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Biomedical subjects

W Stein

Publications and source records attributed to W Stein.

At least 37 records · Page 2Linked to original sources
PubMed1996

Contributions of structure and innervation pattern of the stick insect extensor tibiae muscle to the filter characteristics of the muscle-joint system

It is shown that the low-pass filter characteristics of the muscle­joint system of the femur­tibia joint of the stick insect Cuniculina impigra result from co-contraction of the extensor and flexor tibiae muscles. The most distal region of the extensor muscle, which contains a high percentage of slow muscle fibres, is involved in this co-contraction. This conclusion results from the following evidence. (1) Inertial and friction forces do not affect the characteristics of the low-pass filter of the muscle­joint system. (2) There is some co-contraction of the extensor and flexor muscles during sinusoidal stimulation of the femoral chordotonal organ at high stimulus frequencies. Both muscles generate tonic forces that increase with increasing stimulus frequency and also increase with time from the beginning of stimulation until a plateau is reached. (3) For the extensor muscle, this tonic force is produced by its most distal portion only. (4) Electrical stimulation of the common inhibitory motoneurone (CI1) reduces the tonic force generated in this most distal portion of the extensor muscle. Therefore, CI1 stimulation reduces the amplitude of tibial movement in response to sinusoidal stimulation of the femoral chordotonal organ at stimulus frequencies below 0.5 Hz (over this frequency range, the tibial movement amplitude is a function of the force amplitude produced by the whole extensor muscle and there is no co-contraction), but at chordotonal organ stimulus frequencies of 1 Hz and above, CI1 stimulation increases the tibial movement amplitude (in this case, movement amplitude is limited by the degree of co-contraction of the extensor and flexor muscles). With repeated chordotonal organ stimulation at higher stimulus frequencies, the tibial movement amplitude steadily decreases. This must be a consequence of increasing levels of co-contraction of the extensor and flexor muscles, since at low stimulus frequencies (no co-contraction) there is no reduction in movement amplitude during repeated stimulations. It is concluded that co-contraction of the extensor and flexor tibiae muscles prevents instability in the reflex loop in spite of the high gain necessary for the generation of catalepsy. Therefore, the mechanism described can be considered to be an adaptation to the ecological niche occupied by this animal. The contribution of the distal part of the extensor muscle to this system can be switched off by the CI1 during active movements.

Journal Article↗
PubMed1993

Dispositional traits as risk in problem drinking.

A trait-dispositional paradigm for conceptualizing personality provided the framework for investigating the relationship between personality dispositions and drinking problems. This approach was compared directly with personality research based on the Minnesota Multiphasic Personality Inventory (MMPI). A total of 241 subjects (192 men and 49 women) were tested at a mandatory Driving While Intoxicated (DWI) first-offender education program. Information was gathered from the Michigan Alcoholism Screening Test (MAST), Blood Alcohol Concentration (BAC) at time of arrest, and two personality tests--the MacAndrew Alcoholism Scale (MAC) and the Problem Drinker Trait List (PDTL). The psychometric properties of the PDTL were analyzed and compared with those of the MAC. In comparing the two personality tests in terms of their capacity to predict drinking problems over a wide range of drinking severity, the PDTL performed as well or better than the MAC, particularly for drinkers with low arrest BAC. Comparative analysis between the best predictor items of the MAC and of the PDTL revealed little relationship between the item domains. The predictive trait clusters of the PDTL for men were Emotionality/Depressiveness, Impulsivity, and Low Self-Confidence, whereas predictive clusters for women included Depressiveness, Overcontrol, and Alienation.

Adult↗
PubMed1993

Characteristics of colon cancer at time of presentation.

