Safety and tolerability of solifenacin in children and adolescents with overactive bladder- a systematic review

BACKGROUND

Solifenacin is an anticholinergic that is used to treat overactive bladder syndrome (OAB) in children. It is important to ascertain the safety and tolerability of solifenacin in the paediatric population as solifenacin offers an alternative, is more bladder specific, and should have less anticholinergic side effects than other therapies.

OBJECTIVE

The aim of this study is to systematically evaluate the safety and tolerability of solifenacin in children and adolescents with OAB.

STUDY DESIGN

We included studies that reported the safety and tolerability of solifenacin in children and adolescents. All study types were included. Electronic searches were conducted in Ovid MEDLINE, Ovid Embase, TRIP, CINAHL and ICTRP on the 18th of January 2022. Risk of bias was assessed with the Cochrane Risk of Bias tool 2.0 (ROB-2) for randomised controlled trials (RCTs) and the Newcastle-Ottowa scale for cohort studies.

RESULTS

A total of twelve studies including two RCTs were included in this review. Results from the meta-analysis of RCTs showed the commonest side effects were constipation (RR 3.5, 95%CI 0.9-13.7) and dry mouth (RR 3.1 95%CI 0.2-53). In terms of tolerability, the effect estimate of ceasing solifenacin due to an adverse effect was 2.7 (95%CI 0.8-9.1). Within the cohort studies, out of the 779 patients 21.7% experienced side effects. The most common side effects were constipation (6.8%) and dry mouth/lips (6.0%) and 3.5% of patients ceased solifenacin due to adverse effects. Overall, the certainty of the evidence for side effects and tolerability were very low.

DISCUSSION

The reported incidence of side effects is low, and less than reported with oxybutynin use. However, the very low certainty of the evidence means the findings should be interpreted with caution. There is limited reporting of a prolonged QTc interval on ECG. Studies that described this only had an increase of QTc from baseline and not a clinically significant prolonged QTc that resulted in arrhythmias.

CONCLUSION

Solifenacin is an alternative anticholinergic for the treatment of OAB in children. However, given the paucity of good quality data on safety and tolerability it should be used cautiously in children with close monitoring for potential side effects.

O-261 In-vitro supplementation of vitamin B12 to improve post-thaw viability and DNA integrity

Study question

Does the supplementation of vitamin B12 protect the spermatozoa against damage caused by the freeze-thaw process further improving the overall post-thaw survival and DNA integrity?

Summary answer

The antioxidant property of vitamin B12 protects the spermatozoa and improves the post thaw motility, vitality, and reduces DNA damage caused by freeze-thaw process.

What is known already

Cryopreservation of spermatozoa is an effective way of fertility preservation in humans, often used in Assisted Reproductive Technology(ART). Despite the refinement in cryopreservation, the salvage of post-thaw sperms remains poor. The reactive oxygen species(ROS), that is formed as a result of freeze-thaw process is known to decrease the motility, plasma membrane integrity and increase the DNA fragmentation. Most vitamins have antioxidant properties, that protect the mammalian cells from oxidative stress one such vitamin is cyanocobalamin(vitamin B12). Vitamin B12 modulates oxidative stress through methionine synthase activity and also acts as a scavenger of ROS. Thus protecting the DNA against free radicals.

Study design, size, duration

This prospective observational study was performed for a period of 6 months in 111 men, who attended the fertility clinic. The study population included all semen samples except men with azoospermia, surgically retrieved samples and men on vitamin supplements. The study population contained men ageing between 21-40 years.

Participants/materials, setting, methods

Semen samples were analysed according to WHO 5th edition and were assessed for DNA fragmentation index (DFI) using sperm chromatin dispersion assay (SCD). The ejaculates were split into two as group A: semen samples with equal amount of cryoprotectant and group B: semen samples with equal amount of cryoprotectant supplemented with Vitamin B12 (2mg/ml). They were frozen for a minimum of 24 hrs. Post-thaw motility, vitality and DFI were assessed and compared.

Main results and the role of chance

The mean age of patients in our study was 34.26±4.7yrs. 58.5% of the study population had primary infertility. 37.8% of the study population had male factor infertility, 32.4% had oligoasthenoteratozoospermia(OAT), 31.1% had normozoospermia 16.2% had asthenoteratozoospermia, 13.5% had teratozoospermia, 3.6% had oligozoospermia and rest 2.7% had asthenozoospermia.

