Cardiopulmonary effects of high frequency positive-pressure ventilation versus jet ventilation in respiratory failure

Conventional ventilators are frequently used at high rates in the intensive care nursery to achieve adequate oxygenation and ventilation with reduced peak inspiratory pressure. The efficacy and limitations of high frequency positive-pressure ventilation (HFPPV) using a conventional ventilator were studied by comparing the cardiopulmonary effects of HFPPV with those of high frequency jet ventilation (HFJV) in an animal model of respiratory failure. Sixteen saline-lavaged rabbits were ventilated with either HFPPV or HFJV for 2 h using rates of 200 breaths/min, inspiratory to expiratory ratio of 1:2, and FIO2 of 1.0. As controls an additional eight lavaged rabbits were ventilated at conventional rates (40 to 60 breaths/min). Proximal peak inspiratory pressure as indicated on the ventilator manometer or drive pressure was adjusted to maintain acceptable blood gases. Cardiac output (CO) was measured by thermodilution. Although there was a significant decrease in cardiac function over time, there were no significant differences between the groups in CO or stroke volume. Satisfactory oxygenation and ventilation were maintained in all groups. Static respiratory system compliance and mean airway pressure were similar among the groups. Histologic examination of the lungs revealed no differences between the three ventilator groups. The results of this study indicate that both HFPPV and HFJV are effective in short-term maintenance of normal blood gases in respiratory failure without any discernable differences in their effects on cardiovascular function. At very high rates, however, increases in VT are not possible with HFPPV, which limits its usefulness and flexibility in respiratory failure.

Cutaneous and immunologic reactions to phenytoin

Phenytoin (diphenylhydantoin; Dilantin) is a highly effective and widely prescribed anticonvulsant and antiarrhythmic agent. Since 1938 it has been invaluable in the treatment of grand mal and psychomotor epilepsy. Hydantoin derivatives have been used medicinally for more than a half-century. In recent years dermatologists have broadened the indications for phenytoin use to include recessive dystrophic epidermolysis bullosa, linear scleroderma, and pachyonychia congenita. In spite of widespread use and popularity, it is interesting that the frequency of complications relating to drug therapy remains low, relatively speaking. Nevertheless, a broad spectrum of cutaneous and immunologic reactions to phenytoin have been reported. These range from tissue proliferative syndromes (side effects), drug hypersensitivity syndromes (allergic effects), and a possible linkage with lymphoma (idiosyncratic effects). Therapeutic and toxic reactions to this commonly prescribed drug are comprehensively reviewed, analyzed, and summarized in this monograph.

Spectrophotometric assay for ornithine decarboxylase

A rapid and sensitive spectrophotometric assay for ornithine decarboxylase is described. It is based on the observation that the product of ornithine decarboxylase, putrescine, reacts with 2,4,6-trinitrobenzenesulfonic acid to give a colored product soluble in 1-pentanol whereas ornithine does not. The amount of putrescine produced by the enzyme was determined by measuring the absorbance of the 1-pentanol extract of the reaction mixture at 420 nm, and by comparing the results to those obtained by the trapping of 14CO2 and by HPLC assays. The three assays were found to be equivalent in sensitivity, with the spectrophotometric assay having the advantages of being relatively rapid, requiring only common laboratory equipment, and not requiring the use of radioactive isotopes.

Spider bites

Spiders are a ubiquitous component of the fauna of North America. At least 50 to 60 species in the United States are known to bite humans, although in most cases, the diagnosis is never suspected nor is treatment necessary. A few species of spiders are capable of causing necrotic wounds and, occasionally, death. This review is intended to provide an overview of the recent advances in the diagnosis and treatment of spider bites, as well as a compilation of the many species of spiders that have been reported to give clinically important bites.

