[How does central cornea thickness influence intraocular pressure during applanation and contour tonometry?]

BACKGROUND

Golmann applanation tonometry represents a well-established procedure for measuring intraocular pressure (IOP). This implies the necessity of an accurate measurement of IOP with the reference tonometer. One example is the contour tonometer Pascal with a measuring probe, adapted to the cornea geometry, for measuring the IOP and the ocular pulse amplitude. There is controversy of how strongly corneal thickness affects the measurement of IOP. We thus analysed, for a number of eyes, the correlation of IOP, as measured by two types of applanation tonometers and one contour tonometer and the central corneal thickness.

METHODS

In all 158 patient eyes were investigated in a clinical comparison of applanation tonometers AT 870 and Ocuton-A. The study was performed by a trained ophthalmologist and the comparison was in accordance with international standard ISO 8612. In addition, the corneal thickness in the vertex was repeatedly determined using an Oculus Pentacam. The potential effect of central corneal thickness on the IOP as measured by the mentioned tonometers was statistically evaluated by rank correlation analysis.

RESULTS

We found that the measured IOP values for the three investigated tonometers were not normally distributed. The central corneal thickness values, in contrast, measured on 158 eyes by means of an ultrasound pachymeter and additionally on 235 eyes by the Pentacam, obeyed a Gaussian distribution. For the correlation analysis of both parameters the Spearman linear rank correlation coefficient (r) was considered. We found a very weak (|r| < 0.2) correlation between central corneal thickness and IOP for all 3 tonometers. The softness of the correlation is also illustrated by a large standard deviation of the regression line. A comparison of the different devices for corneal-thickness measurements shows less variance and a smaller variation coefficient when the ultrasoundpachymeter AL-1000 is used.

CONCLUSIONS

The measured values for IOP are only very weakly correlated to the central corneal thickness. For the 3 tonometer types studied there is no need to correct the indicated pressure values according to the central corneal thickness of the investigated eye. Clinical comparisons according to the ISO 8612 standard between a tonometer under test and a reference Goldmann applanation tonometer are always a time-consuming procedure. Additional measures to determine the central corneal thickness of every investigated eyes are dispensable.

Surface-exposed Amino Acid Residues of HPV16 L1 Protein Mediating Interaction with Cell Surface Heparan Sulfate

Efficient infection of cells by human papillomaviruses (HPVs) and pseudovirions requires primary interaction with cell surface proteoglycans with apparent preference for species carrying heparan sulfate (HS) side chains. To identify residues contributing to virus/cell interaction, we performed point mutational analysis of the HPV16 major capsid protein, L1, targeting surface-exposed amino acid residues. Replacement of lysine residues 278, 356, or 361 for alanine reduced cell binding and infectivity of pseudovirions. Various combinations of these amino acid exchanges further decreased cell attachment and infectivity with residual infectivity of less than 5% for the triple mutant, suggesting that these lysine residues cooperate in HS binding. Single, double, or triple exchanges for arginine did not impair infectivity, demonstrating that interaction is dependent on charge distribution rather than sequence-specific. The lysine residues are located within a pocket on the capsomere surface, which was previously proposed as the putative receptor binding site. Fab fragments of binding-neutralizing antibody H16.56E that recognize an epitope directly adjacent to lysine residues strongly reduced HS-mediated cell binding, further corroborating our findings. In contrast, mutation of basic surface residues located in the cleft between capsomeres outside this pocket did not significantly reduce interaction with HS or resulted in assembly-deficient proteins. Computer-simulated heparin docking suggested that all three lysine residues can form hydrogen bonds with 2-O-, 6-O-, and N-sulfate groups of a single HS molecule with a minimal saccharide domain length of eight monomer units. This prediction was experimentally confirmed in binding experiments using capsid protein, heparin molecules of defined length, and sulfate group modifications.

Renal dysfunction according to the ADQI-RIFLE system and clinical practice patterns after cardiac surgery in Germany

AIM

The aim of this study was to determine the incidence of renal dysfunction according to the Acute-Dialysis-Quality Initiative-(ADQI)-RIFLE grading system in cardiac surgery in Germany in 2003 and to determine if variations in the incidence of renal dysfunction are related to clinical practice patterns.

METHODS

DESIGN

prospective cohort analysis and practice pattern survey.

