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Biomedical subjects

Y Jefferson

Publications and source records attributed to Y Jefferson.

14 recordsLinked to original sources
PubMed2003

Differentiation of cartilaginous anlagen in entire embryonic mouse limbs cultured in a rotating bioreactor.

Mechanisms involved in development of the embryonic limb have remained the same throughout eons of genetic and environmental evolution under Earth gravity (1 g). During the spaceflight era it has been of interest to explore the ancient theory that form of the skeleton develops in response to gravity, and that changes in gravitational forces can change the developmental pattern of the limb. This has been shown in vivo and in vitro, allowing the hypergravity of centrifugation and microgravity of space to be used as tools to increase our knowledge of limb development. In recapitulations of spaceflight experiments, premetatarsals were cultured in suspension in a bioreactor, and found to be shorter and less differentiated than those cultured in standard culture dishes. This study only measured length of the metatarsals, and did not account for possible changes due to the skeletal elements having a more in vivo 3D shape while in suspension vs. flattened tissues compressed by their own weight. A culture system with an outcome closer to in vivo and that supports growth of younger limb buds than traditional systems will allow studies of early Hox gene expression, and contribute to the understanding of very early stages of development. The purpose of the current experiment was to determine if entire limb buds could be cultured in the bioreactor, and to compare the growth and differentiation with that of culturing in a culture dish system. Fore and hind limbs from E11-E13 ICR mouse embryos were cultured for six days, either in the bioreactor or in center-well organ culture dishes, fixed, and embedded for histology. E13 specimens grown in culture dishes were flat, while bioreactor culture specimens had a more in vivo-like 3D limb shape. Sections showed excellent cartilage differentiation in both culture systems, with more cell maturation, and hypertrophy in the specimens cultured in the bioreactor. Younger limb buds fused together during culture, so an additional set of E11.5 limb buds was cultured with and without encapsulation in alginate prior to culturing in the bioreactor. Encapsulated limbs grown in the bioreactor did not fuse together, but developed only the more proximal elements while limbs grown in culture dishes formed proximal and distal elements. Alginate encapsulation may have reduced oxygenation to the progress zone of the developing limb bud resulting in lack of development of the more distal elements. These results show that the bioreactor supports growth and differentiation of skeletal elements in entire E13 limb buds, and that a method to culture younger limb buds without fusing together needs to be developed if any morphometric analysis is to be performed.

Alginates↗
PubMed1996

Skeletal types: key to unraveling the mystery of facial beauty and its biologic significance.

In random studies, some faces will deviate toward Type II skeletal and some toward Type III. Some will deviate toward a skeletally short vertical while some toward long. In their study, Langlois and Roggman digitized individual faces through a computer. As more and more faces were entered, the composite of these faces became more and more attractive. From this, they concluded that attractive faces are only average. The "average" face may very well conform to the divine proportion. However, some faces are strikingly beautiful, and Alley and Cunningham in their study attempted to explain these attributes. Individuals who are blessed with attractive features are treated differently in our society. Ackerman states, "Attractive people do better: in school, where they receive more help, better grades and less punishment; at work, where they are rewarded with higher pay, more prestigious jobs and faster promotions; in finding mates, where they tend to be in control of the relationship and make most of the decisions; and among strangers, who assume them to be more interesting, honest, virtuous and successful." Many would find this special treatment objectionable and unfair. The irony is that beautiful individuals make up a very small percentage of the population; they have very little power to dictate how society should act and behave. Various disciplines have studied the nature of facial beauty. Individually, they provide partial answers; however, when viewed together, they begin to weave provocative insights as to its biologic significance. It is intricately related to divine proportion, and all living creatures have the genetic potential to develop toward it. The appreciation for this proportion is primitive and inborn; it is a biologic mechanism by which all living creatures are attracted to potential mates who conform to this strict proportion because they are biologically strong, healthy, and fertile. To date, there is no other profession other than ours that has the knowledge and the expertise to treat facial problems. We have a keen interest in facial and dental esthetics. We understand occlusion, TMJ anatomy, and facial-skeletal relationship to soft tissue profile. Unlike plastic surgery, where the soft tissues are artificially recontoured for better esthetics, we can make real and substantial skeletal changes. We are able to correct the architectural framework of the face to its physiologically correct position. In so doing, we cannot only improve our patients' appearance, but improve their health as well. There are those in our profession who are afraid of changes. They will not accept what has been presented with the usual excuse that they are "anecdotal" and not supported in the scientific world with rat and monkey studies. Although the concepts presented are complicated and controversial, I have attempted to present them clearly and simply with many references. There will be those, however, who will stubbornly continue to disbelieve the efficacy of functional appliance and TMD therapy even though in the real world there are many successes with human patients. With time, the truth will become self-evident. Finally, it is not my intent to say that everyone should look alike. Superficial variations and differences appropriate to certain climatic conditions and other environmental factors are often necessary for the survival of the species. Additionally, in rare instances, some Skeletal Type II individuals have shorter mandibles than normal. To reposition these mandibles forward closer to the anterior arc may create a "dual" bite situation. In other rare instances, Skeletal Type III individuals may have longer mandibles than normal. To reposition these mandibles posteriorly closer to the anterior arc may cause impingement of TMJ spaces and TMD. As more and more information is gathered, it is becoming clear that the physical, emotional, and psychological health of our patients are intimately related to the cranio-mandibular a

