The polarity of the dental lamina in the regenerating salamander jaw

Development ◽  
1973 ◽  
Vol 30 (3) ◽  
pp. 635-646
Author(s):  
Heber T. Graver
Keyword(s):  
Normal Tissue ◽  
Ambystoma Maculatum ◽  
Dental Lamina ◽  
Reversed Polarity ◽  
The Right ◽  
Anterior Direction ◽  
Anterior Posterior

In ¼ and ½ amputated lower jaws of larval Ambystoma maculatum the dental lamina (DL) is replaced from both the anterior and posterior ends of the regenerate area, while in adult Triturus viridescens the DL is regenerated from the posterior stump tissues only. One-fourth and ½ mandibular jaw amputations were performed in such a manner that a short stump of jaw, devoid of DL, remained. Larvae exhibited a posterior regrowth of the DL, while in adults the lamina accumulated at the edge of the regenerate but did not enter the new tissue. Transplantation of a section of jaw from the left to the right side of the mandible resulted in the DL of the inserted piece having a reversed polarity in its new position. In both larval and adult forms, the DL of the transplant established connexions both anteriorly and posteriorly with lamina present. Transverse amputations through the inserted piece resulted in regeneration from the DL in the transplant in an anterior direction. Transplantation of a section of edentulous tissue into normal jaw tissue of the opposite side, or ttansplantation of a section of normal tissue into the edentulous area of the opposite side resulted in no anterior of posterior regrowth of the DL into the edentulous area. Collectively the results indicate that no anterior–posterior polarity exists in the DL of the larval salamander jaw, since regeneration can occur equally well in both directions. The DL of the adult salamander jaw exhibits an anterior–posterior polarity allowing for regrowth in an anterior direction only.

Effect of temperature differentials upon reconstitution of embryonic primordia in Ambystoma

Development ◽  
1971 ◽  
Vol 25 (3) ◽  
pp. 339-345
Author(s):  
Jean Piatt
Keyword(s):  
Statistical Analysis ◽  
Ambystoma Maculatum ◽  
Effect Of Temperature ◽  
Otic Vesicle ◽  
Regenerative Capacity ◽  
Rate Of Development ◽  
The Difference ◽  
The Right ◽  
Two Temperature

Eggs of Ambystoma maculatum in early stages of development were separated into two groups and maintained at 5 and 14 °C, respectively. In one series of animals comprising both temperature groups, the right otic vesicle was extirpated at stage 27. In another series the right forelimb disc was extirpated at stage 30. Following operation, animals of both groups were kept at 18 °C. Frequency and extent of reconstitution were compared between the two temperature groups. The 5° group was superior to the 14° group in the number of ears and forelimbs reconstituted. The extent of ear reconstitution and the initial quality of forelimb reconstitution were also superior in the 5° group. Statistical analysis of the data indicates that the difference between the two temperature groups is highly significant in both series. It is concluded that a slower pre-operative rate of development, caused by hypothermia, enhances the regenerative capacity of both ear and forelimb fields in the salamander embryo.

1. Theory, laboratory behavior, and field orientations

Paleobiology ◽  
1977 ◽  
Vol 3 (3) ◽  
pp. 270-287 ◽  
Author(s):  
Michael LaBarbera
Keyword(s):  
Dynamic Pressure ◽  
Threshold Current ◽  
Shell Shape ◽  
Current Direction ◽  
Pressure Distributions ◽  
Ambient Currents ◽  
The Right ◽  
Orientation Phenomenon ◽  
Anterior Posterior ◽  
Anterior Posterior Axis