There was an overall increase in post thaw motility (41.59±18.09 vs 32.3±18.8,p=0.0005), progressive motility (21.54±13.02 vs 15.91±11.80,p=0.0005), vitality (57.14±15.09 vs 46.76±16.45,p=0.0005) and a significant decrease in DFI (26.69±10.03 vs 32.09±10.00,p=0.0005) in group B compared to group A.

Our study also demonstrated that, Normozoospermia patients had a significant increase in vitality (67.17±13.8 vs 58.51±12.0, p = 0.007) and lower DFI (22.68±9.3 vs 27.6±8.9, p = 0.02) in group B than in group A.

OAT patients had a significant increase in total motility (26.25±12.15 vs 15.7±11.4,p=0.0003), progressive motility (11.69±8.8 vs 6.14±5.8,p=0.0028), vitality (46.06±11.34 vs 34.31±12.99,p=0.0001) and significantly lower DFI (30.22±9.87 vs 36.08±9.7,p=0.012) in group B.

Teratozoospermia patients showed significant increase in progressive motility in group B (27.87±8.81 vs 19.33±10.69,p=0.02) and

Asthenoteratozoospermia patients showed significant increase in total motility (40.72± 13.14 vs 30.89±13.06,p=0.02) and vitality (54.39±12.28 vs 43.78±14.14,p=0.02) in group B.

However, in asthenozoospermic patients the parameters were comparable in both the groups.

Limitations, reasons for caution

Due to ethical reasons the samples were not used for in vitro procedures such as intrauterine insemination(IUI), in vitro fertilization (IVF) and intracytoplasmic sperm injection(ICSI). Hence, no inference was obtained regarding the fertilization rates/ pregnancy rates.

Wider implications of the findings

Our study demonstrated that with supplementation of vitamin B12 the recovery rate significantly increased and also preserved the DNA content. Among the various categories, supplementation of vitamin B12 to OAT samples was more beneficial as it improved the overall viability of the sperms.

Trial registration number

CSP/21/JUL/96/389

Multiresistant E. coli urine infections in children: a case-control study

OBJECTIVE

Urinary tract infections (UTIs) caused by resistant organisms are increasing which poses challenges when selecting empirical antimicrobial therapy. The aim of this study is to determine risk factors for multiresistant Escherichia coli UTIs in children.

DESIGN

We included all reported urinary isolates from a children's hospital collected between January 2010 and June 2013. Patients who had multiresistant E. coli UTIs were identified and a retrospective review of medical records performed. Patient-specific clinical and demographic factors were compared with age-matched and gender-matched controls with non-multiresistant E. coli UTIs. Univariable and multivariable statistical analysis were performed to determine significant risk factors for multiresistant organism E.coli UTIs.

RESULTS

In total, there were 2692 positive urine cultures, 1676 (62.3%) from 1169 patients were E. coli. Multiresistant E. coli was isolated from 139 (8.3% of all E. coli) cultures in 99 patients. Thirteen incomplete medical records were excluded, leaving 86 patients, matched with 86 controls. In multivariable regression, the only significant risk factor was antibiotic use in the previous month (adjusted OR 3.0, 95% CI 1.4 to 6.2), but not previous hospital admission (adjusted OR 1.4, 95% CI 0.6 to 2.9), being an inpatient at the time of diagnosis (adjusted OR 2.4, 95% CI 0.8 to 7.4) and previous instrumentation (adjusted OR 1.0, 95% CI 0.4 to 2.4).

CONCLUSIONS

This is the first case-control study to examine multiresistant UTI in Australian children. Clinicians should be judicious in the use of antibiotics in treatment and prophylaxis of UTIs. In children presenting with UTI and recent antibiotic exposure, amoxicillin-clavulanic acid appears to be an appropriate empiric antibiotic choice in our population.

Range and Heterogeneity of Outcomes in Randomized Trials of Pediatric Chronic Kidney Disease

OBJECTIVE

To determine the range and heterogeneity of outcomes reported in randomized controlled trials of interventions for children with chronic kidney disease (CKD).

