Unenhanced brain CT is useful to decide on further imaging in suspected venous sinus thrombosis

AIM

To assess the value of unenhanced brain computed tomography (CT) in the diagnosis of cerebral venous sinus thrombosis (CVST).

MATERIALS AND METHODS

Unenhanced brain CT images of 26 patients with proven CVST were mixed with 26 age and sex-matched images from patients without CVST. Four readers reviewed the 52 brain CT images and were asked to score the examinations for the absence or presence of CVST on a scale from 0 to 4. The mean density in the different venous sinuses was measured by one radiologist.

RESULTS

The sensitivity of unenhanced brain CT for the diagnosis of CVST was 73%. There were no false-positive readings. A receiver-operating characteristic (ROC) analysis on these data resulted in an area under the curve of 0.86. Density measurements proved to be helpful, but could not detect all cases of CVST.

CONCLUSION

Unenhanced brain CT is a valid initial radiological examination in the diagnosis of CVST. Due to the absence of false-positives in the present series, unenhanced CT can be used to decide whether further imaging with CT angiography or magnetic resonance angiography is required.

The whirl sign in caecal volvulus: a decisive diagnostic clue

The case of a 35-year-old woman with acute right flank pain, right iliac fossa pain, nausea and vomiting for 6 hours is presented. Plain abdominal radiography and CT scan were performed to find the etiology. These exams showed no signs of colonic obstruction but thickened non-enhancing wall of caecum with ascites was suggestive for ischemia. The whirl sign depicted on CT was the decisive feature for the diagnosis of caecal volvulus.

Outcomes following unilateral uterine artery embolisation

Uterine artery embolisation has been described as successful only when both arteries are embolised. However, results in patients with one congenitally absent or previously ligated artery are unknown. Women suffering from symptomatic uterine myomata were treated at a university teaching hospital, a community hospital and an outpatient surgery centre. Retrospective review of patient response to embolisation was assessed by chart review and questionnaire. Uterine and dominant fibroid size response was assessed by comparing pre- and post-embolisation ultrasound examinations. This study analysed three patient groups within the general population: those who underwent unilateral embolisation because of technical failure, those who ultimately underwent bilateral embolisation after initial technical failure and those who underwent unilateral embolisation because of an absent uterine artery. 12 patients underwent unilateral embolisation, 4 of whom underwent this procedure because of an absent uterine artery. Three of these four patients had a congenitally absent uterine artery arising from the internal iliac artery and all three experienced successful outcomes. The fourth patient had a previously ligated internal iliac artery and her symptoms worsened after the procedure. Eight patients had unilateral embolisation due to technical failure. Five of these patients underwent a subsequent procedure during which the contralateral uterine artery was embolised. Four of these five patients had successful outcomes and one was lost to follow-up. Another of the eight patients suffered an arterial injury leading to technical failure, and was lost to follow-up. Of the two remaining patients with unilateral technical failure, only one had a successful outcome. This study concluded that patients who undergo unilateral embolisation for technical reasons should be offered a second embolisation procedure shortly after the initial procedure. Patients with a congenitally absent uterine artery may respond with similar success to those who underwent bilateral embolisation. In contrast, the patient with a previously ligated internal iliac artery failed. The numbers in this study are too small for statistical analysis and subsequent studies should be performed to confirm these findings.

Variation of employee benefit costs by age

Health care, pension, and disability plans account for the bulk of employers' benefit costs, as defined in this article. Because those costs tend to rise as employees get older, the age structure of the workforce affects not only employers' costs but ultimately their competitiveness in global markets. How much costs vary depends in large part on the structure of the benefits package provided. The method a company chooses to finance benefits generally varies with its size. This article focuses primarily on the benefit practices of large, private employers. In the long run, such employers pay the costs associated with the demographics of their workers, whereas small employers can often pool costs with other companies in the community. In addition, small employers often offer fewer benefits, and the costs and financing of those benefits are subject to the insurance markets and state regulations. The discussion of benefit packages is illustrated by case studies based on benefits that are typical for three types of organizations--a large traditional company such as steel, automobile, and manufacturing; a large financial services company such as a bank or health care organization; and a medium-sized retail organization. The case studies demonstrate the extent to which the costs of typical packages vary and reveal that employers differ radically in the incentives they offer employees to retire at a specific time. An employer can shift the variation in cost by age by changing the structure of the benefit program. The major forces that drive age differences in benefit costs are the time value of money (the period of time available to earn investment income and the operation of compound interest) and rates of health care use, disability, and death. Those forces apply universally, in the United States and elsewhere, and they have not changed in recent years. However, the marketplace and the prevalence of various types of benefit programs have changed, and those changes have generally resulted in less cost variation by age and more frequent employer selection of benefit packages that exhibit less variation by age.

