Biomedical subjects

M Daood

Publications and source records attributed to M Daood.

10 recordsLinked to original sources

PubMed2000

Developmental myosin heavy chains in the adult human diaphragm: coexpression patterns and effect of COPD.

In preliminary experiments we noted developmental (i.e., embryonic and neonatal) myosin heavy chains (MHCs) in the diaphragms of patients with severe chronic obstructive pulmonary disease (COPD). We hypothesized that this finding represented new fiber formation secondary to injury associated with the mechanical stress of COPD or previously undescribed MHCs in the human diaphragm. To distinguish between these possibilities, we analyzed diaphragmatic biopsies obtained from 9 patients with severe COPD (forced expiratory volume in 1 s = 21 +/- 2% predicted, residual volume = 283 +/- 22% predicted) and 10 age-matched controls. First, using immunocytochemistry with specific monoclonal antibodies, we noted that control diaphragms had greater proportions of fibers expressing embryonic (50 +/- 2 vs. 28 +/- 3%, P < 0.0001) and neonatal (52 +/- 2 vs. 32 +/- 3%, P < 0.001) MHCs than COPD diaphragms. Second, SDS-PAGE demonstrated that these developmental MHCs represented only a very small fraction of the diaphragmatic MHC content. Third, the RT-PCR demonstrated mRNA coding for embryonic and neonatal MHCs in COPD and control diaphragms. Last, COPD and control diaphragms exhibited normal histology on light microscopy. We conclude that the presence of developmental MHC isoforms does not indicate new fiber formation in diaphragms of patients with severe COPD. Although these results represent the first systematic description of embryonic and neonatal MHCs in normal adult human diaphragms, their function remains to be elucidated.

Adult↗

PubMed1998

Alteration in myosatellite cell commitment with muscle maturation.

Myosatellite cells are myoblasts found between the basal lamina and sarcolemma of myofibers of postnatal mice. The extent to which these cells are programmed, upon differentiation, to express isoforms of contractile protein genes specific to the type of fiber with which they are associated has been evaluated in vitro using myosatellite cells derived from the soleus and the extensor digitorum longus muscles (EDL) of 4-day-old and adult transgenic mice, which express nuclear localizing beta-galactosidase (nlsbeta-gal) under the control of the promoter and 3' enhancer of the gene encoding fast myosin light chain 3F (MLC3F) (Kelly et al. [1995] J. Cell Biol. 129:383-396). Cultures were allowed to differentiate either as myocytes (mononucleated cells), to prevent possible modification of the myosatellite phenotype by other myonuclei in mosaic myotubes, or as myotubes. Transgene expression was age related, with 90% and 70% of the myocytes derived from the neonatal EDL and soleus muscles (muscles that had not yet achieved their mature phenotype), respectively, having nuclei encoding beta-gal; 61% and 32% of the myocyte nuclei derived from myosatellite cells of the adult EDL (a fast muscle) and the adult soleus muscle (a mixed muscle containing many slow myofibers), respectively, expressed this transgene. Because myosatellite cells found in adult muscles are the progeny of those found in the neonate, an alteration of myosatellite cell commitment to express this transgene occurs with muscle maturation. Because expression of the transgene in neonatal and adult muscle in vivo reflects the expression of the endogenous MLC3F gene (Kelly et al. [1995] J. Cell Biol. 129:383-396), it is likely that expression of the transgene by differentiated myosatellite cells reflects the extent of commitment of these cells to produce MLC3F. A hypothesis is presented that MLC3F is widely expressed in developing muscles but eliminated in myofibers that undergo maturation toward a slower phenotype.

Animals↗

PubMed1996

Developmental transitions in the myosin heavy chain phenotype of human respiratory muscle.

We studied the expression of myosin heavy chain (MHC) isoforms in the costal diaphragm (DIA) and the genioglossus (GG) muscles from 16 to 42 weeks gestation in the human using Western blotting techniques. Embryonic/neonatal MHC (MHCemb/neo) was the predominant isoform expressed in the DIA and GG at 16-24 weeks gestation. Subsequently, MHCemb/neo expression declined and the expression of MHCslow and MHC2A increased. At term, the DIA MHC phenotype was a composite of MHCemb/neo (15% of the total MHC complement), MHCslow (32%), MHC2A (47%), and MHC2B (6%); whereas, the GG was largely comprised of MHC2A (74%). We conclude that human DIA and GG demonstrate temporally dependent changes in MHC expression during gestation- and muscle-specific MHC phenotypes as they approach term.

