Structure of cytochrome c2 from Rhodospirillum centenum

Cytochrome c(2) from the purple photosynthetic bacterium Rhodospirillum centenum has been crystallized by the sitting-drop vapour-diffusion method. The crystals belong to the orthorhombic space group P2(1)2(1)2(1), with unit-cell parameters a = 29.7, b = 59.9, c = 65.4 A, and diffract to a resolution limit of 1.7 A. The Fe-atom position was determined from its anomalous scattering contribution and a molecular-replacement solution was calculated. The correctness of the solution was confirmed by parallel isomorphous replacement studies. The resulting model has a type I cytochrome fold with two features, an extended alpha-helix and a surface-charge distribution, that are distinctive to this protein. The implications of these structural features for the ability of the cytochrome to serve as an electron carrier are discussed.

Volunteering and community service in adolescence

Since the 1980s, volunteering has been studied as an avenue for positive development in adolescents. Reviews in the early 1990s were mixed regarding the benefits of volunteering, questioning the ability to transfer volunteer skills to other aspects of life as well as the true reduction in risky behaviors the adolescent will go on to undertake. This article addresses the gaps in the prior reviews and looks more closely at the benefits of volunteering. The author suggests that adolescent volunteers develop fewer problem behaviors in their later teens, enjoy a sense of connection to their community, maintain a better work ethic, and show a greater concern for the welfare of others. There are innumerable options for integrating volunteering into the life of an adolescent. This article offers many options, reviews some of the most popular, and suggests conditions that may increase the success of a volunteering program.

The role of biomarkers in alcoholism medication trials

BACKGROUND

Increasingly, biomarkers are being incorporated into the research design of clinical trials on medications to reduce drinking in alcoholics. To date, however, there has been little analysis of the unique roles that biomarkers can play in such investigations or of the practical and conceptual considerations that surround their best use in this context.

METHODS

Clinical trials of alcoholism medications published between 1985 and the present were abstracted to determine how biomarkers were used and how changes in them related to self-report measures of drinking.

RESULTS

Six uses of biomarkers were identified: determination of subjects to be included or excluded in the trial; description of baseline sample characteristics; primary and secondary outcome assessment; corroboration of self-reports of drinking status; specification of patients likely to respond to the medication; and evaluation of drug safety.

CONCLUSION

Use of biomarkers in such studies appears warranted, particularly as an objective source of information on treatment efficacy that can be considered with patient self-report measures of drinking status. Biomarkers related to liver functioning also can assist in determination of drug safety for medications metabolized by the liver.

Individual interactions influence the crystalline order for membrane proteins

The role of contact interactions in the crystallization of membrane proteins was assessed by mutation of amino-acid residues on the surface of the reaction center from Rhodobacter sphaeroides. Five single-site mutants were constructed, with changes in contact regions found in the trigonal and tetragonal forms but not the orthorhombic form. Crystallization trials for the tetragonal form yielded either no crystals or crystals with an altered morphology, whereas crystals grew in the other two forms, indicating that these interactions are essential for the stability of the tetragonal crystals. Changes in the structures determined by X-ray diffraction of trigonal crystals for each mutant were related to the quality of the diffraction. Significant differences in the resolution limit of the crystals were associated with the loss of specific interactions between neighboring proteins. The results suggest that the contact regions are crucial for obtaining highly ordered crystals of membrane proteins.

Carbohydrate-deficient transferrin: an aid to early recognition of alcohol relapse

Although the primary use of biochemical markers of heavy drinking is to assist in screening for alcohol problems, laboratory tests may also aid in early identification of relapse. This report reviews research findings on a new marker, carbohydrate deficient transferrin (CDT), in alcoholics receiving treatment or in follow-up. It also offers recommendations on how CDT may be employed by clinicians monitoring drinking status.

Association of self-reported diseases and health care use with commonly used laboratory markers for alcohol consumption

The relationships of carbohydrate-deficient transferrin (CDT), gamma-glutamyltransferase (GGT) and their mathematical combination (gamma-CDT) with self-reported diseases were evaluated in a large cross-sectional risk factor survey. Significant gender effects were observed in associations of the markers with several medical conditions as well as with general health care utilization. In men, CDT was associated with rheumatoid arthritis. In both genders, GGT was positively associated with hypertension and diabetes. gamma-CDT was positively associated with hypertension in males and with asthma in females. This general population study demonstrates that these markers, although most commonly used to assess alcohol misuse, might also serve as health risk indicators.

