Calcium Channel Alpha Research Articles

Distribution and regulation of L‐type calcium channels in deep dorsal horn neurons after sciatic nerve injury in rats

Deep dorsal horn neurons are involved in the processing of nociceptive information in the spinal cord. Previous studies revealed a role of the intrinsic bioelectrical properties (plateau potentials) of deep dorsal horn neuron in neuronal hyperexcitability, indicating their function in pain sensitization. These properties were considered to rely on L-type calcium currents. Two different isotypes of L-type calcium channel alpha 1 subunit have been cloned (Ca(V)1.2 and Ca(V)1.3). Both are known to be expressed in the spinal cord. However, no data were available on their subcellular localization. Moreover, possible changes in Ca(V)1.2 and Ca(V)1.3 expression had never been investigated in nerve injury models. Our study provides evidence for a differential expression of Ca(V)1.2 and Ca(V)1.3 subunits in the somato-dendritic compartment of deep dorsal horn neurons. Ca(V)1.2 immunoreactivity is restricted to the soma and proximal dendrites whereas Ca(V)1.3 immunoreactivity is found in the whole somato-dendritic compartment, up to distal dendritic segments. Moreover, these specific immunoreactive patterns are also found in electrophysiologically identified deep dorsal horn neurons expressing plateau potentials. After nerve injury, namely total axotomy or partial nerve ligation, Ca(V)1.2 and Ca(V)1.3 expression undergo differential changes, showing up- and down-regulation, respectively, both at the protein and at the mRNA levels. Taken together, our data support the role of L-type calcium channels in the control of intrinsic biolectrical regenerative properties. Furthermore, Ca(V)1.2 and Ca(V)1.3 subunits may have distinct and specific roles in sensory processing in the dorsal horn of the spinal cord, the former being most likely involved in long-term changes after nerve injury.

Evaluation of antihypertensive medication adherence in a Veteran population

This study evaluates antihypertensive medication adherence using Department of Veterans Affairs pharmacy databases. Automated data extraction routines capture pharmacy, ICD-9, laboratory, and patient demographic data on a monthly basis. We included patients with a diagnosis of hypertension (ICD-9 codes 401.1 to 401.9) who had a history of medication use during July 2002 through December 2003. Medications in the following drug classes were studied: thiazides (TZ), beta blockers (BB), ACE inhibitors (ACE), angiotensin receptor blockers (ARB), calcium channel antagonists (CA) and alpha blockers (AB). We excluded patients with serum creatinine of >2.5 and those receiving K sparing diuretics alone. The first date of prescription filling for each patient within the date range is the index date from which fill and refill dates are collected for one year to calculate posession ratio (MTOT) and days out of medication ratio (MOUT). Data elements for analysis are medication class as listed above, patient's age, gender, ethnicity, VA facility, and co-diagnosis with diabetes, schizophrenia/psychosis, and dementia. The potential effect of these variables on adherence were examined using logistic regression analysis with patients categorized as adherent if MTOT is 80% or greater. In the six VA classes there were 79,055 patients with average age per group ranging from 67.4–72.9 years. 97% were male and when ethnicity was recorded 74.5% were Caucasian, 14% African-American and 5% each Hispanic and Asian. The largest number of patients (22,233) took an ACE whereas a small number used ARB (3,729). Unadjusted adherence rates based on MTOT ranged from 77.9% for TZ to 83.3% for ARB (p<0.01). Similar findings were noted using the MOUT parameter. 8% of patients using an ACE had at least two ICD9 codes for diabetes as compared to 4.6% getting TZ. A dementia and a schizophrenia/psychosis diagnosis occurred in each drug class in up to 3.3% and 3.4% of patients, respectively. Drug class and age were independent predictors of adherence with odds ratios of 1.019 and 1.014, respectively. We conclude that adherence rates with antihypertensive medications are remarkably high. Although there are statistical differences by drug class, these differences are small.

