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D Peck

Publications and source records attributed to D Peck.

At least 37 records · Page 2Linked to original sources
PubMed1993

Differential effects of over-expressed neural cell adhesion molecule isoforms on myoblast fusion.

We have used a transfection based approach to analyze the role of neural cell adhesion molecule (NCAM) in myogenesis at the stage of myoblast fusion to form multinucleate myotubes. Stable cell lines of myogenic C2 cells were isolated that express the transmembrane 140- or 180-kD NCAM isoforms or the glycosylphosphatidylinositol (GPI) linked isoforms of 120 or 125 kD. We found that expression of the 140-kD transmembrane isoform led to a potent enhancement of myoblast fusion. The 125-kD GPI-linked NCAM also enhanced the rate of fusion but less so when a direct comparison of cell surface levels of the 140-kD transmembrane form was carried out. While the 180-kD transmembrane NCAM isoform was effective in promoting C2 cell fusion similar to the 140-kD isoform, the 120-kD isoform did not have an effect on fusion parameters. It is possible that these alterations in cell fusion are associated with cis NCAM interactions in the plane of the membrane. While all of the transfected human NCAMs (the transmembrane 140- and 180-kD isoforms and the 125- and 120-kD GPI isoforms) could be clustered in the plane of the plasma membrane by species-specific antibodies there was a concomitant clustering of the endogenous mouse NCAM protein in all cases except with the 120-kD human isoform. These studies show that different isoforms of NCAM can undergo specific interactions in the plasma membrane which are likely to be important in fusion. While the transmembrane and the 125-kD GPI-anchored NCAMs are capable of enhancing fusion the 120-kD GPI NCAM is not. Thus it is likely that interactions associated with NCAM intracellular domains and also the muscle specific domain (MSD) region in the extracellular domain of the GPI-linked 125-kD NCAM are important. In particular this is the first role ascribed to the O-linked carbohydrate containing MSD region which is specifically expressed in skeletal muscle.

Animals↗
PubMed1991

Temporal evolution of ischemic damage in rat brain measured by proton nuclear magnetic resonance imaging.

We studied the effect of focal cerebral ischemia on the "state" of brain water using proton nuclear magnetic resonance imaging. Focal cerebral ischemia was induced in five halothane-anesthetized rats via tandem occlusion of the left common carotid artery and the left middle cerebral artery. The proton transverse relaxation time, the proton density, and the water diffusion coefficient were measured at various times from the same region of brain tissue from 1.5 to 168 hours after occlusion. Early measurements indicated significant changes in the transverse relaxation time (p = 0.004) and water diffusion coefficient (p = 0.002) of ischemic brain tissue compared with a homologous region from the contralateral hemisphere. However, the transverse relaxation time, proton density, and water diffusion coefficient in ischemic brain tissue showed different temporal evolutions over the study period. Diffusion coefficient weighting was superior to relaxation time and proton density weighting for the visualization of early cerebral ischemia. Our data suggest that nuclear magnetic resonance imaging is sensitive in detecting changes in proton-associated parameters during early cerebral ischemia and confirm significant changes (p less than or equal to 0.01) in the temporal evolution of transverse relaxation times, proton densities, and diffusion coefficients following middle cerebral artery occlusion.

Animals↗
PubMed1990

Enhanced myogenesis in NCAM-transfected mouse myoblasts.

The fusion of mononucleate precursor myoblasts to form the multinucleated skeletal muscle fibre is proceeded by a series of complex cell-cell interactions but the cell-surface molecules involved in these events have not been characterized. During myogenesis in vivo and in vitro, expression of the neural cell adhesion molecule (NCAM) undergoes an isoform transition that precisely correlates with terminal myoblast differentiation and myotube formation. Altered processing of RNA results in the replacement of the transmembrane NCAM (relative molecular mass, 145,000 (145K) in proliferating myoblasts by a predominant 125K NCAM form linked to glycosyl phosphatidylinositol in myotubes. We now report that mouse myoblasts transfected to constitutively express the human muscle-specific 125K glycosylphosphatidylinositol-linked NCAM isoform more readily fuse to form myotubes. This suggests that NCAM plays a part in myoblast fusion and that the isoform switch may promote this function.

Animals↗
PubMed1990

Density of muscle spindle profiles in the intrinsic forelimb muscles of the dog.

The concept of parallel muscle combinations, in which spindle density is significantly higher in small muscles compared to their larger counterparts in large-small muscle combinations acting across a joint, is supported by the results of this study regardless of the joint. Analysis of the canine data as well as previously published guinea pig forelimb and human pelvic limb data revealed no significant difference in spindle density between antigravity and non-antigravity muscles. Furthermore, a gradual increase in spindle density from proximal to distal on the limb was not found, although spindle density was significantly higher in the intrinsic manus or pes muscles compared to more proximal limb muscles in all three species. The significant differences in spindle densities in parallel muscle combinations and in manus/pes versus proximal muscles are discussed relative to their possible role in the control of locomotion.

