Development of the diencephalon in the rat. IV. Quantitative study of the time of origin of neurons and the internuclear chronological gradients in the thalamus

Groups of pregnant rats were injected with two successive daily doses of 3H-thymidine from gestational days 13 and 14 (E13 + 14) until the day before birth (E21 + 22). With this progressively delayed comprehensive labelling procedure we determined the time of origin of neurons in the nuclei of the epithalamus, thalamus, and ventral thalamus. The zona incerta, subthalamic nucleus, reticular nucleus, posterior nucleus, and ventral lateral geniculate nucleus are composed of the earliest arising neurons (E13, or before, to E15). The neurons of the lateral habenular nucleus are produced between days E13--16. The neurons of the medial geniculate and lateral geniculate nuclei, the ventrobasal and ventrolateral complexes, and the nucleus lateralis, pars posterior, arise rapidly on days E14--15; the medial geniculate nucleus with a peak on day E14, the others with a peak on day E15. Neurons of a group of nuclei, with ill-defined boundaries medial to the sensory relax nuclei, arise apparently on days E15--16, with a peak on day E15; these may represent the intralaminar nuclei. The next group is generated on days E15--16 but with peak formation time on day E16; this includes the anteroventral, anterodorsal, anteromedial and mediodorsal nuclei. The rhomboid, reuniens and paratenial nuclei, and the paraventricular nucleus, pars anterior, arise next (E16--17). The medial habenular nucleus forms last and over a protracted period (E15--19). With their lengthy generation time the lateral and medial habenular nuclei resemble more the nuclei of the hypothalamus than the nuclei of the dorsal thalamus.

The postnatal development of the main olfactory bulb of the rat

The postnatal development from birth to 1 year of the main olfactory bulb was examined quantitatively. The volume of the main olfactory bulb increased over seven-fold by day 30 and remained unchanged thereafter. During the same period the volume of the granular layer increased 18-fold and the mean areas of the olfactory glomeruli increased seven-fold. The mean areas of mitral cell perikarya doubled between the neonatal and juvenile periods. The total number of the mitral cells, however, declined during the first three postnatal weeks. In the internal granular layer of the main olfactory bulb, 89% of the granule cells were acquired postnatally. Much of the cellular gain occurred during the first 3 weeks, with the period of maximum acquisition between days 8 and 14. The number of subependymal cells, the precursors of granule cells, reached a peak at 12 days and gradually declined. But some primitive cells could still be found at one year of age and there was an increase in the total number of granule cells beyond day 30. The mean nuber of internal granular layer cells in a single main olfactory bulb of adult rats was about 5 X 10(6); the number of mitral cells about 4 X 10(4). In the animals injected with 3H-thymidine on day 20 and killed 2 h after injection a small but significant proportion of cells was labelled in the subependymal layer but few in the internal granular layer. In the animals killed 20 and 40 days after injection there was a 10--11-fold rise in the proportion of labelled internal granular layer cells. The proportion of labelled internal granular layer cells decreased in longer survival groups but the total number of labelled cells remained the same, even in year-old animals. However, the total number of internal granular layer cells in the sections examined increased with age.

Effects of differential interference with postnatal cerebellar neurogenesis on motor performance, activity level, and maze learning of rats: a developmental study

The region of the cerebellum was X-irradiated in infant rats with selected exposure schedules designed to produce animals in which the cerebellar cortex was (a) essentially normal except for agenesis of late forming granule cells with axons situated in the uppermost molecular layer (12--15X), (b) lacking in stellate cells, with a severe reduction in granule cells with axons in the upper molecular layer (8--15X), (c) morphologically disorganized but had only intermediate cell agenesis (4--5X), or (d) disorganized and devoid of practically all postnatally forming interneurons (4--15X). In the first two experiments young adults had to traverse rotating rods that differed in texture and types of obstacles. The 8--15X animals showed no deficits on any of the rods tested. The third study dealt with spontaneous motor performance in the open field at three ages. The 4--5X and 4--15X animals were hypoactive as infants and young adults; this was attributed to their motor deficits. The 8--15X and 12--15X animals were hyperactive in the open field as young adults. The fourth experiment examined intra- and/or intersession habituation. No group differences were found in habituation patterns. In the fifth experiment, using activity wheels, the 4--15X group was hypoactive, and the 8--15X and 12--15X groups were hyperactive as young adults. In the sixth experiment young adults were tested for learning performance in a multiple-unit water maze. The 4--15X group was deficient on single alternation; the 4--5X and 12--15X groups on double alternation. The seventh experiment shed some light on the single alternation deficit of the 4--15X group; only these animals failed to alternate spontaneously in a nonaversive situation. In conclusion, these behavioral results, combined with those of recent morphological investigations, suggest that the cerebellar cortex is hierarchically organized: The basal domain of Purkinje cells and the lower molecular layer are implicated in the coordination of movements; the apical domain of Purkinje cells and the upper molecular layer, in the coordination of actions.