OBJECTIVE: To evaluate the relationships between demographic and clinical characteristics and the stage and site of colon cancer at the time of presentation. METHODS: New cases of colon cancer identified through a tumor registry at a teaching hospital during 1989 were reviewed retrospectively. Of the 110 cases, 53% of the subjects were female, 95% were white, and 63% were more than 70 years of age. RESULTS: Early stages of colon cancer (Dukes A [11%] or B [41%]) occurred in 52%, and late stages (Dukes C [26%] or D [22%]) in 48%. Most patients (88%) presented with symptoms; 12% of the cases were detected in asymptomatic patients. Of the 13 asymptomatic patients, 7 were identified by positive occult blood in the stool, 5 by colonoscopy, and 1 during a hysterectomy. The stage of colon cancer was more likely to be early in asymptomatic patients (85% Dukes A or B) compared to those with symptoms (47% Dukes A or B) (p < 0.02). Sixty-two percent (62%) of the cecum/ascending colon cancer were early compared to 46% of the cancers in other locations (p = 0.11). Seventy-seven percent (77%) of the asymptomatic cancers were located in the cecum/ascending colon compared to 33% of the symptomatic patients (p < 0.02). Age and gender were not associated with site or stage of colon cancer. CONCLUSION: The majority of patients with colon cancer are diagnosed when symptomatic. When colon cancer is diagnosed while still asymptomatic, it is more likely to be at an early stage. The most common screening procedure leading to diagnosis in asymptomatic patients is the identification of fecal occult blood. Colon cancer is more likely to be located in the cecum/ascending colon when diagnosed at an asymptomatic stage.

Aged↗
PubMed1992

Simple computer-assisted diagnosis of acute myocardial infarction in patients with acute thoracic pain.

In order to minimize the initial diagnostic uncertainty in patients suspected of having acute myocardial infarction, we prospectively extracted predictive variables from previous history, ECG, and clinical chemical parameters of 87 patients, who were admitted for acute thoracic pain. The variables thus extracted were: Thoracic pain in previous history, duration of pain, white blood cell count, blood glucose, creatine-kinase, and S-T elevation in the ECG. These parameters were used for formulating a mathematical model based upon univariate and multivariate statistical methods. The sensitivity of the model in the study population was 95% and the specificity 77%. Correct classification was achieved in 89% of cases. In a second phase, the prognostic index was prospectively evaluated in a second set of 122 consecutive patients. In this test population, the sensitivity was 89% and the specificity 86%. 87% of patients were classified correctly.

Adult↗
PubMed1991

Infradian rhythms of alanine aminopeptidase excretion during gentamicin therapy.

Urinary excretion of alanine aminopeptidase (EC 3.4.11.2) was examined in 30 patients (22 women, 8 men, range 38-81 years; mean age 55.4) receiving gentamicin in a therapeutic dosage, which was based on the monitored blood creatinine concentration. In general, therapy lasted 10 days. The excretion of 24 individuals displayed significant infradian rhythms with periods between 2.2 and 8.1 days. In 10 of these 24 patients (42%) a circaseptan period was detected. The high portion of circaseptan rhythms might have been induced by the detrimental effects of gentamicin on the proximal tubule and the resulting processes of reconstitution.

Adult↗
PubMed1989

Reference ranges for alpha-amylase in serum and urine with 4,6-ethylidene-(G7)-1-4-nitrophenyl-(G1)-alpha,D-maltoheptaoside as substrate.

Reference ranges for alpha-amylase in serum, spontaneously voided urine, and 24 h urine were determined, using 4,6-ethylidene-(G7)-1-4-nitrophenyl-(Gl)-alpha,D-maltoheptaoside as the substrate (EPS method), at 25, 30, and 37 degrees C. The measured values were evaluated with and without the use of a factor which converts the results of the alpha-amylase EPS method into values comparable to those obtained with the alpha-amylase PNP method (substrate: 4-nitrophenyl-alpha,D-maltoheptaoside); comparison with the established reference ranges of the PNP method was therefore possible. The values for urine sometimes deviated markedly from the PNP reference ranges, but the values for serum showed close agreement. With the use of the conversion factor, the following reference ranges are proposed for the new alpha-amylase method: Serum (186 males and 131 females): up to 120 U/l (25 degrees C), up to 160 U/l (30 degrees C), and up to 220 U/l (37 degrees C). Spontaneously voided urine: up to 600 U/l (n = 323, 25 degrees C), up to 800 U/l (n = 373, 30 degrees C), and up to 1000 U/l (n = 373, 37 degrees C). 24 h urine: up to 450 U/24 h (n = 90, 25 degrees C), up to 650 U/24 h (n = 129, 30 degrees C), and up to 900 U/24 h (n = 129, 37 degrees C).

