Ex vivo estimation of thoracolumbar vertebral body compressive strength: The relative contributions of bone densitometry and vertebral morphometry

The estimation of vertebral fracture risk in individuals with suspected osteopenia is commonly based on measurements of lumbar spine bone density. The efficacy of vertebral size and deformity, as assessed by vertebral morphometry, in the prediction of fractures has been less studied. In an ex vivo investigation the regional relationships between vertebral size, vertebral deformity, bone density and compressive strength throughout the thoracolumbar spine were examined. In 16 vertebral columns (T1–L5) the bone mineral content (BMC) and bone mineral density (BMD) of each segment were measured using lateral projection dual-energy X-ray absorptiometry, and the vertebral cancellous density (VCD) and mid-vertebral cross-sectional area (CSA) measured using quantitative computed tomography. Vertebral body heights were determined from mid-sagittal CT scans, and vertical height ratios calculated for each segment. The failure load and failure stress of the isolated vertebral bodies were determined using a material testing device. Separate analyses were performed for the upper (T1–4), middle (T5–8) and lower (T9–12) thoracic, and lumbar (L1–5) segments. In all regions, failure load was strongly correlated with BMD (r=0.82–0.86), moderately correlated with VCD (r=0.60–0.71) and vertebral height (r=0.22–0.49), and poorly correlated with the height ratios (r=0.04–0.33). Failure stress was best predicted by BMD (r=0.73–0.78) and VCD (r=0.70–0.78) but was poorly correlated with all morphometric variables (r=0.01–0.33). The segmental correlations between BMD and VCD ranged fromr=0.49 tor=0.79. For all regions, BMD and VCD were included in the stepwise regression models for predicting failure load and failure stress. Either the mid-vertebral height or CSA were included in all the failure load models, while mid-vertebral height was included in only one of the failure stress models. The results suggest that vertebral deformity and size (as assessed by vertebral morphometry) make only a minor contribution to the prediction of vertebral strength additional to that provided by bone densitometry alone. The consistent regional relationships between variables appear to support the practice of global fracture risk assessment based on lumbar spine densitometry.     

Three-dimensional reconstruction of magnetic resonance images of the temporomandibular joint by I-DEAS.

Evaluation of the temporomandibular joint has been limited by the inability of current technology to image complex morphology and motion in three dimensions. An engineering design program, I-DEAS, has been used to construct solid models from magnetic resonance images. A dried skull with an acrylic resin temporomandibular disc replica, immersed in water, provided sagittal and coronal MR images. Linear dimensions and disc volumes obtained from the models were compared with the original and found to be consistent, within the limits imposed by the slice thickness. We have applied the method to the living joint in an asymptomatic volunteer, and report our initial experience in demonstrating the spatial relationships and motion of the joint components.     

Ganciclovir treatment of cytomegalovirus ventriculitis in a patient infected with human immunodeficiency virus.

Histopathologic evidence of central nervous system involvement with cytomegalovirus (CMV) has been well recognized in patients infected with human immunodeficiency virus (HIV). However, clinically symptomatic disease has been decidedly less common. In this report, we describe a patient infected with HIV who developed an acute change in neurological status. Gadolinium-enhanced magnetic resonance imaging and analysis of cerebrospinal fluid revealed CMV ventriculitis and meningoencephalitis. Treatment with ganciclovir resulted in radiological improvement of the ventriculitis and negative CMV cultures but little clinical neurological improvement.     

Excitatory amino acid receptor regulation after subthalamic nucleus lesions in the rat

The subthalamic nucleus plays a pivotal role in the regulation of basal ganglia output. Recent electrophysiologic, lesion and immunocytochemical studies suggest that the subthalamic nucleus uses an excitatory amino acid as a neurotransmitter. After complete ablation of the subthalamic nucleus, we have examined the NMDA, AMPA, kainate and metabotropic subtypes of excitatory amino acid receptors in two major subthalamic projection areas (globus pallidus and substantia nigra pars reticulata) with quantitative autoradiography. Two weeks after ablation, binding sites for [³H]AMPA and [³H]kainate increased in substantia nigra pars reticulata ipsilateral to the lesion. In globus pallidus on the lesioned side, [³H]glutamate binding to the NMDA recognition site decreased. The results suggest that glutamate receptors regulate after interruption of subthalamic nucleus output.     

Induction of antibody responses to breast carcinoma associated mucins using synthetic peptide constructs as immunogens

A strategy for directing and enhancing B cell immune responses against synthetic peptide determinants has been developed in order to produce antibodies specifically against protein epitopes of clinical relevance. A peptide sequence based upon the MUC-1 mucin protein core was selected for this purpose since anti-MUC-1 antibodies have proven diagnostic application and therapeutic potential in human breast and ovarian cancer. Peptide constructs were synthesised co-linearly linking the immunodominant B cell determinant region, PDTRPAP, in the protein core of the MUC-1 mucin, to sequence 111 – 120 of influenza haemagglutinin A/X-31, a determinant recognised by T helper cells through association with MHC class II molecules. Induction of anti-MUC-1 antibodies to the B cell determinant region by immunisation with peptide was shown to be dependent upon both the presence and the position of the T cell determinant. In addition, haplotype mismatching with respect to the T cell determinant resulted in a significant lowering of the anti-MUC-1 antibody response in peptide construct immunised mice. These findings are relevant to the design of immunogens to produce antibodies against peptide epitopes of tumour associated proteins and glycoproteins.     

Conformation of Replicated Segments of Chromosome Fibres in Human S-phase Nucleus

Recent statistical analysis of the folding of G0/G1 chromosomes using fluorescence in situ hybridization (FISH) allowed development of a random walk/giant loop model of chromosome structure. According to this model there are two levels of organization of G0/G1 chromosome fibres. On the first level, the fibres are arranged in giant loops several Mbp in size, and within each loop the fibres are randomly folded. On the second level, the loop attachment sites form a chromosome backbone that also shows random folding. Newly replicated segments of mammalian chromosomes may be directly visualized at high resolution in S-phase nuclei using immunofluorescent methods and appear as worm-like fibres. In our earlier study, we analysed conformation of the fibres in human cells blocked for 16 h at the G1/S boundary with 5- fluorodeoxyuridine (FdU) and then released into S-phase by the addition of a DNA prec ursor. However, long treatment of cells with FdU induces very short replicons and may promote apoptosis. In this study we analysed conformation of the fibres in normally proliferating human cells that had not been blocked with FdU for a long time. It has been found that replicated chromosome fibres visualized just after 2 h of incubation of the cells with a non-radioactively labelled DNA precursor behave as flexible polymer chains without major constraints, and that their local conformation in the range of several microns of their contour length may be considered as random. Confocal analysis of human X chromosomes visualized in HeLa cells using FISH with a specific painting probe shows that in S-phase the chromosomes occupy distinct nuclear territories and their apparent size does not differ from that in non-S-phase cells. This observation indicates that the second level of chromosome organization also exists in S-phase chromosomes. It appears, theref ore, that the random walk/giant loop model developed earlier for G0/G1 chromosomes is also valid for S-phase chromosomes.