Abrupt hypokalemia with paralysis from a clinician?s perspective

Monogenic hypokalemic periodic paralysis (HypoPP) is an autosomal dominant genetic disease. HypoPP is more common in males than females and has a reduced penetrance in females. Attacks generally begin during adolescence. They are aggravated by exercise, sleep, stress, alcohol, and meals rich in carbohydrates and salt. The episodes last 324h. Attacks often feature a prodrome of stiffness or heaviness in the lower extremities. Some patients report that they can abort their attacks with mild exercise. Various preventive measures have been suggested, including a low-carbohydrate, low sodium diet, acetazolamide, dichlorphenamide, spironolactone, and triamterene, though none of these are very effective. Acute attacks are generally treated with potassium every 30min until strength returns. In patients with severe episodes who also experience gastrointestinal symptoms, parenteral potassium may be necessary. The electrocardiogram should also be monitored. The paralysis is due to abnormal muscle membrane excitability, commonly arising from mutations in the muscle calcium channel alpha1 subunit gene (CACNA1S) on chromosome 1q3132 or in a smaller number of cases, from a mutation in the skeletal muscle sodium channel SCN4A. The alpha1 subunit of the calcium channel contains the dihydropyridine binding site (receptor) that acts as a pore for conducting calcium ions in the T tubule. The mutation results in a reduction of the calcium current in the T tubule. During attacks, there is an influx of potassium into muscle cells and the cells become electrically refractile. The patients have an increased sensitivity to insulin-related effects on potassium. Exactly how the potassium is shifted from the extracellular to the intracellular space as a result of impaired function of the calcium channel dihydropyridine receptor is not entirely clear.

The L-type calcium channel alpha 1C subunit gene undergoes extensive, uncoordinated alternative splicing

The alpha1C subunit is the pore-forming protein for the L-type calcium channel. Previous studies indicate that there is possible tissue-specific alternative splicing of this gene. In this study we cloned the entire open reading frame of the alpha1C subunit cDNA from adult rat cardiac myocytes in a single piece (6.64 kb). Using 75 positive clones that were identified by restriction enzyme mapping, we tested the alternative splicing patterns of the Ca(v) 1.2 gene that encodes the alpha1C subunit protein and focused on five loci: IS6, post-IS6, IIIS2, IVS3, and the c-terminus. The results indicate that: (1) alternative splicing occurs in most of the loci, giving rise to two or three different isoforms at those sites; (2) there is a predominant form for each splicing site, (3) there does not appear to be consistent coordination of splicing at multiple loci of this gene. Alternative splicing is not tissue-specific in most regions.

Pregabalin

Pregabalin, the pharmacologically active S-enantiomer of 3-aminomethyl-5-methylhexanoic acid, possesses anticonvulsant activity. Pregabalin binds with high affinity and specificity to voltage-gated calcium channel alpha(2)-delta proteins. The putative mechanism of action of the drug is reduced excitatory neurotransmitter release caused by binding to the alpha(2)-delta protein, resulting in allosteric modulation of P/Q-type voltage-gated calcium channels. In three well designed trials, oral pregabalin as adjunctive therapy in patients with refractory partial seizures was significantly (p < or = 0.0007) more effective than placebo in reducing seizure frequency when administered at dosages of 150-600 mg/day (as two or three divided doses). Adjunctive pregabalin produced an overall mean 41.3% improvement from baseline in 28-day seizure-free rate in four long-term (maximum exposure 1764 days), open-label studies in 1480 patients. CNS-related effects (e.g. dizziness and somnolence) were the most frequent dose-related treatment-emergent adverse events associated with adjunctive pregabalin therapy.

Smooth Muscle-selective Alternatively Spliced Exon Generates Functional Variation in Cav1.2 Calcium Channels

Voltage-gated calcium channels play a major role in many important processes including muscle contraction, neurotransmission, excitation-transcription coupling, and hormone secretion. To date, 10 calcium channel alpha(1)-subunits have been reported, of which four code for L-type calcium channels. In our previous work, we uncovered by transcript-scanning the presence of 19 alternatively spliced exons in the L-type Ca(v)1.2 alpha(1)-subunit. Here, we report the smooth muscle-selective expression of alternatively spliced exon 9(*) in Ca(v)1.2 channels found on arterial smooth muscle. Specific polyclonal antibody against exon 9(*) localized the intense expression of 9(*)-containing Ca(v)1.2 channels on the smooth muscle wall of arteries, but the expression on cardiac muscle was low. Whole-cell patch clamp recordings of the 9(*)-containing Ca(v)1.2 channels in HEK293 cells demonstrated -9 and -11-mV hyperpolarized shift in voltage-dependent activation and current-voltage relationships, respectively. The steady-state inactivation property and sensitivity to blockade by nifedipine of the +/-exon 9(*) splice variants were, however, not significantly different. Such cell-selective expression of an alternatively spliced exon strongly indicates the customization and fine tuning of calcium channel functions through alternative splicing of the pore-forming alpha(1)-subunit. The generation of proteomic variations by alternative splicing of the calcium channel Ca(v)1.2 alpha(1)-subunit can potentially provide a flexible mechanism for muscle or neuronal cells to respond to various physiological signals or to diseases.

