Tracheal Agenesis: One Hospital's Nursing Experience With This Rare Airway Anomaly Case Report

BACKGROUND

Tracheal agenesis is a rare and often fatal congenital anomaly that occurs early in fetal development. Tracheal agenesis occurs in one in 50,000 to 100,000 live births. This case study describes the nursing aspect of caring for this type of patient.

CLINICAL FINDINGS

Airway anomalies in neonates can be diagnosed immediately at birth or later when the infant develops respiratory distress or respiratory failure. Diagnosis and management of tracheal agenesis is difficult and a complex problem requiring a multidisciplinary medical team's expert approach for its treatment.

PRIMARY DIAGNOSIS

Respiratory distress syndrome versus tracheoesophageal fistula was suspected.

INTERVENTIONS

The infant quickly decompensated, requiring intubation and eventual transfer to our tertiary care center for further evaluation of a possible airway anomaly. Because of deteriorating status, surgery was performed, and it was discovered the patient had tracheal agenesis, requiring the development of a 3-dimensional trachea specific for this patient.

OUTCOMES

This article describes the nursing aspect of caring for this type of patient.

PRACTICE RECOMMENDATIONS

This article describes the success of nursing interventions and teamwork among nursing and the multidisciplinary team for the successful discharge of this patient home to her family.

Gendered Consequences of COVID-19 Among Professional Tennis Players

The COVID-19 pandemic increased the risk of travelling, working, and participating in public events. To test whether there were gendered differences in the response to COVID-19, we examine the behavior of male and female professional tennis players. We use data from major tennis tournaments which included a rather large number of athletes withdrawing from play. After controlling for past performance, wealth, and other relevant player attributes, we find that female tennis players were more likely to withdraw. This suggests that high-earning women may have greater risk aversion, especially related to COVID-19, than their male counterparts. Importantly, women were more risk-averse when it comes to international travel.

Development of a method for treating lower-eyelid carcinomas using superficial high dose rate brachytherapy

In this study, a method was developed for delivering high dose rate (HDR) brachytherapy treatments to basal cell carcinomas (BCCs) as well as squamous cell carcinomas (SCCs) of the lower eyelid via superficial catheters. Clinically-realistic BCC/SCC treatment areas were marked in the lower-eyelid region on a head phantom and several arrangements of catheters and bolus were trialled for treating those areas. The use of one or two catheters of different types was evaluated, and sources of dosimetric uncertainty (including air gaps) were evaluated and mitigated. Test treatments were planned for delivery with an iridium-192 source, using the Oncentra Brachy treatment planning system (Elekta AB, Stockholm, Sweden). Dose distributions were evaluated using radiochromic film. The proposed method was shown to be clinically viable, for using superficial HDR brachytherapy to overcome anatomical difficulties and create non-surgical treatments for BCC and SCC of the lower eyelid.

Pilot study to assess measures to be used in the prospective audit of the management of foot ulcers in people with diabetes

AIM

To design and test a methodology for assessing aspects of the management of foot disease in diabetes.

METHODS

A national working group devised pilot datasets that may be used to document the process of management of active ulceration. Participating volunteer specialist units throughout England were required to characterize newly presenting people with diabetic foot ulcers using a standard questionnaire comprising the dataset and to document outcomes at 6 and 12 months. Semi-structured interviews were later conducted with the volunteers at the units.

RESULTS

A total of 23 units recorded baseline data on 652 people with incident foot ulcers; valid outcome data were available for 541 people (83.0%). Of the 541 index ulcers, 351 (64.9%) healed within 24 weeks, with a median time to healing of 63 days. Ulcer site and depth and peripheral arterial disease were associated with differing ulcer healing rates. By contrast, baseline demographic characteristics were not independently associated with healing. These were used to calculate a standardized case-mix adjusted healing ratio. In most units data collection took < 10 min per person, but participants reported that the burden of local data collection was still excessive.

