Development of customized finite element models of medial column fixation using an intramedullary beam: A computational sensitivity analysis.

Intramedullary beaming is commonly used for medial column arthrodesis to prevent or correct rocker-bottom deformities; however, the biomechanics of these reconstructions have not been rigorously studied. Customized FE models of intramedullary beaming of the medial column were developed and compared to a previous cadaveric study, which resulted in a strong correlation in medial column stiffness (ρ = 0.83, p = .079) and implant failure locations. A design of experiments was performed to quantify the models' sensitivities to varying cortical shell and cartilage thicknesses, cancellous bone and cartilage elastic moduli, and surgical medial column compression distance. Cartilage thickness and cartilage elastic modulus had the largest impact on medial column stiffness and compression distance had the greatest effect on cartilage contact area. Cortical shell thickness and cancellous bone properties did not have a significant effect on the measured parameters for the values tested. Overall, the FE models exhibited behavior that is consistent with known mechanical principles related to bending and composite structures as well as the experimental results. This study elucidates the effects of varying commonly assumed model parameters that can aid future studies aimed at screening implant designs.

Revision total knee arthroplasty using a novel 3D printed titanium augment: A biomechanical cadaveric study.

BACKGROUND: During revision total knee arthroplasty (rTKA), proximal tibial bone loss is frequently encountered and can result in a less-stable bone-implant fixation. A 3D printed titanium revision augment that conforms to the irregular shape of the proximal tibia was recently developed. The purpose of this study was to evaluate the fixation stability of rTKA with this augment in comparison to conventional cemented rTKA. METHODS: Primary total knee arthroplasty (pTKA) surgery was performed on 11 pairs of thawed fresh-frozen cadaveric tibias (22 tibias). Fixation stability testing was conducted using a three-stage eccentric loading protocol. Bone-implant micromotion was measured using a high-resolution optical system. The pTKA were removed. Revision TKA was performed using a 3D printed titanium augment or a standard fully cemented stem. The three-stage eccentric loading protocol was repeated and micromotion was measured for the revision implants. RESULTS: After rTKA, the mean vertical micromotion was 28.1 µm ± (SD) 20.3 µm in the control group and 17.5 µm ± 18.7 µm in the experimental group. There was significantly less micromotion in the experimental group (p = 0.029). CONCLUSIONS: This study suggests that early fixation stability of revision TKA with the novel 3D printed titanium augment is better then the conventional fully cemented rTKA. The early press-fit fixation of the augment is likely sufficient for promoting bony ingrowth of the augment in vivo. Further studies are needed to investigate the long-term in-vivo fixation of the novel 3D printed augment.

Multimodal target point assessment for stereotactic biopsy in children with diffuse bithalamic astrocytomas.

INTRODUCTION: Diffuse glial tumors with bithalamic involvement are rare in children. Diagnostic assessment can be difficult as the radiological findings can be unspecific. MATERIALS AND METHODS: In order to enhance the diagnostic yield metabolic imaging with MRS and PET using FET ( O-(2-[(18)F]fluoroethyl)- L-tyrosine) was performed in two children (2 and 10 years of age). Co-registered images were used for image-guided biopsy, which was planned with neuronavigation and stereotaxy simultaneously. RESULTS: Biopsies from the right thalamus were planned, but locations were changed in both cases after metabolic imaging was available. MRS (thalamic voxel) was typical for a glial tumor in one child. In the older girl FET-PET revealed an unexpected lesion in the left cerebellar hemisphere, with a tumor-to-cortex ratio of 3.8, as against 1.7 in the thalamus. Accordingly, a stereotactic biopsy specimen was taken from the left cerebellar hemisphere, and a final diagnosis of anaplastic astrocytoma was made. The other patient showed a higher uptake (tumor-to-cortex ratio 1.6) in the left dorsal thalamus, compared with bilateral homogeneous hyperintensity of the thalamus structures on MRI. Stereotactic biopsy revealed a low-grade diffuse astrocytoma. CONCLUSION: Stereotactic biopsy using metabolic imaging and image fusion can enhance the diagnostic yield in cases of diffuse pediatric gliomas disclosing unexpected 'hot spots'.

Allozymes in mammalian population genetics and systematics: indicative function of a marker system reconsidered.

