Novel porphyrin derivative containing cations as new photodynamic antimicrobial agent with high efficiency

Bacterial infections from chronic wounds affect about 175 million people each year and are a significant clinical problem. Through the integration of photodynamic therapy (PDT) and chemotherapy, a new photosensitizer consisting of ammonium salt N,N-bis-(2-hydroxyethyl)-N-(6-(4-(10,15,20-trimesitylporphyrin-5-yl) phenoxy) hexane)-N-methanaminium bromide, TMP(+) was successfully synthesized with a total reaction yield of 10%. The novel photosensitizer consists of two parts, a porphyrin photosensitizer part and a quaternary ammonium salt part, to achieve the synergistic effect of photodynamic and chemical antibacterial activity. With the increase of TMP(+) concentration, the diameter of the PCT fiber membranes (POL/COL/TMP(+); POL, polycaprolactone; COL, collagen) gradually increased, which was caused by the charge of the quaternary ammonium salt. At the same time, the antibacterial properties were gradually improved. We finally selected the PCT 0.5% group for the antibacterial experiment, with excellent performance in fiber uniformity, hydrophobicity and biosafety. The antibacterial experiment showed that the modified porphyrin TMP(+) had a better antibacterial effect than others. In vivo chronic wound healing experiments proved that the antibacterial and anti-inflammatory effect of the PCTL group was the best, further confirmed by H&E histological analysis, immunofluorescence and immunohistochemistry mechanism experiments. This research lays the foundation for the manufacture of novel molecules that combine chemical and photodynamic strategies.

A comparative study of pilomatricoma and epidermoid cyst with ultrasound

AIM

To explore and compare the ultrasonic (US) features of pilomatricoma (PM) and epidermoid cyst (EC) in the differential diagnosis and improve the accuracy of US diagnosis of PM.

MATERIALS AND METHODS

Three hundred and nine patients who underwent US examination before surgery with a histopathological diagnosis of PM or EC after surgery were analysed retrospectively. The patients were categorised into the training and validation sets according to the inspection times. Univariate analysis was undertaken on the US and clinical features of PM and statistically significant variables (p<0.05) were included in the multivariate logistic regression model to establish a diagnostic model.

RESULTS

The results demonstrated that the multivariate logistic regression model for PM was statistically significant (p<0.001). The risk factors included posterior echo attenuation and hypoechoic halos (odds ratio [OR] = 9.277, 10.254) and the protective factors included age, diameter thickness, and posterior echo enhancement (OR=0.936, 0.302, 0.156). The performance of the diagnostic model was tested using the training set (area under the receiver operating characteristic curve [AUC] = 0.974, 95% confidence interval [CI] = 0.955-0.994) and the validation set (AUC = 0.967, 95% CI = 0.926-1.000), which demonstrated good discriminant ability.

CONCLUSIONS

The diagnostic accuracy for PM was higher than that for EC when the nodule is characterised by posterior echo attenuation, hypoechoic halos, smaller thickness, and younger age. The US diagnostic model developed may be used to guide the diagnosis of PM.

Transurethral fluorescence cystoscopy guidance for total resection of bladder tumor

The purpose of this work is to investigate the total resection of bladder tumor under transurethral fluorescence cystoscopy. Nineteen patients with bladder tumor, from which we resected a total of 26 tumors, including 16 single tumors with diameters of 0.5~2 cm, were enrolled in the study. All tumors were located in the posterior wall or neck of the bladder. For the surgery, the size and location of tumors in the bladder were observed by fluorescence cystoscopy. Then, plasma electrocision was used to cut the full-thickness of the bladder to the fat outside of the bladder along the near-end of the tumor, then along the left and right side of bladder (to the far-end), and the full-thickness of the tumor was resected. Finally, the far-end tumor was removed and the full-thickness of the bladder at the bottom was completely resected. All operations were completed successfully within 10-40 min. There was little bleeding during surgery and no secondary bleeding after surgery. Tumor staging found 17 patients at T1 stage (20 tumors) and 2 patients at T2 stage (6 tumors). Patients were followed up for 6~12 months without any recurrence. We show here that total resection of bladder tumor can be accomplished under transurethral fluorescence cystoscopy and preventative resection can be conducted on the suspicious bladder wall with precision to eliminate tumor residue that promotes recurrence.

The nature and origin of nucleus-like intracellular inclusions in Paleoproterozoic eukaryote microfossils

