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M Fallon

Publications and source records attributed to M Fallon.

At least 91 records · Page 5Linked to original sources
PubMed1988

2-Amino-4-phosphonobutyric acid receptors are not involved in synaptic transmission from hair cells to auditory neurons.

The chemical 2-amino-4-phosphonobutyric acid (APB, AP4), an excitatory amino acid antagonist, was perfused through the guinea-pig cochlea while monitoring various cochlear potentials. The drug (0.6-10 mM) had no effect on the magnitude of the compound action potential of the cochlear nerve, N1 latency, cochlear microphonics, or the summating potential (SP). The results are consistent with the hypothesis that the APB receptor is not involved in neurotransmission between cochlear hair cells and afferent nerve fibers.

Action Potentials↗
PubMed1988

Hyaline cartilage-origin bone and soft-tissue neoplasms: MR appearance and histologic correlation.

Magnetic resonance (MR) images and histologic studies of 16 chondroid-matrix lesions were reviewed to determine if any distinctive morphologic or signal features might be discerned. Ten biopsy-proved nonchondroid bone lesions were compared in terms of configuration and signal characteristics. The tumor matrix had a distinctive appearance of homogeneous high signal intensity in a defined lobular configuration on images of all hyaline cartilage lesions obtained with a long repetition time and a long echo time. The areas of hyperintensity relative to muscle corresponded to areas of hyaline cartilage matrix with its uniform composition, low cellularity, and high water content; the lobular morphologic characteristic had an identical histologic correlate. The chondroblastomas, clear-cell chondrosarcoma, and synovial chondromatosis demonstrated a much more cellular stroma, with only scattered islands of chondroid matrix, and were isointense or hypointense compared with muscle on all MR sequences. The distinctive lobular, high-intensity MR appearance was not seen in the ten nonchondroid bone lesions.

Adolescent↗
PubMed1988

Bone mineral metabolism in experimental diabetes mellitus: osteocalcin as a measure of bone remodeling.

The etiology of diabetic osteopenia has not been established. The value of serum osteocalcin (BGP) as a marker of the bone abnormalities and the possible role of the polyol pathway in diabetic osteopenia were investigated. Three groups of rats were studied over 7 weeks: group D (n = 12), rats with streptozotocin (55 mg/kg)-induced diabetes given saline by gavage; group DS (n = 12), rats with streptozotocin-induced diabetes given the aldose reductase inhibitor sorbinil (25 mg/kg) daily by gavage; and group C (n = 6), saline-injected controls. Circulating levels of ionized calcium, BGP, amino-terminal PTH, and glucose were measured on days 0, 7, 14, 28, and 49. Tibial bone specimens were examined for the presence of aldose reductase by immunocytochemistry and by histomorphometry after tetracycline labeling. Diabetic rats with or without sorbinil treatment failed to gain weight [group D, 234 +/- 26 g; group DS, 217.0 +/- 40 g; group C, 310 +/- 33 g (mean +/- SD)]. Serum BGP levels decreased significantly in the diabetic rats within 7 days and remained lower throughout the study. BGP values on day 7 were: group D, 47.7 +/- 4.9 ng/ml; group DS, 65.9 +/- 5.5 ng/ml; and group C, 90.4 +/- 4 ng/ml (mean +/- SEM). Serum PTH levels were similar in all groups, except for day 49, when an increase in the D group was observed. Bone histomorphometry showed decreased bone remodeling in the D group, which confirmed the serum BGP findings. Aldose reductase was detectable in the small blood vessels and in bone itself. Sorbinil failed to influence the biochemical or bone histomorphometric abnormalities associated with diabetes. Serum BGP may be a valuable marker for the decreased bone remodeling in insulinopenic diabetes.

Aldehyde Reductase↗
PubMed1988

Cyclosporin-A in vivo produces severe osteopenia in the rat: effect of dose and duration of administration.

Cyclosporin-A (CsA) inhibits the in vitro bone-resorbing effects of cytokines. We investigated the in vivo effects of CsA on rat bone mineral metabolism. Three groups of male Sprague-Dawley rats were administered vehicle or low dose (7.5 mg/kg) or high dose (15 mg/kg) CsA for 14 and 28 days. Ionized calcium, PTH, serum bone Gla protein, blood urea nitrogen, creatinine, magnesium, and 1,25-dihydroxyvitamin D were determined serially. No significant changes in calciotropic hormones or renal function were noted. Significant bone resorption and trabecular bone loss occurred in the high dose group by day 14 and in both groups by day 28. Bone Gla protein was significantly increased within 2 weeks in both dosage groups (P less than 0.005), reflecting increased bone remodeling. CsA in vivo resulted in an unexpected and significant increase in bone remodeling, with striking bone loss. These effects are dependent on the duration and dose of CsA and appear to be mediated at a local level.

Animals↗
PubMed1988

The musculoskeletal manifestations of progeria. A literature review.

