Dynamics of capillary-driven liquid-liquid displacement in open microchannels.

The dynamics of the spontaneous spreading of a liquid droplet along an open hydrophilic microchannel filled with another immiscible liquid is primarily determined by the competition between the capillary driving force and the viscous drag. While the former force depends on the channel cross-section and dimensions, interfacial tension between two liquids and the contact angle formed between the channel's wall and the two liquids, the latter arises from the motion of fluid molecules in the two bulk liquids. This paper focuses on the influence of the outer (displaced) phase viscosity. In general, as the viscosity of the displaced phase increases relative to the viscosity of the displacing phase, the velocity of the liquid-liquid meniscus decreases. The experiments were interpreted by extending a previously established correlation for liquid-vapour systems (J. Phys. Chem. C, 2011, 115(38), 18761-18769) in open microchannels of the same geometry. The relationship between the liquid-liquid flow dynamics and the properties of the liquids (e.g. viscosities) is still unclear. Nonetheless, by taking a self-consistent empirical approach to estimate the influence of the viscosities on the flow kinetics for a given system, it is possible to obtain a reasonable theoretical description for the experimental system over a specific range of viscosity ratios.

Capillary rise dynamics of aqueous glycerol solutions in glass capillaries: a critical examination of the Washburn equation.

The classic description of capillary rise given by the Washburn equation was recently questioned in the light of experimental evidence for a velocity dependent dynamic contact angle at a moving contact line. We present a systematic investigation of the capillary rise dynamics of glycerol and aqueous glycerol solutions in vertical glass capillaries of various radii. For pure glycerol, the results of our experiments are in almost perfect agreement with the predictions of the Washburn equation using independently measured values for the liquid and capillary parameters. For aqueous glycerol solutions we observe discrepancies between the theoretical expectations and the experimental results, which are increasing with the water content of the solution. A thorough analysis, combined with scaling arguments, allows us to conclude that dynamic contact angle effects alone cannot provide a consistent explanation for these discrepancies. Rather, they can be perfectly accounted for if the mixture flowing in the capillary would have an effective, increased viscosity (in respect to the nominal value). We suggest and briefly discuss various mechanisms that could contribute to this observed behavior.

A randomized open-label study of immediate versus delayed polylactic acid injections for the cosmetic management of facial lipoatrophy in persons with HIV infection.

BACKGROUND: Polylactic acid (PLA, New-Fill; Medifill, London, UK and Dermic Labs, a division of Eventis, Strasbourg, France) injections into the deep dermis increase fibroblast numbers and collagen production. The substance is widely used in medical applications including cosmetic procedures. METHODS: HIV-positive individuals with facial lipoatrophy (based on physician assessment) were randomized to immediate (weeks 0, 2 and 4) or delayed (weeks 12, 14 and 16) PLA given as three bilateral injections 2 weeks apart into the deep dermis overlying the buccal fat pad. Assessments included facial ultrasound, visual analogue scales, the Hospital Anxiety and Depression Scale (HADS) and assessment using photographs at weeks 0, 12 and 24. RESULTS: All 30 patients completed 24 weeks of treatment. The median age of the patients was 41 years, with a mean of 80 months of nucleoside reverse transcriptase inhibitor (NRTI) therapy and a mean of 44 months of prior protease inhibitor (PI) therapy. The median CD4 count was 428-460 cells/microL, with 47% of patients in the immediate-treatment group and 93% of patients in the delayed-treatment groups with <50 HIV-1 RNA copies/mL at baseline. No differences in immunological, virological, biochemical, haematological or metabolic parameters emerged during the study. Injections were well tolerated with only two adverse events (cellulitis and bruising) recorded, one of which delayed treatment by 1 week. There were no discontinuations. Patient visual analogue assessments, photographic assessments, and anxiety and depression scores improved with treatment. At week 12, immediate-treatment patients had significantly better visual analogue scores (7 vs. 1, P<0.001) and lower anxiety scores (6 vs. 9, P=0.056) than delayed-treatment patients. Benefits on visual analogue and HADS scores persisted until week 24. CONCLUSIONS: PLA injections led to improvements in patient self-perception, anxiety and depression scores in individuals with facial lipoatrophy. Adverse events were uncommon. The benefits of PLA persisted for at least 18 weeks beyond the last injection.

Gap junction proteins in inhibitory neurons of the adult barrel neocortex.

