Effect of hypoxia exposure on the recovery of skeletal muscle phenotype during regeneration

Hypoxia impairs the muscle fibre-type shift from fast-to-slow during post-natal development; however, this adaptation could be a consequence of the reduced voluntary physical activity associated with hypoxia exposure rather than the result of hypoxia per se. Moreover, muscle oxidative capacity could be reduced in hypoxia, particularly when hypoxia is combined with additional stress. Here, we used a model of muscle regeneration to mimic the fast-to-slow fibre-type conversion observed during post-natal development. We hypothesised that hypoxia would impair the recovery of the myosin heavy chain (MHC) profile and oxidative capacity during muscle regeneration. To test this hypothesis, the soleus muscle of female rats was injured by notexin and allowed to recover for 3, 7, 14 and 28 days under normoxia or hypobaric hypoxia (5,500 m altitude) conditions. Ambient hypoxia did not impair the recovery of the slow MHC profile during muscle regeneration. However, hypoxia moderately decreased the oxidative capacity (assessed from the activity of citrate synthase) of intact muscle and delayed its recovery in regenerated muscle. Hypoxia transiently increased in both regenerated and intact muscles the content of phosphorylated AMPK and Pgc-1α mRNA, two regulators involved in mitochondrial biogenesis, while it transiently increased in intact muscle the mRNA level of the mitophagic factor BNIP3. In conclusion, hypoxia does not act to impair the fast-to-slow MHC isoform transition during regeneration. Hypoxia alters the oxidative capacity of intact muscle and delays its recovery in regenerated muscle; however, this adaptation to hypoxia was independent of the studied regulators of mitochondrial turn-over.

Effect of hypoxia exposure on the phenotypic adaptation in remodelling skeletal muscle submitted to functional overload

AIM

To determine whether hypoxia influences the phenotypic adaptation of skeletal muscle induced by mechanical overload.

METHODS

Plantaris muscles of female rats were submitted to mechanical overload following synergist ablation. After 3 days of overload, rats were exposed to either hypobaric hypoxia (equivalent to 5500 m) or normoxia. Muscles were collected after 5, 12 and 56 days of overload (i.e. after 3, 9 and 53 days of hypoxia). We determined the myosin heavy chain (MHC) distribution, mRNA levels of myocyte-enriched calcineurin-integrating protein 1 (MCIP1) to indirectly assess calcineurin activity, the changes in oxidative capacity from the activities of citrate synthase (CS) and cytochrome c oxidase (COX), and the expression of regulators involved in mitochondrial biogenesis (Pgc-1α, NRF1 and Tfam) and degradation (BNIP-3).

RESULTS

Hypoxia did not alter the fast-to-slow MHC shift and the increase in calcineurin activity induced by overload; it only transiently slowed down the overload-induced transition in MHC isoforms. Hypoxia similarly decreased CS and COX activities in overloaded and control muscles. Nuclear respiratory factor 1 (NRF1) and transcription factor A (Tfam) mRNA and BNIP-3 protein were not influenced by hypoxia in overloaded muscles, whereas Pgc-1α mRNA and protein contents did not correlate with changes in oxidative capacity.

CONCLUSION

Hypoxia is not a critical stimulus to modulate the fast-to-slow MHC transition associated with overload. Thus, the impairment of the fast-to-slow fibre shift often observed during post-natal development in hypoxia could be explained by the lower voluntary locomotor activity associated with hypoxia. Hypoxia alters mitochondrial oxidative capacity, but this adaptive response is similar in overloaded and control muscles.

Ambient hypoxia enhances the loss of muscle mass after extensive injury

Hypoxia induces a loss of skeletal muscle mass and alters myogenesis in vitro, but whether it affects muscle regeneration in vivo following injury remains to be elucidated. We hypothesized that hypoxia would impair the recovery of muscle mass during regeneration. To test this hypothesis, the soleus muscle of female rats was injured by notexin and allowed to recover for 3, 7, 14, and 28 days under normoxia or hypobaric hypoxia (5,500 m) conditions. Hypoxia impaired the formation and growth of new myofibers and enhanced the loss of muscle mass during the first 7 days of regeneration, but did not affect the final recovery of muscle mass at 28 days. The impaired regeneration under hypoxic conditions was associated with a blunted activation of mechanical target of rapamycin (mTOR) signaling as assessed by p70(S6K) and 4E-BP1 phosphorylation that was independent of Akt activation. The decrease in mTOR activity with hypoxia was consistent with the increase in AMP-activated protein kinase activity, but not related to the change in regulated in development and DNA response 1 protein content. Hypoxia increased the mRNA levels of the atrogene muscle ring finger-1 after 7 days of regeneration, though muscle atrophy F box transcript levels remained unchanged. The increase in MyoD and myogenin mRNA expression with regeneration was attenuated at 7 days with hypoxia. In conclusion, our results support the notion that the enhanced loss of muscle mass observed after 1 week of regeneration under hypoxic conditions could mainly result from the impaired formation and growth of new fibers resulting from a reduction in protein synthesis and satellite cell activity.