Beauty↗
PubMed1995

Non-surgical alternative in the treatment of skeletal Class III problems.

The dental profession is not static, but dynamic. New research findings, along with medical and technological advances, necessitate constant re-examination of treatment philosophies and techniques. What were acceptable treatment techniques in the past may not necessarily be the most effective and best techniques for our patients today. Currently, many practitioners feel that the only treatment for the correction of a skeletal Class III abnormality is via orthognathic surgery in older patients. In some cases it may be the only treatment option. But in most cases today, there are more conservative, non-surgical treatment alternatives in correcting Class III problems in younger aged children. In treating facial-skeletal problems, it must be emphasized that the human face is a biological masterpiece of form and function. Its importance has been documented in arts and sciences since the beginning of modern civilization. It is important enough so that individuals who are blessed with attractive features are afforded greater opportunities in our society. Attractive faces are associated with intelligence, honesty and good work ethics. With the advent of orthognathic surgery, functional appliance, functional regulator, and myofunctional therapy, the dental profession has the capability of leveling out the playing field for many individuals in our society. It does so by being able to correct problems closely associated with the human psyche--the human face. The ability to change facial features brings tremendous prestige to our profession. Along with this prestige comes greater responsibility. Our ability to change facial features entails greater understanding of facial balance and harmony. Ricketts states that the face must conform to stringent proportions known as the "divine proportion" in order for it to be esthetically pleasing. Also, our ability to move facial-skeletal structures entails greater understanding of the biomechanics of the human face. Without this knowledge practitioners can cause iatrogenic problems, such as temporomandibular disorders. Conversely, correcting facial-skeletal abnormalities have been found to alleviate many medical problems, such as chronic headaches, neck-back-shoulder pain, respiratory disorders, auditory disorders, etc. As more and more information is gathered, it is becoming clear that the physical, emotional and psychological health of a human being is intimately related to craniomandibular anatomy. In fact, the jaw and dental structures (with the exception of the tooth enamel) is formed from the neural crest cells along with the endocrine system, while the central nervous system is formed from the neural tube. The entire nervous system, the endocrine system and the dental system are formed from common tissue origin. This can explain why many facial-skeletal corrections are often accompanied by alleviation of many medical and physiological problems. These are exciting times for our profession. However, if we wish to address the needs of our patients well into the next century, we must continue to seek greater and greater knowledge in the area of the craniomandibular anatomy relative to the rest of the human body. It has much to do with facial esthetics, physiologic and psychologic harmony, and TMJ health. This knowledge will enable our profession to have the power to change human lives in a very positive way. As doctors, there can be no greater personal and professional satisfaction than to realize that, through our professional intervention, we are able to offer our patients the possibility of achieving greater happiness and quality of life.