Recent studies indicate that electrical coupling among cortical neurons may persist throughout development; electrophysiological recordings made in cortical slices from young rats reveal that numerous GABAergic neurons are electrically coupled. To determine whether these in vitro findings reflect an inhibitory neural circuit that could be functionally relevant in vivo in adult rodents, we sought to identify whether inhibitory, parvalbumin-containing neurons of the mature cortex express gap junction proteins. Immunohistochemistry was used to examine the laminar distribution of the gap junction-forming proteins connexin 32 (Cx32), connexin 36 (Cx36) and connexin 43 (Cx43) in the somatosensory cortex of the adult mouse. Double labeling immunofluorescence identified Cx32, Cx36 and Cx43 in cortical neurons that were immunoreactive (-ir) for the neuronal markers neurofilament 145 kDa and neuronal nuclei (NeuN). Parvalbumin-ir neurons throughout the cortical laminae were labeled with Cx32-ir, Cx36-ir and Cx43-ir. Stereological methods were used to quantify the extent of parvalbumin colocalization with connexins. Analysis indicated that approximately 40% of parvalbumin-ir neurons were double labeled with either Cx32-ir or Cx43-ir, and approximately 50% of parvalbumin-ir neurons were double labeled with Cx36. These findings establish an anatomical substrate for widespread electrical coupling of neurons in somatosensory cortex and suggest that gap junctions among inhibitory interneurons may persist into adulthood, providing an important mechanism for neuronal communication.

Estrogen and tamoxifen differentially regulate beta-endorphin and cFos expression and neuronal colocalization in the arcuate nucleus of the rat.

Estrogen regulates hypothalamic gene expression, synthesis and release of the endogenous opioid peptide beta-endorphin (betaEND), although a consensus estrogen response element sequence has not been identified in the rat proopiomelanocortin (POMC) gene. POMC gene expression is also regulated by the activation of AP-1 promoter elements, which are known to be estrogen sensitive. The present studies examine whether estrogen modulates the hypothalamic POMC system through a non-classical mechanism involving AP-1 binding proteins such as cFos. Immunohistochemical double-labeling for betaEND and cFos was used and immunoreactive (-ir) populations were quantified in the arcuate nucleus and periarcuate area across time using unbiased stereological methods. Ovariectomized rats were injected with 50 microg estradiol (E2), 500 microg tamoxifen citrate (TAM) or both (E2+TAM) and were perfused 1, 2, 4 or 48 h later. E2 rapidly increased numbers of cFos-ir, betaEND-ir and doubly-labeled cells after 4 h, and the number of betaEND-ir cells remained high 48 h later, suggesting that the stimulatory effects of cFos on POMC in the hypothalamus persist after the cFos signal decays. Treatment with TAM alone did not affect the numbers of immunoreactive cells, although E2+TAM blocked the E2-mediated induction in all immunoreactive populations. Similar effects were seen at the transcriptional level. E2 increased hypothalamic POMC mRNA after 4 h, while TAM treatment or coadministration of E2+TAM did not significantly change the levels of POMC mRNA. Cellular colocalization of betaEND-ir and cFos-ir supports a possible intracellular co-regulation of these peptides by an estrogen-dependent mechanism within a subset of hypothalamic neurons. It does not, however, appear that E2 acts directly through an AP-1 site within the POMC gene.

Tonic and synaptically evoked presynaptic inhibition of sensory input to the rat olfactory bulb via GABA(B) heteroreceptors.

Olfactory receptor neurons of the nasal epithelium send their axons, via the olfactory nerve (ON), to the glomeruli of the olfactory bulb (OB), where the axon terminals form glutamatergic synapses with the apical dendrites of mitral and tufted cells, the output cells of the OB, and with juxtaglomerular (JG) interneurons. Many JG cells are GABAergic. Here we show that, despite the absence of conventional synapses, GABA released from JG cells activates GABA(B) receptors on ON terminals and inhibits glutamate release both tonically and in response to ON stimulation. Field potential recordings and current-source density analysis, as well as intracellular and whole cell recording techniques were used in rat OB slices. Baclofen (2-5 microM), a GABA(B) agonist, completely suppressed ON-evoked synaptic responses of both mitral/tufted cells and JG cells, with no evidence for postsynaptic effects. Baclofen (0.5-1 microM) also reversed paired-pulse depression (PPD) of mitral/tufted cell responses to paired-pulse facilitation (PPF), and reduced depression of JG cell excitatory postsynaptic currents (EPSCs) during repetitive ON stimulation. These results suggest that baclofen reduced the probability of glutamate release from ON terminals. The GABA(B) antagonists CGP35348 or CGP55845A increased mitral/tufted cell responses evoked by single-pulse ON stimulation, suggesting that glutamate release from ON terminals is tonically suppressed via GABA(B) receptors. The same antagonists reduced PPD of ON-evoked mitral/tufted cell responses at interstimulus intervals 50-400 ms. This finding suggests that a single ON impulse evokes sufficient GABA release, presumably from JG cells, to activate GABA(B) receptors on ON terminals. Thus GABA(B) heteroreceptors on ON terminals are activated by ambient levels of extrasynaptic GABA, and by ON input to the OB. The time course of ON-evoked, GABA(B) presynaptic inhibition suggests that neurotransmission to M/T cells and JG cells will be significantly suppressed when ON impulses arrive in glomeruli at 2.5-20 Hz. GABA(B) receptor-mediated presynaptic inhibition of sensory input to the OB may play an important role in shaping the activation pattern of the OB glomeruli during olfactory coding.

