Distribution of Ca2+-dependent protein kinase C isoforms in the suprachiasmatic nucleus of the diurnal murid rodent, Arvicanthis niloticus

The suprachiasmatic nuclei (SCN) contain the major 'biological clock' in mammals that controls most circadian rhythms expressed by these animals. The functional importance of protein phosphorylation and intracellular Ca2+ in the mammalian circadian pacemaker is becoming increasingly apparent. Here we report the immunocytochemical localization of the four Ca2+-dependent protein kinase C (PKC) isoforms (alpha, betaI, betaII, gamma) within the SCN of the diurnal murid rodent, Arvicanthis niloticus, and the nocturnal golden hamster. In the SCN of A. niloticus, PKCalpha was the most abundant of the four isoforms. Cells containing PKCalpha were homogeneously distributed throughout the SCN. PKCbetaI cells were sparsely distributed in the perimeter of the SCN and were absent in its central area. PKCbetaII and -gamma were not found in the SCN of A. niloticus. In the SCN of the golden hamster, PKCalpha cells were most heavily concentrated in the dorsomedial region, though some were also present laterally and ventrally. The distribution of arginine-vasopressin (AVP) cells in the SCN overlapped with that of PKC in both species. Species differences in the location of the Ca2+-dependent PKC isoforms suggest differences in function such as the relaying of photic or non-photic information to the clock mechanism, or the synchronization of AVP neurons and their subsequent output signals.     

The ventral lateral geniculate nucleus and the intergeniculate leaflet: interrelated structures in the visual and circadian systems

The ventral lateral geniculate nucleus (vLGN) and the intergeniculate leaflet (IGL) are retinorecipient subcortical nuclei. This paper attempts a comprehensive summary of research on these thalamic areas, drawing on anatomical, electrophysiological, and behavioral studies. From the current perspective, the vLGN and IGL appear closely linked, in that they share many neurochemicals, projections, and physiological properties. Neurochemicals commonly reported in the vLGN and IGL are neuropeptide Y, GABA, enkephalin, and nitric oxide synthase (localized in cells) and serotonin, acetylcholine, histamine, dopamine and noradrenalin (localized in fibers). Afferent and efferent connections are also similar, with both areas commonly receiving input from the retina, locus coreuleus, and raphe, having reciprocal connections with superior colliculus, pretectum and hypothalamus, and also showing connections to zona incerta, accessory optic system, pons, the contralateral vLGN/IGL, and other thalamic nuclei. Physiological studies indicate species differences, with spectral-sensitive responses common in some species, and varying populations of motion-sensitive units or units linked to optokinetic stimulation. A high percentage of IGL neurons show light intensity-coding responses. Behavioral studies suggest that the vLGN and IGL play a major role in mediating non-photic phase shifts of circadian rhythms, largely via neuropeptide Y, but may also play a role in photic phase shifts and in photoperiodic responses. The vLGN and IGL may participate in two major functional systems, those controlling visuomotor responses and those controlling circadian rhythms. Future research should be directed toward further integration of these diverse findings.     

The role of the intergeniculate leaflet in entrainment of circadian rhythms to a skeleton photoperiod

Mammalian circadian rhythms are synchronized to environmental light/dark (LD) cycles via daily phase resetting of the circadian clock in the suprachiasmatic nucleus (SCN). Photic information is transmitted to the SCN directly from the retina via the retinohypothalamic tract (RHT) and indirectly from the retinorecipient intergeniculate leaflet (IGL) via the geniculohypothalamic tract (GHT). The RHT is thought to be both necessary and sufficient for photic entrainment to standard laboratory light/dark cycles. An obligatory role for the IGL-GHT in photic entrainment has not been demonstrated. Here we show that the IGL is necessary for entrainment of circadian rhythms to a skeleton photoperiod (SPP), an ecologically relevant lighting schedule congruous with light sampling behavior in nocturnal rodents. Rats with bilateral electrolytic IGL lesions entrained normally to lighting cycles consisting of 12 hr of light followed by 12 hr of darkness, but exhibited free-running rhythms when housed under an SPP consisting of two 1 hr light pulses given at times corresponding to dusk and dawn. Despite IGL lesions and other damage to the visual system, the SCN displayed normal sensitivity to the entraining light, as assessed by light-induced Fos immunoreactivity. In addition, all IGL-lesioned, free-running rats showed masking of the body temperature rhythm during the SPP light pulses. These results show that the integrity of the IGL is necessary for entrainment of circadian rhythms to a lighting schedule like that experienced by nocturnal rodents in the natural environment.     

