Comparison of in vitro and in vivo development of rat foetuses.

Rat foetuses were explanted at 12.5 and 13.5 days of gestation and cultured for periods of 0, 12, 24, 33 and 42 hr. At the end of the culture period, differentiation of the foetuses was monitored by counting somites, and protein determinations were made to measure growth. These data were compared graphically with values found for foetuses at corresponding ages in vivo. The results for foetuses explanted at 12.5 days show that they grow and differentiate normally throughout a culture period of 42 hr, though at a lower rate than in vivo. Growth is depressed throughout culture, whereas differentiation is initially near normal but falls off after about 24 hr in culture. The results for foetuses explanted at 13.5 days show a similar but more marked retardation of growth and differentiation, and development almost ceases after 33 hr in culture. However, a histological study showed that with shorter periods of culture the tissues and organs of the 13.5-day rat foetus in vitro remain in good condition and develop significantly.     

A technique of measuring cardiac output and peripheral resistance in the conscious rat

A technique for the measurement of cardiac output in the conscious rat by cardiac catherization and application of the Fick principle, with simultaneous measurement of oxygen consumption and aortic pressure, is described. In conscious rats, the cardiac index was found to be 1.5 1/min/m² and the total peripheral resistance 0.8 mm Hg/ml/min per 100g body weight.     

A culture system for the development of the preimplantation rat embryo

We describe a system for the culture of 1-cell rat embryos through to the blastocyst stage, using co-culture on specific feeder cell layers and particular defined media. We show that the use of rat uterine epithelial cells as a feeder layer, together with either M16M, CZB or HECM-1 media at 38.5 degrees C can improve the in vitro development of cultured rat embryos. There was considerable variation in the culture conditions, which were optimal for each strain of rat tested. We show that the 4 to 8-cell embryos are viable after reimplantation and that the second 4 to 8-cell block in the rat can be overcome using HECM-1 in a co-culture system, thus enabling the in vitro culture of rat embryos up to the blastocyst stage.     

A method for mechanised straining of rat and mouse foetuses for teratological examination.

The staining method uses alizarin red S and has been adapted for a 4-5 day cycle on a standard tissue processor. It gives consistently well stained bones and clear soft tissues in both rats and mice.     

A model system and technique to study the effects of ultrasound irradiation on embryonic development

To study the effects of ultrasound on development it is important to have a system which provides reliable results. We have designed a system which allows for reproducible irradiations of chick embryos in ovo. The irradiation system includes a heated sonation tank with ultrasound absorbers and a PC/AT computer-based data acquisition system for on-line monitoring of irradiations. The ultrasound detection microprobe and irradiation transducers were calibrated against an NBS traceable balance meter. An acoustic spacer was utilized to provide a more uniform profile of the irradiation beam. At the position of the embryo the ultrasound field geometry was determined. To maintain the chick embryo in its natural physiological state while minimizing ultrasonic reflections and standing-wave generation, two diametrically opposed windows were made in the eggshell along the ultrasound pathway and covered with polyethylene membranes. Using this irradiation system at intensity levels as high as 1.1 W/cm2 (spatial average, temporal average) for 10 min, the temperature rise is minimal.     

Gangliosides of the peripheral nervous system of the rat

Rats sciatic nerves gangliosides have been studied. We found about 120 nmoles NANA/g dry weight. We studied the relative distribution of the gangliosides, after TLC and densitometry. G4 (G_M1) accounts for about 31 % of total NANA. G5 is absent from our samples ; we found a very low level of G7. Our distribution is different from the data of Svennerholm's group for the gangliosides of the human femoral nerve, and from Yates and Wherrett for the gangliosides of the rabbit sciatic nerves.     

Early events in the development of Drosophila peripheral nervous system

1. We have analysed the development of the larval PNS of Drosophila, with the aim of understanding the genetic programme that underlies this development. 2. The achaete-scute gene complex (AS-C), which is required for the development of the adult PNS, is also necessary for the larval PNS. The analysis of different AS-C lesions shows that the larval PNS results from the superimposition of two independent subpatterns, each of which depends on one AS-C gene. 3. The analysis of the two subpatterns reveals hidden homologies between the very different arrangements of sense organs observed on different segments, suggesting that the initial pattern is the same in all segments and is later modified in the different segments. 4. The early arrangement of sensory mother cells can be visualised in a special transgenic line, A37. In this line the initial repetitive pattern inferred above can be directly observed. Furthermore this line makes it possible to decide whether a given mutation acts on the very early steps of the PNS development (determination) or at later stages (differentiation). 5. The line A37 has been used to show that mutations that reduce the PNS such as AS-C- or da- alter the very first steps of the process, while mutations which result in a hypertrophied PNS such as N seem to alter a subsequent step. We end up with an overview of the genetic operations that generate the arrangement of sense organs and sensory neurons.     

A microcinematographic study of the in vitro development of postimplantation rat embryos

A method for time-lapse cinematography of in vitro cultured rat embryos is presented. Technical details (especially with respect to the possibility of manipulation during filming) and the first results obtained are presented and discussed.     

Advantages of mouse models to study early steps of peripheral nervous system development

The molecular mechanisms involved in the formation of mammalian peripheral nervous system remain largely unknown. Here we describe the new possibilities offered by mouse mutant analysis, new mouse in vitro models and the recent development of molecular genetic techniques which may permit analysis of the peripheral nervous system development at a level that was heretofore restricted to lower vertebrates.     

The development of serum proteins in pig foetuses during prenatal period

The present work describes data dealing with the quantitative relationship between individual serum proteins in pig foetuses of different age (38–112 days). Using immuncelectrophoresis in agar gel, six different fractions were determined (prealbumin, albumin, fetuin, alpha_1-, alpha_2-, and beta globulin). No gamma globulin was found. Using a simple radial immunodiffusion method, an average level of 70 gamma/ml of IgG was found in 112-day-old foetuses. Neither IgM nor IgA could be detected.     

A technique for chronic intragastric drug administration in the rat

An improved method for chronic intragastric delivery of drug solutions in the rat is described. The cannula can be easily constructed while the implantation is a simple and a problem-free procedure. Animals suffered no ill effects and resumed normal weight gain profiles after the operation. Since this is a direct stomach cannulation technique, the problems associated with the nasopharyngeal method are avoided. The cannula was tested by administering methadone and observing the characteristic depression of operant responding for food reinforcement. Using the cumulative records, it was possible to detect the onset of drug effect which was found to be about 10 minutes. The cannula is relatively durable and has remained patent in some animals for as long as 10 months without maintenance.     

Genes involved in the development of the peripheral nervous system of Drosophila

The development of the peripheral nervous system (PNS) requires the activity of a number of genes. The neurogenic and the proneural genes are necessary in the earliest phase; their mutations lead to hyperplasia and partial or total elimination of the PNS respectively. Some of these mutations also affect other developmental processes. Other mutations affect later events: cut transforms one type of sensory organ into another; numb alters the fate of the components of a single sensory organ. We will describe the effects of the best studied mutations on PNS development and discuss the possible role of the wild type genes.