A new model for the mental health nursing change of shift report.

Nursing shift reports are intended to enhance the continuity and quality of nursing care delivered by providing results of nursing assessments, summarizing medical information, and drawing attention to specific nursing interventions and goals anticipated during the upcoming shift. In this article, contemporary literature on shift reports is reviewed with specific attention to the unique characteristics and problems that commonly occur in change of shift reports in a mental health setting. The framework proposed is Gordon's functional health patterns because it provides a holistic structure for organizing patient data in a clear, objective manner. Additional methods for enhancing shift reports are recommended, including the use of specific behavioral descriptions, the inclusion of data from targeted nursing assessments, and the discussion of alternative care approaches that support the development of consistent, collaborative nursing interventions across shifts. A case example is used for demonstration.

Targeted deletion of the Vgf gene indicates that the encoded secretory peptide precursor plays a novel role in the regulation of energy balance.

To determine the function of VGF, a secreted polypeptide that is synthesized by neurons, is abundant in the hypothalamus, and is regulated in the brain by electrical activity, injury, and the circadian clock, we generated knockout mice lacking Vgf. Homozygous mutants are small, hypermetabolic, hyperactive, and infertile, with markedly reduced leptin levels and fat stores and altered hypothalamic proopiomelanocortin (POMC), neuropeptide Y (NPY), and agouti-related peptide (AGRP) expression. Furthermore, VGF mRNA synthesis is induced in the hypothalamic arcuate nuclei of fasted normal mice. VGF therefore plays a critical role in the regulation of energy homeostasis, suggesting that the study of lean VGF mutant mice may provide insight into wasting disorders and, moreover, that pharmacological antagonism of VGF action(s) might constitute the basis for treatment of obesity.

Hypothalamic pro-opiomelanocortin mRNA is reduced by fasting and [corrected] in ob/ob and db/db mice, but is stimulated by leptin.

Reduction in the activity of the alpha-melanocyte-stimulating hormone (alpha-MSH) system causes obesity, and infusions of alpha-MSH can produce satiety, raising the possibility that alpha-MSH may mediate physiological satiety signals. Since alpha-MSH is coded for by the pro-opiomelanocortin (POMC) gene, we examined if POMC gene expression would be inhibited by fasting in normal mice or in models of obesity characterized by leptin insufficiency (ob/ob) or leptin insensitivity (db/db). In wild-type mice, hypothalamic POMC mRNA was decreased > 60% after a 2-day fast and was positively correlated with leptin mRNA. Similarly, compared with controls, POMC mRNA was decreased by at least 60% in both db/db and ob/ob mice. POMC mRNA was negatively correlated with both neuropeptide Y (NPY) and melanin-concentrating hormone (MCH) mRNA. Finally, treatment of both male and female ob/ob mice with leptin stimulated hypothalamic POMC mRNA by about threefold. These results suggest that impairment in production, processing, or responsiveness to alpha-MSH may be a common feature of obesity and that hypothalamic POMC neurons, stimulated by leptin, may constitute a link between leptin and the melanocortin system.

Estrogen and stress interact to regulate the hypothalamic expression of a human proenkephalin promoter-beta-galactosidase fusion gene in a site-specific and sex-specific manner.

