Biomedical subjects

G Zucchelli

Publications and source records attributed to G Zucchelli.

At least 37 records · Page 2Linked to original sources

PubMed1999

The effect of excited state population in photosystem II on the photoinhibition-induced changes in chlorophyll fluorescence parameters

The photoinhibition-induced changes in Photosystem II fluorescence parameters of spinach thylakoids were only slightly sensitive to the excited state population in Photosystem II antenna, as modulated by either quinone quenching or energy spillover. The possibility that this may be due to a small fraction of chlorophyll molecules which are poorly coupled to the antenna is discussed.

Journal Article↗

PubMed1999

The relationship of plasma catecholamine and lactate during anaerobic threshold exercise in mitochondrial myopathies.

Sympathetic system activation is considered one of the main factors influencing lactate production during exercise in normal individuals. In order to assess the role of such activation in mitochondrial myopathies, we compared blood catecholamine levels to those of lactate during an intermittent exercise performed at workloads near anaerobic lactate threshold. Following an initial increment, the patients (n = 10) exhibited a steady-state blood lactate shifted right relative to controls (n = 7), the peaks being respectively 665 +/- 29% and 322 +/- 11% of baseline. Plasma catecholamine increase in mitochondrial myopathies was 272 +/- 21% for norepinephrine and 261 +/- 18% for epinephrine, not statistically different from controls. Lactate/norepinephrine and lactate/epinephrine area ratios were significantly higher in the subjects than in controls (2.36 versus 1.48 and 2.40 versus 1.57, respectively). The study shows that the abnormal lactate production in mitochondrial myopathies is independent of the catecholaminergic response at the transition from aerobic to anaerobic exercise.

Adult↗

PubMed1999

Topical and systemic antimicrobial therapy in guided tissue regeneration.

BACKGROUND: Bacterial contamination of membrane material negatively affects healing after guided tissue regeneration (GTR) procedures; conversely, flap connective tissue integration on barrier material improves the clinical outcomes. The objective of this study was to evaluate the effect of topical application of antibiotics on: 1) clinical outcomes of GTR surgical procedures using titanium reinforced expanded polytetrafluoroethylene (ePTFE) periodontal membrane; 2) bacterial colonization of membrane material; and 3) flap connective tissue-membrane integration. METHODS: Fifty-six deep interproximal bony defects were treated with GTR surgical procedures using titanium reinforced ePTFE periodontal membranes. Patients were randomly assigned to 1 of the 2 antimicrobial treatment groups: the test group received weekly topical application of 25% metronidazole gel and the control group received systemic antibiotics (amoxicillin plus clavulanic acid 1 g/day for 14 days). Clinical outcomes were assessed at 1 year; the amount of bacterial contamination and connective tissue integration on membrane material was evaluated at time of membrane removal by means of a morphological (SEM) method. RESULTS: No statistically significant difference was found between test and control groups in terms of clinical attachment (CAL) gain (baseline CAL - 12 months CAL; P = 0.2) and probing depth (PD) reduction (baseline PD - 12 months PD; P = 0.6). A greater increase in gingival recession (REC) (12 months REC - baseline REC) was found in the test group compared to the control group (P = 0.003). The SEM analysis revealed no statistically significant (t test) difference between test and control groups in the number of fields positive to integrated connective tissue (P = 0.82), while the number of fields positive to bacteria was statistically higher (P < 0.001) in the control group. CONCLUSIONS: Local antibiotic administration is more effective than systemic use in preventing membrane contamination, but it does not improve clinical outcomes due to an interference of the vehicle (gel) with gingival tissues which may reduce the potential benefits derived from better control of the bacterial load.

Administration, Topical↗

PubMed1998

A thermal broadening study of the antenna chlorophylls in PSI-200, LHCI, and PSI core.