Exercise as an anabolic stimulus for bone.

Mechanical loading provides an anabolic stimulus for bone. More importantly, the mechanosensing apparatus in bone directs osteogenesis to where it is most needed for improving bone strength. The biological processes involved in bone mechanotransduction are poorly understood and further investigation of the molecular mechanisms might uncover drug targets for osteoporosis. Several pathways are emerging from current research, including membrane ion channels, ATP signaling, and second messengers such as prostaglandins and nitric oxide. Some key molecular targets include the L-type calcium channel (alpha 1C isoform), a gadolinium-sensitive stretch-activated channel, P2Y(2) and P2X(7) purinergic receptors, EP(2) and EP(4) prostanoid receptors, and the parathyroid hormone receptor. One characteristic of the mechanosensing apparatus that has only recently been studied is the important role of desensitization. Experimental protocols that insert "rest" periods to reduce the effects of desensitization can double anabolic responses to mechanical loading. A drug therapy that suppresses desensitization pathways may provide an effective means to build bone strength.

A Single Gβ Subunit Locus Controls Cross-talk between Protein Kinase C and G Protein Regulation of N-type Calcium Channels

The modulation of N-type calcium channels is a key factor in the control of neurotransmitter release. Whereas N-type channels are inhibited by Gbetagamma subunits in a G protein beta-isoform-dependent manner, channel activity is typically stimulated by activation of protein kinase C (PKC). In addition, there is cross-talk among these pathways, such that PKC-dependent phosphorylation of the Gbetagamma target site on the N-type channel antagonizes subsequent G protein inhibition, albeit only for Gbeta(1)-mediated responses. The molecular mechanisms that control this G protein beta subunit subtype-specific regulation have not been described. Here, we show that G protein inhibition of N-type calcium channels is critically dependent on two separate but adjacent approximately 20-amino acid regions of the Gbeta subunit, plus a highly conserved Asn-Tyr-Val motif. These regions are distinct from those implicated previously in Gbetagamma signaling to other effectors such as G protein-coupled inward rectifier potassium channels, phospholipase beta(2), and adenylyl cyclase, thus raising the possibility that the specificity for G protein signaling to calcium channels might rely on unique G protein structural determinants. In addition, we identify a highly specific locus on the Gbeta(1) subunit that serves as a molecular detector of PKC-dependent phosphorylation of the G protein target site on the N-type channel alpha(1) subunit, thus providing for a molecular basis for G protein-PKC cross-talk. Overall, our results significantly advance our understanding of the molecular details underlying the integration of G protein and PKC signaling pathways at the level of the N-type calcium channel alpha(1) subunit.

Expression of T-type calcium channel splice variants in human glioma.

In humans, three isoforms of the T-type (Ca(v)3.1) calcium-channel alpha(1) subunit have been reported as a result of alternate splicing of exons 25 and 26 in the III-IV linker region (Ca(v)3.1a, Ca(v)3.1b or Ca(v)3.1bc). In the present study, we report that human glioma express Ca(v)3.1 channels in situ, that splicing of these exons is uniquely regulated and that there is expression of a glioma-specific novel T-type variant (Ca(v)3.1ac). Seven human glioma samples were collected at surgery, RNA was extracted, and cDNA was produced for RT-PCR analysis. In addition, three glioma cell lines (U87, U563, and U251N), primary cultures of human fetal astrocytes, as well as adult and fetal human brain cDNA were used. Previously described Ca(v)3.1 splice variants were present in glioma samples, cultured cells and whole brain. Consistent with the literature, our results reveal that in the normal adult brain, Ca(v)3.1a transcripts predominate, while Ca(v)3.1b is mostly fetal-specific. RT-PCR results on glioma and glioma cell lines showed that Ca(v)3.1 expression in tumor cells resemble fetal brain expression pattern as Ca(v)3.1bc is predominantly expressed. In addition, we identified a novel splice variant, Ca(v)3.1ac, expressed in three glioma biopsies and one glioma cell line, but not in normal brain or fetal astrocytes. Transient expression of this variant demonstrates that Ca(v)3.1ac displays similar current-voltage and steady-state inactivation properties compared with Ca(v)3.1b, but a slower recovery from inactivation. Taken together, our data suggest glioma-specific Ca(v)3.1 gene regulation, which could possibly contribute to tumor pathogenesis.

