End effects in low aspect ratio Taylor-Couette flow.

Taylor-Couette flow with a low aspect ratio cylinder suffers from end effects due to the finite-span of the gap between the cylinder sides and the secondary flow in the region below the inner cylinder. We experimentally explore these end effects by varying the cylinder aspect ratio between 6.67 and 40 for a range of wall gap widths and bottom gap heights. For these geometries, end effects (i.e. non-ideal Taylor-Couette flow) can be substantial due to both features of the finite-span and the bottom secondary flow. In some cases, the finite-span effects extended between 20% and 30% of the way into the Taylor-Couette flow region, and the secondary flow at the bottom accounted for nearly half of the total measured torque. By taking these effects into consideration, our high aspect ratio results agreed well with those obtained by Taylor (Taylor 1936 Proc. R. Soc. Lond. A 157, 546-564. (doi:10.1098/rspa.1936.0215)) at considerably higher aspect ratios. This article is part of the theme issue 'Taylor-Couette and related flows on the centennial of Taylor's seminal Philosophical Transactions paper (part 1)'.

First Report of a New Potyvirus, Tricyrtis virus Y, and Lily virus X, a Potexvirus, in Tricyrtis formosana in the United States.

Tricyrtis formosana (toad lily) is an herbaceous perennial in the family Liliaceae. Native to Asia, T. formosana is now used in the United States as an ornamental border plant in woodland and shade gardens. A T. formosana var. stolonifera plant showing chlorosis and mild mosaic symptoms obtained from a commercial grower in Columbia County, Oregon tested positive for potyvirus by ELISA using our genus Potyvirus broad spectrum reacting PTY-1 Mab (3). Electron microscopic examination of negatively stained leaf-dip preparations from symptomatic leaves showed a mixture of two sizes of flexuous rod-shaped particles, approximately 700 nm long (resembling potyviruses) and 470 nm long (resembling potexviruses). Total RNA extracts from symptomatic leaves were used in reverse transcription (RT)-PCR assays with potyvirus- or potexvirus-specific primers. The degenerate primers for the genus Potyvirus (2) direct the amplification of approximately 1,600-bp fragments from the 3' terminus of most potyviruses. Overlapping potexvirus cDNA clones were generated using degenerate genus Potexvirus replicase primers, and later, virus-specific primers in 3' RACE (4). The RT-PCR amplified fragments were cloned and sequenced. Analysis of the 1,688 nt potyvirus sequence (GenBank Accession No. AY864850) using BLAST showed highest identity with members of the Bean common mosaic virus (BCMV) subgroup of potyviruses. Pairwise amino acid comparisons of the CP region of the new potyvirus showed 78% identity to strains of Bean common mosaic necrosis virus, 77% identity with Soybean mosaic virus and Ceratobium mosaic virus, 72 to 76% identity to strains of BCMV, and only 50 to 64% identity with 54 other potyviruses. Additionally, similar pairwise analysis of the CP nucleotide sequence and 3'NCR of the new potyvirus generally revealed the same identity trend as described for the CP amino acid sequences, albeit with the highest nucleotide identities at less than 73% for CP and less than 66% for the 3'NCR. These results suggest that this virus is a new species in the genus Potyvirus (1), which we have tentatively named Tricyrtis virus Y (TrVY). BLAST analysis of the 3' terminal 3,010 nt potexvirus sequence (GenBank Accession No. AY864849) showed 89% nucleotide identity with Lily virus X (LVX). Pairwise amino acid comparisons of the putative gene products revealed 98, 95, 94 and 99% identity with LVX TGBp1, TGBp2, TGBp3-like, and CP, respectively, and 97% identity with the 108 nt 3'NCR. Homology with other members of the genus Potexvirus was less than 50% for these corresponding genes and gene products. ELISA and RT-PCR analysis for these two viruses in toad lily plants obtained from a grower in Illinois also revealed the presence of TrVY in three of seven cultivars and LVX coinfecting only one of the plants. The standard propagation method for T. formosana is plant division, which along with mechanical contact, provides efficient means for spread of both viruses. To our knowledge, this is the first description of this potyvirus and the first report of any potyvirus in T. formosana. LVX has been reported in Lilium formosanum, but to our knowledge, this is also the first report of LVX in T. formosana. References: (1) P. H. Berger et al. Potyviridae. Page 819 in: Virus Taxonomy: 8th Rep. ICTV, 2005. (2) M. A. Guaragna et al. Acta. Hortic. 722:209, 2006. (3) R. L. Jordan and J. Hammond. J. Gen. Virol. 72:1531, 1991. (4) C. J. Maroon-Lango et al. Arch. Virol. 150:1187, 2005.

