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Biomedical subjects

P J Roos

Publications and source records attributed to P J Roos.

At least 19 recordsLinked to original sources
PubMed2005

A new tibial coordinate system improves the precision of anterior-posterior knee laxity measurements: a cadaveric study using Roentgen stereophotogrammetric analysis.

Roentgen stereophotogrammetric analysis (RSA) can be used to measure changes in anterior-posterior (A-P) knee laxity after anterior cruciate ligament (ACL) reconstruction. Previous measurements of A-P knee laxity using RSA have employed a tibial coordinate system with the origin placed midway between the tips of the tibial-eminences. However, the precision in measuring A-P knee laxity might be improved if the origin was placed on the flexion-extension axis of rotation of the knee. The purpose of this study was to determine whether a center-of-rotation tibial coordinate system with the origin placed midway between the centers of the posterior femoral condyles, which closely approximates the flexion-extension center-of-rotation of the knee, improves the precision in measuring A-P knee laxity compared to the tibial-eminence-based coordinate system. A-P knee laxity was measured using each coordinate system six times in three human cadaveric knees implanted with 0.8-mm diameter tantalum markers. For each laxity measurement, the knee was placed in a custom loading apparatus and biplanar radiographs were obtained while the knee resisted a 44 N posterior shear force and 136 N anterior shear force. A-P knee laxity was determined from the change in position of the tibia, with respect to the femur, resulting from the posterior and anterior shear forces. The precision for each coordinate system was calculated as the pooled standard deviation of A-P knee laxity measurements. The precision of the center-of-rotation coordinate system was 0.33 mm, which was about a factor of 2 better than the 0.62 mm precision of the tibial-eminence coordinate system (p=0.006). The 0.33 mm precision with the center-of-rotation coordinate system suggests that an observed change of either 0.56 mm (i.e. 1.7 standard deviations) or greater in A-P knee laxity over time is a real change and not due to measurement error when the new tibial coordinate system is used and other factors contributing to variability are controlled as was done in this study. Accordingly, clinicians and researchers should consider the use of this alternate tibial coordinate system when making serial measurements of A-P knee laxity using RSA because the improved precision allows for the observation of smaller differences.

Adult↗
PubMed2004

Lengthening of double-looped tendon graft constructs in three regions after cyclic loading: a study using Roentgen stereophotogrammetric analysis.

Lengthening of a double-looped tendon graft construct used to reconstruct the anterior cruciate ligament (ACL) can result in an increase in anterior knee laxity and affect the stability of the reconstructed knee. Three possible regions where lengthening of the construct can occur are (1) the region of the tibial fixation, (2) the region of the femoral fixation, and (3) the region of the graft between the fixations. One objective of this study was to demonstrate the feasibility of using Roentgen stereophotogrammetric analysis (RSA) to determine the lengthening in each region of a double-looped graft construct subjected to cyclic loading. A second objective was to determine which region(s) contributes most to an increase in length of this graft construct. Radio-opaque markers were attached to ten grafts to measure the lengthening in each of the three regions. Each graft was passed through a tibial tunnel in a bovine tibia, looped around a rigid cross-pin, and fixed to the tibia with a Washerloc fixation device. The grafts were cyclically loaded for 225,000 cycles from 20 to 170 N. Prior to and at intervals during the cyclic loading, simultaneous radiographs were taken of the tibia and graft. RSA was used to determine the 3-dimensional coordinates of the markers from which the lengthening in each region was computed at each interval. The regions of the tibial and femoral fixations were the largest contributors to the increase in length of the graft, with maximum average values of 0.91 and 0.76 mm respectively after 225,000 cycles. The region between the fixations contributed least to lengthening of the graft, with a maximum average value of 0.23 mm. More than 90% of the lengthening in each region occurred before 100,000 cycles of loading. RSA proved to be a useful method for measuring lengthening in all three regions of the graft construct. Lengthening of the graft construct in both regions of fixation is sufficiently large that the combined contributions may cause a recurrence of instability in some knees.