Although a superficial similarity exists between the musculoskeletal disorders associated with natural aging and those of progeria, an in-depth analysis reveals profound differences in the pathophysiology between the two processes. The protean manifestations of progeria can best be explained on the basis of the vascular changes found at autopsy. A disorder of the vascular endothelium may predispose progeric vessels to atherosclerotic changes. The unique musculoskeletal manifestations of progeria arise from the effects of premature atherosclerosis on the vascularized connective tissues.

Bone and Bones↗
PubMed1988

Alterations in helper-inducer and suppressor-inducer T-cell subsets in human neonatal blood.

The distribution of T-helper cell subsets of human umbilical cord lymphocytes was compared with that of adult peripheral blood lymphocytes. Cytofluorometric analysis revealed a similar Leu 3/Leu 2 (helper/suppressor) ratio in neonates compared with adults. Total T-cell numbers were slightly decreased in neonatal blood. The Leu 3-positive-4B4-positive cell (helper-inducer) subset, however, was markedly reduced in neonatal blood, while the Leu 3-positive-2H4-positive cell (suppressor-inducer) subset was increased compared with that of normal adults. These findings may contribute to the poor help and enhanced suppression observed in vitro with neonatal T cells.

Fetal Blood↗
PubMed1987

Femoral head avascular necrosis: correlation of MR imaging, radiographic staging, radionuclide imaging, and clinical findings.

To better correlate the appearance of avascular necrosis (AVN) of the femoral head on magnetic resonance (MR) images with the stage of disease, MR images of 56 proved AVN lesions were compared with staging from corresponding radiographs (n = 56), Tc-99m scans (n = 41), and grade of symptoms (n = 28). Fractures complicating AVN were seen in 28 (50%) of 56 radiographs (radiographic stages III-V). With long repetition (TR) and echo delay (TE) times, a characteristic "double line sign" consisting of high signal intensity inside a low-intensity peripheral rim was seen in 45 lesions (80%). The central region within the rim was isointense with marrow fat on both short and long TR and TE images in 20 (71%) of 28 lesions uncomplicated by fracture (stages I-II) but in only four (14%) of 28 stage III-V lesions (P less than .001). Symptoms were least severe in lesions isointense with fat and most severe in lesions with low-signal central regions at short and long TRs and TEs. The peripheral double line sign on long TR/TE images may add specificity to the diagnosis of AVN by MR imaging. A chronologic pattern of central MR signal features is presented which may allow staging of AVN by MR imaging.

Female↗
PubMed1987

Chemical-shift MR imaging of the femoral head: an in vitro study of normal hips and hips with avascular necrosis.

To study the conventional and chemical-shift MR images of fatty, hemopoietic, and ischemic bone marrow, four normal femurs from autopsies and six femoral heads from total hip replacement done for avascular necrosis (AVN) were imaged with a small-bore 1.4-T MR unit. T1- and T2-weighted spin-echo images, fat- and water-selective spin-echo images, and out-of-phase images were obtained. The specimens were then sectioned, radiographed, and studied histologically. The capital epiphysis and greater trochanter in normal femurs had the highest signal on T1-weighted, fat-selective, and out-of-phase images owing to their high fat content. Fat-selective and water-selective images accurately depicted regions of fat and water, whereas T1-weighted, T2-weighted, and out-of-phase images were misleading in some cases. On T2-weighted images, a double line consisting of a rim of low signal with a high-signal inner border was noted surrounding AVN lesions. Histologic correlation showed that the low-signal outer rim was due to sclerotic bone, while the high-intensity inner border was due to granulation tissue and/or chondroid metaplasia. Fractures within the six AVN lesions were best seen on T2-weighted images, but these could not be distinguished from granulation tissue. On T2-weighted images, the weight-bearing cartilage had lower signal in five of six femoral heads with AVN. We conclude that the MR appearance of AVN reflects its complex histopathology. Direct spin-echo chemical-shift imaging can help correlate MR images with histology by providing information not available from conventional or out-of-phase images.

Adult↗
PubMed1986

Magnetic resonance imaging of avascular necrosis of the femoral head.

This study investigates the role of magnetic resonance imaging (MR) in identifying avascular necrosis (AVN) of the femoral head and in monitoring its therapy. The detection of AVN, particularly in its early stages, is imperative to give therapeutic intervention the best opportunity for successful management. The results of magnetic resonance imaging are compared with those of the standard diagnostic modalities in evaluation of patients with the lesion. Examinations were performed at 0.12T with a repetition time (TR) of 143 ms and times to echo (TE's) of 10 or 20 ms. This study represents a retrospective review of 90 hips which were examined in 45 consecutive patients. Of these, 52 hips were biopsied as part of treatment. MR was shown to be sensitive in the detection of AVN. Comparison of MR with radionuclide imaging showed comparable sensitivity and specificity. MR was also noted to be sensitive in the detection of early AVN. Preliminary results suggest that MR can monitor treatment of the affected hip, and may even be able to predict patient response to therapy. Although further work is necessary to determine the role of MR in the evaluation of the patient presenting with hip pain, MR is a sensitive method in detecting AVN and in monitoring its course in patients suspected of having the disease.

