Crenation and cupping of the red cell: A new theoretical approach. Part II. Cupping

Typical, axisymmetrical cup shaped cells have been carefully measured and the shapes analyzed mathematically. The results show that the strain energy of a cup shaped cell is always higher than that of a biconcave cell except when the two layers of the membrane involved in resistance to bending are free to slide over one another. This is true whether intrinsic curvature of the membrane is positive, negative or zero. If the two layers can slide over one another, the cup shape becomes the lower energy form. Shear resistance, if appreciable, must cause the cup cell to buckle. Photomicrographs of cup shaped cells show buckled configurations characteristic of those of a partly deflated thin-walled rubber ball, which is a similar object having a low ratio of bending/shear strength.In light of these findings, the cup shape of the red cell can no longer be considered as evidence of intrinsic membrane curvature of opposite sign to that of the crenated cell, but appears to indicate a phase change either in the hydrophobic interior of the bimolecular membrane or in some equivalent interface.     

Interaction of alcohols with proteins

The kinetics of denaturation of egg albumin have been determined for methanol, ethanol, propanol, and butanol. The reactions are first order in respect to protein but between 11th and 18th order for the alcohols. The denaturation reaction is characterized by a large temperature coefficient with little or no dependence on pH. There is a marked change of pH when proteins are denatured. A series of eight proteins has been studied. There is surprisingly little difference in susceptibility to alcohol denaturation between the various proteins. Methanol, ethanol, propanol, and butanol are strongly bound to egg albumin—butanol being the most strongly bound. The binding of alcohol is probably accompanied by protein dehydration. The polyhydric alcohols' behavior is much different. These alcohols do not denature proteins and the protein is hydrated. Sucrose produces the greatest degree of hydration.     

Effects of anisomycin on brain protein synthesis and passive avoidance learning in newborn chicks.

The effects of anisomycin (ANM) on newborn chicks have been studied with respect to brain protein synthesis, growth, EEG, toxicity, and several passive avoidance learning tasks. It was found that intracerebral ANM (80 nmol) gave a maximum inhibition of brain protein synthesis of 30%, while a combination of subcutaneous (10 mumol; 53 mg/kg) plus intracerebral (80 nmol; 21 mug) ANM inhibited by 91% in the first 2 hr and by 75% in the subsequent 2 hr period. Cycloheximide (CXM) also in combined injections at the same doses as ANM, inhibited by 97% in the 4 hr that followed injection. However, all the CXM-injected chicks were dead by 18 hr, while the lethality of ANM did not differ from that of saline. ANM also did not affect EEG measured at 1, 3, 5, or 24 hr following the subcutaneous plus intracerebral injections, nor did ANM affect body or brain growth curves or brain protein accretion. In the learning experiments, animals were initially trained to peck at water-coated metal spheres (type A learning) or at water imbibed birdseed (types B and C learning) in less than 1 sec, and were exposed to the same lures treated with the aversant methylanthranilate (MeA) one day later on one occasion (types A and B learning) or exposed twice (type C learning) and tested for learning retention one day later. Learning criterion was set as failure to peck at the lure during the first 20 sec of presentation. If ANM was injected 1 hr prior to MeA exposure, large and highly significant memory deficits were found during the retention test, as compared with saline injected controls. No effect of ANM was seen, however, if it was injected one day after learning, indicating that it did not interfere with retrieval mechanisms. ANM also decreased the external manifestations of fear or displeasure that chicks express during retention testing. Such manifestations have a high correlation with pecking suppression (r = 0.88, P less than 0.001).     

Meniscofemoral ligaments--structural and material properties

The meniscofemoral ligaments (MFLs) of 28 human cadaveric knees were studied to determine their incidence, structural and material properties. Using the Race–Amis casting method for measurement, the mean cross-sectional area for the anterior MFL (aMFL) was 14.7 mm² (±14.8 mm²) whilst that of the posterior MFL (pMFL) was 20.9 mm² (±11.6 mm²). The ligaments were isolated and tensile tested in a materials testing machine. The mean loads to failure were 300.5 N (±155.0 N) for the aMFL and 302.5 N (±157.9 N) for the pMFL, with elastic moduli of 281 (±239 MPa) and 227 MPa (±128 MPa), respectively. These significant anatomical and material properties suggest a function for the MFL in the biomechanics of the knee, and should be borne in mind when considering hypotheses on MFL function. Such hypotheses include roles for the ligaments in knee stability and guiding meniscal motion.     

Long-term treatment with fluoxetine induces desensitization of 5-HT4 receptor-dependent signalling and functionality in rat brain

The mode of action of antidepressant drugs may be related to mechanisms of monoamines receptor adaptation, including serotonin 5-HT₄ receptor subtypes. Here we investigated the effects of repeated treatment with the selective serotonin reuptake inhibitor fluoxetine for 21 days (5 and 10 mg/kg, p.o., once daily) on the sensitivity of 5-HT₄ receptors by using receptor autoradiography, adenylate cyclase assays and extracellular recording techniques in rat brain. Fluoxetine treatment decreased the density of 5-HT₄ receptor binding in the CA1 field of hippocampus as well as in several areas of the striatum over the doses of 5–10 mg/kg. In a similar way, we found a significant lower response to zacopride-stimulated adenylate cyclase activity in the fluoxetine 10 mg/kg/day treated group. Furthermore, post-synaptic 5-HT₄ receptor activity in hippocampus-measured as the excitatory action of zacopride in the pyramidal cells of CA1 evoked by Schaffer collateral stimulation was attenuated in rats treated with both doses of fluoxetine. Taken together, these results support the concept that a net decrease in the signalization pathway of 5-HT₄ receptors occurs after chronic selective serotonin reuptake inhibitor treatment: this effect may underlie the therapeutic efficacy of these drugs.     

What is Diagnostic Radiology's Place in Medicine?

The question that the title of this lecture poses must depend considerably on the attitude of physicians and surgeons. I have indicated the very low position diagnostic radiology holds in this country relative to our peers in medicine elsewhere.If its improvement is considered to be warranted, we must:(1) Interest medical students at the beginning of their career.(2) Bear in mind that radiologists are likely to be able to teach some anatomy but the reciprocal seldom applies.(3) Obtain chairs in radiology, which are desperately needed.(4) Obtain the acceptance by the medical establishment of the proper place of radiology in clinical medicine.(5) See to the reduction in numbers of unnecessary x-ray examinations.(6) Press for the improvement and enlargement of radiological departments with proper provision for expansion.