Parathyroid Hormone from Gene to Protein Part II
Structure of the PTH mRNA
The 5’ Untranslated Region The 5’ untranslated sequence of the longer forms of the human and bovine mRNAs and rat PTH mRNA contains about 120 nucleotides, and the shorter bovine and human cDNAs contain about 100 nucleotides in the 5’ noncoding region. The average length of the 5' UTR in eukaryotic mRNAs is 80-120 nucleotides. As a result, the m7G cap at the 5’ terminus of the mRNA is a considerable distance from the initiator codon. Parathyroid Hormone from Gene to Protein Part I
Abstract
The biosynthetic pathway of parathyroid hormone (PTH) has been studied from gene expression to PTH intracellular processing. The processing of PTH has been described and involves the synthesis of an initial translational product, preProPTH, and two proteolytic cleavages that in turn produce ProPTH and PTH. The genes and cDNAs from ten different species have been cloned, sequenced and characterized. This chapter will summarize the molecular biology of PTH, from the gene to the mRNA, the initial translational product, preProPTH and the processed mature secreted form of PTH. Development of Parathyroid Glands
The parathyroid glands (PG) are the main source for circulating parathyroid hormone (PTH), a hormone that is essential for the regulation of calcium and phosphate metabolism. The PGs develop during embryogenesis from the pharyngeal pouches with contributions from endodermal and neural crest cells. A few genes have been attributed to the formation, migration and differentiation of the PG anlage. In studies mostly done in genetically manipulated mice it could be demonstrated that Rae28, Hoxa3, Pax1, Pax9 and Gcm2 are essential for proper PG formation. Recently, candidate genes involved in the DiGeorge syndrome have been identified as well. Thorax Part II
Interior of the chambers of the heart
The right atrium The right atrium has a smooth and a rough part which are separated by a vertical ridge, the crista terminalis, extending between the superior and inferior venae cavae which bring systemic venous blood into the smooth part of the atrium. The coronary sinus opens anterior to the opening of the inferior vena cava. Developmentally the smooth part of the atrium is derived from the sinus venosus of the primitive cardiac tube and the rough part which has muscular ridges known as musculae pectinatae from the primitive atrium. The fossa ovalis, an oval depression on the interatrial wall, is the remnant of the foramen ovale in the fetus. Thorax Part I
THE THORACIC CAGE AND THE INTERCOSTAL SPACE
The bony thoracic cage is formed by the 12 thoracic vertebrae at the back, the sternum in front and 12 pairs of ribs in between. The upper seven pairs of ribs articulate anteriorly direct with the sternum through their respective costal cartilages. The costal cartilage of ribs 8, 9 and 10 articulates with that of the rib above. These ribs with the xiphisternum form the lower costal margin. The lowermost point of the thoracic cage is the tenth costal cartilage. Procedures Assays and Normal Values
Taking Blood Samples
This means that blood should always be drawn at about the same time of day and after at least eight hours of fasting, since both circadian rhythm and nutritional status can affect the findings. If strictly comparable values are required, there should also be half an hour of bed rest before the sample is drawn, but this is only practicable in a hospital setting. In other settings (i.e., outpatient clinics), bringing portable instruments to the relaxed, seated patient works well. A sample of capillary blood may be taken when there are no further tests thatwould require venous access for a larger sample volume. Awellperfused fingertip or an earlobe is ideal; in newborns or young infants, the heel is also a good site. If the circulation is poor, the blood flow can be increased by warming the extremity by immersing it in warm water. Immunopathogenesis of HIV Infection
INTRODUCTION
AIDS was recognized in the United States in 1981, when scientists at the Centers for Disease Control and Prevention (CDC) noted a cluster of cases of Pneumocystis carinii pneumonia and Kaposi’s sarcoma in homosexual men in New York City and Los Angeles. HIV was isolated in 1983 and was demonstrated to be the agent of AIDS in 1984. HIV is a retrovirus of the lentivirus family, which !include!s the human lymphotropic viruses (human T-cell lymphoma virus [HTLV]-I and II) and HIV-1 and -2. HIV-2 infection is largely confined to West Africa. HIV-1 is responsible for the world AIDS pandemic, which is now the number one cause of death owing to infectious disease in the world. Currently, 34 million people are estimated to be infected with HIV-1, and 14 million have died from AIDS. Back and Nervous System
VERTEBRAL COLUMN
Embryology During the fourth week, sclerotome cells migrate medially to surround the spinal cord and notochord. After proliferation of the caudal portion of the sclerotomes, the vertebrae are formed, each consisting of the caudal part of one sclerotome and the cephalic part of the next. The notochord persists in the areas between the vertebral bodies, forming the nucleus pulposus. The latter, together with surrounding circular fibers of the anulus fibrosis, forms the intervertebral disc. Atrial arrhythmias
In adults a tachycardia is any heart rate greater than 100 beats per minute.
Supraventricular tachycardias may be divided into two distinct groups depending on whether they arise from the atria or the atrioventricular junction. This article will consider those arising from the atria: sinus tachycardia, atrial fibrillation, atrial flutter, and atrial tachycardia. Tachycardias arising from re-entry circuits in the atrioventricular junction will be considered in the next article in the series. Red eye
The “red eye” is one of the most common ophthalmic problems presenting to the general practitioner.
An accurate history is important and should pay particular attention to vision, degree, and type of discomfort and the presence of a discharge. The history, and a good examination, will usually permit the diagnosis to be made without specialist ophthalmic equipment. |
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