The intact photosystem I of maize containing its full antenna complement (PSI-200) has been purified and fractionated into the core and outer antenna (LHCI) components. It is demonstrated by absorption and fluorescence spectroscopy that at least 80% of the long wavelength absorbing antenna pigments (red forms) are located in LHCI. Absorption spectra in the Qy region of all three preparations were measured between 72 and 300 K and subjected to a thermal broadening analysis. Data are interpreted in the linear electron-phonon coupling assumption, and the average optical reorganization energy (Snum) for the bulk pigment band and the red absorption tail determined. A marked asymmetry in Snum values across the absorption band is demonstrated. The bulk pigments in all three preparations have rather low values, in the range of 15-25 cm-1, suggesting that Stokes shifts for the absorption forms are in the 1. 5-3 nm range. On the other hand the red forms have markedly greater reorganization energies. While a direct thermal analysis of the red tail indicates minimum Snum values of around 60 cm-1, when the contribution of the red tail of the bulk pigments is corrected for in LHCI, the more reliable value of 110 cm-1 is obtained. These high Snum values for the red pigment forms suggest that they have unusually wide homogeneously broadened absorption bands and large Stokes shifts (6-11 nm).

Carrier Proteins↗

PubMed1998

Early bacterial accumulation on guided tissue regeneration membrane materials. An in vivo study.

The aim of the study was to compare the in vivo early bacterial plaque colonization of 3 different guided tissue regeneration (GTR) membrane materials using a morphological (scanning electron microscope) method. Rectangular-shaped strips were cut from 3 periodontal membranes (expanded polytetrafluoroethylene, polyglactin 910, and polylactic acid) and glued to the buccal aspect of removable acrylic devices, which were applied to the molar-premolar region of the upper quadrants in 8 dental students. Each device held 3 strips: one ePTFE, one polyglactin 910, and one polylactic acid. The surface roughness of each membrane material was measured by means of a laser profilometer. During a 24-hour period, the students had to refrain from any oral hygiene procedures and did not use chlorhexidine mouthrinses. In each subject, one device was removed after 4 hours and the other after 24 hours. After removal, the devices were placed in a 2.5% gluteraldehyde solution to fix the membranes, which were then processed for SEM analysis. Fifty-four microscopic fields (at 200x magnification) were randomly selected and analyzed in each strip. Magnification was increased to determine the presence of bacterial morphotypes. The presence or absence of bacteria was assessed in a binomial fashion. In such a system, the field was bacteria-positive when bacteria constituted the deposits covering the surface of the membrane. The microscopic field was considered bacteria-negative when no bacteria were present. Bacteria-positive fields showing rods and filaments as prevalent bacterial morphotypes were recorded as rod-positive fields. A different pattern of plaque accumulation was demonstrated on different membrane materials. The 4-hour results indicated a statistically significant difference (P = 0.008, ANOVA) in the proportion of bacteria-positive fields among the 3 membranes; a greater amount of bacteria was demonstrated on the ePTFE membrane compared to the other 2 membranes. At 24 hours, the difference in the proportion of bacteria-positive fields was statistically significant (P = 0.002, ANOVA); a lesser amount of bacterial plaque was present on the polylactic acid membrane compared to the ePTFE and polyglactin 910 membranes. No difference in the proportion of rod/bacteria-positive fields was demonstrated among the 3 membranes at either 4 or 24 hours. It was concluded that quantitative differences in early plaque accumulation on various membranes seem to be related to the textural and structural characteristics of the surface, which is not adequately represented by the surface Ra value measured with a profilometric instrument.

Absorbable Implants↗

PubMed1998

Mucogingival versus guided tissue regeneration procedures in the treatment of deep recession type defects.

