Desensitization of adenylate cyclase in Chinese hamster ovary cells transfected with human thyroid-stimulating hormone receptor.

Desensitization or decreased response to the same (homologous) or other stimuli (heterologous) is a well known process. Homologous desensitization to TSH has been demonstrated in normal thyroid tissue. Chinese hamster ovary cells (CHO) transfected with normal human TSH receptor (hTSHR) DNA, in contrast, have been reported not to desensitize. The purpose of our investigation was to determine whether CHO cells transfected with hTSHR desensitize in response to TSH and postreceptor stimulation. CHO cells were stably transfected with plasmid DNA containing hTSHR; nontransfected CHO cells served as the control. TSH (10 mU/ml), 5'-beta,gamma-imido-triphosphate [Gpp(NH)p; 0.1 mM], sodium fluoride (NaF; 10 mM), forskolin (10 microM), and (Bu)2cAMP (100 microM) were used to determine whether homologous or postreceptor heterologous desensitization of adenylate cyclase activity occurred in CHO-transfected cells. Intracellular cAMP accumulation was determined by RIA. Cells were incubated with TSH (to stimulate TSH receptor), Gpp(NH)p, NaF (to stimulate G-protein), forskolin (to stimulate adenylate cyclase activity), and (Bu)2cAMP (nonmetabolized cAMP analog). A second incubation was carried out with TSH (10 mU/ml). Maximal desensitization to either TSH or postreceptor stimulation was observed at 2 h. When transfected CHO cells were preexposed to TSH (10 mU/ml) for 4 h, even the smallest dose of TSH (0.001 mU/ml) caused desensitization. All substances that increased the intracellular cAMP concentration, such as TSH, Gpp(NH)p, NaF, forskolin, and (Bu)2cAMP, caused desensitization. The decrease in the cAMP response to TSH added in the second incubation was 63% less than the initial response to TSH or to postreceptor stimulation (P = 0.0001). In conclusion, desensitization of hTSHR-transfected CHO cells occurs in response to both receptor and postreceptor stimulation that increase cAMP levels. Because hTSHR transfected CHO cells desensitize, no specific thyroid factor(s) other than increased levels of cAMP is required.

Vascular endothelial growth factor expression is higher in differentiated thyroid cancer than in normal or benign thyroid.

Vascular endothelial growth factor (VEGF) is an angiogenic factor, and its expression has been rarely demonstrated in thyroid tumors. We, therefore, investigated the expression of VEGF messenger RNA (mRNA) and production of VEGF protein in cell lines from human primary and metastatic follicular (FTC-133, FTC-236, and FTC-238), papillary (TPC-1), Hürthle cell (XTC-1), and medullary thyroid cancers (MTC-1.1 and MTC-2.2), and in human thyroid tissues (papillary, follicular, medullary, and Hürthle cell cancers, follicular adenomas, and Graves' thyroid tissue) by Northern blot, immunohistochemistry, and enzyme-linked immunosorbent assay (ELISA) studies. All thyroid cell lines expressed a 4.2-kilobase VEGF mRNA. The VEGF mRNA levels were higher in the thyroid cancer cell lines than in primary cultures of normal thyroid cells, and higher in thyroid cancers of follicular than those of parafollicular cell origin. The VEGF mRNA levels were similar in primary and metastatic thyroid tumors. Immunohistochemical staining and Northern blot analysis of the cell lines correlated positively, thus thyroid cancer cell lines stained more intensely than normal thyroid cells and follicular tumor cells more intensely than parafollicular tumor cells. Again, no difference was noted in VEGF staining between primary and metastatic thyroid tumors. Deparafinized sections of papillary, follicular, and Hürthle cell cancers also stained much stronger than those of medullary thyroid cancers, benign, or hyperplastic (Graves' disease) thyroid tissue. Thyroid cancer cell lines (XTC-1 > TPC-1 > FTC-133 > MTC-1.1) also secreted more VEGF protein as measured by ELISA than did normal thyroid cells. VEGF secretion of cell lines derived from primary and metastatic thyroid tumors were similar. VEGF mRNA is therefore expressed, and VEGF protein is secreted by normal, hyperplastic, and neoplastic thyroid tissues. The higher levels of VEGF expression in differentiated thyroid cancers of follicular cell origin suggests a role in oncogenesis.

