Control over work pace, job strain and cardiovascular responses in middle-aged men

OBJECTIVE

To assess the effects of control over work pace on cardiovascular stress responses in healthy middle-aged men.

DESIGN

The study involved administration in the laboratory of visual matrix and mirror drawing tasks, the pace of tasks being either under the control of the subject (self-paced) or determined externally (externally paced). The work demands in the two conditions were equated.

METHOD

Forty men aged 55-65 years were randomly assigned to self-paced or externally paced conditions. Blood pressure (recorded continuously using the Finapres), heart rate, cardiac baroreflex sensitivity, salivary cortisol, skin conductance and breathing pattern were monitored at rest, during task performance and at recovery following tasks.

RESULTS

Blood pressure and heart rate responses were significantly greater under the externally paced than self-paced conditions. The mean increase in blood pressure during the visual matrix task averaged 19.8/9.4 versus 34.1/15.5 mmHg for the self- and externally paced conditions, and 28.2/13.7 versus 41.8/19.5 mmHg in response to mirror drawing, respectively. Performance of the matrix task was less accurate under externally paced than self-paced conditions, but the two groups did not differ in mirror drawing. A reduction in baroreflex sensitivity and increases in cortisol, respiration rate, tidal volume and skin conductance responses were recorded during tasks, but these responses did not distinguish the two groups. Men were divided on the basis of reported job strain associated with their regular work, using the demand-control model. Blood pressure and heart rate responses were particularly pronounced among men reporting high job strain who were allocated to the externally paced condition.

CONCLUSIONS

Middle-aged men showed greater stress-related cardiovascular responses when they performed tasks at a pace that they could not control. This pattern may be relevant to the mechanisms through which job strain (high demands associated with low control) influences cardiovascular disease risk.

T cells specific for the myelin oligodendrocyte glycoprotein mediate an unusual autoimmune inflammatory response in the central nervous system

Myelin oligodendrocyte glycoprotein (MOG)-specific T cells mediate an autoimmune inflammatory response in the central nervous system (CNS) that differs radically from conventional models of T cell-mediated experimental allergic encephalomyelitis (EAE). Using synthetic peptides an encephalitogenic T cell epitope of MOG for the Lewis rat was identified within the extracellular IgG V-like domain of the protein, amino acids 44-53 (FSRVVHLYRN). The adoptive transfer of CD4+ T cells specific for this epitope induce an intense, dose-dependent inflammatory response in the CNS of naive syngeneic recipients. However, unlike the inflammatory response induced by myelin basic protein (MBP)-specific T cell lines, inflammation mediated by the MOG peptide-specific T cells failed to induce a gross neurological deficit. This unexpected observation was not due to a reduction in the overall inflammatory response in the CNS, but was specifically associated with a decrease in the extent of parenchymal (as opposed to perivascular) inflammation, a selective decrease in the number of ED1+ macrophages infiltrating the CNS, and a total lack of peripheral nerve inflammation. The decreased recruitment of macrophages into the CNS could not be ascribed to deficiencies in the synthesis of interferon-gamma, tumor necrosis factor-alpha, interleukin (IL)-6 or IL-2 by the T cell line. Moreover, this sub-clinical inflammatory response induced severe blood-brain barrier dysfunction as demonstrated by the induction of severe clinical disease following intravenous injection of a demyelinating MOG-specific monoclonal antibody. The neurological deficit in EAE thus exhibits an unexpected dependence on the identity of the target autoantigen, which determines the extent and nature of the local inflammatory response and ultimately the extent of the neurological deficit.