Immune precipitation and immunoblotting for the detection of Trypanosoma cruzi antigens

The efficiency of immunoprecipitation and immunoblotting for detecting Trypanosoma cruzi antigens using rabbit and mouse antisera has been examined. Comparison of the starting material for each technique showed that the extraction methods resulted in a similar range of polypeptides when assessed by apparent Mr. Reaction with either hyperimmune rabbit sera or a sequential series of sera from infected mice, showed a significant disparity in the range of antigens revealed by each technique. Epitopes on polypeptides greater than 50 kDa were poorly preserved by immunoblotting compared to immunoprecipitation; however, below this threshold both techniques were equally efficient. Under the conditions of assay, it is probable that immunoprecipitation allows effective detection of both sequence and conformational determinants, whereas immunoblotting favours the detection of sequence determinants alone.

Bipyridylium herbicide toxicity in vitro: comparative study of the cytotoxicity of paraquat and diquat toward the pulmonary alveolar macrophage

In vitro exposure of adult rat alveolar macrophages to either paraquat or diquat resulted in concentration dependent cytotoxicity (cell death). The herbicide paraquat, however was statistically significantly more potent toward these cells than was diquat. The LC50 value for paraquat (8-h exposure, 37 degrees C) was determined to be 0.94 mM [95% confidence interval (C.I.) 0.79-1.12 mM], whereas the corresponding LC50 value for diquat was 1.97 mM (C.I. 1.58-2.51 mM). Interestingly, diquat was shown to enter these cells to a much greater extent than was paraquat. The latter data, while seemingly contradictory to the above findings, is consistent with other reported findings in this study that show that cell respiration, as measured by loss of oxygen consumption, was more sensitive to diquat than it was to paraquat. Also, only paraquat cytotoxicity was found to be dependent on oxygen tension and could be altered by the presence of antioxidant enzymes in the culture medium. Both compounds, however, were found to be equipotent toward purified mitochondria. Both paraquat and diquat were able to uncouple oxidative phosphorylation and induce active oxygen species (superoxide anions and hydrogen peroxide) from this organelle. It is concluded that free-radical pathology is the most likely mechanism of action by which paraquat is cytotoxic toward these cells, but that diquat poisoning probably originates from some other mode of action.

Macroglossia. An unusual presentation of pemphigus vulgaris

A 19-year-old woman presented with macroglossia of five months' duration and without bullae or erosions. A biopsy revealed a picture consistent with pemphigus vulgaris. The patient subsequently developed typical oral erosions. Her tongue enlargement and oral ulcerations improved dramatically with topical and systemic steroid therapy. Pemphigus vulgaris should be considered in the differential diagnosis of macroglossia.

Lenticular psoralen photoproducts and cataracts of a PUVA-treated psoriatic patient

Psoralen photoproducts were identified in association with cataracts in a psoriatic patient several years after oral methoxsalen plus ultraviolet A light (PUVA) therapy. Patients should be required to wear adequate optical protection not only during PUVA therapy but 24 hours following ingestion of methoxsalen.

Acquired dermal smooth-muscle hamartoma

We report a patient with a hyperpigmented, non-hairy plaque on the forearm. The presence of disorganized smooth-muscle bundles within the dermis proved this lesion to be a dermal smooth-muscle hamartoma. The relationship of this lesion to the pigmented hairy nevus of Becker is discussed.

Paraquat toxicity in vitro. I. Pulmonary alveolar macrophages

When the herbicide paraquat (1,1'-dimethyl-4,4'-bipyridylium) was administered to adult rat pulmonary alveolar macrophages (PAM) in primary culture, both a time-dependent and a dose-dependent cytotoxic response (cell death) was observed. An LD50 value of 1 mM was calculated when these cells were exposed to paraquat in vitro for 12 h in Ham's F12 culture medium at 30 degrees C. Cell death was accompanied by the formation of TBA-reactive substances (lipid peroxidation) and was potentiated by hyperoxia (95% O2). In a 95% O2-5% CO2 atmosphere, an LD50 value of 0.1 mM was calculated. In addition, the presence of superoxide dismutase in the culture medium (1700 units/ml) inhibited the cytotoxic response. Since [14C]paraquat was not absorbed into these cells, extracellular superoxide anion radical formation was investigated as the cause of the observed cell death. Paraquat (0.5 mM) was found to stimulate extracellular O-2 generation, from PAM, but only in nonactivated cells. A sevenfold enhancement over the resting rate of radical generation was observed in the presence of paraquat. No increase in the O-2 generation rate of activated macrophages was observed upon the addition of paraquat to the culture medium. These data indicate that paraquat is cytotoxic to the pulmonary alveolar macrophage and further suggest that this cytotoxicity is mediated, at least in part, by an excess, extracellular production of active oxygen species. Implications of these findings with respect to the currently accepted hypothesis of paraquat poisoning in vivo are discussed.

