A molecular mechanics and database analysis of the structural preorganization and activation of the chromophore-containing hexapeptide fragment in green fluorescent protein

We propose that heterologous posttranslational chromophore formation in green fluorescent protein (GFP) occurs because the chromophore-forming amino acid residues 65SYG67 are preorganized and activated for imidazolinone ring formation. Based on extensive molecular mechanical conformational searching of the precursor hexapeptide fragment (64FSYGVQ69), we suggest that the presence of low energy conformations characterized by short contacts (approximately 3 A) between the carbonyl carbon of Ser65 and the amide nitrogen of Gly67 accounts for the initial step in posttranslational chromophore formation. Database searches showed that the tight turn required to establish the key short contact is a unique structural motif that is rarely found, except in other FSYG tetrapeptide sequences. Additionally, ab initio calculations demonstrated that an arginine side chain can hydrogen bond to the carbonyl oxygen of Ser65, activating this group for nucleophilic attack by the nearby lone pair of the Gly67 amide nitrogen. We propose that GFP chromophore-formation is initiated by a unique combination of conformational and electronic enhancements, identified by computational methods.

[Age-related force distribution at the proximal end of the femur in normally growing children]

In a group of normally developed children and adolescents the age dependent distribution of forces at the proximal end of the femur was to be described. The results should explain why the shape of the proximal end of the femur changes significantly during the time of growth and why the neck shaft angle decreases. The method applied was the biomechanical computation analyzing in the coronal plane according to Pauwels' biomechanical hip model. The necessary age relevant data was derived from 675 anteroposterior pelvis radiographs of healthy children of both sexes and of varying age. The following can be put down as a result: 1. The proximal end of the femur is stressed by two resultant forces: the hip resultant force R controls the growth of the capital growth plate, the trochanteric resultant force RT regulates the growth of the greater trochanter growth plate. 2. During the growing period the hip resultant force R adjusts itself less vertically: during the second year of life it inclines at an average of 11,6 degrees towards the vertical, towards the end of the growing period it is incident with an inclination angle of 20 degrees. With the older child the magnitude of the hip resultant force R decreases in relation to the exerting body weight. 3. During the time of growth the trochanteric resultant force RT maintains its direction stability with inclination angles of 50-52 degrees towards the vertical. Its magnitude increases significantly (in relation to the exerting body weight). 4. From age 2 to 10 the projected neck shaft angle decreases from an average of 148.2 degrees to 133.7 degrees and usually remains stable. It can be concluded that the shape of the proximal end of the femur is determined by the muscle forces stimulating the greater trochanter apophysis and by gravity. With increasing age the growth of the greater trochanter apophysis shifts the insertions of abductor muscles laterally. As a result the directions of the hip abductors and the hip resultant force R incline. The neck shaft angle decreases consecutively.

[The first invention patents in general anaesthesia]

Dra, Zimmer describes in this work the evolution of general anaesthesia for surgeries, quoting the recorded invention patents, since the 1st one performed in France - an ether anaesthesia - in 1846, 2 years after Wells had used nitrous oxide as gas for a surgery (december 1844).

Albumin kinetics in hypoalbuminemic patients receiving total parenteral nutrition

BACKGROUND

By using undenatured purified albumin preparations radiolabeled with iodine, the half-life of serum albumin in well patients who are stable is known to be approximately 17 days. However, when a patient is suffering with an acute illness such as sepsis, trauma, burns or after an extensive operative procedure, the serum albumin level decreases. It is not known whether this fall in serum albumin is due to increased catabolism, decreased synthesis, or a combination of both factors. This study explores the kinetics of albumin catabolism under these circumstances to clarify the issue.

METHODS

125I-labeled albumin was administered intravenously to 10 critically ill, hypoalbuminemic patients receiving total parenteral nutrition (TPN). Each subject had frequent blood samples taken for at least 10 days to measure the decline of plasma radioactivity over time. None was receiving unlabeled albumin during the investigation. It was assumed that the plasma decay would follow first-order kinetics after the early equilibration phase. Radioactivity of heparinized blood samples (counts/2 mL sample) were counted and the results were graphically expressed.