STUDY DESIGN

The Cochrane Kidney and Transplant Specialized Register was searched to March 2016. Randomized trials involving children across all stages of CKD were selected. All outcome domains and measurements were extracted from included trials. The frequency and characteristics of the outcome domains and measures were evaluated.

RESULTS

From 205 trials included, 6158 different measurements of 100 different outcome domains were reported, with a median of 22 domains per trial (IQR 13-41). Overall, 52 domains (52%) were surrogate, 38 (38%) were clinical, and 10 (10%) were patient-reported. The 5 most commonly reported domains were blood pressure (76 [37%] trials), relapse/remission (70 [34%]), kidney function (66 [32%]), infection (61 [30%]), and height/pubertal development (51 [25%]). Mortality (14%), cardiovascular disease (4%), and quality of life (1%) were reported infrequently. The 2 most frequently reported outcomes, blood pressure and relapse/remission, had 56 and 81 different outcome measures, respectively.

CONCLUSIONS

The outcomes reported in clinical trials involving children with CKD are extremely heterogeneous and are most often surrogate outcomes, rather than clinical and patient-centered outcomes such as cardiovascular disease and quality of life. Efforts to ensure consistent reporting of outcomes that are important to patients and clinicians will improve the value of trials to guide clinical decision-making. In our study, non-English articles were excluded.

Differential regulation of free radicals (reactive oxygen and nitrogen species) by contact allergens and irritants in human keratinocyte cell line

Immune responses to chemicals resulting in sensitization and the appearance of allergic responses following subsequent exposures are dependent upon activation of T lymphocytes. On the contrary, irritant responses are independent of immune response. The aim of this project was to identify the differential signaling cascade operated in allergic and irritant contact dermatitis. Recently, we have shown that keratinocyte cell line A431 can function as an antigen presenting cell (APC) and hence can be used as a model to differentiate between an allergen and irritant molecule. Allergen- and irritant-induced regulation of reactive oxygen species (ROS) and nitric oxide (NO) has been explored. Irritants induce release of ROS even at noncytotoxic concentration. ROS generation by allergens was not detected at nontoxic concentration but as the concentration was increased to a toxic dose there was a drastic increase in the ROS level compared to the untreated cells. Hence, the regulation of ROS is not significant in allergic responses but important in irritant responses. The major difference exists in the fact that the source of ROS for irritants is mitochondria, while that of allergens is mostly cytosolic. Antioxidant-induced protection from irritant-induced cell death has also been demonstrated. NO level was found to increase by allergens and irritants in a concentration-dependent manner. Hence, the regulation of ROS and NO can be used as important mediators in contact allergic and irritant dermatitis.

Connexin modulators and their potential targets under the magnifying glass

Gap junction channels, assembled from connexins, mediate communication and signaling between adjacent cells by allowing the passage of ions, metabolites and signaling molecules. Their physiological significance and importance in cellular homeostasis is reflected by the fact that their dysfunction leads to a multitude of pathologies. However, the complex physiological and pathophysiological roles of connexins are not well understood. Therefore, pharmacological tools to further elucidate their functions and to validate them as drug targets for the development of novel therapies for connexin-based diseases are urgently needed. In this article we will review diseases caused by mutations, abnormal expression and function of connexins (e.g. deafness, atrial fibrillation and other cardiac arrhythmias, peripheral and central nervous system neuropathies, epilepsy, and cancer) and we will discuss the role of connexins as potential therapeutic targets. This will be followed by a detailed overview of the different classes of modulators including proposed mechanisms of action, selectivity and structure-activity relationships. Classical connexin channel uncoupling agent like long-chain alcohols (e.g. heptanol), glycyrrhetinic acid and its derivatives, later discovered connexin blocking chemotypes like 2-aminophenoxyborates, fenamates, quinines and triphenylmethanes, as well as gap junctional coupling enhancing compounds like antiarrhythmic peptides will be discussed.