Oral ibuprofen and tetracycline for the treatment of acne vulgaris

A prospective evaluation of the efficacy and safety of oral ibuprofen and tetracycline hydrochloride was conducted for 8 weeks in patients with moderately severe acne. Sixty-eight patients were randomly assigned in a double-blind fashion to one of four regimens: (1) one 600 mg ibuprofen tablet plus one 250 mg tetracycline capsule four times daily; (2) one 600 mg ibuprofen tablet plus one placebo capsule four times daily; (3) one 250 mg tetracycline capsule plus one placebo tablet four times daily; and (4) one placebo tablet and one placebo capsule four times daily. Sixty patients completed the 8-week study. The mean percent improvement in the groups treated with ibuprofen and tetracycline (56% +/- 5 SE), ibuprofen alone (26% +/- 13 SE), or tetracycline alone (26% +/- 9 SE) was statistically significant. However, only the combination of ibuprofen and tetracycline therapy had an effect statistically better than the placebo response (16+ +/- 11 SE). Adverse effects were transient and were similar in all four groups.

Nifedipine in scleroderma ulcerations

Cutaneous ulcerations may be due to a variety of causes, including vasculitis, infections, arterial insufficiency, and microvascular damage. The net effect is diminished blood flow to the skin. Nifedipine, a calcium antagonist, has been shown to improve cutaneous blood flow and to alleviate reactive vasospastic ischemia (Raynaud's phenomenon). The authors report an ischemic ulcer of scleroderma showing visible improvement with nifedipine therapy.

Cryotherapy improves prurigo nodularis

A 55-year-old black woman with an eight-year history of prurigo nodularis was treated successfully with blistering cryotherapy. Cryotherapy resulted in smooth macule formation and afforded extended relief of pruritus. Several standard modalities of treatment had been used previously and had resulted in only partial relief of symptoms and minimal reduction of nodule size. This case demonstrates that cryotherapy can be a useful therapeutic alternative for prurigo nodularis.

Dermographism: a review

Urticaria is one of the more common skin conditions seen by physicians. Physical agents are an important cause of urticaria, with pressure or shearing forces being the most common. Dermographism is due to a combination of pressure and shearing forces and is present in a large number of healthy individuals. The purpose of this article is to provide a review of dermographism and its clinical variants.

Physiologic skin changes in pregnancy

Pregnancy produces many skin changes, some of which are specifically related to pregnancy (dermatoses of pregnancy) and others that are more common and called physiologic. These physiologic skin changes usually do not impair the health of the mother or the fetus; nevertheless, some can be cosmetically significant and of importance to the dermatologist.