The objective of the study was to compare the clinical efficacy of 3 surgical approaches in the treatment of deep recession type defects. Fifty-four (54) gingival recessions > or = 5 mm were randomly assigned to 1 of the 3 treatment groups by blocking the prognostic variables. The first group was treated with a guided tissue regeneration (GTR) procedure using a bioabsorbable membrane, the second with non-resorbable membrane, and the third with a mucogingival surgical approach consisting of a connective tissue graft combined with a coronally advanced flap (bilaminar technique). No differences, in terms of baseline oral hygiene and defect characteristics, were observed among the 3 groups showing an effective blocking approach. The 1-year results indicated that 1) all treatment approaches resulted in clinically significant root coverage and attachment gain; 2) a statistically significant treatment effect (P = 0.012, ANOVA) was observed comparing the bioabsorbable (4.9+/-0.3 mm), the non-resorbable (4.5+/-0.8 mm), and the bilaminar (5.3+/-0.7 mm) groups, in terms of root coverage; 3) the difference in terms of root coverage between the bilaminar and the non-resorbable membrane groups was statistically significant while differences between the 2 GTR groups or between the bilaminar and the bioabsorbable membrane groups did not reach statistical value; 4) the 95% confidence intervals for the proportions of complete successes showed a similar pattern; 5) no statistical difference was demonstrated in the amount of attachment gain among the 3 groups (P=0.73, ANOVA). A regression model showed that the amount of root coverage was significantly affected by the initial recession depth, the procedure and smoking habits: a poorer root coverage result is expected in case of shallow recession type defects, when either bioabsorbable (P < 0.05) or non-resorbable (P < 0.001) membranes are used instead of a bilaminar technique and if the patient smokes (P < 0.01). It was concluded that the mucogingival bilaminar technique is at least as effective as GTR procedures in the treatment of gingival recession > or = 4 mm and thus recession depth is not the parameter which influences the selection of the surgical procedure.

Absorption↗

PubMed1997

Analysis of some optical properties of a native and reconstituted photosystem II antenna complex, CP29: pigment binding sites can be occupied by chlorophyll a or chlorophyll b and determine spectral forms.

The minor photosystem II antenna complex CP29(Lhcb-4) has been reconstituted in vitro with the Lhcb-4 apoprotein, overexpressed in Escherichia coli, and the native pigments. Modulation of the pigment composition during reconstitution yields binding products with markedly different chlorophyll a/b binding ratios even though the total number of bound chlorophylls (a plus b) remains constant at eight. A thermodynamic analysis of steady state absorption and fluorescence spectra demonstrates that all chlorophylls are energetically coupled, while the kinetics of chlorophyll photooxidation indicate that triplet chlorophyll-carotenoid coupling is also conserved during pigment binding in vitro. The influence of the chlorophyll a/b binding ratio on the absorption spectra measured at 72 and 300 K is analyzed for the Qy absorption region. Increased chlorophyll b binding leads to large increases in absorption in the 640-660 nm region, while absorption in the 675-690 nm interval decreases markedly. These changes are analyzed in terms of a Gaussian decomposition description in which the eight subbands display a temperature-dependent broadening in agreement with the weak electron-phonon coupling demonstrated for other antenna chlorophyll spectral forms. In this way, we demonstrate that increased chlorophyll b binding leads to increased absorption intensity associated with the subbands at 640, 648, 655, and 660 nm and decreased intensity for the long wavelength subbands at 678 and 684 nm. The wavelength position of all subbands is unchanged. The above data are interpreted to indicate that CP29 has eight chlorophyll binding sites, many or all of which can be occupied by either chlorophyll a or chlorophyll b according to the conditions in which pigment binding occurs. Chlorophyll b absorption is primarily associated with four subbands located at 640, 648, 655, and 660 nm. The invariance of the wavelength position of the absorption bands in recombinant products with different chlorophyll a/b binding stoichiometries is discussed in terms of the mechanism involved in the formation of spectral bands. We conclude that pigment-protein interactions dominate in the determination of spectral heterogeneity with probably only minor effects on absorption associated with pigment-pigment interactions.

Apoproteins↗

PubMed1997

Integrated connective tissue in bioabsorbable barrier material and periodontal regeneration.

