Is the motor unit uniform?

Single motor units in the fast-twitch tibialis anterior muscle were functionally isolated by stimulation of microdissected ventral root filaments. The muscle fibres of 35 fast-twitch single motor units (motor unit fibres), 18 units from 3 to 6–month-old and 17 units from 20 to 24–month-old male rats, were identified by glycogen depletion. Measurements were made of staining intensities for intermyofibrillar succinate dehydrogenase, using microphotometric techniques, and of cross-sectional areas of the motor unit fibres. The average coefficients of variation for succinate dehydrogenase activity of the muscle fibres within each unit, between the different units and for repeated measurements of the same fibre in 10 consecutive cross-sections stained on different glasses were 26 , 72 and 14%, respectively. The average coefficients of variation for cross-sectional fibre areas within each unit, between the different units and for repeated measurements were 21 , 53 and 774 , respectively. Further, the succinate dehydrogenase activity of muscle fibres within the motor unit differed significantly depending on the position of the fibre along the superficial-deep axis of the muscle. The average succinate dehydrogenase activity in the 35 motor units was 21% lower (P < 0.001) in the superficial as compared with the deep motor unit fibres. In order to eliminate the influence of altered motoneurone properties related to a transformation process or an age-related motoneurone dysfunction as indicated by a non-homogeneous myosin heavy chain composition in motor unit fibres, cross-sectional fibre areas and enzyme activities were also compared in motor units with a uniform myosin heavy chain composition in young animals. However, the same regional differences were observed in these 16 units as when all the 35 units were pooled together. Thus, in conformity with previous reports, the variability in enzyme activities within single motor unit fibres is small but too Iarge for a motor unit homogeneity to be accepted. In addition, the present results demonstrate that the systematic differences in succinate dehydrogenase activities of motor unit fibres along the superficial-deep axis of the tibialis anterior muscle represent a biological rather than a methodological phenomenon.     

Reducing delirium in elderly patients with hip fracture: a multi‐factorial intervention study

Background: There is an evident need for improved management of elderly patients with trauma in order to avoid common and troublesome complications such as delirium. The aim of this study was to investigate whether an implementation of a multi‐factorial program including intensified pre‐hospital and perioperative treatment and care could reduce the incidence of delirium in elderly patients with hip fracture, cognitively intact at admission to the hospital. In addition, we explored the factors that characterize patients who developed delirium. Methods: A prospective, quasi‐experimental design was used. A total of 263 patients with hip fracture (≥65 years), cognitively intact at admission, were consecutively included between April 2003 and April 2004. On 1 October 2003, a new program was introduced. All patients were screened for cognitive impairment within 30 min after admission to the emergency department using The Short Portable Mental Status Questionnaire (SPMSQ). To screen for delirium, patients were tested within 4 h of admission and thereafter daily, using the Organic Brain Syndrome scale. Results: The number of patients who developed delirium during hospitalization was 74 (28.1%), with a decrease from 34% (45 of 132) in the control group to 22% (29 of 131) in the intervention group (P=0.031). Patients who developed delirium were statistically older, more often had >4 prescribed drugs at admission and scored less well in the SPMSQ test. Conclusion: The use of a multi‐factorial intervention program in elderly hip fracture patients, lucid at admission, reduced the incidence of delirium during hospitalization by 35%.     

Hemodilution significantly decreases tolerance to isoflurane-induced cardiovascular depression

Background: Hemodilution is used to reduce the need for allogenic blood transfusion. The aim of this study was to evaluate to what extent acute extreme normovolemic hemodilution affects the circulatory response to isoflurane. Methods: Ten midazolam-fentanyl-pancuronium anesthetized pigs were exposed to isoflurane at end-tidal concentrations of 0,0.5,1.0,1.5 and 2%, before and after extreme normovolemic hemodilution (hematocrit 33±3% and 11±1%, respectively). Systemic and myocardial hemodynamics and oxygen delivery and consumption were measured. Results: At zero end-tidal isoflurane concentration, hemodilution caused an increase in cardiac output (from 157±12 to 227±39 ml kg min^-1, P <0.01) a decrease in systemic vascular resistance (from 39±7 to 18±5 mmHg · L^-1 · min^-1, P <0.01) a decrease in mean arterial blood pressure (MAP) (from 130±13 to 91±13 mmHg, P <0.01) and a decrease in systemic oxygen delivery (from 23.1±2.7 to 11.8±1.7 ml · kg^-1 min^-1, P <0.01). When the end-tidal isoflurane concentration was increased from 0 to 2% after hemodilution, cardiac output decreased by 86±37 ml · kg^-1 · min^-1, as compared with 36±20 ml · kg^-1 · min^-1 (P <0.01) before hemodilution. Likewise, systemic vascular resistance decreased with increasing isoflurane concentrations; at 2%, the decrease was 7±4 mmHg·L^-1· min^-1 after hemodilution and 18±5 mmHg.L^-1 mid before hemodilution (P < 0.01). At an end-tidal isoflurane concentration of 2%, MAP had decreased to 43±6 mmHg after hemodilution, and to 61±15 mmHg before hemodilution (kO.01). After hemodilution, isoflurane concentrations above 1% decreased systemic oxygen delivery enough to cause delivery-dependent oxygen consumption and hyperlactemia; and at 2% isoflurane, myocardial blood flow became insufficient, as indicated by myocardial lactate production. Conclusions: isoflurane-induced cardiovascular depression had adverse effects on cardiac output and oxygen delivery during extreme hemodilution because: 1) The vasodilatory effect of isoflurane was insufficient to compensate for the myocardial depression, and also contributed to a critically low arterial blood pressure; 2) A decrease in cardiac output produced delivery-dependent oxygen consumption and hyperlactemia; and 3) A decrease in myocardial blood flow caused myocardial ischemia which may have exacerbated the myocardial depression.     

