Absolute electronegativity and hardness correlated with molecular orbital theory

The concepts of absolute electronegativity, χ, and absolute hardness, η, are incorporated into molecular orbital theory. A graphic and concise definition of hardness is given as twice the energy gap between the highest occupied molecular orbital and the lowest unoccupied molecular orbital. Useful correlations can now be made between chemical behavior, visible-UV absorption spectra, optical polarizability, ionization potentials, and electron affinities.     

The impact of SARS-CoV-2 on the cystic fibrosis foundation therapeutics development network

The Severe Acute Respiratory Syndrome Coronavirus (SARS-CoV-2) global pandemic significantly impacted CF clinical research within the Cystic Fibrosis Foundation Therapeutics Development Network (CFF TDN). A Research Electronic Data Capture (REDCap) survey was developed and sent to network sites to monitor and understand the impact on research teams, ongoing and anticipated clinical research, and specific clinical and research procedures. Key findings indicated an early impact on participant enrollment, research team stability, and procedures such as spirometry and sputum induction. These trends steadily improved over the months as research activities began to recover across the TDN. While SARS-CoV-2 created a significant challenge it also highlights new opportunities to expand CF research with greater focus on data collection outside of research centers and increased access for remote participation.     

The physical properties of a polyacetal denture resin

A polyacetal injection-moulded resin is being marketed for the construction of retentive and supportive components of removable partial dentures (RPDs). Specimens of poly(oxymethylene) cast by commercial laboratories were tested to examine the following physical characteristics: the modulus of elasticity in compression, extension and flexure, stress relaxation, the force displacement behaviour of clasp forms, impact strength and glass transition temperature. Results showed that the material has a flexural modulus lower than that of poly(methylmethacrylate) and is insufficiently rigid to be used as a supporting element for partial dentures. Resin clasps may be resilient enough to engage undercuts for the retention of RPDs but the low flexural modulus requires that the resin be used in greater cross-sectional area than metal alloys in order to gain useful retention. This greater bulk has implications for plaque accumulation and maintenance of periodontal health.     

Cationic-amphiphilic arpromidine-derived guanidines and a histamine trifluoromethyl-toluidide derivative may activate pertussis toxin-sensitive G-proteins by a receptor-independent mechanism

Formyl peptides activate superoxide anion (O₂ ^–) formation in human neutrophils and in HL-60 cells via pertussis toxin (PTX)-sensitive guanine nucleotide-binding proteins (G-proteins), and histamine (HA) mediates inhibition of O₂ ^– formation via H₂-receptors. We have studied the effects of lipophilic arpromidine-derived guanidines, which are potent, full H₂-receptor agonists in the guinea pig atrium, on O₂ ^– formation and on activation of G-proteins in HL-60 membranes and on purified G-proteins. We have also studied the effects of a HA trifluoromethyl-toluidide derivative (HTMT), a cationic-amphiphilic HA derivative which activates O₂ ^– formation in HL-60 cells through a mechanism which is independent of known HA receptor subtypes, on G-protein activation. Guanidines, at concentrations, up to 30 mol/l inhibited and, at concentrations above 30 mol/l, enhanced formyl peptide-induce O₂ ^– formation in neutrophils. In HL-60 cells, guanidines per se activated O₂ ^– formation. The stimulatory effects of guanidines on O₂ ^– formation were not inhibited by H₁- or H₂-receptor antagonists. In HL-60 membranes, guanidines and HTMT, activated high-affinity GTPase in a PTX-sensitive manner. These substances also increased GTP hydrolysis effected by transducin and G_i/G_o-proteins. Our data suggest that lipophilic guanidines and HTMT may act as receptor-independent activators of PTX-sensitive G-proteins, resulting in stimulation of O ₂ ^– formation.     