Adolescent↗
PubMed1989

Evaluation of a new alpha-amylase assay using 4.6-ethylidene-(G7)-1-4-nitrophenyl-(G1)-alpha-D-maltoheptaoside as substrate.

The determination of alpha-amylase activity using an ethylidene-blocked 4-nitrophenyl-maltoheptaoside (EPS) has been evaluated in five laboratories on eight different analysers at 25 degrees C, 30 degrees C and 37 degrees C. The protecting ethylidene group inhibits hydrolysis at the non-reducing end of the substrate molecule by the auxiliary enzyme, alpha-glucosidase. The combined reagent is therefore stable for at least 10 days at 2-8 degrees C. HEPES is used, because the molar absorbance of 4-nitrophenol is independent of temperature in the presence of this buffer. Compared with the method using unprotected substrate 4-nitrophenyl-alpha-D-maltoheptaoside (4NP-G7), the present method is equal or better with respect to the imprecision, linearity and interlaboratory transferability of results in human and control sera. Since the protected and unprotected substrates differ in their turnover rate, the new assay yields activities which differ from those of the 4-nitrophenyl-alpha-D-maltoheptaoside method. Based on the homogeneous results obtained in method comparisons between EPS and 4-nitrophenyl-alpha-D-maltoheptaoside, and in order to maintain the 4-nitrophenyl-alpha-D-maltoheptaoside reference values, a conversion factor was derived to eliminate the above differences: activityEPS x 2.50 = activity4NP-G7. The temperature and instrument independence of this relationship was demonstrated in a total of 720 human sera and plasmas.

Glucosides↗
PubMed1988

A comparison of the actions of noradrenaline and UK-14,304 in the longitudinal smooth muscle of the rat isolated portal vein--no evidence for a population of post-junctional alpha 2-adrenoceptors.

The pharmacological characteristics of post-junctional alpha-adrenoceptors mediating contractions of the longitudinal smooth muscle of the rat isolated portal vein have been examined. Responses to the noncumulative addition of either noradrenaline, or the selective alpha 2-adrenoceptor agonist UK-14,304, were equally sensitive to a low concentration (0.005 mumol/l) of prazosin. Idazoxan (0.1 mumol/l-0.5 mumol/l), a selective alpha 2-adrenoceptor antagonist, was less potent than prazosin against both agonists. The combination of 0.1 mumol/l idazoxan and 0.125 mumol/l prazosin failed to produce a greater inhibition of responses to UK-14,304 than 0.125 mumol/l prazosin alone. A study involving the effect of various antagonists against a single concentration producing a submaximal response to UK-14,304, provided evidence for a prazosin-resistant component of responses which was sensitive to phentolamine. This component could, therefore, be attributed to an alpha-adrenoceptor. However, this particular response could not be ascribed to stimulation of an alpha 2-subtype since the selective alpha 1-adrenoceptor antagonist, corynanthine, produced greater inhibition than the selective alpha 2-adrenoceptor diastereoisomer rauwolscine.

Animals↗
PubMed1988

Multicenter evaluation of a specific pancreatic isoamylase assay based on a double monoclonal-antibody technique.