Pitfalls in target mRNA quantification for real-time quantitative RT-PCR in overload-induced skeletal muscle hypertrophy

Quantifying target mRNA using real-time quantitative reverse transcription-polymerase chain reaction requires an accurate normalization method. Determination of normalization factors (NFs) based on validated reference genes according to their relative stability is currently the best standard method in most usual situations. This method controls for technical errors, but its physiological relevance requires constant NF values for a fixed weight of tissue. In the functional overload model, the increase in the total RNA concentration must be considered in determining the NF values. Here, we pointed out a limitation of the classical geNorm-derived normalization. geNorm software selected reference genes despite that the NF values extensively varied under experiment. Only the NF values calculated from four intentionally selected genes were constant between groups. However, a normalization based on these genes is questionable. Indeed, three out of four genes belong to the same functional class (negative regulator of muscle mass), and their use is physiological nonsense in a hypertrophic model. Thus, we proposed guidelines for optimizing target mRNA normalization and quantification, useful in models of muscle mass modulation. In our study, the normalization method by multiple reference genes was not appropriate to compare target mRNA levels between overloaded and control muscles. A solution should be to use an absolute quantification of target mRNAs per unit weight of tissue, without any internal normalization. Even if the technical variations will stay present as a part of the intergroup variations, leading to less statistical power, we consider this method acceptable because it will not generate misleading results.

Blunting effect of hypoxia on the proliferation and differentiation of human primary and rat L6 myoblasts is not counteracted by Epo

OBJECTIVES

The aim of this study was to evaluate whether hypoxia and/or erythropoietin would be able to modulate proliferation/differentiation processes of rat and human myoblasts.

MATERIALS AND METHODS

Rat L6 and primary human myoblasts were grown in 21% or 1% O(2) in the presence or absence of recombinant human erythropoietin (RhEpo). Presence of erythropoietin receptors (EpoR) was assayed using RT-PCR and Western blotting techniques. Cell proliferation was evaluated by determining the doubling time and kinetics of cultures by counting cells. Cell differentiation was analysed by determining myogenic fusion index using antibodies against the myosin heavy chain. Expression of myogenin and myosin heavy chain (MHC) proteins were evaluated using the Western blotting technique.

RESULTS

After 96 h culture in growth medium for 2.5 and 9 h, doubling time of L6 and human primary myoblasts respectively, had increased in 1% O(2) conditions (P < 0.01). Kinetics of culture showed alteration in proliferation at 72 h in L6 myoblast cultures and at 4 days in human primary myoblasts. The myogenic fusion index had reduced by 30% in L6 myoblasts and by 20% in human myoblasts (P < 0.01). Expression of myogenin and MHC had reduced by around 50%. Despite presence of EpoR mRNA and protein, RhEpo did not counteract the effects of hypoxia either in L6 cells or in human myoblasts.

CONCLUSIONS

The data show that exposure to hypoxic conditions (1% O(2)) of rat and human myoblasts altered their proliferation and differentiation processes. They also show that Epo is not an efficient growth factor to counteract this deleterious effect.

A polysomnographic study of daytime sleepiness in myotonic dystrophy type 1

OBJECTIVES

To assess contributors to excessive daytime sleepiness (EDS) in myotonic dystrophy type 1 (DM1), to characterise subjects with sleep-onset REM periods (SOREMPs), and to verify whether self-reported instruments and respiratory function tests can predict multiple sleep latency test (MSLT) and sleep-disordered breathing.

METHODS

A sample of 43 DM1 patients without selection bias underwent polysomnography (PSG) for two consecutive nights and MSLT, completed a sleep diary and Epworth Sleepiness Scale (ESS), and were assessed for respiratory function and narcolepsy symptoms.

RESULTS

ESS scores (ES) > or =11 and MSLT mean sleep latency (MSL) < or =8 min were found in 21 (50.0%) and 19 (44.2%) subjects, and either in 30 (69.8%) subjects. ES did not relate to MSL. Subjects with subjective sleepiness (ES> or =11) reported more cataplexy-like and sleep paralysis symptoms, longer habitual sleep times, and higher sleep efficiency and REM sleep per cent than those without. Subjects with objective sleepiness (MSL< or =8 min) had a higher stage 4 sleep per cent. Subjects with > or =2 SOREMPs (25.6%) showed higher muscular impairment, lower MSL, higher ES, and more cataplexy-like symptoms than those with < or =1 SOREMP. Apnoea-hypopnoea index (AHI) > or =5, predominantly obstructive, was found in 37 (86.0%) subjects, and AHI >30 in 12 (27.9%). Neither subjective nor objective sleepiness could be explained by AHI, nor satisfactorily predicted by daytime respiratory abnormalities.

CONCLUSIONS

DM1 entails frequent EDS but with different phenotypes and distinct mechanisms involved. The high prevalence of daytime sleepiness and severe sleep apnoeas found in this study supports the routine use of clinical sleep interviews, PSG and MSLT in DM1, and emphasises the need for more randomised trials of psychostimulants.

