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J Starr

Publications and source records attributed to J Starr.

At least 37 records · Page 2Linked to original sources
PubMed1987

Historical perspective on asbestos: policies and protective measures in World War II shipbuilding.

Current public health consequences of poorly controlled utilization of asbestos in the past can be traced back, in part, to decisions made 45 or more years ago. This paper focuses on the extensive use of asbestos as a fireproofing and insulating material in shipbuilding in the 1940s, when World War II industrial expansion brought about a hitherto unprecedented rise in the amount of asbestos utilized. Twenty years after World War II, asbestos diseases began to manifest themselves, affecting thousands of shipyard workers as well as other workers who had been exposed in the 1940s and during the postwar period. By scrutinizing past actions, the paper argues that social forces, as well as science and technology, affect the setting of priorities and the determination of policy regarding needed but hazardous materials.

Asbestos↗
PubMed1987

Measurement of regional cerebral blood flow and somatosensory evoked potentials in a canine model of hemispheric ischemia.

Regional cerebral blood flow (rCBF) was studied using the radiolabeled microsphere technique in a canine model of hemispheric ischemia that others have previously examined morphologically with carbon perfusion. It was our goal to ascertain whether this ischemic model, which involves easily accessible occlusions of the ipsilateral circle of Willis, could produce reproducible and significant reduction of hemispheric cerebral blood flow. Seven animals underwent the surgical procedure with measurements of rCBF at base line, after arterial microdissection and brain retraction only, and finally after creation of the lesion. Simultaneous somatosensory evoked potential recordings were also obtained. Bilateral symmetrical flow decreases were referable to anesthetic normalization and maintenance alone before creation of the lesion. The arterial occlusions, however, produced further significant decreases in flow on the ipsilateral side only, sparing all contralateral structures and sparing the brain stem and cerebellum bilaterally. Evoked responses, which had shown no changes in latency or amplitude after dissection and retraction procedures, were completely abolished 15 minutes after the arterial occlusion. Control animals that underwent surgical positioning and anesthesia alone did not show concomitant decreases is rCBF. This model of open craniotomy and direct vascular occlusion is suitable for studies of cerebral ischemia where the therapeutic intervention proposed (such as cerebral revascularization) involves similar surgical manipulations. By this method, a standard and reproducible ischemic lesion is achieved through the surgical field without the need for exposure of the basilar artery.

Animals↗
PubMed1986

Resistance to paraquat in a mammalian cell line.

Paraquat-resistant variants were isolated in Chinese hamster ovary (CHO) cells by stepwise increases in paraquat concentrations. Three series of selective experiments gave variants which appeared to be using one or several different mechanisms of resistance. In all variants tested (PQ-1, PQ-2, PQ-3, PQ-2X and PQ-3X of series 1), radioactively labeled paraquat was taken up by the cells. These variants exhibited no unusual resistance to either oxygen or radiation, nor were increases found in the activities of free-radical scavenging enzymes. They had extra DNA (3-12%) and an unusual acrocentric marker chromosome which was common to all of the variants but never observed in the parental cells. Double minutes were observed in 29% of metaphases of the PQ-3 variant. One of the resistant lines exhibited evidence of an intrinsic chromosomal instability, a phenotype that could conceivably facilitate gene amplification. Selection series 2 and 3 were designed to further evaluate gene amplification as a mechanism of resistance. These variants exhibited high frequencies (40-100%) of tetraploidy or hypotetraploidy with loss of chromosomes and varying frequencies of double minutes (10-75% of metaphases). In two of the variants the same marker chromosome which was observed in the series 1 variants was seen. Two other lines exhibited a variant of this marker, incorporating it into a metacentric chromosome. It may be that gene amplification facilitates resistance to paraquat and that both stable and unstable methods of amplifying genes are used.

Animals↗
PubMed1986

Human platelet alpha-adrenergic receptors and responses during pregnancy: no change except that with differing hematocrit.

The possibility that platelet aggregation is altered during pregnancy is controversial. We tested for alterations of alpha-adrenergic receptor-induced platelet function during pregnancy compared to that in the early phase of the menstrual cycle. We found no change in alpha-adrenergic receptor concentration or in affinity of the receptor for epinephrine. The potency and sensitivity of epinephrine to inhibit adenylate cyclase, a response mediated by alpha 2-adrenergic receptors, was not different in platelets from the two groups of subjects. The ability of epinephrine to potentiate aggregation by adenosine diphosphate was significantly increased during pregnancy; however, this was an artifact introduced by lower hematocrits during pregnancy that resulted in an increased citrate concentration in the preparations of platelet-rich plasma from these women. The difference was eliminated by normalization of citrate concentration. Thus effects of alpha-adrenergic receptors on platelet function are not different during pregnancy. It is mandatory to recognize artifactual effects of differing hematocrits on platelet aggregation studied in vitro.

