Pseudocollinia brintoni gen. nov., sp. nov. (Apostomatida: Colliniidae), a parasitoid ciliate infecting the euphausiid Nyctiphanes simplex.

A novel parasitoid ciliate, Pseudocollinia brintoni gen. nov., sp. nov. was discovered infecting the subtropical sac-spawning euphausiid Nyctiphanes simplex off both coasts of the Baja California peninsula, Mexico. We used microscopic, and genetic information to describe this species throughout most of its life cycle. Pseudocollinia is distinguished from other Colliniidae genera because it exclusively infects euphausiids, has a polymorphic life cycle, and has a small cone-shaped oral cavity whose left wall has a field of ciliated kinetosomes and whose opening is surrounded on the left and right by 2 'oral' kineties (or ciliary rows) that terminate at its anterior border. Two related species that infect different euphausiid species from higher latitudes in the northeastern Pacific Ocean, Collinia beringensis Capriulo and Small, 1986, briefly redescribed herein, and Collinia oregonensis Gómez-Gutiérrez, Peterson, and Morado, 2006, are transferred to the genus Pseudocollinia. P. brintoni has between 12 and 18 somatic kineties, and its oral cavity has only 2 oral kineties, while P. beringensis comb. nov. has more somatic kineties, including 3 oral kineties. P. oregonensis comb. nov. has an intermediate number of somatic kineties. P. beringensis comb. nov. also infects Thysanoessa raschi (a new host species). SSU rRNA and cox1 gene sequences demonstrated that Pseudocollinia ciliates are apostome ciliates and that P. brintoni is different from P. beringensis comb. nov. High densities of rod-shaped bacteria (1.7 µm length, 0.2 to 0.5 µm diameter) were associated with P. brintoni. After euphausiid rupture, high concentrations of P. brintoni and bacteria cluster to form 3 to 6 cm long filaments where tomites encyst and transform to the phoront stage; this is a novel place for encystation. P. brintoni may complete its life cycle when the euphausiids feed on these filaments.

Biological activity of EDQM CRS for Interferon alfa-2a and Interferon alfa-2b - assessment in two in vitro bioassays.

The European Directorate for the Quality of Medicines (EDQM) supplies Chemical Reference Substances (CRS) for Interferon (IFN) alfa-2a (CRS I0320300) and for IFN alfa-2b (CRS I0320301) for specified physicochemical tests. However, no information is provided as to their biological activity. In contrast, the World Health Organization (WHO) provides the 2nd International Standards (IS) for IFN alfa-2a (code 95/650) and for IFN alfa-2b (code 95/566), with activity defined in International Units (IU) for calibration of biological activity of preparations of IFN. We have compared the EDQM CRSs with the WHO ISs in two bioassay systems, one measuring the anti-proliferative activity in the Daudi cell line and the other measuring a reporter gene activation in an A549 cell line. In each of these assay systems, the CRSs gave dose - response relations, which were similar to those for the WHO ISs. Estimates of relative activity for each CRS, in terms of the respective IS, showed specific biological activity for the CRSs of the same order as the nominal specific activity for the ISs. However, the estimates of relative activity were not consistent between the two assays systems, emphasizing the need for calibration within each system, if the CRS were to be used as a working standard for bioassays. For structure-activity studies, both physicochemical and biological activity characterisation are required for the same biopharmaceutical preparation. CRS I0320300 and CRS I0320301 may prove useful as working standards for some bioassay systems.

Rewiring Riboswitches to Create New Genetic Circuits in Bacteria.

Riboswitches are RNA elements that control the expression of genes through a variety of mechanisms in response to the specific binding of small-molecule ligands. Since their discovery, riboswitches have shown promise for the artificial control of transcription or translation of target genes, be it for industrial biotechnology, protein expression, metabolic engineering, antimicrobial target validation, or gene function discovery. However, natural riboswitches are often unsuitable for these purposes due to their regulation by small molecules which are already present within the cell. For this reason, research has focused on creating riboswitches that respond to alternative biologically inert ligands or to molecules which are of interest for biosensing. Here we present methods for the development of artificial riboswitches in Gram-negative and Gram-positive bacteria. These methods are based on reengineering natural aptamers to change their ligand specificity toward molecules which do not bind the original aptamer (ie, that are orthogonal to the original). The first approach involves targeted mutagenesis of native riboswitches to change their specificity toward rationally designed synthetic ligand analogs. The second approach involves the fusion of previously validated orthogonal aptamers with native expression platforms to create novel chimeric riboswitches for the microbial target. We establish the applicability of these methods both for the control of exogenous genes as well as for the control of native genes.