In vivo cardiovascular reactivity and baroreflex activity in diabetic rats.

OBJECTIVES: Abnormalities of the cardiovascular system, e.g. impaired vasoreactivity and changes in baroreflex control of heart rate, are known to occur in experimental diabetes. It is not clear whether these cardiovascular dysfunctions are direct consequences of cardiovascular deficits and/or have autonomic neuropathy as a cause. METHODS: To differentiate between cardiovascular deficits or neuronal impairment as a cause for these cardiovascular dysfunctions, we tested the effects of the ACTH4-9 analogue, Org 2766, a neurotrophic compound without cardiovascular effects, on arterial pressure, heart rate and baroreflex control of heart rate. At 15 weeks, rats were made diabetic by injection of streptozotocin, and from 0-6, 6-12 or 12-18 weeks thereafter 3 groups of rats were treated with Org 2766. These effects were evaluated during phenylephrine-induced increases, and sodium nitroprusside-induced decreases, in blood pressure, in rats that had been diabetic for various periods (2-42 weeks). RESULTS: Throughout, both depressor response and maximal vasodilator activity in response to sodium nitroprusside were significantly (P < 0.05) reduced as compared to those of the non-diabetic controls. The pressor response of the diabetic rats to phenylephrine was only significantly (P < 0.05) reduced at 4, 6 and 12 weeks, and at 18 weeks, the diabetic rats were either hypo- or normoresponsive; Org 2766 did not restore the disturbed pressor response. From weeks 4 to 42 both maximal decrease in heart rate and sensitivity of baroreflex-mediated bradycardia in the diabetic rats were significantly less (P < 0.05) than those in the non-diabetic controls. Org 2766 restored the diminished baroreflex-mediated bradycardia of diabetic rats to non-diabetic control levels at 6 weeks, had an ameliorating effect at 12 weeks and no effect at 18 weeks. CONCLUSIONS: Time-dependent decreases in baroreflex sensitivity in diabetic rats was demonstrated and a much less steep decline of baroreflex sensitivity occurred in non-diabetic control rats. The ACTH4-9 analogue, Org 2766, when given immediately upon the induction of diabetes seem to delay the development of autonomic neuropathy, which suggests that cardiovascular factors appear to be of minor importance.

Vagal efferent control of electrical properties of the heart in experimental diabetes.

Autonomic neuropathy is a common and severe complication of diabetes mellitus that leads to dysfunction of the cardiovascular system. The reduced ability to finely regulate heart rate is attributed to an impairment of cardiac parasympathetic regulation, but it is not known whether this is due to parasympathetic neuropathy and/or direct cardiac impairments. Therefore, we recorded the electrocardiogram of streptozotocin-induced diabetic rats under basal conditions and during electrical stimulation of the vagus nerve. We used the neurotrophic agent Org 2766, an adrenocorticotropic hormone [ACTH]-(4-9) analogue, to investigate the involvement of a neurogenic component in the altered vagal control of heart rate. The R-R interval was increased and atrioventricular transmission time unchanged 1 week after diabetes induction and remained so until 20 weeks. Treatment with Org 2766 could not prevent the bradycardia. After bilateral vagotomy, both diabetic and non-diabetic rats had the same R-R and P-R interval. The response of the R-R interval to electrical stimulation of the right vagus nerve was impaired, and this impairment was not reversed by Org 2766 in diabetic rats. These results suggest that neurogenic factors are of little or no importance in the impaired parasympathetic control of heart rate seen in experimental diabetes.