Brain stem NO modulates ventilatory acclimatization to hypoxia in mice

The objective of our study was to assess the role of neuronal nitric oxide synthase (nNOS) in the ventilatory acclimatization to hypoxia. We measured the ventilation in acclimatized Bl6/CBA mice breathing 21% and 8% oxygen, used a nNOS inhibitor, and assessed the expression of N-methyl-d-aspartate (NMDA) glutamate receptor and nNOS (mRNA and protein). Two groups of Bl6/CBA mice (n = 60) were exposed during 2 wk either to hypoxia [barometric pressure (PB) = 420 mmHg] or normoxia (PB = 760 mmHg). At the end of exposure the medulla was removed to measure the concentration of nitric oxide (NO) metabolites, the expression of NMDA-NR1 receptor, and nNOS by real-time RT-PCR and Western blot. We also measured the ventilatory response [fraction of inspired O(2) (Fi(O(2))) = 0.21 and 0.08] before and after S-methyl-l-thiocitrulline treatment (SMTC, nNOS inhibitor, 10 mg/kg ip). Chronic hypoxia caused an increase in ventilation that was reduced after SMTC treatment mainly through a decrease in tidal volume (Vt) in normoxia and in acute hypoxia. However, the difference observed in the magnitude of acute hypoxic ventilatory response [minute ventilation (Ve) 8% - Ve 21%] in acclimatized mice was not different. Acclimatization to hypoxia induced a rise in NMDA receptor as well as in nNOS and NO production. In conclusion, our study provides evidence that activation of nNOS is involved in the ventilatory acclimatization to hypoxia in mice but not in the hypoxic ventilatory response (HVR) while the increased expression of NMDA receptor expression in the medulla of chronically hypoxic mice plays a role in acute HVR. These results are therefore consistent with central nervous system plasticity, partially involved in ventilatory acclimatization to hypoxia through nNOS.

Role of maximal heart rate and arterial O2 saturation on the decrement of VO2max in moderate acute hypoxia in trained and untrained men

We aimed to evaluate 1) the altitude where maximal heart rate (HR (max)) decreases significantly in both trained and untrained subjects in moderate acute hypoxia, and 2) if the HR (max) decrease could partly explain the drop of V.O (2max). Seventeen healthy males, nine trained endurance athletes (TS) and eight untrained individuals (US) were studied. Subjects performed incremental exercise tests at sea level and at 5 simulated altitudes (1000, 1500, 2500, 3500, 4500 meters). Power output (PO), heart rate (HR), arterial oxygen saturation (SaO (2)), oxygen uptake (V.O (2)), arterialized blood pH and lactate were measured. Both groups showed a progressive reduction in V.O (2max). The decrement in HR (max) (DeltaHR (max)) was significant from 1000 m for TS and 2500 m for US and more important in TS than US (at 1500 m and 3500 m). At maximal exercise, TS had a greater reduction in SaO (2) (DeltaSaO (2)) at each altitude. DeltaHR (max) observed in TS was correlated with DeltaSaO (2). When the two groups were pooled, simple regressions showed that DeltaV.O (2max) was correlated with both DeltaSaO (2) and DeltaHR (max). However, a multiple regression analysis demonstrated that DeltaSaO (2) alone may account for DeltaV.O (2max). Furthermore, in spite of a greater reduction in SaO (2) and HR (max) in TS, no difference was evidenced in relative DeltaV.O (2max) between groups. Thus, in moderate acute hypoxia, the reduction in SaO (2) is the primary factor to explain the drop of V.O (2max) in trained and untrained subjects.

The faculty portfolio: documenting the scholarship of teaching

The scholarship of teaching is considered an essential component of scholarship within academic settings. To promote the transfer of knowledge specific to the discipline of nursing, this category of scholarship must include inquiry into the practice of teaching, program development, and professional role modeling, in addition to excellence in teaching itself. Conveying what constitutes teaching scholarship in nursing may present special challenges for nurse faculty in the university setting. A faculty teaching portfolio is one mechanism for explicating, communicating, and enhancing the scholarship of teaching. The methodology for creating, improving, and maintaining a teaching portfolio includes analyzing the mission of the university, articulating a philosophy of teaching, deciding on goals and objectives, designing evaluative mechanisms, processing data, conducting a self-evaluation, applying new approaches, and revisiting and reflecting on the outcomes. Faculty teaching portfolios serve to display, communicate, and document the scholarship of teaching. The creative endeavors surrounding portfolio development are ongoing and recursive, necessitating self-reflection and new approaches. J Prof Nurs 17:180-186, 2001.