CONCLUSION

This study confirmed the feasibility of routine multi-unit comparative assessment of care of the foot in diabetes, including the generation of meaningful service reports, but for general use the burden of local data collection will need to be reduced (e.g. by using linkage to existing national data collections).

A collaborative approach to advance student research at the University of Southern California

The continued advancement of oral health and science relies upon the cultivation of a student's interest in research. The Student Research Group at the Ostrow School of Dentistry of the University of Southern California is working to increase student involvement in research and develop future academic leaders. This study aims to, through student surveys, quantitatively evaluate students' involvement in research, students' interest in participating in research and to identify specific barriers students feel challenge their ability to participate in research.

Development and evaluation of a standardized registry for diabetes in pregnancy using data from the Northern, North West and East Anglia regional audits

OBJECTIVES

To develop and evaluate a standardized data set for measuring pregnancy outcomes in women with Type 1 and Type 2 diabetes and to compare recent outcomes with those of the 2002-2003 Confidential Enquiry into Maternal and Child Health.

METHODS

Existing regional, national and international data sets were compared for content, consistency and validity to develop a standardized data set for diabetes in pregnancy of 46 key clinical items. The data set was tested retrospectively using data from 2007-2008 pregnancies included in three regional audits (Northern, North West and East Anglia). Obstetric and neonatal outcomes of pregnancies resulting in a stillbirth or live birth were compared with those from the same regions during 2002-2003.

RESULTS

Details of 1381 pregnancies, 812 (58.9%) in women with Type 1 diabetes and 556 (40.3%) in women with Type 2 diabetes, were available to test the proposed standardized data set. Of the 46 data items proposed, only 16 (34.8%), predominantly the delivery and neonatal items, achieved ≥ 85% completeness. Ethnic group data were available for 746 (54.0%) pregnancies and BMI for 627 (46.5%) pregnancies. Glycaemic control data were most complete-available for 1217 pregnancies (88.1%), during the first trimester. Only 239 women (19.9%) had adequate pregnancy preparation, defined as pre-conception folic acid and first trimester HbA(1c) ≤ 7% (≤ 53 mmol/mol). Serious adverse outcome rates (major malformation and perinatal mortality) were 55/1000 and had not improved since 2002-2003.

CONCLUSIONS

A standardized data set for diabetes in pregnancy may improve consistency of data collection and allow for more meaningful evaluation of pregnancy outcomes in women with pregestational diabetes.

Fruit and vegetable intake and knowledge increased following a community-based intervention in older adults in Georgia senior centers

Our purpose was to evaluate a community-based fruit and vegetable intervention conducted in rural and urban areas of Georgia. Participants were a convenience sample from Georgia senior centers that completed a pre-test, the intervention, and a post-test (N = 558, mean age = 75, 83% female, 47% white, 53% black). The 4-month intervention had eight sessions focused on practical ways to increase intake of fruits and vegetables at meals and snacks and included physical activity. Pre- and post-tests examined self-reported intakes of fruits and vegetables at breakfast, lunch, the evening meal, and snacks, knowledge of recommended intakes, and barriers to intake. Following the intervention, the number of participants reporting consumption of at least 7 servings of fruits and vegetables daily increased by 21-percentage points (P < or = 0.001), knowledge that 7 to 10 servings of fruits and vegetables are recommended daily (for 1,600 to 2,200 calories) increased from 7% to 57% (P < or = 0.001), and three barriers to fruit and vegetable intake decreased (P < or = 0.05): "difficulties with digestion," "too many are recommended," and "too much trouble." Regression analyses indicated that increased intake following the intervention was independently associated with living in more urban rather than rural areas, improved knowledge of intake recommendations, decrease in perception of cost as a barrier, and increase in digestive problems as a barrier (P < or = 0.05). These results provide an evidence base for the effectiveness of this community intervention for improving knowledge and intake and decreasing barriers to fruit and vegetable intake in older adults.

