Epidemiology applied to the investigation of infant health determinants: basic concepts and methods

Epidemiologic principles and methods have been widely employed in clinical research. The purpose of this paper is to discuss basic epidemiological concepts applied to the investigation of the determinants of infant diseases. The theoretical framework outlines the hypothesis of the investigation. The design of the study is chosen accordingly. Exposure and outcome are defined, and the sampling criteria and the strategies for its implementation are specified. The researcher can be an observer (as in cross-sectional, cohort and case-control studies) or can determine who will be exposed in the experimental studies (clinical trials). Cross-sectional study is the easiest one to conduct, since exposure and outcome are assessed simultaneously in a well-defined population. In a cohort study, a group of people is assembled according to the exposure and followed over time to detect who will develop the outcome. In a case-control study,people are selected based on disease status. Then, they are investigated about previous exposures which could be associated with the development of the disease. The investigator allocates the exposure and then follows the participants to assess the outcome in clinical trials. Contrasting with the experiment developed in laboratory, the subjects are human beings.     

Zinc and copper in infants fed breast-milk or different formula

In 129 term infants at birth and at the age of 4 months, zinc and copper concentrations of plasma and urine were determined by graphite furnace atomic absorption spectrophotometry and the values correlated to other biochemical parameters and somatic data. Of the infants, 49 were exclusively breast-fed, 44 fed with various commercially available cow's milk formula, 35 fed with a hypollergenic formula (cows's milk whey hydrolysate, commercially available, supplemented with zinc and copper). Plasma zinc values declined from birth to the age of 4 months in all three groups (P<0.001). In formula fed children, 4 months old, the values (11.1±1.7 mol Zn/l) were significantly lower than in breast-fed (12.2±1.7 mol Zn/l;P=0.004) or babies on hypo-allergenic formula (12.4±1.6 mol Zn/l;P=0.0015). In accordance with the literature plasma copper and caeruloplasmin values increased significantly within the first 4 months of life, the plasma levels were similar in either feeding group, only urinary copper excretion was higher in male infants on hypoallergenic formula (P<0.03) at the age of 4 months. There were no correlations between zinc or copper values and alkaline phosphatase. In infants on hypo-allergenic formula there was a negative correlation between plasma zinc and weight or height increments. Despite different zinc and copper supply, presumedly different bioavailability, and different plasma zinc values, all infants thrived and weight and length increments were similar in each group.     

Ochratoxin A in blood of healthy population in Zagreb

Healthy blood donors from the city of Zagreb were checked for the presence of a nephrotoxic mycotoxin ochratoxin A (OTA) in the plasma. Samples of blood were collected in June, September, and December 1997, and March 1998, totalling 200 or 50 in each round. The concentrations of OTA were measured using high pressure liquid chromatography (HPLC) method (detection limit 0.2 ng OTA/ml of plasma). The frequency of OTA-positive samples (> 0.2 ng/ml of plasma) showed significant seasonal variation (P < 0.001). The frequency of OTA-positive samples was the highest in March (65%) and it gradually decreased towards December (12%). The high frequency of positive samples coincided with seasons favouring growth of moulds and production of toxins. The daily intake of OTA by healthy persons in Zagreb was estimated from the mean concentration of OTA in samples collected during the whole year (0.19 ng OTA/ml plasma). The estimated daily intake was 0.26 ng/kg b.w., that is, substantially below the tolerable daily intake proposed by World Health Organization (16.0 ng/kg b.w.).     

