The distribution of collagenase in the rat uterus during postpartum involution. An immunohistochemical study.

A monospecific rabbit anti-rat uterus collagenase antibody has been prepared and used to study the distribution of the enzyme in the rat uterus during postpartum involution. Cryostat sections of rat uteri from 24 to 240 hours postpartum were stained by the indirect immunofluorescent method. Nonpregnant rat uterus revelaed positive staining in basement membranes, in endometrial stroma, in perimuscular and in vascular connective tissue. During postpartum involution of the uterus two types of changes in uterine collagenase were observed: (1) variations in the distrubiton of the enzyme, which became selectively localized in the epithelial basement membrane and in the wall of small blood vessels, and (2) variations in the overall intensity of fluorescent staining, which decreased immediately after delivery and slowly increased back to nonpregnant levels in 5 days. The significance of these findings is discussed in relation to the mechanisms of control of collagenase activity in vivo.     

Neurogenesis in the cerebellum of the rat: An autoradiographic study

Summary Time of origin of various neuronal elements in the cerebellum of rat was established with the aid of tritiated-thymidine-autoradiography. The earliest nerve cells to form were the Purkinje cells, and they came into existence on days 15 and 16 of gestation. Interstitial nerve cells had their genesis on days 15, 16, 17 and 18, and the marginal cells on day 16 of the embryonic development. The Golgi cells were found to come into existence on days 17, 18 and 19 of gestation. On day 21 of gestation a number of small-medium-sized nerve cells, which were smaller than the Golgi cells but larger than the granule cells, were seen to come into existence. Finally, the earliest stock of granule, basket and stellate cells, primarily in the nodulus, flocculus and para-flocculus, were observed to have been formed on the day 21 of embryogenesis.This research was supported by NIH Research Grant No. NS-08817-03. Histological work by Sheila Anderson and photographic work by Donna Whitehurst is gratefully acknowledged.     

An autoradiographic and immunocytochemical study of the neonatal rat pituitary gland

Two-day-old female rats were injected with 5 nmole/kg of 6,7-³H-11β-methoxy-17-ethylestradiol (R 2858 = moxestrol) and killed one hour later. The animals were decapitated and, the pituitary glands were removed, mounted on tissue holders and frozen in liquified propane. The tissue was then processed for autoradiography according to the thaw mount technique. At the end of the exposure time, prior to photographic development, some of the tissue was fixed in 10% formalin and then photographically developed for autoradiography. The fixed tissue was subsequently stained immunocytochemically using antibodies to luteinizing hormone or prolactin. Between 10 and 15% of the cells of the pars distalis concentrated the synthetic estrogen or its metabolite. The immunocytochemical procedure revealed that both LH-gonadotrophs and lactotrophs concentrated the steroid. These studies along with earlier studies suggest that the neonatal rat pituitary contains only a small portion of the adult complement of estrogen receptors and that these receptors are dispersed across a number of cell types.     

An ultrastructural study of pigeon bursa of Fabricius during involution

The ultrastructure of the pigeon bursa of Fabricius during involution is described. According to the AA, the involutive process may be divided into 3 stages: an early involutive stage, a late involutive stage and a residual stage. The involutive process starts from epithelium later affecting the follicular medulla and all other structures of the organ. A mucoid degeneration can be observed, followed by an impressive fatty degeneration.     

Neuronal involution during ageing. Ultrastructural study in the rat cerebellum.

Involutive phenomena have been investigated by electron microscopy in the Purkinje Pk neuron of the cerebellar cortex of the aging rat. The still limited number of specimens available to date, however, suggest an age-related progression of morphological and functional deteriorations involving particularly the intraneuronal "nucleus-ribosome system" (NRS). The impairments are characterized by changes in the nucleolar texture. These alterations are accompanied by modifications in the repartition and relative proportion of RNP components of the nucleolus. In addition, other nuclear elements such as interchromatin and perichromatin granules may vary in importance with age. Recognizable changes in the ribosomal constituents of the NRS are evidenced by modifications in the density and distribution of free ribosomes. An altered structure and organization of GER cisternae are also evident. Furthermore, "light" cytoplasmic areas, an increased evidence of neurotubules and the gradual congestion of the pericaryon by age pigments are other valuable ultrastructural features that may be regarded as part of the sequence of morphologic events occurring during neuonal ageing. The above ultrastructural data will subsequently form the basis of a model of ageing in the nerve cell, which will complete the previously proposed model of neuronal maturation. Therefore, this long-term study essentially purports the investigation of subcellular events taking place in the Pk neuron all along the normal life span in rats. This model will also be used to evaluate the changes in the sequence and the reinforcement of the processes of evolution versus involution as affected by certain xenobiotics, such as abused drugs(alcohol and narcotics). The intraneuronal modifications found in the nuclear and cytoplasmic structures of the NRS could possibly reflect the molecular dysfunction related to the production of various types of RNA and neuronal proteins. This hypothesis is supported by biochemical data obtained from analysis of the brain of aged animals. Ultrastructural and biochemical data appear to be in good agreement with the neurophysiologic interpretation of a slow-down and reduced efficiency of the CNS during the progressive development of senescence in human and animal subjects.     

