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Biomedical subjects

L Barr

Publications and source records attributed to L Barr.

At least 55 records · Page 3Linked to original sources
PubMed1987

A quantitative model of myosin phosphorylation and the photomechanical response of the isolated sphincter pupillae of the frog iris.

The time courses of isometrically recorded photomechanical responses of isolated sphincter pupillae of Rana pipiens can be accurately predicted by a set of differential equations derived from phosphorylation theory of smooth muscle contraction. We compared actual light-stimulated contractions with calculated ones over a wide range of stimulus intensities (56-fold) and durations (0.4-4.0 s). The hypothetical Ca++-calmodulin-myosin light chain kinase cascade acts as a "valve" to control the flow of ATP through a phosphorylation-dephosphorylation cycle. When the rate of flow of ATP through the phosphorylation-dephosphorylation cycle is increased, the percentage of phosphorylated myosin increases. The time courses of the concentrations of phosphorylated myosin during different responses are seen to be functions of the time courses of the opening and closing of the coupling cascade "valve." The calculations predict experimentally measurable intermediate variables, which can aid the investigation of the application of quantitative phosphorylation theory to amphibian sphincter pupillae and to smooth muscle in general.

Adenosine Triphosphate↗
PubMed1986

Trigerminal teratoma of the tonsil.

Teratomas of the head and neck in infants and children, though uncommon, should be included in the differential diagnosis of head and neck masses in this age group. Roentgenographic examinations should be an integral part of the initial evaluation. Characteristic tooth-like calcifications are often present within teratomas. Sonographic procedures may be useful in differentiation of cystic, solid, or mixed tumors. Computerized tomography may be recommended to evaluate the extent of the lesion and to assess intracranial involvement. As in the case we have presented, surgical excision is curative. Complications of surgery have been due to hemorrhage and/or respiratory difficulties.

Adult↗
PubMed1986

Prognostic implications of perineural spread in squamous carcinomas of the head and neck.

The occurrence and prognostic implications of perineural spread were examined in 239 patients with mucosal squamous carcinomas of the head and neck. Perineural spread was demonstrated in resections from 64 patients (27%), the majority having primary tumors at one of three sites: buccal cavity, larynx, and pharynx. Perineural spread near nodal metastases was uncommon. There was no evidence that perineural involvement was more commonly associated with large tumors or less differentiated ones. No association was established between perineural spread and coexistent lymph node deposits in the surgical resections. Perineural spread was, however, shown to be a statistically significant prognostic factor for an increased incidence of subsequent locoregional recurrence and for decreased survival.

Adult↗
PubMed1985

Immunohistochemical localization of basement membrane type IV collagen in invasive and metastatic squamous carcinomas of the head and neck.

The immunohistochemical localization of basement membrane type IV collagen was investigated with a mouse monoclonal antibody in major surgical resections from 25 patients with invasive squamous carcinomas of the head and neck. Irrespective of site, size or stage of the disease, the 16 primary invasive tumours were almost completely surrounded by a layer of type IV collagen. Focal abnormalities were regularly present, consisting of thickening and aggregation of type IV collagen together with attenuation and segmental loss. Similar changes were seen in metastatic squamous carcinomas in 36 cervical lymph nodes. It is suggested that the probable formation of a normal basement membrane protein by these squamous carcinomas indicates the preservation of a normal function of differentiating squamous epithelia. The results indicate that a major basement membrane component, type IV collagen, continues to co-exist with invasive and metastatic squamous carcinomas.

Adult↗
PubMed1984

Sodium channels in vertebrate hearts. Three types of saxitoxin binding sites in heart.

The affinity of saxitoxin binding to cardiac sarcolemmal and cytosolic fractions was examined across species. In amphibia (frog) the plasma membrane site demonstrated a high affinity (Kd approx. 5 X 10(-9) M) but the majority of the total sites in the homogenate appeared to be high affinity soluble sites (Kd approx. 2 X 10(-9) M). Chicken and turtle cardiac plasma membrane fractions bound [3H]saxitoxin with 500-fold less affinity (Kd values of approx. 2 X 10(-6) M). No binding was seen in the cytosol. The affinity of cardiac sarcolemmal binding in amphibians correlates quantitatively with the K0.5 for the inhibition of sodium currents. Physiological correlation of the low affinity saxitoxin sites in chicken and turtle with toxin concentrations necessary to inhibit the sodium current remains unclear. The hypothesis that frog cytosolic saxitoxin binding sites originated from sarcolemma during homogenization is examined. The presence of three types of saxitoxin binding sites in cardiac preparations supports the existence of sodium channel subtypes.

