Intravenous immunoglobulin is safe and effective in controlling pre-existing paraneoplastic neuromuscular diseases in cancer patients treated with immune checkpoint inhibitors: two case reports and literature review

Immune checkpoint inhibitors cause rare but potentially fatal neuromuscular complications, leading to a concern to use these agents in cancer patients with pre-existing autoimmune or inflammatory neuromuscular diseases. We report two such patients with paraneoplastic dermatomyositis and "seronegative" paraneoplastic demyelinating neuropathy, respectively, who have been successfully treated with immune checkpoint inhibitor monotherapy as well as maintenance intravenous immunoglobulin. While controlling the paraneoplastic or autoimmune neuromuscular diseases, the use of intravenous immunoglobulin did not compromise the anti-cancer effect of immune checkpoint inhibitor.

Hospitalized cancer patients with comorbidities and low lymphocyte counts had poor clinical outcomes to immune checkpoint inhibitors

Background

Immune checkpoint inhibitor (ICI) therapy has improved survivals with a favorable toxicity profile in a variety of cancer patients. We hypothesized that hospitalized cancer patients who have acute or chronic comorbidities may have suppressed immune systems and poor clinical outcomes to ICIs. The objective of this study was to explore clinical outcomes and predictive factors of hospitalized cancer patients who received ICI therapy at an NCI-designated Comprehensive Cancer Center.

Methods

A retrospective review of electronic medical records was conducted for adult cancer patients who received an FDA-approved ICI during admission from 08/2016 to 01/2022. For each patient we extracted demographics, cancer histology, comorbidities, reasons for hospitalization, ICI administered, time from treatment to discharge, time from treatment to progression or death, and complete blood counts. Progression-free survival (PFS) and overall survival (OS) were estimated using the Kaplan-Meier method and compared using the log-rank test. The 95% confidence interval for survival was calculated using the exact binomial distribution. Statistical significance was defined as 2-sided p<0.05.

Results

Of 37 patients identified, 2 were excluded due to lack of complete blood counts on admission. Average hospital stay was 24.2 (95% CI 16.5, 31.9) days. Ten (27.0%) patients died during the same hospitalization as treatment. Of those who followed up, 22 (59.5%) died within 90 days of inpatient therapy. The median PFS was 0.86 (95% CI 0.43, 1.74) months and median OS was 1.55 (95% CI 0.76, 3.72) months. Patients with ≥3 comorbidities had poorer PFS (2.4 vs. 0.4 months; p=0.0029) and OS (5.5 vs. 0.6 months; p=0.0006). Pre-treatment absolute lymphocyte counts (ALC) <600 cells/µL were associated with poor PFS (0.33 vs. 1.35 months; p=0.0053) and poor OS (0.33 vs. 2.34 months; p=0.0236). Pre-treatment derived neutrophil to lymphocyte ratio (dNLR) <4 was associated with good median PFS (1.6 vs. 0.4 months; p=0.0157) and OS (2.8 vs. 0.9 months; p=0.0375).

Conclusions

Administration of ICI therapy was associated with poor clinical outcomes and high rates of both inpatient mortality and 90-day mortality after inpatient ICI therapy. The presence of ≥3 comorbidities, ALC <600/μL, or dNLR >4 in hospitalized patients was associated with poor survival outcomes.

beta-adrenergic receptor population is up-regulated by increased cyclic adenosine monophosphate concentration in chicken skeletal muscle cells in culture

Skeletal muscle hypertrophy is promoted in vivo by administration of beta-adrenergic receptor (betaAR) agonists. Chicken skeletal muscle cells were treated with 1 microM isoproterenol, a strong betaAR agonist, between days 7 and 10 in culture. betaAR population increased by approximately 40% during this treatment; however, the ability of the cells to synthesize cyclic adenosine monophosphate (cAMP) was diminished by twofold. Neither the basal concentration of cAMP nor the quantity of myosin heavy chain (MHC) was affected by the 3-d exposure to isoproterenol. To understand further the relationship between intracellular cAMP levels, betaAR population, and muscle protein accumulation, intracellular cAMP levels were artificially elevated by treatment with 0-10 betaM forskolin for 3 d. The basal concentration of cAMP in forskolin-treated cells increased up to sevenfold in a dose-dependent manner. Increasing concentrations of forskolin also led to an increase in betaAR population, with a maximum increase of approximately 40-60% at 10 microM forskolin. A maximum increase of 40-50% in the quantity of MHC was observed at 0.2 microM forskolin, but higher concentrations of forskolin reduced the quantity of MHC back to control levels. At 0.2 microM forskolin, intracellular levels of cAMP were higher by approximately 35%, and the betaAR population was higher by approximately 30%. Neither the number of muscle nuclei fused into myotubes nor the percentage of nuclei in myotubes was affected by forskolin at any of the concentrations studied.

