Biomedical subjects

H Hecht

Publications and source records attributed to H Hecht.

At least 37 records · Page 2Linked to original sources

PubMed1996

Poor renal uptake of 99mtechnetium-dimercaptosuccinic acid and near-normal 99mtechnetium-mercaptoacetyltriglycine renogram in nephronophthisis.

Four patients with the clinical diagnosis of nephronophthisis are presented, all having a very poor renal uptake of 99mtechnetium-dimercaptosuccinic acid (99mTc-DMSA) but clearly visualized kidneys on early images with 99mtechnetium-mercaptoacetyltriglycine and a normal or almost normal renogram. There was no difference between a young patient in an early stage of the disease and the other three patients with more advanced renal disease. In contrast, a patient with tubulointerstitial nephritis with uveitis had considerably better renal uptake of 99mTc-DMSA despite impaired renal function. We suggest that the specific tubular function defect in nephronophthisis might be the cause of the poor uptake of 99mTc-DMSA. We also recommend the method to support the clinical suspicion of nephronophthisis, even in the early stages of the disease.

Adolescent↗

PubMed1996

Gravitational acceleration as a cue for absolute size and distance?

When an object's motion is influenced by gravity, as in the rise and fall of a thrown ball, the vertical component of acceleration is roughly constant at 9.8 m/sec2. In principle, an observer could use this information to estimate the absolute size and distance of the object (Saxberg, 1987a; Watson, Banks, von Hofsten, & Royden, 1992). In five experiments, we examined people's ability to utilize the size and distance information provided by gravitational acceleration. Observers viewed computer simulations of an object rising and falling on a trajectory aligned with the gravitational vector. The simulated objects were balls of different diameters presented across a wide range of simulated distances. Observers were asked to identify the ball that was presented and to estimate its distance. The results showed that observers were much more sensitive to average velocity than to the gravitational acceleration pattern. Likewise, verticality of the motion and visibility of the trajectory's apex had negligible effects on the accuracy of size and distance judgments.

Acceleration↗

PubMed1995

Retinal, attentional, and causal aspects of illusory-motion directionality.

Extended objects presented instantaneously appeared to propagate or grow into their final shape. A strong bias was found toward perceiving straight lines to grow away from the observer's point of fixation. If attention and fixation were not directed to the same point of the visual field, both influenced illusory motion directionality, and if another small object was present on the screen at a location that was neither fixated nor attended to, the object that was instantaneously presented seemed to grow away from this point. Thus, three factors are involved in illusory-motion directionality: biases toward perceiving objects spreading away from the fixation point, away from an attended area, and away from preexisting objects. The experiments indicate that a satisfactory explanation of the illusion has to include bottom-up and top-down processes. They also challenge existing theories of motion detection.

Adult↗

PubMed1995

Assessment of data sets containing a considerable number of values below the detection limits.

Using real examples it is demonstrated that the concentrations of non-essential substances in biological systems always follow a statistical log-normal distribution. This is based on the assumption that in a first-order approximation the rate of excretion of the quantity of unwanted molecules or atoms in the biological system is only dependent on their concentration. Applying a natural logarithmic transformation, the resulting log-normal distribution always has a standard deviation of about 1, as shown by statistical analysis of more than 680 clusters of analytical results. Assuming a log-normal distribution with a standard deviation of 1, it is possible to derive factors for the estimation of percentiles, such as the median, even when this percentile is below the detection limit; quantifiable and higher percentiles only must be multiplied by a specific factor. This new method has the advantage that no arbitrary assumptions must be made about artificial parameters such as the numerical treatment of non-detectable analytical data. The assumptions used for the calculation of the factors are justified by proof with experimental data. The applicability of the new method is demonstrated for various contaminants in various plants and animals.

Animals↗

PubMed1995

Time-to-passage judgments in nonconstant optical flow fields.

The time until an approaching object will pass an observer (time to passage, or TTP) is optically specified by a global flow field even in the absence of local expansion or size cues. Kaiser and Mowafy (1993) have demonstrated that observers are in fact sensitive to this global flow information. The present studies investigate two factors that are usually ignored in work related TTP: (1) non-constant motion functions and (2) concomitant eye rotation. Non-constant velocities violate an assumption of some TTP derivations, and eye rotations may complicate heading extraction. Such factors have practical significance, for example, in the case of a pilot accelerating an aircraft or executing a roll. In our studies, a flow field of constant-sized stars was presented monocularly on a large screen. TTP judgments had to be made on the basis of one target star. The flow field varied in its acceleration pattern and its roll component. Observers did not appear to utilize acceleration information. In particular, TTPs with decelerating motion were consistently underestimated. TTP judgments were fairly robust with respect to roll, even when roll axis and track vector were decoupled. However, substantial decoupling between heading and track vector led to a decrement in performance, in both the presence and the absence of roll.