Data from an extensive research project on lagomorphs were compiled and re-analyzed from a synoptical point of view for examining the indicative function of allozymic variation. Empirical data suggested the Shannon-Weaver information index to be a better indicator of allelic diversity than expected average heterozygosity. There were differences in polymorphism among various structural and physiological classes of enzymes. Reliable estimates of gene diversity and genetic distances can be obtained only if more than 30 loci are examined. At the population level, allozymic diversity was not related to morphological variation. It was, however, indicative of increased developmental homeostasis as assessed by overall fluctuating asymmetry in non-metric morphological traits. Allozymes served well for fully resolving genetic differentiation among populations and for assessing levels of migration, whereas mtDNA and morphological data provided only additional information. The results are discussed with respect to data from other mammalian taxa.

Relationship between allozymes, heterozygosity and morphological characters in red deer (Cervus elaphus), and the influence of selective hunting on allele frequency distribution.

Morphological characters in red deer (Cervus elaphus), which serve as criteria for selective hunting, were examined in relation to electrophoretic variation in three populations from the Vosges in eastern France. From the polymorphic loci examined, certain alleles at Idh-2, Me-1 and Acp-1 showed significant associations with a special development of body and antler characters selected for by hunters. Idh-2(125) was associated with larger hind foot length in females and a higher number of antler points in males. Me-1(90) and Acp-1(100) were associated with small spikes. The populations studied differed from one another in the duration and intensity of selective hunting and the increase or decrease in the respective allele frequencies could be explained by selection for large body size, a high number of antler points and against small spikes in yearlings, rather than by genetic drift. Among other morphological characters examined, the length of the main beam was significantly associated with the allele Acp-2(100). In contrast, no associations could be detected between overall heterozygosity and the development or the degree of asymmetry (in paired structures) of any of the morphological traits in question. Although no obvious differences in the overall values of polymorphism or heterozygosity were found between the populations, selective hunting leads towards a change in allele frequencies and eventually to the loss of one or the other rare allele.

NMR and molecular orbital studies of isomerism and tautomerism in oximes of 2-acyl cyclic 1,3-diones.

Molecular orbital calculations and 13C and 15N NMR experiments have been performed on the O-methyl oximes of two types of 2-acyl cyclic 1,3-diones. One (III; X = CH2) was based on cyclohexane, and the other (X = O) on pyran. The data indicate that both the cyclohexane and pyran compounds prefer to exist as the oxime, rather than the enamine isomer. Two equivalent, interconverting, keto-enol tautomers exist in the cyclohexane compound. The pyran compound exists as the lactone-enol tautomer. Our results have implications in the design of herbicidal compounds and drugs containing similar tautomeric systems.

Genes expressed in the male gametophyte of flowering plants and their isolation.

Recombinant cDNA libraries to poly(A)RNA isolated from mature pollen of Zea mays and Tradescantia paludosa have been constructed. Northern blot analyses indicate that several of the clones are unique to pollen and are not expressed in vegetative tissues. The majority, however, are expressed both in pollen and vegetative tissues. Southern hybridizations show that the pollen specific sequences in corn are present in one or a very few copies in the genome. By using several of the clones as probes, it was found that there are at least two different groups of mRNAs with respect to their synthesis. The mRNAs of the first group represented by the pollen specific clones are synthesized after microspore mitosis and increase in concentration up to maturity. The second group, exemplified by actin mRNA, begins to accumulate soon after meiosis, reaches its maximum by late pollen interphase, and decreases thereafter. Although the actin mRNA and the pollen specific mRNAs studied show very different patterns of initiation of synthesis and accumulation during pollen development, the rates of decline of these mRNAs during the first 60 minutes of germination and pollen tube growth in Tradescantia are similar and reflect the previously observed declines in rates of protein synthesis during this period.

Analysis of the Complexity and Diversity of mRNAs from Pollen and Shoots of Tradescantia.

The mRNAs of the mature pollen grain of Tradescantia paludosa at anesthesia and of vegetative shoots have been compared by analyzing the kinetics of hybridization between homologous and heterologous reactions of cDNA to poly(A)RNA in excess. The mRNAs in pollen can be divided into three abundance classes with complexities of 5.2 x 10(4), 1.6 x 10(6), and 2.1 x 10(7) nucleotides. The three classes are made up of sequences that constitute 15, 60, and 24% of the mRNAs and each sequence is present on an average at 26,000, 3,400, and 100 copies, respectively, per pollen grain. About 20,000 different genes are expressed in pollen as compared to about 30,000 in vegetative shoots. Estimates have been made of pollen mRNA sequences shared with those of shoot tissue and of shoot sequences common to those in pollen.