Adenylyl Cyclase Inhibitors↗
PubMed1986

The antinociceptive action of some beta-adrenoceptor agonists in mice.

The antinociceptive actions of several beta-adrenoceptor agonist drugs have been studied in mice by use of a modified abdominal constriction test. All the drugs studied had high antinociceptive activity, with ID50 values in the nmol kg-1 range. (-)-Isoprenaline and (+/-)-isoxsuprine were the most potent, being about ten times more active than salbutamol, the least potent drug studied. All these drugs produced their action very rapidly and appear to act within the peritoneum. (-)-Isoprenaline had about six times the potency of the (+)-isomer. (+/-)-Propranolol caused rightward shifts, usually parallel, of the dose-response curves for (-)-isoprenaline. (+)-Propranolol was more than ten times less potent than the racemic drug. Practolol also caused parallel, rightward shifts of the dose-response curves for (-)-isoprenaline, and was about twice as potent as (+/-)-propranolol, whether given by subcutaneous or intraperitoneal injection. Atenolol and ICI 118551 had intermediate potencies. Propranolol, practolol and ICI 118551 were all considerably less potent in antagonizing the antinociceptive actions of fenoterol and RO363, than (-)-isoprenaline. None of these antagonist drugs showed more than a slight ability to discriminate between the beta 1- and beta 2-selective agonist drugs. No evidence was found for the involvement of opioid, dopamine, or alpha-adrenoceptors in the antinociceptive action of the beta-adrenoceptor agonist drugs. Evidence for and against the involvement of beta-adrenoceptors is discussed, and it is concluded that if these receptors do mediate the antinociceptive action they appear to be atypical.

Adrenergic beta-Agonists↗
PubMed1986

A study among dietitians and adult members of their households of the practicalities and implications of following proposed dietary guidelines for the UK. British Dietetic Association Community Nutrition Group Nutrition Guidelines Project.

Four hundred and seventy-two dietitians and adult members of their households took part in a research project carried out by the British Dietetic Association's Community Nutrition Group. They first kept 7-day weighed food diaries of their normal eating habits. These were analysed and compared with the dietary goals set by the study. The participants who did not 'achieve' the goals were then asked to keep a second 7-day weighted diary while trying to eat a diet conforming to the dietary goals which were based on the NACNE long-term guidelines; 351 people did so. Mean nutrient intakes on first diaries were within the short-term goals recommended by the NACNE report except for fat and when participants were consciously altering their diets they achieved all the long-term goals. Average intakes were: fat, 30 per cent of energy; saturated fat; 10 per cent of energy; added sugar, 7 per cent of energy; alcohol, 4 per cent of energy; dietary fibre, 38 g; and sodium 2690 mg. The goals for total fat and saturated fat were the hardest to achieve. There was a significant drop in energy intake between the first and second diaries from 7.99 (s.d. +/- 1.54) MJ to 7.05 (s.d. +/- 1.25) for women (P less than 0.001) and 10.92 (+/- s.d. 1.76) MJ to 9.42 (s.d. +/- 1.54) MJ for men (P less than 0.001). The percentage of energy from fat and added sugars and the amount of sodium and fibre in the diet tended to increase with energy intake. None of the men in the highest energy band (12.56 MJ) achieved the goal for sodium. The diet which achieved the goals was more nutrient-dense than the diet which did not with significant increases in 14 vitamins and minerals despite the drop in energy. Participants experienced some problems in achieving the goals but not as many as had been anticipated.

Adult↗
PubMed1984

Acetylcholine "tightens" peripheral capillaries independently of pressure effects.

We previously showed that acetylcholine (ACh) infused into the abdominal aorta of dogs at a rate of 127 micrograms ACh min-1 caused an increase in lumbar trunk lymph flow (L) of 35% while protein clearance into the lymph (LR) remained unchanged. These effects were accounted for by a 34% increase in reflection coefficient (sigma) and a 54% increase in permeability-surface area product (PS). Since arterial pressure decreased, it was possible that the decrease in arterial pressure was responsible for observed changes. The current study was undertaken to test this possibility. Seven female dogs were anesthetized and prepared in the same manner as the previous study except that control abdominal aortic pressure was reduced with an aortic balloon to a mean of 81 mmHg. As ACh was infused, the balloon pressure was released so that the mean pressure for all dogs rose to 96 mmHg. The findings indicated that ACh produced a 24% increase in L (P less than .004) while LR was unaffected. In a similar fashion to the results of the previous study, sigma increased 43% (P less than .0000) and PS rose 51% (P less than 008). These results clearly dissociate the effects of acetylcholine on permeability from any effects on arterial pressure and indicate a more direct effect of acetylcholine on the permeable segment. The results also suggest a general response of the capillary or postcapillary venule to vasodilation which restricts accession of protein into the interstitium during unloading of the vasculature by the process of edema formation.