The objective of this study was to evaluate the relationship between integrated connective tissue (ICT), that is, the presence of connective tissue into the membrane structure, and the clinical outcome of membrane-supported periodontal surgery. Twenty-six systemically healthy subjects affected by chronic adult periodontitis were enrolled in the study. One tooth site per patient, associated with an angular bony defect and an attachment loss of > 7 mm, was selected to be treated by means of a guided tissue regeneration procedure using a bioabsorbable membrane. Barrier material was surgically removed after 4 weeks for SEM analysis. For each treated site, the difference in clinical attachment loss, probing depth, and gingival recession between the baseline examination and follow-up 6 months after the second surgery was calculated. Gain of attachment was statistically (P < 0.001) greater in sites with no membrane exposure when compared to sites with exposed barrier material (5.5 +/- 1.0 vs. 4.0 +/- 0.6), while further gingival recession was greater (3.0 +/- 0.9 vs. 2.1 +/- 0.5) in sites with clinically exposed membranes. The results of SEM analysis revealed that when connective tissue structures were observed on membrane surfaces, no bacteria could be detected; conversely, areas heavily colonized by bacteria did not show the presence of connective tissue. Regression analysis indicated that integrated connective tissue on the external layer of the barrier material was positively correlated with the amount of attachment gain and negatively with the amount of gingival recession. Bacterial colonization of the membrane was negatively correlated with attachment gain and positively with gingival recession. It was concluded that connective tissue integration is an important biological phenomenon in preventing membrane exposure and bacterial plaque colonization and thus in enhancing the clinical outcome following guided tissue regeneration surgery.

Absorption↗

PubMed1996

Thermal broadening analysis of the light harvesting complex II absorption spectrum.

Absorption spectra in the Qy region of the light harvesting complex II (LHCII) have been measured in the temperature range 70-300 K. The spectra were analyzed by evaluating the temperature dependence (a) of the total bandwidth and (b) of the sub-bands obtained by numerical decomposition in terms of double Gaussians. The thermal broadening of the bands are interpreted, in both cases, as a homogeneous component, due to the presence of linear electron-phonon coupling, plus an inhomogeneous component, due to both statistical energy fluctuations at each pigment site and heterogeneity of the sample itself. Sub-bands analysis, in which eight major components are identified, yields a reorganization energy 9 cm(-1) < or = Svm < or = 14 cm(-1) and an inhomogeneous contribution in the range 120-170 cm(-1). In all cases the bands are substantially symmetrical in the 70-300 K temperature range. This observation gains theoretical support from an analysis of the band moments, when the influence of a low-frequency vibrational mode is considered. Analysis of the total absorption band yields Svm approximately 70 cm(-1); however, this high value is reduced to Svm approximately 11-20 cm(-1) when the red-most sub-band, with maximum at 684 nm, is eliminated at all temperatures. These data are discussed in terms of the underlying transitions, giving strong support to the presence of extreme red absorption bands in LHCII. The presence of another low-frequency mode with vm > 20-30 cm(-1) is also proposed.

Kinetics↗

PubMed1996

Excited state equilibration in the photosystem I-light-harvesting I complex: P700 is almost isoenergetic with its antenna.

Photosystem I with its full antenna complement (PSI-LHCI) has been prepared by mild detergent solubilization with octyl beta-D-glucopyranoside from maize thylakoids. A preliminary polypeptide analysis is presented. At room temperature, the steady-state fluorescence derives from an almost perfectly thermalized state, as demonstrated by a Stepanov analysis, in which about 90% of the excited states are associated with the red chlorophyll spectral forms absorbing above 700 nm. Equilibration is temperature-sensitive and is lost at T < 200 K. A careful analysis of fluorescence between 75 and 280 K clearly demonstrates the presence of at least three red chlorophyll spectral forms with emission maxima at 720, 730, and 742 nm, the absorption origin bands of which have been calculated at 714, 725, and 738 nm. On the basis of a minor deviation from thermal equilibration around 695 nm, it is suggested that at least 3-4 antenna chlorophylls, with an average absorption near 695 nm, are strongly coupled to P700. Thermodynamic analysis of absorption and fluorescence spectra indicates that the equilibrium, absorption-weighted excited state population of the P700 dimer is around 0.013 assuming that the low-energy exciton state possesses all the oscillator strength. The average free energy for excitation transfer from antenna to P700 is thus calculated to be -0.26 kT at room temperature. This indicates that P700 is almost isoenergetic with its antenna at room temperature when the red forms are taken fully into account. From the calculated excited state population of P700, we estimate that the primary charge separation rate in PSI is 1-2 ps-1.