Relations between the stage of cell maturation and lactate transporter activities in rat neonatal muscle cells in culture

Lactate transport was investigated in newborn rat muscle cells in culture. The aim was to study the lactate transport function at two stages of cell differentiation in culture: (i) during the proliferative phase characterized by myoblasts and myotubes (MyB/MyT2) obtained after 2-3 seedings, (ii) when myotubes (MyT1) grow old in culture after 8-9 seedings. In both developmental stages MyB/MyT2, lactate was carried following a saturable and sigmoidal velocity curve: the Hill and the Scatchard plot analyses confirmed an allosteric or multisite mechanism of lactate transport with two classes of carriers: one of low and one of high affinity i.e., 8.6 and 0.95 mm, respectively, which are associated with high and low transport capacities (V(m)) i.e., 9.1 and 0.67 nm/min/mg, respectively. With MyT1, the velocity curve of lactate transport presented a hyperbolic profile, and the Hill plot analysis gave a Hill number near one suggesting that for cell aging in culture the decrease in cooperativity shows that lactate transport essentially occurs through the low affinity transport system. Inhibitor effects also contributed to evidence for at least two systems of transport. Results obtained from primary cells give evidence for the early activity of lactate transport system at the Myb/MyT2 stage and its evolution during cell aging in culture (MyT1). Sarcolemmal lactate transport in primary cultures of myocytes is accomplished by multiple carriers, neither of which are MCT1 or MCT2 as confirmed by immunoblots.

Food insecurity: consequences for the household and broader social implications

A conceptual framework showing the household and social implications of food insecurity was elicited from a qualitative and quantitative study of 98 households from a heterogeneous low income population of Quebec city and rural surroundings; the study was designed to increase understanding of the experience of food insecurity in order to contribute to its prevention. According to the respondents' description, the experience of food insecurity is characterized by two categories of manifestations, i.e., the core characteristics of the phenomenon and a related set of actions and reactions by the household. This second category of manifestations is considered here as a first level of consequences of food insecurity. These consequences at the household level often interact with the larger environment to which the household belongs. On a chronic basis, the resulting interactions have certain implications that are tentatively labeled "social implications" in this paper. Their examination suggests that important aspects of human development depend on food security. It also raises questions concerning the nature of socially acceptable practices of food acquisition and food management, and how such acceptability can be assessed. Guidelines to that effect are proposed. Findings underline the relevance and urgency of working toward the realization of the right to food.

Dietary patterns of adults in Québec and their nutritional adequacy

The purpose of this study was to identify dietary patterns among adults in Québec and to determine their relationship to nutritional adequacy of the diet. We used 24-hour food recall data on 2,104 adults from the Québec nutrition survey (1990). Nutritional adequacy was assessed based on the 1990 Nutrition Recommendations for Canadians; dietary patterns were assessed via a factor analysis of the 30 food groups consumed. The three major patterns identified ('high-energy density', 'traditional' and 'health-conscious') explained 18% of the variation in food intake. Only the 'health-conscious' pattern correlated positively with the four chosen indicators of nutritional adequacy. Generally, men scored positively on the 'high-energy density' and the 'traditional' pattern whereas women scored positively on the 'health-conscious' pattern. Aside from sex, scoring was most related to age and education. The use of these patterns to define and target nutrition interventions should be tested in the aim of improving the effectiveness of health promotion.

Lactate transport in L6 skeletal muscle cells and vesicles: allosteric or multisite mechanism and functional membrane marker of differentiation

Membrane lactate transport was studied in skeletal muscle cells and membrane vesicles from the L6 line in relation to in vitro myogenesis. In myoblasts, lactate was transported by simple diffusion and insensitive to classical inhibitors: a positive correlation between onset of creatine kinase activity and lactate transport in differentiated myotubes was observed and could be considered to be a functional marker of cell differentiation. In myotubes, complete analysis of the velocity curves (direct coordinates, Eadie-Scatchard plots, Hill plots) gave parameters showing that lactate was carried by an allosteric or multisite system. This was confirmed by using sarcolemmal vesicles and specific inhibitors. In whole cells, alpha-cyano-4-hydroxycinnamic acid (CIN) and parachloromercuribenzylsulphonic acid (pCMBS) inhibited the maximal velocity without modifying the global cooperativity of the system. The weak effect of 4,4'-diisothiocyanostilbene-2,2'-disulphonic acid (DIDS), which has a low affinity constant (Ki = 22.5 microM), implicated the monocarboxylate system rather than the anionic exchanger as a carrier system in muscle cells. CIN and DIDS exhibited one type of interaction with lactate carriers, and the curvilinear shape of the lactate Hill plot with or without inhibitors suggested that inhibitors were active at the same family of interaction sites and had a common range of affinities. The apparent competitive inhibition of pyruvate (Ki = 3.2 mM) did not modify the transport pathway of lactate in L6 myotubes. In conclusion, kinetic analysis of lactate transport in the presence or absence of inhibitors gave evidence for a multisite lactate carrier activity in myotubes composed of two systems at least, related to two or three isoforms of lactate carriers.

Lipids and stroke: a paradox resolved

BACKGROUND

Although dyslipidemia is a well established risk factor for coronary artery disease, its relationship to ischemic cerebrovascular disease has remained unclear, perhaps because of the heterogeneous nature of strokes.

METHODS

In a case-control study, we measured the serum concentrations of total cholesterol, low-density lipoprotein cholesterol, high-density lipoprotein cholesterol, serum triglycerides, and lipoprotein(a) levels and determined the apolipoprotein E phenotype and serum ferritin level in 90 consecutive systematically investigated patients with stroke or transient ischemic attack of atherothrombotic origin. Ninety age-, sex-, and community-matched subjects served as controls.

