Activity In Other Regions Research Articles

Applying science to the diseases of poverty.

TDR, the Special Programme for Research and Training in Tropical Diseases, was set up in the mid-1970s to promote research to improve the health of the poor. This year TDR celebrates 30 years of its key decision-making body, the Joint Coordinating Board--one of the first such bodies to represent a balance of donor and disease-endemic countries. This year a new strategy marks a turning point for TDR, which is co-sponsored by the United Nations Children's Fund, the United Nations Development Programme (UNDP), the World Bank and the World Health Organization (WHO). Dr Robert Ridley explains. Q: Why was TDR originally set up? A: TDR was set up in the mid-1970s when WHO, through its Advisory Committee on Health Research and the World Health Assembly (WHA), recognized that science was not being applied enough to of poverty. The idea was to create an organization that had a broad-based governance mechanism beyond WHO, since it would rely on voluntary contributions and would not take contributions from the core needs of WHO. WHO and the WHA recognized that this research had to be done through partnerships. UNDP and the World Bank backed the project and other organizations came on board. TDR's original goal was to promote research led by people and institutions in countries that are affected by diseases. That model and goal are as valid today as they were. Q: The concept of tropical diseases originates from the practised by 19th century colonial powers to protect themselves in the tropics. Have you considered changing your name? A: There has been some discussion about the name. Our new strategy refers more to infectious of poverty, but if you look at the terms tropical disease and medicine they still cover a field that is generally recognized today. You still have associations and institutes with the name and--at WHO--a department of neglected diseases, The name has other connotations which we should be aware of, but given the recognition of the name and loyalty to TDR, particularly in developing countries, we decided to keep it. Q: Has the Global Fund to Fight AIDS, Tuberculosis and Malaria drawn donor funds from TDR? A: The fund is not pulling resources from TDR. The fund finances drug procurement and national strategies. We promote research on how to scale up provision of those drugs in resource poor settings for the implementation of public health programmes and the effective delivery of products. Control and implementation are too often seen as distinct, but in fact they are two sides of the same coin. The best control programmes take account of research from the start and vice versa. Q: TDR is working with developing countries to protect clinical trials participants. But do the resulting national ethical review committees have the technical competence? A: There is a common misperception that there isn't adequate capacity to carry out any research in developing countries and that they are reliant on researchers in developed countries. We need partnership between north and south but we also need to recognize the ability of developing countries to fully participate and engage, and to initiate things on their own. That way we can avoid the mistakes often made by top-down approaches, whether in research or in development aid. The Strategic Initiative for Developing Capacity in Ethical Review, or SIDCER, was prompted by the need for strong ethical review in countries. Many ethical committees are now starting to submit themselves to systems and standards of accreditation. It is adding to the quality of clinical research. Most success so far has been in WHO's South-East Asia Region and the Commonwealth of Independent States but there is increasing activity in other regions. Q: One of the most elusive quests of scientific research has been for a malaria vaccine. Why have so many promising candidates failed and should more money be invested in this area? …

Atypical slow waves generated in gastric corpus provide dominant pacemaker activity in guinea pig stomach

When intracellular recordings were made from the circular layer of the intact muscular wall of the isolated guinea pig gastric corpus, an ongoing regular high frequency discharge of slow waves was detected even though this region lacked myenteric interstitial cells. When slow waves were recorded from preparations consisting of both the antrum and the corpus, slow waves of identical frequency, but with different shapes, were generated in the two regions. Corporal slow waves could be distinguished from antral slow waves by their time courses and amplitudes. Corporal slow waves, like antral slow waves, were abolished by buffering the internal concentration of calcium ions, [Ca2+]i, to low levels, or by caffeine, 2-aminoethoxydiphenyl borate or the chloride channel blocker DIDS. Corporal preparations demonstrated an ongoing discharge of unitary potentials, as has been found in all other tissues containing interstitial cells. The experiments show that the corpus provides the dominant pacemaker activity which entrains activity in other regions of the stomach and it is suggested that this activity is generated by corporal intramuscular interstitial cells.