(1) Hydrodynamic principles and experiments with empty shells predict that pressure distributions around brachiopod shells generated by ambient currents should, depending on the orientation of the shell relative to the current, either augment or oppose the ciliary-driven flow of water through the lophophore. For living articulate brachiopods with plectolophes or spirolophes, orientations where the anterior-posterior axis of the shell is parallel to the current direction should result in pressure distributions which oppose active pumping. This effect should be strongest when the excurrent region of the shell faces into the current. Orientations where the anterior-posterior axis is perpendicular to the current direction should result in pressure distributions which act in concert with active pumping, most strongly when one of the incurrent regions is directed into the current. These effects are independent of specific shell shape.(2) Laqueus californianus and Terebratulina unguicula actively reorient to currents in the laboratory, preferring orientations where the anterior-posterior axis of the shell is perpendicular to the current and the right-left axis is parallel to the current. Both species may traverse an arc as great as 120° to achieve their final orientation. Hemithyris psittacea also will actively reorient to currents, moving towards orientations where the anterior-posterior axis is perpendicular to the current. The maximum rotation observed for H. psittacea was 45°. Terebratalia transversa never reoriented in the laboratory.(3) Using epifaunal hydroid colonies as indicators of current direction, both Hemithyris psittacea and Terebratalia transversa are oriented in nature with the anterior-posterior axis of the shell perpendicular to the prevailing currents. While scuba diving, I confirmed this orientation phenomenon for T. transversa by direct measurement of the orientation of the brachiopods relative to prevailing currents.(4) Larval Terebratalia transversa avoid areas with current speeds greater than about 0.2 cm/s during metamorphosis and show no orientation to the ambient currents immediately after metamorphosis. Post-metamorphic T. transversa can actively reorient on the pedicle. The orientation observed in adults is probably achieved by active reorientation to local currents of post-zygolophe juveniles.(5) Threshold current speeds for reorientation in Laqueus californianus and Terebratulina unguicula are low and approximately equal to the excurrent pumping speeds of each species; dynamic pressure rather than viscous entrainment is probably the relevant factor determining reorientation behavior.

scholarly journals Concurrent Prediction of Muscle and Tibiofemoral Contact Forces During Treadmill Gait

2014 ◽  
Vol 136 (2) ◽  
Author(s):  
Trent M. Guess ◽  
Antonis P. Stylianou ◽  
Mohammad Kia
Keyword(s):  
Femoral Component ◽  
Gait Cycle ◽  
Musculoskeletal Model ◽  
Contact Forces ◽  
Grand Challenge ◽  
Subject Specific ◽  
The Right ◽  
Anterior Posterior ◽  
Rms Errors

Detailed knowledge of knee kinematics and dynamic loading is essential for improving the design and outcomes of surgical procedures, tissue engineering applications, prosthetics design, and rehabilitation. This study used publicly available data provided by the “Grand Challenge Competition to Predict in-vivo Knee Loads” for the 2013 American Society of Mechanical Engineers Summer Bioengineering Conference (Fregly et al., 2012, “Grand Challenge Competition to Predict in vivo Knee Loads,” J. Orthop. Res., 30, pp. 503–513) to develop a full body, musculoskeletal model with subject specific right leg geometries that can concurrently predict muscle forces, ligament forces, and knee and ground contact forces. The model includes representation of foot/floor interactions and predicted tibiofemoral joint loads were compared to measured tibial loads for two different cycles of treadmill gait. The model used anthropometric data (height and weight) to scale the joint center locations and mass properties of a generic model and then used subject bone geometries to more accurately position the hip and ankle. The musculoskeletal model included 44 muscles on the right leg, and subject specific geometries were used to create a 12 degrees-of-freedom anatomical right knee that included both patellofemoral and tibiofemoral articulations. Tibiofemoral motion was constrained by deformable contacts defined between the tibial insert and femoral component geometries and by ligaments. Patellofemoral motion was constrained by contact between the patellar button and femoral component geometries and the patellar tendon. Shoe geometries were added to the feet, and shoe motion was constrained by contact between three shoe segments per foot and the treadmill surface. Six-axis springs constrained motion between the feet and shoe segments. Experimental motion capture data provided input to an inverse kinematics stage, and the final forward dynamics simulations tracked joint angle errors for the left leg and upper body and tracked muscle length errors for the right leg. The one cycle RMS errors between the predicted and measured tibia contact were 178 N and 168 N for the medial and lateral sides for the first gait cycle and 209 N and 228 N for the medial and lateral sides for the faster second gait cycle. One cycle RMS errors between predicted and measured ground reaction forces were 12 N, 13 N, and 65 N in the anterior-posterior, medial-lateral, and vertical directions for the first gait cycle and 43 N, 15 N, and 96 N in the anterior-posterior, medial-lateral, and vertical directions for the second gait cycle.

scholarly journals Estimation of Knee Joint Forces in Sport Movements Using Wearable Sensors and Machine Learning

