Pattern of presentation and surgical management of spine tumors in Southeast Nigeria over a 10-year period.

BACKGROUND: Spine tumors could affect the bony elements and/or its neural contents. Clinical manifestations are underlined by their biological behaviors. Aim: This study aims to identify the pattern of presentation and surgical management of spine tumors in southeast Nigeria over a 10-year period. PATIENTS AND METHODS: A retrospective analysis of patients who were managed surgically for the spine and spinal cord neoplastic lesions over a 10-year period. All patients had pre-and post-operative magnetic resonance imaging (MRI) and histological diagnosis. Relevant clinical, radiological, and histological data were extracted and analyzed using Statistical Package for the Social Sciences (SPSS) for windows version 21. RESULTS: Four hundred and seventy-two spine procedures performed within the study period, 39 cases of histologically proven primary spinal cord tumors (PSCT) and non-PSCT were identified. These represented 8.3% of spine procedures. Seventeen were PSCT (3.6% of spine procedures), while 22 (4.7%) had non-PSCT, mean age for the PSCT group was 45 yrs and non-PSCT 59.5 years. A total of 56.5% of tumors are involved in the thoracic region, 43.7% in the cervical region. PSCT was likely to affect the cervical spine; while bony spine tumors, thoracic spine [odds ratio (OR) 4.9, P value 0.019]. A total of 84.6% of non-PSCT affected the bony spine, mainly the vertebral body. The histological result showed metastatic adenocarcinoma to be the most common tumor (33.3%). PSCT was likely to be benign than non-PSCT (P value < 0.00001). Gross total resection (GTR) was done in 100% of PSCT, and 50% in non-PSCT. Thirteen (40.6%) patients improved and 11 (34.4%) patients remained the same. CONCLUSIONS: Metastatic adenocarcinoma was the most common tumor of the spine. There was restricted ability at a GTR for non-PSCT compared to PSCT. Grossly 75% had improved/same neurological status, as such adjudged as a good outcome.

Characterization of human costal cartilage: is it an adapt tissue as graft for articular cartilage repair?

Several techniques and different biological or artificial tissues have been proposed as graft to restore articular defects. However, among the numerous and heterogeneous procedures proposed over time, the current literature findings are not conclusive. The aim of the current study is to evaluate if human costal cartilage can be suitable as graft for restoring articular cartilage defects. Knee articular cartilage and costal cartilage samples were obtained respectively from patients that underwent anterior cruciate ligament reconstruction (samples from notch plasty) or knee joint replacement and ear reconstruction or rhinoplasty through rib graft. The samples were stained with hematoxylin eosin, safranine-O, Gomori paraldehyde-fuchsin and Von Kossa for light microscopy. Immunohistochemistry was performed using anti-collagen I, II, IV and anti-SOX9 antibodies. Furthermore, samples were analyzed by transmission electron microcopy (TEM). In both cartilage, the cells are arranged in quite similar layers and the matrix show the same hyaline appearance: presence of type II collagen and solphated glycosaminoglycans, and absence of type I collagen and SOX-9. The bigger difference between the two hyaline tissues is the presence of perichondrium that surrounds all the specimens of costal cartilage. It consists of two separate layers where the inner one seems to get thinner with aging. The results show that rib cartilage seems to be an adapt tissue as graft for articular cartilage repair from a histological point of view. However, to date its therapeutic potential remains to be clearly defined by animal and clinical studies.

[Surgical management of pleomorphic adenoma of the salivary glands: our experience]. / Trattamento dell'adenoma pleomorfo delle ghiandole salivari: nostra esperienza.

BACKGROUND: Pleomorphic adenoma is a benign epithelial tumour of adenoid structure preferentially arising from the parotid gland. AIM: To analyse the outcome of patients with pleomorphic adenoma from salivary glands in order to evaluate the surgical strategy. PATIENTS AND METHODS: This is an audit of a 15-year period where 347 pleomorphic adenomas of the salivary glands were treated by the authors. Data was collected and reviewed from the records of all the patients in order to analyze gender, age, site, operative procedure, postoperative complications and recurrences. RESULTS: The pleomorphic adenoma preferentially originated in the parotid gland (89.1%), and rarely in other glands. The tumour occurred more often in females than in males (F:M=1.5). Average age was 43.43 years. Pericapsular enucleation of parotid neoplasms was the commonest operation performed. Other procedures were: superficial parotidectomy, total conservative parotidectomy, submandibular total sialoadenectomy and radical surgery for lesions of the palate. Postoperative complication was temporary facial weakness in 18 patients; 2 patients developed the Frey's syndrome. No recurrences were developed in follow-up period (25-177 months). CONCLUSION: The epidemiological aspects of pleomorphic adenoma of salivary glands retrieved in our study are similar to those reported in literature; moreover this study demonstrates that pericapsular enucleation is a viable alternative to superficial parotidectomy for the majority of parotid localizations, associated with reduced morbidity without oncological compromise.