Prediction of Symptomatic Patent Ductus Arteriosus in Preterm Infants Using Doppler and M-mode Echocardiography

ABSTRACT. To investigate whether the development of symptomatic patent ductus arteriosus could be predicted, 26 preterm infants dependent on mechanical ventilation were examined daily with Doppler and M-mode echocardiography until 3 days after birth. The presence or absence of a hemodynamically significant ductus shunt, as judged from echocardiographic criteria, was tested for predictive power in terms of sensitivity, specificity and total error rate. Out of the 26 infants 13 developed symptomatic patent ductus arteriosus at a median age of 5 days (range 2–8). These 13 infants developed echocardiographic evidence of a large shunt at a median age of 2 days (range 1–3). The sensitivity of prediction was 18, 46 and 100% at 1, 2 and 3 days after birth. The specificity was 80, 92 and 85% and the total error rate was 52, 32 and 8%. Thus, accurate prediction was possible 3 days after birth.     

The Ultrastructure of Initial Changes in Hapten-Exposed Rat Oral Mucosa

The experimentally induced cell-mediated immune reaction has been examined ultrastructurally in rat oral mucosa, using DNCB/DNFB as haptens. In skin-presensitized animals, an increased number of mononuclear cells was found in the epithelium at a very early phase (15-60 min) after hapten exposure. In nonsensitized animals, an increased number of cells was evident in hapten-exposed tissue also very early in the reaction. Mononuclear cells appeared in the connective tissue but very few in the epithelium. Interaction between mononuclear cells and Langerhans cells could be demonstrated in both experimental groups.     

Gastrin release and gastric acid secretion in the rat infected with either Helicobacter felis or Helicobacter heilmannii

Helicobacter pylori infection in humans has been shown to be associated with changes in gastric physiology, including exaggerated basal and meal-stimulated gastrin levels. This has been suggested to be due to the direct effects of the bacterium through inflammation and its urease enzyme. The gastric bacteria Helicobacter felis and Helicobacter heilmannii colonize the antrum of rats in large numbers and induce no significant inflammatory response. Thus, the direct effect of Helicobacter infection on gastric physiology, independent of gastritis, could be studied. Basal, freely fed and stimulated acid and gastrin levels were recorded from animals infected with H. felis, H. heilmannii or uninfected controls over a 30 week period. No significant difference was found between freely fed gastrin over 7 weeks or fasting gastrin over 24 weeks or basal and stimulated acid over 30 weeks between all three groups. Triple therapy did not alter gastrin or acid output. The antrum of all Helicobacter-infected rats was well colonized; triple therapy cleared H. felis but not H. heilmannii. Very little inflammation was seen in control or Helicobacter-infected animals. In conclusion, Helicobacter-induced effects on gastric physiology are unlikely to be due to direct bacterial effects, but are best explained by other factors (i.e. inflammatory damage).     

Fel d 1 and Can f 1 in settled dust and airborne Fel d 1 in allergen avoidance day-care centres for atopic children in relation to number of pet-owners, ventilation and general cleaning

BACKGROUND: Special day-care centres for atopic children have been established in Sweden. OBJECTIVE: To study concentrations of cat (Fel d 1) and dog (Can f 1) allergens in settled dust and airborne cat allergen in day-care centres in relation to pet ownership among children and staff, ventilation and general cleaning. METHODS: Twelve allergen avoidance day-care centres and 22 conventional day-care centres were included in the study. Settled dust was collected and analysed with ELISA. Airborne cat allergen levels were measured in eight allergen avoidance and seven conventional centres with a personal air sampler and analysed with an amplified ELISA. Air change rate per hour (ACH) was measured. A questionnaire which focused on keeping of cat and dog among staff and children and frequency of general cleaning was used. RESULTS: In the allergen avoidance day-care centres neither children nor staff reported ownership of cats or dogs, compared with 21/22 of the conventional centres in which children and staff kept furred animals. Fel d 1 and Can f 1 were found in settled dust in all day-care centres. In the allergen avoidance compared with the conventional centres the concentrations of Fel d 1 and Can f 1 were lower, Fel d 1: median 0. 64 microg/g vs 5.45 microg/g and Can f 1: 0.39 microg/g vs 2.51, both P < 0.001, and airborne Fel d 1 was also lower in the allergen avoidance centres compared with the control centres, 1.51 ng/m3 vs 15.8 ng/m3, P = 0.002. A correlation was found between airborne and settled Fel d 1, rs = 0.75, P < 0.001. Furthermore, a correlation was found between increased ACH and decreased levels of Fel d 1 in the air in the day-care centres with no cat-owners, rs = - 0.86, P = 0.007. No relation was found between levels of cat or dog allergen and amount of general cleaning. CONCLUSION: Not keeping pets seems to reduce children's exposure to pet-allergen in their 'working environment'. Additionally, appropriate ventilation seems to reduce Fel d 1 in the air in day-care centres.