Vascular responses of isolated mesenteric resistance and basilar arteries from short- and long-term diabetic rats.

Vascular dysfunctions, e.g. alterations in the reactivity of blood vessels to neurotransmitters and hormones, are a well-established complication of diabetes mellitus. Whether these impairments are a consequence of direct postsynaptic deficits and/or indirect presynaptic deficits remains to be determined. To this end, we investigated the influence of the duration of diabetes on relaxation and contraction responses of isolated mesenteric resistance and equally-sized basilar arteries to postsynaptic activation by various vasoactive agents, using streptozotocin-induced diabetic rats and age-matched controls. Relaxation responses to vasodilator agents were studied in KCl-precontracted arteries. The duration of diabetes (4 or 40 weeks) did not affect the vasodilator responses to sodium nitroprusside or salbutamol in either artery. In mesenteric resistance vessels from short-term (4 weeks) and long-term (40 weeks) diabetic rats the vasoconstrictor responses to KCI, serotonin and vasopressin were the same as those in non-diabetic rats; however, the sensitivity (EC50) to noradrenaline was slightly but significantly enhanced after the long-term diabetic state. In contrast to the mesenteric arteries, noradrenaline did not cause contraction in basilar arteries taken from diabetic and control rats. Thus, there appear to be important differences in the reactivity to noradrenaline of the peripheral and cerebral vasculature. The basilar artery from short-term and long-term diabetic rats did not show different responsiveness to vasopressin whereas to serotonin a significant enhanced and decreased sensitivity (EC10 and EC50) was demonstrated in short-term and long-term diabetes, respectively. Our findings indicate that postsynaptic impairments do not play a major role in the alterations of vasoreactivity to vasodilators, noradrenaline or vasopressin seen in experimental diabetes. However, the duration of the diabetic state may have serious consequences for vasoreactivity of basilar arteries to serotonin and, therefore, warrants further investigations.

A disturbed macrocirculatory supply as a determinant for a reduced sciatic nerve blood flow in diabetic rats.

The aim of this study was to evaluate macrocirculatory disturbances in relation to the reduced sciatic nerve blood flow seen in diabetic rats. Therefore, both femoral blood flow, the macrocirculatory arterial blood supply to the sciatic nerve, and the microcirculatory neuronal blood flow were measured. In order to differentiate between a direct vascular or a neuronal defect as a cause for the disturbed macrocirculatory blood flow the effects of the adrenocorticotropic hormone [ACTH]-(4-9) analogue, Org 2766, a neurotrophic compound without cardiovascular effects, were investigated on the femoral flow under basal as well as adrenergic-stimulated conditions. Adrenergic responsiveness to tyramine and phenylephrine effect on femoral flow was determined. Basal sciatic nerve and femoral blood flow were reduced by 48% and 42%, respectively, after 12 weeks of diabetes, without effect on blood pressure. Treatment with Org 2766, beginning 6 weeks after the induction of diabetes, had no influence on these basal haemodynamic variables. Femoral flow in diabetic rats showed a smaller response to tyramine and phenylephrine compared to the control. Org 2766 restored this disturbed flow response to that of the control rats. In conclusion, the decrease in basal femoral flow might be responsible for the lowered sciatic nerve blood flow. Although neuronal disturbances due to diabetes had a very minor role in the reduction of basal femoral blood flow the adrenergic-stimulated flow responsiveness was seriously affected in diabetic rats.

Presynaptic deficit of sympathetic nerves: a cause for disturbed sciatic nerve blood flow responsiveness in diabetic rats.

