A trade-off between plant and soil carbon storage under elevated CO2.

Terrestrial ecosystems remove about 30 per cent of the carbon dioxide (CO2) emitted by human activities each year1, yet the persistence of this carbon sink depends partly on how plant biomass and soil organic carbon (SOC) stocks respond to future increases in atmospheric CO2 (refs. 2,3). Although plant biomass often increases in elevated CO2 (eCO2) experiments4-6, SOC has been observed to increase, remain unchanged or even decline7. The mechanisms that drive this variation across experiments remain poorly understood, creating uncertainty in climate projections8,9. Here we synthesized data from 108 eCO2 experiments and found that the effect of eCO2 on SOC stocks is best explained by a negative relationship with plant biomass: when plant biomass is strongly stimulated by eCO2, SOC storage declines; conversely, when biomass is weakly stimulated, SOC storage increases. This trade-off appears to be related to plant nutrient acquisition, in which plants increase their biomass by mining the soil for nutrients, which decreases SOC storage. We found that, overall, SOC stocks increase with eCO2 in grasslands (8 ± 2 per cent) but not in forests (0 ± 2 per cent), even though plant biomass in grasslands increase less (9 ± 3 per cent) than in forests (23 ± 2 per cent). Ecosystem models do not reproduce this trade-off, which implies that projections of SOC may need to be revised.

Self-reported prevalence of sleep disorders among medical and nursing students.

BACKGROUND: Sleep disorders are highly prevalent among university students. In particular, the symptoms of sleep disorders are more prevalent among healthcare students. AIMS: To assess the prevalence of risk factors of insomnia and sleep disorders and to examine the correlations between them among nursing and medical students. We also compared the effects of shift work during internship. METHODS: The sample was 417 healthcare students; 202 of them were nursing students, and the remaining 215 were medical students. We used a self-administered questionnaire to assess the risk factors for insomnia (i.e. age, BMI, tobacco consumption, physical activity and perceived stress, using the General Health Questionnaire-12). We also used the Sleep and Daytime Habits Questionnaire and Epworth Sleepiness Scale to assess the prevalence of sleep disorders and daytime sleepiness. RESULTS: A higher percentage of nursing students than medical students were aged 25 years or older, engaged in inadequate levels of physical activity and consumed tobacco. With the exception of tobacco consumption among nursing students, high scores on the GHQ-12 were the only risk factor associated with daytime and nighttime symptoms and poor sleep quality. There was no significant association between the symptoms of sleep disorders and shift work including night shifts. CONCLUSIONS: Since sleep disorders are highly prevalent among healthcare students, early detection and management is recommended. This will decrease the risk of harm to students and patients, due to medical mistakes.

Early regression index (ERI) on MR images as response predictor in esophageal cancer treated with neoadjuvant chemo-radiotherapy: Interim analysis of the prospective ESCAPE trial.

PURPOSE: The early regression index (ERI) predicts treatment response in rectal cancer patients. Aim of current study was to prospectively assess tumor response to neoadjuvant chemo-radiotherapy (nCRT) of locally advanced esophageal cancer using ERI, based on MRI. MATERIAL AND METHODS: From January 2020 to May 2023, 30 patients with esophageal cancer were enrolled in a prospective study (ESCAPE). PET-MRI was performed: i) before nCRT (tpre); ii) at mid-radiotherapy, tmid; iii) after nCRT, 2-6 weeks before surgery (tpost); nCRT delivered 41.4 Gy/23fr with concurrent carboplatin and paclitaxel. For patients that skipped surgery, complete clinical response (cCR) was assessed if patients showed no local relapse after 18 months; patients with pathological complete response (pCR) or with cCR were considered as complete responders (pCR + cCR). GTV volumes were delineated by two observers (Vpre, Vmid, Vpost) on T2w MRI: ERI and other volume regression parameters at tmid and tpost were tested as predictors of pCR + cCR. RESULTS: Complete data of 25 patients were available at the time of the analysis: 3/25 with complete response at imaging refused surgery and 2/3 were cCR; in total, 10/25 patients showed pCR + cCR (pCR = 8/22). Both ERImid and ERIpost classified pCR + cCR patients, with ERImid showing better performance (AUC:0.78, p = 0.014): A two-variable logistic model combining ERImid and Vpre improved performances (AUC:0.93, p < 0.0001). Inter-observer variability in contouring GTV did not affect the results. CONCLUSIONS: Despite the limited numbers, interim analysis of ESCAPE study suggests ERI as a potential predictor of complete response after nCRT for esophageal cancer. Further validation on larger populations is warranted.