Sensors ◽  
2019 ◽  
Vol 19 (17) ◽  
pp. 3690 ◽  
Author(s):  
Bernd J. Stetter ◽  
Steffen Ringhof ◽  
Frieder C. Krafft ◽  
Stefan Sell ◽  
Thorsten Stein
Keyword(s):  
Knee Joint ◽  
Wearable Sensors ◽  
Correlation Coefficients ◽  
Biomechanical Modelling ◽  
Joint Forces ◽  
Measurement Units ◽  
Artificial Neural Network Ann ◽  
The Right ◽  
Anterior Posterior ◽  
Good Agreement

Knee joint forces (KJF) are biomechanical measures used to infer the load on knee joint structures. The purpose of this study is to develop an artificial neural network (ANN) that estimates KJF during sport movements, based on data obtained by wearable sensors. Thirteen participants were equipped with two inertial measurement units (IMUs) located on the right leg. Participants performed a variety of movements, including linear motions, changes of direction, and jumps. Biomechanical modelling was carried out to determine KJF. An ANN was trained to model the association between the IMU signals and the KJF time series. The ANN-predicted KJF yielded correlation coefficients that ranged from 0.60 to 0.94 (vertical KJF), 0.64 to 0.90 (anterior–posterior KJF) and 0.25 to 0.60 (medial–lateral KJF). The vertical KJF for moderate running showed the highest correlation (0.94 ± 0.33). The summed vertical KJF and peak vertical KJF differed between calculated and predicted KJF across all movements by an average of 5.7% ± 5.9% and 17.0% ± 13.6%, respectively. The vertical and anterior–posterior KJF values showed good agreement between ANN-predicted outcomes and reference KJF across most movements. This study supports the use of wearable sensors in combination with ANN for estimating joint reactions in sports applications.

scholarly journals Retinal Changes Induced by Epiretinal Tangential Forces

2015 ◽  
Vol 2015 ◽  
pp. 1-13 ◽  
Author(s):  
Mario R. Romano ◽  
Chiara Comune ◽  
Mariantonia Ferrara ◽  
Gilda Cennamo ◽  
Stefano De Cillà ◽  
...  
Keyword(s):  
Posterior Vitreous Detachment ◽  
Retinal Surface ◽  
Epiretinal Membranes ◽  
Vitreoretinal Traction ◽  
Tangential Forces ◽  
Vitreopapillary Adhesion ◽  
Definition Of ◽  
The Right ◽  
Anterior Posterior ◽  
Anomalous Posterior Vitreous Detachment

Two kinds of forces are active in vitreoretinal traction diseases: tangential and anterior-posterior forces. However, tangential forces are less characterized and classified in literature compared to the anterior-posterior ones. Tangential epiretinal forces are mainly due to anomalous posterior vitreous detachment (PVD), vitreoschisis, vitreopapillary adhesion (VPA), and epiretinal membranes (ERMs). Anomalous PVD plays a key role in the formation of the tangential vectorial forces on the retinal surface as consequence of gel liquefaction (synchysis) without sufficient and fast vitreous dehiscence at the vitreoretinal interface. The anomalous and persistent adherence of the posterior hyaloid to the retina can lead to vitreomacular/vitreopapillary adhesion or to a formation of avascular fibrocellular tissue (ERM) resulting from the proliferation and transdifferentiation of hyalocytes resident in the cortical vitreous remnants after vitreoschisis. The right interpretation of the forces involved in the epiretinal tangential tractions helps in a better definition of diagnosis, progression, prognosis, and surgical outcomes of vitreomacular interfaces.

scholarly journals Canine Bilateral Conjunctivo-Palpebral Dermoid: Description of Two Clinical Cases and Discussion of the Relevance of the Terminology

2015 ◽  
Vol 2015 ◽  
pp. 1-6 ◽  
Author(s):  
O. Balland ◽  
I. Raymond ◽  
I. Mathieson ◽  
P. F. Isard ◽  
Emilie Vidémont-Drevon ◽  
...  
Keyword(s):  
Normal Tissue ◽  
Lower Eyelid ◽  
Definitive Diagnosis ◽  
The Other ◽  
Skin Tissue ◽  
Bulbar Conjunctiva ◽  
Histopathological Analysis ◽  
Lesion Location ◽  
Lateral Portion ◽  
The Right

