Investigation of cutaneous photoadaptation to narrowband ultraviolet B.

BACKGROUND: Photoadaptation describes the skin's ability to withstand an increased dose of ultraviolet (UV) radiation with repeated exposure, and this is the reason for exposure doses being increased during a course of phototherapy. However, directly measured data on photoadaptation are available only for broadband (BB) and not narrowband (NB)-UVB. OBJECTIVES: To measure photoadaptation to narrowband UVB. METHODS: We measured the degree of photoadaptation in patients with psoriasis during a standard course of NB-UVB phototherapy. The minimal erythemal dose (MED) was measured before and towards the end of a course of phototherapy. An adaptation factor (AF) was calculated for each patient using the ratio of final MED to initial MED. Sigmoid dose-response curves were also constructed. RESULTS: MED results were available for 50 patients (mean age 44 years, 28 female). The mean AF was 2·7 (95% confidence interval 2·4-3·0). There was no significant correlation between AF and skin type or initial MED. Dose-response curves were right shifted and parallel after phototherapy, and there was no significant difference in the maximum slope (P = 0·73). CONCLUSIONS: The photoadaptation caused by NB-UVB is considerably less than that reported for BB-UVB. The variation in photoadaptation between patients was not explained by skin type or baseline MED. Physical factors (such as tanning and epidermal thickening) are probably sufficient to account for photoadaptation, rather than downregulation of the inflammatory response. These data should help in the design of phototherapy protocols for NB-UVB to achieve optimal clearance of psoriasis.

Clopidogrel: mechanisms of action and review of the evidence relating to use during skin surgery procedures.

Patients who have skin surgery may be taking medication that increases the likelihood of bleeding, such as clopidogrel, aspirin, warfarin, heparin and nonsteroidal anti-inflammatory drugs (NSAIDS). All of these may increase the risk of perioperative and postoperative bleeding. This article examines the mechanism of action of clopidogrel, current practice, and evidence for or against continuing its use during skin surgery. The mechanisms of action of aspirin, warfarin, heparin and NSAIDS will also be briefly discussed.

A role for unsaturated fatty acids in mitochondrial movement and inheritance.

Yeast cells with the mdm2 mutation display temperature-sensitive growth and defective intracellular mitochondrial movement at the non-permissive temperature. The latter phenotype includes both an absence of mitochondrial transfer into daughter buds of mitotically growing cells and an aberrant mitochondrial distribution in cells exposed to mating pheromone. The wild-type MDM2 gene was cloned by complementation, and DNA sequence analysis revealed a large open reading frame encoding a putative protein of 58.4 kD. The predicted protein sequence is identical to that reported for the yeast OLE1 gene encoding fatty acid desaturase. Unsaturated fatty acid levels are substantially decreased in mdm2 cells after a prolonged incubation at the non-permissive temperature. The addition of oleic acid complements the temperature-sensitive growth and mitochondrial distribution defects of the mutant cells. These results indicate that mdm2 is a temperature-sensitive allele of OLE1 and demonstrate an essential role for unsaturated fatty acids in mitochondrial movement and inheritance.

Temperature-sensitive yeast mutants defective in mitochondrial inheritance.

The distribution of mitochondria to daughter cells is an essential feature of mitotic cell growth, yet the molecular mechanisms facilitating this mitochondrial inheritance are unknown. We have isolated mutants of Saccharomyces cerevisiae that are temperature-sensitive for the transfer of mitochondria into a growing bud. Two of these mutants contain single, recessive, nuclear mutations, mdm1 and mdm2, that cause temperature-sensitive growth and aberrant mitochondrial distribution at the nonpermissive temperature. The absence of mitochondria from the buds of mutant cells was confirmed by indirect immunofluorescence microscopy and by transmission electron microscopy. The mdm1 lesion also retards nuclear division and prevents the transfer of nuclei into the buds. Cells containing the mdm2 mutation grown at the nonpermissive temperature sequentially form multiple buds, each receiving a nucleus but no mitochondria. Neither mdm1 or mdm2 affects the transfer of vacuolar material into the buds or causes apparent changes in the tubulin- or actin-based cytoskeletons. The mdm1 and mdm2 mutations are cell-cycle specific, displaying an execution point in late G1 or early S phase.

Aquagenic palmar wrinkling as a presenting feature of cystic fibrosis gene dysfunction.

