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Biomedical subjects

A M Kelly

Publications and source records attributed to A M Kelly.

At least 91 records · Page 5Linked to original sources

An analysis of unscheduled return visits to an urban emergency department.

AIM: This study was undertaken to identify the reasons for unscheduled return visits to an urban emergency department, particularly those relating to physician errors in diagnosis and management, and, where possible, to identify strategies to reduce unscheduled return visits. METHOD: All patients returning to the Emergency Department, Christchurch Hospital, within seven calendar days of initial visit were identified. These cases were reviewed to identify reasons for return visit. RESULTS: Unscheduled return visits accounted for 2% of patient encounters. Sixty one per cent were due to illness related factors, 27% to patient related factors, 11% to physician related factors and 1% to system related factors. Significant management errors occurred in nine patients (4.4% of unscheduled return visits), three of whom were admitted. There were no ICU or CCU admissions and no deaths. CONCLUSIONS: Significant physician errors were a minor reason for reattendance at the emergency department and no specific areas of deficiency were identified. These might be further reduced by increasing the seniority and experience of staff and by the introduction of regular audit, continuing medical education and vocational training programmes. Interventions to reduce patient related unscheduled return visits might include better explanation of the role of the emergency department and better communication with patients about their illness and treatment.

Adolescent↗

Dystrophin protects the sarcolemma from stresses developed during muscle contraction.

The protein dystrophin, normally found on the cytoplasmic surface of skeletal muscle cell membranes, is absent in patients with Duchenne muscular dystrophy as well as mdx (X-linked muscular dystrophy) mice. Although its primary structure has been determined, the precise functional role of dystrophin remains the subject of speculation. In the present study, we demonstrate that dystrophin-deficient muscle fibers of the mdx mouse exhibit an increased susceptibility to contraction-induced sarcolemmal rupture. The level of sarcolemmal damage is directly correlated with the magnitude of mechanical stress placed upon the membrane during contraction rather than the number of activations of the muscle. These findings strongly support the proposition that the primary function of dystrophin is to provide mechanical reinforcement to the sarcolemma and thereby protect it from the membrane stresses developed during muscle contraction. Furthermore, the methodology used in this study should prove useful in assessing the efficacy of dystrophin gene therapy in the mdx mouse.

Animals↗

The likelihood ratio for comparing means when a portion of the subjects fail to respond.

Results of clinical studies are often obscured by the fact that some of the subjects improve with treatment while others do not. As a consequence, for example, we may obtain a contaminated distribution in a treatment group, having one component similar to the entire distribution for a control group and the other shifted by the treatment effect. Maximum-likelihood estimation and the likelihood ratio test for investigating the proportion of responders together with the treatment effect are based on asymptotic theory and use iterative maximization techniques. We investigate the sampling distribution of the estimates and the test and demonstrate their use in statistical inference. Our results suggest that the chi-square distribution with 1.4 degrees of freedom provides a useful test criterion even when the sample sizes are as small as 10. Only in obvious testing situations is the t-test adequate.

Clinical Trials as Topic↗

Adaptations in myosin heavy chain expression and contractile function in dystrophic mouse diaphragm.

The X chromosome-linked muscular dystrophic (mdx) mouse lacks the subsarcolemmal protein dystrophin and thus represents a genetic homologue of human Duchenne muscular dystrophy. The present study examined alterations in diaphragm contractile properties and myosin heavy chain (MHC) expression in young (3-4 mo) and old (22-24 mo) control and mdx mice. In young mdx mice, maximum isometric tension (Po) was reduced to 50% of control values. An increase in fibers coexpressing types I (slow) and IIa MHC as well as regenerating fibers expressing embryonic MHC occurred, whereas IIx/b fibers were decreased. In the old mdx group, Po underwent a further reduction to 25% of control, and there was a slowing of twitch kinetics along with markedly increased diaphragm endurance. These changes were associated with an approximate sevenfold increase in type I MHC fibers and virtual elimination of the IIx/b fiber population; there was no detectable embryonic MHC expression. We conclude that the mdx diaphragm responds to progressive muscle degeneration with transition to a slower phenotype associated with reduced power output and augmented muscle endurance. In the setting of progressive muscle fiber destruction, these changes may help preserve contractile function and promote greater survival of remaining muscle fibers by decreasing cellular energy requirements.

Adaptation, Physiological↗

Differences in the histogenesis of EDL and diaphragm in rat.