Sweet's syndrome in association with Crohn's disease: report of a case and review of the literature

A 41-year-old woman developed a skin rash as part of Sweet's syndrome concurrent with the first episode of Crohn's disease of the colon. Sweet's syndrome, acute febrile neutrophilic dermatosis, may be associated with inflammatory, infectious, or neoplastic diseases. Its association with Crohn's disease is very rare, and when reported it has been mainly associated with Crohn's colitis. This association has been described in various stages of the disease. Sweet's syndrome may be considered one of the extraintestinal manifestations of Crohn's disease. Early diagnosis of this dermatosis may be important because of the prompt response to treatment with corticosteroids. The value of metronidazole should be considered because this medication may enhance response to treatment.

Pregnancy following uterine fibroid embolization

OBJECTIVE

This paper seeks to evaluate the ability to deliver term pregnancies following uterine fibroid embolization, and to identify impediments to pregnancy in the embolization procedure.

STUDY DESIGN

Four physicians performed embolization procedures at various facilities. Patients were asked if fertility was an issue prior to embolization. We measured follicle-stimulating hormone levels before and after embolization. Clinical follow-up, six months following embolization was obtained by interview. Patients were questioned regarding attempts to conceive, menstrual history, and subsequent pregnancy.

MAIN OUTCOME MEASURES

Complications were calculated upon the entire patient population, whether or not fertility was identified as a goal. Fertility risks from embolization were identified. We measured radiation exposure in a random consecutive group of 50 women undergoing embolization. All patients who conceived were asked the details of the pregnancy.

RESULTS

Four hundred women underwent uterine fibroid embolization between 1996 and 1999. One hundred and thirty nine patients stated a desire for fertility after embolization. Of these, 52 were <40 years old. Seventeen pregnancies have been reported in 14 women. Five spontaneous abortions were observed. Ten women have had normal term deliveries and two women are currently pregnant. No perfusion problems, either during the pregnancy or labor, were reported. The average radiation dosage calculated for 50 women undergoing embolization was 14 rads. Four women under 45 years old suffered premature menopause (10/1000). Two women underwent hysterectomy as a complication of embolization (5/1000).

CONCLUSION

The risks of infertility following embolization, premature menopause, and hysterectomy are small, as is the radiation exposure during embolization. These risks compare favorably with those associated with myomectomy. Fertility rates appear similar to patients undergoing myomectomy. No problems, either during pregnancy or delivery, have been observed after embolization. The course of pregnancy and delivery was normal after embolization with no maternal or fetal complications reported. These findings confirm results from other centers. Desire for future pregnancy is not a contraindication to fibroid embolization.

An integrated laser trap/flow control video microscope for the study of single biomolecules

We have developed an integrated laser trap/flow control video microscope for mechanical manipulation of single biopolymers. The instrument is automated to maximize experimental throughput. A single-beam optical trap capable of trapping micron-scale polystyrene beads in the middle of a 200-microm-deep microchamber is used, making it possible to insert a micropipette inside this chamber to hold a second bead by suction. Together, these beads function as easily exchangeable surfaces between which macromolecules of interest can be attached. A computer-controlled flow system is used to exchange the liquid in the chamber and to establish a flow rate with high precision. The flow and the optical trap can be used to exert forces on the beads, the displacements of which can be measured either by video microscopy or by laser deflection. To test the performance of this instrument, individual biotinylated DNA molecules were assembled between two streptavidin beads, and the DNA elasticity was characterized using both laser trap and flow forces. DNA extension under varying forces was measured by video microscopy. The combination of the flow system and video microscopy is a versatile design that is particularly useful for the study of systems susceptible to laser-induced damage. This capability was demonstrated by following the translocation of transcribing RNA polymerase up to 650 s.