Effect of electrical stimulation on beta-adrenergic receptor population and cyclic amp production in chicken and rat skeletal muscle cell cultures

Expression of the beta-adrenergic receptor (betaAR) and its coupling to cyclic AMP (cAMP) synthesis are important components of the signaling system that controls muscle atrophy and hypertrophy, and the goal of this study was to determine if electrical stimulation in a pattern simulating slow muscle contraction would alter the betaAR response in primary cultures of avian and mammalian skeletal muscle cells. Specifically, chicken skeletal muscle cells and rat skeletal muscle cells that had been grown for 7 d in culture were subjected to electrical stimulation for an additional 2 d at a pulse frequency of 0.5 pulses/sec and a pulse duration of 200 msec. In chicken skeletal muscle cells, the betaAR population was not significantly affected by electrical stimulation; however, the ability of these cells to synthesize cyclic AMP was reduced by approximately one-half. In contrast, the betaAR population in rat muscle cells was increased slightly but not significantly by electrical stimulation, and the ability of these cells to synthesize cyclic AMP was increased by almost twofold. The basal levels of intracellular cyclic AMP in neither rat muscle cells nor chicken muscle cells were affected by electrical stimulation.

Beta-adrenergic receptor gene expression in bovine skeletal muscle cells in culture

Beta-adrenergic receptors (betaAR) are abundant in fetal, neonatal, and adult skeletal muscles of cattle; however, only minimal levels of functional betaAR were detected in multinucleated muscle cell cultures prepared from 90- to 150-d fetal bovine skeletal muscle. Two other lines of evidence were consistent with low levels of betaAR expression in bovine muscle cultures. First, treating the cells with 10(-6)M isoproterenol for up to 20 min did not increase intracellular cAMP concentration. Second, neither the quantity of myosin heavy chain (MHC) nor its apparent synthesis rate were changed by treating the cells for 4 d with 10(-7) or 10(-6) M isoproterenol. Despite these results, the mRNA for the beta2AR could be detected in muscle cultures by PCR and on slot blots. Thus, the beta2AR mRNA was expressed, but significant levels of functional receptors could not be detected. Glucocorticoids are known to activate expression of OAR genes in several tissues, and the effect of dexamethasone on OAR gene expression in bovine multinucleated muscle cell cultures was evaluated. The intracellular concentration of cAMP following treatment with isoproterenol was elevated 10-fold by dexamethasone, and the population of functional receptors was elevated by approximately 50%. The effect of dexamethasone on muscle protein synthesis and accumulation was analyzed after pretreating the cells with dexamethasone for 24 h, followed by treatment with dexamethasone and 10(-6)M isoproterenol for an additional 48 h. The quantity of MHC synthesized and the apparent synthesis rate of MHC were stimulated by 10 to 35%. These effects seem to be due to posttranscriptional events, because the quantity of beta2AR receptor mRNA on slot blots was not increased by treatment with dexamethasone. Results of this study emphasize the importance of verifying that muscle cells contain functional betaAR when they are used to study the effects of betaAR agonists on muscle protein metabolism.

Tumescent mini abdominoplasty

The tumescent technique for liposuction has become a widely accepted procedure in the plastic surgical community. We have used this technique as primary anesthesia for a limited abdominoplasty (mini abdominoplasty) in a series of 35 patients over a 2-year period on an outpatient basis. Anesthesia for the procedure consists of tumescent lidocaine solution and minimal sedation with oral Valium or low-dose intravenous Versed. All patients had good hemodynamic stability and tolerated the procedure well. No complications were noted intra- or postoperatively. The tumescent technique provides adequate and safe anesthesia for mini abdominoplasty with supplemental liposuction. The main advantages of the procedure include avoidance of risks associated with general anesthesia, less bleeding, faster recovery, and probably reduced cost of the operation.

Myosin heavy chain gene expression in bovine fetuses and neonates representing genotypes with contrasting patterns of growth

Fetal and neonatal myosin heavy chain (MHC) gene expression was examined in bovine genotypes that differed in their postnatal growth pattern and mature size. Pregnancies were established that would be expected to produce early-, intermediate-, or late-maturing postnatal growth. Fetal skeletal and cardiac muscles were collected at 100 and 200 days of gestation and at 30 days of age. Muscle tissue was analyzed for relative levels of MHC RNA and protein. Longissimus muscle MHC RNA/microgram RNA was greater at the 100-day time point for the intermediate maturity type (P < 0.05), which differed from the 200-day time point where the early maturity type had the greater RNA level (P < 0.05). Triceps muscle MHC RNA/microgram RNA weights differed due to genotype at 200 days gestation but did not differ at 100 days gestation or at 30 days postnatal. Ventricular muscle MHC RNA did not differ due to genotype at any of the three developmental stages. Differences due to maturity type in MHC protein/mg DNA were observed at 30 days of age, but no differences due to maturity type were observed at the prenatal time points. These results indicate that bovine fetal skeletal muscle MHC RNA production can be influenced by genotype and that genotype may be an important factor for future studies examining the role of external influences on fetal muscle growth.

