Scanning electron microscopic study and shear bond strength measurement with 5% and 37% phosphoric acid

Direct bonding of orthodontic attachments has become a clinical reality with the application of the acid etch technique, using 37% phosphoric acid. The objective of this study was to detect the etch pattern with scanning electron microscopy and the shear bond strength with a Hounsefield tensometer (Nene Instruments Ltd., Northampton, England) by using 37% and 5% phosphoric acid (H3PO4). It was observed that with 5% H3PO4 there was minimal enamel loss compared with 37% H3PO4. There was no significant difference in shear bond strength, when enamel surface was etched with 5% H3PO4 and 37% H3PO4.     

Interaction of fluorescent probes with membranes of sarcoplasmic reticulum in AMP deamination

Gentamicin and ampicillin were dissolved in an L-amino acid solution especially prepared for newborn infants and infused intravenously over 24 h in 7 babies with serious neonatal surgical problems. Serum concentrations of the antibiotics were maintained rather constant and well above the minimal inhibitory concentration for most bacterial strains. One very sick newborn infant died with overwhelming Klebsiella pneumoniae septicemia. No signs of renal toxicity or ototoxicity were found. The serum amino acids remained within the normal range, except in 1 child with cytomegalovirus infection and liver insufficiency.     

Effect of angiotensin-converting enzyme inhibition on bronchial responsiveness

BACKGROUND: Many studies have shown that CA 125 levels frequently rise prior to clinical evidence of progression of ovarian cancer. For clinical trials an accepted definition of progression according to CA 125 is required. We therefore determined what change in CA 125 level was the most accurate predictor of relapse in patients on follow up after therapy for ovarian cancer. PATIENTS AND METHODS: Serial CA 125 levels were studied from 255 patients entering the North Thames Ovary Trial of 5 versus 8 courses of chemotherapy. An initial analysis was made 2 months after closure of the trial, a more detailed analysis was made after 81 confirmed relapses among evaluable patients and a final analysis was made one year later with longer follow-up. RESULTS: On the basis of the results from the interim analyses and the cut-off level of 22-35 U/ml used by different laboratories, 30 U/ml was chosen as the upper limit of normal. In the final analysis a doubling of CA 125 from the upper limit of normal was defined as progression. Using this method sensitivity was 85.9%, specificity 91.3%, positive predictive value 94.8%, and negative predictive value was 77.8%. Insisting on a confirmatory elevated CA 125 level reduced the false positive rate to < 2% with a sensitivity of 83.9%. The median lead-time prior to clinical progression was 63 days. CONCLUSION: A confirmed rise of serum CA 125 level to more than twice the upper limit of normal during follow up after first line chemotherapy accurately predicts tumour relapse.     

Massive haemoptysis death and other morbidity associated with high dose rate intraluminal radiotherapy for carcinoma of the bronchus

Fluctuation analysis allows for the determination of mutation rates in cell cultures in vitro. As originally described by Luria and Delbruck and extended by Lea and Coulson and by Capizzi and Jameson, this analysis has been useful in estimating mutation rates in cultured cells where the frequency of mutational events is low. However. in cultures where high mutation rates and multiple independent mutation events occur, leading to the accumulation of many mutant cells, these standard methods may not apply. Here, we present a new method for the estimation of mutation rates based on the assumption that multiple events may contribute to the accumulation of mutant cells. We compared mutation rates determined by Lea and Coulson's and by Capizzi and Jameson's methods with those determined by our method using experimental and stimulated data from our studies of immunoglobulin gene mutation and isotype switching in B lymphocyte cultures. The three methods resulted in very different calculated rates when many mutants were present in the culture, such as when mutation rates were high, while only small differences in calculated rates were found when mutants were rare. Unlike previous fluctuation analysis calculations, our method is applicable for the estimation of both low and high rates.     

Dopamine release in the nucleus accumbens by hypothalamic stimulation-escape behavior

It is known that lateral hypothalamic stimulation or self-stimulation can release dopamine in the nucleus accumbens (NAc). The present experiment illustrates that an aversively motivated behavior can also do this. Rats were prepared with microdialysis probes in the NAc and electrodes in the lateral hypothalamus (LH) or medial hypothalamus (MH). Automatic stimulation of the LH increased extracellular dopamine in the NAc 30% as reported earlier. The animals would perform both self-stimulation to turn the current on and stimulation-escape to turn it off, suggesting a combination of reward and aversion. Escape responding increased extracellular dopamine (DA) 100%, even though there was less total stimulation. Automatic stimulation of the MH did the opposite of the LH by decreasing accumbens dopamine (-20%), and the animals would only perform stimulation-escape, indicative of pure aversion. But again, extracellular DA in the NAc increased 100% during escape responding. Thus DA can be released during negative reinforcement when an animal's behavior is reinforced by escape from lateral or medial hypothalamic stimulation. This suggests that DA release was correlated with stimulation-escape behavior, rather than the aversiveness of automatic stimulation.     

The biotype and genetic characteristics of an isolate of the cowpox virus causing infection in a child

The study included 138 patients operated on for endo-extracellular pituitary adenomas which extend both intracranially and into the structures of the base of the skull. Operations via transcranial and transsphenoidal access to various tumor sites were performed in 38 patients (a main group), while 100 patients (a control group) underwent one of these operations. Two-stage operations, followed by removal of the suprasellar and basal regions of a tumor, are expedient for enhancing the efficiency of surgical treatment, reducing the incidence of complications associated with traumatic attempts at removing tumor parts hard-to-reach by transcranial or transsphenoidal approaches, as well as at reducing the number of relapses. At the first stage of surgical treatment it is advisable to make an intervention via transcranial access especially in cases of complex configuration of the suprasellar part of a tumor. The recommended interval between transcranial and transsphenoidal surgeries is 3-5 months. Two-stage surgical treatment does not lead to significant structural changes and to the increased number of complications, and to higher mortality rates as compared to one-stage surgery (transcranial or transsphenoidal surgeries alone).     

Interaction between muscle stiffness and stretch reflex sensitivity after long-term stretch-shortening cycle exercise

The short latency stretch-reflex component (M1) and its interactions with muscle stiffness and with muscle performance were investigated before and after long-term stretch-shortening cycle (SSC) exercise. Dramatic fatigue induced reduction in maximal SSC performance capability, and electromyographic activity was accompanied by a consistent decrease in the M1 reflex component and eccentric peak stiffness of the muscle. It can be suggested, therefore, that the decreased muscle performance is not simply a direct effect of central or peripheral fatigue, but is partly due to impairment of the ability to utilize stiffness-related elastic energy.     

Monte carlo simulation for molecular gas dynamics

The dynamics of low-density flows is governed by the Boltzmann equation of the kinetic theory of gases. This is a nonlinear integro-differential equation and, in general, numerical methods must be used to obtain its solution. The present paper, after a brief review of Direct Simulation Monte Carlo (DSMC) methods due to Bird, and Belotserkovskii and Yanitskii, studies the details of theDSMC method of Deshpande for mono as well as multicomponent gases. The present method is a statistical particle-in-cell method and is based upon the Kac-Prigogine master equation which reduces to the Boltzmann equation under the hypothesis of molecular chaos. The proposed Markoff model simulating the collisions uses a Poisson distribution for the number of collisions allowed in cells into which the physical space is divided. The model is then extended to a binary mixture of gases and it is shown that it is necessary to perform the collisions in a certain sequence to obtain unbiased simulation. A part of the material in this paper was presented at the Minisymposium 2 of the ICIAM 87 held in Paris during June 29-July 3, 1987.