RESULTS

One subject was not evaluated because he was discharged on the 8th day. The APACHE (acute physiology and chronic health evaluation) score for the other nine subjects ranged from 4 to 18 (mean, 7.5). The serum albumin remained below 3.0 g/dL in each subject and did not change statistically throughout the study. The radioiodinated albumin half-life ranged from 5.52 to 11.76 days (mean 9.10 days; compared with published normal of approximately 17 days). The equilibration time was 3 to 7 days. The average albumin catabolized for this group is similar to previously reported normal subjects, 0.18 g/kg/d.

CONCLUSION

Hypoalbuminemic patients receiving TPN have markedly shortened plasma albumin half-lives, but the albumin catabolized per day is similar to normal patients. These data argue for both a synthetic and catabolic defect that explains the hypoalbuminemia in this patient group.

Cloning of the VASP (vasodilator-stimulated phosphoprotein) genes in human and mouse: structure, sequence, and chromosomal localization

The genes encoding the vasodilator-stimulated phosphoprotein (VASP) in human and mouse were isolated, and major parts were sequenced. In both species the gene is composed of 13 exons with conserved exon-intron positions. The mouse VASP cDNA sequence was deduced from the genomic sequence. The predicted amino acid sequence is 89% identical to the human protein. The high nucleotide sequence homology extends not only over the coding regions but also into the 3'-UTRs, indicating a possible function in mRNA targeting or regulation of translation. Prominent 5' CpG islands including multiple SP1 sites indicate a housekeeping function of VASP. Using cosmid DNA as a probe for fluorescence in situ hybridization, the human VASP gene was assigned to chromosome 19q13.2-q13.3, an extended region with homology to mouse chromosome 7. A sequence overlap of the VASP 5'-region with the telomeric end of a cosmid contig physically links the VASP gene with ERCC1. VASP is located about 92 kb distal to ERCC1 and about 300 kb proximal to the myotonic dystrophy protein kinase gene.

NONMEM analysis in determining the tri-exponential disposition of cefotaxime: a method of evaluating serum and urinary phase I data

The time above the minimum inhibitory concentration (MIC) is an important surrogate parameter for the efficacy of cephalosporines. In clinical practice cefotaxime (CTX) is usually administered every 8 h or 12 h. Unfortunately the limit of quantification (LOQ) of the available assay is not low enough to detect CTX concentrations in serum later than 6 h after a 2 g i.v. dose. Consequently the time above MIC has to be estimated by extrapolation of the available serum data. Due to the concentrating properties of the kidney, concentrations in urine following a 2 g dose however remain above the LOQ for up to 16 h. It is therefore possible to follow the pharmacokinetics of CTX in urine within a 12 h dosing interval. Due to the linear pharmacokinetics of CTX, serum concentrations, and accordingly the time above MIC, can be estimated by using the measured urinary excretion and the calculated renal clearance. The pharmacokinetics of cefotaxime were studied in 12 healthy subjects who received a single 2 g i.v. dose administered as a short infusion. Blood and fractional urine were collected up to 24 h after dosing. For the characterization of the true terminal half-life only sparse and unbalanced serum and urinary data was available. In such situations, the population approach is the method of choice for estimating the kinetic parameters. The combined analysis of serum and urinary data using NONMEM shows the superiority of a tri-exponential compared to a bi-exponential pharmacokinetics model. As a result, the predicted serum trough levels of cefotaxime following twice daily dosing are about 30-fold higher than those extrapolated from the bi-exponential model. Consequently, the concentrations of CTX- and its metabolite desacetyl-CTX--are above the MIC of many therapeutically relevant pathogens for a longer period of time than previously assumed. In conclusion, a twice daily dosing regimen for cefotaxime is adequate for a number of clinically relevant pathogens. This is supported by the positive outcome in previous clinical trials following this dosing regimen.