IGFBP-1: a metabolic signal associated with exercise-induced amenorrhoea

Severe exercise in young females is a potent cause of menstrual irregularity, although the exact pathogenesis is currently unknown. We performed a cross-sectional endocrine and metabolic analysis of a group of elite athletes and dancers in order to establish which variable, if any, was specifically associated with changes in menstruation. By using a step-wise discriminant analysis, two independent predictors, elevated serum cortisol and insulin-like growth factor binding protein 1 (IGFBP-1) levels, were found to account for the majority (67%) of the variance. IGFBP-1 is a hepatic protein which is acutely and inversely regulated by insulin, and is thought to modulate the peripheral actions of IGF-1. While the change in serum cortisol may reflect activation of central stress pathways, these findings suggest for the first time that there is a second peripheral signal, IGFBP-1, which may relate the availability of metabolic fuels to the control of reproduction.

Age influences magnitude but not duration of response to levodopa

Following an all-night fast, 45 patients with Parkinson's disease were examined using certain motor items present in the United Parkinson's Disease Rating Scale. All were given a single tablet of carbidopa 25 mg and levodopa 250 mg and re-examined 90 minutes later. In addition to this evaluation, 23 of these patients underwent further scoring over a 4-hour period. A significant negative correlation was found between age and one important aspect of drug-derived benefit: magnitude of response. In contrast, age had no apparent influence on duration of benefit from the drug. Although baseline (fasting) scores were predictably correlated with duration of disease, magnitude of response was not adversely influenced by this variable. Not all Parkinsonian signs were equally influenced by age. Whereas the poor response of gait and bradykinesia appeared to be dependent on age, no such effect was noted on rest tremor scores. The data indicate that in patients with Parkinson's disease treated long term, factors associated with age rather than duration of disease may have a stronger adverse influence on magnitude of response to levodopa.

Placental protein 14 secretion during in vitro fertilization cycles with and without human chorionic gonadotropin for luteal support

OBJECTIVE

To investigate levels of placental protein 14 (PP14) in in vitro fertilization (IVF) patients with and without exogenous human chorionic gonadotropin (hCG) for luteal support.

DESIGN, PATIENTS

Thirty-one women undergoing IVF were studied. For 18 women, hCG was administered in the luteal phase, and 12 became pregnant. Five pregnancies occurred in 13 women not receiving exogenous hCG.

SETTING

All the patients attended the University of Southampton/Chalybeate Hospital IVF program.

RESULTS

There was no change in PP14 levels 2 days after embryo transfer (ET), but small significant rises were noted by day 8 in all patients. Thereafter, levels rose further in pregnant subjects but showed no change in nonpregnant patients. The highest level of PP14 was seen in the group of women on hCG support, but there was no overall statistical difference between those on support and those not. In the nonpregnant group, there was no significant correlation between progesterone (P) and PP14 8 days from ET, whereas a highly significant correlation was noted in the pregnant group.

CONCLUSIONS

Neither hCG nor P are primary factors in the control of endometrial PP14 secretion, but PP14 and P may have common underlying control mechanisms.

Mechanical properties of the human lumbar anterior longitudinal ligament

A new technique incorporating a motion analysis system and a materials testing machine was used to investigate regional differences in the tensile mechanical properties of the lumbar spine anterior longitudinal ligament (ALL). Bone-ALL-bone specimens were prepared from young human cadaveric motion segments with no disc or bony pathology. Each specimen was distracted until failure at a constant crosshead displacement rate of 2.5 mm s-1 (approximately 1.0% strain per second). Strains were evaluated from digitized video recordings of markers attached to the ALL at 12 sites along its length and width, including the ligament substance and insertions. The 'overall' strain in the ligament was calculated from the outermost pairs of markers along the ligament length. The average tensile strength, the 'overall' tensile modulus and the 'overall' strain of the ALL at failure were 27.4 MPa (S.D. 5.9), 759 MPa (S.D. 336) and 4.95% (S.D. 1.51), respectively. Large and significant variations in the strains were present along the width and length of the ALL. Peak substance strains were over twofold greater than peak strains at the ligament insertion sites, whereas across the ligament width, peak strains in the outer portion of the ligament were over 40% greater than in the central region. Failure consistently occurred in the ligament mid-substance and ultimate strains at the ligament failure site averaged 12.1% (S.D. 2.3). These results indicate that the strains are highly nonuniform in the normal ALL.