Development of the diencephalon in the rat. II. Correlation of the embryonic development of the hypothalamus with the time of origin of its neurons

The development of the nuclei of the hypothalamus was examined in normal and X-irradiated embryos from day 13 (E13) to the day before birth (E22). The diencephalic neuroepithelium was subdivided into three lobes (dorsal, medial, and ventral) and two lobules (superior and inferior). The hypothalamus is derived from the ventral lobe and the inferior lobule. The ventral neuroepithelial lobe generates the neurons of most of the early arising hypothalamic structures, including those of the lateral tier nuclei associated with the medial forebrain bundle, and the heterogeneous intermediate tier nuclei. A specialized neuroepithelial region lining the diamond shaped ventricle produces the early neurohypophysial magnocellular neurons; the neurons of the paraventricular nucleus remain at this site, whereas the neurons of the supraoptic nucleus could be traced migrating laterally. The neurons of the late arising hypophysiotropic area of the posterior hypothalamus are derived from components of the inferior neuroepithelial lobule: the dorsomedial and ventromedial nuclei apparently from a shared matrix in the main portion of the inferior lobule; the tuberomammillary-arcuate complex from its posteroventral recess. The triple-decked and sequentially produced components of the mammillary system may arise from separate neuroepithelial sites. The autoradiographic results of the previous study (Altman and Bayer, '78a) showed that the structural and functional heterogeneity of the mature hypothalamus is paralleled by cytogenetic heterochronicity; the present embryonic observations indicate that many of the distinguishable components of the hypothalamus arise from a mosaic of heterogeneous neuroepithelial sites.

Development of the diencephalon in the rat. I. Autoradiographic study of the time of origin and settling patterns of neurons of the hypothalamus

Groups of pregnant rats were injected with two successive daily doses of 3H-thymidine from gestational day 13 (E13 + 14) until the day before birth (E21 + 22). This double labelling procedure was combined with an injection schedule of a single day delay between groups (E13 + 14; E14 + 15; E15 + 16 . .). The two injections assured the comprehensive labelling of practically all neurons of a given structure prior to the onset of their differentiation (comprehensive labelling), whereas the progressive daily delay in injections made it possible to estimate the proportion of neurons formed in various regions of the hypothalamus on a single day. Hypothalamic areas or nuclei were assigned into four classes on the basis of their cytogenetic isochronicity. Structures composed of the earliest arising (class 1) neurons constitute a lateral tier that includes the lateral preoptic and lateral hypothalamic areas, and the lateral mammillary nucleus. Structures composed of early arising (class 2) neurons form a heterogeneous collection of nuclear systems, including the paraventricular, internuclear and supraoptic magnocellular neurons, and several intermediate tier nuclei of the anterior and posterior hypothalamus. The late arising (class 3) and latest arising (class 4) nuclei constitute a periventricular system anteriorly and a more extensive region posteriorly. The latter two nuclear systems may constitute the hypophysiotropic area of the hypothalamus. The nuclei of the mammillary system, which are produced sequentially, are distinguished from other hypothalamic structures by their more rapid generation time. Internuclear labelling gradients were used to infer the neuroepithelial site of origin and settling pattern of neurons. Common sites of origin were indicated for the following structures: the magnocellular neurohypophysial neurons; the neurons of the dorsomedial and ventromedial nuclei; and the neurons of the tubermammillary and arcuate nuclei. The sites of origin of these groups of nuclei were related to specialized ventricular linings in the mature hypothalamus.