Light-Harvesting Protein Complexes↗

PubMed1996

Bacterial colonization of barrier material and periodontal regeneration.

The objective of this study was to evaluate the relationship between the presence of bacteria on the tooth-facing surface of ePTFE barriers and the clinical outcome of membrane supported reconstructive periodontal surgery. 20 systemically healthy subjects affected by chronic periodontitis were enrolled. One tooth site per patient, associated with an angular bony defect and a probing attachment loss of > 4 mm, was selected to be treated by means of a guided tissue regeneration procedure using an ePTFE barrier membrane. Antibiotics (Augmentin 1 g/day) for 2 weeks were prescribed. In addition to the use of chlorhexidine for post-surgical plaque control, all patients were recalled once a week for professional tooth cleaning. The barrier material was harvested for SEM analysis after 4-6 weeks. Professional tooth cleaning and reinforcement of sel-performed oral hygiene measures were given at 1 mouth intervals after membrane removal. For each treated site, the difference in probing attachment loss between baseline examination and a follow-up examination after 6 months of healing was calculated. The results of the SEM-analysis revealed that bacterial colonization was evident in the collar area of all the retrieved membranes. In the mid part of the membranes 30 out of 60 microscopic fields (50%) demonstrated microbial colonization, and in the most apical part 9 out of 60 fields (15%). Regression analysis indicated that gain in probing attachment level was positively correlated to initial attachement loss and negatively correlated to microbial colonization of the mid part of the membranes. It was concluded that bacterial colonization in the mid part of the ePTFE membrane reduced the potential gain in probing attachment following GTR-therapy with almost 50%.

Adult↗

PubMed1996

Increased gingival dimensions. A significant factor for successful outcome of root coverage procedures? A 2-year prospective clinical study.

The aim of this study was to evaluate whether an increased thickness of the gingiva through the use of a free connective tissue graft, in conjunction with a coronally advanced flap procedure, may positively influence the treatment outcome with respect to (i) root coverage and (ii) long-term stability of the position of the soft tissue margin following treatment of recession type defects. 67 consecutive patients having a total of 103 buccally located recession type defects of at least 3 mm were included in the study. After an initial phase of prophylaxis including instructions in a tooth brushing technique giving minimal apically directed forces to the gingival margin, the recession sites were surgically covered with a coronally advanced flap alone (control sites), or coronally advanced flap combined with a free connective tissue graft taken from the palate (test sites). Clinical examinations, including assessments of oral hygiene, gingival conditions, recession depth, gingival height, probing pocket depth and probing attachment loss, were performed before and 6, 12 and 24 months after surgical treatment. The mean initial recession depth for both treatment groups was about 4.0 mm (SD 1.0) with a gingival height apical to the recession of 1.0 mm (0.5). At the re-examination performed 6 months after surgical treatment, the mean recession depth had decreased to 0.2 mm in both the test and control groups. Complete root coverage was observed at 72% of the test sites and 74% of the control teeth. At teeth treated with the combined surgical procedure, the mean gain in probing attachment amounted to 3.7 mm and the mean gingival height had increased to 3.5 mm (0.6). The corresponding figures for control teeth were 3.6 mm and 1.5 mm (0.5), respectively. At the 24-month follow-up examination, the mean root coverage amounted to 98.9% (test) and 97.1% (control). 88% of the teeth in the test group showed complete root coverage compared to 80% for teeth in the control group. It was concluded that the 2 surgical procedures resulted in similar degree of root coverage and that changes of tooth brushing habits may be of greater importance than increased gingival thickness for long-term maintenance of the surgically established position of the soft tissue margin.

Adult↗

PubMed1996

Bacterial colonization of bioabsorbable barrier material and periodontal regeneration.