Evidence that a novel type of progestational phase control occurs in the corn mouse, a South American murid rodent

Most Muridae display a short luteal phase that becomes functional as a consequence of the prolactin release induced by the stimulation of copulation and/or lactation. The corn mouse also shows a short luteal phase, and we wanted to know whether copulation and/or lactation would release prolactin and maintain progesterone secretion in this species. Females in postpartum estrus were either allowed to copulate with an intact male or not, and either to lactate their young or not. Afterward, plasma progesterone was elevated over the baseline level only in females that had copulated and were bearing growing embryos (whether or not they were lactating), while prolactin was elevated only in lactating females. In another experiment, endometrial scratching induced decidualization both in females that had copulated with a vasectomized male and in those that had not copulated; sham operations had no effect in either case. Progesterone levels were elevated in decidualized animals as compared with their sham-operated controls. Results indicate that the initiation of the progestational phase in the corn mouse is not dependent on prolactin release. A short luteal phase during which nidation may occur has not yet been described in any other mammal.     

Roles of suprachiasmatic nuclei and intergeniculate leaflets in mediating the phase-shifting effects of a serotonergic agonist and their photic modulation during subjective day

Serotonin (5-HT) has been implicated in the phase adjustment of the circadian system during the subjective day in response to nonphotic stimuli. Two components of the circadian system, the suprachiasmatic nucleus (SCN) (site of the circadian clock) and the intergeniculate leaflet (IGL), receive serotonergic projections from the median raphe nucleus and the dorsal raphe nucleus, respectively. Experiment 1, performed in golden hamsters housed in constant darkness, compared the effects of bilateral microinjections of the 5-HT1A/7 receptor agonist, 8-hydroxydipropylaminotetralin (8-OH-DPAT; 0.5 microgram in 0.2 microliter saline per side), into the IGL or the SCN during the mid-subjective day. Bilateral 8-OH-DPAT injections into either the SCN or the IGL led to significant phase advances of the circadian rhythm of wheel-running activity (p < .001). The phase advances following 8-OH-DPAT injections in the IGL were dose department (p < .001). Because a light pulse administered during the middle of the subjective day can attenuate the phase-resetting effect of a systemic injection of 8-OH-DPAT, Experiment 2 was designed to determine whether light could modulate 5-HT agonist activity at the level of the SCN and/or the IGL. Serotonergic receptor activation within the SCN, followed by a pulse of light (300 lux of white light lasting 30 min), still induced phase advances. In contrast, the effect of serotonergic stimulation within the IGL was blocked by a light pulse. These results indicate that the respective 5-HT projections to the SCN and IGL subserve different functions in the circadian responses to photic and nonphotic stimuli.     

Circannual morphometric investigations of the rat suprachiasmatic nucleus after pinealectomy, ganglionectomy and thyroidectomy

With the advent of combinatorial chemistry a new paradigm is evolving in the field of drug discovery. The approach is based on an integration of chemistry, high-throughput screening and automation engineering. The chemistry arm is usually based on solid-phase synthesis technology as the preferred approach to library construction. One of the most powerful of the solid-phase methods is encoded split synthesis, in which the reaction history experience by each polymeric bead is unambiguously recorded. This split-and-pool approach, employing chemically robust tags, was used to construct a 85,000-membered dihydrobenzopyran library.     

