Biomedical subjects

R M Hays

Publications and source records attributed to R M Hays.

At least 19 recordsLinked to original sources

PubMed1992

Electrodiagnosis reliability in the diagnosis of infant botulism.

Infant botulism is confirmed by isolation of Clostridium botulinum from stool culture or by toxin assay. Although electrodiagnosis has been described as a diagnostic tool in infant botulism, our 11-year review of toxin-confirmed cases suggests that electrodiagnosis is not a reliable tool. In the case report presented, results of electrodiagnosis were negative but enema effluent contained adequate concentrations of organism and toxin to confirm the diagnosis.

Botulinum Toxins↗

PubMed1992

ADH-induced depolymerization of F-actin in the toad bladder granular cell: a confocal microscope study.

Antidiuretic hormone (ADH) induces the fusion of cytoplasmic vesicles containing water channels with the apical membrane of the toad bladder granular cell. Fusion is accompanied by a 30% depolymerization of F-actin. We have used confocal microscopy to determine the region in the cell that undergoes depolymerization. Bladders were mounted in a split chamber, and control halves and halves stimulated by ADH for 15 min were fixed and then stained with rhodamine phalloidin. Vertical sections through the cells were obtained by confocal microscopy, and the fluorescence intensity of the apical and side regions of the cells was determined. To normalize the data, the apex-side intensity was determined for each cell, and these ratios measured for control and ADH-treated halves. In six paired experiments, the ratio for control halves was 3.69 +/- 0.50 and for ADH-treated halves was 2.61 +/- 0.33; the decrease was significant and in good agreement with earlier studies. Thus actin depolymerization takes place in a hormone-sensitive apical pool where vesicle fusion occurs and supports the view that actin depolymerization may be required for fusion.

Actins↗

PubMed1992

Vasopressin decreases immunogold labeling of apical actin in the toad bladder granular cell.

Studies with the confocal microscope have shown that arginine vasopressin (AVP) depolymerizes F-actin in the apical region of the toad bladder granular cell. However, the resolution of the fluorescence microscope is not great enough to reveal the exact pattern of depolymerization or the relative extent to which microvillar and subapical membrane actin pools contribute to overall depolymerization. We have developed an electron microscopic immunogold method that shows a significant decrease in immunogold labeling of actin in the region just below the apical membrane, with the decrease most pronounced in regions adjacent to the microvilli. There was no significant change of immunogold labeling within the microvilli themselves. Our studies show a reorganization of the actin cytoskeleton in the region of the granular cell, where water channel-carrying vesicles are positioned and fuse in response to AVP.

Actins↗

PubMed1992

Effect of cytochalasin D on the actin cytoskeleton of the toad bladder epithelial cell.

Cytochalasins are widely used to determine the role of actin in cellular processes. Their actions include capping of the barbed end of actin filaments as well as dimer formation, nucleation, and polymerization. We determined the effect of cytochalasin D (CD) on F-actin in the toad urinary bladder, an epithelium in which vasopressin depolymerizes F-actin. At a low concentration (0.25 microM), CD depolymerized F-actin in the unstimulated cell; at higher concentrations, there was a progressive reduction of depolymerization until actual polymerization was seen. Vasopressin plus CD produced no greater depolymerization than vasopressin alone, suggesting that CD and vasopressin act to a large extent on the same pool of F-actin. CD plus vasopressin also enhanced the fusion rate of aggrephores compared with vasopressin alone, indicating that intact actin filaments retard aggrephore fusion. Despite the increase in aggrephore fusion, water flow was not enhanced by CD, confirming previous reports that intact actin filaments are required for water channel emergence or stabilization in the apical membrane. Vasopressin plus 1 microM CD produced a striking increase in microvillar length, direct evidence of the polymerizing action of CD in the cell.

Actins↗

PubMed1992

Effects of angiotensin II and arginine vasopressin on F-actin content of cultured mesangial cells.

The actin cytoskeleton of mesangial cells (MC) plays an important role in the contractile response to agonists as well as in the endocytosis of macromolecules. A quantitative study of the F-actin content of MC by the rhodamine-phalloidin binding assay was carried out. Angiotensin II (ANG II) (10(-6) M) significantly increased the F-actin content of MC by 30 min and at later time periods, with increases ranging from 31 to 46%. Arginine vasopressin (10(-8) M) produced a transient decrease of F-actin content of MC at 30 s but then significantly enhanced the F-actin content at later time periods. There was no change in total actin and protein content of MC at 30 min in the presence of either agent. Thus, the increase in F-actin is related to a shift in the G- to F-actin ratio and not to the synthesis of new F-actin. Because the incubation of MC with 1 (5-isoquinolinylsulfonyl)-2-methylpiperazine, an inhibitor of protein kinase C, did not attenuate the ANG II-induced increase in the F-actin content of MC, the shift does not appear to be mediated by the activation of protein kinase C. The removal of external calcium did not prevent the increase in F-actin. Dibutyryl cAMP (5 x 10(-4) M), a smooth muscle cell and MC relaxant, did not alter the F-actin content in MC, and 10(-5) M cytochalasin B significantly lowered F-actin content.(ABSTRACT TRUNCATED AT 250 WORDS)

1-(5-Isoquinolinesulfonyl)-2-Methylpiperazine↗

PubMed1992

Exploration of variables related to children's behavioral distress during electrodiagnosis.