RESULTS

Plasma total cholesterol (5.99 vs 5.45 mmol/L [232 vs 211 mg/dL], P=.003), low-density lipoprotein cholesterol (3.96 vs 3.45 mmol/L [153 vs 133 mg/dL], P=.004), and serum triglyceride (2.09 vs 1.82 mmol/L [8] vs 70 mg/dL], P=.03) levels were significantly higher among the patients with atherothrombotic strokes and transient ischemic attacks than among the control subjects. The inverse was true for high-density lipoprotein cholesterol (1.07 vs 1.18 mmol/L [41 vs 46 mg/dL], P=.02) levels. No significant differences were found in lipoprotein(a) levels or in the distribution of apolipoprotein E phenotypes or allele frequency. Serum ferritin levels did not differ significantly between patients and control subjects.

CONCLUSIONS

Elevated low-density lipoprotein cholesterol and triglyceride levels are significant independent risk factors in patients with proven atherothrombotic cerebrovascular disease manifesting as stroke or transient ischemic attack. The level of stored serum iron, as reflected by serum ferritin levels, does not correlate with the presence of atherothrombotic cerebrovascular or coronary disease.

Alzheimer's disease: preliminary study of spatial distribution at birth place

Alzheimer's disease (AD) is a neurodegenerative disorder which is characterized by a progressive loss of memory and the alteration of cognitive functions. At least three chromosomal segments have been associated with early-onset AD in genetic linkage studies. These results argue for a certain degree of heterogeneity in the genetic origin of some forms of AD, although environmental risk factors cannot be ruled out in late-onset AD. In this preliminary study, we analyzed the geographical distribution of the birth places of a sample of 235 AD cases born in a defined region of Quebec (Canada), between 1895 and 1935. We wished to test the hypothesis that risk factors acting at, or around birth place and time play a role in the etiology of AD. The field of study was divided into rural and urban areas. A reference population of live births was used to compute a measure of odds ratio (OR). The OR results showed a statistically significant excess of AD cases in the rural area as compared to the reference population. When stratified for sex, the OR results showed a global excess of female AD cases in both the rural and the urban areas. For men, only the urban area presented a statistically significant deficit. We also analyzed the structures of the genealogical kinships of the rural and urban sub-groups. Although AD cases from the rural sub-group were more closely related to each other than those from the urban one, removal of the kin pairs from the OR analysis seemed to have little effect on the rural/urban distribution of cases. Therefore, the OR results would not appear to be due primarily to a difference in the kinship structures of the two sub-groups. This could mean that some risk factors for AD afflict women more strongly than men, the effect being different depending on the urban or rural origin. However, potential biases such as a higher rate of report for women, differential migration between birth places or a differential mortality ratio between sexes could produce spurious results in the direction of what we have observed in this preliminary study.

Research utilization: once-a-day temperatures for afebrile patients

CNSs AND OTHER Master's-prepared nurses are usually expected to lead research utilization (RU) efforts in organizations, but they often feel unprepared to do so. In this article, the need for clinical RU is discussed and ideas for implementation, using an adaptation of the Conduct and Utilization of Research in Nursing model, are described. The RU process is applied to research about once-a-day temperatures in afebrile patients. To assist nurses who are implementing research-based practice, we list studies that were used for the practice change, summarize the research base on the topic, and offer an example of clinical use of practice guidelines.

Season of birth and Alzheimer's disease: a population-based study in Saguenay-Lac-St-Jean/Québec (IMAGE Project)

The birth distribution of 399 cases of Alzheimer's disease (AD) identified in the region of Saguenay-Lac-St-Jean (Québec) was compared with that of: (a) the population currently living in the area; and (b) the population born during the same period in the same area. AD cases have been recruited since 1986 by the IMAGE Project. Cases and controls were grouped according to the month of birth and according to the day of birth using density estimation. Analyses showed a significant deficit of births in the month of May. We believe these preliminary results deserve further attention and we suggest two possible explanations that could lead to a deficit of AD births at specific periods during the year.

Genotypic and phenotypic characterization of Escherichia coli isolates from dogs manifesting attaching and effacing lesions

Thirteen Escherichia coli isolates from dogs manifesting attaching and effacing lesions were characterized genetically with respect to the presence of the following virulence determinants associated with human enteropathogenic E. coli (EPEC): eaeA, encoding the outer membrane protein intimin; eaeB, which is necessary for inducing signal transduction; bfpA, encoding the bundle-forming pilus; and the EAF (stands for EPEC adherence factor) plasmid. These isolates were also analyzed phenotypically with respect to adherence to mammalian cells in vivo and in vitro. Nine of these 13 isolates were found to be eaeA positive by PCR: four of these nine were eaeB positive. The 5' end, but not the 3' end, of the eaeA gene was amplified by PCR when primers derived from the eaeA gene of EPEC were used. Six and eight of these 13 isolates were found to be bfpA positive and EAF positive, respectively. The bfpA gene and EAF locus were found on high-molecular-weight plasmids, whereas the eaeA and eaeB genes were chromosomally located when present. Only one canine E. coli isolate, 4221, which was positive for eaeA, eaeB, bfpA, and EAF, adhered to HEp-2 cells in a localized manner and was positive in the fluorescence actin staining test. The nine eaeA-positive isolates adhered to the mucosal surface of piglet ileal explants and induced some microvillus effacement. However, when tested in experimentally inoculated gnotobiotic piglets, isolate 4221 did not induce attaching and effacing lesions at any level of the intestinal tract. Our results indicate that canine E. coli isolates associated with attaching and effacing lesions share some properties with human EPEC but form a heterogeneous group.