Alteration of serotonergic innervation in the suprachiasmatic nucleus of the rat following removal of input fibers from retina and lateral geniculate nucleus

We report the results of sclerotherapy in 20 patients with bleeding gastric varices due to hepatic schistosomiasis. In an endemic area, patients with hepatic schistosomiasis, and bleeding gastric varices seen on endoscopy to be inferior extension of esophageal varices, were treated with emergency endoscopic injection just proximal to the cardia. Hemostasis was achieved in 17. Obliteration of varices was achieved in all patients with sclerotherapy, combined with surgery. Thirteen patients who had not been operated on in the past and consented to surgery underwent esophagogastric devascularization with splenectomy. Surgery was carried out as an emergency in the three patients who did not respond to sclerotherapy and electively in 10 patients after control of bleeding. After surgery, sclerotherapy was required for remnant varices. One patient with Child-Pugh grade C cirrhosis died of hepatic encephalopathy after control of the bleed. During a median follow-up of 9 months (range, 1-25 months), recurrence of bleeding in one patient and recurrent varices in two others were controlled with sclerotherapy. One patient had a fatal hemorrhage at home. We conclude that sclerotherapy effectively controls acutely bleeding type 1 gastric varices. Combined with esophagogastric devascularization and splenectomy, long-term results may be encouraging in patients with hepatic schistosomiasis.     

Expression of brain-derived neurotrophic factor and its cognate receptor, TrkB, in the rat suprachiasmatic nucleus

Brainerd and Reyna (1998, this issue) have described fuzzy-trace theory as a basic-processing theory, emphasizing age differences in children's disposition to use verbatim versus gist representations. The theoretical climate of the 1980's, when fuzzy-trace theory was first formulated, is described. Fuzzy-trace theory integrated new ideas about how cognitive development was viewed into a coherent framework, which only gradually gained acceptance as critical aspects of the theory were confirmed, counterintuitive findings were predicted and demonstrated, and other researchers began applying the theory. Fuzzy-trace theory converges with other contemporary theoretical accounts in raising the general issue of the relation between two developing representational systems and is consistent with the idea that immature (a bias toward verbatim encoding) and mature (a bias toward gist encoding) have both advantages and disadvantages at different times in development. By integrating the theory with ideas from social-contextual perspectives, the theory may have a greater impact in the future for issues of social significance.     

Circadian expression of NMDA receptor mRNAs, epsilon 3 and zeta 1, in the suprachiasmatic nucleus of rat brain

The presence of the N-methyl-D-aspartate (NMDA) receptor channel subunit epsilon 3 and zeta 1 mRNAs in the rat suprachiasmatic nucleus (SCN) was detected by sensitive in situ hybridization. The daily fluctuations in the epsilon 3 and zeta 1 subunit mRNAs in their abundance were found in the SCN to be high during the day and lower during the night under 12 h light:12 h dark conditions (LD 12:12). Under constant darkness for 15 days, both the epsilon 3 and the zeta 1 mRNA levels in the SCN remained cyclic. Furthermore, after exposure of rats to light, the epsilon 3 and zeta 1 subunit mRNAs increased during the subjective night, but not during the subjective day. These results implicate the involvement of the epsilon 3 and zeta 1 subunits in neuronal signaling in the SCN and suggest that these subunits of the NMDA receptor channel are regulated by light and a circadian clock.     

Evidence from confocal fluorescence microscopy for a dense, reciprocal innervation between AVP-, somatostatin-, VIP/PHI-, GRP-, and VIP/PHI/GRP-immunoreactive neurons in the rat suprachiasmatic nucleus