Retrieving accurate and distorted memories: Neuroimaging evidence for effects of emotion

While limbic activity is known to be associated with successful encoding of emotional information, it is less clear whether it is related to successful retrieval. The present fMRI study assessed the effects of emotion on the neural processes engaged during retrieval of accurate compared to distorted memories. Prior to the scan, participants (16 young adults) viewed names of neutral (e.g., frog) and emotional (e.g., snake) objects and formed a mental image of the object named. They were shown photos of half of the objects. During the fMRI scan, participants saw object names and indicated whether or not they had seen the corresponding photo. Memory distortions (misattributions) occurred when participants incorrectly indicated whether or not a photo had been studied. Activity in some regions (e.g., L anterior hippocampus) was related to accurate retrieval (correct attributions > misattributions) for emotional and neutral items. However, activity in other regions corresponded with accurate retrieval specifically for emotional items (e.g., in R amygdala/periamygdaloid cortex and L orbitofrontal cortex) or for neutral items (e.g., in lateral inferior prefrontal cortex and R posterior hippocampus). Results indicate that emotional salience modulates the processes engaged during accurate retrieval and that activity in limbic regions corresponds with accurate memory assignment for emotional items. To our knowledge, this study is the first to demonstrate a link between limbic engagement at retrieval and accurate memory attribution.

Effects of excitotoxic thalamic intralaminar nuclei lesions on attention and working memory

In rats, lesions of the thalamic intralaminar nuclei (ILn) impair measures of working memory, but it is unclear whether alterations of attention contribute to the mnemonic deficits. The present experiment tested the effects of ILn lesions on a two-lever attention task that required discrimination of visual signals and non-signals. Rats were trained presurgically in the task and then received sham surgery or infusions of n-methyl- d-aspartate (NMDA) into the ILn to induce excitotoxic lesions. ILn lesions transiently decreased accurate detection of signals. ILn lesions also increased omissions. Compared to sham-lesioned rats, ILn-lesioned animals were not differentially affected when task demands were increased by presenting a visual distracter. Finally, a retention interval was incorporated into the task to assess whether the lesions affected acquisition of a working memory version of this behavioral paradigm. Unlike sham-lesioned animals, ILn-lesioned rats did not demonstrate a significant improvement in signal detection when a retention interval was introduced. The transient lesion-induced deficits in the attention task suggest that, in rats, the ILn may contribute to aspects of attentional processing, but through neural re-organization or activity in other regions, there is compensation for the loss of ILn functioning. The ILn appear to be necessary for maintaining performance when working memory demands are increased.

‘Against the Grain’: Special Operations Executive in Spain, 1941–45

This article surveys the activities of Special Operations Executive in Spain during the course of the Second World War. Under the constraints of a foreign policy that sought to gradually encourage the regime of General Francisco Franco to become more resolutely neutral rather than pro-Axis and ‘non-belligerent’, SOE nonetheless entered Spain with the hopes of developing a series of contacts with groups and individuals that could be turned into an active Resistance if Spain joined the Axis, or if Nazi Germany either invaded or occupied the Iberian Peninsula. Once the possibility of an Axis landing in Spain was decisively dismissed, SOE had to break away from its mandate to ‘set Europe ablaze’ and find a new role. In Spain, the successful development of SOE's intelligence gathering capabilities in the economic sphere, especially in the Allied campaign against German wolfram smuggling, provided the organization with a purpose that definitely went ‘against the grain’ when compared to activities in other regions and countries.

First report from the Asian Rotavirus Surveillance Network.

Rotavirus remains the most common cause of severe, dehydrating diarrhea among children worldwide. Several rotavirus vaccines are under development. Decisions about new vaccine introduction will require reliable data on disease impact. The Asian Rotavirus Surveillance Network, begun in 2000 to facilitate collection of these data, is a regional collaboration of 36 hospitals in nine countries or areas that conduct surveillance for rotavirus hospitalizations using a uniform World Health Organization protocol. We summarize the Network's organization and experience from August 2001 through July 2002. During this period, 45% of acute diarrheal hospitalizations among children 0–5 years were attributable to rotavirus, higher than previous estimates. Rotavirus was detected in all sites year-round. This network is a novel, regional approach to surveillance for vaccine-preventable diseases. Such a network should provide increased visibility and advocacy, enable more efficient data collection, facilitate training, and serve as the paradigm for rotavirus surveillance activities in other regions.

Brain activation patterns associated with working memory in relapsing-remitting MS.