A comparative study of etching enamel by acid and laser

Acid etching is regarded as one of the main means of providing additional retention in aesthetic dentistry. Alternative methods of achieving bonding to tooth tissue which have been proposed include laser etching. Conflicting results on bond strength to enamel have been reported for laser etching. Here the tensile bond strength of composite resin to acid- and laser-etched enamel was measured and the topographical differences between the surfaces were evaluated using the scanning electron microscope. The laser used was a pulsed Nd-YAG laser at 10 pulses per second with a pulse length of 150s, 80mJ pulse^–1, 1.064m wavelength. The results obtained indicate that the bond strength of laser-etched enamel was significantly lower than that of acid-etched enamel. In this study the difference may be attributable to the chromophore used. Variations in the rate of traverse of the laser tip across the surface did not appear to produce significant alterations in the bond strength.     

Optic nerve edema as a consequence of respiratory disease

The authors describe a patient with bilateral papilledema, visual field abnormalities, poorly reactive pupils, meningeal enhancement on cranial MRI, and diffuse brain parenchymal hypervascularity. The opening pressure at the time of lumbar puncture was normal, and results of other CSF studies were normal. All abnormalities resolved with home oxygen therapy.     

Distribution of 5-hydroxytryptamine-immunoreactive boutons on immunohistochemically-identified Renshaw cells in cat and rat lumbar spinal cord

A combination of anti-gephyrin- and anti-calbindin D28k-immunoreactivity was used to identify 129 and 171 Renshaw cells and their dendrites in cat and rat lumbar spinal cord, respectively. Using anti-5-hydroxytryptamine-immunoreactivity to label serotoninergic fibers and boutons, 1048 serotoninergic boutons were observed in close contact with the immunolabeled Renshaw cells, with an average of 4.4 and 2.8 close contacts on cat and rat Renshaw cells, respectively. Two-thirds of the observed appositions were formed on the somatic membrane.     

Designing an intervention to prevent suicide: PROSPECT (Prevention of Suicide in Primary Care Elderly: Collaborative Trial)

Suicide is a major public health problem with greatest risk in the very old. This paper describes an approach to reducing the risk of suicide by intervening on depression in elderly primary care patients. Depression is an appropriate target for an intervention as it is highly prevalent in primary care, is a strong risk factor for suicide, and is more often than not inadequately treated. PROSPECT (Prevention of Suicide in Primary Care Elderly: Collaborative Trial) is a National institute of Mental Health (NIMH)-funded collaborative study that is testing this approach to suicide risk prevention in 18 primary care practices in the United States. PROSPECT'S intervention of "guideline management" introduces a health specialist into the primary care setting to help physicians provide "on-time, on-target" treatment and long-term management of late-life depression following structured clinical guidelines. The effectiveness of the intervention in reducing suicidal risk and depression is evaluated by following a representative sample of older patients identified using a 2-stage design.     

Differential effects of alcohol on rod and cone temporal processing

OBJECTIVE: One of the more reliable effects of alcohol on sensory processing is the reduction of the critical flicker fusion frequency (CFF). To gain a better understanding of the mechanisms through which alcohol influences the processing of temporal information, we explored the effects of alcohol on CFF at a high level of illumination when performance is mediated by the cones (photopic), and at a lower level when performance is dominated by the rods (low mesopic). METHOD: Measurements of CFF were made under placebo and alcohol conditions (0.06% blood alcohol concentration) in six subjects (three men, three women). Assessments were obtained in both the rising and falling phases of absorption for both light levels at several retinal locations. RESULTS: Alcohol was found to reduce CFF by approximately the same amount at all retinal locations for photopic viewing levels. Mesopic CFF was lower than photopic, as expected. However, it was only minimally affected by alcohol, showing only a slight decline for central viewing. CONCLUSIONS: These results imply a selective effect on alcohol on cone function. In considering the possible mechanisms of such a selective action, we suggest that this effect may be an indirect one. That is, the poorer performance under photopic conditions may be a consequence of an alcohol-induced reduction in the inhibitory interactions that are more prevalent at photopic light levels.