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C S Roberts

Publications and source records attributed to C S Roberts.

At least 91 records · Page 5Linked to original sources
PubMed1986

Kinetic analysis of the triggered exocytosis/endocytosis secretory cycle in cultured bovine adrenal medullary cells.

Cultured bovine adrenal medullary cells are an excellent preparation for quantitative analysis of the secretory exocytosis/endocytosis cycle. In this paper we examine the kinetics of endocytosis after stimulation of secretion. Membrane retrieval was monitored by uptake of the fluid phase marker horseradish peroxidase. Horseradish peroxidase was found to be suitable because it can be washed off completely, assayed quantitatively, and its uptake increases linearly with concentration. If this marker is present during stimulation, the rate of uptake is initially slower than catecholamine secretion but faster at a later time, suggesting that the formation of endocytotic vesicles follows exocytosis. To monitor the time-dependent concentration of secretory vesicle-plasma membrane fusion product (omega-profiles), secretion was halted at various time intervals after stimulation and the excess membrane allowed to transform into endocytotic vesicles in the presence of horseradish peroxidase. By adding horseradish peroxidase at various times after inhibition of secretion, the time course of membrane retrieval could be measured directly. All our results are consistent with a two-step kinetic model in which exocytosis and membrane retrieval are consecutive events. The estimated volumes of the compartments involved are roughly equal. The rate of endocytosis is strongly temperature-dependent but unaffected by extracellular calcium in the range of 10(-8)-2.5 X 10(-3) M, suggesting that calcium is not required at the site of endocytotic membrane fusion. Membrane retrieval is also unaffected by Lanthanum (1 mM) but is slowed by hypertonic media.

Adrenal Medulla↗
PubMed1986

Defining the family in family medicine: implications for social workers.

Physicians and social workers in the family medicine setting anticipate that a substantial portion of their practice will consist of intact, nuclear families. This study examined that expectation by collecting data on age, sex, and marital status of the patients in a family practice residency. Two separate methods of sampling the practice were used, and each resulted in a different picture of the practice. A dramatic finding was that 9% of the patients with active medical charts consumed 45% of the medical care. Women and patients over age 40 were overrepresented in the sample of frequent-user patients. Social work implications are presented.

Adolescent↗
PubMed1985

Contraceptive behavior in college-age males related to Fishbein model.

Fishbein's Belief-Attitude-Intention-Behavior model states that behavior is predicted on intention, intention is predicated on attitudes, and attitudes are predicated on beliefs. Path analysis was used to test the model with respect to the contraceptive behaviors of 54 college males. In spite of the heterogeneity of the sample, the data supported the model, suggesting that nursing interventions may need to be directed toward beliefs rather than behaviors.

Adolescent↗
PubMed1984

Early and late remodeling of the left ventricle after acute myocardial infarction.

This report describes early and later structural changes that occur in infarcted and noninfarcted ventricular myocardium after coronary arterial ligation in the rat. Histologic analysis was conducted of hearts subjected to 2 days (n = 22) and 21 days (n = 22) of coronary arterial occlusion, or to a sham operation (n = 22). Lengths, circumferences and areas of the left ventricle, of infarcted myocardium and of noninfarcted myocardium were obtained by videoplanimetry. Although the left ventricular (LV) endocardial circumference was similarly increased at 2 days (19 +/- 3 mm, mean +/- standard deviation) and 21 days (20 +/- 3 mm) compared with shams (13 +/- 3 mm, p less than 0.01), LV epicardial circumference was similar in all 3 groups (30 +/- 2, 31 +/- 2 and 31 +/- 2 mm, respectively). The area enclosed by the endocardial circumference was significantly (p less than 0.01) increased at 2 days (20 +/- 6 mm2) and 21 days (22 +/- 6 mm2) compared with shams (7 +/- 4 mm2); however, the area enclosed by the epicardial circumference was similar at 2 days, 21 days and in shams (70 +/- 9, 72 +/- 9 and 73 +/- 10 mm2, respectively). The total LV tissue area was similar at 2 and 21 days, but was less than that in shams (p less than 0.01). Between 2 and 21 days, 3 measures of infarcted myocardium significantly decreased: its segments of endocardial and epicardial circumference, its circumference and its area.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1983

Topographic changes in the left ventricle after experimentally induced myocardial infarction in the rat.

