Thermodynamic stability of immunoglobulins and allosteric interactions with ferritin and protein A: distinct properties of the two antibodies of IgG2a subclass

The two anti-ferritin monoclonal antibodies of mouse IgG2a subclass, G10 and F11, are described that have similar affinity to human spleen ferritin and identical protein A-binding affinity. Antigen binding was shown to change significantly the protein A-binding parameters of the IgG2a antibodies. Antigen-induced conformational changes result in enhanced protein A-binding affinity of the G10 antibody while reduced affinity of the F11 antibody. Antigen binding does not change inherently low affinity of the anti-ferritin IgG1 antibody C5 to protein A. Differential scanning calorimetry revealed that the enthalpy and Gibbs free energy of denaturation for G10 was respectively by 19 and 29% higher than the corresponding parameters for F11. The lower structural energetics of F11 is associated with the lack of a calorimetrically revealed folding unit that may be responsible for distinct interaction between the antigen-binding and protein A-binding sites. This work provides experimental demonstration of the fact that functionally significant interactions between the two spatially remote recognition sites in antibodies of the same heavy chain isotype can be modulated by relatively small structural variations that also result in different thermodynamic stability.     

HMPAO brain SPECT in acute carbon monoxide poisoning

Technetium-99m-hexamethylpropylene amine oxime (HMPAO) brain images with fanbeam SPECT, in combination with surface three-dimensional display, were used to detect basal ganglion and cerebral cortex anomalies in the acute phase of carbon monoxide (CO) poisoning. METHODS: Ten patients, aged 16-29 yr, with acute CO poisoning and no past history of neurologic disorders were enrolled in this study. After oxygen treatment, all 10 patients were investigated using 99mTc-HMPAO brain images with fanbeam SPECT and surface three-dimensional display. Meanwhile, 6 of 10 patients also received a brain CT scan. RESULTS: CT scan findings were negative in all 6 patients. Fanbeam SPECT demonstrated unilateral or bilateral hypoactivity of basal ganglia in 6 patients. Local hypoactivity anomalies were found in the brain cortex of 7 patients, using surface three-dimensional display of the brain. Only 2 of 10 patients had normal 99mTc-HMPAO brain images. CONCLUSION: This study suggests that, in comparison with traditional brain imaging techniques, 99mTc-HMPAO brain imaging with fanbeam SPECT in combination with surface three-dimensional display is a better tool for early detection of regional cerebral anomalies in acute CO poisoning.     

Activation of the human estrogen receptor by estrogenic and antiestrogenic compounds in Saccharomyces cerevisiae: a positive selection system

OBJECTIVE: To develop a slow-release carboplatin formulation for intratumoral administration to cats. DESIGN: Preliminary study to analyze pharmacokinetic effects of purified sesame oil in the carboplatin formulation for intratumoral administration, and a second study to evaluate the efficacy and toxicosis of intratumoral administration of carboplatin in purified sesame oil. ANIMALS: 23 cats with squamous cell carcinomas of the nasal plane. PROCEDURE: Eight cats with advanced-stage tumors were submitted to intratumoral administration of 100 mg of carboplatin/m2 of body surface area, with or without purified sesame oil, using a two-period, cross-over design. Fifteen additional cats were treated by intratumoral administration of carboplatin in purified sesame oil. Four weekly intratumoral chemotherapy injections of carboplatin in purified sesame oil at a dosage of 1.5 mg/cm3 of tissue were given. RESULTS: Purified sesame oil in the formulation significantly reduced systemic exposure to carboplatin and drug leakage from the sites of injection. Cumulative effects of repeated intratumoral administrations on plasma concentrations of carboplatin were not observed. Systemic toxicosis was not observed, and local toxicosis was minimal. Healing of ulcerated lesions was not compromised. Rates of complete clinical tumor clearance and complete response were 67 and 73.3%, respectively. Product-limit estimates of mean progression-free survival times was 16 +/- 3.3 months. The 1-year progression-free survival rate was 55.1 +/- 13%. Local recurrence was observed in 7 cats; 4 had marginal tumor recurrence, and 3 had in-field and marginal tumor recurrence. CONCLUSIONS: Intratumoral carboplatin chemotherapy is safe and effective for cats with squamous cell carcinoma of the nasal plane. Future studies to improve treatment efficacy could include evaluation of increased dose-intensity as well as combination of this modality with radiotherapy. CLINICAL RELEVANCE: Intratumoral administration of carboplatin in a water-sesame-oil emulsion was found to be a practical and effective new treatment for facial squamous cell carcinomas in cats.     