In vitro activity of N-benzenesulfonylbenzotriazole on Trypanosoma cruzi epimastigote and trypomastigote forms.

Chagas disease is still an important health problem in Central and South America. However, the only drugs currently available for specific treatment of this disease may induce toxic side effects in the host. The aim of this work was to determine the activity of N-benzenesulfonylbenzotriazole (BSBZT) against the protozoan parasite Trypanosoma cruzi. The effects of BSBZT and benzotriazole (BZT) were compared to those of benznidazole (BZL) on epimastigote and trypomastigote forms. BSBZT was found to have an in vitro growth inhibitory dose-dependent activity against epimastigotes, with flow cytometry analysis confirming that the treated parasites presented size reduction. BSBZT showed an IC(50) of 21.56 µg/mL (81.07 µM) against epimastigotes at 72 h of incubation, whereas BZT did not affect the growth of this parasite form. Furthermore, the toxic effect of BSBZT, was stronger and appeared earlier (at 24h) in trypomastigotes than in epimastigotes, with the LC(50) of this compound being 28.40 µg/mL (106.79 µM) against trypomastigotes. The concentrations of BSBZT used in this study presented low hemolytic activity and cytotoxicity. Consequently, at concentrations near IC(50) and LC(50) (25µg/mL), BSBZT caused only 2.4% hemolysis and 15% of RAW 264.7 cell cytotoxicity. These results reveal the potential of BSBZT as a prototype in drug design for developing new anti-T. cruzi compounds.

Laparoscopic versus laparotomic approach to endometrial cancer.

OBJECTIVE: The aim of our study was to compare the feasibility, morbidity, long-term safety, disease-free survival, and overall survival of the laparoscopic (LPS) approach to early-stage endometrial cancer (EC) compared to the traditional laparotomic approach. METHODS: We reviewed retrospective data of patients who underwent primary surgery from 1997 to 2009. We recorded clinical parameters, surgical stage, histological type, operative and peri-operative complications, time to resumption of normal functions, conversion to laparotomy, overall survival, and disease-free survival. RESULTS: LPS, did not increase operative risk and peri-operative complications even in obese and older women. The number of pelvic lymph and aortic nodes removed was similar for the two groups. One hundred and eight patients had a follow-up of 60 months. The two groups were similar for disease-free survival and overall survival. CONCLUSIONS: Laparoscopic approach to EC provides a reduction in postoperative complications and hospital stay compared to the laparotomic approach.

The effect of self-sampled HPV testing on participation to cervical cancer screening in Italy: a randomised controlled trial (ISRCTN96071600).

BACKGROUND: In Italy, cervical cancer screening programmes actively invite women aged 25-64 years. Programmes are hindered by low participation. METHODS: A sample of non-responder women aged 35-64 years, belonging to three different programmes (in Rome, Florence and Teramo), was randomly split into four arms: two control groups received standard recall letters to perform either Pap-test (first group) or human papillomavirus (HPV) test (second group) at the clinic. A third arm was sent letters offering a self-sampler for HPV testing, to be requested by phone, whereas a fourth group was directly sent the self-samplers home. RESULTS: Compliance with standard recall was 13.9% (N619). Offering HPV test at the clinic had a nonsignificant effect on compliance (N616, relative risk (RR)=1.08; 95% CI=0.82-1.41). Self-sampler at request had the poorest performance, 8.7% (N622, RR=0.62; 95% CI=0.45-0.86), whereas direct mailing of the self-sampler registered the highest compliance: 19.6% (N616, RR=1.41; 95% CI=1.10-1.82). This effect on compliance was observed only in urban areas, Florence and Rome (N438, RR=1.69; 95% CI=1.24-2.30), but not in Abruzzo (N178, RR=0.95; 95% CI=0.61-1.50), a prevalently rural area. CONCLUSIONS: Mailing self-samplers to non-responders may increase compliance as compared with delivering standard recall letters. Nevertheless, effectiveness is context specific and the strategy costs should be carefully considered.