The factors that determine the thickness of transmural myocardial infarcts are unknown. Therefore, the relation between the size and thickness of transmural infarcts in 67 rats 21 days after occlusion of the left main coronary artery was studied. On examination of histologic sections, infarct size was determined by planimetry and expressed as a percentage of the left ventricular (LV) area, and thickness was expressed as a percentage of noninfarcted ventricular septal wall thickness. The circumferential length of the infarcted ventricle was measured in millimeters, as well as the circumferential length of the noninfarcted ventricular septum. Septal wall thickness was similar in rats with transmural infarcts and in sham-operated rats. No significant correlation was observed between infarct size and thickness (r = 0.10) or between circumferential length of the infarct and infarct thickness (r = 0.17). However, large (greater than or equal to 20% of the left ventricle, n = 37) and small (less than 20% of the left ventricle, n = 30) infarcts which were similarly thin (37 +/- 1% and 34 +/- 2% of septal wall thickness, respectively) affected LV topography differently. Large infarcts resulted in a 23% greater loss of myocardium (p less than 0.001), greater expansion of the LV cavity (18 +/- 9 mm2 compared with 14 +/- 1 mm2 in small infarcts, p less than 0.005), and lengthening of the septal wall (7.2 +/- 1.1 mm and 6.7 +/- 1.0 mm in large and small infarcts, respectively [p less than 0.05], and 6.3 +/- 0.1 mm in shams). Increase in cavity area and septal length in infarcted ventricles suggested a volume overload hypertrophy, which at 3 weeks was nonetheless inadequate to provide as much normal muscle as was present in sham-operated rats. In an additional 9 rats with subendocardial infarctions (involving less than 75% of the LV wall from endocardium to epicardium), the LV walls were thicker (94 +/- 5% of septal wall thickness, compared with 35 +/- 1% for transmural infarcts, p less than 0.001) and an inverse correlation was observed between infarct size and thickness. In conclusion, neither the size of a transmural infarct in rat nor the circumferential length of infarction determines the thickness of the infarct; however, infarct size does affect LV topography by increasing LV cavity area and the length of the noninfarcted septal wall. Subendocardial infarcts result in less myocardial thinning than do transmural infarcts.

Animals↗
PubMedDate not supplied

Relation of early mononuclear and polymorphonuclear cell infiltration to late scar thickness after experimentally induced myocardial infarction in the rat.

This report describes the relationship between the intensity of early inflammation after acute myocardial infarction and the later thickness of the left ventricular (LV) scar. Histologic sections of hearts from methylprednisolone-treated (MP), cobra venom factor-treated (CVF), and untreated control rats that had been subjected to either 2 or 21 days of coronary artery occlusion were studied. In the rats examined at 2 days (n = 20 for MP, n = 16 for CVF, and n = 20 for controls), a semiquantitative inflammation score (1-4) was attributed to each infarct. Mononuclear (MN) cells were counted in 4 oil-immersion fields per section and polymorphonuclear (PMN) cells in 9 oil-immersion fields per section. In the rats examined at 21 days (n = 22 for MP, n = 22 for CVF, and n = 26 for controls), the thickness of the LV scar was measured every 1.6 mm along its circumference. Inflammation scores at 2 days were 3.5 +/- .6 for controls, 1.5 +/- .5 for MP, and 2.9 +/- .8 for CVF (p less than .05 among groups). The MN cells counted were 73 +/- 7 for controls, 47 +/- 5 for MP, and 61 +/- 9 for CVF (p less than .05 among groups). There was no difference in PMN infiltrate among groups. Scar thickness at 21 days were .9 +/- .1 mm for controls, .7 +/- .1 mm for MP, and .9 +/- .1 mm for CVF (MP compared to CVF and controls, p less than .01).(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