Stock or cash? The trade-offs for buyers and sellers in mergers and acquisitions

In 1988, less than 2% of large deals were paid for entirely in stock; by 1998, that number had risen to 50%. The shift has profound ramifications for shareholders of both the acquiring and acquired companies. In this article, the authors provide a framework and two simple tools to guide boards of both companies through the issues they need to consider when making decisions about how to pay for--and whether to accept--a deal. First an acquirer has to decide whether to finance the deal using stock or pay cash. Second, if the acquirer decides to issue stock, it then must decide whether to offer a fixed value of shares or a fixed number of them. Offering cash places all the potential risks and rewards with the acquirer--and sends a strong signal to the markets that it has confidence in the value not only of the deal but in its own stock. By issuing shares, however, an acquirer in essence offers to share the newly merged company with the stockholders of the acquired company--a signal the market often interprets as a lack of confidence in the value of the acquirer's stock. Offering a fixed number of shares reinforces that impression because it requires the selling stockholders to share the risk that the value of the acquirer's stock will decline before the deal goes through. Offering a fixed value of shares sends a more confident signal to the markets, as the acquirer assumes all of that risk. The choice between cash and stock should never be made without full and careful consideration of the potential consequences. The all-too-frequent disappointing returns from stock transactions underscore how important the method of payment truly is.

New thinking on how to link executive pay with performance

As the stock market began its ascent in the mid-1990s, executive pay--always the subject of heated debate--mounted along with it. That's because among the largest U.S. companies, stock options now account for more than half of total CEO compensation and about 30% of senior operating managers' pay. One problem became particularly clear during the bull market's astonishing run: even below-average performers reap huge gains from stock options when the market is rising rapidly. The author proposes steps to close the gap between existing compensation practices and those needed to promote higher levels of achievement at all levels of the corporation. For top managers, he recommends replacing conventional stock options with options that are tied to a market or peer index. Below-average performers would not be rewarded under such plans; superior performers could, depending on the way plans were structured, receive even more. He notes that managers at the business unit level should not be judged on the company's stock price--over which they have little control--and advocates an approach that accurately measures the value added by each unit. Finally, he suggests how certain indicators of value can be used to measure the contribution of frontline managers and employees. The concept of pay for performance has gained wide acceptance, but the link between incentive pay and superior performance is still too weak. Reforms must be adopted at all levels of the organization. Shareholders will applaud changes in pay schemes that motivate companies to deliver more value.

Laparoscopic cholecystectomy for acute cholecystitis performed by residents in surgery: a risk factor for conversion to open laparotomy?

Recent observations point to a seemingly high conversion rate to laparotomy in cases of laparoscopic operations for acute cholecystitis that are performed by surgical residents. The purpose of the study is to evaluate those observations. In a retrospective nonrandomized study, conducted between February 1992 and December 1997, 285 laparoscopic operations for acute cholecystitis were analyzed. Those performed by attending surgeons were compared with those performed by residents assisted by attending surgeons. Of 123 laparoscopic operations performed by laparoscopic surgeons between February 1992 and September 1995, 20.3% were converted to laparotomy, compared with 41.3% of the 29 operations performed by the residents (p < 0.017), with no increase in complication rate. Factors like male sex, duration of upper abdominal pain, and severity of the inflammatory process were not significantly different in both groups. The residents' seniority did not influence the conversion rate. A constant and significant decrease in conversion rate to laparotomy was observed over the course of time, as the study proceeded to December 31, 1997 (p < 0.01). We conclude that the performance of difficult laparoscopic cholecystectomy by residents with the assistance of attending surgeons is feasible, but carries a higher conversion rate to laparotomy for reasons that are not entirely clear. The possibility of a learning curve of the residents is suggested.