The rat suprachiasmatic nucleus (SCN) consists of several classes of neurons which can be identified by their transmitter content. Knowledge of putative interaction between these different cell types is essential in order to understand the possibilities of information processing within the SCN. The aim of the present study was therefore to obtain more information about the mutual innervation between the main cell classes in the rat SCN, viz. those containing the neuropeptides arginine vasopressin (AVP), vasoactive intestinal peptide (VIP), peptide histidine isoleucine (PHI), gastrin-releasing peptide (GRP) and somatostatin respectively. For this purpose, vibratome sections were double-immunolabelled for seven different peptide combinations and subsequently analysed by high-resolution confocal laser scanning fluorescence microscopy. Attention was focused on axosomatic appositions, the occurrence and frequency of which were quantitatively estimated. Our analysis of double-immunolabelled sections demonstrated that some of the VIP- and some of the GRP-immunoreactive nerve cells and endings showed colocalization. Assuming, on the basis of literature data, that VIP and PHI are always colocalized at the cellular level, the five main cell classes in the SCN appeared to be interconnected, at least axosomatically, in the following reciprocal way: AVP <--> VIP/PHI, AVP <--> GRP, AVP <--> somatostatin, somatostatin <--> VIP/PHI, somatostatin <--> GRP, VIP/PHI <--> GRP, VIP/PHI/GRP <--> GRP, VIP/PHI/GRP <--> VIP/ PHI. In addition to this heterologous axosomatic innervation, these cell groups also showed substantial homologous innervation. Supported by electron microscope data from the literature showing the existence of axodendritic synapses for some of these peptide combinations, our findings strongly suggest that the rat SCN comprises a complex synaptic network with strong interactive capabilities, which is probably a requisite for its biological clock function.     

Localization and characterization of nitric oxide synthase in the rat suprachiasmatic nucleus: evidence for a nitrergic plexus in the biological clock

Behavioral and electrophysiological evidence indicates that the biological clock in the hypothalamic suprachiasmatic nuclei (SCN) can be reset at night through release of glutamate from the retinohypothalamic tract and subsequent activation of nitric oxide synthase (NOS). However, previous studies using NADPH-diaphorase staining or immunocytochemistry to localize NOS found either no or only a few positive cells in the SCN. By monitoring conversion of L-[3H]arginine to L-[3H]-citrulline, this study demonstrates that extracts of SCN tissue exhibit NOS specific activity comparable to that of rat cerebellum. The enzymatic reaction requires the presence of NADPH and is Ca2+/calmodulin-dependent. To distinguish the neuronal isoform (nNOS; type I) from the endothelial isoform (type III), the enzyme activity was assayed over a range of pH values. The optimal pH for the reaction was 6.7, a characteristic value for nNOS. No difference in nNOS levels was seen between SCN collected in day versus night, either by western blot or by enzyme activity measurement. Confocal microscopy revealed for the first time a dense plexus of cell processes stained for nNOS. These data demonstrate that neuronal fibers within the rat SCN express abundant nNOS and that the level of the enzyme does not vary temporally. The distribution and quantity of nNOS support a prominent regulatory role for this nitrergic component in the SCN.     

Neuronal correlates of sleep, wakefulness and arousal in a diurnal insect

The discovery that various states of sleep, rest, wakefulness and arousal in man can be correlated with specific forms of the electroencephalogram1 has led to intensive studies of these states, mostly in mammals2-5. Today it is generally accepted that circadian sleep-wakefulness cycles occur in mammals and birds2,3,6. Behavioural observations on sleep in moths have also been published7; many other invertebrates demonstrate rest/activity cycles8. Circadian sensitivity fluctuations in both central9 and peripheral10-15 components of the visual system of various nocturnal arthropod species have been demonstrated. We now report that long-term, extracellular, single-unit recordings from optomotor interneurones in the optic lobes of forager honey bees reveal an oscillation in their sensitivity to moving visual stimuli16, 17. The oscillation displays properties typical of a circadian rhythm6, 18. The sensitivity of the neurons is higher during the subjective day than during the subjective night. The locomotor activity of individual, fixed walking forager bees shows a similar circadian oscillation and is also higher during the subjective day. Visual and mechanical stimuli can act directly on the interneurones and restore their sensitivity during times of reduced neuronal responsiveness. A comparison with results available for mammals makes it likely that the neuronal phenomena presented here are correlates of the bee's circadian sleep-wakefulness rhythm.     