Cloning and structure of the gene encoding the human N-methyl-D-aspartate receptor (NMDAR1)

The complete gene encoding the human N-methyl-D-aspartate receptor subunit NR1 (NMDAR1) has been isolated on a single cosmid clone. The gene is composed of 21 exons distributed over a total length of about 31 kb. More than 24 kb were sequenced. Exons 4, 20 and 21 are identical in their amino-acid sequence to those exons that are subject to alternative splicing in rat, indicating that all eight NMDAR1 isoforms found in rat will also be expressed in the human brain. Computer analysis of the pre-mRNA sequence revealed no secondary structures stable enough to explain alternative splicing. We suggest that cell-specific factors control expression of different isoforms. The promoter region contains two perfect copies of the recognition sequence for the Drosophila even-skipped protein, indicating that the developmentally regulated expression of NMDAR1 is controlled by a homeobox protein. The complete cosmid clone covering NMDAR1 was mapped to chromosome 9q34.3-qter by fluorescent in situ hybridization (FISH). The telomeric location is supported by an imperfect (CA)n repeat homologous to a subtelomeric repeat on chromosome 16p.

[Evaluation of the effect of oxytocin use for labor induction on frequency of occurrence and severity of neonatal jaundice]

Authors conducted analysis of effect of method used (which consisted of use of oxytocin, vit B, oestradiol) for labour induction on frequency of occurrence and severity of neonatal jaundice on 3rd day of neonatal life. Analysed material consisted of 1154 deliveries between the years 1990 to 1992 in IInd Department of Obstetrics AM Wrocław. Only completely physiological pregnancies qualified for analysis. The above mentioned sum of analysed deliveries was divided into 2 groups. Ist group consisted of 801 normal deliveries without any oxytocin use 2nd group consisted of 353 normal deliveries during which i.v. oxytocin drip was used either for induction of labour or to intensify uterine contraction during labour. Evaluation of the above data do not show significant increase in cases with hyperbilirubinemia in group with labour induction (7%) in comparison with deliveries without oxytocin use (5%). Moreover eliminating from the analysis cases of jaundice with normal bilirubin level (12 mg%), I degree jaundice, the actual count of cases of hyperbilirubinemia in group without oxytocin use in 26 (3.24%) and in group with oxytocin use is 13 (3.67%) cases (Tab. IV) which is not a significant difference and does not permit us to conclude that oxytocin use for labour induction is responsible for increased frequency of neonatal hyperbilirubinemia.

The human Met-ase gene (GZMM): structure, sequence, and close physical linkage to the serine protease gene cluster on 19p13.3

Cosmid clones containing the genes for the human and murine natural killer cell serine protease Met-ase (gene symbol GZMM; granzyme M) were identified by screening human and murine cosmid libraries with rat Met-ase (RNK-Met-1) cDNA. The human gene has a size of 7.5 kb and an exon-intron structure identical to that of serine protease genes located on human chromosomes 5q11-q12, 14q11.2, and 19p13.3 that are expressed by lymphocytes, mast cells, or myelomonocyte precursors. Using cosmid DNA as a probe for fluorescence in situ hybridization, we identified the chromosomal position of human Met-ase as 19p13.3. Interphase studies with two differentially labeled probes for Met-ase and the azurocidin (AZU1), proteinase 3 (PRTN3), and neutrophil elastase (ELA2) gene cluster revealed that the distance of Met-ase from this gene cluster is in the range of 200 to 500 kb. Using differentially labeled mouse cosmid probes, we also mapped the murine gene for Met-ase to chromosomal band 10C, close to the gene for lamin B2. Thus, the Met-ase, AZU1, PRTN3, and ELA2 genes fall into an established region of homology between mouse chromosomal band 10C and human 19p13.3.

Bone formation in coralline hydroxyapatite. Effects of pore size studied in rabbits

We analyzed osseous reactions in the rabbit femoral condyle to coralline hydroxyapatite bone substitutes of various pore sizes by radiology and histology. The results were compared to bone repair of empty cavities and to integration of allografts. Spontaneous bone repair of the empty cavities took approximately 12 weeks, while integration of the cryopreserved allografts occurred after 9 weeks. However, no signs of new bone formation were found with the 200 microns pore size hydroxyapatite. In contrast, there was substantial production of bone within the 500 microns pore size implants at 12 and 26 weeks. Our results indicate that the pore size of the coralline hydroxyapatite influenced the development of bone in the implants in the cancellous bone bed of the rabbit femoral condyle. The results also show that spontaneous bone repair should be taken into consideration when the integration of implants is evaluated.