The well-known debate on the nature and origin of intracellular inclusions (ICIs) in silicified microfossils from the early Neoproterozoic Bitter Springs Formation has recently been revived by reports of possible fossilized nuclei in phosphatized animal embryo-like fossils from the Ediacaran Doushantuo Formation of South China. The revisitation of this discussion prompted a critical and comprehensive investigation of ICIs in some of the oldest indisputable eukaryote microfossils-the ornamented acritarchs Dictyosphaera delicata and Shuiyousphaeridium macroreticulatum from the Paleoproterozoic Ruyang Group of North China-using a suite of characterization approaches: scanning electron microscopy (SEM), transmission electron microscopy (TEM), and focused ion beam scanning electron microscopy (FIB-SEM). Although the Ruyang acritarchs must have had nuclei when alive, our data suggest that their ICIs represent neither fossilized nuclei nor taphonomically condensed cytoplasm. We instead propose that these ICIs likely represent biologically contracted and consolidated eukaryotic protoplasts (the combination of the nucleus, surrounding cytoplasm, and plasma membrane). As opposed to degradational contraction of prokaryotic cells within a mucoidal sheath-a model proposed to explain the Bitter Springs ICIs-our model implies that protoplast condensation in the Ruyang acritarchs was an in vivo biologically programmed response to adverse conditions in preparation for encystment. While the discovery of bona fide nuclei in Paleoproterozoic acritarchs would be a substantial landmark in our understanding of eukaryote evolution, the various processes (such as degradational and biological condensation of protoplasts) capable of producing nuclei-mimicking structures require that interpretation of ICIs as fossilized nuclei be based on comprehensive investigations.

Composition, Physiochemical Properties, Nitrogen Fraction Distribution, and Amino Acid Profile of Donkey Milk

This study investigated the changes in chemical composition, nitrogen fraction distribution, and AA profile of milk samples obtained during lactation from the Jiangyue breed of donkey in Northwest China. Results showed that donkey milk contained 9.53% total solids, 1.57% protein, 1.16% fat, 6.33% lactose, and 0.4% ash on average, which is more similar to mare and human milk than to the milk of other mammals. Throughout the lactation investigated, pH and density were constant, protein and ash content showed an apparent negative trend (an increase in lactose content during 120 d postpartum, followed by a decrease), fat content exhibited wide variability, and variations in the content and percentage of whey protein, casein, and AA were small. The casein to whey protein ratio of 52:37 was between the lower value of human milk and the higher value of cow milk. Sodium dodecyl sulfate-PAGE results demonstrated that donkey milk is rich in beta-lactoglobulin and lysozyme. The percentages of 8 essential AA in protein of donkey milk were 38.2%, higher than those of mare and cow milk; donkey milk also had higher levels of serine (6.2%), glutamic acid (22.8%), arginine (4.6%), and valine (6.5%) and a lower level of cystine (0.4%).

Non-convulsive status epilepticus: a profile of patients diagnosed within a tertiary referral centre

Non-convulsive status epilepticus (NCSE) is an under-recognised but treatable condition with considerable associated morbidity. The files of adult admissions were reviewed over four years, during which time 50 episodes of NCSE were diagnosed in 45 patients. These findings suggest a broad age range with various states of mental acuity and an association with both learning disabilities and acute systemic infection. Approximately half of the patients had a previous diagnosis of epilepsy at the time of admission, and half had a history of generalised tonic-clonic seizures immediately before the onset of their illness.

The regulation of actin polymerization and cross-linking in Dictyostelium

It is clear that the polymerization and organization of actin filament networks plays a critical role in numerous cellular processes. Inhibition of actin polymerization by pharmacological agents will completely prevent chemotactic motility, macropinocytosis, endocytosis, and phagocytosis. Recently there has been great progress in understanding the mechanisms that control the assembly and structure of the actin cytoskeleton. Members of the Rho family of GTPases have been identified as major players in the signal transduction pathway leading from a cell surface signal to actin polymerization. The Arp2/3 complex has been added to the list of means by which new actin filaments can be nucleated. However, it is clear that actin polymerization by Arp2/3 complex is not the whole story. In principle, the final structures formed by actin filaments will depend on factors such as: the length of actin filaments, the degree of branching, how they are cross-linked and the tensions imparted on them. In addition, the means by which actin polymerization generates protrusion of membranes is still controversial. A phagosome, filopodium and a lamellipodium all require polymerization of new actin filaments, but each has a characteristic morphology and cytoskeletal structure. In the following chapter, we will discuss actin polymerization and filament organization, especially as it relates to the machinery of phagocytosis in Dictyostelium.

Isolation and expression of PASK, a serine/threonine kinase, during rat embryonic development, with special emphasis on the pancreas

We report the isolation and characterization of a serine/threonine kinase expressed during rat pancreas development. This kinase was cloned as part of a general screen using degenerate oligonucleotides to map expression of kinases and receptors during the course of pancreatic development. Sequence analysis showed it to be a member of the ste20-like serine/threonine kinase family. Northern blotting analysis against both fetal and adult tissues showed two transcripts, one of 2 kb and the other of 4 kb. The ratio of transcript expression varied with the tissue. In situ hybridization analysis showed that this gene is expressed in the early gut and pancreatic epithelium. By embryonic Day 15, the transcript is localized to cells that will eventually become exocrine in nature. In situ hybridization analysis also demonstrated high levels of expression in the choroid plexus, the developing myocardium, kidney, CNS, dorsal root ganglia, and testes. In addition, a search of the EST database revealed a related human kinase not previously described.