The role of the calcium channel alpha 2 delta-1 subunit in skeletal muscle.

The role of the calcium channel alpha 2 delta-1 subunit in skeletal muscle.

Absence of ion channels CACN1AS and SCN4A mutations in thyrotoxic hypokalemic periodic paralysis.

Muscle weakness in patients with thyrotoxicosis during hypokalemic episodes (thyrotoxic periodic paralysis [TPP]) occurs sporadically and mostly in males. It is treated by infusion or oral supplementation with potassium and with resolution of the thyrotoxicosis state. The clinical features of TPP resemble familial hypokalemic periodic paralysis (hypoKPP), which has been linked to two mutations in the gene encoding the skeletal muscle calcium channel alpha-1 subunit (CACN1AS; Arg528His and Arg1239His) and to the sodium channel alpha-subunit (SCN4A; Arg672His). We screened for the mutations (CACN1AS by polymerase chain reaction-restriction fragment length polymorphism [PCR-RFLP]; SCN4A by single-strand conformation polymorphism analysis) described in hypoKPP in 20 unrelated patients with documented episodes of TPP (mean age, 40.0 +/- 12.3 years 19 males). Forty-eight patients with hyperthyroidism resulting from Graves' disease (48.5 +/- 12.3 years; 13 males), 1 patient with idiopathic hypoKPP (a 32-year-old male) and 32 healthy subjects (41.0 +/- 19.1 years; 16 males) were included. We found none of the TPP patients carry CACN1AS and SCN4A mutations. The hyperthyroid patients and control subjects were also negative for the mutations. The patient with idiopathic hypoKPP was genotyped to have the Arg528His mutation. These results suggest that despite close similarities between TPP and hypoKPP, a likely genetic basis for TPP does not involve the same gene mutations associated with hypoKPP.

Phenotypes of spinocerebellar ataxia type 6 and familial hemiplegic migraine caused by a unique CACNA1A missense mutation in patients from a large family.

Different mutations in the alpha 1A-subunit of the brain P/Q-type calcium channel gene (CACNA1A) are responsible for familial hemiplegic migraine (FHM), episodic ataxia type 2, and spinocerebellar ataxia type 6 (SCA6). Missense and splice site mutations have been found in FHM and episodic ataxia type 2, respectively, whereas a CAG repeat in the CACNA1A gene was found expanded in patients with SCA6. To identify the disease causing mutation in a large family of patients with phenotypes of hemiplegic migraine with or without cerebellar signs or permanent cerebellar ataxia without migraine inherited in a dominant manner. We examined 15 patients from a large family identified through a systematic survey of hereditary ataxias being conducted in Portugal. Linkage analysis was performed with CACNA1A gene markers, and mutation analysis was performed by single strand conformational polymorphism analysis and sequencing. Genetic linkage analysis with CACNA1A intragenic markers showed positive LOD scores. The maximal LOD score was obtained with the polymorphic CAG repeat (Zmax = 4.47, theta = 0). By single-strand conformational polymorphism analysis, a shift in exon 13 of the CACNA1A gene was detected in all patients. A G-to-A substitution was then identified, resulting in an arginine-to-glutamine change at codon 583 of this calcium channel alpha 1A-subunit. The disease-causing mutation in this family was identified, showing that a unique mutation in the CACNA1A gene causes several phenotypes, including those of SCA6 and FHM, thus suggesting that SCA6 and FHM are not only allelic diseases but are the same disorder with a large phenotypic variability.

Use of antihypertensive drug therapy in older persons in an academic nursing home.