Adult↗

PubMed1994

Evaluating the new ICD-10 categories of depressive episode and recurrent depressive disorder.

The new ICD-10 categories of 'depressive episode' (F32) and 'recurrent depressive disorder' (F33) were evaluated on the levels of diagnoses, subtypes, syndromes and symptoms. Interrater reliability was analyzed from findings of four independent diagnosticians who rated 100 written psychiatric case records with the help of criteria-related checklists. Agreement was sufficient if patients with and without the diagnosis of a depressive disorder were included (kappa = 0.82), but low in the depressed subsample (kappa = 0.40). Unclear boundaries became apparent for the classification of depressive syndromes as moderate or severe. The results suggest that the ICD-10 concept of depressive disorder is very similar to the well-known international concept of 'major depression'.

Adult↗

PubMed1994

A pilot study of chemotherapy alternating with twice-a-day accelerated radiation therapy as an alternative to cystectomy in muscle infiltrating (stages T2 and T3) cancer of the bladder: preliminary results.

Laboratory studies have suggested that rapidly alternating chemotherapy and accelerated radiation therapy might act synergistically. We evaluated the toxicity and effectiveness of this approach in muscle infiltrating transitional cell carcinoma of the bladder in patients who were poor risks for or who refused cystectomy. We treated 18 men and 3 women with stage T2 or T3 transitional cell carcinoma of the bladder by transurethral resection, followed by 3 cycles of chemotherapy (during weeks 1, 4 and 7) rapidly alternating with 3 cycles of twice-a-day radiation therapy (during weeks 2, 5 and 8). Chemotherapy consisted of methotrexate, vinblastine, doxorubicin and cisplatin. The total dose of radiation therapy was 5,400 to 6,000 cGy, during 6 1/2 weeks and the total duration of chemotherapy and radiation therapy was 7 1/2 weeks. One patient died of hematological toxicity during treatment. With a median followup of 2 years (range 0.5 to 5.5 years) the observed survival rate was 72% at 2 years and 60% at 3 years. To date, only 1 patient (5%) had recurrence of invasive cancer in the pelvis. Only 3 others (15%) had carcinoma in situ but to date none has required cystectomy. Bladder function was normal in 15 of 18 evaluable patients (83.5%). This pilot study suggests that chemotherapy alternating with radiation therapy produced an encouraging survival rate without cystectomy and deserves further study. These patients require continued surveillance for carcinoma in situ.

Actuarial Analysis↗

PubMed1994

Testing the comparability of psychiatric diagnoses in ICD-10 and DSM-III-R.

The compatibility of the classification systems ICD-10 and DSM-III-R was investigated in a sample of 100 psychiatric inpatients with severe affective and psychotic disorders. Four independent raters assessed diagnoses by means of checklists from psychopathological descriptions of case records. Congruence between ICD-10 and DSM-III-R was good for depressive disorders with agreement rates above 80% and fair for bipolar disorders with rates above 60%. Less consistent findings were obtained for schizophrenia with rates of 57.5% for ICD-10 diagnoses and 82.6% for DSM-III-R diagnoses. Agreement for schizoaffective disorder was below 40% and thus insufficient. The results indicate that even small differences in the definitions of mental disorders may result in considerable inconsistencies.

Adult↗

PubMed1994

Triple vessel revascularization: coronary angioplasty versus coronary artery bypass surgery: initial results and five-year follow-up. Comparative costs and loss of working days and wages.

OBJECTIVES: The purpose of this study was to compare early and late outcomes in patients undergoing PTCA or CABG for triple vessel disease. BACKGROUND: Although early results of PTCA/CABG randomized trials have recently become available, at present little data exists on long-term medical and socioeconomic effects of these treatment modalities in patients with triple vessel revascularization. METHODS: During 1986-87, 76 patients undergoing triple vessel PTCA and 85 patients having triple vessel CABG were selected from a consecutive series of patients having multivessel revascularization. Initial results and 5 year outcome, hospital stay and charges and out-of-work time were assessed from prospectively collected data. RESULTS: Clinical and morphological factors were similar in the PTCA and CABG groups. Hospital success and complications were also similar, except for higher mortality in the CABG cohort (0 vs. 3.5%). Five year follow-up showed no differences in survival, nonfatal infarction and angina-free status; however, there was a difference in need for repeat revascularization (PTCA 55.4% vs. CABG 6.3%, p less than 0.001). Repeat PTCA accounted for 49% of the revascularization in the PTCA cohort. Crossovers were similar (PTCA[CABG 6.8%; CABG[PTCA 6.3%, pNS). Predictors of late death in the entire population were female gender (p less than 0.0001), diabetes (p<0.05) and depressed LVEF (p less than 0.05). The choice of revascularization procedure (PTCA vs. CABG) was not an independent predictor of late death or MI. Analysis of initial hospital charges showed a 2:1 advantage in favor of PTCA but this advantage was lost in late followup due to the need for repeat revascularization in the PTCA group. However, the PTCA cohort lost fewer working days than CABG patients (3017 vs 5874 days) and therefore, lost less wages ($7,022 vs. $14,685). CONCLUSIONS: The study shows that for selected triple vessel disease patients, PTCA and CABG results are comparable after 5 years, though repeat revascularization (mainly due to restenosis) was necessary in the PTCA group to maintain these favorable results. After 5 years, hospital charges are similar in the 2 groups, though out-of-work time and lost wages were 2:1 in favor of PTCA.