The biomechanical and histopathologic effects of surface texturing with silicone and polyurethane in tissue implantation and expansion

There has been considerable interest in determining the effect of morphologic alterations of prosthetic surfaces on capsule response in breast surgery. The purpose of this study was to provide a precise, three-dimensional evaluation of soft-tissue response to surface modifications in both implantation and expansion. Expandable 100-cc prostheses were designed with one of three surfaces: textured silicone (Biocell), standard smooth silicone, or polyurethane (Natural-Y, Meme). A new submuscular implantation site in the rabbit was developed. Each animal randomly received a smooth-surface device on one side and either a textured silicone or polyurethane device on the other. In one group of animals, the prostheses were expanded monthly. Capsular response was evaluated monthly in vivo using standardized techniques as well as biomechanical methods for up to 6 months in the expander group (n = 7 to 16) and 8 months in the implant group (n = 7 to 15). Analysis of biomechanical and histologic data revealed that prosthetic surface morphology can specifically alter capsular response. Polyurethane was the only effective surface in preventing capsular contracture in implantation. In expansion, both textured silicone and polyurethane surfaces resulted in significantly less capsular contracture and less resistance to expansion than comparable smooth-surfaced controls. Statistical comparisons reveal that the biomechanical methods utilized in this study provide the most precise and objective method of defining overall soft-tissue contracture around implanted biomaterials.

Role and specificity of T-cell subsets in spontaneous recovery from Friend virus-induced leukemia in mice

Spontaneous recovery from Friend virus complex-induced leukemic splenomegaly in H-2Db/b mice correlated with the appearance of Friend virus complex-specific cytotoxic T lymphocytes (CTL) detectable directly in spleen cell populations. By testing CTL on target cells containing expression vectors encoding individual retroviral structural proteins, the main viral protein recognized was shown to be the Friend murine leukemia helper virus envelope glycoprotein. In vivo depletion of CD8-positive T cells drastically reduced the incidence of recovery, providing direct evidence for the role of CD8-positive CTL in the spontaneous recovery process. In vivo depletion of CD4-positive cells had little effect on the early stages of recovery but did cause a marked reduction in the final incidence of recovery at 60 to 90 days. Thus, CD8-positive cells were required for the initiation of the recovery process, whereas CD4-positive cells appeared to be required for maintenance of the recovered status.

Coxsackie virus B4 infection of the mouse pancreas: I. Detection of virus-specific RNA in the pancreas by in situ hybridisation

The pathology of Coxsackie virus B4 (CVB4) infection in a murine model was investigated by in situ hybridisation using a biotinylated cDNA probe derived from CVB4. During the acute phase of infection virus RNA sequences were detected in the exocrine pancreas of 60% of mice infected with a pancreotropic variant of CVB4. A positive hybridisation signal was observed in other organs in some animals including the heart and liver of 1 mouse 28 days after infection. The cellular distribution of virus RNA sequences corresponded well with the histological findings in most tissues. Possible causes for failure of hybridisation in some infected pancreases are discussed in conjunction with potential application of the technique in human pancreas biopsy samples.

Short and long-term responses to metyrapone in the medical management of 91 patients with Cushing's syndrome

OBJECTIVE

To analyse the clinical and biochemical effects of metyrapone in the treatment of Cushing's syndrome.

DESIGN

An evaluation of the standard clinical practice at one institution.

PATIENTS

Ninety-one patients with Cushing's syndrome: 57 pituitary-dependent Cushing's disease, 10 adrenocortical adenomas, six adrenocortical carcinomas and 18 ectopic ACTH syndrome.