To determine the prevalence of hypertension and the appropriate treatment of hypertension in older persons in an academic nursing home. The charts of all persons aged > or = 59 years currently residing in a nursing home affiliated with Westchester Medical Center/New York Medical College were analyzed by two geriatrics fellows according to a protocol designed by one of the authors (W.S.A.). An academic nursing home affiliated with Westchester Medical Center/New York Medical College. The study population included 96 men and 159 women, mean age 77 +/- 9 years (range, 59-100 years). Hypertension was present in 129 of 255 persons (51%). Clinical cardiovascular disease or target organ damage or diabetes mellitus was present in 121 of 129 persons (94%) with hypertension. Hypertension was poorly controlled in 21 of 129 persons (16%). Of 129 persons with hypertension, 70 (54%) were treated with angiotensin-converting enzyme (ACE) inhibitors or angiotensin II type 1 receptor blockers, 61 persons (47%) with beta blockers, 43 persons (33%) with diuretics, 36 persons (28%) with calcium channel blockers, 5 persons (4%) with alpha blockers, and 5 persons (4%) with other antihypertensive drugs. Of 54 persons with hypertension and diabetes mellitus, 37 persons (69%) were treated with ACE inhibitors or angiotensin II type 1 receptor blockers. Of 58 persons with hypertension and coronary artery disease, 33 persons (57%) were treated with ACE inhibitors or angiotensin II type 1 receptor blockers, 31 persons (53%) with beta blockers, 20 persons (34%) with diuretics, 18 persons (31%) with calcium channel blockers, 2 persons (4%) with alpha blockers, and 4 persons (7%) with other antihypertensive drugs. Of 31 persons with hypertension and heart failure, only 5 persons (16%) had measurement of left ventricular ejection fraction. Of 31 persons with hypertension and heart failure, 30 persons (97%) were treated with diuretics, 21 persons (68%) with ACE inhibitors or angiotensin II type 1 receptor blockers, 18 persons (58%) with beta blockers, and 8 persons (26%) with calcium channel blockers. Of older persons with hypertension in an academic nursing home, 16% had poor control of their hypertension. There was overuse of calcium channel blockers and alpha blockers and underuse of diuretics, beta blockers, and ACE inhibitors in treating hypertension. Physician education needs to be intensified to provide better medical care of older persons with hypertension through the use of optimal doses of drugs found to be effective and safe by evidence-based studies.

Use of Antihypertensive Drug Therapy in Older Persons in an Academic Nursing Home

Objectives To determine the prevalence of hypertension and the appropriate treatment of hypertension in older persons in an academic nursing home. Design The charts of all persons aged ≥ 59 years currently residing in a nursing home affiliated with Westchester Medical Center/New York Medical College were analyzed by two geriatrics fellows according to a protocol designed by one of the authors (W.S.A.). Setting An academic nursing home affiliated with Westchester Medical Center/New York Medical College. Participants The study population included 96 men and 159 women, mean age 77 ± 9 years (range, 59–100 years). Results Hypertension was present in 129 of 255 persons (51%). Clinical cardiovascular disease or target organ damage or diabetes mellitus was present in 121 of 129 persons (94%) with hypertension. Hypertension was poorly controlled in 21 of 129 persons (16%). Of 129 persons with hypertension, 70 (54%) were treated with angiotensin-converting enzyme (ACE) inhibitors or angiotensin II type 1 receptor blockers, 61 persons (47%) with beta blockers, 43 persons (33%) with diuretics, 36 persons (28%) with calcium channel blockers, 5 persons (4%) with alpha blockers, and 5 persons (4%) with other antihypertensive drugs. Of 54 persons with hypertension and diabetes mellitus, 37 persons (69%) were treated with ACE inhibitors or angiotensin II type 1 receptor blockers. Of 58 persons with hypertension and coronary artery disease, 33 persons (57%) were treated with ACE inhibitors or angiotensin II type 1 receptor blockers, 31 persons (53%) with beta blockers, 20 persons (34%) with diuretics, 18 persons (31%) with calcium channel blockers, 2 persons (4%) with alpha blockers, and 4 persons (7%) with other antihypertensive drugs. Of 31 persons with hypertension and heart failure, only 5 persons (16%) had measurement of left ventricular ejection fraction. Of 31 persons with hypertension and heart failure, 30 persons (97%) were treated with diuretics, 21 persons (68%) with ACE inhibitors or angiotensin II type 1 receptor blockers, 18 persons (58%) with beta blockers, and 8 persons (26%) with calcium channel blockers. Conclusions Of older persons with hypertension in an academic nursing home, 16% had poor control of their hypertension. There was overuse of calcium channel blockers and alpha blockers and underuse of diuretics, beta blockers, and ACE inhibitors in treating hypertension. Physician education needs to be intensified to provide better medical care of older persons with hypertension through the use of optimal doses of drugs found to be effective and safe by evidence-based studies.