Absenteeism↗

PubMed1994

[Determination of forced expiratory volume (FEV 1) and maximal peak expiratory flow within the scope of routine diagnosis in general practice].

In 5 Viennese general practice offices we investigated patients by spirometry with the following indications: differential diagnosis of dyspnea; every 3rd smoker of more than 10 cigarettes a day (including asymptomatic ones); cough and nasal disorders of more than 4 weeks duration; indicative physical findings (cyanosis or auscultation). The sample control group was matched for age and gender and did not have any symptoms characteristic of the indication group. Nevertheless a spirometric test was also carried out in these patients. A total of 212 patients were examined in 4673 consultations on 202 workdays in the 5 offices. In the group of 109 patients 62 (56.9%) had dyspnea and/or positive signs on auscultation. Of these 62 patients 39 (62.9%) had 1 or more positive findings either from PEF or FEV 1 or both. There were significantly more referrals for X-rays in case of abnormal lung function. The control group of 103 obviously healthy persons in particular showed a significantly higher number of abnormal PEF values than expected (31 persons, 30.1%).

Adolescent↗

PubMed1993

An empirical comparison of diagnoses and reliabilities in ICD-10 and DSM-III-R.

The psychiatric classification systems ICD-10 and DSM-III-R were compared by applying both sets of diagnostic criteria to the same sample of patients suffering from affective and psychotic disorders. Four independent raters assessed diagnoses according to both systems to 100 written case records which had been prepared in a traditional, standard format. The International Diagnostic Checklists (IDCL) were employed to rate relevant psychopathological signs and symptoms and to apply diagnostic decision rules. The results showed that ICD-10 yielded a generally higher reliability for all main disorders except for bipolar disorder. Overall reliability was kappa = 0.53 for diagnoses according to DSM-III-R and 0.59 for diagnoses according to ICD-10. Agreement was best for affective disorders, moderate for schizophrenia and inacceptable for schizoaffective disorder. Insufficient boundaries were found in both systems between schizoaffective disorder on one side and schizophrenia and bipolar disorder on the other side. The different duration criteria for schizophrenia of six months in DSM-III-R and one month in ICD-10 tend to have considerable consequences for frequency rates of schizophrenia in a typical clinical setting.

Adult↗

PubMed1993

Judging rolling wheels: dynamic and kinematic aspects of rotation-translation coupling.

Four experiments were carried out to investigate observers' abilities to judge rolling motions. The experiments were designed to assess whether two important aspects of such motions are appreciated: the kinematic coupling of rotation and translation, and the dynamic effects of gravity. Different motion contexts of rolling wheels were created using computer-generated displays. The first experiment involved wheels rolling down an inclined plane. Observers spontaneously appreciated the anomaly of wheels that failed to accelerate, but they were not able to differentiate between different acceleration functions. Moreover, their judgments were almost exclusively based on the translation component of the rolling motion, neglecting the rotation component. In a second experiment it was found that observers could accurately estimate the perimeter of various objects. Thus, their inability to consider rotation information is not attributable to misperceptions of the geometry of wheels. In a third experiment the finding that rolling wheels appear to overrotate was replicated; however, findings from this experiment also showed, together with those from a fourth experiment, that observers are able to make very accurate judgments about translation-rotation coupling in rolling wheels when information is provided about the orientation of the wheel and the texture of the surface on which it rolls.

Female↗

PubMed1993

Increased sensitivity to agonist stimulation of the Ca2+ response in neutrophils of manic-depressive patients: effect of lithium therapy.