Defective repair of oxidative damage in mitochondrial DNA in Down''s syndrome

BACKGROUND: Synthetic homopyrimidine peptide nucleic acids (PNAs) can bind complementary targets in double-stranded DNA, generating strand-displacement complexes, and so offering an opportunity to modulate specific gene expression. Several issues remain to be addressed before these attributes can be exploited in vivo, however. RESULTS: The kinetics of the interaction between a homopyrimidine PNA and a complementary homopurine target on double-stranded DNA were analyzed in the presence or absence of a preformed strand-displacement complex proximal to the target. The complex was established under low salt conditions by the binding of a different homopyrimidine PNA to a target situated adjacent to the first PNA target. These two targets were placed next to each other on opposite strands at distances of 0, 2, 4 and 8 base pairs apart. The presence of a preformed strand-displacement complex near the target accelerates the binding of PNA to double-stranded DNA in a salt-dependent manner. The influence of salt on the binding rates was also examined. The binding rate is increased by a factor of 1 x exp(70[NaCl]), that is, 16-fold at 40 mM NaCl and more than 10(4)-fold if extrapolated to 140 mM NaCl. This effect is significantly reduced if the two targets are 2 base pairs apart and completely absent if the distance is 4 base pairs or more. CONCLUSIONS: The perturbation of the DNA helix imposed by a PNA strand-displacement complex only propagates a few base pairs. It is therefore possible to target sites in the immediate vicinity of strand invasion complexes specifically. The results presented have implications for the mechanism of strand displacement and for the application of PNA in a genomic context.     

Tonsillar carcinoma: analysis of treatment results

A diffusion cell with an artificial membrane and the single-pass perfused rabbit ear were used to evaluate the percutaneous absorption of clonazepam from various 2-hydroxyethyl acetate (HEA) patches. The influence on drug permeation of the various type of enhancers (isopropylmyristate, lauryl alcohol, propylene glycol and water) in the patches was tested. A comparison between the two types of systems of percutaneous absorption of clonazepam has been done. The results showed that HEA patches produce controlled uniform drug release, modulated by the addition of enhancers.     

Clinical correlates of circulating immune complexes and antibody reactivity in squamous cell carcinoma of the head and neck. The Department of Veterans Affairs Laryngeal Cancer Study Group

PURPOSE: To evaluate the correlation between the presence and titer of host-derived antibody reactivity, circulating immune complexes, and clinical course and prognosis in patients with squamous cell carcinoma of the head and neck (SCCHN). MATERIALS AND METHODS: Serum samples, obtained from untreated patients with squamous cell carcinoma of the larynx entered onto a multiinstitutional trial, were evaluated for the presence of elevated circulating immune complexes (221 patients) and host-derived antibody directed against two SCCHN cell lines (107 patients). RESULTS: Patients had significantly elevated levels of circulating immune complexes as measured by C1q binding compared with normal controls. Patients with higher levels of circulating immune complexes were less likely to respond to chemotherapy. No correlations were noted between immune complex levels and stage of disease, nodal status, site of disease, recurrence, or survival. Evaluation of native antibody titers for their relationship to clinical correlates showed no statistically significant associations. In sera subjected to immune complex dissociation, patients with moderately or poorly differentiated tumors had significantly higher antibody titers when compared with patients with well-differentiated tumors. Because marked variation in the increase of antibody titers following immune complex dissociation was noted, the ratio of immune complex-dissociated to native antibody titer was examined. Patients with a high ratio had a lower proportion of complete and partial responses to chemotherapy. CONCLUSION: Our results support the conclusion that the formation of tumor-associated immune complexes in patients with SCCHN is associated with a decreased response to chemotherapy.     

Non-penetrance and late appearance of polyps in families with familial adenomatous polyposis

One case of non-penetrance of the familial adenomatous polyposis (FAP) gene at 59 years of age and late onset of polyps on endoscopy and biopsy in this and two other families is described. Screening protocols should include dental screening as well as indirect ophthalmoscopy and endoscopy to detect minimal manifestations of the gene. In the absence of a specific DNA predictive test, bowel screening should continue well beyond 30 years of age.