ω-Conotoxin CVID Inhibits a Pharmacologically Distinct Voltage-sensitive Calcium Channel Associated with Transmitter Release from Preganglionic Nerve Terminals

Neurotransmitter release from preganglionic parasympathetic neurons is resistant to inhibition by selective antagonists of L-, N-, P/Q-, R-, and T-type calcium channels. In this study, the effects of different omega-conotoxins from genus Conus were investigated on current flow-through cloned voltage-sensitive calcium channels expressed in Xenopus oocytes and nerve-evoked transmitter release from the intact preganglionic cholinergic nerves innervating the rat submandibular ganglia. Our results indicate that omega-conotoxin CVID from Conus catus inhibits a pharmacologically distinct voltage-sensitive calcium channel involved in neurotransmitter release, whereas omega-conotoxin MVIIA had no effect. omega-Conotoxin CVID and MVIIA inhibited depolarization-activated Ba(2+) currents recorded from oocytes expressing N-type but not L- or R-type calcium channels. High affinity inhibition of the CVID-sensitive calcium channel was enhanced when position 10 of the omega-conotoxin was occupied by the smaller residue lysine as found in CVID instead of an arginine as found in MVIIA. Given that relatively small differences in the sequence of the N-type calcium channel alpha(1B) subunit can influence omega-conotoxin access (Feng, Z. P., Hamid, J., Doering, C., Bosey, G. M., Snutch, T. P., and Zamponi, G. W. (2001) J. Biol. Chem. 276, 15728-15735), it is likely that the calcium channel in preganglionic nerve terminals targeted by CVID is a N-type (Ca(v)2.2) calcium channel variant.

Molecular cloning and characterization of the human voltage-gated calcium channel alpha(2)delta-4 subunit.

The voltage-gated calcium channel is composed of a pore-forming alpha(1) subunit and several regulatory subunits: alpha(2)delta, beta, and gamma. We report here the identification of a novel alpha(2)delta subunit, alpha(2)delta-4, from the expressed sequence tag database followed by its cloning and characterization. The novel alpha(2)delta-4 subunit gene contains 39 exons spanning about 130 kilobases and is co-localized with the CHCNA1C gene (alpha(1C) subunit) on human chromosome 12p13.3. Alternative splicing of the alpha(2)delta-4 gene gives rise to four potential variants, a through d. The open reading frame of human alpha(2)delta-4a is composed of 3363 base pairs encoding a protein with 1120 residues and a calculated molecular mass of 126 kDa. The alpha(2)delta-4a subunit shares 30, 32, and 61% identity with the human calcium channel alpha(2)delta-1, alpha(2)delta-2, and alpha(2)delta-3 subunits, respectively. Primary sequence comparison suggests that alpha(2)delta-4 lacks the gabapentin binding motifs characterized for alpha(2)delta-1 and alpha(2)delta-2; this was confirmed by a [(3)H]gabapentin-binding assay. In human embryonic kidney 293 cells, the alpha(2)delta-4 subunit associated with Ca(V)1.2 and beta(3) subunits and significantly increased Ca(V)1.2/beta(3)-mediated Ca(2+) influx. Immunohistochemical study revealed that the alpha(2)delta-4 subunit has limited distribution in special cell types of the pituitary, adrenal gland, colon, and fetal liver. Whether the alpha(2)delta-4 subunit plays a distinct physiological role in select endocrine tissues remains to be demonstrated.

Thirty distinct CACNA1F mutations in 33 families with incomplete type of XLCSNB and Cacna1f expression profiling in mouse retina.

