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Biomedical subjects

K Jordan

Publications and source records attributed to K Jordan.

At least 109 records · Page 6Linked to original sources
PubMed1988

Morphometry of right ventricular papillary muscle in rat during development and regression of hypoxia-induced hypertension.

Morphometric analyses of the right ventricular papillary muscle, as well as measurements of right ventricular pressure and weight, were carried out in the rat during the development and recovery of hypoxic pulmonary hypertension. Animals were divided into hypoxic and normobaric control groups. The hypoxic rats were placed in hypobaric chambers for 1, 2, and 3 wks; and after 3 wks exposure, subgroups of hypoxic rats were allowed to recover in normoxia for 1 to 9 wks. Hematocrit (HCT) and right ventricular systolic pressure (RVSP) were measured prior to sacrifice. The heart was perfused, and the right ventricle (RV) was separated from the left ventricle and septum (LV+S) and weighed. The papillary muscles were dissected and processed for ultrastructural morphometry. Results showed that HCT, RVSP, and RV weight increased in the rats during the hypoxic exposure and then gradually returned to control levels after 3 to 4 wks of normobaric recovery. The papillary muscle of the hypoxic rats showed increased volume density of interstitium, increased diameter and cross sectional area of the cardiac myocytes, reduced volume density of mitochondria, and reduced mitochondria to myofilament ratio. During normoxic recovery, these morphometric indices returned toward control values at various periods of time ranging from less than 3 wks to 9 wks. The results indicate that the adaptive ultrastructural changes of the papillary muscle in RV hypertrophy paralleled the RVSP changes, and also demonstrate the reversibility of these changes in ambient oxygen.

Animals↗
PubMed1988

Cardiac nuclear medicine tomographic systems.

There are two competitive measuring techniques in emission tomography: SPECT and PET. The superiority of PET is founded not only on using physiological radionuclides and tracers such as carbon 11, oxygen 15, and nitrogen 13, but also on achieving a physical performance far in excess of that of SPECT. Considering the demands of cardiac studies, the performance of both methods is analyzed and compared and the inherent limitations are stated.

Heart↗
PubMed1988

Cholinergic supersensitivity of the iris in primary open angle glaucoma. A clinical study.

Twenty patients with untreated primary open angle glaucoma (POAG) were tested for the presence of cholinergic supersensitivity of the iris using a 0.1% solution of pilocarpine. Nineteen patients had a significant miotic response compared to six of a group of twenty control subjects. We believe that an ocular parasympathetic neuropathy may be an important factor in promoting or perpetuating elevated intra ocular pressure in POAG. The mechanism of this is suggested and several possible areas of further study discussed.

Aged↗
PubMed1988

The Molteno implant in intractable glaucoma.

The long term results in ninety-six cases of intractable glaucoma managed with the Molteno seton are presented. Over 50% of cases achieved satisfactory intraocular pressure control and visual stabilisation.

Adolescent↗
PubMed1988

Comparative tumor-initiating activity of methylene-bridged and bay-region methylated derivatives of benz[a]anthracene and chrysene.

Polycyclic aromatic hydrocarbons (PAHs) with a methylene-bridge spanning the bay region are often detected in higher concentrations in the environment than PAHs which have a bay-region methyl substituent. The tumor-initiating activity of methylene-bridged bay-region derivatives of chrysene and benz[a]anthracene was evaluated on the skin of female CD-1 mice. 4,5-Methylenechrysene elicited twice as many tumors as chrysene at each of the doses tested. At total initiation doses of 1.5, 0.5 and 0.15 mumol/mouse 4,5-methylenechrysene gave rise to 8.5, 6.8 and 1.1 tumors/animal respectively. There was a 100% incidence of tumor-bearing mice at the two higher doses and a 65% incidence at the lowest dose. This methylene-bridged hydrocarbon was less tumorigenic than 5-methylchrysene at each dose tested. Animals treated with 1,12-methylenebenz[a]anthracene developed 7.6, 4.9 and 1.6 tumors/animal at total initiating doses of 4.0, 2.0 and 0.5 mumol/mouse. The incidence of tumor-bearing mice was 90% at the higher doses and 75% at the lowest dose tested. 12-Methylbenz[a]anthracene was more tumorigenic than the methylene-bridged derivative at each dose. The keto-derivative of 1,12-methylenebenz[a]anthracene did not display significant (P greater than 0.05) tumor-initiating activity at these dose levels. Results from these bioassays indicate that methylene-bridged bay-region derivatives of chrysene and benz[a]anthracene contribute to the overall genotoxicity of environmentally occurring PAHs.

Animals↗
PubMed1988

Immunolocalization of islet amyloid polypeptide (IAPP) in pancreatic beta cells by means of peroxidase-antiperoxidase (PAP) and protein A-gold techniques.