MEASUREMENTS

The acute response to metyrapone was assessed by measuring cortisol, 11-desoxycortisol and ACTH at 0, 1, 2, 3, 4 hours after a test dose of 750 mg of metyrapone. The longer-term effect of metyrapone was judged by measuring serum cortisol at 0900, 1200, 1500, 1800, 2100 and sometimes 2400 h and calculating a mean.

RESULTS

A test dose of 750 mg of metyrapone decreased serum cortisol levels within 2 hours in all groups of patients and this effect was sustained at 4 hours. At the same time, serum 11-desoxycortisol levels increased in all patients, while plasma ACTH increased in patients with pituitary Cushing's disease and the ectopic ACTH-syndrome. Fifty-three patients with Cushing's disease were followed on short-term metyrapone therapy (1 to 16 weeks) before other more definitive therapy. Their mean cortisol levels (median 654 nmol/l, range 408-2240) dropped to the target range of less than 400 nmol/l in 40 patients (75%) on a median metyrapone dose of 2250 mg/day (range 750-6000). Metyrapone was given long term in 24 patients with Cushing's disease who had been given pituitary irradiation, for a median of 27 months (range 3-140) with adequate control of hypercortisolaemia in 20 (83%). In 10 patients with adrenocortical adenomas and six with adrenocortical carcinomas, metyrapone in a median dose of 1750 mg/day (range 750-6000) reduced their mean cortisol levels (median 847 nmol/l, range 408-2000) to less than 400 nmol/l in 13 patients (81%). In 18 patients with the ectopic ACTH-syndrome the 'mean cortisol levels', obtained from five or six samples on the test day (median 1023 nmol/l, range 823-6354) were reduced to less than 400 nmol/l in 13 patients (70%), on a median dose of 4000 mg/day (range 1000-6000). Reduction of cortisol levels was clearly associated with clinical and biochemical improvement. The medication was well tolerated. Transient hypoadrenalism and hirsutism were unusual but were the most common side-effects.

CONCLUSIONS

In our experience metyrapone remains a most useful agent for controlling cortisol levels in the management of Cushing's syndrome of all types.

Income guarantee is hospitals' lure of choice

Income guarantees are hospitals' lure of choice when trying to reel in physicians to their facilities. More than 90% of hospitals responding to a recent survey offer the income guarantees, which recruiters say physicians have grown to expect. Some 74% of the hospitals require physicians to repay the loan but will forgive the loan if the physician agrees to take on administrative or clinical duties at the hospital.

Lack of modulation of the adrenocortical response to ACTH by an opioid peptide

Eight normal male subjects received 1 mg dexamethasone at 23.00 h and 0.5 mg on wakening followed by a physiological intravenous dose of synthetic ACTH1-24 250 ng, with and without the administration of a stable met-enkephalin analogue (guanyl-DAMME, 100 micrograms) 10 minutes prior to the ACTH. The opioid analogue caused no change in the peak, incremental, or incremental area under the curve responses of plasma cortisol to the ACTH. This study does not support a role for opioid peptides in the acute modulation of the adreno-cortical response to ACTH.

Technique for quantification of LTB4-induced changes in peripheral granulocyte counts in vivo in the rabbit

A method to quantify leukotriene B4-(LTB4)-induced changes in peripheral granulocyte counts in the rabbit is described. Rabbits were surgically prepared with vascular access ports cannulating the right external jugular vein. This preparation made possible rapid, accurate, and repeated sampling of venous blood. Intravenous infusion of LTB4 (0.5-2 micrograms/mL) into the left marginal ear vein was found reproducibly to cause an initial, rapid (1-5 min) leukopenia (64%-100% reduction) followed by an extended (20-30 min) leukocytosis (121%-178% increase). Saline infusion for 30 min resulted in no changes in peripheral granulocyte number. The method described was sensitive and reproducible enough to allow evaluation of the LTB4 receptor antagonist, LY223982 (10 mg/kg, i.v.), which was shown to block both the leukopenia and the leukocytosis induced by LTB4 infusion.