Relation between infant feeding and infections during the first six months of life

We assessed the effect of the method of feeding on respiratory and gastrointestinal illnesses during the first 6 months of life among 776 infants born in New Brunswick, Canada. During a 1-year period, these infants were drawn from the offspring of a population of primiparous women in the province who, after at least 36 weeks of pregnancy, gave birth to one normal infant weighing 2500 gm or more. Data were collected by means of a self-administered standardized questionnaire mailed to every mother a week before her infant reached 6 months of age. The crude incidence density ratio (IDR) revealed a protective effect of breast-feeding on respiratory illnesses (IDR = 0.66; 95% confidence interval (CI), 0.52 to 0.83), on gastrointestinal illnesses (IDR = 0.53; 95% CI, 0.27 to 1.04) and on all illnesses (IDR = 0.67; 95% CI, 0.54 to 0.82). The protective effect of breast-feeding on respiratory illnesses persisted even after adjustment for age of the infant, socioeconomic class, maternal age, and cigarette consumption (adjusted IDR = 0.78; 95% CI, 0.61 to 1.00). Moreover, if we distinguished ear infection from other respiratory illnesses, we observed a separate protective effect for these two types of events. The results of this retrospective cohort study suggest a protective effect of breast-feeding in our population during the first 6 months of life.

Virulence properties and attaching-effacing activity of Escherichia coli O45 from swine postweaning diarrhea

Escherichia coli O45 isolates associated with swine postweaning diarrhea in Québec were characterized with respect to virulence determinants genetically and investigated for their attaching and effacing (A/E) activities by experimental inoculation of gnotobiotic piglets and by the HEp-2 cell adherence assay. All of 32 isolates tested were negative for enterotoxigenic and verotoxigenic E. coli virulence determinants, heat-labile enterotoxin (LT), heat-stable enterotoxins (STap, STb), verotoxins (VT1, VT2), and F4 (K88), F5 (K99), F6 (987P), and F41, except one STb-positive and two F4-positive isolates. A total of 25 isolates hybridized with an EaeA probe, and 11 hybridized with an enteropathogenic E. coli adherence factor (EAF) probe. None of 32 isolates hybridized with a bundle-forming pilus (BFP) probe. The EAF, EaeA, and BFP factors have been associated with human enteropathogenic E. coli strains. A total of 10 of 12 eaeA-positive porcine O45 isolates induced A/E lesions characterized by intimate adherence of bacteria to the intestinal epithelial cell membrane with effacement of the microvilli, similar to those of human attaching-effacing E. coli. However, A/E lesions were not observed in the piglets inoculated with any one of three eaeA-negative O45 isolates. All E. coli O45 isolates were non-adherent to HEp-2 cells. Thus, we have demonstrated the production of typical A/E lesions by nonenterotoxigenic E. coli O45 isolates from swine postweaning diarrhea. The results indicate the significance of the eaeA gene in A/E activities of these isolates and suggest that EAF and BFP are not involved in O45 E. coli infection of weaning piglets.

From the Canadian Dietetic Association. Concept of dietetic practice and framework for undergraduate education for the 21st century

Rapid change and marked diversity are expected to characterize the 21st century. If dietitians are to serve as change facilitators in this environment they will have to demonstrate greater flexibility and creativity, practise critical analysis and problem solving and employ creative thinking. Although provision of quality nutrition care will remain the unique contribution of dietitians, practitioners in the future will require a greater understanding of the impact of social, economic and political systems on food availability and food consumption and, in turn, health and well-being. Critical to the future practice of dietetics will be a greater understanding of research methodology, computer technology, quality improvement processes and risk management, principles governing learning and behaviour, personnel management and organizational behaviour, family and group dynamics, interpersonal communication and their application to dietetic practice. The Canadian Dietetic Association recently adopted a framework for the development of baccalaureate programs in dietetics designed to enable the dietetic practitioner to continue to make a unique contribution in the 21st century. The framework allows individual institutions the freedom and flexibility to plan programs that are compatible with their philosophy and organizational structure. In addition, it is predicted on the principle that a career in dietetics entails a lifetime commitment to education, of which the baccalaureate program is only the beginning.

Method for the quantification of alginate in microcapsules

Alginate is a key reagent in the preparation of microcapsules for cell transplantation. To address the question of the intracapsular alginate concentration, a sensitive assay has been developed to quantify the alginate content of microcapsules. The method is based on the metachromatic change induced by alginate binding to the dye, 1,9-dimethyl methylene blue (DMMB). The assay has a high sensitivity and precision. It covers a wide concentration range enabling the measurement of alginate in dilute supernatants as well as in microcapsules. For the latter, the membrane is initially dissolved by incubating the microcapsules in an alkaline medium. The effect of potentially interfering substances (poly-L-lysine (PLL), citrate, chloride, sodium) and of pH has been studied. Poly-L-lysine interfered with the assay at pH 6.5 but not at pH 13. Interference by sodium augmented with increasing sodium concentration and reached a plateau at 200 mM. This problem was overcome by routinely adjusting all samples to 500 mM sodium. The other substances tested had a negligible effect on the assay. The reliable measurement of alginate with this new assay will allow the optimization of the intracapsular alginate concentration.