Reproductive biology knowledge, and behaviour of teenagers in East, Central and Southern Africa: the Zimbabwe case study

Sexuality in the teenager is often complicated by unplanned/unwanted pregnancy, abortion and the risks of STDs including AIDS. There is therefore a need for improved understanding of factors affecting adolescent sexuality and the implementation of programmes designed to improve their knowledge, risk awareness and subsequent behavioural outcomes. A multicentre study of reproductive health knowledge and behaviour followed by a health education intervention was undertaken amongst teenagers in selected countries of East, Central and Southern Africa. Reported here are findings at baseline derived from the Zimbabwe component on reproductive biology knowledge and behavior. A self-administered questionnaire was used among 1 689 adolescent pupils drawn from rural, urban, co-education, single sex, boarding and day secondary schools in Zimbabwe. Correct knowledge on reproductive biology as measured by the meaning and interpretation of menstruation and wet dreams varied by school from 68 pc to 86 pc, with a significant trend (p < 0,01) based on level of education at baseline. The reported mean age at which menarche took place was 13,5 years +/- 1,3 (mean +/- SD). First coitus was reported to have taken place at the mean age of 12 years for boys and 13,6 years for girls. Seventeen pc of the adolescent pupils reported that they were sexually experienced and 33,2 had relationships. There were misconceptions reported on menstruation with 23 pc reporting that it was an illness. Peers, followed by magazines were the first sources of information on various aspects of reproductive biology, both of which might not provide the correct first information. Among pupils reporting that they were sexually experienced, the largest proportion (56 pc) had unprotected sex. The findings point to the need for targeting the adolescent pupils for information on reproductive biology and increased awareness on the risks of pregnancy, STDs and HIV.     

Neuronal projections from the mesencephalic raphe nuclear complex to the suprachiasmatic nucleus and the deep pineal gland of the golden hamster (Mesocricetus auratus)

Neuronal projections from the mesencephalic raphe system to the suprachiasmatic nucleus and the pineal complex were mapped in this study of the golden hamster, by use of the anterograde tracer Phaseolus vulgaris-leucoagglutinin and the retrograde tracer cholera toxin subunit B. From the median raphe nucleus, a rostral projection ascended in the ventral part of the mesencephalon to continue in the medial forebrain bundle of the forebrain. Nerve fibres from this bundle innervated the ventral and medial parts of the suprachiasmatic nucleus. At the level of the interpeduncular nucleus of the mesencephalon, fibres of the ventral bundle bent dorsally to reach the epithalamic area and to continue in the forebrain in a periventricular position. Some of these fibres innervated the dorsal tip of the suprachiasmatic nucleus. The dorsal raphe nucleus was the origin of a nerve fibre bundle, located in the periaqueductal gray of the mesencephalon, innervating the deep pineal gland and pineal stalk. Injection of cholera toxin B into the suprachiasmatic nucleus labelled cells in the median raphe. Combination of the retrograde tracing from the suprachiasmatic nucleus and serotonin transmitter immunohistochemistry showed that some of the cholera toxin B-immunoreactive nerve cells also contained serotonin. Thus, this study of the golden hamster shows a serotonergic projection from the median raphe nucleus to the suprachiasmatic nucleus and a projection from the dorsal raphe nucleus to the deep pineal gland supporting physiological indications of an influence of serotonin on the photoreceptive circadian system of the brain.     

The platypus is not a rodent: DNA hybridization, amniote phylogeny and the palimpsest theory

We present DNA-hybridization data on 21 amniotes and two anurans showing that discrimination is obtained among most of these at the class and lower levels. Trees generated from these data largely agree with conventional views, for example in not associating birds and mammals. However, the sister relationships found here of the monotremes to marsupials, and of turtles to the alligator, are surprising results which are nonetheless consistent with the results of some other studies. The Marsupionta hypothesis of Gregory is reviewed, as are opinions about the placement of chelonians. Anatomical and reproductive data considered by Gregory do not unequivocally preclude a marsupial-monotreme special relationship, and there is other recent evidence for placing turtles within the Diapsida. We conclude that the evidential meaning of the molecular data is as shown in the trees, but that the topologies may be influenced by a base-compositional bias producing a seemingly slow evolutionary rate in monotremes, or by algorithmic artefacts (in the case of turtles as well).     