Patients with multiple sclerosis (MS) show changes in brain activation patterns during visual and motor tasks that include decreases in the typical local network for a function and increases in other brain regions. To determine whether brain activation patterns associated with working memory are affected by MS. Activation of working memory circuitry was examined using an fMRI n-back task in adults with mild relapsing-remitting MS (RRMS; n = 10) and demographically matched healthy controls (n = 10). Group differences in brain activation emerged during both low- and high-demand conditions (p < 0.001). Overall, patients showed less activation than controls in core prefrontal and parietal regions of working memory circuitry, and greater activation in other regions within and beyond typical working memory circuitry, including bilateral medial frontal, cingulate, parietal, bilateral middle temporal, and occipital regions. Relative to controls, patients with mild RRMS showed shifts in brain activation patterns within and beyond typical components of working memory circuitry.

Testing for dual brain processing routes in reading: a direct contrast of chinese character and pinyin reading using FMRI.

Chinese offers a unique tool for testing the effects of word form on language processing during reading. The processes of letter-mediated grapheme-to-phoneme translation and phonemic assembly (assembled phonology) critical for reading and spelling in any alphabetic orthography are largely absent when reading nonalphabetic Chinese characters. In contrast, script-to-sound translation based on the script as a whole (addressed phonology) is absent when reading the Chinese alphabetic sound symbols known as pinyin, for which the script-to-sound translation is based exclusively on assembled phonology. The present study aims to contrast patterns of brain activity associated with the different cognitive mechanisms needed for reading the two scripts. fMRI was used with a block design involving a phonological and lexical task in which subjects were asked to decide whether visually presented, paired Chinese characters or pinyin "sounded like" a word. Results demonstrate that reading Chinese characters and pinyin activate a common brain network including the inferior frontal, middle, and inferior temporal gyri, the inferior and superior parietal lobules, and the extrastriate areas. However, some regions show relatively greater activation for either pinyin or Chinese reading. Reading pinyin led to a greater activation in the inferior parietal cortex bilaterally, the precuneus, and the anterior middle temporal gyrus. In contrast, activation in the left fusiform gyrus, the bilateral cuneus, the posterior middle temporal, the right inferior frontal gyrus, and the bilateral superior frontal gyrus were greater for nonalphabetic Chinese reading. We conclude that both alphabetic and nonalphabetic scripts activate a common brain network for reading. Overall, there are no differences in terms of hemispheric specialization between alphabetic and nonalphabetic scripts. However, differences in language surface form appear to determine relative activation in other regions. Some of these regions (e.g., the inferior parietal cortex for pinyin and fusiform gyrus for Chinese characters) are candidate regions for specialized processes associated with reading via predominantly assembled (pinyin) or addressed (Chinese character) procedures.

Functional anatomy of high-resolution visual mental imagery.

This study had two purposes. First, in order to address the controversy regarding activation of the primary visual area (PVA) during visual mental imagery, regional cerebral blood flow (rCBF) was recorded while subjects performed a task that required high-resolution visual mental imagery. Second, in order to discover whether verbal descriptions can engage visual mechanisms during imagery in the same way as visual stimuli, subjects memorized 3D scenes that were visually presented or were based on a verbal description. Comparison of the results from the imagery conditions to a non-imagery baseline condition revealed no activation in PVA for imagery based on a verbal description and a significant decrease of rCBF in this region for imagery based on visual learning. The pattern of activation in other regions was very similar in the two conditions, including parietal, midbrain, cerebellar, prefrontal, left insular, and right inferior, temporal regions. These results provide strong evidence that imagery based on verbal descriptions can recruit regions known to be engaged in high-order visual processing.

Thermoluminescence chronology of sand profiles in the Mu Us Desert, China

Thermoluminescence (TL) is used to calculate the ages of two sand–loess profiles in the marginal zone of the Mu Us Desert, China. Alternating units of dune sand and loess with palaeosols in the two profiles imply episodes of dune formation separated by periods of loess accumulation and pedogenesis. Our results indicate that there are three layers of dune sand intercalated in sediments of the last full glacial cycle, suggesting the occurrence of three arid episodes during this time. The first arid episode within this period occurred between <75 and ∼55 ka, broadly corresponding to marine oxygen isotope Stage 4. The second arid episode, with a TL age around 48 ka, can be correlated with part of Stage 3. The latest arid episode occurred between <27 and ∼10 ka, broadly coincident with Stage 2. These periods of dune activity in northern China are compared with records of aeolian influx from deep-sea cores and the Vostok ice core, and with continental dune activity in other regions.