We have examined the histogenesis of the diaphragm and extensor digitorum muscle in rat embryos, with the aim of defining differences in developmental patterns that can be related to the functional requirements of these muscles during and after development. Patterns of interactions between myotubes and other cells, and frequency of gap junctions are quite different in the two muscles. In diaphragm, primary myotubes (at day 16 in utero) are closely associated with each other, forming parallel sheets or palisades and communicating by gap junctions. Secondary myotubes have formed by day 18, but are immature, and the frequency of gap junctions is lower. The arrangement in palisades is maintained even after fibers are separated from each other by their individual basal lamina. In EDL primary fibers at day 16 have fewer gap junctions, and the peak in communication occurs after the appearance of secondary myotubes (day 18 and 21). Secondary myotubes are more mature than in diaphragm at day 18.

Animals↗

A PCR-based assay for the wild-type dystrophin gene transferred into the mdx mouse.

Myoblast transfer has emerged as a promising treatment for inherited myopathies such as Duchenne muscular dystrophy (DMD). Further development of the technique's therapeutic potential requires an experimental system in which issues of graft rejection can be clearly discriminated from those related to myoblast biology. Here we report the development and initial application of a quantitative assay for myogenic cells bearing a wild-type dystrophin gene following transfer into the mdx mouse. The technique relies upon the ability of a mutagenizing polymerase chain reaction (PCR) primer to create a new restriction site in the amplification production of the wild-type, but not the mdx dystrophin gene. The ratio of host to donor cells can be determined from muscle biopsies as small as 1 mg, regardless of donor H-2 background. This simple technique should allow a number of basic questions related to myoblast and direct gene transfer to be addressed using the mdx mouse model.

Amino Acid Sequence↗

Amniotic fluid platelet-activating factor (PAF) is elevated in patients with tocolytic failure and preterm delivery.

Certain biological properties of PAF, including its ability to promote PGE2 synthesis and to induce myometrial contractions, support its potential role in parturition. The presence of PAF in amniotic fluid of human pregnancy appears to correlate with normal and pathologic labor. To further refine this relationship, we selected the clinical endpoints of preterm labor, tocolytic failure and preterm delivery, and evaluated amniotic fluid PAF within these groups of patients. We also measured acetylhydrolase (AH), PAF's primary degradative enzyme, to identify any correlation with the observed PAF levels. 39 specimens were collected by amniocentesis: 17 for karyotype, 6 to assess lung maturity at term and 16 in cases of preterm labor; 8 each with intact membranes and ruptured membranes at the time of sampling. PAF and AH were measured by a 3H-serotonin release bioassay and an in vitro enzyme assay using radiolabelled substrate, respectively. A 12-fold increase in PAF was found in the 3 preterm labor patients in whom tocolysis failed (delivery less than 48 hrs after treatment) compared to the 7 patients in whom labor was arrested (mean PAF = 35.0 vs 2.9 ng/ml, respectively; p = .017). Four of 8 patients with membrane rupture had preterm deliveries; their PAF levels were also elevated when compared to those that delivered at term (mean PAF = 19.7 vs 4.95 ng/ml). The 2 patients with positive amniotic fluid gram stains had the highest PAF levels in the entire cohort (30.5, 44.1 ng/ml), with low or undetectable AH. These data suggest that increased PAF production may be associated with preterm labor subsequent to tocolytic failure.

1-Alkyl-2-acetylglycerophosphocholine Esterase↗

Factors influencing variability of localisation of antibodies to carcinoembryonic antigen (CEA) in patients with colorectal carcinoma--implications for radioimmunotherapy.

Tumour localisation of anti-tumour antibodies varies greatly between patients. Factors which may be responsible for this have been investigated in 56 patients with colorectal carcinoma with a view to improving radioimmunotherapy. Thirty-seven to seventy-four MBq of 125-I labelled mouse monoclonal antibody to CEA, was given intravenously and tumour resected 70-480 h later. Percentage injected activity kg-1 (% inj.act kg-1) in tumour, was inversely correlated with the time interval between injection and operation (P = 0.004). To assess the influence of other parameters on localisation, patients were divided into two time groups according to time interval between injection and operation, 70-120 h (n = 33) and 144-480 h (n = 23). In neither group was there a significant correlation of % inj.act kg-1 with time. The % inj.act kg-1 in tumour showed a significant correlation with that in the blood for both groups (P = 0.005 and P = 0.01). There was no significant correlation for either time group between % inj.act kg-1 in tumour and serum CEA values, the per cent of tumour cells positive for CEA and vascularity. Tumour to blood ratios varied considerably (range 0.3-28.5:1) suggesting that factors other than time and persistence of activity in the blood contribute to efficient targeting. Tumour to blood ratios were inversely correlated with % inj.act kg-1 in blood for the 70-120 h group (P = 0.007), and were positively correlated with % inj.act kg-1 in tumour (P = 0.012). Autoradiography showed that antibody localised predominantly on tumour cells but was distributed heterogeneously, was not solely related to the expression of antigen and in some cases accumulated in necrotic more than viable areas of tumour. Penetration of antibody into malignant acinar structures was poor and CEA-positive cells closer to the blood supply were targeted to a greater extent than distant cells. Preoperative administration of radiolabelled antibody to CEA may be helpful in selecting patients with favourable localisation for radioimmunotherapy.