Two young dogs were presented for the evaluation of an abnormally haired appearance of both eyes since adoption. In one dog, the lesions were symmetrical and appeared as disorganized skin tissue located on the cutaneous aspect of the lateral portion of both lower eyelids, and continuing to the palpebral and the bulbar conjunctiva, thus forming continuous lesions. In the other dog, a similar lesion was present in the right eye (OD), but the lesion of the left eye (OS) was of discontinuous, disorganized skin tissue located midway on the lower eyelid and on the lateral bulbar conjunctiva. The lesions were surgically removed and routinely processed for histopathological analysis. Definitive diagnosis was conjunctivo-palpebral dermoids for each dog. Dermoids are usually considered to be choristoma (normal tissue in an abnormal location) when they are located on the ocular surface (cornea and/or conjunctiva) and as hamartoma when located on the palpebral skin. The lesion presentation in these two dogs reveals that names of “choristoma” alone or “hamartoma” alone are not accurate to depict the continuous, composite, conjunctivo-palpebral dermoids. These cases suggest that choristoma and hamartoma might develop subsequently from the same abnormal event during the embryonic development, which means that the lesion location might be the only difference between the two terms.

scholarly journals Carpometacarpal Dislocation with Third Metacarpal Fracture

2021 ◽  
Vol 5 (4) ◽  
pp. 488-490
Author(s):  
Colin Jorgensen ◽  
Steve Christos
Keyword(s):  
Soft Tissue ◽  
Plain Radiograph ◽  
Wrist Injuries ◽  
Rare Injury ◽  
Case Presentation ◽  
Metacarpal Fractures ◽  
Soft Tissue Swelling ◽  
Force Impact ◽  
The Right ◽  
Anterior Posterior

Case Presentation: A 17-year-old male presented to the emergency department (ED) due to trauma to the right hand and wrist after punching a locker at school. He had significant soft tissue swelling. Radiographs demonstrated intra-articular metacarpal fractures with associated carpometacarpal dislocations. The dislocation was reduced bedside in the ED and ultimately underwent closed reduction surgical management with orthopedic surgery. Discussion: Metacarpal fractures result from high-force impact injuries and account for 30-40% of all hand injuries. The most common sites of second through fifth metacarpal fractures are at the neck and the shaft, with the majority involving the fifth metacarpal neck (commonly coined “boxer’s fractures”). Carpometacarpal (CMC) dislocations are a rare injury associated with high-force impact trauma to the wrist. These injuries account for as little as 1% of all acute hand and wrist injuries. Carpometacarpal dislocations are often difficult to diagnose on physical examination due to significant soft tissue swelling, and they can easily be missed on anterior-posterior views of the hand. Lateral and oblique plain radiograph views are essential in the diagnosis as they are more likely to show dislocations. Despite appropriate plain radiographic views, subtle CMC dislocations may be difficult to discern dependent on the level of dislocation or subluxation and overlapping of joints. These injuries are rare due to otherwise highly stable ligamentous and muscular attachments within the wrist. Because of these attachments, dislocations are often associated with concomitant metacarpal fractures.

scholarly journals Perspectives and Risk Factors in the Return-to-Sports Decision After Knee Surgery in a Male Elite Handball Player: A Case Report

2020 ◽  
pp. 1-6
Author(s):  
Dr. Juan Castellano ◽  
Keyword(s):  
Risk Factors ◽  
Case Report ◽  
Lateral Collateral Ligament ◽  
Popliteus Tendon ◽  
Return To Sports ◽  
Posterior Surgery ◽  
Ligament Instability ◽  
Screening And Prevention ◽  
The Right ◽  
Anterior Posterior

We present the case of 28 years old male elite Handball Player with a first ACLR (Anterior Cross Ligament reconstruction) under surgery on the 21st of January 2019 in Hungary and a posterior surgery on January 22th 2020 in Barcelona-Spain with Re-tensing and reconstruction of the popliteus tendon and lateral collateral ligament. The reason of the second surgery was the ligament instability of the lateral and collateral posterior of the right knee and a residual laxity of the anterior-posterior cross Ligaments. After 6 months of the first post-operative rehabilitation in Amsterdam the handball Player visited our clinic in Bucharest in August 27th 2019 by petition of the Dinamo Hanball team manager to be re-evaluated and complete his rehabilitation until he will be able to reach the level to return to competition and play the national and European league with the Dinamo handball team Bucharest. The main objective of our Case report is to show the importance to provide further screening and prevention programs to find possibles inter-individual presence of risk factors” in the context of the return-to-sports decision after injury.