Aquagenic palmar wrinkling (APW) is characterized by the rapid and transient oedematous wrinkling of the palms after brief immersion in water. APW has been associated with cystic fibrosis (CF). Since the discovery of the CF gene, the clinical spectrum of CF has broadened from classic severe CF to include milder 'atypical CF' and 'CF-related disorders'. We report an unusual case in which APW occurred in a patient with no lung disease, and in whom investigations showed evidence of CF gene dysfunction. APW may be a presenting feature of a CF-related disorder and should prompt investigation of CF gene dysfunction.

On the revised structure of the major phospholipid of Halobacterium salinarium.

Recent fast atom bombardment-mass spectrometry (FABMS) studies (Tsujimoto, K., Yorimitsu, S., Takahashi, T. and Ohashi, M. (1989) J. Chem. Commun. 668-670; Frederickson, H.L., De Leeuw, J.W., Tas, A.C., Van der Greef, J., LaVos, G.F. and Boon, J.J. (1989) Biomed. Environ. Mass. Spectrom. 18, 96-105; Kloppel, K.D. and Fredrickson, H.L. (1991) J. Chromatogr. 562, 369-376) have indicated that the structure of the major phospholipid of Halobacterium salinarium (formerly Halobacterium cutirubrum) is not 2,3-diphytanyl-sn-glycerol-1-phospho-3'-sn-glycerol-1'- phosphate (PGP), but the monomethylated derivative, 2,3-diphytanyl-sn-glycerol-1-phospho-3'-sn-glycerol-1'-methylphosphate (PGP-Me). We have now confirmed the structure of the major phospholipid of extremely halophilic archaebacteria as being this methylated structure (PGP-Me) by 1H- and 13C-NMR, FABMS and TLC of the native phospholipid and its product of mild acid hydrolysis PGP. The methylated structure (PGP-Me), rather than PGP itself, is also the major phospholipid in species of other genera of extreme halophiles examined so far, such as, Haloferax, Haloarcula, Halococcus, Natronobacterium and Natronococcus.

Synthesis and characterization of deoxy analogues of diphytanylglycerol phospholipids.

Novel analogues of diphytanyl phospholipids, 2,3-diphytanyl sn-1-glycerol-1-phosphoryl-1'-(1',3'-propanediol) (dPG), 2,3-diphytanyl-sn-glycerol-1-phosphoryl-1'-propanol (ddPG) and 2,3-diphytanyl-sn-glycerol-1-phosphoryl-1'-(1',3'-propanediol-3'-p hosphate) (dPGP), were synthesized according to modifications of previously published procedures. The samples were TLC and analytically pure and were characterized by 13C- and 1H-NMR and negative FAB/MS. The pK values of dPGP in aqueous dispersions or in methanol/water (1:1, v/v) were determined by potentiometric titration and compared with those of 2,3-diphytanyl-sn-glycerol-1-phosphoryl-3'-sn-glycerol-1'-phosphat e (PGP). The dissociation constant of the third ionizable POH group of dPGP was more than 2 pK units higher than that of PGP, indicating that the free glycerol hydroxyl group plays an important role in headgroup conformation and stabilization, perhaps through hydrogen bonding with the phosphate group(s).

The role of magnesium in myocardial preservation.

The purpose of this review is to look at the role of magnesium in the formation of preservation and reperfusion solutions for the ischaemic heart. Preservation of the heart during cardiac surgery procedures, including cardiac transplantation, can be divided into distinct phases: arrest, cold storage in the case of transplantation, global ischaemia during implantation or cardiac surgery procedures, followed by reperfusion when the heart is rewarmed and restarted. Although the magnesium ion can play a significant role in myocardial protection, it is important to recognize the different types of protection required during these different phases of surgical procedures. The rationale for the inclusion of magnesium in cardioplegic solutions is threefold: (i) for its negative inotropic effect; (ii) to prevent ischaemia-induced magnesium loss; (iii) to influence cellular ionic movements. Preservation temperature as well as the concentration of other ionic constituents present in the preservation solution alter the effects of magnesium. Results obtained from animal models suggest that elevated magnesium (16 mM) is beneficial to the hypothermic preservation of hearts with extracellular type solutions, especially when calcium is elevated in the solution formulation. Research has shown that the amplitude of the inotropic effect of magnesium varies from one species to another so that the beneficial effect of magnesium is inferior in the less sensitive species. Using the human atrial trabecular preparation as a model for myocardial preservation, we have assessed the effects of elevated magnesium on the recovery of developed force, both for long-term preservation (24 h) during hypothermic arrest (4 degrees C) and for reperfusion during rewarming of the trabeculae. No clear pattern emerged when the ratio of calcium to magnesium was altered in St Thomas' I and II solutions used for the storage. However, when the atrial trabecular preparation was rewarmed in a Krebs Henseleit buffer containing an elevated level of magnesium (16 mM), a greater number of trabeculae reached a greater developed force and had higher levels of energetic metabolites than when the magnesium in the Krebs Henseleit buffer was 1.2 mM. Several studies have suggested that an elevated magnesium prevents calcium overload by competing with this ion at the membrane, and reduces the workload, while ATP reserves and ion homoeostasis are re-established. The role of the magnesium ion in hypothermic preservation of the human myocardium is still not clear after many clinical and experimental studies and requires further investigation.(ABSTRACT TRUNCATED AT 400 WORDS)

Bacterial polysaccharide synthesis: an experiment for the dental biochemistry laboratory.