Modeling the Sustainability of Subsistence Farming and Hunting in the Ituri Forest of Zaire

We used empirical data to simulate the impacts, over the next 40 years, of subsistence‐level agricultural clearing and bushmeat consumption on forest resources within the recently established Okapi Wildlife Reserve in northeastern Zaire. Satellite imagery, human population census data, and field measurements were used to calculate present and projected impacts of agricultural clearing on forest cover. Data on per capita meat consumption and the species captured by hunters were combined with relevant ecological data to estimate ratios of consumption to production and to assess the sustainability of hunting. Even with projected population growth of nearly 300% among local communities over 40 years, sufficient secondary forest is available that agricultural clearing will have minimal effect on mature forest throughout most of the reserve. Impacts on the reserve’s fauna will be more dramatic, particularly within 15 km of villages, where most hunting currently occurs. Subsistence exploitation of forest antelopes may be sustainable in much of the reserve (especially if high estimates of game production are used), but as the human population continues to increase duikers will likely be over‐hunted. Primate populations do not appear to be threatened in the near future in those areas where bow hunters exploit monkeys, but an increase in this specialized activity in other regions of the reserve and growing human populations could change this. Although additional surveys of commonly hunted species throughout the Okapi Wildlife Reserve are essential to enhancing the precision of the simulation, our results suggest that mitigation efforts should be designed and implemented now if the long‐term effects of domestic bushmeat consumption are to be addressed.Modelado de la Sustentabilidad de Cosecha y Caza de Subsistencia en el Bosque Ituri en ZaireUtilizamos datos empíricos para simular los impactos del nivel de persistencia de clareo agricultural y el consumo de carne silvestre en los recursos forestales durante los próximos 40 años, dentro de la recientemente establecida reserva de vida silvestre Okapi en el noreste de Zaire. Imágenes de satélite, datos de censos poblacionales humanos y mediciones de campo fueron usados para calcular los impactos actuales y proyectados del clareo agricultural en la cobertura del bosque. Datos de consumo de carne per cápita y de las especies capturadas por caza fueron combinados con datos ecológicos relevantes para estimar la relación del consumo con la producción y para evaluar la sustentabilidad de la caza. Aún con el crecimiento poblacional proyectado de cerca de un 300% a lo largo de 40 años entre las comunidades locales, existe suficiente bosque secundario viable de tal manera que el clareo agricultural tendrá efectos mínimos sobre el bosque maduro a lo largo de la mayoría de la reserva. Impactos en la fauna de la reserva serán mas dramáticos, particularmente dentro de los 15 km de villas, donde la mayorá de la caza se lleva a cabo actualmente. La explotación de subsistencia de antílopes del bosque podría ser sustentable en gran parte de la reserva (especialmente si se utilizan estimaciones de producción cinegética), pero en vista de que la población humana continúa incrementando, algunos antílopes podrían ser sobre‐cazados. Las poblaciones de primates no parecen estar amenazadas a corto plazo en aquellas áreas donde los cazadores con arco capturan los monos, pero un incremento en esta actividad especializada en otras regiones de la reserva, aunado al crecimiento poblacional humano podría cambiar esta situación. Aunque estudios adicionales sobre las especies comunmente cazadas en la reserva Okapi son escenciales para incrementar la precisión de la simulación, nuestros resultados sugieren que los esfuerzos de mitigación deberán ser diseñados e implementados ahora si es que se pretenden abordar los impactos a largo plazo del consumo de carne silvestre.

El impacto del Tratado de Libre Comercio entre México, Estados Unidos y Canadá en el sector agropecuario de Coahuila

El presente trabajo analiza la importancia que tiene el sector agropecuario en la economía de Coahuila; el impacto del Tratado de Libre Comercio en este sector, y las perspectivas con la operación de dicho tratado. El sector agropecuario de Coahuila se encuentra rezagado en comparación con el resto de los sectores económícos de la entidad, así como de las actividades agrícolas de otras regionesdel país tal como el noroeste y aún más con los Estados Unidos de América y Canadá. En estas condiciones en que se encuentra el sector agropecuario de Coahuila y si continúan las mismas políticas para el campo, el proceso de competencia con la operación del TLC no se presentará en toda su expansión una vez vencidos los plazosacordados para abrir totalmente las fronteras. Del conjunto de ramas que componen el sector agropecuario de Coahuila, son contadas las que tienen posibilidades de competir en el mercado internacional.