Manipulation of pancreatic stem cells for cell replacement therapy

The demonstration of the existence of tissue-specific adult stem cells has had a great impact on our understanding of stem cell biology and its application in clinical medicine. Their existence has revolutionized the implications for the treatment of many degenerative diseases characterized by either the loss or malfunction of discrete cell types. However, successful exploitation of this opportunity requires that we have sufficient know-how of stem cell manipulation. Because stem cells are the founders of virtually all tissues during embryonic development, we believe that understanding the cellular and molecular mechanisms of embryogenesis and organogenesis will ultimately serve as a platform to identify factors and conditions that regulate stem cell behavior. Discovery of stem cell regulatory factors will create potential pharmaceutical opportunities for treatment of degenerative diseases, as well as providing critical knowledge of the processes by which stem cells can be expanded in vitro, differentiated, and matured into desired functional cells for implantation into humans. A well-characterized example of this is the hematopoietic system where the discovery of erythropoietin (EPO) and granulocyte-colony stimulating factor (G-CSF), which regulate hematopoietic progenitor cell behavior, have provided significant clinical success in disease treatment as well as providing important insights into hematopoiesis. In contrast, little is known about the identity of pancreatic stem cells, the focus of this review. Recent reports of the potential existence of pancreatic stem cells and their utility in rescuing the diabetic state now raise the same possibilities of generating insulin-producing beta cells as well as other cell types of the pancreatic islet from a stem cell. In this review, we will focus on the potential of these new developments and how our understanding of pancreas development can help design strategies and approaches by which a cell replacement therapy can be implemented for the treatment of insulin-dependent diabetes which is manifested by the loss of beta cells in the pancreas.

The basal forebrain corticopetal system revisited

The medial septum, diagonal bands, ventral pallidum, substantia innominata, globus pallidus, and internal capsule contain a heterogeneous population of neurons, including cholinergic and noncholinergic (mostly GABA containing), corticopetal projection neurons, and interneurons. This highly complex brain region, which constitutes a significant part of the basal forebrain has been implicated in attention, motivation, learning, as well as in a number of neuropsychiatric disorders, such as Alzheimer's disease, Parkinson's disease, and schizophrenia. Part of the difficulty in understanding the functions of the basal forebrain, as well as the aberrant information-processing characteristics of these disease states lies in the fact that the organizational principles of this brain area remained largely elusive. On the basis of new anatomical data, it is proposed that a large part of the basal forebrain corticopetal system be organized into longitudinal bands. Considering the topographic organization of cortical afferents to different divisions of the prefrontal cortex and a similar topographic projection of these prefrontal areas to basal forebrain regions, it is suggested that several functionally segregated cortico-prefronto-basal forebrain-cortical circuits exist. It is envisaged that such specific "triangular" circuits could amplify selective attentional processing in posterior sensory cortical areas.

Lipid exchange between mixed micelles of phospholipid and triton X-100

If phospholipase catalyzed hydrolysis of phospholipid dissolved in a detergent mixed micelle is limited to the phospholipid carried by a single micelle, then hydrolysis ceases upon exhaustion of that pool. However, if the rate of phospholipid exchange between micelles exceeds the catalytic rate then all of the phospholipid is available for hydrolysis. To determine phospholipid availability we studied the exchange of 1,2-dioleoyl-sn-glycero-3-phosphocholine between mixed micelles of phospholipid and non-ionic Triton detergents by both stopped-flow fluorescence-recovery and nuclear magnetic resonance-relaxation techniques. Stopped-flow analysis was performed by combining mixed micelles of Triton and phospholipid with mixed micelles that contained the fluorescent phospholipid 1-palmitoyl-2-(12-[{7-nitro-2-1, 3-benzoxadiazo-4-yl}amino]dodecanoyl)-sn-glycero-3-phosphocholine (P-2-NBD-PC). The concentration dependence of fluorescence recovery suggested a second-order exchange mechanism that was saturable. The true second-order rate constant depends on the specific mechanism for exchange, which was not determined in this study, but the rate constant will be on the order of 106 to 107 M-1s-1. Incorporation of 1-palmitoyl-2-(16-doxylstearoyl)phosphatidylcholine into micelles increased the rate of proton relaxation and gave a limiting relaxation time of 1.3 ms. The results demonstrate that phospholipid exchange was rapid and that the phospholipid content of a single micelle did not limit the rate of phospholipid hydrolysis by phospholipases.

Morphological and electrophysiological characteristics of noncholinergic basal forebrain neurons

Cholinergic neurons in the basal forebrain are the focus of considerable interest because they are severely affected in Alzheimer's disease. However, both cholinergic and noncholinergic neurons are intermingled in this region. The goal of the present study was to characterize the morphology and in vivo electrophysiology of noncholinergic basal forebrain neurons. Neurons in the ventral pallidum and substantia innominata were recorded extracellularly, labeled juxtacellularly with biocytin and characterized for the presence of choline acetyltransferase immunoreactivity. Two types of ventral pallidal cells were observed. Type I ventral pallidal neurons had axons that rarely branched near the cell body and tended to have smaller somata and lower spontaneous firing rates than did type II ventral pallidal neurons, which displayed extensive local axonal arborizations. Subtypes of substantia innominata neurons could not be distinguished based on axonal morphology. These noncholineregic neurons exhibited local axon arborizations along a continuum that varied from no local collaterals to quite extensive arbors. Substantia innominata neurons had lower spontaneous firing rates, more variable interspike intervals, and different spontaneous firing patterns than did type II ventral pallidal neurons and could be antidromically activated from cortex or substantia nigra, indicating that they were projection neurons. Ventral pallidal neurons resemble, both morphologically and electrophysiologically, previously described neurons in the globus pallidus, whereas the substantia innominata neurons bore similarities to isodendritic neurons of the reticular formation. These results demonstrate the heterogeneous nature of noncholinergic neurons in the basal forebrain.

