Spatiotemporal Control of Vascular CaV1.2 by α1C S1928 Phosphorylation

BACKGROUND

L-type CaV1.2 channels undergo cooperative gating to regulate cell function, although mechanisms are unclear. This study tests the hypothesis that phosphorylation of the CaV1.2 pore-forming subunit α1C at S1928 mediates vascular CaV1.2 cooperativity during diabetic hyperglycemia.

METHODS

A multiscale approach including patch-clamp electrophysiology, super-resolution nanoscopy, proximity ligation assay, calcium imaging' pressure myography, and Laser Speckle imaging was implemented to examine CaV1.2 cooperativity, α1C clustering, myogenic tone, and blood flow in human and mouse arterial myocytes/vessels.

RESULTS

CaV1.2 activity and cooperative gating increase in arterial myocytes from patients with type 2 diabetes and type 1 diabetic mice, and in wild-type mouse arterial myocytes after elevating extracellular glucose. These changes were prevented in wild-type cells pre-exposed to a PKA inhibitor or cells from knock-in S1928A but not S1700A mice. In addition, α1C clustering at the surface membrane of wild-type, but not wild-type cells pre-exposed to PKA or P2Y11 inhibitors and S1928A arterial myocytes, was elevated upon hyperglycemia and diabetes. CaV1.2 spatial and gating remodeling correlated with enhanced arterial myocyte Ca2+ influx and contractility and in vivo reduction in arterial diameter and blood flow upon hyperglycemia and diabetes in wild-type but not S1928A cells/mice.

CONCLUSIONS

These results suggest that PKA-dependent S1928 phosphorylation promotes the spatial reorganization of vascular α1C into "superclusters" upon hyperglycemia and diabetes. This triggers CaV1.2 activity and cooperativity, directly impacting vascular reactivity. The results may lay the foundation for developing therapeutics to correct CaV1.2 and arterial function during diabetic hyperglycemia.

Secondhand Smoke Exposure Impairs Ion Channel Function and Contractility of Mesenteric Arteries

Cigarette smoke, including secondhand smoke (SHS), has significant detrimental vascular effects, but its effects on myogenic tone of small resistance arteries and the underlying mechanisms are understudied. Although it is apparent that SHS contributes to endothelial dysfunction, much less is known about how this toxicant alters arterial myocyte contraction, leading to alterations in myogenic tone. The study's goal is to determine the effects of SHS on mesenteric arterial myocyte contractility and excitability. C57BL/6J male mice were randomly assigned to either filtered air (FA) or SHS (6 h/d, 5 d/wk) exposed groups for a 4, 8, or 12-weeks period. Third and fourth-order mesenteric arteries and arterial myocytes were acutely isolated and evaluated with pressure myography and patch clamp electrophysiology, respectively. Myogenic tone was found to be elevated in mesenteric arteries from mice exposed to SHS for 12 wk but not for 4 or 8 wk. These results were correlated with an increase in L-type Ca2+ channel activity in mesenteric arterial myocytes after 12 wk of SHS exposure. Moreover, 12 wk SHS exposed arterial myocytes have reduced total potassium channel current density, which correlates with a depolarized membrane potential (Vm). These results suggest that SHS exposure induces alterations in key ionic conductances that modulate arterial myocyte contractility and myogenic tone. Thus, chronic exposure to an environmentally relevant concentration of SHS impairs mesenteric arterial myocyte electrophysiology and myogenic tone, which may contribute to increased blood pressure and risks of developing vascular complications due to passive exposure to cigarette smoke.

Nutritional enhancement of leaves by a psyllid through senescence-like processes: insect manipulation or plant defence?