MEASUREMENTS

81 hospitals were requested to report prospectively sampled quality-management-data on patient load, case mix, aortic-cross-clamp-time, baseline and maximal plasma creatinine (CreaP), new-onset-renal-replacement-therapy, and clinical practice concerning the use of fluids, inotropic and vasopressor drugs, and diuretics. Fifty-one (63%) centers answered the survey. Twenty-six centers (32%)(representative for 29 623 patients(reported creatinine data.

RESULTS

The incidence of a 50%, 100%, or 150% increase in plasma creatinine (graded as risk, injury, and failure according to the ADQI-RIFLE-system) were 9% (2-40%), 5% (0.8-30%), and 2% (0.6-33%), respectively, overall 15.4% (3.1-75%). The incidence of new-onset renal-replacement-therapy was 4.5% (0.6-24%). Centers with a low incidence of renal dysfunction 8.7% (3.1-15.4%)differed from those with a high incidence 51% (15.7-75%)by being more liberal with fluids, not preferring dopamine in ''renal'' or inotropic doses, and preferring noradrenaline as a vasopressor (all: P<0.05), but not by case mix, frequency of urgent or emergency cases, and the use of loop diuretics.

CONCLUSIONS

Renal dysfunction is a frequent complication following cardiac surgery in many German heart centers. The variance between centers may not be explained by patient heterogeneity and may be related to different strategies regarding fluid therapy and the use of inotropes and vasopressors.

cDNA sequences of the authentic keratins 8 and 18 in zebrafish

From the zebrafish Danio rerio, we have cDNA cloned and sequenced a novel type II and a novel type I keratin, termed DreK8 and DreK18, respectively. We identified DreK8/18 as the true orthologs of the human keratin pair K8/18 as follows: (i) MALDI-MS assignment to the biochemically identified K8 and K18 candidates that are co-expressed in simple epithelia and absent in epidermal keratinocytes; (ii) multiple sequence alignments and phylogenetic tree analysis, showing that DreK8, within the phylogenetic tree of type II keratins, forms a highly bootstrap-supported branch together with K8 from goldfish and rainbow trout, whereas DreK18, within the phylogenetic tree of type I keratins, groups with the K18 sequences from all other vertebrates studied; (iii) presence of a conserved motif in the tail domain of DreK8 (VxKxxETxDGxxVSESSxV) that is typical for all hitherto sequenced K8 orthologs. Moreover, several zebrafish type II keratin sequences published by other authors have now been assigned to epidermal keratins, previously identified biochemically.

Ultrasonography-guided fine-needle aspiration for the assessment of cervical metastases

OBJECTIVE

To assess the value of ultrasonography (US) combined with fine-needle aspiration (FNA) cytology for the investigation of lymph node metastases in patients with head and neck cancer.

DESIGN

Comparison of clinical examination (palpation) and preoperative US-FNA examination results of cervical nodes in a sample of patients with head and neck cancer. The histological features of the neck dissection specimens are used to validate these 2 variables.

SETTING

A head and neck oncology service in a tertiary referral hospital.

PATIENTS

A consecutive sample of 56 patients with head and neck squamous cell carcinoma, first seen between April 1, 1996, and July 30, 1998, who had neck dissections performed after the US-FNA examination.

INTERVENTION

Cervical US-FNA preoperatively, followed by elective or therapeutic radical modified or selective neck dissection.

MAIN OUTCOME MEASURES

The histological examination results of subsequent neck dissection specimens are used to determine the sensitivity, specificity, and accuracy of US-FNA for individual nodes. Second, the results of node staging by clinical examination and US-FNA examination are compared.

RESULTS

The sensitivity was 89.2%; specificity, 98.1%; and accuracy, 94.5%. Correct node stages were obtained in 52 (93%) of the patients using US-FNA compared with 34 (61%) using palpation.

CONCLUSIONS

Ultrasonography combined with FNA is a highly accurate technique for the investigation of cervical lymph node metastases. A more accurate diagnosis may result in more appropriate treatment, particularly in a setting with limited resources. Retropharyngeal nodes, micrometastases, and lymph nodes smaller than 4 mm are limitations of US-FNA. Ultrasonography combined with FNA is a useful technique for the staging of head and neck cancer.