An autoradiographic study of cellular proliferation in remyelination of the central nervous system.

The proliferation and origin remyelinating oligodendrocytes was studied by light and electron miscrosopic autoradiography in the superior cerebellar peduncles of mice demyelinated by Cuprizone. In the early phases of demyelination, the cells undergoing mitotic activity were macrophages and astrocytes. In the later phases of demyelination, immature proliferating oligodendrocytes appeared; these differentiated into mature (dark) oligodendrocytes which were responsible for the remyelination of axons seen when animals were again placed on normal diets. The pattern of differentiation recapitulated that seen in developing oligodendrocytes in normal animals. Dark oligodendrocytes did not show mitotic activity. There was no mitotic activity in the subependymal cells around the fourth ventricle adjacent to the superior cerebellar peduncles. This study demonstrates the regenerative capacity of oligodendrocytes and their ability to carry out remeylination in the central nervous system.     

An autoradiographic and immunocytochemical study of the neonatal rat pituitary gland.

Two-day-old female rats were injected with 5 nmole/kg of 6,7-3H-11 beta-methoxy-17-ethylestradiol (R 2858 = moxestrol) and killed one hour later. The animals were decapitated and, the pituitary glands were removed, mounted on tissue holders and frozen in liquified propane. The tissue was then processed for autoradiography according to the thaw-mount technique. At the end of the exposure time, prior to photographic development, some of the tissue was fixed in 10% formalin and then photographically developed for autoradiography. The fixed tissue was subsequently stained immunocytochemically using antibodies to luteinizing hormone or prolactin. Between 10 and 15% of the cells of the pars distalis concentrated the synthetic estrogen or its metabolite. The immunocytochemical procedure revealed that both LH-gonadotrophs and lactotrophs concentrated the steroid. These studies along with earlier studies suggest that the neonatal rat pituitary contains only a small portion of the adult complement of estrogen receptors and that these receptors are dispersed across a number of cell types.     

Topographic organization of the cerebellothalamic projections in the rat. An autoradiographic study

The topographical organization of the subnuclear projections towards the thalamus was studied with autographic methods in adult Wistar rats. The four cerebellar deep nuclei give rise to projections to the ventral region of the rostral thalamus. Most of the fibers end contralaterally, according to a topographical pattern; however, some fibers from each of the cerebellar nuclei recross the midline at the thalamic level and terminate ipsilaterally, within regions symmetric to those receiving the densest contralateral projection. These ipsilateral cerebellothalamic components arise in decreasing order from the caudal nucleus lateralis, the ventrocaudal nucleus medialis and the nucleus interpositus, respectively. The projections of the nucleus lateralis directed to the contralateral thalamus are topographically organized. (1) Within the nucleus ventralis lateralis, the rostral and caudal parts of the cerebellar nucleus lateralis project respectively to rostral and caudal regions; lateral and medial zones of the nucleus lateralis project, respectively, to medial and central aspects of the nucleus ventralis lateralis. (2) The nucleus ventralis medialis and particularly its caudal portion appears to receive the bulk of its afferents from the ventromedial portion of the nucleus lateralis including the "subnucleus lateralis parvocellularis". (3) The nucleus centralis lateralis receives fibers from most parts of the nucleus lateralis including the "dorsolateral hump". (4) The nucleus interpositus anterior projects to the dorsomedial aspect of the rostral nucleus ventralis lateralis. In the latter nucleus, the ventrolateral aspect of the central region receives projections in cases in which the nucleus interpositus posterior is largely involved. A particular emphasis is put on the different projections from the various subnuclear regions of the lateral nucleus. A comparison is attempted with the situation in the primates, particularly with regard to the question of the parvocellular subdivision of the lateral nucleus.     