Protection of islets of Langerhans from antibodies by microencapsulation with alginate-poly-L-lysine membranes

Microencapsulation of islets has been proposed to prevent their immune destruction following transplantation. An indirect immunofluorescence technique has been developed and used to study the permeability of the alginate-poly-L-lysine microcapsules to antibodies. Wistar rat islets were incubated with the R2D6 monoclonal mouse IgM antibody against rat islets, microencapsulated, and incubated with fluorescein-labeled goat IgG antibodies against mouse IgG and IgM. For the negative controls, the first antibody was omitted or both antibodies were omitted. The positive controls included islets incubated with both antibodies before they were encapsulated. Our study demonstrated that the alginate-poly-L-lysine membranes are not permeable to IgG when poly-L-lysine of molecular weights ranging from 21,000 to 390,000 are used. This simple immunofluorescence technique demonstrated the nonpermeability of the microcapsules to IgG, and could be useful for the initial evaluation of new types of membranes.

Lactate transport during differentiation of skeletal muscle cells: evidence for a specific carrier in L6 myotubes

Cellular uptake of lactate involves a carrier in numerous types of mammalian cells. In cultured rat L6 myoblasts, lactate diffuses freely. We show that during myogenesis a carrier appears at the myotube stage. The degree of cellular differentiation was determined by microscopic observation and by measurement of a marker of biochemical differentiation: the increase in specific activity of creatine kinases.

A conceptual framework for dietetics

The model for the practice of dietetics recently adopted by the CDA board of directors clarifies how the different facets of dietetics are interrelated and part of a common definition of dietetics. It is our hope that this discussion will help us to move beyond the question of identity we often feel in our profession and will stimulate debate and the development and testing of alternate models; this should further clarify the essence of dietetic practice and enable us to continue to improve our unique and common contribution towards the provision of quality nutritional care to the population.

[Preliminary results on the residence distribution at birth of patients with Alzheimer's disease in the Saguenay-Lac-Saint-Jean/Quebec (the IMAGE project)]

The IMAGE Project is pursuing the establishment of a population-based registry of Alzheimer's disease (AD) cases in the Saguenay-Lac-Saint-Jean (SLSJ) (Quebec). The authors report on the spatial distribution at birth of 221 possible, probable and definite cases. A large network of key-informants for screening AD cases has been established over SLSJ. The spatial distribution of cases at birth and at the onset of disease has been computed by calculating the Alzheimer birth rate (ABR) on the basis of three scales: six specific geographical spheres of screening, all municipalities, and the public health departments. The statistical significance of results was determined using the theoretical Poisson and the Chi square distributions. ABR for each of the geographical spheres of screening showed no statistically significant differences considering either residence at the onset of the disease or residence at birth. Furthermore, differences were observed between rural and urban areas with an interesting trend for a higher number of cases than expected in one area of SLSJ. The spatial distribution of cases considered on the basis of residence at birth appears to show a different pattern, but no significant, from that measured on the basis of residence at the onset of disease. Screening of cases is actively being pursued all across SLSJ by the IMAGE network. There is a clear trend towards rural residence at birth of cases. It remains to see whether or not this observation is due to a geographical concentration of familial cases.

[Factors of successful breast feeding in New Brunswick: information and compatible working conditions]

Although breastmilk is the best food source for the first six months of life, breastfeeding rates at three and six months of age in New Brunswick are quite low. To determine action priorities to increase the duration of breastfeeding, we tried to identify its most important determining factors. Data were obtained from the 431 breastfeeding mothers in a representative sample of 777 infants born after a normal pregnancy. The mother's knowledge about breastfeeding is the most valuable factor that explains breastfeeding duration, followed by the compatibility of the mother's employment with breastfeeding. Interventions directed at improving either of these two factors should be encouraged particularly among mothers of lower socioeconomic status who breastfeed for shorter periods of time.

[The marriage therapist is a Trojan horse: reflections inspired by the results of research on interventions with couples]

Communication training and positive exchange training are the two methods for improving marital relations that research has established as being the most effective. However, even after conducting therapy involving both partners based on these methods, too few couples (35%) succeed in reaching the same level of satisfaction as couples who are already satisfied with their relationship. The efforts that have been undertaken to increase this rate have focused mainly on developing new therapeutic techniques that include cognitive, emotional and systemic approaches. However, the results of experimental studies to date do not prove the superiority of these new approaches. Given this situation, it is time to pay more attention to particular characteristics of the therapeutic relation in marital therapy and to the means of obtaining the collaboration of the two spouses. As is the opinion of certain authors, the most difficult clinical task does not consist of finding what the clients must do to solve their problems, but rather to determine how to motivate them and help them achieve their goal. An analysis of this task, based on clinical observations and results of recent research in this area, has allowed the authors to present a number of hypotheses about ways to reinforce the therapeutic alliance and eventually reduce the failure rate of marital therapy.

