The characteristics of low and high affinity [3H]-prazosin binding to membranes from rat renal cortex

The characteristics of [3H]-prazosin binding in renal cortical membranes of the rat have been assessed under a variety of buffer conditions. At 37 degrees, in Krebs' phosphate and Tris buffer, [3H]-prazosin bound to two sites, a small population of high affinity sites with properties of alpha1-adrenoceptors and a much larger population of low affinity sites with different characteristics. High affinity [3H]-prazosin binding was insensitive to Na+, K+, Ca2+ and Mg2+ ions, but low affinity [3H]-prazosin binding was markedly increased in Krebs' phosphate or sodium phosphate buffer and further enhanced in membranes pretreated with EGTA. Binding was decreased in the presence of Ca2+, the decrease in binding mainly being due to a decrease in the number of low affinity sites labelled by the ligand. Low affinity [3H]-prazosin binding was increased at 37 degrees and relatively insensitive to alpha-adrenoceptor antagonists which were weak competitors while catecholamines failed to compete for low affinity binding. Scatchard plots of [3H]-prazosin binding performed using (-)-noradrenaline (1 mM) to define non-specific binding defined binding only to alpha 1-adrenoceptors. This provides a means of differentiating high and low affinity [3H]-prazosin binding.     

'Good prognosis tumours' in breast cancer screening.

The Forrest Report led to the introduction of the breast screening programme with the aim of reducing mortality from breast cancer. In 1989 a breast screening programme was introduced to the South Bucks District and now two cycles have been completed. The findings are of a high yield of good prognosis tumours 71% and 72%, respectively. These encouraging figures are reflected in a high response rate and with a fall in the incidence of non-screen-detected tumours.     

Sequential stopping rules in clinical trials

This paper reviews aspects of the development of sequential analysis of clinical trial data in medicine and suggests simple strategies for progress. The emphasis is on the pragmatic and ethical requirements of aspects of the design of phase III trials and in circumstances of genuine uncertainty characterized by much clinical experimentation. In particular consideration is given to the consequences of determining sample sizes from incorrect estimates of treatment effects. Armitage's work on sequential trials is traced to simple group sequential procedures based on repeated significance tests to minimize expected sample sizes in a wide class of experimental situations.     

Thyroid-stimulating hormone restores bone volume, microarchitecture, and strength in aged ovariectomized rats.

We show the systemic administration of low levels of TSH increases bone volume and improves bone microarchitecture and strength in aged OVX rats. TSH's actions are mediated by its inhibitory effects on RANKL-induced osteoclast formation and bone resorption coupled with stimulatory effects on osteoblast differentiation and bone formation, suggesting TSH directly affects bone remodeling in vivo. INTRODUCTION: Thyroid-stimulating hormone (TSH) receptor haploinsufficient mice with normal circulating thyroid hormone levels have reduced bone mass, suggesting that TSH directly affects bone remodeling. We examined whether systemic TSH administration restored bone volume in aged ovariectomized (OVX) rats and influenced osteoclast formation and osteoblast differentiation in vitro. MATERIALS AND METHODS: Sprague-Dawley rats were OVX at 6 months, and TSH therapy was started immediately after surgery (prevention mode; n = 80) or 7 mo later (restoration mode; n = 152). Hind limbs and lumbar spine BMD was measured at 2- or 4-wk intervals in vivo and ex vivo on termination at 8-16 wk. Long bones were subjected to microCT, histomorphometric, and biomechanical analyses. The direct effect of TSH was examined in osteoclast and osteoblast progenitor cultures and established rat osteosarcoma-derived osteoblastic cells. Data were analyzed by ANOVA Dunnett test. RESULTS: In the prevention mode, low doses (0.1 and 0.3 microg) of native rat TSH prevented the progressive bone loss, and importantly, did not increase serum triiodothyroxine (T3) and thyroxine (T4) levels in aged OVX rats. In restoration mode, animals receiving 0.1 and 0.3 microg TSH had increased BMD (10-11%), trabecular bone volume (100-130%), trabecular number (25-40%), trabecular thickness (45-60%), cortical thickness (5-16%), mineral apposition and bone formation rate (200-300%), and enhanced mechanical strength of the femur (51-60%) compared with control OVX rats. In vitro studies suggest that TSH's action is mediated by its inhibitory effects on RANKL-induced osteoclast formation, as shown in hematopoietic stem cells cultivated from TSH-treated OVX rats. TSH also stimulates osteoblast differentiation, as shown by effects on alkaline phosphatase activity, osteocalcin expression, and mineralization rate. CONCLUSIONS: These results show for the first time that systemically administered TSH prevents bone loss and restores bone mass in aged OVX rats through both antiresorptive and anabolic effects on bone remodeling.     

Management of cerebral hemispherectomy in children

Surgical removal of a cerebral hemisphere may be undertaken in patients with intractable seizure disorders. Anesthetic management of such patients has not been reviewed in detail before. This study retrospectively analyzed hospital records of ten patients undergoing cerebral hemispherectomy at the Johns Hopkins Hospital between July 1983 and February 1988. Patient records were reviewed for diagnosis, physical characteristics, preoperative medications, anesthetic management, and postoperative course in the intensive care unit (ICU). Massive and sudden blood loss was a common finding in these patients, and during the intraoperative and postoperative periods, fluid resuscitation frequently was an ongoing process. In some patients, the blood loss exceeded one blood volume and was associated with coagulopathy, hypokalemia, and hypothermia. Urine output was elevated by a glucose-induced diuresis in some patients, giving misleading information as to intravascular volume status. Seizures and hemorrhage into the hemispherectomy cavity were management problems in the ICU. From this review, the authors conclude that blood loss may be marked and precipitous during surgical removal of a cerebral hemisphere. Monitoring of intra-arterial pressure and central venous pressure (CVP) is necessary for patient management during the intraoperative and postoperative periods. Intravenous (IV) access should allow rapid intravascular volume administration as it becomes necessary. Patients should remain intubated and observed closely during the immediate postoperative period due to difficulties with hemodynamic stability, seizures, and hemorrhage.     

Situational panic attacks. Behavioral, physiologic, and biochemical characterization

To investigate the pathophysiology of nonpharmacologically induced panic attacks, 18 drug-free agoraphobic patients and 13 matched healthy subjects underwent structured exposure to phobic situations. Heart rate, blood pressure, and plasma free 3-methoxy-4-hydroxyphenylglycol (MHPG), cortisol, growth hormone, and prolactin levels were measured before, during, and after exposure. Fifteen patients experienced situational panic attacks during exposure. Panicking patients displayed significantly greater increases in heart rate but not blood pressure or plasma free MHPG or cortisol in comparison with the healthy subjects. Growth hormone and prolactin responses tended to be smaller in the patients. If brain noradrenergic hyperactivity occurs during situational panic attacks, it may be too brief or too restricted in regional localization to affect MHPG levels in plasma. Chronically recurrent attacks may cause an adaptation of neuroendocrine mechanisms activated by anxiety or stress.