Inactivation of JNK activity by mitogen-activated protein kinase phosphatase-2 in EAhy926 endothelial cells is dependent upon agonist-specific JNK translocation to the nucleus.

We have investigated the termination of agonist-stimulated mitogen-activated protein (MAP) kinase activity in EAhy926 cells by MAP kinase phosphatase-2 (MKP-2). In cells expressing either wild-type (WT) or catalytically inactive (CI)-MKP-2, there was no significant differences in TNFalpha-stimulated JNK or p38 MAP kinase activity, however hydrogen peroxide (H2O2)-stimulated JNK activity was substantially reduced in WT-MKP-2 expressing clones and enhanced in cells expressing CI-MKP-2. Consistent with these findings, we observed substantial nuclear translocation of JNK occurred in response to H2O2 but not TNFalpha. Using a phosphospecific anti-JNK antibody, we found that TNFalpha-stimulated JNK activity was associated principally with the cytosol while in response to H2O2, JNK activity was found within the nucleus. These results show that the role of MKP-2 in terminating JNK activity is determined by the translocation of JNK to the nucleus, which is under agonist-specific regulation and not a universal cellular response to stimulation.

Stress-activated protein kinases: activation, regulation and function.

The response of cells to extracellular stimuli is mediated in part by a number of intracellular kinase and phosphatase enzymes. Within this area of research the activation of the p42 and p44 isoforms of mitogen-activated protein (MAP) kinases have been extensively described and characterised as central components of the signal transduction pathways stimulated by both growth factors and G-protein-coupled receptor agonists. Signaling events mediated by these kinases are fundamental to cellular functions such as proliferation and differentiation. More recently, homologues of the p42 and p44 isoforms of MAP kinase have been described, namely the stress-activated protein kinases (SAPKs) or alternatively the c-jun N-terminal kinases (JNKs) and p38 MAP kinase (the mammalian homologue of yeast HOG1). These MAP kinase homologues are integral components of parallel MAP kinase cascades activated in response to a number of cellular stresses including inflammatory cytokines (e.g., Interleukin-1 (Il-1) and tumour necrosis factor-alpha (TNF-alpha), heat and chemical shock, bacterial endotoxin and ischaemia/cellular ATP depletion. Activation of these MAP kinase homologues mediates the transduction of extracellular signals to the nucleus and are pivotal events in the regulation of the transcription events that determine functional outcome in response to such stresses. In this review we highlight the identification and characterisation of the stress-activated MAP kinase homologues, their role as components of parallel MAP kinase pathways and the regulation of cellular responses following exposure to cellular stress.

Inhibition of human peptidyl dipeptidase (angiotensin I converting enzyme: kininase II) by human serum albumin and its fragments.

Purified peptidyl dipeptidase (angiotensin I converting enzyme or kininase II) from human lung or hog kidney is inhibited by commercially prepared plasma protein preparations, by human serum albumin and by the additive albumin stabilizer, acetyltryptophan. After the initial steps of purification, albumin was detected by immunodiffusion as a component in human lung peptidyl dipeptidase preparation. Fragment C of albumin (sequence 124-298) is a more potent inhibitor than the parent molecule (Ki = 1.7 X 10(-5)M). Reduction and carboxymethylation of five of the six S-S bridges in Fragment C yield the most potent noncompetitive inhibitor (Ki = 3 X 10(-6)M). Reduction of the sixth bridge raises the K1. This indicates that maintenance of the tertiary structure in Fragment C is of importance for the inhibition. Neither albumin nor Fragment C are substrates of the enzyme. Fragment C and its derivative also inhibit the inactivation of bradykinin by the purified human enzyme and by the peptidyl dipeptidase on the surface of intact cultured human endothelial cells.