Development of the diencephalon in the rat. III. Ontogeny of the specialized ventricular linings of the hypothalamic third ventricle

The development of the specialized linings of the hypothalamic third ventricle was examined autoradiographically in mature rats that were labelled with 3H-thymidine during the developmental period, and in a closely spaced series of embryonic and infant rats. We distinguished in mature rats, apart from the typical ependymal wall, three specialized linings: the convoluted ependyma, the laminated epithelium, and the tanycytic epithelium. The ventricular wall of most of the anterior hypothalamus, and of the dorsal portion of the posterior hypothalamus, is composed of ciliated ependymal cells and most of them are generated several days before birth, soon after the cessation of neurogenesis in the adjacent hypothalamic nuclei. The cells of the rostral convoluted ependyma adjacent to the paraventricular nucleus are produced at about the same time as the neighboring cells of the smooth ependyma. Its cells come from the same germinal region that we have assumed to generate the neurons of the magnocellular neurohypophysial secretory system. The structural differentiation of the convoluted ependyma starts after birth and is completed by the beginning of the second week. Many of the ependymal cells of the laminated epithelium are produced postnatally, and the production of the specialized cells that form a parallel subependymal row extends into the third week. These cells appear to arise from the same matrix that generates earlier the neurons of the dorsomedial and ventromedial hypothalamic nuclei; their structural differentiation begins during the second week. Also the cells of the tanycytic epithelium are produced mostly postnatally, predominantly during the first week. They appear to arise from the same matrix that generated earlier the neurons of the hypophysiotropic tuberomammillary and arcuate nuclei. It is postulated that these three specialized ventricular linings are specifically related to the three cpmponents of the endocrine hypothalamus with which they have shared neuroepithelial sites of origin.

Speckled lentiginous nevus

Speckled lentiginous nevus is, we feel, a distinctive nevocytic disorder and a clinical variety of nevus-cell nevus. The speckled areas show varying histological patterns that range from nevus incipiens to junctional and compound nevi. The background shows histological features of lentigo simplex. It is our contention that speckled lentiginous nevus should be separated from nevus spilus and nevus spilus tardus (Becker's), which we consider to be variants of epidermal nevus.

Effects of cycloate on development of Heterodera schachtii and growth of three Beta species

Greenhouse tests were set up to evaluate the effects of the herbicide, cycloate (S-ethyl cydohexylethylthiocarbamate), oil development of Heterodera schachtii and growth of three Beta species. Cycloate added to infested soil enhanced cyst development/gm root on B. vulgaris and larvae/gm of root in B. patellaris and B. procumbens at 4, 16, and 16 mug(a.i.)/gm of soil, respectively. Total numbers of nematodes/individual root system decreased because of poor root growth of seedlings in cycloate-amended soil. Penetration and larval development through stage three did occur in the wild Beta species in any treatment. Thus, resistance of B. patellaris and B. pocumbens to development of H. schachtii was not altered by cycloate. Cycloate also retarded growth (P = 0.05) of the sugarbeet cultivars and B. patellaris at 4 mug(a.i.)/gm and B. procumbens at 16 mug(a.i.)/gm of soil. Higher concentrations of nematodes/gm root in plants growing in cycloate-amended soil may be attributed to factors such as fewer roots available for penetration, possible effects of cycloate on egg hatch, greater attraction of nematodes to roots, and increased susceptibility of roots to larval penetration. Suppression of seedling growth in cycloate-amended soil may be attributed in part to higher nematode density and in part to direct root damage from cycloate.

Time of origin and distribution of a new cell type in the rat cerebellar cortex

A new cell type was identified in the granular layer of the rat cerebellum. It has a lightly staining nucleus with a nucleolus, it is spherical in shape and is larger than granule cells and smaller than Golgi cells. These pale cells are preferentially concentrated in the nodulus, the ventral uvula, the lingula, the flocculus, and parts of the paraflocculus. According to autoradiographic (3H-thymidine) evidence, over 60% of these pale cells are formed on embryonic days 19 and 20, and their production comes to an end soon after birth, prior to the differentiation of granule cells. The possible relation of pale cells to vestibular afferents of the cerebellar cortex is discussed.

Changes in renal inactivation of angiotensin II in rats with hereditary spontaneous hypertension

The inactivation of the pressor effect of angiotensin II by the renal vascular bed is less in spontaneously hypertensive rats than in normal rats. This phenomenon, which is observed only in adult animals but not in young ones, may be due to a slowing in the functional maturation of the kidney tissue.