Gonadal steroids and physiological stressors affect the regulation of proenkephalin (PPE) gene expression in the paraventricular (PVN) and ventromedial (VMH) hypothalamic nuclei. To examine the effects of these modulators at the cellular level, the current study utilized a transgenic mouse line that expresses a human proenkephalin promoter/bacterial beta-galactosidase fusion gene (ENK-1). Previous studies have demonstrated that the regulatory sequences included in this transgene are sufficient to support appropriate transcriptional regulation of the reported gene in the PVN of male ENK-1 mice in response to stress. The present experimental paradigm was designed to examine possible interactions of sex and circulating estrogen levels with the opioid responses to acute systemic stressors, an intraperitoneal injection of hypertonic (1.5 M) or isotonic (0.15 M) saline. Adult ENK-1 mice were gonadally intact, gonadectomized, or 21 days postpartum. Forty-eight hours before perfusion, castrated males and ovariectomized females received either 10 micrograms estradiol benzoate or oil vehicle and 4 animals per group received no further treatment. Six h before perfusion, remaining animals received a single intraperitoneal injection of either hypertonic or isotonic saline. Tissues were sectioned through the hypothalamus and processed for X-gal histochemistry. In the VMH of ovariectomized females that received isotonic saline, estrogen significantly elevated transgene expression. This effect was not seen in females that only received estrogen or in those that received the severe systemic stressor of a injection of hypertonic saline. Estrogen and stress did not interact to elevate transgene expression in the VMH of males. A different pattern of expression was observed in the PVN; injection of hypertonic saline induced transgene expression only in gonadally intact males and in castrated males given estrogen. These findings demonstrate that stress and estrogen have sex-specific and site-specific regulatory effects on the expression of a PPE promoter transgene in hypothalamic neurons.

Regulation of cholecystokinin receptors in the ventromedial nucleus of the hypothalamus: sex steroid hormone effects.

Quantitative autoradiography was used to analyze cholecystokinin receptor (CCK-R) binding in the ventromedial hypothalamic nucleus (VMH) of gonadectomized rats treated with estrogen or testosterone. In the rostral VMH, sex steroids did not affect binding levels. In the caudal VMH, in both gonadectomized male and female rats, the levels of CCK-R binding were decreased 24 h after injection of 50 micrograms of estrogen benzoate but were not changed after injection of 300 micrograms of testosterone propionate. We hypothesize that these changes in CCK-R binding in the VMH reflect ligand-induced down-regulation that result from an estrogen-facilitation of stimulated CCK release in the VMH.

Estrogen regulates preproenkephalin-A mRNA levels in the rat ventromedial nucleus: temporal and cellular aspects.

Numerous studies suggest that the ventromedial nucleus of the hypothalamus is a primary locus of control for reproductive behavior in the female rat. The display of lordosis behavior is estrogen dependent and its regulation appears to involve the activity of endogenous opioid circuits in the mediobasal hypothalamus and brainstem. Hypothalamic levels of preproenkephalin-A mRNA and the neuropeptide which it encodes, methionine-enkephalin, are dramatically up-regulated by estrogen. To characterize the temporal and cellular aspects of the effect of an acute exposure to estrogen on preproenkephalin-A mRNA levels in the ventromedial nucleus and arcuate nucleus of the hypothalamus, ovariectomized female rats were injected with 50 micrograms estradiol benzoate and used for quantitative in situ hybridization histochemistry of preproenkephalin-A mRNA. In the ventromedial nucleus, estrogen treatment caused a biphasic increase in the number of preproenkephalin-A mRNA cells. Maximal numbers of cells expressing preproenkephalin-A mRNA were observed at 1 and 48 h after estrogen injection. At 4 and 96 h after estrogen injection, the numbers of preproenkephalin-A mRNA cells were similar to that which was seen in the ovariectomized female. The induction of preproenkephalin-A mRNA expression in cells of the arcuate nucleus followed a similar pattern that peaked 48 h after exposure to estrogen. Levels of preproenkephalin-A mRNA per cell did not change in either nucleus as a function of estrogen treatment. Thus, acute estrogen treatment induces expression of preproenkephalin-A mRNA in populations of cells in the ventromedial hypothalamus and arcuate nucleus in which preproenkephalin-A mRNA expression is undetectable by in situ hybridization in the absence of circulating estrogen.

Temporal regulation by estrogen of beta-preprotachykinin mRNA expression in the rat ventromedial nucleus of the hypothalamus.

