Electromyographic assessment of muscle fatigue in massive rotator cuff tear.

Shoulder muscle fatigue has not been assessed in massive rotator cuff tear (MRCT). This study used EMG to measure fatigability of 13 shoulder muscles in 14 healthy controls and 11 patients with MRCT. A hand grip protocol was applied to minimise artifacts due to pain experience during measurement. The fatigue index (median frequency slope) was significantly non-zero (negative) for anterior, middle, and posterior parts of deltoid, supraspinatus and subscapularis muscles in the controls, and for anterior, middle, and posterior parts of deltoid, and pectoralis major in patients (p ≤ 0.001). Fatigue was significantly greater in patients compared to the controls for anterior and middle parts of deltoid and pectoralis major (p ≤ 0.001). A submaximal grip task provided a feasible way to assess shoulder muscle fatigue in MRCT patients, however with some limitations. The results suggest increased activation of deltoid is required to compensate for lost supraspinatus abduction torque. Increased pectoralis major fatigue in patients (adduction torque) likely reflected strategy to stabilise the humeral head against superior subluxing force of the deltoid. Considering physiotherapy as a primary or adjunct intervention for the management of MRCT, the findings of this study generate a base for future clinical studies aiming at the development of evidence-based protocols.

The development of the pituitary-adrenal axis in the guinea pig.

The concentration of cortisol and ACTH in the umbilical vein plasma of the foetal guinea pig has been measured over the later half of gestation. Between 55--60 days there is a large increase in the concentration of both. Injection of ACTH1-24 into the foetal guinea pig elicits a relatively small increase in plasma cortisol at 46--55 days, a somewhat greater response at 56--60 days and a large response at 61--66 days. Between 47--55 days and 58--63 days cells prepared from the foetal adrenal show a large increase in their responsiveness to ACTH stimulation as measured by cortisol and androstenedione output. However, there was no clear difference in responsiveness between 58--60 days and 61--63 days. Thus between 56--60 days the foetal adrenal appears less responsive to ACTH stimulation in vivo than in vitro. ACTH in the circulation of the guinea pig is present in high-molecular-weight and low-molecular-weight forms and the ratio of concentration of ACTH1-39 to that of the high-molecular-weight forms rises after 60 days. It is proposed that this is an important factor in inducing an increased steroid response from the foetal adrenal.

Inhibitory effects on steroid production from isolated adrenal cells of rhesus monkey (Macaca mulatta) of pro-opiomelanocorticotrophic peptides.

Adrenal glands from Rhesus monkeys (Macaca mulatta) of 160 days gestation, newborn, 2 months-old infants or 6 months-old infants were excised and prepared, by a collagenase digestion, as a cell suspension. The cells were incubated with 10 pg/ml, 100 pg/ml or 1 ng/ml of a peptide of the ACTH/pro-opiomelanocortin 'family', 57K, 31K, 20K, alpha MSH, ovine-CLIP or gamma LPH either in the presence or absence of 166 pg/ml ACTH1-39. The production by cortisol and androstenedione was measured by radioimmunoassay. Using the steroid production by aliquots of the cell suspension with either no stimulating agent or ACTH1-39 alone as controls, the net influence of these different peptides on basal or ACTH1-39-stimulated production was observed. alpha MSH, ovine-CLIP and gamma LPH had no influence on either basal or stimulated cortisol or androstenedione production. Corticotrophic peptides of 57K, and 20K and pro-opiomelanocortin each had a steroidogenic activity alone, in all age groups. In the fetal and newborn monkeys' adrenal cells, peptides of 57K and 20K at 1 ng/ml had an inhibitory influence on ACTH1-39 stimulated cortisol and androstenedione production. The influence of the 20K peptide is partially inhibitory as the steroidogenic potential of this peptide is not additive with that of ACTH1-39. These results show that, as observed in other species, that the ACTH/pro-opiomelanocortin range of peptides are inhibitory to the action of ACTH1-39 in the developing adrenal.