Animals↗
PubMed2004

How cyclic loading affects the migration of radio-opaque markers attached to tendon grafts using a new method: a study using roentgen stereophotogrammetric analysis (RSA).

An increase in anterior laxity following reconstruction of the anterior cruciate ligament (ACL) can result from lengthening of the graft construct in either the regions of fixation and/or the region of the graft substance between the fixations. RSA could be a useful technique to determine lengthening in these regions if a method can be devised for attaching radio-opaque markers to soft tissue grafts so that marker migration from repeated loading of the graft is limited. Therefore, the objectives of this study were 1) to develop a method for attaching radio-opaque markers to an ACL graft that limits marker migration within the graft, 2) to characterize the error of an RSA system used to study migration, and 3) to determine the maximum amount of migration and the time when it occurs during cyclic loading of ACL grafts. Tendon markers were constructed from a 0.8-mm tantalum ball and a stainless steel suture. Ten double-looped tendon grafts were passed through tibial tunnels drilled in bovine tibias and fixed with a tibial fixation device. Two tendon markers were sewn to one tendon bundle of each graft and the grafts were cyclically loaded for 225,000 cycles from 20 N to 170 N. At specified intervals, simultaneous radiographs were obtained of the tendon markers and a radiographic standard of known length. The bias and imprecision in measuring the length of the radiographic standard were 0.0 and 0.046 mm respectively. Marker migration was computed as the change in distance between the two tendon markers along the axis of the tibial tunnel. Marker migration was greatest after 225,000 cycles with a root mean square (RMS) value of less than 0.2 mm. Because the RMS value indicates the error introduced into measurements of lengthening and because this error is small, the method described for attaching markers to an ACL graft has the potential to be useful for determining lengthening of ACL graft constructs in in vivo studies in humans.

Animals↗
PubMed1997

Detection of elastin in the human fetal membranes: proposed molecular basis for elasticity.

The human fetal membranes provide a sterile biomechanical container which adjust by growth to mid-pregnancy to the increase in fetal size, and by elasticity to the forceful movements of the fetus. The molecular basis for this elasticity is not known, yet reduced elasticity may lead to their premature rupture and preterm birth, a major problem in perinatal medicine. Classically, elastin confers the property of elastic recoil to elastic fibres which are assembled from a family of tropoelastin precursors. These are covalently cross-linked to form insoluble elastin by formation of desmosine and isodesmosine, catalysed by the enzyme lysyl oxidase. The amnion, chorion and decidua were shown by Northern analysis and RT-PCR to contain detectable levels of tropoelastin mRNA and the mRNA encoding lysyl oxidase. The proteins encoded by these mRNAs were also identified by Western blotting and immunolocalization. Further, insoluble elastin was extracted from the human fetal membranes and shown by comparison to elastin preparations from other elastic tissues to have a reasonable desmosine content. Finally, scanning electron microscopy confirmed the presence of multiple layers of an apparently very thin elastic system in this tissue. This biochemical and histopathologic study has demonstrated therefore that the human fetal membranes synthesize and deposit a novel elastic fibre. The presence of such an elastic system in these tissues provides, for the first time, a probable molecular basis for the elastic properties of this tissue.

Amino Acids↗
PubMed1995

Elastin gene mutations in transgenic mice.

