Contribution of delayed rectifier and inward rectifier to repolarization of the action potential: pharmacologic separation

Outward potassium (K) currents contribute to the repolarization process of cardiac action potentials. There are, however, multiple K currents. Recently, two putatively specific K channel blockers have been developed as potential class III antiarrhythmic agents. E-4031 appears to block specifically a fast component of the delayed rectifier (IK), and RP 58866 is a reported inward rectifier current (IK1) blocker. In the present experiments, we examined the effects of E-4031 and RP 58866 on action potentials recorded from guinea pig papillary muscles to determine whether the properties of IK and IK1 measured in whole-cell experiments would be manifested in distinct effects. Both compounds prolonged the APD50 (action potential duration at 50% repolarization) and APD90 (action potential duration at 90% repolarization). However, RP 58866 did not significantly prolong the action potential at voltages of 0 mV and above, while E-4031 did. The results suggest that preferential IK1 block results in a change in action potential waveform that is distinct from that resulting from block of other outward K currents. This could thus be used as a simple first-pass screening tool in determining a preliminary mechanism of action of class III antiarrhythmics prior to more time-consuming but necessary whole-cell voltage clamp experiments.

The role of cognition in understanding gender effects

Cognitive approaches, such as schematic processing theory, have been heuristic in a number of ways for bettering our understanding of how and why gender effects are so apparent in childhood. First, they provide a new and different perspective. Rather than concentrating on discovering all the instances of gendered information in our worlds and then assuming that this overwhelming amount of information accounts for children's behavior and thinking, cognitive theorists studying gender have reversed the emphasis. That is, we assume that thinking processes influence the world of information that is available to children. Furthermore, the nature of that world of information is then seen to influence behavioral choices. Second, cognitive approaches have been heuristic in providing some understanding of the mismatches that occur between available information and children's gender cognitions. More broadly stated, such approaches have been useful for discovering the reasons that gender cognitions are inaccurate--why some information is misperceived, misremembered, and selectively learned. Third, cognitive approaches have been useful for elaborating the development of children's gender knowledge. Finally, cognitive approaches have been useful for illustrating how cognition may influence behavior. If we go beyond gender for a moment, we see that cognitive approaches can also be useful for our understanding of the broader realm of all types of stereotypes. For instance, they are helpful in understanding the early origins of stereotypes. Why do children and adults develop stereotypes? Given the overwhelming amount of information we must deal with every day, how do we ever notice real but usually minor co-occurrences of group membership and attributes? Furthermore, why do stereotypes contain information that is not grounded in reality? To begin to answer these questions, we need to move cognitive approaches to a higher order of generality, that is, away from the specifics of gender and on to the broader case of concept formation about social groups. When cognitive notions are used in this way, children and adults appear to form higher order schemas concerning the nature of social groups. One such schema is the "if they differ in one way, they differ in other ways" schema. Another such schema represents the flip side: "If they are in the same group, they are the same in many other ways." Exposure to information about groups surely must lead to the formation of these higher order schemas. Once formed, they surely must influence how new information about specific groups is acquired by increasing perceivers' vigilance in noticing and creating supportive information.(ABSTRACT TRUNCATED AT 400 WORDS)

The development of gender stereotype components

Developmental research has been limited by a narrow concept of stereotypes. A more complex model is presented, and developmental changes in gender stereotypes were investigated using the new model. In 2 studies, children were told about several sex-unspecified children, each described as having 1 masculine or 1 feminine characteristic. The children then predicted the likelihood of each story child having other masculine and feminine characteristics. In Study 1, 56 children (4-6 years) were told about target children who liked either a masculine or feminine toy, and then children predicted the targets' interests in other toys. In Study 2, 76 older children (6, 8, 10 years) were told about target children with a masculine or feminine characteristic from 1 of 4 categories (appearance, personality, occupations, toys), and then they predicted the likelihood of targets having other masculine and feminine characteristics from the same and from different categories as the cue. 2 developmental trends emerged: (a) children appear first to learn associations among characteristics relevant to their own sex and, later, to learn them for the other sex, and (b) older children's stereotypic judgments are more extreme than those of younger children. The implications of these results for the development of stereotypes, assessing gender knowledge, and understanding social judgments are discussed.