Sonic Hedgehog Protein : A Novel Approach to the Treatment of Neurodegenerative Disorders?

Sonic hedgehog is a member of a newly discovered family of molecules that are active during development in vertebrates. Sonic hedgehog induces development of key CNS neuronal cell types, including the dopaminergic neurons that are destroyed in Parkinson's disease. In addition to developmental-inducing activity, Sonic hedgehog has neurotrophic and neuroprotective activities on many of these same cell types. These activities suggest interesting clinical potentials for Sonic hedgehog in neurodegenerative diseases such as Parkinson's disease and in acute CNS trauma such as stroke.

Symptomatic lipoma in the right atrial free wall. A case report

Benign non-myxomatous neoplasms of the heart are rare, and lipomas are among those least often encountered. We report the case of a 38-year-old man who presented with palpitations of recent onset, and was found to have a lipoma attached to the free wall of the right atrium. The successful surgical excision of the lipoma is described.

Nonhippocampal muscarinic receptors are required for nonspatial working memory

The effects of scopolamine on nonspatial working memory were examined in rats with hippocampal lesions and sham operations. Performance was examined using a continuous conditional discrimination task in an operant box. Choice accuracy measured nonspatial working memory. Response bias, delay interval responses, and response probability measured response preference, stimulus control, motivation, and sensorimotor ability. Scopolamine (0.05, 0.075, 0.1, and 0.15 mg/kg) or methylscopolamine (0.1 mg/kg) was injected (I.P.) 15 min prior to behavioral testing. In both control and hippocampal lesioned groups, choice accuracy declined as the delay interval increased. Scopolamine, but not methylscopolamine, produced a dose-dependent impairment of choice accuracy (interaction of Dose x Delay) in both groups. The scopolamine-induced impairment was not different between the control and hippocampally lesioned rats. Response bias, delay interval responses, and response probability were not affected by scopolamine except at the highest dose, which increased delay interval responses. The results suggest that central muscarinic receptors outside the hippocampus are important for working memory of nonspatial stimuli.

Sonic hedgehog promotes the survival of specific CNS neuron populations and protects these cells from toxic insult In vitro

Sonic hedgehog (Shh), an axis-determining secreted protein, is expressed during early vertebrate embryogenesis in the notochord and ventral neural tube. In this site it plays a role in the phenotypic specification of ventral neurons along the length of the CNS. For example, Shh induces the differentiation of motor neurons in the spinal cord and dopaminergic neurons in the midbrain. Shh expression, however, persists beyond this induction period, and we have asked whether the protein shows novel activities beyond phenotype specification. Using cultures derived from embryonic day 14.5 (E14. 5) rat ventral mesencephalon, we show that Shh is also trophic for dopaminergic neurons. Interestingly, Shh not only promotes dopaminergic neuron survival, but also promotes the survival of midbrain GABA-immunoreactive (GABA-ir) neurons. In cultures derived from the E15-16 striatum, Shh promotes the survival of GABA-ir interneurons to the exclusion of any other cell type. Cultures derived from E15-16 ventral spinal cord reveal that Shh is again trophic for interneurons, many of which are GABA-ir and some of which express the Lim-1/2 nuclear marker, but it does not appear to support motorneuron survival. Shh does not support the survival of sympathetic or dorsal root ganglion neurons. Finally, using the midbrain cultures, we show that in the presence of MPP+, a highly specific neurotoxin, Shh prevents dopaminergic neuron death that normally would have occurred. Thus Shh may have therapeutic value as a protective agent in neurodegenerative disease.

Induction of dopaminergic neuron phenotype in the midbrain by Sonic hedgehog protein

Loss of substantia nigra dopaminergic neurons, which develop from the ventral region of the midbrain, is associated with Parkinson's disease. During embryogenesis, induction of these and other ventral neurons is influenced by interactions with the induction of mesoderm of the notochord and the floor plate, which lies at the ventral midline of the developing CNS. Sonic hedgehog encodes a secreted peptide, which is expressed in notochord and floor plate cells and can induce appropriate ventral cell types in the basal forebrain and spinal cord. Here we demonstrate that Sonic hedgehog is sufficient to induce dopaminergic and other neuronal phenotypes in chick mesencephalic explants in vitro. We find that Sonic hedgehog is a general ventralizing signal in the CNS, the specific response being determined by the receiving cells. These results suggest that Sonic hedgehog may have utility in the induction of clinically important cell types.

Hippocampal and amygdaloid involvement in nonspatial and spatial working memory in rats: effects of delay and interference

Parametric manipulations of the task demand were used to examine the role of the hippocampus and amygdala in nonspatial and spatial working memory in rats. Hippocampal lesions produced an immediate and long-lasting impairment of nonspatial working memory in an operant task. The memory deficits increased as the delay interval and the amount of proactive interference increased. Hippocampal lesions severely impaired spatial working memory in spatial alternation. Extensive postoperative testing reduced the magnitude of impairment of nonspatial but not spatial working memory. Amygdaloid lesions did not impair any aspect of performance in 2 tasks. The results suggest that the hippocampus, but not the amygdala, is involved in working memory and the task demand is a critical determinant for observing impairments of nonspatial working memory following hippocampal lesions.