Growth and development of bovine fetuses and neonates representing three genotypes

Growth was examined in bovine fetuses and neonates that typically differ in mature size and postnatal developmental pattern. Pregnancies were established from matings expected to produce early (E), late (L), and intermediate (I) maturing postnatal growth patterns. Tissues were collected at 100 and 200 d of gestation and 30 d postnatal. Muscle:body weight ratios were lower at 100 and 200 d for the E maturity type than for the L maturity type (P < .05). This differs from observations of muscle:body weight ratios made at 30 d postnatal, at which time ratios for E were either greater than (triceps brachii, P < .05) or similar to those for L. Few differences due to maturity type were observed at 100 d for bone weight:body weight ratios; however, at 200 d of gestation E bone weight:body weight ratios were generally lower (P < .05) than those for L. The genotypic relationship for bone weight:body weight ratio at 30 d postnatal was similar to that observed at 200 d of gestation. Observations of organ weight:body weight ratios revealed no clear patterns due to maturity type. The genotypic relationship for total muscle DNA content was similar to that observed for muscle weight. These results indicate that fetal muscle development differs in cattle that have different postnatal growth patterns by as early as 100 d of gestation and that differences in fetal muscle growth are related to differences in muscle hyperplasia.

Expression pattern and partial sequence analysis of a fetal bovine myosin heavy-chain gene

A fragment of a bovine myosin heavy-chain (MHC) gene approximately 15 kbp in size (designated MHC 67) was isolated from a bovine genomic DNA library. The direction of transcription was determined, and preliminary experiments indicated that the gene was expressed in fetal skeletal muscle. The expression pattern of this gene was, therefore, evaluated in detail using northern blots containing RNA from eleven different bovine muscle and nonmuscle tissues at three developmental ages. A restriction fragment of clone MHC 67 containing the 3' untranslated sequence (which is specific for each MHC gene) was used as a probe. This gene fragment hybridized predominantly to RNA from fetal skeletal muscles and did not hybridize to RNA from either neonatal or adult skeletal muscles (red or white), smooth muscle tissue, or nonmuscle tissue. A 7-kb EcoRI fragment containing both translated and untranslated regions surrounding the 3' end of the gene was subcloned into pBluescript II KS+ and partially sequenced. When these bovine sequences were aligned to that of the human and rat skeletal and cardiac MHC genes, we found that these sequences corresponded to exons 31, 32, and 33, and that they had homology with human perinatal and fetal MHC as high as 90% at the nucleotide level and 97% at the amino acid level. Comparison of the nucleotide sequences of isoform-specific 3' nontranslated regions from bovine, human, and rat genes further verify that the MHC 67 clone encodes the bovine fetal or perinatal MHC isoform.

Altered blood pressure reactivity in adolescent diabetics

OBJECTIVE

We examined hemodynamic responses to a variety of physiologic stimuli in 14 normotensive adolescents with type I diabetes and 45 healthy controls to determine whether structural vascular changes contribute to a reduced vasodilator capacity in adolescent diabetics. We asked, in adolescents with type I diabetes: (1) Are structural vascular changes present? (2) Are changes in the systemic vascular bed reflected in abnormal blood pressure regulation? and (3) Is abnormal vascular reactivity associated with either diabetes duration or control?

METHODOLOGY

Diabetic subjects were outpatients treated at the Medical College of Virginia, ages 13 to 18 years. Diabetes duration averaged 7.5 years. Each subject underwent an echocardiogram, dynamic and isometric exercise testing, and forearm plethysmography.

RESULTS

Compared to controls, diabetic subjects had (1) higher systolic and diastolic blood pressure during dynamic and handgrip exercise, (2) decreased forearm vasodilator capacity in response to ischemia, and (3) an increased aortic peak velocity. Group diastolic filling abnormalities were found, but these did not persist after adjustment for heart rate. The following variables were related to both diabetes duration and control (average glycosylated hemoglobin): (1) diastolic blood pressure during dynamic exercise, (2) resting forearm vascular resistance, and (3) forearm vascular reactivity. In addition, diabetes duration correlated with isometric exercise diastolic blood pressure, and diabetes control correlated with resting diastolic blood pressure.

CONCLUSION

In young diabetics we found that (1) abnormalities of the resistance vessels of the forearm may be present, (2) the degree of vascular change is related to diabetes duration and control, and (3) aortic distensibility may be impaired.