Construction of a human MluI YAC library

We describe a cloning strategy for the construction of a human genomic library in yeast artificial chromosomes (YACs) based on complete digestion of high-molecular-weight DNA with the infrequently cutting restriction enzyme MluI. Cloning of MluI fragments in the vector pYAC-RC and one subsequent size fractionation by preparative pulsed-field gel electrophoresis yielded a library with average insert sizes of 600 kb. Ninety-seven percent of the colonies were recombinant. An additional size fractionation of MluI fragments prior to ligation had no significant influence on the size of the YACs. The library currently consists of 5000 clones, which is the equivalent of one human genome. Nineteen percent of the YACs were larger than 1.2 Mb. Since smaller MluI fragments are lost during sizing, we also performed cloning without size fractionation. Only 20% of the colonies were recombinant, probably due to unligated vector fragments that were present during the transformation.

Expression of the NMDA R1 receptor in selected human brain regions

The distribution of the N-methyl-D-aspartate R1 receptor was investigated in human hippocampus, cerebellum and frontal cortex by means of in situ hybridization and immunocytochemistry. Expression of N-methyl-D-aspartate R1 receptors was observed in layers II-VI of the frontal cortex with the highest density of positive neurones in layer IV, V and VIa. The entire human hippocampus was labelled, with marked differences in intensity between the CA 1 and CA 2/3 region. Furthermore we found marked differences in the intracellular localization of the protein between granule and pyramidal cells. In the cerebellum granule and Purkinje cells stained positive, as revealed by both in situ hybridization and immunocytochemistry. These findings suggest that the receptor has a less restricted cell specific expression than previously thought, although the distribution is largely in accordance with the expression of N-methyl-D-aspartate R1 mRNA in the rat.

[Results of surgical treatment of posterior knee instability]

A retrospective study was performed to evaluate the outcome of operative treatment of posterior cruciate ligament (PCL) lesions in 115 patients operated on between 1980 and 1989. Follow-up was possible in 89 patients at 18-124 months postoperatively (average 76 months). In 65 re-examination was possible, while 24 patients returned a questionnaire. The results of patients who were operated on in the acute state were superior to those with chronic instabilities (Lysholm 79.9 +/- 18.5 vs 64.3 +/- 22.1; Tegner 5.7 +/- 2.3 vs 4.2 +/- 2.2; instrumented posterior drawer 5.3 +/- 3.5 mm vs 5.9 +/- 3.8 mm). On the other hand, the preoperative scores of symptomatic patients with chronic instabilities (Lysholm 38.8 +/- 22.0; Tegner 2.1 +/- 1.7) were clearly lower. Extraarticular procedures (Hughston) slightly improved symptoms in posterolateral instabilities. Olecranization of the patella had no influence on the results. Interpretation of the data is difficult as there was no matched group of patients with nonoperative treatment. A reviews of the literature suggests that isolated PCL tears are best treated with conservative management. Only in cases where associated ligamentous injuries require operative treatment should PCL reconstruction be performed. Chronic posterior instabilities should be treated operatively only if the patients are severely symptomatic. However, complete restoration of knee stability was usually not achieved with the techniques presented in this paper.

The human granzyme A (HFSP, CTLA3) gene maps to 5q11-q12 and defines a new locus of the serine protease superfamily

Human granzyme A (HFSP, Hanukah factor serine protease; CTLA3, cytotoxic T-lymphocyte-associated serine esterase-3), a homodimeric, trypsin-like serine protease of 60 kDa found in granules of cytolytic T cells and natural killer cells, is implicated in lymphocyte-mediated target cell lysis. It contributes to DNA fragmentation in perforin (PRF1)-lysed target cells through an unknown mechanism. We have isolated a cosmid clone for the functional gene of human granzyme A and established its complete exon-intron map of 10 kb. Using an 11-kb subfragment of the cloned genomic DNA as a probe, we have identified the chromosomal position of human granzyme A on 5q11-q12. Thus, the human granzyme A gene falls into a region of homology between human chromosome 5 and mouse chromosome 13, band D, where the mouse granzyme A gene has been located previously. The granzyme A gene is not linked to known members of the large superfamily of serine proteases.