Antibodies, Monoclonal↗

Effect of thyroid status on the expression of metabolic enzymes during chronic stimulation.

The effect of thyroid status on the expression of cytochrome c oxidase (CYTOX) and the activities of citrate synthase (CS) and phosphofructokinase (PFK) were examined in chronically stimulated (10 Hz; 35 days) and contralateral, nonstimulated rat tibialis anterior muscle of hypothyroid, hyperthyroid, and euthyroid animals. Stimulation increased CYTOX activity by 2.7-, 3.2-, and 4.9-fold in hyperthyroid, euthyroid, and hypothyroid animals, respectively, to similar absolute values. CS displayed similar increases. Stimulation reduced PFK activity in hypothyroid and euthyroid animals to 45% and 60% of control values. This effect was abolished with hyperthyroidism. Thus stimulation and thyroid hormone act antagonistically on PFK activity. Stimulation increased CYTOX subunit III (mitochondrially encoded) mRNA by 2.5- and 2.9-fold in hyperthyroid and euthyroid animals. Similar increases were observed in the nuclear-encoded mRNAs of CYTOX subunit VIc in euthyroid muscle. In hyperthyroid and euthyroid conditions, the mRNA changes paralleled the increases in enzyme activity. In hypothyroid muscle, the increase in mRNA was less for subunit VIc than III, suggesting that hypothyroidism upsets the coordinate expression of nuclear and mitochondrial genes. Further, the increases in CYTOX activity exceeded that of both subunit mRNAs in hypothyroid muscle.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗

Effect of hypothyroidism on myosin heavy chain expression in rat pharyngeal dilator muscles.

Although the association between hypothyroidism and obstructive sleep apnea is well established, the effect of thyroid hormone deficiency on contractile proteins in pharyngeal dilator muscles responsible for maintaining upper airway patency is unknown. In the present study, the effects of hypothyroidism on myosin heavy chain (MHC) expression were examined in the sternohyoid, geniohyoid, and genioglossus muscles of adult rats (n = 20). The relative proportions of MHC isoforms present were determined using MHC-specific monoclonal antibodies and oligonucleotide probes. All control muscles showed a paucity of type I MHC fibers, with greater than 90% of fibers containing fast-twitch type II MHCs. In the genioglossus muscle, a population of non-IIa non-IIb fast-twitch type II fibers (putatively identified as type IIx MHC fibers) were detected. Hypothyroidism induced significant changes in MHC expression in all muscles studied. In the sternohyoid, type I fibers increased from 6.2 to 16.9%, whereas type IIa fibers increased from 25.9 to 30.7%. Type I fibers in the geniohyoid increased from 1.2 to 12.8%, whereas type IIa fibers increased from 34.1 to 42.7%. The genioglossus showed the smallest relative increase in type I expression but the greatest induction of type IIa MHC. None of the muscles examined demonstrated reinduction of embryonic or neonatal MHC in response to thyroid hormone deficiency. In summary, hypothyroidism alters the MHC profile of pharyngeal dilators in a muscle-specific manner. These changes may play a role in the pathogenesis of obstructive apnea in hypothyroid patients.

Animals↗

The mdx mouse diaphragm reproduces the degenerative changes of Duchenne muscular dystrophy.

Although murine X-linked muscular dystrophy (mdx) and Duchenne muscular dystrophy (DMD) are genetically homologous and both characterized by a complete absence of dystrophin, the limb muscles of adult mdx mice suffer neither the detectable weakness nor the progressive degeneration that are features of DMD. Here we show that the mdx mouse diaphragm exhibits a pattern of degeneration, fibrosis and severe functional deficit comparable to that of DMD limb muscle, although adult mice show no overt respiratory impairment. Progressive functional changes include reductions in strength (to 13.5% of control by two years of age), elasticity, twitch speed and fibre length. The collagen density rises to at least seven times that of control diaphragm and ten times that of mdx hind-limb muscle. By 1.5 years of age, similar but less severe histological changes emerge in the accessory muscles of respiration. On the basis of these findings, we propose that dystrophin deficiency alters the threshold for work-induced injury. Our data provide a quantitative framework for studying the pathogenesis of dystrophy and extend the application of the mdx mouse as an animal model.