The use of digital images to evaluate the interobserver agreement on cervical smear readings in Italian cervical cancer screening.

OBJECTIVE: The aim of this study was to measure interobserver agreement among cytologists on using a set of digital images. METHODS: A set of 90 selected Papanicolaou-stained cervical smears were digitalized and the digital images circulated among 117 readers, from laboratories spread across almost all Italian regions. Three representative fields of each smear were displayed at 20× and 40× magnification (overall six images for each case). The diagnoses made by the cytologists who provided the images were taken as target diagnoses. RESULTS: The κ values were: very low for the categories atypical squamous cells of undetermined significance (ASC-US), and atypical squamous cells - cannot exclude high-grade squamous intraepithelial lesion (ASC-H); poor for the categories atypical glandular cells (AGC), high-grade squamous intraepithelial lesion (HSIL) and invasive cancer; and fair to good for the categories negative and low-grade squamous intraepithelial lesion (LSIL). However, we found a cluster of 42 best concordant readers. The overall κ value and overall weighted κ with the target diagnosis for these 42 readers were 0.45 and 0.66, respectively. This finding is in contrast with the overall κ value and overall weighted κ for the other readers of 0.39 and 0.59, respectively. CONCLUSIONS: As this finding is an estimate of the accuracy of the readers, we can infer that it will be very important to reach this level of concordance for all the participating readers. Future effort will facilitate common experiences in order to improve the reproducibility of diagnostic criteria. Digital images could be the key to reach this aim.

Age-specific patterns of unsatisfactory results for conventional Pap smears and liquid-based cytology: data from two randomised clinical trials.

OBJECTIVE: To investigate the rate of unsatisfactory cervical cell samples in liquid-based cytology (LBC) versus conventional cytology (CC) by age. DESIGN: Randomised clinical trials. SETTING: Population-based cervical cancer screening in the Netherlands and Italy. POPULATION: Asymptomatic women invited for screening enrolled in two randomised trials: Netherlands ThinPrep versus conventional cytology (NETHCON; 39 010 CC, 46 064 LBC) and New Technologies in Cervical Cancer Screening (NTCC; 22 771 CC, 22 403 LBC). METHODS: Comparison of categorical variables using Pearson's chi-square test, logistic regression and trend tests. MAIN OUTCOME MEASURES: Proportion of unsatisfactory samples, ratio of LBC versus CC, and variation by 5-year group. RESULTS: In NETHCON, a lower percentage of LBC samples were judged to be unsatisfactory compared with CC samples (0.33 versus 1.11%). There was no significant trend in unsatisfactory results by age group for conventional cytology (P(trend) = 0.54), but there was a trend towards an increasing percentage of unsatisfactory results with increasing age for LBC (P(trend) < 0.001). In NTCC, a lower percentage of LBC samples were judged to be unsatisfactory compared with conventional cytology (2.59 versus 4.10%). There was a decrease in the unsatisfactory results by age group with conventional cytology (P(trend) < 0.001) and with LBC (P(trend) = 0.01), although the latter trend arose from the 55-60-years age group (P(trend) = 0.62 when excluding this group). CONCLUSIONS: The clinical trial in which the results were collected and the cytologic method used were the most important determinants of unsatisfactory cytology. In all situations, the proportion of unsatisfactory samples was lower in LBC compared with CC. The effects of age depended on the criteria used to define unsatisfactory results.