Characterization of mechanical withdrawal responses and effects of mu-, delta- and kappa-opioid agonists in normal and mu-opioid receptor knockout mice

Clinical and experimental observations suggest that opiates can exert different influences on the perception of stimuli from distinct sensory modalities. Thermally-induced nociception is classically responsive to opiate agonists. mu-Opioid receptor-deficient transgenic mice are more sensitive to thermal nociceptive stimuli and morphine fails to attenuate the nociceptive responses to thermal stimuli in these animals. To enhance our understanding of opiate influences on mechanical sensitivity, we have examined withdrawal responses to a sequence of ascending forces of mechanical stimuli in mice with normal (wild type), half-normal (heterozygous) and absent (homozygous) mu-opioid receptor levels. We report data from mice examined without drug pretreatment or following pretreatment with morphine, the selective kappa-opioid agonist, U50488H, and the selective delta-opioid agonist, DPDPE. Saline-pretreated mice of each genotype displayed similar, monotonically increasing frequency of withdrawal responses to the graded stimuli. Subcutaneously administered morphine produced a dose-dependent reduction in withdrawal responses in wild type and heterozygous mice, but had no significant effect in homozygous mice. Intraventricular administration of DPDPE also reduced the frequency of paw withdrawal (FPW) in wild type mice, but not in homozygous mice. In contrast, systemic U50488H produced a dose-dependent attenuation of paw withdrawal in both wild type and homozygous mice. These findings suggest that (1) interactions of endogenous peptides with mu-opioid receptors may not play a significant role in the response to mechanical stimuli in drug-free animals, and (2) deficiency of mu-opioid receptors has no functional consequence on the response to the prototypical kappa-opioid receptor agonist, but decreases responses to the prototypical mu- and delta-opioid receptor agonists.     

Patterns of relation and premorbid personality in late paraphrenia and depression

38 patients with late paraphrenia and 38 with endogenous depression of late onset were compared regarding interpersonal relations and personality traits by means of semistructured interviews. The prevalence of premorbid personality disorder was determined by the Structured Clinical Interview for DSM-III-R Personality Disorders. The main objective of the study was to look for lifetime relation patterns and personality traits distinguishing the two groups and pointing to a specific premorbid vulnerability of paranoid and depressive patients. A high rate of personality disorder comorbidity was found in both groups, with mainly paranoid and schizoid disorder in late paraphrenic patients (39%) and avoidant, dependent or compulsive personality in depressives (35%). As a rule, this corresponded to a lifelong pattern of seclusion and self-sufficiency in the paranoid, and of close intimacy and heteronomy in the depressive patients. On the basis of the results, a polar typology of personality and interpersonal relations in both patient groups is developed.     

Value of alignment osteotomy of the proximal tibia in the endoprosthesis period]

AIM OF THE STUDY: To evaluate the value of high tibial osteotomy in times of growing numbers of endoprostheses we compared our personal with other results of this method as well as of the unilateral sledge prosthesis. MATERIAL AND METHODS: Between 1972 and 1993 the high tibial osteotomy as described by Coventry was performed in 105 patients. 98 patients could be examined clinically-radiologically and evaluated with a questionnaire. The indication for surgery was given in patients with unilateral arthrosis without affection of the retropatellar joint and without significant ligamentous instability. The varus deviation was in no case more than 10 degrees. The average follow-up for the clinical-radiologic examination was 9.4 years. RESULTS: 77 patients (78.6%) were satisfied with the outcome of the surgery. Here it was seen that neither age nor pain or instability had an influence on this judgement. The walking distance on the other hand had a significant influence. Stair climbing and range of motion were significantly important as well. 23 patients gave the judgement "excellent", 31 "good", 36 "satisfactory" and 8 patients were "not satisfied". A significant influence of patient age on the judgement could not be proven. The division in the Japanese Score showed "good" results in 14%, "moderate" in 81% and "poor" in 5%. 13 knee joints (13.3%) were absolutely pain-free and in 67 cases (68.4%) there were a definite pain reduction. A significant correlation between the preoperative axis deviation and pain could not be found. An average flexion of 97.5 degree and an extension deficit of 3.3 degree on average was seen. A significant difference of range of motion dependent on age groups could not be found. In 42 knees (42.9%) the lateral ligaments were clinically stable, in 35 cases (35.7%) there was a first degree lateral stress gap and in 21 cases (21.4%) there was a second degree lateral instability. A significant correlation between the instability and age or pain could not be proven. 13 revision surgeries including 9 endoprosthesis implantations were performed. CLINICAL RELEVANCE: The study showed a high level of satisfaction with an exact surgical indication. When seeing the growing number of implanted uni- or tricompartmental endoprostheses the procedure of tibial osteotomy can be suggested for patients with unilateral arthrosis without retropatellar arthrosis, with an axis deviation less than 15 degrees, with unaffected cartilage of the contralateral compartment and without ligamentous insufficiency independent of patient age.     

