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Biomedical subjects

A Hyman

Publications and source records attributed to A Hyman.

54 records · Page 3Linked to original sources
PubMed1981

Adrenergic mechanisms in canine intralobar pulmonary arteries and veins.

The responses of canine intralobar pulmonary arteries (IPA) and veins (IPV) to transmural nerve stimulation (TNS), and exogenously administered norepinephrine (NE) were studied to evaluate the alpha-adrenergic neuroeffector system in the canine pulmonary vasculature. IPA and IPV elicited contractions in response to both NE (10(-10) to 10(-5) M) and TNS (0.5-32 Hz, 2 ms duration and delay). The equilibrium (steady state) contractile responses of IPA and IPV to TNS were abolished with the adrenergic neuronal blocking agents guanethidine and bretylium and the depolarization blocking agent tetrodotoxin in concentrations which did not affect the responses to NE or KCl. The contractile responses of IPA and IPV to TNS and NE were reduced in a concentration-dependent way, by the alpha-adrenergic receptor-blocking agents phentolamine, tolazoline and clonidine. The contractile responses of IPA and IPV to TNS and NE were enhanced after inhibition of neuronal reuptake of NE (uptake1) with cocaine, as well as after blockade of extraneuronal reuptake of NE (uptake2) with hydrocortisone. Analysis of the equilibrium responses of the IPA and IPV to TNS and NE with an Arunlakshana-Schild plot to define the concentration of alpha 1-receptor antagonists necessary to double the ED50 for TNS and NE (defined as the pA2), demonstrated that the postsynaptic alpha-receptors of IPV differed from that of IPA. These data support the conclusions that IPA and IPV 1) contain a functional adrenergic innervation and neuroeffector system, 2) contract in response to both TNS and NE, 3) demonstrate the presence of mechanisms for both uptake1 and uptake2 of NE, and 4) IPV contain postsynaptic alpha-receptors that may differ from each other.

Animals↗
PubMed1981

Methane deaths? Was it the cause?

In the routine performance of their jobs, three men consecutively descended into an open drainage pit to recover a fallen grate lid. Each man, in turn, was immediately overcome and died within minutes of his descent. Initial analysis of the pit's air indicated a methane level of 15%. Therefore, it was initially assumed that death was attributable to methane poisoning. Postmortem analysis of the victims' tissues, however, yielded methane levels in only faint trace quantities (0-100 mcg/100 g range). Analysis of air samples taken at various pit levels revealed that as one descended, there was a decrease in oxygen levels, from 20% at the top to 3% at the bottom. CO2 levels, however, increased from the top of the pit, and reached a level of 22% at the 6-ft. depth of the pit. The accepted lethal level is only 10%. The cause originally attributed to these deaths was shown to be in error. This paper demonstrates the importance of proper investigation of the "scene of occurrence" in order to properly certify the cause of death.

Adult↗
PubMed1971

Photo-urticaria.

Explore the source record for details and available documents.

Adult↗
PubMed1969

Two temporal parameters of free operant discriminated avoidance in the rhesus monkey.

Four monkeys were exposed to free operant discriminated avoidance (discriminated Sidman avoidance) in a parametric study of safe stimulus and warning stimulus duration. The safe stimulus was assigned values of 2, 5, 10, 20, and 40 sec, the warning stimulus values of 2, 5, and 20 sec. Rate of responding was a decreasing negatively accelerated function of safe stimulus duration, with a small effect attributable to warning stimulus duration. Control of response rate by safe stimulus duration was due to the predominance of responding in the presence of the warning stimulus. Responding during the safe stimulus was independent of the temporal parameters except at schedules combining short safe and short warning stimulus durations. Latencies of responses in the warning stimulus were analyzed, and mean latency was found to be a direct function of warning stimulus duration, with only one exception, resulting from the order in which the warning stimulus values were presented. Shock rate was not systematically related to either of the manipulated parameters.

Journal Article↗
PubMedDate not supplied

Current Canadian approaches to dialysis for acute renal failure in the ICU.

BACKGROUND: Although there is a very high mortality rate (>50%) with acute renal failure (ARF) in the intensive care unit (ICU), there is no general consensus on the best dialysis treatment for this condition. METHODS: We surveyed by mail questionnaire, all adult academic and community registered Canadian nephrology centers that offer treatment for ARF. RESULTS: The overall response rate was 59% (53/90). Comparing current dialysis methods with those utilized 5 years ago, the largest increase was in continuous renal replacement therapies (CRRT) (26 vs. 9%). Both intermittent hemodialysis (IHD) and peritoneal dialysis decreased in utilization. The predominant current CRRT methods utilized venovenous access (80%), as compared to 5 years ago when arteriovenous was the most common (52%). Despite data from chronic dialysis (and preliminary data in ARF) suggesting reduced mortality and morbidity with increasing dialysis dose, there was no formal method of dialysis prescription monitoring in over 75% of the centers. CONCLUSION: Notwithstanding a lack of definitive evidence of superior outcomes with CRRT compared to older methods, the utilization of CRRT is dramatically increasing for the treatment of ARF in Canada. Whether this shift towards CRRT, and whether more attention to dialysis dose in ARF, might be expected to lead to better outcomes, requires further evaluation.