Role of citrate synthase in aldosterone-mediated sodium reabsorption.

Aldosterone and other mineralocorticoids increase citrate synthase activity in the kidney and enhance renal sodium reabsorption, but it is unclear whether the increased citrate synthase activity is involved in renal sodium transport. We used the Wistar-Furth rat, an inbred strain found to be deficient in renal citrate synthase activity, as an experimental model to investigate this issue. We confirmed that renal citrate synthase activity from adrenalectomized Wistar-Furth rats was decreased compared with that from control Wistar rats (by 28%). Similarly, urinary citrate excretion was 23% lower in Wistar-Furth rats. Subnormal citrate formation in Wistar-Furth rats could not be accounted for by differences in systemic pH or circulating potassium levels. Because renal citrate synthase activity was reduced in Wistar-Furth rats, we hypothesized that renal sodium excretory responses to mineralocorticoids would be reduced as well. Four-hour sodium excretion after intraperitoneal injection of 5 microg of aldosterone was reduced by 56% in adrenalectomized Wistar rats and by 52% in adrenalectomized Wistar-Furth rats (both P<0.01 compared with vehicle injection). Similarly, the pattern of urinary sodium excretion in response to subcutaneous injections of deoxycorticosterone acetate over a 2-week period was similar in adrenalectomized Wistar and Wistar-Furth rats. In summary, acute and chronic antinatriuretic responses to mineralocorticoids are maintained in Wistar-Furth rats at the level of Wistar rats, despite the marked reduction in citrate synthase activity. These findings are not consistent with an important role for citrate synthase activity in mineralocorticoid-mediated renal sodium transport.

Somatotopographic organization in the second somatosensory area of M. fascicularis.

The second somatosensory area (SII) of awake, untrained cynomolgus monkeys was surveyed with recordings from nearly 1,000 single neurons. A detailed somatotopographic organization could be demonstrated in SII because the majority of these neurons had contralateral, moderate to well-defined receptive fields of < 10 cm2, and because neighboring neurons possessed receptive fields that were only slightly displaced from one another. Different body regions were represented in successive anterior to posterior strips that were oriented across the parietal operculum with an anterolateral to posteromedial slant. Neurons with trigeminal receptive fields were found in the anterior portion of SII; these neurons were the only ones in SII with predominantly bilateral receptive fields (r.f.'s.). Neurons with digit or hand r.f'.s form the largest component of the map, and were located posterior to those with face r.f.s. Most of these neurons had only contralateral activation. The hand and digit region was followed in turn by the arm, the upper and lower trunk, and the hindlimb regions. Although the overall SII orientation was along an anterior-posterior gradient, recordings at individual coronal planes often demonstrated isolated sequences of receptive fields that exhibited a medial-lateral progression. The principle example of this latter gradient was seen in the forelimb region where digits one through five were represented in an overlapping sequence across the parietal operculum. Except for portions of the digit representation, neighboring sequences of neurons in SII do not form a precise topologic map of the body that is comparable to the somatotopic maps observed in areas 3b and 1. The present findings contrast with previous physiological studies of SII in the primate. These discrepancies are discussed in relation to methodological differences and in terms of distinctions used to define the boundaries of SII.

Organization of somatosensory receptive fields in cortical areas 7b, retroinsula, postauditory and granular insula of M. fascicularis.

