Induction of fracture healing using fibrous calcium phosphate composite spherulites

The healing of large fractural defects is a difficult clinical problem, especially if it occurs in elderly or otherwise debilitated patients. The objective of this study is to determine if a new formulation of fibrous calcium phosphate crystals would induce fracture healing in vivo. Fibrous calcium phosphate (FCP) can be grown with unique size, shape, and surface area characteristics as a resorbable or nonresorbable, osteoconductive or osteoinductive material. In comparison with other conventional calcium phosphate particulates, FCP particles possess approximately x 100 to x 1000 more surface area. One-and-one-half centimeter sections were removed from the ulnas of 12 rabbits. Three groups had fibrous calcium phosphate spherulites (4-8 microns, 150-300 microns, 400-600 microns) mixed with collagen and a growth factor-bonding agent injected into the ulnar defect. One site per group was not treated. X-rays were obtained during the study and the percentage of the ulna defect filled in by callous was measured. The percentage was recorded as the amount of fracture healing for each site. Histologic examination of the ulnas was performed following sacrifice at 12 weeks. Fracture sites treated with fibrous calcium phosphate showed significantly greater healing (0.79 +/- 0.3) than control animals (0.36 +/- 0.1) (P less than .05, unpaired t-test) radiographically. Histologic examination showed that the spherulites remain in situ and become embedded within the new growth of fibrous tissue, collagen and new bone. Radiographically and histologically, FCP preparations appear to accelerate fracture healing by inducing new bone formation, into which they often become embedded.

Exercise as a health-promoting lifestyle choice

The primary purpose of this exploratory study was to examine differences between exercisers and nonexercisers in self-esteem, perceived benefits of exercise, and perceived barriers to exercise. Second, we investigated how much variation in group membership as an exerciser or nonexerciser could be explained by the relationship among self-esteem, perceived benefits of exercise, and perceived barriers to exercise. A sample of 105 university students completed four questionnaires. Using t tests, a significant difference was found between exercisers and nonexercisers on self-esteem, perceived benefits of exercise, and perceived barriers to exercise. It was found that the three variables successfully accounted for 32% of the variation in group membership as an exerciser or nonexerciser.

Methods for the systematic investigation of gastrointestinal contrast media for MRI: evaluation of intestinal distribution by radiographic monitoring

Comparison of the effectiveness of various gastrointestinal (GI) contrast agents for magnetic resonance (MR) imaging is often complicated by varying amounts intraluminal filling with the orally administered agents. To achieve more uniform and reproducible imaging results with GI contrast agents for MR imaging (GICMR), we evaluated a radiographic method for monitoring intraluminal filling and distribution. Solutions of Mn-DPDP (2 mM), to which a small amount of barium sulfate (6 wt/vol%) was added, were administered orally to dogs. Gastric emptying and small bowel transit were monitored fluoroscopically. MR imaging was performed either 1) at a fixed time after administration of the contrast agent or 2) at a variable interval when the contrast agent was observed fluoroscopically to be in the terminal ileum. When initiation of MR imaging was guided by fluoroscopic monitoring of intestinal contrast distribution, uniform and reproducible intestinal contrast enhancement by GICMR was achieved. However, when MR imaging was performed at a fixed time interval after oral administration, non-uniform and variable GI visualization was obtained, and this corresponded to the variable intestinal distribution observed fluoroscopically. We conclude that reproducible intestinal filling with orally administered contrast agents can be accomplished with a radiographic monitoring technique, and this promotes more consistent GI visualization on MR images. Such standardized and reproducible methods are necessary for studies in which the effectiveness of GI contrast media for MR imaging is evaluated and compared.

Magnetic susceptibility effects and their application in the development of new ferromagnetic catheters for magnetic resonance imaging