We have constructed several rat tropoelastin minigene recombinants encoding the complete sequence of rat tropoelastin, two isoforms of rat tropoelastin and a truncated tropoelastin lacking the domains encoded by exons 19-31 of the rat gene. Coding and non-coding domains in all these recombinants were placed under the transcriptional control of 3 kb of the promoter domain of the rat tropoelastin gene. These minigenes were used to prepare a total of 28 separate founder lines of transgenic mice. A species-specific reverse-transcriptase polymerase chain reaction (RT-PCR) assay was established to demonstrate the synthesis of rat and mouse tropoelastin mRNA in several tissues obtained from both neonatal and adult transgenic mice. Thermolytic digestion of insoluble elastin isolated from several neonatal mouse tissues revealed the presence of rat tropoelastin peptides in progeny from all those founder mice in which detectable levels of rat tropoelastin mRNA were noted. Phenotypic and histopathological assessment of transgenic and non-transgenic animals revealed the development of two diverse elastic tissue disorders. The progeny of two separate founder lines overexpressing the rat tropoelastin isoform lacking exon 33, developed an emphysematous phenotype in early adulthood. In contrast, transgenic mice, in which expression of the truncated rat tropoelastin minigene lacking exons 19-31 had been observed, died of a ruptured ascending aortic aneurysm. Tropoelastin gene mutations, therefore, will result in heritable disorders of elastic tissue. Moreover, different mutations in the tropoelastin gene will be responsible for very different abnormalities in elastic tissue function.

Animals↗
PubMed1995

Extensive alternate exon usage at the 5' end of the sheep tropoelastin gene.

Several overlapping cDNA clones were isolated from a lambda gt10 cDNA library constructed using poly A+ RNA from neonatal sheep lung. DNA sequence analysis of these cDNA recombinants revealed the complete derived amino acid sequence of sheep tropoelastin. A comparison of DNA sequences from individual sheep tropoelastin cDNA also confirmed the presence of several tropoelastin mRNA isoforms in neonatal lung tissue. Coding domains corresponding to exons 13, 14 and 33 were present in several of the sheep tropoelastin cDNA fragments but absent in others. The relative amount of alternate usage of these exons was quantitated by polymerase chain amplification. In confirmation of previous studies in other mammalian species, extensive alternate usage of exon 33 was observed in total RNA isolated from aorta, nuchal ligament and pulmonary artery from neonatal sheep. In striking contrast to all previous studies, however, exons 13 and 14 were shown to be subject to almost the same level of alternate usage as exon 33 in all three neonatal sheep tissues examined.

Alternative Splicing↗
PubMed1994

Medical therapy of malignant nerve pain. A randomised double-blind explanatory trial with naproxen versus slow-release morphine.

It is uncertain whether there exists a nociceptive component in malignant nerve pain responsive to NSAIDs and opioids. 20 patients with malignant nerve pain were randomly assigned to treatment with naproxen 1500 mg versus slow-release morphine 60 mg daily during 1 week, followed by cross-over medication during the second week in a double-blind, double-dummy protocol. In the 16 evaluable patients, a significant (P < 0.05) reduction of 26% (S.E. +/- 7.9) in pain intensity was reached at day 7, compared to baseline pain. At day 7, significant pain relief of 32% (P < 0.05) was observed in the naproxen group, but not in the morphine group (21%, P = 0.14). Patients using morphine needed approximately twice as much paracetamol rescue than patients using naproxen. Additional pain relief could be observed in 4/9 patients with cross-over medication. These data support the concept of a nociceptive component in malignant nerve pain responding to NSAIDs and opioids, and favour the combination of both an anti-inflammatory drug and an opioid for symptomatic pain relief.

Adult↗
PubMed1993

Effect of glucose 5% solution and bupivacaine hydrochloride on absorption of sufentanil citrate in a portable pump reservoir during storage and simulated infusion by an epidural catheter.

The stability of sufentanil (5 micrograms/ml as citrate) in admixtures with glucose 5% or bupivacaine hydrochloride (2 mg/ml) in 100 ml polyvinyl chloride portable pump reservoirs was investigated during simulated infusion by an epidural catheter at 32 degrees C for 48 h and during storage at 4 degrees C and 32 degrees C for 30 days. During both experiments a small decrease (< 5%) in concentration of sufentanil and bupivacaine was observed. No loss of sufentanil or bupivacaine could be detected (in both experiments) in the portable pump reservoirs when stored at 4 degrees C for 30 days. A significant decrease of sufentanil was observed when stored at 32 degrees C after 30 days when diluted with glucose (9.2%) or in combination with bupivacaine (8.9%); also, the bupivacaine concentration decreased significantly (4.1%). It is concluded that sufentanil in portable pump reservoirs can be used under patient conditions at 32 degrees C for 7 days when diluted with glucose 5% or 3 days in combination with bupivacaine hydrochloride.