APOE gene polymorphisms and response to statin therapy

Published studies investigating the role of APOE gene on lipid response (total cholesterol (TC), low-density lipoprotein cholesterol (LDL-C), high-density lipoprotein cholesterol (HDL-C) and triglycerides) to statin treatment have reported inconsistent results. A meta-analysis was conducted to estimate the lipid response to statin treatment among APOE genetic variants (e2 carriers, e3e3 homozygotes and e4 carriers). Twenty-four studies were included in the meta-analyses. The pooled mean reduction (Delta mu) in TC from baseline was significant for all variants (e2 carriers: Delta mu=-27.7% (-32.5 to -22.8%), e3e3: Delta mu=-25.3% (-28.0 to -22.6%) and e4 carriers: Delta mu=-25.1% (-29.3 to -21.0%)). Significant changes in LDL-C, HDL-C and triglyceride levels were also noted for all genotypes, although these changes did not differ significantly among genotypic groups. There was significant heterogeneity among the studies. Given these non-significant effects of APOE genotypes on lipid responses, there is little reason to consider the use of APOE genetic testing for guiding treatment with statins.

Sterility induced in male rats by injection of chemical agents into the vas deferens

Changes in the histopathology of the testes with the epididymis were studied 3 months and 6 months after vasocclusion either with ethanol urea mixture or ethanol alone in male rats. A gradual decrease in the fertility of treated animals was observed. The epididymis showed tubules with sperm granuloma and the testis showed empty tubules with Leydig cell hyperplasia in the urea-ethanol treated animals.

Local delivery of the KCa3.1 blocker, TRAM-34, prevents acute angioplasty-induced coronary smooth muscle phenotypic modulation and limits stenosis

OBJECTIVE

We previously demonstrated that upregulation of intermediate-conductance Ca(2+)-activated K(+) channels (K(Ca)3.1) is necessary for mitogen-induced phenotypic modulation in isolated porcine coronary smooth muscle cells (SMCs). The objective of the present study was to determine the role of K(Ca)3.1 in the regulation of coronary SMC phenotypic modulation in vivo using a swine model of postangioplasty restenosis.

METHODS AND RESULTS

Balloon angioplasty was performed on coronary arteries of swine using either noncoated or balloons coated with the specific K(Ca)3.1 blocker TRAM-34. Expression of K(Ca)3.1, c-jun, c-fos, repressor element-1 silencing transcription factor (REST), smooth muscle myosin heavy chain (SMMHC), and myocardin was measured using qRT-PCR in isolated medial cells 2 hours and 2 days postangioplasty. K(Ca)3.1, c-jun, and c-fos mRNA levels were increased 2 hours postangioplasty, whereas REST expression decreased. SMMHC expression was unchanged at 2 hours, but decreased 2 days postangioplasty. Use of TRAM-34 coated balloons prevented K(Ca)3.1 upregulation and REST downregulation at 2 hours, SMMHC and myocardin downregulation at 2 days, and attenuated subsequent restenosis 14 and 28 days postangioplasty. Immunohistochemical analysis demonstrated corresponding changes at the protein level.

CONCLUSIONS

Blockade of K(Ca)3.1 by delivery of TRAM-34 via balloon catheter prevented smooth muscle phenotypic modulation and limited subsequent restenosis.

Pharmacokinetics, toxicity, and functional studies of the selective Kv1.3 channel blocker 5-(4-phenoxybutoxy)psoralen in rhesus macaques

The small molecule 5-(4-phenoxybutoxy)psoralen (PAP-1) is a selective blocker of the voltage-gated potassium channel Kv1.3 that is highly expressed in cell membranes of activated effector memory T cells (TEMs). The blockade of Kv1.3 results in membrane depolarization and inhibition of TEM proliferation and function. In this study, the in vitro effects of PAP-1 on T cells and the in vivo toxicity and pharmacokinetics (PK) were examined in rhesus macaques (RM) with the ultimate aim of utilizing PAP-1 to define the role of TEMs in RM infected with simian immunodeficiency virus (SIV). Electrophysiologic studies on T cells in RM revealed a Kv1.3 expression pattern similar to that in human T cells. Thus, PAP-1 effectively suppressed TEM proliferation in RM. When administered intravenously, PAP-1 showed a half-life of 6.4 hrs; the volume of distribution suggested extensive distribution into extravascular compartments. When orally administered, PAP-1 was efficiently absorbed. Plasma concentrations in RM undergoing a 30-day, chronic dosing study indicated that PAP-1 levels suppressive to TEMs in vitro can be achieved and maintained in vivo at a non-toxic dose. PAP-1 selectively inhibited the TEM function in vivo, as indicated by a modest reactivation of cytomegalovirus (CMV) replication. Immunization of these chronically treated RM with the live influenza A/PR8 (flu) virus suggested that the development of an in vivo, flu-specific, central memory response was unaffected by PAP-1. These RM remained disease-free during the entire course of the PAP-1 study. Collectively, these data provide a rational basis for future studies with PAP-1 in SIV-infected RM.