Animals↗
PubMed1990

Assessment of chronological age of third world children: can a simple tooth count help?

To assess the nutritional status of a child, it is essential to know his chronological age. However, this is often not known accurately by the mothers of children in the Third World. The purpose of this study was an attempt to assess the chronological age of a child by a fairly reliable parameter, i.e. the number of teeth that had erupted, given the fixed pattern of eruption of primary dentition in children. This parameter would have the advantage of being readily assessable by non-trained personnel. One hundred children between the ages of 2 and 44 months, attending a child health clinic in western Kenya, were studied, with measurement of height, weight and number of teeth erupted. By standard statistical analysis, it was investigated whether number of teeth was a more accurate estimation of chronological age than was the child's height. The data indicated that number of teeth is not a useful guide to the age of young children, owing to the variability in dental stage at any given age.

Age Determination by Teeth↗
PubMed1989

Alcohol consumption, cigarette sales and mortality in the United Kingdom: an analysis of the period 1970-1985.

This paper examines official published statistics for various causes of death in the United Kingdom between 1970 and 1985. The variables selected were mainly those that had been linked to alcohol or cigarette use. In particular, changes in mortality due to acute myocardial infarction, cancer of trachea, bronchus and lung, cirrhosis of the liver and 'alcoholism' were found to be associated with each other. Changes in all of these were highly associated with changes in both alcohol consumption and cigarette sales. For most of the causes of death examined, correlations were higher for changes in the current year than they were for lagged data. Thus even chronic disorders related to prolonged heavy alcohol or tobacco use appear to be influenced rapidly by shifts in general levels of drinking and smoking.

Alcohol Drinking↗
PubMed1989

Consistency of reported levels of alcohol-related problems in the community.

Regular drinkers identified in a general population survey of adults in the Lothian region were followed up 3 or 4 years later, with respect to alcohol-related problems. Using a variety of analytic methods, a moderate degree of temporal consistency in problems was found, for total number of problems, and for individual problems, with feeling ashamed of having done something while drunk being the most consistent.

Adult↗
PubMed1987

Algorithms for the segmental motor innervation of the extremities.

The pattern of the segmental motor innervation to the extremities is reflected in the kinematics of their joint linkages. More proximally located joints have more complex movements and are controlled by more spinal cord levels than more distal joints with simpler movements. More proximally located joints are also controlled by more cranially located groups of spinal cord levels while more distal ones are innervated by more caudally located groups. Algorithms are presented that summarize these principles in the form of two simple, concise charts and a stick figure. The cord levels given by the algorithms for the innervation of any particular muscle are in good general agreement with recognized authorities. In addition, these algorithms are easily learned and readily applied to clinical problems by placing the patient in the position assumed when playing the piano or operating an automobile. In this posture, the most cranial two spinal cord levels of a group controlling a joint are responsible for "upward" motion of that joint and the most caudal two or three control "downward" motion thereof.

Algorithms↗
PubMed1986

Are there compartment syndromes in some patients with idiopathic back pain?

Palpable rigidity of the epaxial (paraspinal) muscles, lordotic flattening, and spinal flexion accompanying back pain generally are ascribed to epaxial muscle spasm. However, palpable rigidity without muscle spasm occurs in compartment syndromes and epaxial muscle contractions extend the spine, increasing lordosis. Epaxial compartment syndromes are proposed as a possible cause of palpable rigidity, lordotic flattening, and spinal flexion accompanying idiopathic back pain. This article demonstrates the following: existence of an epaxial compartment by latex and dye injections; simulation of epaxial compartment syndromes in unembalmed cadavers by saline injections; and a "Bourdon tube effect" producing spinal flexion with lordotic flattening during epaxial compartment syndrome simulation in embalmed cadavers. In addition, resting and exercising epaxial compartment pressures were measured in 18 normal volunteers with a slit catheter.

Aged↗
PubMed1986

Comparison of muscle spindle concentrations in large and small human epaxial muscles acting in parallel combinations.

A small short muscle acting across a joint in parallel with vastly larger and longer muscles is clearly unable to play more than a minimal mechanical role in such a "parallel muscle combination" (PMC). This research investigates a feed back role for the small muscles of PMCs, proposing a significantly higher muscle spindle concentration therein to be consistent with this role. Epaxial PMCs (semispinalis and multifidus versus rotatores brevis) from the C5-C6, T6-T7, and L4-L5 regions of three 36-week-old male fetuses and two adult cadavers were removed and fixed in Carnoy's fluid. Tissue samples were embedded in paraffin, cut into 10 microns thick sections perpendicular to the muscle's longitudinal axis and stained by Harris' hematoxylin and eosin. Representative tissue sections were projected onto a sterological grid and the percentage volume of spindles determined. Data were analyzed with Student's unpaired t test. In all PMCs, rotators brevis spindle percentage volumes ranged from 4.58 to 7.30 times higher than those of multifidus and semispinalis. Differences in mean spindle percentage volumes between large and small members of all PMCs were significant (P less than .0001). Our findings are consistent with the notion of a "kinesiological monitor" or feedback role for rotatores brevis.