Absorption↗
PubMed1993

Effect of pH on absorption of sufentanil citrate in a portable pump reservoir during storage and administration under simulated epidural conditions.

Sufentanil (5 micrograms/ml as citrate) was investigated for its stability when diluted with sodium chloride 0.9%, in 100 ml polyvinyl chloride portable pump reservoirs during administration under simulated epidural conditions at 32 degrees C for 48 h. Sufentanil was absorbed into the polyvinyl chloride, resulting in a reduction of 10.9% of the concentration after 48 h. The absorption of sufentanil (5 micrograms/ml as citrate), alone and in combination with bupivacaine hydrochloride (2 mg/ml), was investigated when diluted with sodium chloride 0.9% in combination with a citrate buffer (pH 4.6), in the same reservoirs under similar conditions. There was no loss of sufentanil after 48 h in both experiments. The effect of the pH on the absorption of sufentanil in polyvinyl chloride was investigated at different pH values. After storage for 21 days at 32 degrees C there was 5.1% loss of sufentanil at pH 4 and 80.6% loss at pH 6. The citrate buffer at the optimum pH (4.6) has a low, acceptable buffer capacity for epidural administration.

Absorption↗
PubMed1993

Valyl-alanyl-prolyl-glycine (VAPG) serves as a quantitative marker for human elastins.

Thermolysin digests of human elastins were examined for reliable elastin peptide markers as determined by HPLC followed by amino acid sequencing of promising peaks. The tetrapeptide VAPG was found to occur in the early portion of the chromatogram in a highly reliable fashion. The peptide appears to be significantly amplified, when compared with the other peptides, in that it is derived from the hexapeptide repeat in elastin, VGVAPG, which repeats itself in two three-piece segments in the c-terminal portion of the tropoelastin molecule. VAPG serves as a highly reliable quantitative measure for human elastins, allowing sensitivities to less than a microgram. Thus, it is a significantly more accurate measure than other existing methods. Precision also appears to be enhanced because of the directness of the measurement. The use of VAPG as a quantitative marker for human elastin has clinical application in the study of elastin-based connective tissue diseases.

Adult↗
PubMed1993

Quantitation of lung elastin and collagen in protein and essential fatty acid malnourished rats.

Thirty-nine 40-day old male Sprague-Dawley rats (average wt. 115g) were divided into 4 groups and fed diets A, control; B, essential fatty acid (EFA) deficient; C, protein deficient; D, combined protein and EFA deficient. At the end of 5 weeks, lungs were removed from the animals for collagen and elastin quantitation and for morphometric measurements. The collagen content of the lungs which ranged from 95-100 micrograms/mg dried fat-free (D.F.F.) tissue, was not altered by protein or EFA deficiencies. The elastin content of lungs was markedly increased in diets C and D while the cross-linking (Isodesmosine-desmosine content) expressed as residues per 1,000 (R/1000) was not different in the four groups. The elastin content of lungs from group D animals was greater than group C suggesting an additive effect from the EFA deficiency in diet D. The morphometric measurements indicated no change in alveolar linear diameter (Lm) while the total alveolar surface area (ISAA1V) was decreased by the deficient diets C and D. The protein deficiency and the combined protein and EFA deficiencies produced an increased elastin content in lung. Elastin cross-linking and collagen quantity was not affected by the dietary treatments. The morphometric measurements indicated that protein deficiency in these animals did not produce structural changes in the lungs as indicated by alveolar dimensions.

Animals↗
PubMed1992

Stability of sufentanil citrate in a portable pump reservoir, a glass container and a polyethylene container.