Diaphragm↗

PubMed1993

Regional distribution of myosin heavy chain isoforms in rib cage muscles as a function of postnatal development.

We studied the expression of myosin heavy chain (MHC) isoforms, utilizing electrophoretic methods, in rib cage (RC) muscles: the scalenus medius, the parasternal, cephalic, midthoracic, and caudal intercostal muscles; and in the diaphragm (DI) of rats during postnatal development and when mature. At day 1, all RC muscles and the DI expressed MHC neonatal/embryonic (69-92% of total MHC complement) with little MHC slow and 2A; the RC muscles alone expressed a small proportion of MHC 2B (2-4%). On day 4, MHC neonatal/embryonic expression still predominated (55-71%) but increased MHC 2A expression was observed in both the RC (11-21%) and DI (31%); MHC 2B (5-7%) was noted in the RC muscles but not the DI. By day 14, MHC neonatal/embryonic and 2A expression each comprised a third of the total MHC complement of the RC muscles, MHC 2X was first observed, and MHC 2B expression increased. The day 14 DI was comprised of equal proportions of MHC neonatal/embryonic, slow and 2A with little MHC 2X (11%). The adult and day 30 animals expressed comparable muscle-specific MHC phenotypes: the DI characterized by a proportional mixture of MHC slow, MHC 2A, and MHC 2X, with little MHC 2B, whereas the RC muscles expressed predominantly MHC 2B (40-62%). We conclude that the RC muscles and DI show comparable MHC phenotypes in the immediate newborn period but differ in their MHC expression during postnatal development and when mature. The RC muscles show only minor intermuscle variations in MHC phenotype during development, and when mature are characterized by fast MHC isoform expression, particularly MHC 2B.

Aging↗

PubMed1990

Effects of continuous low-frequency pacing on immature canine diaphragm.

Although diaphragm pacing has been shown to be a practical method of supporting ventilation in children, its usefulness has been limited because of concern that continuous (24 h/day) diaphragm pacing would fatigue and damage the diaphragm. We examined the functional and structural effects of continuous low-frequency diaphragm pacing on the left hemidiaphragm of five immature dogs aged 65 +/- 2 (SD) days at onset of pacing. Stimulus parameters approximated those required to pace infants: frequency 11.1 Hz, inspiratory time 810 ms, and respiratory rate 20 breaths/min. Animals were paced 24 h/day for 24-28 days. Paced tidal volumes and airway occlusion pressures were unchanged at low (less than 15 Hz) stimulus frequencies but were reduced at high (greater than 20 Hz) stimulus frequencies. Although histologically the paced hemidiaphragms appeared normal, histochemical studies showed a conversion from a mixture of type I (54%) and type II (46%) fibers to a uniform population of type I fibers with high oxidative enzyme activity. Transformation of muscle type was also demonstrated by pyrophosphate gel electrophoresis; fast and slow isomyosin bands were noted in control specimens, whereas only slow isomyosin was identified in paced specimens. Thus, in immature dogs, continuous low-frequency pacing affects both function and structure of the diaphragm.

Action Potentials↗

PubMed1985

Development of heart cells in culture: studies using an affinity purified antibody to a myosin light chain.

Cultured neonatal rat heart cells can be used to study the factors that regulate cardiac contractility and myocyte development in vitro. An antibody to the 26,000 dalton light chain of myosin (MLC1), has been produced and purified on a Sepharose 4B affinity column prepared with rat heart myosin. When primary cultures of myocytes are studied by indirect immunofluorescence using this antibody a predictable pattern of myofibrillar structure is observed to develop over 72 h. This myosin cytoskeleton is highly organized and the myosin fibrils exhibit cross striations. The antibody does not stain non-muscle heart cells and there is no evidence for myocyte division in culture. The qualitative immunofluorescent pattern of myosin organization is the same in both spontaneously beating and in non-contracting cells.

Animals↗

PubMed1985

Regulation of the growth of nonmuscle heart cells in culture.

