Biomedical subjects

R M Hays

Publications and source records attributed to R M Hays.

At least 37 records · Page 2Linked to original sources

PubMed1994

Antidiuretic hormone and exocytosis: lessons from neurosecretion.

Many cells, both single and epithelial, are programmed for exocytosis. In most cases, the contents of cytoplasmic vesicles are delivered rapidly and directly to the extracellular fluid. The process has been intensively studied in the chromaffin cell and the nerve terminal, where, as in other cells, exocytosis is under a complex type of cytoskeletal control. An array of vesicle-associated proteins mediates attachment of the vesicles to the cytoskeleton, their release, and their fusion with the plasma membrane. Two functional pools of vesicles, the releasable and reserve pool, carry out immediate and long-term secretory activity. Some of the mediators of neurotransmitter vesicle fusion, originally thought to be restricted to neurosecretory cells, have now been found in nonneuronal cells. The mammalian collecting duct and the amphibian bladder are also engaged in exocytosis. In both epithelia, antidiuretic hormone (ADH) induces the transfer of water channels from cytoplasmic vesicles to the apical cell membrane. The process is slower than in the nerve terminal and ends with channel placement rather than the extrusion of vesicular contents. Nevertheless, there are several respects in which cytoskeletal control, vesicle positioning in the cell, docking, and fusion may prove to resemble the events in neurosecretion. This review begins with a survey of cytoskeletal structure and function in the erythrocyte, the chromaffin cell, and the nerve terminal and then presents current studies of ADH-induced exocytosis, emphasizing common themes in cytoskeletal control.

Actins↗

PubMed1994

Prospective measurement of functional changes after selective dorsal rhizotomy.

Selective dorsal rhizotomy (SDR) followed by intensive postoperative therapy is commonly performed to reduce spasticity in carefully selected children with cerebral palsy. Reduction in spasticity and improvement in range and quality of movements are frequently reported. Functional gains have also been indicated but have not often been examined in a systematic manner. Twenty-nine children with spastic diplegia or quadriplegia received SDR and postoperative physical and occupational therapy. Upper-limb movement, self-care, and functional mobility were evaluated prospectively through preoperative, 6-month, and 12-month follow-up examinations. Significant improvements in the Pediatric Evaluation of Disability Inventory scores for functional mobility and self-care domains were observed for children with spastic diplegia, but not spastic quadriplegia. Children's scores in upper-limb reach and coordination tasks did not consistently improve. When attributing improvements in self-care and mobility independence to SDR and specialized therapy, continued development, new goals, and positive beliefs about progress should also be considered as factors influencing outcome.

Activities of Daily Living↗

PubMed1993

The effect of vasopressin on the cytoskeleton of the epithelial cell.

Vasopressin (AVP) promotes the fusion of vesicles containing water channels with the apical membrane of receptor cells in the amphibian bladder and mammalian kidney. Fusion is accompanied by depolymerization of the actin cytoskeleton. In this review, we present the evidence for actin depolymerization by AVP in the whole cell, and the application of confocal microscopy and immunogold electron microscopy in localizing depolymerization to the apical region of the receptor cell.

Actins↗

PubMed1993

Physicians' practice patterns in pediatric electrodiagnosis.

The medical literature contains contradictory reports and recommendations regarding pediatric patients' pain and distress during electrodiagnosis. We surveyed 117 pediatric neurologists and physiatrists regarding their practice patterns in pediatric electrodiagnosis; 84 (72%) responded, of whom 44 (52%) regularly perform electrodiagnosis on children (mean = 85 per year, representing 3,667 examinations per year). Respondents reported extreme behavioral distress (eg, screaming, flailing, requiring additional restraint, or attempting to leave the examination table) in 35% of examinations, most often among 2- to 6-year-olds. Pain medications are never prescribed by 45%, occasionally by 48%, and always by 2%; general anesthesia is never administered by 75%, occasionally by 21%. Only 32% reported that any psychological intervention is routinely offered to enhance child coping. Wide variability was found in physicians' preferences about parental presence, order of examinations, demonstration of procedures, and other aspects of electrodiagnosis.

Adolescent↗

PubMed1993

Vasopressin depolymerizes apical F-actin in rat inner medullary collecting duct.

In amphibian bladder, arginine vasopressin (AVP) depolymerizes F-actin in the apical region of the granular cell, promoting fusion of water channel-carrying vesicles with the apical membrane. We now report the effect of AVP on F-actin in the mid- and terminal segments of rat inner medullary collecting duct (IMCD2 and IMCD3). In IMCD3, 5 min of stimulation by 2.5-250 nM AVP significantly depolymerized F-actin by 13-24% in whole cell assays employing the rhodamine-phalloidin binding technique. The IMCD2 was more sensitive, responding to subnanomolar (0.25 nM) AVP with 6 +/- 2% depolymerization. Depolymerization occurred as early as 2 min after 2.5 and 25 nM but not 250 nM AVP. 8-Bromoadenosine 3',5'-cyclic monophosphate depolymerized F-actin in IMCD3 at both 2 and 5 min. Immunogold labeling of the apical actin pool in IMCD3 principal cells was reduced by 26 +/- 5% (P < 0.05) by 2.5 nM AVP; the lateral and basal pools showed no significant changes. Capillary endothelial, thin limb of Henle, and intercalated cells showed no changes in immunogold labeling after AVP. Thus reorganization of the apical actin network by AVP is a consistent finding in both mammalian and amphibian target cells.

8-Bromo Cyclic Adenosine Monophosphate↗

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↗