The stability of sufentanil citrate (100 ml, 5 micrograms/ml) in an admixture with sodium chloride 0.9% injection was investigated when filled in a portable pump reservoir with PVC wall, a glass container and a polyethylene container, at 32 degrees C, 4 degrees C and -20 degrees C for up to 21 days. No change in colour was visually observed in any of the samples during the 21-day storage period. A slight precipitation was noticed in three out of nine portable pump reservoirs, one at each storage temperature. There was a slight rise in pH at each storage temperature in all samples. There was approximately 13% loss of sufentanil citrate in the portable pump reservoirs stored at 32 degrees C during 2 days and 60% loss after 21 days, due to absorption of sufentanil citrate in the reservoir wall. No loss of sufentanil citrate could be detected in the portable pump reservoirs when stored at -20 degrees C and 4 degrees C. However, a serious inhomogeneity of the sufentanil citrate solution occurred after thawing at room temperature in the portable pump reservoirs which had been kept at -20 degrees C. The homogeneity could be restored by shaking for approximately 10 min. There was no change in the sufentanil citrate concentrations in the glass containers and polyethylene containers stored at the three temperatures. The portable pump reservoirs stored at 32 degrees C also showed a significant loss of vehicle due to evaporation (1.0 +/- 0.1 ml a week). This could not be detected in any of the other samples.

Absorption↗
PubMed1992

Stability of morphine hydrochloride in a portable pump reservoir.

The stability of morphine hydrochloride in an admixture with sodium chloride 0.9% injection in a portable pump reservoir was investigated. Duplicate samples containing morphine hydrochloride 0.5, 1.5 and 2.5 mg/ml were stored in original 100 ml plastic drug reservoirs at 32 degrees C for 60 days. An amount of 3 ml was removed immediately after preparation and at fixed intervals in the weeks after. All samples were tested for loss of vehicle, for appearance of precipitation and for change in colour or pH. Furthermore, they were analysed for drug concentration using high pressure liquid chromatography. No precipitation or change in colour was observed in any of the sample admixtures. There was no change in the pH values of any of the morphine hydrochloride concentrations from day 4 and later on. Only between day 1 and day 4 a slight, but not significant rise could be detected. There was no loss of morphine hydrochloride of any importance at any concentration in the samples over 60 days when corrected for loss of vehicle. Loss of vehicle (0.8 +/- 0.1 ml a week), on the other hand, gave a rise in morphine hydrochloride concentration.

Diethylhexyl Phthalate↗
PubMed1992

Dietary lipid modulation of connective tissue matrix in rat abdominal aorta.

Dietary lipid modulation of structural and passive mechanical properties of isolated rat abdominal aortic segments were assessed during the early developmental period. Rats were raised from conception to 90 days of age on semisynthetic diets containing various types and amounts of lipids. Aortic segments from three groups of rats fed high-fat diets (15%, wt/wt) consisting of olive oil, corn oil, or lard as the sole lipid sources were compared with those from rats fed a low-fat control diet containing corn oil (5%, wt/wt). Morphometric analysis of the tunica media demonstrated that rats raised on diets with a relatively low polyunsaturated fatty acid content (olive oil and lard) had greater numbers of elastic lamellae than rats raised on diets with opposite fatty acid indexes (high- and low-fat corn oil). Changes in elastin content of the tunica media, determined biochemically, paralleled those seen by morphometric analysis of the elastic lamellar number. Altered dietary fatty acid ratios were also associated with changes in smooth muscle cell number. In this regard, a decreased cellular density was observed in the olive oil and lard diets compared with the corn oil diet. The olive oil diet was unique amongst the dietary lipid regimens in raising, whereas the lard-containing diet lowered, indexes of aortic tissue elasticity. These results demonstrate an effect of chronic feeding of high dietary fat on the composition and biomechanical properties of the connective tissue matrix of abdominal aortic rings from young Sprague-Dawley rats.