Reduced nerve blood flow is thought to play an important role in the pathogenesis of diabetic neuropathy. This disturbance in nerve blood flow might be the consequence of either microangiopathy or an impaired autonomic innervation of the vasa nervorum. In order to differentiate between a vascular or an adrenergic-autonomic defect as the underlying cause of the disturbed nerve blood flow, we investigated the effects of the adrenocorticotropic hormone [ACTH]-(4-9) analogue Org 2766 on sciatic nerve blood flow under basal and adrenergic-stimulated conditions. Org 2766 has neuroprotective effects without cardiovascular effects. Treatment with Org 2766 was started 6 weeks after the induction of experimental diabetes mellitus. At week 12 the sciatic nerve blood flow, measured by laser-Doppler flowmetry, was reduced to 60% of the non-diabetic level; blood pressure was unchanged in diabetic rats compared to non-diabetic rats. Basal haemodynamic values were not affected by Org 2766 treatment. Vasa nervorum adrenergic responsiveness to tyramine (presynaptic) and phenylephrine (postsynaptic) was investigated. Diabetic rats showed adrenergic hyporesponsiveness. Treatment with Org 2766 restored the reduced presynaptic response to tyramine without affecting the reduced postsynaptic response to phenylephrine. It is concluded that a presynaptic-sympathetic deficit of nervi vasorum causes a disturbed flow responsiveness in diabetic rat sciatic nerve and that adrenergic autonomic disturbances in the vasa nervorum have only a small role in the reduced basal nerve blood flow of diabetic rats.

Quantifying intracellular radioresponse diversity in irradiated sandwich cultures via micronucleus expression.

Determining the degree of diversity in therapeutic sensitivity exhibited by a tumour population is of considerable clinical importance. In addition to being a contributor to radiation resistance, diversity is the basis for variation in sensitivity over the course of treatment. To study intrapopulation diversity in radiosensitivity following gamma-irradiation (2 Gy), distributions of the number of micronuclei/binucleate cell were obtained for human cervix carcinoma sandwich populations. Cell-to-cell diversity in radioresponse (micronucleus expression) was quantified using the overdispersion index ((variance/mean)--1). As measured by this index, the radioresponse diversity of sandwich cultures sharply increased after introduction of oxygen/nutrients to the cultures, mimicking tumour reperfusion. In addition, a strong correlation was found between this measure of diversity and the extent to which the fraction of cells without micronuclei exceeds that expected from a Poisson distribution. This correlation indicates that for a diverse population there can be a significant departure of the aggregate population sensitivity (determined, for instance, by log-survival in a clonogenic assay) from that inferable from simply averaging per-cell sensitivities (reflected, e.g. by mean number of chromosome aberrations/cell). Our experimental results suggest a model attributing diversity in a population to its being a mixture of distinct subpopulations, each biologically homogeneous with respect to micronucleus expression, and each contributing an individual Poisson-distributed micronucleus response. We demonstrate how such radiodiversity may be quantified and show that reoxygenation of a microenvironmentally heterogeneous population leads to an increase in its radiobiological diversity.

Beneficial effect of the Ca2+ antagonist, nimodipine, on existing diabetic neuropathy in the BB/Wor rat.

1. Neuropathy is a frequently diagnosed complication of diabetes mellitus. Effective pharmacotherapy is not available. 2. The spontaneously diabetic BB/Wor rats develop secondary complications like neuropathy as do human diabetic patients. 3. BB/Wor rats treated with insulin via a subcutaneous implant show a significant impairment of sensory and motor nerve conduction velocity 6 weeks after the onset of diabetes mellitus. 4. Intraperitoneal treatment of diabetic BB/Wor rats with the Ca2+ antagonist, nimodipine (20 mg kg-1), from week 6 onwards every 48 h for a period of 6 weeks resulted in a significant increase of sensory and motor nerve conduction velocity. 5. Twelve weeks after the onset of diabetes mellitus BB/Wor rats show a 40% impairment of sciatic nerve blood flow as compared to the non-diabetic age-matched controls. Treatment with nimodipine (20 mg kg-1) from week 6 onwards significantly increased the sciatic nerve blood flow as compared to placebo-treated diabetic BB/Wor rats. 6. The adrenergic responsiveness of the vasa nervorum of the sciatic nerve to tyramine and phenylephrine was investigated as a parameter for autonomic neuropathy. 7. The fact that nimodipine treatment restored the reduced response to tyramine independently of the reduced postsynaptic phenylephrine responsiveness indicates that nimodipine improves adrenergic responsiveness mainly at the presynaptic level.