The agonist-stimulated increase of intracellular free-Ca2+ concentration, an indicator of the sensitivity of the inositol phospholipid second-messenger generating system, was measured in neutrophils from patients with manic-depressive disorder, and controls. Dose-response curves of the calcium response were determined by measuring the fluorescence of neutrophils loaded with fura-2 and stimulated with various concentrations of the chemotactic tripeptide formylmethionylleucylphenylalanine. EC50 values were obtained for 14 medication-free patients (5 acutely depressive, and 9 symptom free remitted patients with a history of manic-depression or recurrent major depression), 9 lithium-treated, euthymic manic-depressive patients and 10 drug-free healthy controls. The EC50 values of the untreated patients were significantly lower than in the controls. Lithium-treated patients had EC50 values significantly higher than controls. These results suggest that manic-depressive disorder is associated with an increased sensitivity of the inositol phospholipid second-messenger generating system, which is counteracted by lithium treatment.

Adult↗

PubMed1992

Prospective long-term follow-up of depressed patients with and without suicide attempts.

This 4-6-year prospective follow-up study compared reactive depressives with (n = 48) and without suicide attempts before index admission (n = 24). Both groups showed a favourable course and outcome concerning psychiatric diagnoses (DSM-III), psychopathology, social integration, and social functioning as well as displaying a nearly identical course and outcome. In both groups, two patients committed suicide attempts during the follow-up period. 2 (1) male patients from the group with suicide attempts committed suicide.

Adjustment Disorders↗

PubMed1992

Stereokinetic effect and its relation to the kinetic depth effect.

The stereokinetic effect (SKE) has been defined and studied by nested circular patterns rotating on a turntable. Circles must appear not to rotate as they revolve, which in turn results in their appearing to translate relative to one another. A powerful illusion of object depth results even though the individual circles do not undergo an appropriate foreshortening consistent with their apparent changes in slant. It is suggested and tested that the SKE is based on the changing positions between the nested contours despite the absence of any change within each contour, whereas the kinetic depth effect (KDE) entails both kinds of change. It follows that a turntable method of presentation is not necessary, and between-contour transformations can be simulated by computer animation. Displays consisting of simple translations were shown to evoke robust depth impressions as were patterns consisting of contours of varying shapes. Comparisons of the depth, compellingness, and rigidity of matched SKE and KDE displays are reported. The SKE is taken to be paradigmatic for how the visual system perceives depth when observing small object rotations that occur in everyday situations.

Depth Perception↗

PubMed1992

Influence of animation on dynamical judgments.

The motions of objects in the environment reflect underlying dynamical constraints and regularities. The conditions under which people are sensitive to natural dynamics are considered. In particular, the article considers what determines whether observers can distinguish canonical and anomalous dynamics when viewing ongoing events. The extent to which such perceptual appreciations are integrated with and influence common-sense reasoning about mechanical events is examined. It is concluded that animation evokes accurate dynamical intuitions when there is only 1 dimension of information that is of dynamical relevance. This advantage is lost when the observed motion reflects higher dimension dynamics or when the kinematic information is removed or degraded.

Adult↗

PubMed1991

Apparent extended body motions in depth.

Five experiments were designed to investigate the influence of three-dimensional (3-D) orientation change on apparent motion. Projections of an orientation-specific 3-D object were sequentially flashed in different locations and at different orientations. Such an occurrence could be resolved by perceiving a rotational motion in depth around an axis external to the object. Consistent with this proposal, it was found that observers perceived curved paths in depth. Although the magnitude of perceived trajectory curvature often fell short of that required for rotational motions in depth (3-D circularity), judgments of the slant of the virtual plane on which apparent motions occurred were quite close to the predictions of a model that proposes circular paths in depth.

Adult↗

PubMed1991

Integration of local features as a function of global goodness and spacing.

In two experiments, the accuracy with which subjects detected a conjunction of features was examined as a function of the spacing between items and the goodness of the axis along which they were located. In each array, two items were arranged along a vertical, a horizontal, or a diagonal axis. Based on the well-established oblique effect, the vertical and horizontal axes were considered to be good global patterns and the diagonals were considered to be poor. In Experiment 1, the two items in an array could be two horizontal lines, two vertical lines, a vertical and a horizontal line, or a plus sign with one of the single lines. In Experiment 2, a positive- and a negative-diagonal line were used as the individual features, and an "X" was used as the conjunction. The results from Experiment 1 indicated that global goodness influenced only the rate of illusory conjunctions, and not of feature errors. Illusory conjunctions of vertical and horizontal line segments were more likely to occur in vertical and horizontal arrangements. The results from Experiment 2 revealed a reversal of the effect of global goodness on the rate of illusory conjunctions: Illusory conjunctions of negative- and positive-diagonal line segments were more likely to occur in diagonal arrangements. The results of both experiments taken together showed the existence of an important and new factor that influences the likelihood that features of shape will be conjoined: the ease with which line segments conjoin when they are translated along their extent toward each other. In both experiments, greater spacing between items produced more feature-identification errors and fewer feature-integration errors than did less spacing.

Humans↗