Newly developed ferromagnetic catheters (Fe-Caths) are more conspicuous than conventional radiographic catheters (Rad-Caths) on magnetic resonance (MR) images because they produce recognizable ferromagnetic signal patterns (FSPs). To determine how MRI parameters influence these patterns, the imaging characteristics of nine Fe-Caths (ferromagnetic concentration 0.01 to 1.0 weight/weight %) were studied systematically and compared with three Rad-Caths. All catheters were studied in stationary and moving phantoms at mid-field (0.38 T) and high-field (1.5 T) strength using spin-echo and gradient-echo pulse sequences. Rad-Caths always produced a signal void. Fe-Caths produced FSPs, the size of which depended on the orientation of the catheter with respect to the main magnetic field, the concentration of ferromagnetic agent in the catheter, and the direction and strength of the frequency encoding gradient. When Fe-Caths were positioned perpendicular to the main magnetic field, they produced FSPs; however, when they were parallel to the main magnetic field, Fe-Caths produced no FSP, thus having a similar appearance to the Rad-Caths. Ferromagnetic catheters produce conspicuous patterns on MR images that depend on catheter orientation in the main magnetic field and vary predictably with the MRI parameters.

TMJ meniscus and bilaminar zone: MR imaging of the substructure--diagnostic landmarks and pitfalls of interpretation

Identification of the junction of the posterior band with the bilaminar zone is important to detect anterior displacements of the temporomandibular joint (TMJ) meniscus on magnetic resonance (MR) images. However, significant differences in tissue characteristics within the meniscus itself may cause a confusing appearance that is not easily reconciled with available anatomic references. Six cadaveric TMJ specimens were imaged sagittally at 1.5 T with various combinations of repetition time and echo time and with use of both standard surface coils and a specially developed solenoidal specimen coil. Corresponding histologic sections were correlated with the in vitro MR images to identify the anatomic structure and tissue characteristics. Comparison of these in vitro images with in vivo images of 100 joints identified a vertical, linear, low-signal-intensity band as an important landmark of the junction of the posterior band and bilaminar zone. Recognition of the signal-intensity characteristics of the center and the surfaces of the posterior band as well as the appearance of the insertion of the bilaminar zone also increased confidence of visualization and helped avoid possible false-positive diagnoses.

A double quantum coherence transfer proton NMR spectroscopy technique for monitoring steady-state tumor lactic acid levels in vivo

If proton nuclear magnetic resonance (1H NMR) spectroscopy is to provide a clinically useful modality for monitoring tumor growth and treatment, the technique must be able to unambiguously detect steady-state metabolite concentrations in human tumors and differentiate these from normal tissue levels. To address this problem, a two-dimensional double quantum coherence transfer spectroscopy (2DDQCT) method was developed and tested in a series of tumor cell lines implanted in mice. Lactate-edited proton NMR spectra were determined from a roughly 1-cm3 region of interest in EMT6, RIF-1, and fibroma. In two-dimensional data matrix representations of the 2DDQCT experiments (double quantum frequency on the vertical axis and chemical shift on the horizontal axis) the lactate signal (330 Hz with the transmitter set at the water resonance) was well-resolved from lipid (480 Hz, 600 Hz). The resolution in the double quantum dimension was also sufficient to conclude that a detectable level of alanine, which would reside at 358 Hz, was not present in the three tumor types. Following the NMR experiment, tumors were chemically assayed for lactate giving 8.17, 9.1, and 6.73 mumols/g wet wt for RIF-1, EMT6, and fibroma, respectively. This technique is likely to provide a noninvasive method for monitoring the steady-state lactic acid levels in small tumors before and after therapy, as well as in tissues with impaired oxygen delivery using clinical and research NMR systems.

Detection of hepatic malignancies using Mn-DPDP (manganese dipyridoxal diphosphate) hepatobiliary MRI contrast agent

A new hepatobiliary contrast agent (Mn-DPDP) was used in the detection of liver metastases in six rabbits with seven hepatic V2 carcinomas. This contrast agent is derived from pyridoxyl-5-phosphate which is biomimetically designed to be secreted by the hepatocyte. After Mn-DPDP administration, a 105% increase in liver signal to noise was obtained using a 200/20 (TR/TE) pulsing sequence, and a 62% decrease in intensity was observed using a 1200/60 pulsing sequence. Liver V2 carcinoma contrast enhancement increased 427% using the 200/20 pulsing sequence and 176% using the 1200/60 pulsing sequence. Four of seven V2 carcinomas were not detectable prior to the administration of Mn-DPDP (50 mumol/kg). Two neoplasms were only detectable in retrospect (after Mn-DPDP) on the 1200/60 sequence. The smallest neoplasms detected in this study were 1-4 mm. Mn-DPDP appears to be a promising MRI contrast agent.

