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Biomedical subjects

J Altmann

Publications and source records attributed to J Altmann.

15 recordsLinked to original sources
PubMed1992

Behavioral, endocrine, and immunological correlates of immigration by an aggressive male into a natural primate group.

A very aggressive young adult male entered one of three long-term study groups of yellow baboons. Papio cynocephalus, approximately 3 weeks after an immobilization project began. The immigrant male's rate of agonistic encounters was appreciably higher than average, and these interactions disproportionately involved adult females as targets. Basal cortisol concentrations were higher and total lymphocyte counts lower for individuals immobilized during the immigration situation than for other individuals; these effects were greater for females than for males. Among animals whose endocrine data were obtained during the immigration period, some were specific targets of the immigrant male's aggression and others were not. Lymphocyte counts were significantly lower for those individuals who were victims of the male's aggression than for noninvolved individuals; a nonsignificant tendency toward higher basal cortisol concentrations for victims was observed as well. The immigrant male himself had a high basal cortisol concentration, a low lymphocyte count, and a testosterone concentration that was triple the average for adult males and almost double the second highest value in the population.

Aggression↗
PubMed1991

Incidence of hypercortisolism and dexamethasone resistance increases with age among wild baboons.

While many features of the adrenocortical axis are unchanged with age in humans, there is a pattern of senescent hypercortisolism. This occurs basally, following threshold doses of dexamethasone, and in synergy with depression or Alzheimer's disease. An understanding of neuroendocrine aging is important, for both its gerontological implications, and determination of normative values for comparison with neuropsychiatric states. We have investigated whether aging is associated with hypercortisolism in a population of wild primates. The subjects were 108 yellow baboons (Papio cynocephalus) that have been under long-term study of Amboseli National Park in Kenya. Animals were anesthetized by blowgun under similar circumstances that allow for determination of basal cortisol concentrations. Sixty minutes later, 5.0 mg dexamethasone was administered to each animal, and cortisol determinations were made on serum collected immediately before administration and 6 hr later. Basal cortisol concentrations rose with age (p less than 0.028; r = 0.23). This occurred in a nonprogressive manner, in that there were no differences in concentrations among the youngest three quartiles of animals, whereas animals in the oldest quartile (older than approximately 16 years) had significantly higher values. In addition, there was a significant increase in postdexamethasone cortical concentrations with age (p less than 0.01; r = 0.31). This feature emerged progressively with age in both sexes. A number of possible artifactual causes of this senescent pattern could be eliminated, including medication confound, coincident disease, and body weight. These findings suggest that hypercortisolism and glucocorticoid feedback resistance might be general features of primate aging.

Adrenal Cortex↗
PubMed1987

Stroke: cardiovascular risk factors and the quantitative effects of dietary treatment on them.

A quantitative analysis of the cardiovascular risk factors in 101 stroke patients and their reduction by dietary treatment is given. From the risk factors a risk index was calculated. It was reduced from an average 4.9 at admission to 1.4 at discharge. The most frequent risk factors at admission (high triglycerides, high blood pressure and a high LDL/HDL ratio) are probably caused by 'normal' alcohol consumption and overweight. All patients were disused from smoking and alcohol. Under a low-caloric diet all risk factors were reduced within one month. Most diabetic patients became independent of drug treatment: A treatment of type II diabetes mellitus with oral antidiabetic drugs could be avoided even in the elderly patients by a low caloric diet without alcohol. On average there was a 4.8 mg% decrease of fasting triglycerides and a 5.7 mg% decrease of total cholesterol per 1% Broca Index reduction. HDL was increased in all patients despite withdrawal of alcohol, and the HDL/LDL ratio was significantly improved by the diet. There was a significant blood pressure reduction in the whole group; in addition there was a weight-related reduction in the hypertensive patients only: the systolic blood pressure was reduced by 9.3 mm Hg for each 10% Broca Index decrease. The atherogenic and hypertensive potencies of 'normal' alcohol consumption and sulfonylurea treatment are emphasized.

Adult↗
PubMed1985

[Value of flowmetry in disorders of bladder emptying].