Evidence for a visceral smooth muscle abnormality in Okamoto spontaneous hypertension

1. In order to discover whether the changes in reactivity are related to the primary cause of hypertension in spontaneously hypertensive rats (SHR) or are just an adaptation induced by the high arterial blood pressure we tested the contractile response of a visceral smooth muscle from such rats. 2. Longitudinal strips of the fundus from 20 week old male and female SHR and Wistar normotensive (NW) rats were used. Dose-response curves to Ba2+ in SHR strips were displaced to the right as compared to NW rats. Maximal responses were identical. Male SHR fundus strips contracted much more with Sr2+ (SHR: 42+/-3% of maximum response to Ba2+, n=10; NW: 19+/-4%, n=10, P less than 0.01) than NW strips. There was no difference in the response to both BaCl2 and SrCl2 between female SHR and NW fundus strips, and MnCl2 and LaCl3 were relaxant in all cases. 3. Dose-response curves to Ca2+ of depolarized SHR and NW fundus strips were obtained and the effect of diazoxide on Ca2+ contractions was observed. The contractile action of Ca2+ in depolarized preparations was enhanced in both male and female SHR strips. The effect of diazoxide was more marked in SHR strips than in NW fundus strips. 4. SHR fundus smooth muscle shows the same modification of reactivity to Ba2+, Sr2+, Ca2+ and diazoxide that was previously described in arterial smooth muscle. This indicates that the cellular modification responsible for the increase of vascular tonus in SHR is not an adaptive reaction to high blood pressure. The differences between female SHR and male SHR responses are not unexpected, considering the natural evolution of hypertension in Okamoto rats which is milder in the female.

The effect of ethanol chronically administered to preweanling rats on cerebellar development: a morphological study

The effects of ethanol on body, brain and cerebellar growth of the postnatal rat have been studied. Vapor inhalation, the procedure used to administer ethanol directly to preweanling (3-20-day-old) rats, produced maximal blood ethanol levels that averaged 239 mg/100 ml. Weight determinations indicated that brain but not body growth was significantly stunted by exposure to ethanol. Moreover, cerebellar growth, which occurred largely but not wholly during the period of ethanol treatment, was inhibited twice as much as the rest of the brain. Arrested brain and cerebellar growth appeared shortly after ethanol treatment was begun and persisted into adulthood following a postweaning rehabilitation period. Ethanol treatment diminished the growth of both the anterior and posterior lobes and of all layers of the cerebellar vermis. However, the effect of ethanol was larger in the anterior lobe than the posterior lobe, and the medullary layer was more retarded than the others. Some compensatory growth occurred in the molecular and granular layers of the experimental rats during a postweaning rehabilitation period. The effects of ethanol on 2 major neuronal populations of the cerebellar cortex -- the large, prenatally-formed Purkinje cells and the small, postnatally-formed granule cells -- were assessed via light microscopy. After 2 days of ethanol treatment the number of Purkinje cells in all 10 vermal lobules was reduced; neither additional exposure to ethanol nor a postweaning rehabilitation period subsequently altered cell number. The possibility that the regional magnitude of the Purkinje cell loss was related to the chronology of lobular development was discussed; Purkinje cells in the latest maturing lobules being least affected. The morphological development of surviving Purkinje cells proceeded normally. An autoradiographic study indicated the pattern of granule cell neurogenesis in cerebella of ethanol-treated rats and of control rats did not differ, although the experimental animals had consistently fewer cells in all stages of development. The ultimate loss of 20-25% of their granule cells was accounted for by an early diminution of the stem cell population of the external germinal layer by about 10%. The results suggest the initial targets of ethanol were the immature Purkinje cells, which were reduced in number before the onset of granule cell formation. A complex age-dependent interaction between blood ethanol levels and vulnerable periods in Purkinje cell development was suggested. Mechanisms for the subsequent correlative reduction in the granule cell population were also discussed.