Behçet's disease

Behçet's disease is a multisystem disease featuring mucocutaneous, ocular, intestinal, articular, vascular, urogenital, and neurologic involvement. While classically intermittent in its manifestations, the disease can stabilize and become chronic in a given organ system. The diagnosis of Behçet's disease is based on clinical criteria. Recurrent aphthous ulcerations in the mouth, skin lesions, eye lesions, and genital ulcerations must be present during the course of the disease for a diagnosis of Behçet's disease to be made unequivocally. A nonspecific skin hyperreactivity called pathergy is said to be helpful in the diagnosis. There are no pathognomonic laboratory findings, but biopsy usually shows a venulitis. The pathogenesis of the disease is unknown. No virus has been satisfactorily isolated to date. There is evidence of an increased frequency of HLA-B5 and HLA-B12. Humoral and cellular immunity seem to play a major part in the pathogenesis of the various manifestations of the disease. The treatment of Behçet's disease is difficult to evaluate because of the many spontaneous exacerbations and remissions during the clinical course of the disease. Topical corticosteroids for orogenital ulcers and ocular inflammation are helpful. Intralesional injections for affected joints and retrobulbar tissues are useful in some cases. Systemic corticosteroids have appeared to be helpful for all manifestations of the disease. It is customary to use 60 mg of prednisone by mouth daily during acute exacerbations, then to taper as the condition improves. Chlorambucil has been shown to be safe and effective for various manifestations of Behçet's disease; often it is used in combination with corticosteroids.(ABSTRACT TRUNCATED AT 250 WORDS)

Pigmented purpuric lichenoid dermatitis of Gougerot-Blum mimicking Kaposi's sarcoma

A case of pigmented purpuric lichenoid dermatitis of Gougerot-Blum is presented and the pertinent literature is reviewed. This case is unusual in that the lesions were unilateral and very limited in extent. The patient presented with a localized pigmented purpuric eruption of plaques on the dorsum of one foot which mimicked Kaposi's sarcoma. However, a biopsy confirmed the diagnosis of pigmented purpuric lichenoid dermatitis of Gougerot-Blum.

A comparison of serum phenytoin determination by the substrate-labeled fluorescent immunoassay with gas chromatography, liquid chromatography, radioimmunoassay and "EMIT"

Patients' sera were analyzed for phenytoin by the Substrate-Labeled Fluorescent Immunoassay (SLFIA), gas chromatography (GC), liquid chromatography (LC), Radioimmunoassay (RIA) and EMIT and the results were compared. The EMIT assay was performed using a "PACER Analyzer". All assay results compared favorably. The correlation coefficients were: SLFIA vs GC, 0.995 (n = 45); SLFIA vs. LC, 0.993 (n = 37); SLFIA vs. EMIT, 0.965 (n = 67); SLFIA vs. RIA, 0.977 (n = 34). These results show that phenytoin levels determined by the SLFIA compare well with those obtained by the other four assay techniques.

Substrate-labeled fluorescent immunoassay for phenytoin in human serum

A homogeneous substrate-labeled fluorescent immunoassay has been applied to the measurement of phenytoin concentrations in human serum. We coupled a fluorogenic enzyme substrate, galactosyl-umbelliferone, covalently to a derivative of phenytoin. Under assay conditions, this drug-substrate conjugate was nonfluorescent but became fluorescent upon hydrolysis catalyzed by bacterial beta-galactosidase. When antibody to phenytoin is bound to the drug-substrate conjugate, it is inactive as an enzyme substrate. Addition of phenytoin to competitive-binding reactions relieves the inactivation, and the resulting fluorescence is proportional to the phenytoin concentration. We validated the fluorescent immunoassay by comparing values for phenytoin obtained with this technique to those obtained by gas chromatography and by enzyme immunoassay (EMIT). All three methods correlated well. The major metabolite of phenytoin, 5-(p-hydroxyphenyl)-5-phenylhydantoin, and other drugs at concentrations expected in serum had no effect on the assay. The fluorescent immunoassay is rapid and simple to perform and requires only 2 microL of serum sample per test.

Substrate-labeled fluorescent immunoassay for phenytoin in human serum

A homogeneous substrate-labeled fluorescent immunoassay has been applied to the measurement of phenytoin concentrations in human serum. We coupled a fluorogenic enzyme substrate, galactosyl-umbelliferone, covalently to a derivative of phenytoin. Under assay conditions, this drug-substrate conjugate was nonfluorescent but became fluorescent upon hydrolysis catalyzed by bacterial beta-galactosidase. When antibody to phenytoin is bound to the drug-substrate conjugate, it is inactive as an enzyme substrate. Addition of phenytoin to competitive-binding reactions relieves the inactivation, and the resulting fluorescence is proportional to the phenytoin concentration. We validated the fluorescent immunoassay by comparing values for phenytoin obtained with this technique to those obtained by gas chromatography and by enzyme immunoassay (EMIT). All three methods correlated well. The major metabolite of phenytoin, 5-(p-hydroxyphenyl)-5-phenylhydantoin, and other drugs at concentrations expected in serum had no effect on the assay. The fluorescent immunoassay is rapid and simple to perform and requires only 2 microL of serum sample per test.