Physical activity and physical function improved following a community-based intervention in older adults in Georgia senior centers

We evaluated a community-based physical activity intervention in Georgia senior centers. Participants were a convenience sample that completed the pre-test only (n = 592), or the pre-test, the intervention, and a post-test (n = 418, 98% aged 60 and older, mean age = 75, 83% female, 56% black). The 4-month physical activity intervention, based on the Health Belief Model, included 16 sessions that focused on educator-led chair exercises, promotion of walking, using a pedometer, and recording daily steps. Pre- and post-tests assessed physical activity and physical function, categorized as poor, moderate, or good (Short Physical Performance Battery). Following the intervention, participants improved their physical function (good physical function at pre-test vs. post-test: 16.5% vs. 25.3%, P < or = 0.001), increased minutes of physical activity by 26% (P < or = 0.001) and step counts by 29% (P < or = 0.0001, sub-sample, n = 95), and decreased reports of "it's not safe" as a barrier to physical activity (P < or = 0.05). Increased physical activity (P < or = 0.01) was associated with improved physical function following the intervention. The results of this evaluation provide an evidence base for the effectiveness of this community intervention for improving physical activity and physical function in older adults.

Relationship among respondent ethnicity, ethnic identity, acculturation, and homeless status on a homeless population's functional status

This study investigated the relationship of homeless status, ethnic identity, respondent ethnicity (African American, Latino, Native American, and Anglo), and Latino, Anglo, and Mexican American orientation on the functional impairment (Behavior and Symptom Identification Scale, BASIS-32; S. V. Eisen, 1996) of 355 homeless men and women who were interviewed in Pomona, California. Multivariate analyses of variance results indicated that respondent ethnicity was related to several BASIS-32 subscales. Specifically, Anglo and African American homeless adults had greater functional impairment than did Latino or Native American respondents. In addition, high Anglo orientation among chronically homeless Latino respondents, with low ethnic identity was associated with higher levels of functional impairment on the BASIS-32 Psychosis subscale. The implications of these findings are discussed.

Effects of racial match on Asian American mental health consumer satisfaction

This study investigated the effects of consumer-provider racial match on consumer service satisfaction and treatment outcomes (i.e., Client Satisfaction Questionnaire and GAF-Posttest) of 96 outpatient consumers, 66 of whom were adults and 30 of whom were parent/caregivers of child consumers. Data was obtained by telephone interviews over a 6-week period. After controlling for four other variables, client satisfaction was higher for racially matched consumers. Racially matched child consumers also had higher GAF-Posttest scores. Implications of these findings are discussed.

Mapping MHC-encoded susceptibility and resistance in primary sclerosing cholangitis: the role of MICA polymorphism

BACKGROUND & AIMS

Recent studies suggest that major histocompatibility complex-encoded susceptibility to primary sclerosing cholangitis (PSC) maps to the HLA B-TNFA region on chromosome 6p21.3.

METHODS

The present study uses a standard polymerase chain reaction protocol to investigate the 16 common alleles of the MICA locus as candidates in 2 patient populations (King's College Hospital, London, and John Radcliffe Hospital, Oxford).

RESULTS

The MICA*002 allele was found in 4 of 62 (6.4%) patients and none of 50 patients vs. 41 of 118 (35%) controls (pc = 0.00018, odds ratio [OR] = 0.12, and P = 0.0000016, OR = 0.0, respectively). Overall, the MICA*008 allele was more common in PSC (gene frequency 66% vs. 48% of controls, P = 0.0023, OR = 2.11). However, unlike MICA*002 in which the difference was a result of the absence of MICA*002 heterozygotes, the MICA*008 association may be caused by an increased frequency of MICA*008 homozygosity in patients (58% vs. 22%, pc = 0.000015, OR = 5.01 and 58% vs. 22%, P = 0.0000056, OR = 4.51, respectively). Though MICA*008 is found on the ancestral 8.1 haplotype, stratification analysis indicates that this association is independent of B8 and other HLA haplotypes associated with PSC.

