Physiology and pathophysiology of skeletal muscle contractions

An overview is presented of the physiology and pathophysiology of dynamic skeletal muscle contractions in the intact living organism. Dynamic muscle activities are divided into concentric contractions with shortening of muscle fibres and the production of positive work, and eccentric contractions with lengthening of muscle fibres and the production of negative work. In positive work, muscle tension overcomes external forces. In negative work, external forces overcome muscle tension. The latter phenomenon, with relatively few active motor units, explains the injuries induced by eccentric contractions. Both the contractile and non-contractile elements are involved in the muscle injuries and, clinically, they are referred to as myofibrositis.     

METOPROLOL DECREASES THE AMOUNT OF HALOTHANE REQUIRED TO INDUCE HYPOTENSION DURING GENERAL ANAESTHESIA

A double-blind, randomized and placebo-controlled study wasundertaken to assess the effects of metoprolol on controlledhypotension during halothane anaesthesia. Nineteen patientsundergoing middle ear or nasal septum surgery were studied.The aim was to achieve a 25% reduction of the mean arterialpressure in both groups. Metoprolol was given by mouth on twooccasions in the 10–12 h before operation. In the grouppretreated with metoprolol the halothane concentration was reducedby 35.5%. The duration of bleeding and its degree were reducedsignificantly. The time to awakening was shorter and of betterquality after pretreatment with metoprolol. Rate-pressure productwas less after pretreatment with and rebound hypertension waswell controlled.     

The effect of naloxone on the preoperative gastric volume and pH

The effect of 4 mg oral naloxone on preoperative gastric volume and pH of gastric aspirate was studied in a double-blind, randomized study. Twenty patients received 10 ml of naloxone (4 mg) mixed with 10 ml of orange juice, and 20 patients received 10 ml of isotonic saline mixed with 10 ml of orange juice, 2 h before surgery. Gastric content was obtained immediately after intubation of the trachea. No significant difference in gastric volume and pH of gastric aspirate was found between the two groups. It is concluded that naloxone does not affect gastric emptying and gastric acid secretion to a degree great enough to protect against aspiration of gastric contents into the lungs.     

Malignant Warthin''s tumour: a case study

Malignant transformation of a benign Warthin's tumour (adenolymphoma) is extremely rare. The light microscopic and ultrastructural features of an adenocarcinoma arising in a Warthin's tumour in the parotid gland are described. Light microscopy demonstrated a transition zone from the benign to the malignant component, and the malignant cells revealed oncocytic features by both light- and electronmicroscopy.     

Bilateral masseteric contractile activity in unilateral gum chewing: differential calculus

SUMMARY Twelve healthy subjects performed 10 s, 15 s, 20 s, and 25 s of right-sided and, subsequently, left-sided gum chewing. The contractile activities of the ipsilateral (chewing side) and contralateral (non-chewing side) masseter muscles, mainly the concentric contractions of the phase of jaw closing and the isometric contractions of the phase of dental occlusion, were recorded through cumulative surface electromyography (EMG). A linear function (y = ax + b) described the association between an increase in the duration (x) of unilateral gum chewing and the cumulative EMG (y) of both the ipsilateral and the contralateral masseter muscle, and because of different slopes (a) of the two straight lines a geometric function (y = aqx) described the progressively larger differences between the paired and straight lines. When differential calculus was applied to the exponential functions, it became evident that the chewing forces generated by the ipsilateral masseter muscle continually exceeded those generated by the contralateral masseter muscle, and that the positive work (force x distance) produced by the concentric contractions of the ipsilateral masseter muscle continually exceeded that produced by the concentric contractions of the contralateral masseter muscle. It was inferred that mechanophysical work plays a major role if clinical muscle fatigue develops during prolonged unilateral gum chewing.     

Thoracic epidural analgesia in aortocoronary bypass surgery II: effects on the endocrine metabolic response

Thoracic epidural analgesia (TEA) may offer haemodynamic benefits for patients with coronary heart disease going through major surgery. This may – in part – be secondary to an effect on the endocrine and metabolic response to surgery. We therefore investigated the effect of TEA on the endocrine metabolic response to aortocoronary bypass surgery (ACBS).
Thirty male patients (age < 65 years, ejection fraction > 0.5) were randomized into 3 groups; the HF group receiving a high dose fentanyl (55 μg–kg^-1) anaesthesia, the HF + TEA group with the same fentanyl dose + TEA with 10 ml bupivacain 5 mg ml^-1, followed by 4 ml every hour, and the LF + TEA group receiving fentanyl 15 μg kg^-1 + TEA. Adrenalin, noradrenalin, systemic vascular resistance (SVR), glucose, Cortisol, lactate and free fatty acids were followed during the operation and for 20 h postoperatively.
A significant increase in adrenalin, noradrenalin and SVR was found in the HF group whereas this increase was blocked in both epidural groups. An increase in glucose and Cortisol was noticed in all groups, but the increase was delayed in the epidural groups.
Our results suggest that a more effective blockade of the stress response during ACBS is obtained when TEA is added to general anaesthesia than with high dose fentanyl anaesthesia alone.     