Immunocytochemical detection of p53 in human thyroid carcinomas is associated with mutation and immortalization of cell lines.

Mutations in the tumor suppressor gene p53 are the most-common mutations found in human cancers. In thyroid cancers, p53 mutations generally are found only in poorly differentiated and undifferentiated tumors and in cell lines. To determine the prevalence of p53 mutations in thyroid neoplasms and thyroid cell lines, we screened 58 thyroid tissues and 3 thyroid cell lines, p53 primers bracketing exons 4, 5/6, 7, and 8 were used to amplify genomic DNA using the PCR. Mutations were screened by denaturing gradient gel electrophoresis and confirmed by sequencing. The two papillary thyroid cancer cell lines and the follicular thyroid carcinoma cell line (positive control) had transitions (CGT->CAT) in exon 8, codon 273, resulting in the replacement of arginine with histidine. No normal thyroid tissues or primary tumors from which the cell lines were derived demonstrated exon 8 mutations, using this technique. p53 immunocytochemistry demonstrated a progression of p53 immunopositivity between synchronous and metachronous neoplasms, paralleling the neoplastic progression from a benign adenoma to primary carcinoma, regional, and distant metastasis and ultimately, the cell lines, where intense immunopositivity is noted. In addition, fluorescence in situ hybridization, using probes specific for the p53 locus, revealed the presence of 3 homologues of p53 in the follicular cell line and 2 homologues in the papillary and Hürthle cell lines. These results suggest that a point mutation present in a small number of original tumor cells and amplification of the mutant allele may be responsible for immortalizing well-differentiated thyroid cancer cells into cell lines.

Pulmonary manifestations of familial dysautonomia in an adult.

A patient with familial dysautonomia (Riley-Day syndrome) who illustrates the multiple and varied pulmonary manifestations of this disorder is described. Since many of these patients are now surviving well into adulthood, knowledge of this condition among physicians should be propagated.

Survival after severe hypernatremia due to salt ingestion by an adult.

An 85-year-old woman was brought to the hospital with a serum sodium level of 193 mmol/liter following salt ingestion. She was treated with free water replacement and recovered within 48 hours. She represents the sole survivor of salt ingestion of this severity in the literature.

The value of edema fluid protein measurement in patients with pulmonary edema.

Alveolar fluid and plasma proteins were analyzed in 24 patients with florid pulmonary edema, in 21 of whom pulmonary capillary wedge pressure (Pcw) was also measured. In all patients with Pcw less than 20 mm Hg, the edema fluid to plasma protein ratio exceeded 0.6; the mean edema fluid to plasma protein ratio in the four patients with cardiogenic edema (increased Pcw) was 0.46. In the 21 patients in whom full data were available, the net intravascular filtration force (Pcw - plasma colloid osmotic pressure) was less than -4 mm Hg, the value at which (according to others) pulmonary edema should occur, in only 10. When the interstitial colloid osmotic pressure, approximated by the osmotic pressure of edema fluid protein, was added, the net filtration force became positive in 17 of 21 patients. Comparison of the protein concentrations of edema fluid and plasma aids in the diagnostic separation of increased permeability from high hydrostatic pressure edema and adds to our understanding of the relative osmotic and hydrostatic forces that contribute to pulmonary edema when the alveolar-capillary membrane is damaged.

How do we achieve cost-effective options in lower respiratory tract infection therapy?

Acute bronchitis and acute exacerbations of chronic bronchitis, common illnesses encountered by general and family physicians, account for approximately 14 million physician visits per year. The pattern of antibiotic prescribing for these infections varies from country to country, but there is no clear rationale for these antimicrobial choices. A recent meta-analysis of all randomized, placebo-controlled trials of patients treated with antibiotics for acute exacerbations of chronic bronchitis concluded that a small but statistically significant improvement could be expected in antibiotic-treated patients. Haemophilus influenzae is the most commonly isolated organism from sputum in patients with acute exacerbations of chronic obstructive lung disease but other Haemophilus species, Streptococcus pneumoniae, and Moraxella catarrhalis may also be found. High-risk patients can be defined as being elderly, with significant impairment of lung function, having poor performance status with other comorbid conditions, having frequent exacerbations, and often requiring oral corticosteroid medication. Well-defined clinical trials measure efficacy of a drug but not the effectiveness in a real world situation. Future studies of new antimicrobials should examine their efficacy in patients with an increased risk of true bacterial infection.