Animals↗
PubMed1984

Management of obstructed balloon catheters.

Failure of a balloon catheter to deflate is not uncommon and prevents its removal. Methods of overcoming the problem include traction, bursting the balloon by overinflation, dissolving it with solvents, puncturing it percutaneously with a needle, or puncturing it with a wire stylet passed through the catheter. All except the last technique have major disadvantages and are of questionable safety. Transcatheter puncture of the balloon was used in 16 patients to remove obstructed balloon catheters without any technical difficulty, distress to the patient, or complication. The procedure is safe, simple, and does not require an anaesthetic. If necessary it could be performed safely by nursing or paramedical staff without the patient having to be admitted to hospital. It is the method of choice for the management of this problem.

Aged↗
PubMed1983

Prospective evaluation of doxorubicin-induced cardiomyopathy resulting from postsurgical adjuvant treatment of patients with soft tissue sarcomas.

One hundred and one soft tissue sarcoma patients from an adjuvant chemotherapy study of the Surgery Branch, National Cancer Institute who had received greater than or equal to 430 mg/m2 (range, 430-600 mg/m2) of doxorubicin were followed for evidence of cardiomyopathy. Fourteen patients developed clinical congestive heart failure attributable to doxorubicin. Nine of these fourteen were evaluated by radionuclide angiography (RNA), and all were abnormal with mean ejection fraction both at rest and exercise less than 30%. Sixty-one asymptomatic patients were studied at least once with RNA. In this asymptomatic group, 13 of 61 patients (21%) had abnormal resting left ventricular function. Exercise studies identified an additional 19 abnormal individuals (31%). Overall incidence of cardiomyopathy, as evidenced by RNA, in the asymptomatic group was 52%. By including the fourteen symptomatic patients, the incidence of cardiomyopathy detected either clinically or by RNA in the 75 evaluated patients was 46%. Comparison of patients by age (less than 40 versus greater than 40) revealed a highly significant difference in the incidence of cardiomyopathy (P less than .001). Fourteen of 36 patients (38%) less than or equal to 40 had either clinical or RNA evidence of cardiotoxicity while 32 of 39 (82%) individuals greater than 40 demonstrated cardiomyopathy. No significant difference was seen in those asymptomatic patients in whom RNA was performed less than or equal to 12 months as compared with greater than 12 months after the end of doxorubicin treatment. In the entire group there was no apparent improvement in cardiomyopathy with time, but results suggest that left ventricular function in the group older than 40 years does deteriorate. The cardiac function of patients younger than age 40 appeared to remain stable or possibly improve with time after the completion of treatment. Sex, tumor location, and radiation treatment were not associated with an increased risk of cardiomyopathy. These results emphasize the dangers of full-dose doxorubicin therapy. This high incidence of cardiomyopathy became apparent because of our ability to prospectively evaluate a large group of patients with prolonged life expectancy that received adjuvant doxorubicin chemotherapy after surgery.

Adolescent↗
PubMed1983

The biologic activity of mast cell granules. V. The effects of antihistamine treatment on rat cutaneous early- and late-phase allergic reactions.

Mast cell-dependent late-phase allergic reactions (LPR) as sequelae of immediate hypersensitivity responses (IR) occur in both human and rat skin; thus the rat has served as a useful model to investigate the pathogenesis of cutaneous LPR. To analyze the roles that histamine might play in the generation of rat LPR, the effects of H1 and/or H2 antihistamines on both LPR and antecedent blueing responses (IR) were investigated. Systemically administered diphenhydramine and cimetidine, alone or in combination, reduced blueing reactions to histamine. However, blueing responses to anti-IgE were only partially abrogated by antihistamine treatment with diphenhydramine alone or the combination of antihistamines. Diphenhydramine treatment alone partially inhibited the histologic intensity of LPR in a dose-dependent manner. Although cimetidine treatment alone had no inhibitory effect, it potentiated the diphenhydramine-induced inhibition of LPR. The inhibitory action of antihistamine treatment was apparent only in reactions elicited by anti-IgE or mast cell granules containing histamine, since LPR caused by histamine-free mast cell granules were not affected by antihistamines. This observation suggests that the inhibitory effect of antihistamines on LPR was the result of a specific blockade of histamine receptors rather than the result of a nonspecific suppressive effect. Our findings demonstrate that cutaneous inflammation generated as a result of mast cell degranulation can be significantly reduced by treatment with H1 and H2 histamine receptor antagonists.