Diagnosis and management of metabolic alkalosis

Elevated pH and elevated plasma bicarbonate level above normal characterise metabolic alkalosis. When bicarbonate is elevated pCO2 must also be elevated to maintain pH to its normal range. Therefore with metabolic alkalosis, the compensation is to decrease alveolar ventilation, and increase pCO2. The causes of metabolic alkalosis are gastro-intestinal hydrogen and chloride loss and due to renal cause. For metabolic alkalosis to continue both generation and maintenance of high levels of bicarbonate are necessary. The diagnosis of metabolic alkalosis is established by noting pH, serum bicarbonate (elevated) and pCO2 (compensatory) elevation. To establish the causes it is necessary to determine intravascular volume, supine and standing blood pressure and renin angiotension alolosterone axis. In chloride responsive alkalosis in which the conditions are extracellular volume depletion, hypokalaemia and hypochloraemia correction of intravascular volume with sodium chloride is needed. In severe metabolic alkalosis of any cause dilute hydrochloric acid (0.1 N HCl) may be infused intravenously but haemolysis may be a complication. In emergency situation with severe hypokalaemia dialysis with higher K+, Cl- and low HCO3- bath will be appropriate.

Adding oral talactoferrin to first-line NSCLC chemotherapy safely enhanced efficacy in a randomized trial

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Background: Talactoferrin alfa (TLF) is an oral immunomodulatory protein with a novel mechanism. TLF showed preclinical anti-cancer activity alone and in combination with chemotherapy. In Phase I/II trials, TLF was safe with apparent single-agent anti-cancer activity in non-small cell lung cancer (NSCLC). Methods: 110 chemo-naive patients with advanced or metastatic NSCLC were randomized (1:1) in a multi-center trial to carboplatin/paclitaxel (C/P) therapy plus either TLF or placebo. Starting the day after C/P (C:AUC 5 mg/mL/min; P:175 mg/m2) in chemo-cycles 1, 3 and 5, oral TLF (1.5 g BID) or placebo was administered in 35-day cycles for up to three cycles or until progression. Primary endpoint was Confirmed Response Rate (RR; PR+CR) by CT using RECIST. Secondary endpoints included Progression Free Survival (PFS) and Overall Survival (OS). Results: Baseline patient and disease characteristics were comparable in both groups. All 110 patients were included in the Intent To Treat (ITT) population. 100 patients with at least one CT scan after starting treatment were prospectively defined as the Evaluable population. Adding oral TLF to C/P enhanced efficacy on all endpoints examined including RR, PFS and OS. Confirmed RR in the 100 evaluable patients significantly increased from 29% to 47% (P = 0.05). Confirmed RR in the 110 ITT patients improved from 27% to 42% (P = 0.08). Median PFS in both evaluable and ITT patients improved by 2.8 months (67%). Median OS improved by 31% and 18% in evaluable and ITT patients, respectively. A landmark analysis comparing survival in patients with and without a PR showed a significant difference (P < 0.01), suggesting a strong association between RR and survival. TLF appeared to be very safe and well tolerated with no drug-related SAEs. Fewer AEs were observed in the TLF arm than in the placebo arm, 346 and 432 AEs, respectively (P = 0.0023). The number of Grade 3/4 AEs was also lower in the TLF arm, 60 versus 91 (P = 0.0144). Conclusions: Adding oral TLF to standard C/P chemotherapy in NSCLC was safe and increased efficacy in a randomized, multi-center, double-blind, placebo-controlled trial, with apparent improvements in RR, PFS and OS. Results with TLF compare favorably to other anti-cancer agents. Oral TLF will be further evaluated in a Phase III trial.