Development of an HIV educational needs assessment tool

The learning needs of persons with HIV/AIDS continue to grow more complex as new treatments are developed and HIV disease shifts from being a terminal to a chronic illness. Clinicians could use a simple tool to help them to focus on what clients think is important to know about living with HIV/AIDS. This article describes the development of the HIV Educational Needs Assessment Tool (HENAT). HIV+ persons (N = 363) who were receiving health care in a variety of ambulatory and institutional settings participated in this research during 1990 and 1993-1994. Factor analysis was used to shorten the instrument into a form that could be used in any nurse/client interaction. Principal axis factor extraction and varimax rotation deleted 16 items. The remaining 34 items were grouped into six factors: Treatments, Entitlements, Relationships, Preventing Infections, Social Support, and Working. Cronbach's alphas were computed and results ranged from .70 to .88. Two month test-retest correlations for a subset of participants (n = 195) ranged from .54 to .67. HENAT can be used (a) to examine differences in perception of learning needs between clients with HIV disease and their health care providers, (b) to measure shifts in learning needs over time, (c) to relate HIV-specific learning needs to length of time living with HIV disease, (d) to give clients an opportunity to assess their learning needs, and (e) as part of a larger intervention study that evaluates the effectiveness of patient education.

Splenogonadal fusion diagnosed by spleen scintigraphy

Splenogonadal fusion (SGF) is a rare congenital malformation characterized by fusion of the spleen and a gonad (almost always the left one) frequently associated with orofacial and/or limb developmental abnormalities. Only 125 cases were reported between 1883 and 1994. This report concerns a case of SGF in a 20-yr-old woman with an accidental finding of a splenic space-occupying lesion protruding into the lower abdomen in ultrasound and CT. Radiocolloid spleen scintigraphy and SPECT proved to be the best procedure to establish the correct diagnosis of SGF. As SGF is often asymptomatic, more liberal use of splenic scintigraphy is suggested in patients with congenital limb and/or orofacial anomalies. SGF should be included among the differential diagnoses of left abdominal, pelvic or scrotal masses.

Laparoscopic management of acute cholecystitis. Prognostic factors for success

BACKGROUND

Laparoscopic cholecystectomy for acute cholecystitis is considered feasible and safe, but it is associated with a higher rate of conversion to laparotomy than elective cholecystectomy because of technical reasons and anatomical changes related to the inflammatory process. The value of several factors that might influence its successful completion has not been studied completely yet, including the role of residents in operating such cases under attending-surgeon surveillance.

METHODS

In a retrospective nonrandomized study, the medical charts of 182 patients that were operated for acute cholecystitis (94 of whom via the laparoscopic approach) were studied. The study was also conducted to study the effect of residents as operators.

RESULTS

Male sex, duration of right upper abdominal pain, and the severity of the inflammatory process have all been significantly and independently correlated with increased conversion rate to laparotomy. Operation time was not longer than that of the open approach, and hospital stay and complication rate were lower. Operations performed by residents were associated with twofold conversion rate to laparotomy, without increased complication rate (p < 0.012).

CONCLUSIONS

Laparoscopic management of acute cholecystitis is feasible and safe. Considering the factors discussed above, lowering the threshold for conversion is necessary in selected cases to maintain low morbidity rate. Integrating laparoscopic cholecystectomy for acute cholecystitis into surgical residency should be studied.

Taking the problem oriented medical record forward

The problem oriented medical record (POMR) has proved to be very successful in providing a structure that helps doctors record their notes about patients, and view those notes subsequently in a manner that quickly gives them a good understanding of that patients history. This approach has been validated by the American Institute of Medicine. With the increased use of computer systems that implement the POMR by doctors, the limitations of this structure have become apparent, and there is clearly scope for developing the model further to improve the quality of the data recorded, and adding meaning to it. This paper describes some of the limitations of the POMR, and discusses a number of areas in which it may be extended. Crucially, this is done in a manner which is both implementable, and usable. The extensions explored include some types of entity including encounters, episodes and subproblems; and an alternative view-the Timeline. The terminology used for the extensions is clarified. Mechanisms by which these extensions have been implemented are described. Ways in which systems can manage these extensions automatically are suggested. Such implementations are constrained by the need not to allow the demands of the computer to intrude into the patient encounter. They are also constrained by the requirements for reporting by professional and governmental institutions, and by what is pragmatically feasible in software and hardware.