Diseases and disorders of muscle

Muscle may suffer from a number of diseases or disorders, some being fatal to humans and animals. Their management or treatment depends on correct diagnosis. Although no single method may be used to identify all diseases, recognition depends on the following diagnostic procedures: (1) history and clinical examination, (2) blood biochemistry, (3) electromyography, (4) muscle biopsy, (5) nuclear magnetic resonance, (6) measurement of muscle cross-sectional area, (7) tests of muscle function, (8) provocation tests, and (9) studies on protein turnover. One or all of these procedures may prove helpful in diagnosis, but even then identification of the disorder may not be possible. Nevertheless, each of these procedures can provide useful information. Among the most common diseases in muscle are the muscular dystrophies, in which the newly identified muscle protein dystrophin is either absent or present at less than normal amounts in both Duchenne and Becker's muscular dystrophy. Although the identification of dystrophin represents a major breakthrough, treatment has not progressed to the experimental stage. Other major diseases of muscle include the inflammatory myopathies and neuropathies. Atrophy and hypertrophy of muscle and the relationship of aging, exercise, and fatigue all add to our understanding of the behavior of normal and abnormal muscle. Some other interesting related diseases and disorders of muscle include myasthenia gravis, muscular dysgenesis, and myclonus. Disorders of energy metabolism include those caused by abnormal glycolysis (Von Gierke's, Pompe's, Cori-Forbes, Andersen's, McArdle's, Hers', and Tauri's diseases) and by the acquired diseases of glycolysis (disorders of mitochondrial oxidation). Still other diseases associated with abnormal energy metabolism include lipid-related disorders (carnitine and carnitine palmitoyl-transferase deficiencies) and myotonic syndromes (myotonia congenita, paramyotonia congenita, hypokalemic and hyperkalemic periodic paralysis, and malignant hyperexia). Diseases of the connective tissues discussed include those of nutritional origin (scurvy, lathyrism, starvation, and protein deficiency), the genetic diseases (dermatosparaxis, Ehlers-Danlos syndrome, osteogenesis imperfecta, Marfan syndrome, homocystinuria, alcaptonuria, epidermolysis bullosa, rheumatoid arthritis in humans, polyarthritis in swine, Aleutian disease of mink, and the several types of systemic lupus erythematosus) and the acquired diseases of connective tissues (abnormal calcification, systemic sclerosis, interstitial lung disease, hepatic fibrosis, and carcinomas of the connective tissues). Several of the diseases of connective tissues may prove to be useful models for determining the relationship of collagen to meat tenderness and its other physical properties. Several other promising models for studying the nutrition-related disorders and the quality-related characteristics of meat are also reviewed.

Protein metabolism in chicken muscle cell cultures treated with cimaterol

Primary muscle cell cultures were prepared from the leg muscle of 12-d broiler chicken embryos. The partitioning agent cimaterol (10(-6) to 10(-10) M) was added on d 1 and each day thereafter, and cells were studied after 7 d in culture. Cimaterol had no effect at any level either on the percentage of nuclei within multinucleated myotubes or on the total number of nuclei within myotubes. At 10(-7) M cimaterol, the quantity of the myofibrillar protein fraction was increased by 25.1 +/- 8.0% (P less than .05) and the quantity of myosin heavy chain was increased by 30.9 +/- 4.5% (P less than .05). To understand the basis for the increase in myofibrillar protein, the incorporation rate of [3H]Leu was measured in pulse labeling experiments. The apparent synthesis rate of the soluble protein fraction and the crude myofibrillar fraction was not significantly increased by cimaterol; however, cimaterol levels greater than 10(-8) M caused a 10 to 12% increase (P less than .05) in the incorporation rate of [3H]Leu into myosin heavy chain. The effect of cimaterol on release of [3H]Leu from prelabeled protein also was assessed in pulse-chase experiments; the apparent rate of protein degradation was inhibited by 10 to 15% (P less than .05) at the higher levels of cimaterol. Dot blot analysis indicated that the quantity of myosin heavy chain mRNA was elevated in cimaterol-treated cultures. Thus, the increased quantity of myofibrillar proteins in embryonic broiler muscle cell cultures is the combined result of a stimulation in the rate of protein synthesis and an inhibition in the rate of protein degradation.

Effect of insulin on phosphorus metabolism in red blood cells from patients with schizophrenia and psychotic depressions

In an exploratory study of the metabolism of selected intermediates of glycolysis in rbc of patients with schizophrenia and with major depressive disorders, statistically significant decreases in the RSA of 2,3-DPG were found in the rbc of patients with psychotic disorders compared to normal subjects. No statistically significant differences were observed in the RSA of any of the other glycolytic intermediates studied comparing patients to normal subjects.

Genomic clones encoding chicken myosin heavy-chain genes

A chicken genomic library was screened with a cDNA probe containing the 3' coding and noncoding portions of quail fast-twitch skeletal muscle myosin heavy chain (MHC). This probe hybridized to seven to nine bands on Southern blots of chicken genomic DNA, and 17 clones that hybridized to this probe were obtained from the genomic library. Partial restriction maps were constructed and probable orientation of transcription was determined for each of the 17 clones. These maps indicate the presence of at least 14 unique MHC genes or pseudogenes. Dot-blot hybridization analysis using DNA complementary to RNA from a variety of chicken tissues demonstrated that these genes are all related to the gene for sarcomeric MHC, and permitted tentative assignment of the tissue of expression for several of the MHC isoforms. To substantiate further the dot-blot data, a subclone of one of the genes (4b1), which showed significant homology with adult breast muscle RNA but which also showed weaker hybridization to RNA from other tissues, was sequenced. The sequence data verified that the clone contains a portion of a MHC gene, that it contains both 3' coding and noncoding regions, and that its predicted amino acid sequence is identical (with 96% nucleotide homology) to that of the 75-bp quail fast MHC cDNA clone published by Hastings and Emerson (1982). Thus, clone 4b1 contains a portion of one of the genes that is expressed in adult chicken breast skeletal muscle tissue.