A molecular perspective on the systematics and evolution of the genus Arvicanthis (Rodentia, Muridae): inferences from complete cytochrome b gene sequences

Systematics of the genus Arvicanthis, the African unstriped grass rat, are somewhat controversial. Most recent taxonomic revisions list five to six species but the definition of some of these (Arvicanthis dembeensis, Arvicanthis nairobae, and Arvicanthis niloticus) is uncertain. The complete mitochondrial cytochrome b gene (1140 bp) was sequenced for 20 specimens from throughout the range of the genus to determine the intrageneric genetic structure, construct a molecular phylogeny, and evaluate classical taxonomies. Neighbor-joining and maximum parsimony analyses yielded identical phylogenetic trees that identify two major lineages: the first one (1) is composed of specimens usually referred to A. niloticus but representing several distinct species, and the other (2) is a complex including "true" A. niloticus from Egypt and northern West Africa as well as Arvicanthis abyssinicus, Arvicanthis dembeensis, and Arvicanthis somalicus. An analysis on a 357-bp fragment of the cytochrome b including published data on A. nairobae indicates that this taxon is part of clade (1). Calibration of the number of 3rd position transversion changes with the murid fossil record suggests that clades (1) and (2) diverged approximately 5 Myr ago. Arvicanthis niloticus as currently recognized is a paraphyletic association and this name should be restricted to the Egyptian and northern West African sample. We also suggest referring to A. dembeensis as A. niloticus, as our cytochrome b data do not support its recognition as a distinct species. Clade (1) is subdivided in three lineages, geographically corresponding to southern West, Central, and East Africa. The high genetic divergence detected between the Central African lineage and the other two lineages suggests that they probably represent separate species. Clade (2) experienced rapid cladogenetic events during the late Pliocene, with the A. somalicus lineage being the first to emerge, followed by the ancestor of A. abyssinicus and A. blicki. This period was characterized by significant climatic and environmental changes, such as the extension of open habitats, which might have provided a stimulus for speciation in this savanna-dwelling genus. Confrontation of our molecular results with chromosomal data shows a high degree of congruence between the two datasets.     

Sequence and phylogenetic analyses of a new STLV-I from a naturally infected tantalus monkey from Central Africa

Simian T-cell leukemia virus (STLV-I) is an oncovirus highly related to human T-cell leukemia virus type I (HTLV-I). To further examine the extent of variability, dissemination patterns, phylogeny, and evolution of these viruses, we analyzed a new STLV-I variant from a naturally infected Cercopithecus aethiops var. tantalus from the Central African Republic. Sequence analyses of its LTR, gag, pol, env, and pX (OrfII) genes indicated that this isolate, STLV-I (Tan 90), is 6% divergent from the prototype HTLV-I (ATK) and is the most divergent African STLV-I characterized to date. Our phylogenetic data indicate that southeast Asian and African STLV-I and HTLV-I strains segregated from each other thousands of years ago and that Japanese HTLV-I strains represent a relatively recent introduction of African or New World isolates. The data also indicate that interspecies transmission occurred several times on different continents over prolonged periods of time.     

The early history of tuberculosis in central East Africa: insights from the clinical records of the first twenty years of Mengo Hospital and review of relevant literature

SETTING: Mengo Hospital, in present day Kampala, Uganda, 100 years ago. OBJECTIVE: To determine the presence of tuberculosis in the Bagandan population of central East Africa and elsewhere in Africa at the time of early explorations by Europeans. DESIGN: The case records kept by Albert Cook for two decades beginning in 1897, 35 years after the first visit of Speke to this region, were reviewed for evidence of tuberculosis among Bagandans. Writings of other contemporary medical observers were reviewed for evidence of tuberculosis in pre- and early-colonial Africa. RESULTS: Well documented cases of tuberculosis were observed by Cook beginning in 1897. A minimum total of 93 cases of tuberculosis were included in 26 806 admissions to Mengo Hospital from 1897 through 1916. No secular trend in the prevalence of tuberculosis among patients admitted was apparent. A review of the prior literature concerning tuberculosis in precolonial Africa suggests that tuberculosis may have been present in several regions prior to European exploration, but was probably absent elsewhere. CONCLUSIONS: The concept of all of Africa and all of the people of Africa as virgin soil for tuberculosis is rooted in an archaic Eurocentric view of Africa, and cannot be supported today by available data.     