Eleven evaluators from nine laboratories in five countries evaluated a new immunoinhibition method for pancreatic isoamylase determination that is as simple to perform as that for total amylase. The precision at low and intermediate activity concentrations was superior, and at high concentrations it equalled that of the wheat-germ inhibitor method. The test was linear to approximately 2000 U/L, depending on the instrumentation used. The percentage salivary isoamylase activities remaining in specimens after reaction with two monoclonal antibodies ranged from 2 to 4.4%. Comparative studies showed good correlation with the wheat-germ inhibitor (r greater than 0.978) and electrophoresis methods (r = 0.920). Hemolysis, lipemia, and bilirubinemia have no effect on results. Interlaboratory studies demonstrated excellent transferability of the method, if instruments are calibrated with the same calibrator. Reference intervals for pancreatic isoamylase are 13 to 64 U/L (25 degrees C), 13 to 83 U/L (30 degrees C), and 17 to 115 U/L (37 degrees C). A clinical evaluation of patients with acute pancreatitis showed that pancreatic isoamylase has a greater clinical sensitivity than total amylase.

Acute Disease↗
PubMed1988

The fetal phenotype of the 18p-syndrome. Report of a male fetus at twenty-one weeks.

Morphological and cytogenetic findings in a male fetus at 21 weeks gestation after prenatally detected monosomy 18p are reported. The fetus displayed dysmorphic features resembling the 18p-syndrome, such as decreased head circumference, slightly receding forehead, hypertelorism, epicanthus, horizontal palpebral fissures, depressed nasal bridge, long philtrum, carp mouth, irregular crenated maxillar alveolar ridge, retrognathia, lowset dysplastic ears with posterior rotation, edema of neck, hands and feet respectively, fingers with drop-shaped tips, short first toes with dysplastic nails, hypoplastic male external genitalia. After termination of the pregnancy, biopsies from different fetal organs as well as from the placenta were taken and set up for long term cell cultures. The metaphases of fetal organs all showed the karyotype 46,XY,18p-. A fetal blood culture failed to grow. Unexpectedly, the metaphases of the placenta showed the mosaic karyotype 46,XY/46,XY,18p-/46,XY,18p+.

Chromosome Aberrations↗
PubMed1987

Clinical chemistry.

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Chemistry, Clinical↗
PubMed1987

Macro lipase--a new member of the family of immunoglobulin-linked enzymes.

This first report describes a variant form of lipase in the serum of a woman suffering from a malignant non-Hodgkin lymphoma. Activity measurements of serum lipase and amylase showed persistently elevated activities of lipase with simultaneously normal activities of amylase. Results of exclusion chromatography and immunological investigations clearly demonstrate that the atypical time-course of lipase activity is not due to injury of the pancreas or alterations of the patient's lipase, but rather due to the presence of lipase-binding autoantibodies, resulting in the formation of immune complexes with high molecular mass (Mr greater than 200,000) between lipase and immunoglobulin G lambda. A clinical significance, if any, of this macro lipase has yet to be determined.

Antigen-Antibody Complex↗
PubMed1985

Indices for the age of the creatine kinase M-chain in the blood.

The apparent activation energy of the CK reaction as well as the Michaelis-Menten constants and the isoelectric point of CK MM can be used as indices for the mean age of the CK M-chain in the blood in vivo and in vitro. Modifications in the CK M-chain take place in vivo in the blood and in vitro in a serum matrix. Gradual increases in the apparent activation energy are also observed both in vivo and in vitro. It is confirmed that the modification in the CK M-chain causes a rise in the apparent activation energy, mu. A gradual increase in apparent activation energy, due to the ageing process of the CK M-chain, was observed after myocardial infarction. A significantly increased value for u was observed at the time that total CK activity already had returned to reference values. In spite of the normal CK value, the apparent activation energy still indicated that there had been myocardial damage. The Michaelis-Menten constants for creatine phosphate and ADP are also influenced significantly by the modification in the M-chain. While the apparent activation energy increases, the Michaelis constants decrease in the order MM3, MM2, MM1. The Michaelis-Menten constants for both ADP and CrP can be used as an index for the mean age of the enzyme in the blood. The Michaelis-Menten constants for CrP and ADP show significant variations with the measuring temperature for virtually all CK MM forms.

Creatine Kinase↗