The objective of the study was to evaluate bacterial colonization of the tooth-facing surface of bioabsorbable membranes and to determine its effect on the clinical outcome of membrane supported reconstructive periodontal surgery. Twenty systemically healthy subjects affected by chronic adult periodontitis were enrolled in the study. One non-furcation tooth site per patient, associated with an angular bony defect and a probing attachment loss of > 5 mm, was selected to be treated by means of a guided tissue regeneration procedure using a polyglicolactic membrane. Antibiotics (amoxicillin/clavulanate potassium 1 g per day) for 2 weeks were prescribed, in addition to the use of chlorhexidine for post-surgical plaque control. All patients were recalled once a week for 5 weeks for professional tooth cleaning. At 5 weeks sites with clinically exposed membranes underwent a second surgery to harvest residual barrier material which was analyzed by scanning electronic microscopic (SEM) for bacterial colonization. Sites with no membrane exposure at 5 weeks were allowed to heal without any other surgical intervention. Professional tooth cleaning and reinforcement of self-performed oral hygiene measures were given at 1 month intervals for the duration of the study. For each treated site the difference in probing attachment loss between baseline examination and a follow-up examination made 6 months after the second surgery was calculated. Gain of probing attachment was statistically (P < 0.001) greater in sites with no membrane exposure when compared to sites with partially exposed barrier material (4.2 +/- 0.5 vs. 3.3 +/- 0.6). The results of SEM analysis revealed that bacterial colonization was evident in all the microscopic fields of the exposed areas of the membranes. In the mid-part of the membranes 16 out of 39 microscopic fields (41%) demonstrated microbial colonization, while no bacteria-positive field was observed in the most apical portion of the membranes. Regression analysis indicated that gain in probing attachment level was negatively correlated to microbial colonization of the mid-part of the membranes. It was suggested the midportion of the tooth-facing surface of polyglicolactic membrane is a critical area for the healing process since its bacterial colonization was detrimental to the outcome of the GTR surgery.

Adult↗

PubMed1996

Guided tissue regeneration with a resorbable barrier membrane (Vicryl) for the management of buccal recession: a case report.

Six patients with buccal gingival recession (4 to 6 mm) were treated by means of the guided tissue regeneration technique utilizing a polyglycolactic membrane (Vicryl). Three months following the first surgical procedure, all sites were reentered to evaluate newly formed tissue above the exposed root. Complete root coverage was obtained in four out of six patients; 0.5 and 1.5 mm of recession were still present in the remaining two.

Biocompatible Materials↗

PubMed1995

A thermal broadening analysis of absorption spectra of the D1/D2/cytochrome b-559 complex in terms of Gaussian decomposition sub-bands.

Absorption spectra of the isolated D1/D2/cytochrome b-559 complex have been measured in the temperature range 80-300 K. All spectra were analyzed in terms of a linear combination of Gaussian bands and the thermal broadening data interpreted in terms of a model in which the spectrum of each pigment site is broadened by (a) a homogeneous component due to linear electron-phonon coupling to a low-frequency protein vibration and (b) an inhomogeneous component associated with stochastic fluctuations at each pigment site. In order to obtain a numerically adequate description of the absorption spectra, a minimum number of five sub-bands is required. Further refinement of this sub-band description was achieved by taking into account published data from hole burning and absorption difference spectroscopy. In this way, both a six sub-band description and a seven sub-band description were generated. In arriving at the seven sub-band description, the original five sub-band wavelength positions were essentially unchanged. Thermal broadening analysis of the seven sub-band description yielded data which displayed the closest correspondence with the literature observations. The wavelength positions of the sub-bands were near 661, 667, 670, and 675 nm, with two bands near 680 and 684 nm. The two almost isoenergetic sub-bands near 680 nm, identified as P680 and pheophytin, have optical reorganization energies around 40 and 16 cm-1, respectively. All other sub-bands, identified as accessory pigments, have optical reorganization energies close to 16 cm-1.(ABSTRACT TRUNCATED AT 250 WORDS)

Chemical Phenomena↗

PubMed1995

Thyroid hormones homeostasis in pediatric patients during and after cardiopulmonary bypass.