Amphiphiles modify the properties of detergent solutions used in crystallization of membrane proteins

The effect of the amphiphile heptanetriol on the properties of solutions containing several detergents commonly used for crystallization of membrane proteins was characterized. The critical micelle concentration was found to be relatively unchanged by the presence of the amphiphile. In contrast, the addition of heptanetriol to solutions containing both detergent and polyethylene glycol exhibited significant shifts in the clouding behavior, with the largest shifts being for lauryl dimethylamine oxide. These results suggest that conditions favorable for crystallization of integral membrane proteins can be inferred from the properties of the detergents and amphiphiles.

The role of laboratory tests in alcoholism treatment

Although assessment in the field of alcoholism treatment is generally verbal in nature, biological tests can also provide counselors and program evaluators useful and unique information. Five such laboratory measures are briefly described, with particular emphasis on carbohydrate deficient transferrin, a biomarker recently approved by the FDA. Applications for laboratory tests in alcohol screening, motivating patients, and monitoring treatment progress are also proposed.

Eosinophilic cholangitis: a case of 'malignant masquerade'

BACKGROUND

A variety of causes of inflammatory bile duct stricture can masquerade as hilar cholangiocarcinoma. Eosinophilic cholangitis is a further example.

CASE OUTLINE

A 50-year-old woman with epigastric pain and deranged liver function was found to have a stricture of the common hepatic duct on ERCP with an associated mass on MRl.The lesion was excised with reconstruction of the right and left hepatic ducts, and the patient recovered well. Histopathological examination of the resected gallbladder and bile duct showed diffuse inflammation with a predominant eosinophil infiltrate.The presence of Candida albicans in the bile duct lumen can probably be attributed to the preoperative biliary stent.There was a modest postoperative rise in peripheral eosinophil count.

DISCUSSION

A literature search reveals only six previous cases of eosinophilic cholangitis, but similar infiltrates have also been seen in occasional cholecystectomy specimens. As the present patient did not have gallstones, the aetiology remains unclear. Peripheral eosinophilia is an unreliable clue to the diagnosis, which is usually likely to escape detection until the biliary stricture has been resected.

Autonomy and adolescent social functioning: the moderating effect of risk

This study examined the moderating effect of risk on the relation between autonomy processes and family and adolescent functioning. The present sample comprised 131 adolescents from either a low-risk or high-risk social context, their mothers, and their peers. Observational ratings of autonomy processes within the mother-adolescent dyad were obtained, along with adolescent reports of the quality of the mother-adolescent relationship, and both adolescent and peer reports of the adolescent's functioning. Consistent with past research, in low-risk families, behavior undermining autonomy was negatively related to relationship quality, and adolescents' expressions of autonomy were linked with positive indices of social functioning. In high-risk families, however, undermining of autonomy was positively linked with mother-adolescent relationship quality, and adolescents' expressions of autonomy were linked with negative indices of social functioning. Results are interpreted as demonstrating the ways in which the developmental task of attaining autonomy in adolescence is systematically altered depending on the level of risk and challenge in the adolescent's social context.

Possible reasons why heavy drinking increases carbohydrate-deficient transferrin

BACKGROUND

Transferrin is a globular protein synthesized in the liver that is responsible for iron transport in plasma. The structure of the molecule consists of two carbohydrate residues to which six sialic acid moieties can be attached. After periods of chronic, heavy alcohol consumption, carbohydrate-deficient transferrin (CDT) isoforms often increase, which makes CDT a useful marker in screening for alcohol abuse and monitoring progress of alcoholics in treatment. However, the precise mechanism behind CDT increase remains unknown.

METHODS

A review of the most relevant literature on CDT was conducted with a computer-assisted literature search.

RESULTS

During the past several years, a number of studies have explored possible mechanisms that may account for the alcohol-induced increase of CDT. An inhibition of protein synthesis and a general effect of alcohol on protein glycosylation have been reported. Although the exact mechanisms that underlie production of CDT are not yet fully understood, possible bases for the phenomenon are presented in this article.

CONCLUSIONS

Experimental findings indicate that the ethanol-induced effect on glycoprotein metabolism is a multistep process in which protein transport and changes of enzyme activity may play an important role.

Dose response of laboratory markers to alcohol consumption in a general population

The dose response to alcohol use of carbohydrate-deficient transferrin (CDT), gamma-glutamyltransferase (GGT), and their combination (gamma-CDT) was studied in an age- and gender-stratified, random sample from Finland in 1997. A linear association with a threshold between alcohol consumption and the three markers was observed. Body mass index was negatively associated with CDT and positively with GGT Age was positively associated with GGT and gamma-CDT In conclusion, CDT appears to be an early phase marker of alcohol consumption. The combined marker, gamma-CDT, was less associated with factors such as body mass index but more strongly correlated with alcohol consumption than were the two markers separately.