Adult↗
PubMed1986

In vivo and in vitro effects of WR-2721 in experimental hypercalcemia in the rat.

The effects of WR-2721 [S-2-(3-aminopropylaminoethyl)phosphorothioic acid] in two in vivo and in vitro models of experimental hypercalcemia in the rat were examined. Chronic WR-2721 administration by osmotic minipump (250 mg/kg/24 hr) reduced serum calcium from 12.0 +/- 0.1 to 9.5 +/- 1.0 mg/dl (P less than .01) in rats receiving 1,25-(OH)2 Vitamin D3. Control rats receiving Vitamin D without WR-2721 had a rise in serum calcium to 13.4 +/- 0.2 mg/dl over the same 5-day period. In an experimental form of humoral hypercalcemia of malignancy, the Walker carcinosarcoma tumor-implanted rat, WR-2721 reduced serum calcium from 13.6 +/- 0.3 to 8.4 +/- 0.6 mg/dl by 5 to 6 days (P less than .001). In vitro bone resorption assays utilizing fetal rat long bones in organ culture showed complementary results. WR-2721 (10(-4) M) blocked bone resorption (assayed as percentage of 45Ca release) induced by both conditioned medium derived from cell lines of Walker carcinosarcoma (7.6 +/- 1.4 vs. 24.0 +/- 1.8%, P less than .01) and by addition of 1,25-(OH)2 Vitamin D3 (10(-8) M) (9.8 +/- 0.8 vs. 17.3 +/- 1.0%, P less than .01). These results suggest that WR-2721 may be effective in controlling clinical hypercalcemia due to excess bone resorption.

Amifostine↗
PubMed1986

Immobilization hypercalcemia associated with Landry-Guillain-Barré syndrome. Successful therapy with combined calcitonin and etidronate.

Two patients with immobilization hypercalcemia associated with Landry-Guillain-Barré syndrome had marked hypercalciuria (890 and 1136 mg/d [22.2 and 28.3 mmol/d]) and radiologic evidence of generalized osteopenia. Parathyroid hormone levels were either low or normal by C-terminal radioimmunoassay. Subtotal parathyroidectomy was performed in the one patient, with no improvement in serum or urinary calcium levels. A bone biopsy specimen revealed decreased cellular activity in the first patient and increased bone resorption in the second patient. Treatment with intravenous saline, furosemide, oral phosphate supplementation, mithramycin, and calcitonin alone was ineffective in lowering serum or urinary calcium levels. However, when subcutaneous calcitonin combined with oral etidronate disodium was used, a reduction in the serum calcium level was observed within two days of therapy. Within one week of the start of this combined therapy, the calcium level returned to normal and urinary calcium excretion was substantially reduced.

Adult↗
PubMed1986

Osteoporosis and hip fracture in a young woman with anorexia nervosa.

A 35-year-old woman with a 17-year history of anorexia nervosa (AN) sustained a pathologic fracture of the hip. Osteoporosis was confirmed by quantitative computed tomography of the lumbar spine and transiliac bone biopsy. Severe bone disease may exist in the anorexia nervosa syndrome and may to some extent be reversible on treatment of the underlying condition. AN could have profound effects on the peak bone mass achieved in the lifetime of the individual. Asymptomatic and symptomatic osteoporosis in young women may be based upon AN. Patients should be informed that osteoporosis can cause pathologic fractures as a sequela of self-imposed chronic malnutrition.

Adult↗
PubMed1983

The frequency of apnea and bradycardia in a population of healthy, normal infants.

Twenty-four hour continuous pneumocardiogram recordings were obtained on 250 healthy, normal infants in a hospital nursery on the first to third days of life. 73% of the infants showed no apneic episodes greater than 15 seconds in duration. 5% demonstrated longest apneic episodes greater than 20 seconds in duration with a range up to 32 seconds. 4% showed episodes of periodic breathing and 32% showed bradycardia of less than 80 beats per minute. Subsequent follow-up did not reveal any cases of near miss-SIDS or SIDS. Sustained apnea and periodic breathing appear to be infrequent respiratory patterns in term infants.

Apnea↗
PubMed1982

Formation of bone by isolated, cultured osteoblasts in millipore diffusion chambers.

Osteoblast-like and osteoclast-like cells freed from neonatal calvaria by sequential enzymatic digestion after 6-7 days in culture were placed in diffusion chambers and implanted in the peritoneal cavities of CD-1 mice. About half of the chambers also contained a dead calvarium to test for the need of an "inducer." After 20 days, 11 of 18 chambers containing to osteoblast-like cells formed large foci of mineralized bone that corresponded to alkaline phosphatase activity throughout the chambers. Moreover, only type I (i.e., bone) collagen was formed. Occasional deposits of bone were found in only 3 of 22 chambers containing the osteoclast-like cells. The presence of dead bone did not affect any of the results. These data confirm the osteoblast-like nature of the isolated cell populations and demonstrate that these cells retain their differentiated function in culture.

Animals↗