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Biomedical subjects

J R Hoffman

Publications and source records attributed to J R Hoffman.

At least 73 records · Page 4Linked to original sources
PubMed1997

Acetonitrile as a possible marker of current cigarette smoking.

Volatile nitriles are present in cigarette smoke. We tested the hypothesis that the presence of any of four nitriles in the blood can serve as a marker of recent cigarette smoking. We determined the sensitivity and specificity of these nitriles as indicators of daily cigarette smoking in 24 smokers (Group A) and 18 non-smokers (Group B), as well as the correlation between intensity of daily smoking and the blood concentration of acetonitrile. A new head space GLC assay method was used. Of the four nitriles, only acetonitrile was present in the blood of any study subject. Acetonitrile was moderately sensitive (67%) and entirely specific (100%) for self-reported daily smoking. There was fair correlation between blood acetonitrile concentration and the average daily number of cigarettes smoked (r2 = 0.39; P = 0.001), and the mean blood acetonitrile concentration was significantly higher (P = 0.03) among subjects with higher (> 10 cigarettes per day) current cigarette exposure (148.3 +/- 18.0 micrograms/l) than among smokers with low or minimal (1-10 cigarettes per day) exposure (43.3 +/- 6.0 micrograms/l). Thus, acetonitrile in blood appears to be highly specific and a moderately sensitive marker of cigarette smoking with a dose-effect relationship. As such, acetonitrile shows promise as a marker of current cigarette exposure.

Acetonitriles↗
PubMed1997

The relationship between aerobic fitness and recovery from high-intensity exercise in infantry soldiers.

The relationship between aerobic fitness and recovery from high-intensity exercise was examined in 197 infantry soldiers. Aerobic fitness was determined by a maximal-effort, 2,000-m run (RUN). High-intensity exercise consisted of three bouts of a continuous 140-m sprint with several changes of direction. A 2-minute passive rest separated each sprint. A fatigue index was developed by dividing the mean time of the three sprints by the fastest time. Times for the RUN were converted into standardized T scores and separated into five groups (group 1 had the slowest run time and group 5 had the fastest run time). Significant differences in the fatigue index were seen between group 1 (4.9 +/- 2.4%) and groups 3 (2.6 +/- 1.7%), 4 (2.3 +/- 1.6%), and 5 (2.3 +/- 1.3%). It appears that recovery from high-intensity exercise is improved at higher levels of aerobic fitness (faster time for the RUN). However, as the level of aerobic fitness improves above the population mean, no further benefit in the recovery rate from high-intensity exercise is apparent.

Adult↗
PubMed1997

Relationship of leg strength and power to ground reaction forces in both experienced and novice jump trained personnel.

METHODS: There were 14 male soldiers who participated in this study examining the relationship of leg strength and power on landing performance. Subjects were separated into two groups. The first group (E, n = 7) were parachute training instructors and highly experienced in parachute jumping. The second group of subjects (N, n = 7) had no prior parachute training experience and were considered novice jumpers. All subjects were tested for one-repetition maximum (1 RM) squat strength and maximal jump power. Ground reaction forces (GRF) and the time to peak force (TPF) at landing were measured from jumps at four different heights (95 cm, 120 cm, 145 cm, and 170 cm). All jumps were performed from a customized jump platform onto a force plate. RESULTS: No differences were seen between E and N in either IRM squat strength or in MJP. In addition, no differences were seen between the groups for time to peak force at any jump height. However, significantly greater GRF were observed in E compared to N. Moderate to high correlations between maximal jump power and GRF (r values ranging from 0.62-0.93) were observed in E. Although maximal jump power and the TPF was significantly correlated (r = -0.89) at only 120 cm for E, it was interesting to note that the correlations between MJP and the time to peak force in E were all negative and that the correlations between these variables in N were all positive. CONCLUSIONS: These results suggest that experienced parachutists may use a different landing strategy than novice jumpers. This difference may be reflected by differences in GRF generated during impact and a more efficient utilization of muscle power during the impact phase of the landing.

Aerospace Medicine↗
PubMed1996

Short exposure to methylazoxymethanol causes a long-term inhibition of axonal outgrowth from cultured embryonic rat hippocampal neurons.