Hippocampal and amygdaloid involvement in nonspatial and spatial working memory in rats: effects of delay and interference

Parametric manipulations of the task demand were used to examine the role of the hippocampus and amygdala in nonspatial and spatial working memory in rats. Hippocampal lesions produced an immediate and long-lasting impairment of nonspatial working memory in an operant task. The memory deficits increased as the delay interval and the amount of proactive interference increased. Hippocampal lesions severely impaired spatial working memory in spatial alternation. Extensive postoperative testing reduced the magnitude of impairment of nonspatial but not spatial working memory. Amygdaloid lesions did not impair any aspect of performance in 2 tasks. The results suggest that the hippocampus, but not the amygdala, is involved in working memory and the task demand is a critical determinant for observing impairments of nonspatial working memory following hippocampal lesions.

Beta cells arise from glucose transporter type 2 (Glut2)-expressing epithelial cells of the developing rat pancreas

We observe Glut2 protein in day 11 (E11) rat embryos in an endodermal domain containing the pancreatic primordium. Glut2 expression continues as the endodermal epithelium evaginates into the surrounding mesenchyme to form the pancreatic buds. Cells of the dorsal and ventral pancreatic buds maintain Glut2 expression as the epithelium grows and branches to form ducts. As acini form at the ends of the ducts, acinar cells cease Glut2 expression. Insulin protein is first detected in small clusters at the interface between pancreatic epithelium and mesenchyme. These clusters disperse into the interstitial tissue between E13 and E17. At E17 a distinct, larger population of insulin-expressing cells arises in the Glut2-expressing ductal network. Insulin- and Glut2-coexpressing cells then appear to segregate into large aggregates to form the beta cells of the islets of Langerhans. These observations support the hypothesis that two biologically distinct populations of insulin-expressing cells arise during pancreas formation.

Nucleus basalis magnocellularis and attention: effects of muscimol infusions

The basal forebrain is important in cognitive processing. Most studies have focused on the importance of this area in mnemonic processing. However, the nucleus basalis magnocellularis (NBM), which is a major component of the basal forebrain, may also be involved in attentional processes. Attention can influence the sensitivity of perceptual processes, as assessed by discriminability, or the selection of response strategies, as assessed by bias. This experiment examined whether temporary inactivation of the NBM, using the GABA agonist muscimol, would interfere with attention. Each rat was tested in a 2-choice reaction time (RT) task in which stimulus frequency was varied. RT and error rate increased, and discriminability decreased following muscimol infusions into the NBM. Bias was unchanged. The pattern of results provides evidence that the NBM is important in attention, and this influence of the NBM acts primarily on perceptual aspects of attention.

Acetylcholine release in the hippocampus: effects of cholinergic and GABAergic compounds in the medial septal area

The medial septal area (MSA) contains cholinergic and GABAergic neurons that send projections to the hippocampus. These neurons have both cholinergic and GABAergic receptors. This study was designed to determine the effects of intraseptal infusions of cholinergic and GABAergic drugs, which alter mnemonic processes, on hippocampal acetylcholine (ACh) release. Hippocampal ACh release was assessed using in vivo microdialysis and HPLC-EC. Oxotremorine and scopolamine produced a dose-dependent decrease in hippocampal ACh release. Muscimol decreased hippocampal ACh release at both high and low doses, although not in a dose-dependent manner. The effects of scopolamine and muscimol are consistent with a role of ACh in mnemonic processing.

Activation of the medial septal area attenuates LTP of the lateral perforant path and enhances heterosynaptic LTD of the medial perforant path in aged rats

Age-related memory impairments may be due to dysfunction of the septohippocampal system. The medial septal area (MSA) provides the major cholinergic projection to the hippocampus and is critical for memory. Knowledge of the neurobiological mechanisms by which the cholinergic system can attenuate age-related memory loss can facilitate the development of effective cognitive enhancers. At present, one of the best neurobiological models of memory formation is long-term potentiation/long-term depression (LTP/LTD). In previous studies, intraseptal infusion of the muscarinic agonist oxotremorine, which excites MSA neurons, improved memory in aged rats. The present study examined LTP and LTD in aged Fisher 344 rats following intraseptal infusion of oxotremorine. LTP and LTD were assessed using the slope of the EPSP recorded from the hilar region of the dentate gyrus. Induction of LTP was blocked in the lateral perforant path, but not in the medial perforant path, following intraseptal infusions of oxotremorine. The generation and amplitude of heterosynaptic LTD was enhanced in the medial perforant path, but not in the lateral perforant path. The results provide evidence that pharmacological activation of the MSA can modulate LTP and LTD in the hippocampus of aged rats. The implications of these results with respect to memory and synaptic plasticity in the hippocampus are discussed.