The value of antibiotics and the outcomes of antibiotic therapy in exacerbations of COPD.

COPD is the fifth leading cause of death in the United States, and acute respiratory infections account for a significant proportion of all primary care visits. Approximately one half of all exacerbations of COPD can be attributed to bacterial infection, and antibiotic therapy has been demonstrated to improve clinical outcomes and hasten clinical and physiologic recovery. The major pathogen continues to be Haemophilus influenzae, and resistance to beta-lactam antibiotics such as ampicillin can be expected in 20 to 40% of isolated strains. Certain high-risk patients, in whom the cost of clinical treatment failure is high, can be identified by simple clinical criteria. Patients with significant cardiopulmonary comorbidity, frequent purulent exacerbations of COPD, advanced age, generalized debility, malnutrition, chronic corticosteroid administration, long duration of COPD, and severe underlying lung function tend to fail therapy with older drugs, such as ampicillin, and early relapse can be expected. Treatment directed toward resistant pathogens with potent bactericidal drugs may be expected to lead to improved clinical outcomes and overall lower costs, particularly if hospital admissions and respiratory failure can be prevented. Future studies examining the role of antibiotics should enroll these high-risk patients to determine if new therapies have significant clinical, quality-of-life, and economic advantages over older agents.

Nalbuphine-induced pulmonary edema.

We report the occurrence of acute pulmonary edema in a patient receiving therapy with nalbuphine, a synthetic narcotic analgesic. Other potential causes of acute pulmonary edema were excluded. It is likely that all opiate drugs share the propensity to produce acute pulmonary edema, and nalbuphine resembles other opiates in this regard.

Monitoring intrapulmonary hemorrhage in Goodpasture's syndrome.

Diffusing capacity of carbon monoxide (Dco) was measured frequently in a patient with recurrent intrapulmonary hemorrhage secondary to Goodpasture's syndrome. This simple test was found to be a sensitive and useful indicator of the presence or absence of recurrent intrapulmonary hemorrhage. As this is now the major cause of mortality in this disease, we recommended that frequent measurements of the Dco be an important part of its management.

Acute reversible cardiomyopathy associated with the systemic inflammatory response syndrome.

In the absence of ischemic heart disease, severe acute reversible myocardial dysfunction is uncommon, with sepsis most often being implicated in the ICU. We report a 38-year-old woman who developed profound transient myocardial depression due to nonseptic systemic inflammatory response syndrome caused by a necrotic kidney. Hemodynamic parameters and echocardiographic findings improved dramatically following nephrectomy. Other causes of acute myocardial suppression, including electrolyte abnormalities, drugs, catecholamine excess, and endocrine disease were excluded.

Management of acute respiratory failure due to pulmonary edema with nasal positive pressure support.

The management of patients with respiratory failure from cardiogenic pulmonary edema may require intubation and mechanical ventilation. This provides both ventilatory assistance as well as the beneficial hemodynamic effects of positive intrathoracic pressure. As the need for ventilation is usually short term, noninvasive ventilatory support may be adequate. We report the use of biphasic positive airway pressure by nasal mask (BiPAP system) to successfully manage two patients with respiratory failure due to pulmonary edema.

Carbon monoxide effect on alveolar epithelial permeability.

A carbon monoxide (CO)-intoxicated patient developed increased permeability-type pulmonary edema demonstrated by a normal capillary wedge pressure and production of protein-rich edema fluid. To investigate the effect of CO on alveolar-epithelial permeability, a radio-active labelled isotope, 51Cr-EDTA (MW 377), was instilled into the airways of rabbits. Subsequent egress of the marker from the lungs into arterial blood was determined in serial arterial blood samples. The 51Cr-EDTA counts increased significantly within 15 minutes in the CO-exposed animals, compared with the control animals, while dynamic lung compliance fell, airways resistance rose, and arterial blood pressure decreased. Ultrastructural study of the lungs of CO-exposed animals revealed epithelial and endothelial cell swelling, in terstitial edema, and alveolar type II cells depleted of lamellar bodies. These findings support the possibility that carbon monoxide intoxication is associated with increased alveolar-epithelial permeability.