Messenger RNAs in corn pollen and protein synthesis during germination and pollen tube growth.

Mature ungerminated pollen grains of Zea mays L. contain presynthesized messenger RNAs. This has been demonstrated by the isolation of poly(A)RNA and its translation in the wheat germ and reticulocyte cell free systems into polypeptides many of which are similar to those synthesized in germinating pollen. Each corn pollen grain contains between 352-705 pg of total RNA and 8.9-17.8 pg of poly(A)RNA. During germination of corn pollen at least 260 different polypeptides are synthesized as determined by labeling and 2-dimensional gel electrophoresis. These results are discussed with reference to other plants and the number of different genes expressed during pollen development.

Cellular expansion at low temperature as a cause of membrane lesions.

Rates of solute leakage from excised discs of cucumber (Cucumis sativus L. cv Straight Eight) cotyledons were altered by temperature during plasmolysis in the manner of a simple diffusion phenomenon; the log of the leakage rate increased in proportion to the temperature. During deplasmolysis, however, leakage rates responded to temperature with a very different pattern: chilling conditions (below about 20 degrees C) caused large increases in leakage rates, indicating disruption of membrane integrity in the tissues. The time course of restoration of normal leakage rates after deplasmolysis/chilling damage indicated a rapid repair of the lesions. A similar sensitivity to low temperatures was found during rehydration after leaf desiccation, with low temperatures again causing high leakage rates. It is suggested that low temperatures interfere with membrane expansion, possibly by lowering elasticity and hindering the incorporation of lipid material into the expanding membrane. The expansion of tissues at low temperatures may cause lesions in cellular membranes, contributing to chilling injury.

Preparation and comparison of model bilayer systems from chloroplasts thylakoid membrane lipids for 13C-NMR studies.

Model bilayer systems from individual purified chloroplast thylakoid membrane lipids, from reconstituted mixtures of these purified lipids, and from leaf total polar lipid extracts have been prepared in water, and the longitudinal relaxation times (T1's) of the individual carbon atoms of the fatty acyl chains measured by 13C-NMR spectroscopy. The T1's increase with increasing distance of the carbon atoms from the polar headgroups in all cases, and as the results from each of the preparations are similar, all can be used as models of chloroplast membrane bilayers. Relaxation time measurements on intact chloroplast thylakoid membranes indicate the presence of chlorophyll resonances in the 13C-NMR spectrum of the membrane.

Cimetidine in the management of symptomatic patients with duodenitis: a double-blind controlled trial.

Twenty-one adult outpatients with dyspepsia and endoscopically proven duodenitis without chronic ulceration completed a double-blind trial of either cimetidine (1 g/day) or placebo. Treatment with cimetidine for 6 weeks resulted in a significant improvement in symptoms and in the endoscopic appearance of the duodenitis when compared to treatment with placebo. The symptomatic and endoscopic improvement, however, was not associated with any significant change in the histological grading of the duodenitis.

13C nuclear magnetic resonance studies of the composition and fluidity of several chloroplast monogalactosyldiacylglycerols.

The motional properties of four monogalactosyldiacylglycerols isolated from photosynthetic membranes, and containing different fatty acid chain lengths and degrees of unsaturation, have been determined using 13C nuclear magnetic resonance. These properties have been compared with those of a lipid containing only saturated fatty acids. The 13C longitudinal relaxation times (T1) of the carbon atoms of the acyl chains in [2H4] methanol were measured as an index of the rates of motion of the lipid molecules and used to compare the relative fluidity of the acyl chains. The T1 values of the glyceryl and galactosyl carbon atoms in each monogalactosyldiacylglycerol are essentially constant, when allowance is made for concentration differences and the presence of two hydrogens on a methylene carbon versus one on a methine carbon. These results indicate similar rates of motion for the headgroup carbons in each lipid. However, for the acyl chains, the T1 values increase with the introduction of a double bond and increase further with additional unsaturation. This increase in the rate of motion only occurs at carbon atoms beyond the first double bond in an acyl chain. These results differ to those reported for monolayer experiments where changes in packing characteristics are predominantly dependent on the introduction of the first double bond and then vary little between species.