Nucleus basalis magnocellularis and attention: effects of muscimol infusions

The basal forebrain is important in cognitive processing. Most studies have focused on the importance of this area in mnemonic processing. However, the nucleus basalis magnocellularis (NBM), which is a major component of the basal forebrain, may also be involved in attentional processes. Attention can influence the sensitivity of perceptual processes, as assessed by discriminability, or the selection of response strategies, as assessed by bias. This experiment examined whether temporary inactivation of the NBM, using the GABA agonist muscimol, would interfere with attention. Each rat was tested in a 2-choice reaction time (RT) task in which stimulus frequency was varied. RT and error rate increased, and discriminability decreased following muscimol infusions into the NBM. Bias was unchanged. The pattern of results provides evidence that the NBM is important in attention, and this influence of the NBM acts primarily on perceptual aspects of attention.

Comparative cognition and assessment of cognitive processes in animals

Comparative cognition is an approach that seeks to describe cognitive processes in general computational terms so that the appropriate behavioral testing procedures can be established for any animal, including humans. Some examples of this approach are discussed in the context of memory and attention, emphasizing the ways in which historically disparate research traditions can be integrated together to provide new approaches for behavioral testing in animals. This comparative approach helps to integrate animal models using different species, and to develop tasks that have more direct connection to the assessment of cognitive processes in people.

Expectancy and stimulus frequency: a comparative analysis in rats and humans

We examined whether expectancy, one of several factors influencing attention, is similarly affected in rats and humans by manipulation of relative stimulus frequency. A two-choice reaction time (RT) task was developed for rats, and an analogous task was used for humans. Errors, RTs, discriminability, and response bias were measured. Both rats and humans shifted their response bias to the more frequent stimulus, with no change in overall discriminability. As stimulus probability or stimulus repetition increased, RTs and errors decreased. These results illustrate the similarity of expectancy in rats and humans. This two-choice RT task for rats can be used in future studies to examine the neuronal mechanisms of expectancy and attention.

Electrically-evoked release of norepinephrine in the rat cerebellum: an in vivo electrochemical and electrophysiological study

Norepinephrine (NE) release from the locus coeruleus (LC) afferents to the cerebellar cortex of urethane anesthetized rats was achieved by electrical stimulation of the locus coeruleus or by local administration of potassium into the cerebellum. Both methods evoked an overflow of NE-like electroactive species. Electrically-evoked and potassium-induced overflow of NE-like responses were found to be reversible and reproducible. Releases were not observed in cerebellar white matter, an area which is relatively devoid of monoamine containing terminals. Systemic administration of desipramine, a potent and selective norepinephrine re-uptake blocker, significantly augmented the electrically-evoked electrochemical responses. Measurements of evoked release taken using high-speed chronoamperometry support the idea that a predominant contributor to electrically-induced signals was NE. Electrophysiological recordings of single Purkinje cells were performed with the same Nafion-coated single carbon fiber electrodes used for electrochemical recordings. Electrical stimulation of the LC was seen to depress Purkinje cell firing rates; an increase in electroactive species was detected at the same site that paralleled the time course of the electrophysiological response. These studies provide further direct evidence that the LC norepinephrine-containing cells have a direct inhibitory effect on Purkinje cells in the cerebellum, and that both pre- and postsynaptic events can be measured with the same recording sensor.

Differential effects of methionine5-enkephalin on hippocampal pyramidal cells and interneurons

While the excitatory action of opioids and opiate drugs upon pyramidal neurons in the hippocampus is well known, the mechanism by which this excitation is achieved is still argued. A popular hypothesis is that opiates reduce the activity of inhibitory interneurons, thereby indirectly exciting the pyramidal cells. To validate this idea, it is necessary to show that opiates selectively affect the population of interneurons. The present study therefore examined the effects of met-enkephalin upon pyramidal cells and interneurons located in area CA1. Extracellular action potentials were recorded using multibarrelled micropipettes. Drugs were applied locally by either pressure micro-ejection or microiontophoresis. Met-enkephalin (10(-5) M) elevated the spontaneous discharge of pyramidal cells, while interneurons were inhibited. The responses of both types of cell were blocked by the opiate antagonist naloxone. When the synaptic connections between the pyramidal cells and interneurons were disrupted by local application of magnesium or bicuculline, met-enkephalin had no effect on the pyramidal cells. However, neither magnesium nor bicuculline altered the enkephalin-induced inhibition of theta neurons. These results support the hypothesis that opioids of the enkephalin subclass, excite pyramidal cells in the hippocampus through a disinhibition mechanism.

Molecular approaches to vertebrate limb morphogenesis

It has long been proposed that concentration gradients of morphogens provide cues to specify cell fate in embryonic fields. Recent work in a variety of vertebrate systems give bona fide evidence that retinoic acid, the biologically active form of vitamin A, is a candidate for such a morphogen. In the developing chick wing, for example, locally applied retinoic acid triggers striking changes in the pattern along the anteroposterior axis. Instead of giving rise to a wing with the normal 234 digit pattern, wing buds treated with retinoic acid develop a 432234 mirror-image symmetrical digit pattern.