The use of levonorgestrel implants (Norplant) for contraception in adolescent mothers

BACKGROUND

Although levonorgestrel implants (Norplant) would appear to be a good contraceptive option for adolescent mothers, there is little information about the use of Norplant in this population.

METHODS

We studied 100 postpartum adolescents who chose a contraceptive method at an urban teaching hospital between September 1991 and July 1992. Structured interviews were conducted and medical records were reviewed soon after delivery and at a mean (+/- SD) of 15.5 +/- 2.9 months post partum.

RESULTS

Forty-eight of the adolescent mothers chose Norplant, 50 chose oral contraceptives, and 2 (not further studied) chose barrier methods of contraception. The factors significantly associated with the choice of Norplant were older age (16.7 years among those who chose Norplant, vs. 16.2 years among those who chose oral contraceptives), multiparity (24 subjects vs. 6 subjects), and previous use of oral contraceptives (34 subjects vs. 21 subjects). During follow-up, there were no differences between the Norplant group and the oral-contraceptive group in the frequency of clinic visits (an average of 2.3 visits per subject in each group), failure to return after the postpartum visit (9 subjects vs. 11 subjects), or the incidence of sexually transmitted diseases (42 percent vs. 36 percent). At follow-up, 95 percent of the subjects in the Norplant group and 33 percent of those in the oral-contraceptive group were still using the method they had chosen (P < 0.001). During the first postpartum year 1 subject in the Norplant group and 19 in the oral-contraceptive group became pregnant (P < 0.001). Norplant users did not differ from all other adolescents studied with regard to sexual activity or condom use.

CONCLUSIONS

The selection of Norplant by adolescent mothers as a method of contraception is associated with higher rates of continued use and lower rates of new pregnancy than the selection of oral contraceptives and does not affect the use of health care services, sexual activity, condom use, or the rate of sexually transmitted diseases.

CFOs and strategists: forging a common framework

Companies have become increasingly polarized into two divergent camps: those who consider shareholder value the key to managing the company and those who put their faith in gaining competitive advantage. Indeed, that age-old debate between investing for the long term and showing outstanding short-term results is back - only this time the camps are flying banners with the new buzzwords of corporate America: competitive advantage and shareholder value. In this article, Alfred Rappaport attempts to settle the debate once and for all, arguing forcefully that establishing competitive advantage and creating shareholder value both stem from a common economic framework. In fact, long-term productivity is the hinge from which both sustainable competitive advantage and consistent results for the shareholder hang. But many managers refuse to accept this theory and cling to the mistaken belief that the market does not actually value the long-term productivity of their company but judges it only by its short-term performance. They then jump to a second mistaken conclusion: assuming they must depart from the shareholder-value model to improve their competitive position. Rappaport attacks these mistaken beliefs, showing that the stock market does value the long-term productivity of a company and that it is not necessary to depart from the shareholder-value model to improve a company's competitive position. Maximum returns for current shareholders will materialize only when managers maximize long-term shareholder value and deliver interim results that attest credibly to sustainable competitive advantage.

Low-dose intermittent trimethoprim-sulfamethoxazole for prevention of Pneumocystis carinii pneumonia in patients with human immunodeficiency virus infection

The important role of chemoprophylaxis for the prevention of Pneumocystis carinii pneumonia (PCP) in human immunodeficiency virus type 1 (HIV)-infected patients is undisputed. The most cost-effective regimen, however, is unknown. We reviewed our experience at two hospitals in the New York City area in which low-dose, intermittent therapy with the combination of trimethoprim and sulfamethoxazole was used to prevent PCP in HIV-infected patients. During a total of 202 months of primary prophylaxis in 32 patients and 319 months of secondary prophylaxis in 35 patients, PCP was diagnosed only once. More than 80% of patients were receiving zidovudine concomitantly. Adverse reactions to trimethoprim-sulfamethoxazole occurred in 31% and 52% of those receiving primary or secondary prophylaxis, respectively. When those patients who were considered ineligible to receive trimethoprim-sulfamethoxazole prophylaxis (principally based on a prior adverse drug reaction) are also factored in, then approximately 50% of HIV-infected patients are candidates for long-term trimethoprim-sulfamethoxazole prophylaxis. The projected cost savings of this prophylaxis regimen, compared with those currently recommended by the US Public Health Service, are enormous.