The relation of gender understanding to children's sex-typed preferences and gender stereotypes

Our goal was to explore how children's understanding of gender as a social category relates to their acquisition of sex-typed knowledge and preferences. Children's gender concepts, sex-typed preferences, and stereotyped knowledge were measured in 61 boys and girls (3-5 years). Gender concept measures included ability to identify and to discriminate the sexes, understanding gender group membership, temporal stability of gender, and gender consistency over situational changes. Children improved with age on most of the measures except gender consistency. With the exception of consistency, measures of gender concept understanding were found to be related to children's stereotyped toy and clothing knowledge and/or to their sex-typed toy preferences (with age controlled). It was shown that only rudimentary gender understanding is needed prior to children learning about sex stereotypes and prior to showing strong sex-typed preferences for peers or toys. The roles of gender identity, stability, consistency, and group membership in the sex-typing process are discussed.

Pinacidil opens ATP-dependent K+ channels in cardiac myocytes in an ATP- and temperature-dependent manner

Pinacidil is an antihypertensive agent that has been found to increase potassium conductance. This study examined the type of K channel affected by pinacidil in cardiac myocytes. Pinacidil shortened the action potential duration in papillary muscle. The effect was reversible upon addition of glyburide, a known IKATP blocker. The effect of pinacidil was temperature-dependent. Action potential duration was shortened more rapidly and to a greater extent at 37 degrees C than at 23 degrees C. Whole-cell experiments showed that I-V curves lost rectification after pinacidil treatment. As with the action potential experiments, the effect was more rapid at 37 degrees C than at 23 degrees C. Rectification was restored after exposure to glyburide. The I-V curve generated after pinacidil exposure was similar to that observed by others after treatment with metabolic inhibitors that activate IKATP. The effect of pinacidil was also ATP-dependent. Addition of 5 mM ATP to the internal solution prevented activation of IKATP. These data indicate that pinacidil activates IKATP.

Distribution of cholinergic and adrenergic nerve fibers in the lacrimal glands of dogs

The distribution of postganglionic autonomic nerve fibers in the lacrimal gland and gland of the third eyelid of dogs was studied by use of histochemical techniques. Adrenergic nerve distribution was identified by use of the sucrose-potassium phosphate-glyoxylic acid technique. A loose network of adrenergic nerves was found throughout the interstitium around acini and blood vessels and in vessel walls. Acetylcholinesterase staining was used to identify cholinergic nerve fibers. A cholinergic distribution pattern was found, although the cholinergic innervation appeared more dense than the adrenergic. In the gland of the third eyelid, mucus-secreting lobules and lipid-secreting lobules appeared to be equally innervated by parasympathetic fibers. These lobules could not be differentiated when the sucrose-potassium phosphate-glyoxylic acid technique was used. The techniques used in this study could not demonstrate whether direct contact was made by either cholinergic or adrenergic nerve fibers with secretory or myoepithelial cells. The presence of both nerve fiber types around acini suggests an interrelationship between the sympathetic and parasympathetic nervous system in lacrimal gland secretion in dogs.

Orbital neoplasia with enophthalmos in a cat

A 9-year-old cat was evaluated for left-sided enophthalmos and protrusion of the third eyelid. A primary orbital fibrosarcoma was diagnosed. During the orbital exploration, normal periorbital fascia could not be identified in the lateral and ventral region, thus accounting for the enophthalmos.

Topically applied cyclosporin for modulation of induced immunogenic uveitis in rabbits

The experimental model of immunogenic uveitis induced by intraocular injection of human serum albumin in rabbits was inhibited by the topical application of cyclosporin A. The acute nonspecific inflammatory response that immediately follows intravitreous injection was not affected. However, the severe panuveitis that develops during the second week was markedly reduced. The safety and efficacy of topically applied cyclosporin A in this model of uveitis suggests that topical administration of this antigen-nonspecific immunosuppressor may be an effective route of therapy for certain immune-mediated forms of uveitis.