A novel putative polypeptide hormone identified as islet amyloid polypeptide (IAPP) was recently purified from islet amyloid (IA) of diabetic humans and cats, and also from amyloid of a human insulinoma. Although the function of IAPP is yet unknown, its occurrence in pancreatic endocrine tissue and its partial amino acid sequence identity with calcitonin gene-related peptide (CGRP) suggests an endocrine regulatory effect. In the present investigation, the authors utilized antisera to insulin, glucagon, somatostatin, pancreatic polypeptide, synthetic human CGRP, and a synthetic human IAPP (7-17) undecapeptide to immunohistochemically (PAP technique) document the presence of IAPP immunoreactive cells in the islets of the cat, dog, mouse, and rat, but not in the islets of the horse or calf. In serial sections of islets from these species it was shown that IAPP immunoreactivity occurred in insulin-reactive beta cells. This observation was confirmed immunocytochemically in cat islets by means of protein A-gold probes. With protein A-gold labeling techniques, IAPP immunoreactivity was localized to the outer lucent compartment of the beta cell secretory granule, whereas insulin immunoreactivity was associated with the electron-dense core. These findings provide strong evidence that IAPP or an IAPP precursor is synthesized by beta cells and is stored in beta cell granules for subsequent co-secretion with insulin. The conservation of IAPP in humans and multiple animal species and the localization of IAPP to pancreatic beta cells provide further evidence that IAPP has an important endocrine regulatory function. The propensity of IAPP to polymerize and form IA fibrils in diabetes associated with aging may indicate that IAPP is in some way also linked to the development of Type 2 diabetes.

Amyloid↗
PubMed1987

Cerebral vasoconstriction in toxemia.

Three patients with toxemia developed acute neurologic deterioration postpartum. In all, cerebral angiography revealed widespread arterial vasoconstriction. Cerebral vasoconstriction may be an important cause of neurologic complications in toxemia.

Adult↗
PubMed1986

Responses to partial nasal obstruction in sleeping infants.

Partial nasal obstruction was performed during a morning of quiet sleep (QS: non-REM) and active sleep (AS: REM) at ages 1 week, 2 weeks, 1, 2, 3, 4 and 6 months on 12 normal infants, 15 subsequent siblings of victims of the Sudden Infant Death Syndrome (SIDS) and 12 infants admitted for investigation of infant apnoea ('near-miss' SIDS). In all three groups the numbers failing to arouse after 240 s (FTA-240) in QS were significantly greater than those in AS. After 2 months of age all groups showed a decrease in the number FTA-240 in AS, whereas in QS the number did not change significantly. Subsequent siblings of SIDS had a significantly higher number FTA-240 in QS than controls. There was no significant difference in FTA-240 in QS between controls and infant apnoeas, although there was a trend for this to be higher in subsequent siblings of SIDS than infant apnoeas. It was concluded that arousal from AS is more marked than from QS, that after 2 months of age the ability to arouse from AS increases, and that in relation to SIDS, QS is the sleep state in which the infant is less able to arouse. Furthermore, subsequent siblings of SIDS differ from normal infants in their ability to arouse from QS.

Airway Obstruction↗
PubMed1985

Psychiatric disorders. A rural/urban comparison.

We studied rural/urban differences in the prevalence of nine psychiatric disorders from a community survey (part of the Epidemiologic Catchment Area Program) of 3,921 adults living in the Piedmont of North Carolina. Crude comparisons disclosed that major depressive episodes and drug abuse and/or dependence were more common in the urban area, whereas alcohol abuse/dependence was more common in the rural area. When prevalence for these disorders was stratified for age, sex, race, and education (factors that may confound urban/rural comparisons), a number of significant differences were identified, such as higher prevalence of major depression in female and white subjects and higher prevalence of alcohol abuse/dependence in the less educated subjects. A logistic-regression analysis was used to determine if significant urban/rural differences persisted when these potential confounders were controlled. Major depressive disorders were found to be twice as frequent in the urban area in this controlled analysis.

Adolescent↗
PubMed1985

Optimization of collimators for imaging positron emitters by a gamma camera.

The imaging of positron-emitting isotopes using a gamma camera requires special collimators. A ray-tracing method for simulating the point-spread function of collimators and, therefore, the total gamma camera system is presented. Simulated data obtained by this method showed good agreement with experimental data. Using this method, optimal lead and tungsten collimators for positron emitters were devised; at an object distance of B = 100 mm, these yielded a point-spread function with an FWHMtot = 9.1 mm using an intrinsic resolution of FWHMintr = 8.0 mm.

Electrons↗
PubMed1985

Extragenic revertants of rad50, a yeast mutation causing defects in recombination and repair.

The RAD50 gene in yeast is required for recombination-repair (i.e., the double strand break repair pathway) in mitosis, and for meiotic recombination and sporulation. Both of these processes are complex and seem likely to require a relatively large number of gene products. In order to help define other genes required for recombination and repair processes in yeast, we have isolated extragenic revertants of rad50-4 which restore the ability to grow in the presence of MMS. Evidence from segregation indicates the extragenic revertants fall into at least five loci. Two of them reduce sporulation and spore viability at high temperature; another mutation confers a spontaneous hyperrec phenotype on mitotic cells. Thus, at least three revertants are candidates for mutations which affect recombination functions.

DNA Repair↗