Hypertrophic pulmonary osteoarthropathy in four patients with interstitial pulmonary disease.

The association between digital clubbing and idiopathic pulmonary fibrosis has been well established; however, the simultaneous occurrence of hypertrophic pulmonary osteoarthropathy and interstitial fibrosis, in the absence of neoplastic disease, has only been described in two case reports and was not mentioned in any of 336 patients described in several recent reviews. Among 70 patients referred for investigation of pulmonary infiltrates, four were found to have hypertrophic pulmonary osteoarthropathy associated with interstitial pulmonary disease, in the absence of malignant disease. We conclude that the use of bone scans and roentgenographic examination of the extremities may draw attention to an association between hypertrophic pulmonary osteoarthropathy and idiopathic pulmonary fibrosis.

Infectious complications following isolated lung transplantation.

STUDY OBJECTIVE: To ascertain the incidence, types, morbidity, and mortality of infectious episodes in isolated lung transplant recipients. DESIGN: Retrospective chart review of patients who have undergone transplants over a six-year period in one institution. PATIENTS: Twenty-three single and 17 double lung transplants followed up between 2 and 68 months. RESULTS: Fifty-one episodes of infection occurred in the group with a slight predominance in the double lung transplants. The 32 episodes of bacterial infection constituted the largest group of infection and more than half of these were pneumonias. Organisms identified were predominantly Gram negative. While bacterial processes made up the bulk of infections, fatalities were rare. Viral and fungal infections were less common, but more often fatal. Of six cases of viral pneumonitis, two were fatal; two of five cases of invasive fungal infection were also fatal. Overall, six patients died of infection. CONCLUSION: Our findings support previous reports from heart-lung centers documenting a high rate of infectious complications, particularly pneumonia, in recipients of lung grafts. In our experience, bacterial infections are the most common (two of three infections), but have the lowest mortality. Efforts should be directed toward establishing effective prophylaxis programs and early detection of infection.

A placebo-controlled dose-finding study with bambuterol in elderly patients with asthma.

A new long-acting bronchodilator prodrug, bambuterol hydrochloride, was tested in a randomized, crossover, and double-blind study in elderly asthmatic patients (aged 64 to 82 years). They received placebo and 5-mg, 10-mg, and 20-mg tablets once daily for a week at each dose. The plasma concentration of the active metabolite, terbutaline, increased linearly with the dose of drug (p < 0.001). Peak expiratory flow rate increased with dose in the morning (p < 0.001 for 10-mg and 20-mg doses) and afternoon (p < 0.05 for 10 mg; p < 0.001 for 20 mg) and was different from placebo for the 10-mg/d and 20-mg/d regimens. The use of supplemental inhaled beta 2-adrenergic agonist therapy was reduced during the night for the 10-mg (p < 0.05) and 20-mg (p < 0.01) doses in comparison to placebo. No significant effects of treatment on blood pressure and pulse were demonstrated. Tremor and palpitations were mild and related to the dose. These data suggest that treatment once daily with bambuterol hydrochloride in a dose of 10 or 20 mg improves pulmonary function and is well tolerated as bronchodilator therapy in elderly patients with asthma.

Physiological determinants of nocturnal arterial oxygenation in patients with obstructive sleep apnea.