The boundaries of the second somatic sensory cortex (SII) in primates are difficult to define physiologically because cutaneous stimulation activates several regions around SII that do not receive projections from the ventroposterior nucleus of the thalamus. These cortical regions, which include portions of area 7b, the retroinsular (Ri) and postauditory fields (PA), and the granular insula (Ig) are largely buried within the lateral sulcus and most lie posterior to the caudal end of the insula. The differences in somatic activity in these various cortical fields in the unanesthetized cynomolgus monkey became apparent only after the properties of many neighboring neurons could be compared. Receptive fields for area 7b and Ig neurons were generally large (< 10 cm2), with bilateral, moderately defined boundaries; some neurons in area 7b had receptive fields with labile borders as a function of wakefulness. In contrast, receptive fields for Ri neurons were generally (< 10 cm2 and contralateral, with stable, well-defined boundaries. Taken as an ensemble, the neurons in areas neighboring SII exhibited a very crude topography; but at the level of an individual neuron and its neighbor, there was never a pattern of gradual transition in peripheral receptive field locations between one unit and the next, like that seen in SII. In area 7b, this crude map was organized mediolaterally across the inferior parietal lobule and into the upper bank of the lateral sulcus, with the head represented medially and the lower trunk and hindlimb laterally. In Ri-PA, an anteroposterior organization was noted along the fundus of the lateral sulcus with the head represented anterior to the lower trunk and hindlimb. No organization was apparent in Ig. Additional sensitivity to visual stimuli was noted in the more medial aspects of area 7b that were located on the exposed inferior parietal lobule. Sensitivity to auditory stimuli was principally found in PA and occasionally in Ri. The results, especially from area 7b, are discussed with respect to previous notions about the organization of SII.

Somatic submodality distribution within the second somatosensory (SII), 7b, retroinsular, postauditory, and granular insular cortical areas of M. fascicularis.

Somatic response properties were determined for over 1,300 neurons isolated within and near the lateral sulci of unanesthetized and unparalyzed cynomolgus monkeys. Somatic stimuli unequivocally activated the majority of units studied in SII (93%) and in cortical fields surrounding SII: area 7b (65%), the retroinsular field (74%), and the granular insula (76%). No activation other than somatic was seen for SII neurons, and noxious somatic stimulation was rarely required. The SII units almost always responded in a rapidly adapting manner to hair or skin stimulation, but not both; however, the submodality distribution seen in SII varied as a function of peripheral receptor locations. Two small zones within SII contained neurons that responded only if the animal actively interacted with the stimulus. In contrast, one-half of the sample of neurons from area 7b unequivocally responded only to somatic stimulation. Although many neurons in the lateral parts of area 7b were vigorously activated by innocuous tactile stimulation, others demonstrated little association with an identifiable somatic submodality, had sluggish responses, required complex, noxious, visual or other non-somatic stimuli for activation, and had labile response properties and receptive fields. Indeed, the responses of some area 7b neurons suggested a possible relationship with the animal's attention towards or anticipation of a noxious or a novel somatic stimulus. Neurons within the retroinsular cortex (Ri), which receives projections from the posterior nucleus (PO), primarily responded to light tactile stimulation of rapidly adapting skin receptors; less than 3% responded to moderate or high threshold mechanical stimulation. The sensitivity to tactile stimulation in Ri closely resembled the responses of SII neurons. Neurons in the granular insula (Ig) often responded to gentle hair deflection within receptive fields covering large areas of the body. Ig and area 7b were the principle loci within the lateral sulcus that contained neurons responding to noxious stimulation. Owing to the great similarity in the somatic response properties within these areas in the awake and unparalyzed animal, the designation of cortical areas could only be made after correlating the recording sites with connectional and cytoarchitectonic analyses in the same animal. Consequently, previous physiological studies may have attributed to SII some of the response characteristics of neurons in neighboring areas.

The first international standard for human leptin and the first international standard for mouse leptin: comparison of candidate preparations by in vitro bioassays and immunoassays.

In an international collaborative study, two preparations of human sequence recombinant leptin and two preparations of mouse sequence recombinant leptin were evaluated, using in vitro bioassays and immunoassays, by eight laboratories, in three countries, for their suitability to serve as the international standard (IS) for human and mouse leptin respectively. The bioassays detected the human and mouse leptin with similar potency, while the immunoassays showed a greater response to the leptin of the species against which the antibody preparation had been raised. Comparison of the candidate standards with the various preparations of leptin of the same species currently assayed in the participating laboratories showed that immunoassay measurements cannot be used to predict the biological potency. On the basis of the results reported here, in October 1999 the Expert Committee on Biological Standardization of the World Health Organization established the preparation coded 97/594 as the first IS for human leptin, with an assigned unitage of 4000 IU/ampoule, and the preparation coded 97/626 as the first IS for mouse leptin, with an assigned unitage of 4000 IU/ampoule. The ISs for leptin are distributed by the National Institute for Biological Standards and Control, UK, http://www.nibsc.ac.uk.