The staying power of the public corporation

Has the publicly held corporation out-lived its usefulness? In HBR's September-October 1989 issue, Michael C. Jensen of the Harvard Business School said "yes." The institutional shortcomings of the public corporation are so grave, he argued, that it must be considered fatally flawed. He described the emergence of a new form of enterprise-the LBO Association-that releases much of the untapped value and corrects many of the inefficiencies of large public companies. Alfred Rappaport, a professor and consultant who advises large public companies, joins the debate with a rebuttal to Jensen. Rappaport shares many of Jensen's criticisms of current strategic and financial practices among public companies. But he does not believe leveraged buyouts and other going-private transactions can replace the public corporation. This is so, he asserts, for two reasons: LBOs have a limited demand and a limited life. Rappaport argues that the publicly held corporation is worth saving. It is inherently flexible and self-renewing-properties that are fundamental to stability and progress in a market-driven economy and that transitory organizations like LBOs cannot replicate. Rappaport advances a four-point program to overhaul strategic planning, compensation, and governance to maximize shareholder value in public companies: 1. Find the highest valued use for all assets. 2. Limit investment to opportunities with credible potential to create value. 3. Return cash to shareholders when such value-creating investments are not available. 4. Establish incentives for managers and employees to focus on the critical business drivers that create value.

Postherpetic neuralgia: clinical experience with a conservative treatment

Ninety-seven consecutive cases of postherpetic neuralgia (PHN) were retrospectively reviewed. Patients comprised 49 women and 48 men with a mean age of 71.6 years. The most common painful locations were the chest and upper back (34%), abdomen and lower back (25.2%), and face (20.2%). Burning pain was the most common type of pain (61.3%). Lancinating pain was reported by 40% and throbbing pain by 22.6%. Treatments included drugs (mainly tricyclic antidepressant, anticonvulsant, and neuroleptic drugs), transcutaneous electrical nerve stimulation (TENS), and dry needling of muscles in the affected dermatomes. Positive response to treatment occurred in 18.5% of the patients after one visit. In 9.3% of the patients, the pain still could not be controlled after 10 visits of 2-week intervals. TENS proved to be effective in patients whose skin sensation was preserved. It was concluded that in most PHN cases, pain can be effectively controlled by conservative noninvasive therapy.

Role of central alpha-1 adrenoceptors in canine narcolepsy

The role of central alpha-1 adrenergic receptors in cataplexy was investigated in genetically narcoleptic Doberman pinschers. Treatment of narcoleptic dogs with 25-600 micrograms/kg prazosin, a selective alpha-1 adrenergic receptor blocker, exacerbated cataplexy, whereas treatment with the alpha-1 agonist, methoxamine, ameliorated it. Subsequent studies showed that the beneficial effects of classical treatments of human narcolepsy (amphetamines and tricyclic antidepressants) are antagonized by prazosin, suggesting that these drugs are active through an indirect alpha-1 stimulation (via an increase of norepinephrine in the synaptic cleft). Other studies confirmed that the observed effects were not due to peripheral alpha-1 cardiovascular involvement. Atropine, a central anticholinergic agent, but not methylatropine, a peripheral one, completely suppressed the prazosin effect, which suggests that adrenergic and cholinergic systems act sequentially and not independently to generate cataplexy. Little is known about the physiological role of central alpha-1 adrenoceptors. This series of experiments implicates these receptors in narcolepsy-cataplexy.

Effect of alpha 1-adrenoceptors blockade with prazosin in canine narcolepsy

The role of central alpha 1-adrenergic receptors in cataplexy was investigated in 4 narcoleptic poodles and 6 genetically narcoleptic Doberman pinschers. Treatment of narcoleptic dogs with prazosin, a selective alpha 1-adrenergic receptor blocker, exacerbated cataplexy in both narcoleptic dog breeds. Control and heterozygous Dobermans were not affected by the drug. Binding studies using [3H]prazosin revealed an increase in alpha 1-receptor binding apparently limited to the amygdala. The present study suggests that central alpha 1-adrenoceptors, whose role is still mostly unknown, play a fundamental role in controlling mechanisms involved in cataplexy and REM sleep.