A simple experiment is described for demonstrating the formation of a high molecular-weight polysaccharide from sucrose by a bacterial enzyme. The polysaccharide confers high viscosity on solutions. Dental students are encouraged to consider this as a component of the system leading to the formation of dental plaque and the initiation of carious lesions.

Identification and management of the anxious patient within a model family practice unit.

Because anxiety is the third most common problem encountered in this Model Family Practice unit, the presentation and management of 36 randomly selected cases were reviewed. The incidence was not greater in one race, but was increased in all married females (age 25 to 35) who, despite wife or husband working, had a very low income. The foremost complaints were insomnia, headaches, and chest pain with 80% of the patients maintaing the same symptoms. The resident identified a conflict (the most frequent being marital problems) in 47% of the cases. Drug therapy was used in 86.1% with ten percent selected for symptom relief. Because there are times when an alternate to drug therapy is needed, an overview teaching series on brief psychotherapy is suggested as an appropriate part of the behavioral science curriculum in a residency program.

Patient problems in the office practice of six family physicians in Louisiana.

Using the Royal College of General Practitioners (RCGP) classification of disease, the patient problems encountered in six family practice offices were classified. The top 20 diagnoses are identified, collectively and individually, and compared with the top 20 diagnoses encountered in a similar, but larger study done in Virginia. The present study includes a regional practice profile based on the disease categories of Royal College of General Practitioners, which was compared with the distribution of problems in the Virginia data. This study confirms the Virginia information on the most frequently encountered problems. Collectively, southeastern Louisiana profiles show fewer respiratory problems and more circulatory problems than the Virginia study. Individually, each practice has a distinct enough profile to warrant consideration of individual practice profiles at the time of re-certification examination or planning of continuing education programs.

Cooperativity in the dopamine beta-monooxygenase reaction. Evidence for ascorbate regulation of enzyme activity.

The steady-state kinetic behavior of dopamine beta-monooxygenase (D beta M) has been examined over a 1000-fold range of ascorbate concentrations. Kinetic plots exhibit extreme curvature indicative of apparent negative cooperativity in the interaction of D beta M with ascorbate, with a calculated Hill coefficient of 0.15-0.30. The observed cooperativity is found to be independent of enzyme concentration and tyramine and oxygen concentrations, as well as the pH employed for the assay. Similar kinetic data have been obtained with both soluble and purified membrane-derived forms of enzyme. An investigation of the effect of the anion activator fumarate upon the observed kinetic patterns has demonstrated a conversion to a less cooperative kinetic pattern at low pH and high concentrations of fumarate. This phenomenon is attributed to an inhibitory binding of the structurally similar monoanionic species of fumarate to the ascorbate reductant site. A simple model has been used to assess the change in apparent Vmax and Km parameters with increased ascorbate concentrations. At all pH values examined, there is a dramatic decrease in the affinity of D beta M for ascorbate from a Km of approximately 0.05-0.10 mM (ascorbate concentration less than 1 mM) to Km greater than 10 mM at limiting ascorbate; at the same time there is a 3- to 4-fold increase in the limiting Vmax value. Several models have been considered to explain the observed activation of D beta M by high levels of ascorbic acid.

Characterization of alternate reductant binding and electron transfer in the dopamine beta-monooxygenase reaction.