Some herbivores can modify the physiology of plant modules to meet their nutritional requirements. Induction of premature leaf senescence could benefit herbivores since it is associated with the mobilisation of nutrients. We compared the effects of nymphal feeding by Cardiaspina near densitexta on Eucalyptus moluccana with endogenous processes associated with senescence to assess the relative merits of an insect manipulation or plant defence interpretation of responses. Evidence supporting insect manipulation included increased size of fourth and fifth instar nymphs (in the latter the effect was restricted to forewing pad length of females) on leaves supporting high numbers of conspecifics and feeding preventing leaf necrosis. Intra-specific competition negated greater performance at very high densities. High and very high abundances of nymphs were associated with increased concentrations of amino acid N but only very high abundances of nymphs tended to be associated with increased concentrations of six essential amino acids. Contrary to the insect manipulation interpretation, feeding by very high abundances of nymphs was associated with significant reductions in chlorophyll, carotenoids and anthocyanins. Evidence supporting plant defence included the severity of chlorosis increasing with the abundance of nymphs. Leaf reddening did not develop because ambient conditions associated with photoinhibition (high irradiance and low temperature) were not experienced by leaves with chlorotic lesions. Leaf reddening (from anthocyanins) alone is not expected to adversely affect nymphal survival; only leaf necrosis would kill nymphs. For senescence-inducing psyllids, nutritional enhancement does not fit neatly into either an insect manipulation or plant defence interpretation.

Impaired vascular contractility and blood pressure homeostasis in the smooth muscle alpha-actin null mouse

The smooth muscle (SM) alpha-actin gene activated during the early stages of embryonic cardiovascular development is switched off in late stage heart tissue and replaced by cardiac and skeletal alpha-actins. SM alpha-actin also appears during vascular development, but becomes the single most abundant protein in adult vascular smooth muscle cells. Tissue-specific expression of SM alpha-actin is thought to be required for the principal force-generating capacity of the vascular smooth muscle cell. We wanted to determine whether SM alpha-actin gene expression actually relates to an actin isoform's function. Analysis of SM alpha-actin null mice indicated that SM alpha-actin is not required for the formation of the cardiovascular system. Also, SM alpha-actin null mice appeared to have no difficulty feeding or reproducing. Survival in the absence of SM alpha-actin may result from other actin isoforms partially substituting for this isoform. In fact, skeletal alpha-actin gene, an actin isoform not usually expressed in vascular smooth muscle, was activated in the aortas of these SM alpha-actin null mice. However, even with a modest increase in skeletal alpha-actin activity, highly compromised vascular contractility, tone, and blood flow were detected in SM alpha-actin-defective mice. This study supports the concept that SM alpha-actin has a central role in regulating vascular contractility and blood pressure homeostasis, but is not required for the formation of the cardiovascular system.

Use of small cannulated screws for fixation in foot surgery

Use of cannulated bone screws, as compared with use of traditional bone screws, has been reported to decrease surgical time, allow for more precise screw placement, and reduce sources of error. Cannulation of the smaller-size screws that are routinely used in foot surgery has not been available until the last few years. This article reports on the use of the small cannulated screws manufactured by Alphatec Manufacturing, Inc (Palm Desert, California). The screw sizes available in the Mini Lag Screw System are 2.7, 3.5, and 4.0 mm. A long-term clinical and radiographic prospective evaluation of 70 procedures performed on 49 patients was conducted. The follow-up time for all patients was 2 years. None of the 70 implants fractured, and seven procedures (in seven patients) resulted in some type of implant-fixation failure. All of the fixation failures, however, appeared to be related to an untoward event or patient noncompliance. These smaller cannulated screws proved to be a reliable and effective means of fixation in foot surgery.

Poly-L-lactic acid rod fixation results in foot surgery

The purpose of this study was to evaluate the effectiveness and possible complications of polylactic absorbable devices in surgical procedures involving fixation of the foot. This was a prospective study in which biodegradable rods of poly-L-lactide were used in the fixation of 41 metatarsal osteotomies and digital arthrodeses and one midtarsal fusion in 23 patients. The follow-up time ranged from 6 months to 23 months. Ages ranged from 18 to 70 years with a mean age of 42 years. Clinical and radiographic examination was scheduled for each patient postoperatively at 1 week, 3 weeks, 6 weeks, 3 months, 6 months, 1 year, and 2 years. The gender distribution was 18 female and 5 males. Two patients who had three procedures were lost to follow-up. All of the procedures were evaluated for failure of fixation, radiographic osteolysis, foreign-body reaction, sinus formation, and infection. We noted one failure of fixation and two complications unrelated to the type of fixation. There were no foreign-body reactions, sinus formulations, or infections. We conclude that the poly-L-lactic acid rod is a viable method of fixation for these procedures.