Magnetic resonance imaging of the larynx

Magnetic resonance imaging (MRI) is now considered the imaging modality of choice for the evaluation of the larynx. The most common indication for MRI of the larynx is to aid in the staging of patients with possible or known laryngeal carcinoma. This article presents the normal MRI anatomy of the larynx in three orthogonal planes. Respiratory maneuvers were also performed during imaging sequences to demonstrate their physiological effects and to examine the feasibility of performing such maneuvers during an imaging sequence. Included in this article is a brief discussion of the use of MRI in the staging and treatment of laryngeal carcinoma.

Insulin gene expression in chicken ontogeny: pancreatic, extrapancreatic, and prepancreatic

Insulin has metabolic, growth, and differentiation effects in chicken embryos in vivo and it is required for normal development. Whether the pancreas is the sole source of insulin in embryogenesis is controversial. In the present study we investigated (1) the developmental pattern of expression of the chicken insulin gene in the pancreas; (2) the expression of the insulin gene in three nonpancreatic tissues, liver, brain, and lower limb, during chicken development; and (3) the expression of the insulin gene at prepancreatic stages and during chicken embryo organogenesis. Hybridization of synthetic species-specific insulin oligonucleotides to pancreatic frozen section in situ and to Northern blots revealed a major increase in insulin messenger RNA (mRNA) levels during the third week of embryonic development. The hybridization histochemistry showed both an increase in the levels of insulin mRNA per pancreatic islet and, in addition, an increase in the number of insulin mRNA containing islets with development. By Northern analysis there was a major polyadenylated transcript of 0.6 kb, which increased in abundance approximately 30-fold during this interval. Under the same stringency conditions used for pancreatic RNA an insulin transcript was detected in liver RNA blots. The abundance of this hepatic insulin mRNA was about 100-fold less than the pancreatic insulin mRNA and, in contrast to the latter, did not increase in late development. Primer extension experiments demonstrated that the insulin transcripts of pancreas and liver had similar 5' ends. No insulin mRNA was detected by Northern analysis or primer extension either in whole brain or lower limb total RNA from several developmental stages. A very low abundance insulin mRNA was detected in whole embryo at Day 8 and body regions at Day 4 and Day 5 when organogenesis of the pancreas takes place. Interestingly, a polyadenylated insulin transcript was detected, as well, in whole Day 2 and Day 3 embryos (stages 10 to 20, with 20 to 40 somites) before differentiation of beta cells occurs. Thus, there is differential developmental regulation of the insulin gene in several chicken embryo tissues and the expression of insulin precedes pancreatic maturation. These findings support the proposed role of insulin in differentiation and development in vivo and suggest a paracrine type of action of the hormone in early embryos before blood circulation begins.

MRI measurement of hepatocyte toxicity using the new MRI contrast agent manganese dipyridoxal diphosphate, a manganese/pyridoxal 5-phosphate chelate

This study reports the first in vivo results using an MR contrast agent manganese dipyridoxal diphosphate (Mn-DPDP) designed to estimate the functional status of the hepatocyte. Thirty New Zealand white rabbits were studied in groups of 5 as follows: No. 1, control, MRI scans only; No. 2 MRI before and up to 90 min following 50 mumol/kg of Mn-DPDP iv; No. 3, rabbits received 9.3 g ethanol/kg and MRI; No. 4, as in No. 3 but following Mn-DPDP; No. 5, MRI as in No. 2 but 18 h. following 1000 mg/kg D-galactosamine used to induce hepatocyte necrosis; and No. 6, rabbits received D-galactosamine and MN-DPDP. In this study significant ethanol- and D-galactosamine-induced hepatocyte damage was indicated by the increased SGPt serum levels in the rabbit. The use of Mn-DPDP allowed detection of early hepatocyte necrosis in these animals whereas conventional spin-echo MRI did not. The fact that D-galactosamine curves with and without Mn-DPDP were not significantly different indicated virtually no membrane transport or metabolism of Mn-DPDP in the liver. Ethanol curves were not normal, but there was still considerable residual Mn-DPDP metabolism. Mn-DPDP appears to be an attractive agent in assessing hepatocyte function.