International Standards for hepatocyte growth factor/scatter factor: initial assessment of candidate materials and their evaluation by multicentre collaborative study.

Hepatocyte growth factor/scatter factor (HGF/SF) is a potent paracrine growth factor with motogenic, mitogenic and morphogenic activities, and a potential therapeutic role in hepatic and renal disease, as well as diagnostic and prognostic applications. It is synthesised as an inactive, single-chain precursor that is cleaved by serine proteases to give a biologically active, heterodimeric form. To develop World Health Organization (WHO) International Standards (IS) for HGF/SF, candidate preparations of the two forms were assessed in a multicentre study in which they were compared with local standards by bioassay and immunoassay. Among laboratories, there was a wide variation in the estimates of potencies of the candidate standards in terms of in-house reference preparations, but between-assay and within-assay variabilities were low within laboratories. In some assay systems, the precursor and heterodimer showed different responses. Since both molecular forms are widely used in current assay systems, this suggested that a reference preparation was required for each form of the HGF/SF molecule. Accordingly, the Expert Committee on Biological Standardization of WHO established the heterodimeric material (96/564) as the first IS for HGF/SF, human, recombinant, with an assigned unitage of 4000 IU/ampoule and, for the purpose of immunoassay calibration, a nominal HGF/SF content of 4 microg/ampoule. The precursor preparation (96/556) was established as the first IS for HGF/SF (precursor) with an assigned unitage of 2000 IU/ampoule and, for the purpose of immunoassay calibration, a nominal HGF/SF (precursor) content of 4 microg/ampoule. The preparations can be obtained upon written request to the National Institute for Biological Standards and Control (NIBSC, PO Box 1193), by e-mail (standards@nibsc.ac.uk) or ordered at http://www.nibsc.ac.uk.

Photometric assays for FcRI-dependent binding, phagocytosis, and antibody-dependent cellular cytotoxicity mediated by monomeric IgG gamma 2a in murine peritoneal macrophages.

Mouse peritoneal macrophages possess distinct Fc receptors (FcR) for binding the various murine IgG isotypes. FcRI binds monomeric IgG gamma 2a, but not monomeric IgG gamma 2b or IgG gamma 1 with high affinity at 4 degrees C and is sensitive to trypsin degradation. We have assessed the functional consequences of the cytophilic binding at 4 degrees C of monomeric IgG gamma 2a to FcRI of mouse peritoneal macrophages using newly developed photometric microassays for quantification of binding, phagocytosis, and antibody dependent cellular cytotoxicity (ADCC) of post-opsonized sheep red blood cell (SRBC) targets. Dose-dependent binding specificity of monomeric IgG gamma 2a, but not IgG gamma 2b or IgG gamma 1 to FcRI of oil-elicited mouse peritoneal macrophages at 4 degrees C for 2 h was confirmed to display typical saturation kinetics both by the photometric assay and by a cellular enzyme-linked immunosorbent assay (CELISA). Binding of monomeric IgG gamma 2a to macrophage FcRI promoted highly efficient phagocytosis of opsonized SRBC in that most cells that were bound were also rapidly internalized by the phagocytic process during a 1 h incubation at 37 degrees C. Upregulation of FcRI-dependent binding and phagocytosis occurred during 24-48 h in vitro culture of macrophages as shown both by the photometric assays and CELISA. Trypsin treatment of macrophages abrogated FcRI-dependent binding and phagocytosis by monomeric IgG gamma 2a, but had little effect on FcRII-dependent functions. Cytophilic binding of monomeric IgG gamma 2a to FcRI failed to trigger ADCC activation. Thus functional characterization of macrophage FcRI-dependent effector functions confirmed the fidelity of binding specificity of monomeric IgG gamma 2a to a trypsin degradable receptor which mediates highly efficient phagocytosis but fails to initiate the signal for ADCC activation. It appears that passively bound immune monomeric IgG gamma 2a could provide an efficient mechanism by macrophages in vivo for FcRI-dependent immune clearance of soluble or particulate cellular antigens without elicitation of potentially harmful cytolytic factors associated with ADCC activation.