Animals↗
PubMed1991

Oxysterol incorporation into rat aorta resulting in elastin compositional changes.

The incorporation of dietary cholestan-3 beta,5 alpha,6 beta-triol (triol) into rat thoracic aortic tissue and changes in amino acid composition of the elastin were investigated to identify the cytotoxic properties of the triol. Weanling male Sprague-Dawley rats were fed the following diets for three months: (i) normal chow, (ii) normal chow with 1% (w/w) cholesterol added, or (iii) normal chow with 0.9% (w/w) cholesterol and 0.1% (w/w) triol added. Triol levels in the blood and in the thoracic aortic tissue were measured. Compositional changes of elastin were also determined. After three months on the triol-containing diet, triol was found in the thoracic aorta but was not detected in the blood. Amino acid analyses of the aortic tissue elastin revealed that the proline levels in the triol-fed animals were significantly greater than in the other two diet groups, while the elastin levels of leucine, aspartate, arginine, and phenylalanine decreased significantly. The mechanism for these observed changes induced by triol may reflect alternate splicing of elastin messenger ribonucleic acid (mRNA) resulting in structual changes in the elastin molecule. Dietary triol does contribute to tissue triol content and is associated with aortic elastin compositional changes. How these changes may contribute to the development of cardiovascular disease is not known.

Amino Acid Sequence↗
PubMed1991

Modification of the pulmonary connective tissue developmental response in the neonatal rat by ciclosporin.

Neonatal rat pups were treated either with ciclosporin at 10 mg/kg/day dissolved in olive oil (experimental) or with pure olive oil (control). Lung protein biosynthesis was evaluated in a protocol which involved the measurement of total accumulated protein, collagen and elastin. Four time points were studied in the first 21 days of life, 12 animals contributing to each point (6 control and 6 ciclosporin). Ciclosporin levels in the treated group ranged widely (2,000-4,000 ng/ml). There were significant differences in total body weight and lung weight in treated vs. controls during and after the first week. DNA contents per unit wet weight varied significantly during the second week of life, indicating increased cellularity of the ciclosporin-treated animals. Associated with this was an increase in the lung protein/DNA ratio as well as the elastin/DNA ratio in the control animals, but not in the treated ones. The lung collagen/DNA ratio was not as dramatically affected by the ciclosporin treatment. However, the collagen content per unit wet weight of lung tissue was increased in the ciclosporin-treated animals at 15 days of life. We conclude that ciclosporin has a marked effect on lung connective tissue metabolism in early life, the long-term effects of which are unappreciated and undocumented but may well be of vital importance in the lungs of long-surviving organ transplant patients.

Animals↗
PubMed1990

Quantitation of elastin in tissues and culture: problems related to the accurate measurement of small amounts of elastin with special emphasis on the rat.

Both rat and sheep elastin can be quantified by measurement of discrete peptides released from the insoluble protein by thermolysin digestion. These peptides are easily visualized and measured by HPLC. With the sheep the tallest peak on the chromatogram represents the VGVPG pentapeptide derived from a repeating sequence seen in elastin from many species. This repeating sequence allows for amplification of the signal significantly above background so that accurate quantitation can be carried out. The measurement is reproducible over a wide range of protein concentrations. With the rat however the pentapeptide is not present but appears to be replaced by other repeating sequences. We quantitated and determined amino acid sequence on 8 peaks present in the early portion of the chromatogram for purposes of quantifying rat elastin. That signal most reliably present over a range of concentrations was tyrosyl-glycine (YG) which eluted at 8.5 minutes. We have used YG as a basis for quantitation of rat elastin both from tissues and tissue culture. We have also shown that the desmosine crosslinks are not constant in elastin produced in a neonatal rat smooth muscle culture system but vary with the age of the culture. We thus propose that an index of maturation be considered for a given elastin in the form of mumoles of crosslink per gram of elastin so as to better define its quality.

Amino Acid Sequence↗