Salivary glands tumours: a retrospective study of 454 patients.

AIM: Salivary glands tumors constitute a highly heterogeneous group in human oncological pathology. They show different clinical, epidemiological, histopathological and evolutionary characteristics. METHODS: In this paper we have analysed their epidemiological aspects in 454 patients with salivary glands tumors surgically treated at the Maxillofacial Surgical Unit of the Azienda Ospedaliero-Universitaria ''Ospedali Riuniti Umberto I-G.M. Lancisi-G. Salesi'', Ancona, Italy, from 1990 to 2002, to evaluate the incidence of the different types of neoplasia and their age and sex distribution. RESULTS: Our results show that 63.22% of salivary glands tumors occur in the parotid gland, with a predominance of benign tumours, pleomorphic adenoma being the most prevalent histological type. A higher prevalence was observed in the female sex. CONCLUSIONS: Malignant tumors were more common in the elderly than in young patients and the most common histological types were mucoepidermoid carcinoma and adenoid cystic carcinoma.

Angiogenesis in oral squamous cell carcinoma.

Many retrospective studies have recently shown that microvessel density could represent a valid independent prognostic factor for overall survival and disease-free survival for primary tumours. The fact that oral tumours with a higher microvessel density showed a tendency to present distant metastasis and a bad prognosis, suggested that angiogenetic activity would play a pivotal role also in oral carcinomas, exerting a negative effect on the clinical course and representing an independent negative prognostic factor also for this type of tumour. Based on these results, microvessel density was evaluated, in the present study, in 64 cases of squamous cell carcinoma of the oral cavity, using immunohistochemical analysis with anti-CD34 monoclonal antibody. Possible correlations between microvessel density and clinico-pathological parameters were analysed, such as: age, sex, tumour localization and size, TNM stage and histological grading. Statistical analysis has shown that microvessel density differs in the 3 histological groups (G1, G2, G3) (p = 0.0331), and between node-positive and node-negative patients (p < 0.0001). No statistical correlation was observed between microvessel density and other clinical parameters such as age, sex, tumour site and size.

Patch-clamp recording of charge movement, Ca2+ current, and Ca2+ transients in adult skeletal muscle fibers.

Intramembrane charge movement (Q), Ca(2+) conductance (G(m)) through the dihydropyridine-sensitive L-type Ca(2+) channel (DHPR) and intracellular Ca(2+) fluorescence (F) have been recorded simultaneously in flexor digitorum brevis muscle fibers of adult mice, using the whole-cell configuration of the patch-clamp technique. The voltage distribution of Q was fitted to a Boltzmann equation; the Q(max), V(1/2Q), and effective valence (z(Q)) values were 41 +/- 3.1 nC/microF, -17.6 +/- 0.7 mV, and 2.0 +/- 0.12, respectively. V(1/2G) and z(G) values were -0.3 +/- 0.06 mV and 5.6 +/- 0.34, respectively. Peak Ca(2+) transients did not change significantly after 30 min of recording. F was fit to a Boltzmann equation, and the values for V(F1/2) and z(F) were 6.2 +/- 0.04 mV and 2.4, respectively. F was adequately fit to the fourth power of Q. These results demonstrate that the patch-clamp technique is appropriate for recording Q, G(m), and intracellular [Ca(2+)] simultaneously in mature skeletal muscle fibers and that the voltage distribution of the changes in intracellular Ca(2+) can be predicted by a Hodgkin-Huxley model.

Overexpression of hIGF-1 exclusively in skeletal muscle increases the number of dihydropyridine receptors in adult transgenic mice.