Cephalometry↗
PubMed1994

Spontaneous correction of long face tendency--a case report.

Many studies have described long face syndrome as being caused by excessive lower facial height. No other literature, apparently, has described the possibility that this vertical imbalance may also be caused by the underdevelopment of the upper portion of the face. The unexpected and unplanned treatment result from this case report clearly shows the possibility that vertical imbalances can also be the result of short upper facial height. This finding may have clinical and physiological ramifications that need further studies.

Adolescent↗
PubMed1993

Facial esthetics--presentation of an ideal face.

There appears to be a general consensus that a universal standard for facial esthetics is impossible due to so many variables that must be considered such as race, age, sex, cultural biases, etc. It is my conviction that a universal standard is not only possible, but highly desirable. In order for this to occur, it must be fully understood that facial esthetics is directly related to ideal facial proportions. Treating toward ideal facial proportions is desirable because it in turn appears to be directly related to ideal physiologic harmony. By clearly illustrating those faces considered to be ideal, it is hoped that this article will offer practitioners a greater understanding of this most important subject matter. Visual, cephalometric and physiologic criteria were used to assess facial esthetics.

Adult↗
PubMedDate not supplied

Functional appliances and functional regulators.

Patients with dental malocclusions and facial-skeletal problems often have unattractive facial and dental features that can create social and emotional problems such as lack of self-confidence and poor self-image. In addition, a number of medical problems are associated with facial-skeletal disharmonies. Here, we review three functional appliances--the Schwarz, Bionator, and Frankel III --that can be used to correct dental and facial-skeletal problems.

Cephalometry↗
PubMedDate not supplied

Skeletal type III abnormalities--a simplified treatment.

There are various forms of skeletal Type III abnormalities. The most common occurs when the maxilla is underdeveloped and the mandible grows ahead of it. In severe cases, skeletal Type III abnormalities are considered the most unattractive as well as being one of the most difficult to treat in orthodontics. A simplified approach is presented for using the Frankel III appliance to treat skeletal Type III abnormalities in young children.

Child↗
PubMedDate not supplied

Skeletal classification of maxillary and mandibular malpositions.

Criteria used to establish ideal skeletal position of the maxilla and mandible relative to the cranial base is exacting. It must first enhance facial esthetics and facial profile. Secondly, it must improve TMJ health; and finally, it must improve physiologic harmony. Physiologic harmony include alleviation of many medical symptoms such as migraine headaches, neck-shoulder-back pain, myalgia, mouth breathing, otitis media, ringing in the ear, dizziness, vertigo, etc. The Skeletal Archial Analysis is a powerful diagnostic aid. Once the skeletal landmarks are learned, it takes clinicians less than 5 minutes to trace and diagnose. This is because it uses visual references rather than columns of angles and linear measurements. How powerful and accurate is this analysis? If done correctly, patients treated to their anterior arc and correct vertical arc will often times achieve significant facial esthetics, TMJ health, and physiologic harmony. Both the Skeletal Archial Analysis and the Skeletal Classification System indicate whether the disharmony is in the maxilla, mandible, or both. They clearly show in which direction these skeletal structures must be moved to enhance facial appearance and health. In all cases, the direction is to move these structures as close to skeletal Type I, Normal, as physiologically possible. Figure 8 shows a 21-year-old female individual with this skeletal classification. She has ideal maxillary and mandibular A-P position and ideal lower facial height. As can be seen, she has an attractive facial profile and she has no clinical symptoms of temporomandibular disorder or other medical problems. Conversely, patients with facial disharmony often seem to have various medical problems, including premenstrual syndrome and infertility. Once clinicians become adept at using the Skeletal Archial Analysis, they will begin to see many more types of facial disharmonies than previously thought. It then becomes a verbal challenge to accurately describe the multitude of different types of skeletal malpositions. In light of this, it is important that a universal Skeletal Classification System be established to promote better understanding in the diagnosis and treatment of facial-skeletal problems.

Adolescent↗