Lactate transport in skeletal muscle cells: uptake in L6 myoblasts

During exercise, lactate is produced by degradation of glucose-6-phosphate during glycolysis in the contracting muscles. This lactate is metabolized during and after exercise in the muscle itself and also in the liver and other muscles, which can use it as an energy metabolite or can resynthetize glycogen. Lactate is transported in the blood, and the rate of muscular utilization may be limited by two factors: the rate of metabolic utilization by the muscle cell; and the rate of transport across the membrane regulating lactate transfer from the blood to the cell. We have studied lactate uptake in L6 muscle cells by incorporation of 14C-lactate. The uptake rates were linear for 20 seconds with 5 mM lactate and 10 seconds with 20 mM. The uptake during 10 seconds for physiological lactate concentrations (1-20 mM) gave a straight line passing through the origin. Lactate uptake was not altered by specific inhibitors of lactate transport (2.5 mM alpha cyano-4-hydroxycinnamic acid. 5 microM 4,4'-diisothiocyanostilbene-2,2'disulphonic acid) or by the stereospecific D-lactate inhibitor. The results suggest that L-lactate uptake in L6 cells occurs by passive diffusion.

Temporal intermittent rhythmic delta activity (TIRDA) in the diagnosis of complex partial epilepsy: sensitivity, specificity and predictive value

Temporal interictal rhythmic delta activity or TIRDA was found in 45 of the 127 recordings of patients with complex partial epilepsy (CPE) referred for both awake and sleep EEG. TIRDA was more abundant during drowsiness and light sleep; it occurred more characteristically as trains of 50-100 microv sinusoidal or saw-toothed 1-4Hz activity, recorded predominantly from anterior temporal regions. When occurring bilaterally and independently, TIRDA varied from side to side. TIRDA is often found in association with anterior temporal spikes or sharp waves (TS) particularly during sleep, as observed in 43 out of 45 EEGs. TIRDA can nevertheless occur as an isolated abnormality, as noted in two sleep and 12 awake study recordings. Because of its high specificity and positive predictive value over a large range of prevalence, TIRDA should be singled out as an accurate interictal indicator of CPE. In patients with isolated TIRDA, the cost of prolonged EEG recording during sleep for the purpose of activating TS has to be weighed against the yield of eventually confirming the obvious.

Who breastfeeds in New Brunswick, when and why?

We studied infant feeding in a representative sample of primiparous mothers of six-month-old infants in New Brunswick in 1982-83. At birth, 56% of infants were breastfed, decreasing to 31% at three months and 16% at six months; fewer were breastfed, and this for shorter periods of time, among the French population, those of lower socio-economic status or younger mothers. Most of the mothers who did not breastfeed did not attend prenatal classes and almost half had decided before their pregnancy to breastfeed or not. Most mothers breastfed because they felt their milk was better. Bottlefeeding mothers were mainly motivated by its convenience.

Measurement of atherosclerosis: development of an atherosclerosis severity index

Treatment of hypertension has succeeded in preventing the complications attributable to pressure, including heart failure and the arteriolar complications such as brain hemorrhage and renal failure. Recent understanding that antihypertensive drugs have effects on lipoproteins and flow disturbances that may be important in atherosclerosis progression, and the recent development of drugs that are more effective in treating hyperlipidemia, have given impetus to the design of studies to test whether interventions are anti-atherosclerotic. Since studies depending on clinical endpoints by necessity consume vast resources, it is desirable to develop methods for measurement of atherosclerosis, in order to make it possible to conduct intervention studies efficiently. Because angiographic methods are costly and associated with risk, and many patients are unable or unwilling to undergo followup angiography at the end of a study, we are developing an atherosclerosis severity index based on clinical and noninvasive ultrasound assessment. This scale can be used as a surrogate outcome in place of, or complementary to angiographic measurement of atherosclerosis, to avoid costly loss of subjects in intervention studies. It has the additional advantage that it is suitable for repeated assessment over time, permitting the power of analyses such as life table analysis which look at time to development of endpoints.

Umbilical cord cutting triggers hypertriiodothyroninemia and nonshivering thermogenesis in the newborn lamb

The present studies in the newborn sheep were undertaken to further clarify the mechanism or mechanisms for the early increases in serum thyroid hormone concentrations in the newborn as well as the significance of these changes to newborn nonshivering thermogenesis. Six groups of animals were studied to determine the influence of neonatal cooling, cord cutting, and the effects of thyrotropin-releasing hormone (TRH) and triiodothyronine (T3) injections. Group I newborns were delivered into room air with immediate cord cutting. Group II animals were delivered into room air and cord cutting was delayed 60 min. Group II animals were delivered into a 39 degrees water bath and maintained for 60 min with the umbilical cord intact; the cord was cut at the time of removal from the water bath...

Chromoblastomycosis due to a New Species of Fungus: (First Canadian Case)

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