Methylazoxymethanol (MAM) is an alkylating agent that is used to induce microencephaly by killing mitotically active neuroblasts. We found that at later developmental times, MAM exposure can result in abnormal fiber growth in vivo. However, there have not been any previous studies on the effects of MAM on differentiating neurons. We examined the outcome of short exposure to MAM on postmitotic embryonic hippocampal cultures during the establishment of axonal polarity. At 0, 1, or 2 days in vitro (DIV), neurons were treated with 0.1 nM-1 microM MAM for 3 hr and then transferred to glial conditioned media. At 3 DIV, the cells were fixed and analyzed by immunofluorescent staining for neuron viability and differentiation. Control cells initiate several minor processes; one process elongates rapidly at about 1 DIV eventually becoming an axon, while extensive dendritic growth occurs after 3-4 DIV. Neurons treated with 1 microM MAM at 0 or 1 DIV showed a marked inhibition of neurite growth and withdrawal of axons without affecting cell viability. These cells continued to show minimal neurite outgrowth at 7 DIV, even when transferred to a glial coculture. In contrast, cells treated initially with MAM, after neuronal polarity is established at 2 DIV, showed no effect on axonal growth. To determine the effects of MAM on the neuronal cytoskeleton, we examined the in vitro assembly of brain microtubules in a one cycle assay. Exposure to MAM depleted the soluble pool of proteins, including microtubule-associated protein 1B (MAP1B) and MAP2, which are required for neurite outgrowth, through a nonspecific process. Under non-saturating conditions, there were no changes in the total amount of microtubules assembled or the coassembly of MAP1B and MAP2 in the presence of MAM. These results demonstrate that MAM can directly affect differentiating neurons, indicating that an early disruption of axonal outgrowth may have long-term effects.

Alkylating Agents↗
PubMed1996

Admission decisions in emergency department chest pain patients at low risk for myocardial infarction: patient versus physician preferences.

STUDY OBJECTIVE: Patient involvement in medical decisionmaking is accepted as an ethical and a legal imperative. Medical decisions are based in part on individuals' knowledge and acceptance of risk of adverse consequences. It is unclear whether actions taken to protect against low risk of poor outcome reflect patient or physician preferences. We sought to test the hypothesis that emergency department chest pain patients presented with a hypothetical situation involving a low risk of myocardial infarction are more willing than ED physicians to accept the risk associated with discharge from the hospital. METHODS: We prospectively surveyed 89 ED patients with chest pain and a cohort of physicians in the ED who had been presented a hypothetical case in which the risk of AMI was quoted as 5% and the risk of death or disability if the patient was discharged was 1% and .2% if the patient was admitted. All the patients had presented to the ED with a chief complaint of chest pain; the 31 physicians, all residents, were approached at a teaching conference separate from their clinical duties. RESULTS: Twenty-eight patients (31%), compared with 2 physicians (6%), chose discharge for the hypothetical patient with chest pain (25% difference; 95% confidence interval [CI], 6% to 41%). Forty-four patients (49%), compared with 30 physicians (97%), correctly identified the risks associated with admission and discharge (46% difference; 95% CI, 29% to 63%). Of the subjects who correctly identified the risks, 19 patients (43%) preferred discharge, compared with 1 physician (3%) (40% difference; 95% CI, 18% to 60%). CONCLUSION: ED patients with chest pain appear to be more likely than physicians to accept a small risk of poor outcome in a hypothetical circumstance. Many patients cannot identify the risks associated with their decision.

Adult↗
PubMed1996

Empiric use of flumazenil in comatose patients: limited applicability of criteria to define low risk.

STUDY OBJECTIVE: To develop clinical rules for the safe and effective use of flumazenil in suspected benzodiazepine overdose. METHODS: We assembled a retrospective series of 35 consecutive comatose patients admitted between October 1992 and July 1993 to a toxicologic ICU with the presumptive diagnosis of drug overdose. These patients were divided into two groups. Group A (low-risk) patients had a clinical picture compatible with uncomplicated benzodiazepine intoxication (calm, without abnormalities in pulse or blood pressure, lateralizing signs, hypertonia, hyperreflexia, or myoclonus) in the absence of predefined electrocardiographic or clinical signs of tricyclic antidepressant or other proconvulsant overdose, and absence of an available history of long-term benzodiazepine treatment or an underlying seizure disorder. Group B ("non-low risk") comprised all other patients. Efficacy of flumazenil was categorized as complete awakening (with normal level of alertness), partial awakening, or no change in alertness level. The safety of flumazenil was defined on the basis of the absence of seizures or death. RESULTS: In group A (n=4), flumazenil was associated with complete awakening in three patients and partial awakening in one. No seizures were observed. In group B (n=31), flumazenil was associated with complete awakening in 4 patients, partial awakening in 5, and no response in 22. In group B, five seizures occurred. CONCLUSION: Comatose patients with clinical or ECG criteria thought to contraindicate the use of flumazenil have a reasonably high risk of seizures after administration of this drug. Low-risk patients may be able to receive flumazenil safely, but they may be only a small portion of comatose patients with suspected overdose.