Studies on the growth of the fetal guinea pig. Changes in plasma hormone concentration during normal and abnormal growth.

The endocrine changes associated with fetal growth retardation caused by unilateral uterine artery ligation of guinea pigs at day 30 of pregnancy were studied. Plasma hormone levels in fetuses that, about 20 or 30 days later, were 35-50% of normal size were measured by radioimmunoassay. The small fetuses were severely hypoglycaemic and hypoinsulinaemic; both showing close correlation and relationship to the degree of growth retardation. Plasma thyroid and cortisol and concentrations were much lower than normal and that glucagon and androstenedione were much higher. Plasma growth hormone level appeared to be unaffected by growth retardation. The developmental changes in glucagon and thyroid hormone concentrations were consistent with a delay in the timing of prenatal events in growth-retarded fetuses. However the late cortisol rise, although somewhat blunted, still occurred at 58-60 in the small fetal guinea pigs.

Modulation of the responses of fetal sheep to adrenergic stimulation by adrenal demedullation and chemical sympathectomy.

The responses to sympathetic stimulation of fetal sheep adrenal-demedullated or sympathectomised by infusion of guanethidine sulphate have been studied. Sympathetic responses in such denervated or sympathectomised fetuses was studied by intravenous infusion of adrenaline or noradrenaline at about 0.4 micrograms/min per kg. This infusion increased plasma concentration 100-200 fold and there was no significant difference between the control fetuses and those in the vasrious treatment groups. Catecholamine infusions at these rates normally have little effect upon fetal blood gas and pH values, but in adrenal-demedullated fetuses adrenaline infusion drepressed fetal arterial PO2 by 4-6 mmHg (P less than 0.05). The heart rate and blood pressure responses to catecholamine infusion in sympathectomised fetuses was, as expected, much increased. Similar observations were made on adrenal-demedullated fetuses, an unexpected finding, and this is taken to illustrate loss of the adrenal medulla is associated with enhanced responsiveness to adrenergic stimulation in peripheral tissues. The majority of the endocrine and metabolic responses, as reflected in fetal plasma concentrations of ACTH, cortisol, insulin, glucose, lactate and fatty acids, to catecholamine infusion were similarly much enhanced by adrenal-demedullation and chemical sympathectomy. Of particular note was a substantial increase in the responsiveness of the fetal adrenal, as reflected in plasma cortisol, to stimulation by ACTH, a change that usually induces labour, but not so in the present sheep. The results on increased sensitivity in adrenal-demedullated fetuses are discussed in relation to likely tissue mechanisms mediating the changes.

The role of the adrenal medulla and peripheral sympathetic nerves in the physiological responses of the fetal sheep to hypoxia.

In studies on the role of the peripheral sympathetic system during fetal life the effects of adrenal demedullation or chemical sympathectomy on the responses of the fetal sheep to hypoxaemia have been studied. Fetal sheep of 127-138 days gestation were either adrenal demedullated by injection of acid formalin into the adrenal medulla, chemically sympathectomised by chronic treatment with guanethidine sulphate, or subjected to both manipulations. None of these treatments had any effect upon resting heart rate and blood pressure, or blood gas status. Hypoxia was induced by giving the pregnant ewe 9% O2 and 3% CO2 in N2 to breathe for 60 min. This depressed fetal PO2 by about 30% in the intact and all but the adrenal-demedullated, chemically-sympathectomised fetuses, where the fall was about 50%. Similarly in this group of fetuses there was a sharp fall in plasma pH contrasting with little change in the other fetuses. Adrenal demedullation blocked completely the hypoxia-induced rise in fetal plasma adrenaline, and reduced that of noradrenaline to 10% of normal, implying that during hypoxia most of the plasma elevation of catecholamines is of adrenal origin. In contrast, and possibly to compensate for the blunted catecholamine response, plasma AVP increases during hypoxia were substantially enhanced by adrenal demedullation. Fetal hypoxia was associated normally with a fall in heart rate and rise in blood pressure. Adrenal demedullation had no effect on the heart rate changes, thought to be a reflex response to rise in blood pressure, but abolished the rise in blood pressure during hypoxia. Chemical sympathectomy, in contrast, abolished the fall in heart rate even though blood pressure rose. This shows clearly that reflex changes in heart rate during hypoxia can be uncoupled from those in blood pressure. Turning to the endocrine effects of demullation, cortisol and ACTH responses to hypoxia were much increased, whilst those of insulin were depressed. During chemical sympathectomy these responses were much accentuated in the case of cortisol and ACTH but depressed for insulin. A feature of these effects was that the endocrine changes in the adrenal-demedullated fetuses, whilst initially high, were not sustained for the 60 min of hypoxia. The same was true of the fetal matabolic responses to hypoxia reflected in plasma glucose, lactate and non-esterified fatty acids. Most of the results in this study are consistent with the proposal that in the fetus adrenal catecholamines are important in sustaining responses to hypoxia, but not normally initiating them.