For this review, we focus on three aspects of limb morphogenesis. (1) We summarize the experimental evidence supporting the notion that retinoic acid is a candidate morphogen. (2) Limb buds contain high levels of cellular retinoic-acid-binding protein (CRABP). Using order of magnitude calculations, we evaluate how the concentration of CRABP might affect the occupancy state of the retinoic acid receptor. (3) We discuss the spatio-temporal expression pattern of homeobox-containing genes in the developing limb and speculate about the possibility that retinoic acid influences the pattern of expression of homeobox genes.

Expression pattern of homeobox-containing genes during chick embryogenesis

We have isolated, sequenced and examined the expression pattern of two tandemly arranged homeobox-containing genes from the chicken. The predicted amino acid sequences of the homeodomain and the adjacent carboxyterminal portion of the protein of the first gene is virtually identical (99%) to that of murine homeobox 2.1 and hence we refer to it as Ghox 2.1 (Gallus homeobox). The closest mouse homologue of the second homeodomain is Hox 2.2 (95% identical within the homeobox), and hence referred to as Ghox 2.2. Northern analysis of embryonic RNA reveals major transcripts of 2 kb for Ghox 2.1 and 1.7 kb for Ghox 2.2. To investigate the transcript pattern, embryos of various stages were dissected into heads, trunks and limb buds and the RNA was analysed by Northern blotting and RNase protection assays. Ghox 2.1 transcripts are present in all three regions. Ghox 2.2 RNA is found in trunks and limb buds, but it is strikingly absent from the developing head. In situ hybridization with 35S-labelled antisense riboprobes derived from Ghox 2.1 demonstrates that this gene is expressed at high levels in spinal chord, myelencephalon and mesonephros. Dorsal root ganglia and the lung rudiment also contain Ghox 2.1 message, but in somewhat lower amounts. Mid- and forebrain, the heart, presomitic mesenchyme and notochord do not contain detectable levels of Ghox 2.1 mRNA. Of particular interest is the expression of Ghox 2.1 in a well-defined patch of mesenchymal tissue situated in an anterioproximal region of the limb bud.

Turnover of epidermal growth factor binding sites in mouse mammary epithelial cells

An in vitro method of studying epidermal growth factor (EGF) receptors in mouse mammary epithelial cells in serum-free collagen gel culture has been developed. Binding of EGF averaged 108 +/- 19 fmol/mg DNA in cells isolated from freshly dissociated virgin mammary tissue. Initial binding values were maintained in cells cultured in the presence of 0.1 ng/ml EGF, but decreased in either 0 ng/ml or 10 ng/ml EGF. Addition of either chloroquine (100 microM) or ammonium chloride (10 mM) to the culture medium increased receptor levels 10-fold. Cycloheximide (0.1 microgram/ml), ouabain (3 mM), and actinomycin D (5 x 10(-2) micrograms/ml) each decreased receptor levels, in some cases by as much as 80%. Both methylamine (10 mM) and dinitrophenol (0.1 mM) had no significant effect. These studies suggest that the net level of EGF receptors in these target cells is the result of an equilibrium between synthesis and degradation. The difference between the effects of the compounds tested on either receptor degradation or synthesis in comparison to cell growth, may be indicative that receptor degradation is not linked to cell proliferation.

A novel cancer therapy using a Mössbauer-isotope compound

Cancer radiotherapy uses high doses of ionizing radiation (1-10(2) Gy; 10(2)-10(4) rad) because only a small fraction of the absorbed dose leads to lethal double-strand breaks in DNA. These breaks are more efficiently produced by Auger electrons (1-10 eV nm-1) generated in proximity to the DNA. The energy of these electrons (on average 21 electrons for the decay of 125I) is dissipated within 10-100 nm of the Auger event and produces multiple double-strand DNA breaks. A single Auger event can be lethal to a cell and is comparable to more than 10(5) photon absorption events in conventional radiotherapy. We now report that 57Fe(III).bleomycin, administered to malignant cells in vitro and in vivo and irradiated with resonant Mössbauer gamma rays (14.4 keV), causes ablation of the malignant cells, presumably by Auger cascade, with extremely small radiation doses--about 10(-5) Gy. As a basis for comparison, about 5 Gy is necessary to achieve a similar effect with conventional radiotherapy.

Modulation of the gating of auditory evoked potentials by norepinephrine: pharmacological evidence obtained using a selective neurotoxin

Central mechanisms of sensory gating were assessed in Sprague-Dawley rats using an evoked potential technique similar to one that we have previously employed to show diminished sensory gating in psychotic patients. Gating mechanisms were examined using a conditioning-testing paradigm in which pairs of 74-dB clicks were delivered; the interval between the conditioning and test stimuli was 0.5 sec. A middle latency auditory evoked response (N50) recorded from the skull of unanesthetized, freely moving rats demonstrated significant suppression to the test click. Systemic administration of amphetamine (1 mg/kg, ip) significantly reduced the amount of suppression of the response to the test stimulus; haloperidol (1 mg/kg), injected after the amphetamine, returned the conditioning-testing suppression ratio toward normal values. Amphetamine also decreased the latency and amplitude of the conditioning response, an effect that was also reversed by haloperidol. Both decreased suppression of the test response and reduced amplitude and latency of the conditioning response have been observed in schizophrenia. To aid in determining the underlying mechanism of these effects, the animals were treated with two doses, given at a 1-week interval, of N-(2-chloroethyl-N-ethyl-2-bromobenzylamine) (DSP4; 50 mg/kg, ip), an agent that selectively depletes central norepinephrine. The extent and selectivity of the depletions were confirmed by chemical analysis. Following DSP4, the effects of amphetamine on the amplitude and latency of the conditioning response were largely unchanged. However, pretreatment with DSP4 significantly attenuated the reduction in conditioning-testing suppression observed following the administration of amphetamine. The data suggest a specific role for norepinephrine in the modulation of sensory processing.