X-linked CSNB patients may exhibit myopia, nystagmus, strabismus and ERG abnormalities of the Schubert-Bornschein type. We recently identified the retina-specific L-type calcium channel alpha1 subunit gene CACNA1F localised to the Xp11.23 region, which is mutated in families showing the incomplete type (CSNB2). Here, we report comprehensive mutation analyses in the 48 CACNA1F exons in 36 families, most of them from Germany. All families were initially diagnosed as having the incomplete type of CSNB, except for two which have been designated as Aland Island eye disease (AIED)-like. Out of 33 families, a total of 30 different mutations were identified, of which 24 appear to be unique for the German population. The mutations, 20 of which are published here for the first time, were found to be equally distributed over the entire gene sequence. No mutation could be found in a classic AIED family previously shown to map to the CSNB2 interval. Cacna1f expression in photoreceptor-negative mice strains indicate that the gene is expressed in the outer nuclear, the inner nuclear, and the ganglion cell layer. Such a distribution points to the central role of calcium regulation in the interaction of retinal cells that mediate signal transmission.

Synaptic calcium-channel function in Drosophila: analysis and transformation rescue of temperature-sensitive paralytic and lethal mutations of cacophony.

Voltage-gated calcium channels play a key role in chemical synaptic transmission by providing the calcium trigger for regulated neurotransmitter release. Genes encoding the primary structural subunit, alpha1, as well as accessory subunits of presynaptic calcium channels have now been identified in a variety of organisms. The cacophony (cac) gene in Drosophila, also known as nightblind A, encodes a voltage-gated calcium-channel alpha1 subunit homologous to vertebrate alpha1 subunits implicated in neurotransmitter release. A recent genetic screen in our laboratory isolated cac(TS2), a conditional cac mutant exhibiting rapid paralysis at elevated temperatures. This mutant has allowed synaptic electrophysiology after acute perturbation of a specific calcium-channel gene product, demonstrating that cac encodes a primary calcium channel functioning in neurotransmitter release. Here we report the molecular lesion in cac(TS2), a missense mutation within a calcium-dependent regulatory domain of the alpha1 subunit, as well as phenotypic rescue of temperature-sensitive and lethal cac mutations by transgenic expression of a wild-type cac cDNA. Notably, rescue of rapid, calcium-triggered neurotransmitter release was achieved by neural expression of a single cDNA containing a subset of alternative exons and lacking any conserved synaptic-protein interaction sequence. Possible implications of these findings are discussed in the context of structure-function studies of synaptic calcium channels, as well as alternative splicing and mRNA editing of the cac transcript.

Use of Antihypertensive Drug Therapy in Older Persons in an Academic Nursing Home

