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Biomedical subjects

P Froom

Publications and source records attributed to P Froom.

At least 19 recordsLinked to original sources
PubMed1992

Selection bias in using data from one population to another: common pitfalls in the interpretation of medical literature.

The prevalence, course and prognosis of diseases in patients referred to tertiary medical centers frequently differ from those treated in primary care settings. Extrapolation of findings from one population to another may therefore be unwarranted. Other factors that contribute to misinterpretation of medical literature include failure to distinguish statistical from clinical significance and advocacy of medical interventions prior to adequate clinical trials.

Epidemiology↗
PubMed1992

Extreme airborne asbestos concentrations in a public building.

Fibre concentrations of asbestos were measured in the air of a communal dining room in which the damaged ceiling had a sprayed on coating of insulation containing asbestos. The average concentration of crocidolite asbestos fibres was 4 f/cm3, 20 times the highest air concentration that appears to have been reported previously for a public building. It is concluded that although air concentrations of asbestos fibres in public buildings containing asbestos insulation materials are usually low, high concentrations can occur. This may have implications for the risk of exposed persons developing diseases associated with asbestos.

Air Pollution, Indoor↗
PubMed1992

The incidence of myopia in the Israel Air Force rated population: a 10-year prospective study.

It is important to define the risk in pilots of becoming myopic in order to determine the need for yearly screening, and to predict pilot eligibility in environments where the use of corrective lenses may present problems. We conducted a prospective study of 1400 air force personnel followed for 10 years, who could be divided into three major groups; those with 20/20 vision in both eyes, those with 20/25 in one eye only and whose vision was 20/20 using both eyes together, and those who were accepted despite the fact that they required corrective lenses. Over the 10-year period, 23.1% of those with 20/25 visual acuity in one eye needed corrective lenses, significantly more than the 7.4% observed in those with 20/20 vision in both eyes (relative risk 3.1, 95% confidence interval 2.2-4.3, p less than 0.0000). The prevalence of corrective lenses increased until age 26. We conclude that 7.4% of pilots will become myopic over a 10-year period if accepted with 20/20 vision in both eyes. The risk, however, is much higher in those with incipient growth myopia starting in one eye at entry. Therefore, the annual screening of visual acuity in air force personnel is essential.

Adolescent↗
PubMed1991

Increased spontaneous secretion of IL-6 from B cells of patients with B chronic lymphatic leukaemia (B-CLL) and autoimmunity.

We studied B cells from 18 patients with B-CLL, six of them with autoimmune haemolytic anaemia, for spontaneous secretion of IL-6. Our aim was to determine whether the increased incidence of autoimmune disease found in B-CLL patients is associated with enhanced spontaneous IL-6 secretion. IL-6 was measured by the effect of B cell supernatants on the proliferation of an IL-6 dependent plasmacytoma cell line T1165. The highest IL-6 values (7.4 +/- 1.8 U/ml) were measured in supernatants derived on day 3 of culture from lymphocytes of the six patients with B-CLL and concomitant autoimmune disease. The maximal IL-6 values for 10 patients with B-CLL only were 2.8 +/- 0.3 U/ml and for 10 age-matched controls, 0.8 +/- 0.3 U/ml (P less than 0.01, each group compared with the other). We conclude that there is an association between B-CLL, autoimmune disease and the spontaneous in vitro secretion of IL-6. Further studies are needed to determine whether the IL-6 secretion plays a role in the pathogenesis of autoimmune disease in patients with B-CLL.

Aged↗
PubMed1991

Heat stress on helicopter pilots during ground standby.

We attempted to use measurements of ambient thermal conditions to characterize and then predict thermal conditions in the cockpit before takeoff and during an hour standby period in Bell 206 and Bell 212 helicopters with a crew of two and with the cockpit doors opened. Dry bulb, wet bulb, and globe temperatures were measured on 28 separate summer days. The wet bulb globe temperature index (WBGT) was used to estimate heat stress. Ambient WBGT at time 0 ranged from 13 degrees C to 31 degrees C. There was a 2.9 +/- 3.7 degree difference in WBGT between ambient and cockpit conditions at time 0 which increased to 7.2 +/- 3.5 degrees after 1 h. Because of the cooling effect of opening the helicopter cockpit doors, the cockpit WBGT actually decreased over the standby period when cockpit WBGT values were 30 degrees C or more at time 0. Thus, there was an inverse correlation between cockpit WBGT at time 0 and the change in cockpit WBGT over the 1-h period (r = -0.767, p less than 0.001). The mean WBGT in the cockpit over the 1-h standby period was positively correlated with the ambient WBGT at time 0 (r = 0.783, p less than 0.001). We conclude that the greenhouse effect results in a cockpit WBGT which is significantly higher than ambient conditions. Subsequent changes in cockpit WBGT depend on the balance between heat transfer from the pilot's bodies to the cockpit and the loss of heat after the doors of the helicopters are opened. Ambient thermal conditions can be used to predict heat stress during the ground standby period.

Aerospace Medicine↗
PubMed1991

Factors associated with leukocyturia in asymptomatic pilots.