Empirical force field analysis of the revised structure of coenzyme F430. Epimerization and geometry of the corphinoid tetrapyrrole

We undertook an empirical force field analysis of the conformational changes that accompany the diepimerization of coenzyme F430. The crystal structure of 12,13-diepi F430M was used as a test of the parameter set and as the basis for the calculations. The individual pyrrole rings in 13-epi and 12,13-diepi F430 adopt alternating half chair conformations leading to a ruffled macrocycle, native F430 is also ruffled but the individual pyrroles are planar. The 12,13 di-dehydro F430 and native F430 conformations are extremely similar, this accounts for the experimental observation that reduction of 12,13 di-dehydro-F430 forms native F430 and not 12,13-diepi F430. Native F430 can easily accommodate both square planar and, by bending, trigonal bipyramidal coordination geometries about nickel. We suggest that bent trigonal bipyramidal form is the conformer bound to the protein and that direct binding of the amino acid side chains to nickel is probably not important.

[Initial stability of an implanted cement-canal prosthesis. Results in experimental studies on human cadaver femurs]

Upon implantation of a cement-canal prosthesis in the proximal femur in total hip replacement, the bone cement is injected through the prosthesis via a system of drill holes. A second system of drill holes is used in this endoprosthesis to drain the distal femoral space as well as the cavities within the cement layer which form when the cement is being injected. Since the cement pressure is sustained until the cement has cured, substantial penetration of the cement into the cancellous bone can be achieved by using low intra-medullary cement pressures. Using cadaveric human femurs, the initial stability in the trabecular intertrochanteric region was determined in pull-out experiments for three different curing cement pressures (0.5 bar, 1.0 bar and 1.5 bar). The results were compared to corresponding controls in which a conventional cementation technique was used. With respect to the contact area of the bone/bone-cement interface, the initial stability increased by the factor 2.8 (cement-curing pressure 0.5 bar), 3.7 (cement-curing pressure 1.0 bar) and 2.9 (cement-curing pressure 1.5 bar) compared to the control group.

[Blood lamination in bone cement--effect of cementing technique]

The quality of the cement layer influences the long-term survival of cemented endoprostheses. However, blood and fluid laminations within the cement layer, which can form during implantation of endoprostheses, lead to the deterioration of bone cement. Since the bone cement is the weakest part in the construction consisting of prosthesis, bone and bone cement, further weakening of the bone cement should be avoided if possible. By means of in vitro studies, three different cementing techniques were tested, measuring quantitatively the amount of fluid within the cement layer after implantation. The least amount of fluid within the cement layer was found in the cement-canal technique, and the highest amount in anterograde cement injection. Retrograde cement injection led to intermediate values.

Human clusterin (CLI) maps to 8p21 in proximity to the lipoprotein lipase (LPL) gene

Clusterin (gene symbol: CLI) is a post-translationally nicked, two-chain plasma and tissue glycoprotein of 80 kDa. It forms high-density lipoprotein complexes with apolipoprotein A-I in plasma, functions as an inhibitor of the cytolytic reaction of the terminal complement proteins C5 to C9, and is secreted by Sertoli cells in large amounts into the seminal fluid. By isolating and characterizing three partially overlapping cosmid clones, we have established the complete physical map of the clusterin gene which spans about 20 kb. The subchromosomal position of the clusterin gene (CLI) and the order of CLI and the lipoprotein lipase (LPL) gene were determined by fluorescence in situ hybridization. We show that CLI, previously assigned to chromosome 8, is located on 8p21 proximal to the LPL locus. Based on this localization we consider clusterin as a novel candidate gene determining susceptibility to atherosclerosis.