After definition of the 'rate of increase in urinary flow' uroflowmetry still does not seem to be of any value for the differentiation of abnormalities of micturition in women as a screening method. Correlating several parameters of uroflowmetry with different subjective and objective data and the final urodynamic diagnosis in 1113 sophisticated urodynamic studies we did not find a discriminatory value of any of the parameters described.

Adult↗
PubMed1984

A model for size- and rotation-invariant pattern processing in the visual system.

The mapping of retinal space onto the striate cortex of some mammals can be approximated by a log-polar function. It has been proposed that this mapping is of functional importance for scale- and rotation-invariant pattern recognition in the visual system. An exact log-polar transform converts centered scaling and rotation into translations. A subsequent translation-invariant transform, such as the absolute value of the Fourier transform, thus generates overall size- and rotation-invariance. In our model, the translation-invariance is realized via the R-transform. This transform can be executed by simple neural networks, and it does not require the complex computations of the Fourier transform, used in Mellin-transform size-invariance models. The logarithmic space distortion and differentiation in the first processing stage of the model is realized via "Mexican hat" filters whose diameter increases linearly with eccentricity, similar to the characteristics of the receptive fields of retinal ganglion cells. Except for some special cases, the model can explain object recognition independent of size, orientation and position. Some general problems of Mellin-type size-invariance models-that also apply to our model-are discussed.

Animals↗
PubMed1978

Primate infant's effects on mother's future reproduction.

Female savanna baboons (Papio cynocephalus) had a longer postpartum amenorrhea and thereafter cycled longer before conceiving if their previous infant survived than if that infant died. Among mothers of surviving infants, differences in maternal care produced differences in age of weaning and age of independence but did not result in differences in interbirth intervals.

Amenorrhea↗
PubMed1977

On the analysis of rates of behaviour.

Formulas are developed for calculating the expected frequency of behaviour and of social interactions in each age-sex category or other class, particularly when the study population changes composition during the study, given the null hypothesis either of constant but unknown rates of behaviour that are independent of class, or of class-specific rates per individual.

Age Factors↗
PubMedDate not supplied

Corneal lathing using the excimer laser and a computer-controlled positioning system: Part I--Lathing of epikeratoplasty lenticules.

Precise lathing of epikeratoplasty lenticules is difficult to achieve with the cryolathe due to unpredictable expansion of the lathing tools and the corneal tissue during the freezing process. In addition, the procedure destroys all viable cells in the transplant thereby possibly contributing to the prolonged period of visual rehabilitation. Non-freezing techniques using the microkeratome or the rotor-trephine, on the other hand, are technically demanding, can cause mechanical damage during cutting or fixation, and, have not given consistently reproducible refractive results. A new system is presented that allows a variable laser ablation of donor corneas into lenticules for aphakic and myopic epikeratoplasty, as well as for lamellar keratoplasty. With the help of a computer-controlled positioning system that uses high-precision micropositioning elements (both translation and rotational stages) the donor cornea is moved, epithelial side down, in a holding device in front of a focused excimer laser beam (ArF, lambda = 193 nm). This photoablation lathing process assures the viability of the stromal cells in the lenticule in close approximation to the treated surface. The user friendly computer software allows the fast and convenient selection of a variety of parameters, such as the diameter of the optical zone, the shape of the wing zone, the refractive power, the central thickness of the lenticule and the overall contour of the transplant. The first laboratory data of lenticules prepared from human corneas with this "Excimer Laser Corneal Shaping System" are presented.

Cornea↗
PubMedDate not supplied

Corneal lathing using the excimer laser and a computer-controlled positioning system: Part II--Variable trephination of corneal buttons.

A new system is presented that allows a variable trephination of donor corneas for the preparation of corneal buttons used in penetrating keratoplasty. With the help of a computer-controlled positioning system that uses high-precision micropositioning elements (both translation and rotational stages) the donor cornea is removed, epithelial side up, in a fixation device in front of a focused excimer laser beam (ArF, lambda = 193 nm). User friendly computer software allows the surgeon to select a variety of parameters (diameter, shape, angle of trephination) of the corneal graft. Histological and electron microscopical data of human corneas trephined with this "Excimer Laser Corneal Shaping System" are presented.

Cornea↗