Adolescent↗
PubMed1996

Effect of cardiologist ECG review on emergency department practice.

STUDY OBJECTIVE: To determine the effect of cardiology review of ECGs on emergency department practice. METHODS: We carried out a prospective cohort study at an urban teaching ED. Our subjects were adult patients undergoing electrocardiography. We prospectively collected 1,000 consecutive ECGs and classified them by severity according to the following system: class 1, normal or minor abnormalities only; class 2, abnormalities with potential to alter case management; and class 3, potentially life-threatening abnormalities. Actual ECG readings by ED physicians (who had access to computerized interpretations at the time of treatment) were compared with those of staff cardiology quality-assurance reviewers; if they were not in agreement, an expert cardiology panel blindly chose the superior interpretation. Subsequently, an expert emergency physician panel reviewed discordant readings for discharged patients to determine the need for further action. RESULTS: Of 1,000 ECGs, the readings for 190 (19%) were significantly discordant. The expert cardiology panel preferred the ED reading in 72 cases (38%) and the staff cardiology reading in 118 (62%). In 30 other cases no ED reading was recorded in the medical record. Of the 148 cases in which the expert cardiology panel agreed with the cardiology reading or there was no ED reading, 102 patients were admitted and 46 discharged. Of the 46 discharges, 8 cardiology readings were categorized as class 1, leaving only 38 cases in which the staff cardiology reading might have affected the ED decision to discharge a patient. All of these readings were in class 2, with the exception of one unclassifiable diagnosis. There were no class 3 readings. On expert emergency physician panel review of these 38 ECGs and interpretations, only 8 (.8%, 95% confidence interval, .3% to 1.6%) were considered sufficiently important to warrant chart review. In actual practice, none of these cases was affected by the ECG quality-assurance (QA) process. Two of these patients died during our 1-year follow-up. In one of these cases, the ECG QA process could have altered the patient's outcome. CONCLUSION: The existing ECG review process as mandated by the Joint Commission on Accreditation of Healthcare Organizations (JCAHO) will likely have minimal influence on patient outcomes at our institution. We should establish the effectiveness of this mandated QA process before committing scarce resources to its performance.

Adult↗
PubMed1996

Plasma volume responses to consecutive anaerobic exercise tests.

This study examined the change in plasma volume (% delta PV) in response to consecutive Wingate tests (30 sec Anaerobic Power test). Twelve active men (21 +/- 1.6 yr, 81.3 +/- 6.6 kg) performed two Wingate tests (W1 and W2, separated by 10 min) on three occasions (T1-T3, tests were two weeks apart). Exercise resistance was maintained at 75 g.kg-1 body weight during testing. Blood samples were taken immediately before (Pre) and after (IP) W1 and W2. There were no significant differences in hematocrit, hemoglobin, mean power (MP) or peak power (PP) between T1-T3. There was a marked hemoconcentration in response to W1 (IP W1, -17.4 +/- 2.6% delta PV), with a further, but not significantly greater, hemoconcentration following W2 (IP W2, -8.2 +/- 1.1% delta PV). The % delta PV, between PRE W1 and IP W2 was-20.1 +/- 3.1%. These results suggest that an existing hemoconcentration (W1) may affect the magnitude of the % delta PV response to subsequent supramaximal exercise (W2).

Adult↗
PubMed1996

Treatment of acute chloroquine poisoning: a 5-year experience.