Among patients with similar degrees of obstructive sleep apnea (OSA) there is considerable variability in the degree of associated nocturnal hypoxemia. The factors responsible for this variability have not been clearly defined. Therefore we studied 44 patients with OSA to identify the physiological determinants of nocturnal arterial O2 saturation (SaO2). All patients underwent pulmonary function testing, arterial blood gas analysis, and overnight polysomnography. Mean nocturnal SaO2 ranged from 96 to 66% and apnea-hypopnea index from 11 to 128 per hour of sleep. Several anthropometric, respiratory physiological, and polysomnographic variables that could be expected to influence nocturnal SaO2 were entered into a stepwise multiple linear regression analysis, with mean nocturnal SaO2 as the dependent variable. Three variables [awake supine arterial PO2 (PaO2), expiratory reserve volume, and percentage of sleep time spent in apnea] were found to correlate strongly with mean nocturnal SaO2 (multiple R, 0.854; P less than 0.0001) and accounted for 73% of its variability among patients. Body weight, other lung volumes, and airflow rates influenced awake PaO2 and expiratory reserve volume but had no independent influence on nocturnal SaO2. In a further group of 15 patients with OSA a high correlation was obtained between measured nocturnal SaO2 and that predicted by the model (r = 0.87; P less than 0.001). We conclude that derangements of pulmonary mechanics and awake PaO2 (generally attributable to obesity and diffuse airway obstruction) are of major importance in establishing the severity of nocturnal hypoxemia in patients with OSA.

Airway infection.

Bronchitis in its acute and chronic forms with recurrent acute exacerbations is one of the most common reasons for physician visits, accounting for a significant cost to the health-care system, lost work days, and increased morbidity and mortality. Smoking and recurrent lower respiratory tract infections are major risk factors for chronic bronchitis. Therefore, smoking cessation and vaccination strategies are cornerstones of management in terms of halting disease progression and reducing the frequency of infectious exacerbations. Bacterial infection is the main culprit in acute flares of the disease. Routine antimicrobial therapy fails in a significant number of patients, and therapeutic failures lead to increased costs. Several stratification schemes have been proposed to improve initial antimicrobial selection. These schemes identify patient's age, severity of underlying pulmonary dysfunction, frequency of exacerbations, and the presence of comorbid illnesses as predictors for likely pathogens and to guide antimicrobial selection. This approach may reduce the risk for treatment failure, which would have significant medical and economic implications. Improved understanding of the roles of airway inflammation and infection in the pathogenesis of progressive airway disease, in addition to future studies examining the efficacy of newer classes of antimicrobials, should guide physicians to target early and effective treatment to high-risk patients.

Familial nonmedullary thyroid cancer. An emerging entity that warrants aggressive treatment.

OBJECTIVE: To determine whether familial nonmedullary thyroid carcinoma behaves like sporadic carcinoma of follicular cell origin. DESIGN: Retrospective review. SETTING: University medical center. PATIENTS: Fourteen patients were treated for familial nonmedullary thyroid carcinoma between 1980 and 1994. Thirteen families were identified, with 30 affected individuals. INTERVENTIONS: Patients were treated with total or completion total thyroidectomy. Thirteen additional operations were performed to control recurrent disease. MAIN OUTCOME MEASURES: Stage, recurrence, and survival. Patients were followed up for a mean of 6.5 years. RESULTS: In our 14 patients, 13 tumors were multifocal, and six of these were bilateral. The incidences of lymph node metastasis and local invasion were both 57% (n = 8). Seven patients (50%) had recurrences during follow-up. CONCLUSIONS: Familial nonmedullary thyroid carcinoma has a high incidence of multifocality and invasion and a high rate of local recurrence. Aggressive initial treatment and careful follow-up seem to be indicated.

The relationship of absorption characteristics and gastrointestinal side effects of oral antimicrobial agents.

Normal bowel flora play an important role in preserving gastrointestinal (GI) function. They inhibit colonization by pathogenic bacteria, help in the metabolism of by-products of drugs and endogenous substances, aid in the synthesis of vitamins, and stimulate nonspecific host immune systems that protect against potential pathogens. Antimicrobial agents that are poorly absorbed from the GI tract can substantially alter the bowel flora. Narrow-spectrum antimicrobial agents are less likely to disrupt the bowel flora than broad-spectrum agents. Drugs that undergo extensive enterohepatic circulation can also disrupt normal flora. Knowledge of the extent of GI absorption, bile excretion, and spectrum of activity allows prediction of the likelihood of GI side effects. For example, clindamycin, which is relatively poorly absorbed and has significant bile secretion, is associated with a high incidence of diarrhea. The use of an antibiotic with a relatively narrow spectrum, excellent GI absorption, and minimal bile excretion should reduce the incidence of GI side effects.