Regulation of central alpha-adrenoceptors by serotoninergic denervation

Alpha 1- and alpha 2-adrenoceptors were assessed by binding studies using [3H]prazosin and [3H]p-aminoclonidine as ligands in membrane preparations from the cortex, hippocampus and hypothalamus of rats, 3 weeks after intracerebroventricular injection of the neurotoxin 5,7-dihydroxytryptamine. Cortical alpha 1 and hippocampal alpha 2 adrenoceptors were significantly increased. Treatment also affected the affinity of cortical alpha 2 adrenoceptors. These results suggest a heterologous, region-specific regulation of both subtypes of central alpha-adrenergic receptors by serotonin.

Solubilization of active brain alpha 1-adrenoceptors by a zwitterionic detergent

Solubilization of rat brain alpha 1-adrenoceptors was performed by treatment with 6 mM CHAPS (3-[(3-cholamidopropyl)dimethylammonio] - 1 - propanesulfonate). The alpha 1-adrenoceptor antagonist [3H]prazosin was shown to bind reversibly and specifically to the soluble extract obtained after centrifugation at 150,000 X g for 1 h. Separation of the soluble [3H]prazosin-bound complexes was performed by the polyethylene glycol precipitation technique followed by filtration. A Scatchard plot of the concentration-dependent binding curve showed only one class of binding sites, with a high affinity for [3H]prazosin. Affinity of the solubilized receptors for the ligand increased as the CHAPS concentration in the assay medium decreased; the number of binding sites remained unchanged (approximately equal to 70 fmol/mg protein). This corresponds to a 30% recovery of original membrane sites. The solubilized receptors presented the same characteristics of specificity and stereospecificity as membrane alpha 1-adrenoceptors. Moreover, 150 mM NaCl was found to modulate the affinity of epinephrine for the [3H]prazosin-bound soluble complex, as previously described for membrane preparations. Thus, CHAPS appears to be a suitable detergent for solubilizing rat brain alpha 1-adrenoceptors and preserving their functional activities.

Biochemical analysis and solubilization of central alpha 1-adrenoceptors in the rat

To study the structure and the molecular mechanisms of action of brain alpha-adrenoceptors, their solubilization was undertaken. alpha 1-Adrenoceptors were first successfully solubilized from fresh rat brain membranes by treatment with 0.3 percent deoxycholate, after prelabeling of the binding site by the highly specific tritiated antagonist 3H-prazosin. The complex thus solubilized underwent a rapid loss of activity at 25 degrees C. Direct solubilization of brain alpha 1-adrenoceptors was obtained by treatment with a new zwitterionic derivative of cholic acid (CHAPS) at a concentration of 5 to 10 mM. The soluble complex was detected by precipitation by polyethylene glycol 6,000 with gamma globulin as a carrier. Binding of 3H-prazosin at 25 degrees C was rapid; at 4 degrees C the steady state was obtained within two hours and remained unchanged for at least six hours. The affinity of the soluble binding site, determined by Scatchard analysis (congruent to 0.6 nM), varied with the concentration of detergent. Specificity of the membrane-bound receptor was preserved as demonstrated by incubation in the presence of alpha 1- and alpha 2-antagonists at various concentrations (by order of potency: prazosin greater than phentolamine greater than yohimbine). Stereoselectivity was also retained in the solubilized binding protein. The solubilization of an active brain alpha 1-adrenoceptor will allow further investigation at the molecular level.

A multivariate analysis of dichotomous opinions in dissensus disaster

Despite the absence of evidence supporting either environmental or economic damages resulting from the Argo Merchant oil spill of 1976, a questionnaire administered 11 months afterward to 258 randomly selected heads of households in four towns contiguous to the spill revealed that 60 percent thought damages had occurred. In a secondary analysis of the original data to examine the causes of the damage perceptions, a discriminant function was developed on a randomly selected test group and evaluated on a control group. The results support the hypothesis that incorrect damage perceptions resulted from a priori views on the part of younger, socially conscious, higher-achieving heads of households. Support is indicated for the hypothesis that a priori perceptions were reinforced after the event. The index for total discriminating power was .43 for the test group and .38 for the control group. Television was the major media information source.