Presentation of intravascular lymphomatosis as lumbosacral polyradiculopathy

A 53-year-old man developed progressive sensory disturbance and weakness in the legs, sphincter disturbance, back pain, systemic symptoms, and pancytopenia. Electrophysiological tests indicated a widespread lumbosacral polyradiculopathy. Spinal magnetic resonance imaging and routine cerebrospinal fluid analysis showed minor nonspecific abnormalities. Bone marrow and liver biopsies showed hemophagocytosis; and polymerase chain reaction of cerebrospinal fluid, bone marrow, and serum suggested active infection with human herpesvirus-6. Autopsy revealed that his neurological symptoms resulted from intravascular lymphomatosis (angiotropic large cell lymphoma), a rare variant of lymphoma with predilection for the nervous system.

Advances in understanding neuronal somatostatin receptors

It has long been considered that somatostatin acts as a neuromodulator in the mammalian central nervous system but its precise physiological roles remain elusive. Early studies to identify somatostatin-binding sites revealed a widespread heterogeneous pattern, especially in the CNS. More recently, a family of somatostatin receptors have been identified, of which five genes (sst(1-5)) have been cloned. In this review, we discuss current data describing the localisation of the five receptor types. Recent progress in understanding their function has been made using high-affinity, selective receptor ligands and transgenic animal technology. Finally, the therapeutic potential for somatostatin receptor-selective compounds as analgesics is considered.

Carbohydrate-deficient transferrin, gamma-glutamyltransferase, and macrocytic volume as biomarkers of alcohol problems in women

BACKGROUND

Early identification of alcohol problems in women is important. Differences in patterns of drinking and in biological function between genders, however, may present unique difficulties in biochemical screening.

METHODS

Published alcohol-screening studies with female samples and use as biomarkers of carbohydrate-deficient transferrin (CDT), gamma-glutamyltransferase (GGT), and macrocytic volume were reviewed.

RESULTS

A wide range of sensitivities and specificities of GGT and CDT have been reported, although, in general, the two markers seem approximately equal in accuracy. As in the case of males, use of them in combination substantially enhances sensitivity and little reduces specificity. Use of macrocytic volume improves the sensitivity of both GGT and CDT as alcohol-screening markers.

CONCLUSIONS

GGT and CDT have moderate sensitivity in screening for alcohol problems in women. Use of them in concert offers further advantage.

Measuring treatment process variables in Alcoholics Anonymous

Alcoholism treatment research has traditionally focused on direct questions of efficacy, such as is a particular intervention better than no treatment or is one treatment more effective than another. Recent projects, however, have also attempted to identify variables explaining why treatments vary in their effects. Many of these variables relate to the process of treatment itself or changes that may occur within the patients. Clinicians also need to continuously monitor progress of patients in engaging in behaviors supportive of long-term sobriety and how well the values and behaviors fostered by the particular treatment regimen are being incorporated into daily life. Measurement of process variables may assist in both regards. In the last decade several psychometric instruments have been developed to elucidate the processes involved in Alcoholic Anonymous (AA), a key adjunct of most formal alcoholism programs in the United States. These instruments measure dimensions such as involvement in AA, completion of steps, and adoption of values encouraged by AA. Six such measures are summarized here and several fruitful topics for future research on the measures are suggested.

P+HA- charge recombination reaction rate constant in Rhodobacter sphaeroides reaction centers is independent of the P/P+ midpoint potential

The kinetics of the P+HA- (oxidized donor, reduced bacteriopheophytin acceptor) recombination reaction was measured in a series of reaction center mutants of Rhodobacter sphaeroides with altered P/P+ midpoint potentials between 410 and 765 mV. The time constant for P+HA- recombination was found to range between 14 and 26 ns and was essentially independent of P/P+ midpoint potential. Previous work has shown that the time constant for initial electron transfer in these mutants at room temperature is also only weakly dependent on the P/P+ midpoint potential, ranging from about 2.5 ps to about 50 ps. These results, taken together, imply that heterogeneity in the P/P+ midpoint potential within the reaction center population is not likely the dominant cause of the substantial kinetic complexity observed in the decay of the excited singlet state of P on the picosecond to nanosecond time scale. In addition, the pathway of P+HA- decay appears to be direct or via P+BA- rather than proceeding back through P, even in the highest-potential mutant, as is evident from the fact that the rate of P+HA- recombination is unaltered by pushing P+HA- much closer to P in energy. Finally, the midpoint potential independence of the P+HA- recombination rate constant suggests that the slow rate of P+HA- recombination arises from an inherent limitation in the maximum rate of this process rather than because it occurs in the inverted region of a classical Marcus rate vs free energy curve.