Transhepatic embolisation of gastro-oesophageal varices in the management of variceal haemorrhage.

The difficulty of controlling variceal haemorrhage has led to the recent development of methods designed to sclerose the bleeding vessels. This study describes the application of percutaneous transhepatic portal catheterization with embolisation and sclerosis of varices in eight consecutive patients admitted with bleeding oesophago-gastric varices. Portal hypertension was documented and varices demonstrated in each case. Bleeding ceased rapidly in seven patients, two patients rebled 1-3 weeks after the procedure, and five patients were subsequently discharged from hospital. In no instance was death related to continued gastrointestinal haemorrhage. Initial experience with transheptic embolisation of bleeding oesophago-gastric varices indicates that this technique is effective in controlling variceal haemorrhage.

Effect of eucalyptus growth regulators on the water loss from plant leaves.

Three closely related growth regulators (G) that are present in some myrtaceous plants were examined for possible anti-transpirant effects. The bioassay material involved cuttings of mung bean and Eucalyptus rupicola. Stomatal resistance was determined by a diffusion porometer. Water loss was equated with water uptake by the cutting over a 24-hour period.In both bioassays, G reduced water loss. The reduced water loss was associated with stomatal closure. This anti-transpirant effect of G was five to ten times less than that of abscisic acid. The stomatal resistance to the diffusion of water vapor from mung bean leaves increased within 1 hour of application of G. Marked stomatal closure occurred after 6 hours when 5 to 7 micrograms of G had accumulated in the leaves.These results and earlier evidence, suggest that G growth regulators are involved in the water economy of Eucalyptus and perhaps other related genera.

Gastro-colic fistula complicating benign gastric ulcer in analgesic abusers.

Two cases of gastro-colic fistula occurring in analgesic abusers are described. In both patients, the fistulous communication was diagnosed at endoscopy and subsequently verified by upper gastrointestinal tract barium studies. Gastro-colic fistula is a rare complication of benign peptic ulcer disease. Whilst salcylates and cortico-steroids have been implicated as aetiological agents, abuse of compound analgesics has not previously been reported. Since the first description of gastro-colic fistula in 1755, thirty documented cases associated with benign gastric ulcer have been reported. Most often, gastro-colic fistula occurs secondary to gastric or colonic malignancy. Barium enema examination is the most accurate diagnostic study. Endoscopy has been confined to the visual inspection of the ulcer and establishing the benign nature of these lesions.

Occurrence and bioassay responses of G : A plant growth regulator in Eucalyptus and other Myrtaceae.

A growth regulator (G) occurs at high concentrations in adult leaves of E. grandis Maiden. Low concentrations of G are present in juvenile leaves of this species and also in adult leaves of some other Myrtaceae. Low concentrations of G (5×10(-6) and 10(-5) M) promote rooting in mung-bean cuttings and elongation in Avena coleoptile sections; high concentrations (5×10(-4) M) inhibit. These and other bioassay results indicate that G may have auxin-like activity.

Solitary ulcer of the rectum, A report of fiteen cases.

Fifteen cases of solitary ulcer of the rectum are described. The patients complained mainly of rectal bleeding, discomfort and passage per rectum of mucus. The lesion is most commonly situated on the anterior wall of the rectum and can be red and granular, nodular or ulcerating. Peolapse was found in nine cases. The histological lesion is similar to that seen in rectal prolapse. The condition can be mistaken for colitis, adenomatous polyp or carcinoma. Reassurance, defaecation reeducation and dealing with the patients'emotional problems alleviated the condition in some cases. Surgery to remove a prolapsing segment was performed in one case only.

Interspecific hybridisation in poplar.

Interspecific compatibility and incompatibility have been examined through the genus Populus. General methods of manipulation have been developed to break the incompatibility barriers. These methods are described and a hypothesis is put forward to account for the results. This proposes that at least two factors are involved, one attached to the pollen (P) and one to the stigma (S), and that the interaction of these (PS) is critically involved in the total process. Implications for future plant breeding are discussed.