Postnatal development of the cerebellar cortex in the rat. V. Spatial organization of purkinje cell perikarya

The development of the spatial organization of Purkinje cell perikarya was examined in the rat cerebellum from birth to adulthood. Dispersion of the perikarya following birth is made possible by the rapid expansion of the cortical surface. Their subsequent regular monocellular alignment is ensured by mechanical factors, the pressure exerted from below by the expanding granular layer and the barrier formed above by the pile of parallel fibers which prevent the penetration of the bulky perikarya into the molecular layer. The perikarya remain in this position even after the slender stem dendrite pierces the molecular layer along the descending axons of basket cells. The increase in interperikaryal distance between Purkinje cells is rapid up to day 12, then declines. This is temporally associated with the growth of the basket cell plexus and glial envelope around the perikaryon. The increase in perikaryal size continues up to day 30. This may be temporally associated with the growth of the Purkinje cell dendritic arbor as reflected by the expansion of the molecular layer up to day 30. The spatial arrangement of Purkinje cells within the monocellular sheet was graphically displayed with computer aid. In the adult cerebellum a hexagonal arrangement could be recognized in a proportion of "near-neighborhoods," consisting of about six Purkinje cells and their neighbors. When the neighborhoods were extended with fixed orientation with respect to the axis of the folium, the hexagonal arrangement disappeared. When orientation was ignored, the superimposed near-neighborhoods could be rotated to produce a hexagonal pattern. In the infant cerebellum the hexagonal arrangement could not be demonstrated before the alignment of Purkinje cells in a monolayer. Thereafter there appeared to be an increase with age in the proportion of hexagonally arranged near-neighborhoods. It was concluded that in the monocellular ganglionic layer Purkinje cells are not aligned in regular rows with respect to the geometrically arranged elements of the supraganglionic layer. The formation of an imprecise hexagonal pattern, like the alignment of Purkinje cells in a monolayer, was attributed to mechanical factors.

Lack of hypotensive effect on central injection of angiotensin inhibitors in spontaneously hypertensive (SH) and normotensive rats

1. Injections of antagonists of angiotensin II into the cerebral ventricles of normotensive and spontaneously hypertensive rats were performed in order to assess the role of the isorenin-angiotensin system in the brain. 2. No hypotensive effect was obtained in either normotensive or hypertensive rats, suggesting that intracranial isoangiotensin has little role in the pathogenesis of spontaneous hypertension in the rat.

[Effect of furosemide, potassium canrenoate and D-L-propranolol on blood pressure in spontaneously hypertensive rat]

Spontaneously hypertensive rats (japanese strain) have been treated with furosemide, potassium canrenoate or d-l-propranolol. Present results indicate that: 1)furosemide admiinistration, from the 3rd to the 15th week of life, does not prevent the development of hypertension but the blood pressure rises more slowly in treated rats. In the established phase of hypertension furosemide administration produces a decrease in blood pressure; the blood pressure increases rapidly after cessation of the treatment. 2) potassium canrenoate, injected from the 3rd to the 14th week of life, does not prevent the rise in blood pressure.3) d-l-propranolol, administered from the 5th to the 34th week of life, is without effect on the development of hypertension, though it significantly decreases heart rate.

Experimental reorganization of the cerebellar cortex. VII. Effects of late x-irradiation schedules that interfere with cell acquisition after stellate cells are formed

In Long-Evans rats the area of the cerebellum was irradiated with multiple doses of low-level X-ray beginning on day 12 after the bulk of stellate cells were acquired. The treatment spared basket, stellate and early-forming granule cells but led to a substantial reduction in the total granule cell population and a correlated miniaturization of the cerebellar cortex. Nevertheless most Purkinje cells had normally shaped planar dendritic arbors, with an upward directed stem dendrite, several smooth branches and a multitude of spiny branchlets. The frequency piling up of spiny branchlets near the surface was attributed to the truncation of the bed of parallel fibers by this radiation schedule. In this last paper of the series the accumulated results are summarized and evaluated. The hypothesis is offered that while the growth of the Purkinje cell perikaryon is an autonomous process, the oriented perpendicular growth of a single stem dendrite depends on the presence of basket cell axons, the outgrowth of smooth branches on the presence of stellate cell axons, and the proliferation of spiny branchlets on interaction with parallel fibers. The parallel fibers are responsible for the orthogonal, planar growth of the dendritic arbor and a hypothesis is offered about the mechanisms involved.