Prostaglandin A2 at low rates of infusion restores the antidiuretic effect of vasopressin in lithium-treated rats.

To test the effect of prostaglandin A2 (PGA2) on renal function, infusions of PGA2 (0-7 ng/kg/min), arginine-vasopressin (AVP) (1-25 ng/kg/min) and PGA2 plus AVP were administered to male rats made resistant to the antidiuretic effect of AVP by pre-treatment with lithium. In non-lithium-treated control rats, AVP had its expected antidiuretic action but in lithium-treated rats neither urinary volume nor osmolarity was changed. Prostaglandin A2 alone had no effect on urine output in lithium-treated rats; AVP plus PGA2 infused together evoked a near normal antidiuretic response. This antidiuretic action of PGA2 contrasts with the diuretic action reported by others. However, our infusion rates were 300-4000 times lower than those of other workers and it is suggested that PGs may have opposite actions on the kidney depending on their concentration. The effect of indomethacin (a blocker of prostaglandin synthesis) on urine flow was tested in five groups of rats on different régimes of liquid intake. Urine flow was reduced in the three groups with the highest urine volumes before treatment, and increased in the two groups with the lowest urinary volumes, again indicating that PGs may have both diuretic and antidiuretic actions.

Role of prolactin in vitamin D metabolism and calcium absorption during lactation in the rat.

Intestinal calcium absorption and plasma levels of 1,25-dihydroxycholecalciferol (1,25(OH)2D3) were measured in lactating and non-lacting rats and the effects of bromocriptine and exogenous prolactin treatment were evaluated. In lacting rats calcium absorption and plasma levels of parathyroid hormone, 1,25(OH)2D3 and alkaline phosphatase activity were significantly increased. Bromocriptine treatment significantly reduced the enhanced calcium absorption and levels of plasma 1,25(OH)2D3 and alkaline phosphatase but had no significant effect on plasma levels of parathyroid hormone. Prolactin administered with bromocriptine to lactating animals prevented all the changes observed with bromocriptine treatment alone. It was concluded that the increased plasma levels of prolacting during lactation lead to high plasma levels of 1,25(OH)2D3 which are responsible for the enhanced intestinal calcium absorption.

Using engineering and assistive technologies for rehabilitation after electrical trauma.

A framework is presented for judging when, how, and why rehabilitation engineering and its related assistive technologies are appropriate interventions following electrically induced trauma or burns. Instead of relying on the World Health Organization's medically based classification scheme of "Impairment, Disability, and Handicap," this newer framework is built on a rational demarcation proposed by the National Center for Medical Rehabilitation and Research at the U.S. National Institutes of Health. This latter client-centered framework encompasses pathophysiology, impairment, functional limitations, "disability", and societal limitations. This framework is well suited to handle the varied sequelae of electrical trauma and burn injuries and provides guidance towards the most effective use of traditional rehabilitation interventions and of assistive technologies. For electrical injuries, rehabilitative technologies can be classified as those promoting job accommodations (i.e., that help an individual return to active employment, albeit possibly in a different role) or as aids to the other activities of daily living (ADLs) that provide an enhanced quality of life to the individual with disability. While the traditional rehabilitative focus has been on return-to-work, especially among professional tradesmen, a more productive rehabilitative effort in some cases may occur through psychosocial adjustments achieved via effective technological interventions that enhance ADLs.

Psychophysical detection and pain ratings of incremental thermal stimuli: a comparison with nociceptor responses in humans.