Cardiovascular, metabolic and endocrine effects of chemical sympathectomy and of adrenal demedullation in fetal sheep.

A procedure in fetal sheep for causing peripheral sympathectomy by regular intravascular guanethidine sulphate administration and for causing adrenal demedullation by intragland injection of acid formalin is reported. Demedullation substantially removed adrenaline from the fetal circulation, but has a small effect only on noradrenaline. Plasma noradrenaline levels were depressed by 50% when demedullated fetuses were also subject to peripheral sympathectomy by guanethidine sulphate treatment. This provides some evidence that the paraganglia in the sheep fetus contributes to resting plasma catecholamines. Furthermore the ability of adrenal demedullation to increase markedly this pool of extra-adrenal chromaffin tissue indicates that in the fetus adrenal activity regulates the growth of these para-aortic bodies. In response to sympathectomy plasma vasopressin concentrations rose substantially, whilst adrenal demedullation caused a small rise. Demedullation and sympathectomy depressed fetal plasma glucose and elevated plasma cortisol. In both sympathectomised and adrenal demedullated fetuses resting heart rate and blood pressure was not depressed. However in those with a depleted peripheral nervous system periods of cardiovascular instability were apparent after 2-3 days of treatment with guanethidine sulphate. Hence there were regular episodes where fetal blood pressure and heart rate fell sharply followed 60-90s later by very large increases in blood pressure sustained for up to 10 min and associated with substantial production of plasma vasopressin and catecholamines. These results show that fine cardiovascular control in the fetus requires an intact sympathetic system as the endocrine system is too slow responding to effectively maintain reflex vascular control.

In vitro effects of high molecular weight forms of ACTH on the fetal sheep adrenal.

The direct involvement of the pituitary-adrenal axis in birth has been well established, at least in sheep, and its removal prolongs pregnancy. As part of the process the fetal sheep adrenal grows rapidly during the 10-15 d prepartum and is associated with a large rise in the plasma corticosteroid concentration. This does not seem to result from an increased ACTH secretion. The fetal adrenal in vivo seems refractory to circulating ACTH and shows poor response to elevation of plasma concentration. Thus the signal for the adrenal hypertrophy and the initiation of parturition remains unclear. The responsiveness of the fetal adrenal to ACTH has been re-examined using isolated adrenal cells. The study shows that in the fetal sheep these are not inherently unresponsive to ACTH, but that high-molecular-weight forms of ACTH block the action of ACTH. These peptides may be responsible for controlling the activity of the adrenal in situ.

ACTH control of steroid secretion from adrenal cells of the developing rhesus monkey (Macaca mulatta).