Animals↗
PubMed1983

The biologic activity of mast cell granules. VI. The effect of vinblastine-induced neutropenia on rat cutaneous late phase reactions.

Type I immediate hypersensitivity reactions in human and rat skin may be followed by late phase reactions (LPR). A consistent feature of both human and rat LPR is the early histologic appearance of neutrophils, which, in rats, is followed by the later appearance (8 to 24 hr) of mononuclear cells. To determine the importance of the neutrophil in the development of LPR, rats were depleted of neutrophils using parenteral injections of vinblastine sulfate (VS). VS produced a dose-dependent neutropenia, with the maximal effect on day 4. LPR that were induced with anti-IgE, isolated mast cell granules (MCG), or purified high (greater than 10,000 daltons) and low (500 to 10,000 daltons) m.w. fractions obtained from MCG were significantly abrogated in VS-treated rats. In neutropenic rats previously immunized with complete Freund's adjuvant, the intensity of inflammatory reactions produced by skin testing with purified protein derivatives was also significantly reduced. Administration of exogenous neutrophils to neutropenic animals partially reconstituted the reduced LPR. These data confirm and extend previous observations on the contribution of neutrophils to delayed hypersensitivity reactions and provide evidence that the neutrophil is critical for the development of rat cutaneous LPR as well.

Agranulocytosis↗
PubMed1982

Saxitoxin binding sites in frog-myocardial cytosol.

Cytosolic fractions of frog heart homogenates contain large amounts of a soluble, large molecular weight protein that binds the specific neurotoxin saxitoxin with the same high affinity as does the plasma membrane. Another neurotoxin, tetrodotoxin, which ordinarily is competitive with saxitoxin, does not displace saxitoxin from the cytosolic sites or from plasma membrane-enriched vesicular fractions even when its concentration exceeds that of saxitoxin by a factor of 1000. Thus, cytosolic sites are similar to membrane sites in this respect. The vesicular fraction accounts quantitatively for the amount of saxitoxin bound by whole ventricles, so that no appreciable losses seem to occur. Therefore, the cytosolic site probably is a membrane site precursor, although other possibilities cannot be ruled out. In any case, the occurrence of a soluble molecule closely related to the sodium channel provides opportunities for further study of the structure of the sodium channel.

Animals↗
PubMed1979

Action potentials can propagate along small strands of smooth muscle.

Bundles of taenia coli muscle as small as 25 micrometers in diameter were dissected from guinea pigs and incubated in an organ culture media for several days. We found that use of an organ-culture bathing solution greatly extended the in vitro responsiveness as well as survival of such small bundles. Electronmicrographs showed that surviving strands of cells constituted only a very small fraction of the cross section of these bundles. Nonetheless, still they supported propagating nondecrementing action potentials. This means that in some cases strands, only a few cells in cross section, supported propagating action potentials. The long length constant and parallel orientation of cells provide a basis assuming cells act as parallel core conductor segments. For these reasons we have called into question the notion that for propagation to occur there must be a facilitating cooperation between large numbers of smooth muscle cells in parallel. Indeed we suggest that the limiting size for propagation is a strand of single cells.

Action Potentials↗
PubMed1978

Antibody deposition in the pleura: a finding in drug-induced lupus.

Pleural tissues from a group of 36 consecutive patients comprised of 15 malignancies, 3 tuberculous, 2 rheumatoid arthritis, 3 procainamide-induced systemic lupus erythematosus (SLE) syndromes, 1 infectious mononucleosis, and 12 nonspecific pleural effusions undergoing needle biopsy were studied by immunofluorescent techniques for antibody deposition. Specific nuclear fluorescence was detected only in procainamide-induced SLE and was characterized by in vivo staining with either IgG, IgM, and in one case, also C3. C1q could not be detected. Two other patients who had antinuclear antibodies (ANA) in their peripheral blood did not have detectable in vivo antinuclear staining in their pleural tissue. The presence of in vivo fixation of ANA in the pleura may be of etiologic and diagnostic significance in procainamide-induced SLE syndrome.

Antibody Formation↗