Acetylcholine↗
PubMed1984

Effects of acetylcholine on peripheral vascular protein permeability.

It is common practice to assume that when a vasodilator such as acetylcholine (ACh) produces a decrease in lymph/plasma protein ratio (R) while lymph flow (L) increases, permeability-surface area product (PS) and reflection coefficient (sigma) are unchanged. However, if PS and sigma are unaltered by alpha stimulus that increases L, then alpha decreased R can be associated with an elevated, constant, or reduced sigma and PS. To test what the effect of ACh, alpha "pure vasodilator," is in the hindquarters of the anesthetized dog, we infused 127 micrograms ACh min-1 into the abdominal aorta of 6 female mongrel dogs while collecting lumbar trunk lymph in order to measure L and R. sigma and PS were computed by the method of fluctuations over 15 min collections. The rise or decrease in LR was well correlated with L (r = .951) as expected, but was much less than predicted if sigma and PS had been unaltered during ACh infusion. Computations indicated that sigma rose with ACh approximately 34% (P = .0007) and PS rose 54% (P = .042) above control. This can be interpreted as a decrease in the radial dimension of the protein transport channels and an increase in the number of such channels per unit area, with both changes induced either by altered capillary anatomy or redistribution in a heteroporous system. Such an analysis seems compatible with the results of other studies in a variety of tissues which indicate that ACh tightens membranes either directly or through an effect mediated by reduced arterial pressure.

Acetylcholine↗
PubMed1983

Studies on the antinociceptive action of alpha-agonist drugs and their interactions with opioid mechanisms.

1 A modified abdominal constriction test, whereby the drugs used are injected intraperitoneally when the writhing response is maximal, has been used to study the antinociceptive activity of various sympathomimetic drugs. Of those tested, clonidine was the most potent, with an ID(50) value in the nanomolar range. (-)-Isoprenaline, (-)-adrenaline and (-)-noradrenaline were only a little less potent. Phenylephrine, the least potent, had only about one-sixtieth of the activity of clonidine.2 The antinociceptive action appears to occur within the peritoneum, since it was apparent almost immediately after the drugs were injected and was produced by doses far smaller than were effective by the subcutaneous route.3 alpha-Adrenoceptors appear to be involved in the reaction, since noradrenaline showed stereospecificity, and the alpha-adrenoceptor antagonists phentolamine and piperoxan both shifted the dose-response curves of the alpha-adrenoceptor agonist drugs to the right, usually parallel to the control curves.4 The high antinociceptive potency of clonidine and oxymetazoline, indicate the importance of alpha(2)-adrenoceptors and this was supported by the finding that piperoxan was a more effective antagonist than phentolamine. The moderate potency of phenylephrine suggests that alpha(1)-adrenoceptors may also be involved, although the selective alpha(1)-antagonist, prazosin, did not antagonize noradrenaline and had antinociceptive activity of its own.5 beta-Adrenoceptors also appear to be involved in the antinociceptive response, since propranalol antagonized the effect of isoprenaline, but not that of clonidine.6 Piperoxan was a very effective antagonist of morphine, while phentolamine had a weaker action. Naloxone had little action against the alpha-adrenoceptor agonists.7 Mice pretreated with clonidine or oxymetazoline but not noradrenaline showed a very great cross-tolerance to morphine. Morphine pretreatment caused marked desensitization of itself, but little cross-tolerance to clonidine or oxymetazoline.8 It is suggested that sensory nerves in the mouse peritoneum have alpha(2)- and beta-adrenoceptors on their terminals, and possibly alpha(1)-receptors also. It is possible that when activated by the appropriate agonists they depress the generation of pain impulses. There is an interaction between the alpha-adrenoceptors and opioid receptors in the mouse peritoneum.

Adrenergic alpha-Agonists↗
PubMed1982

"Lying" in the pigeon.

Two pigeons were taught to use symbols to communicate information about hidden colors to each other. When reporting red was more generously reinforced than reporting yellow or green, both birds passed through a period in which they "lied" by reporting another color as red.