Screening of a bovine genomic library for myosin heavy-chain genes

Restriction enzyme digests of bovine genomic DNA were hybridized against a .37-kilobase (kb) quail embryonic myosin heavy-chain (MHC) copy deoxyribonucleic acid (cDNA) probe; containing both translated and nontranslated regions surrounding the 3' end of the gene. These experiments revealed seven to eight different bands of hybridization, indicative of multiple genes of MHC in the bovine genome. Additionally, a bovine genomic recombinant DNA library was screened with the .37-kb probe. Of the 10(6) phage screened, 11 clones containing portions of the MHC genome were identified, and four were selected for further analyses. Characterization of these four clones was carried out by constructing partial restriction enzyme maps of the inserts using six restriction enzymes singly or in combination. Orientation of the inserts with respect to the arms of the vector and with respect to direction of transcription was determined by hybridizing the DNA fragments against either the .37-kb Pst 1 fragment of pcC128 or to the .23-kb Pst I fragment of pcC128. The .23-kb fragment is located upstream from the .37-kg fragment and contains only coding sequence. Therefore, the differential hybridization pattern of these two probes provided a means for determining the probable direction of transcription. These data provide evidence for a myosin multigene family in cattle, as well as illustrating that the organization of these genes around the 3' end is unique for each of the genes analyzed.

Structural analysis of myosin genes using recombinant DNA techniques

Myosin, the major protein of the myofibril, consists of two heavy chains with a molecular weight (MW) of 200,000, complexed with four light chains of MW 17,000 to 21,000. Both the heavy and light chains exhibit polymorphisms that are tissue-specific and developmental stage-specific. Myosin heavy chains and light chains appear to be represented in the genome as multigene families in various species, including chickens, cattle, humans, rats, rabbits and nematodes. Myosin heavy-chain proteins have a high amino acid sequence homology among isoforms, and the genes for each isoform likewise exhibit a high degree of nucleotide sequence conservation. The myosin heavy-chain genes have a complex structure and contain up to 65% intervening sequence composed of up to 20 or more individual introns. Partial sequence data, transcriptional orientation and tissue of expression have been determined for several myosin heavy-chain genes. The use of recombinant DNA and associated techniques will eventually yield definitive information on the control of expression of each individual gene, as well as factors that regulate expression of closely related isoforms.

Premature adrenarche. Clinical and diagnostic features

Premature adrenarche (PA) or isolated growth of sexual hair in young children, is a benign condition that may initially be confused with true precocious puberty or pathologic virilizing disorders. The clinical findings, family history, and serum concentrations of dehydroepiandrosterone sulfate (DHEA-S) were compared in 24 children with PA (79% black females) seen in a 2-year period and in an age-matched control group of 17 black females. Twenty three of 24 patients, but none of the controls, had an adult-type axillary odor. There was a positive family history of PA in only three of 24 children with PA, and in one of 17 controls. The mean serum DHEA-S was significantly higher in the PA children than in the controls, but there was a broad range of concentrations (10-143 micrograms/dl), with values in 10 of 24 cases falling within the control range for age. We conclude that: (1) PA is a relatively common finding in black females between ages 3 and 8, (2) an axillary odor is almost always present in children with PA, and (3) determination of serum DHEA-S may be of some help in confirming the clinical impression of a modest increase in adrenal androgen secretion and in ruling out a more serious disorder. In most cases, however, the diagnosis of PA can be made on the basis of the history, physical examination, and lack of rapid progression over time; the use of laboratory tests to rule out a pathologic virilizing process may best be reserved for those children with very early onset, increased linear growth, or other signs of virilization.

Calcium and phosphate metabolism in children with idiopathic hypoparathyroidism or pseudohypoparathyroidism: effects of 1,25-dihydroxyvitamin D3

Two children with congenital hypoparathyroidism and two children with pseudohypoparathyroidism were given maintenance doses of 15 to 45 ng/kg/day 1,25-dihydroxyvitamin D3 for a total of 255 months. The urinary calcium excretion showed an upward elevation after the first 2 years of treatment but was not significantly higher than that in 10 normal control subjects. The renal threshold for phosphate excretion stayed within the normal ranges compared with control values. Two hypercalcemic and two hypocalcemic episodes occurred during this period of treatment. Hypercalcemia was reversed within 1 week after withdrawal of 1,25-dihydroxyvitamin D3. Hypocalcemia was countered by increasing the dose of 1,25-dihydroxyvitamin D3. Renal functions were not adversely affected, as estimated by creatinine clearance and reciprocals of serum creatinine concentrations. The mean serum calcium concentration during 1,25-dihydroxyvitamin D3 treatment was significantly higher (P = 0.001) compared with that obtained during vitamin D2 treatment at a dose of 500 to 3000 IU/kg/day. These data provide additional support for the long-term use of 1,25-dihydroxyvitamin D3 in idiopathic hypoparathyroidism and pseudohypoparathyroidism.

Elevated ammonia release from dystrophic chicken muscle cell and fibroblast cultures

The activity of adenosine monophosphate (AMP)-aminohydrolase, the major NH3-producing enzyme in skeletal muscle, was approximately 35% lower in 7-day dystrophic muscle cell cultures than in normal muscle cell cultures. However, the release rate of NH3 from dystrophic muscle cells was 45% higher than that from normal muscle cells. The reasons for this apparent discrepancy are not clear. To determine indirectly if deamination of amino acids from protein degradation contributed to NH3 release, cells were incubated with 100 micrograms/ml of the protease inhibitor, leupeptin. Leupeptin reduced the rate of NH3 release by only 18.8% in normal muscle cells and 16% in dystrophic muscle cells. The release of NH3 was also higher from dystrophic chicken fibroblast cultures.

