1) and TR-beta, but the function of specific TRs in regulating MHC isoform expression has remained undefined. In this study, TR-deficient mice were used to expand our knowledge of the mechanisms by which T(3) regulates the expression of specific MHC isoforms via distinct TRs. In fast-twitch extensor digitorum longus (EDL) muscle, TR-alpha(1)-, TR-beta-, or TR-alpha(1)beta-deficient mice showed a small but statistically significant decrease (P < 0.05) of type IIB MHC content and an increased number of type I fibers. In the slow-twitch soleus, the beta/slow MHC (type I) isoform was significantly (P < 0. 001) upregulated in the TR-deficient mice, but this effect was highly dependent on the type of receptor deleted. The lack of TR-beta had no significant effect on the expression of MHC isoforms. An increase (P < 0.05) of type I MHC was observed in the TR-alpha(1)-deficient muscle. A dramatic overexpression (P < 0.001) of the slow type I MHC and a corresponding downregulation of the fast type IIA MHC (P < 0.001) was observed in TR-alpha(1)beta-deficient mice. The muscle- and fiber-specific differences in MHC isoform expression in the TR-alpha(1)beta-deficient mice resembled the MHC isoform transitions reported in hypothyroid animals, i.e., a mild MHC transition in the EDL, a dramatic but not complete upregulation of the beta/slow MHC isoform in the soleus, and a variable response to TR deficiency in different soleus muscle fibers. Thus the consequences on muscle are similar in the absence of thyroid hormone or absence of thyroid hormone receptors, indicating that TR-alpha(1) and TR-beta together mediate the known actions of T(3). However, it remains unknown how thyroid hormone exerts muscle- and muscle fiber-specific effects in its action. Finally, although developmental MHC transitions were not studied specifically in this study, the absence of embryonic and fetal MHC isoforms in the TR-deficient mice indicates that ultimately the transition to the adult MHC isoforms is not solely mediated by TRs.

Adenosine Triphosphatases↗