[Ectopic breast fibroadenoma. Case report]. / Fibroadenoma in mammella ectopica. Case report.

Among the rare anomalies of the breast development, polythelia is the most common, between 1% and 5% of women and men present supernumerary nipples. Polymastia, usually presenting as ectopic breast tissue without areola-nipple complex, is seen mostly along the milk line, extending from the axilla to the pubic region. Ectopic breast tissue is functionally analogous to mammary gland and it is subjected to the same alterations and diseases, whether benign or malignant, that affect normal breast tissue. We report the case of a 21 years-old female evaluated by the medical staff after founding a solid nodular mass by suspect axillary lymphadenopathy. Differential diagnosis with lymphoma is the major problem in these cases. The mass was removed and the intraoperative histological examination showed fibroadenoma in axillary supernumerary breast. Presence of ectopic breast tissue is a rare condition; development of benign mass or malignant degeneration is possible, but it is very unusual. In case of polymastia diagnosis is simple; in case of isolated nodule, without local inflammation or infection, there are greater difficulties. Ultrasonography is diagnostic in case of breast fibroadenoma, but it might be inadequate in ectopic localizations owing to the shortage of mammary tissue around the mass. Preoperative diagnosis is important to plan an adequate surgical treatment; lumpectomy is indicated in case of benign tissue; in case of malignancy, therapy is based on the standard treatment used for breast cancer (surgery, chemotherapy and radiation therapy).

Genetic diversity of Armillaria spp. infecting highbush blueberry in northern Italy (Trentino region).

Armillaria spp. are the causal agents of root rots of several woody plants, including highbush blueberry. Since 2003, highbush blueberry plants infected by Armillaria spp. have been found in Valsugana Valley, Trentino region, northern Italy. Our aim was to identify the Armillaria spp. involved in these infections, as well as possible sources of inoculum in blueberry fields. Samples of Armillaria spp. were collected from diseased blueberry plants in 13 infected blueberry fields, from bark spread along the blueberry rows, from infected trees in the vicinity of the fields, and from four forest locations. The identification of Armillaria spp. was accomplished using a species-specific multiplex polymerase chain reaction method and by sequencing the rDNA at a specific locus. The differentiation between genotypes was performed by using simple-sequence repeat analysis. Armillaria mellea and A. gallica were the most frequently observed species infecting blueberry in the Valsugana Valley. Three to eight Armillaria genotypes were identified in each blueberry field. No individual genotypes were found in more than one blueberry field. Two-thirds of the genotypes found colonizing trees in the immediate vicinity of infected fields and two-thirds of the genotypes found colonizing the bark spread in blueberry rows were also isolated from blueberry plants in the field, indicating that bark used as mulch and infected trees surrounding the fields may be important sources of inoculum.

Secondary breast angiosarcoma: A multicentre retrospective survey by the national Italian association of Breast Surgeons (ANISC).

BACKGROUND: Breast angiosarcoma is a malignant mesenchymal neoplasm, which accounts for approximately 2% of all soft tissue sarcomas. Secondary breast angiosarcoma (SBA) may be related to chronic lymphedema after a mastectomy with lymph node dissection (Stewart Treves syndrome) and previous radiotherapy for complications from breast radiation treatment. It is a very rare condition; therefore, diagnosis and management are still a challenge. METHODS: The ANISC collected SBA data by means of a survey sent to all Italian breast centres in the ANISC. The clinicopathological characteristics and the management of this disease were analysed. RESULTS: Twenty-four centres participated in this survey in which 112 cases of SBA were analysed. The median age of the women with SBA was 68.9 years and it appeared approximately 90 months after the first irradiation for breast cancer. In 92% of cases, a mastectomy was performed without axillary dissection for those patients having a high grade of SBA (74.2%). The prognosis was worse in the high-grade cases (overall survival-OS: 36 months) as compared with the low-grade cases (OS: 48 months). After a follow-up of 5 years, 50.5% of the patients were still alive. Disease-free survival (DFS) was 35 months, and there were no differences between the groups of patients with either high- or low-grade histology. CONCLUSIONS: Secondary breast angiosarcoma is a very aggressive disease associated with a short survival outcome. The surgical approach still remains an important step in the course of treatment; furthermore, an accurate histological examination is helpful in establishing the prognosis of the patient. A mastectomy is mandatory. A longer OS was observed in patients with low-grade angiosarcoma as compared to high-grade angiosarcoma (C.I. 40-57 vs. 31-41 months).