Normal ultrastructure and histochemical characteristics of canine lacrimal glands

Lacrimal glands of 12 dogs free of ocular disease were examined to determine the normal structure of these glands. The glands consisted of tubuloacinar cells that ultrastructurally and histochemically were of a single type of secretory cell in the tubules and possibly 3 types of secretory cells in the acini. The tubular epithelium contained homogenous electron-dense granules that stained as neutral glycoconjugates (periodic acid-Schiff positive and Alcian blue and high iron diamine negative). The predominant acinar cells contained granules of lesser electron density than those of the tubules, and stained as sialomucin (Alcian blue [pH 2.5] and periodic acid-Schiff-positive, and high iron diamine-negative). A second type of acinar cell was in peripheral lobules that ultrastructurally and histochemically appeared like lipid granules (positive with oil red O and osmium tetroxide). Ultrastructurally, a third type of acinar granule was finely granular, electron-lucent, and frequently coalesced. It was not readily apparent whether the latter was an artifact, a stage in the maturation of the sialomucin granules, or a third type of acinar granule. Individual acinar cells usually had a predominance of 1 granule type, but greater than 1 granule type could be found in some cells. The basal surfaces of the acinar, tubular, and ductal cells were incompletely ensheathed by myoepithelial cells. Plasma cells, lymphocytes, mast cells, endothelial cells, fat cells, and Schwann cells composed the cellular elements of the interstitium. Lymphocytes, mast cells, and nerve endings also were found in the parenchyma.

Cellular electrophysiological properties of a new aminosteroid antiarrhythmic agent, SC-35135

SC-35135 is a structurally unique class I antiarrhythmic agent previously shown to suppress arrhythmias produced by a two-stage coronary artery ligation or by administration of ouabain, but to be arrhythmogenic at high doses. SC-35135 was evaluated in guinea pig papillary muscle using standard microelectrode techniques to record transmembrane action potentials. SC-35135 markedly blocked Vmax (maximum rate of membrane depolarization) as a function of pacing frequency in the concentration range of 3 x 10(-6) to 3 x 10(-5) M, and was without effect on action potential duration. The effective refractory period was significantly shortened only at the highest concentration tested (3 x 10(-5) M). Rate constants for the onset of Vmax block determined at two stimulation rates, 60 and 200 pulses/min, were 0.17 +/- 0.052 and 0.06 +/- 0.005 (action potentials)-1, respectively, in the presence of 10(-5) M SC-35135. The recovery from Vmax depression following a train of stimuli was very slow in the presence of SC-35135. The average time constant for the recovery from block of Vmax after addition of 10(-5) M SC-35135 was 10.2 +/- 0.94 s. SC-35135 caused both a concentration- and stimulation frequency-dependent hyperpolarizing shift in the half point of the relationship between Vmax and resting membrane potential. Slow response (Ca current-dependent) action potentials were not changed by SC-35135 at concentrations less than or equal to 3 x 10(-5) M, indicating a lack of class IV antiarrhythmic activity. The results of these experiments indicate that SC-35135 has electrophysiological properties similar to other previously studied aminosteroid antiarrhythmics such as amafolone and CCI 22277. Its onset and recovery kinetics also resemble the well known class IC antiarrhythmics flecainide, lorcainide, and encainide. The arrhythmogenic activity of SC-35135 has prevented further development of this compound.