Myosin heavy chain concentration, synthesis rate and degradation rate in normal and dystrophic chicken muscle cells in culture

Myosin heavy chain concentrations, synthesis rates and degradation rates were studied in muscle cell cultures prepared from the breast muscle of 13-day normal (white leghorn) and dystrophic (line 307) chicken embryos. Muscle cells were studied after 7 days in culture, at which time they had reached a steady state with respect to myofibrillar protein synthesis and degradation. The quantity of myosin heavy chain was 10.5 +/- 0.9 micrograms/culture (n = 32) in normal cells and 8.10 +/- 1.2 micrograms/culture (n = 31) in dystrophic cells. However, the myosin heavy chain synthesis rate was 23 500 molecules/min/nucleus in normal cells and 39 900 molecules/min/nucleus in dystrophic cells, as determined by pulse labeling with [3H]leucine and measurement of the specific radioactivity of tRNA precursor pools. Myosin heavy chain half-lives rates were calculated to be 30.6 h in normal cells and 15.6 h in dystrophic cells when corrections were made for reutilization of [3H]leucine. Thus, dystrophic muscle cultures accumulate less myosin heavy chain, despite their faster synthesis rate, because of faster degradation of myosin heavy chain.

Effect of creatine on contents of myosin heavy chain and myosin-heavy-chain mRNA in steady-state chicken muscle-cell cultures

Embryonic-chick muscle cells reach a steady state with respect to protein metabolism after approx. 1 week in cell culture. To determine if this steady state could be altered by the administration of agents that have been reported to stimulate myosin heavy-chain synthesis, 7-day muscle-cell cultures were treated with 0-1 mM-creatine. Incorporation of [3H]leucine into myosin heavy chain was stimulated by 30-40% at the optimum creatine concentration (0.2 mM), but this stimulation was blocked when actinomycin D (10 micrograms/ml) was also present. However, the quantity of myosin-heavy-chain mRNA as measured by hybridization in vitro was only 15% higher in creatine-treated cultures, and was therefore not entirely responsible for the observed effect. It is important to note that creatine only exerted its action on myosin-heavy-chain synthesis rate in steady-state cultures; creatine was ineffective in altering this rate in rapidly differentiating 3-day muscle cultures. Finally, muscle-cell cultures that had been grown for the entire 7-day culture period in the presence of 0.2 mM-creatine were assayed for quantity of myosin heavy chain. Control and creatine-treated cultures contained 12.7 +/- 1.5 and 20.5 +/- 1.8 micrograms/dish respectively. In conclusion, creatine apparently enhances the quantity of myosin heavy chain in steady-state embryonic muscle-cell cultures, but it probably does not mediate regulation of myosin content in adult skeletal muscle.

Leucine pools in normal and dystrophic chicken skeletal muscle cells in culture

The specific radioactivity of [3H]Leu in the extracellular, intracellular, and Leu-tRNA pools of normal (white leghorn) and dystrophic (line 307) embryonic chick breast muscle cultures was analyzed as a function of equilibration time and extracellular Leu concentration (0.05-5 mM). The primary results were the following 1) [3H]Leu equilibrated to a constant specific radioactivity in the intracellular and Leu-tRNA pools within 2 min after addition to both normal and dystrophic cultures. 2) After equilibration, the extracellular [3H] Leu specific radioactivity in dystrophic cell culture medium was lower than that of medium exposed to normal cells (especially at low Leu concentrations), probably because of increased release of unlabeled Leu from the dystrophic cells as a result of faster protein breakdown. Accordingly, the specific radioactivities in the intracellular and the Leu-tRNA pools were also lower in dystrophic cells. 3) At 5 mM extracellular Leu, the specific radioactivity in the Leu-tRNA pool was approximately 40% lower than the specific radioactivity in the intracellular pool in both normal and dystrophic cells. Thus, high concentrations of extracellular Leu cannot be used to "flood out" reutilization of unlabeled Leu (released by protein degradation) during protein synthesis. 4) At 5.0 mM extracellular Leu, the specific radioactivity of [3H]Leu in the intracellular pool was comparable to that in the extracellular pool in normal and dystrophic cells; however, the specific radioactivity of Leu-tRNA (i.e. the immediate precursor to protein synthesis) was only 55-65% of the extracellular specific radioactivity in normal and dystrophic cells. In conclusion, reutilization of Leu from protein degradation is higher in dystrophic muscle cell cultures than in normal muscle cell cultures, and accurate rates of protein synthesis in cell cultures can only be obtained if specific radioactivity of amino acid in tRNA is measured.