Synergistic effect between different milk-derived peptides and proteins.

Antimicrobial peptides derived from food proteins constitute a new field in the combined use of antimicrobial agents in food. The best examples of milk-derived peptides are those constituted by bovine lactoferricin [lactoferrin f(17-41)] (LFcin-B) and bovine alpha(s2)-casein f(183-207). The aim of this work was to study if the antimicrobial activity of a natural compound employed in food preservation, nisin, could be enhanced by combination with the aforementioned milk-derived peptides. Furthermore, the possibility of a synergistic effect between these peptides and bovine lactoferrin (LF) against Escherichia coli and Staphylococcus epidermidis was also studied. Finally, the most active combinations were assayed against the foodborne pathogens Listeria monocytogenes and Salmonella choleraesuis. Results showed a synergistic effect when LFcin-B was combined with bovine LF against E. coli. In the same way, the combination of LFcin-B with bovine LF was synergistic against Staph. epidermidis. Bovine LF and nisin increased their antimicrobial activity when they were assayed together with bovine alpha(s2)-casein f(183-207). It is important to note the synergistic effect among LFcin-B and bovine LF, because both compounds might be simultaneously in the suckling gastrointestinal tract and could, therefore, have a protective effect on it. The other synergistic effect high-lighted is that between alpha(s2)-casein f(183-207) and nisin against L. monocytogenes because of the ability of L. monocytogenes to develop resistance to nisin.

Deltoid muscle activity in patients with reverse shoulder prosthesis at 2-year follow-up.

PURPOSE: The reverse shoulder prosthesis (RSP) was developed to relieve pain and improve functional outcomes in patients with glenohumeral arthritis and deficiency of the rotator cuff. Even if clinical and functional outcomes regarding the use of the RSP were reported by literature, data concerning progressive deltoid adaptation to this non-anatomic implant are still missing. The purpose of our study was to correlate clinical and functional outcomes with deltoid fibers activity and muscle fatigability in patients with reverse shoulder prosthesis at 2 years follow-up. METHODS: Twenty patients with reverse shoulder prosthesis due to symptomatic deficient or nonfunctional rotator cuff associated with osteoarthritis were referred by Cervesi Hospital Shoulder and Elbow Surgery Unit. Exclusion criteria were: axillary nerve palsy, a nonfunctioning deltoid muscle, diabetes, previous trauma, malignancy. Furthermore patients who received the RSP for revision arthroplasty, proximal humerus fractures were excluded. All the patients underwent clinical and functional evaluation with the support of electromyography measurement focused on deltoid activity. RESULTS: RSP surgical treatment in shoulder osteoarthritis confirms his good outcome in terms of pain relief. At 2 years anterior and lateral deltoid electromyographic activity was significantly lower compared with contralateral side (p < 0.001). Posterior deltoid activity was no detectable. Range of motion at 2 years of follow-up decreased in terms of forward flexion (p = 0.045), abduction (p = 0.03) and external rotation (p < 0.001). CONCLUSIONS: Our study demonstrates that even if the patients remain pain-free, progressive deterioration of the deltoid activity is unavoidable and may lead to poor functional outcomes overtime.

Imaging of postoperative shoulder instability.

Postoperative imaging in shoulder instability is still a challenge for radiologists due to various postsurgical anatomical findings that could be considered pathologic in treated shoulder. For this reason is very important a deep knowledge about surgical procedures, anatomical changes after surgery and the appropriate diagnostic imaging modalities to work up the symptomatic postoperative shoulder. Postoperative imaging options include use conventional radiography, magnetic resonance imaging (MRI), MRI arthrography, computed tomography (CT) and CT arthrography. The purpose of our review is to explain the different surgical procedures and to describe postoperative changes detected with radiological imaging.