Adult↗
PubMed1984

Usefulness of mammography in the diagnosis and management of breast disease in postmenopausal women.

We evaluated the clinical usefulness of mammography in postmenopausal women by conducting a "vertical" analysis using indexes of sensitivity and specificity, and a separate "horizontal" analysis assessing the relationship between the mammographic test result and the occurrence of specific clinical management decisions. The patients included 105 women with breast cancer, 104 women with fibrocystic breast disease, and 103 women with clinically benign breasts. Our study confirmed the generally accepted high values reported for the sensitivity and for the specificity of mammography as a test for breast cancer, while also helping to reconcile the widely varying indexes of test efficacy reported in some studies. We also observed that physicians' management decisions vary according to the mammographic interpretation, and include such distinctive clinical strategies as watchful expectancy (observe and follow), repeated mammograms, or breast biopsy. Future studies will need to determine reasons for specific management decisions, especially when they appear to contradict authoritative recommendations.

Breast Neoplasms↗
PubMed1984

A comparison of spindle concentrations in large and small muscles acting in parallel combinations.

A small short muscle frequently acts across a joint in parallel with a vastly larger and longer muscle; therefore it should play a minimal role in the mechanical control of that joint. This study provides evidence suggesting that the small member of such a "parallel muscle combination" (PMC) may serve an important sensory feedback role. The spindle densities of large and small members of PMCs in man and the dog were determined and compared. Epaxial PMCs controlling canine intervertebral joints were dissected and tissue samples were embedded in paraffin, sectioned transversely to the muscles' long axis and, stained with hematoxylin-periodic acid-Schiff (PAS). Representative tissue sections were projected on to stereological grids and the percentage volume of spindles was determined. Data existing in the literature were used to ascertain spindle densities in human PMCs controlling joints in the cervico-occipital region and the extremities. The spindle density for each muscle in a group of PMCs controlling a particular motion was listed, and the mean spindle densities were determined for both the large and the small members of the group. Student's unpaired t test was used to determine the significance of the differences between mean spindle densities. Linear regression was calculated and the data were plotted graphically. In all PMCs examined, the spindle density of the small muscles was significantly higher than that of their large counterparts. It is therefore proposed that the small muscles of PMCs may function as "kinesiological monitors" generating important proprioceptive feedback to the central nervous system.

Animals↗
PubMed1984

Mammographic parenchymal patterns and risk of breast cancer in postmenopausal women.

A case-control study was conducted to assess whether certain "high-risk" mammographic parenchymal patterns are associated with the increased occurrence of breast cancer in postmenopausal women. Patients in the case group included 105 women with histologically confirmed breast cancer; subjects in the control group included 104 women with fibrocystic breast disease and 103 women with clinically normal breasts. All mammographic results were evaluated "blindly" by a radiologist who classified the breast parenchyma into "high-risk" and "low-risk" categories according to the criteria proposed by Wolfe. These data showed a similar proportion of allegedly "high-risk" breast parenchymal patterns among patients in all three groups. The finding that breast parenchymal patterns are not associated with an increased risk of breast cancer in women 50 years of age or older is consistent with the results of earlier studies in which the association is present only in younger, premenopausal women, and is absent in older, predominantly postmenopausal women. Consequently, it is concluded that these parenchymal patterns should not be used to select postmenopausal women for breast cancer screening programs, or to guide the evaluation of postmenopausal women with breast lumps or symptoms.

Breast Neoplasms↗
PubMed1983

The microbiology of childhood gastroenteritis: Aeromonas species and other infective agents.

A prospective, 12-month study of 975 non-Aboriginal children with diarrhea and age- and sex-matched children without diarrhea, in Perth, Western Australia, was designed to investigate the significance of enterotoxigenic Aeromonas species as a cause of diarrhea. Enterotoxigenic Aeromonas species were found in the fecal specimens of 10.8% of the patients with diarrhea but in only 0.7% of those without diarrhea. Most Aeromonas species were isolated during the summer. Other important bacterial pathogens included Campylobacter, Salmonella, Shigella, and enterotoxigenic Escherichia coli; rotavirus infections appeared to be much less important in the Western Australian environment. Most of the patients were younger than two years of age and about one-quarter had mixed bacterial and/or viral intestinal infections. Enterotoxigenic Aeromonas species can be identified with 97% accuracy using a simple hemolysin assay which should be considered for use by routine diagnostic laboratories, particularly in children's hospitals.

Aeromonas↗
PubMed1983

Compartment syndromes. Early diagnosis and a bedside operation.

Delays in diagnosis and treatment of compartment syndromes of the lower extremities result in significant morbidity and mortality. Knowledge of the anatomy of the lower leg compartments provides clues to earlier diagnosis as to the specific compartments involved in these syndromes. A simple physical examination is described that focuses on this. Furthermore, a simple "bedside" operation is described that provides excellent decompression of all of these compartments without fibulectomy.

Adult↗