Detection of acute radiation damage to the spleen in mice by using fluorine-19 MR imaging

Previous work in our laboratory has shown that an IV-administered emulsion of perfluorooctylbromide, an agent known to localize in functioning macrophages in the reticuloendothelial system, can be detected in the liver and spleen by using fluorine-19 (19F) MR imaging. In mice that have received a single radiation dose of 1300 rad (13 Gy) (250 kVp) to the abdomen, relatively diminished uptake of perfluorooctylbromide emulsion in the spleen is seen as few as 12 days after irradiation when using 19F MR. When a GE NMR CSI 2-T spectroscopy/imaging system was used, 19F MR images were obtained in 2-16 min, and the postirradiation changes in the spleen were shown. This approach is the first that allows detection of acute postirradiation damage in the spleen in as few as 12 days and potentially allows assessment of macrophage dysfunction in vivo.

19F magnetic resonance imaging and spectroscopy of a fluorinated neuroleptic ligand: in vivo and in vitro studies

The bulk biodistribution of a trifluorinated neuroleptic (fluphenazine) was studied using 19F magnetic resonance imaging (MRI). Fifteen male Sprague-Dawley rats were injected with fluphenazine (120 mg/kg) and scanned in a G.E. CSI 2.0 tesla MRI system. The rats were killed following scanning and the brains were removed. The excised brains were then scanned using 1H and 19F MR techniques. The fluorinated neuroleptic was imaged at the injection site, spectroscopically detected in vivo in the head, and spectroscopically localized in the whole brain. These data suggest that in vivo 19F MRI of fluorinated agents is possible and could have clinical and research applications to the neurosciences.

Detection of tumors with 19F magnetic resonance imaging

Previous 19F magnetic resonance imaging studies showed that the reticuloendothelial system can be imaged with an emulsion of perfluorooctyl bromide (PFOB). Similar techniques can be used to detect previously implanted RIF-1 tumors in mice after intravenous PFOB administration. Accumulation of PFOB within these neoplasms is due to egress of the emulsion through tumor capillary fenestrations. This is the first report in which 19F MRI and PFOB are used to detect tumors. This technique may allow clinical detection of cancer with 19F MRI.

19F magnetic resonance imaging of the reticuloendothelial system

In this study sequential 1H and 19F magnetic resonance imaging methods were used to map the distribution of fluorinated compounds in vivo. An intravenously administered emulsion of perfluorooctylbromide (PFOB), an agent known to localize in the reticuloendothelial system, was detected in the liver and spleen of all studied hamsters and mice using 19F MRI. Lungs and salivary glands were also affected in some animals. Using a G. E. NMR CSI 2-T spectroscopy/imaging system, projection 19F images were obtained in 4 to 8 min. Subsequent mouse studies using a thick-slice driven equilibrium pulse sequence produced 19F images with an improved signal-to-noise ratio in a shorter acquisition time. With PFOB, 19F MRI has the capability of detecting macrophages in the reticulo-endothelial system and in other sites where macrophages congregate. This is the first report where the reticuloendothelial system was specifically imaged in live animals and where driven equilibrium imaging techniques have been applied to 19F MRI.

Microsphere distribution in normal and tumor-bearing (DMBA-induced carcinogenesis) hamster cheek pouch

This study evaluates, for the first time by direct visualization, the microvascular distribution of microspheres in normal hamster cheek pouch and in hamster cheek pouch bearing tumor induced by 7, 12 Dimethylbenz (A) Anthracene solution (DMBA). In contrast to the results of the previously used open-chest technique, this carotid injection technique does not lead to irregular distribution of 15-mu carbonized microspheres, chain, or impaction phenomena. It is concluded that methodology differences may account for different results.

The critical importance of convolution function (algorithm) selection in the measurement of blood flow in small blood vessels by computed tomography scanning

In order to assess the capability for measuring blood flow in small vessels, the cardiac output was measured directly by either the microsphere reference sample technique or by obtaining blood samples simultaneously with the CT scan. The cardiac output was also measured in vivo by dynamic CT scanning and intravenous contrast as the indicator in an indicator dilution curve. Cardiac output was then calculated by two convolution back projection algorithms which optimized for either contrast or spatial resolution. The results of this study suggest that CT scanners are capable of accurately averaging intravascular changes in contrast density. Although it is good to optimize contrast resolution, the convolution back projection algorithm selected must have a pixel matrix which is much smaller than the vessel being analyzed.