Crystallization and preliminary X-ray diffraction studies of the 51 kDa protein of the mosquito-larvicidal binary toxin from Bacillus sphaericus

Certain strains of Bacillus sphaericus produce a highly toxic mosquito-larvicidal protein during sporulation which is active against vectors of dengue, encephalitis and malaria. This toxin is initially expressed as 51 and 42 kDa proteins and is converted to 43 and 39 kDa proteins, respectively, which form the active heterodimer complex. For a better understanding of the toxicity mechanism at the molecular level, the 51 kDa protein of the binary toxin of B. sphaericus strain 2297 was expressed as a glutathione-S-transferase fusion protein and purified by affinity chromatography. Protein crystals were grown from an amorphous precipitate in five months using the hanging-drop vapor-diffusion method. The protein crystals were dissolved and were found to be composed of a proteolytically modified 45.2 kDa derivative similar to the active form of this protein. The crystals form in space group P43212 (or P41212) and diffract to 2.6 A, with unit-cell dimensions a = b = 133.48, c = 69. 76 A.

Medications for alcohol, illicit drug, and tobacco dependence. An update of research findings

Physiologic, behavioral, and social factors contribute to dependence on alcohol, nicotine, and other drugs. During the past decade substantial research has focused on identification/development of medications to assist in reducing urge to use these substances. This article describes these agents and reviews recent research findings on them.

Contribution of carbohydrate deficient transferrin to gamma glutamyl transpeptidase in evaluating progress of patients in treatment for alcoholism

Eight previous investigations have suggested that conjoint consideration of findings on tests for gamma glutamyl transpeptidase (GGT) and carbohydrate deficient transferrin (CDT) substantially enhances sensitivity of screening for alcohol problems while minimally diminishing specificity. Using results from a large clinical trial, the current study evaluated the two tests singly and in combination as measures of three clinically important treatment outcome criteria: any drinking, at least one day of heavy drinking, and at least three consecutive days of heavy drinking during the past month. When scored by quartile, CDT is slightly better at screening for alcohol problems in males than GGT. However, CDT seems less accurate in females than GGT. Use of the two tests in consort moderately improves the individual test accuracy in predicting drinking status for both genders.

Photosynthetic reaction centers

The reaction center is the key component for the primary events in the photochemical conversion of light into chemical energy. After excitation by light, a charge separation that spans the cell membrane is formed in the reaction center in a few hundred picoseconds with a quantum yield of essentially one. A conserved pattern in the cofactors and core proteins of reaction centers from different organisms can be defined based on comparisons of the three dimensional structure of two types of reaction centers. Different functional aspects of the reaction center are discussed, including the properties of the bacteriochlorophyll or chlorophyll dimer that constitutes the primary electron donor, the pathway of electron transfer, and the different functional roles of the electron acceptors. The implication of these results on the evolution of the reaction center is presented.

The effect of drinking intensity and frequency on serum carbohydrate-deficient transferrin and gamma-glutamyl transferase levels in outpatient alcoholics

Whereas heavy alcohol consumption is known to elevate serum carbohydrate-deficient transferrin (CDT) and gamma-glutamyl transferase (GGT) levels, the contribution of drinking pattern to these effects is not completely understood. We present data on 423 men and 146 women evaluated 1 year after treatment in a large-scale alcoholism treatment study (Project MATCH). Relationships between drinking frequency (number of days drinking), intensity (drinks per drinking day), and blood levels of CDT and GGT were analyzed by using response surface regression models and thin-plate spline-smoothing techniques. Both models indicated differences between CDT- and GGT-drinking pattern relationships in men and, also, a difference between men and women in CDT drinking-pattern relationships. For men, CDT levels appeared to respond primarily to frequency of drinking, whereas GGT was influenced primarily by drinking intensity. For women, both CDT and GGT were influenced more by drinks per drinking day (intensity) than by number of days drinking (frequency). The data confirm both the independent nature of these biological markers of alcohol consumption and gender differences in alcohol-induced CDT response reported previously.