Experimental reorganization of the cerebellar cortes. VI. Effects of x-irradiation schedules that allow or prevent cell acquisition after basket cells are formed

In Long-Evans rats the area of the cerebellum was X-irradiated with two schedules beginning on day 8 by which time the bulk of basket cells were formed. The shorter schedule of four successive daily doses of 200 r between 8-11 days was designed to allow some cell recovery, the longer schedule between 8-15 days was expected to prevent it. Neither of the schedules interfered with the differentiation of basket cells. Purkinje cells remained aligned in a monocellular layer and formed singularly long, upright stem dendrites which were surrounded by the descending collaterals of basket cell axons. This supported the hypothesis that the directed growth of Purkinje cell stem dendrite is promoted by morphogenic interaction with basket cells. The upright stem dendrites had few or no smooth branches where cell recovery was prevented or had few such branches where recovery occurred. It was postulated that the out-growth of smooth branches is dependent on interaction with stellate cells which form after the acquisition of basket cells. The absence or scarcity of smooth branches did not prevent the formation of spiny branchlets which grew downward to establish synaptic contacts with the spared parallel fibers of granule cells formed before the start of irradiation. In the group with some granule cell recovery, spiny branchlets grew to a limited extent upward into the pile of parallel fibers formed after the irradiation.

Experimental reorganization of the cerebellar cortes. V. Effects of early x-irradiation schedules that allow or prevent the acquisition of basket cells

In neonate and infant rats the area of cerebellum was irradiated with different schedules of single or multiple doses of low-level X-ray. One set of schedules allowed the early recovery of the external germinal layer and the differentiation of all the postnatally-forming cell types while the other selectively prevented the acquisition of basket cells. The first schedule did not interfere with the development of normally oriented and arborizing Purkinje cells. The second schedule led to the growth of twisted and entwined stem dendrites even when, in association, with the recovered granule cells, parallel fibers were present in the molecular layer together with Purkinje cell spiny branchlets. Evidence was presented that the alignment of Purkinje cell perikarya in a monolayer does not guarantee the normal growth of Purkinje cell stem dendrites which may be dependent on the presence of basket cells. The problem was discussed whether cell differentiation in the cerebellar cortex is governed by a chronological or sequential principle.

Postnatal development of locomotion in the laboratory rat

In laboratory rats (Rattus norvegicus) aged 1 to 21 days emergence of postural and locomotor skills was studied in the open field and in experimental situations with homing used as motivation. Righting is mediated initially by curving and rocking of the trunk, later head and shoulder are rotated, and lastly the hindlimbs turn and provide co-ordinated support. Pivoting prodominates during the second half of the first week, crawling during most of the second week, and walking or running by the end of the second week. Balancing on narrow paths and compensating for lateral displacement on rotating rods mature later, as do various skills (climbing up or down on inclined surfaces, rods and ropes, and jumping across gaps) that require substantial hindlimb co-ordiantion.

Postnatal development of the cerebellar cortex in the rat. IV. Spatial organization of bipolar cells, parallel fibers and glial palisades

The ontogeny of the spatial organization of some components of the molecular layer was investigated in cerebella sectioned systematically in the sagittal, coronal and horizontal planes. There is no discernible organization in the distribution of cells of the proliferative zone of the external germinal layer (EGL) but from birth the differentiating bipolar cells of the subproliferative zone are aligned parallel to the surface and to the long axis of the folium. While they are still in or at the base of the EGL, the bipolar cells emit long processes, the future parallel fibers. The next step is the outgrowth of a vertical process which may reach the base of the molecular layer before the granule cell nucleus becomes translocated. The idea that the cell body truly migrates through the molecular layer is not supported by the observations. Bergmann glia cells are frequently seen in Golgi material in neonates but they are probably less numerous than in older infants and their processes are not as well aligned. It is only gradually that the EGL is perforated by flial endfeet which in older infants are occasionally organized into longitudinal rows. In mature cerebella the parallel fibers are separated by thin and relatively narrow, unstained spaces which are oriented in the longitudinal plane and can be traced from the pial surface to a zone just above the layer of Purkinje cells. It is postulated that these spaces are occupied by glial palisades formed by apposed thin vertical processes to which many Bergmann glia cells contribute. The alignment of these palisades is dependent on the orientation of parallel fibers. When the parallel fibers are reoriented by X-irradiation the glial palisades become correspondingly realigned. These observation indicate that the oriented growth of parallel fibers, which follows the polarization of bipolar cells, determines the spatial organization of the glial framework of the molecular layer. They also suggest that the glial palisades mediate functions that are not primarily developmental in nature.