Hyperreactivity, muricide, and intraspecific aggression in the rat produced by infusion of local anesthetic into the lateral septum or surrounding areas

Intracranial infusions of a local anesthetic (lidocaine, 2%) were made bilaterally (4 microliter over 20 min) through permanently implanted cannulas ending in the lateral septum or adjacent areas. Increases in irritability and reactivity to the experimenter, muricide, and intermale aggression were produced by injections into the lateral septum and the region ventral to it. The increases in reactivity and interanimal aggresion occurred in varying degrees and were independent of one another, but intermale aggression occurred only in animals showing muricide. The most effective site for eliciting the entire spectrum of aggressive behaviors was the region ventral to the anterior septum. The region ventral to the posterior septum (medial preoptic area, anterior hypothalamic area, straia terminalis) was unique in that it tended to produce a high incidence of muricide, with only modest increases in reactivity. The lateral septum was moderately effective in producing the entire range of aggressive behaviors. No changes in behavior were noted with infusions into the medial septum or th medial forebrain bundle/lateral preoptic area ventrolateral to the septum. It is suggested that the hyperreactivity and irritability may be relat to hyperdefensiveness and that muricide and intermale aggression are points on a continuum of interanimal aggressiveness.

Homogeneous reactant-labeled fluorescent immunoassay for therapeutic drugs exemplified by gentamicin determination in human serum

We applied a homogeneous reactant-labeled fluorescent immunoassay to the measurement of therapeutic drug concentrations in human serum, exemplified here by gentamicin. A derivative of umbelliferyl-beta-galactoside was coupled covalently to the drug and this conjugate was found to be nonfluorescent under assay conditions. The drug/dye conjugate was a substrate for bacterial beta-galactosidase and yielded a fluorescent product. When the drug/dye conjugate was bound to anti-gentamicin antibody it was inactive as an enzymatic substrate. This inactivation was relieved by the presence of gentamicin in competitive binding reactions. Hence, the rate of production of fluorescence was proportional to the gentamicin concentration. The fluorescent assay yielded values which compared favorably to a radioimmunoassay for gentamicin in clinical serum samples (r=0.94, standard error of estimate=0.66 mg/liter). The fluorescent assay requires only 1 microliter of serum and offers several advantages over existing techniques: sensitivity, specificity, simplicity, and the obviation of radioisotopes.

Homogeneous reactant-labeled fluorescent immunoassay for therapeutic drugs exemplified by gentamicin determination in human serum

We applied a homogeneous reactant-labeled fluorescent immunoassay to the measurement of therapeutic drug concentrations in human serum, exemplified here by gentamicin. A derivative of umbelliferyl-beta-galactoside was coupled covalently to the drug and this conjugate was found to be nonfluorescent under assay conditions. The drug/dye conjugate was a substrate for bacterial beta-galactosidase and yielded a fluorescent product. When the drug/dye conjugate was bound to anti-gentamicin antibody it was inactive as an enzymatic substrate. This inactivation was relieved by the presence of gentamicin in competitive binding reactions. Hence, the rate of production of fluorescence was proportional to the gentamicin concentration. The fluorescent assay yielded values which compared favorably to a radioimmunoassay for gentamicin in clinical serum samples (r=0.94, standard error of estimate=0.66 mg/liter). The fluorescent assay requires only 1 microliter of serum and offers several advantages over existing techniques: sensitivity, specificity, simplicity, and the obviation of radioisotopes.