Control of respiratory pattern in conscious dog: effects of heat and CO2

We measured tidal volume (VT) and inspiratory (TI) and expiratory (TE) durations in five conscious tracheostomized dogs breathing air or 5% CO2 in air either at normal (20 degrees C) or elevated (30 degrees C) ambient temperatures. Respiratory frequency ranged between 16 and 333/min due to changes in both TI and TE. During panting TI exceeded TE. During air inhalation instantaneous ventilation (V) spontaneously ranged from 100 to 1,600 ml . kg-1 . min-1. Hypercapnia, heat stress, or both, increased this range of V by increasing maximum V, primarily due to increases in mean inspiratory flow. Under these conditions, changes in TI accounted for more of the spontaneous changes in breath duration. During inhalation of air and 5% CO2, a positive correlation between VT and TI was obtained for TI between 0.13 and 1.05 s; above 1.05 s VT decreased. Heat stress increased VT at a given TI. We suggest that either the decay rate or position of the inspiratory off-switch threshold curve (Clark and von Euler, J. Physiol. London 222: 267, 1972) varies in conscious dogs. Shifts in either the reset (onset) value or decay rate of the curve yield a positive correlation between VT and TI. This modification to the Clark-von Euler model implies that the primary effect of anesthesia on respiratory control is fixation of the inspiratory off-switch threshold curve.

Myocardial pH during regional ischemia: evaluation of a fiber-optic photometric probe

The relationship between the decrease in intramyocardial extracellular pH and the degree of stenosis of the left anterior descending (LAD) coronary artery was studied in eight dogs pretreated with propranolol. Intramyocardial pH was measured with a miniature glass pH electrode and with a new photometric pH probe that uses fiber-optic filaments to measure the color change of an indicator substance in a small permeable chamber. The LAD was cannulated and perfused from the axillary artery. Cannula flow was measured with an electromagnetic flow probe, and regional myocardial blood flow (RMBF) was measured with radioactive microspheres before and at the end of a period of critical stenosis, 2/3 reduction of flow, or total occlusion of the LAD cannula. In the region of the glass electrode, the mean RMBF (+/-SE) decreased by 16.3 +/- 3.3, 52.7 +/- 7.3, and 84.8 +/- 6.5% during the three levels of stenosis, and the pH correspondingly decreased by 0.05 +/- 0.01, 0.29 +/- 0.10, and 0.94 +/- 0.17 units. In the region of the photometric probe, the RMBF decreased 19.1 +/- 1.3, 47.2 +/- 6.7, and 84.3 +/- 6.0%, and the pH decreased by 0.05 +/- 0.02, 0.14 +/- 0.04, and 0.76 +/- 0.18 units. There was no statistically significant difference between the two types of pH sensor.

Cell differentiation, protein synthesis rate and protein accumulation in muscle cell cultures isolated from embryos of layer and broiler chickens

Muscle cell cultures were prepared from the leg muscle of 12-d layer and broiler chicken embryos. Cultures were then compared over a 10-d period from their capacity to differentiate into multinucleated myotubes and to synthesize and accumulate protein. Differentiation was qualitatively similar in the two cell types as evidenced by myoblast fusion that occurred rapidly during the first 2 d and remained essentially constant between d 3 and 10. However, several quantitative differences were observed. Even though the number of myotubes per culture was comparable between layers and broilers throughout development, layer muscle cultures usually exhibited a higher percentage fusion and more myonuclei per culture than broiler muscle cultures. Additionally, the nuclear density (i.e., the number of nuclei per myotube segment) was approximately 25% greater in layer cultures than in broilers between d 2 and 10 in culture. The rate of incorporation of 3H-leucine into total protein during pulse labeling experiments was comparable in muscle cultures of layers and broilers; however, broiler muscle cells accumulated approximately 40% more total protein per nucleus between d 6 and 10. Myosin heavy chain synthesis rate was higher in layer than in broiler muscle cultures, but broiler muscle cultures accumulated approximately 30% more myosin heavy chain than layers between d 6 and 10. The half-life of myosin heavy chain was 45 h in layer muscle cultures and 103 h in broiler muscle cultures. Thus, the capacity of broiler cells to accumulate more muscle protein was primarily due to a drastically slower protein breakdown rate.

Stimulation of myosin heavy chain synthesis in steady-state muscle cultures by the ionophore, A23187, requires transcription of messenger RNA

After approximately one week in culture, embryonic chick skeletal muscle cells are at a steady state with respect to myosin heavy chain (MHC) concentration and synthesis rate. Muscle cells normally synthesize MHC at a maximum rate of 2.3 X 10 4 MHC/min/nucleus and contain approximately 3 X 10 7 MHC/nucleus. These cells also contain approximately 3500 copies/nucleus of MHC mRNA associated with polysomes and 1600 copies/nucleus of MHC mRNA localized in the nonpolysomal fraction. To determine if nonpolysomal MHC mRNA in mature muscle cultures could be recruited into active translation complexes when MHC synthesis was stimulated, muscle cultures were treated with the Ca 2+ ionophore, A23187 (0-1 micro M). The MHC synthesis rate was stimulated by 25 to 50% relative to stimulation of the rate of total protein synthesis in the presence of A23187, but this stimulation was blocked when 10 microgram/ml actinomycin D was also present. These results suggest that even though 30% of MHC mRNA is not actively engaged in MHC synthesis in mature muscle cultures, stimulation of MHC synthesis by A23187 results from transcription of new MHC mRNA rather than from utilization of pre-existing mRNA.