To investigate variables potentially related to children's distress during electromyography/nerve conduction studies (EMG/NCS), mothers of 39 children ages two to 17 years reported the child's gender, experience with EMG/NCS, previous negative medical/dental experiences, general response to painful procedures, information-seeking style prior to procedures, health care fears, and information about the mothers' own health care fears and their anxiety regarding EMG/NCS. Physicians who performed the studies completed a behavioral distress checklist for each child. Results indicated that children exhibiting more behavioral distress were younger, had been uncooperative with previous painful procedures, were more likely to have had more negative medical/dental experiences, and had mothers who themselves reported greater fear and anxiety about undergoing EMG/NCS. Regression analyses indicated that previous negative medical/dental experiences accounted for additional variance in distress beyond that attributed to the child's age. Significant positive correlations between children's distress and specific previous negative medical/dental experiences were found.

Adolescent↗

PubMed1991

Actin depolymerization in the cyclic AMP-stimulated toad bladder epithelial cell, determined by the DNAse method.

Previous studies with the rhodamine phalloidin binding assay have shown that antidiuretic hormone and 8-Br-cAMP rapidly depolymerize F-actin in toad bladder epithelial cells. We have extended these studies with the DNAse inhibition assay and have found that in isolated epithelial cell suspensions, G-actin increases from 37 to 56% of total actin following 8-br-cAMP stimulation. The G-actin concentration in the epithelial cell greatly exceeds its critical concentration, indicating the requirement for a G-actin sequestering protein or proteins in this system.

8-Bromo Cyclic Adenosine Monophosphate↗

PubMed1991

Quantitative measurement of spasticity in children with cerebral palsy.

Spasticity was quantified in nine children with spastic diplegia, using a sinusoidal displacement of the foot at frequencies from 3 to 12Hz. Ankle-joint stiffness was separated into elastic (energy-storing) and viscous (energy-dissipating) components. 'Path length' was used to represent the variation in stiffness over this frequency range. Compared with 11 unaffected children, a significant difference in path lengths was demonstrated for the children with spasticity. An age-dependent effect was demonstrated when path lengths of unaffected children were compared with those of 10 unaffected adults. A modified path-length measure is proposed which minimizes age dependency, yet enables detection of spasticity. Passive stiffness properties of unaffected adults showed higher elastic stiffness, viscosity and friction than unaffected children. A method was developed to evade the need for temporary nerve blocks to calculate inerital properties of the foot in persons with spasticity.

Biomechanical Phenomena↗

PubMed1991

Vasopressin depolymerizes F-actin in toad bladder epithelial cells.

Vasopressin (AVP) induces the rapid fusion of water channel-containing vesicles with the luminal membrane of its target cell. We have carried out a quantitative study of the F-actin content of toad bladder epithelial cells, using the rhodamine phalloidin binding assay. As early as 1 min after AVP stimulation, there is a significant 15% reduction of cellular F-actin, which remains reduced by 20-30% for the duration of action of AVP. Comparable reductions were seen following 8-bromoadenosine 3',5'-cyclic monophosphate, 1-desamino-8-D-arginine vasopressin, and forskolin. F-actin content rose to and then exceeded that of control bladders after AVP washout. Inhibition of prostaglandin synthesis enhanced both water flow and the decrease of F-actin. In the living cell, stabilization of F-actin with NBD-phallacidin selectively inhibited water flow. In view of the rapidity of the response, we conclude that AVP shifts the equilibrium between F-actin and G-actin monomers, and this depolymerization may be required for vesicle fusion.

8-Bromo Cyclic Adenosine Monophosphate↗

PubMed1991

Misconceptions.

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Career Choice↗

PubMed1990

Effects of vasoactive agents on uptake of immunoglobulin G complexes by mesangial cells.