The effects of normal, frozen, and hyaluronidase-digested nucleus pulposus on nerve root structure and function

STUDY DESIGN: Autologous nucleus pulposus was modified and applied to the cauda equina in pigs. Histology and neurophysiology were assessed after 7 days. OBJECTIVES: To assess if alterations of the nucleus pulposus would change the degree and distribution of the nerve injury induced by autologous nucleus pulposus. SUMMARY OF BACKGROUND DATA: It was reported recently that nucleus pulposus may induce structural and functional changes in nerve roots after epidural application. The basic mechanisms causing these changes are not fully understood. METHODS: Nucleus pulposus was harvested from lumbar discs and submitted to either of three treatments; 37 C for 24 hours (n = 5), -20 C for 24 hours (n = 5), or digestion by hyaluronidase for 24 hours (n = 6). In two additional pigs, nucleus pulposus was applied just after harvest as a control to verify previous observations. After 7 days, nerve conduction velocity was recorded, and specimens were processed for blinded light microscopic assessment. RESULTS: When nucleus pulposus was applied just after harvest, or when it had been kept at 37 C or digested by hyaluronidase for 24 hours, there was a significant reduction in nerve conduction velocity similar to previous observations. When nucleus pulposus had been kept at -20 C for 24 hours, however, there was no reduction in conduction velocity. There were no apparent differences between the groups at the histologic assessment. Staining of the nucleus pulposus showed that the cells in the nucleus pulposus exposed to -20 C were lysed, whereas the cells in the nucleus pulposus treated by the two other methods were mainly unaffected. CONCLUSIONS: Because freezing of the nucleus pulposus probably kills the cells but does not affect other components, one may assume that the biologic effects induced by the nucleus pulposus may be related to its cell population.     

The chemotherapy of rodent malaria, XXV. Antimalarial activity of WR 122,455 (a 9-phenanthrenemethanol) in vivo and in vitro

WR 122,455, 3,6-bis-(trifluoromethyl)-alpha-(2-piperidinyl)-9-phenanthrenemethanol HCl, suppresses infection with drug-sensitive Plasmodium berghei N strain in mice. It acts rapidly and affects all the stages of the asexual intraerythrocytic parasites, the effective dose levels being about three times those of chloroquine and one-twelfth to one-fifteenth those of quinine. Under the influence of WR 122,455 haemozoin seems to disappear from the affected parasites following an initial coarsening of the fine pigment granules. These changes are similar to those exerted by quinine. Large doses of WR 122,455 have a residual affect due in part, at least, to deposition of insoluble material in the tissues. The drug appears to exert an antagonistic action on chloroquine when both drugs are administered simultaneously. It has no causal prophylactic effect. In vitro WR 122,455 is a competitive antagonist of chloroquine in a similar manner to quinine, and appears to have a dissociation constant (Ki) of 2-26 x 10(-8) M, making it about 18 times as active as quinine. WR 122,455 interacts strongly with calf thymus DNA, but the mechanism of interaction has yet to be defined. Mice tolerate single doses of a saline/Tween 80 suspensions up to about 400 mg/kg but sc administration induces necrotic changes at the injection site. Up to 30 mg/kg daily po for seven consecutive days is well tolerated systemically but local tissue reaction may occur if the drug is given by the sc or ip routes. However, systemically up to 60 mg/kg is tolerated sc or ip. The relation of WR 122,455 to drug resistant malaria will be reported later.