Animals↗
PubMed1981

Evidence for an action of morphine and the enkephalins on sensory nerve endings in the mouse peritoneum.

1 A modification of the abdominal constriction test in mice has been developed, and used to study the antinociceptive effects of morphine and several related drugs. In most experiments, acetic acid (0.6% i.p.) was used as the nociceptive stimulus, and in a few cases, acetylcholine (3.2 mg/kg i.p.) was used. When the abdominal constriction response had reached a maximum, the drugs under test were given intraperitoneally, and their ability to decrease the number of abdominal constrictions was determined, beginning immediately after its administration. The aim of this study was to investigate the possibility that morphine and its congeners may produce an antinociceptive effect by an action within the peritoneum.2 It was found that morphine was an extremely potent antinociceptive agent in this modified test, with an ID(50) of 5.4 x 10(-9) mol/kg (1.54 mug/kg). Codeine and pentazocine were about 40 times less active and oxymorphine was about twice as potent as morphine. Met- and Leu-enkephalin were also potent but their action diminished very rapidly with time. Ketocyclazocine was the most potent substance tested, and had an ID(50) value of 1.26 x 10(-10) mol/kg (0.036 mug/kg). All the drugs tested produced their maximal effect within 1 or 2 min of administration.3 Pretreatment of the mice with naloxone caused a dose-dependent shift to the right of the dose-response curve to morphine. The pAx plot was linear over part of the range, with a slope of -1.02 and the ;apparent pA(2)' value was 6.14. Naloxone was much less effective in antagonizing Met-enkephalin, and caused a slight potentiation of ketocyclazocine and pentazocine and of cocaine, which was used for comparison.4 Pretreatment of mice with morphine, 3 h earlier, caused a marked tolerance to a subsequent dose of morphine, and a potentiation of the antagonist potency of naloxone. However, there was little cross-tolerance between morphine and Leu-enkephalin.5 It is concluded that morphine and its congeners can produce an antinociceptive effect by an action within the mouse peritoneum, presumably by interacting with one or more types of opioid receptors which may be situated on sensory nerve endings.

Analgesics↗
PubMed1976

The vectorcardiogram in right bundle branch block: correlation with cardiac failure and pulmonary disease.

Frank vectorcardiograms (VCG) and clinical records of 243 patients with right bundle branch block (RBBB) were compared. The patients were classified into three categories on the basis of VCG criteria. The first category included 100 patients with a normal frontal axis, and the second category included 44 patients with concomitant left anterior hemiblock. The third category consisted of 99 patients with RBBB and myocardial infarction. The VCGs were classified into three types accoriding to the QRS configuration in the transverse plane. In type I the initial forces were anterior and counterclockwise and the afferent limb crossed the midline posterior to E point; in type II the initial forces were anterior and counterclockwise and the afferent limb crossed the midline posterior to E point; in type II the initial forces were anterior and counterclockwise and the afferent limb crossed the midline anterior to or through E point; and in type III the entire transverse loop was clockwise and anterior to E point. The patients were further classified according to the presence or absence of cardic failure or severe pulmonary disease. In patients with RBBB and a normal axis, cardiac failure or severe pulmonary disease was found in five of 49 patients wtih type I, 17 of 31 with type II, and 18 of 20 with type III pattern. In patients with RBBB and left anterior hemiblock, significant disease was found in one of 17 with type I, five of 16 with type II, and eight of 11 with type III pattern. These data show that, in patients with RBBB, the position of the afferent limb in the transverse plane can be used to predict cardiac failure or severe pulmonary disease.

Adolescent↗
PubMed1975

Insulin and proinsulin release during calcium infusion in a patient with islet-cell tumor.

The infusion of calcium results in the release of gastrin, calcitonin, and serotonin from certain nonbeta islet cell tumors of the pancreas, medullary carcinomas of the thyroid, and carcinoid tumors, respectively. In this study, intravenous infusion of either calcium chloride or calcium aluconate in a patient with an islet-cell carcinoma resulted in a simultaneous rise in plasma immunoreactive insulin and proinsulin, and concurrent hypoglycemia. After resection of the tumor, calcium infusion caused no change in these parameters. Similarly, calcium infusion caused no change in plasma insulin or glucose in normal volunteers. The response of this tumor suggests that calcium infusion may be a useful provocative test to detect insulin-secreting neoplasia. A derangement of the stimulus-secretion coupling mechanism for insulin in the tumor cells may be responsible for their abnormal sensitivity to calcium ion.

Adenoma, Islet Cell↗