Mesangial handling of immune complexes may be important in immune injury. We examined whether vasoactive agents, independent of hemodynamic effects, could directly influence uptake of immunoglobulin G (IgG) complexes by mesangial cells (MC). Under basal conditions, MC took up more gold particles coated with IgG2b (P less than 0.05) than coated with IgG2a. Preincubation of MC with angiotensin II (ANG II) (5 x 10(-7) M) resulted in enhancement of uptake (P less than 0.05) of IgG2b-gold [7,578 +/- 968 counts per minute (cpm) per well], IgG2a-gold (4,566 +/- 295 cpm/well; P less than 0.01), and bovine serum albumin (BSA)-gold (2,532 +/- 66; P less than 0.05) when compared with respective controls (IgG2b-gold, 5,513 +/- 762 cpm/well; IgG2a-gold, 3,282 +/- 439; BSA-gold, 2,279 +/- 97). Cytochalasin B produced a significant reduction of uptake of IgG2b-gold (2,224 +/- 88 cpm/well) when compared with the uptake by control cells (3,711 +/- 287 cpm/well) (P less than 0.05). Pretreatment of MC with atrial natriuretic peptide (ANP, 10(-9) M) slightly decreased uptake of IgG-gold under basal conditions (P less than 0.05) and decreased the response to ANG II (P less than 0.05). Similarly, dopamine (DA, 10(-6) M) attenuated uptake of IgG2b-gold under basal (P less than 0.01) as well as ANG II-stimulated (P less than 0.01) states. ANP increased mesangial guanosine 3',5'-cyclic monophosphate (cGMP), DA, adenosine 3',5'-cyclic monophosphate (cAMP) content.(ABSTRACT TRUNCATED AT 250 WORDS)

Angiotensin II↗

PubMed1990

Congenital carpal tunnel syndrome: case report of autosomal dominant inheritance and review of the literature.

Carpal tunnel syndrome (CTS) is unusual in childhood, and familial occurrence has been reported infrequently. A case of CTS in a seven-year-old boy, associated with abnormal thickening of the transverse carpal ligament and aplasia of the median nerve distal to this ligament, is described. Clinical, electrodiagnostic, and surgical findings are presented: all were consistent with absence of the median nerve distal to the transverse carpal ligament. Family history of CTS was positive in a pattern consistent with autosomal dominant transmission in three generations. Thickening of the transverse carpal ligament has been described, although infrequently, in childhood and familial CTS. Aplasia of the median nerve distally has not been reported in association with this anatomic abnormality. Case reports of familial CTS are reviewed, and other congenital anomalies which should be considered in the differential diagnosis of CTS in children and adults are discussed.

Carpal Tunnel Syndrome↗

PubMed1989

Central ventilatory dysfunction in myelodysplasia: an independent determinant of survival.

Central ventilatory dysfunction (CVD) is a significant complication of myelodysplasia with Arnold-Chiari type II defect. The records of 616 patients with myelodysplasia were reviewed and CVD was documented in 35 cases (5.7 per cent): it was the single most common cause of death in this population. There was no significant association between CVD and level of lesion, severity of hydrocephalus, hemorrhage or infection. The effects of CVD may be variable, with some patients having spontaneous remission and others having severe, often fatal, disruption of ventilation.

Follow-Up Studies↗

PubMed1989

Atrial natriuretic peptide and nitroprusside cause relaxation of cultured rat mesangial cells.

These studies evaluate the effects of atrial natriuretic peptide (ANP) and nitroprusside (NP) on cultured mesangial cells (MC) grown on a flexible silicone rubber surface. The basal tone of the MC produced wrinkles on the silicone rubber surface. A decrease in number or magnitude of wrinkles was considered to represent cell relaxation, whereas an increase represented cell contraction. ANP (10(-9) M) produced a relaxation in greater than 60% of the cells by 10 min. The percentage of cells showing a decrease of wrinkles was significantly higher (P less than 0.05 at 5 min and P less than 0.001 at 10 min) during the ANP-treated period than during the control period. NP (10(-5) M) caused a decrease of wrinkles in greater than 80% of cells (P less than 0.02 at 5 min and P less than 0.01 at 10 min) compared with a 5% decrease in the control period. Dibutyryl guanosine 3',5'-cyclic monophosphate (DBcGMP; 10(-4) M) also produced a decrease of wrinkles in 81% of the cells (P less than 0.02) compared with a 9% decrease in the control period. MC treated with ANP, NP, or DBcGMP and then labeled with 7-nitrobenz-2-oxa-1,3-diazol-4-yl (NBD)-phallacidin did not show obvious alteration of morphology of actin filaments compared with untreated cells. ANP could inhibit as well as partially reverse the agonist (angiotensin II)-induced contractile response. ANP (10(-10)-10(-8) M) as well as NP (10(-5) M) increased intracellular cGMP content of MC (P less than 0.005) compared with control cells.(ABSTRACT TRUNCATED AT 250 WORDS)

Amanitins↗

PubMed1989

Active urea transport in toad skin is coupled to H+ gradients.