The number of dihydropyridine receptors (DHPR) and sarcoplasmic reticulum (SR) Ca2+ release channels (RyR1) and their interaction determine the efficacy of the sarcolemmal excitation-SR Ca2+ release-contraction coupling (ECC). Both receptors play a central role in ECC as demonstrated in various animal species and muscle subtypes. In the present work we studied the effect of transgenic overexpression of human insulin-like growth factor 1 (hIGF-1) on the levels of these two Ca2+ channels in extensor digitorum longus (EDL) (fast-twitch), soleus (slow-twitch) and pool of fast- and slow-twitch muscles from adult C57BL/6 mice. Muscles from hIGF-1 transgenic mice showed a significant increase in IGF-1 concentration (20-30-fold) and in the number of DHPR (52% increase) whereas no significant change in RyR1 binding sites was detected. The differential effect on DHPR and RyR1 resulted in a 30% increase in DHPR/RyR1 ratio. Fast- and slow-twitch muscles showed 50 and 70% increase in the number of DHPR and 30 and 80% increase in DHPR/RyR1, respectively. These results support the concept that the increased autocrine/paracrine secretion of hIGF-1 exerts potent stimulatory effects on DHPR alpha1 subunit expression in adult skeletal muscle.

Activation of alpha7 nicotinic acetylcholine receptor promotes survival of spinal cord motoneurons.

Spinal cord motoneurons (MNs) undergo a process of cell death during embryonic development and are the target of lethal acquired or inherited disorders, such as the amyotrophic lateral sclerosis. Therefore, the identification of mechanisms leading to MN survival is of crucial importance. Elevations in intracellular Ca2+ promote chicken MN survival during the embryonic period of naturally occurring cell death. We have recently demonstrated that the alpha7 nicotinic acetylcholine receptor (nAChR) mediates significant increases in free Ca2+ concentration at membrane potentials at which other pathways for Ca2+ influx are inactive. Although it is possible that Ca2+ influx through alpha7 nAChR promotes cell survival, the relation between alpha7 nAChR activation, cytosolic free Ca2+ and mammalian spinal cord MN survival has not been established. In the present study we have now demonstrated that Ca2+ influx through the alpha7-subunit is sufficient to rescue a significant number of cultured spinal cord MNs from programmed cell death induced by trophic factor deprivation. This is the first demonstration that neuronal nAChRs are involved in the regulation of MN survival.

Age-dependent IGF-1 regulation of gene transcription of Ca2+ channels in skeletal muscle.

In the present work, we investigated whether IGF-1 regulates the transcription of the genes encoding the L-type Ca2+ channel (DHPR) channel and RyR1 in young adult and senescent mice. To this end, a transgenic mouse model overexpressing IGF-1 exclusively in skeletal muscle (S1S2) was studied at different ages and the results were compared with wild type age-matched mice (FVB). We found that ribosomal RNA expression did not change significantly either with age or IGF-1 according to ribonuclease protection and nuclear run-on transcription assays. Transgenic overexpression of IGF-1 resulted in marked increases in skeletal muscle DHPR alpha(1S) and RyR1 mRNA in young and old mice and in enhanced DHPR alpha(1S) nuclear transcription in skeletal muscles from young mice when normalized to 28S ribosomal RNA. These results support the concept that IGF-1 regulates the expression of DHPR by modulating DHPR alpha(1S) nuclear transcription.

Up-regulation of human alpha7 nicotinic receptors by chronic treatment with activator and antagonist ligands.

This study examined the binding and functional properties of human alpha7 neuronal nicotinic acetylcholine receptors stably expressed in human embryonic kidney (HEK) 293 cells following chronic treatment with nicotinic receptor ligands. Treatment of cells with (-)-nicotine (100 microM) for 120 h increased the Bmax values of [125I]alpha-bungarotoxin binding 2.5-fold over untreated cells. This effect was concentration-dependent (EC50) = 970 microM) and a 6-fold upregulation was observed with the maximal concentration of (-)-nicotine tested. Also, treatment of cells with ligands of varying intrinsic activities including (+/-)-epibatidine, (2,4)-dimethoxybenzylidene anabaseine (GTS-21) and 1,1-dimethyl-4-phenyl piperazinium iodide (DMPP) also upregulated [125I]alpha-bungarotoxin binding. A concentration-dependent upregulation of binding sites was also observed following treatment with the alpha7 nicotinic receptor antagonist, methyllycaconitine (EC50 = 92 microM) with a maximal upregulation of about 7-fold. Functionally, the peak amplitude of the whole-cell currents recorded by fast application of (-)-nicotine after chronic treatment of cells with concentrations of (-)-nicotine (1000 microM) or methyllycaconitine (10 microM) that elicited similar increases in binding levels (3.5-fold) resulted in increases of 2-fold (505 +/- 21 pA) and 6-fold (1820 +/- 137 pA) respectively in whole cell current amplitude compared to untreated cells (267 +/- 24 pA). These studies clearly demonstrate that long-term exposure to both activator and antagonist ligands can increase the density of alpha7 nicotinic receptors and can differentially enhance nicotinic receptor function.