In the rat, reproduction and sexual behavior are controlled by the gonadal steroid regulation of synaptic interactions within the sexually dimorphic limbic-hypothalamic system. The effects of estrogen on the ventromedial nucleus of the hypothalamus, one nucleus within the circuit, are central to the modulation of this behavior. Involvement of the neuropeptide substance P, a member of the tachykinin family of neuropeptides, has been implicated in the regulation of both lordosis behavior and gonadotropin release. However, previous studies have provided conflicting evidence as to whether levels of substance P in the ventromedial nucleus of the hypothalamus are modulated by circulating estrogens. To study this question further, in situ hybridization histochemistry was used to examine levels of beta-preprotachykinin mRNA, which encodes substance P and other tachykinins, in the ventrolateral subdivision of the ventromedial hypothalamus at 10 consecutive timepoints over a 4 day period subsequent to an acute administration of estrogen. Following estrogen treatment, beta-preprotachykinin mRNA expression was increased in cells of the ventrolateral portion of the ventromedial nucleus of the hypothalamus which constitutively express beta-preprotachykinin mRNA; however, there were no statistically significant changes in the number of cells that express detectable levels of beta-preprotachykinin mRNA in the ventrolateral portion of the ventromedial nucleus. Estrogen treatment produced two peaks of beta-preprotachykinin mRNA expression, the first at 2 h and the second at 48 h after the injection of estrogen. These data indicate that estrogen has both rapid and prolonged effects on beta-preprotachykinin mRNA levels, suggesting that estrogen may affect different cellular mechanisms relevant to the induction of beta-preprotachykinin mRNA expression.

Actions of sex steroids on behaviours beyond reproductive reflexes.

The actions of sex steroids in the brain have been shown, from molecular to systems levels, to control reproductive behaviour in a wide range of vertebrates. It has become increasingly clear that gonadal steroid hormones have regulatory functions which extend far beyond the direct coordination of an animal's physiological state and its display of sexual behaviour. While some of these actions may include changes in mood or other behavioural measures, such as exploration or excitability, sex steroid hormones also influence neural plasticity, neuronal activity and, possibly, learning and memory, as reflected by long-term potentiation or age-related deficits. Here we describe two systems that have been used to explore the non-reproductive roles of gonadal steroid hormones. The first of these is to examine the oestrogen-sensitive opioid peptide gene expression in the hypothalamus. Currently, we are attempting to identify the types of behaviour which may be altered consequent to the oestrogenic induction of the preproenkephalin gene. The second approach involves studying the effects of progesterone at the neuronal cell membrane and characterizing the metabolites of progesterone which have benzodiazepine-like actions in the brain. A number of studies suggest that this may provide an alternative mechanism through which progesterone can influence mood or behaviour.

Gonadal steroid control of preprocholecystokinin mRNA expression in the limbic-hypothalamic circuit: comparison of adult with neonatal steroid treatments.

The neuropeptide cholecystokinin (CCK) is involved in the regulation of female, but not male, reproductive behavior. In both sexes, estrogen regulates the expression of CCK in adulthood within the bed nucleus of the stria terminalis and medial amygdaloid nucleus. These areas are parts of an interconnected limbic system-hypothalamic circuit, the development of which is influenced by estrogen during the early postnatal period. This is the same period during which central nervous system (CNS) expression of CCK is dramatically increased, suggesting that the male and female patterns of CCK expression may be the result of early postnatal exposure to estrogen. In the present experiment, the expression of preprocholecystokinin (pCCK) mRNA was determined by in situ hybridization with an isotopically labeled pCCK complementary RNA and emulsion autoradiography in animals whose neonatal and adult gonadal steroid levels had been manipulated. The number of pCCK-expressing cells in animals that were gonadectomized as adults was determined by neonatal estrogen, but stimulation with steroids in adulthood induced a similar number of pCCK-expressing cells in both sexes in the medial amygdala and bed nucleus of the stria terminalis. Neonatal treatment of females with estrogen or testosterone, followed by ovariectomy in adulthood, eliminated the sex difference in pCCK mRNA expression. Males treated neonatally with the aromatase inhibitor androstenedione (to block metabolism of testosterone to estrogen) and orchidectomized in adulthood had a level of pCCK mRNA expression that was similar to that of ovariectomized females. These data suggest that, during neonatal development, estrogen determines the constitutive expression of pCCK mRNA in the medial amygdala and bed nucleus of the stria terminalis, resulting in higher levels of pCCK mRNA expression in males than in females. However, exogenous gonadal steroids induce the same levels of pCCK mRNA expression in adult females, indicating that the levels of gonadal steroids and the patterns of their secretion are the predominant influences on the sexually dimorphic adult levels of pCCK mRNA expression.

Microinjection of cholecystokinin into the medial preoptic nucleus facilitates lordosis behavior in the female rat.