CONCLUSIONS

The MICA*002 allele has a strong dominant effect in reducing the risk of PSC, whereas the increased risk of disease associated with MICA*008 may be a recessive effect requiring 2 copies of the MICA*008 allele.

Epidemiologic and biologic characterization of a cohort of human immunodeficiency virus type 1 highly exposed, persistently seronegative female sex workers in northern Thailand. Chiang Mai HEPS Working Group

Characterization of persons highly exposed to human immunodeficiency virus (HIV)-1 who remain uninfected may help define protective immunity. Seventeen HIV-1-seronegative Thai female sex workers (CSWs) with epidemiologic evidence of exposure to HIV-1 were studied for humoral immune responses and phenotypic and genotypic analyses of HLA class I and CCR5 allelic profiles. Infected CSWs and low-risk HIV-1-seronegative Thai women were controls. Highly exposed, persistently seronegative (HEPS) CSWs did not differ from HIV-infected CSWs in HIV risks, condom use, or sexually transmitted diseases. Significant differences were seen in humoral immune responses: gp160-specific IgA responses were detected in cervicovaginal lavage fluids in 6 of 13 HEPS CSWs but 0 of 21 seronegative subjects. All women had wild-type CCR5. HEPS CSWs were more likely to have the HLA-B18 phenotype and genotype than were matched controls (corrected P=.018). Epidemiologic exposure to HIV-1 without apparent infection, an unusual distribution of HLA class I alleles, and HIV-1 gp160-specific IgA responses suggest a biologic basis for this phenomenon.

Mental health. Making the right links

Intensive care management has not been widely adopted, partly because of the initial costs involved. Control of inpatient beds is crucial to successful initiatives. Implementing this approach in part of Newport, including appointing a link nurse who liaises with acute and community teams, has led to reduced bed use.

Physiologic and pathologic alterations associated with ultrasonically generated shock waves

Kidneys of 25 dogs were treated with ultrasonic shock waves and examined for both physiologic and pathologic changes. The number of pulses ranged from 2,000 to 8,000. The rate of the shock waves varied from one to 20 pulses per second. The difference in pulse rate did not affect the changes seen either acutely or in the delayed examination of the kidneys during the repair process. The physiologic and pathologic changes which occurred involved the renal tubule to a greater degree than the glomerulus. These alterations were resolving by one week following exposure to the shock waves.

Chronic doxorubicin induced cardiomyopathy in rabbits: mechanical, intracellular action potential, and beta adrenergic characteristics of the failing myocardium

STUDY OBJECTIVE

The aim was to assess myocardial, electrophysiological, and adrenergic changes caused by chronic administration of doxorubicin.

DESIGN

Doxorubicin induced cardiotoxicity was produced in three groups of rabbits by injecting doxorubicin 0.75 mg.kg-1 three times a week for 7, 9 and 11 weeks. There were 36 controls. All studies were conducted within 16 to 36 h after the last injection. Histological, mechanical, and action potential changes produced by doxorubicin were examined in vitro. The effects of doxorubicin on beta adrenergic receptors and cyclic adenosine monophosphate (AMP) generation in myocardial membrane preparations were also evaluated.

EXPERIMENTAL MATERIAL

145 New Zealand white rabbits, 2.4-2.7 kg, were used. After excision of the heart, a papillary muscle was used for mechanical studies, a portion of the septum for intracellular action potential studies, and the rest of the heart for histological or biochemical studies.