Synchronous bilateral Warthin's tumours of the parotid glands: a case report.

Warthin's tumour is the most frequent monomorphic adenoma of the major salivary glands, representing about 2-15% of all parotid tumours. Most of the multifocal Warthin's tumours are unilateral, whereas bilateral Warthin's tumours are far less common; bilateral Warthin's tumours are metachronous with few synchronous cases having been described in the literature. The Authors present an interesting case of simultaneously occurring bilateral Warthin's tumours growing in the parotid glands.

Myeloid sarcoma of the maxillary bone.

Myeloid sarcoma (MS) is a malignant tumour of myeloblasts rarely occurring in the maxillary bone. The tumour may precede or be concurrent with leukaemic infiltration of the bone marrow or herald blastic transformation of a myelodysplastic syndrome or a chronic myeloproliferative disorder. Myeloid sarcoma is uncommon in the oral cavity, but it can involve the palate, gingiva, extraction socket, and cheek. Recognition and diagnosis of myeloid sarcoma involving the soft tissues of the oral cavity in an otherwise asymptomatic patient is important and mandates an appropriate haematological diagnostic workup. We herein report on a new case without any evidence of haematological disorders. We discuss the pathological diagnosis and the therapeutical approaches.

Overexpression of IGF-1 exclusively in skeletal muscle prevents age-related decline in the number of dihydropyridine receptors.

Excitation-contraction uncoupling has been identified as a mechanism underlying skeletal muscle weakness in aging mammals (sarcopenia). The basic mechanism for excitation-contraction uncoupling is a larger number of ryanodine receptors (RyR1) uncoupled to dihydropyridine receptors (DHPRs) (Delbono, O., O'Rourke, K. S., and Ettinger, W. H. (1995) J. Membr. Biol. 148, 211-222). In the present study, we used transgenic mice overexpressing human insulin-like growth factor-1 exclusively in skeletal muscle to test the hypothesis that a high concentration of IGF-1 prevents age-related decreases in DHPR number and in muscle force. Transgenic mice express 10-20-fold higher IGF-1 concentrations than nontransgenic mice at all ages (1-24 months). The number of DHPRs is 50-100% higher, and the DHPR/RyR1 ratio is 40% higher in transgenic soleus (predominantly type I fiber muscles), extensor digitorum longus (predominantly type II fiber muscles), and the pool of type I and type II fiber muscles than in nontransgenic young (6 months), adult (12 months), and old (24 months) mice. Furthermore, no age-related changes in DHPRs and the DHPR/RyR1 ratio were observed in transgenic muscles. The specific single twitch and tetanic muscle force in old transgenic soleus and extensor digitorum longus muscles are 50% higher than in old nontransgenic muscles. Taken together, these results support the concept that IGF-1- dependent prevention of age-related decline in DHPR expression is associated with stronger muscle contraction in older transgenic mice.

[Functional verification of palatoplasty using two different technics, using spectroacoustical analysis of the voice]. / Considerazioni critiche su verifiche funzionali di palatoplastiche eseguite secondo due tecniche diverse, mediante analisi spettroacustica della voce.

The authors present the final conclusions of a comparative study performed on a population of 26 patients, who underwent palatoplasties following the Push-Back and modified Longebeck techniques. The functional results of these two metodiques have been compared by the spetroacustic analysis of the voice.

L-Type Ca(2+) channel charge movement and intracellular Ca(2+) in skeletal muscle fibers from aging mice.

