Signal sequences function in protein targeting to and translocation across the endoplasmic reticulum membrane. To investigate the structural requirements for signal sequence function, chimeras of the Escherichia coli LamB signal peptide and prolactin were prepared. The LamB signal peptide was chosen by virtue of the extensive biophysical and biological characterization of its activity. In vitro...

The appearance of newly induced LamB protein at the cell surface of Escherichia coli was followed topographically by immuno-electron microscopy. LamB protein was induced in E. coli wild-type or lac-lamB cells for a short period of time (4 to 6 min), such that the overall level of LamB protein in induced cells was at least twofold higher than that in uninduced cells. Antibodies bound to LamB pro...

a four- year-old moghanian breed ewe was admitted to the large animal veterinary clinic, university of tabriz due to dystocia. during obstetrical examination, it was revealed that the cervix has been closed firmly and vagina protruded about 5 cm through the vulva (vaginal prolaps). based on clinical findings and for saving the dam and lamb(s), the cesarean section was done. a normal alive femal...

Border Disease (BD) is a condition of newborn sheep that results from congenital infection by a non-cytopathic pestivirus, occurring during the first half of gestation. The variations in expression of the virus directly relate to the age of the fetus at the time of infection. There are four distinct disease syndromes: (1) early embryonic death, (2) abortion and stillbirth, (3) birth of lambs wi...

To test the hypothesis that the rise in arterial pressure occurring with maturation is due to an increase in the vascular responsiveness to angiotensin II, sequential cumulative doses of angiotenmn II were infused intravenously into chronically catheterized newborn lambs maintained on a constant, weight-adjusted sodium intake from birth to 8 weeks of age. Basal mean arterial pressure correlated...

Adenosine is a metabolic vasodilator of the coronary vessels in the adult. Whether it plays a similar role in the regulation of coronary blood flow (CBF) in the newborn is not known. We evaluated changes in adenosine release during periods of decreased oxygen supply (hypoxia) and increased oxygen demand (dobutamine infusions). In anesthetized open-chest lambs (age 1 to 8 days), aortic and coron...

Although the role of PGE2 in maintaining ductus arteriosus (DA) patency is well established, the specific PGE2 receptor subtype(s) (EP) involved have not been clearly identified. We used late gestation fetal and neonatal lambs to study developmental regulation of EP receptors. In the fetal DA, radioligand binding and RT-PCR assays virtually failed to detect EP1 but detected EP2, EP3D, and EP4 r...

Glucocorticoids are administered for preterm labor to improve postnatal adaptation. We assessed the effect of antenatal betamethasone (Beta) treatment on preterm newborn lamb neuroendocrine [catecholamine, arginine vasopressin (AVP)] and endocrine [triiodothyronine (T(3)), ANG II, and atrial natriuretic factor (ANF)] adaptive responses following delivery and a hypoxic challenge. Beta treatment ...

• Within a few days after birth, the pulmonary circulation changes from a high pressure, low flow system to the low pressure, high flow system which persists throughout life. Several factors are potentially important in causing this decrease in pulmonary vascular resistance: 1) The expansion of the fetal lung allows tortuous pulmonary vessels to straighten. 2) Hypoxia, a known pulmonary vasocon...

There is limited information available on which to base decisions regarding red blood cell (RBC) transfusion treatment in anemic newborn infants. Using a conscious newborn lamb model of progressive anemia, we sought to identify accessible metabolic and cardiovascular measures of hypoxia that might provide guidance in the management of anemic infants. We hypothesized that severe phlebotomy-induc...