The capacity of humans to detect and scale the magnitude of pain elicited by small increments in temperature, delivered by a contact thermal stimulator to localized areas of the arm or leg, was measured on non-painful and painful adaptation temperatures. Subjects continuously rated the magnitude of any pain sensation elicited by heat increments superimposed on base temperatures of 38, 44, 47 or 48 degrees C. Detection threshold was also measured using a two-alternative forced choice method. The increment detection thresholds were lower for a continuously painful base of 47 degrees C than for a non-painful base of 38 degrees C in normal skin, and likewise were lower for a base of 38 degrees C following hyperalgesia induced by a mild burn. Incremental pain thresholds were nearly equal to detection thresholds on the base of 47 degrees C. The sensitivity with which subjects could scale the magnitude of pain was 2-7 times better for increments delivered on a 48 degrees C as opposed to a 38 degrees C base. Evoked responses in 6 single C-fiber mechanoheat nociceptive afferents (CMHs) were recorded percutaneously from the peroneal nerves of 3 humans, who were simultaneously judging pain magnitude. For a base of 38 degrees C, both the pain and the neural response thresholds were an order of magnitude higher than corresponding thresholds on a base of 48 degrees C. For a base of 47 degrees C, response thresholds of the CMHs ranged from 0.1 to 0.5 degrees C and were comparable to detection thresholds of 0.1 to 0.3 degrees C. The sensitivity with which most nociceptors could signal increment size was 3-4 times better on a 48 degrees C than a 38 degrees C base. Incremental pain sensitivity was not altered by a compression block of activity in myelinated afferents that eliminated the sense of cool and touch. Thus, activity in unmyelinated fibers alone could account for the sensitivity to incremental thermal stimuli that were superimposed on a painful base temperature. Further, it is likely that CMH nociceptors alone could provide the peripheral information necessary to detect and to make magnitude judgments of pain elicited by these stimuli.

Drug-induced antinuclear antibodies in the guinea pig.

Antinuclear antibodies (ANA) development was studied in male guinea pigs in response to chronic treatment with procainamide, hydralazine, acetanilide or caffeine. Acetanilide and caffeine have not previously been associated with ANA induction. Fifty-one weanling Hartley guinea pigs were divided into five groups which received either procainamide, hydralazine, acetanilide, caffeine or saline sc for 55 weeks; drug dosage was 10 mg/kg initially and was increased incrementally to 40 mg/kg by 10 months except for hydralazine, which was increased to 20 mg/kg. Two weeks before initiation of treatment, 1 mg of the appropriate drug in 0.4 ml of buffered Freund's complete adjuvant (FCA-PBS) was administered intradermally. Controls received FCA-PBS only. Sera ANA were assayed at 6, 10 and 13 months. After 13 months of treatment, those sera which were ANA positive were assayed for anti-deoxyribonucleoprotein antibodies and were titered for ANA. Chi-square analyses were performed on results of the 10- and 13-month ANA screening results. ANA induction was significant at P = 0.05 only for the group receiving procainamide at both 10 and 13 months of treatment. When the cumulative results of all ANA screens were analyzed, ANA induction was significant for procainamide, acetanilide and caffeine. The test system did not prove to be promising for unambiguous identification of drugs with ANA-inducing potential, but may be useful for studies of mechanisms of ANA induction by chemicals.

Acceleration threshold detection during short anterior and posterior perturbations on a translating platform.

Balance control systems have usually been studied under two conditions, during quiet standing or under large postural perturbations of a magnitude that requires a postural adjustment to prevent falling. Between these two extremes lie perturbations that can be repeated and measured while not forcing adaptive strategies from the postural control system. Unlike other studies of postural control, we employed very short translations with varying accelerations at the edge of psychophysical detectability. These perturbations were vibration-free anterior or posterior translations of the platform on which a subject stood. Using a full Latin-square design set of perturbations in the forward or backward direction, with a smooth or jerk acceleration profile, and of length 4 or 20 mm, were presented to five subjects. Perceptual peak acceleration thresholds were determined by an iterative psychophysical method that forced the subjects to choose in which of two sequential intervals that they perceived a stimulus to have been presented. The only factor found that significantly correlated with detection was perturbation length. The 4 mm peak thresholds averaged 14.51 mm/s2 while 20 mm thresholds averaged 8.55 mm/s2. For the short perturbations employed in this study, detection of motion thus was dependent upon the magnitude of the acceleration, but it was independent of the acceleration profile (jerk versus smooth) or movement direction. By understanding the influences on the ability to perceptually detect motion underfoot, we can begin to understand what elements of the postural control system might be involved in the second-to-second control of balance.