The effect of methamphetamine on histamine level and histidine decarboxylase activity in the rat brain

To examine biochemical changes in the brain histamine (HA) neuron system after acute and chronic administrations of methamphetamine (MAP), HA levels and histidine decarboxylase (HDC) activities in the rat cortex, striatum, diencephalon, midbrain, pons-medulla and cerebellum were measured. In the cortex and striatum, acute administration of MAP (1 and 3 mg/kg) increased HA levels 1 h later. Acute administration of MAP (10 mg/kg) and chronic administration of MAP (3 mg/kg) for 21 days also increased HA levels and HDC activities in the cortex and striatum 1 h after the last injection. In the diencephalon, acute administration of MAP (3 and 10 mg/kg) and chronic administration of MAP (3 mg/kg) decreased HA level 1 h after the last injection, but chronic administration of MAP (3 mg/kg) increased HDC activity 1 h after the last injection. There were no significant changes in HA levels and HDC activities in other regions after acute and chronic administrations of MAP. These findings suggest that MAP may activate the brain HA neuron system, although MAP acts more strongly on the cortex and striatum than on the diencephalon.

Sequential alteration of [ 3H]rolipram binding in gerbil brain after transient cerebral ischemia

The time course of rolipram (Ca 2+/calmodulin independent cyclic adenosine monophosphate inhibitor) binding sites changes following gerbil transient forebrain ischemia was determined using receptor autoradiography. Gerbils subjected to 10-min ischemia revealed a significant reduction in rolipram binding in most selectively vulnerable regions early in the recirculation (1–5 h). Marked reduction in the rolipram binding was seen in the selectively vulnerable areas 48 h or 7 days after ischemia. Thereafter, the rolipram binding in the hippocampal CA1 and CA3 sectors, which were most vulnerable to ischemia, was severely reduced up to 1 month after recirculation. In contrast, the reduction of the rolipram binding activity in other regions recovered to sham-operated level or showed a slight recovery. Interestingly, the dentate gyrus, which was resistant to ischemia, also exhibited a significant reduction of the rolipram binding activity up to I month after ischemia. Eight months after ischemia, the hippocampal CA 1 and CA3 sectors showed severe shrinkage and marked reduction in the rolipram binding. Other regions exhibited no significant reduction in the rolipram binding except for a slight reduction in the thalamus. These results demonstrate that transient cerebral ischemia causes severe reduction in rolipram binding sites in selectively vulnerable areas, and this reduction precedes the neuronal cell loss. These findings may reflect the alteration of an intracellular phosphodiesterase activity after ischemia.

Neurophysiological correlates of the affective-motivational dimension of pain

P rice and Harkins present compelling evidence that pain sensation and pain-related affect constitute two distinct dimensions of I pain that can be separately measured and manipulated. Furthermore, their differentiation of immediate and secondary affective stages adds new precision to our understanding of pain perception and pain treatment. The authors hypothesize that neural responses in some areas of the brain should covary more closely with the sensory-discriminative dimension of pain while the activity in other regions would better correlate with the affective dimension of pain. Further, neurons in such “affective” areas would show modulation by factors that selectively influence pain-related affect. We would like to present evidence that regions of thalamus meet these criteria. During the past several years we have studied the response properties of nociceptive neurons within the thalamic ventroposterior medial nucleus (VPM), as well as those within the more medial thalamic regions (primarily, parafascicularis or Pf). Discharge frequency of neurons in both of these regions correlate well with the intensity of noxious heat stimuli and thus codes heat pain intensity.13The most salient differences between these regions are: (1) only those cells in the ventroposterior thalamus have small receptive fields and (2) only those cells in medial thalamus are obviously modulated by behavioral factors, such as attention and task relevance.1-5

Testosterone locally increases vasopressin content but fails to restore choline acetyltransferase activity in other regions in the senescent male rat brain

Age-related decreases have been reported in both vasopressinergic and cholinergic innervation in the rat brain. Since both systems are also sensitive to sex steroids, the effect of testosterone supplementation on vasopressin (AVP) levels and on choline acetyltransferase (ChAT) activity was investigated in the brains of young, middle-aged and aged male rats. Although no age-related changes in AVP levels were observed in the lateral septum or the medial amygdala (MA), peripheral testosterone administration raised AVP levels in the MA in all age groups. ChAT activity decreased with age in the medial preoptic area and was not restored by testosterone.

Unique properties of non-N-methyl-D-aspartate excitatory responses in cultured purkinje neurons.

