A surgical approach to the motor branch of the ulnar nerve

Isolated injury to the motor branch of the ulnar nerve is a relatively rare injury, often initially misdiagnosed. If repair is attempted through the original laceration without complete motor branch exposure, results can be less than satisfactory. A recent case illustrates this injury and provides us with an opportunity to review the surgical anatomy of the motor branch of the ulnar nerve. The surgical approach to the motor branch has been detailed and specifically emphasizes complete motor branch exposure from the main ulnar nerve trunk to the most distal motor branch entry into the adductor pollicis muscle. This approach permits definition of the exact level of the nerve injury, preservation of any intact proximal fine motor branches, and facilitates the mechanics of nerve repair.     

Recurrent anterior dislocation of the ulnar nerve at the cubital tunnel

Recurrent anterior dislocation of the ulnar nerve at the cubital tunnel is reported in two patients. This was due to traumatic attenuation of the flexor carpi ulnaris retinaculum. The mechanism of injury in both patients was a fall with the shoulder abducted and the elbow acutely flexed. Both patients had relief of their neurologic symptoms following anterior submuscular transposition of the ulnar nerve.     

The involvement of the root apex and cytokinins in the control of lateral root emergence in lettuce seedlings

Removal of the apical 3 mm of the primary root of hydroponically-grown lettuce seedlings 3 or 5 days after sowing, prevented further elongation of the root and increased both the number and total length of lateral roots. The length of the lateral zone, i.e. the distance from the base of the parent root to the lateral nearest the tip, except on one occasion, remained the same as the control in both 3 and 5 day treatments, until the length of the decapitated root (which had ceased elongating) became limiting.Zeatin applied via the roots, at a concentration range from 3 × 10^–10 M to 10^–8 M reduced tap root extension growth at all concentrations. Lateral root emergence was enhanced by low zeatin concentrations and retarded by higher ones. In general, the lateral zone length was the same in cytokinin-treated plants as in untreated controls.     

The first branch of the lateral plantar nerve and heel pain

The course and ramification pattern of the lateral plantar nerve was studied in serial sections from 4 fetal feet and in dissections from 34 adult feet with special reference to the so called first branch. This branch was found in all of the observed fetal and adult specimen. From its originating point the nerve runs immediately distally to the medial process of the calcaneal tuberosity in a lateral direction to the proximal part of the abductor digiti minimi muscle. During its course the FB gives two branches. One of them penetrates sometimes the insertion of the quadratus plantae muscle, whereas in adult feet it always sends fibres to the periosteum around the medial process of the calcaneal tuberosity and the long plantar ligament. The other innervates the flexor digitorum brevis muscle. The site of a possible entrapment is located between the abductor hallucis muscle and the medial head of the quadratus plantae muscle. There is strong indirect evidence that the nerve is of a mixed type consisting of sensory fibres for the calcaneal periosteum and the medial head of the quadratus plantae muscle. There is strong indirect evidence that the nerve is of a mixed type consisting of sensory fibres for the calcaneal periosteum and the long plantar ligament as well as motor fibres for the quadratus plantae, flexor digitorum brevis and abductor digiti minimi muscles, which may explain the characteristic pain complaints of the heel pain syndrome. The occurrence of a stiff fascia perforated by the nerve branch or a bursa around the insertion of the plantar aponeurosis as has been described by several authors and which was put forward as a possible aetiological factor could not be confirmed in our material.     

Dissecting Arabidopsis lateral root development

Recent studies in the model plant Arabidopsis provide new insight into the regulation of root architecture, a key determinant of nutrient- and water-use efficiency in crops. Lateral root (LR) primordia originate from a subset of pericycle founder cells. Sophisticated mass-spectroscopy-based techniques have been used to map the sites of biosynthesis of auxin and its distribution in Arabidopsis seedlings, highlighting the importance of the phytohormone during LR initiation and emergence. Key components of the cell cycle and signal-transduction pathway(s) that promote and attenuate auxin-dependent LR initiation have recently been identified. Additional signals, such as abscisic acid and nitrate, also regulate LR emergence, raising intriguing questions about the cross-talk between their transduction pathways.     

The jasmonate receptor COI1 plays a role in jasmonate-induced lateral root formation and lateral root positioning in Arabidopsis thaliana

Jasmonic acid (JA) regulates a broad range of plant defense and developmental responses. COI1 has been recently found to act as JA receptor. In this report, we show that low micromolar concentrations of JA inhibited primary root (PR) growth and promoted lateral root (LR) formation in Arabidopsis wild-type (WT) seedlings. It was observed that the coi1-1 mutant was less sensitive to JA on pericycle cell activation to induce lateral root primordia (LRP) formation and presented alterations in lateral root positioning and lateral root emergence on bends. To investigate JA-auxin interactions important for remodeling of root system (RS) architecture, we tested the expression of auxin-inducible markers DR5:uidA and BA3:uidA in WT and coi1-1 seedlings in response to indole-3-acetic acid (IAA) and JA and analyzed the RS architecture of a suite of auxin-related mutants under JA treatments. We found that JA did not affect DR5:uidA and BA3:uidA expression in WT and coi1-1 seedlings. Our data also showed that PR growth inhibition in response to JA was likely independent of auxin signaling and that the induction of LRP required ARF7, ARF19, SLR, TIR1, AFB2, AFB3 and AXR1 loci. We conclude that JA regulation of postembryonic root development involves both auxin-dependent and independent mechanisms.     