Cells from adrenal glands of 140-160 days foetal, neonatal and infant Rhesus monkeys (Macaca mulatta) were prepared, by collagenase digestion and incubated with 10 pg-16 ng/ml ACTH. The production of cortisol, androstenedione, corticosterone, progesterone and prostaglandins was measured. The cortisol production in the 140 day and 160 day foetuses and in the neonatal adrenal cells was comparable. It was 2-fold higher in adrenal cells of 6 month infant monkeys. In all the groups there was an increasing production of cortisol with increasing ACTH concentration, and a response to low physiological concentrations of ACTH. The androstenedione production was significantly greater in the 160 day foetuses than in either those of 140 days or of the neonate which demonstrated a poor response to increasing ACTH concentrations. It responded well to increasing ACTH in adrenal cells from 6 month infant monkeys. Corticosterone output was 1/10th of cortisol with only the 140 day foetuses showing an increase in production with increasing ACTH concentrations. The results demonstrate that cells of the primate foetal adrenal gland are not inherently unresponsive to ACTH stimulation as regards cortisol production, which per/micrograms DNA does not appear to change over the last 25 days before term.

Mutation in the PTEN/MMAC1 gene in archival low grade and high grade gliomas.

The PTEN gene, located on 10q23.3, has recently been described as a candidate tumour suppressor gene that may be important in the development of advanced cancers, including gliomas. We have investigated mutation in the PTEN gene by direct sequence analysis of PCR products amplified from samples microdissected from 19 low grade (WHO Grade I and II) and 27 high grade (WHO grade III and IV) archival, formalin-fixed, paraffin-embedded gliomas. Eleven genetic variants in ten tumours have been identified. Eight of these are DNA sequence changes that could affect the encoded protein and were present in 0/2 pilocytic astrocytomas, 0/2 oligoastrocytomas, 0/1 oligodendroglioma, 0/14 astrocytomas, 3/13 (23%) anaplastic astrocytomas and 5/14 (36%) glioblastomas. PTEN mutations were found exclusively in high grade gliomas; this finding was statistically significant. Only two of the PTEN genetic variants have been reported in other studies; two of the genetic changes are in codons in which mutations have not been found previously. The results of this study indicate that mutation in the PTEN gene is present only in histologically more aggressive gliomas, may be associated with the transition from low histological grade to anaplasia, but is absent from the majority of high grade gliomas.

Characterisation of molecular alterations in microdissected archival gliomas.

Classification of gliomas according to their molecular characteristics may be important in future histopathological diagnosis. However, gliomas frequently display heterogeneity at the histological, biological and molecular level. In this study of archival diagnostic gliomas, precision microdissection was used to enrich samples in the most malignant cells or to investigate intratumoural histological heterogeneity. Analysis of tumour samples microdissected from the most aggressive regions, representative of the histopathological diagnosis, revealed PTEN mutations in 4/14 anaplastic astrocytomas, 4/13 glioblastomas and 1 gliosarcoma, but not in 19 low-grade gliomas. Using a novel PCR procedure and direct sequence analysis of the entire coding sequence, TP53 mutations were detected in 1/3 pilocytic astrocytomas, 3/13 astrocytomas, 4/14 anaplastic astrocytomas, 5/13 glioblastomas and 1 gliosarcoma. All but one of the tumours with TP53 mutation showed p53 immunopositivity, but 5 low-grade and 10 high-grade gliomas had p53 protein nuclear accumulation in the absence of detectable mutation. p53 status was unrelated to p21 expression. Neither PTEN nor TP53 mutations influenced the proliferative index or microvessel density of high-grade astrocytomas. Unusual findings include: TP53 mutation in a juvenile pilocytic astrocytoma; TP53 and PTEN mutations in a de novo glioblastoma, a gliosarcoma with identical mutations in gliomatous and sarcomatous components, and an infratentorial anaplastic astrocytoma with an earlier supratentorial grade II astrocytoma bearing the same TP53 mutation but not the PTEN mutation or loss of heterozygosity (LOH) of 10q23. Similarly, the transition to high-grade histology was associated with acquisition of PTEN mutations and 10q23.3 LOH in two de novo high-grade tumours with regions of low-grade histology.