Multiple hereditary ocular anomalies in a herd of cattle

A Brahman x Santa Gertrudis herd of cows bred to a Hereford bull was evaluated because of a 3-year history of several calves born with congenital blindness. Multiple congenital ocular anomalies in 2 calves included microphthalmos, microcornea, microcoria, heterochromia iridis, microlentia, cataracts, retinal dysplasia, retinal detachment, anterior segment dysgenesis, acorea, and proliferation of the anterior neuroectoderm. On the basis of the lack of environmental factors and persistence of an intermittent problem when breeding to a single bull, a genetic defect was diagnosed as the probable cause. Dominant inheritance with varied expressivity may have best explained the lack of obvious signs in the bull, with emergence of various anterior and posterior segment defects in offspring from unrelated cows.

Blindness and convulsions associated with vitamin A deficiency in feedlot steers

Blindness and convulsions were the predominant clinical signs in a group of feedlot steers inadvertently fed a vitamin-A deficient diet. Although vitamin A had been added to the feed at the time of preparation, it was believed that the vitamin A had been destroyed by heat, humidity, and minerals mixed in the feed. Feedlot heifers fed the same high-grain diet were clinically normal, and one heifer from which a blood sample was obtained had normal serum vitamin A content. The ingestion of sparse grasses and weeds found along the fence row of the heifers' pens was thought to have provided sufficient vitamin A to these animals. This episode demonstrated the importance of monitoring vitamin A and vitamin A precursor concentrations in stored feeds, especially those stored under adverse conditions and those fed to animals ingesting only a high-grain diet.

Raman spectroscopy of oxidized and reduced nicotinamide adenine dinucleotides

We have measured the Raman spectra of oxidized nicotinamide adenine dinucleotide, NAD+, and its reduced form, NADH, as well as a series of fragments and analogues of NAD+ and NADH. In addition, we have studied the effects of pH as well as deuteration of the exchangeable protons on the Raman spectra of these molecules. In comparing the positions and intensities of the peaks in the fragment and analogue spectra with those of NADH and NAD+, we find that it is useful to consider these large molecules as consisting of component parts, namely, adenine, two ribose groups, two phosphate groups, and nicotinamide, for the purpose of assigning their spectral features. The Raman bands of NADH and NAD+ are found generally to arise from molecular motions in one or another of these molecular moieties, although some peaks are not quite so easily identified in this way. This type of assignment is the first step in a detailed understanding of the Raman spectra of NAD+ and NADH. This is needed to understand the binding properties of NADH and NAD+ acting as coenzymes with the NAD-linked dehydrogenases as deduced recently by using Raman spectroscopy.

Predicting adult temperament from minor physical anomalies

It is known that in children, individual differences in temperament are linked to rates of minor physical anomalies (MPAs). These anomalies are a standard set of 17 nonobvious but measurable characteristics of the face, hands, and feet. We explored the relation between MPAs and temperament in adults. An intact sample of 88 undergraduates completed a battery of personality tests and lifestyle questions, and then were examined for MPAs. The index of MPAs for each subject was simply the total count out of 17. The results showed a pattern of correlates parallel to that found in children. Among male subjects, correlations with MPAs were significant for the Physical Activity and Clumsiness factors of the lifestyle inventory as well as for measures of emotionality, extraversion, masculinity, femininity, and Type A personality. The MPA index was also predictive of a behavioral index of temperament in male subjects. No correlations were significant among female subjects.

AVGs: framework for ambulatory care payment

In preparation for an ambulatory care prospective payment system, the Health Care Financing Administration (HCFA), Office of Research and Demonstration, supported a two-year grant project at Yale University for further development of an ambulatory patient classification system based on Ambulatory Visit Groups (AVGs). This article explains the premises of the study and gives us insight into what we may ultimately expect in an ambulatory care prospective payment system.

Predicting adult temperament from minor physical anomalies

It is known that in children, individual differences in temperament are linked to rates of minor physical anomalies (MPAs). These anomalies are a standard set of 17 nonobvious but measurable characteristics of the face, hands, and feet. We explored the relation between MPAs and temperament in adults. An intact sample of 88 undergraduates completed a battery of personality tests and lifestyle questions, and then were examined for MPAs. The index of MPAs for each subject was simply the total count out of 17. The results showed a pattern of correlates parallel to that found in children. Among male subjects, correlations with MPAs were significant for the Physical Activity and Clumsiness factors of the lifestyle inventory as well as for measures of emotionality, extraversion, masculinity, femininity, and Type A personality. The MPA index was also predictive of a behavioral index of temperament in male subjects. No correlations were significant among female subjects.

