The primitive ribosome model

A new model is proposed on the origin of crystallizable ribosomes and the kinetics of ribosome crystallization. The model assumes that ribosome crystallizability is a property the ribosomes have only in a well-defined period of their life cycle and implies a close relationship between cellular differentiation and structural rearrangements at the ribosome level. The model is used to interpret a variety of cases in which ribosome crystallization occurs, such as chick embryo tissues during development, tissue cultures treated with different antibiotics, chick adult tissues infected by viruses, lizard oocytes, degenerating cells and dedifferentiated cellular systems.     

The structure of a primitive kinetochore

The isolation of yeast centromeres has provided the opportunity to describe the molecular structure of chromosome attachments to the mitotic spindle. Nucleolytic probes of chromatin structure and construction of conditional mutants in centromere function have been used to study the regulation and assembly of centromeres throughout the cell cycle in Saccharomyces cerevisiae.     

The art of entrainment

The circadian system actively synchronizes the temporal sequence of biological functions with the environment. The oscillatory behavior of the system ensures that entrainment is not passive or driven and therefore allows for great plasticity and adaptive potential. With the tools at hand, we now can concentrate on the most important circadian question: How is the complex task of entrainment achieved by anatomical, cellular, and molecular components? Understanding entrainment is equal to understanding the circadian system. The results of this basic research will help us to understand temporal ecology and will allow us to improve conditions for humans in industrialized societies.     

The art of otology

Management of chronic ear infections dependent on recognition of the differences (pathological and clinical) between tympano-tubal lesions and attico-antral disease. Chronic suppurative otitis media as a reason for rejection for military service. Statistics obtained from the Ministry of Labour and National Service. Relative incidence of tympanic and attico-antral disease in a series of 500 hospital patients at the present time. Resistant chronic tympanic disease still a problem. Relation to acute suppurative otitis media. Recurrent and relapsing attacks of acute otitis media. Does early chemotherapy interfere with development of immunity?Problems presented by acute otitis media likely to be elucidated by the general practitioner rather than by the otologist. The general practitioner's opportunities for research in this clinical problem. Incidence of ear diseases in average general practice.Training of medical students in diseases of the ear, nose and throat. Methods of instruction followed in the teaching schools of Great Britain and Northern Ireland and attitude of the Examining Bodies to this subject. The contribution of otologists to the education of doctors.Some observations on facial paralysis. Importance of prognosis. Different criteria in early and late stages of paralysis. Reasons for abandoning the faradic-galvanic tests in the management of facial paralysis. Use of constant current square pulse stimulators in early days of facial paralysis. Electromyography of value in later stages.Present-day difficulties in acquiring skill for facial nerve surgery. Importance of the stylomastoid artery. Recent investigations on the blood supply of the facial nerve: gross vascular pattern and the interfascicular plexus. Further work necessary to relate these anatomical facts to the condition of Bell's palsy.     

The art of arteriogenesis

The identification of collateral artery growth (arteriogenesis) as the only mechanism to compensate for the loss of an occluded artery forced us to define the mechanisms responsible for this type of vessel growth. To achieve this, a variety of coronary as well as peripheral models of arteriogenesis have been developed. Based on these studies it is obvious that arteriogenesis obeys different mechanisms than angiogenesis, the sprouting of capillaries. Upon occlusion of an artery, the blood flow is redirected into preexisting arteriolar anastomoses that experience increased mechanical forces such as shear stress and circum ferential wall stress. The endothelium of the arteriolar connections is then activated, resulting in an increased release of monocyte-attracting proteins as well as an upregulation of adhesion molecules. Upon adherence and extravasation, monocytes promote arteriogenesis by supplying growth factors and cytokines that bind to receptors that are expressed on vascular cells within a limited time frame. Animal studies evidenced that factors, such as monocyte chemoattractant protein-1, granulocyte-monocyte colony-stimulating factor, or transforming growth factor-β₁, that either attract or prolong the lifetime of monocytes efficiently enhance collateral artery growth, an effect that was seen only to a minor degree after application of a single growth factor. Bone marrow-derived stems cells and endothelial progenitor cells do not incorporate in growing arteries but, rather, function as supporting cells. Complete elucidation of the mechanisms of arteriogenesis may lead to efficacious therapies counteracting the devastating consequences of vascular occlusive diseases.