OBJECTIVE: To describe various aspects of prognostic and therapeutic importance in patients treated for acute chloroquine poisoning. DESIGN: Retrospective study. SETTING: Toxicology intensive care unit (ICU) of a university hospital. INTERVENTIONS: None. PATIENTS: One hundred sixty-seven consecutive patients with acute chloroquine overdose admitted to our toxicology ICU. MEASUREMENTS AND MAIN RESULTS: The mean amount ingested by history was 4.5 +2- 2.8 g. and 43 (26%) of 167 patients ingested > 5 g. The mean blood chloroquine concentration on admission was 20.5 +/- 13.4 mumol/L The majority (87%) of our patients received at least one arm of a combination therapy regimen (epinephrine, mechanical ventilation, diazepam). cardiac arrest occurred in 25 patients before hospital arrival; In seven of these patients, cardiac arrest occurred immediately after injection of thiopental. The mortality rate was 8.4% overall, and was 9.3% in patients with massive ingestions (NS vs. the group as a whole). We did not find a meaningful correlation between the amount ingested as estimated by history and the peak blood chloroquine concentration; the latter was highly correlated with the mortality rate. CONCLUSIONS: The mortality rate in patients with acute chloroquine poisoning, including those patients sick enough to be referred to a specialty unit such as ours, can be limited to < or = 10%. This finding appears to be true even in patients with massive ingestions. We were not able to correlate mortality with amount ingested by history, although the mortality rate does correlate with blood chloroquine concentration. While early use of diazepam, epinephrine, and mechanical ventilation in most of our patients may have contributed to the excellent overall results, these elements, either singly or in combination, do not appear to have a truly antidotal effect in acute chloroquine poisoning. Thiopental, on the other hand, should be used with great caution, if at all, in such cases.

Acute Disease↗
PubMed1996

A treadmill test of sprint running.

Anaerobic power is characterized by a high degree of specificity regarding both the recruited muscles as well as the recruitment pattern. The popular Wingate Anaerobic Test (WAnT) is a cycling test that does not satisfy the need for a running-specific anaerobic test. We describe such a test, using a novel type of a commercially available treadmill (BRL 1800, Gymrol, France). The ergometer is equipped with a torque motor to neutralize the frictional resistance of the treadmill belt, and a hip-belt harness connected to a horizontal rod. Force applied to the harness is monitored by a strain gauge mounted on the rod, while vertical movement is monitored by a potentiometer at the posterior fixed end of the rod. These, in conjunction with the treadmill belt speed, enable the computation of horizontal and vertical power as well as the combined total output. Power is calculated both as 'peak' power (highest 2.5 s segment) and 'mean' power (20 s duration). Preliminary results of young athletes were generally consistent with the expected age-related changes in anaerobic power. Values obtained on the anaerobic treadmill were always higher than the corresponding WAnT values previously obtained in comparable age groups. The higher values were probably due to the larger muscle mass involved and the shorter peak and mean power durations (2.5 and 20 s versus 5 and 30 s in the WAnT, respectively). This test should enable not only running-specific anaerobic power monitoring but also the characterization of the relationship between the horizontal and vertical components of that power.

Adolescent↗
PubMed1995

Relation of blood cyanide to plasma cyanocobalamin concentration after a fixed dose of hydroxocobalamin in cyanide poisoning.

Hydroxocobalamin combines with cyanide to form cyanocobalamin. We hypothesised that the amount of cyanocobalamin formed after a fixed dose of hydroxocobalamin given for cyanide poisoning would correlate with initial blood cyanide concentration. We determined blood cyanide concentration in 12 patients exposed to residential fires, and compared this with markers of the amount of cyanocobalamin formed after treatment with 5 g intravenous hydroxocobalamin. All relationships were highly correlated (r2 0.79-0.95), for the whole group, and there appeared to be an almost linear relationship for the 9 patients with initial cyanide concentration below 40 mumol/L. Above this concentration, no further cyanocobalamin was formed from a single 5 g dose of hydroxocobalamin. In one patient with initial blood cyanide concentration of 96 mumol/L, however, plasma cyanocobalamin concentration approximately doubled after a second 5 g dose of hydroxocobalamin. 5 g of hydroxocobalamin appears capable of binding all available cyanide ions for blood cyanide concentrations up to about 40 mumol/L. Beyond this, more hydroxocobalamin must be given for remaining cyanide ions to be bound. This information will allow clinicians to use rapidly measurable plasma cyanocobalamin concentrations to gauge severity of exposure and evaluate adequacy of treatment.

Adult↗
PubMed1995

The effect of water restriction on anaerobic power and vertical jumping height in basketball players.