Effects of nimodipine on sciatic nerve blood flow and vasa nervorum responsiveness in the diabetic rat.

Evidence is accumulating that impairment of nerve blood flow is a key factor in the pathogenesis of diabetic neuropathy. Nimodipine, a 1,4-dihydropyridine type Ca2+ channel antagonist, has been shown to ameliorate an existing neuropathy in the streptozotocin-induced diabetic rat. In the present study the effect of diabetes mellitus itself and the effect of chronic nimodipine treatment on the sciatic nerve blood flow of streptozotocin-induced diabetic rats were investigated. Nerve blood flow was assessed using laser-Doppler flowmetry. Nerve blood flow gradually decreased during the first 10 weeks of diabetes mellitus and remained relatively stable thereafter. Intervention with nimodipine significantly improved the flow deficit observed in the diabetic rats. Vasa nervorum adrenergic responsiveness was also investigated. Diabetic rats showed a postsynaptic adrenergic hyporesponsiveness. Treatment with nimodipine restored the reduced presynaptic responsiveness independent of the postsynaptic adrenergic hyporesponsiveness. It was concluded that, in addition to direct neuroprotective effects, nimodipine exerts beneficial effects on disturbed nerve blood flow and on reduced presynaptic adrenergic responsiveness of the vasa nervorum in experimental diabetic neuropathy.

Amelioration by the Ca2+ antagonist, nimodipine of an existing neuropathy in the streptozotocin-induced, diabetic rat.

1. Neuropathy is a frequently diagnosed complication in diabetic patients but an effective treatment does not exist. 2. The development of neuropathy in streptozotocin-induced diabetic rats was monitored by measuring the motor and sensory nerve conduction velocity in the sciatic nerve. 3. A significant decrease in sensory and motor nerve conduction velocity was apparent in young, 14-week-old diabetic rats as compared to non-diabetic, age-matched controls 4 weeks after the induction of diabetes with streptozotocin. 4. Intraperitoneal treatment with the Ca2+ channel blocker, nimodipine, from week 4 onwards, in a dosage of 10 mg kg-1 or 20 mg kg-1 intraperitoneally per 48 h, resulted in a significant increase in sensory and motor nerve conduction velocity whereas treatment with 5 mg kg-1 intraperitoneally per 48 h was not effective. 5. One-year-old, adult, diabetic rats treated with nimodipine 20 mg kg-1 (treatment started again 4 weeks after induction of diabetes mellitus) also showed an increase of both sensory and motor nerve conduction velocity as compared to diabetic rats treated with placebo. 6. It is concluded that nimodipine ameliorates existing experimental diabetic neuropathy in streptozotocin-induced diabetic rats in both young and adult animals.

ACTH4-9 analogue ORG 2766 can improve existing neuropathy in streptozocin-induced diabetic rats.

