Asynchronous Maturation Research Articles

Asynchronous maturation of pathways for impulses from muscle and skin receptors to the sensomotor cortex in rabbits

A comparative analysis was undertaken of the functional and structural maturation of peripheral pathways for the conduction of afferent impulses to the sensomotor cortex from muscle and skin receptors of the sciatic nerve during postnatal ontogeny in rabbits. The criterion of functional maturity of the fibers was their sensitivity to the blocking action of procaine when applied to muscular and cutaneous nerves. Structural maturation of peripheral nerve fibers was determined by the degree of their myelination. Successive blocking of fibers of muscular and cutaneous nerves by procaine was shown to depress certain components of the cortical evoked potential. As the animal develops, the sensitivity of its nerve fibers to procaine and the configuration of the evoked response are modified. Different peripheral projections, maturing at different times, participate in the organization of individual components of the cortical evoked potentials. This also takes place during maturation of peripheral afferent projections from muscular and cutaneous receptors.

The fine structure of sporogony in Myxidium zealandicum (Protozoa: Myxosporidia)

Studies of the ultrastructure of the trophozoite (plasmodium) and the process of sporogony and polar capsule development of Myxidium zealandicum from gill and kidney of the North American eel Anguilla rostrata are described. Although the basic steps and characteristics of sporogony are similar to those previously reported for other myxosporidians, we report three new and significant observations in this study: (1) the identification of a uninucleate germ cell for the binucleate sporocyst; (2) the asynchronous maturation of polar capsules within a single sporocyst; and (3) the existence of a mitochondrial layer at the periphery of the Plasmodium that may have a transport function. We also observed cylindrical and spherical structures, either of which might be the primordium of the polar capsule, but we were unable to resolve this problem. These observations are discussed with reference to previous descriptions of myxosporidians.

Ver�nderungen des x/?-Verh�ltnisses der menschlichen Serumimmunglobuline im Verlaufe der Entwicklung

In sera of normal individuals of different age groups the kappa- and lambda-type immunoglobulins were measured and the kappa/lambda ratio was calculated. The relative concentration of lambda-immunoglobulins in sera of newborns and young children was found to be significantly higher than in the adult sera. The well-known asynchronous maturation of immunoglobulin classes and IgG subclasses in the early childhood is evidently accompagnied by a asynchronous maturation of immunoglobulin types.

Investigations of intrauterine devices in Macaca mulatta monkeys.

During the past decade, several explanations have been advanced to account for the highly effective antifertility action of an intrauterine device. These include: 1) the IUD acts as a mechanical abortifacient disrupting the implantation process; 2) the IUD increases tubal peristalsis, thereby prematurely propelling unfertilized and/or fertilized eggs into the uterine cavity; 3) the IUD initiates an asynchronous maturation of the endometrium so that the endometrium is either underripe or overripe at the time that the fertilized ovum would normally implant; 4) the IUD produces alterations in the life span of the corpus luteum and the production of progesterone; 5) the IUD acts as a foreign body producing a sterile inflammatory exudate which in turn results in an embryotoxic effect exerted by the cellular degeneration products of leukocytes. The study of this foreign body reaction suggests that it is the unifying principle for the events related to the antifertility action of the IUD.

SYNCHRONY AND THE ELIMINATION OF CHANCE DELAYS IN THE GROWTH OF POLIOVIRUS.

SUMMARY: The effect of multiplicity of infection on the growth kinetics of poliovirus suggests that the eclipse period usual for singly infected cells (3·6–3·8 hr) includes variable delays averaging about 1 hr. These delays are overcome at multiplicities above 3, and are sometimes spontaneously absent. They are ascribed largely to chance effects, and lead to markedly asynchronous maturation of virus; in their absence, maturation is almost synchronous. The kinetics of acid-irreversible eclipse and of the development of antiserum resistance show that about half of the delays must occur during viral penetration; in support of this, virus growth initiated with infective RNA is 0·5 hr less delayed than that of intact virus, although otherwise similar. However, infective RNA synthesis was not detected earlier than 2 hr after infection, even in the absence of chance delays.