Animals↗

A phase-I study of repeated therapy with radiolabelled antibody to carcinoembryonic antigen using intermittent or continuous administration of cyclosporin A to suppress the immune response.

The anti-mouse antibody response was examined in patients receiving repeated i.v. therapy with radiolabelled mouse monoclonal antibody (MAb) to carcinoembryonic antigen (CEA): 131I anti-CEA was given approximately every 2 weeks with cyclosporin A, to suppress the anti-mouse antibody response. Two schedules of cyclosporin A--intermittent therapy for 6 days with each course of anti-CEA and continuous therapy--were compared. Suppression of the immune response in the intermittent high-dose (3 patients) and continuous low-dose groups (4 patients) was equivalent, but the latter regimen was less toxic. Repeated therapy led to the formation of small amounts of anti-mouse antibody, but provided that cyclosporin A was continued it did not prevent further therapy or lead to an increase in the rate of clearance of anti-CEA from blood. Without cyclosporin A no more than 2 courses of antibody therapy could be given. Patients received up to 4 doses of 131I anti-CEA. The nadir platelet count was related to the half-life of 131I anti-CEA in blood. Thrombocytopenia limited the amount of 131I anti-CEA that could be given and determined the interval between treatments. Effective suppression of the anti-antibody response is possible and this study has determined that myelosuppression is the principal obstacle to repeated therapy with radiolabelled antibody.

Adult↗

Expression of slow and fast myosin heavy chains in overload muscles of the developing rat.

The present study examines the developmental accumulation of slow myosin heavy chain in the extensor digitorum longus, soleus and plantaris muscles of rats after early post-natal imposition of mechanical overload by removal of synergistic muscles. The proportions of slow and fast myosin heavy chain were measured in each muscle by ELISA. Fibres expressing slow myosin were examined immunocytochemically using a monoclonal antibody specific for slow MHC. Between 30 and 60 days of age, MHC increases by 15% (p less than 0.001) in the soleus and by 27% (p less than 0.001) in the plantaris of normally developing, unoperated animals. The effect of overload on the soleus and plantaris is to accelerate the rate of increase in slow MHC accumulation so that levels are respectively 16 and 39% higher than controls by 30 days of age (p less than 0.001). By 60 days, the control soleus and plantaris attain levels of slow MHC roughly equivalent to their overloaded counterparts. In overloaded plantaris the increase in levels of slow myosin does not occur at the expense of fast myosin expression. In the EDL there is a normal developmentally regulated decrease in slow MHC accumulation, reflected by a 40% decrease in levels of slow MHC (p less than 0.0001) and a 50% decrease in the number of slow fibres (p less than 0.001), between 30 days and 20 weeks of age. This elimination of slow myosin accumulation in the EDL is unimpeded by chronic overload. Thus, muscles react to mechanical overload in a tissue specific manner.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗

The value of radioimmunoguided surgery in first and second look laparotomy for colorectal cancer.

Radioimmunoguided surgery (RIGS) using an anti-CEA (A5B7) monoclonal antibody has been assessed in 52 patients (43 primary excisions and nine second look procedures) undergoing surgery for colorectal carcinoma. The antibody localized in 97.8 percent of primary tumours and in 88.8 percent of the principal tumor in second look procedures. Additional information concerning the extent of primary tumor was obtained in 11 of 43 patients (25.5 percent) undergoing excision of primary carcinoma and five of nine patients (55 percent) in the second look series. Incorrect information was obtained about the extent of the primary tumour in six patients (11.3 percent), whereas no incorrect information was obtained during second look procedures. RIGS correctly predicted the subsequent Dukes' staging in 77 percent of first look cases (sensitivity 65 percent, specificity 90 percent), although accurate identification of individual nodes was impossible. The technique influenced the surgical procedure performed in 2 of 43 cases (4.6 percent) in primary surgery and in three of nine patients undergoing second look laparotomy (33 percent). RIGS in primary colorectal carcinoma may provide additional information concerning extent of locally advanced tumors in particular and the principle that the subsequent surgery may be influenced has been established. The technique appears to have a greater role in second look procedures where it may help determine the extent of recurrent tumour. Larger follow-up series are required to define how the additional information provided by this technique may best be exploited.

Aged↗

Metabolic and contractile protein expression in developing rat diaphragm muscle.