Effect of patient age on use of the knee joint score

AIM OF THE STUDY: Clinical studies are done with the help of scores though different factors of influence lower comparability. The underlying study examines the influence of patient age as this always presents a certain span. METHOD: 96 degree I damaged knee joints were examined by 3 examiners using the Larson-, Lysholm-, Marshall-, HSS- and OAK-score. Furthermore ratings by a VAS and the Tegner activity score were done. With the Friedman test, the rank correlation coefficient by Spearman and the contingency chart by Bowker it was tested if the examiners and the scores rate equally. To find out the influence of the age three age groups were made up. RESULTS: The examiners judged significantly different excluding the Marshall and the OAK scores. In between two examiners no significant difference could be found between the young and the middle-aged patient group. Between two other examiners no significant difference was found only for the Lysholm and the HSS score in the young group and only for the Lysholm score in the middle-aged group. In the group of the senior patients no significant difference for the scores by Lysholm, Marshall and OAK were found. In the comparison of the second examiner pair no significant differences could be proven by the scores by Larson, the OAK and the HSS. All other comparisons were significantly different. In the comparison of all five scores significant differences were seen between the Larson score and the HSS and the Lysholm and the HSS. The Lysholm score proved to be the strictest, the HSS to be the leanest. CONCLUSION: Especially for the senior patients in dependency of the examiner and the chosen score significant differences were found concluding that the relevance of results lessens for future times as the score results drop with patient age anyway. The age span in one study should have a maximum of 10-20 years to reduce the influence of age on the final result.     

A cross-sectional study of workers in the chemical industry with occupational exposure to hexamethylenetetramine

Objectives: To assess the health effects of hexamethylenetetramine (HMT) on the airways and the skin of workers in the chemical industry. Methods: A cross-sectional study was performed with 17 employees of a HMT-producing chemical plant and 16 control subjects from the plant. In addition, we examined 4 out of 5 subjects who had left the production for medical reasons during the last 10 years. Anamnestic data, total and specific IgE to four environmental allergens, lung function and bronchial responsiveness to methacholine were assessed by standard procedures. Skin prick tests (SPT) and patch tests were performed with known sensitizing substances and HMT 100 mg/ml and 2% pet and aq. Results: A high number of exposed subjects and controls reported symptoms during the previous year (64.7% vs 68.8%), most of them were not related to work. Work-related symptoms and objective parameters did not show differences between groups. No sensitizations to HMT as assessed by SPT or patch tests were found. Among those who had left the HMT production for medical reasons, 2 former baggers showed sensitizations to HMT by patch tests. These reported eczema during exposure but lost symptoms after removal from exposure. Geometric mean HMT concentrations as assessed by personal sampling were 0.3 [95% confidence intervals (CI) 0.1; 0.9] mg/m³ in shiftleaders and 0.6 (95% CI 0.3; 1.1) mg/m³ in baggers. Conclusion: High exposures to HMT may cause allergic contact dermatitis. There was no evidence of an increased risk for occupational asthma at mean airborne HMT concentrations below 1 mg/m³. Received: 4 February 1999 / Accepted: 10 July 1999     

Xanthine oxidase inhibition by allopurinol affects the reliability of urinary caffeine metabolic ratios as markers for N-acetyltransferase 2 and CYP1A2 activities