MEASUREMENTS AND RESULTS

Histological studies showed widespread myocardial damage that became more severe as the cumulative doses increased. Right ventricular papillary muscles of doxorubicin treated rabbits had lower total tension (1.5 v 3.3 g.mm-2 for controls, p less than 0.05) and dT/dt, shorter contraction duration, and lower velocity of shortening than the control muscles under all loading conditions. The changes progressed as the cumulative doxorubicin dose increased. Action potential duration was shorter in the doxorubicin treated groups (APD50 = 76 v 62 ms for controls, p less than 0.01), although resting action potential amplitude was normal. Tension-frequency response (6-36 stimuli.min-1) and response to increasing calcium concentrations (2.54-6.32 mM) were attenuated in the doxorubicin group. Percent change in tension and dT/dt in response to noradrenaline (50 microM), isoprenaline (20 microM), or dibutyryl cyclic AMP (40 mM), was increased in the doxorubicin group v controls (300-600% v 100-200% respectively), despite chronic increase in circulating catecholamines, depletion of myocardial catecholamines, and no change in beta adrenergic receptor number or affinity. The apparent increase in beta adrenergic responsiveness in the doxorubicin group may have been partly due to decreased basal cyclic AMP production (13 v 31 pMol.mg-1 protein.min-1, p less than 0.01), although maximum catecholamine stimulated cyclic AMP production was only mildly decreased (251 v 315 pMol.mg-1 protein.min-1, p less than 0.05). CONCLUSIONS - The subacute effects of chronic doxorubicin become progressively more marked as the cumulative dose increases, and there are significant differences in the myocardial characteristics between this chronic model and other models of heart failure. These differences may be related to the cytotoxic effects of doxorubicin on membranes and membrane bound enzymes.

Mechanical properties of papillary muscle in cardiac failure: importance of pathogenesis and of ventricle of origin

In an attempt to better understand what causes impairment of failing myocardium, the mechanical characteristics of papillary muscles from three different models of congestive heart failure were compared at varying stages of hypertrophy and failure: adriamycin cardiotoxic rabbit, cardiomyopathic hamster and infra-renal aorto-caval shunted dog. Except for right ventricular muscles from the shunted dogs, in all groups there was a significant decrease in total twitch tension, +dT/dt, -dT/dt, Vmax, +dL/dt, and -dL/dt. However, there were major differences in twitch duration between the three models with time to attain peak tension and peak shortening and time to attain half tension decline decreasing in right ventricular papillary muscles from adriamycin rabbits but increasing in right ventricular papillary muscles from shunted dogs and no change occurring in left ventricular papillary muscles from cardiomyopathic hamsters or shunted dogs. Load dependence as assessed by time to relaxation index for 30% afterload contractions was decreased in all but right ventricular muscles from shunted dogs. These results indicate that despite some common characteristics, major differences exist between papillary muscles from different models of congestive heart failure depending on the pathophysiological process involved and the ventricle of origin.

Effects of flurazepam on sleep, arousal threshold, and the perception of being asleep

This study examined the effects of flurazepam on arousal threshold and on quality of sleep during nights in which arousal threshold studies were performed. Ten patients with subjective insomnia received 30 mg flurazepam or placebo on nights in which arousal thresholds in response to electronic tones or a recording of the subjects' names were determined. Arousal thresholds differed across waking and sleep stages, but there was less difference in response to the subjects' names than to electronic tones. Flurazepam raised arousal thresholds to both stimuli, but did not selectively influence response in any individual sleep stage. Flurazepam did not alter subjects' estimates of elapsed time or duration of sleep between tests.

Simultaneous labelling of basal lamina components and acetylcholinesterase at the neuromuscular junction

A double labelling technique has been developed which permits the concomitant localization of basal lamina constituents together with acetylcholinesterase in mouse skeletal muscles. First, using the protein A-gold technique, type IV collagen and laminin were revealed on basal laminae ensheathing skeletal muscle fibres. The immunolabelling for both proteins was higher in synaptic than extrasynaptic regions. At synaptic sites the anti-type IV collagen immunolabelling exhibited an asymmetry; it was more intense on the portion of basal lamina closest to the postsynaptic membrane, whereas the anti-laminin immunolabelling was more uniformly distributed. It was also observed that the laminin immunoreactivity associated with Schwann and perineural cells was higher than that of skeletal muscle fibres. Secondly, the two basal lamina antigens were revealed simultaneously with another synaptic protein, acetylcholinesterase, using a refined cytochemical technique prior to the immunolabelling. The cytochemical reaction, which facilitates the location of endplates, did not alter the immunolabelling pattern. This double labelling procedure permits ready comparison of the distributions of type IV collagen and laminin with that of acetylcholinesterase, and may prove to be a useful approach in studies on synaptic components in developing and diseased muscle.