We attempted to relate the prevalence of leukocyturia during annual examinations to recent activities and history data in 923 pilots. Urinary analysis was done and the results cross-tabulated with answers from a questionnaire and with a past history of leukocyturia obtained from the pilot's chart. The prevalence of 4 to 6 or more white blood cells (WBCs) in the urinary sediment was 5.3%. Leukocyturia was 35.7 times more common (odds ratio) in those with a previous history of leukocyturia and a concomitant history of urethritis (p less than 0.0001). Yet, a history of leukocyturia accounted for only 18.1% of the cases of leukocyturia. There was a trend for an association between jogging and leukocyturia. The prevalence of leukocyturia was not affected by smoking, other physical exercise, a history of nephrolithiasis, air duty in the preceding 24 h or a history of transient illness during the last 2 weeks. We conclude that there is an association between a history of both leukocyturia and urethritis and leukocyturia. In most cases, however none of the variables tested were found to be associated with leukocyturia.

Aerospace Medicine↗
PubMed1990

Multiple myeloma in the geriatric patient.

Consecutive patients with multiple myeloma were studied. The clinical characteristics and survival of 17 patients aged 75 years or more were compared to 42 patients younger than 75 years of age. Of the patients older than 75 years, 14/17 (82%) died in less than 12 months compared to only 11/42 (26%) of those under 75 years old (P less than 0.001). Multivariate analysis showed that both age and hemoglobin were significant predictors of survival (P less than 0.012 and P less than 0.002, respectively) explaining 34.6% of the variance (r = 0.588, P less than 0.000), whereas the extent of bone lesions, the presence of more than 50% plasma cells in the bone marrow, the amount of serum monoclonal protein, functional class, and the Salmon and Durie staging system did not significantly add to the analysis. We conclude that the factors that best predict prognosis are hemoglobin levels and age at presentation. Different approaches including more appropriate chemotherapeutic regimes and comprehensive geriatric assessment with improved supportive treatment need to be developed for the geriatric patient with multiple myeloma.

Age Factors↗
PubMed1990

Effect of adherent cells on the regulation of BFU-E in patients with myeloproliferative disease.

The interaction between adherent cells and red cell progenitors from peripheral blood of patients with polycythemia vera (PV), essential thrombocytosis (ET), and healthy controls was studied. Various combinations of adherent and nonadherent cells were co-cultured in a semisolid system. Adherent cells from controls, when added at low concentrations, stimulated BFU-E proliferation, whereas high concentrations (40% of total cells in the culture) caused a significant decrease in the number of BFU-E colonies in 6/8 PV patients, 4/4 ET patients, and 8/12 controls. On the other hand, low and high concentrations of adherent cells from both patients with PV and ET caused a significant increase in BFU-E from either patients or controls. Moreover, adherent cells from these patients induced endogenous BFU-E proliferation (independent of erythropoietin) in nonadherent cells of 12/12 normal controls. The results show that BFU-E from patients with PV and ET are sensitive to suppression by normal adherent cells. On the other hand, adherent cells from these patients possess stimulatory activity on BFU-E from peripheral blood at all concentrations and are devoid of the inhibitory activity. This suggests a possible defect in the functioning of adherent cells in PV and ET patients which may contribute to the abnormal regulation of hematopoiesis in these disorders.

Cell Adhesion↗
PubMed1990

Concomitant effect of 2'-deoxycoformycin on natural killer cell activity and tumour cell sensitivity to lysis in hairy cell leukaemia--discordant effects of alpha interferon.

The effects of 2'-deoxycoformycin (dCF) and alpha interferon (IFN-alpha) on natural killer (NK) cell-enriched fractions and hairy cell (HC) targets from three patients with HC leukaemia (HCL) were investigated. There was no significant increase in NK activity when either the HC targets or NK-enriched cells were preincubated with dCF. However, preincubation of both HC and NK cells with dCF resulted in increased NK activity. Culture of enriched NK cells with IFN-alpha enhanced their activity. However, preincubation of HC targets with this drug in the presence or absence of dCF resulted in a protective effect. Maximal NK activity towards HCL was obtained when the target tumour cells were separately precultured with dCF and the NK-enriched effectors precultured with dCF + IFN-alpha. The effect of dCF and IFN-alpha was also measured using the standard K562 cells as targets for NK activity. dCF enhanced NK activity following preculture of both effector and target K562 cells, but IFN-alpha did not reduce K562 cell susceptibility to NK lysis as it did for HC cells. Our findings suggest that (a) dCF and IFN-alpha, which are used to treat HC, could function via activation of NK cells, (b) effects on both effector and tumour target cells should be taken into account, and (c) caution should be exercised in extrapolating the effects of NK-cell activity against K562 cells to those on HC targets.

Cytotoxicity, Immunologic↗
PubMed1990

The effect of desmopressin on massive gastrointestinal bleeding in hereditary telangiectasia unresponsive to treatment with cryoprecipitate.