We examined the effect of cholecystokinin (CCK) on lordosis behavior when administered into the medial preoptic area or the nucleus accumbens (NAcc) of ovariectomized estrogen-primed female rats. The frequency of lordotic responses was measured subsequent to unilateral microinjections of sulphated octapeptide CCK (sCCK-8) into the medial preoptic nucleus (MPN) or the NAcc. In the first experiment, three doses of sCCK-8 (1, 5, and 50 ng) microinjected into the MPN, and 50 ng injected into the NAcc produced a marked facilitation of lordosis. In a separate experiment, unilateral injections of an undiluted sCCK-8 antiserum into the MPN produced significant reduction in lordosis behavior in highly receptive females when compared with a normal rabbit serum injected control group. The results of the present study indicate that the CCK innervation of the MPN is involved in the neural regulation of lordosis behavior in the female rat.

Effects of six-month afterload reduction therapy with hydralazine in chronic aortic regurgitation.

Seventeen patients with chronic asymptomatic aortic regurgitation (AR) were studied to determine whether 6 months of hydralazine therapy can reduce the severity of AR or reverse left ventricular (LV) enlargement and hypertrophy. Echocardiography, radionuclide angiography at rest and during exercise, and maximal treadmill exercise with respiratory gas analysis were performed at intake and after a 6-month double-blind treatment period. After dose titration with hydralazine, patients were randomized to their maximal tolerated hydralazine dose or to placebo. At intake, hydralazine and placebo groups were similar. Six patients taking hydralazine and 8 taking placebo completed the study protocol. One patient taking placebo died and 2 patients taking hydralazine withdrew with drug-related adverse effects. The mean titrated dose of hydralazine was 96 +/- 9 mg, but the mean treatment dose was 63 +/- 21 mg administered 3 times daily because of drug intolerance. After 6 months, mean systolic blood pressure with hydralazine therapy decreased from 136 to 125 mm Hg (p less than 0.02), and end-systolic posterior wall thickness increased from 1.58 to 1.70 cm (p less than 0.05), resulting in a significant reduction in M-mode meridional end-systolic stress (from 104 to 80 kdynes/cm2) (p less than 0.05). M-mode fractional shortening increased from 0.28 to 0.31 (p less than 0.05) with hydralazine, but mean LV echocardiographic dimensions were unchanged. LV mass increased from 383 to 434 g (p less than 0.05) with hydralazine primarily because of an increase in end-diastolic wall thickness. In the placebo group, there was no change in any of the hemodynamic or echocardiographic parameters at 6 months.(ABSTRACT TRUNCATED AT 250 WORDS)

Antianginal effects of nitroglycerin patches.

Nitroglycerin (NTG) patches provide potentially therapeutic NTG blood levels for 24 hours, but their effects on exercise tolerance (ExT) in patients with angina have not been well characterized. Therefore, blinded, randomized trials were performed of the acute effects of both low-dose and maximal-tolerated-dose NTG patches and placebo on ExT in 14 patients with coronary artery disease and typical exertional angina. The bicycle exercise protocol of the National Institutes of Health was used and sublingual NTG administered as a positive control. In 7 subjects, low-dose patches produced no statistically significant effect on ExT at 4, 8 or 24 hours after administration. Comparable doses of sublingual and oral isosorbide dinitrate, NTG ointment and transmucosal NTG in previous studies have produced effects similar to those of conventional doses of sublingual NTG. Maximally tolerated doses of 2 types of NTG patches were then tested. The first (n = 8, mean NTG dose delivered 25 mg) produced increases in ExT of 82 and 72 seconds at 4 and 8 hours, respectively (both p less than 0.01), but was ineffective at 24 hours. The second patch type (n = 5, mean NTG dose delivered 22 mg) was also ineffective at 24 hours. Furthermore, even at maximal doses, peak effects on ExT were about half of those of sublingual NTG. Thus, NTG patches, even at maximal doses, appear to have smaller therapeutic effects than other long-acting nitrates and are ineffective at 24 hours. These results suggest rapid attenuation of NTG effect during prolonged maintenance of constant blood levels.

The Ultra-Flo 100 platelet counter: a new approach to platelet counting.

The Clay Adams Ultra-Flo 100 whole blood platelet counter is a semiautomated instrument. The count is made on dilute whole blood by the detection of comparatively small current changes induced by the cells suspended in a conducting diluent as they flow thrugh an orifice. Alarm systems are incorporated in the instrument to detect sample irregularities due to microcytosis, and large and small platelets. The results of this evaluation are given, and confirm that the results using the Ultra-Flo 100 compare very favourably with those obtained using phase contrast microscopy.