The concentrations of thyroid hormones were measured in 14 pediatric patients before, during, and after cardiopulmonary bypass. The ages of the patients ranged between 18 months and 14 years. Patients were kept normothermic, or moderate or deep hypothermia was induced depending on the specific pathologic condition involved. A marked reduction in the levels of total triiodothyronine, total thyroxine, free triiodothyronine, and thyroid-stimulating hormone, and in the ratio of free triiodothyronine to free thyroxine was detected during the time frame of the study. The minimum levels of each hormone were reached between 12 and 48 hours after cardiopulmonary bypass, indicating that changes in thyroid function and in the conversion of thyroxine to triiodothyronine are triggered by cardiopulmonary bypass and represent specific phenomena, and that these changes are progressively exacerbated during the post-operative period. The thyroid-stimulating hormone level was markedly reduced versus its baseline values (24% +/- 0.13%), despite low levels of both total (40% +/- 18%) and free (39% +/- 20%) triiodothyronine: it returned to its preoperative level by the third postoperative day, but both the total (75% +/- 10%) and free (74% +/- 3%) triiodothyronine levels remained below their baseline values for 7 days postoperatively. Neither hemodilution nor hypothermia was responsible for the alteration observed. We conclude that pediatric patients undergoing cardiopulmonary bypass manifest changes in hormone metabolism similar to those seen in adult patients. These changes increase progressively during the postoperative period, and are still present 7 days postoperatively. The exact mechanism responsible for causing these changes is not thoroughly understood. Whether triiodothyronine replacement therapy is beneficial or deleterious remains controversial.

Adolescent↗

PubMed1995

Italian external quality assessment scheme in immunoassay.

This paper deals with the organization, the data processing and some of the results obtained in Italian external quality assessment (EQA) schemes for hormones, tumor markers and hepatitis B markers. The EQA for hormones and tumor markers includes up to sixteen analytes together with the participation, in 1990, of about 250 laboratories. Laboratory results were used to prepare periodic and end-of-period reports. The former includes the results (with the related statistical parameters) obtained by all participants and by laboratories using the same method, as well as the histogram of the data. The end-of-period report contains estimates of imprecision and average bias for all laboratories, for each laboratory and for the more widely employed kits. From 1980 to 1988, laboratory variability improved significantly for TSH, progesterone, estradiol, testosterone, CEA and ferritin, slightly for cortisol, FSH, prolactin and AFP, while there was no improvement for both total T3 and T4. For LH we found an unusually high variability mainly due to systematic differences between kits based on different monoclonal antibodies. About 200 laboratories participated in the EQA for hepatitis B markers (HBsAg and anti-HBs) organized in 1990. For these analytes the periodic reports show the percentage of negative and positive results and the histogram of the responses (absorbance or counts) normalized with respect to the cut off.

Diagnostic Tests, Routine↗

PubMed1994

Gaussian decomposition of absorption and linear dichroism spectra of outer antenna complexes of photosystem II.

Room temperature and 10 K absorption and linear dichroism spectra of the chlorophyll-protein complexes comprising the outer antenna of PSII (LHCII, CP29, CP26, CP24) have been analyzed in terms of a linear combination of asymmetric Gaussian bands. The results demonstrate the following: (a) The absorption and linear dichroism spectra of each sample can be described by nearly the same set of Gaussian bands at room temperature and 10 K. (b) The relative distributions of the transition moments of the major red-absorbing spectral forms seem to be similar in all four outer antenna chlorophyll-protein complexes at room temperature, with the 684-nm band being oriented closest to the particle plane at room temperature and the 677- and 669-nm bands being tilted at progressively greater angles out of the particle plane. The shorter wavelength transitions seem to be oriented close to the magic angle, but interpretation is complicated in this spectral region due to the low linear dichroism values and by overlap with vibrational bands. (c) The 684-nm band, detected in room temperature absorption and linear dichroism spectra of all complexes, vanishes at 10 K.

Chlorophyll↗