Normal and dystrophic embryonic chicken pectoralis muscle cultures: II. Ultrastructural comparison

Ultrastructural comparison was made between dystrophic and normal chicken breast muscle cells which had been isolated from 12-day-old embryos and cultured for up to 14 days. All electron microscopic examinations were conducted in the absence of any knowledge as to the dystrophic or normal origin of the cells, or the day on which the cells had been harvested from culture. The same blind procedures were applied to attempts to reconstruct from electron micrographs the correct sequence of days for a particular experiment and to identify the origin of the cells as normal or dystrophic. No consistent differences between normal and dystrophic cells were apparent either in extent of differentiation, such as the formation of mature sarcomeres, or in degenerative properties, such as disintegrating mitochondria, lipid aggregations, or extracellular debris. In light of metabolic and developmental differences in these cultures, the absence of ultrastructural differences was attributed in part to the presence of cells with widely different degrees of integrity, differentiation, and degeneration in both normal and dystrophic cultures.

Normal and dystrophic embryonic chicken pectoralis muscle cultures: I. Cell differentiation, protein synthesis, and enzyme levels

Normal (line 200) and dystrophic (line 307) embryonic chicken pectoralis muscle cells were studied in cell culture over a period of 2 weeks. During the first 4 days, normal and dystrophic cultures exhibited similar developmental increases in the number of nuclei within multinucleated myotubes, however, dystrophic muscle cells degenerated approximately twice as fast as normal cells once the initial burst of myoblast fusion was complete. The apparent synthesis rate of nonmyofibrillar proteins was similar in normal aand dystrophic cells throughout development, but the apparent synthesis rates of myosin heavy chain and the myofibrillar protein fraction were 50%--90% higher in dystrophic muscle cultures once maturity had been reached (days 6--14). The specific activities of creatine kinase and phosphofructokinase were not affected by the dystrophic condition; however, specific activity of AMP-deaminase was depressed 25%--40% in the dystrophic muscle cultures.

Normal and dystrophic embryonic chicken pectoralis muscle cultures: III. Viral infection of normal cell cultures

Twelve-day normal and dystrophic chick embryo breast muscle cells were cultured for up to 14 days, using normal embryo extract in the culture medium. Fluorodeoxyuridine was added on day 3 to suppress fibroblast overgrowth. Three of 6 experiments with normal cells were severely infected with avian leucosis/sarcoma (ALS) virus particles. The findings appear to lend support to the suggestion that the ALS virus is a mitochondriophage. Infected cultures demonstrated a depressed rate of total protein synthesis as reflected by incorporation of [3H]leucine. Extractable protein and total protein content were also depressed within several days after ALS particles were identified. These findings reinforce caution in acceptance of the common assumption that viral infections are an unavoidable and metabolically benign component of muscle cell cultures.

Metabolism of myosin heavy chain in steady-state chick skeletal muscle cultures

Synthesis, accumulation and breakdown of the 200000-mol.wt. heavy subunit of myosin were analysed over an 11 day period in muscle cell cultures isolated from the leg muscle of 12-day chick embryos. Muscle cells accumulated myosin heavy chain rapidly from days 2 to 5 and maintained a maximum, constant myosin-heavy-chain concentration between days 7 and 11. Myosin-heavy-chain content and breakdown rate were compared in steady-state muscle cultures grown either in the presence of an optimum batch of horse serum (control) or in the presence of horse serum that had been pre-selected for its ability to inhibit several-fold the rate of synthesis of myosin heavy chain (inhibitory). The quantity of myosin heavy chain in the inhibited cultures was decreased in direct proportion to the decrease in the rate of synthesis of myosin heavy chain; however, the half-lives of myosin heavy chain (control, 17.7h; inhibitory, 17.0h) were virtually identical. In contrast, the absolute rate of breakdown of myosin heavy chain, expressed as molecules/min per nucleus, was approx. 5-fold lower in the inhibited cultures (4.3 X 10(3) molecules/min per nucleus) than in the control cultures (21.7 X 10(3) molecules/min per nucleus). Thus, inhibition of myosin-heavy-chain synthesis in this case was accompanied by diminished myosin-heavy-chain concentration and absolute breakdown rate at the altered steady state, but relative myosin-heavy-chain breakdown rates were unchanged.

Myosin synthesis in embryonic chicken fibroblasts

The rate of constitutive myosin synthesis was measured in cultures of replicating embryonic chicken skin fibroblasts by pulse labeling with [3H]leucine. These cells synthesized the 200,000-dalton heavy chain of myosin (MHC) at a rate of 3.2 x 10(3) molecules/cell/min. Additionally, an independent estimate of the MHC synthesis rate needed to maintain a constant level of constitutive MHC/cell was calculated from total protein content, percentage MHC, fibroblast doubling time, and MHC half-life. This calculated rate of approximately 2.9 x 10(3) molecules/cell/min was in close agreement with the measured rate. By comparison, the synthesis rate of myofibrillar MHC in fully activated muscle cell cultures was approximately 2.9 x 10(4) molecules/nucleus/min.

Cytogenetics of recurrent abortions

Chromosome banding studies were carried out on both partners of 37 couples who had had two or more spontaneous abortions. Three patients had chromosome disorders; one was a triple-X female and the other two (one male and one female) were t(13;14) translocation carriers. Review of the literature indicates that the over-all frequency of major chromosome disorders in couples with repeated abortions is 2.6%. About three-fourths of these disorders are reciprocal and Robersonian translocations.