Myogenic cell formation in regenerating rat skeletal muscle injured by mincing II. An autoradiographic study

Myonuclei and satellite cell nuclei were differentially labelled with ³H-thymidine in uninjured skeletal muscle of young rats and then traced autoradiographically at intervals after mincing the radioactive hindlimb muscles to determine the source of regenerating presumptive myoblasts. Labelled nuclei were detected by light microscopic examination of 1-m? thick autoradiographs and identified by electron microscopic examination of an adjacent section. Repeated injections of ³H-thymidine during fetal and neonatal development, followed by a 4- to 5-week maturation period, resulted in labelling of 20% of the myonuclei. Satellite cells were not observed to be labelled in this series. Eight to sixteen hours after mincing, 20% of the pyknotic myonuclei were labelled, whereas none of the regenerating presumptive myoblasts appeared labelled. A single injection of ³H-thymidine administered to 18-day-old rats, followed by sacrifice within ten hours, resulted in labelling of 23% of the satellite cell nuclei. Myonuclei were not observed to be labelled in this series. Eight to sixteen hours after mincing, silver grains were detected over both pyknotic and regenerating cell nuclei. These experiments indicate that many satellite cells survive muscle injury and transplantation to become regenerating myogenic cells at a time when most, if not all, myonuclei are undergoing pyknosis.     

An ipsilateral olivocerebellar connection: an autoradiographic study in the unilaterally pedunculotomised neonatal rat

Summary Using autoradiographic techniques the olivocerebellar pathway was investigated in neonatal rats which had undergone a left cerebellar pedunculotomy on postnatal day 7 (p7). Tritiated (³H) leucine was injected into the right inferior olive at the same time as the pedunculotomy and the animals were allowed to survive for two or four days. Autoradiographs were then made of the brainstem and the cerebellum. Only those animals which had had a total left cerebellar pedunculotomy and in which the ³H-leucine did not spill into the left inferior olive were included in the experiment. The results showed the presence of climbing fibres in the cerebellar hemisphere ipsilateral to the injection site, arranged in sagittal bands and topographically organised. The only route for those fibres to enter the cerebellum is through the inferior cerebellar peduncle ipsilateral to the injected olive which is a pathway not present in the adult animal. The possible explanations for these results are discussed.     

An autoradiographic study of neuroblast proliferation in the rhombencephalon of a reptile, Lacerta sicula

Summary Early ontogenetic events in the brain of a lizard, Lacerta sicula, were investigated by means of H³-thymidine autoradiography. Varying dynamic properties—beginning, duration, and end of the proliferating activity, dynamics of the generation cycle—of the matrix zones of different regions and areas of the brain were observed. The main interest was focused on the rhombencephalon, where a distinct heterochronism of proliferation was described for different systems and nuclear groups. Eye muscle nuclei, the trigeminal system, and the hypoglossal nucleus arrive earliest (stage day 1/2–1 1/2). The vestibular and the cochlear system cease their proliferation at stage day 2 1/2 and stage day 3 1/2 respectively. Their proliferation is very rapid. In contrast, the sensory regions of the VIIth, IXth, and Xth nerves and the tegmental regions show a slow, long-lasting proliferation.The great difficulties for embryologic and experimental approach in reptiles are discussed.     

An autoradiographic assessment of epithelial cell proliferation and post-natal maturation of the tracheal epithelium in infant ferrets.

The tracheal epithelium of infant ferrets undergoes rapid postnatal maturation over the first month of life to achieve the pseudostratified columnar configuration characteristic of the large airways of other mammals. We have used in vivo pulsing with tritiated thymidine ((3)HT) to elicit autoradiographic labeling of cells synthesizing nucleic acids in order to characterize more fully the contribution to development of different cell types comprising the nascent epithelial layer during this period of rapid growth. These studies indicate that two distinct populations of epithelial cells possess proliferative potential and contribute to the establishment of the mature adult epithelial layer. These investigations further confirm the mitotic potential of basal cells during a period of rapid postnatal growth and development of the tracheal epithelial layer. These studies also document the contribution to early airway development by non-ciliated cells, which predominate on the luminal border of the ferret trachea at birth. The temporal and histologic patterns of airway epithelial maturation during post-natal life in the ferret as contained in this study exhibit similarities to those which occur with recovery from injury by infection and irritant exposure in mature airways. Thus, the characterization of epithelial cell compartments having proliferative potential may provide insights into the mechanisms whereby normal airway epithelial organization is established and maintained during development as well as the possible recapitulation of these mechanisms during times of epithelial regeneration following injury.     

Electron-microscopic and autoradiographic study of the pancreas at different stages of postmortem ischemia

Experiments on dogs showed that the maximal allowable period of normothermic postmortem ischemia of the pancreas must not exceed 45 min, for irreversible destructive changes develop later in the ultrastructural formations of cells of the exocrine parenchyma. Cells of the islets of Langerhans are more resistant to ischemia.Kiev Research Institute of Clinical and Experimental Surgery. (Presented by Academician of the Academy of Medical Sciences of the USSR V. V. Kovanov.) Translated from Byulleten' Éksperimental'noi Biologii i Meditsiny, Vol. 85, No. 5, pp. 610–613, May, 1978.