A patient with hereditary hemorrhagic telangiectasia and reduced levels of von Willebrand factor had severe recurrent gastrointestinal bleeding. Treatment with either desmopressin acetate or cryoprecipitate normalized both bleeding time and kaolin-activated partial thromboplastin time. Hematochezia (five episodes) continued, however, for a week despite daily treatment with cryoprecipitate, whereas treatment with desmopressin at the onset of three later episodes of hematochezia resulted in the prompt cessation of bleeding. After an episode of life-threatening gastrointestinal bleeding, desmopressin administration allowed a total colectomy without excessive bleeding. During the 3 years after colectomy, no further gastrointestinal bleeding occurred. In the past year, however, three episodes of severe epistaxis responded promptly to intravenous infusion of desmopressin. We conclude that desmopressin may be useful in the management of bleeding in patients with hereditary hemorrhagic telangiectasia with or without von Willebrand factor deficiency.

Adult↗
PubMed1990

Antithrombin III levels in preeclampsia.

Antithrombin III (AT-III) activity was measured and compared in 29 patients with preeclampsia and 31 women with normal pregnancies. AT-III levels were 83 +/- 25% in preeclamptic patients with greater than 5 g/l proteinuria compared with 102 +/- 11% in the controls. Less severe proteinuria was not associated with decreased AT-III levels. Multivariate analysis revealed that the duration of pregnancy and the degree of proteinuria had an independent negative effect on AT-III levels. AT-III activity correlated poorly with platelet counts and blood pressure measurements. We conclude that urinary loss appears to be the major mechanisms of lower AT-III levels observed in our patients with preeclampsia.

Adult↗
PubMed1990

Blood pressure response to exercise in normotensive and hypertensive young men.

We attempted to determine the optimal cut-off value of blood pressure defining a hypertensive response to exercise testing in 90 asymptomatic Israeli candidates for flight training with casual resting blood pressure of 140/90 mm Hg or more, and 72 age-matched normotensive controls tested in the Israel Air Force Aeromedical Center. Exercise testing (Bruce protocol) was performed using a calibrated Quinton Treadmill and a Hewlett Packard 151711-A three-channel ECG recording system. Recordings were made at 3-min intervals. At 3 min of exercise 12/87 (14%) of the hypertensive subjects had a SBP of greater than or equal to 210, compared to only 1/71 (1%) of the control group (relative risk 14). At 12 min of exercise 27/51 (53%) of the hypertensives and 9/55 (16%) of the controls had similar elevations of SBP (relative risk 3.3). At 6 min of exercise 11/87 (13%) of hypertensives had SBP greater than or equal to 220, whereas none of the normal controls had SBPs elevated to that degree. We concluded that an increase in SBP to 210 mm Hg or more after 3 min or to 220 mm Hg after 6 min of exercise testing by the Bruce protocol best separates the hypertensive group from the control group. This occurs at the expense of sensitivity. Only appropriate longitudinal studies can compare the degree to which various definitions of the hypertensive response to exercise will predict future hypertension.

Adolescent↗
PubMed1989

Decreased natural killer (NK) activity in patients with myeloproliferative disorders.

Natural killer (NK) cell number and activity were measured in 26 patients with myeloproliferative disorders and the results were compared with 16 age-matched control patients. The percent of Leu-11b-positive cells was 11% +/- 3% in the patients, compared with 12% +/- 4% in the control patients. Ten of 26 patients, however, had NK activity lower than all of the control values at three different effector to target cell ratios (E:T) (P less than 0.005). The values of those patients with low unstimulated NK activity remained low despite stimulation with interleukin-2 (IL-2) or alpha-interferon (alpha-IFN), whereas the values of those patients with normal unstimulated activity responded to IL-2 and alpha-IFN like the control patients. Three of the ten patients with low NK activity had a history of malignant neoplasms. None of the 16 patients with normal NK activity had a history of malignant neoplasms (P less than 0.05). We conclude that patients with myeloproliferative disorders frequently have low endogenous NK cell activity in vitro. The dysfunction of the NK system appears to be intrinsic because the relative number of NK cells was similar to control values and the response to stimulation with IL-2 and alpha-IFN was suboptimal. There may be a relationship between low NK activity and the development of malignant disease in such patients.

Bloodletting↗
PubMed1989

Mitral leaflet motion: age and implications for the diagnosis of mitral valve prolapse.

The extent of posterior mitral leaflet motion (PMLM) during systole in relation to age was studied in 300 asymptomatic men aged 18-42 years. PMLM of 4 mm or more on two-dimensional directed M-mode echocardiography was found in 8% (16/200) of subjects under age 35 years, but in only 2% (2/100) of those aged 35 years or more (p less than 0.05). On two-dimensional echocardiography, 16% (31/200) of men under 35 years old had PMLM greater than or equal to 0.40 mm2 compared with 1% (1/100) of those 35 years or more (p less than 0.001). The findings were not related to differences in left ventricular cavity dimensions or in the extent of systolic ventricular contraction. Body mass index (BMI) increased with age, but there was a significant and independent negative correlation of age with PMLM after controlling for BMI. The data are compatible with the hypothesis that the aging process is associated with decreased mobility of the mitral valve or annulus with lesser degrees of backward bowing or billowing of the leaflets during systole. Age should be taken into account in determining "normal" values for mitral leaflet motion.

Adolescent↗