In this work we tested the hypothesis that skeletal muscle fibers from aging mice exhibit a significant decline in myoplasmic Ca(2+) concentration resulting from a reduction in L-type Ca(2+) channel (dihydropyridine receptor, DHPR) charge movement. Skeletal muscle fibers from the flexor digitorum brevis (FDB) muscle were obtained from 5-7-, 14-18-, or 21-24-month-old FVB mice and voltage-clamped in the whole-cell configuration of the patch-clamp technique according to described procedures (Wang, Z.-M., M. L. Messi, and O. Delbono. 1999. Biophys. J. 77:2709-2716). Total charge movement or the DHPR charge movement was measured simultaneously with intracellular Ca(2+) concentration. The maximum charge movement (Q(max)) recorded (mean +/- SEM, in nC microF(-1)) was 53 +/- 3.2 (n = 47), 51 +/- 3.2 (n = 35) (non-significant, ns), and 33 +/- 1.9 (n = 32) (p < 0.01), for the three age groups, respectively. Q(max) corresponding to the DHPR was 43 +/- 3.3, 38 +/- 4.1 (ns), and 25 +/- 3.4 (p < 0.01) for the three age groups, respectively. The peak intracellular [Ca(2+)] recorded at 40 mV (in microM) was 15.7 +/- 0. 12, 16.7 +/- 0.18 (ns), and 8.2 +/- 0.07 (p < 0.01) for the three age groups, respectively. No significant changes in the voltage distribution or steepness of the Q-V or [Ca(2+)]-V relationship were found. These data support the concept that the reduction in the peak intracellular [Ca(2+)] results from a larger number of ryanodine receptors uncoupled to DHPRs in skeletal muscle fibers from aging mammals.

The specific force of single intact extensor digitorum longus and soleus mouse muscle fibers declines with aging.

In the present study we measured, for the first time, the isometric specific force (SF, force normalized to cross sectional area) generated by single intact fibers from fast- (extensor digitorum longus, EDL) and slow-twitch (soleus) muscles from young adult (2-6), middle-aged (12-14) and old (20-24 month-old) mice. SF has also been measured in single intact flexor digitorum brevis fibers from young mice. Muscle fibers have been classified into fast- or slow-twitch based on the contraction kinetics. Maximum SF recorded in EDL and soleus fibers from young and middle-aged mice did not differ significantly. A significant age-dependent decline in maximum SF was recorded in EDL and soleus fibers from young or middle-aged to old mice. The SF was 377 +/- 18, 417 +/- 20 and 279 +/- 18 kPa for EDL fibers from young, middle-aged and old mice, respectively and 397 +/- 17, 405 +/- 24 and 320 +/- 33 kPa for soleus fibers from age-matched mice, respectively. The frequency needed to elicit maximum force in EDL and soleus fibers from middle-aged to old mice did not differ significantly. In conclusion, the specific force developed by both fast and slow-twitch single intact muscle fibers declines with aging and more significantly in the former.

Kinetics of dendritic cell activation: impact on priming of TH1, TH2 and nonpolarized T cells.

To prime immune responses, dendritic cells (DCs) need to be activated to acquire T cell stimulatory capacity. Although some stimuli trigger interleukin 12 (IL-12) production that leads to T helper cell type I (TH1) polarization, others fail to do so and favor TH2 polarization. We show that after activation by lipopolysaccharide, DCs produced IL-12 only transiently and became refractory to further stimulation. The exhaustion of cytokine production impacted the T cell polarizing process. Soon after stimulation DCs primed strong TH1 responses, whereas at later time points the same cells preferentially primed TH2 and nonpolarized T cells. These findings indicate that during an immune response, T cell priming conditions may change in the lymph nodes, suggesting another mechanism for the regulation of effector and memory T cells.

Dihydropyridine receptor-ryanodine receptor uncoupling in aged skeletal muscle.

The mechanisms underlying skeletal muscle functional impairment and structural changes with advanced age are only partially understood. In the present study, we support and expand our theory about alterations in sarcolemmal excitation-sarcoplasmic reticulum Ca2+ release-contraction uncoupling as a primary skeletal muscle alteration and major determinant of weakness and fatigue in mammalian species including humans. To test the hypothesis that the number of RYR1 (ryanodine receptor) uncoupled to DHPR (dihydropyridine receptor) increases with age, we performed high-affinity ligand binding studies in soleus, extensor digitorum longus (EDL) and in a pool of several skeletal muscles consisting of a mixture of fast- and slow-twitch muscle fibers in middle-aged (14-month) and old (28-months) Fisher 344 Brown Norway F1 hybrids rats. The number of DHPR, RYR1, the coupling between both receptors expressed as the DHPR/RYR1 maximum binding capacity, and their dissociation constant for high-affinity ligands were measured. The DHPR/RYR1 ratio was significantly reduced in the three groups of muscles (pool: 1.03 +/- 0.15 and 0.80 +/- 0.11, soleus: 0.44 +/- 0. 12 and 0.26 +/- 0.10, and EDL: 0.95 +/- 0.14 and 0.68 +/- 0.10, for middle-aged and old muscles, respectively). These data support the concept that DHPR-RYR1 uncoupling results in alterations in the voltage-gated sarcoplasmic reticulum Ca2+ release mechanism, decreases in myoplasmic Ca2+ elevation in response to sarcolemmal depolarization, reduced Ca2+ supply to contractile proteins and reduced contraction force with aging.