[Clinical course of a late aseptically loosened PCA hip prosthesis shaft]

The surface of the proximal part of a PCA endoprosthesis stem in total hip replacement is structured with small beads to provide good conditions for bone ingrowth. The distal part of the stem has a smooth surface. For the mechanical fixation concept, this means anchorage of the proximal part and free axial mobility of the distal part of the prosthesis. We present a clinical case in which bone remodeling processes finally led to complete loosening of the prosthesis. The described mechanism of loosening could be reconstructed by radiological findings, bone scan, two digital subtraction arthrographies of the hip and by evaluation of the fibrous tissue formation around the stem after explanation. In this case, after an initial period of no measureable bone reactions, distal endosteal bone and proximal radiolucent space developed without loss of contact with the prosthesis. Later, a mechanical interruption between the proximal part of the prosthesis and bone occurred. There was no loosening of the distal part of the prosthesis at this time. Despite remarkable hypertrophy of the distal femoral bone, eventually the distal part of the prosthesis loosened so that a revision arthroplasty had to be performed. The described mechanism of loosening has not be proven to pertain to all such prostheses.

Investigations on mechanism of Salter-1-fractures of the greater trochanter

This study aims at clarifying why the apophysis of the greater trochanter very rarely separates, in contrast to other apophyses of the hip region. The inclination and area measurement of the greater trochanteric growth plate and the mode of insertion of the muscles on the apophysis were analyzed on the basis of 16 anatomic femoral specimens from newborn to children of 14 years of age. The physiological muscle cross section Q of the muscles inserting at the greater trochanter was determined on 6 specimens. In a cross-sectional radiological study, carried out on 1350 hip joints of healthy children, the inclination of the greater trochanter growth plate was measured. The anatomical and radiological findings show that the nearly plane-shaped greater trochanter growth plate remains inclined at a 50 degree angle to the horizontal body line and is loaded from a diagonally craniolateral direction throughout the total growth period. The lateral surface of the apophysis is covered by a fibrous connection which joins the insertion areas of the gluteus medius, minimus and vastus lateralis muscles. The vastus lateralis muscle is intimately bound to the vastus intermedius muscle by fibrous tissue. According to the results of the physiological muscle cross sections these four muscle groups can form a counteracting muscle sling, which transforms the traction forces at the surface of the greater trochanter into pressure forces in line with a tension band effect.(ABSTRACT TRUNCATED AT 250 WORDS)

Stress transfer at the femoral bone/bone cement interface as a function of the cement thickness

When a cement canal prosthesis is used as the femoral component in total hip replacement (THR), the penetration depth of the bone cement can be varied according to the cement implantation pressure. Using experimental data which give a relation between the pressure applied to the cement at implantation and the resulting shape of the cement layer, a three-dimensional finite element study was performed to calculate the stress distribution at the bone/bone cement interface. The calculations show that the interface stresses increase with increasing depth of penetration by the cement layer. The explanation of this effect is that as the bone cement penetrates further into the cancellous bone, the cancellous bone is stiffened and can no longer act as a soft interposition between cortical bone and bone cement. From these results and from the clinical requirement that as little bone as possible be destroyed in any kind of allo-arthroplasty, we conclude that the penetration depth of bone cement into cancellous bone in THR should be minimized to the depth necessary in order to achieve sufficient initial stability of the implant. The results show that a cement-canal prosthesis meets these requirements if a cement implantation pressure of 1.0 bar is used.

[A phosphine-substituted diphosphonic acid (HMPD) for improved scintigraphic detection of bone lesions]

Although the radiopharmaceuticals used for bone scintigraphy are of very high quality, the search for an "ideal" agent continues. To optimise the detectability of bone lesions, we analysed 244 different 99mTc-labeled phosphonates in animal experiments. In osteosarcoma-carrying rats 99mTc-labeled 1-Hydroxy-3-methyl-phosphinic-1, 1-propanediphosphonic acid (HMPD) was shown to produce the best lesion/normal bone ratio. 99mTc-MDP was used as reference. The ratio was found to be 1.28 for 99mTc-HMPD. The transferability of our results in animals to the situation in man was studied in 10 patients with bone metastases. There was for 99mTc-HMPD an improvement of the lesion/normal bone ratio by more than 60% but also an additional reduction of the soft tissue contrast by about 40%. 15% of the metastases were detected by scintigraphy using 99mTc-HMPD only and not with 99mTc-MDP. The new agent should make possible a better and earlier discrimination of bone lesions in the scintigram.