The effects of root decapitation on lateral root formation and cytokinin production in Pisum sativum

Decapitation of the primary roots of Pisum sativum L. resulted in a significant increase in the initiation of lateral root primordia within 12 h of the surgical treatment. Although this increase occurred both in the light and in the dark, lateral root initiation and development was much more rapid in the dark. The formation of lateral root primordia was accompanied by increased levels of endogenous cytokinins suggesting that newly formed root primordia start producing cytokinins very soon after being initiated. The significance of the present results in terms of possible sites of synthesis in vegetative tissue is discussed.     

Two novel methods to assess ulnar nerve conduction across the elbow

PurposeNerve conduction studies (NCS) are used as an electrodiagnostic method for diagnosing ulnar neuropathy of the elbow (UNE). The purpose of this study was to determine normal and reliability values of across elbow ulnar nerve conduction velocity using two novel methods.MethodsUlnar nerve conduction studies were performed on both upper extremities of 104 healthy subjects. Two different techniques were used to evaluate ulnar nerve function at the elbow: Technique 1 (W-BE-AE) determined mixed NCV across the elbow indirectly while Technique 2 (BE-AE) measured conduction time directly. Twenty subjects returned within one week for re-testing to generate reliability data.ResultsThe mean NCV for the BE-AE segment using Technique 1 was 59.68 m/s (±8.91 m/s). The mean peak latency for the BE-AE segment using Technique 2 was 2.03 ms (±0.24 ms). The interrater and intrarater reliability intraclass correlation coefficient (ICC) for Technique 1 was 0.454 and 0.756, respectively. For Technique 2, the interrater and intrarater reliability ICC was 0.76 and 0.814, respectively.ConclusionThis study identified normal values for ulnar nerve conduction across the elbow with reliability ranging from poor to good, depending on the technique. These two novel techniques provide alternative methods to traditional techniques to measure ulnar nerve conduction across the elbow.     

Light modulates the root tip excision induced lateral root formation in tomato

During plant growth and development, root tip performs multifarious functions integrating diverse external and internal stimuli to regulate root elongation and architecture. It is believed that a signal originating from root tip inhibits lateral root formation (LRF). The excision of root tip induced LRF in tomato seedlings associated with accumulation of auxin in pericycle founder cells. The excision of cotyledons slightly reduced LRF, whereas severing shoot from root completely abolished LRF. Exogenous ethylene application did not alter LRF. The response was modulated by light with higher LRF in seedlings exposed to light. Our results indicate that light plays a role in LRF in seedlings by likely modulating shoot derived auxin.     

Cadmium stress suppresses lateral root formation by interfering with the root clock

A biological clock activated by oscillating signals, known as root clock, has been linked to lateral root (LR) formation and is essential for regular LR spacing along the primary root. However, it remains unclear how this internal mechanism is influenced by environmental factors known to affect the LR pattern. Here, we report that excessive cadmium (Cd) inhibits LR formation by disrupting the lateral root cap (LRC)‐programmed cell death (PCD)‐regulated root clock. Cd restricts the frequency of the oscillating signal rather than its amplitude. This could be attributed to the inhibition on meristematic activity by Cd, which resulted in decreased LRC cell number and LRC‐PCD frequency. Genetic evidence further showed that LRC cell number is positively correlated with root resistance to Cd. Our study reveals root cap dynamics as a novel mechanism mediating root responses to Cd, providing insight into the signalling pathways of the root clock responding to environmental cues.     

Auxin fluxes in the root apex co-regulate gravitropism and lateral root initiation

Root architecture plays an important role in water and nutrient acquisition and in the ability of the plant to adapt to the soil. Lateral root development is the main determinant of the shape of the root system and is controlled by external factors such as nutrient concentration. Here it is shown that lateral root initiation and root gravitropism, two processes that are regulated by auxin, are co-regulated in Arabidopsis. A mathematical model was generated that can predict the effects of gravistimulations on lateral root initiation density and suggests that lateral root initiation is controlled by an inhibitory fields mechanism. Moreover, gene transactivation experiments suggest a mechanism involving a single auxin transport route for both responses. Finally, co-regulation may offer a selective advantage by optimizing soil exploration as supported by a simple quantitative analysis.