Regulation of mouse skeletal muscle L-type Ca2+ channel by activation of the insulin-like growth factor-1 receptor.

We investigated the modulation of the skeletal muscle L-type Ca2+ channel/dihydropyridine receptor in response to insulin-like growth factor-1 receptor (IGF-1R) activation in single extensor digitorum longus muscle fibers from adult C57BL/6 mice. The L-type Ca2+ channel activity in its dual role as a voltage sensor and a selective Ca2+-conducting pore was recorded in voltage-clamp conditions. Peak Ca2+ current amplitude consistently increased after exposure to 20 ng/ml IGF-1 (EC50 = 5.6 +/- 1.8 nM). Peak IGF-1 effect on current amplitude at -20 mV was 210 +/- 18% of the control. Ca2+ current potentiation resulted from a shift in 13 mV of the Ca2+ current-voltage relationship toward more negative potentials. The IGF-1-induced facilitation of the Ca2+ current was not associated with an effect on charge movement amplitude and/or voltage distribution. These phenomena suggest that the L-type Ca2+ channel structures involved in voltage sensing are not involved in the response to the growth factor. The modulatory effect of IGF-1 on L-type Ca2+ channel was blocked by tyrosine kinase and PKC inhibitors, but not by a cAMP-dependent protein kinase inhibitor. IGF-1-dependent phosphorylation of the L-type Ca2+ channel alpha1 subunit was demonstrated by incorporation of [gamma-32P]ATP to monolayers of adult fast-twitch skeletal muscles. IGF-1 induced phosphorylation of a protein at the 165 kDa band, corresponding to the L-type Ca2+ channel alpha1 subunit. These results show that the activation of the IGF-1R facilitates skeletal muscle L-type Ca2+ channel activity via a PKC-dependent phosphorylation mechanism.

Calcium regulates L-type Ca2+ channel expression in rat skeletal muscle cells.

Primary skeletal muscle cells were cultured in a normal- (1.8 mM) or high- (4.8 mM) Ca2+ culture medium to determine whether Ca2+ modulates the number of L-type Ca2+ channels. Skeletal myoballs cultured in a normal medium showed, when exposed to a high extracellular [Ca2+], ([Ca2+]e) a transient increase in intracellular [Ca2+] ([Ca2+]i) from a resting concentration of 60 to 160 nM. By day 3, however, when the experiments were made, [Ca2+]i no longer differed from control (pre-exposure to high Ca2+). The maximum charge movements in myoballs incubated in 1.8 and 4.8 mM were 16.4+/-1.05 (n=56) and 24.1+/-1.18 nC/microF (n=58; P<0.01), respectively, and peak Ca2+ currents at 20 mV were -10.8+/-1.09 (n=46) and -12.8+/-0.75 nA/microF (n=82), respectively (P>0.05). The tail current amplitudes in 1.8 and 4.8 mM Ca2+-treated cells were -9.3+/-1.23 and -14.2+/-1.37 nA/microF (P<0.05), respectively, at 10 mV and -15.3+/-1.76 and -23.6+/-2.02 nA/microF (P<0.05), respectively at 60 mV. The maximum binding of [3H]PN200-110 (a radioligand specific for L-type Ca2+ channel alpha1 subunits) in myoballs cultured in 1.8 and 4.8 mM [Ca2+]e was 1.34+/-0.23 and 3.2+/-0.63 pmol/mg protein (n=8; P<0.02), respectively. The increase in [Ca2+]i associated with the increases in charge movements, tail currents and the number of L-type Ca2+ channel alpha1 subunits in skeletal muscle cells cultured in high [Ca2+]e support the concept that extracellular Ca2+ influx modulates the expression of L-type Ca2+ channels in skeletal muscle cells.