Objectives: To evaluate the in vivo effect of xanthine oxidase (XO) inhibition by allopurinol on the determination of polymorphic N-acetyltransferase 2 (NAT2) and cytochrome P450 1A2 (CYP1A2) with urinary caffeine metabolic ratios. Methods: In an open, prospective study involving 21 healthy subjects (eight fast, 13 slow NAT2 acetylators) allopurinol (300 mg perday) was administered orally on trial days 1–8, followed by a wash-out period of 8 days. Urinary caffeine tests (200 mg caffeine p.o.) were performed repetitively. Urine was collected for 8 h and venous blood samples for the determination of allopurinol, oxypurinol and uric acid were drawn. The urinary caffeine metabolites 1-methyluric acid (1MU), 1-methylxanthine (1MX), 1,7-dimethyluric acid (17MU), 1,7-dimethylxanthine (17MX), 5-acetylamino-6-formylamino-3-methyluracil (AFMU), plasma allopurinol and oxypurinol were analysed using high-performance liquid chromatography (HPLC). Results: During XO inhibition by allopurinol, the formation of 1MU from 1MX and therefore the XO ratio 1MU/1MX decreased to 15.9 (1.2)% [mean with (SEM)] of baseline values (P < 0.005). The NAT2 ratio AFMU/1MX decreased likewise to 56.7 (6.3)% (P < 0.005). AFMU/(AFMU + 1MX + 1MU), an alternative NAT2 ratio, remained constant, but the CYP1A2 ratio (AFMU + 1MX + 1MU)/17MU, used to express CYP1A2 activity, transiently increased to 167 (13)% (P < 0.005). The NAT2 phenotype did not influence CYP1A2 and XO ratios or plasma oxypurinol pharmacokinetics. Conclusions: Several caffeine metabolic ratios are commonly used to express the activities of NAT2, CYP1A2 and XO both in healthy volunteers and in polymedicated patients, although their reliability has not been evaluated thoroughly during concurrent drug administration. The findings of this study suggest that NAT2 phenotyping should be performed using the ratio AFMU/(AFMU + 1MX + 1MU) if an XO inhibitor may be present. It also shows that the determination of CYP1A2 activity with caffeine as a metabolic probe is considerably altered under these conditions. Thus, concomitant drug administration may impair the robustness of multiple pathways of the complex caffeine test. This points to the need for alternative probes, designed to assess only the activity of a single enzyme because, in contrast to healthy volunteers, in patients known or unknown drug interactions may often be present. Received: 10 August 1998 / Accepted in revised form: 5 October 1998     

Cardiac effects of beta-adrenoceptor antagonists with intrinsic sympathomimetic activity in humans: beta1- and/or beta2-adrenoceptor mediated?

The aim of this study was to find out whether cardiac responses to the beta-adrenoceptor antagonists with intrinsic sympathomimetic activity (ISA) xamoterol and celiprolol are mediated by cardiac beta1- or beta2-adrenoceptors or both. For this purpose we assessed, in six healthy male volunteers, the effects of xamoterol (100 and 200 mg, p.o.) and celiprolol (200, 600, and 1,200 mg, p.o.) on blood pressure, heart rate, and heart rate-corrected duration of the electromechanical systole (QS2c, as a measure of inotropism). Xamoterol, in both doses, increased systolic blood pressure and heart rate, transiently decreased diastolic blood pressure, and shortened QS2c; all these effects were attenuated after pretreatment of the volunteers with the beta1-adrenoceptor antagonist bisoprolol. Celiprolol, in all three doses, increased heart rate, decreased diastolic blood pressure, and shortened QS2c but only marginally increased systolic blood pressure. Bisoprolol did not attenuate these celiprolol effects but rather enhanced celiprolol effects on systolic blood pressure and heart rate. In a further set of experiments, we studied cardiovascular effects of celiprolol in six healthy volunteers whose beta2-adrenoceptors had been desensitized by a 2-week treatment with 3x5 mg/day terbutaline. Under these conditions, celiprolol failed to increase heart rate or to shorten QS2c. We conclude that, under resting conditions, in healthy volunteers, beta-adrenoceptor antagonists with ISA can exert increases in heart rate and contractility that are mediated by either cardiac beta1-adrenoceptor (xamoterol) or cardiac beta2-adrenoceptor (celiprolol) stimulation. Thus in the human heart, the ISA of beta-adrenoceptor antagonists can be a beta1- or beta2-adrenoceptor agonistic component.