The effect of treatment of an existing neuropathy in streptozocin-induced diabetic rats with the ACTH4-9 analogue ORG 2766 was examined. Four groups of rats were studied: group 1 consisted of age-matched, non-diabetic controls and groups 2, 3 and 4 of diabetic rats. Sensory and motor nerve conduction velocity (SNCV and MNCV) were measured at weeks 0, 4, 6, 8 and 10. Four weeks after the administration of streptozocin (STZ) all diabetic rats showed a significant slowing of SNCV and MNCV. Treatment was then started: group 2 was treated with placebo, group 3 with a low dos (1 microgram) of ACTH4-9 subcutaneously every 48 h, and group 4 with a high dos (10 micrograms) of ACTH4-9 subcutaneously every 48 h. The animals treated with the high peptide dosage showed a significant improvement in both SNCV and MNCV from week 6 onwards, whereas this beneficial effect was not demonstrated for the rats treated with the low dosage. This study demonstrates that the ACTH4-9 analogue ORG 2766 can ameliorate existing diabetic neuropathy in STZ-induced diabetic rats.

Potential use of glutathione for the prevention and treatment of diabetic neuropathy in the streptozotocin-induced diabetic rat.

It has been shown that parameters of oxidative stress are increased in experimental diabetic neuropathy. The glutathione redox system is one of the intracellular scavenger systems for neutralizing free oxygen radicals. In this investigation we studied the effect of glutathione-treatment on the development of diabetic neuropathy in streptozotocin-induced diabetic rats by measuring sensory and motor nerve conduction velocities. The total study period was 10 weeks. Four groups of rats were studied: Group 1 consisted of non-diabetic, age-matched control rats; Group 2, of diabetic rats treated with placebo from week 0 to 10; Group 3, of diabetic rats treated with 200 mg glutathione/kg body weight i.v. two times per week from weeks 0 to 10; and Group 4, of diabetic rats treated with placebo from weeks 0 to 4 and as Group 3 from weeks 4 to 10. The sensory and motor nerve conduction velocity of rats treated prophylactically with glutathione (Group 3) were significantly different from those of rats treated with placebo (Group 2) or with glutathione administered at a later time point (Group 4). Complete restoration of sensory and motor nerve conduction velocity was not reached. There was a significant improvement in motor nerve conduction velocity from weeks 4 to 6 (p less than 0.005), but not in sensory nerve conduction velocity in the delayed treatment group (Group 4). In conclusion, treatment with glutathione, a free radical scavenger, is partially effective in the prevention of diabetic neuropathy in streptozotocin-induced diabetic rats, but is of limited value when the neuropathy is already present.

TRH pharmacokinetics and nerve stimulation evoked prostatic fluid secretion during TRH infusion in the dog.

The pharmacokinetics of TRH have been determined in man and the rat as well as other species whose serum contains TRH degrading enzymes, TRH pharmacokinetics have not been determined in the dog. This species is unusual in that its serum contains little or no TRH degrading activity. TRH pharmacokinetics were determined from measurements of plasma TRH concentrations during and following a 1-h infusion of TRH, 20 micrograms.kg-1.min-1, into dogs bearing prostatic urethral cannula. During TRH administration prostatic fluid secretion was evoked by hypogastric nerve stimulation and the content of TRH immunoreactive material in prostatic fluid was determined. Prostatic fluid was also collected after hypogastric nerve stimulation in dogs that did not receive TRH infusion. The TRH plasma profile in TRH-infused dogs exhibited two-compartment characteristics with an initial half-time of 10.4 +/- 5.4 (mean +/- SD) min, a terminal half-time of 69.4 +/- 24 min, and a metabolic clearance rate of 7.64 +/- 4.48 ml.min-1.kg-1. These findings suggest that the half-time of TRH is longer, and its metabolic clearance rate is less, in the dog than in humans or rats. TRH administration was not associated with altered nerve induced prostatic fluid secretion. Prostatic fluid samples contained TRH immunoreactive material regardless of whether they were collected after epithelial cell stimulation with pilocarpine, or after hypogastric nerve stimulation. In contrast to previous results with vasoactive intestinal peptide, TRH does not acutely alter prostatic fluid secretion. As has been reported for prostatic tissue extracts, immunoreactive material is present in prostatic fluid and appears to arise from epithelial cells.