[Table: see text]

Rice HYDROPEROXIDE LYASES with unique expression patterns generate distinct aldehyde signatures in Arabidopsis

HYDROPEROXIDE LYASE (HPL) genes encode enzymes that catalyze the cleavage of fatty acid hydroperoxides into aldehydes and oxoacids. There are three HPLs in rice (Oryza sativa), designated OsHPL1 through OsHPL3. To explore the possibility of differential functional activities among these genes, we have examined their expression patterns and biochemical properties of their encoded products. Transcript analysis indicates that these genes have distinct patterns and levels of expression. OsHPL1 is ubiquitously expressed, OsHPL2 is expressed in the leaves and leaf sheaths, whereas OsHPL3 is wound inducible and expressed exclusively in leaves. OsHPLs also differ in their substrate preference as determined by in vitro enzyme assays using 9-/13-hydroperoxy linolenic and 9-/13-hydroperoxy linoleic acids as substrates. OsHPL1 and OsHPL2 metabolize 9-/13-hydroperoxides, whereas OsHPL3 metabolizes 13-hydroperoxy linolenic acid exclusively. Sequence alignments of the HPL enzymes have identified signature residues potentially responsible for the substrate specificity/preference of these enzymes. All three OsHPLs are chloroplast localized as determined by chloroplast import assays and green fluorescent protein (GFP) fusion studies. Aldehyde measurements in transgenic Arabidopsis (Arabidopsis thaliana) plants overexpressing individual OsHPL-GFP fusions indicate that all rice HPLs are functional in a heterologous system, and each of them generates a distinct signature of the metabolites. Interestingly, these aldehydes were only detectable in leaves, but not in roots, despite similar levels of OsHPL-GFP proteins in both tissues. Similarly, there were undetectable levels of aldehydes in rice roots, in spite of the presence of OsHPL1 transcripts. Together, these data suggest that additional tissue-specific mechanism(s) beyond transcript and HPL enzyme abundance, regulate the levels of HPL-derived metabolites.

Role of Keratinocytes in Antigen Presentation and Polarization of Human T Lymphocytes

Allergic contact dermatitis is a T-cell-mediated inflammatory skin disease in which interaction between skin keratinocytes and migrating T lymphocytes may play a critical part. In this study, the role of keratinocytes as allergen-/antigen-presenting cells (APCs) leading to activation of T lymphocytes is investigated using a human epidermal cell line A431. It is known that cultured cells do not express human leucocyte antigen (HLA) and hence can be used as APCs independent of HLA profile of both APCs and T cells from human volunteers. This cell line responded to common allergens and irritants by inducing or upregulating the cell-surface expression of HLA-DR, and intercellular adhesion molecule-1 and B7 mRNA transcripts in keratinocytes. In addition, allergen-primed A431 cells also induced allergen-specific proliferation of human T lymphocytes in cocultures. Anti-HLA-DR, interleukin-1alpha (IL-1alpha) antibodies and lysosomotropic agent chloroquine inhibited the proliferation. Allergens also upregulated cytokines IL-1alpha, granulocyte-macrophage colony-stimulating factor, Gro-alpha and IL-12 in keratinocytes. Further, keratinocytes activated by allergens induced polarization of activated T lymphocytes to the Th1 phenotype.

Role of different valence states of chromium in the elicitation of allergic contact dermatitis

Chromium, a known contact sensitizer, is present at high levels in certain detergent bars (40-50 p.p.m.) sold in India. A concern was whether chromium present in such detergent bars could sensitize users or their use lead to the elicitation of allergic contact dermatitis. Chromium present in detergent bars was analyzed for its valence state. It was found to be trivalent [Cr (III)] and not hexavalent [Cr (VI)]. An elicitation test on normal volunteers, as well as on volunteers who were sensitive to chromium, was carried out to determine the elicitation potential of chromium (III) in the bars. Of the 48 volunteers who completed the study, 30 did not show any positive response to either potassium dichromate, the positive control, or the detergent bar containing chromium (III). 18 volunteers who were identified as chromium-sensitive showed a positive response to potassium dichromate but not to the detergent bar containing trivalent chromium. This study clearly showed that the detergent bar with 40-50 p.p.m. of trivalent chromium did not elicit any allergic contact dermatitis even in individuals known to be chromium-sensitive. Hexavalent chromium (potassium dichromate) did however, elicit allergic contact dermatitis in these subjects.