The steady-state limiting kinetic parameters Vmax, V/KDA, and V/KO2, together with deuterium isotope effects on these parameters, have been determined for the dopamine beta-monooxygenase (D beta M) reaction in the presence of structurally distinct reductants. The results show the one-electron reductant ferrocyanide to be nearly as kinetically competent as the presumed in vivo reductant ascorbate. Further, a reductant system of ferricyanide plus substrate dopamine yields steady-state kinetic parameters and isotope effects very similar to those measured solely in the presence of ferrocyanide, indicating a role for catecholamine in the rapid recycling of oxidized ferrocyanide. Use of substrate dopamine as the sole reductant is found to lead to a highly unusual kinetic independence of oxygen concentration, as well as significantly reduced values of Vmax and V/KDA, and we conclude that dopamine reduces enzymic copper in a rate-limiting step that is 40-fold slower than with ascorbate. The near-identical kinetic parameters measured in the presence of either ascorbate or ferrocyanide, together with markedly reduced rates with dopamine, are interpreted in terms of a binding site for reductant that is physically distinct from the substrate binding site. This view is supported by molecular modeling, which reveals ascorbate and ferrocyanide to possess an unexpected similarity in potential sites for interaction with enzymic residues. With regard to electron flux, identical values of V/KO2 have been measured with [2,2-2H2]dopamine as substrate both in the presence and in the absence of added ascorbate.(ABSTRACT TRUNCATED AT 250 WORDS)

Bovine membranous dopamine beta-hydroxylase is not anchored via covalently attached phosphatidylinositol.

The mode of attachment of the membrane-bound form of the chromaffin granule glycoprotein dopamine beta-hydroxylase has been investigated; specifically, the possibility of a covalently attached glycosyl phosphatidylinositol anchor has been examined in detail. Incubation of fragmented chromaffin granule membranes with phosphatidylinositol-specific phospholipase C led to no solubilization of dopamine beta-hydroxylase activity. Further, chemical analyses of the inositol and phosphate content of the soluble form of dopamine beta-hydroxylase indicate that the enzyme contains no covalently attached phosphate or inositol. The results of these studies allow elimination of phosphatidylinositol as a source of membrane anchoring for dopamine beta-hydroxylase and, coupled with previously available data, argue against a post-translational covalent modification of the enzyme as the mechanism of membrane attachment. Possible alternative models for the anchoring of membranous dopamine beta-hydroxylase are discussed.

Relationships between cytosolic [ATP], [ATP]/[ADP] and ionic fluxes in the perfused rat heart: A 31P, 23Na and 87Rb NMR study.

In order to assess the relationship between cytosolic [ATP] or [ATP]/[ADP] and the intracellular Na+ concentration ([Na+]i), we have used the phosphate trap 2-deoxy-D-glucose (DG) to alter the high energy phosphate levels in rat cardiomyocytes. Pyruvate-perfused rat hearts were treated with 2 mM DG in the presence of 10IU/l of insulin for 28 min, followed by perfusion with DG without insulin for 60 min. The DG + insulin treatment resulted in dramatic changes in the 31P NMR spectra: phosphocreatine (PCr) and total ATP decreased (to 15 and 35%, respectively) and deoxyglucose-6-phosphate accumulated, with little change in either inorganic phosphate or intracellular pH. These changes corresponded to a decrease in cytoplasmic [ATP] (from 7.6 to 1.8 mM), [ATP]/[ADP] (from 494 to 24) and ATP affinity [A(ATP), by 8.9 kJ/mol] and an increase in [ADP] (five-fold) and free [Mg2+] (two-fold). Subsequent perfusion with DG--insulin resulted in slow recovery of PCr, [ATP]/[ADP] and A(ATP) such that the "low energy" state lasted an additional 16 min during which ATP remained low and constant. There were no detectable changes in the intracellular Na+ content as assessed by shift reagent-aided 23Na NMR at the end of DG + insulin treatment (98 +/- 18%, 28-36 min of the protocol). In addition, there was no change in the Rb+ influx rate as measured by 87Rb NMR at the beginning of insulin washout which was achieved by replacing 20% of the KCl with RbCl ([K+] = 3.76 mM, [Rb+] = 0.94 mM). During DG + insulin treatment the pressure-rate product (PRP) decreased by half and was restored upon insulin washout to 80% of its initial value both in the presence and in the absence of the shift reagent [5 mM Dy (triethylenetetraminehexaacetate)3-]. These data imply that unfavorable thermodynamic [low A(ATP)] and kinetic (low [ATP] and [ATP]/[ADP]) conditions induced by DG treatment do not inhibit Na+, K(+)-ATPase activity. We speculate that during anoxia when changes in [ATP]/[ADP] are comparable to those induced by DG treatment, the observed increase in [Na+]i is not due to inhibition of the Na+ pump by reduced [ATP] or [ATP]/[ADP].

Polarized attenuated total reflectance spectra of oriented purple membranes.

The technique of polarized Fourier transform infrared attenuated total reflectance spectroscopy has been applied to the study of oriented purple membranes of Halobacterium cutirubrum. This method offers a fast and simple approach for probing conformations of proteins in-situ and capable of obtaining polarized infrared spectra at an angle of incidence that is much greater than the Brewster angle.