Differential effects of norepinephrine on hippocampal complex-spike and theta-neurons

The central noradrenergic system has long been postulated to modulate learning and memory. A brain structure known to be important in these functions is the hippocampus. Since the hippocampus receives a noradrenergic projection from the locus coeruleus, knowledge of norepinephrine's actions in the hippocampus may help determine its role in learning and memory. In the present study, the effects of norepinephrine were examined on two hippocampal cell types: complex-spike and theta-neurons. In the hippocampus, there is good evidence that complex-spike cells are pyramidal neurons, while theta-neurons are interneurons. Extracellular action potentials from hippocampal neurons were recorded using multibarrel glass micropipettes. Drugs were locally applied using pressure micro-ejection. Norepinephrine inhibited the spontaneous firing of complex-spike cells, while theta-neurons were excited. The inhibitory response of complex-spike neurons was mediated by an alpha 1-receptor. However, selective agonists for the alpha 2- and beta-noradrenergic receptors excited the complex-spike cells. The noradrenergic-induced excitatory response of theta-neurons was also mediated by alpha 2- and beta-receptors. This study provides evidence that locally applied norepinephrine produces different responses on two types of hippocampal neurons. Furthermore, these differential responses arise primarily from the activation of distinct populations of noradrenergic receptors.

In vivo electrochemical demonstration of the presynaptic actions of phencyclidine in rat caudate nucleus

In vivo electrochemical recordings, coupled with local application of drugs from micropipettes, were used to determine the presynaptic effects of phencyclidine (PCP) on dopamine-containing nerve terminals in the intact rat striatum. Local application of PCP did not elicit an observable increase in extracellular levels of the monoamine neurotransmitters. However, pretreatment with PCP significantly potentiated the potassium-evoked release of monoamines. Nomifensine, a potent catecholamine reuptake blocker, produced effects that were analogous with PCP. Local pretreatment with PCP was also found to potentiate the electrochemical signal detected after pressure ejection of dopamine directly into the caudate nucleus. Finally, electrophysiological studies showed that locally applied PCP and nomifensine solutions had similar potencies in depressing the spontaneous firing of striatal neurons. Taken together, these data suggest that the major presynaptic action of PCP in the rat caudate nucleus is inhibition of the reuptake, and not alteration of release, of the monoamine neurotransmitters.

Interactions of phencyclidine with hippocampal circuitry: evidence for neuronal heterogeneity

The discovery of phencyclidine (PCP) receptors has stimulated the search for specific PCP antagonists. A direct product of this research is metaphit, an irreversible PCP ligand, which has recently been synthesized. In this study we examined the effects of metaphit on the responses of hippocampal neurons to PCP. On the basis of unfiltered action potential durations, hippocampal cells were divided into two groups, complex-spike cells and theta neurons. Local application of PCP caused inhibitions of the spontaneous firing rates of complex-spike cells. Metaphit, locally applied, antagonized approximately 50% of these responses, while the remaining responses were unaffected. In contrast, PCP caused increases in the spontaneous firing rates of theta cells and in almost all cases, these responses to PCP were attenuated by metaphit administration. These effects of metaphit were specific for PCP as the responses to locally applied norepinephrine were not altered by metaphit. The data suggest two mechanisms of action of PCP in the hippocampus. In addition, these mechanisms may be localized in part to different cell types.

Heterogeneity in the hormonal responsiveness of clones derived from the 13762NF rat mammary tumor

The transplantable hormone-responsive rat mammary adenocarcinoma 13762NF was dissociated with collagenase and hyaluronidase. Cells were cloned directly or lines were established from mass cultures and cells from these lines were cloned. Clones differed in cellular morphology, colony morphology on plastic or in collagen gel, growth rate, growth response to hormones, and hormone receptor levels. Growth response to prolactin, estradiol, progesterone, cortisol, and epidermal growth factor (EGF) was determined by culturing the cells within collagen gel and using a serum-free medium base of DME/F12 (1:1) with insulin, linoleic acid, and BSA. The clones varied in their hormone responses, with all 20 of the clones tested responding to cortisol in combination with EGF. Some clones would respond to EGF, cortisol, or progesterone when used alone. None of the clones tested could be stimulated by prolactin or estradiol. Receptor levels for estradiol, progesterone, glucocorticoids, and EGF were assessed in 3 selected clones differing in their hormone responsiveness. Receptor levels appeared to correlate with hormonal sensitivity. Selected clones transplanted into female F344 rats produced carcinomas with histopathologies similar to the original tumor.