Atrial natriuretic factor (ANF) does not affect ion transport in human intestine but does in porcine intestine

The aim of this study was to test whether atrial natriuretic factor (ANF) exerts any effect on human intestinal ion transport, and the porcine intestine was used as a positive control of ANF's effects. Tissues from human proximal (n = 6) and distal (n = 6) colons, and from distal ileum (n = 6) were mounted in Ussing chambers, and short circuit current (I_sc) was measured subsequent to serosal application of ANF (10^--⁶ m), 8–Br-cyclic guanosine monophosphate (8–Br-cGMP) (10^--⁴ m), and theophylline (10^--² m). ANF did not affect I_sc whereas 8–Br-cGMP increased I_sc by 28 (8–53), 16 (3–36), and 16 (5–41) μA cm^-2 in the distal colon (DC), proximal colon (PC) and distal ileum (DI), respectively. Likewise, transepithelial potential difference (PD) became more negative by 5.0 (0.6–8.9), 2.5 (0.4–4.0) and 0.9 (0.3–2.3) mV in DC, PC, and DI, respectively, subsequent to addition of 8–Br-cGMP. I_sc and PD were further increased by theophylline. Additional radio-isotope flux studies in human colon revealed that ANF did not affect electroneutral sodium and chloride transport either. For comparison, ANF (10^--⁶ m) was administered to large intestinal tissues from young pigs in which ANF induced a significant increase in I_sc which was comparable to the 8–Br-cGMP response in humans. The porcine I_sc response was partly inhibited by chloride-free solution on the serosal side, by serosal application of bumetanide (10^--⁴ m) and BaCl₂ (10^--³ m), and mucosal application of the chloride-channel blocker diphenylamine-2–carboxylate (DPC) (10^--³ m). Mucosal amiloride (10^--⁵ m) pre-treatment reduced baseline I_sc but did not affect the porcine intestinal I_sc response to ANF. In vitro radio-autography demonstrated specific binding sites for ANF in porcine distal colon, whereas no apparent labelling was observed in human distal colon. These findings suggest that the lack of effect of ANF on sodium and chloride transport in human distal ileum and colon is probably due to lack of ANF receptors. In the porcine intestine, however, the I_S0 response induced by ANF seems to involve stimulation of electrogenic chloride secretion, whereas electrogenic sodium absorption seems unaffected.     

Previously unrecognized advanced liver disease unveiled by transient elastography in patients with Haemophilia and chronic hepatitis C

Summary. Before the introduction of viral inactivation procedures and viral screening of plasma‐products, haemophiliacs were at high risk of infection with HCV. Those who acquired HCV infection in the 1980s, and are still alive today, may have developed significant liver fibrosis or cirrhosis. However, liver biopsy has not routinely been utilized in the evaluation of haemophiliacs with HCV in Denmark. The aim of this study was to investigate the prevalence of significant fibrosis/cirrhosis among haemophiliacs as evaluated by transient elastography (TE). Cross‐sectional investigation of adult patients with haemophilia A or B. TE with liver stiffness measurements (LSM) ≥8 kPa were repeated after 4–6 weeks. Significant fibrosis and cirrhosis was defined as measurements ≥8 kPa or ≥12 kPa respectively. Among 307 patients with haemophilia A or B registered at the two Haemophilia centres, 141(46%) participate in this study. Forty (28.4%) had chronic hepatitis C, 33 (23.4%) past hepatitis C and 68 (48.2%) had never been infected, at screening LSM ≥8 kPa were found in 45.7%, 24.7% and 4.6% respectively. Among patients with chronic hepatitis C significant fibrosis was confirmed in 17.1% and cirrhosis in 2.9% by repeated LSM ≥8 and ≥12 kPa respectively. The median TE‐value in never HCV‐infected haemophiliacs was comparable with what has been found in healthy non‐haemophiliacs. In Danish haemophiliacs where liver biopsy has not routinely been used for assessing severity of liver fibrosis, LSM identified advanced liver disease in one‐fifth of cases that had not been recognized during clinical follow‐up.