Lactoferrin-melanin interaction and its possible implications in melanin polymerization: crystal structure of the complex formed between mare lactoferrin and melanin monomers at 2.7-A resolution

The concentration of melanin determines the intensity of colors of the skin and hair of animals. Melanin pigments are tyrosine-based polymers formed in melanocytes within specialized organelles called melanosomes. In order to understand the mechanism of melanin polymerization, lactoferrin, a basic protein with a pI value of 9.0, has been used to produce melanin. Lactoferrin is a monomeric iron-binding protein with a molecular weight of 80 kDa. The crystals of lactoferrin were soaked in a solution containing dihydroxyphenylalanine (DOPA) and tyrosinase enzyme. These crystals were used for X-ray intensity data collection. The intensity data were collected to 2.7-A resolution to an overall completeness of 91% with an R(sym) of 0.071. The crystals belong to orthorhombic space group P2(1)2(1)2(1) with cell dimensions: a = 85.0 A, b = 99.8 A, c = 103.4 A. The structure was determined by molecular replacement method, using the model of diferric mare lactoferrin, and refined to an R-factor 0.215 (R(free) = 0.287) for all the data to 2.7-A resolution. The final model comprises 5,281 protein atoms from 689 amino acids, 2Fe(3+), 2CO(2-)(3) ions, 2 indole-5,6-quinone molecules (IQ), and 73 water molecules. Two IQ molecules, one in each lobe, bind to lactoferrin. In the C-lobe, the IQ binds in the iron-binding cleft, whereas in the N-lobe, it is located in the side pocket between two alpha-helices, filled with solvent molecules in the native iron-saturated mare lactoferrin. The IQ molecules interact with protein molecule mainly through glutamic acid in both lobes, without significant perturbation to the protein structure. The orientation of N- and C-lobes in the present structure is similar to that observed in the native iron-saturated protein. However, as a result of the binding of IQ molecules, the orientations of the domains N1, N2 and C1, C2 in the two cases differ slightly.

Interaction of melanin with proteins--the importance of an acidic intramelanosomal pH

Melanin is a highly irregular heteropolymer consisting of monomeric units derived from the enzymatic oxidation of the amino acid tyrosine. The process of melanin formation takes place in specialized acidic organelles (melanosomes) in melanocytes. The process of melanin polymerization requires an alkaline pH in vitro, and therefore, the purpose of an acidic environment in vivo remains a mystery. It is known that melanin is always bound to protein in vivo. It is also seen that polymerization in vitro at an acidic pH necessarily requires the presence of proteins. The effect of various model proteins on melanin synthesis and their interaction with melanin was studied. It was seen that many proteins could increase melanin synthesis at an acidic pH, and that different proteins resulted in the formation of different states of melanin, i.e., a precipitate or a soluble, protein-bound form. We also present evidence to show that soluble protein-bound melanin is present in vivo (in B16 cells as well as in B16 melanoma tissue). An acidic pH appeared to be necessary to ensure the formation of a uniform, very high molecular weight melano-protein complex. The interaction between melanin and proteins appears to be largely charge-dependent as evidenced by zeta potential measurements, and this interaction is also increased in an acidic pH. Thus, it appears that an acidic intramelanosomal pH is essential to ensure maximum interaction between protein and melanin, and also to ensure that all the melanin formed is protein-bound.

Recombinant growth hormone enhances muscle myosin heavy-chain mRNA accumulation and amino acid accrual in humans

A potentially lethal complication of trauma, malignancy, and infection is a progressive erosion of muscle protein mass that is not readily reversed by nutritional support. Growth hormone is capable of improving total body nitrogen balance, but its role in myofibrillar protein synthesis in humans is unknown. The acute, in situ muscle protein response to an infusion of methionyl human growth hormone was investigated in the limbs of nutritionally depleted subjects during a period of intravenous refeeding. A 6-hr methionyl growth hormone infusion achieved steady-state serum levels comparable to normal physiologic peaks and was associated with a significant increase in limb amino acid uptake, without a change in body amino acid oxidation. Myosin heavy-chain mRNA levels, measured by quantitative dot blot hybridization, were also significantly elevated after growth hormone administration. The data indicate that methionyl growth hormone can induce intracellular amino acid accrual and increased levels of myofibrillar protein mRNA during hospitalized nutritional support and suggest growth hormone to be a potential therapy of lean body wasting.