Biofix fixation techniques and results in foot surgery

Biofix absorbable rods have been used for internal fixation for 10 years, and one of its most utilized applications has been osteotomies of the first metatarsal. This study evaluates 59 procedures on 49 patients completed over a 3-year period, using the 2.0-mm. Biofix rods. The transarticular technique for the fixation of osteotomies in the 1st and 5th metatarsals and the intramedullary technique used for digital fusions are described. All of the patients were followed for a minimum of 3 months, but most for > 1 year, and all of the procedures were evaluated for failure of fixation, osteolytic bone changes, sterile sinus development, and infection. There were no failures of fixation and no infections in this series. Patients (22.4%) developed radiographic osteolytic changes, and 4.1% of the patients developed sterile sinus discharge. However, these had no effect on the procedures' success or outcomes. An introduction to future application of the technology using Biofix screws and plates is made with a pantalar fusion case as an example.

Enchondroma: two case reports

Although bone tumors of any type are rare in the foot, if they do occur, enchondroma is among the most common. Asymptomatic enchondromas do not warrant treatment, but aggressive treatment is warranted when these tumors are painful. Pain occurs when there is a fracture, compression of soft tissues, or malignant conversion. Methods of treatment include excision, curettage and packing with bone chips, and subtotal or total resection and bone grafting. Two cases of painful enchondroma and how they were treated by different means is presented.

Digital arthroplasty

Correction of digital deformities by an arthroplasty procedure is by far the most commonly used technique. However, the choice of procedure is complicated by contradictory methods described in many texts. The goal of surgery is to maintain as much function as possible, achieve a cosmetic result, and give the best prognosis for avoidance of recurrence.

Comparison of total hinged and total nonhinged implants for the lesser digits

The purpose of this paper is to present preliminary findings of an ongoing prospective study of the effectiveness of total digital implants. Forty hinged implants and 22 nonhinged implants have been evaluated to compare the two implants and establish preoperative criteria for their use. Our findings indicate better results for toe purchase and stability with the nonhinged implant and marginally better joint range of movement with the hinged implant. Preoperative dorsal contracture at the metatarsophalangeal joint leads to the most consistent postoperative complications.

Fractures of the calcaneus

Fractures of the calcaneus account for approximately 60 per cent of all tarsal injuries and 1 to 2 per cent of all diagnosed fractures. The length of treatment and rehabilitation and disability has a marked effect on the working population. This helps to explain the great disparity in the classification and treatment of calcaneal fractures.

Revised tarsectomy for correction of relapsed clubfoot

A modification of the wedge tarsectomy used for correction of components of talipes equinovarus that helps preserve the length of the foot is presented. The procedure is demonstrated with the report of a case that was treated successfully. Correction of deformity in all three body planes in the relation of the forefoot to the rearfoot can be achieved with this combination tarsectomy-bone graft procedure that will simultaneously prevent gross shortening of the foot.

Comprehensive pediatric care: the patient viewpoint

Two meanings of the term comprehensive care are delineated. The first refers to a wide scope of health services, the second to a humanistic approach to the patient. Findings from a sample of patients from one pediatric practice suggest that the two meanings constitute two independent variables with respect to patient expeciations. Patient responses to questions regarding their expectations of the pediatrician revealed a tendency to hold a traditional disease orientation. Comprehensive care as a broad scope of health services that include mother guidance in child rearing is not a common goal for mothers utilizing the pediatric practice under study. On the other hand, a comprehensive approach by the pediatrician is a standard shared by most respondents in the sample: high priority is accorded the pattern of the personal physician with whom a patient forms a continuous doctor-patient relationship which instills in the patient trust that the physician's recommendations are based on thorough knowledge of the patient as an individual.