Effect of xylazine and ketamine on intraocular pressure in horses

Intraocular pressure was measured with a MacKay-Marg tonometer in eight horses following auriculopalpebral nerve block and topical application of lignocaine. Measurements were recorded before and after xylazine, 1.1 mg/kg intravenously, every two minutes for 16 minutes after administration of ketamine, 2.2 mg/kg intravenously, and after recovery from anaesthesia. Before xylazine, intraocular pressure was 17.1 +/- 3.9 and 18.4 +/- 2.2 mm Hg in the left and right eyes, respectively. Intraocular pressure tended to decrease after administration of xylazine and ketamine, with a significant decrease in one eye six minutes after injection of ketamine.

Keratoconjunctivitis sicca: immunological evaluation of 62 canine cases

The etiology of keratoconjunctivitis sicca (KCS) in 62 dogs was evaluated, using immunologic techniques. Using direct fluorescent antibody testing, autoantibodies within the lacrimal, salivary, or pancreatic glands were detected in 5 of 8 dogs tested. Circulating antibodies to the nictitating membrane gland, main lacrimal gland, parotid salivary gland, or mandibular salivary gland were detected using indirect fluorescent antibodies in 9 of 31, 3 of 31, 5 of 31, and 5 of 31 sera, respectively. Using radial immunodiffusion, hyper-gamma-globulinemia was detected in 21 of 30 dogs with KCS. Antinuclear antibodies, primarily in a nucleolar pattern, were demonstrated in 20 of 50 dogs with KCS. Lymphocytic infiltrates were evident in 5 of 9 labial salivary biopsies, 2 of 4 parotid gland specimens, 2 of 4 mandibular gland specimens, and 2 of 3 thyroid gland specimens taken from dogs with KCS. Autoimmune diseases had been previously documented in 4 of 62 dogs. Twenty-five of the 62 dogs (40%) had concurrent problems indicative of an underlying immunologic disorder.

Raman study of reduced nicotinamide adenine dinucleotide bound to liver alcohol dehydrogenase

We report the first Raman spectra of reduced nicotinamide adenine dinucleotide (NADH) when bound to an enzymatic active site, that of liver alcohol dehydrogenase (LADH). This was obtained by subtracting the Raman spectrum of LADH from that of the binary LADH/NADH complex. There are significant changes in the spectrum of bound NADH as compared to that in solution. The data indicate that both the nicotinamide moiety and the adenine moiety are involved in the binding. At least one of the two NH2 moieties of NADH also participates.

Raman spectroscopy of liver alcohol dehydrogenase

We report the Raman spectrum of liver alcohol dehydrogenase in solution. The enzyme's secondary structure as determined from an examination of the Raman bands is slightly different than that found in crystals by X-ray diffraction.

Leber's congenital amaurosis associated with familial juvenile nephronophthisis and cone-shaped epiphyses of the hands (the Saldino-Mainzer syndrome)

Three affected children (a 13-year-old girl and her 7- and 8-year-old brothers) in a sibship of eight had findings consistent with the Saldino-Mainzer syndrome (skeletal dysplasia associated with Leber's congenital amaurosis, familial juvenile nephronophthisis, and cone-shaped epiphyses of the hands). Two also had pigmented midline nevi. Although tapetoretinal degeneration and familial juvenile nephronophthisis are associated in the inherited Senior-Loken syndrome, the rare association of these abnormalities with cone-shaped epiphyses of the hands suggested an autosomal recessive syndrome with variable expression remarkably similar to the Saldino-Mainzer syndrome, which may or may not be distinct from the Senior-Loken syndrome. The association of tapetoretinal degeneration with skeletal dysplasia may indicate asymptomatic renal or hepatic disease.