Radiation-induced interference with postnatal hippocampal cytogenesis in rats and its long-term effects on the acquisition of neurons and glia

The long term consequences of graduated interference with the acquisition of hippocampal neurons and glia during early infancy were examined with quantitative histology and 3H-thymidine autoradiography. the head region containing the hippocampus was irradiated from day two on with either two (2X), four (4X), six (6X) or eight (8X) doses of 150-200r X-rays. The animals were killed at 30, 60, 90 and 120 days of age. The morphology of the hippocampus was normal in all irradiated groups with the characteristic interlocking flods of the pyramidal and granular layers. While the number of pyramidal calls of Ammon's horn was unaffected, the number of granule cells of the dentate gyrus was progressively and permanently reduced from control levels by the different dosage schedules (2X, 59% reduction; 4X, 77%; 6X, 83%; 8X, 84%). Incidental observations in control animals indicated a 20% increase in granule cells between 30 and 120 days of age in agreement with earlier observations of granule cell labelling after 3H-thymidine injections in adult rats. The time of origin of tha approximately 15-16% of the granule cells surviving irradiation in the 8X group was determined by injecting either pregnant females (gestation days 19-20) or pups (days 0 and 1) with two successive dosed of 3H-thymidine; the animals were irradiated from day two on the eight X-ray doses. The granule cells surviving in the postnatally injected group were all unlabelled and comparable in number to the unlabelled cells in control animals that were given five successive postnatal injections of 3H-thymidine. This established that the radioresistant complement of granule cells is formed prenatally. In the prenatally injected group, over half the surviving cells were labelled; it was assumed that those not labelled were formed befor gestation day 19. In contrast to the permanent reduction in the number of granule cells, there was some reestablishment of the number of cells in the dentate molecular layer and the Ammonic stratum oriens; in the fimbria, recovery in cell number was complete by 60 days. In a supplementary autoradiographic experiment, cell proliferation in the granular layer and in the fimbria was determined at 60 days of age after a single postnatal injection of 3H-thymidine on either day 15 or day 20 in the control, 2X, 4X and 6X groups. The number of labelled cells in the irradiated groups was always well below control levels in the granular layer, but it was wither above or at the same level as controls in the fimbria. Tentative interpretations were offered for the differential long-term effects of variable X-ray schedules on the neuronal and glial populationf of the hippocampus.

7-N-amidinocephalosporins

7-Aminocephalosporanic acid tert-butyl ester reacts quantitatively at--20 degrees with iminium chlorides to give amidino derivatives. Removal of the tert-butyl protecting group with trifluoroacetic acid and treatment with 1 equiv of triethylamine yield the corresponding zwitterions. These compounds were less active than their penicillin analogs.

Survey of malpractice claims in dermatology

A statistical survey of malpractice claims asserted against dermatologists was made. The subject matter of the claims was divided into eight major categories: (1) drug reactions, (2) x-ray burns, (3) poor cosmetic result following surgery, (4) poor cosmetic result following medication, (5) failure to diagnose cancer, (6) improper diagnosis, (7) infection from treatment, and (8) miscellaneous. The study showed that a group of "serious" damage cases, which accounted for 34% of total claims, generated 94% of total dollar losses. The problem areas for malpractice claims appeared to be drug reactions, cosmetic chemosurgery, and failure to diagnose cancer.

Pseudo-malignant lesions in Paget's disease of bone

Two patients with unusual features of Paget's disease are reported. In one patient a circumferential focal and periosteally based mass of Paget's disease presented as a mass lesion superimposed on the sclerotic phase of Paget's disease in the distal femur. Biopsy of the mass showed Paget's disease without neoplasia. The mass has remained unchanged roentgenographically in a 2 year period. In a second patient, a lesion occurred in the mid-portion of the tibia and showed features of the early and radiolucent phase of Paget's disease. In a 4 year period, the lesion has progressed to a more sclerotic phase and to occupy the proximal end of the tibia as well as its mid and lower portions.