Objectives To determine the prevalence of hypertension and the appropriate treatment of hypertension in older persons in an academic nursing home. Design The charts of all persons aged ≥ 59 years currently residing in a nursing home affiliated with Westchester Medical Center/New York Medical College were analyzed by two geriatrics fellows according to a protocol designed by one of the authors (W.S.A.). Setting An academic nursing home affiliated with Westchester Medical Center/New York Medical College. Participants The study population included 96 men and 159 women, mean age 77 ± 9 years (range, 59–100 years). Results Hypertension was present in 129 of 255 persons (51%). Clinical cardiovascular disease or target organ damage or diabetes mellitus was present in 121 of 129 persons (94%) with hypertension. Hypertension was poorly controlled in 21 of 129 persons (16%). Of 129 persons with hypertension, 70 (54%) were treated with angiotensin-converting enzyme (ACE) inhibitors or angiotensin II type 1 receptor blockers, 61 persons (47%) with beta blockers, 43 persons (33%) with diuretics, 36 persons (28%) with calcium channel blockers, 5 persons (4%) with alpha blockers, and 5 persons (4%) with other antihypertensive drugs. Of 54 persons with hypertension and diabetes mellitus, 37 persons (69%) were treated with ACE inhibitors or angiotensin II type 1 receptor blockers. Of 58 persons with hypertension and coronary artery disease, 33 persons (57%) were treated with ACE inhibitors or angiotensin II type 1 receptor blockers, 31 persons (53%) with beta blockers, 20 persons (34%) with diuretics, 18 persons (31%) with calcium channel blockers, 2 persons (4%) with alpha blockers, and 4 persons (7%) with other antihypertensive drugs. Of 31 persons with hypertension and heart failure, only 5 persons (16%) had measurement of left ventricular ejection fraction. Of 31 persons with hypertension and heart failure, 30 persons (97%) were treated with diuretics, 21 persons (68%) with ACE inhibitors or angiotensin II type 1 receptor blockers, 18 persons (58%) with beta blockers, and 8 persons (26%) with calcium channel blockers. Conclusions Of older persons with hypertension in an academic nursing home, 16% had poor control of their hypertension. There was overuse of calcium channel blockers and alpha blockers and underuse of diuretics, beta blockers, and ACE inhibitors in treating hypertension. Physician education needs to be intensified to provide better medical care of older persons with hypertension through the use of optimal doses of drugs found to be effective and safe by evidence-based studies. To determine the prevalence of hypertension and the appropriate treatment of hypertension in older persons in an academic nursing home. The charts of all persons aged ≥ 59 years currently residing in a nursing home affiliated with Westchester Medical Center/New York Medical College were analyzed by two geriatrics fellows according to a protocol designed by one of the authors (W.S.A.). An academic nursing home affiliated with Westchester Medical Center/New York Medical College. The study population included 96 men and 159 women, mean age 77 ± 9 years (range, 59–100 years). Hypertension was present in 129 of 255 persons (51%). Clinical cardiovascular disease or target organ damage or diabetes mellitus was present in 121 of 129 persons (94%) with hypertension. Hypertension was poorly controlled in 21 of 129 persons (16%). Of 129 persons with hypertension, 70 (54%) were treated with angiotensin-converting enzyme (ACE) inhibitors or angiotensin II type 1 receptor blockers, 61 persons (47%) with beta blockers, 43 persons (33%) with diuretics, 36 persons (28%) with calcium channel blockers, 5 persons (4%) with alpha blockers, and 5 persons (4%) with other antihypertensive drugs. Of 54 persons with hypertension and diabetes mellitus, 37 persons (69%) were treated with ACE inhibitors or angiotensin II type 1 receptor blockers. Of 58 persons with hypertension and coronary artery disease, 33 persons (57%) were treated with ACE inhibitors or angiotensin II type 1 receptor blockers, 31 persons (53%) with beta blockers, 20 persons (34%) with diuretics, 18 persons (31%) with calcium channel blockers, 2 persons (4%) with alpha blockers, and 4 persons (7%) with other antihypertensive drugs. Of 31 persons with hypertension and heart failure, only 5 persons (16%) had measurement of left ventricular ejection fraction. Of 31 persons with hypertension and heart failure, 30 persons (97%) were treated with diuretics, 21 persons (68%) with ACE inhibitors or angiotensin II type 1 receptor blockers, 18 persons (58%) with beta blockers, and 8 persons (26%) with calcium channel blockers. Of older persons with hypertension in an academic nursing home, 16% had poor control of their hypertension. There was overuse of calcium channel blockers and alpha blockers and underuse of diuretics, beta blockers, and ACE inhibitors in treating hypertension. Physician education needs to be intensified to provide better medical care of older persons with hypertension through the use of optimal doses of drugs found to be effective and safe by evidence-based studies.

Changes in cardiac myocyte morphology alter the properties of voltage-gated ion channels.

The goal of this study was to determine if the properties of the transient outward potassium (I(to)), TTX-resistant sodium (I(Na)) and L-type calcium (I(Ca)) currents are altered during changes in cardiac cell shape. Ventricular myocytes were isolated from 3- to 4-day-old neonatal rats and cultured on either non-aligned or aligned collagen thin gels. In contrast to the flat, stellar-shaped myocytes obtained when the cells are plated on non-aligned collagen gels, myocytes plated on aligned gels display an elongated, rod-like shape. Ion channel expression was measured using the whole-cell arrangement of the patch clamp technique and Western blot analysis. Peak values for I(to), I(Na) and I(Ca) were 9+/-1, 71+/-13 and 7+/-1 pA/pF, respectively, in the flat cells, and increased to 21+/-2, 190+/-26 and 13+/-1 pA/pF, respectively, in the aligned cells. Application of forskolin (2 microM) and 3-isobutyl-1-methylxanthine (100 microM) resulted in a 101+/-18% increase in I(Ca) in the flat cells, but increased the current by only 43+/-9% in the aligned cells. Internal dialysis of the myocytes with cAMP strongly increased the peak I(Ca) in the flat cells, but caused no significant change in the aligned cells. While both basal and forskolin-stimulated levels of cAMP were the same in the two cell morphologies, the expression of the calcium channel alpha(1C) subunit was increased in the aligned cells. The expression and regulatory properties of voltage-gated calcium channels are modified during changes in neonatal rat myocyte shape.