The EEG assessment of low-grade hepatic encephalopathy: comparison of an artificial neural network-expert system (ANNES) based evaluation with visual EEG readings and EEG spectral analysis.

OBJECTIVE: The EEG provides an objective staging of hepatic encephalopathy (HE), but its interpretation may be biased by inter-observer variability. This study aims at comparing an entirely automatic EEG classification of HE based on an artificial neural network-expert system procedure (ANNES) with visual and spectral analysis based EEG classifications. METHODS: Two hundred and thirty-eight consecutive cirrhotic patients underwent closed-eye EEG. They were followed up for up to one-year to detect bouts of overt HE and death. The EEG was classified by ANNES, qualitative visual reading, main basic rhythm frequency and spectral analysis. The classifications were assessed on the basis of: (i) match with liver function, (ii) prognostic value and (iii) repeatability. RESULTS: All classifications were found to be related to the severity of liver failure, with cognitive findings and a history of previous bouts of HE. All of them had prognostic value on the occurrence of overt HE and on survival. The ANNES based classification was more repeatable than the qualitative visual one, and had the advantage of detecting low power EEG, but its efficiency in analyzing low-grade alterations was questionable. CONCLUSIONS: An entirely automatic - ANNES based - EEG classification of HE can improve the repeatability of EEG assessment, but further improvement of the device is required to classify mild alterations. SIGNIFICANCE: The ANNES based EEG grading of HE needs further improvements to be recommended in clinical practice, but it is already sufficient for detecting normal and clearly altered EEG tracings.

A short overview on the role of alpha-synuclein and proteasome in experimental models of Parkinson's disease.

The Ubiquitin Proteasome System is a multi-enzymatic pathway which degrades polyubiquinated soluble cytoplasmic proteins. This biochemical machinery is impaired both in sporadic and inherited forms of Parkinsonism. In the present paper we focus on the role of the pre-synaptic protein alpha-synuclein in altering the proteasom based on the results emerging from experimental models showing a mechanistic chain of events between altered alpha-synuclein, proteasome impairment and formation of neuronal inclusions and catecholamine cell death.

Analysis of EEG tracings in frequency and time domain in hepatic encephalopathy.

Spectral EEG analysis in hepatic encephalopathy (HE) is usually performed disregarding the effect of epoch length, statistical errors and equipment noise. A study on these items was carried out. In addition, spectral analysis and a new analysis, performed in time domain, were compared in the assessment of HE. The EEG tracings of 73 cirrhotic patients with HE were analyzed. Artifact-free periods of about 1 min were selected. Equipment noise was measured by short-circuiting all the electrodes. The equipment noise was notable below 1.5 Hz; the best epoch length was 4s and the statistical errors were minimal for the band with the highest relative power. Nineteen per cent of the tracings were unstable. The spectral values were found to be related to liver function and to the degree of HE, whereas the relationship with psychometric variables was poor. The indexes computed by time-domain analysis were found to be better related to psychometric findings. We have provided information on the optimisation of spectral EEG analysis and presented a time-domain analysis giving results related to psychometric tests and liver function.

Can posterior capsular stretching rehabilitation protocol change scapula kinematics in asymptomatic baseball pitchers?