Progressive changes in myosin isozyme expression and in energy-generating enzyme activities were followed in the diaphragm and, for comparison, in axial and appendicular muscles of rats from 18 d gestation to maturity. Native myosins were characterized by pyrophosphate gel electrophoresis. Myosin heavy-chain (MHC) isozymes were measured with ELISA using monoclonal antibodies and were localized by immunocytochemistry. RNA transcripts for the MHCs were demonstrated on Northern blots and by RNase protection assays. Quantitative activities of malate dehydrogenase (MDH), beta-hydroxyacyl CoA dehydrogenase (beta OAC), 1-phosphofructokinase (PFK), lactate dehydrogenase (LDH), creatine kinase (CK), and adenylokinase (AK) were measured in muscle homogenates and in individual fibers by fluorometric pyridine nucleotide-dependent assays. Compared to limb muscles, expression of neonatal myosin in the diaphragm is precocious. Neonatal MHC mRNA is prominent in the diaphragm at 19 d gestation, and neonatal myosin is the major MHC isoform present at birth. Slow and fast IIa MHCs are also present at birth. Transcripts for IIa MHC are detectable in the diaphragm at 21 d gestation and are upregulated at birth. Comparable signal for IIa MHC mRNA is not found in the gastrocnemius until 10 d postpartum. Adult fast IIb MHC mRNA was detected only as a faint signal at 30-40 d in the diaphragm and then disappeared. Results indicate that a separate phenotype, the IIx type, matures late in diaphragmatic development. The activities of enzymes representing all of the major energy pathways are higher in the fetal diaphragm than in the fetal hindlimb muscles. For example, beta OAC had sixfold higher activity in the diaphragm than in the extensor digitorum longus (EDL) muscle at birth, activity in the diaphragm than in the extensor digitorum longus (EDL) muscle at birth.

Aging↗

Antagonistic effects of chronic low frequency stimulation and thyroid hormone on myosin expression in rat fast-twitch muscle.

This study investigates effects of chronic low frequency stimulation (CLFS) on myosin heavy (MHC) and light chain (MLC) expression in fast-twitch muscles in hypothyroid, euthyroid, and hyperthyroid rats. The changes at both the mRNA and protein level indicated antagonistic effects of thyroid hormone and CLFS: under euthyroid conditions, CLFS mainly elicited a MHCIIb----MCHIId----MHCIIa transition. Whereas CLFS did not induce the slow MHCI in the euthyroid state, this isoform was present in the hypothyroid state and was further enhanced with CLFS indicating the suppressive effect of thyroid hormone to be stronger than the inductive influence of CLFS. Hyperthyroidism alone suppressed the expression MHCIIa and enhanced a MHCIId to MHCIIb transition. This shift to the faster MHC isoforms was only partially counteracted by CLFS. Thus, it appeared that thyroid hormone had a graded suppressive effect on the expression of MHC isoforms in the order MHCIId less than MHCIIa less than MHCI. Elevated neuromuscular activity partially counteracted these hormone effects. Changes in MLC mRNAs were consistent with those in the MHC pattern, i.e. increases or decreases in MHCIIb led to corresponding changes in the expression of MLC3f. A similar relationship existed for the slow MHCI and the slow MLC isoforms.

Animals↗

The human embryonic myosin heavy chain. Complete primary structure reveals evolutionary relationships with other developmental isoforms.

We have isolated a single 6021-nucleotide cDNA fragment encoding the full length of the myosin heavy chain (MHC) isoform initially expressed in developing human limb muscle. The corresponding transcript is expressed in fetal, but not adult, human muscle, and the corresponding gene maps to human chromosome 17. Comparison of the full length nucleotide sequence with that of the orthologous rat gene transcript reveals 74, 90, and 80% similarities in the 5'-untranslated, coding, and 3'-untranslated regions, respectively. To precisely quantitate the degree of nucleotide sequence divergence between the human embryonic and other developmentally regulated MHC gene transcripts, we utilize the algorithm of Perler et al. (Perler, F., Efstratiadis, A., Lomedico, P., Gilbert, W., Kolodner, R. & Dodgson, J. (1980) Cell 20, 555-566) and make use of the codon-for-codon register attainable in alignments of the MHC rod encoding cDNA fragments. The results allow reconstruction of the order and relative timing of certain gene duplication events involved in the evolution of the multimembered mammalian MHC loci. By this analysis, the principal sarcomeric MHC gene expressed in the 14-day chick embryo is shown to be more distantly related to the mammalian embryonic MHC genes than to those expressed peri- and postnatally. Attention is focused on regional patterns of MHC sequence conservation, ordered with reference to the topology of our phylogenetic tree. We present a composite map depicting the deduced evolutionary age of various primary structural subdomains of the human embryonic MHC.

Algorithms↗