Cerebellar Purkinje neurons respond to glutamate and to the agonists quisqualate (QA) and kainate (KA) with prolonged, multiphasic, voltage-dependent depolarizations. In contrast, N-methyl-D-aspartate (NMDA) at equivalent doses is not effective as an agonist for Purkinje neurons. The responses to QA and KA are reduced by extracellular Cd2+ (30 microM), by increased Mg2+ or Ca2+ (12 mM), and by the glutamate antagonist kynurenic acid (1 mM) but not by the NMDA-selective antagonist 2-amino-5-phosphonovalerate (100 microM). The short pressure application of 1 microM QA (less than or equal to 0.5 s) produces a response often exceeding 1 min in duration, which consists of several phases: rapid initial depolarization, followed by a long plateau, repolarization, and a subsequent small hyperpolarization. A similar response is evoked by glutamate and KA at higher doses (30-50 microM). The initial and plateau depolarizations are dependent on Na+, being reduced by substitution of external Na+ with sucrose or choline, but are not affected by the Na+ channel blocker tetrodotoxin. Rectification, observed at hyperpolarized potentials below -60 mV set by current clamp, is attributed in part to an intrinsic voltage sensitivity of the agonist-activated response. Both the duration and the magnitude of the excitatory responses were found to be voltage-dependent. Single-channel recordings of a Ca2+-sensitive K+ channel, activated selectively during the excitatory response, suggest that intracellular Ca2+ increases during the plateau phase. Certain properties of the excitatory responses in the Purkinje neuron resemble those associated with NMDA-receptor activation in other regions of the central nervous system, including voltage-sensitive rectification, blockade by divalent cations, and the induction of increased intracellular Ca2+ during the excitatory response. These unique properties may enable the Purkinje neuron to express both rapid and long-term effects of glutamatergic transmission with non-NMDA receptors alone.

Transcription of spacer sequences flanking the rat 45S ribosomal DNA gene.

The transcriptional activity of spacer sequences flanking the rat 45S ribosomal DNA (rDNA) gene were studied. Nascent RNA labeled in in vitro nuclear run-on reactions hybridized with both 5' and 3' spacer regions. The highest level of hybridization was seen with an rDNA fragment containing tandem repeats of a 130-base-pair sequence upstream of the 45S rRNA initiation site. Synthesis of RNA transcripts homologous to this internally repetitious spacer region was insensitive to high levels of alpha-amanitin, suggesting that it is mediated by RNA polymerase I. Analysis of steady-state RNA showed that these transcripts were present at extremely low levels in vivo relative to precursor rRNA transcripts. In contrast, precursor and spacer run-on RNAs were synthesized at similar levels. This suggests that spacer transcripts are highly unstable in vivo; therefore, it may be the process of transcription rather than the presence of spacer transcripts that is functionally important. Transcription in this upstream rDNA region may be involved in regulation of 45S rRNA synthesis in rodents, as has been suggested previously for frog rRNA. In addition, the presence of transcriptional activity in other regions of the spacer suggests that some polymerase I molecules may transcribe through the spacer from one 45S gene to the next on rodent rDNA.

Transcription of spacer sequences flanking the rat 45S ribosomal DNA gene.

The transcriptional activity of spacer sequences flanking the rat 45S ribosomal DNA (rDNA) gene were studied. Nascent RNA labeled in in vitro nuclear run-on reactions hybridized with both 5' and 3' spacer regions. The highest level of hybridization was seen with an rDNA fragment containing tandem repeats of a 130-base-pair sequence upstream of the 45S rRNA initiation site. Synthesis of RNA transcripts homologous to this internally repetitious spacer region was insensitive to high levels of alpha-amanitin, suggesting that it is mediated by RNA polymerase I. Analysis of steady-state RNA showed that these transcripts were present at extremely low levels in vivo relative to precursor rRNA transcripts. In contrast, precursor and spacer run-on RNAs were synthesized at similar levels. This suggests that spacer transcripts are highly unstable in vivo; therefore, it may be the process of transcription rather than the presence of spacer transcripts that is functionally important. Transcription in this upstream rDNA region may be involved in regulation of 45S rRNA synthesis in rodents, as has been suggested previously for frog rRNA. In addition, the presence of transcriptional activity in other regions of the spacer suggests that some polymerase I molecules may transcribe through the spacer from one 45S gene to the next on rodent rDNA.

Prolyl-hydroxylase activity in odontoblasts from bovine incisor and premolar teeth

Odontoblasts of incisor and premolar teeth showed high prolyl-hydroxylase (EC 1.14.11.2; proline, 2-oxoglutarate dioxygenase) activity, but the activities in other regions of these dental pulps were low. These results suggest that these odontoblasts are concerned with the biosynthesis and processing of dentine collagen.