This study examined the effect of high intensity, moderate duration (40 min) exercise and water restriction on anaerobic power, vertical jumping height, and basketball shooting performance. Ten healthy male basketball players participated in two simulated '2 on 2 full-court' basketball games. Water consumption was permitted in one game (Wa) but not in the other (NWa), in a balanced cross-over design. Subjects began each game euhydrated. All jump tests (squat jump, counter movement jump, and 30 second jump test) were performed prior to, at half-time, and immediately following each game (POST). Performance was measured by both field goal (FG%) and free throw (FT%) percentages recorded during each half. Players incurred a -1.9 +/- 0.4% body weight loss during NWa. No significant differences were observed between WA and NWa in anaerobic power, squat jump, or counter movement jump. However, a 19% difference in anaerobic power (p > 0.05) was observed between Wa (36.1 +/- 4.8 W.kg-1) and NWa (30.4 +/- 6.6 W.kg-1) at POST. No significant differences were observed between Wa and NWa in both FG% and FT% however, an 8.1% decrease (p > 0.05) in FG% was seen between the first and second half during NWa. Although the decreases in anaerobic power and FG% did not reach significance, the results suggest that the combination of high intensity, moderate duration exercise, and fluid restriction might be detrimental to performance.

Adolescent↗
PubMed1995

Ethylenebisdithiocarbamates and ethylenethiourea: possible human health hazards.

Humans are exposed to ethylenebisdithiocarbamates (EBDCs) from environmental sources. Exposure to EBDCs is chronic for workers in a variety of industries, where EBDCs are used for their properties as slimicides, vulcanization accelerators, antioxidants, and scavengers in waste-water treatment. EBDCs, and particularly the EBDC metabolite ethylenethiourea, have clearly defined, important toxic effects in various animal species, and there is reason to suspect they are carcinogenic in humans. In the absence of definitive information regarding human risk, further studies need to be done. In the interim, regular surveillance of workers with high levels of exposure to EBDCs, with specific attention to markers of thyroid and hepatic pathology, should be considered.

Animals↗
PubMed1995

Thrombolytic therapy.

If the electrocardiogram is diagnostic of acute myocardial infarction (AMI) in the patient complaining of typical chest pain, then indications and contraindications for thrombolytic therapy must be assessed immediately. The goal is to administer a thrombolytic agent within 30 to 60 minutes of presentation to the emergency department. Whether or not thrombolytic therapy is administered, other standard therapies for AMI must not be neglected. In addition, the medical record would reflect the clinical decision-making process and consultation with an admitting physician(s).

Angioplasty, Balloon, Coronary↗
PubMed1994

Expression of thrombospondin in the adult nervous system.

Thrombospondin (TSP) is an extracellular matrix molecule that has been previously associated with neural development and neurite outgrowth in vitro. Little is known, however, about the expression of TSP in the adult nervous system. In this study, TSP localization was examined in nervous tissue from adult mouse, goldfish, newt, and adult and juvenile Xenopus. TSP was associated with neurons in the brains of all species examined. TSP was present in central nerve tracts capable of regeneration, such as the goldfish, Xenopus, and newt optic nerves, but was absent from tracts not capable of regeneration, such as the mouse optic nerve. TSP was also present in the neuropil of goldfish and newt spinal cord, but was restricted to motor neurons in mice and adult Xenopus. In addition, TSP was observed in sciatic nerves of mice, Xenopus, and newt. These results indicate a correlation between the presence of TSP and the potential for successful nerve regeneration across a wide range of animal classes.

Animals↗
PubMed1994

Effects of hydration state on plasma testosterone, cortisol and catecholamine concentrations before and during mild exercise at elevated temperature.

This investigation examined the influence of pre-exercise hydration status, and water intake during low intensity exercise (5.6 km.h-1 at 5% gradient) in the heat (33 degrees C), on plasma testosterone (TEST), cortisol (CORT), adrenaline (A), and noradrenaline (NA) concentrations at baseline (BL), pre-exercise (PRE), and immediately (IP), 24 h (24 P), and 48 h postexercise (48 P). Ten active men participated in four experimental treatments. These treatments differed in pre-exercise hydration status [euhydrated or hypohydrated (HY, -3.8 (SD 0.7)% body mass)] and water intake during exercise (water ad libitum or no water intake during exercise, NW). There were no significant changes in TEST, CORT, or A concentrations with time (BL, PRE, IP, 24 P, and 48 P), or among treatments. However, significant increases from BL and PRE plasma NA concentrations were observed at IP during all four treatment conditions. In addition, HY+NW resulted in significantly higher plasma NA concentrations at IP compared to all other treatments. These results suggest that moderate levels of hypohydration during prolonged, low intensity exercise in the heat do not influence plasma TEST, CORT, or A concentrations. However, plasma NA appears to respond in a sensitive manner to these hydration and exercise stresses.

Adult↗