Active transport of urea exists inwardly through the skin of the toad Bufo viridis and is enhanced by adapting the toads to hypertonic saline solutions. In this paper, we report our studies on the energy coupling of this active transport system. We have shown previously that this system is independent of sodium transport. We thus studied the possibility of coupling to proton transport by studying the following: 1) the effect of acidifying the epithelium by means of CO2 and protonophores, 2) the effect of alkalinizing the epithelium with the anion-exchange inhibitor 4,4'-diisothiocyanatostilbene-2,2'-disulfonic acid (DIDS) and by removal of chloride from the serosal medium, 3) the effect of inhibiting the proton-translocating ATPase of the skin, 4) dependence on mucosal pH. We found that 1) acidification of the epithelium by means of 5% CO2 and the protonophores carbonyl cyanide m-chlorophenylhydrazone (CCCP) and nigericin inhibited urea influx; 2) alkalinization of the epithelium by means of the disulfonic stilbene DIDS and by removal of serosal chloride increased urea influx; 3) inhibition of the proton-translocating ATPase of the skin by means of 1,3-dicyclohexylcarbodiimide (DCCD), N-ethylmaleimide (NEM), and sodium orthovanadate inhibited urea transport; 4) urea influx was unaffected by alkalinizing the external medium to 8.5 or by acidifying to 6.5; it was significantly suppressed by a mucosal pH of 5.5.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗

PubMed1989

Evidence that monensin inhibits vasopressin-stimulated water flow at an early step in the receptor-adenylate cyclase sequence.

Monensin, a highly selective sodium ionophore, inhibits vasopressin-stimulated water flow in toad urinary bladder pretreated with naproxen, an inhibitor of prostaglandin synthesis. Inhibition is partially dependent on the presence of sodium in the serosal medium, but not on serosal calcium. We have found that monensin does not inhibit water flow generated by forskolin, cyclic AMP, or isobutyl methyl xanthine (MIX); indeed, an enhancement of water flow was seen following cAMP and MIX, as well as following 0.2 microM forskolin. Our findings suggest that monensin uncouples the vasopressin-receptor-G protein-adenylate cyclase sequence at some early step, by a mechanism that remains unknown, but that may directly or indirectly involve intracellular sodium.

1-Methyl-3-isobutylxanthine↗

PubMed1988

Role of vesicular transport in ADH-stimulated aggregate delivery.

It has been assumed from studies in toad bladder that antidiuretic hormone (ADH)-stimulated particle delivery to the luminal membrane is mediated by particle-carrying tubular structures (aggrephores). We report studies in frog and toad urinary bladder showing that vesicles, rather than aggrephores, appear to play the major role in particle delivery in the frog and that vesicle and aggrephore delivery proceed in parallel in the toad. Our principal evidence for this view is that in the frog, transmission electron microscopy shows virtually no fused aggrephores. Supporting evidence includes the following. 1) Freeze-fracture studies show that the diameters of fusion events delivering particles can be quite small, indicating that they are formed by fused vesicles rather than fused aggrephores. 2) A significant population of small fusion events is also seen in the toad, along with larger fusion events related to both aggrephores and large vesicles. 3) Surface aggregate areas in both species are small, consistent with vesicular delivery. 4) Freeze-fracture replicas indicate delivery from shallow pits. We propose a system of transport of particles in which aggrephores act largely as intermediate storage organelles in the frog and as storage and fusion organelles in the toad.

Animals↗

PubMed1988

Active urea transport by the skin of Bufo viridis: amiloride- and phloretin-sensitive transport sites.

Urea is actively transported inwardly (Ji) across the skin of the green toad Bufo viridis. Ji is markedly enhanced in toads adapted to hypertonic saline. We studied urea transport across the skin of Bufo viridis under a variety of experimental conditions, including treatment with amiloride and phloretin, agents that inhibit urea permeability in the bladder of Bufo marinus. Amiloride (10(-4) M) significantly inhibited Ji in both adapted and unadapted animals and was unaffected by removal of sodium from the external medium. Phloretin (10(-4) M) significantly inhibited Ji in adapted animals by 23-46%; there was also a reduction in Ji in unadapted toads at 10(-4) and 5 x 10(-4) M phloretin. A dose-response study revealed that the concentration of phloretin causing half-maximal inhibition (K1/2) was 5 x 10(-4) M for adapted animals. Ji was unaffected by the substitution of sucrose for Ringer solution or by ouabain. We conclude 1) the process of adaptation appears to involve an increase in the number of amiloride- and phloretin-inhibitable urea transport sites in the skin, with a possible increase in the affinity of the sites for phloretin; 2) the adapted skin resembles the Bufo marinus urinary bladder with respect to amiloride and phloretin-inhibitable sites; 3) we confirm earlier observations that Ji is independent of sodium transport.

Amiloride↗