Acquired immunodeficiency syndrome in New York City. Evaluation of an active surveillance system

In January 1983, the New York City Department of Health initiated an active surveillance program for acquired immunodeficiency syndrome (AIDS) in 19 hospitals and a modified-active surveillance program in the remaining 69 hospitals. We reviewed hospital laboratory and autopsy records in 12 active surveillance hospitals and three modified-active surveillance hospitals six months later. Patients who had opportunistic diseases characteristic of AIDS diagnosed in 1982 (before active surveillance) and 1983 (after implementation of active surveillance) were matched against health department AIDS surveillance reports. For the 16 months we evaluated, 96% of patients identified with AIDS in the 12 active surveillance hospitals and 100% of those in the three modified-active surveillance hospitals had been reported to the health department. The delay between diagnosing a case and reporting it to the health department significantly decreased between 1981 and the first six months of 1983 in all hospitals. The proportion of cases reported within one month of diagnosis increased from 45% to 69% during this period. We conclude that the current surveillance program for AIDS in New York City is effective and that case reporting is sufficiently complete for accurate analysis of disease trends.

Abuse of a fire-extinguishing agent and sudden death in adolescents

Two cases of abuse of bromochlorodifluoromethane (BCF - a fire-extinguishing agent) by inhalation are reported. In the first case, a 15-year-old youth presented in ventricular fibrillation; the second youth was dead on arrival at hospital. Port-mortem toxicological investigations confirmed BCF inhalation in the latter patient. Management of the surviving patient included cardioversion, controlled mandatory hyperventilation, intravenous infusions of mannitol, and barbiturate protection against cerebral ischaemia. He had completely recovered after eight days. Community agencies report that BCF inhalation occurs frequently on the Gold Coast, Queensland. This behaviour can be associated with sudden death from ventricular arrhythmias after cardiac sensitization to endogenous adrenaline. The "lone sniffer" is at greatest risk, and identification of such individuals may prevent a fatal outcome.

The ontogeny of seizures induced by leucine-enkephalin and beta-endorphin

Rats ranging in postnatal age from 6 hours to 28 days were implanted with cortical and depth electrodes as well as an indwelling cannula in the lateral ventricle. We then administered varying amounts of the opiate peptides leucine-enkephalin and beta-endorphin intracerebroventricularly with continuous electroencephalographic monitoring. Leucine-enkephalin produced electrical seizure activity in rats as young as 2 days. beta-Endorphin administration was associated with seizures at the fifth postnatal day, with a high incidence of apnea resulting in death in animals as young as 6 hours. An adult seizure response to beta-endorphin and leucine-enkephalin was seen at 15 and 28 days of age, respectively. Naloxone blocked the seizure produced by these opiate peptides in all age groups. The data indicate that the opiate peptides are potent epileptogenic compounds in developing brain, that seizures induced by leucine-enkephalin differ from those caused by beta-endorphin, and that petit mal-like seizure activity can be an adult response in the rodent.

Dedifferentiation of a transplantable papillary thyroid carcinoma over a 15-year period

Fischer 344 rats on a prolonged low-iodine diet developed thyroid nodules which were transplanted subcutaneously into 33 thyroidectomized rats. One graft took and gave a papillary carcinoma. Serially transplanted syngeneically at 3- to 4-month intervals, it became autonomous in third generation hosts. With electron microscopy examination it was microfollicular in year 8 and anaplastic, with totally unpolarized epithelial cells, in year 15. Basement membrane present in year 1 was no longer visible in specimens of years 8 and 15. Tight and gap junctions still present in year 8 were absent in year 15, although a few desmosomes persisted. From years 8 to 15, free ribosomes and microfilaments became more frequent, whereas the number of mitochondria and the development of the Golgi complex declined.