PURPOSE: Scapular dyskinesis is a recognized cause of shoulder pain in the throwing shoulder of baseball pitchers and athletes who participate in overhead sports. Past studies have assessed scapular kinematics using electromagnetic tracking devices and have shown a correlation between posterior shoulder tightness and forward scapular posture. The purpose of our study is to evaluate the scapular kinematics, before and after a 4-week posterior stretching protocol in asymptomatic pitchers. METHOD: Eleven asymptomatic collegiate baseball pitchers were involved in the study and divided into group A (6 pitchers) underwent 4 weeks of a regimented therapy protocol and group B (5 pitchers) did not receive any treatment. Each pitcher was tested on two separate days: at the first day of the study (S1) and after 4 weeks (S2). RESULTS: The results demonstrate that there are statistically significant differences in the kinematics of several athletes from the "treated group" (group A) between S1 and S2. It is also important to notice that variations in group A occurred in both flexextension and ab/adduction movements, strengthening the conclusion that the variation was real. CONCLUSION: The results of the study can indicate that, in order to prevent the pathologic cascade linked to these sports activities, this physical training protocol might become integral part of the normal daily exercises of baseball pitchers and overhead athletes. Level of evidence II.

Fractionation and partial characterization of alpha-1-protease isoinhibitors of horse.

The principal alpha-1-protease inhibitor of horse was fractionated by classical methods and analysed with a modified fibrinogen-agarose gel electrophoretic method of high sensitivity and resolving power. Starting with an electrophoretically homogeneous inhibitor in unfractionated serum, two isoinhibitor bands became apparent after fractionation with (NH4)2SO4 and DEAE-cellulose DE-52 ion-exchange chromatography. The isoinhibitors differed in electrophoretic migration and in the elution pattern from Sephadex G-100 gel filtration, but possessed identical antigenic determinants and enzyme specificity. The slower migrating isoinhibitor with an apparent molecular weight of 90 000 could be highly purified. In contrast the faster moving isoinhibitor (molecular weight 65 000) could not be completely freed from a contaminating alpha-2-protease inhibitor. The formation of the two isoinhibitors is discussed considering conformational changes analogous to phenomena observed with alpha-2-macroglobulin, or dimer formation in combination with altered conformations. The isoinhibitors described here are new additions to the different heterogeneities which exist in alpha-1-protease inhibitors in horse. They also supplement the different heterogeneities which exist among the alpha-1-protease inhibitors of mammals.

Design of synthetic bactericidal peptides derived from the bactericidal domain P(18-39) of aprotinin.

A bactericidal domain, P(18-39), of the proteinase inhibitor aprotinin, possesses the structural feature of two antiparallel beta-sheets connected by a short turn. In order to understand the structural requirements for antibacterial activity, two peptides, each having the sequence corresponding to a single beta-sheet structure of P(18-39), were synthesized and their antibacterial properties investigated. One peptide, P(18-28), with the sequence IIRYFYNAKAG, was active against almost all the bacterial strains investigated. However, the bactericidal activity of P(18-28) was reduced compared to the parent molecule, P(18-39). The other peptide, P(29-39), with the sequence LCQTFVYGGCR, was only weakly bactericidal against Pseudomonas aeruginosa. A peptide, P(18-26), devoid of the C-terminus dipeptide Ala-Gly of P(18-28), retained the bactericidal activity of P(18-28) against most of the bacterial strains investigated. Only Klebsiella pneumoniae, P. aeruginosa and Staphylococcus aureus were resistant to P(18-26). Replacement of lysine 26 by arginine in P(18-26) (IIRYFYNAR) improved the bactericidal activity. The retropeptide, RANYFYRII, retained the antibacterial activity of IIRYFYNAR toward Gram-negative bacteria, but it was less active against Gram-positive bacteria. The random peptide, IANRIYRYF, was as bactericidal as IIRYFYNAR. Moreover, the random peptide possessed, in contrast to IIRYFYNAR, a strong antifungal activity against Candida albicans. Elimination of the N-hydrophobic terminal Ile-Ile from P(18-26) (RYFYNAK) strongly reduced the bactericidal potency of the peptide. Attaching the hydrophobic peptide, FFVAP, to the C-terminal of P(18-26) (IIRYFYNAKFFVAP) increased the bactericidal potency of the peptides considerably. We concluded that the order of the amino acids in the sequence of the peptides is not, per se, a critical feature for bactericidal activity. Hydrophobic interaction between peptide and bacterial membrane is probably the most important feature involved in the bactericidal mechanism of the antibiotic peptides.