scholarly journals Baseline Eyeball Biometrics on Computed Tomography in Makurdi, North Central Nigeria

2018 ◽  
Vol 1 (1) ◽  
pp. 17-21
Author(s):  
I T Annongu ◽  
H Mohammad ◽  
M Chia ◽  
K Chaha ◽  
G O Magaji
Keyword(s):  
Reference Values ◽  
Radiology Department ◽  
Slight Reduction ◽  
Transverse Diameter ◽  
North Central ◽  
Eye Size ◽  
The Mean ◽  
Ct Brain ◽  
The Right ◽  
Anterior Posterior

Variations in ocular sizes exist in the population and this may be congenital or pathological. Reference values are therefore essential in management of ophthalmic pathologies in the fields of Ophthalmology and Neurology. The aim of the study was to establish computer tomography (CT) scan reference values of ocular sizes in Makurdi, north central Nigeria. To avoid unjustifiable radiation dose, data obtained for this study was on 111 patients referred on account of other medical conditions, to the Radiology department for CT brain scan using Philip Brilliance 16. Measurements were taken at mid-ocular axial slices with maximum anterior-posterior and transverse dimensions. The mean  ± 2 SD) ocular sizes in anterior-posterior(AP) and transverse diameter(TD) for both eyes were 22.1mm ± 1.88mm and 22.9mm ± 1.20mm respectively. The right eye was 21.9mm ± 2.33mm and 22.9mm ± 1.09mm and the left eye was 22.3mm ± 1.24mm and 23.0 ± 1.30 mm in both AP and TD respectively. The measurements were slightly higher on the left. The mean ocular measurements were higher in males and were statistically significant in the transverse measurements on both sides (P<0.04). Adult eye size was attained at age group 11-20 years and subsequently at age >70 years, there was slight reduction in ocular dimensions. Established ocular sizes on CT therefore showed that males had slightly larger eyeballs in comparison to females and there was some reduction of ocular sizes with age.

scholarly journals Management of Shoulder Dislocation by Prakash Method

2021 ◽  
Vol 8 (1) ◽  
pp. 21-24
Author(s):  
Ihsan Ullah ◽  
Samir Khan Kabir ◽  
Khalid . ◽  
Mohammad Inaam ◽  
Gul Hassan ◽  
...  
Keyword(s):  
Success Rate ◽  
Shoulder Dislocation ◽  
Recurrent Dislocation ◽  
Study Data ◽  
Posterior Shoulder ◽  
Fracture Dislocations ◽  
History Of ◽  
The Right ◽  
First Time ◽  
Anterior Posterior

OBJECTIVES: The objective of the study is to evaluate the effectiveness and safety of shoulder reduction developed by Prakash. METHODOLOGY: This descriptive study was carried out at Rehman Medical and Surgical Center District Buner and Naseer Teaching Hospital Peshawar from June 2017 to December 2019. All patients with a history of trauma to either shoulder were subjected to anterior-posterior shoulder radiograph. Those having shoulder dislocation were enrolled in the study. Data including age, gender, previous dislocation history, duration of dislocation and associated fracture, and fracture type were recorded in patient case sheet. Patients having recurrent dislocation, polytrauma, low GCS, fracture-dislocations, and more than a week history of dislocation were excluded from the study. RESULTS: This study was performed on 30 patients. The mean age of the patients was 36.46±11.58 years. Among them, 83.3% (n=25) were male and 16.7% (n=5) were female. While dislocation occurred on the right shoulder in 63.3% (n=19) and in 36.7% (n=11) on the left side. All the patients have dislocation for the first time. The reduction was performed using Prakash’s method. The success rate was 90% (n=27) and 10% (n=3) the reduction failed, which was then reduced under anesthesia using the Hippocratic method. CONCLUSION: The Prakash's method for reducing anterior shoulder dislocation requires minimum assistance with no anesthesia, it is safe, less time consuming, has a high success rate, less pain, and has minimal complications.  

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