Acute Kidney Injury↗
PubMedDate not supplied

Vein of Galen malformation: correlation of clinical presentation, arteriography, and MR imaging.

To test the value of currently proposed angiographic categorizations of vein of Galen malformations and a hypothesis regarding the causes of vein of Galen malformations and of accompanying hydrocephalus, as well as to assess the relative utility of MR imaging and CT in clinical evaluation, we reviewed the clinical and radiologic records of 34 patients with vein of Galen malformations. Patients were divided into two groups on the basis of the angiographic demonstration of either an arteriovenous malformation nidus or a direct arteriovenous fistula to the wall of the vein of Galen or one of its tributaries. Patients with such a nidus (n = 17) could be distinguished from those with arteriovenous fistulas alone (n = 17) on the basis of age at presentation (p less than .01) and presenting symptoms. Venous constraints, thought to be etiologically important, were identified in 31 of 34 patients. The presence or absence of hydrocephalus was explainable by mass effect in only 24 of 32 patients. In seven of 32 cases, no obvious mass effect was seen in the presence of hydrocephalus, but arteriographic evidence of venous hypertension was present in all patients with hydrocephalus. MR provided improved depiction of both arterial and venous anatomy as compared with CT. Parenchymal abnormalities were uncommon. No patients had subarachnoid hemorrhages. We conclude that MR is superior to CT in the clinical evaluation of vein of Galen malformations, that the angiographic finding of a nidus separates patients with vein of Galen malformations into clinical and therapeutically relevant groups, and that simple mass effect on the aqueduct is not an adequate explanation for all cases of hydrocephalus in patients with this disease.

Cerebral Angiography↗
PubMedDate not supplied

Influence of nifedipine, verapamil and diltiazem on pulmonary vascular resistance and vasoconstrictors in cats.

In the present study, the effects of three classes of L-type calcium channel-blocking agents, nifedipine, verapamil and diltiazem, on the lobar arterial pressure and the vasoconstrictor responses in the pulmonary vascular bed were compared to those of cromakalim, a KATP channel activator, in the anaesthetized cat under controlled pulmonary blood flow and constant left atrial pressure. These drugs were infused intralobarly in doses selected which did not raise left atrial pressure, change cardiac output or alter systemic arterial pressure. Intralobar bolus injections of calcium channel-blocking agents and of the K+ channel activator decreased the lobar arterial pressure in a dose-related manner when pulmonary vasomotor tone was actively elevated by intralobar arterial infusion of U46619. The pulmonary vasodilator response to these agents was accompanied by a dose-related decrease of systemic arterial pressure. In decreasing lobar arterial pressure at elevated pulmonary vasomotor tone, the order of potency was nifedipine > verapamil > diltiazem, whereas in reducing systemic arterial pressure, the order of potency was nifedipine > diltiazem > verapamil. The calcium channel-blocking agents were less active than the reference drug, cromakalim, in both vascular beds. Intralobar arterial infusions of nifedipine, verapamil and diltiazem, at the rates of 0.03 mumol/min, 0.2 mumol/min and 0.1 mumol/min, respectively, caused no changes in cardiac output and in systemic and pulmonary arterial pressure. Infusion of all three calcium-channel-blocking agents blocked the pulmonary vasoconstrictor responses to BAY K 8644 (calcium entry promoter) and U46619 (thromboxane A2 mimic). Nifedipine infusion also reduced the pulmonary vasoconstrictor responses to methoxamine and BHT933 (alpha 1- and alpha 2-adrenoceptor agonists, respectively), whereas verapamil infusion reduced the responses only to methoxamine. Infusion of diltiazem caused no significant decrease of responses to either alpha-adrenoceptor agonist. The results of the present study suggest that the dihydropyridine, nifedipine, is more potent than the non-dihydropyridines, verapamil and diltiazem, in reducing the pulmonary vascular resistance and more effective in inhibiting the vasoconstrictor responses to the alpha-adrenoceptor agonists, to U46619 and to BAY K 8644 in the feline pulmonary circulation at the infusion rates which cause no or little hemodynamic changes.

15-Hydroxy-11 alpha,9 alpha-(epoxymethano)prosta-5↗
PubMedDate not supplied

Domestic violence: legal issues for health care practitioners and institutions.

If health care practitioners and institutions became familiar with legal options available to survivors of domestic violence, they could better facilitate their patients' access to potentially life-saving recourses. Such options include calling the police and obtaining civil protection orders and bringing custody, divorce, and support actions. Provider awareness of legal obligations and other legal considerations that arise when handling domestic violence cases is important for patient care and the practice of good risk management. Examples of such issues include domestic violence protocol requirements, documentation of abuse, and repercussions of mandatory reporting laws. Health care providers should work in collaboration with community domestic violence programs in educating staff on issues pertaining to domestic violence and in crafting policies that promote patient safety and autonomy.

Battered Women↗