Recognition and regulation of progenitor marrow elements by NK cells in the mouse

The cytotoxicity of radiolabelled YAC-1 target cells by natural killer (NK) cells from the spleens of immunocompetent CBA mice is inhibited by unlabelled YAC-1 competitor cells, but not by resting bone marrow from syngeneic or allogeneic adult mice. Rapidly proliferating haemopoietic cells recovered from the spleens of lethally irradiated, bone marrow-reconstituted CBA mice, however, compete strongly in the NK assay. The competitive ability of early regenerating marrow correlates with the presence of an increased percentage of morphologically immature cells of mixed lineages. Competition declines in reconstituted spleens recovered more than 10 days after engraftment, as the proportion of immature elements falls towards that of resting marrow. Although the numbers of unlabelled YAC-1 cells required to produce equivalent competition of unstimulated and interferon-activated NK killing are similar, 10 times fewer regenerating marrow competitors compete cytotoxicity by unstimulated NK effectors to the same degree as interferon activated cells. The numbers of granulocyte-macrophage colonies formed in soft agar by regenerating marrow is also influenced by prior incubation of the marrow cells with NK effector populations. Spleen cells from homozygous athymic mice produce the same effect as cells from their heterozygous littermates. These data suggest that NK cells recognize and regulate the differentiation of progenitor elements within the marrow.

Acetylcholinesterase content in both motor nerve and muscle is correlated with twitch properties

The activity and molecular forms of acetylcholinesterase (AChE) were studied in the rat soleus muscle and its nerve, as compared to their fast-twitch counterparts. The soleus muscle and its nerve exhibited both significantly lower AChE activity and less of the G4 (10S) molecular form. In addition, the soleus muscle displayed a specific increase in the A8 (13S) and A4 (8.8S) asymmetric forms, not seen in any of the fast-twitch muscles examined. These results indicate that the AChE content of a muscle and its nerve are linked and depend on the twitch properties, and that the slow-twitch muscle is characterized by a specific set of AChE molecular forms.

Enhanced noradrenaline response in cardiomyopathic hamsters: possible relation to changes in adrenoceptors studied by radioligand binding

To assess the possible relation between catecholamine responses and adrenoceptor affinity and density, we compared the effect of noradrenaline, isoprenaline and ouabain on the right ventricular muscle strips from normal and cardiomyopathic hamsters with alpha 1- and beta-adrenoceptor characteristics assessed by radioligand binding methods. At concentrations of 1.28, 2.56, 5.0 and 10 x 10 (-6) mol . litre (-1) noradrenaline raised isometric tension by 27 +/- 4, 39 +/- 5, 52 +/- 5 and 61 +/-6% in normal animals (n = 6). Corresponding increase of 65 +/- 8, 92 +/- 8, 109 +/- 9 and 115 +/- 10% occurred in cardiomyopathic hamsters (n=11, all P less than 0.02). The responses to isoprenaline (Emax =82%) and ouabain did not differ between the two groups of hamsters. [3H]-prazosin, a new radioligand, and [-3H]-dihydroalprenolol were used to assess alpha 1- and beta-adrenoceptors in cardiac membranes. By Scatchard analysis, the KD values for both ligands did not differ between normal and cardiomyopathic hamsters, but the maximum number of binding sites was higher in the myopathic group: 5.5 vs 3.9 fmol . mg [-1] protein for [3H]-prazosin and 27 vs 20 fmol . mg [-1] protein for [-3H]-dihydroalprenolol (both P less than 0.05). Histochemically, oxidative and glycolytic activity were normal but lysosomal acid phosphatase was high. Possible explanations for the raise response to noradrenaline in cardiomyopathic hamster include and increased concentration of noradrenaline in the synaptic cleft due to defective neuronal uptake and / or stimulation of an augmented population of alpha 1-(postsynaptic) adrenoceptors.