Primary cultures of neonatal rat hearts contain both striated muscle (myocytes) as well as nonmuscle heart cells (NMHC). Although myocytes do not divide in culture, NMHC do increase in number. The growth of NMHC is dependent on the concentration of serum in the media over a range of 1 to 10%. When compared to growth in 10%, cells in 1% serum have a prolonged doubling time and reach a maximum density that is 70% less. Thus, 1% serum which supports normal myocyte development is a useful culture media to also maintain muscle heart cell homogeneity by its failure to support optimum NMHC division.

Adenosine Triphosphatases↗

PubMed1985

Measurement of myosin adenosinetriphosphatase and myosin content in cultured heart cells.

An assay specific for myosin ATPase in whole-cell extracts of cultured heart cells has been developed. Myosin ATPase is measured by the production of Pi from ATP in the presence of high ionic strength (0.5 M KCl) at pH 9.1. Enzyme activity is maximal with 10 mM CaCl2 and completely inhibited with 5 mM MgCl2. Spontaneously beating myocytes grown in the presence of 10% newborn calf serum and 0.1 mM 5-bromo-2'-deoxyuridine show a significant rise in myosin ATPase between Days 1 and 4 in culture. The measurement of myosin ATPase allows for the quantitation of cellular myosin content, and can be used to assess changes in myosin content that occur during growth, development, and cellular repair.

Adenosine Triphosphatases↗

PubMed1985

Contraction regulates myosin synthesis and myosin content of cultured heart cells.

Cultured neonatal rat heart cells are a useful model for studying the regulation of myocyte growth. The myosin content of heart cells increases between days 1 and 4 in culture. To determine if contraction per se can regulate myocyte growth, myosin content and protein synthesis were compared in spontaneously contracting and noncontracting cultured heart cells. Myosin content, assayed as the total myosin ATPase activity per culture dish, was significantly increased in contracting cells after 3, 4, and 5 days in culture. Protein synthesis was measured by incorporation of [14C]lysine into total cell protein and into sodium dodecyl sulfate-polyacrylamide gel electrophoresis resolved myosin. Contraction stimulated both total cell protein content and protein synthesis by day 3 in culture. Compared with heart cells arrested with 50 mM KCl, myosin synthesis was significantly increased by 96, 112, and 46% at days 2, 3, and 4, respectively. Similar results were observed when myosin content and protein synthesis in contracting myocytes were compared with cells arrested with either 25 mM KCl or 10(-5) M verapamil. The present studies suggest that contraction increases the myosin content in cultured heart cells and that this increase is mediated via a stimulation of myosin synthesis in association with cell growth.

Adenosine Triphosphatases↗

PubMed1974

Double-blind comparison of cephacetrile with cephalothin-cephaloridine.

Under double-blind protocol, a controlled comparison was made between a new cephalosporin, cephacetrile, and cephalothin or cephaloridine. The patient's primary physician determined the indications for treatment, and the dosage was uniform for each route of administration. Infecting strains of staphylococci and Proteus mirabilis had a lower median inhibitory concentration for cephalothin than cephacetrile; the opposite was true for Escherichia coli and Klebsiella species. The average peak serum level 1 h after a dose of 2 g intravenously was 74.9 +/- 21 and 21.5 +/- 8.7 mug/ml for cephacetrile and cephalothin, respectively; 6 h after the dose, the respective levels were 12.4 +/- 4.3 and 3.7 +/- 0.9 mug/ml. Renal clearances were similar and the plasma clearance was proportional to the serum levels. In the urine, the concentration of cephacetrile was three times higher than that of cephalothin. Based on a percentage of therapeutic potential, success in the treatment of infections with susceptible organisms was 42 and 44% for the two different drug regimens. Initial bacterial resistance was found in about one-fifth of infections, and concomitant therapy with other drugs was practiced in one-half of the treatment courses. Intravenous use of cephacetrile was discontinued prematurely more often than was use of cephalothin, suggesting less tolerance. Although there was no overt toxicity, more than 75% of patients on either regimen had some form of unwanted response to treatment, the most common being superinfection. From this limited but controlled experience, cephacetrile can be considered comparable to cephalothin in antimicrobial treatment and overall side reactions.

Acetamides↗